laminate

Abstract

The present invention relates to a laminate which comprises a polyimide-based film that contains a polyimide-based resin and metal layers that are provided on both surfaces of the film, wherein when the Vickers hardness and the Martens hardness are determined on both surfaces of the laminate in accordance with ISO 14577 under the conditions in which if an indenter is pressed into the laminate from the surface of one metal layer of the laminate in the thickness direction of the laminate, the maximum indentation depth exceeds the thickness of the metal layer on the side where the indenter is pressed into the laminate and is 10% to 50% inclusive of the thickness of the polyimide-based film, formula (I) PV / PM ≤ 0.135 is satisfied. (In the formula, PV represents the difference between the Vickers hardness determined on one surface of the laminate and the Vickers hardness determined on the other surface, and PM represents the difference between the Martens hardness determined on one surface of the laminate and the Martens hardness determined on the other surface.)

Description

Laminate

[0001] The present invention relates to a laminate including a polyimide film containing a polyimide resin and metal layers provided on both sides of the film, particularly a laminate that can be used as a substrate material compatible with printed circuit boards and antenna boards for high-frequency bands, and a flexible printed circuit board including the laminate.

[0002] Flexible printed circuit boards (hereinafter sometimes referred to as FPCs) are thin, lightweight, and flexible, allowing for three-dimensional, high-density mounting. They are used in many electronic devices such as mobile phones and hard disks, contributing to their miniaturization and weight reduction. Conventionally, polyimide resins, which have excellent heat resistance, mechanical properties, and electrical insulation properties, have been widely used in FPCs. For example, metal-clad laminates such as copper-clad laminates (hereinafter sometimes abbreviated as CCL) used in FPCs are known as laminates having metal layers on one or both sides of a resin film. In recent years, fifth-generation mobile communication systems, known as 5G, have become widely used (e.g., Patent Document 1), and laminates suitable for high-speed communication applications beyond 5G are being considered.

[0003] Japanese Patent Application Laid-Open No. 2021-161285

[0004] Laminates used in FPCs may be subject to deformation, such as bending, during processing or repeated use, and are therefore required to be resistant to deformation to prevent deterioration of electrical properties, etc., due to deformation. However, it is difficult to increase the resistance to deformation while controlling the dielectric properties of the laminate within an appropriate range. For this reason, there is a need to develop a laminate that is resistant to deformation and can be used for high-speed communication applications beyond 5G. Therefore, an object of the present invention is to provide a laminate having a high flexural modulus and a flexible printed circuit board including the laminate.

[0005] The present inventors conducted extensive research to solve the above-mentioned problems and found that the above-mentioned problems can be solved when the Vickers hardness and Martens hardness measured on one surface and the other surface of the laminate when an indenter is pressed from the surface of the metal layer of the laminate into the thickness direction of the laminate satisfy a specific formula. Furthermore, the present inventors also found that the above-mentioned problems can be solved when the average elastic modulus of the polyimide film measured by a scanning probe microscope (sometimes referred to as SPM) at a cross section in the thickness direction of the laminate in a curved state satisfies a specific formula, or when the average orientation parameter of the polyimide film measured by a laser Raman spectrometer at a cross section in the thickness direction of the laminate in both a curved and flat state has a specific relationship, thereby completing the present invention. Specifically, the present invention includes the following aspects.

[0006] [1] A laminate comprising a polyimide film containing a polyimide resin and metal layers provided on both sides of the film, wherein when an indenter is pressed from the surface of the metal layer of the laminate in the thickness direction of the laminate, the maximum indentation depth exceeds the thickness of the metal layer on the side where the indenter is pressed and is 10% to 50% of the thickness of the polyimide film, and when the Vickers hardness and Martens hardness of both sides of the laminate are measured according to ISO 14577, the laminate satisfies the relationship of formula (I): PV / PM≦0.135 (I), where PV represents the difference between the Vickers hardness measured on one side of the laminate and the Vickers hardness measured on the other side, and PM represents the difference between the Martens hardness measured on one side of the laminate and the Martens hardness measured on the other side. [2] The laminate according to [1], wherein the PV is 9.5 or less. [3] The laminate according to [1] or [2], wherein the PM is 70.0 or less. [4] A laminate comprising a polyimide film containing a polyimide resin and metal layers provided on both sides of the film, wherein the average Martens hardness of the polyimide film measured in accordance with ISO 14577 at three points in a cross section in the thickness direction of the laminate, the three points being the center in the thickness direction of the polyimide film, a position 0.5 to 5 μm from the interface between the polyimide film and one of the metal layers, and a position 0.5 to 5 μm from the interface between the polyimide film and the other metal layer, is 0.35 GPa or more, and the standard deviation of the elastic deformation power is 2.50% or less. [5] The laminate according to [4], wherein the average creep deformation rate of the polyimide film is 11.20% or less when held for 20 seconds under an indentation load of 1 mN as measured in accordance with ISO 14577 at three points in a cross section of the laminate in the thickness direction: a central part in the thickness direction of the polyimide film; a position 0.5 to 5 μm from the interface between the polyimide film and one metal layer; and a position 0.5 to 5 μm from the interface between the polyimide film and the other metal layer.[6] The laminate according to [4] or [5], wherein the standard deviation of the elastic deformation work of the polyimide film measured in accordance with ISO 14577 at three points in a cross section of the laminate in the thickness direction: a central part in the thickness direction of the polyimide film; a position 0.5 to 5 μm from the interface between the polyimide film and one metal layer; and a position 0.5 to 5 μm from the interface between the polyimide film and the other metal layer; is 3.00 mN nm or less. [7] A laminate comprising a polyimide film containing a polyimide resin and metal layers provided on both sides of the film, wherein when one metal layer surface of the laminate is surface A and the other metal layer surface is surface B, the average elastic modulus measured by a scanning probe microscope in a cross section in the thickness direction of the laminate is expressed by formula (II) and formula (III): |1-EAa / EBa|≦0.12 (II) |1-EAb / EBb|≦0.12 (III) wherein EAa, EBa, EAb and EBb are each the average elastic modulus in the process of pulling back a cantilever probe, and EAa represents the average elastic modulus of the polyimide film measured at a position 0.5 to 5 μm from the interface between the metal layer on the surface A side and the polyimide film when the laminate is bent with a curvature radius of 400 μm with the surface A facing inward, a laminate satisfying the relationships: EBa represents the average elastic modulus of the polyimide film measured at a position 0.5 to 5 μm from the interface between the metal layer and the polyimide film on the A-side when the laminate is bent with a radius of curvature of 400 μm, with the B-side facing inward; EAb represents the average elastic modulus of the polyimide film measured at a position 0.5 to 5 μm from the interface between the metal layer and the polyimide film on the B-side when the laminate is bent with a radius of curvature of 400 μm, with the A-side facing inward; and EBb represents the average elastic modulus of the polyimide film measured at a position 0.5 to 5 μm from the interface between the metal layer and the polyimide film on the B-side when the laminate is bent with a radius of curvature of 400 μm, with the B-side facing inward. [8] The laminate according to [7] above, which satisfies the relationship of formula (IV): |1-EAa / EBb|+|1-EBa / EAb|≦0.25 (IV) [wherein EAa, EBb, EBa and EAb are as defined above].[9] The laminate according to [7] or [8], which satisfies the relationship of formula (V): |Era-Erb|≦0.34 (V) [wherein Era and Erb are each the average elastic modulus in the process of pulling back the cantilever probe, Era represents the average elastic modulus of the polyimide film measured at a position 0.5 to 5 μm from the interface between the metal layer and the polyimide film on the A-side in a cross section in the thickness direction of the laminate in a flat state, and Erb represents the average elastic modulus of the polyimide film measured at a position 0.5 to 5 μm from the interface between the metal layer and the polyimide film on the B-side in a cross section in the thickness direction of the laminate in a flat state].

[10] The laminate according to any one of the above items [7] to [9], which satisfies the relationship of formula (VI): Erc / Eac≦1.80 (VI) [wherein Erc represents the average elastic modulus during the retraction process of the cantilever probe at the center in the thickness direction of the polyimide film in a cross section in the thickness direction of the laminate in a planar state, and Eac represents the average elastic modulus during the indentation process of the cantilever probe at the center in the thickness direction of the polyimide film in a cross section in the thickness direction of the laminate in a planar state].

[11] Formula (VII): |(EAa / EaAa)-(EBb / EaBb)|+|(EBa / EaBa)-(EAb / EaAb)|≦0.48 (VII) [wherein EaAa, EaBa, EaAb, and EaBb are average elastic moduli during the indentation process of the cantilever probe, and EaAa represents the average elastic modulus of the polyimide-based film measured at a position 0.5 to 5 μm from the interface between the metal layer on the A-side side and the polyimide-based film in a cross section in the thickness direction of the laminate when the laminate is bent with a curvature radius of 400 μm with the A-side facing inward, EaBa represents the average elastic modulus of the polyimide-based film measured at a position 0.5 to 5 μm from the interface between the metal layer on the A-side side and the polyimide-based film in the cross section of the laminate in the thickness direction when the laminate is bent with a radius of curvature of 400 μm with the B-side facing inward; EaAb represents the average elastic modulus of the polyimide-based film measured at a position 0.5 to 5 μm from the interface between the metal layer on the B-side side and the polyimide-based film in the cross section of the laminate in the thickness direction when the laminate is bent with a radius of curvature of 400 μm with the A-side facing inward; EaBb represents the average elastic modulus of the polyimide-based film measured at a position 0.5 to 5 μm from the interface between the metal layer on the B-side side and the polyimide-based film in the cross section of the laminate in the thickness direction when the laminate is bent with a radius of curvature of 400 μm with the B-side facing inward; and EAa, EBb, EBa and EAb are as defined above. The laminate according to any one of [7] to

[10] above, which satisfies the relationship:

[12] Formula (VIII) and Formula (IX): wrBa / wra≦1.250 (VIII) wrAb / wrb≦1.250 (IX) [wherein, wrBa, wra, wrAb, and wrb are standard deviations of adhesion energy in the process of pulling back the cantilever probe, wrBa represents the standard deviation of adhesion energy of the polyimide-based film measured at a position 0.5 to 5 μm from the interface between the metal layer on the A-side and the polyimide-based film in a cross section in the thickness direction of the laminate when the laminate is bent with a curvature radius of 400 μm with the B-side facing inward, and wra represents the standard deviation of adhesion energy of the polyimide-based film measured at a position 0.5 to 5 μm from the interface between the metal layer on the A-side and the polyimide-based film in a cross section in the thickness direction of the laminate in a flat state, The laminate according to any one of items [7] to

[11] above, satisfying the relationship: wrAb represents the standard deviation of the adhesion energy of the polyimide film measured at a position 0.5 to 5 μm from the interface between the metal layer on surface B and the polyimide film in a cross section in the thickness direction of the laminate when the laminate is curved with surface A facing inward at a curvature radius of 400 μm; and wrb represents the standard deviation of the adhesion energy of the polyimide film measured at a position 0.5 to 5 μm from the interface between the metal layer on surface B and the polyimide film in a cross section in the thickness direction of the laminate in a flat state.

[13] A laminate comprising a polyimide-based film containing a polyimide-based resin and metal layers provided on both sides of the film, wherein when one metal layer surface of the laminate is designated as surface A and the other metal layer surface is designated as surface B, an average orientation parameter measured using a laser Raman spectrometer in a cross section of the laminate in the thickness direction is expressed by formula (XI): |1-PAa / Pa|+|1-PBb / Pb|≦1.10 (XI) In formula (XI), PAa represents the average orientation parameter of the polyimide-based film measured at a position 0.5 to 5 μm in the thickness direction from the interface between the metal layer and the polyimide-based film on the surface A side when the laminate is curved with a curvature radius of 400 μm with the surface A facing inward, and Pa represents the average orientation parameter of the polyimide-based film measured at a position 0.5 to 5 μm in the thickness direction from the interface between the metal layer and the polyimide-based film on the surface A side when the laminate is in a flat state, PBb represents the average orientation parameter of the polyimide-based film measured at a position 0.5 to 5 μm from the interface between the metal layer and the polyimide-based film on the B-side side in the thickness direction when the laminate is curved with a curvature radius of 400 μm with the B-side facing inward, and Pb represents the average orientation parameter of the polyimide-based film measured at a position 0.5 to 5 μm from the interface between the metal layer and the polyimide-based film on the B-side side in the thickness direction when the laminate is in a flat state, and each of the average orientation parameters is 1615 cm (1615 cm in a polarization configuration that coincides with the in-plane direction of the laminate). －１ Peak intensity around 1615 cm in a polarization configuration coinciding with the thickness direction of the laminated film －１

[14] The laminate according to

[13] , wherein |1-PAa / Pa| and |1-PBb / Pb| in formula (XI) are each 0.52 or less.

[15] The average orientation parameter in the cross section of the laminate in the thickness direction is expressed by the formula (XII): |1-PBa / Pa|+|1-PAb / Pb|≦1.40 (XII) [In formula (XII), PBa represents the average orientation parameter of the polyimide-based film measured at a position of 0.5 to 5 μm in the thickness direction from the interface between the metal layer and the polyimide-based film on the A-side when the laminate is bent with a curvature radius of 400 μm, with the B-side facing inward, PAb represents the average orientation parameter of the polyimide-based film measured at a position of 0.5 to 5 μm in the thickness direction from the interface between the metal layer and the polyimide-based film on the B-side when the laminate is bent with a curvature radius of 400 μm, with the A-side facing inward, and each of the average orientation parameters is expressed by the formula (XII): |1-PBa / Pa|+|1-PAb / Pb|≦1.40 (XII) [In formula (XII), PBa represents the average orientation parameter of the polyimide-based film measured at a position of 0.5 to 5 μm in the thickness direction from the interface between the metal layer and the polyimide-based film on the B-side when the laminate is bent with a curvature radius of 400 μm, with the A-side facing inward, －１ Peak intensity around 1615 cm in a polarization configuration coinciding with the thickness direction of the laminated film －１ The laminate according to the above

[13] or

[14] , wherein the average of the orientation parameters represented by the peak intensities around the peak intensities is satisfied.

[16] The average orientation parameter in the cross section of the laminate in the thickness direction is expressed by the formula (XIII): |1-PAc / Pc|+|1-PBc / Pc|≦0.70 (XIII) [In formula (XIII), PAc represents the average orientation parameter of the polyimide film measured at the center position in the thickness direction of the polyimide film when the laminate is bent with a curvature radius of 400 μm with the A surface facing inward, Pc represents the average orientation parameter of the polyimide film measured at the center position in the thickness direction of the polyimide film in the planar laminate, PBc represents the average orientation parameter of the polyimide film measured at the center position in the thickness direction of the polyimide film when the laminate is bent with a curvature radius of 400 μm with the B surface facing inward, and each of the average orientation parameters is expressed by the formula (XIII): |1-PAc / Pc|+|1-PBc / Pc|≦0.70 (XIII) [In formula (XIII), PAc represents the average orientation parameter of the polyimide film measured at the center position in the thickness direction of the polyimide film when the laminate is bent with a curvature radius of 400 μm with the B surface facing inward, －１Peak intensity around 1615 cm in a polarization configuration coinciding with the thickness direction of the laminated film －１

[17] The laminate according to any one of [1] to

[16] above, wherein the linear expansion coefficient of the polyimide-based film is 10 to 29 ppm / K.

[18] The laminate according to any one of [1] to

[17] above, wherein the polyimide-based film comprises a polyimide-based resin-containing layer (PI-1) and a polyimide-based resin-containing layer (PI-2).

[19] The laminate according to

[18] above, wherein the thickness of the polyimide-based resin-containing layer (PI-2) is 0.05 to 0.3 times the thickness of the polyimide-based resin-containing layer (PI-1).

[20] The laminate according to

[18] or

[19] above, wherein the polyimide-based film further comprises a polyimide-based resin-containing layer (PI-3).

[21] The polyimide resin contained in the polyimide resin-containing layer (PI-1), the polyimide resin contained in the polyimide resin-containing layer (PI-2), and the polyimide resin contained in the polyimide resin-containing layer (PI-3) each have a storage modulus at 40°C of 1.0 × 10 ９

[22] At least one of the polyimide-based resin-containing layer (PI-1) and the polyimide-based resin-containing layer (PI-2) contains a polyimide-based resin having a structural unit (A) derived from a tetracarboxylic acid anhydride, and the structural unit (A) is represented by the formula (A1): [In formula (A1), R ａ１ each independently represent a halogen atom, or an alkyl group, alkoxy group, aryl group, or aryloxy group which may have a halogen atom, and k represents an integer of 0 to 2], and / or a structural unit (A1) derived from a tetracarboxylic acid anhydride represented by formula (A2): [In formula (A2), R ａ２

[23] The laminate according to any one of items

[18] to

[21] , comprising a structural unit (A2) derived from a tetracarboxylic acid anhydride represented by the formula (B1): wherein each of the 1's and 1's independently represents a halogen atom, or an alkyl group, alkoxy group, aryl group, or aryloxy group which may have a halogen atom, and each of the 1's independently represents an integer of 0 to 3.

[23] At least one of the polyimide-based resin-containing layer (PI-1) and the polyimide-based resin-containing layer (PI-2) comprises a polyimide-based resin having a structural unit (B) derived from a diamine, and the structural unit (B) is represented by the formula (B1): [In formula (B1), R ｂ１ each independently represents a halogen atom, or an alkyl group, alkoxy group, aryl group, or aryloxy group which may have a halogen atom; and each W independently represents —O—, —CH ２ -, -CH ２ -CH ２ -, -CH(CH ３ ) -, -C(CH ３ ) ２ -, -C(CF ３ ) ２ -, -COO-, -OOC-, -SO-, -SO ２ -, -S-, -CO-, -N(R ｃ )- and -CONH-, or a single bond (where m is 2 or more and at least one W is the divalent linking group); R ｃ represents a hydrogen atom or a monovalent hydrocarbon group having 1 to 12 carbon atoms which may be substituted with a halogen atom, m represents an integer of 1 to 4, and each q independently represents an integer of 0 to 4.

[24] At least the polyimide-based resin-containing layer (PI-1) contains a polyimide-based resin having a tetracarboxylic acid anhydride-derived structural unit (A), and the structural unit (A) is represented by formula (A3): [In formula (A3), Z represents a divalent organic group, R ａ３each independently represent a halogen atom, or an alkyl group, alkoxy group, aryl group, or aryloxy group which may have a halogen atom, and each s independently represent an integer of 0 to 3.

[25] The laminate according to any one of items

[18] to

[23] , comprising a structural unit (A3) derived from an ester bond-containing tetracarboxylic acid anhydride represented by the formula (A3): [In formula (A3), Z represents a divalent organic group, R ａ３ each independently represent a halogen atom, or an alkyl group, alkoxy group, aryl group, or aryloxy group which may have a halogen atom, and each s independently represent an integer of 0 to 3.

[26] The laminate according to any one of [1] to

[25] above, wherein the metal layer is a copper layer.

[27] A flexible printed circuit board comprising the laminate according to any one of [1] to

[26] above.

[0007] According to the present invention, it is possible to provide a laminate having high bending elasticity and a flexible printed circuit board including the laminate.

[0008] 1 is a graph showing an example of a load-displacement curve obtained from an indentation test by a nanoindentation method in accordance with ISO 14577. FIG. 2 is a schematic diagram for explaining a method for preparing a curved sample for measuring the average DMT elastic modulus. FIG. 3 is a diagram for explaining a method for determining the radius of curvature of a curved sample. FIG. 4 is a graph showing a force curve obtained at an arbitrary point on the cross section of a sample in a laminate according to one embodiment of the present invention. FIG. 5 is a schematic diagram showing the relationship between the polarization vibration direction of laser Raman and the direction of the cross section of the sample in a measurement method using a laser Raman spectrometer in the present invention. FIG. 6 is a schematic cross-sectional view showing an example of the layer structure of a laminate of the present invention.

[0009] Hereinafter, embodiments of the present invention will be described in detail. Note that the scope of the present invention is not limited to the embodiments described herein, and various modifications can be made within the scope that does not impair the spirit of the present invention. Note that the upper and lower limit values ​​described in this specification can be arbitrarily combined to form a suitable numerical range. Hereinafter, in this specification, polyimide-based resins may be abbreviated as "PI-based resins" and polyimide-based films may be abbreviated as "PI-based films."

[0010] [Laminate] (First embodiment) In a first embodiment of the present invention, the laminate of the present invention comprises a polyimide film containing a polyimide resin and metal layers provided on both sides of the film, and when an indenter is pressed into the laminate from the surface of the metal layer in the thickness direction of the laminate, the maximum indentation depth exceeds the thickness of the metal layer on the side where the indenter is pressed and is 10% to 50% of the thickness of the polyimide film, and when the Vickers hardness and Martens hardness are measured on both sides of the laminate according to ISO 14577, the following relationship is satisfied: PV / PM≦0.135 (I) [wherein PV represents the difference between the Vickers hardness measured on one side of the laminate and the Vickers hardness measured on the other side, and PM represents the difference between the Martens hardness measured on one side of the laminate and the Martens hardness measured on the other side].

[0011] In the present invention, Vickers hardness (hereinafter sometimes referred to as "HV") is determined by a nanoindentation method in accordance with ISO 14577 and is an index representing the resistance to plastic deformation. ＩＴ It represents the hardness obtained by multiplying the indentation hardness by a constant (0.0945) that depends on the indenter. In other words, the Vickers hardness is a hardness that takes into account the plastically deformed portion.

[0012] In contrast, Martens hardness (hereinafter sometimes referred to as "HM") is determined by a nanoindentation method in accordance with ISO 14577, and is the hardness measured under an applied test load, and represents the hardness obtained by dividing the test load by the surface area of ​​the indenter that presses the material beyond the contact point. Martens hardness includes both plastic and elastic deformation components.

[0013] The inventors conducted research focusing on the hardness of the laminate and unexpectedly discovered that when the ratio (the difference between the Vickers hardness measured on one side and the other side of the laminate) / (the difference between the Martens hardness measured on one side and the other side of the laminate) is 0.135 or less, the flexural modulus of the laminate increases, i.e., the laminate's resistance to deformation is improved. The reason for this is unclear, but it is thought that the ease and variability of plastic deformation and elastic deformation occurring in the metal layers, polyimide films, and their interfaces on both sides of the laminate affect the manner in which stress is relaxed and dispersed when a bending load is applied. When the laminate satisfies formula (I), the difference between the Vickers hardness measured on one side and the other side of the laminate is small, and the difference between the Martens hardness measured on one side and the other side is likely to be large. It is believed that the more uniform the Vickers hardness (reflecting plastic deformation) on both sides of the laminate, the more uniform the susceptibility to plastic deformation on both sides, which means that stress is less likely to concentrate when an external force is applied, and stress is more efficiently distributed on both sides of the laminate.It is also believed that the more uneven the Martens hardness (including elastic deformation in addition to plastic deformation) on both sides of the laminate, the more likely stress relaxation occurs due to differences in the susceptibility to elastic deformation, which results in increased resistance to deformation of the entire laminate.

[0014] The Vickers hardness and Martens hardness of the laminate of the present invention can be determined by the nanoindentation method in accordance with ISO 14577, as described above, and can be calculated from the average value of three measurement data points by, for example, measuring arbitrary locations on one side and the other side of the laminate using a microhardness tester and a Vickers indenter (a diamond square pyramid indenter with a facing angle of 136°). Specifically, the Vickers hardness and Martens hardness can be determined by the method described in the examples below.

[0015] In the present invention, PV / PM is preferably 0.130 or less, more preferably less than 0.125 or 0.125 or less, even more preferably 0.124 or less, still more preferably 0.120 or less, and particularly preferably 0.115 or less. PV / PM is preferably 0.080 or more, more preferably 0.085 or more, and even more preferably 0.090 or more. When PV / PM is within the above range, stress concentration is unlikely to occur when an external force is applied to the laminate, and stress relaxation is likely to occur. As a result, the strength of the entire laminate against deformation is increased, and the flexural modulus of the laminate can be further improved.

[0016] In the present invention, the PV is preferably 9.5 or less, more preferably 9.0 or less, even more preferably 8.5 or less, even more preferably 8.3 or less, even more preferably 7.0 or less, and particularly preferably 6.0 or less, and may be, for example, 5.0 or less, 4.0 or less, 3.0 or less, 2.0 or less, or 1.0 or less. The lower limit of the PV is not particularly limited and may be, for example, 0.1 or more, or 0.3 or more. When the PV is within the above range, when an external force is applied to the laminate, stress can be efficiently dispersed and stress concentration is less likely to occur, thereby further improving the flexural modulus of the laminate.

[0017] In the present invention, the PM is preferably 70.0 N / mm ２ or less, more preferably 65.0 N / mm ２ or less, more preferably 50.0 N / mm ２ or less, and even more preferably 40.0 N / mm ２ Below 30.0 N / mm ２ or less, for example, 20.0 N / mm ２ The PM may be 3.0 N / mm or less. ２ More preferably, 5.0 N / mm ２ When the PM is within the above range, stress relaxation is likely to occur when an external force is applied to the laminate, and this can further improve the flexural modulus of the laminate.

[0018] (Second Embodiment) In a second embodiment of the present invention, the laminate of the present invention is a laminate including a polyimide film containing a polyimide resin and metal layers provided on both sides of the film, wherein in a cross section in the thickness direction of the laminate, the average Martens hardness of the polyimide film measured in accordance with ISO 14577 at three points: a central portion in the thickness direction of the polyimide film; a position 0.5 to 5 μm from the interface between the polyimide film and one metal layer; and a position 0.5 to 5 μm from the interface between the polyimide film and the other metal layer, is 0.35 GPa or more, and the standard deviation of the elastic deformation power of the polyimide film is 2.50% or less.

[0019] The elastic deformation power is a value obtained from a load-displacement curve obtained from an indentation test using a nanoindentation method in accordance with ISO 14577, and represents the ratio of the work of elastic deformation to the work, including both plastic deformation and elastic deformation, applied to the laminate by the indentation test, and can be calculated using the following formula: W ｔｏｔａｌ =W ｐ +W ｅ η ｉｔ = 1 - W ｐ / W ｔｏｔａｌ [In the formula, W ｔｏｔａｌ is the total work, W ｐ is the plastic deformation work, W ｅ is the elastic deformation work, η ｉｔ represents the elastic deformation power. ] η ｉｔ The closer to 1 (100%) the laminate is to elastically deforming. ｔｏｔａｌ is the area surrounded by ABCE in Figure 1, W ｅ is calculated from the area enclosed by C-D-E in Figure 1.

[0020] The inventors of the present invention have conducted research focusing on the mechanical properties of the polyimide film in the laminate and have unexpectedly found that the smaller the variation in the elastic deformation power of the polyimide film in the laminate, the more robust the laminate against deformation. While the reason for this is unclear, it is believed that the smaller the variation in the elastic deformation power of the polyimide film in the laminate, the more consistent the deformation in the polyimide film portion, which reduces stress concentration when an external force is applied, resulting in efficient stress dispersion on both sides of the laminate. Furthermore, the higher the Martens hardness on both sides of the laminate, the higher the robustness against deformation.

[0021] In the present invention, the average Martens hardness of the polyimide film measured according to ISO 14577 is 0.35 GPa or more, preferably 0.36 GPa or more, more preferably 0.37 GPa or more, even more preferably 0.38 GPa or more, and particularly preferably 0.39 GPa or more or 0.40 GPa or more, and is preferably 1.0 GPa or less, more preferably 0.80 GPa or less or 0.60 GPa or less. When the average Martens hardness of the polyimide film measured according to ISO 14577 is within the above range, the strength of the laminate against deformation is increased, and thereby the flexural modulus of the laminate can be further improved.

[0022] In the present invention, the standard deviation of the elastic deformation power measured according to ISO 14577 at three points in the thickness direction cross section of the laminate: the center in the thickness direction of the polyimide film, a position 0.5 to 5 μm from the interface between the polyimide film and one metal layer, and a position 0.5 to 5 μm from the interface between the polyimide film and the other metal layer, is 2.55% or less, preferably 2.00% or less, more preferably 1.80% or less, even more preferably 1.60% or less, still more preferably 1.55% or less, and particularly preferably 1.45% or less, and may be, for example, 1.30% or less, 1.00% or less, 0.75% or less, or 0.60% or less. The standard deviation of the elastic deformation power is usually 0.01% or more, preferably 0.05% or more, more preferably 0.10% or more, and may be, for example, 0.20% or more. When the standard deviation of the elastic deformation power is within the above range, it is thought that when an external force is applied, stress is efficiently distributed on both sides of the laminate, making stress concentration less likely to occur, thereby further improving the bending modulus of the laminate.

[0023] In the present invention, the average value of the elastic deformation power measured in accordance with ISO 14577 at three points in the thickness direction cross section of the laminate: the central portion in the thickness direction of the polyimide film; a position 0.5 to 5 μm from the interface between the polyimide film and one metal layer; and a position 0.5 to 5 μm from the interface between the polyimide film and the other metal layer. is 25% or more, preferably 28% or more, more preferably 30% or more, even more preferably 31% or more, still more preferably 32% or more, and particularly preferably 33% or more. The average value of the elastic deformation power is preferably 70% or more, more preferably 60% or more, and even more preferably 50% or less, and may be, for example, 45% or less, 40% or less, or 35% or less. When the average value of the elastic deformation power is within the above range, stress concentration is unlikely to occur when an external force is applied, and stress is thought to be efficiently dispersed on both sides of the laminate, thereby further improving the flexural modulus of the laminate.

[0024] In the present invention, in a cross section of the laminate in the thickness direction, the average creep deformation rate measured in accordance with ISO 14577 at three points, namely, the center in the thickness direction of the polyimide film, a position 0.5 to 5 μm from the interface between the polyimide film and one metal layer, and a position 0.5 to 5 μm from the interface between the polyimide film and the other metal layer, when held for 20 seconds under an indentation load of 1 mN is preferably 11.20% or less, more preferably 11.15% or less, even more preferably 11.10% or less, still more preferably 11.05% or less, and particularly preferably 11.00% or less, and is usually 6.00% or more, preferably 7.00% or more, more preferably 8.00% or more, and even more preferably 9.00% or more. The creep deformation rate represents the rate of increase in displacement when a constant load is applied to the laminate, and can be calculated using the following formula: C ＩＴ [%] = (h ２ -h １ ) / h １ ×100 [wherein, C ＩＴ represents the creep deformation rate, and h １ represents the dent depth when the set test load is reached, and h ２ represents the indentation depth after a set test load is maintained for a certain period of time.] In the present invention, when the average creep deformation rate is within the above range, stress is efficiently dispersed when an external force is applied, making it difficult for stress to concentrate, thereby further improving the flexural modulus of the laminate.

[0025] In the present invention, the value of the laminate calculated by (the above Martens hardness) x |(the above creep deformation rate) x 0.12-1| x 100 is preferably 13.8 or less, more preferably 13.4 or less, even more preferably 13.0 or less, and still more preferably 12.6 or less, and may be, for example, 12.2 or less, 12.1 or less, or 12.0 or less, and is preferably 0.30 or more, more preferably 0.50 or more, and even more preferably 3.00 or more, and may be, for example, 7.50 or more. In the present invention, when the value calculated by (the above Martens hardness) x |(the above creep deformation rate) x 0.12-1| x 100 is within the above range, the resistance to deformation of the resin is increased, and the flexural modulus of the laminate can be further improved.

[0026] In the present invention, the standard deviation of the elastic deformation work measured in accordance with ISO 14577 at three points in the thickness direction cross section of the laminate: the center in the thickness direction of the polyimide film, a position 0.5 to 5 μm from the interface between the polyimide film and one metal layer, and a position 0.5 to 5 μm from the interface between the polyimide film and the other metal layer is preferably 3.00 mN nm or less, more preferably 2.00 mN nm or less, even more preferably 1.55 mN nm or less, even more preferably 1.30 mN nm or less, and particularly preferably 1.20 mN nm or less, and may be, for example, 0.80 mN nm or less, or even 0.70 mN nm or less. The standard deviation of the elastic deformation work is usually 0.01 mN nm or more, preferably 0.05 mN nm or more, more preferably 0.10 mN nm or more, and even more preferably 0.20 mN nm or more. The elastic deformation work load corresponds to We in the above formula, and if the standard deviation of the elastic deformation work load is within the above range, when an external force is applied, stress is efficiently distributed on both sides of the laminate, making it less likely for stress to concentrate, thereby further improving the bending modulus of the laminate.

[0027] In the present invention, the average value of the elastic deformation work measured in accordance with ISO 14577 at three points in the thickness direction cross section of the laminate: the center in the thickness direction of the polyimide film, a position 0.5 to 5 μm from the interface between the polyimide film and one metal layer, and a position 0.5 to 5 μm from the interface between the polyimide film and the other metal layer, is preferably 12.0 mN nm or more, more preferably 15.0 mN nm or more, even more preferably 16.0 mN nm or more, and is preferably 25.0 mN nm or less, more preferably 20.0 mN nm or less, and even more preferably 17.0 mN nm or less. When the average value of the elastic deformation work is within the above range, stress is efficiently dispersed on both sides of the laminate when an external force is applied, making stress concentration less likely to occur, and therefore the flexural modulus of the laminate can be further improved.

[0028] The Martens hardness, elastic deformation power, creep deformation rate, and elastic deformation work capacity of the resin can be calculated from a load-displacement curve obtained by nanoindentation according to ISO 14577. For example, using a microhardness tester and a Berkovich indenter, measurements are taken at three points in the cross section of the laminate in the thickness direction: the center of the polyimide film in the thickness direction, a position 0.5 to 5 μm from the interface between the polyimide film and one metal layer, and a position 0.5 to 5 μm from the interface between the polyimide film and the other metal layer, and the values ​​can be calculated from the average value of the three measurement data points. The Martens hardness, elastic deformation power, creep deformation rate, and elastic deformation work capacity of the resin can be specifically determined by the methods described in the Examples below.

[0029] In the laminate of the present invention, the hardness, elastic deformation power, creep deformation rate, elastic deformation work capacity, etc. can be controlled by appropriately adjusting the type and composition of the structural units of the resin constituting the PI film, the molecular weight of the resin, and / or the production conditions such as coating during film formation, selection of the supporting substrate, drying, standing and / or thawing steps, imidization, etc. For example, the hardness, elastic deformation power, creep deformation rate, elastic deformation work capacity, etc. can be adjusted within the above-mentioned ranges based on the preferred aspects herein that are advantageous for improving the flexural modulus and dielectric properties, specifically, the preferred structural units of the PI resin and their content, the preferred solvent contained in the PI resin precursor solution, the preferred conveying speed during coating, the drying temperature, the standing and / or thawing steps, preferred imidization conditions, etc.

[0030] (Third Embodiment) In a third embodiment of the present invention, a laminate of the present invention comprises a polyimide film containing a polyimide resin and metal layers provided on both sides of the film, wherein when one metal layer surface of the laminate is designated as side A and the other metal layer surface is designated as side B, the average elastic modulus measured by a scanning probe microscope in a cross section in the thickness direction of the laminate satisfies the relationships of formulas (II) and (III): |1-EAa / EBa|≦0.12 (II) |1-EAb / EBb|≦0.12 (III) In formulas (II) and (III), EAa, EBa, EAb, and EBb are the average elastic moduli during the pullback process of the cantilever probe, measured at the following measurement locations, respectively. The EAa represents the average elastic modulus of the polyimide-based film measured at a position 0.5 to 5 μm from the interface between the metal layer and the polyimide-based film on the A-side when the laminate is bent with a radius of curvature of 400 μm, with the A-side facing inward; the EBa represents the average elastic modulus of the polyimide-based film measured at a position 0.5 to 5 μm from the interface between the metal layer and the polyimide-based film on the A-side when the laminate is bent with a radius of curvature of 400 μm, with the B-side facing inward; the EAb represents the average elastic modulus of the polyimide-based film measured at a position 0.5 to 5 μm from the interface between the metal layer and the polyimide-based film on the B-side when the laminate is bent with a radius of curvature of 400 μm, with the A-side facing inward; and the EBb represents the average elastic modulus of the polyimide-based film measured at a position 0.5 to 5 μm from the interface between the metal layer and the polyimide-based film on the B-side when the laminate is bent with a radius of curvature of 400 μm, with the B-side facing inward. Hereinafter, in this specification, "elastic modulus measured by a scanning probe microscope" may be referred to as "elastic modulus by SPM" or "DMT elastic modulus."

[0031] In the present invention, EAa is the average DMT elastic modulus of the PI film near the metal layer on the A-side of a laminate curved toward the A-side, and EBa is the average DMT elastic modulus of the PI film near the metal layer on the A-side of a laminate curved toward the B-side. Similarly, EAb is the average DMT elastic modulus of the PI film near the metal layer on the B-side of a laminate curved toward the A-side, and EBb is the average DMT elastic modulus of the PI film near the metal layer on the B-side of a laminate curved toward the B-side. The present inventors have found that when the average DMT elastic moduli of the PI film measured by bending a laminate including a PI film and a metal layer satisfy the relationships of both formulas (II) and (III), the bending elastic modulus of the laminate is increased, i.e., the strength of the laminate against deformation is improved. Although the reason for this is unclear, it is believed that the ease and variability of shrinkage and elongation deformation occurring at the interface between the PI film and the metal layer on both sides of the laminate and the PI film affect the manner in which stress relaxation and stress dispersion occur when a bending load is applied to the laminate. When a laminate satisfies formula (II) and formula (III), the difference between the average DMT modulus of the PI film measured on one side of the laminate stretched by bending and the other side of the laminate contracted by bending is small, making it difficult for the average DMT modulus of the PI film to change due to expansion and contraction of the laminate. This is presumably because such a laminate is more likely to disperse and absorb forces applied in the thickness direction, increasing the overall laminate's resistance to deformation. In this specification, "curving toward the A-side" refers to curving the laminate so that the A-side is inward (i.e., the A-side is in a contracted state), and "curving toward the B-side" refers to curving so that the B-side is inward (i.e., the B-side is in a contracted state).

[0032] In one embodiment of the present invention, the value of |1-EAa / EBa| in formula (II) is 0.12 or less, preferably 0.11 or less, more preferably 0.10 or less, even more preferably 0.09 or less, and particularly preferably 0.08 or less. When the value of |1-EAa / EBa| is equal to or less than the above upper limit, the PI film is less likely to undergo shrinkage deformation or elongation deformation when the laminate is bent, thereby improving the flexural modulus of the laminate. Theoretically, the difference between the average DMT moduli measured on both sides of the laminate can be zero, but the value of |1-EAa / EBa| may be, for example, 0.01 or more, 0.02 or more, 0.03 or more, or 0.04 or more.

[0033] In one embodiment of the present invention, the value of |1-EAb / EBb| in formula (III) is 0.12 or less, preferably 0.11 or less, more preferably 0.10 or less, even more preferably 0.09 or less, and particularly preferably 0.08 or less. When the value of |1-EAb / EBb| is equal to or less than the above upper limit, the PI film is less likely to undergo shrinkage or elongation deformation when the laminate is bent, thereby improving the flexural modulus of the laminate. Theoretically, the closer the difference between the average DMT moduli measured on both sides of the laminate is to 0, the less likely the laminate is to undergo shrinkage or elongation deformation when bent. Therefore, the lower limit of |1-EAb / EBb| can be 0, but may also be, for example, 0.01 or more, 0.02 or more, 0.03 or more, or 0.04 or more.

[0034] In one embodiment of the present invention, the value of |1-EAa / EBa| in formula (II) and the value of |1-EAb / EBb| in formula (III) are both 0.12 or less, preferably 0.11 or less, more preferably 0.10 or less, even more preferably 0.09 or less, and particularly preferably 0.08 or less. When the relationships of formula (II) and formula (III) are both satisfied, both surfaces of the laminate are less likely to undergo shrinkage deformation or elongation deformation in both the extended and contracted states, and the flexural modulus tends to be higher. Note that in the present invention, side A and side B of the laminate may be either of two planes facing each other in the planar direction of the laminate, and when one plane is defined as side A, the opposite plane is defined as side B. For example, in one embodiment of the present invention, in the case of a laminate produced by forming a PI-based film on a metal layer by a casting method and then laminating the remaining metal layer on the PI-based film by thermocompression bonding, the DMT elastic modulus is measured with the surface on the cast metal layer side as side A and the surface on the thermocompression bonded metal layer side as side B.

[0035] In one embodiment of the present invention, the values ​​of EAa, EBa, EAb, and EBb are preferably 3.20 GPa or more, more preferably 3.50 GPa or more, even more preferably 3.80 GPa or more, particularly preferably 4.00 GPa or more, and are preferably 5.50 GPa or less, more preferably 5.00 GPa or less, even more preferably 4.85 GPa or less, still more preferably 4.55 GPa or less, particularly preferably 4.30 GPa or less. When the values ​​of EAa, EBa, EAb, and EBb are within the above ranges, the flexural modulus of the obtained laminate can be improved.

[0036] In one embodiment of the present invention, the laminate of the present invention preferably satisfies the relationship of formula (IV): |1-EAa / EBb|+|1-EBa / EAb|≦0.25 (IV). In formula (IV), EAa, EBb, EBa, and EAb are defined as defined in formulas (II) and (III). When the relationship of formula (IV) is satisfied, the difference between the average DMT elastic modulus of the PI film near the metal layer on the curved side (contracted side) of the laminate and the average DMT elastic modulus of the PI film near the metal layer on the opposite side to the curved side (stretched side) of the laminate is small between the A-side and the B-side of the laminate, and it can be said that the DMT elastic modulus of both sides of the laminate is unlikely to change during contraction and stretching, thereby making it possible to obtain a laminate with excellent flexural modulus. The value of |1-EAa / EBb|+|1-EBa / EAb| in formula (IV) is more preferably 0.22 or less, even more preferably 0.20 or less, even more preferably 0.18 or less, and particularly preferably 0.15 or less, and may be, for example, 0.14 or less, 0.12 or less, or 0.07 or less. The lower limit may be 0, and is preferably 0.01 or more, more preferably 0.02 or more. When the value of |1-EAa / EBb|+|1-EBa / EAb| is within the above range, stress concentration at curved portions is unlikely to occur when shrinkage deformation or elongation deformation occurs on both sides of the laminate when the laminate is stretched, and a laminate with a superior flexural modulus can be obtained.

[0037] In one embodiment of the present invention, the value of |1-EAa / EBb| in formula (IV) is preferably 0.20 or less, more preferably 0.12 or less, and even more preferably 0.10 or less, and may be, for example, 0.07 or less, or 0.05 or less. Theoretically, the value of |1-EAa / EBb| can be 0, but it may usually be 0.005 or more, for example, 0.01 or more, or 0.02 or more. When the value of |1-EAa / EBb| is within the above range, stress concentration at curved portions is unlikely to occur when shrinkage deformation or elongation deformation occurs on both sides of the laminate, and the flexural modulus of the laminate can be further improved.

[0038] In one embodiment of the present invention, the value of |1-EBa / EAb| in formula (IV) is preferably 0.20 or less, more preferably 0.12 or less, and even more preferably 0.10 or less, and may be, for example, 0.07 or less, or 0.05 or less. Theoretically, the value of |1-EBa / EAb| can be 0, but it may usually be 0.01 or more, for example, 0.02 or more. When the value of |1-EBa / EAb| is within the above range, stress concentration at curved portions is unlikely to occur when shrinkage deformation or elongation deformation occurs on both sides of the laminate, and the flexural modulus of the laminate can be further improved.

[0039] In one embodiment of the present invention, the laminate of the present invention preferably satisfies the relationship of formula (V): |Era-Erb|≦0.34 (V) In formula (V), Era and Era are the average elastic moduli during the retraction process of the cantilever probe, measured at the following measurement locations, respectively, Era represents the average elastic modulus of the PI-based film measured at a position 0.5 to 5 μm from the interface between the metal layer and the PI-based film on the A-side in a cross section in the thickness direction of the laminate in a flat state, and Erb represents the average elastic modulus of the PI-based film measured at a position 0.5 to 5 μm from the interface between the metal layer and the PI-based film on the B-side in a cross section in the thickness direction of the laminate in a flat state.

[0040] Formula (V) means that the difference in the average DMT elastic modulus of the PI film near the metal layer on each of the A-side and B-side surfaces, measured in a planar laminate, is small. In other words, when the relationship of formula (V) is satisfied, the difference between the average DMT elastic modulus of the PI film near the metal layer on one side of the laminate and the average DMT elastic modulus of the PI film near the metal layer on the other side is small, and both sides of the laminate can be said to have similar DMT elastic modulus. Such a laminate tends to have similar resistance to shrinkage deformation and elongation deformation on both sides, further improving the flexural modulus of the laminate. In one embodiment of the present invention, the value of |Era - Erb| in formula (V) is preferably 0.34 GPa or less, more preferably 0.30 GPa or less, even more preferably 0.25 GPa or less, even more preferably 0.20 GPa or less, and particularly preferably 0.16 GPa or less. The lower limit may be 0 GPa, preferably 0.01 GPa or more, more preferably 0.05 GPa or more, and even more preferably 0.05 GPa or more, for example, 0.12 GPa or more. When the value of |Era - Erb| is within the above range, stress concentration on curved portions is unlikely to occur when shrinkage deformation or elongation deformation occurs on both sides of the laminate, and a laminate with a superior flexural modulus can be obtained.

[0041] In one embodiment of the present invention, the values ​​of Era and Erb in formula (V) are each preferably 5.00 GPa or less, more preferably 4.80 GPa or less, even more preferably 4.55 GPa or less, still more preferably 4.20 GPa or less, and particularly preferably 4.10 GPa or less, and are also preferably 3.50 GPa or more, more preferably 3.60 GPa or more, even more preferably 3.75 GPa or more, and particularly preferably 3.80 GPa or more. When the values ​​of Era and Erb are preferably both within the above ranges, it is easy to control the value of formula (V) within a desired range, and the flexural modulus of the laminate can be further improved.

[0042] In one embodiment of the present invention, the laminate of the present invention preferably satisfies the relationship of formula (VI): Erc / Eac≦1.80 (VI). In formula (VI), Erc represents the average elastic modulus during the retraction process of the cantilever probe at the center of the thickness direction of the PI film in a cross section of the laminate in a planar state in the thickness direction (sometimes simply referred to as the "retraction process"); and Eac represents the average elastic modulus during the indentation process of the cantilever probe at the center of the thickness direction of the PI film in a cross section of the laminate in a planar state in the thickness direction (sometimes simply referred to as the "indentation process"). In this specification, the "center in the thickness direction" of the PI film refers to a region extending from the interface between the metal layer and the PI film in the thickness direction of the laminate, the region being ½ the length (μm) of the total thickness of the PI film ±2.5 μm. For example, when the total thickness of the PI film is 50 μm, the central region in the thickness direction of the laminate refers to the region located 25±2.5 μm in the thickness direction toward the PI film from the interface between the metal layer and the PI film.

[0043] Formula (VI) represents the ratio of the average elastic modulus when a cantilever is pressed into a PI film (PI resin layer) near the center of the PI film in the thickness direction in a planar laminate to the average elastic modulus when the pressed cantilever is pulled back. In SPM measurements, during the indentation process of the cantilever probe, the probe is pressed into the PI film (PI resin layer), resulting in plastic deformation, viscous deformation, and other deformations in addition to elastic deformation. On the other hand, the pullback process of the cantilever probe occurs after these deformations have occurred, so it can be considered that only elastic deformation occurs. Therefore, the closer the average DMT elastic modulus Eac (a value taking into account not only elastic deformation but also other deformations) during the indentation process is to the average DMT elastic modulus Erc (a value essentially consisting of elastic deformation) during the pullback process, i.e., the smaller the value of (Erc / Eac), the greater the degree of elastic deformation of the PI film, and it is considered that the film has physical properties similar to those of an elastic body. Therefore, when the relationship of formula (VI) is satisfied, when the laminate is bent and shrinkage deformation or elongation deformation occurs on both sides of the laminate, stress concentration on the curved portion is unlikely to occur, and the flexural modulus of the laminate tends to be further improved. In one embodiment of the present invention, the value of Erc / Eac in formula (VI) is more preferably 1.60 or less, even more preferably 1.55 or less, even more preferably 1.50 or less, and particularly preferably 1.48 or less. The lower limit is usually 1.00 or more, preferably 1.10 or more, more preferably 1.20 or more, even more preferably 1.30 or more, and may be, for example, 1.40 or more. When the value of Erc / Eac is within the above range, stress concentration on the curved portion is unlikely to occur when shrinkage deformation or elongation deformation occurs on both sides of the laminate, and a laminate with a superior flexural modulus can be obtained.

[0044] In one embodiment of the present invention, the value of Erc in formula (VI) is preferably 4.00 GPa or more, more preferably 4.10 GPa or more, even more preferably 4.20 GPa or more, and is preferably 5.00 GPa or less, more preferably 4.80 GPa or less, even more preferably 4.60 GPa or less, and still more preferably 4.50 GPa or less. When the value of Erc is within the above range, it is easy to control the value of formula (VI) within a desired range, and the flexural modulus of the laminate can be further improved.

[0045] In one embodiment of the present invention, the value of Eac in formula (VI) is preferably 2.25 GPa or more, more preferably 2.60 GPa or more, even more preferably 3.00 GPa or more, and is preferably 4.00 GPa or less, more preferably 3.60 GPa or less, even more preferably 3.50 GPa or less, and even more preferably 3.30 GPa or less. When the value of Eac is within the above range, it is easy to control the value of formula (VI) within a desired range, and the flexural modulus of the laminate can be further improved.

[0046] In one embodiment of the present invention, the laminate of the present invention preferably satisfies the relationship of formula (VII): |(EAa / EaAa)-(EBb / EaBb)|+|(EBa / EaBa)-(EAb / EaAb)|≦0.48 (VII). In formula (VII), EaAa, EaBa, EaAb, and EaBb are average elastic moduli during the indentation process of the cantilever probe, EaAa represents the average elastic modulus of the PI-based film measured at a position 0.5 to 5 μm from the interface between the metal layer on the A-side surface and the PI-based film in a cross section in the thickness direction of the laminate when the laminate is bent with a radius of curvature of 400 μm with the A-side surface facing inward, and EaBa represents the average elastic modulus of the PI-based film measured at a position 0.5 to 5 μm from the interface between the metal layer on the A-side surface and the PI-based film in a cross section in the thickness direction of the laminate when the laminate is bent with a radius of curvature of 400 μm with the B-side surface facing inward, EaAb represents the average elastic modulus of the PI-based film measured at a position 0.5 to 5 μm from the interface between the metal layer on the side B and the PI-based film in the cross section of the laminate in the thickness direction when the laminate is bent with a radius of curvature of 400 μm with the side A facing inward, and EaBb represents the average elastic modulus of the PI-based film measured at a position 0.5 to 5 μm from the interface between the metal layer on the side B and the PI-based film in the cross section of the laminate in the thickness direction when the laminate is bent with a radius of curvature of 400 μm with the side B facing inward. EAa, EBb, EBa, and EAb in formula (VII) are as defined above.

[0047] Formula (VII) means that the sum of the ratio of the average DMT elastic modulus during the cantilever pressing process to the average DMT elastic modulus during the pull-back process of the PI film in the vicinity of the metal layer, measured on the contraction side (inside of the bend) of the laminate curved toward the A-side and the B-side (EAa / EaAa: hereinafter also referred to as "T1"; EBb / EaBb: hereinafter also referred to as "T4"), and the ratio of the average DMT elastic modulus during the cantilever pressing process to the average DMT elastic modulus during the pull-back process of the PI film in the vicinity of the metal layer, measured on the extension side (outside of the bend) of the laminate curved toward the A-side and the B-side (EBa / EaBa: hereinafter also referred to as "T2"; EAb / EaAb: hereinafter also referred to as "T3"), is small. |(EAa / EaAa)-(EBb / EaBb)| (|T1-T4|) means the difference in elasticity between both surfaces of the laminate during contraction, and |(EBa / EaBa)-(EAb / EaAb)| (|T2-T3|) means the difference in elasticity between both surfaces of the laminate during extension, and it is preferable that both differences are small. The meaning of the average DMT elastic modulus during the cantilever push-in and pull-back processes is as described above, and satisfying formula (VII) tends to further improve the flexural modulus of the laminate. In one embodiment of the present invention, the value of |(EAa / EaAa)-(EBb / EaBb)|+|(EBa / EaBa)-(EAb / EaAb)| in formula (VII) is preferably 0.40 or less, more preferably 0.35 or less, even more preferably 0.30 or less, even more preferably 0.25 or less, and particularly preferably 0.18 or less. When the value of |(EAa / EaAa)-(EBb / EaBb)|+|(EBa / EaBa)-(EAb / EaAb)| is within the above range, stress concentration at curved portions is unlikely to occur when shrinkage deformation or elongation deformation occurs on both surfaces of the laminate, and a laminate having a superior flexural modulus can be obtained.

[0048] In the laminate according to one embodiment of the present invention, the value of ||(EAa / EaAa)-(EBb / EaBb)|-|(EBa / EaBa)-(EAb / EaAb)|| is preferably 0.20 or less, more preferably 0.17 or less, even more preferably 0.15 or less, and particularly preferably 0.10 or less, and is preferably 0.01 or more, more preferably 0.02 or more, and even more preferably 0.03 or more. When the value of ||(EAa / EaAa)-(EBb / EaBb)|-|(EBa / EaBa)-(EAb / EaAb)|| is within the above range, stress concentration at curved portions is unlikely to occur when shrinkage deformation or elongation deformation occurs on both surfaces of the laminate, and a laminate having a superior flexural modulus can be obtained.

[0049] In one embodiment of the present invention, the values ​​of T1, T2, T3, and T4 are each independently preferably 1.60 GPa or less, more preferably 1.50 GPa or less, even more preferably 1.45 GPa or less, particularly preferably 1.40 GPa or less, and are preferably 1.10 GPa or more, more preferably 1.15 GPa or more, and may be, for example, 1.20 GPa or more. When the values ​​of T1, T2, T3, and T4 are preferably all within the above ranges, it is easy to control the value of formula (VII) within a desired range, and a laminate having an even more excellent flexural modulus can be obtained.

[0050] Furthermore, in one embodiment of the present invention, the value of |T1-T4| is preferably 0.35 or less, more preferably 0.30 or less, and even more preferably 0.20 or less, and may be, for example, 0.18 or less, 0.15 or less, or 0.12 or less. The lower limit of the value of |T1-T4| may be 0.00, but may also be, for example, 0.01 or more, or 0.02 or more. When |T1-T4| is within the above range, stress concentration at curved portions is less likely to occur when shrinkage deformation or elongation deformation occurs on both sides of the laminate, and a laminate with a superior flexural modulus can be obtained.

[0051] In one embodiment of the present invention, the value of |T2-T3| is preferably 0.30 or less, more preferably 0.20 or less, even more preferably 0.18 or less, and even more preferably 0.12 or less. The lower limit of |T2-T3| is 0.00. When |T2-T3| is within the above range, stress concentration on curved portions is less likely to occur when shrinkage deformation or elongation deformation occurs on both sides of the laminate, and a laminate with a superior flexural modulus can be obtained.

[0052] In one embodiment of the present invention, the values ​​of EaAa, EaBa, EaAb, and EaBb are each preferably 2.50 or more, more preferably 2.80 or more, even more preferably 3.00 or more, particularly preferably 3.30 or more, and are preferably 4.50 or less, more preferably 4.00 or less, even more preferably 3.80 or less, particularly preferably 3.70 or less. When the values ​​of EaAa, EaBa, EaAb, and EaBb are each within the above ranges, it becomes easy to adjust the value of formula (VII) in the obtained laminate to be within a predetermined range.

[0053] In the present invention, the average DMT elastic modulus of the PI film in the laminate is measured either in a curved state with the A-side or B-side facing inward at a curvature radius of 400 μm, or in a flat state, at a position 0.5 to 5 μm from the interface between the metal layer and the PI film on the measurement target side, or near the center in the thickness direction of the PI film. The method for measuring the DMT elastic modulus of the PI film using SPM is specifically described below. In addition, each average DMT elastic modulus can be determined in detail, for example, by the method described in the Examples. In the present invention, the average DMT elastic modulus may be measured either in a curved state or in a flat state without being curved. Hereinafter, a curved sample may be referred to as a "curved sample," and a flat sample may be referred to as a "flat sample."

[0054] (1) Preparation of Measurement Samples The preparation method of the samples for measuring the average DMT elastic modulus is not particularly limited for both curved and flat samples, as long as the cross section of the laminate in the thickness direction can be observed. However, when the laminate is thin, it is preferable to cut the laminate to be measured into suitable strips, embed a part of them in resin, and prepare a test piece with the cross section exposed.

[0055] A curved sample can be prepared by aligning both ends of a laminate cut into a rectangular shape, bending the laminate to the A-side or B-side, and then embedding the laminate in a resin. Specifically, as shown in FIG. 2, a rectangular laminate 2 cut into a box-shaped mold 1 is placed in a bent state with a curvature radius of approximately 400 μm, pouring in a resin 3 such as an epoxy resin, and then covering the mold with a lid 4 and allowing the mold to stand. A weight 5 may be placed on the lid 4 before allowing the mold to stand. To accurately measure the relationships between the average DMT modulus and the laminate, the curved sample is prepared so as not to leave any traces of bending. A flat sample can be obtained in the same manner as the curved sample by embedding the cut laminate in a flat state without bending it.

[0056] The curved and flat samples obtained by resin embedding can be cut into sections by, for example, using a knife attached to a microtome to cut the surface of the resin-embedded laminate (thickness cross section of the laminate) so that the cross section in the thickness direction can be seen.

[0057] (2) Acquisition of DMT Elastic Modulus Image The DMT elastic modulus in a laminate can be determined by applying the DMT (Derjaguim-Muller-Toporov) theory to the relationship between the deformation amount of the sample and the load on the sample (force curve) determined by SPM. In the present invention, when determining the average DMT elastic modulus of each PI film in a laminate, it is preferable to first obtain a low-resolution DMT elastic modulus image in a region including the range in which the average DMT elastic modulus is to be determined, and then use the DMT elastic modulus image to align the position of the range in which the average DMT elastic modulus is to be determined. The DMT elastic modulus image can be obtained by performing mapping measurement of the DMT elastic modulus on a two-dimensional plane on the sample. For example, a cantilever with a spring constant of 4 to 60 N / m is attached to a Bruker SPM, and a DMT elastic modulus image can be obtained by measuring using a Peak Force QNM (Quantitative Nanomechanical Mapping) mode or a Force Volume mode.

[0058] The range in which the DMT elastic modulus image is obtained can be determined appropriately depending on the region to be measured, but it is preferable to set it so that it includes the metal layer and PI film on the surface to be measured. For example, it is preferable to set the interface between two adjacent layers on the horizontal or vertical axis of the DMT elastic modulus image so that the metal layer and the PI film are included in a ratio of, for example, about 1:1 to 1:5, so that the measurement region described below is included on the PI film side (PI resin portion). The range in which the DMT elastic modulus image is obtained can be determined appropriately depending on the configuration of the laminate. The range in which the DMT elastic modulus image is obtained is preferably 0.1 to 0.6 times, more preferably 0.15 to 0.5 times, and even more preferably 0.2 to 0.4 times the thickness of the laminate in terms of the horizontal (in-plane direction) and vertical (thickness direction) distances.

[0059] The range for acquiring a DMT elastic modulus image of a curved sample is determined by setting a point where the radius of curvature is 400 μm, and then setting the point in the thickness direction of the laminate from that point to the PI film portion (PI resin portion). Here, in the present invention, "when curved with a radius of curvature of 400 μm" and "the point where the radius of curvature is 400 μm" mean bending the sample to a radius of curvature of approximately 400 μm, and the point where the radius of curvature is approximately 400 μm. Specifically, "approximately 400 μm" means a range of 400±30 μm. The radius of curvature of a curved sample can be determined, for example, using image processing software on an optical microscope image of the cut cross section of the curved sample laminate obtained using a measuring laser microscope, as follows. Referring to Figure 3, first, an arbitrary point 1 is set on the outer contour of the metal layer located outside the curved portion near the center of the curved portion in the optical microscope image. Next, points 2 and 3 are set on the outer contour at the same linear distance from point 1. A circle is created that passes through these three points and whose periphery overlaps with the outer contour, and the radius of this circle is calculated as the radius of curvature of Point 1. By changing the positions of the three points, it is possible to set Point 1 at which the radius of curvature is approximately 400 μm, and this point is defined as the point at which the radius of curvature on the curved sample is 400 μm.

[0060] Next, the details of the method for measuring the DMT elastic modulus at each measurement point will be explained using FIG. 4. Note that FIG. 4 is used to clearly explain the method for determining the DMT elastic modulus, and the present invention is not limited to these embodiments. FIG. 4 is a graph showing a force curve obtained at any point within the range in which a DMT elastic modulus image of a sample cross section is acquired in a laminate according to one embodiment of the present invention. In FIG. 4, the vertical axis of the force curve (applied load / nN) is represented by load F = kd, and the horizontal axis (indentation depth / nm) is represented by the deformation amount δ = Δz-d of the sample specimen. k represents the spring constant (N / m), d represents the amount of warping of the spring (m), and z represents the needle position (m). d can be detected by a laser, and z can be sensed by a piezo scanner.

[0061] First, when the cantilever is brought close to the sample, the cantilever probe comes into contact with the sample and is then pushed into the sample until the tip of the probe reaches a maximum load. Accordingly, a force curve (point A → point B → point C) for the pushing process can be obtained, as shown in Figure 4. At point B, the cantilever is affected by the adhesive force when it comes into contact with the sample, and the load is applied in the negative direction. Next, when the cantilever that has been pushed into the sample up to the maximum load is pulled back, the load is released at the sample surface, and after adhesion, the cantilever probe leaves the sample surface. Accordingly, a force curve (point C → point D → point E) for the pulling back process can be obtained, as shown in Figure 4.

[0062] The DMT elastic modulus at each point can be calculated by analyzing the force curves during the indentation and pullback processes using the DMT theoretical formula. Specifically, when the numerical values ​​from the minimum to maximum F values ​​during the pullback process of the force curve are replaced with numerical values ​​from 0 to 1, fitting is performed for the range from 0.1 to 0.7 to calculate the DMT elastic modulus. A DMT elastic modulus image during the pullback process can be obtained by acquiring the DMT elastic modulus at all measurement points within the desired range. Similarly, fitting is performed during the indentation process of the force curve, acquiring the DMT elastic modulus at all measurement points, thereby acquiring the DMT elastic modulus image during the indentation process. Analysis using the DMT theoretical formula can be performed using analysis software included with the SPM (e.g., NanoScope Analysis ver. 2.00) or by a known method. In the latter case, calculation can be performed using, for example, the following formula (a): [wherein F represents the load (the force sensed by the cantilever (spring)), F ｅｌａｓ denotes the stress of elastic deformation, and F ａｄｈ indicates the adhesive force, and E is the elastic modulus (Pa or N / m ２ ), R is the tip radius of the cantilever probe (m), δ is the indentation depth (m), and w is the adhesion energy (N / m or J / m ２ ), and F ａｄｈ The minimum value of the force curve (F value at point D) can be substituted for

[0063] In SPM measurements, the measurement atmosphere can be room temperature, e.g., 24°C, under atmospheric air, and the cantilever movement speed can be set to 0.4 μm / s and the maximum load to 40 nN. The spring constant of the cantilever and the tip radius of the probe can be calculated using values ​​stored in the SPM device or by known methods. For example, the spring constant may be a value calculated by the Sader method, and the tip radius of the probe may be a value calculated by the reconstruction method.

[0064] (3) Calculation of Average DMT Elastic Modulus After confirming the positions of the metal layer and PI film of the laminate using the DMT elastic modulus image obtained above, measurement regions for the average DMT elastic modulus (sometimes simply referred to as "measurement regions") are set at positions 0.5 to 5 μm toward the PI film from the interface between the metal layer and the PI film on the A-side and B-side sides, and at the center of the PI film in the thickness direction, and the average DMT elastic modulus for each measurement region is calculated to obtain the average DMT elastic modulus for the measurement region (EAa, EBa, EAb, EBb, Era, Erb, Erc, Eac, EaAa, EaAb, EaBa, EaBb). The DMT elastic modulus image used to set the measurement region may be a DMT elastic modulus image during the pull-back process or a DMT elastic modulus image during the push-in process.

[0065] The range for obtaining the average DMT elastic modulus can be appropriately determined depending on the configuration of the laminate. For example, in a laminate film having a thickness of 20 to 65 μm, the range for obtaining the average DMT elastic modulus may be 1 μm or more in width and 1 μm or more in length. In one embodiment of the present invention, the range for obtaining the average DMT elastic modulus is, for example, 2 μm in width and 2 μm in length.

[0066] The number of points (locations) at which the DMT elastic modulus is measured to obtain the average DMT elastic modulus is not particularly limited, but from the viewpoint of measurement accuracy, it is usually 100 or more (e.g., 10 or more × 10 or more), preferably 225 or more (e.g., 15 or more × 15 or more), more preferably 400 or more (e.g., 20 or more × 20 or more). The resolution is uniquely determined by the range and number of measurement points for obtaining the DMT elastic modulus image, but when the measurement area is small, it is desirable to measure at a resolution of preferably 40 nm / pixel or less, more preferably 20 nm / pixel or less. When obtaining multiple DMT elastic modulus images for the same measurement object (laminate), it is preferable that the setting conditions (such as the range for obtaining the DMT elastic modulus image and the number of points for measuring the DMT elastic modulus) are all set to the same or similar levels.

[0067] When determining the average DMT elastic modulus in a region near the interface between a PI film such as EAa, EBa, EAb, or EBb and a metal layer, the measurement region is selected from any range that allows measurement of the DMT elastic modulus at 100 or more points within a range of 0.5 to 5 μm from the interface between the metal layer and the PI film toward the PI film. That is, the measurement region in this case is set in the PI film (within the resin layer). From the viewpoint of measurement accuracy, the measurement region is set within a range of preferably 0.5 to 5 μm, more preferably 1 to 4 μm, in the thickness direction of the interface, depending on the thickness of the laminate and the condition (unevenness) of the interface between the metal layer and the PI film.

[0068] When determining the average DMT modulus in the central region of the thickness direction of the PI film, such as Erc or Eac, the center of the measurement region is selected within an arbitrary range of 1 / 2 the length (μm) of the total thickness of the PI film in the thickness direction of the laminate from the interface between the metal layer and the PI film ±2.5 μm. In this case, the measurement region is set in the PI film (within the resin layer). Although it depends on the thickness of the laminate and the state (unevenness) of the interface between the metal layer and the PI film, from the viewpoint of measurement accuracy, the center of the measurement region is set from the interface between the metal layer and the PI film toward the PI film side, preferably within a range of 1 / 2 the length (μm) of the total thickness of the PI film ±2.0 μm, more preferably within a range of 1 / 2 the length (μm) of the total thickness of the PI film ±1.5 μm.

[0069] As described above, the number of DMT elastic moduli to be measured in one measurement region (measurement points) in order to calculate the average DMT elastic modulus is usually 100 or more, preferably 225 or more, more preferably 400 or more, and usually 62,500 or less. The size of one measurement region may be determined according to the resolution of the measurement, and there are no particular restrictions on the size as long as it is possible to measure 100 or more DMT elastic moduli within each target measurement region. The higher the resolution, the smaller the size of the measurement region can be, but from the viewpoint of understanding the variation in the DMT elastic modulus, the size of the measurement region is preferably within the above range.

[0070] In one embodiment of the present invention, the laminate of the present invention preferably satisfies the relationships of formula (VIII) and formula (IX): wrBa / wra≦1.250 (VIII) wrAb / wrb≦1.250 (IX). In formula (VIII) and formula (IX), wrBa, wra, wrAb, and wrb are standard deviations of adhesion energy in the process of pulling back the cantilever probe, wrBa represents the standard deviation of adhesion energy of the PI-based film measured at a position 0.5 to 5 μm from the interface between the metal layer on the A-side surface and the PI-based film in a cross section in the thickness direction of the laminate when the laminate is bent with a curvature radius of 400 μm with the B-side surface facing inward, and wra represents the standard deviation of adhesion energy of the PI-based film measured at a position 0.5 to 5 μm from the interface between the metal layer on the A-side surface and the PI-based film in a cross section in the thickness direction of the laminate in a flat state, wrAb represents the standard deviation of the adhesion energy of the PI-based film measured at a position 0.5 to 5 μm from the interface between the metal layer on the surface B side and the PI-based film in a cross section in the thickness direction of the laminate when the laminate is curved with a radius of curvature of 400 μm with the surface A facing inward, and wrb represents the standard deviation of the adhesion energy of the PI-based film measured at a position 0.5 to 5 μm from the interface between the metal layer on the surface B side and the PI-based film in a cross section in the thickness direction of the laminate in a flat state. Note that the standard deviation of the adhesion energy is the standard deviation of w in formula (a).

[0071] Formulas (VIII) and (IX) respectively mean that the standard deviation of the adhesion energy in the PI film close to the metal layer on the side opposite to the curved side of the laminate (i.e., the stretched side) does not change significantly from the standard deviation of the adhesion energy when measured in a flat state. When the relationship of formula (VIII) and the relationship of formula (IX) are satisfied, it can be said that there is no significant change in the adhesion energy in a flat state when the laminate is curved toward either the A-side or the B-side. In such a laminate, the density of the PI film is unlikely to change even in a curved state, so that when shrinkage deformation or elongation deformation occurs on both sides of the laminate, stress concentration on the curved portion is unlikely to occur, and the flexural modulus of the laminate can be further improved.

[0072] In one embodiment of the present invention, the value of wrBa / wra in formula (VIII) is preferably 1.200 or less, even more preferably 1.150 or less, and is preferably 0.500 or more, more preferably 0.800 or more, even more preferably 0.850 or more. When the value of wrBa / wra is within the above range, stress concentration on curved portions is unlikely to occur when shrinkage deformation or elongation deformation occurs on both sides of the laminate, and the flexural modulus of the laminate can be further improved.

[0073] In one embodiment of the present invention, the value of wrAb / wrb in formula (IX) is more preferably 1.200 or less, even more preferably 1.150 or less, and is preferably 0.500 or more, more preferably 0.800 or more, and even more preferably 0.850 or more. When the value of wrAa / wra is within the above range, stress concentration on curved portions is unlikely to occur when shrinkage deformation or elongation deformation occurs on both surfaces of the laminate, and the flexural modulus of the laminate can be further improved.

[0074] In one embodiment of the present invention, the value of wra is preferably 0.024 N / m or more, more preferably 0.025 N / m or more, even more preferably 0.026 N / m or more, and is preferably 0.040 N / m or less, more preferably 0.035 N / m or less, even more preferably 0.032 N / m or less, particularly preferably 0.030 N / m or less. When the value of wra is within the above range, it becomes easier to control the value of formula (VIII) within a predetermined range.

[0075] In one embodiment of the present invention, the value of wrBa is preferably 0.020 N / m or more, more preferably 0.026 N / m or more, even more preferably 0.030 N / m or more, and is preferably 0.040 N / m or less, more preferably 0.035 N / m or less, even more preferably 0.032 N / m or less. When the value of wrBa is within the above range, it becomes easier to control the value of formula (VIII) within a predetermined range.

[0076] In one embodiment of the present invention, the value of wrb is preferably 0.024 N / m or more, more preferably 0.025 N / m or more, even more preferably 0.026 N / m or more, and is preferably 0.040 N / m or less, more preferably 0.035 N / m or less, even more preferably 0.032 N / m or less, particularly preferably 0.030 N / m or less. When the value of wra is within the above range, it becomes easier to control the value of formula (IX) within a predetermined range.

[0077] In one embodiment of the present invention, the value of wrAb is preferably 0.020 N / m or more, more preferably 0.026 N / m or more, even more preferably 0.030 N / m or more, and is preferably 0.040 N / m or less, more preferably 0.035 N / m or less, even more preferably 0.032 N / m or less. When the value of wrAb is within the above range, it becomes easier to control the value of formula (IX) within a predetermined range.

[0078] The standard deviation of the adhesion energy in the laminate can be determined, for example, as follows. The standard deviation of the adhesion energy can be determined from the force curve at each measurement point where the average DMT elastic modulus was determined. Specifically, the adhesion force Fadh at point D in Figure 1 is substituted into formula (a) to determine the adhesion energy w at each measurement point, and the standard deviation can be calculated from w at all measurement points. Specifically, the standard deviation can be determined by the method described in the Examples below.

[0079] In the laminate of the present invention, the average elastic modulus of each DMT and the adhesion energy can be controlled by appropriately adjusting the type and composition of the structural units of the resin constituting the PI film, the molecular weight of the resin, and / or the production conditions such as coating during film formation, selection of the support substrate, drying, standing and / or thawing process, imidization, etc. For example, the average elastic modulus of each DMT and the adhesion energy can be adjusted within the above ranges based on the preferred embodiment advantageous for improving the bending modulus and dielectric properties herein, specifically, the preferred structural units of the PI resin and their content, the solvent contained in the preferred PI resin precursor solution, the preferred conveying speed during coating, the drying temperature, the standing and / or thawing process, preferred imidization conditions, etc.

[0080] (Fourth embodiment) In a fourth embodiment of the present invention, the laminate of the present invention comprises a polyimide-based film containing a PI-based resin and metal layers provided on both sides of the film, and when one metal layer surface of the laminate is designated as surface A and the other metal layer surface is designated as surface B, the average orientation parameter measured using a laser Raman spectrometer in a cross section in the thickness direction of the laminate satisfies the relationship of formula (XI). |1-PAa / Pa|+|1-PBb / Pb|≦1.10 (XI) In formula (XI), PAa represents the average orientation parameter of the polyimide film measured at a position 0.5 to 5 μm in the thickness direction from the interface between the metal layer and the polyimide film on the A-side side when the laminate is bent with a radius of curvature of 400 μm, with the A-side facing inward; Pa represents the average orientation parameter of the polyimide film measured at a position 0.5 to 5 μm in the thickness direction from the interface between the metal layer and the polyimide film on the A-side side when the laminate is in a flat state; and PBb represents the average orientation parameter of the polyimide film measured at a position 0.5 to 5 μm in the thickness direction from the interface between the metal layer and the polyimide film on the B-side side when the laminate is bent with a radius of curvature of 400 μm, with the B-side facing inward; Pb represents the average orientation parameter of the polyimide film measured at a position 0.5 to 5 μm from the interface between the metal layer on the B-side side and the polyimide film in the thickness direction in the laminate in a flat state, and each of the average orientation parameters is －１ Peak intensity around 1615 cm in a polarization configuration coinciding with the thickness direction of the laminated film －１ Hereinafter, in this specification, the term "peak intensity at 1615 cm in a polarization configuration that coincides with the in-plane direction of the laminate" is used. －１ "Peak intensity near ０ ", "1615 cm in a polarization configuration that coincides with the thickness direction of the laminate －１ "Peak intensity near ９０ ", and each orientation parameter in the present invention is expressed as I ０ / I ９０ The value is expressed as:

[0081] I in the orientation parameter ０ and I ９０ In the －１ The peak intensity around 1615 cm can be a peak derived from the C=C stretching vibration of the aromatic ring in the PI resin constituting the PI film. The C=C stretching vibration of the aromatic ring vibrates along the polymer chain of the PI resin, so the vibration direction of the C=C stretching vibration of the aromatic ring can be regarded as the orientation direction of the polymer chain. Therefore, when the orientation direction of the PI resin and the vibration direction of the laser polarization coincide with each other, the peak intensity around 1615 cm can be determined. －１ The intensity of the peaks near the center of the crystal may be strong, and conversely, if they do not match, the intensity of the peaks may be weak. ０ / I ９０ ) in which I ０ can be said to be the peak intensity resulting from the C=C stretching vibration of the aromatic ring when a laser beam having a polarization arrangement that coincides with the in-plane direction of the laminate, i.e., a polarization vibration direction that coincides with the in-plane direction, is applied to the cross section. ９０ can be said to be the peak intensity resulting from the C=C stretching vibration of the aromatic ring when a laser beam having a polarization arrangement that coincides with the thickness direction of the laminate, that is, a polarization vibration direction that coincides with the thickness direction, is applied to the cross section. ０ The larger the value, the higher the degree of orientation of the PI film in the in-plane direction. ９０ It can be said that the larger the value, the higher the degree of orientation in the thickness direction of the PI film. Therefore, the orientation parameter can be regarded as the ratio of the degree of orientation in the in-plane direction to the degree of orientation in the thickness direction. In this specification, "peak intensity" means the height of the peak, and "near" means ±30 cm. －１ range, preferably ±10 cm －１ More preferably, ±5 cm －１ For example, 1615 cm －１ The peak intensity around 1615±30 cm －１ within the range of 1615±10 cm －１ more preferably in the range of 1615±5 cm －１ This means the maximum peak intensity in the range.

[0082] In formula (XI), PAa and PBb are the average orientation parameters of the PI film near the curved side, i.e., the metal layer on the inside of the curved portion, obtained by performing line analysis along the thickness direction cross section of a laminate curved toward the A-side or B-side using a laser Raman spectrometer. Furthermore, Pa and Pb in formula (XI) are the average orientation parameters of the PI film near the metal layer on the A-side or B-side, respectively, measured in a flat laminate. The inventors have found that when the average orientation parameters of the PI film measured by bending a laminate containing a PI film and a metal layer both satisfy the relationship of formula (XI), the flexural modulus of the laminate is increased, i.e., the strength of the laminate against deformation is improved. The reason for this is unclear, but it is expected that the ease and variability of shrinkage deformation occurring at the interface between the PI film and the metal layer on both sides of the laminate affect the orientation when a bending load is applied to the laminate. When the laminate satisfies formula (XI), the average orientation parameter of the PI film near the interface between the metal layer and the PI film on the curved side (inside of the bend) is unlikely to change between the laminate in a flat state and the laminate in a contracted state. That is, high or low orientation due to curvature (contraction) is unlikely to occur. This is presumably because such a laminate easily disperses and absorbs forces applied in the thickness direction, increasing the strength of the entire laminate against deformation.

[0083] In one embodiment of the present invention, the value of |1-PAa / Pa| + |1-PBb / Pb| in formula (XI) is 1.10 or less, preferably 1.00 or less, more preferably 0.90 or less, even more preferably 0.85 or less, even more preferably 0.75 or less, and particularly preferably 0.60 or less, and may be, for example, 0.45 or less, 0.40 or less, or 0.35 or less. Furthermore, the value of |1-PAa / Pa| + |1-PBb / Pb| is preferably 0.01 or more, more preferably 0.05 or more, and may be, for example, 0.08 or more. When the value of |1-PAa / Pa| + |1-PBb / Pb| is within the above range, stress concentration at curved portions is less likely to occur when the laminate undergoes shrinkage or elongation deformation, and the flexural modulus of the laminate can be improved.

[0084] In one embodiment of the present invention, the value of |1-PAa / Pa| in formula (XI) is preferably 0.55 or less, more preferably 0.52 or less, even more preferably 0.50 or less, even more preferably 0.45 or less, and particularly preferably 0.40 or less. Furthermore, the value of |1-PAa / Pa| is preferably 0.01 or more, more preferably 0.03 or more, and may be, for example, 0.05 or more. When the value of |1-PAa / Pa| is within the above range, stress concentration at curved portions is unlikely to occur when the laminate undergoes shrinkage deformation or elongation deformation, and the flexural modulus of the laminate can be improved.

[0085] In one embodiment of the present invention, the value of |1-PBb / Pb| in formula (XI) is preferably 0.55 or less, more preferably 0.52 or less, even more preferably 0.50 or less, even more preferably 0.45 or less, and particularly preferably 0.40 or less. Furthermore, the value of |1-PBb / Pb| is preferably 0.01 or more, more preferably 0.03 or more, and may be, for example, 0.05 or more. When the value of |1-PBb / Pb| is within the above range, stress concentration at curved portions is unlikely to occur when the laminate undergoes shrinkage deformation or elongation deformation, and the flexural modulus of the laminate can be improved.

[0086] In one embodiment of the present invention, the values ​​of |1-PAa / Pa| and |1-PBb / Pb| in formula (XI) are both preferably 0.52 or less, more preferably 0.50 or less, even more preferably 0.45 or less, and particularly preferably 0.40 or less. When these relationships are both satisfied, when shrinkage deformation or elongation deformation occurs on both sides of the laminate, whether in an elongated state or a contracted state, stress concentration on the curved portion is less likely to occur, and the flexural modulus tends to be higher. In addition, in the present invention, the A-side and B-side of the laminate may be either of two planes facing each other in the planar direction of the laminate, and when one plane is designated as the A-side, the opposite plane is designated as the B-side. For example, in one embodiment of the present invention, in the case of a laminate produced by forming a PI-based film on a metal layer by a casting method and then laminating the remaining metal layer to the PI-based film by thermocompression bonding, the orientation parameter is measured with the side facing the cast metal layer designated as the A-side and the side facing the thermocompression-bonded metal layer designated as the B-side.

[0087] In one embodiment of the present invention, the PAa value is preferably 0.90 or more, more preferably 1.00 or more, for example 1.50 or more or 1.80 or more, and is preferably 4.50 or less, more preferably 4.00 or less, and even more preferably 3.50 or less. When the PAa value is within the above range, the flexural modulus of the obtained laminate can be improved.

[0088] In one embodiment of the present invention, the Pa value is preferably 0.60 or more, more preferably 0.80 or more, even more preferably 1.00 or more, for example 1.20 or more, 1.60 or more, or 2.20 or more, and is preferably 4.00 or less, more preferably 3.50 or less, even more preferably 3.00 or less. When the Pa value is within the above range, the flexural modulus of the obtained laminate can be improved.

[0089] In one embodiment of the present invention, the PBb value is preferably 0.90 or more, more preferably 1.00 or more, for example, 1.50 or more or 1.80 or more, and is preferably 4.50 or less, more preferably 4.00 or less, and even more preferably 3.50 or less. When the PBb value is within the above range, the flexural modulus of the obtained laminate can be improved.

[0090] In one embodiment of the present invention, the value of Pb is preferably 0.60 or more, more preferably 0.80 or more, even more preferably 1.00 or more, for example, 1.20 or more, 1.60 or more, or 2.20 or more, and is preferably 4.00 or less, more preferably 3.50 or less, even more preferably 3.00 or less. When the value of Pb is within the above range, the flexural modulus of the obtained laminate can be improved.

[0091] In one embodiment of the present invention, the laminate of the present invention preferably satisfies the relationship of formula (XII): |1-PBa / Pa|+|1-PAb / Pb|≦1.40 (XII) In formula (XII), PBa represents an average orientation parameter of the polyimide film measured at a position 0.5 to 5 μm in the thickness direction from the interface between the metal layer and the polyimide film on the surface A side when the laminate is bent with a radius of curvature of 400 μm, with the surface B facing inward, PAb represents an average orientation parameter of the polyimide film measured at a position 0.5 to 5 μm in the thickness direction from the interface between the metal layer and the polyimide film on the surface B side when the laminate is bent with a radius of curvature of 400 μm, with the surface A facing inward, and each of the average orientation parameters is a value obtained by multiplying the average orientation parameter by 1615 cm (in a polarization configuration that coincides with the in-plane direction of the laminate). －１ Peak intensity around 1615 cm in a polarization configuration coinciding with the thickness direction of the laminated film －１ In formula (XII), Pa and Pb are defined as in formula (XI) above.

[0092] PBa and PAb in formula (XII) are the average orientation parameters of the PI film on the opposite side of the curved side, i.e., in the vicinity of the metal layer on the outside of the curved portion, obtained by performing line analysis along the thickness direction cross section of a laminate curved toward the B-side or A-side using a laser Raman spectrometer. When the relationship of formula (XII) is satisfied, the average orientation parameter of the PI film near the interface between the metal layer and the PI film on the opposite side of the curved side is unlikely to change between a laminate in a flat state and a laminate in an elongated state. In other words, high orientation or low orientation due to curvature (elongation) is unlikely to occur. Such a laminate easily disperses and absorbs forces applied in the thickness direction, making it easier to increase the strength of the entire laminate against deformation, and a laminate with excellent flexural modulus can be obtained. The value of |1-PBa / Pa|+|1-PAb / Pb| in formula (XII) is more preferably 1.20 or less, even more preferably 1.00 or less, still more preferably 0.90 or less, and may be, for example, 0.75 or less. It is also preferably 0.10 or more, more preferably 0.20 or more, and even more preferably 0.30 or more, and may be, for example, 0.40 or more. When the value of |1-PBa / Pa|+|1-PAb / Pb| is within the above range, stress concentration at curved portions is less likely to occur when the laminate undergoes shrinkage deformation or elongation deformation, and a laminate with a superior flexural modulus can be obtained.

[0093] In one embodiment of the present invention, the value of |1-PBa / Pa| in formula (XII) is preferably 1.00 or less, more preferably 0.50 or less, and even more preferably 0.40 or less, and may be, for example, 0.35 or less or 0.30 or less. Furthermore, the value of |1-PBa / Pa| is preferably 0.01 or more, more preferably 0.03 or more, and may be, for example, 0.05 or more or 0.10 or more. When the value of |1-PBa / Pa| is within the above range, stress concentration at curved portions is unlikely to occur when the laminate undergoes shrinkage deformation or elongation deformation, and the flexural modulus of the laminate can be improved.

[0094] In one embodiment of the present invention, the value of |1-PAb / Pb| in formula (XII) is preferably 1.00 or less, more preferably 0.50 or less, and even more preferably 0.40 or less, and may be, for example, 0.35 or less or 0.30 or less. Furthermore, the value of |1-PBb / Pb| is preferably 0.01 or more, more preferably 0.03 or more, and may be, for example, 0.05 or more or 0.10 or more. When the value of |1-PAb / Pb| is within the above range, stress concentration at curved portions is unlikely to occur when the laminate undergoes shrinkage deformation or elongation deformation, and the flexural modulus of the laminate can be improved.

[0095] In one embodiment of the present invention, the value of |1-PBa / Pa| and the value of |1-PAb / Pb| in formula (XII) are both preferably 0.50 or less, more preferably 0.40 or less, even more preferably 0.35 or less, and particularly preferably 0.30 or less, and are preferably 0.01 or more, more preferably 0.03 or more, and may be, for example, 0.05 or more or 0.10 or more. When both of these relationships are satisfied, stress concentration on curved portions is less likely to occur when the laminate undergoes shrinkage deformation or elongation deformation, and the flexural modulus tends to be further increased.

[0096] In one embodiment of the present invention, the PBa value is preferably 0.50 or more, more preferably 1.00 or more, even more preferably 1.10 or more, and may be, for example, 1.20 or more, 1.23 or more, 1.30 or more, or 2.00 or more, and is preferably 5.00 or less, more preferably 4.50 or less, even more preferably 4.00 or less, still more preferably 3.50 or less, and particularly preferably 3.20 or less. When the PBa value is within the above range, the flexural modulus of the obtained laminate can be improved.

[0097] In one embodiment of the present invention, the PAb value is preferably 0.50 or more, more preferably 1.00 or more, even more preferably 1.10 or more, and may be, for example, 1.20 or more, 1.23 or more, 1.30 or more, or 2.00 or more, and is preferably 5.00 or less, more preferably 4.50 or less, even more preferably 4.00 or less, still more preferably 3.50 or less, and particularly preferably 3.20 or less. When the PAb value is within the above range, the flexural modulus of the obtained laminate can be improved.

[0098] In one embodiment of the present invention, the laminate of the present invention preferably satisfies the relationship of formula (XIII): |1-PAc / Pc|+|1-PBc / Pc|≦0.70 (XIII) In formula (XIII), PAc represents the average orientation parameter of the polyimide film measured at the center position in the thickness direction of the polyimide film when the laminate is bent with a radius of curvature of 400 μm with the A surface facing inward, Pc represents the average orientation parameter of the polyimide film measured at the center position in the thickness direction of the polyimide film in the planar laminate, PBc represents the average orientation parameter of the polyimide film measured at the center position in the thickness direction of the polyimide film when the laminate is bent with a radius of curvature of 400 μm with the B surface facing inward, and each of the average orientation parameters is a value obtained by multiplying the average orientation parameter by 1615 cm (at a polarization orientation that coincides with the in-plane direction of the laminate). －１ Peak intensity around 1615 cm in a polarization configuration coinciding with the thickness direction of the laminated film －１ The "center in the thickness direction" of the PI film in this specification refers to a region from the interface between the metal layer and the PI film to a length (μm) of half the total thickness of the PI film in the thickness direction of the laminate ±2.5 μm. For example, when the total thickness of the PI film is 50 μm, the center in the thickness direction of the laminate refers to a region located 25±2.5 μm from the interface between the metal layer and the PI film toward the PI film in the thickness direction.

[0099] In formula (XIII), Pc represents the average orientation parameter near the center of the thickness direction of the PI film, obtained by performing line analysis along the thickness cross section of a laminate curved toward the A-side or B-side using a laser Raman spectrometer. When the relationship of formula (XIII) is satisfied, the average orientation parameter near the center of the thickness direction of the PI film is unlikely to change between the laminate in a planar state and the laminate in a stretched state. In other words, high or low orientation due to bending (stretching) is unlikely to occur. Such a laminate easily disperses and absorbs forces applied in the thickness direction, increasing the overall laminate's resistance to deformation and resulting in a laminate with excellent flexural modulus. The value of |1-PAc / Pc| + |1-PBc / Pc| in formula (XIII) is more preferably 0.50 or less, even more preferably 0.40 or less, and even more preferably 0.35 or less. Furthermore, it is preferably 0.01 or more, more preferably 0.05 or more, and even more preferably 0.10 or more. When the value of |1-PAc / Pc|+|1-PBc / Pc| is within the above range, stress concentration at curved portions is less likely to occur when the laminate undergoes shrinkage deformation or elongation deformation, and a laminate with a superior flexural modulus can be obtained.

[0100] In one embodiment of the present invention, the value of |1-PAc / Pc| in formula (XIII) is preferably 0.45 or less, more preferably 0.40 or less, even more preferably 0.30 or less, even more preferably 0.25 or less, and particularly preferably 0.20 or less, and may be, for example, 0.15 or less or 0.13 or less. Furthermore, the value of |1-PAc / Pc| is usually 0.00 or more, preferably 0.01 or more, more preferably 0.03 or more, even more preferably 0.04, and may be, for example, 0.06 or more. When the value of |1-PAc / Pc| is within the above range, stress concentration at curved portions is unlikely to occur when the laminate undergoes shrinkage deformation or elongation deformation, and the flexural modulus of the laminate can be improved.

[0101] In one embodiment of the present invention, the value of |1-PBc / Pc| in formula (XIII) is preferably 0.45 or less, more preferably 0.40 or less, even more preferably 0.30 or less, still more preferably 0.25 or less, and particularly preferably 0.20 or less, and may be, for example, 0.15 or less or 0.13 or less. Furthermore, the value of |1-PBc / Pc| is usually 0.00 or more, more preferably 0.01 or more, even more preferably 0.03, and still more preferably 0.04 or more. When the value of |1-PBc / Pc| is within the above range, stress concentration at curved portions is unlikely to occur when the laminate undergoes shrinkage deformation or elongation deformation, and the flexural modulus of the laminate can be improved.

[0102] In one embodiment of the present invention, the values ​​of |1-PAc / Pc| and |1-PBc / Pc| in formula (XIII) are both preferably 0.45 or less, more preferably 0.40 or less, even more preferably 0.30 or less, still more preferably 0.25 or less, and particularly preferably 0.20 or less, and may be, for example, 0.15 or less or 0.13 or less, and are preferably 0.01 or more, more preferably 0.03 or more, and even more preferably 0.04 or more. When these relationships are both satisfied, stress concentration on curved portions is less likely to occur when the laminate undergoes shrinkage deformation or elongation deformation, and the flexural modulus tends to be further increased.

[0103] In one embodiment of the present invention, the PAc value is preferably 3.30 or less, more preferably 3.00 or less, even more preferably 2.80 or less, still more preferably 2.75 or less, and is preferably 0.50 or more, more preferably 1.00 or more, even more preferably 1.50 or more. When the PAc value is within the above range, it is easy to adjust each average orientation parameter required in the obtained laminate within a predetermined range.

[0104] In one embodiment of the present invention, the PBc value is preferably 3.30 or less, more preferably 3.00 or less, even more preferably 2.80 or less, still more preferably 2.75 or less, and is preferably 0.50 or more, more preferably 1.00 or more, even more preferably 1.50 or more. When the PBc value is within the above range, the flexural modulus of the obtained laminate can be improved.

[0105] In one embodiment of the present invention, the Pc value is preferably 0.50 or more, more preferably 1.00 or more, even more preferably 1.50 or more, and may be, for example, 2.30 or more, and is preferably 3.50 or less, more preferably 3.00 or less, even more preferably 2.80 or less. When the Pc value is within the above range, the flexural modulus of the obtained laminate can be improved.

[0106] In the present invention, the average orientation parameters of the PI film in the laminate are measured in a state where the laminate is curved with a curvature radius of 400 μm with the A-side or B-side facing inward, or in a flat state, at a position 0.5 to 5 μm from the interface between the metal layer and the PI film on the measurement target side, or near the center in the thickness direction of the PI film. Below, using the figures, the laser Raman spectroscopy measurement method in the present invention and how to determine PAa, PBb, PBa, PAb, PAc, PBc, Pa, Pb, and Pc are explained in detail. In addition, each average orientation parameter can be determined in detail, for example, by the method described in the Examples.

[0107] (1) Preparation of Measurement Samples In the present invention, the average orientation parameter may be measured in a curved state or in a flat state of the laminate. The curved sample in the curved state and the flat sample in the flat state can be prepared by the same method as the curved sample and the flat sample for measuring the average DMT elastic modulus in the third embodiment.

[0108] (2) Obtaining the orientation parameter at each measurement point on the sample cross section The sample is placed in a laser Raman spectrometer with a half-wave plate set at a 90° angle, and the sample is adjusted so that the vibration direction of the laser polarization (0° direction) and the thickness direction of the sample are parallel (the vibration direction of the polarization is parallel to the X-axis direction in FIG. 5). Raman spectroscopy is then performed at multiple measurement points along the planar direction of the sample. Next, the sample is rotated 90°, and the sample angle is adjusted so that the vibration direction of the laser polarization and the planar direction of the sample are parallel (the thickness direction of the laminate is perpendicular to the X-axis direction in FIG. 5). As described above, Raman spectroscopy is performed at multiple measurement points along the planar direction of the sample. It is preferable to perform smoothing or fluorescence removal processing, for example, using a moving average method, on the Raman spectrum obtained by Raman spectroscopy.

[0109] Measurement points are usually set at multiple locations in the measurement area to calculate each average orientation parameter. For example, when measuring PAa or Pa, measurement points are set at preferably three or more locations in the in-plane direction of the laminate within a region of the PI resin film located within a range of 0.5 to 5 μm in the thickness direction from the interface between the metal layer and the PI film on the A-side. In this case, it is preferable to set each measurement point at intervals of preferably 5 μm or more, more preferably 10 μm or more, in the in-plane direction. For PBa, PBb, PAb, Pb, etc., measurement points can also be set in the same manner as above within a region of the PI resin film located within a range of 0.5 to 5 μm in the thickness direction from the interface between the metal layer and the PI film on the measurement surface.

[0110] When measuring PAc, PBc, or Pc, the measurement area is selected from the center position in the thickness direction of the laminate from the interface between the metal layer and the PI film, usually within an arbitrary range of 1 / 2 the length (μm) of the total thickness of the PI film in the thickness direction from the interface. In this case, the measurement area is set in the PI film (within the resin layer). Although it depends on the thickness of the laminate and the state (unevenness) of the interface between the metal layer and the PI film, from the viewpoint of measurement accuracy, the measurement area is set from the interface between the metal layer and the PI film toward the PI film, preferably within a range of 1 / 2 the length (μm) of the total thickness of the PI film ±2.0 μm, more preferably within a range of 1 / 2 the length (μm) of the total thickness of the PI film ±1.5 μm. Within this measurement area, measurement locations can be set in the same manner as described above.

[0111] The measurement area for the curved sample is set at a point where the radius of curvature is 400 μm, and set in the PI film portion (PI resin portion) located in the thickness direction of the laminate from that point. In the present invention, "when curved with a radius of curvature of 400 μm" and "the point where the radius of curvature is 400 μm" mean bending so that the radius of curvature is about 400 μm, and the point where the radius of curvature is about 400 μm, and "about 400 μm" specifically means a range of 400±30 μm. The radius of curvature of the curved sample can be determined by the method described for measuring the average DMT elastic modulus in the third embodiment.

[0112] (3) Calculation of the average orientation parameter From the Raman spectra obtained in each of the above measurements, －１ By obtaining the intensity of the peak near I (a peak that may correspond to the C═C stretching vibration of the aromatic ring), ０ , and I ９０ This gives the orientation parameter (I ０ / I ９０ ) can be calculated.

[0113] Measurement areas are set up at positions 0.5 to 5 μm toward the PI film from the interface between the metal layer and the PI film on the A-side and B-side sides, and at the center of the PI film in the thickness direction.The orientation parameter at each measurement point along the thickness direction of the laminate is obtained in each measurement area using the above-mentioned method, and then the average orientation parameters measured at measurement points within the ranges specified by PAa, PBb, PBa, PAb, PAc, PBc, Pa, Pb and Pc can be obtained by calculating the average of the orientation parameters measured at measurement points within the ranges specified by PAa, PBb, PBa, PAb, PAc, PBc, Pa, Pb and Pc.

[0114] In the laminate of the present invention, each average orientation parameter can be controlled by appropriately adjusting the type and composition of the structural units of the resin constituting the PI film, the molecular weight of the resin, and / or the production conditions such as coating during film formation, selection of the support substrate, drying, standing and / or thawing steps, imidization, etc. For example, each average orientation parameter can be adjusted within the above range based on the preferred aspects herein that are advantageous for improving the flexural modulus and dielectric properties, specifically, the preferred structural units of the PI resin and their content, the preferred solvent contained in the PI resin precursor solution, the preferred conveying speed during coating, the drying temperature, standing and / or thawing steps, preferred imidization conditions, etc.

[0115] [Polyimide Film] The laminate of the present invention includes a polyimide film containing a polyimide resin. The polyimide resin makes it easy to control the Martens hardness, elastic deformation power, creep deformation rate, elastic deformation work amount, DMT elastic modulus in the resin layer, or average orientation parameter within a desired range, thereby improving the flexural modulus of the laminate.

[0116] The PI film may be a single layer film or a laminated film.

[0117] In a preferred embodiment of the present invention, when the PI film is a laminate film, the PI film preferably includes a polyimide resin-containing layer (PI-1) and a polyimide resin-containing layer (PI-2). The PI film may include a PI resin-containing layer other than these PI resin-containing layers, or may include a layer other than the PI resin-containing layer. Examples of such a layer include a pressure-sensitive adhesive layer. In a preferred embodiment of the present invention, from the viewpoint of increasing the flexural modulus of the laminate, the PI film of the present invention preferably includes a PI resin-containing layer (PI-3) in addition to the PI resin-containing layer (PI-1) and the PI resin-containing layer (PI-2). In such an embodiment, from the viewpoint of increasing the flexural modulus of the laminate, the PI film of the present invention preferably includes the PI resin-containing layer (PI-2), the PI resin-containing layer (PI-1), and the PI resin-containing layer (PI-3) in this order, and more preferably includes the layers adjacent to each other in this order. A PI film including the PI resin-containing layer (PI-1), the PI resin-containing layer (PI-2), and the PI resin-containing layer (PI-3) (sometimes referred to as PI resin-containing layers (PI-1) to (PI-3) or layers (PI-1) to (PI-3)) is sometimes referred to as the PI film (L). In this specification, unless otherwise specified, the term "PI film" includes both a single-layer film and a laminate film, and when a PI resin-containing layer, particularly the PI resin-containing layer (PI-1), the PI resin-containing layer (PI-2), and / or the PI resin-containing layer (PI-3), is mentioned, it relates to a PI film in the form of a laminate film.

[0118] As shown in FIG. 6 , a PI film 10 according to a preferred embodiment of the present invention is composed of three adjacent layers: a PI resin-containing layer 11, a PI resin-containing layer 12, and a PI resin-containing layer 13. A metal layer 14 adjacent to the PI film 11 and a metal layer 15 adjacent to the PI film 13 constitute a laminate 16. From the viewpoint of improving the flexural modulus and dielectric properties of the laminate, the PI resin-containing layer 11 preferably corresponds to layer (PI-2), the PI resin-containing layer 12 preferably corresponds to layer (PI-1), and the PI resin-containing layer 13 preferably corresponds to layer (PI-3). The PI film 10 may also include a PI resin-containing layer other than layers (PI-1), (PI-2), and (PI-3), or a layer other than the PI resin-containing layer. Examples of such layers include pressure-sensitive adhesive layers formed from polymeric materials such as acrylic resins other than PI resins.

[0119] In this specification, "dielectric properties" refers to dielectric properties such as Df and Dk, and "enhancement or improvement of dielectric properties" refers to a decrease in Df and / or Dk. The dielectric properties of a laminate can be evaluated based on the dielectric properties of the PI film in the laminate. Mechanical properties may also refer to properties such as flexural modulus, yield strength, puncture strength, bending resistance, and flexibility. "Enhancement or improvement of mechanical properties" refers to, for example, an increase in flexural modulus, yield strength, bending resistance, and / or flexibility. Thermal properties may include CTE, glass transition temperature (hereinafter sometimes referred to as Tg), and the degree of thermal denaturation or degradation. "Enhancement or improvement of thermal properties" refers to, for example, a decrease in CTE, a increase in Tg, and / or less thermal denaturation or degradation.

[0120] In one embodiment of the present invention, the thickness of the PI film is preferably 20 μm or more, more preferably 25 μm or more, even more preferably 30 μm or more, even more preferably 35 μm or more, and particularly preferably 40 μm or more, and is preferably 150 μm or less, more preferably 130 μm or less, even more preferably 100 μm or less, even more preferably 90 μm or less, particularly preferably 80 μm or less, especially more preferably 70 μm or less, and particularly more preferably 60 μm or less. When the thickness of the PI film is within the above range, the laminate can have mechanical properties such as a high flexural modulus and flexibility suitable for flexible printed circuit boards and the like. Furthermore, since the Df can be reduced and the flexural modulus can be improved, a laminate can be obtained that has a good balance of mechanical properties suitable for flexible printed circuit boards and dielectric properties suitable for high-speed communication applications such as 5G.

[0121] When the PI film of the present invention is a laminate film, the film thickness can be selected from the thickness range of the resin film described above. However, the thickness of layer (PI-1) is preferably 10 μm or more, and the thickness of layer (PI-2) is preferably 2 μm or more. When the thicknesses of layer (PI-1) and layer (PI-2) are equal to or greater than the above-mentioned lower limits, the flexural modulus of the laminate can be further improved. The thickness of layer (PI-1) is more preferably 15 μm or more, even more preferably 20 μm or more, even more preferably 30 μm or more, and is preferably 80 μm or less, more preferably 60 μm or less, even more preferably 55 μm or less, and even more preferably 50 μm or less. Furthermore, the thickness of layer (PI-2) is more preferably 2.5 μm or more, even more preferably 3 μm or more, even more preferably 3.5 μm or more, and is preferably 20 μm or less, more preferably 15 μm or less, even more preferably 10 μm or less, and even more preferably 8 μm or less.

[0122] When the PI film of the present invention has a layer (PI-3), the thickness of the layer (PI-3) may be selected from the range of the thickness of the layer (PI-2) described above. The thicknesses of the layers (PI-2) and (PI-3) may be the same or different from each other, but from the viewpoint of suppressing warpage of the laminate, the thickness of one layer is preferably within ±25% of the thickness of the other layer, more preferably within ±20%. The thickness of each layer can be measured using a laser microscope or the like, for example, by the method described in the Examples.

[0123] In one embodiment of the present invention, the thickness of layer (PI-2) is preferably 0.05 to 0.3 times the thickness of layer (PI-1). When the thicknesses satisfy this relationship, the laminate can have mechanical properties such as a high flexural modulus and flexibility suitable for flexible printed circuit boards and the like. Furthermore, since the flexural modulus can be improved while reducing Df, a laminate can be obtained that has a good balance of mechanical properties suitable for flexible printed circuit boards and dielectric properties suitable for high-speed communication applications such as 5G. In particular, the effects of the present invention are more easily achieved when the thickness of the PI film is 20 to 100 μm and the thickness of layer (PI-2) is 0.05 to 0.3 times the thickness of layer (PI-1). The thickness of layer (PI-2) is more preferably 0.08 times or more, even more preferably 0.10 times or more, and particularly preferably 0.11 times or more, and more preferably 0.25 times or less, even more preferably 0.23 times or less, and particularly preferably 0.20 times or less, the thickness of layer (PI-1). When the PI film of the present invention has layer (PI-3), the thickness of layer (PI-3) may be selected from a range that is similar to the relationship between layer (PI-1) and layer (PI-2).

[0124] In the PI film of the present invention, the type of PI resin constituting layers (PI-1) to (PI-3) is not particularly limited as long as the PV / PM in the laminate can satisfy 0.135 or less, or the average DMT elastic modulus or average orientation parameter required in the laminate can satisfy the desired relationship, but from the viewpoint of increasing the flexural modulus while maintaining excellent dielectric properties, layers (PI-1) to (PI-3) are preferably non-thermoplastic polyimide resin-containing layers (hereinafter sometimes referred to as mPI layers) or thermoplastic polyimide resin-containing layers (hereinafter sometimes referred to as TPI layers). In particular, from the viewpoint of increasing the flexural modulus, layers (PI-1) and (PI-2) are preferably mPI layers or TPI layers, respectively, and more preferably one of layers (PI-1) and (PI-2) is an mPI layer and the other is a TPI layer. The mPI layer is generally the main PI resin-containing layer in a PI film for use in flexible printed circuit boards. The TPI layer can also function as an adhesive layer that bonds the PI film to a metal layer (e.g., a copper layer), and is preferably located as the outermost layer in the PI film that can contact the metal layer. In a PI film containing three or more PI resin-containing layers, it is preferred that at least one PI resin-containing layer is an mPI layer and at least one (preferably at least two) PI resin-containing layer is a TPI layer, and it is more preferred that the PI film has a TPI layer, an mPI layer, and a TPI layer in this order. Therefore, in the PI film (L), it is preferred that the layer (PI-1) is an mPI layer, and the layers (PI-2) and (PI-3) are each a TPI layer. When the PI film (L) has such a layer structure, the mPI layer has improved thermal properties, suppresses thermal denaturation and deterioration, and ensures the dimensional stability of the PI film. The TPI layer can also enhance adhesion to a metal layer (e.g., a copper layer), and can improve the flexural modulus of the PI film. When the PI film (L) contains multiple TPI or mPI layers, the structures of the multiple TPI or mPI layers may be the same or different.In the PI film (L), the layer (PI-1), the layer (PI-2), and the layer (PI-3) usually have different structures, but the structures of the layer (PI-2) and the layer (PI-3) may be the same or different.

[0125] Regarding the third embodiment of the present invention, when the PI film of the present invention has layers (PI-1) to (PI-3), EAa, EBa, EAb, EBb, Era, Erb, EaAa, EaBa, EaAb, EaBb, wrBa, wra, wrAb, and wrb are preferably measured in either layer (PI-2) or layer (PI-3). For example, when layer (PI-2) is on the A-side side and layer (PI-3) is on the B-side side, EAa, EBa, Era, EaAa, EaBa, wrBa, and wra are measured in layer (PI-2), and EAb, EBb, Erb, EaAb, EaBb, wrAb, and wrb are measured in layer (PI-3). Additionally, Erc and Eac are measured in layer (PI-1).

[0126] Regarding the fourth embodiment of the present invention, when the PI film of the present invention has layers (PI-1) to (PI-3), PAa, Pa, PBb, Pb, PBa, and PAb are preferably measured in either layer (PI-2) or layer (PI-3). For example, when layer (PI-2) is on the A-side and layer (PI-3) is on the B-side, PAa, Pa, and PBa are measured in layer (PI-2), and PBb, Pb, and PAb are measured in layer (PI-3). Furthermore, PAc, PBc, and Pc are measured in layer (PI-1).

[0127] In another preferred embodiment of the present invention, when the PI film is a monolayer film, it is composed of one PI resin-containing layer, and the type of layer is not particularly limited as long as the PV / PM of the laminate is 0.135 or less, or the average DMT elastic modulus or average orientation parameter required for the laminate can satisfy the desired relationship, but it is preferable to adopt the configuration of the layer (PI-1) from the viewpoint of increasing the flexural modulus while maintaining excellent dielectric properties. When the PI film is a monolayer film, the thickness of the film can be selected from the thickness range of the PI film described above.

[0128] <PI Resin> The PI resin contained in the PI film is a resin containing a repeating structural unit containing an imide group, and may contain a repeating structural unit containing both an imide group and an amide group. In the present invention, a "non-thermoplastic" polyimide resin is a polyimide resin having a storage modulus of 1.0 × 10 at 40°C measured using a dynamic mechanical analyzer (DMA). ９ Pa or more, and the storage modulus at 300°C is 1.0 × 10 ８ The term "thermoplastic" refers to a polyimide resin having a storage modulus of 1.0 × 10 Pa or more at 40°C. ９ Pa or more, and the storage modulus at 300°C is 1.0 × 10 ８ The storage modulus refers to a polyimide resin having a storage modulus of less than Pa. The storage modulus can be measured, for example, by the method described in the examples.

[0129] From the viewpoint of improving the flexural modulus and dielectric properties of the laminate, the PI resin constituting the PI film preferably contains a tetracarboxylic anhydride-derived structural unit (A) and a diamine-derived structural unit (B). In the present invention, the term "structural unit derived from" means "a structural unit derived from," for example, "tetracarboxylic anhydride-derived structural unit (A)" means "tetracarboxylic anhydride-derived structural unit (A)." Furthermore, "the PI film contains the structural unit (A)" means "the PI resin constituting the PI film contains the structural unit (A)," and "the PI resin-containing layer contains the structural unit (A)" means "the PI resin constituting the PI resin-containing layer contains the structural unit (A)," and the same applies to other structural units. In this specification, unless otherwise specified, the PI resin constituting (or contained in) the PI film can be interpreted as the PI resin constituting (or contained in) at least one of the PI resin-containing layers, at least one of the layers (PI-1) and (PI-2), or at least one of the layers (PI-1) to (PI-3) (or contained in at least one of the layers).

[0130] (Tetracarboxylic Acid Anhydride-Derived Structural Unit (A)) The tetracarboxylic acid anhydride-derived structural unit (A) (hereinafter, sometimes simply referred to as structural unit (A)) is, for example, a structural unit represented by the formula (1): In the formula (1), Y represents a tetravalent organic group.

[0131] In formula (1), Y's each independently represent a tetravalent organic group, preferably a tetravalent organic group having 4 to 40 carbon atoms, and more preferably a tetravalent organic group having 4 to 40 carbon atoms and a cyclic structure. Examples of the cyclic structure include an alicyclic, aromatic ring, and heterocyclic structure. The organic group may have a hydrogen atom substituted with a halogen atom, a hydrocarbon group, an alkoxy group, or a halogenated hydrocarbon group, and in such cases, the number of carbon atoms in these groups is preferably 1 to 8. In the present invention, the PI resin may contain multiple types of Y's, and the multiple types of Y's may be the same or different. Examples of Y include groups or structures represented by formulas (31) to (40); groups in which a hydrogen atom in a group represented by formulas (31) to (40) is substituted with a methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, isobutyl group, sec-butyl group, tert-butyl group, fluoro group, chloro group, or trifluoromethyl group; and tetravalent chain hydrocarbon groups having 1 to 8 carbon atoms.

[0132] [In formulas (31) to (33), R １９ ~R ２６ and R ２３’ ~R ２６’ each independently represents a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, or an aryl group having 6 to 12 carbon atoms; R １９ ~R ２６ and R ２３’ ~R ２６’ The hydrogen atoms contained in V may be substituted with halogen atoms, independently of one another; １ and V ２ are each independently a single bond (except when e+d=1), —O—, or —CH ２ -, -CH ２ -CH ２ -, -CH(CH３ ) -, -C(CH ３ ) ２ -, -C(CF ３ ) ２ -, -SO ２ -, -S-, -CO-, -N(R ｊ ) - or formula (a) (In formula (a), R ２７ ~R ３０ each independently represents a hydrogen atom or an alkyl group having 1 to 6 carbon atoms; and each D independently represents a single bond, —C(CH ３ ) ２ - or - C(CF ３ ) ２ -, i represents an integer of 1 to 3, * represents a bond, ｊ represents a hydrogen atom or a monovalent hydrocarbon group having 1 to 12 carbon atoms which may be substituted with a halogen atom; e and d each independently represent an integer of 0 to 2 (provided that e+d is not 0); f represents an integer of 0 to 3; g and h each independently represent an integer of 0 to 4; in formula (39), Z represents a divalent organic group; R ａ３ each independently represents a halogen atom, or an alkyl group, alkoxy group, aryl group, or aryloxy group which may have a halogen atom; each s independently represents an integer of 0 to 3; and in formula (40), R ａ２ each independently represents a halogen atom, or an alkyl group, alkoxy group, aryl group, or aryloxy group which may have a halogen atom; each 1 independently represents an integer of 0 to 3; and * represents a bond.

[0133] In the present invention, from the viewpoint of improving the flexural modulus and dielectric properties of the laminate, the PI resin constituting the PI film preferably contains, as Y in formula (1), at least one structure selected from the group consisting of structures represented by formula (31), formula (32), formula (33), formula (39), and formula (40), more preferably at least one structure selected from the group consisting of structures containing a benzene skeleton, and even more preferably at least one structure selected from the group consisting of structures represented by formula (32), formula (39), and formula (40).

[0134] In formulas (31) to (33), R １９ ~R ２６ and R ２３’ ~R ２６’ are each independently preferably a hydrogen atom or an alkyl group having 1 to 6 carbon atoms, more preferably a hydrogen atom or an alkyl group having 1 to 3 carbon atoms, and even more preferably a hydrogen atom.

[0135] In formula (31), V １ and V ２ are each independently preferably a single bond (except when e+d=1), —O—, or —CH ２ -, -C(CH ３ ) ２ -, -C(CF ３ ) ２ - or -CO-, and more preferably a single bond (except when e+d=1), -O-, -C(CH ３ ) ２ - or - C(CF ３ ) ２ Represents -.

[0136] In formula (31), e and d each independently preferably represent 0 or 1 (provided that e+d is not 0). Also, e+d preferably represents 1. In formula (31), when e is 0, the two benzene rings are V １ When d is 0, the two benzene rings are V ２ indicates that there is no bond.

[0137] In the formulas (32) and (33), f preferably represents 0 or 1, and more preferably 0.

[0138] In formula (33), g and h each independently represent preferably an integer of 0 to 2, more preferably 0 or 1. Furthermore, g+h preferably represents an integer of 0 to 2. When f is 1 or greater, multiple g's and multiple h's may each independently be the same or different.

[0139] In formula (a), R ２７ ~R ３０are each independently preferably a hydrogen atom or an alkyl group having 1 to 3 carbon atoms, more preferably a hydrogen atom. i is preferably 1 or 2, and when i is 2 or more, a plurality of D and R ２７ ~R ３０ may be the same or different, independently of each other.

[0140] In formula (39), Z preferably represents a divalent organic group having 4 to 40 carbon atoms, more preferably a divalent organic group having 4 to 40 carbon atoms and a cyclic structure, still more preferably a divalent organic group having 4 to 40 carbon atoms and an aromatic ring, and particularly preferably a divalent organic group represented by formula (z1), formula (z2), or formula (z3): [In formula (z1) to formula (z3), R ｚ１１ ~R ｚ１４ each independently represents a hydrogen atom or a monovalent hydrocarbon group which may have a halogen atom; R ｚ２ each independently represents a monovalent hydrocarbon group which may have a halogen atom; n represents an integer of 1 to 4; j represents each independently an integer of 0 to 3; * represents a bond], and particularly preferably represents a divalent organic group represented by formula (z1).

[0141] In formula (z1), R ｚ１１ ~R ｚ１４ are each independently preferably a hydrogen atom or an alkyl group which may have a halogen atom, more preferably a hydrogen atom or an alkyl group having 1 to 6 carbon atoms which may have a halogen atom, still more preferably a hydrogen atom or an alkyl group having 1 to 3 carbon atoms which may have a halogen atom, and particularly preferably a hydrogen atom. ｚ１１ ~R ｚ１４ In the benzene ring having R ｚ１１ ~R ｚ１４ At least one of R may be a monovalent hydrocarbon group which may have a halogen atom. ｚ１１ ~R ｚ１４ are particularly preferably all hydrogen atoms.

[0142] In formula (z1), n ​​is preferably an integer of 1 to 3, more preferably 1 or 2, and even more preferably 2.

[0143] In formula (z2), R ｚ２ are each independently preferably an alkyl group which may have a halogen atom, more preferably an alkyl group having 1 to 6 carbon atoms which may have a halogen atom, and even more preferably an alkyl group having 1 to 3 carbon atoms which may have a halogen atom.

[0144] In formula (z2), j's are preferably each independently 0 or 1, more preferably 0, and even more preferably all j's are 0.

[0145] In formula (39), R ａ３ Preferably, each independently represents an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, or an aryl group having 6 to 12 carbon atoms. ａ３ The hydrogen atoms contained in R may be substituted with halogen atoms independently of each other. ａ３ are each independently an alkyl group preferably having 1 to 6 carbon atoms, more preferably an alkyl group having 1 to 3 carbon atoms.

[0146] In formula (39), each s preferably represents an integer of 0 to 2, more preferably 0 or 1, independently of one another.

[0147] In formula (40), R ａ２ Preferably, each independently represents an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, or an aryl group having 6 to 12 carbon atoms. ａ２ The hydrogen atoms contained in R may be substituted with halogen atoms independently of each other. ａ２ are each independently preferably an alkyl group having 1 to 6 carbon atoms, more preferably an alkyl group having 1 to 3 carbon atoms.

[0148] In formula (40), 1 preferably represents an integer of 0 to 2, more preferably 0 or 1, independently of one another.

[0149] Specific examples of the structures represented by formulas (31) to (33), (39) and (40) include structures represented by formulas (41) to (56). In these formulas, * represents a bond.

[0150]

[0151] In one embodiment of the present invention, when the PI resin constituting the PI film contains, as Y in formula (1), at least one structure selected from the group consisting of structures represented by formulas (31) to (33), (39), and (40), the proportion of structural units derived from tetracarboxylic acid anhydrides in which Y in formula (1) is at least one structure selected from the group consisting of structures represented by formulas (31) to (33), (39), and (40), particularly the proportion of structural units derived from tetracarboxylic acid anhydrides in which Y in formula (1) is at least one structure selected from the group consisting of structures represented by formulas (32), (39), and (40), is preferably 30 mol% or more, more preferably 50 mol% or more, even more preferably 70 mol% or more, particularly preferably 90 mol% or more, and preferably 100 mol% or less, relative to the total amount of structural units (A). Having this proportion within the above range is advantageous in improving the flexural modulus and dielectric properties of the laminate. The proportion of these structural units is, for example, １ This can be measured using H-NMR or calculated from the ratio of raw materials used. The same applies hereinafter to the calculation of the proportion of structural units in PI resins. In addition, in this specification, the "total amount" of structural units refers to the amount of one unit when the structural unit consists of one unit, and refers to the total amount of those units when the structural unit consists of two or more units.

[0152] (Structural Unit (A1) and Structural Unit (A2)) In one embodiment of the present invention, the PI resin contained in the PI film, preferably the PI resin contained in at least one of the layers (PI-1) and (PI-2), or at least one of the layers (PI-1) to (PI-3), contains a structural unit (A), and the structural unit (A) is represented by the formula (A1): [In formula (A1), R ａ１ each independently represent a halogen atom, or an alkyl group, alkoxy group, aryl group, or aryloxy group which may have a halogen atom, and k represents an integer of 0 to 2], and / or a structural unit (A1) (hereinafter, may be simply referred to as structural unit (A1)) derived from a tetracarboxylic acid anhydride represented by formula (A2): [In formula (A2), Rａ２ each independently represent a halogen atom, or an alkyl group, alkoxy group, aryl group, or aryloxy group which may have a halogen atom, and each l independently represent an integer of 0 to 3.

[0153] When the PI resin contains the structural unit (A1) and / or the structural unit (A2) as the structural unit (A), the flexural modulus and dielectric properties of the laminate can be improved. In addition, the CTE tends to decrease, and improved dimensional stability of the laminate can be expected.

[0154] From the viewpoint of improving the flexural modulus, dielectric properties, CTE, etc. of the laminate, in the formula (A1) and the formula (A2), R ａ１ and R ａ２ are preferably, each independently, an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, or an aryl group having 6 to 12 carbon atoms. Examples of the alkyl group having 1 to 6 carbon atoms include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a sec-butyl group, a tert-butyl group, an n-pentyl group, a 2-methylbutyl group, a 3-methylbutyl group, a 2-ethylpropyl group, and an n-hexyl group. Examples of the alkoxy group having 1 to 6 carbon atoms include a methoxy group, an ethoxy group, a propyloxy group, an isopropyloxy group, an n-butoxy group, an isobutoxy group, a sec-butoxy group, a tert-butoxy group, a pentyloxy group, a hexyloxy group, and a cyclohexyloxy group. Examples of the aryl group having 6 to 12 carbon atoms include a phenyl group, a tolyl group, a xylyl group, a naphthyl group, and a biphenyl group. R ａ１ and R ａ２ The hydrogen atoms contained in R may be substituted with halogen atoms, independently of one another, and examples of the halogen atoms include fluorine atoms, chlorine atoms, bromine atoms, and iodine atoms. ａ１ and R ａ２ are each independently preferably an alkyl group having 1 to 6 carbon atoms, more preferably an alkyl group having 1 to 3 carbon atoms.

[0155] The bonding positions of the two carboxylic acid anhydrides bonded to the benzene ring in formula (A1) are not particularly limited, but from the viewpoint of improving the flexural modulus, dielectric properties, CTE, etc. of the laminate, the bonding positions are preferably the 1,2-positions and the 4,5-positions, or the 1,2-positions and the 3,4-positions, and more preferably the 1,2-positions and the 4,5-positions. k is preferably 0 or 1, and more preferably 0.

[0156] The bonding positions of the two carboxylic acid anhydrides bonded to the benzene rings constituting the biphenyl skeleton in formula (A2) are not particularly limited, and may be independently at the 3,4-positions or the 2,3-positions based on the single bond bonding the two benzene rings, with the 3,4-positions being preferred from the viewpoint of improving the flexural modulus, dielectric properties, CTE, etc. of the laminate. In formula (A2), 1 is independently preferably an integer of 0 to 2, more preferably 0 or 1, and even more preferably 0.

[0157] In a preferred embodiment of the present invention, formula (A1) is represented by formula (A1-1): In another preferred embodiment of the present invention, the structural unit (A2) is a structural unit (A1-1) represented by the formula (A2-1): When the PI resin contains the structural unit (A1-1) and / or the structural unit (A2-1) as the structural unit (A), it is advantageous in improving the flexural modulus and dielectric properties of the laminate. Furthermore, the CTE tends to decrease, and improved dimensional stability of the laminate can be expected.

[0158] In one embodiment of the present invention, when the PI resin contains the structural unit (A1) and / or the structural unit (A2), the content thereof is preferably 10 mol% or more, more preferably 15 mol% or more, even more preferably 20 mol% or more, even more preferably 25 mol% or more, and particularly preferably 30 mol% or more, based on the total amount of the structural unit (A), and is preferably 90 mol% or less, more preferably 85 mol% or less, even more preferably 80 mol% or less, even more preferably 75 mol% or less, and particularly preferably 70 mol% or less. When the contents of the structural unit (A1) and the structural unit (A2) are within the above ranges, this is advantageous in improving the flexural modulus and dielectric properties of the laminate. Furthermore, the CTE tends to decrease, and improved dimensional stability of the laminate can be expected.

[0159] Furthermore, in one embodiment of the present invention, when the PI resin contains the structural unit (A1) and the structural unit (A2), the content ratio (molar ratio, (A1):(A2)) is preferably 10:90 to 90:10, more preferably 15:85 to 80:20, even more preferably 20:80 to 70:30, and even more preferably 25:75 to 65:35. When the content ratio of the structural unit (A1) to the structural unit (A2) is within the above range, the above-mentioned effects of the present invention that are expected from the PI resin containing the structural unit (A1) and / or the structural unit (A2) are more easily achieved, and these effects can be further enhanced.

[0160] In one embodiment of the present invention, the PI resin-containing layer preferably comprises one or more of the following structures: - In layers (PI-1) and (PI-2), or layers (PI-1) to (PI-3) in the PI film, the PI resin each comprises at least one of the structural unit (A1) and the structural unit (A2); - In layers (PI-1) and (PI-2), or layers (PI-1) to (PI-3) in the PI film, the PI resin each comprises the structural unit (A1); - In at least one PI resin-containing layer in the PI film, preferably the TPI layer, the PI resin comprises the structural unit (A1) and the structural unit (A2); In at least one PI resin-containing layer in the PI film, preferably a TPI layer, the PI resin contains the structural unit (A1) and the structural unit (A2), and in at least another PI resin-containing layer, preferably an mPI layer, the PI resin contains the structural unit (A1) and / or the structural unit (A2). In at least one PI resin-containing layer in the PI film, preferably a TPI layer, the PI resin contains the structural unit (A1) and the structural unit (A2), and in at least another PI resin-containing layer, preferably an mPI layer, the PI resin contains the structural unit (A1) but is substantially free of the structural unit (A2). In this specification, "substantially free of structural units" means that the content of the structural unit is 1% by mass or less, preferably 0.1% by mass or less, more preferably 0.01% by mass or less, and particularly preferably 0.001% by mass or less. For example, "substantially free of the structural unit (A2)" means that the content of the structural unit (A2) is 1% by mass or less, preferably 0.1% by mass or less, more preferably 0.01% by mass or less, and particularly preferably 0.001% by mass or less, relative to the total amount of the structural unit (A). Hereinafter, the same applies to other structural units, unless otherwise clearly stated. In this specification, "at least one PI resin-containing layer" or "at least one PI resin-containing layer" can be interpreted as "at least one of the PI resin-containing layers (PI-1) and (PI-2), or at least one of the PI resin-containing layers (PI-1) to (PI-3)."

[0161] (Structural Unit (A3)) In one embodiment of the present invention, the resin contained in the PI film, preferably the PI resin contained in at least one of the layers (PI-1) and (PI-2), or at least one of the layers (PI-1) to (PI-3), contains, as the structural unit (A), a PI resin represented by the formula (A3): [In formula (A3), Z represents a divalent organic group, R ａ３ each independently represent a halogen atom, or an alkyl group, alkoxy group, aryl group, or aryloxy group which may have a halogen atom, and each s independently represent an integer of 0 to 3.

[0162] When the PI resin contains the structural unit (A3) as the structural unit (A), it can be advantageous in improving the flexural modulus and dielectric properties of the laminate. Furthermore, the CTE tends to decrease, and the dimensional stability of the laminate can be expected to improve. Furthermore, even at a relatively low imidization temperature (e.g., 350°C or lower), the flexural modulus and dielectric properties of the resulting laminate can be improved. Therefore, even when a laminate is produced by thermally imidizing a PI resin precursor coating film in a laminate configuration with a metal layer, deterioration of the metal layer surface can be suppressed, and a laminate having a high flexural modulus and excellent high-frequency characteristics can be obtained.

[0163] R in formula (A3) ａ３ As the formula (39), R ａ３ In formula (A3), each s independently preferably represents 0 or 1, more preferably 0.

[0164] Examples of Z in formula (A3) include the same divalent organic groups as those exemplified as Z in formula (39) above, and preferred embodiments are also the same.

[0165] In a preferred embodiment of the present invention, formula (A3) is preferably a structural unit (A3-1) represented by formula (A3-1) or a structural unit (A3-2) represented by formula (A3-2).

[0166] When the PI resin contained in the PI film contains the structural unit (A3-1) and / or the structural unit (A3-2) as the structural unit (A), this can be advantageous in improving the flexural modulus and dielectric properties of the laminate. Furthermore, the CTE tends to decrease, and improved dimensional stability of the laminate can be expected. Furthermore, even at relatively low imidization temperatures (e.g., 350°C or lower), the flexural modulus and dielectric properties of the resulting laminate can be improved. Therefore, even when a laminate is produced by thermally imidizing a PI resin precursor coating film in a laminate configuration with a metal layer, deterioration of the metal layer surface can be suppressed, and a laminate having a high flexural modulus and excellent high-frequency characteristics can be obtained.

[0167] In one embodiment of the present invention, when the PI resin contained in the PI film, preferably in at least one PI resin-containing layer, more preferably in at least layer (PI-1), and even more preferably in the mPI layer, contains the structural unit (A3), particularly the structural unit (A3-1) and / or the structural unit (A3-2), as the structural unit (A), the PI resin is not too rigid and can have a flexible structure with a certain degree of freedom, which makes it easier to form a branched structure by heating during imidization and further improves the flexural modulus of the resulting laminate. Furthermore, Df is more likely to be reduced, and the CTE is reduced, tending to improve the dimensional stability of the laminate.

[0168] In one embodiment of the present invention, when the PI resin contains the structural unit (A3), the content thereof is preferably 3 mol% or more, more preferably 5 mol% or more, even more preferably 7 mol% or more, and even more preferably 10 mol% or more, relative to the total amount of the structural unit (A). It may be, for example, 20 mol% or more, 30 mol% or more, or 40 mol% or more. Furthermore, the content of the structural unit (A3) is preferably 80 mol% or less, more preferably 70 mol% or less, even more preferably 65 mol% or less, and even more preferably 60 mol% or less. When the content of the structural unit (A3) is within the above range, the effects of the present invention that are expected from the PI resin containing the structural unit (A3) are more easily achieved, and these effects can be further enhanced.

[0169] In another embodiment of the present invention, when the PI resin contained in the PI film, preferably at least the PI resin-containing layer (PI-1), contains the structural unit (A3), the structural unit (A3) preferably accounts for 50 mol% or less (0 to 50 mol%) of the structural unit (A3) relative to the total amount of the structural units (A). That is, in such an embodiment, the structural unit (A) contained in the PI resin may or may not contain the structural unit (A3). When the structural unit (A3) is contained, it is contained in an amount of 50 mol% or less. Furthermore, the content of the structural unit (A3) relative to the total amount of the structural units (A) is more preferably 45 mol% or less, even more preferably 35 mol% or less, even more preferably 25 mol% or less, particularly preferably 15 mol% or less, especially more preferably 5 mol% or less, and especially preferably 1 mol% or less, and the lower limit may be 0 mol% or more. When the content of the structural unit (A3), particularly the structural unit (A3-1) and / or the structural unit (A3-2) in the PI resin is at most the upper limit, the flexural modulus and dielectric properties of the laminate can be further improved. In addition, the CTE tends to decrease, and improved dimensional stability of the laminate can be expected.

[0170] In one embodiment of the present invention, it is more preferable that the PI resin in at least one PI resin-containing layer constituting the PI film, preferably the TPI layer, contains the structural unit (A1) and the structural unit (A2), and that the PI resin in at least another PI resin-containing layer, preferably the mPI layer, contains at least two structural units selected from the structural unit (A1), the structural unit (A2), and the structural unit (A3), preferably the structural unit (A1) and the structural unit (A2) and / or the structural unit (A3).

[0171] (Structural Unit (A4)) In one embodiment of the present invention, the PI resin may contain, as the structural unit (A), a structural unit (A4) (hereinafter sometimes simply referred to as structural unit (A4)) derived from a tetracarboxylic acid anhydride other than the structural units (A1), (A2), and (A3). In this specification, "structural unit (A4) derived from a tetracarboxylic acid anhydride other than the structural units (A1), (A2), and (A3)" refers to a structural unit derived from a tetracarboxylic acid anhydride that does not fall under any of the structural units (A1), (A2), and (A3), and the "content of structural unit (A4)" refers to the total amount of structural unit (A4) when multiple structural units (A4) are present.

[0172] In one embodiment of the present invention, examples of the structural unit (A4) include a structural unit derived from a tetracarboxylic acid anhydride in which Y in formula (1) is represented by formula (31) or formula (33) to formula (38). From the viewpoint of improving the flexural modulus and dielectric properties of the laminate, preferably, Y in formula (1) is a structural unit derived from a tetracarboxylic acid anhydride represented by formula (42), formula (44) to formula (49), or formula (53), and more preferably, Y in formula (1) is a structural unit derived from a tetracarboxylic acid anhydride represented by formula (42), formula (46), formula (49), or formula (53).

[0173] In one embodiment of the present invention, when the PI resin contains the structural unit (A4), the content thereof, relative to the total amount of the structural unit (A), may be, for example, 0.01 to 55 mol %, or 0.01 to 40 mol %, and is preferably 40 mol % or less, more preferably 35 mol % or less, even more preferably 30 mol % or less, and particularly preferably 25 mol % or less, and is usually 0.01 mol % or more, and preferably 10 mol % or more.

[0174] (Diamine-derived structural unit (B)) The PI resin constituting the PI film usually contains a diamine-derived structural unit (B) (hereinafter, sometimes simply abbreviated as structural unit (B)). The structural unit (B) is, for example, a structural unit represented by formula (2): In the formula (2), X represents a divalent organic group.

[0175] In formula (2), X represents a divalent organic group, preferably a divalent organic group having 2 to 100 carbon atoms. Examples of divalent organic groups include divalent aromatic groups and divalent aliphatic groups. Examples of divalent aliphatic groups include divalent acyclic aliphatic groups and divalent cyclic aliphatic groups. Among these, from the viewpoint of improving the flexural modulus and dielectric properties of the laminate, divalent cyclic aliphatic groups and divalent aromatic groups are preferred, and divalent aromatic groups are more preferred. The divalent organic group may have a hydrogen atom substituted with a halogen atom, a hydrocarbon group, an alkoxy group, or a halogenated hydrocarbon group. In such cases, the number of carbon atoms in these groups is preferably 1 to 8. In this specification, a divalent aromatic group is a divalent organic group having an aromatic group, and may include an aliphatic group or other substituent as part of its structure. Furthermore, a divalent aliphatic group is a divalent organic group having an aliphatic group, and may contain other substituents as part of its structure, but does not include an aromatic group.

[0176] In one embodiment of the present invention, the PI resin may contain multiple types of X, which may be the same or different from one another. Examples of X in formula (2) include groups (structures) represented by formulas (60) to (65); and groups in which a hydrogen atom in a group represented by formulas (60) to (65) is substituted with a methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, isobutyl group, sec-butyl group, tert-butyl group, fluoro group, chloro group, or trifluoromethyl group.

[0177] [In formula (60) and formula (61), R ａ and R ｂ each independently represents a halogen atom, or an alkyl group, alkoxy group, aryl group, or aryloxy group which may have a halogen atom; R ａ and R ｂ Each hydrogen atom contained in may be substituted with a halogen atom, and each W is independently a single bond, —O—, or —CH ２ -, -CH ２ -CH ２ -, -CH(CH ３ ) -, -C(CH３ ) ２ -, -C(CF ３ ) ２ -, -COO-, -OOC-, -SO-, -SO ２ -, -S-, -CO-, -N(R ｃ )- or -CONH-, R ｃ represents a monovalent hydrocarbon group having 1 to 12 carbon atoms which may be substituted with a hydrogen atom or a halogen atom; t' represents an integer of 0 to 4; u represents an integer of 0 to 4; n represents an integer of 0 to 4; in formula (62), ring A represents a cycloalkane ring having 3 to 8 carbon atoms; R ｄ represents an alkyl group having 1 to 20 carbon atoms; r represents an integer of 0 or more and (the number of carbon atoms in ring A - 2) or less; S1 and S2 each independently represent an integer of 0 to 20; and in formulas (60) to (65), * represents a bond.

[0178] Other examples of X in formula (2) include divalent acyclic aliphatic groups such as linear or branched alkylene groups, such as ethylene, trimethylene, tetramethylene, pentamethylene, hexamethylene, propylene, 1,2-butanediyl, 1,3-butanediyl, 1,12-dodecanediyl, 2-methyl-1,2-propanediyl, and 2-methyl-1,3-propanediyl. In the divalent acyclic aliphatic groups, hydrogen atoms may be substituted with halogen atoms, and carbon atoms may be substituted with heteroatoms, such as oxygen atoms and nitrogen atoms.

[0179] Among these, from the viewpoint of improving the flexural modulus and dielectric properties of the laminate, the PI resin in the present invention preferably contains, as X in formula (2), a structure represented by formula (60) or formula (61), and more preferably contains a structure represented by formula (60).

[0180] In formula (60) and formula (61), the bond of each benzene ring or each cyclohexane ring may be bonded at any of the ortho-, meta-, or para-position, or the α-, β-, or γ-position, based on -W- or the single bond connecting each benzene ring or each cyclohexane ring, and from the viewpoint of improving the flexural modulus and dielectric properties of the laminate, it can be bonded preferably at the meta- or para-position, or the β- or γ-position, more preferably at the para- or γ-position. When the amino group directly bonded to the benzene ring and the divalent linking group -W- are at the meta-position, the flexibility of the polyimide molecular chain tends to be improved.

[0181] In formula (60) and formula (61), R ａ and R ｂ are each independently preferably a halogen atom, or an alkyl group, alkoxy group or aryl group which may have a halogen atom, more preferably a halogen atom, an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, or an aryl group having 6 to 12 carbon atoms. Examples of the alkyl group having 1 to 6 carbon atoms, the alkoxy group having 1 to 6 carbon atoms, and the aryl group having 6 to 12 carbon atoms include those exemplified above. ａ and R ｂ The hydrogen atoms contained in R may be substituted, independently of one another, with a halogen atom, and examples of the halogen atom include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom. ａ and R ｂ are preferably, independently of one another, an alkyl group having 1 to 6 carbon atoms or a fluorinated alkyl group having 1 to 6 carbon atoms, and from the viewpoint of adhesion to a metal layer or the like, are more preferably fluorine-free alkyl groups having 1 to 6 carbon atoms, even more preferably fluorine-free alkyl groups having 1 to 3 carbon atoms, and particularly preferably a methyl group.

[0182] In the formula (60) and the formula (61), t' and u are each independently preferably an integer of 0 to 2, more preferably 0 or 1.

[0183] In the formula (60) and the formula (61), each W is preferably a single bond, —O—, or —CH ２ -, -C(CH ３ )２ -, -C(CF ３ ) ２ -, -SO ２ -, -S-, -COO-, -OOC- or -CO-, and more preferably a single bond, -O- or -CH ２ -, -C(CH ３ ) ２ -, -C(CF ３ ) ２ -, -COO-, -OOC- or -CO-, and more preferably a single bond, -O- or -CH ２ - or -C(CH ３ ) ２ -, and particularly preferably -O- or -C(CH ３ ) ２ - is.

[0184] In formula (60) and formula (61), n ​​is preferably an integer of 0 to 3, more preferably 1 to 3. When n is 2 or more, a plurality of W, R ａ and t' may be the same or different, and the positions of the bonds of each benzene ring relative to -W- may be the same or different.

[0185] When the PI resin of the present invention contains two or more structures represented by either formula (60) or formula (61) as X in formula (2), W, n, R in one of formulas (60) and (61) ａ , R ｂ , t′ and u are independently W, n, R in the other formulas (60) and (61). ａ , R ｂ , t' and u may be the same or different.

[0186] In formula (62), examples of the cycloalkane ring having 3 to 8 carbon atoms represented by ring A include a cyclopropane ring, a cyclobutane ring, a cyclopentane ring, a cyclohexane ring, a cycloheptane ring, and a cyclooctane ring, and preferably a cycloalkane ring having 4 to 6 carbon atoms. In ring A, the bonds may or may not be adjacent to each other. For example, when ring A is a cyclohexane ring, the two bonds may be in the α-position, β-position, or γ-position relationship, and preferably in the β-position or γ-position relationship.

[0187] R in formula (62) ｄ is preferably an alkyl group having 1 to 10 carbon atoms. In formula (62), r is preferably 0 or more and preferably 4 or less. S1 and S2 in formula (62) are each independently preferably 0 or more, more preferably 2 or more, and preferably 15 or less.

[0188] Specific examples of the structures represented by formulas (60) to (62) include structures represented by formulas (71) to (92). In these formulas, * represents a bond.

[0189]

[0190] In one embodiment of the present invention, when the PI resin constituting the PI film contains at least one diamine-derived structural unit represented by formula (60) or formula (61) as X in formula (2), the proportion of the diamine-derived structural unit represented by formula (60) or formula (61) as X in formula (2) is preferably 30 mol% or more, more preferably 50 mol% or more or more than 50 mol%, even more preferably 70 mol% or more, particularly preferably 90 mol% or more, and preferably 100 mol% or less, relative to the total amount of structural unit (B). When the proportion of the diamine-derived structural unit represented by formula (60) or formula (61) as X in formula (2) is within the above range, the flexural modulus and dielectric properties of the laminate can be improved. Furthermore, the CTE tends to decrease, and improved dimensional stability of the laminate can be expected.

[0191] (Structural Unit (B1)) In one embodiment of the present invention, the PI resin contained in the PI film, preferably the PI resin contained in at least one of the layers (PI-1) and (PI-2), or at least one of the layers (PI-1) to (PI-3), contains a structural unit (B), and the structural unit (B) is represented by the formula (B1): [In formula (B1), R ｂ１ each independently represents a halogen atom, or an alkyl group, alkoxy group, aryl group, or aryloxy group which may have a halogen atom; and each W independently represents —O—, —CH ２ -, -CH ２ -CH ２ -, -CH(CH ３ ) -, -C(CH ３ ) ２ -, -C(CF ３ ) ２ -, -COO-, -OOC-, -SO-, -SO ２ -, -S-, -CO-, -N(R ｃ )- and -CONH-, or a single bond (where m is 2 or more and at least one W is the divalent linking group); R ｃ represents a hydrogen atom or a monovalent hydrocarbon group of 1 to 12 carbon atoms which may be substituted with a halogen atom, m represents an integer of 1 to 4, and each q independently represents an integer of 0 to 4.

[0192] When the PI resin contains the structural unit (B1) as the structural unit (B), the flexural modulus and dielectric properties of the laminate can be increased. Furthermore, the CTE can be reduced, which is expected to improve the dimensional stability of the laminate and also contribute to improving adhesion to the metal layer. Furthermore, even at a relatively low imidization temperature (e.g., 350°C or lower), the flexural modulus and dielectric properties of the resulting laminate can be increased. Therefore, even when a laminate is produced by thermally imidizing a PI resin precursor coating film in a laminate configuration with a metal layer, deterioration of the metal layer surface can be suppressed, and a laminate having a high flexural modulus and excellent high-frequency properties can be obtained.

[0193] R in formula (B1) ｂ１ As the formula (60), R ａ and R ｂ In formula (B1), q's are each independently an integer of 0 to 2, more preferably 0 or 1. In formula (B1), m's is preferably an integer of 1 to 3, more preferably 2 or 3, from the viewpoint of improving the flexural modulus, dielectric properties, CTE, etc. of the laminate. In formula (B1), when a plurality of W, R ｂ１ and q may be the same or different, and each benzene ring is -NH ２ The positions of -W- relative to the reference atom may be the same or different.

[0194] In formula (B1), each —W— is independently —NH of each benzene ring. ２ With respect to m, they may be bonded at any of the ortho, meta, or para positions, or the α, β, or γ positions, preferably the meta or para positions, or the β or γ positions, more preferably the para or γ positions. When m is 2 or more, in the benzene ring to which two Ws are bonded, the bonding positions of the two Ws may be in an ortho, meta, or para relationship, or in an α, β, or γ relationship, preferably in a meta or para relationship, or in a β or γ relationship.

[0195] Specific examples of the structure represented by formula (B1) include structures represented by formulas (B1-1) to (B1-6). R in formulas (B1-1) to (B1-6) ｂ１ and q is R in formula (B1). ｂ１ and q are defined the same as W １ ~W ６ are each independently —O—, —CH ２ -, -CH ２ -CH ２ -, -CH(CH ３ ) -, -C(CH ３ ) ２ -, -C(CF ３ ) ２-, -COO-, -OOC-, -SO-, -SO ２ -, -S-, -CO-, -N(R ｃ represents a divalent linking group selected from the group consisting of ——— and —CONH—; R ｃ represents a monovalent hydrocarbon group having 1 to 12 carbon atoms which may be substituted with a hydrogen atom or a halogen atom. Note that compounds of formula (B1-4) which overlap with formula (B1-3) are treated as compounds of formula (B1-3). Hereinafter, the structural units derived from formulas (B1-1) to (B1-6) may be referred to as structural unit (B1-1) to structural unit (B1-6), respectively.

[0196] R in formulas (B1-1) to (B1-6) ｂ１ and q is R in formula (B1). ｂ１ The same embodiments as those exemplified as and q are exemplified, and the preferred embodiments are also the same.

[0197] W in formulas (B1-1) to (B1-6) １ ~W ６ are each independently —O—, —CH ２ -, -CH ２ -CH ２ -, -CH(CH ３ ) -, -C(CH ３ ) ２ -, -C(CF ３ ) ２ -, -COO-, -OOC-, -SO ２ W in formula (B1-1) is preferably -, -S-, -CO- or -CONH-. １ is preferably —O—, —CH ２ -, -C(CH ３ ) ２ -, -SO ２ -, -S- or -CO-. W in formula (B1-2), formula (B1-4) and formula (B1-6) ２ , W ４ and W ６ are each preferably —O—. ３ is preferably —O—, —CH ２ -, -C(CH ３ ) ２ -, -SO ２-, -CO- or -CONH-, and W in formula (B1-5) ５ is preferably —C(CH ３ ) ２ -, -O-, -SO ２ - or -CO-.

[0198] In one embodiment of the present invention, the PI film in the laminate of the present invention preferably contains, as the structural unit (B), a structural unit derived from a diamine in which m in formula (B1) is 1 or 2, such as the structural unit (B1-1) and / or the structural unit (B1-2). A preferred structural unit derived from a diamine in which m is 2 is, for example, the structural unit (B1-2). The inclusion of such a structural unit can enhance the flexural modulus and dielectric properties of the laminate. Furthermore, the CTE tends to decrease, and improved dimensional stability of the laminate can be expected. Furthermore, the inclusion of these structural units can also contribute to improved adhesion between the PI film and the metal layer.

[0199] In another embodiment of the present invention, the PI film in the laminate of the present invention preferably contains, as the structural unit (B), a structural unit derived from a diamine in which m is 3 or 4, such as the structural units (B1-3) to (B1-6), and more preferably a structural unit derived from a diamine in which m is 3. A preferred structural unit derived from a diamine in which m is 3 is, for example, the structural unit (B1-5). The inclusion of such a structural unit can enhance the flexural modulus and dielectric properties of the laminate. Furthermore, the CTE tends to decrease, and improved dimensional stability of the laminate can be expected. Furthermore, the inclusion of these structural units can also contribute to improved adhesion between the PI film and the metal layer.

[0200] In one embodiment of the present invention, the structural unit (B1) is preferably the structural unit (B1-2), and the structural unit (B1-2) is more preferably a structural unit represented by formula (B1-2') and / or formula (B1-2''). R in formula (B1-2') and formula (B1-2'') ｂ１ , W ２ , and q is R in formula (B1-2). ｂ１ , W ２ , and q are defined the same.

[0201] In one embodiment of the present invention, the structural unit represented by formula (B1-2') or formula (B1-2'') is preferably a structural unit represented by formula (B1-2'a) or formula (B1-2''a), respectively. The inclusion of the above structural units as structural unit (B) can improve the flexural modulus and dielectric properties of the laminate. Furthermore, the CTE tends to decrease, which is expected to improve the dimensional stability of the laminate. Furthermore, the inclusion of these structural units can also contribute to improving the adhesion between the PI film and the metal layer.

[0202] In another embodiment of the present invention, the structural unit (B1) is preferably the structural unit (B1-5), and the structural unit (B1-5) is more preferably a structural unit represented by formula (B1-5a). When the structural unit (B) contains the structural unit, it is advantageous in improving the flexural modulus and dielectric properties of the laminate, reducing the CTE, and the like.

[0203] In one embodiment of the present invention, when the PI resin constituting the PI film contains the structural unit (B1), its content is preferably 3 mol% or more, more preferably 5 mol% or more, even more preferably 7 mol% or more, and even more preferably 10 mol% or more, relative to the total amount of the structural units (B), and may be, for example, 20 mol% or more, 30 mol% or more, or 40 mol% or more. Having the content of the structural unit (B1) at or above the above-mentioned lower limit is advantageous in improving the flexural modulus and dielectric properties of the laminate, reducing the CTE, and the like. Furthermore, since a higher total amount of the structural unit (B1) tends to increase adhesion to the metal layer, from this perspective, the content of the structural unit (B1) may be, for example, 50 mol% or more, 60 mol% or more, or 70 mol% or more, relative to the total amount of the structural units (B). The content of the structural unit (B1) is preferably 99 mol% or less, more preferably 95 mol% or less, and even more preferably 90 mol% or less, relative to the total amount of the structural units (B).

[0204] <Structural Unit (B2)> In one embodiment of the present invention, the PI resin contained in the PI film, preferably the PI resin contained in at least one of the layers (PI-1) and (PI-2), or at least one of the layers (PI-1) to (PI-3), contains, as the structural unit (B), a PI resin represented by the formula (B2): [In formula (B2), R ｂ２ are each independently a halogen atom, or an alkyl group, alkoxy group, aryl group, or aryloxy group which may have a halogen atom, and p is an integer of 0 to 4. When the structural unit (B) contains the structural unit (B2), the PI resin can have a flexible structure that is not too rigid and has a certain degree of freedom, making it easier to form a branched structure by heating during imidization and also tends to have higher crystallinity, which is advantageous in terms of improving the flexural modulus and dielectric properties of the laminate and reducing the CTE.

[0205] In formula (B2), R ｂ２ preferably each independently represents a halogen atom, or an alkyl group, alkoxy group, or aryl group which may have a halogen atom, and more preferably represents a halogen atom, an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, or an aryl group having 6 to 12 carbon atoms. Examples of the alkyl group having 1 to 6 carbon atoms, the alkoxy group having 1 to 6 carbon atoms, and the aryl group having 6 to 12 carbon atoms include those exemplified above. R ｂ２ The hydrogen atoms contained in R may be substituted with halogen atoms, independently of each other, and examples of the halogen atoms include the same as those mentioned above. ｂ２ are each independently preferably an alkyl group having 1 to 6 carbon atoms or a fluorinated alkyl group having 1 to 6 carbon atoms, and from the viewpoint of adhesion to a metal layer or the like, are more preferably a fluorine-free alkyl group having 1 to 6 carbon atoms, even more preferably a fluorine-free alkyl group having 1 to 3 carbon atoms, and particularly preferably a methyl group.

[0206] In formula (B2), p's are each independently preferably an integer of 0 to 2, more preferably 0 or 1.

[0207] In formula (B2), —NH bonded to each benzene ring ２ The groups may be bonded at any of the ortho-, meta-, or para-positions, or the α-, β-, or γ-positions, based on the single bond connecting each benzene ring. From the viewpoint of improving the flexural modulus and dielectric properties of the laminate and reducing the CTE, the groups can be bonded preferably at the meta- or para-positions, or the β- or γ-positions, and more preferably at the para- or γ-positions.

[0208] In a preferred embodiment of the present invention, formula (B2) is represented by formula (B2'): It is preferably represented by the formula (B2). When the PI resin constituting at least one PI resin-containing layer contains a PI resin having, as the structural unit (B), the structural unit (B2), particularly a diamine-derived structural unit represented by formula (B2'), the PI resin is not too rigid and can have a flexible structure with a certain degree of freedom. This makes it easier to form a branched structure by heating during imidization, and also tends to increase crystallinity, which is advantageous in improving the flexural modulus and dielectric properties of the laminate and reducing the CTE. Furthermore, since the above effect can be obtained even at a relatively low imidization temperature (e.g., 350°C or lower), even when a laminate is produced by thermally imidizing a PI resin precursor coating film in a laminate configuration with a metal layer, deterioration of the metal layer surface can be suppressed, and a laminate having both a high flexural modulus and excellent high-frequency characteristics can be obtained.

[0209] In one embodiment of the present invention, when the PI resin contains the structural unit (B2), its content is preferably 1 mol% or more, more preferably 5 mol% or more, and even more preferably 10 mol% or more, relative to the total amount of the structural units (B). For example, it may be 20 mol% or more, 30 mol% or more, more than 30 mol%, 40 mol% or more, or 50 mol% or more. When the content of the structural unit (B2) is equal to or greater than the above-mentioned lower limit, it is advantageous for improving the flexural modulus and dielectric properties of the laminate, reducing the CTE, etc. Furthermore, the content of the structural unit (B1) is preferably 99 mol% or less, more preferably 95 mol% or less, and even more preferably 92 mol% or less, relative to the total amount of the structural units (B). For example, it may be 90 mol% or less, 80 mol% or less, 70 mol% or less, or 60 mol% or less.

[0210] In one embodiment of the present invention, when the PI resin constituting the PI film contains the structural unit (B1) and the structural unit (B2), the total content thereof is preferably 30 mol% or more, more preferably 40 mol% or more, even more preferably 60 mol% or more, particularly preferably 70 mol% or more, particularly more preferably 80 mol% or more, particularly more preferably 90 mol% or more, particularly more preferably 95 mol% or more, and preferably 100 mol% or less, relative to the total amount of the structural unit (B). When the total content of the structural unit (B1) and the structural unit (B2) is at least the above-mentioned lower limit, the above-mentioned effects of the present invention expected from the PI resin containing the structural unit (B1) and the structural unit (B2) are more easily achieved, and these effects can be further enhanced.

[0211] Furthermore, in one embodiment of the present invention, when the PI resin contains the structural unit (B1) and the structural unit (B2), the content ratio (molar ratio, (B1):(B2)) is preferably 99:1 to 1:99, more preferably 95:5 to 5:95, and even more preferably 92:8 to 8:92, and may be, for example, 92:8 to 20:80, or 90:10 to 60:40. When the content ratio of the structural unit (B1) to the structural unit (B2) is within the above range, the effects of the present invention that are expected from the PI resin containing the structural unit (B1) and the structural unit (B2) are more easily achieved, and these effects can be further enhanced.

[0212] In one embodiment of the present invention, the PI resin-containing layer constituting the PI film preferably comprises one or more of the following structures: - In layers (PI-1) and (PI-2), or layers (PI-1) to (PI-3) in the PI film, the PI resin comprises at least one of the structural unit (B1) and the structural unit (B2); - In layers (PI-1) and (PI-2), or layers (PI-1) to (PI-3) in the PI film, the PI resin comprises the structural unit (B1); - In at least one PI resin-containing layer in the PI film, the PI resin comprises the structural unit (B1) and the structural unit (B2); - In layers (PI-1) and (PI-2), or layers (PI-1) to (PI-3) in the PI film, the PI resin comprises the structural unit (B1) and the structural unit (B2).

[0213] (Structural Unit (B3)) In one embodiment of the present invention, the structural unit (B) may include a diamine-derived structural unit (B3) (hereinafter, sometimes simply referred to as structural unit (B3)) other than the structural unit (B1) and the structural unit (B2). Examples of the structural unit (B3) include a diamine-derived structural unit in which m in formula (B1) is 0, and a diamine-derived structural unit in formula (2) where X is represented by formulas (61) to (64). Among these, a diamine-derived structural unit in formula (2) where X is represented by formula (74) (a p-phenylenediamine-derived structural unit) is preferred. In this specification, "a diamine-derived structural unit (B3) other than the structural unit (B1) and the structural unit (B2)" refers to a diamine-derived structural unit that is different from both the structural unit (B1) and the structural unit (B2).

[0214] In one embodiment of the present invention, when the structural unit (B) includes the structural unit (B3), the content of the structural unit (B3) relative to the total amount of the structural unit (B) is preferably 25 mol% or less, more preferably 20 mol% or less, and even more preferably 10 mol% or less, and is typically 0.01 mol% or more.

[0215] In one embodiment of the present invention, the polyimide resin contained in the PI resin-containing layer (PI-1) may be the same as or different from the PI resin contained in the PI resin-containing layer (PI-2) and / or the PI resin-containing layer (PI-3). From the viewpoints of improving the flexural modulus and dielectric properties of the laminate, reducing the CTE, etc., it is preferable that the PI resins contained in each layer be different resins. Here, "different resins" refers not only to resins having different types of structural units, but also to resins having the same type of structural units but different contents (or ratios) of the structural units.

[0216] In one embodiment of the present invention, the PI resin-containing layer (PI-1) and the PI resin-containing layer (PI-2), or the PI resin-containing layers (PI-1) to (PI-3), each preferably contains a polyimide resin having at least two types of tetracarboxylic acid anhydride-derived structural units (A). In such an embodiment, the flexural modulus and dielectric properties of the laminate are easily improved, and the CTE is easily reduced.

[0217] In one embodiment of the present invention, the PI resin in the PI resin-containing layer (PI-1) and the PI resin-containing layer (PI-2), or the PI resin-containing layers (PI-1) to (PI-3), preferably the mPI layer and the TPI layer, preferably contains the structural unit (A1) and / or the structural unit (A2) as the structural unit (A) and the structural unit (B1), preferably the structural unit (B1) and the structural unit (B2), as the structural unit (B).

[0218] In a preferred embodiment of the present invention, the PI resin contained in the PI resin-containing layer (PI-1), preferably the mPI layer, constituting the PI film, contains, as the structural unit (A), at least two structural units selected from the structural unit (A1), the structural unit (A2), and the structural unit (A3) (preferably the structural unit (A1) and the structural unit (A2) and / or the structural unit (A3)); the PI resin contained in the PI resin-containing layer (PI-2), preferably the TPI layer, contains, as the structural unit (A), the structural unit (A1) and the structural unit (A2); and the PI resins constituting the PI resin-containing layer (PI-1) and the PI resin-containing layer (PI-2), preferably the mPI layer and the TPI layer, each contain, as the structural unit (B1), preferably the structural unit (B1) and the structural unit (B2), as the structural unit (B).

[0219] In a preferred embodiment of the present invention, when the PI film (L) further comprises a PI resin-containing layer (PI-3), the PI resin contained in the PI resin-containing layer (PI-1), preferably the mPI layer, comprises, as the structural unit (A), at least two structural units selected from the structural unit (A1), the structural unit (A2), and the structural unit (A3) (preferably the structural unit (A1) and the structural unit (A2) and / or the structural unit (A3)); the PI resin contained in the PI resin-containing layer (PI-2) and the PI resin-containing layer (PI-3), preferably the TPI layer, comprises, as the structural unit (A), the structural unit (A1) and the structural unit (A2); and the PI resins contained in the PI resin-containing layers (PI-1) to (PI-3), preferably the mPI layer and the TPI layer, each comprise, as the structural unit (B1), preferably the structural unit (B1) and the structural unit (B2), as the structural unit (B).

[0220] When the mPI layer, TPI layer, layer (PI-1), layer (PI-2), and optionally layer (PI-3) are each configured to contain a combination of the above-described structural units, the PI resin in each layer is not too rigid and can have a flexible structure with a certain degree of freedom, which tends to facilitate the formation of a branched structure upon heating during imidization and to increase crystallinity. Furthermore, the interaction between two adjacent layers can be enhanced. Therefore, the PI resin containing each structural unit makes it easier to achieve the above-described effects of the present invention, and these effects can be further enhanced.

[0221] <Layer (PI-1)> In one embodiment of the present invention, the PI resin constituting layer (PI-1) contains, as the structural unit (A), the structural unit (A1) and / or the structural unit (A2), preferably at least two structural units selected from the structural unit (A1), the structural unit (A2), and the structural unit (A3), and more preferably the structural unit (A1) and the structural unit (A2) and / or the structural unit (A3). When layer (PI-1) contains these structural units, the content of the structural unit (A1) relative to the total amount of the structural units (A) is preferably 20 mol% or more, more preferably 30 mol% or more, even more preferably 35 mol% or more, particularly preferably 40 mol% or more, and is preferably 80 mol% or less, more preferably 75 mol% or less, even more preferably 70 mol% or less, and particularly preferably 65 mol% or less. The content of the structural unit (A2) is preferably 20 mol% or more, more preferably 30 mol% or more, even more preferably 35 mol% or more, particularly preferably 40 mol% or more, and is preferably 80 mol% or less, more preferably 75 mol% or less, even more preferably 70 mol% or less, particularly preferably 65 mol% or less, relative to the total amount of the structural unit (A). The content of the structural unit (A3) is preferably 3 mol% or more, more preferably 5 mol% or more, even more preferably 7 mol% or more, even more preferably 10 mol% or more, and may be, for example, 20 mol% or more, 30 mol% or more, or 40 mol% or more, and is preferably 75 mol% or less, more preferably 70 mol% or less, even more preferably 65 mol% or less, particularly preferably 60 mol% or less, relative to the total amount of the structural unit (A). In another embodiment, the content of the structural unit (A3) is preferably 50 mol% or less, more preferably 45 mol% or less, even more preferably 35 mol% or less, still more preferably 25 mol% or less, particularly preferably 15 mol% or less, particularly preferably 5 mol% or less, and particularly preferably 1 mol% or less, and the lower limit may be 0 mol%. When the contents of the structural unit (A1), the structural unit (A2), and / or the structural unit (A3) are each within the above ranges, the PI resin is not too rigid and can have a flexible structure with a certain degree of freedom, which makes it easier to form a branched structure by heating during imidization and also tends to increase crystallinity.Therefore, a laminate having excellent flexural modulus, dielectric properties and thermal properties can be obtained.

[0222] On the other hand, in another embodiment of the present invention, the content of the structural unit (A2) in the PI resin constituting layer (PI-1) is preferably less than 30 mol %, more preferably 25 mol % or less, even more preferably 20 mol % or less, and particularly preferably 10 mol % or less, relative to the total amount of structural units (A). In one embodiment of the present invention, layer (PI-1) may be substantially free of structural unit (A2), and the lower limit of the content of structural unit (A2) may be 0 mol %.

[0223] In one embodiment of the present invention, the PI resin constituting layer (PI-1) preferably contains the structural unit (B1) as the structural unit (B). The structural unit (B1) preferably contains the structural unit (B1-2) and the structural unit (B1-5), more preferably the structural unit (B1-2), and even more preferably the structural unit (B1-2″). The content of the structural unit (B1) in the PI resin constituting layer (PI-1), relative to the total amount of the structural units (B), is preferably 3 mol% or more, more preferably 5 mol% or more, even more preferably 7 mol% or more, and even more preferably 10 mol% or more. For example, it may be 20 mol% or more, 30 mol% or more, or 40 mol% or more. It is also preferably 80 mol% or less, more preferably 75 mol% or less, even more preferably 70 mol% or less, and particularly preferably 65 mol% or less. Furthermore, the PI resin constituting layer (PI-1) preferably further contains the structural unit (B2) as the structural unit (B), and the content thereof, relative to the total amount of the structural units (B), is preferably 10 mol% or more, more preferably 20 mol% or more, even more preferably 30 mol% or more or more than 30 mol%, even more preferably 35 mol% or more, and particularly preferably 40 mol% or more, and is preferably 99 mol% or less, more preferably 95 mol% or less, and even more preferably 92 mol% or less, for example, 90 mol% or less, 80 mol% or less, 70 mol% or less, or 60 mol% or less. When the contents of the structural units (B1) and / or the structural units (B2) are each within the above ranges, the PI resin is not too rigid and can have a flexible structure with a certain degree of freedom, which makes it easier to form a branched structure by heating during imidization and also tends to increase crystallinity. This makes it possible to improve the mechanical properties of the layer (PI-1) and reduce Df, and furthermore, to effectively reduce the CTE, thereby making it possible to obtain a laminate having excellent flexural modulus, dielectric properties, and thermal properties.

[0224] <Layer (PI-2) and Layer (PI-3)> In one embodiment of the present invention, the PI-based film includes a layer (PI-2) and may further include a layer (PI-3). The PI-based resins that make up Layer (PI-2) and Layer (PI-3) each include the structural unit (A) as the structural unit (A1), and preferably include the structural unit (A1) and the structural unit (A2). When these structural units are included, the content of the structural unit (A1) is preferably 10 mol% or more, more preferably 15 mol% or more, and even more preferably 20 mol% or more, relative to the total amount of the structural units (A), and is preferably 80 mol% or less, more preferably 70 mol% or less, and even more preferably 60 mol% or less. Furthermore, the content of the structural unit (A2) is preferably 20 mol% or more, more preferably 30 mol% or more, even more preferably 40 mol% or more, even more preferably 50 mol% or more, and particularly preferably 60 mol% or more, relative to the total amount of the structural unit (A), and is preferably 90 mol% or less, more preferably 85 mol% or less, even more preferably 80 mol% or less, and even more preferably 75 mol% or less. When the content of the structural unit (A1) and / or the structural unit (A2) is within the above range, the PI resin is not too rigid and can have a flexible structure with a certain degree of freedom, which makes it easier to form a branched structure upon heating during imidization and also tends to increase crystallinity. This enables improved mechanical properties and reduced Df of the layers (PI-2) and (PI-3), and further effectively reduces the CTE, resulting in a laminate with excellent flexural modulus, dielectric properties, and thermal properties. Furthermore, improved adhesion between the PI film and the metal layer can be expected.

[0225] In one embodiment of the present invention, the content of the structural unit (A3) in the PI resin constituting Layer (PI-2) and Layer (PI-3) is preferably 10 mol % or less, more preferably 8 mol % or less, even more preferably 5 mol % or less, and particularly preferably 3 mol % or less, relative to the total amount of the structural unit (A). In one embodiment of the present invention, Layer (PI-2) and Layer (PI-3) may be substantially free of the structural unit (A3), and the lower limit of the content of the structural unit (A3) may be 0 mol %.

[0226] In one embodiment of the present invention, the PI resin constituting Layer (PI-2) and Layer (PI-3) preferably contains the structural unit (B1) as the structural unit (B). The structural unit (B1) preferably contains the structural unit (B1-2), and more preferably contains the structural unit (B1-2'), which enhances the flexibility of the PI resin. The content of the structural unit (B1) in the PI resin constituting these layers is preferably 20 mol% or more, more preferably 30 mol% or more, even more preferably 35 mol% or more, and particularly preferably 40 mol% or more, relative to the total amount of structural units (B). It is preferably 99 mol% or less, more preferably 95 mol% or less, and even more preferably 92 mol% or less, and may be, for example, 90 mol% or less, 80 mol% or less, 70 mol% or less, or 60 mol% or less. Furthermore, it is preferable that the structural unit (B) further contains a structural unit (B2), and the content thereof is preferably 1 mol% or more, more preferably 5 mol% or more, and even more preferably 10 mol% or more. For example, it may be 20 mol% or more, 30 mol% or more, more than 30 mol%, or 40 mol% or more. It is also preferably 80 mol% or less, more preferably 70 mol% or less, even more preferably 65 mol% or less, and particularly preferably 60 mol% or less. When the content of the structural unit (B1) and / or the structural unit (B2) in the PI resin constituting layers (PI-2) and (PI-3) is within the above ranges, the PI resin is not too rigid and can have a flexible structure with a certain degree of freedom. This makes it easier to form a branched structure by heating during imidization and also tends to increase crystallinity. This enables the mechanical properties of layers (PI-2) and (PI-3) to be improved and Df to be reduced. Furthermore, CTE can also be effectively reduced, resulting in a laminate having even better flexural modulus, dielectric properties, and thermal properties. In addition, the adhesiveness between the PI film and the metal layer can be expected to be improved.

[0227] The various physical properties (e.g., molecular weight, glass transition temperature) of the PI resin containing the structural unit (A) and / or the structural unit (B) may be appropriately determined based on, for example, the following preferred ranges depending on the role and application of each PI resin-containing layer in the PI film.

[0228] In one embodiment of the present invention, the PI resin constituting the PI film may contain halogen atoms, preferably fluorine atoms, which can be introduced, for example, by the above-mentioned halogen-containing substituents. When the PI resin contains fluorine atoms, the relative permittivity of the resulting PI film is easily reduced, leading to improved dielectric properties of the laminate. Preferred fluorine-containing substituents for incorporating fluorine atoms into the PI resin include, for example, a fluoro group and a trifluoromethyl group. In another embodiment of the present invention, the PI resin preferably does not contain fluorine atoms, from the viewpoint of improving the adhesion of the PI film to the metal layer. For this reason, for example, the PI resin constituting the PI resin-containing layer in contact with the metal layer, preferably the TPI layer, particularly layers (PI-2) and (PI-3) in the PI film, preferably does not contain fluorine atoms. Furthermore, since fluorine-containing PI resins tend to weaken the interactions between molecular chains, if the PI resin does not contain fluorine atoms, the Df of the PI film tends to be reduced.

[0229] When the PI resin contains halogen atoms, the content of halogen atoms, particularly fluorine atoms, in the PI resin is preferably 0.1 to 35 mass%, more preferably 0.1 to 30 mass%, even more preferably 0.1 to 20 mass%, and particularly preferably 0.1 to 10 mass%, based on the mass of the PI resin. When the halogen atom content is equal to or greater than the lower limit, the heat resistance and dielectric properties of the resulting PI film are likely to be enhanced, leading to improved dielectric properties and thermal properties of the laminate. When the halogen atom content is equal to or less than the upper limit, it is advantageous in terms of cost, facilitates a reduction in CTE, and facilitates the synthesis of the PI resin.

[0230] In one embodiment of the present invention, the imidization ratio of the PI resin is preferably 90% or more, more preferably 93% or more, and even more preferably 95% or more, and typically 100% or less. From the viewpoint of improving the flexural modulus, dielectric properties, and thermal properties of the laminate, the imidization ratio is preferably equal to or greater than the lower limit. The imidization ratio indicates the ratio of the molar amount of imide bonds in the PI resin to twice the molar amount of structural units derived from tetracarboxylic acid compounds in the PI resin. When the PI resin contains a tricarboxylic acid compound, the imidization ratio indicates the ratio of the molar amount of imide bonds in the PI resin to the sum of twice the molar amount of structural units derived from tetracarboxylic acid compounds in the PI resin and the molar amount of structural units derived from tricarboxylic acid compounds. The imidization ratio can be determined by IR, NMR, or the like.

[0231] In one embodiment of the present invention, the polystyrene-equivalent weight-average molecular weight (Mw) of the PI resin is preferably 5,000 or more, more preferably 10,000 or more, even more preferably 15,000 or more, and particularly preferably 20,000 or more, from the viewpoint of increasing the flexural modulus of the laminate. Furthermore, from the viewpoint of ease of varnish production and film-forming properties, it is preferably 1,200,000 or less, more preferably 1,000,000 or less, even more preferably 800,000 or less, and particularly preferably 700,000 or less. For example, the Mw of the mPI layer, particularly layer (PI-1) in the PI film, is preferably 5,000 to 800,000, more preferably 10,000 to 700,000. Furthermore, the Mw of the TPI layer, particularly layers (PI-2) and (PI-3) in the PI film, is preferably 10,000 to 1,000,000, more preferably 20,000 to 900,000, respectively.

[0232] In one embodiment of the present invention, the ratio (Mw / Mn) of the weight-average molecular weight (Mw) to the number-average molecular weight (Mn) of the PI resin is preferably 1.1 or more, more preferably 1.3 or more, even more preferably 1.5 or more, and particularly preferably 1.7 or more, from the viewpoint of the flexural modulus of the laminate and the adhesion between the PI film and the metal layer, and is preferably 15 or less, more preferably 12 or less, even more preferably 11 or less, and particularly preferably 10 or less. For example, the Mw / Mn of an mPI layer, particularly layer (PI-1) in a PI film, is preferably 1.1 to 15, more preferably 1.5 to 10. Furthermore, the Mw / Mn of a TPI layer, particularly layers (PI-2) and (PI-3) in a PI film, is preferably 1.1 to 15, more preferably 1.5 to 10. Note that Mw and Mn can be determined by gel permeation chromatography (hereinafter sometimes referred to as GPC) measurement and standard polystyrene equivalent.

[0233] In one embodiment of the present invention, the Tg of the PI resin is preferably 350°C or lower, more preferably 330°C or lower, even more preferably 310°C or lower, and particularly preferably 300°C or lower, from the viewpoint of improving the flexural modulus of the resulting laminate and reducing Df. Furthermore, the Tg of the PI resin is preferably 200°C or higher, more preferably 205°C or higher, even more preferably 210°C or higher, and particularly preferably 220°C or higher, from the viewpoint of improving the flexural modulus of the laminate, reducing Df, and improving thermal properties. When the PI resin-containing layer includes an mPI layer and a TPI layer, the Tg of the PI resin constituting the mPI layer is preferably 350°C or lower, more preferably 330°C or lower, even more preferably 310°C or lower, and particularly preferably 295°C or lower, and preferably 220°C or higher, more preferably 230°C or higher, even more preferably 250°C or higher, even more preferably 260°C or higher, and particularly preferably 270°C or higher. When the Tg of the PI resin constituting the mPI layer is within the above range, the flexural modulus of the laminate can be increased, and the dielectric properties and thermal properties can be improved. The Tg of the PI resin constituting the TPI layer is preferably 310°C or less, more preferably 300°C or less, even more preferably 290°C or less, even more preferably 270°C or less, and particularly preferably 250°C or less, and is preferably 200°C or more, more preferably 210°C or more, even more preferably 220°C or more, and particularly preferably 230°C or more. When the Tg of the PI resin constituting the TPI layer is within the above range, the flexural modulus of the laminate can be increased, and in addition to reducing Df and improving thermal properties, the adhesion between the PI film and the metal layer can be improved. The Tg of the PI resin can be measured by dynamic viscoelasticity measurement. For example, it can be calculated based on the peak of a tan δ curve, which is the ratio of the storage modulus (E') to the loss modulus (E'') obtained using a dynamic viscoelasticity measuring device.

[0234] In one embodiment including an mPI layer and a TPI layer as the PI resin-containing layers, when the Tg of the PI resin constituting the mPI layer is within the above-mentioned range, preferably 250 to 330°C, and the Tg of the PI resin constituting the TPI layer is within the above-mentioned range, preferably 220 to 300°C, each PI resin tends to form a preferred high-order structure with suppressed rotational motion. Therefore, in this embodiment, each PI resin-containing layer can be formed using a PI resin having a high-order structure that maintains orientation, which is thought to contribute to improving the strength against deformation of the resulting laminate. Furthermore, because the rotation of polar groups in each PI resin is suppressed and the loss of electrical energy as thermal motion is presumably reduced, using a PI resin with a Tg within the above-mentioned range is thought to result in a PI film with a low Df. Furthermore, by using such a PI resin, the flexural modulus and dielectric properties of the resulting laminate can be increased even at a low imidization temperature of, for example, 350°C or lower. Therefore, even when a laminate is produced by thermally imidizing a PI resin precursor coating film in a laminate configuration with a metal layer (copper layer), deterioration of the metal layer surface can be suppressed, and a laminate having a high flexural modulus and excellent high-frequency properties can be obtained.

[0235] In one embodiment of the present invention, the PI resin contained in the PI film in the laminate, preferably the PI resin contained in the polyimide resin-containing layer (PI-1), the PI resin contained in the polyimide resin-containing layer (PI-2), and the PI resin contained in the polyimide resin-containing layer (PI-3), each have a storage modulus at 40° C. of 1.0×10 ９ It is preferable that the storage modulus of the PI resin is in the above range, which makes it easy to increase the flexural modulus of the laminate. The reason for this is unclear, but it is thought that the PI resin is likely to have crystallinity and orientation that facilitates improving strength due to the influence of the unevenness at the interface between the PI film and the metal layer, which makes it easy to improve the flexural modulus. Note that suitable ranges for the storage modulus at 40°C of the polyimide resin contained in layer (PI-1), layer (PI-2), and layer (PI-3) can be appropriately selected from the ranges E'1, E'2, and E'3 described below, respectively.

[0236] In one embodiment of the present invention, the PI film preferably satisfies the following relationships between formulas (X) and (Y): 0.8≦E′1 / E′2≦4.5 (X) 0.8≦E′1 / E′3≦4.5 (Y) [wherein E′1 represents the storage modulus at 40°C of the PI resin contained in the PI resin-containing layer (PI-1), E′2 represents the storage modulus at 40°C of the PI resin contained in the PI resin-containing layer (PI-2), and E′3 represents the storage modulus at 40°C of the PI resin contained in the PI resin-containing layer (PI-3)]. When the laminate film of the present invention satisfies formulas (X) and (Y), the flexural modulus of the laminate is easily increased. Although the reason for this is unclear, it is thought to be because it is easy to alleviate forces applied to the laminate, particularly in the thickness direction.

[0237] E'1 / E'2 in formula (X) and E'1 / E'3 in formula (Y) are each preferably 0.90 or more, more preferably 0.95 or more, even more preferably 0.98 or more, and particularly preferably 1.00 or more, and are preferably 4.00 or less, more preferably 3.50 or less, even more preferably 3.00 or less, even more preferably 2.50 or less, particularly preferably 2.00 or less, and particularly preferably 1.50 or less. When E'1 / E'2 and E'1 / E'3 are within the above ranges, the flexural modulus of the laminate is easily improved. Note that E'1 / E'2 and E'1 / E'3 may be the same or different values.

[0238] In one embodiment of the present invention, E′1 in formula (X) and formula (Y) is, but is not limited to, preferably 1.0×10 ９ Pa or more, more preferably 1.5 × 10 ９ Pa or more, more preferably 2.0 × 10 ９ Pa or more, preferably 1.0 × 10 １１ Pa or less, more preferably 5.0 × 10 １０ Pa or less, more preferably 1.0 × 10 １０ Pa or less, and even more preferably 8.0 × 10 ９ Pa or less, particularly preferably 5.0 × 10 ９ Pa or less or 3.5 x 10 ９When E'1 is in the above range, the flexural modulus of the laminate is easily improved.

[0239] In one embodiment of the present invention, E'2 in formula (X) and E'3 in formula (Y) are each, but are not limited to, preferably 1.0 × 10 ９ Pa or more, more preferably 1.5 × 10 ９ Pa or more, more preferably 2.0 × 10 ９ Pa or more, preferably 5.0 × 10 １０ Pa or less, more preferably 1.0 × 10 １０ Pa or less, more preferably 8.0 × 10 ９ Pa or less, and even more preferably 5.0 × 10 ９ Pa or less or 3.5 x 10 ９ When E'2 and / or E'3 are in the above range, the flexural modulus of the laminate is easily improved. E'2 and E'3 may be the same value or different values.

[0240] In one embodiment of the present invention, the PI resin contained in the PI film in the laminate, preferably the PI resin contained in the PI resin-containing layer (PI-1), the PI resin contained in the PI resin-containing layer (PI-2), and the PI resin contained in the PI resin-containing layer (PI-3), each have a storage modulus at 300° C. of 1.0×10 ８ Pa or more, or 1.0 x 10 ８ In order to increase the flexural modulus of the laminate, the storage modulus at 300°C (sometimes referred to as E'1a) of the PI resin contained in the PI resin-containing layer (PI-1) is not limited, but is preferably 1.0 x 10 ８ Pa or more, more preferably 1.5 × 10 ８ Pa or more, more preferably 2.0 × 10 ８ Pa or more, for example, 2.5×10 ８ E'1a may be equal to or greater than 1.0 x 10 Pa. １０ Pa or less, more preferably 5.0 × 10 ９ Pa or less, more preferably 1.0 × 10 ９ Pa or less, and even more preferably 8.0 × 10 ８Pa or less, particularly preferably 5.0 × 10 ８ Pa or less, for example, 4.0 × 10 ８ If E'1a is in the above range, the flexural modulus of elasticity of the laminated film is easily improved.

[0241] In one embodiment of the present invention, the storage modulus at 300°C of the PI resin contained in the PI resin-containing layer (PI-2) (sometimes referred to as E'2a) and the storage modulus at 300°C of the PI resin contained in the PI resin-containing layer (PI-3) (sometimes referred to as E'3a) are not limited, but are preferably 1.0 x 10 ８ Pa, more preferably less than 8.0 × 10 ７ Pa or less, more preferably 5.0 × 10 ７ Pa or less, and even more preferably 3.0 × 10 ７ Pa or less, particularly preferably 2.0 × 10 ７ Pa or less, preferably 1.0 × 10 ６ Pa or more, more preferably 5.0 × 10 ６ Pa or more, more preferably 1.0 × 10 ７ When E'2a and / or E'3a are in the above range, the flexural modulus of the laminate is easily improved. E'2a and E'3a may be the same value or different values.

[0242] The storage modulus of the PI resin contained in each PI resin-containing layer can be measured using a dynamic viscoelasticity measuring device, for example, under conditions of a temperature rise rate of 5°C / min from room temperature (e.g., 25°C) to 342°C. The storage modulus of the PI resin may be measured using a PI resin film made of the PI resin, and can be measured, for example, by the method described in the examples.

[0243] E'1 / E'2 and E'1 / E'3 can be controlled by appropriately adjusting the type and composition of the structural units constituting the PI resin contained in each PI resin-containing layer, the molecular weight of the PI resin, the composition and combination of each PI resin-containing layer in the laminate film, etc. For example, E'1 / E'2 can be appropriately adjusted to fall within the range of formula (X), and E'1 / E'3 can be appropriately adjusted to fall within the range of formula (Y) based on a preferred embodiment advantageous for improving the flexural modulus and dielectric properties of the laminate, such as the preferred structural units of the PI resin and their contents.

[0244] The Tg and storage modulus of the PI resin can be adjusted by appropriately adjusting the type and composition of the structural units constituting the PI resin, the molecular weight and production method of the PI resin, particularly the imidization conditions, etc. For example, the Tg and storage modulus can be adjusted to fall within the above-mentioned ranges by adjusting them to fall within the ranges described as preferred embodiments in this specification.

[0245] <Additives> In one embodiment of the present invention, the content of the PI resin in the PI film is preferably 60% by mass or more, more preferably 70% by mass or more, even more preferably 80% by mass or more, and particularly preferably 90% by mass or more, relative to the mass of the PI film. The upper limit of the PI resin content is not particularly limited, and may be, for example, 100% by mass or less, 99% by mass or less, or 95% by mass or less, relative to the mass of the PI film. When the PI resin content is within the above range, a laminate having improved flexural modulus, dielectric properties, and thermal properties can be obtained.

[0246] Each PI resin-containing layer constituting the PI film of the present invention may contain a filler as needed. Examples of fillers include metal oxide particles such as silica and alumina, inorganic salts such as calcium carbonate, and polymer particles such as fluororesins and cycloolefin polymers. A single filler may be used, or two or more fillers may be used in combination. When a filler is contained, the content thereof is preferably 50% by mass or less, more preferably 40% by mass or less, and even more preferably 30% by mass or less, relative to the mass of each PI resin-containing layer constituting the PI film, and is preferably 0.01% by mass or more.

[0247] In one embodiment of the present invention, each PI resin-containing layer constituting the PI film of the present invention may contain additives as needed. Examples of additives include antioxidants, flame retardants, crosslinking agents, surfactants, compatibilizers, imidization catalysts, weathering agents, lubricants, antiblocking agents, antistatic agents, antifogging agents, anti-dripping agents, and pigments. The additives may be used alone or in combination. The content of each additive may be appropriately selected within a range that does not impair the effects of the present invention. When various additives are included, the total content of the additives is preferably 7% by mass or less, more preferably 5% by mass or less, even more preferably 4% by mass or less, and particularly preferably 1% by mass or less, and preferably 0.001% by mass or more, based on the mass of each PI resin-containing layer constituting the PI film.

[0248] <Physical Properties of PI Films> Printed circuits are required to have low transmission loss. Transmission loss is expressed as the sum of dielectric loss, which is loss caused by an electric field generated in a dielectric, and conductor loss, which is loss caused by a current flowing through a conductor. Dielectric loss is known to be approximately proportional to the index E expressed by formula (i): E = Df × (Dk) １／２ (i) [In formula (i), Df represents the dielectric loss tangent, and Dk represents the relative permittivity] In the high frequency range used in FPCs for high-speed communication such as 5G, dielectric loss tends to increase, so materials with a small value of the index E and capable of suppressing dielectric loss are particularly sought after. On the other hand, high-frequency signals concentrate current on the very surface of the conductor. Therefore, conductor loss is related to the dielectric properties of the adjacent dielectric and can be approximately expressed as (Dk) １／２ is known to be proportional to

[0249] The PI film in the laminate of the present invention has small Df and Dk, and also has small dielectric loss index E and conductor loss, so that the transmission loss can be reduced in a circuit including the laminate of the present invention. Therefore, the laminate of the present invention can exhibit a high flexural modulus while maintaining excellent dielectric properties (especially while maintaining a low Df).

[0250] In one embodiment of the present invention, the dielectric loss index E at 10 GHz of the PI film in the laminate may be preferably 0.0080 or less, more preferably 0.0075 or less, even more preferably 0.0070 or less, still more preferably 0.0065 or less, particularly preferably 0.0060 or less, and particularly preferably 0.0059 or less, 0.0058 or less, 0.0057 or less, or 0.0056 or less. The smaller the index E, the lower the transmission loss of an electronic circuit including the laminate. Therefore, the lower limit of the index E is not particularly limited and may be, for example, 0 or more.

[0251] In one embodiment of the present invention, the Df at 10 GHz of the PI film in the laminate is preferably 0.0040 or less, more preferably 0.0035 or less, even more preferably 0.0034 or less, and even more preferably 0.0033 or less, from the viewpoint of reducing transmission loss in an electronic circuit when the laminate is incorporated into the electronic circuit. The smaller the Df, the lower the transmission loss of an electronic circuit comprising the laminate. Therefore, the lower limit of Df is not particularly limited and may be, for example, 0 or more.

[0252] In one embodiment of the present invention, the Dk at 10 GHz of the PI-based film in the laminate is preferably 3.500 or less, more preferably 3.450 or less, even more preferably 3.400 or less, still more preferably 3.380 or less, particularly preferably 3.360 or less, or 3.350 or less.

[0253] The Df and Dk of the PI film in the laminate can be measured using a vector network analyzer and a resonator, for example, by the method described in the Examples.

[0254] In one embodiment of the present invention, the coefficient of linear expansion (CTE) of the PI film in the laminate is preferably less than 45 ppm / K, more preferably 40 ppm / K or less, even more preferably 35 ppm / K or less, even more preferably 30 ppm / K or less, particularly preferably 29 ppm / K or less, and particularly preferably 28 ppm / K or less, and may be, for example, 27 ppm / K or less, or 26 ppm / K or less. When the CTE of the PI film is below the upper limit, excellent thermal properties and high dimensional stability can be expected. Furthermore, the CTE of the PI film is preferably 0 ppm / K or more, more preferably 5 ppm / K or more, even more preferably 8 ppm / K or more, and particularly preferably 10 ppm / K or more. When the CTE of the PI film is within the above upper and lower limits, the CTE of the metal layer (particularly the copper layer) and the CTE of the PI resin-containing layer in the PI film are close to each other, thereby suppressing peeling of the PI film from the metal layer. Note that the CTE can be measured, for example, by a thermomechanical analyzer (hereinafter sometimes referred to as "TMA") and is determined by the method described in the Examples.

[0255] The PI film of the present invention may be subjected to a surface treatment such as corona discharge treatment, plasma treatment, or ozone treatment by a method generally employed in industry.

[0256] <Production Method of PI Film> The production method of the PI film of the present invention is not particularly limited, as long as at least the PV / PM of the resulting laminate satisfies the above-mentioned range, or as long as the average DMT elastic modulus or average orientation parameter required for the laminate satisfy the desired relationship. Depending on the type, the PI film may be produced by a conventional method or a commercially available product. For example, the PI film can be produced by cast molding, injection molding, heat press molding, calendar molding, vacuum molding, compression molding, extrusion molding, etc. As described below, the PI film of the present invention can be produced by a method including a step of reacting a tetracarboxylic acid compound and a diamine compound, each appropriately selected depending on the composition of the PI resin, to obtain a PI resin precursor, and a step of imidizing the obtained PI resin precursor. For example, a method for producing the PI film of the present invention includes applying a solution of the corresponding PI resin precursor to a support substrate, pre-drying the coating, and then performing imidization. Imidization may be performed with the support substrate peeled off. In one embodiment of the present invention, the flexural modulus of the laminate can be increased by imidizing the coating film in a state where sufficient solvent remains throughout the coating film or where the resin layers are well-mixed. While the reason for this is unclear, it is believed that such a state increases the degree of freedom of the resin molecules until imidization, making it easier for the state of the resin molecules to remain constant between the PI resin-containing layers. When producing a PI film by extrusion molding, the surface properties can be adjusted by adjusting the production conditions, such as the die lip opening, coating speed, surface roughness of the forming roll and cooling roll, and cooling profile.

[0257] In one embodiment of the present invention, a PI film can be produced by, for example, applying a solution of a corresponding PI resin precursor to a supporting substrate, pre-drying the coating to obtain a single-layer or multi-layer coating, and then imidizing the coating. Imidization may be carried out with the supporting substrate peeled off.

[0258] Examples of the supporting substrate include metal foil (e.g., copper foil), metal plate (e.g., copper plate, etc.), SUS foil, SUS plate such as SUS belt, glass substrate, resin film other than the resin film of the present invention (e.g., PET film, PEN film, PI-based resin film, polyamide-based resin film), etc. By using a metal layer (e.g., metal foil, etc.) as the supporting substrate, it is also possible to form a PI-based film directly on the metal layer.

[0259] [Metal Layer] The laminate of the present invention includes a metal layer on both sides of the PI film.

[0260] In one embodiment of the present invention, examples of metals constituting the metal layer include aluminum, copper, iron, nickel, chromium, titanium, tantalum, stainless steel, and alloys thereof. Among these, the metal layer is preferably a copper layer, a copper alloy layer, a SUS layer, an aluminum layer, etc., and from the viewpoints of electrical conductivity and metal workability, a copper layer or a copper alloy layer is more preferred, and a copper layer is particularly preferred. Furthermore, from the viewpoint of metal workability, the metal layer is preferably a metal foil layer, and a metal foil of each of the above-mentioned metals is more preferred, a copper foil layer or a copper alloy foil layer is even more preferred, and a copper foil layer is particularly preferred.

[0261] In one embodiment of the present invention, the thickness of the metal layer, particularly the copper layer, is preferably 1 μm or more, more preferably 5 μm or more, and even more preferably 10 μm or more. From the viewpoint of facilitating circuit miniaturization and improving bending resistance, the thickness is preferably 100 μm or less, more preferably 50 μm or less, even more preferably 30 μm or less, and particularly preferably 20 μm or less. The thickness of the metal layer, particularly the copper layer, can be measured using a film thickness meter or the like. Note that when a metal layer, particularly a copper layer, is included on both sides of the resin film, the thickness of each metal layer, particularly each copper layer, may be the same or different.

[0262] In one embodiment of the present invention, the ten-point average roughness RzJIS of the surface of the metal layer in contact with the PI film, as measured in accordance with JIS B0601:2013 using a laser microscope at a magnification of 100 times, is preferably 0.05 to 2 μm, more preferably 0.1 to 1.5 μm, even more preferably 0.2 to 1.0 μm, still more preferably 0.30 to 0.80 μm, and particularly preferably 0.30 to 0.70 μm.

[0263] The analysis of RzJIS can be performed in accordance with JIS B0601:2013 by analyzing a contour curve obtained at any point in an acquired three-dimensional shape image under the conditions that λs is 2.5 μm, and λc and λf are not set.

[0264] The metal layer may be manufactured by, for example, electrolytic casting such as electroplating or plastic processing such as rolling, or a commercially available product may be used. When the metal layer is a metal foil, a surface treatment layer may be provided on at least one surface of the metal foil by electroplating. Examples of the surface treatment layer include a roughened layer, an anti-rust layer, and, if necessary, an alloy layer provided between the surface of the metal foil and the roughened layer, and a chromate layer or a silane coupling agent layer provided on the surface of the anti-rust layer. When the metal layer is a copper foil, an electrolytic copper foil or a rolled copper foil can be used. The metal layer preferably has a roughened layer made of copper, zinc, titanium, tungsten, molybdenum, nickel, cobalt, iron, or two or more of these elements, and / or an anti-rust layer made of zinc, tin, nickel, cobalt, chromium, molybdenum, or two or more of these elements. From the viewpoint of providing a uniform roughened layer, it is preferable to further provide an alloy layer of copper and at least one element selected from molybdenum, zinc, tungsten, nickel, cobalt, and iron on the surface of the copper foil. The thickness of the surface treatment layer is 2.0 μm or less, preferably 0.2 μm or more and 1.5 μm or less, from the viewpoint of easily adjusting the RzJIS of the metal foil surface. In this specification, the surface treatment layer is also referred to as the "metal layer." Methods for adjusting the surface of the metal layer to the above RzJIS range include using a commercially available product whose surface satisfies the above RzJIS range, and forming a surface treatment layer with a predetermined roughness on the metal surface.

[0265] [Physical Properties of the Laminate] The laminate of the present invention, in which the PV / PM is 0.135 or less, or the average three-point Martens hardness of the polyimide film is 0.35 GPa or more, and the standard deviation of the elastic deformation power is 2.50% or less, and the laminate of the present invention, in which the average DMT elastic modulus or the average orientation parameter in the laminate satisfy a predetermined relationship, has a high flexural modulus and excellent resistance to deformation. It also has excellent dielectric properties, achieving both excellent flexural modulus and dielectric properties. Therefore, the laminate of the present invention can be suitably used as a substrate material for printed circuit boards and antenna substrates. Furthermore, because the laminate of the present invention has a low Df, it can achieve low transmission loss even in high-frequency bands that transmit high-frequency signals. Therefore, it is particularly suitable as a substrate material for printed circuit boards and antenna substrates for high-speed communication applications such as 5G.

[0266] The laminate of the present invention may further include other layers, such as functional layers, provided that metal layers are laminated (or provided) directly (in contact) on both sides of the PI film so that the average Martens hardness and the standard deviation of the elastic deformation power at three points of at least the PV / PM or the polyimide film satisfy the above-mentioned ranges, or so that the respective average DMT elastic moduli or respective average orientation parameters required in the laminate satisfy the desired relationships. For example, at least one of the metal layers may include another layer on the side opposite the PI film. Furthermore, when the PI film is a laminate film, other layers may be included between the respective layers in the PI film (each PI resin-containing layer in the PI film). Examples of functional layers include adhesive layers. The functional layers may be used alone or in combination of two or more. From the viewpoints of the flexural modulus, heat resistance, dimensional stability, dielectric properties, and weight reduction of the laminate, it is preferable that the laminate does not include a functional layer, especially an adhesive layer.

[0267] In the present invention, as long as the average Martens hardness and the standard deviation of the elastic deformation power at at least three points of the PV / PM or the polyimide-based film satisfy the above-mentioned ranges, or as long as the respective average DMT elastic moduli or respective average orientation parameters required in the laminate satisfy the desired relationships, the metal layer may be laminated on the entire surface of the PI-based film or may be laminated on only a portion of the surface of the PI-based film.

[0268] The laminate of the present invention can be formed at a relatively low imidization temperature, and even when a laminate in which the metal layer is a copper layer (preferably a copper foil layer) is produced by thermally imidizing a PI resin precursor coating film on a metal layer, a sufficiently high flexural modulus and low Df can be achieved while suppressing deterioration of the copper layer surface. Therefore, the laminate of the present invention has excellent high-frequency characteristics even without an adhesive layer.

[0269] In one embodiment of the present invention, the flexural modulus of the laminate of the present invention is preferably 60,000 MPa or more, more preferably 62,000 MPa or more, even more preferably 64,000 MPa or more, even more preferably 64,500 MPa or more, and particularly preferably 65,000 MPa or more, for example, 68,500 MPa or more, 69,000 MPa or more, or 70,000 MPa or more. When the flexural modulus of the laminate is above the lower limit, the laminate has excellent resistance to deformation and can suppress deterioration of electrical properties due to plastic deformation when used as an FPC or the like containing the laminate. The upper limit of the flexural modulus of the laminate of the present invention is not particularly limited, but is, for example, 150,000 MPa or less, preferably 100,000 MPa or less. The flexural modulus of the laminate can be determined using an autograph under conditions of a temperature of 23°C, a relative humidity of 50%, a support distance of 20 mm, and a test speed of 1 mm / min. The flexural modulus can be determined, for example, by the method described in the examples.

[0270] [Method for Manufacturing Laminate] The method for manufacturing the laminate of the present invention is not particularly limited as long as it is a method that allows metal layers to be directly laminated on both sides of a PI film so that at least the PV / PM satisfies the above range, or so that the average DMT elastic modulus or average orientation parameter required in the laminate satisfies the desired relationship. Examples of the method include a method of forming metal layers on both sides of a PI film by plating; a method of applying a solution of a resin constituting the PI film or a solution of a precursor of the resin onto the surface of the metal layer, drying the solution, and then imidizing (casting method), and then laminating a metal layer on the side of the PI film that does not have the metal layer; and a method of laminating metal layers on both sides of a PI film.

[0271] In one embodiment of the present invention, a method for producing a laminate by plating includes, for example, producing a resin film by cast molding, extrusion molding, or the like, as described in the section <Production Method of PI Film>, and then plating the surface of the resin film with a metal to provide a metal layer (metal plating layer) on both surfaces of the resin film. From the viewpoint of the conductivity of the laminate, the metal plating layer is preferably a copper plating layer or a copper alloy plating layer, and a copper plating layer is more preferred. Methods known in the art can be used for the metal plating process. In the production of a PI film, the method of applying the PI resin precursor solution to the support substrate, the pre-drying method, the standing method, and the heating conditions for imidization can be the same as those when a metal layer is used as the support substrate, as described below. In another embodiment of the present invention, a laminate can also be produced by embossing, matting, hairline finishing, blasting, desmearing, or the like to create irregularities on the surface of the PI film, and then metal plating the surface of the PI film to provide a metal layer (metal plating layer) on the surface of the PI film.

[0272] In a preferred embodiment of the present invention, a method for forming a PI film directly on the surface of a metal layer using a metal layer as a support substrate includes, for example, a process for applying a solution of a corresponding PI resin precursor to the surface of the metal layer and pre-drying it to obtain a coating film (also referred to as a coating and pre-drying process); a process for allowing the resulting coating film to stand (also referred to as a standing process); and a process for heating the coating film to imidize the PI resin (also referred to as an imidization process), thereby producing a PI film having a metal layer on one side, and then bonding the metal layer to the other side of the PI film by thermocompression bonding such as thermal lamination or heat pressing. The coating film is a single-layer coating film when the PI film is a single-layer film, and a multi-layer coating film when the PI film is a laminate film. While the production of the laminate does not necessarily require a standing process, including a standing process tends to make it easier to adjust the hardness, average DMT modulus, or average orientation parameter of the resulting laminate within the above-mentioned ranges. Furthermore, the mechanical properties of the resulting laminate, such as the flexural modulus, can be improved.

[0273] (Preparation of PI Resin Precursor) The PI resin precursor can be obtained by reacting a tetracarboxylic acid compound with a diamine compound. Examples of the tetracarboxylic acid compound used in synthesizing the PI resin precursor include aromatic tetracarboxylic acid compounds such as aromatic tetracarboxylic acid dianhydrides; and aliphatic tetracarboxylic acid compounds such as aliphatic tetracarboxylic acid dianhydrides. The tetracarboxylic acid compounds may be used alone or in combination of two or more. The tetracarboxylic acid compound may be a dianhydride or a tetracarboxylic acid compound analog such as an acid chloride compound.

[0274] Examples of the tetracarboxylic acid compound include tetracarboxylic acid anhydrides represented by formula (A1), tetracarboxylic acid anhydrides represented by formula (A2), and tetracarboxylic acid anhydrides represented by formula (A3). Tetracarboxylic acid compounds known in the art can be appropriately selected and used. Examples of such tetracarboxylic acid compounds include pyromellitic anhydride (hereinafter sometimes referred to as PMDA), 4,4'-(4,4'-isopropylidenediphenoxy)diphthalic anhydride (hereinafter sometimes referred to as BPADA), 1,4,5,8-naphthalenetetracarboxylic dianhydride, 3,3',4,4'-biphenyltetracarboxylic dianhydride (hereinafter sometimes referred to as BPDA), and 4,4'-(hexafluoroisopropylidene)diphthalic dianhydride. (hereinafter, sometimes referred to as 6FDA), 4,4'-oxydiphthalic dianhydride (hereinafter, sometimes referred to as ODPA), 2,2',3,3'-, 2,3,3',4'- or 3,3',4,4'-benzophenonetetracarboxylic dianhydride, 2,3',3,4'-biphenyltetracarboxylic dianhydride, 2,2',3,3'-biphenyltetracarboxylic dianhydride, p-phenylenebis(trimellitic acid monoester dianhydride) (hereinafter, sometimes referred to as TAHQ), ester of trimellitic anhydride and 2,2',3,3',5,5'-hexamethyl-4,4'-biphenol (hereinafter sometimes referred to as TMPBP), 4,4'-bis(1,3-dioxo-1,3-dihydroisobenzofuran-5-ylcarbonyloxy)biphenyl (hereinafter sometimes referred to as BP-TME), 2,3',3,4'-diphenyl ether tetracarboxylic acid dianhydride, bis(2,3-dicarboxyphenyl) ether dianhydride, 3,3', 4,4"-p-terphenyltetracarboxylic dianhydride, 2,3,3",4"-p-terphenyltetracarboxylic dianhydride, 2,2",3,3"-p-terphenyltetracarboxylic dianhydride, 2,2-bis(2,3-dicarboxyphenyl)-propane dianhydride, 2,2-bis(3,4-dicarboxyphenyl)-propane dianhydride, bis(2,3-dicarboxyphenyl)methane dianhydride, bis(3,4-dicarboxyphenyl)methane dianhydride, 1,1-bis(2,1,1-bis(3,4-dicarboxyphenyl)ethane dianhydride, 1,2,7,8-,1,2,6,7-phenanthrene-tetracarboxylic dianhydride, 1,2,9,10-phenanthrene-tetracarboxylic dianhydride, 2,2-bis(3,4-dicarboxyphenyl)tetrafluoropropane dianhydride, 1,2,4,5-cyclohexanetetracarboxylic dianhydride (hereinafter sometimes referred to as HPMDA), 2,3,5,6-cyclohexanetetracarboxylic dianhydride, 2,3,6,7-naphthalenetetracarboxylic dianhydride tetracarboxylic dianhydride, 1,2,5,6-naphthalenetetracarboxylic dianhydride, cyclopentane-1,2,3,4-tetracarboxylic dianhydride, 4,4'-bis(2,3-dicarboxyphenoxy)diphenylmethane dianhydride, 1,2,3,4-cyclobutanetetracarboxylic dianhydride (hereinafter sometimes referred to as CBDA), norbornane-2-spiro-α'-spiro-2"-norbornane-5,5',6,6'-tetracarboxylic anhydride, p-phenylenebis(trimellitate anhydride), 3,3',4,4'-diphenylsulfonetetracarboxylic dianhydride carboxylic acid dianhydride, 2,3,6,7-anthracenetetracarboxylic acid dianhydride, 4,8-dimethyl-1,2,3,5,6,7-hexahydronaphthalene-1,2,5,6-tetracarboxylic acid dianhydride, 2,6-dichloronaphthalene-1,4,5,8-tetracarboxylic acid dianhydride, 2,7-dichloronaphthalene-1,4,5,8-tetracarboxylic acid dianhydride, 2,3,6,7-tetrachloronaphthalene-1,4,5,8-tetracarboxylic acid dianhydride, 2,3,6,7-tetrachloronaphthalene-2,3,6,7-tetracarboxylic acid dianhydride, 1,4,5,8- Tetrachloronaphthalene-1,4,5,8-tetracarboxylic dianhydride, 1,4,5,8-tetrachloronaphthalene-2,3,6,7-tetracarboxylic dianhydride, 2,3,8,9-perylene-tetracarboxylic dianhydride, 3,4,9,10-perylene-tetracarboxylic dianhydride, 4,5,10,11-perylene-tetracarboxylic dianhydride, 5,6,11,12-perylene-tetracarboxylic dianhydride, pyrazine-2,3,5,6-tetracarboxylic dianhydride, pyrrolidine-2,3,4,5-tetracarboxylic dianhydride, thiophene-2,3,4,Examples of suitable tetracarboxylic acid compounds include 5-tetracarboxylic acid dianhydride, bis(2,3-dicarboxyphenyl)sulfone dianhydride, and bis(3,4-dicarboxyphenyl)sulfone dianhydride. Among these, it is preferable to use a combination of BPDA, PMDA, TAHQ, and / or BP-TME from the viewpoints of improving the flexural modulus of the resulting laminate and reducing Df and CTE. These tetracarboxylic acid compounds can be used alone or in combination of two or more.

[0275] Examples of diamine compounds used in the synthesis of PI resin precursors include aliphatic diamines, aromatic diamines, and mixtures thereof. In this embodiment, "aromatic diamine" refers to a diamine having an aromatic ring, which may contain an aliphatic group or other substituents as part of its structure. This aromatic ring may be a single ring or a condensed ring, and examples include, but are not limited to, a benzene ring, a naphthalene ring, an anthracene ring, and a fluorene ring. Among these, a benzene ring is preferred. Furthermore, "aliphatic diamine" refers to a diamine having an aliphatic group, which may contain other substituents as part of its structure, but does not have an aromatic ring.

[0276] Examples of diamine compounds include diamines represented by formula (B1), diamines represented by formula (B2), and diamines represented by formula (2), and diamine compounds known in the art can be appropriately selected and used. Examples of such diamine compounds include 1,4-diaminocyclohexane, 4,4'-diamino-2,2'-dimethylbiphenyl (hereinafter sometimes referred to as m-Tb), 4,4'-diamino-3,3'-dimethylbiphenyl, 2,2'-bis(trifluoromethyl)-4,4'-diaminodiphenyl (hereinafter sometimes referred to as TFMB), 4,4'-diaminodiphenyl ether, and 1,3-bis(3-aminophenoxy)benzene (hereinafter sometimes referred to as 1,3-APB). , 1,4-bis(4-aminophenoxy)benzene (hereinafter sometimes referred to as TPE-Q), 1,3-bis(4-aminophenoxy)benzene (hereinafter sometimes referred to as TPE-R), 2,2-bis[4-(4-aminophenoxy)phenyl]propane (hereinafter sometimes referred to as BAPP), 2,2'-dimethyl-4,4'-diaminobiphenyl, 3,3'-dihydroxy-4,4'-diaminobiphenyl, 2,2-bis-[4-(3-aminophenoxy)phenyl]propane, biphenyl Bis[4-(4-aminophenoxy)]biphenyl, bis[4-(3-aminophenoxy)]biphenyl, bis[1-(4-aminophenoxy)]biphenyl, bis[1-(3-aminophenoxy]biphenyl, bis[4-(4-aminophenoxy)phenyl]methane, bis[4-(3-aminophenoxy)phenyl]methane, bis[4-(4-aminophenoxy)phenyl]ether, bis[4-(3-aminophenoxy)phenyl]ether, bis[4-(4-aminophenoxy]benzo Phenone, bis[4-(3-aminophenoxy)]benzophenone, 2,2-bis-[4-(4-aminophenoxy)phenyl]hexafluoropropane, 2,2-bis-[4-(3-aminophenoxy)phenyl]hexafluoropropane, 4,4'-methylenedi-o-toluidine, 4,4'-methylenedi-2,6-xylidine, 4,4'-methylene-2,6-diethylaniline, 4,4'-methylenedianiline, 3,3'-methylenedianiline, 4,4'-diaminodiphenylpropane, 3,3'-Diaminodiphenylpropane, 4,4'-diaminodiphenylethane, 3,3'-diaminodiphenylethane, 4,4'-diaminodiphenylmethane, 3,3'-diaminodiphenylmethane, 3,3-diaminodiphenylether, 3,4'-diaminodiphenylether, benzidine, 3,3'-diaminobiphenyl, 3,3'-dimethoxybenzidine, 4,4"-diamino-p-terphenyl, 3,3"-diamino-p-terphenyl, m-phenylenediamine, p-phenylenediamine (hereinafter sometimes referred to as p-PDA), rezo Rucinol bis(3-aminophenyl) ether, 4,4'-[1,4-phenylenebis(1-methylethylidene)]bisaniline, 4,4'-[1,3-phenylenebis(1-methylethylidene)]bisaniline, bis(p-aminocyclohexyl)methane, bis(p-β-amino-tert-butylphenyl)ether, bis(p-β-methyl-δ-aminopentyl)benzene, p-bis(2-methyl-4-aminopentyl)benzene, p-bis(1,1-dimethyl-5-aminopentyl)benzene, 1,5-diaminonaphthalene, 2,6-diamino Aminonaphthalene, 2,4-bis(β-amino-tert-butyl)toluene, 2,4-diaminotoluene, m-xylene-2,5-diamine, p-xylene-2,5-diamine, m-xylylenediamine, p-xylylenediamine, piperazine, 4,4'-diamino-2,2'-bis(trifluoromethyl)bicyclohexane, 4,4'-diaminodicyclohexylmethane, 4,4"-diamino-p-terphenyl, bis(4-aminophenyl)terephthalate, 1,4-bis(4-aminophenoxy)-2,5-di-tert-butylbenzene, 4, 4'-(1,3-phenylenediisopropylidene)bisaniline, 1,4-bis[2-(4-aminophenyl)-2-propyl]benzene, 2,4-diamino-3,5-diethyltoluene, 2,6-diamino-3,5-diethyltoluene, 4,4'-bis(3-aminophenoxy)biphenyl, 4,4'-(hexafluoropropylidene)dianiline, 1,2-diaminoethane, 1,3-diaminopropane, 1,4-diaminobutane, 1,5-diaminopentane, 1,6-diaminohexane, 1,2-diaminopropane, 1,2-diaminobutane, 1,3-Diaminobutane, 2-methyl-1,2-diaminopropane, 2-methyl-1,3-diaminopropane, 1,3-bis(aminomethyl)cyclohexane, 1,4-bis(aminomethyl)cyclohexane, norbornanediamine, 2'-methoxy-4,4'-diaminobenzanilide, 4,4'-diaminobenzanilide, bis[4-(4-aminophenoxy)phenyl]sulfone, bis[4-(3-aminophenoxy)phenyl]sulfone, 9,9-bis[4-(4-aminophenoxy)phenyl]fluoro Examples of suitable diamine compounds include fluorene, 9,9-bis[4-(3-aminophenoxy)phenyl]fluorene, 4,4'-diaminodiphenyl sulfide, 3,3'-diaminodiphenyl sulfide, 4,4'-diaminodiphenyl sulfone, 3,3'-diaminodiphenyl sulfone, 2,5-diamino-1,3,4-oxadiazole, bis[4,4'-(4-aminophenoxy)]benzanilide, bis[4,4'-(3-aminophenoxy)]benzanilide, 2,6-diaminopyridine, and 2,5-diaminopyridine. Among these, m-Tb, BAPP, TPE-Q, 1,3-bis(4-aminophenoxy)benzene, and / or TPE-R are preferably used in combination, from the viewpoints of improving the flexural modulus of the resulting laminate and reducing Df and CTE. The diamine compounds can be used alone or in combination of two or more.

[0277] The PI resin precursor may be a product obtained by further reacting, in addition to the tetracarboxylic acid compound used in the synthesis of the PI resin precursor, other tetracarboxylic acids, dicarboxylic acids, tricarboxylic acids, and anhydrides and derivatives thereof, as long as the various physical properties of the resulting PI film are not impaired.

[0278] Other tetracarboxylic acids include water adducts of the anhydrides of the above tetracarboxylic acid compounds.

[0279] Examples of the dicarboxylic acid compound include aromatic dicarboxylic acids, aliphatic dicarboxylic acids, and their analogous acid chloride compounds, acid anhydrides, etc., and two or more of these may be used in combination. Specific examples include dicarboxylic acid compounds of terephthalic acid, isophthalic acid, naphthalenedicarboxylic acid, 4,4'-biphenyldicarboxylic acid, 3,3'-biphenyldicarboxylic acid, and chain hydrocarbons having 8 or less carbon atoms, and compounds in which two benzoic acids are bonded to a single bond, -O-, -CH ２ -, -C(CH ３ ) ２ -, -C(CF ３ ) ２ -, -SO ２ Examples of such compounds include compounds linked by a phenylene group or a phenylene group, and acid chloride compounds thereof.

[0280] Examples of tricarboxylic acid compounds include aromatic tricarboxylic acids, aliphatic tricarboxylic acids, and acid chloride compounds and acid anhydrides related thereto, and two or more of these may be used in combination. Specific examples include anhydride of 1,2,4-benzenetricarboxylic acid; 2,3,6-naphthalenetricarboxylic-2,3-anhydride; and compounds in which phthalic anhydride and benzoic acid are bonded by a single bond, —O—, —CH ２ -, -C(CH ３ ) ２ -, -C(CF ３ ) ２ -, -SO ２ or a compound linked by a phenylene group.

[0281] In the production of a PI resin precursor, the amounts of diamine compounds, tetracarboxylic acid compounds, dicarboxylic acid compounds, and tricarboxylic acid compounds used can be appropriately selected depending on the ratio of each structural unit of the desired PI resin precursor. In the present invention, the total number of moles of diamine compounds used per mole of the total amount of tetracarboxylic acid compounds is defined as the amine ratio. In a preferred embodiment of the present invention, the amine ratio is preferably 0.90 moles or more and preferably 0.999 moles or less per mole of the total amount of tetracarboxylic acid compounds. In another embodiment, the amine ratio is preferably 1.001 moles or more and preferably 1.10 moles or less per mole of the total amount of tetracarboxylic acid compounds. In one embodiment of the present invention, when the amine ratio is 1 or less, the amine ratio is preferably 0.90 moles or more and 0.999 moles or less, more preferably 0.95 moles or more and 0.997 moles or less, and even more preferably 0.97 moles or more and 0.995 moles or less. In one embodiment of the present invention, when the amine ratio is 1 or more, the amine ratio is preferably 1.001 mol or more and 1.10 mol or less, more preferably 1.002 mol or more and 1.06 mol or less, and even more preferably 1.003 mol or more and 1.05 mol or less. If the amine ratio is close to 1.0 mol, the molecular weight tends to increase rapidly during synthesis, while if it is significantly different from 1.0 mol, the molecular weight of the resulting PI resin tends to decrease. If the molecular weight increases rapidly, it grows unevenly within the synthesis mass, and the physical properties of the PI resin obtained from the PI resin precursor tend to become unstable. On the other hand, if the molecular weight is too low, the mechanical properties tend to decrease.

[0282] The reaction temperature between the diamine compound and the tetracarboxylic acid compound is preferably 50°C or lower, more preferably 40°C or lower, and even more preferably 30°C or lower. The reaction temperature between the diamine compound and the tetracarboxylic acid compound is preferably 5°C or higher, more preferably 10°C or higher, and even more preferably 15°C or higher. When the reaction temperature is within the above upper and lower limits, the effects of the present invention are easily achieved, and the reaction rate tends to be increased and the polymerization time shortened. The reaction time is not particularly limited and may be, for example, about 0.5 to 36 hours, and preferably 1 to 24 hours.

[0283] The reaction between the diamine compound and the tetracarboxylic acid compound is preferably carried out in a solvent. The solvent is not particularly limited as long as it does not affect the reaction, and examples thereof include alcoholic solvents such as water, methanol, ethanol, ethylene glycol, isopropyl alcohol, propylene glycol, ethylene glycol methyl ether, ethylene glycol butyl ether, 1-methoxy-2-propanol, 2-butoxyethanol, and propylene glycol monomethyl ether; phenolic solvents such as phenol and cresol; ester solvents such as ethyl acetate, butyl acetate, ethylene glycol methyl ether acetate, propylene glycol methyl ether acetate, and ethyl lactate; lactone solvents such as γ-butyrolactone (hereinafter sometimes referred to as GBL) and γ-valerolactone; acetone, methyl ethyl ketone, cyclopentanone, cyclohexanone, 2-heptanone, methyl methyl ether ... Examples of suitable solvents include ketone-based solvents such as triisobutyl ketone; aliphatic hydrocarbon solvents such as pentane, hexane, and heptane; alicyclic hydrocarbon solvents such as ethylcyclohexane; aromatic hydrocarbon solvents such as toluene and xylene; nitrile-based solvents such as acetonitrile; ether-based solvents such as tetrahydrofuran and dimethoxyethane; chlorine-containing solvents such as chloroform and chlorobenzene; amide-based solvents such as N,N-dimethylacetamide (hereinafter sometimes referred to as DMAc) and N,N-dimethylformamide (hereinafter sometimes referred to as DMF); sulfur-containing solvents such as dimethyl sulfone, dimethyl sulfoxide, and sulfolane; carbonate-based solvents such as ethylene carbonate and propylene carbonate; pyrrolidone-based solvents such as N-methylpyrrolidone (hereinafter sometimes referred to as NMP); and combinations thereof. Among these, from the viewpoint of solubility, phenol-based solvents, lactone-based solvents, amide-based solvents, and pyrrolidone-based solvents are preferred, and amide-based solvents are more preferred.

[0284] In one embodiment of the present invention, the boiling point of the solvent used in the reaction of the diamine compound with the tetracarboxylic acid compound is preferably suitable for imidization conditions that are advantageous in terms of the flexural modulus and dielectric properties of the resulting laminate, and is preferably 230°C or lower, more preferably 200°C or lower, and even more preferably 180°C or lower, and is preferably 100°C or higher, and more preferably 120°C or higher.

[0285] The reaction of the diamine compound with the tetracarboxylic acid compound may be carried out, as necessary, in an inert atmosphere such as a nitrogen atmosphere or an argon atmosphere or under reduced pressure. It is preferable to carry out the reaction in an inert atmosphere, such as a nitrogen atmosphere or an argon atmosphere, in a strictly controlled dehydrated solvent while stirring.

[0286] The resulting PI resin precursor may be isolated once by a conventional method, but the reaction solution containing the PI resin precursor obtained by synthesis of the PI resin precursor may be appropriately diluted with a solvent as needed and used as a PI resin precursor solution without isolation.

[0287] (Coating and Pre-drying Steps) In the production of the laminate of the present invention, the coating and pre-drying steps are steps of applying a solution of a corresponding PI resin precursor onto the surface of a metal layer and pre-drying it to obtain a coating film (single-layer coating film or multi-layer coating film). When the PI film in the laminate is a laminate film, examples of the method include a method of applying a solution of a corresponding PI resin precursor onto the surface of the metal layer and pre-drying it multiple times to obtain a multi-layer coating film (sometimes referred to as a sequential pattern), and a method of applying a solution of a corresponding PI resin precursor onto each layer in a multi-layer laminated state by multi-layer extrusion and pre-drying it to obtain a multi-layer coating film (sometimes referred to as a simultaneous pattern). For example, in the case of a PI film (L) having a PI resin-containing layer (PI-2), a PI resin-containing layer (PI-1), and a PI resin-containing layer (PI-3) in this order, the sequential pattern may be a process in which a PI resin precursor solution corresponding to the PI resin-containing layer (PI-2) is applied onto the surface of a metal layer and pre-dried to form a coating film, a PI resin precursor solution corresponding to the PI resin-containing layer (PI-1) is applied onto the coating film and pre-dried to form a two-layer coating film, and a PI resin precursor solution corresponding to the PI resin-containing layer (PI-3) is applied onto the two-layer coating film and pre-dried to form a three-layer coating film. In addition, the simultaneous patterning may be a process in which a PI-based resin precursor solution corresponding to the PI-based resin-containing layer (PI-2), a PI-based resin precursor solution corresponding to the PI-based resin-containing layer (PI-1), and a PI-based resin precursor solution corresponding to the PI-based resin-containing layer (PI-3) are simultaneously applied onto the surface of a metal layer by multilayer extrusion or the like, and then pre-dried to form a three-layer coating film.

[0288] The solvent contained in the PI resin precursor solution may be any of the solvents exemplified for use in the reaction of a diamine compound with a tetracarboxylic acid compound in the production of a PI resin precursor, and is preferably a lactone solvent, an amide solvent, or a pyrrolidone solvent, more preferably an amide solvent. In one embodiment of the present invention, the boiling point of the solvent contained in the PI resin precursor solution is preferably suitable for imidization conditions that are advantageous in terms of the flexural modulus and dielectric properties of the resulting laminate, and is preferably 230°C or lower, more preferably 200°C or lower, even more preferably 180°C or lower, and particularly preferably 170°C or lower, and is preferably 100°C or higher, more preferably 120°C or higher.

[0289] The content of the PI resin precursor in the PI resin precursor solution is preferably 8% by mass or more, more preferably 10% by mass or more, even more preferably 12% by mass or more, particularly preferably 13% by mass or more, relative to the total amount of the PI resin precursor solution, and is preferably 30% by mass or less, more preferably 25% by mass or less, even more preferably 23% by mass or less, particularly preferably 20% by mass or less. When the content of the PI resin precursor is within the above range, excellent processability during film formation is achieved.

[0290] A coating film of a PI resin precursor solution can be formed by applying the PI resin precursor solution to a metal surface using a known coating or application method. Examples of known coating methods include roll coating methods such as wire bar coating, reverse coating, and gravure coating, die coating, comma coating, lip coating, spin coating, screen printing coating, fountain coating, dipping, spraying, curtain coating, slot coating, applicator coating, and drip molding. When the PI film in the laminate is a laminate film, the PI resin precursor solution may be applied to the metal surface layer by layer or in multiple applications to form multiple coating films of the PI resin precursor solution, or multiple layers of laminate coating films of the PI resin precursor solution may be formed simultaneously. Examples of methods for simultaneously forming multiple coating films include coextrusion and multilayer curtain coating.

[0291] In the coating and pre-drying steps, the coating speed of the PI resin precursor solution is preferably 0.1 m / min or more, more preferably 0.3 m / min or more, even more preferably 0.5 m / min or more, and is preferably 2.0 m / min or less, more preferably 1.0 m / min or less, and even more preferably 0.8 m / min or less. When the coating speed is within the above range, the hardness, average DMT elastic modulus, and average orientation parameter of the obtained laminate tend to be easily adjusted within the above ranges in combination with the standing step and thawing step described below.

[0292] In the coating and pre-drying steps, the temperature at which the coating film (preferably a multilayer coating film) is pre-dried is preferably 60° C. or higher, more preferably 70° C. or higher, even more preferably 80° C. or higher, still more preferably 90° C. or higher, and preferably 200° C. or lower, more preferably 150° C. or lower, and even more preferably 130° C. or lower. The pre-drying time is preferably 30 seconds or longer, more preferably 1 minute or longer, even more preferably 5 minutes or longer, and even more preferably 10 minutes or longer, and may be, for example, 15 minutes or longer, 20 minutes or longer, or 25 minutes or longer, and is preferably 24 hours or shorter, more preferably 12 hours or shorter, even more preferably 6 hours or shorter, and particularly preferably 1 hour or shorter. When the pre-drying temperature and pre-drying time are within the above ranges, the hardness, each average DMT modulus, or each average orientation parameter of the resulting laminate tends to be easily adjusted within the above ranges when combined with the standing step and thawing step described below.

[0293] (Standing Step) The standing step is a step in which the coating film (preferably a multilayer coating film) obtained in the coating and pre-drying steps is left standing. By subjecting the coating film to the standing step before the imidization step, sufficient solvent remains throughout the coating film at the time of imidization, or the resin layers tend to be well-mixed, thereby increasing the degree of freedom of the resin molecules until imidization. Although the reason is unclear, including such a standing step tends to make it easier to adjust the hardness, average DMT modulus, or average orientation parameter of the resulting laminate to within the above-mentioned ranges. Furthermore, the standing step is thought to facilitate mixing of the PI resins constituting each layer near the interface of each PI resin-containing layer, forming a mixed region near the interface, which tends to improve the mechanical properties of the resulting laminate.

[0294] In the standing step, the time for standing the coating film (also referred to as standing time) can be appropriately selected depending on the temperature at which it is stood (also referred to as standing temperature), and is not particularly limited, but is preferably 3 hours or more, more preferably 6 hours or more, even more preferably 12 hours or more, still more preferably 18 hours or more, and particularly preferably 22 hours or more. The upper limit of the standing time for the coating film is not particularly limited, and may usually be 450 hours or less, preferably 100 hours, more preferably 50 hours or less. When the standing time for the coating film is within the above range, the hardness, each average DMT elastic modulus, or each average orientation parameter of the obtained laminate tends to be more easily controlled within the above range, and the mechanical properties of the laminate can be improved.

[0295] In a preferred embodiment of the present invention, the standing step is preferably a step of standing (or storing) the coating film at a low temperature (preferably under refrigeration). Standing (or storing) at a low temperature tends to make it easier to control the hardness of the resulting laminate within the above range, and the mechanical properties of the laminate can be improved.

[0296] In the standing step, the standing temperature of the coating film is preferably 20°C or lower, more preferably 15°C or lower, even more preferably 10°C or lower, even more preferably 8°C or lower, and particularly preferably 5°C or lower. When the standing temperature of the coating film is below the above-mentioned upper limit, the hardness, each average DMT modulus, or each average orientation parameter of the resulting laminate tends to be more easily controlled within the above-mentioned ranges, and the mechanical properties of the laminate can be improved. Furthermore, the lower limit of the standing temperature of the multilayer coating film is usually −30°C or higher, preferably −20°C or higher, even more preferably −10°C or higher, even more preferably −5°C or higher, and particularly preferably 0°C or higher. The standing step may be carried out, for example, in air or an inert gas atmosphere, or in a sealed space. In one embodiment of the present invention, the standing step is preferably carried out with the coating film sealed. For example, it is preferable to place the coating film in a sealed container or laminate it with a film having low moisture permeability (e.g., an aluminum laminate film) and then stand it.

[0297] In a preferred embodiment of the present invention, after the standing step, the coating film is preferably allowed to stand (preferably in a sealed state) at a low temperature (e.g., 5°C or below) and then returned to room temperature (e.g., 20°C) (hereinafter, sometimes referred to as the "thawing step") before being subjected to the imidization step described below. The time for the thawing step is preferably 4 hours or more, more preferably 8 hours or more, even more preferably 12 hours or more, even more preferably 16 hours or more, and particularly preferably 20 hours or more. When the time for the thawing step is equal to or longer than the above-mentioned lower limit, the coating film is less likely to absorb moisture, and the well-ordered orientation of the PI resin surface upon standing at low temperature is less likely to be lost. This makes it easier to control the hardness, average DMT modulus, or average orientation parameter of the resulting laminate within the above-mentioned ranges, thereby improving the mechanical properties of the laminate, such as the flexural modulus. The time for the thawing step is typically 60 hours or less, or 48 hours or less. Examples of thawing methods include, when the standing step is carried out in a sealed state, a method in which the coating film that has been stood at low temperature is allowed to reach room temperature while still in a sealed state; when a refrigerator is used for the standing step, a method in which the power is turned off after the standing step is completed and the coating film is allowed to slowly return to room temperature while still in a sealed state; and a method in which the temperature is gradually raised to room temperature in a temperature-controllable device (e.g., a thermal shock test device, etc.).

[0298] (Imidization Step) The imidization step is a step of imidizing the PI resin in the coating film on the surface of the metal by heat treatment at a temperature of, for example, 200° C. or higher and 500° C. or lower.

[0299] In one embodiment of the present invention, the imidization step preferably includes a step of increasing the temperature from a low temperature (referred to as a first temperature) to a high temperature (referred to as a second temperature) at a relatively high rate and maintaining the temperature at that high temperature. By increasing the temperature at a relatively high rate, preferably rapidly, to proceed with imidization, and then maintaining the temperature at that temperature for a certain period of time to complete the imidization, this can be advantageous in terms of forming a higher-order structure or branched structure of the PI resin, and the resulting laminate can easily maintain a low Df and improve the flexural modulus. This can also be advantageous in terms of obtaining a smooth laminate.

[0300] In one embodiment of the present invention, the first temperature is preferably 20°C or higher and 50°C or lower, more preferably 25°C or higher and 35°C or lower, and the second temperature is preferably 200°C or higher and 450°C or lower, more preferably 250°C or higher and 400°C or lower, even more preferably 270°C or higher and 380°C or lower, particularly preferably 290°C or higher and 360°C or lower, and particularly preferably 300°C or higher and 350°C or lower, for example, 300°C or higher and 340°C or lower, 300°C or higher and 330°C or lower, or 310°C or higher and 320°C or lower. According to the laminate of the present invention, even when imidization is performed at a relatively low temperature, for example, 350°C or lower (preferably 320°C or lower), a high flexural modulus can be exhibited and Df can be reduced. Furthermore, when the imidization temperature is 350°C or lower (preferably 320°C or lower), thermal degradation of the copper layer can be suppressed even when a copper layer is used as the metal layer, making it easier to obtain a laminate with excellent high-frequency characteristics. The imidization temperature is preferably 200°C or higher, more preferably 210°C or higher, and even more preferably 220°C or higher, from the viewpoint of sufficiently improving the imidization rate, improving the flexural modulus, and reducing Df.

[0301] In one embodiment of the present invention, the temperature increase from the first temperature to the second temperature may be carried out in a single stage or in two or more stages. In one embodiment of the present invention, when the temperature increase from the first temperature to the second temperature is carried out in a single stage, the temperature increase rate is preferably 2°C / min or more, more preferably 3°C / min or more, even more preferably 4°C / min or more, and preferably 30°C / min or less, more preferably 20°C / min or less, even more preferably 10.5°C / min or less, and even more preferably 10°C / min or less. Adopting such a temperature increase rate can be advantageous in terms of forming a higher-order structure or branched structure of the PI resin, making it easier for the resulting laminate to maintain a low Df while improving its flexural modulus. It can also be advantageous in terms of obtaining a smooth laminate.

[0302] In one embodiment of the present invention, the temperature rise time from the first temperature to the second temperature can be appropriately selected depending on the temperature and the temperature rise rate, and is preferably 5 hours or less, more preferably 3 hours or less, even more preferably 2 hours or less, particularly preferably 1.5 hours or less, and is preferably 3 minutes or more, more preferably 10 minutes or more, and even more preferably 30 minutes or more. When the temperature rise time from the first temperature to the second temperature is within the above range, the resulting laminate tends to have an improved flexural modulus while maintaining a low Df.

[0303] In one embodiment of the present invention, the holding time at the second temperature is preferably 1 minute or more, more preferably 5 minutes or more, even more preferably 10 minutes or more, even more preferably 30 minutes or more, and preferably 5 hours or less, more preferably 3 hours or less, even more preferably 2 hours or less, and particularly preferably 1 hour or less. When the heating rate from the first temperature to the second temperature is within the above range and the holding time at the second temperature is within the above range, this can be advantageous in terms of forming a higher-order structure or branched structure of the PI resin, making it easier for the resulting laminate to maintain a low Df and improve its flexural modulus. Adopting the above-described imidization process, particularly a preferred imidization process (imidization temperature, heating rate, heating time, holding time, etc.), tends to make it easier to control the hardness, average DMT modulus, and average orientation parameter of the resulting laminate within the above ranges. The imidization process is preferably carried out under conditions of low oxygen concentration, and heat treatment may be carried out under inert atmosphere conditions such as nitrogen or argon, or under vacuum or reduced pressure conditions.

[0304] In one embodiment of the present invention, the imidization step preferably involves multiple heat treatments, and more preferably involves a heat treatment under vacuum conditions followed by a further heat treatment under a second higher temperature condition, which can prevent warping of the laminate and foaming of the coating film during the heat treatment and can uniformly form a higher-order structure and a branched structure of the PI resin on the surface of the PI film, thereby facilitating an improvement in the flexural modulus.

[0305] In one embodiment of the present invention, examples of a method for bonding a PI film and a metal layer include, as described in the section <PI Film Manufacturing Method>, a method in which a PI film is produced by cast molding, extrusion molding, or the like, and then the PI film is bonded to a metal layer by heat pressing, heat lamination, or the like. Alternatively, a method may be used in which a PI resin precursor solution is applied to a supporting substrate other than the metal layer contained in the laminate, and the resulting coating film of the PI resin precursor is dried, and then the resulting coating film of the PI resin precursor is peeled off from the substrate, and the peeled coating film of the PI resin precursor is bonded to a metal layer.

[0306] The method of providing the metal layer on the PI film may be the same on both sides or different on both sides.

[0307] In a preferred embodiment of the present invention, from the viewpoint of easily adjusting the hardness, each average DMT modulus, or each average orientation parameter within the above range and realizing a high flexural modulus, it is preferred to thermally imidize a coating film of a PI resin precursor on a metal layer to prepare a one-sided metal layer laminate, and then thermocompression-bond a metal layer to the side not having the metal layer, thereby forming a laminate having metal layers on both sides of the PI film. １ (°C), linear pressure is P (kN / m), and linear speed is Sp (m / min), [T １ × (P) １／２ When the value of [Sp / Sp] is 1800 or more, preferably 2000 or more, more preferably 2500 or more, further preferably 3500 or more, and particularly preferably 4000 or more, the adhesion to the metal layer is easily improved. ２ n (°C), and the holding time at the second temperature is Hn (hours), [T １ × (P) １／２ ÷Sp] / Σ[T ２ n × (Hn) １／２ ] is preferably 23 or less, more preferably 20 or less, even more preferably 15 or less, even more preferably 11.5 or less, particularly preferably 11 or less, and is preferably 3.0 or more, more preferably 5.0 or more, even more preferably more than 5.5, even more preferably 5.7 or more, particularly preferably 7.0 or more. １ × (P) １／２ ÷Sp] / Σ[T ２ n × (Hn) １／２ When the Σ[T ２ n × (Hn) １／２] is preferably 100 or more, more preferably 150 or more, even more preferably 300 or more, still more preferably 350 or more, and is preferably 700 or less, more preferably 600 or less, even more preferably 550 or less, and may be 500 or less. ２ n × (Hn) １／２ When the value of ] is within the above range, it is easy to prevent the PI film near the interface with the metal layer from becoming too hard, and it is easy to increase the flexural modulus of the obtained laminate.

[0308] In a fourth embodiment of the present invention, the second temperature in the imidization step is T ２ (°C), and the holding time at the second temperature is H (hours), [T １ × (P) １／２ ÷Sp] / [T ２ × (H) １／２ ] is preferably 23 or less, more preferably 21 or less, even more preferably 20 or less, and is preferably 8 or more, more preferably 10 or more, even more preferably 10.5 or more, even more preferably 12 or more, and particularly preferably 15 or more. ２ × (H) １／２ ÷Sp] / [T １ × (P) １／２ When [T] is within the above range, the resin near both interfaces of the laminate tends to maintain a high-order structure or a branched structure, which makes it easier to improve the bending modulus. Furthermore, by combining with the above-mentioned leaving step or thawing step, it is easy to adjust each average orientation parameter in the obtained laminate to fall within a predetermined range, which makes it easier to further improve the bending modulus. ２ × (H) １／２ ] is preferably 100 or more, more preferably 150 or more, even more preferably 200 or more, and is preferably 400 or less, more preferably 300 or less, even more preferably 250 or less, and may be 235 or less. ２ × (H) １／２ When the value of ] is within the above range, it is easy to prevent the PI film near the interface with the metal layer from becoming too hard, and it is easy to increase the flexural modulus of the obtained laminate.

[0309] [Flexible Printed Circuit Board] The laminate of the present invention has a high flexural modulus and can therefore be suitably used as an FPC board material. Furthermore, the laminate of the present invention can have a low Df, thereby reducing the transmission loss of an electrical circuit incorporating the laminate. Furthermore, the laminate of the present invention has a low CTE and excellent thermal properties, and can therefore be suitably used as an FPC board material, particularly as an FPC board material for high-speed communications such as 5G. Therefore, the present invention also encompasses a flexible printed circuit board comprising the laminate of the present invention.

[0310] The present invention will be described in more detail below based on examples and comparative examples, but the present invention is not limited to the following examples.

[0311] The abbreviations used in the examples and comparative examples represent the following compounds: BPDA: 3,3',4,4'-biphenyltetracarboxylic dianhydride BP-TME: 4,4'-bis(1,3-dioxo-1,3-dihydroisobenzofuran-5-ylcarbonyloxy)biphenyl PMDA: pyromellitic anhydride m-Tb: 4,4'-diamino-2,2'-dimethylbiphenyl TPE-Q: 1,4-bis(4-aminophenoxy)benzene TPE-R: 1,3-bis(4-aminophenoxy)benzene DMAc: N,N-dimethylacetamide

[0312] 1. Preparation of Polyimide Resin Precursor Solution (1) Polyimide Resin Precursor Solution 1: 48.61 g (228.9 mmol) of m-Tb and 66.92 g (228.9 mmol) of TPE-Q were dissolved in 1598 g of DMAc, and then 118.22 g (221.2 mmol) of BP-TME was added and stirred for 1 hour at 20°C under a nitrogen atmosphere. 48.25 g (221.2 mmol) of PMDA was then added and stirred for 3 hours at 20°C under a nitrogen atmosphere to obtain PI resin precursor solution 1. The molar ratio of diamine monomer to acid dianhydride monomer used was 1.04.

[0313] (2) Polyimide-based resin precursor solution 2: 11.22 g (52.9 mmol) of m-Tb and 15.45 g (52.9 mmol) of TPE-R were dissolved in 405 g of DMAc, and then 21.67 g (73.7 mmol) of BPDA and 6.89 g (31.6 mmol) of PMDA were added in that order, followed by stirring for 3 hours at 20°C under a nitrogen atmosphere to obtain PI-based resin precursor solution 2. The molar ratio of the diamine monomer to the acid dianhydride monomer used was 1.005.

[0314] 2. Preparation of Laminate and Resin Film (Example 1) PI resin precursor solution 2 was applied to the roughened surface (10-point average roughness; RzJIS = 0.34 μm) of an electrolytic copper foil (thickness 12 μm) at a speed of 0.6 m / min to a dry thickness of 5 μm, to obtain a coating film. The coating film was dried by heating at 120°C for 10 minutes, and PI resin precursor solution 1 was applied to the dried coating film at a speed of 0.6 m / min to a dry thickness of 41 μm, to obtain a two-layer laminate coating film. The two-layer laminate coating film was dried by heating at 120°C for 30 minutes, and PI resin precursor solution 2 was applied to the dried two-layer laminate coating film at a speed of 0.6 m / min to a dry thickness of 5 μm, to obtain a three-layer laminate coating film. The three-layer laminate coating film was heated at 120°C for 30 minutes to dry, and then a laminate consisting of the copper foil and the three-layer laminate coating film was placed in a sealed container and left to stand for 24 hours in an environment at 4°C. The laminate was then left in the sealed container for 24 hours in an environment at 25°C, returned to room temperature, and then removed from the sealed container. The removed laminate was fixed to a metal frame and heated in vacuum at 300°C for 30 minutes using a vacuum dryer. The temperature was then raised from 30°C to 340°C over 30 minutes in a nitrogen atmosphere with an oxygen concentration of 0.02%, and then heated at 340°C for 30 minutes to obtain a single-sided copper foil laminate 1 consisting of a PI resin-containing layer and a copper foil layer, in which the copper foil layer, layer (PI-2) (copper foil layer side), layer (PI-1), and layer (PI-3) (TPI layer, mPI layer, and TPI layer) were laminated in this order. The layer (PI-3) side of the obtained single-sided copper foil laminate 1 was bonded to the roughened side (10-point average roughness; RzJIS = 0.34 μm) of an electrolytic copper foil (thickness 12 μm) under conditions of a temperature of 310°C, a linear pressure of 60.7 kN / m, and a linear speed of 1 m / min to produce a double-sided copper foil laminate 1. The obtained double-sided copper foil laminate 1 was immersed in a large volume of a 40% by mass aqueous ferric chloride solution at room temperature for 10 minutes, and then the aqueous ferric chloride solution was washed with pure water. After visually confirming that no copper remained, the laminate was dried at 80°C for 1 hour to obtain a resin film 1 composed of layer (PI-2) (copper foil layer side), layer (PI-1), and layer (PI-3) (TPI layer, mPI layer, and TPI layer) laminated in this order. The thickness of the resin film 1 was 51 μm.The PI resin precursor solution was applied using an automatic coating device (manufactured by Tester Sangyo Co., Ltd., PI-1210) equipped with an applicator (manufactured by Tester Sangyo Co., Ltd., SA-204 (width 250 mm)).

[0315] Example 2 A double-sided copper foil laminate 2 consisting of a PI resin-containing layer and copper foil, which were formed by laminating copper foil, layer (PI-2) (copper foil layer side), layer (PI-1), layer (PI-3) (TPI layer, mPI layer, and TPI layer), and copper foil in this order, and a resin film 2 from which the copper foil had been removed were obtained in the same manner as in Example 1, except that the layers were coated so that the dry thicknesses of layer (PI-2) (copper layer side) / layer (PI-1) / layer (PI-3) were 5 μm / 40 μm / 5 μm, and the temperature was raised from 30° C. to 320° C. over 30 minutes in a nitrogen atmosphere with an oxygen concentration of 0.02%, and then heated at 320° C. for 30 minutes.

[0316] Example 3 A laminate consisting of a copper foil and a three-layer laminate coating film was heated from 30°C to 330°C over 30 minutes in a nitrogen atmosphere with an oxygen concentration of 0.02%, and then heated at 330°C for 60 minutes. The layer (PI-3) side of the obtained single-sided copper foil laminate was bonded to the roughened side (10-point average roughness; RzJIS=0.34µm) of an electrolytic copper foil (thickness 12µm) under conditions of a temperature of 300°C, a linear pressure of 150kN / m, and a linear speed of 1m / min. A double-sided copper foil laminate 3 consisting of a PI resin-containing layer and copper foil laminated in the order of copper foil, layer (PI-2) (copper foil layer side), layer (PI-1), layer (PI-3) (TPI layer, mPI layer, and TPI layer), and copper foil, and a resin film 3 from which the copper foil had been removed were obtained in the same manner as in Example 1, except that

[0317] Example 4 A laminate consisting of a copper foil and a three-layer laminate coating film was heated from 30°C to 320°C over 30 minutes in a nitrogen atmosphere with an oxygen concentration of 0.02% without heat treatment in a vacuum, and then heated at 320°C for 60 minutes, and the layer (PI-3) side of the obtained single-sided copper foil laminate was bonded to the roughened side (10-point average roughness; RzJIS=0.34μm) of an electrolytic copper foil (thickness 12μm) under conditions of a temperature of 310°C, a linear pressure of 150 kN / m, and a linear speed of 1 m / min. In the same manner as in Example 2, except that the copper foil, layer (PI-2) (copper foil layer side), layer (PI-1) and layer (PI-3) (TPI layer, mPI layer and TPI layer) were laminated in this order, and a double-sided copper foil laminate 4 consisting of a PI resin-containing layer and copper foil, and a resin film 4 from which the copper foil had been removed were obtained.

[0318] Example 5 A double-sided copper foil laminate 5 consisting of a PI-based resin-containing layer and copper foil, which were formed by laminating the copper foil, layer (PI-2) (copper foil layer side), layer (PI-1) and layer (PI-3) (TPI layer, mPI layer and TPI layer) in this order, and a resin film 5 from which the copper foil had been removed were obtained in the same manner as in Example 2, except that the layer (PI-3) side of the single-sided copper foil laminate and the roughened side (10-point average roughness; RzJIS=0.34 μm) of an electrolytic copper foil (thickness 12 μm) were bonded under conditions of a temperature of 340° C., a linear pressure of 150 kN / m and a linear speed of 1 m / min.

[0319] Comparative Example 1 A double-sided copper foil laminate 6 consisting of a copper foil and a PI-based resin-containing layer formed by laminating copper foil, layer (PI-2) (copper foil layer side), layer (PI-1) and layer (PI-3) (TPI layer, mPI layer and TPI layer) in this order, and a resin film 6 from which the copper foil was removed were obtained in the same manner as in Example 2, except that the laminate cooled to a temperature of 4°C was removed from the sealed container, left to stand at room temperature for 2 hours, and after confirming that the laminate had reached room temperature, the temperature was raised from 30°C to 360°C over 30 minutes in a nitrogen atmosphere with an oxygen concentration of 0.02%, and then heated at 360°C for 5 minutes.

[0320] Measurements and evaluations were carried out on the double-sided copper foil laminates 1 to 6 and resin films 1 to 6 obtained in the examples and comparative examples. The measurement and evaluation methods are explained below. Note that when referring to side A and side B of a laminate, the copper foil side coated with the PI resin precursor solution in the manufacturing method of each laminate is referred to as side A, and the copper foil side thermocompression bonded is referred to as side B.

[0321] <Film Thickness Measurement> A 5 ​​mm x 5 mm arbitrary portion was cut out from each of the resin films 1 to 6 obtained in the Examples and Comparative Examples, and embedded in resin to prepare a film thickness measurement sample. The prepared film thickness measurement sample was cut using a microtome to prepare a measurement cross section, and the thickness of each of the three PI resin-containing layers and the thickness of the resin film were measured using a laser microscope under the following conditions. Apparatus: LEXT OLS4100 manufactured by Olympus Corporation Observation magnification: 100x

[0322] <Measurement of Df and Dk> Measurement samples of 50 mm x 50 mm were cut out from each of the resin films 1 to 6 obtained in the Examples and Comparative Examples, and Df and Dk were measured under the following conditions. The measurements were carried out after conditioning the measurement samples at 23°C / 50% RH for 24 hours. Apparatus: Compact USB Vector Network Analyzer (product name: MS46122B) manufactured by Anritsu Corporation Cavity resonator (TE mode 10 GHz type) manufactured by AET Corporation Measurement frequency: 10 GHz Measurement atmosphere: 23°C / 50% RH

[0323] <Measurement of coefficient of linear expansion (CTE)> The CTE of resin films 1 to 6 obtained in the examples and comparative examples was measured using a thermomechanical analyzer TMA under the following conditions, and the CTE was calculated from 50°C to 100°C. Apparatus: TMA / SS7100 manufactured by Hitachi High-Tech Science Corporation Load: 50.0 mN Temperature program: temperature increased from 20°C to 130°C at a rate of 5°C / min Test piece: length 40 mm, width 5 mm

[0324] <Measurement of Storage Modulus> The storage modulus of each PI resin formed from the above PI resin precursor solutions 1 and 2 was determined by measuring the storage modulus of a PI resin film prepared by the following method under the following conditions. Each PI resin precursor solution was cast onto a glass substrate to a dry thickness of 30 μm to form a coating film of the PI resin precursor solution. The coating film was heated at 120°C for 30 minutes, and the resulting film was peeled from the glass substrate and then fixed to a metal frame. The film fixed to the metal frame was maintained at 320°C for 5 minutes in an atmosphere with an oxygen concentration of 1%, yielding a PI resin film. The storage modulus (E') was determined using a dynamic viscoelasticity measuring device (DVA-220, manufactured by IT Measurement & Control Co., Ltd.) under the following sample and conditions. Test piece: rectangular parallelepiped with a length of 40 mm, a width of 5 mm, and a thickness of 30 μm. Experimental mode: single frequency, constant rate heating. Experimental style: tensile sample grip length: 15 mm. Measurement start temperature: room temperature to 342°C. Heating rate: 5°C / min. Frequency: 10 Hz. Static / dynamic stress ratio: 1.8. As a result of measurement using the above method, the PI resin film formed from the PI resin precursor solution 1 had a storage modulus of 2.3 × 10 at 40°C. ９ Pa, storage modulus at 300°C is 2.8 × 10 ８ The PI resin film formed from the PI resin precursor solution 2 had a storage modulus of 2.3 × 10 at 40 °C. ９ Pa, storage modulus at 300°C is 1.2 × 10 ７ It was Pa.

[0325] <Measurement of Martens Hardness and Vickers Hardness of Laminate> Two 50 mm x 50 mm films were cut from adjacent positions from each of the double-sided copper foil laminates 1 to 6 obtained in the Examples and Comparative Examples, and measurement samples were prepared by fixing the films with the measurement surface facing up to a glass plate with tape. The Martens hardness and Vickers hardness were measured at arbitrary locations on one side (side A) and the other side (side B) of the double-sided copper foil laminate using a Fischer Instruments "FISCHERSCOPE HM2000" under the following conditions, and the average values ​​of three measurement data points with a maximum indentation depth of 18 mm to 35 mm (a depth of 12% to 46% of the thickness of the PI resin-containing layer) were used. Analysis software: Win-HCU ver. 8.5.0.0 Measurement environment: 23°C, 50% RH Indenter used: Vickers indenter VV1048 (facing angle of the tip of the square pyramid: 136°) Loading speed: 3.33 μm / sec Maximum load: 1000 mN Loading time: 15 sec Holding time: 5 sec

[0326] <Measurement of flexural modulus> Two 100 mm x 10 mm films were cut out from adjacent positions from each of the double-sided copper foil laminates 1 to 6 obtained in the Examples and Comparative Examples to prepare measurement samples. The flexural modulus was measured on both sides of the double-sided copper foil laminate in accordance with JIS K7171 using a "Desktop Precision Universal Testing Machine Autograph AGS-1kNX" manufactured by Shimadzu Corporation under the following conditions, and the average value was used. Distance between two supports: 20 mm Measurement environment: 23°C, 50% RH Test speed: 1 mm / min

[0327] <Measurement of Resin with Nanoindenter> A portion of each laminate obtained in the Examples and Comparative Examples was cut and embedded in resin so that the cross section in the thickness direction was visible. Next, a glass knife was attached to an ultramicrotome (Leica, "Leica EM UC7"), and after reaching the surface of the resin-embedded laminate, the test piece was cut to a depth of 100 μm or more. Then, a SYM knife (Syntec, "SYM2045 Ultra") was attached, and the test piece was cut to a depth of 1 μm at a scanning speed of 0.6 mm / s and a processing depth of 100 nm per scan. Further, the test piece was cut to a depth of 1 μm at a scanning speed of 0.6 mm / s and a processing depth of 50 nm per scan. Finally, the test piece was cut to a depth of 0.3 μm at a scanning speed of 0.3 mm / s and a processing depth of 30 nm per scan. Under the following conditions, load-displacement curves were obtained in accordance with ISO 14577 at three points in the thickness direction of the polyimide film of each laminate: the center; a portion 2 μm inward from the interface between the polyimide film and one metal layer (side A); and a portion 2 μm inward from the interface between the polyimide film and the other metal layer (side B). Martens hardness, elastic deformation power, creep deformation rate, and elastic deformation work were calculated. Apparatus: ENT2100 (ELIONIX) Test mode: Indentation depth setting Test indenter shape: Berkovich Pressurization conditions Starting load: 0 mN Ending load: 1.0 mN Indentation depth: 200 nm Pressurization end condition: When either the end load or indentation depth condition is reached Step interval: 20 ms Holding conditions Maximum load holding: Yes Holding time: 20,000 ms Unloading conditions Starting load: 1.0 mN Ending load: 0 mN Step interval: 20 ms Analysis Indenter tip correction method: Oliver method Unloading fitting method: Power law method (20-95%)

[0328] The results of each measurement are shown in Tables 1 and 2.

[0329]

[0330]

[0331] <Measurement of Average DMT Elastic Modulus> (1) Preparation of Measurement Samples (i) Preparation of Curved Samples Two silicone sheets measuring 50 mm long x 50 mm wide x 1 mm thick were prepared. A cavity measuring 8 mm long x 20 mm wide was created near the center of one of the sheets, and the sheets were then bonded together to create a mold with a depth of 1 mm. Next, strip samples measuring 20 mm long x 4 mm wide were cut out from the double-sided copper foil laminates 1 to 6 obtained in the Examples and Comparative Examples, and placed in a bent state with both ends aligned in the mold. Epoxy resin was poured into the cavity containing the laminate sample, and the sample was then covered with a silicone sheet, fixed with a weight, and left to stand at room temperature for two days. A curved sample with side A positioned on the inside of the curve and a curved sample with side B positioned on the inside of the curve were prepared.

[0332] (ii) Preparation of Planar Samples A portion of each of the double-sided copper foil laminates 1 to 6 obtained in the Examples and Comparative Examples was cut and embedded in epoxy resin so that the cross section in the thickness direction could be seen, thereby preparing a planar sample.

[0333] (iii) Cross-section preparation The curved sample and the flat sample were each attached to an AFM sample holder (manufactured by Leica), and the holder was attached to an ultramicrotome (manufactured by Leica, "Leica EM UC7"). First, a glass knife was used to scan the blade perpendicular to the laminate, and after reaching the side of the resin-embedded laminate, the test piece was cut 1 μm in the depth direction under the conditions of a scanning speed of 0.6 mm / sec and a processing depth of 100 nm per scan, further cut 1 μm in the depth direction under the conditions of a scanning speed of 0.6 mm / sec and a processing depth of 50 nm per scan, and finally cut 0.3 μm in the depth direction under the conditions of a scanning speed of 0.3 mm / sec and a processing depth of 30 nm per scan.

[0334] (2) Evaluation of Curvature Radius The DMT elastic modulus of the curved samples was measured in a region with a curvature radius of 400 nm, determined according to the following method. (i) Method for Determining Curvature Radius The curvature radius of the curved samples of double-sided copper foil laminates 1 to 6 was determined according to the following procedure. First, an optical microscope image of the cut cross section of the laminate of the curved sample was obtained using a measuring laser microscope (OLYMPUS LEXT OLS4000) under the following conditions. Apparatus: LEXT OLS4000 (OLYMPUS) Objective lens: MPLAPONLEXT10 Scanning mode: Color snapshot Image size: 128 μm × 128 μm (1024 × 1024) Contrast correction: None

[0335] Next, using the image processing software LEXT OLS4100 (OLYMPUS; ver. 3.1.15.1), point 1 was arbitrarily set on the outer contour of the metal layer located outside the curved portion near the center of the curved portion in the obtained optical microscope image, as shown in Figure 3, and then points 2 and 3 were set on the outer contour at the same linear distance from point 1. A circle was created that passed through these three points and whose outer periphery overlapped the outer contour, and the radius of this circle was calculated as the radius of curvature of point 1. By changing the positions of the three points, point 1 was set so that the radius of curvature was approximately 400 μm, and this point was designated as the point where the radius of curvature on the curved sample was 400 μm.

[0336] (3) Obtaining Elastic Modulus Image and Average DMT Elastic Modulus by SPM Mechanical properties of the sample cross section were evaluated under the following conditions, and the DMT elastic modulus (GPa) of each sample of double-sided copper foil laminates 1 to 6 was calculated based on the DMT (Derjaguim-Muller-Toporov) theory to obtain a DMT elastic modulus image. Next, based on the DMT elastic modulus image, the position of the measurement region for the average DMT elastic modulus was determined, and the average DMT elastic modulus was calculated from the DMT elastic moduli obtained at multiple measurement points within that range.

[0337] Specifically, a 10 μm × 10 μm measurement range was set on the sample cross section to capture a DMT elastic modulus image, encompassing the metal layer and the PI film. Within this measurement range, the displacement of the piezo scanner and the amount of cantilever warpage during contact between the cantilever probe and the sample were measured, yielding a curve (force curve) showing the relationship between the load F and the sample deformation δ. For each measurement point, the force curve was analyzed using the DMT theoretical formula for the pullback process (from the point at which the cantilever probe was pressed into the sample up to the preset maximum load until the probe completely separated from the sample surface, i.e., the process from point C to point D to point E as shown in Figure 4 ). The DMT elastic modulus during the pullback process was calculated.

[0338] In the analysis, analysis software (NanoScope Analysis ver. 2.00) was used, and when the numerical values ​​from the minimum to the maximum F value during the pullback process of the force curve were replaced with nu...

Claims

1. A laminate comprising a polyimide film containing a polyimide resin and metal layers provided on both sides of the film, wherein when an indenter is pressed from the surface of the metal layer of the laminate in the thickness direction of the laminate, the maximum indentation depth exceeds the thickness of the metal layer on the side where the indenter is pressed and is 10% to 50% of the thickness of the polyimide film, and when the Vickers hardness and Martens hardness are measured on both sides of the laminate in accordance with ISO 14577, the laminate satisfies the relationship of formula (I): PV / PM≦0.135 (I) [wherein PV represents the difference between the Vickers hardness measured on one side of the laminate and the Vickers hardness measured on the other side, and PM represents the difference between the Martens hardness measured on one side of the laminate and the Martens hardness measured on the other side].

2. The laminate of claim 1, wherein the PV is 9.5 or less.

3. The laminate according to claim 1 or 2, wherein the PM is 70.0 or less.

4. A laminate comprising a polyimide film containing a polyimide resin and metal layers provided on both sides of the film, wherein the average Martens hardness of the polyimide film measured in accordance with ISO 14577 at three points in a cross section of the laminate in the thickness direction, namely, the center of the polyimide film in the thickness direction, a position 0.5 to 5 μm from the interface between the polyimide film and one metal layer, and a position 0.5 to 5 μm from the interface between the polyimide film and the other metal layer, is 0.35 GPa or more, and the standard deviation of the elastic deformation power is 2.50% or less.

5. The laminate according to claim 4, wherein the average creep deformation rate of the polyimide film is 11.20% or less when held for 20 seconds under an indentation load of 1 mN as measured in accordance with ISO 14577 at three points in a cross section of the laminate in the thickness direction: the center in the thickness direction of the polyimide film; a position 0.5 to 5 μm from the interface between the polyimide film and one metal layer; and a position 0.5 to 5 μm from the interface between the polyimide film and the other metal layer.

6. The laminate according to claim 4, wherein the standard deviation of the elastic deformation work of the polyimide film measured in accordance with ISO 14577 at three points in a cross section of the laminate in the thickness direction: the center in the thickness direction of the polyimide film; a position 0.5 to 5 μm from the interface between the polyimide film and one metal layer; and a position 0.5 to 5 μm from the interface between the polyimide film and the other metal layer; is 3.00 mN-nm or less.

7. A laminate comprising a polyimide film containing a polyimide resin and metal layers provided on both sides of the film, wherein when one metal layer surface of the laminate is designated as surface A and the other metal layer surface is designated as surface B, the average elastic modulus measured by a scanning probe microscope in a cross section in the thickness direction of the laminate is expressed by formula (II) and formula (III): |1-EAa / EBa|≦0.12 (II) |1-EAb / EBb|≦0.12 (III) [wherein EAa, EBa, EAb and EBb are respectively the average elastic modulus in the process of pulling back the cantilever probe, and EAa represents the average elastic modulus of the polyimide film measured at a position 0.5 to 5 μm from the interface between the metal layer on surface A and the polyimide film when the laminate is bent with a curvature radius of 400 μm with surface A facing inward, a laminate satisfying the relationships: EBa represents the average elastic modulus of the polyimide film measured at a position 0.5 to 5 μm from the interface between the metal layer and the polyimide film on the A-side when the laminate is bent with a radius of curvature of 400 μm, with the B-side facing inward; EAb represents the average elastic modulus of the polyimide film measured at a position 0.5 to 5 μm from the interface between the metal layer and the polyimide film on the B-side when the laminate is bent with a radius of curvature of 400 μm, with the A-side facing inward; and EBb represents the average elastic modulus of the polyimide film measured at a position 0.5 to 5 μm from the interface between the metal layer and the polyimide film on the B-side when the laminate is bent with a radius of curvature of 400 μm, with the B-side facing inward.

8. The laminate according to claim 7, which satisfies the relationship of formula (IV): |1-EAa / EBb|+|1-EBa / EAb|≦0.25 (IV) [wherein EAa, EBb, EBa and EAb are as defined above].

9. The laminate according to claim 7, which satisfies the relationship of formula (V): |Era - Erb|≦0.34 (V) [wherein Era and Erb are each the average elastic modulus in the process of pulling back the cantilever probe, Era represents the average elastic modulus of the polyimide film measured at a position 0.5 to 5 μm from the interface between the metal layer and the polyimide film on the A-side side in a cross section in the thickness direction of the laminate in a flat state, and Erb represents the average elastic modulus of the polyimide film measured at a position 0.5 to 5 μm from the interface between the metal layer and the polyimide film on the B-side side in a cross section in the thickness direction of the laminate in a flat state].

10. The laminate according to claim 7, which satisfies the relationship of formula (VI): Erc / Eac≦1.80 (VI) [wherein Erc represents the average elastic modulus during the retraction process of the cantilever probe at the center in the thickness direction of the polyimide film in a cross section in the thickness direction of the laminate in a planar state, and Eac represents the average elastic modulus during the pressing process of the cantilever probe at the center in the thickness direction of the polyimide film in a cross section in the thickness direction of the laminate in a planar state].

11. Formula (VII): |(EAa / EaAa)-(EBb / EaBb)|+|(EBa / EaBa)-(EAb / EaAb)|≦0.48 (VII) [wherein EaAa, EaBa, EaAb, and EaBb are average elastic moduli during the indentation process of the cantilever probe, and EaAa represents the average elastic modulus of the polyimide-based film measured at a position 0.5 to 5 μm from the interface between the metal layer on the A-side side and the polyimide-based film in a cross section in the thickness direction of the laminate when the laminate is bent with a curvature radius of 400 μm with the A-side facing inward, EaBa represents the average elastic modulus of the polyimide-based film measured at a position 0.5 to 5 μm from the interface between the metal layer on the A-side side and the polyimide-based film in the cross section of the laminate in the thickness direction when the laminate is bent with a radius of curvature of 400 μm with the B-side facing inward; EaAb represents the average elastic modulus of the polyimide-based film measured at a position 0.5 to 5 μm from the interface between the metal layer on the B-side side and the polyimide-based film in the cross section of the laminate in the thickness direction when the laminate is bent with a radius of curvature of 400 μm with the A-side facing inward; EaBb represents the average elastic modulus of the polyimide-based film measured at a position 0.5 to 5 μm from the interface between the metal layer on the B-side side and the polyimide-based film in the cross section of the laminate in the thickness direction when the laminate is bent with a radius of curvature of 400 μm with the B-side facing inward; and EAa, EBb, EBa and EAb are as defined above. The laminate according to claim 7 , which satisfies the relationship:

12. Equation (VIII) and Equation (IX): wrBa / wra≦1.250 (VIII) wrAb / wrb≦1.250 (IX) [wherein wrBa, wra, wrAb, and wrb are the standard deviations of adhesion energy in the process of pulling back the cantilever probe, wrBa represents the standard deviation of adhesion energy of the polyimide-based film measured at a position 0.5 to 5 μm from the interface between the metal layer on the A-side and the polyimide-based film in a cross section in the thickness direction of the laminate when the laminate is bent with a curvature radius of 400 μm with the B-side facing inward, and wra represents the standard deviation of adhesion energy of the polyimide-based film measured at a position 0.5 to 5 μm from the interface between the metal layer on the A-side and the polyimide-based film in a cross section in the thickness direction of the laminate in a flat state, The laminate according to claim 7, wherein wrAb represents the standard deviation of adhesion energy of the polyimide-based film measured at a position 0.5 to 5 μm from the interface between the metal layer on the side B and the polyimide-based film in a cross section in the thickness direction of the laminate when the laminate is curved with a radius of curvature of 400 μm with the side A facing inward, and wrb represents the standard deviation of adhesion energy of the polyimide-based film measured at a position 0.5 to 5 μm from the interface between the metal layer on the side B and the polyimide-based film in a cross section in the thickness direction of the laminate in a flat state.

13. A laminate comprising a polyimide film containing a polyimide resin and metal layers provided on both sides of the film, wherein one metal layer surface of the laminate is designated as surface A and the other metal layer surface is designated as surface B, the average orientation parameter measured using a laser Raman spectrometer in a cross section of the laminate in the thickness direction is expressed by the following formula (XI): |1-PAa / Pa|+|1-PBb / Pb|≦1.10 (XI) In formula (XI), PAa represents the average orientation parameter of the polyimide film measured at a position 0.5 to 5 μm in the thickness direction from the interface between the metal layer and the polyimide film on the surface A side when the laminate is bent with a curvature radius of 400 μm with the surface A facing inward, and Pa represents the average orientation parameter of the polyimide film measured at a position 0.5 to 5 μm in the thickness direction from the interface between the metal layer and the polyimide film on the surface A side when the laminate is in a flat state, PBb represents the average orientation parameter of the polyimide-based film measured at a position 0.5 to 5 μm from the interface between the metal layer and the polyimide-based film on the B-side in the thickness direction when the laminate is curved with a curvature radius of 400 μm with the B-side facing inward, and Pb represents the average orientation parameter of the polyimide-based film measured at a position 0.5 to 5 μm from the interface between the metal layer and the polyimide-based film on the B-side in the thickness direction when the laminate is in a flat state, and each of the average orientation parameters is －１ Peak intensity around 1615 cm in a polarization configuration coinciding with the thickness direction of the laminated film －１ The average of the orientation parameters represented by the peak intensities around the peak intensity (peak intensity around the peak intensity) satisfies the relationship:

14. The laminate according to claim 13, wherein |1-PAa / Pa| and |1-PBb / Pb| in formula (XI) are each 0.52 or less.

15. The average orientation parameter of the cross section of the laminate in the thickness direction is expressed by the formula (XII): |1-PBa / Pa|+|1-PAb / Pb|≦1.40 (XII) [In formula (XII), PBa represents the average orientation parameter of the polyimide film measured at a position 0.5 to 5 μm in the thickness direction from the interface between the metal layer and the polyimide film on the surface A side when the laminate is bent with a radius of curvature of 400 μm, with the surface B facing inward, PAb represents the average orientation parameter of the polyimide film measured at a position 0.5 to 5 μm in the thickness direction from the interface between the metal layer and the polyimide film on the surface B side when the laminate is bent with a radius of curvature of 400 μm, with the surface A facing inward, and each of the average orientation parameters is expressed by the formula (XII): |1-PBa / Pa|+|1-PAb / Pb|≦1.40 (XII) [In formula (XII), PBa represents the average orientation parameter of the polyimide film measured at a position 0.5 to 5 μm in the thickness direction from the interface between the metal layer and the polyimide film on the surface B side when the laminate is bent with a radius of curvature of 400 μm, with the surface A facing inward, －１ Peak intensity around 1615 cm in a polarization configuration coinciding with the thickness direction of the laminated film －１ The laminate according to claim 13, wherein the average of the orientation parameters represented by the peak intensities around the peak intensities is 0.

015.

16. The average orientation parameter of the cross section of the laminate in the thickness direction is expressed by the formula (XIII): |1-PAc / Pc|+|1-PBc / Pc|≦0.70 (XIII) [In formula (XIII), PAc represents the average orientation parameter of the polyimide film measured at the center position in the thickness direction of the polyimide film when the laminate is bent with a curvature radius of 400 μm with the A surface facing inward, Pc represents the average orientation parameter of the polyimide film measured at the center position in the thickness direction of the polyimide film in the planar laminate, PBc represents the average orientation parameter of the polyimide film measured at the center position in the thickness direction of the polyimide film when the laminate is bent with a curvature radius of 400 μm with the B surface facing inward, and each of the average orientation parameters is expressed by the formula (XIII): |1-PAc / Pc|+|1-PBc / Pc|≦0.70 (XIII) －１ Peak intensity around 1615 cm in a polarization configuration coinciding with the thickness direction of the laminated film －１ The laminate according to claim 13, wherein the average of the orientation parameters represented by the peak intensities around the peak intensities is 0.

015.

17. The laminate according to claim 1, 4, 7 or 13, wherein the linear expansion coefficient of the polyimide film is 10 to 29 ppm / K.

18. The laminate according to claim 1, 4, 7 or 13, wherein the polyimide-based film comprises a polyimide-based resin-containing layer (PI-1) and a polyimide-based resin-containing layer (PI-2).

19. The laminate according to claim 18, wherein the thickness of the polyimide-based resin-containing layer (PI-2) is 0.05 to 0.3 times the thickness of the polyimide-based resin-containing layer (PI-1).

20. The laminate according to claim 18, wherein the polyimide film further comprises a polyimide resin-containing layer (PI-3).

21. The polyimide resin contained in the polyimide resin-containing layer (PI-1), the polyimide resin contained in the polyimide resin-containing layer (PI-2), and the polyimide resin contained in the polyimide resin-containing layer (PI-3) each have a storage modulus at 40°C of 1.0 × 10 ９ The laminate according to claim 20, wherein the modulus is 100 Pa or more.

22. At least one of the polyimide-based resin-containing layer (PI-1) and the polyimide-based resin-containing layer (PI-2) contains a polyimide-based resin having a structural unit (A) derived from a tetracarboxylic acid anhydride, and the structural unit (A) is represented by the formula (A1): [In formula (A1), R ａ１ each independently represent a halogen atom, or an alkyl group, alkoxy group, aryl group, or aryloxy group which may have a halogen atom, and k represents an integer of 0 to 2], and / or a structural unit (A1) derived from a tetracarboxylic acid anhydride represented by formula (A2): [In formula (A2), R ａ２ each independently represent a halogen atom, or an alkyl group, alkoxy group, aryl group, or aryloxy group which may have a halogen atom, and each 1 is independently an integer of 0 to 3.

23. At least one of the polyimide-based resin-containing layer (PI-1) and the polyimide-based resin-containing layer (PI-2) contains a polyimide-based resin having a diamine-derived structural unit (B), and the structural unit (B) is represented by the formula (B1): [In formula (B1), R ｂ１ each independently represents a halogen atom, or an alkyl group, alkoxy group, aryl group, or aryloxy group which may have a halogen atom; W each independently represents -O-, -CH ２ -, -CH ２ -CH ２ -, -CH(CH ３ ) -, -C(CH ３ ) ２ -, -C(CF ３ ) ２ -, -COO-, -OOC-, -SO-, -SO ２ -, -S-, -CO-, -N(R ｃ )- and -CONH-, or a single bond (where m is 2 or more and at least one W is the divalent linking group); R ｃ represents a hydrogen atom or a monovalent hydrocarbon group having 1 to 12 carbon atoms which may be substituted with a halogen atom; m represents an integer of 1 to 4; and q each independently represents an integer of 0 to 4.

24. At least the polyimide-based resin-containing layer (PI-1) contains a polyimide-based resin having a structural unit (A) derived from a tetracarboxylic acid anhydride, and the structural unit (A) is represented by the formula (A3): [In formula (A3), Z represents a divalent organic group, R ａ３ each independently represent a halogen atom, or an alkyl group, alkoxy group, aryl group, or aryloxy group which may have a halogen atom; and each s independently represent an integer of 0 to 3.

25. At least the polyimide-based resin-containing layer (PI-1) contains a polyimide-based resin having the structural unit (A), and the structural unit (A) further contains 50 mol % or less of a compound represented by formula (A3): [In formula (A3), Z represents a divalent organic group, R ａ３ each independently represent a halogen atom, or an alkyl group, alkoxy group, aryl group, or aryloxy group which may have a halogen atom; and each s independently represent an integer of 0 to 3.

26. The laminate of claim 1, 4, 7 or 13, wherein the metal layer is a copper layer.

27. A flexible printed circuit board comprising the laminate of claim 1, 4, 7 or 13.

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