laminate

Abstract

The present application provides a laminate with high yield strength. The laminate, which is a laminate comprising a resin film, and a metal layer provided on at least one face of the resin film, has a skewness Psk of 0.05 or more in a cross-sectional image of the laminate in the thickness direction, obtained by a scanning electron microscope, from a cross-sectional curve of the interface between the resin film and the metal layer.

Description

Technical Field

[0001] The present invention relates to a laminate comprising a resin film and a metal layer, particularly a laminate applicable to substrate materials such as printed circuit boards and antenna boards capable of handling high-frequency bands, and a flexible printed circuit board comprising the laminate. Background Technology

[0002] Flexible printed circuit boards (hereinafter, sometimes referred to as FPCs) are thin, lightweight, and flexible, enabling three-dimensional, high-density mounting. They are used in various electronic devices such as mobile phones and hard drives, contributing to their miniaturization and weight reduction. Previously, polyimide resins with excellent heat resistance, mechanical properties, and electrical insulation have been widely used in FPCs. For example, as metal-clad laminates such as copper-clad laminates (hereinafter, sometimes abbreviated as CCL) for FPCs, laminates with metal layers on one or both sides of the resin film are known.

[0003] In recent years, the fifth-generation mobile communication system known as 5G has been officially popularized (for example, patent document 1), and stacks suitable for high-speed communication applications after 5G are being studied.

[0004] Existing technical documents Patent documents Patent Document 1: Japanese Patent Application Publication No. 2021-161285 Summary of the Invention

[0005] The problem that the invention aims to solve For laminates used in FPCs, deformation may occur during processing and repeated use. To prevent degradation of electrical properties and other characteristics caused by deformation, strength to resist deformation is required. However, it is difficult to improve the strength to resist deformation while controlling the dielectric properties of the laminate within an appropriate range. Therefore, there is a need to develop laminates that are resistant to deformation and can be used for high-speed communication applications beyond 5G.

[0006] The inventors of this application have discovered that, in order to suppress the deterioration of the properties of laminates, it is particularly important to improve the strength of laminates against plastic deformation. Therefore, the object of the present invention is to provide a laminate with a high yield strength of 0.2% (also referred to as yield strength), which is an indicator of the strength against plastic deformation, and a flexible printed circuit board comprising the laminate.

[0007] Methods for solving problems The inventors of this application conducted in-depth research to solve the aforementioned problems and discovered that when the skewness Psk obtained from the cross-sectional curve of the interface between the resin film and the metal layer in the laminate is within a specific range, the aforementioned problems can be solved. Furthermore, it was discovered that when the skewness Psk and kurtosis Pku obtained from the cross-sectional curve of the interface between the resin film and the metal layer in the laminate satisfy a specific relationship, the aforementioned problems can be solved, thus completing the present invention. That is, the present invention includes the following aspects.

[0008] [1] A laminate comprising a resin film and a metal layer disposed on at least one side of the resin film, wherein, In the cross-sectional image of the aforementioned laminate obtained using a scanning electron microscope in the thickness direction, the skewness Psk obtained from the cross-sectional curve of the interface between the aforementioned resin film and the aforementioned metal layer is -0.05 or higher.

[0009] [2] A laminate comprising a resin film and a metal layer disposed on at least one side of the resin film, wherein, In the cross-sectional image of the aforementioned laminate obtained using a scanning electron microscope along its thickness direction, the skewness Psk and kurtosis Pku obtained from the cross-sectional curve of the interface between the aforementioned resin film and the aforementioned metal layer satisfy the relationship of equation (I). |Pku / Psk|≤100 (I).

[0010] [3] As described in [1] or [2], wherein the maximum peak height Pp and the maximum valley depth Pv obtained from the aforementioned cross-sectional curves satisfy the relationship of equation (II). |Pp-Pv|≥1.5nm (II).

[0011] [4] The laminate as described in any one of [1] to [3], wherein the aforementioned resin film comprises at least one resin selected from the group consisting of polyimide resin, liquid crystal polymer, fluorine resin, aromatic polyether resin, epoxy resin and maleimide resin.

[0012] [5] The laminate as described in any one of [1] to [4], wherein the linear expansion coefficient of the aforementioned resin film is 10 to 29 ppm / K.

[0013] [6] The laminate as described in any one of [1] to [5], wherein the aforementioned resin film is a polyimide film containing a polyimide resin.

[0014] [7] The laminate as described in [6], wherein the aforementioned polyimide film comprises a layer (PI-1) containing a polyimide resin and a layer (PI-2) containing a polyimide resin.

[0015] [8] The laminate as described in [7], wherein the aforementioned polyimide resin-containing layer (PI-2) is located on the side of the aforementioned metal layer, and the thickness of the polyimide resin-containing layer (PI-2) is 0.05 to 0.3 times the thickness of the aforementioned polyimide resin-containing layer (PI-1).

[0016] [9] The laminate as described in [7] or [8], wherein the aforementioned polyimide film further comprises a layer (PI-3) containing a polyimide resin.

[0017]

[10] The laminate as described in [9], wherein the polyimide resin contained in the aforementioned polyimide resin-containing layer (PI-1), the polyimide resin contained in the aforementioned polyimide resin-containing layer (PI-2), and the polyimide resin contained in the polyimide resin-containing layer (PI-3) each have a storage modulus of 1.0 × 10⁻⁶ at 40°C. 9 Pa or above.

[0018]

[11] The laminate as described in any one of [7] to

[10] , wherein at least one of the aforementioned polyimide resin-containing layer (PI-1) and the aforementioned polyimide resin-containing layer (PI-2) comprises a polyimide resin having a structural unit (A) derived from tetracarboxylic anhydride, The aforementioned structural unit (A) comprises a structural unit (A1) of tetracarboxylic anhydride represented by formula (A1) and / or a structural unit (A2) of tetracarboxylic anhydride represented by formula (A2). [Chemical Formula 1] In formula (A1), R a1 Each can independently represent a halogen atom, or an alkyl, alkoxy, aryl, or aryloxy group that may have a halogen atom. k represents an integer from 0 to 2. [Chemical Formula 2] In formula (A2), R a2 Each of the above can independently represent a halogen atom, or an alkyl, alkoxy, aryl, or aryloxy group that may have a halogen atom, and each of the above can independently be an integer from 0 to 3.

[0019]

[12] The laminate as described in any one of [7] to

[11] , wherein at least one of the aforementioned polyimide resin-containing layer (PI-1) and the aforementioned polyimide resin-containing layer (PI-2) comprises a polyimide resin having a structural unit (B) derived from a diamine. The aforementioned structural unit (B) comprises a structural unit (B1) derived from a diamine represented by formula (B1). [Chemical Formula 3] In formula (B1), R b1 Each can independently represent a halogen atom, or an alkyl, alkoxy, aryl, or aryloxy group that may have a halogen atom. W can be independently represented by the following octets: -O-, -CH2-, -CH2-CH2-, -CH(CH3)-, -C(CH3)2-, -C(CF3)2-, -COO-, -OOC-, -SO-, -SO2-, -S-, -CO-, -N(R) c The divalent linking group or single bond in the group consisting of - and -CONH- (where m is 2 or more, and at least one W is the aforementioned divalent linking group), R c A monovalent hydrocarbon group representing a hydrogen atom or a carbon atom that can be substituted by a halogen atom, having 1 to 12 carbon atoms. m represents an integer from 1 to 4. q represents integers from 0 to 4 independently.

[0020]

[13] The laminate as described in any one of [7] to

[12] , wherein at least the aforementioned layer (PI-1) containing a polyimide resin comprises a polyimide resin having a structural unit (A) derived from a tetracarboxylic anhydride, the structural unit (A) comprising a structural unit (A3) of a tetracarboxylic anhydride containing an ester bond represented by formula (A3). [Chemical Formula 4] In formula (A3), Z represents a divalent organic group. R a3 Each can independently represent a halogen atom, or an alkyl, alkoxy, aryl, or aryloxy group that may have a halogen atom. s represent integers from 0 to 3 independently.

[0021]

[14] The laminate as described in any one of

[11] to

[13] , wherein at least the aforementioned layer (PI-1) containing a polyimide resin comprises a polyimide resin having the aforementioned structural unit (A), the structural unit (A) further comprising a structural unit (A3) of a tetracarboxylic anhydride containing an ester bond represented by formula (A3) in a amount of less than 50 mol% relative to the total amount of the structural unit (A). [Chemical Formula 5] In formula (A3), Z represents a divalent organic group. R a3 Each can independently represent a halogen atom, or an alkyl, alkoxy, aryl, or aryloxy group that may have a halogen atom. s represent integers from 0 to 3 independently.

[0022]

[15] The laminate as described in any one of [1] to

[14] , wherein the aforementioned metal layer is a copper layer.

[0023]

[16] A flexible printed circuit board comprising any one of the following: [1] to

[15]

[0024] Invention Effects According to the present invention, it is possible to provide laminates with high yield strength. Attached Figure Description

[0025] [ Figure 1 This is a schematic diagram illustrating a method for measuring cross-sectional images in the thickness direction of a laminate using a scanning electron microscope.

[0026] [ Figure 2 [A diagram is used to illustrate the profile curve before correction, the profile curve after tilt correction, and the profile curve (section curve) after tilt correction and average correction in a laminate.]

[0027] [ Figure 3 [Illustration] is a schematic cross-sectional view showing an example of the layer structure of the laminate of the present invention. Detailed Implementation

[0028] The embodiments of the present invention will now be described in detail. It should be noted that the scope of the present invention is not limited to the embodiments described herein, and various modifications can be made without prejudice to the spirit of the invention. It should also be noted that the multiple upper and lower limits described in this specification can be arbitrarily combined to form preferred numerical ranges.

[0029] [Layered Body] In a first embodiment of the present invention, the laminate of the present invention comprises a resin film and a metal layer disposed on at least one side of the resin film, wherein the skewness Psk (sometimes simply referred to as "Psk") obtained from the cross-sectional image of the laminate in the thickness direction obtained by scanning electron microscopy (also known as SEM) is -0.05 or more.

[0030] [Roughness Parameters] In this invention, Psk is an index representing the symmetry of the height distribution obtained from the cross-sectional curve of the interface between the resin film and the metal layer. Psk represents the average value of the cube of the height Z(x) of the cross-sectional curve obtained from the reference length obtained by dimensionless transformation of the cube of the root mean square height Pq, and can be expressed by the following formula. [Mathematical Expression 1] [In the formula, Psk represents skewness, Pq represents root mean square height, Lr represents reference length, and Z(x) represents the height of the cross-sectional curve at any position x within the reference length.]

[0031] Psk refers to skewness, representing the symmetry of the height distribution of the cross-sectional curve, that is, the symmetry of the convex and concave parts relative to the average baseline. When Psk > 0, it means that the height distribution of the interface's cross-sectional curve is biased downwards relative to the average baseline; when Psk < 0, it means that the height distribution of the interface's cross-sectional curve is biased upwards relative to the average baseline; when Psk = 0, it means that the height distribution of the interface's cross-sectional curve is symmetrical about the average baseline (normal distribution). It should be noted that, as described later, the analysis is performed with the metal layer on the lower side (the negative side of the y-coordinate) and the resin film (also called the resin layer) on the upper side (the positive side of the y-coordinate). Therefore, the convex part represents the portion protruding in the positive direction of the y-axis, that is, from the metal layer to the resin layer (equivalent to the protrusion on the metal layer), and the concave part represents the portion protruding in the negative direction of the y-axis, that is, from the resin layer to the metal layer (the concave part on the metal layer).

[0032] The inventors of this application conducted research focusing on the interlayer interfaces in laminates. They discovered that when the skewness Psk obtained from the cross-sectional curve of the resin film and metal layer interface was -0.05 or higher, the 0.2% yield strength unexpectedly increased. The reason for this is still uncertain, but it is believed that in the thickness direction cross-section, depending on the unevenness of the interface, the stress concentration acting on the resin film and metal layer differs, resulting in different magnitudes of strain induced at the interface and internal stress. Furthermore, it is expected that the crystallinity and orientation of the resin layer near the interface also change. It is thought that if Psk is -0.05 or higher, the convex portions of the interface cross-sectional curve tend to become sharper, and the amount of resin present between the convex portions increases. Therefore, it is speculated that this is because the increased crystallinity and / or orientation of the resin layer near the interface makes it easier to reduce the internal stress generated at the interface, especially between the convex portions, or that the overall strength of the resin film is increased due to the influence of the resin orientation near the interface, thus increasing the overall resistance to deformation of the laminate.

[0033] Psk is obtained from the cross-sectional curve when a cross-sectional image of the thickness direction of the laminate is obtained using SEM, and the cross-sectional curve of the interface between the resin film and the metal foil layer is prepared from the cross-sectional image. Psk can be obtained by calculating the cross-sectional curve of the interface between the resin film (resin layer) and the metal layer, and then using the obtained cross-sectional curve to derive the cross-sectional curve from the above formula. The cross-sectional curve can be obtained by performing SEM observation, obtaining an SEM image of the thickness direction cross-section of the laminate, and then performing image processing and analysis on the obtained SEM image. In addition, in order to obtain a clear SEM image, it is preferable to perform FIB (Focused Ion Beam) processing pretreatment, FIB processing, and SEM observation pretreatment sequentially in the SEM observation sample preparation process. Hereinafter, an example of a method for obtaining the cross-sectional curve will be specifically described.

[0034] (1) FIB processing like Figure 1 As shown in (a), as a pretreatment for FIB processing, the end faces of the laminate were machined using a slicing machine to create a sample with a smooth thickness-direction cross-section. Then, platinum was deposited on the metal layer surface of the laminate using an ion sputtering apparatus. Next, as... Figure 1 As shown in (b), a focused ion beam is irradiated vertically onto the surface of the metal layer of the laminate, and a portion of the center of the end face, which has been processed using a slicing machine, is cut out in a U-shape when viewed from the side of the metal layer surface, creating a smooth cross-section. Figure 1 As shown in (c), the surface in the processed section that is parallel to the surface processed by the slicer is set as the observation surface.

[0035] (2) SEM observation As a pretreatment for SEM observation, platinum deposition was performed on the FIB processing surface (observation surface) using an ion sputtering apparatus. Next, on the FIB processing surface, the angle was adjusted so that the interface between the metal layer and the resin layer was horizontal relative to the acquired image, and then SEM observation was performed.

[0036] (3) Image processing For the obtained SEM images (cross-sectional images), image processing software (such as ImageJ) was used to perform image processing in the following order: image import, smoothing, contrast adjustment, binarization (converting to a black and white image), noise removal, and contour extraction. In image import, the metal layer protrusions were imported with the metal layer facing upwards (in the obtained image of the laminated interface, the metal layer is the lower side and the resin layer is the upper side). In contrast adjustment, the high-brightness side of the histogram from the resin layer (located on the low-brightness side) was used as the minimum value, and the low-brightness side of the histogram from the metal layer (located on the high-brightness side) was used as the maximum value. In noise removal, after removing noise spots, portions isolated from both the metal layer and resin layer were manually removed (e.g., in cases where the metal layer is white and the resin layer is black due to binarization, white particles isolated from the metal layer and black particles isolated from the resin layer and located in the resin layer). In contour extraction, after creating the contour curve, the coordinates of the contour curve were output in CSV format.

[0037] (4) Analysis In the contour curve obtained through image processing, after resetting the unit of the contour curve from pixels to distances (nm), tilt correction and averaging correction are performed sequentially using Excel, for example, to obtain the cross-sectional curve of the interface between the metal layer and the resin layer. It should be noted that the roughness parameter is calculated by making the metal layer side the lower side (negative side of the y-axis) and the resin layer side the upper side (positive side of the y-axis).

[0038] For example, Figure 2 This diagram illustrates the profile curves before and after each correction. The profile curve before correction is 7. The profile curve after tilt correction (obtained by tilt correction of profile curve 7) is 8. The profile curve after tilt correction and average correction (also called the cross-sectional curve) obtained by further averaging correction of profile curve 8 is 9. In tilt correction, the slope 'a' of the regression line of the profile curve is calculated, and y' = yx × a is obtained at each coordinate (x, y), resetting to (x, y'). In average correction, the average value 'b' is calculated using the y' values ​​of all coordinates, and y'' = y' - b is obtained at each coordinate (x, y'), resetting to (x, y''). Here, the cross-sectional curves obtained through the above analysis are denoted as y''(x).

[0039] The obtained cross-sectional curve y” (x) can be used to determine Pq and Psk using the following formula. It should be noted that the cross-sectional curve, Pq, and Psk can be determined, for example, by the method described in the embodiments.

[0040] [Mathematical Expression 2] [In the formula, Psk represents skewness, Pq represents root mean square height, L represents the maximum x value minus the minimum x value (i.e., the distance from the endpoint to the endpoint of the cross-sectional curve; the reference length), and y''(x) represents the cross-sectional curve.] Other roughness parameters besides Psk can also be calculated using the cross-sectional curve y" (x).

[0041] In one embodiment of the present invention, when the laminate is used as a metal laminate or the like, the metal layer on the resin film is sometimes locally removed by etching or the like. In this laminate, from the viewpoint of dielectric properties and drying efficiency during FPC manufacturing, it is preferable that the resin film after removing the metal layer has high water resistance. The inventors of this application have also discovered that when the cross-sectional profile Psk of the laminate interface is -0.05 or higher, the water resistance and drying speed of the resin film after removing the metal layer are unexpectedly improved. The reason for this is not yet certain, but it is speculated that the surface texture of the resin film becomes an uneven structure that does not easily absorb water, or that the crystallinity and / or orientation near the surface of the resin layer (i.e., the interface on the resin film side in the laminate) is improved. In this specification, water resistance refers to the characteristic that the resin film after removing the metal layer in the laminate is not easily water-absorbing when immersed in pure water, and can be evaluated, for example, by the methods described in the examples. In addition, drying speed refers to the rate at which pure water decreases when the resin film after removing the metal layer is water-containing and then heated and dried, and can be evaluated, for example, by the methods described in the examples. The water resistance and drying speed of the resin film after the metal layer is removed can also be said to be characteristics of the laminate, and are therefore referred to as the water resistance of the laminate and the drying speed of the laminate, respectively.

[0042] In this specification, dielectric properties refer to dielectric-related properties such as Df and Dk. An improvement or enhancement of dielectric properties means a decrease in Df and / or Dk. The dielectric properties of a laminate can be evaluated through the dielectric properties of the resin film within the laminate. Furthermore, mechanical properties refer to mechanical properties including yield strength, puncture strength, flexural strength, and modulus of elasticity. An improvement or enhancement of mechanical properties means, for example, an increase in yield strength, flexural strength, and / or modulus of elasticity. Additionally, thermal properties may include CTE, glass transition temperature (hereinafter sometimes referred to as Tg), and the degree of thermal degradation or deterioration. An improvement or enhancement of thermal properties means, for example, a decrease in CTE, an increase in Tg, and / or less thermal degradation or deterioration.

[0043] In the laminate of the present invention, Psk is preferably 0 or greater than 0, more preferably 0.05 or greater, even more preferably 0.10 or greater, even more preferably 0.15 or greater, particularly preferably 0.20 or greater, even more preferably 0.25 or greater, even more preferably 0.30 or greater, and extremely preferably 0.35 or greater. Furthermore, Psk is preferably 5.0 or less, more preferably 3.0 or less, even more preferably 2.5 or less, even more preferably 2.0 or less, particularly preferably 1.6 or less, even more preferably 1.5 or less, even more preferably 1.0 or less, even more preferably 0.80 or less, and extremely preferably 0.60 or less or 0.50 or less. If Psk is above the aforementioned lower limit and / or below the aforementioned upper limit, the interfacial structure, the crystallinity and / or orientation of the resin layer in the laminate are more likely to exhibit the effects of the present invention, thus further improving the yield strength, water resistance, and drying speed of the laminate.

[0044] In a second embodiment of the present invention, the laminate of the present invention comprises a resin film and a metal layer disposed on at least one side of the resin film. In a cross-sectional image of the laminate in the thickness direction obtained using a scanning electron microscope, the skewness Psk and kurtosis Pku (sometimes simply expressed as "Pku") obtained from the cross-sectional curve of the interface between the resin film and the metal layer satisfy the relationship of equation (I). |Pku / Psk|≤100 Equation (I).

[0045] The inventors of this application discovered that when Pku and Psk obtained from the cross-sectional curve of the interface between the resin film and the metal layer satisfy Equation (I), the 0.2% yield strength unexpectedly increases. The reason for this is not yet certain, but it is believed that in the thickness direction cross-section of the laminate, depending on the unevenness of the interface, the stress concentration state acting on the resin film and the metal layer differs, resulting in different magnitudes of strain induced at the interface and internal stress. Furthermore, it is expected that the crystallinity and orientation of the resin layer near the interface also change. When the interface of the laminate satisfies Equation (I), the vertical symmetry of the cross-sectional curve relative to the average baseline is disrupted, and the surface characteristics, including convex and concave portions, are not excessively sharp. Therefore, it is believed that because stress concentration is less likely to occur at the interface, and due to the influence of the aforementioned surface characteristics during film formation, the crystallinity and / or orientation of the resin layer near the interface in the laminate increases, thus increasing the overall strength of the laminate against deformation.

[0046] The skewness Psk in Equation (I) is as described above. The kurtosis Pku in Equation (I) is an index representing the sharpness of the height distribution obtained from the cross-sectional curve of the interface between the resin film and the metal layer. Pku represents the average value of the fourth power of the cross-sectional curve Z(x) over a reference length obtained by dimensionless transformation of the fourth power of the root-mean-square height Pq, and can be expressed by the following formula: [Mathematical Expression 3] [In the formula, Pku represents kurtosis, Pq represents root mean square height, Lr represents reference length, and Z(x) represents the height of the cross-sectional curve at any position x in the reference length.]

[0047] It should be noted that Pq is as described above.

[0048] Pku refers to the sharpness or sharpness of the height distribution of a cross-sectional curve. When Pku>3, it means there are many sharp convex and concave parts. When Pku<3, it means there are many concave and convex parts, like a flattened tip, resulting in a relatively flat surface. When Pku=3, it means the height distribution is normally distributed.

[0049] Pku can be obtained by producing the cross-sectional curve (cross-sectional curve of the interface between the resin film and the metal foil layer) y””x” of the laminate as described above, and using the cross-sectional curve, it can be obtained by the following formula, for example, by the method described in the embodiments.

[0050] [Mathematical Expression 4] [In the formula, Pku represents kurtosis, Pq represents root mean square height, L represents the maximum x value minus the minimum x value (i.e., the distance from endpoint to endpoint of the cross-sectional curve; the reference length), and y''(x) represents the cross-sectional curve.] In a second embodiment of the present invention, the inventors of this application discovered that when the interface of the laminate satisfies formula (I), the water resistance and drying speed of the resin film after the metal layer is removed are unexpectedly improved. The reason for this is not yet certain, but it is speculated that when formula (I) is satisfied, the unevenness of the resin layer surface tends to become an uneven structure that does not easily absorb water, and the crystallinity and / or orientation of the resin layer near the interface of the laminate is improved.

[0051] In the second embodiment of the present invention, |Pku / Psk| in formula (I) is preferably 90 or less, more preferably 70 or less, further preferably 60 or less, further more preferably 50 or less, particularly preferably 40 or less, and particularly more preferably 35 or less. Furthermore, |Pku / Psk| in formula (I) is preferably 1.0 or more, more preferably 5.0 or more, further preferably 9.0 or more, further more preferably greater than 10.0 or more or 11.0 or more, particularly preferably 12.0 or more, particularly more preferably 15.0 or more, particularly more preferably 20.0 or more, and particularly more preferably 30.0 or more. If |Pku / Psk| is above the aforementioned lower limit and / or below the aforementioned upper limit, the uneven structure of the interface in the laminate, the crystallinity and / or orientation of the resin layer are more likely to become states that further exhibit the effects of the present invention, thus further improving the yield strength, water resistance, and drying speed of the laminate.

[0052] In the second embodiment of the present invention, Psk in formula (I) is not particularly limited as long as it satisfies formula (I). It is preferably -0.05 or more, more preferably 0 or more or greater than 0, further preferably 0.05 or more, further more preferably 0.10 or more, particularly preferably 0.15 or more, particularly more preferably 0.20 or more, particularly more preferably 0.25 or more, extremely preferably 0.30 or more, and extremely more preferably 0.35 or more. Furthermore, Psk in formula (I) is preferably 5.0 or less, more preferably 3.0 or less, further preferably 2.5 or less, further more preferably 2.0 or less, particularly preferably 1.6 or less, particularly more preferably 1.5 or less, particularly more preferably 1.0 or less, particularly more preferably 0.80 or less, and extremely preferably 0.60 or less or 0.50 or less. If Psk is within the aforementioned range, the yield strength, water resistance, and drying speed of the laminate can be improved.

[0053] In the second embodiment of the present invention, Pku in formula (I) is not particularly limited as long as it satisfies formula (I), but is preferably 3.0 or more, more preferably 5.0 or more, and even more preferably 7.0 or more. For example, it can be 9.0 or more, 10.0 or more, or 11.0 or more. In addition, Pku in formula (I) is preferably 30 or less, more preferably 20 or less, even more preferably 18 or less, and even more preferably 16 or less. If Pku is within the aforementioned range, the yield strength, water resistance, and drying speed of the laminate can be improved.

[0054] In one embodiment of the present invention, for the laminate of the present invention, it is preferable that the skewness Psk obtained from the cross-sectional curve of the interface between the resin film and the metal layer is -0.05 or more, and that Pku and Psk obtained from the cross-sectional curve of the interface between the resin film and the metal layer satisfy Equation (I). When these conditions are met, the yield strength, water resistance, and drying speed of the laminate can be further improved. The reasons are not yet certain, but when these conditions are met, the vertical symmetry of the cross-sectional curve of the interface relative to the average baseline is disrupted, and the surface characteristics of the cross-sectional curve are such that the convex portions are relatively sharp but not excessively sharp, and the concave portions are not excessively sharp. Therefore, it is considered that the amount of resin present between the convex portions is sufficient, stress concentration at the interface caused by the shape of the convex and concave portions is less likely to occur, and during film formation, the crystallinity and / or orientation of the resin layer near the interface in the laminate is improved due to the aforementioned surface characteristics, thus increasing the strength of the laminate as a whole against deformation. Furthermore, it is believed that the unevenness of the resin layer surface can easily become an uneven structure that does not easily absorb water, and as mentioned above, the crystallinity and / or orientation of the resin layer near the interface in the laminate is improved, thus enhancing the water resistance and drying speed of the laminate.

[0055] In the first and second embodiments of the present invention, for the laminate of the present invention, it is preferable that the maximum peak height Pp and the maximum valley depth Pv obtained from the aforementioned cross-sectional curves satisfy the relationship of equation (II). |Pp-Pv|≥1.5nm (II) If formula (II) is satisfied, the yield strength, water resistance, and drying speed of the laminate can be improved. The reason for this is uncertain, but when the interface of the laminate satisfies formula (II), it can become a surface characteristic where the interface's unevenness is skewed relative to the baseline. Therefore, it is speculated that stress concentration is less likely to occur at the interface, and the crystallinity and / or orientation of the resin layer near the interface in the laminate is improved due to the aforementioned surface characteristics during film formation. Furthermore, if formula (II) is satisfied, the unevenness of the resin film surface easily becomes an uneven structure that does not readily absorb water, and the crystallinity and / or orientation near the surface of the resin layer (i.e., the interface on the resin film side in the laminate) is easily improved, thus improving the water resistance and drying speed of the laminate. It should be noted that, unless otherwise explicitly stated, the laminate described below refers to both the laminates of the first and second embodiments of the present invention.

[0056] The maximum peak height Pp represents the maximum height of the height from the average baseline (the straight line with y-coordinate = 0) in the aforementioned cross-sectional curve; more specifically, it represents the height of the largest convex portion in the positive direction of the y-coordinate. Similarly, the maximum valley depth Pv represents the absolute value of the minimum height of the height from the average baseline in the aforementioned cross-sectional curve; more specifically, it represents the depth of the largest concave portion in the negative direction of the y-coordinate. Both Pp and Pv can be determined by creating the cross-sectional curve of the laminate as described above and from that curve, for example, by the method described in the embodiments.

[0057] In one embodiment of the present invention, |Pp-Pv| in formula (II) is preferably 3 nm or more, more preferably 5 nm or more, further preferably 10 nm or more, further more preferably 30 nm or more, particularly preferably 50 nm or more, particularly more preferably 70 nm or more, and particularly more preferably 80 nm or more. Furthermore, |Pp-Pv| in formula (II) is preferably 1000 nm or less, more preferably 500 nm or less, further preferably 400 nm or less, further more preferably 300 nm or less, particularly preferably 200 nm or less, particularly more preferably 163 nm or less or 160 nm or less, and particularly more preferably 100 nm or less or 88 nm or less. If |Pp-Pv| in formula (II) is above the aforementioned lower limit and / or below the aforementioned upper limit, the uneven structure of the interface in the laminate, the crystallinity and / or orientation of the resin layer are more likely to become states that further exhibit the effects of the present invention, thus further improving the yield strength, water resistance, and drying speed of the laminate.

[0058] In one embodiment of the present invention, Pp in formula (II) is preferably 100 nm or more, more preferably 200 nm or more, further preferably 275 nm or more, even more preferably 300 nm or more, particularly preferably 330 nm or more, preferably 1000 nm or less, more preferably 900 nm or less, even more preferably 800 nm or less, even more preferably 700 nm or less, particularly preferably 600 nm or less, and even more preferably 550 nm or less. For example, it can be 500 nm or less, 450 nm or less, or 400 nm or less. If Pp is within the above range, the yield strength, water resistance, and drying speed of the laminate can be improved.

[0059] In one embodiment of the present invention, Pv in formula (II) is preferably 50 nm or more, more preferably 100 nm or more, even more preferably 200 nm or more, even more preferably 250 nm or more, preferably 1000 nm or less, even more preferably 900 nm or less, even more preferably 800 nm or less, even more preferably 700 nm or less, particularly preferably 650 nm or less, for example, it can be 500 nm or less, 400 nm or less, 350 nm or less, 300 nm or less, or 270 nm or less. If Pv is within the aforementioned range, the yield strength, water resistance, and drying speed of the laminate can be improved.

[0060] In the laminate of the present invention, the maximum height Pz obtained from the aforementioned cross-sectional curve of the interface between the resin film and the metal layer is preferably 2000 nm or less, more preferably 1500 nm or less, even more preferably 1200 nm or less, and even more preferably 1060 nm or less. For example, it can be 1000 nm or less, 900 nm or less, or 700 nm or less. The maximum height Pz is not particularly limited, but is 30 nm or more, preferably 50 nm or more, more preferably 100 nm or more, even more preferably 150 nm or more, even more preferably 300 nm or more, particularly preferably 550 nm or more, and even more preferably 600 nm or more. If the maximum height Pz is within the aforementioned range, it is easy to improve the yield strength, water resistance, and drying speed of the laminate, and it is possible to reduce the transmission loss of the FPC using the laminate.

[0061] In the laminate of the present invention, the arithmetic mean height Pa obtained from the aforementioned cross-sectional curve of the interface between the resin film and the metal layer is not particularly limited, but is preferably 0.50 nm or more, more preferably 1.0 nm or more, further preferably 5.0 nm or more, even more preferably 10.0 nm, particularly preferably 20.0 nm or more, preferably 100 nm or less, more preferably 80 nm or less, even more preferably 60 nm or less, for example, it can be 55 nm or less, 45 nm or less, or 30 nm or less. If the arithmetic mean height Pa is within the aforementioned range, it is easy to improve the yield strength, water resistance, and drying speed of the laminate, and it is possible to reduce the transmission loss of the FPC using the laminate.

[0062] The maximum height Pz represents the maximum height in the aforementioned cross-sectional curve (the distance from the highest point to the lowest point), and the arithmetic mean height Pa represents the average height difference from the average baseline in the aforementioned cross-sectional curve. Pz and Pa can each be obtained by creating the cross-sectional curve of the laminate as described above and by using that cross-sectional curve, for example, by the method described in the embodiments.

[0063] In this specification, Psk, Pku, Pz, Pa, Pp, Pv, |Pp-Pv|, |Pku / Psk| are sometimes collectively referred to as roughness parameters.

[0064] In the laminate of the present invention, Psk, |Pku / Psk|, and |Pp-Pv| can each be controlled by the following methods: (1) using a metal whose surface roughness parameters (especially Sal×Str) are adjusted to the range described below; (2) appropriately adjusting the types and composition of the structural units of the resin constituting the resin film, the molecular weight of the resin, and / or the coating, support substrate selection, drying, imidization, and other manufacturing conditions during film formation. For example, based on preferred methods that are beneficial to improving the yield strength and dielectric properties described in this specification, specifically, in addition to preferred surface roughness parameters such as Sal×Str of the metal, Psk, |Pku / Psk|, and |Pp-Pv| can be adjusted to the above ranges based on preferred structural units and their content of PI-based resin, preferred solvent contained in preferred PI-based resin precursor solutions, preferred conveying speed during coating, drying temperature, settling process, preferred imidization conditions, etc. It should be noted that roughness parameters other than these can be adjusted to the range described below by, for example, using the roughness parameters of the relevant metal surface to adjust the metal to the range described below, or by using the method described in (2) above.

[0065] In the case where the laminate of the present invention includes metal layers on both sides of the resin film, it is sufficient that the roughness parameters are within the aforementioned range at least on the surface where at least one metal layer is in contact with the resin film. From the viewpoint of yield strength, water resistance, and drying speed of the laminate, the aforementioned roughness parameters may also be within the aforementioned range at the interfaces between the two metal layers and the resin film. Furthermore, the roughness parameters may be the same or different at the interfaces of one metal layer and the resin film and the other metal layer and the resin film.

[0066] [Resin film] The laminate of the present invention comprises a resin film. The resin constituting the resin film is not particularly limited, but examples include: thermosetting resins selected from diallyl phthalate resin, silicone resin, phenolic resin, unsaturated polyester resin, polyurethane resin, melamine resin, urea resin, xylene resin, furan resin, aniline resin, acetone-formaldehyde resin, alkyd resin, maleimide resin, maleimide-cyanate ester resin, cyanate ester resin, benzoxazine resin, polybenzimidazole resin, and polycarbodiimide resin; olefin resins; acrylic resins; styrene resins; rubber resins; fluorine resins; vinyl resins; general-purpose engineering plastics; liquid crystal polymers, aromatic polyether resins, and other super engineering plastics; polyamide resins; polyimide resins, polyamide-imide resins, and other polyimide-based resins; and biodegradable plastics. These resins can be used alone or in combination of two or more. From the viewpoint of improving the yield strength, water resistance, drying speed and dielectric properties of the laminate, the resin film preferably contains at least one resin selected from the group consisting of polyimide resin, liquid crystal polymer, fluorine resin, aromatic polyether resin, epoxy resin and maleimide resin, more preferably contains polyimide resin and / or liquid crystal polymer, and even more preferably contains polyimide resin.

[0067] At least one resin constituting the resin film preferably has orientation and / or crystallinity. The orientation of the resin in the resin film can be confirmed by laser Raman spectroscopy, etc., and the crystallinity can be confirmed by small-angle X-ray scattering, wide-angle X-ray scattering, and IR measurement.

[0068] The weight-average molecular weight, the ratio of weight-average molecular weight to number-average molecular weight, the glass transition temperature, and the tensile modulus of elasticity of the resin constituting the resin film are not particularly limited, and can be selected from the same range as the polyimide resins described later.

[0069] In a preferred embodiment of the present invention, the aforementioned resin film is preferably a polyimide-based film containing a polyimide-based resin. The presence of a polyimide-based resin can improve the yield strength, water resistance, and drying speed of the laminate. In this specification, the polyimide-based film is sometimes referred to as a "PI-based film," and the polyimide-based resin is sometimes referred to as a "PI-based resin."

[0070] The resin film can be a single-layer film or a multilayer film.

[0071] In a preferred embodiment of the present invention, when the PI-based film is a laminated film, it preferably includes a layer containing a polyimide resin (PI-1) and a layer containing a polyimide resin (PI-2). The PI-based film may include other layers containing PI resin besides these PI-based resin layers, or it may include other layers besides the PI-based resin layers. Examples of other layers include adhesive layers, etc. In a preferred embodiment of the present invention, from the viewpoint of improving the yield strength of the laminate, the PI-based film of the present invention preferably includes a layer containing a PI resin (PI-3) in addition to the PI-based resin layers (PI-1) and (PI-2). In this embodiment, from the viewpoint of improving the yield strength of the laminate, the PI-based film of the present invention preferably comprises a layer containing PI-based resin (PI-2), a layer containing PI-based resin (PI-1), and a layer containing PI-based resin (PI-3) in sequence, and more preferably comprises layers containing PI-based resin (PI-2), PI-based resin (PI-1), and PI-based resin (PI-3) in a manner adjacent to each other in sequence. It should be noted that sometimes a PI-based film comprising layers containing PI-based resin (PI-1), PI-based resin (PI-2), and PI-based resin (PI-3) (sometimes described as layers containing PI-based resin (PI-1) to (PI-3) or layers (PI-1) to (PI-3)) is referred to as a PI-based film (L). In addition, unless otherwise specified in this specification, "PI-based membrane" includes both single-layer membrane and multilayer membrane. When referring to layers containing PI-based resin, especially layers containing PI-based resin (PI-1), layers containing PI-based resin (PI-2) and / or layers containing PI-based resin (PI-3), it refers to PI-based membranes in the form of multilayer membranes.

[0072] like Figure 3 As shown, in a preferred embodiment of the present invention, the PI-based film 10 is composed of three adjacent layers containing PI-based resin: layer 11, layer 12, and layer 13, which are stacked on a metal layer 14 to form a laminate 15. From the viewpoint of improving the yield strength, water resistance, drying speed, and dielectric properties of the laminate, layer 11 containing PI-based resin is preferably equivalent to layer (PI-2), layer 12 containing PI-based resin is equivalent to layer (PI-1), and layer 13 containing PI-based resin is equivalent to layer (PI-3). Alternatively, the PI-based film 10 may also include other layers containing PI-based resin besides layers (PI-1), (PI-2), and (PI-3), or other layers besides those containing PI-based resin. Examples of other layers include adhesive layers formed from polymeric materials such as acrylic resins other than PI-based resins.

[0073] In one embodiment of the present invention, the thickness of the resin film is preferably 20 μm or more, more preferably 25 μm or more, further preferably 30 μm or more, more preferably 35 μm or more, particularly preferably 40 μm or more, preferably 150 μm or less, more preferably 130 μm or less, further preferably 100 μm or less, more preferably 90 μm or less, particularly preferably 80 μm or less, particularly more preferably 70 μm or less, and particularly even more preferably 60 μm or less. If the thickness of the resin film is within the aforementioned range, the laminate can possess high yield strength, flexibility suitable for flexible printed circuit boards, and other mechanical properties. Furthermore, by reducing yield strength (Df) and increasing yield strength, a laminate with well-balanced mechanical properties suitable for flexible printed circuit boards and dielectric properties suitable for high-speed communication applications such as 5G can be obtained.

[0074] When the PI-based film in this invention is a laminated film, the film thickness can be selected from the range of the aforementioned resin film thickness. 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. If the thicknesses of layers (PI-1) and (PI-2) are at or above the aforementioned lower limit, the yield strength of the laminate can be further improved. The thickness of layer (PI-1) is more preferably 15 μm or more, more preferably 20 μm or more, more preferably 30 μm or more, preferably 80 μm or less, more preferably 60 μm or less, more preferably 55 μm or less, and more preferably 50 μm or less. Furthermore, the thickness of layer (PI-2) is more preferably 2.5 μm or more, more preferably 3 μm or more, more preferably 3.5 μm or more, preferably 20 μm or less, more preferably 15 μm or less, more preferably 10 μm or less, and more preferably 8 μm or less.

[0075] When the PI-based film of the present invention has a layer (PI-3), the thickness of layer (PI-3) can be selected from the range of the thickness of layer (PI-2) described above. The thickness of layer (PI-2) and the thickness of layer (PI-3) can be the same or different from each other, but from the viewpoint of suppressing warping of the laminate, it is preferable that the value of one is within ±25% of the value of the other, and more preferably within ±20%. It should be noted that the thickness of each layer can be measured using a laser microscope or the like, for example, by the method described in the examples.

[0076] 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 thickness is in the aforementioned relationship, the laminate can possess mechanical properties such as high yield strength and flexibility suitable for flexible printed circuit boards. In addition, Df can be reduced and yield strength can be increased, thus obtaining a laminate with 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, when layer (PI-2) is located on the metal layer side and the thickness of layer (PI-2) is 0.05 to 0.3 times the thickness of layer (PI-1), or 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 aforementioned effects of the present invention are more easily obtained. The thickness of layer (PI-2) is more preferably 0.08 times or more, further preferably 0.10 times or more, particularly preferably 0.12 times or more, more preferably 0.25 times or less, further preferably 0.23 times or less, and particularly preferably 0.20 times or less, relative to the thickness of layer (PI-1). It should be noted that when the PI-based film of the present invention has layer (PI-3), the thickness of layer (PI-3) can be selected from the range of layer (PI-2) described above.

[0077] In the PI-based film of the present invention, the type of PI-based resin constituting layers (PI-1) to (PI-3) is not particularly limited as long as the skewness Psk obtained from the cross-sectional curve of the interface between the obtained PI-based film and the metal layer is -0.05 or more, or as long as the interface of the laminate satisfies formula (I). From the viewpoint of maintaining excellent dielectric properties and improving yield strength, each of layers (PI-1) to (PI-3) preferably contains a layer containing a non-thermoplastic polyimide resin (hereinafter, sometimes referred to as an mPI layer) and / or a layer containing a thermoplastic polyimide resin (hereinafter, sometimes referred to as a TPI layer). In particular, from the viewpoint of improving yield strength, each of layers (PI-1) and (PI-2) is preferably an mPI layer or a TPI layer, and more preferably one of layers (PI-1) and (PI-2) is an mPI layer and the other is a TPI layer.

[0078] The mPI layer is generally the main PI-containing resin layer in PI-based films used in flexible printed circuit boards. The TPI layer can also function as an adhesive layer to bond the PI-based film to a metal layer (such as a copper layer), and is preferably located as the outermost layer of the PI-based film that can be bonded to the metal layer.

[0079] In a PI-based resin film having three or more layers containing a PI-based resin layer, it is preferable that at least one layer containing a PI-based resin layer is an mPI layer, and at least one layer (preferably at least two layers) containing a PI-based resin layer is a TPI layer. More preferably, a TPI layer, an mPI layer, and a TPI layer are provided in this order. Therefore, in the PI-based resin film (L), the layer (PI-1) is preferably an mPI layer, and each of the layer (PI-2) and the layer (PI-3) is preferably a TPI layer. If the PI-based resin film (L) has such a layer structure, improved thermal properties can be ensured in the mPI layer, thermal deformation and deterioration can be suppressed, and the dimensional stability of the PI-based resin film can be ensured. Further, the adhesion to a metal layer (e.g., a copper layer) can be improved using the TPI layer, and thus the yield strength of the PI-based resin film can be increased.

[0080] When the PI-based resin film (L) contains multiple TPI layers or mPI layers, the structures of the multiple TPI layers or mPI layers contained may be the same or different from each other. In addition, in the PI-based resin film (L), generally, the structure of the layer (PI-1) is different from those of the layer (PI-2) and the layer (PI-3), but the structures of the layer (PI-2) and the layer (PI-3) may be the same or different.

[0081] In another preferred embodiment of the present invention, when the PI-based resin film is a single-layer film, as long as it is composed of one layer containing a PI-based resin, the skewness Psk obtained from the cross-sectional curve of the interface between the obtained PI-based resin film and the metal layer is -0.05 or more, or the interface of the laminate satisfies formula (I), its type is not particularly limited. From the viewpoint of maintaining excellent dielectric properties and increasing the yield strength, it is preferable to adopt the structure of the aforementioned layer (PI-1). When the PI-based resin film is a single-layer film, the thickness of the film can be selected from the range of the thickness of the above resin film.

[0082] <PI-based resin> The PI-based resin contained in the PI-based resin film is a resin containing a repeating structural unit containing an imide group, and may also contain a repeating structural unit containing both an imide group and an amide group. Note that in the present invention, the "non-thermoplastic" polyimide-based resin means that the storage elastic modulus at 40°C measured using a dynamic viscoelasticity measuring device (DMA) is 1.0×10 9 Pa or more, and the storage elastic modulus at 300°C is 1.0×10 8 Pa or more, and the "thermoplastic" polyimide-based resin means that the storage elastic modulus at 40°C is 1.0×10 9 Pa or more, and the storage elastic modulus at 300°C is less than 1.0×10 8 Pa. Note that the storage elastic modulus can be measured by the method described in the examples, for example.

[0083] From the viewpoint of improving the yield strength, water resistance, drying speed, and dielectric properties of the laminate, the PI-based resin constituting the PI-based film preferably includes structural units (A) derived from tetracarboxylic anhydride and structural units (B) derived from diamine. It should be noted that in this invention, "structural unit derived from..." means "structural unit derived from...", for example, "structural unit derived from tetracarboxylic anhydride (A)" means "structural unit derived from tetracarboxylic anhydride (A)". Furthermore, "PI-based film containing structural unit (A)" means "the PI-based resin constituting the PI-based film contains structural unit (A)", and "layer containing PI-based resin containing structural unit (A)" means "the PI-based resin constituting the layer containing PI-based resin contains structural unit (A)", and the same applies to other structural units. In addition, unless otherwise specified in this specification, the PI resin constituting the PI film (or contained in the PI film) may be replaced by the PI resin described as constituting at least one layer of the layers containing PI resin, at least one layer of layer (PI-1) and layer (PI-2), or at least one layer of layers (PI-1) to (PI-3) (or contained in the at least one layer).

[0084] (Structural unit (A) from tetracarboxylic anhydride) The structural unit (A) derived from tetracarboxylic anhydride (hereinafter sometimes abbreviated as structural unit (A)) is preferably, for example, derived from the structural unit of tetracarboxylic anhydride represented by formula (1). [Chemical Formula 6] [In formula (1), Y represents a tetravalent organic group].

[0085] In formula (1), Y independently represents a tetravalent organic group, preferably a tetravalent organic group with 4 to 40 carbon atoms, and more preferably a tetravalent organic group with 4 to 40 carbon atoms having a cyclic structure. Examples of cyclic structures include alicyclic, aromatic, and heterocyclic structures. In the aforementioned organic groups, the hydrogen atoms in the organic groups can be replaced by halogen atoms, hydrocarbon groups, alkoxy groups, or haloalkyl groups. In this case, the number of carbon atoms in these groups is preferably 1 to 8. In the present invention, the PI-based resin may contain a variety of Ys, and the various Ys may be the same or different from each other. Examples of Ys include: groups or structures represented by formulas (31) to (40); groups obtained by replacing the hydrogen atoms in the groups represented by formulas (31) to (40) with methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, fluoro, chloro, or trifluoromethyl groups; and chain hydrocarbon groups with 1 to 8 carbon atoms in tetravalent form.

[0086] [Chemical Formula 7] In equations (31) to (33), R19 ~R 26 and R 23’ ~R 26’ Each of the following groups 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 therein can be replaced by halogen atoms independently. V 1 and V 2 These can be used to represent single bonds independently (excluding the case where e+d=1), -O-, -CH2-, -CH2-CH2-, -CH(CH3)-, -C(CH3)2-, -C(CF3)2-, -SO2-, -S-, -CO-, -N(R)-, -O-, -CH2-, -CH2-CH2-, -CH(CH3)-, -C(CF3)2-, -SO2-, -S-, -CO-, -N(R)-, -C(CH3)-, -C(CH3)-, -C(CF3)-, -C(CH3)-, -C(CF3)-, -SO2-, -S-, -CO-, -N( ... j - or formula (a), [Chemical Formula 8] (In formula (a), R) 27 ~R 30 Alkyl groups, which can be independently represented by 1 to 6 hydrogen atoms or carbon atoms, D can represent a single bond, -C(CH3)2-, or -C(CF3)2- independently. i represents an integer from 1 to 3. (Indicates a connection key) R j A monovalent hydrocarbon group representing a hydrogen atom or a carbon atom that can be substituted by a halogen atom, having 1 to 12 carbon atoms. e and d represent integers from 0 to 2 independently (where e+d is not 0). f represents an integer from 0 to 3. g and h represent integers from 0 to 4 independently. In formula (39), Z represents a divalent organic group. R a3 Each can independently represent a halogen atom, or an alkyl, alkoxy, aryl, or aryloxy group that may have a halogen atom. s represent integers from 0 to 3 independently. In equation (40), R a2 Each can independently represent a halogen atom, or an alkyl, alkoxy, aryl, or aryloxy group that may have a halogen atom. l represents integers from 0 to 3 independently. (Indicates a connection key).

[0087] In this invention, from the viewpoint of improving the yield strength, water resistance, drying speed and dielectric properties of the laminate, the PI resin constituting the PI film preferably includes at least one structure selected from the group consisting of structures represented by formulas (31), (32), (33), (39) and (40) as Y in formula (1), more preferably includes at least one structure selected from the group consisting of structures containing a benzene skeleton, and even more preferably includes at least one structure selected from the group consisting of structures represented by formulas (32), (39) and (40).

[0088] In equations (31) to (33), R 19 ~R 26 and R 23’ ~R 26’ The atoms are preferably hydrogen atoms or alkyl groups having 1 to 6 carbon atoms, more preferably hydrogen atoms or alkyl groups having 1 to 3 carbon atoms, and even more preferably hydrogen atoms.

[0089] In equation (31), V 1 and V 2 The terms are preferably independent of each other and represent single bonds (excluding the case where e+d=1), -O-, -CH2-, -C(CH3)2-, -C(CF3)2- or -CO-, and more preferably single bonds (excluding the case where e+d=1), -O-, -C(CH3)2- or -C(CF3)2-.

[0090] In equation (31), e and d are preferably 0 or 1, independent of each other (where e+d is not 0). Additionally, e+d preferably represents 1. It should be noted that in equation (31), when e is 0, it indicates that the two benzene rings have not passed through V. 1 When bonding occurs, a value of d = 0 indicates that the two benzene rings did not pass through V. 2 Perform bonding.

[0091] In equations (32) and (33), f preferably represents 0 or 1, and more preferably 0.

[0092] In equation (33), g and h preferably represent integers from 0 to 2, and more preferably 0 or 1. Additionally, g+h preferably represents integers from 0 to 2. It should be noted that when f is 1 or higher, multiple g and h can be the same or different.

[0093] In equation (a), R 27 ~R 30 Each is preferably represented independently by an alkyl group having 1 to 3 carbon atoms, more preferably by hydrogen atoms. i is preferably 1 or 2; when i is 2 or more, multiple D and R... 27 ~R 30 They can be the same or different on their own.

[0094] In formula (39), Z preferably represents a divalent organic group with 4 to 40 carbon atoms, more preferably a divalent organic group with 4 to 40 carbon atoms having a cyclic structure, even more preferably a divalent organic group with 4 to 40 carbon atoms having an aromatic ring, particularly preferably a divalent organic group selected from the group consisting of formulas (z1), (z2), and (z3), and particularly more preferably a divalent organic group represented by formula (z1). [Chemical Formula 9] In equations (z1) to (z3), R z11 ~R z14 Each of the following groups independently represents a hydrogen atom, or a monovalent hydrocarbon group that may have a halogen atom: R z2 Each group independently represents a monovalent hydrocarbon group that may have a halogen atom; n represents an integer from 1 to 4; and j independently represents an integer from 0 to 3. (Indicates a connection key).

[0095] In equation (z1), R z11 ~R z14 Alkyl groups, which independently represent hydrogen atoms or may have halogen atoms, are preferred; more preferably, they are alkyl groups with 1 to 6 carbon atoms, representing hydrogen atoms or may have halogen atoms; even more preferably, they are alkyl groups with 1 to 3 carbon atoms, representing hydrogen atoms or may have halogen atoms; and particularly preferably, they represent hydrogen atoms. In formula (z1), the alkyl group containing R... z11 ~R z14 In the benzene ring, R z11 ~R z14 At least one of them can be a monovalent hydrocarbon group that may have a halogen atom, with R being particularly preferred. z11 ~R z14 It consists entirely of hydrogen atoms.

[0096] In formula (z1), n ​​preferably represents an integer from 1 to 3, more preferably 1 or 2, and even more preferably 2.

[0097] In equation (z2), R z2 The terms "alkyl group" and "alkyl group" are preferred to be alkyl groups that may have halogen atoms, more preferably alkyl groups that may have halogen atoms and have 1 to 6 carbon atoms, and even more preferably alkyl groups that may have halogen atoms and have 1 to 3 carbon atoms.

[0098] In equation (z2), j is preferably 0 or 1 independently of each other, more preferably 0, and even more preferably all j are 0.

[0099] In equation (39), R a3 Preferably, the alkyl group having 1 to 6 carbon atoms, the alkoxy group having 1 to 6 carbon atoms, or the aryl group having 6 to 12 carbon atoms are independently represented.

[0100] R a3 The hydrogen atoms contained therein can be replaced independently by halogen atoms, among which R a3 Alkyl groups, which are independently represented by 1 to 6 carbon atoms, are preferred, and alkyl groups, which are more preferably represented by 1 to 3 carbon atoms, are preferred.

[0101] In equation (39), s preferably represents an integer from 0 to 2 independently of each other, and more preferably represents 0 or 1.

[0102] In equation (40), R a2 Preferably, the alkyl group having 1 to 6 carbon atoms, the alkoxy group having 1 to 6 carbon atoms, or the aryl group having 6 to 12 carbon atoms are independently represented.

[0103] R a2 The hydrogen atoms contained therein can be independently replaced by halogen atoms, among which, as R a2 Alkyl groups having 1 to 6 carbon atoms are preferred examples, and alkyl groups having 1 to 3 carbon atoms are more preferred examples.

[0104] In equation (40), l preferably represents an integer from 0 to 2 independently of each other, and more preferably represents 0 or 1.

[0105] As specific examples of the structures represented by equations (31) to (33), (39), and (40), the structures represented by equations (41) to (56) can be given. It should be noted that in these equations, Indicates a connection key.

[0106] [Chemical Formula 10] In one embodiment of the present invention, when the PI-based resin constituting the PI-based film comprises at least one of the structures selected from the group consisting of formulas (31) to (33), (39), and (40) as Y in formula (1), the proportion of tetracarboxylic anhydride structural units representing at least one of the structures selected from the group consisting of formulas (31) to (33), (39), and (40), particularly the proportion of tetracarboxylic anhydride structural units representing at least one of the structures selected from the group consisting of formulas (32), (39), and (40), is preferably 30 mol% or more, more preferably 50 mol% or more, further preferably 70 mol% or more, particularly preferably 90 mol% or more, and preferably 100 mol% or less. If the aforementioned proportions are within the above range, it is beneficial to improve the yield strength, water resistance, drying speed, and dielectric properties of the laminate.

[0107] The proportions of the aforementioned structural units can be used as follows:1 The determination can be performed using ¹H-NMR, or it can be calculated based on the input ratio of raw materials. The calculation of the proportion of structural units in PI-based resins will follow the same procedure below. Furthermore, in this specification, the term "total amount" of structural units refers to the quantity of a single unit when the structural unit is formed from one type of unit, and the total quantity of these units when the structural unit is formed from two or more types of units.

[0108] (Structural unit (A1) and structural unit (A2)) In one embodiment of the present invention, preferably, the PI-based resin contained in the PI-based film, preferably at least one of layer (PI-1) and layer (PI-2), or the PI-based resin contained in at least one of layer (PI-1) to layer (PI-3) includes a structural unit (A), which includes a structural unit (A1) of tetracarboxylic anhydride represented by formula (A1) (hereinafter, sometimes abbreviated as structural unit (A1)) and / or a structural unit (A2) of tetracarboxylic anhydride represented by formula (A2) (hereinafter, sometimes abbreviated as structural unit (A2)). [Chemical Formula 11] In formula (A1), R a1 Each can independently represent a halogen atom, or an alkyl, alkoxy, aryl, or aryloxy group that may have a halogen atom. k represents an integer from 0 to 2. [Chemical Formula 12] In formula (A2), R a2 Each of the above can independently represent a halogen atom, or an alkyl, alkoxy, aryl, or aryloxy group that may have a halogen atom, and each of the above can independently be an integer from 0 to 3.

[0109] If the PI-based resin includes structural units (A1) and / or structural units (A2) as structural units (A), the yield strength, water resistance, drying speed, and dielectric properties of the laminate can be improved. Furthermore, there is a tendency for a decrease in CTE, which suggests an improvement in the dimensional stability of the laminate.

[0110] From the perspective of improving the yield strength, water resistance, drying speed, dielectric properties, CTE, etc. of laminates, in equations (A1) and (A2), R a1 and R a2 Preferably, the alkyl group having 1 to 6 carbon atoms, the alkoxy group having 1 to 6 carbon atoms, or the aryl group having 6 to 12 carbon atoms are independently formed.

[0111] Examples of alkyl groups having 1 to 6 carbon atoms include methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, n-pentyl, 2-methylbutyl, 3-methylbutyl, 2-ethylpropyl, and n-hexyl.

[0112] Examples of alkoxy groups with 1 to 6 carbon atoms include methoxy, ethoxy, propyloxy, isopropyloxy, n-butoxy, isobutoxy, sec-butoxy, tert-butoxy, pentoxy, hexyloxy, and cyclohexyloxy.

[0113] Examples of aryl groups with 6 to 12 carbon atoms include phenyl, tolyl, xylyl, naphthyl, and biphenyl.

[0114] R a1 and R a2 The hydrogen atoms contained therein can be independently replaced by halogen atoms, such as fluorine, chlorine, bromine, and iodine atoms. Among them, R a1 and R a2 Alkyl groups having 1 to 6 carbon atoms are preferred, and alkyl groups having 1 to 3 carbon atoms are more preferred.

[0115] The bonding positions of the two carboxylic anhydrides bonded to the benzene ring in formula (A1) are not particularly limited, but from the viewpoint of improving the yield strength, water resistance, drying speed, dielectric properties, CTE, etc. of the laminate, it is preferable to be at positions 1,2- and 4,5-, or positions 1,2- and 3,4-, more preferably positions 1,2- and 4,5-. k is preferably 0 or 1, more preferably 0.

[0116] The bonding positions of the two carboxylic anhydrides in formula (A2) that are bonded to the benzene rings constituting the biphenyl skeleton are not particularly limited. Based on the single bond that bonds the two benzene rings, they can be 3,4-position or 2,3-position independently of each other. From the viewpoint of improving the yield strength, water resistance, drying speed, dielectric properties, CTE, etc. of the laminate, the 3,4-position is preferred.

[0117] In formula (A2), l is preferably an integer from 0 to 2, more preferably 0 or 1, and even more preferably 0.

[0118] In one preferred embodiment of the present invention, formula (A1) represents the structural unit (A1-1) represented by formula (A1-1). In another preferred embodiment of the present invention, formula (A2) represents the structural unit (A2-1) represented by formula (A2-1). [Chemical Formula 13] [Chemical Formula 14] .

[0119] If the PI-based resin contains structural units (A1-1) and / or structural units (A2-1) as structural units (A), it is beneficial to improve the yield strength, water resistance, drying speed, and dielectric properties of the laminate. In addition, there is a tendency for CTE to decrease, which can be expected to improve the dimensional stability of the laminate.

[0120] In one embodiment of the present invention, when the PI-based resin comprises structural unit (A1) and / or structural unit (A2), the content of each structural unit (A1) relative to the total amount of the structural unit (A2) is preferably 10 mol% or more, more preferably 15 mol% or more, further preferably 20 mol% or more, more preferably 25 mol% or more, particularly preferably 30 mol% or more, and preferably 90 mol% or less, more preferably 85 mol% or less, further preferably 80 mol% or less, more preferably 75 mol% or less, and particularly preferably 70 mol% or less. If the content of structural unit (A1) and structural unit (A2) is within the above-mentioned range, it is beneficial to improve the yield strength, water resistance, drying speed, and dielectric properties of the laminate. Furthermore, there is a tendency for a decrease in CTE, and an improvement in the dimensional stability of the laminate is expected.

[0121] In another embodiment of the present invention, when the PI-based resin comprises structural unit (A1) and 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 structural unit (A1) to structural unit (A2) is within the above range, the aforementioned effects of the present invention, which are expected due to the presence of structural unit (A1) and / or structural unit (A2) in the PI-based resin, can be readily obtained, and these effects can be further enhanced.

[0122] In one embodiment of the present invention, the layer containing PI-based resin preferably comprises any one or more of the following compositions.

[0123] • In the PI-based film, each of the layers (PI-1) and (PI-2), or layers (PI-1) to (PI-3), comprises at least one of the structural units (A1) and (A2). • In the PI-based film, each of the layers (PI-1) and (PI-2), or layers (PI-1) to (PI-3), contains a structural unit (A1). • In at least one layer of the PI-based film containing PI resin, preferably a TPI layer, the PI-based resin comprises structural unit (A1) and structural unit (A2). • In at least one layer containing a PI resin in a PI-based film, preferably a TPI layer, the PI resin comprises structural units (A1) and structural units (A2), and in at least one other layer containing a PI resin, preferably an mPI layer, the PI resin comprises structural units (A1) and / or structural units (A2).

[0124] In at least one PI-based resin layer, preferably a TPI layer, of the PI-based film, the PI-based resin comprises structural units (A1) and structural units (A2). Furthermore, in at least one other PI-based resin layer, preferably an mPI layer, the PI-based resin comprises structural units (A1) but substantially does not contain structural units (A2). It should be noted that, in this specification, "substantially does not contain 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 does not contain structural units (A2)" means that, relative to the total amount of structural units (A), the content of structural units (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. Hereinafter, unless otherwise explicitly stated, the same applies to other structural units.

[0125] In this specification, "at least one layer of PI-based resin" or "at least one layer of PI-based resin" can be replaced with "at least one layer of PI-based resin (PI-1) and PI-based resin (PI-2), or at least one layer of PI-based resin (PI-1) to (PI-3)".

[0126] (Structural Unit (A3)) In one embodiment of the present invention, the resin contained in the PI-based film, preferably at least one of layer (PI-1) and layer (PI-2), or the PI-based resin contained in at least one of layer (PI-1) to layer (PI-3) may also contain structural units (A3) of tetracarboxylic anhydride containing ester bonds represented by formula (A3) (hereinafter sometimes abbreviated as structural unit (A3)) as structural unit (A). [Chemical Formula 15] In formula (A3), Z represents a divalent organic group. R a3 Each can independently represent a halogen atom, or an alkyl, alkoxy, aryl, or aryloxy group that may have a halogen atom. s represent integers from 0 to 3 independently.

[0127] If the PI-based resin includes structural unit (A3) as structural unit (A), it is beneficial to improve the yield strength, water resistance, drying speed, and dielectric properties of the laminate. In addition, there is a tendency for CTE to decrease, which can be expected to improve the dimensional stability of the laminate. Furthermore, even at relatively low imidization temperatures (e.g., below 350°C), the yield strength and dielectric properties of the obtained laminate can be improved. Therefore, even if the laminate is manufactured by thermal imidizing the PI-based resin precursor coating with a lamination structure with a metal layer, the deterioration of the metal layer surface can be suppressed, resulting in a laminate with high yield strength and excellent high-frequency characteristics.

[0128] As R in equation (A3) a3 One example is R in equation (39) mentioned above. a3 For the same groups illustrated, the preferred method is also the same.

[0129] In equation (A3), s is preferably represented by 0 or 1, and more preferably by 0, as they are independent of each other.

[0130] As Z in formula (A3), the same divalent organic group as the divalent organic group exemplified as Z in formula (39) described above can be cited, and the preferred mode is also the same.

[0131] 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).

[0132] [Chemical Formula 16] If the PI-based resin contained in the PI-based film includes structural units (A3-1) and / or structural units (A3-2) as structural units (A), it is beneficial to improve the yield strength, water resistance, drying speed, and dielectric properties of the laminate. In addition, there is a tendency to reduce CTE, which can be expected to improve the dimensional stability of the laminate. Furthermore, even at relatively low imidization temperatures (e.g., below 350°C), the yield strength and dielectric properties of the obtained laminate can be improved. Therefore, even if the laminate is manufactured by thermal imidizing the PI-based resin precursor coating with a lamination configuration with a metal layer, the deterioration of the metal layer surface can be suppressed, resulting in a laminate with high yield strength and excellent high-frequency characteristics.

[0133] In one embodiment of the present invention, if the PI-based film, preferably at least one layer containing a PI-based resin, more preferably at least one layer (PI-1), and even more preferably an mPI layer, contains PI-based resin comprising structural units (A3), particularly structural units (A3-1) and / or structural units (A3-2) as structural units (A), then the PI-based resin will not be excessively rigid and will become a flexible structure with a certain degree of freedom. Therefore, during imidization, it is easy to form a branched structure by heating, which can further improve the yield strength of the obtained laminate. In addition, there is a tendency for Df to be further reduced, and CTE to be reduced, thus improving the dimensional stability of the laminate.

[0134] In one embodiment of the present invention, when the PI-based resin contains structural unit (A3), its content relative to the total amount of structural unit (A) 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 for example, it may also be 20 mol% or more, 30 mol% or more, or 40 mol% or more. Furthermore, the content of 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 structural unit (A3) is within the above range, the aforementioned effects of the present invention, which are expected due to the presence of structural unit (A3) in the PI-based resin, can be easily obtained, and these effects can be further improved.

[0135] In another embodiment of the present invention, when the PI-based film, preferably a layer (PI-1) containing at least a PI-based resin, contains structural units (A3), the structural units (A3) preferably comprise 50 mol% or less (0 to 50 mol%) of structural units (A) relative to the total amount of structural units (A). That is, in this embodiment, the structural units (A) of the PI-based resin may or may not contain structural units (A3), and when structural units (A3) are included, they are included in an amount of 50 mol% or less. Furthermore, relative to the total amount of structural units (A), the content of structural units (A3) is more preferably 45 mol% or less, further preferably 35 mol% or less, more preferably 25 mol% or less, particularly preferably 15 mol% or less, particularly more preferably 5 mol% or less, especially preferably 1 mol% or less, and the lower limit may be 0 mol% or more. If the content of structural unit (A3), especially structural unit (A3-1) and / or structural unit (A3-2) in the PI-based resin is below the aforementioned upper limit, the yield strength, water resistance, drying speed, and dielectric properties of the laminate can be further improved. In addition, there is a tendency for CTE to decrease, which can be expected to improve the dimensional stability of the laminate.

[0136] In one embodiment of the present invention, more preferably, in at least one layer containing a PI resin, preferably a TPI layer constituting a PI-based film, the PI resin comprises structural unit (A1) and structural unit (A2), and in other at least one layer containing a PI resin, preferably an mPI layer, the PI resin comprises at least two structural units selected from structural unit (A1), structural unit (A2) and structural unit (A3) (preferably structural unit (A1) and structural unit (A2) and / or structural unit (A3)).

[0137] (Structural Unit (A4)) In one embodiment of the present invention, the PI-based resin may also include structural units (A4) derived from tetracarboxylic anhydride (hereinafter, sometimes abbreviated as structural unit (A4)) as structural units (A), in addition to structural units (A1), structural units (A2) and structural units (A3).

[0138] It should be noted that in this specification, "structural units (A4) derived from tetracarboxylic anhydride other than structural units (A1), (A2) and (A3)" refers to structural units derived from tetracarboxylic anhydride that do not belong to any of the structural units (A1), (A2) and (A3). The term "content of structural units (A4)" refers to the total amount of structural units (A4) when multiple structural units (A4) are present.

[0139] In one embodiment of the present invention, as a structural unit (A4), for example, a tetracarboxylic anhydride structural unit represented by Y in formula (1) as expressed by formulas (31), (33) to (38) can be cited. From the viewpoint of improving the yield strength, water resistance, drying speed and dielectric properties of the laminate, a tetracarboxylic anhydride structural unit represented by Y in formula (1) as expressed by formulas (42), (44) to (49) or (53) is preferred, and a tetracarboxylic anhydride structural unit represented by Y in formula (1) as expressed by formulas (42), (46), (49) or (53) is more preferred.

[0140] In one embodiment of the present invention, when the PI-based resin contains structural unit (A4), its content relative to the total amount of structural unit (A) can be, for example, 0.01 to 55 mol%, or 0.01 to 40 mol%, preferably 40 mol% or less, more preferably 35 mol% or less, further preferably 30 mol% or less, particularly preferably 25 mol% or less, and generally 0.01 mol% or more, preferably 10 mol% or more.

[0141] (Structural unit (B) from diamine) The PI-based resin constituting the PI-based film typically contains structural units (B) derived from diamines (hereinafter sometimes simply referred to as structural units (B)). Structural units (B) are preferably, for example, structural units derived from diamines represented by formula (2). [Chemical Formula 17] [In formula (2), X represents a divalent organic group].

[0142] In formula (2), X represents a divalent organic group, preferably a divalent organic group with 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 or divalent cyclic aliphatic groups. Among these, divalent cyclic aliphatic groups and divalent aromatic groups are preferred from the viewpoint of improving the yield strength, water resistance, drying speed, and dielectric properties of the laminate, and divalent aromatic groups are more preferred. For divalent organic groups, the hydrogen atoms in the organic group can be replaced by halogen atoms, hydrocarbon groups, alkoxy groups, or haloalkyl groups. In this case, the number of carbon atoms in these groups is preferably 1 to 8. It should be noted that in this specification, a divalent aromatic group is a divalent organic group having an aromatic group, and an aliphatic group or other substituents may be included in a part of its structure. In addition, a divalent aliphatic group is a divalent organic group that has an aliphatic group and may contain other substituents in part of its structure, but does not contain aromatic groups.

[0143] In one embodiment of the present invention, the PI-based resin may contain a variety of X, which may be the same as or different from each other. Examples of X in formula (2) include: groups (structures) represented by formulas (60) to (65); groups obtained by replacing the hydrogen atoms in the groups represented by formulas (60) to (65) with methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, fluoro, chloro, or trifluoromethyl.

[0144] [Chemical Formula 18] In equations (60) and (61), R a and R b R represents halogen atoms independently, or alkyl, alkoxy, aryl, or aryloxy groups that may have halogen atoms. a and R b The hydrogen atoms contained therein can be replaced by halogen atoms independently. W represents, independently, single bonds, -O-, -CH2-, -CH2-CH2-, -CH(CH3)-, -C(CH3)2-, -C(CF3)2-, -COO-, -OOC-, -SO-, -SO2-, -S-, -CO-, -N(R) c - or -CONH-, R c A monovalent hydrocarbon group consisting of 1 to 12 carbon atoms that can be substituted by halogen atoms, representing a hydrogen atom. t' represents an integer from 0 to 4, u represents an integer from 0 to 4, and n represents an integer from 0 to 4. In formula (62), ring A represents a cycloalkane ring with 3 to 8 carbon atoms. R d Alkyl groups having 1 to 20 carbon atoms r represents an integer greater than 0 and less than (the number of carbon atoms in ring A - 2). S1 and S2 represent integers from 0 to 20 independently. In equations (60) to (65), (Indicates a connection key).

[0145] Other examples of X in formula (2) include divalent acyclic aliphatic groups such as ethylene, 1,3-propylene, 1,4-butylene, 1,5-pentane, 1,6-hexane, 1,2-propylene, 1,2-butanediyl, 1,3-butanediyl, 1,12-dodecanediyl, 2-methyl-1,2-propanediyl, and 2-methyl-1,3-propanediyl. In these divalent acyclic aliphatic groups, hydrogen atoms can be replaced by halogen atoms, and carbon atoms can be replaced by heteroatoms, such as oxygen atoms, nitrogen atoms, etc.

[0146] Among them, from the viewpoint of improving the yield strength, water resistance, drying speed and dielectric properties of the laminate, the PI resin of the present invention preferably includes the structure represented by formula (60) and formula (61) as X in formula (2), and more preferably includes the structure represented by formula (60).

[0147] In formulas (60) and (61), the connecting bonds of each benzene ring or each cyclohexane ring can be bonded at any position among ortho, meta, para, α, β, or γ, based on -W- or the single bond connecting each benzene ring or each cyclohexane ring. From the viewpoint of improving the yield strength, water resistance, drying speed, and dielectric properties of the laminate, it is preferable to bond at the meta or para, or β or γ position, and more preferably at the para or γ position. If the amino group directly connected to the benzene ring and the divalent connecting group -W- are in the meta position, there is a tendency to improve the flexibility of the polyimide molecular chain.

[0148] In equations (60) and (61), R a and R b The groups are preferably halogen atoms, or alkyl, alkoxy, or aryl groups that may have halogen atoms, and more preferably halogen atoms, alkyl groups having 1 to 6 carbon atoms, alkoxy groups having 1 to 6 carbon atoms, or aryl groups having 6 to 12 carbon atoms. Examples of alkyl groups having 1 to 6 carbon atoms, alkoxy groups having 1 to 6 carbon atoms, and aryl groups having 6 to 12 carbon atoms include the groups exemplified above. a and R b The hydrogen atoms contained therein can be independently replaced by halogen atoms, such as fluorine, chlorine, bromine, and iodine atoms. a and R b Alkyl groups having 1 to 6 carbon atoms or fluoroalkyl groups having 1 to 6 carbon atoms are preferred independently. From the viewpoint of adhesion to metal layers, etc., fluorine-free alkyl groups having 1 to 6 carbon atoms are more preferred, fluorine-free alkyl groups having 1 to 3 carbon atoms are even more preferred, and methyl groups are particularly preferred.

[0149] In equations (60) and (61), t' and u are preferably integers from 0 to 2, and more preferably 0 or 1.

[0150] In formulas (60) and (61), W is preferably a single bond, -O-, -CH2-, -C(CH3)2-, -C(CF3)2-, -SO2-, -S-, -COO-, -OOC- or -CO-, more preferably a single bond, -O-, -CH2-, -C(CH3)2-, -C(CF3)2-, -COO-, -OOC- or -CO-, even more preferably a single bond, -O-, -CH2- or -C(CH3)2-, and particularly preferably -O- or -C(CH3)2-.

[0151] In equations (60) and (61), n ​​is preferably an integer from 0 to 3, more preferably from 1 to 3. When n is 2 or more, multiple W and R... a The , , and t' can be the same or different from each other, and the positions of the connecting bonds of each benzene ring based on -W- can also be the same or different.

[0152] In the case where the PI-based 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, and R in formula (60) and formula (61) are... a R b , t' and u can be independently combined with W, n, and R in another equation (60) and equation (61). a R b , t' and u are the same or different.

[0153] In formula (62), ring A represents a cycloalkane ring with 3 to 8 carbon atoms, such as cyclopropane, cyclobutane, cyclopentane, cyclohexane, cycloheptane, and cyclooctane rings, and preferably cycloalkane rings with 4 to 6 carbon atoms. In ring A, the connecting bonds may be adjacent to each other or not. For example, if ring A is a cyclohexane ring, the two connecting bonds may be in an α-position, β-position, or γ-position relationship, and are preferably in a β-position or γ-position relationship.

[0154] R in equation (62) d Preferably, it is an alkyl group having 1 to 10 carbon atoms. In formula (62), r is preferably 0 or more, more preferably 4 or less. In formula (62), S1 and S2 are each preferably 0 or more, more preferably 2 or more, and more preferably 15 or less.

[0155] As specific examples of the structures represented by equations (60) to (62), structures represented by equations (71) to (92) can be cited. It should be noted that in these equations, Indicates a connection key.

[0156] [Chemical Formula 19] In one embodiment of the present invention, when the PI-based resin constituting the PI-based film contains at least one structural unit of a diamine represented by formulas (60) and (61) as X in formula (2), the proportion of X in formula (2) from the diamine structural unit represented by formulas (60) and (61) relative to the total amount of structural unit (B) is preferably 30 mol% or more, more preferably 50 mol% or more or greater than 50 mol%, further preferably 70 mol% or more, particularly preferably 90 mol% or more, and preferably 100 mol% or less. If the proportion of X in formula (2) from the diamine structural unit represented by formulas (60) and (61) is within the aforementioned range, the yield strength, water resistance, drying speed, and dielectric properties of the laminate can be improved. In addition, there is a tendency for CTE to decrease, and an improvement in the dimensional stability of the laminate can be expected.

[0157] (Structural Unit (B1)) In one embodiment of the present invention, preferably, the PI-based film contains at least one layer of the PI-based resin, preferably layer (PI-1) and layer (PI-2), or the PI-based resin contained in at least one layer of layer (PI-1) to layer (PI-3) contains a structural unit (B) that contains a structural unit (B1) derived from a diamine represented by formula (B1) (hereinafter, sometimes abbreviated as structural unit (B1)). [Chemical Formula 20] In formula (B1), R b1 Each can independently represent a halogen atom, or an alkyl, alkoxy, aryl, or aryloxy group that may have a halogen atom. W can be independently represented by the following octets: -O-, -CH2-, -CH2-CH2-, -CH(CH3)-, -C(CH3)2-, -C(CF3)2-, -COO-, -OOC-, -SO-, -SO2-, -S-, -CO-, -N(R) c The divalent linking group or single bond in the group consisting of - and -CONH- (where m is 2 or more, and at least one W is the aforementioned divalent linking group), R c A monovalent hydrocarbon group representing a hydrogen atom or a carbon atom that can be substituted by a halogen atom, having 1 to 12 carbon atoms. m represents an integer from 1 to 4. q represents integers from 0 to 4 independently.

[0158] If the PI-based resin includes structural unit (B1) as structural unit (B), the yield strength, water resistance, drying speed, and dielectric properties of the laminate can be improved. Furthermore, the CTE can be reduced, leading to improved dimensional stability of the laminate and enhancing adhesion to the metal layer. Moreover, even at relatively low imidization temperatures (e.g., below 350°C), the yield strength and dielectric properties of the resulting laminate can be improved. Therefore, even when manufacturing a laminate by thermally imidizing a PI-based resin precursor coating with a metal layer, surface degradation of the metal layer can be suppressed, resulting in a laminate with high yield strength and excellent high-frequency characteristics.

[0159] As R in equation (B1) b1 One example is R in equation (60) mentioned above. a and R b The groups shown are the same as those in the example. In formula (B1), q is preferably an integer from 0 to 2, more preferably 0 or 1. Furthermore, from the viewpoint of improving the yield strength, water resistance, drying speed, dielectric properties, CTE, etc., of the laminate, m in formula (B1) is preferably an integer from 1 to 3, more preferably 2 or 3. In (B1), multiple W, R... b1 The , , and q can be the same or different from each other, and the positions of -W- based on -NH2 of each benzene ring can also be the same or different.

[0160] In formula (B1), -W- can be independently bonded to any position among ortho, meta, para, α, β, or γ, based on -NH2 of each benzene ring. Preferably, they are bonded to meta or para, β or γ, and more preferably to para or γ. When m is 2 or more, on the benzene ring bonded by the two W-, the bonding positions of the two W- can be ortho, meta, or para, or α, β, or γ, preferably meta or para, or β or γ.

[0161] As specific examples of the structure represented by equation (B1), the structures represented by equations (B1-1) to (B1-6) can be cited.

[0162] [Chemical Formula 21] R in equations (B1-1) to (B1-6) b1 and q and R in equation (B1) b1 And q is defined similarly, W 1 ~W 6 The options for each option, which can be chosen independently, are -O-, -CH2-, -CH2-CH2-, -CH(CH3)-, -C(CH3)2-, -C(CF3)2-, -COO-, -OOC-, -SO-, -SO2-, -S-, -CO-, and -N(R). c The divalent linking group in the group consisting of - and -CONH-, R c This represents a monovalent hydrocarbon group consisting of 1 to 12 carbon atoms that can be substituted by halogen atoms, and a hydrogen atom. It should be noted that compounds in formula (B1-4) that are repeated in formula (B1-3) are treated as compounds of formula (B1-3). Hereinafter, structural units from formulas (B1-1) to (B1-6) will sometimes be referred to as structural units (B1-1) to (B1-6), respectively.

[0163] R in equations (B1-1) to (B1-6) b1 And q, can be exemplified as R in equation (B1) b1 The preferred method is the same as the one exemplified by q.

[0164] W in equations (B1-1) to (B1-6) 1 ~W 6 The preferred alternatives, independently of each other, are -O-, -CH2-, -CH2-CH2-, -CH(CH3)-, -C(CH3)2-, -C(CF3)2-, -COO-, -OOC-, -SO2-, -S-, -CO-, or -CONH-. W in formula (B1-1) 1Preferably, it is -O-, -CH2-, -C(CH3)2-, -SO2-, -S-, or -CO-. W in formulas (B1-2), (B1-4), and (B1-6) 2 W 4 and W 6 Each is preferably -O-. W in equation (B1-3) 3 Preferably, it is -O-, -CH2-, -C(CH3)2-, -SO2-, -CO-, or -CONH-, where W in formula (B1-5) 5 Preferably, it is -C(CH3)2-, -O-, -SO2- or -CO-.

[0165] In one embodiment of the present invention, the PI-based film in the laminate preferably comprises structural units derived from diamines of formula (B1) with m=1 or 2, such as the aforementioned structural units (B1-1) and / or (B1-2) as structural units (B). As structural units derived from diamines with m=2, the aforementioned structural unit (B1-2) is preferred. The inclusion of such structural units improves the yield strength, water resistance, drying speed, and dielectric properties of the laminate. Furthermore, there is a tendency for a decrease in CTE, leading to an improvement in the dimensional stability of the laminate. In addition, the inclusion of these structural units also helps to improve the adhesion between the PI-based film and the metal layer.

[0166] In another embodiment of the present invention, the PI-based film in the laminate of the present invention preferably includes structural units (B) derived from diamines with m = 3 or 4, such as the aforementioned structural units (B1-3) to (B1-6), and more preferably structural units derived from diamines with m = 3. For example, the aforementioned structural units (B1-5) are preferably included as structural units derived from diamines with m = 3. Including such structural units can improve the yield strength, water resistance, drying speed, and dielectric properties of the laminate. Furthermore, there is a tendency for a decrease in CTE, and an improvement in the dimensional stability of the laminate is expected. In addition, the inclusion of these structural units also helps to improve the adhesion between the PI-based film and the metal layer.

[0167] In one embodiment of the present invention, the structural unit (B1) is preferably the structural unit (B1-2), and more preferably the structural unit (B1-2) is the structural unit represented by formula (B1-2') and / or formula (B1-2'').

[0168] [Chemical Formula 22] In equation (B1-2') and equation (B1-2''), R b1 W 2 , and q and R in equation (B1-2) b1 W2 、 and q are defined in the same way.

[0169] 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).

[0170] [Chemical Formula 23] Including the aforementioned structural units as structural unit (B) can improve the yield strength, water resistance, drying speed, and dielectric properties of the laminate. Furthermore, there is a tendency for a decrease in CTE, suggesting an improvement in the dimensional stability of the laminate. In addition, the inclusion of these structural units also helps to improve the adhesion between the PI-based film and the metal layer.

[0171] In another embodiment of the present invention, the structural unit (B1) is preferably the structural unit (B1-5), and more preferably the structural unit (B1-5) is the structural unit represented by formula (B1-5a).

[0172] [Chemical Formula 24] If the aforementioned structural unit is included as structural unit (B), it is beneficial to improve the yield strength, dielectric properties, and reduce the CTE of the laminate.

[0173] In one embodiment of the present invention, when the PI-based resin constituting the PI-based film includes structural units (B1), the content of structural units (B) relative to the total amount of the structural units (B) is preferably 3 mol% or more, more preferably 5 mol% or more, further preferably 7 mol% or more, and even more preferably 10 mol% or more. For example, it may also be 20 mol% or more, 30 mol% or more, or 40 mol% or more. If the content of structural units (B1) is at or above the aforementioned lower limit, it is beneficial to improve the yield strength, water resistance, drying speed, dielectric properties, and reduce the CTE of the laminate. In addition, if the total amount of structural units (B1) is higher, there is a tendency for increased adhesion to the metal layer. Therefore, from this point of view, the content of structural units (B1) relative to the total amount of structural units (B) may be, for example, 50 mol% or more, 60 mol% or more, or 70 mol% or more. The content of structural units (B1) relative to the total amount of structural units (B) is preferably 99 mol% or less, more preferably 95 mol% or less, and even more preferably 90 mol% or less.

[0174] <Structural Unit (B2)> In one embodiment of the present invention, preferably, the PI-based resin contained in the PI-based film, preferably at least one of the layers (PI-1) and (PI-2), or the PI-based resin contained in at least one of the layers (PI-1) to (PI-3) contains a structural unit (B2) of a diamine containing a biphenyl skeleton represented by formula (B2) (hereinafter sometimes abbreviated as structural unit (B2)) as structural unit (B). [Chemical Formula 25] In formula (B2), R b2 Each can independently represent a halogen atom, or an alkyl, alkoxy, aryl, or aryloxy group that may have a halogen atom. p represents an integer from 0 to 4.

[0175] If structural unit (B) includes the aforementioned structural unit (B2), the PI resin will not be excessively rigid and will become a flexible structure with a certain degree of freedom. Therefore, it is easy to form a branched structure through heating during imidization. In addition, there is a tendency to increase crystallinity. Therefore, it is beneficial to improve the yield strength, dielectric properties, water resistance, drying speed, and reduce CTE of the laminate.

[0176] In equation (B2), R b2 Preferably, the groups represent halogen atoms independently, or alkyl, alkoxy, or aryl groups that may have halogen atoms; more preferably, they represent halogen atoms, alkyl groups having 1 to 6 carbon atoms, alkoxy groups having 1 to 6 carbon atoms, or aryl groups having 6 to 12 carbon atoms. Examples of alkyl groups having 1 to 6 carbon atoms, alkoxy groups having 1 to 6 carbon atoms, and aryl groups having 6 to 12 carbon atoms include the groups exemplified above. b2 The hydrogen atoms contained therein can be independently replaced by halogen atoms, and the same halogen atoms mentioned above can be cited as examples of such halogen atoms. R b2 Alkyl groups having 1 to 6 carbon atoms or fluoroalkyl groups having 1 to 6 carbon atoms are preferred independently. Furthermore, from the viewpoint of adhesion to metal layers, etc., fluorine-free alkyl groups having 1 to 6 carbon atoms are more preferred, fluorine-free alkyl groups having 1 to 3 carbon atoms are even more preferred, and methyl groups are particularly preferred.

[0177] In formula (B2), p is preferably an integer from 0 to 2, and more preferably 0 or 1.

[0178] In formula (B2), the -NH2 group bonded to each benzene ring can be bonded to any position among the ortho, meta, para, α, β, or γ positions, based on the single bond that connects each benzene ring. From the viewpoint of improving the yield strength, dielectric properties, water resistance, drying speed, and reducing CTE of the laminate, it is preferable to bond to the meta or para position, or the β or γ position, and even more preferable to bond to the para or γ position.

[0179] In a preferred embodiment of the present invention, formula (B2) is preferably represented by formula (B2').

[0180] [Chemical Formula 26] If the PI-based resin constituting at least one layer comprises a PI-based resin having structural units (B2), particularly structural units derived from diamines represented by formula (B2') as structural units (B), the PI-based resin will not be excessively rigid and will become a flexible structure with a certain degree of freedom. Therefore, it is easy to form a branched structure by heating during imidization. In addition, there is a tendency to increase crystallinity. Therefore, it is beneficial to improve the yield strength, water resistance, drying speed, dielectric properties, and reduce CTE of the laminate. Furthermore, the aforementioned effects can be obtained even at relatively low imidization temperatures (e.g., below 350°C). Therefore, even if a laminate is manufactured by thermally imidizing a PI-based resin precursor coating with a laminate structure to a metal layer, the deterioration of the metal layer surface can be suppressed, resulting in a laminate with high yield strength and excellent high-frequency characteristics.

[0181] In one embodiment of the present invention, when the PI-based resin includes structural unit (B2), its content relative to the total amount of structural unit (B) is preferably 1 mol% or more, more preferably 5 mol% or more, and even more preferably 10 mol% or more. For example, it may also be 20 mol% or more, 30 mol% or more, greater than 30 mol%, 40 mol% or more, or 50 mol% or more. If the content of structural unit (B2) is at or above the above-mentioned lower limit, it is beneficial to improve the yield strength, water resistance, drying speed, dielectric properties, and reduce CTE of the laminate. In addition, relative to the total amount of structural unit (B), the content of structural unit (B1) is preferably 99 mol% or less, more preferably 95 mol% or less, and even more preferably 92 mol% or less. For example, it may also be 90 mol% or less, 80 mol% or less, 70 mol% or less, or 60 mol% or less.

[0182] In one embodiment of the present invention, when the PI-based resin constituting the PI-based film comprises structural units (B1) and (B2), their total content relative to the total amount of structural units (B) is preferably 30 mol% or more, more preferably 40 mol% or more, further 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. If the total content of structural units (B1) and (B2) is at or above the aforementioned lower limit, the aforementioned effects of the present invention, which are expected due to the presence of structural units (B1) and (B2) in the PI-based resin, can be readily obtained, and these effects can be further improved.

[0183] In another embodiment of the present invention, when the PI-based resin comprises structural unit (B1) and 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. For example, it can also be 92:8 to 20:80 or 90:10 to 60:40. If the content ratio of structural unit (B1) to structural unit (B2) is within the above range, the above-mentioned effects of the present invention, which can be expected due to the presence of structural unit (B1) and structural unit (B2) in the PI-based resin, can be easily obtained, and these effects can be further improved.

[0184] In one embodiment of the present invention, the PI-containing resin layer constituting the PI-based film preferably comprises any one or more of the following compositions.

[0185] • In the PI-based film, in layers (PI-1) and (PI-2), or layers (PI-1) to (PI-3), the PI-based resin includes at least one of structural unit (B1) and structural unit (B2); • In layers (PI-1) and (PI-2), or layers (PI-1) to (PI-3) of the PI-based film, the PI-based resin contains structural unit (B1). • In the PI-based film, in layers (PI-1) and (PI-2), or layers (PI-1) to (PI-3), the PI-based resin contains structural units (B1) and (B2).

[0186] • In at least one layer of a PI-based film containing a PI-based resin, the PI-based resin comprises structural unit (B1) and structural unit (B2).

[0187] (Structural Unit (B3)) In one embodiment of the present invention, the structural unit (B) may also include a structural unit (B3) derived from a diamine other than structural units (B1) and structural units (B2) (hereinafter sometimes abbreviated as structural unit (B3)). Examples of structural units (B3) include structural units derived from a diamine where m is 0 in formula (B1), structural units derived from a diamine where X in formula (2) is represented by formulas (61) to (64), etc., among which, structural units derived from a diamine where X in formula (2) is represented by formula (74) (structural units derived from p-phenylenediamine) are preferred. In this specification, "structural unit (B3) derived from a diamine other than structural units (B1) and structural units (B2)" refers to a structural unit derived from a diamine that is different from either structural unit (B1) or structural unit (B2).

[0188] In one embodiment of the present invention, when the structural unit (B) includes the structural unit (B3), the content of the structural unit (B3) is preferably 25 mol% or less, more preferably 20 mol% or less, even more preferably 10 mol% or less, and typically 0.01 mol% or more, relative to the total amount of the structural unit (B).

[0189] In one embodiment of the present invention, the polyimide resin contained in the PI-based resin layer (PI-1) and the PI-based resin contained in the PI-based resin layer (PI-2) can be the same resin or different resins. From the viewpoint of improving the yield strength, water resistance, drying speed, dielectric properties, and reducing CTE of the laminate, it is preferable that the PI-based resins contained in each layer are different resins. It should be noted that the meaning of "different resins" includes not only resins with different types of structural units, but also resins whose content (or ratio) differs even if the types of structural units are the same.

[0190] In one embodiment of the present invention, the PI-based resin layer (PI-1) and the PI-based resin layer (PI-2) each preferably comprise a polyimide-based resin having at least two structural units (A) derived from tetracarboxylic anhydride. With such an embodiment, the yield strength and dielectric properties of the laminate are easily improved, and the CTE is easily reduced.

[0191] In one embodiment of the present invention, preferably, in the PI-based resin layer (PI-1) and the PI-based resin layer (PI-2), or the PI-based resin layers (PI-1) to (PI-3), preferably the mPI layer and the TPI layer, the PI-based resin includes structural unit (A1) and / or structural unit (A2) as structural unit (A), and structural unit (B1) as structural unit (B) (preferably structural unit (B1) and structural unit (B2)).

[0192] In a preferred embodiment of the present invention, the PI-resin-containing layer (PI-1) constituting the PI-based film, and preferably the mPI layer, contains PI-based resin comprising at least two structural units selected from structural units (A1), (A2), and (A3) (preferably structural units (A1), (A2), and / or (A3)) as structural units (A). The PI-resin-containing layer (PI-2) and preferably the TPI layer contain PI-based resin comprising structural units (A1) and (A2) as structural units (A). Furthermore, the PI-based resin constituting the PI-resin-containing layer (PI-1), the PI-resin-containing layer (PI-2), the mPI layer, and the TPI layer each comprises structural unit (B1) (preferably structural units (B1) and (B2)) as structural units (B).

[0193] In a preferred embodiment of the present invention, when a PI-based resin layer (PI-3) is further included, the PI-based resin layer (PI-1) constituting the PI-based film (L), preferably the mPI layer, contains at least two structural units selected from structural units (A1, A2, and A3) (preferably structural units (A1 and A2 and / or structural units (A3)) as structural units (A). The PI-based resin layer (PI-2), the PI-based resin layer (PI-3), preferably the TPI layer, contains structural units (A1) and (A2) as structural units (A). Furthermore, the PI-based resin constituting the PI-based resin layers (PI-1) to (PI-3), preferably the mPI layer and the TPI layer, each contains structural unit (B1) (preferably structural units (B1) and (B2)) as structural units (B).

[0194] If the mPI layer, TPI layer, layer (PI-1), layer (PI-2), and optional layer (PI-3) are each combined to include the above-described structural units, the PI-based resin in each layer will not be excessively rigid and will become a flexible structure with a certain degree of freedom. Therefore, it is easy to form a branched structure through heating during imidization, and there is a tendency to increase crystallinity. In addition, the interaction between two adjacent layers can be improved. Therefore, the above-described effects of the present invention, which are expected due to the presence of each structural unit in the PI-based resin, can be easily obtained, and these effects can be further improved.

[0195] <Layer (PI-1)> In one embodiment of the present invention, the PI-based resin constituting the layer (PI-1) includes structural unit (A1) and / or structural unit (A2) as structural unit (A), preferably including at least two structural units selected from structural unit (A1), structural unit (A2) and structural unit (A3), more preferably including structural unit (A1) and structural unit (A2) and / or structural unit (A3). When the layer (PI-1) includes these structural units, the content of structural unit (A1) relative to the total amount of structural unit (A) is preferably 20 mol% or more, more preferably 30 mol% or more, further preferably 35 mol% or more, particularly preferably 40 mol% or more, preferably 80 mol% or less, more preferably 75 mol% or less, further preferably 70 mol% or less, and particularly preferably 65 mol% or less. Relative to the total amount of structural unit (A), the content of structural unit (A2) is preferably 20 mol% or more, more preferably 30 mol% or more, further preferably 35 mol% or more, particularly preferably 40 mol% or more, preferably 80 mol% or less, more preferably 75 mol% or less, further preferably 70 mol% or less, and particularly preferably 65 mol% or less. Furthermore, relative to the total amount of structural unit (A), the content of structural unit (A3) is preferably 3 mol% or more, more preferably 5 mol% or more, further preferably 7 mol% or more, and even more preferably 10 mol% or more. For example, it may also be 20 mol% or more, 30 mol% or more, or 40 mol% or more, preferably 75 mol% or less, more preferably 70 mol% or less, further preferably 65 mol% or less, and particularly preferably 60 mol% or less. 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, even more preferably 25 mol% or less, particularly preferably 15 mol% or less, even more preferably 5 mol% or less, even more preferably 1 mol% or less, and the lower limit can be 0 mol%.

[0196] If the contents of structural units (A1), (A2), and / or (A3) are each within the aforementioned range, the PI-based resin will not be excessively rigid but will become a flexible structure with a certain degree of freedom. Therefore, it is easy to form a branched structure through heating during imidization, and there is also a tendency to increase crystallinity. Thus, a laminate with excellent yield strength, dielectric properties, and thermophysical properties can be obtained. Furthermore, the laminate exhibits excellent water resistance and drying speed.

[0197] On the other hand, in another embodiment of the present invention, the content of structural unit (A2) in the PI-based 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 unit (A). In one embodiment of the present invention, layer (PI-1) may substantially contain no structural unit (A2), and the lower limit of the content of structural unit (A2) may be 0 mol%.

[0198] In one embodiment of the present invention, the PI-based resin constituting layer (PI-1) preferably includes structural unit (B1) as structural unit (B). As structural unit (B1), it preferably includes structural units (B1-2) and (B1-5), more preferably structural unit (B1-2), and even more preferably structural unit (B1-2''). Relative to the total amount of structural units (B), the content of structural unit (B1) in the PI-based resin constituting layer (PI-1) 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, for example, it may also be 20 mol% or more, 30 mol% or more, or 40 mol% or more, and 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. In addition, the PI-based resin constituting the layer (PI-1) preferably also includes structural unit (B2) as structural unit (B), and its content relative to the total amount of structural unit (B) is preferably 10 mol% or more, more preferably 20 mol% or more, further preferably 30 mol% or more or greater than 30 mol%, more preferably 35 mol% or more, particularly preferably 40 mol% or more, preferably 99 mol% or less, more preferably 95 mol% or less, further preferably 92 mol% or less, for example, it may also be 90 mol% or less, 80 mol% or less, 70 mol% or less, or 60 mol% or less.

[0199] If the contents of structural units (B1) and / or (B2) are each within the aforementioned range, the PI-based resin will not be excessively rigid but will become a flexible structure with a certain degree of freedom. Therefore, it is easy to form a branched structure through heating during imidization, and there is also a tendency to increase crystallinity. As a result, the mechanical properties of layer (PI-1) can be improved, the dielectric constant (Df) can be reduced, and the coulombic ester (CTE) can be effectively reduced. Therefore, a laminate with excellent yield strength, dielectric properties, and thermal properties can be obtained. In addition, the laminate can have excellent water resistance and drying speed.

[0200] <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 resin constituting layers (PI-2) and (PI-3) each includes a structural unit (A1) as a structural unit (A), preferably including both structural units (A1) and (A2) as structural units (A). When these structural units are included, the content of structural unit (A1) relative to the total amount of structural units (A) is preferably 10 mol% or more, more preferably 15 mol% or more, further preferably 20 mol% or more, preferably 80 mol% or less, more preferably 70 mol% or less, and further preferably 60 mol% or less. Furthermore, the content of structural unit (A2) relative to the total amount of structural units (A) is preferably 20 mol% or more, more preferably 30 mol% or more, further preferably 40 mol% or more, further preferably 50 mol% or more, particularly preferably 60 mol% or more, preferably 90 mol% or less, more preferably 85 mol% or less, further preferably 80 mol% or less, and further preferably 75 mol% or less.

[0201] If the contents of structural units (A1) and / or (A2) are each within the aforementioned range, the PI-based resin will not be excessively rigid but will become a flexible structure with a certain degree of freedom. Therefore, it is easy to form a branched structure through heating during imidization, and there is also a tendency to increase crystallinity. As a result, the mechanical properties of layers (PI-2) and (PI-3) can be improved, the dielectric constant (Df) can be reduced, and the coulombic ester (CTE) can be effectively reduced. Therefore, a laminate with excellent yield strength, dielectric properties, and thermal properties can be obtained. In addition, it is expected to improve the adhesion between the PI-based film and the metal layer. Furthermore, the laminate exhibits excellent water resistance and drying speed.

[0202] In one embodiment of the present invention, the content of structural unit (A3) in the PI-based resin constituting layer (PI-2) and layer (PI-3) is preferably 10 mol% or less, more preferably 8 mol% or less, further preferably 5 mol% or less, and particularly preferably 3 mol% or less, relative to the total amount of structural unit (A). In one embodiment of the present invention, layer (PI-2) and layer (PI-3) may substantially contain no structural unit (A3), and the lower limit of the content of structural unit (A3) may be 0 mol%.

[0203] In one embodiment of the present invention, the PI-based resin constituting layer (PI-2) and layer (PI-3) preferably includes structural unit (B1) as structural unit (B). As structural unit (B1), it preferably includes structural unit (B1-2), and more preferably includes structural unit (B1-2') that improves the flexibility of the PI-based resin. Regarding the content of structural unit (B1) in the PI-based resin constituting these layers, relative to the total amount of structural unit (B), it is preferably 20 mol% or more, more preferably 30 mol% or more, further preferably 35 mol% or more, particularly preferably 40 mol% or more, preferably 99 mol% or less, more preferably 95 mol% or less, further preferably 92 mol% or less, and for example, it may also be 90 mol% or less, 80 mol% or less, 70 mol% or less, or 60 mol% or less. In addition, as structural unit (B), it is preferable to also include structural unit (B2), the content of which is preferably 1 mol% or more, more preferably 5 mol% or more, even more preferably 10 mol% or more, for example, it may also be 20 mol% or more, 30 mol% or more, greater than 30 mol%, or 40 mol% or more, and 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.

[0204] In the PI-based resin constituting layers (PI-2) and (PI-3), if the content of structural units (B1) and / or (B2) is within the aforementioned range, the PI-based resin will not be excessively rigid and will become a flexible structure with a certain degree of freedom. Therefore, it is easy to form a branched structure through heating during imidization, and there is a tendency to increase crystallinity. As a result, the mechanical properties of layers (PI-2) and (PI-3) can be improved, the dielectric constant (Df) can be reduced, and the coulombic ester (CTE) can be effectively reduced. Therefore, a laminate with superior yield strength, dielectric properties, and thermal properties can be obtained. In addition, it is expected to improve the adhesion between the PI-based film and the metal layer. Furthermore, the laminate exhibits excellent water resistance and drying speed.

[0205] The various physical properties (molecular weight, glass transition temperature, etc.) of the PI-based resin comprising the above-mentioned structural unit (A) and / or structural unit (B) can be appropriately determined based on the function and use of each PI-based resin-containing layer in the PI-based film, and on the following preferred ranges, for example.

[0206] In one embodiment of the present invention, the PI-based resin constituting the PI-based film may contain halogen atoms, preferably fluorine atoms, which can be introduced, for example, using the aforementioned halogen-containing substituents. When the PI-based resin contains fluorine atoms, it is easier to reduce the relative permittivity of the obtained PI-based film, resulting in improved dielectric properties of the laminate. Examples of preferred fluorine-containing substituents for containing fluorine atoms in the PI-based resin include fluorinated groups and trifluoromethyl groups.

[0207] In another embodiment of the present invention, from the viewpoint of improving the adhesion between the PI-based film and the metal layer, the PI-based resin is preferably free of fluorine atoms. Therefore, for example, it is preferable that the PI-based resin constituting the layer containing the PI-based resin in contact with the metal layer, preferably the TPI layer, and particularly layers (PI-2) and (PI-3) in the PI-based film, is free of fluorine atoms. Furthermore, if the PI-based resin contains fluorine, there is a tendency to weaken the interactions between molecular chains; therefore, in the case where the PI-based resin is free of fluorine atoms, there is a tendency to reduce the Df of the PI-based film.

[0208] When the PI-based resin contains halogen atoms, the content of halogen atoms, especially fluorine atoms, in the PI-based resin is preferably 0.1 to 35% by mass, more preferably 0.1 to 30% by mass, even more preferably 0.1 to 20% by mass, and particularly preferably 0.1 to 10% by mass, based on the mass of the PI-based resin. If the content of halogen atoms is above the aforementioned lower limit, it is easy to improve the heat resistance and dielectric properties of the obtained PI-based film, resulting in improved dielectric properties and thermal properties of the laminate. If the content of halogen atoms is below the aforementioned upper limit, it is advantageous in terms of cost, as it is easy to reduce CTE, and it is also easier to synthesize the PI-based resin.

[0209] In one embodiment of the present invention, the imidization rate of the PI-based resin is preferably 90% or more, more preferably 93% or more, even more preferably 95% or more, and typically 100% or less. From the viewpoint of improving the yield strength, water resistance, drying speed, dielectric properties, and thermophysical properties of the laminate, the imidization rate is preferably at or above the aforementioned lower limit. The imidization rate represents the ratio of the molar amount of imide bonds in the PI-based resin to twice the molar amount of structural units derived from the tetracarboxylic acid compound in the PI-based resin. It should be noted that when the PI-based resin contains a tricarboxylic acid compound, the imidization rate represents the ratio of the molar amount of imide bonds in the PI-based resin to twice the molar amount of structural units derived from the tetracarboxylic acid compound in the PI-based resin, and the total molar amount of structural units derived from the tricarboxylic acid compound. Furthermore, the imidization rate can be determined using IR, NMR, or the like.

[0210] In one embodiment of the present invention, from the viewpoint of improving the yield strength of the laminate, the weight-average molecular weight (Mw) of the PI-based resin, converted to polystyrene, is preferably 5,000 or more, more preferably 10,000 or more, further preferably 15,000 or more, and particularly preferably 20,000 or more. Furthermore, from the viewpoint of ease of manufacture and film-forming properties of the varnish, it is preferably 1,200,000 or less, more preferably 1,000,000 or less, further 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 a PI-based film, is preferably 5,000 to 800,000, more preferably 10,000 to 700,000. Additionally, the Mw of the TPI layer, particularly layers (PI-2) and (PI-3) in a PI-based film, is preferably 10,000 to 1,000,000, more preferably 20,000 to 900,000.

[0211] In one embodiment of the present invention, from the viewpoint of yield strength of the laminate and adhesion between the PI-based film and the metal layer, the ratio of weight-average molecular weight (Mw) to number-average molecular weight (Mn) of the PI-based resin (Mw / Mn) is preferably 1.1 or more, more preferably 1.3 or more, further preferably 1.5 or more, particularly preferably 1.7 or more, preferably 15 or less, more preferably 12 or less, further preferably 11 or less, and particularly preferably 10 or less. For example, the Mw / Mn of the mPI layer, especially layer (PI-1) in the PI-based film, is preferably 1.1 to 15, more preferably 1.5 to 10. Furthermore, the Mw / Mn of the TPI layer, especially layers (PI-2) and (PI-3) in the PI-based film, is preferably 1.1 to 15, more preferably 1.5 to 10. It should be noted that Mw and Mn can be determined by gel permeation chromatography (hereinafter, sometimes referred to as GPC) and calculated according to standard polystyrene.

[0212] In one embodiment of the present invention, from the viewpoint of improving the yield strength and reducing the yield strength (Df) of the resulting laminate, the Tg of the PI-based resin is preferably 350°C or lower, more preferably 330°C or lower, further preferably 310°C or lower, and particularly preferably 300°C or lower. Furthermore, from the viewpoint of improving the yield strength of the laminate, reducing the yield strength (Df), and improving thermal properties, the Tg of the PI-based resin is preferably 200°C or higher, more preferably 205°C or higher, further preferably 210°C or higher, and particularly preferably 220°C or higher. When both an mPI layer and a TPI layer are included as the PI-based resin-containing layers, the Tg of the PI-based resin constituting the mPI layer is preferably 350°C or lower, more preferably 330°C or lower, further preferably 310°C or lower, particularly preferably 295°C or lower, preferably 220°C or higher, more preferably 230°C or higher, further preferably 250°C or higher, further more preferably 260°C or higher, and particularly preferably 270°C or higher. If the Tg of the PI-based resin constituting the mPI layer is within the above-mentioned range, the yield strength of the laminate can be improved, and the dielectric and thermal properties can also be improved. The Tg of the PI-based resin constituting the TPI layer is preferably 310°C or lower, more preferably 300°C or lower, even more preferably 290°C or lower, even more preferably 270°C or lower, particularly preferably 250°C or lower, preferably 200°C or higher, more preferably 210°C or higher, even more preferably 220°C or higher, and particularly preferably 230°C or higher. If the Tg of the PI-based resin constituting the TPI layer is within the above-mentioned range, the yield strength of the laminate can be improved. In addition, besides reducing Df and improving thermal properties, the adhesion between the PI film and the metal layer can also be improved. The Tg of the PI-based resin can be measured by dynamic viscoelasticity testing. For example, it can be calculated based on the peak of the tanδ curve, which is the ratio of the storage modulus (E') to the loss modulus (E'') obtained using a dynamic viscoelasticity testing device.

[0213] In one embodiment where an mPI layer and a TPI layer are included as layers containing PI-based resins, the Tg of the PI-based resin constituting the mPI layer is preferably 250–330°C within the aforementioned range, and the Tg of the PI-based resin constituting the TPI layer is preferably 220–300°C within the aforementioned range. This tends to allow each PI-based resin to easily form an ideal high-order structure where rotational motion is suppressed. Therefore, it is believed that in this embodiment, the ability to form each PI-based resin layer using a PI-based resin with a high-order structure that maintains orientation contributes to improving the deformation resistance of the resulting laminate. Furthermore, it is speculated that the rotation of polar groups in each PI-based resin is suppressed, reducing the loss of electrical energy through thermal motion. Therefore, it is believed that by using PI-based resins with Tg within the aforementioned ranges, a PI film with low Df can be obtained. Furthermore, by using such a PI-based resin, even at low temperatures such as imidization temperature below 350°C, the yield strength and dielectric properties of the resulting laminate can be improved. Therefore, even when a laminate is manufactured by thermally imidizing a PI-based resin precursor coating with a metal layer (copper layer) as a laminate, the deterioration of the metal layer surface can be suppressed, and a laminate with high yield strength and excellent high-frequency characteristics can be obtained.

[0214] In one embodiment of the present invention, the PI-based resin contained in the PI-based film of the laminate, the PI-based resin contained in the layer (PI-1) preferably containing a polyimide-based resin, the PI-based resin contained in the layer (PI-2) containing a polyimide-based resin, and the PI-based resin contained in the layer (PI-3) containing a polyimide-based resin each preferably have a storage modulus of 1.0 × 10⁻⁶ at 40°C. 9 Pa or higher. If the storage modulus of the PI-based resin is within the aforementioned range, the yield strength of the laminate can be easily increased. The reason for this is uncertain, but it is believed that due to the unevenness of the interface between the PI-based film and the metal layer, the PI-based resin tends to have crystallinity and orientation that easily improves strength, thus easily increasing the yield strength. It should be noted that the preferred range of the storage modulus of the polyimide-based resin contained in layers (PI-1), (PI-2), and (PI-3) at 40°C can be appropriately selected from the ranges E'1, E'2, and E'3 described later, respectively.

[0215] In one embodiment of the present invention, the PI film preferably satisfies the relationship between equations (X) and (Y). 0.8 ≤ E'1 / E'2 ≤ 4.5 (X) 0.8≤E'1 / E'3≤4.5 (Y) [In the formula, E'1 represents the storage elastic modulus of the PI resin contained in the aforementioned PI-1 layer at 40°C, E'2 represents the storage elastic modulus of the PI resin contained in the aforementioned PI-2 layer at 40°C, and E'3 represents the storage elastic modulus of the PI resin contained in the aforementioned PI-3 layer at 40°C.]

[0216] If the laminated film of the present invention satisfies formulas (X) and (Y), the yield strength of the laminate is easily improved. The reason for this is not yet certain, but it is believed to be because it easily mitigates the force applied to the laminate, particularly in the thickness direction. Furthermore, it also easily improves the water resistance and drying speed of the laminate.

[0217] In formula (X), E'1 / E'2 and in formula (Y), E'1 / E'3 are preferably 0.90 or more, more preferably 0.95 or more, even more preferably 0.98 or more, particularly preferably 1.00 or more, 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 even more preferably 1.50 or less. If E'1 / E'2 and E'1 / E'3 are within the aforementioned ranges, the yield strength, water resistance, and drying speed of the laminate can be easily improved. It should be noted that E'1 / E'2 and E'1 / E'3 can be the same value or different values.

[0218] In one embodiment of the present invention, E'1 in formulas (X) and (Y) is not limited, but is preferably 1.0 × 10⁻⁶. 9 Pa or higher, more preferably 1.5 × 10 Pa. 9 Pa or higher, more preferably 2.0 × 10 Pa. 9 Pa or higher, preferably 1.0 × 10 Pa 11 Pa or less, more preferably 5.0 × 10 Pa. 10 Pa below, more preferably 1.0 × 10 Pa 10 Pa or less, and more preferably 8.0 × 10 Pa. 9 Pa below, particularly preferably 5.0 × 10 Pa. 9 Pa or below or 3.5 × 10 9 Below Pa. If E'1 is within the aforementioned range, the yield strength of the laminate can be easily increased.

[0219] In one embodiment of the present invention, E'2 in formula (X) and E'3 in formula (Y) are not limited, and are each preferably 1.0 × 10⁻⁶. 9 Pa or higher, more preferably 1.5 × 10 Pa. 9 Pa or higher, more preferably 2.0 × 10 Pa. 9Pa or higher, preferably 5.0 × 10 Pa. 10 Pa or less, more preferably 1.0 × 10 Pa. 10 Pa below, more preferably 8.0 × 10 Pa 9 Pa or less, and more preferably 5.0 × 10 Pa. 9 Pa or below or 3.5 × 10 9 Below Pa. If E'2 and / or E'3 are within the aforementioned range, the yield strength, water resistance, and drying speed of the laminate can be easily improved. It should be noted that E'2 and E'3 can be the same value or different values.

[0220] In one embodiment of the present invention, the storage modulus of the PI-based resin contained in the PI-based film in the laminate, preferably the PI-based resin contained in the PI-based resin layer (PI-1), the PI-based resin contained in the PI-based resin layer (PI-2), and the PI-based resin contained in the PI-based resin layer (PI-3) at 300°C can each be 1.0 × 10⁻⁶. 8 Pa or higher, or less than 1.0 × 10 8 From the viewpoint of improving the yield strength of the laminate, the storage modulus (sometimes referred to as E'1a) of the PI-based resin contained in the PI-based resin layer (PI-1) at 300°C is not limited, but is preferably 1.0 × 10⁻⁶. 8 Pa or higher, more preferably 1.5 × 10 Pa. 8 Pa or higher, more preferably 2.0 × 10 Pa. 8 Pa or higher, for example, 2.5 × 10 Pa. 8 Pa or higher. E'1a is preferably 1.0 × 10⁻⁶. 10 Pa or less, more preferably 5.0 × 10 Pa. 9 Pa below, more preferably 1.0 × 10 Pa 9 Pa or less, and more preferably 8.0 × 10 Pa. 8 Pa below, particularly preferably 5.0 × 10 Pa. 8 Below Pa, for example, it can be 4.0 × 10⁻⁶ Pa. 8 Below Pa. If E'1a is within the aforementioned range, the yield strength of the laminated film can be easily increased.

[0221] In one embodiment of the present invention, the storage modulus of the PI-based resin contained in the PI-based resin layer (PI-2) at 300°C (sometimes referred to as E'2a) and the storage modulus of the PI-based resin contained in the PI-based resin layer (PI-3) at 300°C (sometimes referred to as E'3a) are not limited, but are preferably less than 1.0 × 10⁻⁶. 8 Pa, more preferably 8.0 × 10 Pa. 7Pa or less, more preferably 5.0 × 10 Pa. 7 Pa or less, and more preferably 3.0 × 10 Pa. 7 Pa below, particularly preferably 2.0 × 10 Pa 7 Pa below, preferably 1.0 × 10 Pa 6 Pa or higher, more preferably 5.0 × 10 Pa. 6 Pa or higher, more preferably 1.0 × 10 Pa. 7 Pa or higher. If E'2a and / or E'3a are within the aforementioned range, the yield strength, water resistance, and drying speed of the laminate can be easily improved. It should be noted that E'2a and E'3a can be the same value or different values.

[0222] The storage modulus of the PI-based resin contained in each PI-based resin layer can be measured using a dynamic viscoelasticity measuring device, for example, at a heating rate of 5°C / min from room temperature (e.g., 25°C) to 342°C. The storage modulus of the PI-based resin can be measured using a PI-based resin film formed from the PI-based resin, for example, by the method described in the examples.

[0223] E'1 / E'2 and E'1 / E'3 can each be controlled by appropriately adjusting the types and composition of the structural units of the PI-based resin contained in each PI-based resin layer, the molecular weight of the PI-based resin, and the composition and combination of each PI-based resin layer in the laminated film. For example, based on the aforementioned preferred methods that are beneficial to the improvement of yield strength, water resistance, drying speed, and dielectric properties of the laminate, such as the aforementioned preferred structural units of the PI-based resin and their content, E'1 / E'2 can be appropriately adjusted to the range of formula (X), and E'1 / E'3 can be appropriately adjusted to the range of formula (Y).

[0224] The Tg and storage modulus of PI-based resins can be adjusted to the ranges described above by appropriately adjusting the types of structural units constituting the PI-based resin, their composition, the molecular weight of the PI-based resin, the manufacturing method, and especially the imidization conditions, for example, to the ranges described as preferred embodiments in this specification.

[0225] <Additives> In one embodiment of the present invention, the resin content in the resin film is preferably 60% by mass or more, more preferably 70% by mass or more, further preferably 80% by mass or more, and particularly preferably 90% by mass or more, relative to the mass of the resin film. Furthermore, there is no particular limitation on the upper limit of the resin content; it can 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 resin film. In a preferred embodiment of the present invention, the content of PI-based resin in each PI-based resin-containing layer constituting the PI-based film is preferably 60% by mass or more, more preferably 70% by mass or more, further preferably 80% by mass or more, and particularly preferably 90% by mass or more, 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-based resin-containing layer. If the resin content is within the above range, a laminate with improved yield strength, dielectric properties, and thermal properties can be obtained.

[0226] The resin membrane of the present invention, and preferably each PI-based resin-containing layer constituting the PI-based membrane, may contain fillers as needed. Examples of fillers include metal oxide particles such as silica and alumina, inorganic salts such as calcium carbonate, polymer particles such as fluororesins and cyclic olefin polymers. Fillers may be used alone or in combination of two or more. When fillers are included, their content relative to the mass of the resin membrane, preferably each PI-based resin-containing layer constituting the PI-based membrane, is preferably 50% by mass or less, more preferably 40% by mass or less, further preferably 30% by mass or less, and most preferably 0.01% by mass or more.

[0227] In another embodiment of the present invention, the resin film of the present invention, and each layer of PI-based resin constituting the PI-based film, may contain additives as needed. Examples of additives include antioxidants, flame retardants, crosslinking agents, surfactants, compatibilizers, imidization catalysts, weather-resistant agents, lubricants, anti-blocking agents, antistatic agents, anti-dizziness agents, anti-drip agents, pigments, etc. Additives may be used alone or in combination of two or more. 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 relative to the mass of the resin film, and preferably each layer of PI-based resin constituting the PI-based film, is preferably 7% by mass or less, more preferably 5% by mass or less, further preferably 4% by mass or less, particularly preferably 1% by mass or less, and preferably 0.001% by mass or more.

[0228] <Physical Properties of Resin Films> For printed circuits, it is required that transmission loss be minimized. Transmission loss is represented by the sum of dielectric loss, which is the loss caused by the electric field generated by the dielectric, and conductor loss, which is the loss caused by the current flowing through the conductor. Moreover, it is known that dielectric loss is approximately proportional to the index E expressed by equation (i).

[0229] E = Df × (Dk) 1 / 2 (i) [In equation (i), Df represents the dielectric loss tangent, and Dk represents the relative permittivity.] In the high-frequency region used by FPCs for high-speed communications such as 5G, there is a tendency for dielectric loss to increase. Therefore, materials with a small value of the aforementioned index E and the ability to suppress dielectric loss are particularly needed.

[0230] On the other hand, the current of high-frequency signals is concentrated at the outermost surface of the conductor. Therefore, the conductor loss is related to the dielectric properties of the adjacent dielectric, which is known to be related to (Dk). 1 / 2 Approximately proportional.

[0231] The resin film in the laminate of the present invention has small Df and Dk values, resulting in lower dielectric loss index E and conductor loss. Therefore, transmission loss can be reduced in circuits incorporating the laminate of the present invention. Consequently, the laminate of the present invention maintains excellent dielectric properties (especially low Df) and exhibits high yield strength.

[0232] In one embodiment of the present invention, the dielectric loss index E of the resin film in the laminate at 10 GHz is preferably 0.0080 or less, more preferably 0.0075 or less, even more preferably 0.0070 or less, even more preferably 0.0065 or less, particularly preferably 0.0060 or less, even more preferably 0.0059 or less, even more preferably 0.0056 or less, for example, it can be 0.0053 or less, 0.0052 or less, 0.0051 or less, 0.0050 or less, or 0.0049 or less. The smaller the aforementioned index E, the lower the transmission loss of the electronic circuit comprising the laminate. Therefore, the lower limit of the aforementioned index E is not particularly limited, for example, it can be 0 or more.

[0233] In one embodiment of the present invention, from the viewpoint of reducing the transmission loss of an electronic circuit when the laminate is assembled into it, the Df of the resin film in the laminate at 10 GHz is preferably 0.0040 or less, more preferably 0.0035 or less, even more preferably 0.0034 or less, even more preferably 0.0033 or less, particularly preferably 0.0032 or less, particularly more preferably 0.0031 or less, and particularly more preferably 0.0030 or less. For example, it can be 0.0029 or less, 0.0028 or less, or 0.0027 or less. The smaller the aforementioned Df, the lower the transmission loss of the electronic circuit comprising the laminate. Therefore, the lower limit of the aforementioned Df is not particularly limited, and for example, it can be 0 or more.

[0234] In one embodiment of the present invention, the Dk of the resin film in the laminate at 10 GHz is preferably 3.500 or less, more preferably 3.450 or less, and even more preferably 3.400 or less.

[0235] The Df and Dk of the resin film in the laminate can be determined using a vector network analyzer and a resonator, for example, by the method described in the embodiments.

[0236] In one embodiment of the present invention, the coefficient of linear expansion (CTE) of the resin 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, even more preferably 28 ppm / K or less, for example, it can be 27 ppm / K or less, 26 ppm / K or less, 25 ppm / K or less, 24 ppm / K or less, or 23 ppm / K or less. If the CTE of the resin film is below the aforementioned upper limit, the thermal properties are excellent, and high dimensional stability is expected. In addition, the CTE of the resin 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. If the CTE of the resin film is within the aforementioned upper and lower limits, the CTE of the metal layer (especially the copper layer) and the PI-containing resin layer in the resin film become close, thus the effect of suppressing the peeling of the resin film from the metal layer can be obtained. It should be noted that CTE can be determined using, for example, a thermomechanical analysis apparatus (hereinafter, sometimes referred to as "TMA"), and can be obtained by the methods described in the examples.

[0237] The water resistance of the resin film in the laminate can be evaluated by the moisture content after immersing the resin film, after removing the metal layer, in pure water at 25°C for 24 hours. This moisture content can be determined by the method described in the examples. The lower the moisture content, the higher the water resistance. In one embodiment of the present invention, the moisture content after immersing the resin film in pure water at 25°C for 24 hours is preferably 4% or less, more preferably 3.8% or less, even more preferably 3.5% or less, even more preferably 3.0% or less, particularly preferably 2.5% or less, even more preferably 2.0% or less, even more preferably 1.8% or less, for example, it can be 1.7% or less, 1.6% or less, or 1.5% or less. If the aforementioned moisture content is below the aforementioned upper limit, the surface of the resin film after removing the metal layer from the laminate by etching or the like can have high water resistance, and therefore the deterioration of dielectric properties caused by moisture in the aforementioned etching and subsequent washing processes can also be suppressed. In addition, for reasons that are not yet certain, if the aforementioned moisture content is below the aforementioned upper limit, there is a tendency for the yield strength of the laminate to increase. The aforementioned moisture content is usually above 0%.

[0238] The drying rate (% / min) of the resin film in the laminate of the present invention is preferably 0.38% / min or more, more preferably 0.40% / min or more, even more preferably 0.45% / min or more, even more preferably 0.50% / min or more, particularly preferably 0.53% / min or more, even more preferably 0.57% / min or more, even more preferably 0.60% / min or more, for example, 0.62% / min or more. If the aforementioned drying rate is above the aforementioned lower limit, the surface of the resin film after the metal layer is etched can have excellent drying performance, thus enabling rapid drying after the etching and washing processes during FPC fabrication. In addition, the aforementioned drying rate is generally 3% / min or less, preferably 1% / min or less. The aforementioned drying rate can be obtained by dividing the difference between the moisture content of the resin film after the metal layer has been removed, immediately after immersing it in pure water at 25°C for 24 hours, and the moisture content after heating and drying for a certain time, by the heating and drying time, for example, by the method described in the examples.

[0239] The resin film of this invention can be surface-treated using methods commonly employed in industry, such as corona discharge treatment, plasma treatment, and ozone treatment.

[0240] <Method for manufacturing resin film> Regarding the manufacturing method of the resin film in this invention, there are no particular limitations as long as the obtained laminate at least satisfies the above-mentioned range of Psk, or as long as the interface of the laminate satisfies formula (I). It can be manufactured by commonly used methods according to its type, or commercially available products can be used. For example, it can be manufactured by casting, injection molding, hot pressing, calendering, vacuum forming, compression molding, and extrusion molding. As described below, the PI-based film of the preferred embodiment of this invention can be manufactured by a method (casting method) including the following steps: reacting a tetracarboxylic acid compound appropriately selected according to the composition of the PI-based resin with a diamine compound to obtain a PI-based resin precursor; and imidizing the obtained PI-based resin precursor. For example, as a manufacturing method of the PI-based film in this invention, the following method can be cited: coating a solution of the corresponding PI-based resin precursor onto a support substrate, pre-drying it to obtain a coating film, and then imidizing it. Imidization can also be performed in the state where the support substrate has been peeled off. In one embodiment of the present invention, imidization is performed when the solvent is sufficiently retained throughout the coating or when the resin layers are well fused together, thereby increasing the yield strength of the laminate. The reason is uncertain, but it is believed that in such a state, the degree of freedom of the resin molecules increases until imidization, and the state of the resin molecules between the PI-based resin layers tends to stabilize.

[0241] Furthermore, soluble liquid crystal polymers, similar to the aforementioned PI-based resins, can be manufactured by casting molding, while insoluble liquid crystal polymers, epoxy resins, and fluorinated resins (e.g., PTFE) can be manufactured by extrusion molding (melt extrusion, etc.), compression molding, and calendering. When manufacturing resin films by extrusion molding, the surface properties can be adjusted by modifying manufacturing conditions such as the die lip opening, coating speed, surface roughness of the forming roller and cooling roller, and changes in the cooling profile.

[0242] In a preferred embodiment of the present invention, when the resin film is a PI-based film, a manufacturing method for it may include, for example, the following method: coating a solution of the corresponding PI-based resin precursor onto a support substrate, pre-drying it to obtain a single-layer or multi-layer coating, and then performing imidization. Imidization may also be performed with the support substrate already removed.

[0243] Examples of supporting substrates include metal foils (e.g., copper foil), metal plates (e.g., copper plates), SUS foils, SUS strips, glass substrates, and other resin films besides the resin film of this invention (e.g., PET film, PEN film, PI-based resin film, polyamide-based resin film). By using a metal layer (e.g., metal foil) as a supporting substrate, a resin film can also be formed directly on the metal layer.

[0244] [Metallic layer] The laminate of the present invention includes a metal layer on at least one side of the resin film. That is, the metal layer may be included on only one side of the resin film or on both sides.

[0245] In one embodiment of the present invention, the metal constituting the metal layer may include, for example, 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, or an aluminum layer, and from the viewpoint of conductivity and metal processability, a copper layer or a copper alloy layer is more preferred, and a copper layer is particularly preferred. Furthermore, from the viewpoint of metal processability, the metal layer is preferably a metal foil layer, more preferably a metal foil of the aforementioned metals, and even more preferably a copper foil layer or a copper alloy foil layer, and a copper foil layer is particularly preferred.

[0246] 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. Furthermore, from the viewpoint of facilitating circuit miniaturization and improving bend resistance, it 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 gauge or the like. It should be noted that when both sides of the resin film contain a metal layer, particularly a copper layer, the thickness of each metal layer, particularly each copper layer, can be the same or different.

[0247] In one embodiment of the present invention, preferably, the minimum autocorrelation length Sal of the surface of the metal layer in contact with the resin film, measured using a laser microscope according to ISO 25178 at a magnification of 100x, a cutoff wavelength of 0.375 μm based on an S-filter, and without an L-filter, satisfies the relationship between the aspect ratio Str of the surface properties and Equation (III). Sal×Str≥0.21 (III).

[0248] Unless otherwise specified, the surface roughness parameters (kurtosis Sku, etc.) described below are also measured in accordance with ISO 25178 using a laser microscope at a magnification of 100x, with a cutoff wavelength of 0.375 μm based on an S-filter, and without an L-filter.

[0249] The minimum autocorrelation length Sal in Equation (III) is obtained by quantifying the density of the unevenness of the metal surface in units of length, and is one of the spatial parameters of surface roughness. More specifically, Sal represents the periodicity of the surface roughness in the planar direction, and represents the horizontal distance of the direction in which the autocorrelation function decays towards a specific value. The smaller Sal is, the more abrupt the difference in elevation; the larger Sal is, the more gradual the shape. In addition, the aspect ratio Str of the surface morphology in Equation (III) is a three-dimensional surface morphology parameter obtained by quantifying the intensity of isotropy or anisotropy of the metal surface, and takes a value between 0 and 1. When Str is close to 1, it means that the metal surface exhibits strong isotropy, and no regular directionality is seen in the unevenness of the surface, that is, there are no textures on the surface. When Str is close to 0, it means that the metal surface exhibits strong anisotropy, and regular directionality is seen in the unevenness of the surface, that is, there are textures on the surface.

[0250] In the interface between the metal layer and the resin film, if Sal and Str satisfy equation (III), the roughness parameters of the interface in the obtained laminate, such as Psk, |Pku / Psk|, and |Pp-Pv|, can be easily adjusted to the above range, which can improve the yield strength, water resistance, and drying speed of the laminate. It should be noted that it is believed that the larger Sal×Str is, the more irregular the peaks and valleys on the metal surface will be.

[0251] In formula (III), Sal×Str is preferably 0.23 μm or more, more preferably 0.25 μm or more, even more preferably 0.30 μm or more, even more preferably 0.40 μm or more, particularly preferably 0.50 μm or more, even more preferably 1.0 μm or more, 2.0 μm or more, 3.0 μm or more, 5.0 μm or more, or 7.0 μm or more, even more preferably 8.0 μm or more, even more preferably 8.5 μm or more, and extremely preferably 9.5 μm or more. If Sal×Str is at or above the aforementioned lower limit, it is easy to adjust the roughness parameters such as Psk, |Pku / Psk|, and |Pp-Pv| in the obtained laminate to the above range, which can further improve the yield strength, water resistance, and drying speed of the laminate. In formula (III), Sal×Str is preferably 20 μm or less, more preferably 17 μm or less, even more preferably 15 μm or less, even more preferably 13 μm or less, particularly preferably 12.0 μm or less, and even more preferably 11.5 μm or less, 11.0 μm or less, or 10.5 μm or less. If Sal×Str is below the aforementioned upper limit, it is easy to adjust the roughness parameters such as Psk, |Pku / Psk|, and |Pp-Pv| in the obtained laminate to the above range, which can further improve the yield strength, water resistance, and drying speed of the laminate.

[0252] In one embodiment of the present invention, the aforementioned minimum autocorrelation length Sal can be, for example, 0.50 μm or more, 1.00 μm or more, 1.30 μm or more, 1.50 μm or more, or 2.00 μm or more, preferably 2.2 μm or more, more preferably 3.0 μm or more, further preferably 5.0 μm or more, further more preferably 7.0 μm or more, particularly preferably 10.0 μm or more, particularly more preferably 11.0 μm or more, and particularly more preferably 11.6 μm or more. Sal in Formula (III) can be, for example, 30 μm or less, 25 μm or less, or 20 μm or less, preferably 17 μm or less, more preferably 15 μm or less, and further preferably 14.0 μm or less. If Sal is within the aforementioned range, there is a tendency to improve the yield strength, water resistance, and drying speed of the obtained laminate.

[0253] In one embodiment of the present invention, the aspect ratio Str of the aforementioned surface property can be, for example, 0.05 or more, preferably 0.07 or more, more preferably 0.10 or more, even more preferably 0.20 or more, even more preferably 0.30 or more, particularly preferably 0.50 or more, even more preferably 0.60 or more, even more preferably 0.81 or more, preferably 0.98 or less, more preferably 0.95 or less, and even more preferably 0.90 or less. If Str is within the aforementioned range, there is a tendency to improve the yield strength, water resistance, and drying speed of the obtained laminate.

[0254] In one embodiment of the present invention, the horizontal difference Sk of the center portion of the surface of the metal layer in contact with the resin film, measured under the above-described measurement conditions, is preferably 0.40 μm or more. The horizontal difference Sk of the center portion is a value obtained by subtracting the minimum height from the maximum height of the center portion after removing the protruding protrusions and recesses, representing the variation in the height of the center portion. More preferably, Sk is 0.42 μm or more; even more preferably, 0.44 μm or more; preferably 2.0 μm or less; more preferably 1.0 μm or less; even more preferably 0.60 μm or less; even more preferably 0.55 μm or less; and particularly preferably 0.50 μm or less. If Sk is above the aforementioned lower limit and / or below the aforementioned upper limit, the yield strength, water resistance, and drying speed of the obtained laminate can be improved.

[0255] In one embodiment of the present invention, the absolute value (|Sp-Sv|) of the difference between the maximum peak height Sp and the maximum valley depth Sv measured under the above-described measurement conditions on the surface of the metal layer in contact with the resin film is preferably 0.48 μm or less, more preferably 0.45 μm or less or 0.40 μm or less, even more preferably 0.33 μm or less, even more preferably 0.27 μm or less, particularly preferably 0.25 μm or less, even more preferably 0.15 μm or less, even more preferably 0.10 μm or less, extremely preferably 0.04 μm or less, for example, 0.03 μm or less or 0.02 μm or less. |Sp-Sv| is preferably 0.001 μm or more, more preferably 0.005 μm or more. If |Sp-Sv| is below the aforementioned upper limit and / or above the aforementioned lower limit, the yield strength, water resistance, and drying speed of the obtained laminate can be improved.

[0256] In one embodiment of the present invention, the aforementioned maximum peak height Sp is preferably 2.00 μm or less, more preferably 1.70 μm or less, even more preferably 1.50 μm or less, even more preferably 1.20 μm or less, particularly preferably 1.10 μm or less or 1.00 μm, even more preferably 0.90 μm or less, preferably 0.10 μm or more, more preferably 0.30 μm or more, even more preferably 0.50 μm or more, and even more preferably 0.70 μm or more. If the aforementioned Sp is within the aforementioned range, there is a tendency to improve the yield strength, water resistance, and drying speed of the obtained laminate.

[0257] In one embodiment of the present invention, the aforementioned maximum valley depth Sv is preferably 1.50 μm or less, more preferably 1.30 μm or less, for example, 1.20 μm or less, 1.00 μm or less, or 0.90 μm or less, preferably 0.30 μm or more, more preferably 0.50 μm or more, and even more preferably 0.70 μm or more. If Sv is within the aforementioned range, there is a tendency to improve the yield strength, water resistance, and drying speed of the obtained laminate.

[0258] In one embodiment of the present invention, the expanded area ratio Sdr of the surface of the metal layer in contact with the resin film, measured under the above-described measurement conditions, can be, for example, 100% or less or 50% or less, preferably 35.0% or less, and more preferably 20% or less. The expanded area ratio Sdr indicates how much the expanded area (i.e., surface area) of the defined region increases relative to the area of ​​the defined region. Specifically, it indicates the rate of increase in surface area compared to a completely flat surface when a completely flat surface is set to 100%. The smaller the Sdr, the closer the surface shape is to a flat surface; the Sdr for a completely flat surface is 0%. On the other hand, the larger the Sdr, the more uneven the surface shape. The aforementioned Sdr is more preferably less than 20%, further preferably 18% or less or 15% or less, more preferably 13% or less, particularly preferably 10% or less, particularly more preferably 5% or less, preferably 0.5% or more, more preferably 1.0% or more, and more preferably 2% or more. If the expansion area ratio Sdr is below the aforementioned upper limit and / or above the lower limit, the yield strength, water resistance, and drying speed of the obtained laminate can be improved.

[0259] In one embodiment of the present invention, the kurtosis Sku of the surface of the metal layer in contact with the resin film, measured under the above-described measurement conditions, is preferably 3.80 or less, more preferably 3.50 or less, preferably 1.0 or more, more preferably 1.5 or more, further preferably 2.0 or more, further more preferably 2.5 or more, particularly preferably 2.8 or more, particularly more preferably 3.00 or more, particularly more preferably 3.10 or more, and extremely preferably 3.30 or more. If the aforementioned Sku is within the aforementioned range, the yield strength, water resistance, and drying speed of the obtained laminate can be improved. The kurtosis Sku obtained using a laser microscope is an indicator of the sharpness of the height distribution on the surface of the metal layer.

[0260] Sku refers to the sharpness or sharpness of the height distribution. When Sku>3, it means there are many sharp protrusions and concave parts; when Sku<3, it means the metal surface is flat; when Sku=3, it means the height distribution is normally distributed.

[0261] In one embodiment of the present invention, the arithmetic mean height Sa of the surface of the metal layer in contact with the resin film, measured under the above-described measurement conditions, can be, for example, 0.05 μm or more or 0.10 μm or more, preferably 0.14 μm or more. Alternatively, it can be, for example, 0.5 μm or less, 0.4 μm or less, or 0.3 μm or less, preferably less than 0.25 μm, more preferably 0.22 μm or less, even more preferably 0.20 μm or less, and even more preferably 0.17 μm or less or 0.16 μm or less. If Sa is within the aforementioned range, the yield strength, water resistance, and drying speed of the laminate can be improved. The arithmetic mean height Sa is a parameter that extends Ra, a two-dimensional parameter, to a three-dimensional parameter, representing the average value of the height difference relative to the average surface.

[0262] In one embodiment of the present invention, the maximum height Sz of the surface of the metal layer in contact with the resin film, measured under the above-described measurement conditions, is preferably 3.5 μm or less, more preferably 3.0 μm or less, further preferably 2.8 μm or less, 2.50 μm or less, or 2.1 μm or less, even more preferably 2.00 μm or less, particularly preferably 1.90 μm or less or 1.80 μm or less, preferably 0.1 μm or more, more preferably 0.5 μm or more, even more preferably 1.0 μm or more, even more preferably 1.3 μm or more, and particularly preferably 1.5 μm or more. If the aforementioned Sz is within the aforementioned range, the yield strength, water resistance, and drying speed of the laminate can be improved.

[0263] In one embodiment of the present invention, the arithmetic mean height Ra, measured using a laser microscope at 100x magnification according to JIS B0601:2013, is preferably 0.01 to 0.5 μm, more preferably 0.05 to 0.3 μm, and even more preferably 0.1 to 0.25 μm, for example, 0.12 to 0.20 μm. Furthermore, the maximum height Rz is preferably 0.1 to 2 μm, more preferably 0.5 to 1.6 μm, for example, 0.60 to 1.0 μm. Additionally, the ten-point average roughness Rzjis is preferably 0.05 to 2 μm, more preferably 0.1 to 1.5 μm, even more preferably 0.2 to 1.0 μm, even more preferably 0.30 to 0.80 μm, and particularly preferably 0.30 to 0.70 μm.

[0264] In this specification, Sal, Str, Sk, Sdr, Sp, Sv, Sku, Sa, Sz, Sal×Str, |Sp-Sv| are sometimes collectively referred to as surface roughness parameters of metal surfaces.

[0265] The surface roughness parameters of a metal surface can be determined as follows: A three-dimensional shape image is obtained by laser observation of the side of the metal layer in contact with the resin film at 100x magnification using a laser microscope, and the obtained three-dimensional shape image is analyzed. The analyses of Sal, Str, Sk, Sdr, Sp, Sv, Sku, Sa, and Sz can each be performed according to ISO 25178 under conditions of an S-filter cutoff wavelength of 0.375 μm and no L-filter. The analyses of Ra, Rz, and Rzjis can be performed as follows: According to JIS B0601:2013, the contour curves obtained at any location in the obtained three-dimensional shape image are analyzed under conditions of λs of 2.5 μm and λc and λf not being set. The surface roughness parameters of the metal surface can be obtained, for example, by the methods described in the examples.

[0266] The metal layer can be manufactured by electrolytic casting (e.g., electroplating) or plastic processing (e.g., rolling), or commercially available products can be used. When the metal layer is a metal foil, a surface treatment layer can be formed on at least one side of the metal foil by electroplating. Examples of surface treatment layers include a roughening layer, a rust-preventing layer, an alloy layer further disposed between the surface of the metal foil and the aforementioned roughening layer as needed, a chromate layer disposed on the surface of the rust-preventing layer, and a silane coupling agent layer. When the metal layer is a copper foil, electrolytic copper foil or rolled copper foil can be used. This metal layer preferably has a roughening layer formed of two or more elements selected from copper, zinc, titanium, tungsten, molybdenum, nickel, cobalt, and iron, and / or a rust-preventing layer formed of two or more elements selected from zinc, tin, nickel, cobalt, chromium, and molybdenum. From the viewpoint of uniformly distributing the roughening layer, it is preferable to further pre-distribute 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.

[0267] From the viewpoint of easily adjusting the surface roughness parameters of the metal foil surface, the thickness of the aforementioned surface treatment layer is 2.0 μm or less, preferably 0.2 μm or more and 1.5 μm or less. In this specification, the aforementioned surface treatment layer is also included and referred to as the "metal layer". Methods for adjusting the surface of the metal layer to the aforementioned range of surface roughness parameters include methods using commercially available products whose metal layer surface meets the aforementioned range of surface roughness parameters, and methods for forming a surface treatment layer with a specified roughness on a metal surface.

[0268] [Physical properties of layered bodies] Regarding the laminate of the present invention, since the skewness Psk obtained from the cross-sectional curve of the interface between the aforementioned resin film and the aforementioned metal layer is -0.05 or more, or since the interface of the laminate satisfies formula (I), it has a high yield strength of 0.2% and excellent resistance to deformation. Furthermore, it also exhibits excellent dielectric properties, achieving a balance between excellent yield strength and dielectric properties. In addition, the laminate of the present invention has excellent water resistance, thus effectively suppressing the intrusion of water from the resin film surface at locations where the metal layer has been removed by etching or the like. Furthermore, due to its excellent drying speed, even if water is present, it is easily and efficiently released by heating. Therefore, the laminate of the present invention can be suitable for use as a substrate material for printed circuit boards, antenna substrates, etc. Moreover, the laminate of the present invention has a low Df, thus achieving low transmission loss even in high-frequency bands for transmitting high-frequency signals. Therefore, it is suitable as a substrate material for printed circuit boards and antenna substrates, particularly for high-speed communication applications such as 5G.

[0269] The laminate of the present invention may also include other layers such as functional layers, provided that a metal layer is directly (in contact) laminated (or disposed) on at least one side of the resin film in a manner that satisfies at least the above-mentioned Psk range or at least satisfies formula (I). For example, if a metal layer is laminated on one side of the resin film, other layers may be included on the other side of the resin film and / or on the side of the metal layer opposite to the resin film. In addition, if metal layers are laminated on both sides of the resin film, other layers may be included on the side of at least one metal layer opposite to the resin film. Furthermore, if the resin film is a laminated film, other layers may be included between the layers in the resin film (preferably the layers containing PI resin in a PI-based film). Examples of functional layers include adhesive layers. Functional layers may be used alone or in combination of two or more. From the viewpoints of yield strength, water resistance, drying speed, heat resistance, dimensional stability, dielectric properties, and lightweight of the laminate, the laminate is preferably free of functional layers, especially adhesive layers.

[0270] At the interface between the metal layer and the resin film, as long as at least the above-mentioned Psk satisfies the above-mentioned range, or at least satisfies formula (I), the metal layer can be stacked on the surface of the resin film as a whole or partially stacked on the surface of the resin film.

[0271] In one embodiment of the present invention, when the resin film is a PI-based film, the laminate of the present invention can be formed at a relatively low imidization temperature. Even when a laminate with a copper layer (preferably a copper foil layer) as the metal layer is manufactured by thermal imidization of a PI-based resin precursor coating on the metal layer, the degradation of the copper layer surface can be suppressed, and sufficiently high yield strength and low Df can be achieved. Therefore, the laminate of the present invention has excellent high-frequency characteristics even without an adhesive layer.

[0272] In one embodiment of the present invention, the 0.2% yield strength of the laminate is preferably 66 MPa or more, more preferably 70 MPa or more, further preferably 72 MPa or more, even more preferably 75 MPa or more, particularly preferably 80 MPa or more, particularly more preferably 85 MPa or more, particularly more preferably 87 MPa or more, and extremely preferably 90 MPa or more, for example, 92 MPa or more or 95 MPa or more. If the 0.2% yield strength of the laminate is above the aforementioned lower limit, the strength against deformation is excellent, and the degradation of electrical properties caused by plastic deformation when used as an FPC or the like containing the laminate is suppressed. Furthermore, the upper limit of the 0.2% yield strength of the laminate of the present invention is not particularly limited, for example, it is 300 MPa or less, preferably 150 MPa or less. The 0.2% yield strength of the laminate represents the stress value at which the tangent line at 0 strain intersects the SS curve obtained using a tensile testing machine under conditions of 25°C, 50% relative humidity, 50mm chuck spacing, and 20mm / min tensile speed.

[0273] [Manufacturing method of laminated bodies] The method for manufacturing the laminate of the present invention is not particularly limited as long as it is a method of directly laminating a metal layer on at least one side of a resin film in a manner that satisfies at least the above-mentioned range of Psk or at least satisfies formula (I). Examples include: a method of forming a metal layer on a resin film by plating; a manufacturing method of coating a solution of the resin constituting the resin film or a solution of the precursor of the resin on the surface of the metal layer and drying it; and a method of bonding the resin film to the metal layer.

[0274] In one embodiment of the present invention, as a method for manufacturing a laminate based on plating treatment, for example, a method described in the section on "Method for Manufacturing Resin Films" can be used, which involves manufacturing a resin film by casting, extrusion, etc., and then metal plating the surface of the resin film to form a metal layer (metal plating layer) on the surface 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 more preferably a copper plating layer. In this case, the surface of the support substrate on the side in contact with the resin film preferably satisfies the same surface properties as the "surface roughness parameter of the metal surface" described above. When the resin film is a PI-based film, the coating method of the PI-based resin precursor solution onto the support substrate, the pre-drying method, the settling method, and the heating conditions for imidization can be the same as those described later when using a metal layer on the support substrate.

[0275] In another embodiment of the present invention, after embossing, matte finishing, hairline finishing, sandblasting, and desmearing treatment are performed on the surface of the resin film to create an uneven surface, metal plating is performed on the surface of the resin film to form a metal layer (metal plating layer) on the surface of the resin film, thereby enabling the manufacture of a laminate.

[0276] In a preferred embodiment of the present invention, when the resin film is a PI-based film, a method for directly forming the resin film on the surface of the metal layer using a metal layer as a supporting substrate can be exemplified by a method including the following steps: coating a solution of the corresponding PI-based resin precursor onto the surface of the metal layer and pre-drying it to obtain a coating film (also called a coating and pre-drying step); allowing the obtained coating film to stand (also called a standing step); and heating the coating film to imidize the PI-based resin (also called an imidization step). It should be noted that when the PI-based film is a single-layer film, the aforementioned coating film is a single-layer coating film; when the PI-based film is a multilayer film, the aforementioned coating film is a multilayer coating film. It should be noted that in the manufacture of the laminate, the standing step may not be necessary, but when the standing step is included, there is a tendency, for example, that by combining it with the surface roughness parameters of the metal layer, the roughness parameters of the obtained laminate can be easily adjusted to the aforementioned range. Furthermore, the mechanical properties of the obtained laminate, such as the yield strength, can be improved. When a metal layer is also formed on the other side of a PI film, a method can be used to bond the metal layer to the other side of the PI film by hot lamination, hot pressing, or other hot pressing techniques.

[0277] (Preparation of PI-based resin precursors) PI-based resin precursors can be obtained by reacting a tetracarboxylic acid compound with a diamine compound. Examples of tetracarboxylic anhydrides used in the synthesis of PI-based resin precursors include aromatic tetracarboxylic acid dianhydrides and aliphatic tetracarboxylic acid dianhydrides. Tetracarboxylic acid compounds can be used alone or in combination of two or more. Besides dianhydrides, tetracarboxylic acid compounds can also be tetracarboxylic acid analogs such as acyl chlorides.

[0278] As a tetracarboxylic acid compound, examples include tetracarboxylic anhydride represented by formula (A1), tetracarboxylic anhydride represented by formula (A2), and tetracarboxylic anhydride represented by formula (A3). Tetracarboxylic acid compounds known in the art can be appropriately selected and used.

[0279] Examples of such tetracarboxylic acid compounds include, for example, pyromellitic dianhydride (hereinafter, sometimes referred to as PMDA), 4,4'-(4,4'-isopropylidenediphenoxy)phthalic 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), 4,4'-(hexafluoroisopropylidene)phthalic anhydride (hereinafter, sometimes referred to as 6FDA), 4,4'-oxophthalic anhydride (hereinafter, sometimes referred to as ODPA), 2,2',3,3'-, 2,3,3',4'- or 3,3',4,4'-benzophenonetetracarboxylic dianhydride, and 2,3',3,4'-biphenyltetracarboxylic dianhydride. Formic dianhydride, 2,2',3,3'-biphenyltetracarboxylic dianhydride, p-phenylene bis(triphenylene oxide monoester dianhydride) (hereinafter, sometimes referred to as TAHQ), trimellitic anhydride esterified with 2,2',3,3',5,5'-hexamethyl-4,4'-biphenyl (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 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 Benzenetetracarboxylic 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(2,3-dicarboxyphenyl)ethane dianhydride, 1,1-bis(3,4-dicarboxyphenyl)ethane dianhydride, 1,2,7,8-, 1,2,6,7-phenanthrenetetracarboxylic dianhydride, 1,2,9,10-phenanthrenetetracarboxylic 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 Citric acid 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-phenylene bis(trimethoxymethyl ester anhydride), 3,3',4,4'-diphenylsulfonetetracarboxylic dianhydride, 2,3,6,7-anthracitetetracarboxylic dianhydride, 4,8-dimethyl-1,2,3,5,6,7-hexahydronaphthalene-1,2,5,6-tetracarboxylic dianhydride, 2,6-dichloronaphthalene-1,4,5,8-tetracarboxylic dianhydride, 2,7-dichloronaphthalene-1,4,5,8-Tetracarboxylic dianhydride, 2,3,6,7-Tetrachloronaphthalene-1,4,5,8-Tetracarboxylic dianhydride, 2,3,6,7-Tetrachloronaphthalene-2,3,6,7-Tetracarboxylic 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-Perylenetetracarboxylic dianhydride, 3, 4,9,10-Perylenetetracarboxylic dianhydride, 4,5,10,11-Perylenetetracarboxylic dianhydride, 5,6,11,12-Perylenetetracarboxylic dianhydride, pyrazine-2,3,5,6-tetracarboxylic dianhydride, pyrrolidine-2,3,4,5-tetracarboxylic dianhydride, thiophene-2,3,4,5-tetracarboxylic dianhydride, bis(2,3-dicarboxyphenyl)sulfone dianhydride, bis(3,4-dicarboxyphenyl)sulfone dianhydride, etc. Among these, from the viewpoint of improving the yield strength of the resulting laminate and reducing Df and CTE, the combination of BPDA, PMDA, TAHQ, and / or BP-TME is preferred. These tetracarboxylic acid compounds can be used alone or in combination of two or more.

[0280] Examples of diamine compounds used in the synthesis of PI-based resin precursors include aliphatic diamines, aromatic diamines, and mixtures thereof. It should be noted that in this embodiment, "aromatic diamine" refers to a diamine having an aromatic ring, which may contain an aliphatic group or other substituents in a portion of its structure. This aromatic ring can be a monocyclic or fused ring, and examples include benzene rings, naphthalene rings, anthracene rings, and fluorene rings, but are not limited thereto. Among these, a benzene ring is preferred. Additionally, "aliphatic diamine" refers to a diamine having an aliphatic group, which may contain other substituents in a portion of its structure, but does not have an aromatic ring.

[0281] As a diamine compound, examples include diamines represented by formula (B1), diamines represented by formula (B2), diamines represented by formula (2), etc., and diamine compounds known in the art can be appropriately selected and used.

[0282] Examples of such diamine compounds include, for instance, 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'-diaminobiphenyl (hereinafter, sometimes referred to as TFMB), 4,4'-diaminodiphenyl ether, 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), and 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, 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)]benzophenone, 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-ditoluidine, 4,4'-methylene-2,6-diethylaniline, 4,4'-methylenediphenylamine, 3,3'-methylenediphenylamine, 4,4'-diaminodiphenylpropane, 3,3'-diaminodiphenylpropane, 4,4'-diaminodiphenylethane, 3,3'-diaminodiphenylethane, 4,4'-diaminodiphenylmethane, 3,3'-diaminodiphenylmethane, 3,3-diaminodiphenyl ether, 3,4'-diaminodiphenyl ether , 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), resorcinol-bis(3-aminophenyl) ether, 4,4'-[1,4-phenylenebis(1-methylethoxy)]bisaniline, 4,4'-[1,3-phenylenebis(1-methylethoxy)]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-Diaminonaphthalene, 2,4-bis(β-amino-tert-butyl)toluene, 2,4-diaminotoluene, m-xylene-2,5-diamine, p-xylene-2,5-diamine, m-phenylenediamine, p-phenylenediamine, 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-phenylene diisopropylidene)bisaniline, 1,4-bis[ 2-(4-aminophenyl)-2-propylbenzene, 2,4-diamino-3,5-diethyltoluene, 2,6-diamino-3,5-diethyltoluene, 4,4'-bis(3-aminophenoxy)biphenyl, 4,4'-(hexafluoropropylene)diphenylamine, 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, norbornene diamine, 2'-methoxy-4,4'-diaminobenzoyl aniline, 4,4'-diaminobenzoyl aniline, bis[4-(4-aminophenoxy)phenyl] sulfone, bis[4-(3-aminophenoxy)phenyl] sulfone, 9,9-bis[4-(4-aminophenoxy)phenyl]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)]benzoyl aniline, bis[4,4'-(3-aminophenoxy)]benzoyl aniline, 2,6-diaminopyridine, 2,5-diaminopyridine, etc. Among these, from the viewpoint of improving the yield strength of the resulting laminate and reducing Df and CTE, a combination of m-Tb, BAPP, TPE-Q, 1,3-bis(4-aminophenoxy)benzene, and / or TPE-R is preferred. Two or more diamine compounds can be used alone or in combination.

[0283] It should be noted that the aforementioned PI-based resin precursor can also be a product obtained by further reacting other tetracarboxylic acids, dicarboxylic acids, and tricarboxylic acids, as well as their anhydrides and derivatives, in addition to the tetracarboxylic acid compound used in the synthesis of the aforementioned PI-based resin precursor, without impairing the various physical properties of the obtained PI-based film.

[0284] Other tetracarboxylic acids include the hydroadditions of the anhydrides of the aforementioned tetracarboxylic acid compounds.

[0285] Examples of dicarboxylic acid compounds include aromatic dicarboxylic acids, aliphatic dicarboxylic acids and their similar acyl chloride compounds, acid anhydrides, etc., and two or more can be used in combination. Specific examples include terephthalic acid; isophthalic acid; naphthalenedicarboxylic acid; 4,4'-biphenyl dicarboxylic acid; 3,3'-biphenyl dicarboxylic acid; dicarboxylic acid compounds of chain hydrocarbons with 8 or fewer carbon atoms; compounds in which two benzoic acids are linked by single bonds, -O-, -CH2-, -C(CH3)2-, -C(CF3)2-, -SO2- or phenylene oxides; and their acyl chloride compounds.

[0286] Examples of tricarboxylic acid compounds include aromatic tricarboxylic acids, aliphatic tricarboxylic acids and their similar acyl chloride compounds, acid anhydrides, etc., and two or more can be used in combination. Specific examples include the anhydride of 1,2,4-benzenetricarboxylic acid; 2,3,6-naphthalenetricarboxylic acid-2,3-anhydride; and compounds formed by the linkage of phthalic anhydride and benzoic acid through single bonds, -O-, -CH2-, -C(CH3)2-, -C(CF3)2-, -SO2-, or phenylene oxide.

[0287] In the manufacture of PI-based resin precursors, the amounts of diamine compounds, tetracarboxylic acid compounds, dicarboxylic acid compounds, and tricarboxylic acid compounds used can be appropriately selected according to the desired ratio of each structural unit of the PI-based resin precursor.

[0288] In this invention, the total number of moles of diamine compound used relative to 1 mole of the total amount of tetracarboxylic acid compound is defined as the amine ratio. In a preferred embodiment of this invention, the amine ratio is preferably 0.90 moles or more, and more preferably 0.999 moles or less, relative to 1 mole of the total amount of tetracarboxylic acid compound. In another embodiment, the amine ratio is preferably 1.001 moles or more, and more preferably 1.10 moles or less, relative to 1 mole of the total amount of tetracarboxylic acid compound.

[0289] In one embodiment of the present invention, when the amine ratio is 1 or less, the amine ratio is preferably 0.90 mol or more and 0.999 mol or less, more preferably 0.95 mol or more and 0.997 mol or less, and even more preferably 0.97 mol or more and 0.995 mol or less.

[0290] 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.

[0291] If the amine ratio is close to 1.0 molar, there is a tendency for the molecular weight to increase sharply during synthesis. If the amine ratio differs significantly from 1.0 molar, there is a tendency for the molecular weight of the obtained PI-based resin to decrease easily. If the molecular weight increases sharply, there is a tendency for uneven growth in the synthesized material and for the PI-based resin obtained from the PI-based resin precursor to have unstable physical properties. On the other hand, if the molecular weight is too low, there is a tendency for the mechanical properties to decrease.

[0292] The reaction temperature between the diamine compound and the tetracarboxylic acid compound is preferably below 50°C, more preferably below 40°C, and even more preferably below 30°C. Furthermore, the reaction temperature between the diamine compound and the tetracarboxylic acid compound is preferably above 5°C, more preferably above 10°C, and even more preferably above 15°C. If the reaction temperature is within the aforementioned upper and lower limits, the effects of the present invention are easily obtained, and there is a tendency to increase the reaction rate and shorten the polymerization time. The reaction time is not particularly limited, for example, it can be about 0.5 to 36 hours, preferably 1 to 24 hours.

[0293] The reaction between diamine compounds and tetracarboxylic acid compounds is preferably carried out in a solvent. There are no particular limitations on the solvent, as long as it does not affect the reaction. Examples of solvents include: alcohols such as water, methanol, ethanol, ethylene glycol, isopropanol, propylene glycol, ethylene glycol methyl ether, ethylene glycol butyl ether, 1-methoxy-2-propanol, 2-butoxyethanol, and propylene glycol monomethyl ether; phenols such as phenol and cresol; esters such as ethyl acetate, butyl acetate, ethylene glycol methyl ether acetate, propylene glycol methyl ether acetate, and ethyl lactate; lactones such as γ-butyrolactone (hereinafter sometimes referred to as GBL) and γ-valerolactone; and ketones such as acetone, methyl ethyl ketone, cyclopentanone, cyclohexanone, 2-heptanone, and methyl isobutyl 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 solvents such as acetonitrile; ether solvents such as tetrahydrofuran and dimethoxyethane; chlorine-containing solvents such as chloroform and chlorobenzene; amide 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 solvents such as ethylene carbonate and propylene carbonate; pyrrolidone solvents such as N-methylpyrrolidone (hereinafter, sometimes referred to as NMP); and combinations thereof. Among these, from the viewpoint of solubility, phenolic solvents, lactone solvents, amide solvents, and pyrrolidone solvents are preferably suitable, and amide solvents are more preferred.

[0294] In one embodiment of the present invention, the solvent used in the reaction of the diamine compound with the tetracarboxylic acid compound preferably has a boiling point suitable for imidization conditions that are advantageous in terms of yield strength and dielectric properties of the resulting laminate, preferably below 230°C, more preferably below 200°C, further preferably below 180°C, preferably above 100°C, and more preferably above 120°C.

[0295] The reaction between the diamine compound and the tetracarboxylic acid compound can be carried out under inactive atmospheres such as nitrogen or argon, or under reduced pressure, as needed. It is preferred to carry out the reaction under an inactive atmosphere, such as nitrogen or argon, while stirring in a tightly controlled dehydrating solvent.

[0296] The obtained PI-based resin precursor can be temporarily separated by common methods, but separation is also optional. The reaction solution containing the PI-based resin precursor obtained by the synthesis of the PI-based resin precursor can be appropriately diluted with a solvent as needed to prepare a PI-based resin precursor solution for use.

[0297] (Coating and pre-drying process) In the manufacture of the laminate in this invention, the coating and pre-drying process involves coating the surface of the metal layer with a solution of the corresponding PI-based resin precursor and pre-drying it to obtain a coating film (single-layer coating film or multi-layer coating film). When the PI-based film in the laminate is a multilayer film, the following methods can be used: repeating the process of coating the surface of the metal layer with a solution of the corresponding PI-based resin precursor and pre-drying it multiple times to obtain a multilayer coating film (sometimes called a step-by-step method); or simultaneously coating and pre-drying the PI-based resin precursor solution corresponding to each layer in a multilayer extrusion process to obtain a multilayer coating film (sometimes called a simultaneous method).

[0298] For example, in the case of a PI film (L) having a PI-based resin layer (PI-2), a PI-based resin layer (PI-1), and a PI-based resin layer (PI-3) in sequence, in a step-by-step mode, the following steps can be performed: applying a PI-based resin precursor solution corresponding to the PI-based resin layer (PI-2) to the surface of the metal layer, pre-drying it to form a coating film, applying a PI-based resin precursor solution corresponding to the PI-based resin layer (PI-1) to the coating film, pre-drying it to form a 2-layer coating film, and then applying a PI-based resin precursor solution corresponding to the PI-based resin layer (PI-3) to the 2-layer coating film, pre-drying it to form a 3-layer coating film. Alternatively, in the simultaneous mode, the following process can be performed: by multi-layer extrusion or the like, simultaneously applying a PI-based resin precursor solution corresponding to the PI-based resin layer (PI-2), a PI-based resin precursor solution corresponding to the PI-based resin layer (PI-1), and a PI-based resin precursor solution corresponding to the PI-based resin layer (PI-3) to the surface of the metal layer, and pre-drying to form a three-layer coating film.

[0299] The solvent contained in the PI-based resin precursor solution can be exemplified by solvents used in the reaction of diamine compounds and tetracarboxylic acid compounds in the manufacture of PI-based resin precursors, preferably lactone-based solvents, amide-based solvents, pyrrolidone-based solvents, and more preferably amide-based solvents. Furthermore, in one embodiment of the present invention, the boiling point of the solvent contained in the PI-based resin precursor solution is preferably suitable for imidization conditions that are advantageous in terms of yield strength and dielectric properties of the resulting laminate, preferably below 230°C, more preferably below 200°C, further preferably below 180°C, particularly preferably below 170°C, preferably above 100°C, and more preferably above 120°C.

[0300] Relative to the total amount of the PI-based resin precursor solution, the content of the PI-based resin precursor in the PI-based 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, preferably 30% by mass or less, more preferably 25% by mass or less, even more preferably 23% by mass or less, and particularly preferably 20% by mass or less. If the content of the PI-based resin precursor is within the aforementioned range, the processability during film formation is excellent.

[0301] A coating film of a PI-based resin precursor solution can be formed by applying the PI-based resin precursor solution to the surface of a metal using known coating or application methods. Known coating methods include, for example, wire rod coating, reverse coating, gravure coating, roller coating, die coating, comma coating, lip coating, spin coating, screen printing coating, spray-on doctor blade coating, dip coating, spray coating, curtain coating, slot coating, applicator coating, and casting. When the PI-based film in the laminate is a multilayer film, the PI-based resin precursor solution can be applied to the metal surface in one layer at a time or in multiple layers to form a multilayer PI-based resin precursor solution coating film, or multiple multilayer PI-based resin precursor solution laminated coating films can be formed simultaneously. Methods for simultaneously forming multilayer coating films include, for example, co-extrusion processing and multilayer curtain coating.

[0302] In the coating and pre-drying process, the coating speed of the PI-based 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, 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. If the coating speed is within the aforementioned range, there is a tendency that, by combining it with the roughness parameters of the metal surface, the roughness parameters of the resulting laminate can be easily adjusted to the aforementioned range.

[0303] In the coating and pre-drying process, the temperature for pre-drying the coating film (preferably a multilayer coating film) is preferably 60°C or higher, more preferably 70°C or higher, even more preferably 80°C or higher, even more preferably 90°C or higher, preferably 200°C or lower, even more preferably 150°C or lower, and even more preferably 130°C or lower. Furthermore, the pre-drying time is preferably 30 seconds or higher, more preferably 1 minute or higher, even more preferably 5 minutes or higher, even more preferably 10 minutes or higher, for example, 15 minutes or higher, 20 minutes or higher, or 25 minutes or higher. It is also preferably 24 hours or lower, more preferably 12 hours or lower, even more preferably 6 hours or lower, and particularly preferably 1 hour or lower. If the pre-drying temperature and pre-drying time are within the aforementioned ranges, there is a tendency that, by combining them with the roughness parameters of the metal surface, the roughness parameters of the resulting laminate can be easily adjusted to the aforementioned ranges.

[0304] (Static setting process) The settling process is a process of allowing the coating film (preferably a multilayer coating film) obtained in the coating and pre-drying processes to stand. By providing a settling process before the imidization process, it is easier for the solvent to remain sufficiently throughout the coating film during imidization, or for the resin layers to be well-fused, thus increasing the degree of freedom of the resin molecules during imidization. The reason is not yet certain, but when such a settling process is included, there is a tendency that, by combining it with the surface roughness parameters of the metal layer, the roughness parameters of the resulting laminate interface can be easily adjusted to the aforementioned range. Furthermore, when the settling process is provided, it is believed that the PI-based resins constituting each layer can easily mix with each other near the interface, forming a mixed region near the interface, which tends to improve the mechanical properties of the resulting laminate.

[0305] In the settling process, the settling time of the coating (also called settling time) can be appropriately selected based on the settling temperature (also called settling temperature), and is not particularly limited. Preferably, it is 3 hours or more, more preferably 6 hours or more, further preferably 12 hours or more, even more preferably 18 hours or more, and particularly preferably 22 hours or more. The upper limit of the settling time of the coating is not particularly limited, and is generally 450 hours or less, preferably 100 hours, and more preferably 50 hours or less. If the settling time of the coating is within the aforementioned range, there is a tendency to more easily control the roughness parameters of the resulting laminate interface within the aforementioned range by combining it with the surface roughness parameters of the metal layer, thereby improving the mechanical properties of the laminate.

[0306] Furthermore, in a preferred embodiment of the present invention, the settling process is preferably a process of settling (or storing) the coating at a low temperature (preferably under refrigeration). By settling (or storing) at a low temperature, there is a tendency to more easily control the roughness parameters of the resulting laminate interface within the aforementioned range by combining them with the surface roughness parameters of the metal layer, thereby improving the mechanical properties of the laminate.

[0307] In the settling process, the settling temperature of the coating is preferably below 20°C, more preferably below 15°C, further preferably below 10°C, even more preferably below 8°C, and particularly preferably below 5°C. When the settling temperature of the coating is below the aforementioned upper limit, there is a tendency to more easily control the roughness parameter of the resulting laminate interface within the aforementioned range by combining it with the surface roughness parameter of the metal layer, thereby improving the mechanical properties of the laminate. In addition, the lower limit of the settling temperature of the multilayer coating is generally above -30°C, preferably above -20°C, more preferably above -10°C, even more preferably above -5°C, and particularly preferably above 0°C. It should be noted that the settling process can be carried out, for example, in air or in an inactive gas atmosphere, or in a closed space. In one embodiment of the present invention, the settling process is preferably carried out in a closed state of the coating, for example, preferably by placing the coating in a closed container, or by settling it in a state of lamination with a film with low moisture permeability (e.g., aluminum laminate).

[0308] (Imidification process) The imidization process is a process of imidizing PI-based resins in a coating on a metal surface by heat treatment, for example, at temperatures above 200°C and below 500°C.

[0309] In one embodiment of the invention, the imidization process preferably includes the following steps: rapidly heating from a low temperature (referred to as the first temperature) to a high temperature (referred to as the second temperature), and holding at that high temperature. By performing imidization at a rapid, preferably rapid, temperature increase, and then holding at that temperature for a certain time after reaching the high temperature, imidization is completed. This is advantageous in terms of the formation of higher-order structures and branched structures in the PI-based resin, thus maintaining a low yield strength (Df) in the resulting laminate and easily improving the yield strength. Furthermore, it is also advantageous from the viewpoint of obtaining a smooth laminate.

[0310] In one embodiment of the present invention, the first temperature is preferably 20°C to 50°C, more preferably 25°C to 35°C, and the second temperature is preferably 200°C to 450°C, more preferably 250°C to 400°C, further preferably 270°C to 380°C, particularly preferably 290°C to 360°C, and particularly more preferably 300°C to 350°C. For example, it can be 300°C to 340°C, 300°C to 330°C, or 310°C to 320°C. According to the laminate of the present invention, even if imidization is performed at a lower temperature, such as 350°C or below (preferably 320°C or below), high yield strength or reduced Df can be exhibited. Furthermore, if the imidization temperature is 350°C or below (preferably 320°C or below), thermal degradation of the copper layer can be suppressed even when a copper layer is used as the metal layer, thus easily obtaining a laminate with excellent high-frequency characteristics. Furthermore, from the viewpoints of sufficiently increasing the imidization rate, increasing the yield strength, and reducing Df, the imidization temperature is preferably 200°C or higher, more preferably 210°C or higher, and even more preferably 220°C or higher.

[0311] In one embodiment of the present invention, the heating from the first temperature to the second temperature can be performed at a single-stage heating rate or at a multi-stage heating rate of two or more stages. In one embodiment of the present invention, when the heating from the first temperature to the second temperature is performed at a single stage, the heating rate is preferably 2°C / min or more, more preferably 3°C / min or more, further preferably 4°C / min or more, preferably 30°C / min or less, more preferably 20°C / min or less, and even more preferably 10°C / min or less. Using such a heating rate is advantageous in terms of the formation of higher-order structures and branched structures in the PI-based resin, thus maintaining a low yield strength (Df) of the resulting laminate and easily improving the yield strength. Furthermore, it is also advantageous from the viewpoint of obtaining a smooth laminate.

[0312] In one embodiment of the present invention, the heating time from the first temperature to the second temperature can be suitably selected according to their temperature and heating rate, preferably 5 hours or less, more preferably 3 hours or less, further preferably 2 hours or less, particularly preferably 1.5 hours or less, and preferably 3 minutes or more, more preferably 10 minutes or more, and further preferably 30 minutes or more. If the heating time from the first temperature to the second temperature is within the aforementioned range, the yield strength (Df) of the resulting laminate is maintained at a low level, and the yield strength is easily improved.

[0313] In one embodiment of the present invention, the holding time at the second temperature is preferably 1 minute or more, more preferably 10 minutes or more, further preferably 30 minutes or more, even more preferably 60 minutes or more, preferably 5 hours or less, and more preferably 3 hours or less. If 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, it becomes advantageous in terms of the formation of higher-order structures and branched structures of the PI-based resin. Therefore, the yield strength (Df) of the resulting laminate is maintained low, and the yield strength is easily improved.

[0314] If the imidization process described above is used, especially the preferred imidization process (imidization temperature, heating rate, heating time, holding time, etc.), there is a tendency that, by combining it with the roughness parameters of the metal layer, it is easier to control the roughness parameters of the resulting laminate within the above-mentioned range.

[0315] In one embodiment of the present invention, as a method for bonding a resin film to a metal layer, for example, a method described in the item "Method for Manufacturing a Resin Film" is to manufacture a resin film by casting, extrusion, etc., and then bond it to a metal layer by hot pressing, hot lamination, etc.

[0316] When the resin film is a PI-based film, the following method can also be used: a PI-based resin precursor coating film is obtained by applying a PI-based resin precursor solution to a support substrate other than the metal layer contained in the laminate and drying it, and then peeling the coating film off the aforementioned substrate so that the peeled-off PI-based resin precursor coating film adheres to the metal layer.

[0317] From the viewpoint that the roughness parameters can be easily adjusted to the above range by combining them with the roughness parameters of the metal surface, and that high yield strength can be achieved, the above-described method of thermal imidization of PI-based resin precursor coating on the metal layer is preferred.

[0318] When a resin film has metal layers on both sides, the two sides can be the same or different depending on the method of setting the metal layers.

[0319] Flexible printed circuit board The laminate of the present invention has high yield strength, thus making it suitable for use as an FPC substrate material. Furthermore, the laminate of the present invention can have low Df (displacement factor), thereby reducing transmission losses in electrical circuits formed by assembling the laminate. In addition, the laminate of the present invention also has low CTE (conversion factor) and excellent thermal properties, making it suitable for use as an FPC substrate material, particularly for FPC substrates used in high-speed communications such as 5G. Therefore, the present invention also includes a flexible printed circuit board comprising the laminate of the present invention.

[0320] Example The present invention will now be described in more detail based on embodiments and comparative examples, but the present invention is not limited to the following embodiments.

[0321] The abbreviations used in the examples and comparative examples refer to the following compounds.

[0322] BPDA: 3,3',4,4'-Biphenyltetracarboxylic dianhydride BP-TME: 4,4'-bis(1,3-dioxo-1,3-dihydroisobenzofuran-5-ylcarbonyloxy)biphenyl PMDA: Pyromellitic dianhydride m-Tb: 4,4'-diamino-2,2'-dimethylbiphenyl TPE-Q: 1,4-Bis(4-aminophenoxy)benzene TPE-R: 1,3-Bis(4-aminophenoxy)benzene 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. The mixture was stirred at 20 °C for 1 hour under a nitrogen atmosphere. Then, 48.25 g (221.2 mmol) of PMDA was added, and the mixture was stirred at 20 °C for 3 hours under a nitrogen atmosphere to obtain PI-based resin precursor solution 1. The molar ratio of the diamine monomer to the acid dianhydride monomer used was 1.04.

[0323] (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. Then, 21.67 g (73.7 mmol) of BPDA and 6.89 g (31.6 mmol) of PMDA were added sequentially. The mixture was stirred at 20 °C for 3 hours 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.

[0324] (3) Polyimide-based resin precursor solution 3 9.87 g (46.5 mmol) of m-Tb and 122.29 g (418.3 mmol) of TPE-R were dissolved in 1890 g of DMAc. Then, 30.28 g (138.8 mmol) of PMDA and 95.30 g (323.9 mmol) of BPDA were added sequentially. The mixture was stirred at 20 °C for 3 hours under a nitrogen atmosphere to obtain PI-based resin precursor solution 3. The molar ratio of the diamine monomer to the acid dianhydride monomer used was 1.005.

[0325] 2. Fabrication of laminates and resin films (Example 1) On the roughened surface of an electrolytic copper foil (12 μm thick) having the roughness characteristics shown in Table 3, a PI-based resin precursor solution 2 is applied at a speed of 0.6 m / min to achieve a dry thickness of 5 μm, resulting in a coating film. The coating film is then dried by heating at 120°C for 10 minutes. On this dried coating film, a PI-based resin precursor solution 1 is applied at a speed of 0.6 m / min to achieve a dry thickness of 41 μm, resulting in a double-layer laminated film. The double-layer laminated film is then dried by heating at 120°C for 30 minutes. On this dried double-layer laminated film, a PI-based resin precursor solution 2 is applied at a speed of 0.6 m / min to achieve a dry thickness of 5 μm, resulting in a triple-layer laminated film. After drying the aforementioned three-layer laminated coating film by heating it at 120°C for 30 minutes, the laminate formed by the copper foil and the aforementioned three-layer laminated coating film was placed in a sealed container and left to stand at 4°C for 24 hours. Then, after confirming that the laminate taken out of the sealed container had reached room temperature, it was fixed in a metal frame and heated from 30°C to 320°C over 60 minutes in an atmosphere with an oxygen concentration of 0.02%, and then held at 320°C for 120 minutes, thereby obtaining a laminate 1 formed by a layer containing PI-based resin and a copper foil layer, which is laminated in the order of copper foil layer, layer (PI-2), layer (PI-1), and layer (PI-3) (TPI layer, mPI layer, and TPI layer).

[0326] The obtained laminate 1 was immersed in a large volume of 40% (w / w) ferric chloride aqueous solution at room temperature for 10 minutes, and then washed with pure water. After visually confirming that there was no copper residue, it was dried at 80°C for 1 hour to obtain a resin film 1 formed by stacking layers (PI-2) (copper foil layer side), (PI-1), and (PI-3) (TPI layer, mPI layer, and TPI layer) in that order. The thickness of the resin film 1 is 51 μm. It should be noted that the above-mentioned PI-based resin precursor solution was coated using an automatic coating device (TESTERSANGYO CO., LTD., SA-204 (width 250 mm)) equipped with a coating tool (TESTER SANGYO CO., LTD., SA-204 (width 250 mm)).

[0327] (Example 2) Using electrolytic copper foils (12 μm thick, see Table 3) with different roughness characteristics on the roughened side, the coating was applied so that the dry thickness of layer (PI-2) (copper layer side) / layer (PI-1) / layer (PI-3) was 5 μm / 39 μm / 5 μm. Otherwise, the same procedure as in Example 1 was followed to obtain a laminate 2 consisting of a layer containing PI-based resin and a copper foil layer, which were stacked in the order of copper foil layer, layer (PI-2), layer (PI-1) and layer (PI-3) (TPI layer, mPI layer and TPI layer), and a resin film 2 with the copper foil layer removed.

[0328] (Example 3) Using electrolytic copper foils (12 μm thick, see Table 3) with different roughness characteristics on the roughened side, the coating was applied so that the dry thickness of layer (PI-2) (copper layer side) / layer (PI-1) / layer (PI-3) was 5 μm / 43 μm / 5 μm. Otherwise, the same procedure as in Example 1 was followed to obtain a laminate 3 consisting of a layer containing PI-based resin and a copper foil layer, which was stacked in the order of copper foil layer, layer (PI-2) (copper foil layer side), layer (PI-1) and layer (PI-3) (TPI layer, mPI layer and TPI layer), and a resin film 3 with the copper foil layer removed.

[0329] (Example 4) Electrolytic copper foils (12 μm thick, see Table 3) with different roughness characteristics on the roughened side were used as layers (PI-2) (copper layer side) / layer (PI-1) / layer (PI-3). The coating was applied by drying the PI-based resin precursor solution 3 / PI-based resin precursor solution 1 / PI-based resin precursor solution 3 to a thickness of 5 μm / 38 μm / 5 μm, respectively. Otherwise, the operation was the same as in Example 1 to obtain a laminate 4 consisting of a PI-based resin layer and a copper foil layer, which were stacked in the order of copper foil layer, layer (PI-2), layer (PI-1) and layer (PI-3) (TPI layer, mPI layer and TPI layer), and a resin film 4 with the copper foil layer removed.

[0330] (Example 5) Using electrolytic copper foils (12 μm thick, see Table 3) with different roughness characteristics on the roughened side, the coating was applied so that the dry thickness of layer (PI-2) (copper foil layer side) / layer (PI-1) / layer (PI-3) was 5 μm / 35 μm / 5 μm. Otherwise, the same procedure as in Example 4 was followed to obtain a laminate 5 consisting of a PI-based resin layer and a copper foil layer, which were stacked in the order of copper foil layer, layer (PI-2), layer (PI-1) and layer (PI-3) (TPI layer, mPI layer and TPI layer), and a resin film 5 with the copper foil layer removed.

[0331] (Example 6) Using electrolytic copper foils (12 μm thick, see Table 3) with different roughness characteristics on the roughened side, the coating was applied so that the dry thickness of layer (PI-2) (copper foil layer side) / layer (PI-1) / layer (PI-3) was 5 μm / 41 μm / 5 μm. Otherwise, the same procedure as in Example 4 was followed to obtain a laminate 6 consisting of a PI-based resin layer and a copper foil layer, which were stacked in the order of copper foil layer, layer (PI-2), layer (PI-1) and layer (PI-3) (TPI layer, mPI layer and TPI layer), and a resin film 6 with the copper foil layer removed.

[0332] (Example 7) Using electrolytic copper foils (12 μm thick, see Table 3) with different roughness characteristics on the roughened side, the coating was applied so that the dry thickness of layer (PI-2) (copper foil layer side) / layer (PI-1) / layer (PI-3) was 5 μm / 34 μm / 5 μm. Otherwise, the same procedure as in Example 4 was followed to obtain a laminate 7 consisting of a PI-based resin layer and a copper foil layer, which were stacked in the order of copper foil layer, layer (PI-2), layer (PI-1) and layer (PI-3) (TPI layer, mPI layer and TPI layer), and a resin film 7 with the copper foil layer removed.

[0333] (Example 8) Electrolytic copper foils with different roughness characteristics on the roughened surface side (thickness: 12 μm, see Table 3) were used, and coating was carried out in such a manner that the dry thickness of layer (PI-2) (copper foil layer side) / layer (PI-1) / layer (PI-3) became 5 μm / 35 μm / 5 μm. Except for this, the operation was carried out in the same manner as in Example 4, and a laminate 8 formed of a PI-based resin-containing layer and a copper foil layer laminated in the order of the copper foil layer, layer (PI-2), layer (PI-1), and layer (PI-3) (TPI layer, mPI layer, and TPI layer), and a resin film 8 from which the copper foil layer was removed were obtained.

[0334] (Comparative Example 1) Electrolytic copper foils with different roughness characteristics on the roughened surface side (thickness: 12 μm, see Table 3) were used, and coating was carried out in such a manner that the dry thickness of layer (PI-2) (copper layer side) / layer (PI-1) / layer (PI-3) became 5 μm / 42 μm / 5 μm. Except for this, the operation was carried out in the same manner as in Example 1, and a laminate 9 formed of a PI-based resin-containing layer and a copper foil layer laminated in the order of the copper foil layer, layer (PI-2), layer (PI-1), and layer (PI-3) (TPI layer, mPI layer, and TPI layer), and a resin film 9 from which the copper foil layer was removed were obtained.

[0335] For the laminates 1 to 9 and resin films 1 to 9 obtained in the examples and comparative examples, various measurements and evaluations were carried out. The measurement and evaluation methods will be described below.

[0336] <Film Thickness Measurement> Arbitrary portions were cut out from the resin films 1 to 9 obtained in the examples and comparative examples in the size of 5 mm × 5 mm, and embedded with resin to prepare samples for film thickness measurement. In the prepared samples for film thickness measurement, cutting was carried out using a microtome to prepare a measurement cross-section, and the thicknesses of the three PI-based resin-containing layers and the thickness of the resin film were measured using a laser microscope under the following conditions.

[0337] Device: LEXT OLS4100 manufactured by Olympus Corporation Observation magnification: 100 times <Measurement of Df and Dk> Measurement samples of 50 mm × 50 mm were cut out from the resin films 1 to 9 obtained in the examples and comparative examples, and Df and Dk were measured under the following conditions. It should be noted that the measurement was carried out after conditioning the measurement samples at 23°C / 50%RH for 24 hours.

[0338] Device: Compact USB Vector Network Analyzer manufactured by Anritsu Corporation (Product name: MS46122B) AET Inc. manufactures cavity resonators (TE mode 10GHz type). Measurement frequency: 10GHz Measurement atmosphere: 23℃ / 50%RH <Determination of the coefficient of linear thermal expansion (CTE)> Regarding the CTE of the resin films 1 to 9 obtained in the examples and comparative examples, the CTE at 50°C to 100°C was calculated by using a thermomechanical analysis apparatus (TMA) under the following conditions.

[0339] Device: TMA / SS7100 manufactured by Hitachi High-Tech Science Corporation Load: 50.0mN Temperature program: Increase the temperature from 20°C to 130°C at a rate of 5°C / minute. Test piece: 40mm in length, 5mm in width <Determination of Energy Storage Elastic Modulus> The storage modulus of each PI resin formed from the above-mentioned PI resin precursor solutions 1 to 3 was determined by measuring the PI resin film prepared by the following method under the following conditions.

[0340] Each PI-based resin precursor solution was cast onto a glass substrate to a dry thickness of 30 μm, thereby forming a coating film of the PI-based resin precursor solution. The coating film was heated at 120°C for 30 minutes, and after peeling it off from the glass substrate, the film was fixed to a metal frame. Under an atmosphere with an oxygen concentration of 1%, the film fixed to the metal frame was maintained at 320°C for 5 minutes to obtain a PI-based resin film.

[0341] The storage modulus (E') was obtained by measuring the sample and conditions described below using a dynamic viscoelasticity measuring device (IT Keisoku Seigyo Co., Ltd., DVA-220).

[0342] Test piece: a cuboid with a length of 40 mm, a width of 5 mm, and a thickness of 30 μm. Experimental mode: Single frequency, constant rate of heating Experimental method: stretching Sample clamping interval length: 15mm Measurement starting temperature: room temperature ~ 342℃ Heating rate: 5℃ / minute Frequency: 10Hz Static / dynamic stress ratio: 1.8 The results obtained by the above method show that the storage elastic modulus of the PI-based resin film formed from PI-based resin precursor solution 1 at 40°C is 2.3 × 10⁻⁶. 9 The energy storage elastic modulus at 300℃ is 2.8 × 10 Pa. 8 Pa, the storage elastic modulus of the PI-based resin film formed from PI-based resin precursor solution 2 at 40°C is 2.3 × 10⁻⁶. 9 The energy storage elastic modulus at 300℃ is 1.2 × 10 Pa. 7 Pa, the storage elastic modulus of the PI-based resin film formed from PI-based resin precursor solution 3 at 40°C is 2.4 × 10⁻⁶. 9 The storage elastic modulus at 300℃ is 1.1 × 10 Pa. 7 Pa.

[0343] <Determination of moisture content and drying rate of resin film> Arbitrary portions of resin films 1-3 and 5-9 obtained in the Examples and Comparative Examples were cut out at 50mm × 50mm to prepare samples for drying rate measurement. The prepared samples were immersed in pure water at 25°C for 24 hours to ensure full water absorption. After removal, the surface water droplets were wiped off with a cloth, and the weight of the sample was measured. Then, the water-containing samples were immediately placed in a forced-circulation oven and dried at 120°C for 60 minutes, and the weight of the sample was measured again. Based on the weight of the resin film after 60 minutes of drying, the moisture content before drying (moisture content after 24 hours of immersion) was calculated using the following formula. Furthermore, for resin films 1-2 and 6-9, the weight of the samples was also measured at 5 minutes of drying at 120°C, and the rate of change of moisture content after 5 minutes of drying (drying rate) was calculated using the following formula.

[0344] The moisture contents of resin films 1-3 and 5-9 are 3.12%, 3.74%, 1.58%, 1.84%, 1.86%, 1.37%, 1.46%, and 4.18%, respectively.

[0345] In addition, the drying rates of resin films 1-2 and 6-9 are 0.47% / min, 0.52% / min, 0.55% / min, 0.63% / min, 0.65% / min, and 0.37% / min, respectively.

[0346] Moisture content before drying (%) = (Weight immediately after moisture absorption - Weight after 60 minutes of drying) / Weight immediately after moisture absorption × 100 Drying speed (% / minute) = [{(Weight immediately after moisture absorption - Weight after 60 minutes of drying) / Weight immediately after moisture absorption × 100} - {(Weight after 5 minutes of drying - Weight after 60 minutes of drying) / Weight immediately after 5 minutes of drying × 100}] / 5 <0.2% Yield Strength Determination> Test pieces were prepared by cutting arbitrary portions of the laminates 1-9 obtained in the examples and comparative examples, each measuring 100mm × 10mm. Stress-strain curves (SS curves) were measured using an "AUTOGRAPH AG-IS" chuck manufactured by Shimadzu Corporation under conditions of 25°C, 50% relative humidity, 50mm chuck spacing, and a tensile speed of 20mm / min. The 0.2% yield strength was calculated as described below.

[0347] 1) Data processing of SS curves Starting from the initial measurement point in the SS curve, 10 consecutive points are sampled and fitted to a quadratic function using the least squares method. Then, until the fitted quadratic function from the 10 sample points exhibits an upward convex shape, one point is removed from the left side of the initial measurement point, and one point is added from the right side. Data processing ends at the point where the fitted function exhibits an upward convex shape.

[0348] 2) Calculation of the tangent equation for the SS curve Using the n=i to j (j=2 to 50) data points from the data in 1) above, the slope and intercept are calculated using the least squares method. Then, for the j-1 slope, the k (k=1 to 48) to 49th data points are fitted into a linear function using the least squares method, and the slope when the strain is 0 is calculated by extrapolation. The median of the obtained 48 points is defined as the slope of the line when the strain is 0 (the tangent line of the SS curve). The intercept is calculated in the same way to obtain the equation of the tangent line of the SS curve when the strain is 0.

[0349] 3) Calculation of 0.2% yield strength The tangent line of the SS curve obtained in 2) above when the strain is 0 is shifted by 0.2% along the strain direction. The stress value at which the shifted straight line intersects the SS curve is taken as the 0.2% yield strength.

[0350] <Determination of roughness parameters at the copper foil-resin film interface> (FIB pretreatment) A portion of the laminates 1-9 obtained in the examples and comparative examples was cut, and the end faces of the cut test pieces were processed using an ultramicrotome (Leica EM UC7) to prepare specimens with smooth thickness-direction cross-sections. Then, the specimens were fixed to the sample holder of an SEM using carbon tape, with the resin side of the laminate as the adhesive surface. Next, the copper foil surface of the laminate was subjected to two platinum vapor depositions using an ion sputtering apparatus under the following conditions (see...). Figure 1 (a)).

[0351] Ion sputtering conditions Device: MC1000 (Hitachi High-Tech Co., Ltd.) Current value: 10mA Splash time: 300 seconds (FIB processing) The copper foil surface of the laminate is irradiated with an ion beam from a vertical direction. A portion of the center of the end face, which has already been processed using a slicing machine, is cut out in a U-shape when viewed from the copper foil surface side, creating a smooth cross-section (observation plane). The accelerating voltage and beam current are appropriately adjusted during processing. The final processing step is completed under the following conditions (see...). Figure 1 (b)). The plane in the processed section parallel to the slicer surface described above is designated as the observation plane (see [reference]). Figure 1 (c)).

[0352] Processing conditions FIB-SEM device: Helios G4 UX (ThermoFisher SCIENTIFIC) Accelerating voltage: 20kV Beam current: 1.2 nA (Preprocessing before SEM observation) Platinum vapor deposition was performed on the FIB processing surface (observation surface) under the following conditions using an ion sputtering apparatus.

[0353] Ion sputtering conditions Device: MC1000 (Hitachi High-Tech Co., Ltd.) Current value: 10mA Splash time: 20 seconds (SEM observation) SEM observations of the observation surfaces of laminates 1 to 9 were performed under the following conditions to obtain SEM images. The angle was adjusted so that the interface between the copper foil layer and the resin film was horizontal relative to the image.

[0354] SEM observation conditions Device: Helios G4 UX (ThermoFisher SCIENTIFIC) SEM Mode: Mode2 Detector: Thru-the-Lens detector Photography conditions: Observation magnification: 10,000x Observe the image: BSE image Accelerating voltage: 5kV Beam current: 0.1 nA Dwell time: 5us Line Integration: 1 Resolution: 3072×2048 (0.147 pixels / nm) Save format: TIFF (Creating the cross-sectional curve) Using Image J (NIH), the following steps are used to create the cross-sectional curves (interface profile curves) of the interface between the copper foil layers and the resin film of laminates 1 to 9 (the English term is the tool name in Image J).

[0355] 1) Importing images Import the SEM image obtained above into Image J. At this point, import the image with the copper foil layer's protrusions facing upwards.

[0356] 2) Smoothing Use the Smooth feature to perform two smoothing processes.

[0357] 3) Contrast Adjustment Contrast adjustment is performed by taking the high-brightness side end of the histogram from the resin film (resin layer) present on the low-brightness side as the minimum value and the low-brightness side end of the histogram from the copper foil layer present on the high-brightness side as the maximum value.

[0358] 4) Binarization Using the Threshold feature as the Auto threshold method, the Default (modifiedIsoData Algorithm) is selected to be executed.

[0359] 5) Noise Removal Use the Remove Outliers feature to perform the following processing in sequence.

[0360] 1st time Radius=4pixel Threshold=50 Witch Outlier=white 2nd time Radius=4pixel Threshold=50 Witch Outlier=Black Then, use the fill tool to manually remove the white granular parts isolated from the copper foil and the black granular parts isolated from the resin.

[0361] 6) Contour Extraction The Find Edge and Skeletonize functions are executed sequentially to extract the contour of the interface between the copper foil layer and the resin film, thus obtaining the contour curve. Then, Save XY Coordinates is used to output the coordinates of the contour curve in CSV format (the contour curve is the curve with the peak facing upwards corresponding to the convex part of the copper foil layer, that is, the contour line of the interface when the copper foil layer is on the lower side and the resin film side is on the upper side).

[0362] 7) Correction of cross-sectional curves First, using Excel, calculate the slope 'a' of the regression line of the profile curve. At each coordinate (x, y), calculate y' = yx × a, reset to (x, y'), and perform skew correction on the profile curve. Then, calculate the average value 'b' using the y' values ​​from all coordinates. At each coordinate (x, y'), calculate y'' = y' - b, reset to (x, y''), and perform average correction on the profile curve. At this point, convert the unit from pixels to nm (0.147 pixels / nm). Thus, the skew-corrected and average-corrected profile curve, i.e., the cross-sectional curve, is obtained.

[0363] (Calculation of the roughness parameter of the interface) Using the above cross-sectional curves, calculate Pq, Pku, and Psk using the following formula, and then determine |Pku / Psk|. Additionally, calculate the maximum peak height Pp, maximum valley depth Pv, maximum height Pz, and arithmetic mean height Pa from the above cross-sectional curves, and then determine |Pp-Pv|.

[0364] [Mathematical Expression 5] [In the formula, Pku represents kurtosis, Psk represents skewness, Pq represents root mean square height, and L represents the difference between the maximum and minimum x-values ​​(i.e., the distance from one endpoint to the other of the cross-sectional curve; the reference length)] <Surface Roughness Measurement of Copper Foil Layer> Using a laser microscope (OLYMPUS LEXT OLS4000), a three-dimensional shape image was obtained by laser observation of the side of the copper foil layer in contact with the resin film under the following observation conditions. Next, the three-dimensional shape image was analyzed using the photographic image processing software LEXT OLS4100 (OLYMPUS; ver. 3.1.15.1) under the following analysis conditions, and the surface roughness parameters were calculated. The measurements of Sal, Str, Sk, Sdr, Sp, Sv, Sku, Sa, and Sz were performed according to ISO 25178, and the measurements of Ra, Rz, and Rzjis were performed according to JIS B0601:2013.

[0365] [Observation Conditions] Device: LEXT OLS4000 (manufactured by OLYMPUS) Observation magnification: 100x Objective lens: MPLAPON 100LEXT Photography conditions: photography; laser observation Scanning mode: XYZ high precision Measurement interval: 0.06μm Measurement range: 128μm × 128μm [Analysis conditions] (Sal, Str, Sk, Sdr, Sp, Sv, Sku, Sa, Sz) Analysis software: LEXT OLS4100 (OLYMPUS) Ver.3.1.15.1 S-filter: 0.375 μm L-filter: None [Analysis conditions] (Ra, Rz, Rzjis) Analysis software: LEXT OLS4100 (OLYMPUS) Ver.3.1.15.1 In the obtained three-dimensional shape image, five cross-sectional curves were obtained at 25 μm intervals, starting from a position 4 μm from the bottom of the image. Each curve was analyzed under the following conditions to evaluate Ra, Rz, and Rzjis, and the average value was calculated.

[0366] λs: 2.5μm λc, λf: Not set The results of the various measurements are shown in Tables 1 to 3.

[0367] [Table 1] [Table 2] [Table 3] As shown in Table 1, it was confirmed that the laminates 1 to 8 obtained in the examples have a higher yield strength by 0.2% compared to the laminate 9 obtained in Comparative Example 1. Therefore, it was confirmed that the laminates of the present invention have high yield strength.

[0368] Explanation of reference numerals in the attached figures 1… Platinum vapor deposition 2…sample 3…Sample holder 4…Processed surface (pre-processed using a slicer) 5…FIB irradiation 6…SEM observation orientation (direction of electron beam illumination) 7…Contour curve before correction 8… Profile curve after tilt correction 9… Profile curves (section curves) after tilt correction and average value correction. 10…resin film 11…Layer containing polyimide resin (equivalent to layer (PI-2)) 12…Layer containing polyimide resin (equivalent to layer (PI-1)) 13…Layer containing polyimide resin (equivalent to layer (PI-3)) 14…Metal layer 15…Laminated bodies

Claims

1. A laminate comprising a resin film and a metal layer disposed on at least one side of the resin film, wherein, In the cross-sectional image of the laminate in the thickness direction obtained using a scanning electron microscope, the skewness Psk obtained from the cross-sectional curve of the interface between the resin film and the metal layer is greater than -0.

05.

2. A laminate comprising a resin film and a metal layer disposed on at least one side of the resin film, wherein, In the cross-sectional image of the laminate along the thickness direction obtained using a scanning electron microscope, the skewness Psk and kurtosis Pku obtained from the cross-sectional curve of the interface between the resin film and the metal layer satisfy the relationship of equation (I). |Pku / Psk|≤100 (I).

3. The laminate as described in claim 1 or 2, wherein, The maximum peak height Pp and the maximum valley depth Pv obtained from the cross-sectional curve satisfy the relationship of equation (II). |Pp-Pv|≥1.5nm (II).

4. The laminate as described in claim 1 or 2, wherein, The resin film comprises at least one resin selected from the group consisting of polyimide resins, liquid crystal polymers, fluorine resins, aromatic polyether resins, epoxy resins and maleimide resins.

5. The laminate as described in claim 1 or 2, wherein, The coefficient of linear expansion of the resin film is 10 to 29 ppm / K.

6. The laminate as described in claim 1 or 2, wherein, The resin film is a polyimide-based film containing a polyimide-based resin.

7. The laminate as claimed in claim 6, wherein, The polyimide membrane comprises a layer (PI-1) containing a polyimide resin and a layer (PI-2) containing a polyimide resin.

8. The laminate as claimed in claim 7, wherein, The polyimide-based resin layer (PI-2) is located on the side of the metal layer, and the thickness of the polyimide-based resin layer (PI-2) is 0.05 to 0.3 times the thickness of the polyimide-based resin layer (PI-1).

9. The laminate as claimed in claim 7, wherein, The polyimide membrane further comprises a layer (PI-3) containing a polyimide resin.

10. The laminate as claimed in claim 9, wherein, The polyimide resin contained in layer PI-1, layer PI-2, and layer PI-3 each have a storage modulus of 1.0 × 10⁻⁶ at 40°C. 9 Pa or above.

11. The laminate as claimed in claim 7, wherein, At least one of the polyimide-based resin layers (PI-1) and (PI-2) comprises a polyimide-based resin having a structural unit (A) derived from tetracarboxylic anhydride. The structural unit (A) comprises a structural unit (A1) of tetracarboxylic anhydride represented by formula (A1) and / or a structural unit (A2) of tetracarboxylic anhydride represented by formula (A2). [Chemical Formula 1] In equation (A1), R a1 Each can independently represent a halogen atom, or an alkyl, alkoxy, aryl, or aryloxy group that may have a halogen atom. k represents an integer from 0 to 2; [Chemical Formula 2] In equation (A2), R a2 Each of the halogen atoms, or alkyl, alkoxy, aryl, or aryloxy groups that may have halogen atoms, is an integer from 0 to 3, and each of the halogen atoms is an integer.

12. The laminate as claimed in claim 7, wherein, At least one of the polyimide-based resin layers (PI-1) and (PI-2) comprises a polyimide-based resin having a structural unit (B) derived from a diamine. The structural unit (B) comprises a structural unit (B1) derived from a diamine represented by formula (B1). [Chemical Formula 3] In equation (B1), R b1 Each can independently represent a halogen atom, or an alkyl, alkoxy, aryl, or aryloxy group that may have a halogen atom. W can be independently represented by the following octets: -O-, -CH2-, -CH2-CH2-, -CH(CH3)-, -C(CH3)2-, -C(CF3)2-, -COO-, -OOC-, -SO-, -SO2-, -S-, -CO-, -N(R) c The divalent linking group or single bond in the group consisting of - and -CONH- (where m is 2 or more, and at least one W is said divalent linking group), R c A monovalent hydrocarbon group representing a hydrogen atom or a carbon atom that can be substituted by a halogen atom, having 1 to 12 carbon atoms. m represents an integer from 1 to 4. q represents integers from 0 to 4 independently.

13. The laminate as claimed in claim 7, wherein, At least the polyimide-based resin layer (PI-1) comprises a polyimide-based resin having a structural unit (A) derived from a tetracarboxylic anhydride, the structural unit (A) comprising a structural unit (A3) of a tetracarboxylic anhydride containing an ester bond, represented by formula (A3). [Chemical Formula 4] In formula (A3), Z represents a divalent organic group. R a3 Each can independently represent a halogen atom, or an alkyl, alkoxy, aryl, or aryloxy group that may have a halogen atom. s represent integers from 0 to 3 independently.

14. The laminate as claimed in claim 11, wherein, At least the layer (PI-1) containing the polyimide resin comprises a polyimide resin having the structural unit (A), which further comprises a structural unit (A3) of ester-bonded tetracarboxylic anhydride represented by formula (A3) in a amount of less than 50 mol% relative to the total amount of the structural unit (A). [Chemical Formula 5] In formula (A3), Z represents a divalent organic group. R a3 Each can independently represent a halogen atom, or an alkyl, alkoxy, aryl, or aryloxy group that may have a halogen atom. s represent integers from 0 to 3 independently.

15. The laminate as claimed in claim 1 or 2, wherein, The metal layer is a copper layer.

16. A flexible printed circuit board comprising the laminate of claim 1 or 2.

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