Laminate

Abstract

The present invention provides a laminate which has a high 0.2% proof stress (also simply referred to as proof stress) that is an index of strength against plastic deformation. This laminate includes a resin film and a metal layer that is provided on at least one surface of the resin film. The cross-sectional curve of the interface between the resin film and the metal layer obtained from a cross-sectional image of the laminate in the thickness direction, which is acquired by means of a scanning electron microscope, satisfies the relational expression (I) [Σ(Ln / Sn)] / Na ≥ 0.046 (in expression (I), Ln represents the contour length (nm) of each protrusion region that is surrounded by the cross-sectional curve and a straight line connecting the minimum point of each protrusion of the cross-sectional curve, Sn represents the area (nm2) of each protrusion region, and Na represents the total number of the plurality of protrusion regions), and the evaluation length of the cross-sectional curve is 3,000 nm or more.

Description

Laminate

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

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

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

[0004] Laminates used in FPCs may deform during processing or repeated use, and are required to be resistant to deformation to prevent deterioration of electrical properties, etc., due to deformation. However, it is difficult to increase the resistance to deformation while controlling the dielectric properties of the laminate within an appropriate range. For this reason, there is a need to develop a laminate that is resistant to deformation and can be used for high-speed communication applications beyond 5G.

[0005] The present inventors have found that in order to suppress deterioration of the properties of a laminate, it is particularly important to increase the strength of the laminate against plastic deformation. Therefore, an object of the present invention is to provide a laminate having a high 0.2% proof stress (also simply referred to as proof stress), which is an index of strength against plastic deformation, and a flexible printed circuit board including the laminate.

[0006] As a result of extensive research to solve the above-mentioned problems, the inventors have found that the above-mentioned problems can be solved when the cross-sectional curve of the interface between the resin film and the metal layer obtained from a cross-sectional image of the laminate in the thickness direction acquired by a scanning electron microscope satisfies the relationship of a specific formula (I). Furthermore, they have found that the above-mentioned problems can be solved when the total area of ​​resin defects calculated from the cross-sectional image after processing the laminate under specific conditions is within a specific range. Furthermore, they have found that the above-mentioned problems can be solved by suppressing the variation in the elastic modulus measured by a scanning probe microscope (sometimes referred to as SPM) at the interface between the resin film and the metal layer in the laminate, and have thus completed the present invention. That is, the present invention includes the following aspects.

[0007] [1] A laminate including a resin film and a metal layer provided on at least one surface of the resin film, wherein a cross-sectional curve of an interface between the resin film and the metal layer obtained from a cross-sectional image of the laminate in the thickness direction obtained by a scanning electron microscope is expressed by the formula (I): [Σ(Ln / Sn)] / Na≧0.046 (I) In the formula (I), Ln represents the contour length (nm) of each convex region surrounded by a line connecting the minimum points of each convex portion of the cross-sectional curve and the cross-sectional curve, and Sn represents the area (nm) of each convex region. ２ [2] The cross-sectional curve satisfies the relationship of formula (II): Sa / A≦100 (II) [wherein Sa is the total area (nm ２ ) and A represents an evaluation length (nm) of the profile curve. [3] The profile curve satisfies the relationship of formula (III): Na / A≧2.80×10 ー３(III) The laminate according to [1] or [2], which satisfies the relationship: [In formula (III), Na represents the total number of the convex regions, and A represents the evaluation length (nm) of the cross-sectional curve.] [4] A laminate comprising a resin film and a metal layer provided on at least one surface of the resin film, wherein a cross section in the thickness direction of the laminate is processed with a microtome equipped with a diamond knife under conditions of a cutting amount of 300 nm per cut and a processing speed of 1.0 mm / sec, and then, in a cross-sectional image in the thickness direction of the laminate obtained with a scanning electron microscope, the interface between the resin film and the metal layer is located at the center of the cross-sectional image in the thickness direction, and the total area of ​​the resin defects calculated based on the brightness distribution of the cross-sectional image is 0.300 μm per an area of ​​an evaluation range of 4.2 μm × 2.8 μm. ２A laminate comprising a resin film and a metal layer provided on at least one surface of the resin film, wherein, when the elastic modulus of a thickness cross section of the laminate is measured using a scanning probe microscope at five measurement regions set at intervals of 2 μm or more within a range of 500 nm from the interface between the resin film and the metal layer toward the resin film in the thickness direction, the laminate satisfies the relationship of formula (V): [Σ(Sn / En)] / 5≦0.480 (V), where En represents the average elastic modulus of the resin film in each measurement region, and Sn represents the standard deviation of the elastic modulus in each measurement region. [6] The laminate according to [5], wherein the minimum value of Sn / En in each of the five measurement regions is 0.400 or less. [7] The laminate according to [5] or [6], wherein the maximum value of Sn / En in each of the five measurement regions is 0.540 or less. [8] The laminate according to any one of [5] to [7], wherein the Sn / En ratio in each of the five measurement regions is 0.520 or less. [9] The laminate according to any one of [5] to [8], wherein the surface of the metal layer in contact with the resin film is a roughened surface having a plurality of convex portions, and when the elastic modulus is measured in five measurement regions set between adjacent two convex portions on the roughened surface in a thickness direction cross section of the laminate, the relationship of formula (V) is satisfied.

[10] The laminate according to any one of [1] to [9], wherein the resin film contains at least one resin selected from the group consisting of polyimide-based resins, liquid crystal polymers, fluorine-based resins, aromatic polyether-based resins, epoxy-based resins, and maleimide-based resins.

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

[10] , wherein the thermal expansion coefficient of the resin film is 10 to 29 ppm / K.

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

[11] , wherein the resin film is a polyimide-based film containing a polyimide-based resin.

[13] The laminate according to

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

[14] The laminate according to

[13] , wherein the polyimide-based resin-containing layer (PI-2) is located on the metal layer side, and the thickness of the polyimide-based resin-containing layer (PI-2) is 0.05 to 0.3 times the thickness of the polyimide-based resin-containing layer (PI-1).

[15] The laminate according to

[13] or

[14] , wherein the polyimide-based film further includes a polyimide-based resin-containing layer (PI-3).

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

[17] The laminate according to

[15] , comprising a polyimide-based resin having a viscosity of 100 Pa or more.

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

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

[19] The laminate according to any one of

[13] to

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

[19] The laminate according to any one of

[13] to

[18] , wherein the polyimide resin contained in at least the polyimide resin-containing layer (PI-1) has the structural unit (A), and the structural unit (A) further contains 45 mol% or less of the structural unit (A3) of the formula (A3): [In formula (A3), Z represents a divalent organic group, R ａ３each independently represent a halogen atom, or an alkyl group, alkoxy group, aryl group, or aryloxy group which may have a halogen atom, and each s independently represent an integer of 0 to 3.

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

[19] , which has metal layers on both sides of the resin film.

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

[20] , wherein the metal layer is a copper layer.

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

[21] .

[0008] According to the present invention, a laminate having high yield strength can be provided.

[0009] FIG. 1 is a schematic diagram for explaining a method for measuring a cross-sectional image in the thickness direction of a laminate using a scanning electron microscope. FIG. 2 is a diagram for explaining a profile curve before correction, a profile curve after tilt correction, and a profile curve (cross-sectional curve) after tilt correction and average correction in a laminate. FIG. 3 is a schematic diagram for explaining a method for connecting minimum points of peaks (convex portions) with a baseline (straight line) in a cross-sectional curve of a laminate interface. FIG. 4 is a schematic diagram for explaining an evaluation length and a convex portion area in a graph image of a laminate interface. FIG. 5 is a diagram showing an example of a cross-sectional image in the thickness direction of a processed laminate (enlarged interface portion) obtained by a scanning electron microscope. FIG. 6 is a graph showing a force curve obtained at an arbitrary point on a sample cross-section in a laminate according to one embodiment of the present invention. FIG. 7 is a diagram showing a DMT elastic modulus image and one measurement area of ​​a sample cross-section in a laminate according to one embodiment of the present invention. FIG. 8 is a schematic cross-sectional view showing an example of the layer structure of a laminate of the present invention.

[0010] Hereinafter, embodiments of the present invention will be described in detail. Note that the scope of the present invention is not limited to the embodiments described here, and various modifications can be made within the scope that does not impair the spirit of the present invention. Note that the multiple upper and lower limit values ​​described in this specification can be arbitrarily combined to form a suitable numerical range.

[0011] [Laminate] In a first embodiment of the present invention, the laminate includes a resin film and a metal layer provided on at least one surface of the resin film, and a cross-sectional curve of an interface between the resin film and the metal layer obtained from a cross-sectional image of the laminate in the thickness direction obtained by a scanning electron microscope (also referred to as SEM) satisfies the formula (I): [Σ(Ln / Sn)] / Na≧0.046 (I) (In formula (I), Ln represents the contour length (nm) of each convex region surrounded by a straight line connecting the minimum points of each convex portion of the cross-sectional curve and the cross-sectional curve, and Sn represents the area (nm) of each convex region). ２ ) and Na represents the total number of the convex regions. The evaluation length of the cross-sectional curve is 3,000 nm or more.

[0012] Ln, Sn, and Na in formula (I) are obtained by obtaining a cross-sectional image of the laminate in the thickness direction using an SEM and using a cross-sectional curve of the interface between the resin film and the metal layer obtained from the cross-sectional image. Ln, Sn, and Na in formula (I) can be calculated by determining the cross-sectional curve of the interface between the resin film (resin layer) and the metal layer, creating a diagram from the obtained cross-sectional curve by adding a baseline connecting the minimum points of the peaks (convex portions) with a straight line, and then analyzing the convex portion region surrounded by the cross-sectional curve and the baseline.

[0013] <Acquisition of Profile Curve> The profile curve can be acquired by performing SEM observation to acquire an SEM image of the cross section in the thickness direction of the laminate, and then performing image processing of the obtained SEM image and correction of the obtained profile curve. Furthermore, in order to obtain a clear SEM image, it is preferable to perform pretreatment for FIB (focused ion beam) processing, FIB processing, and pretreatment for SEM observation in this order in the process of preparing the SEM observation sample. An example of a method for acquiring the profile curve will be specifically described below.

[0014] (1) FIB Processing As shown in Figure 1(a), as a pretreatment for FIB processing, the end face of the laminate is processed with a microtome to create a sample with a smooth cross section in the thickness direction. Then, platinum is deposited on the metal layer surface of the laminate using an ion sputtering device. Next, as shown in Figure 1(b), a focused ion beam is irradiated perpendicularly to the metal layer surface of the laminate, and a portion of the center of the end face processed with the microtome is cut out so that it forms a U-shape when viewed from the metal layer surface, creating a smooth cross section. As shown in Figure 1(c), the surface of the processed cross section that is parallel to the microtome-processed surface is used as the observation surface.

[0015] (2) SEM Observation As a pretreatment for SEM observation, platinum is vapor-deposited on the FIB-processed surface (observation surface) using an ion sputtering device. Next, the angle of the FIB-processed surface is adjusted so that the interface between the metal layer and the resin layer is horizontal to the image to be acquired, and then SEM observation is performed.

[0016] (3) Image Processing The obtained SEM image (cross-sectional image) is processed using image processing software (e.g., Image J) in the following order: image capture, smoothing, contrast adjustment, binarization (black and white imaging), noise removal, and contour extraction. Image capture is performed in the direction in which the convex portions on the metal layer face upward (in the acquired image of the laminate interface, the metal layer is on the bottom and the resin layer is on the top). Contrast adjustment is performed by setting the high-brightness end of the histogram derived from the resin layer present on the low-brightness side as the minimum value and the low-brightness end of the histogram derived from the metal layer present on the high-brightness side as the maximum value. In the noise removal process, after removing noise bright spots, parts isolated from the metal layer and resin layer are manually removed (for example, if the metal layer portion is white and the resin layer portion is black, white particles isolated from the metal layer and present in the resin layer portion, and black particles isolated from the resin layer and present in the metal layer portion). In the contour extraction process, after a contour curve is created, the coordinates of the contour curve are output in CSV format.

[0017] (4) Correction: For the contour curve obtained by image processing, after converting the contour curve unit from pixels to distance (nm), slope correction and average correction are performed sequentially, for example, using Excel, to obtain a cross-sectional curve of the interface between the metal layer and the resin layer. The metal layer side is positioned on the lower side (negative side of the y-axis) and the resin layer side is positioned on the upper side (positive side of the y-axis). For example, FIG. 2 is a diagram illustrating the contour curves before and after each correction. The contour curve before correction is 7, the contour curve after slope correction performed on the contour curve 7 is 8, and the contour curve (also referred to as the cross-sectional curve) after slope correction and average correction performed on the contour curve 8 is 9. The slope correction is performed by calculating the slope a of the regression line of the contour curve, and then calculating y' = y - x × a at each coordinate (x, y), and recalculating it as (x, y'). In addition, the average value correction is performed by calculating the average value b using the y' values ​​of all coordinates, finding y''=y'-b at each coordinate (x, y'), and replacing it with (x, y'').

[0018] <Calculation of Ln, Sn, Na, and A> The contour length (Ln) of each convex region, the area (Sn) of each convex region, the total number of convex regions (Na), and the evaluation length (A) can be calculated by using data analysis software (e.g., Python, Matlab, Igor, etc.) to create a diagram of the cross-sectional curve obtained above, adding a baseline connecting the minimum points of the peaks (convex portions) with a straight line, and then using an image analysis tool (e.g., Image J) to calculate the convex regions surrounded by the cross-sectional curve and the baseline. An example of creating the baseline and image analysis will be described in detail below.

[0019] [Creating a Baseline] FIG. 3 is a schematic diagram illustrating a method for connecting the minimum points of peaks (convex portions) with a baseline (straight line) in a cross-sectional curve at the interface of a laminate. As shown in FIG. 3, the minimum points of peaks 16 (convex portions) are detected using data analysis software, and the minimum points of peaks 16 (convex portions) are connected with a baseline 17 (straight line), thereby obtaining each convex portion region 18 surrounded by the baseline and the cross-sectional curve. The metal layer side is positioned on the lower side (negative side of the y-axis) and the resin layer side is positioned on the upper side (positive side of the y-axis). Python is preferably used as the data analysis software, and can be performed, for example, as follows. First, data (e.g., an Excel file) containing a cross-sectional curve f(x) (x, y coordinates in nm) is loaded into Python. If there are multiple coordinates at the same x value in the peak (convex portion) of the cross-sectional curve f(x), a process is performed to convert the data into a cross-sectional curve f′(x) that retains only the coordinate with the smallest y value. Next, the profile curve f'(x) is normalized and then inverted symmetrically about the x-axis so that the peak points downward. The find_peaks function is used to find the coordinates (valley_x, valley_y) of the local maximum of the profile curve f'(x). Next, a plotting range of 1 pixel = 1 nm is prepared, the profile curve f(x) is plotted within this range, and a graph is created by adding a baseline connecting the coordinates (valley_x, valley_y) determined from the profile curve f'(x) with a straight line, and the graph is saved, for example, in JPEG format. This process can be performed, for example, by using an Excel file containing the profile curve and executing the code listed in Table 1 in Python.

[0020]

[0021] In Table 1, "file name" in row 5 can be freely changed depending on the Excel file name storing the profile, and "N1" in row 6 can be changed depending on the sheet name in the Excel file. The code in row 15 indicates the creation of an n-point moving average, where n in (n) / n is entered as a number between 1 and 5 depending on the noise influence on the profile. If there is no noise influence, enter n = 1. If the noise is significant (e.g., low image resolution), enter a number between 2 and 5 appropriately to eliminate the noise. "distance" in row 17 represents the distance between minimum points, and "prominence" represents the degree of prominence. If the minimum points are difficult to see, decrease the value; if they are clear, increase the value. The value in row 24 represents dots per inch, and the value in row 25 represents inches. The value in row 26 represents the y-coordinate width, which can be changed appropriately depending on the peak height (height of the convex part) in the profile. The value in line 27 represents the width of the x-coordinate and can be changed as appropriate depending on the length of the cross-sectional curve. The value of "s" in line 30 and the value of "linewidth" in line 31 are set to the minimum value when no gaps are formed in the contour of the metal protrusion during analysis using the image analysis tool described below.

[0022] [Analysis by Image Analysis Tool] Using the image with the baseline added (also referred to as a graph image), the contour length (Ln) of each convex region, the area (Sn) of each convex region, the total number (Na) of convex regions, and the evaluation length (A) can be calculated by an image analysis tool. Note that the following convex noise is removed during image analysis.

[0023] (Noise Removal of Convex Portions) Among the convex portions in the graph image, (i) the area range derived from the convex portion where the cross-sectional curve is located below the baseline is a region generated in the baseline creation process, and is not the convex portion itself, so it is removed as noise. ２ Convex portions less than 100% are removed as they are considered to be noise caused by low contrast near the interface in the SEM image.

[0024] (Calculation of Evaluation Length (A)) The evaluation length refers to the distance between the x-coordinate of the left end of the leftmost convex portion determined as the evaluation range in the graph image and the x-coordinate of the right end of the rightmost convex portion, i.e., the distance between the x-coordinates of both ends of the cross-sectional curve determined as the evaluation range (the width or length in the major axis direction of the cross-sectional curve). Note that the left end and the right end of the convex portion are both the minimum points of each convex portion, and the evaluation length is calculated using the graph image before noise removal described below. FIG. 4 is a schematic diagram illustrating the evaluation length and convex portion area in a graph image of the laminate interface [schematic diagram of a graph image obtained by performing the following steps 1) to 4) using Image j], where each convex portion area is 18' and the evaluation length is 19.

[0025] Below is a description of a calculation method using Image J as an image analysis tool. When using Image J, Ln, Sn, Na, and A can be calculated, for example, by the following steps: 1) Import a graph image (at this time, only the outlines of the cross-sectional curve and baseline will be black). 2) Select Make binary and edit the image so that only the outlines of the cross-sectional curve and baseline are white. 3) Use the Flood fill tool to paint the background (outside the convex parts surrounded by the cross-sectional curve and baseline) white (only the inside of the convex parts is black, so only the convex parts remain). 4) Use Invert to invert the brightness (the inside of the convex parts will be white, and the background will be black). 5) Remove noise from the convex parts as described above. 6) Use Analyze Particles to perform particle analysis under the conditions of Size: 0-infinity and Circularity: 0-1, and calculate Ln, Sn, and Na. 7) Calculate A using Measure.

[0026] As described above, Ln and Sn are determined within the range of the evaluation length, and [Σ(Ln / Sn)] / Na (the average value of [the contour length / area of ​​each convex region]) can be calculated. The contour length Ln of each convex region is obtained by an analysis including noise removal of the convex regions [e.g., steps 1) to 6)] using an image analysis tool (e.g., Image J), ​​and the area Sn of each convex region is also obtained similarly. Furthermore, Σ(Ln / Sn) represents the sum of the contour length / area of ​​each convex region within the range of the evaluation length, and Na represents the total number of convex regions within the range of the evaluation length. In this specification, "within the range of the evaluation length" means "within the range from the left-most minimum point of the leftmost convex used when deriving the evaluation length to the right-most minimum point of the rightmost convex."

[0027] The inventors conducted research focusing on the interface between layers in the laminate and unexpectedly found that when the cross-sectional curve of the interface between the resin film and the metal layer satisfies formula (I), the 0.2% proof stress is improved. The reason for this is unclear, but it is thought that the stress concentration state acting on the resin film and the metal layer in the thickness direction cross section varies depending on the unevenness of the interface, which may lead to differences in the magnitude of the strain induced at the interface and the internal stress generated. It is also expected that the crystallinity and orientation of the resin layer near the interface may also change. When [Σ(Ln / Sn)] / Na is 0.046 or more, the convex portions of the cross-sectional curve at the interface tend to have a sharp or distorted shape, which is thought to increase the amount of resin present between the convex portions. Therefore, it is presumed that the crystallinity and / or orientation of the resin layer near the interface is enhanced, or the internal stress generated at the interface, particularly between the convex portions, tends to be reduced, or the orientation of the resin near the interface may affect the strength of the resin film as a whole, thereby increasing the resistance to deformation of the entire laminate.

[0028] In one embodiment of the present invention, when the laminate is used as a metal laminate, the metal layer on the resin film may be partially removed by etching or the like. In such a laminate, it is preferable that the resin film have high water resistance after removal of the metal layer, from the viewpoint of dielectric properties and drying efficiency during FPC manufacturing. The inventors have also unexpectedly discovered that when the cross-sectional curve of the laminate interface satisfies formula (I), the water resistance and drying speed of the resin film after removal of the metal layer can be improved. While the reason for this is unclear, it is presumed that the unevenness of the resin film surface is an uneven structure that is less likely to 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 of the laminate) is enhanced. In this specification, water resistance refers to the property of the resin film in the laminate after removal of the metal layer being less likely to absorb water when immersed in pure water, and can be evaluated, for example, by the method described in the Examples. Furthermore, drying rate refers to the rate at which pure water is reduced when the resin film after removal of the metal layer is hydrated and then heated and dried, and can be evaluated, for example, by the method described in the Examples. The water resistance and drying speed of the resin film after removing the metal layer can also be considered properties of the laminate, and are therefore referred to as the water resistance and drying speed of the laminate, respectively. In this specification, "dielectric properties" refer to dielectric properties such as Df and Dk, and "increased or improved" dielectric properties refer to a decrease in Df and / or Dk. The dielectric properties of a laminate can be evaluated based on the dielectric properties of the resin films in the laminate. Furthermore, "mechanical properties" refer to mechanical properties including yield strength, puncture strength, flexural resistance, and elastic modulus, and "increased or improved" mechanical properties refer to, for example, increased yield strength, flexural resistance, and / or elastic modulus. Furthermore, thermal properties may include CTE, glass transition temperature (hereinafter sometimes referred to as Tg), and the degree of thermal denaturation or degradation. "Increased or improved" thermal properties refer to, for example, a lower CTE, a higher Tg, and / or less thermal denaturation or degradation.

[0029] In formula (I), [Σ(Ln / Sn)] / Na is preferably 0.047 or more, more preferably 0.049 or more, even more preferably 0.054 or more, even more preferably 0.057 or more, particularly preferably 0.059 or more, and particularly preferably 0.061 or more. Furthermore, [Σ(Ln / Sn)] / Na is preferably 1.00 or less, 0.50 or less, or 0.30 or less, more preferably 0.10 or less, more preferably 0.090 or less, even more preferably 0.085 or less, even more preferably 0.080 or less, particularly preferably 0.075 or less, particularly preferably 0.070 or less, or 0.067 or less, and particularly preferably 0.064 or less. When [Σ(Ln / Sn)] / Na is above the lower limit and / or below the upper limit, the uneven structure of the interface in the laminate and the crystallinity and / or orientation of the resin layer are more likely to be in a state that allows the effects of the present invention to be further exhibited, thereby further improving the yield strength, water resistance, and drying speed of the laminate.

[0030] In the first embodiment of the present invention, Σ(Sn) / Na represents the average value of the area of ​​each convex region within the range of the evaluation length. Σ(Sn) / Na is not particularly limited as long as it satisfies formula (I), but may be, for example, 5.00×10 ４ nm ２ Below, 4.00 x 10 ４ nm ２ or less, or 3.00 x 10 ４ nm ２ or less, preferably 2.50 × 10 ４ nm ２ or less, more preferably 2.30 × 10 ４ nm ２ More preferably, 2.00 x 10 ４ nm ２ or less, and even more preferably 1.90 x 10 ４ nm ２ Below, particularly preferably 1.70 × 10 ４ nm ２ Σ(Sn) / Na is, for example, 1.00×10 ２ nm ２ That's it, 1.00 x 10 ３ nm ２ or more or 5.00 x 10 ３ nm２ or more, preferably 1.00×10 ４ nm ２ or more, more preferably 1.15 × 10 ４ nm ２ More preferably, 1.30 × 10 ４ nm ２ or more, 1.40 × 10 ４ nm ２ When Σ(Sn) / Na is within the above range, the yield strength, water resistance and drying speed of the laminate can be improved.

[0031] In the first embodiment of the present invention, Σ(Ln) / Na represents the average value of the contour length of each convex region within the range of the evaluation length. Σ(Ln) / Na is not particularly limited as long as it satisfies formula (I), but may be, for example, 3.00×10 ３ nm or less, 2.00×10 ３ nm or less, or 1.00 x 10 ３ nm or less, and preferably 9.00 × 10 ２ nm or less, more preferably 8.50 × 10 ２ nm or less, more preferably 8.10 × 10 ２ nm or less, and even more preferably 7.00 × 10 ２ nm or less, particularly preferably 6.80 × 10 ２ Σ(Ln) / Na is, for example, 5.00×10 nm or more, or 1.00×10 ２ nm or more, and preferably 3.00 × 10 ２ nm or more, more preferably 5.00 × 10 ２ nm or more, more preferably 6.20 × 10 ２ nm or more, and even more preferably 6.50 × 10 ２ When Σ(Ln) / Na is within the above range, the yield strength, water resistance and drying speed of the laminate can be improved.

[0032] In the first embodiment of the present invention, the evaluation length (A) of the profile is 3,000 nm or more, preferably 4,000 nm or more, more preferably 4,500 nm or more, even more preferably 5,000 nm or more, particularly preferably 6,000 nm or more, and particularly preferably 7,000 nm or more. The upper limit of the evaluation length (A) of the profile is not particularly limited, and may be, for example, 50,000 nm or less, 30,000 nm or less, or 10,000 nm or less.

[0033] In the first embodiment of the present invention, the total number Na of the convex regions is not particularly limited as long as the evaluation length (A) is 3,000 nm or more, but is usually a plurality (2 or more), preferably 5 or more, more preferably 10 or more, even more preferably 15 or more, still more preferably 20 or more, and particularly preferably 25 or more. The upper limit of Na is not particularly limited, but may be, for example, 100 or less, 80 or less, or 50 or less.

[0034] In a first embodiment of the present invention, the cross-sectional curve is expressed by the formula (II): Sa / A≦100 (II) (where Sa is the total area (nm ２ ), and A represents the evaluated length (nm) of the cross-sectional curve. When the cross-sectional curve at the interface of the laminate satisfies formula (II), the yield strength, water resistance, and drying speed of the laminate can be improved. Although the reason for this is unclear, when the cross-sectional curve at the interface of the laminate satisfies formula (II), the unevenness at the interface is not too large, and the surface texture can be such that the density of the unevenness is not too high. Therefore, it is presumed that stress concentration at the interface is less likely to occur, and the influence of the surface texture during film formation increases the crystallinity and / or orientation of the resin layer near the interface in the laminate. Furthermore, when formula (II) is satisfied, the unevenness of the resin film surface is more likely to have an uneven structure that is less likely to absorb water, and the crystallinity and / or orientation near the surface of the resin layer (i.e., the interface on the resin film side of the laminate) is more likely to be increased, thereby improving the water resistance and drying speed of the laminate.

[0035] In formula (II), Sa / A is preferably 95.0 nm ２ / nm or less, more preferably 90.0nm２ / nm or less, more preferably 78.0nm ２ / nm or less, and even more preferably 75.0nm ２ / nm or less, particularly preferably 70.0nm ２ / nm or less, particularly preferably 68.0nm ２ / nm or less, particularly preferably 66.0nm ２ The Sa / A is, for example, 10.0 nm or less. ２ / nm or more, or 30.0nm ２ / nm or more, preferably 50 nm ２ When Sa / A is equal to or less than the upper limit and / or equal to or more than the lower limit, the uneven structure at the interface of the laminate and the crystallinity and / or orientation of the resin layer are likely to be in a state in which the effects of the present invention can be more effectively exhibited, and therefore the yield strength, water resistance, and drying speed of the laminate can be further improved.

[0036] Sa is the total area (nm ) of the convex regions within the range of the evaluation length. ２ ) and is the same as the above Σ(Sn). Therefore, Sa can be calculated by determining the cross-sectional curve of the interface between the resin film (resin layer) and the metal layer in the same manner as the above Ln, Sn, and Na, and then creating a diagram from the obtained cross-sectional curve by adding a baseline connecting the minimum points of the peaks (convex portions) with a straight line, and then analyzing the convex portion region surrounded by the cross-sectional curve and the baseline. Note that the evaluation length A in formula (II) is synonymous with the evaluation length in formula (I) and can be determined in the same manner.

[0037] In a first embodiment of the present invention, the profile curve satisfies the formula (III): Na / A≧2.80×10 ー３(III) [In formula (III), Na represents the total number of the convex regions, and A represents the evaluated length (nm) of the cross-sectional curve]. When the cross-sectional curve at the interface of the laminate satisfies formula (III), the yield strength, water resistance, and drying speed of the laminate can be improved. While the reason for this is unclear, when the cross-sectional curve at the interface of the laminate satisfies formula (III), a certain number of concaves and convexes are present at the interface, resulting in a surface texture with a moderate contact area between the metal surface and the resin. Therefore, it is presumed that stress concentration at the interface is unlikely to occur, and the influence of the surface texture during film formation increases the crystallinity and / or orientation of the resin layer near the interface in the laminate. Furthermore, when formula (III) is satisfied, the surface texture of the resin film is likely to have a concave-convex structure that is less likely to absorb water, and the crystallinity and / or orientation near the surface of the resin layer (i.e., the interface on the resin film side of the laminate) is likely to be increased, thereby improving the water resistance and drying speed of the laminate.

[0038] In formula (III), Na / A is preferably 3.00×10 ー３ particles / nm or more, more preferably 4.05 × 10 ー３ particles / nm or more, more preferably 4.10 × 10 ー３ pcs / nm or more, preferably 10.0 × 10 ー３ particles / nm or less, more preferably 8.00×10 ー３ particles / nm or less, more preferably 6.00 × 10 ー３ particles / nm or less, and even more preferably 5.10 × 10 ー３ particles / nm or less, for example, 4.50×10 ー３ particles / nm or less, or 4.25 x 10 ー３ When Na / A is equal to or greater than the lower limit and / or equal to or less than the upper limit, the uneven structure at the interface of the laminate and the crystallinity and / or orientation of the resin layer are likely to be in a state in which the effects of the present invention can be further exhibited, thereby further improving the yield strength, water resistance, and drying speed of the laminate. Note that Na and A in formula (III) have the same meanings as Na and A in formula (I) and can be determined by the same method.

[0039] In a laminate according to one embodiment of the present invention, Σ(Ln / Sn) / Na, Sa / A, and Na / A can be controlled by (1) using a metal whose surface roughness parameter (particularly Sal×Str) is adjusted to fall within the ranges described below; or (2) appropriately adjusting the type and composition of the structural units of the resin constituting the resin film, the molecular weight of the resin, and / or the manufacturing conditions during film formation, such as coating, selection of the supporting substrate, drying, and imidization. For example, Σ(Ln / Sn) / Na, (Sa / A), and (Na / A) can be adjusted to fall within the above-mentioned ranges based on the preferred aspects advantageous for improving yield strength and dielectric properties herein, specifically, the preferred structural units and their contents of the PI resin, the preferred solvent contained in the PI resin precursor solution, the preferred conveying speed during coating, the drying temperature and standing step, and the preferred imidization conditions, in addition to the preferred metal surface roughness parameter such as Sal×Str. In this specification, [Σ(Ln / Sn)] / Na, Σ(Sn) / Na, Σ(Ln) / Na, (Sa / A), and (Na / A) may be collectively referred to as "roughness parameters."

[0040] In the first embodiment of the present invention, when the laminate of the present invention includes metal layers on both sides of a resin film, it is sufficient that the interface between at least one of the metal layers and the resin film satisfies formula (I). From the viewpoint of the yield strength, water resistance, and drying speed of the laminate, the interfaces between both metal layers and the resin film may satisfy formula (I). Furthermore, each roughness parameter may be the same or different at the interface between one metal layer and the resin film and the interface between the other metal layer and the resin film.

[0041] In a second embodiment of the present invention, the laminate of the present invention includes a resin film and a metal layer provided on at least one surface of the resin film, and after processing a cross section of the laminate in the thickness direction with a microtome equipped with a diamond knife under conditions of a cutting amount of 300 nm per cut and a processing speed of 1.0 mm / sec, in a cross section image of the laminate in the thickness direction obtained by a scanning electron microscope, the interface between the resin film and the metal layer is located at the center of the cross section image in the thickness direction, and the total area of ​​the resin defects calculated based on the brightness distribution of the cross section image is 0.300 μm per an area of ​​an evaluation range of 4.2 μm × 2.8 μm ２ The following is the result.

[0042] The inventors have conducted research focusing on the interface between layers in a laminate, and have found that the total area of ​​resin defects near the interface caused by microtoming under specific conditions is 0.300 μm per an evaluation area of ​​4.2 μm × 2.8 μm. ２ It was unexpectedly found that the 0.2% yield strength improved when the thickness was less than 1 / 2 mm. The reason for this is unclear, but it is presumed that if the laminate is such that the occurrence of defects in the resin is suppressed when processed under specific conditions in the cross section of the laminate including the interface between the resin film and the metal layer, yielding starting from the interface is unlikely to occur, and stress against deformation increases.

[0043] The microtome processing procedure and the method for obtaining the area of ​​the resin defect from the cross-sectional image in the present invention will be specifically described below.

[0044] (1) Microtome Processing A laminate including a resin film and a metal layer provided on at least one side of the resin film is cut out to obtain a test piece that is trapezoidal when the surface of the laminate film is viewed in plan. The test piece is attached to an ultramicrotome so that the thickness cross section of the short side portion becomes the processed surface. First, the entire thickness cross section of the test piece is cut with a glass knife. Then, using a diamond knife (preferably new), further cutting is performed under conditions of a cutting amount of 300 nm per cut and a processing speed of 1.0 mm / sec. Unlike general processing conditions, when the laminate is processed under such high load conditions, it is presumed that damage to the resin portion will occur depending on the difference in mechanical strength between the metal layer and the resin film and the state of the interface between the metal layer and the resin film.

[0045] (2) SEM Observation As a pretreatment for SEM observation, platinum is vapor-deposited on the processed surface of the test piece using an ion sputtering device. Next, on the platinum-deposited processed surface, the angle is adjusted so that the interface between the metal layer and the resin layer is horizontal to the image, and further adjusted so that the interface is located at the center in the thickness direction, and then SEM observation is performed. Furthermore, at this time, the magnification is adjusted so that the size of the obtained SEM image (the size of only the portion depicting the laminate) is 4.2 μm horizontal (length in the planar direction of the laminate) × 2.8 μm vertical (length in the thickness direction of the laminate) or more. The SEM image may be larger than the above size, but from the viewpoint of accuracy in calculating the defect area, it is preferable that the horizontal length be 6.0 μm or less and the vertical length be 4.0 μm or less. Furthermore, from the viewpoint of the resolution of the SEM image and ease of obtaining the image, the number of pixels in the SEM image is preferably 777,600 pixels or more and 6,291,456 pixels or less, more preferably 884,736 pixels or more and 6,291,456 pixels or less, even more preferably 1,093,120 pixels or more and 3,110,400 pixels or less, and particularly preferably 1,382,400 pixels or more and 2,457,600 pixels or less.

[0046] (3) Calculation of the Resin Defect Area The obtained SEM image (cross-sectional image) is imported using image processing software (e.g., Image J) and converted into an observation image consisting of, for example, a pixel count corresponding to the SEM resolution (e.g., 1536 x 1024 points). If the SEM image is larger than 4.2 μm wide x 2.8 μm high, the SEM image is trimmed to a size of 4.2 μm wide x 2.8 μm high so that the interface between the resin film and the metal layer is located at the center. The resulting image is then converted into an observation image (pixel image) consisting of a pixel count (e.g., 1536 x 1024 points) taking into account the changed size and the resolution of the SEM image. The resolution of the pixel image is preferably 1.0 x 10 ―３ μm / pixel or more, more preferably 1.5×10 ―３ μm / pixel or more, more preferably 2.0×10 ―３ μm / pixel or more, particularly preferably 2.5×10 ―３ μm / pixel, preferably 6.0×10 ―３ μm / pixel or less, more preferably 4.0×10 ―３ μm / pixel or less, and even more preferably 3.0×10 ―３ μm / pixel or less. By the following process, a luminance histogram (preferably 65,536 gradations (256 bins)) is obtained from the observed image in four regions: the entire region, the resin region, the metal region, and the region containing metal and resin (hereinafter referred to as the composite region), and a probability density distribution is obtained. The following is an example of a method for calculating the area of ​​a resin defect when using Image J. 1) Entire region The histogram function is used to obtain an entire luminance histogram. By normalizing with the total number of points in the histogram, the probability density distribution H for luminance x is obtained. ａｌｌ 2) Resin Region Using the Selection function, a region (rectangular) consisting of only resin that does not contain defects or metal (hereinafter referred to as the resin region, for example, the region corresponding to 103 in FIG. 5) is extracted, and a brightness histogram of the extracted portion is obtained. By normalizing it by the total number of points in the histogram, the probability density distribution H for brightness x is obtained. ｒ3) Metal Region Using the Selection function, extract a range (rectangular) consisting of only metal that does not contain resin (hereinafter referred to as the metal region, for example, the region corresponding to 101 in FIG. 5), and obtain a brightness histogram of the extracted portion. By normalizing it by the total number of points in the histogram, the probability density distribution H for brightness x is obtained. ｍe 4) Composite Region Using the Selection function, a range (rectangular) that includes resin and metal but does not include a missing portion (hereinafter referred to as a composite region, for example, the region corresponding to 102 in FIG. 5) is extracted, and a brightness histogram of the extracted portion is obtained. By normalizing with the total number of points in the histogram, a probability density distribution H ｍ,ｍe,ｒ (x) is obtained. In the case of an SEM image in which the areas are metal, composite area, resin, and defect area in descending order of brightness, the area is set so as not to include areas with lower brightness than the resin area in order to prevent the defect area from being included in the composite area. ｍｅ’Ａｖｅ and ｒ’Ａｖｅ (see below) ｍｅ’Ａｖｅ / h ｒ’Ａｖｅ The range is extracted so that the value of the probability density distribution obtained from each of the above-mentioned analysis regions falls within the range of 0.33 to 3. The total number of points required to obtain a brightness histogram in each of the above-mentioned regions is 100,000 or more, preferably 200,000 or more. If the total number of points in one analysis region does not satisfy the above-mentioned range, multiple analysis regions can be defined so that the total number of points obtained from each of the multiple analysis regions falls within the above-mentioned range, and an average probability density distribution can be used by averaging the probability density distributions obtained from each analysis region.

[0047] (4) Analysis By the following analysis, H ｍｅ (x) and H ｒ (x) is a probability density distribution H ｍ (x) is obtained. First, H ｍｅ The average value h of the probability density of the five points, i.e., the brightness x at which the peak top of (x) is located ±2 points Ａｖｅ Next, H ｍ，ｍｅ，ｒ In (x), H ｍｅ The average value h' of the probability density of the luminance at which the peak top of (x) is located ±2 points, totaling 5 points Ａｖｅ Find a = h' Ａｖｅ / h ＡｖｅSimilarly, a is calculated from the relation ｒ The average value h1 of the probability density of the five points, i.e., the brightness x at which the peak top of (x) is located ±2 points Ａｖｅ Furthermore, H ｍ，ｍｅ，ｒ In (x), H ｒ The average value h1' of the probability density of the luminance at which the peak top of (x) is located ±2 points, totaling 5 points Ａｖｅ Find b = h1' Ａｖｅ / h1 Ａｖｅ From the following relational expression (VI), H ｍ Calculate (x). ｍ (x) = H ｍ，ｍｅ，ｒ (x)-H ｍｅ (x) × a-H ｒ (x) × b (VI)

[0048] Next, the probability density distribution H of the defect portion is calculated by the following formula (VII): ｄ (x) is obtained. ｄ (x) = H ａｌｌ (x)-H ｍｅ (x) × c-H ｒ (x) × d-H ｍ (x)×e (VII) c, d, and e are calculated under the following conditions, for example, by using the solver function of Excel. Fitting conditions Convergence condition: Root mean square error of the right side becomes the minimum value (where x is the luminance and N is the number of x). Variables: c, d, e Constraints: None Initial conditions: c = 0.4, d = 0.4, e = 0.2 Solution method: GRG nonlinear

[0049] From the viewpoint of facilitating detection of peaks in the probability density distribution, N (the number of luminances x) may be 128 or more and 512 or less, and preferably 256. Furthermore, x (luminance) is 128 or more points in the range of 0 to 16,384 gradations, and 512 or less points in the range of 0 to 262,144 gradations, and preferably 256 points in the range of 0 to 65,536 gradations.

[0050] The probability density distribution H of the defect obtained above ｄ For (x), H ｄ H at luminance x where (x)<0 ｄ (x) to H ｄ(x) = 0. Next, the brightness is changed from x = 0 to H ｒ In the range of brightness x=x' where the peak top of (x) is located, H ｄ Integrate (x), get. The area of ​​the missing portion (for example, the area corresponding to 104 in FIG. 5) is calculated by multiplying this by the total number of points in the brightness histogram of the entire region. A specific method for calculating this is described in the Examples section below.

[0051] In one embodiment of the present invention, when the laminate is used as a metal laminate plate or the like, the metal layer on the resin film may be partially removed by etching or the like. In such a laminate, it is preferable that the resin film after removing the metal layer has high water resistance from the viewpoint of dielectric properties and drying efficiency during FPC manufacturing. The inventors have found that the total area of ​​resin defects near the interface caused by microtoming under specific conditions is 0.300 μm per an evaluation area of ​​4.2 μm × 2.8 μm. ２ It has also been found that, unexpectedly, the water resistance and drying speed of the resin film after removal of the metal layer can be improved when the temperature is below 100°C. The reason for this is unclear, but it is presumed that the more difficult the resin film surface is to absorb water, the higher the crystallinity and / or orientation near the surface of the resin layer (i.e., the interface on the resin film side in the laminate).

[0052] In the laminate according to the second embodiment of the present invention, the total area of ​​the resin defects is preferably 0.250 μm per evaluation area of ​​4.2 μm×2.8 μm. ２ or less, more preferably 0.200 μm ２ or less, and even more preferably 0.183 μm ２ Below 0.150 μm, particularly preferably ２ Less than 0.125 μm, particularly preferably ２ More preferably, 0.100 μm or less ２ Below 0.084 μm, very preferably ２ Below, for example, 0.0800 μm ２ Below, 0.0700μm ２ or less, or 0.0600 μm ２ or less, or 0.055 μm ２When the total area of ​​the resin vacancies is equal to or less than the upper limit, the yield strength, water resistance, and drying speed of the laminate can be further improved. In addition, the total area of ​​the resin vacancies is preferably 0.010 μm per evaluation area of ​​4.2 μm × 2.8 μm. ２ More preferably, 0.015 μm ２ More preferably, 0.020 μm or more ２ More preferably, 0.025 μm or more ２ More preferably, 0.030 μm or more ２ More preferably, 0.032 μm or more ２ More preferably, 0.035 μm or more ２ More than 0.040 μm, most preferably ２ More preferably, 0.044 μm or more ２ That's all. When the total area of ​​the resin defect portions is equal to or greater than the lower limit, the yield strength, water resistance, and drying speed of the laminate can be further improved. The reason for this is unclear, but it is presumed that when a laminate is processed under specific conditions and a certain number of defect portions are generated, the presence of flexible portions at the interface can relieve the stress applied to the laminate, making it less likely to yield and increasing the stress against deformation.

[0053] In the laminate of the present invention, the total area of ​​resin defects near the interface caused by microtoming under specific conditions can be controlled by (1) using a metal whose metal surface roughness parameter (particularly Sal x Str, as described below) is adjusted to fall within the range described below; or (2) appropriately adjusting the type and composition of the resin structural units constituting the resin film, the molecular weight of the resin, and / or the manufacturing conditions during film formation, such as coating, selection of the support substrate, drying, and imidization. For example, the total area of ​​resin defects near the interface caused by microtoming under specific conditions can be adjusted within the above range based on the preferred embodiments advantageous for improving yield strength and dielectric properties herein, specifically, the preferred metal surface roughness parameter such as Sal x Str, as well as the preferred structural units and their content of the PI resin, the solvent contained in the preferred PI resin precursor solution, the preferred conveying speed during coating, the drying temperature and standing process, and the preferred imidization conditions. Note that other roughness parameters can be adjusted within the range described below, for example, by using a metal whose relevant metal surface roughness parameter is adjusted to fall within the range described below or by employing the method (2) above.

[0054] In a third embodiment of the present invention, the laminate of the present invention includes a resin film and a metal layer provided on at least one surface of the resin film. When the elastic modulus of a thickness cross section of the laminate is measured using a scanning probe microscope (SPM) at five measurement regions set at intervals of 2 μm or more within a range of 500 nm in the thickness direction from the interface between the resin film and the metal layer toward the resin film, the relationship of formula (V) is satisfied: [Σ(Sn / En)] / 5≦0.480 (V) [In formula (V), En represents the average elastic modulus of the resin film in each measurement region, and Sn represents the standard deviation of the elastic modulus in each measurement region.] Hereinafter, the elastic modulus measured using a scanning probe microscope is also referred to as the "DMT elastic modulus" or the "elastic modulus measured by SPM." Therefore, En in formula (V) is also referred to as the "average DMT elastic modulus," and Sn is also referred to as the "standard deviation of the DMT elastic modulus."

[0055] In formula (V), Sn / En represents the ratio of the standard deviation of the DMT elastic modulus to the average DMT elastic modulus in one measurement region. In formula (V), [Σ(Sn / En)] / 5 represents the average value of the ratios of the standard deviation of the DMT elastic modulus in each of the five measurement regions to the average DMT elastic modulus in each of the five measurement regions. This average value is an index showing the degree of variation in the average DMT elastic modulus between the measurement regions; the smaller this value, the smaller the variation in the average DMT elastic modulus between the measurement regions.

[0056] The inventors have surprisingly found that when the DMT elastic modulus at the interface between the resin film and the metal layer satisfies the relationship of formula (V), i.e., when the value of [Σ(Sn / En)] / 5 is 0.480 or less, the 0.2% yield strength of the laminate is improved. The reason for this is unclear, but is presumed to be as follows. It is believed that in the thickness direction cross section, the state of stress concentration acting on the resin film and the metal layer differs depending on the unevenness of the interface, resulting in different strains induced at the interface and different magnitudes of internal stress. It is also expected that the crystallinity and orientation of the resin layer near the interface will change. In a laminate satisfying the relationship of formula (V), there is less variation in the elastic modulus of the resin present between the unevenness at the interface between the resin film and the metal layer, thereby increasing durability against stress concentration occurring at the interface. Furthermore, it is believed that the unevenness at the interface during film formation enhances the crystallinity and / or orientation of the resin layer near the interface in the laminate. It is presumed that these factors increase the strength of the resin film and increase the yield strength of the entire laminate.

[0057] Furthermore, the present inventors have unexpectedly discovered that in a laminate including a resin film and a metal layer, if the DMT elastic modulus at the interface between the resin film and the metal layer satisfies the relationship of formula (V), the water resistance and drying speed of the resin film after removing the metal layer can be improved. Although the reason for this is unclear, it is presumed that the unevenness of the resin film surface is an uneven structure that is less likely to 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 of the laminate) is increased.

[0058] The DMT elastic modulus at the interface between the resin film and the metal layer is measured in a measurement area set within a range of 500 nm in the thickness direction from the interface toward the resin film in the thickness direction cross section of the laminate. In the present invention, five measurement areas are set on the laminate to be measured, and the DMT elastic modulus is measured at 60 or more points in each measurement area. The average DMT elastic modulus (En) of the resin film in each measurement area is calculated as the average value of all DMT elastic moduli measured in the measurement area. Below, a method for measuring the DMT elastic modulus at the interface between the resin film and the metal layer using SPM will be specifically described. In addition, the DMT elastic modulus can be determined in detail, for example, by the method described in the Examples.

[0059] (1) Preparation of Test Piece (Sample) The method for preparing the test piece is not particularly limited as long as the cross section of the laminate in the thickness direction can be observed. When the thickness of the laminate to be measured is thin, it is preferable to prepare a test piece by embedding a cut part of the laminate in resin and exposing the cross section. After embedding in resin so that the cross section in the thickness direction can be seen, the surface of the resin-embedded laminate (the cross section in the thickness direction of the laminate) can be cut with, for example, a knife attached to a microtome to expose the cross section.

[0060] (2) Acquisition of DMT Elastic Modulus Image The DMT elastic modulus of the laminate can be determined by applying the DMT (Derjaguim-Muller-Toporov) theory to the relationship between the deformation of the sample and the load on the sample (force curve) determined by SPM, and a DMT elastic modulus image can be obtained by performing mapping measurement on a two-dimensional plane on the sample. For example, a cantilever with a spring constant of 4 to 60 N / m is attached to a Bruker SPM, and a DMT elastic modulus image can be obtained by measuring using the Peak Force QNM (Quantitative Nanomechanical Mapping) mode. The range in which the DMT elastic modulus image is obtained should include at least two adjacent layers and their interface, and it is preferable to set the interface between the two adjacent layers on the vertical axis of the DMT elastic modulus image so that the ratio of the resin layer to the metal layer is preferably about 1:1 to 5:1, so that the measurement area described below can be set on the resin film side (resin layer).

[0061] Next, the method for measuring the DMT elastic modulus at each point will be described in detail using the figures. Note that FIGS. 6 and 7 are used to clearly explain the method for determining the DMT elastic modulus and average DMT elastic modulus, and the present invention is not limited to these embodiments. FIG. 6 is a graph showing a force curve obtained at an arbitrary point within the measurement region of a sample cross-section in a laminate according to one embodiment of the present invention. FIG. 2 is a diagram showing a DMT elastic modulus image, coordinate axes, and measurement region of a sample cross-section in a laminate according to one embodiment of the present invention. In FIG. 6, the vertical axis of the force curve (applied load / nN) represents the load F = kd, and the horizontal axis (indentation depth / nm) represents the sample deformation δ = Δz-d. k represents the spring constant (N / m), d represents the spring deflection (m), and z represents the needle position (m). d can be detected by a laser, and z can be sensed by a piezo scanner.

[0062] First, when the cantilever is brought close to the sample, it comes into contact with the sample and is then pushed into the sample until the tip of the cantilever probe reaches its maximum load. Accordingly, a force curve (point A → point B → point C) for the pushing process can be obtained, as shown in Figure 6. At point B, when it comes into contact with the sample, it is affected by the adhesive force, and the load is applied in the negative direction. Next, when the cantilever that has been pushed into the sample up to its maximum load is pulled back, the load is released at the sample surface, and after adhesion, the cantilever probe leaves the sample surface. Accordingly, a force curve (point C → point D → point E) for the pulling back process can be obtained, as shown in Figure 6.

[0063] The DMT elastic modulus at each point can be calculated by analyzing the force curve during the pullback process using the DMT theoretical formula. Specifically, when the numerical values ​​from the minimum to maximum F value during the pullback process of the force curve are replaced with numerical values ​​from 0 to 1, fitting is performed for the range from 0.05 to 0.5 to calculate the DMT elastic modulus. A DMT elastic modulus image can be obtained by acquiring the DMT elastic modulus at all measurement points in the measurement region where a DMT elastic modulus image is desired. Analysis using the DMT theoretical formula can be performed using analysis software included with the SPM (e.g., NanoScope Analysis ver. 2.00) or by known methods. In the latter case, calculation can be performed using, for example, the following formula (a): [wherein F represents the load (the force sensed by the cantilever (spring)), F ｅｌａｓ denotes the stress of elastic deformation, and F ａｄｈ indicates the adhesive force, and E is the elastic modulus (Pa or N / m ２ ), R is the tip radius of the cantilever probe (m), δ is the indentation depth (m), and w is the adhesion energy (N / m or J / m ２ ), and F ａｄｈ The minimum value of the force curve (F value at point E) can be substituted for

[0064] In SPM measurements, the measurement atmosphere can be room temperature, e.g., 24°C, under atmospheric air, and the cantilever movement speed can be set to 0.4 μm / s and the maximum load to 30 nN. The spring constant of the cantilever and the tip radius of the probe can be calculated using values ​​stored in the SPM device or by known methods. For example, the spring constant may be a value calculated by the Sader method, and the tip radius of the probe may be a value calculated by the reconstruction method.

[0065] (3) Calculation of the Average DMT Elastic Modulus In the DMT elastic modulus image obtained above, five measurement regions were set within a range of 500 nm from the interface between the resin film and the metal layer toward the resin film in the thickness direction, and the average DMT elastic modulus in each measurement region was calculated to obtain the average DMT elastic modulus (En) of the measurement region. At the same time, the standard deviation (Sn) can also be calculated. For example, Figure 7 shows a DMT elastic modulus image obtained by measuring 256 horizontal points and 256 vertical points within a range of 4 μm horizontal (in-plane direction) × 4 μm vertical (thickness direction) of the sample cross section, with the upper left corner at (X,Y) = (0,0), the lower left corner at (X,Y) = (0,255), the upper right corner at (X,Y) = (255,0), and the lower right corner at (X,Y) = (255,255). By calculating the DMT elastic modulus at 256×256 points from (0,0) to (255,255), a DMT elastic modulus image is obtained.

[0066] The range in which the DMT elastic modulus image is obtained can be determined appropriately depending on the configuration of the laminate. The horizontal (in-plane direction) and vertical (thickness direction) distances are preferably 0.05 to 0.6 times, more preferably 0.08 to 0.5 times, and even more preferably 0.1 to 0.4 times the thickness of the laminate. For example, in a laminate having a thickness of 20 to 65 μm, the range in which the DMT elastic modulus image is obtained may be 2 μm or more in width × 2 μm or more in height, preferably 3 μm or more in width × 3 μm or more in height, and more preferably 4 μm or more in width × 4 μm or more in height. In one embodiment of the present invention, the range in which the DMT elastic modulus image is obtained is, for example, 4 μm or more in width × 4 μm or more in height. Furthermore, the number of points (locations) at which the DMT elastic modulus is measured to obtain the DMT elastic modulus image is typically 64 or more × 64 or more, preferably 128 or more × 128 or more, and more preferably 256 or more × 256 or more, from the viewpoint of increasing measurement accuracy. The resolution is uniquely determined by the range in which the DMT elastic modulus image is obtained and the number of measurement points, but when the measurement area is small, it is desirable to measure at a resolution of preferably 62 nm / pixel or less, more preferably 40 nm / pixel or less, even more preferably 31 nm / pixel or less, and particularly preferably 20 nm / pixel or less. When multiple DMT elastic modulus images are obtained for the same measurement object (laminate), it is preferable that the setting conditions (range in which the DMT elastic modulus image is obtained, number of points in which the DMT elastic modulus is measured, etc.) are all set to the same or similar levels.

[0067] Next, in the obtained DMT elastic modulus image, a measurement region (referred to as measurement region 1) is set within a range of 500 nm in the thickness direction from the interface between the resin film and the metal layer, where DMT elastic modulus values ​​are obtained at 60 or more points, and the average DMT elastic modulus (En1) and the standard deviation (Sn1) of the DMT elastic modulus can be determined from the DMT elastic moduli measured at the 60 or more points in the measurement region. Similarly, measurement regions (referred to as measurement regions 2 to 5) are set within the DMT elastic modulus image, and the average DMT elastic modulus (En2 to En5) and the standard deviation (Sn2 to Sn5) can be determined from the DMT elastic moduli measured in these regions. Note that measurement regions 1 to 5 may be set within the same DMT elastic modulus image, or may be set on different DMT elastic modulus images.

[0068] Measurement regions 1 to 5 are each set within a range of 500 nm from the interface between the resin film and the metal layer in the thickness direction, within an arbitrary range that allows measurement of 60 or more DMT elastic moduli. That is, the measurement region is set on the resin film side (within the resin layer). From the viewpoint of measurement accuracy, each measurement region is set within a range of 20 nm to 500 nm, more preferably 50 nm to 500 nm, in the thickness direction of the interface, depending on the thickness of the laminate and the state (unevenness) of the interface between the metal layer and the resin film. The number of DMT elastic moduli (measurement points) to be measured in one measurement region to calculate the average DMT elastic modulus is usually 60 or more, preferably 80 or more, more preferably 100 or more, and usually 300 or less. The set ranges of measurement regions 1 to 5 for the same measurement object (laminate) do not need to be the same shape, but the size and the number of measurement points for DMT elastic modulus in each measurement region are set to be approximately the same in principle. The size of one measurement area is determined depending on the resolution of the measurement. There are no particular limitations on the size as long as the DMT elastic modulus can be measured at 60 or more points within a range of 500 nm from the interface between the resin film and the metal layer in the thickness direction of the resin film. For example, if the resolution is 15.625 nm / pixel, the size is 15,000 nm. ２ or more, preferably 16,500 nm ２ More preferably, 20,000 nm ２ More preferably, 22,500 nm or more ２ More preferably, 25,000 nm or more ２ The higher the resolution, the smaller the size of the measurement region can be, but from the viewpoint of grasping the variation in the DMT elastic modulus, the size of the measurement region is preferably in the above range.

[0069] Measurement areas 1 to 5 are set at intervals of 2 μm or more from each other. The intervals of 2 μm or more refer to the intervals in the planar direction (width direction) of the laminate, and can be determined appropriately depending on the state (unevenness) of the interface between the metal layer and the resin film. The intervals between two adjacent measurement areas in measurement areas 1 to 5 may be the same or different, but it is preferable that the measurement areas are set so as to be scattered at a distance of 2.5 times or more, preferably 3 times or more, the width of the measurement area.

[0070] In the laminate according to the third embodiment of the present invention, the value of [Σ(Sn / En)] / 5 in formula (V) is 0.480 or less, preferably 0.450 or less, more preferably 0.420 or less, even more preferably 0.400 or less, and particularly preferably 0.390 or less, and may be, for example, 0.380 or less, 0.350 or less, or 0.320 or less. The smaller the value of [Σ(Sn / En)] / 5, the smaller the variation in the DMT elastic modulus at the interface, which is advantageous for improving the yield strength, water resistance, and drying speed of the laminate. The lower limit of [Σ(Sn / En)] / 5 is not particularly limited and may be, for example, 0, but is usually 0.100 or more, preferably 0.200 or more. When the lower limit of [Σ(Sn / En)] / 5 is within the above range, the elastic modulus of the resin present between the irregularities at the interface between the resin film and the metal layer varies to some extent, which facilitates dispersion of stress generated at the interface and facilitates increasing the yield strength of the laminate.

[0071] In a third embodiment of the present invention, the minimum value of the Sn / En value in each of the five measurement regions is preferably 0.400 or less, more preferably 0.370 or less, even more preferably 0.340 or less, even more preferably 0.300 or less, and particularly preferably 0.280 or less. When the minimum value of Sn / En in each of the five measurement regions is below the upper limit, the yield strength, water resistance, and drying speed of the laminate can be improved. Furthermore, the minimum value of the Sn / En value in each of the five measurement regions is preferably 0.100 or more, more preferably 0.150 or more, even more preferably 0.200 or more, for example, 0.250 or more. When the minimum value of Sn / En in each of the five measurement regions is above the lower limit, there is some variation in the elastic modulus of the resin present between the unevenness of the interface, which makes it easier to disperse the stress generated at the interface, thereby increasing the yield strength of the laminate.

[0072] In a third embodiment of the present invention, the maximum value of Sn / En in each of the five measurement regions is preferably 0.540 or less, more preferably 0.510 or less, even more preferably 0.500 or less, even more preferably 0.460 or less, particularly preferably 0.420 or less, and particularly preferably 0.400 or less. When the maximum value of Sn / En in each of the five measurement regions is below the upper limit, the yield strength, water resistance, and drying speed of the laminate can be improved. Furthermore, the maximum value of Sn / En in each of the five measurement regions is preferably 0.150 or more, more preferably 0.200 or more, and even more preferably 0.250 or more. When the maximum value of Sn / En in each of the five measurement regions is above the lower limit, there is some variation in the elastic modulus of the resin present between the unevenness of the interface, which makes it easier to disperse the stress generated at the interface, thereby increasing the yield strength of the laminate.

[0073] In the third embodiment of the present invention, the Sn / En values ​​in each of the five measurement regions are preferably 0.520 or less, more preferably 0.500 or less, even more preferably 0.460 or less, even more preferably 0.420 or less, and particularly preferably 0.400 or less. When the Sn / En values ​​in each of the five measurement regions are all below the upper limit, the yield strength, water resistance, and drying speed of the laminate can be improved. Furthermore, the Sn / En values ​​in each of the five measurement regions are preferably 0.100 or more, more preferably 0.150 or more, even more preferably 0.200 or more, and even more preferably 0.250 or more. When the Sn / En values ​​in each of the five measurement regions are all above the lower limit, there is some variation in the elastic modulus of the resin present between the unevenness of the interface, which makes it easier to disperse the stress generated at the interface, thereby improving the yield strength of the laminate.

[0074] In the third embodiment of the present invention, the average DMT elastic modulus (En) in each of the five measurement regions varies depending on the type of resin and metal layer used, but is preferably 1.50 GPa or more, more preferably 2.00 GPa or more, even more preferably 2.20 GPa or more, and particularly preferably 2.40 GPa or more. Also, the average DMT elastic modulus (En) is preferably 10.0 GPa or less, more preferably 8.00 GPa or less, even more preferably 6.00 GPa or less, still more preferably 4.50 GPa or less, and particularly preferably 4.00 GPa or less.

[0075] In the third embodiment of the present invention, the standard deviation (Sn) of the DMT elastic modulus in each of the five measurement regions is preferably 1.50 GPa or less, more preferably 1.20 GPa or less, even more preferably 1.10 GPa or less, particularly preferably 1.00 GPa or less, and particularly preferably 0.90 GPa or less. The standard deviation (Sn) of the DMT elastic modulus is preferably 0.1 GPa or more, more preferably 0.2 GPa or more. When the standard deviation (Sn) of the DMT elastic modulus in each measurement region is within the above range, variation in the average DMT elastic modulus among the five measurement regions is unlikely to occur, and the yield strength, water resistance, and drying speed of the obtained laminate can be improved.

[0076] In the third embodiment of the present invention, when the surface of the metal layer constituting the laminate that contacts the resin film is a roughened surface having a plurality of convex portions, it is preferable that measurement areas 1 to 5 are each set between two adjacent convex portions on the roughened surface. Specifically, for example, in FIG. 7 , which shows the DMT elastic modulus image of the interface between the metal layer 1 and the resin film 2 in a laminate according to one embodiment of the present invention, one measurement area 203 is set between two convex portions 21a and 21b on the surface of the metal layer 202. The remaining measurement areas are also set, one each, between two other convex portions on the surface of the metal layer 201 in the same manner as described above. When the surface of the metal layer constituting the laminate that contacts the resin film is a roughened surface having a plurality of convex portions, the presence of a large amount of resin between the convex portions increases the crystallinity and / or orientation of the resin layer near the interface, or reduces the internal stress generated between the convex portions, which is thought to increase the strength of the entire resin film and further improve the yield strength, water resistance, and drying speed of the laminate. In addition, it is believed that the presence of an appropriate number of convex portions on the surface of the metal layer in contact with the resin film also tends to cause crystallization and / or orientation starting from the interface, thereby further improving the yield strength, water resistance, and drying speed of the laminate. Note that the "roughened surface" of the metal layer is exemplified by an uneven surface of the metal layer that satisfies the various surface roughness parameters described in the section [Metal Layer] below.

[0077] In a third embodiment of the present invention, when the DMT elastic modulus is measured in five measurement areas, the relationship of the formula (V) is preferably satisfied. In this case, it is preferable that the value of [Σ(Sn / En)] / 5, the value of Sn / En, the average DMT elastic modulus (En), and the standard deviation of the DMT elastic modulus (Sn) each fall within the ranges described above.

[0078] In the laminate of the present invention, the value of [Σ(Sn / En)] / 5, the value of Sn / En, the average DMT elastic modulus (En) and the standard deviation of the DMT elastic modulus (Sn) in each measurement region can be controlled by (1) using a metal whose surface roughness parameter (particularly Sal×Str) is adjusted to fall within the range described below; and (2) appropriately adjusting the type and composition of the structural units of the resin constituting the resin film, the molecular weight of the resin, and / or the production conditions during film formation, such as coating, selection of the supporting substrate, drying, and imidization. For example, the DMT elastic modulus (En) and the standard deviation of the DMT elastic modulus (Sn) can be controlled to fall within the above ranges by controlling the [Σ(Sn / En)] / 5 value and the Sn / En value based on the preferred aspects of the present specification that are advantageous for improving yield strength and dielectric properties, specifically, the preferred roughness parameters of the metal surface such as Sal×Str, the preferred structural units of the PI resin and their content, the preferred solvent contained in the PI resin precursor solution, the preferred conveying speed during coating, the drying temperature and standing step, the preferred imidization conditions, etc. Hereinafter, the [Σ(Sn / En)] / 5 value, the Sn / En value, the average DMT elastic modulus (En) in each measurement region, the standard deviation of the DMT elastic modulus (Sn), etc., may be collectively referred to as the DMT elastic modulus parameters.

[0079] In the third embodiment of the present invention, when the laminate of the present invention includes a metal layer on both sides of the resin film, it is sufficient that the relationship of formula (V) is satisfied at the interface between at least one of the metal layers and the resin film. From the viewpoint of the yield strength, water resistance, and drying speed of the laminate, the relationship of formula (V) may be satisfied at the interfaces between both metal layers and the resin film. In addition, each DMT elastic modulus parameter may be the same or different at the interface between one metal layer and the resin film and the interface between the other metal layer and the resin film. Hereinafter, when referring to the laminate of the present invention, unless otherwise clearly stated, it means any of the laminates of the first embodiment, the second embodiment, and the third embodiment of the present invention.

[0080] [Resin Film] The laminate of the present invention includes a resin film. The resin constituting the resin film is not particularly limited, and examples thereof include thermosetting resins selected from diallyl phthalate resins, silicone resins, phenolic resins, unsaturated polyester resins, polyurethane resins, melamine resins, urea resins, xylene resins, furan resins, aniline resins, acetone-formaldehyde resins, alkyd resins, maleimide resins, maleimide-cyanate ester resins, cyanate ester resins, benzoxazine resins, polybenzimidazole resins, and polycarbodiimide resins; olefin resins; acrylic resins; styrene resins; rubber resins; fluorine-containing resins; vinyl resins; general-purpose engineering plastics; super engineering plastics such as liquid crystal polymers and aromatic polyether resins; polyamide resins; polyimide resins such as polyimide resins and polyamideimide resins; and biodegradable plastics. These resins can be used alone or in combination of two or more. Among these, 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 resins, liquid crystal polymers, fluorine-based resins, aromatic polyether resins, epoxy resins, and maleimide resins, more preferably polyimide resins and / or liquid crystal polymers, and even more preferably polyimide resins. Furthermore, it is preferable that at least one resin constituting the resin film has orientation and / or crystallinity. The orientation of the resin in the resin film can be confirmed by laser Raman spectroscopy or the like, and the crystallinity can be confirmed by small-angle X-ray scattering, wide-angle X-ray scattering, or IR measurement. 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 the resin constituting the resin film are not particularly limited, but can be selected, for example, from the same ranges as those for the polyimide resins described below.

[0081] In a preferred embodiment of the present invention, the resin film is preferably a polyimide-based film containing a polyimide-based resin. The inclusion of a polyimide-based resin can improve the strength, water resistance, and drying speed of the laminate. In this specification, a polyimide-based film may be referred to as a "PI-based film," and a polyimide-based resin may be referred to as a "PI-based resin."

[0082] The resin film may be a single-layer film or a laminated film.

[0083] In a preferred embodiment of the present invention, when the PI film is a laminate film, it preferably contains a polyimide-based resin-containing layer (PI-1) and a polyimide-based resin-containing layer (PI-2). The PI film may contain a PI-based resin-containing layer other than these PI-based resin-containing layers, or may contain a layer other than the PI-based resin-containing layer. Examples of such a layer include a pressure-sensitive adhesive layer. In a preferred embodiment of the present invention, from the viewpoint of increasing the yield strength of the laminate, the PI film of the present invention preferably further contains a PI-based resin-containing layer (PI-3) in addition to the PI-based resin-containing layer (PI-1) and the PI-based resin-containing layer (PI-2). In such an embodiment, from the viewpoint of increasing the yield strength of the laminate, the PI film of the present invention preferably contains the PI-based resin-containing layer (PI-2), the PI-based resin-containing layer (PI-1), and the PI-based resin-containing layer (PI-3) in this order, and more preferably contains them adjacent to each other in this order. A PI film including the PI resin-containing layer (PI-1), the PI resin-containing layer (PI-2), and the PI resin-containing layer (PI-3) (sometimes referred to as PI resin-containing layers (PI-1) to (PI-3) or layers (PI-1) to (PI-3)) is sometimes referred to as the PI film (L). In this specification, unless otherwise specified, the term "PI film" includes both a single-layer film and a laminate film, and when a PI resin-containing layer, particularly the PI resin-containing layer (PI-1), the PI resin-containing layer (PI-2), and / or the PI resin-containing layer (PI-3), is mentioned, it relates to a PI film in the form of a laminate film.

[0084] 8 , a PI film 10 according to a preferred embodiment of the present invention is composed of three adjacent PI resin-containing layers: 11, 12, and 13, which are laminated 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, the PI resin-containing layer 11 preferably corresponds to layer (PI-2), the PI resin-containing layer 12 preferably corresponds to layer (PI-1), and the PI resin-containing layer 13 preferably corresponds to layer (PI-3). The PI film 10 may also include a PI resin-containing layer other than layers (PI-1), (PI-2), and (PI-3), or a layer other than the PI resin-containing layer. Examples of such layers include pressure-sensitive adhesive layers formed from polymeric materials such as acrylic resins other than PI resins.

[0085] 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, even more preferably 30 μm or more, even more preferably 35 μm or more, and particularly preferably 40 μm or more, and is preferably 150 μm or less, more preferably 130 μm or less, even more preferably 100 μm or less, even more preferably 90 μm or less, particularly preferably 80 μm or less, especially more preferably 70 μm or less, and particularly more preferably 60 μm or less. When the thickness of the resin film is within the above range, the laminate can have mechanical properties such as high yield strength and flexibility suitable for flexible printed circuit boards and the like. Furthermore, since the Df can be reduced and the yield strength can be improved, a laminate can be obtained that has a good balance of mechanical properties suitable for flexible printed circuit boards and dielectric properties suitable for high-speed communication applications such as 5G.

[0086] When the PI film of the present invention is a laminate film, the film thickness can be selected from the thickness range of the resin film described above. However, the thickness of layer (PI-1) is preferably 10 μm or more, and the thickness of layer (PI-2) is preferably 2 μm or more. When the thicknesses of layer (PI-1) and layer (PI-2) are equal to or greater than the above-mentioned lower limits, the yield strength of the laminate can be further improved. The thickness of layer (PI-1) is more preferably 15 μm or more, even more preferably 20 μm or more, even more preferably 30 μm or more, and is preferably 80 μm or less, more preferably 60 μm or less, even more preferably 55 μm or less, and even more preferably 50 μm or less. Furthermore, the thickness of layer (PI-2) is more preferably 2.5 μm or more, even more preferably 3 μm or more, even more preferably 3.5 μm or more, and is preferably 20 μm or less, more preferably 15 μm or less, even more preferably 10 μm or less, and even more preferably 8 μm or less.

[0087] When the PI film of the present invention has a layer (PI-3), the thickness of the layer (PI-3) may be selected from the range of the thickness of the layer (PI-2) described above. The thicknesses of the layers (PI-2) and (PI-3) may be the same or different from each other, but from the viewpoint of suppressing warpage of the laminate, the thickness of one layer is preferably within ±25% of the thickness of the other layer, more preferably within ±20%. The thickness of each layer can be measured using a laser microscope or the like, for example, by the method described in the Examples.

[0088] In one embodiment of the present invention, the thickness of layer (PI-2) is preferably 0.05 to 0.3 times the thickness of layer (PI-1). When the thicknesses satisfy this relationship, the laminate can have mechanical properties such as high yield strength and flexibility suitable for flexible printed circuit boards and the like. Furthermore, since the Df can be reduced and the yield strength can be improved, a laminate can be obtained that has a good balance of mechanical properties suitable for flexible printed circuit boards and dielectric properties suitable for high-speed communication applications such as 5G. In particular, the effects of the present invention are more easily achieved 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 thickness of layer (PI-2) is more preferably 0.08 times or more, even more preferably 0.10 times or more, particularly preferably 0.12 times or more, and more preferably 0.25 times or less, even more preferably 0.23 times or less, particularly preferably 0.20 times or less, the thickness of layer (PI-1). When the PI film of the present invention has layer (PI-3), the thickness of layer (PI-3) may be selected from the range of the above-mentioned layer (PI-2).

[0089] In the PI film of the present invention, the PI resin constituting the layers (PI-1) to (PI-3) has a cross-sectional curve at the interface of the laminate satisfying formula (I), and the total area of ​​the resin defects near the interface caused by microtoming under specific conditions is 0.300 μm per an evaluation area of ​​4.2 μm × 2.8 μm. ２The type of the layer is not particularly limited as long as it satisfies the following conditions or satisfies the relationship of formula (V) at the interface between the PI film and the metal layer of the resulting laminate; however, from the viewpoint of improving yield strength while maintaining excellent dielectric properties, it is preferred that each of layers (PI-1) to (PI-3) include a non-thermoplastic polyimide resin-containing layer (hereinafter sometimes referred to as an mPI layer) and / or a thermoplastic polyimide resin-containing layer (hereinafter sometimes referred to as a TPI layer). In particular, from the viewpoint of improving yield strength, it is preferred that each of layers (PI-1) and (PI-2) is an mPI layer or a TPI layer, and it is more preferred that one of layers (PI-1) and (PI-2) is an mPI layer and the other is a TPI layer. The mPI layer generally serves as the main PI resin-containing layer in a PI film for use in flexible printed circuit boards. The TPI layer can also function as an adhesive layer that bonds the PI film to a metal layer (e.g., a copper layer), and is preferably located as the outermost layer in the PI film that can come into contact with the metal layer. In a PI film containing three or more PI resin-containing layers, it is preferred that at least one PI resin-containing layer is an mPI layer and at least one (preferably at least two) PI resin-containing layer is a TPI layer, and it is more preferred that the PI film has a TPI layer, an mPI layer, and a TPI layer in this order. Therefore, in the PI film (L), it is preferred that the layer (PI-1) is an mPI layer, and the layers (PI-2) and (PI-3) are each a TPI layer. When the PI film (L) has such a layer structure, the mPI layer ensures improved thermal properties, suppresses thermal denaturation and degradation, and ensures the dimensional stability of the PI film. The TPI layer can also enhance adhesion to a metal layer (e.g., a copper layer), thereby improving the yield strength of the PI film. When the PI film (L) contains multiple TPI or mPI layers, the structures of the multiple TPI or mPI layers may be the same or different. Furthermore, in the PI film (L), the structures of the layer (PI-1), the layer (PI-2), and the layer (PI-3) are usually different, but the structures of the layer (PI-2) and the layer (PI-3) may be the same or different.

[0090] In another preferred embodiment of the present invention, when the PI-based film is a single-layer film, it is composed of one PI-based resin-containing layer, and the cross-sectional curve of the laminate interface satisfies formula (I). The total area of ​​resin defects near the interface caused by microtome processing under specific conditions is 0.300 μm per an evaluation area of ​​4.2 μm × 2.8 μm. ２ The type of layer is not particularly limited as long as it satisfies the following or satisfies the relationship of formula (V) at the interface between the PI film and the metal layer of the resulting laminate, but it is preferable to adopt the structure of the layer (PI-1) from the viewpoint of increasing the yield strength while maintaining excellent dielectric properties. When the PI film is a single-layer film, the thickness of the film can be selected from the range of the thickness of the resin film described above.

[0091] <PI Resin> The PI resin contained in the PI film is a resin containing a repeating structural unit containing an imide group, and may contain a repeating structural unit containing both an imide group and an amide group. In the present invention, a "non-thermoplastic" polyimide resin is a polyimide resin having a storage modulus of 1.0 × 10 at 40°C measured using a dynamic mechanical analyzer (DMA). ９ Pa or more, and the storage modulus at 300°C is 1.0 × 10 ８ The term "thermoplastic" refers to a polyimide resin having a storage modulus of 1.0 × 10 Pa or more at 40°C. ９ Pa or more, and the storage modulus at 300°C is 1.0 × 10 ８ The storage modulus refers to a polyimide resin having a storage modulus of less than Pa. The storage modulus can be measured, for example, by the method described in the examples.

[0092] 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 contains a tetracarboxylic anhydride-derived structural unit (A) and a diamine-derived structural unit (B). In the present invention, the term "structural unit derived from" means "a structural unit derived from," for example, "tetracarboxylic anhydride-derived structural unit (A)" means "tetracarboxylic anhydride-derived structural unit (A)." Furthermore, "the PI film contains the structural unit (A)" means "the PI resin constituting the PI film contains the structural unit (A)," and "the PI resin-containing layer contains the structural unit (A)" means "the PI resin constituting the PI resin-containing layer contains the structural unit (A)," and the same applies to other structural units. In this specification, unless otherwise specified, the PI resin constituting (or contained in) the PI film can be interpreted as the PI resin constituting (or contained in) at least one of the PI resin-containing layers, at least one of the layers (PI-1) and (PI-2), or at least one of the layers (PI-1) to (PI-3) (or contained in at least one of the layers).

[0093] (Tetracarboxylic Acid Anhydride-Derived Structural Unit (A)) The tetracarboxylic acid anhydride-derived structural unit (A) (hereinafter, sometimes simply referred to as structural unit (A)) is, for example, a structural unit represented by the formula (1): In the formula (1), Y represents a tetravalent organic group.

[0094] In formula (1), Y's each independently represent a tetravalent organic group, preferably a tetravalent organic group having 4 to 40 carbon atoms, and more preferably a tetravalent organic group having 4 to 40 carbon atoms and a cyclic structure. Examples of the cyclic structure include an alicyclic, aromatic ring, and heterocyclic structure. The organic group may have a hydrogen atom substituted with a halogen atom, a hydrocarbon group, an alkoxy group, or a halogenated hydrocarbon group, and in such cases, the number of carbon atoms in these groups is preferably 1 to 8. In the present invention, the PI resin may contain multiple types of Y's, and the multiple types of Y's may be the same or different. Examples of Y include groups or structures represented by formulas (31) to (40); groups in which a hydrogen atom in a group represented by formulas (31) to (40) is substituted with a methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, isobutyl group, sec-butyl group, tert-butyl group, fluoro group, chloro group, or trifluoromethyl group; and tetravalent chain hydrocarbon groups having 1 to 8 carbon atoms.

[0095] [In formulas (31) to (33), R １９ ~R ２６ and R ２３’ ~R ２６’ each independently represents a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, or an aryl group having 6 to 12 carbon atoms; R １９ ~R ２６ and R ２３’ ~R ２６’ The hydrogen atoms contained in V may be substituted with halogen atoms, independently of one another; １ and V ２ are each independently a single bond (except when e+d=1), —O—, or —CH ２ -, -CH ２ -CH ２ -, -CH(CH ３ ) -, -C(CH ３ ) ２ -, -C(CF ３ ) ２ -, -SO ２ -, -S-, -CO-, -N(R ｊ ) - or formula (a) (In formula (a), R ２７ ~R ３０each independently represents a hydrogen atom or an alkyl group having 1 to 6 carbon atoms; and each D independently represents a single bond, —C(CH ３ ) ２ - or - C(CF ３ ) ２ -, i represents an integer of 1 to 3, * represents a bond, ｊ represents a hydrogen atom or a monovalent hydrocarbon group having 1 to 12 carbon atoms which may be substituted with a halogen atom; e and d each independently represent an integer of 0 to 2 (provided that e+d is not 0); f represents an integer of 0 to 3; g and h each independently represent an integer of 0 to 4; in formula (39), Z represents a divalent organic group; R ａ３ each independently represents a halogen atom, or an alkyl group, alkoxy group, aryl group, or aryloxy group which may have a halogen atom; each s independently represents an integer of 0 to 3; and in formula (40), R ａ２ each independently represents a halogen atom, or an alkyl group, alkoxy group, aryl group, or aryloxy group which may have a halogen atom; each 1 independently represents an integer of 0 to 3; and * represents a bond.

[0096] In the present 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 contains, as Y in formula (1), at least one structure selected from the group consisting of structures represented by formula (31), formula (32), formula (33), formula (39), and formula (40), more preferably at least one structure selected from the group consisting of structures containing a benzene skeleton, and even more preferably at least one structure selected from the group consisting of structures represented by formula (32), formula (39), and formula (40).

[0097] In formulas (31) to (33), R １９ ~R ２６ and R ２３’ ~R ２６’ are each independently preferably a hydrogen atom or an alkyl group having 1 to 6 carbon atoms, more preferably a hydrogen atom or an alkyl group having 1 to 3 carbon atoms, and even more preferably a hydrogen atom.

[0098] In formula (31), V １ and V ２ are each independently preferably a single bond (except when e+d=1), —O—, or —CH ２ -, -C(CH ３ ) ２ -, -C(CF ３ ) ２ - or -CO-, and more preferably a single bond (except when e+d=1), -O-, -C(CH ３ ) ２ - or - C(CF ３ ) ２ Represents -.

[0099] In formula (31), e and d each independently preferably represent 0 or 1 (provided that e+d is not 0). Also, e+d preferably represents 1. In formula (31), when e is 0, the two benzene rings are V １ When d is 0, the two benzene rings are V ２ indicates that there is no bond.

[0100] In the formulas (32) and (33), f preferably represents 0 or 1, and more preferably 0.

[0101] In formula (33), g and h each independently represent preferably an integer of 0 to 2, more preferably 0 or 1. Furthermore, g+h preferably represents an integer of 0 to 2. When f is 1 or greater, multiple g's and multiple h's may each independently be the same or different.

[0102] In formula (a), R ２７ ~R ３０ are each independently preferably a hydrogen atom or an alkyl group having 1 to 3 carbon atoms, more preferably a hydrogen atom. i is preferably 1 or 2, and when i is 2 or more, a plurality of D and R ２７ ~R ３０ may be the same or different, independently of each other.

[0103] In formula (39), Z preferably represents a divalent organic group having 4 to 40 carbon atoms, more preferably a divalent organic group having 4 to 40 carbon atoms and a cyclic structure, still more preferably a divalent organic group having 4 to 40 carbon atoms and an aromatic ring, and particularly preferably a divalent organic group represented by formula (z1), formula (z2), or formula (z3): [In formulas (z1) to (z3), R ｚ１１ ~R ｚ１４ each independently represents a hydrogen atom or a monovalent hydrocarbon group which may have a halogen atom; R ｚ２ each independently represents a monovalent hydrocarbon group which may have a halogen atom; n represents an integer of 1 to 4; j represents each independently an integer of 0 to 3; * represents a bond], and particularly preferably represents a divalent organic group represented by formula (z1).

[0104] In formula (z1), R ｚ１１ ~R ｚ１４ are each independently preferably a hydrogen atom or an alkyl group which may have a halogen atom, more preferably a hydrogen atom or an alkyl group having 1 to 6 carbon atoms which may have a halogen atom, still more preferably a hydrogen atom or an alkyl group having 1 to 3 carbon atoms which may have a halogen atom, and particularly preferably a hydrogen atom. ｚ１１ ~R ｚ１４ In the benzene ring having R ｚ１１ ~R ｚ１４ At least one of R may be a monovalent hydrocarbon group which may have a halogen atom. ｚ１１ ~R ｚ１４ are particularly preferably all hydrogen atoms.

[0105] In formula (z1), n ​​is preferably an integer of 1 to 3, more preferably 1 or 2, and even more preferably 2.

[0106] In formula (z2), R ｚ２ are each independently preferably an alkyl group which may have a halogen atom, more preferably an alkyl group having 1 to 6 carbon atoms which may have a halogen atom, and even more preferably an alkyl group having 1 to 3 carbon atoms which may have a halogen atom.

[0107] In formula (z2), j's are preferably each independently 0 or 1, more preferably 0, and even more preferably all j's are 0.

[0108] In formula (39), R ａ３ Preferably, each independently represents an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, or an aryl group having 6 to 12 carbon atoms. ａ３ The hydrogen atoms contained in R may be substituted with halogen atoms independently of each other. ａ３ are each independently an alkyl group preferably having 1 to 6 carbon atoms, more preferably an alkyl group having 1 to 3 carbon atoms.

[0109] In formula (39), each s preferably represents an integer of 0 to 2, more preferably 0 or 1, independently of one another.

[0110] In formula (40), R ａ２ Preferably, each independently represents an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, or an aryl group having 6 to 12 carbon atoms. ａ２ The hydrogen atoms contained in R may be substituted with halogen atoms independently of each other. ａ２ are each independently preferably an alkyl group having 1 to 6 carbon atoms, more preferably an alkyl group having 1 to 3 carbon atoms.

[0111] In formula (40), 1 preferably represents an integer of 0 to 2, more preferably 0 or 1, independently of one another.

[0112] Specific examples of the structures represented by formulas (31) to (33), (39) and (40) include structures represented by formulas (41) to (56). In these formulas, * represents a bond.

[0113]

[0114] In one embodiment of the present invention, when the PI resin constituting the PI film contains, as Y in formula (1), at least one structure selected from the group consisting of structures represented by formulas (31) to (33), (39), and (40), the proportion of structural units derived from tetracarboxylic acid anhydrides in which Y in formula (1) is at least one structure selected from the group consisting of structures represented by formulas (31) to (33), (39), and (40), particularly the proportion of structural units derived from tetracarboxylic acid anhydrides in which Y in formula (1) is at least one structure selected from the group consisting of structures represented by formulas (32), (39), and (40), is preferably 30 mol% or more, more preferably 50 mol% or more, even more preferably 70 mol% or more, particularly preferably 90 mol% or more, and preferably 100 mol% or less, relative to the total amount of structural units (A). This proportion within the above range is advantageous in improving the yield strength, water resistance, drying speed, and dielectric properties of the laminate. The proportion of the structural units, for example, １ This can be measured using H-NMR or calculated from the ratio of raw materials used. The same applies hereinafter to the calculation of the proportion of structural units in PI resins. In addition, in this specification, the "total amount" of structural units refers to the amount of one unit when the structural unit consists of one unit, and refers to the total amount of those units when the structural unit consists of two or more units.

[0115] (Structural Unit (A1) and Structural Unit (A2)) In one embodiment of the present invention, the PI resin contained in the PI film, preferably the PI resin contained in at least one of the layers (PI-1) and (PI-2), or at least one of the layers (PI-1) to (PI-3), contains a structural unit (A), and the structural unit (A) is represented by the formula (A1): [In formula (A1), R ａ１ each independently represent a halogen atom, or an alkyl group, alkoxy group, aryl group, or aryloxy group which may have a halogen atom, and k represents an integer of 0 to 2], and / or a structural unit (A1) (hereinafter, may be simply referred to as structural unit (A1)) derived from a tetracarboxylic acid anhydride represented by formula (A2): [In formula (A2), R ａ２each independently represent a halogen atom, or an alkyl group, alkoxy group, aryl group, or aryloxy group which may have a halogen atom, and each l independently represent an integer of 0 to 3.

[0116] When the PI resin contains the structural unit (A1) and / or the structural unit (A2) as the structural unit (A), the yield strength, water resistance, drying speed, and dielectric properties of the laminate can be improved. In addition, the CTE tends to decrease, and improved dimensional stability of the laminate can be expected.

[0117] From the viewpoint of improving the yield strength, water resistance, drying speed, dielectric properties, CTE, etc. of the laminate, in the formulas (A1) and (A2), R ａ１ and R ａ２ are preferably, each independently, an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, or an aryl group having 6 to 12 carbon atoms. Examples of the alkyl group having 1 to 6 carbon atoms include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a sec-butyl group, a tert-butyl group, an n-pentyl group, a 2-methylbutyl group, a 3-methylbutyl group, a 2-ethylpropyl group, and an n-hexyl group. Examples of the alkoxy group having 1 to 6 carbon atoms include a methoxy group, an ethoxy group, a propyloxy group, an isopropyloxy group, an n-butoxy group, an isobutoxy group, a sec-butoxy group, a tert-butoxy group, a pentyloxy group, a hexyloxy group, and a cyclohexyloxy group. Examples of the aryl group having 6 to 12 carbon atoms include a phenyl group, a tolyl group, a xylyl group, a naphthyl group, and a biphenyl group. R ａ１ and R ａ２ The hydrogen atoms contained in R may be substituted with halogen atoms, and examples of the halogen atoms include fluorine atoms, chlorine atoms, bromine atoms, and iodine atoms. ａ１ and R ａ２ are each independently preferably an alkyl group having 1 to 6 carbon atoms, more preferably an alkyl group having 1 to 3 carbon atoms.

[0118] The bonding positions of the two carboxylic acid anhydrides bonded to the benzene ring in formula (A1) are not particularly limited, but from the viewpoint of improving the yield strength, water resistance, drying speed, dielectric properties, CTE, etc. of the laminate, the bonding positions are preferably the 1,2-positions and the 4,5-positions, or the 1,2-positions and the 3,4-positions, and more preferably the 1,2-positions and the 4,5-positions. k is preferably 0 or 1, and more preferably 0.

[0119] The bonding positions of the two carboxylic acid anhydrides bonded to the benzene rings constituting the biphenyl skeleton in formula (A2) are not particularly limited, and may be independently at the 3,4-position or the 2,3-position based on the single bond bonding the two benzene rings, with the 3,4-position being preferred from the viewpoint of improving the yield strength, water resistance, drying speed, dielectric properties, CTE, etc. of the laminate. In formula (A2), 1 is independently preferably an integer of 0 to 2, more preferably 0 or 1, and even more preferably 0.

[0120] In a preferred embodiment of the present invention, formula (A1) is represented by formula (A1-1): In another preferred embodiment of the present invention, the structural unit (A2) is a structural unit (A1-1) represented by the formula (A2-1): The structural unit (A2-1) is represented by the following formula: When the PI resin contains the structural unit (A1-1) and / or the structural unit (A2-1) as the structural unit (A), the laminate is advantageously improved in terms of yield strength, water resistance, drying speed, and dielectric properties. Furthermore, the CTE tends to decrease, and improved dimensional stability of the laminate can be expected.

[0121] In one embodiment of the present invention, when the PI resin contains the structural unit (A1) and / or the structural unit (A2), the content thereof is preferably 10 mol% or more, more preferably 15 mol% or more, even more preferably 20 mol% or more, even more preferably 25 mol% or more, and particularly preferably 30 mol% or more, based on the total amount of the structural unit (A), and is preferably 90 mol% or less, more preferably 85 mol% or less, even more preferably 80 mol% or less, even more preferably 75 mol% or less, and particularly preferably 70 mol% or less. When the contents of the structural unit (A1) and the structural unit (A2) are within the above ranges, the laminate is advantageously improved in terms of yield strength, water resistance, drying speed, and dielectric properties. Furthermore, the CTE tends to decrease, and improved dimensional stability of the laminate can be expected.

[0122] Furthermore, in one embodiment of the present invention, when the PI resin contains the structural unit (A1) and the structural unit (A2), the content ratio (molar ratio, (A1):(A2)) is preferably 10:90 to 90:10, more preferably 15:85 to 80:20, even more preferably 20:80 to 70:30, and even more preferably 25:75 to 65:35. When the content ratio of the structural unit (A1) to the structural unit (A2) is within the above range, the above-mentioned effects of the present invention that are expected from the PI resin containing the structural unit (A1) and / or the structural unit (A2) are more easily achieved, and these effects can be further enhanced.

[0123] In one embodiment of the present invention, the PI resin-containing layer preferably comprises one or more of the following structures: - In layers (PI-1) and (PI-2), or layers (PI-1) to (PI-3) in the PI film, the PI resin each comprises at least one of the structural unit (A1) and the structural unit (A2); - In layers (PI-1) and (PI-2), or layers (PI-1) to (PI-3) in the PI film, the PI resin each comprises the structural unit (A1); - In at least one PI resin-containing layer in the PI film, preferably the TPI layer, the PI resin comprises the structural unit (A1) and the structural unit (A2); In at least one PI resin-containing layer in the PI film, preferably a TPI layer, the PI resin contains the structural unit (A1) and the structural unit (A2), and in at least another PI resin-containing layer, preferably an mPI layer, the PI resin contains the structural unit (A1) and / or the structural unit (A2). In at least one PI resin-containing layer in the PI film, preferably a TPI layer, the PI resin contains the structural unit (A1) and the structural unit (A2), and in at least another PI resin-containing layer, preferably an mPI layer, the PI resin contains the structural unit (A1) but is substantially free of the structural unit (A2). In this specification, "substantially free of structural units" means that the content of the structural unit is 1% by mass or less, preferably 0.1% by mass or less, more preferably 0.01% by mass or less, and particularly preferably 0.001% by mass or less. For example, "substantially free of the structural unit (A2)" means that the content of the structural unit (A2) is 1% by mass or less, preferably 0.1% by mass or less, more preferably 0.01% by mass or less, and particularly preferably 0.001% by mass or less, relative to the total amount of the structural unit (A). Hereinafter, the same applies to other structural units, unless otherwise clearly stated. In this specification, "at least one PI resin-containing layer" or "at least one PI resin-containing layer" can be interpreted as "at least one of the PI resin-containing layers (PI-1) and (PI-2), or at least one of the PI resin-containing layers (PI-1) to (PI-3)."

[0124] (Structural Unit (A3)) In one embodiment of the present invention, the resin contained in the PI film, preferably the PI resin contained in at least one of the layers (PI-1) and (PI-2), or at least one of the layers (PI-1) to (PI-3), contains, as the structural unit (A), a PI resin represented by the formula (A3): [In formula (A3), Z represents a divalent organic group, R ａ３ each independently represent a halogen atom, or an alkyl group, alkoxy group, aryl group, or aryloxy group which may have a halogen atom, and each s independently represent an integer of 0 to 3.

[0125] When the PI resin contains the structural unit (A3) as the structural unit (A), it can be advantageous in improving the yield strength, water resistance, drying speed, and dielectric properties of the laminate. Furthermore, the CTE tends to decrease, and the dimensional stability of the laminate can be expected to improve. Furthermore, even at a relatively low imidization temperature (e.g., 350°C or lower), the yield strength and dielectric properties of the resulting laminate can be improved. Therefore, even when a laminate is produced by thermally imidizing a PI resin precursor coating film in a laminate configuration with a metal layer, deterioration of the metal layer surface can be suppressed, and a laminate having high yield strength and excellent high-frequency characteristics can be obtained.

[0126] R in formula (A3) ａ３ As the formula (39), R ａ３ In formula (A3), each s independently preferably represents 0 or 1, more preferably 0.

[0127] Examples of Z in formula (A3) include the same divalent organic groups as those exemplified as Z in formula (39) above, and preferred embodiments are also the same.

[0128] 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).

[0129] When the PI resin contained in the PI film contains the structural unit (A3-1) and / or the structural unit (A3-2) as the structural unit (A), this can be advantageous in improving the yield strength, water resistance, drying speed, and dielectric properties of the laminate. Furthermore, the CTE tends to decrease, and improved dimensional stability of the laminate can be expected. Furthermore, even at relatively low imidization temperatures (e.g., 350°C or lower), the yield strength and dielectric properties of the resulting laminate can be improved. Therefore, even when a laminate is produced by thermally imidizing a PI resin precursor coating film in a laminate configuration with a metal layer, deterioration of the metal layer surface can be suppressed, resulting in a laminate that has high yield strength and excellent high-frequency characteristics.

[0130] In one embodiment of the present invention, when the PI resin contained in the PI film, preferably at least one PI resin-containing layer, more preferably at least layer (PI-1), and even more preferably the mPI layer, contains the structural unit (A3), particularly the structural unit (A3-1) and / or the structural unit (A3-2), as the structural unit (A), the PI resin is not too rigid and can have a flexible structure with a certain degree of freedom, which makes it easier to form a branched structure by heating during imidization and further improves the yield strength of the resulting laminate. Furthermore, Df is more likely to be reduced, and the CTE is reduced, tending to improve the dimensional stability of the laminate.

[0131] In one embodiment of the present invention, when the PI resin contains the structural unit (A3), the content thereof is preferably 3 mol% or more, more preferably 5 mol% or more, even more preferably 7 mol% or more, and even more preferably 10 mol% or more, relative to the total amount of the structural unit (A). It may be, for example, 20 mol% or more, 30 mol% or more, or 40 mol% or more. Furthermore, the content of the structural unit (A3) is preferably 80 mol% or less, more preferably 70 mol% or less, even more preferably 65 mol% or less, and even more preferably 60 mol% or less. When the content of the structural unit (A3) is within the above range, the effects of the present invention that are expected from the PI resin containing the structural unit (A3) are more easily achieved, and these effects can be further enhanced.

[0132] In another embodiment of the present invention, when the PI resin contained in the PI film, preferably at least the PI resin-containing layer (PI-1), contains the structural unit (A3), the structural unit (A3) preferably accounts for 50 mol% or less (0 to 50 mol%) of the structural unit (A3) relative to the total amount of the structural units (A). That is, in such an embodiment, the structural unit (A) contained in the PI resin may or may not contain the structural unit (A3). When the structural unit (A3) is contained, it is contained in an amount of 50 mol% or less. Furthermore, the content of the structural unit (A3) relative to the total amount of the structural units (A) is more preferably 45 mol% or less, even more preferably 35 mol% or less, even more preferably 25 mol% or less, particularly preferably 15 mol% or less, especially more preferably 5 mol% or less, and especially preferably 1 mol% or less, and the lower limit may be 0 mol% or more. When the content of the structural unit (A3), particularly the structural unit (A3-1) and / or the structural unit (A3-2) in the PI resin is at most the above upper limit, the yield strength, water resistance, drying speed, and dielectric properties of the laminate can be further improved. In addition, the CTE tends to decrease, and improved dimensional stability of the laminate can be expected.

[0133] In one embodiment of the present invention, it is more preferable that the PI resin in at least one PI resin-containing layer constituting the PI film, preferably the TPI layer, contains the structural unit (A1) and the structural unit (A2), and that the PI resin in at least another PI resin-containing layer, preferably the mPI layer, contains at least two structural units selected from the structural unit (A1), the structural unit (A2), and the structural unit (A3), preferably the structural unit (A1) and the structural unit (A2) and / or the structural unit (A3).

[0134] (Structural Unit (A4)) In one embodiment of the present invention, the PI resin may contain, as the structural unit (A), a structural unit (A4) (hereinafter sometimes simply referred to as structural unit (A4)) derived from a tetracarboxylic acid anhydride other than the structural units (A1), (A2), and (A3). In this specification, "structural unit (A4) derived from a tetracarboxylic acid anhydride other than the structural units (A1), (A2), and (A3)" refers to a structural unit derived from a tetracarboxylic acid anhydride that does not fall under any of the structural units (A1), (A2), and (A3), and the "content of structural unit (A4)" refers to the total amount of structural unit (A4) when multiple structural units (A4) are present.

[0135] In one embodiment of the present invention, examples of the structural unit (A4) include a structural unit derived from a tetracarboxylic acid anhydride in which Y in formula (1) is represented by formula (31) or formula (33) to formula (38). From the viewpoint of improving the yield strength, water resistance, drying speed, and dielectric properties of the laminate, preferably, Y in formula (1) is a structural unit derived from a tetracarboxylic acid anhydride represented by formula (42), formula (44) to formula (49), or formula (53), and more preferably, Y in formula (1) is a structural unit derived from a tetracarboxylic acid anhydride represented by formula (42), formula (46), formula (49), or formula (53).

[0136] In one embodiment of the present invention, when the PI resin contains the structural unit (A4), the content thereof, relative to the total amount of the structural unit (A), may be, for example, 0.01 to 55 mol %, or 0.01 to 40 mol %, and is preferably 40 mol % or less, more preferably 35 mol % or less, even more preferably 30 mol % or less, and particularly preferably 25 mol % or less, and is usually 0.01 mol % or more, and preferably 10 mol % or more.

[0137] (Diamine-derived structural unit (B)) The PI resin constituting the PI film usually contains a diamine-derived structural unit (B) (hereinafter, sometimes simply abbreviated as structural unit (B)). The structural unit (B) is, for example, a structural unit represented by formula (2): In the formula (2), X represents a divalent organic group.

[0138] In formula (2), X represents a divalent organic group, preferably a divalent organic group having 2 to 100 carbon atoms. Examples of divalent organic groups include divalent aromatic groups and divalent aliphatic groups. Examples of divalent aliphatic groups include divalent acyclic aliphatic groups and divalent cyclic aliphatic groups. Among these, from the viewpoint of improving the strength, water resistance, drying speed, and dielectric properties of the laminate, divalent cyclic aliphatic groups and divalent aromatic groups are preferred, and divalent aromatic groups are more preferred. The divalent organic group may have a hydrogen atom substituted with a halogen atom, a hydrocarbon group, an alkoxy group, or a halogenated hydrocarbon group. In such cases, the number of carbon atoms in these groups is preferably 1 to 8. In this specification, a divalent aromatic group is a divalent organic group having an aromatic group, and may include an aliphatic group or other substituent as part of its structure. Furthermore, a divalent aliphatic group is a divalent organic group having an aliphatic group, and may contain other substituents as part of its structure, but does not include an aromatic group.

[0139] In one embodiment of the present invention, the PI resin may contain multiple types of X, which may be the same or different from one another. Examples of X in formula (2) include groups (structures) represented by formulas (60) to (65); and groups in which a hydrogen atom in a group represented by formulas (60) to (65) is substituted with a methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, isobutyl group, sec-butyl group, tert-butyl group, fluoro group, chloro group, or trifluoromethyl group.

[0140] [In formula (60) and formula (61), R ａ and R ｂ each independently represents a halogen atom, or an alkyl group, alkoxy group, aryl group, or aryloxy group which may have a halogen atom; R ａ and R ｂ Each hydrogen atom contained in may be substituted with a halogen atom, and each W is independently a single bond, —O—, or —CH ２ -, -CH ２ -CH ２ -, -CH(CH ３ ) -, -C(CH３ ) ２ -, -C(CF ３ ) ２ -, -COO-, -OOC-, -SO-, -SO ２ -, -S-, -CO-, -N(R ｃ )- or -CONH-, R ｃ represents a monovalent hydrocarbon group having 1 to 12 carbon atoms which may be substituted with a hydrogen atom or a halogen atom; t' represents an integer of 0 to 4; u represents an integer of 0 to 4; n represents an integer of 0 to 4; in formula (62), ring A represents a cycloalkane ring having 3 to 8 carbon atoms; R ｄ represents an alkyl group having 1 to 20 carbon atoms; r represents an integer of 0 or more and (the number of carbon atoms in ring A - 2) or less; S1 and S2 each independently represent an integer of 0 to 20; and in formulas (60) to (65), * represents a bond.

[0141] Other examples of X in formula (2) include divalent acyclic aliphatic groups such as linear or branched alkylene groups, such as ethylene, trimethylene, tetramethylene, pentamethylene, hexamethylene, propylene, 1,2-butanediyl, 1,3-butanediyl, 1,12-dodecanediyl, 2-methyl-1,2-propanediyl, and 2-methyl-1,3-propanediyl. In the divalent acyclic aliphatic groups, hydrogen atoms may be substituted with halogen atoms, and carbon atoms may be substituted with heteroatoms, such as oxygen atoms and nitrogen atoms.

[0142] Among these, from the viewpoint of improving the yield strength, water resistance, drying speed, and dielectric properties of the laminate, the PI resin in the present invention preferably contains, as X in formula (2), a structure represented by formula (60) or formula (61), and more preferably contains a structure represented by formula (60).

[0143] In formula (60) and formula (61), the bond of each benzene ring or each cyclohexane ring may be bonded at any of the ortho-, meta-, or para-position, or the α-, β-, or γ-position, based on -W- or the single bond connecting each benzene ring or each cyclohexane ring, and from the viewpoint of improving the yield strength, water resistance, drying speed, and dielectric properties of the laminate, it can be bonded preferably at the meta- or para-position, or the β- or γ-position, more preferably at the para- or γ-position. When the amino group directly bonded to the benzene ring and the divalent linking group -W- are at the meta-position, the flexibility of the polyimide molecular chain tends to be improved.

[0144] In formula (60) and formula (61), R ａ and R ｂ are each independently preferably a halogen atom, or an alkyl group, alkoxy group or aryl group which may have a halogen atom, more preferably a halogen atom, an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, or an aryl group having 6 to 12 carbon atoms. Examples of the alkyl group having 1 to 6 carbon atoms, the alkoxy group having 1 to 6 carbon atoms, and the aryl group having 6 to 12 carbon atoms include those exemplified above. ａ and R ｂ The hydrogen atoms contained in R may be substituted, independently of one another, with a halogen atom, and examples of the halogen atom include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom. ａ and R ｂ are preferably, independently of one another, an alkyl group having 1 to 6 carbon atoms or a fluorinated alkyl group having 1 to 6 carbon atoms, and from the viewpoint of adhesion to a metal layer or the like, are more preferably fluorine-free alkyl groups having 1 to 6 carbon atoms, even more preferably fluorine-free alkyl groups having 1 to 3 carbon atoms, and particularly preferably a methyl group.

[0145] In the formula (60) and the formula (61), t' and u are each independently preferably an integer of 0 to 2, more preferably 0 or 1.

[0146] In the formula (60) and the formula (61), each W is preferably a single bond, —O—, or —CH ２ -, -C(CH３ ) ２ -, -C(CF ３ ) ２ -, -SO ２ -, -S-, -COO-, -OOC- or -CO-, and more preferably a single bond, -O- or -CH ２ -, -C(CH ３ ) ２ -, -C(CF ３ ) ２ -, -COO-, -OOC- or -CO-, and more preferably a single bond, -O- or -CH ２ - or -C(CH ３ ) ２ -, and particularly preferably -O- or -C(CH ３ ) ２ - is.

[0147] In formula (60) and formula (61), n ​​is preferably an integer of 0 to 3, more preferably 1 to 3. When n is 2 or more, a plurality of W, R ａ and t' may be the same or different, and the positions of the bonds of each benzene ring relative to -W- may be the same or different.

[0148] When the PI resin of the present invention contains two or more structures represented by either formula (60) or formula (61) as X in formula (2), W, n, R ａ , R ｂ , t′ and u are independently W, n, R in the other formulas (60) and (61). ａ , R ｂ , t' and u may be the same or different.

[0149] In formula (62), examples of the cycloalkane ring having 3 to 8 carbon atoms represented by ring A include a cyclopropane ring, a cyclobutane ring, a cyclopentane ring, a cyclohexane ring, a cycloheptane ring, and a cyclooctane ring, and preferably a cycloalkane ring having 4 to 6 carbon atoms. In ring A, the bonds may or may not be adjacent to each other. For example, when ring A is a cyclohexane ring, the two bonds may be in the α-position, β-position, or γ-position relationship, and preferably in the β-position or γ-position relationship.

[0150] R in formula (62) ｄ is preferably an alkyl group having 1 to 10 carbon atoms. In formula (62), r is preferably 0 or more and preferably 4 or less. S1 and S2 in formula (62) are each independently preferably 0 or more, more preferably 2 or more, and preferably 15 or less.

[0151] Specific examples of the structures represented by formulas (60) to (62) include structures represented by formulas (71) to (92). In these formulas, * represents a bond.

[0152]

[0153] In one embodiment of the present invention, when the PI resin constituting the PI film contains at least one diamine-derived structural unit represented by formula (60) or formula (61) as X in formula (2), the proportion of the diamine-derived structural unit represented by formula (60) or formula (61) in formula (2) relative to the total amount of structural unit (B) is preferably 30 mol% or more, more preferably 50 mol% or more or more than 50 mol%, even more preferably 70 mol% or more, particularly preferably 90 mol% or more, and preferably 100 mol% or less. When the proportion of the diamine-derived structural unit represented by formula (60) or formula (61) in formula (2) is within the above range, the yield strength, water resistance, drying speed, and dielectric properties of the laminate can be improved. Furthermore, the CTE tends to decrease, and improved dimensional stability of the laminate can be expected.

[0154] (Structural Unit (B1)) In one embodiment of the present invention, the PI resin contained in the PI film, preferably the PI resin contained in at least one of the layers (PI-1) and (PI-2), or at least one of the layers (PI-1) to (PI-3), contains a structural unit (B), and the structural unit (B) is represented by the formula (B1): [In formula (B1), R ｂ１ each independently represents a halogen atom, or an alkyl group, alkoxy group, aryl group, or aryloxy group which may have a halogen atom; W each independently represents -O-, -CH ２ -, -CH ２ -CH ２ -, -CH(CH ３ ) -, -C(CH ３ ) ２ -, -C(CF ３ ) ２ -, -COO-, -OOC-, -SO-, -SO ２ -, -S-, -CO-, -N(R ｃ )- and -CONH-, or a single bond (where m is 2 or more and at least one W is the divalent linking group); R ｃ represents a hydrogen atom or a monovalent hydrocarbon group of 1 to 12 carbon atoms which may be substituted with a halogen atom, m represents an integer of 1 to 4, and each q independently represents an integer of 0 to 4.

[0155] When the PI resin contains the structural unit (B1) as the 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, which is expected to improve the dimensional stability of the laminate and may also contribute to improving adhesion to the metal layer. Furthermore, even at a relatively low imidization temperature (e.g., 350°C or lower), the yield strength and dielectric properties of the resulting laminate can be improved. Therefore, even when a laminate is produced by thermally imidizing a PI resin precursor coating film in a laminate configuration with a metal layer, deterioration of the metal layer surface can be suppressed, and a laminate having high yield strength and excellent high-frequency characteristics can be obtained.

[0156] R in formula (B1) ｂ１ As the formula (60), R ａ and R ｂ In formula (B1), q's are each independently preferably an integer of 0 to 2, more preferably 0 or 1. In formula (B1), m's is preferably an integer of 1 to 3, more preferably 2 or 3, from the viewpoint of improving the yield strength, water resistance, drying speed, dielectric properties, CTE, etc. of the laminate. In formula (B1), when a plurality of W, R ｂ１ and q may be the same or different, and each benzene ring is -NH ２ The positions of -W- relative to the reference atom may be the same or different.

[0157] In formula (B1), each —W— is independently —NH of each benzene ring. ２ With respect to m, they may be bonded at any of the ortho, meta, or para positions, or the α, β, or γ positions, preferably the meta or para positions, or the β or γ positions, more preferably the para or γ positions. When m is 2 or more, in the benzene ring to which two Ws are bonded, the bonding positions of the two Ws may be in an ortho, meta, or para relationship, or in an α, β, or γ relationship, preferably in a meta or para relationship, or in a β or γ relationship.

[0158] Specific examples of the structure represented by formula (B1) include structures represented by formulas (B1-1) to (B1-6). R in formula (B1-1) to formula (B1-6) ｂ１ and q is R in formula (B1). ｂ１ and q are defined the same as W １ ~W ６ are each independently —O—, —CH ２ -, -CH ２ -CH ２ -, -CH(CH ３ ) -, -C(CH ３ ) ２ -, -C(CF ３ ) ２-, -COO-, -OOC-, -SO-, -SO ２ -, -S-, -CO-, -N(R ｃ represents a divalent linking group selected from the group consisting of ——— and —CONH—; R ｃ represents a monovalent hydrocarbon group having 1 to 12 carbon atoms which may be substituted with a hydrogen atom or a halogen atom. Note that compounds of formula (B1-4) which overlap with formula (B1-3) are treated as compounds of formula (B1-3). Hereinafter, the structural units derived from formulas (B1-1) to (B1-6) may be referred to as structural unit (B1-1) to structural unit (B1-6), respectively.

[0159] R in formulas (B1-1) to (B1-6) ｂ１ and q is R in formula (B1). ｂ１ The same embodiments as those exemplified as and q are exemplified, and the preferred embodiments are also the same.

[0160] W in formulas (B1-1) to (B1-6) １ ~W ６ are each independently —O—, —CH ２ -, -CH ２ -CH ２ -, -CH(CH ３ ) -, -C(CH ３ ) ２ -, -C(CF ３ ) ２ -, -COO-, -OOC-, -SO ２ W in formula (B1-1) is preferably -, -S-, -CO- or -CONH-. １ is preferably —O—, —CH ２ -, -C(CH ３ ) ２ -, -SO ２ -, -S- or -CO-. W in formula (B1-2), formula (B1-4) and formula (B1-6) ２ , W ４ and W ６ are each preferably —O—. ３ is preferably —O—, —CH ２ -, -C(CH ３ ) ２ -, -SO ２-, -CO- or -CONH-, and W in formula (B1-5) ５ is preferably —C(CH ３ ) ２ -, -O-, -SO ２ - or -CO-.

[0161] In one embodiment of the present invention, the PI film in the laminate of the present invention preferably contains, as the structural unit (B), a structural unit derived from a diamine in which m in formula (B1) is 1 or 2, such as the structural unit (B1-1) and / or the structural unit (B1-2). A preferred structural unit derived from a diamine in which m is 2 is, for example, the structural unit (B1-2). The inclusion of such a structural unit can improve the yield strength, water resistance, drying rate, and dielectric properties of the laminate. Furthermore, the CTE tends to decrease, and improved dimensional stability of the laminate can be expected. Furthermore, the inclusion of these structural units can also contribute to improved adhesion between the PI film and the metal layer.

[0162] In another embodiment of the present invention, the PI film in the laminate of the present invention preferably contains, as the structural unit (B), a structural unit derived from a diamine in which m is 3 or 4, such as the structural units (B1-3) to (B1-6), and more preferably a structural unit derived from a diamine in which m is 3. A preferred structural unit derived from a diamine in which m is 3 is, for example, the structural unit (B1-5). The inclusion of such a structural unit can improve the yield strength, water resistance, drying rate, and dielectric properties of the laminate. Furthermore, the CTE tends to decrease, and improved dimensional stability of the laminate can be expected. Furthermore, the inclusion of these structural units can also contribute to improved adhesion between the PI film and the metal layer.

[0163] In one embodiment of the present invention, the structural unit (B1) is preferably the structural unit (B1-2), and the structural unit (B1-2) is more preferably a structural unit represented by formula (B1-2') and / or formula (B1-2''). R in formula (B1-2') and formula (B1-2'') ｂ１ , W ２ , and q is R in formula (B1-2). ｂ１ , W ２, and q are defined the same.

[0164] In one embodiment of the present invention, the structural unit represented by formula (B1-2') or formula (B1-2'') is preferably a structural unit represented by formula (B1-2'a) or formula (B1-2''a), respectively. The inclusion of the above structural units as structural unit (B) can improve the yield strength, water resistance, drying speed, and dielectric properties of the laminate. Furthermore, the CTE tends to decrease, and the dimensional stability of the laminate can be expected to improve. Furthermore, the inclusion of these structural units can also contribute to improving the adhesion between the PI film and the metal layer.

[0165] In another embodiment of the present invention, the structural unit (B1) is preferably the structural unit (B1-5), and the structural unit (B1-5) is more preferably a structural unit represented by formula (B1-5a). When the structural unit (B) contains the above structural unit, it is advantageous in terms of improving the yield strength and dielectric properties of the laminate and reducing the CTE.

[0166] In one embodiment of the present invention, when the PI resin constituting the PI film contains the structural unit (B1), its content is preferably 3 mol% or more, more preferably 5 mol% or more, even more preferably 7 mol% or more, and even more preferably 10 mol% or more, relative to the total amount of the structural units (B), and may be, for example, 20 mol% or more, 30 mol% or more, or 40 mol% or more. Having the content of the structural unit (B1) at or above the above-mentioned lower limit is advantageous in improving the yield strength, water resistance, drying speed, and dielectric properties of the laminate, and reducing the CTE. Furthermore, since a higher total amount of the structural unit (B1) tends to increase adhesion to the metal layer, from this perspective, the content of the structural unit (B1) may be, for example, 50 mol% or more, 60 mol% or more, or 70 mol% or more, relative to the total amount of the structural units (B). The content of the structural unit (B1) is preferably 99 mol% or less, more preferably 95 mol% or less, and even more preferably 90 mol% or less, relative to the total amount of the structural units (B).

[0167] <Structural Unit (B2)> In one embodiment of the present invention, the PI resin contained in the PI film, preferably the PI resin contained in at least one of the layers (PI-1) and (PI-2), or at least one of the layers (PI-1) to (PI-3), contains, as the structural unit (B), a PI resin represented by the formula (B2): [In formula (B2), R ｂ２ are each independently a halogen atom, or an alkyl group, alkoxy group, aryl group, or aryloxy group which may have a halogen atom, and p is an integer of 0 to 4. When the structural unit (B) contains the structural unit (B2), the PI resin can have a flexible structure with a certain degree of freedom without being too rigid, which makes it easier to form a branched structure by heating during imidization and also tends to increase crystallinity, which is advantageous in terms of improving the yield strength, dielectric properties, water resistance, and drying speed of the laminate, as well as reducing the CTE.

[0168] In formula (B2), R ｂ２ preferably each independently represents a halogen atom, or an alkyl group, alkoxy group, or aryl group which may have a halogen atom, and more preferably represents a halogen atom, an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, or an aryl group having 6 to 12 carbon atoms. Examples of the alkyl group having 1 to 6 carbon atoms, the alkoxy group having 1 to 6 carbon atoms, and the aryl group having 6 to 12 carbon atoms include those exemplified above. R ｂ２ The hydrogen atoms contained in R may be substituted with halogen atoms, independently of each other, and examples of the halogen atoms include the same as those mentioned above. ｂ２ are each independently preferably an alkyl group having 1 to 6 carbon atoms or a fluorinated alkyl group having 1 to 6 carbon atoms, and from the viewpoint of adhesion to a metal layer or the like, are more preferably a fluorine-free alkyl group having 1 to 6 carbon atoms, even more preferably a fluorine-free alkyl group having 1 to 3 carbon atoms, and particularly preferably a methyl group.

[0169] In formula (B2), p's are each independently preferably an integer of 0 to 2, more preferably 0 or 1.

[0170] In formula (B2), —NH bonded to each benzene ring ２ The groups may be bonded at any of the ortho-, meta-, or para-positions, or the α-, β-, or γ-positions, based on the single bond connecting each benzene ring. From the viewpoint of improving the strength, dielectric properties, water resistance, and drying speed of the laminate, and reducing the CTE, the groups are preferably bonded at the meta- or para-positions, or the β- or γ-positions, and more preferably at the para- or γ-positions.

[0171] In a preferred embodiment of the present invention, formula (B2) is represented by formula (B2'): It is preferably represented by the formula (B2). When the PI resin constituting at least one PI resin-containing layer contains, as the structural unit (B), a PI resin having a structural unit (B2), particularly a diamine-derived structural unit represented by formula (B2'), the PI resin is not too rigid and can have a flexible structure with a certain degree of freedom. This makes it easier to form a branched structure by heating during imidization, and also tends to increase crystallinity, which is advantageous in improving the strength, water resistance, drying speed, and dielectric properties of the laminate, as well as reducing the CTE. Furthermore, since the above effects can be obtained even at relatively low imidization temperatures (e.g., 350°C or lower), even when a laminate is produced by thermally imidizing a PI resin precursor coating film in a laminate configuration with a metal layer, deterioration of the metal layer surface can be suppressed, resulting in a laminate having both high strength and excellent high-frequency characteristics.

[0172] In one embodiment of the present invention, when the PI resin contains the structural unit (B2), its content is preferably 1 mol% or more, more preferably 5 mol% or more, and even more preferably 10 mol% or more, relative to the total amount of the structural units (B). For example, it may be 20 mol% or more, 30 mol% or more, more than 30 mol%, 40 mol% or more, or 50 mol% or more. When the content of the structural unit (B2) is equal to or greater than the above-mentioned lower limit, it is advantageous in improving the yield strength, water resistance, drying speed, and dielectric properties of the laminate, reducing the CTE, etc. Furthermore, the content of the structural unit (B1) is preferably 99 mol% or less, more preferably 95 mol% or less, and even more preferably 92 mol% or less, relative to the total amount of the structural units (B). For example, it may be 90 mol% or less, 80 mol% or less, 70 mol% or less, or 60 mol% or less.

[0173] In one embodiment of the present invention, when the PI resin constituting the PI film contains the structural unit (B1) and the structural unit (B2), the total content thereof is preferably 30 mol% or more, more preferably 40 mol% or more, even more preferably 60 mol% or more, particularly preferably 70 mol% or more, particularly more preferably 80 mol% or more, particularly more preferably 90 mol% or more, particularly more preferably 95 mol% or more, and preferably 100 mol% or less, relative to the total amount of the structural unit (B). When the total content of the structural unit (B1) and the structural unit (B2) is at least the above-mentioned lower limit, the above-mentioned effects of the present invention expected from the PI resin containing the structural unit (B1) and the structural unit (B2) are more easily achieved, and these effects can be further enhanced.

[0174] Furthermore, in one embodiment of the present invention, when the PI resin contains the structural unit (B1) and the structural unit (B2), the content ratio (molar ratio, (B1):(B2)) is preferably 99:1 to 1:99, more preferably 95:5 to 5:95, and even more preferably 92:8 to 8:92, and may be, for example, 92:8 to 20:80, or 90:10 to 60:40. When the content ratio of the structural unit (B1) to the structural unit (B2) is within the above range, the effects of the present invention that are expected from the PI resin containing the structural unit (B1) and the structural unit (B2) are more easily achieved, and these effects can be further enhanced.

[0175] In one embodiment of the present invention, the PI-based resin-containing layer constituting the PI-based film preferably comprises one or more of the following structures: - In layers (PI-1) and (PI-2), or layers (PI-1) to (PI-3) in the PI-based film, the PI-based resin comprises at least one of the structural unit (B1) and the structural unit (B2); - In layers (PI-1) and (PI-2), or layers (PI-1) to (PI-3) in the PI-based film, the PI-based resin comprises the structural unit (B1); - In layers (PI-1) and (PI-2), or layers (PI-1) to (PI-3) in the PI-based film, the PI-based resin comprises the structural unit (B1) and the structural unit (B2). - In at least one PI-based resin-containing layer in the PI-based film, the PI-based resin comprises the structural unit (B1) and the structural unit (B2).

[0176] (Structural Unit (B3)) In one embodiment of the present invention, the structural unit (B) may include a diamine-derived structural unit (B3) (hereinafter, sometimes simply referred to as structural unit (B3)) other than the structural unit (B1) and the structural unit (B2). Examples of the structural unit (B3) include a diamine-derived structural unit in which m in formula (B1) is 0, and a diamine-derived structural unit in formula (2) where X is represented by formulas (61) to (64). Among these, a diamine-derived structural unit in formula (2) where X is represented by formula (74) (a p-phenylenediamine-derived structural unit) is preferred. In this specification, "a diamine-derived structural unit (B3) other than the structural unit (B1) and the structural unit (B2)" refers to a diamine-derived structural unit that is different from both the structural unit (B1) and the structural unit (B2).

[0177] In one embodiment of the present invention, when the structural unit (B) includes the structural unit (B3), the content of the structural unit (B3) relative to the total amount of the structural unit (B) is preferably 25 mol% or less, more preferably 20 mol% or less, and even more preferably 10 mol% or less, and is typically 0.01 mol% or more.

[0178] In one embodiment of the present invention, the polyimide resin contained in the PI resin-containing layer (PI-1) may be the same as or different from the PI resin contained in the PI resin-containing layer (PI-2). From the viewpoints of improving the yield strength, water resistance, drying speed, and dielectric properties of the laminate, reducing the CTE, and the like, it is preferable that the PI resins contained in each layer be different resins. Note that the different resins include not only resins with different types of structural units, but also resins with the same type of structural units but different contents (or ratios) thereof.

[0179] In one embodiment of the present invention, the PI resin-containing layer (PI-1) and the PI resin-containing layer (PI-2) each preferably contain a polyimide resin having structural units (A) derived from at least two types of tetracarboxylic acid anhydrides. In such an embodiment, the yield strength and dielectric properties of the laminate are easily improved, and the CTE is easily reduced.

[0180] In one embodiment of the present invention, the PI resin in the PI resin-containing layer (PI-1) and the PI resin-containing layer (PI-2), or the PI resin-containing layers (PI-1) to (PI-3), preferably the mPI layer and the TPI layer, preferably contains the structural unit (A1) and / or the structural unit (A2) as the structural unit (A) and the structural unit (B1), preferably the structural unit (B1) and the structural unit (B2), as the structural unit (B).

[0181] In a preferred embodiment of the present invention, the PI resin contained in the PI resin-containing layer (PI-1), preferably the mPI layer, constituting the PI film, contains, as the structural unit (A), at least two structural units selected from the structural unit (A1), the structural unit (A2), and the structural unit (A3) (preferably the structural unit (A1) and the structural unit (A2) and / or the structural unit (A3)); the PI resin contained in the PI resin-containing layer (PI-2), preferably the TPI layer, contains, as the structural unit (A), the structural unit (A1) and the structural unit (A2); and the PI resins constituting the PI resin-containing layer (PI-1) and the PI resin-containing layer (PI-2), preferably the mPI layer and the TPI layer, each contain, as the structural unit (B1), preferably the structural unit (B1) and the structural unit (B2), as the structural unit (B).

[0182] In a preferred embodiment of the present invention, when the PI film (L) further comprises a PI resin-containing layer (PI-3), the PI resin contained in the PI resin-containing layer (PI-1), preferably the mPI layer, comprises, as the structural unit (A), at least two structural units selected from the structural unit (A1), the structural unit (A2), and the structural unit (A3) (preferably the structural unit (A1) and the structural unit (A2) and / or the structural unit (A3)); the PI resin contained in the PI resin-containing layer (PI-2) and the PI resin-containing layer (PI-3), preferably the TPI layer, comprises, as the structural unit (A), the structural unit (A1) and the structural unit (A2); and the PI resins contained in the PI resin-containing layers (PI-1) to (PI-3), preferably the mPI layer and the TPI layer, each comprise, as the structural unit (B1), preferably the structural unit (B1) and the structural unit (B2), as the structural unit (B).

[0183] When the mPI layer, TPI layer, layer (PI-1), layer (PI-2), and optionally layer (PI-3) are each configured to contain a combination of the above-described structural units, the PI resin in each layer is not too rigid and can have a flexible structure with a certain degree of freedom, which tends to facilitate the formation of a branched structure upon heating during imidization and to increase crystallinity. Furthermore, the interaction between two adjacent layers can be enhanced. Therefore, the PI resin containing each structural unit makes it easier to achieve the above-described effects of the present invention, and these effects can be further enhanced.

[0184] <Layer (PI-1)> In one embodiment of the present invention, the PI resin constituting layer (PI-1) contains, as the structural unit (A), the structural unit (A1) and / or the structural unit (A2), preferably at least two structural units selected from the structural unit (A1), the structural unit (A2), and the structural unit (A3), and more preferably the structural unit (A1) and the structural unit (A2) and / or the structural unit (A3). When layer (PI-1) contains these structural units, the content of the structural unit (A1) relative to the total amount of the structural units (A) is preferably 20 mol% or more, more preferably 30 mol% or more, even more preferably 35 mol% or more, particularly preferably 40 mol% or more, and is preferably 80 mol% or less, more preferably 75 mol% or less, even more preferably 70 mol% or less, and particularly preferably 65 mol% or less. The content of the structural unit (A2) is preferably 20 mol% or more, more preferably 30 mol% or more, even more preferably 35 mol% or more, particularly preferably 40 mol% or more, and is preferably 80 mol% or less, more preferably 75 mol% or less, even more preferably 70 mol% or less, particularly preferably 65 mol% or less, relative to the total amount of the structural unit (A). The content of the structural unit (A3) is preferably 3 mol% or more, more preferably 5 mol% or more, even more preferably 7 mol% or more, even more preferably 10 mol% or more, and may be, for example, 20 mol% or more, 30 mol% or more, or 40 mol% or more, and is preferably 75 mol% or less, more preferably 70 mol% or less, even more preferably 65 mol% or less, particularly preferably 60 mol% or less, relative to the total amount of the structural unit (A). In another embodiment, the content of the structural unit (A3) is preferably 50 mol% or less, more preferably 45 mol% or less, even more preferably 35 mol% or less, still more preferably 25 mol% or less, particularly preferably 15 mol% or less, particularly preferably 5 mol% or less, and particularly preferably 1 mol% or less, and the lower limit may be 0 mol%. When the contents of the structural unit (A1), the structural unit (A2), and / or the structural unit (A3) are each within the above ranges, the PI resin is not too rigid and can have a flexible structure with a certain degree of freedom, which makes it easier to form a branched structure by heating during imidization and also tends to increase crystallinity.Therefore, a laminate having excellent strength, dielectric properties, and thermal properties can be obtained. Furthermore, the laminate can have excellent water resistance and drying speed.

[0185] On the other hand, in another embodiment of the present invention, the content of the structural unit (A2) in the PI resin constituting layer (PI-1) may be less than the content of the structural unit (A1), and is preferably less than 30 mol %, more preferably 25 mol % or less, even more preferably 20 mol % or less, and particularly preferably 10 mol % or less, relative to the total amount of structural units (A). In one embodiment of the present invention, layer (PI-1) may be substantially free of the structural unit (A2), and the lower limit of the content of the structural unit (A2) may be 0 mol %.

[0186] In one embodiment of the present invention, the PI resin constituting layer (PI-1) preferably contains the structural unit (B1) as the structural unit (B). The structural unit (B1) preferably contains the structural unit (B1-2) and the structural unit (B1-5), more preferably the structural unit (B1-2), and even more preferably the structural unit (B1-2″). The content of the structural unit (B1) in the PI resin constituting layer (PI-1), relative to the total amount of the structural units (B), is preferably 3 mol% or more, more preferably 5 mol% or more, even more preferably 7 mol% or more, and even more preferably 10 mol% or more. For example, it may be 20 mol% or more, 30 mol% or more, or 40 mol% or more. It is also preferably 80 mol% or less, more preferably 75 mol% or less, even more preferably 70 mol% or less, and particularly preferably 65 mol% or less. Furthermore, the PI resin constituting layer (PI-1) preferably further contains the structural unit (B2) as the structural unit (B), and the content thereof, relative to the total amount of the structural units (B), is preferably 10 mol% or more, more preferably 20 mol% or more, even more preferably 30 mol% or more or more than 30 mol%, even more preferably 35 mol% or more, and particularly preferably 40 mol% or more, and is preferably 99 mol% or less, more preferably 95 mol% or less, and even more preferably 92 mol% or less, for example, 90 mol% or less, 80 mol% or less, 70 mol% or less, or 60 mol% or less. When the contents of the structural units (B1) and / or the structural units (B2) are each within the above ranges, the PI resin is not too rigid and can have a flexible structure with a certain degree of freedom, which makes it easier to form a branched structure by heating during imidization and also tends to increase crystallinity. This makes it possible to improve the mechanical properties of the layer (PI-1) and reduce Df, and furthermore, to effectively reduce CTE, thereby obtaining a laminate having excellent yield strength, dielectric properties, and thermal properties. Furthermore, the laminate can have excellent water resistance and drying speed.

[0187] <Layer (PI-2) and Layer (PI-3)> In one embodiment of the present invention, the PI-based film includes a layer (PI-2) and may further include a layer (PI-3). The PI-based resins that make up Layer (PI-2) and Layer (PI-3) each include the structural unit (A) as the structural unit (A1), and preferably include the structural unit (A1) and the structural unit (A2). When these structural units are included, the content of the structural unit (A1) is preferably 10 mol% or more, more preferably 15 mol% or more, and even more preferably 20 mol% or more, relative to the total amount of the structural units (A), and is preferably 80 mol% or less, more preferably 70 mol% or less, and even more preferably 60 mol% or less. Furthermore, the content of the structural unit (A2) is preferably 20 mol% or more, more preferably 30 mol% or more, even more preferably 40 mol% or more, even more preferably 50 mol% or more, and particularly preferably 60 mol% or more, relative to the total amount of the structural unit (A), and is preferably 90 mol% or less, more preferably 85 mol% or less, even more preferably 80 mol% or less, and even more preferably 75 mol% or less. When the content of the structural unit (A1) and / or the structural unit (A2) is within the above range, the PI resin is not too rigid and can have a flexible structure with a certain degree of freedom. This makes it easier to form a branched structure upon heating during imidization and also tends to increase crystallinity. This enables improved mechanical properties and reduced Df of the layers (PI-2) and (PI-3). Furthermore, the CTE can be effectively reduced, resulting in a laminate with excellent yield strength, dielectric properties, and thermal properties. Furthermore, improved adhesion between the PI film and the metal layer can be expected. Furthermore, the laminate can have excellent water resistance and drying speed.

[0188] In one embodiment of the present invention, the content of the structural unit (A3) in the PI resin constituting Layer (PI-2) and Layer (PI-3) is preferably 10 mol % or less, more preferably 8 mol % or less, even more preferably 5 mol % or less, and particularly preferably 3 mol % or less, relative to the total amount of the structural unit (A). In one embodiment of the present invention, Layer (PI-2) and Layer (PI-3) may be substantially free of the structural unit (A3), and the lower limit of the content of the structural unit (A3) may be 0 mol %.

[0189] In one embodiment of the present invention, the PI resin constituting Layer (PI-2) and Layer (PI-3) preferably contains the structural unit (B1) as the structural unit (B). The structural unit (B1) preferably contains the structural unit (B1-2), and more preferably contains the structural unit (B1-2'), which enhances the flexibility of the PI resin. The content of the structural unit (B1) in the PI resin constituting these layers is preferably 20 mol% or more, more preferably 30 mol% or more, even more preferably 35 mol% or more, and particularly preferably 40 mol% or more, relative to the total amount of structural units (B). It is preferably 99 mol% or less, more preferably 95 mol% or less, and even more preferably 92 mol% or less, and may be, for example, 90 mol% or less, 80 mol% or less, 70 mol% or less, or 60 mol% or less. Furthermore, it is preferable that the structural unit (B) further contains a structural unit (B2), and the content thereof is preferably 1 mol% or more, more preferably 5 mol% or more, and even more preferably 10 mol% or more. For example, it may be 20 mol% or more, 30 mol% or more, more than 30 mol%, or 40 mol% or more. It is also preferably 80 mol% or less, more preferably 70 mol% or less, even more preferably 65 mol% or less, and particularly preferably 60 mol% or less. When the content of the structural unit (B1) and / or the structural unit (B2) in the PI resin constituting layers (PI-2) and (PI-3) is within the above ranges, the PI resin is not too rigid and can have a flexible structure with a certain degree of freedom. This makes it easier to form a branched structure by heating during imidization and also tends to increase crystallinity. This enables the mechanical properties of layers (PI-2) and (PI-3) to be improved and Df to be reduced. Furthermore, CTE can also be effectively reduced, resulting in a laminate with even better yield strength, dielectric properties, and thermal properties. Furthermore, the adhesiveness between the PI film and the metal layer can be improved, and the laminate can have excellent water resistance and drying speed.

[0190] The various physical properties (e.g., molecular weight, glass transition temperature) of the PI resin containing the structural unit (A) and / or the structural unit (B) may be appropriately determined based on, for example, the following preferred ranges depending on the role and application of each PI resin-containing layer in the PI film.

[0191] In one embodiment of the present invention, the PI resin constituting the PI film may contain halogen atoms, preferably fluorine atoms, which can be introduced, for example, by the above-mentioned halogen-containing substituents. When the PI resin contains fluorine atoms, the relative permittivity of the resulting PI film is easily reduced, leading to improved dielectric properties of the laminate. Preferred fluorine-containing substituents for incorporating fluorine atoms into the PI resin include, for example, a fluoro group and a trifluoromethyl group. In another embodiment of the present invention, the PI resin preferably does not contain fluorine atoms, from the viewpoint of improving the adhesion of the PI film to the metal layer. For this reason, for example, the PI resin constituting the PI resin-containing layer in contact with the metal layer, preferably the TPI layer, particularly layers (PI-2) and (PI-3) in the PI film, preferably does not contain fluorine atoms. Furthermore, since fluorine-containing PI resins tend to weaken the interactions between molecular chains, if the PI resin does not contain fluorine atoms, the Df of the PI film tends to be reduced.

[0192] When the PI resin contains halogen atoms, the content of halogen atoms, particularly fluorine atoms, in the PI resin is preferably 0.1 to 35 mass%, more preferably 0.1 to 30 mass%, even more preferably 0.1 to 20 mass%, and particularly preferably 0.1 to 10 mass%, based on the mass of the PI resin. When the halogen atom content is equal to or greater than the lower limit, the heat resistance and dielectric properties of the resulting PI film are likely to be enhanced, leading to improved dielectric properties and thermal properties of the laminate. When the halogen atom content is equal to or less than the upper limit, it is advantageous in terms of cost, facilitates a reduction in CTE, and facilitates the synthesis of the PI resin.

[0193] In one embodiment of the present invention, the imidization ratio of the PI resin is preferably 90% or more, more preferably 93% or more, and even more preferably 95% or more, and typically 100% or less. From the viewpoint of improving the yield strength, water resistance, drying speed, dielectric properties, and thermal properties of the laminate, the imidization ratio is preferably equal to or greater than the lower limit. The imidization ratio indicates the ratio of the molar amount of imide bonds in the PI resin to twice the molar amount of structural units derived from tetracarboxylic acid compounds in the PI resin. When the PI resin contains a tricarboxylic acid compound, the imidization ratio indicates the ratio of the molar amount of imide bonds in the PI resin to the sum of twice the molar amount of structural units derived from tetracarboxylic acid compounds in the PI resin and the molar amount of structural units derived from tricarboxylic acid compounds. The imidization ratio can be determined by IR, NMR, or the like.

[0194] In one embodiment of the present invention, the polystyrene-equivalent weight-average molecular weight (Mw) of the PI resin is preferably 5,000 or more, more preferably 10,000 or more, even more preferably 15,000 or more, and particularly preferably 20,000 or more, from the viewpoint of increasing the yield strength of the laminate. Furthermore, from the viewpoint of ease of varnish production and film-forming properties, it is preferably 1,200,000 or less, more preferably 1,000,000 or less, even more preferably 800,000 or less, and particularly preferably 700,000 or less. For example, the Mw of the mPI layer, particularly layer (PI-1) in the PI film, is preferably 5,000 to 800,000, more preferably 10,000 to 700,000. Furthermore, the Mw of the TPI layer, particularly layers (PI-2) and (PI-3) in the PI film, is preferably 10,000 to 1,000,000, more preferably 20,000 to 900,000, respectively.

[0195] In one embodiment of the present invention, the ratio (Mw / Mn) of the weight-average molecular weight (Mw) to the number-average molecular weight (Mn) of the PI resin is preferably 1.1 or more, more preferably 1.3 or more, even more preferably 1.5 or more, and particularly preferably 1.7 or more, from the viewpoint of the yield strength of the laminate and the adhesion between the PI film and the metal layer, and is preferably 15 or less, more preferably 12 or less, even more preferably 11 or less, and particularly preferably 10 or less. For example, the Mw / Mn of an mPI layer, particularly layer (PI-1) in a PI film, is preferably 1.1 to 15, more preferably 1.5 to 10. Furthermore, the Mw / Mn of a TPI layer, particularly layers (PI-2) and (PI-3) in a PI film, is preferably 1.1 to 15, more preferably 1.5 to 10. Note that Mw and Mn can be determined by gel permeation chromatography (hereinafter sometimes referred to as GPC) measurement and standard polystyrene equivalent.

[0196] In one embodiment of the present invention, the Tg of the PI resin is preferably 350°C or lower, more preferably 330°C or lower, even more preferably 310°C or lower, and particularly preferably 300°C or lower, from the viewpoint of improving the yield strength of the resulting laminate and reducing Df. Furthermore, the Tg of the PI resin is preferably 200°C or higher, more preferably 205°C or higher, even more preferably 210°C or higher, and particularly preferably 220°C or higher, from the viewpoint of improving the yield strength of the laminate, reducing Df, and improving thermal properties. When the PI resin-containing layer includes an mPI layer and a TPI layer, the Tg of the PI resin constituting the mPI layer is preferably 350°C or lower, more preferably 330°C or lower, even more preferably 310°C or lower, and particularly preferably 295°C or lower, and preferably 220°C or higher, more preferably 230°C or higher, even more preferably 250°C or higher, even more preferably 260°C or higher, and particularly preferably 270°C or higher. When the Tg of the PI resin constituting the mPI layer is within the above range, the yield strength of the laminate can be increased, and the dielectric properties and thermal properties can be improved. The Tg of the PI resin constituting the TPI layer is preferably 310°C or less, more preferably 300°C or less, even more preferably 290°C or less, even more preferably 270°C or less, and particularly preferably 250°C or less, and is preferably 200°C or more, more preferably 210°C or more, even more preferably 220°C or more, and particularly preferably 230°C or more. When the Tg of the PI resin constituting the TPI layer is within the above range, the yield strength of the laminate can be increased, and in addition to reducing Df and improving thermal properties, the adhesion between the PI film and the metal layer can be improved. The Tg of the PI resin can be measured by dynamic viscoelasticity measurement. For example, it can be calculated based on the peak of a tan δ curve, which is the ratio of the storage modulus (E') to the loss modulus (E'') obtained using a dynamic viscoelasticity measuring device.

[0197] In one embodiment including an mPI layer and a TPI layer as the PI resin-containing layers, when the Tg of the PI resin constituting the mPI layer is within the above-mentioned range, preferably 250 to 330°C, and the Tg of the PI resin constituting the TPI layer is within the above-mentioned range, preferably 220 to 300°C, each PI resin tends to form a preferred high-order structure with suppressed rotational motion. Therefore, in this embodiment, each PI resin-containing layer can be formed using a PI resin having a high-order structure that maintains orientation, which is thought to contribute to improving the strength against deformation of the resulting laminate. Furthermore, because the rotation of polar groups in each PI resin is suppressed and the loss of electrical energy as thermal motion is presumably reduced, using a PI resin with a Tg within the above-mentioned range is thought to result in a PI film with a low Df. Furthermore, by using such a PI resin, the yield strength and dielectric properties of the resulting laminate can be improved even at a low imidization temperature of, for example, 350°C or lower. Therefore, even when a laminate is produced by thermally imidizing a PI resin precursor coating film in a laminate configuration with a metal layer (copper layer), deterioration of the metal layer surface can be suppressed, and a laminate having high yield strength and excellent high-frequency properties can be obtained.

[0198] In one embodiment of the present invention, the PI resin contained in the PI film in the laminate, preferably the PI resin contained in the polyimide resin-containing layer (PI-1), the PI resin contained in the polyimide resin-containing layer (PI-2), and the PI resin contained in the polyimide resin-containing layer (PI-3), each have a storage modulus at 40° C. of 1.0×10 ９ It is preferable that the storage modulus of the PI resin is in this range. When the storage modulus of the PI resin is in this range, the yield strength of the laminate is easily increased. Although the reason for this is not clear, it is thought that the PI resin is likely to have crystallinity and orientation that facilitates improving strength due to the influence of the unevenness at the interface between the PI film and the metal layer, and thus the yield strength is easily improved. Note that suitable ranges for the storage modulus at 40°C of the polyimide resin contained in layer (PI-1), layer (PI-2), and layer (PI-3) can be appropriately selected from the ranges E'1, E'2, and E'3 described below, respectively.

[0199] In one embodiment of the present invention, the PI film preferably satisfies the following relationships: 0.8≦E′1 / E′2≦4.5 (X) 0.8≦E′1 / E′3≦4.5 (Y) [wherein E′1 represents the storage modulus at 40°C of the PI resin contained in the PI resin-containing layer (PI-1), E′2 represents the storage modulus at 40°C of the PI resin contained in the PI resin-containing layer (PI-2), and E′3 represents the storage modulus at 40°C of the PI resin contained in the PI resin-containing layer (PI-3)]. When the PI film satisfies formulas (X) and (Y), the yield strength of the laminate is likely to be increased. While the reason for this is unclear, it is thought to be because the laminate is likely to be less susceptible to stress, particularly in the thickness direction. Furthermore, the water resistance and drying speed of the laminate are also likely to be increased.

[0200] E'1 / E'2 in formula (X) and E'1 / E'3 in formula (Y) are each preferably 0.90 or more, more preferably 0.95 or more, even more preferably 0.98 or more, and particularly preferably 1.00 or more, and are preferably 4.00 or less, more preferably 3.50 or less, even more preferably 3.00 or less, even more preferably 2.50 or less, particularly preferably 2.00 or less, and particularly preferably 1.50 or less. When E'1 / E'2 and E'1 / E'3 are within the above ranges, the yield strength, water resistance, and drying speed of the laminate are likely to be improved. Note that E'1 / E'2 and E'1 / E'3 may be the same or different values.

[0201] In one embodiment of the present invention, E′1 in formula (X) and formula (Y) is, but is not limited to, preferably 1.0×10 ９ Pa or more, more preferably 1.5 × 10 ９ Pa or more, more preferably 2.0 × 10 ９ Pa or more, preferably 1.0 × 10 １１ Pa or less, more preferably 5.0 × 10 １０ Pa or less, more preferably 1.0 × 10 １０ Pa or less, and even more preferably 8.0 × 10 ９ Pa or less, particularly preferably 5.0 × 10 ９ Pa or less or 3.5 x 10 ９When E'1 is in the above range, the yield strength of the laminate is easily improved.

[0202] In one embodiment of the present invention, E'2 in formula (X) and E'3 in formula (Y) are each, but are not limited to, preferably 1.0 × 10 ９ Pa or more, more preferably 1.5 × 10 ９ Pa or more, more preferably 2.0 × 10 ９ Pa or more, preferably 5.0 × 10 １０ Pa or less, more preferably 1.0 × 10 １０ Pa or less, more preferably 8.0 × 10 ９ Pa or less, and even more preferably 5.0 × 10 ９ Pa or less or 3.5 x 10 ９ When E'2 and / or E'3 are within the above ranges, the yield strength of the laminate, as well as the water resistance and drying speed, are likely to be improved. Note that E'2 and E'3 may be the same value or different values.

[0203] In one embodiment of the present invention, the PI resin contained in the PI film in the laminate, preferably the PI resin contained in the PI resin-containing layer (PI-1), the PI resin contained in the PI resin-containing layer (PI-2), and the PI resin contained in the PI resin-containing layer (PI-3), each have a storage modulus at 300° C. of 1.0×10 ８ Pa or more, or 1.0 x 10 ８ From the viewpoint of increasing the yield strength of the laminate, the storage modulus at 300°C of the PI resin contained in the PI resin-containing layer (PI-1) (sometimes referred to as E'1a) is not limited, but is preferably 1.0 x 10 ８ Pa or more, more preferably 1.5 × 10 ８ Pa or more, more preferably 2.0 × 10 ８ Pa or more, for example, 2.5×10 ８ E'1a may be equal to or greater than 1.0 x 10 Pa. １０ Pa or less, more preferably 5.0 × 10 ９ Pa or less, more preferably 1.0 × 10 ９ Pa or less, and even more preferably 8.0 × 10 ８Pa or less, particularly preferably 5.0 × 10 ８ Pa or less, for example, 4.0 × 10 ８ If E'1a is in the above range, the yield strength of the laminate is likely to be improved.

[0204] In one embodiment of the present invention, the storage modulus at 300°C of the PI resin contained in the PI resin-containing layer (PI-2) (sometimes referred to as E'2a) and the storage modulus at 300°C of the PI resin contained in the PI resin-containing layer (PI-3) (sometimes referred to as E'3a) are not limited, but are preferably 1.0 x 10 ８ Pa, more preferably less than 8.0 × 10 ７ Pa or less, more preferably 5.0 × 10 ７ Pa or less, and even more preferably 3.0 × 10 ７ Pa or less, particularly preferably 2.0 × 10 ７ Pa or less, preferably 1.0 × 10 ６ Pa or more, more preferably 5.0 × 10 ６ Pa or more, more preferably 1.0 × 10 ７ When E'2a and / or E'3a are in the above range, the yield strength of the laminate, as well as the water resistance and drying speed, are likely to be improved. Note that E'2a and E'3a may be the same value or different values.

[0205] The storage modulus of the PI resin contained in each PI resin-containing layer can be measured using a dynamic viscoelasticity measuring device, for example, under conditions of a temperature rise rate of 5°C / min from room temperature (e.g., 25°C) to 342°C. The storage modulus of the PI resin may be measured using a PI resin film made of the PI resin, and can be measured, for example, by the method described in the examples.

[0206] E'1 / E'2 and E'1 / E'3 can be controlled by appropriately adjusting the type and composition of the structural units constituting the PI resin contained in each PI resin-containing layer, the molecular weight of the PI resin, the composition and combination of each PI resin-containing layer in the laminate, etc. For example, E'1 / E'2 can be appropriately adjusted to fall within the range of formula (X), and E'1 / E'3 can be appropriately adjusted to fall within the range of formula (Y) based on a preferred embodiment advantageous for improving the yield strength, water resistance, drying speed, and dielectric properties of the laminate, such as the preferred structural units of the PI resin and their contents.

[0207] The Tg and storage modulus of the PI resin can be adjusted by appropriately adjusting the type and composition of the structural units constituting the PI resin, the molecular weight and production method of the PI resin, particularly the imidization conditions, etc. For example, the Tg and storage modulus can be adjusted to fall within the above-mentioned ranges by adjusting them to fall within the ranges described as preferred embodiments in this specification.

[0208] <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, even more preferably 80% by mass or more, and particularly preferably 90% by mass or more, relative to the mass of the resin film. The upper limit of the resin content is not particularly limited, and may be, for example, 100% by mass or less, 99% by mass or less, or 95% by mass or less, relative to the mass of the resin film. In a preferred embodiment of the present invention, the PI resin content in each PI resin-containing layer constituting the PI film is preferably 60% by mass or more, more preferably 70% by mass or more, even more preferably 80% by mass or more, and particularly preferably 90% by mass or more, relative to the mass of the PI resin-containing layer, and may be, for example, 100% by mass or less, 99% by mass or less, or 95% by mass or less. When the resin content is within the above range, a laminate with improved yield strength, dielectric properties, and thermal properties can be obtained.

[0209] Each PI-based resin-containing layer constituting the resin film, preferably the PI-based film, of the present invention may contain a filler as needed. Examples of fillers include metal oxide particles such as silica and alumina, inorganic salts such as calcium carbonate, and polymer particles such as fluororesins and cycloolefin polymers. Fillers can be used alone or in combination of two or more. When a filler is contained, the content of the filler is preferably 50% by mass or less, more preferably 40% by mass or less, and even more preferably 30% by mass or less, relative to the mass of each PI-based resin-containing layer constituting the resin film, preferably the PI-based film, and is preferably 0.01% by mass or more.

[0210] In one embodiment of the present invention, each PI-based resin-containing layer constituting the resin film, preferably the PI-based film, of the present invention may contain additives as needed. Examples of additives include antioxidants, flame retardants, crosslinking agents, surfactants, compatibilizers, imidization catalysts, weathering agents, lubricants, antiblocking agents, antistatic agents, antifogging agents, anti-dripping agents, and pigments. The additives may be used alone or in combination. The content of each additive may be appropriately selected within a range that does not impair the effects of the present invention. When various additives are included, the total content of the additives is preferably 7% by mass or less, more preferably 5% by mass or less, even more preferably 4% by mass or less, particularly preferably 1% by mass or less, and preferably 0.001% by mass or more, based on the mass of each PI-based resin-containing layer constituting the resin film, preferably the PI-based film.

[0211] <Physical Properties of Resin Film> Printed circuits are required to have low transmission loss. Transmission loss is expressed as the sum of dielectric loss, which is loss caused by an electric field generated in a dielectric, and conductor loss, which is loss caused by a current flowing through a conductor. Dielectric loss is known to be approximately proportional to an index E expressed by formula (i): E = Df × (Dk) １／２(i) [In formula (i), Df represents the dielectric loss tangent, and Dk represents the relative permittivity] In the high frequency range used in FPCs for high-speed communication such as 5G, dielectric loss tends to increase, so materials with a small value of the index E and capable of suppressing dielectric loss are particularly sought after. On the other hand, high-frequency signals concentrate current on the very surface of the conductor. Therefore, conductor loss is related to the dielectric properties of the adjacent dielectric and can be approximately expressed as (Dk) １／２ is known to be proportional to

[0212] The resin film in the laminate of the present invention has small Df and Dk, and also has small dielectric loss index E and conductor loss, so that the transmission loss can be reduced in a circuit including the laminate of the present invention. Therefore, the laminate of the present invention can exhibit high yield strength while maintaining excellent dielectric properties (especially while maintaining low Df).

[0213] In one embodiment of the present invention, the dielectric loss index E at 10 GHz of the resin film in the laminate 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, particularly more preferably 0.0059 or less, and particularly more preferably 0.0056 or less, and may be, for example, 0.0053 or less, 0.0052 or less, 0.0051 or less, 0.0050 or less, or 0.0049 or less. The smaller the index E, the lower the transmission loss of an electronic circuit comprising the laminate. Therefore, the lower limit of the index E is not particularly limited and may be, for example, 0 or more.

[0214] In one embodiment of the present invention, the Df at 10 GHz of the resin film in the laminate, from the viewpoint of reducing transmission loss of an electronic circuit when the laminate is incorporated into the electronic circuit, is preferably 0.0040 or less, more preferably 0.0035 or less, even more preferably 0.0034 or less, still 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, and may be, for example, 0.0029 or less, 0.0028 or less, or 0.0027 or less. The smaller the Df, the lower the transmission loss of an electronic circuit comprising the laminate. Therefore, the lower limit of Df is not particularly limited and may be, for example, 0 or more.

[0215] In one embodiment of the present invention, the Dk at 10 GHz of the resin film in the laminate is preferably 3.500 or less, more preferably 3.450 or less, and even more preferably 3.400 or less.

[0216] The Df and Dk of the resin film in the laminate can be measured using a vector network analyzer and a resonator, for example, by the method described in the Examples.

[0217] 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, and particularly preferably 28 ppm / K or less, for example, 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. When the CTE of the resin film is below the upper limit, excellent thermal properties and high dimensional stability can be expected. Furthermore, 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. In one embodiment of the present invention, the CTE of the resin film in the laminate is preferably in the range of 10 to 29 ppm / K. When the CTE of the resin film is within the above upper and lower limits, the CTE of the metal layer (particularly the copper layer) and the CTE of the PI-based resin-containing layer in the resin film become close to each other, thereby suppressing peeling of the resin film from the metal layer. Note that the CTE can be measured, for example, by a thermomechanical analyzer (hereinafter sometimes referred to as "TMA") and is determined by the method described in the Examples.

[0218] The water resistance of the resin film in the laminate can be evaluated by the moisture content after immersing the resin film in pure water at 25°C for 24 hours after removing the metal layer. The moisture content can be measured by the method described in the Examples. A lower moisture content indicates higher 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, especially more preferably 2.0% or less, and especially more preferably 1.8% or less, for example, 1.7% or less, 1.6% or less, or 1.5% or less. When the moisture content is below the 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, thereby suppressing deterioration of the dielectric properties due to moisture content during the etching and subsequent cleaning processes. Furthermore, although the reason is unclear, when the moisture content is below the upper limit, the yield strength of the laminate tends to increase. The moisture content is usually 0% or more.

[0219] 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, particularly preferably 0.57% / min or more, and particularly preferably 0.60% / min or more, and may be, for example, 0.62% / min or more. When the drying rate is above the lower limit, the surface of the resin film from which the metal layer has been etched can have excellent drying performance, allowing for rapid drying after etching and cleaning processes during FPC production. The drying rate may also be typically 3% / min or less, preferably 1% / min or less. The drying rate is determined by dividing the difference between the moisture content immediately after immersing the resin film after removing the metal layer in pure water at 25°C for 24 hours and the moisture content after heat drying for a certain period of time by the heat drying time, as determined, for example, by the method described in the Examples.

[0220] The resin film of the present invention may be subjected to a surface treatment such as corona discharge treatment, plasma treatment, or ozone treatment by a method generally employed industrially.

[0221] <Method of manufacturing resin film> The method of manufacturing a resin film in the present invention is a method of manufacturing a resin film in which the cross-sectional curve at the interface of the obtained laminate satisfies formula (I), and the total area of ​​resin defects near the interface caused by microtoming under specific conditions is 0.300 μm per an evaluation area of ​​4.2 μm × 2.8 μm. ２ The PI film may be produced by any conventional method or a commercially available product depending on the type of film, as long as it satisfies the following formula (V) or satisfies the relationship of formula (V) at the interface between the resin film and the metal layer of the resulting laminate. For example, the PI film may be produced by cast molding, injection molding, hot press molding, calendar molding, vacuum molding, compression molding, extrusion molding, or the like. A preferred embodiment of the PI film of the present invention can be produced by a method (casting method) including a step of reacting a tetracarboxylic acid compound and a diamine compound, each appropriately selected depending on the composition of the PI resin, to obtain a PI resin precursor, and a step of imidizing the obtained PI resin precursor, as described below. For example, a method for producing the PI film of the present invention includes applying a solution of the corresponding PI resin precursor to a supporting substrate, pre-drying the coating, and then performing imidization. Imidization may be performed with the supporting substrate peeled off. In one embodiment of the present invention, the yield strength of the laminate can be increased by imidizing the coating when sufficient solvent remains in the entire coating or when the resin layers are well integrated. Although the reason is unclear, it is believed that in this state, the degree of freedom of the resin molecules is high until imidization, and the state of the resin molecules tends to be constant between the PI-based resin-containing layers. Also, for example, soluble liquid crystal polymers can be produced by cast molding, similar to the above-mentioned PI-based resins, while insoluble liquid crystal polymers, epoxy resins, and fluorine-based resins (e.g., PTFE, etc.) can be produced by extrusion molding (melt extrusion, etc.), compression molding, calendar molding, etc. When producing a resin film by extrusion molding, the surface properties can be adjusted by adjusting production conditions such as the die lip opening size, coating speed, surface roughness of the forming roll and cooling roll, and cooling profile.

[0222] In a preferred embodiment of the present invention, when the resin film is a PI film, the production method thereof may include, for example, a method in which a solution of a corresponding PI resin precursor is applied to a supporting substrate, the resulting solution is pre-dried to obtain a single-layer or multi-layer coating film, and then imidization is performed. The imidization may be performed in a state in which the supporting substrate is peeled off.

[0223] Examples of the supporting substrate include metal foil (e.g., copper foil), metal plate (e.g., copper plate, etc.), SUS foil, SUS plate such as SUS belt, glass substrate, resin film other than the resin film of the present invention (e.g., PET film, PEN film, PI-based resin film, polyamide-based resin film), etc. By using a metal layer (e.g., metal foil, etc.) as the supporting substrate, it is also possible to form a resin film directly on the metal layer.

[0224] [Metal Layer] The laminate of the present invention includes a metal layer on at least one surface of the resin film, that is, the resin film may include a metal layer on only one surface or on both surfaces.

[0225] In one embodiment of the present invention, examples of metals constituting the metal layer include aluminum, copper, iron, nickel, chromium, titanium, tantalum, stainless steel, and alloys thereof. Among these, the metal layer is preferably a copper layer, a copper alloy layer, a SUS layer, an aluminum layer, etc., and from the viewpoints of electrical conductivity and metal workability, a copper layer or a copper alloy layer is more preferred, and a copper layer is particularly preferred. Furthermore, from the viewpoint of metal workability, the metal layer is preferably a metal foil layer, and a metal foil of each of the above-mentioned metals is more preferred, a copper foil layer or a copper alloy foil layer is even more preferred, and a copper foil layer is particularly preferred.

[0226] In one embodiment of the present invention, the thickness of the metal layer, particularly the copper layer, is preferably 1 μm or more, more preferably 5 μm or more, and even more preferably 10 μm or more. From the viewpoint of facilitating circuit miniaturization and improving bending resistance, the thickness is preferably 100 μm or less, more preferably 50 μm or less, even more preferably 30 μm or less, and particularly preferably 20 μm or less. The thickness of the metal layer, particularly the copper layer, can be measured using a film thickness meter or the like. Note that when a metal layer, particularly a copper layer, is included on both sides of the resin film, the thickness of each metal layer, particularly each copper layer, may be the same or different.

[0227] In one embodiment of the present invention, the surface of the metal layer in contact with the resin film preferably has a minimum autocorrelation length Sal and an aspect ratio Str of the surface texture measured by a laser microscope in accordance with ISO 25178 at a magnification of 100x, a cutoff wavelength of 0.375 μm using an S filter, and no L filter, that satisfy the relationship of formula (IV): Sal × Str ≧ 0.21 (IV) Unless otherwise specified, the surface roughness parameters (kurtosis Sku, etc.) described below were also measured by a laser microscope in accordance with ISO 25178 at a magnification of 100x, a cutoff wavelength of 0.375 μm using an S filter, and no L filter.

[0228] The minimum autocorrelation length Sal in formula (IV) is a numerical representation of 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, indicating the horizontal distance in the direction in which the autocorrelation function decays to a specific value. A smaller Sal indicates a more abrupt step, while a larger Sal indicates a more gradual shape. Furthermore, the aspect ratio Str of the surface texture in formula (IV) is a three-dimensional surface texture parameter that quantifies the strength of the isotropy or anisotropy of the metal surface, and takes a value between 0 and 1. When Str is close to 1, the metal surface exhibits strong isotropy, meaning that the surface unevenness does not have a regular directionality, i.e., there are no streaks or the like on the surface. When Str is close to 0, the metal surface exhibits strong anisotropy, meaning that the surface unevenness has a regular directionality, i.e., there are streaks or the like on the surface.

[0229] When Sal and Str satisfy formula (IV) on the surface of the metal layer in contact with the resin film, the roughness parameters such as Σ(Ln / Sn) / Na, Sa / A, and Na / A at the interface of the obtained laminate, the total area of ​​resin defects near the interface caused by microtoming under specific conditions, and the DMT elastic modulus parameter at the interface between the resin film and the metal layer in the obtained laminate can be easily adjusted to each within the above range, thereby increasing the yield strength, water resistance, and drying speed of the laminate. Note that the larger Sal × Str, the more gently sloping peaks and valleys are thought to be present randomly on the metal surface.

[0230] In formula (IV), 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, particularly 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, particularly more preferably 8.0 μm or more, particularly more preferably 8.5 μm or more, and extremely preferably 9.5 μm or more. When Sal × Str is above the lower limit, the roughness parameters such as Σ(Ln / Sn) / Na, (Sa / A) and (Na / A) in the obtained laminate, the total area of ​​the resin defects near the interface caused by microtoming under specific conditions, and the DMT elastic modulus parameter of the interface between the resin film and the metal layer in the obtained laminate can be easily adjusted within the above ranges, and the yield strength, water resistance and drying speed of the laminate can be further improved. In formula (IV), 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, particularly preferably 11.5 μm or less, 11.0 μm or less, or 10.5 μm or less. When Sal × Str is below the upper limit, the roughness parameters such as Σ(Ln / Sn) / Na, (Sa / A) and (Na / A) in the obtained laminate, the total area of ​​resin defects near the interface caused by microtoming under specific conditions, and the DMT elastic modulus parameter of the interface between the resin film and the metal layer in the obtained laminate can be easily adjusted within the above ranges, and the yield strength, water resistance and drying speed of the laminate can be further improved.

[0231] In one embodiment of the present invention, the minimum autocorrelation length Sal may 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, even more preferably 5.0 μm or more, even 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 (IV) may 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 even more preferably 14.0 μm or less. When Sal is within the above range, the yield strength, water resistance, and drying speed of the resulting laminate tend to be improved.

[0232] In one embodiment of the present invention, the aspect ratio Str of the surface texture may 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, still more preferably 0.30 or more, particularly preferably 0.50 or more, particularly more preferably 0.60 or more, particularly more preferably 0.81 or more, and preferably 0.98 or less, more preferably 0.95 or less, and still more preferably 0.90 or less. When Str is within the above range, the yield strength, water resistance, and drying speed of the obtained laminate tend to be improved.

[0233] In one embodiment of the present invention, the surface of the metal layer in contact with the resin film preferably has a core level difference Sk of 0.40 μm or more measured under the above measurement conditions. The core level difference Sk is the maximum height minus the minimum height of the core excluding the protruding convex portions and protruding concave portions, and represents the variation in the height of the core portion. The Sk is more preferably 0.42 μm or more, even more preferably 0.44 μm or more, and is 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. When Sk is equal to or greater than the above lower limit and / or equal to or less than the above upper limit, the yield strength, water resistance, and drying speed of the resulting laminate can be improved.

[0234] In one embodiment of the present invention, the absolute value of the difference between the maximum peak height Sp and the maximum valley depth Sv (|Sp - Sv|) of the metal layer on the surface in contact with the resin film, as measured under the above measurement conditions, 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, particularly more preferably 0.15 μm or less, especially more preferably 0.10 μm or less, and extremely preferably 0.04 μm or less, for example, 0.03 μm or less or even 0.02 μm or less. |Sp - Sv| is preferably 0.001 μm or more, more preferably 0.005 μm or more. When |Sp - Sv| is less than the above upper limit and / or greater than the above lower limit, the yield strength, water resistance, and drying speed of the resulting laminate can be improved.

[0235] In one embodiment of the present invention, the 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, still more preferably 1.20 μm or less, particularly preferably 1.10 μm or less or 1.00 μm or less, particularly preferably 0.90 μm or less, and is preferably 0.10 μm or more, more preferably 0.30 μm or more, even more preferably 0.50 μm or more, and still more preferably 0.70 μm or more. When the Sp is within the above range, the yield strength, water resistance, and drying speed of the obtained laminate tend to be improved.

[0236] In one embodiment of the present invention, the maximum valley depth Sv is preferably 1.50 μm or less, more preferably 1.30 μm or less, and may be, for example, 1.20 μm or less, 1.00 μm or less, or 0.90 μm or less, and is preferably 0.30 μm or more, more preferably 0.50 μm or more, and even more preferably 0.70 μm or more. When Sv is within the above range, the yield strength, water resistance, and drying speed of the obtained laminate tend to be improved.

[0237] In one embodiment of the present invention, the surface of the metal layer in contact with the resin film may have a developed area ratio Sdr measured under the above measurement conditions of, for example, 100% or less or 50% or less, preferably 35.0% or less, and more preferably 20% or less. The developed area ratio Sdr represents the increase in the developed area (i.e., surface area) of a defined region relative to the area of ​​the defined region. Specifically, it represents the rate of increase in surface area from a completely flat surface, where a completely flat surface is taken as 100%. A smaller Sdr indicates a more flat surface shape, with the Sdr of a completely flat surface being 0%. On the other hand, a larger Sdr indicates a more uneven surface shape. The Sdr is more preferably less than 20%, even more preferably 18% or less or 15% or less, even more preferably 13% or less, particularly preferably 10% or less, and particularly preferably 5% or less, and is preferably 0.5% or more, more preferably 1.0% or more, and even more preferably 2% or more. When the developed area ratio Sdr is equal to or less than the upper limit and / or equal to or more than the lower limit, the yield strength, water resistance and drying speed of the obtained laminate can be increased.

[0238] In one embodiment of the present invention, the surface of the metal layer in contact with the resin film has a kurtosis Sku measured under the above-mentioned measurement conditions of preferably 3.80 or less, more preferably 3.50 or less, and preferably 1.0 or more, more preferably 1.5 or more, even more preferably 2.0 or more, even more preferably 2.5 or more, particularly preferably 2.8 or more, particularly preferably 3.00 or more, especially more preferably 3.10 or more, and extremely preferably 3.30 or more. When the Sku is within the above range, the yield strength, water resistance, and drying speed of the resulting laminate can be improved. The kurtosis Sku measured by a laser microscope is an index showing the sharpness of the height distribution on the surface of the metal layer.

[0239] Sku means kurtosis, which is a measure of sharpness, and represents the sharpness (pointedness) of the height distribution. When Sku>3, it means that there are many sharp convex and concave portions, when Sku<3, it means that there are many concave and convex portions with flattened tips and the metal surface is relatively flat, and when Sku=3, it means that the height distribution is a normal distribution.

[0240] In one embodiment of the present invention, the surface of the metal layer in contact with the resin film may have an arithmetic mean height Sa, measured under the above measurement conditions, of, for example, 0.05 μm or more or 0.10 μm or more, preferably 0.14 μm or more, and may also 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. When Sa is within the above range, the yield strength, water resistance, and drying speed of the laminate can be improved. The arithmetic mean height Sa is a parameter that expands the two-dimensional parameter Ra into three dimensions and represents the average height difference from the mean plane.

[0241] In one embodiment of the present invention, the surface of the metal layer in contact with the resin film has a maximum height Sz measured under the above measurement conditions of preferably 3.5 μm or less, more preferably 3.0 μm or less, even more preferably 2.8 μm or less, 2.50 μm or less, or 2.1 μm or less, still more preferably 2.00 μm or less, particularly preferably 1.90 μm or less, or 1.80 μm or less, and is preferably 0.1 μm or more, more preferably 0.5 μm or more, even more preferably 1.0 μm or more, still more preferably 1.3 μm or more, particularly preferably 1.5 μm or more. When the Sz is within the above range, the yield strength, water resistance, and drying speed of the laminate can be improved.

[0242] In one embodiment of the present invention, the arithmetic mean height Ra of the metal layer on the surface in contact with the resin film, as measured using a laser microscope at a magnification of 100x in accordance with JIS B0601:2013, is preferably 0.01 to 0.5 μm, more preferably 0.05 to 0.3 μm, even more preferably 0.1 to 0.25 μm, and may be, for example, 0.12 to 0.20 μm. The maximum height Rz is preferably 0.1 to 2 μm, more preferably 0.5 to 1.6 μm, and may be, for example, 0.60 to 1.0 μm. The ten-point mean roughness Rz 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.

[0243] In this specification, Sal, Str, Sk, Sdr, Sp, Sv, Sku, Sa, Sz, Sal×Str, |Sp−Sv|, etc. may be collectively referred to as surface roughness parameters of a metal surface.

[0244] The surface roughness parameters of a metal surface can be measured by laser observation of the surface of the metal layer in contact with the resin film using a laser microscope at a magnification of 100x to obtain a three-dimensional shape image and then analyzing the obtained three-dimensional shape image. Analysis of Sal, Str, Sk, Sdr, Sp, Sv, Sku, Sa, and Sz can be performed in accordance with ISO 25178 using an S filter with a cutoff wavelength of 0.375 μm and without an L filter. Analysis of Ra, Rz, and Rzjis can be performed in accordance with JIS B0601:2013 by analyzing a profile curve obtained at any point in the obtained three-dimensional shape image under conditions of λs of 2.5 μm, λc, and λf not set. The surface roughness parameters of a metal surface can be determined, for example, by the method described in the Examples.

[0245] The metal layer may be manufactured by, for example, electrolytic casting such as electroplating or plastic processing such as rolling, or a commercially available product may be used. When the metal layer is a metal foil, a surface treatment layer may be provided on at least one surface of the metal foil by electroplating. Examples of the surface treatment layer include a roughened layer, an anti-rust layer, and, if necessary, an alloy layer provided between the surface of the metal foil and the roughened layer, and a chromate layer or a silane coupling agent layer provided on the surface of the anti-rust layer. When the metal layer is a copper foil, an electrolytic copper foil or a rolled copper foil can be used. The metal layer preferably has a roughened layer made of copper, zinc, titanium, tungsten, molybdenum, nickel, cobalt, iron, or two or more of these elements, and / or an anti-rust layer made of zinc, tin, nickel, cobalt, chromium, molybdenum, or two or more of these elements. From the viewpoint of uniformly providing the roughened layer, it is preferable to further provide an alloy layer of copper and at least one element selected from molybdenum, zinc, tungsten, nickel, cobalt, and iron on the surface of the copper foil. The thickness of the surface treatment layer is 2.0 μm or less, preferably 0.2 μm or more and 1.5 μm or less, from the viewpoint of easily adjusting the surface roughness parameter of the metal surface. In this specification, the surface treatment layer is also referred to as the "metal layer." Methods for adjusting the surface of the metal layer to the above-mentioned surface roughness parameter range include using a commercially available product whose metal layer surface satisfies the above-mentioned surface roughness parameter range, and forming a surface treatment layer with a predetermined roughness on the metal surface.

[0246] [Physical Properties of Laminate] The laminate of the present invention has a cross-sectional curve at the interface of the laminate that satisfies formula (I), and therefore the total area of ​​resin defects near the interface caused by microtoming under specific conditions is 0.300 μm per an evaluation area of ​​4.2 μm × 2.8 μm. ２or less, or because the relationship of formula (V) is satisfied at the interface between the resin film and the metal layer of the laminate, the laminate has a high 0.2% proof stress and excellent resistance to deformation. It also has excellent dielectric properties, allowing for both excellent proof stress and dielectric properties to be achieved. Furthermore, the laminate of the present invention has excellent water resistance, which effectively prevents water from penetrating through the resin film surface in areas where the metal layer has been removed by etching or the like. Furthermore, it has an excellent drying speed, so even if it absorbs water, it easily releases it efficiently by heating. Therefore, the laminate of the present invention can be suitably used as a substrate material suitable for printed circuit boards and antenna substrates. Furthermore, because the laminate of the present invention has a low Df, it can achieve low transmission loss even in high-frequency bands that transmit high-frequency signals. Therefore, the laminate is particularly suitable as a substrate material suitable for printed circuit boards and antenna substrates for high-speed communication applications such as 5G.

[0247] The laminate of the present invention may further include other layers, such as a functional layer, as long as a metal layer is laminated (or provided) directly (in contact with) at least one surface of the resin film so as to satisfy at least formula (I), or so that the total area of ​​resin defects near the interface caused by microtoming under specific conditions satisfies the above range, or so that the interface between the resin film and the metal layer satisfies the DMT elastic modulus parameter. For example, when a metal layer is laminated on one surface of the resin film, another layer may be included on the other surface of the resin film and / or on the surface of the metal layer opposite the resin film. Also, when metal layers are laminated on both surfaces of the resin film, another layer may be included on the surface of at least one metal layer opposite the resin film. Furthermore, when the resin film is a laminate film, another layer may be included between each layer in the resin film (preferably each PI-based resin-containing layer in a PI-based film). Examples of functional layers include adhesive layers. The functional layers can be used alone or in combination of two or more. From the viewpoint of the strength, water resistance, drying speed, heat resistance, dimensional stability, dielectric properties, and weight reduction of the laminate, it is preferable that the laminate does not include a functional layer, in particular an adhesive layer.

[0248] As long as the interface between the metal layer and the resin film satisfies at least formula (I), or the total area of ​​resin defects near the interface caused by microtoming under specific conditions satisfies the above range, or the interface between the resin film and the metal layer satisfies the DMT elastic modulus parameter, the metal layer may be laminated over the entire surface of the resin film or may be laminated only partially over the surface of the resin film.

[0249] In one embodiment of the present invention, when the resin film is a PI film, the laminate of the present invention can be formed at a relatively low imidization temperature, and even when a laminate in which the metal layer is a copper layer (preferably a copper foil layer) is produced by thermally imidizing a PI resin precursor coating film on a metal layer, sufficiently high yield strength and low Df can be achieved while suppressing deterioration of the copper layer surface. Therefore, the laminate of the present invention has excellent high-frequency characteristics even without an adhesive layer.

[0250] In one embodiment of the present invention, the 0.2% yield strength of the laminate of the present invention is preferably 66 MPa or more, more preferably 70 MPa or more, even more 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. When the 0.2% yield strength of the laminate is above the lower limit, the laminate has excellent resistance to deformation and can suppress deterioration of electrical properties due to plastic deformation when used as an FPC or the like containing the laminate. Furthermore, the upper limit of the 0.2% yield strength of the laminate of the present invention is not particularly limited, but is, for example, 300 MPa or less, preferably 150 MPa or less. The 0.2% proof stress of the laminate is the stress value at which a tangent line at zero strain is translated 0.2% in the direction of strain and the translated straight line intersects with the stress-strain curve (hereinafter also referred to as the S-S curve) obtained using a tensile tester under the conditions of a temperature of 25°C, a relative humidity of 50%, a chuck distance of 50 mm, and a tensile speed of 20 mm / min. The 0.2% proof stress can be determined, for example, by the method described in the Examples.

[0251] [Method for producing laminate] The method for producing the laminate of the present invention is not particularly limited as long as it is a method that allows a metal layer to be directly laminated on at least one surface of a resin film so that at least formula (I) is satisfied, or so that the total area of ​​resin defects near the interface caused by microtoming under specific conditions satisfies the above range, or so that the interface between the resin film and the metal layer satisfies the DMT elastic modulus parameter. Examples of such a method include a method of forming a metal layer on a resin film by plating; a production method in which a solution of a resin that constitutes the resin film or a solution of a precursor of the resin is applied to the surface of the metal layer and dried; and a method in which a resin film and a metal layer are bonded together.

[0252] In one embodiment of the present invention, a method for producing a laminate by plating includes, for example, forming a resin film by cast molding, extrusion molding, or the like, as described in the section "Method for Producing a Resin Film," and then plating the surface of the resin film with a metal to provide 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 supporting substrate that contacts the resin film preferably has surface properties similar to those of the "surface roughness parameter of the metal surface" described above. When the resin film is a PI-based film, the method of applying the PI-based resin precursor solution to the supporting substrate, the pre-drying method, the standing method, and the heating conditions for imidization can be similar to those when a metal layer is used as the supporting substrate, as described below. In another embodiment of the present invention, a laminate can also be produced by embossing, matting, hairline finishing, blasting, desmearing, or the like to create irregularities on the surface of the resin film, and then metal plating the surface of the resin film to provide a metal layer (metal plating layer) on the surface of the resin film.

[0253] In a preferred embodiment of the present invention, when the resin film is a PI-based film, a metal layer is used as a support substrate. Examples of a method for directly forming a resin film on the surface of the metal layer include a process for applying a solution of a corresponding PI-based resin precursor to the surface of the metal layer and pre-drying the solution to obtain a coating film (also referred to as a coating and pre-drying process); a process for allowing the resulting coating film to stand (also referred to as a standing process); and a process for heating the coating film to imidize the PI-based resin (also referred to as an imidization process). The coating film is a single-layer coating film when the PI-based film is a single-layer film, and a multi-layer coating film when the PI-based film is a laminate film. While the standing process may not be included in the production of the laminate, including the standing process tends to make it easier to adjust the roughness parameter of the resulting laminate, the total area of ​​resin defects near the interface caused by microtoming under specific conditions, or the DMT elastic modulus parameter of the resulting laminate within the above-mentioned ranges, depending on, for example, the surface roughness parameter of the metal layer. Furthermore, the mechanical properties of the resulting laminate, such as its yield strength, can be improved. When a metal layer is also formed on the other surface of the PI film, a method of bonding the metal layer to the other surface of the PI film by thermal compression bonding such as thermal lamination or thermal pressing can be used.

[0254] (Preparation of PI Resin Precursor) The PI resin precursor can be obtained by reacting a tetracarboxylic acid compound with a diamine compound. Examples of the tetracarboxylic acid compound used in synthesizing the PI resin precursor include aromatic tetracarboxylic acid compounds such as aromatic tetracarboxylic acid dianhydrides; and aliphatic tetracarboxylic acid compounds such as aliphatic tetracarboxylic acid dianhydrides. The tetracarboxylic acid compounds may be used alone or in combination of two or more. The tetracarboxylic acid compound may be a dianhydride or a tetracarboxylic acid compound analog such as an acid chloride compound.

[0255] Examples of the tetracarboxylic acid compound include tetracarboxylic acid anhydrides represented by formula (A1), tetracarboxylic acid anhydrides represented by formula (A2), and tetracarboxylic acid anhydrides represented by formula (A3). Tetracarboxylic acid compounds known in the art can be appropriately selected and used. Examples of such tetracarboxylic acid compounds include pyromellitic anhydride (hereinafter sometimes referred to as PMDA), 4,4'-(4,4'-isopropylidenediphenoxy)diphthalic anhydride (hereinafter sometimes referred to as BPADA), 1,4,5,8-naphthalenetetracarboxylic dianhydride, 3,3',4,4'-biphenyltetracarboxylic dianhydride (hereinafter sometimes referred to as BPDA), and 4,4'-(hexafluoroisopropylidene)diphthalic dianhydride. (hereinafter, sometimes referred to as 6FDA), 4,4'-oxydiphthalic dianhydride (hereinafter, sometimes referred to as ODPA), 2,2',3,3'-, 2,3,3',4'- or 3,3',4,4'-benzophenonetetracarboxylic dianhydride, 2,3',3,4'-biphenyltetracarboxylic dianhydride, 2,2',3,3'-biphenyltetracarboxylic dianhydride, p-phenylenebis(trimellitic acid monoester dianhydride) (hereinafter, sometimes referred to as TAHQ), ester of trimellitic anhydride and 2,2',3,3',5,5'-hexamethyl-4,4'-biphenol (hereinafter sometimes referred to as TMPBP), 4,4'-bis(1,3-dioxo-1,3-dihydroisobenzofuran-5-ylcarbonyloxy)biphenyl (hereinafter sometimes referred to as BP-TME), 2,3',3,4'-diphenyl ether tetracarboxylic acid dianhydride, bis(2,3-dicarboxyphenyl) ether dianhydride, 3,3', 4,4"-p-terphenyltetracarboxylic dianhydride, 2,3,3",4"-p-terphenyltetracarboxylic dianhydride, 2,2",3,3"-p-terphenyltetracarboxylic dianhydride, 2,2-bis(2,3-dicarboxyphenyl)-propane dianhydride, 2,2-bis(3,4-dicarboxyphenyl)-propane dianhydride, bis(2,3-dicarboxyphenyl)methane dianhydride, bis(3,4-dicarboxyphenyl)methane dianhydride, 1,1-bis(2,1,1-bis(3,4-dicarboxyphenyl)ethane dianhydride, 1,2,7,8-,1,2,6,7-phenanthrene-tetracarboxylic dianhydride, 1,2,9,10-phenanthrene-tetracarboxylic dianhydride, 2,2-bis(3,4-dicarboxyphenyl)tetrafluoropropane dianhydride, 1,2,4,5-cyclohexanetetracarboxylic dianhydride (hereinafter sometimes referred to as HPMDA), 2,3,5,6-cyclohexanetetracarboxylic dianhydride, 2,3,6,7-naphthalenetetracarboxylic dianhydride tetracarboxylic dianhydride, 1,2,5,6-naphthalenetetracarboxylic dianhydride, cyclopentane-1,2,3,4-tetracarboxylic dianhydride, 4,4'-bis(2,3-dicarboxyphenoxy)diphenylmethane dianhydride, 1,2,3,4-cyclobutanetetracarboxylic dianhydride (hereinafter sometimes referred to as CBDA), norbornane-2-spiro-α'-spiro-2"-norbornane-5,5',6,6'-tetracarboxylic anhydride, p-phenylenebis(trimellitate anhydride), 3,3',4,4'-diphenylsulfonetetracarboxylic dianhydride carboxylic acid dianhydride, 2,3,6,7-anthracenetetracarboxylic acid dianhydride, 4,8-dimethyl-1,2,3,5,6,7-hexahydronaphthalene-1,2,5,6-tetracarboxylic acid dianhydride, 2,6-dichloronaphthalene-1,4,5,8-tetracarboxylic acid dianhydride, 2,7-dichloronaphthalene-1,4,5,8-tetracarboxylic acid dianhydride, 2,3,6,7-tetrachloronaphthalene-1,4,5,8-tetracarboxylic acid dianhydride, 2,3,6,7-tetrachloronaphthalene-2,3,6,7-tetracarboxylic acid dianhydride, 1,4,5,8- Tetrachloronaphthalene-1,4,5,8-tetracarboxylic dianhydride, 1,4,5,8-tetrachloronaphthalene-2,3,6,7-tetracarboxylic dianhydride, 2,3,8,9-perylene-tetracarboxylic dianhydride, 3,4,9,10-perylene-tetracarboxylic dianhydride, 4,5,10,11-perylene-tetracarboxylic dianhydride, 5,6,11,12-perylene-tetracarboxylic dianhydride, pyrazine-2,3,5,6-tetracarboxylic dianhydride, pyrrolidine-2,3,4,5-tetracarboxylic dianhydride, thiophene-2,3,4,Examples of suitable tetracarboxylic acid compounds include 5-tetracarboxylic acid dianhydride, bis(2,3-dicarboxyphenyl)sulfone dianhydride, and bis(3,4-dicarboxyphenyl)sulfone dianhydride. Among these, it is preferable to use a combination of BPDA, PMDA, TAHQ, and / or BP-TME from the viewpoints of improving the yield strength of the resulting laminate and reducing Df and CTE. These tetracarboxylic acid compounds can be used alone or in combination of two or more.

[0256] Examples of diamine compounds used in the synthesis of PI resin precursors include aliphatic diamines, aromatic diamines, and mixtures thereof. In this embodiment, "aromatic diamine" refers to a diamine having an aromatic ring, which may contain an aliphatic group or other substituents as part of its structure. This aromatic ring may be a single ring or a condensed ring, and examples include, but are not limited to, a benzene ring, a naphthalene ring, an anthracene ring, and a fluorene ring. Among these, a benzene ring is preferred. Furthermore, "aliphatic diamine" refers to a diamine having an aliphatic group, which may contain other substituents as part of its structure, but does not have an aromatic ring.

[0257] Examples of diamine compounds include diamines represented by formula (B1), diamines represented by formula (B2), and diamines represented by formula (2), and diamine compounds known in the art can be appropriately selected and used. Examples of such diamine compounds include 1,4-diaminocyclohexane, 4,4'-diamino-2,2'-dimethylbiphenyl (hereinafter sometimes referred to as m-Tb), 4,4'-diamino-3,3'-dimethylbiphenyl, 2,2'-bis(trifluoromethyl)-4,4'-diaminodiphenyl (hereinafter sometimes referred to as TFMB), 4,4'-diaminodiphenyl ether, and 1,3-bis(3-aminophenoxy)benzene (hereinafter sometimes referred to as 1,3-APB). , 1,4-bis(4-aminophenoxy)benzene (hereinafter sometimes referred to as TPE-Q), 1,3-bis(4-aminophenoxy)benzene (hereinafter sometimes referred to as TPE-R), 2,2-bis[4-(4-aminophenoxy)phenyl]propane (hereinafter sometimes referred to as BAPP), 2,2'-dimethyl-4,4'-diaminobiphenyl, 3,3'-dihydroxy-4,4'-diaminobiphenyl, 2,2-bis-[4-(3-aminophenoxy)phenyl]propane, biphenyl Bis[4-(4-aminophenoxy)]biphenyl, bis[4-(3-aminophenoxy)biphenyl, bis[1-(4-aminophenoxy)]biphenyl, bis[1-(3-aminophenoxy)]biphenyl, bis[4-(4-aminophenoxy)phenyl]methane, bis[4-(3-aminophenoxy)phenyl]methane, bis[4-(4-aminophenoxy)phenyl]ether, bis[4-(3-aminophenoxy)phenyl]ether, bis[4-(4-aminophenoxy]benzof phenone, bis[4-(3-aminophenoxy)]benzophenone, 2,2-bis-[4-(4-aminophenoxy)phenyl]hexafluoropropane, 2,2-bis-[4-(3-aminophenoxy)phenyl]hexafluoropropane, 4,4'-methylenedi-o-toluidine, 4,4'-methylenedi-2,6-xylidine, 4,4'-methylene-2,6-diethylaniline, 4,4'-methylenedianiline, 3,3'-methylenedianiline, 4,4'-diaminodiphenylpropane, 3,3'-Diaminodiphenylpropane, 4,4'-diaminodiphenylethane, 3,3'-diaminodiphenylethane, 4,4'-diaminodiphenylmethane, 3,3'-diaminodiphenylmethane, 3,3-diaminodiphenylether, 3,4'-diaminodiphenylether, benzidine, 3,3'-diaminobiphenyl, 3,3'-dimethoxybenzidine, 4,4"-diamino-p-terphenyl, 3,3"-diamino-p-terphenyl, m-phenylenediamine, p-phenylenediamine (hereinafter sometimes referred to as p-PDA), rezo Rucinol bis(3-aminophenyl) ether, 4,4'-[1,4-phenylenebis(1-methylethylidene)]bisaniline, 4,4'-[1,3-phenylenebis(1-methylethylidene)]bisaniline, bis(p-aminocyclohexyl)methane, bis(p-β-amino-tert-butylphenyl)ether, bis(p-β-methyl-δ-aminopentyl)benzene, p-bis(2-methyl-4-aminopentyl)benzene, p-bis(1,1-dimethyl-5-aminopentyl)benzene, 1,5-diaminonaphthalene, 2,6-diamino Aminonaphthalene, 2,4-bis(β-amino-tert-butyl)toluene, 2,4-diaminotoluene, m-xylene-2,5-diamine, p-xylene-2,5-diamine, m-xylylenediamine, p-xylylenediamine, piperazine, 4,4'-diamino-2,2'-bis(trifluoromethyl)bicyclohexane, 4,4'-diaminodicyclohexylmethane, 4,4"-diamino-p-terphenyl, bis(4-aminophenyl)terephthalate, 1,4-bis(4-aminophenoxy)-2,5-di-tert-butylbenzene, 4, 4'-(1,3-phenylenediisopropylidene)bisaniline, 1,4-bis[2-(4-aminophenyl)-2-propyl]benzene, 2,4-diamino-3,5-diethyltoluene, 2,6-diamino-3,5-diethyltoluene, 4,4'-bis(3-aminophenoxy)biphenyl, 4,4'-(hexafluoropropylidene)dianiline, 1,2-diaminoethane, 1,3-diaminopropane, 1,4-diaminobutane, 1,5-diaminopentane, 1,6-diaminohexane, 1,2-diaminopropane, 1,2-diaminobutane, 1,3-Diaminobutane, 2-methyl-1,2-diaminopropane, 2-methyl-1,3-diaminopropane, 1,3-bis(aminomethyl)cyclohexane, 1,4-bis(aminomethyl)cyclohexane, norbornanediamine, 2'-methoxy-4,4'-diaminobenzanilide, 4,4'-diaminobenzanilide, bis[4-(4-aminophenoxy)phenyl]sulfone, bis[4-(3-aminophenoxy)phenyl]sulfone, 9,9-bis[4-(4-aminophenoxy)phenyl]fluoro Examples of suitable diamine compounds include fluorene, 9,9-bis[4-(3-aminophenoxy)phenyl]fluorene, 4,4'-diaminodiphenyl sulfide, 3,3'-diaminodiphenyl sulfide, 4,4'-diaminodiphenyl sulfone, 3,3'-diaminodiphenyl sulfone, 2,5-diamino-1,3,4-oxadiazole, bis[4,4'-(4-aminophenoxy)]benzanilide, bis[4,4'-(3-aminophenoxy)]benzanilide, 2,6-diaminopyridine, and 2,5-diaminopyridine. Among these, m-Tb, BAPP, TPE-Q, 1,3-bis(4-aminophenoxy)benzene, and / or TPE-R are preferably used in combination, from the viewpoints of improving the yield strength of the resulting laminate and reducing Df and CTE. The diamine compounds can be used alone or in combination of two or more.

[0258] The PI resin precursor may be a product obtained by further reacting, in addition to the tetracarboxylic acid compound used in the synthesis of the PI resin precursor, other tetracarboxylic acids, dicarboxylic acids, tricarboxylic acids, and anhydrides and derivatives thereof, as long as the various physical properties of the resulting PI film are not impaired.

[0259] Other tetracarboxylic acids include water adducts of the anhydrides of the above tetracarboxylic acid compounds.

[0260] Examples of the dicarboxylic acid compound include aromatic dicarboxylic acids, aliphatic dicarboxylic acids, and their analogous acid chloride compounds, acid anhydrides, etc., and two or more of these may be used in combination. Specific examples include terephthalic acid, isophthalic acid, naphthalenedicarboxylic acid, 4,4'-biphenyldicarboxylic acid, 3,3'-biphenyldicarboxylic acid, dicarboxylic acid compounds of chain hydrocarbons having 8 or less carbon atoms, and compounds in which two benzoic acids are bonded to a single bond, -O-, -CH ２ -, -C(CH ３ ) ２ -, -C(CF ３ ) ２ -, -SO ２ Examples of such compounds include compounds linked by a phenylene group or a phenylene group, and acid chloride compounds thereof.

[0261] Examples of tricarboxylic acid compounds include aromatic tricarboxylic acids, aliphatic tricarboxylic acids, and acid chloride compounds and acid anhydrides related thereto, and two or more of these may be used in combination. Specific examples include anhydride of 1,2,4-benzenetricarboxylic acid; 2,3,6-naphthalenetricarboxylic-2,3-anhydride; and compounds in which phthalic anhydride and benzoic acid are bonded by a single bond, —O—, —CH ２ -, -C(CH ３ ) ２ -, -C(CF ３ ) ２ -, -SO ２ or a compound linked by a phenylene group.

[0262] In the production of a PI resin precursor, the amounts of diamine compounds, tetracarboxylic acid compounds, dicarboxylic acid compounds, and tricarboxylic acid compounds used can be appropriately selected depending on the ratio of each structural unit of the desired PI resin precursor. In the present invention, the total number of moles of diamine compounds used per mole of the total amount of tetracarboxylic acid compounds is defined as the amine ratio. In a preferred embodiment of the present invention, the amine ratio is preferably 0.90 moles or more and preferably 0.999 moles or less per mole of the total amount of tetracarboxylic acid compounds. In another embodiment, the amine ratio is preferably 1.001 moles or more and preferably 1.10 moles or less per mole of the total amount of tetracarboxylic acid compounds. In one embodiment of the present invention, when the amine ratio is 1 or less, the amine ratio is preferably 0.90 moles or more and 0.999 moles or less, more preferably 0.95 moles or more and 0.997 moles or less, and even more preferably 0.97 moles or more and 0.995 moles or less. In one embodiment of the present invention, when the amine ratio is 1 or more, the amine ratio is preferably 1.001 mol or more and 1.10 mol or less, more preferably 1.002 mol or more and 1.06 mol or less, and even more preferably 1.003 mol or more and 1.05 mol or less. If the amine ratio is close to 1.0 mol, the molecular weight tends to increase rapidly during synthesis, while if it is significantly different from 1.0 mol, the molecular weight of the resulting PI-based resin tends to decrease. If the molecular weight increases rapidly, it grows unevenly within the synthesis mass, and the physical properties of the PI-based resin obtained from the PI-based resin precursor tend to be unstable. On the other hand, if the molecular weight is too low, the mechanical properties tend to decrease.

[0263] The reaction temperature between the diamine compound and the tetracarboxylic acid compound is preferably 50°C or lower, more preferably 40°C or lower, and even more preferably 30°C or lower. The reaction temperature between the diamine compound and the tetracarboxylic acid compound is preferably 5°C or higher, more preferably 10°C or higher, and even more preferably 15°C or higher. When the reaction temperature is within the above upper and lower limits, the effects of the present invention are easily achieved, and the reaction rate tends to be increased and the polymerization time shortened. The reaction time is not particularly limited and may be, for example, about 0.5 to 36 hours, and preferably 1 to 24 hours.

[0264] The reaction between the diamine compound and the tetracarboxylic acid compound is preferably carried out in a solvent. The solvent is not particularly limited as long as it does not affect the reaction, and examples thereof include alcoholic solvents such as water, methanol, ethanol, ethylene glycol, isopropyl alcohol, propylene glycol, ethylene glycol methyl ether, ethylene glycol butyl ether, 1-methoxy-2-propanol, 2-butoxyethanol, and propylene glycol monomethyl ether; phenolic solvents such as phenol and cresol; ester solvents such as ethyl acetate, butyl acetate, ethylene glycol methyl ether acetate, propylene glycol methyl ether acetate, and ethyl lactate; lactone solvents such as γ-butyrolactone (hereinafter sometimes referred to as GBL) and γ-valerolactone; acetone, methyl ethyl ketone, cyclopentanone, cyclohexanone, 2-heptanone, methyl methyl ether ... Examples of suitable solvents include ketone-based solvents such as triisobutyl ketone; aliphatic hydrocarbon solvents such as pentane, hexane, and heptane; alicyclic hydrocarbon solvents such as ethylcyclohexane; aromatic hydrocarbon solvents such as toluene and xylene; nitrile-based solvents such as acetonitrile; ether-based solvents such as tetrahydrofuran and dimethoxyethane; chlorine-containing solvents such as chloroform and chlorobenzene; amide-based solvents such as N,N-dimethylacetamide (hereinafter sometimes referred to as DMAc) and N,N-dimethylformamide (hereinafter sometimes referred to as DMF); sulfur-containing solvents such as dimethyl sulfone, dimethyl sulfoxide, and sulfolane; carbonate-based solvents such as ethylene carbonate and propylene carbonate; pyrrolidone-based solvents such as N-methylpyrrolidone (hereinafter sometimes referred to as NMP); and combinations thereof. Among these, from the viewpoint of solubility, phenol-based solvents, lactone-based solvents, amide-based solvents, and pyrrolidone-based solvents are preferred, and amide-based solvents are more preferred.

[0265] In one embodiment of the present invention, the boiling point of the solvent used in the reaction of the diamine compound with the tetracarboxylic acid compound is preferably suitable for imidization conditions that are advantageous in terms of the yield strength and dielectric properties of the resulting laminate, and is preferably 230°C or lower, more preferably 200°C or lower, and even more preferably 180°C or lower, and is preferably 100°C or higher, and more preferably 120°C or higher.

[0266] The reaction of the diamine compound with the tetracarboxylic acid compound may be carried out, as necessary, in an inert atmosphere such as a nitrogen atmosphere or an argon atmosphere or under reduced pressure. It is preferable to carry out the reaction in an inert atmosphere, such as a nitrogen atmosphere or an argon atmosphere, in a strictly controlled dehydrated solvent while stirring.

[0267] The resulting PI resin precursor may be isolated once by a conventional method, but the reaction solution containing the PI resin precursor obtained by synthesis of the PI resin precursor may be appropriately diluted with a solvent as needed and used as a PI resin precursor solution without isolation.

[0268] (Coating and Pre-drying Steps) In the production of the laminate of the present invention, the coating and pre-drying steps are steps of applying a solution of a corresponding PI resin precursor onto the surface of a metal layer and pre-drying it to obtain a coating film (single-layer coating film or multi-layer coating film). When the PI film in the laminate is a laminate film, examples of the method include a method of applying a solution of a corresponding PI resin precursor onto the surface of the metal layer and pre-drying it multiple times to obtain a multi-layer coating film (sometimes referred to as a sequential pattern), and a method of applying a solution of a corresponding PI resin precursor onto each layer in a multi-layer laminated state by multi-layer extrusion and pre-drying it to obtain a multi-layer coating film (sometimes referred to as a simultaneous pattern). For example, in the case of a PI film (L) having a PI resin-containing layer (PI-2), a PI resin-containing layer (PI-1), and a PI resin-containing layer (PI-3) in this order, the sequential pattern may be a process in which a PI resin precursor solution corresponding to the PI resin-containing layer (PI-2) is applied onto the surface of a metal layer and pre-dried to form a coating film, a PI resin precursor solution corresponding to the PI resin-containing layer (PI-1) is applied onto the coating film and pre-dried to form a two-layer coating film, and a PI resin precursor solution corresponding to the PI resin-containing layer (PI-3) is applied onto the two-layer coating film and pre-dried to form a three-layer coating film. In addition, the simultaneous patterning may be a process in which a PI-based resin precursor solution corresponding to the PI-based resin-containing layer (PI-2), a PI-based resin precursor solution corresponding to the PI-based resin-containing layer (PI-1), and a PI-based resin precursor solution corresponding to the PI-based resin-containing layer (PI-3) are simultaneously applied onto the surface of a metal layer by multilayer extrusion or the like, and then pre-dried to form a three-layer coating film.

[0269] The solvent contained in the PI resin precursor solution may be any of the solvents exemplified for use in the reaction of a diamine compound with a tetracarboxylic acid compound in the production of a PI resin precursor, and is preferably a lactone solvent, an amide solvent, or a pyrrolidone solvent, more preferably an amide solvent. In one embodiment of the present invention, the boiling point of the solvent contained in the PI resin precursor solution is preferably suitable for imidization conditions that are advantageous in terms of the yield strength and dielectric properties of the resulting laminate, and is preferably 230°C or lower, more preferably 200°C or lower, even more preferably 180°C or lower, and particularly preferably 170°C or lower, and is preferably 100°C or higher, more preferably 120°C or higher.

[0270] The content of the PI resin precursor in the PI resin precursor solution is preferably 8% by mass or more, more preferably 10% by mass or more, even more preferably 12% by mass or more, particularly preferably 13% by mass or more, relative to the total amount of the PI resin precursor solution, and is preferably 30% by mass or less, more preferably 25% by mass or less, even more preferably 23% by mass or less, particularly preferably 20% by mass or less. When the content of the PI resin precursor is within the above range, excellent processability during film formation is achieved.

[0271] A coating film of a PI resin precursor solution can be formed by applying the PI resin precursor solution to a metal surface using a known coating or application method. Examples of known coating methods include roll coating methods such as wire bar coating, reverse coating, and gravure coating, die coating, comma coating, lip coating, spin coating, screen printing coating, fountain coating, dipping, spraying, curtain coating, slot coating, applicator coating, and drip molding. When the PI film in the laminate is a laminate film, the PI resin precursor solution may be applied to the metal surface layer by layer or in multiple applications to form multiple coating films of the PI resin precursor solution, or multiple layers of laminate coating films of the PI resin precursor solution may be formed simultaneously. Examples of methods for simultaneously forming multiple coating films include coextrusion and multilayer curtain coating.

[0272] In the coating and pre-drying steps, the coating speed of the PI resin precursor solution is preferably 0.1 m / min or more, more preferably 0.3 m / min or more, even more preferably 0.5 m / min or more, and is preferably 2.0 m / min or less, more preferably 1.0 m / min or less, and even more preferably 0.8 m / min or less. When the coating speed is within the above range, in combination with the roughness parameter of the metal surface, the roughness parameter of the obtained laminate, the total area of ​​resin defects near the interface caused by microtoming under specific conditions, or the DMT elastic modulus parameter of the obtained laminate tends to be easily adjusted within the above range.

[0273] In the coating and pre-drying steps, the temperature at which the coating film (preferably the multilayer coating film) is pre-dried is preferably 60°C or higher, more preferably 70°C or higher, even more preferably 80°C or higher, still more preferably 90°C or higher, and preferably 200°C or lower, more preferably 150°C or lower, and even more preferably 130°C or lower. The pre-drying time is preferably 30 seconds or longer, more preferably 1 minute or longer, even more preferably 5 minutes or longer, and even more preferably 10 minutes or longer, for example, 15 minutes or longer, 20 minutes or longer, or 25 minutes or longer, and is preferably 24 hours or shorter, more preferably 12 hours or shorter, even more preferably 6 hours or shorter, and particularly preferably 1 hour or shorter. When the pre-drying temperature and pre-drying time are within the above ranges, in combination with the roughness parameter of the metal surface, the roughness parameter of the resulting laminate, the total area of ​​resin defects near the interface caused by microtoming under specific conditions, or the DMT elastic modulus parameter of the resulting laminate tend to be easily adjusted within the above ranges.

[0274] (Standing Step) The standing step is a step in which the coating film (preferably a multilayer coating film) obtained in the coating and pre-drying steps is left standing. By subjecting the coating film to the standing step before the imidization step, sufficient solvent remains throughout the coating film during imidization, or the resin layers are more likely to blend well with each other, thereby increasing the degree of freedom of the resin molecules until imidization. Although the reason for this is unclear, including such a standing step tends to facilitate adjusting the roughness parameter of the interface of the resulting laminate, the total area of ​​resin defects near the interface caused by microtoming under specific conditions, or the DMT elastic modulus parameter of the resulting laminate within the above-mentioned ranges, in combination with the surface roughness parameter of the metal layer. Furthermore, the standing step is thought to facilitate mixing of the PI resins constituting each layer near the interface of each PI resin-containing layer, forming mixed regions near the interface, which tends to improve the mechanical properties of the resulting laminate.

[0275] In the standing step, the time for standing the coating film (also referred to as standing time) can be appropriately selected depending on the temperature (also referred to as standing temperature) during standing, and is not particularly limited, but is preferably 3 hours or more, more preferably 6 hours or more, even more preferably 12 hours or more, even more preferably 18 hours or more, and particularly preferably 22 hours or more. The upper limit of the standing time of the coating film is not particularly limited, and may usually be 450 hours or less, preferably 100 hours, and more preferably 50 hours or less. When the standing time of the coating film is within the above range, in combination with the surface roughness parameter of the metal layer, the roughness parameter of the interface of the obtained laminate, the total area of ​​resin defects near the interface caused by microtoming under specific conditions, or the DMT elastic modulus parameter of the obtained laminate tend to be more easily controlled within the above range, and the mechanical properties of the laminate can be improved.

[0276] In a preferred embodiment of the present invention, the standing step is preferably a step of standing (or storing) the coating film at a low temperature (preferably refrigerated). Standing (or storing) at a low temperature tends to make it easier to control, in combination with the surface roughness parameter of the metal layer, the roughness parameter of the interface of the resulting laminate, the total area of ​​resin defects near the interface caused by microtoming under specific conditions, or the DMT elastic modulus parameter of the resulting laminate within the above-mentioned ranges, thereby improving the mechanical properties of the laminate.

[0277] In the standing step, the standing temperature of the coating film is preferably 20°C or lower, more preferably 15°C or lower, even more preferably 10°C or lower, even more preferably 8°C or lower, and particularly preferably 5°C or lower. When the standing temperature of the coating film is below the above-mentioned upper limit, the roughness parameter of the interface of the resulting laminate, the total area of ​​resin defects near the interface caused by microtoming under specific conditions, or the DMT elastic modulus parameter of the resulting laminate tends to be more easily controlled within the above-mentioned ranges, depending on the combination with the surface roughness parameter of the metal layer, and the mechanical properties of the laminate can be improved. Furthermore, the lower limit of the standing temperature of the multilayer coating film is usually -30°C or higher, preferably -20°C or higher, more preferably -10°C or higher, even more preferably -5°C or higher, and particularly preferably 0°C or higher. The standing step may be carried out, for example, in air or an inert gas atmosphere, or in a sealed space. In one embodiment of the present invention, the standing step is preferably carried out with the coating film sealed, for example, by placing the coating film in a sealed container or laminating it with a film having low moisture permeability (for example, an aluminum laminate film) and then standing it.

[0278] (Imidization Step) The imidization step is a step of imidizing the PI resin in the coating film on the surface of the metal by heat treatment at a temperature of, for example, 200° C. or higher and 500° C. or lower.

[0279] In one embodiment of the present invention, the imidization step preferably includes a step of increasing the temperature from a low temperature (referred to as a first temperature) to a high temperature (referred to as a second temperature) at a relatively high rate and maintaining the temperature at that high temperature. By increasing the temperature at a relatively high rate, preferably rapidly, to proceed with imidization, and then maintaining the temperature at that temperature for a certain period of time to complete the imidization, this can be advantageous in terms of forming a higher-order structure or branched structure of the PI resin, and the resulting laminate can easily maintain a low Df and improve its yield strength. This can also be advantageous in terms of obtaining a smooth laminate.

[0280] In one embodiment of the present invention, the first temperature is preferably 20°C or higher and 50°C or lower, more preferably 25°C or higher and 35°C or lower, and the second temperature is preferably 200°C or higher and 450°C or lower, more preferably 250°C or higher and 400°C or lower, even more preferably 270°C or higher and 380°C or lower, particularly preferably 290°C or higher and 360°C or lower, and particularly preferably 300°C or higher and 350°C or lower, for example, 300°C or higher and 340°C or lower, 300°C or higher and 330°C or lower, or 310°C or higher and 320°C or lower. According to the laminate of the present invention, even when imidization is performed at a relatively low temperature, for example, 350°C or lower (preferably 320°C or lower), high yield strength can be exhibited and Df can be reduced. Furthermore, when the imidization temperature is 350°C or lower (preferably 320°C or lower), thermal degradation of the copper layer can be suppressed even when a copper layer is used as the metal layer, making it easier to obtain a laminate with excellent high-frequency characteristics. The imidization temperature is preferably 200°C or higher, more preferably 210°C or higher, and even more preferably 220°C or higher, from the viewpoint of sufficiently improving the imidization rate, improving the yield strength, and reducing Df.

[0281] In one embodiment of the present invention, the temperature increase from the first temperature to the second temperature may be performed in a single stage or in two or more stages. In one embodiment of the present invention, when the temperature increase from the first temperature to the second temperature is performed in a single stage, the temperature increase rate is preferably 2°C / min or more, more preferably 3°C / min or more, even more preferably 4°C / min or more, and preferably 30°C / min or less, more preferably 20°C / min or less, and even more preferably 10°C / min or less. The use of such a temperature increase rate can be advantageous in terms of the formation of a higher-order structure or branched structure of the PI resin, making it easier for the resulting laminate to maintain a low Df while improving its yield strength. It can also be advantageous in terms of obtaining a smooth laminate.

[0282] In one embodiment of the present invention, the temperature rise time from the first temperature to the second temperature can be appropriately selected depending on the temperature and the temperature rise rate, and is preferably 5 hours or less, more preferably 3 hours or less, even more preferably 2 hours or less, particularly preferably 1.5 hours or less, and is preferably 3 minutes or more, more preferably 10 minutes or more, and even more preferably 30 minutes or more. When the temperature rise time from the first temperature to the second temperature is within the above range, the obtained laminate tends to maintain a low Df while improving its yield strength.

[0283] 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, even more preferably 30 minutes or more, even more preferably 60 minutes or more, and preferably 5 hours or less, more preferably 3 hours or less. When the heating rate from the first temperature to the second temperature is within the above range and the holding time at the second temperature is within the above range, this can be advantageous in terms of forming a higher-order structure or a branched structure of the PI resin, and the resulting laminate tends to maintain a low Df while improving its yield strength. By adopting the above-described imidization process, particularly a preferred imidization process (imidization temperature, heating rate, heating time, holding time, etc.), in combination with the roughness parameter of the metal layer, it tends to be easier to control the roughness parameter of the resulting laminate, the total area of ​​resin defects near the interface caused by microtoming under specific conditions, or the DMT elastic modulus parameter of the resulting laminate within the above range.

[0284] In one embodiment of the present invention, examples of a method for bonding a resin film and a metal layer include, as described in the section "Method for Producing a Resin Film," a method in which a resin film is produced by cast molding, extrusion molding, or the like, and then bonded to a metal layer by heat pressing, thermal lamination, or the like. When the resin film is a PI-based film, a method may be used in which a PI-based resin precursor solution is applied to a support substrate other than the metal layer contained in the laminate, and then dried to obtain a coating film of the PI-based resin precursor, which is then peeled from the substrate and bonded to the metal layer. From the viewpoint of easily adjusting the roughness parameter and the total area of ​​resin defects near the interface caused by microtoming under specific conditions, or the DMT elastic modulus parameter of the resulting laminate, within the above-mentioned ranges by combining them with the roughness parameter of the metal surface, and thus realizing high yield strength, the above-mentioned method in which the PI-based resin precursor coating film is thermally imidized on the metal layer is preferred.

[0285] When the resin film has metal layers on both sides, the metal layers may be provided on both sides by the same or different methods.

[0286] [Flexible Printed Circuit Board] The laminate of the present invention has high yield strength and can be suitably used as an FPC board material. Furthermore, the laminate of the present invention can have a low Df, which can reduce the transmission loss of an electrical circuit incorporating the laminate. Furthermore, the laminate of the present invention has a low CTE and excellent thermal properties, so it can be suitably used as an FPC board material, particularly an FPC board material for high-speed communications such as 5G. Therefore, the present invention also encompasses a flexible printed circuit board comprising the laminate of the present invention.

[0287] The present invention will be described in more detail below based on examples and comparative examples, but the present invention is not limited to the following examples.

[0288] The abbreviations used in the examples and comparative examples represent the following compounds: BPDA: 3,3',4,4'-biphenyltetracarboxylic dianhydride BP-TME: 4,4'-bis(1,3-dioxo-1,3-dihydroisobenzofuran-5-ylcarbonyloxy)biphenyl PMDA: pyromellitic anhydride m-Tb: 4,4'-diamino-2,2'-dimethylbiphenyl TPE-Q: 1,4-bis(4-aminophenoxy)benzene TPE-R: 1,3-bis(4-aminophenoxy)benzene

[0289] 1. Preparation of Polyimide Resin Precursor Solution (1) Polyimide Resin Precursor Solution 1: 48.61 g (228.9 mmol) of m-Tb and 66.92 g (228.9 mmol) of TPE-Q were dissolved in 1598 g of DMAc, and then 118.22 g (221.2 mmol) of BP-TME was added and stirred for 1 hour at 20°C under a nitrogen atmosphere. 48.25 g (221.2 mmol) of PMDA was then added and stirred for 3 hours at 20°C under a nitrogen atmosphere to obtain PI Resin Precursor Solution 1. The molar ratio of diamine monomer to acid dianhydride monomer used was 1.04.

[0290] (2) Polyimide-based resin precursor solution 2: 11.22 g (52.9 mmol) of m-Tb and 15.45 g (52.9 mmol) of TPE-R were dissolved in 405 g of DMAc, and then 21.67 g (73.7 mmol) of BPDA and 6.89 g (31.6 mmol) of PMDA were added in that order, followed by stirring 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.

[0291] (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 1,890 g of DMAc, and then 30.28 g (138.8 mmol) of PMDA and 95.30 g (323.9 mmol) of BPDA were added in this order, followed by stirring for 3 hours at 20°C 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.

[0292] 2. Preparation of Laminate and Resin Film (Example 1) PI resin precursor solution 2 was applied to the roughened surface of an electrolytic copper foil (thickness 12 μm) having the roughness properties of the roughened surface shown in Table 4 at a speed of 0.6 m / min to a dry thickness of 5 μm, thereby obtaining a coating film. The coating film was heated and dried at 120°C for 10 minutes, and PI resin precursor solution 1 was applied to the dried coating film at a speed of 0.6 m / min to a dry thickness of 41 μm, thereby obtaining a two-layer laminate coating film. The two-layer laminate coating film was heated and dried at 120°C for 30 minutes, and PI resin precursor solution 2 was applied to the dried two-layer laminate coating film at a speed of 0.6 m / min to a dry thickness of 5 μm, thereby obtaining a three-layer laminate coating film. The three-layer laminate coating film was heated and dried at 120°C for 30 minutes, and then the laminate consisting of the copper foil and the three-layer laminate coating film was placed in a sealed container and left to stand at a temperature of 4°C for 24 hours. Thereafter, the laminate was removed from the sealed container and confirmed to have reached room temperature. Then, it was fixed to 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. This resulted in a laminate 1 consisting of a PI resin-containing layer and a copper foil layer, in which the copper foil layer, layer (PI-2), layer (PI-1), and layer (PI-3) (TPI layer, mPI layer, and TPI layer) were laminated in this order. The resulting laminate 1 was immersed in a large volume of a 40% by mass aqueous ferric chloride solution at room temperature for 10 minutes, after which the aqueous ferric chloride solution was washed with pure water. After visually confirming that no copper remained, the laminate was dried at 80°C for 1 hour to obtain a resin film 1 consisting of the layer (PI-2) (copper foil layer side), layer (PI-1), and layer (PI-3) (TPI layer, mPI layer, and TPI layer) laminated in this order. The thickness of the resin film 1 was 51 μm. The PI resin precursor solution was applied using an automatic coating device (manufactured by Tester Sangyo Co., Ltd., PI-1210) equipped with an applicator (manufactured by Tester Sangyo Co., Ltd., SA-204 (width 250 mm)).

[0293] Example 2 A laminate 2 composed of a PI resin-containing layer and a copper foil layer, which were formed by laminating a copper foil layer, a layer (PI-2), a layer (PI-1), and a layer (PI-3) (TPI layer, mPI layer, and TPI layer) in this order, and a resin film 2 from which the copper foil layer was removed were obtained in the same manner as in Example 1, except that electrodeposited copper foils (thickness: 12 μm, see Table 4) with different roughness properties on the roughened side were used and coated so that the dry thicknesses of layer (PI-2) (copper layer side) / layer (PI-1) / layer (PI-3) were 5 μm / 39 μm / 5 μm.

[0294] Example 3 A laminate 3 composed of a PI resin-containing layer and a copper foil layer, which were formed by laminating the copper foil layer, layer (PI-2) (copper foil layer side), layer (PI-1) and layer (PI-3) (TPI layer, mPI layer and TPI layer) in this order, and a resin film 3 from which the copper foil layer was removed were obtained in the same manner as in Example 1, except that electrodeposited copper foils (thickness: 12 μm, see Table 4) with different roughness properties on the roughened side were used and coated so that the dry thicknesses of layer (PI-2) (copper layer side) / layer (PI-1) / layer (PI-3) were 5 μm / 43 μm / 5 μm.

[0295] Example 4 A laminate 4 composed of a PI-based resin-containing layer and a copper foil layer, which were formed by laminating a copper foil layer, a layer (PI-2), a layer (PI-1), and a layer (PI-3) (TPI layer, mPI layer, and TPI layer) in this order, and a resin film 4 from which the copper foil layer was removed were obtained in the same manner as in Example 1, except that electrodeposited copper foils (thickness: 12 μm, see Table 4) having different roughness properties on the roughened side were used and PI-based resin precursor solution 3 / PI-based resin precursor solution 1 / PI-based resin precursor solution 3 were coated in the order of layer (PI-2) (copper layer side) / layer (PI-1) / layer (PI-3) to give dry thicknesses of 5 μm / 38 μm / 5 μm, respectively.

[0296] Example 5 A laminate 5 consisting of a PI resin-containing layer and a copper foil layer, which were formed by laminating the copper foil layer, layer (PI-2), layer (PI-1), and layer (PI-3) (TPI layer, mPI layer, and TPI layer) in this order, and a resin film 5 from which the copper foil layer was removed were obtained in the same manner as in Example 4, except that electrodeposited copper foils (thickness: 12 μm, see Table 4) with different roughness properties on the roughened side were used and coated so that the dry thicknesses of layer (PI-2) (copper foil layer side) / layer (PI-1) / layer (PI-3) were 5 μm / 35 μm / 5 μm.

[0297] Example 6 A laminate 6 consisting of a PI resin-containing layer and a copper foil layer, which were formed by laminating a copper foil layer, a layer (PI-2), a layer (PI-1), and a layer (PI-3) (TPI layer, mPI layer, and TPI layer) in this order, and a resin film 6 from which the copper foil layer was removed were obtained in the same manner as in Example 4, except that electrodeposited copper foils (thickness: 12 μm, see Table 4) with different roughness properties on the roughened side were used and coated so that the dry thicknesses of Layer (PI-2) (copper foil layer side) / Layer (PI-1) / Layer (PI-3) were 5 μm / 41 μm / 5 μm.

[0298] Example 7 Laminate 7, which was composed of a PI resin-containing layer and a copper foil layer, and resin film 7, which was obtained by laminating a copper foil layer, layer (PI-2), layer (PI-1), and layer (PI-3) (TPI layer, mPI layer, and TPI layer) in this order, and copper foil layer, were obtained in the same manner as in Example 4, except that electrodeposited copper foils (thickness: 12 μm, see Table 4) with different roughness properties on the roughened side were used and coated so that the dry thicknesses of layer (PI-2) (copper foil layer side) / layer (PI-1) / layer (PI-3) were 5 μm / 34 μm / 5 μm.

[0299] Comparative Example 1 A laminate 8 composed of a PI resin-containing layer and a copper foil layer, which were formed by laminating a copper foil layer, a layer (PI-2), a layer (PI-1), and a layer (PI-3) (TPI layer, mPI layer, and TPI layer) in this order, and a resin film 8 from which the copper foil layer was removed were obtained in the same manner as in Example 1, except that electrolytic copper foils (thickness: 12 μm, see Table 4) with different roughness properties on the roughened side were used and coated so that the dry thicknesses of layer (PI-2) (copper layer side) / layer (PI-1) / layer (PI-3) were 5 μm / 42 μm / 5 μm.

[0300] Measurements and evaluations were carried out on the laminates 1 to 8 and resin films 1 to 8 obtained in the examples and comparative examples. The measurement and evaluation methods are explained below.

[0301] <Film Thickness Measurement> A 5 ​​mm x 5 mm arbitrary portion was cut out from each of the resin films 1 to 8 obtained in the Examples and Comparative Examples, and embedded in resin to prepare a film thickness measurement sample. The prepared film thickness measurement sample was cut using a microtome to prepare a measurement cross section, and the thickness of each of the three PI resin-containing layers and the thickness of the resin film were measured using a laser microscope under the following conditions. Apparatus: LEXT OLS4100 manufactured by Olympus Corporation Observation magnification: 100x

[0302] <Measurement of Df and Dk> Measurement samples of 50 mm x 50 mm were cut out from each of the resin films 1 to 8 obtained in the Examples and Comparative Examples, and Df and Dk were measured under the following conditions. The measurements were carried out after conditioning the measurement samples at 23°C / 50% RH for 24 hours. Apparatus: Compact USB Vector Network Analyzer (product name: MS46122B) manufactured by Anritsu Corporation; Cavity resonator (TE mode 10 GHz type) manufactured by AET Corporation; Measurement frequency: 10 GHz; Measurement atmosphere: 23°C / 50% RH

[0303] <Measurement of coefficient of linear thermal expansion (CTE)> The CTE of resin films 1 to 8 obtained in the examples and comparative examples was measured using a thermomechanical analyzer TMA under the following conditions, and the CTE was calculated from 50°C to 100°C. Apparatus: TMA / SS7100 manufactured by Hitachi High-Tech Science Corporation Load: 50.0 mN Temperature program: Heating from 20°C to 130°C at a rate of 5°C / min Test piece: Length 40 mm, width 5 mm

[0304] <Measurement of Storage Modulus> The storage modulus of each PI resin formed from the above PI resin precursor solutions 1 to 3 was determined by measuring the storage modulus of the PI resin film prepared by the following method under the following conditions. Each PI resin precursor solution was cast onto a glass substrate to a dry thickness of 30 μm to form a coating film of the PI resin precursor solution. The coating film was heated at 120°C for 30 minutes, and the resulting film was peeled from the glass substrate and then fixed to a metal frame. The film fixed to the metal frame was maintained at 320°C for 5 minutes in an atmosphere with an oxygen concentration of 1%, to obtain a PI resin film. The storage modulus (E') was determined using a dynamic viscoelasticity measuring device (DVA-220, manufactured by IT Measurement & Control Co., Ltd.) under the following sample and conditions. Test piece: rectangular parallelepiped with a length of 40 mm, a width of 5 mm, and a thickness of 30 μm Experimental mode: single frequency, constant rate of temperature increase Experimental style: tension Sample grip length: 15 mm Measurement start temperature: room temperature to 342°C Temperature increase rate: 5°C / min Frequency: 10 Hz Static / dynamic stress ratio: 1.8 As a result of measurement using the above method, the PI resin film formed from the PI resin precursor solution 1 had a storage modulus of 2.3 × 10 at 40°C. ９ Pa, storage modulus at 300°C is 2.8 × 10 ８ The PI resin film formed from the PI resin precursor solution 2 had a storage modulus of 2.3 × 10 at 40 °C. ９ Pa, storage modulus at 300°C is 1.2 × 10 ７ The PI resin film formed from the PI resin precursor solution 3 had a storage modulus of 2.4 × 10 at 40 °C. ９ Pa, storage modulus at 300°C is 1.1 x 10 ７ It was Pa.

[0305] <Measurement of Moisture Content and Drying Rate of Resin Film> A 50 mm x 50 mm sample was cut out from each of the resin films 1 to 3 and 5 to 8 obtained in the Examples and Comparative Examples to prepare samples for drying rate measurement. The prepared samples were immersed in pure water at 25°C for 24 hours to fully absorb moisture, then removed, surface water droplets were wiped off with a rag, and the sample weight was measured. Immediately thereafter, the hydrated sample was placed in a forced circulation oven and dried at 120°C for 60 minutes, after which the sample weight was measured again. Using the weight of the resin film after 60 minutes of drying as a reference, the moisture content before drying (moisture content after 24 hours of immersion) was calculated using the following formula. Furthermore, for resin films 1 to 2 and 6 to 8, the sample weight was also measured after drying for 5 minutes at 120°C, and the rate of change in moisture content (drying rate) after 5 minutes of drying was calculated using the following formula. The moisture contents of resin films 1 to 3 and 5 to 8 were 3.12%, 3.74%, 1.58%, 1.84%, 1.86%, 1.37%, 1.46%, and 4.18%, respectively. The drying rates of resin films 1 to 2 and 6 to 8 were 0.47% / min, 0.52% / min, 0.55% / min, 0.63% / min, and 0.37% / min, respectively. Moisture content before drying (%) = (weight immediately after hydration - weight after 60 minutes of drying) / weight immediately after hydration x 100 Drying rate (% / min) = [{(weight immediately after hydration - weight after 60 minutes of drying) / weight immediately after hydration x 100} - {(weight after 5 minutes of drying - weight after 60 minutes of drying) / weight immediately after hydration x 100}] / 5

[0306] <0.2% Proof Stress Measurement> Test specimens measuring 100 mm x 10 mm were prepared by cutting out randomly selected locations from each of the laminates 1 to 8 obtained in the Examples and Comparative Examples. Using an Autograph AG-IS manufactured by Shimadzu Corporation, stress-strain curves (SS curves) were measured under conditions of a temperature of 25°C, a relative humidity of 50%, a chuck distance of 50 mm, and a tensile speed of 20 mm / min, and the 0.2% proof stress was calculated as follows. 1) Data Reduction of SS Curve: Ten consecutive points were sampled from the measurement start point on the SS curve, and the curves were fitted to a quadratic function using the least squares method. Subsequently, one point was removed from the left side of the measurement start point and one point was added to the right side until the quadratic function fitting of the 10 sampling points resulted in an upwardly convex shape. Data reduction was completed when the fitting function became upwardly convex.

[0307] 2) Calculation of the Tangent Equation of the S-S Curve The slope and intercept were determined by the least squares method using the data n = i to j (j = 2 to 50) from the data in 1) above. Then, for the j-1 slopes, the kth (k = 1 to 48) to 49th data were fitted to a linear function using the least squares method, and the slope when the strain was 0 was determined by extrapolation. The median of the obtained 48 points was taken and defined as the slope of the line when the strain was 0 (the tangent to the S-S curve). The intercept was calculated in the same way, and an equation for the tangent to the S-S curve at a strain of 0 was obtained.

[0308] 3) Calculation of 0.2% proof stress The tangent to the S-S curve obtained in 2) above at strain 0 was translated by 0.2% in the strain direction. The stress value at which the translated line intersects with the S-S curve was taken as the 0.2% proof stress.

[0309] <Measurement of roughness parameters of copper foil layer-resin film interface> (FIB processing pretreatment) A portion of each of the laminates 1 to 8 obtained in the examples and comparative examples was cut, and the end faces of the cut specimens were processed with an ultramicrotome (Leica EM UC7, manufactured by Leica) to create a smooth cross section in the thickness direction. The specimens were then fixed to the SEM sample holder with carbon tape so that the resin side of the laminate was the adhesive surface. Furthermore, platinum was vapor-deposited twice on the copper foil surface of the laminate using an ion sputtering device under the following conditions (see Figure 1(a)). Ion sputtering conditions: Device: MC1000 (Hitachi) Current: 10 mA Sputtering time: 300 seconds

[0310] (FIB Processing) A beam was irradiated perpendicularly to the copper foil surface of the laminate, and a portion of the center of the microtome-processed edge was cut out so that it had a U-shape when viewed from the copper foil surface side, creating a smooth observation surface. The acceleration voltage and beam current during processing were adjusted appropriately, and the final processing step was finished under the following conditions (see Figure 1(b)). Of the processed cross sections, the surface parallel to the microtome-processed surface was used as the observation surface (see Figure 1(c)). Finishing conditions FIB-SEM device: Helios G4 UX (ThermoFisher SCIENTIFIC) Acceleration voltage: 20 kV Beam current: 1.2 nA

[0311] (Pretreatment for SEM Observation) Platinum was vapor-deposited on the FIB-processed surface (observation surface) using an ion sputtering device under the following conditions: Ion sputtering conditions Device: MC1000 (Hitachi High-Tech Corporation) Current value: 10 mA Sputtering time: 20 seconds

[0312] (SEM Observation) SEM observation of the observation surface of Laminates 1 to 8 was carried out under the following conditions, and SEM images were obtained. At that time, the angle was adjusted so that the interface between the copper foil layer and the resin film was horizontal to the image. SEM Observation Conditions Apparatus: Helios G4 UX (ThermoFisher SCIENTIFIC) SEM Mode: Mode 2 Detector: Through-the-Lens Detector Photography Conditions: Observation Magnification: 10,000x Observed Image: BSE Image Acceleration Voltage: 5 kV Beam Current: 0.1 nA Dwell Time: 5 μs Line Integration: 1 Resolution: 3072 × 2048 (0.147 pixels / nm) Save Format: Tiff

[0313] (Creation of cross-sectional curves) Using Image J (NIH), cross-sectional curves (interface contour curves) of the interfaces between the copper foil layer and resin film of laminates 1 to 8 were created using the following steps (English names are tool names within Image J). 1) Image capture The SEM images obtained above were captured using Image J. At this time, the images were captured in a direction in which the convex portions of the copper foil layer were facing upward. 2) Smoothing Smoothing was performed twice using the Smooth function. 3) Contrast adjustment Contrast was adjusted by setting the high-luminance end of the histogram derived from the resin film (resin layer) present on the low-luminance side as the minimum value, and the low-luminance end of the histogram derived from the copper foil layer present on the high-luminance side as the maximum value. 4) Binarization The Threshold function was used, with Default (modified IsoData Algorithm) selected as the Auto threshold method. 5) Noise removal The Remove Outliers function was used, and processing was carried out in the following order under the following conditions. 1st time: Radius = 4 pixels, Threshold = 50, Witch Outlier = white 2nd time: Radius = 4 pixels, Threshold = 50, Witch Outlier = black Then, the white granular areas isolated from the copper foil part and the black granular areas isolated from the resin part were manually removed using the fill tool. 6) Contour Extraction: Find Edge and Skeletonize were executed in that order to extract the contour portion, which is the interface between the copper foil layer and the resin film, to obtain a contour curve. Then, Save XY Coordinates was used to output the contour curve coordinates in CSV format (the contour curve is a curve with an upward-pointing peak corresponding to the convex portion of the copper foil layer; that is, it is the contour line of the interface when the copper foil layer is on the bottom and the resin film is on the top). 7) Cross-Section Curve Correction: First, using Excel, the slope a of the regression line of the contour curve was calculated, and y' = y - x × a was calculated for each coordinate (x, y), and this was rewritten as (x, y') to correct the slope of the contour curve. Then, the average value b was calculated using the y' values ​​of all coordinates, and y'' = y' - b was calculated for each coordinate (x, y'), and this was rewritten as (x, y''), to correct the average value of the contour curve.At this time, the unit was converted from pixel to nm (0.147 pixel / nm). As a result, the profile curves after tilt correction and average correction, i.e., the cross-sectional curves, were obtained. The above processing was performed on the SEM images of laminates 1 to 8, and the cross-sectional curve data obtained up to this point was entered into Excel sheets N1 to N8, respectively, and saved with the file name "Book1" (the sheets were configured so that laminate X was sheet NX).

[0314] <Calculation of Area and Contour Length of Copper Foil Convex Region> The area and contour length of the copper foil convex region were calculated by using Python to create a diagram of the cross-sectional curve obtained above, adding a baseline connecting the minimum points of the peaks with a straight line, and then using the particle analysis tool in Image J for the convex region surrounded by the cross-sectional curve and the baseline.

[0315] (Creating a baseline connecting the minimum points of the peaks in the profile curve) By executing the following code in Python, the minimum points of the peaks in the profile curve created above were detected, a baseline connecting the minimum points of the peaks was created, and a diagram with the baseline added to the profile curve was obtained.

[0316]

[0317] The specific processing performed by the above code is as follows. First, an Excel file containing the profile curve f(x) (x, y coordinates in nm) was loaded into Python. Next, if there were multiple coordinates at the same x value at the peak (convex portion) of the profile curve f(x), the file was converted to a profile curve f'(x) that retained only the coordinate at the minimum y value. Next, the profile curve f'(x) was standardized, and then the profile curve was inverted symmetrically about the x axis so that the peak was pointing downward. The find_peaks function was used to find the coordinates (valley_x, valley_y) of the maximum of the profile curve f'(x). A plotting range where 1 pixel = 1 nm was prepared, and the profile curve f(x) was plotted within this range. A graph was then created by adding a baseline connecting the coordinates (valley_x, valley_y) obtained from the profile curve f'(x) with a straight line. This resulted in a graph in which the peaks representing the respective convex portions of the interface were surrounded by the cross-sectional curve and the baseline, and the graph was saved in JPEG format. The creation of the graph image was similarly carried out for Laminates 1 to 8.

[0318] (Analysis with Image J) Using Image J (NIH), the area and contour length of each convex region of the copper foil at the laminate interface were calculated by the following steps.

[0319] 1) Import the graph image (at this time, only the outline of the cross section curve and baseline will be black) 2) Select Make binary and edit the image so that only the outline of the cross section curve and baseline will be white 3) Use the Flood fill tool to paint the background (outside the convex part surrounded by the cross section curve and baseline) white (only the convex part will remain, only the inside of the convex part will be black) 4) Use Invert to invert the brightness (the inside of the convex part will be white, the background will be black) 5) Remove noise from the convex part as described in the section below (Removing convex part noise). 6) Use Analyze Particles to perform particle analysis under the following conditions and calculate the area and outline length of each convex part region Size: 0-infinity Circularity: 0-1

[0320] (Removal of convex noise) Of the convex parts extracted above, those that satisfied the following (i) and (ii) were judged to be noise and were excluded from the calculation of the area and contour length. (i) was judged to be a region that occurred during the baseline creation process and was not a convex part itself, and (ii) was judged to be noise that occurred due to low contrast near the interface in the SEM image. (i) Area range derived from a convex part where the cross-sectional curve is located below the baseline (ii) Area is 1000 nm ２ Less than 100mm convex part

[0321] (Calculation of Evaluation Length) In the above graph image (before removing convex noise), the distance between the x-coordinate of the left end of the convex portion located at the leftmost end and the x-coordinate of the right end of the convex portion located at the rightmost end determined as the evaluation range (the left end and right end of the convex portion are both the minimum points of each convex portion) was taken as the evaluation length (meaning the length of a straight line parallel to the x-axis of the graph). The evaluation length was determined using the measurement function of Image J.

[0322] Within the above range of evaluation length, the values ​​of the average contour length / area of ​​each convex region ([Σ(Ln / Sn)] / Na), the average area of ​​the convex regions (Σ(Sn) / Na), the average contour length of the convex regions (Σ(Ln) / Na), the total area of ​​the convex regions / evaluation length (Sn / A), and the number of convex regions / evaluation length (Na / A) were calculated.

[0323] <Measurement of Copper Foil Layer Surface Roughness> Using a laser microscope (OLYMPUS Corporation, LEXT OLS4000), the surface of the copper foil layer in contact with the resin film was observed with a laser under the following observation conditions to obtain a three-dimensional shape image. Subsequently, the three-dimensional shape image was analyzed under the following analysis conditions using image processing software LEXT OLS4100 (OLYMPUS; ver. 3.1.15.1) to calculate surface roughness parameters. Measurements of Sal, Str, Sk, Sdr, Sp, Sv, Sku, Sa, and Sz were performed in accordance with ISO 25178, respectively, and measurements of Ra, Rz, and Rzjis were performed in accordance with JIS B0601:2013, respectively.

[0324] [Observation conditions] Apparatus: LEXT OLS4000 (manufactured by Olympus Corporation) Observation magnification: 100x Objective lens: MPLAPON100LEXT Photography conditions: Photography method: laser observation Scanning mode: XYZ high precision Measurement pitch: 0.06 μm Measurement range: 128 μm × 128 μm

[0325] [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

[0326] [Analysis conditions] (Ra, Rz, Rzjis) Analysis software: LEXT OLS4100 (OLYMPUS) Ver. 3.1.15.1 In the acquired three-dimensional shape image, five cross-sectional curves were acquired at 25 μm intervals from a position 4 μm away from the bottom of the image. Each curve was analyzed under the following conditions to evaluate Ra, Rz, and Rzjis, and the average values ​​were calculated. λs: 2.5 μm λc, λf: Not set

[0327] The results of each measurement are shown in Tables 3 and 4.

[0328]

[0329]

[0330] <Calculation of Resin Defect Area> 1) Preparation of Test Pieces A portion of each of the laminates 1, 2, 5, and 7 obtained in the examples was cut using a carbon steel single-edged blade (manufactured by Feather Safety Razor Co., Ltd.) with a blade thickness of 0.245 μm to cut out a trapezoidal test piece with an upper base of 1 mm, a lower base of 3 mm, and a height of 4 mm. The sample was attached to an AFM sample holder (manufactured by Leica) so that the thickness direction cross section of the upper base with a length of 1 mm became the processed surface, and then the holder was attached to an ultramicrotome (manufactured by Leica, "Leica EM UC7") (at this time, the test piece was installed so that the in-plane direction of the laminate was vertical). First, using a glass knife, the test piece was scanned vertically (in-plane direction of the laminate), and the thickness direction cross section of the test piece was cut by 20 μm at a processing speed of 500 nm / s. Thereafter, further cutting was performed using a new SYM knife (diamond knife "SYM2045 Ultra" manufactured by Shintech Co., Ltd.) under the following processing conditions. The cross section cut with the microtome was used as the observation surface. (SYM knife cutting conditions) Return speed: High Angle: 4° Cutting amount (per cut): 300 nm Cutting speed: 1.0 mm / sec Number of cuts: 5

[0331] 2) Pretreatment for SEM Observation Platinum was vapor-deposited on the processed surface (observation surface) of the test piece using an ion sputtering device under the following conditions: (Ion sputtering conditions) Device: MC1000 (Hitachi) Current value: 10 mA Sputtering time: 20 seconds

[0332] 3) SEM Observation Under the following conditions, the angle was adjusted so that the interface between the copper foil and the resin film was horizontal to the image, and the observation position was adjusted so that the interface was located at the center of the image in the height direction and so that nothing other than the laminate was included in the angle of view. Then, SEM observation of the observation surface was performed, and an SEM image showing a width of 4.2 μm (length in the planar direction of the laminate) × length of 2.8 μm (length in the thickness direction of the laminate) was obtained. (SEM observation conditions) Apparatus: Helios G4 UX (ThermoFisher SCIENTIFIC) SEM mode: Inner Detector: DBS detector (only the central annular segment of the ABS detector was selected) (Photography conditions) Observation magnification: 50,000x Observed image: ABS image Acceleration voltage: 2.00 kV Beam current: 0.10 nA Dwell time: 20 μsec Line integration: 1 Resolution: 1536 × 1024 Bit: 16 bit Save format: Tiff

[0333] 4) Calculation of resin portion defect area The SEM image obtained above (the size of the portion depicting the laminate was 4.2 μm horizontally × 2.8 μm vertically) was imported into Image J, and using the Duplicate function, it was converted into an observation image consisting of 1536 × 1024 points (resolution 2.7 × 10 ―３ μm / pixel). From the observed image, a 65,536-level (256-bin) brightness histogram was obtained for each of four regions: the entire region, the resin region, the copper foil region, and the region containing both copper foil and resin (hereinafter referred to as the composite region), and a probability density distribution was obtained by the following processing.

[0334] A) Whole region: Using the Histogram function, the entire brightness histogram was obtained. By normalizing it by the total number of points in the histogram, the probability density distribution H for brightness x was obtained. ａｌｌ (x) was obtained. B) Resin Region Using the Selection function, an analysis range (rectangular) consisting of only resin without defects or copper foil was extracted, and a brightness histogram of the extracted area was obtained. By normalizing it by the total number of points in the histogram, the probability density distribution H for brightness x was obtained. ＰＩC) Copper foil area Using the Selection function, a rectangular area consisting of only copper foil without resin was extracted, and a brightness histogram of the extracted area was obtained. By normalizing the total number of points in the histogram, the probability density distribution H for brightness x was obtained. Ｃｕ (x) was obtained. D) Composite Region Using the Selection function, a range (rectangular) that includes resin and copper foil but does not include any missing parts was extracted, and a brightness histogram of the extracted part was obtained. By normalizing it by the total number of points in the histogram, the probability density distribution H for brightness x was obtained. ｍ，Ｃｕ，ＰＩ (x) was obtained. At this time, h Ｃｕ’Ａｖｅ and ＰＩ’Ａｖｅ (See below) Ｃｕ’Ａｖｅ / h ＰＩ’Ａｖｅ A range was extracted so that the value was between 0.33 and 3.

[0335] The brightness histogram for each region was obtained under the condition that the total number of points was 200,000 or more. When it was difficult to set a range containing 200,000 or more points in a single analysis region, multiple analysis regions were set, and an average probability density distribution was created from the probability density distributions obtained in each analysis region under the condition that the sum of the total points in each analysis region was 200,000 or more points. The analysis regions were selected so that they did not overlap. Furthermore, under the SEM observation conditions described above, the brightness was, in descending order, copper foil, composite region, resin, and defect area. Therefore, when the peak top of the histogram obtained from the selected region was located at a lower brightness than the peak top of the histogram obtained from the region containing only resin, the selected region was identified as a defect area.

[0336] Next, by the following analysis, H Ｃｕ (x) and H ＰＩ (x) is a probability density distribution H ｍ (x) was obtained. First, H Ｃｕ The average value h of the probability density of the five points, i.e., the brightness x at which the peak top of (x) is located ±2 points Ａｖｅ Next, H ｍ，Ｃｕ，ＰＩ In (x), H Ｃｕ The average value h' of the probability density of the luminance at which the peak top of (x) is located ±2 points, totaling 5 points Ａｖｅ Find a = h'Ａｖｅ / h Ａｖｅ Similarly, a was calculated from the relation ＰI The average value h1 of the probability density of the 5 points of the brightness x where the peak top of (x) is located ±2 points Ａｖｅ Furthermore, H ｍ，Ｃｕ，ＰＩ In (x), H ＰＩ The average value h1' of the probability density of the luminance at which the peak top of (x) is located ±2 points, totaling 5 points Ａｖｅ Find b = h1' Ａｖｅ / h1 Ａｖｅ b was calculated from the following relational expression (VI). ｍ (x) was calculated. ｍ (x) = H ｍ，Ｃｕ，ＰＩ (x)-H Ｃｕ (x) × a-H ＰＩ (x) × b (VI)

[0337] Next, the probability density distribution H of the defect portion is calculated by the following formula (VII): ｄ (x) was obtained. ｄ (x) = H ａｌｌ (x)-H Ｃｕ (x) × c-H ＰＩ (x) × d-H ｍ (x)×e (VII) c, d, and e were calculated using the solver function of Excel under the following conditions: (Fitting conditions) Convergence condition: Root mean square error of the right side becomes the minimum value. Here, x is the brightness (256 points from 0 to 65536 gradations), and N is the number of x (256). Variables: c, d, e Constraints: None Initial conditions: c = 0.4, d = 0.4, e = 0.2 Solution method: GRG nonlinear

[0338] The probability density distribution H of the defect obtained above ｄ For (x), H ｄ H at luminance x where (x)<0 ｄ (x) to H ｄ (x) = 0. Next, the brightness is changed from x = 0 to H ＰＩ In the range of brightness x=x' where the peak top of (x) is located, H ｄ Integrate (x), obtained. The total area of ​​the defects was calculated by multiplying this by the total number of points in the brightness histogram of the entire region, and the total area of ​​the defects in the resin per evaluation length of 4.2 μm was obtained. At this time, the total area obtained was 2.7 × 10 ―３ A conversion from pixels to μm was also performed by dividing by μm / pixel. The results are shown in Table 5.

[0339]

[0340] <Scanning probe microscope (SPM) measurement> (Preparation of test pieces) A ​​portion of each of the laminates 1, 2, 5, 7, and 8 obtained in the examples and comparative examples was cut and embedded in resin so that the cross section in the thickness direction could be seen. Next, a glass knife was attached to an ultramicrotome (Leica, "Leica EM UC7"), and the blade was scanned perpendicular to the surface of the laminate. After reaching the surface of the resin-embedded film, 100 μm or more was cut in the depth direction of the test piece (in the planar direction relative to the laminate). Then, a SYM knife (Syntec, "SYM2045 Ultra") was attached, and 1 μm was cut at a cutting depth of 100 nm per scan at a scanning speed of 0.6 mm / sec., 1 μm was cut at a cutting depth of 50 nm per scan at a scanning speed of 0.6 mm / sec., and finally 0.3 μm was cut at a cutting depth of 30 nm per scan at a scanning speed of 0.3 mm / sec. The cut cross section was used as the observation surface, and the obtained test piece (sample) was set in an SPM (Dimension Icon manufactured by Bruker). The cut cross section (observation surface) included the metal layer, layer (PI-2) (TPI layer), layer (PI-1) (mPI layer), and layer (PI-3) (TPI layer).

[0341] (Acquisition of Elastic Modulus Image by SPM) The mechanical properties of the sample cross section were evaluated under the following conditions, and the DMT elastic modulus (GPa) was calculated based on the DMT (Derjaguim-Muller-Toporov) theory to obtain a DMT elastic modulus image. Specifically, first, the displacement of the piezo scanner and the amount of warping of the cantilever were measured during the process of contact between the cantilever probe and the sample, and a curve (force curve) showing the relationship between the load F and the amount of sample deformation δ was obtained. For each measurement point, the pullback process of the obtaine...

Claims

1. A laminate including a resin film and a metal layer provided on at least one surface of the resin film, wherein a cross-sectional curve of an interface between the resin film and the metal layer obtained from a cross-sectional image in a thickness direction of the laminate obtained by a scanning electron microscope is expressed by the formula (I): [Σ(Ln / Sn)] / Na≧0.046 (I) In the formula (I), Ln represents the contour length (nm) of each convex region surrounded by a straight line connecting the minimum points of each convex portion of the cross-sectional curve and the cross-sectional curve, and Sn represents the area (nm) of each convex region. ２ ) and Na represents the total number of the convex regions, and the evaluation length of the cross-sectional curve is 3,000 nm or more.

2. The cross-sectional curve satisfies the formula (II): Sa / A≦100 (II) (wherein Sa is the total area (nm ２ 2. The laminate according to claim 1, wherein A represents an evaluation length (nm) of the cross-sectional curve.

3. The profile curve satisfies the formula (III): Na / A≧2.80×10 ー３ The laminate according to claim 1 or 2, which satisfies the relationship of (III): (In formula (III), Na represents the total number of the convex regions, and A represents the evaluation length (nm) of the cross-sectional curve.

4. A laminate comprising a resin film and a metal layer provided on at least one surface of the resin film, wherein a cross section of the laminate in the thickness direction is processed with a microtome equipped with a diamond knife under the conditions of a cutting amount of 300 nm per cut and a processing speed of 1.0 mm / sec., and then, in a cross-sectional image of the laminate in the thickness direction obtained with a scanning electron microscope, the interface between the resin film and the metal layer is located at the center of the cross-sectional image in the thickness direction, and the total area of ​​the resin defects calculated based on the brightness distribution of the cross-sectional image is 0.300 μm per evaluation range of 4.2 μm × 2.8 μm. ２ The laminate is as follows:

5. A laminate comprising a resin film and a metal layer provided on at least one surface of the resin film, wherein when the elastic modulus is measured by a scanning probe microscope in five measurement regions set at intervals of 2 μm or more in a range of 500 nm in the thickness direction from the interface between the resin film and the metal layer toward the resin film in a thickness direction cross section of the laminate, the relationship of formula (V) is satisfied: [Σ(Sn / En)] / 5≦0.480 (V), where En represents the average elastic modulus of the resin film in each measurement region, and Sn represents the standard deviation of the elastic modulus in each measurement region.

6. The laminate according to claim 5, wherein the minimum value of Sn / En in each of the five measurement regions is 0.400 or less.

7. A laminate as described in claim 5 or 6, wherein the maximum value of Sn / En in each of the five measurement regions is 0.540 or less.

8. A laminate according to claim 5 or 6, wherein the Sn / En ratio in each of the five measurement regions is 0.520 or less.

9. The laminate according to claim 5 or 6, wherein the surface of the metal layer in contact with the resin film is a roughened surface having a plurality of convex portions, and when the elastic modulus is measured in five measurement regions each set between two adjacent convex portions of the roughened surface in a thickness direction cross section of the laminate, the relationship of formula (V) is satisfied.

10. The laminate according to claim 1 or 4, wherein the resin film contains at least one resin selected from the group consisting of polyimide-based resins, liquid crystal polymers, fluorine-based resins, aromatic polyether-based resins, epoxy-based resins, and maleimide-based resins.

11. The laminate according to claim 1 or 4, wherein the thermal expansion coefficient of the resin film is 10 to 29 ppm / K.

12. The laminate according to claim 1 or 4, wherein the resin film is a polyimide-based film containing a polyimide-based resin.

13. The laminate according to claim 12, wherein the polyimide-based film comprises a polyimide-based resin-containing layer (PI-1) and a polyimide-based resin-containing layer (PI-2).

14. The laminate according to claim 13, wherein the polyimide resin-containing layer (PI-2) is located on the metal layer side, and the thickness of the polyimide resin-containing layer (PI-2) is 0.05 to 0.3 times the thickness of the polyimide resin-containing layer (PI-1).

15. The laminate according to claim 13, wherein the polyimide film further comprises a polyimide resin-containing layer (PI-3).

16. The polyimide-based resin-containing layer (PI-1), the polyimide-based resin-containing layer (PI-2), and the polyimide-based resin-containing layer (PI-3) each have a storage modulus of 1.0×10 at 40° C. ９ The laminate according to claim 15 , comprising a polyimide resin having a modulus of at least 10 Pa. At least one of the polyimide-based resin-containing layer (PI-1) and the polyimide-based resin-containing layer (PI-2) contains a polyimide-based resin having a structural unit (A) derived from a tetracarboxylic acid anhydride, and the structural unit (A) is represented by the formula (A1): [In formula (A1), R ａ１ each independently represents a halogen atom, or an alkyl group, an alkoxy group, an aryl group, or an aryloxy group which may have a halogen atom, and k represents an integer of 0 to 2], and / or a structural unit (A1) derived from a tetracarboxylic acid anhydride represented by the formula (A2): [In formula (A2), R ａ２ each independently represents a halogen atom, or an alkyl group, an alkoxy group, an aryl group, or an aryloxy group which may have a halogen atom, and each 1 independently represents an integer of 0 to 3.

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

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

20. At least the polyimide resin contained in the polyimide resin-containing layer (PI-1) has the structural unit (A), and the structural unit (A) further contains 45 mol % or less of the formula (A3): [In formula (A3), Z represents a divalent organic group, R ａ３ each independently represents a halogen atom, or an alkyl group, an alkoxy group, an aryl group, or an aryloxy group which may have a halogen atom, and each s independently represents an integer of 0 to 3.

21. The laminate according to claim 1 or 4, having metal layers on both sides of the resin film.

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

23. A flexible printed circuit board comprising the laminate of claim 1 or 4.

Images