TW202337956A - Polyimide-based film - Google Patents

Abstract

The invention relates to a polyimide film. A polyimide film which contains a polyimide resin that contains a structural unit (A) derived from a tetracarboxylic acid anhydride and a structural unit (B) derived from a diamine, and which has an in-plane orientation index, as defined by formula 1, of 58 or more. Formula (1): In-plane orientation index=[(180-FWHW)/180]*100. In formula 1, FWHM represents a half-value width of a peak appearing at an azimuth angle corresponding to an ND direction of the film in an azimuth angle profile at 2[Theta]=16 DEG, which is measured by making X rays incident parallel to a TD direction of the film and is obtained by analysis of a two-dimensional diffraction image in X-ray diffraction measurement with a transmission method.

Description

Polyimide film

Regarding polyimide-based films that can be used as substrate materials for printed circuit boards or antenna substrates applicable to high-frequency bands, and their manufacturing methods, as well as laminated films and flexible printing containing the polyimide-based films Circuit substrate.

Flexible printed circuit boards (hereinafter, sometimes referred to as FPCs) are thin, lightweight, and flexible, so they can be mounted in three-dimensional and high-density formats, and are used in various electronic devices such as mobile phones and hard disks. , contributing to its miniaturization and lightweight. In the past, polyimide resins that are excellent in heat resistance, mechanical properties, and electrical insulation have been widely used in FPCs, for example, as metal-clad laminates such as copper-clad laminates (hereinafter, sometimes abbreviated as CCL) used in FPCs. As a board, a laminated body having a copper foil layer on one or both sides of a polyimide film of a single layer or multiple layers is known. In recent years, the fifth generation mobile communication system called 5G has been officially popularized (for example, Patent Document 1).

[Patent Document 1] Japanese Patent Application Publication No. 2021-161285

However, when metal-clad laminates using polyimide materials used in the past are used to transmit high-frequency signals used in 5G communications, problems such as large transmission losses, loss of electrical signals, or longer signal delay times occur. Therefore, for the purpose of reducing transmission loss, polyimide films with low dielectric loss tangent (hereinafter, sometimes referred to as Df) and relative dielectric coefficient (hereinafter, sometimes referred to as Dk) have been studied, but have not yet A polyimide film with sufficiently low relative dielectric coefficient and dielectric loss tangent was found.

Therefore, an object of the present invention is to provide a polyimide-based film with low Df that can be formed into a metal-clad laminate such as CCL with low transmission loss in a high-frequency band, and a manufacturing method thereof, as well as a polyimide-based film containing the polyimide-based film. Thin laminated films and flexible printed circuit boards.

As a result of intensive research by the present inventors in order to solve the above-mentioned problems, they found that by adjusting the higher-order structure of the polyimide-based resin to specific conditions, a polyimide-based film with reduced Df can be obtained, thereby achieving the present invention. . That is, the present invention provides the following preferred aspects.

[1] A polyimide-based film comprising a polyimide-based resin containing a structural unit (A) derived from tetracarboxylic anhydride and a structural unit (B) derived from a diamine, and the surface defined in Formula 1 The internal alignment index is above 58, [In Formula 1, FWHM represents the azimuth angle section of 2θ=16° obtained by the two-dimensional diffraction image analysis of the transmission X-ray diffraction measurement measured by incident X-rays parallel to the TD direction of the film. Corresponding to the half-width of the wave peak appearing at the azimuth angle of the ND direction of the aforementioned film]. [2] The polyimide film as described in [1], wherein the molecular periodicity index represented by Formula 2 is 7.0 or more, [In Formula 2, I (16°) represents the maximum value of the diffraction intensity at 2θ ₁ =15.5~16.5° in the diffraction intensity profile obtained by the reflection X-ray diffraction measurement, and I (min) represents the diffraction intensity profile obtained by the reflection method In the diffraction intensity profile obtained by X-ray diffraction measurement, 2θ ₁ = the minimum value of the diffraction intensity between 20 and 30°]. [3] The polyimide film as described in [1] or [2], wherein the in-plane anisotropy index A defined in Formula 3 is 0.8 or more and 1.2 or less, and the in-plane anisotropy index A defined in Formula 4 is Index B is greater than 1.1, [In Formulas 3 and 4, in the azimuth angle section of 2θ ₂ =16° obtained by the two-dimensional diffraction image analysis of the transmission X-ray diffraction measurement measured by incident X-rays parallel to the ND direction of the film , I (MD) represents the diffraction intensity corresponding to the MD direction of the aforementioned film, I (TD) represents the diffraction intensity corresponding to the TD direction, I (MAX) represents the maximum value of the diffraction intensity, and I (MIN) represents the diffraction intensity. minimum value]. [4] The polyimide film according to any one of [1] to [3], wherein the structural unit (A) includes a structural unit (A1) derived from a tetracarboxylic anhydride containing an ester bond. [5] The polyimide film according to any one of [1] to [4], wherein the structural unit (A) includes a structural unit (A2) derived from a tetracarboxylic anhydride containing a biphenyl skeleton. [6] The polyimide film according to [5], wherein the structural unit (A) satisfies the relationship of the formula (X): (derived from sources other than the structural unit (A1) and the structural unit (A2) Content of the structural unit of tetracarboxylic anhydride)/(total amount of the aforementioned structural unit (A1) and the aforementioned structural unit (A2)) <1.1 (X). [7] The polyimide film according to any one of [4] to [6], wherein the structural unit (A1) is a structural unit (a1) derived from the tetracarboxylic anhydride represented by the formula (a1) : [In formula (a1), Z represents a divalent organic group, R ^a1 is independent of each other and represents a halogen atom, or an alkyl group, alkoxy group, aryl group or aryloxy group that may have a halogen atom, and s is independent of each other and represents 0 ~an integer of 3]. [8] The polyimide film according to any one of [5] to [7], wherein the structural unit (A2) is a structural unit (a2) derived from the tetracarboxylic anhydride represented by the formula (a2) : [In formula (a2), R ^a2 are independent of each other and represent a halogen atom, or an alkyl group, alkoxy group, aryl group or aryloxy group that may have a halogen atom, and t is independent of each other and represents an integer of 0 to 3]. [9] The polyimide film according to any one of [1] to [8], wherein the structural unit (B) includes a structural unit (B1) derived from a diamine containing a biphenyl skeleton. [10] The polyimide film according to [9], wherein the structural unit (B1) is a structural unit (b1) derived from the diamine represented by the formula (b1): [In the formula (b1), R ^b1 are independent of each other and represent a halogen atom, or an alkyl group, an alkoxy group, an aryl group or an aryloxy group which may have a halogen atom, and p represents an integer from 0 to 4]. [11] The polyimide film according to [9] or [10], wherein the content of the structural unit (B1) exceeds 30 mol% relative to the total amount of the structural unit (B). . [12] The polyimide film according to any one of [1] to [11], wherein the structural unit (B) includes the structural unit (b2) derived from the diamine represented by the formula (b2): [In formula (b2), R ^b2 are independent of each other and represent a halogen atom, or an alkyl group, alkoxy group, aryl group or aryloxy group that may have a halogen atom. The hydrogen atoms contained in R ^b2 are independent of each other and may be a halogen atom. Substitution, W is independent of each other and represents -O-, -CH ₂ -, -CH ₂ -CH ₂ -, -CH(CH ₃ )-, -C(CH ₃ ) ₂ -, -C(CF ₃ ) ₂ -, -COO-, -OOC-, -SO ₂ -, -S-, -CO- or -N(R ^c )-, R ^c represents a hydrogen atom, a monovalent hydrocarbon group with 1 to 12 carbon atoms that can be substituted by a halogen atom , m represents an integer from 0 to 4, q is independent of each other and represents an integer from 0 to 4]. [13] The polyimide film according to [12], wherein in the structural unit (b2), m is 3, and W is independent of each other and represents -O- or -C(CH ₃ ) ₂ -. [14] The polyimide film as described in any one of [1] to [13] has a dielectric loss tangent of less than 0.004 at 10 GHz. [15] The polyimide film according to any one of [1] to [14], wherein the storage modulus of the polyimide resin at 280°C is less than 3×10 ⁸ Pa. [16] The polyimide film according to any one of [1] to [15], wherein the glass transition temperature of the polyimide resin is 200 to 290°C. [17] The polyimide film according to any one of [1] to [16], the thickness of which is 5 to 100 μm. [18] A laminated film including a metal foil layer on one or both sides of the polyimide film according to any one of [1] to [17]. [19] A flexible printed circuit board including the polyimide film according to any one of [1] to [17]. [20] A method for producing a polyimide-based film as described in any one of [1] to [17], which includes: combining a structural unit derived from a tetracarboxylic anhydride and a structural unit derived from a diamine. The steps of coating the polyimide resin precursor solution on the substrate, and the step of imidizing the polyimide resin precursor by heat treatment at 200°C or more and 500°C or less. [Effects of the invention]

According to the present invention, a polyimide-based film with low Df can be provided, which can form a metal-clad laminate such as CCL with low transmission loss in a high-frequency band.

[Polyimide film] (in-plane alignment index)

The polyimide film of the present invention contains a polyimide resin containing a structural unit (A) derived from tetracarboxylic anhydride and a structural unit (B) derived from a diamine, and is defined in the following formula 1 The in-plane alignment index (also simply called the in-plane alignment index) is 58 or more.

[In Formula 1, FWHM represents the azimuth angle section of 2θ=16° obtained by the two-dimensional diffraction image analysis of the transmission X-ray diffraction measurement measured by incident X-rays parallel to the TD direction of the film. Corresponding to the half-width of the wave peak appearing at the azimuth angle of the ND direction of the aforementioned film].

The in-plane alignment index can be determined by measuring the FWHM by transmission X-ray measurement, and substituting the obtained FWHM value into Equation 1.

The method of measuring FWHM will be explained below using Figures 1 and 2 . FIG. 1 is a schematic diagram illustrating a method of determining an in-plane alignment index through transmission X-ray diffraction measurement. In addition, in FIG. 1 , the size of the test piece for measurement, such as the aspect ratio, is adjustable for ease of explanation and is not limited.

First, the film is cut and/or overlapped to prepare a test piece for measurement. The size of the test piece for measurement is not limited as long as sufficient resolution and diffraction intensity can be obtained, but preferably the width in the MD direction is 0.5 to 3 cm, the width in the TD direction is 0.5 to 2 mm, and the width in the ND direction is preferably 0.5 to 3 cm. The thickness in the direction is 100μm or more. The upper limit of the thickness in the ND direction is preferably 2 mm or less. This thickness can be obtained by stacking a plurality of films. Next, as shown in FIG. 1 , the test piece 1 a for measurement is set in the X-ray device so that the irradiation direction of the X-ray becomes parallel to the TD direction of the film. Then, X-rays are incident on the measurement test piece 1a from the X-ray source 2a, and a two-dimensional diffraction image is obtained by the detector 3a. The obtained two-dimensional diffraction image was corrected using a two-dimensional diffraction image (air blank) obtained without installing the test piece 1a for measurement. Furthermore, from the two-dimensional diffraction image, the azimuth angle section 0° and 180° correspond to the MD direction of the measurement test piece 1a, and the azimuth angle section 90° and 270° correspond to the ND direction of the measurement test piece 1a. Azimuth profile of diffraction angle 2θ=16°. The diffraction intensity at each azimuth angle uses the average value of the diffraction intensity in the range of 2θ=15.5~16.5°.

In the obtained azimuth angle profile (azimuth angle β=0~360°), find the half-width of the wave peaks existing at 90° and 270°, and determine the average of the two half-widths as FWHM. In addition, the half-width represents the intensity position that exists in the center between the peak intensity of 90° or 270° and the minimum intensity in the range of the azimuth angle of the peak intensity -90° to the azimuth angle of the peak intensity +90°. Peak width (that is, the peak width at a position that is half the intensity of the peak intensity at 90° or 270° based on the minimum intensity). For example, in the azimuthal profile shown in Figure 2, the half-width of the wave peak existing at 270° corresponding to the ND direction is half the intensity of the minimum intensity in the range of 180 to 360°. Figure 2 4 The width of the wave crest shown in Figure 2-5 at the position shown. In addition, in this specification, the MD direction is the direction parallel to the mechanical flow direction in the film plane during production, the TD direction is the direction perpendicular to the aforementioned mechanical flow direction, and the ND direction is the thickness direction of the film, that is, The direction is perpendicular to the plane of the film. If the MD direction and TD direction in the film plane are unknown, they can be determined by the following method. Among the azimuth angle profiles of 2θ=16° measured by transmitting X-rays from the ND direction, the azimuth angle with the strongest diffraction intensity is designated as the MD direction.

In addition, the above-mentioned X-ray device can be set to the following measurement conditions. ・X-ray source: Cu-Kα line ・Voltage: 40kV ・Current: 20mA ・Camera length: 70mm ・Exposure time: 10 minutes ・Beam diameter: 0.25mm

In the azimuthal profile of 2θ=16°, the sharper the wave peak appearing in the ND direction, the smaller the value of FWHM becomes, and the in-plane alignment index in the formula becomes larger.

In this specification, polyimide may be described as PI. The present inventors discovered that in a PI-based film containing a polyimide-based resin containing a structural unit (A) derived from tetracarboxylic anhydride and a structural unit (B) derived from a diamine, the in-plane value defined in Formula 1 If the alignment index is 58 or more, the Df of the PI-based film can unexpectedly be reduced. The diffraction peak in X-ray diffraction measurement shows a periodic structure corresponding to the distance of the diffraction angle 2θ. When the peak intensity is strong, it indicates that the periodic structure has many components, or the periodicity of the component has Higher regularity. In addition, when the diffraction peak is detected to be very strong at a specific azimuth angle, it indicates that a periodic structure is formed in the direction of that azimuth angle, or that the molecular main chain is aligned in the direction perpendicular to the azimuth angle. In the X-ray measurement of the PI-based film, it is known that the complex periodicity in the higher-order structure of the molecular chain of the PI-based resin is reflected, and many diffraction peaks such as those shown in Figure 4 are detected. If the in-plane alignment index defined in Equation 1 is 58 or above, then there is a certain degree of PI resin aligned along the plane of the film, which is equivalent to being distributed at a distance equivalent to the diffraction angle 2θ = 16° in the vertical direction of the film. When the PI-based resin forms such a regular higher-order structure, it is presumed that the rotational motion of the molecular chain of the resin is suppressed for some reason, and the Df of the PI-based film is reduced. On the other hand, if the in-plane alignment index defined in Formula 1 does not reach 58, the rotational motion of the molecular chains of the resin is not sufficiently suppressed, and the Df of the PI-based film cannot be sufficiently reduced.

In the PI-based film of the present invention, the in-plane alignment index is preferably 60 or more, more preferably 62 or more, still more preferably 64 or more, still more preferably 66 or more, particularly preferably 68 or more, particularly more preferably 69 or more. . If the in-plane alignment index is above the above lower limit, the Df of the PI film will be easily reduced. The upper limit of the in-plane alignment index is preferably 95 or less, more preferably 90 or less, still more preferably 85 or less, still more preferably 80 or less. If the in-plane alignment index is equal to or less than the above-mentioned upper limit, the relative dielectric coefficient can be maintained low, and extreme mechanical strength anisotropy can easily be suppressed, and bending resistance can easily be improved. The in-plane alignment index can be obtained by the method described above, or by the method described in the Examples, for example.

The in-plane alignment index can be adjusted by appropriately adjusting the type and composition of the structural units constituting the PI-based resin, the molecular weight of the PI-based resin, and the manufacturing method such as coating and imidization conditions. For example, It can also be adjusted to be within the above range by adopting a preferred aspect described below, particularly an aspect that improves the dielectric properties such as reducing Df. For example, it can also be achieved by using the structural units and contents of the preferred PI-based resin described below, the solvent contained in the preferred PI-based resin precursor solution described below, the preferred imidization conditions described below, etc. Adjust appropriately. In addition, if the PI-based resin contains an ester bond, the in-plane alignment index tends to become higher. If the PI-based resin contains more soft components, the in-plane alignment index tends to decrease.

(Molecular periodicity index) In one embodiment of the present invention, the PI-based film of the present invention preferably has a molecular periodicity index represented by the following formula 2 of 7.0 or more. [In Formula 2, I (16°) represents the maximum value of the diffraction intensity at 2θ ₁ =15.5~16.5° in the diffraction intensity profile obtained by the reflection X-ray diffraction measurement, and I (min) represents the diffraction intensity profile obtained by the reflection method In the diffraction intensity profile obtained by X-ray diffraction measurement, 2θ ₁ = the minimum value of the diffraction intensity between 20 and 30°].

The molecular periodicity index can be calculated by measuring I (16°) and I (min) through reflection X-ray diffraction measurement and substituting into Equation 2.

Using Figures 3 and 4, the measurement methods of I (16°) and I (min) are explained below. FIG. 3 is a schematic diagram for explaining a method of determining the molecular periodicity index by reflection X-ray diffraction measurement. In addition, in FIG. 3 , the size of the test piece for measurement, such as the aspect ratio, is adjustable for ease of explanation and is not limited.

First, the film is cut and/or overlapped to prepare a test piece for measurement. The size of the test piece for measurement is not limited as long as sufficient resolution and diffraction intensity can be obtained, but preferably the width in the MD direction is 0.5cm~5cm and the width in the TD direction is 0.5cm~ 5cm. Next, as shown in Figure 3, the ND direction of the film becomes parallel to the normal direction of the surface of the sample holder 6 (the direction perpendicular to the surface), and when the sample holder 6 is installed in the X-ray device, it is connected The measurement sample 1b is attached to the sample holder 6 so that the line 7 formed by the detection positions of the X-ray source 2b and the detector 3b becomes parallel to the MD direction of the film. Next, while maintaining the line 7 parallel to the MD direction, the reflection measurement of the film surface is performed at the diffraction angle 2θ ₁ =5~30° to obtain the diffraction profile A of the film. Furthermore, the film was cut and/or overlapped to obtain another test piece for measurement. Next, as shown in Figure 3, the ND direction of the film becomes parallel to the normal direction of the surface of the sample holder 6 (the direction perpendicular to the surface), and when the sample holder 6 is installed in the X-ray device, it is connected The measurement sample 1b is attached to the sample holder 6 so that the line 7 formed by the detection positions of the X-ray source 2b and the detector 3b becomes parallel to the TD direction of the film. Then, the reflection measurement of the film surface is carried out in the range of 2θ ₁ =5~30° to obtain the diffraction profile B of the film. Each diffraction profile was blank corrected by subtracting the background. The average value of the blank-corrected diffraction profile A and the diffraction profile B is determined as the diffraction intensity profile of the film. From the diffraction intensity profile of the film, the maximum value of the diffraction intensity in the range of 2θ ₁ =15.5~16.5° is determined as I (16°), and the minimum value of the diffraction intensity in the range of 2θ ₁ =20~30° is determined is I(min). For example, in the diffraction intensity profile shown in Figure 4, I (16°) becomes the maximum value of the diffraction intensity in the range of 2θ ₁ =15.5~16.5° (8 in the figure), and I (min) becomes 2θ ₁ =minimum value of diffraction intensity between 20 and 30° (9 in the figure). In addition, the above-mentioned X-ray device can be set to the following measurement conditions.・X-ray source: Cu-Kα line ・Tube voltage: 40kV ・Tube current: 150mA ・Divergence slit: 1° ・Scattering slit: 1° ・Light-receiving slit: 0.15mm ・Longitudinal divergence limiting slit: 10mm ・Measurement Range: 2θ ₁ =5~30° ・Measurement step: 0.02° ・Scan speed: 0.5°/min ・Sample holder: aluminum sample plate

If the molecular periodicity index shown in Formula 2 is 7.0 or more, the Df of the PI-based film can be further reduced. If the PI-based resin is distributed at a distance equivalent to the diffraction angle 2θ ₁ =16°, it is speculated that the rotational motion of the molecular chain of the resin is suppressed for some reason, and the Df of the PI-based film is reduced. However, if the molecular periodicity index If it is 7.0 or more, it is estimated that the number of components arranged at a constant distance increases regardless of the direction of the molecular chain, and therefore the Df becomes low.

In the PI-based film of the present invention, the molecular periodicity index is preferably 7.1 or more, more preferably 7.3 or more, further preferably 7.5 or more, still more preferably 7.7 or more, and particularly preferably 7.8 or more. If the molecular periodicity index is above the above-mentioned lower limit, the Df of the PI-based film is likely to be reduced. The upper limit of the molecular periodicity index is preferably 20 or less, more preferably 15 or less, still more preferably 12 or less, still more preferably 10 or less. If the molecular periodicity index is equal to or less than the above-mentioned upper limit, the bending resistance can be easily improved. The molecular periodicity index can be obtained by the method described above, or by the method described in the Examples, for example.

The molecular periodicity index can be adjusted by appropriately adjusting the type and composition of the structural units constituting the PI-based resin, the molecular weight of the PI-based resin, and the production method of the imidization conditions. For example, it can also be adjusted by The adjustment is within the above range by adopting preferred aspects described below, particularly aspects that improve dielectric properties such as reducing Df. For example, it can also be achieved by using the structural units and contents of the preferred PI-based resin described below, the solvent contained in the preferred PI-based resin precursor solution described below, the preferred imidization conditions described below, etc. Adjust appropriately. In addition, if the PI-based resin contains an ester bond, the molecular periodicity index tends to become higher. If the PI-based resin contains more soft components, the molecular periodicity index tends to decrease.

(in-plane anisotropy index) In one embodiment of the present invention, the PI-based film of the present invention has an in-plane anisotropy index A defined in the following formula 3 of 0.8 or more and 1.2 or less, and an in-plane anisotropy index B defined in the following formula 4 is greater than 1.1 is better.

[In Formulas 3 and 4, the diffraction angle 2θ ₂ = azimuth angle of 16° obtained from the two-dimensional diffraction image analysis of the transmission X-ray diffraction measurement measured by incident X-rays parallel to the ND direction of the film In the cross-section, I (MD) represents the diffraction intensity corresponding to the MD direction of the aforementioned film, I (TD) represents the diffraction intensity corresponding to the TD direction, I (MAX) represents the maximum value of the diffraction intensity, and I (MIN) represents the diffraction intensity. the minimum value of radiation intensity].

The in-plane anisotropy indexes A and B are determined by measuring I (MD), I (TD), I (MAX) and I (MIN) through transmission X-ray diffraction measurement and substituting into Equations 3 and 4 to obtain them. out.

Using Figures 5 and 6, the measurement methods of I (MD), I (TD), I (MAX), and I (MIN) will be explained as follows. FIG. 5 is a schematic diagram for explaining the method of determining the in-plane anisotropy index by X-ray diffraction measurement using the retrotransmission method. In addition, in FIG. 5 , aspects such as the aspect ratio of the test piece for measurement are adjusted to make the explanation easier to understand and are not limited.

First, the film is cut and/or overlapped to prepare a test piece for measurement. The size of the test piece for measurement is not limited as long as sufficient resolution and diffraction intensity can be obtained, but preferably the width in the MD direction is 0.5cm~3cm and the width in the TD direction is 0.5cm~ 3cm. The width in the ND direction is preferably adjusted to 0.1mm~2mm. Next, as shown in FIG. 5 , the test piece 1 c for measurement is set in the X-ray device so that the irradiation direction of the X-ray becomes parallel to the ND direction of the film. Then, X-rays are incident on the measurement test piece 1c from the X-ray source 2c, and a two-dimensional diffraction image is obtained by the detector 3c. The obtained two-dimensional diffraction image was corrected using the two-dimensional diffraction image (air blank) obtained without installing the test piece 1c for measurement. Furthermore, from the two-dimensional diffraction image, the azimuth angle section 0° and 180° correspond to the MD direction of the measurement test piece 1c, and the azimuth angle section 90° and 270° correspond to the TD direction of the measurement test piece 1c. 2θ ₂ =16° azimuth angle profile. The diffraction intensity at each azimuth angle uses the average value of the diffraction intensity in the range of 2θ ₂ =15.5~16.5°. In the obtained azimuth angle profile (azimuth angle β ₁ =0~360°), find the diffraction intensity of 0° and 180°, set the average value as I (MD), and find the diffraction intensity of 90° and 270°. Diffraction intensity, the average value is designated as I (TD). In addition, in the azimuth angle profile (β ₁ =0~360°) obtained above, the maximum value of the diffraction intensity in the range of 0~360° is defined as I (MAX), and the minimum value of the diffraction intensity is defined as I (MAX). is I(MIN). For example, in the azimuth profile shown in Figure 6, I (MD) is the average of the diffraction intensity 10 at 0° and the diffraction intensity 12 at 180°, and I (TD) is the diffraction intensity 11 and 270 at 90°. The average value of the diffraction intensity 14°, I (MAX) is the maximum value in the range of 0~360° (15 in the figure), I (MIN) is the minimum value in the range of 0~360° (in the figure) of 13). In addition, the above-mentioned X-ray device can be set to the following measurement conditions.・X-ray source: Cu-Kα line ・Camera length: 70mm ・Exposure time: 10 minutes ・Voltage: 40kV ・Current: 20mA ・Beam diameter: 0.25mm

The inventors found that in a PI-based film containing a PI-based resin containing a structural unit (A) derived from tetracarboxylic anhydride and a structural unit (B) derived from a diamine, the in-plane anisotropy defined by Formula 3 If the index A is between 0.8 and 1.2, and the in-plane anisotropy index B defined in Formula 4 is greater than 1.1, unexpectedly, the Df of the PI-based film can be further reduced.

The in-plane anisotropy index A represents the ratio of the alignment and regularity of the molecular chains of the resin in the MD direction and the TD direction. The closer the in-plane anisotropy index A is to 1, the difference in anisotropy between MD and TD. The smaller. When the in-plane anisotropy index A is 0.8 or more and 1.2 or less, the film has isotropic physical properties in the plane of the film, and it tends to have isotropic film properties in terms of thermal and mechanical properties. As a printed circuit board Operation during processing becomes easier. On the other hand, the in-plane anisotropy index B represents the ratio of the diffraction intensity in the direction with the strongest diffraction intensity to the direction with the weakest diffraction intensity in the azimuth angle profile. Although the in-plane anisotropy index A is 0.8 or more and 1.2 or less, the in-plane anisotropy index B is more than 1.1. As a property of the PI-based resin itself, it is considered that a distance corresponding to the diffraction angle 2θ ₂ =16° is formed. It is speculated that the rotational motion of the molecular chain of the resin in such a structure is easily suppressed, so the Df of the PI film is reduced.

In the PI-based film of the present invention, the in-plane anisotropy index A is preferably 0.8 or more, more preferably 0.83 or more, still more preferably 0.87 or more, still more preferably 0.9 or more, particularly preferably 0.93 or more, and still more preferably It is 0.97 or more, preferably 1.2 or less, more preferably 1.17 or less, still more preferably 1.13 or less, still more preferably 1.1 or less, particularly preferably 1.07 or less, particularly preferably 1.03 or less. When the in-plane anisotropy index A is within the above range, the physical properties of the film are likely to be isotropic in both thermal and mechanical properties, and the workability during processing as a printed circuit board is easily improved.

In the PI-based film of the present invention, the in-plane anisotropy index B is preferably 1.12 or more, more preferably 1.15 or more, further preferably 1.17 or more, still more preferably 1.2 or more. If the in-plane anisotropy index B is above the above-mentioned lower limit, the Df of the PI-based film is likely to be reduced. The upper limit of the in-plane anisotropy index B is preferably 3.0 or less, more preferably 2.5 or less, still more preferably 2.0 or less, still more preferably 1.7 or less, and particularly preferably 1.5 or less. The in-plane anisotropy index can be obtained by the method described above, or by the method described in the Examples, for example.

The in-plane anisotropy indexes A and B can be adjusted by appropriately adjusting the types of structural units constituting the PI-based resin and their composition, the molecular weight of the PI-based resin, and the production method of the imidization conditions. , for example, it can also be adjusted to be within the above range by adopting a preferred aspect described below, especially an aspect that improves the dielectric properties such as reducing Df. For example, it can also be achieved by using the structural units and contents of the preferred PI-based resin described below, the solvent contained in the preferred PI-based resin precursor solution described below, the preferred imidization conditions described below, etc. Adjust appropriately. In addition, if the PI-based resin contains an ester bond, the in-plane alignment index B tends to increase. If the PI-based resin contains more soft components, the in-plane alignment index B tends to decrease.

In one embodiment of the present invention, the PI-based film of the present invention has a low coefficient of linear expansion (hereinafter, may be referred to as CTE). The CTE of the PI-based film is preferably 50 ppm/K or less, more preferably 40 ppm/K or less, further preferably 30 ppm/K or less, further preferably 25 ppm/K or less, particularly preferably 21 ppm/K or less, and more preferably 0 ppm/K or more, more preferably 5 ppm/K or more, still more preferably 8 ppm/K or more, still more preferably 12 ppm/K or more. By setting it within the above range, since the CTEs of the copper foil and the PI layer become closer, peeling off of the laminated film can be suppressed. In addition, CTE can be measured by, for example, a thermomechanical analysis device (sometimes described as "TMA"), and can be determined by the method described in the Examples.

In printed circuits, transmission loss is required to be reduced. Transmission loss is represented by the sum of dielectric loss, which is a loss caused by an electric field generated by a dielectric body, and conductor loss, which is a loss caused by an electric current flowing through a conductor. Then, the dielectric loss is known to be approximately proportional to the index E shown in formula (i).

[In formula (i), Df represents the dielectric loss tangent, and Dk represents the relative dielectric coefficient]

In the high-frequency domain where FPC for 5G is used, dielectric loss tends to increase, so materials that have a small value of the aforementioned index E and can suppress dielectric loss are particularly required. On the other hand, high-frequency signals are currents concentrated on the surface of conductors. Therefore, conductor loss is related to the dielectric properties of the dielectric in contact, and is known to be approximately proportional to (Dk) ^1/2 .

The PI-based film of the present invention, as described above, contains a PI-based resin containing a structural unit (A) derived from tetracarboxylic anhydride and a structural unit (B) derived from a diamine. The PI-based resin has an in-plane alignment index due to the above-mentioned It is 58 or more, so as Df and Dk become smaller, the dielectric loss index E and the conductor loss also become smaller, and the transmission loss can be reduced in the circuit including the PI-based film. In one embodiment of the present invention, the dielectric loss index E of the PI film at 10 GHz is preferably 0.009 or less, more preferably 0.008 or less, further preferably 0.007 or less, and particularly preferably 0.006 or less. The smaller the index E, the lower the transmission loss of the electronic circuit including the PI-based film. Therefore, the lower limit of the index E is not particularly limited, and may be 0 or more, for example.

In one embodiment of the present invention, the Df of the PI-based film at 10 GHz is preferably less than 0.004, and more preferably less than 0.0038, from the viewpoint of easily reducing the transmission loss of an electronic circuit including the PI-based film. It is more preferably 0.0035 or less, still more preferably 0.0033 or less, particularly preferably 0.003 or less, particularly preferably 0.0027 or less, and particularly preferably 0.0024 or less. The smaller the Df, the lower the transmission loss of the electronic circuit including the PI-based film. Therefore, the lower limit of the Df is not particularly limited, and may be, for example, 0 or more.

In one embodiment of the present invention, the Dk of the PI film at 10 GHz is preferably less than 3.50, more preferably 3.45 or less, further preferably 3.40 or less, still more preferably 3.38 or less, and particularly preferably 3.36 or less.

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

In one embodiment of the present invention, the number of bends until fracture of the PI film of the present invention in the MIT folding fatigue test in accordance with ASTM specification D2176-16 is 15,000 times or more, preferably 20,000 times or more, and more preferably More than 50,000 times, preferably more than 100,000 times, more preferably more than 150,000 times, particularly preferably more than 200,000 times. If the number of times of bending is equal to or greater than the lower limit, the occurrence of cracks, cracks, creases, etc. can be effectively suppressed even if the bending is repeated. In addition, the upper limit of the number of bending times is not particularly limited, and may be, for example, 10,000,000 times or less. In addition, the MIT folding fatigue resistance test can be measured using an MIT folding fatigue resistance testing machine, for example, it can be measured by the method described in the embodiment.

The thickness of the PI-based film of the present invention can be appropriately selected depending on the application. It is preferably 5 μm or more, more preferably 10 μm or more, further preferably 20 μm or more, preferably 500 μm or less, more preferably 300 μm or less, and still more preferably 100 μm or less. , particularly preferably below 80 μm, particularly preferably below 50 μm. The thickness of the film can be measured using a film thickness meter. In addition, when the film of the present invention is a multilayer film, the above-mentioned thickness represents the thickness of a single layer portion. In addition, as the film thickness decreases, the in-plane alignment index and the molecular periodicity index tend to increase.

The PI film of the present invention can also be subjected to surface treatment such as corona discharge treatment, plasma treatment, ozone treatment, etc. by methods commonly used in industry.

Since the PI-based film of the present invention has low Df, it can be suitably used as a substrate material for printed circuit boards or antenna substrates that can cope with high-frequency bands. CCL used in FPC is widely used as a laminate of single or multiple layers of PI-based resin with copper foil layers on one or both sides.

＜Polyimide resin＞ The PI-based film of the present invention includes a PI-based resin containing a structural unit (A) derived from tetracarboxylic anhydride and a structural unit (B) derived from a diamine. The so-called "structural unit derived from..." in the present invention means "structural unit derived from...", for example, "structural unit (A) derived from tetracarboxylic anhydride" means "structural unit derived from tetracarboxylic anhydride (A)" A)".

(Structural unit (A) derived from tetracarboxylic anhydride) The PI-based resin contains a structural unit (A) derived from tetracarboxylic anhydride (hereinafter, it may be simply referred to as structural unit (A)). The structural unit (A) is not particularly limited as long as the in-plane alignment index of the PI-based film is within the above range. However, for example, it is preferably a structural unit derived from the tetracarboxylic anhydride represented by formula (1): [In formula (1), Y represents a tetravalent organic group].

In the formula (1), Y independently represents a tetravalent organic group, preferably a tetravalent organic group having a carbon number of 4 to 40, more preferably a tetravalent organic group having a cyclic structure having a carbon number of 4 to 40. . Examples of the cyclic structure include alicyclic, aromatic, and heterocyclic structures. The aforementioned organic group, the hydrogen atom in the organic group can also be substituted by a halogen atom, a hydrocarbon group, an alkoxy group or a halogenated hydrocarbon group. In this case, the carbon number of these groups is preferably 1 to 8. The PI resin of the present invention may contain multiple types of Y, and the multiple types of Y may be the same as each other or different. As Y, the groups or structures represented by formula (31) to formula (40) can be exemplified; the hydrogen atom in the group represented by formula (31) to formula (40) is separated by methyl, ethyl, n-propyl, A base substituted by isopropyl, n-butyl, isobutyl, sec-butyl, tertiary butyl, fluoro, chloro or trifluoromethyl; tetravalent chain with 1 to 8 carbon atoms Hydrocarbyl etc.

[In Formula (31) ~ Formula (33), R ¹⁹ ~ R ²⁶ and R ^23' ~ R ^26' are independent of each other and represent a hydrogen atom, an alkyl group with 1 to 6 carbon atoms, and an alkoxy group with 1 to 6 carbon atoms. Or the hydrogen atoms contained in aryl groups with 6 to 12 carbon atoms R ¹⁹ ~ R ²⁶ and R ^23' ~ R ^26' are independent of each other and can be replaced by halogen atoms. V ¹ and V ² are independent of each other and represent single bonds (only, Excluding the case where e+d=1), -O-, -CH ₂ -, -CH ₂ -CH ₂ -, -CH(CH ₃ )-, -C(CH ₃ ) ₂ -, -C(CF ₃ ) ₂ -, -SO ₂ -, -S-, -CO-, -N(R ^j )-, formula (a) (In formula (a), R ²⁷ ~ R ³⁰ are independent of each other and represent a hydrogen atom or an alkyl group with 1 to 6 carbon atoms; D is independent of each other and represents a single bond, -C(CH ₃ ) ₂ - or -C(CF ₃ ) ₂ , i represents an integer from 1 to 3, * represents the bonding point), R ^j represents a hydrogen atom, or a monovalent hydrocarbon group with 1 to 12 carbon atoms that can be replaced by a halogen atom, e and d are independent of each other, representing 0~ An integer of 2 (but e+d is not 0), f represents an integer from 0 to 3, g and h are independent of each other, and represents an integer from 0 to 4. In formula (39), Z represents a divalent organic group, R ^a1 is independent of each other and represents a halogen atom, or an alkyl group, alkoxy group, aryl group or aryloxy group that may have a halogen atom, s is independent of each other and represents an integer from 0 to 3, in formula (40), R ^a2 is independent of each other, represents a halogen atom, or an alkyl group, alkoxy group, aryl group or aryloxy group that may have a halogen atom, t is independent of each other and represents an integer from 0 to 3, * represents the bonding point].

The PI-based resin in the present invention, from the viewpoint of easily improving the mechanical properties, thermal properties and dielectric properties of the PI-based film, Y in formula (1) is selected from formula (31), formula (32) ), formula (33), formula (39) and formula (40) are preferably at least one structure in the group of structures, including a structure selected from the group consisting of a structure containing an ester bond and a structure containing a biphenyl skeleton. It is more preferable that it contains at least one structure of the group, and it is more preferable that it contains at least one structure selected from the group consisting of the structures represented by formula (39) and formula (40). In addition, in this specification, mechanical properties mean mechanical properties including bending resistance, folding resistance, and elastic modulus. Improvement in mechanical properties means, for example, that bending resistance and/or elastic modulus become higher. In addition, thermal physical properties include glass transition temperature (Tg), CTE, thermal physical properties with less denaturation and deterioration due to heat, and less deformation after heating. The so-called thermal physical properties improvement means, for example, that Tg becomes higher, and/ Or the CTE becomes low. In addition, the dielectric properties mean dielectric properties including Df and Dk, and the improvement or enhancement of the dielectric properties means a decrease in Df and/or Dk.

In Formula (31) ~ Formula (33), R ¹⁹ ~ R ²⁶ and R ^23' ~ R ^26' are independent of each other and represent a hydrogen atom, an alkyl group with 1 to 6 carbon atoms, an alkoxy group with 1 to 6 carbon atoms, or Aryl group with 6 to 12 carbon atoms. Examples of the alkyl group having 1 to 6 carbon atoms include methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tertiary butyl, and n-pentyl. , 2-methyl-butyl, 3-methylbutyl, 2-ethyl-propyl, n-hexyl, etc. Examples of the alkoxy group having 1 to 6 carbon atoms include methoxy, ethoxy, propyloxy, isopropyloxy, n-butoxy, isobutoxy, sec-butoxy, tert -Butoxy, pentyloxy, hexyloxy and cyclohexyloxy, etc. Examples of the aryl group having 6 to 12 carbon atoms include phenyl, tolyl, xylyl, naphthyl, biphenyl, and the like. The hydrogen atoms contained in R ¹⁹ to R ²⁶ and R ^23' to R ^26' are independent of each other and may be replaced by a halogen atom. Examples of the halogen atom include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom. Among them, from the viewpoint of easily improving the mechanical and thermal properties of the PI-based film, R ¹⁹ to R ²⁶ and R ^23' to R ^26' are independent of each other and are composed of hydrogen atoms or alkyl groups with 1 to 6 carbon atoms. Preferably, a hydrogen atom or an alkyl group having 1 to 3 carbon atoms is more preferred, and a hydrogen atom is still more preferred.

In formula (31), V ¹ and V ² are independent of each other and represent single bonds (except that the case of e+d=1 is excluded), -O-, -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), by From the viewpoint of easily improving the mechanical and thermal properties of the PI-based film, it is preferable to represent single bonds (but excluding the case of e+d=1), -O-, -CH ₂ -, -C(CH ₃ ) ₂ -, -C(CF ₃ ) ₂ - or -CO-, preferably a single bond (excluding the case of e+d=1), -O-, -C(CH ₃ ) ₂ - or -C (CF ₃ ) ₂ -. ^Rj represents a hydrogen atom and a monovalent hydrocarbon group having 1 to 12 carbon atoms that may be substituted by a halogen atom. Examples of the monovalent hydrocarbon group having 1 to 12 carbon atoms include methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tertiary butyl, n- Pentyl, 2-methyl-butyl, 3-methylbutyl, 2-ethyl-propyl, n-hexyl, n-heptyl, n-octyl, tert-octyl, n-nonyl and n-decyl, etc., which may also be substituted by halogen atoms. Examples of the halogen atom include the same ones as described above.

In formula (31), e and d are independent of each other and represent an integer from 0 to 2 (however, e+d is not 0). From the viewpoint of easily reducing the Df of the PI-based film, it is preferable to represent 0 or 1. Moreover, e+d preferably represents 1. In addition, in formula (31), when e is 0, it means that the two benzene rings are not bonded with V ¹ , and when d is 0, it means that the two benzene rings are not bonded with V ² .

In Formula (32) and Formula (33), f represents an integer from 0 to 3. From the viewpoint of easily reducing the Df of the PI-based film, f represents preferably 0 or 1, and more preferably represents 0.

In formula (33), g and h are independent of each other and represent an integer between 0 and 4. From the viewpoint of easily improving the mechanical and thermal properties of the PI-based film, it is preferably an integer between 0 and 2, and more preferably 0 or 1. Moreover, g+h is preferably an integer representing 0 to 2. In addition, when f is 1 or more, the plural numbers g and h are independent of each other and may be the same or different.

In formula (a), R ²⁷ to R ³⁰ are independent of each other and represent a hydrogen atom or an alkyl group having 1 to 6 carbon atoms. Examples of the alkyl group having 1 to 6 carbon atoms include those illustrated above. Among these, from the viewpoint of easily improving the mechanical and thermal properties of the PI-based film, R ²⁷ to R ³⁰ are independent of each other, and preferably represent a hydrogen atom or an alkyl group having 1 to 3 carbon atoms, and more preferably Hydrogen atoms.

In formula (a), D represents a single bond, -C(CH ₃ ) ₂ - or -C(CF ₃ ) ₂ -. If D has such a structure, it is easy to improve the mechanical and thermal properties of the PI film. i represents an integer from 1 to 3, and from the viewpoint of easily improving the mechanical properties and thermal properties of the PI-based film, 1 or 2 is preferred. When i is 2 or more, the plural D and R ²⁷ ~ R ³⁰ are independent of each other and may be the same or different.

In formula (39), Z represents a divalent organic group. From the viewpoint of easily improving the mechanical properties, thermal properties and dielectric properties of the PI-based film, it is preferable to represent a divalent organic group with a carbon number of 4 to 40. More preferably, it represents a divalent organic group having 4 to 40 carbon atoms having a cyclic structure, and even more preferably, it represents a divalent organic group having 4 to 40 carbon atoms having an aromatic ring. Particularly preferably, it represents formula (z1), formula ( z2) or a divalent organic group represented by formula (z3): [In formula (z1) ~ formula (z3), R ^z11 ~ R ^z14 are independent of each other, representing a hydrogen atom, or a 1-valent hydrocarbon group that may have a halogen atom, R ^z2 is independent of each other, representing a 1-valent hydrocarbon group that may have a halogen atom, n represents an integer from 1 to 4, j is independent of each other, represents an integer from 0 to 3, and * represents a bonding point], particularly preferably a divalent organic group represented by formula (z1).

In the formula (z1), R ^z11 to R ^z14 are independent of each other and represent a hydrogen atom or a monovalent hydrocarbon group which may have a halogen atom. Examples of the monovalent hydrocarbon group include aromatic hydrocarbon groups, alicyclic hydrocarbon groups, and aliphatic hydrocarbon groups. Examples of the aromatic hydrocarbon group include aryl groups such as phenyl, tolyl, xylyl, naphthyl, and biphenyl groups. Examples of the alicyclic hydrocarbon group include cycloalkyl groups such as cyclopentyl group and cyclohexyl group. Examples of the aliphatic hydrocarbon group include methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, tertiary butyl, n-pentyl, and 2-methyl-butyl. , 3-methylbutyl, 2-ethyl-propyl, n-hexyl, n-heptyl, n-octyl, tert-octyl, n-nonyl, n-decyl and other alkyl groups. Examples of the halogen atom include those described above. R ^z11 ~ R ^z14 , from the viewpoint of easily improving the mechanical properties, thermal properties and dielectric properties of the PI-based film, independently of each other, preferably represent a hydrogen atom, or an alkyl group that may have a halogen atom, more preferably It represents a hydrogen atom, or an alkyl group having 1 to 6 carbon atoms which may have a halogen atom, and more preferably it represents a hydrogen atom, or an alkyl group having 1 to 3 carbon atoms which may have a halogen atom, particularly preferably it represents a hydrogen atom.

In formula (z1), n represents an integer of 1 to 4. From the viewpoint of easily reducing the Df of the PI-based film, n represents an integer of 1 to 3, more preferably 1 or 2, and particularly preferably 2. .

In the formula (z2), R ^z2 are independent of each other and represent a monovalent hydrocarbon group which may have a halogen atom. Examples of the monovalent hydrocarbon group include those illustrated above. R ^z2 , independently of each other, preferably represents an alkyl group that can have a halogen atom, and more preferably represents a carbon that can have a halogen atom, from the perspective of easily improving the mechanical properties, thermal properties and dielectric properties of the PI-based film. The alkyl group having 1 to 6 carbon atoms preferably represents an alkyl group having 1 to 3 carbon atoms which may have a halogen atom.

In the formula (z2), j is independent of each other and represents an integer from 0 to 3. From the viewpoint of easily reducing the Df of the PI-based film, j is preferably 0 or 1, and more preferably 0.

In formula (39), R ^a1 are independent of each other and represent a halogen atom, or an alkyl group, an alkoxy group, an aryl group or an aryloxy group that may have a halogen atom, which can easily improve the mechanical properties, thermal properties and dielectric properties of the PI film. From the viewpoint of characteristics, it is preferable to independently represent 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 illustrated above. The hydrogen atoms contained in R ^a1 are independent of each other and may be replaced by a halogen atom. Examples of the halogen atom include those exemplified above. Among these, R ^a1 is independent of each other from the viewpoint of easily reducing the Df of the PI-based film, and preferably represents an alkyl group having 1 to 6 carbon atoms, and more preferably represents an alkyl group having 1 to 3 carbon atoms.

In formula (39), s is independent of each other and represents an integer between 0 and 3. From the viewpoint of easily improving the mechanical properties, thermal properties and dielectric properties of the PI-based film, s is preferably an integer between 0 and 2, and more preferably means 0 or 1.

In formula (40), R ^a2 are independent of each other and represent a halogen atom, or an alkyl group, an alkoxy group, an aryl group or an aryloxy group that may have a halogen atom, which can easily improve the mechanical properties, thermal properties and dielectric properties of the PI film. From the viewpoint of characteristics, it is preferable to independently represent 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 illustrated above. The hydrogen atoms contained in R ^a2 are independent of each other and may be replaced by a halogen atom. Examples of the halogen atom include those exemplified above. Among these, from the viewpoint of easily improving the mechanical physical properties, thermal physical properties and dielectric properties of the PI-based film, R ^a2 are independent of each other. For example, an alkyl group having 1 to 6 carbon atoms is preferred, and a carbon group is more preferred. Alkyl groups with numbers 1 to 3.

In formula (40), t is independent of each other and represents an integer between 0 and 3. From the viewpoint of easily improving the mechanical properties, thermal properties and dielectric properties of the PI-based film, it is preferably an integer between 0 and 2, and more preferably means 0 or 1.

Specific examples of the structures represented by Formula (31) to Formula (33), Formula (39) and Formula (40) include structures represented by Formula (41) to Formula (56). In addition, in this equation, * represents the bonding point.

In one embodiment of the present invention, Y in formula (1) includes at least one selected from the group consisting of structures represented by formula (31) to formula (33), formula (39) and formula (40). When 1, Y derived from formula (1) is represented by at least one selected from the group consisting of the structures shown in formula (31) ~ formula (33), formula (39) and formula (40) The proportion of structural units of tetracarboxylic anhydride, especially the tetracarboxylic anhydride represented by at least one selected from the group consisting of structures represented by formula (39) and formula (40), in which Y in formula (1) The proportion of the structural units relative to the total molar amount of the structural unit (A) is preferably 30 mol% or more, more preferably 50 mol% or more, further preferably 70 mol% or more, and particularly preferably It is 90 mol% or more, and preferably it is 100 mol% or less. If the aforementioned ratio is within the above range, the Df of the PI-based film is likely to be reduced. The proportion of the aforementioned structural units can be measured using ¹ H-NMR, for example, or can also be calculated from the feed ratio of the raw materials.

(Structural unit (A1) derived from tetracarboxylic anhydride containing ester bond) In one embodiment of the present invention, the structural unit (A) preferably contains a structural unit (A1) derived from a tetracarboxylic anhydride containing an ester bond (hereinafter, it may be simply referred to as the structural unit (A1)). If the structural unit (A) includes the aforementioned structural unit (A1), since the ester bond with molecular orientation is incorporated into the PI-based resin, the PI-based resin precursor solution is coated on the substrate, and the coating film is In the step of imidization, it is easy to adjust the X-ray parameters to the above range and reduce Df. In addition, for the same reason, it is easy to reduce CTE and improve the dimensional stability of PI-based films. Furthermore, since the imidization temperature Df tends to be low even at a low temperature of, for example, 350° C. or lower, the PI-based resin precursor coating film is thermally imidized in a laminated structure with a copper foil to produce this product. CCL also easily suppresses the deterioration of the copper foil surface, making it easy to obtain CCL with excellent high-frequency characteristics. In addition, in this specification, the in-plane alignment index, the molecular periodicity index and the in-plane anisotropy index are sometimes collectively referred to as X-ray parameters.

In one embodiment of the present invention, the structural unit (A1) is not particularly limited as long as it contains an ester bond. Although the ester bond contained in the structural unit (A1) may be one or two or more, it is easy to reduce the PI. From the viewpoint of Df of the film, the structural unit (a1) derived from the tetracarboxylic anhydride represented by formula (a1) is preferred: [In formula (a1), Z represents a divalent organic group, R ^a1 is independent of each other and represents a halogen atom, or an alkyl group, alkoxy group, aryl group or aryloxy group that may have a halogen atom, and s is independent of each other and represents 0 ~an integer of 3].

R ^a1 in the formula (a1) are independent of each other and represent a halogen atom, or an alkyl group, an alkoxy group, an aryl group or an aryloxy group that may have a halogen atom. This is preferred from the viewpoint of easily reducing the Df of the PI-based film. 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. 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 illustrated above. The hydrogen atoms contained in R ^a1 are independent of each other and may be replaced by a halogen atom. Examples of the halogen atom include those exemplified above. Among these, from the viewpoint of easily reducing the Df of the PI-based film, R ^a1 is independent of each other. Preferably, it is an alkyl group having 1 to 6 carbon atoms, and more preferably, it is an alkyl group having 1 to 3 carbon atoms. base. In addition, s in the formula (a1) are independent of each other and represent an integer from 0 to 3, preferably 0 or 1, more preferably 0.

Z in the formula (a1) represents a divalent organic group. Examples of the divalent organic group include those exemplified above as the divalent organic group in the formula (39). Among these, from the viewpoint of easily reducing the Df of the PI-based film, Z is preferably a divalent organic group represented by formula (z1), formula (z2), or formula (z3): [In formula (z1) and formula (z2), R ^z11 ~ R ^z14 are independent of each other and represent a hydrogen atom or a univalent hydrocarbon group that may have a halogen atom, R ^z2 are independent of each other and represent a univalent hydrocarbon group that may have a halogen atom, n represents an integer from 1 to 4, j is independent of each other, represents an integer from 0 to 3, * represents the bonding point].

A divalent organic group represented by formula (z1) is more preferred.

In one embodiment of the present invention, R ^z11 to R ^z14 in the formula (z1) are independent of each other and represent a hydrogen atom or a monovalent hydrocarbon group that may have a halogen atom. Examples of the monovalent hydrocarbon group include those exemplified above. R ^z11 ~ R ^z14 , independently of each other, preferably represent a hydrogen atom or an alkyl group that may have a halogen atom, more preferably represent a hydrogen atom or an alkyl group that may have a halogen atom, from the viewpoint of easily reducing the Df of the PI-based film. The alkyl group having 1 to 6 carbon atoms preferably represents a hydrogen atom, or an alkyl group having 1 to 3 carbon atoms which may have a halogen atom, particularly preferably represents a hydrogen atom.

In one embodiment of the present invention, R ^z2 in the formula (z2) are independent of each other and represent a monovalent hydrocarbon group that may have a halogen atom. Examples of the monovalent hydrocarbon group include those illustrated above. R ^z2 , independently of each other, preferably represents an alkyl group that can have a halogen atom, and more preferably represents a carbon that can have a halogen atom, from the perspective of easily improving the mechanical properties, thermal properties and dielectric properties of the PI-based film. The alkyl group having 1 to 6 carbon atoms preferably represents an alkyl group having 1 to 3 carbon atoms which may have a halogen atom.

In one embodiment of the present invention, from the viewpoint of easily reducing the Df of the PI-based film, among the benzene rings having R ^z11 to R ^z14 in formula (z1), at least one of R ^z11 to R ^z14 may be A monovalent hydrocarbon group having a halogen atom may be used, but it is preferred that all R ^z11 to R ^z14 be hydrogen atoms.

j in formula (z2) are independent of each other and represent 0~3. In one embodiment of the present invention, from the viewpoint of easily reducing the Df of the PI-based film, j is preferably 0 or 1 independently of each other, more preferably 0, and even more preferably all j are 0.

In the formula (z1), n represents an integer of 1 to 4. From the viewpoint of easily reducing the Df of the PI-based film, n is preferably an integer of 1 to 3, more preferably 1 or 2, and particularly preferably 2. .

In a suitable embodiment of the present invention, formula (a1) is formula (a1′) or formula (a1″): The one shown is better. If the PI-based resin as the structural unit (A1) contains a structural unit derived from the formula (a1), especially a tetracarboxylic anhydride represented by the formula (a1') or the formula (a1″), the yield will be easily reduced. The Df of the PI-based film. Furthermore, since the Df of the PI-based film is easily lowered even at a low temperature such as 350° C. or lower, the PI-based resin precursor is thermally coated with a thin film by laminating it with a copper foil. The production of CCL by imidization can also easily suppress the deterioration of the copper foil surface, and it is easy to obtain CCL with excellent high-frequency characteristics.

In one embodiment of the present invention, the content of the structural unit (A1) is preferably 10 mol% or more, more preferably 20 mol% or more, and further preferably 10 mol% or more relative to the total amount of the structural unit (A). 30 mol% or more, more preferably 35 mol% or more, particularly preferably 40 mol% or more. Moreover, the content of the structural unit (A1) is preferably 75 mol% or less, more preferably 70 mol% or less, and still more preferably 65 mol% or less, relative to the total amount of the structural unit (A). Especially good is 60 mol% or less. If the content of the structural unit (A1) is in the above range, it is easy to adjust the X-ray parameters to the above range, and it is easy to reduce the Df of the PI-based film. The proportion of the aforementioned structural units can be measured using ¹ H-NMR, for example, or can also be calculated from the feed ratio of the raw materials.

(Structural unit (A2) derived from tetracarboxylic anhydride containing biphenyl skeleton) In one embodiment of the present invention, the structural unit (A) preferably includes a structural unit (A2) derived from a tetracarboxylic anhydride containing a biphenyl skeleton (hereinafter, sometimes simply referred to as the structural unit (A2)). If the structural unit (A) contains the aforementioned structural unit (A2), the Df of the obtained PI-based film is likely to be reduced.

In one embodiment of the present invention, the structural unit (A2) is not particularly limited as long as it contains a biphenyl skeleton. The number of biphenyl skeletons contained in the structural unit (A2) may be one or two or more. Furthermore, in one embodiment of the present invention, the structural unit (A2) is preferably a structural unit containing a biphenyl skeleton and not containing an ester bond. In this specification, the structural unit (A2) is derived from a four-dimensional unit containing both an ester bond and a biphenyl skeleton. The structural unit of carboxylic anhydride is not classified as structural unit (A2), but is classified as structural unit (A1) derived from tetracarboxylic anhydride containing an ester bond.

In one embodiment of the present invention, the structural unit (A2) is preferably a structural unit (a2) derived from the tetracarboxylic anhydride represented by the formula (a2): [In formula (a2), R ^a2 are independent of each other and represent a halogen atom, or an alkyl group, alkoxy group, aryl group or aryloxy group that may have a halogen atom, and t is independent of each other and represents an integer of 0 to 3].

R ^a2 in the formula (a2) are independent of each other and represent a halogen atom, or an alkyl group, an alkoxy group, an aryl group or an aryloxy group that may have a halogen atom. This is preferred from the viewpoint of easily reducing the Df of the PI-based film. 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. 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 illustrated above. The hydrogen atoms contained in R ^a2 are independent of each other and may be replaced by a halogen atom. Examples of the halogen atom include those exemplified above. Among these, from the viewpoint of easily reducing the Df of the PI-based film, R ^a2 is independent of each other, and an alkyl group having 1 to 6 carbon atoms is preferred, and an alkyl group having 1 to 3 carbon atoms is more preferred.

The bonding positions of the two carboxylic acid anhydrides bonded to the benzene ring constituting the biphenyl skeleton in the formula (a2) are not particularly limited. Based on the single bond bonding the two benzene rings, they can be 3 or 4 independently of each other. - or 2,3-. From the viewpoint of easily reducing the Df of the PI film, 3,4- is preferred.

In a suitable embodiment of the present invention, formula (a2) is formula (a2'): The one shown is better. If the PI-based resin as the structural unit (A2) contains a structural unit derived from the formula (a2), especially a tetracarboxylic anhydride represented by the formula (a2'), the Df of the obtained PI-based film will be easily reduced. . Furthermore, since the imidization temperature Df tends to be low even at a low temperature of, for example, 350° C. or lower, the PI-based resin precursor coating film is thermally imidized in a laminated structure with a copper foil to produce this product. CCL also easily suppresses the deterioration of the copper foil surface, making it easy to obtain CCL with excellent high-frequency characteristics.

In one embodiment of the present invention, the content of the structural unit (A2) is preferably 25 mol% or more, more preferably 30 mol% or more, and further preferably 25 mol% or more relative to the total amount of the structural unit (A). More than 35 mol%, particularly preferably more than 40 mol%. Furthermore, the content of the structural unit (A2) is preferably 90 mol% or less, more preferably 80 mol% or less, and still more preferably 70 mol% or less, relative to the total amount of the structural unit (A). Especially good is 60 mol% or less. If the content of the structural unit (A2) is in the above range, it is easy to adjust the X-ray parameters to the above range, and it is easy to reduce the Df of the PI-based film. The proportion of the aforementioned structural units can be measured using ¹ H-NMR, for example, or can also be calculated from the feed ratio of the raw materials.

(Structural unit (A3)) In one embodiment of the present invention, the structural unit (A) may also include a structural unit (A3) derived from tetracarboxylic anhydride other than the structural unit (A1) and the structural unit (A2) (hereinafter, sometimes simply referred to as the structural unit Unit (A3)). In addition, in this specification, the term "structural unit (A3) derived from tetracarboxylic anhydride other than structural unit (A1) and structural unit (A2)" means those that do not conform to structural unit (A1) and structural unit (A2). For any structural unit derived from tetracarboxylic anhydride, the "content of structural unit (A3)" means the total amount of structural unit (A3) when there are plural structural units (A3).

In one embodiment of the present invention, as the structural unit (A3), a structural unit derived from a tetracarboxylic anhydride that does not contain either an ester bond or a biphenyl skeleton, for example, derived from Y in the formula (1) From the viewpoint of easily reducing the Df of the PI-based film, the structural units of the tetracarboxylic anhydride represented by formula (31) to formula (38) are preferably derived from Y in formula (1) to formula (42)~ The structural unit of the tetracarboxylic anhydride represented by formula (49) or formula (53) is preferably derived from formula (1) in which Y is represented by formula (42), formula (46), formula (49), formula (43) Or the structural unit of the tetracarboxylic anhydride represented by formula (53), more preferably derived from the tetracarboxylic acid anhydride represented by formula (1) in which Y is represented by formula (42), formula (46), formula (49) or formula (53) Structural unit of acid anhydride.

In one embodiment of the present invention, when the structural unit (A3) is included, its content, relative to the total amount of the structural unit (A), can be, for example, 0.01 to 55 mol%, or 0.01 to 40 mol%. It is preferably 40 mol% or less, more preferably 35 mol% or less, further preferably 30 mol% or less, particularly preferably 25 mol% or less, and usually 0.01 mol% or more, preferably 10 mol%. More than % of ears. If the content of the structural unit (A3) is in the above range, it is easy to adjust the X-ray parameters to the above range, and it is easy to reduce the Df of the PI-based film. The proportion of the aforementioned structural units can be measured using ¹ H-NMR, for example, or can also be calculated from the feed ratio of the raw materials. In one embodiment of the present invention, the structural unit (A3) preferably includes a structural unit derived from tetracarboxylic anhydride represented by formula (32) as Y in formula (1), more preferably derived from formula (1) When Y is a structural unit of tetracarboxylic anhydride represented by formula (32) with f=0, its content is preferably 10 mol% or more relative to the total amount of structural unit (A), and more preferably 20 mol% or more, more preferably 30 mol% or more, particularly preferably 40 mol% or more, more preferably 90 mol% or less, more preferably 80 mol% or less, still more preferably 70 mol% or less , the best value is less than 60 mol%. If the content is within the above range, it is easy to adjust the X-ray parameters to the above range, and it is easy to reduce the Df of the PI-based film. The proportion of the aforementioned structural units can be measured using ¹ H-NMR, for example, or can also be calculated from the feed ratio of the raw materials.

In one embodiment of the present invention, when the structural unit (A) includes the structural units (A1) and (A2), the structural unit (A) satisfies the formula (X): (Total amount of structural unit (A3))/(Total amount of structural unit (A1) and structural unit (A2))＜1.1　(X) relationship is better. When the structural unit (A) satisfies the relationship of the formula (X), that is, if the value on the left side of the formula (X) does not reach 1.1, especially less than 0.67, it is easy to reduce the Df of the obtained PI-based film, and further, it can be obtained as A PI-based film with excellent balance of mechanical properties.

In one embodiment of the present invention, the value on the left side of formula (X) is preferably 0.6 or less, more preferably 0.5 or less, and even more preferably 0.4 or less, especially preferably from the viewpoint of easily reducing the Df of the PI-based film. is less than 0.3. In addition, the lower limit of the value on the left side of the formula (X) is not particularly limited and may be 0 or more. In one embodiment of the present invention, the structural unit (A) contains a structural unit derived from the tetracarboxylic anhydride represented by the formula (a2), and/or derived from the viewpoint of easily reducing the Df of the PI-based film. The structural unit of tetracarboxylic anhydride represented by the formula (32) in which Y in the formula (1) is f=0 is preferred. In one embodiment of the present invention, the structural unit (A) includes a structural unit selected from the group consisting of structural units derived from the tetracarboxylic anhydride represented by the formula (a1) and derived from the formula, from the viewpoint of easily reducing the Df of the PI-based film. At least one of the group consisting of the structural unit of the tetracarboxylic anhydride represented by (a2) and the structural unit derived from the tetracarboxylic anhydride represented by the formula (32) in which Y in the formula (1) is f=0 is relatively Preferably, in addition to the structural units derived from the tetracarboxylic anhydride represented by formula (a1), it also includes structural units derived from the tetracarboxylic anhydride represented by formula (a2) and/or derived from Y in formula (1) with f The structural unit of tetracarboxylic anhydride represented by formula (32) =0 is more preferable.

(Structural unit (B) derived from diamine) PI-based resin contains a structural unit (B) derived from diamine (hereinafter, it may be simply referred to as structural unit (B)). The structural unit (B) and the in-plane alignment index of the PI-based film are not particularly limited as long as they are within the above range. However, for example, it is derived from formula (2): [In formula (2), X represents a divalent organic group] The structural unit of the diamine shown is preferred.

In formula (2), X represents a divalent organic group, preferably a divalent organic group having 2 to 100 carbon atoms. Examples of the divalent organic group include a divalent aromatic group, a divalent aliphatic group, and the like. Examples of the divalent aliphatic group include a divalent acyclic aliphatic group or a divalent cyclic group. Aliphatic base. Among these, from the viewpoint of easily improving the mechanical and thermal properties of the PI-based film, a divalent cyclic aliphatic group and a divalent aromatic group are preferred, and a divalent aromatic group is even more preferred. Divalent organic groups, the hydrogen atoms in the organic groups can be substituted by halogen atoms, hydrocarbon groups, alkoxy groups or halogenated hydrocarbon groups. In this case, the carbon number of these groups is preferably 1 to 8. In addition, in this specification, a divalent aromatic group refers to a divalent organic group having an aromatic group, and a part of its structure may also include an aliphatic group or other substituent. In addition, the divalent aliphatic group is a divalent organic group having an aliphatic group, and although a part of its structure may contain other substituents, it does not contain an aromatic group.

In one embodiment of the present invention, the PI-based resin may contain multiple types of X, and the plural types of X may be the same or different from each other. As the Ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tertiary butyl, fluoro, chloro or trifluoromethyl substituted groups, etc.

[In formula (60) and formula (61), R ^a and R ^b are independent of each other and represent a halogen atom, or an alkyl group, an alkoxy group, an aryl group or an aryloxy group that may have a halogen atom, and R ^a and R ^b represent The hydrogen atoms contained are independent of each other and can be replaced by halogen atoms. The W atoms are independent of each other and represent single bonds, -O-, -CH ₂ -, -CH ₂ -CH ₂ -, -CH(CH ₃ )-, -C(CH ₃ ) ₂ -, -C(CF ₃ ) ₂ -, -COO-, -OOC-, -SO ₂ -, -S-, -CO- or -N(R ^c )-, R ^c represents a hydrogen atom, which can A monovalent hydrocarbon group with 1 to 12 carbon atoms substituted by a halogen atom, t represents an integer from 0 to 4, u represents an integer from 0 to 4, n represents an integer from 0 to 4, in formula (62), ring A represents the carbon number 3~8 cycloalkane ring, ^Rd represents an alkyl group with 1~20 carbon atoms, r represents an integer above 0 and below (carbon number of ring A -2), S1 and S2 are independent of each other, representing 0~20 Integer, in formula (60) ~ formula (65), * represents the bonding point].

Other examples of X in formula (2) include ethylene, trimethylene, tetramethylene, pentamethylene, hexamethylene, propylene, and 1,2-butanediyl. , 1,3-butanediyl, 1,12-dodecanediyl, 2-methyl-1,2-propanediyl, 2-methyl-1,3-propanediyl, etc. Or a divalent acyclic aliphatic group such as a branched alkylene group. The hydrogen atom in the divalent acyclic aliphatic group can be replaced by a halogen atom, and the carbon atom can also be replaced by a heteroatom, such as an oxygen atom, a nitrogen atom, etc.

Among these, from the viewpoint of easily improving the mechanical properties, thermal properties and dielectric properties of the PI-based film, the PI-based resin in the present invention, as X in the formula (2), includes the formula (60) and The structure shown in formula (61) is better, and the structure shown in formula (60) is even better.

In formula (60) and formula (61), the bonding point of each benzene ring or each cyclohexane ring is based on -W- or the single bond connecting each benzene ring or each cyclohexane ring, which can be based on ortho From the viewpoint of easily reducing the Df of the PI-based film, and from the viewpoint of easily improving the dimensional stability, bonding at any of the α, β or γ positions is preferred. The meta-position or the para-position, or the β-position or the γ-position, more preferably, the para-position or the γ-position can be bonded. R ^a and R ^b are independent of each other and represent a halogen atom, or an alkyl group, alkoxy group, aryl group or aryloxy group that may have a halogen atom. Preferably, they represent a halogen atom, or an alkyl group or alkoxy group that may have a halogen atom. group or aryl group, 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 are those mentioned above. The hydrogen atoms contained in R ^a and R ^b are independent of each other and may be replaced by a halogen atom. Examples of the halogen atom include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom. From the viewpoint of easily reducing the Df of the PI-based film and improving the dimensional stability, R ^a and R ^b are independent of each other, and an alkyl group with 1 to 6 carbon atoms or a fluorinated alkyl group with 1 to 6 carbon atoms is preferred. From the viewpoint of easily improving the adhesion to a base material such as copper foil, an alkyl group having 1 to 6 carbon atoms that does not contain fluorine is more preferred, and an alkyl group with 1 to 3 carbon atoms that does not contain fluorine is even more preferred. Kitja.

In formula (60) and formula (61), t and u are independent of each other and are integers between 0 and 4. From the viewpoint of easily reducing the Df of the PI-based film and improving the dimensional stability, t and u are preferably between 0 and 2. An integer, preferably 0 or 1.

In formula (60) and formula (61), W is independent of each other and represents a single bond, -O-, -CH ₂ -, -CH ₂ -CH ₂ -, -CH(CH ₃ )-, -C(CH ₃ ) ₂ -, -C(CF ₃ ) ₂ -, -COO-, -OOC-, -SO ₂ -, -S-, -CO- or -N(R ^c )-, which easily reduces the Df of the PI film, From the viewpoint of easily improving dimensional stability, it is preferable to represent -O-, -CH ₂ -, -C(CH ₃ ) ₂ -, -C(CF ₃ ) ₂ -, -COO-, -OOC- or - CO-, and further preferably a single bond, -O-, -CH ₂ - or -C(CH ₃ ) ₂ -, from the viewpoint of easily improving the adhesion with a base material such as copper foil, etc. -O- or -C(CH ₃ ) ₂ -. R ^c represents a hydrogen atom and a monovalent hydrocarbon group having 1 to 12 carbon atoms that may be substituted by a halogen atom. Examples of the monovalent hydrocarbon group having 1 to 12 carbon atoms include those exemplified above.

In formula (60) and formula (61), n is an integer between 0 and 4. From the viewpoint of easily reducing the Df of the PI film and improving the dimensional stability, n is preferably an integer between 0 and 3, and more preferably 1~3. When n is 2 or more, the plural W, R ^a and t may be the same or different from each other, and the bonding positions of the benzene rings based on -W- may also be the same or different.

When the PI-based resin in the present invention, as X in formula (2), contains two or more structures represented by formula (60) and formula (61), one of the formulas (60) and (61) W, n, R ^a , R ^b , t and u are independent of each other, and may be the same or similar to W, n, R ^a , R ^b , t and u in the other formula (60) and formula (61). Different.

In formula (62), ring A represents a cycloalkane ring having 3 to 8 carbon atoms. Examples of the cycloalkane ring include a cyclopropane ring, a cyclobutane ring, a cyclopentane ring, a cyclohexane ring, a cycloheptane ring, and a cyclooctane ring. Preferred examples include cycloalkanes having 4 to 6 carbon atoms. ring. In ring A, each bonding point may or may not be adjacent to each other. For example, when ring A is a cyclohexane ring, the positional relationship between the two bonding positions may be α-position, β-position or γ-position, and preferably the positional relationship may be β-position or γ-position.

R ^d in formula (62) represents an alkyl group having 1 to 20 carbon atoms. Examples of the alkyl group having 1 to 20 carbon atoms include hydrocarbons having 1 to 20 carbon atoms in R ⁷ to R ¹⁸ . Based on the above examples, an alkyl group having 1 to 10 carbon atoms is preferred. r in formula (62) represents an integer equal to or greater than 0 and equal to or less than "the carbon number of ring A -2". r is preferably 0 or more, and preferably 4 or less. S1 and S2 in formula (62) are independent of each other and represent integers from 0 to 20. S1 and S2 are independent of each other, and are preferably 0 or more, more preferably 2 or more, and more preferably 15 or less.

Specific examples of the structures represented by Formula (60) to Formula (62) include structures represented by Formula (71) to Formula (92). In addition, in this equation, * represents the bonding point.

In a suitable embodiment of the present invention, when X in formula (2) contains at least one structural unit derived from the diamine represented by formula (60) and formula (61), it is derived from formula (2) where Relative to the total molar amount of the structural unit (B), it is preferably 25 mol% or more, more preferably more than 30 mol%, further preferably 50 mol% or more, still more preferably 70 mol% Above, particularly preferably 90 mol% or more, more preferably 100 mol% or less. If X in the formula (2) is derived from the ratio of structural units of the diamine represented by the formula (60) and the formula (61), especially from the diamine in which at least one W in the formula (60) represents a single bond When the proportion of structural units is within the above range, the Df of the PI film can be easily reduced and the dimensional stability can be easily improved. The proportion of the aforementioned structural units can be measured using ¹ H-NMR, for example, or can also be calculated from the feed ratio of the raw materials.

(Structural unit (B1) derived from diamine containing biphenyl skeleton) In one embodiment of the present invention, the structural unit (B) preferably includes a structural unit (B1) derived from a diamine containing a biphenyl skeleton (hereinafter, sometimes simply referred to as the structural unit (B1)). The structural unit (B) includes the PI-based resin of the aforementioned structural unit (B1). Since the Df of the obtained PI-based film is easily reduced, the transmission loss of the circuit formed from the obtained PI-based film is easily reduced.

In one embodiment of the present invention, the structural unit (B1) is not particularly limited as long as it contains a biphenyl skeleton. The number of biphenyl skeletons contained in the structural unit (B1) may be one or two or more. In one embodiment of the present invention, the structural unit (B1) is preferably a structural unit (b1) derived from the diamine represented by the formula (b1) from the viewpoint of easily reducing the Df of the PI-based film: [In the formula (b1), R ^b1 are independent of each other and represent a halogen atom, or an alkyl group, an alkoxy group, an aryl group or an aryloxy group which may have a halogen atom, and p represents an integer from 0 to 4].

In the formula (b1), R ^b1 are independent of each other and represent a halogen atom, or an alkyl group, an alkoxy group, an aryl group or an aryloxy group that may have a halogen atom, which can easily reduce the Df of the PI film and improve the dimensional stability. From a viewpoint, it is preferable to independently represent a halogen atom, or an alkyl group, an alkoxy group or an aryl group which may have a halogen atom, and more preferably it represents a halogen atom, an alkyl group having 1 to 6 carbon atoms, or an alkyl group having 1 carbon number. An alkoxy group with 6 to 6 carbon atoms, or an aryl group with 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 are those mentioned above. The hydrogen atoms contained in R ^b1 are independent of each other and may be replaced by a halogen atom. Examples of the halogen atom are the same as those described above. From the viewpoint of easily reducing the Df of the PI film and improving the dimensional stability, R ^b1 is independent of each other, and an alkyl group with 1 to 6 carbon atoms or a fluorinated alkyl group with 1 to 6 carbon atoms is preferred, since it is easy to increase the dimensional stability. From the viewpoint of adhesion to substrates such as copper foil, an alkyl group with 1 to 6 carbon atoms that does not contain fluorine is more preferred, an alkyl group with 1 to 3 carbon atoms that does not contain fluorine is even more preferred, and a methyl group is particularly preferred. .

In the formula (b1), p is independent of each other and represents an integer from 0 to 4. From the viewpoint of easily reducing the Df of the PI-based film and improving the dimensional stability, p is preferably an integer from 0 to 2, more preferably 0 or 1.

In formula (b1), the -NH ₂ group bonded to each benzene ring, based on the single bond connecting each benzene ring, can be in the ortho position, meta position or para position, or α position, β position or γ position. From the viewpoint of easily reducing the Df of the PI-based film and improving the dimensional stability, any bonding is preferably at the meta or para position, or at the β or γ position, and more preferably at the Para position, or γ position bonding.

In a suitable embodiment of the present invention, formula (b1) is formula (b1'): The one shown is better. If the PI-based resin contains, as the structural unit (B1), a structural unit derived from the formula (b1), especially a structural unit derived from the diamine represented by the formula (b1′), the Df of the obtained PI-based film will be easily reduced. Furthermore, since the imidization temperature Df tends to be low even at a low temperature of, for example, 350° C. or lower, the PI-based resin precursor coating film is thermally imidized in a laminated structure with a copper foil to produce this product. CCL also easily suppresses the deterioration of the copper foil surface, making it easy to obtain CCL with excellent high-frequency characteristics.

In one embodiment of the present invention, the content of structural unit (B1), preferably structural unit (b1), relative to the total amount of structural unit (B), is preferably 25 mol% or more, more preferably More than 30 mol%, more preferably 40 mol% or more, still more preferably 60 mol% or more, particularly preferably 70 mol% or more, particularly preferably 80 mol% or more, and particularly preferably 90 mol% or more More than % of ears. As for the structural unit (B1), if the content of the structural unit (b1) is more than the above-mentioned lower limit, it is easy to reduce Df. Furthermore, the upper limit of the content of the structural unit (B1), preferably the structural unit (b1), is not particularly limited, and may be 100 mol% or less relative to the total amount of the structural unit (B). The proportion of the aforementioned structural units can be measured using ¹ H-NMR, for example, or can also be calculated from the feed ratio of the raw materials.

(Structural unit (B2)) In one embodiment of the present invention, the structural unit (B) includes a structural unit derived from a diamine having two or more aromatic rings, and each aromatic ring is bonded through a divalent organic group. (B2) (hereinafter, may be simply referred to as structural unit (B2)) is preferred. Examples of the divalent organic group in the structural unit (B2) include an alkylene group which may have a halogen atom, -O-, -COO-, -OOC-, -SO ₂ -, -S-, -CO- or -N(R ^c )-, etc., R ^c represents a hydrogen atom and a monovalent hydrocarbon group with 1 to 12 carbon atoms that can be substituted by a halogen atom. Among these, as the divalent organic group in the structural unit (B2), -O-, -CH ₂ -, -CH ₂ -CH ₂ -, -CH(CH ₃ )-, -C(CH ₃ ) ₂ -, -C(CF ₃ ) ₂ -, -COO-, -OOC-, -SO ₂ -, -S-, -CO- or -N(R ^c )- are preferred.

In one embodiment of the present invention, structural unit (B), as structural unit (B2), is derived from formula (b2): [In formula (b2), R ^b2 are independent of each other and represent a halogen atom, or an alkyl group, alkoxy group, aryl group or aryloxy group that may have a halogen atom, and W are independent of each other and represent -O-, -CH ₂ -, -CH ₂ -CH ₂ -, -CH(CH ₃ )-, -C(CH ₃ ) ₂ -, -C(CF ₃ ) ₂ -, -COO-, -OOC-, -SO ₂ -, -S- , -CO- or -N(R ^c )-, R ^c represents a hydrogen atom, a monovalent hydrocarbon group with 1 to 12 carbon atoms that can be substituted by a halogen atom, m represents an integer from 1 to 4, q is independent of each other and represents 0~ Integer of 4] The structural unit (b2) of the diamine shown (hereinafter, sometimes simply referred to as the structural unit (b2)) is preferred. If the structural unit (B) contains the above-mentioned structural unit (B2), especially the structural unit (b2), the Df of the obtained PI-based film is likely to be reduced, and the transmission of the electronic circuit including the obtained PI-based film is likely to be reduced. loss.

In formula (b2), R ^b2 are independent of each other and represent a halogen atom, or an alkyl group, an alkoxy group, an aryl group or an aryloxy group that may have a halogen atom, preferably a halogen atom or an alkyl group with 1 to 6 carbon atoms. , an alkoxy group with 1 to 6 carbon atoms, or an aryl group with 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 are those mentioned above. The hydrogen atoms contained in R ^b2 are independent of each other and may be replaced by a halogen atom. Examples of the halogen atom are the same as those described above. From the viewpoint of easily reducing the Df of the PI-based film and improving the dimensional stability, R ^b2 is independent of each other, and an alkyl group with 1 to 6 carbon atoms or a fluorinated alkyl group with 1 to 6 carbon atoms is preferred, since it is easy to increase the dimensional stability. From the viewpoint of adhesion to substrates such as copper foil, an alkyl group with 1 to 6 carbon atoms that does not contain fluorine is more preferred, an alkyl group with 1 to 3 carbon atoms that does not contain fluorine is even more preferred, and a methyl group is particularly preferred. .

In the formula (b2), q is independent of each other and represents an integer from 0 to 4. From the viewpoint of easily reducing the Df of the PI film and improving the dimensional stability, it is preferably an integer from 0 to 2, more preferably 0 or 0. 1.

In formula (b2), W are independent of each other and represent -O-, -CH ₂ -, -CH ₂ -CH ₂ -, -CH(CH ₃ )-, -C(CH ₃ ) ₂ -, -C(CF ₃ ) ₂ -, -COO-, -OOC-, -SO ₂ -, -S-, -CO- or -N(R ^c )-, from the viewpoint of easily reducing the Df of the PI film and improving the dimensional stability See, it is better to represent -O-, -CH ₂ -, -C(CH ₃ ) ₂ -, -C(CF ₃ ) ₂ -, -COO-, -OOC- or -CO-, which can easily be improved with From the viewpoint of adhesion to base materials such as copper foil, -O-, -CH ₂ - or -C(CH ₃ ) ₂ - is more preferred, and further preferably -O- or -C(CH ₃ ) ₂ -. R ^c represents a hydrogen atom and a monovalent hydrocarbon group having 1 to 12 carbon atoms that may be substituted by a halogen atom. Examples of the monovalent hydrocarbon group having 1 to 12 carbon atoms include those shown above, and these may be substituted by a halogen atom. Examples of the halogen atom include the same ones as described above.

In formula (b2), m is an integer between 1 and 4. From the viewpoint of easily reducing the Df of the PI film and improving the dimensional stability, m is preferably an integer between 1 and 3, and more preferably 2 or 3. In the formula (b2), the plural W, R ^b2 and q may be the same or different from each other, and the position of -W- based on -NH ₂ of each benzene ring may be the same or different.

In formula (b2), -W- is based on -NH ₂ of each benzene ring, and can be bonded at the ortho, meta or para position, or at any of the α, β or γ positions. From the viewpoint of reducing the Df of the PI-based film and easily improving the dimensional stability, it is preferable to be bonded at the meta or para position, or at the β or γ position, and more preferably at the para or γ position.

In one embodiment of the present invention, from the viewpoint of easily reducing the Df of the PI-based film and from the viewpoint of easily improving the adhesion between the PI-based film and the copper foil, in the formula (b2), m is 3 and W are independent of each other. Represents -O- or -C(CH ₃ ) ₂ - preferably, formula (b2), with formula (b2'): The one shown is better. If the PI-based resin contains a structural unit derived from the structural unit (b2), especially a structural unit derived from the diamine represented by (b2'), the storage modulus at 280°C is likely to be reduced (hereinafter, sometimes referred to as 280°C (E') below, as a result, the Df of the PI-based film tends to be reduced, and it is easy to obtain a PI-based film with excellent adhesion to copper foil. Furthermore, since the imidization temperature Df tends to be low even at a low temperature of, for example, 350° C. or lower, the PI-based resin precursor coating film is thermally imidized in a laminated structure with a copper foil to produce this product. CCL also easily suppresses the deterioration of the copper foil surface, making it easy to obtain CCL with excellent high-frequency characteristics.

In one embodiment of the present invention, the structural unit (b2), in addition to or instead of the structural unit derived from the diamine represented by the formula (b2'), may also include the structural unit derived from the formula (b2) in which m is 1, and W represents the structural unit of -O- diamine.

In one embodiment of the present invention, the content of the structural unit (B2) is preferably 0 mol% or more, more preferably 0.3 mol% or more, and even more preferably 0 mol% or more relative to the total amount of the structural unit (B). 0.5 mol% or more, more preferably 0.8 mol% or more, particularly preferably 1 mol% or more, particularly preferably 5 mol% or more, and extremely good, 8 mol% or more. If the content of the structural unit (B2) is more than the above-mentioned lower limit, the adhesiveness of the obtained PI-based film to a base material such as copper foil can be easily improved. Moreover, the upper limit of the content of the structural unit (B2) is preferably 75 mol% or less, more preferably 60 mol% or less, and still more preferably 40 mol% or less relative to the total amount of the structural unit (B). , more preferably 30 mol% or less, particularly preferably 20 mol% or less. If the content of the structural unit (B2) is less than the above-mentioned upper limit, the mechanical properties and dielectric properties of CTE etc. tend to be easily improved. The proportion of the aforementioned structural units can be measured using ¹ H-NMR, for example, or can also be calculated from the feed ratio of the raw materials.

(Structural unit (B3)) The PI-based resin may also contain a structural unit (B3) derived from a diamine in addition to the structural unit (B1) and the structural unit (B2) (hereinafter, it may be simply referred to as the structural unit (B3)). As the structural unit (B3), for example, a structural unit derived from a diamine in which m in the formula (b2) is 0, or a structural unit derived from a diamine in which X in the formula (2) is represented by the formula (61) to the formula (64). Structural units of amines, etc., among these, structural units derived from diamine (structural units derived from p-phenylenediamine) in which X in formula (2) is represented by formula (74) are preferred. In this specification, "structural unit (B3) derived from diamine other than structural unit (B1) and structural unit (B2)" means any one of structural unit (B1) and structural unit (B2). Different structural units derived from diamines.

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

In one embodiment of the present invention, the PI-based resin may also contain halogen atoms, preferably fluorine atoms, which may be introduced through the above-mentioned halogen atom-containing substituents. When the PI resin contains fluorine atoms, the relative dielectric coefficient of the resulting PI film is easily reduced. In order for the PI-based resin to contain fluorine atoms, preferred fluorine-containing substituents include fluorine groups and trifluoromethyl groups. In another embodiment of the present invention, the PI-based resin preferably does not contain fluorine atoms from the viewpoint of easily improving the adhesion of the obtained PI-based film to a base material such as copper foil. In addition, if the PI-based resin contains fluorine, the interaction between molecular chains tends to be weakened. Therefore, if it does not contain fluorine atoms, it is easy to adjust the X-ray parameters to the above range, and it is easy to reduce the Df of the obtained PI-based film. tendency.

When the PI-based resin contains halogen atoms, the content of halogen atoms, especially fluorine atoms, in the PI-based resin is preferably 0.1~35% by mass, more preferably 0.1~30% by mass, based on the mass of the PI-based resin. More preferably, it is 0.1 to 20% by mass, and particularly preferably 0.1 to 10% by mass. If the content of halogen atoms is above the above-mentioned lower limit, the heat resistance and dielectric properties of the obtained PI-based film will be easily improved. If the content of halogen atoms is below the above-mentioned upper limit, it is advantageous in terms of cost, it is easy to reduce the CTE of the PI-based film, and the synthesis of the PI-based resin becomes easier.

In one embodiment of the present invention, the imidization rate of the PI-based resin is preferably 90% or more, more preferably 93% or more, further preferably 95% or more, and usually 100% or less. From the viewpoint of easily improving the mechanical properties, thermal properties and dielectric properties, it is preferable that the acyl imidization rate is not less than the above-mentioned lower limit. The acyl imidization rate represents the ratio of the molar amount of acyl imine bonds in the PI-based resin relative to twice the molar amount of the structural unit derived from the tetracarboxylic acid compound in the PI-based resin. . In addition, when the PI-based resin contains a tricarboxylic acid compound, it means a value that is twice the molar amount of the structural unit derived from the tetracarboxylic acid compound in the PI-based resin and the molar amount of the structural unit derived from the tricarboxylic acid compound. In terms of the total molar amount, it is the ratio of the molar amount of the imine bonds in the PI resin. In addition, the acyl imidization rate can be determined by an IR method, an NMR method, or the like.

In one embodiment of the present invention, the polystyrene-reduced weight average molecular weight (hereinafter, the weight average molecular weight may be described as Mw) of the PI-based resin is preferably 100,000 or more, more preferably more than 100,000, and even more preferably 110,000. or above, more preferably 120,000 or more, particularly preferably 130,000 or more, preferably 1,000,000 or less, more preferably 700,000 or less, further preferably 500,000 or less, particularly preferably 300,000 or less. If Mw is more than the above-mentioned lower limit, mechanical properties such as folding resistance can be easily improved. If Mw is below the above-mentioned upper limit, it is advantageous from the viewpoint of processability during film formation.

In one embodiment of the present invention, the ratio (Mw/Mn) between the Mw of the PI-based resin and the number average molecular weight (hereinafter, the number average molecular weight may be described as Mn) is easy to improve the bending resistance. In terms of polystyrene, it is preferably 3.5 or more, more preferably 4.0 or more, still more preferably 4.2 or more, particularly preferably 4.5 or more, further preferably 4.7 or more, preferably 8.0 or less, more preferably 7.0 or less, and still more preferably The best is below 6.0, and the best is below 5.5. In addition, Mw and Mn can be determined by gel permeation chromatography (hereinafter, sometimes referred to as GPC) measurement and conversion to standard polystyrene.

In one embodiment of the present invention, the E' of the PI-based resin at 280°C is preferably less than 3×10 ⁸ Pa, and more preferably 3×10 ⁸ from the viewpoint of easily reducing the Df of the PI-based film. Pa or less, more preferably 2×10 ⁸ Pa or less, still more preferably 1.5×10 ⁸ Pa or less, particularly preferably 1×10 ⁸ Pa or less, particularly preferably 0.8×10 ⁸ Pa or less. Furthermore, the E' of the PI-based resin at 280°C is preferably 1×10 ⁴ Pa or more, more preferably 1×10 ⁵ Pa or more, from the viewpoint of easily suppressing deformation during processing of the PI-based film. Preferably, it is 1×10 ⁶ Pa or more. E' of the PI-based resin can be measured by dynamic viscoelasticity measurement, for example, by the method described in the Examples.

The E' at 280°C of the PI-based resin can be determined by appropriately adjusting the types of structural units constituting the PI-based resin and their composition, as well as the molecular weight and manufacturing method of the PI-based resin, especially the imidization conditions, etc. For example, it can be adjusted to be within the above range by adjusting the range described as a preferred aspect in the cost specification.

In one embodiment of the present invention, the Tg of the PI-based resin is preferably 290°C or less, more preferably less than 290°C, and even more preferably 280°C or less, from the viewpoint of easily reducing the Df of the obtained PI-based film. , more preferably 275°C or lower, particularly preferably 260°C or lower, particularly preferably 250°C or lower, still more preferably 240°C or lower. In addition, the Tg of the PI-based resin is preferably 200°C or higher, more preferably 202°C or higher, and further preferably Above 205℃. The Tg of the PI-based resin can be measured by dynamic viscoelasticity measurement, for example, by the method described in the Examples.

The Tg of the PI-based resin can be adjusted by appropriately adjusting the types of structural units constituting the PI-based resin and their compositions, as well as the molecular weight and manufacturing method of the PI-based resin, especially the imidization conditions, etc., for example The above-mentioned range is adjusted by adjusting to the range described as a preferred aspect in the description below.

In one embodiment of the present invention, if the E' and Tg of the PI-based resin at 280°C are set within the above ranges, the PI-based resin can easily form a better high-order structure in which rotational motion is suppressed. Therefore, it is speculated that the PI-based resin The rotation of polar groups in the resin is suppressed, reducing the loss of electrical energy due to thermal movement, thereby making it easier to reduce the Df of the PI film. In addition, polyamide, which is a PI-based resin precursor, begins to imidize at about 200°C. Generally speaking, although the degree of freedom of the molecular structure of polyamide is high, after imidization, it becomes relatively rigid and the degree of freedom of the molecular structure is reduced. If the Tg of the PI-based resin is preferably 200~290°C, when imidization is performed, the thermal imidization temperature exceeds the Tg of the PI-based resin, and the amide acid site and the amide imine site move simultaneously to form a higher-order structure. , so it is believed that the resin as a whole can easily form a better high-order structure in which rotational motion is suppressed. In addition, if E' at 280°C is preferably less than 3 × 10 ⁸ Pa, the imine moiety can move sufficiently softly when forming a higher-order structure. Therefore, it is considered that the rotational movement of the entire resin in particular is easily suppressed. Better high-order structure. As a result, Df can be lowered even if the imidization temperature is as low as 350° C. or lower, so it can be produced by thermally imidizing a PI-based resin precursor coating film in a laminate configuration with copper foil. This CCL can still suppress the deterioration of the copper foil surface, so a CCL with excellent high-frequency characteristics can be obtained.

In one embodiment of the present invention, the content of the PI-based resin in the PI-based film is preferably 60 mass% or more, more preferably 70 mass% or more, and even more preferably 60 mass% or more relative to the mass of the PI-based film of the present invention. It is 80 mass % or more, especially preferably 90 mass % or more. In addition, the upper limit of the content of the PI-based resin is not particularly limited, but it is, for example, 100 mass% or less, preferably 99 mass% or less, and more preferably 95 mass% or less relative to the mass of the PI-based film. If the content of the PI resin is within the above range, the mechanical properties, thermal properties and dielectric properties can be easily improved.

The PI film of the present invention may contain fillers if necessary. Examples of fillers include metal oxide particles such as silica and alumina, inorganic salt particles 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 types. When a filler is included, its content is preferably 50 mass% or less, more preferably 40 mass% or less, further preferably 30 mass% or less, and more preferably 0.01 mass% or more relative to the mass of the PI-based film.

Furthermore, in one embodiment of the present invention, the PI-based film of the present invention may contain additives if necessary. Examples of additives include antioxidants, flame retardants, cross-linking agents, surfactants, compatibilizers, imidization catalysts, weathering agents, lubricants, anti-blocking agents, antistatic agents, and anti-fogging agents. No drops, pigments, etc. The additives can be used alone or in combination of two or more types. The content of various additives can be appropriately selected within the range that does not impair the effect of the present invention. When various additives are included, the total content is preferably 7% by mass or less relative to the mass of the PI-based film, and more preferably 5 mass% or less, more preferably 4 mass% or less, more preferably 0.001 mass% or more.

[Production method of polyimide film] Although the method for manufacturing the PI-based film of the present invention is not particularly limited, for example, it can be manufactured by a method including the following steps: The step of coating a PI-based resin precursor solution containing a structural unit (A) derived from tetracarboxylic anhydride and a structural unit (B) derived from a diamine on a substrate, and A step of imidizing the PI resin precursor through heat treatment at 200°C or more and 500°C or less.

＜Coating steps of polyimide resin precursor solution＞ (Preparation of PI resin precursor solution) A PI-based resin precursor solution includes: a PI-based resin precursor containing a structural unit (A) derived from tetracarboxylic anhydride and a structural unit (B) derived from a diamine, and a solvent, which can be obtained by mixing the aforementioned PI-based resin precursor materials and solvents. Furthermore, in one embodiment of the present invention, the reaction liquid containing the PI-based resin precursor obtained by the synthesis of the above-mentioned PI-based resin precursor can also be appropriately diluted with a solvent as needed to prepare a PI-based resin precursor solution for use. .

The PI-based resin precursor in the present invention is obtained by reacting tetracarboxylic anhydride and diamine. In addition to the tetracarboxylic acid compound, a dicarboxylic acid compound and a tricarboxylic acid compound may be reacted.

Examples of the tetracarboxylic acid anhydride used in the synthesis of the PI-based resin precursor include aromatic tetracarboxylic acid compounds such as aromatic tetracarboxylic dianhydride; and aliphatic tetracarboxylic acid compounds such as aliphatic tetracarboxylic dianhydride. wait. The tetracarboxylic acid compound can be used alone or in combination of two or more kinds. In addition to the tetracarboxylic acid compound and dianhydride, tetracarboxylic acid compound analogs such as chloride compounds may also be used. Examples of the tetracarboxylic acid compound include the tetracarboxylic anhydride represented by the above formula (1), preferably the tetracarboxylic anhydride represented by the formula (a1), the tetracarboxylic anhydride represented by the formula (a2), or the tetracarboxylic anhydride represented by the formula (a2). Y in (1) is tetracarboxylic anhydride represented by formula (32).

Specific examples of the tetracarboxylic acid compound include pyromellitic anhydride (hereinafter sometimes referred to as PMDA), 4,4'-(4,4'-isopropylidene diphenoxy) diphthalic anhydride ( Hereinafter, it may be described as BPADA), 1,4,5,8-naphthalenetetracarboxylic dianhydride, 3,3',4,4'-biphenyltetracarboxylic dianhydride (hereinafter, it may be described as BPDA) , 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'-benzophenone tetracarboxylic dianhydride, 2,3',3, 4'-biphenyltetracarboxylic dianhydride, 2,2',3,3'-biphenyltetracarboxylic dianhydride, p-phenylene bis(trimellitic acid monoester dianhydride) (hereinafter, there are when recorded as TAHQ), the esterification product of trimellitic anhydride and 2,2',3,3',5,5'-hexamethyl-4,4'-biphenol (hereinafter, sometimes described as TMPBP), 4,4'-bis(1,3-dilateral oxy-1,3-dihydroisobenzofuran-5-ylcarbonyloxy)biphenyl (hereinafter, sometimes referred to as BP-TME), 2, 3',3,4'-diphenyl ether tetracarboxylic dianhydride, bis(2,3-dicarboxyphenyl) ether dianhydride, 3,3”,4,4”-p-triphenyl tetracarboxylic acid Acid dianhydride, 2,3,3”,4”-p-triphenyltetracarboxylic dianhydride, 2,2”,3,3”-p-triphenyltetracarboxylic dianhydride, 2,2- Bis(2,3-dicarboxyphenyl)-propane dianhydride, 2,2-bis(3,4-dicarboxyphenyl)-propane dianhydride, bis(2,3-dicarboxyphenyl)methane dianhydride , bis(3,4-dicarboxyphenyl)methane dianhydride, 1,1-bis(2,3-dicarboxyphenyl)ethane dianhydride, 1,1-bis(3,4-dicarboxyphenyl) )Ethane dianhydride, 1,2,7,8-, 1,2,6,7-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, 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-cyclobutane tetracarboxylic dianhydride ( Hereinafter, sometimes described as CBDA), norbornane-2-spiro-α'-spiro-2"-norbornane-5,5',6,6'-tetracarboxylic anhydride, p-phenylenebis( Trimellitic anhydride), 3,3',4,4'-diphenyltetracarboxylic dianhydride, 2,3,6,7-anthracenetetracarboxylic dianhydride, 4,8-dimethyl-1,2, 3,5,6,7-Hexahydronaphthalene-1,2,5,6-tetracarboxylic dianhydride, 2,6-dichloronaphthalene-1,4,5,8-tetracarboxylic dianhydride, 2, 7-Dichloronaphthalene-1,4,5,8-tetracarboxylic dianhydride, 2,3,6,7-tetrachloronaphthalene-1,4,5,8-tetracarboxylic dianhydride, 2,3, 6,7-Tetrachloronaphthalene-2,3,6,7-tetracarboxylic dianhydride, 1,4,5,8-tetrachloronaphthalene-1,4,5,8-tetracarboxylic dianhydride, 1, 4,5,8-Tetrachloronaphthalene-2,3,6,7-tetracarboxylic dianhydride, 2,3,8,9-perylene-tetracarboxylic dianhydride, 3,4,9,10-perylene- Tetracarboxylic dianhydride, 4,5,10,11-perylene-tetracarboxylic dianhydride, 5,6,11,12-perylene-tetracarboxylic dianhydride, pyridine -2,3,5,6-tetracarboxylic dianhydride, pyrrolidine-2,3,4,5-tetracarboxylic dianhydride, thiophene-2,3,4,5-tetracarboxylic dianhydride, bis( 2,3-dicarboxyphenyl)sebacodianhydride, bis(3,4-dicarboxyphenyl)sebacodianhydride, etc. Among these, BPDA, TAHQ, PMDA or BP-TME is preferable, and BPDA, TAHQ or BP-TME is more preferable from the viewpoint that the Df of the obtained PI-based film can be easily reduced even if the imidization temperature is low. good. These tetracarboxylic acid compounds can be used alone or in combination of two or more.

Examples of the diamine compound used in the synthesis of the PI-based resin precursor include aliphatic diamines, aromatic diamines, and mixtures thereof. In addition, the "aromatic diamine" in this embodiment means a diamine having an aromatic ring, and a part of its structure may contain an aliphatic group or other substituent. This aromatic ring may be a single ring or a condensed ring, and examples thereof include benzene ring, naphthalene ring, anthracene ring, fluorine ring, etc., but are not limited thereto. Among these, a benzene ring is preferred. The so-called "aliphatic diamine" refers to a diamine with an aliphatic group. Although part of its structure may also contain other substituents, it does not have an aromatic ring. Examples of the diamine compound include the diamine compound represented by the above formula (2), and preferably, the diamine compound represented by the formula (b1) or the diamine compound represented by the formula (b2).

Specific examples of the diamine compound include 1,4-diaminocyclohexane and 4,4'-diamino-2,2'-dimethylbiphenyl (hereinafter, sometimes referred to as m-Tb ), 4,4'-diamino-3,3'-dimethylbiphenyl, 2,2'-bis(trifluoromethyl)-4,4'-diaminobiphenyl (hereinafter, sometimes Described as TFMB), 4,4'-diaminodiphenyl ether, 1,3-bis(3-aminophenoxy)benzene (hereinafter sometimes referred to as 1,3-APB), 1,4- Bis(4-aminophenoxy)benzene (hereinafter sometimes referred to as 1,4-APB), 1,3-bis(4-aminophenoxy)benzene, 2,2-bis[4-( 4-Aminophenoxy)phenyl]propane (hereinafter sometimes referred to as BAPP), 2,2'-dimethyl-4,4'-diaminobiphenyl, 3,3'-dihydroxy- 4,4'-Diaminobiphenyl, 2,2-bis-[4-(3-aminophenoxy)phenyl]propane, bis[4-(4-aminophenoxy)]biphenyl , bis[4-(3-aminophenoxy)biphenyl, bis[1-(4-aminophenoxy)]biphenyl, bis[1-(3-aminophenoxy)]biphenyl , bis[4-(4-aminophenoxy)phenyl]methane, bis[4-(3-aminophenoxy)phenyl]methane, bis[4-(4-aminophenoxy) Phenyl] ether, bis[4-(3-aminophenoxy)phenyl]ether, bis[4-(4-aminophenoxy)]benzophenone, bis[4-(3-amine phenoxy)]benzophenone, 2,2-bis-[4-(4-aminophenoxy)phenyl]hexafluoropropane, 2,2-bis-[4-(3-amino) Phenoxy)phenyl] hexafluoropropane, 4,4'-methylene di-o-toluidine, 4,4'-methylene di-2,6-dimethylaniline, 4,4'-methylene di-o-toluidine Methyl-2,6-diethylaniline, 4,4'-methylenediphenylamine, 3,3'-methylenediphenylamine, 4,4'-diaminodiphenylpropane, 3,3 '-Diaminodiphenylpropane, 4,4'-diaminodiphenylethane, 3,3'-diaminodiphenylethane, 4,4'-diaminodiphenylmethane , 3,3'-diaminodiphenylmethane, 3,3'-diaminodiphenyl ether, 3,4'-diaminodiphenyl ether, benzidine, 3,3'-diaminobiphenyl ether , 3,3'-dimethoxybenzidine, 4,4”-diamino-p-terphenyl, 3,3”-diamino-p-terphenyl, m-phenylenediamine, p -Phenylenediamine (hereinafter, sometimes referred to as p-PDA), resorcinol-bis(3-aminophenyl) ether, 4,4'-[1,4-phenylenebis(1-methyl) methylethylene)]bisaniline, 4,4'-[1,3-phenylenebis(1-methylethylene)]bisaniline, bis(p-aminocyclohexyl)methane, bis(p -β-Amino-tertiary butylphenyl) ether, bis(p-β-methyl-δ-aminopentyl)benzene, p-bis(2-methyl-4-aminopentyl)benzene , p-bis(1,1-dimethyl-5-aminopentyl)benzene, 1,5-diaminonaphthalene, 2,6-diaminonaphthalene, 2,4-bis(β-aminonaphthalene) -Tertiary butyl)toluene, 2,4-diaminotoluene, m-xylene-2,5-diamine, p-xylene-2,5-diamine, m-styrenediamine, p -Diamine, 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-tertiary 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'-( Hexafluoropropylene)diphenylamine, 1,2-diaminoethane, 1,3-diaminopropane, 1,4-diaminobutane, 1,5-diaminopentane, 1, 6-Diaminohexane, 1,2-diaminopropane, 1,2-diaminobutane, 1,3-diaminobutane, 2-methyl-1,2-diaminopropane , 2-methyl-1,3-diaminopropane, 1,3-bis(aminomethyl)cyclohexane, 1,4-bis(aminomethyl)cyclohexane, norbornanediamine , 2'-methoxy-4,4'-diamine benzamide, 4,4'-diamine benzamide, bis[4-(4-aminophenoxy)phenyl]terine, Bis[4-(3-aminophenoxy)phenyl]benzoate, 9,9-bis[4-(4-aminophenoxy)phenyl]benzoate, 9,9-bis[4-(3 -Aminophenoxy)phenyl]fluoride, 4,4'-diaminodiphenyl sulfide, 3,3'-diaminodiphenyl sulfide, 4,4'-diaminodiphenyl Diphenyl sulfide, 3,3'-diaminodiphenyl sulfide, 2,5-diamino-1,3,4- Oxidazole, bis[4,4'-(4-aminophenoxy)]benzamidebenzene, bis[4,4'-(3-aminophenoxy)]benzamidebenzene, 2 ,6-diaminopyridine, 2,5-diaminopyridine, etc. Among these, m-Tb, BAPP, etc. are preferable from the viewpoint that the Df of the obtained PI-based film can be easily reduced even if the imidization temperature is low. The diamine compound can be used individually or in combination of 2 or more types.

In addition, the above-mentioned PI-based resin precursor can also be other tetracarboxylic acid, dicarboxylic acid compound in addition to the tetracarboxylic acid compound used in the synthesis of the above-mentioned resin precursor, within the scope that does not impair various physical properties of the PI-based film. It is formed by the reaction of acids and tricarboxylic acids and their anhydrides and derivatives.

Examples of other tetracarboxylic acids include water adducts of anhydrides of the above tetracarboxylic acid compounds.

Examples of the dicarboxylic acid compound include aromatic dicarboxylic acids, aliphatic dicarboxylic acids, and similar chloride compounds, acid anhydrides, and the like, and two or more types may be used in combination. Specific examples include terephthalic acid; isophthalic acid; naphthalenedicarboxylic acid; 4,4'-biphenyldicarboxylic acid; 3,3'-biphenyldicarboxylic acid; and chain hydrocarbons having 8 or less carbon atoms. A dicarboxylic acid compound and two benzoic acids are linked by a single bond, -O-, -CH ₂ -, -C(CH ₃ ) ₂ -, -C(CF ₃ ) ₂ -, -SO ₂ - or phenylene group compounds and such chloride compounds.

Examples of the tricarboxylic acid compound include aromatic tricarboxylic acids, aliphatic tricarboxylic acids, and similar chloride compounds, acid anhydrides, and the like, and two or more types may be used in combination. As specific examples, 1,2,4-benzenetricarboxylic acid anhydride; 2,3,6-naphthalenetricarboxylic acid-2,3-anhydride; phthalic anhydride and benzoic acid with a single bond, -O-, -CH ₂ -, -C(CH ₃ ) ₂ -, -C(CF ₃ ) ₂ -, -SO ₂ - or phenylene-linked compounds.

In the production of the PI-based resin precursor, the usage amounts of the diamine compound, tetracarboxylic acid compound, dicarboxylic acid compound, and tricarboxylic acid compound can be appropriately selected depending on the desired ratio of each structural unit of the PI-based resin. In the present invention, the total number of moles of diamine compounds used relative to 1 mol of the total amount of tetracarboxylic acid compounds is defined as the amine ratio. In a suitable embodiment of the present invention, the amine ratio is preferably 0.90 mol or more and preferably 0.999 mol or less per 1 mol of the total amount of the tetracarboxylic acid compound. In another embodiment, the amine ratio is preferably 1.001 mol or more, and preferably 1.10 mol or less per 1 mol of the total amount of the tetracarboxylic acid compound. In one embodiment of the present invention, when the amine ratio is 1 or less, the amine ratio is preferably 0.90 mol or more and 0.999 mol or less, more preferably 0.95 mol or more and 0.997 mol or less, still more preferably 0.97 mol or more and 0.995 mol. the following. 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 1.1 mol or less, more preferably 1.002 mol or more and 1.05 mol or less, further preferably 1.003 mol or more and 1.03 mol. the following. If the amine ratio is close to 1.0 mol, the molecular weight tends to increase rapidly during synthesis. If the amine ratio is significantly away from 1.0 mol, the molecular weight of the resulting PI-based resin tends to decrease. If the molecular weight increases rapidly, it will grow unevenly during synthesis, making it difficult to stabilize the physical properties of the PI-based resin. On the other hand, if the molecular weight is too low, mechanical properties tend to decrease.

The reaction temperature of the diamine compound and the tetracarboxylic acid compound is preferably 50°C or lower, more preferably 40°C or lower, further preferably 30°C or lower. If the reaction temperature is below the above-mentioned upper limit, the Df of the obtained PI-based film is likely to be reduced. This tendency occurs in PI-based films containing PI-based resins containing ester bonds, especially PI-based resins containing structural unit (A1). Particularly significant. Moreover, the reaction temperature of the diamine compound and the tetracarboxylic acid compound is preferably 5°C or higher, more preferably 10°C or higher, and still more preferably 15°C or higher. When the reaction temperature is equal to or higher than the above lower limit, the reaction rate tends to be increased and the polymerization time tends to be shortened. The reaction time is not particularly limited. For example, it can be about 0.5 to 72 hours, preferably 3 to 24 hours. If the reaction time is within the above range, even if the imidization temperature is low, the Df of the obtained PI-based thin film will be easily reduced.

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, but examples include water, methanol, ethanol, ethylene glycol, isopropyl alcohol, propylene glycol, ethylene glycol methyl ether, ethylene glycol butyl ether, and 1-methyl ether. Alcohol-based solvents such as oxy-2-propanol, 2-butoxyethanol, and propylene glycol monomethyl ether; phenol-based solvents such as phenol and cresol; ethyl acetate, butyl acetate, and ethylene glycol methyl ether Ester-based solvents such as acetate, propylene glycol methyl ether acetate, ethyl lactate, etc.; lactone-based solvents such as γ-butyrolactone (hereinafter, sometimes referred to as GBL), γ-valerolactone, etc.; acetone, Ketone solvents such as methyl ethyl ketone, cyclopentanone, cyclohexanone, 2-heptanone, methyl isobutyl ketone, etc.; aliphatic hydrocarbon solvents such as pentane, hexane, heptane, etc.; ethylcyclohexane Alicyclic hydrocarbon solvents such as alkanes; aromatic hydrocarbon solvents such as toluene and xylene; nitrile solvents such as acetonitrile; ether solvents such as tetrahydrofuran and dimethoxyethane; chlorine-containing solvents such as chloroform and chlorobenzene ; Amide-based solvents such as N,N-dimethylacetamide (hereinafter, sometimes described as DMAc), N,N-dimethylformamide (hereinafter, sometimes described as DMF); dimethyl Sulfur-containing solvents such as sulfuric acid, dimethyl styrene, cycloterine, etc.; carbonate-based solvents such as ethylene carbonate, propylene carbonate, etc.; N-methylpyrrolidone (hereinafter, sometimes referred to as NMP), etc. Pyrrolidone solvents; and combinations thereof, etc. Among these, from the viewpoint of solubility, phenol-based solvents, lactone-based solvents, amide-based solvents, and pyrrolidone-based solvents are preferably used, and amide-based solvents are more preferably used.

In one embodiment of the present invention, the boiling point of the solvent used for the reaction of the diamine compound and the tetracarboxylic acid compound is relatively low from the viewpoint that the Df of the obtained PI-based film can be easily reduced even if the imidization temperature is low. The temperature is preferably 230°C or lower, more preferably 200°C or lower, and still more preferably 180°C or lower. In addition, the boiling point of the solvent is preferably 100°C or higher, and more preferably 120°C or higher, from the viewpoint of easily reducing the Df of the obtained PI-based film.

The reaction of the diamine compound and the tetracarboxylic acid compound can also be carried out under an inert atmosphere such as a nitrogen atmosphere, an argon atmosphere, or under reduced pressure if necessary. Under an inert atmosphere, such as a nitrogen atmosphere or an argon atmosphere, etc., It is better to carry out the process while stirring in a carefully controlled dehydration solvent.

The solvent contained in the PI-based resin precursor solution can be exemplified as a solvent used in the reaction of a diamine compound and a tetracarboxylic acid compound. Preferably, it is a lactone-based solvent, an amide-based solvent, or a pyrrolidone-based solvent. More preferably, it is an amide solvent. Furthermore, in one embodiment of the present invention, the boiling point of the solvent contained in the PI-based resin precursor solution is preferably such that the Df of the obtained PI-based film can be easily reduced even if the imidization temperature is low. The temperature is 230°C or lower, more preferably 200°C or lower, further preferably 180°C or lower, and particularly preferably 170°C or lower. In addition, the boiling point of the solvent is preferably 100°C or higher, and more preferably 120°C or higher, from the viewpoint of easily reducing the Df of the obtained PI-based film.

The content of the PI-based resin precursor contained in the PI-based resin precursor solution is preferably 8 mass% or more, more preferably 10 mass% or more, and further preferably 12 mass % or more, particularly preferably 13 mass % or more, more preferably 30 mass % or less, more preferably 25 mass % or less, further preferably 23 mass % or less, particularly preferably 20 mass % or less. If the content of the PI-based resin precursor is within the above range, the processability during film formation will be excellent.

(Coating of polyimide resin precursor solution) The coating step of the PI-based resin precursor solution is a step of coating the PI-based resin precursor solution on the substrate to form a coating film.

In the coating step, the PI-based resin precursor solution is coated on the substrate by a known coating method or coating method to form a coating film. Examples of known coating methods include roll coating, die coating, comma coating, lip coating, spin coating, mesh coating, etc., such as wire bar coating, reverse coating, and gravure coating. Printing coating method, fountain coating method, dipping method, spray method, curtain coating method, slit coating method, drool forming method, etc. When the PI-based resin precursor solution is coated or coated on the substrate, a single layer of the PI-based resin precursor solution can be coated on the substrate, or multiple layers of PI-based resin precursor solution can be coated on the substrate. material solution. When coating multiple layers of PI resin precursor solution on the substrate, the coating can be divided into multiple times and dried, or multiple layers can be coated at the same time.

Examples of the base material include metal plates (such as copper foil), SUS plates such as SUS foil and SUS tape, glass substrates, PET films, PEN films, and the PI-based film of the present invention. Other than PI resin film, polyamide resin film, etc. Among them, from the viewpoint of excellent heat resistance, preferred examples include copper plates, SUS plates, glass substrates, PET films, PEN films, etc., and from the viewpoints of adhesion to films and cost, preferred examples include Copper plate, SUS plate, glass substrate or PET film, etc.

＜Imination step＞ The imidization step is a step of imidizing the PI resin precursor coated on the substrate through heat treatment at 200°C or more and 500°C or less. In one embodiment of the present invention, the imidization step involves heating and drying the PI resin precursor solution coated on the substrate at a relatively low temperature before the imidization of the PI resin precursor. The dry film containing the obtained PI-based resin precursor is preferably subjected to a step of imidization by heat treatment at 200°C or more and 500°C or less. Furthermore, in one embodiment of the present invention, the dry film of the PI-based resin precursor on the base material can be imidized to obtain the PI-based film, or the dry film of the PI-based resin precursor can be peeled off from the base material. The dry film peeled off from the base material is imidized to obtain a PI-based film.

In one embodiment of the present invention, the drying temperature of the PI-based resin precursor coated on the base material is not particularly limited as long as it is within the temperature range for solvent drying and solidification. However, in order to avoid the occurrence of surface damage during rapid drying, From the viewpoint of roughness and suppression of wrinkles or wrinkles generated during processing, the temperature is preferably less than 300°C, more preferably not more than 260°C, still more preferably not more than 200°C, still more preferably not more than 180°C, and, From the viewpoint of productivity, the temperature is preferably 50°C or higher, more preferably 80°C or higher, and further preferably 100°C or higher.

In one embodiment of the present invention, the PI-based resin precursor in the present invention can reduce the Df of the resulting PI-based film even if it is imidized at a low temperature. The heat treatment temperature in the imidization step, that is, the imidization temperature, is preferably 500°C or less, more preferably 400°C or less, more preferably less than 350°C, still more preferably 340°C or less, and particularly preferably The temperature should be below 330°C, preferably below 310°C, and below 300°C as the best. If the imidization temperature is below the above-mentioned upper limit, oxidative deterioration of the resin will be less likely to occur, and CCL with excellent high-frequency characteristics will be easily obtained. In addition, the imidization temperature is preferably 200°C or higher, more preferably 210°C or higher, and still more preferably 220°C or higher, from the viewpoint of easily increasing the acylimidation rate sufficiently. In addition, from the viewpoint of easily obtaining a smooth film, it is preferable to perform heating in stages. For example, the solvent can also be removed by heating at a relatively low temperature of 50 to 300°C, and then heated in stages to a temperature above 200°C and below 500°C, preferably above 200°C and below 400°C, and more preferably above 200°C but below 350°C. The imidization is carried out at a temperature within the range. In one embodiment of the present invention, the PI-based film of the present invention includes a PI-based resin precursor that is heated at a temperature of 200°C or more and 500°C or less, preferably 200°C or more and 400°C or less, more preferably 200°C or more but less than 200°C. PI resin obtained by heat treatment at 350°C for imidization is preferred.

In one embodiment of the present invention, the reaction time in the imidization is preferably 30 minutes to 24 hours, more preferably 1 to 12 hours. Moreover, in one embodiment of the present invention, the time for maintaining the temperature above 200°C is preferably 10 to 90 minutes, more preferably 15 to 70 minutes, and even more preferably 20 to 50 minutes. If the reaction time above 200°C in the imidization is within the above range, it is easy to fully increase the imidization rate, it becomes easy to prevent oxidative degradation of the resin, and it is easy to improve the dielectric properties of the obtained PI-based film or Resistance to bending.

After imidization, a PI-based film can be obtained by peeling off the coating film formed on the base material. In one embodiment of the present invention, when the base material is copper foil, a PI-based film may be formed without peeling the coating film from the copper foil, and a laminated film in which a PI-based film is laminated on the obtained copper foil may be used for CCL.

When the film of the present invention is a multilayer film, it can be produced by a multilayer film forming method such as co-extrusion processing, extrusion lamination, thermal lamination, dry lamination, or the like.

[Laminated film] Since the PI film of the present invention has low Df, it can be suitably used in the formation of metal-clad laminates used in FPC. Therefore, the PI film of the present invention is used as the PI layer, including a laminated film containing a PI layer and a metal foil layer. In one embodiment of the present invention, the laminated film of the present invention may include a metal foil layer only on one side of the PI layer, or may include a metal foil layer on both sides.

In one embodiment of the present invention, examples of the metal foil include copper foil, SUS foil, aluminum foil, etc., but from the viewpoint of electrical conductivity and metal workability, copper foil is preferred.

Since the PI-based film of the present invention has low Df, it can be suitably used for the formation of CCL with excellent high-frequency characteristics. Therefore, in a suitable embodiment of the present invention, the laminated film of the present invention is used in combination with the PI-based film of the present invention. A laminated film containing a copper foil layer on one or both sides is preferred.

In one embodiment of the present invention, the thickness of the metal foil layer, especially the copper foil layer, is preferably 1 μm or more, more preferably 5 μm or more. In addition, the circuit is miniaturized and the folding resistance is easily improved. , preferably 100 μm or less, more preferably 50 μm or less, further preferably 30 μm or less, particularly preferably 20 μm or less. The thickness of the metal foil layer, especially the copper foil layer, can be measured using a film thickness meter. In addition, when both sides of the PI film include metal foil layers, especially copper foil layers, the thicknesses of each metal foil layer, especially each copper foil layer, may be the same or different from each other.

In one embodiment of the present invention, the thickness of the laminated film is preferably 5 μm or more, more preferably 10 μm or more, further preferably 15 μm or more, preferably 100 μm or less, more preferably 80 μm or less, still more preferably 60 μm or less. The thickness of the laminated film can be measured using a film thickness meter.

The laminated film of the present invention may include other layers such as functional layers in addition to the PI film and the metal foil layer, especially the copper foil layer. Examples of the functional layer include those exemplified above. For example, the functional layer may be a thermoplastic PI-based resin layer or an adhesive layer containing a thermoplastic PI-based resin. The functional layer can be used alone or in combination of two or more types.

In one embodiment of the present invention, the laminated film of the present invention may be a two-layer metal-clad laminated board composed of a metal foil layer and a PI layer, or may be a three-layer composed of a metal foil layer, a PI layer, and an adhesive layer. Metal-clad laminated boards, but from the viewpoint of heat resistance, dimensional stability and lightweight, a two-layer metal-clad laminated board without an adhesive layer is better. In a suitable embodiment of the present invention, the PI-based film of the present invention has a low imidization temperature Df even if the imidization temperature is low, so even if the PI-based resin precursor is coated on a copper foil, the film is thermally imidized. The metal foil produced by amination is a laminated film of copper foil, which can still inhibit the deterioration of the copper foil surface. Therefore, in a suitable embodiment of the present invention, the laminated film of the present invention has excellent high-frequency characteristics even if it does not include an adhesive layer.

Furthermore, in one embodiment of the present invention, the PI film and the metal foil layer of the present invention may be in direct contact with the metal foil layer, particularly the copper foil layer. Alternatively, the PI film and the metal foil layer, particularly the copper foil layer, may be in direct contact. A functional layer is inserted between them, and these are in contact through the functional layer. However, from the perspective of easily improving the mechanical and thermal properties, it is better for the PI film to be in direct contact with the metal foil layer, especially the copper foil layer. The functional layer that can be inserted between the PI film and the metal foil layer of the present invention can be a thermoplastic PI layer. From the viewpoint of easily improving the mechanical and thermal properties, the thermoplastic PI layer of the PI film or functional layer of the present invention is preferably a layer that is in direct contact with the metal foil layer, especially the copper foil layer.

[Manufacturing method of laminated film] The present invention also includes a method for manufacturing a laminated film, which includes the following steps: The step of coating a PI-based resin precursor solution containing a structural unit (A) derived from tetracarboxylic anhydride and a structural unit (B) derived from a diamine on a substrate, and The step of imidizing the PI-based resin precursor through heat treatment at 200°C or more and 500°C or less to form the PI-based thin film of the present invention on the substrate.

Regarding the manufacturing method of the laminated film of the present invention, "coating a PI-based resin precursor solution containing a structural unit (A) derived from tetracarboxylic anhydride and a structural unit (B) derived from a diamine on a substrate "Step" and "step of imidizing the PI resin precursor to form the PI thin film of the present invention on the substrate by heat treatment at 200°C or more and 500°C or less", the same applies to [polyimide-based Description of each step described in "Method for Manufacturing Thin Film".

In one embodiment of the present invention, the base material is preferably a metal foil, and particularly preferably a copper foil. Regarding the description of metal foil, especially copper foil, the same applies to the description of metal foil described in the "Laminated Film" section.

The laminated film of the present invention can also be produced by methods other than the above-mentioned methods. For example, by coating and drying a structural unit (A) derived from tetracarboxylic anhydride on a base material other than metal foil contained in the laminated film. ) and a PI-based resin precursor solution derived from the structural unit (B) of the diamine, peel the obtained dry film of the PI-based resin precursor from the aforementioned base material, so that the peeled-off dry film of the aforementioned PI-based resin precursor Made by laminating metal foil. As a method of laminating the dry film of the PI resin precursor and the metal foil, the method of pressing, the lamination method using a hot roller, etc. can be used. The PI resin precursor can also be performed at the same time during the laminating step. The imidization of substances.

[Flexible printed circuit board] The PI-based film of the present invention can reduce the transmission loss of a circuit made of the PI-based film, and can be suitably used as an FPC substrate material. Therefore, the present invention also includes an FPC substrate including the PI-based film of the present invention. [Example]

Hereinafter, the present invention will be described in more detail based on Examples and Comparative Examples, but the present invention is not limited to the following Examples.

The abbreviations used in the examples and comparative examples represent the following compounds. BPDA: 3,3’,4,4’-biphenyltetracarboxylic dianhydride TAHQ: p-phenylene bis (trimellitic acid monoester dianhydride) BP-TME: 4,4’-bis(1,3-bisoxy-1,3-dihydroisobenzofuran-5-ylcarbonyloxy)biphenyl PMDA: pyromellitic anhydride m-Tb: 4,4’-diamino-2,2’-dimethylbiphenyl BAPP: 2,2-bis[4-(4-aminophenoxy)phenyl]propane

[Synthesis of polyimide resin precursor] (Example 1) After m-Tb 17.95g (84.5mmol) and BAPP 0.35g (0.9mmol) were dissolved in DMAc 284g, TAHQ 19.38g (42.3mmol) was added and stirred at 20°C for 1 hour under a nitrogen atmosphere. Then, 12.44g (42.3mmol) of BPDA was added and stirred at 20°C for 24 hours under a nitrogen atmosphere to obtain a PI resin precursor composition. The molar ratio of the diamine monomer relative to the acid dianhydride monomer used was 1.01.

(Examples 2 to 8 and Comparative Example 1) A PI resin precursor composition was obtained in the same manner as in Example 1, except that the types of monomers used and the monomer composition were changed as shown in Table 1. The order of adding the monomers, unless otherwise stated, is defined as the order of diamine and acid dianhydride. The diamine is the order of diamine derived from structural units (B1), (B2), and (B3). The order of acid dianhydride is The acid dianhydride derived from the structural units (A1), (A2) and (A3) is added in this order.

[Manufacture of polyimide film] The PI resin precursor compositions obtained in Examples 2 to 8 and Comparative Example 1 were appropriately diluted so that the content of the PI resin precursor would be 10% by mass or more using the solvent used for the synthesis of the PI resin precursor. Adjust the viscosity to 40,000 cps or less to prepare a PI resin precursor solution. The PI resin precursor solutions were each shown in Table 1 and film-formed under any of the following film-forming conditions 1 to 4 to obtain a PI film made of PI resin. In Example 4, the azimuth angle profile in the measurement of the in-plane alignment index is shown in Figure 2, the diffraction intensity profile in the measurement of the molecular periodicity index is shown in Figure 4, and the azimuth angle profile in the measurement of the in-plane anisotropy index. The cross section is shown in Figure 6.

＜Film production conditions 1＞ The PI resin precursor solution was cast onto the glass substrate, and an applicator was used to form a thin film of the PI resin precursor solution at a line speed of 0.4 m/min. The aforementioned coating film was heated at 120° C. for 30 minutes, and the obtained film was peeled off from the glass substrate, and then the film was fixed to a metal frame. The film fixed on the metal frame was heated from 30°C to 270°C in 19 minutes in an atmosphere with an oxygen concentration of 7%, and then cooled to 200°C in 35 minutes to produce a PI film. The time to maintain the temperature above 220℃ is 23 minutes. In addition, the time to maintain the temperature above 200°C is 34 minutes.

＜Film production conditions 2＞ The PI resin precursor solution was cast onto the glass substrate, and an applicator was used to form a thin film of the PI resin precursor solution at a line speed of 0.4 m/min. The aforementioned coating film was heated at 120° C. for 30 minutes, and the obtained film was peeled off from the glass substrate, and then the film was fixed to a metal frame. The film fixed on the metal frame was heated from 30°C to 320°C for 9 minutes in an atmosphere with an oxygen concentration of 1%, then heated at 320°C for 6 minutes, and cooled to 200°C for 15 minutes to produce a PI film. The time to maintain the temperature above 220℃ is 21 minutes. In addition, the time to maintain the temperature above 200°C is 25 minutes.

＜Film production conditions 3＞ The PI resin precursor solution was cast onto the glass substrate, and an applicator was used to form a thin film of the PI resin precursor solution at a line speed of 0.4 m/min. The aforementioned coating film was heated at 120° C. for 30 minutes, and the obtained film was peeled off from the glass substrate, and then the film was fixed to a metal frame. The film fixed on the metal frame was heated from 30°C to 320°C for 5 minutes in an atmosphere with an oxygen concentration of 1%, then heated at 320°C for 5 minutes, and cooled to 200°C for 15 minutes to produce a PI film. The time to maintain the temperature above 220℃ is 17 minutes. In addition, the time to maintain the temperature above 200°C is 21 minutes.

＜Film production conditions 4＞ The PI resin precursor solution is cast onto the roughened surface side (surface roughness; Rz=1.3μm) of electrolytic copper foil (made by JX Metal Co., Ltd., JXEFL-BHM thickness: 12μm), using an applicator at line speed. Form the thin film coated with the PI resin precursor solution at 0.4m/min. The coating film was dried by heating at 120° C. for 30 minutes. After that, the laminated film of copper foil and precursor was fixed on a metal frame, and in an atmosphere with an oxygen concentration of 1%, it took 9 minutes to raise the temperature from 30°C to 320°C, then heated to 320°C for 6 minutes, and cooled to 320°C in 15 minutes. Make a laminated film of PI film and copper foil at 200℃. The time to maintain the temperature above 220℃ is 21 minutes. In addition, the time to maintain the temperature above 200°C is 25 minutes. The obtained laminated film of the PI film and the copper foil was immersed in a large volume of a 40% by mass ferric chloride aqueous solution at room temperature for 10 minutes. After visually confirming that no copper remained, it was dried at 80°C for 1 hour to obtain a single PI. film.

[Synthesis of polyimide resin precursor and production of polyimide film] (Comparative Example 2) After m-Tb 70.33g (331mmol) was dissolved in NMP 720g, BPDA 73.06g (248mmol) and TAHQ 37.94g were added. (83 mmol) was stirred at room temperature for 1 hour under nitrogen atmosphere. Thereafter, the mixture was stirred at 60°C for 20 hours to obtain a PI resin precursor composition. In addition, the Mw of the PI resin precursor in terms of polystyrene is 91,000, and the Mn is 27,000. The PI resin precursor composition is appropriately diluted with NMP to adjust the viscosity to prepare a PI resin precursor solution. The obtained PI resin precursor solution is film-formed using the aforementioned film-forming condition 1 to obtain a PI film. The thickness of the obtained PI film was 30 μm, Dk was 3.45, Df was 0.0040, index E was 0.0074, and CTE was 38.2ppm. In addition, the Tg of the PI resin is 255°C, and the E' at 280°C is 5.53×10 ⁸ Pa. In addition, the Tg obtained from the self-storage module curve using the tangent method is 230°C. The in-plane alignment index of the obtained PI film was 57.3, the molecular periodicity index was 7.55, the in-plane anisotropy index A was 1.0, and the in-plane anisotropy index B was 1.1.

Regarding the PI thin films obtained in the Examples and Comparative Examples, each measurement and evaluation was performed. The measurement and evaluation methods are explained below.

<Measurement of glass transition temperature Tg> The Tg of the PI resin obtained in the Examples and Comparative Examples was determined by measuring the PI film as follows. Using a dynamic viscoelasticity measuring device (IT Measurement Control Co., Ltd., DVA-220), measurements were made on the following samples and conditions to obtain the storage modulus (E') and loss modulus (Loss modulus, The ratio of the values of E") is the tan δ curve. The top of the peak of the tan δ curve is designated as Tg. Test piece: rectangular parallelepiped with length 40mm, width 5mm, and thickness 30μm (in addition, the thickness varies depending on the film used) Experimental mode: single frequency, constant speed heating Experimental Style: Stretch Sample clamp length: 15mm Measurement starting temperature: room temperature ~ 342°C Heating rate: 5℃/min Frequency: 10Hz Static/dynamic stress ratio: 1.8 Main data collected: (1)Storage modulus (E’) (2) Loss modulus (E”) (3)tanδ (E”/E’)

＜Measurement of storage modulus (E’)＞ The E' at 280°C of the PI resin obtained in the Examples and Comparative Examples was determined by performing dynamic viscoelasticity measurement in the same manner as the measurement of Tg.

<Measurement of X-rays> (1) In-plane alignment index The PI films obtained in the Examples and Comparative Examples were subjected to wide-angle X-ray diffraction measurement using the transmission method under the following conditions. ・Device name: (Co., Ltd.) Small-angle/wide-angle X-ray scattering/diffraction device Nanoviwer manufactured by Rigaku Co., Ltd. ・Detector: Pilatus 100k ・X-ray source: Cu-Kα line ・Voltage: 40kV ・Current: 20mA ・Camera length: 70mm ・Exposure time: 10 minutes ・Beam diameter: 0.25mm

Specifically, four films were stacked in the ND direction so that the MD direction was consistent. The stacked films were cut with a trimming knife so that the width in the MD direction became 1 cm and the width in the TD direction became 1 mm, and a test piece for measurement was obtained. Next, as shown in FIG. 1 , the test piece 1 a for measurement is set in the X-ray device so that the irradiation direction of the X-ray becomes parallel to the TD direction of the film, and X-rays are incident on the test piece for measurement from the X-ray source 2 a. 1a, the two-dimensional diffraction image is obtained by the detector 3a. The obtained two-dimensional diffraction image was corrected using the two-dimensional diffraction image (air blank) obtained without installing the test piece 1a for measurement. Furthermore, from the two-dimensional diffraction image, the azimuth angle section of 0° and 180° corresponds to the MD direction of the measurement test piece 1a, and the azimuth angle section of 90° and 270° corresponds to the ND direction of the measurement test piece 1a. Azimuth angle profile of 2θ=16°. The diffraction intensity at each azimuth angle uses the average value of the diffraction intensity in the range of 2θ=15.5~16.5°. In the obtained azimuth angle profile (β=0~360°), find the half-width of the wave crests existing at 90° and 270°, set the average of the two half-widths as FWHM, and substitute it into Equation 1 to find the surface Internal alignment index. In addition, the half-width of the wave peak existing at 90° is the peak width existing at the intensity position in the center between the wave peak intensity at 90° and the minimum intensity in the range of 0 to 180° (that is, the minimum intensity is At the base point, the peak width at a position that is half the intensity of the peak intensity at 90°), and the half-width of the peak at 270° is the minimum between the peak intensity at 270° and the range of 180~360° The peak width at the intensity position in the center between the intensities (that is, the peak width at the position where half the intensity of the peak intensity at 270° exists based on the minimum intensity).

(2) Molecular Periodicity Index The PI films obtained in the Examples and Comparative Examples were subjected to reflection method wide-angle X-ray diffraction measurement under the following conditions.・Device name: (Co., Ltd.) X-ray diffraction device RINT-2000 manufactured by Rigaku ・X-ray source: Cu-Kα line ・Tube voltage: 40kV ・Tube current: 150mA ・Divergence slit: 1° ・Scattering slit: 1°・Light-receiving slit: 0.15mm ・Longitudinal divergence limiting slit: 10mm ・Measurement range: 2θ ₁ =5~30° ・Measurement step: 0.02° ・Scanning speed: 0.5°/min ・Sample holder: (share) ) Aluminum sample plate (bottomless) made by Rigaku ・Detector: (Co., Ltd.) Scintillation counter made by Rigaku

Specifically, the film was cut into 3 cm in the MD direction and 2.5 cm in the TD direction to obtain a measurement sample 1b. Next, as shown in Figure 3, the ND direction of the film becomes parallel to the normal direction of the surface of the sample holder 6, that is, parallel to the direction perpendicular to the surface, and when the sample holder 6 is installed in the X-ray device , the measurement sample 1b is attached to the sample holder 6 so that the line 7 connecting the detection positions of the X-ray source 2b and the detector 3b becomes parallel to the MD direction of the film. Next, while maintaining the line 7 parallel to the MD direction, the reflection measurement of the film surface is performed in the range of 2θ ₁ =5~30° to obtain the diffraction profile A of the film. Furthermore, the film was cut into 2.5 cm in the MD direction and 3 cm in the TD direction to obtain a measurement sample 1b. Next, as shown in Figure 3, the ND direction of the film becomes parallel to the normal direction of the surface of the sample holder 6, that is, parallel to the direction perpendicular to the surface, and when the sample holder 6 is installed in the X-ray device , the measurement sample 1b is attached to the sample holder 6 so that the line 7 connecting the detection positions of the X-ray source 2b and the detector 3b becomes parallel to the TD direction of the film. Next, while maintaining the line 7 parallel to the TD direction, the reflection measurement of the film surface is performed in the range of 2θ ₁ =5~30° to obtain the diffraction profile B of the film. Each diffraction profile was blank corrected by subtracting the background. The average value of the blank-corrected diffraction profile A and the diffraction profile B is determined as the diffraction intensity profile of the film. From the diffraction intensity profile of the film, the maximum value of the diffraction intensity in the range of 2θ ₁ =15.5~16.5° is determined as I (16°), and the minimum value of the diffraction intensity in the range of 2θ ₁ =20~30° is determined is I (min), substitute it into Equation 2 to obtain the molecular periodicity index.

(3) In-plane anisotropy index A, B The PI films obtained in the Examples and Comparative Examples were subjected to wide-angle X-ray diffraction measurement using the transmission method under the following conditions. ・Device name: (Co., Ltd.) Small-angle/wide-angle X-ray scattering/diffraction device Nanoviwer manufactured by Rigaku Co., Ltd. ・Detector: Pilatus 100k ・X-ray source: Cu-Kα line ・Camera length: 70mm ・Exposure time: 10 minutes ・Voltage: 40kV ・Current: 20mA ・Beam diameter: 0.25mm

Specifically, four films were stacked in the ND direction so that the MD direction was consistent. The stacked films were cut with a trimming knife so that the width in the MD direction became 2 cm and the width in the TD direction became 2 cm, and a test piece for measurement was obtained. Next, as shown in FIG. 5 , the test piece 1 c for measurement is set in the X-ray device so that the irradiation direction of the X-ray becomes parallel to the ND direction of the film. Then, X-rays are incident on the measurement test piece 1 c from the X-ray source 2 c, and a two-dimensional diffraction image is obtained by the detector 3 c. The obtained two-dimensional diffraction image was corrected using the air blank of the two-dimensional diffraction image obtained without installing the test piece 1c for measurement. Furthermore, from the two-dimensional diffraction image, the azimuth angle section 0° and 180° correspond to the MD direction of the measurement test piece 1c, and the azimuth angle section 90° and 270° correspond to the TD direction of the measurement test piece 1c. 2θ ₂ =16° azimuth angle profile. The diffraction intensity at each azimuth angle uses the average value of the diffraction intensity in the range of 2θ ₂ =15.5~16.5°. In the obtained azimuth angle profile (β ₁ =0~360°), find the diffraction intensity at 0° and 180°, set the average value as I (MD), and find the diffraction intensity at 90° and 270° , let its average value be I (TD). In addition, in the azimuth angle profile (β ₁ =0~360°) obtained above, the maximum value of the diffraction intensity in the range of 0~360° is defined as I (MAX), and the minimum value of the diffraction intensity is defined as I(MIN). Finally, by substituting these equations 3 and 4, the in-plane anisotropy index A and the in-plane anisotropy index B are obtained.

<Measurement of weight average molecular weight Mw and number average molecular weight Mn> The polystyrene-equivalent Mw and Mn of the PI resin precursor obtained during the synthesis were measured using GPC. GPC measurement was performed under the following conditions. (1) Pretreatment method The sample was diluted with DMF and filtered through a 0.45 μm membrane filter as the measurement solution. (2)Measurement conditions Pipe string: Connect 2 TSKgel SuperAWM-H (inner diameter 6.0mm, length 150mm) Eluent: DMF (add 10mmol/L lithium bromide, add 30mmol/L phosphoric acid) Flow: 0.6mL/min Detector: RI detector Tube string temperature: 40℃ Injection volume: 20μL Molecular Weight Standard: Standard Polystyrene

<Measurement of Coefficient of Linear Thermal Expansion (CTE)> The CTE of the PI films obtained in the Examples and Comparative Examples was measured using TMA under the following conditions, and the CTE at 50°C to 100°C was calculated. Device: (share) Hitachi Advanced Technology Co., Ltd. TMA/SS7100 Load: 50.0mN Temperature program: from 20°C to 130°C at a rate of 5°C/minute Test piece: rectangular parallelepiped with length 40mm, width 5mm, and thickness 30μm (in addition, the thickness varies depending on the film used)

<Evaluation of Dielectric Loss Index E> The dielectric loss index E of the PI films obtained in the Examples and Comparative Examples was calculated by the following formula. Df: dielectric loss tangent Dk: relative dielectric coefficient

(Measurement of Df and Dk) A measurement sample of 50 mm × 50 mm was cut out from the PI film obtained in the Example and Comparative Example, and Df and Dk were measured under the following conditions. Humidify the sample at 25°C/55%RH for 24 hours before measuring. Device: Compact USB vector network analyzer manufactured by Anritsu Co., Ltd. (Product name: MS46122B) (Stock) AET cavity resonator (TE mode 10GHz type) Measuring frequency: 10GHz Measuring atmosphere: 23℃/50%RH

＜Evaluation of bending resistance＞ The bending resistance of the PI films obtained in Examples 3, 6 and 8 was evaluated by measuring the number of bends of the films under the following conditions. Use a dumbbell cutter to cut the film into short sticks with a length of 100 mm and a width of 10 mm. The cut film was placed on an MIT folding fatigue testing machine (MIT-DA manufactured by Toyo Seiki Seisakusho Co., Ltd.) that complies with ASTM specification D2176-16, and the test speed was 175cpm, the bending angle was 135°, the load was 750g, and the Under the condition of bending clamp R=1.0mm, bend the film alternately in both forward and reverse directions, and measure the number of bends until it breaks. The greater the number of bends, the better the bending resistance. The number of bending times of the PI films obtained in Examples 3, 6 and 8 were 240,000 times, 160,000 times and 20,000 times respectively.

Table 1 shows the measurement and evaluation results of the PI films obtained in the Examples and Comparative Examples.

As shown in Table 1, it was confirmed that the PI films obtained in Examples 1 to 8 had lower Df and lower dielectric loss index E than Comparative Examples 1 and 2. Therefore, the PI film of the present invention can be suitably used in metal-clad laminates such as CCL with small transmission loss that can cope with high-frequency bands.

1a, 1b, 1c: Test piece for measurement 2a, 2b, 2c: X-ray source 3a, 3b, 3c: Detector 4: Based on the minimum intensity in the range of azimuth angle 180 to 360°, it exists at 270° The position of half the intensity of the wave peak intensity 5: The width of the wave peak at the position 4 6: Sample holder 7: The line connecting the detection positions of 2b and 3b 8: 2θ ₁ = Diffraction intensity in the range of 15.5~16.5° The maximum value 9: 2θ ₁ = The minimum value of the diffraction intensity of 20°~30° 10: The diffraction intensity of the azimuth angle 0° 11: The diffraction intensity of the azimuth angle 90° 12: The diffraction intensity of the azimuth angle 180° 13: Minimum value in the range of azimuth angle 0~360° 14: Diffraction intensity at azimuth angle 270° 15: Maximum value in the range of azimuth angle 0~360° 16: Diffraction intensity at azimuth angle 360°

[Fig. 1] Fig. 1 is a schematic diagram for explaining a method of determining an in-plane alignment index by transmission X-ray diffraction measurement. [Fig. 2] Fig. 2 is a diagram showing an azimuthal cross-section of the polyimide-based film of Example 4 measured by transmission X-ray diffraction. [Fig. 3] Fig. 3 is a schematic diagram for explaining the method of determining the molecular periodicity index by reflection X-ray diffraction measurement. [Fig. 4] Fig. 4 is a diagram showing the diffraction intensity profile of the polyimide-based film of Example 4 measured by reflection X-ray diffraction. [Fig. 5] Fig. 5 is a schematic diagram for explaining the method of determining the in-plane anisotropy index by X-ray diffraction measurement using the retrotransmission method. [Fig. 6] Fig. 6 is a diagram showing an azimuthal cross-section of the polyimide-based film of Example 4 measured by transmission X-ray diffraction.

Claims (20)

A polyimide-based film, which contains a polyimide-based resin containing a structural unit (A) derived from tetracarboxylic anhydride and a structural unit (B) derived from a diamine, and has an in-plane alignment defined in Formula 1 The index is above 58, [In Formula 1, FWHM represents the azimuth angle section of 2θ=16° obtained by the two-dimensional diffraction image analysis of the transmission X-ray diffraction measurement measured by incident X-rays parallel to the TD direction of the film. Corresponding to the half-width of the wave peak appearing at the azimuth angle of the ND direction of the aforementioned film]. For example, the polyimide film of claim 1, wherein the molecular periodicity index shown in Formula 2 is above 7.0, [In Formula 2, I (16°) represents the maximum value of the diffraction intensity at 2θ ₁ =15.5~16.5° in the diffraction intensity profile obtained by the reflection X-ray diffraction measurement, and I (min) represents the diffraction intensity profile obtained by the reflection method In the diffraction intensity profile obtained by X-ray diffraction measurement, 2θ ₁ = the minimum value of the diffraction intensity between 20 and 30°]. For example, the polyimide-based film of claim 1 or 2, wherein the in-plane anisotropy index A defined in Formula 3 is not less than 0.8 and not more than 1.2, and the in-plane anisotropy index B defined in Formula 4 is greater than 1.1, [In Formulas 3 and 4, in the azimuth angle section of 2θ ₂ =16° obtained by the two-dimensional diffraction image analysis of the transmission X-ray diffraction measurement measured by incident X-rays parallel to the ND direction of the film , I (MD) represents the diffraction intensity corresponding to the MD direction of the aforementioned film, I (TD) represents the diffraction intensity corresponding to the TD direction, I (MAX) represents the maximum value of the diffraction intensity, and I (MIN) represents the diffraction intensity. minimum value]. The polyimide film according to any one of claims 1 to 3, wherein the structural unit (A) includes a structural unit (A1) derived from a tetracarboxylic anhydride containing an ester bond. The polyimide film according to any one of claims 1 to 4, wherein the structural unit (A) includes a structural unit (A2) derived from tetracarboxylic anhydride containing a biphenyl skeleton. Such as the polyimide film of claim 5, wherein the aforementioned structural unit (A) satisfies the relationship of formula (X): (Content of structural units derived from tetracarboxylic anhydride other than the aforementioned structural unit (A1) and the aforementioned structural unit (A2))/(the total amount of the aforementioned structural unit (A1) and the aforementioned structural unit (A2)) <1.1　 (X ). The polyimide film according to any one of claims 4 to 6, wherein the aforementioned structural unit (A1) is a structural unit (a1) derived from the tetracarboxylic anhydride represented by formula (a1): [In formula (a1), Z represents a divalent organic group, R ^a1 is independent of each other and represents a halogen atom, or an alkyl group, alkoxy group, aryl group or aryloxy group that may have a halogen atom, and s is independent of each other and represents 0 ~an integer of 3]. The polyimide film according to any one of claims 5 to 7, wherein the aforementioned structural unit (A2) is a structural unit (a2) derived from the tetracarboxylic anhydride represented by formula (a2): [In formula (a2), R ^a2 are independent of each other and represent a halogen atom, or an alkyl group, alkoxy group, aryl group or aryloxy group that may have a halogen atom, and t is independent of each other and represents an integer of 0 to 3]. The polyimide film according to any one of claims 1 to 8, wherein the structural unit (B) includes a structural unit (B1) derived from a diamine containing a biphenyl skeleton. The polyimide film of claim 9, wherein the aforementioned structural unit (B1) is a structural unit (b1) derived from the diamine represented by formula (b1): [In the formula (b1), R ^b1 are independent of each other and represent a halogen atom, or an alkyl group, an alkoxy group, an aryl group or an aryloxy group which may have a halogen atom, and p represents an integer from 0 to 4]. For example, the polyimide film of claim 9 or 10, wherein the content of the aforementioned structural unit (B1) exceeds 30 mol% relative to the total amount of the aforementioned structural unit (B). The polyimide film according to any one of claims 1 to 11, wherein the aforementioned structural unit (B) includes a structural unit (b2) derived from the diamine represented by formula (b2): [In formula (b2), R ^b2 are independent of each other and represent a halogen atom, or an alkyl group, alkoxy group, aryl group or aryloxy group that may have a halogen atom. The hydrogen atoms contained in R ^b2 are independent of each other and may be a halogen atom. Substitution, W is independent of each other and represents -O-, -CH ₂ -, -CH ₂ -CH ₂ -, -CH(CH ₃ )-, -C(CH ₃ ) ₂ -, -C(CF ₃ ) ₂ -, -COO-, -OOC-, -SO ₂ -, -S-, -CO- or -N(R ^c )-, R ^c represents a hydrogen atom, a monovalent hydrocarbon group with 1 to 12 carbon atoms that can be substituted by a halogen atom , m represents an integer from 0 to 4, q is independent of each other and represents an integer from 0 to 4]. For example, the polyimide film of claim 12, wherein in the aforementioned structural unit (b2), m is 3, and W are independent of each other and represent -O- or -C(CH ₃ ) ₂ -. For example, the dielectric loss tangent of the polyimide-based film in any one of claims 1 to 13 at 10 GHz does not reach 0.004. The polyimide film according to any one of claims 1 to 14, wherein the storage modulus of the polyimide resin at 280°C does not reach 3×10 ⁸ Pa. The polyimide film according to any one of claims 1 to 15, wherein the glass transition temperature of the polyimide resin is 200 to 290°C. For example, the polyimide film according to any one of claims 1 to 16 has a thickness of 5 to 100 μm. A laminated film including a metal foil layer on one or both sides of the polyimide film according to any one of claims 1 to 17. A flexible printed circuit substrate comprising the polyimide film according to any one of claims 1 to 17. A method for manufacturing a polyimide film according to any one of claims 1 to 17, which includes: The step of coating a polyimide resin precursor solution containing structural units derived from tetracarboxylic anhydride and structural units derived from diamine on a substrate, and The step of imidizing the polyimide resin precursor through heat treatment at 200°C or more and 500°C or less.