Films and laminates

Abstract

To provide a film that can suppress distortion of metal wiring when bonded to it, and a laminate using the above film. [Solution] A film having a dielectric loss tangent of 0.005 or less, and the elastic modulus of at least one surface at 160°C being smaller than the elastic modulus of the interior at 160°C, and a laminate using the above film.

Description

[Technical Field]

[0001] This disclosure relates to films and laminates. [Background technology]

[0002] In recent years, the frequencies used in communication equipment have tended to become extremely high. To suppress transmission loss in the high-frequency band, it is required to lower the relative permittivity and dielectric loss tangent of the insulating materials used in circuit boards. Traditionally, polyimides have been widely used as insulating materials for circuit boards, but liquid crystal polymers, which have high heat resistance, low water absorption, and low loss in the high-frequency range, are attracting attention.

[0003] Conventional liquid crystal polymer films include, for example, a liquid crystal polyester film containing at least a liquid crystal polyester, wherein when the first degree of orientation is defined as the degree of orientation in a first direction parallel to the main surface of the liquid crystal polyester film, and the second degree of orientation is defined as the degree of orientation in a second direction parallel to the main surface and perpendicular to the first direction, the ratio of the first degree of orientation to the second degree of orientation, i.e., the first degree of orientation / second degree of orientation, is 0.95 or more and 1.04 or less, and the third degree of orientation of the liquid crystal polyester, measured by wide-angle X-ray scattering in a direction parallel to the main surface, is 60.0% or more.

[0004] Furthermore, as an example of a conventional laminated film, Patent Document 2 describes a method for manufacturing a releaseable laminated film comprising an A layer containing a cellulose ester and a B layer containing a solution-forming resin different from the cellulose ester, wherein the adhesion between the A layer and the B layer is 5 N / cm or less. The method is characterized by simultaneously or sequentially casting a dope A for forming the A layer, comprising at least the cellulose ester and a solvent, and a dope B for forming the B layer, comprising at least a solution-forming resin different from the cellulose ester and a solvent, onto a casting support to laminate the dope A and dope B, and then peeling the laminate of dope A and dope B from the casting support and drying it.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0006] One problem to be solved by an embodiment of the present invention is to provide a film capable of suppressing distortion of a metal wiring when adhered to the metal wiring. Another problem to be solved by another embodiment of the present invention is to provide a laminate using the above film.

Means for Solving the Problems

[0007] Means for solving the above problems include the following aspects. <1> A film having a dielectric loss tangent of 0.005 or less and an elastic modulus at 160°C on at least one surface being smaller than the elastic modulus at 160°C inside. <2> The film according to <1>, wherein the loss tangent at 160°C on the above surface is 0.03 or more. <3> The film according to <1> or <2>, wherein the elastic modulus at 160°C inside is 0.5 GPa or more. <4> A film having a dielectric loss tangent of 0.005 or less and an elastic modulus at 300°C on at least one surface being smaller than the elastic modulus at 300°C inside. <5> The film according to <4>, wherein the loss tangent at 300°C on the above surface is 0.1 or more. <6> The film according to <4> or <5>, wherein the elastic modulus at 300°C inside is 0.1 GPa or more. <7>The film according to any one of <1> to <6>, having a linear expansion coefficient of -20 ppm / K to 50 ppm / K. <8>The film according to any one of <1> to <7>, containing a filler. <9>The film according to <8>, having a higher number density of the filler inside than on the surface. <10>The film according to any one of <1> to <9>, containing at least one polymer selected from the group consisting of a liquid crystal polymer, a fluorine-based polymer, a polymer of a compound having a cyclic aliphatic hydrocarbon group and an ethylenically unsaturated bond, a polyphenylene ether, and an aromatic polyether ketone. <11>The film according to <10>, wherein the liquid crystal polymer has a structural unit represented by any one of Formula (1) to Formula (3). Formula (1) -O-Ar 1 -CO- Formula (2) -CO-Ar 2 -CO- Formula (3) -X-Ar 3 -Y- In Formulas (1) to (3), Ar 1 represents a phenylene group, a naphthylene group or a biphenylylene group, Ar 2 and Ar 3 each independently represents a phenylene group, a naphthylene group, a biphenylylene group or a group represented by the following Formula (4), X and Y each independently represents an oxygen atom or an imino group, and the hydrogen atoms in Ar 1 ~Ar 3 may each independently be substituted with a halogen atom, an alkyl group or an aryl group. Formula (4) -Ar 4 -Z-Ar 5 - In Formula (4), Ar 4 and Ar 5 each independently represents a phenylene group or a naphthylene group, and Z represents an oxygen atom, a sulfur atom, a carbonyl group, a sulfonyl group or an alkylene group. <12>The film having a dielectric tangent of 0.010 or less and an elastic modulus at 160°C of at least one surface being smaller than the elastic modulus at 160°C inside. <13> A film having a dielectric loss tangent of 0.010 or less, and where the modulus of elasticity at 300°C of at least one surface is less than the modulus of elasticity at 300°C of the interior. <14> The material comprises layer A and layer B provided on at least one surface of layer A, wherein the elastic modulus of the surface of layer B at 160°C is smaller than the elastic modulus of the interior at 160°C. <1> ~ <3> , and <7> ~ <12> The film described in any one of the following. <15> The material comprises layer A and layer B provided on at least one surface of layer A, wherein the elastic modulus of the surface of layer B at 300°C is smaller than the elastic modulus of the interior at 300°C. <4> ~ <11> or <13> The film described in any one of the items. <16> It further has layer C, and the above layers B, A and C are in this order. <14> or <15> The film described above. <17> <14> or <15> A laminate comprising the film described above and a metal layer disposed on the surface of the film on the layer A side. <18> <14> ~ <16> A laminate having a film according to any one of the above and a metal layer disposed on the surface of the film on the layer B side. <19> <16> A laminate comprising the film described above, a metal layer disposed on the layer B side of the film, and a metal layer disposed on the layer C side of the film. <20> The metal layer positioned on the side of layer B is a copper layer positioned on the surface of layer B, and the peel strength between layer B and the copper layer is 0.5 kN / m or more. <18> or <19> The laminate described above. <21> The metal layer located on the side of layer C is a copper layer located on the surface of layer C, and the peel strength between layer C and the copper layer located on the side of layer C is 0.5 kN / m or more. <19> The laminate described above. <22> The thickness of layer B is greater than the thickness of the metal layer. <17> ~ <21> A laminate described in any one of the following. [Effects of the Invention]

[0008] According to one embodiment of the present invention, it is possible to provide a film that can suppress distortion of metal wiring when bonded to it. Furthermore, according to another embodiment of the present invention, a laminate using the above-mentioned film can be provided. [Modes for carrying out the invention]

[0009] The contents of this disclosure are described in detail below. The descriptions of the constituent elements described below may be based on representative embodiments of this disclosure, but this disclosure is not limited to such embodiments. In this specification, the "~" symbol indicating a numerical range is used to mean that the numbers before and after it are included as the lower and upper limits, respectively. In numerical ranges described in stages within this disclosure, the upper or lower limit of one numerical range may be replaced with the upper or lower limit of another numerical range described in stages. Furthermore, in numerical ranges described within this disclosure, the upper or lower limit of that range may be replaced with the values ​​shown in the examples. Furthermore, in the notation of groups (atomic groups) in this specification, the notation that does not specify whether they are substituted or unsubstituted includes both those with and without substituents. For example, "alkyl group" includes not only alkyl groups without substituents (unsubstituted alkyl groups) but also alkyl groups with substituents (substituted alkyl groups). In this specification, "(meth)acrylic" is a term used to encompass both acrylic and methacrylic, and "(meth)acryloyl" is a term used to encompass both acryloyl and methacryloyl. Furthermore, the term "process" as used in this specification includes not only independent processes, but also processes that cannot be clearly distinguished from other processes, as long as their intended purpose is achieved. Furthermore, in this disclosure, "mass%" and "weight%" are synonymous, and "parts of mass" and "parts of weight" are synonymous. Furthermore, in this disclosure, a combination of two or more preferred embodiments is a more preferred embodiment. Furthermore, unless otherwise specified, the weight-average molecular weight (Mw) and number-average molecular weight (Mn) in this disclosure are molecular weights obtained by detecting the solvent PFP (pentafluorophenol) / chloroform = 1 / 2 (mass ratio) using a gel permeation chromatography (GPC) analyzer with a TSKgel SuperHM-H (product name of Tosoh Corporation) column, and converting them using a differential refractometer, with polystyrene as the standard substance.

[0010] (film) In a first embodiment of the film according to this disclosure, the dielectric loss tangent is 0.005 or less, and the modulus of elasticity at 160°C of at least one surface is smaller than the modulus of elasticity at 160°C of the interior. Furthermore, in the second embodiment of the film according to this disclosure, the dielectric loss tangent is 0.005 or less, and the elastic modulus at 300°C of at least one surface is smaller than the elastic modulus at 300°C of the interior. Furthermore, in the third embodiment of the film according to this disclosure, the dielectric loss tangent is 0.010 or less, and the modulus of elasticity at 160°C of at least one surface is smaller than the modulus of elasticity at 160°C of the interior. Furthermore, in the fourth embodiment of the film according to this disclosure, the dielectric loss tangent is 0.010 or less, and the elastic modulus at 300°C of at least one surface is smaller than the elastic modulus at 300°C of the interior.

[0011] Here, the surface of a polymer film refers to the outer surface of the polymer film (the surface in contact with air or the substrate). In this disclosure, if the film thickness is 30 μm or less, the "surface" of the film refers to the area from the outermost surface of the film to a position corresponding to 10% of the film thickness. If the film thickness is greater than 30 μm, the "surface" refers to the area from the outermost surface of the film to a position 3 μm away in the thickness direction.

[0012] In this disclosure, "inside" of the film means, if the film thickness is 30 μm or less, the region from the center in the thickness direction of the film to a position corresponding to ±5% of the film thickness. If the film thickness is greater than 30 μm, "inside" means the region from the center in the thickness direction of the film to a position ±1.5 μm away in the thickness direction.

[0013] In this specification, unless otherwise specified, the terms "film relating to this disclosure" or "film" refer to both the first embodiment and the second embodiment described above.

[0014] Conventional films, such as the film described in Patent Document 1, often have a large coefficient of thermal expansion. It has been found that when the film described in Patent Document 1 is bonded to metal wiring, distortion of the metal wiring occurs. As a result of diligent research by the inventors, it has been found that by adopting the above configuration, it is possible to provide a film that can suppress distortion of metal wiring when bonded to it. The detailed mechanism by which the above effects are achieved is unknown, but it is speculated to be as follows. In the film according to this disclosure, the elastic modulus at 160°C of at least one surface is smaller than the elastic modulus at 160°C of the interior, so when bonded to metal wiring, the film can deform to follow the shape of the metal wiring. Furthermore, in the film according to this disclosure, the elastic modulus at 300°C of at least one surface is smaller than the elastic modulus at 300°C of the interior, so when bonded to metal wiring, the film can deform to follow the shape of the metal wiring. As a result, it is believed that distortion of the metal wiring is suppressed.

[0015] The dielectric loss tangent of the film according to this disclosure is 0.010 or less, preferably 0.005 or less, and more preferably greater than 0 and 0.003 or less, from the viewpoint of suppressing distortion of the metal wiring when bonded to the metal wiring.

[0016] The dielectric loss tangent in this disclosure shall be measured by the following method. The dielectric loss tangent is measured using the resonant perturbation method at a frequency of 10 GHz. A 10 GHz cavity resonator (CP531, Kanto Electronics Applied Development Co., Ltd.) is connected to a network analyzer (E8363B, Agilent Technology). A sample (width: 2.0 mm x length: 80 mm) is inserted into the cavity resonator, and the dielectric loss tangent is measured from the change in resonant frequency before and after insertion over 96 hours under conditions of 25°C and 60% RH. When measuring each layer, you may use a razor or similar tool to scrape off unnecessary layers and prepare an evaluation sample containing only the desired layer. Alternatively, if it is difficult to extract a single film due to the thinness of the layer, you may scrape off the layer to be measured with a razor or similar tool and use the resulting powdered sample. In the first embodiment of the film according to this disclosure, the modulus of elasticity at 160°C of at least one surface is smaller than the modulus of elasticity at 160°C of the interior. Furthermore, in the second embodiment of the film according to this disclosure, the modulus of elasticity at 300°C of at least one surface is smaller than the modulus of elasticity at 300°C of the interior. Preferably, the film according to this disclosure has an elastic modulus at 160°C of at least one surface that is smaller than the elastic modulus at 160°C of the interior, and an elastic modulus at 300°C of at least one surface that is smaller than the elastic modulus at 300°C of the interior.

[0017] The difference between the elastic modulus of at least one surface at 160°C and the elastic modulus of the interior at 160°C is preferably 0.1 GPa or more, more preferably 0.8 GPa or more, and even more preferably 1.5 GPa or more. The upper limit of the above difference is not particularly limited, and is, for example, 3.0 GPa. The difference between the elastic modulus of at least one surface at 300°C and the elastic modulus of the interior at 300°C is preferably 0.1 GPa or more, more preferably 0.5 GPa or more, and even more preferably 0.8 GPa or more. The upper limit of the above difference is not particularly limited, and is, for example, 2.0 GPa.

[0018] The film according to this disclosure preferably has a loss loss tangent of 0.03 or higher at 160°C on at least one surface, more preferably 0.1 or higher, and even more preferably 0.2 or higher. The upper limit of the loss loss tangent of the surface at 160°C is not particularly limited, and is, for example, 1.0. Furthermore, the loss loss tangent at 300°C of at least one surface of the film according to this disclosure is preferably 0.1 or higher, more preferably 0.3 or higher, and even more preferably 1.0 or higher. The upper limit of the loss loss tangent at 300°C of the surface is not particularly limited and is, for example, 10.

[0019] The film according to this disclosure preferably has an internal elastic modulus of 0.5 GPa or higher, more preferably 1.0 GPa or higher, even more preferably 1.5 GPa or higher, and particularly preferably 2.0 GPa or higher. The upper limit of the internal elastic modulus at 160°C is not particularly limited, and is, for example, 3.0 GPa. Furthermore, the film relating to this disclosure preferably has an internal elastic modulus of 0.1 GPa or higher, more preferably 0.5 GPa or higher, even more preferably 0.7 GPa or higher, and particularly preferably 1.0 GPa or higher. The upper limit of the internal elastic modulus at 300°C is not particularly limited, and is, for example, 2.0 GPa.

[0020] The film according to this disclosure preferably has an elastic modulus at 160°C of 3.0 GPa or less, more preferably 1.0 GPa or less, and even more preferably 0.7 GPa or less on at least one surface. The lower limit of the elastic modulus at 160°C of the surface is not particularly limited, and is, for example, 0.01 GPa.

[0021] Furthermore, the film relating to this disclosure preferably has an elastic modulus at 300°C of 2.0 GPa or less, more preferably 0.7 GPa or less, and even more preferably 0.3 GPa or less on at least one surface. The lower limit of the elastic modulus at 300°C of the surface is not particularly limited, and is, for example, 0.001 GPa.

[0022] Because the elastic modulus of the film relating to this disclosure is within the above range at each temperature, when bonded to a metal wiring, the film can deform to follow the shape of the metal wiring, and as a result, distortion of the metal wiring is suppressed. Therefore, each temperature of the elastic modulus can be used as an indicator of the processing temperature in the manufacturing process when bonding the film relating to this disclosure to a metal (for example, metal foil and metal wiring).

[0023] From the viewpoint of suppressing distortion of the metal wiring, it is preferable that the elastic modulus of one side in contact with the metal layer is within the above range.

[0024] The modulus of elasticity and loss tangent in this disclosure shall be measured by the following method. The film is embedded in UV (ultraviolet-curable) resin, and a sample for cross-sectional evaluation is prepared by cutting with a microtome. Subsequently, a scanning probe microscope (SPA400, manufactured by SII Nanotechnology Co., Ltd.) is used to observe the sample in VE-AFM mode, and the storage modulus of the surface and interior, as well as the loss tangent (loss modulus / storage modulus), are calculated. In this disclosure, the modulus of elasticity refers to the "storage modulus of elasticity." The elastic modulus at 160°C refers to the elastic modulus measured when the sample temperature has been adjusted to 160°C. The elastic modulus at 300°C refers to the elastic modulus measured when the sample temperature has been adjusted to 300°C.

[0025] The coefficient of linear expansion of the film according to this disclosure is preferably -20 ppm / K to 50 ppm / K, more preferably -10 ppm / K to 40 ppm / K, even more preferably 0 ppm / K to 35 ppm / K, particularly preferably 10 ppm / K to 30 ppm / K, and particularly more preferably 15 ppm / K to 25 ppm / K, from the viewpoint of suppressing distortion of the metal wiring when bonded to the metal wiring.

[0026] The coefficient of thermal expansion in this disclosure shall be measured by the following method. Using a thermomechanical analyzer (TMA), a tensile load of 1g is applied to both ends of a 5mm wide, 20mm long film, and the temperature is increased from 25°C to 200°C at a rate of 5°C / min. Then, it is cooled to 30°C at a rate of 20°C / min, and the temperature is increased again at a rate of 5°C / min. The coefficient of linear expansion is calculated from the slope of the TMA curve between 30°C and 150°C.

[0027] Furthermore, if it is difficult to measure the coefficient of thermal expansion using the method described above, the following method shall be used for measurement. The film is cut with a microtome to prepare section samples, which are then placed in an optical microscope equipped with a heating stage system (HS82, Mettler-Toledo). The temperature is then increased from 25°C to 200°C at a rate of 5°C / min. After that, the film is cooled to 30°C at a rate of 20°C / min, and then heated again at a rate of 5°C / min. The film thickness at 30°C (ts30) and 150°C (ts150) is evaluated, and the coefficient of linear expansion of the film is calculated by dividing the dimensional change by the temperature change ((ts150-ts30) / (150-30)).

[0028] The film according to this disclosure preferably contains a polymer having a dielectric loss tangent of 0.01 or less. The dielectric loss tangent of the polymer is, for example, 0.010 or less, preferably 0.008 or less, more preferably 0.0075 or less, even more preferably 0.006 or less, and particularly preferably 0.005 or less. Furthermore, from the viewpoint of the dielectric loss tangent of the polymer film and adhesion to the metal (e.g., the metal layer), the dielectric loss tangent of the polymer is preferably 0.004 or less, more preferably 0.0035 or less, and particularly preferably 0.003 or less. The lower limit of the dielectric loss tangent of the polymer is not particularly limited and is, for example, greater than 0.

[0029] The dielectric loss tangent of a polymer in this disclosure shall be determined by identifying or isolating the chemical structure of the polymer and using a sample of the polymer in powder form, in accordance with the above-described method for measuring the dielectric loss tangent.

[0030] Examples of polymers with a dielectric loss tangent of 0.005 or less include liquid crystal polymers, fluorine-based polymers, polymers of compounds having a cyclic aliphatic hydrocarbon group and a group having an ethylenically unsaturated bond, polyether ether ketones, polyolefins, polyamides, polyesters, polyphenylene sulfide, polyether ketones, polycarbonates, polyethersulfones, polyphenylene ethers and their modified products, and thermoplastic resins such as polyetherimides; elastomers such as copolymers of glycidyl methacrylate and polyethylene; and thermosetting resins such as phenolic resins, epoxy resins, polyimide resins, and cyanate resins. Among these, from the viewpoint of further reducing the dielectric loss tangent of the film, the polymer is preferably at least one polymer selected from the group consisting of liquid crystal polymers, fluorine-based polymers, polymers of compounds having a cyclic aliphatic hydrocarbon group and a group having an ethylenically unsaturated bond, polyphenylene ethers, and aromatic polyether ketones, and more preferably at least one polymer selected from the group consisting of liquid crystal polymers and fluorine-based polymers. From the viewpoint of film-forming properties and mechanical strength, the polymer is preferably a liquid crystal polymer, and from the viewpoint of dielectric loss tangent, a fluorine-based polymer is preferred.

[0031] -Liquid crystal polymer- In this disclosure, the type of liquid crystal polymer is not particularly limited, and known liquid crystal polymers can be used. Furthermore, the liquid crystal polymer may be a thermotropic liquid crystal polymer that exhibits liquid crystallinity in a molten state, or a lyotropic liquid crystal polymer that exhibits liquid crystallinity in a solution state. If the liquid crystal polymer is a thermotropic liquid crystal polymer, it is preferable that it is a liquid crystal polymer that melts at a temperature of 450°C or lower. Examples of liquid crystal polymers include liquid crystal polyester, liquid crystal polyesteramide (in which amide bonds are introduced into liquid crystal polyester), liquid crystal polyester ether (in which ether bonds are introduced into liquid crystal polyester), and liquid crystal polyester carbonate (in which carbonate bonds are introduced into liquid crystal polyester). Furthermore, from the viewpoint of liquid crystalline properties, the liquid crystal polymer is preferably a polymer having an aromatic ring, and more preferably an aromatic polyester or an aromatic polyesteramide. Furthermore, the liquid crystal polymer may be a polymer in which an aromatic polyester or aromatic polyesteramide is further modified by introducing isocyanate-derived bonds such as imide bonds, carbodiimide bonds, or isocyanurate bonds. Furthermore, it is preferable that the liquid crystal polymer is a fully aromatic liquid crystal polymer made using only aromatic compounds as raw material monomers.

[0032] Examples of liquid crystal polymers include the following: 1) A compound obtained by polycondensing (i) an aromatic hydroxycarboxylic acid, (ii) an aromatic dicarboxylic acid, and (iii) at least one compound selected from the group consisting of aromatic diols, aromatic hydroxyamines, and aromatic diamines. 2) A compound formed by polycondensation of multiple types of aromatic hydroxycarboxylic acids. 3) A compound obtained by polycondensing (i) an aromatic dicarboxylic acid with (ii) at least one compound selected from the group consisting of aromatic diols, aromatic hydroxyamines, and aromatic diamines. 4) A material obtained by polycondensing (i) a polyester such as polyethylene terephthalate and (ii) an aromatic hydroxycarboxylic acid. Here, aromatic hydroxycarboxylic acid, aromatic dicarboxylic acid, aromatic diol, aromatic hydroxyamine, and aromatic diamine may each be independently replaced with polycondensable derivatives.

[0033] For example, aromatic hydroxycarboxylic acids and aromatic dicarboxylic acids can be replaced with aromatic hydroxycarboxylic acid esters and aromatic dicarboxylic acid esters by converting the carboxyl group to an alkoxycarbonyl group or an aryloxycarbonyl group. By converting the carboxyl group to a haloformyl group, aromatic hydroxycarboxylic acids and aromatic dicarboxylic acids can be replaced with aromatic hydroxycarboxylic acid halogens and aromatic dicarboxylic acid halogens. By converting the carboxyl group to an acyloxycarbonyl group, aromatic hydroxycarboxylic acids and aromatic dicarboxylic acids can be replaced with aromatic hydroxycarboxylic acid anhydrides and aromatic dicarboxylic acid anhydrides. Examples of polymerizable derivatives of compounds having a hydroxyl group, such as aromatic hydroxycarboxylic acids, aromatic diols, and aromatic hydroxyamines, include those obtained by acyling the hydroxyl group to convert it into an acyloxy group (acylated compounds). For example, by acyling a hydroxyl group to convert it into an acyloxy group, aromatic hydroxycarboxylic acids, aromatic diols, and aromatic hydroxyamines can be replaced with acylated compounds, respectively. Examples of polymerizable derivatives of compounds having an amino group, such as aromatic hydroxyamines and aromatic diamines, include those obtained by acyling the amino group to convert it into an acylamino group (acylated compounds). For example, by acylating an amino group to convert it into an acylamino group, aromatic hydroxyamines and aromatic diamines can be replaced with acylated products, respectively.

[0034] From the viewpoint of liquid crystalline properties, liquid crystal polymers preferably have a constituent unit represented by any of the following formulas (1) to (3), more preferably a repeating constituent unit represented by formula (1), and particularly preferably a constituent unit represented by formula (1), formula (2), and formula (3). Hereinafter, the constituent unit represented by formula (1), etc., will also be referred to as "unit (1)," etc. Equation (1) -O-Ar 1 -CO- Equation (2) -CO-Ar 2 -CO- Equation (3) -X-Ar 3 -Y- In formulas (1) to (3), Ar 1 represents a phenylene group, a naphthylene group, or a biphenylylene group, and Ar 2 and Ar 3 Each of the following independently represents a phenylene group, a naphthylene group, a biphenylylene group, or a group represented by formula (4) below, and X and Y each independently represent an oxygen atom or an imino group, and Ar 1 ~Ar 3 Each hydrogen atom in may be independently substituted with a halogen atom, an alkyl group, or an aryl group. Equation (4) -Ar 4 -Z-Ar 5 - In formula (4), Ar 4 and Ar 5 Each of the symbols independently represents either a phenylene group or a naphthylene group, and Z represents either an oxygen atom, a sulfur atom, a carbonyl group, a sulfonyl group, or an alkylene group.

[0035] Examples of the halogen atoms mentioned above include fluorine, chlorine, bromine, and iodine atoms. Examples of the alkyl groups mentioned above include methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, s-butyl, t-butyl, n-hexyl, 2-ethylhexyl, n-octyl, and n-decyl groups. The number of carbon atoms in the alkyl group is preferably 1 to 10. Examples of the above-mentioned aryl groups include the phenyl group, o-tolyl group, m-tolyl group, p-tolyl group, 1-naphthyl group, and 2-naphthyl group. The number of carbon atoms in the aryl group is preferably 6 to 20. Ar 1 ~Ar 3 When the hydrogen atom in is substituted with a halogen atom, an alkyl group, or an aryl group, the number of substituents is preferably two or less, and more preferably one, independently of each other.

[0036] Examples of the alkylene groups mentioned above include the methylene group, 1,1-ethanediyl group, 1-methyl-1,1-ethanediyl group, 1,1-butanediyl group, and 2-ethyl-1,1-hexanediyl group. The number of carbon atoms in the alkylene group is preferably 1 to 10.

[0037] Unit (1) is a constituent unit derived from an aromatic hydroxycarboxylic acid. As a unit (1), Ar 1 A form in which the group is a p-phenylene group (a constituent unit derived from p-hydroxyammonium acid), Ar 1 A preferred embodiment is one in which the group is a 2,6-naphthylene group (a constituent unit derived from 6-hydroxy-2-naphthoic acid), or a preferred embodiment is one in which the group is a 4,4'-biphenylylene group (a constituent unit derived from 4'-hydroxy-4-biphenylcarboxylic acid).

[0038] Unit (2) is a constituent unit derived from an aromatic dicarboxylic acid. As a unit (2), Ar 2 A form in which the group is a p-phenylene group (a constituent unit derived from terephthalic acid), Ar 2 A form in which is an m-phenylene group (a constituent unit derived from isophthalic acid), Ar 2 A mode in which is a 2,6-naphthylene group (a constituent unit derived from 2,6-naphthalenedicarboxylic acid), or Ar 2 An embodiment in which is a diphenyl ether-4,4'-diyl group (a constituent unit derived from diphenyl ether-4,4'-dicarboxylic acid) is preferred.

[0039] Unit (3) is a constituent unit derived from an aromatic diol, aromatic hydroxylamine, or aromatic diamine. The unit (3) is Ar 3 Embodiments in which is a p-phenylene group (constituent unit derived from hydroquinone, p-aminophenol, or p-phenylenediamine), Ar 3 A form in which is an m-phenylene group (a constituent unit derived from isophthalic acid), or Ar 3An embodiment in which is a 4,4'-biphenylylene group (a constituent unit derived from 4,4'-dihydroxybiphenyl, 4-amino-4'-hydroxybiphenyl, or 4,4'-diaminobiphenyl) is preferred.

[0040] The content of unit (1) is preferably 30 mol% or more, more preferably 30 mol% to 80 mol%, even more preferably 30 mol% to 60 mol%, and particularly preferably 30 mol% to 40 mol%, relative to the total amount of all constituent units. The content of unit (2) is preferably 35 mol% or less, more preferably 10 mol% to 35 mol%, even more preferably 20 mol% to 35 mol%, and particularly preferably 30 mol% to 35 mol%, relative to the total amount of all constituent units. The content of unit (3) is preferably 35 mol% or less, more preferably 10 mol% to 35 mol%, even more preferably 20 mol% to 35 mol%, and particularly preferably 30 mol% to 35 mol%, relative to the total amount of all constituent units. The higher the content of unit (1), the easier it is to improve heat resistance, strength, and rigidity, but if there is too much, the solubility in the solvent tends to decrease. The total amount of all constituent units is the sum of the amount of substance (moles) of each constituent unit. The amount of substance of each constituent unit is calculated by dividing the mass of each constituent unit that makes up the liquid crystal polymer by the formula weight of that constituent unit.

[0041] The ratio of the content of unit (2) to the content of unit (3), when expressed as [content of unit (2)] / [content of unit (3)] (moles / moles), is preferably 0.9 / 1 to 1 / 0.9, more preferably 0.95 / 1 to 1 / 0.95, and even more preferably 0.98 / 1 to 1 / 0.98.

[0042] Furthermore, the liquid crystal polymer may have two or more independent units (1) to (3). In addition, the liquid crystal polymer may have other constituent units other than units (1) to (3). The content of other constituent units is preferably 10 mol% or less, more preferably 5 mol% or less, relative to the total amount of all constituent units.

[0043] Since liquid crystal polymers have excellent solubility in solvents, it is preferable that they have a unit (3) in which at least one of X and Y is an imino group, that is, they have at least one of a constituent unit derived from an aromatic hydroxylamine and a constituent unit derived from an aromatic diamine, and it is more preferable that they have only a unit (3) in which at least one of X and Y is an imino group.

[0044] Liquid crystal polymers are preferably produced by melt polymerization of raw material monomers corresponding to the constituent units of the liquid crystal polymer. Melt polymerization may be carried out in the presence of a catalyst. Examples of catalysts include metal compounds such as magnesium acetate, stannous acetate, tetrabutyl titanate, lead acetate, sodium acetate, potassium acetate, and antimony trioxide; and nitrogen-containing heterocyclic compounds such as 4-(dimethylamino)pyridine and 1-methylimidazole. Nitrogen-containing heterocyclic compounds are preferred as catalysts. If necessary, melt polymerization may be further carried out by solid-phase polymerization.

[0045] The flow initiation temperature of the liquid crystal polymer is preferably 180°C or higher, more preferably 200°C or higher, and even more preferably 250°C or higher. Furthermore, the flow initiation temperature is preferably 350°C or lower, more preferably 330°C or lower, and even more preferably 310°C or lower. When the flow initiation temperature of the liquid crystal polymer is within the above range, it exhibits excellent solubility, heat resistance, strength, and rigidity, and the viscosity of the solution is appropriate.

[0046] The flow start temperature, also called the flow temperature or fluid temperature, is measured using a capillary rheometer at 9.8 MPa (100 kg / cm²). 2 This temperature, when a liquid crystal polymer is melted under a load and heated at a rate of 4°C / min, and extruded from a nozzle with an inner diameter of 1 mm and a length of 10 mm, exhibits a viscosity of 4,800 Pa·s (48,000 poise), and serves as an indicator of the molecular weight of the liquid crystal polymer (see Naoyuki Koide (ed.), "Liquid Crystal Polymers - Synthesis, Molding, and Applications," CMC Corporation, June 5, 1987, p. 95).

[0047] Furthermore, the weight-average molecular weight of the liquid crystal polymer is preferably 1,000,000 or less, more preferably 3,000 to 300,000, even more preferably 5,000 to 100,000, and particularly preferably 5,000 to 30,000. When the weight-average molecular weight of the liquid crystal polymer is within the above range, the heat-treated film exhibits excellent thermal conductivity, heat resistance, strength, and rigidity in the thickness direction.

[0048] -Fluorine-based polymers- In this disclosure, the type of fluorinated polymer is not particularly limited, and known fluorinated polymers can be used.

[0049] Furthermore, examples of fluorinated polymers include homopolymers and copolymers containing constituent units derived from fluorinated α-olefin monomers, that is, α-olefin monomers containing at least one fluorine atom. Also, examples of fluorinated polymers include copolymers containing constituent units derived from fluorinated α-olefin monomers and constituent units derived from non-fluorinated ethylenically unsaturated monomers that are reactive with fluorinated α-olefin monomers.

[0050] Examples of fluorinated α-olefin monomers include CF2=CF2, CHF=CF2, CH2=CF2, CHCl=CHF, CClF=CF2, CCl2=CF2, CClF=CClF, CHF=CCl2, CH2=CClF, CCl2=CClF, CF3CF=CF2, CF3CF=CHF, CF3CH=CF2, CF3CH=CH2, CHF2CH=CHF, CF3CF=CF2, and perfluoro(alkyl) vinyl ethers (e.g., perfluoromethyl vinyl ether, perfluoropropyl vinyl ether, and perfluorooctyl vinyl ether). In particular, the fluorinated α-olefin monomer is preferably at least one monomer selected from the group consisting of tetrafluoroethylene (CF2=CF2), chlorotrifluoroethylene (CClF=CF2), (perfluorobutyl)ethylene, vinylidene fluoride (CH2=CF2), and hexafluoropropylene (CF2=CFCF3). Examples of non-fluorinated ethylenically unsaturated monomers include ethylene, propylene, butene, and ethylenically unsaturated aromatic monomers (e.g., styrene and α-methylstyrene). Fluorinated α-olefin monomers may be used individually or in combination of two or more. Furthermore, non-fluorinated ethylenically unsaturated monomers may be used individually or in combination of two or more.

[0051] Examples of fluorinated polymers include polychlorotrifluoroethylene (PCTFE), poly(chlorotrifluoroethylene-propylene), poly(ethylene-tetrafluoroethylene) (ETFE), poly(ethylene-chlorotrifluoroethylene) (ECTFE), poly(hexafluoropropylene), poly(tetrafluoroethylene) (PTFE), poly(tetrafluoroethylene-ethylene-propylene), poly(tetrafluoroethylene-hexafluoropropylene) (FEP), poly(tetrafluoroethylene-propylene) (FEPM), poly(tetrafluoroethylene-perfluoropropylene vinyl ether), poly(tetrafluoroethylene-perfluoroalkyl vinyl ether) (PFA) (for example, poly(tetrafluoroethylene-perfluoropropyl vinyl ether)), polyvinyl fluoride (PVF), polyvinylidene fluoride (PVDF), poly(vinylidene fluoride-chlorotrifluoroethylene), perfluoropolyether, perfluorosulfonic acid, and perfluoropolyoxetane.

[0052] Fluorine-based polymers may have constituent units derived from fluorinated ethylene or fluorinated propylene. Fluorine-based polymers may be used individually or in combination of two or more types.

[0053] The fluorine-based polymer is preferably FEP, PFA, ETFE, or PTFE. FEP is available from DuPont under the brand name TEFLON® FEP, or from Daikin Industries, Ltd. under the brand name NEOFLON FEP. PFA is available from Daikin Industries, Ltd. under the brand name NEOFLON PFA, from DuPont under the brand name TEFLON® PFA, or from Solvay Solexis under the brand name HYFLON PFA.

[0054] The fluorine-based polymer more preferably contains PTFE. The PTFE may be a PTFE homopolymer, a partially modified PTFE homopolymer, or a combination containing one or both of these. The partially modified PTFE homopolymer preferably contains less than 1% by mass of constituent units derived from comonomers other than tetrafluoroethylene, based on the total mass of the polymer.

[0055] The fluorinated polymer may be a crosslinkable fluoropolymer having crosslinkable groups. Crosslinkable fluoropolymers can be crosslinked by conventionally known crosslinking methods. One typical crosslinkable fluoropolymer is a fluoropolymer having (meth)acryloyloxy. For example, a crosslinkable fluoropolymer has the formula: H2C = CR'COO - (CH2) n -R-(CH2) n -OOCR'=CH2 It can be expressed as follows: In the formula, R is an oligomer chain containing constituent units derived from a fluorinated α-olefin monomer, R' is H or -CH3, and n is 1 to 4. R may also be a fluorinated oligomer chain containing constituent units derived from tetrafluoroethylene.

[0056] To initiate a radical crosslinking reaction via (meth)acryloyloxy groups on a fluorinated polymer, a crosslinked fluoropolymer network structure can be formed by exposing a fluoropolymer having (meth)acryloyloxy groups to a free radical source. While there are no particular limitations on the free radical source, photoradical polymerization initiators or organic peroxides are preferred. Suitable photoradical polymerization initiators and organic peroxides are well known in the art. Crosslinkable fluoropolymers are commercially available, such as Viton B from DuPont.

[0057] - A polymer of a compound having a cyclic aliphatic hydrocarbon group and a group having an ethylenically unsaturated bond - Polymers of compounds having a cyclic aliphatic hydrocarbon group and a group having an ethylenically unsaturated bond include, for example, thermoplastic resins having constituent units derived from cyclic olefin monomers such as norbornene or polycyclic norbornene monomers. Polymers of compounds having a cyclic aliphatic hydrocarbon group and a group having an ethylenically unsaturated bond may be ring-opened polymers of the above-mentioned cyclic olefins or hydrogenated ring-opened copolymers using two or more cyclic olefins, or they may be addition polymers of cyclic olefins with aromatic compounds having an ethylenically unsaturated bond, such as chain olefins or vinyl groups. Furthermore, polar groups may be introduced into polymers of compounds having a cyclic aliphatic hydrocarbon group and a group having an ethylenically unsaturated bond. Polymers of compounds having a cyclic aliphatic hydrocarbon group and a group having an ethylenically unsaturated bond may be used individually or in combination of two or more.

[0058] The ring structure of the cyclic aliphatic hydrocarbon group may be a monoring, a fused ring formed by the fusion of two or more rings, or a bridging ring. Examples of ring structures of cyclic aliphatic hydrocarbon groups include cyclopentane rings, cyclohexane rings, cyclooctane rings, isophorone rings, norbornane rings, and dicyclopentane rings. There are no particular limitations on the compounds having a cyclic aliphatic hydrocarbon group and a group having an ethylenically unsaturated bond. Examples include (meth)acrylate compounds having a cyclic aliphatic hydrocarbon group, (meth)acrylamide compounds having a cyclic aliphatic hydrocarbon group, and vinyl compounds having a cyclic aliphatic hydrocarbon group. Among these, (meth)acrylate compounds having a cyclic aliphatic hydrocarbon group are preferred. Furthermore, the compounds having a cyclic aliphatic hydrocarbon group and a group having an ethylenically unsaturated bond may be monofunctional ethylenically unsaturated compounds or polyfunctional ethylenically unsaturated compounds. In a compound having a cyclic aliphatic hydrocarbon group and a group having an ethylenically unsaturated bond, the number of cyclic aliphatic hydrocarbon groups may be one or more, or it may be two or more. A polymer of a compound having a cyclic aliphatic hydrocarbon group and a group having an ethylenically unsaturated bond may be any polymer obtained by polymerizing a compound having at least one cyclic aliphatic hydrocarbon group and a group having an ethylenically unsaturated bond, and may be a polymer of a compound having two or more cyclic aliphatic hydrocarbon groups and groups having an ethylenically unsaturated bond, or it may be a copolymer with another ethylenically unsaturated compound that does not have a cyclic aliphatic hydrocarbon group. Furthermore, the polymer of a compound having a cyclic aliphatic hydrocarbon group and a group having an ethylenically unsaturated bond is preferably a cycloolefin polymer.

[0059] -Polyphenylene ether- The weight-average molecular weight (Mw) of polyphenylene ether is preferably 500 to 5,000, and more preferably 500 to 3,000, from the viewpoint of heat resistance and film-forming properties, when thermal curing is performed after film formation. When thermal curing is not performed, the Mw is not particularly limited, but is preferably 3,000 to 100,000, and more preferably 5,000 to 50,000.

[0060] From the viewpoint of dielectric loss tangent and heat resistance, the average number of phenolic hydroxyl groups at the molecular ends of polyphenylene ethers per molecule (number of terminal hydroxyl groups) is preferably 1 to 5, and more preferably 1.5 to 3. The number of terminal hydroxyl groups in a polyphenylene ether can be determined, for example, from the product specifications of the polyphenylene ether. Alternatively, the number of terminal hydroxyl groups can be expressed as the average number of phenolic hydroxyl groups per molecule of all polyphenylene ether present in one mole of polyphenylene ether. Polyphenylene ethers may be used individually or in combination of two or more types.

[0061] Examples of polyphenylene ethers include polyphenylene ethers comprising 2,6-dimethylphenol and at least one of a difunctional phenol and a trifunctional phenol, and poly(2,6-dimethyl-1,4-phenylene oxide). More specifically, the polyphenylene ether is preferably a compound having a structure represented by formula (PPE).

[0062] [ka]

[0063] In formula (PPE), X represents an alkylene group or single bond having 1 to 3 carbon atoms, m represents an integer from 0 to 20, n represents an integer from 0 to 20, and the sum of m and n represents an integer from 1 to 30. Examples of the alkylene group in X above include a dimethylmethylene group.

[0064] -Aromatic polyether ketone- The aromatic polyether ketone is not particularly limited, and any known aromatic polyether ketone can be used. The aromatic polyether ketone is preferably a polyether ether ketone. Polyether ether ketones are a type of aromatic polyether ketone, and are polymers in which ether bonds, ether bonds, and carbonyl bonds are arranged in that order. Preferably, each bond is linked by a divalent aromatic group. Aromatic polyether ketones may be used individually or in combination of two or more.

[0065] Examples of aromatic polyetherketones include polyether ether ketone (PEEK) having the chemical structure represented by formula (P1) below, polyether ketone (PEK) having the chemical structure represented by formula (P2) below, polyether ketone ketone (PEKK) having the chemical structure represented by formula (P3) below, polyether ether ketone ketone (PEEKK) having the chemical structure represented by formula (P4) below, and polyether ketone ether ketone ketone (PEKEKK) having the chemical structure represented by formula (P5) below.

[0066] [ka]

[0067] In formulas (P1) to (P5), n is preferably 10 or greater, and more preferably 20 or greater, from the viewpoint of mechanical properties. On the other hand, in terms of easily producing aromatic polyether ketones, n is preferably 5,000 or less, and more preferably 1,000 or less. That is, n is preferably 10 to 5,000, and more preferably 20 to 1,000.

[0068] The polymer contained in the film relating to this disclosure is preferably a polymer soluble in a specific organic solvent (hereinafter also referred to as "soluble polymer"). Specifically, the soluble polymer in this disclosure is a polymer that dissolves at 25°C in 0.1 g or more of 100 g of at least one solvent selected from the group consisting of N-methylpyrrolidone, N-ethylpyrrolidone, dichloromethane, dichloroethane, chloroform, N,N-dimethylacetamide, γ-butyrolactone, dimethylformamide, ethylene glycol monobutyl ether, and ethylene glycol monoethyl ether.

[0069] The film relating to this disclosure may contain only one polymer or two or more polymers. From the viewpoint of the dielectric loss tangent of the film and adhesion to the metal, the polymer content is preferably 20% to 99% by mass, more preferably 30% to 98% by mass, even more preferably 40% to 97% by mass, and particularly preferably 50% to 95% by mass, based on the total mass of the film.

[0070] The film relating to this disclosure preferably contains a filler.

[0071] -Filler- The filler may be particulate or fibrous, and may be inorganic or organic.

[0072] In the film relating to this disclosure, the number density of the filler is preferably greater in the interior than on the surface, from the viewpoint of suppressing distortion of the metal wiring when it is bonded to the metal wiring.

[0073] The number density of fillers shall be measured by the following method. The film is cut with a microtome to prepare cross-sectional samples. The cross-sectional samples are observed with a scanning electron microscope (approximately 100x to 300x magnification). The total observation area is 0.5 mm². 2 Observe at least three locations to achieve the above result, 1 mm 2 The average number of fillers per unit is calculated.

[0074] Furthermore, if the film according to this disclosure includes a polymer and a filler, it is preferable that the film surface contains a filler having an elastic modulus lower than that of the polymer, and that the interior of the film contains a filler having an elastic modulus higher than that of the polymer.

[0075] As the inorganic filler, known inorganic fillers can be used. Examples of inorganic filler materials include BN, Al2O3, AlN, TiO2, SiO2, barium titanate, strontium titanate, aluminum hydroxide, calcium carbonate, and materials containing two or more of these. In particular, among the inorganic fillers, metal oxide particles or fibers are preferred from the viewpoint of thermal expansion coefficient and adhesion to metal, silica particles, titania particles, or glass fibers are more preferred, and silica particles or glass fibers are especially preferred. The average particle size of the inorganic filler is preferably 5 nm to 20 μm, more preferably 10 nm to 10 μm, even more preferably 20 nm to 1 μm, and particularly preferably 25 nm to 500 nm, from the viewpoint of thermal expansion coefficient and adhesion to metal. If the particles or fibers are flattened, the length in the short side direction is indicated.

[0076] As the organic filler, known organic fillers can be used. Examples of organic filler materials include polyethylene, polystyrene, urea-formaldehyde filler, polyester, cellulose, acrylic resin, fluororesin, cured epoxy resin, crosslinked benzoguanamine resin, crosslinked acrylic resin, liquid crystal polymer, and materials containing two or more of these. Furthermore, the organic filler may be in the form of fibers such as nanofibers, or it may be hollow resin particles. In particular, the organic filler is preferably a nanofiber of fluororesin particles, polyester resin particles, polyethylene particles, liquid crystal polymer particles, or cellulose resin, from the viewpoint of thermal expansion coefficient and adhesion to metal, and more preferably a polytetrafluoroethylene particle, polyethylene particle, or liquid crystal polymer particle. Here, liquid crystal polymer particles can be produced, for example, by polymerizing a liquid crystal polymer and then grinding it into a powder using a pulverizer or the like. It is preferable that the average particle size of the liquid crystal polymer particles is smaller than the thickness of each layer.

[0077] The average particle size of the organic filler is preferably 5 nm to 20 μm, more preferably 10 nm to 1 μm, even more preferably 20 nm to 500 nm, and particularly preferably 25 nm to 90 nm, from the viewpoint of thermal expansion coefficient and adhesion to metal.

[0078] The film relating to this disclosure may have a single-layer structure or a multi-layer structure. When the film has a single-layer structure, a preferred configuration is one in which the composition changes from the inside to the surface, and the elastic modulus changes.

[0079] The film according to this disclosure has a layer A and a layer B provided on at least one surface of layer A, and it is preferable that the elastic modulus of the surface of layer B at 160°C is smaller than the elastic modulus of the interior at 160°C. Furthermore, the film according to this disclosure has a layer A and a layer B provided on at least one surface of layer A, and it is preferable that the elastic modulus of the surface of layer B at 300°C is smaller than the elastic modulus of the interior at 300°C.

[0080] Layer B is preferably the surface layer (outermost layer). The elastic modulus of layer B at 160°C is preferably smaller than that of layer A at 160°C. Furthermore, the elastic modulus of layer B at 300°C is preferably smaller than that of layer A at 300°C.

[0081] In this disclosure, the "surface" of each layer refers to the region from the outermost surface of the layer to a position corresponding to 10% of the layer's thickness, if the layer's thickness is 30 μm or less. If the layer's thickness is greater than 30 μm, the "surface" refers to the region from the outermost surface of the layer to a position 3 μm away in the thickness direction. In this disclosure, the "interior" of a layer refers to the region from the center in the thickness direction of the layer to a position corresponding to ±5% of the layer's thickness, if the layer's thickness is 30 μm or less. If the layer's thickness is greater than 30 μm, the "interior" refers to the region from the center in the thickness direction of the layer to a position ±1.5 μm away in the thickness direction.

[0082] <Layer A> Layer A preferably contains a liquid crystal polymer. Layer A may contain only one type of liquid crystal polymer or two or more types. From the viewpoint of thermal expansion coefficient and adhesion to metal, the liquid crystal polymer content in layer A is preferably 20% to 100% by volume, more preferably 20% to 90% by volume, even more preferably 30% to 80% by volume, and particularly preferably 40% to 70% by volume, relative to the total volume of layer A.

[0083] From the viewpoint of making the elastic modulus of layer A greater than that of layer B, layer A preferably contains a filler, more preferably a filler with a melting point of 200°C or higher, and even more preferably an inorganic filler. The average particle size of the filler is preferably about 20% to about 40% of the thickness of layer A, for example, a filler with a particle size of 25%, 30%, or 35% of the thickness of layer A may be selected.

[0084] Layer A may contain only one type of filler, or it may contain two or more types. From the viewpoint of thermal expansion coefficient and adhesion to the metal, the filler content in layer A is preferably 5% to 80% by volume, more preferably 10% to 70% by volume, even more preferably 20% to 70% by volume, and particularly preferably 30% to 60% by volume, relative to the total volume of layer A.

[0085] Layer A may contain other additives besides the liquid crystal polymer and filler. Other known additives can be used. Specifically, examples include leveling agents, defoaming agents, antioxidants, UV absorbers, flame retardants, and colorants.

[0086] Furthermore, layer A may contain resins other than liquid crystal polymers as other additives. Examples of resins other than liquid crystal polymers include polypropylene, polyamide, polyesters other than liquid crystal polyester, polyphenylene sulfide, polyether ketone, polycarbonate, polyethersulfone, polyphenylene ether and its modified products, polyetherimide and other thermoplastic resins other than liquid crystal polyester; elastomers such as copolymers of glycidyl methacrylate and polyethylene; and thermosetting resins such as phenolic resins, epoxy resins, polyimide resins, and cyanate resins.

[0087] The total content of other additives in layer A is preferably 25 parts by mass or less, more preferably 10 parts by mass or less, and even more preferably 5 parts by mass or less, based on the content of 100 parts by mass of liquid crystal polymer.

[0088] The average thickness of layer A is not particularly limited, but from the viewpoint of thermal expansion coefficient and adhesion to the metal, it is preferably 5 μm to 90 μm, more preferably 10 μm to 70 μm, and particularly preferably 15 μm to 50 μm.

[0089] The method for measuring the average thickness of each layer in the film relating to this disclosure is as follows: The film is cut with a microtome, and the cross-section is observed with an optical microscope to evaluate the thickness of each layer. Three or more cross-sectional samples are cut, and the thickness is measured at three or more points in each cross-section. The average of these measurements is taken as the average thickness.

[0090] The dielectric loss tangent of layer A is preferably 0.005 or less, and more preferably greater than 0 and 0.003 or less.

[0091] <Layer B> Layer B preferably contains a liquid crystal polymer. The preferred embodiment of the liquid crystal polymer used in layer B is the same as the preferred embodiment of the liquid crystal polymer used in layer A, except as described later. The liquid crystal polymer contained in layer B may be the same as or different from the liquid crystal polymer contained in layer A. From the viewpoint of making the elastic modulus of layer B smaller than that of layer A, it is preferable that layer B contains a liquid crystal polymer with a lower elastic modulus than the liquid crystal polymer contained in layer A.

[0092] From the viewpoint of thermal expansion coefficient and adhesion to the metal, it is preferable that the liquid crystal polymer content in layer B is greater than the liquid crystal polymer content in layer A. Furthermore, from the viewpoint of thermal expansion coefficient and adhesion to metal, the liquid crystal polymer content in layer B is preferably 50% to 100% by volume, more preferably 80% to 100% by volume, even more preferably 90% to 100% by volume, and particularly preferably 95% to 100% by volume, relative to the total volume of layer B.

[0093] Layer B preferably contains a filler, more preferably a filler with a melting point of less than 300°C, and even more preferably an organic filler, from the viewpoint of making the elastic modulus of layer B smaller than that of layer A.

[0094] Layer B may contain only one type of filler, or it may contain two or more types. The filler content in layer B is preferably 5% to 80% by volume, more preferably 10% to 70% by volume, even more preferably 20% to 70% by volume, and particularly preferably 30% to 60% by volume, based on the total volume of layer B, from the viewpoint of thermal expansion coefficient and adhesion to the metal.

[0095] Layer B may contain other additives besides the liquid crystal polymer and filler. Preferred embodiments of other additives used in layer B are the same as preferred embodiments of other additives used in layer A.

[0096] From the viewpoint of thermal expansion coefficient and adhesion to the metal, the average thickness of layer B is preferably thinner than the average thickness of layer A. Average thickness T of layer A A and the average thickness T of layer B B T is the ratio of A / T B The value of is preferably greater than 1, more preferably between 2 and 100, even more preferably between 2.5 and 20, and particularly preferably between 3 and 10, from the viewpoint of thermal expansion coefficient and adhesion to metal. Furthermore, the average thickness of layer B can be arbitrarily set according to the thickness of the metal to be bonded to layer B, but from the viewpoint of adhesion with the metal, it is preferable that it be thicker than the thickness of the metal. Specifically, the average thickness of layer B is preferably 0.1 μm to 20 μm, more preferably 0.5 μm to 15 μm, even more preferably 1 μm to 10 μm, and particularly preferably 3 μm to 8 μm.

[0097] The dielectric loss tangent of layer B is preferably 0.01 or less, and more preferably greater than 0 and 0.005 or less. The dielectric loss tangent of layer B can be evaluated by scraping off layers other than layer B from the film. In some cases, layer B can be scraped off from the film, and the resulting powdered sample can be evaluated.

[0098] Preferred embodiments of layers A and B include the following embodiments (1) to (4), and combinations of any of (1) to (3) and (4). (1) An embodiment in which layer A contains a filler with a melting point of 200°C or higher (preferably an inorganic filler, more preferably an inorganic oxide filler, and particularly preferably silica particles). (2) Embodiments in which layer B contains a filler with a melting point of less than 300°C (preferably an organic filler, more preferably a polyolefin filler, and particularly preferably a polyethylene filler). (3) an embodiment in which layer A contains a filler with a melting point of 200°C or higher (preferably an inorganic filler, more preferably an inorganic oxide filler, particularly preferably silica particles), and layer B contains a filler with a melting point of less than 300°C (preferably an organic filler, more preferably a polyolefin filler, particularly preferably a polyethylene filler). (4) An embodiment in which layer B contains a liquid crystal polymer with a lower elastic modulus than the liquid crystal polymer contained in layer A.

[0099] The film according to this disclosure preferably further comprises a layer C in addition to the above layers A and B, from the viewpoint of thermal expansion coefficient and adhesion to metal, and more preferably comprises the above layers B, A and C in this order.

[0100] <Layer C> Layer C is preferably the surface layer (outermost layer), and more preferably the surface layer on the side to which the metal is attached. Furthermore, when the film according to this disclosure is used as a laminate having a metal layer (for example, a metal foil or metal wiring), it is preferable that layer C is placed between the metal layer and layer A. preferable. Layer C preferably contains a liquid crystal polymer from the viewpoint of thermal expansion coefficient and adhesion to the metal. The preferred embodiment of the liquid crystal polymer used in layer C is the same as the preferred embodiment of the liquid crystal polymer used in layer A, except as will be described later. The liquid crystal polymer contained in layer C may be the same as or different from the liquid crystal polymer contained in layer A or layer B, but it is preferable that it be the same as the liquid crystal polymer contained in layers A and B.

[0101] From the viewpoint of thermal expansion coefficient and adhesion to the metal, it is preferable that the liquid crystal polymer content in layer C is greater than the liquid crystal polymer content in layer A. Furthermore, from the viewpoint of thermal expansion coefficient and adhesion to metal, the liquid crystal polymer content in layer C is preferably 50% to 100% by volume, more preferably 80% to 100% by volume, even more preferably 90% to 100% by volume, and particularly preferably 95% to 100% by volume, relative to the total volume of layer C.

[0102] Layer C may contain fillers. The preferred embodiment of the filler used in layer C is the same as the preferred embodiment of the filler used in layer A, except as will be described later.

[0103] From the viewpoint of thermal expansion coefficient and adhesion to the metal, it is preferable that the filler content in layer C be less than the filler content in layer A. Furthermore, from the viewpoint of thermal expansion coefficient and adhesion to the metal, the filler content in layer C is preferably either no filler or greater than 0 volume% and 20 volume% or less of the total volume of layer C, more preferably no filler or greater than 0 volume% and 10 volume% or less of the total volume of layer C, even more preferably no filler or greater than 0 volume% and 5 volume% or less of the total volume of layer C, and particularly preferably no filler at all.

[0104] Layer C may contain additives other than liquid crystal polymers and fillers. Preferred embodiments of other additives used in layer C are the same as preferred embodiments of other additives used in layer A.

[0105] From the viewpoint of thermal expansion coefficient and adhesion to the metal, the average thickness of layer C is preferably thinner than the average thickness of layer A. Average thickness T of layer A A and the average thickness T of layer C C T is the ratio of A / T C The value of is preferably greater than 1, more preferably between 2 and 100, even more preferably between 2.5 and 20, and particularly preferably between 3 and 10, from the viewpoint of thermal expansion coefficient and adhesion to metal. Also, the average thickness T of layer C C and the average thickness T of layer B B T is the ratio of C / T B The value of is preferably 0.2 to 5, more preferably 0.5 to 2, and particularly preferably 0.8 to 1.2, from the viewpoint of thermal expansion coefficient and adhesion to metal. Furthermore, the average thickness of layer C is preferably 0.1 μm to 20 μm, more preferably 0.5 μm to 15 μm, even more preferably 1 μm to 10 μm, and particularly preferably 3 μm to 8 μm, from the viewpoint of thermal expansion coefficient and adhesion to the metal.

[0106] The dielectric loss tangent of layer C is preferably 0.005 or less, and more preferably greater than 0 and 0.003 or less. The dielectric loss tangent of layer C can be evaluated by scraping off layers other than layer C from the film. In some cases, layer C can be scraped off from the film, and the resulting powdered sample can be evaluated.

[0107] The average thickness of the film relating to this disclosure is preferably 6 μm to 500 μm, more preferably 6 μm to 100 μm, and particularly preferably 12 μm to 100 μm, from the viewpoint of strength and electrical properties (characteristic impedance) when laminated with a metal layer.

[0108] The average thickness of the film is measured at five arbitrary locations using an adhesive film thickness gauge, such as an electronic micrometer (product name "KG3001A", manufactured by Anritsu Corporation), and the average of these measurements is used.

[0109] <Film manufacturing method> (Film forming) The method for manufacturing the film relating to this disclosure is not particularly limited and may refer to known methods. Suitable methods for manufacturing the film according to this disclosure include, for example, casting, coating, and extrusion. Among these, casting is particularly preferred for relatively thin films, and co-extrusion is particularly preferred for thick films. Furthermore, if the film according to this disclosure has a multilayer structure, suitable methods include, for example, co-casting, multilayer coating, and co-extrusion. Among these, co-casting is particularly preferred. When manufacturing a multilayer structure in a film using the co-casting method and the multi-layer coating method, it is preferable to use a composition for forming layer A, a composition for forming layer B, a composition for forming layer C, etc., which are obtained by dissolving or dispersing the components of each layer in a solvent, when performing the co-casting method or the multi-layer coating method.

[0110] Examples of solvents include halogenated hydrocarbons such as dichloromethane, chloroform, 1,1-dichloroethane, 1,2-dichloroethane, 1,1,2,2-tetrachloroethane, 1-chlorobutane, chlorobenzene, and o-dichlorobenzene; halogenated phenols such as p-chlorophenol, pentachlorophenol, and pentafluorophenol; ethers such as diethyl ether, tetrahydrofuran, and 1,4-dioxane; ketones such as acetone and cyclohexanone; esters such as ethyl acetate and γ-butyrolactone; and ethylene carbonate. Examples include carbonates such as propyl carbonate; amines such as triethylamine; nitrogen-containing heterocyclic aromatic compounds such as pyridine; nitriles such as acetonitrile and succinonitrile; amides such as N,N-dimethylformamide, N,N-dimethylacetamide, and N-methylpyrrolidone; urea compounds such as tetramethylurea; nitro compounds such as nitromethane and nitrobenzene; sulfur compounds such as dimethyl sulfoxide and sulfolane; and phosphorus compounds such as hexamethylphosphate and tri-n-butyl phosphate. Two or more of these may be used.

[0111] As a solvent, it is preferable to include an aprotic compound, particularly an aprotic compound without halogen atoms, because it has low corrosiveness and is easy to handle. The proportion of the aprotic compound in the total solvent is preferably 50% to 100% by mass, more preferably 70% to 100% by mass, and particularly preferably 90% to 100% by mass. Furthermore, the above aprotic compound is preferably an amide such as N,N-dimethylformamide, N,N-dimethylacetamide, tetramethylurea, N-methylpyrrolidone, or an ester such as γ-butyrolactone, because it readily dissolves liquid crystal polymers, and more preferably N,N-dimethylformamide, N,N-dimethylacetamide, and N-methylpyrrolidone.

[0112] Furthermore, the solvent preferably contains a compound with a dipole moment of 3 to 5, as it readily dissolves the liquid crystal polymer. The proportion of the compound with a dipole moment of 3 to 5 in the total solvent is preferably 50% to 100% by mass, more preferably 70% to 100% by mass, and particularly preferably 90% to 100% by mass. It is preferable to use a compound with a dipole moment of 3 to 5 as the above-mentioned aprotic compound.

[0113] Furthermore, since the solvent is easily removed, it is preferable that it contains a compound whose boiling point at 1 atmosphere is 220°C or lower. The proportion of the compound with a boiling point at 1 atmosphere of 220°C or lower in the total solvent is preferably 50% to 100% by mass, more preferably 70% to 100% by mass, and particularly preferably 90% to 100% by mass. It is preferable to use a compound with a boiling point of 220°C or lower at 1 atmosphere as the above-mentioned aprotic compound.

[0114] Furthermore, when manufacturing the film according to this disclosure by the above-mentioned co-casting method, multi-layer coating method, and co-extrusion method, a support may be used. Examples of support materials include metal drums, metal bands, glass plates, resin films, and metal foils. Among these, the support material is preferably a metal drum, a metal band, or a resin film. Examples of resin films include polyimide (PI) film. Examples of commercially available resin films include U-Pyrex S and U-Pyrex R manufactured by Ube Industries, Ltd., Kapton manufactured by Toray DuPont, Ltd., and IF30, IF70, and LV300 manufactured by SKC Kolon PI. Furthermore, the support may have a surface treatment layer formed on its surface so that it can be easily peeled off. Examples of surface treatment layers include hard chrome plating and fluororesin. The average thickness of the support is not particularly limited, but is preferably 25 μm to 75 μm, and more preferably 50 μm to 75 μm.

[0115] Furthermore, there are no particular restrictions on the method for removing at least a portion of the solvent from the cast or coated film-like composition (coating), and known drying methods can be used.

[0116] (Stretching) The films according to this disclosure can be appropriately combined with stretching in order to control molecular orientation and adjust the coefficient of thermal expansion and mechanical properties. The stretching method is not particularly limited and known methods can be referred to, and may be carried out with a solvent or with a dry film. Stretching with a solvent may be carried out by gripping and stretching the film, or by utilizing auto-shrinkage due to drying without stretching. Stretching is particularly effective for improving elongation at break and tensile strength when film brittleness is reduced by the addition of inorganic fillers, etc.

[0117] (Heat treatment) The method for manufacturing the film according to this disclosure preferably includes a step of heat-treating (annealing) the film after it has been formed. The heat treatment temperature in the above heat treatment process is preferably 260°C to 370°C, more preferably 280°C to 360°C, and even more preferably 300°C to 350°C, from the viewpoint of dielectric loss tangent and peel strength. The heat treatment time is preferably 15 minutes to 10 hours, and even more preferably 30 minutes to 5 hours. Furthermore, the method for manufacturing the film according to this disclosure may include other known steps as necessary.

[0118] <Application> The film relating to this disclosure can be used for various applications, and in particular, the film relating to this disclosure can be suitably used as a film for electronic components such as printed wiring boards, and is suitably used for flexible printed circuit boards. Furthermore, the film relating to this disclosure can be suitably used as a film for metal bonding.

[0119] (Laminated structure) The laminate according to this disclosure may be any laminate in which the films according to this disclosure are laminated. Preferably, the laminate according to this disclosure has the films according to this disclosure and a metal layer disposed on the surface of the film on the layer A side, and more preferably the metal layer is a copper layer. Since the metal layer is disposed on the surface on the layer A side, layer B is the outermost layer in the laminate.

[0120] Furthermore, the laminate according to the present disclosure preferably comprises a film according to the present disclosure and a metal layer disposed on the surface of the film on the layer B side, and more preferably the metal layer is a copper layer. The metal layer positioned on the side of layer B is preferably a metal layer positioned on the surface of layer B. Furthermore, the laminate according to the present disclosure preferably comprises a film having layer B, layer A, and layer C in that order, a metal layer disposed on the layer B side of the film, and a metal layer disposed on the layer C side of the film, and more preferably all of the metal layers are copper layers. The metal layer positioned on the side of layer C is preferably a metal layer positioned on the surface of layer C, the metal layer positioned on the side of layer B is preferably a metal layer positioned on the surface of layer B, and the metal layer positioned on the side of layer C is more preferably a metal layer positioned on the surface of layer C.

[0121] Furthermore, the metal layer on the side of layer B and the metal layer on the side of layer C may be made of the same material, have the same thickness and shape, or they may be made of different materials, have different thicknesses and shapes. From the viewpoint of adjusting characteristic impedance, the metal layer on the side of layer B and the metal layer on the side of layer C may be made of different materials and have different thicknesses, and the metal layer may be laminated on only one side of layer B or layer C. Furthermore, from the viewpoint of adjusting characteristic impedance, a configuration in which a metal layer is laminated on one side of layer B or layer C, and another film (preferably another liquid crystal polymer film) is laminated on the other side is also preferred.

[0122] When the metal layer disposed on the surface of layer B is a copper layer disposed on the surface of layer B, the peel strength between layer B and the copper layer is preferably 0.5 kN / m or more, more preferably 0.7 kN / m or more, even more preferably 0.7 kN / m to 2.0 kN / m, and particularly preferably 0.9 kN / m to 1.5 kN / m. Furthermore, if the metal layer disposed on the surface of layer C is a copper layer disposed on the surface of layer C, the peel strength between layer C and the copper layer is preferably 0.5 kN / m or more, more preferably 0.7 kN / m or more, even more preferably 0.7 kN / m to 2.0 kN / m, and particularly preferably 0.9 kN / m to 1.5 kN / m.

[0123] In this disclosure, the peel strength between layer B or layer C of the film and the metal layer (e.g., copper layer) shall be measured by the following method. A 1.0 cm wide peel test specimen was prepared from a laminate of film and a metal layer. The film was fixed to a flat plate with double-sided adhesive tape, and the strength (kN / m) of peeling the metal layer from the film at a speed of 50 mm / min using the 180° method in accordance with JIS C 5016 (1994) was measured.

[0124] The metal layer is preferably a copper layer. The copper layer is preferably a rolled copper foil formed by a rolling method or an electrolytic copper foil formed by an electrolytic method, and from the viewpoint of flexibility, a rolled copper foil is more preferable.

[0125] The average thickness of the metal layer (preferably a copper layer) is not particularly limited, but is preferably 2 μm to 20 μm, more preferably 3 μm to 18 μm, and even more preferably 5 μm to 12 μm. The metal layer may be a carrier-attached metal layer formed peelably on a support (carrier). Known carriers can be used. The average thickness of the carrier is not particularly limited, but is preferably 10 μm to 100 μm, and more preferably 18 μm to 50 μm.

[0126] The thickness of layer B is preferably greater than the thickness of the metal layer (for example, the copper layer) from the viewpoint of suppressing distortion of the metal wiring when it is bonded to the metal wiring.

[0127] The metal layer in the laminate according to this disclosure may be a metal layer having a circuit pattern. It is also preferable to process the metal layer in the laminate according to this disclosure into a desired circuit pattern by etching, for example, to form a flexible printed circuit board. There are no particular restrictions on the etching method, and known etching methods can be used. [Examples]

[0128] The present disclosure will be further explained with reference to the following examples. The materials, amounts used, proportions, processing content, and processing procedures shown in the following examples may be modified as appropriate, as long as they do not deviate from the spirit of this disclosure. Therefore, the scope of this disclosure is not limited to the following specific examples.

[0129] <<Measurement Method>> [Dielectric Loss Tangent] The dielectric loss tangent was measured using the resonant perturbation method at a frequency of 10 GHz. A 10 GHz cavity resonator (Kanto Electronics Applied Development Co., Ltd. CP531) was connected to a network analyzer (Agilent Technology "E8363B"). A film sample (width: 2.0 mm x length: 80 mm) was inserted into the cavity resonator, and the dielectric loss tangent of the film was measured from the change in the resonant frequency before and after insertion over 96 hours under conditions of 25°C and 60% RH.

[0130] [Modulus of elasticity and loss tangent] The film was embedded in UV resin, and samples for cross-sectional evaluation were prepared by cutting with a microtome. Subsequently, observation was performed using a scanning probe microscope (SPA400, manufactured by SII Nanotechnology) in VE-AFM mode, and the storage modulus of the surface and interior, as well as the loss tangent (loss modulus / storage modulus), were calculated.

[0131] [Coefficient of thermal expansion] Using a thermomechanical analyzer (TMA), a tensile load of 1g was applied to both ends of a 5mm wide, 20mm long film. The film was heated from 25°C to 200°C at a rate of 5°C / min, then cooled to 30°C at a rate of 20°C / min, and then heated again at a rate of 5°C / min. The coefficient of thermal expansion (= linear expansion coefficient of the film) was calculated from the slope of the TMA curve between 30°C and 150°C.

[0132] [Peel strength] A 1.0 cm wide peel test specimen was prepared from a laminate of film and copper foil. The film was fixed to a flat plate with double-sided adhesive tape, and the strength (kN / m) of peeling the copper foil from the film at a speed of 50 mm / min using the 180° method in accordance with JIS C 5016 (1994) was measured. The peel strength between layer B of the film and the copper foil was evaluated by fixing the side opposite to layer B with double-sided adhesive tape. The peel strength between layer C of the film and the copper foil was evaluated by fixing the side opposite to layer C with double-sided adhesive tape.

[0133] <<Manufacturing Example>> <polymer> LC-A: Liquid crystal polymer prepared according to the manufacturing method described below.

[0134] -LCA Manufacturing- In a reactor equipped with a stirrer, torque meter, nitrogen gas inlet tube, thermometer, and reflux condenser, 940.9 g (5.0 mol) of 6-hydroxy-2-naphthoic acid, 377.9 g (2.5 mol) of 4-hydroxyacetaminophen, 415.3 g (2.5 mol) of isophthalic acid, and 867.8 g (8.4 mol) of acetic anhydride were added. After replacing the gas in the reactor with nitrogen gas, the temperature was raised from room temperature (23°C) to 140°C over 60 minutes while stirring under a nitrogen gas stream, and then refluxed at 140°C for 3 hours. Next, while distilling off the by-product acetic acid and unreacted acetic anhydride, the temperature was raised from 150°C to 300°C over 5 hours, and held at 300°C for 30 minutes. After that, the contents were removed from the reactor and cooled to room temperature. The obtained solid was pulverized to obtain powdered liquid crystal polyester (A1). The flow initiation temperature of this liquid crystal polyester (A1) was 193.3°C.

[0135] The liquid crystal polyester (A1) obtained above was heated in a nitrogen atmosphere from room temperature to 160°C over 2 hours and 20 minutes, then heated from 160°C to 180°C over 3 hours and 20 minutes, and held at 180°C for 5 hours to undergo solid-phase polymerization. After cooling, it was pulverized in a pulverizer to obtain powdered liquid crystal polyester (A2). The flow initiation temperature of this liquid crystal polyester (A2) was 220°C.

[0136] The liquid crystal polyester (A2) obtained above was heated in a nitrogen atmosphere from room temperature (23°C) to 180°C over 1 hour and 25 minutes, then heated from 180°C to 255°C over 6 hours and 40 minutes, and held at 255°C for 5 hours to undergo solid-phase polymerization. After cooling, powdered liquid crystal polyester (A) (LC-A) was obtained. The flow initiation temperature of liquid crystal polyester (B) was 302°C. Furthermore, the melting point of this liquid crystal polyester (A) was measured using a differential scanning calorimetry analyzer and found to be 311°C.

[0137] LC-B: Liquid crystal polymer prepared according to the manufacturing method described below.

[0138] -LCB Manufacturing- In a reactor equipped with a stirrer, torque meter, nitrogen gas inlet tube, thermometer, and reflux condenser, 940.9 g (5.0 mol) of 6-hydroxy-2-naphthoic acid, 377.9 g (2.5 mol) of 4-hydroxyacetaminophen, 415.3 g (2.5 mol) of isophthalic acid, and 867.8 g (8.4 mol) of acetic anhydride were added. After replacing the gas in the reactor with nitrogen gas, the temperature was raised from room temperature (23°C) to 143°C over 60 minutes while stirring under a nitrogen gas stream, and then refluxed at 143°C for 1 hour. Next, while distilling off the by-product acetic acid and unreacted acetic anhydride, the temperature was raised from 150°C to 300°C over 5 hours, and held at 300°C for 30 minutes. After that, the contents were removed from the reactor and cooled to room temperature. The obtained solid was pulverized to obtain powdered liquid crystal polyester (B1). The flow initiation temperature of this liquid crystal polyester (B1) was 191°C.

[0139] The liquid crystal polyester (B1) obtained above was heated in a nitrogen atmosphere from room temperature to 160°C over 2 hours and 20 minutes, then heated from 160°C to 180°C over 3 hours and 20 minutes, and held at 180°C for 5 hours to undergo solid-phase polymerization. After cooling, it was pulverized with a pulverizer to obtain powdered liquid crystal polyester (B2). The flow initiation temperature of this liquid crystal polyester (B2) was 220°C.

[0140] The liquid crystal polyester (B2) obtained above was heated in a nitrogen atmosphere from room temperature (23°C) to 180°C over 1 hour and 20 minutes, then heated from 180°C to 240°C over 5 hours, and held at 240°C for 5 hours to undergo solid-phase polymerization. After cooling, powdered liquid crystal polyester (B) (LC-B) was obtained. The flow initiation temperature of liquid crystal polyester (B) was 285°C.

[0141] LC-C: Liquid crystal polymer manufactured according to the manufacturing method described below.

[0142] -LC-C manufacturing- In a reactor equipped with a stirrer, torque meter, nitrogen gas inlet tube, thermometer, and reflux condenser, 1034.99 g (5.5 mol) of 6-hydroxy-2-naphthoic acid, 378.33 g (1.75 mol) of 2,6-naphthalenedicarboxylic acid, 83.07 g (0.5 mol) of terephthalic acid, 272.52 g (2.475 mol, 0.225 mol excess of the total molar amount of 2,6-naphthalenedicarboxylic acid and terephthalic acid), 1226.87 g (12 mol) of acetic anhydride, and 0.17 g of 1-methylimidazole as a catalyst were added. After replacing the gas in the reactor with nitrogen gas, the temperature was raised from room temperature to 145°C over 15 minutes while stirring under a nitrogen gas stream, and then refluxed at 145°C for 1 hour.

[0143] Next, while distilling off the by-product acetic acid and unreacted acetic anhydride, the temperature was raised from 145°C to 310°C over 3 hours and 30 minutes, and held at 310°C for 3 hours. After that, the solid liquid crystal polyester (C1) was extracted and cooled to room temperature. The flow initiation temperature of this polyester (C1) was 265°C.

[0144] [Manufacturing of liquid crystal polyester microparticles (LC-C)] Using a jet mill (KJ-200 from Kurimoto Iron Works), liquid crystal polyester (C1) was pulverized to obtain liquid crystal polyester fine particles (LC-C). The average particle size of these liquid crystal polyester fine particles was 9 μm.

[0145] LC-D: Liquid crystal polymer manufactured according to the manufacturing method described below.

[0146] -LCD Manufacturing- In a reactor equipped with a stirrer, torque meter, nitrogen gas inlet tube, thermometer, and reflux condenser, 941 g (5.0 mol) of 6-hydroxy-2-naphthoic acid, 273 g (2.5 mol) of 4-aminophenol, 415 g (2.5 mol) of isophthalic acid, and 1123 g (11 mol) of acetic anhydride were added. After replacing the gas in the reactor with nitrogen gas, the temperature was raised from room temperature (23°C) to 150°C over 15 minutes while stirring under a nitrogen gas stream, and then refluxed at 150°C for 3 hours. Next, while distilling off the by-product acetic acid and unreacted acetic anhydride, the temperature was raised from 150°C to 320°C over 3 hours and maintained until an increase in viscosity was observed. After that, the contents were removed from the reactor and cooled to room temperature. The resulting solid was pulverized in a pulverizer to obtain powdered liquid crystal polyester (D1).

[0147] The liquid crystal polyester (D1) obtained above was subjected to solid-phase polymerization by holding it at 250°C for 3 hours under a nitrogen atmosphere, then cooled, and subsequently pulverized with a pulverizer to obtain powdered liquid crystal polyester (LC-D).

[0148] [Polyphenylene ether] P-1: A mixture of commercially available polyphenylene ether pellets (SA120, manufactured by SABIC, weight-average molecular weight Mw2,600) / bisphenol A type epoxy resin (Epiclon 850S, manufactured by DIC Corporation, average number of epoxy groups: 2) / bisphenol A type cyanate ester resin (Badcy, manufactured by Lonza Japan Co., Ltd.) / aromatic condensed phosphate ester (PX-200, manufactured by Daihachi Chemical Industry Co., Ltd.) / aluminum tris-diethylphosphinate (Exolit OP-935, manufactured by Clariant Japan Co., Ltd.) / zinc octanoate = 25 / 34 / 25 / 8 / 8 / 0.01 (mass ratio)

[0149] <Curable compound> M-1: A commercially available aminophenol-type epoxy resin (jER630LSD, manufactured by Mitsubishi Chemical Corporation) was used, with the solid content being the amount shown in Table 1. M-2: A commercially available thermosetting resin (SLK, manufactured by Shin-Etsu Chemical Co., Ltd., mainly containing polymer-type curable compounds) was used, with the solid content being the amount shown in Table 1.

[0150] <Filler> A-1: Commercially available ultra-high molecular weight polyethylene microparticles with an average particle size of 10 μm (Mipelon PM200, manufactured by Mitsui Chemicals, Inc.) were used, and the amount of solid content was as shown in Table 1. F-1: A commercially available hydrophobic silica sol with an average particle size of 45 nm (MEK-ST-L, 30% by mass solids, methyl ethyl ketone (MEK) solvent, manufactured by Nissan Chemical Corporation) was used, with the amount of solids being as shown in Table 1. F-2: Commercially available silica microparticles with an average particle size of 0.5 μm (SO-C2, manufactured by Admatex Co., Ltd.) were used, and the amount of solid content was as shown in Table 1. A mixture of F-3:LC-C and F-2 (mass ratio 1:1) was used, with the solid content being the amount shown in Table 1. F-4: Commercially available polytetrafluoroethylene (PTFE) nanoparticles (Polyflon PTFE D-210C, average particle size 0.25 μm, manufactured by Daikin Industries, Ltd.) were used with the solvent replaced with N-methylpyrrolidone solvent, so that the solid content in the liquid crystal polymer film was as shown in Table 1. F-5: Copolymer (PFA) particles of tetrafluoroethylene and perfluoroalkoxyethylene, melting point 280°C, average particle size 0.2 μm~0.5 μm, dielectric loss tangent 0.001 F-6: Commercially available hollow powder with an average particle size of 16 μm (Glass Bubbles iM30K, manufactured by 3M Japan Ltd.) F-7: Boron nitride particles, melting point > 500°C, HP40MF100 (manufactured by Mizushima Iron Alloy Co., Ltd.), dielectric loss tangent 0.0007

[0151] <Film forming> The film was formed according to the following co-casting or multi-layer coating methods.

[0152] [Co-casting (solution casting)] -Preparation of polymer solutions- The above-mentioned liquid crystal polymer and additives were added to N-methylpyrrolidone and stirred under a nitrogen atmosphere at 140°C for 4 hours to obtain a liquid crystal polymer solution. The liquid crystal polymer and additives were added in the volume ratios shown in Table 1. The solid content concentrations of the solutions for layer B (surface layer), layer A (core layer), and layer C (support layer) were as shown in Table 1. Next, the liquid crystal polymer solutions were obtained by first passing them through a sintered fiber metal filter with a nominal pore size of 10 μm, and then through another sintered fiber metal filter with the same nominal pore size of 10 μm. If the additive did not dissolve in N-methylpyrrolidone, the liquid crystal polymer solution was prepared without the additive, passed through the sintered fiber metal filter, and then the additive was added and stirred.

[0153] - Fabrication of single-sided copper-clad laminate (Examples 1-4, Comparative Example 1) - The obtained polymer solutions for layer A and layer B were fed into a casting die equipped with a feed block adjusted for co-casting, and cast onto the treated surface of copper foil (Fukuda Metal Foil & Powder Industry Co., Ltd., CF-T9DA-SV-12, average thickness 12 μm) so that the copper foil and layer A were in contact. The solvent was removed from the cast film by drying at 40°C for 4 hours. Furthermore, a laminate (single-sided copper-clad laminate) having a copper layer and a film was obtained by holding at 300°C for 3 hours under a nitrogen atmosphere.

[0154] - Fabrication of double-sided copper-clad laminated boards - (Copper-clad laminate precursor process) A copper foil (Fukuda Metal Foil & Powder Industry Co., Ltd., CF-T9DA-SV-12, average thickness 12 μm) was placed on a single-sided copper-clad laminate so that its treated surface was in contact with the film. Lamination was then performed for 1 minute at 140°C and a lamination pressure of 0.4 MPa using a laminator (Nikko Materials Co., Ltd., "Vacuum Laminator V-130") to obtain a precursor for a double-sided copper foil laminate.

[0155] - Fabrication of single-sided copper-clad laminates (Examples 5 to 20) - The polymer solutions obtained for layer B (surface layer), layer A (core layer), and layer C (support layer) were fed into a casting die equipped with a feed block adjusted for co-casting, and cast onto the treated surface of copper foil (Fukuda Metal Foil & Powder Industry Co., Ltd., CF-T9DA-SV-18, average thickness 18 μm) so that the copper foil and layer C were in contact. The solvent was removed from the cast film by drying at 40°C for 4 hours, and then the film was held at 300°C under a nitrogen atmosphere for 3 hours to obtain a laminate (single-sided copper-clad laminate) having a copper layer and a film.

[0156] [Multi-layer application] -Preparation of polymer solutions- The polymers and additives listed in Table 1 were added to toluene, and the mixture was stirred for 60 minutes to obtain polymer solutions for layer A and layer B, respectively.

[0157] - Fabrication of single-sided copper-clad laminate (Example 21) - Polymer solutions for layer A and layer B were applied in multiple layers to the treated surface of copper foil (Fukuda Metal Foil & Powder Industry Co., Ltd., CF-T9DA-SV-18, 18 μm thick, surface roughness Rz 0.85 μm) by supplying them to a slot die coater equipped with a slide coater. After drying at 100°C for 3 minutes, the solvent was removed from the coating film by drying at 170°C for 3 minutes. Further heat treatment was performed by raising the temperature from room temperature to 200°C at a rate of 1°C / min and holding it at that temperature for 2 hours to obtain a laminate with a copper layer (single-sided copper-clad laminate).

[0158] (Main thermocompression bonding process) Using a thermocompression press (MP-SNL, manufactured by Toyo Seiki Seisakusho), the obtained copper-clad laminate precursor was thermocompressed at 300°C and 4.5 MPa for 10 minutes to produce a double-sided copper-clad laminate.

[0159] <Fabrication of Flexible Wiring Boards> Using the single-sided copper-clad laminate and the double-sided copper-clad laminate described above, a flexible wiring board having a four-layer stripline structure for the outer layer plane (ground layer) was fabricated.

[0160] (Process for forming wiring substrate) Using a known photofabrication technique, the copper foil of the double-sided copper-clad laminate described above was patterned to create a wiring substrate containing three pairs of signal lines. The length of the signal lines was set to 100 mm, and the width was set so that the characteristic impedance was 50 Ω.

[0161] (Lamination process) Using the above-mentioned wiring substrate and a pair of the above-mentioned single-sided copper-clad laminates, the single-sided copper-clad laminates were stacked so that the film side of the single-sided copper-clad laminates was in contact with the wiring substrate, resulting in the configuration of single-sided copper-clad laminate / wiring substrate / single-sided copper-clad laminate. A flexible wiring board was fabricated by laminating the layers using a vacuum press at the pressing temperatures listed in Table 1.

[0162] We evaluated the wiring distortion using the fabricated flexible wiring board. The evaluation method is as follows. The evaluation results are shown in Table 1.

[0163] <Wiring distortion> Flexible wiring boards were cut using a microtome, and the cross-sections were observed with an optical microscope. Wiring distortion was then evaluated based on the following evaluation criteria. A: No distortion is detected in the signal lines and ground lines. B: No distortion is observed in the signal lines, but distortion is observed in the ground line. C: Distortion is observed in one pair of signal lines. D: Distortion is observed in two or three pairs of signal lines.

[0164] [Table 1]

[0165] As shown in Table 1, in Examples 1 to 21, the dielectric loss tangent was 0.005 or less, and the elastic modulus of the surface at 160°C was smaller than the elastic modulus of the interior at 160°C, thus suppressing wiring distortion. Furthermore, in Examples 1 to 21, the dielectric loss tangent was 0.005 or less, and the elastic modulus at 300°C of at least one surface was smaller than the elastic modulus at 300°C of the interior, thus suppressing wiring distortion. On the other hand, in Comparative Example 1, it was found that wiring distortion occurred because the elastic modulus of the surface at 160°C was the same as the elastic modulus of the interior at 160°C. Furthermore, in Comparative Example 1, it was found that wiring distortion occurred because the elastic modulus of the surface at 300°C was the same as the elastic modulus of the interior at 300°C. In the laminate of Example 14, the peel strength between layer B and the copper foil was 7 kN / m, and the peel strength between layer C and the copper foil was 0.9 kN / m, confirming sufficient adhesion. On the other hand, in the laminate of Comparative Example 1, the peel strength between the film and the copper foil was 3 kN / m, which was insufficient.

Images