Liquid crystal polymer film, polymer film, and laminate

Abstract

Provided are a liquid crystal polymer film or polymer film having a small dielectric loss tangent and excellent rupture strength, and a laminate in which said liquid crystal polymer film or said polymer film is used. The liquid crystal polymer film comprises a liquid crystal polymer A and a compound having a melting point that is lower than that of the liquid crystal polymer A and a dielectric loss tangent of less than 0.01.

Description

[Technical Field]

[0001] This disclosure relates to liquid crystal polymer films, polymer 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 polymers include, for example, a liquid crystal polymer composition described in Patent Document 1, which comprises a solvent, a soluble liquid crystal polymer dissolved in the solvent, and an additive comprising at least one organic polymer or inorganic filler, which is dispersed or dissolved in the solvent.

[0004] Patent Document 2 describes a method for producing a liquid crystal polymer film, in which a liquid crystal polymer film is sandwiched between heat-resistant laminate films, stretched near the melting point of the liquid crystal polymer, and then the laminate films are peeled off, as well as the liquid crystal polymer film itself.

[0005] Furthermore, Patent Document 3 describes a liquid crystal polyester film obtained by coating a dispersion of liquid crystal polyester fine particle powder, removing the solvent, and then fusing the particles together by heat treatment. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Japanese Patent Publication No. 2019-52288 [Patent Document 2] Japanese Patent Publication No. 2003-340918 [Patent Document 3] International Publication No. 2020 / 166644

Summary of the Invention

Problems to be Solved by the Invention

[0007] A problem to be solved by one embodiment of the present invention is to provide a liquid crystal polymer film or a polymer film having a low dielectric loss tangent and excellent breaking strength. Another problem to be solved by another embodiment of the present invention is to provide a laminate using the liquid crystal polymer film or the polymer film.

Means for Solving the Problems

[0008] Means for solving the above problems include the following aspects. <1> A liquid crystal polymer film containing a liquid crystal polymer A and a compound having a melting point lower than that of the liquid crystal polymer A and a dielectric loss tangent of less than 0.01. <2> The liquid crystal polymer film according to <1>, wherein the melting point of the liquid crystal polymer A is 280°C or higher. <3> The liquid crystal polymer film according to <1> or <2>, wherein the liquid crystal polymer A has a structural unit represented by any one of formulas (1) to (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 represent a phenylene group, a naphthylene group, a biphenylylene group or a group represented by the following formula (4), X and Y each independently represent 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. <4> The liquid crystal polymer film according to any one of <1> to <3>, wherein the compound having a dielectric loss tangent of less than 0.01 is a polymer. <5> The liquid crystal polymer film according to any one of <1> to <4>, wherein the compound having a dielectric loss tangent of less than 0.01 is a liquid crystal polymer B having a melting point lower than that of the liquid crystal polymer A and a dielectric loss tangent of less than 0.01. <6> The liquid crystal polymer film according to any one of <1> to <5>, wherein the compound having a dielectric loss tangent of less than 0.01 is a particle. <7> The liquid crystal polymer film according to any one of <1> to <6>, wherein the compound having a dielectric loss tangent of less than 0.01 is a fluorine-based polymer. <8> The liquid crystal polymer film according to any one of <1> to <7>, wherein the content of the compound having a dielectric loss tangent of less than 0.01 is 10% to 90% by mass based on the total mass of the liquid crystal polymer film. <9> The liquid crystal polymer film according to any one of <1> to <8>, wherein the dielectric loss tangent of the liquid crystal polymer film is 0.001 or less. <10> The liquid crystal polymer film according to any one of <1> to <9>, wherein the linear expansion coefficient of the liquid crystal polymer film is -20 ppm / K to 50 ppm / K. <11> A polymer film containing at least one polymer selected from the group consisting of a fluorine-based polymer, a polymer of a compound having a cycloaliphatic hydrocarbon group and a group having an ethylenic unsaturated bond, polyphenylene ether, and aromatic polyether ketone, and a compound having a melting point lower than that of the polymer and a dielectric loss tangent of less than 0.01. <12> <1> ~ <10> A liquid crystal polymer film as described in any one of the following, <11> A laminate having a polymer film as described above and a metal layer disposed on at least one surface of the liquid crystal polymer film or the polymer film. <13> The above liquid crystal polymer film or the above polymer film having metal layers disposed on both sides, respectively. <12> The laminate described above. <14> The above metal layer is a copper layer, and the peel strength between the above liquid crystal polymer film or the above polymer film and the above copper layer is 0.5 kN / m or more. <12> or <13> The laminate described above. [Effects of the Invention]

[0009] According to one embodiment of the present invention, a liquid crystal polymer film or polymer film having a low dielectric loss tangent and excellent tensile strength can be provided. Furthermore, according to another embodiment of the present invention, the above-mentioned liquid crystal polymer film or a laminate using the above-mentioned polymer film can be provided. [Modes for carrying out the invention]

[0010] 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.

[0011] (Liquid crystal polymer film or polymer film) A first embodiment of the polymer film according to this disclosure is a polymer film comprising a liquid crystal polymer A and a compound having a melting point lower than that of the liquid crystal polymer A and a dielectric loss tangent of less than 0.01. A second embodiment of the polymer film according to this disclosure is a liquid crystal polymer film comprising a fluorine-based polymer, a polymer of a compound having a cyclic aliphatic hydrocarbon group and a group having an ethylenically unsaturated bond, polyphenylene ether, and aromatic polyether ketone, and a compound having a melting point lower than that of the above polymer and a dielectric loss tangent of less than 0.01. In this disclosure, the polymer film containing liquid crystal polymer A is also referred to as a liquid crystal polymer film.

[0012] In this specification, unless otherwise specified, the term "polymer film relating to this disclosure" refers to both the first embodiment and the second embodiment described above. Furthermore, in this specification, unless otherwise specified, the term "liquid crystal polymer film relating to this disclosure" refers to the first embodiment described above.

[0013] The inventors have found that many conventional polymer films have insufficient dielectric loss tangent, and that among conventional polymer films, those with low dielectric loss tangent have insufficient tensile strength. As a result of diligent research by the inventors, it has been found that by adopting the above configuration, a polymer film with a low dielectric loss tangent and excellent tensile strength can be provided. The detailed mechanism by which the above effects are achieved is unknown, but it is speculated to be as follows. By including a compound with a dielectric loss tangent of less than 0.01, the dielectric loss tangent of the polymer film can be reduced. Furthermore, while ensuring the mechanical strength of the web during the manufacturing process with at least one polymer selected from the group consisting of liquid crystal polymer A, fluorine-based polymers, polymers of compounds having a cyclic aliphatic hydrocarbon group and a group having an ethylenically unsaturated bond, polyphenylene ether, and aromatic polyether ketone, it is estimated that excellent tensile strength can be achieved by fusing compounds that have a melting point lower than that of the liquid crystal polymer A, fluorine-based polymers, polymers of compounds having a cyclic aliphatic hydrocarbon group and a group having an ethylenically unsaturated bond, polyphenylene ether, and aromatic polyether ketone, and that also have a dielectric loss tangent of less than 0.01.

[0014] <Liquid crystal polymer A> A first embodiment of the polymer film relating to this disclosure includes a liquid crystal polymer A. In this disclosure, the type of liquid crystal polymer A is not particularly limited, and known liquid crystal polymers can be used. Furthermore, liquid crystal polymer A may be a thermotropic liquid crystal polymer that exhibits liquid crystalline properties in a molten state, or a lyotropic liquid crystal polymer that exhibits liquid crystalline properties in a solution state. If liquid crystal polymer A 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.

[0015] The melting point of liquid crystal polymer A is its peak temperature, and from the viewpoint of ensuring the mechanical strength of the web during the manufacturing process, it is preferably 280°C or higher, more preferably 300°C or higher, even more preferably 315°C or higher, and particularly preferably 330°C to 400°C.

[0016] The melting point shall be measured using a differential scanning calorimetry (DSC) instrument. 5 mg of the sample is placed in the DSC measurement pan, and when it is heated from 30°C at 10°C / min in a nitrogen stream, the peak temperature of the endothermic peak observed is defined as the melting point (Tm) of liquid crystal polymer A. If a metal layer is laminated to the polymer film, the metal layer can be etched with an aqueous ferric chloride solution, and the extracted polymer film can be washed with water and dried before measurement.

[0017] Examples of liquid crystal polymer A include liquid crystal polyester, liquid crystal polyesteramide obtained by introducing amide bonds into liquid crystal polyester, liquid crystal polyester ether obtained by introducing ether bonds into liquid crystal polyester, and liquid crystal polyester carbonate obtained by introducing carbonate bonds into liquid crystal polyester. Furthermore, from the viewpoint of liquid crystalline properties and thermal expansion coefficient, liquid crystal polymer A is preferably a polymer having an aromatic ring, and more preferably an aromatic polyester or aromatic polyesteramide. Furthermore, liquid crystal polymer A 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 A is a fully aromatic liquid crystal polymer made using only aromatic compounds as raw material monomers.

[0018] Examples of liquid crystal polymer A include the following liquid crystal polymers. 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 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.

[0019] 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.

[0020] From the viewpoint of liquid crystalline properties, thermal expansion coefficient, and adhesion to the metal layer, liquid crystal polymer A preferably has a constituent unit represented by any of the following formulas (1) to (3) (hereinafter, the constituent unit represented by formula (1), etc. may be referred to as constituent unit (1), etc.), more preferably has a constituent unit represented by formula (1), and particularly preferably has a constituent unit represented by formula (1), a constituent unit represented by formula (2), and a constituent unit represented by formula (3). 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 these 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.

[0021] 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 groups is preferably 1 to 10. Examples of the aryl group mentioned above include a phenyl group, an o-tolyl group, an m-tolyl group, a p-tolyl group, a 1-naphthyl group, and a 2-naphthyl group. The number of carbon atoms in the aryl group is preferably 6 to 20. If the above hydrogen atoms are substituted with these groups, the number of substitutions is: Ar 1 Ar 2 Or Ar 3 In each case, there are preferably two or fewer, and more preferably one, independently.

[0022] Examples of the alkylene group mentioned above include a methylene group, a 1,1-ethanediyl group, a 1-methyl-1,1-ethanediyl group, a 1,1-butanediyl group, and a 2-ethyl-1,1-hexanediyl group. The number of carbon atoms in the alkylene group is preferably 1 to 10.

[0023] The constituent unit (1) is a constituent unit derived from an aromatic hydroxycarboxylic acid. The constituent unit (1) is Ar 1 Embodiments in which is a p-phenylene group (constituent unit derived from p-hydroxyammonium acid), and 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).

[0024] The constituent unit (2) is a constituent unit derived from an aromatic dicarboxylic acid. The constituent unit (2) is 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 Embodiments 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.

[0025] The constituent unit (3) is a constituent unit derived from an aromatic diol, an aromatic hydroxylamine, or an aromatic diamine. The constituent 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 3 An 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.

[0026] The content of constituent 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 amount of substance equivalent (moles) of each constituent unit, obtained by dividing the mass of each constituent unit constituting the liquid crystal polymer (also called a "monomer unit") by the formula weight of that constituent unit, and then summing them up). The content of constituent 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 constituent 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 constituent unit (1), the easier it is to improve heat resistance, strength, and rigidity, but if it is too high, the solubility in the solvent tends to decrease.

[0027] The ratio of the content of constituent unit (2) to the content of constituent unit (3) is expressed as [content of constituent unit (2)] / [content of constituent unit (3)] (moles / moles), and 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.

[0028] Furthermore, liquid crystal polymer A may have two or more independent constituent units (1) to (3). In addition, liquid crystal polymer A may have constituent units other than constituent units (1) to (3), but the content of these other units is preferably 10 mol% or less, more preferably 5 mol% or less, relative to the total amount of all constituent units.

[0029] From the viewpoint of solubility in solvents, liquid crystal polymer A preferably has a constituent unit (3) in which at least one of X and Y is an imino group, that is, it is preferable that the constituent unit (3) has 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 it has only a constituent unit (3) in which at least one of X and Y is an imino group.

[0030] Liquid crystal polymer A is preferably produced by melt polymerization of raw material monomers corresponding to the constituent units of liquid crystal polymer A. 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, with nitrogen-containing heterocyclic compounds being preferred. If necessary, melt polymerization may be further carried out by solid-phase polymerization.

[0031] The lower limit of the flow initiation temperature for liquid crystal polymer A is preferably 180°C or higher, more preferably 200°C or higher, and even more preferably 250°C or higher. The upper limit of the flow initiation temperature is preferably 350°C, more preferably 330°C, and even more preferably 300°C. 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.

[0032] 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).

[0033] Furthermore, the weight-average molecular weight of liquid crystal polymer A 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 liquid crystal polymer A is within the above range, the heat-treated film exhibits excellent thermal conductivity in the thickness direction, heat resistance, strength, and rigidity.

[0034] Liquid crystal polymer A is preferably a liquid crystal polymer that is soluble in a specific organic solvent (hereinafter also referred to as "soluble liquid crystal polymer"). Specifically, the soluble liquid crystal polymer in this disclosure is preferably a liquid crystal 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.

[0035] <Fluorine-based polymers> A second embodiment of the polymer film according to this disclosure preferably includes a fluoropolymer from the viewpoint of heat resistance and mechanical strength. The type of fluorinated polymer is not particularly limited, and any known fluorinated polymer can be used.

[0036] Furthermore, fluorinated polymers include homopolymers and copolymers comprising fluorinated α-olefin monomers, i.e., α-olefin monomers containing at least one fluorine atom, and, if necessary, non-fluorinated ethylenically unsaturated monomers reactive with fluorinated α-olefin monomers. 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 with 2 to 8 carbon atoms) vinyl ethers (e.g., perfluoromethyl vinyl ether, perfluoropropyl vinyl ether, perfluorooctyl vinyl ether). Among these, 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) is preferred. Examples of non-fluorinated monoethylenically 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.

[0037] 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. Fluorine-based polymers may be used individually or in combination of two or more types.

[0038] The fluorine-based polymer is preferably at least one of FEP, PFA, ETFE, or PTFE. FEP is available from DuPont under the trade name TEFLON® FEP, or from Daikin Industries, Ltd. under the trade name NEOFLON FEP; PFA is available from Daikin Industries, Ltd. under the trade name NEOFLON PFA, from DuPont under the trade name TEFLON® PFA, or from Solvay Solexis under the trade name HYFLON PFA.

[0039] The fluorine-based polymer preferably contains PTFE. The PTFE may include a PTFE homopolymer, a partially modified PTFE homopolymer, or a combination of 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.

[0040] The fluorinated polymer may be a crosslinkable fluoropolymer having a crosslinkable group. Crosslinkable fluoropolymers can be crosslinked by conventionally known crosslinking methods. One typical crosslinkable fluoropolymer is a fluoropolymer having a (meth)acryloxy group. For example, a crosslinkable fluoropolymer has the formula: H2C=CR'COO-(CH2) n -R-(CH2) n -OOCR' can be represented as CH2, where R is a fluorinated oligomer chain having two or more constituent units derived from a fluorinated α-olefin monomer or a non-fluorinated monoethylenically unsaturated monomer, R' is H or -CH3, and n is 1 to 4. R may be a fluorinated oligomer chain containing constituent units derived from tetrafluoroethylene.

[0041] To initiate a radical crosslinking reaction via (meth)acryloxy groups on a fluorinated polymer, a crosslinked fluoropolymer network structure can be formed by exposing a fluoropolymer having (meth)acryloxy 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.

[0042] - A polymer of a compound having a cyclic aliphatic hydrocarbon group and a group having an ethylenically unsaturated bond - A second embodiment of the polymer film according to this disclosure preferably includes a polymer of a compound having a cyclic aliphatic hydrocarbon group and a group having an ethylenically unsaturated bond. Examples of polymers of compounds having a cyclic aliphatic hydrocarbon group and a group having an ethylenically unsaturated bond include thermoplastic resins having structural units formed from monomers consisting of cyclic olefins 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.

[0043] 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, isoborone rings, norbornane rings, and dicyclopentane rings. A compound having a cyclic aliphatic hydrocarbon group and a group having an ethylenically unsaturated bond may be a monofunctional ethylenically unsaturated compound or a polyfunctional ethylenically unsaturated compound. 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.

[0044] -Polyphenylene ether- A second embodiment of the polymer film according to this disclosure preferably contains a 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. For polyphenylene ethers, the average number of phenolic hydroxyl groups at the molecular ends per molecule (number of terminal hydroxyl groups) is preferably 1 to 5, and more preferably 1.5 to 3, from the viewpoint of dielectric loss tangent and heat resistance. The number of hydroxyl groups or phenolic 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 or terminal phenolic hydroxyl groups can be expressed as a numerical value representing the average number of hydroxyl groups or 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.

[0045] Examples of polyphenylene ethers include polyphenylene ethers composed of 2,6-dimethylphenol and at least one of a difunctional phenol and a trifunctional phenol, or polyphenylene ethers such as poly(2,6-dimethyl-1,4-phenylene oxide) as the main component. More specifically, it is preferable that the compound has a structure represented by formula (PPE).

[0046] [ka]

[0047] 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.

[0048] -Aromatic polyether ketone- A second embodiment of the polymer film according to this disclosure preferably contains an 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 the bonds are arranged in the order of ether bond, ether bond, and carbonyl bond (ketone). Preferably, each bond is linked by a divalent aromatic group. Aromatic polyether ketones may be used individually or in combination of two or more.

[0049] 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.

[0050] [ka]

[0051] 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.

[0052] The polymer film may contain only one or more polymers selected from the group consisting of liquid crystal polymer A, fluorine-based polymers, polymers of compounds having a cyclic aliphatic hydrocarbon group and a group having an ethylenically unsaturated bond, polyphenylene ether, and aromatic polyether ketone (hereinafter, liquid crystal polymer A, fluorine-based polymers, polymers of compounds having a cyclic aliphatic hydrocarbon group and a group having an ethylenically unsaturated bond, polyphenylene ether, and aromatic polyether ketone are also referred to as "specific polymers"). From the viewpoint of ensuring the mechanical strength of the web during the manufacturing process, the content of a specific polymer in the polymer film is preferably 10% to 90% by mass, more preferably 20% to 80% by mass, and particularly preferably 30% to 70% by volume, relative to the total mass of the polymer film.

[0053] <A compound whose melting point is lower than that of the above-mentioned liquid crystal polymer A, or at least one polymer selected from the group consisting of 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 whose dielectric loss tangent is less than 0.01> The polymer film relating to this disclosure includes a compound having a melting point lower than that of a specific polymer and a dielectric loss tangent of less than 0.01 (hereinafter also simply referred to as "a compound with a dielectric loss tangent of less than 0.01"). For compounds with a dielectric loss tangent of less than 0.01, the dielectric loss tangent is preferably 0.005 or less, more preferably 0.002 or less, even more preferably 0.001 or less, and particularly preferably greater than 0 and 0.001 or less, from the viewpoint of the dielectric loss tangent of the polymer film and the tensile strength.

[0054] The melting point of compounds with a dielectric loss tangent of less than 0.01 shall be measured using differential scanning calorimetry (DSC). 5 mg of the sample was placed in the DSC measurement pan, and when it was heated from 30°C at 10°C / min in a nitrogen stream, the peak temperature of the endothermic peak that appeared was defined as the melting point Tm of the compound with a dielectric loss tangent of less than 0.01. Furthermore, if a compound with a dielectric loss tangent of less than 0.01 does not exhibit a melting point, the flow initiation temperature shall be used as the melting point. The flow initiation temperature, also called the flow temperature or fluid temperature, is measured using a capillary rheometer at 9.8 MPa (100 kg / cm²). 2 This is the temperature at which a compound with a dielectric loss tangent of less than 0.01 is melted under a load of ) while being 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, exhibiting a viscosity of 4,800 Pa·s (48,000 poise). If a metal layer is laminated onto the polymer film, the metal layer is etched with a ferric chloride aqueous solution, then the film is washed and dried to remove it. Subsequently, the film is placed in a DSC measurement pan and measured. Among the multiple endothermic peaks that appear, those not originating from the specific polymer can be identified and evaluated. Furthermore, as an alternative method when peaks do not clearly appear in DSC measurements, the chemical structure of a compound with a dielectric loss tangent of less than 0.01 can be identified, and multiple particles made from that material can be heated and evaluated as the temperature at which they fuse together.

[0055] The dielectric loss tangent in this disclosure shall be measured by the following method. Dielectric constant measurement is performed using the resonant perturbation method at a frequency of 10 GHz. A 10 GHz cavity resonator (CP531, manufactured by Kanto Electronics Applied Development Co., Ltd.) is connected to a network analyzer (E8363B, manufactured by Agilent Technology). A sample (width: 2 mm x length: 80 mm) is inserted into the cavity resonator, and the dielectric constant and dielectric loss tangent of the sample are measured from the change in resonant frequency before and after insertion over 96 hours under conditions of 20°C and 65% RH. When measuring the dielectric loss tangent of each layer, unnecessary layers may be scraped off with a razor or the like to prepare an evaluation sample containing only the target layer. Furthermore, if it is difficult to extract a single film due to the thinness of the layer, the layer to be measured may be scraped off with a razor or the like, and the resulting powdered sample may be used. The measurement of the dielectric loss tangent of the polymer in this disclosure shall be performed according to the above-described dielectric loss tangent measurement method, using a sample made from the powdered polymer of the polymer to be measured, after identifying or isolating the chemical structure of the polymer constituting each layer. The dielectric constant and dielectric loss tangent of the sample are measured from the change in frequency.

[0056] Compounds with a dielectric loss tangent of less than 0.01 are not particularly limited in any way other than being compounds with a dielectric loss tangent of less than 0.01, and may be low-molecular-weight compounds or high-molecular-weight compounds, with high-molecular-weight compounds being preferred. As a compound having a dielectric loss tangent of less than 0.01, it is preferable that it be a resin from the viewpoint of the dielectric loss tangent of the polymer film and the tensile strength, and more preferably a liquid crystal polymer B, a fluorine-based polymer, a cycloolefin polymer, a polyphenylene ether, or an aromatic vinyl resin, which has a melting point lower than that of a specific polymer and a dielectric loss tangent of less than 0.01. In the first embodiment described above, from the viewpoint of tensile strength, the liquid crystal polymer B is particularly preferred, and from the viewpoint of the dielectric loss tangent of the polymer film, the fluorine-based polymer is particularly preferred. In the second embodiment described above, from the viewpoint of tensile strength, the liquid crystal polymer B is particularly preferred. Alternatively, it is also possible to use a material in which the surface of inorganic particles having a dielectric loss tangent of less than 0.01 is coated with an organic substance exhibiting a melting point. Polytetrafluoroethylene is a preferred example of a fluorine-based polymer. Furthermore, as a resin used as a compound with a dielectric loss tangent of less than 0.01, from the viewpoint of tensile strength, it is preferable that the resin has a weight-average molecular weight of 1,000 or more, more preferably 2,000 or more, even more preferably 3,000 or more, and particularly preferably 5,000 to 200,000. In the case of a liquid crystal polymer, it is preferable that the weight-average molecular weight be 13,000 or less.

[0057] Liquid crystal polymer B, which has a melting point lower than that of a specific polymer and a dielectric loss tangent of less than 0.01, is similar to the preferred embodiment of liquid crystal polymer A described above, except for the melting point. The melting point of the liquid crystal polymer B used as a compound with a dielectric loss tangent of less than 0.01 is preferably 200°C or higher and less than the melting point Tm of the specific polymer contained, more preferably 250°C or higher and less than the melting point Tm of the specific polymer contained, and particularly preferably 280°C or higher and less than the melting point Tm of the specific polymer. Furthermore, the upper limit of the melting point Tm of liquid crystal polymer B is preferably less than 330°C, and more preferably less than 315°C.

[0058] As a compound having a dielectric loss tangent of less than 0.01, from the viewpoint of the dielectric loss tangent of the polymer film and the tensile strength, it is preferable that the compound has a melting point lower than the melting point of the specific polymer, and more preferably that the liquid crystal polymer B has a melting point lower than the specific polymer and a dielectric loss tangent of less than 0.01. Furthermore, the melting point (preferably the melting point Tm) of a compound with a dielectric loss tangent of less than 0.01 is preferably 10°C or more lower than the melting point of the specific polymer, more preferably 20°C or more lower than the melting point of the specific polymer, even more preferably 30°C to 100°C lower than the melting point of the specific polymer, and particularly preferably 30°C to 70°C lower than the melting point of the specific polymer, from the viewpoint of the dielectric loss tangent of the polymer film and the tensile strength.

[0059] Furthermore, compounds with a dielectric loss tangent of less than 0.01 are preferably in the form of particles or fibers, more preferably resin particles, even more preferably fluorine-based polymer particles, and particularly preferably polytetrafluoroethylene particles, from the viewpoint of the dielectric loss tangent and tensile strength of the polymer film. In addition, from the viewpoint of promoting the fusion of compounds with a dielectric loss tangent of less than 0.01, it is preferable to increase the surface area per unit mass, for example, by reducing the particle size. The average particle size of the above particles is preferably 5 nm to 20 μm, more preferably 20 nm to 2 μm, even more preferably 50 nm to 1 μm, and particularly preferably 100 nm to 500 nm, from the viewpoint of the dielectric loss tangent of the polymer film and the breaking strength.

[0060] Furthermore, from the viewpoint of mechanical strength, it is preferable that the compound having a dielectric loss tangent of less than 0.01 is a polymer having a melting point greater than the melting point of the specific polymer. As a polymer having a melting point greater than that of liquid crystal polymer A, fluorine-based polymers are preferred. Examples of fluorine-based polymers include those mentioned above.

[0061] For compounds with a dielectric loss tangent of less than 0.01, the crystallization enthalpy ΔHc is preferably 3 J / g or less, more preferably 2 J / g or less, even more preferably 1 J / g or less, and particularly preferably greater than 0 J / g and 0.6 J / g or less, from the viewpoint of the dielectric loss tangent and tensile strength of the polymer film. Furthermore, from the viewpoint of the dielectric loss tangent and tensile strength of the polymer film, it is preferable that the crystallization enthalpy ΔHc is close to 0 J / g.

[0062] The method for measuring the crystallization enthalpy ΔHc in this disclosure shall be as follows: When 2 mg of the film is placed in the measurement pan of a differential scanning calorimetry (DSC) instrument and heated from 25°C to 350°C at a rate of 20°C / min in a nitrogen stream, the heat of the exothermic peak observed is defined as the film's ΔHc. Furthermore, the assignment of the exothermic peak is performed by isolating the materials constituting the film and separately measuring them using DSC under the above conditions to determine the exothermic peak temperature originating from each material.

[0063] The polymer film may contain only one compound or two or more compounds having a dielectric loss tangent of less than 0.01. The content of compounds with a dielectric loss tangent of less than 0.01 in the polymer film is preferably 10% to 90% by mass, more preferably 20% to 80% by mass, and particularly preferably 30% to 70% by mass, based on the total mass of the polymer film, from the viewpoint of dielectric loss tangent and tensile strength. Furthermore, the content M of a specific polymer in the polymer film A The content M of compounds whose dielectric loss tangent is less than 0.01 B The mass ratio M A / M B From the viewpoint of dielectric loss tangent and fracture strength, the value is preferably 0.1 to 10, more preferably 0.2 to 5, and particularly preferably 0.5 to 2.

[0064] -Filler- The polymer film according to this disclosure preferably contains a filler other than the compound whose dielectric loss tangent is less than 0.01 (hereinafter also simply referred to as "filler"), from the viewpoint of the coefficient of linear expansion and adhesion to the metal layer. The filler may be particulate or fibrous, and may be inorganic or organic. In the polymer film according to this disclosure, the number density of the filler is preferably greater inside the polymer film than on the surface, from the viewpoint of the coefficient of linear expansion and adhesion to the metal layer.

[0065] 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. Among these, from the viewpoint of the coefficient of linear expansion and adhesion to the metal layer, metal oxide particles or fibers are preferred as inorganic fillers, silica particles, titania particles, or glass fibers are more preferred, and silica particles or glass fibers are particularly preferred. The average particle size of the inorganic filler is preferably about 20% to about 40% of the thickness of layer A, for example, a particle size of 25%, 30%, or 35% of the thickness of layer A may be selected. If the particles or fibers are flattened, the length in the short side direction is indicated. Furthermore, 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 the coefficient of linear expansion and adhesion to the metal layer.

[0066] 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, from the viewpoint of the coefficient of linear expansion and adhesion to the metal layer, the organic filler is preferably fluororesin particles, polyester resin particles, polyethylene particles, liquid crystal polymer particles, or cellulose resin nanofibers, and more preferably polytetrafluoroethylene particles, polyethylene particles, or liquid crystal polymer particles. 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 the coefficient of linear expansion and adhesion to the metal layer.

[0067] The polymer film may contain only one type of filler or two or more types. The filler content in the polymer film is preferably 5% to 80% by volume, more preferably 10% to 70% by volume, even more preferably 15% to 70% by volume, and particularly preferably 20% to 60% by volume, based on the total volume of the polymer film, from the viewpoint of thermal expansion coefficient and adhesion to the metal layer.

[0068] -Other additives- The polymer film may contain other additives besides the components described above. Other known additives can be used. Specifically, examples include leveling agents, defoaming agents, antioxidants, UV absorbers, flame retardants, and colorants.

[0069] Furthermore, the polymer film may also contain other resins as additives, other than specific polymers and compounds with a dielectric loss tangent of less than 0.01. Other examples of resins 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.

[0070] The total content of other additives in the polymer film 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 the specific polymer per 100 parts by mass.

[0071] Furthermore, the polymer film relating to this disclosure may have a multilayer structure. For example, the polymer film according to this disclosure may have a structure comprising a layer A containing a specific polymer and a compound having a dielectric loss tangent of less than 0.01, and a layer B on at least one side of layer A, or it may have a structure comprising layer B, a layer A containing a specific polymer and a compound having a dielectric loss tangent of less than 0.01, and a layer C in that order. In particular, it is preferable that layer A contains particles or further contains fillers, as a compound having a dielectric loss tangent of less than 0.01. Furthermore, it is preferable that each layer B and layer C independently contain a specific polymer, and more preferably that they contain a specific polymer and a compound having a dielectric loss tangent of less than 0.01. Furthermore, it is preferable that the polymer contained in layer B has higher tensile strength (toughness) than the polymer contained in layer A. The fracture strength shall be measured by the following method. A sample consisting of the polymer to be measured is prepared, and the stress on elongation is measured using a Toyo Baldwin Co., Ltd. universal tensile testing machine "STM T50BP" at 25°C, 60% RH atmosphere, and a tensile speed of 10% / min to determine the breaking strength. Furthermore, the following methods can be used to detect or determine the layer structure and the thickness of each layer in a polymer film. First, a cross-sectional sample of the polymer film is cut using a microtome, and the layer structure and the thickness of each layer are determined using an optical microscope. If determination is difficult with an optical microscope, morphological observation using a scanning electron microscope (SEM) or component analysis using time-of-flight secondary ion mass spectrometry (TOF-SIMS) may be performed to determine the structure.

[0072] Furthermore, if layer B or layer C is a layer that comes into contact with the metal layer as part of a laminate, it is preferable that it contains a compound having a functional group described later, and more preferably that it contains a compound having a curing reaction-capable group described later. The functional group is preferably at least one group selected from the group consisting of covalently bondable groups, ionically bondable groups, hydrogen bondable groups, dipole interacting groups, and curing reaction-capable groups. The compound having a functional group may be a low-molecular-weight compound or a high-molecular-weight compound. From the viewpoint of compatibility between the polymer and the compound having the functional group, and the dielectric loss tangent of the polymer film, the compound having the functional group is preferably a low molecular weight compound, while from the viewpoint of heat resistance and mechanical strength of the polymer film, it is preferably a high molecular weight compound. The number of functional groups in a compound having functional groups may be one or more, or two or more, but it is preferable that it be two or more. Furthermore, from the viewpoint of setting an appropriate amount of functional groups and reducing the dielectric loss tangent of the polymer film, it is preferable that the number be 10 or less. Furthermore, a compound having a functional group may have only one functional group or two or more functional groups.

[0073] As for low molecular weight compounds used as compounds having functional groups, from the viewpoint of adhesion to the metal layer, a molecular weight of 50 or more and less than 2,000 is preferred, a molecular weight of 100 or more and less than 1,000 is more preferred, and a molecular weight of 200 or more and less than 1,000 is particularly preferred. When the compound having a functional group is a low-molecular-weight compound, the compound's spread is narrow, and in order to increase the probability of contact between functional groups, it is preferable that the compound having a functional group be present in an amount of 10% by mass or more relative to the total mass of layer B. Furthermore, as a polymer compound used as a compound having a functional group, from the viewpoint of adhesion to the metal layer, it is preferable that the polymer has a weight-average molecular weight of 1,000 or more, more preferably a polymer with a weight-average molecular weight of 2,000 or more, even more preferably a polymer with a weight-average molecular weight of 3,000 to 1,000,000, and particularly preferably a polymer with a weight-average molecular weight of 5,000 to 200,000.

[0074] Furthermore, from the viewpoint of the dielectric loss tangent of the polymer film and adhesion to the metal layer, it is preferable that the polymer having a dielectric loss tangent of 0.005 or less and the compound having a functional group are compatible. The difference between the Hoy method SP value of the above polymer and the Hoy method SP value of the compound having a functional group is 5 MPa, from the viewpoint of compatibility between the polymer with a dielectric loss tangent of 0.005 or less and the compound having a functional group, the dielectric loss tangent of the polymer film, and adhesion to the metal layer. 0.5 The following is preferable. The lower limit is 0 MPa. 0.5 That is the case.

[0075] The SP value (solubility parameter value) using the Hoy method is calculated from the molecular structure of the resin using the method described in the Polymer Handbook fourth edition. If the resin is a mixture of multiple resins, the SP value is calculated separately for each constituent unit.

[0076] <<Functional group>> In a compound having a functional group, it is preferable that the functional group is at least one group selected from the group consisting of covalently bondable groups, ionically bondable groups, hydrogen bondable groups, dipole interacting groups, and curing reaction-capable groups. From the viewpoint of adhesion between layer C and the metal layer, the functional group is preferably a covalently bondable group or a curing reaction-capable group, and more preferably a covalently bondable group. Furthermore, from the viewpoint of storage stability and handling ease, it is preferable that the functional group is a group capable of ionic bonding, a group capable of hydrogen bonding, or a group capable of dipole interaction.

[0077] -Covalently bondable group- There are no particular restrictions on the covalently bondable group as long as it is a group capable of forming a covalent bond. Examples include epoxy groups, oxetanyl groups, isocyanate groups, acid anhydride groups, carbodiimide groups, N-hydroxyester groups, glyoxal groups, imide ester groups, alkyl halogenates, thiol groups, hydroxyl groups, carboxyl groups, amino groups, amide groups, isocyanate groups, aldehyde groups, and sulfonic acid groups. Among these, from the viewpoint of adhesion between layer C and the metal layer, it is preferable that at least one functional group is selected from the group consisting of epoxy groups, oxetanyl groups, N-hydroxyester groups, isocyanate groups, imide ester groups, alkyl halogenates, and thiol groups, with epoxy groups being particularly preferred.

[0078] Furthermore, as will be described later, it is preferable that the surface of the metal bonded to layer C has a group that pairs with the functional group of the compound having a functional group. Examples of combinations between a covalently bondable group and a group that pairs with it (a combination between a functional group in a compound having a functional group and a group on the surface of a metal) include, for example, when one of the groups is an epoxy group or an oxetanyl group, the other group may be a hydroxyl group, an amino group, etc. Furthermore, if one of the above combinations is, for example, an N-hydroxyester group or an imide ester group, the other may be an amino group, etc.

[0079] -Ionically bondable group- Examples of groups capable of ionic bonding include cationic groups and anionic groups. The cationic group described above is preferably an onium group. Examples of onium groups include ammonium, pyridinium, phosphonium, oxonium, sulfonium, selenonium, and iodonium groups. Among these, from the viewpoint of adhesion between layer C and the metal layer, ammonium, pyridinium, phosphonium, or sulfonium groups are preferred, ammonium or phosphonium groups are more preferred, and ammonium groups are particularly preferred. There are no particular restrictions on the anionic group, and examples include phenolic hydroxyl groups, carboxyl groups, -SO3H, -OSO3H, -PO3H, -OPO3H2, -CONHSO2-, -SO2NHSO2-, etc. Among these, a phosphate group, phosphonic acid group, phosphinic acid group, sulfate group, sulfonic acid group, sulfinic acid group, or carboxyl group is preferred, a phosphate group or a carboxyl group is more preferred, and a carboxyl group is even more preferred.

[0080] Examples of combinations of ionically bondable groups and their counterparts (combinations of functional groups in a compound and groups on the surface of a metal) include cases where one group is acidic and the other is basic. Examples of the above-mentioned acidic groups include carboxyl groups, sulfol groups, and phosphate groups, with carboxyl groups being preferred. Furthermore, if one of the above combinations is, for example, a carboxyl group, then groups that can ionically bond with the carboxyl group include tertiary amino groups, pyridyl groups, piperidyl groups, and so on.

[0081] -Hydrogen-bondable groups- Examples of hydrogen-bonding-capable groups include groups having a hydrogen bond-donating site and groups having a hydrogen bond-accepting site. The above-mentioned hydrogen bond donating site may be any structure having an active hydrogen atom capable of forming hydrogen bonds, but it is preferably a structure represented by XH. X represents a heteroatom, preferably a nitrogen atom or an oxygen atom. From the viewpoint of adhesion between layer C and the metal layer, the hydrogen bond donating site is preferably at least one structure selected from the group consisting of a hydroxyl group, carboxyl group, primary amide group, secondary amide group, primary amino group, secondary amino group, primary sulfonamide group, secondary sulfonamide group, imide group, urea bond, and urethane bond; more preferably at least one structure selected from the group consisting of a hydroxyl group, carboxyl group, primary amide group, secondary amide group, primary sulfonamide group, secondary sulfonamide group, maleimide group, urea bond, and urethane bond; even more preferably at least one structure selected from the group consisting of a hydroxyl group, carboxyl group, primary amide group, secondary amide group, primary sulfonamide group, secondary sulfonamide group, and maleimide group; and particularly preferably at least one structure selected from the group consisting of a hydroxyl group and a secondary amide group.

[0082] The hydrogen bond accepting site is preferably a structure containing an atom with a lone pair of electrons, more preferably a structure containing an oxygen atom with a lone pair of electrons, more preferably at least one structure selected from the group consisting of carbonyl groups (including carbonyl structures such as carboxyl groups, amide groups, imide groups, urea bonds, and urethane bonds) and sulfonyl groups (including sulfonyl structures such as sulfonamide groups), and particularly preferably a carbonyl group (including carbonyl structures such as carboxyl groups, amide groups, imide groups, urea bonds, and urethane bonds).

[0083] The hydrogen-bonding group is preferably a group having both a hydrogen bond donating site and a hydrogen bond accepting site, and is preferably a carboxyl group, amide group, imide group, urea bond, urethane bond, or sulfonamide group, and more preferably a carboxyl group, amide group, imide group, or sulfonamide group.

[0084] Combinations of a hydrogen-bonding group and a group that is paired with the hydrogen-bonding group (combinations of a functional group in a compound having a functional group and a group on the surface of a metal) include cases where one group has a hydrogen bond-donating site and the other group has a hydrogen bond-accepting site. For example, if one of the above combinations is a carboxyl group, examples include an amide group, a carboxyl group, etc. Furthermore, if one of the above combinations is, for example, a phenolic hydroxyl group, the other can be a phenolic hydroxyl acid, etc.

[0085] -A dipole-interacting group- The dipole-interacting group can be any group having a polarized structure other than the XH structure (where X represents a heteroatom, such as a nitrogen atom or an oxygen atom) in the hydrogen-bonding group described above, and groups in which atoms with different electronegativity are bonded are preferred. As for combinations of atoms with different electronegativity, a combination of at least one atom selected from the group consisting of oxygen atoms, nitrogen atoms, sulfur atoms, and halogen atoms with a carbon atom is preferred, and a combination of at least one atom selected from the group consisting of oxygen atoms, nitrogen atoms, and sulfur atoms with a carbon atom is more preferred. Among these, from the viewpoint of adhesion between layer C and the metal layer, combinations of nitrogen atoms and carbon atoms, and combinations of carbon atoms with nitrogen atoms, oxygen atoms, and sulfur atoms are preferred, and specifically, cyano groups, cyanuric groups, and sulfonate amide groups are more preferred.

[0086] As for combinations of dipole-interacting groups and groups that are paired with the above-mentioned dipole-interacting groups (combinations of functional groups in a compound having a functional group and groups on the surface of a metal), combinations of the same dipole-interacting groups are preferred. If one of the above combinations is, for example, a cyano group, then the other can be a cyano group. Furthermore, if one of the above combinations is, for example, a sulfonic acid amide group, the other can also be a sulfonic acid amide group.

[0087] -Cureable group- Examples of groups that can undergo curing reactions include ethylenically unsaturated groups, cyclic ether groups, cyanate groups, reactive silyl groups, oxazine ring groups, and urethane groups. As compounds having a group capable of curing, the following curable compounds may be used.

[0088] ~Curing compound~ Curable compounds are compounds that harden upon irradiation with heat or light (e.g., visible light, ultraviolet light, near-infrared light, far-infrared light, electron beams, etc.), and may require a curing aid as described later. Examples of such curable compounds include epoxy compounds, cyanate ester compounds, vinyl compounds, silicone compounds, oxazine compounds, maleimide compounds, allyl compounds, acrylic compounds, methacrylic compounds, and urethane compounds. These may be used individually or in combination of two or more. Among these, from the viewpoint of compatibility with the polymer and heat resistance, it is preferable to use at least one selected from the group consisting of epoxy compounds, cyanate ester compounds, vinyl compounds, silicone compounds, oxazine compounds, maleimide compounds, and allyl compounds, and more preferably at least one selected from the group consisting of epoxy compounds, cyanate ester compounds, vinyl compounds, allyl compounds, and silicone compounds. The content of the curable compound in layer B is preferably 10% by mass or more and 90% by mass or less, and more preferably 20% by mass or more and 80% by mass or less, based on the total mass of layer C.

[0089] ~Hardening aid~ Examples of curing aids include polymerization initiators such as photoreaction initiators (photoradical generators, photoacid generators, and photobase generators). Specific examples of curing aids include onium salt compounds, sulfone compounds, sulfonic acid ester compounds, sulfonimide compounds, disulfonyldiazomethane compounds, disulfonylmethane compounds, oxime sulfonate compounds, hydrazine sulfonate compounds, triazine compounds, nitrobenzyl compounds, benzylimidazole compounds, organic halides, octoyl metal salts, and disulfones. These curing aids may be used individually or in combination of two or more types, regardless of their type. The content of the curing aid in layer B is preferably 5% by mass or more and 20% by mass or less, and more preferably 5% by mass or more and 10% by mass or less, based on the total mass of layer B.

[0090] In compounds having a functional group, the functional group preferably includes at least one selected from the group consisting of epoxy group, oxetanyl group, isocyanate group, acid anhydride group, carbodiimide group, N-hydroxyester group, glyoxal group, imide ester group, halogenated alkyl group, thiol group, hydroxyl group, carboxyl group, amino group, amide group, isocyanate group, aldehyde group, sulfonic acid group, ammonium group, pyridinium group, phosphonium group, oxonium group, sulfonium group, selenonium group, iodonium group, phosphate group, phosphonic acid group, phosphinic acid group, sulfate group, sulfonic acid group, sulfinic acid group or carboxyl group, hydroxyl group, carboxyl group, primary amide group, secondary amide group, primary amino group, secondary amino group, primary sulfonamide group, secondary sulfonamide group, imide group, urea bond, and urethane bond. From the viewpoint of improving adhesion, epoxy groups, oxetanyl groups, isocyanate groups, acid anhydride groups, carbodiimide groups, N-hydroxyester groups, glyoxal groups, imide ester groups, halogenated alkyl groups, or thiol groups are more preferred.

[0091] Specific examples of bonding or interaction between two functional groups are shown below, but the bonding or interaction described herein is not limited to these examples.

[0092] [ka]

[0093] From the viewpoint of the dielectric loss tangent of the polymer film and adhesion to the metal layer, the compound having a functional group is preferably a polyfunctional epoxy compound or a polymer of a polyfunctional epoxy compound, more preferably a difunctional epoxy compound or a polymer of a difunctional epoxy compound, and particularly preferably a difunctional epoxy compound.

[0094] Layer B or Layer C may contain only one compound having a functional group, or it may contain two or more compounds having a functional group. The content of the functional group compound in layer B or layer C is preferably 1% to 80% by mass, more preferably 5% to 70% by mass, even more preferably 10% to 60% by mass, and particularly preferably 20% to 60% by mass, based on the total mass of the polymer film, from the viewpoint of the dielectric loss tangent of the polymer film and adhesion to the metal layer.

[0095] The average thickness of layer A is not particularly limited, but from the viewpoint of thermal expansion coefficient and adhesion to the metal layer, it is preferably 5 μm to 90 μm, more preferably 10 μm to 70 μm, and particularly preferably 15 μm to 50 μm.

[0096] The method for measuring the average thickness of each layer in the polymer film relating to this disclosure is as follows: The polymer film is cut using 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.

[0097] The average thickness of layer B and layer C is preferably thinner than the average thickness of layer A, from the viewpoint of thermal expansion coefficient and adhesion to the metal layer. Average thickness T of layer AA 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 the coefficient of thermal expansion and adhesion to the metal layer. 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 the coefficient of thermal expansion and adhesion to the metal layer. 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 the metal layer. Furthermore, the average thickness of layer B and 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 layer.

[0098] The average thickness of the polymer film relating to this disclosure is preferably 6 μm to 200 μm, more preferably 12 μm to 100 μm, and particularly preferably 20 μm to 60 μm, from the viewpoint of strength, coefficient of thermal expansion, and adhesion to the metal layer.

[0099] The average thickness of the polymer 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.

[0100] The dielectric loss tangent of the polymer film relating to this disclosure is preferably 0.005 or less, more preferably 0.002 or less, even more preferably 0.001 or less, and particularly preferably greater than 0 and 0.001 or less, from the viewpoint of dielectric constant.

[0101] The linear expansion coefficient of the polymer 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, and particularly preferably 10 ppm / K to 30 ppm / K, from the viewpoint of the thermal expansion coefficient.

[0102] The method for measuring the coefficient of linear expansion in this disclosure shall be as follows: Using a thermomechanical analyzer (TMA), a tensile load of 1g is applied to both ends of a polymer film or sample of each layer measuring a polymer film with a width of 5mm and a length of 20mm. The temperature is then raised at a rate of 5°C / min from 25°C to 200°C, 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 linear expansion is calculated from the slope of the TMA curve between 30°C and 150°C. When measuring each layer, you may prepare a measurement sample by scraping off the layer to be measured with a razor or similar tool. Furthermore, if it is difficult to measure the coefficient of linear expansion using the method described above, the following method shall be used for measurement. A polymer film can be prepared by cutting it with a microtome to create section samples, which are then placed in an optical microscope equipped with a heating stage system (HS82, Mettler Toledo). Subsequently, the temperature is increased at a rate of 5°C / min from 25°C to 200°C, then cooled to 30°C at a rate of 20°C / min, and then heated again at a rate of 5°C / min. The thickness of the polymer film or each layer at 30°C (ts30) and the thickness of the polymer film or each layer at 150°C (ts150) are evaluated, and the coefficient of linear expansion of the polymer film or each layer can be calculated by dividing the dimensional change by the temperature change ((ts150-ts30) / (150-30)).

[0103] <Method for manufacturing polymer films> [Film forming] The method for manufacturing the polymer film relating to this disclosure is not particularly limited and may refer to known methods. Suitable methods for manufacturing the polymer film according to this disclosure include, for example, casting, coating, and extrusion. Among these, casting is particularly preferred. Furthermore, if the polymer 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 for relatively thin films, and co-extrusion is particularly preferred for thick films. When producing a multilayer structure in a polymer film by co-casting and layer coating, 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, such as a specific polymer and a compound with a dielectric loss tangent of less than 0.01, in a solvent, and then perform the co-casting or layer coating method.

[0104] 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.

[0105] As a solvent, it is preferable to include an aprotic compound (particularly preferably an aprotic compound without halogen atoms) because it is less corrosive and 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, as the above aprotic compound, it is preferable to include amides such as N,N-dimethylformamide, N,N-dimethylacetamide, tetramethylurea, N-methylpyrrolidone, or esters such as γ-butyrolactone, because they readily dissolve liquid crystal polymers, and N,N-dimethylformamide, N,N-dimethylacetamide, or N-methylpyrrolidone are more preferable.

[0106] Furthermore, the solvent preferably contains a compound with a dipole moment of 3 to 5, as it readily dissolves specific polymers. 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.

[0107] Furthermore, the solvent preferably contains a compound with a boiling point of 220°C or lower at 1 atmosphere, as it is easy to remove. The proportion of the compound with a boiling point of 220°C or lower at 1 atmosphere 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.

[0108] Furthermore, when the polymer film is manufactured by the co-casting method, multi-layer coating method, co-extrusion method, etc., as described above, a support may be used. Also, when a metal layer (metal foil) used in the laminate described later is used as a support, it may be used as is without peeling. Examples of support materials include metal drums, metal bands, glass plates, resin films, or metal foils. Among these, metal drums, metal bands, and resin films are preferred. Examples of resin films include polyimide (PI) films, and commercially available examples 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. The surface treatment layer can be made of hard chrome plating, fluororesin, or the like. 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.

[0109] Furthermore, there are no particular limitations on the method for removing at least a portion of the solvent from the cast or coated film-like composition (cast film or coating film), and known drying methods can be used.

[0110] [Stretching] The polymer film 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 the film and stretching it, or by utilizing the self-shrinking force of the web due to drying without stretching, or a combination of these. Stretching is particularly effective for improving the elongation at break and tensile strength when the film brittleness is reduced by the addition of inorganic fillers, etc.

[0111] [Heat treatment] The method for producing a polymer film according to this disclosure preferably includes a step of heat treatment (annealing) of the polymer film. The heat treatment temperature in the above heat treatment process is preferably below the melting point Tm of the specific polymer, and more preferably above the melting point of the compound with a dielectric loss tangent of less than 0.01 and below the melting point of the specific polymer, from the viewpoint of the mechanical strength of the web during the manufacturing process and the breaking strength of the manufactured polymer film. Furthermore, if the compound having a dielectric loss tangent of less than 0.01 is a polymer having a melting point higher than the melting point Tm of the specific polymer, the heat treatment temperature in the above heat treatment step is preferably a temperature exceeding the melting point of the specific polymer, and more preferably a temperature exceeding the melting point of the specific polymer and below the melting point Tm of the compound having a dielectric loss tangent of less than 0.01, from the viewpoint of fracture strength. Furthermore, the heat treatment temperature in the above heat treatment process is more preferably 260°C to 370°C, and particularly preferably 310°C to 350°C, from the viewpoint of fracture strength. The annealing time is preferably 30 minutes to 5 hours, and more preferably 30 minutes to 3 hours. Furthermore, the method for producing a polymer film according to this disclosure may include other known steps as necessary.

[0112] <Application> The polymer film according to this disclosure can be used for various applications, and is particularly suitable for use as a film for electronic components such as printed wiring boards, and is especially suitable for use as a flexible printed circuit board. Furthermore, the polymer film according to this disclosure can be suitably used as a polymer film for metal bonding.

[0113] (Laminated structure) The laminate according to this disclosure may be any laminate in which polymer films according to this disclosure are laminated, but it is preferable that it has a polymer film according to this disclosure and a metal layer disposed on at least one surface of the polymer film, and it is more preferable that it has a polymer film according to this disclosure and copper layers disposed on both sides of the polymer film. Furthermore, it is more preferable that the metal layer is a copper layer. Furthermore, the laminate according to the present disclosure preferably comprises a polymer film having layer B, layer A, and layer C in that order, a metal layer disposed on the layer B side of the polymer film, and a metal layer disposed on the layer C side of the polymer film, and it is more preferable that all of the metal layers are copper layers. The metal layer positioned on the side of layer B is preferably a metal layer positioned on the surface of layer B. 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. 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, thickness, and shape, or they may be made of different materials, 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 thicknesses, and the metal layer may be laminated on only one side of layer B or C.

[0114] There are no particular limitations on the method for bonding the polymer film and the metal layer according to this disclosure, and known lamination methods can be used.

[0115] The peel strength between the polymer film 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.

[0116] In this disclosure, the peel strength between the polymer 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 a polymer film and a metal layer. The polymer film was fixed to a flat plate with double-sided adhesive tape, and the strength (kN / m) of peeling the polymer film from the metal layer at a speed of 50 mm / min using the 180° method in accordance with JIS C 5016 (1994) was measured.

[0117] The surface roughness Rz of the metal layer in contact with the polymer film is preferably 1 μm to 10 μm, more preferably 1 μm to 5 μm, and particularly preferably 1.5 μm to 3 μm if there is no layer C containing the compound having the functional group. If there is a layer C containing the compound having the functional group, from the viewpoint of reducing transmission loss of high-frequency signals, it is preferably less than 1 μm, more preferably 0.5 μm or less, and particularly preferably 0.3 μm or less.

[0118] In this disclosure, "surface roughness Rz" means the sum of the maximum peak height and maximum valley depth observed in the roughness curve at a reference length, expressed in micrometers. In this disclosure, the surface roughness Rz of a metal layer (e.g., a copper layer) shall be measured by the following method. Using the VertScan non-contact surface and layer cross-sectional shape measurement system (manufactured by Ryoka Systems Co., Ltd.), a 465.48 μm x 620.64 μm area is measured to create a roughness curve and an average line of the roughness curve on the surface of the object to be measured (metal layer). A portion corresponding to a reference length is extracted from the roughness curve. The surface roughness Rz of the object to be measured is determined by finding the sum of the maximum peak height (i.e., the height from the average line to the peak) and the maximum valley depth (i.e., the height from the average line to the valley bottom) observed in the extracted roughness curve.

[0119] 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.

[0120] The average thickness of the metal layer, preferably the 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.

[0121] 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]

[0122] 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.

[0123] <<Measurement Method>> [Dielectric loss tangent] Dielectric constant measurements were performed using the resonant perturbation method at a frequency of 10 GHz. A 10 GHz cavity resonator (CP531, manufactured by Kanto Electronics Applied Development Co., Ltd.) was connected to a network analyzer (E8363B, manufactured by Agilent Technology). A polymer film or sample of each layer (width: 2.0 mm x length: 80 mm) was inserted into the cavity resonator, and the dielectric constant and dielectric loss tangent of the polymer film or each layer were measured from the change in resonant frequency before and after insertion over 96 hours under conditions of 25°C and 60% RH.

[0124] [Enthalpy of crystallization ΔHc (Cold crystallization peak heat)] A polymer film was placed in the measurement pan of a differential scanning calorimetry (DSC) instrument, and the heat of the exothermic peak observed when the film was heated from 25°C to 350°C at a rate of 20°C / min in a nitrogen stream was defined as the film's ΔHc. The assignment of the exothermic peaks was performed by isolating the materials constituting the film and separately measuring them using DSC under the same conditions to determine the exothermic peak temperatures originating from each material.

[0125] [Breaking strength] A 150mm x 10mm sample was cut from the prepared polymer film, and the stress on elongation was measured using a Toyo Baldwin Co., Ltd. universal tensile testing machine "STM T50BP" at 25°C, 60%RH atmosphere, and a tensile speed of 10% / min to determine the breaking strength.

[0126] <<Manufacturing Example>> <Liquid crystal polymer> LC-A: A liquid crystal polymer prepared by adjusting the monomer addition ratio and thermal polymerization conditions, based on the production method of liquid crystal polyester (B) described in Comparative Example 2 of International Publication No. 2020 / 166644. LC-C: Liquid crystal polymer (dielectric loss tangent 0.004) manufactured according to the following manufacturing method.

[0127] -LC-C 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 resulting solid was pulverized to obtain powdered liquid crystal polyester (C1).

[0128] The liquid crystal polyester (C1) 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 then pulverized with a pulverizer to obtain powdered liquid crystal polyester (C2).

[0129] The liquid crystal polyester (C2) 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 (C) (LC-C) was obtained.

[0130] LC-D: Liquid crystal polymer (dielectric loss tangent 0.004) manufactured according to the following manufacturing method.

[0131] -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 the mixture was 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).

[0132] 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).

[0133] LC-E: Commercially available liquid crystal polymer resin (A-8100, manufactured by Ueno Pharmaceutical Co., Ltd.) 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)

[0134] <Compounds with a dielectric loss tangent of less than 0.01> LC-B: Commercially available liquid crystal polymer resin powder (Vectra A950, manufactured by Polyplastics Co., Ltd., liquid crystal polyester) A-1: 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 polymer film was as shown in Table 1. A-2: Copolymer (PFA) particles of tetrafluoroethylene and perfluoroalkoxyethylene (melting point 280°C, average particle size 0.2 μm to 0.5 μm, dielectric loss tangent 0.001) A-3: Commercially available ultra-high molecular weight polyethylene particles with an average particle size of 10 μm (Mipelon PM200, manufactured by Mitsui Chemicals, Inc.) were used so that the solid content was as shown in Table 1.

[0135] <Curable compound> M-1: A commercially available aminophenol-type epoxy resin (jER630LSD, manufactured by Mitsubishi Chemical Corporation) was used.

[0136] <Film forming> The film was formed according to the casting procedure described below.

[0137] [Casting A (solution casting)] -Preparation of polymer solutions- The specific polymers listed in Table 1 and the compounds with a dielectric loss tangent of less than 0.01 listed in Table 1 were added to N-methylpyrrolidone and stirred at 140°C for 4 hours under a nitrogen atmosphere to obtain a liquid crystal polymer solution. The liquid crystal polymer and the compounds with a dielectric loss tangent of less than 0.01 were added in the mass ratios listed in Table 1, and the solid content concentration was 23% by mass. Next, the polymer solution was obtained by first passing it 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.

[0138] -Film Production- The obtained polymer solution was fed into a casting die and cast onto the roughened surface of copper foil (3EC-VLP manufactured by Mitsui Mining & Smelting Co., Ltd., 18 μm thick, surface roughness Rz 3.0 μm). The solvent was removed from the cast film by drying at 40°C for 4 hours. Further heat treatment was performed under a nitrogen atmosphere by raising the temperature from room temperature (25°C) to the annealing temperature listed in Table 1 at a rate of 1°C / min and holding it at that temperature for 2 hours to obtain a polymer film (laminated) having a copper layer. As shown in Table 1, no annealing (heat treatment) was performed in Comparative Example 1.

[0139] [Casting B (solution casting)] -Preparation of Polymer Solution A- The specific polymers listed in Table 1 were added to N-methylpyrrolidone and stirred under a nitrogen atmosphere at 140°C for 4 hours to obtain a polymer solution with a solid content of 8% by mass. Next, the solution was passed 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. Furthermore, compounds with a dielectric loss tangent of less than 0.01, as listed in Table 1, were added in the mass ratios listed in Table 1, and the mixture was thoroughly stirred to obtain polymer solution A.

[0140] -Preparation of polymer solution C- In the preparation of polymer solution A, the compound with a dielectric loss tangent of less than 0.01 was replaced with the curable compound M-1, and the mass ratio of the polymer to M-1 listed in Table 1 was set to 95:5. The procedure was carried out in the same manner as the preparation of polymer solution A to obtain polymer solution C.

[0141] -Film Production- The obtained polymer solutions A and C were fed into a casting die and cast onto the treated side of a copper foil (Fukuda Metal Foil & Powder Industry Co., Ltd., CF-T9DA-SV-18, 18 μm thick, surface roughness Rz 0.85 μm) to form a layer structure of copper foil / polymer solution C (3 μm thick after drying) / polymer solution A. The solvent was removed from the cast film by drying at 40°C for 4 hours, and then a heat treatment was performed under a nitrogen atmosphere by raising the temperature from room temperature (25°C) to the annealing temperature listed in Table 1 at a rate of 1°C / min and holding it at that temperature for 2 hours to obtain a polymer film (laminated) having a copper layer. Note that the average thickness listed in Table 1 includes the thickness of layer C.

[0142] [Multi-layer application] -Preparation of polymer solutions- The polymers listed in Table 1 and the compounds with a dielectric loss tangent of less than 0.01 listed in Table 1 were added to toluene to a solid content concentration of 80%, and the mixture was stirred for 60 minutes to obtain polymer solution A.

[0143] -Film Production- The obtained polymer solution was fed into a slot die coater and applied 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). Subsequently, the solvent was removed from the coating by drying at 100°C for 3 minutes, then at 170°C for 3 minutes. A heat treatment was then 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 polymer film (laminated) having a copper layer.

[0144] <<Rating>> The polymer film obtained by peeling the copper layer from the fabricated laminate was evaluated using the method described above, and the results are shown in Table 1. Furthermore, 1.0 cm wide peel test pieces were cut from the polymer film and copper layer laminates prepared in each example. The polymer film was fixed to a flat plate with double-sided adhesive tape, and the copper layer was peeled from the polymer film at a speed of 50 mm / min using the 180° method in accordance with JIS C 5016 (1994). It was confirmed that sufficient adhesion of 5 kN / m or more was obtained in each case. Furthermore, it was confirmed that the ΔHc value for all films in Examples 3 to 5 was 0 J / g.

[0145] [Table 1]

[0146] As shown in Table 1, the polymer films of Examples 1 to 13, which are polymer films according to this disclosure, have a smaller dielectric loss tangent and superior tensile strength compared to the polymer film of Comparative Example 1. In addition, in Comparative Example 2, layers A and C failed to maintain their shape during heat treatment, and a polymer film could not be produced.

Claims

1. Liquid crystal polymer A, and The compound comprises a compound whose melting point is 30°C to 100°C lower than the melting point of the liquid crystal polymer A, and whose dielectric loss tangent is less than 0.

01. The liquid crystal polymer A is a soluble liquid crystal 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. Liquid crystal polymer film.

2. The liquid crystal polymer film according to claim 1, wherein the melting point of the liquid crystal polymer A is 280°C or higher.

3. The liquid crystal polymer film according to claim 1 or claim 2, wherein the liquid crystal polymer A has a constituent unit represented by any one of formulas (1) to (3). Equation (1) -O-Ar １ -CO- Formula (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 the following formula (4): 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. Formula (4) -Ar ４ -Z-Ar ５ - In formula (4), Ar ４ and Ar ５ Each of these 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.

4. The liquid crystal polymer film according to any one of claims 1 to 3, wherein the compound having a dielectric loss tangent of less than 0.01 is a polymer.

5. The liquid crystal polymer film according to any one of claims 1 to 4, wherein the compound having a dielectric loss tangent of less than 0.01 is liquid crystal polymer B having a melting point lower than that of liquid crystal polymer A and a dielectric loss tangent of less than 0.

01.

6. The liquid crystal polymer film according to any one of claims 1 to 5, wherein the compound having a dielectric loss tangent of less than 0.01 is a particle.

7. The liquid crystal polymer film according to any one of claims 1 to 6, wherein the compound having a dielectric loss tangent of less than 0.01 is a fluorine-based polymer.

8. The liquid crystal polymer film according to any one of claims 1 to 7, wherein the content of the compound having a dielectric loss tangent of less than 0.01 is 10% by mass to 90% by mass with respect to the total mass of the liquid crystal polymer film.

9. The liquid crystal polymer film according to any one of claims 1 to 8, wherein the dielectric loss tangent of the liquid crystal polymer film is 0.001 or less.

10. The liquid crystal polymer film according to any one of claims 1 to 9, wherein the coefficient of linear thermal expansion of the liquid crystal polymer film is -20 ppm / K to 50 ppm / K.

11. A laminate comprising a liquid crystal polymer film according to any one of claims 1 to 10 and a metal layer disposed on at least one surface of the liquid crystal polymer film.

12. The laminate according to claim 11, having metal layers disposed on both sides of the liquid crystal polymer film.

13. The aforementioned metal layer is a copper layer, The laminate according to claim 11 or claim 12, wherein the peel strength between the liquid crystal polymer film and the copper layer is 0.5 kN / m or more.

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