Polymer films and laminates

Abstract

Provided are a polymer film having excellent substrate adhesion, and a laminate using the polymer film. This polymer film has a layer A and a layer B on at least one surface of the layer A. The layer B includes: a polymer or a liquid crystal polymer having a dielectric loss tangent of no more than 0.01 or no more than 0.005; and a compound having a functional group. The functional group is at least one type of group selected from the group consisting of groups that can form a covalent bond, groups that can form an ionic bond, groups that can form a hydrogen bond, groups that can participate in a dipole interaction, and groups that can be involved in a curing reaction.

Description

[Technical Field]

[0001] The present disclosure relates to polymer films and laminates. [Background technology]

[0002] In recent years, the frequencies used in communication devices have tended to become very high. To suppress transmission loss in high-frequency bands, it has become necessary to lower the relative permittivity and dielectric loss tangent of insulating materials used in circuit boards. Conventionally, polyimide has been widely used as an insulating material for circuit boards, but liquid crystal polymers have been attracting attention because of their high heat resistance, low water absorption, and low loss in the high frequency band.

[0003] As an example of a conventional liquid crystal polymer film, Patent Document 1 describes a liquid crystal polyester film containing at least a liquid crystal polyester, in which when a first orientation degree is an orientation degree in a first direction parallel to the main surface of the liquid crystal polyester film and a second orientation degree is an orientation degree in a second direction parallel to the main surface and perpendicular to the first direction, the ratio of the first orientation degree to the second orientation degree, i.e., first orientation degree / second orientation degree, is 0.95 or more and 1.04 or less, and the third orientation degree of the liquid crystal polyester measured by wide-angle X-ray scattering in a direction parallel to the main surface is 60.0% or more.

[0004] Furthermore, as a conventional functional film, the one described in Patent Document 2 is known. Patent Document 2 describes a laminate for high-frequency circuits, which is laminated with a resin layer containing a polymer and a curable compound and having excellent adhesion to a metal layer, and a metal foil. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2020-26474 [Patent Document 2] International Publication No. 2019 / 054334 Summary of the Invention [Problem to be solved by the invention]

[0006] The problem to be solved by the embodiments of the present invention is to provide a polymer film that has excellent adhesion to a substrate. Another problem to be solved by the embodiments of the present invention is to provide a laminate using the above polymer film. [Means for solving the problem]

[0007] The means for solving the above problems include the following aspects. <1> A polymer film having a layer A and a layer B on at least one surface of the layer A, wherein the layer B contains a polymer having a dielectric tangent of 0.005 or less and a compound having a functional group, and the functional group is at least one type of group selected from the group consisting of a group capable of forming a covalent bond, a group capable of forming an ionic bond, a group capable of forming a hydrogen bond, a group capable of forming a dipole-dipole interaction, and a group capable of undergoing a curing reaction. <2> The melting point Tm or 5% mass loss temperature Td of the polymer having a dielectric dissipation factor of 0.005 or less is 200°C or higher. <1> The polymer film according to claim 1. <3> The polymer having a dielectric loss tangent of 0.005 or less has a glass transition temperature Tg of 200°C or higher. <1> The polymer film according to claim 1. <4> The polymer having a dielectric loss tangent of 0.005 or less is at least one polymer selected from the group consisting of a liquid crystal polymer, a fluorine-containing 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. <1> ~ <3> 10. The polymer film according to any one of the preceding items. <5> The functional group is a group capable of covalent bonding. <1> ~ <4> 10. The polymer film according to any one of the preceding items. <6> The covalently bondable group is at least one functional group selected from the group consisting of an epoxy group, an oxetanyl group, an isocyanate group, an acid anhydride group, a carbodiimide group, an N-hydroxyester group, a glyoxal group, an imide ester group, a halogenated alkyl group, and a thiol group. <5> The polymer film according to claim 1. <7> The functional group is a group capable of forming an ionic bond, a group capable of forming a hydrogen bond, or a group capable of forming a dipole-dipole interaction. <1> ~ <4> 10. The polymer film according to any one of the preceding items. <8> The polymer film contains a cured product of a multifunctional reactive compound. <1> ~ <7> 10. The polymer film according to any one of the preceding items. <9> The layer B contains a polymer having a functional group as the compound having a functional group. <1> ~ <8> 10. The polymer film according to any one of the preceding items. <10> The polymer having the functional group is a liquid crystal polymer precursor. <9> The polymer film according to claim 1. <11> The polymer having a dielectric loss tangent of 0.005 or less and the compound having a functional group are compatible with each other. <1> ~ <10> 10. The polymer film according to any one of the preceding items. <12> The difference between the SP value by the Hoy method of the polymer having a dielectric loss tangent of 0.005 or less and the SP value by the Hoy method of the compound having the functional group is 5 MPa 0.5 Below is the <1> ~ <11> 10. The polymer film according to any one of the preceding items. <13> The polymer having a dielectric loss tangent of 0.005 or less is a liquid crystal polymer having a constitutional unit represented by any one of formulas (1) to (3). <1> ~ <12> 10. The polymer film according to any one of the preceding items. 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 3each 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, 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 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. <14> The laminate further includes a layer C, and includes the layer B, the layer A, and the layer C in this order. <1> ~ <13> 10. The polymer film according to any one of the preceding items. <15> The dielectric loss tangent of the polymer film is 0.01 or less. <1> ~ <14> 10. The polymer film according to any one of the preceding items. <16> The dielectric loss tangent of the layer B is 0.02 or less. <1> ~ <15> 10. The polymer film according to any one of the preceding items. <17> The dielectric loss tangent of the layer C is 0.02 or less. <14> The polymer film according to claim 1. <18> A polymer film having a layer A and a layer B on at least one surface of the layer A, wherein the layer B contains a liquid crystal polymer and a compound having a functional group, and the functional group is at least one type of group selected from the group consisting of a group capable of forming a covalent bond, a group capable of forming an ionic bond, a group capable of forming a hydrogen bond, a group capable of forming a dipole-dipole interaction, and a group capable of undergoing a curing reaction. <19> A polymer film having a layer A and a layer B on at least one surface of the layer A, wherein the layer B contains a polymer having a dielectric dissipation factor of 0.01 or less and a compound having a functional group, and the functional group is at least one type of group selected from the group consisting of a group capable of forming a covalent bond, a group capable of forming an ionic bond, a group capable of forming a hydrogen bond, a group capable of forming a dipole-dipole interaction, and a group capable of undergoing a curing reaction. <20> The compound having the functional group interacts with, bonds to, or forms entanglements with the polymer having a dielectric loss tangent of 0.005 or less, the liquid crystal polymer, or the polymer having a dielectric loss tangent of 0.01 or less. <1> ~ <18> 10. The polymer film according to any one of the preceding items. <21> <1> ~ <19> 1. A laminate comprising the polymer film according to any one of 1 to 8 above and a metal layer disposed on at least one surface of the polymer film. <22> A metal layer is disposed on each side of the polymer film. <21> The laminate according to claim 1. <23> The surface roughness Rz of the metal layer on the side in contact with the polymer film is 5 μm or less. <21> or <22> The laminate according to claim 1. <24> The metal layer is a copper layer, and the peel strength between the polymer film and the copper layer is 0.5 kN / m or more. <21> ~ <23> 10. The laminate according to claim 9, wherein the first and second layers are laminates. <25> The copper layer has a group capable of interacting with the polymer film on the surface that contacts the polymer film. <21> ~ <24> 10. The laminate according to claim 9, wherein the first and second layers are laminates. <26> The interactable group is an amino group. <25> The laminate according to claim 1. [Effects of the Invention]

[0008] According to an embodiment of the present invention, a polymer film having excellent adhesion to a substrate can be provided. According to another embodiment of the present invention, a laminate using the above polymer film can be provided. DETAILED DESCRIPTION OF THE INVENTION

[0009] The present disclosure will be described in detail below. The following description of the components may be based on representative embodiments of the present disclosure, but the present disclosure is not limited to such embodiments. In this specification, the use of "to" to indicate a range of values ​​means that the values ​​before and after it are included as the lower and upper limits. In the numerical ranges described in stages in this disclosure, the upper or lower limit value described in one numerical range may be replaced with the upper or lower limit value of another numerical range described in stages. Furthermore, in the numerical ranges described in this disclosure, the upper or lower limit value of that numerical range may be replaced with a value shown in the examples. Furthermore, in the description of groups (atomic groups) in this specification, a description that does not specify whether it is substituted or unsubstituted includes both unsubstituted and substituted groups. For example, the term "alkyl group" includes not only alkyl groups that do not have a substituent (unsubstituted alkyl groups) but also alkyl groups that have a substituent (substituted alkyl groups). In this specification, "(meth)acrylic" is a term used as a concept that includes both acrylic and methacrylic, and "(meth)acryloyl" is a term used as a concept that includes both acryloyl and methacryloyl. Furthermore, the term "process" in this specification does not only refer to an independent process, but also includes a process that cannot be clearly distinguished from other processes as long as the intended purpose of the process is achieved. In addition, in the present disclosure, "mass %" and "wt %" are synonymous, and "parts by mass" and "parts by weight" are synonymous. Furthermore, in the present 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 the present disclosure are molecular weights calculated using a gel permeation chromatography (GPC) analyzer with a TSKgel SuperHM-H (trade name of Tosoh Corporation) column, a solvent of PFP (pentafluorophenol) / chloroform = 1 / 2 (mass ratio), detection with a differential refractometer, and conversion using polystyrene as a standard substance. The present disclosure will be described in detail below.

[0010] (polymer film) A first embodiment of a polymer film according to the present disclosure has a layer A and a layer B on at least one surface of the layer A, wherein the layer B contains a polymer having a dielectric tangent of 0.005 or less and a compound having a functional group, and the functional group is at least one type of group selected from the group consisting of a group capable of forming a covalent bond, a group capable of forming an ionic bond, a group capable of forming a hydrogen bond, a group capable of forming a dipole-dipole interaction, and a group capable of undergoing a curing reaction. A second embodiment of the polymer film according to the present disclosure has a Layer A and a Layer B on at least one surface of Layer A, wherein Layer B contains a polymer having a dielectric tangent of 0.01 or less and a compound having a functional group, and the functional group is at least one type of group selected from the group consisting of a group capable of forming a covalent bond, a group capable of forming an ionic bond, a group capable of forming a hydrogen bond, a group capable of forming a dipole-dipole interaction, and a group capable of undergoing a curing reaction. A third embodiment of the polymer film according to the present disclosure has a layer A and a layer B on at least one surface of the layer A, wherein the layer B contains a liquid crystal polymer and a compound having a functional group, and the functional group is at least one type of group selected from the group consisting of a group capable of forming a covalent bond, a group capable of forming an ionic bond, a group capable of forming a hydrogen bond, a group capable of forming a dipole-dipole interaction, and a group capable of undergoing a curing reaction.

[0011] In this specification, when the term "polymer film according to the present disclosure" is used without any particular specification, it refers to all of the first embodiment, the second embodiment, and the third embodiment.

[0012] The present inventors have found that conventional polymer films, such as the polymer film described in Patent Document 1, which have a small dielectric loss tangent, do not have sufficient adhesion to a substrate (e.g., a plastic film, a metal foil, or a metal wiring), and that conventional polymer films, such as the resin layer described in Patent Document 2, which have excellent adhesion to a metal layer, do not have sufficient dielectric loss tangent. As a result of extensive research, the present inventors have found that the above-described structure makes it possible to provide a polymer film having excellent adhesion to a substrate. The detailed mechanism by which adhesion can be ensured is unknown, but is speculated as follows. The composition comprises a polymer or liquid crystal polymer having a dielectric dissipation factor of 0.01 or less or 0.005 or less, and a compound having a functional group, wherein the functional group is at least one group selected from the group consisting of groups capable of covalent bonding, groups capable of ionic bonding, groups capable of hydrogen bonding, and groups capable of dipole-dipole interaction. It is presumed that even when a polymer or liquid crystal polymer having a dielectric dissipation factor of 0.01 or less or 0.005 or less is used, the specific functional group interacts with groups present on the substrate or the surface of the substrate (e.g., a metal or metal surface), resulting in excellent adhesion to a metal layer.

[0013] <Layer B> The polymer film according to the present disclosure has a layer A and a layer B on at least one surface of the layer A, and the layer B contains a polymer having a dielectric loss tangent of 0.01 or less or 0.005 or less, or a liquid crystal polymer, and a compound having a functional group. Furthermore, the layer structure and thickness of each layer in the polymer film can be detected or determined by the following methods. First, a cross-sectional sample of the polymer film is cut out using a microtome, and the layer structure and thickness of each layer are determined using an optical microscope. If determination using an optical microscope is difficult, morphological observation using a scanning electron microscope (SEM) or component analysis using time-of-flight secondary ion mass spectrometry (TOF-SIMS) or the like may be used for determination.

[0014] [Polymer with a dielectric loss tangent of 0.01 or less] Layer B in the first embodiment of the polymer film according to the present disclosure comprises a polymer having a dielectric loss tangent of 0.005 or less. Layer B in the second embodiment of the polymer film according to the present disclosure comprises a polymer having a dielectric loss tangent of 0.01 or less. The dielectric loss tangent of the polymer contained in Layer B of the polymer film according to the present disclosure is, for example, 0.01 or less, preferably 0.008 or less, more preferably 0.0075 or less, even more preferably 0.006 or less, and particularly preferably 0.005 or less. The dielectric loss tangent of a polymer having a dielectric loss tangent of 0.005 or less is preferably 0.004 or less, more preferably 0.0035 or less, and particularly preferably 0.003 or less, from the viewpoints of the dielectric loss tangent of the polymer film and adhesion to the metal layer. No lower limit is particularly set for either, but examples include values ​​greater than 0.

[0015] The dielectric loss tangent in the present disclosure is measured by the following method. The dielectric constant is measured at a frequency of 10 GHz using the resonance perturbation method. A 10 GHz cavity resonator (Kanto Electronics Application Development Co., Ltd. CP531) is connected to a network analyzer (Agilent Technology "E8363B"), and a sample of the polymer film or each layer (width: 2 mm x length: 80 mm) is inserted into the cavity resonator. The dielectric constant and dielectric loss tangent of the polymer film or each layer are measured from the change in resonance frequency before and after insertion for 96 hours in an environment of 25°C and 60% RH. When measuring each layer, unnecessary layers may be scraped off with a razor or the like to prepare an evaluation sample of only the target layer. Furthermore, if it is difficult to extract a single film due to reasons such as the layer being thin, 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 a polymer in the present disclosure is carried out by identifying or isolating the chemical structure of the polymer constituting each layer, and using a powdered sample of the polymer to be measured, according to the above-described method for measuring the dielectric loss tangent.

[0016] The melting point Tm or 5% mass loss temperature Td of a polymer having a dielectric dissipation factor of 0.01 or less or 0.005 or less is preferably 200° C. or more, more preferably 250° C. or more, even more preferably 280° C. or more, and particularly preferably 300° C. or more, from the viewpoints of the dielectric dissipation factor of the polymer film, adhesion to the metal layer, and heat resistance. There is no particular upper limit, but it is preferably 500° C. or less, and more preferably 420° C. or less, for example. The melting point (Tm) in this disclosure is measured using a differential scanning calorimetry (DSC) analyzer. 5 mg of a sample was placed in a DSC measurement pan, and the temperature was increased from 30°C at a rate of 10°C / min in a nitrogen stream. The peak temperature of the endothermic peak that appeared when the sample was heated was taken as the Tm of the film. The 5% mass loss temperature Td in this disclosure is measured using a thermogravimetric analyzer (TGA). That is, the weight of the sample placed in the measuring pan is set as an initial value, and the 5% mass loss temperature Td is the temperature at which the weight decreases by 5% from the initial value due to heating.

[0017] The glass transition temperature Tg of a polymer having a dielectric dissipation factor of 0.01 or less or 0.005 or less is preferably 150° C. or more, more preferably 200° C. or more, and particularly preferably 200° C. or more, from the viewpoints of the dielectric dissipation factor of the polymer film, adhesion to metal, and heat resistance. There is no particular restriction on the upper limit, but it is, for example, preferably less than 350° C., less than 280° C., and more preferably 280° C. or less. The glass transition temperature Tg in the present disclosure is measured using a differential scanning calorimetry (DSC) device.

[0018] The weight-average molecular weight Mw of the polymer having a dielectric dissipation factor of 0.01 or less or 0.005 or less is preferably 1,000 or more, more preferably 2,000 or more, and particularly preferably 5,000 or more.The weight-average molecular weight Mw of the polymer having a dielectric dissipation factor of 0.01 or less or 0.005 or less is preferably 50,000 or less, more preferably 20,000 or less, and particularly preferably less than 13,000.

[0019] In the present disclosure, the type of polymer having a dielectric loss tangent of 0.01 or less or 0.005 or less is not particularly limited, and known polymers can be used. Examples of polymers having a dielectric dissipation factor of 0.01 or less or a dielectric dissipation factor of 0.005 or less include thermoplastic resins such as liquid crystal polymers, fluorine-based polymers, polymers of compounds having a cyclic aliphatic hydrocarbon group and a group having an ethylenically unsaturated bond, polyether ether ketone, polyolefin, polyamide, polyester, polyphenylene sulfide, aromatic polyether ketone, polycarbonate, polyether sulfone, polyphenylene ether and modified products thereof, and polyether imide; elastomers such as copolymers of glycidyl methacrylate and polyethylene; and thermosetting resins such as phenolic resins, epoxy resins, polyimide resins, and cyanate resins. Among these, from the viewpoints of the dielectric loss tangent of the polymer film, adhesion to metal, and heat resistance, at least one polymer selected from the group consisting of liquid crystal polymers, fluoropolymers, polymers of compounds having a cyclic aliphatic hydrocarbon group and a group having an ethylenically unsaturated bond, polyphenylene ether, and aromatic polyether ketone is preferred, and at least one polymer selected from the group consisting of liquid crystal polymers and fluoropolymers is more preferred. From the viewpoints of adhesion and mechanical strength of the polymer film, liquid crystal polymers are preferred, and from the viewpoints of heat resistance and dielectric loss tangent, fluorine-based polymers are preferred.

[0020] -Liquid Crystal Polymer- Layer B in the third embodiment of the polymer film according to the present disclosure comprises a liquid crystal polymer. In the first embodiment of the polymer film according to the present disclosure, the polymer having a dielectric loss tangent of 0.005 or less is preferably a liquid crystal polymer from the viewpoint of the dielectric loss tangent of the polymer film. In addition, the polymer having a dielectric loss tangent of 0.01 or less in the second embodiment of the polymer film according to the present disclosure is preferably a liquid crystal polymer from the viewpoint of the dielectric loss tangent of the polymer film. In the present disclosure, the type of liquid crystal polymer is not particularly limited, and known liquid crystal polymers can be used. The liquid crystal polymer may be a thermotropic liquid crystal polymer that exhibits liquid crystallinity in a molten state, or a lyotropic liquid crystal polymer that exhibits liquid crystallinity in a solution state. When the liquid crystal polymer is a thermotropic liquid crystal polymer, it is preferably a liquid crystal polymer that melts at a temperature of 450°C or less. Examples of the liquid crystal polymer include liquid crystal polyester, liquid crystal polyester amide in which an amide bond is introduced into liquid crystal polyester, liquid crystal polyester ether in which an ether bond is introduced into liquid crystal polyester, and liquid crystal polyester carbonate in which a carbonate bond is introduced into liquid crystal polyester. Furthermore, from the viewpoints of liquid crystallinity and thermal expansion coefficient, the liquid crystal polymer is preferably a polymer having an aromatic ring, and more preferably an aromatic polyester or an aromatic polyester amide. Furthermore, the liquid crystal polymer may be a polymer in which an imide bond, a carbodiimide bond, an isocyanate-derived bond such as an isocyanurate bond, or the like is further introduced into an aromatic polyester or an aromatic polyester amide. The liquid crystal polymer is preferably a wholly aromatic liquid crystal polymer made using only aromatic compounds as raw material monomers.

[0021] Examples of the liquid crystal polymer include the following liquid crystal polymers: 1) A compound obtained by polycondensation of (i) an aromatic hydroxycarboxylic acid, (ii) an aromatic dicarboxylic acid, and (iii) at least one compound selected from the group consisting of an aromatic diol, an aromatic hydroxyamine, and an aromatic diamine. 2) A compound obtained by polycondensation of multiple types of aromatic hydroxycarboxylic acids. 3) (i) A compound obtained by polycondensation of an aromatic dicarboxylic acid and (ii) at least one compound selected from the group consisting of an aromatic diol, an aromatic hydroxyamine, and an aromatic diamine. 4) (i) Polyester such as polyethylene terephthalate and (ii) aromatic hydroxycarboxylic acid are polycondensed. Here, the aromatic hydroxycarboxylic acid, aromatic dicarboxylic acid, aromatic diol, aromatic hydroxyamine and aromatic diamine may each independently be replaced with a derivative capable of undergoing polycondensation.

[0022] 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. Aromatic hydroxycarboxylic acids and aromatic dicarboxylic acids can be replaced with aromatic hydroxycarboxylic acid halides and aromatic dicarboxylic acid halides by converting the carboxy groups to haloformyl groups. Aromatic hydroxycarboxylic acids and aromatic dicarboxylic acids can be replaced with aromatic hydroxycarboxylic acid anhydrides and aromatic dicarboxylic acid anhydrides by converting the carboxy groups to acyloxycarbonyl groups. Examples of polymerizable derivatives of compounds having a hydroxy group, such as aromatic hydroxycarboxylic acids, aromatic diols, and aromatic hydroxyamines, include those obtained by acylation of the hydroxy group to convert it into an acyloxy group (acylated products). For example, aromatic hydroxycarboxylic acids, aromatic diols, and aromatic hydroxyamines can be substituted with their acylated products by acylation of the hydroxy groups to convert them into acyloxy groups. Examples of polymerizable derivatives of compounds having an amino group, such as aromatic hydroxyamines and aromatic diamines, include those obtained by acylation of the amino group to convert it into an acylamino group (acylated product). For example, aromatic hydroxyamines and aromatic diamines can be substituted with their acylated products by acylation of the amino groups to convert them into acylamino groups.

[0023] From the viewpoints of liquid crystallinity, the dielectric loss tangent of the polymer film, and adhesion to a metal layer, the liquid crystal polymer preferably has a structural unit represented by any one of the following formulas (1) to (3) (hereinafter, a structural unit represented by formula (1) etc. may be referred to as structural unit (1) etc.), more preferably has a structural unit represented by formula (1) below, and particularly preferably has a structural unit represented by formula (1) below, a structural unit represented by formula (2) below, and a structural unit represented by formula (3) below. Formula (1) -O-Ar 1 -CO- Formula (2) -CO-Ar 2 -CO- Formula (3) -X-Ar 3 -Y- In formulas (1) to (3), Ar 1 represents a phenylene group, a naphthylene group, or a biphenylylene group; Ar 2 and Ar 3 each independently represents a phenylene group, a naphthylene group, a biphenylylene group, or a group represented by the following formula (4), X and Y each independently represent an oxygen atom or an imino group, 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 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.

[0024] The halogen atom includes a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom. Examples of the alkyl group include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a s-butyl group, a t-butyl group, an n-hexyl group, a 2-ethylhexyl group, an n-octyl group, and an n-decyl group. The alkyl group preferably has 1 to 10 carbon atoms. Examples of the aryl group 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. When the hydrogen atoms are substituted with these groups, the number of substitutions is 1 , Ar 2 or Ar 3 In each of the above, the number is preferably 2 or less, and more preferably 1.

[0025] Examples of the alkylene group 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 alkylene group preferably has 1 to 10 carbon atoms.

[0026] The structural unit (1) is a structural unit derived from an aromatic hydroxycarboxylic acid. The structural unit (1) is Ar 1 is a p-phenylene group (a structural unit derived from p-hydroxybenzoic acid), and Ar 1 is preferably a 2,6-naphthylene group (a structural unit derived from 6-hydroxy-2-naphthoic acid) or a 4,4'-biphenylylene group (a structural unit derived from 4'-hydroxy-4-biphenylcarboxylic acid).

[0027] The structural unit (2) is a structural unit derived from an aromatic dicarboxylic acid. The structural unit (2) is Ar 2 is a p-phenylene group (a structural unit derived from terephthalic acid), Ar 2 is an m-phenylene group (a structural unit derived from isophthalic acid), Ar 2 is a 2,6-naphthylene group (a structural unit derived from 2,6-naphthalenedicarboxylic acid), or Ar 2 is a diphenylether-4,4'-diyl group (a structural unit derived from diphenylether-4,4'-dicarboxylic acid).

[0028] The structural unit (3) is a structural unit derived from an aromatic diol, an aromatic hydroxylamine, or an aromatic diamine. The structural unit (3) is Ar 3 is a p-phenylene group (a structural unit derived from hydroquinone, p-aminophenol, or p-phenylenediamine), Ar 3 is an m-phenylene group (a structural unit derived from isophthalic acid), or Ar 3 is a 4,4'-biphenylylene group (a structural unit derived from 4,4'-dihydroxybiphenyl, 4-amino-4'-hydroxybiphenyl, or 4,4'-diaminobiphenyl).

[0029] The content of the structural 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% of the total amount of all structural units (the mass of each structural unit (also referred to as a "monomer unit") constituting the liquid crystal polymer is divided by the formula weight of that structural unit to determine the substance equivalent (moles) of each structural unit, and the sum of these values). The content of the structural unit (2) relative to the total amount of all structural units 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 %. The content of the structural unit (3) relative to the total amount of all structural units 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 %. The greater the content of the structural unit (1), the more likely it is that the heat resistance, strength, and rigidity will improve, but if the content is too high, the solubility in solvents will tend to decrease.

[0030] The ratio of the content of the structural unit (2) to the content of the structural unit (3), expressed as [content of the structural unit (2)] / [content of the structural unit (3)] (mol / mol), 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.

[0031] The liquid crystal polymer may independently contain two or more of the structural units (1) to (3). The liquid crystal polymer may also contain structural units other than the structural units (1) to (3), provided that the content of such structural units is preferably 10 mol % or less, more preferably 5 mol % or less, based on the total amount of all structural units.

[0032] From the viewpoint of solubility in a solvent, the liquid crystal polymer preferably has, as the structural unit (3), a structural unit (3) in which at least one of X and Y is an imino group, that is, the structural unit (3) preferably has at least one of a structural unit derived from an aromatic hydroxylamine and a structural unit derived from an aromatic diamine, and more preferably has only a structural unit (3) in which at least one of X and Y is an imino group.

[0033] The liquid crystal polymer is preferably produced by melt-polymerizing raw material monomers corresponding to the structural units constituting the liquid crystal polymer. The melt polymerization may be carried out in the presence of a catalyst. Examples of the catalyst 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. The melt polymerization may be further subjected to solid-state polymerization if necessary.

[0034] The lower limit of the flow initiation temperature of the liquid crystal polymer is preferably 180° C. or higher, more preferably 200° C. or higher, and even more preferably 250° C. or higher, and the upper limit of the flow initiation temperature is preferably 350° C., more preferably 330° C., and even more preferably 310° C. When the flow initiation temperature of the liquid crystal polymer is within the above range, the polymer has excellent solubility, heat resistance, strength, and rigidity, and the viscosity of the solution is appropriate.

[0035] The flow initiation temperature is also called the flow temperature or flow temperature, and is measured using a capillary rheometer at 9.8 MPa (100 kg / cm 2 When a liquid crystal polymer is melted and extruded through a nozzle with an inner diameter of 1 mm and a length of 10 mm while heating at a rate of 4°C / min under a load of 1000 kJ / s, the temperature at which the polymer shows a viscosity of 4,800 Pa·s (48,000 poise) is measured. This temperature is an indicator of the molecular weight of the liquid crystal polymer (see "Liquid Crystal Polymer - Synthesis, Molding, and Applications," edited by Naoyuki Koide, CMC Corporation, June 5, 1987, p. 95).

[0036] The weight-average molecular weight of the liquid crystal polymer is preferably 1,000,000 or less, more preferably 3,000 to 300,000, even more preferably 5,000 to 100,000, and particularly preferably 5,000 to 30,000. When the weight-average molecular weight of the liquid crystal polymer is within the above range, the film after heat treatment has excellent thermal conductivity in the thickness direction, heat resistance, strength, and rigidity.

[0037] -Fluorine-based polymer- The polymer having a dielectric loss tangent of 0.005 or less is preferably a fluorine-based polymer from the viewpoints of heat resistance and mechanical strength. In the present disclosure, the fluoropolymer used as the polymer having a dielectric dissipation factor of 0.005 or less is not particularly limited to a particular type, and any known fluoropolymer can be used, as long as it has a dielectric dissipation factor of 0.005 or less. Examples of fluorine-based polymers include polytetrafluoroethylene, polychlorotrifluoroethylene, polyvinylidene fluoride, polyvinyl fluoride, perfluoroalkoxy fluororesin, tetrafluoroethylene / hexafluoropropylene copolymer, ethylene / tetrafluoroethylene copolymer, and ethylene / chlorotrifluoroethylene copolymer. Of these, polytetrafluoroethylene is preferred.

[0038] Further, the fluorine-based polymer includes homopolymers and copolymers containing constitutional units derived from a fluorinated α-olefin monomer, i.e., an α-olefin monomer containing at least one fluorine atom, and, if necessary, a non-fluorinated ethylenically unsaturated monomer reactive with the fluorinated α-olefin monomer. 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, perfluoro(alkyl having 2 to 8 carbon atoms)vinyl ether (e.g., perfluoromethyl vinyl ether, perfluoropropyl vinyl ether, perfluorooctyl vinyl ether), etc. 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. Non-fluorinated monoethylenically unsaturated monomers include ethylene, propylene, butene, ethylenically unsaturated aromatic monomers (eg, styrene and α-methylstyrene), and the like. The fluorinated α-olefin monomers may be used alone or in combination of two or more. The non-fluorinated ethylenically unsaturated monomers may be used alone or in combination of two or more.

[0039] Examples of fluorine-based 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) (e.g., poly(tetrafluoroethylene-perfluoropropyl vinyl ether)), polyvinyl fluoride (PVF), polyvinylidene fluoride (PVDF), poly(vinylidene fluoride-chlorotrifluoroethylene), perfluoropolyether, perfluorosulfonic acid, and perfluoropolyoxetane. The fluorine-based polymers may be used alone or in combination of two or more kinds.

[0040] The fluoropolymer is preferably at least one of FEP, PFA, ETFE, and 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.

[0041] The fluoropolymer preferably includes PTFE. The PTFE may include a PTFE homopolymer, a partially modified PTFE homopolymer, or a combination including one or both of these. The partially modified PTFE homopolymer preferably includes less than 1% by mass of structural units derived from comonomers other than tetrafluoroethylene, based on the total mass of the polymer.

[0042] The fluorine-based polymer may be a crosslinkable fluoropolymer having a crosslinkable group. The crosslinkable fluoropolymer can be crosslinked by a conventionally known crosslinking method. One of the representative crosslinkable fluoropolymers is a fluoropolymer having a (meth)acryloxy group. For example, the crosslinkable fluoropolymer has the formula: H2C=CR'COO-(CH2) n -R-(CH2) n -OOCR'=CH2 In the formula, R is a fluorine-based oligomer chain having two or more structural 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 fluorine-based oligomer chain containing a structural unit derived from tetrafluoroethylene.

[0043] A crosslinked fluoropolymer network can be formed by exposing a fluoropolymer having (meth)acryloxy groups to a free radical source to initiate a radical crosslinking reaction via the (meth)acryloxy groups on the fluoropolymer. The free radical source is not particularly limited, but suitable examples include a photoradical polymerization initiator or an organic peroxide. Suitable photoradical polymerization initiators and organic peroxides are well known in the art. Crosslinkable fluoropolymers are commercially available, for example, Viton B manufactured by DuPont.

[0044] -Polymer of a compound having a cyclic aliphatic hydrocarbon group and a group having an ethylenically unsaturated bond- The polymer having a dielectric loss tangent of 0.005 or less may be 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 a monomer consisting of a cyclic olefin such as norbornene or a polycyclic norbornene-based monomer, and these are also called thermoplastic cyclic olefin-based resins. The polymer of a compound having a cyclic aliphatic hydrocarbon group and a group having an ethylenically unsaturated bond may be a ring-opening polymer of the above-mentioned cyclic olefin, a hydrogenated product of a ring-opening copolymer using two or more kinds of cyclic olefins, or an addition polymer of a cyclic olefin and an aromatic compound having an ethylenically unsaturated bond such as a chain olefin or a vinyl group. In addition, a polar group may be introduced into the polymer of a compound having a cyclic aliphatic hydrocarbon group and a group having an ethylenically unsaturated bond. The polymer of a compound having a cyclic aliphatic hydrocarbon group and a group having an ethylenically unsaturated bond may be used alone or in combination of two or more kinds.

[0045] The ring structure of the cyclic aliphatic hydrocarbon group may be a monocyclic ring, a fused ring in which two or more rings are fused, or a bridged ring. Examples of the ring structure of the cycloaliphatic hydrocarbon group include a cyclopentane ring, a cyclohexane ring, a cyclooctane ring, an isophorone ring, a norbornane ring, and a dicyclopentane ring. The 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. The number of alicyclic hydrocarbon groups in the compound having a alicyclic hydrocarbon group and a group having an ethylenically unsaturated bond may be one or more, and may be two or more. The polymer of a compound having a cyclic aliphatic hydrocarbon group and a group having an ethylenically unsaturated bond may be a polymer obtained by polymerizing at least one compound having a cyclic aliphatic hydrocarbon group and a group having an ethylenically unsaturated bond, and may be a polymer of a compound having two or more types of cyclic aliphatic hydrocarbon groups and a group having an ethylenically unsaturated bond, or may be a copolymer with another ethylenically unsaturated compound that does not have a cyclic aliphatic hydrocarbon group. The polymer of a compound having a cyclic aliphatic hydrocarbon group and a group having an ethylenically unsaturated bond is preferably a cycloolefin polymer.

[0046] -Polyphenylene ether- Layer A preferably comprises a polyphenylene ether. When the polyphenylene ether is thermally cured after film formation, from the viewpoints of heat resistance and film formability, the weight average molecular weight (Mw) is preferably 500 to 5,000, and more preferably 500 to 3,000. When the polyphenylene ether is not thermally cured, the weight average molecular weight (Mw) is not particularly limited, but is preferably 3,000 to 100,000, and more preferably 5,000 to 50,000. The polyphenylene ether preferably has an average number of phenolic hydroxyl groups at the molecular terminals per molecule (number of terminal hydroxyl groups) of 1 to 5, more preferably 1.5 to 3, from the viewpoints of dielectric tangent and heat resistance. The number of hydroxyl groups or phenolic hydroxyl groups in a polyphenylene ether can be determined, for example, from the specification values ​​of the polyphenylene ether product. The number of terminal hydroxyl groups or terminal phenolic hydroxyl groups can be, for example, a numerical value representing the average number of hydroxyl groups or phenolic hydroxyl groups per molecule of all polyphenylene ethers present in 1 mole of polyphenylene ether. The polyphenylene ether may be used alone or in combination of two or more kinds.

[0047] Examples of polyphenylene ether include polyphenylene ethers composed of 2,6-dimethylphenol and at least one of a difunctional phenol and a trifunctional phenol, or those containing polyphenylene ether such as poly(2,6-dimethyl-1,4-phenylene oxide) as a main component. More specifically, for example, a compound having a structure represented by formula (PPE) is preferred.

[0048] [ka]

[0049] In formula (PPE), X represents an alkylene group having 1 to 3 carbon atoms or a single bond, m represents an integer of 0 to 20, n represents an integer of 0 to 20, and the sum of m and n represents an integer of 1 to 30. The alkylene group in X includes, for example, a dimethylmethylene group.

[0050] -Aromatic polyether ketone- The polymer having a dielectric loss tangent of 0.005 or less may be 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 polyether ether ketone. Polyether ether ketone is a type of aromatic polyether ketone, and is a polymer in which bonds are arranged in the following order: ether bond, ether bond, and carbonyl bond (ketone). Each bond is preferably connected by a divalent aromatic group. The aromatic polyether ketones may be used alone or in combination of two or more.

[0051] Examples of aromatic polyetherketones include polyetheretherketone (PEEK) having a chemical structure represented by the following formula (P1), polyetherketone (PEK) having a chemical structure represented by the following formula (P2), polyetherketoneketone (PEKK) having a chemical structure represented by the following formula (P3), polyetheretherketoneketone (PEEKK) having a chemical structure represented by the following formula (P4), and polyetherketoneetherketoneketone (PEKEKK) having a chemical structure represented by the following formula (P5).

[0052] [ka]

[0053] In terms of mechanical properties, n in each of the formulas (P1) to (P5) is preferably 10 or more, and more preferably 20 or more. On the other hand, in terms of ease of production of the aromatic polyether ketone, 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.

[0054] The polymer having a dielectric loss tangent of 0.01 or less or 0.005 or less is preferably a polymer that is soluble in a specific organic solvent (hereinafter also referred to as a "soluble polymer"). Specifically, the soluble polymer in the present disclosure is a liquid crystal polymer that dissolves at 25°C in an amount of 0.1 g or more in 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.

[0055] Layer B may contain only one type, or two or more types, of polymers or liquid crystal polymers having a dielectric loss tangent of 0.01 or less or 0.005 or less. The content of the polymer or liquid crystal polymer having a dielectric loss tangent of 0.01 or less or 0.005 or less in Layer B is preferably 10% by mass to 99% by mass, more preferably 20% by mass to 95% by mass, even more preferably 30% by mass to 90% by mass, and particularly preferably 40% by mass to 80% by mass, relative to the total mass of the polymer film, from the viewpoints of the dielectric loss tangent of the polymer film and adhesion to metal. The content of the polymer or liquid crystal polymer having a dielectric loss tangent of 0.01 or less or 0.005 or less in the polymer film is preferably 20% by mass to 99% by mass, more preferably 30% by mass to 98% by mass, even more preferably 40% by mass to 97% by mass, and particularly preferably 50% by mass to 95% by mass, relative to the total mass of the polymer film, from the viewpoints of the dielectric loss tangent of the polymer film and adhesion to metal.

[0056] [Compounds having functional groups] Layer B contains a compound having a functional group, and the functional group is at least one type of group selected from the group consisting of a group capable of forming a covalent bond, a group capable of forming an ionic bond, a group capable of forming a hydrogen bond, a group capable of dipole-dipole interaction, and a group capable of undergoing a curing reaction. It is presumed that the compound having a functional group contained in Layer B interacts or bonds with the metal or groups present on the metal surface, thereby improving adhesion to the metal. Furthermore, the compound having the functional group interacts, bonds, or becomes entangled with the polymer or liquid crystal polymer having a dielectric dissipation factor of 0.01 or less or 0.005 or less contained in Layer B. Examples of entanglement include interpenetration of the continuous phase of the compound having the functional group with the continuous phase of the polymer or liquid crystal polymer having a dielectric dissipation factor of 0.01 or less or 0.005 or less, and an increase in the coefficient of friction due to the morphology of each continuous phase. In the laminate described below, when the metal layer that is to be brought into contact with Layer B has been surface-treated, the functional group is preferably capable of interacting with or bonding to groups present on the surface of the metal. In the case where a compound having a functional group interpenetrates a polymer or liquid crystal polymer having a dielectric dissipation factor of 0.01 or less or 0.005 or less, the compound having a functional group is preferably a compound that undergoes phase separation with the polymer or liquid crystal polymer having a dielectric dissipation factor of 0.01 or less or 0.005 or less, or a compound that undergoes phase separation with the polymer or liquid crystal polymer having a dielectric dissipation factor of 0.01 or less or 0.005 or less during or as a result of bonding between the compounds having functional groups. In this embodiment, the adhesion between Layer B and the metal is improved. From the viewpoint of adhesion between Layer B and Layer A, it is preferred that Layer A and Layer B contain a polymer or liquid crystal polymer having a common dielectric dissipation factor of 0.01 or less or 0.005 or less, that the difference in surface energy between the layers be small, or that the difference in solubility parameter between the layers be small. Furthermore, the bonding of a compound having a functional group with a component contained in Layer A (for example, a polymer or liquid crystal polymer having a dielectric tangent of 0.01 or less or 0.005 or less) can also improve the adhesion between Layer B and Layer A.

[0057] The compound having a functional group may be a low molecular weight compound or a high molecular weight compound. The compound having a functional group is preferably a low molecular weight compound from the viewpoints of compatibility between the polymer having a dielectric tangent of 0.005 or less and the compound having a functional group, and of the dielectric tangent of the polymer film, and is preferably a high molecular weight compound from the viewpoints of the heat resistance and mechanical strength of the polymer film. The number of functional groups in the compound having functional groups may be 1 or more, and may be 2 or more, but is preferably 2 or more, and is preferably 10 or less from the viewpoint of maintaining an appropriate amount of functional groups and reducing the dielectric loss tangent of the polymer film. Furthermore, the compound having a functional group may have only one type of functional group, or may have two or more types of functional groups.

[0058] From the viewpoint of adhesion to the metal layer, the low molecular weight compound used as the compound having a functional group preferably has a molecular weight of 50 or more and less than 2,000, more preferably 100 or more and less than 1,000, and particularly preferably 200 or more and less than 1,000. When the compound having a functional group is a low molecular weight compound, the compound has a narrow distribution, and in order to increase the probability of contact between the functional groups, the content of the compound having a functional group is preferably 10 mass% or more relative to the total mass of Layer B. Furthermore, from the viewpoint of adhesion to metals, the polymer compound used as the compound having a functional group is preferably a polymer having a weight-average molecular weight of 1,000 or more, more preferably a polymer having a weight-average molecular weight of 2,000 or more, even more preferably a polymer having a weight-average molecular weight of 3,000 or more and 1,000,000 or less, and particularly preferably a polymer having a weight-average molecular weight of 5,000 or more and 200,000 or less.

[0059] 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 with each other. Here, compatibility means that no phase separation is observed within Layer B. The difference between the SP value by the Hoy method of a polymer with a dielectric dissipation factor of 0.005 or less and the SP value by the Hoy method of a compound having a functional group is 5 MPa from the viewpoints of the compatibility between the polymer with a dielectric dissipation factor of 0.005 or less and the compound having a functional group, the dielectric dissipation factor of the polymer film, and the adhesion to the metal layer. 0.5 The lower limit is preferably 0 MPa or less. 0.5 is.

[0060] The SP value (solubility parameter value) according to 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 for each constituent unit.

[0061] <<Functional group>> The functional group in the compound having a functional group is at least one type of group selected from the group consisting of a group capable of forming a covalent bond, a group capable of forming an ionic bond, a group capable of forming a hydrogen bond, a group capable of dipole-dipole interaction, and a group capable of undergoing a curing reaction. From the viewpoint of adhesion to metal, the functional group is preferably a group capable of forming a covalent bond or a group capable of undergoing a curing reaction, and more preferably a group capable of forming a covalent bond. From the viewpoint of storage stability and ease of handling, the functional group is preferably a group capable of forming an ionic bond, a group capable of forming a hydrogen bond, or a group capable of dipole-dipole interaction.

[0062] -Covalently bondable group- The covalently bondable group is not particularly limited as long as it is a group capable of forming a covalent bond, and examples thereof include an epoxy group, an oxetanyl group, an isocyanate group, an acid anhydride group, a carbodiimide group, an N-hydroxyester group, a glyoxal group, an imide ester group, a halogenated alkyl group, a thiol group, a hydroxy group, a carboxy group, an amino group, an amide group, an isocyanate group, an aldehyde group, a sulfonic acid group, etc. Among these, from the viewpoint of adhesion to the metal layer, at least one functional group selected from the group consisting of an epoxy group, an oxetanyl group, an N-hydroxyester group, an isocyanate group, an imide ester group, a halogenated alkyl group, and a thiol group is preferred, and an epoxy group is particularly preferred.

[0063] As will be described later, it is preferable that the surface of the metal to be bonded has a group that pairs with the functional group of the compound having a functional group. Specific examples of combinations of groups capable of covalent bonding (combinations of a functional group of a compound having a functional group and a group on the surface of a metal) include when one is, for example, an epoxy group or an oxetanyl group, the other is a hydroxy group, an amino group, or the like. Furthermore, when one is, for example, an N-hydroxyester group or an imide ester group, the other may be an amino group or the like.

[0064] -Ionic bonding capable group- Examples of the group capable of forming an ionic bond include a cationic group and an anionic group. The cationic group is preferably an onium group. Examples of the onium group include an ammonium group, a pyridinium group, a phosphonium group, an oxonium group, a sulfonium group, a selenonium group, and an iodonium group. Among these, from the viewpoint of adhesion to the metal layer, an ammonium group, a pyridinium group, a phosphonium group, or a sulfonium group is preferred, an ammonium group or a phosphonium group is more preferred, and an ammonium group is particularly preferred. The anionic group is not particularly limited and examples thereof include a phenolic hydroxyl group, a carboxyl group, -SO3H, -OSO3H, -PO3H, -OPO3H2, -CONHSO2-, -SONHSO2-, etc. Among these, a phosphate group, a phosphonate group, a phosphinate group, a sulfate group, a sulfonic acid group, a sulfinic acid group, or a carboxyl group is preferred, a phosphate group or a carboxyl group is more preferred, and a carboxyl group is even more preferred.

[0065] Specific examples of combinations of groups capable of forming ionic bonds (combinations of a functional group of a compound having a functional group and a group on the surface of a metal) include when one has an acidic group and the other has a basic group. Examples of the acidic group include a carboxy group, a sulfo group, and a phosphate group, with a carboxy group being preferred. When one of the groups is, for example, a carboxy group, examples of the group capable of forming an ionic bond with the carboxy group include a tertiary amino group, a pyridyl group, and a piperidyl group.

[0066] -Hydrogen-bonding groups- Examples of groups capable of forming hydrogen bonds include groups having a hydrogen bond donating site and groups having a hydrogen bond accepting site. The hydrogen bond donor site may be any structure having an active hydrogen atom capable of forming a hydrogen bond, but is preferably a structure represented by XH. X represents a heteroatom, and is preferably a nitrogen atom or an oxygen atom. From the viewpoint of adhesion to the metal layer, the hydrogen bond donor moiety is preferably at least one structure selected from the group consisting of a hydroxy group, a carboxy group, a primary amide group, a secondary amide group, a primary amino group, a secondary amino group, a primary sulfonamide group, a secondary sulfonamide group, an imide group, a urea bond, and a urethane bond; more preferably at least one structure selected from the group consisting of a hydroxy group, a carboxy group, a primary amide group, a secondary amide group, a primary sulfonamide group, a secondary sulfonamide group, a maleimide group, a urea bond, and a urethane bond; still more preferably at least one structure selected from the group consisting of a hydroxy group, a carboxy group, a primary amide group, a secondary amide group, a primary sulfonamide group, a secondary sulfonamide group, and a maleimide group; and particularly preferably at least one structure selected from the group consisting of a hydroxy group and a secondary amide group.

[0067] The hydrogen bond accepting site is preferably a structure containing an atom having an unshared electron pair, more preferably a structure containing an oxygen atom having an unshared electron pair, and more preferably at least one structure selected from the group consisting of a carbonyl group (including carbonyl structures such as a carboxy group, an amide group, an imide group, a urea bond, and a urethane bond) and a sulfonyl group (including sulfonyl structures such as a sulfonamide group), and particularly preferably a carbonyl group (including carbonyl structures such as a carboxy group, an amide group, an imide group, a urea bond, and a urethane bond).

[0068] The group capable of forming a hydrogen bond is preferably a group having both the above-mentioned hydrogen bond donor site and hydrogen bond acceptor site, and preferably has a carboxy group, an amide group, an imide group, a urea bond, a urethane bond, or a sulfonamide group, and more preferably has a carboxy group, an amide group, an imide group, or a sulfonamide group.

[0069] Specific examples of combinations of groups capable of forming hydrogen bonds (combinations of a functional group of a compound having a functional group and a group on the surface of a metal) include combinations in which one has a group having a hydrogen bond donor site and the other has a group having a hydrogen bond acceptor site. For example, when one is a carboxy group, examples include an amide group and a carboxy group. Furthermore, when one is, for example, a phenolic hydroxyl group, the other may be a phenolic hydroxyl group, etc.

[0070] -Group capable of dipole-dipole interaction- The group capable of dipole-dipole interaction may be any group having a polarized structure other than the structure represented by XH (X represents a heteroatom, such as a nitrogen atom or an oxygen atom) in the above-mentioned groups capable of forming hydrogen bonds, and preferred examples include groups to which atoms with different electronegativities are bonded. As a combination of atoms having different electronegativities, a combination of at least one atom selected from the group consisting of oxygen atoms, nitrogen atoms, sulfur atoms, and halogen atoms and carbon atoms is preferred, and a combination of at least one atom selected from the group consisting of oxygen atoms, nitrogen atoms, and sulfur atoms and carbon atoms is more preferred. Among these, from the viewpoint of adhesion to the metal layer, a combination of a nitrogen atom and a carbon atom, and a combination of a carbon atom with a nitrogen atom, an oxygen atom, and a sulfur atom are preferred, and specifically, a cyano group, a cyanuric group, and a sulfonic acid amide group are more preferred.

[0071] As a combination of groups capable of dipole-dipole interaction (a combination of a functional group of a compound having a functional group and a group on the surface of a metal), a combination of the same groups capable of dipole-dipole interaction is preferably exemplified. When one is, for example, a cyano group, the other can be a cyano group. Furthermore, when one is, for example, a sulfonic acid amide group, the other may be a sulfonic acid amide group.

[0072] -Curing reaction group- Preferred examples of the compound having a curable group include the following curable compounds: When Layer B contains a curable compound, Layer B preferably contains a curable compound and a curing aid.

[0073] ~Curing compound~ The curable compound is a compound that cures upon irradiation with heat or light (for example, visible light, ultraviolet light, near-infrared light, far-infrared light, electron beam, etc.), and may require a curing aid, as described below. 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 alone or in combination of two or more. Among these, from the viewpoint of properties such as compatibility with the polymer and heat resistance, 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 is preferred, and at least one selected from the group consisting of epoxy compounds, cyanate ester compounds, vinyl compounds, allyl compounds, and silicone compounds is more preferred. 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 B.

[0074] ~Curing aid~ Examples of the curing aid include polymerization initiators such as photoinitiators (photoradical generators, photoacid generators, photobase generators). Specific examples of the curing aid include onium salt compounds, sulfone compounds, sulfonate ester compounds, sulfonimide compounds, disulfonyldiazomethane compounds, disulfonylmethane compounds, oxime sulfonate compounds, hydrazine sulfonate compounds, triazine compounds, nitrobenzyl compounds, benzylimidazole compounds, organic halides, metal octylate salts, and disulfones. These curing aids may be used alone or in combination of two or more, regardless of 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.

[0075] Specifically, the functional group in the compound having a functional group preferably includes at least one selected from the group consisting of an epoxy group, an oxetanyl group, an isocyanate group, an acid anhydride group, a carbodiimide group, an N-hydroxyester group, a glyoxal group, an imide ester group, a halogenated alkyl group, a thiol group, a hydroxy group, a carboxy group, an amino group, an amide group, an isocyanate group, an aldehyde group, a sulfonic acid group, an ammonium group, a pyridinium group, a phosphonium group, an oxonium group, a sulfonium group, a selenonium group, an iodonium group, a phosphate group, a phosphonic acid group, a phosphinic acid group, a sulfate group, a sulfonic acid group, a sulfinic acid group, or a carboxy group, a hydroxy group, a carboxy group, a primary amide group, a secondary amide group, a primary amino group, a secondary amino group, a primary sulfonamide group, a secondary sulfonamide group, an imide group, a urea bond, and a urethane bond. From the viewpoint of improving adhesion, an epoxy group, an oxetanyl group, an isocyanate group, an acid anhydride group, a carbodiimide group, an N-hydroxyester group, a glyoxal group, an imide ester group, a halogenated alkyl group, or a thiol group is more preferred.

[0076] Specific examples of bonds or interactions between two types of functional groups are shown below, but the above bonds or interactions in the present disclosure are not limited thereto.

[0077] [ka]

[0078] From the viewpoints of the dielectric loss tangent of the polymer film and adhesion to metal, the compound having a functional group is preferably a polyfunctional epoxy compound or a polymer of a polyfunctional epoxy compound, more preferably a bifunctional epoxy compound or a polymer of a bifunctional epoxy compound, and particularly preferably a bifunctional epoxy compound.

[0079] Layer B may contain only one type of compound having a functional group, or may contain two or more types of compounds having a functional group. The content of the compound having a functional group in Layer B is preferably higher than the content of the compound having a functional group in Layer A. From the viewpoints of the dielectric loss tangent of the polymer film and adhesion to metals, the content of the compound having a functional group in Layer B is preferably 1% by mass to 80% by mass, more preferably 5% by mass to 70% by mass, even more preferably 10% by mass to 60% by mass, and particularly preferably 20% by mass to 60% by mass, relative to the total mass of the polymer film. From the viewpoints of the dielectric loss tangent of the polymer film and adhesion to metals, the content of the compound having a functional group in the polymer film is preferably 0.5% by mass to 80% by mass, more preferably 1% by mass to 70% by mass, even more preferably 2% by mass to 60% by mass, and particularly preferably 3% by mass to 60% by mass, relative to the total mass of the polymer film.

[0080] -Three-dimensional crosslinked structure- Layer B preferably has a three-dimensional crosslinked structure from the viewpoints of the dielectric loss tangent of the polymer film, adhesion to metals, heat resistance, and mechanical strength. A method for forming a three-dimensional crosslinked structure includes a method in which at least one selected from the group consisting of a polymer having a dielectric dissipation factor of 0.005 or less and a compound having a functional group is a cured product of a multifunctional reactive compound. Here, a cured product of a multifunctional reactive compound refers to a compound in which the reactive groups of the multifunctional reactive compound have substantially lost their reactivity due to various curing reactions such as crosslinking and polymerization. That is, some of the reactive groups of the multifunctional reactive compound may remain unreacted; for example, it is sufficient that 50% or more of all the reactive groups of the multifunctional reactive compound have disappeared. The proportion of the reactive groups of the multifunctional reactive compound that have disappeared is preferably 80% or more, more preferably 90% or more, and even more preferably 100% (i.e., a state in which all the reactive groups of the multifunctional reactive compound have disappeared). The degree of disappearance of the reactive groups can be measured by known methods, such as a method in which a cured product of the multifunctional reactive compound contained in a polymer film is identified and measured by infrared absorption spectroscopy or the like. Furthermore, the polymer film according to the present disclosure preferably contains a polyfunctional reactive compound as a polymer having a dielectric loss tangent of 0.005 or less, from the viewpoints of the dielectric loss tangent of the polymer film, adhesion to a metal layer, heat resistance, and mechanical strength, and more preferably contains a liquid crystal polymer precursor. The liquid crystal polymer precursor is not particularly limited as long as it is a polymerizable liquid crystal polymer. The liquid crystal polymer precursor may be one in which a polymerizable group has been generated by a predetermined treatment (e.g., annealing treatment, surface treatment such as plasma) during the production of a polymer film, or the polymer precursor itself may have a polymerizable group. Furthermore, from the viewpoints of the dielectric loss tangent of the polymer film, adhesion to a metal layer, heat resistance, and mechanical strength, the polymer film according to the present disclosure preferably contains, as a compound having a functional group, a cured product of a polyfunctional reactive compound, more preferably a polymer of a polyfunctional epoxy compound, and particularly preferably a polymer of a bifunctional epoxy compound. As the polyfunctional reactive compound, polyfunctional ethylenically unsaturated compounds are preferred, and polyfunctional styrene compounds are more preferred. The cured product of the polyfunctional reactive compound may be a homopolymer of the polyfunctional reactive compound, a copolymer of two or more polyfunctional reactive compounds, or a copolymer of one or more polyfunctional reactive compounds and one or more monofunctional reactive compounds. The cured product of the polyfunctional reactive compound is not particularly limited, but is preferably an addition polymerization resin. In addition, it is preferable to use a polymerization initiator for polymerizing the liquid crystal polymer precursor having a polymerizable group and for forming a cured product of the polyfunctional reactive compound. As the polymerization initiator, a known photopolymerization initiator, a known thermal polymerization initiator, etc. can be used.

[0081] -Filler- Layer B may contain a filler from the viewpoint of the thermal expansion coefficient and adhesion to the metal layer. The filler may be particulate or fibrous, and may be an inorganic filler or an organic filler. In the polymer film according to the present disclosure, the number density of the filler is preferably greater inside than on the surface of the polymer film, from the viewpoints of the thermal expansion coefficient and adhesion to the metal layer. Here, the surface of a polymer film refers to the outer surface of the polymer film (the surface in contact with air or a substrate), and refers to the smaller of a range of 3 μm from the surface in the depth direction, or a range of 10% or less of the total thickness of the polymer film from the surface. The interior of a polymer film refers to the portion other than the surface of the polymer film, i.e., the inner surface of the polymer film (the surface not in contact with air or a substrate), and refers to, but is not limited to, a range of ±1.5 μm from the center of the thickness of the polymer film, or a range of ±5% of the total thickness from the center of the thickness of the polymer film, whichever is smaller.

[0082] 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, as the inorganic filler, from the viewpoints of the thermal expansion coefficient and adhesion to the metal layer, metal oxide particles or fibers are preferred, 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, and may be, for example, 25%, 30%, or 35% of the thickness of Layer A. When the particles or fibers are flat, this indicates the length in the direction of the short side. Furthermore, from the viewpoint of the thermal expansion coefficient and adhesion to the metal layer, 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.

[0083] As the organic filler, known organic fillers can be used. Examples of organic filler materials include polyethylene, polystyrene, urea-formalin filler, polyester, cellulose, acrylic resin, fluororesin, hardened epoxy resin, crosslinked benzoguanamine resin, crosslinked acrylic resin, liquid crystal polymer, and materials containing two or more of these. The organic filler may be in the form of fibers such as nanofibers, or may be hollow resin particles. Among these, from the viewpoints of thermal expansion coefficient and adhesion to metal, the organic filler is preferably fluororesin particles, polyester-based resin particles, polyethylene particles, liquid crystal polymer particles, or nanofibers of cellulose-based resin, and more preferably polytetrafluoroethylene particles, polyethylene particles, or liquid crystal polymer particles. Here, the liquid crystal polymer particles refer to, but are not limited to, powdered liquid crystal obtained by polymerizing a liquid crystal polymer and pulverizing it with a pulverizer or the like. The liquid crystal polymer particles are preferably smaller than the thickness of each layer. From the viewpoints of the thermal expansion coefficient and adhesion to the metal layer, 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.

[0084] Layer B may contain only one type of filler, or may contain two or more types of fillers. The filler content in Layer B is preferably less than the filler content in Layer A from the viewpoint of adhesion to the metal layer. From the viewpoint of adhesion to the metal layer, the filler content in Layer B is preferably either zero or more than 0% by volume and not more than 20% by volume relative to the total volume of Layer B, more preferably either zero or more than 0% by volume and not more than 10% by volume relative to the total volume of Layer B, even more preferably either zero or more than 0% by volume and not more than 5% by volume relative to the total volume of Layer B, and particularly preferably zero filler. The filler content in Layer B is preferably 0% to 15% by mass, more preferably 0% to 5% by mass, relative to the total mass of Layer B. The filler such as polyethylene or olefin elastomer is preferably contained in an amount of 50 to 90% by volume, more preferably 75 to 85% by volume, and in this case, the content of the filler in Layer B is preferably 55 to 90% by mass, more preferably 80 to 85% by mass, based on the total mass of Layer B. From the viewpoints of the thermal expansion coefficient and adhesion to the metal layer, the content of the filler 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, relative to the total volume of the polymer film.

[0085] -Other additives- Layer B may contain additives other than the above-mentioned components. As other additives, known additives can be used, such as leveling agents, antifoaming agents, antioxidants, ultraviolet absorbers, flame retardants, and colorants.

[0086] Furthermore, Layer B may contain, as other additives, other resins other than the polymer having a dielectric loss tangent of 0.01 or less or 0.005 or less, the liquid crystal polymer, and the compound having a functional group. Examples of other resins include thermoplastic resins such as polypropylene, polyamide, polyester, polyphenylene sulfide, polyether ketone, polycarbonate, polyether sulfone, polyphenylene ether and modified products thereof, and polyether imide; elastomers such as copolymers of glycidyl methacrylate and polyethylene; and thermosetting resins such as phenolic resins, epoxy resins, polyimide resins, and cyanate resins.

[0087] The total content of other additives in Layer B 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, per 100 parts by mass of the content of the polymer having a dielectric tangent of 0.005 or less. The total content of other additives in Layer B is preferably less than the content of the compound having a functional group.

[0088] The average thickness of Layer B is preferably smaller than the average thickness of Layer A from the viewpoints of the dielectric loss tangent of the polymer film and adhesion to metals. Average thickness T of layer AA and the average thickness of layer B, T B T is the ratio of A / T B The value of is preferably greater than 1, more preferably 2 to 100, even more preferably 2.5 to 20, and particularly preferably 3 to 10, from the viewpoint of the dielectric loss tangent of the polymer film and adhesion to metal. Furthermore, from the viewpoint of the dielectric loss tangent of the polymer film and adhesion to metals, the average thickness of Layer B is preferably 0.1 μm to 20 μm, more preferably 0.5 μm to 15 μm, even more preferably 1 μm to 10 μm, and particularly preferably 3 μm to 8 μm.

[0089] The method for measuring the average thickness of each layer in the polymer film according to the present disclosure is as follows. The polymer film is cut with a microtome, and the cross section is observed under an optical microscope to evaluate the thickness of each layer. Cross-sectional samples are cut out from three or more locations, and the thickness is measured at three or more points on each cross section, and the average of these measurements is taken as the average thickness.

[0090] The polymer film according to the present disclosure has excellent adhesion to metals due to the inclusion of Layer B. For example, when Layer A contains a filler, Layer A is embrittled due to the addition of the filler, but it is presumed that the inclusion of Layer B improves the surface of the polymer film, resulting in improved adhesion and other effects. Furthermore, Layer B is preferably a surface layer (outermost layer). When the polymer film is used as a laminate (metal layer-attached laminate) having a layer structure of, for example, metal layer / Layer A / Layer B, another metal layer or metal layer-attached laminate may be further disposed on the Layer B side. In this case, interfacial breakdown between Layer B and the other metal layer in the laminate is suppressed, and adhesion to the metal layer is improved. Furthermore, the polymer contained in Layer B preferably contains a polymer having higher breaking strength (toughness) than the polymer contained in Layer A. The breaking strength shall be measured by the following method. A sample made of the polymer to be measured is prepared, and the stress relative to elongation is measured using a universal tensile tester "STM T50BP" manufactured by Toyo Baldwin Co., Ltd. in an atmosphere of 25°C and 60% RH at a tension rate of 10% / min to determine the breaking strength.

[0091] <Layer A> The polymer film according to the present disclosure has a layer A and a layer B on at least one side of the layer A. From the viewpoint of the dielectric loss tangent of the polymer film and the adhesion to the metal layer, the layer A preferably contains a polymer having a dielectric loss tangent of 0.01 or less or 0.005 or less. Preferred embodiments of the polymer having a dielectric loss tangent of 0.01 or less or 0.005 or less used in Layer A are the same as preferred embodiments of the polymer having a dielectric loss tangent of 0.01 or less or 0.005 or less used in Layer B, except as described below. The polymer contained in Layer A and having a dielectric dissipation factor of 0.01 or less or 0.005 or less may be the same as or different from the polymer contained in Layer B and having a dielectric dissipation factor of 0.005 or less. From the viewpoint of adhesion between Layer A and Layer B, however, it is preferable that Layer A contains the same polymer as Layer B and having a dielectric dissipation factor of 0.01 or less or 0.005 or less.

[0092] Layer A may contain only one type of polymer or two or more types of polymers having a dielectric loss tangent of 0.01 or less or 0.005 or less. The content of the polymer having a dielectric loss tangent of 0.01 or less or 0.005 or less in Layer A is preferably equal to or greater than the content of the polymer having a dielectric loss tangent of 0.005 or less in Layer B. The content of the polymer having a dielectric loss tangent of 0.01 or less or 0.005 or less in Layer A is preferably 20% by mass to 100% by mass, more preferably 30% by mass to 100% by mass, and particularly preferably 40% by mass to 100% by mass, relative to the total mass of the polymer film, from the viewpoints of the dielectric loss tangent of the polymer film and adhesion to the metal layer.

[0093] Layer A may contain a compound having a functional group. Preferred embodiments of the compound having a functional group used in Layer A are the same as the preferred embodiments of the compound having a functional group used in Layer B, except as described below. The compound having a functional group contained in Layer A may be the same as or different from the compound having a functional group contained in Layer B.

[0094] Layer A may contain only one type of compound having a functional group, or may contain two or more types of compounds having a functional group. From the viewpoints of the dielectric loss tangent of the polymer film and adhesion to the metal layer, the content of the compound having a functional group in the polymer film is preferably 0.5% by mass to 80% by mass, more preferably 1% by mass to 70% by mass, even more preferably 2% by mass to 60% by mass, and particularly preferably 3% by mass to 60% by mass, relative to the total mass of the polymer film.

[0095] From the viewpoints of the dielectric loss tangent of the polymer film and the adhesion to the metal layer, it is more preferable that Layer A contains a filler. Preferred embodiments of the filler used in Layer A are the same as preferred embodiments of the filler used in Layer B, except as described below.

[0096] Layer A may contain only one type of filler, or may contain two or more types of fillers. The filler content in Layer A is preferably higher than the filler content in Layer B. From the viewpoints of the dielectric loss tangent of the polymer film and adhesion to metals, the content of the filler in Layer A is preferably 5 to 80% by volume, more preferably 10 to 70% by volume, even more preferably 20 to 70% by volume, and particularly preferably 30 to 60% by volume, relative to the total volume of Layer A.

[0097] From the viewpoints of the dielectric loss tangent of the polymer film, adhesion to the metal layer, heat resistance, and mechanical strength, it is preferable that Layer A has a three-dimensional crosslinked structure. A method for forming a three-dimensional crosslinked structure includes a method in which at least one selected from the group consisting of a polymer having a dielectric tangent of 0.01 or less or 0.005 or less and a compound having a functional group is a cured product of a multifunctional reactive compound. A preferred embodiment of the cured product of the polyfunctional reactive compound in Layer A is the same as a preferred embodiment of the cured product of the polyfunctional reactive compound in Layer B.

[0098] Layer A may contain additives other than those mentioned above. Preferred embodiments of the other additives used in Layer A are the same as the preferred embodiments of the other additives used in Layer B, except as described below.

[0099] The average thickness of Layer A is not particularly limited, but from the viewpoint of the dielectric loss tangent of the polymer film 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.

[0100] <Layer C> The polymer film according to the present disclosure preferably further comprises Layer C, and from the viewpoint of adhesion to the metal layer, more preferably comprises Layer B, Layer A, and Layer C in this order. Furthermore, when a metal layer is present in addition to the above layers, Layer C is preferably a surface layer (outermost layer), and more preferably a surface layer on the side where the metal is attached. Furthermore, when the polymer film according to the present disclosure is used as a laminate having a metal layer (for example, a metal foil or metal wiring), Layer C is preferably disposed between the metal layer and Layer A. From the viewpoint of the dielectric loss tangent of the polymer film and the adhesion to the metal layer, Layer C preferably contains a polymer having a dielectric loss tangent of 0.01 or less or 0.005 or less. Preferred embodiments of the polymer having a dielectric loss tangent of 0.01 or less or 0.005 or less used in Layer C are the same as preferred embodiments of the polymer having a dielectric loss tangent of 0.01 or less or 0.005 or less used in Layer A, except as described below. The liquid crystal polymer contained in Layer C may be the same as or different from the polymer contained in Layer A or Layer B having a dielectric dissipation factor of 0.01 or less or 0.005 or less. From the viewpoint of adhesion between Layer A and Layer C, however, it is preferable that Layer C contains the same polymer as the polymer contained in Layer A having a dielectric dissipation factor of 0.01 or less or 0.005 or less. From the viewpoint of conformability to unevenness, the layer C preferably contains a material (such as polyethylene) that is flexible at the pressing temperature. Moreover, from the viewpoint of adhesion to metal, Layer C preferably contains a compound having the above-mentioned functional group.

[0101] From the viewpoint of adhesion to metal, the content of the polymer having a dielectric loss tangent of 0.01 or less or 0.005 or less in Layer C is preferably equal to or less than the content of the polymer having a dielectric loss tangent of 0.01 or less or 0.005 or less in Layer A. The content of the polymer having a dielectric loss tangent of 0.01 or less or 0.005 or less in Layer B is preferably 10% by mass to 99% by mass, more preferably 20% by mass to 95% by mass, even more preferably 30% by mass to 90% by mass, and particularly preferably 40% by mass to 80% by mass, relative to the total mass of the polymer film, from the viewpoints of the dielectric loss tangent of the polymer film and adhesion to the metal layer.

[0102] Layer C preferably contains a compound having a functional group. Preferred embodiments of the compound having a functional group used in Layer C are the same as the preferred embodiments of the compound having a functional group used in Layer B, except as described below. The compound having a functional group contained in Layer C may be the same as or different from the compound having a functional group contained in Layer B.

[0103] Layer C may contain only one type of compound having a functional group, or may contain two or more types of compounds having a functional group. The content of the compound having a functional group in Layer C is preferably higher than the content of the compound having a functional group in Layer A. From the viewpoints of the dielectric loss tangent of the polymer film and adhesion to the metal layer, the content of the compound having a functional group in Layer C is preferably 1% by mass to 80% by mass, more preferably 5% by mass to 70% by mass, even more preferably 10% by mass to 60% by mass, and particularly preferably 20% by mass to 60% by mass, relative to the total mass of the polymer film.

[0104] Layer C may contain a filler. Preferred embodiments of the filler used in Layer C are the same as the preferred embodiments of the filler used in Layer B, except as described below.

[0105] The filler content in Layer C is not particularly limited and can be set as desired. However, when metal layers are provided on both sides of the polymer film, it is preferable that the filler content be less than that in Layer A from the viewpoint of adhesion to the metal layers. Furthermore, when metal layers are provided on both sides of the polymer film, the content of filler in Layer C is preferably either zero or more than 0 volume % and not more than 20 volume % relative to the total volume of Layer C, from the viewpoint of adhesion to the metal layer; more preferably either zero or more than 0 volume % and not more than 10 volume % relative to the total volume of Layer C; even more preferably either zero or more than 0 volume % and not more than 5 volume % relative to the total volume of Layer C; and particularly preferably zero. The content of the filler in Layer C is preferably 0% by mass to 15% by mass, and more preferably 0% by mass to 5% by mass, relative to the total mass of Layer C. The filler such as polyethylene or olefin elastomer is preferably contained in an amount of 50 to 90% by volume, more preferably 75 to 85% by volume, based on the total mass of Layer C. In this case, the content of the filler in Layer C is preferably 55 to 90% by mass, more preferably 80 to 85% by mass.

[0106] Layer C may have a three-dimensional crosslinked structure. A preferred embodiment of the cured product of the polyfunctional reactive compound in Layer C is the same as a preferred embodiment of the cured product of the polyfunctional reactive compound in Layer B.

[0107] Layer C may contain additives other than those mentioned above. Preferred embodiments of the other additives used in Layer C are the same as the preferred embodiments of the other additives used in Layer B, except as described below.

[0108] The average thickness of Layer C is preferably smaller than the average thickness of Layer A from the viewpoints of the dielectric loss tangent of the polymer film and adhesion to metals. Average thickness T of layer A A and the average thickness T of layer C C T is the ratio of A / T C From the viewpoint of the dielectric loss tangent of the polymer film and the adhesion to the metal layer, the value of is preferably greater than 1, more preferably 2 to 100, even more preferably 2.5 to 20, and particularly preferably 3 to 10. Also, the average thickness T of layer C C and the average thickness of layer B, T B T is the ratio of C / T B From the viewpoint of the dielectric loss tangent of the polymer film and the adhesion to the metal layer, the value of is preferably 0.2 to 5, more preferably 0.5 to 2, and particularly preferably 0.8 to 1.2. Furthermore, from the viewpoint of the dielectric loss tangent of the polymer film and adhesion to the metal layer, the average thickness of Layer C is preferably 0.1 μm to 20 μm, more preferably 0.5 μm to 15 μm, even more preferably 1 μm to 10 μm, and particularly preferably 3 μm to 8 μm.

[0109] The average thickness of the polymer film according to the present 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 viewpoints of strength and electrical properties (characteristic impedance) when laminated with a metal layer.

[0110] The average thickness of the polymer film is determined by measuring any five points using an adhesive film thickness meter, for example, an electronic micrometer (product name "KG3001A" manufactured by Anritsu Corporation), and averaging these values.

[0111] From the viewpoint of dielectric constant, the dielectric loss tangent of the polymer film according to the present disclosure is preferably 0.02 or less, more preferably 0.01 or less, even more preferably 0.005 or less, and particularly preferably greater than 0 and 0.003 or less.

[0112] <Method of manufacturing polymer film> [Film forming] The method for producing the polymer film according to the present disclosure is not particularly limited, and known methods can be used. Suitable methods for producing a polymer film according to the present disclosure include, for example, a co-casting method, a multi-layer coating method, a co-extrusion method, etc. Among these, the co-casting method is particularly preferred for producing a relatively thin film, and the co-extrusion method is particularly preferred for producing a thick film. When the film is produced by the co-casting method or the multi-layer coating method, it is preferable to use a layer A-forming composition, a layer B-forming composition, a layer C-forming composition, etc., in which the components of each layer, such as a polymer or liquid crystal polymer having a dielectric tangent of 0.01 or less or 0.005 or less, and a compound having a functional group, are dissolved or dispersed in a solvent.

[0113] Examples of the solvent 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. nitriles such as acetonitrile and succinonitrile; amides such as N,N-dimethylformamide, N,N-dimethylacetamide, and N-methylpyrrolidone, and 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 hexamethylphosphoramide and tri-n-butylphosphate, and two or more of these may be used.

[0114] The solvent preferably contains an aprotic compound (particularly preferably an aprotic compound having no halogen atoms) because it is less corrosive and easier to handle. The proportion of the aprotic compound in the entire solvent is preferably 50% to 100% by mass, more preferably 70% to 100% by mass, and particularly preferably 90% to 100% by mass. Furthermore, the aprotic compound preferably contains an amide such as N,N-dimethylformamide, N,N-dimethylacetamide, tetramethylurea, or N-methylpyrrolidone, or an ester such as γ-butyrolactone, because they easily dissolve the liquid crystal polymer, and N,N-dimethylformamide, N,N-dimethylacetamide, or N-methylpyrrolidone are more preferred.

[0115] Furthermore, since the solvent easily dissolves the above-mentioned polymers such as liquid crystal polymers, it is preferable that the solvent contains a compound having a dipole moment of 3 to 5. The proportion of the compound having a dipole moment of 3 to 5 in the entire solvent is preferably 50% by mass to 100% by mass, more preferably 70% by mass to 100% by mass, and particularly preferably 90% by mass to 100% by mass. As the aprotic compound, a compound having a dipole moment of 3 to 5 is preferably used.

[0116] Furthermore, the solvent preferably contains a compound having a boiling point of 220° C. or lower at 1 atmosphere, as this facilitates removal. The proportion of the compound having a boiling point of 220° C. or lower at 1 atmosphere in the entire solvent is preferably 50% by mass to 100% by mass, more preferably 70% by mass to 100% by mass, and particularly preferably 90% by mass to 100% by mass. As the aprotic compound, it is preferable to use a compound having a boiling point of 220° C. or lower at 1 atmospheric pressure.

[0117] In addition, in the method for producing a polymer film according to the present disclosure, a support may be used when the film is produced by the co-casting method, multi-layer coating method, co-extrusion method, etc. In addition, when a metal layer (metal foil) or the like used in the laminate described below is used as a support, it may be used as is without peeling it off. Examples of the support include a metal drum, a metal band, a glass plate, a resin film, and a metal foil, among which a metal drum, a metal band, and a resin film are preferred. Examples of resin films include polyimide (PI) films, and examples of commercially available products include U-Pirex S and U-Pirex R manufactured by Ube Industries, Ltd., Kapton manufactured by DuPont-Toray Co., Ltd., and IF30, IF70, and LV300 manufactured by SKC Kolon PI. The support may have a surface treatment layer formed on its surface to facilitate peeling, which may be made of hard chrome plating, fluororesin, or the like. The average thickness of the support is not particularly limited, but is preferably from 25 μm to 75 μm, and more preferably from 50 μm to 75 μm.

[0118] The method for removing at least a part of the solvent from the cast or coated film-like composition (cast film or coating film) is not particularly limited, and any known drying method can be used.

[0119] [Stretching] The polymer film according to the present disclosure can be appropriately combined with stretching in order to control molecular orientation and adjust the linear expansion coefficient and mechanical properties. The stretching method is not particularly limited, and known methods can be used. The stretching may be performed in a solvent-containing state or in a dry film state. Stretching in a solvent-containing state may be performed by gripping the film and stretching, or by utilizing autogenous shrinkage due to drying without stretching. Stretching is particularly effective for improving breaking elongation and breaking strength when the film brittleness has decreased due to the addition of inorganic fillers, etc.

[0120] Furthermore, the method for producing a polymer film according to the present disclosure may include a step of polymerization using light or heat, if necessary. The light irradiation means and heat applying means are not particularly limited, and known light irradiation means such as a metal halide lamp and known heat applying means such as a heater can be used. The light irradiation conditions and heat application conditions are not particularly limited, and the irradiation can be carried out at a desired temperature and time in a known atmosphere.

[0121] [Heat treatment] The method for producing a polymer film according to the present disclosure preferably includes a step of heat-treating (annealing) the polymer film. Specifically, from the viewpoints of dielectric loss tangent and peel strength, the heat treatment temperature in the heat treatment step is preferably 260° C. to 370° C., more preferably 280° C. to 360° C., and even more preferably 300° C. to 350° C. The heat treatment time is preferably 15 minutes to 10 hours, and more preferably 30 minutes to 5 hours. Furthermore, the method for producing a polymer film according to the present disclosure may include other known steps as necessary.

[0122] <Application> The polymer film according to the present disclosure can be used in a variety of applications, and is particularly suitable for use as a film for electronic components such as printed wiring boards, and is more particularly suitable for use in flexible printed circuit boards. Furthermore, the polymer film according to the present disclosure can be suitably used as a polymer film for bonding metals.

[0123] (Laminate) The laminate according to the present disclosure may be any laminate in which the polymer film according to the present disclosure is laminated, but it preferably has the polymer film according to the present disclosure and a metal layer disposed on the surface of the polymer film facing Layer B, and it is more preferable that the metal layer is a copper layer. The metal layer disposed on the surface on the layer B side is preferably a metal layer disposed on the surface of the layer B. Furthermore, the laminate according to the present disclosure preferably comprises a polymer film according to the present disclosure having Layer B, Layer A, and Layer C in this order, a metal layer disposed on the surface of the polymer film facing Layer B, and a metal layer disposed on the surface of the polymer film facing Layer C, and it is more preferable that both of the metal layers are copper layers. It is preferable that the metal layer arranged on the surface on the layer C side is a metal layer arranged on the surface of the layer C, and it is more preferable that the metal layer arranged on the surface on the layer B side is a metal layer arranged on the surface of the layer B, and that the metal layer arranged on the surface on the layer C side is a metal layer arranged on the surface of the layer C. Furthermore, the metal layer disposed on the surface on the layer B side and the metal layer disposed on the surface on the layer C side may be metal layers of the same material, thickness, and shape, or may be metal layers of different material, thickness, and shape. From the viewpoint of adjusting the characteristic impedance, the metal layer disposed on the surface on the layer B side and the metal layer disposed on the surface on the layer C side may be metal layers of different material and thickness, and a metal layer may be laminated on only one of the layers B and C. Furthermore, from the viewpoint of adjusting the characteristic impedance, a preferred embodiment is one in which a metal layer is laminated on one side of Layer B or Layer C, and another polymer film is laminated on the other side.

[0124] The method for attaching the polymer film according to the present disclosure to the metal layer is not particularly limited, and any known lamination method can be used.

[0125] When the metal layer is the copper layer, 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.

[0126] In the present disclosure, the peel strength between a polymer film and a metal layer (for example, a copper layer) is measured by the following method. A 1.0 cm wide peel test piece is prepared from a laminate of a polymer film and a metal layer, and the polymer film is fixed to a flat plate with double-sided adhesive tape. The strength (kN / m) is measured when the polymer film is peeled from the metal layer at a rate of 50 mm / min using the 180° method in accordance with JIS C 5016 (1994).

[0127] The surface roughness Rz of the metal layer on the side in contact with the polymer film is preferably less than 1 μm, more preferably 0.5 μm or less, and particularly preferably 0.3 μm or less, from the viewpoint of reducing transmission loss of high frequency signals. The surface roughness Rz of the metal layer is preferably as small as possible, and therefore no particular lower limit is set, but may be, for example, 0 or more.

[0128] In this disclosure, "surface roughness Rz" means the sum of the maximum peak height and the maximum valley depth observed on a roughness curve over a reference length, expressed in micrometers. In the present disclosure, the surface roughness Rz of a metal layer (for example, a copper layer) is measured by the following method. Using the non-contact surface / layer cross-sectional shape measurement system VertScan (manufactured by Ryoka Systems Co., Ltd.), an area 465.48 μm long and 620.64 μm wide is measured to create a roughness curve for the surface of the object (metal layer) and the average line of said roughness curve. A section corresponding to the reference length is extracted from the roughness curve. The surface roughness Rz of the object is measured by calculating 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 on the extracted roughness curve.

[0129] The metal layer is preferably a copper layer, and the copper layer is preferably a rolled copper foil formed by a rolling method or an electrolytic copper foil formed by an electrolytic method.

[0130] 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 copper foil may be a carrier-attached copper foil formed on a support (carrier) in a peelable manner. Any known carrier 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.

[0131] In order to further enhance the effects of the present disclosure, the metal layer preferably has a known surface treatment layer (e.g., a chemical treatment layer) on the surface that contacts the polymer film to ensure adhesion to the resin. The interactive group is preferably a group corresponding to the functional group of the compound having the functional group contained in the polymer film, such as an amino group and an epoxy group, or a hydroxy group and an epoxy group. Examples of the group capable of interacting include the groups exemplified as functional groups in the compound having the functional group. Among these, from the viewpoints of adhesion and ease of processing, a group capable of forming a covalent bond is preferred, an amino group or a hydroxy group is more preferred, and an amino group is particularly preferred.

[0132] The metal layer in the laminate according to the present disclosure may be a metal layer having a circuit pattern. It is also preferable to process the metal layer in the laminate according to the present disclosure into a desired circuit pattern by, for example, etching, to form a flexible printed circuit board. The etching method is not particularly limited, and known etching methods can be used. [Example]

[0133] The present disclosure will be described in more detail below with reference to examples. The materials, amounts used, ratios, processing details, processing procedures, etc. shown in the following examples can be appropriately changed without departing from the spirit of the present disclosure. Therefore, the scope of the present disclosure is not limited to the specific examples shown below.

[0134] <<Measurement method>> [Dielectric loss tangent] The dielectric constant was measured at a frequency of 10 GHz using the resonance perturbation method. A 10 GHz cavity resonator (Kanto Electronics Application Development Co., Ltd. CP531) was connected to a network analyzer (Agilent Technology E8363B). A sample (width: 2 mm x length: 80 mm) was inserted into the cavity resonator, and the sample's dielectric constant and dielectric loss tangent were measured from the change in resonance frequency before and after insertion for 96 hours under an environment of 25°C and 60% RH. When a metal layer was laminated on the polymer film, the metal layer was etched and only the removed polymer film was used for evaluation.

[0135] [Peel strength] A 1.0 cm wide peel test piece was prepared from a laminate of a polymer film and a copper layer, and the polymer film was fixed to a flat plate with double-sided adhesive tape. The strength (kN / m) when the copper layer was peeled from the polymer film at 25°C and a peel rate of 50 mm / min was measured using the 180° method in accordance with JIS C 5016 (1994). For laminates in which copper layers were disposed on both sides of the polymer film, the peel strength of both sides was evaluated, and the lower value is listed in Table 1.

[0136] <<Production Example>> <Polymer or liquid crystal polymer with a dielectric dissipation factor of 0.01 or less or 0.005 or less> LC-A: Liquid crystal polymer prepared according to the following manufacturing method

[0137] -Production of LC-A- A reactor equipped with a stirrer, a torque meter, a nitrogen gas inlet tube, a thermometer, and a reflux condenser was charged with 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. The gas in the reactor was replaced with nitrogen gas, and the mixture was heated from room temperature (23°C) to 140°C over 60 minutes while stirring under a nitrogen gas stream, and then refluxed at 140°C for 3 hours. Next, while distilling off by-product acetic acid and unreacted acetic anhydride, the temperature was raised from 150°C to 300°C over 5 hours, and after holding at 300°C for 30 minutes, the contents were removed from the reactor and cooled to room temperature. The resulting solid was pulverized in a pulverizer to obtain a powdered liquid crystalline polyester (B1). The flow initiation temperature of this liquid crystalline polyester (B1) was 193.3°C.

[0138] The liquid crystal polyester (B1) obtained above was heated in a nitrogen atmosphere from room temperature to 160°C over 2 hours and 20 minutes, then heated from 160°C to 180°C over 3 hours and 20 minutes, and held at 180°C for 5 hours to undergo solid-state polymerization. The mixture was then cooled and pulverized in a pulverizer to obtain powdered liquid crystal polyester (B2). The flow initiation temperature of this liquid crystal polyester (B2) was 220°C.

[0139] The liquid crystalline polyester (B2) obtained above was heated in a nitrogen atmosphere from room temperature (23°C) to 180°C over 1 hour 25 minutes, then heated from 180°C to 255°C over 6 hours 40 minutes, and held at 255°C for 5 hours to undergo solid-state polymerization. The resulting mixture was then cooled to obtain a powdered liquid crystalline polyester (LC-A). The flow initiation temperature of LC-A was 302°C. The melting point of this LC-A was measured using a differential scanning calorimeter and found to be 311°C.

[0140] LC-C: Liquid crystal polymer prepared according to the following manufacturing method

[0141] -LC-C Manufacturing- A reactor equipped with a stirrer, a torque meter, a nitrogen gas inlet tube, a thermometer, and a reflux condenser was charged with 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. The gas in the reactor was replaced with nitrogen gas, and the mixture was heated 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 by-product acetic acid and unreacted acetic anhydride, the temperature was raised from 150°C to 300°C over 5 hours, and after holding at 300°C for 30 minutes, the contents were removed from the reactor and cooled to room temperature. The obtained solid was pulverized in a pulverizer to obtain a powdered liquid crystal polyester (C1).

[0142] The liquid crystal polyester (C1) obtained above was heated from room temperature to 160°C over 2 hours and 20 minutes under a nitrogen atmosphere, 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-state polymerization. The mixture was then cooled and pulverized in a pulverizer to obtain powdered liquid crystal polyester (C2).

[0143] The liquid crystal polyester (C2) obtained above was heated from room temperature (23°C) to 180°C over 1 hour and 20 minutes in a nitrogen atmosphere, then heated from 180°C to 240°C over 5 hours, and held at 240°C for 5 hours to undergo solid-state polymerization. The mixture was then cooled to obtain powdered liquid crystal polyester (C) (LC-C).

[0144] LC-D: Liquid crystal polymer prepared according to the following manufacturing method

[0145] -LCD manufacturing- A reactor equipped with a stirrer, a torque meter, a nitrogen gas inlet tube, a thermometer, and a reflux condenser was charged with 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 1,123 g (11 mol) of acetic anhydride. The gas inside the reactor was replaced with nitrogen gas, and then 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 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. The contents were then removed from the reactor and cooled to room temperature. The resulting solid was pulverized in a pulverizer to obtain a powdered liquid crystal polyester (D1).

[0146] The liquid crystal polyester (D1) obtained above was solid-phase polymerized by holding it at 250°C for 3 hours under a nitrogen atmosphere, then cooled and pulverized in a pulverizer to obtain a powdered liquid crystal polyester (LC-D).

[0147] P-1: A mixture of commercially available polyphenylene ether pellets (SA120, manufactured by SABIC, weight-average molecular weight Mw 2,600) / bisphenol A epoxy resin (Epicron 850S, manufactured by DIC Corporation, average number of epoxy groups 2) / bisphenol A cyanate ester resin (Badcy, manufactured by Lonza Japan Co., Ltd.) / aromatic condensed phosphate ester (PX-200, manufactured by Daihachi Chemical Industry Co., Ltd.) / aluminum trisdiethylphosphinate (Exolit OP-935, manufactured by Clariant Japan Co., Ltd.) / zinc octanoate = 25 / 34 / 25 / 8 / 8 / 0.01 (mass ratio) P-2: Commercially available cyclic olefin resin (Arton F3500, manufactured by JSR Corporation)

[0148] <Additives> [Compounds having functional groups] A-1: The following mixture was added so that the solid content in the mixture was in the mass ratio shown in Table 1. Celloxide 2021P (3',4'-epoxycyclohexylmethyl 3,4-epoxycyclohexanecarboxylate, manufactured by Daicel Corporation): 100 parts by mass IRGACURE 290 (cationic polymerization initiator, sulfonium salt compound, manufactured by BASF): 3 parts by mass

[0149] A-2: The following compound was added so that the solid content was in the mass ratio shown in Table 1. Celloxide 2021P (manufactured by Daicel Corporation): 100 parts by weight

[0150] A-3: The following compound was added so that the solid content was in the mass ratio shown in Table 1. 2,2'-bis(4-cyanatophenyl)propane (curable compound, manufactured by Tokyo Chemical Industry Co., Ltd.): 100 parts by mass 1-benzyl-2-methylimidazole (Mitsubishi Chemical Corporation, BMI12): 10 parts by mass A-4: A commercially available aminophenol-type epoxy resin (jER630LSD, manufactured by Mitsubishi Chemical Corporation) was used so that the solid content was the amount shown in Table 1. A-5: A commercially available thermosetting resin (SLK, manufactured by Shin-Etsu Chemical Co., Ltd., mainly containing a polymer-type curable compound) was used so that the solid content was the amount shown in Table 1. A-6: A mixture of A-4 and F-7 (described later) (mass ratio 6:94) was used so that the solid content was the amount shown in Table 1. A-7: A mixture of bisphenol A epoxy resin (Epicron 850S, manufactured by DIC Corporation, average number of epoxy groups: 2) / bisphenol A cyanate ester resin (Badcy, manufactured by Lonza Japan Co., Ltd.) / aromatic condensed phosphate ester (PX-200, manufactured by Daihachi Chemical Industry Co., Ltd.) / aluminum trisdiethylphosphinate (Exolit OP-935, manufactured by Clariant Japan Co., Ltd.) / zinc octanoate = 45 / 33 / 11 / 11 / 0.01 (mass ratio)

[0151] [Filler] F-1: Liquid crystal polymer particles prepared according to the following manufacturing method

[0152] -Production of LC-B- A reactor equipped with a stirrer, torque meter, nitrogen gas inlet tube, thermometer, and reflux condenser was charged with 1034.99 g (5.5 mol) of 2-hydroxy-6-naphthoic acid, 378.33 g (1.75 mol) of 2,6-naphthalenedicarboxylic acid, 83.07 g (0.5 mol) of terephthalic acid, 272.52 g of hydroquinone (2.475 mol, 0.225 molar excess relative to the combined molar amount of 2,6-naphthalenedicarboxylic acid and terephthalic acid), 1226.87 g (12 mol) of acetic anhydride, and 0.17 g of 1-methylimidazole as a catalyst. After the gas in the reactor was replaced with nitrogen gas, the mixture was heated from room temperature to 145°C over 15 minutes under nitrogen gas flow with stirring and refluxed at 145°C for 1 hour.

[0153] Next, while distilling off the by-product acetic acid and unreacted acetic anhydride, the temperature was raised from 145°C to 310°C over 3 hours and 30 minutes, and after maintaining at 310°C for 3 hours, the solid liquid crystalline polyester (LC-B) was taken out and cooled to room temperature. The flow initiation temperature of this polyester (LC-B) was 265°C.

[0154] [Production of Liquid Crystal Polyester Particles (F-1)] The liquid crystalline polyester (LC-B) was pulverized using a jet mill (KJ-200 manufactured by Kurimoto Iron Works, Ltd.) to obtain liquid crystalline polyester particles (F-1). The liquid crystalline polyester particles had an average particle size of 9 μm.

[0155] F-2: Commercially available silica particles (SO-C2, manufactured by Admatechs Co., Ltd.) having an average particle size of 0.5 μm were used so that the solid content was the amount shown in Table 1. F-3: Commercially available polytetrafluoroethylene (PTFE) nanoparticles (Polyflon PTFE D-210C, average particle size 0.25 μm, manufactured by Daikin Industries, Ltd.) were used in a manner that the solvent was replaced with N-methylpyrrolidone solvent, and the solid content in the polymer film was the amount listed in Table 1. F-4: Tetrafluoroethylene and perfluoroalkoxyethylene copolymer (PFA) particles (melting point 280°C, average particle size 0.2 μm to 0.5 μm, dielectric dissipation factor 0.001) F-5: Commercially available hollow powder with an average particle size of 16 μm (Glass Bubbles iM30K, manufactured by 3M Japan Ltd.) F-6: Boron nitride particles (melting point > 500°C, HP40MF100 (manufactured by Mizushima Ferroalloy Co., Ltd.), dielectric dissipation factor 0.0007) F-7: Commercially available ultra-high molecular weight polyethylene particles having an average particle size of 10 μm (Mipelon PM200, manufactured by Mitsui Chemicals, Inc.) were used so that the solid content was the amount shown in Table 1.

[0156] (Examples 1 to 25 and Comparative Example 1) <Film forming> The methods shown in Table 1 were selected from the following multi-layer coating methods A and B and co-casting methods A to D.

[0157] [Multilayer Coating A] -Preparation of polymer solution- A polymer having a dielectric dissipation factor of 0.005 or less, as shown in Table 1, was added to N-methylpyrrolidone and stirred at 140°C for 4 hours under a nitrogen atmosphere to form a solution, after which additives shown in Table 1 were added so as to achieve the mass ratios shown in Table 1, and the mixture was stirred at 25°C for 30 minutes to obtain a polymer solution. The solids concentration of the polymer solution for Layer A was 10 mass% and that for Layer B (surface layer) was 7 mass%. Subsequently, the mixture was first passed through a sintered fiber metal filter having a nominal pore size of 5 μm, and then passed through another sintered fiber metal filter also having a nominal pore size of 5 μm to obtain a polymer solution. When the additive was not soluble in N-methylpyrrolidone, a liquid crystal polymer solution was prepared without adding the additive, and after passing it through the sintered fiber metal filter, the additive was added and stirred.

[0158] -Film production- The obtained polymer solutions for Layer A and Layer B were transferred to a slot die coater equipped with a slide coater and applied to the treated surface of a copper foil (manufactured by Fukuda Metal Foil & Powder Co., Ltd., CF-T9DA-SV-18, thickness 18 μm, surface roughness of the attachment surface (treated surface) Rz 0.85 μm) to form a three-layer film (Layer B / Layer A / Layer B). The cast film was dried at 40° C. for 4 hours to remove the solvent, thereby obtaining a polymer film.

[0159] [Multilayer coating B] -Preparation of polymer solution- The polymers and additives shown in Table 1 were added to toluene to a solid concentration of 80%, and the mixture was stirred for 60 minutes to obtain polymer solutions for Layer A and Layer B, respectively.

[0160] -Film production- The polymer solutions for Layer A and Layer B were applied in a multilayer manner to the treated surface of a copper foil (manufactured by Fukuda Metal Foil & Powder Co., Ltd., CF-T9DA-SV-18, thickness 18 μm, surface roughness Rz 0.85 μm on the treated surface) using a slot die coater equipped with a slide coater. The coating was dried at 100°C for 3 minutes and then at 170°C for 3 minutes to remove the solvent from the coating. The temperature was then increased from room temperature to 200°C at a rate of 1°C / min and maintained at that temperature for 2 hours for heat treatment, yielding a polymer film (laminate) with a copper layer.

[0161] [Co-casting A (solution casting)] -Preparation of polymer solution- A polymer having a dielectric loss tangent of 0.005 or less as shown in Table 1 was added to N-methylpyrrolidone and stirred under a nitrogen atmosphere at 140°C for 4 hours to form a solution, after which additives as shown in Table 1 were added so as to obtain the mass ratios shown in Table 1, and the mixture was stirred at 25°C for 30 minutes to obtain a liquid crystal polymer solution. The solid concentration of the solution for Layer A was 23 mass% and that for Layer B (surface layer) was 20 mass%. Subsequently, the mixture was first passed through a sintered fiber metal filter having a nominal pore size of 10 μm, and then passed through a sintered fiber metal filter also having a pore size of 10 μm to obtain a polymer solution.

[0162] -Film production- The obtained polymer solutions for Layer A and Layer B were sent to a casting die equipped with a feed block adjusted for co-casting a three-layer structure (Layer B / Layer A / Layer B), and cast onto the treated surface of a copper foil (manufactured by Fukuda Metal Foil & Powder Co., Ltd., CF-T9DA-SV-18, thickness 18 μm, surface roughness of the attached surface (treated surface) Rz 0.85 μm). The cast film was dried at 40°C for 4 hours to remove the solvent, and a polymer film was obtained.

[0163] [Co-casting B (solution casting)] -Preparation of polymer solution- The polymers listed in Table 1 were added to N-methylpyrrolidone and stirred at 140°C for 4 hours under a nitrogen atmosphere to form a solution, which was then passed through a sintered fiber metal filter with a nominal pore size of 10 μm, followed by another sintered fiber metal filter with a nominal pore size of 10 μm. Next, the additives listed in Table 1 were added in the mass ratios listed in Table 1, and the mixture was stirred at 25°C for 30 minutes to obtain a polymer solution.

[0164] -Film production- The resulting polymer solutions for Layer A, Layer B, and Layer C were sent to a casting die equipped with a multi-manifold adjusted for co-casting a three-layer structure (Layer B / Layer A / Layer C) and cast onto the treated surface of a copper foil (Fukuda Metal Foil & Powder Co., Ltd., CF-T9DA-SV-18, thickness 18 μm, surface roughness Rz 0.85 μm on the attachment surface (treated surface)) with Layer B in contact with the copper foil. The cast film was dried at 60°C for 4 hours to remove the solvent, yielding a polymer film. When no polymer solution for Layer C was available, the three-layer structure was changed to a three-layer structure (Layer B / Layer A / Layer B).

[0165] [Co-casting C (solution casting)] A polymer solution was prepared in the same manner as in Co-casting B. Furthermore, casting was performed in the same manner as in Co-casting B, and after removing the solvent from the cast film, the temperature was increased from room temperature (25°C) to 280°C at a rate of 1°C / min in a nitrogen atmosphere and maintained at that temperature for 2 hours for heat treatment to obtain a polymer film (laminate) having a copper layer.

[0166] [Co-casting D (solution casting)] -Preparation of polymer solution- The polymer shown in Table 1 was added to dichloromethane and stirred at 60°C for 30 minutes to form a solution, which was then passed through a sintered fiber metal filter with a nominal pore size of 10 μm, followed by another sintered fiber metal filter with a nominal pore size of 10 μm. Next, the additives shown in Table 1 were added in the mass ratios shown in Table 1, and the mixture was stirred at 25°C for 30 minutes to obtain a polymer solution.

[0167] -Film production- The obtained polymer solutions for Layer A and Layer B were sent to a casting die equipped with a multi-manifold adjusted for co-casting a three-layer structure (Layer B / Layer A / Layer B), and cast onto the treated side of a copper foil (Fukuda Metal Foil & Powder Co., Ltd., CF-T9DA-SV-18, thickness 18 μm, surface roughness Rz 0.85 μm of the attachment surface (treated surface)) so that Layer B was in contact with the copper foil. The cast film was dried at 100°C for 3 minutes and then at 170°C for 3 minutes to remove the solvent, yielding a polymer film (laminate (Layer B / Layer A / Layer B)).

[0168] <Preparation of copper clad laminate> [Film pretreatment] For polymer films containing A-1 as a compound having a functional group, an air-cooled metal halide lamp (manufactured by Eye Graphics Co., Ltd.) was used to irradiate the film with a dose of 300 mJ / cm immediately before laminating the copper foil. 2 The celloxide 2021P was polymerized by irradiating it with ultraviolet light.

[0169] [Metal layer formation] - Copper clad laminate precursor process - Copper foil (Fukuda Metal Foil & Powder Co., Ltd., CF-T9DA-SV-18, thickness 18 μm, surface roughness of the attached surface (treated surface) Rz 0.85 μm) was placed on the film formed by multilayer coating, co-casting A, or co-casting B so that it was in contact with the side of the polymer film on which the copper layer was not formed, and laminated for 1 minute using a laminator (Nikko Materials Co., Ltd., "Vacuum Laminator V-130") at 140°C and a lamination pressure of 0.4 MPa to obtain a copper-clad laminate precursor.

[0170] -Main thermocompression bonding process- The obtained copper clad laminate precursor was subjected to thermocompression bonding using a thermocompression bonding machine ("MP-SNL" manufactured by Toyo Seiki Seisakusho, Ltd.) at 300°C and 4.5 MPa for 10 minutes to produce a copper clad laminate.

[0171] -Annealing process- The film of Example 5 was further heated in an oven at 250° C. for 3 hours after the main thermocompression bonding step.

[0172] <<Evaluation>> The prepared polymer films were evaluated by the methods described above, and the results are shown in Table 1. Furthermore, for each of the prepared polymer films, a resin film was laminated in place of the copper foil, and the peel strength was measured.

[0173] [Table 1]

[0174] The results shown in Table 1 show that the polymer films of Examples 1 to 25 according to the present disclosure are superior to the polymer film of Comparative Example 1 in adhesion to the metal layer. Furthermore, from the results shown in Table 1, the polymer films of Examples 1 to 25 according to the present disclosure are polymer films with low dielectric loss tangents. Furthermore, the polymer films of Examples 1 to 25, which are polymer films according to the present disclosure in which a resin film was laminated instead of a copper foil, showed superior adhesion to the resin film to the polymer film of Comparative Example 1.

Claims

1. A layer A and a layer B on at least one surface of the layer A, the layer A contains a polymer having a dielectric loss tangent of 0.005 or less, the polymer in Layer A having a dielectric dissipation factor of 0.005 or less includes at least one polymer selected from the group consisting of a liquid crystal polymer, a fluorine-containing polymer, a polymer of a compound having a cyclic aliphatic hydrocarbon group and a group having an ethylenically unsaturated bond, polyphenylene ether, and an aromatic polyether ketone; the layer B contains a polymer having a dielectric loss tangent of 0.005 or less and a compound having a functional group, The functional group is at least one group selected from the group consisting of a group capable of forming a covalent bond, a group capable of forming an ionic bond, a group capable of forming a hydrogen bond, a group capable of forming a dipole-dipole interaction, and a group capable of undergoing a curing reaction. Polymer film.

2. A polymer film as described in claim 1, wherein the melting point Tm or 5 mass % weight loss temperature Td of the polymer in layer B having a dielectric tangent of 0.005 or less is 200°C or higher.

3. A polymer film as described in claim 1, wherein the glass transition temperature Tg of the polymer in layer B having a dielectric tangent of 0.005 or less is 200°C or higher.

4. A polymer film described in any one of claims 1 to 3, wherein the polymer in layer B having a dielectric tangent of 0.005 or less is at least one polymer selected from the group consisting of liquid crystal polymers, fluorine-based polymers, polymers of compounds having a cyclic aliphatic hydrocarbon group and a group having an ethylenically unsaturated bond, polyphenylene ether, and aromatic polyether ketone.

5. 5. The polymer film according to claim 1, wherein the functional group is a group capable of forming a covalent bond.

6. 6. The polymer film according to claim 5, wherein the covalently bondable group is at least one functional group selected from the group consisting of an epoxy group, an oxetanyl group, an isocyanate group, an acid anhydride group, a carbodiimide group, an N-hydroxyester group, a glyoxal group, an imide ester group, a halogenated alkyl group, and a thiol group.

7. 5. The polymer film according to claim 1, wherein the functional group is a group capable of forming an ionic bond, a group capable of forming a hydrogen bond, or a group capable of forming a dipole-dipole interaction.

8. The polymer film according to any one of claims 1 to 7, wherein the polymer film comprises a cured product of a polyfunctional reactive compound.

9. 9. The polymer film according to claim 1, wherein the layer B contains a polymer having a functional group as the compound having a functional group.

10. 10. The polymer film according to claim 9, wherein the polymer having functional groups is a liquid crystal polymer precursor.

11. A polymer film described in any one of claims 1 to 10, wherein the polymer in layer B having a dielectric tangent of 0.005 or less and the compound having the functional group are compatible with each other.

12. The difference between the SP value of the polymer in layer B having a dielectric loss tangent of 0.005 or less by the Hoy method and the SP value of the compound having the functional group by the Hoy method is 5 MPa ０．５ The polymer film according to any one of claims 1 to 11, wherein:

13. A polymer film described in any one of claims 1 to 12, wherein the polymer in layer B having a dielectric tangent of 0.005 or less is a liquid crystal polymer having 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 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, 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 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.

14. Further comprising a layer C, The polymer film according to any one of claims 1 to 13, comprising the Layer B, the Layer A, and the Layer C in this order.

15. The polymer film according to any one of claims 1 to 14, wherein the polymer film has a dielectric loss tangent of 0.01 or less.

16. The polymer film according to any one of claims 1 to 15, wherein the dielectric loss tangent of the layer B is 0.02 or less.

17. The polymer film according to claim 14, wherein the dielectric loss tangent of the layer C is 0.02 or less.

18. A layer A and a layer B on at least one surface of the layer A, the layer A contains a polymer having a dielectric loss tangent of 0.005 or less, the polymer in Layer A having a dielectric dissipation factor of 0.005 or less includes at least one polymer selected from the group consisting of a liquid crystal polymer, a fluorine-containing polymer, a polymer of a compound having a cyclic aliphatic hydrocarbon group and a group having an ethylenically unsaturated bond, polyphenylene ether, and an aromatic polyether ketone; the layer B contains a liquid crystal polymer and a compound having a functional group, The functional group is at least one group selected from the group consisting of a group capable of forming a covalent bond, a group capable of forming an ionic bond, a group capable of forming a hydrogen bond, a group capable of forming a dipole-dipole interaction, and a group capable of undergoing a curing reaction. Polymer film.

19. A layer A and a layer B on at least one surface of the layer A, the layer A contains a polymer having a dielectric loss tangent of 0.005 or less, the polymer in Layer A having a dielectric dissipation factor of 0.005 or less includes at least one polymer selected from the group consisting of a liquid crystal polymer, a fluorine-containing polymer, a polymer of a compound having a cyclic aliphatic hydrocarbon group and a group having an ethylenically unsaturated bond, polyphenylene ether, and an aromatic polyether ketone; the layer B contains a polymer having a dielectric loss tangent of 0.01 or less and a compound having a functional group, The functional group is at least one group selected from the group consisting of a group capable of forming a covalent bond, a group capable of forming an ionic bond, a group capable of forming a hydrogen bond, a group capable of forming a dipole-dipole interaction, and a group capable of undergoing a curing reaction. Polymer film.

20. The polymer film according to any one of claims 1 to 19, wherein the compound having a functional group is a compound that interacts with, bonds to, or forms entanglements with the polymer in Layer B having a dielectric loss tangent of 0.005 or less, the liquid crystal polymer, or the polymer having a dielectric loss tangent of 0.01 or less.

21. A laminate comprising the polymer film according to any one of claims 1 to 20 and a metal layer disposed on at least one surface of the polymer film.

22. 22. The laminate of claim 21, further comprising a metal layer disposed on each side of the polymer film.

23. 23. The laminate according to claim 21 or 22, wherein the surface roughness Rz of the metal layer on the side in contact with the polymer film is 5 μm or less.

24. the metal layer is a copper layer, The laminate according to any one of claims 21 to 23, wherein the peel strength between the polymer film and the copper layer is 0.5 kN / m or more.

25. The laminate according to any one of claims 21 to 24, wherein the metal layer has a group capable of interacting with the polymer film on the surface thereof that comes into contact with the polymer film.

26. 26. The laminate according to claim 25, wherein the interactive group is an amino group.

Images