Polymer film, manufacturing method thereof, and laminate

Abstract

To provide a polymer film with improved brittleness and a method of producing the same, and a laminate including the polymer film.SOLUTION: Provided is a polymer film including a particle A having a constricted structure and a polymer B. In the polymer film, the particle A is a particle having one or more minimum values in a central portion excluding end portions of the particle A, in terms of a length of the particle A in a direction perpendicular to the longitudinal direction in at least one cross section of the particle A. There is also provided a laminate including the polymer film.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to a polymer film, a method for producing the same, and a laminate. [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.

[0003] As a conventional thermoplastic resin composition, for example, the one described in Patent Document 1 is known. Patent Document 1 describes a thermoplastic resin composition that contains a random copolymer containing two or more monomer units that have different glass transition temperatures when made into a homopolymer, and that, when molded into a plate, has a structure in which components with different elastic moduli are phase-separated on the nanoscale when the elastic moduli are mapped using an atomic force microscope (AFM). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2020-105415 Summary of the Invention [Problem to be solved by the invention]

[0005] The problem that embodiments of the present invention aim to solve is to provide a polymer film with improved brittleness and a method for producing the same. Another problem to be solved by another embodiment of the present invention is to provide a laminate using the above polymer film. [Means for solving the problem]

[0006] The means for solving the above problems include the following aspects. <1> A polymer film comprising particles A having a constricted structure and polymer B. <2> A polymer film comprising a particle A and a polymer B, wherein the particle A is a particle in which, in at least one cross section of the particle A, the length in a direction perpendicular to the longitudinal direction of the particle A has one or more minimum values in the central part of the particle A excluding the ends. <3> The melting point Tm of the particles A is 400°C or less. <1> or <2> The polymer film according to claim 1. <4> The content of the particles A is 10% by volume or more relative to the total volume of the polymer film. <1> ~ <3> 10. The polymer film according to any one of the preceding items. <5> The particle A is a particle formed by fusing a plurality of particles together, or a particle formed by bonding a plurality of particles together by chemical bonds on the particle surface. <1> ~ <4> 10. The polymer film according to any one of the preceding items. <6> The particle A is a particle formed by fusing a plurality of particles together. <5> The polymer film according to claim 1. <7> The dielectric loss tangent of the particle A is less than 0.01. <1> ~ <6> 10. The polymer film according to any one of the preceding items. <8> The particles A contain at least one polymer selected from the group consisting of fluoropolymers, liquid crystal polymers, and polyethylene. <1> ~ <7> 10. The polymer film according to any one of the preceding items. <9> The thermal expansion coefficient of the particles A is smaller than the thermal expansion coefficient of the polymer B. <1> ~ <8> 10. The polymer film according to any one of the preceding items. <10> The tensile strength of the polymer B is 50 MPa or more. <1> ~ <9> 10. The polymer film according to any one of the preceding items. <11> The polymer B has at least one bond selected from the group consisting of a urethane bond, a urea bond, an amide bond, an ester bond, an ether bond, an N-C bond, an S-C bond, and a siloxane bond. <1> ~ <10> 10. The polymer film according to any one of the preceding items. <12> Further containing a polymerizable compound <1> ~ <11> 10. The polymer film according to any one of the preceding items. <13> The polymerizable compound has at least one group selected from the group consisting of a (meth)acryloyl group, 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 hydroxy group, a carboxy group, an amino group, an imidazole group, and a thiol group. <12> The polymer film according to claim 1. <14> The content of the polymerizable compound is more than 0% by mass and less than 5% by mass with respect to the total mass of the polymer film. <12> or <13> The polymer film according to claim 1. <15> <1> ~ <14> 1. A laminate comprising the polymer film according to any one of 1 to 8 above, and a metal layer or metal wiring disposed on at least one surface of the polymer film. <16> A method for producing a polymer film, comprising a heating step of heating a polymer film precursor containing particles to form particles A having a constricted structure from the particles. <17> A method for producing a polymer film, comprising a heating step of heating a polymer film precursor containing particles to form particles A from the particles, wherein the particles A are particles in which, in at least one cross section of the particles A, the length in a direction perpendicular to the longitudinal direction of the particles A has one or more minimum values in the central part of the particles A excluding the ends. <18> The polymer film precursor contains a polymerizable compound, and the heating step is followed by a polymerization step of polymerizing the polymerizable compound. <16> or <17> 1. A method for producing a polymer film according to claim 1. <19> The polymer film obtained after the polymerization step shrinks by 0.01% by volume or more compared to the polymer film precursor before the polymerization step. <18> 1. A method for producing a polymer film according to claim 1. [Effects of the Invention]

[0007] According to an embodiment of the present invention, a polymer film having improved brittleness and a method for producing the same can be provided. According to another embodiment of the present invention, a laminate using the above polymer film can be provided. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a schematic cross-sectional view of an example of particle A having a constricted structure that is preferably used in the present disclosure. 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 "step" in this specification does not only refer to an independent step, but also includes a step that cannot be clearly distinguished from other steps as long as the intended purpose of the step is achieved. Furthermore, in this disclosure, "% by mass" and "% by weight" 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.

[0010] (polymer film) A first embodiment of the polymer film according to the present disclosure includes particles A having a constricted structure and polymer B. A second embodiment of the polymer film according to the present disclosure comprises a particle A and a polymer B, wherein the particle A is a particle in which, in at least one cross section of the particle, the length in a direction perpendicular to the longitudinal direction of the particle has one or more minimum values in the central part of the particle excluding the ends.

[0011] In this specification, unless otherwise specified, simply referring to a "polymer film according to the present disclosure" or simply "polymer film" refers to both the first embodiment and the second embodiment. Furthermore, unless otherwise specified, simply referring to "particles A" or the like refers to both the particles A and the like of the first embodiment and the second embodiment.

[0012] Conventional polymer films containing particles have the problem of increased brittleness. The polymer film according to the present disclosure includes particles A having a constricted structure, or particles A in which, in at least one cross section of the particle, the length perpendicular to the longitudinal direction of the particle has one or more minimum values in the center of the particle excluding the ends. This allows the polymer to penetrate into the narrowed structure in the center of the particle A, the so-called constricted structure, creating an anchor effect, which suppresses peeling due to stress at the interface between the polymer and the particle A and suppresses stress concentration in the voids that occur in the peeled portions, making it possible to provide a polymer film with improved brittleness. The brittleness can be evaluated, for example, by the breaking elongation. It can be determined that the greater the breaking elongation, the more improved the brittleness.

[0013] <Particle A> A first embodiment of the polymer film according to the present disclosure includes particles A having a constricted structure. A second embodiment of the polymer film according to the present disclosure comprises a particle A in which, in at least one cross section of the particle A, the length in a direction perpendicular to the longitudinal direction of the particle A has one or more minimum values in the central part of the particle A excluding the ends. Particle A in the first embodiment of the polymer film according to the present disclosure and particle A in the second embodiment of the polymer film according to the present disclosure are particles of the same structure or particles of a similar structure, and it is preferable that the constricted structure is a structure in which, in at least one cross section of particle A, the length in the direction perpendicular to the longitudinal direction of particle A has one or more minimum values in the central part of particle A excluding the ends.

[0014] FIG. 1 shows a schematic cross-sectional view of an example of particle A having a constricted structure that is preferably used in the present disclosure. FIG. 1 is a schematic diagram showing a cross section of a particle A10 formed by fusion of three particles 12a, 12b, and 12c. In the cross section of particle 10 in FIG. 1, region A represents the end of particle A, and region B represents the center of particle A. In the present disclosure, the "end of particle A" refers to the part of particle A that is longer in the direction perpendicular to the longitudinal direction of particle A from the end of particle A, and the "center of particle A" refers to the part of particle A other than the end of particle A. In region B, which is the center of particle A, portions 14a and 14b where the length in the direction perpendicular to the longitudinal direction 16 of particle A shows a minimum value are constricted structures. That is, particle A10 in FIG. 1 has two constricted structures and also has two of the above-mentioned minimum values.

[0015] The particles A may be inorganic particles or organic particles, but are preferably organic resin particles. When the particles A are organic particles, preferably organic resin particles, examples of a method for producing the particles A include a method for fusing the particles together, or a method for bonding the particles together via chemical bonds on the surfaces, and a method for fusing the particles together is more preferred. When the particles A are inorganic particles, a suitable method for producing the particles A is, for example, a method in which the particles are chemically bonded to each other on the surface. Furthermore, from the viewpoint of improving brittleness, particles A are preferably particles formed by fusing together a plurality of particles, or particles formed by chemically bonding together a plurality of particles on the particle surface, and more preferably particles formed by fusing together a plurality of particles. Furthermore, the group that forms the chemical bond is preferably at least one type of group selected from the group consisting of a group capable of covalent bonding, a group capable of ionic bonding, a group capable of hydrogen bonding, and a group capable of dipole-dipole interaction, and from the viewpoint of the strength of the bonding portion in particle A, it is more preferably a group capable of covalent bonding. The covalently bondable group is appropriately selected depending on the type of group present on the surface of the particles to be used. 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 epoxy groups, oxetanyl groups, isocyanate groups, acid anhydride groups, carbodiimide groups, N-hydroxyester groups, glyoxal groups, imide ester groups, halogenated alkyl groups, thiol groups, hydroxy groups, carboxy groups, amino groups, amide groups, aldehyde groups, sulfonic acid groups, etc. Among these, from the viewpoint of adhesion to metal foil or metal wiring, at least one functional group selected from the group consisting of epoxy groups, oxetanyl groups, isocyanate groups, acid anhydride groups, carbodiimide groups, N-hydroxyester groups, glyoxal groups, imide ester groups, halogenated alkyl groups, and thiol groups is preferred. When one of the groups capable of forming a covalent bond is, for example, a carboxy group, examples of the group capable of forming a covalent bond with the carboxy group include a hydroxy group and an epoxy group. Furthermore, when one of the groups capable of forming a covalent bond is, for example, a hydroxy group or -NH2 (primary amino group), examples of the group capable of forming a covalent bond with the hydroxy group or -NH2 include an isocyanate group and an epoxy group. Among these, from the viewpoint of the strength of the bonded portion in particle A, it is preferable that the particle surface has an isocyanate group or an epoxy group, and an epoxy group is particularly preferable, as the group capable of forming a covalent bond. Furthermore, the isocyanate group can generate an amino group upon thermal decomposition, and the epoxy group can also generate a hydroxyl group upon thermal decomposition.

[0016] When particle A is an inorganic particle, examples of the material of particle A include BN, Al2O3, AlN, TiO2, SiO2, barium titanate, strontium titanate, aluminum hydroxide, calcium carbonate, and materials containing two or more of these. When the particles A are organic particles, the material of the particles A is preferably a polymer, more preferably a thermoplastic resin. Among these, from the viewpoint of improving the dielectric loss tangent and brittleness of the film, it is preferable that the particles A contain at least one polymer selected from the group consisting of fluoropolymers, liquid crystal polymers, and polyethylene. From the viewpoint of the dielectric loss tangent of the film, a liquid crystal polymer is more preferable, and from the viewpoint of heat resistance and mechanical strength, a fluoropolymer is more preferable. The polymer preferably has a dielectric loss tangent of 0.01 or less.

[0017] In the present disclosure, the type of polymer used for the particles A is not particularly limited, and known polymers can be used. Examples of polymers include thermoplastic resins such as liquid crystal polymers, fluoropolymers, polymers of compounds having a cyclic aliphatic hydrocarbon group and an ethylenically unsaturated group, polyether ether ketone, polyolefin, 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 phenol resins, epoxy resins, polyimide resins, and cyanate resins.

[0018] -Liquid Crystal Polymer- The polymer used for the particles A is preferably a liquid crystal polymer from the viewpoint of the dielectric loss tangent of the film. The type of liquid crystal polymer is not particularly limited, and any known liquid crystal polymer 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. In the case of a thermotropic liquid crystal, it is preferable that the polymer 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 in which a carbonate bond is introduced into liquid crystal polyester. Examples include steric carbonate. Furthermore, from the viewpoints of liquid crystallinity and linear expansion coefficient, the liquid crystal polymer is preferably a polymer having an aromatic ring, and more preferably an aromatic polyester or aromatic polyester amide. Furthermore, the liquid crystal polymer may be a polymer in which an isocyanate-derived bond such as an imide bond, a carbodiimide bond or an isocyanurate bond 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.

[0019] Examples of liquid crystal polymers include the following: 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 in part or in whole by a polycondensable derivative thereof.

[0020] Examples of polymerizable derivatives of compounds having a carboxy group, such as aromatic hydroxycarboxylic acids and aromatic dicarboxylic acids, include those in which the carboxy group is converted to an alkoxycarbonyl group or an aryloxycarbonyl group (esters), those in which the carboxy group is converted to a haloformyl group (acid halides), and those in which the carboxy group is converted to an acyloxycarbonyl group (acid anhydrides). 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). 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).

[0021] From the viewpoints of liquid crystallinity, dielectric loss tangent of the film, and adhesion to metal foil or metal wiring, the liquid crystal polymer preferably has a constitutional repeating unit represented by any one of the following formulas (1) to (3) (hereinafter, the constitutional repeating unit represented by formula (1) etc. may be referred to as repeating unit (1) etc.), more preferably has a constitutional repeating unit represented by formula (1) below, and particularly preferably has a constitutional repeating unit represented by formula (1) below, a constitutional repeating unit represented by formula (2) below, and a constitutional repeating unit represented by formula (2) 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 the group represented by the formula (I) 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.

[0022] 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, an s-butyl group, a t-butyl group, an n-hexyl group, a 2-ethylhexyl group, an n-octyl group, and an n-decyl group, and the number of carbon atoms thereof is preferably 1 to 10. 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, and the number of carbon atoms therein is preferably 6 to 20. When the hydrogen atoms are substituted with these groups, the number of the groups is 1 , Ar 2 or Ar 3 The number of the groups represented by the formula (I) is preferably two or less, and more preferably one.

[0023] 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, and the number of carbon atoms is preferably 1 to 10.

[0024] The repeating unit (1) is a constituent repeating unit derived from a specific aromatic hydroxycarboxylic acid. The repeating unit (1) is Ar 1is a p-phenylene group (constituent repeating unit derived from p-hydroxybenzoic acid), and Ar 1 is preferably a 2,6-naphthylene group (a repeating unit derived from 6-hydroxy-2-naphthoic acid) or a 4,4'-biphenylylene group (a repeating unit derived from 4'-hydroxy-4-biphenylcarboxylic acid).

[0025] The repeating unit (2) is a constituent repeating unit derived from a specific aromatic dicarboxylic acid. The repeating unit (2) is Ar 2 is a p-phenylene group (constituent repeating unit derived from terephthalic acid), Ar 2 is an m-phenylene group (a repeating unit derived from isophthalic acid), Ar 2 is a 2,6-naphthylene group (a repeating unit derived from 2,6-naphthalenedicarboxylic acid), or Ar 2 is a diphenylether-4,4'-diyl group (constituent repeating unit derived from diphenylether-4,4'-dicarboxylic acid) is preferred.

[0026] The repeating unit (3) is a constituent repeating unit derived from a specific aromatic diol, aromatic hydroxylamine, or aromatic diamine. The repeating unit (3) is Ar 3 is a p-phenylene group (constituent repeating units derived from hydroquinone, p-aminophenol or p-phenylenediamine), Ar 3 is an m-phenylene group (a repeating unit derived from isophthalic acid), or Ar 3 is a 4,4'-biphenylylene group (constituent repeating units derived from 4,4'-dihydroxybiphenyl, 4-amino-4'-hydroxybiphenyl or 4,4'-diaminobiphenyl).

[0027] The content of the repeating 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 constituent repeating units (the value obtained by dividing the mass of each constituent repeating unit constituting the liquid crystal polymer by the formula weight of that repeating unit to determine the substance equivalent (mol) of each repeating unit, and then adding these values up). The content of the repeating unit (2) is preferably 35 mol % or less, more preferably 10 mol % to 35 mol %, even more preferably 20 mol % to 35 mol %, and particularly preferably 30 mol % to 35 mol %, based on the total amount of all constituent repeating units. The content of the repeating unit (3) is preferably 35 mol % or less, more preferably 10 mol % to 35 mol %, even more preferably 20 mol % to 35 mol %, and particularly preferably 30 mol % to 35 mol %, based on the total amount of all constituent repeating units. The greater the content of the repeating 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.

[0028] The ratio of the content of repeating unit (2) to the content of repeating unit (3), expressed as [content of repeating unit (2)] / [content of repeating 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.

[0029] The liquid crystal polymer may have two or more types of repeating units (1) to (3) independently. The liquid crystal polymer may also have a constituent repeating unit other than the repeating units (1) to (3), but the content of such a unit is preferably 10 mol % or less, more preferably 5 mol % or less, based on the total amount of all repeating units.

[0030] The liquid crystal polymer preferably has, as the repeating unit (3), a repeating unit in which at least one of X and Y is an imino group, i.e., a repeating unit derived from a specific aromatic hydroxylamine and a repeating unit derived from an aromatic diamine, since this has excellent solubility in a solvent. It is more preferable that the liquid crystal polymer has, as the repeating unit (3), only a repeating unit in which at least one of X and Y is an imino group.

[0031] The liquid crystal polymer is preferably produced by melt-polymerizing raw material monomers corresponding to the constituent repeating units thereof. 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. Nitrogen-containing heterocyclic compounds are preferably used. The melt-polymerization may be further subjected to solid-state polymerization if necessary.

[0032] The liquid crystal polymer has a flow initiation temperature of preferably 250° C. or higher, more preferably 250° C. or higher and 350° C. or lower, and even more preferably 260° C. or higher and 330° C. or lower. 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.

[0033] 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 liquid crystal polyester (see "Liquid Crystal Polymer - Synthesis, Molding, and Applications," edited by Naoyuki Koide, CMC Corporation, June 5, 1987, p. 95).

[0034] The liquid crystal polymer preferably has a weight-average molecular weight of 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 will have excellent thermal conductivity in the thickness direction, heat resistance, strength, and rigidity.

[0035] -Fluoropolymer- The polymer used for the particles A is preferably a fluoropolymer from the viewpoints of heat resistance and mechanical strength. The fluoropolymer used in the present disclosure is not particularly limited, and any known fluoropolymer can be used. Examples of fluoropolymers include polytetrafluoroethylene, polychlorotrifluoroethylene, polyvinylidene fluoride, polyvinyl fluoride, perfluoroalkoxy fluororesin, tetrafluoroethylene / hexafluoropropylene copolymer, ethylene / tetrafluoroethylene copolymer, and ethylene / chlorotrifluoroethylene copolymer. Of these, polytetrafluoroethylene is preferred.

[0036] -Polyolefin- The polymer used for the particles A preferably contains polyolefin. The polyolefin is not particularly limited, but from the viewpoint of improving brittleness, it is preferably a poly-α-olefin, more preferably polyethylene or polypropylene, and particularly preferably polyethylene.

[0037] The weight-average molecular weight Mw of the polymer used in the particles A 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 loss tangent of 0.01 or less is preferably 1,000,000 or less, more preferably 300,000 or less, and particularly preferably less than 100,000.

[0038] From the viewpoint of improving brittleness, the melting point Tm of the particles A is preferably 400° C. or lower, more preferably 350° C. or lower, and particularly preferably 320° C. or lower. From the viewpoints of the dielectric loss tangent of the polymer film, adhesion to the metal foil or metal wiring, and heat resistance, the lower limit of the melting point Tm of the particles A is preferably 200° C. or higher, more preferably 230° C. or higher, even more preferably 260° C. or higher, and particularly preferably 280° C. or higher. The melting point Tm of the particles A is preferably lower than the melting point Tm of the polymer B, more preferably 10°C or more lower, further preferably 20°C or more lower, and particularly preferably 30°C or more lower. The melting point Tm in this disclosure is measured using a differential scanning calorimetry (DSC) device.

[0039] From the viewpoint of improving the dielectric tangent and brittleness of the polymer film, the dielectric tangent of the particles A is preferably less than 0.01, more preferably 0.008 or less, even more preferably 0.005 or less, and particularly preferably greater than 0 and 0.004 or less.

[0040] The method for measuring the dielectric loss tangent of a polymer film, particle, or polymer in the present disclosure is as follows. The dielectric loss tangent 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 film or polymer sample (width: 2.0 mm x length: 80 mm) is inserted into the cavity resonator. The film's dielectric loss tangent is measured from the change in resonance frequency before and after insertion for 96 hours in an environment of 25°C and 60% RH. If the laminate contains metal foil or metal wiring, the metal foil or metal wiring is removed with ferric chloride before measurement. The dielectric loss tangent of particle A is measured by the above-mentioned method using a green powder sample (width: 2.0 mm x length: 80 mm) prepared by compression molding.

[0041] The thermal expansion coefficient of the particles A is preferably smaller than the thermal expansion coefficient of the polymer B from the viewpoint of improving brittleness. From the viewpoint of improving brittleness, the thermal expansion coefficient of particles A is preferably −30 ppm / K to 40 ppm / K, more preferably −20 ppm / K to 35 ppm / K, even more preferably −10 ppm / K to 30 ppm / K, and particularly preferably 0 ppm / K to 25 ppm / K.

[0042] The thermal expansion coefficient in the present disclosure is measured by the following method. Using a thermomechanical analyzer (TMA), a tensile load of 1 g is applied to both ends of a polymer film or polymer sample 5 mm wide and 20 mm long, and the sample is heated from 25°C to 200°C at a rate of 5°C / min, then cooled to 30°C at a rate of 20°C / min, and heated again at a rate of 5°C / min. The thermal expansion coefficient is calculated from the slope of the TMA curve between 30°C and 150°C. The thermal expansion coefficient of particle A is measured by the above-mentioned method using a green compact sample (width 5 mm, length 20 mm) prepared by compression molding.

[0043] From the viewpoints of the linear expansion coefficient and adhesion to the metal foil, the average maximum length of the particles A is preferably 20 nm to 5 μm, more preferably 30 nm to 2 μm, even more preferably 50 nm to 1 μm, and particularly preferably 50 nm to 500 nm.

[0044] The polymer film may contain one type of particle A alone or two or more types, or may contain particles formed by fusion of particles of different materials. From the viewpoint of improving brittleness, the content of particles A in the polymer film according to the present disclosure is preferably 5% by volume or more, more preferably 10% by volume or more, even more preferably 15% by volume to 80% by volume, and particularly preferably 20% by volume to 75% by volume, relative to the total volume of the polymer film.

[0045] <Polymer B> The polymer film according to the present disclosure comprises polymer B. The polymer B preferably includes a polymer having a dielectric loss tangent of 0.01 or less. From the viewpoint of the dielectric tangent of the polymer film and adhesion to the metal foil or metal wiring, the dielectric tangent of the polymer B is preferably 0.005 or less, more preferably 0.004 or less, and particularly preferably greater than 0 and 0.003 or less.

[0046] The weight-average molecular weight Mw of the polymer B 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 loss tangent of 0.005 or less is preferably 1,000,000 or less, more preferably 300,000 or less, and particularly preferably less than 100,000.

[0047] From the viewpoints of the dielectric loss tangent of the polymer film, adhesion to metal foil or metal wiring, and heat resistance, the melting point Tm of polymer B is preferably 200°C or higher, more preferably 250°C or higher, even more preferably 280°C or higher, and particularly preferably 300°C or higher and 420°C or lower.

[0048] The glass transition temperature Tg of polymer B is preferably 150°C or higher, more preferably 200°C or higher, and particularly preferably 200°C or higher but lower than 280°C, from the viewpoints of the dielectric loss tangent of the polymer film, adhesion to metal foil or metal wiring, and heat resistance. The glass transition temperature Tg in the present disclosure is measured using a differential scanning calorimetry (DSC) device.

[0049] In the present disclosure, the type of polymer B is not particularly limited, and known polymers can be used. Examples of polymer B include thermoplastic resins such as liquid crystal polymers, fluoropolymers, 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, 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 phenol 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 foil or metal wiring, 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 an ethylenically unsaturated group, and polyether ether ketone is preferred, and at least one polymer selected from the group consisting of liquid crystal polymers and fluoropolymers is more preferred. From the viewpoint of the dielectric loss tangent of the polymer film, liquid crystal polymers are particularly preferred, and from the viewpoints of heat resistance and mechanical strength, fluoropolymers are preferred.

[0050] Preferred embodiments of the liquid crystal polymer and fluoropolymer used in polymer B are the same as those of the liquid crystal polymer and fluoropolymer described in the particle A.

[0051] From the viewpoint of improving strength and brittleness, it is preferable that polymer B has a crosslinked structure. From the viewpoint of improving strength and brittleness, polymer B preferably has at least one bond selected from the group consisting of a urethane bond, a urea bond, an amide bond, an ester bond, an ether bond, a C-C bond, an N-C bond, an SC bond, and a siloxane bond, more preferably has at least one bond selected from the group consisting of a urethane bond, a urea bond, an amide bond, an ester bond, an ether bond, an N-C bond, an SC bond, and a siloxane bond, and particularly preferably has an N-C bond.

[0052] Furthermore, the weight-average molecular weight of polymer B 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 polymer B is within the above range, the film after heat treatment will have excellent thermal conductivity in the thickness direction, heat resistance, strength, and rigidity.

[0053] From the viewpoint of improving brittleness, the tensile strength of Polymer B is preferably 50 MPa or more. In the present disclosure, the tensile strength is measured by cutting a 10 mm × 200 mm sample from a polymer film, conditioning it at 23°C and 60% relative humidity for 2 hours, and then measuring the maximum stress at break using a Tensilon tensile tester (Orientec Co., Ltd., RTA-100) with an initial sample length of 100 mm and a pulling rate of 10 mm / min, to determine the tensile strength.

[0054] Polymer B 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 polymer that dissolves in an amount of 0.1 g or more at 25°C 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] The polymer film according to the present disclosure may contain only one type of polymer B, or may contain two or more types. From the viewpoint of improving brittleness, the content of polymer B in the polymer film according to the present disclosure is preferably 20% by volume to 95% by volume, more preferably 20% by volume to 80% by volume, even more preferably 20% by volume to 70% by volume, and particularly preferably 25% by volume to 65% by volume, relative to the total volume of the polymer film.

[0056] <Polymerizable compound> From the viewpoint of improving brittleness, the polymer film according to the present disclosure preferably further contains a polymerizable compound. The polymerizable compound is preferably an unpolymerized polymerizable compound formed by polymerizing at least a portion of the polymer B.

[0057] The polymerizable compound is not particularly limited, and known polymerizable compounds can be used. Furthermore, the polymerizable compound preferably has at least one group selected from the group consisting of a (meth)acryloyl group, 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 hydroxy group, a carboxy group, an amino group, an imidazole group, and a thiol group, and more preferably has a (meth)acryloyl group. Furthermore, the polymerizable compound is preferably an ethylenically unsaturated compound.

[0058] The polymerizable compound may be a low molecular weight compound having a molecular weight of less than 1,000, or may be a high molecular weight compound having a weight average molecular weight Mw of 1,000 or more.

[0059] The polymer film according to the present disclosure may contain only one type of polymerizable compound, or may contain two or more types of polymerizable compounds. From the viewpoint of improving brittleness, the content of the polymerizable compound in the polymer film according to the present disclosure is preferably more than 0% by mass and less than 5% by mass, and more preferably more than 0% by mass and less than 3% by mass, relative to the total mass of the polymer film.

[0060] <Other additives> The polymer films according to the present disclosure may also contain other additives. As other additives, known additives can be used, such as leveling agents, antifoaming agents, antioxidants, ultraviolet absorbers, flame retardants, and colorants.

[0061] The total content of other additives 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, relative to 100 parts by mass of the content of Polymer B.

[0062] <Dielectric loss tangent> From the viewpoints of suppressing fracture failure during peeling and reducing transmission loss of the produced substrate, the polymer film according to the present disclosure preferably has a dielectric loss tangent of 0.01 or less, more preferably 0.005 or less, even more preferably 0.004 or less, and particularly preferably greater than 0 and 0.003 or less.

[0063] <Thermal expansion coefficient> From the viewpoint of thermal stability, the thermal expansion coefficient of the polymer film according to the present disclosure is preferably from -20 ppm / K to 50 ppm / K, more preferably from -10 ppm / K to 40 ppm / K, even more preferably from 0 ppm / K to 35 ppm / K, and particularly preferably from 10 ppm / K to 30 ppm / K.

[0064] The thermal expansion coefficient in the present disclosure is measured by the following method. Using a thermomechanical analyzer (TMA), a tensile load of 1 g is applied to both ends of a film 5 mm wide and 20 mm long, and the film is heated from 25°C to 200°C at a rate of 5°C / min, cooled to 30°C at a rate of 2°C / min, and then heated again at a rate of 5°C / min. The thermal expansion coefficient is calculated from the slope of the TMA curve between 30°C and 150°C. If the laminate contains metal foil or metal wiring, the metal foil or metal wiring is removed with ferric chloride before measurement.

[0065] The polymer film according to the present disclosure may have a single layer structure or a multilayer structure. For example, the polymer film according to the present disclosure may have a structure including a layer A containing particles A and polymer B and a layer B on at least one side of the layer A, or a structure including a layer B, a layer A containing particles A and polymer B, and a layer C, in this order. Furthermore, it is preferable that Layer B and Layer C each independently contain a liquid crystal polymer.

[0066] 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 foil or metal wiring, it is preferably 5 μm to 90 μm, more preferably 10 μm to 70 μm, and particularly preferably 15 μm to 50 μm.

[0067] 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.

[0068] The average thicknesses of Layer B and Layer C are preferably each independently smaller than the average thickness of Layer A from the viewpoints of the dielectric loss tangent of the polymer film and the adhesion to the metal foil or metal wiring. Average thickness T of layer A A and the average thickness of layer B, T B T is the ratio of A / T B From the viewpoint of the dielectric loss tangent of the polymer film and the adhesion to the metal foil or metal wiring, 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. 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 foil or metal wiring, 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 BFrom the viewpoint of the linear expansion coefficient and adhesion to the metal foil or metal wiring, the value of is preferably 0.2 to 5, more preferably 0.5 to 2, and particularly preferably 0.8 to 1.2. Furthermore, the average thickness of Layer B and Layer C is preferably 0.1 μm to 20 μm, more preferably 0.5 μm to 15 μm, even more preferably 1 μm to 10 μm, and particularly preferably 3 μm to 8 μm, from the viewpoints of the dielectric loss tangent of the polymer film and the adhesion to the metal foil or metal wiring.

[0069] 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, thermal expansion coefficient, and adhesion to metal foil or metal wiring.

[0070] 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.

[0071] <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 film for bonding metals.

[0072] (Method of manufacturing polymer film) A first embodiment of the method for producing a polymer film according to the present disclosure includes a heating step of heating a polymer film precursor containing particles to form particles A having a constricted structure from the particles. A second embodiment of the method for producing a polymer film according to the present disclosure includes a heating step of heating a polymer film precursor containing particles to form particles A from the particles, wherein the length of the particles A in a direction perpendicular to the longitudinal direction of the particles A in at least one cross section of the particles A has one or more minimum values in the central part of the particles A excluding the ends.

[0073] In this specification, unless otherwise specified, simply referring to a "polymer film manufacturing method according to the present disclosure" or simply referring to a "polymer film manufacturing method" refers to both the first embodiment and the second embodiment. Furthermore, unless otherwise specified, simply referring to a "heating step" or the like refers to both the heating step of the first embodiment and the heating step of the second embodiment.

[0074] The polymer film according to the present disclosure is preferably a film produced by the polymer film production method according to the present disclosure.

[0075] In the method for producing a polymer film according to the present disclosure, the preferred aspects of the components used, as well as the preferred aspects of the components and contents contained in the resulting film, are the same as the preferred aspects of the polymer film according to the present disclosure described above. In addition, in the method for producing a polymer film according to the present disclosure, the amount of each component used is the same as the preferred amount corresponding to the preferred embodiment of the content of each component in the polymer film according to the present disclosure. In the method for producing a polymer film according to the present disclosure, the preferable physical property values of the produced film are the same as those of the preferable aspects of the polymer film according to the present disclosure described above.

[0076] <Heating process> A first embodiment of the method for producing a polymer film according to the present disclosure includes a heating step of heating a polymer film precursor containing particles to form particles A from the particles. The preferred embodiments of the material of the particles contained in the polymer film precursor are the same as the preferred embodiments of the material of the particles A described above. The particles contained in the polymer film precursor preferably contain a polymer. The polymer film precursor preferably contains polymer B or a polymerizable compound that forms polymer B. Preferred examples of the polymer B and the polymerizable compound in the polymer film precursor include those mentioned above for the polymer film.

[0077] When the particles are inorganic particles, the average particle size of the inorganic particles is preferably 5 nm to 2 μm, more preferably 10 nm to 1 μm, even more preferably 20 nm to 1 μm, and particularly preferably 25 nm to 500 nm, from the viewpoint of improving brittleness. When the particles are organic particles, the average particle size of the organic particles is preferably 5 nm to 2 μm, more preferably 10 nm to 1 μm, even more preferably 20 nm to 500 nm, and particularly preferably 25 nm to 90 nm, from the viewpoint of improving brittleness.

[0078] The heating temperature in the heating step is not particularly limited as long as it allows the formation of particles A. However, when the particles contain a polymer, the heating temperature is preferably not less than the melting point (Tm) of the polymer -30°C and not more than the melting point (Tm) of polymer B, and more preferably not less than the melting point (Tm) of the polymer -20°C and not more than the melting point (Tm) of polymer B -10°C. The heating temperature is preferably the melting point (Tm) of the polymer + 40°C or less, more preferably the melting point (Tm) of the polymer + 30°C or less, and particularly preferably the melting point (Tm) of the polymer + 20°C or less. The heating time in the heating step is not particularly limited and can be appropriately selected depending on the formation state of the particles A. For example, it is preferably 0.1 minutes to 10 hours. The heating temperature and heating time can be appropriately changed depending on the types of particles and polymer B, and can also be lowered or shortened by other means such as adding a catalyst.

[0079] In the method for producing a polymer film according to the present disclosure, the dissolved oxygen content is preferably 500 ppm or less, more preferably 300 ppm or less, at the start of heating the film. When the dissolved oxygen content is within this range, a film with a lower dielectric loss tangent can be obtained. The above-mentioned "start of heating" refers to the time when heat application to the film begins. It is presumed that the heating step promotes crystallization of polymer B (particularly when it is a liquid crystal polymer) in the polymer film, thereby lowering the dielectric loss tangent of the polymer film.

[0080] In the present disclosure, the amount of dissolved oxygen is measured using a dissolved oxygen meter, for example, the portable oxygen analyzer "ORBISPHERE 3650" manufactured by Hack Ultra.

[0081] The heating step may be carried out in an inert gas atmosphere or an atmosphere containing oxygen. From the viewpoint of production efficiency, the heating step is preferably carried out in an atmosphere having an oxygen concentration of 500 ppm or more, and more preferably in an atmospheric (air) atmosphere.

[0082] <Polymerization process> In the method for producing a polymer film according to the present disclosure, the polymer film precursor preferably contains a polymerizable compound, and the method preferably includes, after the heating step, a polymerization step of polymerizing the polymerizable compound.

[0083] The content of the polymerizable compound in the polymer film precursor is preferably 10% by mass to 80% by mass, and more preferably 20% by mass to 75% by mass, based on the total mass of the polymer film precursor.

[0084] In addition, when the polymer film precursor contains a polymerizable compound, the polymer film precursor preferably contains a polymerization initiator. The polymerization initiator may be a known one, such as a photopolymerization initiator or a thermal polymerization initiator. The polymerization initiator may be either a radical polymerization initiator or a cationic polymerization initiator, but is preferably a radical polymerization initiator.

[0085] The polymerization in the polymerization step can be carried out by a known method, such as exposure to light or heating, depending on the polymerization initiator used. The polymerization in the polymerization step may be carried out during heating in the heating step.

[0086] Furthermore, in the polymer film manufacturing method according to the present disclosure, from the viewpoint of improving brittleness, it is preferable that the polymer film obtained after the polymerization step shrinks by 0.005% by volume or more, and more preferably by 0.01% by volume or more, relative to the polymer film precursor before the polymerization step. The occurrence of the shrinkage enhances the anchoring effect of the particles A, thereby further improving brittleness.

[0087] <Formation process> The method for producing a polymer film according to the present disclosure preferably includes a forming step of forming a polymer film precursor by applying a composition containing the particles, polymer B, and a solvent onto a support and drying the composition. The method for forming the film is not particularly limited, and known methods can be used. For example, a casting method, a coating method, an extrusion method, etc. are preferred, and among these, the casting method is particularly preferred. When the polymer film has a multilayer structure, for example, a co-casting method, a multilayer coating method, a co-extrusion method, etc. are preferred. Among these, the co-casting method is particularly preferred for forming a relatively thin film, and the co-extrusion method is particularly preferred for forming a thick film. When a multilayer structure in a polymer film is produced by the co-casting method or the multi-layer coating method, it is preferable to carry out the co-casting method or the multi-layer coating method using a layer A-forming composition, a layer B-forming composition, etc., in which the components of each layer, such as a liquid crystal polymer, are dissolved or dispersed in a solvent.

[0088] 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.

[0089] As the solvent, a solvent mainly composed of an aprotic compound, particularly an aprotic compound having no halogen atoms, is preferred because it is less corrosive and easier to handle, and the proportion of the aprotic compound 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. Furthermore, as the aprotic compound, an amide such as N,N-dimethylformamide, N,N-dimethylacetamide, tetramethylurea, N-methylpyrrolidone, or an ester such as γ-butyrolactone is preferably used because it easily dissolves the liquid crystal polymer, and N,N-dimethylformamide, N,N-dimethylacetamide, and N-methylpyrrolidone are more preferred.

[0090] Furthermore, as the solvent, a solvent containing a compound having a dipole moment of 3 to 5 as a main component is preferred because it easily dissolves the liquid crystal polymer, and 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.

[0091] Furthermore, as the solvent, a solvent containing as its main component a compound having a boiling point of 220°C or less at 1 atmosphere is preferred because it is easy to remove, and the proportion of the compound having a boiling point of 220°C or less 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.

[0092] In addition, a support may be used in the production method of the polymer film when it is produced by the casting method, co-casting method, coating method, multilayer coating method, extrusion 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 it 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, fluoropolymer, or the like. The average thickness of the resin film support is not particularly limited, but is preferably 25 μm or more and 75 μm or less, and more preferably 50 μm or more and 75 μm or less.

[0093] 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.

[0094] <Stretching process> The method for producing a polymer film according to the present disclosure preferably includes a stretching step of stretching the polymer film precursor, and more preferably includes a stretching step of stretching the polymer film precursor between the forming step and the heating step. In the polymer film manufacturing method according to the present disclosure, stretching can be appropriately combined to control the molecular orientation of the resulting film and adjust the linear expansion coefficient and mechanical properties. The stretching method is not particularly limited, and known methods can be used. 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 it, or by utilizing the self-shrinkage force of the web due to drying without stretching, or a combination thereof. Stretching is particularly effective for improving breaking elongation and breaking strength when the film brittleness has been reduced by the addition of an inorganic filler or the like.

[0095] <Winding process> The method for producing a polymer film according to the present disclosure preferably includes a winding step of winding the polymer film or the polymer film precursor into a roll, and more preferably includes a winding step of winding the polymer film precursor into a roll after the forming step and before the heating step. The step of winding into a roll is preferably carried out under a nitrogen atmosphere, which can further reduce the amount of dissolved oxygen in the polymer film precursor at the start of heating the polymer film precursor.

[0096] <Unwinding process> The method for producing a polymer film according to the present disclosure preferably includes, after the winding step, an unwinding step of unwinding the rolled polymer film. Furthermore, the peel force when unwinding the polymer film in the unwinding step is preferably 1.0 kN / m or less.

[0097] <Peeling process> The method for producing a polymer film according to the present disclosure preferably includes a peeling step of peeling the polymer film or the polymer film precursor from the substrate after the forming step or the heating step, more preferably includes a peeling step of peeling the polymer film or the polymer film precursor from the substrate after the forming step, and particularly preferably includes a peeling step of peeling the polymer film precursor from the substrate after the forming step and before the heating step. By peeling the polymer film or the polymer film precursor from the substrate, a polymer film is obtained, which can be used for other applications.

[0098] <Other processes> The method for producing a polymer film according to the present disclosure may include other steps in addition to those described above. Other steps may include known steps.

[0099] (Laminate) The laminate according to the present disclosure may be any laminate comprising a polymer film according to the present disclosure laminated thereon, but preferably comprises a polymer film according to the present disclosure and a metal layer or metal wiring disposed on at least one surface of the polymer film, and more preferably comprises a polymer film according to the present disclosure and a copper layer or copper wiring disposed on at least one surface of the polymer film.

[0100] The surface roughness Ra of the polymer film-side surface of the metal layer or metal wiring is preferably 1.0 μm or less, more preferably 0.5 μm or less. If the surface roughness Ra is 1.0 μm or less, the surface resistance at the interface between the polymer film and the metal substrate decreases.

[0101] The surface roughness Ra in the present disclosure is calculated using a surface roughness meter, for example, a stylus-type surface roughness meter "Surfcorder SE3500" manufactured by Kosaka Laboratory Ltd., based on the calculation method for arithmetic mean surface roughness Ra of JIS B0601:2013. In measuring the surface roughness Ra, the metal layer or metal wiring in the laminate is removed by etching using an iron chloride solution, and then the surface roughness Ra of the polymer film surface that was in contact with the metal layer or metal wiring to which the surface roughness of the metal layer or metal wiring has been transferred is measured, and this is taken as the surface roughness Ra of the polymer film side surface of the metal layer or metal wiring.

[0102] Furthermore, the laminate according to the present disclosure preferably has a metal layer or metal wiring, a polymer film according to the present disclosure, and a metal layer or metal wiring, in this order, and more preferably has a copper layer or copper wiring, a polymer film according to the present disclosure, and a copper layer or copper wiring, in this order. Furthermore, the laminate according to the present disclosure preferably comprises, in this order, a polymer film according to the present disclosure, a copper layer or copper wiring, a polymer film according to the present disclosure, a metal layer or metal wiring, and a polymer film according to the present disclosure. The two polymer films according to the present disclosure used in the laminate may be the same or different. The metal layer and metal wiring are not particularly limited and may be any known metal layer and metal wiring, but are preferably, for example, a silver layer, silver wiring, a copper layer or copper wiring, and more preferably a copper layer or copper wiring. The metal layer and metal wiring are preferably metal wiring. Furthermore, the metal in the metal layer and metal wiring is preferably silver or copper, and more preferably copper.

[0103] The method for attaching the polymer film according to the present disclosure to the metal layer or metal wiring is not particularly limited, and any known lamination method can be used.

[0104] 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.

[0105] 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 film is fixed to a flat plate with double-sided adhesive tape. The strength (kN / m) is measured when the 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).

[0106] The metal layer is preferably a silver layer or a copper layer, more preferably a copper layer. The copper layer is preferably a rolled copper foil formed by a rolling method or an electrolytic copper foil formed by an electrolytic method, and more preferably a rolled copper foil from the viewpoint of flex resistance.

[0107] 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.

[0108] In order to further enhance the effects of the present disclosure, the metal layer preferably has a group capable of interacting with the polymer film on the surface thereof that contacts the polymer film, and examples of the group capable of interacting with the polymer film include the groups listed above as groups that form chemical bonds, such as an amino group and an epoxy group, or a hydroxy group and an epoxy 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.

[0109] 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.

[0110] The method for producing the laminate according to the present disclosure is not particularly limited, but preferably includes a lamination step of laminating the polymer film according to the present disclosure and a metal substrate. In the lamination step, it is preferable to attach metal wiring. The lamination method in the lamination step is not particularly limited, and any known lamination method can be used. The lamination pressure in the lamination step is not particularly limited, but is preferably 0.1 MPa or more, and more preferably 0.2 MPa to 10 MPa. The lamination temperature in the lamination step can be appropriately selected depending on the polymer film used, etc., but is preferably 150°C or higher, more preferably 280°C or higher, and particularly preferably 280°C or higher and 420°C or lower. [Example]

[0111] 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. Unless otherwise specified, "parts" and "%" are by mass.

[0112] Details of the materials used in the examples and comparative examples are as follows.

[0113] <Polymer> LC-A: Liquid crystal polymer prepared according to the following manufacturing method, melting point 335°C

[0114] -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, 272.8 g (2.5 mol) of 4-aminophenol, 415.3 g (2.5 mol) of isophthalic acid, and 1,123.0 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; the same applies hereinafter) 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 when an increase in viscosity was observed, 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 (B1).

[0115] The liquid crystal polyester (B1) obtained above was solid-phase polymerized by holding it at 250°C for 3 hours under a nitrogen atmosphere, and then cooled to obtain a powdered liquid crystal polyester (LC-A). The obtained LC-A was dissolved in N-methylpyrrolidone and formed into a film. The sample was heated at 280°C for 3 hours under a nitrogen atmosphere and had a thermal expansion coefficient of 31 ppm / K and a tensile strength of 100 MPa. MA: Low dielectric adhesive (SLK series varnish (thermosetting resin manufactured by Shin-Etsu Chemical Co., Ltd.) mainly containing polymer-type curable compounds)

[0116] <Particle> A-1: Liquid crystal polymer particles, melting point 285°C, prepared by grinding commercially available II-type liquid crystal polymer pellets, dielectric tangent 0.002 A-2: 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 A-3: Boron nitride particles with epoxy groups on the surface, melting point >500℃ A-4: Boron nitride particles, melting point >500°C, HP40MF100 (manufactured by Mizushima Ferroalloy Co., Ltd.), dielectric dissipation factor 0.0007

[0117] Details of Examples 1 to 9 and Comparative Examples 1 to 3 are shown below.

[0118] (Examples 1 to 9 and Comparative Examples 1 to 3) <Film forming> A film was formed according to the following casting method.

[0119] [Single-layer casting (solution film)] -Preparation of polymer solution- The polymer and particles shown in Table 1 were added to N-methylpyrrolidone and stirred at 140°C for 4 hours under a nitrogen atmosphere to obtain a polymer solution. The polymer and particles were added at the volume ratio shown in Table 1, and the solid concentration was 23% by 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 filter also having a nominal pore size of 10 μm to obtain each polymer solution.

[0120] -Preparation of single-sided copper-clad laminates- The obtained polymer solution was sent to a single-layer casting die and cast onto the treated surface of a copper foil (CF-T4X-SV-12, average thickness 12 μm, manufactured by Fukuda Metal Foil & Powder Co., Ltd.). The solvent was removed from the cast film by drying at 40°C for 4 hours, and a laminate (single-sided copper-clad laminate) having a copper layer and a polymer film having the thickness shown in Table 1 was obtained.

[0121] -Heating process- The obtained single-sided copper-clad laminate was heated at the heating temperature shown in Table 1 for 10 minutes to prepare a single-sided copper-clad laminate.

[0122] The dielectric loss tangent and breaking elongation of the polymer film were measured using the obtained single-sided copper-clad laminate. The measurement methods were as follows.

[0123] <Dielectric loss tangent> The dielectric loss tangent 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"), and a film sample (width: 2.0 mm x length: 80 mm) was inserted into the cavity resonator. The film's dielectric loss tangent was measured from the change in resonance frequency before and after insertion for 96 hours under an environment of 25°C and 60% RH. Note that the copper foil was removed with ferric chloride before measurement.

[0124] <Evaluation of breaking elongation (brittleness)> The polymer film was peeled from the obtained single-sided copper-clad laminate, and a film sample 200 mm long (measurement direction) and 10 mm wide was cut out. The distance between the chucks was set to 100 mm. Using a universal tensile tester "STM T50BP" manufactured by Toyo Baldwin Co., Ltd., measurements were taken at a tensile speed of 10% / min in an atmosphere of 25°C and 60% RH until the sample broke, and the breaking elongation was calculated. The higher the breaking elongation value, the more improved the brittleness of the polymer film.

[0125] Table 1 shows the measurement results.

[0126] [Table 1]

[0127] As shown in Table 1, the polymer films of Examples 1 to 9 had larger values of elongation at break than the polymer films of Comparative Examples 1 to 3, and were polymer films with improved brittleness. [Explanation of symbols]

[0128] 10: particle A, 12a, 12b, 12c: fused particles, 14a, 14b: constricted structure, 16: longitudinal direction of particle A, region A: end of particle A, region B: center of particle A

Claims

1. Particles A having a constricted structure, and comprising polymer B, the particles A contain at least one polymer selected from the group consisting of a fluoropolymer, a liquid crystal polymer, and polyethylene, The polymer B is at least one polymer selected from the group consisting of a liquid crystal polymer, a fluoropolymer, a polymer of a compound having a cyclic aliphatic hydrocarbon group and a group having an ethylenically unsaturated bond, polyether ether ketone, polyolefin, polyamide, polyester, polyphenylene sulfide, polyether ketone, polycarbonate, polyether sulfone, polyphenylene ether and modified products thereof, polyetherimide, a copolymer of glycidyl methacrylate and polyethylene, a phenol resin, an epoxy resin, a polyimide resin, and a cyanate resin. Polymer film.

2. Particle A, and Polymer B, the particle A is a particle in which, in at least one cross section of the particle A, the length in a direction perpendicular to the longitudinal direction of the particle A has one or more minimum values in a central part of the particle A excluding the ends thereof, the particles A contain at least one polymer selected from the group consisting of a fluoropolymer, a liquid crystal polymer, and polyethylene, The polymer B is at least one polymer selected from the group consisting of a liquid crystal polymer, a fluoropolymer, a polymer of a compound having a cyclic aliphatic hydrocarbon group and a group having an ethylenically unsaturated bond, polyether ether ketone, polyolefin, polyamide, polyester, polyphenylene sulfide, polyether ketone, polycarbonate, polyether sulfone, polyphenylene ether and modified products thereof, polyetherimide, a copolymer of glycidyl methacrylate and polyethylene, a phenol resin, an epoxy resin, a polyimide resin, and a cyanate resin. Polymer film.

3. 3. The polymer film according to claim 1, wherein the particles A have a melting point Tm of 400° C. or lower.

4. 4. The polymer film according to claim 1, wherein the content of the particles A is 10% by volume or more based on the total volume of the polymer film.

5. The polymer film according to any one of claims 1 to 4, wherein the particles A are particles formed by fusing a plurality of particles together, or particles formed by chemically bonding a plurality of particles together on the particle surfaces.

6. 6. The polymer film according to claim 5, wherein the particles A are particles formed by fusing a plurality of particles together.

7. 7. The polymer film according to claim 1, wherein the dielectric loss tangent of the particles A is less than 0.

01.

8. 8. The polymer film according to claim 1, wherein the thermal expansion coefficient of the particles A is smaller than the thermal expansion coefficient of the polymer B.

9. 9. The polymer film according to claim 1, wherein the polymer B has a tensile strength of 50 MPa or more.

10. 10. The polymer film according to any one of claims 1 to 9, wherein the polymer B has at least one bond selected from the group consisting of a urethane bond, a urea bond, an amide bond, an ester bond, an ether bond, an N-C bond, an S-C bond, and a siloxane bond.

11. The polymer film according to any one of claims 1 to 10, further comprising a polymerizable compound.

12. 12. The polymer film according to claim 11, wherein the polymerizable compound has at least one group selected from the group consisting of a (meth)acryloyl group, an epoxy group, an oxetanyl group, an isocyanate group, an acid anhydride group, a carbodiimide group, an N-hydroxy ester group, a glyoxal group, an imide ester group, a halogenated alkyl group, a hydroxy group, a carboxy group, an amino group, an imidazole group, and a thiol group.

13. 13. The polymer film according to claim 11, wherein the content of the polymerizable compound is more than 0% by mass and less than 5% by mass with respect to the total mass of the polymer film.

14. A laminate comprising the polymer film according to any one of claims 1 to 13 and a metal layer or metal wiring disposed on at least one surface of the polymer film.

15. a heating step of heating a polymer film precursor containing particles to form particles A having a constricted structure from the particles, a polymer film obtained from the polymer film precursor contains the particles A and a polymer B; the particles A contain at least one polymer selected from the group consisting of a fluoropolymer, a liquid crystal polymer, and polyethylene, The polymer B is at least one polymer selected from the group consisting of a liquid crystal polymer, a fluoropolymer, a polymer of a compound having a cyclic aliphatic hydrocarbon group and a group having an ethylenically unsaturated bond, polyether ether ketone, polyolefin, polyamide, polyester, polyphenylene sulfide, polyether ketone, polycarbonate, polyether sulfone, polyphenylene ether and modified products thereof, polyetherimide, a copolymer of glycidyl methacrylate and polyethylene, a phenol resin, an epoxy resin, a polyimide resin, and a cyanate resin. A method for producing a polymer film.

16. a heating step of heating a polymer film precursor containing particles to form particles A from the particles, the particle A is a particle in which, in at least one cross section of the particle A, the length in a direction perpendicular to the longitudinal direction of the particle A has one or more minimum values in a central part of the particle A excluding the ends thereof, a polymer film obtained from the polymer film precursor contains the particles A and a polymer B; the particles A contain at least one polymer selected from the group consisting of a fluoropolymer, a liquid crystal polymer, and polyethylene, The polymer B is at least one polymer selected from the group consisting of a liquid crystal polymer, a fluoropolymer, a polymer of a compound having a cyclic aliphatic hydrocarbon group and a group having an ethylenically unsaturated bond, polyether ether ketone, polyolefin, polyamide, polyester, polyphenylene sulfide, polyether ketone, polycarbonate, polyether sulfone, polyphenylene ether and modified products thereof, polyetherimide, a copolymer of glycidyl methacrylate and polyethylene, a phenol resin, an epoxy resin, a polyimide resin, and a cyanate resin. A method for producing a polymer film.

17. the polymer film precursor comprises a polymerizable compound; After the heating step, a polymerization step of polymerizing the polymerizable compound is included. The method for producing the polymer film according to claim 15 or 16.

18. The method for producing a polymer film according to claim 17 , wherein the polymer film obtained after the polymerization step shrinks by 0.01% by volume or more compared to the polymer film precursor before the polymerization step.

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