JP7684112B2 - Film, manufacturing method thereof, and laminate - Google Patents

Description

This disclosure relates to a film, a method for producing the film, and a laminate.

In recent years, the frequencies used in communication devices have tended to become very high. To reduce transmission loss in the high-frequency band, there is a demand for lowering the dielectric constant and dielectric tangent of insulating materials used in circuit boards.

As a conventional method for producing a liquid crystal film, for example, the method described in Patent Document 1 is known.
Patent Document 1 describes a method for producing a liquid crystal polyester film, which includes a liquid crystal polyester precursor film preparation step of preparing a liquid crystal polyester precursor film containing the solvent by casting a liquid composition containing a liquid crystal polyester and a solvent onto a substrate and drying it; a first laminate preparation step of preparing a first laminate consisting of the liquid crystal polyester precursor film and the metal substrate by peeling the liquid crystal polyester precursor film from the substrate and then transferring the liquid crystal polyester precursor film to a metal substrate having a release layer on its surface; a second laminate preparation step of preparing a second laminate consisting of a liquid crystal polyester film and the metal substrate that does not substantially contain a solvent by heat treating the first laminate; and a film peeling step of peeling the liquid crystal polyester film from the metal substrate.

JP 2011-167847 A

An object of the present invention is to provide a film and a method for producing the same that can suppress film breakage and roughness of the film surface during peeling.
Another object of the present invention is to provide a laminate using the above film.

Means for solving the above problems include the following aspects.
<1> A film having a dielectric loss tangent of 0.01 or less and a surface free energy of 15 mN/m to 36 mN/m on at least one surface.
<2> A film having a dielectric loss tangent of 0.01 or less, and a surface coverage of at least one surface of the film with at least one compound selected from the group consisting of fluorine-containing compounds and silicon-containing compounds of 30% to 100%.
<3> The film according to <2>, wherein the film contains the fluorine atom-containing compound.
<4> The film according to <2> or <3>, wherein the at least one compound selected from the group consisting of fluorine atom-containing compounds and silicon atom-containing compounds is at least one compound selected from the group consisting of fluorine resins and silicone resins.
<5> The film according to any one of <2> to <4>, wherein the at least one compound selected from the group consisting of fluorine-containing compounds and silicon-containing compounds includes a surfactant.
<6> The film according to any one of <2> to <5>, wherein at least one compound selected from the group consisting of fluorine-atom-containing compounds and silicon-atom-containing compounds has a group capable of forming a covalent bond.
<7> The film according to <6>, wherein the covalently bondable group is an epoxy group.
<8> The film according to any one of <1> to <7>, further comprising an oxygen scavenger.
<9> The film according to any one of <1> to <8>, wherein at least one surface of the film has a surface roughness Rz of 10 nm to 10,000 nm.
<10> The film according to any one of <1> to <9>, wherein at least one surface of the film has a modulus of elasticity at 25° C. of 100 MPa or more.
<11> The film according to any one of <1> to <10>, which is a roll-shaped film.
<12> A laminate comprising the film according to any one of <1> to <11> and a metal layer or metal wiring on at least one surface of the film.
<13> The laminate according to <12>, wherein the surface roughness Ra of the film-side surface of the metal layer or metal wiring is 1.0 μm or less.
<14> A method for producing a film, comprising: a forming step of forming a film by applying, onto a substrate, a composition containing a polymer, at least one compound selected from the group consisting of a fluorine atom-containing compound and a silicon atom-containing compound, and a solvent, and drying the composition; and a heating step of heating the film, wherein the resulting film has a dielectric loss tangent of 0.01 or less, and one surface of the film before the heating step has a surface free energy of 15 mN/m to 36 mN/m.
<15> A method for producing a film, comprising: a forming step of forming a film by applying, onto a substrate, a composition containing a polymer, at least one compound selected from the group consisting of fluorine-atom-containing compounds and silicon-atom-containing compounds, and a solvent, and drying the composition; and a heating step of heating the film, wherein the resulting film has a dielectric loss tangent of 0.01 or less, and a surface coverage of at least one surface of the film with the at least one compound selected from the group consisting of fluorine-atom-containing compounds and silicon-atom-containing compounds before the heating step is 30% to 100%.
<16> The method for producing a film according to <14> or <15>, further comprising, after the forming step, a peeling step of peeling the film from the substrate.
<17> The method for producing a film according to any one of <14> to <16>, further comprising a winding step of winding the film into a roll after the forming step and before the heating step.
<18> The method for producing a film according to <15>, wherein the surface coverage of the obtained film is smaller than the surface coverage of the film after the forming step and before the heating step.
<19> The method for producing a film according to <14>, wherein the surface free energy of the obtained film is greater than the surface free energy of the film after the forming step and before the heating step.
<20> The method for producing a film according to <17>, further comprising, after the winding step, an unwinding step of unwinding a roll of the film, wherein a peel force when unwinding the film in the unwinding step is 1.0 kN/m or less.

According to the embodiments of the present invention, it is possible to provide a film that can suppress film breakage and roughness of the film surface when peeled off, and a method for producing the same.
According to another embodiment of the present invention, a laminate using the above film can be provided.

The contents of the present disclosure will be described in detail below. The following description of the components may be based on a representative embodiment of the present disclosure, but the present disclosure is not limited to such an embodiment.
In this specification, the use of "to" indicating a range of values means that the values before and after it are included as the lower limit and upper limit.
In the numerical ranges described in the present disclosure in stages, 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. In addition, in the numerical ranges described in the present disclosure, the upper or lower limit value of the numerical range may be replaced with a value shown in the examples.
In addition, in the description of groups (atomic groups) in this specification, descriptions that do not indicate whether they are substituted or unsubstituted include those that have a substituent as well as those that have no substituent. For example, an "alkyl group" includes not only an alkyl group that has no substituent (an unsubstituted alkyl group) but also an alkyl group that has a substituent (a substituted alkyl group).
In this specification, "(meth)acrylic" is a term used as a concept including both acrylic and methacrylic, and "(meth)acryloyl" is a term used as a concept including both acryloyl and methacryloyl.
In addition, the term "step" in this specification includes not only an independent step, but also a step that cannot be clearly distinguished from other steps, as long as the intended purpose of the step is achieved. In addition, in this disclosure, "mass %" and "weight %" are synonymous, and "parts by mass" and "parts by weight" are synonymous.
Furthermore, in the present disclosure, combinations of two or more preferred aspects are more preferred aspects.
In addition, unless otherwise specified, the weight average molecular weight (Mw) and number average molecular weight (Mn) in the present disclosure are molecular weights detected by a gel permeation chromatography (GPC) analyzer using a column of TSKgel Super HM-H (product name of Tosoh Corporation) in a solvent of PFP (pentafluorophenol)/chloroform = 1/2 (mass ratio) and a differential refractometer, and converted using polystyrene as a standard substance.

(film)
A first embodiment of the film according to the present disclosure has a dielectric loss tangent of 0.01 or less, and a surface free energy on at least one surface of 15 mN/m to 36 mN/m.
A second embodiment of the film according to the present disclosure has a dielectric loss tangent of 0.01 or less, and a surface coverage of at least one surface with at least one compound selected from the group consisting of fluorine atom-containing compounds and silicon atom-containing compounds is 30% to 100%.

In this specification, when the term "film according to the present disclosure" or "film" is used without any particular specification, it refers to both the first embodiment and the second embodiment.

Conventionally, when a film with a dielectric tangent of 0.01 or less is used to adhere to an adherend (a metal layer, metal wiring, a resin layer, another film, or, in the case of a roll-type film, the film itself), adhesion occurs between the film and the adjacent adherend, and the occurrence of breakage during peeling could not be sufficiently suppressed.
As a result of extensive investigations, the present inventors have found that the above-mentioned configuration makes it possible to provide a film that can suppress film breakage and surface roughness during peeling.
Although the detailed mechanism by which the above effects are obtained is unclear, it is speculated as follows.
The film according to the present disclosure has a surface free energy of 15 mN/m to 36 mN/m on one surface of the film, or a surface coverage of 30% to 100% with at least one compound selected from the group consisting of fluorine-atom-containing compounds and silicon-atom-containing compounds on one surface of the film, and thus has excellent releasability on the surface while maintaining a low dielectric tangent, and can provide a film that can suppress film breakage and roughness of the film surface when peeled from an adherend.
Furthermore, when at least one compound selected from the group consisting of fluorine atom-containing compounds and silicon atom-containing compounds is covalently bonded to an adjacent adherend, this compound forms a weak boundary layer and is pulled out from the film surface, making it possible to provide a film that can suppress film breakage and roughness of the film surface when peeled off from the adherend.

<Surface free energy>
In a first embodiment of the film according to the present disclosure, the surface free energy on at least one surface is 15 mN/m to 36 mN/m, and from the viewpoint of suppressing breakage failure during peeling, it is preferably 15 mN/m to 30 mN/m, more preferably 15 mN/m to 25 mN/m, and particularly preferably 15 mN/m to 20 mN/m.
In the second embodiment of the film according to the present disclosure, from the viewpoint of suppressing fracture failure during peeling, the surface free energy on at least one surface is preferably 15 mN/m to 36 mN/m, more preferably 15 mN/m to 30 mN/m, even more preferably 15 mN/m to 25 mN/m, and particularly preferably 15 mN/m to 20 mN/m.

In the present disclosure, the method for measuring the surface free energy of a film surface is as follows.
Based on the method by Owens, water and methylene iodide, whose surface free energies are known, are used, and water is dropped onto the film surface to measure the contact angle of water, and methylene iodide is dropped onto the film surface to measure the contact angle of methylene iodide, and the surface free energy (mN/m) is calculated.

In the film according to the present disclosure, the surface that satisfies the above surface free energy is preferably the surface that is attached to the adherend.
Furthermore, from the viewpoint of better exerting the effects of the present disclosure, the film according to the present disclosure is preferably a roll-shaped film.
In the case of a roll-shaped film, the surface satisfying the above-mentioned range of surface free energy is bonded to the surface opposite to the above-mentioned surface. It is presumed that the film according to the present disclosure, which is a roll-shaped film, is excellent in suppressing peeling failure when the film is unwound from the roll-shaped film.

<Surface Coverage by at least one compound selected from the group consisting of fluorine atom-containing compounds and silicon atom-containing compounds>
In a second embodiment of the film according to the present disclosure, the surface coverage of at least one surface by at least one compound selected from the group consisting of fluorine atom-containing compounds and silicon atom-containing compounds is 30% to 100%, and from the viewpoint of suppressing fracture failure upon peeling, it is preferably 50% to 100%, more preferably 80% to 100%, particularly preferably 90% to 100%, and most preferably 100%.
In the first embodiment of the film according to the present disclosure, from the viewpoint of suppressing fracture failure during peeling, the surface coverage of at least one surface by at least one compound selected from the group consisting of fluorine atom-containing compounds and silicon atom-containing compounds is preferably 30% to 100%, more preferably 50% to 100%, even more preferably 80% to 100%, particularly preferably 90% to 100%, and most preferably 100%.
Furthermore, from the viewpoint of suppressing breakage failure during peeling, the film according to the present disclosure preferably has a total content of the fluorine atom-containing compound and the silicon atom-containing compound greater in the surface portion of the film than in the central portion of the film in the thickness direction of the film.

The method for measuring the surface coverage of the film surface in the present disclosure is as follows.
The surface free energy is calculated from the contact angle measurement of the film, and is compared with the surface free energy of a film that does not contain a compound having a functional group (coverage rate 0%) and the surface free energy of the compound having a functional group alone (coverage rate 100%) to determine the surface coverage.

In the film according to the present disclosure, the surface that satisfies the above surface coverage is preferably the surface that is attached to the adherend.
Furthermore, from the viewpoint of better exerting the effects of the present disclosure, the film according to the present disclosure is preferably a roll-shaped film.
In the case of a roll-shaped film, the surface satisfying the above-mentioned range of surface coverage is bonded to the surface opposite to the above-mentioned surface. It is presumed that the film according to the present disclosure, which is a roll-shaped film, is excellent in suppressing peeling failure when the film is unwound from the roll-shaped film.

<Dielectric tangent>
The film according to the present disclosure has a dielectric tangent of 0.01 or less, and from the viewpoints of suppressing fracture failure upon peeling and reducing transmission loss of the produced substrate, it is preferably 0.005 or less, more preferably 0.004 or less, even more preferably 0.0035 or less, and particularly preferably greater than 0 and 0.003 or less.

The method for measuring the dielectric loss tangent of a film or polymer in the present disclosure is as follows.
The dielectric loss tangent is measured by the resonance perturbation method at a frequency of 10 GHz. A 10 GHz cavity resonator (Kanto Electronics Application Development Co., Ltd. CP531) is connected to a network analyzer (Agilent Technology's "E8363B"), and a film sample (width: 2.0 mm x length: 80 mm) is inserted into the cavity resonator, and the dielectric loss tangent of the film is measured from the change in resonance frequency before and after insertion for 96 hours under a temperature of 25°C and a humidity of 60% RH environment. Note that the copper foil is removed with ferric chloride before the measurement.

<At least one compound selected from the group consisting of fluorine atom-containing compounds and silicon atom-containing compounds>
A second embodiment of the film according to the present disclosure contains at least one compound selected from the group consisting of fluorine atom-containing compounds and silicon atom-containing compounds.
From the viewpoint of suppressing breakage failure during peeling, the first embodiment of the film according to the present disclosure preferably contains at least one compound selected from the group consisting of fluorine atom-containing compounds and silicon atom-containing compounds.
The film according to the present disclosure may contain a fluorine atom-containing compound alone, a silicon atom-containing compound alone, both a fluorine atom-containing compound and a silicon atom-containing compound, or a compound containing both a fluorine atom and a silicon atom.

From the viewpoints of suppressing fracture failure upon peeling and of uneven distribution on the surface, the film according to the present disclosure preferably contains a fluorine atom-containing compound as at least one compound selected from the group consisting of fluorine atom-containing compounds and silicon atom-containing compounds.
Furthermore, from the viewpoint of suppressing fracture failure during peeling, the at least one compound selected from the group consisting of fluorine atom-containing compounds and silicon atom-containing compounds is preferably at least one compound selected from the group consisting of fluororesin and silicone resin, and more preferably a fluororesin.

When at least one compound selected from the group consisting of fluorine atom-containing compounds and silicon atom-containing compounds is a resin, its weight average molecular weight Mw is not particularly limited, but is preferably 1,000 or more and 1,000,000 or less, more preferably 5,000 or more and 200,000 or less, and particularly preferably 10,000 or more and 100,000 or less.

From the viewpoints of suppressing fracture failure during peeling and of uneven distribution on the surface, it is preferable that the at least one compound selected from the group consisting of fluorine atom-containing compounds and silicon atom-containing compounds contains a surfactant, and it is more preferable that the at least one compound selected from the group consisting of fluorine-based surfactants and silicone-based surfactants is contained.
In the present disclosure, a "surfactant" may be any compound having a hydrophobic portion and a hydrophilic portion.
For example, the fluorosurfactant preferably has a perfluoroalkyl structure as the hydrophobic portion.

Furthermore, from the viewpoints of suppressing fracture failure during peeling and of adhesion, it is preferable that at least one compound selected from the group consisting of fluorine atom-containing compounds and silicon atom-containing compounds has a group capable of forming a covalent bond, and it is more preferable that the compound has a group capable of forming a covalent bond with a group present on the surface of the adherend to be bonded.
The group capable of forming a covalent bond is appropriately selected depending on the type of adherend to be bonded, particularly depending on the type of groups present on the surface thereof.
The group capable of forming a covalent bond 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 aldehyde group, a sulfonic acid group, etc. Among these, from the viewpoint of adhesion to a metal foil or a metal wiring, 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 is preferable.
When the group present on the surface of the adherend to be bonded is, for example, a carboxy group, examples of the group capable of covalently bonding with the carboxy group include a hydroxy group and an epoxy group.
Furthermore, when the group present on the surface of the adherend to be bonded is, for example, _--NH.sub.2 (primary amino group), examples of the group capable of forming a covalent bond with _--NH.sub.2 include an isocyanate group and an epoxy group.
Among these, from the viewpoints of preventing breakage failure during peeling and adhesion, the covalently bondable group is preferably an isocyanate group or an epoxy group, and is particularly preferably an epoxy group.

The at least one compound selected from the group consisting of fluorine atom-containing compounds and silicon atom-containing compounds may be used alone or in combination of two or more kinds.
From the viewpoint of suppressing breakage failure during peeling, the content of at least one compound selected from the group consisting of the fluorine atom-containing compound and the silicon atom-containing compound is preferably 0.01 mass % to 10 mass %, more preferably 0.02 mass % to 2 mass %, and particularly preferably 0.05 mass % to 1 mass %, relative to the total mass of the film.

<Polymer>
From the viewpoints of mechanical strength and dielectric loss tangent of the film, the film according to the present disclosure preferably contains a polymer, and preferably contains a polymer having a dielectric loss tangent of 0.01 or less.
The dielectric tangent of a polymer having a dielectric tangent of 0.01 or less is preferably 0.005 or less, more preferably 0.004 or less, and particularly preferably greater than 0 and 0.003 or less, from the viewpoints of the dielectric tangent of the film and adhesion to a metal foil or metal wiring.

The weight average molecular weight Mw of the polymer 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 is preferably 1,000,000 or less, more preferably 300,000 or less, and particularly preferably less than 100,000.

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

In the present disclosure, the type of polymer is not particularly limited, and any known polymer can be used.
For example, examples of polymers having a dielectric tangent of 0.01 or less include thermoplastic resins such as liquid crystal polymers, fluororesins, 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 film, adhesion to a metal foil or metal wiring, and heat resistance, it is preferable to use at least one polymer selected from the group consisting of a liquid crystal polymer, a fluororesin, a polymer of a compound having a cyclic aliphatic hydrocarbon group and a group having an ethylenically unsaturated bond, and polyether ether ketone, and it is more preferable to use at least one polymer selected from the group consisting of a liquid crystal polymer and a fluororesin. From the viewpoint of the dielectric loss tangent of the film, it is particularly preferable to use a liquid crystal polymer, and from the viewpoints of heat resistance and mechanical strength, it is preferable to use a fluororesin.

- Liquid crystal polymer -
From the viewpoint of the dielectric loss tangent of the film, the polymer having a dielectric loss tangent of 0.01 or less is preferably a liquid crystal polymer.
In the present disclosure, the liquid crystal polymer used as the polymer having a dielectric loss tangent of 0.01 or less is not particularly limited in type as long as it has a dielectric loss tangent of 0.01 or less, 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 liquid crystal 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 a liquid crystal polyester, liquid crystal polyester ether in which an ether bond is introduced into a liquid crystal polyester, and liquid crystal polyester carbonate in which a carbonate bond is introduced into a liquid crystal polyester.
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 an aromatic polyester amide.
Furthermore, the liquid crystal polymer may be a polymer in which an imide bond, a carbodiimide bond, or a bond derived from an isocyanate such as 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.

Examples of liquid crystal polymers include, for example:
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) Those obtained by polycondensation of multiple types of aromatic hydroxycarboxylic acids.
3) (i) a polycondensation product 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 whole or in part by a polycondensable derivative thereof.

Examples of polymerizable derivatives of compounds having a carboxy group, such as aromatic hydroxycarboxylic acids and aromatic dicarboxylic acids, include those obtained by converting a carboxy group to an alkoxycarbonyl group or an aryloxycarbonyl group (esters), those obtained by converting a carboxy group to a haloformyl group (acid halides), and those obtained by converting a carboxy group 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 a hydroxy group 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 products).

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

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, and the number of carbon atoms 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 is preferably 6 to 20.
When the hydrogen atoms are substituted with these groups, the number thereof is preferably 2 or less, more preferably 1, for each of the groups represented by Ar ¹ , Ar ² or Ar ³ .

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.

The repeating unit (1) is a constituent repeating unit derived from a specific aromatic hydroxycarboxylic acid.
As the repeating unit (1), those in which Ar ¹ is a p-phenylene group (constituent repeating unit derived from p-hydroxybenzoic acid), those in which Ar ¹ is a 2,6-naphthylene group (constituent repeating unit derived from 6-hydroxy-2-naphthoic acid), or those in which Ar 1 is a 4,4'-biphenylylene group (constituent repeating unit derived from 4'-hydroxy-4-biphenylcarboxylic acid) are preferred.

The repeating unit (2) is a constituent repeating unit derived from a specific aromatic dicarboxylic acid.
As the repeating unit (2), those in which Ar ² is a p-phenylene group (constituent repeating unit derived from terephthalic acid), those in which Ar ² is an m-phenylene group (constituent repeating unit derived from isophthalic acid), those in which Ar ² is a 2,6-naphthylene group (constituent repeating unit derived from 2,6-naphthalenedicarboxylic acid), or those in which Ar ² is a diphenylether-4,4'-diyl group (constituent repeating unit derived from diphenylether-4,4'-dicarboxylic acid) are preferred.

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

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 %, based on the total amount of all constituent repeating units (the mass of each constituent repeating unit constituting the liquid crystal polymer is divided by the formula weight of that repeating unit to determine the substance amount equivalent (mol) of each repeating unit, and the total value).
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. However, if the content is too high, the solubility in a solvent will tend to decrease.

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.

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.

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

The liquid crystal polymer is preferably produced by melt-polymerizing raw material monomers corresponding to the constituent repeating units that constitute the 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. Nitrogen-containing heterocyclic compounds are preferably used. The melt polymerization may be further subjected to solid-phase polymerization as necessary.

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

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

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 this 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.

-Fluorine resin-
The polymer having a dielectric loss tangent of 0.01 or less is preferably a fluororesin from the viewpoints of heat resistance and mechanical strength.
In the present disclosure, the type of fluororesin used as the polymer having a dielectric dissipation factor of 0.01 or less is not particularly limited as long as the fluororesin has a dielectric dissipation factor of 0.01 or less, and any known fluororesin can be used.
Examples of fluororesins include polytetrafluoroethylene, polychlorotrifluoroethylene, polyvinylidene fluoride, polyvinyl fluoride, perfluoroalkoxy fluororesins, tetrafluoroethylene/hexafluoropropylene copolymers, ethylene/tetrafluoroethylene copolymers, and ethylene/chlorotrifluoroethylene copolymers.
Of these, polytetrafluoroethylene is preferred.

--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 0.01 or less may be a polymer of a compound having a cyclic aliphatic hydrocarbon group and a group having an ethylenically unsaturated bond.
The ring structure of the cyclic aliphatic hydrocarbon group may be a monocyclic ring, a condensed ring in which two or more rings are condensed, or a bridged ring.
Examples of the ring structure of the cyclic aliphatic hydrocarbon group include a cyclopentane ring, a cyclohexane ring, a cyclooctane ring, an isoborone 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 cycloaliphatic hydrocarbon groups in the compound having a cycloaliphatic 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 a compound having at least one type of 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.

-Polyetheretherketone-
The polymer having a dielectric loss tangent of 0.01 or less may be polyetheretherketone.
Polyetheretherketone is a type of aromatic polyetherketone, 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 linked by a divalent aromatic group.
In the present disclosure, the polyether ether ketone used as the polymer having a dielectric tangent of 0.01 or less is not particularly limited to a specific type as long as the polyether ether ketone has a dielectric tangent of 0.01 or less, and any known polyether ether ketone can be used.

The polymer having a dielectric loss tangent of 0.01 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 polymer that dissolves 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 at 25° C.

The films according to the present disclosure may contain only one type of polymer or two or more types of polymer.
The polymer content in the film according to the present disclosure is preferably 20% by mass to 99% by mass, more preferably 30% by mass to 98% by mass, and particularly preferably 40% by mass to 95% by mass, relative to the total mass of the film, from the viewpoints of the dielectric tangent of the film and the adhesion to a metal foil or metal wiring.

<Oxygen absorber>
The film according to the present disclosure preferably contains an oxygen scavenger from the viewpoints of the dielectric tangent of the film and suppressing crystallization of the polymer during heat treatment (for example, the heating step described below).
The oxygen scavenger is preferably at least one compound selected from the group consisting of oxygen-reactive compounds and oxygen-adsorbing compounds.

An oxygen-reactive compound means a compound that is reactive to oxygen. A reaction product of an oxygen-reactive compound with oxygen means a compound that is produced by reacting an oxygen-reactive compound with oxygen.

Examples of oxygen-reactive compounds include oxime compounds, hydroxylamine compounds, and N-substituted aminoheterocyclic compounds. Among them, from the viewpoint of the reaction rate with oxygen, it is preferable that the oxygen-reactive compound is a combination of a hydroxylamine compound and an N-substituted aminoheterocyclic compound.

Examples of oxime compounds include methyl ethyl ketoxime, dimethyl ketoxime, methyl propyl ketoxime, and methyl butyl ketoxime.

Examples of hydroxylamine compounds include diethylhydroxylamine and diisopropylhydroxylamine. Of these, the hydroxylamine compound is preferably diethylhydroxylamine.

Examples of N-substituted amino heterocyclic compounds include 1-amino-4-methylpiperazine, 1-aminopyrrolidine, 1-aminopiperidine, N-aminomorpholine, and N-aminohexamethyleneimine. Of these, the N-substituted amino heterocyclic compound is preferably 1-amino-4-methylpiperazine or 1-aminopyrrolidine.

An oxygen-adsorbing compound means a compound that has the property of allowing oxygen to exist without forming a chemical bond with the oxygen atom. An oxygen adsorbate of an oxygen-adsorbing compound means an oxygen-adsorbing compound in a state in which oxygen is adsorbed.

The oxygen-adsorbing compound preferably has a porous structure. Examples of oxygen-adsorbing compounds include zeolite, porous calcium silicate, and porous silica.

The film according to the present disclosure may contain only one type of oxygen scavenger, or may contain two or more types.
From the viewpoints of the dielectric tangent of the film and suppressing crystallization of the polymer during heat treatment, the content of the oxygen scavenger is preferably 0.0001% by mass to 10% by mass, and more preferably 0.001% by mass to 1% by mass, relative to the total mass of the film.

<Filler>
The film according to the present disclosure preferably contains a filler from the viewpoints of dielectric properties, thermal expansion coefficient, and adhesion to metal foil or metal wiring.
The filler may be particulate or fibrous, and may be an inorganic filler or an organic filler.
In the film according to the present disclosure, the number density of the filler is preferably greater inside the film than on the surface thereof, from the viewpoints of dielectric properties, thermal expansion coefficient, and adhesion to metal foil or metal wiring.

As the inorganic filler, a known inorganic filler can be used.
Examples of the inorganic filler material 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 viewpoint of adhesion to the metal foil or metal wiring, 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 not particularly limited, but is preferably about 20% to about 40% of the thickness of the layer containing the filler, and may be, for example, 25%, 30%, or 35% of the thickness of the layer containing the filler. In the case where the particles or fibers are flat, the length indicates the length in the direction of the short side.
Moreover, from the viewpoint of adhesion to the metal foil or metal wiring, 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.

As the organic filler, a known organic filler can be used.
Examples of the organic filler material include polyethylene, polystyrene, urea-formalin filler, polyester, cellulose, acrylic resin, fluororesin, hardened epoxy resin, crosslinked benzoguanamine resin, crosslinked acrylic resin, crosslinked styrene, and materials containing two or more of these.
The organic filler may be in the form of fibers such as nanofibers, or may be in the form of hollow resin particles.
Among these, from the viewpoint of adhesion to metal foil or metal wiring, the organic filler is preferably fluororesin particles, polyester-based resin particles, or nanofibers of cellulose-based resin, and more preferably polytetrafluoroethylene particles.
From the viewpoint of adhesion to the metal foil or metal wiring, 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.

The films according to the present disclosure may contain only one type of filler or two or more types of fillers.
From the viewpoints of the thermal expansion coefficient and adhesion to a metal foil or metal wiring, the content of the filler in the film according to the present disclosure is preferably 5% by mass to 80% by mass, more preferably 10% by mass to 70% by mass, even more preferably 20% by mass to 70% by mass, and particularly preferably 25% by mass to 60% by mass, relative to the total volume of the film.

-Other additives-
The films according to the present disclosure may also contain other additives.
As the other additives, known additives can be used, specifically, for example, a leveling agent, a defoaming agent, an antioxidant, an ultraviolet absorbing agent, a flame retardant, a colorant, etc.

Furthermore, as other additives, resins other than the above-mentioned components may be contained.
Examples of resins other than polymers having a dielectric tangent of 0.01 or less include thermoplastic resins such as polyolefins, cycloolefin polymers, polyamides, polyesters, polyphenylene sulfide, polyether ketones, polycarbonates, polyether sulfones, polyphenylene ethers and modified products thereof, and polyether imides; elastomers such as copolymers of glycidyl methacrylate and polyethylene; and thermosetting resins such as phenol resins, epoxy resins, polyimide resins, and cyanate resins.

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, per 100 parts by mass of the polymer content.

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

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 having a width of 5 mm and a length of 20 mm, 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. Note that the copper foil is removed with ferric chloride before the measurement.

<Surface roughness>
The film according to the present disclosure preferably has a surface roughness Rz of at least one surface of 10 nm to 10,000 nm, more preferably 10 nm to 5,000 nm, even more preferably 20 nm to 1,000 nm, and even more preferably 50 nm to 500 nm.
Furthermore, it is preferable that a surface that satisfies the above-mentioned range of surface roughness Rz is a surface that satisfies the above-mentioned range of surface free energy, a surface that satisfies the above-mentioned range of surface coverage, or a surface that satisfies the above-mentioned range of surface free energy and the above-mentioned range of surface coverage.

In this disclosure, "surface roughness Rz" refers to the sum of the maximum peak height and the maximum valley depth observed on a roughness curve over a reference length, expressed in nanometers.
In the present disclosure, the surface roughness Rz of the film surface is measured by the following method.
A non-contact surface/layer cross-sectional shape measurement system, VertScan (manufactured by Ryoka Systems Co., Ltd.), is used to measure an area of 465.48 μm long and 620.64 μm wide, and a roughness curve and an average line of the roughness curve are created on the surface of the object to be measured (liquid crystal polymer film). A portion corresponding to the reference length is extracted from the roughness curve. The surface roughness Rz of the object to be measured 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.

Methods for forming a film with a surface roughness Rz of 10 nm to 10,000 nm include, for example, a method of generating Benard cells during film formation, a method of using a solution containing a filler and a liquid crystal polymer, a method of phase-separating a material mixed with a liquid crystal polymer during film formation, a method of forming a skin on the surface during the film formation process and using the difference in the amount of shrinkage with the inside (reticulation), a method of performing a replica process using a mold with an uneven surface during solution film formation, and a method of roughening the film after film formation by surface treatment such as sputtering.

<Elastic modulus>
The elastic modulus at 25° C. of at least one surface of the film according to the present disclosure is preferably 100 MPa or more from the viewpoints of mechanical strength and suppression of fracture failure during peeling.
Furthermore, it is preferable that a surface that satisfies the above elastic modulus range is a surface that satisfies the above surface free energy range, a surface that satisfies the above surface coverage range, or a surface that satisfies the above surface free energy range and the above surface coverage range.

In the present disclosure, the elastic modulus of a film surface is measured by the following method.
The elastic modulus of the film surface is determined using a micro-surface hardness tester (Fisherscope H100VP-HCU, manufactured by Fisher Instruments, Inc.). Specifically, a diamond pyramidal indenter (tip facing angle: 136°) is used to measure the indentation depth under an appropriate test load at 25° C. within a range not exceeding 1 μm, and the storage elastic modulus is calculated from the change in load and displacement when the load is removed.

The film according to the present disclosure may have a single layer structure or a multilayer structure.

The film according to the present disclosure may be used as a membrane provided on a substrate such as a metal substrate.
From the viewpoint of adhesion to a metal substrate, for example, the film according to the present disclosure preferably includes a layer A containing a polymer and at least one compound selected from the group consisting of the above-mentioned fluorine atom-containing compound and silicon atom-containing compound, and a layer B disposed on the layer A and containing a polymer and a curable compound described later. For example, a laminate having excellent adhesion can be obtained by bonding the layer A side of the film to a metal substrate.

The content of the polymer in Layer A is preferably 25% by mass to 99% by mass, and more preferably 40% by mass to 60% by mass, based on the total mass of Layer A.

The average thickness of layer A is not particularly limited, but is preferably 5 μm to 100 μm, more preferably 10 μm to 80 μm, and even more preferably 20 μm to 70 μm.

The preferred aspects of the polymer used in layer B are the same as the preferred aspects of the polymer described above, except as described above.

The content of the curable compound in Layer B is preferably 5% by mass to 75% by mass, and more preferably 10% by mass to 50% by mass, based on the total mass of Layer B.

The average thickness of layer B is not particularly limited, but is preferably 1 μm to 10 μm, and more preferably 1 μm to 5 μm.

The average thickness of each layer in the film according to the present disclosure is measured using the following method.
The wiring board 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 places, 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.

Layer A and Layer B may each independently contain other additives.
The preferred embodiments of the other additives used in Layer A or Layer B are the same as those of the other additives described above.

-Curable compound-
Layer B preferably contains a curable compound, and more preferably the curable compound contains a curable compound A which is an oligomer or a polymer.
The curable compound in the present disclosure is a compound having a curable group, and may be any of a monomer, an oligomer, and a polymer.
The curable compound A is an oligomer or a polymer, and is preferably a polymer from the viewpoint of mechanical strength.
In the present disclosure, an oligomer is a polymer having a weight average molecular weight of 1,000 or more and less than 2,000, and a polymer is a polymer having a weight average molecular weight of 2,000 or more.
From the viewpoints of adhesion and uneven distribution to the metal foil or metal wiring, the curable compound A is preferably an oligomer or 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 200,000 or less, and particularly preferably a polymer having a weight-average molecular weight of 5,000 or more and 100,000 or less.
Furthermore, from the viewpoint of suppressing wiring distortion, the weight average molecular weight of the curable compound A is preferably 100,000 or less, more preferably 50,000 or less, and particularly preferably 10,000 or less.
The polymer having a dielectric loss tangent of 0.01 or less may have a curable group, but is a compound different from the curable compound A. The curable compound A preferably has a dielectric loss tangent of more than 0.01 and is preferably not a liquid crystal polymer.

In addition, from the viewpoint of suppressing wiring distortion, the film according to the present disclosure preferably has a higher content of the curable compound A on at least one surface of the film than in the interior thereof.
Furthermore, from the viewpoint of suppressing wiring distortion, it is preferable that Layer A contains particles, and the particles contain the curable compound inside or on the surface thereof.
The above particles include microcapsules or microgels having the above curable compound inside or on the surface thereof.
Among these, preferred examples include microcapsules or microgels having the above-mentioned curable compound therein.
The particles are preferably organic resin particles.

The number of curable groups in the curable compound may be one or more, and may be two or more, but is preferably two or more.
The curable compound may have only one type of curable group, or may have two or more types of curable groups.

The curable group is not particularly limited as long as it is curable, and examples thereof include an ethylenically unsaturated 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 thiol group, a hydroxy group, a carboxy group, an amino group, an amide group, an aldehyde group, and a sulfonic acid group.
When the curable compound A is formed by half curing, which will be described later, the curable group is preferably an ethylenically unsaturated group. In this case, the curable compound is preferably a polyfunctional ethylenically unsaturated compound.

The curable compound A is preferably a thermosetting resin.
Examples of the thermosetting resin include epoxy resin, phenol resin, unsaturated imide resin, cyanate resin, isocyanate resin, benzoxazine resin, oxetane resin, amino resin, unsaturated polyester resin, allyl resin, dicyclopentadiene resin, silicone resin, triazine resin, and melamine resin. The thermosetting resin is not particularly limited to these, and any known thermosetting resin can be used. These thermosetting resins can be used alone or in combination.
As the curable compound A, a commercially available adhesive (so-called varnish or hot melt adhesive, etc.) can also be used.

As the curable compound A, a curable compound obtained by half-curing a monomer is preferably used.
The monomer is preferably an ethylenically unsaturated compound, more preferably a polyfunctional ethylenic compound.
Examples of the ethylenically unsaturated compound include a (meth)acrylate compound, a (meth)acrylamide compound, a (meth)acrylic acid, a styrene compound, a vinyl acetate compound, a vinyl ether compound, and an olefin compound.
Of these, (meth)acrylate compounds are preferred.
From the viewpoint of adhesion to metal foil or metal wiring, the molecular weight of the monomer is preferably 50 or more and less than 1,000, more preferably 100 or more and less than 1,000, and particularly preferably 200 or more and 800 or less.

In addition, when the curable compound contains an ethylenically unsaturated compound, the film according to the present disclosure preferably contains a polymerization initiator. The polymerization initiator is preferably a thermal polymerization initiator or a photopolymerization initiator.
As the thermal polymerization initiator or photopolymerization initiator, known initiators can be used.
The thermal polymerization initiator may be a thermal radical generator, specifically, a peroxide initiator such as benzoyl peroxide or azobisisobutyronitrile, or an azo-based initiator.
Examples of the photopolymerization initiator include photoradical generators. Specific examples of the photopolymerization initiator include (a) aromatic ketones, (b) onium salt compounds, (c) organic peroxides, (d) thio compounds, (e) hexaarylbiimidazole compounds, (f) ketoxime ester compounds, (g) borate compounds, (h) azinium compounds, (i) active ester compounds, (j) compounds having a carbon-halogen bond, and (k) pyridium compounds.
The polymerization initiator may be added alone or in combination of two or more kinds.
The content of the polymerization initiator is preferably 0.01% by mass to 30% by mass, more preferably 0.05% by mass to 25% by mass, and further preferably 0.1% by mass to 20% by mass, based on the total mass of the curable compound.

Layer B may contain only one type of curable compound, for example, only one type of curable compound A, or may contain two or more types of curable compounds.
Furthermore, the layer B may contain only one type of the curable compound A, or may contain two or more types of the curable compound A.
The content of the curable compound in Layer B is preferably 0.1% by mass to 70% by mass, more preferably 1% by mass to 60% by mass, even more preferably 5% by mass to 60% by mass, and particularly preferably 10% by mass to 55% by mass, relative to the total mass of Layer B, from the viewpoints of the dielectric tangent of the film and the wiring distortion suppression property.
From the viewpoints of the dielectric tangent of the film and the wiring distortion suppression property, the content of the curable compound A in Layer B is preferably 0.1% by mass to 70% by mass, more preferably 1% by mass to 60% by mass, even more preferably 5% by mass to 60% by mass, and particularly preferably 10% by mass to 55% by mass, relative to the total mass of Layer B.

In addition, from the viewpoint of suppressing wiring distortion, the content of the curable compound A in layer B is preferably 30% by mass to 100% by mass, more preferably 50% by mass to 100% by mass, and particularly preferably 70% by mass to 100% by mass, based on the total mass of the curable compound.

- Hardening inhibitor -
From the viewpoints of controlling the curing state and suppressing wiring distortion, it is preferable that Layer B contains a curing inhibitor.
Examples of the curing inhibitor include a polymerization inhibitor and a heat stabilizer, each of which may be a known agent.
Examples of the polymerization inhibitor include p-methoxyphenol, quinones (e.g., hydroquinone, benzoquinone, methoxybenzoquinone, etc.), phenothiazine, catechols, alkylphenols (e.g., dibutylhydroxytoluene (BHT)), alkylbisphenols, zinc dimethyldithiocarbamate, copper dimethyldithiocarbamate, copper dibutyldithiocarbamate, copper salicylate, thiodipropionic acid esters, mercaptobenzimidazole, phosphites, 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO), 2,2,6,6-tetramethyl-4-hydroxypiperidine-1-oxyl (TEMPOL), tris(N-nitroso-N-phenylhydroxylamine) aluminum salt (also known as Cupferron Al), and the like.
Examples of the heat stabilizer include phosphorus-based heat stabilizers such as tris(2,4-di-tert-butylphenyl)phosphite, bis[2,4-bis(1,1-dimethylethyl)-6-methylphenyl]ethyl ester phosphorous acid, tetrakis(2,4-di-tert-butylphenyl)[1,1-biphenyl]-4,4'-diylbisphosphonite, and bis(2,4-di-tert-butylphenyl)pentaerythritol diphosphite, and lactone-based heat stabilizers such as a reaction product of 8-hydroxy-5,7-di-tert-butyl-furan-2-one and o-xylene.

The curing inhibitor may be used alone or in combination of two or more kinds.
The content of the curing inhibitor is not particularly limited, but is preferably 0.0001% by mass to 2.0% by mass relative to the total mass of Layer B.

The average thickness of the 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.

The average thickness of the film is determined by measuring any five points using an adhesive film thickness gauge, such as an electronic micrometer (product name "KG3001A", manufactured by Anritsu Corporation), and averaging these values.

<Application>
The film according to the present disclosure can be used for various applications, and among others, can be suitably used as a film for electronic components such as printed wiring boards, and can be even more suitably used for flexible printed circuit boards.
Moreover, the film according to the present disclosure can be suitably used as a film for bonding metals.

(Film manufacturing method)
A first embodiment of the method for producing a film according to the present disclosure includes a forming step of forming a film by applying a composition containing a polymer, at least one compound selected from the group consisting of a fluorine atom-containing compound and a silicon atom-containing compound, and a solvent onto a substrate and drying the composition, and a heating step of heating the film, wherein the dielectric tangent of the obtained film is 0.01 or less, and the surface free energy of one surface of the film before the heating step is 15 mN/m to 36 mN/m.
A second embodiment of the method for producing a film according to the present disclosure includes a forming step of forming a film by applying a composition containing a polymer, at least one compound selected from the group consisting of a fluorine atom-containing compound and a silicon atom-containing compound, and a solvent onto a substrate and drying the composition, and a heating step of heating the film, wherein the dielectric tangent of the obtained film is 0.01 or less, and the surface coverage of at least one compound selected from the group consisting of the fluorine atom-containing compound and the silicon atom-containing compound on at least one surface of the film before the heating step is 30% to 100%.

In this specification, when the term "film manufacturing method according to the present disclosure" or "film manufacturing method" is used without any particular specification, it refers to both the first embodiment and the second embodiment.

In the manufacturing method of the 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 obtained film, are the same as the preferred aspects of the film according to the present disclosure described above.
In addition, in the film manufacturing method 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 film according to the present disclosure.

In the film production method according to the present disclosure, the preferred physical property values of the film obtained are the same as those of the preferred aspects of the film according to the present disclosure described above.
In a first embodiment of the method for producing a film according to the present disclosure, the surface free energy of at least one surface of the film before the heating step is 15 mN/m to 36 mN/m, and from the viewpoint of suppressing breakage failure during peeling, it is preferably 15 mN/m to 30 mN/m, more preferably 15 mN/m to 25 mN/m, and particularly preferably 15 mN/m to 20 mN/m.
In a second embodiment of the film manufacturing method according to the present disclosure, from the viewpoint of suppressing breakage failure during peeling, the surface free energy of at least one surface of the film before the heating step is preferably 15 mN/m to 36 mN/m, more preferably 15 mN/m to 30 mN/m, even more preferably 15 mN/m to 25 mN/m, and particularly preferably 15 mN/m to 20 mN/m.
In the film manufacturing method according to the present disclosure, from the viewpoint of suppressing breakage failure during peeling, the surface free energy of at least one surface of the resulting film is preferably 15 mN/m to 36 mN/m, more preferably 15 mN/m to 30 mN/m, even more preferably 15 mN/m to 25 mN/m, and particularly preferably 15 mN/m to 20 mN/m.

In a second embodiment of the method for producing a film according to the present disclosure, the surface coverage of at least one compound selected from the group consisting of fluorine atom-containing compounds and silicon atom-containing compounds on at least one surface of the film before the heating step is 30% to 100%, and from the viewpoint of suppressing fracture failure during peeling, it is preferably 50% to 100%, more preferably 80% to 100%, particularly preferably 90% to 100%, and most preferably 100%.
In a first embodiment of the method for producing a film according to the present disclosure, from the viewpoint of suppressing fracture failure during peeling, the surface coverage of at least one compound selected from the group consisting of fluorine atom-containing compounds and silicon atom-containing compounds on at least one surface of the film before the heating step is preferably 30% to 100%, more preferably 50% to 100%, even more preferably 80% to 100%, particularly preferably 90% to 100%, and most preferably 100%.
In the film production method according to the present disclosure, from the viewpoint of suppressing breakage failure during peeling, the surface coverage of at least one surface of the obtained film with at least one compound selected from the group consisting of fluorine atom-containing compounds and silicon atom-containing compounds is preferably 30% to 100%, more preferably 50% to 100%, even more preferably 80% to 100%, particularly preferably 90% to 100%, and most preferably 100%.

Furthermore, in the film manufacturing method according to the present disclosure, the surface free energy of the obtained film is preferably greater than the surface free energy of the film after the forming step and before the heating step, from the viewpoint of the dielectric tangent of the film.
Furthermore, in the film manufacturing method according to the present disclosure, the surface coverage of the obtained film is preferably smaller than the surface coverage of the film after the forming step and before the heating step, from the viewpoint of the dielectric tangent of the film.

<Formation process>
The method for producing a film according to the present disclosure includes a formation step of forming a film by applying a composition containing a polymer, at least one compound selected from the group consisting of a fluorine atom-containing compound and a silicon atom-containing compound, and a solvent onto a substrate and drying the composition.
The method for forming the film is not particularly limited, and known methods can be referred to, and for example, the casting method, coating method, extrusion method, etc. are preferably mentioned, and among them, the casting method is particularly preferred. In addition, when the film has a multilayer structure, for example, the co-casting method, multi-layer coating method, co-extrusion method, etc. are preferably mentioned. Among them, the co-casting method is particularly preferred for the production of a relatively thin film, and the co-extrusion method is particularly preferred for the production of 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 composition for forming layer A, a composition for forming layer B, etc., in which the components of each layer, such as a liquid crystal polymer, are dissolved or dispersed in a solvent.

Examples of solvents include halogenated hydrocarbons such as dichloromethane, chloroform, 1,1-dichloroethane, 1,2-dichloroethane, 1,1,2,2-tetrachloroethane, 1-chlorobutane, chlorobenzene, and o-dichlorobenzene; halogenated phenols such as p-chlorophenol, pentachlorophenol, and pentafluorophenol; ethers such as diethyl ether, tetrahydrofuran, and 1,4-dioxane; ketones such as acetone and cyclohexanone; esters such as ethyl acetate and γ-butyrolactone; and ethylene carbonate. Examples of the organic solvent include carbonates such as propylene carbonate and propylene carbonate; amines such as triethylamine; nitrogen-containing heterocyclic aromatic compounds such as pyridine; nitriles such as acetonitrile and succinonitrile; amides such as N,N-dimethylformamide, N,N-dimethylacetamide, and N-methylpyrrolidone, 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-butylphosphoric acid, and two or more of these may be used.

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 ratio of the aprotic compound to 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 preferred to use amides such as N,N-dimethylformamide, N,N-dimethylacetamide, tetramethylurea, and N-methylpyrrolidone, or esters such as γ-butyrolactone, because they easily dissolve the liquid crystal polymer, and N,N-dimethylformamide, N,N-dimethylacetamide, and N-methylpyrrolidone are more preferred.

As the solvent, a solvent mainly composed of a compound having a dipole moment of 3 to 5 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, it is preferable to use a compound having a dipole moment of 3 to 5.

In addition, the solvent is preferably a solvent mainly composed of a compound having a boiling point of 220° C. or lower at 1 atmospheric pressure, because it is easy to remove. The proportion of the compound having a boiling point of 220° C. or lower at 1 atmospheric pressure 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.

In addition, the film may be produced using a support when 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 a laminate described later 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 these, a metal drum, a metal band, and a resin film are preferred.
An example of the resin film is a polyimide (PI) film. 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 so that it can be easily peeled off. The surface treatment layer may be made of hard chrome plating, fluororesin, or the like.
The average thickness of the resin film support is not particularly limited, but is preferably from 25 to 75 μm, and more preferably from 50 to 75 μm.

The method for removing at least a portion 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.

<Stretching process>
The method for producing a film according to the present disclosure preferably includes a stretching step of stretching the film, and more preferably includes a stretching step of stretching the film between the forming step and the heating step.
In the film manufacturing method according to the present disclosure, stretching can be appropriately combined from the viewpoint of controlling the molecular orientation of the obtained film and adjusting the linear expansion coefficient and mechanical properties. The stretching method is not particularly limited, and known methods can be referred to. It may be performed in a state containing a solvent or in a dry film state. Stretching in a state containing a solvent may be performed by gripping the film and stretching it, or by using the self-shrinking force of the web due to drying without stretching it, or a combination thereof. Stretching is particularly effective for the purpose of improving the breaking elongation and breaking strength when the brittleness of the film is reduced by the addition of inorganic fillers, etc.

<Heating process>
The method for producing a film according to the present disclosure includes a heating step of heating the film.
It is believed that the heating step promotes crystallization of the polymer in the film, thereby lowering the dielectric tangent of the film.
In the film manufacturing method according to the present disclosure, the amount of dissolved oxygen is preferably 500 ppm or less, more preferably 300 ppm or less, at the start of heating the film. When the amount of dissolved oxygen is within the above range, a film with a lower dielectric loss tangent can be obtained.
The above-mentioned heating start time refers to the time when application of heat to the film begins.

In this 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.

The heating temperature in the heating step is preferably 100°C to 400°C. The heating time is preferably 0.1 minutes to 10 hours. The heating temperature and heating time can be changed appropriately depending on the type of polymer, and can also be lowered or shortened by other means such as the addition of a catalyst.

The heating step may be carried out in an inert gas atmosphere or in 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.

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

<Unwinding process>
The film manufacturing method according to the present disclosure preferably includes, after the winding step, an unwinding step of unwinding the rolled film.
In addition, it is preferable that the peel force when unwinding the film in the unwinding step is 1.0 kN/m or less.

<Peeling process>
The method for producing a film according to the present disclosure preferably includes a peeling step of peeling the film from the substrate after the forming step or the heating step, more preferably includes a peeling step of peeling the film from the substrate after the forming step, and particularly preferably includes a peeling step of peeling the film from the substrate after the forming step and before the heating step. By peeling the film from the substrate, a film is obtained and can be applied to other uses.

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

(Laminate)
The laminate according to the present disclosure may be any laminate in which the film according to the present disclosure is laminated, but it preferably has the film according to the present disclosure and a metal layer or metal wiring arranged on at least one surface of the film, and it is more preferable that the laminate has the film according to the present disclosure and a copper layer or copper wiring arranged on at least one surface of the film.
In addition, it is preferable that the surface of the film on which the metal layer or metal wiring is arranged is a surface that satisfies the above-mentioned surface free energy range, a surface that satisfies the above-mentioned surface coverage range, or a surface that satisfies the above-mentioned surface free energy range and the above-mentioned surface coverage range.

The surface roughness Ra of the film side surface of the metal layer or metal wiring is preferably 1.0 μm or less, and 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 film and the metal substrate decreases.

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 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 regarded as the surface roughness Ra of the film side surface of the metal layer or metal wiring.

Moreover, the laminate according to the present disclosure preferably has a metal layer or metal wiring, a film according to the present disclosure, and a metal layer or metal wiring, in that order, and more preferably has a copper layer or copper wiring, a film according to the present disclosure, and a copper layer or copper wiring, in that order.
Furthermore, the laminate according to the present disclosure preferably comprises, in this order, a film according to the present disclosure, a copper layer or copper wiring, a film according to the present disclosure, a metal layer or metal wiring, and a film according to the present disclosure. The two 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. For example, a silver layer, silver wiring, a copper layer or copper wiring is preferable, and a copper layer or copper wiring is more preferable.
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.
Since the film according to the present disclosure can be further cured, for example, after attachment of a metal layer or metal wiring, the laminate according to the present disclosure preferably contains a cured product obtained by curing the curable compound A from the viewpoint of durability.

There are no particular limitations on the method for attaching the film according to the present disclosure to the metal layer or metal wiring, and any known lamination method can be used.

The peel strength between the 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.

In the present disclosure, the peel strength between a film and a metal layer (e.g., a copper layer) is measured by the following method.
A peel test piece having a width of 1.0 cm is prepared from a laminate of a 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 by the 180° method in accordance with JIS C 5016 (1994).

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

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 copper foil with a carrier that is formed releasably on a support (carrier). 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.

In order to further exert the effects of the present disclosure, the metal layer preferably has a group capable of interacting with the film on the surface in contact with the film, and the group capable of interacting with the film is preferably a group corresponding to a functional group of a compound having a functional group contained in the film, such as an amino group and an epoxy group, or a hydroxyl group and an epoxy group.
Examples of the group capable of interacting with another molecule include the groups exemplified as functional groups in the compound having the above 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.

It is also preferable to process the metal layer in the laminate according to the present disclosure into a desired circuit pattern, for example, by etching, to produce a flexible printed circuit board. There are no particular limitations on the etching method, and any known etching method can be used.

The method for producing a laminate according to the present disclosure preferably includes a lamination step of laminating the film with a metal layer or metal wiring, and more preferably includes a lamination step of laminating the film with a copper layer or copper wiring at a temperature of from −30° C. to +30° C. (the melting point of the additive) or a lamination step of laminating the film with a copper layer or copper wiring at a pressure of from −5 MPa to +10 MPa (the pressure at which the elastic modulus of the layer B changes). It is particularly preferable that the film and layer B include a lamination step of laminating the film with a copper layer or copper wiring at a temperature of from −30° C. to +30° C. (the melting point of the additive) and a lamination step of laminating the film with a copper layer or copper wiring at a pressure of from −5 MPa to +10 MPa (the pressure at which the elastic modulus of the layer B changes).

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.
From the viewpoint of suppressing wiring distortion, the bonding pressure in the lamination process is preferably a pressure of not less than the pressure at which the elastic modulus of the layer B changes -5 MPa and not more than the pressure at which the elastic modulus of the layer B changes +10 MPa, and more preferably a pressure of not less than the pressure at which the elastic modulus of the layer B changes -5 MPa and not more than the pressure at which the elastic modulus of the layer B changes +5 MPa.
The lamination temperature in the lamination step can be appropriately selected depending on the film to be 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.
From the viewpoint of suppressing wiring distortion, the lamination temperature in the lamination step is preferably a temperature of not less than the melting point of the additive -30°C and not more than the melting point +50°C, more preferably a temperature of not less than the melting point of the additive -30°C and not more than the melting point +30°C, and particularly preferably a temperature of not less than the melting point of the additive -20°C and not more than the melting point +20°C.

The present disclosure will be explained in more detail below with reference to examples. The materials, amounts used, ratios, processing contents, processing procedures, etc. shown in the following examples can be changed as appropriate without departing from the spirit of this disclosure. Therefore, the scope of this disclosure is not limited to the specific examples shown below.

Details of the materials used in the examples and comparative examples are as follows:

<Liquid Crystal Polymer>
LC-A: Liquid crystal polymer prepared according to the following manufacturing method

-Production of LC-A-
Into a reactor equipped with a stirrer, a torque meter, a nitrogen gas inlet tube, a thermometer, and a reflux condenser, 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 1123.0 g (11 mol) of acetic anhydride were placed, and the gas in the reactor was replaced with nitrogen gas. After that, 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 with a pulverizer to obtain a powdered liquid crystal polyester (B1).

The liquid crystal polyester (B1) obtained above was solid-phase polymerized by holding it at 250°C for 3 hours in a nitrogen atmosphere, and then cooled to obtain a powdered liquid crystal polyester (LC-A). The resulting LC-A was heated at 280°C for 3 hours in a nitrogen atmosphere, and the dielectric tangent of the sample was 0.01 or less.

<Fluorine Atom-Containing Compound or Silicon Atom-Containing Compound>
S-1: Polymer prepared according to the following production method (fluorine atom-containing compound (fluorine-based surfactant), Mw 10,000)

-Production of S-1-
In a 100 mL recovery flask, 5.0 g of 1,1-dimethoxycyclohexane, 9.0 g of 2-hydroxymethacrylate, 25.0 g of 1H,1H,2H,2H-perfluorooctanol, 0.87 g of pyridinium p-toluenesulfonate, and 30 mL of toluene were weighed and stirred at 40° C. for 1 hour, and then stirred under a reduced pressure of 100 mmHg at 40° C. for 4 hours. The resulting reaction liquid was cooled to room temperature (23° C.), and then separated and washed with saturated aqueous sodium bicarbonate. The resulting organic layer was dried over anhydrous magnesium sulfate, concentrated, and subjected to silica gel column chromatography to obtain 8.0 g of Monomer 1 represented by the following formula as a colorless liquid.

100 g of 2-hydroxyethyl methacrylate and 240 mL of N,N-dimethylacetamide (DMAc) were added to a 2,000 mL three-neck flask equipped with a stirring blade, a thermometer, and a dropping funnel, and cooled in an ice bath. Next, 126.8 g of 3-chloropropionyl chloride was added dropwise, and the mixture was stirred for 3 hours under ice cooling. After the resulting reaction liquid was cooled to room temperature, 1,000 mL of ethyl acetate was separated and washed with 1 mol/L hydrochloric acid, a saturated aqueous solution of sodium bicarbonate, and water, and the resulting organic layer was dried over anhydrous magnesium sulfate and concentrated to obtain 85 g of the target monomer 2 as a pale yellow liquid.

2.34 g of Monomer 1, 3.60 g of Cyclomer M100 (manufactured by Daicel Corporation), 4.05 g of Monomer 2, 18.57 g of methyl ethyl ketone (MEK), and 3.760 g of dimethyl 2,2'-azobis(isobutyrate) (polymerization initiator, manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) were weighed out and stirred at 70°C for 6 hours.
After the reaction, reprecipitation was performed using 500 mL of methanol. The obtained solid was dissolved in 15 g of MEK, and 5.57 g of triethylamine and 0.01 g of p-methoxyphenol were added thereto, followed by stirring at 60° C. for 4 hours. The reaction liquid was returned to room temperature, and then reprecipitation was performed using 500 mL of methanol, and the resulting mixture was dissolved in 25 g of MEK, thereby obtaining 5.1 g of polymer S-1.
In the following reaction formula, "M100" represents CYCLOMER M100. The unit of the content (content ratio) of each structural unit in the polymer is "mol %".

S-2: Polymer produced according to the following manufacturing method (silicon and fluorine atom-containing compound (silicone surfactant), Mw 20,000)

-Production of S-2-
Monomer 3 was synthesized using (3-mercaptopropyl)trimethoxysilane and 2-(perfluorohexyl)ethyl vinyl ether (CHEMINOX FAVE-6 (Unimatec Co., Ltd.) according to the method described in Tetrahedron, 1991, 47, 4927-4940. In the following structural formula, Et represents an ethyl group.

3.90 g of Monomer 3, 6.59 g of 3-glycidoxypropyltrimethoxysilane (manufactured by FUJIFILM Wako Pure Chemical Industries, Ltd.), 6.93 g of 3-methacryloxypropyltrimethoxysilane (manufactured by FUJIFILM Wako Pure Chemical Industries, Ltd.), 50 g of acetone, 1.38 g of 5% aqueous potassium carbonate solution, and 9.0 g of pure water were weighed out and stirred at 50 ° C. for 5 hours. The resulting reaction liquid was cooled to room temperature, and 50 g of methyl isobutyl ketone (MIBK) and 50 g of 5% saline were added to extract the organic layer. The organic layer was further washed once with 50 g of 5% saline and twice with 50 g of pure water, and then 10 g of magnesium sulfate and 0.01 g of p-methoxyphenol were added. After filtering off the magnesium sulfate, the solvent was distilled off under reduced pressure at 50 ° C. and 35 mmHg to obtain 20.2 g of Polymer S-2 as a 60.5 mass % MIBK solution.
In the following structural formula, Me represents a methyl group, and Et represents an ethyl group. The content (content ratio) of each structural unit in the polymer is expressed in "mol %".

S-3: Polymer with the following structure (fluorine atom-containing compound (fluorine-based surfactant), Mw 20,000)

<Additives>
- Inorganic filler -
F-1: Hydrophobic silica having an average primary particle size of 20 nm (NX90S (surface treated with hexamethyldisilazane, manufactured by Nippon Aerosil Co., Ltd.) was used so that the solid content was the amount shown in Table 1).
F-2: Hydrophobic silica having an average primary particle size of 16 nm (R972 (surface treated with dimethyldichlorosilane, manufactured by Nippon Aerosil Co., Ltd.) was used so that the solid content was the amount shown in Table 1).
-Oxygen-reactive compounds-
A-1: Diethylhydroxylamine and 1-amino-4-methylpiperazine were used in a mass ratio of 4:3, with the total amount added being the amount shown in Table 1.
-Oxygen-adsorbing compound-
B-1: A calcium silicate compound powder (Fluorite R, manufactured by Tokuyama Corp.) consisting of corolla-like curved plate-like crystals made of gyrolite-type calcium silicate and amorphous silicon dioxide was used.
-Curable compound-
M-1: Low dielectric adhesive (SLK series varnish (thermosetting resin manufactured by Shin-Etsu Chemical Co., Ltd.) mainly containing polymer-type curable compounds)

Details of Examples 1 to 12 and Comparative Examples 1 and 2 are provided below.

(Examples 1 to 12 and Comparative Example 2)
Single-sided copper-clad laminates were fabricated using the co-casting method.

[Co-casting (solution casting)]
- Preparation of polymer solution -
LC-A was added to N-methylpyrrolidone, and dissolved by heating and stirring at 120° C. under a nitrogen atmosphere. The mixture was passed through a sintered fiber metal filter having a nominal pore size of 10 μm, and then passed through the same sintered fiber metal filter having a nominal pore size of 10 μm as above. The additives shown in Table 1 were then added and stirred to prepare a liquid crystal polymer solution for layer A and a liquid crystal polymer solution for layer B. LC-A and the additives were added in the mass ratios shown in Table 1, and the solid content concentration was 10 mass% for each.

- Fabrication of single-sided copper-clad laminate -
<Forming process and film winding process>
The polymer solution for Layer A and the polymer solution for Layer B were sent to a casting die equipped with a multi-manifold adjusted for co-casting, and cast onto the treated surface of a copper foil (manufactured by Fukuda Metal Foil & Powder Co., Ltd., CF-T9DA-SV-12, average thickness 12 μm; metal substrate (metal layer)) so that Layer B was in contact with the copper foil. The solvent was removed from the cast film by drying at 110° C., and a film having Layer B and Layer A in this order on the copper foil was obtained. Next, the obtained film was wound up to a length of 2,000 m at a speed of 15 m/min under a nitrogen atmosphere, with the copper foil on the outside of the winding, to prepare a roll.

<Measurement of surface free energy>
A laminate having a film was sampled from the obtained roll, and the contact angle of water and the contact angle of methylene iodide on the surface of the Layer A side were measured, and the surface free energy (mN/m) was calculated.

<Heating process>
The obtained roll was heat-treated by increasing the temperature from room temperature to 300° C. over 10 hours in an atmosphere shown in Table 1, and then cooled to room temperature. A laminate (single-sided copper-clad laminate) having copper foil, Layer B, and Layer A in this order was obtained. The average thicknesses of Layer A and Layer B are shown in Table 1.
The copper foil (metal layer) in the single-sided copper-clad laminate had an oxygen permeability coefficient of less than 0.01 cm ³ /m ² ·day and a thermal expansion coefficient of 16 ppm/K.

The dielectric tangent and thermal expansion coefficient of the film were measured using the obtained single-sided copper-clad laminate. The measurement method is as follows.

<Dielectric tangent>
The dielectric loss tangent was measured by the resonance perturbation method at a frequency of 10 GHz. A 10 GHz cavity resonator (Kanto Electronics Application Development Co., Ltd. CP531) was connected to a network analyzer (Agilent Technology's "E8363B"), and a film sample (width: 2.0 mm x length: 80 mm) was inserted into the cavity resonator, and the dielectric loss tangent of the film was measured from the change in resonance frequency before and after insertion for 96 hours under a temperature of 25°C and a humidity of 60% RH environment. The copper foil was removed with ferric chloride before the measurement.

<Thermal expansion coefficient>
Using a thermomechanical analyzer (TMA), a tensile load of 1 g was applied to both ends of a film having a width of 5 mm and a length of 20 mm, and the film was heated from 25° C. to 200° C. at a rate of 5° C./min, cooled to 30° C. at a rate of 20° C./min, and then heated again at a rate of 5° C./min. The thermal expansion coefficient was calculated from the slope of the TMA curve between 30° C. and 150° C. Note that the copper foil was removed with ferric chloride before the measurement.

<Evaluation of peelability>
The peel strength between a film and an adjacent adherend can be measured by a test in which the laminate of the film and the adherend is peeled off in a 90° direction from a sample in which the laminate is laminated. In samples with a peel strength exceeding 0.35 kN/m, the film broke or the film surface became rough sporadically when the line speed was increased in the peeling process.

The measurement results are shown in Table 1.

(Comparative Example 1)
A film was produced in the same manner as in Example 1 of JP-A-2011-167847, except that the liquid crystal polyester powder described in Example 1 of JP-A-2011-167847 was replaced with LC-A. Evaluation was also performed in the same manner as in Example 1. The evaluation results are shown in Table 1.

As shown in Table 1, the films of Examples 1 to 12 contain a polymer and at least one compound selected from the group consisting of fluorine atom-containing compounds and silicon atom-containing compounds, and because the surface energy of the film is low, the peel strength is low, allowing the laminate to be unwound from the roll after heat treatment without resistance, and film breakage during peeling and roughening of the film surface are suppressed.

On the other hand, the films of Comparative Example 1 and Comparative Example 2 did not contain at least one compound selected from the group consisting of fluorine atom-containing compounds and silicon atom-containing compounds, or contained only a small amount of the compound. Also, the surface energy of the film was high. Therefore, blocking occurred after the heat treatment, and when the laminate was unwound, knicks (uneven defects caused by the surface coming into contact with a roll or the like and rubbing against the roll) or sporadic breakage occurred.

Claims (18)

The dielectric loss tangent is 0.01 or less,
The composition comprises at least one compound selected from the group consisting of a fluorine atom-containing compound and a silicon atom-containing compound, and a filler,
at least one compound selected from the group consisting of fluorine atom-containing compounds and silicon atom-containing compounds has an epoxy group,
A film having a surface free energy of 15 mN/m to 36 mN/m on at least one surface. The dielectric loss tangent is 0.01 or less,
The composition comprises at least one compound selected from the group consisting of a fluorine atom-containing compound and a silicon atom-containing compound, and a filler,
at least one compound selected from the group consisting of fluorine atom-containing compounds and silicon atom-containing compounds has an epoxy group,
A film, wherein a surface coverage rate of at least one surface of the film with at least one compound selected from the group consisting of fluorine atom-containing compounds and silicon atom-containing compounds is 30% to 100%. The film according to claim 1 or 2, comprising the fluorine atom-containing compound. The film according to any one of claims 1 to 3, wherein the at least one compound selected from the group consisting of fluorine atom-containing compounds and silicon atom-containing compounds is at least one compound selected from the group consisting of fluorine resins and silicone resins. The film according to any one of claims 1 to 4, wherein the at least one compound selected from the group consisting of fluorine atom-containing compounds and silicon atom-containing compounds includes a surfactant. The film according to any one of claims 1 to 5 , further comprising an oxygen scavenger. The film according to any one of claims 1 to 6 , wherein the surface roughness Rz of at least one surface of the film is from 10 nm to 10,000 nm. The film according to any one of claims 1 to 7 , wherein at least one surface of the film has an elastic modulus of 100 MPa or more at 25°C. The film according to any one of claims 1 to 8, which is in the form of a roll. The film according to any one of claims 1 to 9 ,
A laminate comprising the film and a metal layer or metal wiring on at least one surface of the film. 11. The laminate according to claim 10 , wherein the surface roughness Ra of the film-side surface of the metal layer or metal wiring is 1.0 μm or less. a forming step of forming a film by applying a composition containing a polymer, at least one compound selected from the group consisting of a fluorine atom-containing compound and a silicon atom-containing compound, a filler, and a solvent onto a substrate and drying the composition;
and a heating step of heating the film,
The dielectric loss tangent of the obtained film is 0.01 or less,
at least one compound selected from the group consisting of fluorine atom-containing compounds and silicon atom-containing compounds has an epoxy group,
the surface free energy of one surface of the film before the heating step is 15 mN/m to 36 mN/m. a forming step of forming a film by applying a composition containing a polymer, at least one compound selected from the group consisting of a fluorine atom-containing compound and a silicon atom-containing compound, a filler, and a solvent onto a substrate and drying the composition;
and a heating step of heating the film,
The dielectric loss tangent of the obtained film is 0.01 or less,
at least one compound selected from the group consisting of fluorine atom-containing compounds and silicon atom-containing compounds has an epoxy group,
a surface coverage of at least one surface of the film with the at least one compound selected from the group consisting of fluorine atom-containing compounds and silicon atom-containing compounds is 30% to 100% before the heating step. The method for producing a film according to claim 12 or 13 , further comprising, after the forming step, a peeling step of peeling the film from the substrate. The method for producing a film according to any one of claims 12 to 14 , further comprising a winding step of winding the film into a roll after the forming step and before the heating step. The method of claim 13 , wherein the surface coverage of the resulting film is less than the surface coverage of the film after the forming step and before the heating step. The method of claim 12 , wherein the surface free energy of the resulting film is greater than the surface free energy of the film after the forming step and before the heating step. a winding step of winding a roll-shaped film after the winding step,
The method for producing a film according to claim 15 , wherein a peel force when the film is unwound in the unwinding step is 1.0 kN/m or less.