Film and manufacturing method thereof, laminated film, and laminate

Abstract

To provide a film excellent in peel strength from a metal substrate with an in-between adhesive layer, a production method thereof, a laminate film and a laminate article made of the film.SOLUTION: There is provided a film, a production method thereof, and a laminate film and a laminate article made of the film. The film contains a liquid crystal polymer and has a difference of a contact angle with water measured by a water droplet method in the air of 25°C, 50% RH between the inside of the film and one surface of the film of 7° or more. The production method of the film includes an oxidation step for oxidizing the surface of the film that contains the liquid crystal polymer and produces the film having a difference of a contact angle with water measured by a water droplet method in the air of 25°C, 50% RH between the inside of the film and one surface of the film of 7° or more.SELECTED DRAWING: None

Description

[Technical Field]

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

[0002] In recent years, the frequencies used in communication devices have tended to become very high. To suppress transmission loss in high-frequency bands, it has become necessary to lower the relative permittivity and dielectric loss tangent of insulating materials used in circuit boards.

[0003] As a conventional method for manufacturing a liquid crystal film, for example, the method described in Patent Document 1 is known. Patent Document 1 describes a method for modifying the surface of an article made of a liquid crystal polymer material, which includes irradiating the surface of the article made of a liquid crystal polymer material with ions. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2008-308616 Summary of the Invention [Problem to be solved by the invention]

[0005] An object of the present invention is to provide a film having excellent peel strength from a metal substrate via an adhesive layer, and a method for producing the same. Another problem to be solved by another embodiment of the present invention is to provide a laminated film and a laminated body using the above film. [Means for solving the problem]

[0006] The means for solving the above problems include the following aspects. <1> A film containing a liquid crystal polymer, in which the difference in contact angle with water between the interior of the film and one surface of the film measured by the water drop method in air at 25°C and 50% RH is 7° or more. <2> The surface free energy of one surface of the film is 47 N / m to 60 N / m. <1> The film according to claim 1. <3> The contact angle of one surface of the film with water measured by a water drop method in the air at 25°C and 50% RH is 50° or more and less than 75° <1> or <2> The film according to claim 1. <4> The difference in contact angle with water measured by the air water drop method at 25°C and 50% RH between the inside of the film and one of the surfaces of the film is 7° or more and 32° or less. <1> ~ <3> 10. The film according to any one of the preceding items. <5> The surface roughness Ra of one surface of the film is 0.05 μm or less. <1> ~ <4> 10. The film according to any one of the preceding items. <6> The liquid crystal polymer includes a liquid crystal polymer having at least one constituent unit selected from the group consisting of a constituent unit derived from parahydroxybenzoic acid and a constituent unit derived from 6-hydroxy-2-naphthoic acid. <1> ~ <5> 10. The film according to any one of the preceding items. <7> The liquid crystal polymer includes a liquid crystal polymer having at least one type of structural unit selected from the group consisting of a structural unit derived from 6-hydroxy-2-naphthoic acid, a structural unit derived from an aromatic diol compound, a structural unit derived from terephthalic acid, and a structural unit derived from 2,6-naphthalenedicarboxylic acid. <1> ~ <5> 10. The film according to any one of the preceding items. <8> Further containing polyolefin <1> ~ <7> 10. The film according to any one of the preceding items. <9> The content of the polyolefin is 0.1% by mass to 40% by mass relative to the total mass of the film. <8> The film according to claim 1. <10> In the film, the polyolefin forms a dispersed phase. <8> or <9> The film according to claim 1. <11> The average dispersed diameter of the dispersed phase is 0.01 μm to 10 μm. <10> The film according to claim 1. <12> The elastic modulus of one surface of the film at 240°C is 300 MPa or more. <1> ~ <11> 10. The film according to any one of the preceding items. <13> A laminated film having a layer A and a layer B on at least one surface of the layer A, wherein the layer A is <1> ~ <12> A laminated film which is the film according to any one of the above. <14> The layer B has an elastic modulus of 0.1 MPa or less at 140°C. <13> The laminated film according to claim 1. <15> <1> ~ <12> One surface of the film according to any one of the above, or <13> or <14> A laminate having a metal substrate on the surface of Layer B side of the laminate film described in 1. <16> <1> ~ <12> One surface of the film according to any one of the above, or <13> or <14> A laminate comprising a metal substrate and a resin layer containing a compound having a functional group on any one surface of the laminate film described in 1., wherein the functional group contains one or more 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. <17> The maximum height Rz of the film side surface of the metal substrate is 2.0 μm or less. <15> or <16> The laminate according to claim 1. <18> A method for producing a film, which includes an oxidation treatment step of oxidizing the surface of a film containing a liquid crystal polymer, and in which the difference in contact angle with water between the interior of the film and one surface of the film measured by the air water drop method at 25°C and 50% RH is 7° or more. <19> an oxidation treatment step in which the contact angle with water measured by a water drop method in the air at 25°C and 50% RH on one surface of the film produced is 50° or more and less than 75°; <18> A method for producing the film described in claim 1. <20> The oxidation treatment step is a step of contacting the surface of the film with an oxidizing agent in an aqueous solution. <18> or <19> A method for producing the film described in claim 1. <21> The standard redox potential of the oxidizing agent is 1.5 V or more. <20> A method for producing the film described in claim 1. <22> The oxidizing agent contains at least one compound selected from the group consisting of sodium persulfate, potassium persulfate, ammonium persulfate, hydrogen peroxide, potassium permanganate, sodium hypochlorite, ammonium cerium nitrate, potassium chromate, potassium dichromate, and a double salt of potassium peroxymonosulfate, potassium hydrogen sulfate, and potassium sulfate. <20> or <21> A method for producing the film described in claim 1. <23> The pH of the above aqueous solution is 12 or higher <20> ~ <22> 10. A method for producing a film according to any one of the preceding claims. [Effects of the Invention]

[0007] According to an embodiment of the present invention, it is possible to provide a film having excellent peel strength from a metal substrate via an adhesive layer, and a method for producing the same. According to another embodiment of the present invention, a laminate film and a laminate using the above film can be provided. DETAILED DESCRIPTION OF THE INVENTION

[0008] The present disclosure will be described in detail below. The following description of the components may be based on representative embodiments of the present disclosure, but the present disclosure is not limited to such embodiments. In this specification, the use of "to" to indicate a range of values ​​means that the values ​​before and after it are included as the lower and upper limits. In the numerical ranges described in stages in this disclosure, the upper or lower limit value described in one numerical range may be replaced with the upper or lower limit value of another numerical range described in stages. Furthermore, in the numerical ranges described in this disclosure, the upper or lower limit value of that numerical range may be replaced with a value shown in the examples. Furthermore, in the description of groups (atomic groups) in this specification, a description that does not specify whether it is substituted or unsubstituted includes both unsubstituted and substituted groups. For example, the term "alkyl group" includes not only alkyl groups that do not have a substituent (unsubstituted alkyl groups) but also alkyl groups that have a substituent (substituted alkyl groups). In this specification, "(meth)acrylic" is a term used as a concept that includes both acrylic and methacrylic, and "(meth)acryloyl" is a term used as a concept that includes both acryloyl and methacryloyl. Furthermore, the term "step" in this specification does not only refer to an independent step, but also includes a step that cannot be clearly distinguished from other steps as long as the intended purpose of the step is achieved. Furthermore, in this disclosure, "% by mass" and "% by weight" are synonymous, and "parts by mass" and "parts by weight" are synonymous. Furthermore, in the present disclosure, a combination of two or more preferred embodiments is a more preferred embodiment. Furthermore, unless otherwise specified, the weight-average molecular weight (Mw) and number-average molecular weight (Mn) in the present disclosure are molecular weights calculated using a gel permeation chromatography (GPC) analyzer with a TSKgel SuperHM-H (trade name of Tosoh Corporation) column, a solvent of PFP (pentafluorophenol) / chloroform = 1 / 2 (mass ratio), detection with a differential refractometer, and conversion using polystyrene as a standard substance.

[0009] (film) The film according to the present disclosure contains a liquid crystal polymer, and the difference in contact angle with water between the interior of the film and one surface of the film measured by a water drop method in air at 25°C and 50% RH is 7° or more.

[0010] Conventional films containing liquid crystal polymers sometimes have problems with the peel strength between the film and a metal substrate via an adhesive layer. The film according to the present disclosure has a difference in contact angle with water between the interior of the film and one surface of the film, as measured by the water droplet method in air at 25°C and 50% RH, of 7° or more, making the surface of the film more hydrophilic and improving the adhesion between the surface and an adhesive layer containing an epoxy resin or the like, thereby providing a film with excellent peel strength to a metal substrate via the adhesive layer. Furthermore, due to the above-described aspect, the film according to the present disclosure also exhibits excellent peel strength to the metal substrate via the adhesive layer, even after aging under moist heat.

[0011] <Difference in contact angle with water between the inside of the film and one surface of the film> The film according to the present disclosure has a difference in contact angle with water between the interior of the film and one surface of the film, measured by a water drop method in air at 25°C and 50% RH, of 7° or more, and from the viewpoint of improving the peel strength to the metal substrate via the adhesive layer (hereinafter also referred to simply as "peel strength") and improving the peel strength to the metal substrate via the adhesive layer after aging in wet heat (hereinafter also referred to as "peel strength after aging in wet heat"), the difference is preferably 7° or more and 32° or less, more preferably 10° or more and 30° or less, and particularly preferably 20° or more and 28° or less. Furthermore, it is preferable that one surface of the film according to the present disclosure that satisfies the above-mentioned range of difference in water contact angle is the surface that comes into contact with the adhesive layer, i.e., the surface that is bonded to the metal substrate via the adhesive layer.

[0012] From the viewpoint of peel strength and peel strength after aging under moist heat, the value of the contact angle with water on one surface of the film is preferably smaller than the value of the contact angle with water inside the film. Furthermore, from the viewpoints of peel strength and peel strength after aging under wet heat, the value of the contact angle with water on one surface of the film is preferably 50° or more and less than 75°, more preferably 55° or more and 73° or less, and particularly preferably 60° or more and 70° or less. The value of the contact angle with water inside the film is preferably 75° or more and 100° or less, more preferably 80° or more and 90° or less, from the viewpoints of peel strength and peel strength after aging under wet heat.

[0013] In the present disclosure, the water contact angle of the film surface at 25° C. and 50% RH is measured by the water drop method in the air as follows. The contact angle of one surface of the film with water is measured at 25°C and 50% RH. A contact angle meter (DM700) manufactured by Kyowa Interface Science Co., Ltd. is used for the measurement. The contact angle is calculated by reading the contact angle value 5 seconds after the droplet is created and averaging it over 10 points.

[0014] In the present disclosure, the water contact angle inside the film is measured by the air water drop method at 25°C and 50% RH as follows. The film is heated above the melting point of the liquid crystal polymer contained in the film to melt it, and then molded into a film again. Since the molded film has been heated above the melting point once, it is believed that the original surface and interior are completely mixed together. The water contact angle of one surface of the film thus obtained is measured using the same method as above, and this value is defined as the contact angle with water inside the film.

[0015] <Surface free energy> The surface free energy of one surface of the film is preferably 46 N / m to 65 N / m, more preferably 47 N / m to 60 N / m, and particularly preferably 49 N / m to 60 N / m, from the viewpoints of peel strength and peel strength after aging under wet heat. Furthermore, in the film according to the present disclosure, it is preferable that one surface of the film that satisfies the above-mentioned surface free energy range is the surface on which an adhesive layer is formed, i.e., the surface on which an adhesive layer is formed and which is bonded to a metal substrate.

[0016] The method for measuring the surface free energy of a film surface in the present disclosure is as follows. Based on the method by Owens, water and methylene iodide, whose surface free energies are known, are used, and the contact angle of water is measured by dropping water onto the film surface, and the contact angle of methylene iodide is measured by dropping methylene iodide onto the film surface, and the surface free energy (N / m) is calculated. The method for measuring each contact angle is the same as the method for measuring the water contact angle of the film surface described above.

[0017] <Surface roughness Ra> In the film according to the present disclosure, the surface roughness Ra of one surface of the film is preferably 0.05 μm or less, more preferably 0.03 μm or less, and particularly preferably 0.025 μm or less. The lower limit is preferably 0.001 μm or more, more preferably 0.005 μm or more, and particularly preferably 0.010 μm or more.

[0018] 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 roughness Ra of JIS B0601:2013.

[0019] <Dielectric loss tangent> From the viewpoints of suppressing fracture failure during peeling and reducing transmission loss of the produced substrate, the dielectric loss tangent of the film according to the present disclosure is preferably 0.01 or less, more preferably 0.005 or less, even more preferably 0.004 or less, and particularly preferably greater than 0 and 0.003 or less.

[0020] 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 at a frequency of 10 GHz using the resonance perturbation method. A 10 GHz cavity resonator (Kanto Electronics Application Development Co., Ltd. CP531) is connected to a network analyzer (Agilent Technology "E8363B"), and a film sample (width: 2.0 mm x length: 80 mm) is inserted into the cavity resonator. The film's dielectric loss tangent is measured from the change in resonance frequency before and after insertion for 96 hours in an environment of 25°C and 60% RH.

[0021] <Liquid Crystal Polymer> The film according to the present disclosure comprises a liquid crystal polymer. The liquid crystal polymer may be a thermotropic liquid crystal polymer that exhibits liquid crystallinity in a molten state, or a lyotropic liquid crystal polymer that exhibits liquid crystallinity in a solution state. In the case of a thermotropic liquid crystal, it is preferable that the polymer melts at a temperature of 450°C or less. Examples of the liquid crystal polymer include liquid crystal polyester, liquid crystal polyester amide in which an amide bond is introduced into liquid crystal polyester, liquid crystal polyester ether in which an ether bond is introduced into liquid crystal polyester, and liquid crystal polyester in which a carbonate bond is introduced into liquid crystal polyester. Examples include steric carbonate. Furthermore, from the viewpoints of liquid crystallinity and linear expansion coefficient, the liquid crystal polymer is preferably a polymer having an aromatic ring, and more preferably an aromatic polyester or aromatic polyester amide. Furthermore, the liquid crystal polymer may be a polymer in which an isocyanate-derived bond such as an imide bond, a carbodiimide bond or an isocyanurate bond is further introduced into an aromatic polyester or an aromatic polyester amide. The liquid crystal polymer is preferably a wholly aromatic liquid crystal polymer made using only aromatic compounds as raw material monomers.

[0022] Examples of liquid crystal polymers include the following: 1) A compound obtained by polycondensation of (i) an aromatic hydroxycarboxylic acid, (ii) an aromatic dicarboxylic acid, and (iii) at least one compound selected from the group consisting of an aromatic diol, an aromatic hydroxyamine, and an aromatic diamine. 2) A compound obtained by polycondensation of multiple types of aromatic hydroxycarboxylic acids. 3) (i) A compound obtained by polycondensation of an aromatic dicarboxylic acid and (ii) at least one compound selected from the group consisting of an aromatic diol, an aromatic hydroxyamine, and an aromatic diamine. 4) (i) Polyester such as polyethylene terephthalate and (ii) aromatic hydroxycarboxylic acid are polycondensed. Here, the aromatic hydroxycarboxylic acid, aromatic dicarboxylic acid, aromatic diol, aromatic hydroxyamine and aromatic diamine may each independently be replaced in part or in whole by a polycondensable derivative thereof.

[0023] Examples of polymerizable derivatives of compounds having a carboxy group, such as aromatic hydroxycarboxylic acids and aromatic dicarboxylic acids, include those in which the carboxy group is converted to an alkoxycarbonyl group or an aryloxycarbonyl group (esters), those in which the carboxy group is converted to a haloformyl group (acid halides), and those in which the carboxy group is converted to an acyloxycarbonyl group (acid anhydrides). Examples of polymerizable derivatives of compounds having a hydroxy group, such as aromatic hydroxycarboxylic acids, aromatic diols, and aromatic hydroxyamines, include those obtained by acylation of the hydroxy group to convert it into an acyloxy group (acylated products). Examples of polymerizable derivatives of compounds having an amino group, such as aromatic hydroxyamines and aromatic diamines, include those obtained by acylation of the amino group to convert it into an acylamino group (acylated product).

[0024] From the viewpoints of liquid crystallinity, dielectric loss tangent of the film, and adhesion to a metal substrate, the liquid crystal polymer preferably has a constitutional repeating unit represented by any one of the following formulas (1) to (3) (hereinafter, a constitutional repeating unit represented by formula (1) etc. may be referred to as repeating unit (1) etc.), more preferably has a constitutional repeating unit represented by formula (1) below, and particularly preferably has a constitutional repeating unit represented by formula (1) below, a constitutional repeating unit represented by formula (2) below, and a constitutional repeating unit represented by formula (2) below. Formula (1) -O-Ar 1 -CO- Formula (2) -CO-Ar 2 -CO- Formula (3) -X-Ar 3 -Y- In formulas (1) to (3), Ar 1 represents a phenylene group, a naphthylene group, or a biphenylylene group; Ar 2 and Ar 3 each independently represents a phenylene group, a naphthylene group, a biphenylylene group, or a group represented by the following formula (4), X and Y each independently represent an oxygen atom or an imino group, Ar 1 ~Ar 3 Each hydrogen atom in the group represented by the formula (I) may be independently substituted with a halogen atom, an alkyl group, or an aryl group. Formula (4) -Ar 4 -Z-Ar 5 - In formula (4), Ar 4 and Ar 5 each independently represents a phenylene group or a naphthylene group, and Z represents an oxygen atom, a sulfur atom, a carbonyl group, a sulfonyl group, or an alkylene group.

[0025] The halogen atom includes a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom. Examples of the alkyl group include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, an s-butyl group, a t-butyl group, an n-hexyl group, a 2-ethylhexyl group, an n-octyl group, and an n-decyl group, and the number of carbon atoms thereof is preferably 1 to 10. Examples of the aryl group include a phenyl group, an o-tolyl group, an m-tolyl group, a p-tolyl group, a 1-naphthyl group, and a 2-naphthyl group, and the number of carbon atoms therein is preferably 6 to 20. When the hydrogen atoms are substituted with these groups, the number of the groups is 1 , Ar 2 or Ar 3 The number of the groups represented by the formula (I) is preferably two or less, and more preferably one.

[0026] 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.

[0027] The repeating unit (1) is a constituent repeating unit derived from a specific aromatic hydroxycarboxylic acid. The repeating unit (1) is Ar 1 is a p-phenylene group (constituent repeating unit derived from p-hydroxybenzoic acid), and Ar 1 is preferably a 2,6-naphthylene group (a repeating unit derived from 6-hydroxy-2-naphthoic acid) or a 4,4'-biphenylylene group (a repeating unit derived from 4'-hydroxy-4-biphenylcarboxylic acid).

[0028] The repeating unit (2) is a constituent repeating unit derived from a specific aromatic dicarboxylic acid. The repeating unit (2) is Ar 2 is a p-phenylene group (constituent repeating unit derived from terephthalic acid), Ar 2is an m-phenylene group (a repeating unit derived from isophthalic acid), Ar 2 is a 2,6-naphthylene group (a repeating unit derived from 2,6-naphthalenedicarboxylic acid), or Ar 2 is a diphenylether-4,4'-diyl group (constituent repeating unit derived from diphenylether-4,4'-dicarboxylic acid) is preferred.

[0029] The repeating unit (3) is a constituent repeating unit derived from a specific aromatic diol, aromatic hydroxylamine, or aromatic diamine. The repeating unit (3) is Ar 3 is a p-phenylene group (constituent repeating units derived from hydroquinone, p-aminophenol or p-phenylenediamine), Ar 3 is an m-phenylene group (a repeating unit derived from isophthalic acid), or Ar 3 is a 4,4'-biphenylylene group (constituent repeating units derived from 4,4'-dihydroxybiphenyl, 4-amino-4'-hydroxybiphenyl or 4,4'-diaminobiphenyl).

[0030] The content of the repeating unit (1) is preferably 30 mol% or more, more preferably 30 mol% to 80 mol%, even more preferably 30 mol% to 60 mol%, and particularly preferably 30 mol% to 40 mol% of the total amount of all constituent repeating units (the value obtained by dividing the mass of each constituent repeating unit constituting the liquid crystal polymer by the formula weight of that repeating unit to determine the substance equivalent (mol) of each repeating unit, and then adding these values ​​up). The content of the repeating unit (2) is preferably 35 mol % or less, more preferably 10 mol % to 35 mol %, even more preferably 20 mol % to 35 mol %, and particularly preferably 30 mol % to 35 mol %, based on the total amount of all constituent repeating units. The content of the repeating unit (3) is preferably 35 mol % or less, more preferably 10 mol % to 35 mol %, even more preferably 20 mol % to 35 mol %, and particularly preferably 30 mol % to 35 mol %, based on the total amount of all constituent repeating units. The greater the content of the repeating unit (1), the more likely it is that the heat resistance, strength and rigidity will improve, but if the content is too high, the solubility in solvents will tend to decrease.

[0031] 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.

[0032] 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.

[0033] The liquid crystal polymer preferably has, as the repeating unit (3), a repeating unit in which at least one of X and Y is an imino group, i.e., a repeating unit derived from a specific aromatic hydroxylamine and a repeating unit derived from an aromatic diamine, since this has excellent solubility in a solvent. It is more preferable that the liquid crystal polymer has, as the repeating unit (3), only a repeating unit in which at least one of X and Y is an imino group.

[0034] Among these, from the viewpoints of dispersibility and tensile strength, the liquid crystal polymer preferably contains a liquid crystal polymer having at least one structural unit selected from the group consisting of structural units derived from parahydroxybenzoic acid and structural units derived from 6-hydroxy-2-naphthoic acid, and more preferably contains a liquid crystal polymer having structural units derived from parahydroxybenzoic acid and structural units derived from 6-hydroxy-2-naphthoic acid. Furthermore, from the viewpoints of dispersibility and tensile strength, the liquid crystal polymer preferably comprises a liquid crystal polymer having at least one structural unit selected from the group consisting of structural units derived from 6-hydroxy-2-naphthoic acid, structural units derived from aromatic diol compounds, structural units derived from terephthalic acid, and structural units derived from 2,6-naphthalenedicarboxylic acid, and more preferably comprises a liquid crystal polymer having structural units derived from 6-hydroxy-2-naphthoic acid, structural units derived from aromatic diol compounds, structural units derived from terephthalic acid, and structural units derived from 2,6-naphthalenedicarboxylic acid.

[0035] The liquid crystal polymer is preferably produced by melt-polymerizing raw material monomers corresponding to the constituent repeating units thereof. The melt-polymerization may be carried out in the presence of a catalyst. Examples of the catalyst include metal compounds such as magnesium acetate, stannous acetate, tetrabutyl titanate, lead acetate, sodium acetate, potassium acetate, and antimony trioxide, and nitrogen-containing heterocyclic compounds such as 4-(dimethylamino)pyridine and 1-methylimidazole. Nitrogen-containing heterocyclic compounds are preferably used. The melt-polymerization may be further subjected to solid-state polymerization if necessary.

[0036] The liquid crystal polymer has a flow initiation temperature of preferably 250° C. or higher, more preferably 250° C. or higher and 350° C. or lower, and even more preferably 260° C. or higher and 330° C. or lower. When the flow initiation temperature of the liquid crystal polymer is within the above range, the polymer has excellent solubility, heat resistance, strength, and rigidity, and the viscosity of the solution is appropriate.

[0037] The flow initiation temperature is also called the flow temperature or flow temperature, and is measured using a capillary rheometer at 9.8 MPa (100 kg / cm 2When a liquid crystal polymer is melted and extruded through a nozzle with an inner diameter of 1 mm and a length of 10 mm while heating at a rate of 4°C / min under a load of 1000 kJ / s, the temperature at which the polymer shows a viscosity of 4,800 Pa·s (48,000 poise) is measured. This temperature is an indicator of the molecular weight of liquid crystal polyester (see "Liquid Crystal Polymer - Synthesis, Molding, and Applications," edited by Naoyuki Koide, CMC Corporation, June 5, 1987, p. 95).

[0038] The liquid crystal polymer preferably has a weight-average molecular weight of 1,000,000 or less, more preferably 3,000 to 300,000, even more preferably 5,000 to 100,000, and particularly preferably 5,000 to 30,000. When the weight-average molecular weight of the liquid crystal polymer is within the above range, the film after heat treatment will have excellent thermal conductivity in the thickness direction, heat resistance, strength, and rigidity.

[0039] The liquid crystal polymer is preferably a polymer that is soluble in a specific organic solvent (hereinafter also referred to as a "soluble polymer"). Specifically, the soluble polymer in the present disclosure is a polymer that dissolves in an amount of 0.1 g or more at 25°C in 100 g of at least one solvent selected from the group consisting of N-methylpyrrolidone, N-ethylpyrrolidone, dichloromethane, dichloroethane, chloroform, N,N-dimethylacetamide, γ-butyrolactone, dimethylformamide, ethylene glycol monobutyl ether, and ethylene glycol monoethyl ether.

[0040] The film according to the present disclosure may contain only one type of liquid crystal polymer, or may contain two or more types of liquid crystal polymer. The content of the liquid crystal polymer in the film according to the present disclosure is preferably 20% by mass to 100% by mass, more preferably 30% by mass to 100% by mass, and particularly preferably 40% by mass to 100% by mass, relative to the total mass of the film, from the viewpoints of the dielectric loss tangent of the film and adhesion to the metal substrate.

[0041] <Polyolefin> From the viewpoints of peel strength and peel strength after aging under moist heat, the film according to the present disclosure preferably further contains a polyolefin. The polyolefin is not particularly limited, but is preferably a poly-α-olefin, and more preferably polyethylene or polypropylene.

[0042] When the film contains a polyolefin, from the viewpoints of peel strength and peel strength after aging under wet heat, it is preferable that the polyolefin forms a dispersed phase in the film, and it is more preferable that the film has a sea-island structure in which the polyolefin forms an island structure and the liquid crystal polymer forms a sea structure. The average dispersed diameter of the dispersed phase is preferably 0.01 μm to 20 μm, more preferably 0.01 μm to 10 μm, from the viewpoint of peel strength and peel strength after aging under wet heat. The average dispersed diameter of the dispersed phase is measured by observing the cross section of the film, measuring the maximum diameter of 10 dispersed phases in descending order of size, and averaging the results.

[0043] The film according to the present disclosure may contain one type of polyolefin alone, or two or more types. From the viewpoints of peel strength and peel strength after aging under moist heat, the content of the polyolefin is preferably 0.1% by mass to 40% by mass, and more preferably 1% by mass to 30% by mass, relative to the total mass of the film.

[0044] <Filler> The film according to the present disclosure preferably contains a filler from the viewpoints of dielectric properties, thermal expansion coefficient, and adhesion to a metal substrate. 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 a metal substrate.

[0045] As the inorganic filler, known inorganic fillers can be used. Examples of inorganic filler materials include BN, Al2O3, AlN, TiO2, SiO2, barium titanate, strontium titanate, aluminum hydroxide, calcium carbonate, and materials containing two or more of these. Among these, as the inorganic filler, from the viewpoint of adhesion to the metal substrate, 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 for example, a particle size that is 25%, 30%, or 35% of the thickness of the layer containing the filler may be selected. When the particles or fibers are flat, the length indicates the length in the direction of the short side. From the viewpoint of adhesion to the metal substrate, 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.

[0046] As the organic filler, known organic fillers can be used. Examples of organic filler materials include polyethylene, polystyrene, urea-formalin filler, polyester, cellulose, acrylic resin, fluororesin, hardened epoxy resin, crosslinked benzoguanamine resin, crosslinked acrylic resin, 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 hollow resin particles. Among these, from the viewpoint of adhesion to the metal substrate, 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 substrate, 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.

[0047] The film according to the present disclosure may contain only one type of filler, or may contain two or more types of filler. From the viewpoints of the thermal expansion coefficient and adhesion to the metal substrate, the filler content 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.

[0048] -Other additives- Films according to the present disclosure may also contain other additives. As other additives, known additives can be used, such as leveling agents, antifoaming agents, antioxidants, ultraviolet absorbers, flame retardants, and colorants.

[0049] Furthermore, as other additives, resins other than the above-mentioned components may be contained. Examples of resins other than those mentioned above include thermoplastic resins such as 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 phenolic resins, epoxy resins, polyimide resins, and cyanate resins.

[0050] 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, based on 100 parts by mass of the polymer content.

[0051] <Thermal expansion coefficient> From the viewpoint of thermal stability, the thermal expansion coefficient of the film according to the present disclosure is preferably from -20 ppm / K to 50 ppm / K, more preferably from -10 ppm / K to 40 ppm / K, even more preferably from 0 ppm / K to 35 ppm / K, and particularly preferably from 10 ppm / K to 30 ppm / K.

[0052] The thermal expansion coefficient in the present disclosure is measured by the following method. Using a thermomechanical analyzer (TMA), a 1g tensile load is applied to both ends of a 5mm wide, 20mm long film, and the film is heated from 25°C to 200°C at a rate of 5°C / min, then cooled to 30°C at a rate of 2°C / min, and heated again at a rate of 5°C / min. The thermal expansion coefficient is calculated from the slope of the TMA curve between 30°C and 150°C. Note that the copper foil is removed with ferric chloride before measurement.

[0053] <Elastic modulus> The elastic modulus at 240°C of one surface of the film according to the present disclosure is preferably 100 MPa or more, and more preferably 300 MPa or more, from the viewpoints of mechanical strength and suppression of fracture failure during peeling. Moreover, the elastic modulus at 25° C. of 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, the surface that satisfies the above range of elastic modulus is preferably a surface that satisfies the above range of difference in water contact angle, a surface that satisfies the above range of surface free energy, or a surface that satisfies the above range of surface roughness Ra.

[0054] In the present disclosure, the elastic modulus of the film surface is measured by the following method. The elastic modulus of the film surface is determined using a microsurface hardness tester (Fisherscope H100VP-HCU, manufactured by Fischer Instruments, Inc.). Specifically, a diamond pyramidal indenter (tip-to-face angle: 136°) is used to measure the indentation depth under an appropriate test load at 240°C or 25°C, within a range not exceeding 1 μm, and the storage modulus is calculated from the change in load and displacement when the load is removed.

[0055] The film according to the present disclosure may have a single layer structure or a multilayer structure.

[0056] 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.

[0057] The average thickness of the polymer film is determined by measuring any five points using an adhesive film thickness meter, for example, an electronic micrometer (product name "KG3001A" manufactured by Anritsu Corporation), and averaging these values.

[0058] <Application> The film according to the present disclosure can be used in a variety of applications, and is particularly suitable for use as a film for electronic components such as printed wiring boards, and is even more suitable for use in flexible printed circuit boards. Furthermore, the film according to the present disclosure can be suitably used as a film for bonding metals.

[0059] (Film manufacturing method) The method for producing a film according to the present disclosure includes an oxidation treatment step of oxidizing the surface of a film containing a liquid crystal polymer, and the difference in the contact angle with water measured by the air water drop method at 25°C and 50% RH between the interior of the produced film and one surface of the produced film is 7° or more. The film according to the present disclosure is preferably a film produced by the film production method according to the present disclosure.

[0060] In the film manufacturing method according to the present disclosure, the preferred aspects of the components used, as well as the preferred aspects of the components and contents contained in the resulting film, are the same as the preferred aspects of the 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 manufacturing method according to the present disclosure, the preferable physical property values ​​of the manufactured film are the same as those of the preferable aspects of the film according to the present disclosure described above.

[0061] <Oxidation treatment process> The method for producing a film according to the present disclosure preferably includes an oxidation treatment step of oxidizing the surface of a film containing a liquid crystal polymer. The oxidation treatment step is preferably a step of oxidizing the surface of the film using an oxidizing agent, and more preferably a step of contacting the surface of the film with an oxidizing agent in an aqueous solution to oxidize at least one surface of the film. Also, it is preferable that the process be a step of oxidizing both surfaces of the film containing the liquid crystal polymer. The pH of the aqueous solution is not particularly limited as long as it is oxidizable, but is preferably 8 or higher, more preferably 12 or higher, and even more preferably 13 or higher. There is no upper limit to the pH of the aqueous solution, and it is 14, for example.

[0062] The time for which the surface of the film is brought into contact with the oxidizing agent in the aqueous solution is preferably from 1 minute to 24 hours, more preferably from 3 minutes to 5 hours, and even more preferably from 5 minutes to 3 hours. The temperature of the aqueous solution when the film surface is brought into contact with the oxidizing agent is preferably 1°C to 95°C, more preferably 25°C to 80°C, and even more preferably 45°C to 65°C.

[0063] There are no limitations on the method for bringing the surface of the film into contact with the oxidizing agent in the aqueous solution, and examples thereof include a method in which the film is immersed in an aqueous solution of the oxidizing agent.

[0064] It is preferable that after the surface of the film is brought into contact with the oxidizing agent in the aqueous solution, the resulting film is taken out of the aqueous solution. It is also preferable to wash the obtained film with water, an organic solvent, or the like.

[0065] -Oxidizing agent- In the oxidation treatment step, it is preferable to use an oxidizing agent. The aqueous solution preferably contains an oxidizing agent. chromium compounds such as potassium chromate and potassium dichromate; hypervalent iodine compounds such as potassium periodate and sodium periodate; quinone compounds such as p-benzoquinone, 1,2-naphthoquinone, anthraquinone, and chloranil; amine oxide compounds such as N-methylmorpholine N-oxide; salts of halogen oxoacids such as sodium hypochlorite and sodium chlorite; and a double salt of potassium peroxymonosulfate, potassium hydrogen sulfate, and potassium sulfate (OXONE, manufactured by DuPont). Among these, the oxidizing agent preferably contains a persulfate, and more preferably is a persulfate, from the viewpoints of oxidizing property, dispersibility, and tensile strength. Furthermore, from the viewpoint of oxidizing properties, the oxidizing agent preferably contains at least one compound selected from the group consisting of sodium persulfate, potassium persulfate, ammonium persulfate, hydrogen peroxide, potassium permanganate, sodium hypochlorite, ammonium cerium nitrate, potassium chromate, potassium dichromate, and a double salt of potassium peroxymonosulfate-potassium hydrogen sulfate-potassium sulfate; more preferably contains at least one compound selected from the group consisting of sodium persulfate, potassium persulfate, ammonium persulfate, hydrogen peroxide, sodium hypochlorite, ammonium cerium nitrate, and a double salt of potassium peroxymonosulfate-potassium hydrogen sulfate-potassium sulfate; and particularly preferably contains at least one compound selected from the group consisting of sodium persulfate, potassium persulfate, and ammonium persulfate.

[0066] In addition, a catalyst may be used in addition to the oxidizing agent to assist the action of the oxidizing agent. Examples of the catalyst include divalent iron compounds (such as FeSO4) and trivalent iron compounds. The oxidizing agent and the catalyst may each be a hydrate.

[0067] From the viewpoint of oxidizing property, the standard oxidation-reduction potential of the oxidizing agent is preferably 0.30 V or more, more preferably 1.50 V or more, and even more preferably 1.70 V or more. There is no particular upper limit to the standard oxidation-reduction potential of the oxidizing agent, and it is, for example, preferably 4.00 V or less, and more preferably 2.50 V or less. The above standard oxidation-reduction potentials are based on the standard hydrogen electrode.

[0068] The content of the oxidizing agent in the aqueous solution is preferably 0.05 to 20 parts by mass, more preferably 0.1 to 20 parts by mass, and particularly preferably 1 to 20 parts by mass, per 100 parts by mass of water in the aqueous solution. The oxidizing agent may be used alone or in combination of two or more. When the aqueous solution contains a catalyst, the content of the oxidizing agent is preferably 0.005 to 20 parts by mass, more preferably 0.01 to 10 parts by mass, and even more preferably 0.1 to 2 parts by mass, per 100 parts by mass of water in the aqueous solution. The catalyst may be used alone or in combination of two or more.

[0069] -Alkaline compounds- The aqueous solution preferably contains an alkaline compound in addition to the above components in order to adjust the pH of the aqueous solution. Examples of the alkaline compound include inorganic bases such as alkali metal hydroxides (e.g., sodium hydroxide) and alkaline earth metal hydroxides, as well as organic bases. Among these, alkali metal hydroxides are preferred. The content of the alkaline compound in the aqueous solution may be adjusted appropriately so that the pH of the aqueous solution can be adjusted to the desired temperature. For example, it is preferably 0.1 to 10 parts by mass per 100 parts by mass of water in the aqueous solution.

[0070] <Formation process> The method for producing a film according to the present disclosure preferably includes a forming step of applying a composition containing a liquid crystal polymer and a solvent onto a substrate and drying the composition to form a film. The method for forming the film is not particularly limited, and known methods can be used. For example, a casting method, a coating method, an extrusion method, etc. are preferred, and among these, the casting method is particularly preferred. When the film has a multilayer structure, for example, a co-casting method, a multilayer coating method, a co-extrusion method, etc. are preferred. Among these, the co-casting method is particularly preferred for forming a relatively thin film, and the co-extrusion method is particularly preferred for forming a thick film. When a multilayer structure in a film is produced by a co-casting method or a multi-layer coating method, it is preferable to carry out the co-casting method or the multi-layer coating method using a layer A-forming composition, a layer B-forming composition, etc., in which the components of each layer, such as a liquid crystal polymer, are dissolved or dispersed in a solvent.

[0071] Examples of the solvent include halogenated hydrocarbons such as dichloromethane, chloroform, 1,1-dichloroethane, 1,2-dichloroethane, 1,1,2,2-tetrachloroethane, 1-chlorobutane, chlorobenzene, and o-dichlorobenzene; halogenated phenols such as p-chlorophenol, pentachlorophenol, and pentafluorophenol; ethers such as diethyl ether, tetrahydrofuran, and 1,4-dioxane; ketones such as acetone and cyclohexanone; esters such as ethyl acetate and γ-butyrolactone; and ethylene carbonate. nitriles such as acetonitrile and succinonitrile; amides such as N,N-dimethylformamide, N,N-dimethylacetamide, and N-methylpyrrolidone, and urea compounds such as tetramethylurea; nitro compounds such as nitromethane and nitrobenzene; sulfur compounds such as dimethyl sulfoxide and sulfolane; and phosphorus compounds such as hexamethylphosphoramide and tri-n-butylphosphate, and two or more of these may be used.

[0072] As the solvent, a solvent mainly composed of an aprotic compound, particularly an aprotic compound having no halogen atoms, is preferred because it is less corrosive and easier to handle, and the proportion of the aprotic compound in the entire solvent is preferably 50% by mass to 100% by mass, more preferably 70% by mass to 100% by mass, and particularly preferably 90% by mass to 100% by mass. Furthermore, as the aprotic compound, an amide such as N,N-dimethylformamide, N,N-dimethylacetamide, tetramethylurea, N-methylpyrrolidone, or an ester such as γ-butyrolactone is preferably used because it easily dissolves the liquid crystal polymer, and N,N-dimethylformamide, N,N-dimethylacetamide, and N-methylpyrrolidone are more preferred.

[0073] Furthermore, as the solvent, a solvent containing a compound having a dipole moment of 3 to 5 as a main component is preferred because it easily dissolves the liquid crystal polymer, and the proportion of the compound having a dipole moment of 3 to 5 in the entire solvent is preferably 50% by mass to 100% by mass, more preferably 70% by mass to 100% by mass, and particularly preferably 90% by mass to 100% by mass. As the aprotic compound, a compound having a dipole moment of 3 to 5 is preferably used.

[0074] Furthermore, as the solvent, a solvent containing as its main component a compound having a boiling point of 220°C or less at 1 atmosphere is preferred because it is easy to remove, and the proportion of the compound having a boiling point of 220°C or less at 1 atmosphere in the entire solvent is preferably 50% by mass to 100% by mass, more preferably 70% by mass to 100% by mass, and particularly preferably 90% by mass to 100% by mass. As the aprotic compound, it is preferable to use a compound having a boiling point of 220° C. or lower at 1 atmospheric pressure.

[0075] Furthermore, a support may be used when the film is produced by the casting method, co-casting method, coating method, multilayer coating method, extrusion method, co-extrusion method, etc. Furthermore, when a metal layer (metal foil) or the like used in the laminate described below is used as a support, it may be used as is without peeling. Examples of the support include a metal drum, a metal band, a glass plate, a resin film, and a metal foil, among which a metal drum, a metal band, and a resin film are preferred. Examples of resin films include polyimide (PI) films, and examples of commercially available products include U-Pirex S and U-Pirex R manufactured by Ube Industries, Ltd., Kapton manufactured by DuPont-Toray Co., Ltd., and IF30, IF70, and LV300 manufactured by SKC Kolon PI. The support may have a surface treatment layer formed on its surface to facilitate peeling, which may be made of hard chrome plating, fluororesin, or the like. The average thickness of the resin film support is not particularly limited, but is preferably 25 μm or more and 75 μm or less, and more preferably 50 μm or more and 75 μm or less.

[0076] The method for removing at least a part of the solvent from the cast or coated film-like composition (cast film or coating film) is not particularly limited, and any known drying method can be used.

[0077] <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 oxidation treatment step. In the film manufacturing method according to the present disclosure, stretching can be appropriately combined to control the molecular orientation of the resulting film and adjust the linear expansion coefficient and mechanical properties. The stretching method is not particularly limited, and known methods can be used. It may be performed in a solvent-containing state or in a dry film state. Stretching in a solvent-containing state may be performed by gripping the film and stretching it, or by utilizing the self-shrinkage force of the web due to drying without stretching, or a combination thereof. Stretching is particularly effective for improving breaking elongation and breaking strength when the film brittleness has been reduced by adding an inorganic filler or the like.

[0078] <Heating process> The method for producing a film according to the present disclosure may include a heating step of heating the film. The heating step may be performed before or after the oxidation treatment step. It is believed that the heating step promotes crystallization of the liquid crystal polymer in the film, thereby lowering the dielectric loss tangent of the film. In the film manufacturing method according to the present disclosure, the dissolved oxygen content at the start of heating the film is preferably 500 ppm or less, more preferably 300 ppm or less. When the dissolved oxygen content is within this range, a film with a lower dielectric loss tangent can be obtained. The above-mentioned "start of heating" refers to the time when heat application to the film begins.

[0079] In the present disclosure, the amount of dissolved oxygen is measured using a dissolved oxygen meter, for example, the portable oxygen analyzer "ORBISPHERE 3650" manufactured by Hack Ultra.

[0080] 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 appropriately changed depending on the type of polymer, and can also be lowered or shortened by other means such as adding a catalyst.

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

[0082] <Winding process> The film manufacturing method 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.

[0083] <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. Furthermore, it is preferable that the peel force when unwinding the film in the unwinding step is 1.0 kN / m or less.

[0084] <Peeling process> The film manufacturing method according to the present disclosure preferably includes a peeling step of peeling the film from the substrate after the forming step or after the heating step and before the oxidation treatment 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 that can be used for other applications.

[0085] <Other processes> The film manufacturing method according to the present disclosure may include other steps in addition to those described above. Other steps may include known steps.

[0086] (Laminated film) The laminated film according to the present disclosure has a layer A and a layer B on at least one surface of the layer A, and the layer A is the film according to the present disclosure.

[0087] The elastic modulus of Layer B at 140°C is preferably 0.1 MPa or less, and more preferably 0.08 MPa or less, from the viewpoint of improving wiring conformability and further suppressing wiring distortion. The lower limit of the elastic modulus is not particularly limited, and is, for example, 0.0001 MPa.

[0088] Layer B preferably comprises a polymer. Examples of the polymer contained in Layer B include thermoplastic polymers such as liquid crystal polymers, fluorine-based polymers, polymers of compounds having a cyclic aliphatic hydrocarbon group and a group having an ethylenically unsaturated bond, polyether ether ketone, polyolefin, polyamide, polyester, polyphenylene sulfide, 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 polymers such as phenol resins, epoxy resins, polyimide resins, and cyanate resins.

[0089] Among these, from the viewpoint of dielectric loss tangent, it is preferable that Layer B contains a thermoplastic polymer. Furthermore, the thermoplastic polymer is preferably a liquid crystal polymer. In the present disclosure, a thermoplastic polymer refers to a polymer that softens when heated to its melting point.

[0090] Layer B preferably has a dielectric loss tangent of 0.006 or less, more preferably greater than 0 and 0.003 or less.

[0091] The polymer content is preferably 10% by mass or more, and more preferably 50% by mass or more, based on the total mass of Layer B. There is no particular upper limit to the polymer content, and it may be 100% by mass.

[0092] The average thickness of Layer B is not particularly limited, but is preferably 0.1 μm to 10 μm, and more preferably 1 μm to 5 μm.

[0093] 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.

[0094] 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 the preferred embodiments of the other additives described above.

[0095] (Laminate) The laminate according to the present disclosure may be any laminate in which the film according to the present disclosure is laminated, but is preferably a laminate having a metal substrate on one surface of the film according to the present disclosure or on the surface on the Layer B side of the laminate film according to the present disclosure, and more preferably a laminate having a resin layer containing a compound having a functional group and a metal substrate on one surface of the film according to the present disclosure or on either surface of the laminate film according to the present disclosure, wherein the functional group contains one or more 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. Furthermore, it is preferable that the surface of the film on which the metal substrate is placed 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.

[0096] The surface roughness Rz of the film-side surface of the metal substrate is preferably 2.0 μm or less, more preferably 1.0 μm or less, and particularly preferably 0.5 μm or less. Within this range, the surface resistance at the interface between the film and the metal substrate is reduced.

[0097] In this disclosure, "surface roughness Rz" means the sum of the maximum peak height and the maximum valley depth observed on a roughness curve over a reference length, expressed in nanometers. In the present disclosure, the surface roughness Rz of the film-side surface of the metal substrate is measured by the following method. Using the non-contact surface / layer cross-sectional shape measurement system VertScan (manufactured by Ryoka Systems Co., Ltd.), an area 465.48 μm long and 620.64 μm wide is measured to create a roughness curve and the average line of the roughness curve for the surface of the object to be measured (liquid crystal polymer film). A section corresponding to the reference length is extracted from the roughness curve. The surface roughness Rz of the object to be measured is calculated 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.

[0098] The metal substrate preferably has a metal layer or metal wiring on the surface, and more preferably has a copper layer or copper wiring on the surface. The metal substrate, metal layer, and metal wiring are not particularly limited and may be any known metal substrate, metal layer, and metal wiring. The metal layer and metal wiring are preferably, for example, a silver layer, silver wiring, or a copper layer or copper wiring, and more preferably a copper layer or copper wiring. The metal substrate preferably has metal wiring. Furthermore, the metal in the metal layer and metal wiring is preferably silver or copper, and more preferably copper.

[0099] The method for attaching the film according to the present disclosure to the metal substrate is not particularly limited, and any known lamination method can be used.

[0100] 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.

[0101] In the present disclosure, the peel strength between a film and a metal layer (for example, a copper layer) is measured by the following method. A 1.0 cm wide peel test piece is prepared from the laminate of film and metal layer, and the film is fixed to a flat plate with double-sided adhesive tape. The strength (kN / m) is measured when the film is peeled from the metal layer at a rate of 50 mm / min using the 90° method in accordance with JIS C 5016 (1994).

[0102] The metal layer is preferably a silver layer or a copper layer, more preferably a copper layer. The copper layer is preferably a rolled copper foil formed by a rolling method or an electrolytic copper foil formed by an electrolytic method, and more preferably a rolled copper foil from the viewpoint of flex resistance.

[0103] The average thickness of the metal substrate is not particularly limited, but is preferably 2 μm to 20 μm, more preferably 3 μm to 18 μm, and even more preferably 5 μm to 12 μm. The metal substrate may be a carrier-attached metal foil formed on a support (carrier) in a peelable manner. Any known carrier can be used, and a resin film or the like can be suitably 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.

[0104] The laminate according to the present disclosure preferably includes the film according to the present disclosure or the laminate film according to the present disclosure, a resin layer, and a metal substrate. The resin layer contains a polymer, and a suitable example of the polymer is a thermoplastic resin. Examples of thermoplastic resins include (meth)acrylic resins, polyvinyl cinnamate, polycarbonate, polyimide, polyamideimide, polyesterimide, polyetherimide, polyetherketone, polyetheretherketone, polyethersulfone, polysulfone, polyparaxylene, polyester, polyvinyl acetal, polyvinyl chloride, polyvinyl acetate, polyamide, polystyrene, polyurethane, polyvinyl alcohol, cellulose acylate, fluorinated resins, liquid crystal polymers, syndiotactic polystyrene, silicone resins, epoxysilicone resins, phenolic resins, alkyd resins, epoxy resins, maleic acid resins, melamine resins, urea resins, aromatic sulfonamides, benzoguanamine resins, silicone elastomers, aliphatic polyolefins (e.g., polyethylene, polypropylene), and cyclic olefin copolymers. Among these, from the viewpoint of further exerting the effects of the present disclosure, at least one resin selected from the group consisting of polyimide, liquid crystal polymer, syndiotactic polystyrene, and cyclic olefin copolymers is preferred, and polyimide is more preferred.

[0105] The content of the resin is preferably 60% by mass to 99.9% by mass, more preferably 70% by mass to 99.0% by mass, and even more preferably 80% by mass to 97.0% by mass, based on the total mass of the resin layer.

[0106] The materials other than the polymer that constitute the resin layer are not particularly limited, and may be either organic or inorganic, or a combination of organic and inorganic materials. From the viewpoint of adhesion to the metal substrate, the resin layer is preferably an adhesive layer, and more preferably an adhesive layer containing an adhesive.

[0107] In the present disclosure, the type of adhesive is not particularly limited, and any known adhesive can be used. As the adhesive, a thermosetting resin is preferably used as the polymer. Examples of thermosetting resins include epoxy resins, phenolic resins, unsaturated imide resins, cyanate resins, isocyanate resins, benzoxazine resins, oxetane resins, amino resins, unsaturated polyester resins, allyl resins, dicyclopentadiene resins, silicone resins, triazine resins, and melamine resins. 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. Furthermore, as the adhesive, a commercially available adhesive containing a thermosetting resin can also be used.

[0108] From the viewpoint of adhesion to the metal substrate, the resin layer preferably contains a compound having a reactive group. The reactive group is preferably a group capable of reacting with groups that may be present on the surface of the polymer film (particularly groups having an oxygen atom such as a carboxy group and a hydroxy group). From the viewpoint of further exerting the effects of the present disclosure, the reactive group is preferably at least one 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, more preferably at least one group selected from the group consisting of an epoxy group, an acid anhydride group, and a carbodiimide group, and even more preferably an epoxy group.

[0109] Specific examples of the reactive compound having an epoxy group include aromatic glycidylamine compounds (e.g., N,N-diglycidyl-4-glycidyloxyaniline, 4,4'-methylenebis(N,N-diglycidylaniline), N,N-diglycidyl-o-toluidine, N,N,N',N'-tetraglycidyl-m-xylylenediamine, 4-t-butylphenyl glycidyl ether), aliphatic glycidylamine compounds (e.g., 1,3-bis(diglycidylaminomethyl)cyclohexane, etc.), and aliphatic glycidyl ether compounds (e.g., sorbitol polyglycidyl ether). Among these, aromatic glycidylamine compounds are preferred from the viewpoint of further exerting the effects of the present disclosure.

[0110] Specific examples of reactive compounds having an acid anhydride group include tetracarboxylic acid dianhydrides (e.g., 3,3',4,4'-benzophenonetetracarboxylic acid dianhydride, 3,3',4,4'-biphenyltetracarboxylic acid dianhydride, pyromellitic acid dianhydride, 2,3,3',4'-biphenyltetracarboxylic acid dianhydride, oxydiphthalic acid dianhydride, diphenylsulfone-3,4,3',4'-tetracarboxylic acid dianhydride, bis(3,4-dicarboxyphenyl)sulfide dianhydride, 2,2-bis(3,4-dicarboxyphenyl)-1,1,1,3,3,3-hexafluoropropane dianhydride, 2,3,3',4'-benzophenonetetracarboxylic acid dianhydride, bis(3,4-dicarboxyphenyl)methane dianhydride, 2,2-bis(3,4-dicarboxyphenyl)propane dianhydride, p p-phenylenebis(trimellitic acid monoester acid anhydride), p-biphenylenebis(trimellitic acid monoester acid anhydride), m-terphenyl-3,4,3',4'-tetracarboxylic acid dianhydride, p-terphenyl-3,4,3',4'-tetracarboxylic acid dianhydride, 1,3-bis(3,4-dicarboxyphenoxy)benzene dianhydride, 1,4-bis(3,4-dicarboxyphenoxy)benzene dianhydride, 1,4-bis(3,4-dicarboxyphenoxy)biphenyl dianhydride, 2,2-bis[(3,4-dicarboxyphenoxy)phenyl]propane dianhydride, 2,3,6,7-naphthalenetetracarboxylic acid dianhydride, 1,4,5,8-naphthalenetetracarboxylic acid dianhydride, 4,4'-(2,2-hexafluoroisopropylidene)diphthalic dianhydride).

[0111] Specific examples of reactive compounds having a carbodiimide group include monocarbodiimide compounds (e.g., dicyclohexylcarbodiimide, diisopropylcarbodiimide, dimethylcarbodiimide, diisobutylcarbodiimide, dioctylcarbodiimide, t-butylisopropylcarbodiimide, diphenylcarbodiimide, di-t-butylcarbodiimide, di-β-naphthylcarbodiimide, and N,N'-di-2,6-diisopropylphenylcarbodiimide), and polycarbodiimide compounds (e.g., compounds produced by the methods described in U.S. Pat. No. 2,941,956, Japanese Patent Publication No. 47-33279, J. Org. Chem., Vol. 28, pp. 2069-2075 (1963), and Chemical Review, 1981, Vol. 81, No. 4, pp. 619-621, etc.). Commercially available reactive compounds having a carbodiimide group include Carbodilite HMV-8CA, LA-1, and V-03 (manufactured by Nisshinbo Chemical Inc.), Stabaxol P, P100, and P400 (manufactured by Rhein Chemie), and Stabilizer 9000 (manufactured by Rashihi Chemie).

[0112] The number of reactive groups that the reactive compound has is one or more, but is preferably three or more in terms of better adhesion to the metal layer. The number of reactive groups possessed by the reactive compound is preferably 6 or less, more preferably 5 or less, and even more preferably 4 or less, in order to obtain a laminate having a lower dielectric loss tangent in the portions other than the metal layer.

[0113] The resin layer may contain only one type of reactive compound, or may contain two or more types of reactive compounds. The content of the reactive compound is preferably 0.1% by mass to 40% by mass, more preferably 1% by mass to 30% by mass, and even more preferably 3% by mass to 20% by mass, relative to the total mass of the resin layer. If the content is equal to or greater than the lower limit, the adhesion of the metal layer is superior, and if the content is equal to or less than the upper limit, a laminate having a lower dielectric loss tangent in the portion other than the metal layer can be obtained.

[0114] The resin layer may contain additives other than the adhesive. As the other additives, known additives can be used, such as leveling agents, antifoaming agents, antioxidants, ultraviolet absorbers, flame retardants, colorants, and fillers.

[0115] The thickness of the resin layer is 1 μm or less, and is preferably 0.8 μm or less, more preferably 0.7 μm or less, and even more preferably 0.6 μm or less, in order to form a laminate with a lower dielectric loss tangent in the portions other than the metal layer. The thickness of the resin layer is preferably 0.05 μm or more, more preferably 0.1 μm or more, and even more preferably 0.2 μm or more, in terms of better adhesion to the metal layer. The thickness of the resin layer is measured based on a cross-sectional image of the film with the resin layer taken with a scanning electron microscope (SEM), and is the arithmetic mean value of the thickness of the resin layer measured at 100 randomly selected different points.

[0116] -Elastic modulus- The elastic modulus of the resin layer at 25° C. after curing is 0.8 GPa or more, and from the viewpoint of better adhesion to the metal layer, it is preferably 1.0 GPa or more, more preferably 1.1 GPa or more, and even more preferably 1.2 GPa or more. The upper limit of the elastic modulus of the resin layer after curing is not particularly limited, and is, for example, 5 GPa or less.

[0117] -Dielectric loss tangent- The dielectric loss tangent of the resin layer after curing is preferably 0.01 or less, more preferably 0.008 or less, and even more preferably 0.005 or less, from the viewpoint of forming a laminate in which the dielectric loss tangent of the portion other than the metal layer is lower. The lower limit is not particularly limited, and may be 0.0001 or more.

[0118] It is also preferable to process the metal layer in the laminate according to the present disclosure into a desired circuit pattern by, for example, etching to form a flexible printed circuit board. The etching method is not particularly limited, and known etching methods can be used.

[0119] The method for producing a laminate according to the present disclosure preferably includes a resin layer forming step of providing a resin layer on at least one surface of the film, and a lamination step of laminating the resin layer and a metal substrate. The method for forming the resin layer is not particularly limited, and known coating methods and known adhesive application methods can be used. In the lamination step, it is preferable to attach metal wiring. The lamination method in the lamination step is not particularly limited, and any known lamination method can be used. The lamination pressure in the lamination step is not particularly limited, but is preferably 0.1 MPa or more, and more preferably 0.2 MPa to 10 MPa. The lamination temperature in the lamination step can be appropriately selected depending on the film to be used, etc., but is preferably 150°C or higher, and more preferably 170°C or higher and 250°C or lower. Furthermore, in order to harden and bond the resin layer, the method for producing a laminate according to the present disclosure preferably includes a step of cooling the laminate, for example, when a hot melt adhesive is used as the resin layer. [Example]

[0120] The present disclosure will be described in more detail below with reference to examples. The materials, amounts used, ratios, processing details, processing procedures, etc. shown in the following examples can be appropriately changed without departing from the spirit of the present disclosure. Therefore, the scope of the present disclosure is not limited to the specific examples shown below. Unless otherwise specified, "parts" and "%" are by mass.

[0121] LCP film A (LCP-A): "Vecstar CTQ-25" manufactured by Kuraray Co., Ltd., 25 μm thick, polymer film containing liquid crystal polymer

[0122] LCP film B (LCP-B): A film in which polyolefin forms a dispersed phase, produced by the method described below.

[0123] <Ingredients used> Liquid crystal polymer B: A polymer synthesized based on Example 1 of JP 2019-116586 A. It is a thermotropic liquid crystal polymer with a melting point of 320°C. LCP-B is composed of repeating units derived from 6-hydroxy-2-naphthoic acid, 4,4'-dihydroxybiphenyl, terephthalic acid, and 2,6-naphthalenedicarboxylic acid. Polyolefin: Novatec LD (low-density polyethylene) manufactured by Japan Polyethylene Co., Ltd. Compatible component: Ethylene / glycidyl methacrylate copolymer Heat stabilizer: ADEKA Corporation "AO-80" (semi-hindered phenol stabilizer)

[0124] <Supply process> The liquid crystal polymer B, polyolefin, compatible component, and heat stabilizer were mixed in the following proportions, and the mixture was kneaded and pelletized using an extruder. Liquid crystal polymer B: 84.5% Polyolefin: 12.4% ·Compatible components: 2.5% Heat stabilizer: 0.6% The pellets obtained by kneading and pelletizing were dried for 12 hours at 80°C using a dehumidifying hot air dryer with a dew point temperature of -45°C to reduce the moisture content to 200 ppm or less. The pellets dried in this manner are also referred to as raw material A.

[0125] <Film forming process> Raw material A was fed into the cylinder of a twin-screw extruder with a screw diameter of 50 mm from the same feed port, heated and kneaded, and then extruded from a die with a die width of 750 mm onto a rotating cast roll in the form of a film, which was then cooled and solidified.The film was then stretched as desired to obtain a film with a thickness of 150 μm. The temperature of the heat kneading, the discharge speed when discharging raw material A, the clearance of the die lip, and the peripheral speed of the cast roll were adjusted within the following ranges. Heating and kneading temperature: 270℃~350℃ Clearance: 0.01mm~5mm ·Discharge speed: 0.1mm / sec~1,000mm / sec Cast roll peripheral speed: 0.1m / min to 100m / min

[0126] <Horizontal stretching process> The film produced in the film-forming process was stretched in the TD direction (the width direction of the film) using a tenter at a stretching ratio of 3.2.

[0127] <Post-heat treatment> Both ends of the film in the width direction after the transverse stretching step were held with jigs to fix the film so that it would not shrink in the width direction. The film in this fixed state was subjected to a post-heating treatment using an infrared heater or a hot air dryer. In the post-heating treatment using infrared heaters, both sides of the film were heated using one pair of infrared heaters at a film surface temperature of 300° C. for 30 seconds. In the post-heating treatment using a hot air dryer, the film held in place with a jig was placed in the hot air dryer and heated for 180 seconds at a film surface temperature of 300°C. After that, the film was removed from the hot air dryer to obtain LCP film B (55 μm). In the heat treatment process, a film for measuring the film surface temperature was placed near the film to be heat treated, and the film surface temperature was measured using a thermocouple attached to the surface of the film surface temperature measurement film with polyimide tape.

[0128] Example 1 Sodium persulfate solution (2.4 g sodium persulfate / 25 mL water) was added to NaOH solution (10 g NaOH / 100 mL water), and the solution was heated to 50°C. LCP film A (3 cm x 8 cm) was immersed in the solution for 20 minutes. After 20 minutes, the LCP film was removed, washed with 100 mL of water, and then dried at room temperature (25°C, hereinafter the same) to obtain surface-modified LCP film 1 (LCP-F1).

[0129] Example 2 Sodium persulfate solution (2.4 g sodium persulfate / 25 mL water) and iron sulfate heptahydrate (0.28 g) were added to NaOH solution (10 g NaOH / 100 mL water), and the solution was heated to 50°C. LCP film A (3 cm x 8 cm) was immersed in the solution for 20 minutes. After 20 minutes, the LCP film was removed, washed with 100 mL of water, and dried at room temperature to obtain surface-modified LCP film 2 (LCP-F2).

[0130] Example 3 Sodium hypochlorite solution (2.4 g sodium hypochlorite pentahydrate / 25 mL water) was added to 100 mL of water, and the mixture was heated to 50°C. LCP film A (3 cm x 8 cm) was immersed in the solution for 20 minutes. After 20 minutes, the LCP film was removed, washed with 100 mL of water, and dried at room temperature to obtain surface-modified LCP film 3 (LCP-F3).

[0131] Example 4 After adding cerium ammonium nitrate water (cerium ammonium nitrate: 2.4 g / water: 25 mL) to NaOH water (NaOH: 10 g / water: 100 mL), the NaOH water was heated to 50°C and LCP film A (3 cm × 8 cm) was immersed in the solution for 20 minutes. After 20 minutes, the LCP film was removed, washed with 100 mL of water, and dried at room temperature to obtain surface-modified LCP film 4 (LCP-F4).

[0132] Example 5 Surface-modified LCP film 5 (LCP-F5) was obtained in the same manner as in Example 1, except that the sodium persulfate water having a composition of "sodium persulfate: 2.4 g / water: 25 mL" in Example 1 was changed to sodium persulfate water having a composition of "sodium persulfate: 12 g / water: 25 mL."

[0133] Example 6 Surface-modified LCP film 6 (LCP-F6) was obtained using the same manufacturing method as in Example 1, except that the NaOH water in Example 1 with a composition of "NaOH: 10 g / water: 100 mL" was changed to NaOH water with a composition of "NaOH: 0.5 g / water: 100 mL".

[0134] Example 7 Surface-modified LCP film 7 (LCP-F7) was obtained using the same manufacturing method as in Example 1, except that the sodium persulfate water having a composition of "sodium persulfate: 2.4 g / water: 25 mL" in Example 1 was changed to potassium iodate water having a composition of "potassium iodate: 2.4 g / water: 25 mL."

[0135] Example 8 Surface-modified LCP film 8 (LCP-F8) was obtained using the same manufacturing method as in Example 1, except that the NaOH water in Example 1 was changed to a NaOH water mixture of "NaOH: 10 g / water: 100 mL" with "NaOH: 0.005 g / water: 100 mL."

[0136] Example 9 Surface-modified LCP film 9 (LCP-F9) was obtained using the same manufacturing method as in Example 1, except that the sodium persulfate water having a composition of "sodium persulfate: 2.4 g / water: 25 mL" in Example 1 was changed to potassium persulfate water having a composition of "potassium persulfate: 2.4 g / water: 25 mL."

[0137] Example 10 A surface-modified LCP film 10 (LCP-F10) was obtained using the same manufacturing method as in Example 1, except that the sodium persulfate water having a composition of "sodium persulfate: 2.4 g / water: 25 mL" in Example 1 was changed to ammonium persulfate water having a composition of "ammonium persulfate: 2.4 g / water: 25 mL."

[0138] Example 11 A surface-modified LCP film 11 (LCP-F11) was obtained in the same manner as in Example 1, except that LCP film A in Example 1 was changed to LCP film B.

[0139] Example 12 After adding sodium persulfate water (2.4 g sodium persulfate / 25 mL water) to NaOH water (10 g NaOH / 100 mL water), LCP film A (3 cm x 8 cm) was floated in the solution heated to 50°C for 20 minutes so that only one side of the film was in contact with the treatment solution. After 20 minutes, the LCP film was removed, washed with 100 mL of water, and dried at room temperature to obtain surface-modified LCP film 12 (LCP-F12), which had only one side surface modified.

[0140] (Comparative Example 3) LCP film A (3 cm × 8 cm) was immersed for 20 minutes in a solution of NaOH water (10 g NaOH / 100 mL water) heated to 50°C. After 20 minutes, the LCP film was removed, washed with 100 mL of water, and dried at room temperature to obtain surface-modified LCP film 13 (LCP-F13).

[0141] <Method for measuring water contact angle on film surface> The contact angles of LCP films (LCP-F1 to 13, and LCP-A and B) with water were measured at 25°C and 50% RH (the treated surface of LCP-12 was measured). A contact angle meter (DM700) manufactured by Kyowa Interface Science Co., Ltd. was used for the measurements. The contact angle was read 5 seconds after the droplet was created and calculated as a 10-point average. The values ​​measured by the above method are defined as the water contact angles of the film surfaces of the LCP films (LCP-F1 to 13, and LCP-A and B).

[0142] <Method for measuring surface free energy> The contact angle of the film surface with diiodomethane was measured using the same method as in the method for measuring the water contact angle of the film surface, and the surface free energy was calculated based on Owens' equation.

[0143] <Method for measuring water contact angle inside film> The LCP films (LCP-F1 to 13, and LCP-A and B) were heated above their melting points to melt them, and then remolded into films. Because they had been heated above their melting points once, it is believed that the original surface and interior were completely mixed together. The water contact angles of the LCP films thus obtained were measured in the same manner as above, and are defined as the water contact angles of the interior of the LCP films (LCP-F1 to 13, and LCP-A and B).

[0144] The water contact angle on the particle surface of the LCP films (LCP-A and B) before the surface modification treatment was consistent with the water contact angle inside the film. Furthermore, the water contact angles inside the LCP films (LCP-F1 to 13) were consistent with the water contact angles on the film surface and inside the LCP films (LCP-A and B) before the surface modification treatment.

[0145] <Peel strength> -Laminate manufacturing method- 17.7 g of polyimide resin solution ("PIAD-200" manufactured by Arakawa Chemical Industries, Ltd., solid content 30% by mass, solvent: cyclohexane, methylcyclohexane, and ethylene glycol dimethyl ether), 0.27 g of N,N-diglycidyl-4-glycidyloxyaniline (manufactured by Sigma-Aldrich Co.), and 1.97 g of toluene were mixed and stirred to obtain adhesive varnish 1 (adhesive layer-forming composition) with a solid content concentration of 28% by mass. The resulting adhesive varnish 1 was applied to one side of an LCP film (the treated side for LCP-12) using an applicator. The applied film was dried at 85°C for 1 hour to form an adhesive layer (resin layer) with a thickness of 0.8 μm, producing an LCP film with an adhesive layer.

[0146] An LCP film with an adhesive layer and unroughened copper foil ("CF-T9DA-SV-18" manufactured by Fukuda Metal Foil and Powder Co., Ltd., thickness 18 μm) were laminated together so that the adhesive layer of the film with an adhesive layer and the unroughened surface of the unroughened copper foil (maximum height Rz 0.85 μm) were in contact with each other, and then the laminate was pressed together for 1 hour using a heat press (manufactured by Toyo Seiki Seisakusho, Ltd.) at 200°C and 4 MPa to produce a laminate consisting of an LCP film, a resin layer (cured film of the adhesive layer), and a metal layer (copper foil) laminated in this order.

[0147] -Initial peel strength test measurement- Each laminate was cut into a 1 cm x 5 cm strip to prepare a sample. The peel strength (unit: N / cm) of the obtained sample was measured according to the method for measuring peel strength under normal conditions described in JIS C 6481. In the peel strength test, the metal layer was peeled from the sample at an angle of 90° to the sample at a peel rate of 50 mm / min. The evaluation criteria are shown below. A: Peel strength is 4N / cm or more B: Peel strength is 3N / cm or more and less than 4N / cm C: Peel strength is 2N / cm or more and less than 3N / cm D: Peel strength is less than 2N / cm

[0148] -Peel strength measurement after aging under heat and humidity- Each laminate was left in an atmosphere of 85°C and 85% RH for 500 hours, and then the same peel strength test as above was carried out. The evaluation criteria are as follows: A: Peel strength is 4N / cm or more B: Peel strength is 3N / cm or more and less than 4N / cm C: Peel strength is 2N / cm or more and less than 3N / cm D: Peel strength is less than 2N / cm

[0149] [Table 1]

[0150] The internal contact angle of each of the films of Examples 1 to 10 and 12 was 84°, and the internal contact angle of the film of Example 11 was 85°. Moreover, in each of the films of Examples 1 to 12, the modulus of elasticity at 240° C. on one surface was 300 MPa or more.

[0151] As shown in Table 1, the films of Examples 1 to 12 were superior to the films of Comparative Examples 1 to 3 in peel strength to the metal substrate via the adhesive layer.

[0152] (Examples 101 to 112) 17.7 g of polyimide resin solution (the above-mentioned "PIAD-200"), 0.27 g of 3,3',4,4'-benzophenonetetracarboxylic dianhydride (manufactured by Tokyo Chemical Industry Co., Ltd.), and 1.97 g of toluene were mixed and stirred to obtain adhesive varnish 2 (adhesive layer-forming composition) with a solids concentration of 28 mass%. In Examples 1 to 12, even when Adhesive Varnish 2 was used instead of Adhesive Varnish 1, the peel strength and peel strength after aging under moist heat were similar to those of Examples 1 to 12, respectively.

Claims

1. an oxidation treatment step of oxidizing the surface of a film containing a liquid crystal polymer, The difference in contact angle of the produced film with water measured by a water drop method in the air at 25°C and 50% RH between the inside of the film and one surface of the film is 7° or more, the oxidation treatment step is a step of contacting the surface of the film with an oxidizing agent in an aqueous solution, The pH of the aqueous solution is 8 or more, The contact angle of one surface of the produced film with water measured by a water drop method in the air at 25°C and 50% RH is 50° or more and less than 75°. Film manufacturing method.

2. 2. The method for producing a film according to claim 1, wherein the standard oxidation-reduction potential of the oxidizing agent is 1.5 V or more.

3. 3. The method for producing a film according to claim 1 or 2, wherein the oxidizing agent comprises at least one compound selected from the group consisting of sodium persulfate, potassium persulfate, ammonium persulfate, hydrogen peroxide, potassium permanganate, sodium hypochlorite, ammonium cerium nitrate, potassium chromate, potassium dichromate, and a double salt of potassium peroxymonosulfate, potassium hydrogen sulfate, and potassium sulfate.

4. The method for producing a film according to any one of claims 1 to 3, wherein the aqueous solution has a pH of 12 or higher.

5. The method for producing a film according to any one of claims 1 to 4, wherein the difference in contact angle with water measured by a water drop method in air at 25°C and 50% RH between the inside of the produced film and one surface of the produced film is 7° or more and 32° or less.

6. The method for producing a film according to any one of claims 1 to 5, wherein the surface roughness Ra of one surface of the produced film is 0.05 µm or less.

7. The method for producing a film according to any one of claims 1 to 6, wherein the liquid crystal polymer contains a liquid crystal polymer having at least one structural unit selected from the group consisting of a structural unit derived from parahydroxybenzoic acid and a structural unit derived from 6-hydroxy-2-naphthoic acid.

8. The method for producing a film according to any one of claims 1 to 7, wherein the liquid crystal polymer contains a liquid crystal polymer having at least one structural unit selected from the group consisting of a structural unit derived from 6-hydroxy-2-naphthoic acid, a structural unit derived from an aromatic diol compound, a structural unit derived from terephthalic acid, and a structural unit derived from 2,6-naphthalenedicarboxylic acid.

9. The method for producing a film according to any one of claims 1 to 8, wherein the produced film further contains a polyolefin.

10. The method for producing a film according to claim 9, wherein the content of the polyolefin is 0.1% by mass to 40% by mass relative to the total mass of the film.

11. The method for producing a film according to claim 9 or 10, wherein the polyolefin forms a dispersed phase in the produced film.

12. The method for producing a film according to claim 11, wherein the average dispersed diameter of the dispersed phase is 0.01 μm to 10 μm.

13. The method for producing a film according to any one of claims 1 to 12, wherein the modulus of elasticity at 240°C of one surface of the produced film is 300 MPa or more.

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