CN115667398B - Liquid-crystalline polyester liquid composition, liquid-crystalline polyester film, laminate, and method for producing liquid-crystalline polyester film - Google Patents

Abstract

The present application relates to a liquid-crystalline polyester composition comprising a liquid-crystalline polyester (A) soluble in an aprotic solvent, an aprotic solvent (S) and a fluorine-containing resin (B) having a melting point of 305 ℃ or lower.

Description

Liquid crystal polyester liquid composition, liquid crystal polyester film, laminate, and method for producing liquid crystal polyester film

Technical Field

The present invention relates to a liquid crystal polyester liquid composition, a liquid crystal polyester film, a laminate and a method for producing the liquid crystal polyester film.

This application claims priority based on Japanese Patent Application No. 2020-088885 filed in Japan on May 21, 2020, the contents of which are incorporated herein by reference.

Background Art

Printed circuit boards on which electronic components are mounted use insulating materials. In recent years, with the development of communication systems, etc., there is a demand for insulating materials to have further improved physical properties such as dielectric properties.

As a method for improving the dielectric properties of insulating materials, the use of fluorine-containing resins with excellent dielectric properties is being promoted. For example, according to Patent Document 1, a sheet formed by melt-kneading a fluorine-containing polymer containing a carbonyl group and a resin composition containing a liquid crystal polymer is believed to have excellent electrical properties, impact resistance, and mechanical strength.

Prior art literature

Patent Literature

Patent Document 1: Japanese Patent Application Publication No. 2018-177931

Summary of the invention

Problem to be solved by the invention

However, the insulating material containing the fluorine-containing resin has a problem of reduced adhesion strength with the copper foil.

The present invention has been made in order to solve the above-mentioned problems, and an object of the present invention is to provide a liquid crystal polyester liquid composition capable of producing a film having excellent adhesion strength to copper foil and dielectric properties.

Another object of the present invention is to provide a liquid crystal polyester film, a laminate, and a method for producing a liquid crystal polyester film that are excellent in adhesion strength with copper foil and dielectric properties.

Means used to solve problems

The inventors conducted intensive research to solve the above-mentioned problems and found that by using a liquid crystal polyester soluble in aprotic solvents, a film-making method capable of producing an excellent isotropic film can be applied, and further, by using a fluorine-containing resin with a melting point of 305° C. or less in combination with the liquid crystal polyester, the dielectric properties can be improved while maintaining the adhesion strength with the copper foil, thereby completing the present invention.

That is, the present invention has the following aspects.

[1] A liquid crystal polyester liquid composition comprising a liquid crystal polyester (A) soluble in an aprotic solvent, an aprotic solvent (S), and a fluorine-containing resin (B) having a melting point of 305° C. or less.

[2] The liquid crystal polyester liquid composition according to [1] above, wherein the liquid crystal polyester (A) contains an amide bond.

[3] The liquid crystal polyester liquid composition described in [1] or [2] above, wherein the liquid crystal polyester (A) comprises a structural unit represented by the following formula (A1), a structural unit represented by the following formula (A2), and a structural unit represented by the following formula (A3).

(A1)-O-Ar1-CO-

(A2)-CO-Ar2-CO-

(A3)-X-Ar3-Y-

(In the formula, Ar1 represents 1,4-phenylene, 2,6-naphthalene diyl or 4,4'-biphenylene, Ar2 represents 1,4-phenylene, 1,3-phenylene or 2,6-naphthalene diyl, Ar3 represents 1,4-phenylene or 1,3-phenylene, X represents -NH-, and Y represents -O- or -NH-.)

[4] The liquid crystal polyester liquid composition described in [3] above, wherein Ar1 is 2,6-naphthalenediyl, Ar2 is 1,3-phenylene, Ar3 is 1,4-phenylene, and Y is -O-.

[5] The liquid crystal polyester liquid composition described in any one of [1] to [4] above, wherein the content of the liquid crystal polyester (A) is 10% to 90% by mass, and the content of the fluorine-containing resin (B) is 10% to 90% by mass, relative to the total solid content of the liquid crystal polyester liquid composition.

[6] The liquid crystal polyester liquid composition according to any one of [1] to [5] above, further comprising an inorganic filler (C).

[7] The liquid crystal polyester liquid composition described in [6] above, wherein the content of the liquid crystal polyester (A) is 25% to 40% by mass, the content of the fluorine-containing resin (B) is 25% to 40% by mass, and the content of the inorganic filler (C) is 20% to 50% by mass, relative to the total content of the solid components of the liquid crystal polyester liquid composition.

[8] The liquid crystal polyester liquid composition described in [6] or [7] above, wherein the inorganic filler (C) is a silica filler.

[9] The liquid crystal polyester composition according to any one of [1] to [8] above, wherein the crystallite size of the fluorine-containing resin (B) is 2.9×10 ^-8 m or less.

[10] The liquid crystal polyester liquid composition described in any one of [1] to [9] above, wherein the fluorine-containing resin (B) is at least one fluorine-containing resin selected from tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (perfluoroalkoxyalkane, PFA), polytetrafluoroethylene (PTFE), tetrafluoroethylene-hexafluoropropylene copolymer (FEP), polychlorotrifluoroethylene (PCTFE), ethylene-tetrafluoroethylene copolymer, ethylene-chlorotrifluoroethylene copolymer and polyvinylidene fluoride (PVDF).

[11] The liquid crystal polyester liquid composition according to any one of [1] to [10] above, wherein the content of the liquid crystal polyester (A) is 0.01 to 100 parts by mass relative to 100 parts by mass of the aprotic solvent (S).

[12] The liquid crystal polyester liquid composition according to any one of [1] to [11] above, wherein the aprotic solvent (S) is N-methylpyrrolidone.

[13] A liquid crystal polyester film comprising a liquid crystal polyester (A) and a fluorine-containing resin (B) having a melting point of 305° C. or less,

The liquid crystal polyester (A) includes an amide bond.

[14] The liquid crystal polyester film described in [13] above, wherein the liquid crystal polyester (A) contains a structural unit represented by the following formula (A1), a structural unit represented by the following formula (A2), and a structural unit represented by the following formula (A3).

(A1)-O-Ar1-CO-

(A2)-CO-Ar2-CO-

(A3)-X-Ar3-Y-

(In the formula, Ar1 represents 1,4-phenylene, 2,6-naphthalene diyl or 4,4'-biphenylene, Ar2 represents 1,4-phenylene, 1,3-phenylene or 2,6-naphthalene diyl, Ar3 represents 1,4-phenylene or 1,3-phenylene, X represents -NH-, and Y represents -O- or -NH-.)

[15] A laminate comprising a metal layer and the liquid crystal polyester film according to [13] or [14] laminated on the metal layer.

[16] A laminate comprising a metal layer and a liquid crystal polyester film formed by applying the liquid crystal polyester liquid composition according to any one of [1] to [12] above onto the metal layer.

[17] A method for producing a liquid crystal polyester film, comprising: coating a liquid crystal polyester liquid composition described in any one of [1] to [12] on a support, removing the aprotic solvent (S) from the liquid crystal polyester liquid composition, and performing a heat treatment to obtain a liquid crystal polyester film.

Effects of the Invention

According to the present invention, a liquid crystal polyester liquid composition capable of producing a film having excellent adhesion strength with copper foil and dielectric properties can be provided.

Furthermore, according to the present invention, a liquid crystal polyester film, a laminate, and a method for producing a liquid crystal polyester film having excellent adhesion strength with copper foil and dielectric properties can be provided.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram showing the structure of a liquid crystal polyester film according to one embodiment of the present invention.

FIG. 2 is a schematic diagram showing the structure of a laminate according to one embodiment of the present invention.

FIG. 3A is a schematic diagram showing a process for producing a liquid crystal polyester film and a laminate according to one embodiment of the present invention.

FIG. 3B is a schematic diagram showing a process of producing a liquid crystal polyester film and a laminate according to one embodiment of the present invention.

FIG. 3C is a schematic diagram showing a process of producing a liquid crystal polyester film and a laminate according to one embodiment of the present invention.

FIG. 3D is a schematic diagram showing a process of manufacturing a liquid crystal polyester film and a laminate according to one embodiment of the present invention.

DETAILED DESCRIPTION

Hereinafter, embodiments of the liquid crystal polyester liquid composition, the liquid crystal polyester film, the laminate, and the method for producing the liquid crystal polyester film of the present invention will be described.

《Liquid crystal polyester liquid composition》

The liquid crystal polyester liquid composition of the embodiment contains a liquid crystal polyester (A) soluble in an aprotic solvent, an aprotic solvent (S), and a fluorine-containing resin (B) having a melting point of 305° C. or lower.

In this specification, "liquid composition" refers to a solution or dispersion that is liquid at normal temperature and pressure (25°C, 1atm). In the case of a dispersion, it refers to a dispersion in which the dispersion medium is liquid at normal temperature and pressure (25°C, 1atm). A dispersion is a dispersion in which solid components that are insoluble in a solution are dispersed. In this specification, "solid components" refers to components contained in a liquid composition other than a solvent. Examples of the dispersed solid components include the above-mentioned fluorine-containing resin (B), the inorganic filler (C) described later, and the like. As a solvent, for example, the aprotic solvent (S) described later is suitable.

With regard to the liquid composition of the embodiment, the proportion of the solid content relative to the total mass of the liquid composition is not particularly limited, and may be greater than 0.5 mass %, 0.5 mass % to 80 mass %, 1 mass % to 70 mass %, or 5 mass % to 50 mass %.

Hereinafter, the liquid crystal polyester liquid composition according to one embodiment of the present invention will be simply referred to as “liquid composition” according to the embodiment.

<(A) Ingredients>

The component (A) is a liquid crystal polyester soluble in an aprotic solvent (S).

When the liquid composition of the embodiment is formed into a film on a metal foil, the component (A) contributes to improving the adhesion strength with the metal foil and improving the mechanical strength.

The liquid crystal polyester is a liquid crystal polyester that exhibits liquid crystallinity in a molten state, and is preferably a liquid crystal polyester that melts at a temperature of 450° C. or less. In addition, the liquid crystal polyester may be a liquid crystal polyester amide, a liquid crystal polyester ether, a liquid crystal polyester carbonate, or a liquid crystal polyester imide. The liquid crystal polyester is preferably a fully aromatic liquid crystal polyester having only structural units derived from aromatic compounds as raw material monomers.

In addition, "derived from" in this specification means that the chemical structure of the functional group that contributes to the polymerization is changed in order to polymerize the raw material monomer, and no other structural changes occur.

Whether the liquid crystal polyester is soluble in the aprotic solvent (S) can be confirmed by performing the following test.

Test methods

At a temperature of 180°C, 5 parts by mass of the liquid crystal polyester was stirred in 95 parts by mass of an aprotic solvent at a stirring condition of 200 rpm using an anchor blade for 6 hours, and then cooled to room temperature. Next, a membrane filter with a mesh of 5 μm and a pressure filter were used for filtration, and then the residue on the membrane filter was confirmed. At this time, the situation where no solid matter was confirmed was judged to be soluble in an aprotic solvent. The situation where a solid matter was confirmed was judged to be insoluble in an aprotic solvent. The solid matter can be confirmed by microscopic observation.

The liquid crystal polyester (A) preferably contains an amide bond. When the liquid crystal polyester (A) contains an amide bond, the adhesion strength with the copper foil when the film is laminated with the copper foil can be improved.

An example of the aprotic solvent-soluble liquid crystal polyester (A) containing an amide bond includes a structural unit represented by the following formula (A1), a structural unit represented by the following formula (A2), and a structural unit represented by the following formula (A3).

(A1)-O-Ar1-CO-

(A2)-CO-Ar2-CO-

(A3)-X-Ar3-Y-

(In the formula, Ar1 represents 1,4-phenylene, 2,6-naphthalene diyl or 4,4'-biphenylene, Ar2 represents 1,4-phenylene, 1,3-phenylene or 2,6-naphthalene diyl, Ar3 represents 1,4-phenylene or 1,3-phenylene, X represents -NH-, and Y represents -O- or -NH-.)

In this embodiment, it is particularly preferred that Ar2 is 1,3-phenylene. When Ar2 is 1,3-phenylene, the dissolution in aprotic solvents becomes better. This is believed to be because when Ar2 is 1,3-phenylene, a bent structure is introduced into the polymer.

With regard to the present embodiment, from the viewpoint of good solubility in aprotic solvents and easy display of adhesion strength and dielectric properties with copper foil when laminated with copper foil in the form of a film, it is preferred that Ar1 is 2,6-naphthalenediyl, Ar2 is 1,3-phenylene, Ar3 is 1,4-phenylene, and Y is -O-.

When the liquid crystal polyester has all types of structural units represented by the above formulae (A1) to (A3), the preferred content ratio of each structural unit in the liquid crystal polyester can be exemplified as follows.

The content of the structural unit represented by the above formula (A1) relative to the total content of all structural units constituting the above liquid crystal polyester (A) (the value obtained by dividing the mass of each structural unit constituting the liquid crystal polyester by the formula weight of each structural unit to obtain the mass equivalent (molar) of each structural unit, and adding them together) is preferably 30 mol% to 80 mol%, more preferably 40 mol% to 70 mol%, and further preferably 45 mol% to 65 mol%.

When the content of the structural unit (A1) is below the above upper limit, the solubility in a solvent tends to be good, and when it is above the above lower limit, the liquid crystallinity tends to be good.

The content of the structural unit represented by the above formula (A2) is preferably 10 mol% to 35 mol%, more preferably 15 mol% to 30 mol%, and further preferably 17.5 mol% to 27.5 mol%, relative to the total content of all structural units constituting the above liquid crystal polyester (A).

When the content of the structural unit (A2) is not more than the above upper limit, the liquid crystal properties tend to be good, and when it is not less than the above lower limit, the solubility in a solvent tends to be good.

The content of the structural unit represented by the above formula (A3) is preferably 10 mol% to 35 mol%, more preferably 15 mol% to 30 mol%, and further preferably 17.5 mol% to 27.5 mol%, relative to the total content of all structural units constituting the above liquid crystal polyester (A).

When the content of the structural unit (A3) is not more than the above upper limit, the liquid crystal properties tend to be good, and when it is not less than the above lower limit, the solubility in a solvent tends to be good.

In addition, the content of the structural unit (A2) in the liquid crystal polyester (A) is preferably equal to the content of the structural unit (A3). When the contents are different, the difference between the content of the structural unit (A2) and the content of the structural unit (A3) is preferably 10 mol% or less. By this difference, the degree of polymerization of the liquid crystal polyester can also be controlled.

The preferred content ratio of each structural unit in the liquid crystal polyester (A) is preferably 30 mol% to 80 mol% of the structural unit represented by the above formula (A1) relative to the total content of all structural units constituting the above liquid crystal polyester (A), the content of the structural unit represented by the above formula (A2) is preferably 10 mol% to 35 mol%, and the content of the structural unit represented by the above formula (A3) is preferably 10 mol% to 35 mol%.

The preferred content ratio of each structural unit in the liquid crystal polyester (A) is preferably 40 mol% to 70 mol% of the structural unit represented by the above formula (A1) relative to the total content of all structural units constituting the above liquid crystal polyester (A), more preferably 15 mol% to 30 mol% of the structural unit represented by the above formula (A2), and more preferably 15 mol% to 30 mol% of the structural unit represented by the above formula (A3).

The preferred content ratio of each structural unit in the liquid crystal polyester (A) is further preferably that the content of the structural unit represented by the above formula (A1) is 45 mol% to 65 mol% or less relative to the total content of all structural units constituting the above liquid crystal polyester (A), the content of the structural unit represented by the above formula (A2) is further preferably 17.5 mol% to 27.5 mol%, and the content of the structural unit represented by the above formula (A3) is further preferably 17.5 mol% to 27.5 mol%.

The structural unit (A1) may be, for example, a structural unit derived from an aromatic hydroxycarboxylic acid. The structural unit (A2) may be, for example, a structural unit derived from an aromatic dicarboxylic acid. The structural unit (A3) may be, for example, a structural unit derived from an aromatic diamine or an aromatic amine having a phenolic hydroxyl group. The component (A) may also use an ester- or amide-forming derivative of the above structural unit instead of the above structural unit.

Examples of ester-forming derivatives of carboxylic acids include those whose carboxyl groups become highly reactive derivatives such as acid chlorides and acid anhydrides that promote the reaction of producing polyesters, and those whose carboxyl groups form esters with alcohols, ethylene glycol, etc. that produce polyesters by transesterification.

Examples of the ester-forming derivatives of the phenolic hydroxyl group include those in which the phenolic hydroxyl group forms an ester with carboxylic acids.

Examples of the amide-forming derivatives of an amino group include those in which an amino group forms an amide with a carboxylic acid.

Examples of the structural unit of the component (A) used in the present embodiment include the following, but the present invention is not limited to these.

As the structural unit represented by formula (A1), for example, structural units derived from p-hydroxybenzoic acid, 6-hydroxy-2-naphthoic acid, 4-hydroxy-4'-biphenylcarboxylic acid, etc. can be listed, and the whole structural unit can also contain two or more of the above structural units. Among these structural units, the structural unit derived from 6-hydroxy-2-naphthoic acid is preferred.

As the structural unit represented by formula (A2), for example, structural units derived from terephthalic acid, isophthalic acid, 2,6-naphthalene dicarboxylic acid, etc. can be listed, and the whole structural unit can also contain two or more of the above structural units. Among these structural units, from the viewpoint of solubility in solvents, structural units derived from isophthalic acid are preferred.

As the structural unit represented by formula (A3), for example, structural units derived from 3-aminophenol, 4-aminophenol, 1,4-phenylenediamine, 1,3-phenylenediamine, 4-aminobenzoic acid, 4'-hydroxyacetanilide, etc. can be listed, and the whole structural unit may contain two or more of the above structural units. Among these structural units, from the viewpoint of reactivity, structural units derived from 4-aminophenol or 4'-hydroxyacetanilide are preferred.

The liquid crystal polyester soluble in an aprotic solvent may be a liquid crystal polyester containing a structural unit derived from 4'-hydroxyacetanilide.

The liquid crystal polyester soluble in an aprotic solvent may be a liquid crystal polyester composed of a structural unit derived from 6-hydroxy-2-naphthoic acid, a structural unit derived from 4'-hydroxyacetanilide, and a structural unit derived from isophthalic acid.

The method for producing the component (A) used in the present embodiment is not particularly limited, and examples thereof include a method in which an aromatic hydroxy acid corresponding to the structural unit (A1), an aromatic amine having a phenolic hydroxyl group corresponding to the structural unit (A3), a phenolic hydroxyl group of an aromatic diamine, and an amino group are acylated with an excess amount of fatty acid anhydride to obtain an acylated product, and the obtained acylated product is subjected to ester/amide exchange (polycondensation) with an aromatic dicarboxylic acid corresponding to the structural unit (A2) to carry out melt polymerization (see JP-A-2002-220444 and JP-A-2002-146003).

In the case of acylation reaction, the amount of fatty acid anhydride added is preferably 1.0 to 1.2 equivalents relative to the total of phenolic hydroxyl group and amino group, and more preferably 1.05 to 1.1 equivalents. When the amount of fatty acid anhydride added is too small, there is a tendency that the acylate, raw material monomer, etc. sublimate during transesterification/amide exchange (polycondensation), and the reaction system is easily blocked, while when the amount of fatty acid anhydride added is too large, there is a tendency that the coloring of the obtained liquid crystal polyester becomes obvious.

The acylation reaction is preferably carried out at 130 to 180° C. for 5 minutes to 10 hours, and more preferably at 140 to 160° C. for 10 minutes to 3 hours.

The fatty acid anhydride for acylation reaction is not particularly limited, for example, acetic anhydride, propionic anhydride, butyric anhydride, isobutyric anhydride, valeric anhydride, pivalic anhydride, 2-ethylhexanoic anhydride, monochloroacetic anhydride, dichloroacetic anhydride, trichloroacetic anhydride, monobromoacetic anhydride, dibromoacetic anhydride, tribromoacetic anhydride, monofluoroacetic anhydride, difluoroacetic anhydride, trifluoroacetic anhydride, glutaric anhydride, maleic anhydride, succinic anhydride, β-bromopropionic anhydride etc. can be listed, and they can also be mixed with two or more and use. With regard to the present embodiment, acetic anhydride, propionic anhydride, butyric anhydride or isobutyric anhydride are preferred, and acetic anhydride is more preferred.

In the case of transesterification/transamidation (polycondensation), the acyl group of the acylated product is preferably 0.8 to 1.2 times the equivalent of the carboxyl group.

The transesterification/transamidation (polycondensation) is preferably performed while increasing the temperature to 400° C. at a rate of 0.1 to 50° C./min, and more preferably performed while increasing the temperature to 350° C. at a rate of 0.3 to 5° C./min.

When the acylated product and the carboxylic acid are subjected to transesterification/transamidation (polycondensation), it is preferred to remove by-produced fatty acids and unreacted fatty acid anhydrides by evaporation or the like and distillation to the outside of the system.

In addition, the acylation reaction and transesterification/transamidation (polycondensation) can also be carried out in the presence of a catalyst. As the catalyst, substances known as catalysts for polymerization of polyesters can be used, for example, metal salt catalysts such as magnesium acetate, stannous acetate, tetrabutyl titanate, lead acetate, sodium acetate, potassium acetate, antimony trioxide, and organic compound catalysts such as N,N-dimethylaminopyridine and N-methylimidazole can be listed.

Among these catalysts, heterocyclic compounds containing two or more nitrogen atoms, such as N,N-dimethylaminopyridine and N-methylimidazole, are preferably used (see Japanese Patent Application Laid-Open No. 2002-146003).

The catalyst is usually added when the monomers are added, and does not necessarily need to be removed after the acylation. Transesterification can be directly carried out without removing the catalyst.

Condensation polymerization based on transesterification/transamide exchange is usually carried out by melt polymerization, and melt polymerization and solid phase polymerization can also be used in combination. Solid phase polymerization is preferably carried out in the following manner: the polymer is extracted from the melt polymerization process, and then crushed into powder or flakes, and then carried out by a known solid phase polymerization method. Specifically, for example, a method of heat treatment in a solid phase state at 20 to 350°C for 1 to 30 hours under an inactive atmosphere such as nitrogen can be cited. Solid phase polymerization can be carried out while stirring, or it can be carried out in a static state without stirring. In addition, by having an appropriate stirring mechanism, the melt polymerization tank and the solid phase polymerization tank can also be the same reaction tank. After solid phase polymerization, the obtained liquid crystal polyester can also be pelletized and formed by a known method.

The liquid crystal polyester can be produced by using, for example, a batch device or a continuous device.

The content of the component (A) may be 10% to 90% by mass, 15% to 50% by mass, or 25% to 40% by mass relative to the total content of the solid content of the liquid composition of the embodiment.

By using the liquid composition containing the component (A) within the above numerical range, the adhesion strength with copper foil and the dielectric properties of the produced liquid crystal polyester film can be easily improved.

<(S) Ingredients>

The component (S) is an aprotic solvent. Aprotic solvents have the advantages of low corrosion resistance and easy handling.

In the present embodiment, the aprotic solvent is a solvent containing an aprotic compound. In the present embodiment, examples of the aprotic solvent include: halogen solvents such as 1-chlorobutane, chlorobenzene, 1,1-dichloroethane, 1,2-dichloroethane, trichloromethane, 1,1,2,2-tetrachloroethane; ether solvents such as diethyl ether, tetrahydrofuran, 1,4-dioxane; ketone solvents such as acetone and cyclohexanone; ester solvents such as ethyl acetate; lactone solvents such as γ-butyrolactone; carbonate solvents such as ethylene carbonate and propylene carbonate; amine solvents such as triethylamine and pyridine; nitrile solvents such as acetonitrile and succinonitrile; amide solvents such as N,N'-dimethylformamide, N,N'-dimethylacetamide, tetramethylurea, N-methylpyrrolidone; nitro solvents such as nitromethane and nitrobenzene; sulfur compound solvents such as dimethyl sulfoxide and cyclopentane; phosphoric acid solvents such as hexamethylphosphoric acid amide and tri-n-butylphosphoric acid, etc., and a mixture of two or more of them can also be used.

Among them, it is preferred to use aprotic compounds having no halogen atom from the viewpoint of environmental influence, and it is preferred to use a solvent having a dipole moment of 3 to 5 from the viewpoint of solubility. Specifically, it is more preferred to use an amide solvent such as N,N'-dimethylformamide, N,N'-dimethylacetamide, tetramethylurea, N-methylpyrrolidone, or a lactone solvent such as γ-butyrolactone, and it is further preferred to use N,N'-dimethylformamide, N,N'-dimethylacetamide, or N-methylpyrrolidone.

With regard to the liquid composition of the embodiment, from the viewpoint of reducing the viscosity of the liquid composition and making it easier to coat the support, the content of the component (S) may be greater than 20% by mass, may be 20% to 99% by mass, or may be 50% to 95% by mass to facilitate coating on the support.

In the liquid composition of the embodiment, the content of the liquid crystal polyester (A) is preferably 0.01 to 100 parts by mass, more preferably 1 to 70 parts by mass, and even more preferably 5 to 40 parts by mass, based on 100 parts by mass of the aprotic solvent (S).

In the embodiment, when the content of the liquid crystal polyester (A) is within the above range, coating onto a support such as a metal foil is easy. The content of the liquid crystal polyester (A) can be appropriately adjusted within the above range according to the desired film thickness.

<(B) Component>

The component (B) is a fluorine-containing resin having a melting point of 305° C. or less. The “fluorine-containing resin” refers to a resin containing fluorine atoms in the molecule, and examples thereof include polymers having a structural unit containing fluorine atoms.

Examples of the fluorine-containing resin (B) include polytetrafluoroethylene (PTFE), tetrafluoroethylene-hexafluoropropylene copolymer (FEP), polychlorotrifluoroethylene (PCTFE), ethylene-tetrafluoroethylene copolymer, ethylene-chlorotrifluoroethylene copolymer, polyvinylidene fluoride (PVDF), tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (perfluoroalkoxyalkane, PFA), and the like.

The fluorine-containing resin (B) is preferably at least one fluorine-containing resin selected from tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (perfluoroalkoxyalkane, PFA), polytetrafluoroethylene (PTFE), tetrafluoroethylene-hexafluoropropylene copolymer (FEP), polychlorotrifluoroethylene (PCTFE), ethylene-tetrafluoroethylene copolymer, ethylene-chlorotrifluoroethylene copolymer and polyvinylidene fluoride (PVDF).

The fluorine-containing resin (B) is preferably a perfluoroalkoxyalkane (PFA) having a melting point of 305° C. or lower.

The liquid composition of the embodiment may contain two or more fluorine-containing resins.

The fluorine-containing resin contains fluorine atoms in its molecules, and thus a film containing the fluorine-containing resin can have excellent dielectric properties.

The melting point of the fluorine-containing resin (B) of the embodiment is 305°C or lower, preferably 303°C or lower, more preferably 301°C or lower.

By making the melting point of the fluorine-containing resin (B) below the above upper limit, the film containing the fluorine-containing resin (B) can have excellent properties of adhesion strength with copper foil. Although the above mechanism is not clear, it can be considered that the low melting point of the fluorine-containing resin reflects the low molecular weight of the fluorine-containing resin, thereby improving the adhesion with the copper foil.

From the viewpoint of practicality in applications requiring heat resistance, the lower limit of the melting point of the fluorinated resin (B) of the embodiment may be 280°C or higher, 290°C or higher, or even 295°C or higher.

The upper limit and lower limit of the melting point of the fluorine-containing resin (B) of the embodiment can be freely combined. As an example of the numerical range of the melting point of the fluorine-containing resin (B), it can be 280°C to 305°C, 290°C to 303°C, or 295°C to 301°C.

The melting point of the fluorine-containing resin (B) is a value measured in accordance with JIS K 6935 as a value of an endothermic peak in differential scanning calorimetry (DSC).

The melting point of the fluorine-containing resin (B) can be adjusted by selecting the raw material of the fluorine-containing resin and also by controlling the molecular weight of the fluorine-containing resin. The molecular weight of the fluorine-containing resin can be adjusted to a desired value by appropriately adjusting the polymerization rate and polymerization time during production.

The crystallite size of the fluorine-containing resin (B) of the embodiment is preferably 2.9×10 ^-8 m or less, more preferably 2.7×10 ^-8 m or less, further preferably 2.5×10 ^-8 m or less.

By making the crystallite size of the fluorine-containing resin (B) below the above upper limit, the film containing the fluorine-containing resin (B) can have excellent properties of adhesion strength with copper foil. Although the above mechanism is not clear, it can be considered that the small crystallite size of the fluorine-containing resin reflects the low molecular weight of the fluorine-containing resin, thereby improving the adhesion with the copper foil.

The lower limit of the crystallite size of the fluorine-containing resin (B) of the embodiment may be, for example, 2.0×10 ^-8 m or more, 2.1×10 ^-8 m or more, or 2.2×10 ^-8 m or more.

The upper limit and lower limit of the crystallite size of the fluorine-containing resin (B) of the embodiment can be freely combined. As an example of the numerical range of the crystallite size of the fluorine-containing resin (B), it can be 2.0× ^10-8 m to 2.9× ^10-8 m, 2.1× ^10-8 m to 2.7× ^10-8 m, or 2.2× ^10-8 m to 2.5× ^10-8 m.

The crystallite size of the fluorine-containing resin (B) can be measured by the following method using a wide angle X-ray scattering (WAXS: Wide Anle X-Ray Scattering) measuring apparatus.

The fluorine-containing resin powder sample is sandwiched between bag-shaped Kapton films and the X-ray beam size is adjusted so that it becomes smaller than the size of the sample. The measurement was performed in the range of the diffraction angle 2θ=5° to 30°.

For the fluorine-containing resin powder sample, X-rays were irradiated in the thickness direction of the Kapton film, and the transmission X-ray intensity and WAXS measurement were performed to obtain the transmission X-ray intensity _AS and the WAXS scattering intensity _IS . The transmission X-ray intensity and WAXS measurement were performed under the same conditions except that the fluorine-containing resin powder was not included, and the background transmission X-ray intensity _AB and WAXS scattering intensity I _B were obtained. The transmission X-ray intensity correction and background subtraction were performed according to the following formula (1), and the corrected WAXS scattering intensity I _C was obtained.

I _C =I _S / _AS -I _B / _AB (1)

The crystallite size measurement method based on X-ray diffraction can be carried out as follows.

Crystallite size of fluorine-containing resin powder The half-value width (β) of the scattering intensity at the diffraction peak of the Debye ring obtained by wide-angle X-ray diffraction measurement (set to a diffraction peak having a peak in the range of diffraction angle 2θ=17.93±0.2°) can be calculated using the Scherrer equation of the following formula (2).

D＝K·λ/βcosθ (2)

Where D is the crystallite size, λ is the measured X-ray wavelength, β is the half-peak width (radians), θ is the diffraction angle, and K is the Scherrer constant (0.94).

From the same viewpoint, the fluorine-containing resin (B) of the embodiment has a peak top at a diffraction angle of 20 = 17.93 ± 0.2° in X-ray diffraction analysis, and the half-value width of the peak is preferably 0.29 to 0.43, more preferably 0.31 to 0.41, and further preferably 0.33 to 0.39.

A commercially available fluorine-containing resin satisfying the above-mentioned values of melting point, crystallite size and half-peak width may be used, and for example, EA2000 manufactured by AGC may be used.

Furthermore, by making the liquid composition of the embodiment contain the fluorine-containing resin (B), the water absorption rate when formed into a film can be made appropriate.

The fluorine-containing resin contained in the liquid composition of the embodiment may be a powder. The volume average particle size of the fluorine-containing resin may be 0.1 μm to 30 μm, 0.5 μm to 10 μm, or 1 μm to 5 μm. When the volume average particle size of the fluorine-containing resin is within the above range, the surface smoothness when the film is made is excellent, so it is preferred. The volume average particle size of the fluorine-containing resin can be measured wetly using a laser diffraction/scattering particle size distribution measuring device with water as the dispersion medium.

The shape of the fluorine-containing resin contained in the liquid composition of the embodiment is not particularly limited, and may be, for example, spherical, blocky, fibrous or flaky. Spherical and blocky shapes are particularly preferred from the viewpoint of excellent dispersibility in the liquid crystal polyester liquid composition.

The mass ratio (solid content) of the component (A) to the component (B) [component (A):component (B)] contained in the liquid composition of the embodiment may be, for example, 9:1 to 1:9, 5:1 to 1:5, or 3:2 to 2:3.

By using the liquid composition containing the (A) component and the (B) component in the above ratio, the adhesion strength with copper foil, the dielectric properties, and the water resistance of the produced liquid crystal polyester film can be easily improved.

The content of the component (B) may be 10% to 90% by mass, 15% to 50% by mass, or 25% to 40% by mass relative to the total content of the solid content of the liquid composition.

By using a liquid composition containing the component (B) in the above numerical range, the adhesion strength with copper foil, dielectric properties, and water resistance of the produced liquid crystal polyester film can be easily improved.

The liquid composition of the embodiment may contain (A) component, (B) component and (S) component. As a preferred example of the proportion of each component in the composition, it can be illustrated that the content of the above-mentioned (A) component is 10% by mass to 90% by mass, and the content of the (B) component is 10% by mass to 90% by mass relative to the total content of the solid component of the liquid composition. In addition, the combination of these numerical ranges is an example, and for example, the numerical values exemplified as an example of the content ratio of each component can be freely combined.

<Other ingredients>

The liquid composition of the embodiment may contain other components as needed in addition to the (A) component, the (B) component, and the (S) component, for example, additives such as fillers, antioxidants, heat stabilizers, ultraviolet absorbers, antistatic agents, surfactants, flame retardants, colorants, and resins that are not equivalent to the (A) component and the (B) component.

Examples of fillers include inorganic fillers (C) such as silica, alumina, titanium oxide, barium titanate, strontium titanate, aluminum hydroxide, and calcium carbonate; and organic fillers such as cured epoxy resins, cross-linked benzoguanamine resins, and cross-linked acrylic resins.

From the viewpoint of improving the dielectric loss tangent of the liquid crystal polyester film, the inorganic filler (C) is preferably a silica filler.

It is known that the dielectric loss tangent can be improved by adding a silica filler. However, when the silica filler is used in combination with a liquid crystal polyester, a problem of a decrease in the adhesion strength with the copper foil may occur.

However, in the case of a liquid composition comprising the fluorine-containing resin (B) having a melting point of 305°C or less, by combining the fluorine-containing resin (B) having a melting point of 305°C or less with an inorganic filler (C) such as a silica filler (hereinafter also referred to as component (C)), even if component (C) is added, the adhesion strength with the copper foil is not easily reduced, the water resistance is excellent, the balance between the adhesion strength with the copper foil and the dielectric properties can be extremely good, and a liquid crystal polyester film having particularly excellent properties can be manufactured.

The above-mentioned filler is preferably granular. The volume average particle size of the filler can be 0.1 μm to 10 μm, or 0.2 μm to 5 μm, or 0.3 μm to 1 μm. When the volume average particle size of the filler is within the above range, the dispersibility in the liquid crystal polyester liquid composition is excellent, so it is preferred. The volume average particle size of the filler can be measured by a laser diffraction/scattering particle size distribution measuring device.

When the liquid composition of the embodiment contains the inorganic filler (C), the content thereof may be 5 to 70% by mass, 20 to 50% by mass, or 30 to 45% by mass relative to the total solid content of the liquid composition.

By containing an inorganic filler (C) within the above numerical range, the characteristics of the inorganic filler are well exerted. For example, by using a liquid composition containing, for example, a silica filler above the above lower limit, the dielectric properties of the manufactured liquid crystal polyester film can be improved. In addition, by using a liquid composition containing a silica filler below the above upper limit, the adhesion strength of the manufactured liquid crystal polyester film with copper foil can be good.

The liquid composition of the embodiment may contain the (A) component, the (B) component, and the (S) component, and may further contain the (C) component.

As a preferred example of the mixing ratio of each component in the composition, it can be illustrated that the content ratio of the above-mentioned (A) component is 25% by mass to 40% by mass, the content ratio of the (B) component is 25% by mass to 40% by mass, and the content ratio of the above-mentioned (C) component is 20% by mass to 50% by mass, relative to the total content of the solid content of the liquid composition.

As a more preferred example of the mixing ratio of each component in the composition, it can be illustrated that the content ratio of the above-mentioned (A) component is 25% by mass to 35% by mass, the content ratio of the (B) component is 25% by mass to 35% by mass, and the content ratio of the above-mentioned (C) component is 30% by mass to 45% by mass, relative to the total content of the solid content of the liquid composition.

In addition, the combination of these numerical ranges is an example, and for example, the numerical values exemplified as an example of the content ratio of each component mentioned above can be freely combined.

Examples of resins not corresponding to components (A) and (B) include thermoplastic resins other than liquid crystal polyesters such as polypropylene, polyamide, polyesters other than liquid crystal polyesters, polyphenylene sulfide, polyether ketone, polycarbonate, polyether sulfone, polyphenylene ether and its modified products, polyether imide, etc.; elastomers such as copolymers of glycidyl methacrylate and polyethylene; and thermosetting resins such as phenolic resins, epoxy resins, polyimide resins, and cyanate resins. The content of these resins can be 0, preferably 20 parts by mass or less, relative to 100 parts by mass of the liquid crystal polyester.

According to the liquid crystal polyester liquid composition of the embodiment, a film having excellent adhesion strength with copper foil and dielectric properties can be produced.

By making the liquid composition of the embodiment contain (A) component, it is possible to produce a film which is particularly excellent in adhesion strength with copper foil and dielectric properties.

According to the liquid composition of the present embodiment, a film forming method capable of producing a film having excellent isotropy can be applied.

Conventionally, liquid crystal polyester films are generally produced by a melt molding method or a solution casting method in which liquid crystal polyester is melted.

The melt molding method is a method of molding a film by extruding a kneaded product from an extruder. However, for a film produced by the melt molding method, liquid crystal polyester molecules are more oriented in the film-forming direction than in the lateral direction relative to the extrusion direction, making it difficult to obtain a liquid crystal polyester with excellent isotropy.

In the solution casting method, since a film is formed without applying a force such as extrusion, the orientation of the liquid crystal polyester becomes more isotropic compared to a liquid crystal polyester film formed by a melt molding method.

According to the liquid composition of the embodiment, the liquid crystal polyester (A) is soluble in the aprotic solvent (S), so that a solution casting method can be applied, and a liquid crystal polyester film having excellent isotropy can be produced.

By making the liquid composition of the embodiment contain (B) component, it is possible to produce a film excellent in adhesion strength with copper foil, dielectric properties, and water resistance.

By making the liquid composition of the embodiment further contain the (C) component, a film having more excellent dielectric properties and water resistance can be produced.

Moreover, by making the liquid composition contain (C)component, it is possible to produce an excellent film having an extremely good balance among adhesion strength with copper foil, dielectric properties, and water resistance.

《Liquid crystal polyester film》

The liquid crystal polyester film of the embodiment contains a liquid crystal polyester (A) and a fluorine-containing resin (B) having a melting point of 305° C. or less, wherein the liquid crystal polyester (A) contains an amide bond.

Hereinafter, the liquid crystal polyester film according to one embodiment of the present invention will be simply referred to as “film” of the embodiment.

FIG. 1 is a schematic diagram showing a structure of a liquid crystal polyester film 10 according to an embodiment.

As the liquid crystal polyester (A), the substances described as the above-mentioned (A) component can be listed, and detailed description is omitted here. In addition, the liquid crystal polyester (A) in the state of being formed into a film may also be insoluble in aprotic solvents due to changes in physical properties during the film formation process. The above-mentioned physical property changes refer to, for example, an increase in the degree of polymerization.

The above-mentioned liquid crystal polyester (A) preferably contains a structural unit represented by the following formula (A1), a structural unit represented by the following formula (A2), and a structural unit represented by the following formula (A3).

(A1)-O-Ar1-CO-

(A2)-CO-Ar2-CO-

(A3)-X-Ar3-Y-

(In the formula, Ar1 represents 1,4-phenylene, 2,6-naphthalene diyl or 4,4'-biphenylene, Ar2 represents 1,4-phenylene, 1,3-phenylene or 2,6-naphthalene diyl, Ar3 represents 1,4-phenylene or 1,3-phenylene, X represents -NH-, and Y represents -O- or -NH-.)

Examples of the fluorine-containing resin (B) having a melting point of 305° C. or lower include those described as the above-mentioned component (B), and detailed description thereof is omitted here.

The film of the embodiment, like the liquid composition of the above-mentioned embodiment, may contain other components as needed in addition to the (A) component and the (B) component, for example, fillers, antioxidants, heat stabilizers, ultraviolet absorbers, antistatic agents, surfactants, flame retardants, colorants and other additives, resins that are not equivalent to the (A) component and the (B) component, etc., and detailed descriptions are omitted here.

The film of the embodiment preferably contains the above-mentioned (A) component, (B) component, and an inorganic filler (C).

The liquid crystal polyester film containing the components (A), (B) and (C) is less likely to suffer from a decrease in adhesion strength with copper foil, has a good balance between adhesion strength with copper foil and dielectric properties, is also excellent in water resistance, and has particularly excellent properties.

Examples of the inorganic filler (C) include those described as the above-mentioned component (C), and detailed description thereof is omitted here.

The inorganic filler (C) is preferably a silica filler.

The contents of the various components in the film of the embodiment may be the same as the contents of the various components as the solid content of the liquid composition of the embodiment exemplified above.

The film of the embodiment exhibits excellent dielectric properties.

The relative dielectric constant of the film of the embodiment at a frequency of 1 GHz is preferably 3.1 or less, more preferably 3.0 or less, further preferably 2.9 or less, and particularly preferably 2.8 or less. In addition, the relative dielectric constant of the film may be 2.3 or more, 2.4 or more, or 2.5 or more.

An example of the numerical range of the relative dielectric constant of the film may be 2.3 to 3.1, 2.4 to 3.0, 2.5 to 2.9, or 2.5 to 2.8.

The dielectric loss tangent of the film of the embodiment at a frequency of 1 GHz is 0.005 or less, preferably 0.004 or less, more preferably 0.003 or less, further preferably 0.002 or less, and particularly preferably 0.0015 or less. The dielectric loss tangent of the liquid crystal polyester film may be 0.0003 or more, 0.0005 or more, or 0.0007 or more.

An example of the numerical range of the dielectric loss tangent of the film may be 0.0003 to 0.005, 0.0005 to 0.004, 0.0007 to 0.003, 0.0007 to 0.002, or 0.0007 to 0.0015.

The relative dielectric constant and dielectric loss tangent of the film at a frequency of 1 GHz can be measured by a capacitance method using an impedance analyzer under the conditions described in Examples.

The film of the embodiment can be made excellent in isotropy.

The film of the embodiment has a molecular orientation ratio (MOR) value measured by a microwave orientation meter in the range of preferably 1 to 1.1, more preferably 1 to 1.08, further preferably 1 to 1.06, particularly preferably 1 to 1.04.

The molecular orientation ratio (MOR) is measured by a microwave molecular orientation meter (e.g., MOA-5012A manufactured by Oji Instruments Co., Ltd.). The microwave molecular orientation meter is a device that utilizes the fact that the transmission intensity of microwaves is different in the orientation direction and the right-angle direction depending on the molecular orientation. Specifically, while rotating the sample, microwaves with a fixed frequency (12 GHz is used) are irradiated, and the intensity of the transmitted microwaves that varies according to the molecular orientation is measured, and the ratio of the maximum value to the minimum value is the MOR. The interaction between the microwave electric field with a fixed frequency and the dipoles that constitute the molecules is related to the inner product of the two vectors. Due to the anisotropy of the dielectric constant of the sample, the intensity of the microwaves varies according to the angle at which the sample is configured, so the orientation ratio can be known.

The film of the embodiment preferably has a linear expansion coefficient of 85ppm/℃ or less, more preferably 57ppm/℃ or less, further preferably 45ppm/℃ or less, and particularly preferably 40ppm/℃ or less, under the condition of a heating rate of 5℃/min. The lower limit of the linear expansion coefficient is not particularly limited, for example, it is 0ppm/℃ or more. In addition, in the case where, for example, copper foil is laminated with a film, since the linear expansion coefficient of the copper foil is 18ppm/℃, the linear expansion coefficient of the film of the embodiment is preferably a value close to this value. In other words, the linear expansion coefficient of the film of the embodiment is preferably 0ppm/℃ to 57ppm/℃, more preferably 10ppm/℃ to 45ppm/℃, and further preferably 20ppm/℃ to 40ppm/℃. In the case where the linear expansion coefficient varies depending on the direction and position of the film, a high value is adopted as the linear expansion coefficient of the film. The film of the embodiment satisfying the above numerical range has a low linear expansion coefficient and high dimensional stability.

The film of the embodiment exhibits excellent water resistance.

As an index of water resistance, the water absorption of the film of the embodiment measured based on JIS K 7209 is preferably 0.8% by mass or less, more preferably 0.5% by mass or less, further preferably 0.4% by mass or less, and particularly preferably 0.3% by mass or less. In addition, the water absorption of the film can be 0.05% by mass or more, 0.1% by mass or more, or 0.15% by mass or more.

An example of the numerical range of the water absorption value of the film may be 0.05% by mass to 0.8% by mass, 0.1% by mass to 0.5% by mass, 0.15% by mass to 0.4% by mass, or 0.15% by mass to 0.3% by mass.

The thickness of the film of the embodiment is not particularly limited, but a film thickness suitable for an electronic component film is preferably 5 to 50 μm, more preferably 7 to 40 μm, further preferably 10 to 33 μm, and particularly preferably 15 to 30 μm.

The method for producing the film of the embodiment is not particularly limited, and for example, the liquid composition of the embodiment can be formed into a film. From the viewpoint of being able to produce a film having excellent isotropy, the film of the embodiment is preferably produced by the "method for producing a liquid crystal polyester film" described later.

《Method for producing liquid crystal polyester film》

The method for producing a liquid crystal polyester film of the embodiment includes applying the liquid composition of the embodiment on a support, and removing the aprotic solvent (S) from the liquid composition to obtain a liquid crystal polyester film.

The above-mentioned manufacturing method may be equivalent to a solution casting method.

Examples of the liquid composition of the embodiment include those exemplified in the above-mentioned "Liquid Crystal Polyester Liquid Composition".

The method for producing the liquid crystal polyester film may further include the following steps.

A step of coating the liquid crystal polyester liquid composition of the embodiment on a support (coating step). A step of removing the aprotic solvent (S) from the coated liquid crystal polyester liquid composition (drying step).

The method for producing a liquid crystal polyester film of the embodiment may include a step of heat-treating the liquid crystal polyester liquid composition or the precursor of the liquid crystal polyester film from which the aprotic solvent (S) is removed after the coating step (heat-treating step).

The method for manufacturing the liquid crystal polyester film of the embodiment may further include: coating the liquid crystal polyester liquid composition of the embodiment on a support, removing the aprotic solvent (S) from the liquid crystal polyester liquid composition, and performing heat treatment to obtain the liquid crystal polyester film. The heat treatment can promote the polymerization reaction of the polymer in the liquid crystal polyester liquid composition, and further promote the volatilization of the aprotic solvent (S).

The heat treatment can also serve as the above-mentioned drying step.

Therefore, the method for producing the liquid crystal polyester film of the embodiment may also include: coating the liquid crystal polyester liquid composition of the embodiment on a support, and heat-treating the composition to obtain the liquid crystal polyester film.

In addition, the method for producing the liquid crystal polyester film may further include a step of separating the support from the laminate (separation step). In addition, the liquid crystal polyester film can be used as a film for electronic components even in a state where it is formed on the support as a laminate, so the separation step is not an essential step in the production process of the liquid crystal polyester film.

Hereinafter, an example of a method for producing a liquid crystal polyester film according to an embodiment will be described with reference to the drawings.

FIG. 3 is a schematic diagram showing an example of a production process of a liquid crystal polyester film and a laminate according to an embodiment.

First, a liquid crystal polyester liquid composition 30 is applied to a support 12 (coating process in FIG. 3A ). The application of the liquid composition to the support can be carried out by methods such as roller coating, dip coating, spray coating, spin coating, curtain coating, slot coating, and screen printing, and a method that can be applied smoothly and evenly on the upper surface of the support can be appropriately selected. In addition, in order to make the distribution of the filling material that can be matched with the liquid composition uniform, the operation of stirring the liquid composition can also be performed before coating.

The viscosity of the liquid crystal polyester liquid composition 30 is not particularly limited. From the perspective of simplifying the coating operation and shortening the drying time, the viscosity measured by a B-type viscometer at 23°C is preferably 200 mPa·s to 2000 mPa·s, more preferably 250 mPa·s to 1500 mPa·s, and further preferably 300 mPa·s to 1000 mPa·s.

Examples of the support 12 include a glass plate, a resin film, and a metal foil. Among them, a resin film or a metal foil is preferred, and a copper foil is particularly preferred because it has excellent heat resistance, is easy to apply the liquid composition, and is easy to remove from the liquid crystal polyester film.

Examples of commercially available polyimide (PI) films include "UPILEX S" and "UPILEX R" from Ube Industries, Ltd., "Kapton" from DuPont Toray Industries, and "IF30", "IF70", and "LV300" from Eska Siklon PI.

The thickness of the resin film is usually 25 μm to 75 μm, preferably 50 μm to 75 μm.

The thickness of the metal foil is usually 3 μm to 75 μm, preferably 5 μm to 30 μm, and more preferably 10 μm to 25 μm.

Next, the aprotic solvent is removed from the liquid crystal polyester liquid composition 30 coated on the support 12 (drying process in FIG. 3B ). The liquid composition after the aprotic solvent is removed becomes the liquid crystal polyester film precursor 40 to be subjected to heat treatment. In addition, the aprotic solvent does not have to be completely removed from the liquid composition, and a part of the aprotic solvent contained in the liquid composition can be removed, or all of the aprotic solvent can be removed. The proportion of the aprotic solvent contained in the liquid crystal polyester film precursor 40 is preferably 50% by mass or less, more preferably 3% by mass to 12% by mass, and further preferably 5% by mass to 10% by mass relative to the total mass of the liquid crystal polyester film precursor. By making the content of the aprotic solvent in the liquid crystal polyester film precursor above the above lower limit, the risk of reduced thermal conductivity of the liquid crystal polyester film can be reduced. In addition, by making the content of the aprotic solvent in the liquid crystal polyester film precursor below the above upper limit, the risk of deterioration of the appearance of the liquid crystal polyester film due to foaming during heat treatment can be reduced.

The removal of the aprotic solvent is preferably carried out by evaporating the aprotic solvent, and the method thereof can be, for example, heating, decompression and ventilation, or a combination thereof. In addition, the removal of the aprotic solvent can be carried out in a continuous manner or in a monolithic manner. From the viewpoint of productivity and operability, the removal of the aprotic solvent is preferably carried out by heating in a continuous manner, and more preferably by heating while ventilating in a continuous manner. The removal temperature of the aprotic solvent is preferably a temperature lower than the melting point of the liquid crystal polyester (A) and the fluorine-containing resin (B), for example, 40°C to 200°C. The time for the removal of the aprotic solvent is appropriately adjusted, for example, so that the aprotic solvent content in the liquid crystal polyester film precursor reaches 3 to 12% by mass. The time for the removal of the aprotic solvent is, for example, 0.2 hours to 12 hours, preferably 0.5 hours to 8 hours.

The laminate precursor 22 having the support 12 and the liquid crystal polyester film precursor 40 thus obtained is subjected to heat treatment, thereby obtaining a laminate 20 having the support 12 and the liquid crystal polyester film 10 (a film obtained by heat-treating the liquid crystal polyester film precursor 40) (heat-treatment step in FIG. 3C ). At this time, a liquid crystal polyester film 10 formed on the support is obtained.

The heat treatment conditions include, for example, heating the medium from the boiling point - 50°C to the heat treatment temperature and then performing the heat treatment at a temperature equal to or higher than the melting points of the liquid crystal polyester (A) and the fluorine-containing resin (B).

The heat treatment may be performed in a continuous manner or in a single-chip manner similarly to the removal of the aprotic solvent. From the viewpoint of productivity and operability, the heat treatment is preferably performed in a continuous manner, and more preferably performed in a continuous manner followed by the removal of the aprotic solvent.

Next, the liquid crystal polyester film 10 is separated from the laminate 20 having the support 12 and the liquid crystal polyester film 10, so that the liquid crystal polyester film 10 can be obtained as a single layer film (separation step in FIG. 3D). When a glass plate is used as the support 12, the liquid crystal polyester film 10 can be separated from the laminate 20 by peeling the liquid crystal polyester film 10 from the laminate 20. When a resin film is used as the support 12, the separation can be carried out by peeling the resin film or the liquid crystal polyester film 10 from the laminate 20. When a metal foil is used as the support 12, the metal foil can be removed by etching and separated from the laminate 20. When a resin film, particularly a polyimide film, is used as the support, the polyimide film or the liquid crystal polyester film is easily peeled from the laminate 20, and a liquid crystal polyester film with good appearance can be obtained. When a metal foil is used as the support, the liquid crystal polyester film can be used as a metal-clad laminate for printed wiring without separating the liquid crystal polyester film from the laminate 20.

According to the method for producing a liquid crystal polyester film of the embodiment, a liquid crystal polyester film having excellent isotropy can be produced.

Layered

The laminated body of the embodiment includes a metal layer and the liquid crystal polyester film of the embodiment laminated on the metal layer.

2 is a schematic diagram showing the structure of a laminate 21 according to one embodiment of the present invention. The laminate 21 includes a metal layer 13 and a liquid crystal polyester film 10 laminated on the metal layer 13. Examples of the liquid crystal polyester film 10 included in the laminate include those exemplified above, and description thereof is omitted.

The metal layer of the laminate can be exemplified as the support in the "Method for Producing Liquid Crystal Polyester Film" and the "Method for Producing Laminated Body" described later, preferably metal foil. The metal constituting the metal layer is preferably copper from the viewpoint of conductivity and cost, and the metal foil is preferably copper foil.

The thickness of the laminated body of the embodiment is not particularly limited, but is preferably 5 to 130 μm, more preferably 10 to 70 μm, and further preferably 15 to 60 μm.

The method for producing the laminated body according to the embodiment is not particularly limited, and the laminated body according to the embodiment can be produced by the "method for producing laminated body" described later.

As one embodiment of the present invention, there is provided a laminate including a metal layer and a liquid crystal polyester film formed by applying the liquid composition of the embodiment on the metal layer.

The laminated body of the embodiment can be suitably used for films for electronic components such as printed wiring boards.

《Method for producing laminated body》

The method for manufacturing a laminate of an embodiment includes: coating a liquid crystal polyester liquid composition of an embodiment on a support, removing an aprotic solvent (S) from the liquid crystal polyester liquid composition to form a liquid crystal polyester film on the support, thereby obtaining a laminate having the support and the film.

The method for producing the laminated body according to the embodiment may include the following steps.

A step of coating the liquid crystal polyester liquid composition of the embodiment on a support (coating step). A step of removing the aprotic solvent (S) from the coated liquid crystal polyester liquid composition (drying step).

Similar to the method for producing the liquid crystal polyester film, the method for producing the laminate of the embodiment may also include a step (heat treatment step) of heat treating the liquid crystal polyester liquid composition or the liquid crystal polyester film precursor after removing the aprotic solvent (S) after the coating step.

The method for manufacturing the laminated body of the embodiment may further include: coating the liquid crystal polyester liquid composition of the embodiment on a support, removing the aprotic solvent (S) from the liquid crystal polyester liquid composition, and performing heat treatment to form a liquid crystal polyester film on the support, thereby obtaining a laminated body having the support and the film. The heat treatment can promote the polymerization reaction of the polymer in the liquid composition, and further promote the volatilization of the aprotic solvent (S).

The heat treatment can also serve as the above-mentioned drying step.

Therefore, the method for producing a laminated body of the embodiment may further include: applying the liquid crystal polyester liquid composition of the embodiment on a support, performing heat treatment to form a liquid crystal polyester film on the support, thereby obtaining a laminated body including the support and the film.

Fig. 3 is a schematic diagram showing an example of a manufacturing process of a liquid crystal polyester film and a laminate according to an embodiment. The manufacturing method of the laminate illustrated in Fig. 3 is the same as that described in the manufacturing method of the liquid crystal polyester film except that the separation step (Fig. 3D) is not performed, and therefore the description thereof is omitted.

According to the method for producing a laminated body according to the embodiment, a laminated body including the liquid crystal polyester film according to the embodiment can be produced.

The present invention has the following aspects.

<1> A liquid crystal polyester liquid composition comprising a liquid crystal polyester (A) soluble in an aprotic solvent, an aprotic solvent (S), and a fluorine-containing resin (B) having a melting point of any one of 305°C or less, 280°C to 305°C, 290°C to 303°C, and 295°C to 301°C,

The above-mentioned liquid crystal polyester (A) contains a structural unit represented by the following formula (A1), a structural unit represented by the following formula (A2), and a structural unit represented by the following formula (A3).

(A1)-O-Ar1-CO-

(A2)-CO-Ar2-CO-

(A3)-X-Ar3-Y-

(In the formula, Ar1 represents 1,4-phenylene, 2,6-naphthalene diyl or 4,4'-biphenylene, Ar2 represents 1,4-phenylene, 1,3-phenylene or 2,6-naphthalene diyl, Ar3 represents 1,4-phenylene or 1,3-phenylene, X represents -NH-, and Y represents -O- or -NH-.)

<2> The liquid crystal polyester liquid composition described in <1> above, wherein Ar1 is 2,6-naphthalenediyl, Ar2 is 1,3-phenylene, Ar3 is 1,4-phenylene, and Y is -O-.

<3> The liquid crystal polyester liquid composition according to <1> or <2>, wherein the liquid crystal polyester liquid composition comprises the liquid crystal polyester (A) and the fluorine-containing resin (B) as solid components,

The ratio of the content of the solid component to the total mass of the liquid composition is 5% by mass to 50% by mass.

<4> The liquid crystal polyester liquid composition described in any one of <1> to <3> above, wherein the content of the liquid crystal polyester (A) is 10% to 90% by mass, and the content of the fluorine-containing resin (B) is 10% to 90% by mass, relative to the total content of the solid component of the liquid crystal polyester liquid composition.

<5> The liquid crystal polyester liquid composition according to any one of <1> to <4>, further comprising a silica filler.

<6> The liquid crystal polyester liquid composition described in <5> above, wherein the volume average particle size of the silica filler is any one of 0.1 μm to 10 μm, 0.2 μm to 5 μm, and 0.3 μm to 1 μm.

<7> The liquid crystal polyester liquid composition described in <5> or <6> above, wherein, relative to the total content of the solid component of the liquid crystal polyester liquid composition, the content of the liquid crystal polyester (A) is 25% to 40% by mass, the content of the fluorine-containing resin (B) is 25% to 40% by mass, and the content of the silica filler is 20% to 50% by mass.

<8> The liquid crystal polyester liquid composition according to any one of <1> to <7>, wherein the crystallite size of the fluorine-containing resin (B) is any one of 2.0×10 ^-8 m to 2.9×10 ^-8 m, 2.1×10 ^-8 m to 2.7×10 ^-8 m, and 2.2×10 ^-8 m to 2.5×10 ^-8 m.

<9> The liquid crystal polyester liquid composition described in any one of <1> to <8> above, wherein the fluorine-containing resin (B) is at least one fluorine-containing resin selected from tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (perfluoroalkoxyalkane, PFA), polytetrafluoroethylene (PTFE), tetrafluoroethylene-hexafluoropropylene copolymer (FEP), polychlorotrifluoroethylene (PCTFE), ethylene-tetrafluoroethylene copolymer, ethylene-chlorotrifluoroethylene copolymer and polyvinylidene fluoride (PVDF).

<10> The liquid crystal polyester liquid composition according to any one of <1> to <9>, wherein the volume average particle size of the fluorine-containing resin (B) is any one of 0.1 μm to 30 μm, 0.5 μm to 10 μm, and 1 μm to 5 μm.

<11> The liquid crystal polyester liquid composition according to any one of <1> to <10>, wherein the aprotic solvent (S) is N-methylpyrrolidone.

<12> A liquid crystal polyester film comprising a liquid crystal polyester (A) and a fluorine-containing resin (B) having a melting point of 305° C. or less,

The liquid crystal polyester (A) includes an amide bond.

<13> The liquid crystal polyester film according to <12>, wherein the liquid crystal polyester (A) comprises a structural unit represented by the following formula (A1), a structural unit represented by the following formula (A2), and a structural unit represented by the following formula (A3).

(A1)-O-Ar1-CO-

(A2)-CO-Ar2-CO-

(A3)-X-Ar3-Y-

(In the formula, Ar1 represents 1,4-phenylene, 2,6-naphthalene diyl or 4,4'-biphenylene, Ar2 represents 1,4-phenylene, 1,3-phenylene or 2,6-naphthalene diyl, Ar3 represents 1,4-phenylene or 1,3-phenylene, X represents -NH-, and Y represents -O- or NH-.)

<14> The liquid crystal polyester film described in <13> above, wherein Ar1 is 2,6-naphthalenediyl, Ar2 is 1,3-phenylene, Ar3 is 1,4-phenylene, and Y is -O-.

<15> The liquid crystal polyester film described in any one of <12> to <14> above, wherein the content of the liquid crystal polyester (A) is 10% to 90% by mass, and the content of the fluorine-containing resin (B) is 10% to 90% by mass, relative to the total content of the liquid crystal polyester film.

<16> The liquid crystal polyester film according to any one of <12> to <15>, further comprising an inorganic filler (C).

<17> The liquid crystal polyester film described in <16> above, wherein, relative to the total content of the liquid crystal polyester film, the content of the liquid crystal polyester (A) is 25% to 40% by mass, the content of the fluorine-containing resin (B) is 25% to 40% by mass, and the content of the inorganic filler (C) is 20% to 50% by mass.

<18> The liquid crystal polyester film according to <16> or <17>, wherein the inorganic filler (C) is a silica filler.

<19> The liquid crystal polyester film according to any one of <12> to <18>, wherein the fluorine-containing resin (B) has a crystallite size of 2.9×10 ^-8 m or less.

<20> The liquid crystal polyester film described in any one of <12> to <19> above, wherein the fluorine-containing resin (B) is at least one fluorine-containing resin selected from tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (perfluoroalkoxyalkane, PFA), polytetrafluoroethylene (PTFE), tetrafluoroethylene-hexafluoropropylene copolymer (FEP), polychlorotrifluoroethylene (PCTFE), ethylene-tetrafluoroethylene copolymer, ethylene-chlorotrifluoroethylene copolymer and polyvinylidene fluoride (PVDF).

<21> The liquid crystal polyester film according to any one of <12> to <20> above, wherein the thickness is 5 to 50 μm, preferably 7 to 40 μm, more preferably 10 to 33 μm, and even more preferably 15 to 30 μm.

<22> The liquid crystal polyester film according to any one of <12> to <21> above, wherein the relative dielectric constant at a frequency of 1 GHz is 2.3 to 3.1, preferably 2.4 to 3.0, more preferably 2.5 to 2.9, and even more preferably 2.5 to 2.8.

<23> The liquid crystal polyester film described in any one of <12> to <22> above has a dielectric loss tangent of 0.0003 to 0.005 at a frequency of 1 GHz, preferably 0.0005 to 0.004, more preferably 0.0007 to 0.003, further preferably 0.0007 to 0.002, and particularly preferably 0.0007 to 0.0015.

<24> The liquid crystal polyester film according to any one of <12> to <23> has a molecular orientation ratio (MOR) of 1 to 1.1, preferably 1 to 1.08, more preferably 1 to 1.06, and even more preferably 1 to 1.04, as measured by a microwave orientation meter.

<25> The liquid crystal polyester film described in any one of <12> to <24> above has a linear expansion coefficient of 0 ppm/°C to 57 ppm/°C, preferably 10 ppm/°C to 45 ppm/°C, and more preferably 20 ppm/°C to 40 ppm/°C, obtained at a temperature range of 50 to 100°C at a heating rate of 5°C/min.

<26> The liquid crystal polyester film described in any one of <12> to <25> above, wherein the water absorption as measured based on JIS K7209 is 0.05% to 0.8% by mass, preferably 0.1% to 0.5% by mass, more preferably 0.15% to 0.4% by mass, and further preferably 0.15% to 0.3% by mass.

<27> A laminate comprising a metal layer and the liquid crystal polyester film according to any one of <12> to <26> laminated on the metal layer.

<28> A laminate comprising a metal layer and a liquid crystal polyester film formed by applying the liquid crystal polyester liquid composition according to any one of <1> to <11> above onto the metal layer.

<29> The laminate according to <28>, wherein the liquid crystal polyester film has a thickness of 5 to 50 μm, preferably 7 to 40 μm, more preferably 10 to 33 μm, and even more preferably 15 to 30 μm.

<30> The laminate described in <28> or <29>, wherein the metal layer is copper foil, and the peel strength (90° peel strength) of the single-sided copper-clad laminate of the liquid crystal polyester film measured by peeling off the copper foil in the direction of 90° at a peeling speed of 50 mm/min is 6.5 N/cm to 10.0 N/cm, preferably 7.5 N/cm to 9.8 N/cm, and more preferably 7.9 N/cm to 9.0 N/cm.

<31> The laminate according to any one of <28> to <30>, wherein the relative dielectric constant of the liquid crystal polyester film at a frequency of 1 GHz is 2.3 to 3.1, preferably 2.4 to 3.0, more preferably 2.5 to 2.9, and even more preferably 2.5 to 2.8.

<32> The laminate described in any one of <28> to <31> above, wherein the dielectric loss tangent of the liquid crystal polyester film at a frequency of 1 GHz is 0.0003 to 0.005, preferably 0.0005 to 0.004, more preferably 0.0007 to 0.003, further preferably 0.0007 to 0.002, and particularly preferably 0.0007 to 0.0015.

<33> The laminate described in any one of <28> to <32>, wherein the molecular orientation degree (MOR) of the liquid crystal polyester film measured by a microwave orientation meter is 1 to 1.1, preferably in the range of 1 to 1.08, more preferably 1 to 1.06, and even more preferably 1 to 1.04.

<34> The laminate described in any one of <28> to <33> above, wherein the linear expansion coefficient of the liquid crystal polyester film measured at a temperature range of 50 to 100°C at a heating rate of 5°C/min is 0 ppm/°C to 57 ppm/°C, preferably 10 ppm/°C to 45 ppm/°C, and more preferably 20 ppm/°C to 40 ppm/°C.

<35> The laminate described in any one of <28> to <34>, wherein the water absorption of the liquid crystal polyester film measured based on JIS K7209 is 0.05% by mass to 0.8% by mass, preferably 0.1% by mass to 0.5% by mass, more preferably 0.15% by mass to 0.4% by mass, and further preferably 0.15% by mass to 0.3% by mass.

<36> A method for producing a liquid crystal polyester film, comprising: coating a liquid crystal polyester liquid composition described in any one of <1> to <11> on a support, removing the aprotic solvent (S) from the liquid crystal polyester liquid composition, and performing a heat treatment to obtain a liquid crystal polyester film.

Example

Next, the present invention will be described in more detail with reference to Examples, but the present invention is not limited to the following Examples.

<Measurement method>

[Determination of melting point of fluorine-containing resin]

The melting point of the fluorine-containing resin was measured as the value of the endothermic peak of differential scanning calorimetry (DSC) in accordance with JIS K 6935.

[Measurement of crystallite size of fluorine-containing resin]

Wide angle X-ray scattering (WAXS) measurement was performed using NanoViewer manufactured by Rigaku Corporation.

The fluorine-containing resin powder sample was sandwiched between bag-shaped Kapton films and the X-ray beam size was adjusted to be smaller than the sample size. The wavelength of the X-ray was set to The measurement was carried out in the range of diffraction angle 2θ=5° to 30°.

For the fluorine-containing resin powder sample, X-rays were irradiated in the thickness direction of the Kapton film, and the transmission X-ray intensity measurement and WAXS measurement were performed to obtain the transmission X-ray intensity _AS and the WAXS scattering intensity _IS . The transmission X-ray intensity measurement and WAXS measurement were performed under the same conditions except that the fluorine-containing resin powder was not included, and the background transmission X-ray intensity _AB and WAXS scattering intensity I _B were obtained. The transmission X-ray intensity correction and background subtraction were performed according to the following formula (1), and the corrected WAXS scattering intensity I _C was obtained.

I _C =I _S / _AS -I _B / _AB (1)

The crystallite size was measured by X-ray diffraction as follows.

Crystallite size of fluorine-containing resin powder The half-value width (β) of the scattering intensity at the diffraction peak of the Debye ring obtained by wide-angle X-ray diffraction measurement (a diffraction peak having a peak in the range of diffraction angle 2θ=17.93±0.2°) was calculated by the Scherrer equation of the following equation (2).

D＝K·λ/βcosθ (2)

Where D is the crystallite size, λ is the measured X-ray wavelength, β is the half-peak width (radians), θ is the diffraction angle, and K is the Scherrer constant (0.94).

[Measurement of Flow Initiation Temperature of Liquid Crystalline Polyester]

Using a flow tester ("CFT-500" manufactured by Shimadzu Corporation), about 2 g of the liquid crystal polyester was filled in a cylinder equipped with a die having a nozzle having an inner diameter of 1 mm and a length of 10 mm, and the liquid crystal polyester was melted while being heated at a rate of 4°C/min under a load of 9.8 MPa (100 kg/cm ² ), extruded from the nozzle, and the temperature at which a viscosity of 4800 Pa·s (48000 P) was measured.

[Measurement of volume average particle size of PFA particles]

The volume average particle size of PFA was measured in a wet manner using a scattering type particle size distribution measuring apparatus ("LA-950V2" manufactured by Horiba, Ltd.) with water as a dispersion medium.

[Viscosity measurement of liquid crystal polyester solution]

The solution viscosity of the liquid crystal polyester solution was measured under the following measurement conditions using a B-type viscometer ("TV-22" manufactured by Toki Sangyo Co., Ltd.).

Measurement conditions: temperature 23°C, rotor speed 20 rpm

[Determination of peel strength of single-sided copper-clad laminate of liquid crystal polyester film]

The single-sided copper-clad laminate with a liquid crystal polyester film was cut into strips with a width of 10 mm to make three test pieces. For each test piece, the liquid crystal polyester film was fixed and the peel strength (90° peel strength) of the single-sided copper-clad laminate with a liquid crystal polyester film was measured by peeling off the copper foil in the direction of 90° at a peeling speed of 50 mm/min. The average value of the three test pieces was then calculated.

[Measurement of Linear Expansion Coefficient of Liquid Crystalline Polyester Film]

The linear expansion coefficient was measured at a temperature increase rate of 5° C./min from 50° C. to 100° C. using a thermomechanical analyzer (manufactured by Rigaku Corporation, model: TMA8310).

[Measurement of relative dielectric constant and dielectric loss tangent of liquid crystal polyester film]

The copper foil of the single-sided copper-clad plate of the liquid crystal polyester film was etched and removed using a ferric chloride solution. The obtained single-layer liquid crystal polyester film was melted at 350°C using a flow tester ("CFT-500" of Shimadzu Corporation), and then cooled and solidified to produce a tablet with a diameter of 1 cm and a thickness of 0.5 cm. For the obtained tablet, the relative dielectric constant and dielectric loss tangent at 1 GHz were measured under the following conditions.

·Measurement method: Capacitance method (device: impedance analyzer (manufactured by Agilent Technologies, model: E4991A))

Electrode model: 16453A

·Measurement environment: 23℃, 50%RH

Applied voltage: 1V

[Measurement of water absorption of liquid crystal polyester film]

The water absorption of the liquid crystal polyester films of Examples 1 to 10 and Comparative Example 1 was measured in accordance with JIS K 7209.

[Production Example of Liquid Crystalline Polyester (A)]

940.9 g (5.0 mol) of 6-hydroxy-2-naphthoic acid, 377.9 g (2.5 mol) of 4'-hydroxyacetanilide, 415.3 g (2.5 mol) of isophthalic acid and 867.8 g (8.4 mol) of acetic anhydride were added to a reactor equipped with a stirring device, a torque meter, a nitrogen inlet pipe, a thermometer and a reflux cooler, and the gas in the reactor was replaced with nitrogen. Then, the temperature was raised from room temperature to 140°C for 60 minutes while stirring under a nitrogen flow, and refluxed at 140°C for 3 hours. Then, while distilling off the by-product acetic acid and unreacted acetic anhydride, the temperature was raised from 150°C to 300°C for 5 hours, maintained at 300°C for 30 minutes, and then the contents were taken out of the reactor and cooled to room temperature. The obtained solid material was crushed with a pulverizer to obtain a powdered liquid crystal polyester (A1). The flow starting temperature of the liquid crystal polyester (A1) was 193.3°C.

Liquid crystal polyester (A1) was heated from room temperature to 160°C in a nitrogen atmosphere for 2 hours and 20 minutes, then heated from 160°C to 180°C for 3 hours and 20 minutes, and kept at 180°C for 5 hours to perform solid phase polymerization, and then cooled and pulverized using a pulverizer to obtain a powdered liquid crystal polyester (A2). The flow initiation temperature of the liquid crystal polyester (A2) was 220°C.

Liquid crystal polyester (A2) was heated from room temperature to 180°C in a nitrogen atmosphere for 1 hour and 25 minutes, then heated from 180°C to 255°C for 6 hours and 40 minutes, and maintained at 255°C for 5 hours to perform solid phase polymerization, and then cooled to obtain a powdery liquid crystal polyester (A). The flow initiation temperature of the liquid crystal polyester (A) was 302°C.

[Preparation of Liquid Crystalline Polyester Solution]

8 parts by mass of the liquid crystal polyester (A) was added to 92 parts by mass of N-methylpyrrolidone (boiling point (1 atmosphere) 204° C.), and stirred at 140° C. for 4 hours under a nitrogen atmosphere to prepare a liquid crystal polyester solution (A). The viscosity of the liquid crystal polyester solution was 955 mPa·s.

[Preparation of liquid composition]

(Examples 1 to 5)

To the liquid crystal polyester solution obtained above, a fluorine-containing resin PFA (EA2000 manufactured by AGC, melting point: 300.82°C, crystallite size: 2.28×10 ^-8 m, volume average particle size: 2 μm) was added in an amount (solid content) shown in Table 1, and liquid compositions of Examples 1 to 5 were prepared using a stirring degassing apparatus (Ar-500 manufactured by Shinki Corporation).

(Comparative Examples 2 to 4)

To the liquid crystal polyester solution obtained above, silicon dioxide (SO-C2 manufactured by Yaduma Technology, average particle size recorded in the catalog: 0.5 μm) was added in the amount (solid content) shown in Table 2, and liquid compositions of Comparative Examples 2 to 4 were prepared using a stirring degassing apparatus (Ar-500 manufactured by Shinki Co., Ltd.).

(Examples 6 to 10)

To the liquid crystal polyester solution obtained above, fluorine-containing resin PFA (EA2000 manufactured by AGC, melting point: 300.82°C, crystallite size: 2.28×10 ^-8 m, volume average particle size: 2 μm) and silica (SO-C2 manufactured by Yaduma Technology, average particle size listed in the catalog: 0.5 μm) were added in the amounts (solid content) shown in Table 3, and liquid compositions of Examples 6 to 10 were prepared using a stirring degassing apparatus (Ar-500 manufactured by Shinki Co., Ltd.).

(Comparative Examples 5 to 10)

Fluorine-containing resin PFA (9738-JN manufactured by Chemours, Mitsui, melting point: 308.68°C, crystallite size: 2.97× ^10-8 m) and silica (SO-C2 manufactured by Yaduma Technology, average particle size listed in the catalog: 0.5 μm) were added to the liquid crystal polyester solution obtained above in the amounts (solid content) shown in Table 4, and liquid compositions of Comparative Examples 5 to 10 were prepared using a stirring degassing device (Ar-500 manufactured by Shinki Co., Ltd.). PFA (9738-JN manufactured by Chemours, Mitsui) was sieved before addition to adjust the average particle size to 10 μm.

[Manufacture of Liquid Crystal Polyester Film]

The liquid compositions of Examples 1 to 10, the liquid compositions of Comparative Examples 2 to 10, and the liquid crystal polyester solution (A) to which no microparticles were added (Comparative Example 1) were cast onto the rough surface of a copper foil (JX EFL-V2 manufactured by JX Metal, with a thickness of 12 μm) using a film applicator with a micrometer (manufactured by TESTER Industry Co., Ltd.) and an automatic coating device (manufactured by TESTER Industry Co., Ltd., model: PI-1210) so that the thickness of the cast film became the thickness shown in Tables 1 to 4, respectively, and then dried at 40° C. and normal pressure (1 atmosphere) for 4 hours to partially remove the solvent from the cast film. In addition, in the case of performing two castings, the second casting and drying were performed after the first casting and drying under the above-mentioned drying conditions. The dried film with copper foil was further subjected to a heat treatment in a hot oven under a nitrogen atmosphere, where the temperature was raised from room temperature to 310°C over 4 hours and maintained at this temperature for 2 hours, to obtain a film with copper foil (liquid crystal polyester film single-sided copper clad laminate) having films of each embodiment or comparative example formed by each solution or liquid composition of Examples 1 to 10 and Comparative Examples 1 to 9. For the film with copper foil, the peel strength as an indicator of the adhesion strength with the copper foil was measured; for the single-layer liquid crystal polyester film after the copper foil was etched away from the film with copper foil, the linear expansion coefficient (CTE), water absorption, relative dielectric constant and dielectric loss tangent were measured. The results are shown in Tables 1 to 4.

The liquid crystal polyester films of Examples 1 to 10 had higher peel strength values than the liquid crystal polyester films of Comparative Examples 5 to 10, and were excellent in adhesion strength to copper foil.

This can be considered to be because the liquid crystal polyester films of Examples 1 to 10 are formed from a liquid crystal polyester liquid composition containing a fluorine-containing resin PFA (EA2000) having a melting point below 305°C, while the liquid crystal polyester films of Comparative Examples 5 to 10 are formed from a liquid crystal polyester liquid composition containing a fluorine-containing resin PFA (9738-JN) having a higher melting point.

The liquid crystal polyester films of Examples 1 to 5 have the same peel strength as that of the liquid crystal polyester film of Comparative Example 1, while having improved water absorption and dielectric properties such as relative dielectric constant and dielectric loss tangent.

This shows that the liquid crystal polyester film formed from a liquid crystal polyester liquid composition containing both a liquid crystal polyester (A) and a fluorine-containing resin (B) having a melting point of 305° C. or less has a good balance among peel strength, water resistance and dielectric properties and has excellent properties.

The liquid crystal polyester films of Comparative Examples 2 to 4 in which silicon dioxide was added to the liquid crystal polyester (A) tended to have good CTE values, but the degree of improvement in the values of dielectric properties was insufficient.

The liquid crystal polyester films of Examples 6 to 10 tend to have a more suppressed increase in CTE values compared to the liquid crystal polyester films of Examples 1 to 5. In addition, the liquid crystal polyester films of Examples 6 to 10 have improved dielectric constants and dielectric loss tangent values while having the same peel strength as those of Examples 1 to 2 and Comparative Examples 2 to 4, which have lower CTE values. In addition, the water absorption value is also good.

This shows that the liquid crystal polyester film formed by the liquid crystal polyester liquid composition containing a liquid crystal polyester (A) and a fluorine-containing resin (B) with a melting point below 305°C and further containing silicon dioxide has a good balance in CTE, water resistance, peel strength and dielectric properties and has particularly excellent properties.

Each configuration and combination thereof in each embodiment is an example, and addition, omission, substitution and other changes of configurations may be made without departing from the gist of the present invention. In addition, the present invention is not limited to each embodiment, but only to the scope of claims.

Explanation of symbols

10 liquid crystal polyester film, 12 support, 13 metal layer, 20, 21 laminate, 22 laminate precursor, 30 liquid crystal polyester liquid composition, 40 liquid crystal polyester film precursor.

Claims (15)

1. A liquid-crystalline polyester composition comprising a liquid-crystalline polyester (A) soluble in an aprotic solvent, an aprotic solvent (S), a fluorine-containing resin (B) having a melting point of 305 ℃ or lower, and an inorganic filler (C),

The crystallite size of the fluorine-containing resin (B) is 2.9X10 ^-8 m or less,

The liquid-crystalline polyester (A) is contained in an amount of 25 to 50% by mass, the fluorine-containing resin (B) is contained in an amount of 25 to 50% by mass, and the inorganic filler (C) is contained in an amount of 11.2 to 50% by mass, based on the total solid content of the liquid-crystalline polyester liquid composition.

2. The liquid-crystalline polyester liquid composition according to claim 1, wherein the liquid-crystalline polyester (a) contains an amide bond.

3. The liquid-crystalline polyester liquid composition according to claim 1 or 2, wherein the liquid-crystalline polyester (A) comprises a structural unit represented by the following formula (A1), a structural unit represented by the following formula (A2) and a structural unit represented by the following formula (A3),

(A1)-O-Ar1-CO-

(A2)-CO-Ar2-CO-

(A3)-X-Ar3-Y-

Wherein Ar1 represents 1, 4-phenylene, 2, 6-naphthalenediyl or 4,4' -biphenylene, ar2 represents 1, 4-phenylene, 1, 3-phenylene or 2, 6-naphthalenediyl, ar3 represents a1, 4-phenylene group or a1, 3-phenylene group, X represents-NH-, Y represents-O-or-NH-.

4. The liquid-crystalline polyester composition according to claim 3, wherein Ar1 is 2, 6-naphthalenediyl, ar2 is 1, 3-phenylene, ar3 is 1, 4-phenylene, and Y is-O-.

5. The liquid-crystalline polyester liquid composition according to claim 1 or 2, wherein the fluorine-containing resin (B) is contained in an amount of 25 to 40% by mass relative to the total content of solid components of the liquid-crystalline polyester liquid composition.

6. The liquid-crystalline polyester liquid composition according to claim 5, wherein the content of the liquid-crystalline polyester (A) is 25 to 40% by mass and the content of the inorganic filler (C) is 20 to 50% by mass, based on the total content of solid components of the liquid-crystalline polyester liquid composition.

7. The liquid crystalline polyester liquid composition according to claim 5, wherein the inorganic filler (C) is a silica filler.

8. The liquid-crystalline polyester liquid composition according to claim 1 or 2, wherein the fluorine-containing resin (B) is at least one fluorine-containing resin selected from tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA), polytetrafluoroethylene (PTFE), tetrafluoroethylene-hexafluoropropylene copolymer (FEP), polychlorotrifluoroethylene (PCTFE), ethylene-tetrafluoroethylene copolymer, ethylene-chlorotrifluoroethylene copolymer and polyvinylidene fluoride (PVDF).

9. The liquid-crystalline polyester liquid composition according to claim 1 or 2, wherein the content of the liquid-crystalline polyester (a) is 0.01 to 100 parts by mass with respect to 100 parts by mass of the aprotic solvent (S).

10. Liquid crystalline polyester liquid composition according to claim 1 or 2, wherein the aprotic solvent (S) is N-methylpyrrolidone.

11. A liquid crystal polyester film comprising a liquid crystal polyester (A), a fluorine-containing resin (B) having a melting point of 305 ℃ or lower, and an inorganic filler (C),

The liquid crystalline polyester (A) contains an amide bond,

The crystallite size of the fluorine-containing resin (B) is 2.9X10 ^-8 m or less,

The content of the liquid crystal polyester (A) is 25 to 50% by mass, the content of the fluorine-containing resin (B) is 25 to 50% by mass, and the content of the inorganic filler (C) is 11.2 to 50% by mass, relative to the total content of the liquid crystal polyester film.

12. The liquid-crystalline polyester film according to claim 11, wherein the liquid-crystalline polyester (A) comprises a structural unit represented by the following formula (A1), a structural unit represented by the following formula (A2) and a structural unit represented by the following formula (A3),

(A1)-O-Ar1-CO-

(A2)-CO-Ar2-CO-

(A3)-X-Ar3-Y-

Wherein Ar1 represents 1, 4-phenylene, 2, 6-naphthalenediyl or 4,4' -biphenylene, ar2 represents 1, 4-phenylene, 1, 3-phenylene or 2, 6-naphthalenediyl, ar3 represents a1, 4-phenylene group or a1, 3-phenylene group, X represents-NH-, Y represents-O-or-NH-.

13. A laminate comprising a metal layer and the liquid crystal polyester film according to claim 11 or 12 laminated on the metal layer.

14. A laminate comprising a metal layer and a liquid crystal polyester film formed by coating the liquid crystal polyester liquid composition according to any one of claims 1 to 10 on the metal layer.

15. A method for producing a liquid crystal polyester film, comprising: a liquid-crystalline polyester film obtained by applying the liquid-crystalline polyester composition according to any one of claims 1 to 10 to a support, removing the aprotic solvent (S) from the liquid-crystalline polyester composition, and performing a heat treatment.