Liquid Crystal Polyester Liquid Composition, Liquid Crystal Polyester Film, Laminate, and Method for Producing Liquid Crystal Polyester Film

Abstract

The present invention relates to a liquid crystalline polyester liquid composition that comprises: a liquid crystalline polyester (A) which is soluble in aprotic solvents; an aprotic solvent (S); and a fluororesin (B) which has a melting point of 305°C or lower.

Description

Technical Field

[0001] The present invention relates to a liquid crystal polyester composition, a liquid crystal polyester film, a laminate, and a method for producing a liquid crystal polyester film. This application claims priority based on Japanese Patent Application No. 2020-088885 filed in Japan on May 21, 2020, and incorporates its content herein by reference.

Background Art

[0002] An insulating material is used for a printed circuit board on which electronic components are mounted. In recent years, due to the development of communication systems and the like, further improvement in physical properties such as dielectric properties of the insulating material has been desired. As a method for improving the dielectric properties of an insulating material, using a fluororesin having good dielectric properties has been carried out. For example, according to Patent Document 1, a sheet formed after melt-kneading a resin composition containing a fluoropolymer having a carbonyl group-containing group and a liquid crystal polymer or the like is said to be excellent in electrical properties, impact resistance, and mechanical strength.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, an insulating material containing a fluororesin has a problem that the adhesion strength to a copper foil decreases.

[0005] The present invention has been made to solve the above problems, and an object thereof is to provide a liquid crystal polyester liquid composition capable of producing a film excellent in adhesion strength to a 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, which are excellent in adhesion strength to a copper foil and dielectric properties. **Means for Solving the Problems**

[0006] As a result of intensive studies to solve the above problems, the present inventors have found that by using a liquid crystal polyester soluble in an aprotic solvent, a film-forming method capable of producing a film with excellent isotropy can be applied. Furthermore, by using a fluororesin having a melting point of 305°C or lower in combination with the liquid crystal polyester, it is possible to improve the dielectric properties while maintaining the adhesion strength to the copper foil, and thus the present invention has been completed. That is, the present invention has the following aspects.

[0007] [1] A liquid crystal polyester liquid composition containing a liquid crystal polyester (A) soluble in an aprotic solvent, an aprotic solvent (S), and a fluororesin (B) having a melting point of 305°C or lower. [2] The liquid crystal polyester liquid composition according to [1], wherein the liquid crystal polyester (A) contains an amide bond. [3] The liquid crystal polyester liquid composition according to [1] or [2], 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). The liquid crystal polyester liquid composition according to [1] or [2] above. (A1) -O-Ar1-CO- (A2) -CO-Ar2-CO- (A3) -X-Ar3-Y- (In the formula, Ar1 represents a 1,4-phenylene group, a 2,6-naphthalenediyl group, or a 4,4'-biphenylene group, Ar2 represents a 1,4-phenylene group, a 1,3-phenylene group, or a 2,6-naphthalenediyl group, Ar3 represents a 1,4-phenylene group or a 1,3-phenylene group, X represents -NH-, and Y represents -O- or -NH-.) [4] The liquid crystal polyester liquid composition according to [3], wherein Ar1 is a 2,6-naphthalenediyl group, Ar2 is a 1,3-phenylene group, Ar3 is a 1,4-phenylene group, and Y is -O-. [5] The liquid crystal polyester liquid composition according to any one of [1] to [4], wherein the content ratio of the liquid crystal polyester (A) is 10% by mass or more and 90% by mass or less, and the content ratio of the fluororesin (B) is 10% by mass or more and 90% by mass or less, based on the total content of the solid components of the liquid crystal polyester liquid composition. [6] The liquid crystal polyester liquid composition according to any one of [1] to [5], further containing an inorganic filler (C). [7] The liquid crystal polyester liquid composition according to [6], wherein the content ratio of the liquid crystal polyester (A) is 25% by mass or more and 40% by mass or less, the content ratio of the fluororesin (B) is 25% by mass or more and 40% by mass or less, and the content ratio of the inorganic filler (C) is 20% by mass or more and 50% by mass or less, based on the total content of the solid components of the liquid crystal polyester liquid composition. [8] The liquid crystal polyester liquid composition according to [6] or [7], wherein the inorganic filler (C) is a silica filler. [9] The liquid crystal polyester liquid composition according to any one of [1] to [8], wherein the crystallite size of the fluororesin (B) is 2.9×10 -8 m or less.

[10] The liquid crystal polyester liquid composition according to any one of [1] to [9], wherein the fluororesin (B) is at least one fluororesin selected from the group consisting of 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 composition according to any one of [1] to

[10] , wherein the content of the liquid crystal polyester (A) is 0.01 part by mass or more and 100 parts by mass or less with respect to 100 parts by mass of the aprotic solvent (S).

[12] The liquid crystal polyester composition according to any one of [1] to

[11] , wherein the aprotic solvent (S) is N-methylpyrrolidone.

[13] Containing a liquid crystal polyester (A) and a fluororesin (B) having a melting point of 305°C or lower. The liquid crystal polyester film, wherein the liquid crystal polyester (A) contains an amide bond.

[14] 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). The liquid crystal polyester film according to

[13] . (A1) -O-Ar1-CO- (A2) -CO-Ar2-CO- (A3) -X-Ar3-Y- (In the formula, Ar1 represents a 1,4-phenylene group, a 2,6-naphthalenediyl group, or a 4,4'-biphenylene group; Ar2 represents a 1,4-phenylene group, a 1,3-phenylene group, or a 2,6-naphthalenediyl group; Ar3 represents a 1,4-phenylene group or a 1,3-phenylene group; X represents -NH-; Y represents -O- or -NH-.)

[15] A laminate including a metal layer and the liquid crystal polyester film according to

[13] or

[14] laminated on the metal layer.

[16] A laminate including a metal layer and a liquid crystal polyester film formed by coating the liquid crystal polyester composition according to any one of [1] to

[12] on the metal layer.

[17] A method for producing a liquid crystal polyester film, including coating the liquid crystal polyester composition according to any one of [1] to

[12] on a support, removing the aprotic solvent (S) from the liquid crystal polyester composition, and performing heat treatment to obtain a liquid crystal polyester film.

Advantages of the Invention

[0008] According to the present invention, a liquid crystal polyester composition capable of producing a film excellent in adhesion strength to a copper foil and dielectric properties can be provided. Further, according to the present invention, a liquid crystal polyester film, a laminate, and a method for producing a liquid crystal polyester film, which are excellent in adhesion strength to a copper foil and dielectric properties, can be provided.

Brief Description of the Drawings

[0009]

Figure 1

Figure 2

Figure 3A

Figure 3B

Figure 3C

Figure 3D

Modes for Carrying Out the Invention

[0010] Hereinafter, embodiments of the liquid crystal polyester composition, liquid crystal polyester film, laminate, and method for producing a liquid crystal polyester film of the present invention will be described.

[0011] ≪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 fluororesin (B) having a melting point of 305°C or lower. In this specification, the "liquid composition" means a solution or dispersion that is liquid at normal temperature and pressure (25°C, 1 atm). In the case of a dispersion, it means a dispersion in which the dispersion medium is liquid at normal temperature and pressure (25°C, 1 atm). A dispersion means a substance in which solid components that are not dissolved in the solution are dispersed. In this specification, the "solid content" refers to components other than the solvent contained in the liquid composition. Examples of the solid content to be dispersed include the above-mentioned fluororesin (B) and the inorganic filler (C) described later. Examples of the solvent include the aprotic solvent (S) described later.

[0012] In the liquid composition of the embodiment, the ratio of the content of the solid content to the total mass of the liquid composition is not particularly limited and may be 0.5% by mass or more, may be 0.5% by mass or more and 80% by mass or less, may be 1% by mass or more and 70% by mass or less, or may be 5% by mass or more and 50% by mass or less.

[0013] Hereinafter, the liquid crystal polyester liquid composition according to an embodiment of the present invention will also be simply referred to as the "liquid composition" of the embodiment.

[0014] <Component (A)> Component (A) is a liquid crystal polyester soluble in an aprotic solvent (S). Component (A) also contributes to increasing the adhesion strength with the metal foil and enhancing the mechanical strength when the liquid composition of the embodiment is formed into a film on the metal foil.

[0015] The liquid crystal polyester is a liquid crystal polyester that exhibits liquid crystallinity in a molten state and preferably melts at a temperature of 450°C or lower. 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 an all-aromatic liquid crystal polyester having only structural units derived from aromatic compounds as raw material monomers. In this specification, "derived from" means that for the raw material monomer to polymerize, the chemical structure of the functional group contributing to the polymerization changes, and no other structural changes occur.

[0016] The solubility of the liquid crystal polyester in the aprotic solvent (S) can be confirmed by conducting the following test.

[0017] · Test method 5 parts by mass of the liquid crystal polyester is stirred in 95 parts by mass of the aprotic solvent at a temperature of 180 °C for 6 hours under stirring conditions of 200 rpm using an anchor blade, and then cooled to room temperature. Next, after filtration using a membrane filter with a pore size of 5 μm and a pressure-type filter, the residue on the membrane filter is confirmed. At this time, if no solid matter is confirmed, it is determined to be soluble in the aprotic solvent. If solid matter is confirmed, it is determined to be insoluble in the aprotic solvent. The solid matter can be confirmed by microscopic observation.

[0018] The liquid crystal polyester (A) preferably contains an amide bond. By the liquid crystal polyester (A) containing an amide bond, the adhesion strength with the copper foil when laminated with the copper foil as a film can be improved.

[0019] As an example of the liquid crystal polyester (A) containing an amide bond and soluble in an aprotic solvent, those containing 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) can be exemplified.

[0020] (A1) -O-Ar1-CO- (A2) -CO-Ar2-CO- (A3) -X-Ar3-Y- (In the formula, Ar1 represents a 1,4-phenylene group, a 2,6-naphthalenediyl group, or a 4,4'-biphenylene group, Ar2 represents a 1,4-phenylene group, a 1,3-phenylene group, or a 2,6-naphthalenediyl group, Ar3 represents a 1,4-phenylene group or a 1,3-phenylene group, X represents -NH-, and Y represents -O- or -NH-.)

[0021] In this embodiment, in particular, it is preferable that the above Ar2 is a 1,3-phenylene group. When Ar2 is a 1,3-phenylene group, the solubility in an aprotic solvent becomes even better. This is presumably because when Ar2 is a 1,3-phenylene group, a bent structure is introduced into the polymer.

[0022] In this embodiment, from the viewpoint that the solubility in an aprotic solvent is good and the adhesion strength and dielectric properties with a copper foil are likely to be exhibited when laminated with the copper foil as a film, it is preferable that the above Ar1 is a 2,6-naphthalenediyl group, the above Ar2 is a 1,3-phenylene group, the above Ar3 is a 1,4-phenylene group, and the above Y is -O-.

[0023] When the liquid crystal polyester has all types of structural units represented by the above formulas (A1) to (A3), the preferable content ratios of the respective structural units in the liquid crystal polyester can be exemplified as follows.

[0024] The content of the structural unit represented by the above formula (A1) is preferably 30 mol% or more and 80 mol% or less, more preferably 40 mol% or more and 70 mol% or less, and even more preferably 45 mol% or more and 65 mol% or less with respect to the total content of all structural units constituting the liquid crystal polyester (A) (by dividing the mass of each structural unit constituting the liquid crystal polyester by the formula weight of each structural unit to obtain the equivalent amount (mol) of the amount of substance of each structural unit and summing them up). When the content of the structural unit (A1) is below the above upper limit value, the solubility in the solvent tends to be good, and when it is above the above lower limit value, the liquid crystallinity tends to be good.

[0025] The content of the structural unit represented by the above formula (A2) is preferably 10 mol% or more and 35 mol% or less, more preferably 15 mol% or more and 30 mol% or less, and even more preferably 17.5 mol% or more and 27.5 mol% or less with respect to the total content of all the structural units constituting the liquid crystal polyester (A). When the content of the structural unit (A2) is not more than the above upper limit value, the liquid crystallinity tends to be good, and when it is not less than the above lower limit value, the solubility in the solvent tends to be good.

[0026] The content of the structural unit represented by the above formula (A3) is preferably 10 mol% or more and 35 mol% or less, more preferably 15 mol% or more and 30 mol% or less, and even more preferably 17.5 mol% or more and 27.5 mol% or less with respect to the total content of all the structural units constituting the liquid crystal polyester (A). When the content of the structural unit (A3) is not more than the above upper limit value, the liquid crystallinity tends to be good, and when it is not less than the above lower limit value, the solubility in the solvent tends to be good.

[0027] Moreover, in the liquid crystal polyester (A), the content of the structural unit (A2) and the content of the structural unit (A3) are preferably equal. However, when the contents are different, the difference between the content of the structural unit (A2) and the content of the structural unit (A3) is desirably 10 mol% or less. The degree of polymerization of the liquid crystal polyester can also be controlled by this difference.

[0028] Regarding the preferable content ratio of each structural unit in the liquid crystal polyester (A), with respect to the total content of all the structural units constituting the liquid crystal polyester (A), the content of the structural unit represented by the above formula (A1) is preferably 30 mol% or more and 80 mol% or less, the content of the structural unit represented by the above formula (A2) is preferably 10 mol% or more and 35 mol% or less, and the content of the structural unit represented by the above formula (A3) is preferably 10 mol% or more and 35 mol% or less.

[0029] The preferable content ratio of each structural unit in the liquid crystal polyester (A) is such that, with respect to the total content of all the structural units constituting the liquid crystal polyester (A), the content of the structural unit represented by the above formula (A1) is more preferably 40 mol% or more and 70 mol% or less, the content of the structural unit represented by the above formula (A2) is more preferably 15 mol% or more and 30 mol% or less, and the content of the structural unit represented by the above formula (A3) is more preferably 15 mol% or more and 30 mol% or less.

[0030] The preferable content ratio of each structural unit in the liquid crystal polyester (A) is such that, with respect to the total content of all the structural units constituting the liquid crystal polyester (A), the content of the structural unit represented by the above formula (A1) is even more preferably 45 mol% or more and 65 mol% or less, the content of the structural unit represented by the above formula (A2) is even more preferably 17.5 mol% or more and 27.5 mol% or less, and the content of the structural unit represented by the above formula (A3) is even more preferably 17.5 mol% or more and 27.5 mol% or less.

[0031] 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. Instead of the above-described structural units, the component (A) may use an ester or amide-forming derivative of the above-described structural units.

[0032] Examples of the ester-forming derivative of the carboxylic acid include those in which the carboxy group is a highly reactive derivative such as an acid chloride or an acid anhydride that promotes the reaction for forming a polyester, and those in which the carboxy group forms an ester with alcohols, ethylene glycol, etc. that produce a polyester by transesterification. Examples of the ester-forming derivative of the phenolic hydroxyl group include those in which the phenolic hydroxyl group forms an ester with carboxylic acids. Examples of the amide-forming derivative of the amino group include those in which the amino group forms an amide with carboxylic acids.

[0033] Examples of the structural unit of the component (A) used in the present embodiment include, but are not limited to, the following.

[0034] Examples of the structural unit represented by the formula (A1) include structural units derived from p-hydroxybenzoic acid, 6-hydroxy-2-naphthoic acid, 4-hydroxy-4'-biphenylcarboxylic acid, etc., and two or more of the above structural units may be included in all the structural units. Among these structural units, the structural unit derived from 6-hydroxy-2-naphthoic acid is preferable.

[0035] Examples of the structural unit represented by the formula (A2) include structural units derived from terephthalic acid, isophthalic acid, 2,6-naphthalenedicarboxylic acid, etc., and two or more of the above structural units may be included in all the structural units. Among these structural units, from the viewpoint of solubility in a solvent, the structural unit derived from isophthalic acid is preferable.

[0036] Examples of the structural unit represented by the formula (A3) include structural units derived from 3-aminophenol, 4-aminophenol, 1,4-phenylenediamine, 1,3-phenylenediamine, 4-aminobenzoic acid, 4'-hydroxyacetanilide, etc., and two or more of the above structural units may be included in all the structural units. Among these structural units, from the viewpoint of reactivity, the structural unit derived from 4-aminophenol or 4'-hydroxyacetanilide is preferable.

[0037] The liquid crystal polyester soluble in an aprotic solvent may be a liquid crystal polyester containing a structural unit derived from 4'-hydroxyacetanilide. Examples of the liquid crystal polyester soluble in an aprotic solvent include 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.

[0038] The method for producing the component (A) used in the present embodiment is not particularly limited. For example, an aromatic hydroxy acid corresponding to the structural unit (A1), an aromatic amine having a phenolic hydroxyl group corresponding to the structural unit (A3), and an acylating agent obtained by acylating the phenolic hydroxyl group and amino group of an aromatic diamine with an excessive amount of a fatty acid anhydride, and then subjecting the obtained acylating agent and an aromatic dicarboxylic acid corresponding to the structural unit (A2) to transesterification - amidation (polycondensation) and melt polymerization (see JP - A - 2002 - 220444 and JP - A - 2002 - 146003).

[0039] In the acylation reaction, the addition amount of the fatty acid anhydride is preferably 1.0 to 1.2 fold equivalents, more preferably 1.05 to 1.1 fold equivalents, relative to the total of the phenolic hydroxyl group and the amino group. If the addition amount of the fatty acid anhydride is too small, acylating agents and raw material monomers tend to sublime during transesterification - amidation (polycondensation), and the reaction system tends to be blocked. If it is too large, the resulting liquid crystal polyester tends to be significantly colored.

[0040] The acylation reaction is preferably carried out at 130 to 180°C for 5 minutes to 10 hours, more preferably at 140 to 160°C for 10 minutes to 3 hours.

[0041] The fatty acid anhydrides used in the acylation reaction are 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. may be mentioned, and two or more of these may be used in combination. In this embodiment, acetic anhydride, propionic anhydride, butyric anhydride, or isobutyric anhydride is preferred, and more preferably acetic anhydride.

[0042] In the transesterification and amide exchange (polycondensation), it is preferable that the acyl group of the acylating agent is 0.8 to 1.2 times the equivalent of the carboxyl group.

[0043] The transesterification and amide exchange (polycondensation) are preferably carried out while raising the temperature at a rate of 0.1 to 50 °C / min up to 400 °C, and more preferably while raising the temperature at a rate of 0.3 to 5 °C / min up to 350 °C.

[0044] When the acylating agent and the carboxylic acid are subjected to transesterification and amide exchange (polycondensation), it is preferable to distill off the by-produced fatty acid and the unreacted fatty acid anhydride out of the system by evaporation or the like.

[0045] Incidentally, the acylation reaction and the transesterification and amide exchange (polycondensation) may be carried out in the presence of a catalyst. As the catalyst, those conventionally known as catalysts for the 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 mentioned. Among these catalysts, heterocyclic compounds containing two or more nitrogen atoms such as N,N-dimethylaminopyridine and N-methylimidazole are preferably used (see JP-A-2002-146003). The catalyst is usually added when monomers are introduced, and it is not always necessary to remove it even after acylation. When the catalyst is not removed, transesterification can be carried out as it is.

[0046] Polycondensation by transesterification or amidation is usually carried out by melt polymerization, but melt polymerization and solid-phase polymerization may be used in combination. For solid-phase polymerization, it is preferable to extract the polymer from the melt polymerization step, then pulverize it into powder or flake form, and then carry out the process by a known solid-phase polymerization method. Specifically, for example, there are methods such as heat treatment in a solid state at 20 to 350 °C for 1 to 30 hours in an inert atmosphere such as nitrogen. Solid-phase polymerization may be carried out while stirring or in a stationary state without stirring. By providing an appropriate stirring mechanism, the melt polymerization tank and the solid-phase polymerization tank can be made into the same reaction tank. After solid-phase polymerization, the obtained liquid crystal polyester may be pelletized and molded by a known method. The production of liquid crystal polyester can be carried out using, for example, a batch apparatus, a continuous apparatus, or the like.

[0047] (A) The content of the component may be 10% by mass or more and 90% by mass or less, may be 15% by mass or more and 50% by mass or less, or may be 25% by mass or more and 40% by mass or less with respect to the total content of the solid components of the liquid composition of the embodiment. By using the liquid composition containing the component (A) within the above numerical range, the adhesion strength and dielectric properties of the produced liquid crystal polyester film with respect to the copper foil can be easily improved.

[0048] <(S) component> (S) The component is an aprotic solvent. Aprotic solvents have the advantages of low corrosiveness and ease of handling. In this embodiment, an aprotic solvent is a solvent containing an aprotic compound. In this embodiment, examples of the aprotic solvent include halogenated solvents such as 1-chlorobutane, chlorobenzene, 1,1-dichloroethane, 1,2-dichloroethane, chloroform, 1,1,2,2-tetrachloroethane; ether solvents such as diethyl ether, tetrahydrofuran, 1,4-dioxane; ketone solvents such as acetone, cyclohexanone; ester solvents such as ethyl acetate; lactone solvents such as γ-butyrolactone; carbonate solvents such as ethylene carbonate, propylene carbonate; amine solvents such as triethylamine, pyridine; nitrile solvents such as acetonitrile, succinonitrile; amide solvents such as N,N'-dimethylformamide, N,N'-dimethylacetamide, tetramethylurea, N-methylpyrrolidone; nitro solvents such as nitromethane, nitrobenzene; sulfide solvents such as dimethyl sulfoxide, sulfolane; phosphate solvents such as hexamethylphosphoric triamide, tri-n-butyl phosphate, etc. A mixture of two or more of these may also be used.

[0049] Among these, aprotic compounds having no halogen atom are preferably used from the viewpoint of environmental impact, and solvents having a dipole moment of 3 or more and 5 or less are preferably used from the viewpoint of solubility. Specifically, amide solvents such as N,N'-dimethylformamide, N,N'-dimethylacetamide, tetramethylurea, N-methylpyrrolidone, or lactone solvents such as γ-butyrolactone are more preferably used, and N,N'-dimethylformamide, N,N'-dimethylacetamide, or N-methylpyrrolidone are even more preferably used.

[0050] In the liquid composition of the embodiment, the ratio of the content of the (S) component to the total mass of the liquid composition may be 20% by mass or more, may be 20% by mass or more and 99% by mass or less, or may be 50% by mass or more and 95% by mass or less from the viewpoint of reducing the viscosity of the liquid composition and facilitating coating on the support.

[0051] In the liquid composition of the embodiment, the content of the liquid crystal polyester (A) is preferably 0.01 part by mass or more and 100 parts by mass or less, more preferably 1 part by mass or more and 70 parts by mass or less, and still more preferably 5 parts by mass or more and 40 parts by mass or less with respect to 100 parts by mass of the aprotic solvent (S).

[0052] In the embodiment, when the content of the liquid crystal polyester (A) is within the above range, it is easy to coat a support such as a metal foil. The content of the liquid crystal polyester (A) can be appropriately adjusted within the above range according to the desired film thickness.

[0053] <Component (B)> Component (B) is a fluororesin having a melting point of 305 °C or lower. The "fluororesin" means a resin containing fluorine atoms in the molecule, and examples thereof include polymers having structural units containing fluorine atoms. Examples of the fluororesin (B) include polytetrafluoroethylene (PTFE), tetrafluoroethylene-hexafluoropropylene copolymer (FEP), polychlorotrifluoroethylene (PCTFE), ethylene-tetrafluoroethylene copolymer, ethylene-chlorotrifluoroethylene copolymer, polyvinylidene fluoride (PVDF), tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (perfluoroalkoxy alkane, PFA), and the like. The fluororesin (B) is preferably at least one fluororesin selected from the group consisting of tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (perfluoroalkoxy alkane, PFA), polytetrafluoroethylene (PTFE), tetrafluoroethylene-hexafluoropropylene copolymer (FEP), polychlorotrifluoroethylene (PCTFE), ethylene-tetrafluoroethylene copolymer, ethylene-chlorotrifluoroethylene copolymer, and polyvinylidene fluoride (PVDF). The fluororesin (B) is preferably perfluoroalkoxy alkane (PFA) having a melting point of 305 °C or lower. The liquid composition of the embodiment may contain two or more kinds of fluororesins.

[0054] By containing fluorine atoms in the molecule, the fluororesin can make the dielectric properties of the film containing the fluororesin excellent.

[0055] The melting point of the fluororesin (B) according to the embodiment is 305°C or lower, preferably 303°C or lower, and more preferably 301°C or lower.

[0056] When the melting point of the fluororesin (B) is below the above upper limit value, the characteristic of the adhesion strength between the film containing the fluororesin (B) and the copper foil can be made excellent. Although the mechanism is not clear, it is considered that the low melting point of the fluororesin reflects the low molecular weight of the fluororesin, and thus the adhesion to the copper foil is considered to be enhanced.

[0057] The lower limit value of the melting point of the fluororesin (B) according to the embodiment may be 280°C or higher, may be 290°C or higher, and may be 295°C or higher in consideration of the practicality in applications where heat resistance is required.

[0058] The upper limit value and the lower limit value of the melting point of the fluororesin (B) according to the embodiment can be freely combined. As an example of the numerical range of the melting point of the fluororesin (B), it may be 280°C or higher and 305°C or lower, may be 290°C or higher and 303°C or lower, and may be 295°C or higher and 301°C or lower.

[0059] The melting point of the fluororesin (B) shall be measured as the value of the endothermic peak of differential scanning calorimetry (DSC) in accordance with JIS K 6935.

[0060] The melting point of the fluororesin (B) can be adjusted not only by selecting the raw materials of the fluororesin but also by controlling the molecular weight of the fluororesin. The molecular weight of the fluororesin can be adjusted to a desired value by appropriately adjusting the polymerization rate, polymerization time, etc. during production.

[0061] The fluororesin (B) according to the embodiment has a crystallite size of 2.9×10 -8It is preferably m or less, more preferably 2.7×10 -8 m or less, and even more preferably 2.5×10 -8 m or less.

[0062] When the crystallite size of the fluororesin (B) is equal to or less than the above upper limit value, the adhesion strength characteristics of the film containing the fluororesin (B) with the copper foil can be made excellent. Although the mechanism is not clear, it is considered that the small crystallite size of the fluororesin reflects the low molecular weight of the fluororesin, and thus the adhesion to the copper foil is considered to be enhanced.

[0063] The lower limit value of the crystallite size of the fluororesin (B) according to the embodiment may be, for example, 2.0×10 -8 m or more, may be 2.1×10 -8 m or more, and may be 2.2×10 -8 m or more.

[0064] The upper limit value and the lower limit value of the crystallite size of the fluororesin (B) according to the embodiment can be freely combined. As an example of the numerical range of the crystallite size of the fluororesin (B), it may be 2.0×10 -8 m or more and 2.9×10 -8 m or less, may be 2.1×10 -8 m or more and 2.7×10 -8 m or less, may be 2.2×10 -8 m or more and 2.5×10 -8 m or less.

[0065] The crystallite size of the fluororesin (B) can be measured by the following method using a wide-angle X-ray scattering (WAXS) measurement device. The fluororesin powder sample is sandwiched between Kapton films in a bag shape, and the X-ray beam size is adjusted to be smaller than the size of the sample. The wavelength of the X-ray is set to λ = 1.5418 Å, and the measurement is carried out in the range of diffraction angle 2θ = 5° to 30°. For the fluororesin powder sample, X-rays were incident in the thickness direction of the Kapton film, and transmission X-ray intensity measurement and WAXS measurement were performed to obtain the transmission X-ray intensity A S and the WAXS scattering intensity I S . Transmission X-ray intensity measurement and WAXS measurement were performed under the same conditions except that no fluororesin powder was included to obtain the background transmission X-ray intensity A B and the WAXS scattering intensity I B . Based on the following formula (1), transmission X-ray intensity correction and background subtraction were performed to obtain the corrected WAXS scattering intensity I C . I C =I S / A S -I B / A B (1)

[0066] The method for measuring the crystallite size by X-ray diffraction can be carried out as follows. The crystallite size (Å) of the fluororesin powder can be calculated from the half-width (β) of the scattering intensity at the diffraction peak of the Debye ring obtained by wide-angle X-ray diffraction measurement (the diffraction peak having a peak top within the range of diffraction angle 2θ = 17.93 ± 0.2°) using Scherrer's formula of the following formula (2). D = K·λ / βcosθ ···(2) In the formula, D is the crystallite size, λ is the measured X-ray wavelength, β is the half-width (radian), θ is the diffraction angle, and K is the Scherrer constant (0.94).

[0067] From the same viewpoint, the fluororesin (B) according to the embodiment preferably has a half-width of 0.29 to 0.43, more preferably 0.31 to 0.41, and even more preferably 0.33 to 0.39 for the peak having a peak top at a diffraction angle 2θ = 17.93 ± 0.2° in X-ray diffraction analysis.

[0068] As the fluororesin satisfying the above numerical values of the melting point, crystallite size, and half-width, commercially available products may be used. For example, EA2000 manufactured by AGC can be used.

[0069] Furthermore, the liquid composition of the embodiment contains the fluororesin (B), so that the water absorption rate when made into a film can be made favorable.

[0070] The fluororesin contained in the liquid composition of the embodiment may be a powder. The volume average particle diameter of the fluororesin may be 0.1 μm to 30 μm, 0.5 μm to 10 μm, or 1 μm to 5 μm. If the volume average particle diameter of the fluororesin is within the above range, it is preferable because the surface smoothness is excellent when it is made into a film. The volume average particle diameter of the fluororesin can be measured in a wet manner using water as a dispersion medium by a laser diffraction / scattering type particle size distribution measuring device.

[0071] The shape of the fluororesin contained in the liquid composition of the embodiment is not particularly limited, and for example, spherical, lumpy, fibrous, or scaly fluororesin can be used. In particular, spherical or lumpy fluororesin is preferred from the viewpoint of excellent dispersibility in the liquid crystal polyester liquid composition.

[0072] The mass ratio (solid content) of the (A) component to the (B) component contained in the liquid composition of the embodiment [(A) component:(B) component] may be, for example, 9:1 to 1:9, 5:1 to 1:5, or 3:2 to 2:3. By using a liquid composition containing the (A) component and the (B) component in the above ratio, the adhesive strength with the copper foil, the dielectric properties, and the water resistance of the liquid crystal polyester film produced can be easily improved.

[0073] The content of the (B) component may be 10% by mass or more and 90% by mass or less, 15% by mass or more and 50% by mass or less, or 25% by mass or more and 40% by mass or less, relative to the total solid content of the liquid composition. By using a liquid composition containing the component (B) in the above numerical range, the adhesive strength to the copper foil, the dielectric properties and the water resistance of the produced liquid crystal polyester film can be easily improved.

[0074] The liquid composition of the embodiment can contain component (A), component (B), and component (S). As a preferable example of the blending ratio of each component in such a composition, the content ratio of the component (A) is 10% by mass or more and 90% by mass or less, and the content ratio of the component (B) is 10% by mass or more and 90% by mass or less, with respect to the total solid content of the liquid composition. It should be noted that the combination of these numerical ranges is just an example. For example, the numerical values exemplified above as an example of the content ratio of each component can be freely combined.

[0075] <Other components> In addition to component (A), component (B), and component (S), the liquid composition of the embodiment may, if necessary, contain other components, for example, fillers, antioxidants, heat stabilizers, ultraviolet absorbers, antistatic agents, surfactants, flame retardants, colorants, and other additives, or resins that do not correspond to component (A) and component (B).

[0076] Examples of the filler 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, crosslinked benzoguanamine resins, and crosslinked acrylic resins. As the inorganic filler (C), a silica filler is preferable from the viewpoint of improving the dielectric loss tangent of the liquid crystal polyester film.

[0077] Although it has been conventionally known that the addition of a silica filler can improve the dielectric loss tangent, when used in combination with a liquid crystal polyester, there may be a problem that the adhesion strength with a copper foil decreases. However, in the liquid composition containing the fluororesin (B) having a melting point of 305°C or lower, the fluororesin (B) having a melting point of 305°C or lower and the inorganic filler (C) such as a silica filler (hereinafter also referred to as component (C)) are combined and blended. Thus, even when component (C) is blended, a decrease in the adhesion strength with a copper foil hardly occurs, the water resistance is excellent, and the balance between the adhesion strength with a copper foil and the dielectric properties can be made extremely good, and a liquid crystal polyester film having particularly excellent properties can be manufactured.

[0078] The above filler is preferably granular. The volume average particle diameter of the filler may be 0.1 μm or more and 10 μm or less, may be 0.2 μm or more and 5 μm or less, or may be 0.3 μm or more and 1 μm or less. When the volume average particle diameter of the filler is within the above range, it is preferable because the dispersibility in the liquid crystal polyester liquid composition is excellent. The volume average particle diameter of the filler can be measured by a laser diffraction / scattering particle size distribution measuring device.

[0079] When the liquid composition of the embodiment contains the inorganic filler (C), its content may be 5% by mass or more and 70% by mass or less, may be 20% by mass or more and 50% by mass or less, or may be 30% by mass or more and 45% by mass or less with respect to the total content of the solid content of the liquid composition. By containing the inorganic filler (C) within the above numerical range, the characteristics of the inorganic filler are exhibited well. For example, by using a liquid composition containing, for example, a silica filler at or above the above lower limit value, the dielectric properties of the produced liquid crystal polyester film can be improved. Also, by using a liquid composition containing a silica filler at or below the above upper limit value, the adhesion strength with the copper foil of the produced liquid crystal polyester film can be made good.

[0080] The liquid composition of the embodiment can contain the component (A), the component (B), the component (S), and further the component (C). As a preferable example of the blending ratio of each component in such a composition, with respect to the total content of the solid content of the liquid composition, the content ratio of the component (A) is 25% by mass or more and 40% by mass or less, the content ratio of the component (B) is 25% by mass or more and 40% by mass or less, and the content ratio of the component (C) is 20% by mass or more and 50% by mass or less. As a more preferable example of the blending ratio of each component in such a composition, with respect to the total content of the solid content of the liquid composition, the content ratio of the component (A) is 25% by mass or more and 35% by mass or less, the content ratio of the component (B) is 25% by mass or more and 35% by mass or less, and the content ratio of the component (C) is 30% by mass or more and 45% by mass or less. Note that the combinations of these numerical ranges are merely examples, and for instance, the numerical values exemplified above as examples of the content ratios of the respective components can be freely combined.

[0081] Examples of resins that do not correspond to component (A) and component (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, and polyetherimide; elastomers such as copolymers of glycidyl methacrylate and polyethylene; and thermosetting resins such as phenol resin, epoxy resin, polyimide resin, and cyanate resin. The content thereof may be 0, and preferably 20 parts by mass or less with respect to 100 parts by mass of the liquid crystal polyester.

[0082] According to the liquid crystal polyester liquid composition of the embodiment, it is possible to produce a film excellent in adhesion strength to a copper foil and dielectric properties.

[0083] Since the liquid composition of the embodiment contains component (A), it is possible to produce a film particularly excellent in adhesion strength to a copper foil and dielectric properties.

[0084] According to the liquid composition of the present embodiment, a film-forming method capable of producing a film excellent in isotropy can be applied. Conventionally, liquid crystal polyester films are generally produced by a melt molding method of melting a liquid crystal polyester or a solution casting method. The melt molding method is a method of forming a film by extruding a kneaded product from an extruder. However, in the film produced by the melt molding method, the liquid crystal polyester molecules are oriented in the film-forming direction rather than in the lateral direction with respect to the extrusion direction, and it is difficult to obtain a liquid crystal polyester excellent in isotropy. On the other hand, in the solution casting method, since a film is formed without applying a force such as extrusion, the orientation of the liquid crystal polyester is more isotropic than that of the liquid crystal polyester film formed by the melt molding method.

[0085] According to the liquid composition of the embodiment, since the liquid crystal polyester (A) is soluble in the aprotic solvent (S), the solution casting method can be applied, and a liquid crystal polyester film excellent in isotropy can be produced.

[0086] By containing the component (B) in the liquid composition of the embodiment, a film excellent in adhesion strength to a copper foil, dielectric properties, and water resistance can be produced.

[0087] By further containing the component (C) in the liquid composition of the embodiment, a film further excellent in dielectric properties and water resistance can be produced. Moreover, by containing the component (C) in the liquid composition, an excellent film having an extremely good balance of adhesion strength to a copper foil, dielectric properties, and water resistance can be produced.

[0088] ≪Liquid crystal polyester film≫ The liquid crystal polyester film of the embodiment contains a liquid crystal polyester (A) and a fluororesin (B) having a melting point of 305°C or lower, and the liquid crystal polyester (A) contains an amide bond. Hereinafter, the liquid crystal polyester film according to an embodiment of the present invention is also simply referred to as the "film" of the embodiment.

[0089] FIG. 1 is a schematic diagram showing the configuration of the liquid crystal polyester film 10 of the embodiment.

[0090] Examples of the liquid crystal polyester (A) include those described as the component (A) above, and detailed description thereof is omitted here. Note that the liquid crystal polyester (A) in the state formed into a film may not be soluble in an aprotic solvent due to changes in physical properties such as those occurring during the film-forming process. The above-mentioned changes in physical properties include, for example, an increase in the degree of polymerization.

[0091] 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 a 1,4-phenylene group, a 2,6-naphthalenediyl group, or a 4,4'-biphenylene group; Ar2 represents a 1,4-phenylene group, a 1,3-phenylene group, or a 2,6-naphthalenediyl group; Ar3 represents a 1,4-phenylene group or a 1,3-phenylene group; X represents -NH-; and Y represents -O- or -NH-.)

[0092] Examples of the fluororesin (B) having a melting point of 305°C or lower include those described as the component (B) above, and detailed description thereof is omitted here.

[0093] Similar to the liquid composition of the above embodiment, the film of the embodiment may contain, in addition to the components (A) and (B), other components as necessary, such as fillers, antioxidants, heat stabilizers, ultraviolet absorbers, antistatic agents, surfactants, flame retardants, colorants, and other additives, as well as resins that do not correspond to the components (A) and (B). Detailed description thereof is omitted here.

[0094] The film of the embodiment preferably contains the above component (A), component (B), and inorganic filler (C). The liquid crystal polyester film containing the components (A), (B), and (C) is less likely to cause a decrease in the adhesion strength to the copper foil, has a good balance between the adhesion strength to the copper foil and the dielectric properties, and is also excellent in water resistance, and has particularly excellent properties. Examples of the inorganic filler (C) include those described as the component (C) above, and detailed description thereof is omitted here. The inorganic filler (C) is preferably a silica filler.

[0095] The content of each component in the film of the embodiment can be the same as the content of each component as the solid content of the liquid composition of the embodiment exemplified above.

[0096] The film of the embodiment exhibits excellent dielectric properties. The film of the embodiment preferably has a relative permittivity of 3.1 or less, more preferably 3.0 or less, still more preferably 2.9 or less, and particularly preferably 2.8 or less at a frequency of 1 GHz. Also, the relative permittivity of the film may be 2.3 or more, may be 2.4 or more, or may be 2.5 or more. As an example of the numerical range of the relative permittivity value of the above film, it may be 2.3 or more and 3.1 or less, may be 2.4 or more and 3.0 or less, may be 2.5 or more and 2.9 or less, or may be 2.5 or more and 2.8 or less.

[0097] The film of the embodiment has a dielectric loss tangent of 0.005 or less at a frequency of 1 GHz, preferably 0.004 or less, more preferably 0.003 or less, still more 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, may be 0.0005 or more, or may be 0.0007 or more. As an example of the numerical range of the dielectric loss tangent value of the above film, it may be 0.0003 or more and 0.005 or less, may be 0.0005 or more and 0.004 or less, may be 0.0007 or more and 0.003 or less, may be 0.0007 or more and 0.002 or less, or may be 0.0007 or more and 0.0015 or less. Note that the relative permittivity and dielectric loss tangent of the film at a frequency of 1 GHz can be measured under the conditions described in the examples by the capacitance method using an impedance analyzer.

[0098] The film of the embodiment can be excellent in isotropy. The film of the embodiment preferably has a molecular orientation degree (MOR) value measured by a microwave orientation meter in the range of 1 to 1.1, more preferably in the range of 1 to 1.08, still more preferably in the range of 1 to 1.06, and particularly preferably in the range of 1 to 1.04.

[0099] The molecular orientation degree (MOR) is measured by a microwave molecular orientation meter (for example, MOA-5012A manufactured by Oji Scientific Instruments Co., Ltd.). The microwave molecular orientation meter is a device that utilizes the fact that the transmission intensity of microwaves differs between the orientation direction and the direction perpendicular to the orientation direction due to the orientation of molecules. Specifically, while rotating the sample, microwaves having a constant frequency (12 GHz is used) are irradiated, the intensity of the transmitted microwaves that changes due to the molecular orientation is measured, and the ratio of the maximum value / minimum value is defined as MOR. The interaction between a microwave electric field having a constant frequency and the dipoles constituting the molecules is related to the inner product of the vectors of both. Since the intensity of the microwaves changes depending on the angle at which the sample is placed due to the anisotropy of the dielectric constant of the sample, it is possible to know the orientation degree.

[0100] The film of the embodiment preferably has a linear expansion coefficient of 85 ppm / °C or less, more preferably 57 ppm / °C or less, still more preferably 45 ppm / °C or less, and particularly preferably 40 ppm / °C or less in the temperature range of 50 to 100°C under the condition of a temperature increase rate of 5°C / min. The lower limit value of the linear expansion coefficient is not particularly limited, but is, for example, 0 ppm / °C or more. Further, for example, when a copper foil and a film are laminated, since the linear expansion coefficient of the copper foil is 18 ppm / °C, the linear expansion coefficient of the film of the embodiment is preferably a value close thereto. That is, the linear expansion coefficient of the film of the embodiment is preferably 0 ppm / °C or more and 57 ppm / °C or less, more preferably 10 ppm / °C or more and 45 ppm / °C or less, and still more preferably 20 ppm / °C or more and 40 ppm / °C or less. When the linear expansion coefficient varies depending on the direction or part of the film, the higher value shall be 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.

[0101] The film of the embodiment exhibits excellent water resistance. As an index of water resistance, it is preferable that the water absorption rate of the film of the embodiment, measured in accordance with JIS K 7209, is 0.8% by mass or less, more preferably 0.5% by mass or less, still more preferably 0.4% by mass or less, and particularly preferably 0.3% by mass or less. Further, the water absorption rate of the film may be 0.05% by mass or more, may be 0.1% by mass or more, or may be 0.15% by mass or more. As an example of the numerical range of the value of the water absorption rate of the above film, it may be 0.05% by mass or more and 0.8% by mass or less, may be 0.1% by mass or more and 0.5% by mass or less, may be 0.15% by mass or more and 0.4% by mass or less, or may be 0.15% by mass or more and 0.3% by mass or less.

[0102] The thickness of the film of the embodiment is not particularly limited, but as a thickness suitable for a film for electronic components, it is preferably 5 to 50 μm, more preferably 7 to 40 μm, still more preferably 10 to 33 μm, and particularly preferably 15 to 30 μm.

[0103] The manufacturing method of the film of the embodiment is not particularly limited, and for example, it can be obtained by forming the liquid composition of the embodiment into a film shape. From the viewpoint of being able to manufacture a film having excellent isotropy, the film of the embodiment is preferably manufactured by the ≪Manufacturing method of liquid crystal polyester film≫ described later.

[0104] ≪Manufacturing method of liquid crystal polyester film≫ The manufacturing method of the 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 manufacturing method may correspond to the solution casting method.

[0105] Examples of the liquid composition of the embodiment include those exemplified in the above ≪Liquid crystal polyester liquid composition≫.

[0106] The method for manufacturing a liquid crystal polyester film may include the following steps. A step of applying the liquid crystal polyester liquid composition of the embodiment onto a support (coating step). A step of removing the aprotic solvent (S) from the applied liquid crystal polyester liquid composition (drying step).

[0107] The method for manufacturing a liquid crystal polyester film of the embodiment may include a step of heat-treating the liquid crystal polyester liquid composition or a precursor of the liquid crystal polyester film from which the aprotic solvent (S) has been removed after the coating step (heat treatment step).

[0108] The method for manufacturing a liquid crystal polyester film of the embodiment may include applying the liquid crystal polyester liquid composition of the embodiment onto a support, removing the aprotic solvent (S) from the liquid crystal polyester liquid composition, and performing heat treatment to obtain a liquid crystal polyester film. According to the heat treatment, the polymerization reaction of the polymer in the liquid crystal polyester liquid composition can be promoted, and furthermore, the volatilization of the aprotic solvent (S) can be promoted.

[0109] The heat treatment can also serve as the above drying step. Therefore, the method for manufacturing a liquid crystal polyester film of the embodiment may include applying the liquid crystal polyester liquid composition of the embodiment onto a support and performing heat treatment to obtain a liquid crystal polyester film.

[0110] Further, the method for manufacturing a liquid crystal polyester film may further include a step of separating the support from the laminate (separation step). Note that since the liquid crystal polyester film can be suitably used as a film for electronic components even when formed on a support as a laminate, the separation step is not an essential step in the manufacturing process of the liquid crystal polyester film.

[0111] Hereinafter, an example of the method for manufacturing a liquid crystal polyester film of the embodiment will be described with reference to the drawings.

[0112] Figure 3 is a schematic diagram showing an example of the manufacturing process of the liquid crystal polyester film and the laminate according to the embodiment. First, a liquid crystal polyester liquid composition 30 is applied onto a support 12 (coating step in Fig. 3A). The application of the liquid composition onto the support can be carried out by methods such as the roller coating method, dip coating method, spray coating method, spinner coating method, curtain coating method, slot coating method, and screen printing method, etc., and a method that can coat the support smoothly and uniformly on the surface can be appropriately selected. Also, in order to make the distribution of fillers and the like that may be blended in the liquid composition uniform, an operation of stirring the liquid composition may be performed before coating. The viscosity of the liquid crystal polyester liquid composition 30 is not particularly limited, but from the viewpoints 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 or more and 2000 mPa·s or less, more preferably 250 mPa·s or more and 1500 mPa·s or less, and even more preferably 300 mPa·s or more and 1000 mPa·s or less.

[0113] Examples of the support 12 include a glass plate, a resin film, or a metal foil. Among them, a resin film or a metal foil is preferred, and particularly, a copper foil is 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 "U-Pyrex S" and "U-Pyrex R" of Ube Industries, Ltd., "Kapton" of Toray DuPont Co., Ltd., and "IF30", "IF70", and "LV300" of SKC Kolon PI Co., Ltd. The thickness of the resin film is usually 25 μm or more and 75 μm or less, preferably 50 μm or more and 75 μm or less. The thickness of the metal foil is usually 3 μm or more and 75 μm or less, preferably 5 μm or more and 30 μm or less, and more preferably 10 μm or more and 25 μm or less.

[0114] Next, the aprotic solvent is removed from the liquid crystal polyester liquid composition 30 applied on the support 12 (drying step in FIG. 3B). The liquid composition from which the aprotic solvent has been removed becomes the liquid crystal polyester film precursor 40 to be heat-treated. Note that the aprotic solvent does not have to be completely removed from the liquid composition, and part of the aprotic solvent contained in the liquid composition may be removed, or all of the aprotic solvent may 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 or more and 12% by mass or less, and even more preferably 5% by mass or more and 10% by mass or less with respect to the total mass of the liquid crystal polyester film precursor. When the content of the aprotic solvent in the liquid crystal polyester film precursor is equal to or higher than the above lower limit value, the risk of a decrease in the thermal conductivity of the liquid crystal polyester film is reduced. Further, when the content of the aprotic solvent in the liquid crystal polyester film precursor is equal to or lower than the above upper limit value, the risk of a decrease in the appearance of the liquid crystal polyester film due to foaming or the like during heat treatment is reduced.

[0115] The removal of the aprotic solvent is preferably performed by evaporating the aprotic solvent. Examples of the method include heating, reduced pressure, and ventilation, and these may be combined. Also, the removal of the aprotic solvent may be performed continuously or batchwise. From the viewpoints of productivity and operability, the removal of the aprotic solvent is preferably performed by continuous heating, and more preferably performed by continuous heating while ventilating. The removal temperature of the aprotic solvent is preferably lower than the melting points of the liquid crystal polyester (A) and the fluororesin (B), and is, for example, 40°C or higher and 200°C or lower. The time for removing the aprotic solvent is appropriately adjusted so that, for example, the aprotic solvent content in the liquid crystal polyester film precursor becomes 3 to 12% by mass. The time for removing the aprotic solvent is, for example, 0.2 hours or more and 12 hours or less, preferably 0.5 hours or more and 8 hours or less.

[0116] The laminate precursor 22 having the support 12 and the liquid crystal polyester film precursor 40 thus obtained is heat-treated to obtain 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, the liquid crystal polyester film 10 formed on the support is obtained. Examples of the heat treatment conditions include heating from -50°C of the boiling point of the medium to the heat treatment temperature and then heat-treating at a temperature equal to or higher than the melting points of the liquid crystal polyester (A) and the fluororesin (B).

[0117] The heat treatment may be carried out continuously or batchwise, similar to the removal of the aprotic solvent. However, from the viewpoints of productivity and operability, it is preferably carried out continuously, and more preferably carried out continuously following the removal of the aprotic solvent.

[0118] Next, the liquid crystal polyester film 10 can be obtained as a single-layer film by separating the liquid crystal polyester film 10 from the laminate 20 having the support 12 and the liquid crystal polyester film 10 (separation step in FIG. 3D). When a glass plate is used as the support 12, the separation of the liquid crystal polyester film 10 from the laminate 20 is preferably carried out by peeling the liquid crystal polyester film 10 from the laminate 20. When a resin film is used as the support 12, it is preferably 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, it is preferably separated from the laminate 20 by etching and removing the metal foil. 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 laminate 20 may be used as a metal-clad laminate for a printed wiring board without separating the liquid crystal polyester film from the laminate 20.

[0119] According to the method for manufacturing a liquid crystal polyester film of the embodiment, a liquid crystal polyester film excellent in isotropy can be manufactured.

[0120] ≪Laminate≫ The laminate of the embodiment includes a metal layer and the liquid crystal polyester film of the embodiment laminated on the metal layer. FIG. 2 is a schematic diagram showing the configuration of a laminate 21 according to an 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. As for the liquid crystal polyester film 10 included in the laminate, those exemplified above are mentioned and the description thereof is omitted. As for the metal layer included in the laminate, those exemplified as a support in the ≪Method for manufacturing a liquid crystal polyester film≫ described later and the ≪Method for manufacturing a laminate≫ described later are mentioned, and a metal foil is preferable. As the metal constituting the metal layer, copper is preferable from the viewpoints of conductivity and cost, and as the metal foil, a copper foil is preferable.

[0121] The thickness of the laminate of the embodiment is not particularly limited, but is preferably 5 to 130 μm, more preferably 10 to 70 μm, and even more preferably 15 to 60 μm.

[0122] The method for manufacturing the laminate of the embodiment is not particularly limited, but the laminate of the embodiment can be manufactured by the ≪Method for manufacturing a laminate≫ described later.

[0123] As one embodiment of the present invention, 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 can be provided.

[0124] The laminate of the embodiment can be suitably used for film applications for electronic components such as printed wiring boards.

[0125] ≪Method for manufacturing a laminate≫ The method for manufacturing the laminate of the embodiment includes applying the liquid crystal polyester composition of the embodiment onto a support, removing the aprotic solvent (S) from the liquid crystal polyester composition, and forming a liquid crystal polyester film on the support to obtain a laminate including the support and the film.

[0126] The method for manufacturing the laminate of the embodiment may include the following steps. A step of applying the liquid crystal polyester composition of the embodiment onto a support (coating step). A step of removing the aprotic solvent (S) from the applied liquid crystal polyester composition (drying step).

[0127] Similar to the method for manufacturing the liquid crystal polyester film of the embodiment, the method for manufacturing the laminate of the embodiment may include a step of heat-treating the liquid crystal polyester composition or the precursor of the liquid crystal polyester film from which the aprotic solvent (S) has been removed after the coating step (heat treatment step).

[0128] The method for manufacturing the laminate of the embodiment may include applying the liquid crystal polyester composition of the embodiment onto a support, removing the aprotic solvent (S) from the liquid crystal polyester composition, heat-treating to form a liquid crystal polyester film on the support, and obtaining a laminate including the support and the film. According to the heat treatment, the polymerization reaction of the polymer in the liquid composition can be promoted, and furthermore, the volatilization of the aprotic solvent (S) can be promoted.

[0129] The heat treatment can also serve as the above drying step. Therefore, the method for manufacturing the laminate of the embodiment may include applying the liquid crystal polyester composition of the embodiment onto a support, heat-treating to form a liquid crystal polyester film on the support, and obtaining a laminate including the support and the film.

[0130] FIG. 3 is a schematic diagram showing an example of the manufacturing process of the liquid crystal polyester film and the laminate of the embodiment. Regarding the manufacturing method of the laminate exemplified in FIG. 3, since it is the same as that described in the above-described manufacturing method of the liquid crystal polyester film except that the above-described separation step (FIG. 3D) is not performed, the description thereof will be omitted.

[0131] According to the manufacturing method of the laminate of the embodiment, a laminate having the liquid crystal polyester film of the embodiment can be manufactured.

[0132] The present invention has the following aspects. <1> A liquid crystal polyester (A) soluble in an aprotic solvent, an aprotic solvent (S), and a fluororesin (B) having a melting point of 305° C. or lower, 280° C. or higher and 305° C. or lower, 290° C. or higher and 303° C. or lower, or 295° C. or higher and 301° C. or lower, The liquid crystal polyester (A) 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), and is a liquid crystal polyester liquid composition. (A1) -O-Ar1-CO- (A2) -CO-Ar2-CO- (A3) -X-Ar3-Y- (In the formula, Ar1 represents a 1,4-phenylene group, a 2,6-naphthalenediyl group, or a 4,4'-biphenylene group, Ar2 represents a 1,4-phenylene group, a 1,3-phenylene group, or a 2,6-naphthalenediyl group, Ar3 represents a 1,4-phenylene group or a 1,3-phenylene group, X represents -NH-, and Y represents -O- or -NH-.) <2> The liquid crystal polyester liquid composition according to <1>, wherein Ar1 is a 2,6-naphthalenediyl group, Ar2 is a 1,3-phenylene group, Ar3 is a 1,4-phenylene group, and Y is -O-. <3> The liquid crystal polyester liquid composition contains the liquid crystal polyester (A) and the fluororesin (B) as solid components, The liquid crystal polyester liquid composition according to the above <1> or <2>, wherein the ratio of the solid content to the total mass of the liquid composition is 5% by mass or more and 50% by mass or less. <4> The liquid crystal polyester liquid composition according to any one of the above <1> to <3>, wherein the content ratio of the liquid crystal polyester (A) is 10% by mass or more and 90% by mass or less, and the content ratio of the fluororesin (B) is 10% by mass or more and 90% by mass or less, based on the total content of the solid content of the liquid crystal polyester liquid composition. <5> The liquid crystal polyester liquid composition according to any one of the above <1> to <4>, further containing a silica filler. <6> The liquid crystal polyester liquid composition according to the above <5>, wherein the volume average particle diameter of the silica filler is any one of 0.1 μm or more and 10 μm or less, 0.2 μm or more and 5 μm or less, and 0.3 μm or more and 1 μm or less. <7> The liquid crystal polyester liquid composition according to the above <5> or <6>, wherein the content ratio of the liquid crystal polyester (A) is 25% by mass or more and 40% by mass or less, the content ratio of the fluororesin (B) is 25% by mass or more and 40% by mass or less, and the content ratio of the silica filler is 20% by mass or more and 50% by mass or less, based on the total content of the solid content of the liquid crystal polyester liquid composition. <8> The liquid crystal polyester liquid composition according to any one of the above <1> to <7>, wherein the crystallite size of the fluororesin (B) is any one of 2.0×10 -8 m or more and 2.9×10 -8 m or less, 2.1×10 -8 m or more and 2.7×10 -8 m or less, and 2.2×10 -8 m or more and 2.5×10 -8 m or less. <9> The fluororesin (B) is at least one fluororesin selected from the group consisting of 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), and the liquid crystal polyester composition according to any one of <1> to <8> above. <10> The volume average particle diameter of the fluororesin (B) is any one of 0.1 μm or more and 30 μm or less, 0.5 μm or more and 10 μm or less, and 1 μm or more and 5 μm or less, and the liquid crystal polyester composition according to any one of <1> to <9> above. <11> The aprotic solvent (S) is N-methylpyrrolidone, and the liquid crystal polyester composition according to any one of <1> to <10> above.

[0133] <12> It contains liquid crystal polyester (A) and a fluororesin (B) having a melting point of 305 °C or lower. The liquid crystal polyester (A) contains an amide bond, and it is a liquid crystal polyester film. <13> 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). The liquid crystal polyester film according to <12> above. (A1) -O-Ar1-CO- (A2) -CO-Ar2-CO- (A3) -X-Ar3-Y- (In the formula, Ar1 represents a 1,4-phenylene group, a 2,6-naphthalenediyl group, or a 4,4'-biphenylene group; Ar2 represents a 1,4-phenylene group, a 1,3-phenylene group, or a 2,6-naphthalenediyl group; Ar3 represents a 1,4-phenylene group or a 1,3-phenylene group; X represents -NH-; and Y represents -O- or -NH-.) <14> The liquid crystal polyester film according to <13>, wherein Ar1 is a 2,6-naphthalenediyl group, Ar2 is a 1,3-phenylene group, Ar3 is a 1,4-phenylene group, and Y is -O-. <15> The liquid crystal polyester film according to any one of <12> to <14>, wherein the content ratio of the liquid crystal polyester (A) is 10% by mass or more and 90% by mass or less, and the content ratio of the fluororesin (B) is 10% by mass or more and 90% by mass or less, based on the total content of the liquid crystal polyester film. <16> The liquid crystal polyester film according to any one of <12> to <15>, further containing an inorganic filler (C). <17> The liquid crystal polyester film according to <16>, wherein the content ratio of the liquid crystal polyester (A) is 25% by mass or more and 40% by mass or less, the content ratio of the fluororesin (B) is 25% by mass or more and 40% by mass or less, and the content ratio of the inorganic filler (C) is 20% by mass or more and 50% by mass or less, based on the total content of the liquid crystal polyester film. <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 crystallite size of the fluororesin (B) is 2.9×10 -8 m or less. <20> The liquid crystal polyester film according to any one of <12> to <19>, wherein the fluororesin (B) is at least one fluororesin selected from the group consisting of 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>, having a thickness of 5 to 50 μm, preferably 7 to 40 μm, more preferably 10 to 33 μm, and still more preferably 15 to 30 μm. <22> The liquid crystal polyester film according to any one of <12> to <21>, having a relative permittivity at a frequency of 1 GHz of 2.3 or more and 3.1 or less, preferably 2.4 or more and 3.0 or less, more preferably 2.5 or more and 2.9 or less, and still more preferably 2.5 or more and 2.8 or less. <23> The liquid crystal polyester film according to any one of <12> to <22>, having a dielectric tangent at a frequency of 1 GHz of 0.0003 or more and 0.005 or less, preferably 0.0005 or more and 0.004 or less, more preferably 0.0007 or more and 0.003 or less, still more preferably 0.0007 or more and 0.002 or less, and particularly preferably 0.0007 or more and 0.0015 or less. <24> The liquid crystal polyester film according to any one of <12> to <23>, having a molecular orientation degree (MOR) value measured by a microwave orientation meter of 1 to 1.1, preferably in the range of 1 to 1.08, more preferably 1 to 1.06, and still more preferably 1 to 1.04. <25> The liquid crystal polyester film according to any one of <12> to <24>, having a linear expansion coefficient determined in a temperature range of 50 to 100 °C under the condition of a heating rate of 5 °C / min of 0 ppm / °C or more and 57 ppm / °C or less, preferably 10 ppm / °C or more and 45 ppm / °C or less, and more preferably 20 ppm / °C or more and 40 ppm / °C or less. <26> The liquid crystal polyester film according to any one of <12> to <25>, having a water absorption rate measured in accordance with JIS K 7209 of 0.05 mass% or more and 0.8 mass% or less, preferably 0.1 mass% or more and 0.5 mass% or less, more preferably 0.15 mass% or more and 0.4 mass% or less, and still more preferably 0.15 mass% or more and 0.3 mass% or less.

[0134] <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.

[0135] <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> on the metal layer. <29>The laminate according to <28>, wherein the thickness of the liquid crystal polyester film is 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 according to <28> or <29>, wherein the metal layer is a copper foil, and the peel strength (90° peel strength) of the single-sided copper-clad liquid crystal polyester film measured by peeling the copper foil at a peeling rate of 50 mm / min in a direction of 90° with respect to the liquid crystal polyester film is 6.5 N / cm or more and 10.0 N / cm or less, preferably 7.5 N / cm or more and 9.8 N / cm or less, more preferably 7.9 N / cm or more and 9.0 N / cm or less. <31>The laminate according to any one of <28> to <30>, wherein the relative permittivity of the liquid crystal polyester film at a frequency of 1 GHz is 2.3 or more and 3.1 or less, preferably 2.4 or more and 3.0 or less, more preferably 2.5 or more and 2.9 or less, and even more preferably 2.5 or more and 2.8 or less. <32>The laminate according to any one of <28> to <31>, wherein the dielectric tangent of the liquid crystal polyester film at a frequency of 1 GHz is 0.0003 or more and 0.005 or less, preferably 0.0005 or more and 0.004 or less, more preferably 0.0007 or more and 0.003 or less, even more preferably 0.0007 or more and 0.002 or less, and particularly preferably 0.0007 or more and 0.0015 or less. <33> The value of the molecular orientation degree (MOR) measured by the microwave orientation meter of the liquid crystal polyester film 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. The laminate according to any one of <28> to <32>. <34> The linear expansion coefficient determined in the temperature range of 50 to 100 °C under the condition of a heating rate of 5 °C / min of the liquid crystal polyester film is 0 ppm / °C or more and 57 ppm / °C or less, preferably 10 ppm / °C or more and 45 ppm / °C or less, more preferably 20 ppm / °C or more and 40 ppm / °C or less. The laminate according to any one of <28> to <33>. <35> The water absorption rate of the liquid crystal polyester film measured in accordance with JIS K 7209 is 0.05% by mass or more and 0.8% by mass or less, preferably 0.1% by mass or more and 0.5% by mass or less, more preferably 0.15% by mass or more and 0.4% by mass or less, and even more preferably 0.15% by mass or more and 0.3% by mass or less. The laminate according to any one of <28> to <34>.

[0136] <36> A method for producing a liquid crystal polyester film, comprising applying the liquid crystal polyester liquid composition according to any one of <1> to <11> on a support, removing the aprotic solvent (S) from the liquid crystal polyester liquid composition, and performing heat treatment to obtain a liquid crystal polyester film.

Example

[0137] Next, examples are shown to explain the present invention in more detail, but the present invention is not limited to the following examples.

[0138] <Measurement method>

[0139] [Measurement of the melting point of the fluororesin] In accordance with JIS K 6935, the melting point of the fluororesin was measured as the value of the endothermic peak of differential scanning calorimetry (DSC).

[0140] [Measurement of the Crystallite Size of Fluororesin] Wide-angle X-ray scattering (WAXS) measurements were carried out using a Nano Viewer manufactured by Rigaku Corporation. The fluororesin powder sample was sandwiched between Kapton films made into a bag shape, and the X-ray beam size was adjusted so as to be smaller than the size of the sample. The wavelength of the X-ray was set to λ = 1.5418 Å, and the measurement was carried out in the range of diffraction angle 2θ = 5° to 30°. For the fluororesin powder sample, X-rays were incident in the thickness direction of the Kapton film, and transmission X-ray intensity measurement and WAXS measurement were performed to obtain the transmission X-ray intensity A S and the WAXS scattering intensity I S . Transmission X-ray intensity measurement and WAXS measurement were performed under the same conditions except that the fluororesin powder was not included, and the background transmission X-ray intensity A B and the WAXS scattering intensity I B were obtained. Based on the following formula (1), transmission X-ray intensity correction and background subtraction were performed to obtain the corrected WAXS scattering intensity I C . I C = I S / A S - I B / A B (1)

[0141] The measurement of the crystallite size by X-ray diffraction was carried out as follows. The crystallite size (Å) of the fluororesin powder was calculated from the Scherrer's formula of the following formula (2) using 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 (the diffraction peak having a peak top within the range of diffraction angle 2θ = 17.93 ± 0.2°). D = K·λ / βcosθ ···(2) In the formula, D is the crystallite size, λ is the measured X-ray wavelength, β is the half-value width (radian), θ is the diffraction angle, and K is the Scherrer constant (0.94).

[0142] [Measurement of the Flow Initiation Temperature of Liquid Crystal Polyester] Using a flow tester (the "CFT-500 type" manufactured by Shimadzu Corporation), approximately 2 g of liquid crystal polyester was filled into a cylinder equipped with a die having a nozzle with an inner diameter of 1 mm and a length of 10 mm. While increasing the temperature at a rate of 4 °C / min under a load of 9.8 MPa (100 kg / cm 2 ), the liquid crystal polyester was melted, extruded from the nozzle, and the temperature at which a viscosity of 4800 Pa·s (48000 P) was exhibited was measured.

[0143] [Measurement of the volume average particle diameter of PFA fine particles] Using a scattering-type particle size distribution measuring device ("LA-950V2" manufactured by HORIBA, Ltd.), the volume average particle diameter of PFA was measured wet using water as a dispersion medium.

[0144] [Measurement of the viscosity of the liquid crystal polyester solution] Using a B-type viscometer ("TV-22" manufactured by Toki Sangyo Co., Ltd.), the solution viscosity of the liquid crystal polyester solution was measured under the following measurement conditions. Measurement conditions: Temperature 23 °C, rotor rotation speed 20 rpm

[0145] [Measurement of the peel strength of the single-sided copper-clad laminate of the liquid crystal polyester film] The single-sided copper-clad laminate of the liquid crystal polyester film was cut into strips with a width of 10 mm to prepare three test pieces. For each test piece, with the liquid crystal polyester film fixed, using an autograph ("AG-1KNIS" manufactured by Shimadzu Corporation), the copper foil was peeled off at a peeling speed of 50 mm / min in a direction 90° to the liquid crystal polyester film to measure the peel strength (90° peel strength) of the single-sided copper-clad laminate of the liquid crystal polyester film. Then, the average value of the three test pieces was calculated.

[0146] [Measurement of the linear expansion coefficient of the liquid crystal polyester film] Using a thermomechanical analyzer (manufactured by Rigaku Corporation, model: TMA8310), the linear expansion coefficient from 50 °C to 100 °C was measured at a heating rate of 5 °C / min.

[0147] [Measurement of the relative permittivity and dielectric loss tangent of the liquid crystal polyester film] The copper foil of the single-sided copper-clad liquid crystal polyester film was etched and removed using a ferric chloride solution. Regarding the obtained single-layer liquid crystal polyester film, after melting it at 350 °C using a flow tester (the "CFT-500 type" manufactured by Shimadzu Corporation), tablets with a diameter of 1 cm and a thickness of 0.5 cm were produced by cooling and solidifying. For the obtained tablets, the relative permittivity and dielectric tangent at 1 GHz were measured under the following conditions. · Measurement method: Capacitance method (Apparatus: Impedance Analyzer (manufactured by Agilent Technologies, model: E4991A)) · Electrode type: 16453A · Measurement environment: 23 °C, 50% RH · Applied voltage: 1 V

[0148] 〔Measurement of water absorption rate of liquid crystal polyester film〕 In accordance with JIS K 7209, the water absorption rates of the liquid crystal polyester films of Examples 1 to 10 and Comparative Example 1 were measured.

[0149] 〔Production example of liquid crystal polyester (A)〕 Into a reactor equipped with a stirrer, torque meter, nitrogen gas inlet pipe, thermometer, and reflux condenser, 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 placed. After replacing the gas in the reactor with nitrogen gas, while stirring under a nitrogen gas stream, the temperature was raised from room temperature to 140 °C over 60 minutes and refluxed at 140 °C for 3 hours. Then, while distilling off the by-produced acetic acid and unreacted acetic anhydride, the temperature was raised from 150 °C to 300 °C over 5 hours and held at 300 °C for 30 minutes. After that, the content was taken out from the reactor and cooled to room temperature. The obtained solid was pulverized with a pulverizer to obtain a powdery liquid crystal polyester (A1). The flow start temperature of this liquid crystal polyester (A1) was 193.3 °C.

[0150] The liquid crystal polyester (A1) was heated from room temperature to 160°C over 2 hours and 20 minutes under a nitrogen atmosphere, then heated from 160°C to 180°C over 3 hours and 20 minutes, and held at 180°C for 5 hours for solid-phase polymerization. After cooling, it was then pulverized with a pulverizer to obtain a powdery liquid crystal polyester (A2). The flow start temperature of this liquid crystal polyester (A2) was 220°C.

[0151] The liquid crystal polyester (A2) was heated from room temperature to 180°C over 1 hour and 25 minutes under a nitrogen atmosphere, then heated from 180°C to 255°C over 6 hours and 40 minutes, and held at 255°C for 5 hours for solid-phase polymerization. After cooling, a powdery liquid crystal polyester (A) was obtained. The flow start temperature of the liquid crystal polyester (A) was 302°C.

[0152] 〔Preparation of liquid crystal 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 atm) 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 this liquid crystal polyester solution was 955 mPa·s.

[0153] 〔Preparation of liquid composition〕 (Examples 1 to 5) To the liquid crystal polyester solution obtained above, PFA of fluororesin (EA2000 manufactured by AGC, melting point: 300.82°C, crystallite size: 2.28×10 -8 m, volume average particle size: 2 μm) was added so as to have the compounding amounts (solid content) shown in Table 1, and the liquid compositions of Examples 1 to 5 were prepared using a stirring and defoaming device (AR-500 of Shinky Co., Ltd.).

[0154] (Comparative Examples 2 to 4) To the liquid crystal polyester solution obtained above, silica (SO-C2 manufactured by Admatechs, average particle size described in the catalog: 0.5 μm) was added so as to have the compounding amounts (solid content) shown in Table 2, and the liquid compositions of Comparative Examples 2 to 4 were prepared using a stirring and defoaming device (AR-500 of Shinky Co., Ltd.).

[0155] (Examples 6 to 10) To the liquid crystal polyester solution obtained above, PFA of fluororesin (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 Admatechs, catalog-described average particle size: 0.5 μm) were added, and using a stirring and defoaming device (AR-500 of Shin-Ke Co., Ltd.), the liquid compositions of Examples 6 to 10 were prepared.

[0156] (Comparative Examples 5 to 10) To the liquid crystal polyester solution obtained above, PFA of fluororesin (9738-JN manufactured by Mitsui Chemicals, melting point: 308.68 °C, crystallite size: 2.97×10 -8 m), and silica (SO-C2 manufactured by Admatechs, catalog-described average particle size: 0.5 μm) were added, and using a stirring and defoaming device (AR-500 of Shin-Ke Co., Ltd.), the liquid compositions of Comparative Examples 5 to 10 were prepared. PFA (9738-JN manufactured by Mitsui Chemicals) was sieved before addition and adjusted to an average particle size of 10 μm.

[0157] 〔Production 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 (Comparative Example 1) without added fine particles were cast onto the roughened surface of a copper foil (JX Metal JXEFL-V2, thickness 12 μm) using a film applicator with a micrometer (manufactured by Tester Sangyo) and an automatic coating device (manufactured by Tester Sangyo Co., Ltd., model: PI-1210) so that the thickness of the cast film was as shown in Tables 1 to 4. After casting, the solvent was partially removed from the cast film by drying at 40°C and normal pressure (1 atm) for 4 hours. When casting twice, after the first casting and drying under the above drying conditions, the second casting and drying were further carried out. The film with the copper foil after drying was further heat-treated in a hot air oven under a nitrogen atmosphere by raising the temperature from room temperature to 310°C over 4 hours and holding at that temperature for 2 hours, to obtain a copper foil-attached film (one-sided copper-clad liquid crystal polyester film) provided with the films of each Example or Comparative Example formed from each solution or liquid composition of Examples 1 to 10 and Comparative Examples 1 to 9. For this copper foil-attached film, the peel strength, which is an index of the adhesion strength with the copper foil, was measured, and for the single-layer liquid crystal polyester film obtained by etching and removing the copper foil from this copper foil-attached film, the coefficient of linear expansion (CTE), water absorption rate, relative permittivity, and dielectric loss tangent were measured. The results are shown in Tables 1 to 4.

[0158]

Table 1

[0159]

Table 2

[0160]

Table 3

[0161]

Table 4

[0162] The liquid crystal polyester films of Examples 1 to 10 had higher peel strength values and excellent adhesion strength to copper foil compared to the liquid crystal polyester films of Comparative Examples 5 to 10. This is presumably because the liquid crystal polyester films of Examples 1 to 10 were formed from a liquid crystal polyester liquid composition containing a fluororesin PFA (EA2000) with a melting point of 305°C or lower, while the liquid crystal polyester films of Comparative Examples 5 to 10 were formed from a liquid crystal polyester liquid composition containing a fluororesin PFA (9738-JN) with a higher melting point.

[0163] The liquid crystal polyester films of Examples 1 to 5 had equivalent peel strength compared to the liquid crystal polyester film of Comparative Example 1, while the water absorption rate and the values of the dielectric properties of relative permittivity and dielectric tangent were improved. From this, it was shown that the liquid crystal polyester film formed from a liquid crystal polyester liquid composition containing both liquid crystal polyester (A) and a fluororesin (B) with a melting point of 305°C or lower had a good balance of peel strength, water resistance, and dielectric properties and had excellent properties.

[0164] The liquid crystal polyester films of Comparative Examples 2 to 4, in which silica was added to liquid crystal polyester (A), had a tendency for good CTE values, but the degree of improvement in the dielectric property values was poor.

[0165] The liquid crystal polyester films of Examples 6 to 10 had a tendency for the increase in CTE value to be suppressed compared to the liquid crystal polyester films of Examples 1 to 5. Also, the liquid crystal polyester films of Examples 6 to 10 had equivalent peel strength compared to Examples 1 to 2 and Comparative Examples 2 to 4, which did not have very high CTE values, while the values of the dielectric properties of relative permittivity and dielectric tangent were improved. Also, the water absorption rate value was good. From this, it was shown that the liquid crystal polyester film formed from the liquid crystal polyester composition containing the liquid crystal polyester (A), the fluororesin (B) having a melting point of 305°C or lower, and further silica has a good balance of CTE, water resistance, peel strength, and dielectric properties, and has particularly excellent properties.

[0166] Each configuration and their combinations, etc. in each embodiment are examples, and additions, omissions, substitutions, and other changes of the configuration are possible without departing from the gist of the present invention. Further, the present invention is not limited by each embodiment, but is limited only by the scope of the claims.

Explanation of Reference Numerals

[0167] 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

1. It contains a liquid crystal polyester (A) soluble in an aprotic solvent, an aprotic solvent (S), and a fluororesin (B) having a melting point of 280 °C or higher and 305 °C or lower, wherein the liquid crystal polyester (A) contains an amide bond, 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), the content of the structural unit represented by the following formula (A1) is 30 mol% or more and 80 mol% or less based on the total content of all structural units constituting the liquid crystal polyester (A), the content of the structural unit represented by the following formula (A2) is 10 mol% or more and 35 mol% or less based on the total content of all structural units constituting the liquid crystal polyester (A), and the content of the structural unit represented by the following formula (A3) is 10 mol% or more and 35 mol% or less based on the total content of all structural units constituting the liquid crystal polyester (A), the fluororesin (B) is at least one fluororesin selected from the group consisting of a tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (perfluoroalkoxy alkane, PFA), polytetrafluoroethylene (PTFE), a tetrafluoroethylene-hexafluoropropylene copolymer (FEP), polychlorotrifluoroethylene (PCTFE), an ethylene-tetrafluoroethylene copolymer, an ethylene-chlorotrifluoroethylene copolymer, and polyvinylidene fluoride (PVDF), and the mass ratio (solid content) of the liquid crystal polyester (A) to the fluororesin (B) [the liquid crystal polyester (A): the fluororesin (B)] is 9:1 to 2:

3. A liquid crystal polyester liquid composition. (A1) -O-Ar1-CO- (A2) -CO-Ar2-CO- (A3) -X-Ar3-Y- (In the formula, Ar1 represents a 1,4-phenylene group, a 2,6-naphthalenediyl group, or a 4,4'-biphenylene group, Ar2 represents a 1,4-phenylene group, a 1,3-phenylene group, or a 2,6-naphthalenediyl group, Ar3 represents a 1,4-phenylene group or a 1,3-phenylene group, X represents -NH-, and Y represents -O- or -NH-.)

2. The liquid crystal polyester liquid composition according to claim 1, wherein Ar1 is a 2,6-naphthalenediyl group, Ar2 is a 1,3-phenylene group, Ar3 is a 1,4-phenylene group, and Y is -O-.

3. The liquid crystal polyester liquid composition according to claim 1 or 2, further containing an inorganic filler (C).

4. The liquid crystal polyester liquid composition according to claim 3, wherein the content ratio of the liquid crystal polyester (A) is 25% by mass or more and 40% by mass or less, the content ratio of the fluororesin (B) is 25% by mass or more and 40% by mass or less, and the content ratio of the inorganic filler (C) is 20% by mass or more and 50% by mass or less, based on the total content of the solid components of the liquid crystal polyester liquid composition.

5. The liquid crystal polyester liquid composition according to claim 3 or 4, wherein the inorganic filler (C) is a silica filler.

6. The crystallite size of the fluororesin (B) is 2.9×10 －８ m or less, and the liquid crystal polyester composition according to any one of claims 1 to 5.

7. The liquid crystal polyester liquid composition according to any one of claims 1 to 6, wherein the content of the liquid crystal polyester (A) is 0.01 part by mass or more and 100 parts by mass or less with respect to 100 parts by mass of the aprotic solvent (S).

8. The liquid crystal polyester liquid composition according to any one of claims 1 to 7, wherein the aprotic solvent (S) is N-methylpyrrolidone.

9. Containing a liquid crystal polyester (A) and a fluororesin (B) having a melting point of 280 °C or higher and 305 °C or lower. The liquid crystal polyester (A) contains an amide bond. 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). The content of the structural unit represented by the following formula (A1) is 30 mol% or more and 80 mol% or less with respect to the total content of all the structural units constituting the liquid crystal polyester (A). The content of the structural unit represented by the following formula (A2) is 10 mol% or more and 35 mol% or less with respect to the total content of all the structural units constituting the liquid crystal polyester (A). The content of the structural unit represented by the following formula (A3) is 10 mol% or more and 35 mol% or less with respect to the total content of all the structural units constituting the liquid crystal polyester (A). The fluororesin (B) is at least one fluororesin selected from the group consisting of 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 mass ratio (solid content) of the liquid crystal polyester (A) to the fluororesin (B) [the liquid crystal polyester (A): the fluororesin (B)] is 9:1 to 2:

3. Liquid crystal polyester film. (A1) -O-Ar1-CO- (A2) -CO-Ar2-CO- (A3) -X-Ar3-Y- (In the formula, Ar1 represents a 1,4-phenylene group, 2,6-naphthalenediyl group, or 4,4'-biphenylene group; Ar2 represents a 1,4-phenylene group, 1,3-phenylene group, or 2,6-naphthalenediyl group; Ar3 represents a 1,4-phenylene group or 1,3-phenylene group; X represents -NH-; Y represents -O- or -NH-.)

10. A laminate comprising a metal layer and the liquid crystal polyester film according to Claim 9 laminated on the metal layer.

11. 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 Claims 1 to 8 on the metal layer.

12. A method for producing a liquid crystal polyester film, comprising applying the liquid crystal polyester liquid composition according to any one of Claims 1 to 8 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.

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