Liquid composition, liquid crystal polyester film and method for producing the liquid crystal polyester film, and laminated film and method for producing the laminated film

Abstract

To provide a liquid composition for forming a liquid crystal polyester film, which can form the liquid crystal polyester film having flexibility and being less prone to cracking.SOLUTION: A liquid composition 1 contains liquid crystal polyester powder and a nonsolvent for the liquid crystal polyester powder, and further contains crystalline polyester or dispersant.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a liquid composition used in the production of a liquid crystal polyester film, a liquid crystal polyester film obtained from the liquid composition, a method for producing the liquid crystal polyester film, and further to a laminated film having the liquid crystal polyester film and a method for producing the laminated film. [Background technology]

[0002] Liquid crystal polyester film has excellent low moisture absorption, high frequency characteristics, flexibility, high gas barrier properties, and thin-wall formability, making it suitable for use as an insulating film for electronic substrates such as flexible printed wiring boards, rigid printed wiring boards, and module boards, or as a surface protection film, and therefore demand for it has been increasing in recent years.

[0003] Various methods for producing the above-mentioned liquid crystal polyester film (film-forming method) have been proposed. For example, Patent Document 1 discloses an example of a coating film-forming method (so-called casting method) in which a liquid composition consisting of a solvent and a liquid crystal polyester dissolved in the solvent (hereinafter, the liquid crystal polyester dissolved in the solvent is referred to as a liquid crystal polyester precursor) is cast onto a substrate, dried, and then heat-treated.

[0004] When a liquid crystal polyester film is formed by a casting method using a liquid composition containing the solvent and the liquid crystal polyester precursor, a film with improved anisotropy (non-oriented film) can be obtained. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2011-167847 Summary of the Invention [Problem to be solved by the invention]

[0006] Furthermore, the present inventors have independently discovered that a liquid crystal polyester film can be formed by the above-mentioned casting method from a liquid composition in which liquid crystal polyester powder (LCP powder) is simply added to water (the liquid crystal polyester powder is not dissolved in water) without using a liquid composition containing the above-mentioned liquid crystal polyester precursor.

[0007] However, the liquid crystal polyester film obtained from the liquid composition containing the liquid crystal polyester powder in the above-mentioned water does not have sufficient flexibility, and there is a problem that the film is prone to cracking.

[0008] The present invention has been made to solve the above-mentioned problems, and aims to provide a liquid composition for forming a liquid crystal polyester film, which is capable of forming a liquid crystal polyester film that is flexible and less susceptible to cracking, even when the liquid crystal polyester precursor is not used. [Means for solving the problem]

[0009] The means for solving the problems are described below together with the reference numerals used in the description of the embodiment of the invention. These reference numerals are used to clarify the correspondence between the description of the claims and the description of the embodiment of the invention, and needless to say, are not used to restrict the interpretation of the technical scope of the present invention.

[0010] In order to achieve the above-mentioned objective, the liquid composition 1 of the present invention contains a liquid crystalline polyester powder, a non-solvent for the liquid crystalline polyester powder (a non-solvent is a solvent that has no or almost no ability to dissolve the target substance, which is the solute, within an experimental temperature range), and further contains a crystalline polyester (Claim 1).

[0011] Furthermore, the non-solvent is preferably an organic solvent (claim 2).

[0012] The crystalline polyester may be poorly soluble in the non-solvent (claim 3).

[0013] It is more preferable that the liquid crystal polyester powder is 10 to 800 parts by weight, preferably 20 to 800 parts by weight in order to provide heat resistance, per 100 parts by weight of the crystalline polyester (claim 4).

[0018] The liquid crystal polyester film 10 of the present invention is formed using the liquid composition 1 described above. , containing a copolymer of crystalline polyester and liquid crystal polyester (claim 5 ).

[0019] In particular, a crystalline polyester formed from a liquid composition containing a crystalline polyester (claims 1 to 4) and a liquid crystal polyester. Cocrystals A liquid crystal polyester film containing 6 ).

[0020] Moreover, the liquid crystal polyester film 10 is non-oriented (claim 7 ).

[0021] The method for producing the liquid crystal polyester film 10 of the present invention includes the steps of casting the liquid composition 1 on a substrate 15 to form a coating film 11, removing the non-solvent from the coating film 11 on the substrate 15, heating the coating film 11 from which the non-solvent has been removed to obtain the liquid crystal polyester film 10 on the substrate 15, and peeling off the substrate 15 (see claim 1). 8 ).

[0022] Furthermore, the laminated film 20 of the present invention is ,liquid The liquid crystal polyester film layer 21 has a liquid crystal polyester film 10, and the liquid crystal polyester film layer 21 is laminated on the surface of the liquid crystal polyester film layer 21, for example, a metal layer 26 (see claim 1). 9 ).

[0023] The liquid crystal polyester film layer 21 may have a laminated structure in which liquid crystal polyester layers 22 and 24 made of liquid crystal polyester without filler added are laminated on both sides of a filler-added layer 23 made of liquid crystal polyester with filler added (see claims).10 ).

[0024] The filler is preferably silica, talc, silica nitride, aluminum nitride or fluorine-based powder (see claim 11 ).

[0025] Furthermore, a conductor pattern may be formed on the metal layer 26 of the laminated film 20 to form a printed wiring board (see claims). 12 ).

[0026] The method for producing the laminated film 20 of the present invention is characterized by including the steps of forming a metal layer 26 on the surface of a substrate 40 by vapor deposition or sputtering, casting the above-mentioned liquid composition 1 to form a coating film 30 on the metal layer 26, drying to remove the non-solvent from the coating film 30, and peeling off the substrate 40 and then heat-treating the coating film 30 to obtain a laminated film having the metal layer 26 and the liquid crystal polyester film layer 21 (see claim 1). 13 ). [Effects of the Invention]

[0027] The liquid composition of the present invention described above, specifically, the composition containing liquid crystal polyester powder and a non-solvent for the liquid crystal polyester powder, and further containing a crystalline resin such as a crystalline polyester (Claim 1) or a dispersant (Claim 5), has made it possible to obtain the following remarkable effects.

[0028] The liquid crystal polyester film 10 produced (by a casting method) using the liquid composition 1 of the present invention is flexible and is less susceptible to cracking. In particular, when the liquid composition of the present invention contains a crystalline polyester, a highly crystalline liquid crystal polyester film (a liquid crystal polyester film containing a polymer alloy of a crystalline polyester and a liquid crystal polyester) can be obtained by polymer alloying (co-crystallizing) the crystalline polyester and the liquid crystal polyester through heat treatment during the production process of the liquid crystal polyester film.

[0029] Furthermore, the liquid crystal polyester film 10 obtained from the liquid composition 1 of the present invention can be made non-oriented, does not have the anisotropy that general liquid crystal polyester films have, and has improved mechanical strength such as tensile force in the width direction. [Brief explanation of the drawings]

[0030] [Figure 1] 1 is a diagram showing steps in a method for producing a liquid crystal polyester film 10 of the present invention. [Figure 2] 1 is a cross-sectional schematic diagram of a laminated film 20 of the present invention (a laminated film 20 having a single liquid crystal polyester film layer 21). [Figure 3] 1 is a cross-sectional schematic diagram of a laminated film 20 of the present invention (a laminated film 20 having a three-layer structure including a liquid crystal polyester film layer 21). [Figure 4] 3A to 3C are diagrams showing an example of a method for manufacturing the laminated film 20 of FIG. 2. [Figure 5] 4A to 4C are diagrams showing an example of a method for manufacturing the laminated film 20 of FIG. 3. [Figure 6] 4A to 4C are diagrams showing another example of a method for manufacturing the laminated film 20 of FIG. 3. [Figure 7] The chemical formula of an example of a fluorine-based powder is shown below. DETAILED DESCRIPTION OF THE INVENTION

[0031] Below, with reference to the attached drawings, we will explain the liquid composition 1 of the present invention used to form a liquid crystal polyester film, the liquid crystal polyester film 10 produced from the liquid composition 1 and a method for producing the liquid crystal polyester film 10, as well as a laminated film 20 having the liquid crystal polyester film 10 and a method for producing the laminated film 20.

[0032] [Liquid composition] Liquid composition 1 of the present invention is a liquid composition containing liquid crystal polyester powder (hereinafter also referred to as LCP powder in the specification) and a non-solvent for the liquid crystal polyester powder, and further contains a crystalline polyester or a dispersant as another component.

[0033] The liquid crystal polyester powder, the non-solvent, the crystalline polyester, and the dispersant will be described below.

[0034] [Liquid Crystal Polyester Powder] The liquid crystal polyester (liquid crystal polyester resin) constituting the liquid crystal polyester powder of the present invention is a polyester resin that exhibits optical anisotropy when melted and has the property of forming an anisotropic melt at a temperature of 450°C or less.

[0035] The liquid crystal polyester preferably has at least two structural units (for example, it may be composed of two different structural units of formula 1) selected from the structural unit shown in the following formula 1 (hereinafter referred to as "formula 1 structural unit"), the structural unit shown in the following formula 2 (hereinafter referred to as "formula 2 structural unit"), and the structural unit shown in the following formula 3 (hereinafter referred to as "formula 3 structural unit"), and for example, it is preferable that the liquid crystal polyester has a content of structural units shown in formula 1 of 30 to 80 mol%, a content of structural units shown in formula 2 of 10 to 35 mol%, and a content of structural units shown in formula 3 of 10 to 35 mol% relative to the total content of all structural units. -O-Ar 1 -CO- (Formula 1) -CO-Ar 2 -CO- (Formula 2) -X-Ar 3 -Y- (Equation 3) (In formulas 1 to 3, Ar 1 represents a phenylene group or a naphthylene group, and Ar 2 represents a phenylene group, a naphthylene group, or a group represented by the following formula 4, and Ar 3 represents a phenylene group or a group represented by the following formula 4, and X and Y each independently represent O or NH. 1 ,Ar 2 and Ar 3 The hydrogen atoms bonded to the aromatic ring may be substituted with halogen atoms, alkyl groups, or aryl groups. -Ar 11 -Z-Ar 12 -(Formula 4) (where, Ar 11 ,Ar 12 each independently represents a phenylene group or a naphthylene group, and Z represents O, CO, or SO2.

[0036] The structural unit of formula 1 is a structural unit derived from an aromatic hydroxycarboxylic acid, and examples of this aromatic hydroxycarboxylic acid include p-hydroxybenzoic acid, m-hydroxybenzoic acid, 6-hydroxy-2-naphthoic acid, 3-hydroxy-2-naphthoic acid, and 4-hydroxy-1-naphthoic acid.

[0037] The structural unit of formula 2 is a structural unit derived from an aromatic dicarboxylic acid, and examples of the aromatic dicarboxylic acid include terephthalic acid, isophthalic acid, 2,6-naphthalenedicarboxylic acid, 1,5-naphthalenedicarboxylic acid, diphenyl ether-4,4'-dicarboxylic acid, diphenyl sulfone-4,4'-dicarboxylic acid, and diphenyl ketone-4,4'-dicarboxylic acid.

[0038] The structural unit of formula 3 is a structural unit derived from an aromatic diol, an aromatic amine having a phenolic hydroxyl group, or an aromatic diamine. Examples of the aromatic diol include hydroquinone, resorcinol, 2,2-bis(4-hydroxy-3,5-dimethylphenyl)propane, bis(4-hydroxyphenyl)ether, bis(4-hydroxyphenyl)ketone, and bis(4-hydroxyphenyl)sulfone.

[0039] Furthermore, examples of aromatic amines having this phenolic hydroxyl group include 4-aminophenol (p-aminophenol) and 3-aminophenol (m-aminophenol), and examples of aromatic diamines include 1,4-phenylenediamine and 1,3-phenylenediamine.

[0040] Such a solvent-soluble liquid crystal polyester may contain a structural unit derived from an aromatic amine having a phenolic hydroxyl group and / or a structural unit derived from an aromatic diamine as the structural unit of formula 3. That is, it may contain a structural unit represented by formula 3' (formula 3') in which at least one of X and Y is NH (hereinafter referred to as "structural unit of formula 3'"). -X-Ar 3 -NH-(Formula 3') (where, Ar 3 and X have the same meanings as above.

[0041] The structural unit of formula 3 may be contained in the range of 25 to 33 mol % relative to the total content of all structural units.

[0042] The structural unit of formula 1 is preferably contained in a range of 30 to 80 mol %, more preferably in a range of 35 to 50 mol %, based on the total content of all structural units. Liquid crystal polyesters containing the structural unit of formula 1 at such a molar fraction tend to have better heat resistance while adequately maintaining liquid crystallinity. Furthermore, taking into consideration the availability of the aromatic hydroxycarboxylic acid from which the structural unit of formula 1 is derived, p-hydroxybenzoic acid and / or 6-hydroxy-2-naphthoic acid are suitable as this aromatic hydroxycarboxylic acid.

[0043] The structural unit of formula 2 is preferably contained in a range of 10 to 35 mol %, more preferably in a range of 25 to 33 mol %, based on the total content of all structural units. Liquid crystal polyesters containing the structural unit of formula 2 at such a molar fraction tend to have better heat resistance while adequately maintaining liquid crystallinity. Furthermore, taking into consideration the availability of the aromatic dicarboxylic acid from which the structural unit of formula 2 is derived, it is preferable that this aromatic dicarboxylic acid be at least one selected from the group consisting of terephthalic acid, isophthalic acid, and 2,6-naphthalenedicarboxylic acid.

[0044] In addition, in order for the resulting liquid crystal polyester to exhibit a higher degree of liquid crystallinity, it is preferable that the molar fraction of the structural unit of formula 2 and the structural unit of formula 3, expressed as [structural unit of formula 2] / [structural unit of formula 3], is in the range of 0.9 / 1 to 1 / 0.9.

[0045] Next, a method for producing the liquid crystal polyester will be described.

[0046] This liquid crystalline polyester can be produced by various known methods. When producing a suitable liquid crystalline polyester, that is, a liquid crystalline polyester consisting of structural units of formula 1, structural units of formula 2, and structural units of formula 3, a method of converting monomers that derive these structural units into ester-forming or amide-forming derivatives and then polymerizing them to produce a liquid crystalline polyester is preferred because of its simple operation.

[0047] The ester-forming / amide-forming derivatives will be explained below with examples.

[0048] Ester-forming and amide-forming derivatives of monomers having a carboxyl group, such as aromatic hydroxycarboxylic acids and aromatic dicarboxylic acids, include those in which the carboxyl group is a highly reactive group such as an acid chloride or acid anhydride to promote the reaction that produces polyesters or polyamides, and those in which the carboxyl group forms an ester with alcohols or ethylene glycol to produce polyesters or polyamides through an ester exchange or amide exchange reaction.

[0049] Ester-forming and amide-forming derivatives of monomers with phenolic hydroxyl groups, such as aromatic hydroxycarboxylic acids and aromatic diols, include those in which the phenolic hydroxyl groups form esters with carboxylic acids, such as those used to produce polyesters and polyamides through transesterification.

[0050] Furthermore, amide-forming derivatives of monomers having amino groups, such as aromatic diamines, include, for example, those in which the amino group forms an amide with a carboxylic acid, such as to produce a polyamide by an amide exchange reaction.

[0051] Among these, in order to more easily produce liquid crystal polyester, a particularly preferred method is to acylate aromatic hydroxycarboxylic acid and a monomer having a phenolic hydroxyl group and / or an amino group, such as an aromatic diol, an aromatic amine having a phenolic hydroxyl group, or an aromatic diamine, with a fatty acid anhydride to form an ester-forming or amide-forming derivative (acylated product), and then polymerize the acyl group of this acylated product with the carboxyl group of a monomer having a carboxyl group to cause ester exchange or amide exchange, thereby producing liquid crystal polyester.

[0052] A method for producing such liquid crystal polyester is described, for example, in Japanese Patent Application Laid-Open No. 2002-220444 or Japanese Patent Application Laid-Open No. 2002-146003.

[0053] In the acylation, the amount of fatty acid anhydride added is preferably 1 to 1.2 equivalents, more preferably 1.05 to 1.1 equivalents, relative to the total of the phenolic hydroxyl groups and amino groups. If the amount of fatty acid anhydride added is less than 1 equivalent, the acylated product and raw material monomers tend to sublimate during polymerization, causing blockage of the reaction system. If the amount exceeds 1.2 equivalents, the resulting liquid crystalline polyester tends to become significantly discolored.

[0054] The acylation 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.

[0055] From the viewpoints of cost and ease of handling, the fatty acid anhydride used in acylation is preferably acetic anhydride, propionic anhydride, butyric anhydride, isobutyric anhydride or a mixture of two or more selected from these, and particularly preferably acetic anhydride.

[0056] The polymerization following the acylation is preferably carried out at 130 to 400°C while increasing the temperature at a rate of 0.1 to 50°C / min, more preferably at 150 to 350°C while increasing the temperature at a rate of 0.3 to 5°C / min.

[0057] In addition, in the polymerization, it is preferable that the acyl group of the acylated product is 0.8 to 1.2 times the equivalent of the carboxyl group.

[0058] During acylation and / or polymerization, the equilibrium is shifted according to Le Châtelier-Brown's law (the principle of equilibrium shift), so it is preferable to distill off the by-product fatty acids and unreacted fatty acid anhydrides from the system by evaporation or other methods.

[0059] The acylation and polymerization may be carried out in the presence of a catalyst, which may be any of those conventionally known as catalysts for polyester polymerization, such as metal salt catalysts such as magnesium acetate, stannous acetate, tetrabutyl titanate, lead acetate, sodium acetate, potassium acetate, and antimony trioxide, and organic compound catalysts such as N,N-dimethylaminopyridine and N-methylimidazole.

[0060] Among these catalysts, heterocyclic compounds containing two or more nitrogen atoms, such as N,N-dimethylaminopyridine and N-methylimidazole, are preferably used (see Japanese Patent Application Laid-Open No. 2002-146003).

[0061] This catalyst is usually added together with the monomer when it is added, and it is not necessarily necessary to remove it after acylation. If the catalyst is not removed, polymerization can proceed directly from acylation.

[0062] The liquid crystalline polyester (liquid crystalline polyester resin) obtained by such polymerization can be used in the present invention as is. However, to further improve the properties of heat resistance and liquid crystallinity, it is preferable to increase the molecular weight, and solid-phase polymerization is preferably used for such increase in molecular weight. A series of operations related to this solid-phase polymerization is explained below. The relatively low-molecular-weight liquid crystalline polyester obtained by the polymerization is extracted and pulverized into powder or flakes. The pulverized liquid crystalline polyester is then heat-treated in a solid state at 20 to 350°C for 1 to 30 hours under an inert gas atmosphere such as nitrogen. This solid-phase polymerization can be carried out by this operation. This solid-phase polymerization can be carried out with stirring or in a stationary state without stirring. From the viewpoint of obtaining a liquid crystalline polyester with a suitable flow initiation temperature, as described below, the preferred conditions for this solid-phase polymerization are as follows: the reaction temperature is preferably above 210°C, and more preferably in the range of 220 to 350°C. The reaction time is preferably selected from the range of 1 to 10 hours.

[0063] The liquid crystalline polyester used in the present invention preferably has a flow initiation temperature of 250°C or higher. When the flow initiation temperature of this liquid crystalline polyester is within this range, a higher degree of adhesion tends to be obtained between the layer containing the liquid crystalline polyester and a conductive metal layer (electrode) formed on the layer containing the liquid crystalline polyester. The flow initiation temperature here refers to the temperature at which the melt viscosity of the liquid crystalline polyester becomes 4800 Pa·s or less under a pressure of 9.8 MPa, as evaluated by a flow tester. This flow initiation temperature is well known to those skilled in the art as a guide to the molecular weight of liquid crystalline polyester (see, for example, "Liquid Crystal Synthesis, Molding, and Applications," edited by Koide Naoyuki, pp. 95-105, CMC, published June 5, 1987).

[0064] The upper limit of the flow initiation temperature of the liquid crystalline polyester is preferably 350°C or lower. If the upper limit of the flow initiation temperature is within this range, the viscosity of the liquid composition of the present invention does not increase significantly when obtained, and the handleability of this liquid composition tends to be good. In order to control the flow initiation temperature of the liquid crystalline polyester within this suitable range, the polymerization conditions for the solid-state polymerization can be appropriately optimized.

[0065] In the present invention, liquid crystal polyester powder (LCP powder) is used, which is the above-mentioned liquid crystal polyester powder in powder form. The particle size of the liquid crystal polyester powder is preferably 0.01 μm to 1000 μm, and from the viewpoint of smoothness of the fired film, it is 0.1 to 30 μm, more preferably 0.1 to 10 μm.

[0066] [Non-solvent] The liquid composition of the present invention contains a non-solvent for the liquid crystal polyester film powder. Here, the non-solvent refers to a solvent that has no or little ability to dissolve the substance (liquid crystal polyester film powder) (a solvent that has almost no ability to dissolve the solute).

[0067] The non-solvent used in the present invention is preferably water, an organic solvent, a polar solvent, or the like.

[0068] In particular, when the liquid composition of the present invention contains the crystalline polyester, it is preferable to use an organic solvent, and when it contains the dispersant instead of the liquid crystal polyester powder, it is preferable to use a polar solvent.

[0069] The organic solvent used in the present invention is not particularly limited, but specific examples include aromatic solvents such as toluene, xylene, solvent naphtha, and solvent, as well as ethyl acetate, dimethylformamide (DMF), and N-methylpyrrolidone.

[0070] When a dispersant is used in the liquid composition 1, it is preferable to use a polar solvent as the non-solvent. Examples of polar solvents include lower alcohols such as methanol, ethanol, and isopropyl alcohol.

[0071] Furthermore, the amount of non-solvent used in the present invention can be appropriately selected depending on the type of non-solvent used, and it is preferable that the amount of liquid crystal polyester powder be 20 to 200 parts by weight, and more preferably 50 to 100 parts by weight, per 100 parts by weight of non-solvent.

[0072] [Crystalline polyester] The crystalline polyester contained in the liquid composition 1 of the present invention is a crystalline polyester made of a polyester-based resin having crystallinity.

[0073] The crystalline polyester used in the present invention does not exhibit thixotropy or the like relative to the liquid crystal polyester powder, and in the production of the liquid crystal polyester film described below, the crystalline polyester functions as a binder for the liquid crystal polyester powder, resulting in the formation of a film. More specifically, during the heat treatment process carried out after the drying process in which the non-solvent is removed from the liquid composition 1 (coating film) after it has been applied to a substrate, the liquid crystal polyester powder melts and copolymerizes with the crystalline polyester (the polymers that make up the crystalline polyester and the polymers that make up the liquid crystal polyester are chemically bonded (for example, block copolymerization or graft copolymerization) to form a polymer), and ultimately, a highly crystalline (highly crystallized and with excellent mechanical and chemical properties, etc.) liquid crystal polyester film is obtained that contains the liquid crystal polyester powder and the crystalline polyester co-crystallized (polymer alloyed).

[0074] As a result, the resulting liquid crystal polyester film is flexible and does not crack.

[0075] Examples of the crystalline polyester used in the present invention include polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, etc., and either commercially available products or synthesized products may be used.

[0076] Examples of commercially available products include the Byron (registered trademark) series manufactured by Toyobo Co., Ltd.

[0077] Furthermore, as the crystalline polyester, semi-crystalline polyarylate (PAR) or the like can be used.

[0078] Furthermore, when synthesizing crystalline polyester, it is synthesized by dehydration condensation using polycarboxylic acid and polyhydric alcohol (polyol).

[0079] Examples of the polycarboxylic acids include aromatic dicarboxylic acids such as terephthalic acid, isophthalic acid, orthophthalic acid, 1,4-naphthalenedicarboxylic acid, 1,5-naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, 2,7-naphthalenedicarboxylic acid, and biphenyldicarboxylic acid; aromatic oxycarboxylic acids such as p-oxybenzoic acid and p-(hydroxyethoxy)benzoic acid; saturated aliphatic dicarboxylic acids such as succinic acid, adipic acid, azelaic acid, sebacic acid, and dodecanedicarboxylic acid; unsaturated aliphatic dicarboxylic acids such as fumaric acid, maleic acid, and itaconic acid; unsaturated alicyclic dicarboxylic acids such as tetrahydrophthalic acid; alicyclic dicarboxylic acids such as hexahydrophthalic acid, 1,2-cyclohexanedicarboxylic acid, 1,3-cyclohexanedicarboxylic acid, and 1,4-cyclohexanedicarboxylic acid; and tricarboxylic acids such as trimellitic acid, trimesic acid, and pyromellitic acid.

[0080] On the other hand, examples of the polyol include aliphatic glycols such as ethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, 2,3-butanediol, 1,5-pentanediol, 1,6-hexanediol, neopentyl glycol, 3-methyl-1,5-pentanediol, and 2-butyl-2-ethyl-1,3-propanediol; oligoalkylene glycols such as diethylene glycol, triethylene glycol, and dipropylene glycol; 1,2 Alicyclic glycols such as 1,3-cyclohexanedimethanol, 1,4-cyclohexanedimethanol, etc.; polyalkylene ether glycols such as polyethylene glycol, polypropylene glycol, polytetramethylene glycol, etc.; triols such as trimethylolethane, trimethylolpropane, glycerin, pentaerythritol, etc.; ethylene oxide adducts and propylene oxide adducts of bisphenol A, and ethylene oxide adducts and propylene oxide adducts of hydrogenated bisphenol A, etc.

[0081] The crystalline polyester is preferably a low-melting crystalline polyester having a melting point lower than that of the liquid crystal polyester powder described above, and in particular, it is preferable that it melts during the drying process in which the non-solvent is removed from the liquid composition (coating film) after application to the substrate described below, and the melting point is preferably 140 to 260°C.

[0082] It is also preferable to use the crystalline polyester of the present invention in the form of powder.

[0083] The crystalline polyester of the present invention may be poorly soluble in the solvent used in the present invention.

[0084] Furthermore, the crystalline polyester used in the present invention is preferably a polyester-based hot melt resin (hot melt adhesive) that exhibits adhesive strength when melted.

[0085] In the production of the liquid crystal polyester film described below, polyester-based hot melt resins melt and exhibit adhesive strength due to the heat generated during the drying process that removes the solvent (non-solvent) from the liquid composition (coating film) after it has been applied to a substrate, thereby improving the functionality of the liquid crystal polyester powder as a bonding agent.

[0086] The polyester hot melt resin used in the present invention includes a polyester hot melt resin which is a polycondensation polymer of a dicarboxylic acid and a diol.

[0087] Specific examples of dicarboxylic acids used as raw material monomers for the polyester hot melt resin include terephthalic acid, isophthalic acid, succinic acid, adipic acid, sebacic acid, dodecanedioic acid, 2,6-naphthalenedicarboxylic acid, malonic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, undecanedioic acid, cyclohexanedicarboxylic acid, dimer acid, 1,2-polybutadiene dicarboxylic acid, etc.

[0088] Specific examples of diols include ethylene glycol, propylene glycol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,9-nonanediol, neopentylene glycol, diethylene glycol, triethylene glycol, cyclohexanedimethanol, 1,2-polybutadiene glycol, polyolefin glycol, polyethylene glycol, polytetramethylene ether glycol, bisphenol A-bis-2-hydroxyethyl ether, etc. In the present invention, a hot melt resin made of a polyester resin containing adipic acid, 1,4-butanediol, etc. in its molecular skeleton is preferably used.

[0089] Commercially available polyester hot melt resins include, for example, the "Vylon (registered trademark) series" manufactured by Toyobo Co., Ltd., which contains, as its main component, a polyester hot melt resin that is a polycondensation polymer of dicarboxylic acid and diol.

[0090] Furthermore, when the liquid composition of the present invention contains a crystalline polyester, the amount of the liquid crystal polyester powder is more preferably 10 to 800 parts by weight per 100 parts by weight of the crystalline polyester, and more preferably 20 to 800 parts by weight in order to impart heat resistance.

[0091] [Dispersant] The present inventors have found that by using a dispersing agent instead of the above-mentioned crystalline polyester, the resulting liquid crystal polyester film has flexibility and is also less susceptible to cracking.

[0092] Examples of dispersants include water-soluble polymers such as ethyl acetate, dimethylformamide (DMF), N-methylpyrrolidone, polyvinyl alcohol, methyl cellulose, ethyl cellulose, hydroxyethyl cellulose, carboxymethyl cellulose, sodium polyacrylate, and sodium polymethacrylate; anionic surfactants such as sodium dodecylbenzenesulfonate, sodium octadecyl sulfate, sodium oleate, sodium laurate, and potassium stearate; cationic surfactants such as laurylamine acetate, stearylamine acetate, and lauryltrimethylammonium chloride; zwitterionic surfactants such as lauryldimethylamine oxide; and nonionic surfactants such as polyoxyethylene alkyl ethers, polyoxyethylene alkylphenyl ethers, and polyoxyethylene alkylamines; and inorganic salts such as tricalcium phosphate, aluminum hydroxide, calcium sulfate, calcium carbonate, and barium carbonate.

[0093] When the liquid composition of the present invention contains the above-mentioned dispersant, the amount of the liquid crystal polyester powder to be blended is preferably 10 to 300 parts by weight per 100 parts by weight of the dispersant, and more preferably 20 to 150 parts by weight from the viewpoint of drying efficiency.

[0094] [Liquid Crystal Polyester Film] The liquid crystal polyester film 10 of the present invention is formed from the above-mentioned liquid composition 1, and preferably has a final concentration of 0.5 g / m2 The liquid crystal polyester film has a moisture permeability of 24 hours or less and a moisture absorption rate of 0.04% (KGK method, 23°C, 60% RH), and the thickness of the liquid crystal polyester film is preferably 0.1 to 100 μm, more preferably 0.3 to 20 μm.

[0095] Furthermore, by forming the liquid crystal polyester film 10 of the present invention using the above-mentioned liquid composition 1 by a casting method, the liquid crystal polyester film 10 can be made non-oriented, does not have the anisotropy that general liquid crystal polyester films have, and can improve mechanical strength such as tensile force in the width direction.

[0096] [Method for producing liquid crystal polyester film] The liquid crystal polyester film 10 of the present invention can be manufactured, for example, by a so-called casting method which includes a coating step of casting the liquid composition 1 of the present invention onto a substrate, a drying step of removing the non-solvent from the liquid composition on the substrate, and a heat treatment (baking) step of heat treating at a temperature higher than that in the drying step.An example of a desirable manufacturing method is shown below.

[0097] As shown in Figure 1, the general flow of producing the liquid crystal polyester film 10 is as follows: the liquid composition 1 of the present invention is cast from a coater 13 onto a substrate 15 to form a coating film 11 on the substrate 15 (coating process); the coating film 11 is dried in a dryer 14 at a predetermined temperature for a predetermined time to remove the non-solvent from the coating film 11 (drying process); the coating film 11 is then continuously heat-treated (baked) in a heating furnace (baking furnace) 17 to form the liquid crystal polyester film 10 on the substrate 15 (heat treatment process); and the substrate 15 is peeled off from the liquid crystal polyester film 10 by a peeler (peeling process) to obtain the liquid crystal polyester film 10.

[0098] The substrate 15 is not particularly limited as long as it can be peeled off from the liquid crystal polyester film 10, but glass plates, metal foils (e.g., stainless steel, gold, copper, iron), resin films (e.g., polyimide) that can withstand heat of 350°C or higher, etc. are preferred.

[0099] Furthermore, examples of the means for casting the liquid composition 1 onto the substrate 15 include roller coating, gravure coating, knife coating, blade coating, rod coating, dip coating, spray coating, curtain coating, slot coating, and screen printing. Among these, the knife coating or slot coating is preferred from the viewpoints of ease of control and ability to achieve a uniform film thickness with high precision.

[0100] Furthermore, there are no particular restrictions on the temperature and time when drying liquid composition 1 (drying process), but if the drying temperature is too high, the liquid crystal polyester powder may melt and begin to polymerize before the baking process described below, resulting in film formation and defects on the coating surface. On the other hand, a temperature is required that can remove the non-solvent from liquid composition 1, and it is preferable that it be, for example, between 60°C and 200°C.

[0101] When the liquid composition 1 contains the crystalline polyester, a temperature is required that can melt the crystalline polyester, and specifically, a temperature of 180°C to 200°C is preferable.

[0102] If the drying temperature is too high, defects may occur on the coating surface, while if the temperature is too low, it may take a long time to remove the non-solvent, which may reduce productivity.

[0103] In addition, in the heat treatment process after the drying process, the laminate 12 consisting of the liquid crystal polyester film 10 and the substrate 15 is obtained by continuously heat treating (baking) the film in a heating furnace (baking furnace) 17 at a predetermined temperature for a predetermined time under a nitrogen atmosphere.

[0104] At this time, since the heat treatment is carried out in a nitrogen atmosphere, it is possible to prevent deterioration of the liquid crystal polyester film 10 due to oxidation of the liquid crystal polyester.

[0105] Here, the heat treatment temperature must be such that the liquid crystalline polyester powder melts and then polymerizes to form a liquid crystalline polyester film, and is preferably within the range of 300 to 350°C. If the heat treatment temperature is 300°C or higher, the liquid crystalline polyester powder melts during the heat treatment, and the molecular weight of the liquid crystalline polyester increases (polymerization), allowing the liquid crystalline polyester film 10 to exhibit its properties. If the heat treatment temperature is 350°C or lower, thermal decomposition of the liquid crystalline polyester film 10 can be suppressed.

[0106] Once the laminate 12 has been produced, the process moves to a film peeling step, in which the liquid crystal polyester film 10 is peeled off from the substrate 15 as shown in FIG.

[0107] Here, the method for peeling off the liquid crystal polyester film 10 is not particularly limited, but a method in which the substrate 15 and the liquid crystal polyester film 10 are continuously peeled off using a pair of peeling rollers 18, 18 as shown in Figure 1 is preferred.

[0108] When the liquid crystal polyester film 10 is peeled off from the substrate 15 in this manner, the manufacturing process for the liquid crystal polyester film 10 is completed.

[0109] Furthermore, after peeling off the liquid crystal polyester film 10, contaminants and the like may be removed by solvent washing, UV treatment, corona treatment, plasma treatment, flame treatment or other methods, if necessary.

[0110] Furthermore, the liquid crystal polyester film of the present invention may have a multilayer structure. For example, when forming a liquid crystal polyester film with a three-layer structure, in the coating process, three liquid compositions 1a to 1c are simultaneously superimposed and cast in three layers onto the substrate 15 using, for example, a three-layer extrusion die or a three-layer slot coating method (not shown), and then the above-mentioned drying process, heat treatment process, and peeling process are carried out to produce a liquid crystal polyester film with a three-layer structure.

[0111] [Laminated film] Next, the laminated film 20 of the present invention will be described.

[0112] The laminated film 20 of the present invention is a film having a liquid crystal polyester film layer 21 formed from the above-mentioned liquid composition 1 of the present invention, and a metal layer 26.

[0113] The laminated film 20 of the present invention can be used for printed wiring boards and the like.

[0114] [Liquid Crystal Polyester Film Layer] The liquid crystal polyester film layer 21 is a liquid crystal polyester film formed from the liquid composition 1, and preferably has a moisture permeability of 0.5 g / m 2 A layer having a liquid crystal polyester film of 24 hours or less, for example, having a thickness of 3 to 100 μm.

[0115] Furthermore, by forming the liquid crystal polyester film layer 21 of the present invention using the above-mentioned liquid composition 1 by a casting method, the liquid crystal polyester film layer 21 can be made non-oriented, and does not have the anisotropy that general liquid crystal polyester films have, thereby improving mechanical strength such as tensile force in the width direction.

[0116] Furthermore, this liquid crystal polyester film layer 21 may have a single layer structure as shown in FIG. 2, or may have a multi-layer structure as shown in FIG. 3 (a three-layer structure in the figure).

[0117] Furthermore, as an example of a case where the liquid crystal polyester film layer 21 has a multi-layer structure, as shown in Figure 3, the liquid crystal polyester film layer 21 laminated on the surface of the metal layer 26 may have a three-layer structure in which liquid crystal polyester layers 22, 24 (for convenience, in this specification, reference numeral 22 is also referred to as the first liquid crystal polyester layer and reference numeral 24 is also referred to as the second liquid crystal polyester layer) which are liquid crystal polyester films that do not contain filler are laminated on both sides of a filler-added layer 23 which is a liquid crystal polyester film with added filler.

[0118] The liquid crystal polyester layers 22 and 24 and the filler-added layer 23 shown in FIG. 3 will be described below.

[0119] [Liquid Crystal Polyester Layer] The liquid crystal polyester layers 22 and 24 shown in Figure 3 are liquid crystal polyester films formed using the liquid composition 1 of the present invention described above, and have a structure that does not contain a filler, and preferably have a moisture absorption rate of 0.04% or less (KGK method, 23°C, 60% RH).

[0120] The thickness of the liquid crystal polyester layers 22 and 24 is preferably 0.3 to 20 μm.

[0121] Furthermore, if the thickness of the liquid crystal polyester layers 22, 24 is made 1 μm or less, it may not be possible to absorb variations in the surface irregularities of the metal layer to be laminated, which may result in an increase in dielectric loss.Therefore, from the viewpoint of maintaining the bonding strength with the metal layer 26 and the dielectric properties, the preferred thickness of the liquid crystal polyester layers 22, 24 is 2 to 15 μm.

[0122] Furthermore, with regard to the thickness of the liquid crystal polyester layers 22, 24, in view of the need to reduce the linear expansion coefficient of the entire liquid crystal polyester film layer 21, it is preferable that they are formed so as not to exceed the thickness of the filler-added layer 23 described below, for example, to a thickness of 50% or less of the filler-added layer 23, more preferably 40% or less.

[0123] Furthermore, the thickness of the first liquid crystal polyester layer 22 and the thickness of the second liquid crystal polyester layer 24 do not have to be the same.

[0124] It is not preferable to add inorganic filler to the liquid crystal polyester layers 22 and 24 in terms of dielectric loss.

[0125] [Filler-added layer] As shown in Figure 3, the laminated film 20 of the present invention has a filler-added layer 23 composed of a liquid crystal polyester film to which an inorganic filler or fluorine-based powder described below has been added, which reduces the linear expansion coefficient of the entire liquid crystal polyester film layer 21 and makes it closer to the linear expansion coefficient of the metal layer 26 laminated on the liquid crystal polyester film layer 21.

[0126] The liquid crystal polyester film constituting this filler-added layer 23 is formed by adding the filler described below to the liquid crystal composition 1 of the present invention, but it is preferable that the liquid crystal polyester powder contained in the liquid crystal composition 1 used to form the filler-added layer 23 is the same as or similar to the liquid crystal polyester powder used in the liquid crystal polyester layers 22 and 24 described above.

[0127] The filler added to the filler-added layer 23 is added to adjust (mainly to lower) the linear expansion coefficient of the entire liquid crystal polyester film layer 21, and is preferably an insulating inorganic filler, such as silica, talc, silica nitride, or aluminum nitride. In addition to the inorganic filler, a fluorine-based powder, which will be described later, may also be added. Inorganic fillers will be described below.

[0128] The mixing ratio of the inorganic filler is in the range of 0.5 to 30 parts by mass per 100 parts by mass of the solid content of the liquid crystal polyester, preferably 1 to 15 parts by mass to maintain the toughness of the finished film, and more preferably 0.5 to 7 parts by mass to achieve a low dielectric constant.

[0129] The average particle size of the inorganic filler used is 0.001 to 15 μm, and based on the thickness of the filler-added layer 23, it is 0.05 to 3 μm, more preferably 0.05 to 1 μm, and the particle shape may be spherical, needle-like, or other shapes, or may be irregular.

[0130] In order to give the entire liquid crystal polyester film layer 21 a low dielectric constant, it is preferable to use inorganic fillers such as fumed silica that do not contain moisture and are obtained by a combustion method.

[0131] It is also possible to use insulating inorganic powder produced by methods other than those described above, such as wet grinding or normal grinding, as filler. In this case, however, in order to obtain a filler with a low moisture content, it is desirable to heat-dry the powder at a temperature of 100°C to 400°C or higher for 30 minutes to 12 hours.

[0132] In the present invention, in addition to the inorganic filler described above, a fluorine-based powder may be added to the filler-added layer 23 as a linear expansion modifier or extender.

[0133] The fluorine-based powder is a powder of a composition that contains fluorine in its composition, and is preferably hydrophobic.

[0134] Examples of fluorine-based powders that can be used include powders such as PTFE (polytetrafluoroethylene), PFA (perfluoroalkoxyalkane), and FEP (perfluoroethylenepropene copolymer).Furthermore, it is also possible to use fluorine-based powders made of, for example, a copolymer of tetrafluoroethylene (component A) and a monomer (component B) whose main component is unsaturated hydrocarbon (see Figure 7. Note that R in the figure is preferably a hydrogen atom, a hydroxyl group, an organic group having a hydroxyl group, or an alkyl group).

[0135] The monomer mainly composed of unsaturated hydrocarbon may have a hydroxyl group. For example, the hydroxyl group is involved in an ester bond accompanying polymerization of the liquid crystal polyester that forms the filler-added layer 23, and the hydroxyl group is dropped to make the layer hydrophobic.

[0136] The fluorine-based powder preferably has a particle size of 0.01 to 5 microns (μm), but is not limited to this.The average particle size of the fluorine-based powder is particularly preferably, but is not limited to, 0.2 to 0.25 (μm).

[0137] The compounding ratio of the fluorine-based powder is in the range of 1 to 10 parts by mass, preferably 2 to 4 parts by mass, per 100 parts by mass of the solid content of the liquid crystal polymer forming the filler-added layer 23 .

[0138] As described above, the filler is added by adjusting the amount of filler added within the range described above, and the thicknesses of the liquid crystal polyester layers 22, 24 and the filler-added layer 23 are adjusted, thereby adjusting the linear expansion coefficient of the entire liquid crystal polyester film layer 21, for example, so that it approaches the linear expansion coefficient of the metal layer 26 laminated on the liquid crystal polyester film layer 21. Then, for example, the difference between the linear expansion coefficient of the metal layer 26 and the linear expansion coefficient of the liquid crystal polyester film layer 21 may be adjusted so that the value of the linear expansion coefficient of the liquid crystal polyester film layer 21 is 25% or less of the linear expansion coefficient of the metal layer 26.

[0139] As an example, if the linear expansion coefficient of the copper foil forming the metal layer 26 is 19 ppm, 25% of that is 4.75, and in this case the linear expansion coefficient of the liquid crystal polyester film layer 21 is adjusted to be 23.75 ppm or less.

[0140] As described above, by using the filler-added layer 23 to bring the linear expansion coefficient of the entire liquid crystal polyester film layer 21 closer to the linear expansion coefficient of the metal layer 26, the warping and distortion of the entire laminated film 20 caused by the difference in linear expansion coefficients can be further reduced.

[0141] Furthermore, in the laminated film 20 of Figure 3, both sides (front and back) of the filler-added layer 23 are covered with liquid crystal polyester layers 22, 24 made of liquid crystal polyester film with no added filler, which allows the low water absorption properties of the original liquid crystal polyester film to be maintained regardless of the hygroscopicity of the inorganic filler, prevents surface precipitation of the filler, reduces dielectric loss due to surface unevenness of the filler, and further prevents the filler from falling off from the filler-added layer 23.

[0142] The surface of the filler-added layer 23 can become rough and matte due to the addition of filler, but a liquid crystal polyester film layer in which the liquid crystal polyester layers 22, 24 to which no filler has been added are laminated on both sides of the filler-added layer 23 can have a surface that is smooth, glossy, and beautiful.

[0143] Although Figure 3 shows an example in which the filler-added layer 23 has a single-layer structure, the filler-added layer 23 may have a multi-layer structure in which the amount of filler added is changed in each layer, thereby creating a gradient in the amount of filler added in the thickness direction.

[0144] In this case, it is preferable to have a gradient structure in which the amount of filler added decreases toward the first liquid crystal polyester layer 22 side and the second liquid crystal polyester layer 24 side.

[0145] [Metal layer] As the raw material for the metal layer 26 constituting the laminated film of the present invention, various conductive metals such as copper and copper alloys, as well as aluminum, iron, gold, silver, and alloys thereof can be used.

[0146] Furthermore, the metal layer 26 of the present invention can be formed by vacuum deposition or sputtering, and it is particularly preferable to use a deposition method which has lower molecular energy and weaker adhesive force than sputtering.

[0147] The thickness of the metal layer of the present invention is preferably 1 to 6 μm.

[0148] [Method for producing laminated film] Next, a method for producing the laminated film 20 of the present invention will be described.

[0149] First, an example of a method for manufacturing a laminated film 20 having a single-layer structure liquid crystal polyester film layer 21 as shown in FIG. 2 will be described.

[0150] First, copper is vapor-deposited onto one side of an OPP (biaxially oriented polypropylene) film as the base material 40 to form a copper foil (metal layer) 26 (vapor deposition step, not shown).

[0151] The thickness of the OPP film 40 is 10 to 200 μm, preferably 25 to 50 μm, and the thickness of the copper vapor deposition is preferably 1 to 6 μm.

[0152] Then, the liquid composition 1 of the present invention is cast from a coating machine onto the surface of the deposited copper foil 26 (coating process, not shown), and the liquid composition 1 coated on the copper foil surface is dried in a dryer (drying process, not shown), to obtain a first laminate (OPP film 40 / copper foil 26 / coating film 30) 31 (not shown).

[0153] Examples of methods for casting the liquid composition 1 onto the copper foil 26 include roller coating, gravure coating, knife coating, blade coating, rod coating, dip coating, spray coating, curtain coating, slot T-die coating, and screen printing. Among these, the knife coating or slot T-die coating is preferred from the viewpoints of ease of control and ability to achieve a uniform film thickness with high precision.

[0154] Furthermore, in the drying step, if the drying temperature is too high, the liquid crystal polyester powder may melt and start to polymerize before the baking step described below, resulting in film formation and the possibility of defects on the coating surface, while if the temperature is too low, the time required for solvent removal may become long, which may reduce productivity, so the drying temperature is preferably set to 60°C or higher and 200°C or lower. Note that, when liquid composition 1 contains a crystalline polyester, a temperature capable of melting the crystalline polyester is required, and specifically, a temperature of 180°C to 200°C is preferred.

[0155] In the step following the drying step, the OPP film 40 is peeled off from the first laminate 31 (peeling step, not shown), to obtain a second laminate (copper foil 26 / coating film 30) 32.

[0156] The method for peeling off the OPP film 40 is not particularly limited, but for example, there is a method in which the OPP film 40 and the second laminate 32 are continuously peeled off using a pair of peeling rollers.

[0157] After the peeling process, the second laminate (copper foil 26 / coating film 30) 32 is continuously heat-treated (continuously fired) in a firing furnace 51 at a predetermined temperature for a predetermined time, as shown in Figure 4, to convert the coating film 30 into a liquid crystal polyester film layer 21, thereby obtaining the laminate film (copper foil 26 / liquid crystal polyester film layer 21) 20 of the present invention (firing process).

[0158] At this time, by filling the baking furnace 51 with nitrogen and performing the heat treatment in a nitrogen atmosphere, it is possible to prevent deterioration of the liquid crystal polyester film due to oxidation of the liquid crystal polyester. Note that the heat treatment may also be performed in an atmosphere of an inert gas other than nitrogen (for example, helium, argon, etc.).

[0159] In addition, in order to prevent oxygen from entering the firing furnace 51, it is preferable to constantly blow inert gas into the openings (clearances) of the transfer inlet and transfer outlet of the firing furnace 51.

[0160] Furthermore, the baking temperature (heat treatment temperature) of the second laminate 32 is preferably within a range of 300 to 350°C. If the heat treatment temperature is 300°C or higher, the liquid crystal polyester powder melts by the heat treatment, and then a liquid crystal polyester film is formed, increasing the fusion bonding (anchoring) and intermolecular bonding at the interface between the liquid crystal polyester film layer 21 and the copper foil (metal layer) 26, allowing the coating film 30 to exhibit the properties of the liquid crystal polyester film layer 21. If the heat treatment temperature is 350°C or lower, thermal decomposition of the liquid crystal polyester film can be suppressed.

[0161] Furthermore, within the firing furnace 51, air nozzles (not shown) are arranged above and below the continuously transported second laminate 32, alternately in the direction of travel of the second laminate 32, and within the firing furnace 51, the second laminate 32 is held in a state where the tension acting on the second laminate 32 is released (non-contact transport), and air (inert gas) is blown from the air nozzles toward the second laminate 32 from above and below the second laminate 32, causing the second laminate 32 to be transported while moving (vibrating) up and down in a direction perpendicular to the transport direction (plane of the precursor laminate). As a result, the second laminate 32 within the firing furnace 51 is heat-treated while being transported in a state where it is floated in a continuous, approximately wave-like manner in the transport direction, as shown in Figure 4.

[0162] As described above, by heat treating the second laminate 32 while moving (vibrating) it up and down, first, the shrinkage reaction of the coating film 30 is alleviated, and then intermolecular behavior is imparted between the liquid crystal polyester film layer 21 and the copper foil 26 obtained by the heat treatment, resulting in an intricate structure at the interface between the liquid crystal polyester film layer 21 and the copper foil 26, and in the finished product, the copper foil (metal) and the liquid crystal polyester film are integrated together in such a way that peeling cannot be measured (i.e., the adhesion and bonding strength between them are significantly improved), as if the liquid crystal polyester film layer 21 had obtained an anchoring effect at the nano-level at the interface region with the copper foil 26.

[0163] Furthermore, when a liquid crystal polyester film is prepared from the coating film 30 by heat treatment, shrinkage, warping, distortion within the polymer, etc. usually occur. However, as the film is loosened by the above-mentioned up and down movement during heat treatment, the prepared liquid crystal polyester film layer becomes non-oriented, and the distortion within the polymer and the stress on the film are removed, so that the laminated film of the present invention having the prepared liquid crystal polyester film layer becomes straight without shrinkage, warping, or distortion of the polymer.

[0164] Therefore, there is no need to use the clip tenter that has been used conventionally to prevent warping.

[0165] In addition, the above-mentioned up and down movement loosens the liquid crystal polyester film, which promotes degassing of the solvent (non-solvent), dehydration, and other residues (including impure gases) within the liquid crystal polyester polymer, thereby avoiding shrinkage or foaming of the film (air bubbles from desolvation) and preventing the formation of residual marks such as air bubbles and pinholes.

[0166] Furthermore, residues and impurities in the liquid crystal polyester polymer can cause foaming, which can cause noise in electronic devices when the laminated film 20 of the present invention is used as a flexible substrate (printed wiring board), for example.

[0167] The height of the up and down movement of the second laminate 32 in the above-mentioned firing furnace 51 is 3 mm to 900 mm, preferably 20 mm to 200 mm, and more preferably, the height of the up and down movement (wave height) of the second laminate 32 is 50 mm to 200 mm by non-contact transport in which the second laminate 32 is floated and transported between the above-mentioned upper and lower air nozzles.

[0168] The installation interval of the air nozzles is preferably 3 mm to 900 mm, and in view of the installation cost of the air nozzles, it is more preferably 100 mm to 500 mm, and more preferably 200 mm to 300 mm.

[0169] Furthermore, heat treatment is carried out in the baking furnace 51 using far-infrared heating, and since liquid crystal polyester easily absorbs far-infrared rays deep into the interior, the absorbed far-infrared rays (energy) excite and shake the monomer or polymer, releasing (degassing) impurity gases within the film and further alleviating polymer distortion.

[0170] The wavelength range of infrared radiation emitted by far-infrared heaters is approximately 3 to 25 μm, which coincides with the wavelength range of thermal vibrations (molecular vibrations or lattice vibrations of crystals) of almost all substances except metals.

[0171] As described above, the second laminate 32 is heat-treated (firing process) to obtain a laminated film 20 having a copper foil (metal layer) 26 and a liquid crystal polyester film layer 21, and then, to improve the surface smoothness, it is continuously pressed with a heating calendar 52 (150 to 200°C), cooled at room temperature, and then wound up.

[0172] The laminated film 20 that has passed through the heating calendar 52 may be pressed by a press (not shown) to further pressure-bond the copper foil 26 and the liquid crystal polyester film layer 21 together.

[0173] Next, an example of a method for manufacturing a laminated film 20 having a three-layer structure of liquid crystal polyester film layers 21 as shown in FIG. 3 will be described.

[0174] First, copper is vapor-deposited onto the OPP (biaxially oriented polypropylene) film 40 that serves as the base material, to form the copper foil (metal layer) 26 .

[0175] The thickness of the OPP film 40 is 10 to 200 μm, preferably 25 to 50 μm, and the thickness of the copper vapor deposition is preferably 1 to 6 μm.

[0176] Then, the liquid compositions 1a to 1c that form each layer of the liquid crystal polyester film layer 21 are cast in order from a coater onto the copper foil surface deposited on the OPP film 40 (coating process), and then the liquid compositions 1a to 1c coated on the copper foil 26 are dried in a dryer to form coating films 30a to 30c on the copper foil 26 (drying process).

[0177] More specifically, as shown in FIG. 5, first, a liquid composition of the present invention (conveniently also referred to as the first liquid composition) 1a that forms the first liquid crystal polyester layer 22 is cast on a copper foil 26 vapor-deposited on an OPP film 40 using a coater 61a and then dried in a dryer 63a, and a liquid composition of the present invention (conveniently also referred to as the second liquid composition) 1b that contains the filler and forms a filler-added layer 23 on top of that is cast on a coater 61b and then dried in a dryer 63b, and further, a liquid composition (conveniently also referred to as the third liquid composition) 1c that forms the second liquid crystal polyester layer 24 on top of that is cast on a coater 61c and then dried in a dryer 63c, thereby forming coating films 30a to 30c on the copper foil 26.

[0178] The method for casting the liquid composition 1 in the coating step and the drying temperature in the drying step are the same as those explained in the manufacturing method for the laminated film 20 when the liquid crystal polyester film layer 21 is a single layer.

[0179] Furthermore, as shown in Figure 6, the above-mentioned three liquid compositions 1a to 1c may be simultaneously superimposed in three layers and cast onto copper foil 26 vapor-deposited on OPP film 40 using a three-layer extrusion die or a three-layer slot coating method, and the three layers may be simultaneously dried in a dryer 63.

[0180] As a result of the drying, the solvent is removed from the liquid compositions 1a to 1c of each layer on the copper foil 26, and they become coating films 30a to 30c.The OPP film 40 is then peeled off (OPP peeling process, not shown), thereby obtaining a laminate 33 (not shown) in which three layers of the coating films 30a to 30c are laminated on the surface of the copper foil (metal layer) 26.

[0181] The laminate 33 is then heat-treated in a heating furnace (baking furnace) (baking process, not shown) to obtain a three-layer liquid crystal polyester film layer 21, thereby producing the laminate film 20 of the present invention as shown in Figure 3.

[0182] The baking step may be the same as the baking step described in the method for producing the laminated film 20 when the liquid crystal polyester film layer 21 is a single layer.

[0183] In the manufacturing method of the laminated film 20 of the present invention described above, the sputtering or vapor deposition of copper foil is carried out before the firing of the liquid crystal polyester film, rather than after the firing of the liquid crystal polyester film, as mentioned above.

[0184] This solves the problem of pinholes caused by sputtering or vapor deposition of metal foil. In other words, when the liquid crystal polyester film condenses during baking, the metal foil follows and closes the pinholes.

[0185] Furthermore, when the liquid crystal polyester film is baked, thermal activation and high bonding with the sputtered interface of the metal foil are achieved, and for example, when the laminated film 20 of the present invention is used as a flexible substrate (printed wiring board), the metal layer 26 can withstand the formation of fine etching in a subsequent process.

[0186] Furthermore, as described above, by using the liquid composition 1 of the present invention in film formation by the casting method, the drying time in the drying process and the baking time in the heat treatment process can be significantly reduced, and foaming of the film during molding can be suppressed.

[0187] Furthermore, as mentioned above, the manufacturing method of the laminated film 20 of the present invention does not involve forming a film by flowing the liquid crystal polyester in a molten state in a certain direction as in the hot melt casting method, so the liquid crystal polyester film layer of the resulting laminated film 20 can be made non-oriented, eliminating the problem of general liquid crystal polyesters being prone to tearing in the orientation direction, and furthermore, by mitigating the anisotropy, a laminated film 20 can be obtained that is less likely to warp or distort.

[0188] Furthermore, even when the liquid crystal polyester film layer 21 manufactured by the above method has a three-layer structure, not only the liquid crystal polyester layers 22 and 24 to which no filler has been added, but also the filler-added layer 23 are non-oriented, and it has been confirmed that the film has excellent mechanical strength in all directions.

[0189] Furthermore, by providing a filler-added layer 23 in the liquid crystal polyester film layer 21 of the laminated film 20, the linear expansion coefficient of the entire film can be made closer to that of the metal layer (copper foil) 26, thereby preventing warping or distortion of the entire laminated film 20. On the other hand, since the lamination surface with the metal layer 26 is the liquid crystal polyester layer 22 (or 24) which does not contain filler, the adhesion between the liquid crystal polyester film layer 21 and the metal layer 26 is not impaired even by the addition of filler, and further, low moisture absorption is maintained, thereby enabling the advantageous properties of liquid crystal polyester to be exhibited, making the laminated film 20 highly functional. [Explanation of symbols]

[0190] 1. Liquid composition 1a First liquid composition 1b Second liquid composition 1c Third liquid composition 10 Liquid crystal polyester film 11 Paint film 12 Laminate 13 Coating machine 14 Dryer 15 Base material 17 Heating furnace (firing furnace) 18 Peeling roller 20 Laminated Film 21 Liquid crystal polyester film layer 22 Liquid crystal polyester layer (first liquid crystal polyester layer) 23 Filler-added layer 24 Liquid crystal polyester layer (second liquid crystal polyester layer) 26 Metal layer (copper foil) 30(30a,30b,30c) Paint film 31 first laminate 32 Second laminate 33 Laminate 40 Base material (OPP film) 51 Kiln 52 Heating Calendar 61 (61a, 61b, 61c) Coating machine 63(63a,63b,63c) Dryer

Claims

1. A liquid composition comprising a liquid crystal polyester powder, a non-solvent for the liquid crystal polyester powder, and a crystalline polyester.

2. The liquid composition according to claim 1, wherein the non-solvent is an organic solvent.

3. 3. The liquid composition according to claim 1, wherein the crystalline polyester is poorly soluble in the non-solvent.

4. 4. The liquid composition according to claim 1, wherein the liquid crystal polyester powder is contained in an amount of 10 to 800 parts by weight per 100 parts by weight of the crystalline polyester.

5. A liquid crystal polyester film comprising a copolymer of a crystalline polyester and a liquid crystal polyester formed from the liquid composition according to any one of claims 1 to 4.

6. A liquid crystal polyester film as described in claim 5, which contains a co-crystal of a crystalline polyester and a liquid crystal polyester.

7. 7. The liquid crystal polyester film according to claim 5, which is non-oriented.

8. A method for producing a liquid crystal polyester film, comprising: a step of casting the liquid composition according to any one of claims 1 to 4 onto a substrate to form a coating film; a step of removing the non-solvent from the coating film on the substrate; a step of heating the coating film from which the non-solvent has been removed to obtain a liquid crystal polyester film on the substrate; and a step of peeling off the substrate.

9. A laminated film comprising a liquid crystal polyester film layer having the liquid crystal polyester film according to any one of claims 5 to 7, and a metal layer laminated on the surface of the liquid crystal polyester film layer.

10. The laminated film according to claim 9, characterized in that the liquid crystal polyester film layer has a laminated structure in which a liquid crystal polyester layer made of a liquid crystal polyester without a filler added thereto is laminated on both sides of a filler-added layer made of a liquid crystal polyester with a filler added thereto.

11. 11. The laminated film according to claim 10, wherein the filler is silica, talc, silica nitride, aluminum nitride or fluorine-based powder.

12. A printed wiring board having a conductor pattern formed on the metal layer of the laminated film according to any one of claims 9 to 11.

13. forming a metal layer on the surface of the substrate by vapor deposition or sputtering; a step of casting the liquid composition according to any one of claims 1 to 4 onto the metal layer to form a coating film on the metal layer; drying to remove the non-solvent from the coating; and A method for producing a laminated film, comprising the step of peeling off the substrate and then heat-treating the coating film to obtain a laminated film having the metal layer and the liquid crystal polyester film layer.

Images