LCP membrane

Abstract

This invention provides an LCP film with relatively excellent manufacturability and low manufacturing cost, excellent thickness accuracy, and improved anisotropy such as the coefficient of linear expansion in the MD and TD directions. The LCP film of this invention comprises a thermoplastic liquid crystal polymer, and has a coefficient of linear expansion in the TD direction of -30.0 to 30.0 ppm / K, a coefficient of linear expansion in the MD direction of -10.0 to 30.0 ppm / K, and a CV value of the film thickness measured according to JIS K7130:1999 (calculated from the thickness of 275 points measured at 1.0 mm intervals in the MD direction, their average value, and their standard deviation) of 0.030 or less.

Description

LCP film The present invention relates to an LCP film and the like. Previously, liquid crystal polymer (LCP, Liquid Crystal Polymer) films manufactured by melt extrusion molding using the inflation method or the T-die method have been widely used in various fields. In particular, thermotropic liquid crystal polymers that exhibit liquid crystallinity in the molten state or solution state can be extrusion molded and have excellent properties such as high gas barrier properties, high film strength, high heat resistance, high insulation, low water absorption, and low dielectric properties at high frequencies. Therefore, research is being conducted on their practical use for gas barrier film materials, electronic materials, electrical insulation materials, etc. Also, since the high-frequency characteristics and low dielectric properties of insulating materials for circuit boards using liquid crystal polymers are excellent, in recent years, they have emerged as insulating materials for circuit boards such as flexible printed wiring boards (FPCs), flexible printed wiring board laminates, and fiber-reinforced flexible laminates in the fifth-generation mobile communication system (5G) or millimeter-wave radar, etc., which are expected to develop in the future. However, regarding the LCP film obtained by melt extrusion molding, it is known that due to the high liquid crystal alignment or relatively rigid molecular chains of the liquid crystal polymer, etc., and further due to shear stress generated by die swell or die lip expansion during melt extrusion, etc., the polymer chains are highly molecularly aligned in the traveling direction of the film, that is, the MD direction (Machine Direction, length direction). Therefore, various physical properties such as film strength, thermal expansion coefficient, and dimensional accuracy exhibit significant anisotropy between the MD direction and the TD direction (Transverse Direction, lateral direction), and it is difficult to obtain a thermoplastic liquid crystal polymer film with a relatively high industrial utilization value. In order to improve the anisotropy between the MD direction and the TD direction, research has been conducted on stretching treatment of liquid crystal polymer films. However, since the stretching treatment is a technique for stretching the entire liquid crystal polymer film in the uniaxial or biaxial direction to a large extent, the direction or degree of alignment cannot be finely adjusted. Therefore, at present, the stretching treatment of liquid crystal polymer films is mainly used to adjust the surface roughness or surface accuracy of liquid crystal polymer films. For example, Patent Document 1 discloses a manufacturing method in which a laminate is first prepared by sandwiching a liquid crystal polymer film between a pair of laminated films (fluororesin porous films having a specific gravity of 1.3 or more and an elongation at break in the stretching direction of 400% or more), and the laminate is stretched in the uniaxial or biaxial direction under temperature conditions where the fluororesin porous film is softened but not substantially melted and the liquid crystal polymer film is softened or melted. Prior Art Documents Patent Documents Patent Document 1: Japanese Patent No. 3958629 [Problems to be Solved by the Invention] However, the manufacturing technology described in Patent Document 1 only stays at adjusting the surface roughness or surface accuracy of the obtained stretched LCP film, and does not consider anything about the thickness accuracy of the obtained LCP film itself. The electrical properties of an insulator are thickness-dependent. In order to develop an insulating substrate material with stable dielectric properties, it is necessary to improve the thickness accuracy of the LCP film. In recent years, in the applications of electronic materials, the requirement for the thickness accuracy of the insulating film has been increasing. Moreover, the inventors have newly found that when using the LCP film as an insulating substrate material, especially when performing sputtering or the like on a metal or the like, the higher the thickness accuracy of the LCP film as an insulating substrate material, the finer the pattern that can be formed, and the higher the electrical reliability during circulation, storage, and use after manufacturing can be maintained. In addition, the manufacturing technology described in the above Patent Document 1 is premised on using a special laminated film, i.e., a fluororesin porous film with a relatively large specific gravity and a relatively large elongation at break, and its versatility is poor. In fact, Patent Document 1 has shown that when using a turned film of PTFE (Polytetrafluoroethylene) with a relatively large specific gravity or a polyimide film with a relatively small elongation at break, the laminated film will break during the stretching process, and the required stretching process cannot be carried out. As a result, the cost of the LCP film obtained by the manufacturing technology described in Patent Document 1 becomes relatively high. Moreover, the above Patent Document 1 only stays at obtaining an LCP film with a relatively low surface roughness and relatively high surface accuracy by performing a biaxial stretching process of stretching 1.3 times in the MD direction and 3.9 times in the TD direction on a special laminate in which a liquid crystal polymer film is sandwiched between fluororesin porous films with a relatively large specific gravity and a relatively large elongation at break at a temperature near the melting point of the liquid crystal polymer film. That is, the manufacturing technology described in Patent Document 1 only stays at adjusting the surface roughness or surface accuracy of the obtained stretched LCP film, and does not consider anything about improving the anisotropy such as the linear expansion coefficient in the MD direction and the TD direction. The present invention has been made in view of the above problems. The object of the present invention is to provide an LCP film or the like with relatively excellent productivity, which can be manufactured at low cost, has excellent thickness accuracy, and has improved anisotropy such as the linear expansion coefficient in the MD direction and the TD direction. [Technical means for solving the problem] In order to solve the above problems, the inventors have conducted intensive research and as a result, have newly found an LCP film with relatively excellent productivity, which can be manufactured at low cost, has excellent thickness accuracy, and has improved anisotropy such as the linear expansion coefficient in the MD direction and the TD direction, thereby completing the present invention. That is, the present invention provides the following various specific embodiments. <1> An LCP film comprising a thermoplastic liquid crystal polymer, having a linear expansion coefficient in the TD direction of -30.0 to 30.0 ppm / K and a linear expansion coefficient in the MD direction of -10.0 to 30.0 ppm / K, and having a CV value of the film thickness (calculated based on the thicknesses of 275 points measured at 1.0 mm intervals in the MD direction, their average value, and their standard deviation) measured according to JIS K7130:1999 of 0.030 or less. <2> The LCP film according to <1>, wherein the LCP film is a biaxially stretched LCP film stretched in the biaxial direction. <3> The LCP film according to <1> or <2>, wherein the ratio of the CV value of the film thickness after the biaxial stretching treatment to the CV value of the film thickness before the biaxial stretching treatment is 2.00 or less. <4> The LCP film according to any one of <1> to <3>, wherein the LCP film has a thickness of 15 μm or more and 300 μm or less. <5> The LCP film according to any one of <1> to <4>, wherein the CV value is 0.020 or less. <6> The LCP film according to any one of <1> to <5>, having a linear expansion coefficient in the TD direction of -20.0 to 5.0 ppm / K and a linear expansion coefficient in the MD direction of -10.0 to 10.0 ppm / K. <7> The LCP film according to any one of <1> to <6>, having a linear expansion coefficient in the TD direction of -15.0 to 0.0 ppm / K and a linear expansion coefficient in the MD direction of -10.0 to 5.0 ppm / K. <8> The LCP film according to any one of <1> to <7>, having an orientation degree of 0.0 to 30.0%. [Effects of the Invention] According to the present invention, it is possible to provide an LCP film or the like with relatively excellent productivity, capable of being manufactured at low cost, having excellent thickness accuracy, and improved anisotropy such as the linear expansion coefficients in the MD direction and the TD direction. Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. Furthermore, unless otherwise specified, the positional relationships such as up, down, left, and right are based on the positional relationships shown in the drawings. Also, the dimensional ratios of the drawings are not limited to the ratios shown. Among them, the following embodiments are examples for explaining the present invention, and the present invention is not limited thereto. That is, the present invention can be arbitrarily changed and implemented within the scope of its gist. Furthermore, in this specification, for example, the expression of the numerical range of "1 to 100" includes both the lower limit value "1" and the upper limit value "100". The same applies to the expression of other numerical ranges. FIG. 1 is a conceptual diagram showing the LCP film 100 of the present embodiment. The LCP film of the present embodiment is characterized in that it is an LCP film 100 containing a thermoplastic liquid crystal polymer, the linear expansion coefficient in the TD direction is -30.0 to 30.0 ppm / K, the linear expansion coefficient in the MD direction is -10.0 to 30.0 ppm / K, and the CV value of the film thickness measured according to JIS K7130:1999 (calculated based on the thickness of 275 points measured at an interval of 1.0 mm in the MD direction, its average value, and its standard deviation) is 0.030 or less. As long as the LCP film 100 of the present embodiment has the above configuration, its type is not particularly limited. Examples of such LCP films 100 of the present embodiment include: LCP extrusion films manufactured by multilayer coextrusion methods such as the T-die method, the inflation method, the coextrusion method, the two-layer coextrusion method, and the three-layer coextrusion method; pressure-heat treated products of LCP extrusion films; uniaxially stretched films of LCP extrusion films (LCP films stretched in the TD direction); biaxially stretched films of LCP extrusion films (LCP films stretched in the MD direction and the TD direction); biaxially expanded and contracted LCP films of LCP extrusion films (LCP films contracted in the MD direction and stretched in the TD direction), etc., but are not particularly limited to these. From the viewpoints of thickness accuracy, anisotropy, productivity, cost, etc., the biaxially expanded and contracted LCP film of the LCP extrusion film is particularly preferred as the LCP film 100. Hereinafter, an example of manufacturing the LCP film 100 by the biaxial expansion and contraction treatment (MD contraction-TD stretching) method will be given and described in further detail. <Manufacturing method of LCP film> FIG. 2 is a conceptual diagram showing the biaxial expansion and contraction treatment (MD contraction-TD stretching treatment) in the manufacturing method of the LCP film 100 of the present embodiment. The manufacturing method of the LCP film of the present embodiment includes at least the following steps: preparing an LCP extrusion film 10 (hereinafter, also referred to as the preparation step S1); and subjecting the LCP extrusion film 10 to a contraction treatment at a contraction ratio of 0.80 times to 0.99 times in the MD direction and a stretching treatment in the TD direction to obtain an LCP film 100 (hereinafter, also referred to as the biaxial expansion and contraction step S2). Hereinafter, each step will be described in detail. (Preparation Step S1) In this preparation step S1, an LCP extrusion film 10 containing liquid crystal polymer (LCP, Liquid Crystal Polymer) is prepared. As the LCP extrusion film 10, those well-known in the industry can be used, and the type thereof is not particularly limited. In the manufacturing method of the present embodiment, when a liquid crystal polymer film with higher molecular orientation is used, the effect becomes more significant. As the liquid crystal polymer contained in the LCP extrusion film 10, those well-known in the industry can be used, and the type thereof is not particularly limited. The liquid crystal polymer is a polymer that forms an optically anisotropic molten phase, and typically, thermotropic liquid crystal compounds can be exemplified. Furthermore, the properties of the anisotropic molten phase can be confirmed by a known method such as a polarization inspection method using a cross-polarizing element. More specifically, the confirmation of the anisotropic molten phase can be carried out by the following method, that is, using a Leitz polarizing microscope, observing the sample placed on the Leitz high-temperature stage at a magnification of 40 times in a nitrogen atmosphere. As a specific example of the liquid crystal polymer, a liquid crystal polymer obtained by polycondensing an aromatic or aliphatic dihydroxy compound, an aromatic or aliphatic dicarboxylic acid, an aromatic hydroxycarboxylic acid, an aromatic diamine, an aromatic hydroxylamine, an aromatic aminocarboxylic acid, etc. is preferably used. As the liquid crystal polymer, examples include: homopolymers thereof; copolymers thereof; modified products thereof; polymer blends of these with other thermoplastic resins other than liquid crystal polymers, polymer alloys of these with other thermoplastic resins other than liquid crystal polymers, etc., but are not particularly limited to these. From the perspective of obtaining the LCP extrusion film 10 by an extrusion molding method, the liquid crystal polymer is preferably a thermoplastic liquid crystal polymer. As a specific example of a preferred liquid crystal polymer, examples include: an aromatic polyamide resin obtained by polycondensing monomers such as aromatic hydroxycarboxylic acid, aromatic diamine, aromatic hydroxylamine, etc.; a (fully) aromatic polyester resin obtained by polycondensing monomers such as aromatic diol, aromatic carboxylic acid, aromatic hydroxycarboxylic acid, etc., but are not particularly limited to these. These can be used alone in one kind, or two or more kinds can be used in any combination and ratio. Thermoplastic liquid crystal polymers are generally classified into type I, type II, type III, etc. from the perspective of the heat distortion temperature (TDUL). Any type of thermoplastic liquid crystal polymer can be preferably used in the present embodiment, as long as it is appropriately selected and used according to the application purpose. For example, in the application to an electronic circuit board for lead-free solder at around 260 to 290 °C, a high heat-resistant type I thermoplastic liquid crystal polymer with a TDUL of around 250 to 350 °C and a relatively high heat-resistant type II thermoplastic liquid crystal polymer with a TDUL of around 240 to 250 °C are respectively preferably used. Among these, (entirely) aromatic polyester resins that exhibit properties similar to thermotropic liquid crystals and have a melting point of 250 °C or higher, preferably 280 °C to 380 °C, can be used favorably. As such (entirely) aromatic polyester resins, for example, (entirely) aromatic polyester resins synthesized from monomers such as aromatic diols, aromatic carboxylic acids, and hydroxycarboxylic acids and exhibiting liquid crystallinity when melted are known. As representative examples thereof, polycondensates of ethylene terephthalate and p-hydroxybenzoic acid, polycondensates of phenol and phthalic acid and p-hydroxybenzoic acid, polycondensates of 2,6-dihydroxynaphthalene carboxylic acid and p-hydroxybenzoic acid, etc. can be cited, but they are not particularly limited to these. Furthermore, the (entirely) aromatic polyester resin can be used alone, or two or more thereof can be used in any combination and ratio. Depending on the required performance, an entirely aromatic polyester resin with a relatively high melting point or high heat distortion temperature and high heat resistance can be used, or an aromatic polyester resin with a relatively low melting point or low heat distortion temperature and excellent moldability can be used. As a preferred aspect, the following (entirely) aromatic polyester resin can be cited, which has 6-hydroxy-2-naphthoic acid and its derivatives (hereinafter sometimes simply referred to as "monomer component A") as the basic structure and has at least one selected from the group consisting of p-hydroxybenzoic acid, terephthalic acid, isophthalic acid, 6-naphthalenedicarboxylic acid, 4,4'-biphenol, bisphenol A, hydroquinone, 4,4-dihydroxybiphenol, ethylene terephthalate, and their derivatives as monomer components (hereinafter sometimes simply referred to as "monomer component B"). Regarding such (entirely) aromatic polyester resins, the linear chains of the molecules are regularly arranged in the molten state to form an anisotropic molten phase, typically exhibiting properties similar to thermotropic liquid crystals and having excellent basic properties in terms of mechanical properties, electrical properties, high-frequency properties, heat resistance, hygroscopicity, etc. Furthermore, the (entirely) aromatic polyester resin in the above preferred embodiment may have any constitution as long as it has monomer component A and monomer component B as essential units. For example, it may have two or more types of monomer component A, or may have three or more types of monomer component A. Also, the (entirely) aromatic polyester resin in the above preferred embodiment may also contain other monomer components (hereinafter sometimes simply referred to as "monomer component C") in addition to monomer component A and monomer component B. That is, the (entirely) aromatic polyester resin in the above preferred embodiment may be a polycondensate of a binary system or higher composed only of monomer component A and monomer component B, or may be a polycondensate of monomer components of a ternary system or higher including monomer component A, monomer component B, and monomer component C. As other monomer components, monomer components other than the above monomer component A and monomer component B can be exemplified. Specifically, aromatic or aliphatic dihydroxy compounds and their derivatives; aromatic or aliphatic dicarboxylic acids and their derivatives; aromatic hydroxycarboxylic acids and their derivatives; aromatic diamines, aromatic hydroxylamines, or aromatic aminocarboxylic acids and their derivatives, etc. can be exemplified, but are not particularly limited to these. Other monomer components can be used alone in one type, or two or more types can be used in any combination and ratio. Furthermore, in this specification, "derivative" means that a halogen atom (for example, a fluorine atom, a chlorine atom, a bromine atom, an iodine atom), an alkyl group having 1 to 5 carbon atoms (for example, a methyl group, an ethyl group, a n-propyl group, an isopropyl group, a n-butyl group, an isobutyl group, a sec-butyl group, a tert-butyl group, etc.), an aryl group such as a phenyl group, a hydroxyl group, an alkoxy group having 1 to 5 carbon atoms (for example, a methoxy group, an ethoxy group, etc.), a carbonyl group, -O-, -S-, -CH 2 - and other modifying groups are introduced into a part of the above monomer components (hereinafter sometimes referred to as "monomer components having substituents"). Here, the "derivative" may also be an ester-forming monomer such as an acyl compound, an ester derivative, or an acyl halide of monomer component A and monomer component B that may have the above modifying groups. As an excellent embodiment, examples include: binary condensation polymers of p-hydroxybenzoic acid and its derivatives and 6-hydroxy-2-naphthoic acid and its derivatives; condensation polymers of a ternary system or higher of p-hydroxybenzoic acid and its derivatives, 6-hydroxy-2-naphthoic acid and its derivatives, and monomer component C; condensation polymers of a ternary system or higher containing p-hydroxybenzoic acid and its derivatives, 6-hydroxy-2-naphthoic acid and its derivatives, and at least one selected from the group consisting of terephthalic acid, isophthalic acid, 6-naphthalenedicarboxylic acid, 4,4'-biphenol, bisphenol A, hydroquinone, 4,4-dihydroxybiphenol, ethylene terephthalate and its derivatives; and condensation polymers of a quaternary system or higher containing p-hydroxybenzoic acid and its derivatives, 6-hydroxy-2-naphthoic acid and its derivatives, at least one selected from the group consisting of terephthalic acid, isophthalic acid, 6-naphthalenedicarboxylic acid, 4,4'-biphenol, bisphenol A, hydroquinone, 4,4-dihydroxybiphenol, ethylene terephthalate and its derivatives, and at least one monomer component C. These can be obtained, for example, in the form of those having a relatively low melting point compared to homopolymers of p-hydroxybenzoic acid and the like. Therefore, the thermoplastic liquid crystal polymers using these are excellent in formability when thermocompression-bonded to an adherend. From the viewpoints of lowering the melting point of the (entirely) aromatic polyester resin and improving the formability when thermocompression-bonding the LCP film 100 to an adherend, or obtaining a high peel strength when thermocompression-bonding the LCP film 100 to a metal foil, the content ratio of monomer component A in terms of molar ratio relative to the (entirely) aromatic polyester resin is preferably 10 mol% or more and 90 mol% or less, more preferably 30 mol% or more and 85 mol% or less, still more preferably 50 mol% or more and 80 mol% or less. Similarly, the content ratio of monomer component B in terms of molar ratio relative to the (entirely) aromatic polyester resin is preferably 10 mol% or more and 90 mol% or less, more preferably 15 mol% or more and 70 mol% or less, still more preferably 20 mol% or more and 50 mol% or less. Further, the content ratio of monomer component C that can be contained in the (entirely) aromatic polyester resin in terms of molar ratio is preferably 10 mol% or less, more preferably 8 mol% or less, still more preferably 5 mol% or less, and particularly preferably 3 mol% or less. Furthermore, the method for synthesizing the liquid crystal polymer is not particularly limited, and known methods can be applied. Known polycondensation methods using monomer components to form ester bonds can be applied, such as: melt polymerization, melt acidolysis method, slurry polymerization method, etc. When applying these polymerization methods, an acylation or acetylation step can also be carried out according to a conventional method. The LCP extruded film 10 may further contain an inorganic filler. By containing the inorganic filler, it is thus easy to obtain the LCP film 100 with reduced anisotropy in the linear expansion coefficients in the MD direction, TD direction, and ZD direction (Z-axis Direction, film thickness direction). For example, in applications such as rigid substrate uses that require multi-layer lamination, such LCP films 100 are particularly useful. As the inorganic filler, those known in the industry can be used, and the type thereof is not particularly limited. For example, it can be exemplified: kaolin, calcined kaolin, calcined clay, uncalcined clay, silica (e.g., natural silica, fused silica, amorphous silica, hollow silica, wet silica, synthetic silica, AEROSIL, etc.), aluminum compounds (e.g., boehmite, aluminum hydroxide, alumina, hydrotalcite, aluminum borate, aluminum nitride, etc.), magnesium compounds (e.g., magnesium aluminum silicate, magnesium carbonate, magnesium oxide, magnesium hydroxide, etc.), calcium compounds (e.g., calcium carbonate, calcium hydroxide, calcium sulfate, calcium sulfite, calcium borate, etc.), molybdenum compounds (e.g., molybdenum oxide, zinc molybdate, etc.), talc (e.g., natural talc, calcined talc, etc.), mica, titanium oxide, zinc oxide, zirconium oxide, barium sulfate, zinc borate, barium metaborate, sodium borate, boron nitride, aggregated boron nitride, silicon nitride, carbon nitride, strontium titanate, barium titanate, zinc stannate and other stannates, etc., but it is not particularly limited to these. These can be used alone as one kind, or two or more kinds can also be used in combination. Among these, from the viewpoint of dielectric properties, etc., silica is preferably used. In addition, the inorganic filler used herein may also be one that has been subjected to surface treatment known in the industry. By surface treatment, the moisture resistance, adhesion strength, dispersibility, etc. can be improved. As the surface treatment agent, it can be exemplified: silane coupling agent, titanate coupling agent, sulfonate ester, carboxylate ester, phosphate ester, etc., but it is not particularly limited to these. Regarding the median diameter (d50) of the inorganic filler, from the viewpoint of the reduction effect of requirements, etc., the d50 of the inorganic filler is preferably 0.01 μm or more and 50 μm or less, more preferably 0.03 μm or more and 50 μm or less, and still more preferably 0.1 μm or more and 50 μm or less. Furthermore, in this specification, the median diameter (d50) of the inorganic filler means the value measured based on volume by the laser diffraction-scattering method using a laser diffraction / scattering particle size distribution measuring device (LA-500 manufactured by Horiba, Ltd.). The content of the inorganic filler is not particularly limited, and can be appropriately set according to the required performance in consideration of the blending balance with other essential components and optional components. From the viewpoints of kneadability or processability during preparation, the effect of reducing the linear expansion coefficient, etc., the content of the inorganic filler, in terms of the solid content conversion relative to the total amount of the LCP extrusion film 10, is preferably 1% by mass or more and 45% by mass or less in total, more preferably 3% by mass or more and 40% by mass or less in total, and still more preferably 5% by mass or more and 35% by mass or less in total. The LCP extrusion film 10 may also contain resin components other than the above-mentioned thermoplastic resin (hereinafter sometimes simply referred to as "other resin components"), such as thermosetting resins or elastomers, etc., within the range that does not excessively impair the effects of the present invention. Also, the LCP extrusion film 10 may also contain additives known in the industry, such as mold release improvers such as higher fatty acids having 10 to 25 carbon atoms, higher fatty acid esters, higher fatty acid amides, higher fatty acid metal salts, polysiloxanes, fluororesins, etc.; colorants such as dyes and pigments; organic fillers; antioxidants; heat stabilizers; light stabilizers; ultraviolet absorbers; flame retardants; antistatic agents; surfactants; rust preventives; defoamers; fluorescent agents, etc., within the range that does not excessively impair the effects of the present invention. These additives can be used alone, one kind at a time, or in combination of two or more kinds. These additives can be included in the molten resin composition prepared during the formation of the LCP extrusion film 10. The content of these resin components or additives is not particularly limited. From the viewpoints of forming processability or heat stability, etc., relative to the total amount of the LCP extrusion film 10, it is preferably 0.01 to 10% by mass respectively, more preferably 0.1 to 7% by mass respectively, and still more preferably 0.5 to 5% by mass respectively. As the above-described LCP extrusion film 10, a melt extrusion film such as a T-die extrusion film or a blown film can be preferably used. The melt extrusion film can be obtained by extruding a resin composition containing the above-described liquid crystal polymer and optional components such as inorganic fillers or other resin components as required into a specified thickness. The type of extrusion method is not particularly limited, and various known methods can be applied. For example, the following methods can be arbitrarily combined and applied: a T-die method or a blown method, such as a co-extrusion method of a manifold type or a co-extrusion method of a feedblock type, such as a multi-layer co-extrusion method such as a two-layer co-extrusion method or a three-layer co-extrusion method. Among these, from the viewpoint of the ease of controlling the molecular orientation of the liquid crystal polymer on the film surface and inside the film, as a preferred embodiment, the following method can be exemplified: an extrusion molding method using a T-shaped die head (hereinafter sometimes simply referred to as "T-die extrusion method"), extruding the above-described resin composition from the T-shaped die head and forming it into a film shape, and then, if necessary, performing a cooling treatment, a crimping treatment, a pressure heating treatment, etc., to obtain a specific LCP extrusion film 10. Further, as the LCP extrusion film 10, a liquid crystal polymer film layer having a laminated structure in which at least a thermoplastic resin layer, a liquid crystal polymer film layer, and a thermoplastic resin layer are arranged in sequence can also be preferably used as an intermediate layer (core layer) of a three-layer co-extrusion film. In this case, by removing the thermoplastic resin layers of the two outer layers of the three-layer co-extrusion film, a single-layer liquid crystal polymer film layer (LCP extrusion film 10) can be taken out. The thickness of the LCP extrusion film 10 is not particularly limited and can be appropriately set according to the required performance. Considering the processability or productivity during extrusion molding, etc., it is preferably 15 μm or more and 300 μm or less, more preferably 18 μm or more and 250 μm or less, and still more preferably 20 μm or more and 200 μm or less. The melting point (melting temperature) of the LCP extrusion film 10 is not particularly limited. From the viewpoints of the heat resistance or processability of the film, etc., the melting point (melting temperature) is preferably 200 to 400 °C, more preferably 250 to 360 °C, still more preferably 260 to 355 °C, and even more preferably 270 to 350 °C, and particularly preferably 275 to 345 °C. Further, in this specification, the melting point of the LCP extrusion film 10 refers to the value obtained by observing the elimination of the thermal history. When the extrusion film is heated (1st heating) at a heating rate of 20 °C / minute in the temperature range of 30 to 400 °C and then cooled (1st cooling) at a cooling rate of 50 °C / minute, and then heated for the second time (2nd heating) at a heating rate of 20 °C / minute, using DSC8500 (manufactured by PerkinElmer), the temperature of the melting peak obtained by differential scanning calorimetry (DSC). Here, the coefficient of linear thermal expansion (CTE, α2, 23 to 200 °C) in the TD direction of the LCP extruded film 10 is not particularly limited, preferably 5.0 to 60.0 ppm / K, more preferably 5.0 to 55.0 ppm / K, and still more preferably 5.0 to 50.0 ppm / K. Also, the coefficient of linear thermal expansion (CTE, α2, 23 to 200 °C) in the MD direction of the LCP extruded film 10 is preferably -30.0 to 5.0 ppm / K, more preferably -25.5 to 5.0 ppm / K, and still more preferably -23.0 to 5.0 ppm / K. Furthermore, the LCP extruded film 10 to be subjected to the biaxial stretching treatment may be an unstretched film, a uniaxially stretched film, or a biaxially stretched film. Furthermore, in this specification, the measurement of the coefficient of linear thermal expansion is carried out by the TMA (Thermomechanical Analysis) method in accordance with JIS K7197, and the average coefficient of linear thermal expansion means the average value of the coefficient of linear thermal expansion at 23 to 200 °C measured by this method. Here, the coefficient of linear thermal expansion to be measured means the value for observing the value after eliminating the thermal history. When the target film as the measurement sample is heated (1st heating) at a heating rate of 5 °C / minute and then cooled to the measurement ambient temperature (23 °C) (1st cooling), and then heated for the second time (2nd heating) at a heating rate of 5 °C / minute. Also, other detailed measurement conditions are based on the conditions described in the following examples. On the other hand, the dielectric properties of the LCP extruded film 10 are not particularly limited and can be appropriately set according to the required performance. From the viewpoint of obtaining higher dielectric properties, the relative dielectric constant ε r (36 GHz) is preferably 3.0 or more and 3.7 or less, more preferably 3.0 to 3.5. Similarly, the dielectric loss tangent tanδ (36 GHz) is preferably 0.0010 or more and 0.0050 or less, more preferably 0.0010 or more and 0.0045 or less. Furthermore, in this specification, the relative dielectric constant ε r (36 GHz) and the dielectric loss tangent tanδ (36 GHz) mean the values at 36 GHz measured by the resonant cavity perturbation method in accordance with JIS K6471. Furthermore, the LCP extruded film 10 can be used directly, or further, if necessary, a pressure heating step can be carried out to further reduce the molecular orientation (anisotropy) of the liquid crystal polymer or further relieve internal strain, thereby also enabling the LCP film 100 with more reduced anisotropy of the dimensional change rate or the LCP film 100 with a smaller absolute value of the dimensional change rate to be realized. The type of the pressure heating treatment is not particularly limited, and it may be carried out by using a method known in the industry, such as contact heat treatment, non-contact heat treatment, etc. For example, a non-contact heater, an oven, a blowing device, a hot roller, a cooling roller, a hot press, a double-belt hot press and other known machines can be used to carry out the thermosetting type. At this time, a release film or a porous film known in the industry may be disposed on the surface of the LCP extrusion film 10 as needed for heat treatment. Further, when carrying out this heat treatment, from the viewpoint of controlling the orientation, the following hot pressing method can be preferably used, that is, a release film or a porous film is disposed on the front and back surfaces of the LCP extrusion film 10, and while being clamped between a pair of endless belts of a double-belt press, hot pressing bonding is carried out, and then the release film or the porous film is removed. Regarding the hot pressing method, it may be carried out by referring to, for example, Japanese Patent Laid-Open No. 2010-221694, etc. As the treatment temperature when the LCP extrusion film 10 using the above resin composition is hot pressed between a pair of endless belts of a double-belt press, in order to control the crystal state of the LCP extrusion film 10, it is preferably carried out at a temperature higher than the melting point of the liquid crystal polymer and lower than a temperature 70 °C higher than the melting point, more preferably at a temperature higher than the melting point +5 °C and lower than a temperature 60 °C higher than the melting point, and still more preferably at a temperature higher than the melting point +10 °C and lower than a temperature 50 °C higher than the melting point. The hot pressing bonding conditions at this time are not particularly limited and can be appropriately set according to the required performance. It is preferably carried out under the conditions of a surface pressure of 0.5 to 10 MPa and a heating temperature of 250 to 430 °C, more preferably under the conditions of a surface pressure of 0.6 to 8 MPa and a heating temperature of 260 to 400 °C, and still more preferably under the conditions of a surface pressure of 0.7 to 6 MPa and a heating temperature of 270 to 370 °C. On the other hand, when using a non-contact heater or an oven, for example, it is preferably carried out under the conditions of 200 to 320 °C for 1 to 20 hours. (Biaxial stretching step S2) In this biaxial stretching step S2, the above-mentioned LCP extrusion film 10 as the object to be treated is subjected to a shrinkage treatment in the MD direction at a shrinkage ratio of 0.80 times to 0.99 times, and an extension treatment is carried out in the TD direction to obtain an LCP film 100 (the LCP film 11 after biaxial stretching). Regarding the LCP film 100 obtained after such a biaxial stretching step (MD shrinkage - TD extension treatment), if regarded as a shrinkage film, it is classified as a uniaxial shrinkage film (MD shrinkage film), if regarded as an extension film, it is classified as a uniaxial extension film (TD extension film), and if regarded as a biaxially stretched film, it is classified as a uniaxial shrinkage uniaxial extension film (MD shrinkage TD extension film). When the LCP extruded film 10 is contracted in the MD direction and extended in the TD direction, a known stretching machine or a biaxial stretching and contracting machine (biaxial expansion and contraction machine) can be used. As a simultaneous biaxial expansion and contraction machine (stretch blow molding machine), for example, those described in Japanese Patent Application Laid-Open No. 2022-051372 are known. Specifically, the simultaneous biaxial stretching and contracting machine 20 shown in FIG. 3 is used to feed the LCP extruded film 10 in a state where it is held between a plurality of clamps 21a and 22a of endless loops 21 and 22 arranged symmetrically left and right. By reducing the distance between the clamps 21a and the distance between the clamps 22a, the LCP extruded film 10 is contracted in the MD direction. At the same time, since the distance between the endless loops 21 and 22 gradually increases in the film conveyance direction, the LCP extruded film 10 held between the endless loops 21 and 22 is gradually pulled outward and extended in the TD direction. The processing temperature of the biaxial expansion and contraction step S2 is not particularly limited as long as it is above the glass transition point of the LCP extruded film 10, preferably 70 to 180 °C, more preferably 90 to 180 °C. After the contraction in the MD direction and the extension in the TD direction are performed, for example, it is preferably heat-treated (thermosetting type) at 100 to 240 °C for 1 to 600 seconds. When performing the thermosetting type, methods known in the industry can be used, such as: contact heat treatment, non-contact heat treatment, etc., and the type is not particularly limited. For example, a non-contact heater, an oven, a blowing device, a hot roller, a cooling roller, a hot press, a double-belt hot press, and other known machines can be used to perform the thermosetting type. At this time, a release film or a porous film known in the industry can be arranged on the surface of the LCP film 100 as needed for hot pressing treatment. Furthermore, in the biaxial expansion and contraction step S2, the stretching treatment and the contraction treatment can be performed sequentially, or the contraction treatment and the stretching treatment can be performed sequentially in the reverse order, or the contraction treatment and the stretching treatment can be performed simultaneously. The draw ratio and shrinkage ratio of the LCP extruded film 10 in the biaxial stretching and shrinking step S2 are not particularly limited, and can be set according to the degree of improvement of the required anisotropy. From the viewpoint of alleviating the directional anisotropy of the LCP extruded film with highly molecular orientation in the MD direction, the shrinkage ratio in the MD direction is preferably 0.80 to 0.99 times, more preferably 0.80 to 0.95 times, and still more preferably 0.80 to 0.93 times, based on the length in the MD direction before shrinkage. Similarly, from the viewpoint of alleviating the directional anisotropy of the LCP extruded film with highly molecular orientation in the MD direction, the draw ratio in the TD direction is preferably 1.20 to 2.50 times, more preferably 1.30 to 2.50 times, and still more preferably 1.40 to 2.50 times, based on the length in the TD direction before drawing. Also, the draw-shrinkage ratio represented by the product of the shrinkage ratio in the MD direction and the draw ratio in the TD direction (when the shrinkage ratio in the MD direction is set as m and the draw ratio in the TD direction is set as n, the draw-shrinkage ratio represented by m×n) is preferably 0.960 to 2.475 times, more preferably 1.040 to 2.375 times, and still more preferably 1.120 to 2.325 times. According to this manufacturing method, although the draw-shrinkage ratio in the biaxial stretching and shrinking step S2 is relatively low, an LCP film 100 with a small absolute value of the linear expansion coefficient in the MD direction and the TD direction and a small anisotropy of the linear expansion coefficient in the MD direction and the TD direction can be easily manufactured. Also, after the shrinkage and stretching treatment, the LCP film 100 can be cooled (or slowly cooled) as needed. The cooling of the LCP film 100 can be carried out, for example, using a pair of cooling rollers, or can also be carried out by natural cooling. Then, for the LCP film 100 after the biaxial stretching treatment, by, for example, using a traction roller to perform traction and winding it in a roll shape on a winding roller, a roll stock sheet can be manufactured. Furthermore, although an example of separately shrinking and stretching the LCP extrusion film 10 is shown in this embodiment, the first film member and the second film member may be respectively disposed on the front and back surfaces of the LCP extrusion film 10 so that they are respectively in close contact with the front side and the back side of the LCP extrusion film 10, thereby forming a crimped body having a laminated structure of the first film member / LCP extrusion film 10 / second film member, and performing a biaxial expansion and contraction treatment on the crimped body. The raw materials constituting the first film member and the second film member are not particularly limited as long as they can be in close contact with the LCP extrusion film 10 and have a strength that will not break when subjected to MD shrinkage-TD stretching treatment. For example, a laminate or an impregnated body containing any combination of paper, woven fabric, non-woven fabric, metal plate, alloy plate, metal foil, alloy foil, resin film, rubber sheet, foamed sheet, etc. can be used as the first film member and the second film member. Among these, a thermosetting resin film such as a polyimide film is preferred; a thermoplastic resin film having a melting point higher than that of the LCP extrusion film 10; a metal foil such as an aluminum foil or a copper foil, etc. Furthermore, the first film member and the second film member may be made of raw materials having the same structure or different structures. The method for producing the crimped body is not particularly limited, and a known lamination formation method can be applied. By overlapping the first film member, the LCP extrusion film 10, and the second film member in sequence, and performing crimping or thermocompression bonding using known machines such as a press, a crimping roller, a non-contact heater, an oven, a blowing device, a hot roller, a cooling roller, a hot press, a double-belt press, etc., a crimped body can be obtained. Also, the processing conditions during crimping are not particularly limited as long as they are appropriately set according to the raw materials used. For example, it can be performed under the conditions of a surface pressure of 0.3 to 10 MPa and a heating temperature above the heat distortion temperature of the LCP extrusion film 10 and below the melting point +70°C, preferably under the conditions of a surface pressure of 0.6 to 8 MPa and a heating temperature above the melting point of the LCP extrusion film 10 and below a temperature 60°C higher than the melting point. Furthermore, in order to achieve the required peelability, various release agents can also be disposed between the LCP extrusion film 10 and the first film member or between the LCP extrusion film 10 and the second film member of the crimped body. Also, in order to achieve the required adhesion, various primer agents or easy adhesives, etc. can be disposed instead of the release agent. Then, after performing MD shrinkage-TD stretching treatment on the LCP extrusion film 10, the crimped body is cooled as needed, and then the first film member and the second film member crimped to the two surfaces of the crimped body are peeled off (removed), whereby the LCP film 100 after MD shrinkage-TD stretching treatment can be obtained. Cooling of the crimped body can be performed using a pair of cooling rollers, for example, and can also be performed by natural cooling. Then, for the LCP film 100 after MD shrinkage-TD stretching treatment, for example, by being pulled using a traction roller and being wound around a winding roller in a roll shape, a roll stock sheet can be produced. <LCP Film> The LCP film 100 obtained by the above manufacturing method is an MD shrinkage-TD extension of the LCP extrusion film 10 (hereinafter sometimes referred to as a biaxially stretched LCP film). In the LCP film 100 of the present embodiment, the CV value of the film thickness is not particularly limited, preferably 0.030 or less, more preferably 0.028 or less, and still more preferably 0.025 or less. Here, the lower limit of the CV value of the film thickness is not particularly limited, as long as it is 0.000 or more, and it may also be 0.005 or more. Furthermore, in this specification, the CV value of the film thickness means the value measured according to JIS K7130:1999. Specifically, it means making the probe of the contact thickness gauge contact the central part in the TD direction of the automatically conveyed film, measuring the thickness of 275 points measured at intervals of 1.0 mm in the MD direction, and the value calculated from the average value and the standard deviation of the measured thickness. Also, other detailed measurement conditions are based on the conditions described in the examples below. The smaller the CV value of the film thickness, the more excellent the thickness accuracy. Also, when the LCP film 100 of the present embodiment is a biaxially stretched LCP film, the comparison of the above CV value of the film thickness after the biaxial stretching treatment with the CV value of the film thickness before the biaxial stretching treatment is preferably 2.00 or less, more preferably 1.80 or less, and still more preferably 1.50 or less. Here, the lower limit of the ratio of the CV values is not particularly limited, as long as it is 0.00 or more, and it may also be 0.10 or more. Generally, there is a tendency for the CV value of the extension of the LCP film to be larger after the extension treatment than before the extension treatment, and the extension treatment becomes one of the reasons for the excessive deterioration of the thickness accuracy. In contrast, in the LCP film 100 of the present embodiment, the excessive deterioration of the thickness accuracy before and after the biaxial stretching treatment is suppressed. The thickness of the LCP film 100 is not particularly limited and can be appropriately set according to the required performance. Considering the processability or productivity during extrusion molding, etc., it is preferably 15 μm or more and 300 μm or less, more preferably 18 μm or more and 250 μm or less, and still more preferably 20 μm or more and 200 μm or less. The linear expansion coefficient (CTE, α2, 23 to 200 °C) in the MD direction of the LCP film 100 is not particularly limited and can be appropriately set according to the required performance. From the viewpoints of reducing the anisotropy of the dimensional change rate and the absolute value of the dimensional change rate and improving the adhesion to the metal foil, etc., it is preferably -10.0 to 30.0 ppm / K in the MD direction, more preferably -10.0 to 10.0 ppm / K, and still more preferably -10.0 to 5.0 ppm / K. According to the manufacturing method of the present embodiment, an LCP film 100 having a negative linear expansion coefficient in the MD direction can be easily obtained. The linear expansion coefficient (CTE, α2, 23 to 200 °C) of the LCP film 100 in the TD direction is not particularly limited and can be appropriately set according to the required performance. From the viewpoints of reducing the anisotropy of the dimensional change rate and the absolute value of the dimensional change rate and improving the adhesion to the metal foil, it is preferably -30.0 to 30.0 ppm / K, more preferably -20.0 to 5.0 ppm / K, and still more preferably -15.0 to 0.0 ppm / K in the TD direction. According to the manufacturing method of the present embodiment, an LCP film 100 having a negative linear expansion coefficient in the TD direction can be easily obtained. Here, the orientation of the LCP film 100 is not particularly limited and can be appropriately set according to the required performance. From the viewpoints of reducing the anisotropy of the dimensional change rate and the absolute value of the dimensional change rate and improving the adhesion to the metal foil, the degree of orientation is preferably 0.0 to 30.0%, more preferably 0.0 to 28.0%, still more preferably 0.0 to 26.0%, and particularly preferably 0.0 to 25.0%. The smaller this value, the more isotropic the in-plane physical properties are. Furthermore, in this specification, the degree of orientation (%) of the LCP film 100 means a value calculated according to the following formula, which is the area ratio of the orientation peak in the diffraction intensity distribution curve obtained by performing X-ray diffraction measurement by the transmission method using an X-ray diffraction apparatus. Generally, in the case of a measurement object with a small degree of orientation (%), a diffraction peak with a small and wide peak intensity is observed in the X-ray diffraction measurement. Therefore, the calculation method based on the half-width at half-maximum of the orientation peak cannot ensure high measurement accuracy. Therefore, in this specification, the degree of orientation (%) is calculated from the area ratio of the orientation peak rather than the half-width at half-maximum of the orientation peak by performing X-ray diffraction measurement from one film surface side of the LCP film 100. Specifically, as shown in FIG. 4 and Equation 1, as the calculation method based on the area ratio of the orientation peak, the peak intensity (orientation component) is measured under 2θ / θ scanning, and the intensity in the azimuthal direction from 0° to 360° is measured under β scanning to obtain the intensity distribution in the azimuthal direction (basic intensity (isotropic component)). The ratio of the area occupied by the orientation component excluding the area of the isotropic component as the basis in the overall area (area of the orientation component + area of the isotropic component) is calculated as the degree of orientation (%). [Equation 1] The dielectric properties of the LCP film 100 are not particularly limited and can be appropriately set according to the required performance. From the viewpoint of obtaining higher dielectric properties, the relative dielectric constant εr (36 GHz) is preferably 3.0 or more and 3.7 or less, more preferably 3.0 to 3.5. Similarly, the dielectric loss tangent tanδ (36 GHz) is preferably 0.0010 or more and 0.0050 or less, more preferably 0.0010 or more and 0.0045 or less. Furthermore, in this specification, the relative dielectric constant εr (36 GHz) and the dielectric loss tangent tanδ (36 GHz) mean the values at 36 GHz measured by the cavity perturbation method according to JIS K6471. Also, other detailed measurement conditions are based on the conditions described in the following examples. Furthermore, similar to the above-mentioned LCP extrusion film, the LCP film 100 may also contain inorganic fillers, resin components other than the above-mentioned thermoplastic resins, additives well-known in the industry, and the like. Specific examples thereof are as described in the item of the LCP extrusion film, and repeated explanations are omitted here. As described in the above detailed description, according to the manufacturing method of the LCP film 100 of the present embodiment, unlike the prior art, it is possible to easily and stably manufacture the LCP film 100 having a small absolute value of the linear expansion coefficient in the MD direction and the TD direction and a small anisotropy of the linear expansion coefficient in the MD direction and the TD direction at low cost without requiring a special laminated film. Therefore, the industrial usefulness of the manufacturing method of the LCP film 100 of the present embodiment is excellent. Also, LCP films having excellent high-frequency characteristics and low dielectric properties are not only used in applications such as electronic circuit boards, multilayer boards, high heat dissipation boards, flexible printed wiring boards, antenna boards, optoelectronic hybrid boards, and IC (Integrated Circuit) packages, but in recent years, they have also emerged as insulating materials for circuit boards such as flexible printed wiring boards (FPCs), flexible printed wiring board laminates, and fiber-reinforced flexible laminates in the future-developed fifth-generation mobile communication system (5G) or millimeter-wave radar. Therefore, compared with the prior art, the LCP film 100 obtained by applying the manufacturing method of the LCP film 100 of the present embodiment has a smaller absolute value of the linear expansion coefficient in the MD direction and the TD direction, and a smaller in-plane anisotropy of the linear expansion coefficient. The occurrence of bending during manufacturing is suppressed, making it suitable for recent ultra-fine processing. Therefore, it can be widely used as a raw material particularly useful in this application. Examples Hereinafter, examples and comparative examples will be given to specifically illustrate the features of the present invention, but the present invention is not limited by any of them. That is, as long as the gist of the present invention is not departed from, the materials, usage amounts, ratios, treatment contents, treatment sequences, etc. shown in the following examples can be appropriately changed. Also, the values of various manufacturing conditions or evaluation results in the following examples have the meaning of preferably upper limits or preferably lower limits in the embodiments of the present invention, and the preferably numerical range can also be a range defined by the above upper limit or lower limit, and the values of the following examples or the combination of the values of the examples with each other. [Coefficient of linear expansion] Using the TMA method according to JIS K7197, the coefficients of linear expansion (CTE, α2, 23 to 200 °C) in the MD direction and TD direction of each film were measured respectively. Measuring instrument: TMA 4000SE (manufactured by NETZSCH) Measuring method: Tensile mode Measuring conditions: Sample size 25 mm × 4 mm × thickness 50 μm Clamping distance 20 mm Temperature range 23 to 200 °C (second run) Heating rate 5 °C / min Atmosphere Nitrogen (flow rate 50 ml / min) Test load 5 gf ※ In order to observe the value after eliminating the thermal history, the value of the second run was adopted. [Thickness accuracy] According to JIS K7130:1999, the probe of the contact thickness gauge was brought into contact with the central part in the TD direction of each automatically conveyed film, and the film thickness at 275 points was measured at 1.0 mm intervals in the MD direction. Based on the obtained measurement results, the average value and standard deviation of the film thickness were calculated, and the CV value was obtained based on these values. Measuring instrument: Desktop offline contact thickness measuring device TOF-5R01 (manufactured by Yamabun Electric Co., Ltd.) Contact thickness gauge Probe: Made of Teflon (registered trademark) Measuring conditions: By using the above-mentioned measuring device and automatically conveying the film, the film thickness at 275 points in the measurement traveling direction was continuously measured. Based on the obtained results, the average value and standard deviation σ of the film thickness were calculated, and the CV value (= standard deviation σ / average value of the film thickness) was obtained based on these values respectively. Also, the CV values before and after the stretching treatment and before and after the biaxial stretching and shrinking treatment were obtained respectively, and the ratio of after treatment / before treatment was calculated. The larger this value is, the worse the thickness accuracy can be judged due to the stretching treatment or biaxial stretching and shrinking treatment, and the smaller this value is, the better the deterioration of the thickness accuracy due to the stretching treatment or biaxial stretching and shrinking treatment can be judged to be suppressed. [Orientation degree] Using an X-ray diffractometer Smartlab (manufactured by Rigaku Corporation), X-ray diffraction measurements of the LCP film were performed from the film surface side using the transmission method, and the orientation degree was measured separately. Here, a Cu sealed tube was used as the X-ray source, and X-ray diffraction measurements (2θ / θ scan, β scan) were performed using a parallel beam optical system and the transmission method. First, a peak was confirmed at 2θ = 19.5° in the 2θ / θ scan. Next, for the diffraction peak at 2θ = 19.5, the intensity from 0° to 360° in the azimuthal direction was measured under β scan, and thus the intensity distribution in the azimuthal direction was obtained. Based on the base intensity (isotropic component) and the peak intensity (orientation component) of the obtained β curve, the orientation degree was calculated according to the above formula based on the area ratio of the orientation peaks. (Comparative Example 1) Using the T-die casting method, a type II thermoplastic liquid crystal polymer (a copolymer with a monomer composition of 74 mol% p-hydroxybenzoic acid and 26 mol% 6-hydroxy-2-naphthoic acid, and a melt viscosity of 80 Pa·sec at a temperature of 300°C and a shear rate of 500 sec -1 was extruded from an extruder to obtain a comparative example 1 LCP extruded film (unoriented LCP film) with a width of 300 mm, an average thickness of 65.5 μm, and a melting point of 280°C. By feeding the comparative example 1 LCP extruded film to a uniaxial tenter stretching machine, after preheating at 130°C for 10 - 30 seconds, stretching treatment with a stretching ratio of 1.50 times was performed in the TD direction at a temperature of 130°C, and then heat setting was performed at 130°C for 30 seconds, thereby obtaining a comparative example 1 LCP film (TD stretched LCP film) with an average thickness of 48.6 μm. (Example 1) Using the T-die casting method, a type II thermoplastic liquid crystal polymer (a copolymer with a monomer composition of 74 mol% p-hydroxybenzoic acid and 26 mol% 6-hydroxy-2-naphthoic acid, and a melt viscosity of 80 Pa·sec at a temperature of 300°C and a shear rate of 500 sec -1 was extruded from an extruder to obtain an example 1 LCP extruded film (unoriented LCP film) with a width of 300 mm, an average thickness of 71.0 μm, and a melting point of 280°C. By feeding the example 1 LCP extruded film to a shrink tenter, after preheating at 130°C for 10 - 30 seconds, a shrinkage treatment with a shrinkage ratio of 0.90 times in the MD direction and a shrinkage stretching treatment with a stretching ratio of 1.45 times in the TD direction were performed simultaneously at a temperature of 130°C, and then heat setting was performed at 130°C for 30 seconds, thereby obtaining an example 1 LCP film (biaxially expanded and shrunk LCP film) with an average thickness of 55.7 μm. The manufacturing conditions and measurement results are shown in Table 1. [Table 1] (Example 2) Except that the shrinkage ratio in the MD direction was changed to 0.85 times and the elongation ratio in the TD direction was changed to 1.70 times, the same operations as in Example 1 were carried out to obtain an LCP film (biaxially stretched LCP film) of Example 2 having an average thickness of 51.7 μm. (Example 3) Except that the shrinkage ratio in the MD direction was changed to 0.80 times and the elongation ratio in the TD direction was changed to 1.70 times, the same operations as in Example 1 were carried out to obtain an LCP film (biaxially stretched LCP film) of Example 3 having an average thickness of 45.6 μm. From Table 1, it was confirmed that the LCP film of Example 1 was excellent in thickness accuracy and the anisotropy such as the linear expansion coefficient in the MD direction and the TD direction was improved as compared with Comparative Example 1. [Industrial Applicability] According to the present invention, it is possible to provide an LCP film or the like having relatively excellent productivity, capable of being manufactured at low cost, excellent in thickness accuracy, and improved in anisotropy such as the linear expansion coefficient in the MD direction and the TD direction, and thus it can be widely and effectively used in the raw material field of LCP films. 10: LCP extruded film 11: LCP extruded film after biaxial stretching 20: Simultaneous biaxial stretching and shrinking machine 21: Endless loop 22: Endless loop 21a: Clamp 22a: Clamp 100: LCP film MD: Length direction TD: Transverse direction FIG. 1 is a conceptual diagram showing an LCP film. FIG. 2 is a conceptual diagram showing a biaxial stretching process in the manufacturing method of an LCP film. FIG. 3 is a schematic diagram showing an MD shrinkage-TD elongation process of an LCP film performed by a simultaneous biaxial stretching and shrinking machine. FIG. 4 is a conceptual diagram showing the principle of calculating the degree of orientation based on the area ratio of the orientation peaks.

Claims

1. An LCP film comprising a thermoplastic liquid crystal polymer, wherein the coefficient of linear expansion in the TD direction is -30.0 to 30.0 ppm / K, the coefficient of linear expansion in the MD direction is -10.0 to 30.0 ppm / K, and the CV value of the film thickness measured according to JIS K7130:1999 (calculated from the thickness of 275 points measured at 1.0 mm intervals in the MD direction, their average value, and their standard deviation) is 0.030 or less, wherein the LCP film is a biaxially expanded LCP film that has undergone expansion and contraction in the biaxial direction.

2. The LCP membrane of claim 1, wherein the ratio of the CV value of the membrane thickness after biaxial expansion treatment to the CV value of the membrane thickness before biaxial expansion treatment is 2.00 or less.

3. The LCP membrane of claim 1, wherein the LCP membrane has a thickness of 15 μm or more and 300 μm or less.

4. The LCP membrane of request item 1, wherein the above CV value is 0.020 or less.

5. The LCP membrane of request item 1 has a linear expansion coefficient of -20.0 to 5.0 ppm / K in the TD direction and a linear expansion coefficient of -10.0 to 10.0 ppm / K in the MD direction.

6. The LCP membrane of request item 1 has a linear expansion coefficient of -15.0 to 0.0 ppm / K in the TD direction and a linear expansion coefficient of -10.0 to 5.0 ppm / K in the MD direction.

7. The alignment degree of the LCP membrane as requested in item 1 is 0.0 to 30.0%.

8. The LCP film of claim 1, wherein the thermoplastic liquid crystal polymer comprises a (fully) aromatic polyester resin having a melting point of 250°C or higher.

9. The LCP film of claim 1, wherein the thermoplastic liquid crystal polymer contains a (fully)aromatic polyester resin, the (fully)aromatic polyester resin having at least monomer component A and monomer component B, wherein monomer component A comprises one or more selected from the group consisting of 6-hydroxy-2-naphthoic acid and its derivatives, and wherein monomer component B comprises one or more selected from the group consisting of p-hydroxybenzoic acid, terephthalic acid, isophthalic acid, 6-naphthoic acid, 4,4'-biphenol, bisphenol A, hydroquinone, 4,4-dihydroxybiphenol, polyethylene terephthalate and its derivatives.

10. The LCP membrane of claim 9, wherein the content of monomer component A relative to the (fully) aromatic polyester resin is 10 mol% or more and 90 mol% or less, and the content of monomer component B relative to the (fully) aromatic polyester resin is 10 mol% or more and 90 mol% or less.

11. For the LCP membrane of Request 1, the shrinkage ratio in the MD direction is 0.80 to 0.99 times the length in the MD direction before shrinkage, and the elongation ratio in the TD direction is 1.20 to 2.50 times the length in the TD direction before elongation.

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