LCP film

Abstract

The present invention provides an LCP film which can be relatively efficiently produced at low cost and has excellent thickness accuracy and reduced anisotropy in, for example, the coefficients of MD and TD linear expansion. This LCP film contains a thermoplastic liquid-crystal polymer and has a coefficient of TD linear expansion of -30.0 to 30.0 ppm / K, a coefficient of MD linear expansion of -10.0 to 30.0 ppm / K, and a film-thickness CV value (calculated from the thicknesses at 275 points measured at intervals of 1.0 mm along the MD, the average thereof, and the standard deviation thereof), as determined in accordance with JIS K7130:1999, of 0.030 or less.

Description

Technical Field

[0001] The present invention relates to LCP films and the like.

Background Art

[0002] Conventionally, liquid crystal polymer (LCP: Liquid Crystal Polymer) films produced by melt extrusion molding such as the inflation method and the T-die method have been widely used in various fields. In particular, thermotropic liquid crystal polymers that exhibit liquid crystallinity in a molten state or a 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 in the high-frequency range. Therefore, their practical application has been studied in applications such as gas barrier film materials, electronic materials, and electrical insulating materials. In addition, insulating materials for circuit boards using liquid crystal polymers are excellent in high-frequency characteristics and low dielectric properties, and have recently been in the spotlight 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-developing fifth-generation mobile communication system (5G) and millimeter-wave radars.

[0003] However, the LCP film obtained by melt extrusion molding is subjected to shear stress and the like caused by the high degree of liquid crystal orientation and relatively rigid molecular chains of the liquid crystal polymer, and further caused by the die and die swell during melt extrusion. It is known that the polymer chains are highly molecularly oriented in the film flow direction, that is, the MD direction (Machine Direction; longitudinal direction). Therefore, in various physical properties such as film strength, coefficient of thermal expansion, and dimensional accuracy, for example, significant anisotropy occurs between the MD direction and the TD direction (Transverse Direction; transverse direction), and it has been difficult to obtain a thermoplastic liquid crystal polymer film with high industrial utility value.

[0004] In the past, stretching of liquid crystal polymer films was considered to improve the anisotropy in the MD and TD directions. However, since stretching is a technique that significantly stretches the entire liquid crystal polymer film in one or two axial directions, it is not possible to precisely adjust the orientation or degree of orientation. Therefore, currently, stretching of liquid crystal polymer films is mainly performed to adjust the surface roughness and surface precision of the liquid crystal polymer film.

[0005] For example, Patent Document 1 discloses a manufacturing method in which a laminate body is prepared in advance by sandwiching a liquid crystal polymer film between a pair of laminate films (fluororesin porous films having a specific gravity of 1.3 or more and a breaking elongation in the stretching direction of 400% or more), and this laminate body is stretched in one or two axes under temperature conditions in which the fluororesin porous film is softened but not substantially melted, while the liquid crystal polymer film is softened or melted. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Patent No. 3958629 [Overview of the project] [Problems that the invention aims to solve]

[0007] However, the manufacturing technology described in Patent Document 1 only adjusts the surface roughness and surface accuracy of the resulting stretched LCP film, and does not consider the thickness accuracy of the LCP film itself. The electrical properties of an insulator are film thickness dependent, and in order to develop an insulating substrate material with stable dielectric properties, it is necessary to improve the film thickness accuracy of the LCP film. In recent years, the demand for thickness accuracy of insulating films has been increasing in electronic material applications. The inventors have newly discovered that when using LCP film as an insulating substrate material, especially when sputtering metals, 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 distribution, storage, and use after manufacturing.

[0008] Furthermore, the manufacturing technology described in Patent Document 1 above is based on the premise of using a special laminate film, a porous fluororesin film with a high specific gravity and high elongation at break, and is therefore inherently less versatile. In fact, Patent Document 1 shows that when a skived PTFE film with a high specific gravity or a polyimide film with a low elongation at break is used, the laminate film breaks during the stretching process, making it impossible to perform the desired stretching process. As a result, LCP films obtained by the manufacturing technology described in Patent Document 1 are relatively expensive.

[0009] Furthermore, as described in Patent Document 1 above, a special laminate is created by sandwiching a liquid crystal polymer film between porous fluororesin films with high specific gravity and high elongation at break. This laminate is then subjected to biaxial stretching near the melting point of the liquid crystal polymer film, by 1.3 times in the MD direction and 3.9 times in the TD direction, thereby obtaining an LCP film with low surface roughness and high surface accuracy. In other words, the manufacturing technology described in Patent Document 1 only adjusts the surface roughness and surface accuracy of the resulting stretched LCP film and does not consider any improvement of anisotropy such as the coefficient of linear expansion in the MD and TD directions.

[0010] The present invention has been made in view of the above problems. The object of the present invention is to provide an LCP film, etc., which is relatively productive, can be manufactured at low cost, has excellent thickness accuracy, and has improved anisotropy such as the coefficient of linear expansion in the MD direction and TD direction. [Means for solving the problem]

[0011] As a result of diligent research to solve the above problems, the inventors have discovered a new LCP film that is relatively productive, can be manufactured at low cost, has excellent thickness accuracy, and exhibits improved anisotropy such as the coefficient of linear expansion in the MD and TD directions, thus completing the present invention.

[0012] In other words, the present invention provides various specific embodiments as shown below. <1> An LCP film containing 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 in accordance with 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.

[0013] <2> The LCP film is a biaxially expandable / contractible LCP film that is expanded or contracted in two axial directions. <1> The LCP film described above.

[0014] <3> The ratio of the CV value of the film thickness after biaxial expansion / contraction to the CV value of the film thickness before biaxial expansion / contraction is 2.00 or less. <1> or <2> The LCP film described above.

[0015] <4> The LCP film has a thickness of 15 μm or more and 300 μm or less. <1> ~ <3> LCP film as described in any one of the items.

[0016] <5> The aforementioned CV value is 0.020 or less. <1> ~ <4> LCP film as described in any one of the items.

[0017] <6>The LCP film according to any one of <1> to <5>, wherein the linear expansion coefficient in the TD direction is -20.0 to 5.0 ppm / K and the linear expansion coefficient in the MD direction is -10.0 to 10.0 ppm / K.

[0018] <7>The LCP film according to any one of <1> to <6>, wherein the linear expansion coefficient in the TD direction is -15.0 to 0.0 ppm / K and the linear expansion coefficient in the MD direction is -10.0 to 5.0 ppm / K.

[0019] <8>The LCP film according to any one of <1> to <7>, wherein the degree of orientation is 0.0 to 30.0%.

Advantages of the Invention

[0020] According to the present invention, it is possible to provide an LCP film or the like that is relatively excellent in productivity, 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.

Brief Description of the Drawings

[0021] [Figure 1] FIG. 1 is a conceptual diagram showing an LCP film. [Figure 2] FIG. 2 is a conceptual diagram showing a biaxial scaling process in a method for manufacturing an LCP film. [Figure 3] FIG. 3 is a schematic diagram showing an MD shrinkage - TD stretching process of an LCP film by a simultaneous biaxial stretching and shrinking machine. [Figure 4] FIG. 4 is a conceptual diagram showing the calculation principle of the degree of orientation based on the area ratio of the orientation peak.

Modes for Carrying Out the Invention

[0022] Embodiments of the present invention will be described in detail below with reference to the drawings. Unless otherwise specified, positional relationships such as up, down, left, and right shall be based on the positional relationships shown in the drawings. Furthermore, the dimensional ratios in the drawings are not limited to those shown. However, the following embodiments are illustrative examples for explaining the present invention, and the present invention is not limited to these. That is, the present invention can be implemented with arbitrary modifications without departing from its essence. In this specification, for example, the notation of a numerical range such as "1 to 100" shall include both the lower limit value "1" and the upper limit value "100". The same applies to other numerical range notations.

[0023] Figure 1 is a conceptual diagram showing the LCP film 100 of this embodiment. The LCP film of this embodiment is an LCP film 100 containing a thermoplastic liquid crystal polymer, characterized in that 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 in accordance with JIS K7130:1999 (calculated from the thickness of 275 points measured at 1.0 mm pitches in the MD direction, their average value, and their standard deviation) is 0.030 or less.

[0024] The LCP film 100 of this embodiment is not particularly limited in type, as long as it has the above configuration. Examples of LCP film 100 of this embodiment include, but are not particularly limited to, LCP extruded films manufactured by multilayer co-extrusion methods such as the T-die method, inflation method, co-extrusion method, two-layer co-extrusion method, and three-layer co-extrusion method; pressurized and heat-treated LCP extruded films; uniaxially oriented films of LCP extruded films (TD-oriented LCP films); biaxially oriented films of LCP extruded films (MD-oriented - TD-oriented LCP films); and biaxially expanding and contracting LCP films of LCP extruded films (MD-shrinking - TD-oriented LCP films). In particular, it is preferable for the LCP film 100 to be a biaxially expanding and contracting LCP film of an LCP extruded film from the viewpoint of thickness accuracy, anisotropy, productivity, cost, etc. The following will provide further details with reference to an example in which the LCP film 100 is manufactured by a biaxial expanding and contracting treatment (MD-shrinking - TD-oriented) method.

[0025] <Method for manufacturing an LCP film> FIG. 2 is a conceptual diagram showing a biaxial scaling process (MD shrinkage - TD stretching process) in the method for manufacturing the LCP film 100 of the present embodiment. The method for manufacturing the LCP film of the present embodiment includes at least a step of preparing an LCP extruded film 10 (hereinafter also referred to as a preparation step S1), and a step of subjecting the LCP extruded film 10 to a shrinkage process at a shrinkage ratio of 0.80 to 0.99 times in the MD direction and a stretching process in the TD direction to obtain the LCP film 100 (hereinafter also referred to as a biaxial scaling step S2). Hereinafter, each step will be described in detail.

[0026] (Preparation step S1) In this preparation step S1, an LCP extruded film 10 containing a liquid crystal polymer (LCP; Liquid Crystal Polymer) is prepared. As the LCP extruded film 10, those known in the art can be used, and the type thereof is not particularly limited. In the manufacturing method of the present embodiment, the effect is more prominent when a liquid crystal polymer film with high molecular orientation is used. As the liquid crystal polymer contained in the LCP extruded film 10, those known in the art 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 includes a thermotropic liquid crystal compound. The properties of the anisotropic molten phase can be confirmed by a known method such as a polarization inspection method using crossed polarizers. More specifically, the confirmation of the anisotropic molten phase can be carried out by observing a sample placed on a Leitz hot stage under a nitrogen atmosphere at a magnification of 40 times using a Leitz polarizing microscope.

[0027] Specific examples of liquid crystal polymers include, but are not limited to, liquid crystal polymers obtained by polycondensation of aromatic or aliphatic dihydroxy compounds, aromatic or aliphatic dicarboxylic acids, aromatic hydroxycarboxylic acids, aromatic diamines, aromatic hydroxyamines, aromatic aminocarboxylic acids, etc. Examples of liquid crystal polymers include homopolymers thereof; copolymers thereof; modified products thereof; polymer blends of these with other thermoplastic resins other than liquid crystal polymers, etc.; and polymer alloys of these with other thermoplastic resins other than liquid crystal polymers. From the viewpoint of obtaining LCP extruded film 10 by extrusion molding, thermoplastic liquid crystal polymers are preferred.

[0028] Specific examples of preferred liquid crystal polymers include, but are not limited to, aromatic polyamide resins obtained by polycondensation of monomers such as aromatic hydroxycarboxylic acids, aromatic diamines, and aromatic hydroxyamines; and (all) aromatic polyester resins obtained by polycondensation of monomers such as aromatic diols, aromatic carboxylic acids, and aromatic hydroxycarboxylic acids. These can be used individually or in any combination and ratio of two or more types. Thermoplastic liquid crystal polymers are generally classified into Type I, Type II, Type III, etc., from the viewpoint of their heat distortion temperature (TDUL). Any type of thermoplastic liquid crystal polymer can be suitably used in this embodiment, and can be appropriately selected depending on the application. For example, in applications for electronic circuit boards that require application to lead-free solder at temperatures of around 260 to 290°C, a Type I thermoplastic liquid crystal polymer with a high heat resistance of around 250 to 350°C is suitably used, while a Type II thermoplastic liquid crystal polymer with a relatively high heat resistance of around 240 to 250°C is suitably used.

[0029] Among these, (all) aromatic polyester resins exhibiting thermotropic liquid crystal-like properties and having a melting point of 250°C or higher, preferably 280°C to 380°C, are preferably used. Examples of such (all) aromatic polyester resins include those synthesized from monomers such as aromatic diols, aromatic carboxylic acids, and hydroxycarboxylic acids, which exhibit liquid crystallinity upon melting. Representative examples include, but are not limited to, polycondensates of ethylene terephthalate and parahydroxybenzoic acid, polycondensates of phenol and phthalic acid and parahydroxybenzoic acid, and polycondensates of 2,6-hydroxynaphthoic acid and parahydroxybenzoic acid. The (all) aromatic polyester resin can be used alone or in any combination and ratio of two or more types. Depending on the required performance, an all-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.

[0030] A preferred embodiment is a (whole) aromatic polyester resin having 6-hydroxy-2-naphthoic acid and its derivatives (hereinafter sometimes simply referred to as "monomer component A") as its basic structure, and having at least one monomer component (hereinafter sometimes simply referred to as "monomer component B") selected from the group consisting of parahydroxybenzoic acid, terephthalic acid, isophthalic acid, 6-naphthalenedicarboxylic acid, 4,4'-biphenol, bisphenol A, hydroquinone, 4,4-dihydroxybiphenol, ethylene terephthalate, and their derivatives. In the molten state, the linear chains of molecules are regularly arranged to form an anisotropic molten phase, typically exhibiting thermotropic liquid crystal-like properties, and possessing excellent basic performance in terms of mechanical properties, electrical properties, high-frequency properties, heat resistance, moisture absorption, etc.

[0031] Furthermore, the (whole) aromatic polyester resin of the preferred embodiment described above can have any configuration 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 three or more types of monomer component A. Also, the (whole) aromatic polyester resin of the preferred embodiment described above may contain other monomer components other than monomer components A and monomer component B (hereinafter sometimes simply referred to as "monomer component C"). That is, the (whole) aromatic polyester resin of the preferred embodiment described above may be a binary or more polycondensate consisting only of monomer component A and monomer component B, or a ternary or more polycondensate of monomer components consisting of monomer component A, monomer component B, and monomer component C. Other monomer components include, but are not particularly limited to, those other than monomer components A and monomer component B described above, 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 hydroxyamines, or aromatic aminocarboxylic acids and their derivatives; etc. Other monomer components can be used individually or in any combination and ratio of two or more.

[0032] In this specification, "derivative" means a monomer component to which a halogen atom (e.g., fluorine atom, chlorine atom, bromine atom, iodine atom), a C1-C5 alkyl group (e.g., methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, isobutyl group, s-butyl group, t-butyl group, etc.), an aryl group such as a phenyl group, a hydroxyl group, a C1-C5 alkoxy group (e.g., methoxy group, ethoxy group, etc.), a carbonyl group, -O-, -S-, -CH2-, etc.) has been introduced (hereinafter, this may be referred to as a "substituted monomer component"). Here, "derivative" may be an acylated product, an ester derivative, or an ester-forming monomer such as an acid halide of monomer components A and B, which may have the above-mentioned modifying groups.

[0033] Particularly preferred embodiments include binary polycondensates of p-hydroxybenzoic acid and its derivatives with 6-hydroxy-2-naphthoic acid and its derivatives; ternary or more polycondensates of p-hydroxybenzoic acid and its derivatives with 6-hydroxy-2-naphthoic acid and its derivatives with monomer component C; and p-hydroxybenzoic acid and its derivatives with 6-hydroxy-2-naphthoic acid and its derivatives with terephthalic acid, isophthalic acid, 6-naphthalenedicarboxylic acid, 4,4'-biphenol, bisphenol A, hydroquinone, and 4,4-dihydroxybiphenone. Examples include ternary or higher polycondensates consisting of one or more selected from the group consisting of p-hydroxybenzoic acid and its derivatives, ethylene terephthalate and its derivatives, and one or more selected from the group consisting of p-hydroxybenzoic acid and its derivatives, 6-hydroxy-2-naphthoic acid and its derivatives, terephthalic acid, isophthalic acid, 6-naphthalenedicarboxylic acid, 4,4'-biphenol, bisphenol A, hydroquinone, 4,4-dihydroxybiphenol, ethylene terephthalate and its derivatives, and one or more monomer components C. These can be obtained as having a relatively low melting point compared to, for example, a homopolymer of p-hydroxybenzoic acid, and therefore, thermoplastic liquid crystal polymers using these have excellent moldability when heat-pressed onto an adherend.

[0034] From the viewpoint of lowering the melting point of the (whole) aromatic polyester resin, improving the moldability when the LCP film 100 is heat-pressed onto the adherend, or obtaining high peel strength when the LCP film 100 is heat-pressed onto a metal foil, the molar ratio content of monomer component A to the (whole) 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, and even more preferably 50 mol% or more and 80 mol% or less. Similarly, the molar ratio content of monomer component B to the (whole) 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, and even more preferably 20 mol% or more and 50 mol% or less. Furthermore, the molar ratio content of monomer component C, which may be contained in the (whole) aromatic polyester resin, is preferably 10 mol% or less, more preferably 8 mol% or less, even more preferably 5 mol% or less, and particularly preferably 3 mol% or less.

[0035] The method for synthesizing the liquid crystal polymer is not particularly limited and can be any known method. Known polycondensation methods for forming ester bonds with the above-mentioned monomer components, such as melt polymerization, melt acidolysis, and slurry polymerization, can be applied. When applying these polymerization methods, an acylation or acetylation step may be carried out according to conventional methods.

[0036] The LCP extruded film 10 may further contain inorganic fillers. By including inorganic fillers, it is easier to obtain an LCP film 100 in which the anisotropy of the coefficient of linear expansion in the MD direction, TD direction, and ZD direction (Z-axis direction; film thickness direction) is reduced. Such an LCP film 100 is particularly useful in rigid substrate applications where multilayer lamination is required, for example.

[0037] Inorganic fillers can be those known in the industry, and their types are not particularly limited. For example, 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 aluminometasilicate, magnesium carbonate, magnesium oxide, magnesium hydroxide, etc.), calcium compounds (e.g., calcium carbonate) Examples of materials that can be used include, but are not limited to, silica, 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 dioxide, zinc oxide, zirconium oxide, barium sulfate, zinc borate, barium metaborate, sodium borate, boron nitride, agglomerated boron nitride, silicon nitride, carbon nitride, strontium titanate, barium titanate, zinc stinate, and other stannates. These can be used individually or in combination of two or more. Among these, silica is preferred from the viewpoint of dielectric properties, etc.

[0038] Furthermore, the inorganic filler used herein may be one that has undergone surface treatment known in the industry. Surface treatment can improve moisture resistance, adhesive strength, dispersibility, etc. Examples of surface treatment agents include, but are not limited to, silane coupling agents, titanate coupling agents, sulfonic acid esters, carboxylic acid esters, and phosphate esters.

[0039] From the viewpoint of reducing the required particle size, the median diameter (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 even more preferably 0.1 μm or more and 50 μm or less. In this specification, the median diameter (d50) of the inorganic filler refers to the value measured on a volume basis by the laser diffraction / scattering method using a laser diffraction / scattering particle size distribution analyzer (LA-500 manufactured by Horiba, Ltd.).

[0040] The inorganic filler content is not particularly limited and can be set appropriately according to the required performance, taking into consideration the balance of other essential and optional components. From the viewpoint of kneadability and handling during preparation, and the effect of reducing the coefficient of linear expansion, the inorganic filler content, calculated on a solid content basis relative to the total amount of LCP extruded film 10, is preferably 1% to 45% by mass in total, more preferably 3% to 40% by mass in total, and even more preferably 5% to 35% by mass in total.

[0041] The LCP extruded film 10 may contain resin components other than the thermoplastic resin described above (hereinafter sometimes simply referred to as "other resin components"), such as thermosetting resins or elastomers, to the extent that they do not excessively impair the effects of the present invention. Furthermore, the LCP extruded film 10 may 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, and fluororesins; colorants such as dyes and pigments; organic fillers; antioxidants; heat stabilizers; light stabilizers; ultraviolet absorbers; flame retardants; antistatic agents; surfactants; rust inhibitors; defoamers; fluorescent agents, etc., to the extent that they do not excessively impair the effects of the present invention. Each of these additives can be used individually or in combination of two or more. These additives can be included in the molten resin composition prepared during the molding of the LCP extruded film 10. The content of these resin components and additives is not particularly limited, but from the viewpoint of moldability and thermal stability, it is preferably 0.01 to 10% by mass of each, more preferably 0.1 to 7% by mass of each, and even more preferably 0.5 to 5% by mass of each, relative to the total amount of the LCP extruded film 10.

[0042] As the LCP extruded film 10 described above, a melt extruded film such as a T-die extruded film or an inflation film is preferably used. The melt extruded film can be obtained by extruding a resin composition containing the liquid crystal polymer described above and, if necessary, an inorganic filler or other resin component to a predetermined thickness. Various known extrusion methods can be applied, and the type is not particularly limited. For example, the T-die method or the inflation method; for example, the multi-manifold co-extrusion method or the feed-block co-extrusion method; for example, the two-layer co-extrusion method or the three-layer co-extrusion method; can be applied in any combination. Among these, from the viewpoint of ease of controlling the molecular orientation of the liquid crystal polymer on the film surface and inside the film, a preferred embodiment is a method in which the above-mentioned resin composition is extruded from a T-die using an extrusion molding method using a T-die (hereinafter sometimes simply referred to as the "T-die extrusion method") to form a film, and then subjected to a cooling treatment, a pressing treatment, a pressurized heating treatment, etc., as necessary, to obtain a predetermined LCP extruded film 10. Furthermore, as the LCP extruded film 10, a liquid crystal polymer film layer which is the intermediate layer (core layer) of a three-layer co-extruded film having a laminated structure in which a thermoplastic resin layer, a liquid crystal polymer film layer, and a thermoplastic resin layer are arranged in at least this order is also preferably used. In this case, a single-layer liquid crystal polymer film layer (LCP extruded film 10) can be obtained by removing the thermoplastic resin layers of both outer layers of the three-layer co-extruded film.

[0043] The thickness of the LCP extruded film 10 can be set appropriately according to the required performance and is not particularly limited. Considering handling and productivity during extrusion molding, a thickness of 15 μm to 300 μm is preferred, more preferably 18 μm to 250 μm, and even more preferably 20 μm to 200 μm.

[0044] The melting point (melting temperature) of the LCP extruded film 10 is not particularly limited, but from the viewpoint of the heat resistance and processability of the film, the melting point (melting temperature) is preferably 200 to 400°C, preferably 250 to 360°C, more preferably 260 to 355°C, even more preferably 270 to 350°C, and particularly preferably 275 to 345°C. In this specification, the melting point of the LCP extruded film 10 refers to the melting peak temperature in differential scanning calorimetry (DSC) when the extruded film is heated at a heating rate of 20°C / min in the temperature range of 30 to 400°C (1st heating), then cooled at a cooling rate of 50°C / min (1st cooling), and then heated a second time at a heating rate of 20°C / min (2nd heating) using a DSC8500 (manufactured by PerkinElmer) to obtain a value after eliminating the thermal history.

[0045] Here, the coefficient of linear expansion of the LCP extruded film 10 in the TD direction (CTE, α2, 23~200℃) is not particularly limited, but is preferably 5.0~60.0 ppm / K, more preferably 5.0~55.0 ppm / K, and even more preferably 5.0~50.0 ppm / K. Furthermore, the coefficient of linear expansion of the LCP extruded film 10 in the MD direction (CTE, α2, 23~200℃) is preferably -30.0~5.0 ppm / K, more preferably -25.5~5.0 ppm / K, and even more preferably -23.0~5.0 ppm / K. Note that the LCP extruded film 10 to be subjected to biaxial expansion and contraction treatment may be an unstretched film, a uniaxially oriented film, or a biaxially oriented film.

[0046] In this specification, the coefficient of linear expansion is measured using the TMA method in accordance with JIS K7197, and the average coefficient of linear expansion refers to the average value of the coefficients of linear expansion measured by this method between 23 and 200°C. The coefficient of linear expansion measured here refers to the value obtained when the target film, which is the measurement sample, is heated at a heating rate of 5°C / min (1st heating), then cooled to the ambient temperature (23°C) (1st cooling), and then heated a second time at a heating rate of 5°C / min (2nd heating) in order to obtain a value after eliminating the thermal history. Furthermore, other detailed measurement conditions shall follow the conditions described in the examples below.

[0047] On the other hand, the dielectric properties of the LCP extruded film 10 can be set appropriately according to the desired performance and are not particularly limited. From the viewpoint of obtaining higher dielectric properties, the relative permittivity ε r The dielectric loss tangent tanδ (36 GHz) is preferably 3.0 to 3.7, and more preferably 3.0 to 3.5. Similarly, the dielectric loss tangent tanδ (36 GHz) is preferably 0.0010 to 0.0050, and more preferably 0.0010 to 0.0045. In this specification, relative permittivity ε r (36GHz) and dielectric loss tangent tanδ(36GHz) refer to the values ​​at 36GHz measured by the cavity resonator contact method in accordance with JIS K6471.

[0048] Furthermore, while the LCP extruded film 10 can be used as is, if necessary, a pressurized heating process can be performed to further reduce the molecular orientation (anisotropy) of the liquid crystal polymer or to further release internal strain. This makes it possible to realize an LCP film 100 with even lower anisotropy in dimensional change rate or an LCP film 100 with a smaller absolute value of dimensional change rate.

[0049] The pressurized heat treatment can be carried out using methods known in the industry, such as contact heat treatment or non-contact heat treatment, and the type is not particularly limited. For example, it can be heat-set using known equipment such as a non-contact heater, oven, blow device, heat roll, cooling roll, heat press, or double-belt heat press. At this time, if necessary, a release film or porous film known in the industry can be placed on the surface of the LCP extruded film 10 before heat treatment. Furthermore, when performing this heat treatment, from the viewpoint of controlling orientation, a hot-press molding method is preferably used in which a release film or porous film is placed on both sides of the LCP extruded film 10, and the film is heat-pressed while sandwiched between the endless belts of a double-belt press, and then the release film or porous film is removed. The hot-press molding method can be carried out by referring to, for example, Japanese Patent Application Publication No. 2010-221694. When hot-press molding the LCP extruded film 10 using the above resin composition between the endless belts of a double belt press, the processing temperature is preferably above the melting point of the liquid crystal polymer and below 70°C above the melting point, more preferably above 5°C above the melting point and below 60°C above the melting point, and even more preferably above 10°C above the melting point and below 50°C above the melting point. The hot-pressure bonding conditions at this time can be appropriately set according to the desired performance and are not particularly limited, but it is preferably carried out under conditions of a surface pressure of 0.5 to 10 MPa and a heating temperature of 250 to 430°C, more preferably under conditions of a surface pressure of 0.6 to 8 MPa and a heating temperature of 260 to 400°C, and even more preferably under 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 oven, it is preferable to carry out the process under conditions of 200 to 320°C for 1 to 20 hours, for example.

[0050] (Biaxial expansion / contraction process S2) In this biaxial expansion and contraction process S2, the LCP extruded film 10, which is the workpiece, is subjected to a shrinkage treatment in the MD direction with a shrinkage ratio of 0.80 to 0.99 times, and a stretching treatment in the TD direction, thereby obtaining an LCP film 100 (LCP film 11 after biaxial expansion and contraction). The LCP film 100 obtained after the biaxial expansion and contraction process (MD shrinkage-TD stretching treatment) is classified as a uniaxially shrinkable film (MD shrinkage film) if viewed as a shrinkage film, a uniaxially stretched film (TD stretched film) if viewed as a stretched film, and a uniaxially shrinkable and uniaxially stretched film (MD shrinkage TD stretched film) if viewed as a biaxially expanding and contraction film.

[0051] When shrinking the LCP extruded film 10 in the MD direction and stretching it in the TD direction, known stretchers and biaxial stretchers (biaxial expanders) can be used. As an example of a simultaneous biaxial expander (shrink tenter), the one described in Japanese Patent Application Publication No. 2022-051372 is known. Specifically, using the simultaneous biaxial stretcher 20 shown in Figure 3, the LCP extruded film 10 is fed while being gripped between a number of clips 21a, 22a of endless loops 21, 22 arranged symmetrically on the left and right sides. By reducing the spacing between clips 21a and clips 22a, the LCP extruded film 10 is shrunk in the MD direction. At the same time, as the spacing between the endless loops 21, 22 gradually expands in the film transport direction, the LCP extruded film 10 gripped between the endless loops 21, 22 is gradually pulled outward and stretched in the TD direction.

[0052] The processing temperature of the biaxial expansion / contraction process S2 is not particularly limited as long as it is above the glass transition temperature of the LCP extruded film 10, but is preferably 70 to 180°C, and more preferably 90 to 180°C. After shrinking in the MD direction and stretching in the TD direction, it is preferable to perform a heat treatment (heat setting) at, for example, 100 to 240°C for 1 to 600 seconds. During heat setting, methods known in the industry, such as contact heat treatment and non-contact heat treatment, can be used, and the type is not particularly limited. For example, known equipment such as non-contact heaters, ovens, blow devices, heat rolls, cooling rolls, heat presses, and double-belt heat presses can be used for heat setting. At this time, if necessary, a release film or porous film known in the industry can be placed on the surface of the LCP film 100 and heat pressure treatment can be performed. In addition, in the biaxial expansion / contraction process S2, the stretching and shrinking processes can be performed sequentially, or the shrinking and stretching processes can be performed sequentially in the reverse order, or the shrinking and stretching processes can be performed simultaneously.

[0053] The stretching ratio and shrinking ratio of the LCP extruded film 10 in the biaxial expanding and shrinking process S2 can be set according to the desired degree of improvement in anisotropy and are not particularly limited. From the viewpoint of mitigating the directional anisotropy of the LCP extruded film which is highly molecularly oriented in the MD direction, the shrinking ratio in the MD direction is preferably 0.80 to 0.99 times, more preferably 0.80 to 0.95 times, and even more preferably 0.80 to 0.93 times, based on the length in the MD direction before shrinking. Similarly, from the viewpoint of mitigating the directional anisotropy of the LCP extruded film which is highly molecularly oriented in the MD direction, the stretching ratio in the TD direction is preferably 1.20 to 2.50 times, more preferably 1.30 to 2.50 times, and even more preferably 1.40 to 2.50 times, based on the length in the TD direction before stretching. Furthermore, the stretch-shrinkage ratio (expressed as m × n, where m is the shrinkage ratio in the MD direction and n is the stretch-shrinkage ratio in the TD direction), which is the product of the shrinkage ratio in the MD direction and the stretch-shrinkage ratio in the TD direction, is preferably 0.960 to 2.475 times, more preferably 1.040 to 2.375 times, and even more preferably 1.120 to 2.325 times. According to this manufacturing method, even though the stretch-shrinkage ratio of the biaxial expansion and contraction process S2 is relatively low, an LCP film 100 can be easily manufactured in which the absolute values ​​of the linear expansion coefficients in the MD and TD directions are small and the anisotropy of the linear expansion coefficients in the MD and TD directions is small.

[0054] Furthermore, after the shrinkage and stretching process, the LCP film 100 can be cooled (or slowly cooled) as needed. Cooling of the LCP film 100 can be carried out, for example, using a pair of cooling rolls, or by natural cooling. The LCP film 100 after the biaxial expansion and contraction process can then be taken up by a take-up roll and wound into a roll on a winding roll to form a roll of raw material.

[0055] In this embodiment, an example of shrinking and stretching the LCP extruded film 10 alone is shown. However, the first and second film members may be placed on the front and back surfaces of the LCP extruded film 10, respectively, and adhered to the front and back surfaces of the LCP extruded film 10, respectively, to form a laminated body having a first film member / LCP extruded film 10 / second film member structure, and this laminated body may be subjected to biaxial expansion and contraction. The materials constituting the first and second film members are not particularly limited, as long as they can adhere to the LCP extruded film 10 and have sufficient strength to not break during MD shrinkage-TD stretching. For example, paper, woven fabric, nonwoven fabric, metal plate, alloy plate, metal foil, alloy foil, resin film, rubber sheet, foam sheet, laminate or impregnated body made of any combination thereof can be used as the first and second film members. Among these, thermosetting resin films such as polyimide film; thermoplastic resin films having a higher melting point than the LCP extruded film 10; and metal foils such as aluminum foil and copper foil are preferred. The first and second film members may be made of the same or different materials.

[0056] The method for manufacturing the crimped body is not particularly limited, and known lamination methods can be applied. The first film member, the LCP extruded film 10, and the second film member are stacked in this order, and the crimped body can be obtained by crimping or heat-crimping them using known equipment such as a press, crimping roll, non-contact heater, oven, blow device, heat roll, cooling roll, hot press, or double belt press. Furthermore, the processing conditions during crimping can be set appropriately according to the materials used and are not particularly limited. For example, it can be carried out under conditions of a surface pressure of 0.3 to 10 MPa and a heating temperature of above the heat distortion temperature of the LCP extruded film 10 and below the melting point + 70°C, preferably under conditions of a surface pressure of 0.6 to 8 MPa and a temperature above the melting point of the LCP extruded film 10 and below 60°C above the melting point.

[0057] Furthermore, in order to achieve the desired release properties, various release agents may be placed between the LCP extruded film 10 of the crimped body and the first film member, or between the LCP extruded film 10 and the second film member. In addition, in order to achieve the desired adhesion, various primers or adhesives may be placed instead of release agents.

[0058] Then, after applying MD shrinkage-TD stretching treatment to the LCP extruded film 10, the crimped body is cooled as necessary, and the first and second film members crimped to both surfaces of the crimped body are peeled off (removed) to obtain the LCP film 100 after MD shrinkage-TD stretching treatment. Cooling of the crimped body can be performed, for example, using a pair of cooling rolls, or it can be done by natural cooling. The LCP film 100 after MD shrinkage-TD stretching treatment can then be taken up by a take-up roll, for example, and wound into a roll on a winding roll to become a roll material.

[0059] <LCPフィルム> The LCP film 100 obtained by the above manufacturing method is an MD-shrink-TD-stretched product of the LCP extruded film 10 (hereinafter sometimes referred to as biaxially expanded and contracted LCP film).

[0060] In the LCP film 100 of this embodiment, the CV value of the film thickness is not particularly limited, but is preferably 0.030 or less, more preferably 0.028 or less, and even more preferably 0.025 or less. Here, the lower limit of the CV value of the film thickness is not particularly limited, and may be 0.000 or more, or 0.005 or more. In this specification, the CV value of the film thickness refers to the value measured in accordance with JIS K7130:1999. Specifically, the measuring probe of a contact-type thickness measuring instrument is brought into contact with the central portion of the automatically transported film in the TD direction, and the thickness is measured at 275 points at 1.0 mm intervals in the MD direction, and the value is calculated from the average value and standard deviation of the measured thickness. Furthermore, other detailed measurement conditions shall follow the conditions described in the examples described later. A smaller CV value of the film thickness means better thickness accuracy.

[0061] Furthermore, if the LCP film 100 of this embodiment is a biaxially expandable LCP film, the ratio of the CV value of the film thickness after biaxial expansion and contraction to the CV value of the film thickness before biaxial expansion and contraction is preferably 2.00 or less, more preferably 1.80 or less, and even more preferably 1.50 or less. Here, the lower limit of the CV value ratio is not particularly limited and may be 0.00 or more, or 0.10 or more. Generally, stretched LCP films tend to have a larger CV value after stretching than before stretching, and stretching has been one of the causes of excessive deterioration of thickness accuracy. In contrast, the LCP film 100 of this embodiment suppresses excessive deterioration of thickness accuracy before and after biaxial expansion and contraction.

[0062] The thickness of the LCP film 100 can be set appropriately according to the required performance and is not particularly limited. Considering handling and productivity during extrusion molding, a thickness of 15 μm to 300 μm is preferred, more preferably 18 μm to 250 μm, and even more preferably 20 μm to 200 μm.

[0063] The coefficient of linear expansion (CTE, α2, 23~200℃) of the LCP film 100 in the MD direction can be set appropriately according to the desired performance and is not particularly limited, but from the viewpoint of reducing the anisotropy of the dimensional change rate and the absolute value of the dimensional change rate and improving adhesion to the metal foil, it is preferably -10.0~30.0 ppm / K in the MD direction, more preferably -10.0~10.0 ppm / K, and even more preferably -10.0~5.0 ppm / K. According to the manufacturing method of this embodiment, an LCP film 100 having a negative coefficient of linear expansion in the MD direction can be easily obtained.

[0064] The coefficient of linear expansion (CTE, α2, 23~200℃) of the LCP film 100 in the TD direction can be set appropriately according to the desired performance and is not particularly limited, but from the viewpoint of reducing the anisotropy of the dimensional change rate and the absolute value of the dimensional change rate and improving adhesion to the metal foil, it is preferably -30.0~30.0 ppm / K in the TD direction, more preferably -20.0~5.0 ppm / K, and even more preferably -15.0~0.0 ppm / K. According to the manufacturing method of this embodiment, an LCP film 100 having a negative coefficient of linear expansion in the TD direction can be easily obtained.

[0065] Here, the orientation of the LCP film 100 can be appropriately set according to the desired performance and is not particularly limited, but from the viewpoint of reducing the anisotropy of the dimensional change rate and the absolute value of the dimensional change rate and improving adhesion to the metal foil, the degree of orientation is preferably 0.0 to 30.0%, more preferably 0.0 to 28.0%, even more preferably 0.0 to 26.0%, and particularly preferably 0.0 to 25.0%. The smaller this value, the more isotropic the physical properties are in the plane.

[0066] In this specification, the degree of orientation (%) of the LCP film 100 refers to the value calculated from the following formula based on the area ratio of orientation peaks in the diffraction intensity distribution curve obtained by performing X-ray diffraction measurement using the transmission method with an X-ray diffractometer. Generally, when the degree of orientation (%) of a measurement target is small, the peak intensity is small and broad diffraction peaks are observed in the X-ray diffraction measurement, so a calculation method based on the full width at half maximum of the orientation peak cannot guarantee high measurement accuracy. Therefore, in this specification, the degree of orientation (%) is calculated based on the area ratio of orientation peaks, rather than the full width at half maximum of the orientation peak, by performing X-ray diffraction measurement from one side of the film surface of the LCP film 100 and obtaining the area ratio of orientation peaks. Specifically, as shown in Figure 4 and Equation 1, the calculation method is based on the area ratio of the orientation peak. The peak intensity (orientation component) is measured using a 2θ / θ scan, and the intensity from 0° to 360° in the azimuthal direction is measured using a β scan to obtain the intensity distribution in the azimuthal direction (base intensity (isotropic component)). The area occupied by the orientation component, excluding the area of ​​the base isotropic component, is then used to calculate the degree of orientation (%) as the ratio of the total area (area of ​​orientation component + area of ​​isotropic component) to the total area.

number

[0067] The dielectric properties of the LCP film 100 can be set appropriately according to the desired performance and are not particularly limited. From the viewpoint of obtaining higher dielectric properties, the relative permittivity εr (36 GHz) is preferably 3.0 to 3.7, and more preferably 3.0 to 3.5. Similarly, the dielectric loss tangent tanδ (36 GHz) is preferably 0.0010 to 0.0050, and more preferably 0.0010 to 0.0045. In this specification, the relative permittivity εr (36 GHz) and dielectric loss tangent tanδ (36 GHz) refer to the values ​​at 36 GHz measured by the cavity resonator contact method in accordance with JIS K6471. Furthermore, other detailed measurement conditions shall follow the conditions described in the examples below.

[0068] Furthermore, the LCP film 100 may contain inorganic fillers, resin components other than the thermoplastic resins mentioned above, and additives known in the industry, similar to the LCP extruded film described above. Specific examples of these are as explained in the section on LCP extruded film, and therefore, redundant explanations are omitted here.

[0069] As detailed above, the manufacturing method for the LCP film 100 of this embodiment makes it possible to easily, stably, and at low cost manufacture an LCP film 100 with small absolute values ​​of the coefficient of linear expansion in the MD and TD directions and small anisotropy of the coefficient of linear expansion in the MD and TD directions, without requiring a special laminate film as in the conventional technology. Therefore, the manufacturing method for the LCP film 100 of this embodiment has excellent industrial utility. Furthermore, LCP films, which have excellent high-frequency characteristics and low dielectric properties, have recently attracted attention not only for applications such as electronic circuit boards, multilayer boards, high heat dissipation boards, flexible printed wiring boards, antenna boards, optoelectronic mixed-signal boards, and IC packages, but also 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 upcoming fifth-generation mobile communication systems (5G) and millimeter-wave radar. Therefore, the LCP film 100 obtained by applying the manufacturing method of the LCP film 100 of this embodiment has a smaller absolute value of the coefficient of linear expansion in the MD and TD directions, and less in-plane anisotropy of the coefficient of linear expansion compared to the conventional technology. This suppresses warping during manufacturing and makes it suitable for recent ultrafine processing. As a result, it can be widely used as a particularly useful material in such applications. [Examples]

[0070] The features of the present invention will be further described below with reference to examples and comparative examples, but the present invention is not limited in any way by these. That is, the materials, amounts used, proportions, processing content, processing procedures, etc., shown in the following examples can be changed as appropriate, as long as they do not depart from the spirit of the present invention. Furthermore, the various manufacturing conditions and evaluation result values ​​in the following examples have meaning as preferred upper or lower limits in embodiments of the present invention, and the preferred numerical range may be defined by a combination of the above upper or lower limits and the values ​​of the following examples or the values ​​of the examples themselves.

[0071] [Coefficient of linear expansion] The coefficient of linear expansion (CTE, α2, 23~200°C) of each film was measured in the MD direction and TD direction using the TMA method in accordance with JIS K7197. Measuring instrument: TMA 4000SE (manufactured by NETZSCH) Measurement method: Tensile mode Measurement conditions: Sample size 25mm x 4mm x 50μm thickness Chuck spacing: 20mm Temperature range: 23-200℃ (2nd RUN) Heating rate: 5°C / min Atmosphere: Nitrogen (flow rate 50 ml / min) Test load 5gf *The value from 2ndRUN was used to see the value after the thermal history had been eliminated.

[0072] [Thickness accuracy] In accordance with JIS K7130:1999, the probe of a contact-type thickness gauge was brought into contact with the center of each automatically transported film in the TD direction, and the film thickness was measured at 275 points at 1.0 mm intervals in the MD direction. From the obtained measurement results, the average value and its standard deviation of the film thickness were calculated, and the CV value was determined based on these. Measuring instrument: Tabletop offline contact-type thickness measuring device TOF-5R01 (manufactured by Yamabun Electric Co., Ltd.) Contact-type thickness measuring instrument Measuring probe; made of Teflon®. Measurement conditions: Using the above measuring device, the film was automatically transported and measured continuously at 1.0 mm intervals. The film thickness was measured at 275 points in the flow direction, and the average value and standard deviation σ of the film thickness were calculated from the obtained results. Based on these, the CV value (= standard deviation σ / average value of film thickness) was determined. In addition, the CV value before and after stretching and before and after biaxial expansion / contraction were also calculated, and the ratio of after / before treatment was calculated. A larger value indicates that the thickness accuracy has deteriorated due to stretching or biaxial expansion / contraction, while a smaller value indicates that the deterioration of thickness accuracy due to stretching or biaxial expansion / contraction has been suppressed.

[0073] [Orientation degree] X-ray diffraction measurements were performed on LCP films from one film surface side using the transmission method with an X-ray diffractometer Smartlab (manufactured by Rigaku Corporation), and the degree of orientation was measured for each. Here, a Cu-encased 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, the peak top was confirmed to be at 2θ = 19.5° using the 2θ / θ scan. Next, the intensity in the azimuthal direction from 0° to 360° was measured for the diffraction peak at 2θ = 19.5° using the β scan, thereby obtaining the intensity distribution in the azimuthal direction. From the base intensity (isotropic component) and peak intensity (orientation component) of the obtained β profile, the degree of orientation was calculated from the above formula based on the area ratio of the orientation peak.

[0074] (Comparative Example 1) Type II thermoplastic liquid crystal polymer (a copolymer with monomer composition of 74 mol% p-hydroxybenzoic acid and 26 mol% 6-hydroxy-2-naphthoic acid, measured at a temperature of 300°C and a shear rate of 500 sec) -1 The melt viscosity of the material was 80 Pa·sec. The material was extruded from an extruder at 300°C using the T-die casting method to obtain Comparative Example 1, an LCP extruded film (unstretched LCP film) having a width of 300 mm, an average thickness of 65.5 μm, and a melting point of 280°C. The LCP extruded film of Comparative Example 1 was supplied to a uniaxial tenter stretcher, preheated at 130°C for 10 to 30 seconds, then stretched at 130°C in the TD direction with a stretching ratio of 1.50 times, and then heat-set at 130°C for 30 seconds to obtain the LCP film of Comparative Example 1 (TD-stretched LCP film) having an average thickness of 48.6 μm.

[0075] (Example 1) Type II thermoplastic liquid crystal polymer (a copolymer with monomer composition of 74 mol% p-hydroxybenzoic acid and 26 mol% 6-hydroxy-2-naphthoic acid, measured at a temperature of 300°C and a shear rate of 500 sec) -1 The melt viscosity was 80 Pa·sec), and the LCP extruded from an extruder at 300°C using the T die casting method to obtain the LCP extruded film of Example 1 (unstretched LCP film) having a width of 300 mm, an average thickness of 71.0 μm, and a melting point of 280°C. The LCP extruded film of Example 1 was supplied to a shrink tenter machine, preheated at 130°C for 10 to 30 seconds, then simultaneously subjected to a shrink-to-stretch treatment at 130°C with a shrink-to-medium-dimension (MD) direction of 0.90 times and a stretch-to-tension (TD) direction of 1.45 times. After that, it was heat-set at 130°C for 30 seconds to obtain the LCP film of Example 1 (biaxially expanded and contracted LCP film) having an average thickness of 55.7 μm.

[0076] Table 1 shows the manufacturing conditions and measurement results. [Table 1]

[0077] (Example 2) Except for changing the shrinkage ratio in the MD direction to 0.85 times and the stretching ratio in the TD direction to 1.70 times, the procedure was carried out in the same manner as in Example 1 to obtain an LCP film of Example 2 (biaxially expanding and contracting LCP film) having an average thickness of 51.7 μm.

[0078] (Example 3) Except for changing the shrinkage ratio in the MD direction to 0.80 times and the stretching ratio in the TD direction to 1.70 times, the procedure was carried out in the same manner as in Example 1 to obtain an LCP film of Example 3 (biaxially expanding and contracting LCP film) having an average thickness of 45.6 μm.

[0079] As is clear from Table 1, the LCP film of Example 1 was found to have superior thickness accuracy and improved anisotropy, such as the coefficient of linear expansion in the MD and TD directions, compared to Comparative Example 1. [Industrial applicability]

[0080] According to the present invention, it is possible to provide LCP films and the like that are relatively productive, can be manufactured at low cost, have excellent thickness accuracy, and have improved anisotropy such as the coefficient of linear expansion in the MD and TD directions. Therefore, they can be widely and effectively used in the field of LCP film materials. [Explanation of symbols]

[0081] 100 ···LCP film 10 ···LCP extruded film 11. LCP extruded film after biaxial expansion and contraction. 20... Simultaneous biaxial stretching and shrinking machine 21...Endless Loop 22 ···Endless Loop 21a... Clip 22a... Clip

Claims

1. This is an LCP film containing a thermoplastic liquid crystal polymer. 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. The CV value of the film thickness, measured in accordance with 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. LCP film.

2. The LCP film is a biaxially expandable and contractible LCP film that is expanded and contracted in two axial directions. The LCP film according to claim 1.

3. The ratio of the CV value of the film thickness after biaxial expansion / contraction to the CV value of the film thickness before biaxial expansion / contraction is 2.00 or less. The LCP film according to claim 2.

4. The LCP film has a thickness of 15 μm or more and 300 μm or less. The LCP film according to claim 1.

5. The aforementioned CV value is 0.020 or less. The LCP film according to claim 1.

6. The coefficient of linear expansion in the TD direction is -20.0 to 5.0 ppm / K. The coefficient of linear expansion in the MD direction is -10.0 to 10.0 ppm / K. The LCP film according to claim 1.

7. The coefficient of linear expansion in the TD direction is -15.0 to 0.0 ppm / K. The coefficient of linear expansion in the MD direction is -10.0 to 5.0 ppm / K. The LCP film according to claim 1.

8. The degree of orientation is 0.0 to 30.0%. The LCP film according to claim 1.

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