LCP film

Abstract

Provided is an LCP film or the like which has relatively excellent productivity, can be manufactured at low cost, has excellent thickness accuracy, and has improved anisotropy such as linear expansion coefficients in the MD direction and the TD direction. This LCP film contains a thermoplastic liquid crystal polymer, has a linear expansion coefficient in the TD direction of-30.0 to 30.0 ppm / K, a linear expansion coefficient in the MD direction of-10.0 to 30.0 ppm / K, and a CV value of the film thickness measured in accordance with JIS K7130: 1999 (calculated from the average thickness at 275 as measured at a pitch of 1.0 mm in the MD direction and the standard deviation thereof) of 0.030 or less.

Description

Technical Field

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

[0002] In the past, liquid crystal polymer (LCP: Liquid Crystal Polymer) films manufactured 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 show liquid crystal properties in a molten state or a solution state can be extruded 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 high frequency domains. Therefore, their practical application in gas barrier film materials, electronic materials, and electrical insulation materials is being studied. In addition, insulating materials for circuit substrates using liquid crystal polymers have excellent high-frequency characteristics and low dielectric properties. Therefore, in recent years, they have attracted much attention as insulating materials for circuit substrates such as flexible printed wiring boards (FPCs), flexible printed wiring board laminates, and fiber-reinforced flexible laminates in the fifth-generation mobile communication systems (5G) and millimeter-wave radars to be developed in the future.

[0003] However, it is known that in LCP films obtained by melt extrusion, the polymer chains are highly oriented in the film's outflow direction, i.e., the MD (Machine Direction) (longitudinal direction), due to the high liquid crystal orientation and relatively rigid molecular chains of the liquid crystal polymer, as well as shear stress generated by the die head and die swell during melt extrusion. This results in significant anisotropy in various physical properties such as film strength, thermal expansion coefficient, and dimensional accuracy, for example, between the MD and TD directions, making it difficult to obtain thermoplastic liquid crystal polymer films with high industrial utilization value.

[0004] To improve anisotropy in the MD and TD directions, stretching liquid crystal polymer films has been studied. However, stretching involves significantly stretching the entire liquid crystal polymer film in either a uniaxial or biaxial direction, making it difficult to finely adjust the orientation direction and degree. Therefore, stretching liquid crystal polymer films is currently primarily performed to adjust their surface roughness and surface accuracy.

[0005] For example, Patent Document 1 discloses a production method in which a laminated body is pre-made by sandwiching a liquid crystal polymer film between a pair of laminated films (a fluororesin porous film having a specific gravity of 1.3 or more and an elongation at break of 400% or more in the stretching direction), and the laminated body is stretched in a uniaxial direction or a biaxial direction under temperature conditions at which the fluororesin porous film is softened but not substantially melted and the liquid crystal polymer film is softened to melt.

[0006] Prior art literature

[0007] Patent Literature

[0008] Patent Document 1: Japanese Patent No. 3958629 Summary of the Invention

[0009] Problems to be solved by the invention

[0010] However, the manufacturing technology described in Patent Document 1 is limited to adjusting the surface roughness and surface accuracy of the obtained stretched LCP film, and does not take into account the thickness accuracy of the obtained LCP film itself. The electrical properties of the insulator are dependent on the film thickness. 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, in the use of electronic materials, the requirements for the thickness accuracy of insulating films have become increasingly higher. Therefore, the inventors of the present application discovered for the first time that when the LCP film is used as an insulating substrate material, especially when a metal is sputtered, 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.

[0011] Furthermore, the manufacturing technique described in Patent Document 1 is based on the use of a specialized laminated film, such as a porous fluororesin film with a high specific gravity and high elongation at break, resulting in poor versatility. In fact, Patent Document 1 shows that when using a skived film of PTFE with a high specific gravity or a polyimide film with a low elongation at break, the laminated film breaks during stretching, preventing the desired stretching process. As a result, the LCP film obtained using the manufacturing technique described in Patent Document 1 becomes a relatively high-cost product.

[0012] Furthermore, Patent Document 1, described above, states that a special laminated product comprising a liquid crystal polymer film sandwiched between porous fluororesin films having high specific gravity and high elongation at break is subjected to biaxial stretching near the melting point of the liquid crystal polymer film at a ratio of 1.3 in the MD direction and 3.9 in the TD direction, thereby producing an LCP film with low surface roughness and high surface precision. In other words, the manufacturing technique described in Patent Document 1 is limited to adjusting the surface roughness and surface precision of the resulting stretched LCP film, without any consideration of improving anisotropy such as the linear expansion coefficient in the MD and TD directions.

[0013] The present invention has been made in view of the above problems and has an object to provide an LCP film or the like which has excellent thickness accuracy and improved anisotropy of linear expansion coefficients in the MD and TD directions and can be manufactured at low cost with relatively high productivity.

[0014] Means for solving problems

[0015] The inventors of this application conducted intensive research to solve the above-mentioned problems and discovered for the first time an LCP film with relatively excellent productivity, excellent thickness accuracy, improved anisotropy of linear expansion coefficient in MD and TD directions, which can be manufactured at low cost, thus completing the present invention.

[0016] That is, the present invention provides various specific aspects shown below.

[0017] <1> An LCP film comprising a thermoplastic liquid crystal polymer has a linear expansion coefficient in the TD direction of -30.0 to 30.0 ppm / K, a linear expansion coefficient in the MD direction of -10.0 to 30.0 ppm / K, and a CV value of the film thickness measured in accordance with JIS K7130:1999 (calculated based on the thickness measured at 275 locations at a spacing of 1.0 mm along the MD direction, the average value thereof, and the standard deviation thereof) of not more than 0.030.

[0018] <2> like <1> The LCP film is a biaxially expanded and shrunk LCP film that has been expanded and shrunk along the biaxial directions.

[0019] <3> like <1> or <2> The LCP film has a ratio of the CV value of the film thickness after the biaxial expansion and contraction process to the CV value of the film thickness before the biaxial expansion and contraction process of 2.00 or less.

[0020] <4> like <1> ~ <3> The LCP film according to any one of the preceding claims, wherein the LCP film has a thickness of 15 μm to 300 μm.

[0021] <5> like <1> ~ <4> The LCP film according to any one of the preceding claims, wherein the CV value is 0.020 or less.

[0022] <6> like <1> ~ <5> The LCP film according to any one of the preceding claims has 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.

[0023] <7> like <1> ~ <6> The LCP film according to any one of the above aspects has 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.

[0024] <8> like <1> ~ <7> The LCP film described above has an orientation degree of 0.0 to 30.0%.

[0025] Effects of the Invention

[0026] According to the present invention, it is possible to provide an LCP film or the like which has excellent thickness accuracy and improved anisotropy of linear expansion coefficients in the MD and TD directions, can be produced at low cost with relatively excellent productivity. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] [ Figure 1 ] is a conceptual diagram showing the LCP film.

[0028] [ Figure 2 ] is a conceptual diagram showing the biaxial expansion and contraction process in the manufacturing method of the LCP film.

[0029] [ Figure 3 ] is a schematic diagram showing the MD shrinkage-TD stretching process of the LCP film using a simultaneous biaxial stretching shrinkage machine.

[0030] [ Figure 4 ] is a conceptual diagram showing the principle of calculating the orientation degree based on the area ratio of the orientation peak. DETAILED DESCRIPTION

[0031] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. It should be noted that, unless otherwise specified, positional relationships such as up and down, left and right are based on the positional relationships shown in the accompanying drawings. In addition, the dimensional ratios of the accompanying drawings are not limited to the ratios shown in the drawings. Among them, the following embodiments are examples for illustrating the present invention, and the present invention is not limited to these. That is, the present invention can be implemented with arbitrary changes within the scope of its main purpose. It should be noted that in this specification, for example, the expression of a numerical range of "1 to 100" includes both its lower limit "1" and upper limit "100". In addition, the expression of other numerical ranges is the same.

[0032] Figure 1 This is a conceptual diagram illustrating an LCP film 100 according to the present embodiment. The LCP film 100 according to the present embodiment is characterized in that it comprises a thermoplastic liquid crystal polymer, has a linear expansion coefficient in the TD direction of -30.0 to 30.0 ppm / K, a linear expansion coefficient in the MD direction of -10.0 to 30.0 ppm / K, and a film thickness CV value (calculated from the thickness measured at 275 locations at 1.0 mm intervals along the MD direction, the average value, and the standard deviation thereof) of 0.030 or less as measured in accordance with JIS K7130:1999.

[0033] As long as the LCP film 100 of the present embodiment has the above-described configuration, its type is not particularly limited. As the LCP film 100 of such a present embodiment, it includes: an LCP extruded film manufactured by a multi-layer co-extrusion method such as a T-die method, a blown film method, a co-extrusion method, a two-layer co-extrusion method, a three-layer co-extrusion method, etc.; a pressure-heat treated product of the LCP extruded film; a uniaxially stretched film (TD-stretched LCP film) of the LCP extruded film; a biaxially stretched film (MD-stretched - TD-stretched LCP film) of the LCP extruded film; a biaxially expanded and contracted LCP film (MD-contracted - TD-stretched LCP film) of the LCP extruded film; and so on, but is not particularly limited to these. In particular, as the LCP film 100, from the viewpoints of thickness accuracy, anisotropy, productivity, cost, etc., a biaxially expanded and contracted LCP film of the LCP extruded film is preferred. Hereinafter, an example of manufacturing the LCP film 100 by a biaxially expanded and contracted treatment (MD-contracted - TD-stretched) method will be further described in detail.

[0034] <Manufacturing Method of LCP Film>

[0035] Figure 2 FIG. is a conceptual diagram showing a biaxially expanded and contracted treatment (MD-contracted - TD-stretched 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 at least includes: 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 contraction treatment at a contraction ratio of 0.80 times to 0.99 times in the MD direction and performing a stretching treatment in the TD direction to obtain an LCP film 100 (hereinafter also referred to as a biaxially expanded and contracted step S2). Hereinafter, each step will be described in detail.

[0036] (Preparation Step S1)

[0037] 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, a film known in the art can be used, and its type is not particularly limited. In the manufacturing method of the present embodiment, when a liquid crystal polymer film with high molecular orientation is used, the effect is more remarkable. As the liquid crystal polymer contained in the LCP extruded film 10, a liquid crystal polymer known in the art can be used, and its type is not particularly limited. The liquid crystal polymer is a polymer that forms an optically anisotropic molten phase, and a thermotropic liquid crystal compound can be typically cited. It should be noted that the properties of the anisotropic molten phase can be confirmed by known methods such as a polarized light inspection method using crossed polarizers. More specifically, the confirmation of the anisotropic molten phase can be carried out as follows: using a Leitz polarizing microscope, observing a specimen placed on a Leitz hot stage at a magnification of 40 times in a nitrogen atmosphere.

[0038] As a specific example of a liquid crystal polymer, a liquid crystal polymer preferably is one obtained by polycondensing aromatic or aliphatic dihydroxy compounds, aromatic or aliphatic dicarboxylic acids, aromatic hydroxycarboxylic acids, aromatic diamines, aromatic hydroxylamines, aromatic aminocarboxylic acids, and the like. Examples of liquid crystal polymers include homopolymers thereof, copolymers thereof, modified products thereof, polymer blends thereof with other thermoplastic resins other than liquid crystal polymers, and polymer alloys thereof with other thermoplastic resins other than liquid crystal polymers, etc., but are not particularly limited thereto. From the perspective of obtaining the LCP extruded film 10 by extrusion molding, the liquid crystal polymer is preferably a thermoplastic liquid crystal polymer.

[0039] As specific examples of preferred liquid crystal polymers, there can be cited aromatic polyamide resins formed by polycondensing monomers such as aromatic hydroxycarboxylic acids, aromatic diamines, and aromatic hydroxylamines; (wholly) aromatic polyester resins formed by polycondensing monomers such as aromatic diols, aromatic carboxylic acids, and aromatic hydroxycarboxylic acids; and the like, but are not particularly limited to these. These can be used alone or in any combination and ratio. Thermoplastic liquid crystal polymers are generally classified into type I, type II, type III, etc. from the perspective of heat distortion temperature (TDUL). For the thermoplastic liquid crystal polymer used in this embodiment, any type of thermoplastic liquid crystal polymer can be appropriately used as long as it is appropriately selected according to the application. For example, in the application of electronic circuit substrates that require application to lead-free solders of about 260 to 290°C, a highly heat-resistant type I thermoplastic liquid crystal polymer with a TDUL of about 250 to 350°C and a relatively high heat-resistant type II thermoplastic liquid crystal polymer with a TDUL of about 240 to 250°C can be appropriately used.

[0040] Among them, it is preferred to use a (wholly) aromatic polyester resin that exhibits thermotropic liquid crystal properties and a melting point of 250°C or higher, preferably a melting point of 280°C to 380°C. As such a (wholly) aromatic polyester resin, for example, a (wholly) aromatic polyester resin that exhibits liquid crystal properties when melted and is synthesized from monomers such as aromatic diols, aromatic carboxylic acids, and hydroxycarboxylic acids is known. Representative substances include condensates of ethylene terephthalate and p-hydroxybenzoic acid, condensates of phenol and phthalic acid and p-hydroxybenzoic acid, and condensates of 2,6-hydroxynaphthoic acid and p-hydroxybenzoic acid, but are not particularly limited to these. It should be noted that the (wholly) aromatic polyester resin can be used alone or in any combination and ratio. Depending on the required performance, a wholly aromatic polyester resin with a higher melting point or a higher heat deformation temperature and high heat resistance can be used, or an aromatic polyester resin with a lower melting point or a lower heat deformation temperature and excellent molding processability can be used.

[0041] A preferred embodiment includes a (wholly) aromatic polyester resin having a basic structure of 6-hydroxy-2-naphthoic acid and its derivatives (hereinafter sometimes referred to as "monomer component A") and at least one monomer component 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 (hereinafter sometimes referred to as "monomer component B"). Such (wholly) aromatic polyester resins have linear molecular chains arranged regularly in the molten state, forming an anisotropic melt phase. They typically exhibit thermotropic liquid crystal-like properties and possess excellent basic performance in terms of mechanical properties, electrical properties, high-frequency properties, heat resistance, and hygroscopicity.

[0042] In addition, the (wholly) aromatic polyester resin of one preferred embodiment described above may have any structure as long as it contains monomer component A and monomer component B as essential units. For example, it may contain two or more monomer components A, or it may contain three or more monomer components A. In addition, the (wholly) aromatic polyester resin of one preferred embodiment described above may also contain other monomer components (hereinafter sometimes referred to as "monomer component C") in addition to monomer components A and monomer component B. That is, the (wholly) aromatic polyester resin of one preferred embodiment described above may be a condensation product of two or more monomer components formed only by monomer components A and monomer component B, or it may be a condensation product of three or more monomer components formed by monomer components A, monomer component B, and monomer component C. Examples of other monomer components include monomer components other than the above-mentioned monomer components A and monomer component B, 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., but are not particularly limited to these. The other monomer components may be used alone or in any combination and ratio of two or more.

[0043] It should be noted that, in this specification, "derivatives" refer to substances obtained by introducing a halogen atom (e.g., a fluorine atom, a chlorine atom, a bromine atom, an iodine atom), an alkyl group having 1 to 5 carbon atoms (e.g., a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an 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 (e.g., a methoxy group, an ethoxy group, etc.), a carbonyl group, or a modifying group such as -O-, -S-, or -CH2- into a portion of the above-mentioned monomer components (hereinafter sometimes referred to as "monomer components having a substituent"). Here, "derivatives" may also refer to ester-forming monomers such as acylates, ester derivatives, or acyl halides of monomer components A and B that may have the above-mentioned modifying groups.

[0044] As a particularly preferred embodiment, there are: binary polycondensates of p-hydroxybenzoic acid and its derivatives and 6-hydroxy-2-naphthoic acid and its derivatives; ternary or higher polycondensates of p-hydroxybenzoic acid and its derivatives, 6-hydroxy-2-naphthoic acid and its derivatives and monomer component C; polycondensates of p-hydroxybenzoic acid and its derivatives, 6-hydroxy-2-naphthoic acid and its derivatives, and a monomer selected from terephthalic acid, isophthalic acid, 6-naphthalene dicarboxylic acid, 4,4'-biphenol, bisphenol A, hydroquinone, 4,4-dihydroxy-2-naphthoic acid ... A ternary or higher polycondensate formed from one or more members selected from the group consisting of phenol, ethylene terephthalate, and their derivatives; and a quaternary or higher polycondensate formed from one or more members 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 their derivatives, and one or more monomer components C. These can be obtained as materials having a lower melting point than, for example, homopolymers of p-hydroxybenzoic acid. Therefore, thermoplastic liquid crystal polymers using these materials provide films with excellent moldability during thermal compression bonding to adherends.

[0045] From the perspective of lowering the melting point of the (wholly) aromatic polyester resin, improving the molding processability during thermocompression bonding of the LCP film 100 and the adherend, or obtaining high peel strength when thermocompression bonding the LCP film 100 to a metal foil, the content ratio of the monomer component A relative to the (wholly) 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 further preferably 50 mol% or more and 80 mol% or less. Similarly, the content ratio of the monomer component B relative to the (wholly) 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 further preferably 20 mol% or more and 50 mol% or less. In addition, the content ratio of the monomer component C that may be contained in the (wholly) aromatic polyester resin is preferably 10 mol% or less, more preferably 8 mol% or less, further preferably 5 mol% or less, and particularly preferably 3 mol% or less, in terms of molar ratio conversion.

[0046] It should be noted that the synthesis method of the liquid crystal polymer can be a known method and is not particularly limited. Known polycondensation methods that form ester bonds using the above-mentioned monomer components, such as melt polymerization, melt acid hydrolysis, and slurry polymerization, can be used. When these polymerization methods are used, an acylation or acetylation step can also be performed according to conventional methods.

[0047] The LCP extruded film 10 may further contain an inorganic filler. By including an inorganic filler, an LCP film 100 with reduced anisotropy of the linear expansion coefficient in the MD, TD, and ZD (Z-axis) directions (thickness direction of the film) can be easily obtained. Such an LCP film 100 is particularly useful in applications such as rigid substrates requiring multi-layer lamination.

[0048] As the inorganic filler, any known inorganic filler in the art can be used, and the type thereof is not particularly limited. Examples thereof include 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, aluminum oxide, hydrotalcite, aluminum borate, aluminum nitride, etc.), magnesium compounds (e.g., magnesium aluminum metasilicate, 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, stannates such as zinc stannate, etc., but are not particularly limited to these. These may be used alone or in combination of two or more. Among them, silicon dioxide is preferred from the viewpoint of dielectric properties.

[0049] In addition, the inorganic filler used herein may be one that has been subjected to a surface treatment known in the art. Surface treatment can improve moisture resistance, adhesive strength, dispersibility, and the like. Surface treatment agents include, but are not particularly limited to, silane coupling agents, titanate coupling agents, sulfonates, carboxylates, and phosphates.

[0050] With regard to the median particle size (d50) of the inorganic filler, from the viewpoint of requiring a reduction effect, 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 further preferably 0.1 μm or more and 50 μm or less. It should be noted that, in this specification, the median particle size (d50) of the inorganic filler refers to a value measured on a volume basis by a laser diffraction / scattering particle size distribution measuring device (LA-500 manufactured by Horiba, Ltd.).

[0051] The content of the inorganic filler can be appropriately set based on the required performance and the balance of other essential and optional components, and is not particularly limited. From the perspectives of kneading properties, workability, and the effect of reducing the linear expansion coefficient during production, the content of the inorganic filler, calculated as solids relative to the total amount of the LCP extruded film 10, is preferably 1% by mass or more and 45% by mass or less, more preferably 3% by mass or more and 40% by mass or less, and even more preferably 5% by mass or more and 35% by mass or less.

[0052] The LCP extruded film 10 may contain resin components other than the above-mentioned thermoplastic resins (hereinafter sometimes referred to as "other resin components"), such as thermosetting resins, elastomers, etc., within the scope that does not excessively damage the effects of the present invention. In addition, the LCP extruded film 10 may contain additives known in the art, such as release modifiers such as higher fatty acids with 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. These additives can be used alone 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. From the viewpoint of moldability, thermal stability, etc., each is preferably 0.01 to 10% by mass, more preferably 0.1 to 7% by mass, and further preferably 0.5 to 5% by mass, relative to the total amount of the LCP extruded film 10.

[0053] As the above-mentioned LCP extruded film 10, it is preferred to use melt extruded films such as T-die extruded film and inflation film. The melt extruded film can be obtained by extruding a resin composition comprising the above-mentioned liquid crystal polymer and any components such as inorganic fillers and other resin components added as needed into a specified thickness. The extrusion method can be applied to various known methods, and its type is not particularly limited. The following methods can be arbitrarily combined and applied: for example, T-die method, inflation method; for example, co-extrusion method of multi-manifold mode, co-extrusion method of feed block mode; for example, multi-layer co-extrusion method such as two-layer co-extrusion method and three-layer co-extrusion method. Among them, from the viewpoint of the ease of controlling the molecular orientation of the liquid crystal polymer on the surface of the film and inside the film, as a preferred embodiment, the following method can be cited: utilizing an extrusion molding method using a T-die (hereinafter sometimes referred to as "T-die extrusion method"), the above-mentioned resin composition is extruded from the T-die and molded into a film shape, and thereafter subjected to cooling treatment, crimping treatment, pressurized heating treatment, etc. as needed to obtain a specified LCP extruded film 10. Alternatively, a liquid crystal polymer film layer that is the middle layer (core layer) of a three-layer co-extruded film having a laminated structure comprising at least a thermoplastic resin layer, a liquid crystal polymer film layer, and a thermoplastic resin layer arranged in this order may be preferably used as the LCP extruded film 10. In this case, a single-layer liquid crystal polymer film layer (LCP extruded film 10) can be obtained by removing the two outer thermoplastic resin layers of the three-layer co-extruded film.

[0054] The thickness of the LCP extruded film 10 can be appropriately set according to the required performance and is not particularly limited. Considering the operability and productivity during extrusion molding, it is preferably 15 μm to 300 μm, more preferably 18 μm to 250 μm, and even more preferably 20 μm to 200 μm.

[0055] The melting point (melting temperature) of the LCP extruded film 10 is not particularly limited. From the perspectives of heat resistance and processability of the film, the melting point (melting temperature) is preferably 200-400°C, preferably 250-360°C, more preferably 260-355°C, further preferably 270-350°C, and particularly preferably 275-345°C. It should be noted that in this specification, the melting point of the LCP extruded film 10 refers to the melting peak temperature measured by differential scanning calorimetry (DSC) using a DSC8500 (manufactured by PerkinElmer) in the temperature range of 30-400°C at a heating rate of 20°C / min (first heating), followed by cooling at a cooling rate of 50°C / min (first cooling), and then performing a second heating at a heating rate of 20°C / min (second heating) to observe the value after eliminating the thermal history.

[0056] Here, the coefficient of linear expansion in the TD direction (CTE, α2, 23 to 200°C) of the LCP extruded film 10 is not particularly limited, but is preferably 5.0 to 60.0 ppm / K, more preferably 5.0 to 55.0 ppm / K, and even more preferably 5.0 to 50.0 ppm / K. In addition, the coefficient of linear expansion in the MD direction (CTE, α2, 23 to 200°C) 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 even more preferably -23.0 to 5.0 ppm / K. It should be noted that the LCP extruded film 10 to be subjected to the biaxial expansion and contraction treatment may be an unstretched film, a uniaxially stretched film, or a biaxially stretched film.

[0057] In this specification, the linear expansion coefficient is measured using the TMA method in accordance with JIS K7197, and the average linear expansion coefficient refers to the average value of the linear expansion coefficients measured at 23°C to 200°C using this method. The linear expansion coefficient measured here refers to the value obtained by heating the film as a measurement sample at a heating rate of 5°C / minute (first heating), cooling it to the measurement environment temperature (23°C) (first cooling), and then heating it at a heating rate of 5°C / minute (second heating) to observe the value after thermal history elimination. Other detailed measurement conditions follow those described in the Examples below.

[0058] On the other hand, the dielectric properties of the LCP extruded film 10 can be appropriately set according to the desired performance and are not particularly limited. r (36GHz) is preferably 3.0 to 3.7, more preferably 3.0 to 3.5. Similarly, the dielectric loss tangent tanδ (36GHz) is preferably 0.0010 to 0.0050, more preferably 0.0010 to 0.0045. It should be noted that in this specification, the relative dielectric constant ε r (36 GHz) and dielectric loss tangent tan δ (36 GHz) are values ​​measured at 36 GHz by a cavity resonator perturbation method in accordance with JIS K6471.

[0059] It should be noted that the LCP extruded film 10 can be used directly, or it can be further subjected to a pressurized heating process as needed to further reduce the molecular orientation (anisotropy) of the liquid crystal polymer or further relieve the internal strain. In this way, it is also possible to achieve an LCP film 100 with a further reduced anisotropy of the dimensional change rate and an LCP film 100 with a smaller absolute value of the dimensional change rate.

[0060] The pressurized heat treatment can be carried out using methods known in the art, such as contact heat treatment, non-contact heat treatment, etc., and its type is not particularly limited. For example, known equipment such as non-contact heater, baking oven, blowing device, hot roller, cooling roller, hot press, double belt hot press can be used to carry out heat setting. At this time, the surface of LCP extruded film 10 can be configured with a release film or porous film known in the art and heat treated as needed. In addition, from the viewpoint of controlling the orientation, it is preferred to use the following hot pressing method: the surface and back of LCP extruded film 10 are configured with a release film or porous film, while being sandwiched between a pair of endless belts of a double belt press and hot pressing is carried out, and thereafter the release film or porous film is removed. The hot pressing method can be carried out with reference to, for example, Japanese Patent Application Laid-Open No. 2010-221694. The processing temperature when hot-pressing the LCP extruded film 10 using the above-mentioned resin composition between a pair of endless belts of a double-belt press is preferably higher than the melting point of the liquid crystal polymer and lower than 70°C in order to control the crystallization state of the LCP extruded film 10. It is more preferably higher than +5°C and lower than 60°C, and even more preferably higher than +10°C and lower than 50°C. The hot-pressing conditions at this time can be appropriately set according to the desired performance and are not particularly limited. It is preferably carried out under conditions of a surface pressure of 0.5-10 MPa and a heating temperature of 250-430°C, more preferably under conditions of a surface pressure of 0.6-8 MPa and a heating temperature of 260-400°C, and even more preferably under conditions of a surface pressure of 0.7-6 MPa and a heating temperature of 270-370°C. On the other hand, when using a non-contact heater or oven, it is preferably carried out under conditions of 200-320°C for 1-20 hours.

[0061] (Biaxial expansion and contraction process S2)

[0062] In the biaxial expansion and contraction step S2, the LCP extruded film 10 as the processed object is subjected to a shrinkage treatment at a shrinkage ratio of 0.80 to 0.99 in the MD direction 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 step (MD shrinkage-TD stretching treatment) is classified as a uniaxial shrinkage film (MD shrinkage film) when regarded as a shrink film, as a uniaxial stretching film (TD stretching film) when regarded as a stretch film, and as a uniaxial shrinkage and uniaxial stretching film (MD shrinkage and TD stretching film) when regarded as a biaxial expansion and contraction film.

[0063] When the LCP extruded film 10 is shrunk in the MD direction and stretched in the TD direction, a known stretching machine, a biaxial stretching shrinking machine (biaxial expansion machine), etc. can be used. As a simultaneous biaxial expansion machine (shrinkage tenter), for example, there is a known example described in Japanese Patent Publication No. 2022-051372. Specifically, using Figure 3 The simultaneous biaxial stretching and shrinking machine 20 shown feeds out the LCP extruded film 10 while holding it between a plurality of clamps 21a, 22a of endless rings 21, 22 that are symmetrically arranged on the left and right, and reduces the intervals between the clamps 21a and the intervals between the clamps 22a. Thus, while the LCP extruded film 10 is contracted along the MD direction, the intervals between the endless rings 21, 22 are gradually expanded in the film conveying direction. Therefore, the LCP extruded film 10 held between the endless rings 21, 22 is gradually pulled outward and stretched along the TD direction.

[0064] The processing temperature of the biaxial expansion and contraction process S2 is not particularly limited as long as it is above the glass transition point of the LCP extruded film 10, and is preferably 70 to 180°C, more preferably 90 to 180°C. After shrinking in the MD direction and stretching in the TD direction, it is preferably subjected to a heat treatment (heat setting) at 100 to 240°C for 1 to 600 seconds. During heat setting, methods known in the art, such as contact heat treatment, non-contact heat treatment, etc., can be carried out, and the types are not particularly limited. For example, known equipment such as non-contact heaters, ovens, blowing devices, hot rollers, cooling rollers, hot presses, and double-belt hot presses can be used for heat setting. At this time, a release film or a porous film known in the art can be configured on the surface of the LCP film 100 as needed and subjected to heat pressing. It should be noted that in the biaxial expansion and contraction process S2, the stretching treatment and the shrinking treatment can be carried out one after another, or the shrinking treatment and the stretching treatment can be carried out one after another in reverse order. In addition, the shrinking treatment and the stretching treatment can also be carried out simultaneously.

[0065] The stretching ratio and shrinkage ratio of the LCP extruded film 10 in the biaxial expansion and contraction process S2 can be set according to the desired degree of improvement of the anisotropy, and are not particularly limited. From the viewpoint of alleviating the directional anisotropy of the LCP extruded film that has been molecularly oriented 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 further preferably 0.80 to 0.93 times, based on the length in the MD direction before shrinkage. In addition, similarly, from the viewpoint of alleviating the directional anisotropy of the LCP extruded film that has been 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 further preferably 1.40 to 2.50 times, based on the length in the TD direction before stretching. In addition, the stretching shrinkage ratio represented by the product of the shrinkage ratio in the MD direction and the stretching ratio in the TD direction (when the shrinkage ratio in the MD direction is set to m and the stretching ratio in the TD direction is set to n, the stretching shrinkage ratio represented by m×n) is preferably 0.960 times to 2.475 times, more preferably 1.040 times to 2.375 times, and even more preferably 1.120 times to 2.325 times. According to this production method, although the stretching shrinkage ratio in the biaxial expansion step S2 is low, it is still possible to easily produce 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.

[0066] In addition, 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, the LCP film 100 after the biaxial shrinkage treatment can be pulled by a pulling roller and wound into a roll on a winding roller to form a roll.

[0067] It should be noted that, in this embodiment, an example of shrinking and stretching the LCP extruded film 10 alone is shown, but the first film member and the second film member can also be arranged on the surface and back of the LCP extruded film 10, respectively, so that they are respectively in close contact with the surface side and back side of the LCP extruded film 10, forming a pressed body having a laminated structure of the first film member / LCP extruded film 10 / second film member, and the pressed body is subjected to a biaxial expansion and contraction treatment. 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 extruded film 10 and have a strength that does not break when subjected to MD shrinkage-TD stretching treatment. For example, paper, woven fabric, non-woven fabric, metal plate, alloy plate, metal foil, alloy foil, resin film, rubber sheet, foam sheet, a laminate or impregnation body containing any combination thereof, etc. can be used as the first film member and the second film member. Among them, thermosetting resin films such as polyimide films; thermoplastic resin films having a higher melting point than the LCP extruded film 10; metal foils such as aluminum foil and copper foil, etc. are preferred. It should be noted that the first membrane member and the second membrane member may be made of the same constituent material or different constituent materials.

[0068] There is no particular limitation on the method for making the pressed body, and a known lamination forming method can be applied. By sequentially overlapping the first film member, the LCP extruded film 10 and the second film member, a pressed body can be obtained by pressing or hot pressing using known equipment such as a press, a pressing roller, a non-contact heater, an oven, a blowing device, a hot roller, a cooling roller, a hot press, a double-belt press, etc. In addition, the processing conditions during the pressing can be appropriately set according to the raw materials used and are not particularly limited. For example, it can be carried out under the conditions of a surface pressure of 0.3 to 10 MPa and a heating temperature of more than the thermal deformation temperature of the LCP extruded film 10 and less than the melting point + 70°C, preferably under the conditions of a surface pressure of 0.6 to 8 MPa, more than the melting point of the LCP extruded film 10 and less than a temperature 60°C higher than the melting point.

[0069] It should be noted that, in order to achieve the desired peelability, various release agents may be placed between the LCP extruded film 10 of the press-bonded body and the first film member, and between the LCP extruded film 10 and the second film member. In addition, in order to achieve the desired adhesion, various primers, adhesives, etc. may be placed instead of release agents.

[0070] Next, after subjecting the LCP extruded film 10 to MD shrinkage-TD stretching treatment, the crimping body is cooled as needed, and then the first film member and the second film member crimped to the two surfaces of the crimping body are peeled off (removed), whereby the LCP film 100 after MD shrinkage-TD stretching treatment can be obtained. Cooling of the crimping body can be carried out, for example, using a pair of cooling rollers, or alternatively, natural cooling can be performed. Then, the LCP film 100 after MD shrinkage-TD stretching treatment can be formed into a roll stock, for example, by being pulled by a pulling roller and wound around a winding roller in a roll shape.

[0071] <LCP film>

[0072] The LCP film 100 obtained by the above manufacturing method is a MD shrinkage-TD stretch product of the LCP extruded film 10 (hereinafter sometimes referred to as a biaxially expanded and shrunk LCP film).

[0073] 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 further preferably 0.025 or less. Here, the lower limit value of the CV value of the film thickness is not particularly limited, and it may be 0.000 or more, and may be 0.005 or more. It should be noted that in this specification, the CV value of the film thickness refers to the value measured according to JIS K7130:1999. Specifically, it means: making the probe of the contact thickness measuring instrument contact the central part in the TD direction of the film automatically conveyed, measuring the thickness at 275 positions at a pitch of 1.0 mm in the MD direction, and calculating the value based on the average value and the standard deviation of the measured thickness. In addition, regarding other detailed measurement conditions, follow the conditions described in the examples below. The smaller the CV value of the film thickness, the better the thickness accuracy.

[0074] In addition, when the LCP film 100 of the present embodiment is a biaxially expanded and shrunk LCP film, the ratio of the aforementioned CV value of the film thickness after biaxial expansion and shrinkage treatment to the CV value of the film thickness before biaxial expansion and shrinkage treatment is preferably 2.00 or less, more preferably 1.80 or less, and further preferably 1.50 or less. Here, the lower limit value of the ratio of the CV value is not particularly limited, and it may be 0.00 or more, and may be 0.10 or more. Generally, the stretched product of the LCP film tends to have a larger CV value after stretching treatment than before stretching treatment, and the stretching treatment becomes a factor that excessively deteriorates the thickness accuracy. In contrast, in the LCP film 100 of the present embodiment, the excessive deterioration of the thickness accuracy before and after biaxial expansion and shrinkage treatment is suppressed.

[0075] The thickness of the LCP film 100 can be appropriately set according to the required performance and is not particularly limited. Considering operability and productivity during extrusion molding, it is preferably 15 μm to 300 μm, more preferably 18 μm to 250 μm, and even more preferably 20 μm to 200 μm.

[0076] The coefficient of linear expansion (CTE, α2, 23-200°C) of the LCP film 100 in the MD direction can be appropriately set according to the desired performance and is not particularly limited. From the perspectives of reducing the anisotropy of the dimensional change rate and the absolute value of the dimensional change rate, and improving adhesion to metal foil, it is preferably -10.0 to 30.0 ppm / K in the MD direction, more preferably -10.0 to 10.0 ppm / K, and even more preferably -10.0 to 5.0 ppm / K. The production method of this embodiment allows for the simple production of an LCP film 100 having a negative coefficient of linear expansion in the MD direction.

[0077] The coefficient of linear expansion (CTE, α2, 23-200°C) of the LCP film 100 in the TD direction can be appropriately set according to the desired performance, without particular limitation. From the perspectives of reducing the anisotropy of the dimensional change rate and the absolute value of the dimensional change rate, and improving adhesion to metal foil, the coefficient of linear expansion in the TD direction is preferably -30.0 to 30.0 ppm / K, more preferably -20.0 to 5.0 ppm / K, and even more preferably -15.0 to 0.0 ppm / K. The production method of this embodiment allows for the simple production of an LCP film 100 having a negative coefficient of linear expansion in the TD direction.

[0078] Here, the orientation of the LCP film 100 can be appropriately set according to the desired performance and is not particularly limited. From the perspectives 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 orientation degree is preferably 0.0 to 30.0%, more preferably 0.0 to 28.0%, further preferably 0.0 to 26.0%, and particularly preferably 0.0 to 25.0%. The smaller the value, the more isotropic the physical properties within the plane.

[0079] It should be noted that, in this specification, the orientation degree (%) of the LCP film 100 refers to: in the diffraction intensity distribution curve obtained by performing X-ray diffraction measurement using a transmission method using an X-ray diffraction device, based on the area ratio of the orientation peak, the value calculated according to the following formula. Usually, in the case of a measurement object with a small orientation degree (%), a diffraction peak with a small and wide peak intensity can be observed in the X-ray diffraction measurement, so the calculation method based on the half-value width of the orientation peak cannot ensure high measurement accuracy. Therefore, in this specification, an X-ray diffraction measurement is performed from one film surface side of the LCP film 100 by a calculation method based on the area ratio of the orientation peak rather than the half-value width of the orientation peak, and the orientation degree (%) is calculated based on the area ratio of the orientation peak obtained. Specifically, as Figure 4 As shown in Mathematical Formula 1, as a 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 from 0° to 360° in the azimuthal direction is measured under β scanning to obtain the intensity distribution in the azimuthal direction (reference intensity (isotropic component)), and the ratio of the area occupied by the orientation component other than the area of ​​the isotropic component serving as the reference to the total area (area of ​​the orientation component + area of ​​the isotropic component) is calculated as the orientation degree (%).

[0080] [Mathematical formula 1]

[0081]

[0082] The dielectric properties of the LCP film 100 can be suitably set according to the desired performance and are not particularly limited. 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 tan δ (36 GHz) is preferably 0.0010 or more and 0.0050 or less, more preferably 0.0010 or more and 0.0045 or less. It should be noted that, in this specification, the relative dielectric constant εr (36 GHz) and the dielectric loss tangent tan δ (36 GHz) refer to the values ​​at 36 GHz measured by the cavity resonator perturbation method according to JIS K6471. In addition, for other detailed measurement conditions, follow the conditions described in the embodiments described later.

[0083] It should be noted that, like the above-mentioned LCP extruded film, the LCP film 100 may contain inorganic fillers, resin components other than the above-mentioned thermoplastic resin, additives known in the art, etc. Specific examples thereof are described in the section of the LCP extruded film, and repeated descriptions are omitted here.

[0084] As described in detail above, according to the manufacturing method of the LCP film 100 of the present embodiment, 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 can be manufactured simply, stably and at low cost without the need for a special laminated film as in the prior art. Therefore, the industrial usefulness of the manufacturing method of the LCP film 100 of the present embodiment is excellent. In addition, the LCP film with excellent high-frequency characteristics and low dielectric properties is not only used in electronic circuit substrates, multi-layer substrates, high heat dissipation substrates, flexible printed wiring boards, antenna substrates, optoelectronic hybrid substrates, IC packaging and other applications, but also in recent years as an insulating material for circuit substrates 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) to be developed in the future, millimeter-wave radars, etc., and has attracted much attention. 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 smaller absolute values ​​of the linear expansion coefficient in the MD direction and the TD direction, and smaller in-plane anisotropy of the linear expansion coefficient. The occurrence of warping during manufacturing can be suppressed, and the film can be adapted to ultra-fine processing in recent years. Therefore, the film can be widely used as a particularly useful raw material in this application.

[0085] Example

[0086] The following examples and comparative examples are given to more specifically illustrate the features of the present invention, but the present invention is not subject to any limitation thereof. That is, the material, usage, ratio, processing content, processing steps etc. shown in the following examples can be suitably changed as long as they do not depart from the purport of the present invention. In addition, the values ​​of the various manufacturing conditions and evaluation results in the following examples have the meaning of the preferred upper limit or preferred lower limit in the embodiment of the present invention, and preferred numerical ranges can also be the scope specified by the combination of the aforementioned upper limit or lower limit and the value of the following examples or the values ​​of the embodiments each other.

[0087] [Linear expansion coefficient]

[0088] The linear expansion coefficient (CTE, α2, 23 to 200° C.) in the MD direction and the TD direction of each film was measured by the TMA method in accordance with JIS K7197.

[0089] Measuring equipment: TMA 4000SE (manufactured by NETZSCH)

[0090] Measurement method: tensile mode

[0091] Measurement conditions:

[0092] ※In order to observe the value after eliminating the thermal history, the value of 2ndRUN is used.

[0093] [Thickness accuracy]

[0094] In accordance with JIS K7130:1999, the probe of a contact-type thickness gauge was brought into contact with the center of each film in the TD direction while it was being automatically conveyed. The film thickness was measured at 275 locations along the MD direction at 1.0 mm intervals. The average film thickness and its standard deviation were calculated from the measurement results, and the CV value was determined based on these values.

[0095] Measurement equipment: Desktop off-line contact thickness measurement device TOF-5R01 (made by Sanbun Electric Co., Ltd.)

[0096] Probe: Made of Teflon (registered trademark)

[0097] Measurement conditions: The film is automatically conveyed using the above-mentioned measuring device and continuously measured at 1.0 mm intervals. The film thickness is measured at 275 locations in the direction of travel. The average value and standard deviation σ of the film thickness are calculated based on the obtained results. Based on these values, the CV value (= standard deviation σ / average value of the film thickness) is obtained. In addition, the CV values ​​before and after the stretching treatment and before and after the biaxial expansion treatment are also obtained, and the ratio after treatment / before treatment is calculated. The larger the value, the more deteriorated the thickness accuracy due to the stretching treatment or biaxial expansion treatment. The smaller the value, the more suppressed the deterioration of the thickness accuracy caused by the stretching treatment or biaxial expansion treatment.

[0098] [Orientation degree]

[0099] The X-ray diffraction device Smartlab (made by Rigaku) ​​was used to measure the X-ray diffraction of the LCP film from one film surface side by transmission method, and the orientation degree was measured respectively. Here, the X-ray source uses a Cu closed tube, and the X-ray diffraction measurement (2θ / θ scanning, β scanning) is carried out using a parallel beam optical system and a transmission method. First, a 2θ / θ scan was used to confirm that there was a peak at 2θ=19.5°. Then, the intensity of 0° to 360° in the azimuthal direction was measured for the diffraction peak of 2θ=19.5 by β scanning, thereby obtaining the intensity distribution in the azimuthal direction. According to the reference intensity (isotropic component) and peak intensity (orientation component) of the obtained β distribution diagram (profile), the orientation degree was calculated according to the above formula based on the area ratio of the orientation peak.

[0100] (Comparative Example 1)

[0101] A type II thermoplastic liquid crystal polymer (a copolymer of 74 mol% p-hydroxybenzoic acid and 26 mol% 6-hydroxy-2-naphthoic acid) was prepared at a temperature of 300°C and a shear rate of 500 sec. -1The LCP film (with a melt viscosity of 80 Pa·sec) was extruded from an extruder at 300° C. by a T-die casting method to obtain an LCP extruded film (unstretched LCP film) of Comparative Example 1 having a width of 300 mm, an average thickness of 65.5 μm and a melting point of 280° C.

[0102] The LCP extruded film of Comparative Example 1 was supplied to a uniaxial tenter stretching machine, preheated at 130°C for 10 to 30 seconds, stretched at a temperature of 130°C with a stretching ratio of 1.50 times in the TD direction, 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.

[0103] (Example 1)

[0104] A type II thermoplastic liquid crystal polymer (a copolymer of 74 mol% p-hydroxybenzoic acid and 26 mol% 6-hydroxy-2-naphthoic acid) was prepared at a temperature of 300°C and a shear rate of 500 sec. -1 The LCP film (with a melt viscosity of 80 Pa·sec) was extruded from an extruder at 300° C. by a T-die casting method to obtain the LCP extruded film (unstretched LCP film) of Example 1 having a width of 300 mm, an average thickness of 71.0 μm and a melting point of 280° C.

[0105] The LCP extruded film of Example 1 is supplied to a shrinkage tenter, preheated at 130°C for 10 to 30 seconds, and then simultaneously subjected to a shrinkage treatment of 0.90 times in the MD direction and a shrinkage stretching treatment of 1.45 times in the TD direction at a temperature of 130°C, followed by heat setting at 130°C for 30 seconds, thereby obtaining the LCP film of Example 1 (biaxially expanded LCP film) having an average thickness of 55.7 μm.

[0106] Table 1 shows the production conditions and measurement results.

[0107] [Table 1]

[0108]

[0109] (Example 2)

[0110] An LCP film (biaxially expanded LCP film) of Example 2 having an average thickness of 51.7 μm was obtained in the same manner as in Example 1 except that the shrinkage ratio in the MD direction was changed to 0.85 times and the stretching ratio in the TD direction was changed to 1.70 times.

[0111] (Example 3)

[0112] An LCP film (biaxially expanded LCP film) of Example 3 having an average thickness of 45.6 μm was obtained in the same manner as in Example 1 except that the shrinkage ratio in the MD direction was changed to 0.80 times and the stretching ratio in the TD direction was changed to 1.70 times.

[0113] Table 1 clearly shows that the LCP film of Example 1 is superior in thickness accuracy and has improved anisotropy of the linear expansion coefficient and the like in the MD and TD directions, compared to the LCP film of Comparative Example 1.

[0114] Industrial applicability

[0115] According to the present invention, an LCP film having excellent thickness accuracy, improved anisotropy of the linear expansion coefficient in the MD and TD directions, etc., which can be manufactured at low cost and has relatively excellent productivity can be provided. Therefore, it can be widely and effectively used in the field of raw materials for LCP films.

[0116] Description of Reference Numerals

[0117] 100···LCP film

[0118] 10···LCP extruded film

[0119] 11···LCP extruded film after biaxial expansion

[0120] 20···Simultaneous biaxial stretching and shrinking machine

[0121] 21···Endless Ring

[0122] 22···Endless Ring

[0123] 21a···Clamp

[0124] 22a···Clamp

Claims

1. An LCP film comprising a thermoplastic liquid crystal polymer, The linear expansion coefficient of the LCP film in the TD direction is -30.0 to 30.0 ppm / K. The linear expansion coefficient of the LCP film 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 measured at 275 locations at 1.0 mm intervals in the MD direction, the average value thereof, and the standard deviation thereof) is 0.030 or less.

2. The LCP film according to claim 1, wherein The LCP film is a biaxially expanded and shrunk LCP film that has been expanded and shrunk along biaxial directions.

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

4. The LCP film according to claim 1, wherein The LCP film has a thickness of 15 μm to 300 μm.

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

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

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

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

Images