LCP film and LCP stretched film

Abstract

The present invention provides LCP films and the like that offer excellent continuous stretchability in a roll-to-roll method, and enable the high productivity of LCP stretched films with low anisotropy and absolute value of dimensional change. [Solution] An LCP film containing a thermoplastic liquid crystal polymer, characterized in that, in the stress-strain curve measured by extensional viscosity measurement test (in accordance with JIS K7127-1:2014), the extensional viscosity ηEt in the TD direction of the LCP film is 2.00E+07Pa·s or more, and the value of the coefficient of linear expansion at CTE-2ndRUN in the TD direction of the LCP film, measured by thermomechanical analysis (TMA method in accordance with JIS K7197: temperature range: 23℃~200℃), is 65 ppm / K or less.

Description

[Technical Field]

[0001] This invention relates to LCP film and LCP stretched film, etc. [Background technology]

[0002] Conventionally, varnish-impregnated composite materials have been known as insulating materials for circuit boards. These are produced by impregnating glass cloth with a varnish containing a thermosetting resin such as epoxy resin, inorganic fillers, and solvents, and then hot-pressing it. However, this manufacturing method has poor process tolerance and low productivity, for example, in terms of resin flowability during varnish impregnation and curing properties during hot-pressing. Furthermore, thermosetting resins are prone to hygroscopicity, and their dimensions change as they absorb moisture, resulting in poor dimensional accuracy (heat-induced dimensional accuracy) of the resulting varnish-impregnated composite material.

[0003] On the other hand, liquid crystal polymers (LCPs) are polymers that exhibit liquid crystalline properties in a molten or solution state. In particular, thermotropic liquid crystal polymers that exhibit liquid crystalline properties in a molten state can be extruded and possess 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. For this reason, films using thermoplastic liquid crystal polymers are being considered for practical use in gas barrier film materials, electronic materials, and electrical insulating materials. Furthermore, insulating materials for circuit boards using liquid crystal polymers have recently attracted attention as insulating materials for circuit boards such as flexible printed circuit boards (FPCs), flexible printed circuit board laminates, and fiber-reinforced flexible laminates in the upcoming fifth-generation mobile communication systems (5G) and millimeter-wave radar, due to their excellent high-frequency properties and low dielectric properties.

[0004] However, when actually performing single-layer extrusion molding of thermoplastic liquid crystal polymers, it was found that due to the high liquid crystal orientation properties of thermoplastic liquid crystal polymers, it is difficult to obtain thermoplastic liquid crystal polymer films with high industrial value, i.e., thermoplastic liquid crystal polymer films with excellent thickness accuracy and good appearance and surface flatness.

[0005] For example, Patent Document 1 discloses that by using a three-layer co-extrusion die instead of a single-layer extrusion die, and simultaneously extruding a fully aromatic polyester-based thermotropic liquid crystal polymer as the intermediate layer and polyolefin-based resin or polycarbonate resin as the two outer layers, a three-layer laminated film is formed in which the intermediate layer is a thermoplastic liquid crystal polymer layer and the two outer layers are thermoplastic resin layers, and by peeling off the two outer thermoplastic resin layers to extract the intermediate layer as a film, a thermoplastic liquid crystal polymer film with excellent thickness accuracy and good appearance and surface flatness can be obtained.

[0006] Furthermore, for example, Patent Document 2 discloses that, in the thermoplastic liquid crystal polymer film described in Patent Document 1, the strength in the TD direction (Transverse Direction) is insufficient for practical use with respect to the MD direction (Machine Direction). It also discloses that by using a feed block type three-layer co-extrusion die instead of a multi-manifold type co-extrusion die, the anisotropy of the strength in the TD direction and MD direction of the resulting thermoplastic liquid crystal polymer film can be mitigated.

[0007] The technologies described in Patent Documents 1 and 2 above state that by employing three-layer co-extrusion molding, it is possible to realize a thermoplastic liquid crystal polymer film with excellent thickness accuracy, appearance, and surface flatness. However, in reality, the thermoplastic liquid crystal polymer as a whole still exhibits a high degree of molecular orientation, and the difference in dimensional change rates between the TD direction and the MD direction remains large, leaving room for improvement.

[0008] To address this, Patent Document 3 proposes an LCP extruded film having predetermined tensile properties. Furthermore, Patent Document 3 states that since the resulting LCP extruded film exhibits excellent stretchability during stretching, stretching it makes it possible to realize a heat-shrinkable stretched LCP film with low anisotropy and absolute value of dimensional change. [Prior art documents] [Patent Documents]

[0009] [Patent Document 1] Japanese Patent Application Publication No. 63-31729 [Patent Document 2] Japanese Patent Application Publication No. 2-178016 [Patent Document 3] Japanese Patent Publication No. 2023-070392 [Overview of the Initiative] [Problems that the invention aims to solve]

[0010] Patent Document 3 shows that when LCP film is uniaxially stretched in the TD direction film by film (in a sheet-fed manner) using a uniaxial stretcher, it exhibits excellent stretchability (see the example in Patent Document 3). However, the inventors of the present invention conducted further research and found that when the LCP film described in Patent Document 3 was continuously uniaxially stretched in the TD direction using, for example, a tenter-type roll-to-roll method, problems arose such as film breakage occurring, including streaky cracks in the MD direction, during continuous stretching.

[0011] As described above, the LCP film described in Patent Document 3 has excellent stretchability in sheet processing, but there was room for further improvement in continuous stretchability in roll-to-roll processing.

[0012] The present invention has been made in view of the above problems. The object of the present invention is to provide an LCP film and an LCP stretched film using the same, which have high industrial utility, and which can be provided with high productivity, exhibiting excellent continuous stretchability in a roll-to-roll method, and having low anisotropy and absolute value of dimensional change rate. [Means for solving the problem]

[0013] As a result of intensive studies conducted by the present inventors to solve the above problems, the present inventors have found that an LCP film having a predetermined elongational viscosity (ηEt) and a predetermined coefficient of linear expansion (CTE-2ndRUN) is excellent in continuous stretchability in a roll-to-roll process, and have found that a stretched LCP film having small anisotropy of dimensional change rate and a small absolute value of dimensional change rate can be achieved with high productivity, thereby completing the present invention.

[0014] That is, the present invention provides various specific embodiments shown below. (1) An LCP film comprising a thermotropic liquid crystal polymer, wherein in a stress-strain curve measured by an elongational viscosity measurement test (in accordance with JIS K7127-1:2014), the elongational viscosity ηEt in a TD direction of the LCP film is 2.00E+07 Pa·s or more, and a value of a coefficient of linear expansion in CTE-2ndRUN in the TD direction of the LCP film measured by thermomechanical analysis (TMA method in accordance with JIS K7197, temperature range: 23°C to 200°C) is 65 ppm / K or less.

[0015] (2) The LCP film according to (1), wherein the elongational viscosity ηEt in the TD direction of the LCP film is 10.00E+08 Pa·s or less.

[0016] (3) The LCP film according to (1) or (2), wherein a value of the coefficient of linear expansion in CTE-2ndRUN in the TD direction of the LCP film is 0 to 62 ppm / K.

[0017] (4) The LCP film according to any one of (1) to (3), wherein a value of a coefficient of linear expansion in CTE-2ndRUN in an MD direction of the LCP film is -30 to 55 ppm / K.

[0018] (5) The LCP film according to any one of (1) to (4), wherein the LCP film is a T-die extruded film.

[0019] (6) The LCP film according to any one of (1) to (5), wherein the LCP film is the intermediate layer obtained by removing both outer layers from a three-layer co-extruded film having an outer layer, an intermediate layer, and an outer layer.

[0020] (7) The LCP film according to any one of (1) to (6), wherein the thermoplastic liquid crystal polymer comprises one type selected from the group consisting of a type I thermoplastic liquid crystal polymer and a type II thermoplastic liquid crystal polymer.

[0021] (8) The LCP film according to (7), wherein the content ratio of the type I thermoplastic liquid crystal polymer to the type II thermoplastic liquid crystal polymer is 0:100 to 90:10.

[0022] (9) The LCP film according to any one of (1) to (8), wherein the LCP film has a thickness of 15 µm or more and 300 µm or less.

[0023] (10) A stretched LCP film comprising a stretched body of the LCP film according to any one of (1) to (9), wherein a coefficient of linear expansion in CTE-2ndRUN in the MD direction of the stretched body is in a range of -10 ppm / K or more and less than 10 ppm / K, and a coefficient of linear expansion in CTE-2ndRUN in the TD direction of the stretched body is in a range of -20 ppm / K or more and less than 20 ppm / K.

Effects of the Invention

[0024] According to one aspect of the present invention, an LCP film having high industrial utility value, which can achieve a stretched LCP film that is excellent in continuous stretchability in a roll-to-roll process and has small anisotropy of dimensional change rate and a small absolute value of dimensional change rate with high productivity, can be realized. Further, according to one aspect of the present invention, a novel heat-shrinkable stretched LCP film having small anisotropy of dimensional change rate and a small absolute value of dimensional change rate, as well as an insulating material for circuit boards and a metal foil-clad laminate using the same can be realized. Therefore, according to various aspects of the present invention, highly reliable products adapted to recent ultra-fine processing can be realized.

Mode for Carrying Out the Invention

[0025] The embodiments of the present invention will be described in detail below. However, the following embodiments are illustrative for explaining the present invention, and the present invention is not limited thereto. That is, the present invention can be modified and implemented as appropriate without departing from its essence. In this specification, for example, the notation of a numerical range "1 to 100" includes both the lower limit "1" and the upper limit "100". The same applies to other numerical range notations.

[0026] (LCP film) The LCP film of this embodiment is an LCP film (stretched LCP film) containing a thermoplastic liquid crystal polymer that can be uniformly stretched during continuous stretching using a roll-to-roll method. The LCP film of this embodiment has an extensional viscosity ηEt in the TD direction of the LCP film of 2.00E+07Pa·s or more in the stress-strain curve measured by extensional viscosity measurement test (in accordance with JIS K7127-1:2014), and the value of the coefficient of linear expansion of the LCP film at CTE-2ndRUN in the TD direction of the LCP film is 65 ppm / K or less, measured by thermomechanical analysis (TMA method in accordance with JIS K7197: temperature range: 23℃~200℃).

[0027] As mentioned earlier, conventional LCP extruded films exhibited extreme molecular orientation of the thermoplastic liquid crystal polymer on the film surface, resulting in peeling of the skin layer and fibrillated fibers. This is presumed to be due to shear stress from the side of the apparatus during extrusion, which results in high orientation of the thermoplastic liquid crystal polymer on the surface of the extruded product. It was expected that even with conventional LCP extruded films exhibiting such high orientation of the thermoplastic liquid crystal polymer, stretching treatment could be applied to achieve stretched LCP films with low anisotropy and absolute values ​​of dimensional change. However, according to the inventors' findings, conventional LCP extruded films have almost no stretchability during stretching treatment, making it substantially difficult to obtain industrially useful stretched LCP films. Specifically, conventional LCP extruded films exhibited substantially poor stretchability; for example, even stretching treatment at a stretching ratio of 1.1 times in the TD direction resulted in uneven stretching, and increasing the stretching ratio in the TD direction to 1.2 times caused film breakage.

[0028] On the other hand, it has been confirmed that by employing three-layer co-extrusion molding as described in Patent Documents 1 and 2, the extreme molecular orientation on the film surface of the thermoplastic liquid crystal polymer can be mitigated. However, at the same time, our findings have revealed that controlling the molecular orientation of the thermoplastic liquid crystal polymer on the film surface alone is insufficient to achieve a material that can withstand the required performance as an insulating material for circuit boards.

[0029] Furthermore, as mentioned earlier, although the LCP extruded film in Patent Document 3 exhibits excellent stretchability in sheet-fed processing by controlling its tensile properties, it was not suitable for continuous stretching using a roll-to-roll method. This is presumed to be because Patent Document 3 does not take into account that tension (stress) is also applied to the film being stretched in the MD direction when stretching in the TD direction during continuous stretching using a roll-to-roll method. Based on the inventors' knowledge, the reason why unintended film breakage occurred during continuous stretching using a roll-to-roll method is presumed to be as follows: In other words, in sheet-fed processing where each film is uniaxially stretched in the TD direction, the film being stretched is not fixed in the MD direction, meaning that tension (stress) is not applied in the MD direction. Therefore, thermal shrinkage (neck-in) is likely to occur in the MD direction when stretching in the TD direction, and the contribution of this neck-in enhances the stretchability in the TD direction, resulting in excellent stretchability in the sheet-fed method. On the other hand, in the roll-to-roll continuous stretching process, tension (stress) is also applied to the stretched film in the MD direction during stretching in the TD direction, suppressing neck-in in the MD direction. Therefore, it is presumed that in the roll-to-roll continuous stretching process, the contribution of neck-in, which was unintentionally utilized in the sheet-fed method, is reduced, resulting in film breakage.

[0030] Thus, the inventors have found that simply increasing the film strength (tensile properties), as described in Patent Document 3, is insufficient to suppress film rupture during continuous stretching using the roll-to-roll method. Furthermore, they have found that dynamic properties (strain hardening) that can alleviate the stress generated during continuous stretching are necessary to suppress film rupture during continuous stretching using the roll-to-roll method. Here, strain hardening refers to the phenomenon in which, when an external force is applied to a film, the internal structure of the film changes as the plastic deformation of the film progresses, causing it to harden. Strain hardening leads to hardening of the film, a decrease in fluidity, and a change in viscoelasticity, thus greatly affecting the continuous stretchability of the film. The coefficient of linear expansion refers to a physical quantity that indicates how much the dimensions (length) change when the temperature changes. If the coefficient of linear expansion is too high, film rupture tends to occur more easily before the aforementioned strain hardening occurs. Furthermore, the LCP film (stretched LCP film) of this embodiment has film properties with a predetermined elongation viscosity (ηEt) and coefficient of linear expansion (CTE-2ndRUN), thereby suppressing the occurrence of film breakage during continuous stretching using a roll-to-roll method, which was difficult with conventional techniques. In addition, by stretching this stretched LCP film, even when continuous stretching using a roll-to-roll method is performed, the molecular orientation and internal strain of the thermoplastic liquid crystal polymer occurring on the film surface and / or inside the film can be reduced, making it possible to realize an LCP stretched film with low anisotropy in dimensional change rate and low absolute value of dimensional change rate.

[0031] In this specification, the extensional viscosity ηEt in the TD direction of the LCP film refers to the value calculated from the stress-strain curve measured under the following condition B in an extensional viscosity measurement test (compliant with JIS K7127-1:2014). When the extensional viscosity ηEt is 2.00E+07Pa·s or higher, strain hardening occurs continuously during continuous stretching, enabling uniform stretching and suppressing film rupture. If the extensional viscosity ηEt is low, film rupture may occur during continuous stretching; therefore, the extensional viscosity ηEt is preferably 2.30E+07Pa·s or higher, and more preferably 2.60E+07Pa·s or higher. The upper limit of the extensional viscosity ηEt is not particularly limited, but it is preferably 10.00E+08Pa·s or lower, and more preferably 2.00E+08Pa·s or lower. <Condition B> (a) Prepare a sample measuring 3 mm in width and 40 mm in length, (b) The extensional viscosity of the sample is measured using the DHR-2 dynamic viscoelasticity measuring device in extensional mode, (c) The measurement temperature shall be set based on the formula X: Tm - {140 + 2(Tm - 280)}, provided that if the melting point (Tm) is less than 270°C, the measurement temperature shall be 140°C, and if the melting point (Tm) is 330°C or higher, the measurement temperature shall be 90°C. (d) Set the strain rate to 0.33, (e) Record the relationship between extensional viscosity (Pa) and time (seconds) obtained by measurement as a profile. (f) In the profile, within the range of 0.1 to 10 seconds, the slope is calculated from the change in extensional viscosity for each 0.1-second interval, the range of time change with the smallest slope is identified, and the extensional viscosity ηEt is calculated as the difference between the extensional viscosity (Pa) at the center of that time change range and the extensional viscosity (Pa) at the fracture point.

[0032] The extensional viscosity ηEt in the TD direction of the LCP film can be adjusted as appropriate by, for example, the type of thermoplastic liquid crystal polymer used, the copolymerization ratio of the thermoplastic liquid crystal polymer, the alloy ratio (blending ratio) of the thermoplastic liquid crystal polymer, and the manufacturing conditions during melt extrusion molding. Specifically, it can be adjusted by combining two or more thermoplastic liquid crystal polymers with different monomer composition ratios.

[0033] In this specification, the coefficient of linear expansion of the LCP film in the TD direction at CTE-2ndRUN refers to the value measured by thermomechanical analysis (TMA method in accordance with JIS K7197: temperature range: 23°C to 200°C) based on the following condition X. A coefficient of linear expansion of 65 ppm / K or less suppresses the occurrence of film rupture before the aforementioned strain hardening occurs, enabling uniform stretching. The coefficient of linear expansion is preferably 62 ppm / K or less, and more preferably 60 ppm / K or less. While there is no particular lower limit, it is preferably 0 ppm / K or higher. <Condition X> (a) Using a sample measuring 25 mm in width and 4 mm in length, (b) The sample is subjected to measurement in tensile mode using a thermomechanical analyzer TMA 4000SE with a chuck distance of 20 mm. (c) Set the temperature range to 23~200℃ (2nd RUN), (d) The heating rate is 5°C / min. (e) The test is performed under a nitrogen atmosphere (flow rate 50 ml / min) with a test load of 5 gf.

[0034] The coefficient of linear thermal expansion of the LCP film in the TD direction at CTE-2ndRUN can be appropriately adjusted depending on factors such as the type of thermoplastic liquid crystal polymer used, the copolymerization ratio of the thermoplastic liquid crystal polymer, the alloy ratio (blend ratio) of the thermoplastic liquid crystal polymer, and the manufacturing conditions during melt extrusion molding. Specifically, the shear rate of the lip wall (sec -1This can be adjusted by the shear stress during co-extrusion (kPa), which is expressed as the product of the shear stress and the melt viscosity (Pa·sec) of the thermoplastic liquid crystal polymer, and the drawdown ratio during co-extrusion, which is expressed as the take-up rate (mm / sec) / flow rate of the thermoplastic liquid crystal polymer (mm / sec).

[0035] The thermoplastic liquid crystal polymer contained in the LCP film can be one known in the industry, and its type is not particularly limited. Liquid crystal polymers are polymers that form an optically anisotropic molten phase, and typical examples include thermotropic liquid crystal compounds. The properties of the anisotropic molten phase can be confirmed by known methods such as polarization inspection using orthogonal polarizers. More specifically, the anisotropic molten phase can be confirmed by using a Leitz polarizing microscope and observing a sample placed on a Leitz hot stage under a nitrogen atmosphere at 40x magnification.

[0036] Specific examples of thermoplastic liquid crystal polymers include, but are not limited to, those obtained by polycondensing monomers such as aromatic or aliphatic dihydroxy compounds, aromatic or aliphatic dicarboxylic acids, aromatic hydroxycarboxylic acids, aromatic diamines, aromatic hydroxyamines, and aromatic aminocarboxylic acids. Copolymers are preferred for thermoplastic liquid crystal polymers. Specifically, examples include, but are not limited to, aromatic polyamide resins obtained by polycondensing monomers such as aromatic hydroxycarboxylic acids, aromatic diamines, and aromatic hydroxyamines; and (all) aromatic polyester resins obtained by polycondensing 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.

[0037] Thermoplastic liquid crystal polymers are generally classified into Type I, Type II, Type III, etc., from the viewpoint of their melting point. The LCP film of this embodiment can suitably use any type of thermoplastic liquid crystal polymer, and the appropriate type can be selected and used 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, Type I thermoplastic liquid crystal polymers with a high heat resistance and a melting point of 310°C or higher, and Type II thermoplastic liquid crystal polymers with a relatively high heat resistance and a melting point between 260°C and 310°C are suitably used.

[0038] 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.

[0039] 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.

[0040] 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 components 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.

[0041] 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.

[0042] 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. Among these, preferred thermoplastic liquid crystal polymers are (1) binary polycondensates of parahydroxybenzoic acid and its derivatives and 6-hydroxy-2-naphthoic acid and its derivatives, (2) binary polycondensates of parahydroxybenzoic acid and its derivatives and 6-hydroxy-2-naphthoic acid and its derivatives, and ternary or higher polycondensate alloys consisting of parahydroxybenzoic acid and its derivatives, 6-hydroxy-2-naphthoic acid and its derivatives, and one or more selected from the group consisting of terephthalic acid, isophthalic acid, 6-naphthalenedicarboxylic acid, 4,4'-biphenol, bisphenol A, hydroquinone, 4,4-dihydroxybiphenol, ethylene terephthalate, and derivatives thereof.

[0043] From the viewpoint of lowering the melting point of the (whole) aromatic polyester resin, improving the moldability when heat-pressing the LCP film or its stretched form to an adherend, or obtaining high peel strength when heat-pressing the LCP film or its stretched form to a metal foil, the molar ratio content of monomer component A to the (whole) aromatic polyester resin is preferably 60 mol% to 90 mol%, more preferably 65 mol% to 85 mol%, and even more preferably 70 mol% to 80 mol%. Similarly, the molar ratio content of monomer component B to the (whole) aromatic polyester resin is preferably 10 mol% to 40 mol%, more preferably 15 mol% to 35 mol%, and even more preferably 20 mol% to 30 mol%. Furthermore, the molar ratio content of monomer component C, which may be contained in the (whole) aromatic polyester resin, is preferably 5 mol% or less, more preferably 3 mol% or less, even more preferably 2 mol% or less, and particularly preferably 1 mol% or less.

[0044] Furthermore, the synthesis method for (all) aromatic polyester resins 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.

[0045] The LCP film may further contain inorganic fillers. By including inorganic fillers, an LCP film with a reduced coefficient of thermal expansion can be realized. Specifically, an LCP film with reduced anisotropy in the coefficient of thermal expansion in the MD direction, TD direction, and ZD direction (Z-axis direction; film thickness direction) can be easily obtained. Such an LCP film is particularly useful in rigid substrate applications where multilayer lamination is required.

[0046] 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.

[0047] 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.

[0048] The median diameter (d50) of the inorganic filler can be set appropriately according to the required performance and is not particularly limited. From the viewpoint of kneadability and handling during preparation, and the effect of reducing the coefficient of linear expansion, 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 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.).

[0049] 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 film, is preferably 1% to 45% by mass, more preferably 3% to 40% by mass, and even more preferably 5% to 35% by mass.

[0050] The LCP film may contain resin components other than the thermoplastic liquid crystal polymer described above (hereinafter sometimes simply referred to as "other resin components"), such as thermosetting resins or thermoplastic resins, to the extent that they do not excessively impair the effects of the present invention. Furthermore, the LCP film may contain additives known in the industry, such as mold release agents 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 resin composition prepared during the molding of the LCP film. 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 LCP film.

[0051] As the LCP film, a melt-extruded film (LCP extruded film) such as a T-die extruded film is preferably used. Furthermore, as the LCP extruded film, a thermoplastic liquid crystal polymer 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 thermoplastic liquid crystal polymer layer, and a thermoplastic resin layer are arranged in at least this order is also preferably used. In this case, by removing the thermoplastic resin layers of both outer layers of the three-layer co-extruded film, it can be used as a single-layer thermoplastic liquid crystal polymer film (LCP film). Compared to woven or nonwoven fabrics made of thermoplastic liquid crystal polymer fibers, extruded films of thermoplastic liquid crystal polymers can be manufactured at a lower cost and with greater uniformity.

[0052] The thickness of the LCP film can be set as appropriate according to requirements 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.

[0053] On the other hand, it is preferable that the LCP film of this embodiment has a sufficiently reduced molecular orientation of the thermoplastic liquid crystal polymer, as expressed by the coefficient of linear expansion in the MD and TD directions. As mentioned earlier, in the LCP extruded films described in Patent Documents 1 and 2 of the prior art, the molecular orientation of the thermoplastic liquid crystal polymer is slightly relaxed by protection from the thermoplastic resin layers of both outer layers during three-layer co-extrusion, and it can be seen that this reduces the anisotropy of the strength in the MD and TD directions of the resulting thermoplastic liquid crystal polymer film. However, in reality, while the LCP extruded films described in Patent Documents 1 and 2 consistently achieve a coefficient of linear expansion of about -20 ppm / K in the MD direction, the coefficient of linear expansion in the TD direction exceeds 55 ppm, and sometimes reaches about 100 ppm / K. As is clear from this, it can be easily understood that the LCP extruded films described in Patent Documents 1 and 2 of the prior art still have a large amount of molecular orientation of the thermoplastic liquid crystal polymer as a whole film, or that a large amount of internal strain remains.

[0054] In this embodiment, the linear expansion coefficient (CTE, α2, 23~200℃, 2ndRUN) in the MD and TD directions of the LCP film is preferably within the range of -30 to 55 ppm / K. An LCP film with a linear expansion coefficient within this range has reduced internal strain, and compared to those without, it can be an LCP film with smaller anisotropy in dimensional change rate and a sufficiently small absolute value of dimensional change rate. From the viewpoint of improving adhesion to metal foil, the linear expansion coefficient (CTE, α2, 23~200℃, 2ndRUN) of the LCP film is preferably within the range of -30 to 10 ppm / K, more preferably within the range of -25 to 5 ppm / K, and even more preferably within the range of -20 to 0 ppm / K. Furthermore, the coefficient of linear expansion of the LCP film in the TD direction (CTE, α2, 23~200℃, 2ndRUN) is preferably in the range of 0~65 ppm / K, more preferably in the range of 0~62 ppm / K, and even more preferably in the range of 0~60 ppm / K, from the viewpoint of improving adhesion to the metal foil. In this specification, the coefficient of linear expansion (CTE, α2, 23~200℃, 2ndRUN) refers to the value measured in the temperature range of 23~200℃ by thermomechanical analysis using the TMA method in accordance with JIS K7197. Other detailed measurement conditions shall follow the conditions described in the examples below.

[0055] On the other hand, the dielectric properties of the LCP film in this embodiment 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 The values ​​for (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. Other detailed measurement conditions shall follow those described in the examples below.

[0056] (Manufacturing method for LCP film) The LCP film of this embodiment can be obtained by molding a resin composition containing the above-mentioned thermoplastic liquid crystal polymer and, if necessary, inorganic fillers or other resin components to a predetermined thickness. In one embodiment, the above-mentioned resin composition can be obtained by extrusion molding to a predetermined thickness. Various known extrusion methods can be applied, and the type is not particularly limited. For example, T-die methods and inflation methods; for example, multi-manifold co-extrusion methods and feed-block co-extrusion methods; for example, multi-layer co-extrusion methods such as two-layer co-extrusion and three-layer co-extrusion; can be applied in any combination.

[0057] Among these, one preferred embodiment is a method in which the above-mentioned resin composition is co-extruded from a T-die using an extrusion molding method (hereinafter sometimes simply referred to as the "T-die extrusion method") to form a film by co-extruding two types of three layers from a T-die, and then subjected to cooling treatment, pressing treatment, pressurized heating treatment, etc. as necessary to obtain a predetermined LCP film. Specifically, a resin composition A for the first surface layer containing a thermoplastic resin, a resin composition B for the intermediate layer containing a thermoplastic liquid crystal polymer, and a resin composition C for the second surface layer containing a thermoplastic resin are prepared, and these are co-extruded from the co-extrusion die of an extruder to extrude a three-layer co-extruded molten material to form an LCP film as the intermediate thermoplastic liquid crystal polymer layer. With such co-extrusion molding, the molecular orientation of the thermoplastic liquid crystal polymer in the intermediate thermoplastic liquid crystal polymer layer is relaxed by protection from the thermoplastic resin layers of both outer layers. Such a co-extrusion method is described in, for example, Japanese Patent Application Publication No. 2023-070392, the contents of which are incorporated herein by reference. A preferred embodiment of the method for manufacturing the LCP film according to this embodiment will be described in detail below.

[0058] In one preferred embodiment, the above-mentioned resin composition B, which contains the thermoplastic liquid crystal polymer and optionally other components such as inorganic fillers and other resin components, is melt-extruded into a film from the T-die of an extruder. At this time, resin compositions A and C, which contain thermoplastic resins, are co-extruded on both sides of the above-mentioned film-like molten extruded product to produce a co-extruded molten product (3-layer laminated film) of a predetermined thickness having a first outer layer (release layer) containing thermoplastic resin, an intermediate layer (LCP layer) containing thermoplastic liquid crystal polymer, and a second outer layer (release layer) containing thermoplastic resin. This co-extruded molten product is drawn out by a take-up roll and sent to a cooling roll and a crimping roll. Thereafter, the first and second outer layers are peeled off from the intermediate layer, and the thermoplastic resin layers of both outer layers and the thermoplastic liquid crystal polymer layer (LCP film) of the intermediate layer are wound onto a winding roll, respectively.

[0059] The preparation of resin composition B containing the thermoplastic liquid crystal polymer described above may be carried out according to conventional methods and is not particularly limited. Each of the above-mentioned components can be manufactured and processed by known methods such as kneading, melt kneading, granulation, extrusion molding, pressing, or injection molding. When performing melt kneading, kneading equipment such as commonly used single-screw or twin-screw extruders or various kneaders can be used. When supplying each component to these melt kneading equipment, the liquid crystal polymer, other resin components, inorganic fillers, additives, etc. may be dry-blended in advance using a mixing device such as a tumbler or Henschel mixer. When performing melt kneading, the cylinder setting temperature of the kneading equipment can be set appropriately and is not particularly limited, but generally a range of above the melting point of the liquid crystal polymer and below 360°C is preferred, and more preferably a range of above the melting point of the liquid crystal polymer + 10°C and below 360°C.

[0060] The preparation of resin compositions A and C containing thermoplastic resins may also be carried out according to conventional methods and is not particularly limited. Examples of thermoplastic resins include, but are not particularly limited to, polyolefin resins such as polyethylene, polypropylene, polymethylpentene, and ethylene-α-olefin copolymers, acrylic resins such as PMMA, polyamide resins, acrylonitrile-butadiene-styrene copolymer (ABS resin), polystyrene (PS), polyvinyl chloride, polybutylene terephthalate (PBT), polyethylene terephthalate (PET), polycarbonate (PC), polyetheretherketone (PEEK), and polyphenyl sulfide (PPS). When formed into a co-extruded melt, both polar resins such as polycarbonate and nonpolar resins such as polymethylpentene function effectively as release layers. These thermoplastic resins may be blended with other resin components that may be included in the LCP film described above, or with other optional components such as inorganic fillers. Resin composition A and resin composition C may have the same resin composition or different resin compositions, and may contain the same thermoplastic resin or different thermoplastic resins. Resin compositions A and C, which contain thermoplastic resins, can be manufactured and processed by known methods such as kneading, melt kneading, granulation, extrusion molding, pressing, or injection molding. When performing melt kneading, kneading equipment such as commonly used single-screw or twin-screw extruders or various kneaders can be used. When supplying each component to these melt kneading equipment, the thermoplastic resin, other resin components, inorganic fillers, additives, etc. may be pre-blended using a mixing device such as a tumbler or Henschel mixer. When performing melt kneading, the cylinder setting temperature of the kneading equipment is not particularly limited and should be set appropriately below the temperature at which the thermoplastic resin does not deteriorate due to thermal decomposition, but it is generally preferable to be above the melting point of the thermoplastic resin, and more preferably above the melting point of the thermoplastic resin + 10°C.

[0061] The setting conditions for co-extrusion may be appropriately set according to the type and composition of the resin composition used, the desired performance of the target extruded film, and the like, and are not particularly limited. For example, the set temperature of the cylinder of an extruder may be appropriately set according to the type and composition of the resin composition used, the desired performance of the target extruded film, and the like, and is not particularly limited, but is preferably 230 to 360°C, more preferably 280 to 350°C.

[0062] In addition, for example, the die width (mm) of a T-die may also be appropriately set according to the type and composition of the resin composition used, the desired performance of the target extruded film, and the like, and is not particularly limited. Generally, it is preferably 200 to 2000 mm, more preferably 400 to 1500 mm.

[0063] Furthermore, for example, the lip opening (mm) of a T-die may also be appropriately set according to the type and composition of the resin composition used, the desired performance of the target extruded film, and the like, and is not particularly limited. Generally, it is preferably 0.1 to 3.0 (mm), more preferably 0.2 to 2.0 (mm).

[0064] Further, for example, the shear rate on the lip wall surface of the T-die (sec -1 ) may also be appropriately set according to the type and composition of the resin composition used, the desired performance of the target extruded film, and the like, and is not particularly limited. Generally, it is 100 to 1500 (sec -1 ) is preferable, more preferably 150 to 1000 (sec -1 ).

[0065] In addition, the total discharge rate of the resin composition from the T-die (mm 3 / sec) may also be appropriately set according to the type and composition of the resin composition used, the desired performance of the target extruded film, and the like, and is not particularly limited. Generally, it is 500 to 15000 (mm 3 / sec) is preferable, more preferably 1500 to 10000 (mm 3 / sec).

[0066] On the other hand, the melt viscosity (Pa·sec) of the thermoplastic liquid crystal polymer can also be appropriately set according to the type and composition of the resin composition used, the desired performance of the extruded film, etc., and is not particularly limited, but is generally preferably 10 to 300 (Pa·sec), and more preferably 20 to 250 (Pa·sec). The melt viscosity (Pa·sec) of the thermoplastic liquid crystal polymer refers to the value measured in accordance with JIS K7199, using a Capillograph 1D (manufactured by Toyo Seiki Seisakusho Co., Ltd.) under the conditions of a cylinder length of 10.00 mm, a cylinder diameter of 1.00 mm, and a barrel diameter of 9.55 mm, under the conditions used in the manufacture of LCP film (die temperature and shear rate of the lip wall).

[0067] Similarly, the take-up speed (mm / sec) of the co-extruded film can be appropriately set according to the type and composition of the resin composition used, the desired performance of the extruded film, etc., and is not particularly limited, but is generally 15 to 1000 (mm / sec) preferred, and more preferably 20 to 500 (mm / sec).

[0068] Here, from the viewpoint of reducing the molecular orientation of the thermoplastic liquid crystal polymer in the MD direction during co-extrusion, it is desirable that the shear stress (kPa) during co-extrusion be low. When the shear stress during co-extrusion is high, the thermoplastic liquid crystal polymer tends to be highly oriented in the MD direction, and internal strain tends to remain. When the shear stress during co-extrusion is low, the molecular orientation of the thermoplastic liquid crystal polymer tends to be reduced both on the film surface and inside the film, and internal strain tends to remain less. The shear stress (kPa) during co-extrusion is determined by the shear rate (sec) of the lip wall. -1The shear rate is a value expressed as the product of the saturation rate and the melt viscosity (Pa·sec) of the thermoplastic liquid crystal polymer, and the shear rate is a value calculated based on the total discharge volume of the resin composition during co-extrusion, the die width, and the lip opening. Therefore, the shear stress during co-extrusion can be controlled by adjusting each of these values. Specifically, the shear stress during co-extrusion is preferably 40 kPa or less, more preferably 38 kPa or less, and even more preferably 36 kPa or less. The lower limit is not particularly limited, but considering productivity, it is preferably 5 kPa or more, and more preferably 10 kPa or more.

[0069] Furthermore, from the viewpoint of reducing the molecular orientation of the thermoplastic liquid crystal polymer in the MD direction during co-extrusion, a low drawdown ratio during co-extrusion is desirable. When the drawdown ratio during co-extrusion is high, the thermoplastic liquid crystal polymer tends to be highly oriented in the MD direction, and internal strain tends to remain. When the drawdown ratio during co-extrusion is low, the molecular orientation of the thermoplastic liquid crystal polymer tends to be reduced both on the film surface and inside the film, and internal strain tends to remain less. The drawdown ratio is a value expressed as take-up speed (mm / sec) / flow rate of thermoplastic liquid crystal polymer (mm / sec), and the flow rate of thermoplastic liquid crystal polymer is a value calculated based on the total discharge amount of the resin composition, die width, and lip opening during co-extrusion. Therefore, the drawdown ratio during co-extrusion can be controlled by adjusting each of these values. Specifically, the drawdown ratio during co-extrusion is preferably 3.5 or less, more preferably 3.3 or less, and even more preferably 3.1 or less. The lower limit is not particularly limited, but considering productivity and other factors, it is preferably 1.0 or higher, and more preferably 1.2 or higher.

[0070] The thickness of the resulting LCP film can be set as appropriate according to requirements 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.

[0071] The melting point (melting temperature) of the resulting LCP film is not particularly limited, but from the viewpoint of heat resistance and processability of the film, a melting point (melting temperature) of 200 to 400°C is preferred, and from the viewpoint of improving thermocompression adhesion to metal foil, 250 to 360°C is preferred, 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 film 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. In addition, other measurement conditions shall be as described in the examples below.

[0072] Furthermore, while extruded LCP film can be used as is, if necessary, a pressurizing and heating process can be performed to further reduce its orientation (anisotropy) or release internal strain. This makes it possible to achieve LCP films with reduced anisotropy in dimensional change rate or LCP films with a smaller absolute value of dimensional change rate.

[0073] The heat and pressurization 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, heat setting can be performed using known equipment such as non-contact heaters, ovens, blow devices, heat rolls, cooling rolls, heat presses, and double-belt heat presses. 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 before heat treatment. Furthermore, when performing this heat treatment, from the viewpoint of controlling orientation, a heat-press molding method is preferably used in which a release film or porous film is placed on both sides of the LCP film, 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 heat-press molding method can be carried out by referring to, for example, Japanese Patent Application Publication No. 2010-221694. When hot-press molding an LCP film using the above resin composition between endless belt pairs 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 heat-pressing 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.

[0074] (LCP stretched film) The LCP film described above can be used in the form of an LCP stretched film (a stretched LCP film) by subjecting it to uniaxial and / or biaxial stretching. In this case, the LCP film described above is positioned as a stretched LCP film (LCP film for stretching) in relation to the LCP stretched film. That is, an LCP stretched film can be obtained by stretching the stretched LCP film (LCP film for stretching). At this time, the LCP stretched film may be either heat-shrinkable or heat-expandable in the TD direction. In one preferred embodiment, it is preferable that it is heat-shrinkable in the TD direction. Furthermore, the LCP stretched film may be either heat-shrinkable or heat-expandable in the MD direction. In one preferred embodiment, it is preferable that it is heat-shrinkable in the MD direction. In this specification, a heat-shrinkable LCP stretched film means an LCP stretched film that has heat shrinkability in the TD direction and the MD direction, and its heat shrinkability is supported by the fact that the coefficient of linear expansion (ppm / K), which will be described later, shows a negative value.

[0075] The setting conditions for the stretching process can be appropriately set according to the type and composition of the resin composition used, the desired performance of the LCP stretched film, etc., and are not particularly limited. When uniaxial stretching is performed, for example, the above-mentioned LCP film can be stretched 1.3 to 2.5 times in the TD direction at 90 to 180°C, and then preferably subjected to heat treatment (heat setting) for 1 to 600 seconds at 100 to 240°C. The stretching ratio in the TD direction is preferably 1.4 to 2.4 times, more preferably 1.5 to 2.3 times, and even more preferably 1.6 to 2.3 times. When biaxial stretching is performed, for example, the above-mentioned LCP film can be stretched 1.3 to 2.5 times in the MD direction preferably at 70 to 180°C to obtain a uniaxially stretched film, and then further stretched 1.1 to 2.5 times in the TD direction at 90 to 180°C, and then preferably subjected to heat treatment (heat setting) for 1 to 600 seconds at 100 to 240°C. At this time, simultaneous biaxial stretching can be performed instead of sequential stretching. During the stretching process, known stretchers, such as unaxial stretchers, biaxial stretchers, and tenter-type stretchers, can be used. The stretching ratio is not particularly limited, but from the viewpoint of improving film transportability and release properties, and suppressing the occurrence of thickness unevenness and wrinkles, the total stretching ratio in the MD direction × TD direction (a stretching ratio expressed as m × n, where the stretching ratio in the MD direction is m and the stretching ratio in the TD direction is n) is preferably 1.3 times or more, more preferably 1.4 times or more, even more preferably 1.5 times or more, and particularly preferably 1.6 times or more. There is no particular upper limit, but 6.0 times or less is used as a guideline, preferably 5.0 times or less, even more preferably less than 4.0 times, and even more preferably less than 3.0 times. Furthermore, 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, heat setting can be performed using known equipment such as non-contact heaters, ovens, blowing devices, heat rolls, cooling rolls, heat presses, and double-belt heat presses. In this case, if necessary, a release film or porous film known in the industry can be placed on the surface of the LCP stretched film and the heat pressure treatment can be performed.

[0076] The linear expansion coefficients (CTE, α2, 23~200℃) in the MD and TD directions of the stretched LCP film (stretched LCP film) can be set appropriately according to the desired performance and are not particularly limited. However, 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 metal foil, it is preferable that the linear expansion coefficient at CTE-2ndRUN in the MD direction of the stretched body be in the range of -10 ppm / K or more and less than 10 ppm / K. It is preferable that the linear expansion coefficient at CTE-2ndRUN in the TD direction of the stretched body be in the range of -20 ppm / K or more and less than 20 ppm / K.

[0077] (Insulating material for circuit boards) The insulating material for circuit boards of this embodiment comprises a laminate having at least a woven fabric provided on one and / or both sides of the above-mentioned LCP stretched film (stretched LCP film).

[0078] Specifically, the insulating material for circuit boards comprises a laminate having a laminated structure (3-layer structure) in which an LCP stretched film, a woven fabric, and another LCP stretched film are arranged in at least this order. In this laminate, one LCP stretched film is provided on the surface side of the woven fabric, and the other LCP stretched film is provided on the back side of the woven fabric. These three layers are heat-pressed together to form a 3-layer laminate. Although a 3-layer laminate is illustrated here, it goes without saying that the present invention can also be implemented as a 2-layer laminate by omitting one of the LCP stretched films, or as a laminate with 4 or more layers by further laminating LCP stretched films and woven fabrics.

[0079] In this specification, "a woven fabric is provided on one and / or both sides of the stretched LCP film" means not only the configuration in which the stretched LCP film is directly placed on the surface of the woven fabric, as in this embodiment, but also the configuration in which any layer (e.g., a primer layer, an adhesive layer, etc.) is interposed between the stretched LCP film and the woven fabric, and the stretched LCP film is positioned at a distance from the woven fabric.

[0080] Woven fabric is a cloth woven from fibers. The type of fiber used in the woven fabric is not particularly limited, and inorganic fibers, organic fibers, or organic-inorganic hybrid fibers can be used. In particular, woven fabrics made of inorganic fibers are preferred. By heat-pressing the woven fabric of inorganic fibers with an LCP stretched film, the anisotropy of the dimensional change rate in the MD and TD directions can be kept small, and in a more preferred embodiment, the dimensional change rate itself in the MD and TD directions can be reduced. As the woven fabric, commercially available products can be used, or it can be manufactured by methods known in this industry.

[0081] Examples of inorganic fibers include, but are not limited to, glass fibers such as E glass, D glass, L glass, M glass, S glass, T glass, Q glass, UN glass, NE glass, and spherical glass; inorganic fibers other than glass such as quartz; and ceramic fibers such as silica. Woven fabrics of inorganic fibers that have undergone fiber opening treatment or weave tightening treatment are preferred from the viewpoint of dimensional stability. Among these, glass cloth is preferred from the viewpoint of mechanical strength, dimensional stability, and water absorption. Glass cloth that has undergone fiber opening treatment or weave tightening treatment is preferred from the viewpoint of improving thermocompression bonding with LCP stretched film. Glass cloth surface-treated with silane coupling agents such as epoxy silane treatment and amino silane treatment can also be suitably used. The woven fabric can be used individually or in appropriate combinations of two or more types.

[0082] The thickness of the woven fabric can be set appropriately according to the required performance and is not particularly limited. From the viewpoint of lamination, processability, mechanical strength, etc., 10 to 300 μm is preferred, more preferably 10 to 200 μm, and even more preferably 15 to 180 μm.

[0083] The total thickness of the insulating material for circuit boards can be set appropriately according to the required performance and is not particularly limited. From the viewpoint of lamination, processability, mechanical strength, etc., 30 to 500 μm is preferred, more preferably 50 to 400 μm, even more preferably 70 to 300 μm, and particularly preferably 90 to 250 μm.

[0084] The insulating material for circuit boards of this embodiment, by adopting the above-described configuration, exhibits small anisotropy in the dimensional change rate in the MD and TD directions, and in a more preferred embodiment, the dimensional change rate itself in the MD and TD directions can be reduced. Furthermore, it has the remarkable advantages of excellent dielectric properties in the high-frequency range, ease of manufacturing, and excellent productivity.

[0085] The insulating material for circuit boards described above can be manufactured by appropriately applying known manufacturing methods, and the manufacturing method is not particularly limited. For example, an insulating material for circuit boards can be obtained by laminating an LCP stretched film and a woven fabric, heating and pressurizing them to heat-compress the LCP stretched film and the woven fabric. Alternatively, an insulating material for circuit boards can be obtained by stacking an LCP stretched film, a woven fabric, and another LCP stretched film in that order to form a laminate, and then using a press machine or a double-belt press machine to heat and pressurize the laminate while holding it in place, thereby thermo-forming the insulating material for circuit boards. The processing temperature during thermocompression bonding can be appropriately set according to the required performance and is not particularly limited, but is preferably 200 to 400°C, more preferably 250 to 360°C, and even more preferably 270 to 350°C. The processing temperature during thermocompression bonding is the value measured at the surface temperature of the LCP stretched film in the laminate described above. Furthermore, the pressurization conditions at this time can be set appropriately according to the desired performance and are not particularly limited, but for example, a surface pressure of 0.5 to 10 MPa for 1 to 240 minutes, more preferably a surface pressure of 0.8 to 8 MPa for 1 to 120 minutes.

[0086] (Metal foil-clad laminate) The metal foil-clad laminate of this embodiment comprises the above-mentioned LCP stretched film and metal foil provided on one side and / or both sides of the LCP stretched film.

[0087] Specifically, the metal foil-clad laminate is a double-sided metal foil-clad laminate having a laminated structure (3-layer structure) in which metal foil, LCP stretched film, and metal foil are arranged in at least this order. These three layers are heat-pressed together to form a 3-layer laminate. In this embodiment, a double-sided metal foil-clad laminate is shown, but the present invention can also be implemented in a configuration in which metal foil is provided on only one surface of the LCP stretched film. That is, although a 3-layer laminate is exemplified here, it goes without saying that the present invention can also be implemented as a 2-layer laminate with one of the metal foils omitted, or as a laminate with 4 or more layers in which LCP stretched film or woven fabric is further laminated.

[0088] The metal foil-clad laminate of this embodiment comprises a laminate having at least the above-mentioned LCP stretched film and the above-mentioned woven fabric provided on one and / or both sides of the LCP stretched film, and metal foil provided on one and / or both sides of the laminate.

[0089] Specifically, the metal foil-clad laminate is a double-sided metal foil-clad laminate having a laminated structure (5-layer structure) in which metal foil, LCP stretched film, woven fabric, LCP stretched film, and metal foil are arranged in at least this order. These 5 layers are heat-pressed together to form a 5-layer laminate. In this embodiment, a double-sided metal foil-clad laminate is shown, but the present invention can also be implemented in a configuration in which the metal foil is provided on only one surface. That is, although a 5-layer laminate is exemplified here, it goes without saying that the present invention can also be implemented as a 4-layer laminate with one of the metal foils omitted, or as a laminate with 6 or more layers, further laminated with LCP stretched film, insulating material for circuit boards, and woven fabric.

[0090] The material of the metal foil is not particularly limited, but examples include gold, silver, copper, copper alloys, nickel, nickel alloys, aluminum, aluminum alloys, iron, iron alloys, etc. Among these, copper foil, aluminum foil, stainless steel foil, and alloy foil of copper and aluminum are preferred, with copper foil being more preferred. As for such copper foil, any type manufactured by rolling or electrolysis can be used, but electrolytic copper foil or rolled copper foil with a relatively large surface roughness is preferred.

[0091] The thickness of the metal foil can be set appropriately according to the desired performance and is not particularly limited. Typically, 1.5 to 1000 μm is preferred, more preferably 2 to 500 μm, even more preferably 5 to 150 μm, and particularly preferably 7 to 100 μm. The metal foil may be subjected to surface treatments such as acid cleaning or other chemical surface treatments, as long as the effects of the present invention are not impaired. The type and thickness of the metal foil may be the same or different.

[0092] The method for providing metal foil on the surface of LCP stretched film or insulating material for circuit boards can be carried out according to conventional methods and is not particularly limited. It may be any of the following: laminating metal foil onto LCP stretched film or insulating material for circuit boards and bonding or pressing the two layers together; physical methods such as sputtering or vapor deposition (dry methods); chemical methods such as electroless plating or electrolytic plating after electroless plating (wet methods); or applying metal paste. Alternatively, a metal foil-clad laminate can be obtained by heat pressing a laminate formed by laminating LCP stretched film or insulating material for circuit boards with one or more metal foils using, for example, a multi-stage press, a multi-stage vacuum press, a continuous molding machine, or an autoclave molding machine.

[0093] The metal foil laminate described above can be manufactured by applying known manufacturing methods as appropriate, and the manufacturing method is not particularly limited. For example, one method involves layering an LCP stretched film or an insulating material for circuit boards with a metal foil to form a laminate in which the metal foil is placed on the LCP stretched film, and then hot-pressing this laminate while sandwiching it between a pair of endless belts in a double belt press. As described above, the LCP stretched film used in this embodiment has small anisotropy in the dimensional change rate in the MD direction and TD direction, and in a more preferred embodiment, the dimensional change rate in the MD direction and TD direction itself is small, so high peel strength to the metal foil can be obtained.

[0094] The temperature during the heat-compression bonding of the metal foil can be set appropriately according to the required performance and is not particularly limited, but it is preferably 50°C lower than the melting point of the liquid crystal polymer and 50°C higher than the melting point, more preferably 40°C lower than the melting point and 40°C higher than the melting point, more preferably 30°C lower than the melting point and 30°C higher than the melting point, and particularly preferably 20°C lower than the melting point and 20°C higher than the melting point. The temperature during the heat-compression bonding of the metal foil shall be the value measured at the surface temperature of the LCP stretched film as described above. The bonding conditions at this time can be set appropriately according to the desired performance and are not particularly limited, but for example, when using a double belt press machine, it is preferable to perform the bonding under conditions of a surface pressure of 0.5 to 10 MPa and a heating temperature of 200 to 360°C.

[0095] The metal foil-clad laminate of this embodiment may have other or further laminated structures, as long as it comprises a thermocompressed body with a two-layer structure of LCP stretched film and metal foil. For example, it can have a two-layer structure of metal foil / LCP stretched film; a three-layer structure such as metal foil / LCP stretched film / metal foil or LCP stretched film / metal foil / LCP stretched film; a four-layer structure such as metal foil / LCP stretched film / woven fabric / LCP stretched film; a five-layer structure such as metal foil / LCP stretched film / metal foil / LCP stretched film / metal foil or metal foil / LCP stretched film / woven fabric / LCP stretched film / metal foil; and so on. In addition, multiple (for example, 2 to 50) metal foil-clad laminates can be laminated and thermocompressed together.

[0096] In the metal foil-clad laminate of this embodiment, the peel strength between the LCP stretched film and the metal foil is not particularly limited, but from the viewpoint of achieving higher peel strength, it is preferably 0.8 (N / mm) or higher, more preferably 1.0 (N / mm) or higher, and even more preferably 1.2 (N / mm) or higher. As described above, the metal foil-clad laminate of this embodiment can achieve high peel strength, so peeling between the LCP stretched film and the metal foil can be suppressed, for example, during the heating process of substrate manufacturing. Furthermore, since manufacturing conditions that are superior in process tolerance and productivity can be applied to obtain peel strength equivalent to that of the conventional technology, it is possible to suppress the deterioration of the basic performance of the liquid crystal polymer while maintaining peel strength at the same level as the conventional technology.

[0097] Furthermore, the metal foil-clad laminate of this embodiment can be used as a material for circuit boards such as electronic circuit boards and multilayer boards by pattern etching at least a portion of the metal foil. In addition, the metal foil-clad laminate of this embodiment has excellent dielectric properties in the high-frequency range, low anisotropy in the rate of dimensional change in the MD and TD directions, and in a more preferred embodiment, the rate of dimensional change in the MD and TD directions itself is small, resulting in excellent dimensional stability, ease of manufacture and high productivity. Therefore, it is a particularly useful material as an insulating material for flexible printed circuit boards (FPCs) in fifth-generation mobile communication systems (5G) and millimeter-wave radar, etc. [Examples]

[0098] 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.

[0099] [Melting viscosity] The melt viscosity [Pa·sec] of LCP films was measured under the following conditions. Measuring instrument: Capillograph 1D (manufactured by Toyo Seiki Seisakusho Co., Ltd.) Equipment used: Cylinder length 10.00mm, cylinder diameter 1.00mm, barrel diameter 9.55mm Measurement conditions: Temperature [°C] and shear rate [sec] during extrusion molding of LCP film. -1 ]

[0100] [Melting point] The melting points of the LCP films were measured under the following conditions. Measuring instrument: Input-compensated differential scanning calorimetry system DSC8500 Sample quantity: 5 mg Temperature range: 30℃~400℃ Heating rate: 20℃ / min Cooling rate: 50℃ / min Gas used: Nitrogen, flow rate 20 mL / min Piece data analysis method: The temperature of the endothermal peak was used as the melting point.

[0101] [Elongational viscosity ηEt] In accordance with JIS K7127-1:2014, the extensional viscosity of LCP film in the TD direction was measured under the following conditions, and the extensional viscosity ηEt was determined for each case. (a) Prepare a sample measuring 3 mm in width and 40 mm in length, (b) The extensional viscosity of the sample is measured using the DHR-2 dynamic viscoelasticity measuring device in extensional mode, (c) The measurement temperature shall be set based on the formula X: Tm - {140 + 2(Tm - 280)}, provided that if the melting point (Tm) is less than 270°C, the measurement temperature shall be 140°C, and if the melting point (Tm) is 330°C or higher, the measurement temperature shall be 90°C. (d) Set the strain rate to 0.33, (e) Record the relationship between extensional viscosity (Pa) and time (seconds) obtained by measurement as a profile. (f) In the profile, within the range of 0.1 to 10 seconds, the slope is calculated from the change in extensional viscosity for each 0.1-second interval, the range of time changes with the smallest slope is identified, and the extensional viscosity ηEt is calculated as the difference between the extensional viscosity (Pa) at the center of that time change range (for example, 0.55 seconds if the range is 0.5 to 0.6 seconds) and the extensional viscosity (Pa) at the fracture point.

[0102] [Coefficient of linear expansion] The coefficient of linear thermal expansion of LCP film and LCP stretched film was measured 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 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.

[0103] (Example 1) As an intermediate layer, a type I thermoplastic liquid crystal polymer (a copolymer with monomer composition of 79 mol% p-hydroxybenzoic acid, 20 mol% 6-hydroxy-2-naphthoic acid, and 1 mol% terephthalic acid, with a melting point of approximately 315°C, a temperature of 330°C, and a shear rate of 500 sec) is used. -1The melt viscosity is 70 Pa·sec) and type II thermoplastic liquid crystal polymer (a copolymer with a monomer composition of 74 mol% p-hydroxybenzoic acid and 26 mol% 6-hydroxy-2-naphthoic acid, with a melting point of approximately 280°C, a temperature of 300°C, and a shear rate of 500 sec -1 An alloy resin was prepared by mixing a resin with a melt viscosity of 80 Pa·sec in a 5:5 mass ratio. Polycarbonate PC (Teijin Panlite L-1225L) was used as the surface layer on both sides of the intermediate layer. Under conditions of a shear stress of 35 kPa and a drawdown ratio of 2.8, each resin was co-extruded at 320°C using the T-die casting method from a two-type three-layer extruder equipped with a T-die with a die width of 600 mm and a lip opening of 0.2 to 1.0 mm to form a two-type three-layer film with an intermediate layer thickness of 75 μm. The polycarbonate films on both surface layers were peeled off from the formed two-type three-layer film on the winding line to obtain the LCP film of Example 1 having a melting point of 298°C.

[0104] (Example 2) Except for changing the co-extrusion conditions to a shear stress of 31 kPa and a drawdown ratio of 1.2, the procedure was carried out in the same manner as in Example 1, and a two-type, three-layer film with an intermediate layer thickness of 75 μm was formed. The two surface polycarbonate films were peeled off from the formed two-type, three-layer film on a winding line, respectively, to obtain the LCP film of Example 2 having a melting point of 298°C.

[0105] (Example 3) The co-extrusion conditions were changed to a shear stress of 31 kPa and a drawdown ratio of 2.4, and the process was carried out in the same manner as in Example 1 to form a two-type, three-layer film with an intermediate layer thickness of 35 μm. The two surface polycarbonate films were peeled off from the formed two-type, three-layer film on the winding line to obtain the LCP film of Example 3 having a melting point of 298°C.

[0106] (Example 4) Except for changing the co-extrusion conditions to a shear stress of 31 kPa and a drawdown ratio of 1.0, the procedure was carried out in the same manner as in Example 1, and a two-type, three-layer film with an intermediate layer thickness of 100 μm was formed. The two surface polycarbonate films were peeled off from the formed two-type, three-layer film on a winding line, respectively, to obtain the LCP film of Example 4 having a melting point of 298°C.

[0107] (Example 5) Except for changing the mass ratio of Type I thermoplastic liquid crystal polymer to Type II thermoplastic liquid crystal polymer to 2:8, changing the co-extrusion conditions to a shear stress of 31 kPa and a drawdown ratio of 1.2, and co-extruding at a temperature of 310°C, the procedure was carried out in the same manner as in Example 1, and a two-type, three-layer film with an intermediate layer thickness of 75 μm was formed. The polycarbonate films on both surface layers were peeled off from the formed two-type, three-layer film on a winding line, respectively, to obtain the LCP film of Example 5 having a melting point of 287°C.

[0108] (Example 6) Except for changing the mass ratio of Type I thermoplastic liquid crystal polymer to Type II thermoplastic liquid crystal polymer to 8:2, changing the co-extrusion conditions to a shear stress of 30 kPa and a drawdown ratio of 1.2, and co-extruding at a temperature of 330°C, the procedure was carried out in the same manner as in Example 1, and a two-type, three-layer film with an intermediate layer thickness of 75 μm was formed. The polycarbonate films on both surface layers were peeled off from the formed two-type, three-layer film on a winding line, respectively, to obtain the LCP film of Example 6 having a melting point of 308°C.

[0109] (Example 7) Except for changing the mass ratio of Type I thermoplastic liquid crystal polymer to Type II thermoplastic liquid crystal polymer to 9:1, changing the co-extrusion conditions to a shear stress of 29 kPa and a drawdown ratio of 1.2, and co-extruding at a temperature of 330°C, the procedure was carried out in the same manner as in Example 1, and a two-type, three-layer film with an intermediate layer thickness of 75 μm was formed. The polycarbonate films on both surface layers were peeled off from the formed two-type, three-layer film on a winding line, respectively, to obtain the LCP film of Example 7 having a melting point of 311°C.

[0110] (Example 8) Instead of alloy resin, a type II thermoplastic liquid crystal polymer is used as the intermediate layer (a copolymer with a monomer composition of 72 mol% p-hydroxybenzoic acid and 28 mol% 6-hydroxy-2-naphthoic acid, with a melting point of approximately 268°C, a temperature of 300°C, and a shear rate of 500 sec). -1 Except for using a melt viscosity of 60 Pa·sec, changing the co-extrusion conditions to a shear stress of 26 kPa and a drawdown ratio of 1.2, and co-extruding at a temperature of 300°C, the procedure was carried out in the same manner as in Example 1, and a two-type three-layer film with an intermediate layer thickness of 75 μm was formed. The two surface polycarbonate films were peeled off from the formed two-type three-layer film on the winding line, respectively, to obtain the LCP film of Example 8 having a melting point of 268°C.

[0111] (Comparative Example 1) A single-layer film (LCP film) of Comparative Example 1 having a thickness of 75 μm and a melting point of 280°C was formed in the same manner as in Example 1, except that the liquid crystal polymer was extruded individually by the T-die casting method using a single-layer extruder equipped with a T-die with a die width of 600 mm and a lip opening of 0.2 to 1.0 mm, under conditions of a shear stress of 47 kPa and a drawdown ratio of 4.3, without using the surface layers on both sides of the intermediate layer.

[0112] (Comparative Example 2) Instead of alloy resin, a type I thermoplastic liquid crystal polymer (a copolymer with monomer composition of 79 mol% p-hydroxybenzoic acid, 20 mol% 6-hydroxy-2-naphthoic acid, and 1 mol% terephthalic acid, at a temperature of 330°C and a shear rate of 500 sec) was used as the intermediate layer. -1 Except for using a melt viscosity of 70 Pa·sec, changing the co-extrusion conditions to a shear stress of 40 kPa and a drawdown ratio of 2.0, and co-extruding at a temperature of 330°C, the procedure was carried out in the same manner as in Example 1, and a two-type three-layer film with an intermediate layer thickness of 75 μm was formed. The two surface polycarbonate films were peeled off from the formed two-type three-layer film on the winding line, respectively, to obtain the LCP film of Comparative Example 2 having a melting point of 315°C.

[0113] <Single wafer stretching> The LCP films obtained in Examples 1-8 and Comparative Examples 1-2 were stretched to 2.0 times their original length in the TD direction (total stretching ratio: 2.0 times) at 130°C using a uniaxial stretcher, and then heat-set at 130°C for 30 seconds to obtain the stretched LCP films of Examples 1-8 and Comparative Examples 1-2. In all cases, uniform stretching was confirmed. Subsequently, glass cloth (IPC No. #1037) was sandwiched between each pair of LCP stretched films of Examples 1-8 and Comparative Examples 1-2, and a heat-compression bonding treatment was performed using a hot press machine at 300°C for 5 minutes to obtain the insulating materials for circuit boards of Examples 1-8 and Comparative Examples 1-2.

[0114] <Roll-to-roll extension> The LCP films from Examples 1 to 8 were each wound up to obtain winding rolls. The obtained winding rolls were set in a tenter-type stretcher equipped with tenter clips, and continuously stretched in the TD direction at 130°C using a roll-to-roll method at the stretching ratios shown in Table 1. A shrinkage treatment of 0.85 times in the MD direction was then performed, followed by a heat setting at 130°C for 30 seconds to obtain stretched bodies. In all cases, uniform stretching was confirmed. Subsequently, with a glass cloth (IPC No. #1037) sandwiched between each pair of LCP stretched films of Examples 1 to 8, a heat-pressure bonding treatment was performed using a hot press machine at 300°C for 5 minutes to obtain the insulating materials for circuit boards of Examples 1 to 8. On the other hand, winding rolls were obtained by winding the LCP films of Comparative Examples 1 and 2, respectively. The obtained winding rolls were set in a tenter-type stretcher equipped with tenter clips, as in Examples 1 to 8, and continuously stretched in the TD direction at the stretch ratios shown in Table 1 using a roll-to-roll method at 130°C, followed by a shrinkage treatment of 0.85 times in the MD direction, in an attempt to obtain a similarly stretched body. However, in Comparative Examples 1 and 2, film breakage such as streaky cracks occurred in the MD direction, making uniform stretching impossible. Therefore, it was not possible to continue the experiments.

[0115] The results are shown in Table 1. [Table 1] [Industrial applicability]

[0116] The LCP film of the present invention can be widely and effectively used in applications such as electronic circuit boards, multilayer boards, high heat dissipation boards, flexible printed circuit boards, antenna boards, optoelectronic mixed-signal boards, and IC packages. In particular, because it is suitable for ultra-fine processing and highly reliable, it can be widely and effectively used as an insulating material for flexible printed circuit boards (FPCs) and metal foil-clad laminates in fifth-generation mobile communication systems (5G) and millimeter-wave radar.

Claims

1. This is an LCP film containing a thermoplastic liquid crystal polymer. In the stress-strain curve measured by extensional viscosity measurement test (in accordance with JIS K7127-1:2014), the extensional viscosity ηEt in the TD direction of the LCP film is 2.00E+07Pa·s or higher. The coefficient of linear expansion of the LCP film in the TD direction at CTE-2nd RUN, as measured by thermomechanical analysis (TMA method in accordance with JIS K7197: temperature range: 23°C to 200°C), is 65 ppm / K or less. An LCP film characterized by the following features.

2. The extensional viscosity ηEt in the TD direction of the LCP film is 10.00E+08Pa·s or less. The LCP film according to claim 1.

3. The coefficient of linear expansion of the LCP film in the TD direction CTE-2ndRUN is 0 to 62 ppm / K. The LCP film according to claim 1.

4. The coefficient of linear expansion of the LCP film in the MD direction CTE-2ndRUN is -30 to 55 ppm / K. The LCP film according to claim 1.

5. The LCP film is a T-die extruded film. The LCP film according to claim 1.

6. The LCP film is the intermediate layer obtained by removing both outer layers from a three-layer co-extruded film having an outer layer and an intermediate layer. The LCP film according to claim 1.

7. The thermoplastic liquid crystal polymer includes one selected from the group consisting of type I thermoplastic liquid crystal polymers and type II thermoplastic liquid crystal polymers. The LCP film according to claim 1.

8. The content ratio of the type I thermoplastic liquid crystal polymer to the type II thermoplastic liquid crystal polymer is 0:100 to 90:10 (preferably 0:100 to 55:45). The LCP film according to claim 7.

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

10. An LCP stretched film comprising a stretched LCP film according to any one of claims 1 to 9, wherein the coefficient of linear expansion of the stretched LCP film in the MD direction CTE-2nd RUN is in the range of -10 ppm / K or more and less than 10 ppm / K, and the coefficient of linear expansion of the stretched LCP film in the TD direction CTE-2nd RUN is in the range of -20 ppm / K or more and less than 20 ppm / K.

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