LCP resin composition for circuit boards and LCP film for circuit boards

Abstract

To provide an LCP resin composition for a circuit board which can achieve an LCP film for a circuit board having a small coefficient of linear expansion and excellent dimensional stability, without excessively impairing excellent basic performance such as mechanical characteristics, electric characteristics and heat resistance of liquid crystal polyester.SOLUTION: A method for manufacturing an LCP film for a circuit board includes: at least a composition preparation step of preparing an LCO resin composition containing at least 100 pts.mass of liquid crystal polyester and 1 to 20 pts.mass of an oxazoline group-containing polymer; a film formation step of melt-kneading the LCP resin composition, and forming an LCP film having a coefficient (α2) of linear expansion in a TD direction of 50 ppm / K or more; and a pressurization heating step of subjecting the LCP film to pressurization heating treatment, and obtaining an LCP film for a circuit board having the coefficient (α2) of linear expansion in the TD direction of 16.8±12 ppm / K.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] This invention relates to LCP resin compositions for circuit boards, LCP films for circuit boards, and methods for producing the same. [Background technology]

[0002] Liquid crystal polymers (LCPs) are polymers that exhibit liquid crystallinity in a molten or solution state. In particular, thermotropic liquid crystal polymers, which exhibit liquid crystallinity in a molten state, possess excellent properties such as high gas barrier properties, high film strength, high heat resistance, high insulation, and low water absorption, and are therefore being rapidly put into practical use in gas barrier film materials, electronic materials, and electrical insulating materials.

[0003] As an example of a resin composition using a liquid crystal polymer, Patent Document 1 discloses a liquid crystal polyester resin composition comprising (A) a liquid crystal polyester and (B) an oxazonyl group-containing polymer, wherein the ratio of component (A) to component (B) is 99.9 to 0.1% by weight for component (A) and 0.1 to 99.9% by weight for component (B).

[0004] Furthermore, as a resin composition using liquid crystal polymers, for example, Patent Document 2 discloses a polymer alloy characterized by comprising 97.1 to 99.0% by weight of a thermoplastic polymer capable of forming an optically anisotropic molten phase and 1.0 to 2.9% by weight of an amorphous polymer (based on the total amount of polymer).

[0005] On the other hand, for example, Patent Document 3 discloses a liquid crystal polymer blend film formed from a blend of a liquid crystal polymer and at least one thermoplastic resin selected from polyethersulfone, polyetherimide, polyamideimide, polyetheretherketone, polyarylate, and polyphenylene sulfide, characterized in that the proportion of thermoplastic resin in the blend is 25 to 55% by weight, the linear expansion coefficient of the film in both the MD and TD directions is 5 to 25 ppm / K, and the linear expansion coefficient in the thickness direction of the film does not exceed 270 ppm / K. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Japanese Patent Application Publication No. 09-286903 [Patent Document 2] Japanese Patent Publication No. 2000-290512 [Patent Document 3] Japanese Patent Publication No. 2004-175995 [Overview of the project] [Problems that the invention aims to solve]

[0007] Liquid crystal polymers, particularly LCP resin compositions using liquid crystal polyester, 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 future fifth-generation mobile communication systems (5G) and millimeter-wave radar, due to their excellent high-frequency characteristics and low dielectric properties.

[0008] However, Patent Document 1 focuses on the gas barrier properties and mechanical strength of LCP resin compositions and only explores their application to gas barrier molded articles, containers, tubes, meats, fibers, coating materials, electronic material packaging films, etc., and does not consider their application as an insulating material for flexible printed circuit boards (FPCs) or the like.

[0009] Furthermore, while Patent Document 2 mentions the usefulness of LCP resin compositions as electrical insulating materials and electrical circuit board materials, it actually only offers suggestions for improving the mechanical strength of LCP films (edge ​​tear strength, i.e., strength against defects and tears that occur at the edges of films, etc.).

[0010] On the other hand, in Patent Document 3, after obtaining an LCP blend film by melt-extruding a resin composition of a liquid crystal polymer and a specific thermoplastic resin using a T-die and then biaxially stretching it, a liquid crystal polymer blend film having no anisotropy in the linear expansion coefficient in the plane direction (TD direction and MD direction) and a small linear expansion coefficient in the thickness direction was obtained. However, since the obtained liquid crystal polymer blend film contains a large amount of a thermoplastic resin such as polyarylate, its heat resistance, dielectric properties, tensile strength, etc. are deteriorated, and it is inferior in practicality.

[0011] The present invention has been made in view of the above problems. An object of the present invention is to provide an LCP resin composition for a circuit board, etc., capable of realizing an LCP film for a circuit board having a small linear expansion coefficient and excellent dimensional stability without excessively impairing the excellent basic properties such as mechanical properties, electrical properties, and heat resistance of the liquid crystal polyester.

[0012] Another object of the present invention is to provide an LCP film for a circuit board, and a manufacturing method thereof, etc., having a small linear expansion coefficient and excellent dimensional stability without excessively impairing the excellent basic properties such as mechanical properties, electrical properties, and heat resistance of the liquid crystal polyester.

Means for Solving the Problems

[0013] As a result of intensive studies to solve the above problems, the present inventors have found that by using a predetermined LCP resin composition and by subjecting an LCP film obtained by melt-extruding this predetermined LCP resin composition to a pressure heat treatment, the linear expansion coefficient can be reduced, thereby enhancing the dimensional stability and also enhancing the adhesion to a metal foil, and have found that the above problems can be solved, leading to the completion of the present invention.

[0014] That is, the present invention provides various specific embodiments shown below. (1) Prepare a composition preparation step of preparing an LCP resin composition containing at least 100 parts by mass of liquid crystal polyester and 1 to 20 parts by mass of an oxazoline group-containing polymer, melt-extrude the LCP resin composition to form an LCP film having a linear expansion coefficient (α2) in the TD direction of 50 ppm / K or more, and subject the LCP film to pressure heating treatment to obtain an LCP film for a circuit board having a linear expansion coefficient (α2) in the TD direction of 16.8 ± 12 ppm / K. A method for manufacturing an LCP film for a circuit board, characterized by comprising at least the above steps.

[0015] (2) The method for manufacturing an LCP film for a circuit board according to (1), wherein the LCP resin composition further contains 1 to 20 parts by mass of polyarylate. (3) The LCP film has a tensile elastic modulus Y in the MD direction MD , TD and a tensile elastic modulus Y in the TD direction TD The ratio (Y MD / Y TD ) is 2 or more and 10 or less. In the pressure heating step, the LCP film is pressure-heat treated so that the ratio (Y MD / Y TD ) of the tensile elastic modulus Y in the MD direction and the tensile elastic modulus Y in the TD direction is 0.8 or more and 2.0 or less. The method for manufacturing an LCP film for a circuit board according to (1) or (2), obtaining an LCP film for a circuit board. (4) In the pressure heating step, the LCP film is pressure-heat treated to obtain an LCP film for a circuit board having a linear expansion coefficient in the TD direction of 5.0 ppm / K or more and 16.0 ppm / K or less. The method for manufacturing an LCP film for a circuit board according to any one of (1) to (3). (5) The LCP film has a thickness of 10 μm or more and 500 μm or less. The method for manufacturing an LCP film for a circuit board according to any one of (1) to (4). (6) The LCP film for a circuit board has a relative dielectric constant ε r of 3.0 to 3.9 and a dielectric loss tangent tanδ of 0.0005 to 0.003. The method for manufacturing an LCP film for a circuit board according to any one of (1) to (5). ​​​​

[0016] (7) An LCP resin composition for circuit boards containing at least 100 parts by mass of liquid crystal polyester and 1 to 20 parts by mass of an oxazoline group-containing polymer. (8) The LCP resin composition for circuit boards according to (7), further containing 1 to 20 parts by mass of polyarylate.

[0017] (9) An LCP film for circuit boards containing at least 100 parts by mass of liquid crystal polyester and 1 to 20 parts by mass of an oxazoline group-containing polymer, wherein the coefficient of linear expansion (α2) in the TD direction is 16.8 ± 12 ppm / K.

[0018] (10) The LCP film for circuit boards according to (9), further containing 1 to 20 parts by mass of polyarylate. (11) Tensile modulus Y in the MD direction MD and the tensile modulus of elasticity Y in the TD direction TD The ratio (Y MD / Y TD An LCP film for circuit boards as described in (9) or (10), wherein the ratio is 0.8 or more and 2.0 or less. (12) An LCP film for circuit boards as described in any one of items (9) to (11), wherein the coefficient of linear expansion in the TD direction is 5.0 ppm / K or more and 16.0 ppm / K or less. (13) Specific permittivity ε r An LCP film for circuit boards according to any one of (9) to (12), having dielectric properties (36 GHz) with a dielectric constant of 3.0 to 3.9 and a dielectric loss tangent tanδ of 0.0005 to 0.003. (14) An LCP film for circuit boards as described in any one of items (9) to (13), having a thickness of 10 μm or more and 500 μm or less. [Effects of the Invention]

[0019] According to the present invention, it is possible to provide an LCP film for circuit boards and a method for manufacturing the same, which has a reduced coefficient of linear expansion and thereby improved dimensional stability, without excessively impairing the excellent basic properties of liquid crystal polyester, such as mechanical properties, electrical properties, high-frequency properties, and heat resistance. Furthermore, according to a preferred embodiment of the present invention, it is possible to provide an LCP film for circuit boards that not only has excellent basic properties such as mechanical properties, electrical properties, high-frequency properties, and heat resistance, but also has low anisotropy in the film plane direction and can improve adhesion to metal foil, thereby improving productivity and economic efficiency. [Brief explanation of the drawing]

[0020] [Figure 1] This is a flowchart showing a method for manufacturing an LCP film 11 for a circuit board according to one embodiment. [Figure 2] This is a schematic diagram showing an LCP film 11 for a circuit board according to one embodiment. [Figure 3] This is a schematic diagram showing a metal foil-clad laminate 31 in one embodiment. [Modes for carrying out the invention]

[0021] Embodiments of the present invention will be described in detail below with reference to the drawings. Unless otherwise specified, positional relationships such as up, down, left, and right shall be based on the positional relationships shown in the drawings. Furthermore, the dimensional ratios in the drawings are not limited to those shown. However, the following embodiments are illustrative examples for explaining the present invention, and the present invention is not limited to these. That is, the present invention can be implemented with arbitrary modifications without departing from its essence. In this specification, for example, the notation of a numerical range such as "1 to 100" shall include both the lower limit value "1" and the upper limit value "100". The same applies to other numerical range notations.

[0022] (LCP film) Figure 1 is a flowchart showing the manufacturing method of the circuit board LCP film 11 of this embodiment, and Figure 2 is a schematic diagram showing the circuit board LCP film 11 of this embodiment.

[0023] The manufacturing method of this embodiment comprises at least a composition preparation step (S1) of preparing a predetermined LCP resin composition, a film forming step (S2) of melt-extruding the LCP resin composition to form a predetermined LCP film, and a pressurized heating step (S3) of pressurized heating the LCP film to obtain a predetermined circuit board LCP film 11.

[0024] <Composition preparation step (S1)> In this composition preparation step (S1), an LCP resin composition is prepared that contains at least 100 parts by mass of liquid crystal polyester and 1 to 20 parts by mass of an oxazoline group-containing polymer as the liquid crystal polymer.

[0025] As the liquid crystal polyester, any known material in the industry can be used, and the type is not particularly limited. Liquid crystal polyesters that exhibit thermotropic liquid crystal-like properties and have a melting point of 250°C or higher, preferably 280°C to 380°C, are preferably used. As such liquid crystal polyesters, aromatic polyesters that exhibit liquid crystallinity upon melting are known, synthesized from monomers such as aromatic diols, aromatic carboxylic acids, and hydroxycarboxylic acids. Representative examples include, but are not particularly 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. Each liquid crystal polyester can be used individually or in any combination and ratio of two or more types.

[0026] Among liquid crystal polyesters, aromatic polyester liquid crystal polymers are preferred, from the viewpoint of having excellent basic properties such as mechanical properties, electrical properties, and heat resistance, and having 6-hydroxy-2-naphthoic acid and its derivatives (hereinafter sometimes simply referred to as "monomer component A") as the basic structure, and having at least one 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 (hereinafter sometimes simply referred to as "monomer component B") as monomer components.

[0027] The aromatic polyester liquid crystal polymer containing monomer components A and B described above forms an anisotropic molten phase in the molten state, with the linear chains of the molecules arranged regularly. Typically, it exhibits thermotropic liquid crystal-like properties and possesses excellent basic performance in terms of mechanical properties, electrical properties, high-frequency properties, heat resistance, and hygroscopicity. The properties of the anisotropic molten phase of the aromatic polyester liquid crystal polymer described above can be confirmed by known methods such as polarization inspection using orthogonal polarizers. More specifically, the anisotropic molten phase can be confirmed by observing a sample placed on a Leitz hot stage under a nitrogen atmosphere at 40x magnification using a Leitz polarizing microscope.

[0028] The aromatic polyester liquid crystal polymer described above can have any configuration as long as it contains 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. Furthermore, the aromatic polyester liquid crystal polymer described above may contain other monomer components other than monomer components A and monomer component B. That is, the aromatic polyester liquid crystal polymer may be a binary or higher polycondensate consisting only of monomer components A and monomer component B, or a ternary or higher polycondensate of monomer components consisting of monomer component A, monomer component B, and other monomer components. Other monomer components (hereinafter sometimes simply referred to as "monomer component C") include, but are not 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.

[0029] 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.

[0030] More preferred aromatic polyester liquid crystal polymers include: binary polycondensates of parahydroxybenzoic acid and its derivatives with 6-hydroxy-2-naphthoic acid and its derivatives; ternary or higher polycondensates of parahydroxybenzoic acid and its derivatives with 6-hydroxy-2-naphthoic acid and its derivatives with monomer component C; and parahydroxybenzoic 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, 4,4-dihydroquinone. Examples include ternary or higher polycondensates consisting of one or more selected from the group consisting of cybiphenol, ethylene terephthalate, and their derivatives; and quaternary or higher polycondensates consisting of one or more selected from the group consisting of parahydroxybenzoic acid and its derivatives, 6-hydroxy-2-naphthoic acid and its derivatives, terephthalic acid, isophthalic acid, 6-naphthalenedicarboxylic acid, 4,4'-biphenol, bisphenol A, hydroquinone, 4,4-dihydroxybiphenol, ethylene terephthalate, and their derivatives, and one or more monomer components C. These can be obtained as having a relatively low melting point compared to, for example, a homopolymer of parahydroxybenzoic acid, and therefore, LCP films using these have excellent moldability when heat-pressed onto an adherend.

[0031] From the viewpoint of lowering the melting point of the aromatic polyester liquid crystal polymer, improving the moldability when the LCP film is heat-pressed onto the substrate, or obtaining high peel strength when the LCP film is heat-pressed onto a metal foil, the molar ratio content of monomer component A to the aromatic polyester liquid crystal polymer is preferably 10 mol% to 70 mol%, more preferably 10 mol% to 50 mol%, even more preferably 10 mol% to 40 mol%, and even more preferably 15 mol% to 30 mol%. Similarly, the molar ratio content of monomer component B to the aromatic polyester liquid crystal polymer is preferably 30 mol% to 90 mol%, more preferably 50 mol% to 90 mol%, even more preferably 60 mol% to 90 mol%, and even more preferably 70 mol% to 85 mol%.

[0032] Furthermore, the content of monomer component C, which may be contained in the aromatic polyester liquid crystal polymer, is preferably 10% by mass or less, more preferably 8% by mass or less, even more preferably 5% by mass or less, and preferably 3% by mass or less, on a molar basis.

[0033] The method for synthesizing liquid crystal polyester 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.

[0034] An oxazoline group-containing polymer is a polymer having at least two or more oxazoline groups in its molecule. By including an oxazoline group-containing polymer, the anisotropy in the film plane direction of the LCP film that occurs in the film formation step (S2) can be effectively reduced in the pressurized heating step (S3) by crosslinking with the liquid crystal polyester or promoting compatibility with the liquid crystal polyester. The oxazoline group-containing polymer can be appropriately selected from known polymers and is not particularly limited in type. For example, it can be obtained by polymerization of monomers containing oxazoline compounds having polymerizable groups such as 2-vinyl-2-oxazoline, 2-vinyl-4-methyl-2-oxazoline, and 2-isopropenyl-2-oxazoline; copolymerization of an oxazonyl group-containing unsaturated monomer with a vinyl monomer (e.g., styrene and / or acrylonitrile); or graft copolymerization of an oxazonyl group-containing unsaturated monomer with a thermoplastic resin (e.g., polystyrene, styrene-acrylonitrile copolymer) excluding liquid crystal polyesters and liquid crystal polyester resin compositions. Furthermore, oxazoline group polymers are used in various applications such as modifiers and crosslinking agents for thermoplastic resins, and can be appropriately selected and used from these known types. Commercially available oxazoline group-containing polymers include, for example, Epocross®, Epocross® RPS series, and Epocross® RAS series manufactured by Nippon Shokubai Co., Ltd. Each oxazoline group-containing polymer can be used individually or in any combination and ratio of two or more types.

[0035] The total content of the oxazoline group-containing polymer described above can be appropriately set according to the desired performance and is not particularly limited, but is preferably 1 to 20 parts by mass, more preferably 1 to 15 parts by mass, and even more preferably 1.5 to 10 parts by mass in terms of solid content, per 100 parts by mass of the total amount of the LCP resin composition. When the content of the oxazoline group-containing polymer is within the above preferred range, the effect of reducing anisotropy in the in-plane direction of the LCP film tends to be effectively exhibited. If the content of the oxazoline group-containing polymer exceeds the above preferred range, the content of liquid crystal polyester tends to decrease relatively, and basic performance such as mechanical properties, electrical properties, high-frequency properties, and heat resistance tends to deteriorate. Therefore, the content of the oxazoline group-containing polymer should be adjusted considering the balance between the anisotropy reduction effect according to the present invention and the deterioration of the basic performance of the liquid crystal polyester.

[0036] Furthermore, the LCP resin composition of this embodiment preferably contains polyarylate in addition to the liquid crystal polyester and oxazoline group-containing polymer described above. By including polyarylate, which is an amorphous polymer, it is possible to effectively reduce its composition in the pressurized heating step (S3) by promoting compatibility with the liquid crystal polyester. The polyarylate can be appropriately selected from known types and is not particularly limited in type. For example, amorphous polyester carbonate composed of aromatic dicarboxylic acid units such as isophthalic acid, terephthalic acid, or mixtures thereof, and diphenol units such as bisphenol is preferred. As for commercially available polyarylates, for example, U Polymer (registered trademark) manufactured by Unitika Ltd. and Durell (registered trademark) manufactured by Celanese Corporation in the United States are known. Note that each type of polyarylate can be used alone, or two or more types can be used in any combination and ratio.

[0037] The total content of polyarylate described above can be set appropriately according to the desired performance and is not particularly limited, but is preferably 1 to 20 parts by mass, more preferably 1 to 15 parts by mass, and even more preferably 1.5 to 10 parts by mass in terms of solid content, per 100 parts by mass of the total amount of LCP resin composition. When the polyarylate content is within the above preferred range, the effect of reducing anisotropy in the in-plane direction of the LCP film tends to be effectively exhibited. If the polyarylate content exceeds the above preferred range, the content of liquid crystal polyester and oxazoline group-containing polymer tends to decrease relatively, leading to a decrease in basic performance such as mechanical properties, electrical properties, high-frequency properties, and heat resistance, or a decrease in the anisotropy reduction effect according to the present invention. Therefore, the polyarylate content should be adjusted considering the balance between the anisotropy reduction effect according to the present invention and the decrease in the basic performance of the liquid crystal polyester.

[0038] In addition to the components described above, the LCP resin composition of this embodiment may also contain, to the extent that it does not excessively impair the effects of the present invention, additives known in the industry, such as mold release improvers such as higher fatty acids having 10 to 25 carbon atoms, higher fatty acid esters, higher fatty acid amides, higher fatty acid metal salts, polysiloxanes, and fluororesins; colorants such as dyes, pigments, and carbon black; organic fillers; inorganic fillers; antioxidants; heat stabilizers; light stabilizers; ultraviolet absorbers; flame retardants; lubricants; antistatic agents; surfactants; rust inhibitors; foaming agents; defoaming agents; fluorescent agents, etc. These additives can be incorporated into the molten resin composition during the film formation of the LCP film. Each of these additives can be used individually or in combination of two or more. The content of the additives is not particularly limited, but from the viewpoint of moldability and heat stability, it is preferably 0.01 to 10% by mass, more preferably 0.1 to 7% by mass, and even more preferably 0.5 to 5% by mass, relative to the total amount of the LCP film.

[0039] The preparation of the LCP resin composition of this embodiment 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 polyester or polymer material 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 polyester and below 360°C is preferred, and more preferably, a range of above the melting point of the liquid crystal polyester + 10°C and below 360°C.

[0040] <Film formation process (S2)> In this film formation step (S2), the above-mentioned LCP resin composition is formed into a film by a known melt extrusion film formation method such as the T-die method, to form an LCP film having a linear expansion coefficient (α2) in the TD direction of 50 ppm / K or more. In this specification, the linear expansion coefficient refers to the value obtained when the LCP film or LCP film for circuit boards 11 is heated at a heating rate of 5°C / min (1st heating), then cooled to the measurement ambient temperature (23°C) (1st cooling), and then heated a second time at a heating rate of 5°C / min (2nd heating) to obtain a value after eliminating the thermal history. Other conditions shall be as described in the examples below.

[0041] Specifically, for example, an LCP film can be obtained by melt-kneading the above-mentioned LCP resin composition in an extruder and extruding the molten resin through a die (e.g., a T-die). At this time, it is also possible to prepare the LCP resin composition and obtain the LCP film directly by pre-dry-blending each component and kneading them during the melt-extrusion operation, without going through the melt-kneading process. The settings conditions of the extruder during such film formation can be set appropriately according to the type and composition of the LCP resin composition used, the desired performance of the target LCP film, etc., and are not particularly limited, but generally, the setting temperature of the extruder cylinder is preferably 230 to 360°C, and more preferably 280 to 350°C. Similarly, for example, the slit gap of the T-die can be set appropriately according to the type and composition of the LCP resin composition used, the desired performance of the target LCP film, etc., and are not particularly limited, but generally 0.1 to 1.5 mm is preferred, and more preferably 0.1 to 0.5 mm.

[0042] The thickness of the resulting LCP film can be set appropriately according to requirements and is not particularly limited. Considering handling and productivity during T-die melt extrusion molding, a thickness of 10 μm to 500 μm is preferred, more preferably 20 μm to 300 μm, and even more preferably 30 μm to 250 μm.

[0043] The melting point (melting temperature) of the 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 bonding 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 LCP film to be used for compression is heated at a heating rate of 20°C / min (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) to obtain a value after eliminating the thermal history. For other details, the measurement conditions described in the examples below shall be followed.

[0044] When the above LCP resin composition is melt-extruded to form an LCP film using T-die melt extrusion molding, it is typically easy to obtain an LCP film with a linear expansion coefficient (CTE, α2) in the MD direction (Machine Direction; longitudinal direction) of -40 to 40 ppm / K and a linear expansion coefficient (CTE, α2) in the TD direction (Transverse Direction; transverse direction) of 50 to 120 ppm / K. Furthermore, when the above LCP resin composition is melt-extruded to form an LCP film using T-die melt extrusion molding, it is typically easy to obtain an LCP film with a tensile modulus of elasticity Y in the MD direction. MD and the tensile modulus of elasticity Y in the TD direction TD The ratio (Y MD / Y TD LCP films with a ratio of 2 to 10 are easily obtained. This is because the main chain of liquid crystal polyester tends to be easily oriented in the MD direction during T-die melt extrusion molding, and an anisotropic molten phase of the liquid crystal polyester is present during T-die melt extrusion molding.

[0045] Thus, in the film formation process (S2), LCP films with a high degree of orientation (high anisotropy) are easily formed. In the present invention, even with LCP films with such a high degree of orientation, the orientation (anisotropy) can be significantly reduced by performing a pressurized heating process (S3) using the LCP resin composition of the above composition. Therefore, one of the features of the present invention is that LCP films with a high degree of orientation, which have conventionally been considered to have little industrial applicability, can be used as semi-finished products (intermediate products). For this reason, the effects of the present invention tend to become more apparent when using LCP films with an extremely high degree of orientation (extremely high anisotropy). The coefficient of linear expansion of the LCP film in the MD direction (CTE, α2) is not particularly limited, but is preferably -40 to 0 ppm / K, and more preferably -30 to 0 ppm / K. The coefficient of linear expansion of the LCP film in the TD direction (CTE, α2) is not particularly limited, but is preferably 50 to 120 ppm / K, and more preferably 50 to 100 ppm / K. Furthermore, the tensile modulus Y in the MD direction of the resulting LCP film MD and the tensile modulus of elasticity Y in the TD direction TD The ratio (Y MD / Y TD ) is not particularly limited, but is preferably 2 to 9, and more preferably 3 to 8.

[0046] <Pressurized heating process (S3)> In this pressurized heating process (S3), the LCP film with a high degree of orientation (high anisotropy) described above is subjected to pressurized heating to reduce its degree of orientation (anisotropy), thereby obtaining an LCP film 11 for circuit boards with a coefficient of linear expansion in the TD direction (CTE, α2) of 16.8 ± 12 ppm / K. This pressurized heating relaxes the orientation of the polymer chains of the liquid crystal polyester, thereby improving the dimensional stability of the film and resulting in excellent adhesion to the metal foil.

[0047] 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-mentioned LCP resin composition between endless belt pairs of a double belt press, the processing temperature is preferably above the melting point of the liquid crystal polyester 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 and pressing time of 250 to 430°C, more preferably under conditions of a surface pressure of 0.6 to 8 MPa and a heating and pressing time of 260 to 400°C, and even more preferably under conditions of a surface pressure of 0.7 to 6 MPa and a heating and pressing time 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.

[0048] (LCP film for circuit boards) The thickness of the LCP film 11 for circuit boards obtained after the pressurized heating process (S3) can be set as appropriate according to requirements and is not particularly limited. Considering handling and productivity during the pressurized heating process, a thickness of 10 μm to 500 μm is preferred, more preferably 20 μm to 300 μm, and even more preferably 30 μm to 250 μm.

[0049] The coefficient of linear expansion (CTE,α2) in the TD direction of the LCP film 11 for circuit boards is not particularly limited, but from the viewpoint of improving adhesion to metal foil, it is preferably 16.8±12 ppm / K, more preferably 16.8±10 ppm / K, and even more preferably 16.8±8 ppm / K. The present invention has a remarkable effect in that it can significantly reduce the coefficient of linear expansion (CTE,α2) in the TD direction, even though a highly anisotropic LCP film with a coefficient of linear expansion (CTE,α2) of 50 ppm / K or more is used as the workpiece from the beginning. Furthermore, from the viewpoint of improving adhesion to electrolytic copper foil, in one embodiment of the LCP film 11 for circuit boards, the coefficient of linear expansion (CTE,α2) in the TD direction is preferably 5.0 ppm / K or more and 16.0 ppm / K or less, more preferably 6.0 ppm / K or more and 16.0 ppm / K or less, and even more preferably 7.0 ppm / K or more and 16.0 ppm / K or less.

[0050] The coefficient of linear expansion (CTE, α2) in the MD direction of the LCP film 11 for circuit boards is not particularly limited, but from the viewpoint of improving adhesion to metal foil, it is preferably 0 to 40 ppm / K, more preferably 0 to 30 ppm / K, and even more preferably 0 to 20 ppm / K. The coefficient of linear expansion (CTE, α2) in the film thickness direction is not particularly limited, but it is preferably 150 ppm / K or less.

[0051] On the other hand, the tensile modulus Y in the MD direction of the LCP film 11 for the circuit board MD and the tensile modulus of elasticity Y in the TD direction TD The ratio (Y MD / Y TD From the viewpoint of reducing anisotropy in the film plane direction, the value is preferably 0.8 to 2.0, more preferably 0.9 to 1.5, and even more preferably 0.95 to 1.2.

[0052] The dielectric properties of the LCP film 11 for the circuit board 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 rThe dielectric loss tangent tanδ (36 GHz) is preferably 0.0005 to 0.0030, and more preferably 0.0005 to 0.0025.

[0053] The melting point (melting temperature) of the LCP film 11 for circuit boards is not particularly limited, but from the viewpoint of heat resistance and processability of the film, it is preferable that the melting point (melting temperature) be 200 to 400°C, and in particular from the viewpoint of improving thermocompression adhesion to metal foil, it is preferable that it be 250 to 360°C, more preferably 260 to 355°C, even more preferably 270 to 350°C, and especially preferably 275 to 345°C. In this specification, the melting point of the LCP film 11 for circuit boards refers to the value measured under the same measurement conditions as the melting point of the LCP film described above.

[0054] (Metal foil-clad laminate) Figure 3 is a schematic diagram showing an example of a metal foil-clad laminate 31 of this embodiment. The metal foil-clad laminate 31 (metal foil laminated LCP film) of this embodiment comprises the circuit board LCP film 11 described above and one or more metal foils 21 provided on at least one surface of the circuit board LCP film 11. Hereinafter, in this specification, "provided on one (other) surface side of ~" is a concept that encompasses not only the embodiment in which the metal foil 21 is provided only on one surface 11a of the circuit board LCP film 11, but also the embodiment in which the metal foil 21 is provided on the other surface 11b of the circuit board LCP film 11, and the embodiment in which the metal foil 21 is provided on both surfaces 11a and 11b of the circuit board LCP film 11.

[0055] The material of the metal foil 21 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, and copper foil is 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 relatively large surface roughness is preferred. The thickness of the metal foil 21 can be set appropriately according to the desired performance and is not particularly limited. Usually, 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 21 may be subjected to surface treatment such as chemical surface treatment such as acid cleaning, as long as the effects of the present invention are not impaired.

[0056] The method for providing the metal foil 21 to the surfaces 11a and 11b of the LCP film 11 for circuit boards can be carried out according to conventional methods and is not particularly limited. It may be any of the following methods: laminating the metal foil 21 onto the LCP film 11 for circuit boards and bonding or pressing the two layers together; using physical methods such as sputtering or vapor deposition (dry methods); using chemical methods such as electroless plating or electrolytic plating after electroless plating (wet methods); or applying a metal paste.

[0057] A preferred lamination method involves overlapping the circuit board LCP film 11 and the metal foil 21 to form a laminate in which the metal foil 21 is placed on the circuit board LCP film 11, and then hot-pressing this laminate while sandwiching it between the endless belts of a double belt press machine. As described above, the circuit board LCP film 11 used in this embodiment has a significantly reduced coefficient of linear expansion (CTE, α2) in the TD direction without excessively impairing the excellent basic performance of liquid crystal polyester, and in a preferred embodiment, the tensile modulus of elasticity Y in the MD direction MD and the tensile modulus of elasticity Y in the TD direction TD Since the anisotropy is sufficiently reduced, a higher peel strength to the metal foil 21 can be obtained compared to conventional methods. Therefore, process tolerance during the manufacturing of circuit boards and metal foil-clad laminates 31 can be increased, and productivity and cost-effectiveness can be improved.

[0058] The temperature during the heat-pressing of the metal foil 21 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 polyester and below the melting point, more preferably 40°C lower than the melting point and below the melting point, even more preferably 30°C lower than the melting point and below the melting point, and particularly preferably 20°C lower than the melting point and below the melting point. The temperature during the heat-pressing of the metal foil 21 is the value measured at the surface temperature of the LCP film of the laminate as described above. The pressing 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 process under conditions of a surface pressure of 0.5 to 10 MPa and a heating time of 200 to 360°C.

[0059] The metal foil-clad laminate 31 of this embodiment may have further laminated structures, as long as it comprises a thermocompressed body with a two-layer structure of circuit board LCP film 11 and metal foil 21. For example, it can be a multilayer structure having at least the two-layer structure described above, such as a two-layer structure of metal foil 21 / circuit board LCP film 11 / metal foil 21, or a three-layer structure such as circuit board LCP film 11 / metal foil 21 / circuit board LCP film 11; or a five-layer structure such as metal foil 21 / circuit board LCP film 11 / metal foil 21 / circuit board LCP film 11 / metal foil 21; and so on. In addition, multiple (for example, 2 to 50) metal foil-clad laminates 31 can be laminated and thermocompressed together.

[0060] In the metal foil-clad laminate 31 of this embodiment, the peel strength between the circuit board LCP film 11 and the metal foil 21 is not particularly limited, but from the viewpoint of achieving higher peel strength, it is preferably 1.0 (N / mm) or higher, more preferably 1.1 (N / mm) or higher, and even more preferably 1.2 (N / mm) or higher. As described above, the metal foil-clad laminate 31 of this embodiment can achieve higher peel strength than the conventional technology, so that, for example, peeling between the circuit board LCP film 11 and the metal foil 21 can be suppressed during the heating process of substrate manufacturing. Furthermore, since milder manufacturing conditions can be applied to obtain peel strength equivalent to that of the conventional technology, it is possible to suppress deterioration of the basic performance of liquid crystal polyester while maintaining peel strength at the same level as before.

[0061] The metal foil laminate 31 of this embodiment can be used as a material for electronic circuit boards, multilayer boards, etc., by pattern etching at least a portion of the metal foil 21, and can also be used for applications such as high heat dissipation boards, antenna boards, optoelectronic mixed-signal boards, and IC packages. Furthermore, the metal foil laminate 31 of this embodiment has excellent high-frequency characteristics and low dielectric properties, excellent adhesion between the circuit board LCP film 11 and the metal foil 21, and good dimensional stability, making it 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]

[0062] 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.

[0063] (Example 1) LCP synthesis In a reaction vessel equipped with a stirrer and a vacuum distillation apparatus, p-hydroxybenzoic acid (74 mol%), 6-hydroxy-2-naphthoic acid (26 mol%), and acetic anhydride in an amount equal to 1.025 moles relative to the total amount of monomer were charged. The reaction vessel was heated to 150°C under a nitrogen atmosphere and held for 30 minutes. Then, while distilling off the by-product acetic acid, the temperature was rapidly raised to 190°C and held for 1 hour to obtain the acetylated reaction product. The obtained acetylated reaction product was heated to 320°C over 3.5 hours, then subjected to melt polycondensation under reduced pressure to 2.7 kPa over approximately 30 minutes, and then gradually reduced back to atmospheric pressure to obtain a polymer solid. The obtained polymer solid was pulverized and granulated at 300°C using a twin-screw extruder to obtain LCP pellets of an aromatic polyester liquid crystal polymer (molar ratio 74:26) composed of p-hydroxybenzoic acid and 6-hydroxy-2-naphthoic acid.

[0064] Preparation of LCP resin composition The obtained LCP pellets and oxazoline group-containing polymer (polystyrene containing 5% by mass of oxazoline component, trade name: Epocross RPS-1005, manufactured by Nippon Shokubai Co., Ltd.) were supplied in the proportions shown in Table 1, and the mixture was mixed, reacted, and granulated at 300°C using a twin-screw extruder to obtain LCP resin composition pellets.

[0065] Manufacturing of LCP film Using the obtained LCP resin composition pellets, a film was formed at 300°C by T-die casting to obtain an LCP melt-extruded film having a melting temperature of 280°C and a thickness of 50 μm.

[0066] Manufacturing of pressurized and heat-treated LCP film The obtained LCP melt-extruded film was subjected to a contact-type heat treatment at 320°C for 30 seconds using a double-belt hot press to obtain a pressurized and heat-treated LCP film with a melting point of 280°C and a thickness of 50 μm.

[0067] (Example 2) Preparation of LCP resin composition LCP pellets obtained in Example 1, oxazoline group-containing polymer (polystyrene containing 5% by mass of oxazoline component, trade name: Epocross RPS-1005, manufactured by Nippon Shokubai Co., Ltd.), and polyarylate (trade name: U Polymer POWDER CK, manufactured by Unitika Ltd.) (PAR) were supplied in the proportions shown in Table 1, and the mixtures were mixed, reacted, and granulated at 300°C using a twin-screw extruder to obtain LCP resin composition pellets.

[0068] Manufacturing of LCP film Using the obtained LCP resin composition pellets, a film was formed at 300°C by T-die casting to obtain an LCP melt-extruded film having a melting temperature of 280°C and a thickness of 50 μm.

[0069] Manufacturing of pressurized and heat-treated LCP film The obtained LCP melt-extruded film was subjected to a contact-type heat treatment at 320°C for 30 seconds using a double-belt hot press to obtain a pressurized and heat-treated LCP film with a melting point of 280°C and a thickness of 50 μm.

[0070] (Comparative Example 1) An LCP resin composition was prepared in the same manner as in Example 1, except that the oxazoline group-containing polymer was omitted, and an LCP film having a melting temperature of 280°C and a thickness of 50 μm, and a pressurized and heat-treated LCP film having a melting temperature of 280°C and a thickness of 50 μm were obtained.

[0071] <Performance Evaluation> The performance of the LCP films obtained in Examples 1 and 2 and Comparative Example 1 was evaluated against the pressure-heat-treated LCP film. The measurement conditions were as follows.

[0072] [Coefficient of linear expansion] Measuring instrument: TMA 4000SE (manufactured by NETZSCH) Measurement method: Tensile mode Measurement conditions: Sample size 20mm x 4mm x 50μm thickness Temperature range: Room temperature to 200°C (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.

[0073] [Tensile modulus of elasticity] Measuring instrument: Strograph VE1D (manufactured by Toyo Seiki Seisakusho Co., Ltd.) Measurement method: Tensile test Measurement environment: Temperature 23°C, relative humidity 50% Measurement conditions: Sample size: dumbbell shape, thickness 50 μm Test speed: 50 mm / min Gauge distance 25mm

[0074] [Relative permittivity ε r [Electrical characteristics of dielectric loss tangent tanδ (36 GHz)] Measurement method: Cylindrical cavity resonator method Measurement environment: Temperature 23°C, relative humidity 50% Measurement conditions: Sample size 15mm x 15mm x 200μm thickness Cavity 36GHz

[0075] [Heat resistance] Measuring instrument: DSC8500 (manufactured by PerkinElmer) Measurement method: Differential scanning calorimetry (DSC) Measurement conditions: Temperature range 30-400℃ 1st heating: 20℃ / min 1st Cooling 50℃ / min 2nd heating 20℃ / min *The value from 2ndRUN was used to see the value after the thermal history had been eliminated.

[0076] The measurement results are shown in Table 1. [Table 1]

[0077] (Examples 3-5) An LCP resin composition was prepared in the same manner as in Example 1, except that the blending ratio of the oxazoline group-containing polymer and polyarylate was changed as shown in Table 2, and an LCP film having a melting temperature of 280°C and a thickness of 50 μm, and a pressurized and heat-treated LCP film having a melting temperature of 280°C and a thickness of 50 μm were obtained.

[0078] <Performance Evaluation> The performance of the LCP films obtained in Examples 1-5 and Comparative Example 1 was evaluated against the pressure-heat-treated LCP film.

[0079] The measurement results are shown in Table 2. [Table 2] [Industrial applicability]

[0080] The LCP film for circuit boards 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, due to its excellent high-frequency characteristics and low dielectric properties, it can be widely and effectively used as an insulating material for flexible printed circuit boards (FPCs) in fifth-generation mobile communication systems (5G) and millimeter-wave radar, etc. [Explanation of Symbols]

[0081] 11 ···LCP film for circuit boards 11a...Surface 11b...Surface 21 ···metal foil 31 ···Metal foil-clad laminate

Claims

1. The material contains 100 parts by mass of liquid crystal polyester, 1 to 20 parts by mass of an oxazoline group-containing polymer which is a polymer having at least two or more oxazoline groups in its molecule, and at least 1 to 20 parts by mass of amorphous polyester carbonate in addition to the liquid crystal polyester and the oxazoline group-containing polymer. LCP resin composition for circuit boards.

2. The material contains 100 parts by mass of liquid crystal polyester, 1 to 20 parts by mass of an oxazoline group-containing polymer which is a polymer having at least two or more oxazoline groups in its molecule, and at least 1 to 20 parts by mass of amorphous polyester carbonate in addition to the liquid crystal polyester and the oxazoline group-containing polymer. The coefficient of linear expansion (α2) in the TD direction is 16.8 ± 12 ppm / K. LCP film for circuit boards.

3. Tensile modulus Y in the MD direction MD and the tensile modulus Y in the TD direction TD The ratio (Y MD / Y TD ) is between 0.8 and 2.0 The LCP film for circuit boards according to claim 2.

4. The coefficient of linear expansion in the TD direction is 5.0 ppm / K or more and 16.0 ppm / K or less. The LCP film for circuit boards according to claim 2 or 3.

5. Relative permittivity ε r It has dielectric properties (36 GHz) where the dielectric constant is 3.0 to 3.9 and the dielectric loss tangent tanδ is 0.0005 to 0.

003. LCP film for circuit boards according to any one of claims 2 to 4.

6. Having a thickness of 10 μm or more and 500 μm or less LCP film for circuit boards according to any one of claims 2 to 5.

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