Resin films, resin compositions, metal-clad laminates, and printed wiring boards

Abstract

This invention provides a resin film that balances dielectric properties and dimensional stability without compromising physical properties such as flexibility or toughness, a method for manufacturing the resin film, a resin composition, a metal-clad laminate, and a printed wiring board. A resin film comprises: (A) a liquid crystal polymer filler having an anisotropic shape and an X / Y ratio of 2.5 or higher when the average length of the major axis is X and the average length of the shortest minor axis orthogonal to said axis is Y; and (B) a base polymer coated with and fixed to the (A) component. Preferably, the resin film satisfies: (i) an absolute value of the average linear thermal expansion coefficient from 250°C to 100°C of 50 ppm / K or less; (ii) a dielectric loss tangent of 0.003 or less at 20 GHz in an environment of 23°C and 50%RH; and (iii) a water absorption rate of 0.2% by weight or less when immersed in pure water at 23°C for 24 hours.

Description

[Technical Field]

[0001] The present invention relates, for example, to a resin film that is effective as a circuit board material, a method for manufacturing the same, a resin composition, a metal-clad laminate, and a printed wiring board. [Previous Technology]

[0002] Flexible printed circuit boards (FPCs) can be mounted three-dimensionally and at high density even in limited spaces, thus expanding their applications to wiring or cables, connectors, and other components for moving parts of electronic devices, and are mounted on equipment in many fields. Along with this, the environments in which FPCs are used are becoming increasingly diverse, and the required performance is also increasing. For example, in message processing or communication, efforts have been made to increase transmission frequencies in order to transmit and process large amounts of information; therefore, there is a strong demand for circuit boards to reduce transmission losses by improving the dielectric properties of the insulating resin layer.

[0003] As one method to improve the dielectric properties of insulating resin layers, research is underway to include resins with low dielectric loss tangents in the base material constituting the insulating resin layer. For example, liquid crystal polymers are resins characterized by low dielectric constants and low dielectric loss tangents; by using them as base materials, the dielectric properties of insulating resin layers can be significantly improved. However, films using liquid crystal polymers as base materials suffer from problems such as low heat resistance and poor adhesion to metal foils, failing to meet all the properties required as circuit board materials. In addition, fluoropolymers, polyolefins, polystyrene, and polyesters are also known as resin materials with excellent dielectric properties. However, these resins have the following problem: their coefficient of linear thermal expansion is very large, which significantly impairs the dimensional stability of the circuit board when used in insulating resin layers.

[0004] In addition, as another method, it has been proposed to composite the base material constituting the insulating resin layer with filler or non-woven fabric that can reduce the dielectric constant or dielectric loss tangent (Patent Document 1 to Patent Document 3).

[0005] Patent Document 1 proposes to formulate liquid crystal polymer particles in a thermoplastic resin or a thermosetting resin. However, Patent Document 1 does not study the shape of the liquid crystal polymer particles.

[0006] Patent Document 2 proposes to achieve a low dielectric constant by adding polytetrafluoroethylene microparticle filler with a low dielectric constant to a continuous phase containing para-aligned aromatic polyamide. However, Patent Document 2 does not study the control of the dielectric loss tangent, which is closely related to the transmission loss of high-frequency signals. In addition, for the purpose of improving mechanical properties, aromatic polyamide short fibers are added together with polytetrafluoroethylene microparticle filler, resulting in a complex composition.

[0007] In Patent Document 3, in order to achieve low water absorption, low dielectric constant, and low dielectric loss tangent while considering the thinning, cost reduction, laser processability, and copper migration resistance of printed wiring boards, a method was proposed to reinforce the matrix resin containing bismaleimide triazine resin or epoxy resin with a nonwoven fabric containing molten liquid crystal polyester fibers. However, Patent Document 3 did not consider coping with the increasingly important high-frequency signal transmission above 20 GHz in the future, and research on reducing the dielectric loss tangent, which is closely related to the transmission loss of high-frequency signals, is insufficient.

[0008] On the other hand, regarding the control of the coefficient of thermal expansion of resin films, for example, in Non-Patent Literature 1, research is being conducted on composite resins with inorganic fillers such as carbon fibers. However, there is a problem that the addition of inorganic fillers reduces the flexibility or toughness of the resin film, thereby impairing the physical properties required as a circuit board material.

[0009] Furthermore, it is widely known that methods to improve functionality by adding fillers to an insulating resin layer for composite formation are not limited to improving dielectric properties. For example, Patent Document 4 proposes to obtain an insulating resin with excellent mechanical strength and low thermal expansion coefficient by adding aramid fibers or glass fibers to an injection-molded epoxy resin. Patent Document 4 also describes how the anisotropy of the thermal expansion coefficient characteristic of fibrous fillers can be eliminated by further adding particulate fillers, but it does not study dielectric properties or flexibility.

[0010] Furthermore, Patent Document 5 proposes to produce a high-strength molding material with low anisotropy in the coefficient of thermal expansion by adding fibrous fillers and spherical fillers to epoxy resin. However, in Patent Document 5, because inorganic fibers are used, it is difficult to mold into a flexible resin film, and no research has been conducted on improving the dielectric properties. [Prior Art Documents] [Patent Documents]

[0011] [Patent Document 1] Japanese Patent No. 6295013 [Patent Document 2] Japanese Patent Application Publication No. 10-338809 [Patent Document 3] Japanese Patent Application Publication No. 2002-64254 [Patent Document 4] Japanese Patent Application Publication No. 11-273456 [Patent Document 5] Japanese Patent No. 6547277 [Non-Patent Documents]

[0012] [Non-Patent Document 1] Proceedings of the Japan Society of Mechanical Engineers (Series A), Vol. 74, No. 740 (2008-4), Paper No. 07-0770 [Summary of the Invention]

[0013] [Problem to be solved by the invention] Therefore, the object of the present invention is to provide a resin film that takes into account both dielectric properties and dimensional stability without compromising physical properties such as softness or toughness.

[0014] [Technical means to solve the problem] Efforts were made to solve the problem, and it was found that by incorporating liquid crystal polymer fillers with anisotropic shapes into the resin that serves as the base material, the dielectric properties and dimensional stability can be improved simultaneously without damaging the physical properties of the resin film, thus completing the present invention.

[0015] That is, the resin film of the present invention contains the following (A) component and (B) component: (A) liquid crystal polymer filler, having an anisotropic shape and having an X / Y ratio of 2.5 or more when the average length of the major axis is set as X and the average length of the shortest minor axis among the axes orthogonal to said axis is set as Y; and (B) a parent polymer, which is coated with said (A) component and fixed thereon.

[0016] The resin film of the present invention preferably satisfies the following conditions (i) to (iii): (i) the absolute value of the average linear thermal expansion coefficient from 250°C to 100°C is 50 ppm / K or less, (ii) the dielectric loss tangent at 20 GHz in an environment of 23°C and 50%RH is 0.003 or less, and (iii) the water absorption rate after immersion in pure water at 23°C for 24 hours is 0.2% by weight or less.

[0017] In the resin film of the present invention, component (B) may be the most abundant organic component in the composition after removing component (A), and may be one or more selected from the group consisting of fluoropolymers, polyolefins, polystyrene, polyimide, polyamide, polyether, polyetherketone and polyester.

[0018] In the resin film of the present invention, the liquid crystal polymer filler may be anisotropic in molecular alignment, and the difference between the maximum and minimum values ​​of the average linear thermal expansion coefficients measured in the three axial directions, which are orthogonal to each other in shape, is 30 ppm / K or more.

[0019] In the resin film of the present invention, the melting point of the liquid crystal polymer filler can be above 290°C.

[0020] In the resin film of the present invention, the average length Y of the short axis of the liquid crystal polymer filler can be less than 200 μm.

[0021] In the resin film of the present invention, the dielectric loss tangent of the liquid crystal polymer filler at 20 GHz under an environment of 23°C and 50%RH can be less than 0.002.

[0022] In the resin film of the present invention, the liquid crystal polymer constituting component (A) may have a polyester structure.

[0023] In the resin film of the present invention, the content of component (A) may be in the range of 2% by weight or more and 80% by weight or less relative to the total amount of component (A) and component (B).

[0024] In the resin film of the present invention, the (B) component may be a polymer using a diamine component as a raw material or a curing agent, wherein the diamine component in the polymer contains a dimer diamine composition with a main component being a dimer diamine in which the two terminal carboxylic acid groups of the dimer acid are replaced with primary amino methyl or amino groups in an amount of 30 moles or more relative to all diamine components.

[0025] In the resin film of the present invention, the (B) component may be a polyimide formed by reacting a tetracarboxylic anhydride component as a raw material with a diamine component, wherein the polyimide may contain a total of 50 mol or more of the tetracarboxylic anhydride represented by the following general formula (1) and / or general formula (2) relative to 100 mol of the tetracarboxylic anhydride component.

[0026] [Chemical 1]

[0027] In general formula (1), X represents a single bond or a divalent group selected from the following formulas. In general formula (2), the cyclic part represented by Y represents a cyclic saturated hydrocarbon group selected from four-membered rings, five-membered rings, six-membered rings, seven-membered rings or eight-membered rings.

[0028] [Chemical 2]

[0029] In the formula, Z represents -C6H4-, -(CH2)n- or -CH2-CH(-OC(=O)-CH3)-CH2-, and n represents an integer from 1 to 20.

[0030] The resin film of the present invention can be an adhesive sheet.

[0031] The method for manufacturing the resin film of the present invention is the method for manufacturing the resin film according to any one of the claims, comprising: preparing a first polymer as a liquid crystal polymer and a second polymer that is the same as or different from the first polymer; aligning the molecules of the first polymer; and compounding the first polymer with the second polymer as a filler.

[0032] The resin composition of the present invention contains the following (A) and (B) components: (A) a liquid crystal polymer filler having anisotropic shape and having an X / Y ratio of 2.5 or more when the average length of the major axis is set as X and the average length of the shortest minor axis among the axes orthogonal to said axis is set as Y; and (B) a parent polymer.

[0033] In the resin composition of the present invention, the component (A) may be a fibrous liquid crystal polymer filler, and the resin composition of the present invention may also contain the following component (C): (C) particulate metal oxide filler and / or particulate thermoplastic resin filler.

[0034] In the resin composition of the present invention, the total content of the filler of the (A) component and the (C) component relative to the content of the solid component in the resin composition may be in the range of 10 vol% to 90 vol%, and the content of the (B) component may be in the range of 10 vol% to 90 vol%.

[0035] In the resin composition of the present invention, the ratio L / D of the average length L of the long axis of the fibrous liquid crystal polymer filler of component (A) to the average diameter D of the short axis orthogonal to the long axis may be 2.5 or more.

[0036] In the resin composition of the present invention, the average length L of the long axis of the fibrous liquid crystal polymer filler of component (A) can be in the range of 0.1 mm to 5 mm, and the average diameter D of the short axis can be in the range of 5 μm to 50 μm.

[0037] In the resin composition of the present invention, the melting point of the fibrous liquid crystal polymer filler of component (A) can be above 290°C.

[0038] In the resin composition of the present invention, the content of the fibrous liquid crystal polymer filler of component (A) may be in the range of 5% to 60% by volume, relative to the content of the solid components in the resin composition.

[0039] In the resin composition of the present invention, the volume average particle size D50 of the particulate metal oxide filler and the particulate thermoplastic resin filler of component (C) can be in the range of 1 μm to 100 μm.

[0040] In the resin composition of the present invention, the particulate thermoplastic resin filler of component (C) may be one or more particles selected from the group consisting of thermoplastic polyimide, liquid crystal polymer and fluororesin.

[0041] In the resin composition of the present invention, the particulate metal oxide filler of component (C) may be silicon dioxide particles in the range of 2θ=10° to 90° of X-ray diffraction analysis spectrum of CuKα rays, the total area of ​​the peaks originating from the white silica crystal phase and the quartz crystal phase relative to the total area of ​​all peaks originating from SiO2 is 20% by weight or more.

[0042] In the resin composition of the present invention, the content of component (C) may be in the range of 20% to 80% by volume, relative to the content of solid components in the resin composition.

[0043] In the resin composition of the present invention, the ratio of the content of the fibrous liquid crystal polymer filler of component (A) to the content of component (C) [component (A) / component (C)] can be in the range of 0.1 to 10, based on volume.

[0044] In the resin composition of the present invention, the ratio [D / D50] of the average diameter D of the short axis of the fibrous liquid crystal polymer filler of component (A) to the volume average particle size D50 of the particulate metal oxide filler or particulate thermoplastic resin filler of component (C) can be in the range of 1 to 50.

[0045] In the resin composition of the present invention, the ratio [L / D50] of the average length L of the long axis of the fibrous liquid crystal polymer filler of component (A) to the volume average particle size D50 of the particulate metal oxide filler or particulate thermoplastic resin filler of component (C) can be in the range of 10 to 1000.

[0046] In the resin composition of the present invention, component (B) may be one or more selected from thermoplastic polyimide, liquid crystal polymer and fluororesin.

[0047] In the resin composition of the present invention, component (B) may be a polyimide using a diamine component as a raw material, wherein the diamine component in the polyimide contains a dimer diamine composition whose main component is a dimer diamine formed by replacing the two terminal carboxylic acid groups of a dimer acid with primary amino methyl or amino groups at a rate of 30 mol% or more relative to all diamine components.

[0048] The resin film of the present invention is a resin film having a single layer or multiple layers of resin layers, and at least one layer of the resin layer is a filler-containing resin layer formed using the resin composition of any one of the claims.

[0049] In the resin film of the present invention, after the resin layer containing filler is conditioned for 24 hours under constant temperature and humidity conditions of 23°C and 50%RH, the relative permittivity at 10 GHz measured by a split post dielectric resonator (SPDR) can be less than 3, and the dielectric loss tangent can be less than 0.003.

[0050] In the resin film of the present invention, the absolute value of the average coefficient of thermal expansion (CTE) in the longitudinal (machine direction, MD) direction of the resin layer containing filler at 10°C to 20°C may be less than 50 ppm / K, and the absolute value of the average coefficient of thermal expansion (CTE) in the transverse (TD) direction may be less than 100 ppm / K.

[0051] The metal-clad laminate of the present invention is a metal-clad laminate comprising a single or multiple insulating resin layers and a metal layer deposited on at least one side of the insulating resin layers, wherein at least one layer constituting the insulating resin layer comprises the resin film described in any one of the claims.

[0052] The printed wiring board of the present invention includes a single or multiple insulating resin layers and a circuit wiring layer deposited on at least one side of the insulating resin layers, wherein at least one layer constituting the insulating resin layer includes the resin film described in any one of the claims.

[0053] [Effects of the Invention] The resin film of the present invention contains liquid crystal polymer fillers with anisotropic shapes, thus achieving excellent dielectric properties and dimensional stability without compromising the required flexibility or toughness of the resin film. The resin film of the present invention effectively reduces transmission loss of high-frequency signals (e.g., high-frequency signals above 10 GHz, especially above 20 GHz) through a low dielectric loss tangent, and also exhibits excellent dimensional stability, making it suitable for use as a circuit board material for FPCs and the like in various electronic devices.

Implementation Method

[0055] Hereinafter, embodiments of the present invention will be described. One embodiment of the resin film of the present invention comprises: component (A) and component (B) as described below: (A) a liquid crystal polymer filler having an anisotropic shape and an X / Y ratio of 2.5 or more when the average length of the major axis is defined as X and the average length of the shortest minor axis orthogonal to said axis is defined as Y; and (B) a parent polymer, which is coated with component (A) and fixed thereon. Here, the liquid crystal polymer filler with an X / Y ratio of 2.5 or more also includes fibrous liquid crystal polymer fillers (hereinafter, similarly).

[0056] In addition, the resin composition of one embodiment of the present invention contains: the following (A) component and (B) component: (A) liquid crystal polymer filler having anisotropic shape and X / Y being 2.5 or more when the average length of the long axis is set as X and the average length of the shortest short axis among the axes orthogonal to said axis is set as Y; and (B) parent polymer.

[0057] Next, as preferred embodiments of the present invention, a first embodiment and a second embodiment will be listed, and then the metal-clad laminate and printed wiring board utilizing these embodiments will be described.

[0058] {First Embodiment} [Resin Film] The resin film of this embodiment contains: the following components (A) and (B): (A) a liquid crystal polymer filler having an anisotropic shape and an X / Y ratio of 2.5 or more when the average length of the major axis is set as X and the average length of the shortest minor axis orthogonal to said axis is set as Y; and (B) a base polymer, which is coated with and fixed to component (A). Furthermore, conditions (i) to (iii) described later are satisfied. Here, components (A) and (B) may be the same type of polymer, and may include combinations such as (A) being a liquid crystal polyester and (B) being a non-liquid crystal polyester.

[0059] If the resin film as a whole satisfies conditions (i) to (iii), the resin film of this embodiment may be a single layer or may contain multiple layers. For example, the resin film as a whole may be a layer containing component (A) and component (B), or may contain any resin layer other than the layer containing component (A) and component (B). However, the layer containing component (A) and component (B) is preferably the main layer of the resin film. Here, "main layer" refers to a layer that has a thickness of more than 50% relative to the overall thickness of the resin film.

[0060] In addition, the resin film can be used as an adhesive layer to form part of the insulating resin layer, or it can be used as an adhesive sheet in the form of a film. Here, "adhesive sheet" refers to a material used for bonding films to each other, films to metals, and metals to metals. Its use is not limited to lamination bonding in the form of a film; for example, it can be applied as an adhesive layer in the form of a varnish and then cured.

[0061] [(A) Component: Liquid Crystal Polymer Filler] The liquid crystal polymer constituting the liquid crystal polymer filler of component (A) is a resin that exhibits liquid crystal properties when melted, and can be a fully aromatic liquid crystal polymer or a semi-aromatic liquid crystal polymer. The liquid crystal polymer filler of component (A) has shape anisotropy. The shape anisotropy of the present invention refers to the ratio (X / Y) of the average length of the major axis (X) to the average length of the minor axis (Y) of the liquid crystal polymer filler being 2.5 or more. Here, when conceiving a virtual cuboid circumscribed to the liquid crystal polymer filler in a linearly extending state, the length of the shortest of the three mutually perpendicular sides of the cuboid is set as the length of the minor axis, the length of the longest side is set as the length of the major axis, and the length of the remaining side is set as the length of the intermediate axis. Furthermore, in the liquid crystal polymer filler, it is preferable that X / Y is 4.5 or more, more preferably X / Y is 15.0 or more, and even more preferably X / Y is 30.0 or more. When X / Y is less than 2.5, the liquid crystal polymer filler tends to be disordered in the resin film, thus reducing the CTE improvement effect. Furthermore, it exhibits undesirable characteristics such as easy aggregation of the liquid crystal polymer filler.

[0062] The average length (Y) of the short axis of the liquid crystal polymer filler is preferably in the range of 0.1 μm or more and less than 200 μm, and more preferably in the range of 1 μm or more and less than 150 μm. If the average length (Y) of the short axis is within the range described above, the surface smoothness during resin film formation will not deteriorate, and a resin film with good appearance can be obtained.

[0063] The average length (X) of the long axis of the liquid crystal polymer filler can be appropriately selected according to the method of compounding the liquid crystal polymer filler with component (B). For example, if the method is to disperse the liquid crystal polymer filler in component (B), it is preferably in the range of 0.5 μm or more and 5000 μm or less, and more preferably in the range of 5 μm or more and 2500 μm or less. In addition, if the method is to impregnate component (B) in the liquid crystal polymer filler, it is preferably 1 cm or more, and more preferably 3 cm or more. If the average length (X) of the long axis is within the above range, the processability will not be compromised, the surface smoothness during resin film formation will not be deteriorated, and a resin film with good appearance can be obtained.

[0064] In the liquid crystal polymer filler, the liquid crystal polymer molecular chains are preferably strongly aligned in the long axis direction of the filler, resulting in anisotropy of the coefficient of thermal expansion in the shortest axis direction (Y-axis direction) among the axes orthogonal to the long axis direction (X-axis direction). Particularly when the coefficient of thermal expansion in the X-axis direction is negative, the shrinkage relative to the X-axis direction is greater than the elongation relative to the Y-axis direction, which can reduce the CTE of the resin film, thus being even better. From the same point of view, by means of molecular chain alignment, the difference between the maximum and minimum values ​​of the average linear thermal expansion coefficients measured in the three axial directions—the long axis, short axis, and intermediate axis—which are orthogonal to each other in the shape of the liquid crystal polymer filler, is preferably 30 ppm / K or more, more preferably 50 ppm / K or more. Furthermore, the minimum value is preferably 50 ppm / K or less, more preferably 20 ppm / K or less, and even more preferably 5 ppm / K or less.

[0065] Various methods for manufacturing liquid crystal polymer fillers with anisotropic coefficients of thermal expansion can be considered. For example, there is a manufacturing method that applies shear force to a polymer having a rigid main chain and no rigid substituents or large volume in the side chains. This allows for the acquisition of fillers with high orientation in the shear direction. Examples of polymers having a rigid main chain and no rigid substituents or large volume in the side chains include polyesters, aromatic polyimides, aromatic polyamides (also known as aromatic polyamides), aromatic polyamide-imides, and fluoropolymers that do not have multiple phenyl groups, liquid crystal atom groups, saturated or unsaturated aliphatic chains or alicyclic structures with more than 6 carbon atoms on the side chains. From the viewpoints of dielectric properties, flame retardancy, thermal stability in circuit board manufacturing processes, hygroscopicity, and CTE, aromatic polyesters are preferred. However, in this invention, polyarylates are considered as one type of polyester.

[0066] The liquid crystal polymer is not particularly limited, but preferably includes known thermotropic liquid crystal polyesters and polyesteramides derived from compounds classified as (1) to (4) below and their derivatives, which have a polyester structure. (1) Aromatic or aliphatic dihydroxy compounds (2) Aromatic or aliphatic dicarboxylic acids (3) Aromatic hydroxycarboxylic acids (4) Aromatic diamines, aromatic hydroxyamines or aromatic aminocarboxylic acids

[0067] As a representative example of a liquid crystal polymer obtained from these raw material compounds, it is preferably a copolymer having a combination of two or more structural units selected from those represented by formulas (a) to (n) below, and containing either the structural unit represented by formula (a) or the structural unit represented by formula (e), particularly preferably a copolymer containing both the structural unit represented by formula (a) and the structural unit represented by formula (e). In addition, in view of the greater the number of aromatic rings in the liquid crystal polymer, the more likely it is to improve the dielectric properties and flame retardancy, it is preferably to contain an aromatic dihydroxy compound as (1) and an aromatic dicarboxylic acid as (2).

[0068] [Chemical 3]

[0069] As a manufacturing method for applying shear force, there are various methods such as melt spinning, melt extrusion, solution casting, and casting. However, in order to effectively orient the liquid crystal polymer molecules, it is preferable to form the liquid crystal polymer based on the melting step and the extrusion step. In particular, it is preferable to set the maximum shear rate u during extrusion, which is calculated by the following formula, to be at least 102 sec-1, and more preferably at least 104 sec-1. u=4Q / {π×(d / 2)3} [where Q represents the amount of polymer ejected per unit time through the extrusion nozzle profile (cm3 / sec), and d represents the length of the shortest diameter of the extrusion nozzle profile (cm), for example, the diameter (cm) in the case of a circular extrusion nozzle such as a tubular nozzle or a fine orifice.] If such a maximum shear rate u is used, the orientation of the liquid crystal polymer molecules becomes sufficient, and it is easy to obtain controllability of the CTE when used as a liquid crystal polymer filler.

[0070] In particular, by ejecting resin from fine orifices, liquid crystal polymer fibers with strong alignment of liquid crystal polymer molecules along the long axis can be obtained. Fine orifices refer, for example, to orifices with a diameter of 1 mm or less, and more preferably 0.5 mm or less.

[0071] The obtained fiber may also be provided as a bond formed by combining more than one. As a bond, jig threads, woven fabrics, knitwear, nonwoven fabrics may be exemplified. The conjugate can also be used in subdivisions by cutting, pulverizing, etc. In addition, it can also be set as an aggregate formed by combining multiple fillers showing shape anisotropy. For example, aggregates can also be made by heating or chemical action. Agglomerates can also be used in fine divisions by cutting, pulverizing, etc. Furthermore, with respect to the conjugates or aggregates, it is not their overall shape as long as the shape anisotropy can be mastered in the state of the fibers.

[0072] A short-fiber-like (also referred to as short-fiber-like, cut-fiber-like) liquid crystal polymer filler can be obtained, for example, by bundling and cutting liquid crystal polymer fibers fabricated utilizing the method described to a specified length. Further, grinding fibrous fillers can be produced by performing pulverization. In this case, the fibers can be frozen, and the liquid crystal polymer filler can be finely subdivided by freezing.

[0073] In addition, liquid crystal polymer fillers can also be prepared by crushing molds that improve the alignment of the liquid crystal polymer molecules without being made into fibers. In this case, the pulverization step can be passed through several times, or grading using wind, or buoyancy, sieves can be carried out.

[0074] As specific shapes of liquid crystal polymer fillers, for example, fibrous (including needle-like), plate-like, and the like as described above may be enumerated. As plate-like, discoidal, flattened, flat-plate, flaky, scaly, short stripe, etc. may be exemplified. In addition, the cross-sectional shape of liquid crystal polymer fillers is not limited to circular, but can also be star or flower, cross, and hollow. By changing the cross-sectional shape of the liquid crystal polymer filler, the surface area of ​​the liquid crystal polymer filler can be adjusted to control the adequacy to the polyimide or control the viscosity of the resin solution.

[0075] In addition, the shape of liquid crystal polymer fillers can also be deformed in the resin film. For example, by extending a resin film containing a spherical or amorphous liquid crystal polymer filler, the liquid crystal polymer filler can be made to exhibit shape anisotropy in the resin film.

[0076] For the purpose of improving dispersibility or adhesion to component (B), the liquid crystal polymer filler may also undergo surface modification treatment. Examples of surface modification treatments include plasma treatment and coating treatment. In addition, the liquid crystal polymer filler may also be a multilayer structure or a core-sheath type structure. As a multilayer structure, hollow liquid crystal polymer filler or porous liquid crystal polymer filler is preferred, and as a core-sheath type structure, the core portion is preferably a liquid crystal polymer and the sheath portion is a resin with high adhesion to component (B). As a resin with high adhesion to component (B), thermoplastic resins such as polyimide, polyamide, perfluoroalkoxy fluoropolymer (perfluoroalkoxy alkane (PFA)), and polyolefin are preferred.

[0077] Liquid crystal polymers possess excellent dielectric properties, and by using them as fillers in formulations, the deterioration of the dielectric properties of resin films can be prevented. As monomers, the liquid crystal polymer filler preferably uses materials with a relative permittivity of 2 to 3.5, more preferably 2.7 to 3.2, at 10 GHz or 20 GHz under conditions of 23°C and 50% RH, and a dielectric loss tangent preferably below 0.002, more preferably below 0.0015. By setting these values ​​within the aforementioned ranges, the deterioration of the dielectric properties of the composition when using liquid crystal polymer fillers can be prevented.

[0078] As a method for determining the dielectric properties of liquid crystal polymer fillers, the liquid crystal polymer filler can be measured directly as an aggregate or by melt molding. When it is necessary to separate the liquid crystal polymer filler and other components from the resin film, the difference in melting point or solubility between the liquid crystal polymer filler and the other components can be appropriately selected as the separation method. For example, the resin film can be dissolved in a solvent insoluble in the liquid crystal polymer filler but soluble in the other components, and the unwanted substances can be separated by filtration and centrifugation. Alternatively, the liquid crystal polymer filler can be separated by pulverizing the resin film and processing it at a temperature at which only the liquid crystal polymer filler melts.

[0079] The melting point of the liquid crystal polymer is sometimes referred to as the liquid crystal transition temperature or liquid crystallization temperature, and is preferably 290°C or higher, more preferably 300°C or higher, and even more preferably 310°C or higher. If the melting point is lower than 290°C, there is a risk of melting during the manufacturing process of electronic devices, etc., which may lead to changes in properties.

[0080] [(B) Component: A base polymer that coats and fixes component (A)] The base polymer of component (B) is a polymer that coats and fixes part or all of component (A), is the matrix resin of the resin film, and is the most abundant organic component in the composition after removing the liquid crystal polymer filler from the resin film. The base polymer of component (B) may be the same as or different from the liquid crystal polymer constituting the liquid crystal polymer filler of component (A), but since it is amorphous, it can be distinguished from the liquid crystal polymer filler of component (A) which has a specific anisotropic shape. That is, even if both component (A) and component (B) contain liquid crystal polymers, components with anisotropic shapes can be excluded from component (B). There is no particular limitation on the base polymer of component (B), but from the viewpoint of obtaining a resin film with good dielectric properties and low water absorption, it is preferably, for example, a fluoropolymer, polyolefin, polystyrene, polyimide, polyamide, polyether, polyetherketone, polyester, etc. Two or more of these may also be used. Alternatively, the precursor of component (B) can be composited with the liquid crystal polymer filler during the intermediate stage of the manufacturing process. Furthermore, for the purpose of controlling dielectric properties or CTE, air bubbles can be incorporated into component (B) to achieve porosity.

[0081] [Fluoropolymers] Fluoropolymers are not particularly limited to polymers obtained by polymerizing fluorine-containing monomers. Examples include polymers obtained by polymerizing polytetrafluoroethylene and ethylene with one or more hydrogen groups replaced by fluorine groups as raw materials. Copolymers of tetrafluoroethylene and olefins are preferred, such as tetrafluoroethylene-perfluoroalkyl vinyl ether copolymers, tetrafluoroethylene-ethylene copolymers, and tetrafluoroethylene-hexafluoropropylene copolymers. Fluoropolymers with excellent heat resistance, dielectric properties, and low water absorption are preferred.

[0082] Fluoropolymer films generally exhibit excellent heat resistance, dielectric properties, and low water absorption, especially their dielectric properties, which are superior to those of films containing only liquid crystal polymers. However, since the coefficient of linear thermal expansion exceeds 100 ppm / K, warping, peeling, or shifting due to stress caused by temperature changes is likely to occur when used in combination with dissimilar materials, especially metallic materials. In this embodiment, by compounding fluoropolymer with component (A), a resin film with fluoropolymer as the matrix resin can achieve low CTE while maintaining the aforementioned properties.

[0083] [Polyolefins] Polyolefins, with polyethylene as a representative example, refer to polymers formed by the polymerization of olefins having carbon-carbon double bonds. As monomers, ethylene, propylene, eicosene, cyclohexene, cyclohexadiene, norbornene, norbornadiene, dicyclopentadiene, and other chain or cyclic olefins are preferred, and monomers or copolymers of multiple olefins can be used.

[0084] Polyolefin films generally exhibit excellent dielectric properties and low water absorption, especially their dielectric properties, which are superior to those of films containing only liquid crystal polymers. However, they have a high coefficient of linear thermal expansion (CTE), and when used in combination with dissimilar materials, particularly metals, they are prone to warping, peeling, or shifting due to stress caused by temperature changes. By combining them with liquid crystal polymer fillers, it is possible to achieve low CTE while maintaining the aforementioned properties.

[0085] [Polystyrene] Polystyrene refers to polymers formed by the addition polymerization of compounds with aromatic rings and carbon-carbon double bonds directly or indirectly bonded to them, such as styrene and divinylbenzene.

[0086] [Polyimide] Polyimide is a polymer having an imide group represented by the following general formula (3). Furthermore, when it has an imide group or an ether bond, it is sometimes called polyamide imide or polyether imide, but in this specification, these are collectively referred to as polyimide. Such polyimide can be manufactured, for example, by known methods such as polymerizing a maleimide component with a diamine or triamine component, crosslinking a bismaleimide with an aromatic cyanate, or substantially using a diamine component and an acid dianhydride component and polymerizing them in an organic polar solvent. Heating may also be performed in this case. In such cases, to achieve a desired viscosity range, the molar ratio of the acid dianhydride component to the diamine component can be adjusted, preferably within a range of, for example, a molar ratio of 0.98 to 1.03.

[0087] [Chemical 4]

[0088] In general formula (3), Ar1 represents a tetravalent group derived from an anhydride containing a tetracarboxylic acid dianhydride residue, R2 represents a divalent diamine residue derived from a diamine, and n is an integer greater than or equal to 1.

[0089] As an acid dianhydride, preferably an aromatic tetracarboxylic acid dianhydride represented by O(OC)2-Ar1-(CO)2O, examples can be provided with the following aromatic acid anhydride residues as Ar1 acid dianhydrides.

[0090] [Chemical 5]

[0091] In addition, relative to 100 moles of all tetracarboxylic anhydride components, it is particularly preferred to contain tetracarboxylic anhydride represented by the following general formula (1) and / or general formula (2) with a total of 50 moles or more, and more preferably to contain 80 moles or more.

[0092] [Chemical 6]

[0093] In general formula (1), X represents a single bond or a divalent group selected from the following formulas. In general formula (2), the cyclic part represented by Y represents a cyclic saturated hydrocarbon group selected from four-membered rings, five-membered rings, six-membered rings, seven-membered rings or eight-membered rings.

[0094] [Chemical 7]

[0095] In the formula, Z represents -C6H4-, -(CH2)n- or -CH2-CH(-OC(=O)-CH3)-CH2-, and n represents an integer from 1 to 20.

[0096] As a diamine, preferably a diamine represented by H2N-R2-NH2, examples can be provided of diamines with the following diamine residues as R2.

[0097] [Chemical 8]

[0098] Examples of these diamines include diaminodiphenyl ether (DAPE), 2,2'-dimethyl-4,4'-diaminobiphenyl (m-TB), p-phenylenediamine (p-PDA), 1,3-bis(4-aminophenoxy)benzene (TPE-R), 1,3-bis(3-aminophenoxy)benzene (APB), and 1,4-bis(4-aminophenoxy)benzene (…). Preferred substances include 1,4-bis(4-aminophenoxy)benzene (TPE-Q), 2,2-bis[4-(4-aminophenoxy)phenyl]propane (BAPP), 2,2-bis(trifluoromethyl)benzidine (TFMB), and dimer diamines formed by replacing the two terminal carboxylic acid groups of dimer acids (dimer fatty acids) with primary aminomethyl or amino groups, as well as dimer diamine compositions with these as the main components.

[0099] In particular, the dimer diamine composition not only achieves low dielectric loss tangent but also improves the toughness of the resin film. Therefore, it is preferable to contain structural units derived from the diamine component of the dimer diamine composition, which contains 30 mol% or more, preferably 40 mol% or more, relative to all diamine components. Here, the dimer diamine composition is a refined product containing the following component (a) as the main component and the amounts of components (b) and (c) are controlled. (a) Dimer diamine (b) Monoamine compound obtained by replacing the terminal carboxylic acid group of a monocarboxylic acid compound in the range of 10 to 40 carbon atoms with a primary aminomethyl or amino group (c) Amine compound obtained by replacing the terminal carboxylic acid group of a polycarboxylic acid compound having a hydrocarbon group in the range of 41 to 80 carbon atoms with a primary aminomethyl or amino group (except for the dimer diamine).

[0100] The dimer diamine as component (a) refers to a diamine formed by replacing the two terminal carboxylic acid groups (-COOH) of a dimer acid with primary aminomethyl (-CH2-NH2) or amino (-NH2) groups. It can be defined as a diamine compound obtained by replacing the terminal carboxylic acid groups of a dicarboxylic acid compound having 18 to 54 carbon atoms, preferably 22 to 44 carbon atoms, with primary aminomethyl or amino groups. The dimer diamine composition preferably uses a dimer diamine composition in which the content of the dimer diamine as component (a) is increased to 96% by weight or more, preferably 97% by weight or more, and more preferably 98% by weight or more by purification methods such as molecular distillation. By setting the content of the dimer diamine as component (a) to 96% by weight or more, the expansion of the molecular weight distribution of polyimide can be suppressed. Furthermore, if technically feasible, it is preferable that the entire (100% by weight) of the dimer diamine composition contains the dimer diamine as component (a).

[0101] The dimer diamine composition can be a commercially available product, preferably refined to reduce components other than the dimer diamine as component (a), for example, preferably to make component (a) 96% by weight or more. There are no particular limitations on the refining method, but known methods such as distillation or precipitation refining are preferred. Examples of commercially available dimer diamine compositions include PRIAMINE 1073 (trade name), PRIAMINE 1074 (trade name), and PRIAMINE 1075 (trade name) manufactured by Croda Japan.

[0102] The synthesized polyamide or polyimide is generally advantageously used as a reaction solvent solution, and can be concentrated, diluted, or replaced with other organic solvents as needed to form a resin composition. There are no particular limitations on the method of amide-modifying the polyamide; for example, heat treatment, such as heating in the solvent at a temperature range of 80°C to 400°C for 1 hour to 24 hours, is preferred.

[0103] Furthermore, when the polyimide has a ketone group, the ketone group is reacted with the amino group of an amino compound (hereinafter sometimes referred to as "crosslinking-forming amino compound") having at least two primary amino groups as functional groups to form a C=N bond, thereby forming a crosslinked structure. By forming a crosslinked structure, the heat resistance of the polyimide can be improved. As preferred tetracarboxylic anhydrides for forming polyimides with ketone groups, examples include 3,3',4,4'-benzophenone tetracarboxylic dianhydride (BTDA). As diamine compounds, examples include aromatic diamines such as 4,4'-bis(3-aminophenoxy)benzophenone (BABP) and 1,3-bis[4-(3-aminophenoxy)benzoyl]benzene (BABB).

[0104] Examples of amine compounds for crosslinking formation include (I) diacetic acid compounds, (II) aromatic diamines, and (III) aliphatic amines. Among these, diacetic acid compounds are preferred because they can balance the preservation stability of the varnish with the reduction of curing time. Examples of preferred diacetic acid compounds include diacetic acid oxalate, diacetic acid malonate, diacetic acid succinate, diacetic acid glutarate, diacetic acid adipic acid, diacetic acid pimecrolate, diacetic acid octanoate, diacetic acid azelaate, diacetic acid sebacate, diacetic acid dodecanoate, diacetic acid maleate, diacetic acid fumarate, and diethylene glycol. Diacylhydrazine compounds include diacylhydrazine tartrate, diacylhydrazine malate, diacylhydrazine phthalate, diacylhydrazine isophthalate, diacylhydrazine terephthalate, diacylhydrazine 2,6-naphthoic acid, diacylhydrazine 4,4-bisphenyldiacylhydrazine, diacylhydrazine 1,4-naphthoic acid, diacylhydrazine 2,6-pyridinediic acid, and diacylhydrazine itaconic acid. These diacylhydrazine compounds can be used alone or in combination of two or more.

[0105] In the case of crosslinking polyimide with a crosslinking-forming amino compound, the crosslinking-forming amino compound is added to a resin solution containing polyimide, causing a condensation reaction between the ketone groups in the polyimide and the primary amino groups of the crosslinking-forming amino compound. Through this condensation reaction, the resin solution is cured to form a cured product. In this case, the amount of the crosslinking-forming amino compound added is preferably 0.004 mol to 1.5 mol, more preferably 0.005 mol to 1.2 mol, relative to 1 mol of ketone groups. Regarding the amount of crosslinking-forming amino compounds added, such as those with a total amount of primary amino groups less than 0.004 mol relative to 1 mol of ketone groups, there is a tendency that the crosslinking of the crosslinking-forming amino compounds is insufficient, thus making it difficult to exhibit the heat resistance after curing. If the amount of crosslinking-forming amino compounds added exceeds 1.5 mol, the unreacted crosslinking-forming amino compounds will act as thermoplasticizers, which tends to reduce the heat resistance of the adhesive layer.

[0106] The conditions for the condensation reaction used to carry out the crosslinking formation are not particularly limited if the ketone group in the polyimide reacts with the primary amino group of the amino compound used for crosslinking formation to form an imine bond (C=N bond). Regarding the temperature of the heating condensation, for reasons such as releasing the water generated by the condensation to the outside of the system, or simplifying the condensation step when the heating condensation reaction is carried out after the synthesis of the polyimide, a temperature range of 120°C to 220°C is preferred, and more preferably, a temperature range of 140°C to 200°C is preferred. The reaction time is preferably about 30 minutes to 24 hours. The endpoint of the reaction can be determined, for example, by measuring the infrared absorption spectrum using a Fourier transform infrared spectrophotometer (commercially available: FT / IR620 manufactured by Nippon Spectrophotometer), and confirmed by the reduction or disappearance of the absorption peak near 1670 cm⁻¹ derived from ketone groups in polyimide resin, and the appearance of the absorption peak near 1635 cm⁻¹ derived from imide groups.

[0107] The above examples of cross-linked polyimides that form a cross-linked structure by forming imine bonds have been given to illustrate the purpose of imparting heat resistance to polyimides. However, the method is not limited to this. As a curing method for polyimides, compounds with unsaturated bonds, such as epoxy resins, epoxy resin curing agents, maleimides, activated ester resins, and resins with styrene skeletons, can also be formulated for curing.

[0108] Polyimide films generally exhibit excellent heat resistance, and there are also polyimide films with low linear thermal expansion coefficients. However, due to the polarity of the propylene structure, it has a high dielectric loss tangent and high water absorption. In the design of the resin composition, a trade-off must be made between low linear thermal expansion coefficient, low dielectric loss tangent, and low water absorption. By compounding with liquid crystal polymer fillers, it is possible to achieve low dielectric loss tangent and low water absorption while maintaining the aforementioned properties. Furthermore, it is expected that the heat resistance will be further improved compared to films containing only liquid crystal polymers.

[0109] [Polyamide] Polyamide is not particularly limited, and is a polymer with amide bonds (-CO-NH-) in its backbone. Such polyamides can be manufactured by known methods such as ring-opening reactions of amides, polymerization of diamine components with dicarboxylic acid derivatives, and polymerization of carboxylic acid derivatives containing amine groups. From the viewpoint of heat resistance, polyamides containing an aromatic backbone (also collectively referred to as aromatic polyamides) are preferred.

[0110] Polyamide generally exhibits excellent heat resistance, and polyamide films with low coefficients of linear thermal expansion also exist. However, due to the polarity of the amide structure, it has a high dielectric loss tangent and high water absorption. In the design of the resin composition, lowering the dielectric loss tangent and reducing water absorption can lead to an increase in the coefficient of linear thermal expansion or a decrease in heat resistance. By compounding with liquid crystal polymer fillers, it is possible to achieve low dielectric loss tangent and low water absorption while maintaining the aforementioned properties. Furthermore, it is expected that the heat resistance will be further improved compared to films containing only liquid crystal polymers.

[0111] [Polyether] Polyether is not particularly limited, and is a polymer with ether bonds (-O-) in its backbone. Such polyethers can be manufactured by known methods such as free radical polymerization of phenols. From the viewpoint of heat resistance, polyphenylene oxide (also known as polyphenylene oxide) containing an aromatic backbone is preferred.

[0112] Polyphenylene ether (PPE) is generally used in alloys with other synthetic resins to improve processability and functionality, and is referred to as modified PPE. Modified PPE exhibits excellent heat resistance, and by combining it with liquid crystal polymer fillers, it can achieve a low coefficient of linear thermal expansion, a low dielectric loss tangent, and low water absorption. Furthermore, it is expected to further improve heat resistance compared to films containing only liquid crystal polymers.

[0113] [Polyetherketone] Polyetherketone is not particularly limited and is a polymer with ether bonds (-O-) and carbonyl groups (-CO-) in its backbone. Generally, polyetherketone is referred to as polyetherketone, polyetheretherketone, polyetherketoneketone, or polyetherketone ester containing ester bonds, depending on its bond configuration. From the viewpoint of heat resistance, it is preferable to have an aromatic backbone.

[0114] Polyetheretherketone (PEEK) films generally exhibit excellent heat resistance, and some films have been modified to have a low coefficient of linear thermal expansion. However, due to their ketone structure, it is difficult to reduce the dielectric loss tangent. By combining them with liquid crystal polymer fillers, a low dielectric loss tangent can be achieved while maintaining the aforementioned properties. Furthermore, it is expected that the heat resistance will be further improved compared to films containing only liquid crystal polymers.

[0115] [Polyester] Polyester is not particularly limited, but is a polymer with ester bonds (-COO-) in its backbone. Such polyesters can be manufactured by known methods such as polymerization of glycols and dicarboxylic acid derivatives, and transesterification of phenol acetate and carboxylic acid. From the viewpoint of heat resistance, polyesters containing an aromatic backbone, such as divalent phenols, are preferred.

[0116] The polyester used as component (B) preferably has a melting point lower than that of the liquid crystal polymer filler. Therefore, the composite can be performed while maintaining the liquid crystal polymer filler.

[0117] [Other Polymers] The dimerized diamine composition not only achieves low dielectric loss tangent but also improves the toughness of the resin film. Therefore, as the base polymer for component (B), examples include thermoplastic bismaleimide resin, thermoplastic epoxy resin, and thermoplastic polyamide resin, which contain at least 30 moles, preferably at least 40 moles, of dimerized diamine compositions relative to all diamine components, and are used as polymers that use diamine components as raw materials or curing agents. By incorporating liquid crystal polymer fillers of component (A) into these polymers, excellent dielectric properties and dimensional stability can be achieved, thereby forming a resin film suitable as a circuit board material.

[0118] [Precursor] As the parent polymer of component (B), a precursor of the polymer illustrated above may be used. A precursor refers to a substance that exists before the formation of a substance. In this specification, oligomers are also included as precursors of resins. Examples of preferred precursors include those that are soluble in solvents, such as polymers that are insoluble in solvents. Specifically, most fully aromatic polyimides are insoluble in common solvents, but polyamides, as precursors, are readily soluble in amide-based solvents. Furthermore, even when the high molecular weight polyester is insoluble in solvents, its oligomers may be solvent-soluble. Generally, oligomers refer to polymers with a low degree of polymerization. In this specification, oligomers refer to polymers with a repeat number in the range of 2 to 50 and a molecular weight of 5000 or less. When oligomers have active sites, the degree of polymerization can be increased by energizing the reaction through heating or other means, by increasing the solution concentration, or by adding activators or crosslinking agents.

[0119] [Any Components] The resin film may contain, in addition to components (A) and (B), pigments, flame retardants, heat dissipation agents, etc., as inorganic components, without impairing the effects of the invention. Examples of inorganic components include amorphous silicon dioxide, crystalline silicon dioxide (e.g., quartz silicon dioxide, white silica silicon dioxide), aluminum oxide, magnesium oxide, beryllium oxide, niobium oxide, titanium oxide, boron nitride, aluminum nitride, silicon nitride, aluminum fluoride, calcium fluoride, magnesium fluoride, potassium fluorosilicate, and metal salts of phosphonates. One or more of these may be used.

[0120] In addition, component (B) may also include, for example, catalysts, plasticizers, elastomers, coupling agents, hardeners, hardening accelerators, and heat-insulating materials as additives. These additives may be used alone or in combination. Here, there is no particular limitation on the plasticizer, and a plasticizer corresponding to the type of resin may be used. Examples of preferred plasticizers include trimellitic esters, phthalates, low molecular weight polyesters, phosphate esters, hydrogenated styrene-based and / or hydrogenated butadiene-based elastomers, rubber particles, imidazole compounds, acid anhydrides, dicyandiamide, acehydrazine, amine adducts, strontium salts, formaldehyde, ketimines, tertiary amines, and organophosphorus compounds.

[0121] The content of the additive is not particularly limited and can be appropriately selected according to the resin composition and process conditions used. For example, relative to the content of component (B), it is preferably 110% by weight or less, and more preferably 90% by weight or less.

[0122] [Formulation Ratio] In the resin film, the formulation ratio of component (A) and component (B) can be appropriately set according to their types. Relative to the total amount of component (A) and component (B), the content of component (A) is preferably in the range of 2% by weight or more and 80% by weight or less, more preferably in the range of 5% by weight or more and 60% by weight or less, and most preferably in the range of 10% by weight or more and 50% by weight or less. When the content of component (A) is less than 2% by weight, it is difficult to exhibit the effects of the invention; if it exceeds 80% by weight, the liquid crystal polymer filler may sometimes be exposed on the film surface, thus impairing smoothness.

[0123] The resin film of this embodiment having the above composition has the following conditions (i), (ii) and (iii).

[0124] [Condition (i): Average linear thermal expansion coefficient (CTE)] The resin film preferably has an absolute value of an average linear thermal expansion coefficient of 50 ppm / K or less at 250°C to 100°C, and more preferably 30 ppm / K or less. If the absolute value of the average linear thermal expansion coefficient is 50 ppm / K or less, the rate of dimensional change during heating can be suppressed, thus preventing positional shift when wiring, such as wiring boards, is joined together. Furthermore, if the absolute value of the average linear thermal expansion coefficient is 30 ppm / K or less, the wiring can be made more precise. In addition, if the absolute value of the average linear thermal expansion coefficient exceeds 50 ppm / K, stress will be generated at the interface when bonding or adhering to dissimilar materials such as metals, which can easily lead to brittleness. Furthermore, the average linear thermal expansion coefficient under condition (i) refers to the linear thermal expansion coefficient along the length direction (MD direction) of the resin film.

[0125] [Condition (ii): Dielectric Loss Tangent] When the resin film is used as an insulating resin layer in a circuit board, in order to reduce dielectric loss during high-frequency signal transmission, the dielectric loss tangent (Tanδ) at 20 GHz, as a whole film, is preferably 0.003 or less, and more preferably 0.002 or less, when measured using a split dielectric resonator (SPDR) at 23°C and 50%RH. To improve the transmission loss of the circuit board, it is particularly important to control the dielectric loss tangent of the insulating resin layer. By keeping the dielectric loss tangent within the aforementioned range, the effect of reducing transmission loss is increased. Therefore, for example, when the resin film is used as an insulating resin layer in a high-frequency circuit board, transmission loss can be reduced efficiently. If the dielectric loss tangent at 20 GHz exceeds 0.003, when the resin film is used as an insulating resin layer in a circuit board, adverse conditions such as increased electrical signal loss are likely to occur in the high-frequency signal transmission path. There is no particular limitation on the lower limit of the dielectric loss tangent at 20 GHz, but the physical property control needs to be considered when the resin film is used as the insulating resin layer of the circuit board.

[0126] [Condition (iii): Water Absorption Rate] To reduce the impact of moisture when used in circuit boards such as printed wiring boards, the water absorption rate of the resin film should preferably be 0.2% by weight or less, and more preferably 0.1% by weight or less. Here, water absorption rate refers to the water absorption rate after immersion in pure water at 23°C for 24 hours (the same meaning applies in this specification). If the water absorption rate exceeds 0.2% by weight, it will be easily affected by humidity when used in circuit boards such as FPCs, and adverse conditions such as fluctuations in the transmission speed of high-frequency signals may occur. That is, if the water absorption rate of the resin film exceeds the above range, it will easily absorb water with a high dielectric constant, which will lead to an increase in the dielectric constant and dielectric loss tangent, and adverse conditions such as loss of electrical signals in the transmission path of high-frequency signals may occur.

[0127] [Function] Existing resin films struggle to simultaneously satisfy both conditions (i) and (ii), but the resin film of this embodiment satisfies both conditions (i) and (ii) by setting the X / Y ratio of the liquid crystal polymer filler of component (A) to 2.5 or more. The reason for this is not fully explained, but if the X / Y ratio of the liquid crystal polymer filler with a low dielectric loss tangent is 2.5 or more, a shear force is applied during the manufacturing process of the liquid crystal polymer filler, causing the liquid crystal polymer molecular chains to align in the same direction. As a result, it can be inferred that the average coefficient of linear thermal expansion (CTE) of the resin film containing the liquid crystal polymer filler is significantly reduced. Thus, the ability to control the average coefficient of linear thermal expansion (CTE) of the resin film by utilizing the shape anisotropy of the filler is an insight discovered for the first time in this invention.

[0128] [Thickness] The overall thickness of the resin film is preferably in the range of 15 μm to 250 μm, and more preferably in the range of 25 μm to 200 μm. If the thickness of the resin film is less than 15 μm, the surface smoothness of the film may deteriorate, and defects such as wrinkles in the metal foil and damage to the resin film may easily occur during the handling process when manufacturing metal-clad laminates. Conversely, if the thickness of the resin film exceeds 250 μm, there is a tendency for the resin film to become less flexible.

[0129] [Method for manufacturing a resin film] The method for manufacturing a resin film may include: a step of preparing a first polymer as a liquid crystal polymer and a second polymer that is the same as or different from the first polymer; a step of aligning the molecules of the first polymer; and a step of compounding the first polymer with the second polymer as a filler. Here, the method of compounding the first polymer with the second polymer as a filler may be appropriately selected according to the shape of the liquid crystal polymer filler of component (A) and the combination of component (B), and is therefore not particularly limited. As a preferred method, examples include (1) to (3) below: (1) A method of coating a mixture of liquid crystal polymer filler of component (A), component (B) and a solvent or dispersion medium as needed onto any substrate and drying it, thereby forming a film; (2) A method of immersing liquid crystal polymer filler of component (A) in a liquid containing component (B), thereby forming a film; (3) A method of laminating liquid crystal polymer filler of component (A) and component (B) formed into a film and pressing them together, etc.

[0130] Preferred solvents or dispersion media include, for example: N,N-dimethylformamide (DMF), N,N-dimethylacetamide (DMAc), N,N-diethylacetamide, N-methyl-2-pyrrolidone (NMP), 2-butanone, dimethylsulfoxide (DMSO), hexamethylformamide, N-methylcaprolactam, dimethyl sulfate, cyclohexane, dioxane, tetrahydrofuran, diethylene glycol dimethyl ether (diglyme), triethylene glycol dimethyl ether (triglyme), cresol, water, etc. Two or more of these solvents or dispersion media may be used in combination, and furthermore, aromatic hydrocarbons such as xylene and toluene may be used in combination. There are no particular restrictions on the content of the solvent or dispersion medium, but it is preferable to adjust it to an amount of about 5% to 70% by weight.

[0131] When a resin solution containing a liquid crystal polymer filler with a long axis length of 10 mm or less is coated onto a substrate, shear stress is generated in the resin solution, and the long axis direction of the filler is aligned with the resin flow direction. Therefore, the film properties may sometimes exhibit in-plane anisotropy. To suppress this in-plane anisotropy, coating methods that do not easily generate shear stress in a specific direction, such as spray coating machines or curtain coating machines, can be used. Alternatively, methods can be used to disrupt the aligned filler by applying an electromagnetic field or causing the obtained film to extend in a specific direction after coating. Furthermore, films with in-plane anisotropy can be laminated at specific angles.

[0132] This embodiment also provides a resin composition containing the aforementioned component (A) and component (B). The composition, mixing ratio, etc., of component (A) and component (B) in the resin composition of this embodiment are as described for the resin film. In addition, the resin composition may also contain any of the exemplary components, solvents, or dispersion media as needed.

[0133] {Second Embodiment} [Resin Composition] The resin composition of this embodiment contains the following components (A) to (C): (A) fibrous liquid crystal polymer filler, (B) thermoplastic resin and / or thermosetting resin as the base polymer, and (C) particulate metal oxide filler and / or particulate thermoplastic resin filler.

[0134] [(A) Component: Fibrous Liquid Crystal Polymer Filler] The fibrous liquid crystal polymer filler of component (A) is a fibrous filler with anisotropic shape. Since the average coefficient of thermal expansion (hereinafter sometimes simply referred to as "CTE") in the long axis direction of the filler is low, it helps to reduce the CTE of the resin film. In addition, since the fibrous liquid crystal polymer filler is flexible, it is effective in maintaining the flexibility of the resin film. In this embodiment, "fibrous" means that the ratio L / D of the average length L of the long axis of the filler to the average diameter D of the short axis orthogonal to the long axis is 2.5 or more. The L / D of the fibrous liquid crystal polymer filler is preferably 4.5 or more, more preferably 15.0 or more, and even more preferably 30.0 or more. When L / D is less than 2.5, the fibrous liquid crystal polymer filler is prone to disordered arrangement in the resin film, thereby reducing the improvement effect of CTE. In addition, the fibrous liquid crystal polymer filler tends to agglomerate with each other, which is undesirable.

[0135] The average length L of the long axis of the fibrous liquid crystal polymer filler can be appropriately selected according to the composite method of the fibrous liquid crystal polymer filler and component (B). Considering the dispersibility when the fibrous liquid crystal polymer filler is dispersed in component (B), it is preferably in the range of 0.1 mm to 5 mm, and more preferably in the range of 0.2 mm to 1 mm. When the average length L of the long axis is less than 0.1 mm, when a resin film is formed by casting the resin composition, the proportion of the fibrous liquid crystal polymer filler aligned in the thickness direction of the film increases, resulting in a reduction in CTE. On the other hand, if the average length L of the long axis exceeds 5 mm, the fibrous liquid crystal polymer filler becomes entangled with each other, making it difficult to cast the resin composition to form a resin film. If the average length L of the long axis is within the aforementioned range, the processability is not compromised, and the surface smoothness during resin film formation is not deteriorated, resulting in a resin film with a good appearance.

[0136] The average diameter D of the short axis of the fibrous liquid crystal polymer filler is preferably in the range of 5 μm to 50 μm, and more preferably in the range of 10 μm or more and 30 μm or less. If the average diameter D of the short axis is within the range described above, the surface smoothness during resin film formation will not deteriorate, and a resin film with good appearance can be obtained.

[0137] The liquid crystal polymer constituting the fibrous liquid crystal polymer filler can be the same polymer as in the first embodiment. That is, the structure, structural units, manufacturing method, surface modification treatment, dielectric properties and their measurement methods, melting point, etc., of the liquid crystal polymer constituting the liquid crystal polymer filler are the same as in the first embodiment.

[0138] The cross-sectional shape of the fibrous liquid crystal polymer filler is not limited to a circle, but can also be star-shaped, flower-shaped, cross-shaped, or hollow. By changing the cross-sectional shape of the fibrous liquid crystal polymer filler, the surface area of ​​the fibrous liquid crystal polymer filler can be adjusted to control the adhesion with component (B) or to control the viscosity of the resin solution.

[0139] [(B) Component: Thermoplastic resin and / or thermosetting resin as the base polymer] Component (B) is the component that becomes the matrix resin when forming a resin film. Examples of thermoplastic resins that can be used as component (B) include thermoplastic polyimide, thermoplastic bismaleimide resin, thermoplastic epoxy resin, thermoplastic polyamide, liquid crystal polymer, fluoropolymer, polyolefin, polystyrene, polyether, polyetherketone, polyester, etc. Examples of thermosetting resins that can be used as component (B) include: non-thermoplastic polyimide, thermosetting epoxy resin, thermosetting polyphenylene ether, phenolic resin, etc. Two or more of the thermoplastic resins and thermosetting resins can be used in combination. In addition, in this specification, "thermoplastic resin" generally refers to a resin that softens by heating, hardens by cooling, and can be repeatedly subjected to the above operations, and whose glass transition temperature (Tg) can be clearly identified; "non-thermoplastic resin" generally refers to a resin that does not soften even when heated. The material of component (B) may be the same as or different from the fibrous liquid crystal polymer filler of component (A) or the particulate thermoplastic resin filler of component (C), but component (B) is of amorphous shape and can be distinguished from the fibrous liquid crystal polymer filler of component (A) or the particulate thermoplastic resin filler of component (C). That is, even if the materials of components (A), (B) and (C) all contain liquid crystal polymers, components with fibrous or particulate shapes can be excluded from component (B).

[0140] As component (B), the precursor of the illustrated polymer can be used. A precursor refers to a substance that exists before the formation of a substance. In this specification, oligomers are also included as precursors of resins. For example, in the case of polyimides, polyamide is equivalent to a precursor. As a preferred use of a precursor, cases where the precursor is soluble in a polymer that is insoluble in a solvent can be cited. Specifically, most fully aromatic polyimides are insoluble in common solvents, but polyamide, as a precursor, is readily soluble in amide-based solvents. In addition, even when the high molecular weight of the polyester is insoluble in a solvent, its oligomer can be solvent-soluble. Generally, oligomers refer to polymers with a low degree of polymerization. In this specification, oligomers refer to polymers with a repeat number in the range of 2 to 50 and a molecular weight of 5000 or less. When oligomers have active sites, the degree of polymerization can be increased by energizing the reaction through heating or other means, increasing the solution concentration, or adding activators or crosslinking agents.

[0141] Among the resins that can be used as component (B), particularly preferred resins are polyimide (thermoplastic, non-thermoplastic), liquid crystal polymers, and fluoropolymers, which can be used with the resins described in the first embodiment.

[0142] Polyimide films generally exhibit excellent heat resistance, and low-CTE polyimide films also exist. However, due to the polarity of the polyimide structure, it has a high dielectric loss tangent and high water absorption. In the design of the resin composition, low CTE and low dielectric loss tangent are trade-offs. In this invention, by combining it with components (A) and (C), a resin film with polyimide as the matrix resin can achieve low dielectric loss tangent while maintaining the aforementioned characteristics.

[0143] Furthermore, fluoropolymer films generally exhibit excellent heat resistance, dielectric properties, and low water absorption, especially their dielectric properties, which are superior to those of films containing only liquid crystal polymers. However, fluoropolymer films generally have a CTE exceeding 100 ppm / K, making them prone to warping, peeling, or shifting due to stress caused by temperature changes when used in combination with dissimilar materials, particularly metallic materials. In this invention, by compounding fluoropolymer with components (A) and (C), a resin film with fluoropolymer as the matrix resin can achieve a low CTE while maintaining the aforementioned properties.

[0144] In addition, liquid crystal polymer films generally have excellent dielectric properties. In order to reduce the CTE difference between the MD direction and the TD direction, special manufacturing methods such as expansion methods are required. In this invention, by compounding the liquid crystal polymer with components (A) and (C), the CTE difference between the MD direction and the TD direction of the resin film with liquid crystal polymer as the matrix resin can be mitigated by a simple method without using special manufacturing methods, and the dielectric properties can be further improved, thereby achieving low dielectric loss tangent.

[0145] [(C) Components: Particulate metal oxide filler and / or particulate thermoplastic resin filler] Particulate metal oxide filler: The particulate metal oxide filler of component (C) refers to a filler with metal oxide as the main component and a particulate shape. "Particulate" means that when the average length of the major axis is set as X, and the average length of the shortest minor axis orthogonal to the major axis is set as Y, X / Y is less than 2.5, preferably 2 or less, more preferably 1.5 or less, for example, it can be plate-shaped, spherical, polyhedral, etc. Furthermore, "plate-shaped" is used to include, for example, flat, plate-shaped, sheet-shaped, scaly, etc. The thickness of the particulate metal oxide filler refers to a thickness that is sufficiently smaller than the major or minor axis of the planar portion, preferably 1 / 2 or less. By formulating particulate metal oxide filler, the CTE and dielectric loss tangent during resin film formation can be reduced. In addition, particulate metal oxide fillers do not undergo thermal decomposition at normal combustion temperatures, so flame retardancy can be improved by adding them.

[0146] As particulate metal oxide fillers, spherical fillers are preferred. Spherical refers to particles with a shape close to a sphere and a ratio of average major axis to average minor axis of 1 or close to 1. Furthermore, for particulate metal oxide fillers, it is preferable that 90% or more of the particles have a roundness of 0.7 or higher, more preferably 0.9 or higher. The roundness of the particulate metal oxide filler can be determined using image analysis, assuming a circle with the same projected area as the photographed particle, and by the ratio of the circumference of the circle to the circumference of the particle. If the roundness is less than 0.7, the surface area increases, which may adversely affect the dielectric properties, leading to a greater increase in viscosity when mixed into the resin solution, making it difficult to handle. Furthermore, it is preferable to have a value that substantially corresponds to the roundness value in the three-dimensionally determined roundness.

[0147] The particulate metal oxide filler preferably contains 50% by weight or more of a metal oxide, more preferably 70% by weight or more. Examples of metal oxides constituting the particulate metal oxide filler include amorphous silicon dioxide, crystalline silicon dioxide, aluminum oxide, magnesium oxide, beryllium oxide, niobium oxide, and titanium oxide. Among these, from the viewpoint of achieving a low dielectric loss tangent when forming a resin film, as described later, crystalline silicon dioxide particles having a white silica crystalline phase or a quartz crystalline phase are preferred.

[0148] In particulate metal oxide fillers, compared with ordinary silica particles, silica particles with a white silica crystalline phase have excellent dielectric properties (for example, silica particles containing more than 90% by weight of the white silica crystalline phase have a dielectric loss tangent of about 0.0001 per monomer at 20 GHz), which can greatly contribute to the low dielectric loss tangent of the resin film. Therefore, from the viewpoint of achieving a low dielectric loss tangent when forming a resin film, as a whole silica particles, it is preferable that the total area of ​​the peaks originating from the white silica crystalline phase and the quartz crystalline phase in the range of 2θ = 10° to 90° of the X-ray diffraction spectrum of CuKα rays is more than 20% by weight, more preferably more than 40% by weight, and ideally more than 80% by weight. By increasing the proportion of siliceous silica and / or quartz crystalline phases in the overall silica particles, further reduction in the dielectric loss tangent of the resin film can be achieved. If the area ratio of peaks originating from the siliceous silica and quartz crystalline phases in the overall silica particles is less than 20% by weight, the effect on improving dielectric properties is not significant. Furthermore, in cases where the peaks of the object in X-ray diffraction analysis are difficult to separate from the broad peaks of amorphous materials or overlap with peaks of other crystalline phases, various known analytical methods, such as the internal standard method or the PONKCS method, can be used.

[0149] Commercially available particulate metal oxide fillers can be appropriately selected for use. For example, spherical white silica powder (manufactured by Nippon Steel Chemical & Materials Co., Ltd., trade name: CR10-20) and spherical amorphous silica powder (manufactured by Nippon Steel Chemical & Materials Co., Ltd., trade name: SC70-2) are preferred. Furthermore, particles of two or more different metal oxides can be used as particulate metal oxide fillers.

[0150] Particulate thermoplastic resin filler: (C) The particulate thermoplastic resin filler refers to a filler with thermoplastic resin as the main component and in the form of particles. Furthermore, "particulate" means that when the average length of the major axis is set as X, and the average length of the shortest minor axis orthogonal to the major axis is set as Y, X / Y is less than 2.5, preferably 2 or less, and more preferably 1.5 or less. For example, it can be plate-shaped, spherical, polyhedral, etc. Furthermore, "plate-shaped" is used to include, for example, flat, plate-shaped, sheet-shaped, scaly, etc. The thickness of the particulate thermoplastic resin filler refers to a thickness that is sufficiently smaller than the major or minor axis of the planar portion, preferably 1 / 2 or less. By formulating particulate thermoplastic resin filler, the CTE and dielectric loss tangent during resin film formation can be reduced.

[0151] As a particulate thermoplastic resin filler, spherical fillers are preferred. Spherical refers to particles that are nearly spherical in shape and whose average major axis to average minor axis ratio is 1 or close to 1.

[0152] Regarding the type of resin constituting the particulate thermoplastic resin filler, there is no particular limitation if it is a thermoplastic resin, but it is preferable to use, for example, thermoplastic polyimide, liquid crystal polymer, fluoropolymer, polyolefin, etc. In this embodiment, when components (A), (B), and (C) are all resin materials, a resin film without inorganic fillers can be formed. In this case, when forming the resin film, the disadvantages of the film becoming brittle or having its surface smoothness damaged due to inorganic fillers can be avoided. In addition, for example, when performing laser processing during the manufacturing process of printed circuit boards, the reduction in precision caused by inorganic fillers can be avoided, thus ensuring good laser processability. Furthermore, particles of two or more different types of resins can also be formulated.

[0153] Among the resin types described, liquid crystal polymers, in particular, have a significant effect on reducing the dielectric loss tangent when forming a resin film, and are made of the same material as the fibrous liquid crystal polymer filler in component (A). Therefore, the control of the physical properties of the resin composition and the resin film becomes easier, making it the optimal resin. Furthermore, as the liquid crystal polymer, polymers with the same structure as component (A) can be preferably used, and as thermoplastic polyimide and fluororesin, polymers with the same structure as component (B) can be preferably used.

[0154] Particulate thermoplastic resin fillers may be selected from commercially available products. For example, substances made by processing commercially available molded products such as UENO LCP (registered trademark) manufactured by Ueno Pharmaceutical Co., Ltd., VECTRA / ZENITE (registered trademark) manufactured by Celanese Japan Co., Ltd., Laperos (registered trademark) manufactured by Polyplastics Co., Ltd., Siveras (registered trademark) manufactured by Toray Industries, Ltd., Xydar (registered trademark) manufactured by ENEOS Co., Ltd., Teflon (registered trademark) manufactured by Mitsui Chemours Fluoroproducts Co., Ltd., Fluon (registered trademark) manufactured by AGC Co., Ltd., and ZEONEX (registered trademark) manufactured by ZEON Co., Ltd. into powder form are preferred. Furthermore, as a particulate thermoplastic resin filler, particles of two or more different thermoplastic resins can also be used together.

[0155] In addition, as component (C), particulate metal oxide fillers and particulate thermoplastic resin fillers may also be used together.

[0156] The volume average particle size D50 of the particulate metal oxide filler and the particulate thermoplastic resin filler is preferably in the range of 1 μm to 100 μm, and more preferably in the range of 2 μm to 50 μm. Here, "volume average particle size D50" is the value of 50% of the cumulative value in the frequency distribution curve obtained by measuring the particle size distribution using a volume-based method of laser diffraction. If the volume average particle size D50 is less than 1 μm, the specific surface area of ​​the particulate metal oxide filler increases, and adsorbed water or polar groups on the particle surface may sometimes affect the dielectric properties. If the volume average particle size D50 exceeds 100 μm, it may appear as a depression or protrusion on the resin film surface, sometimes deteriorating the smoothness of the film surface. If the volume average particle size D50 of the particulate metal oxide filler is in the range of 1 μm to 100 μm, it becomes similar in size to the average diameter D of the minor axis of the fibrous liquid crystal polymer filler of composition (A). Therefore, it does not affect the smoothness of the film surface. The particulate metal oxide filler can effectively hinder the orientation and alignment of the fibrous liquid crystal polymer filler. In addition, by using an appropriate particle size, the amount of adsorbed water or surface functional groups can be reduced, thereby effectively improving the dielectric properties. Therefore, the surface smoothness of the resin film formed from the resin composition is not deteriorated, and a resin film with a good appearance and a low dielectric loss tangent with mitigated CTE anisotropy can be obtained.

[0157] Furthermore, regarding the relationship between the average diameter D of the minor axis of the fibrous liquid crystal polymer filler of component (A) and the volume average particle size D50 of the particulate metal oxide filler and particulate thermoplastic resin filler of component (C), from the viewpoint of effectively hindering the orientation and alignment of the fibrous liquid crystal polymer filler and mitigating the anisotropy of CTE in the resin film, [D / D50] is preferably in the range of 1 to 50, and more preferably in the range of 2 to 30. If [D / D50] is in the range of 1 to 50, the particulate metal oxide filler strongly plays the role of hindering the orientation and alignment of the fibrous liquid crystal polymer filler, and the CTE difference between the MD direction and the TD direction during resin film formation can be reduced.

[0158] Furthermore, regarding the relationship between the average length L of the long axis of the fibrous liquid crystal polymer filler of component (A) and the volume average particle size D50 of the particulate metal oxide filler and particulate thermoplastic resin filler of component (C), from the viewpoint of effectively hindering the orientation and alignment of the fibrous liquid crystal polymer filler and mitigating the anisotropy of CTE in the resin film, [L / D50] is preferably in the range of 10 to 1000, and more preferably in the range of 20 to 500. If [L / D50] is in the range of 10 to 1000, the particulate metal oxide filler strongly plays the role of hindering the orientation and alignment of the fibrous liquid crystal polymer, and the CTE difference between the MD direction and the TD direction during resin film formation can be reduced.

[0159] [Any Components] The resin composition of this embodiment may contain any components other than components (A) to (C) without impairing the effects of the invention. Examples of arbitrary components include solvents such as organic solvents, organic or inorganic fillers other than components (A) and (C), catalysts, plasticizers, elastomers, coupling agents, hardeners, pigments, flame retardants, heat dissipation agents, etc. Examples of organic solvents include N,N-dimethylformamide (DMF), N,N-dimethylacetamide (DMAc), N,N-diethylacetamide, N-methyl-2-pyrrolidone (NMP), 2-butanone, dimethylsulfoxide (DMSO), hexamethylformamide, N-methylcaprolactam, dimethyl sulfate, cyclohexane, dioxane, tetrahydrofuran, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, and cresol. Two or more of these solvents may be used in combination, and aromatic hydrocarbons such as xylene and toluene may also be used in combination. There are no particular limitations on the content of the organic solvent, but it is preferable to use an amount adjusted to approximately 5% to 50% by weight of component (B). Organic fillers other than components (A) and (C) can include, for example, elastomer particles and rubber particles. Inorganic fillers other than component (C) can include, for example, nitrides such as boron nitride, aluminum nitride, and silicon nitride, fluorides such as aluminum fluoride, calcium fluoride, magnesium fluoride, and potassium fluorosilicate, and metal salts such as phosphonates. One or more of these can be used in combination.

[0160] [Formulation Ratio] In the resin composition, the formulation ratio of each component can be appropriately set according to their type. Relative to the content of solid components (the portion remaining after removing the solvent) in the resin composition, it is preferable that the total content of fillers in components (A) and (C) is in the range of 10 vol% to 90 vol%, and the content of component (B) is in the range of 10 vol% to 90 vol%. More preferably, the total content of fillers in components (A) and (C) is in the range of 20 vol% to 70 vol%, and the content of component (B) is in the range of 30 vol% to 90 vol%. When the total content of fillers in components (A) and (C) is less than 10 vol%, it is difficult to exhibit the effect of improving dielectric properties and dimensional stability. If it exceeds 90 vol%, the filler is exposed on the film surface, sometimes resulting in impaired smoothness.

[0161] Relative to the content of solid components in the resin composition, the content of the fibrous liquid crystal polymer filler in component (A) is preferably in the range of 5 vol% to 60 vol%, more preferably in the range of 10 vol% to 50 vol%. When the content of component (A) is less than 5 vol%, it is difficult to exhibit the effect of improving dielectric properties. If it exceeds 60 vol%, the fibrous liquid crystal polymer filler will become entangled with each other, easily forming agglomerates, reducing processability or impairing surface smoothness.

[0162] Relative to the content of solid components in the resin composition, the total content of the particulate metal oxide filler and the particulate thermoplastic resin filler in component (C) is preferably in the range of 20 vol% to 80 vol%, and more preferably in the range of 30 vol% to 70 vol%. When the total content of component (C) is less than 20 vol%, it is difficult to fully exhibit the effect of improving dielectric properties and hindering the orientation of the fibrous liquid crystal polymer filler in component (A). If it exceeds 80 vol%, the resin film is prone to embrittlement and the surface smoothness is impaired.

[0163] In addition, the ratio of the content of component (A) to the total content of component (C) [(A) component / (C) component] is preferably in the range of 0.1 to 10 on a volume basis. If the ratio [(A) component / (C) component] is in the range of 0.1 to 10, the particulate metal oxide filler and / or particulate thermoplastic resin filler of component (C) can effectively hinder the orientation and arrangement of the fibrous liquid crystal polymer filler of component (A), and the CTE difference between the MD direction and the TD direction during resin film formation can be reduced.

[0164] [Method for Manufacturing Resin Composition] The method for manufacturing the resin composition in this embodiment can be appropriately selected according to the types and combinations of components (A) to (C), and is therefore not particularly limited. As a preferred method, it is preferable to first add particulate metal oxide filler and / or particulate thermoplastic resin filler of component (C) to a resin solution obtained by dissolving component (B) in an organic solvent, mix them uniformly, and then add fibrous liquid crystal polymer filler of component (A) and mix them uniformly. If the order of adding component (C) and component (A) is reversed, and component (A) is added before component (C) in a resin solution obtained by dissolving component (B) in an organic solvent, the fibrous liquid crystal polymer filler will entangle or agglomerate with each other, making it difficult to form a uniform resin composition.

[0165] [Resin Film] In this embodiment, a resin film containing components (A) to (C) is also provided. The resin film of this embodiment is a resin film having a single layer or multiple layers of resin, provided that at least one layer of the resin is a filler-containing resin layer formed using the resin composition. Preferably, the filler-containing resin layer is the main layer of the resin film. Here, "main layer" refers to a layer having a thickness of more than 50% relative to the overall thickness of the resin film. Therefore, it is more preferable that the entire resin film comprises a filler-containing resin layer. In addition, the resin film can, for example, serve as an adhesive layer to form part of an insulating resin layer, and similarly to the first embodiment, can be used as an adhesive sheet in the film state, for example.

[0166] Furthermore, after the resin layer containing filler is conditioned for 24 hours under constant temperature and humidity conditions of 23°C and 50%RH, the relative permittivity at 10 GHz, measured using a split dielectric resonator (SPDR), is preferably 3 or less, and the dielectric loss tangent is preferably 0.003 or less. To improve the transmission loss of the circuit board, it is particularly important to control the dielectric loss tangent of the insulating resin layer. By making the dielectric loss tangent below the aforementioned value, the effect of reducing transmission loss is increased. Therefore, for example, when a resin film is used as the insulating resin layer of a high-frequency circuit board, transmission loss can be reduced efficiently. If the dielectric loss tangent at 10 GHz exceeds 0.003, when a resin film is used as the insulating resin layer of a circuit board, adverse conditions such as increased electrical signal loss are likely to occur in the transmission path of high-frequency signals.

[0167] Furthermore, the absolute value of the CTE in the MD direction of the resin layer containing filler at 10°C to 20°C is preferably 50 ppm / K or less, and the absolute value of the CTE in the TD direction is preferably 100 ppm / K or less. By ensuring that the absolute values ​​of the CTE in the MD direction and the TD direction are less than or equal to these values, dimensional changes within the film surface before and after heating can be suppressed, thus suppressing warping and preventing positional misalignment of the wirings on the printed wiring board when they are joined together.

[0168] [Thickness] The overall thickness of the resin film is preferably in the range of 15 μm to 250 μm, and more preferably in the range of 25 μm to 200 μm. If the thickness of the resin film is less than 15 μm, the surface smoothness of the film may deteriorate, and defects such as wrinkles in the metal foil and damage to the resin film may easily occur during the handling process when manufacturing metal-clad laminates. Conversely, if the thickness of the resin film exceeds 250 μm, there is a tendency for the resin film to become less flexible.

[0169] [Method for manufacturing resin film] The method for manufacturing resin film can be appropriately selected according to the types and combinations of components (A) to (C), and therefore there is no particular limitation. As a preferred method, it is preferred to coat a resin composition containing components (A) to (C) and an organic solvent onto any substrate and dry it to form a film.

[0170] [Function] In this embodiment, the resin composition contains component (C) along with components (A) and (B), thereby mitigating the anisotropy of CTE during resin film formation. This is because, when the resin composition is cast to form the film, the particulate metal oxide filler and / or particulate thermoplastic resin filler of component (C) moderately hinder the alignment of the fibrous liquid crystal polymer filler of component (A) along the MD direction, thereby mitigating the anisotropy of the filler-containing resin layer. As a result, dimensional changes after heating can be suppressed, and therefore, by using the resin film of this embodiment, finer and more precise printed wiring boards can be manufactured.

[0171] {Metal-Clad Laminate} The metal-clad laminate of this embodiment is a metal-clad laminate comprising an insulating resin layer and a metal layer deposited on at least one side of the insulating resin layer, wherein at least one layer of the insulating resin layer comprises the resin film (preferably the resin film of the first embodiment or the second embodiment). The metal-clad laminate may be a single-sided metal-clad laminate with a metal layer on only one side of the insulating resin layer, or a double-sided metal-clad laminate with metal layers on both sides of the insulating resin layer.

[0172] [Insulating Resin Layer] The insulating resin layer comprises a single layer or multiple layers, and includes a layer containing the resin film. For example, the resin film may also be formed as a non-thermoplastic layer serving as the main layer of the insulating resin layer to ensure mechanical or thermal properties. Alternatively, the resin film may also be formed as a thermoplastic resin layer serving as an adhesive layer to bear the adhesion strength to metal layers such as copper foil. Furthermore, "main layer" refers to a layer that accounts for more than 50% of the total thickness of the insulating resin layer. In addition, the use of an adhesive for bonding the resin film to the metal foil is not excluded in the metal-clad laminate of this embodiment. Wherein, when an adhesive layer is interposed between two metal-clad laminates having metal layers on both sides of the insulating resin layer, in order not to impair the dielectric properties, the thickness of the adhesive layer is preferably less than 30% of the total thickness of the insulating resin layer, and more preferably less than 20%. Furthermore, when an adhesive layer is present as an intervening element in a single-sided metal-clad laminate where only one side of the insulating resin layer has a metal layer, the thickness of the adhesive layer is preferably less than 15% of the total thickness of the insulating resin layer, and more preferably less than 10%, in order not to impair the dielectric properties. Additionally, since the adhesive layer constitutes part of the insulating resin layer, it is preferably a layer containing component (B). For high-frequency circuit applications, the thickness of the insulating resin layer is preferably in the range of 35 μm or more and 200 μm or less, and more preferably in the range of 50 μm or more and 150 μm or less. Within this range, both the flexibility of the metal-clad laminate and the suppression of high-frequency signal transmission loss during circuit board fabrication can be achieved.

[0173] As a method for manufacturing a metal-clad laminate with a resin film as the insulating resin layer, examples include: coating a metal foil with a resin solution containing components (A) and (B) and performing vacuum and / or heat treatment; or directly or via any adhesive, heat-pressing the metal foil onto the resin film; or forming a metal layer onto the resin film using methods such as metal vapor deposition. Furthermore, a double-sided metal-clad laminate can be obtained, for example, by forming a single-sided metal-clad laminate by pressing resin layers facing each other together with hot pressing, or by pressing a metal foil onto the resin layer of a single-sided metal-clad laminate.

[0174] [Metal Layer] There are no particular limitations on the material used for the metal layer, and examples include: copper, stainless steel, iron, nickel, beryllium, aluminum, zinc, indium, silver, gold, tin, zirconium, tantalum, titanium, lead, magnesium, manganese, and their alloys. Among these, copper, silver, or their alloys are particularly preferred. Especially from the viewpoint of conductivity or cost, it is preferable to use a copper clad laminate (CCL) with copper as the metal layer. The metal layer can be a layer containing metal foil, or a layer obtained by metal vapor deposition on a film, or a layer obtained by printing paste, etc. In addition, in terms of being able to directly coat a resin solution containing components (A) and (B), metal foil or metal plate can be used, but copper foil or copper plate is preferred.

[0175] The thickness of the metal layer is appropriately set according to the intended use of the metal-clad laminate, and therefore there is no particular limitation. For example, it is preferably in the range of 5 μm to 3 mm, and more preferably in the range of 12 μm to 1 mm. If the thickness of the metal layer is less than 5 μm, defects such as wrinkles may occur during the handling of the manufactured metal-clad laminate. Conversely, if the thickness of the metal layer exceeds 3 mm, it will harden and the processability will deteriorate. Regarding the thickness of the metal layer, generally speaking, a thicker metal layer is suitable for applications such as automotive circuit boards, while a thinner metal layer is suitable for applications such as LED circuit boards.

[0176] {Printed Wiring Board} The printed wiring board of this embodiment is formed by using the metal layer of a metal-clad laminate as a conductor to form a circuit. That is, the printed wiring board includes an insulating resin layer comprising one or more layers, and a circuit wiring layer deposited on at least one side of the insulating resin layer, wherein at least one layer constituting the insulating resin layer includes the resin film (preferably the resin film of the first embodiment or the second embodiment). In particular, it is preferable from the viewpoint of conductivity or cost if copper is used in the circuit wiring. Considering the transmission loss caused by high-frequency signals, the roughness Rz on the copper side at the interface between the copper and the insulating resin layer is preferably 1.5 μm or less, more preferably 1 μm or less. Here, high frequency refers to, for example, frequencies above 10 GHz, especially above 20 GHz.

[0177] As described above, the resin film and metal-clad laminate combine excellent dielectric properties and dimensional stability by using liquid crystal polymer filler containing component (A), a base polymer containing component (B), and particulate metal oxide filler and / or particulate thermoplastic resin filler, depending on the requirements, containing component (C). Therefore, since the resin film and metal-clad laminate reduce losses in high-frequency signal transmission and maintain dimensional stability, they are suitable as circuit board materials for FPCs and the like in various electronic devices.

[0178] [Examples] The following examples illustrate the features of the present invention in more detail. However, the scope of the present invention is not limited to the examples. Furthermore, in the following examples, unless otherwise specified, various measurements and evaluations are performed using the methods described below.

[0179] [Determination of Water Absorption Rate] Prepare two resin film test pieces (4 cm wide × 25 cm long) and dry them at 80°C for 1 hour. Immediately after drying, place them in pure water at 23°C and let them stand for 24 hours. Calculate the water absorption rate (by weight) using the following formula based on the weight change before and after drying: Water Absorption Rate (by weight) = [(Weight after water absorption - Weight after drying) / Weight after drying] × 100

[0180] [Method for determining amine value] Weigh about 2 g of the dimer diamine composition into a 200 mL to 250 mL Erlenmeyer flask. Using phenolphthalein as an indicator, add 0.1 mol / L ethanolic potassium hydroxide solution dropwise until the solution turns light pink. Dissolve it in about 100 mL of neutralized butanol. Add 3 to 7 drops of phenolphthalein solution and titrate with 0.1 mol / L ethanolic potassium hydroxide solution while stirring until the sample solution turns light pink. Add 5 drops of bromophenol blue solution and titrate with 0.2 mol / L hydrochloric acid / isopropanol solution while stirring until the sample solution turns yellow. The amine value is calculated using the following formula (1). Amine value = {(V2×C2)-(V1×C1)}×MKOH / m･･･ (1) Here, the amine value is expressed in mg-KOH / g, and MKOH is the molecular weight of potassium hydroxide, 56.1. In addition, V and C represent the volume and concentration of the solution used in the titration, respectively, and the subscripts 1 and 2 represent 0.1 mol / L ethanolic potassium hydroxide solution and 0.2 mol / L hydrochloric acid / isopropanol solution, respectively. Furthermore, m represents the sample weight in grams.

[0181] [Calculation of GPC and Area Percentage of Chromatography] Regarding GPC, a 100 mg solution of a 20 mg dimer diamine composition pretreated with 200 μL of acetic anhydride, 200 μL of pyridine, and 2 mL of THF (tetrahydrofuran) was prepared by diluting with 10 mL of THF (containing 1000 ppm cyclohexanone). The prepared sample was analyzed using a Tosoh (TOSOH) HLC-8220 GPC at the following conditions: column: TSK-gel G2000HXL, G1000HXL; flow rate: 1 mL / min; column (oven) temperature: 40°C; injection volume: 50 μL. Cyclohexanone was used as a standard to correct for elution time.

[0182] At this time, the retention time of the cyclohexanone main peak is adjusted from 27 minutes to 31 minutes, and the time from the start to the end of the cyclohexanone main peak is adjusted to 2 minutes. The time from the start to the end of the main peak excluding the cyclohexanone peak is adjusted from 18 minutes to 19 minutes, and the time from the start to the end of the main peak excluding the cyclohexanone peak is adjusted from 2 minutes to 4 minutes and 30 seconds. Each component (a) to component (c) is detected. (a) The component represented by the main peak; (b) The component represented by the GPC peak detected at a later time based on the minimum value of the later retention time in the main peak; (c) The component represented by the GPC peak detected at an earlier time based on the minimum value of the earlier retention time in the main peak.

[0183] [Determination of the weight-average molecular weight (Mw) of polyimide] The weight-average molecular weight was determined using a gel permeation chromatography system (manufactured by Tosoh Corporation, using an HLC-8220GPC). Polystyrene was used as the standard substance, and tetrahydrofuran was used as the developing solvent.

[0184] [Evaluation of Dielectric Properties] <Liquid Crystal Polymer Filler> A dimethylacetamide dispersion of liquid crystal polymer filler, adjusted to 30% by weight of solid content, was coated onto a smooth surface of copper foil and dried at 120°C for 10 minutes. Subsequently, the temperature was gradually increased from 200°C to the melting point of the liquid crystal polymer +20°C over 10 minutes to etch and remove the copper foil of the resulting laminate, thereby obtaining a liquid crystal polymer film. Using a vector network analyzer (manufactured by Keysight Technologies, trade name: Vector Network Analyzer E8363C) and a split dielectric resonator (SPDR resonator), the relative permittivity and dielectric loss tangent of the obtained liquid crystal polymer film were measured at a frequency of 20 GHz after being placed at a temperature of 23°C and a humidity of 50% for 24 hours.

[0185] <Resin Film> Using a vector network analyzer (manufactured by Keysight Technologies, trade name: Vector Network Analyzer E8363C) and an SPDR resonator, the relative permittivity and dielectric loss tangent of the resin film pressed under the conditions of 160°C, 3.5 MPa and 60 minutes were measured at a frequency of 20 GHz after being placed at a temperature of 23°C and a humidity of 50% for 24 hours.

[0186] [Method for determining CTE] The resin film was cut into 3 mm × 20 mm pieces. Using a thermomechanical analyzer (Bruker 4000SA), a 5.0 g load was applied along the length in stretching mode, while the temperature was increased from 30°C to 260°C at a certain rate. After holding at this temperature for 10 minutes, the film was cooled at a rate of 5°C / min. The average coefficient of thermal expansion (CTE) from 250°C to 100°C was calculated. For the CTE in the normal direction (ND) of the resin film, with a lamination thickness of 1 mm, a 50 g load was applied in compression mode, and the film was heated to 150°C at a rate of 10°C / min, then cooled to 50°C at a rate of 5°C / min. The average coefficient of thermal expansion from 150°C to 50°C was calculated.

[0187] [Determination of melting point] The melting point was determined by differential scanning calorimetry (DSC, manufactured by SII Corporation, trade name: DSC-6200) in an inert gas environment, by heating from room temperature to 450°C at a rate of 1.5°C / min.

[0188] [Method for determining the average length of the major axis and the average length of the minor axis] Take out the packing material and observe it independently using a stereomicroscope. Measure the length of the major axis and the length of the minor axis for each of the removed packing materials.

[0189] [Determination of True Specific Gravity] The true specific gravity was determined using a continuous automatic powder true density measuring device (manufactured by Seishin Corporation, trade name: AUTO TRUE DENSERMAT-7000) and the pycnometer method (liquid phase displacement method).

[0190] [Determination of peel strength] The peel strength was determined using the following method. The copper-clad laminate was cut into test pieces with a width of 3 mm, and a tensile testing machine (manufactured by Toyo Seiki Co., Ltd., trade name: Strograph VE) was used to stretch the test piece at a speed of 50 mm / min in a 90° direction, and the peel strength between the resin layer and the copper foil was measured at this time.

[0191] [Determination of Surface Roughness of Copper Foil] The sample was cut into approximately 10 mm square pieces and fixed to the sample stage using double-sided tape. After irradiating with soft X-rays to remove static electricity from the copper foil surface, the ten-point average roughness Rz (RzJis) of the copper foil surface was measured using a scanning probe microscope (AFM, manufactured by Bruker AXS, trade name: Dimension Icon type SPM) under the following conditions: Measurement mode: tapping mode; Measurement area: 1 μm × 1 μm; Scanning speed: 1 Hz; Probe: Bruker, RTESP-300

[0192] Abbreviations used in embodiments and comparative examples indicate the following compounds. PTFE: polytetrafluoroethylene PFA: tetrafluoroethylene-perfluoroalkylvinyl ether copolymer PS: polystyrene PI: polyimide PEEK: polyether ether ketone BTDA: 3,3',4,4'-dibenzophenone tetracarboxylic acid dianhydride BPDA: 3,3',4,4'-biphenyltetracarboxylic acid dianhydride DDA: da Nippon Heda Japan) Co., Ltd. Trade name: PRIAMINE 1075 Substance refined by distillation (a composition: 99.2%, b composition: 0%, c composition: 0.8%, amine value: 210 mgKOH / g) BAPP: 2,2-bis[4-(4-aminophenoxy)phenyl]propane BAFL: 9,9-bisphenyl) N-12: Dimethylhydrazine dodecanoate NMP: N-methyl-2-pyrrolidone DMAc: N,N-dimethylacetamide Liquid crystal polymer A-1: ​​Liquid crystal polymer with polyester structure, melting point (Tm): 350°C, true specific gravity: 1.4, relative dielectric constant: 3.1, dielectric loss tangent: 0.0010 Liquid crystal polymer A-2: Liquid crystal polymer with polyester structure, melting point (Tm): 330°C, true specific gravity: 1.4, relative dielectric constant: 3.4, dielectric loss tangent: 0.0020 Liquid crystal polymer A-3: Liquid crystal polymer particle with polyester structure, melting point (Tm): 320 °C, true specific gravity: 1.4, relative dielectric constant: 3.4, dielectric loss angle tangent: 0.0010 Shape A-1: ​​short fibrous, length of the long axis: 1 mm, length of the short axis: 28 μm, manufacturing method: Short-fiber-like shape after cutting A-2.5 mm, Length of short axis: 28 μm, Manufacturing method: Melt-spinning and then crop Shape A-3: Fabric, fabric composition: plain weave, (46 bundles of fibers), thread density (vertical): 14 strands / cm, yarn density (horizontal): 14 strands / cm, cut into 10 cm square, length of the long axis: 10 cm, unit of weight of the short axis: 28 µm g / m2、Manufacturing: Plain weave after melt spinning Shape A-4: Indefinite shape, Length of short axis: 8 μm, Length of long axis: 14 μm, Manufacturing method: Pulverized of particles Shape A-5: Plate, length of short axis: 2 μm, length of long axis: 20 μm, Fabrication method: Pulverization of film In addition, in the DDA, the percentage of the a, b% of the layer in the DDA is determined as the PC component, b%.

[0193] [Example A-1] 40 g of liquid crystal polymer A-1 of shape A-1 was added to 100 g of NMP containing 40% by weight PTFE particles to obtain a resin composition dispersion A-1. The obtained resin composition dispersion A-1 was coated onto copper foil A-1 (electrolytic copper foil, thickness: 12 μm, Rz: 0.7 μm) and dried at 80°C for 15 minutes to obtain single-sided CCL A-1. Copper foil A-2 (electrolytic copper foil, thickness: 12 μm) was overlapped on the resin composition layer side of the obtained single-sided CCL A-1 and heated and pressurized at 310°C and 6 MPa for 10 minutes to obtain double-sided CCL A-1. The copper foil of the obtained double-sided CCL A-1 was removed by etching to obtain resin film A-1. The obtained resin film A-1 was evaluated, and the results were: thickness: 53 μm, CTE: 42 ppm / K, dielectric loss tangent: 0.0007, and water absorption rate: 0.03 wt%.

[0194] [Example A-2] 20 g of liquid crystal polymer A-1 of shape A-2 was added to 200 g of DMAc containing 30% by weight PFA microparticles to obtain resin composition dispersion A-2. The obtained resin composition dispersion A-2 was coated onto copper foil A-1 and dried at 100°C for 15 minutes, followed by a phased heat treatment for 20 minutes up to 330°C to obtain single-sided CCL A-2. The copper foil of the obtained single-sided CCL A-2 was removed by etching to obtain resin film A-2. The obtained resin film A-2 was evaluated, and the results were: thickness: 50 μm, CTE: 20 ppm / K, dielectric loss tangent: 0.0007, water absorption: 0.02 wt%.

[0195] [Example A-3] A liquid crystal polymer A-2, shaped A-3 and fixed to a stainless steel frame, was immersed in DMAc containing 30% by weight PFA microparticles for 10 minutes, and then tilted and allowed to stand until no dripping occurred. While fixed in a mold, it was dried at 100°C for 15 minutes, followed by a phased heat treatment for 20 minutes up to 330°C. The resin film A-3 was removed from the mold. The obtained resin film A-3 was evaluated, and the results were: thickness: 140 μm, CTE: 30 ppm / K, dielectric loss tangent: 0.0028, water absorption rate: 0.02 wt%.

[0196] [Example A-4] Copper foil A-1, PFA film (thickness: 75 μm), liquid crystal polymer A-2 of shape A-3, PFA film (thickness: 75 μm) and copper foil A-2 were sequentially laminated. The layers were heated and pressurized at 320°C and 7.5 MPa for 20 minutes under vacuum to obtain double-sided CCL A-4. The copper foil on both sides of the obtained CCL A-4 was etched away to obtain resin film A-4. The obtained resin film A-4 was evaluated, and the results were: thickness: 200 μm, CTE: 40 ppm / K, dielectric loss tangent: 0.0025, water absorption rate: 0.02 wt%. Furthermore, the peel strength of single-sided CCL A-4 obtained by etching the copper foil A-2 on one side of both sides of the CCL A-4 was 1.3 kN / m.

[0197] [Example A-5] Instead of the PFA membrane of Example A-4, a PS membrane (thickness: 75 μm) was used, and the temperature was changed from 320°C to 250°C. Otherwise, resin membrane A-5 was obtained in the same manner as in Example A-4. The obtained resin membrane A-5 was evaluated, and the results were: thickness: 185 μm, CTE: 35 ppm / K, dielectric loss tangent: 0.0025, water absorption rate: 0.10 wt%.

[0198] (Synthesis Example A-1) 33.84 g of BTDA (0.1048 mol) as an anhydride, 56.16 g of DDA (0.1051 mol) as a diamine, 126 g of NMP, and 84 g of xylene were added to a 500 mL separable flask and mixed thoroughly at 40°C for 1 hour to prepare a polyamide solution. The polyamide solution was heated to 190°C and stirred for 8 hours to complete amide imidization. 64 g of xylene was added for dilution to prepare polyimide solution A-1 (solid content: 30% wt%, weight average molecular weight: 58,500). The composition of the polyimide was designated as PI A-1.

[0199] (Synthesis Examples A-2 to A-3) Polyimide solutions A-2 and A-3 were prepared in the same manner as in Synthesis Example A-1, except that the acid anhydride and diamine were changed as shown in Table 1. The polyimide compositions were set as PI A-2 and PI A-3.

[0200] [Table 1] Synthesis Example A-1 Synthesis Example A-2 Synthesis Example A-3 PI composition A-1 A-2 A-3 Acid anhydride addition amount [g] BTDA 33.84 21.15 36.57 BPDA - 12.86 - Diamine addition amount [g] DDA 56.16 47.00 39.61 BAPP - 9.04 - BAFL - - 13.91 Acid anhydride addition amount [mol] BTDA 0.1048 0.0655 0.1133 BPDA - 0.0437 - Diamine addition amount [mol] DDA 0.1051 0.0880 0.0741 BAPP - 0.0220 - BAFL - - 0.0399 Solvent [g] NMP 126 126 126 xylene 84 84 84 Xylene for dilution 64 64 64 Varnish solids concentration [wt%] 30 30 30 Weight average molecular weight 58500 35900 54700

[0201] [Example A-6] 30% by weight of liquid crystal polymer A-1 in shape A-1 and 3.5% by weight of N-12 as a crosslinking agent were prepared in polyimide solution A-1 obtained in synthesis example A-1. Xylene was added to dilute the solution and stirred so that the solid content was 15% by weight, thereby preparing polyimide varnish A-1.

[0202] The prepared polyimide varnish A-1 was cast onto an aluminum substrate, dried at 80°C for 60 minutes, and then peeled off to prepare resin film A-6 (thickness: 100 μm). The evaluation results of resin film A-6 are as follows: Relative permittivity: 2.7, Dielectric loss tangent: 0.0015, CTE: 4 ppm / K, Water absorption: 0.15 wt%.

[0203] [Example A-7] Polyimide solution A-2 was used instead of polyimide solution A-1, and the amount of liquid crystal polymer A-1 in shape A-1 was changed to 35% by weight. Otherwise, resin film A-7 (thickness: 100 μm) was prepared in the same manner as in Example A-6. Various evaluation results of resin film A-7 are as follows: Relative permittivity: 2.7, Dielectric loss tangent: 0.0013, CTE: 2 ppm / K, Water absorption: 0.18 wt%.

[0204] [Example A-8] Polyimide solution A-3 was used instead of polyimide solution A-1, and the amount of liquid crystal polymer A-1 in shape A-1 was changed to 50% by weight. Otherwise, resin film A-8 (thickness: 100 μm) was prepared in the same manner as in Example A-6. Various evaluation results of resin film A-8 are as follows: Relative permittivity: 2.8, Dielectric loss tangent: 0.0015, CTE: 1 ppm / K, Water absorption: 0.12 wt%.

[0205] [Example A-9] In the polyimide solution A-1 obtained in Synthesis Example A-1, 3.5% by weight of N-12 as a crosslinking agent was added, and xylene was added to dilute the solution to a solid content of 15% by weight and stirred to prepare polyimide varnish A-1a. The prepared polyimide varnish A-1a was coated on one side of a PET film that had undergone demolding treatment, dried at 80°C for 15 minutes, dried at 120°C for 5 minutes, and then peeled off to prepare polyimide film A-1a (thickness: 25 μm). Two poly(ethylene glycol) films A-1a were laminated and their thickness was set to 50 μm to replace the 75 μm PFA film of Example A-4. The heating and pressurization conditions were changed to a vacuum environment at 160°C and 5 MPa for 60 minutes. Otherwise, CCL A-9 on both sides and resin film A-9 were obtained in the same manner as in Example A-4. The obtained resin film A-9 was evaluated, and the results were: thickness: 157 μm, CTE: -20 ppm / K, dielectric loss tangent: 0.0027, water absorption rate: 0.15 wt%. In addition, the peel strength of single-sided CCL A-9 obtained by etching the copper foil A-2 on one side of the two-sided CCL A-9 was 1.4 kN / m.

[0206] [Example A-10] A PEEK membrane (thickness: 75 μm) was used instead of a PFA membrane, and resin membrane A-10 was obtained in the same manner as in Example A-4. The obtained resin membrane A-10 was evaluated, and the results were: thickness: 190 μm, CTE: 5 ppm / K, dielectric loss tangent: 0.0025, water absorption rate: 0.05 wt%.

[0207] [Example A-11] In DMAc containing 30% by weight of polyester microparticles having a backbone derived from p-hydroxybenzoic acid and hydroxynaphthoic acid, liquid crystal polymer A-2, shaped A-3, fixed on a stainless steel frame, was immersed for 10 minutes and then tilted and allowed to stand until no dripping occurred. While fixed in a mold, it was dried at 100°C for 15 minutes, followed by a phased heat treatment for 20 minutes up to 330°C. The resin film A-11 was obtained by removing it from the mold. The obtained resin film A-11 was evaluated, and the results were: thickness: 145 μm, CTE: 10 ppm / K, dielectric loss tangent: 0.0015, water absorption: 0.10 wt%.

[0208] [Example A-12] 30 g of liquid crystal polymer A-3 of shape A-5 was mixed into 100 g of water containing 30% by weight of polyester microparticles having a backbone derived from p-hydroxybenzoic acid and hydroxynaphthoic acid and a melting point of 300°C, and then cast onto a polyimide film substrate. The mixture was dried at 100°C for 15 minutes, followed by a phased heat treatment for 20 minutes up to 310°C, and then peeled off from the polyimide film substrate to obtain resin film A-12. The obtained resin film A-12 was evaluated, and the results showed a thickness of 85 μm, a CTE of 14 ppm / K, a dielectric loss tangent of 0.0020, and a water absorption rate of 0.11 wt%. Furthermore, liquid crystal polymer A-3 of shape A-5 was prepared by the following method: First, liquid crystal polymer A-3 was melt-extruded to prepare a sheet with a thickness of 0.4 mm and a square diameter of 10 cm. The CTE in the extrusion direction (MD direction) is -40 ppm / K, the CTE in the thickness direction (ND direction) is 150 ppm / K, and the CTE in the direction perpendicular to the plane formed by the extrusion direction and the thickness direction (TD direction) is 130 ppm / K. Next, the sheet is further subdivided using a crusher to obtain plate-shaped liquid crystal polymer filler.

[0209] [Example A-13] 5% by weight of liquid crystal polymer A-1 in shape A-1 and 3.5% by weight of N-12 as a crosslinking agent were prepared in polyimide solution A-1 obtained in synthesis example A-1. Xylene was added to dilute the solution and stirred so that the solid content was 30% by weight, thereby preparing polyimide varnish A-13.

[0210] The prepared polyimide varnish A-13 was cast onto copper foil A-1, dried at 80°C for 60 minutes, and then heat-treated at 160°C for 1 hour to obtain single-sided CCL A-13. Next, by removing copper foil A-1, resin film A-13 (thickness: 100 μm) was prepared. The various evaluation results of resin film A-13 and single-sided CCL A-13 are as follows: Relative permittivity: 2.1, Dielectric loss tangent: 0.0017, CTE: 26 ppm / K, Water absorption: 0.17 wt%, Peel strength: 1.1 kN / m

[0211] (Comparative Example A-1) Resin film A was prepared in the same manner as in Example A-1, except that liquid crystal polymer A-1 without shape A-1 was not added. The obtained resin film A was evaluated, and the results were: thickness: 50 μm, CTE: 250 ppm / K, dielectric loss tangent: 0.0003, relative permittivity: 2.1, and water absorption rate: 0.01 wt%.

[0212] (Comparative Example A-2) Resin film B was prepared in the same manner as in Example A-2, except that liquid crystal polymer A-1 without shape A-2 was not added. The obtained resin film B was evaluated, and the results were: thickness: 50 μm, CTE: 296 ppm / K, dielectric loss tangent: 0.0009, relative permittivity: 2.0, and water absorption rate: 0.01 wt%.

[0213] (Comparative Example A-3) Except for the liquid crystal polymer A-2 in the unlaminated shape A-3, the resin film C was prepared in the same manner as in Example A-5. The obtained resin film C was evaluated, and the results were: thickness: 145 μm, CTE: 80 ppm / K, dielectric loss tangent: 0.0005, and water absorption rate: 0.12 wt%.

[0214] (Comparative Example A-4) Resin film D (thickness: 100 μm) was prepared in the same manner as in Example A-6, except that liquid crystal polymer A-1 of shape A-1 was not added. Various evaluation results of resin film D are as follows: Relative permittivity: 2.6, Dielectric loss tangent: 0.0017, CTE: 150 ppm / K, Water absorption: 0.10 wt%.

[0215] (Comparative Example A-5) Resin film E (thickness: 100 μm) was prepared in the same manner as in Example A-7, except that liquid crystal polymer A-1 of shape A-1 was not added. Various evaluation results for resin film E are as follows: Relative permittivity: 2.6, Dielectric loss tangent: 0.0014, CTE: 109 ppm / K, Water absorption: 0.08 wt%.

[0216] (Comparative Example A-6) Resin film F (thickness: 100 μm) was prepared in the same manner as in Example A-8, except that liquid crystal polymer A-1 of shape A-1 was not added. Various evaluation results for resin film F are as follows: Relative permittivity: 2.7, Dielectric loss tangent: 0.0017, CTE: 115 ppm / K, Water absorption: 0.12 wt%.

[0217] (Comparative Example A-7) Liquid crystal polymer A-3 with shape A-4 was used instead of liquid crystal polymer A-1 with shape A-1. Otherwise, resin film G was prepared in the same manner as in Example A-6. The obtained resin film G was evaluated, and the results were: thickness: 56 μm, CTE: 70 ppm / K, dielectric loss tangent: 0.0013, relative permittivity: 3.2, and water absorption rate: 0.12 wt%.

[0218] (Comparative Example A-8) Except for the liquid crystal polymer A-2 with unlaminated shape A-3, resin film H was prepared in the same manner as in Example A-10. The obtained resin film H was evaluated, and the results were: thickness: 98 μm, CTE: 40 ppm / K, dielectric loss tangent: 0.0040, relative permittivity: 3.1, and water absorption rate: 0.07 wt%.

[0219] (Comparative Example A-9) Resin film I was prepared in the same manner as in Example A-12, except that liquid crystal polymer A-3 of shape A-5 was not added. The obtained resin film I was evaluated and the results were: thickness: 74 μm, CTE: 90 ppm / K, dielectric loss tangent: 0.0010, water absorption: 0.05 wt%.

[0220] The results above are summarized in Table 2.

[0221] [Table 2] (A) Ingredients packing shape (B) Components Resin composition CTE [ppm / K] Dielectric loss tangent [ / 10 4 ] Water absorption rate [weight%] Example A-1 1 PTFE 42 7 0.03 Example A-2 2 PFA 20 7 0.02 Example A-3 3 PFA 30 28 0.02 Example A-4 3 PFA 40 25 0.02 Example A-5 3 PS 35 25 0.10 Example A-6 1 PI A-1 4 15 0.15 Example A-7 1 PI A-2 2 13 0.18 Example A-8 1 PI A-3 1 15 0.12 Example A-9 3 PI A-1 -20 27 0.15 Example A-10 3 PEEK 5 25 0.05 Example A-11 3 Polyester 10 15 0.10 Example A-12 5 Polyester 14 20 0.11 Example A-13 1 PI A-1 26 17 0.17 Comparative Example A-1 - PTFE 250 3 0.01 Comparative Example A-2 - PFA 296 9 0.01 Comparative Example A-3 - PS 80 5 0.12 Comparative Example A-4 - PI A-1 150 17 0.10 Comparative Example A-5 - PI A-2 109 14 0.08 Comparative Example A-6 - PI A-3 115 17 0.12 Comparative Example A-7 4 PI A-1 70 13 0.12 Comparative Example A-8 - PEEK 40 40 0.07 Comparative Example A-9 - Polyester 90 10 0.05

[0222] Table 2 shows that the resin films of Examples A-1 to A-13, in which the liquid crystal polymer filler of component (A) is incorporated into the parent polymer of component (B), can achieve both a small coefficient of linear thermal expansion and a low dielectric loss tangent, ensuring dimensional stability while handling high-frequency signal transmission. In contrast, the resin films of Comparative Examples A-1 to A-6, A-8, and A-9, which do not contain liquid crystal polymer filler, have a large coefficient of linear thermal expansion or a high dielectric loss tangent. The resin film of Comparative Example A-7, in which the shape anisotropy (X / Y) of the liquid crystal polymer filler is less than 2.5, has a large coefficient of linear thermal expansion.

[0223] In addition to the above, the various measurements and evaluations in the following embodiments are performed using the following methods.

[0224] [Evaluation of Dielectric Properties] <Silicon Dioxide Particles> A vector network analyzer (manufactured by Keysight Technologies, trade name: Vector Network Analyzer E8363C) and a relative permittivity measuring device manufactured by Kanto Electronics Application Development Co., Ltd., utilizing the resonant cavity perturbation method, were used. The relative permittivity measurement mode was set to TM020, and the relative permittivity (ε1) and dielectric loss tangent (Tanδ1) of silicon dioxide particles were measured at a frequency of 10 GHz. Furthermore, the silicon dioxide particles were in powder form and filled into a sample tube (inner diameter 1.68 mm, outer diameter 2.28 mm, height 8 cm) for measurement.

[0225] <Liquid Crystal Polymer Short Fibers> A dimethylacetamide dispersion of liquid crystal polymer short fibers, adjusted to 10% by weight of solid content, was coated onto a smooth surface of a copper foil and dried at 120°C for 20 minutes. Subsequently, a new copper foil was laminated with its smooth surface in contact with the coated liquid crystal polymer short fiber layer. Vacuum bonding was performed at the melting point of the liquid crystal polymer +20°C for 10 minutes. The copper foil of the resulting laminate was etched and removed, thereby obtaining a liquid crystal polymer film. Using a vector network analyzer (manufactured by Keysight Technologies, trade name: Vector Network Analyzer E8363C) and a split dielectric resonator (SPDR resonator), the relative permittivity and dielectric loss tangent of the obtained liquid crystal polymer film were measured at a frequency of 10 GHz after being placed at 23°C and 50% humidity for 24 hours.

[0226] <Resin Film> Using a vector network analyzer (manufactured by Keysight Technologies, trade name: Vector Network Analyzer E8363C) and an SPDR resonator, the relative permittivity and dielectric loss tangent at a frequency of 10 GHz were measured after the resin film was pressed at a temperature of 160°C, a pressure of 3.5 MPa and a time of 60 minutes and then placed at a temperature of 23°C and a humidity of 50% for 24 hours.

[0227] [Method for determining CTE] The resin film was cut into 3 mm × 20 mm pieces. A thermomechanical analyzer (manufactured by Bruker, trade name: 4000SA) was used to apply a load of 5.0 g in stretch mode while simultaneously heating from 5°C to 300°C at a certain heating rate. The average coefficient of thermal expansion (average linear thermal expansion coefficient: CTE) was measured and calculated for both the MD and TD directions of the film from 10°C to 20°C.

[0228] [Method for determining the average length of the major axis and the average length of the minor axis] Ten fibrous liquid crystal polymer fillers were randomly selected and observed independently using a stereomicroscope. The length of the major axis and the length of the minor axis of each selected filler were measured and calculated as average values.

[0229] [Determination of sphericity] Wet flow particle size-shape analyzer (manufactured by Sysmex Corporation, trade name: FPIA-3000) is used to determine the average sphericity of silicon dioxide particles by analyzing dynamic flow particle images.

[0230] [Determination of volume average particle size D50] A laser diffraction particle size distribution measuring device (manufactured by Malvern, trade name: Master Sizer 3000 laser particle size analyzer) was used to determine the volume average particle size of silicon dioxide particles by using laser diffraction-scattering method with water as the dispersion medium and under the condition of particle refractive index of 1.54.

[0231] [Determination of the white silica crystalline phase] Using an X-ray diffraction apparatus (manufactured by Bruker, trade name: D2PHASER), the total area of ​​all peaks originating from SiO2 was calculated based on all diffraction patterns (peak position, peak width, and peak intensity) within the range of diffraction angles (Cu, Kα) 2θ = 10° to 90°. Next, the peak positions of the white silica crystalline phase were determined, the total area of ​​all peaks of the white silica crystalline phase was calculated, and the percentage (wt%) relative to the total area of ​​all peaks originating from SiO2 was determined. Furthermore, the attribution of each peak was referenced to the database of the International Centre for Diffraction Data (ICDD).

[0232] [Evaluation of the heat resistance of the conditioned solder] A double-sided copper-clad laminate was prepared by laminating the roughened surface of the copper foil with the resin side of the prepared copper-clad laminate using heat pressing. The obtained double-sided copper-clad laminate was cut into 30 mm squares. After placing the test pieces at 23°C and 50% relative humidity for 72 hours, they were immersed in a solder bath set to 288°C for 10 seconds. The adhesion was observed to check for any defects such as foaming, expansion, or peeling. Cases without defects were classified as "good," and cases with defects were classified as "unacceptable."

[0233] The abbreviations used in the Examples and Comparative Examples refer to the following compounds: PI: Polyimide; PMDA: Pyromellitic dianhydride; m-TB: 2,2'-Dimethyl-4,4'-Diaminobiphenyl; LCP: Liquid crystal polymer.

[0234] LCP B-1: A liquid crystal polymer with a polyester structure, melting point (Tm): 350℃, true specific gravity: 1.4, relative permittivity: 3.1, dielectric loss tangent: 0.0010. LCP B-2: A liquid crystal polymer with a polyester structure, melting point (Tm): 330℃, true specific gravity: 1.4, relative permittivity: 3.4, dielectric loss tangent: 0.0020. LCP B-3: A liquid crystal polymer with a polyester structure, melting point (Tm): 320℃, true specific gravity: 1.4, relative permittivity: 3.4, dielectric loss tangent: 0.0008.

[0235] Shape B-1: Short fiber, average length of long axis: 0.5 mm, average length of short axis: 28 μm, manufacturing method: melt spinning followed by cutting. Shape B-2: Short fiber, average length of long axis: 3 mm, average length of short axis: 28 μm, manufacturing method: melt spinning followed by cutting.

[0236] Particle B-1: Manufactured by JITAC Chemicals & Materials Co., Ltd., trade name: CR10-20 (spherical white silica powder, sphericity: 0.98, white silica crystalline phase: 98 wt%, true specific gravity: 2.33, D50: 10.8 μm, relative permittivity at 10 GHz: 3.16, dielectric loss tangent at 10 GHz: 0.0008) Particle B-2: Manufactured by Admatech Co., Ltd., trade name: SE4050 (spherical amorphous silica powder, spherical, true specific gravity: 2.21, D50: 1.5 μm, relative permittivity at 10 GHz: 2.92, dielectric loss tangent at 10 GHz: 0.0052) Particle B-3: Manufactured by Nippon Steel Chemicals & Materials Co., Ltd., trade name: SC70-2 (spherical amorphous silicon dioxide powder, sphericity: 0.98, true specific gravity: 2.21, D50: 11.7 μm, relative permittivity at 10 GHz: 3.08, dielectric loss tangent at 10 GHz: 0.0015)

[0237] (Synthesis Examples B-1 to B-3) Polyimide solutions B-1, B-2, and B-3 were prepared in the same manner as in Synthesis Examples A-1, A-2, and A-3.

[0238] (Synthesis Example B-4) 19 g of m-TB (90 mmol) and 230 g of DMAc were added to a 300 ml separable flask and stirred at room temperature under a nitrogen flow. After complete dissolution, 16 g of PMDA (72 mmol) and 5.3 g of BPDA (18 mmol) were added, and the mixture was stirred at room temperature for 18 hours to obtain polyacrylic acid solution B-1. The viscosity of the obtained polyacrylic acid solution B-1 was 22,400 cps. The polyimide obtained after hardening polyacrylic acid solution B-1 was designated as PI B-4.

[0239] (Synthesis Example B-5) 24 g of BAPP (60 mmol) and 230 g of DMAc were added to a 300 ml separable flask and stirred at room temperature under a nitrogen flow. After complete dissolution, 6.5 g of PMDA (30 mmol) and 8.7 g of BPDA (30 mmol) were added, and the mixture was stirred at room temperature for 18 hours to obtain polyacrylic acid solution B-2. The viscosity of the obtained polyacrylic acid solution B-2 was 21,074 cps. The polyimide obtained after hardening polyacrylic acid solution B-2 was designated as PI B-5.

[0240] [Example B-1] In 100 g of the polyimide solution B-1 obtained in Synthesis Example B-1, 1.1 g of N-12 as a crosslinking agent was added, 115 g of particles B-1 was added, and after stirring, 11.7 g of LCP B-1 in shape B-1 was added. Xylene was added to dilute the solution to a total solids concentration of 45% by weight, and the mixture was stirred to prepare polyimide varnish B-1. Regarding the content relative to the volume of all solids in the polyimide varnish B-1, LCP B-1 was 10%, and particles B-1 was 60%.

[0241] The prepared polyimide varnish B-1 was cast onto an electrolytic copper foil (12 μm), dried at 80°C for 20 minutes, and then treated at 160°C for 1 hour to prepare a copper-clad laminate B-1. Subsequently, a resin film B-1 (thickness: 145 μm) was prepared by etching the copper foil. The evaluation results of the resin film B-1 and the copper-clad laminate B-1 are as follows: Relative permittivity: 2.5, Dielectric loss tangent: 0.0009, CTE (TD): 58 ppm / K, CTE (MD): 17 ppm / K, Peel strength: 1.3 kN / m, Heat resistance of conditioned solder: Good.

[0242] [Example B-2] In 100 g of the polyimide solution B-1 obtained in Synthesis Example B-1, 1.1 g of N-12 as a crosslinking agent was added, 19.2 g of particles B-1 was added, and after stirring, 11.7 g of LCP B-1 in shape B-1 was added. Xylene was added to dilute the solution to a total solids concentration of 45% by weight, and the mixture was stirred to prepare polyimide varnish B-2. Regarding the content relative to the volume of all solids in the polyimide varnish B-2, LCP B-1 was 20%, and particles B-1 was 20%.

[0243] The prepared polyimide varnish B-2 was cast onto an electrolytic copper foil (12 μm), dried at 80°C for 20 minutes, and then treated at 160°C for 1 hour to prepare a copper-clad laminate B-2. Subsequently, a resin film B-2 (thickness: 113 μm) was prepared by etching the copper foil. The various evaluation results of the resin film B-2 are as follows: Relative permittivity: 1.9, Dielectric loss tangent: 0.0015, CTE (TD): 91 ppm / K, CTE (MD): 20 ppm / K, Heat resistance of conditioned solder: Good.

[0244] [Example B-3] In 100 g of the polyimide solution B-1 obtained in Synthesis Example B-1, 1.1 g of N-12 as a crosslinking agent was added, along with 57.5 g of particles B-1. After stirring, 17.5 g of LCP B-1 in shape B-1 was added. Xylene was added to dilute the solution to a total solids concentration of 45% by weight, and the mixture was stirred to prepare polyimide varnish B-3. Regarding the content of LCP B-1 relative to the volume of all solids in the polyimide varnish B-3, it was 20%, and the content of particles B-1 was 40%.

[0245] The prepared polyimide varnish B-3 was cast onto an electrolytic copper foil (12 μm), dried at 80°C for 20 minutes, and then treated at 160°C for 1 hour to prepare a copper-clad laminate B-3. Subsequently, a resin film B-3 (thickness: 135 μm) was prepared by etching the copper foil. The various evaluation results of the resin film B-3 are as follows: Relative permittivity: 2.0, Dielectric loss tangent: 0.0013, CTE (TD): 70 ppm / K, CTE (MD): 17 ppm / K

[0246] [Example B-4] In 100 g of the polyimide solution B-1 obtained in Synthesis Example B-1, 1.1 g of N-12 as a crosslinking agent was added, 28.8 g of particles B-1 was added, and after stirring, 35 g of LCP B-1 in shape B-1 was added. Xylene was added to dilute the solution to a total solids concentration of 45% by weight, and the mixture was stirred to prepare polyimide varnish B-4. Regarding the content relative to the volume of all solids in the polyimide varnish B-4, LCP B-1 was 40%, and particles B-1 was 20%.

[0247] The prepared polyimide varnish B-4 was cast onto an electrolytic copper foil (12 μm), dried at 80°C for 20 minutes, and then treated at 160°C for 1 hour to prepare a copper-clad laminate B-4. Subsequently, a resin film B-4 (thickness: 58 μm) was prepared by etching the copper foil. The various evaluation results of the resin film B-4 and the copper-clad laminate B-4 are as follows: Relative permittivity: 1.8, Dielectric loss tangent: 0.0009, CTE (TD): 69 ppm / K, CTE (MD): 30 ppm / K, Peel strength: 1.2 kN / m, Heat resistance of conditioned solder: Good.

[0248] [Example B-5] In 100 g of the polyimide solution B-1 obtained in Synthesis Example B-1, 1.1 g of N-12 as a crosslinking agent was added, 18.3 g of particles B-2 was added, and after stirring, 11.7 g of LCP B-1 in shape B-1 was added. Xylene was added to dilute the solution to a total solids concentration of 45% by weight, and the mixture was stirred to prepare polyimide varnish B-5. Regarding the content relative to the volume of all solids in the polyimide varnish B-5, LCP B-1 was 20%, and particles B-2 were 20%.

[0249] The prepared polyimide varnish B-5 was cast onto an electrolytic copper foil (12 μm), dried at 80°C for 20 minutes, and then treated at 160°C for 1 hour to prepare a copper-clad laminate B-5. Subsequently, the copper foil was etched to prepare a resin film B-5 (thickness: 158 μm). The various evaluation results of the resin film B-5 are as follows: Relative permittivity: 2.0, Dielectric loss tangent: 0.0015, CTE (TD): 87 ppm / K, CTE (MD): 15 ppm / K, Heat resistance of conditioned solder: Good.

[0250] [Example B-6] In 100 g of the polyimide solution B-1 obtained in Synthesis Example B-1, 1.1 g of N-12 as a crosslinking agent was added, 55 g of particles B-2 was added, and after stirring, 17.5 g of LCP B-1 in shape B-1 was added. Xylene was added to dilute the solution to a total solids concentration of 45% by weight, and the mixture was stirred to prepare polyimide varnish B-6. Regarding the content relative to the volume of all solids in the polyimide varnish B-6, LCP B-1 was 20%, and particles B-2 was 40%.

[0251] The prepared polyimide varnish B-6 was cast onto an electrolytic copper foil (12 μm), dried at 80°C for 20 minutes, and then treated at 160°C for 1 hour to prepare a copper-clad laminate B-6. Subsequently, a resin film B-6 (thickness: 178 μm) was prepared by etching the copper foil. The evaluation results of the resin film B-6 and the copper-clad laminate B-6 are as follows: Relative permittivity: 2.2, Dielectric loss tangent: 0.0016, CTE (TD): 57 ppm / K, CTE (MD): 15 ppm / K, Peel strength: 1.1 kN / m, Heat resistance of conditioned solder: Good.

[0252] [Example B-7] In 100 g of the polyimide solution B-1 obtained in Synthesis Example B-1, 1.1 g of N-12 as a crosslinking agent was added, 33 g of particles B-3 was added, and after stirring, 14 g of LCP B-1 in shape B-1 was added. Xylene was added to dilute the solution to a total solids concentration of 45% by weight, and the mixture was stirred to prepare polyimide varnish B-7. Regarding the content relative to the volume of all solids in the polyimide varnish B-7, LCP B-1 was 20%, and particles B-3 was 30%.

[0253] The prepared polyimide varnish B-7 was cast onto an electrolytic copper foil (12 μm), dried at 80°C for 20 minutes, and then treated at 160°C for 1 hour to prepare a copper-clad laminate B-7. Subsequently, a resin film B-7 (thickness: 108 μm) was prepared by etching the copper foil. The various evaluation results of the resin film B-7 are as follows: Relative permittivity: 1.9, Dielectric loss tangent: 0.0016, CTE (TD): 80 ppm / K, CTE (MD): 23 ppm / K, Heat resistance of conditioned solder: Good.

[0254] [Example B-8] In 100 g of the polyimide solution B-2 obtained in Synthesis Example B-2, 1.1 g of N-12 as a crosslinking agent was added, 19.2 g of particles B-1 was added, and after stirring, 11.7 g of LCP B-1 in shape B-1 was added. Xylene was added to dilute the solution to a total solids concentration of 45% by weight, and the mixture was stirred to prepare polyimide varnish B-8. Regarding the content of LCP B-1 relative to the total solids content in the polyimide varnish B-8 on a volume basis, it was 20%, and the content of particles B-1 was 20%.

[0255] The prepared polyimide varnish B-8 was cast onto an electrolytic copper foil (12 μm), dried at 80°C for 20 minutes, and then treated at 160°C for 1 hour to prepare a copper-clad laminate B-8. Subsequently, a resin film B-8 (thickness: 102 μm) was prepared by etching the copper foil. The various evaluation results of the resin film B-8 are as follows: Relative permittivity: 1.9, Dielectric loss tangent: 0.0011, CTE (TD): 70 ppm / K, CTE (MD): 22 ppm / K

[0256] [Example B-9] In 100 g of the polyimide solution B-3 obtained in Synthesis Example B-3, 1.1 g of N-12 as a crosslinking agent was added, 19.2 g of particles B-1 was added, and after stirring, 11.7 g of LCP B-1 in shape B-1 was added. Xylene was added to dilute the solution to a total solids concentration of 45% by weight, and the mixture was stirred to prepare polyimide varnish B-9. Regarding the content relative to the volume of all solids in the polyimide varnish B-9, LCP B-1 was 20%, and particles B-1 was 20%.

[0257] The prepared polyimide varnish B-9 was cast onto an electrolytic copper foil (12 μm), dried at 80°C for 20 minutes, and then treated at 160°C for 1 hour to prepare a copper-clad laminate B-9. Subsequently, a resin film B-9 (thickness: 97 μm) was prepared by etching the copper foil. The various evaluation results of the resin film B-9 and the copper-clad laminate B-9 are as follows: Relative permittivity: 2.0, Dielectric loss tangent: 0.0014, CTE (TD): 75 ppm / K, CTE (MD): 20 ppm / K, Peel strength: 1.5 kN / m, Heat resistance of conditioned solder: Good.

[0258] [Example B-10] To 100 g of the polyacrylic acid solution B-1 obtained in Synthesis Example B-4, 7 g of particles B-1 were added, and after stirring, 2.1 g of LCP B-1 of shape B-2 was added. DMAc was added to dilute the solution to a total solids concentration of 20% by weight, and the mixture was stirred to prepare polyacrylic acid varnish B-1. Regarding the content relative to the volume of all solids in the polyacrylic acid varnish B-1, LCP B-1 was 10%, and particles B-1 was 20%.

[0259] The prepared polyamide varnish B-1 was cast onto an electrolytic copper foil (12 μm) and dried at 130°C for 3 minutes. Subsequently, it underwent staged heat treatment from 155°C to 360°C to perform amide imidization, thereby preparing a copper-clad laminate B-10. Then, by etching the copper foil, a resin film B-10 (thickness: 40 μm) was prepared. Various evaluation results for the resin film B-10 are as follows: Relative permittivity: 2.8, Dielectric loss tangent: 0.0028, CTE (TD): 10 ppm / K, CTE (MD): 4 ppm / K

[0260] [Example B-11] To 100 g of the polyacrylic acid solution B-1 obtained in Synthesis Example B-4, 7 g of particles B-1 were added, and after stirring, 2.1 g of LCP B-2 of shape B-2 was added. DMAc was added to dilute the solution to a total solids concentration of 20% by weight, and the mixture was stirred to prepare polyacrylic acid varnish B-2. Regarding the content relative to the volume of all solids in the polyacrylic acid varnish B-2, LCP B-2 was 10%, and particles B-1 was 20%.

[0261] The prepared polyamide varnish B-2 was cast onto an electrolytic copper foil (12 μm) and dried at 130°C for 3 minutes. Subsequently, a staged heat treatment from 155°C to 360°C was performed to induce amide imidization, thereby preparing a copper-clad laminate B-11. Then, the copper foil was etched to prepare a resin film B-11 (thickness: 48 μm). The various evaluation results of the resin film B-11 are as follows: Relative permittivity: 2.9, Dielectric loss tangent: 0.0028, CTE (TD): 18 ppm / K, CTE (MD): 17 ppm / K, Heat resistance of conditioned solder: Good.

[0262] [Example B-12] To 100 g of the polyacrylic acid solution B-2 obtained in Synthesis Example B-5, 6.9 g of particles B-2 were added. After stirring, 4.2 g of LCP B-1 in shape B-2 was added. DMAc was added to dilute the solution to a total solids concentration of 15% by weight, and the mixture was stirred to prepare polyacrylic acid varnish B-3. Regarding the content relative to the volume of all solids in the polyacrylic acid varnish B-3, LCP B-1 was 20%, and particles B-2 were 20%.

[0263] The prepared polyamide varnish B-3 was cast onto an electrolytic copper foil (12 μm) and dried at 130°C for 3 minutes. Subsequently, a staged heat treatment from 155°C to 360°C was performed to induce amide imidization, thereby preparing a copper-clad laminate B-12. Then, the copper foil was etched to prepare a resin film B-12 (thickness: 55 μm). The various evaluation results of the resin film B-12 are as follows: Relative permittivity: 3.0, Dielectric loss tangent: 0.0040, CTE (TD): 42 ppm / K, CTE (MD): 30 ppm / K, Heat resistance of conditioned solder: Good.

[0264] [Example B-13] In 50 g of DMAc solution containing 50 wt% of LCP B-3 micro powder, 24.6 g of particles B-2 were added. After stirring, 10 g of LCP B-1 in shape B-1 was added. DMAc was added to dilute the solution to a total solids concentration of 50 wt%, and the mixture was stirred to prepare LCP varnish B-1. The content of LCP B-1 relative to the volume of all solids in the LCP varnish B-1 was 20%, and that of particles B-2 was 30%.

[0265] The prepared LCP varnish B-1 was cast onto an electrolytic copper foil (12 μm) and dried at 130°C for 3 minutes. Subsequently, a phased heat treatment was performed from 155°C to 340°C to prepare a copper-clad laminate B-13. Then, the copper foil was etched to prepare a resin film B-13 (thickness: 45 μm). The various evaluation results of the resin film B-13 are as follows: Relative permittivity: 2.8, Dielectric loss tangent: 0.0015, CTE (TD): 40 ppm / K, CTE (MD): 38 ppm / K

[0266] [Comparative Example B-1] Except for the LCP B-1 without the addition of particles B-1 and the shape B-1, copper-clad laminate B-14 and resin film B-14 (thickness: 50 μm) were prepared in the same manner as in Example B-1. Various evaluation results for resin film B-14 and copper-clad laminate B-14 are as follows: Relative permittivity: 2.6, Dielectric loss tangent: 0.0019, CTE (TD): 150 ppm / K, CTE (MD): 150 ppm / K, Peel strength: 1.3 kN / m, Heat resistance of conditioned solder: Good

[0267] [Comparative Example B-2] Except for the LCP B-1 without shape B-1, copper-clad laminate B-15 and resin film B-15 (thickness: 49 μm) were prepared in the same manner as in Example B-3. Various evaluation results for resin film B-15 are as follows: Relative permittivity: 2.8, Dielectric loss tangent: 0.0013, CTE (TD): 90 ppm / K, CTE (MD): 90 ppm / K, Heat resistance of conditioned solder: Good

[0268] [Comparative Example B-3] Except for the LCP B-1 without shape B-1, copper-clad laminate B-16 and resin film B-16 (thickness: 48 μm) were prepared in the same manner as in Example B-6. Various evaluation results for resin film B-16 are as follows: Relative permittivity: 2.9, Dielectric loss tangent: 0.0020, CTE (TD): 72 ppm / K, CTE (MD): 72 ppm / K, Heat resistance of conditioned solder: Good

[0269] [Comparative Example B-4] Except for the LCP B-1 without shape B-1, copper-clad laminate B-17 and resin film B-17 (thickness: 53 μm) were prepared in the same manner as in Example B-7. Various evaluation results for resin film B-17 are as follows: Relative permittivity: 2.8, Dielectric loss tangent: 0.0016, CTE (TD): 129 ppm / K, CTE (MD): 129 ppm / K, Heat resistance of conditioned solder: Good

[0270] [Reference Example B-1] Except for the absence of particles B-1, copper-clad laminate B-18 and resin film B-18 (thickness: 63 μm) were prepared in the same manner as in Example B-2. Various evaluation results for resin film B-18 are as follows: Relative permittivity: 1.9, Dielectric loss tangent: 0.0017, CTE (TD): 120 ppm / K, CTE (MD): 16 ppm / K, Heat resistance of conditioned solder: Good

[0271] In addition to the above, the various measurements and evaluations in the following embodiments are performed using the following methods.

[0272] [Evaluation of Dielectric Properties] <Liquid Crystal Polymer Particles> A dimethylacetamide dispersion of liquid crystal polymer particles, adjusted to 30% by weight of solid content, was coated onto a smooth surface of copper foil and dried at 120°C for 10 minutes. Subsequently, the temperature was gradually increased from 200°C to 360°C over 10 minutes to etch and remove the copper foil of the resulting laminate, thereby obtaining a liquid crystal polymer film. Using a vector network analyzer (manufactured by Keysight Technologies, trade name: Vector Network Analyzer E8363C) and a split dielectric resonator (SPDR resonator), the relative permittivity and dielectric loss tangent of the obtained liquid crystal polymer film were measured at a frequency of 10 GHz after being placed at a temperature of 23°C and a humidity of 50% for 24 hours.

[0273] [Determination of Volume Average Particle Size D50] A laser diffraction particle size distribution measuring device (manufactured by Malvern, trade name: Master Sizer 3000 laser particle size analyzer) was used to determine the volume average particle size of resin particles by using laser diffraction-scattering method under the condition that the particle refractive index is 1.54, with water as the dispersion medium.

[0274] The abbreviations used in the Examples and Comparative Examples refer to the following compounds. LCP C-1: A liquid crystal polymer having a polyester structure, melting point (Tm): 350°C, true specific gravity: 1.4, relative permittivity: 3.1, dielectric loss tangent: 0.0010. LCP C-2: A liquid crystal polymer having a polyester structure, melting point (Tm): 330°C, true specific gravity: 1.4, relative permittivity: 3.4, dielectric loss tangent: 0.0020.

[0275] Shape C-1: Short fiber, average length of long axis: 0.5 mm, average length of short axis: 28 μm, manufacturing method: melt spinning followed by cutting. Shape C-2: Short fiber, average length of long axis: 1 mm, average length of short axis: 28 μm, manufacturing method: melt spinning followed by cutting.

[0276] Particle C-1: A liquid crystal polymer with a polyester structure, melting point (Tm): 320℃, true specific gravity: 1.4, relative permittivity: 3.4, dielectric loss tangent: 0.0008, D50: 10 μm, irregular shape. Particle C-2: A liquid crystal polymer with a polyester structure, melting point (Tm): 325℃, true specific gravity: 1.4, relative permittivity: 3.4, dielectric loss tangent: 0.0007, D50: 5 μm, irregular shape.

[0277] (Synthesis Examples C-1 to C-3) Polyimide solution C-1, polyimide solution C-2, and polyimide solution C-3 were prepared in the same manner as in Synthesis Examples A-1, A-2, and A-3.

[0278] (Synthesis Examples C-4 and C-5) Polyamide solution C-1 and polyamide solution C-2 were prepared in the same manner as in Synthesis Examples B-4 and B-5.

[0279] [Example C-1] In 100 g of the polyimide solution C-1 obtained in Synthesis Example C-1, 1.1 g of N-12 as a crosslinking agent was added, 11.7 g of particles C-1 was added, and after stirring, 11.7 g of LCP C-1 in shape C-1 was added. Xylene was added to dilute the solution to a total solids concentration of 45% by weight, and the mixture was stirred to prepare polyimide varnish C-1. Regarding the content relative to the volume of all solids in the polyimide varnish C-1, the LCP C-1 content was 20%, and the particles C-1 content was 20%.

[0280] The prepared polyimide varnish C-1 was cast onto an electrolytic copper foil (12 μm), dried at 80°C for 20 minutes, and then treated at 160°C for 1 hour to prepare a copper-clad laminate C-1. Subsequently, a resin film C-1 (thickness: 129 μm) was prepared by etching the copper foil. The evaluation results of the resin film C-1 and the copper-clad laminate C-1 are as follows: Relative permittivity: 1.8, Dielectric loss tangent: 0.0015, CTE (TD): 90 ppm / K, CTE (MD): 14 ppm / K, Peel strength: 1.3 kN / m, Heat resistance of conditioned solder: Good.

[0281] [Example C-2] In 100 g of the polyimide solution C-1 obtained in Synthesis Example C-1, 1.1 g of N-12 as a crosslinking agent was added, 35.0 g of particles C-1 was added, and after stirring, 17.5 g of LCP C-1 in shape C-1 was added. Xylene was added to dilute the solution to a total solids concentration of 45% by weight, and the mixture was stirred to prepare polyimide varnish C-2. Regarding the content relative to the volume of all solids in the polyimide varnish C-2, LCP C-1 was 20%, and particles C-1 was 40%.

[0282] The prepared polyimide varnish C-2 was cast onto an electrolytic copper foil (12 μm), dried at 80°C for 20 minutes, and then treated at 160°C for 1 hour to prepare a copper-clad laminate C-2. Subsequently, a resin film C-2 (thickness: 143 μm) was prepared by etching the copper foil. The various evaluation results of the resin film C-2 are as follows: Relative permittivity: 1.9, Dielectric loss tangent: 0.0013, CTE (TD): 64 ppm / K, CTE (MD): 7 ppm / K, Heat resistance of conditioned solder: Good.

[0283] [Example C-3] In 100 g of the polyimide solution C-1 obtained in Synthesis Example C-1, 1.1 g of N-12 as a crosslinking agent was added, 11.7 g of particles C-2 was added, and after stirring, 11.7 g of LCP C-1 in shape C-1 was added. Xylene was added to dilute the solution to a total solids concentration of 45% by weight, and the mixture was stirred to prepare polyimide varnish C-3. Regarding the content of LCP C-1 relative to the volume of all solids in the polyimide varnish C-3, it was 20%, and the content of particles C-2 was 20%.

[0284] The prepared polyimide varnish C-3 was cast onto an electrolytic copper foil (12 μm), dried at 80°C for 20 minutes, and then treated at 160°C for 1 hour to prepare a copper-clad laminate C-3. Subsequently, a resin film C-3 (thickness: 127 μm) was prepared by etching the copper foil. The various evaluation results of the resin film C-3 are as follows: Relative permittivity: 1.9, Dielectric loss tangent: 0.0015, CTE (TD): 96 ppm / K, CTE (MD): 7 ppm / K, Heat resistance of conditioned solder: Good.

[0285] [Example C-4] In 100 g of the polyimide solution C-2 obtained in Synthesis Example C-2, 1.1 g of N-12 as a crosslinking agent was added, 35.0 g of particles C-1 was added, and after stirring, 17.5 g of LCP C-1 in shape C-1 was added. Xylene was added to dilute the solution to a total solids concentration of 45% by weight, and the mixture was stirred to prepare polyimide varnish C-4. Regarding the content of LCP C-1 relative to the volume of all solids in the polyimide varnish C-4, it was 20%, and the content of particles C-1 was 40%.

[0286] The prepared polyimide varnish C-4 was cast onto an electrolytic copper foil (12 μm), dried at 80°C for 20 minutes, and then treated at 160°C for 1 hour to prepare a copper-clad laminate C-4. Subsequently, a resin film C-4 (thickness: 122 μm) was prepared by etching the copper foil. The various evaluation results of the resin film C-4 are as follows: Relative permittivity: 1.9, Dielectric loss tangent: 0.0012, CTE (TD): 60 ppm / K, CTE (MD): 15 ppm / K

[0287] [Example C-5] In 100 g of the polyimide solution C-3 obtained in Synthesis Example C-3, 1.1 g of N-12 as a crosslinking agent was added, 35.0 g of particles C-1 was added, and after stirring, 17.5 g of LCP C-1 in shape C-1 was added. Xylene was added to dilute the solution to a total solids concentration of 45% by weight, and the mixture was stirred to prepare polyimide varnish C-5. Regarding the content relative to the volume of all solids in the polyimide varnish C-5, LCP C-1 was 20%, and particles C-1 was 40%.

[0288] The prepared polyimide varnish C-5 was cast onto an electrolytic copper foil (12 μm), dried at 80°C for 20 minutes, and then treated at 160°C for 1 hour to prepare a copper-clad laminate C-5. Subsequently, a resin film C-5 (thickness: 90 μm) was prepared by etching the copper foil. The evaluation results of the resin film C-5 and the copper-clad laminate C-5 are as follows: Relative permittivity: 2.0, Dielectric loss tangent: 0.0014, CTE (TD): 55 ppm / K, CTE (MD): 5 ppm / K, Peel strength: 1.5 kN / m, Heat resistance of conditioned solder: Good.

[0289] [Example C-6] To 100 g of the polyacrylic acid solution C-1 obtained in Synthesis Example C-4, 5 g of particle C-1 was added, and after stirring, 2.5 g of LCP C-1 of shape C-2 was added. DMAc was added to dilute the solution to a total solids concentration of 20% by weight, and the mixture was stirred to prepare polyacrylic acid varnish C-1. Regarding the content relative to the volume of all solids in the polyacrylic acid varnish C-1, the LCP C-1 content was 10%, and the particle C-1 content was 20%.

[0290] The prepared polyamide varnish C-1 was cast onto an electrolytic copper foil (12 μm) and dried at 130°C for 3 minutes. Subsequently, it underwent staged heat treatment from 155°C to 360°C and amide imidization to prepare a copper-clad laminate C-6. Then, by etching the copper foil, a resin film C-6 (thickness: 52 μm) was prepared. The various evaluation results of the resin film C-6 are as follows: Relative permittivity: 2.7, Dielectric loss tangent: 0.0027, CTE (TD): 15 ppm / K, CTE (MD): 5 ppm / K

[0291] [Example C-7] To 100 g of the polyacrylic acid solution C-2 obtained in Synthesis Example C-5, 5 g of particle C-2 was added, and after stirring, 2.5 g of LCP C-2 in shape C-2 was added. DMAc was added to dilute the solution to a total solids concentration of 15% by weight, and the mixture was stirred to prepare polyacrylic acid varnish C-2. Regarding the content relative to the volume of all solids in the polyacrylic acid varnish C-2, LCP C-2 was 10%, and particle C-2 was 20%.

[0292] The prepared polyamide varnish C-2 was cast onto an electrolytic copper foil (12 μm) and dried at 130°C for 3 minutes. Subsequently, it underwent staged heat treatment from 155°C to 360°C and amide imidization to prepare a copper-clad laminate C-7. Then, by etching the copper foil, a resin film C-7 (thickness: 45 μm) was prepared. The various evaluation results of the resin film C-7 are as follows: Relative permittivity: 2.7, Dielectric loss tangent: 0.0039, CTE (TD): 30 ppm / K, CTE (MD): 28 ppm / K

[0293] [Comparative Example C-1] Except for LCP C-1 without the addition of particles C-1 and shape C-1, copper-clad laminate C-8 and resin film C-8 (thickness: 50 μm) were prepared in the same manner as in Example C-1. Various evaluation results for resin film C-8 and copper-clad laminate C-8 are as follows: Relative permittivity: 2.6, Dielectric loss tangent: 0.0019, CTE (TD): 150 ppm / K, CTE (MD): 150 ppm / K, Peel strength: 1.3 kN / m, Heat resistance of conditioned solder: Good

[0294] [Comparative Example C-2] Except that the amount of particle C-1 added was set to 15 g and LCP C-1 of shape C-1 was not added, copper-clad laminate C-9 and resin film C-9 (thickness: 45 μm) were prepared in the same manner as in Example C-1. The various evaluation results of resin film C-9 and copper-clad laminate C-9 are as follows. Relative permittivity: 2.9, dielectric loss tangent: 0.0017, CTE (TD): 116 ppm / K, CTE (MD): 116 ppm / K, peel strength: 1.3 kN / m, heat resistance of conditioned solder: good

[0295] [Comparative Example C-3] Except that particle C-1 was replaced with particle C-2, copper-clad laminate C-10 and resin film C-10 (thickness: 50 μm) were prepared in the same manner as in Comparative Example C-2. The various evaluation results of resin film C-10 are as follows: Relative permittivity: 2.9, Dielectric loss tangent: 0.0017, CTE (TD): 110 ppm / K, CTE (MD): 110 ppm / K, Heat resistance of conditioned solder: Good

[0296] [Reference Example C-1] Except that no particles were added (C-1), copper-clad laminate C-11 and resin film C-11 (thickness: 63 μm) were prepared in the same manner as in Example C-1. The various evaluation results of resin film C-11 are as follows: Relative permittivity: 1.9, Dielectric loss tangent: 0.0017, CTE (TD): 120 ppm / K, CTE (MD): 16 ppm / K, Heat resistance of conditioned solder: Good.

[0297] The embodiments of the present invention have been described in detail above for illustrative purposes, but the present invention is not limited to the embodiments described above and can be modified in various ways. [Simplified Explanation of the Diagram]

[0054] None

Claims

1. A resin composition comprising: (A), (B), and (C) of the following: (A) a fibrous liquid crystal polymer filler having anisotropic shape and an L / D ratio of 2.5 or more when the average length of the major axis is L and the average length of the shortest minor axis orthogonal to the major axis is D; (B) a thermoplastic resin and / or a thermosetting resin as a base polymer; and (C) a particulate thermoplastic resin filler, wherein the content of the fibrous liquid crystal polymer filler of component (A) is in the range of 5 vol% to 60 vol% relative to the content of solids in the resin composition, the content of component (C) is in the range of 20 vol% to 80 vol% relative to the content of solids in the resin composition, the total content of the filler of component (A) and component (C) is in the range of 25 vol% to 90 vol% relative to the content of solids in the resin composition, and the volume average particle size D50 of the particulate thermoplastic resin filler of component (C) is 1. Within the range of μm to 100 μm.

2. The resin composition as claimed in claim 2, wherein the content of component (B) is in the range of 10% to 75% by volume relative to the content of solid components in the resin composition.

3. The resin composition as claimed in claim 1, wherein the average length L of the long axis of the fibrous liquid crystal polymer filler of component (A) is in the range of 0.1 mm to 5 mm, and the average diameter D of the short axis is in the range of 5 μm to 50 μm.

4. The resin composition as claimed in claim 1, wherein the fibrous liquid crystal polymer filler of component (A) has a melting point of 290°C or higher.

5. The resin composition as claimed in claim 1, wherein the particulate thermoplastic resin filler of component (C) is one or more particles selected from the group consisting of thermoplastic polyimide, liquid crystal polymer and fluororesin.

6. The resin composition as claimed in claim 1, wherein the ratio of the content of the fibrous liquid crystal polymer filler of component (A) to the content of component (C) [component (A) / component (C)] is in the range of 0.1 to 10 on a volume basis.

7. The resin composition as claimed in claim 1, wherein the ratio [D / D50] of the average diameter D of the short axis of the fibrous liquid crystal polymer filler of component (A) to the volume average particle size D50 of the particulate thermoplastic resin filler of component (C) is in the range of 1 to 50.

8. The resin composition as claimed in claim 1, wherein the ratio [L / D50] of the average length L of the long axis of the fibrous liquid crystal polymer filler of component (A) to the volume average particle size D50 of the particulate thermoplastic resin filler of component (C) is in the range of 10 to 1000.

9. The resin composition as claimed in claim 1, wherein the (B) component is selected from one or more thermoplastic polyimide, liquid crystal polymer and fluoropolymer.

10. The resin composition as claimed in claim 1, wherein the (B) component is a polyimide using a diamine component as a raw material, wherein the diamine component in the polyimide comprises a dimer diamine composition having a main component of a dimer diamine in which the two terminal carboxylic acid groups of the dimer acid are replaced with primary amino methyl or amino groups in an amount of 30 moles or more relative to all diamine components.

11. A resin film having a single or multiple resin layers, characterized in that at least one of the resin layers is a filler-containing resin layer formed using the resin composition as described in claim 1, wherein after being conditioned for 24 hours under constant temperature and humidity conditions of 23°C and 50%RH, the relative permittivity of the filler-containing resin layer at 10 GHz, as measured by a discrete dielectric resonator, is 3 or less, the dielectric loss tangent is 0.003 or less, and the overall thickness of the resin film is in the range of 15 μm to 250 μm.

12. The resin film as claimed in claim 11, wherein the absolute value of the average coefficient of thermal expansion in the longitudinal direction at 10°C to 20°C is 50 ppm / K or less, and the absolute value of the average coefficient of thermal expansion in the transverse direction is 100 ppm / K or less.

13. A metal-clad laminate comprising an insulating resin layer comprising one or more layers and a metal layer deposited on at least one side of the insulating resin layer, characterized in that at least one layer constituting the insulating resin layer comprises a resin film as described in claim 11.

14. A printed wiring board, comprising: The invention comprises a single or multiple insulating resin layers and a circuit wiring layer deposited on at least one side of the insulating resin layers, characterized in that at least one layer constituting the insulating resin layers comprises a resin film as described in claim 11.