TWI870299B - Resin composition and resin film - Google Patents

Abstract

A resin composition comprises: (A) a thermoplastic resin containing structural units derived from a diamine component, wherein the diamine component contains a dimer diamine composition having as a main component a dimer diamine in which both terminal carboxylic acid groups of a dimer acid are substituted with primary aminomethyl groups or amino groups in an amount of 40 mol% or more relative to all diamine components; and (B) at least one selected from an aromatic condensed phosphate, silica particles, or a liquid crystal polymer filler.

Description

Resin composition and resin film

The present invention relates to a resin composition which is effectively used as an adhesive in a circuit substrate such as a printed wiring board, and a resin film, a laminate, a cover film, a copper foil with a resin, a metal-clad laminate and a circuit substrate using the same.

In recent years, with the development of miniaturization, lightness and space saving of electronic equipment, the demand for flexible printed circuits (FPC) that are thin, light, flexible and have excellent durability even after repeated bending has increased. FPC can be installed in a three-dimensional and high-density manner even in a limited space, so its use has expanded to wiring of movable parts of electronic equipment such as hard disk drives (HDD), digital video disks (DVD), and mobile phones, or parts such as cables and connectors.

In addition to the above-mentioned high density, the performance of equipment is also constantly developing, so it is also necessary to cope with the high frequency of transmission signals. In information processing or communication, in order to transmit and process large amounts of information, efforts are being made to increase the transmission frequency, and printed circuit board materials are required to reduce transmission losses by thinning the insulation layer and improving the dielectric properties of the insulation layer. In the future, FPCs or adhesives that are required to cope with high frequencies will have a higher reduction in transmission losses.

For example, in millimeter wave transmission, which is one of the 5G transmissions, a direct conversion method is being studied in which millimeter waves flow directly through the FPC connecting the antenna and the substrate. The millimeter wave band is higher in frequency than the previous communication frequency, so the dielectric loss in the transmission loss becomes larger, so it becomes more important to improve the dielectric properties of the insulating resin layer. As a technology for improving the dielectric properties of the insulating resin layer of the circuit substrate, it is proposed to mix liquid crystal polymer particles in a thermoplastic resin or a thermosetting resin (Patent Document 1). However, Patent Document 1 does not include any examples other than epoxy resins, and no detailed research on thermoplastic resins has been conducted. In addition, it has been proposed to reduce the thermal expansion coefficient and relative dielectric constant by blending silicon dioxide particles in a polyimide resin used as an insulating resin layer of a circuit board (Patent Document 2, Patent Document 3).

As a technique related to an adhesive layer having polyimide as a main component, it is proposed to apply a crosslinked polyimide resin obtained by reacting a polyimide having a diamine compound derived from an aliphatic diamine such as dimer acid (dimer fatty acid) as a raw material with an amino compound having at least two primary amine groups as functional groups to an adhesive layer of a coating film (for example, Patent Document 4). In addition, it is proposed to apply a resin composition using such a polyimide together with a thermosetting resin such as an epoxy resin and a crosslinking agent to a copper clad laminate (for example, Patent Document 5). In addition, it is proposed to combine a metal salt of an organic phosphinic acid with a polyimide using a dimer acid-type diamine to achieve both low dielectric loss tangent and flame retardancy (Patent Document 6). However, Patent Documents 4 to 6 do not consider the influence of byproducts other than dimer diamine derived from the dimer acid contained in the raw material.

It is known that dimer acid is a dimerized fatty acid obtained by using natural fatty acids such as soybean oil fatty acid, tall oil fatty acid, rapeseed oil fatty acid, and oleic acid, linoleic acid, linolenic acid, erucic acid, etc., which are purified from these acids, as raw materials and subjecting them to a Diels-Alder reaction. Polyacid compounds derived from dimer acid can be obtained as raw material fatty acids or a composition of trimerized or higher fatty acids (for example, Patent Document 7). [Prior Art Document] [Patent Document]

[Patent Document 1] Japanese Patent No. 6295013 [Patent Document 2] Japanese Patent Publication No. 2001-185853 [Patent Document 3] Japanese Patent Publication No. 2018-012747 [Patent Document 4] Japanese Patent Publication No. 2013-1730 [Patent Document 5] Japanese Patent Publication No. 2017-119361 [Patent Document 6] Japanese Patent No. 6267509 [Patent Document 7] Japanese Patent Publication No. 2017-137375

[Problems to be solved by the invention] Thermoplastic resins such as polyimide (hereinafter sometimes referred to as "aliphatic thermoplastic resins") using aliphatic diamine compounds such as dimer diamine as raw materials have room for improvement in flame retardancy, but have low dielectric loss tangent and flexibility, and the cross-linked resin is a material that has both heat resistance and adhesion. Therefore, aliphatic thermoplastic resins are expected to be used as a material for high-speed transmission FPCs, the use of which will increase with the popularization of 5G communications. On the other hand, the frequency of signals flowing through FPCs is expected to be higher in the future, so a material based on aliphatic thermoplastic resins and having good dielectric properties is required.

In addition, as a method for controlling the physical properties of a resin having polyimide as a main component, it is important to control the molecular weight of polyamic acid or polyimide as a precursor of polyimide. However, when dimer diamine is used as a raw material, it is used in a state containing by-products other than dimer diamine derived from dimer acid. Such by-products not only make it difficult to control the molecular weight of polyimide, but also affect the dielectric properties or humidity dependence in a wide range of frequencies.

Therefore, the first object of the present invention is to provide a resin composition and a resin film that can cope with the high frequency of electronic devices by further improving the dielectric properties of aliphatic thermoplastic resins. In addition, the second object of the present invention is to provide a resin composition and a resin film that can cope with the high frequency of electronic devices by improving the dielectric properties while using dimer diamine as a raw material. [Means for solving the problem]

The resin composition of the present invention contains the following (A) components and (B) components; (A) a thermoplastic resin containing structural units derived from a diamine component, wherein the diamine component contains a dimer diamine composition having as a main component a dimer diamine in which the two terminal carboxylic acid groups of a dimer acid are substituted with primary aminomethyl or amino groups in an amount of 40 mol% or more relative to all diamine components, and (B) one or more selected from aromatic condensed phosphates, silica particles, or liquid crystal polymer fillers.

In the resin composition of the present invention, the component (A) may be a polyimide obtained by reacting a tetracarboxylic anhydride component with a diamine component containing 40 mol% or more of the dimer diamine composition relative to all diamine components, and the component (B) may be the aromatic condensed phosphate. In this case, the weight ratio of the component (B) to the component (A) may be in the range of 0.05 to 0.7, preferably in the range of 0.2 to 0.5. In addition, the weight ratio of phosphorus derived from the aromatic condensed phosphate of the component (B) to the component (A) may be in the range of 0.01 to 0.1. Furthermore, the weight ratio of phosphorus derived from the aromatic condensed phosphate in the component (B) to the dimer diamine composition in the component (A) may be in the range of 0.01 to 0.15.

The resin composition of the present invention may further contain an amino compound having at least two primary amino groups as functional groups.

In the resin composition of the present invention, the component (A) may be a polyamide or polyimide obtained by reacting a tetracarboxylic anhydride component with a diamine component containing 40 mol% or more of the dimer diamine composition relative to all diamine components, and the component (B) may be silica particles having a white silica crystal phase or a quartz crystal phase. In this case, the component (B) may be in a range of 5 wt% to 60 wt% relative to the total of the component (A) (wherein the polyamide is converted into imidized polyimide) and the component (B). In addition, in the silica particles of the component (B), the ratio of the total area of the peaks derived from the white silica crystal phase and the quartz crystal phase in the range of 2θ=10° to 90° in the X-ray diffraction analysis spectrum of CuKα rays to the total area of all peaks derived from _SiO2 can be 20% by weight or more. Furthermore, in the silica particles of the component (B), the average particle size _D50 at which the cumulative value in the frequency distribution curve obtained by volume-based particle size distribution measurement using a laser diffraction scattering method becomes 50% can be in the range of 6 μm to 20 μm.

In the resin composition of the present invention, the component (A) may be a polyimide obtained by reacting a tetracarboxylic anhydride component with a diamine component containing 40 mol% or more of the dimer diamine composition relative to all diamine components, and the component (B) may be the liquid crystal polymer filler. In this case, the component (B) may be in the range of 15 volume % to 50 volume % relative to the total of the components (A) and (B). In addition, when the dielectric loss tangent of the component (A) at 10 GHz is set to Dfa and the dielectric loss tangent of the liquid crystal polymer filler of the component (B) at 10 GHz is set to Dfb, Dfb may be less than 0.0019, and may be Dfa>Dfb. In addition, 15 wt % to 30 wt % of a phosphorus-based flame retardant may be further added relative to 100 wt % of the non-volatile organic compound component of the resin composition.

In the resin composition of the present invention, the component (A) may contain 90 mol parts or more of tetracarboxylic anhydride represented by the following general formula (1) and/or general formula (2) based on 100 mol parts of the tetracarboxylic anhydride component.

[Chemistry 1]

In the general formula (1), X represents a single bond or a divalent group selected from the following formulae. In the general formula (2), the cyclic moiety represented by Y represents a cyclic saturated hydrocarbon group selected from a four-membered ring, a five-membered ring, a six-membered ring, a seven-membered ring or an eight-membered ring.

[Chemistry 2]

In the above formula, Z represents -C ₆ H ₄ -, -(CH ₂ )n- or -CH ₂ -CH(-OC(=O)-CH ₃ )-CH ₂ -, and n represents an integer of 1-20.

The resin film of the present invention is a resin film comprising a thermoplastic resin layer, and contains the following (A) components and (B) components; (A) a thermoplastic resin containing structural units derived from a diamine component, wherein the diamine component contains a dimer diamine composition having as a main component a dimer diamine in which the two terminal carboxylic acid groups of a dimer acid are substituted with primary aminomethyl or amino groups in an amount of 40 mol% or more relative to all diamine components, and (B) one or more selected from aromatic condensed phosphates, silica particles, or liquid crystal polymer fillers.

The thickness of the resin film of the present invention may be in the range of 15 μm to 100 μm.

In the resin film of the present invention, when the component (B) includes silicon dioxide particles having a white silica crystal phase or a quartz crystal phase, the content thereof may be in the range of 3 volume % to 41 volume % relative to the total of the components (A) and (B).

In the resin film of the present invention, when the component (B) includes the liquid crystal polymer filler, the content thereof may be in the range of 15 volume % to 40 volume % relative to the total of the components (A) and (B).

The laminate of the present invention comprises a substrate and an adhesive layer laminated on at least one surface of the substrate, wherein the adhesive layer comprises the resin film.

The covering film of the present invention comprises a covering film material layer and an adhesive layer laminated on the covering film material layer, wherein the adhesive layer includes the resin film.

The resin-coated copper foil of the present invention is obtained by laminating an adhesive layer and a copper foil, wherein the adhesive layer includes the resin film.

The metal-clad laminate of the present invention comprises an insulating resin layer and a metal layer laminated on at least one surface of the insulating resin layer, and at least one layer of the insulating resin layer comprises the resin film.

The circuit board of the present invention is obtained by wiring the metal layer of the metal-clad laminate. [Effect of the invention]

The resin composition of the present invention contains component (A) and component (B), so the resin film formed using the resin composition has excellent dielectric properties and flexibility derived from the dimer diamine, and has dielectric properties further improved by the formulation of component (B). Therefore, the resin composition and resin film of the present invention can be particularly preferably used as a circuit substrate material such as FPC in electronic devices requiring high-speed signal transmission.

The following is a description of the embodiments of the present invention. The resin composition of one embodiment of the present invention contains the following (A) components and (B) components; (A) a thermoplastic resin containing structural units derived from a diamine component, wherein the diamine component contains a dimer diamine composition in which the two terminal carboxylic acid groups of the dimer acid are substituted with primary aminomethyl or amino groups in an amount of 40 mol% or more relative to all diamine components as the main component, and (B) one or more selected from aromatic condensed phosphates, silica particles, or liquid crystal polymer fillers.

[Component (A); thermoplastic resin] The thermoplastic resin of component (A) refers to a resin containing structural units derived from a diamine component and having a maximum value of loss tangent (tanδ) of less than 200°C as measured using a dynamic viscoelasticity measuring device (dynamic mechanical analyzer (DMA)), wherein the diamine component contains a dimer diamine composition having as a main component a dimer diamine in which both terminal carboxylic acid groups of a dimer acid are substituted with primary aminomethyl groups or amino groups in an amount of 40 mol% or more relative to all diamine components. Therefore, the thermoplastic resin includes: thermoplastic polyimide containing 40 mol% or more of the diamine component of the dimer diamine composition as a raw material, polyamide acid as a precursor thereof, thermoplastic dimaleimide resin, thermoplastic epoxy resin, thermoplastic polyamide resin, and cured products thereof. These thermoplastic resins may be prepared in combination of two or more. Among these thermoplastic resins, more preferred are thermoplastic polyimides (hereinafter sometimes referred to as "DDA-based thermoplastic polyimides") obtained by imidizing a polyamic acid precursor obtained by reacting a tetracarboxylic anhydride component with a diamine component, and crosslinked cured products thereof, wherein the diamine component contains a dimer diamine composition in which the two terminal carboxylic acid groups of the dimer acid are substituted with primary aminomethyl or amino groups in an amount of 40 mol% or more relative to all diamine components.

Hereinafter, DDA-based thermoplastic polyimide is listed as a representative example of thermoplastic resin and described in detail. The so-called "thermoplastic polyimide" is generally a polyimide with a clearly confirmed glass transition temperature (Tg), but in the present invention, it refers to a polyimide having a storage modulus of 1.0×10 ⁸ Pa or more at 30°C and a storage modulus of less than 3.0×10 ⁷ Pa at 300°C measured using a dynamic viscoelasticity measuring device (DMA). In addition, the so-called "non-thermoplastic polyimide" is generally a polyimide that does not soften even when heated and exhibits adhesiveness, but in the present invention, it refers to a polyimide having a storage elastic modulus of 1.0×10 ⁹ Pa or more at 30°C and a storage elastic modulus of 3.0×10 ⁸ Pa or more at 300°C as measured using a dynamic viscoelasticity measuring device (DMA).

<DDA-based thermoplastic polyimide> DDA-based thermoplastic polyimide is an aliphatic thermoplastic polyimide with high flexibility. It has sufficient toughness even when a large amount of liquid crystal polymer filler is added, and has a high ability to maintain its shape when forming a resin film. Therefore, the content of DDA-based thermoplastic polyimide in component (A) is preferably 60% by weight or more, more preferably 70% by weight or more, and most preferably 80% by weight or more. If the content of DDA-based thermoplastic polyimide in component (A) is less than 60% by weight, the toughness of the thermoplastic resin is reduced, and the film retention when forming a resin film is reduced.

The DDA-based thermoplastic polyimide contains tetracarboxylic acid residues derived from tetracarboxylic anhydride as a raw material and diamine residues derived from diamine compounds as a raw material. By reacting the tetracarboxylic anhydride and diamine compounds as raw materials in approximately equimolar amounts, the types and amounts of tetracarboxylic acid residues and diamine residues contained in the DDA-based thermoplastic polyimide can be made to roughly correspond to the types and amounts of the raw materials.

(Tetracarboxylic anhydride component) The DDA-based thermoplastic polyimide can use tetracarboxylic anhydride generally used in thermoplastic polyimide as a raw material without particular limitation, and preferably contains 90 mol% or more of tetracarboxylic anhydride represented by the following general formula (1) and/or general formula (2) relative to all tetracarboxylic anhydride components. In other words, the DDA-based thermoplastic polyimide preferably contains 90 mol% or more of tetracarboxylic acid residues derived from tetracarboxylic anhydride represented by the following general formula (1) and/or general formula (2) relative to 100 mol% of all tetracarboxylic acid residues. By containing 90 mol parts or more of tetracarboxylic acid residues derived from tetracarboxylic anhydride represented by the following general formula (1) and/or general formula (2) relative to 100 mol parts of tetracarboxylic acid residues, it is easy to achieve a balance between the softness and heat resistance of the DDA-based thermoplastic polyimide. When the total amount of tetracarboxylic acid residues derived from tetracarboxylic anhydride represented by the following general formula (1) and/or general formula (2) is less than 90 mol parts, the solvent solubility of the DDA-based thermoplastic polyimide tends to decrease.

[Chemistry 3]

In the general formula (1), X represents a single bond or a divalent group selected from the following formulae. In the general formula (2), the cyclic moiety represented by Y represents a cyclic saturated hydrocarbon group selected from a four-membered ring, a five-membered ring, a six-membered ring, a seven-membered ring or an eight-membered ring.

[Chemistry 4]

In the above formula, Z represents -C ₆ H ₄ -, -(CH ₂ )n- or -CH ₂ -CH(-OC(=O)-CH ₃ )-CH ₂ -, and n represents an integer of 1-20.

Examples of the tetracarboxylic anhydride represented by the general formula (1) include 3,3',4,4'-biphenyltetracarboxylic anhydride (BPDA), 3,3',4,4'-benzophenonetetracarboxylic anhydride (BTDA), 3,3',4,4'-diphenylsulfonatetetracarboxylic anhydride (DSDA), 4,4'-oxydiphthalic anhydride (ODPA), 4,4'-(hexafluoroisopropylidene)diphthalic anhydride (6FDA), 2,2-bis[4-(3,4-dicarboxyphenoxy)phenyl]propane dianhydride (BPADA), paraphenylenebis(trimellitic acid monoester anhydride) (TAHQ), ethylene glycol bis(trimellitic acid monoester anhydride) (TMEG), etc. Among these, 3,3',4,4'-benzophenonetetracarboxylic anhydride (BTDA) is particularly preferred. When BTDA is used, the carbonyl group (ketone group) contributes to the adhesion, thus suppressing the decrease in peel strength when adding a liquid crystal polymer filler as the (B) component, and improving the adhesion of the DDA-based thermoplastic polyimide. In addition, the ketone group existing in the molecular skeleton of BTDA reacts with the amino group of the amino compound used for crosslinking to form a C=N bond, which easily shows the effect of improving heat resistance. From this point of view, it is preferable to contain 50 mol parts or more, more preferably 60 mol parts or more of tetracarboxylic acid residues derived from BTDA relative to 100 mol parts of tetracarboxylic acid residues.

Examples of the tetracarboxylic anhydride represented by the general formula (2) include 1,2,3,4-cyclobutanetetracarboxylic dianhydride, 1,2,3,4-cyclopentanetetracarboxylic dianhydride, 1,2,4,5-cyclohexanetetracarboxylic dianhydride, 1,2,4,5-cycloheptanetetracarboxylic dianhydride, and 1,2,5,6-cyclooctanetetracarboxylic dianhydride.

The DDA-based thermoplastic polyimide may contain tetracarboxylic acid residues derived from an acid anhydride other than the tetracarboxylic acid anhydride represented by the general formula (1) and the general formula (2) as long as the effect of the invention is not impaired. Such tetracarboxylic acid residues are not particularly limited, and examples thereof include pyromellitic acid dianhydride, 2,3',3,4'-biphenyltetracarboxylic acid dianhydride, 2,2',3,3'-benzophenonetetracarboxylic acid dianhydride or 2,3,3',4'-benzophenonetetracarboxylic acid dianhydride, 2,3',3,4'-diphenylethertetracarboxylic acid dianhydride, bis(2,3-dicarboxyphenyl)ether dianhydride, 3,3'',4,4''-triphenylenetetracarboxylic acid dianhydride, 2,3,3'',4''-triphenylenetetracarboxylic acid dianhydride or 2,2'',3,3''-triphenylenetetracarboxylic acid dianhydride, 2 ,2-bis(2,3-dicarboxyphenyl)-propane dianhydride or 2,2-bis(3,4-dicarboxyphenyl)-propane dianhydride, bis(2,3-dicarboxyphenyl)methane dianhydride or bis(3,4-dicarboxyphenyl)methane dianhydride, bis(2,3-dicarboxyphenyl)sulfonate dianhydride or bis(3,4-dicarboxyphenyl)sulfonate dianhydride, 1,1-bis(2,3-dicarboxyphenyl)ethane dianhydride or 1,1-bis(3,4-dicarboxyphenyl)ethane dianhydride, 1,2,7,8-phenanthrene-tetracarboxylic dianhydride, 1,2,6,7-phenanthrene-tetracarboxylic dianhydride or 1,2,9,10- Phenanthrene-tetracarboxylic dianhydride, 2,3,6,7-anthracenetetracarboxylic dianhydride, 2,2-bis(3,4-dicarboxyphenyl)tetrafluoropropane dianhydride, 1,2,5,6-naphthalenetetracarboxylic dianhydride, 1,4,5,8-naphthalenetetracarboxylic dianhydride, 2,3,6,7-naphthalenetetracarboxylic dianhydride, 4,8-dimethyl-1,2,3,5,6,7-hexahydronaphthalene-1,2,5,6-tetracarboxylic dianhydride, 2,6-dichloronaphthalene-1,4,5,8-tetracarboxylic dianhydride or 2,7-dichloronaphthalene-1,4,5,8-tetracarboxylic dianhydride, 2,3,6,7-(or 1,4,5,8-) A tetracarboxylic acid residue derived from an aromatic tetracarboxylic acid dianhydride such as tetrachloronaphthalene-1,4,5,8-(or 2,3,6,7-)tetracarboxylic dianhydride, 2,3,8,9-perylene-tetracarboxylic dianhydride, 3,4,9,10-perylene-tetracarboxylic dianhydride, 4,5,10,11-perylene-tetracarboxylic dianhydride or 5,6,11,12-perylene-tetracarboxylic dianhydride, pyrazine-2,3,5,6-tetracarboxylic dianhydride, pyrrolidine-2,3,4,5-tetracarboxylic dianhydride, thiophene-2,3,4,5-tetracarboxylic dianhydride, and 4,4'-bis(2,3-dicarboxyphenoxy)diphenylmethane dianhydride.

(Diamine component) DDA-based thermoplastic polyimide uses a diamine component containing 40 mol% or more, preferably 60 mol% or more of a dimer diamine component relative to all diamine components as a raw material. By containing the dimer diamine component in the above amount, the dielectric properties of the polyimide can be improved, and the heat pressing properties can be improved by lowering the glass transition temperature (lower Tg) of the polyimide, and the internal stress can be relieved by lowering the elastic modulus.

(Dimer diamine composition) The dimer diamine composition contains the following component (a) as a main component, and the amounts of component (b) and component (c) are controlled.

(a) Dimer diamine; The so-called dimer diamine as component (a) refers to a diamine in which the two terminal carboxylic acid groups (-COOH) of dimer acid are replaced by primary aminomethyl groups ( _-CH2 - _NH2 ) or amino groups ( _-NH2 ). Dimer acid is a known dibasic acid obtained by the intermolecular polymerization reaction of unsaturated fatty acids. Its industrial production process has been largely standardized in the industry, and it is obtained by dimerizing unsaturated fatty acids with carbon numbers of 11 to 22 using clay catalysts. The main component of industrially available dimer acid is a dibasic acid with 36 carbon atoms obtained by dimerizing unsaturated fatty acids with 18 carbon atoms, such as oleic acid, linolenic acid, and linolenic acid. Depending on the degree of purification, it contains any amount of monomeric acid (with 18 carbon atoms), trimer acid (with 54 carbon atoms), and other polymerized fatty acids with 20 to 54 carbon atoms. In addition, double bonds remain after the dimerization reaction, but in the present invention, dimer acids that have been further hydrogenated to reduce the degree of unsaturation also include dimer acids. The dimer diamine as component (a) can be defined as a diamine compound obtained by replacing the terminal carboxylic acid group of a dibasic acid compound with a carbon number of 18 to 54, preferably 22 to 44, with a primary aminomethyl group or an amino group.

As a characteristic of dimer diamine, it can be endowed with characteristics derived from the dimer acid skeleton. That is, dimer diamine is a giant aliphatic molecule with a molecular weight of about 560 to 620, so the molar volume of the molecule can be increased, and the polar groups of the DDA-based thermoplastic polyimide can be relatively reduced. It is believed that the characteristics of such dimer acid-type diamines help to suppress the decrease in the heat resistance of the DDA-based thermoplastic polyimide, while reducing the relative dielectric constant and dielectric loss tangent, and improving the dielectric properties. In addition, since it has two freely movable hydrophobic chains with carbon numbers of 7 to 9 and two chain aliphatic amine groups with a length close to carbon numbers of 18, it is possible to impart flexibility to the DDA-based thermoplastic polyimide, and it is also possible to give the DDA-based thermoplastic polyimide an asymmetric chemical structure or a non-planar chemical structure, thereby realizing a low dielectric constant.

The dimer diamine composition preferably has a dimer diamine content as the component (a) increased to 96% by weight or more, preferably 97% by weight or more, and more preferably 98% by weight or more by a purification method such as molecular distillation. By setting the dimer diamine content as the component (a) to 96% by weight or more, the expansion of the molecular weight distribution of the DDA-based thermoplastic polyimide can be suppressed. Furthermore, if technically feasible, it is best that the entirety (100% by weight) of the dimer diamine composition includes the dimer diamine as the component (a).

(b) A monoamine compound obtained by substituting the terminal carboxylic acid group of a monoacid compound having 10 to 40 carbon atoms with a primary aminomethyl group or an amino group; The monoacid compound having 10 to 40 carbon atoms is a mixture of a monobasic unsaturated fatty acid having 10 to 20 carbon atoms, which is a raw material of dimer acid, and a monoacid compound having 21 to 40 carbon atoms, which is a byproduct when producing dimer acid. The monoamine compound is obtained by substituting the terminal carboxylic acid group of these monoacid compounds with a primary aminomethyl group or an amino group.

The monoamine compound as component (b) is a component that suppresses the increase in molecular weight of polyimide. During the polymerization of polyamic acid or polyimide, the monofunctional amine group of the monoamine compound reacts with the terminal anhydride group of polyamic acid or polyimide, thereby sealing the terminal anhydride group, thereby suppressing the increase in molecular weight of polyamic acid or polyimide.

(c) Amine compounds obtained by substituting the terminal carboxylic acid group of a polyacid compound having an alkyl group in the range of 41 to 80 carbon atoms with a primary aminomethyl group or an amino group (except the dimer diamine); The polyacid compound having an alkyl group in the range of 41 to 80 carbon atoms is a polyacid compound having a tribasic acid compound in the range of 41 to 80 carbon atoms as a by-product when producing dimer acid as a main component. In addition, polymerized fatty acids other than dimer acids having 41 to 80 carbon atoms may be included. Amine compounds are obtained by substituting the terminal carboxylic acid group of these polyacid compounds with a primary aminomethyl group or an amino group.

The amine compound as component (c) is a component that promotes the increase in the molecular weight of polyimide. The trifunctional or higher amine group, which is mainly composed of a triamine derived from trimer acid, reacts with the terminal anhydride group of polyamic acid or polyimide, thereby rapidly increasing the molecular weight of polyimide. In addition, amine compounds derived from polymerized fatty acids other than dimer acid having 41 to 80 carbon atoms also increase the molecular weight of polyimide and cause the gelation of polyamic acid or polyimide.

When the dimer diamine composition is quantitatively determined by gel permeation chromatography (GPC), a sample treated with acetic anhydride and pyridine is used to easily confirm the peak start, peak top, and peak end of each component of the dimer diamine composition, and cyclohexanone is used as an internal standard substance. The sample prepared in the above manner is used to quantify each component using the area percentage of the chromatogram of GPC. The peak start and peak end of each component can be used as the minimum value of each peak curve and the area percentage of the chromatogram can be calculated based on it.

In addition, in the dimer diamine composition used in the present invention, the total content of component (b) and component (c) is preferably 4% or less, and more preferably less than 4%, in terms of area percentage of the chromatogram obtained by GPC measurement. By setting the total content of component (b) and component (c) to 4% or less, the expansion of the molecular weight distribution of the polyimide can be suppressed.

In addition, the area percentage of the chromatogram of the component (b) is preferably 3% or less, more preferably 2% or less, and further preferably 1% or less. By setting it within such a range, the decrease in the molecular weight of the polyimide can be suppressed, and the range of the molar ratio of the tetracarboxylic anhydride component and the diamine component can be expanded. In addition, the component (b) may not be included in the dimer diamine composition.

In addition, the area percentage of the chromatogram of the component (c) is preferably 2% or less, preferably 1.8% or less, and more preferably 1.5% or less. By setting it within such a range, the molecular weight of the polyimide can be suppressed from increasing rapidly, and the dielectric loss tangent of the resin film can be suppressed from increasing in a wide frequency range. Furthermore, the component (c) may not be included in the dimer diamine composition.

When the ratio (b/c) of the area percentage of the component (b) to the component (c) in the chromatogram is 1 or more, the molar ratio of the tetracarboxylic anhydride component to the diamine component (tetracarboxylic anhydride component/diamine component) is preferably set to 0.97 or more and less than 1.0. By setting such a molar ratio, the molecular weight of the polyimide can be more easily controlled.

When the ratio (b/c) of the area percentages of the component (b) and the component (c) in the chromatogram is less than 1, the molar ratio of the tetracarboxylic anhydride component to the diamine component (tetracarboxylic anhydride component/diamine component) is preferably set to 0.97 or more and 1.1 or less. By setting such a molar ratio, the molecular weight of the polyimide can be more easily controlled.

The dimer diamine composition used in the present invention is preferably purified for the purpose of reducing components other than the dimer diamine as component (a). There is no particular limitation on the purification method, and a known method such as distillation or precipitation purification is preferred. The dimer diamine composition before purification can be obtained from commercial products, for example, PRIAMINE 1073 (trade name) manufactured by Croda Japan, PRIAMINE 1074 (trade name) manufactured by Croda Japan, PRIAMINE 1075 (trade name) manufactured by Croda Japan, etc.

As diamine compounds other than the dimer diamine used in the DDA-based thermoplastic polyimide, aromatic diamine compounds and aliphatic diamine compounds can be cited. Specific examples thereof include 1,4-diaminobenzene (p-PDA; p-phenylenediamine), 2,2'-dimethyl-4,4'-diaminobiphenyl (m-TB), 2,2'-n-propyl-4,4'-diaminobiphenyl (m-NPB), 4-aminophenyl-4'-aminobenzoate (APAB), 2,2-bis-[4-(3-aminophenoxy)phenyl]propane, bis[4-(3-aminophenoxy)phenyl]sulfone, bis[4-(3-aminophenoxy)]biphenyl, bis[1-(3-aminophenoxy)]biphenyl, bis[4-(3-aminophenoxy)phenyl] Methane, bis[4-(3-aminophenoxy)phenyl]ether, bis[4-(3-aminophenoxy)]benzophenone, 9,9-bis[4-(3-aminophenoxy)phenyl]fluorene, 2,2-bis-[4-(4-aminophenoxy)phenyl]hexafluoropropane, 2,2-bis-[4-(3-aminophenoxy)phenyl]hexafluoropropane, 3,3'-dimethyl-4,4'-diaminobiphenyl, 4,4'-methylenebis-o-toluidine, 4,4'-methylenebis-2,6-dimethylaniline, 4,4'-methylenebis-2,6-diethylaniline, 3,3'-diaminodiphenylethane, 3 ,3'-diaminobiphenyl, 3,3'-dimethoxybenzidine, 3,3''-diamino-p-terphenyl, 4,4'-[1,4-phenylenebis(1-methylethylidene)]bisaniline, 4,4'-[1,3-phenylenebis(1-methylethylidene)]bisaniline, bis(p-aminocyclohexyl)methane, bis(p-β-amino-tert-butylphenyl) ether, bis(p-β-methyl-δ-aminopentyl)benzene, p-bis(2-methyl-4-aminopentyl)benzene, p-bis(1,1-dimethyl-5-aminopentyl)benzene, 1,5-diaminonaphthalene, 2,6-diaminonaphthalene, 2,4-bis(p- diamine compounds such as (β-amino-tert-butyl)toluene, 2,4-diaminotoluene, m-xylene-2,5-diamine, p-xylene-2,5-diamine, m-phenylenediamine, p-phenylenediamine, 2,6-diaminopyridine, 2,5-diaminopyridine, 2,5-diamino-1,3,4-oxadiazole, piperazine, 2'-methoxy-4,4'-diaminobenzanilide, 4,4'-diaminobenzanilide, 1,3-bis[2-(4-aminophenyl)-2-propyl]benzene, 6-amino-2-(4-aminophenoxy)benzoxazole, and 1,3-bis(3-aminophenoxy)benzene.

DDA-based thermoplastic polyimide can be produced by reacting the tetracarboxylic anhydride component and the diamine component in a solvent to generate polyamide, followed by heating for ring closure. For example, the tetracarboxylic anhydride component and the diamine component are dissolved in an organic solvent in approximately equal moles, and the polymerization reaction is carried out by stirring for 30 minutes to 24 hours at a temperature in the range of 0°C to 100°C, thereby obtaining polyamide as a precursor of polyimide. During the reaction, the reaction components are dissolved in such a manner that the generated precursor is in the range of 5% by weight to 50% by weight, preferably in the range of 10% by weight to 40% by weight in the organic solvent. Examples of organic solvents used in the polymerization reaction include N,N-dimethylformamide (DMF), N,N-dimethylacetamide (DMAc), N,N-diethylacetamide, N-methyl-2-pyrrolidone (NMP), 2-butanone, dimethyl sulfoxide (DMSO), hexamethylphosphatamide, N-methylcaprolactam, dimethyl sulfate, cyclohexanone, methylcyclohexane, dioxane, tetrahydrofuran, diethylene glycol dimethyl ether (diglyme), triethylene glycol dimethyl ether (triglyme), methanol, ethanol, benzyl alcohol, cresol, etc. 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. The amount of the organic solvent used is not particularly limited, but is preferably adjusted so that the concentration of the polyamide solution obtained by the polymerization reaction becomes about 5 wt % to 50 wt %.

The synthesized polyamine is usually advantageously used as a reaction solvent solution, and can be concentrated, diluted or replaced with other organic solvents as needed. In addition, polyamine is generally advantageously used due to its excellent solvent solubility. The viscosity of the polyamine solution is preferably in the range of 500 cps to 100,000 cps. If it deviates from this range, it is easy to produce undesirable conditions such as uneven thickness and streaks in the film when applying it using a coating machine.

The method for imidizing polyamic acid to form polyimide is not particularly limited, and for example, a heat treatment such as heating in the solvent at a temperature condition in the range of 80° C. to 400° C. for 1 hour to 24 hours can be preferably adopted. In addition, regarding the temperature, heating can be performed under a fixed temperature condition, or the temperature can be changed in the middle of the step.

In the DDA-based thermoplastic polyimide, by selecting the types of the tetracarboxylic anhydride component and the diamine component, or the molar ratio of each when two or more tetracarboxylic anhydride components or diamine components are used, the dielectric properties, thermal expansion coefficient, tensile elastic modulus, glass transition temperature, etc. can be controlled. In addition, in the DDA-based thermoplastic polyimide, when there are a plurality of structural units of polyimide, they may exist in the form of blocks or randomly, preferably randomly.

The weight average molecular weight of the DDA-based thermoplastic polyimide is preferably in the range of 10,000 to 200,000, and within this range, the weight average molecular weight of the polyimide can be easily controlled. In addition, when used as an adhesive for FPC, the weight average molecular weight of the DDA-based thermoplastic polyimide is more preferably in the range of 20,000 to 150,000, and further preferably in the range of 40,000 to 150,000. When used as an adhesive for FPC, if the weight average molecular weight of the DDA-based thermoplastic polyimide is less than 20,000, there is a tendency for the flow resistance to deteriorate. On the other hand, if the weight average molecular weight of the DDA-based thermoplastic polyimide exceeds 150,000, the viscosity increases excessively and the polyimide becomes insoluble in the solvent, which tends to cause undesirable problems such as uneven thickness and streaks of the adhesive layer during coating.

The imide group concentration of the DDA-based thermoplastic polyimide is preferably 22% by weight or less, and more preferably 20% by weight or less. Here, "imide group concentration" refers to the value obtained by dividing the molecular weight of the imide group (-(CO) ₂ -N-) in the polyimide by the molecular weight of the entire structure of the polyimide. If the imide group concentration exceeds 22% by weight, the molecular weight of the resin itself becomes smaller, and the low hygroscopicity also deteriorates due to the increase in polar groups, and the Tg and elastic modulus increase.

The DDA-based thermoplastic polyimide is preferably a completely imidized structure. Among them, a part of the polyimide can be converted into amide. The imidization rate can be calculated by measuring the infrared absorption spectrum of the polyimide film using a Fourier transform infrared spectrophotometer (commercial product: FT/IR620 manufactured by JASCO Corporation) using the attenuated total reflection (ATR) method, and using the benzene ring absorber near 1015 cm ^-1 as the reference, based on the absorbance of 1780 cm ^-1 derived from the C=O stretching of the imide group.

<Crosslinking> When the DDA-based thermoplastic polyimide in the component (A) has a ketone group, the ketone group is reacted with an amine group of an amino compound having at least two primary amine groups as functional groups (hereinafter, sometimes referred to as "amino compound for crosslinking formation") to form a C=N bond, thereby forming a crosslinking structure. By forming a crosslinking structure, the heat resistance of the DDA-based thermoplastic polyimide can be improved. As a tetracarboxylic anhydride that is preferred for forming a DDA-based thermoplastic polyimide having a ketone group, for example, 3,3',4,4'-benzophenonetetracarboxylic dianhydride (BTDA) can be cited, and as a diamine compound, for example, aromatic diamines such as 4,4'-bis(3-aminophenoxy)benzophenone (BABP) and 1,3-bis[4-(3-aminophenoxy)benzyl]benzene (BABB) can be cited.

In order to form a cross-linked structure, the resin composition of the present embodiment preferably comprises: the DDA-based thermoplastic polyimide in the component (A) containing BTDA residues derived from BTDA in an amount of preferably 50 mol% or more, more preferably 60 mol% or more relative to all tetracarboxylic acid residues, and an amino compound for cross-linking formation. In the present invention, the "BTDA residues" refer to tetravalent groups derived from BTDA.

Examples of the crosslinking amino compound include (I) dihydrazide compounds, (II) aromatic diamines, and (III) aliphatic amines. Among these, dihydrazide compounds are preferred. Aliphatic amines other than dihydrazide compounds easily form a crosslinking structure even at room temperature, which may cause concerns about the storage stability of the varnish. On the other hand, aromatic diamines need to be heated to a high temperature to form a crosslinking structure. In this way, when a dihydrazide compound is used, both the storage stability of the varnish and the shortening of the curing time can be taken into account. Preferred examples of the dihydrazide compound include oxalic acid dihydrazide, malonate dihydrazide, succinate dihydrazide, glutaric acid dihydrazide, adipic acid dihydrazide, pimelic acid dihydrazide, suberic acid dihydrazide, azelaic acid dihydrazide, sebacic acid dihydrazide, dodecanedioic acid dihydrazide, maleic acid dihydrazide, fumaric acid dihydrazide, diethylene glycol, The present invention also includes dihydrazide compounds such as hydrazide of tartrate, hydrazide of apple acid, hydrazide of o-phthalate, hydrazide of isophthalate, hydrazide of terephthalate, hydrazide of 2,6-naphthoic acid, hydrazide of 4,4-diphenylhydrazide, hydrazide of 1,4-naphthoic acid, hydrazide of 2,6-pyridinediacid, and hydrazide of itaconic acid. The above dihydrazide compounds may be used alone or in combination of two or more.

Furthermore, the amino compounds such as (I) dihydrazide compounds, (II) aromatic diamines, and (III) aliphatic amines may be used in combination of two or more, for example, a combination of (I) and (II), a combination of (I) and (III), or a combination of (I) and (II) and (III).

In addition, from the viewpoint of making the network structure formed by crosslinking using the crosslink-forming amino compound denser, the molecular weight of the crosslink-forming amino compound used in the present invention (the weight average molecular weight when the crosslink-forming amino compound is an oligomer) is preferably 5,000 or less, more preferably 90 to 2,000, and further preferably 100 to 1,500. Among these, a crosslink-forming amino compound having a molecular weight of 100 to 1,000 is particularly preferred. If the molecular weight of the crosslink-forming amino compound is less than 90, one amino group of the crosslink-forming amino compound is limited to forming a C=N bond with a ketone group of the DDA-based thermoplastic polyimide, and the surrounding area of the remaining amino group becomes larger in volume in a three-dimensional manner, so there is a tendency that the remaining amino group is not easy to form a C=N bond.

In the case of crosslinking the ketone group in the DDA-based thermoplastic polyimide in the component (A) with the crosslinking amino compound, the crosslinking amino compound is added to the resin solution containing the component (A) to cause the ketone group in the DDA-based thermoplastic polyimide to undergo a condensation reaction with the primary amine group of the crosslinking amino compound. The resin solution is cured by the condensation reaction to form a cured product. In this case, the amount of the crosslinking amino compound added is 0.004 mol to 1.5 mol, preferably 0.005 mol to 1.2 mol, more preferably 0.03 mol to 0.9 mol, and most preferably 0.04 mol to 0.6 mol, per 1 mol of the ketone group. When the amount of the crosslinking amino compound added is less than 0.004 mol of the total primary amine groups per 1 mol of the ketone groups, the crosslinking by the crosslinking amino compound is insufficient, so that the heat resistance after curing tends to be difficult to exhibit. When the amount of the crosslinking amino compound added exceeds 1.5 mol, the unreacted crosslinking amino compound acts as a thermoplastic agent, and there is a tendency to reduce the heat resistance as an adhesive layer.

The conditions for the crosslinking condensation reaction are not particularly limited as long as the ketone group in the DDA-based thermoplastic polyimide in the component (A) reacts with the primary amine group of the crosslinking amine compound to form an imine bond (C=N bond). The temperature of the heat condensation is preferably in the range of 120°C to 220°C, more preferably in the range of 140°C to 200°C, for the reasons of releasing water generated by the condensation to the outside of the system or simplifying the condensation step when the heat condensation reaction is performed after the synthesis of the DDA-based thermoplastic polyimide in the component (A). The reaction time is preferably about 30 minutes to 24 hours. The end point of the reaction can be confirmed, for example, by measuring the infrared absorption spectrum using a Fourier transform infrared spectrophotometer (commercially available product: FT/IR620 manufactured by JASCO Corporation) and by the decrease or disappearance of the absorption peak derived from the ketone group in the polyimide resin at around 1670 cm ^-1 and the appearance of the absorption peak derived from the imine group at around 1635 cm ^-1 .

The heat condensation of the ketone group of the DDA-based thermoplastic polyimide in component (A) and the primary amine group of the crosslinking amino compound can be carried out, for example, by the following methods: (1) a method in which the crosslinking amino compound is added immediately after the synthesis (imidization) of the DDA-based thermoplastic polyimide in component (A) and the crosslinking amino compound is heated; (2) an excess of an amino compound is added as a diamine component in advance, the DDA-based thermoplastic polyimide in component (A) is synthesized (imidized), and the remaining amino compound that does not participate in the imidization or amidation is used as the crosslinking amino compound and heated together with the DDA-based thermoplastic polyimide; or (3) A method of heating the composition of the DDA-based thermoplastic polyimide in the component (A) to which the crosslink-forming amino compound is added after processing it into a predetermined shape (for example, after coating it on an arbitrary substrate or forming it into a film).

In order to impart heat resistance to the DDA-based thermoplastic polyimide in the component (A), the formation of imide bonds in the formation of the cross-linked structure has been described, but the present invention is not limited thereto. As a method for curing the polyimide in the component (A), for example, a compound having an unsaturated bond such as an epoxy resin, an epoxy resin hardener, maleimide, an activated ester resin, or a resin having a styrene skeleton may be formulated for curing.

[Component (B)] The resin composition of this embodiment contains one or more selected from aromatic condensed phosphate, silica particles, or liquid crystal polymer fillers as component (B). Furthermore, as component (B), two or more components may be used in combination. Hereinafter, aromatic condensed phosphate is described as "component (B1)", silica particles as "component (B2)", and liquid crystal polymer filler as "component (B3)".

[Component (B1); aromatic condensed phosphate] The "aromatic condensed phosphate" as component (B1) refers to a phosphate compound having a chemical structure in which two or more phosphate units are linked by a divalent organic group having an aromatic ring, or a reaction product of phosphorus oxychloride, a divalent phenolic compound, and phenol or an alkylphenol. By combining an aromatic condensed phosphate with a polyimide obtained by using a fixed amount or more of a dimer diamine composition, dielectric properties can be improved. The reason is not clear, but it is speculated that due to the unique chemical structure of aromatic condensed phosphate esters, although the dielectric properties of aromatic condensed phosphate esters themselves are compatible with the polyimide obtained by using the dimer diamine composition, since the mobility of the molecular chain is not excessively increased, it helps to lower the dielectric constant and dielectric loss tangent. In addition, the dielectric properties of the resin film obtained by using the (B1) component have low humidity dependence and excellent stability.

Preferred examples of aromatic condensed phosphates include compounds having the structure of the following general formula (3).

[Chemistry 5]

In the general formula (3), a plurality of Rs are independently an aromatic hydrocarbon group which may have a substituent, Ar is a divalent organic group having an aromatic ring, and n is an integer greater than or equal to 1. The aromatic condensed phosphate represented by the general formula (3) may be a dimer in which n is 1 or a polymer in which n is 2 or greater. In addition, it is not limited to a single compound and may be a mixture.

As the aromatic hydrocarbon group which may have a substituent represented by R in the general formula (3), for example, an aryl group having 6 to 15 carbon atoms can be listed, and more specifically, phenyl, methylphenyl, dimethylphenyl, trimethylphenyl, ethylphenyl, butylphenyl, nonylphenyl, etc. can be listed. In addition, as a preferred example of the divalent organic group represented by Ar in the general formula (3), for example, an alkylene group, an arylene group, etc. can be listed, and these groups may have a substituent. As a more preferred example, a phenylene group or a group represented by the following formula (4) can be listed.

[Chemistry 6]

In formula (4), _Y1 represents a single bond, _-CH2- , -C( _CH3 ) _2- , _{-SO2- , -C5H10- , -C6H12-, -C7H14-, -C8H16- , etc. Among the} groups represented by formula (4 ₎ , more preferred is a biphenyldiyl group in which _Y1 is a single bond.

Examples of the aromatic condensation phosphates include resorcinol bis-diphenyl phosphate, resorcinol bis-dixylyl phosphate, and bisphenol A bis-diphenyl phosphate. Commercially available products of these aromatic condensation phosphates include CR-733S (trade name), CR-741 (trade name), CR-747 (trade name), PX-200 (trade name), and PX-200B (trade name) [all manufactured by Daihachi Chemical Industries, Ltd.]. These aromatic condensation phosphates may be used in combination of two or more.

<Amount of component (B1)> The weight ratio of the component (B1) to the component (A) in the resin composition of this embodiment is in the range of 0.05 to 0.7. If the film properties such as the tensile modulus of elasticity when forming the resin film are taken into consideration, it is preferably in the range of 0.2 to 0.5 (the same applies to the resin film described later). When the weight ratio of the component (B1) to the component (A) is less than 0.05, the improvement of the dielectric properties may be insufficient. If it exceeds 0.7, it may be difficult to form polyimide, and the obtained polyimide film may become brittle. By setting the amount of the component (B1) to be within the above range, the dielectric properties can be improved. In addition, in the case of polyamide, component (A) is converted into polyimide to calculate the weight ratio (the same applies hereinafter).

In the resin composition of the present embodiment, the component (B1) is preferably blended so that the weight ratio of phosphorus derived from the component (B1) to the thermoplastic resin of the component (A) is in the range of 0.01 to 0.1. If the weight ratio of phosphorus derived from the component (B1) is less than 0.01, the improvement of the dielectric properties is insufficient, and if it exceeds 0.1, the polyimide film (or polyimide layer) may be embrittled.

The weight ratio of phosphorus derived from component (B1) to the dimer diamine composition contained in component (A) in component (B1) of the resin composition of the present embodiment {phosphorus derived from component (B1)/dimer diamine composition in component (A)} is preferably in the range of 0.01 to 0.15. If the weight ratio is less than the lower limit, the improvement of dielectric properties may be insufficient, and if the weight ratio is greater than the upper limit, polyimide formation may be difficult, and the obtained polyimide film may become brittle.

[Component (B2): Silica particles] As the silica particles of component (B2), either crystalline silica particles or amorphous silica particles can be used, but crystalline silica particles having a white silica crystal phase or a quartz crystal phase are preferred. By preparing silica particles as component (B2), the dielectric loss tangent when forming a resin film can be reduced. From the viewpoint of achieving a low dielectric loss tangent when forming a resin film, it is particularly preferred to use silica particles having a white silica crystal phase as the crystalline silica particles. Compared with general silica particles, silica particles with white silica crystal phases have very excellent dielectric properties (for example, the dielectric loss tangent of silica particles containing more than 90% by weight of white silica crystal phases at 20 GHz is about 0.0001 on a single body basis), which can greatly contribute to the low dielectric loss tangent of resin films.

In addition, as the silica particles of component (B2), spherical silica particles are preferably used. Spherical silica particles are silica particles having a shape close to a sphere and having a ratio of an average major diameter to an average minor diameter of 1 or close to 1.

In addition, since silica does not thermally decompose at normal combustion temperatures, the flame retardancy can be improved by adding silica particles as the component (B2).

In addition, from the perspective of achieving low dielectric loss tangent when forming a resin film, the ratio of the total area of peaks derived from white silica crystal phase and quartz crystal phase in the range of 2θ = 10° to 90° of the X-ray diffraction analysis spectrum of CuKα rays to the total area of all peaks derived from _SiO2 is preferably 20% by weight or more, more preferably 40% by weight or more, and ideally 80% by weight or more. By increasing the ratio of white silica crystal phase and/or quartz crystal phase in the whole silicon dioxide particle, further low dielectric loss tangent of polyimide can be achieved. If the area ratio of the peaks derived from the white silica crystal phase and the quartz crystal phase in the entire silica particle is less than 20% by weight, the effect of improving the dielectric properties is unclear. In addition, when the peak of the object in the X-ray diffraction analysis spectrum is difficult to separate from the broad peak of the amorphous phase or overlaps with the peak of other crystal phases, various known analysis methods such as the internal standard method or the PONKCS method can be used.

The average particle size _D50 of the silicon dioxide particles is preferably in the range of 6 μm to 20 μm, and more preferably in the range of 8 μm to 15 μm. Here, the average particle size _D50 is a value at which the cumulative value in the frequency distribution curve obtained by volume-based particle size distribution measurement using a laser diffraction scattering method becomes 50%. If the average particle size _D50 is within this range, the dielectric properties can be effectively improved, and a low dielectric film with good appearance can be obtained without deteriorating the surface smoothness when the resin film is formed from the resin composition. If the average particle size _D50 is below the above range, the specific surface area of the silica particles increases, and the adsorbed water or polar groups on the surface of the silica particles may affect the dielectric properties. If the average particle size _D50 exceeds the above range, it may appear as unevenness on the surface of the resin film and may deteriorate the smoothness of the film surface.

In addition, more than 90% by weight of the silica particles with a particle size of 3 μm or more preferably have a circularity of 0.7 or more, and more preferably 0.9 or more. The circularity of the silica particles can be obtained by image analysis by assuming a circle with the same projected area as the photographed particles and taking the ratio of the circumference of the circle to the circumference of the particles. If the circularity is less than 0.7, the surface area increases, which sometimes has an adverse effect on the dielectric properties, and the viscosity increase when mixed into the resin solution becomes larger, making it difficult to handle. In addition, it is preferred that the value substantially corresponds to the circularity value in the sphericity obtained three-dimensionally.

In addition, the true specific gravity of the silicon dioxide particles is preferably 2.3 or more. If the true specific gravity is less than 2.3, it is suggested that the crystallinity of the silicon dioxide particles is small, and the effect of improving the dielectric properties becomes small.

The silica particles can be appropriately selected from commercial products. For example, spherical white silica powder (manufactured by Nippon Steel Chemicals & Materials Co., Ltd., trade name: CR10-20), spherical amorphous silica powder (manufactured by Nippon Steel Chemicals & Materials Co., Ltd., trade name: SC70-2), etc. can be preferably used. Furthermore, two or more different silica particles can be used in combination as the silica particles.

<Amount of component (B2)> The weight ratio of component (B2) to the total weight of component (A) and component (B2) in the resin composition of this embodiment is in the range of 5% to 60% by weight (the same applies to the resin film described below). When the weight ratio of component (B2) to the total weight of component (A) and component (B2) is less than 5% by weight, the improvement effect of dielectric properties and flame retardancy may be insufficient. When it exceeds 60% by weight, it may be difficult to form polyimide, and the obtained polyimide film may become brittle. By setting the amount of component (B2) to be within the above range, dielectric properties and flame retardancy can be improved. When the content of the component (B2) is within the range of 5 wt % to 20 wt % relative to the total of the components (A) and (B2), the crystalline silica particles are preferably blended so that the total area of the peaks derived from the white silica crystal phase and the quartz crystal phase in the range of 2θ = 10° to 90° in the X-ray diffraction analysis spectrum using CuKα rays is 40 wt % or more relative to the total area of all peaks derived from SiO _2. On the other hand, when the content of the component (B2) exceeds 20 wt % relative to the total of the components (A) and (B2), the crystalline silica particles are preferably blended so that the peak areas derived from the white silica crystal phase and the quartz crystal phase are 30 wt % or more.

In addition, from the viewpoint of improving the adhesion to a metal layer such as copper foil when forming a resin film, the volume ratio of the component (B2) to the total volume ratio of the components (A) and (B2) is preferably in the range of 3% to 41%, and more preferably in the range of 10% to 35% (the same in the resin film described later). Furthermore, the volume ratio can be calculated based on the density and weight ratio of the components (A) and (B2) to be prepared, or can be obtained by cross-sectional observation using a scanning electron microscope.

[(B3) Component: Liquid crystal polymer filler] Liquid crystal polymer fillers are particles containing liquid crystal polymers that form an optically anisotropic melt phase. Liquid crystal polymers that form an optically anisotropic melt phase are also called thermotropic liquid crystal polymers. A polymer that forms an optically anisotropic melt phase is a polymer that transmits polarized light when a sample in a molten state is observed under crossed Nicols under a polarizing microscope including a heating device. Liquid crystal polymers have almost no frequency dependence, have very excellent dielectric properties, and also contribute to the improvement of flame retardancy. Therefore, by formulating liquid crystal polymers, the dielectric properties and flame retardancy of the resin film can be improved.

The liquid crystal polymer is not particularly limited, and examples thereof include known thermotropic liquid crystal polyesters and polyesteramides derived from compounds classified into the following (1) to (4) and their derivatives. (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 The more aromatic rings there are in the liquid crystal polymer, the more effects of improving dielectric properties or flame retardancy can be expected. Therefore, it is preferred to include an aromatic dihydroxy compound (aromatic diol) as the above (1) and an aromatic dicarboxylic acid as the above (2).

A representative example of a liquid crystal polymer obtained from these raw material compounds is a copolymer having a combination of two or more structural units selected from the following formulas (a) to (g), preferably a copolymer containing any one of the structural units represented by formula (a) and the structural units represented by formula (b), and more preferably a copolymer containing the structural units represented by formula (a) and the structural units represented by formula (b). Formulas (a) and (b) are representative examples of structural units derived from aromatic hydroxycarboxylic acids, formulas (c), (d), and (e) are representative examples of structural units derived from aromatic dicarboxylic acids, and formulas (f) and (g) are representative examples of structural units derived from aromatic dihydroxy compounds (aromatic diols). In the structural units represented by formulas (a) to (g), the aromatic ring may have an arbitrary substituent.

In particular, as liquid crystal polymers with low dielectric loss tangent, the following can be cited: · Liquid crystal polymers containing structural units represented by formula (a) and formula (b), structural units selected from formula (c), formula (d) or formula (e), and structural units selected from formula (f) or formula (g) in a specific ratio; · Liquid crystal polymers containing structural units represented by formula (b), structural units selected from formula (c), formula (d) or formula (e), and structural units selected from formula (f) or formula (g) in a specific ratio.

[Chemistry 7]

In order to improve the dielectric properties of the resin film obtained from the resin composition, the liquid crystal polymer filler is preferably used as follows: as a monomer, the relative dielectric constant at 10 GHz is preferably in the range of 2.8 to 3.6, more preferably in the range of 3.0 to 3.4, and the dielectric loss tangent at 10 GHz is preferably less than 0.0019, more preferably less than 0.0015. In addition, when the dielectric loss tangent of the (A) component at 10 GHz is set to Dfa and the dielectric loss tangent of the (B3) component at 10 GHz is set to Dfb, it is more preferable that Dfb is less than 0.0019, and Dfa＞Dfb.

In addition, the liquid crystal polymer preferably contains a large amount of aromatic rings from the viewpoint of improving flame retardancy. The weight ratio of the aromatic ring in the liquid crystal polymer filler is preferably 60% by weight or more, more preferably 70% by weight or more.

In addition, as the liquid crystal polymer particles, spherical liquid crystal polymer particles are preferably used. Spherical liquid crystal polymer particles are liquid crystal polymer particles whose shape is close to spherical and whose ratio of average major diameter to average minor diameter is 1 or close to 1.

The average particle size _D50 of the liquid crystal polymer particles is preferably in the range of 6 μm to 20 μm, and more preferably in the range of 8 μm to 15 μm. Here, the average particle size _D50 is a value at which the cumulative value in the frequency distribution curve obtained by volume-based particle size distribution measurement using a laser diffraction scattering method becomes 50%. If the average particle size _D50 is within this range, a low dielectric film with good appearance can be obtained without deteriorating the surface smoothness when the resin film is formed from the resin composition. If the average particle size _D50 is lower than the above range, the liquid crystal polymer particles may aggregate when the resin composition is prepared, and there is a possibility that a uniform resin composition cannot be obtained. If the average particle size _D50 is outside the above range, the particles may appear as irregularities on the resin film surface and the smoothness of the film surface may be deteriorated.

The melting point of the liquid crystal polymer is preferably higher than the curing temperature of the resin composition, for example, preferably above 250°C.

Liquid crystal polymer particles can be appropriately selected and used. For example, low dielectric liquid crystal polymer (manufactured by JXTG Energy Corporation) can be preferably used. Furthermore, two or more different liquid crystal polymer particles can be used in combination as the liquid crystal polymer particles.

<Amount of component (B3)> The ratio of component (B3) to the total of components (A) and (B3) in the resin composition of this embodiment is in the range of 15% to 50% by volume, preferably in the range of 15% to 40% by volume (the same applies to the resin film described later). When the volume ratio of component (B3) to the total of components (A) and (B3) is less than 15% by volume, the improvement effect of dielectric properties and flame retardancy may be insufficient. If it exceeds 50% by volume, it may be difficult to form polyimide, and the obtained resin film may become brittle. By setting the amount of component (B3) to the above range, dielectric properties and flame retardancy can be improved. Furthermore, the volume ratio of component (B3) to the total of component (A) and component (B3) can be determined by observing the cross section of the cured film using a scanning electron microscope or the like, and calculating the ratio of the liquid crystal polymer filler in the resin composition.

[Optional ingredients] The resin composition of this embodiment may contain an organic solvent. For example, it may be a polyimide solution containing a solvent-soluble DDA-based thermoplastic polyimide and a solvent. Examples of organic solvents include: N,N-dimethylformamide (DMF), N,N-dimethylacetamide (DMAc), N,N-diethylacetamide, N-methyl-2-pyrrolidone (NMP), 2-butanone, dimethyl sulfoxide (DMSO), hexamethylphosphatamide, N-methylcaprolactam, dimethyl sulfate, cyclohexanone, dioxane, tetrahydrofuran, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, cresol, etc. 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 is no particular restriction on the content of the organic solvent, but it is preferably used in an amount adjusted to a concentration of about 5% to 30% by weight of the thermoplastic resin.

In addition, the resin composition of the present embodiment may contain a flame retardant when a liquid crystal polymer filler is used as the component (B). There is no particular limitation on the flame retardant, but a phosphorus-based flame retardant is preferred. Aliphatic thermoplastic resins such as DDA-based thermoplastic polyimide have low aromatic ring concentrations, so even if a phosphorus-based flame retardant is added, the flame retardant properties cannot be fully exerted. However, in the resin composition containing the liquid crystal polymer filler as the component (B3), the concentration of aromatic rings derived from the liquid crystal polymer becomes high, thereby promoting the formation of carbon (carbonized film) during combustion and exerting a high flame retardant effect. From this viewpoint, when a liquid crystal polymer filler is used as component (B3), it is preferred to further add 15 to 30% by weight of a phosphorus-based flame retardant relative to 100% by weight of the non-volatile organic compound component of the resin composition. Here, the so-called "non-volatile organic compound component" refers to the solid component remaining after removing the solvent and the inorganic solid component from the resin composition. That is, the non-volatile organic compound component contains a thermoplastic resin as component (A) and a liquid crystal polymer filler as component (B3), and may contain, as an optional component, a resin other than the thermoplastic resin, an organic filler other than the liquid crystal polymer filler, a plasticizer, a curing accelerator, a coupling agent, an organic pigment, an organic flame retardant other than the phosphorus flame retardant, and the like.

Phosphorus-based flame retardants include, for example, aromatic condensed phosphates having the same structure as the component (B1), metal salts of organic phosphinic acids, alkyl phosphines (except red phosphorus), etc. These flame retardants may be used in combination of two or more different compounds.

The metal salt of an organic phosphinic acid is, for example, a metal salt of phosphoric acid in which two organic groups are bonded to phosphorus, as represented by the following general formula (5).

[Chemistry 8]

In the general formula (5), the two organic groups R ₁₁ and R ₁₂ are preferably the same or different linear or branched alkyl groups having 1 to 6 carbon atoms, phenyl groups, or tolyl groups. In the general formula (5), the metal species M is preferably selected from the group consisting of Mg, Ca, Al, Sb, Sn, Ge, Ti, Fe, Zr, Ce, Bi, Sr, Mn, Li, Na, and K. Furthermore, when the metal species M is a divalent or higher-valent n-valent metal, M in the general formula (5) is transformed into M1/n. In order to improve the flame retardant effect, it is preferred to increase the phosphorus content. Specifically, the two organic groups R ₁₁ and R ₁₂ are preferably alkyl groups having 1 to 3 carbon atoms. In order to improve flame retardancy and flexibility and suppress solubility in water as a metal salt, the metal species M is preferably aluminum (Al).

As the metal salt of the organic phosphinic acid, commercially available products are available, for example, aluminum phosphinic acid salts manufactured by Clariant Japan Co., Ltd., namely Exolit OP930 (trade name), Exolit OP935 (trade name), Exolit OP940 (trade name), etc.

In the resin composition of this embodiment, other resin components other than the thermoplastic resin of component (A), crosslinking agents, inorganic fillers other than silica particles, organic fillers other than liquid crystal polymer fillers, plasticizers, hardening accelerators, coupling agents, pigments, etc. can be appropriately formulated as arbitrary components as needed. As crosslinking agents, amino compounds having at least two primary amino groups as functional groups (amino compounds for crosslinking formation), epoxy compounds, dimaleimide compounds, acrylic acid (methacrylic acid) compounds, etc. can be listed. As inorganic fillers, for example, aluminum oxide, magnesium oxide, curium oxide, boron nitride, aluminum nitride, silicon nitride, aluminum fluoride, calcium fluoride, etc. can be listed. These can be used alone or in combination of two or more.

[Viscosity] In order to improve the handling properties of the resin composition during coating and to facilitate the formation of a coating film of uniform thickness, the viscosity of the resin composition is preferably set in the range of 3000 cps to 100000 cps, and more preferably in the range of 5000 cps to 50000 cps. If the viscosity deviates from the above range, it is easy to produce defects such as uneven thickness and streaks in the film during coating operations using a coating machine.

[Preparation of resin composition] The resin composition of the present embodiment can be prepared, for example, by using any solvent to prepare a solution of component (A), adding component (B) thereto and uniformly mixing. For example, component (B) can also be directly mixed in a resin solution of DDA-based thermoplastic polyimide. Furthermore, a part of component (A) can be mixed simultaneously with component (B) or after component (B) is added. In any method, component (B) can be added all at once or added little by little in several times. In addition, the raw materials can be added together or mixed little by little in several times.

When the resin composition of the present embodiment is used to form an adhesive layer, it has excellent flexibility and thermoplasticity as well as excellent dielectric properties and flame retardancy. Therefore, the resin composition of the present embodiment has excellent properties as an adhesive for a cover film for protecting wiring parts such as FPCs, rigid/flexible circuit boards, etc.

[Resin film] The resin film of the present embodiment is a resin film comprising a thermoplastic resin layer (preferably a DDA-based thermoplastic polyimide layer), wherein the thermoplastic resin layer is formed by filming the solid component (the remaining portion after removing the solvent) of the resin composition as a main component. That is, the resin film of the present embodiment contains component (A) and component (B), and the weight ratio of component (B) to component (A) is adjusted to be within a prescribed range similar to that of the resin composition. In addition to flexibility and adhesion, the resin film of this embodiment also has excellent high-frequency characteristics and flame retardancy, so it can be preferably used in applications such as adhesive layers for covering films to protect wiring parts such as FPCs, rigid/flexible circuit boards, or bonding sheets for multi-layer FPCs.

The resin film of this embodiment is not particularly limited as long as it is a film of an insulating resin comprising a thermoplastic resin layer formed from the resin composition. It may be a film (sheet) comprising an insulating resin, or a film of an insulating resin in a state of being layered on a substrate such as a resin sheet such as a copper foil, a glass plate, a polyimide film, a polyamide film, or a polyester film.

<Glass transition temperature> The glass transition temperature (Tg) of the resin film of this embodiment is preferably below 250°C, and more preferably within the range of above 40°C and below 200°C. Since the Tg of the resin film is below 250°C, heat pressing can be performed at a low temperature, thereby relieving the internal stress generated during lamination and suppressing dimensional changes after circuit processing. If the Tg of the resin film exceeds 250°C, the temperature will then increase, and there is a risk of damaging the dimensional stability after circuit processing.

When the component (B1) is used as the component (B), the resin film preferably has the following physical properties. <Dielectric properties> When the component (B1) is used as the component (B), the resin film preferably has the following physical properties based on the following formula (i) E ₁ =√ε ₁ ×Tanδ ₁ ···(i) [Here, ε ₁ represents the relative dielectric constant at 10 GHz measured by a separation dielectric resonator (SPDR) after humidification at a constant temperature and humidity of 23°C and 50%RH (normal state) for 24 hours, and Tanδ ₁ represents the dielectric loss tangent at 10 GHz measured by an SPDR after humidification at a constant temperature and humidity of 23°C and 50%RH for 24 hours. Furthermore, "√ε ₁ " refers to the square root of ε ₁ ], and the E ₁ value, which is an index of dielectric properties at 10 GHz after humidification for 24 hours under constant temperature and humidity conditions of 23°C and 50%RH, is 0.010 or less, preferably 0.009 or less, and more preferably 0.008 or less. If the E ₁ value exceeds the upper limit, for example, when used in a circuit board such as an FPC, it is easy to cause disadvantages such as loss of electrical signals in the transmission path of high-frequency signals.

<Relative dielectric constant> When the component (B1) is used as the component (B), the relative dielectric constant (ε _{1 )} at 10 GHz after humidification for 24 hours at a constant temperature and humidity of 23°C and 50%RH is preferably 3.2 or less, and more preferably 3.0 or less, in order to ensure impedance matching when the resin film is used in a circuit board such as an FPC and to reduce the loss of electrical signals. If the relative dielectric constant exceeds 3.2, when used in a circuit board such as an FPC, for example, it is easy to cause disadvantages such as loss of electrical signals in the transmission path of high-frequency signals.

<Dielectric loss tangent> When the component (B1) is used as the component (B), the dielectric loss tangent ( _Tanδ1 ) at 10 GHz after humidification for 24 hours at a constant temperature and humidity of 23°C and 50%RH is preferably less than 0.005, and more preferably less than 0.004. If the dielectric loss tangent is greater than 0.005, for example, when used in a circuit board such as an FPC, it is easy to cause disadvantages such as loss of electrical signals in the transmission path of high-frequency signals.

<Moisture absorption dependence> When the component (B1) is used as the component (B), in order to reduce the loss of electrical signals in dry and wet conditions or to ensure impedance matching when the resin film is used in a circuit board such as an FPC, based on the following formula (ii) E ₂ =√ε ₂ ×Tanδ ₂ ···(ii) [Here, ε ₂ represents the relative dielectric constant at 10 GHz measured by SPDR after water absorption at 23°C for 24 hours, and Tanδ ₂ represents the dielectric loss tangent at 10 GHz measured by SPDR after water absorption at 23°C for 24 hours. Furthermore, "√ε ₂ " refers to the square root of ε ₂ ] The ratio (E ₂ /E 1 ) of the E ₂ value, which is an index of dielectric properties at 10 GHz after absorbing water at 23°C for 24 hours, to the E ₁ value calculated based on the above formula (i) is in the range of 3.0 to 1.0, preferably in the range of 2.5 to 1.0, and more preferably in the range of 2.2 to 1.0. If E ₂ /E ₁ exceeds the above _{upper limit} , when used in a circuit board such as an FPC, for example, the relative dielectric constant and dielectric loss tangent increase when wet, and it is easy to cause disadvantages such as loss of electrical signals in the transmission path of high-frequency signals.

<Moisture absorption rate> When component (B1) is used as component (B), the moisture absorption rate of the resin film is preferably 0.5% by weight or less, and more preferably less than 0.3% by weight, in order to reduce the influence of humidity when used in a circuit board such as an FPC. Here, "moisture absorption rate" refers to the moisture absorption rate after 24 hours or more under constant temperature and humidity conditions of 23°C and 50%RH (the same meaning in this specification). If the moisture absorption rate of the resin film exceeds 0.5% by weight, it is easily affected by humidity when used in a circuit board such as an FPC, and it is easy to cause adverse conditions such as changes in the transmission speed of high-frequency signals. That is, if the moisture absorption rate of the resin film exceeds the above range, it is easy to absorb water with a high relative dielectric constant, thus causing an increase in the relative dielectric constant and dielectric loss tangent, and easily causing adverse conditions such as loss of electrical signals in the transmission path of high-frequency signals.

<Storage elastic coefficient> When component (B1) is used as component (B), the resin film may have a temperature range in the range of 40°C to 250°C in which the storage elastic coefficient decreases at a steep rate as the temperature rises. Such properties of the resin film are believed to be factors for alleviating internal stress during, for example, hot pressing and maintaining dimensional stability after circuit processing. The storage elastic coefficient of the resin film at the upper limit temperature of the temperature range is preferably 5×10 ⁷ [Pa] or less. By setting such a storage elastic coefficient, hot pressing can be performed at below 250°C even if the temperature is set to the upper limit of the temperature range, and adhesion can be ensured, thereby suppressing dimensional changes after circuit processing. Furthermore, the resin film of this embodiment has high thermal expansion but low elasticity, so even if the coefficient of thermal expansion (CTE) exceeds 30 ppm/K, it can alleviate the internal stress generated during lamination.

When component (B2) is used as component (B), the resin film preferably has the following physical properties. <Relative dielectric constant> When component (B2) is used as component (B), the resin film preferably has a relative dielectric constant of 3.2 or less, more preferably 3.0 or less, at 20 GHz after humidification for 24 hours at constant temperature and humidity conditions of 23°C and 50%RH in order to ensure impedance matching when used in a circuit board such as an FPC and to reduce electrical signal loss. If the relative dielectric constant exceeds 3.2, electrical signal loss may occur in the transmission path of high-frequency signals when used in a circuit board such as an FPC.

<Dielectric loss tangent> In addition, when the component (B2) is used as the component (B), in order to reduce the loss of electrical signals when used in circuit boards such as FPC, the dielectric loss tangent at 20 GHz after humidification for 24 hours under constant temperature and humidity conditions of 23°C and 50%RH is preferably less than 0.005, more preferably less than 0.004, and most preferably less than 0.002. If the dielectric loss tangent is greater than 0.005, it is easy to cause disadvantages such as loss of electrical signals in the transmission path of high-frequency signals when used in circuit boards such as FPC.

When component (B3) is used as component (B), the resin film preferably has the following physical properties. <Relative dielectric constant> When component (B3) is used as component (B), the resin film preferably has a relative dielectric constant of 3.2 or less, more preferably 3.0 or less, at 20 GHz after humidification for 24 hours at constant temperature and humidity conditions of 23°C and 50%RH in order to ensure impedance matching when used in a circuit board such as an FPC and to reduce electrical signal loss. If the relative dielectric constant exceeds 3.2, electrical signal loss may occur in the transmission path of high-frequency signals when used in a circuit board such as an FPC.

<Dielectric loss tangent> In addition, when the component (B3) is used as the component (B), in order to reduce the loss of electrical signals when used in circuit boards such as FPC, the dielectric loss tangent at 20 GHz after humidification for 24 hours under constant temperature and humidity conditions of 23°C and 50%RH is preferably less than 0.005, more preferably less than 0.004, and most preferably less than 0.002. If the dielectric loss tangent is greater than 0.005, it is easy to cause disadvantages such as loss of electrical signals in the transmission path of high-frequency signals when used in circuit boards such as FPC.

<Thickness> When the component (B1) is used as the component (B), the thickness of the resin film is preferably within a range of 5 μm or more and 125 μm or less, and more preferably within a range of 8 μm or more and 100 μm or less. If the thickness of the resin film is less than 5 μm, there is a possibility that wrinkles or other defects may occur during transportation during the production of the resin film, etc. On the other hand, if the thickness of the resin film exceeds 125 μm, there is a possibility that the productivity of the resin film may be reduced.

When component (B2) or component (B3) is used as component (B), the thickness of the resin film is preferably in the range of 15 μm to 100 μm, more preferably in the range of 20 μm to 50 μm. If the thickness of the resin film is less than 15 μm, there is a possibility that wrinkles or other defects may occur during transportation during the production of the resin film, while if the thickness of the resin film exceeds 100 μm, there is a possibility that the productivity of the resin film may be reduced. When the thickness of the resin film is in the range of 15 μm to 20 μm, in order to suppress the unevenness of the resin film surface and maintain the smoothness of the film surface, the silica particles as the component (B2) or the liquid crystal polymer filler as the component (B3) preferably have an average particle size _D50 in the range of 9 μm to 12 μm.

[Laminate] A laminate of one embodiment of the present invention comprises a substrate and an adhesive layer laminated on at least one surface of the substrate, wherein the adhesive layer comprises the resin film. Furthermore, the laminate may comprise any layer other than the above. Examples of the substrate in the laminate include: a substrate of an inorganic material such as copper foil or glass plate, or a substrate of a resin material such as polyimide film, polyamide film, or polyester film. Preferred embodiments of the laminate include a covering film, a copper foil with a resin, and the like.

[Coating film] The coating film as one aspect of a laminate has a coating film material layer as a base material and an adhesive layer laminated on one side of the coating film material layer, wherein the adhesive layer includes the resin film. The coating film may include any layer other than the above.

The material of the covering film material layer is not particularly limited, and for example, polyimide films such as polyimide, polyetherimide, polyamideimide, or polyamide films, polyester films, etc. can be used. Among these, it is preferred to use a polyimide film with excellent heat resistance. In addition, in order to effectively show light-shielding properties, concealment, design, etc., the covering film material may also contain a black pigment. In addition, it may contain any component such as a matte pigment that suppresses surface gloss within the range that does not impair the improvement effect of dielectric properties.

The thickness of the covering film material layer is not particularly limited, and is preferably within a range of 5 μm or more and 100 μm or less, for example. In addition, the thickness of the adhesive layer is not particularly limited, and is preferably within a range of 10 μm or more and 75 μm or less, for example.

The covering film of this embodiment can be manufactured by the following exemplary method. First, as a first method, a varnish-like resin composition containing a solvent is applied to one side of the covering film material layer, and then dried at a temperature of, for example, 80°C to 180°C to form an adhesive layer, thereby forming a covering film having a covering film material layer and an adhesive layer.

In addition, as a second method, a varnish-like resin composition containing a solvent is applied to an arbitrary substrate, and then dried at a temperature of, for example, 80°C to 180°C and then peeled off to form an adhesive film for an adhesive layer. The adhesive film is heat-pressed with a covering film material layer at a temperature of, for example, 60°C to 220°C to form a covering film.

[Copper foil with resin] Another aspect of the copper foil with resin as a laminate is a laminate having a bonding agent layer laminated on at least one side of the copper foil as a base material, and the bonding agent layer includes the resin film. Furthermore, the copper foil with resin of this embodiment may include any layer other than the above.

The thickness of the adhesive layer in the resin copper foil is preferably in the range of 2 μm to 125 μm, and more preferably in the range of 2 μm to 100 μm. If the thickness of the adhesive layer is less than the lower limit, problems such as failure to ensure sufficient adhesion may occur. On the other hand, if the thickness of the adhesive layer exceeds the upper limit, undesirable conditions such as reduced dimensional stability may occur. In addition, from the perspective of low dielectric constant and low dielectric loss tangent, it is preferred to set the thickness of the adhesive layer to 3 μm or more.

The material of the copper foil in the resin copper foil is preferably copper or copper alloy as the main component. The thickness of the copper foil is preferably 35 μm or less, and more preferably in the range of 5 μm to 25 μm. From the perspective of production stability and handling, the lower limit of the thickness of the copper foil is preferably 5 μm. Furthermore, the copper foil can be a rolled copper foil or an electrolytic copper foil. In addition, as the copper foil, a commercially available copper foil can be used.

The copper foil with resin can be prepared, for example, by sputtering a metal on a resin film to form a seed layer, and then forming a copper layer by copper plating, or by laminating a resin film and a copper foil by hot pressing, etc. Furthermore, the copper foil with resin can also be prepared by casting a coating liquid of a resin composition, drying to form a coating film, and then performing a required heat treatment in order to form an adhesive layer on the copper foil.

[Metal-clad laminate] (First aspect) A metal-clad laminate of one embodiment of the present invention includes an insulating resin layer and a metal layer laminated on at least one surface of the insulating resin layer, and at least one layer of the insulating resin layer includes the resin film. Furthermore, the metal-clad laminate of this embodiment may include any layer other than the above.

(Second Aspect) Another embodiment of the present invention is a metal-clad laminate, for example, a so-called three-layer metal-clad laminate including an insulating resin layer, an adhesive layer laminated on at least one side of the insulating resin layer, and a metal layer laminated on the insulating resin layer via the adhesive layer, wherein the adhesive layer includes the resin film. Furthermore, the three-layer metal-clad laminate may include any layer other than the above. The adhesive layer of the three-layer metal-clad laminate can be provided on one or both sides of the insulating resin layer, and the metal layer can be provided on one or both sides of the insulating resin layer via the adhesive layer. That is, the three-layer metal-clad laminate can be a single-sided metal-clad laminate or a double-sided metal-clad laminate. A single-sided FPC or a double-sided FPC can be manufactured by etching the metal layer of the three-layer metal-clad laminate and performing wiring circuit processing.

The insulating resin layer in the three-layer metal-clad laminate is not particularly limited as long as it includes a resin having electrical insulation properties, and examples thereof include polyimide, epoxy resin, phenolic resin, polyethylene, polypropylene, polytetrafluoroethylene, silicone, ETFE, etc., preferably polyimide. The polyimide layer constituting the insulating resin layer may be a single layer or a multi-layer, and preferably includes a non-thermoplastic polyimide layer.

The thickness of the insulating resin layer in the three-layer metal-clad laminate is preferably in the range of 1 μm to 125 μm, and more preferably in the range of 5 μm to 100 μm. If the thickness of the insulating resin layer is less than the lower limit, there may be a problem that sufficient electrical insulation cannot be ensured. On the other hand, if the thickness of the insulating resin layer exceeds the upper limit, the three-layer metal-clad laminate may be prone to warping.

The thickness of the adhesive layer in the three-layer metal-clad laminate is preferably in the range of 0.1 μm to 125 μm, and more preferably in the range of 0.3 μm to 100 μm. In the three-layer metal-clad laminate of the present embodiment, if the thickness of the adhesive layer is less than the lower limit, there may be a problem that sufficient adhesion cannot be guaranteed. On the other hand, if the thickness of the adhesive layer exceeds the upper limit, there may be a problem that the dimensional stability is reduced. In addition, from the viewpoint of lowering the dielectric constant and dielectric loss tangent of the entire insulating layer as a laminate of the insulating resin layer and the adhesive layer, the thickness of the adhesive layer is preferably set to 3 μm or more.

In addition, the ratio of the thickness of the insulating resin layer to the thickness of the adhesive layer (thickness of the insulating resin layer/thickness of the adhesive layer) is preferably in the range of 0.1 to 3.0, and more preferably in the range of 0.15 to 2.0. By setting such a ratio, the warping of the three-layer metal-clad laminate can be suppressed. In addition, the insulating resin layer may contain a filler as needed. As fillers, for example: silicon dioxide, aluminum oxide, magnesium oxide, curium oxide, boron nitride, aluminum nitride, silicon nitride, aluminum fluoride, calcium fluoride, metal salts of organic phosphinates, etc. These can be used alone or in a mixture of two or more.

[Circuit board] A circuit board of one embodiment of the present invention is formed by wiring the metal layer of the metal-clad laminate of any of the embodiments described above. A circuit board such as an FPC can be manufactured by processing one or more metal layers of the metal-clad laminate into a pattern using a conventional method to form a wiring layer (conductive circuit layer). Furthermore, the circuit board may also include a covering film covering the wiring layer. [Example]

The following examples are shown to more specifically describe the features of the present invention. 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 following.

[Determination of amine value] Weigh about 2 g of the dimer diamine composition into a 200 mL to 250 mL Erlenmeyer flask, use phenolphthalein as an indicator, add 0.1 mol/L ethanolic potassium hydroxide solution until the solution turns light pink, and 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 = {(V ₂ ×C ₂ )-(V ₁ ×C ₁ )}×M _KOH /m･･･（1） Here, the amine value is expressed in mgKOH/g, and M _KOH is the molecular weight of potassium hydroxide, 56.1. In addition, V and C are 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 is the sample weight expressed in grams.

[Measurement of weight average molecular weight (Mw) of polyimide] The weight average molecular weight was measured by a gel permeation chromatograph (manufactured by TOSOH Co., Ltd., using HLC-8220GPC). Polystyrene was used as a standard substance, and tetrahydrofuran (THF) was used as a developing solvent.

[GPC and calculation of area percentage of chromatogram] For GPC, 100 mg of a solution obtained by pre-treating 20 mg of a dimer diamine composition with 200 μL of acetic anhydride, 200 μL of pyridine, and 2 mL of THF was diluted with 10 mL of THF (containing 1000 ppm of cyclohexanone) to prepare a sample. The prepared sample was measured using HLC-8220GPC manufactured by Tosoh Corporation, column: TSK-gel G2000HXL, G1000HXL, flow rate: 1 mL/min, column (oven) temperature: 40°C, injection volume: 50 μL. Cyclohexanone was treated as a standard substance to correct the elution time.

At this time, the peak top of the main peak of cyclohexanone was adjusted to 31 minutes from the retention time of 27 minutes, and the peak-to-peak time of the main peak of cyclohexanone was 2 minutes, and the peak top of the main peak excluding the peak of cyclohexanone was adjusted to 19 minutes from 18 minutes, and the peak-to-peak time of the main peak excluding the peak of cyclohexanone was adjusted to 4 minutes and 30 seconds from 2 minutes. Components (a) to (c) were detected under the following conditions; (a) Components represented by the main peak; (b) Components represented by the GPC peak detected at a later time based on the minimum value on the later retention time side of the main peak; (c) The component represented by the GPC peak detected at an earlier time, based on the minimum value on the earlier retention time side of the main peak.

[Evaluation of dielectric properties] The relative dielectric constant (ε 1 ) and dielectric loss tangent (Tanδ 1 ) of the polyimide film (cured polyimide film) at a frequency of 10 GHz were measured after the polyimide film (cured polyimide film) was left at a temperature of 23°C and a humidity of 50% for 24 hours using a vector network analyzer (Agilent Corporation, trade name: vector network analyzer E8363C) and an SPDR resonator. In addition, the relative dielectric constant (ε ₂ ) and dielectric loss tangent ( _{Tanδ 2} ) of the polyimide film (cured polyimide film) at a frequency of 10 GHz were measured after the polyimide film (cured polyimide _film ) was allowed to absorb water at 23°C for 24 hours.

[Determination of moisture absorption rate] Prepare two test pieces of polyimide film (width 4 cm × length 25 cm) and dry them at 80°C for 1 hour. Immediately after drying, place them in a constant temperature and humidity chamber at 23°C/50%RH for more than 24 hours, and calculate the moisture absorption rate (weight %) using the following formula based on the weight change before and after.

[Measurement of water absorption] Prepare two test pieces of polyimide film (width 4 cm × length 25 cm) and dry them at 80°C for 1 hour. Immediately after drying, place them in pure water at 23°C and leave them for more than 24 hours. Calculate the water absorption rate (weight %) using the following formula based on the weight change before and after.

[Glass transition temperature (Tg) and storage elastic coefficient] The glass transition temperature (Tg) and storage elastic coefficient were measured on a polyimide film of 5 mm × 20 mm size using a dynamic viscoelasticity measuring device (DMA: manufactured by DBM, trade name: E4000F) from 30°C to 400°C at a heating rate of 4°C/min and a frequency of 11 Hz. The temperature at which the elastic coefficient change (tanδ) is the largest is defined as the glass transition temperature.

[Tensile modulus] The tensile modulus was determined by using a tension tester (manufactured by Orientec, trade name Tensilon) and a test piece with a width of 12.7 mm and a length of 127 mm. The tensile test was performed at 50 mm/min and the tensile modulus was obtained at 25°C.

[Solder heat resistance test (drying)] Prepare the following printed circuit board: Process the circuit of polyimide copper-clad laminate (manufactured by Nippon Steel Chemicals & Materials Co., Ltd., trade name: Espanex MB12-25-12UEG) to form a circuit with wiring width/wiring spacing (L/S) = 1 mm/1 mm. Place the adhesive surface of the test piece on the wiring of the printed circuit board and press it at a temperature of 160°C, a pressure of 3.5 MPa, and a time of 60 minutes. After drying the test piece with copper foil at 105°C, immerse it in a solder bath set to each evaluation temperature for 10 seconds, observe its bonding state, and check whether there are defects such as blistering, expansion, and peeling. Heat resistance is expressed by the upper limit temperature at which no defects occur. For example, "320°C" means that no defects were observed in the evaluation in a 320°C solder bath.

[Solder heat resistance test (moisture absorption)] Prepare the following printed circuit board: Process the circuit of polyimide copper-clad laminate (manufactured by Nippon Steel Chemicals & Materials Co., Ltd., trade name: Espanex MB12-25-12UEG) to form a circuit with a wiring width/wiring spacing (L/S) = 1 mm/1 mm. Place the adhesive surface of the test piece on the wiring of the printed circuit board and press it at a temperature of 160°C, a pressure of 3.5 MPa, and a time of 60 minutes. After the copper foil test piece was placed at 40°C and 80% relative humidity for 72 hours, it was immersed in a solder bath set at each evaluation temperature for 10 seconds and its bonding state was observed to confirm whether there were any defects such as blistering, expansion, and peeling. Heat resistance is expressed by the upper limit temperature at which no defects occur. For example, "260°C" means that no defects were confirmed when the evaluation was performed in a solder bath at 260°C.

[Peel strength measurement] The peel strength is measured using a Strograph VE-10 tester (manufactured by Toyo Seiki Seisaku-sho Co., Ltd.). The resin layer side of a 1 mm wide sample (including a laminate of substrate/resin layer) is fixed to an aluminum plate using double-sided tape. The force when the resin layer and substrate are peeled off at a speed of 50 mm/min in a direction 180° to the substrate is determined.

[Evaluation of warp] The polyimide solution was applied to a 25 μm thick polyimide film material (manufactured by DuPont Toray, trade name: Kapton 100EN) or a 12 μm thick copper foil so that the thickness after drying was 25 μm, thereby preparing a test piece. In this state, the test piece was placed so that the polyimide film material or copper foil became the lower surface, and the average value of the warp height of the four corners of the test piece was measured. A value of less than 5 mm was set as "good", and a value of more than 5 mm was set as "unacceptable".

The abbreviations used in this example represent the following compounds. DDA1: A product manufactured by Croda Japan Co., Ltd. under the trade name: PRIAMINE 1075, which was purified by distillation (component a: 98.2% by weight, component b: 0%, component c: 1.9%, amine value: 206 mgKOH/g) DDA2: A product manufactured by Croda Japan Co., Ltd. under the trade name: PRIAMINE 1075, which was purified by distillation (component a: 99.2% by weight, component b: 0%, component c: 0.8%, amine value: 210 mgKOH/g) APB: 1,3-bis(3-aminophenoxy)benzene BTDA: 3,3',4,4'-benzophenonetetracarboxylic dianhydride N-12: dodecanedioic acid dihydrazide NMP: N-methyl-2-pyrrolidone PX-200: Phosphate ester (manufactured by Daba Chemical Industry Co., Ltd., trade name: PX-200, non-halogen aromatic condensed phosphate ester, phosphorus content: 9.0%) PX-202: Phosphate ester (manufactured by Daba Chemical Industry Co., Ltd., trade name: PX-202, non-halogen aromatic condensed phosphate ester, phosphorus content: 8.1%) SR-3000: Phosphate ester (manufactured by Daba Chemical Industry Co., Ltd., trade name: SR-3000, non-halogen aromatic condensed phosphate ester, phosphorus content: 7.0%) DA-850: Phosphate ester (manufactured by Daba Chemical Industry Co., Ltd., trade name: DAIGUARD-850, non-halogen aromatic condensed phosphate ester, phosphorus content: 16.0% or more) TPP (manufactured by Daba Chemical Industry Co., Ltd., trade name: TPP, non-halogen phosphate ester, phosphorus content: 9.5%) TCP (manufactured by Daba Chemical Industry Co., Ltd., trade name: TCP, non-halogen phosphate ester, phosphorus content: 8.4%) TXP (manufactured by Daba Chemical Industry Co., Ltd., trade name: TXP, non-halogen phosphate ester, phosphorus content: 7.6%) CR-733 (manufactured by Daba Chemical Industry Co., Ltd., trade name: CR-733S, non-halogen aromatic condensed phosphate ester, phosphorus content: 10.9%) CR-741 (manufactured by Daihachi Chemical Industry Co., Ltd., trade name: CR-741, non-halogen aromatic condensed phosphate, phosphorus content: 8.9%) CM-6R: phosphorus-nitrogen compound (manufactured by Yamato Chemical Industry Co., Ltd., trade name: Fran CM-6R, average particle size 5 μm) MC-6000: (manufactured by Nissan Chemical Co., Ltd., trade name: MC-6000, non-halogen melamine isocyanurate) Filler 1: manufactured by Nippon Steel Chemical & Materials Co., Ltd., trade name: CR10-20 (spherical white silica silica powder, spherical shape, silica content: 99.4% by weight, white silica crystal phase: 93% by weight, true specific gravity: 2.33, D ₅₀ : 10.8 μm, D ₉₀ : 16.4 μm, D Filler 2: manufactured by Nippon Steel Chemicals & Materials Co., Ltd., trade name: SC70-2 (spherical amorphous silica powder, spherical shape, silica content: 99.9% by weight, true specific gravity: 2.21, D ₅₀ : 11.7 μm, D ₉₀ : 16.4 μm, D ₁₀₀ : 24.1 μm, relative dielectric constant at 10 GHz: 3.08, _dielectric loss tangent at 10 GHz: 0.0015) Flame retardant 1: manufactured by Clariant Japan, trade name: Exolit OP935 (alkyl aluminum phosphate) Flame retardant 2: manufactured by Daihachi Chemical Co., Ltd., trade name: SR-3000 (condensed phosphate ester) LCP filler: manufactured by JXTG Energy Co., Ltd. (low dielectric liquid crystalline polymer, particle size ( _D50 ): 9.6 μm, relative dielectric constant at 10 GHz: 3.27, dielectric loss tangent at 10 GHz: 0.0009) In DDA1 and DDA2, the "%" of component b and component c refers to the area percentage of the chromatogram in the GPC measurement. In addition, the molecular weight of DDA1 and DDA2 is calculated by the following formula (1). Molecular weight = 56.1×2×1000/amine value... (1)

(Synthesis Example 1-1) 55.51 g of BTDA (0.1721 mol), 94.49 g of DDA1 (0.1735 mol), 210 g of NMP and 140 g of xylene were placed in a 1000 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, stirred for 10 hours, and 125 g of xylene was added to prepare a polyimide solution 1-a (solid content concentration: 30% by weight, weight average molecular weight: 82,900, amine value: 206 mgKOH/g) that had been imidized.

(Synthesis Example 1-2 to Synthesis Example 1-3) Polyimide solution 1-b to polyimide solution 1-c were prepared in the same manner as Synthesis Example 1-1 except that the raw material composition was as shown in Table 1-1.

[Table 1-1] Synthesis Example Polyimide solution Type Diamine (p) [mol %] Anhydride (q) [mol %] q/pMolar ratio Weight average molecular weight Amine value [mgKOH/g] Solid content concentration [weight %] 1-1 1-a DDA1 (100) BTDA (100) 0.992 82,900 206 30 1-2 1-b DDA2 (100) BTDA (100) 1.002 70,100 210 30 1-3 1-c DDA1 (60) APB (40) BTDA (100) 0.996 89,200 206 30

(Preparation Example 1-1) In 169.49 g (50 g as solid content) of the polyimide solution 1-a obtained in Synthesis Example 1-1, 2.7 g of N-12 (0.0105 mol; primary amine groups are equivalent to 0.35 mol per 1 mol of ketone groups of BTDA), 6.0 g of NMP was added for dilution, and the mixture was stirred for 1 hour to obtain a polyimide solution 1-1a.

The obtained polyimide solution 1-1a was coated on one side of a release PET film (manufactured by Dongshan Film Co., Ltd., trade name: HY-S05, length × width × thickness = 200 mm × 300 mm × 25 μm), dried at 80°C for 15 minutes, and peeled off from the release PET film to prepare a polyimide film 1-1a' with a thickness of 25 μm. The polyimide film 1-1a' was pressed at a temperature of 160°C, a pressure of 3.5 MPa, and a time of 60 minutes to obtain a polyimide film 1-1a. The various evaluation results of the polyimide film 1-1a are as follows. Relative dielectric constant (ε ₁ ): 2.7, dielectric loss tangent (Tanδ ₁ ): 0.0024, relative dielectric constant (ε ₂ ): 2.7, dielectric loss tangent (Tanδ ₂ ): 0.0034, moisture absorption rate: 0.07%, water absorption rate: 0.6%, Tg: 54℃, 200℃ storage modulus: 5.0×10 ⁶ Pa, tensile modulus: 0.7 GPa, solder heat resistance (dry): 280℃, solder heat resistance (moisture absorption): 260℃, peel strength: 1.0 kN/m or more

(Preparation Example 1-2, Preparation Example 1-3) Polyimide solution 1-1b, polyimide solution 1-1c and polyimide film 1-1b, polyimide film 1-1c were obtained in the same manner as in Preparation Example 1-1 except that polyimide solution 1-b, polyimide solution 1-c were used instead of polyimide solution 1-a. The various evaluation results of polyimide film 1-1b, polyimide film 1-1c are as follows. ＜Polyimide film 1-1b＞ Relative dielectric constant (ε ₁ ): 2.7, dielectric loss tangent (Tanδ ₁ ): 0.0024, relative dielectric constant (ε ₂ ): 2.7, dielectric loss tangent (Tanδ ₂ ): 0.0034, moisture absorption rate: 0.07%, water absorption rate: 0.2%, Tg: 54℃, 200℃ storage elastic modulus: not determined, tensile elastic modulus: 0.7 GPa ＜Polyimide film 1-1c＞ Relative dielectric constant (ε ₁ ): 2.9, dielectric loss tangent (Tanδ ₁ ): 0.0028, relative dielectric constant (ε ₂ ): 2.9, dielectric loss tangent (Tanδ ₂ ): 0.0052, moisture absorption: 0.17%, water absorption: 0.7%, Tg: 106℃, 200℃ storage elastic coefficient: less than 1.0×10 ⁶ Pa, tensile elastic coefficient: 1.4 GPa

[Example 1-1] 10 parts by weight of SR-3000 was added to the polyimide solution 1-1a obtained in Preparation Example 1-1 (100 parts by weight as solid component) to obtain a polyimide composition 1-1. The obtained polyimide composition 1-1 was applied to one side of a release PET film, dried at 80°C for 15 minutes, and peeled off from the release PET film to prepare a polyimide film 1-1' having a thickness of 25 μm. The polyimide film 1-1' was heated in an oven at a temperature of 160°C for 2 hours to obtain a polyimide film 1-1. The various evaluation results of the polyimide film 1-1 are as follows. Relative dielectric constant (ε ₁ ): 2.6, dielectric loss tangent (Tanδ ₁ ): 0.0022

[Example 1-2 to Example 1-16] The components were mixed in the ratios (parts by weight) listed in Table 1-2 to obtain polyimide compositions 1-2 to 1-16 in the same manner as in Example 1-1. In addition, the "DDA composition" in Table 1-2 refers to a dimer diamine composition (the same as in Table 1-3).

[Table 1-2] Embodiment Polyimide composition Type Ingredient A B ingredient B component/A component [weight ratio] Phosphorus concentration [wt%] Phosphorus in component B/component A [weight ratio] Phosphorus/DDA composition in component B [weight ratio] Polyimide solution [solid content: parts by weight] Phosphorus compound [parts by weight] 1-1 1-1 1-1a (100) SR-3000 (10) 0.1 0.62 0.007 0.011 1-2 1-2 1-1a (100) SR-3000 (20) 0.2 1.13 0.014 0.021 1-3 1-3 1-1a (100) SR-3000 (25) 0.25 1.36 0.018 0.027 1-4 1-4 1-1a (100) SR-3000 (30) 0.3 1.57 0.021 0.032 1-5 1-5 1-1a (100) SR-3000 (50) 0.5 2.28 0.035 0.053 1-6 1-6 1-1a (100) PX-200 (25) 0.25 1.75 0.023 0.034 1-7 1-7 1-1a (100) PX-202 (25) 0.25 1.57 0.020 0.031 1-8 1-8 1-1a (100) PX-202 (28) 0.28 1.72 0.023 0.035 1-9 1-9 1-1a (100) PX-202 (31) 0.31 1.61 0.022 0.038 1-10 1-10 1-1a (100) DA-850 (25) 0.25 3.11 0.040 0.061 1-11 1-11 1-1b (100) SR-3000 (10) 0.1 0.62 0.007 0.011 1-12 1-12 1-1b (100) SR-3000 (20) 0.2 1.13 0.014 0.021 1-13 1-13 1-1b (100) SR-3000 (25) 0.25 1.36 0.018 0.027 1-14 1-14 1-1c (100) SR-3000 (10) 0.1 0.62 0.007 0.011 1-15 1-15 1-1c (100) SR-3000 (20) 0.2 1.13 0.014 0.023 1-16 1-16 1-1c (100) SR-3000 (25) 0.25 1.36 0.018 0.029

Using the obtained polyimide compositions 1-2 to 1-16, polyimide films 1-2 to 1-16 were prepared in the same manner as in Example 1-1. The various evaluation results of the polyimide films 1-2 to 1-16 are as follows. ＜Polyimide film 1-2＞ Relative dielectric constant (ε ₁ ): 2.7, dielectric loss tangent (Tanδ ₁ ): 0.0022, tensile modulus: 0.7 GPa, peel strength: 1.4 kN/m ＜Polyimide film 1-3＞ Relative dielectric constant (ε ₁ ): 2.6, dielectric loss tangent (Tanδ ₁ ): 0.0020, relative dielectric constant (ε 2 ): 2.6, dielectric loss tangent (Tanδ 2 ): 0.0021, water absorption: 0.1%, Tg: 54℃, tensile modulus: 0.7 GPa, peel strength: 1.4 kN/m ＜Polyimide film 1-4＞ Relative dielectric constant (ε ₁ ): 2.6, dielectric loss tangent (Tanδ 1 ): 0.0020, relative dielectric constant (ε 2 ): 2.6, dielectric loss tangent (Tanδ ₂ ): 0.0021, water absorption: 0.1%, Tg: 54℃, tensile modulus: 0.7 GPa, peel strength: 1.4 kN/m ₁ ): 2.6, dielectric loss tangent (Tanδ ₁ ): 0.0024, tensile elastic coefficient: 0.5 GPa, peeling strength: 1.5 kN/m ＜Polyimide film 1-5＞ Relative dielectric constant (ε ₁ ): 2.6, dielectric loss tangent (Tanδ ₁ ): 0.0022, tensile elastic coefficient: 0.7 GPa ＜Polyimide film 1-6＞ Relative dielectric constant (ε ₁ ): 2.7, dielectric loss tangent (Tanδ ₁ ): 0.0023, tensile elastic coefficient: 0.1 GPa, peeling strength: 1.6 kN/m ＜Polyimide film 1-7＞ Relative dielectric constant (ε ₁ ): 2.6, dielectric loss tangent (Tanδ ₁ ): 0.0022, water absorption: 0.29%, tensile modulus: 0.5 GPa, peeling strength: 1.6 kN/m <Polyimide film 1-8> Relative dielectric constant (ε ₁ ): 2.7, dielectric loss tangent (Tanδ ₁ ): 0.0021, water absorption: 0.54%, tensile modulus: 0.4 GPa, peeling strength: 1.3 kN/m <Polyimide film 1-9> Relative dielectric constant (ε ₁ ): 2.6, dielectric loss tangent (Tanδ ₁ ): 0.0021, water absorption: 0.91%, tensile modulus: 0.3 GPa, peeling strength: 1.4 kN/m ＜Polyimide film 1-10＞ Relative dielectric constant (ε ₁ ): 2.7, dielectric loss tangent (Tanδ ₁ ): 0.0020, peeling strength: 0.7 kN/m ＜Polyimide film 1-11＞ Relative dielectric constant (ε ₁ ): 2.6, dielectric loss tangent (Tanδ ₁ ): 0.0022 ＜Polyimide film 1-12＞ Relative dielectric constant (ε ₁ ): 2.7, dielectric loss tangent (Tanδ ₁ ): 0.0021 ＜Polyimide film 1-13＞ Relative dielectric constant (ε ₁ ): 2.6, dielectric loss tangent (Tanδ ₁ ）：0.0020 ＜Polyimide film 1-14＞ Relative dielectric constant (ε ₁ ): 2.8, dielectric loss tangent (Tanδ ₁ ): 0.0027 ＜Polyimide film 1-15＞ Relative dielectric constant (ε ₁ ): 2.7, dielectric loss tangent (Tanδ ₁ ): 0.0026 ＜Polyimide film 1-16＞ Relative dielectric constant (ε ₁ ): 2.7, dielectric loss tangent (Tanδ ₁ ): 0.0025

[Reference Example 1-1 to Reference Example 1-18] The components were mixed in the proportions (parts by weight) listed in Table 1-3 to obtain polyimide compositions 1-17 to 1-34 in the same manner as in Example 1-1.

[Table 1-3] Reference example Polyimide composition Type Ingredient A B ingredient B component/A component [weight ratio] Phosphorus concentration [wt%] Phosphorus in component B/component A [weight ratio] Phosphorus/DDA composition in component B [weight ratio] Polyimide solution [solid content: parts by weight] Phosphorus compound [parts by weight] 1-1 1-17 1-1a (100) - - - - - 1-2 1-18 1-1a (100) CM-6R (25) 0.25 - - - 1-3 1-19 1-1a (100) TPP (5) 0.05 0.355 0.004 0.007 1-4 1-20 1-1a (100) TPP (10) 0.10 0.685 0.008 0.015 1-5 1-21 1-1a (100) TCP (5) 0.05 0.314 0.003 0.006 1-6 1-22 1-1a (100) TCP (10) 0.10 0.606 0.007 0.013 1-7 1-23 1-1a (100) TXP (5) 0.05 0.284 0.003 0.006 1-8 1-24 1-1a (100) TXP (10) 0.10 0.548 0.006 0.012 1-9 1-25 1-1a (100) CR-733 (5) 0.05 0.408 0.004 0.008 1-10 1-26 1-1a (100) CR-733 (10) 0.10 0.786 0.009 0.017 1-11 1-27 1-1a (100) CR-741 (5) 0.05 0.333 0.004 0.007 1-12 1-28 1-1a (100) CR-741 (10) 0.10 0.642 0.007 0.014 1-13 1-29 1-1b (100) TPP (5) 0.05 0.355 0.004 0.007 1-14 1-30 1-1b (100) TCP (5) 0.05 0.314 0.004 0.006 1-15 1-31 1-1c (100) TPP (5) 0.05 0.355 0.004 0.008 1-16 1-32 1-1c (100) TCP (5) 0.05 0.314 0.004 0.007 1-17 1-33 1-1a (100) MC-6000 (25) 0.25 - - - 1-18 1-34 1-1a (100) SR-3000 (80) 0.8 3.05 0.056 0.085

Using the obtained polyimide compositions 1-17 to 1-34, polyimide films 1-17 to 1-34 were prepared in the same manner as in Example 1-1. The various evaluation results of the polyimide films 1-17 to 1-34 are as follows. ＜Polyimide film 1-17＞ Relative dielectric constant (ε ₁ ): 2.7, dielectric loss tangent (Tanδ ₁ ): 0.0024, relative dielectric constant (ε ₂ ): 2.7, dielectric loss tangent (Tanδ ₂ ): 0.0034, water absorption: 0.2%, tensile modulus: 0.9 GPa, peeling strength: 1.2 kN/m ＜Polyimide film 1-18＞ Relative dielectric constant (ε ₁ ): 2.9, dielectric loss tangent (Tanδ ₁ ): 0.0025, tensile modulus: 0.6 GPa, peeling strength: 0.4 kN/m ＜Polyimide film 1-19＞ Relative dielectric constant (ε ₁ ): 2.6, dielectric loss tangent (Tanδ ₁ ): 0.0031, tensile elastic coefficient: 0.3 GPa ＜Polyimide film 1-20＞ Relative dielectric constant (ε ₁ ): 2.8, dielectric loss tangent (Tanδ ₁ ): 0.0041, tensile elastic coefficient: 0.1 GPa ＜Polyimide film 1-21＞ Relative dielectric constant (ε ₁ ): 2.6, dielectric loss tangent (Tanδ ₁ ): 0.0028, tensile elastic coefficient: 0.2 GPa ＜Polyimide film 1-22＞ Relative dielectric constant (ε ₁ ): 2.8, dielectric loss tangent (Tanδ ₁ ): 0.0033, tensile elastic coefficient: 0.0 GPa ＜Polyimide film 1-23＞ Relative dielectric constant (ε ₁ ): 2.7, dielectric loss tangent (Tanδ ₁ ): 0.0026, tensile elastic coefficient: 0.3 GPa ＜Polyimide film 1-24＞ Relative dielectric constant (ε ₁ ): 2.8, dielectric loss tangent (Tanδ ₁ ): 0.0028, tensile elastic coefficient: 0.0 GPa ＜Polyimide film 1-25＞ Relative dielectric constant (ε ₁ ): 2.7, dielectric loss tangent (Tanδ ₁ ): 0.0028, tensile elastic coefficient: 0.3 GPa ＜Polyimide film 1-26＞ Relative dielectric constant (ε ₁ ): 2.7, dielectric loss tangent (Tanδ ₁ ): 0.0034, tensile elastic coefficient: 0.1 GPa <Polyimide film 1-27> Relative dielectric constant (ε ₁ ): 2.7, dielectric loss tangent (Tanδ ₁ ): 0.0027, tensile elastic coefficient: 0.4 GPa <Polyimide film 1-28> Relative dielectric constant (ε ₁ ): 2.7, dielectric loss tangent (Tanδ ₁ ): 0.0031, tensile elastic coefficient: 0.2 GPa <Polyimide film 1-29> Relative dielectric constant (ε ₁ ): 2.7, dielectric loss tangent (Tanδ ₁ ): 0.0031 ＜Polyimide film 1-30＞ Relative dielectric constant (ε ₁ ): 2.6, dielectric loss tangent (Tanδ ₁ ): 0.0027 ＜Polyimide film 1-31＞ Relative dielectric constant (ε ₁ ): 2.8, dielectric loss tangent (Tanδ ₁ ): 0.0035 ＜Polyimide film 1-32＞ Relative dielectric constant (ε ₁ ): 2.9, dielectric loss tangent (Tanδ ₁ ): 0.0031 ＜Polyimide film 1-33＞ Relative dielectric constant (ε ₁ ): 3.0, dielectric loss tangent (Tanδ ₁ ): 0.0140 ＜Polyimide film 1-34＞ Relative dielectric constant (ε ₁ ): 2.6, Dielectric loss tangent (Tanδ ₁ ): 0.0021

Summarizing the above results, the evaluation results of the dielectric properties of the polyimide films 1-1 to 1-34 are shown in Tables 1-4 and 1-5.

[Table 1-4] Embodiment Polyimide film Type Relative dielectric constant (ε ₁ ) Dielectric loss tangent (Tanδ ₁ ) 1-1 1-1 2.6 0.0022 1-2 1-2 2.7 0.0022 1-3 1-3 2.6 0.0020 1-4 1-4 2.6 0.0024 1-5 1-5 2.6 0.0022 1-6 1-6 2.7 0.0023 1-7 1-7 2.6 0.0022 1-8 1-8 2.7 0.0021 1-9 1-9 2.6 0.0021 1-10 1-10 2.7 0.0020 1-11 1-11 2.6 0.0022 1-12 1-12 2.7 0.0021 1-13 1-13 2.6 0.0020 1-14 1-14 2.8 0.0027 1-15 1-15 2.7 0.0026 1-16 1-16 2.7 0.0025

[Table 1-5] Reference example Polyimide film Type Relative dielectric constant (ε ₁ ) Dielectric loss tangent (Tanδ ₁ ) 1-1 1-17 2.7 0.0024 1-2 1-18 2.9 0.0025 1-3 1-19 2.6 0.0031 1-4 1-20 2.8 0.0041 1-5 1-21 2.6 0.0028 1-6 1-22 2.8 0.0033 1-7 1-23 2.7 0.0026 1-8 1-24 2.8 0.0028 1-9 1-25 2.7 0.0028 1-10 1-26 2.7 0.0034 1-11 1-27 2.7 0.0027 1-12 1-28 2.7 0.0031 1-13 1-29 2.7 0.0031 1-14 1-30 2.6 0.0027 1-15 1-31 2.8 0.0035 1-16 1-32 2.9 0.0031 1-17 1-33 3.0 0.0140 1-18 1-34 2.6 0.0021

[Example 1-17] The components were prepared in the proportions (parts by weight) listed in Table 1-2, and the prepared polyimide composition 1-2 was applied to one side of a polyimide film material P1 (manufactured by DuPont Toray, trade name: Kapton 50EN, relative dielectric constant at 10 GHz = 3.6, dielectric loss tangent at 10 GHz = 0.0084, length × width × thickness = 200 mm × 300 mm × 12 μm) in the same manner as in Example 1-1, and dried at 80°C for 15 minutes to obtain a coating film 1-17 having an adhesive layer thickness of 25 μm. The warping condition of the obtained covering film 1-17 is "good".

[Example 1-18] Lamination was performed in a manner that the release PET film was in contact with the adhesive layer side of the covering film 1-17, and the layers were pressed for 2 minutes at a temperature of 160°C and a pressure of 0.8 MPa using a vacuum laminating press. Thereafter, the polyimide composition 1-2 was applied to the polyimide film material P1 side of the covering film 1-17 pressed with the release PET film in a manner that the thickness after drying was 25 μm, and the layers were dried at 80°C for 15 minutes. Then, the demoulding PET film is contacted with the surface coated with the polyimide composition 1-2 and dried, and the vacuum lamination press is used for 2 minutes at a temperature of 160°C and a pressure of 0.8 MPa, thereby obtaining a laminate 1-18 including an adhesive layer on both sides of the polyimide film material P1.

[Example 1-19] The polyimide composition 1-2 was applied to one side of an electrolytic copper foil having a thickness of 12 μm, and dried at 80°C for 15 minutes to obtain a resin-coated copper foil 1-19 having a thickness of 25 μm on the adhesive layer. The curling state of the obtained resin-coated copper foil 1-19 was "good".

[Example 1-20] The polyimide composition 1-2 was applied to one side of an electrolytic copper foil having a thickness of 12 μm, and dried at 80°C for 30 minutes to obtain a resin-coated copper foil 1-20 having a thickness of 50 μm on the adhesive layer. The warp state of the obtained resin-coated copper foil 1-20 was "good".

[Example 1-21] The polyimide composition 1-2 was further coated on the surface of the adhesive layer of the resin-coated copper foil 1-19, and dried at 80°C for 30 minutes to obtain the resin-coated copper foil 1-21 having a total adhesive layer thickness of 100 μm. The warp state of the obtained resin-coated copper foil 1-21 was "good".

[Example 1-22] The polyimide composition 1-2 was coated on one side of a release PET film, dried at 80°C for 30 minutes, and peeled off from the release PET film, thereby obtaining a polyimide film 1-35 having a thickness of 50 μm.

[Example 1-23] Polyimide film 1-2, polyimide film material P2 (manufactured by DuPont, trade name: Kapton 100-EN, thickness 25 μm, relative dielectric constant at frequency 10 GHz = 3.6, dielectric loss tangent at frequency 10 GHz = 0.0084), polyimide film 1-2 and electrolytic copper foil with a thickness of 12 μm are sequentially laminated on an electrolytic copper foil with a thickness of 12 μm, and pressed for 2 minutes at a temperature of 160°C and a pressure of 0.8 MPa using a vacuum lamination press, then heated from room temperature to 160°C, and heat treated at 160°C for 4 hours to obtain a copper-clad laminate 1-23.

[Example 1-24] The adhesive layer side of the coating film 1-17 is laminated on an electrolytic copper foil having a thickness of 12 μm in contact with the copper foil, and is pressed for 2 minutes at a temperature of 160°C and a pressure of 0.8 MPa using a vacuum lamination press, and then the temperature is raised from room temperature to 160°C, and heat-treated at 160°C for 2 hours, thereby obtaining a copper-clad laminate 1-24.

[Example 1-25] A polyimide film 1-2 is laminated on a 12 μm thick rolled copper foil, and the polyimide film material P1 side of the covering film 1-17 is in contact with the polyimide film 1-2. Then, a 12 μm thick rolled copper foil is laminated on the adhesive layer side of the covering film 1-17 in sequence. After lamination at a temperature of 160°C and a pressure of 0.8 MPa for 2 minutes using a vacuum lamination press, the temperature is raised from room temperature to 160°C, and heat-treated at 160°C for 2 hours, thereby obtaining a copper-clad laminate 1-25.

[Example 1-26] Prepare two copper foils 1-19 with resin, and laminate them in a manner that the adhesive layer side of the two copper foils 1-19 with resin is in contact with a polyimide film material P3 (manufactured by DuPont, trade name: Kapton 200-EN, thickness 50 μm, relative dielectric constant at frequency 10 GHz = 3.6, dielectric loss tangent at frequency 10 GHz = 0.0084), and press them for 5 minutes at a temperature of 160°C and a pressure of 0.8 MPa using a vacuum lamination press, then heat the mixture from room temperature to 160°C, and heat treat the mixture at 160°C for 4 hours to obtain a copper-clad laminate 1-26.

[Example 1-27] The polyimide composition 1-2 was coated on the resin layer side of a single-sided copper-clad laminate M1 (manufactured by Nippon Steel Chemicals & Materials Co., Ltd., trade name: Espanex MC12-25-00UEM, length × width × thickness = 200 mm × 300 mm × 25 μm), and dried at 80°C for 30 minutes to obtain a copper-clad laminate 1-27 with an adhesive layer having a thickness of 50 μm. The resin layer side of the single-sided copper-clad laminate M1 is in contact with the adhesive layer side of the copper-clad laminate 1-27 with adhesive, and the copper-clad laminate 1-27 is obtained by pressing at a temperature of 160°C and a pressure of 4.0 MPa for 120 minutes using a small precision pressing machine.

[Example 1-28] A polyimide film 1-2 is laminated on the resin layer side of a single-sided copper-clad laminate M1, and then laminated thereon in a manner such that the resin layer side of the single-sided copper-clad laminate M1 is in contact with the polyimide film 1-2. A small precision press is used for pressing at a temperature of 160°C and a pressure of 4.0 MPa for 120 minutes, thereby obtaining a copper-clad laminate 1-28.

[Example 1-29] The polyimide composition 1-2 was coated on one side of a release PET film, dried at 80°C for 15 minutes, and the adhesive layer was peeled off from the release PET film, thereby obtaining a polyimide film 1-36 having a thickness of 15 μm.

[Example 1-30] A double-sided copper-clad laminate M2 (manufactured by Nippon Steel Chemicals & Materials Co., Ltd., trade name: Espanex MB12-25-00UEG) was prepared, and a circuit was processed by etching the copper foil on one side to obtain a wiring board 1-1A having a conductive circuit layer.

The copper foil on one side of the double-sided copper-clad laminate M2 is removed by etching to obtain a copper-clad laminate 1-1B.

The polyimide film 1-2 is sandwiched between the surface on the conductive circuit layer side of the wiring substrate 1-1A and the surface on the resin layer side of the copper-clad laminate 1-1B, and the laminated surfaces are heat-pressed at a temperature of 160° C. and a pressure of 4.0 MPa for 120 minutes to obtain a multilayer circuit substrate 1-30.

[Example 1-31] A liquid crystal polymer film (manufactured by Kuraray Co., Ltd., trade name: CT-Z, thickness: 50 μm, CTE: 18 ppm/K, thermal deformation temperature: 300°C, relative dielectric constant at a frequency of 10 GHz = 3.40, dielectric loss tangent at a frequency of 10 GHz = 0.0022) is prepared as an insulating substrate, and a copper-clad laminate 1-1C having electrolytic copper foils of 18 μm thickness is provided on both sides thereof. A circuit is processed by etching the copper foil on one side to obtain a wiring board 1-1C having a conductive circuit layer formed thereon.

The copper foil on one side of the copper-clad laminate 1-1C is removed by etching to obtain the copper-clad laminate 1-1D.

A polyimide film 1-2 is sandwiched between the surface on the conductive circuit layer side of the wiring board 1-1C and the surface on the insulating base material layer side of the copper-clad laminate 1-1D, and the laminated surfaces are heat-pressed at a temperature of 160°C and a pressure of 4.0 MPa for 120 minutes to obtain a multilayer circuit board 1-31.

In the following embodiments, unless otherwise specified, various measurements and evaluations were performed as follows.

[Evaluation of Dielectric Properties] ＜Silicon Dioxide Particles＞ Using a vector network analyzer (manufactured by Keysight Technologies, trade name: Vector Network Analyzer E8363C) and a relative dielectric constant measuring device manufactured by Kanto Electronics Application Development Co., Ltd. using the cavity perturbation method, the relative dielectric constant measurement mode: TM020 was set to measure the relative dielectric constant and dielectric loss tangent of silicon dioxide particles at a frequency of 10 GHz. 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. <Resin film> Using a vector network analyzer (Keysight Technologies, trade name: Vector Network Analyzer E8363C) and a separated dielectric resonator (SPDR), the relative dielectric constant and dielectric loss tangent at a frequency of 20 GHz were measured for adhesive sheets 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.

[Particle size measurement] Using a laser diffraction particle size distribution measuring device (manufactured by Malvern, trade name: Master Sizer 3000), water was set as the dispersion medium, and the particle size was measured using the laser diffraction-scattering measurement method under the condition of a particle refractive index of 1.54.

[Measurement of true specific gravity] Using a continuous automatic powder true density measuring device (manufactured by Seishin Enterprise Co., Ltd., trade name: AUTO TRUE DENSERMAT-7000), the true specific gravity was measured using the pycnometer method (liquid phase replacement method).

[Measurement of white silica crystal phase] Using an X-ray diffraction measurement device (manufactured by Bruker, trade name: D2PHASER), the total area of all peaks originating from SiO ₂ was calculated based on all diffraction patterns (peak position, peak width and peak intensity) originating from SiO ₂ in the range of diffraction angle (Cu, Kα) 2θ = 10° to 90°. Next, the peak position originating from the white silica crystal phase was determined, the total area of all peaks of the white silica crystal phase was calculated, and the ratio (weight %) to the total area of all peaks originating from SiO ₂ was obtained. Furthermore, the attribution of each peak was referred to the database of the International Centre for Diffraction Data (ICDD).

[Determination of tensile modulus and maximum elongation] Using a tensile testing machine (Tensilon manufactured by Orientec), a tensile test was performed on a test piece (width: 12.7 mm, length: 127 mm) at 50 mm/min to determine the tensile modulus and maximum elongation at 25°C.

[Measurement of glass transition temperature (Tg)] The adhesive sheet pressed at 160°C, 3.5 MPa, and 60 minutes was cut into test pieces of 5 mm × 20 mm. The test pieces were measured from 30°C to 300°C at a heating rate of 4°C/min and a frequency of 11 Hz using a dynamic viscoelasticity measuring device (DMA: manufactured by DBM, trade name: E4000F). The temperature at which the elastic modulus change (tanδ) was the largest was defined as the glass transition temperature.

[Evaluation of film retention] The film retention is evaluated by the following procedure. Cut the tablet into a test piece with a width of 20 mm and a length of 20 mm, bend it along the diagonal line to form a crease, open it and observe the state of the film. At this time, if the test piece with a crease is opened and there is no crack, it will be rated as "good", and if there is a crack in part, it will be rated as "unacceptable".

[Solder heat resistance test (drying)] Prepare the following printed circuit board: etch and remove one of the copper foils of a double-sided copper-clad laminate (manufactured by Nippon Steel Chemicals & Materials Co., Ltd., trade name: Espanex MB12-25-12UEG), and perform circuit processing on the other copper foil to form a circuit with a wiring width/wiring spacing (L/S) = 1 mm/1 mm. Place an adhesive sheet on the wiring of the printed circuit board, laminate a polyimide film (manufactured by DuPont Toray Co., Ltd., trade name: Kapton 50EN-S) on the opposite side of the adhesive sheet that contacts the printed circuit board, and press at a temperature of 160°C, a pressure of 3.5 MPa, and a time of 60 minutes. After drying the test piece with copper foil at 105°C, immerse it in a solder bath set at each evaluation temperature for 10 seconds, and observe its bonding state to confirm whether there are any defects such as blistering, expansion, and peeling. Heat resistance is expressed by the upper limit temperature at which no defects occur. For example, "320°C" means that no defects were confirmed when evaluating in a solder bath at 320°C.

[Solder heat resistance test (moisture absorption)] Prepare the following printed circuit board: Etch away the copper foil on one side of a double-sided copper-clad laminate (manufactured by Nippon Steel Chemicals & Materials Co., Ltd., trade name: Espanex MB12-25-12UEG), and perform circuit processing on the other copper foil to form a circuit with wiring width/wiring spacing (L/S) = 1 mm/1 mm. The adhesive sheet was placed on the wiring of the printed circuit board, and a polyimide film (manufactured by DuPont Toray Co., Ltd., trade name: Kapton 50EN-S) was laminated on the opposite side of the adhesive sheet that was in contact with the printed circuit board, and then pressed at a temperature of 160°C, a pressure of 3.5 MPa, and a time of 60 minutes. The test piece with copper foil was placed at 40°C and a relative humidity of 80% for 72 hours, and then immersed in a solder bath set at each evaluation temperature for 10 seconds, and its bonding state was observed to confirm whether there were defects such as blistering, expansion, and peeling. Heat resistance is expressed by the upper limit temperature at which no defects occur. For example, "260°C" means that no defects were observed when the product was evaluated in a solder bath at 260°C.

[Peel strength measurement] A double-sided copper-clad laminate (manufactured by Nippon Steel Chemicals & Materials Co., Ltd., trade name: Espanex MB12-25-12UEG) was cut into pieces with a width of 50 mm and a length of 100 mm. An adhesive sheet was placed on the copper foil side of the sample after etching away the copper foil on one side. A polyimide film (manufactured by DuPont Toray Co., Ltd., trade name: Kapton 50EN-S) was then laminated on the adhesive sheet and pressed at a temperature of 160°C, a pressure of 3.5 MPa, and a time of 60 minutes. The laminate was cut into test pieces with a width of 5 mm. A tensile testing machine (manufactured by Toyo Seiki Seisaku-sho, trade name: Strograph VE) was used to stretch the test piece in the 90° direction at a speed of 50 mm/min. The peel strength between the adhesive layer and the copper foil was measured at this time.

[Evaluation method of flame retardancy] Polyimide film (manufactured by DuPont Toray Co., Ltd., trade name: Kapton 50EN-S) was laminated on both sides of the adhesive sheet and pressed at a temperature of 160°C, a pressure of 3.5 MPa, and a time of 60 minutes. The sample was cut into 200 mm ± 5 mm × 50 mm ± 1 mm, rounded to a cylindrical shape of approximately 12.7 mm in diameter and 200 mm ± 5 mm in length, and a test piece in accordance with the UL94VTM standard was prepared and a combustion test was performed. The case where the judgment standard of VTM-0 was achieved was set as "good". If the VTM-1 criteria are met, the result is set to "Yes", and if the VTM-1 criteria are not met, the result is set to "No".

(Synthesis Example 2-1) 55.51 g of BTDA (0.1721 mol), 94.49 g of DDA2 (0.1735 mol), 210 g of NMP and 140 g of xylene were placed in a 1000 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, stirred for 10 hours, and 125 g of xylene was added to prepare a polyimide solution 2-1 (solid content: 30% by weight, weight average molecular weight: 80,900) that had been imidized.

[Example 2-1] 1.09 g of N-12 and 7.50 g of filler 1 were mixed with 100 g of the polyimide solution 2-1 prepared in Synthesis Example 2-1, and xylene was added to dilute and stir in such a way that the solid content became 30% by weight, thereby preparing a polyimide varnish 2-1a.

[Example 2-2 to Example 2-8] Polyimide varnish 2-2a to Polyimide varnish 2-8a were prepared in the same manner as Example 2-1 except that the amounts of filler 1 and filler 2 were changed as shown in Table 2-1.

[Comparative Example 2-1] Polyimide varnish 2-9a was prepared in the same manner as in Example 2-1 except that filler 1 was not added.

[Table 2-1] Polyimide varnish Embodiment Comparison Example 2-1 2-2 2-3 2-4 2-5 2-6 2-7 2-8 2-1 Type 2-1a 2-2a 2-3a 2-4a 2-5a 2-6a 2-7a 2-8a 2-9a Polyimide solution[g] 100 100 100 100 100 100 100 100 100 A Solid content of polyimide solution [g] 30 30 30 30 30 30 30 30 30 N-12[g] 1.09 1.09 1.09 1.09 1.09 1.09 1.09 1.09 1.09 B Filler 1[g] 7.5 15.0 22.5 30.0 0 3.3 9.7 3.1 0 Filler 2[g] 0 0 0 0 28.5 3.7 19.3 0 0 B/(A+B) [wt%] 19 33 42 49 48 18 48 9 0 B/(A+B) [volume %] 11 twenty one 28 34 34 11 34 5 0 Ratio of white silica crystal phase [wt%] 93 93 93 93 0 42 31 93 0 Xylene[g] twenty four 41 59 76 73 twenty three 70 13 6 Solid content concentration [weight %] 30 30 30 30 30 30 30 30 30

[Example 2-9] The polyimide varnish 2-1a prepared in Example 2-1 was applied to one side of a PET film subjected to a mold release treatment, dried at 80°C for 15 minutes, and then peeled off to prepare an adhesive sheet 2-1b (thickness: 25 μm). The various evaluation results of the adhesive sheet 2-1b are as follows. Relative dielectric constant: 2.7, dielectric loss tangent: 0.0015, tensile modulus: 0.6 GPa, maximum elongation: 165%, Tg: 56°C, film retention: good, solder heat resistance test (dry): 320°C, solder heat resistance test (moisture absorption): 260°C, peel strength: 1.8 kN/m, flame retardancy: good

[Example 2-10] Using polyimide varnish 2-2a, adhesive sheet 2-2b was prepared in the same manner as in Example 2-9. The various evaluation results of adhesive sheet 2-2b are as follows. Relative dielectric constant: 2.9, dielectric loss tangent: 0.0013, tensile modulus of elasticity: 0.5 GPa, maximum elongation: 77%, Tg: 56°C, film retention: good, solder heat resistance test (dry): 320°C, solder heat resistance test (moisture absorption): 260°C, peel strength: 1.8 kN/m, flame retardancy: good

[Example 2-11] Using polyimide varnish 2-3a, adhesive sheet 2-3b was prepared in the same manner as in Example 2-9. The various evaluation results of adhesive sheet 2-3b are as follows. Relative dielectric constant: 2.8, dielectric loss tangent: 0.0012, tensile modulus of elasticity: 0.6 GPa, maximum elongation: 59%, Tg: 56°C, film retention: good, solder heat resistance test (dry): 320°C, solder heat resistance test (moisture absorption): 270°C, peel strength: 1.8 kN/m, flame retardancy: good

[Example 2-12] Using polyimide varnish 2-4a, adhesive sheet 2-4b was prepared in the same manner as in Example 2-9. The various evaluation results of adhesive sheet 2-4b are as follows. Relative dielectric constant: 2.8, dielectric loss tangent: 0.0011, tensile modulus: 0.8 GPa, maximum elongation: 31%, Tg: 56°C, film retention: good, solder heat resistance test (dry): 320°C, solder heat resistance test (moisture absorption): 280°C, peel strength: 1.9 kN/m, flame retardancy: good

[Example 2-13] Using polyimide varnish 2-5a, adhesive sheet 2-5b was prepared in the same manner as in Example 2-9. The various evaluation results of adhesive sheet 2-5b are as follows. Relative dielectric constant: 2.8, dielectric loss tangent: 0.0016, tensile modulus of elasticity: 0.8 GPa, maximum elongation: 29%, Tg: 56°C, film retention: good, solder heat resistance test (dry): 320°C, solder heat resistance test (moisture absorption): 270°C, peel strength: 1.9 kN/m, flame retardancy: good

[Example 2-14] Using polyimide varnish 2-6a, adhesive sheet 2-6b was prepared in the same manner as in Example 2-9. The various evaluation results of adhesive sheet 2-6b are as follows. Relative dielectric constant: 2.7, dielectric loss tangent: 0.0015, tensile modulus of elasticity: 0.6 GPa, maximum elongation: 169%, Tg: 56°C, film retention: good, solder heat resistance test (dry): 320°C, solder heat resistance test (moisture absorption): 260°C, peel strength: 1.7 kN/m, flame retardancy: good

[Example 2-15] Using polyimide varnish 2-7a, adhesive sheet 2-7b was prepared in the same manner as in Example 2-9. The various evaluation results of adhesive sheet 2-7b are as follows. Relative dielectric constant: 2.8, dielectric loss tangent: 0.0012, tensile modulus: 0.7 GPa, maximum elongation: 28%, Tg: 56°C, film retention: good, solder heat resistance test (dry): 320°C, solder heat resistance test (moisture absorption): 280°C, peel strength: 1.8 kN/m, flame retardancy: good

[Example 2-16] Using polyimide varnish 2-8a, adhesive sheet 2-8b was prepared in the same manner as in Example 2-9. The various evaluation results of adhesive sheet 2-8b are as follows. Relative dielectric constant: 2.6, dielectric loss tangent: 0.0016, tensile modulus of elasticity: 0.5 GPa, maximum elongation: 177%, Tg: 56°C, film retention: good, solder heat resistance test (dry): 320°C, solder heat resistance test (moisture absorption): 260°C, peel strength: 1.7 kN/m, flame retardancy: acceptable

[Comparative Example 2-2] Using polyimide varnish 2-9a, adhesive sheet 2-9b was prepared in the same manner as in Example 2-9. The various evaluation results of adhesive sheet 2-9b are as follows. Relative dielectric constant: 2.6, dielectric loss tangent: 0.0017, tensile modulus of elasticity: 0.4 GPa, maximum elongation: 197%, Tg: 56°C, film retention: good, solder heat resistance test (dry): 320°C, solder heat resistance test (moisture absorption): 220°C, peel strength: 1.6 kN/m, flame retardancy: unacceptable

The above results are summarized and shown in Table 2-2.

[Table 2-2] Next tablet Embodiment Comparison Example 2-9 2-10 2-11 2-12 2-13 2-14 2-15 2-16 2-2 Type 2-1b 2-2b 2-3b 2-4b 2-5b 2-6b 2-7b 2-8b 2-9b Relative dielectric constant 2.7 2.9 2.8 2.8 2.8 2.7 2.8 2.6 2.6 Dielectric loss tangent 0.0015 0.0013 0.0012 0.0011 0.0016 0.0015 0.0012 0.0016 0.0017 Tensile modulus of elasticity [GPa] 0.6 0.5 0.6 0.8 0.8 0.6 0.7 0.5 0.4 Maximum elongation [%] 165 77 59 31 29 169 28 177 197 Tg[℃] 56 56 56 56 56 56 56 56 56 Film retention good good good good good good good good good Solder heat resistance test (dry) [℃] 320 320 320 320 320 320 320 320 320 Solder heat resistance test (moisture absorption) [℃] 260 260 270 280 270 260 280 260 220 Peel strength [kN/m] 1.8 1.8 1.8 1.9 1.9 1.7 1.8 1.7 1.6 Flame retardant good good good good good good good Can No

According to Table 2-2, it is confirmed that the dielectric properties and solder heat resistance temperature (moisture absorption) of the adhesive sheets 2-1b to 2-8b of Examples 2-9 to 2-16 to which filler 1 and filler 2 are added are improved compared to the adhesive sheet 2-9b of Comparative Example 2-2. Based on such results, the adhesive sheet of the resin film of this embodiment can be expected to reduce the transmission loss in the high frequency band of 20 GHz, for example. In addition, it was confirmed that the adhesive sheets 2-1b to 2-8b of Examples 2-9 to 2-16 to which fillers 1 and 2 were added had improved hygroscopic solder heat resistance, peeling strength, and flame retardancy while maintaining flexibility and film retention, compared with the adhesive sheet 2-9b of Comparative Example 2-2.

As shown in the above examples, by adding white silica particles to DDA/BTDA-based polyimide, a clear effect of reducing the dielectric loss tangent can be seen. In addition, the flame retardancy was evaluated with the layer structure of polyimide film/adhesive layer/polyimide film, and it was confirmed that the adhesive layer containing white silica particles showed a flame retardancy above the VTM-1 level. Furthermore, the adhesive sheet obtained in each example maintained the shape of the film in the practical range of the white silica particle formulation, and the bonding strength relative to polyimide or copper was also improved. Although the mechanism of improved adhesion is not clear, it is speculated that it may contribute to the improvement of the elastic modulus of the adhesive sheet. In addition, the solder heat resistance (drying and/or moisture absorption) of the adhesive sheet obtained in the embodiment is equal to or better than that of the comparative example without white silica particles, showing better characteristics as an adhesive for high-frequency multi-layer FPC.

Based on the above results, it was confirmed that the resin film of this embodiment can be preferably used as a material for a high-frequency compatible flexible printed circuit board.

In the following embodiments, unless otherwise specified, various measurements and evaluations were performed as follows.

[Evaluation of Dielectric Properties] <Liquid Crystalline Polymer Filler> A dimethylacetamide dispersion of a liquid crystal polymer filler adjusted to 30% by weight of solid content was applied to the smooth surface of a copper foil and dried at 120°C for 10 minutes. Thereafter, the temperature was gradually raised from 200°C to 360°C over 10 minutes, and the copper foil of the obtained 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 separated dielectric resonator (SPDR resonator), the obtained liquid crystal polymer film was placed at a temperature of 23°C and a humidity of 50% for 24 hours, and the relative dielectric constant and dielectric loss tangent at a frequency of 10 GHz were measured. <Resin film> Using a vector network analyzer (Keysight Technologies, trade name: Vector Network Analyzer E8363C) and SPDR resonator, the resin film was pressed at 160°C, 3.5 MPa, and 60 minutes. After being placed at 23°C and 50% humidity for 24 hours, the relative dielectric constant and dielectric loss tangent at a frequency of 20 GHz were measured.

[Determination of tensile modulus and maximum elongation] The tensile modulus and maximum elongation were measured by the following procedure. First, a test piece (width 12.7 mm × length 127 mm) was prepared from a resin film using a tensile tester (Tensilon manufactured by Orientec). The tensile test was performed at 50 mm/min using the test piece to determine the tensile modulus and maximum elongation at 25°C.

[Measurement of glass transition temperature (Tg)] The glass transition temperature (Tg) is measured by cutting a resin film pressed at a temperature of 160°C, a pressure of 3.5 MPa, and a time of 60 minutes into a test piece of 5 mm × 20 mm, and using a dynamic viscoelasticity measuring device (DMA: manufactured by DBM, trade name: E4000F), measuring from 30°C to 300°C at a heating rate of 4°C/min and a frequency of 11 Hz. The temperature at which the elastic modulus change (tanδ) is the largest is defined as the glass transition temperature.

[Evaluation of film retention] The film retention is evaluated by the following procedure. Cut the resin film into test pieces with a width of 20 mm and a length of 20 mm, bend it along the diagonal line to form a crease, open it and observe the state of the film. At this time, if the test piece with a crease is opened and there is no crack, it will be rated as "good", and if there is a crack in part, it will be rated as "unacceptable".

[Solder heat resistance test (drying)] Prepare the following printed circuit board: Process the circuit of polyimide copper-clad laminate (manufactured by Nippon Steel Chemicals & Materials Co., Ltd., trade name: Espanex MB12-25-12UEG) to form a circuit with wiring width/wiring spacing (L/S) = 1 mm/1 mm. Place a resin film on the wiring of the printed circuit board, and laminate a polyimide film (manufactured by DuPont Toray Co., Ltd., trade name: Kapton 50EN-S) on the opposite side of the resin film that contacts the printed circuit board, and then press at a temperature of 160°C, a pressure of 3.5 MPa, and a time of 60 minutes. After drying the test piece with copper foil at 105°C, immerse it in a solder bath set at each evaluation temperature for 10 seconds, and observe its bonding state to confirm whether there are any defects such as blistering, expansion, and peeling. Heat resistance is expressed by the upper limit temperature at which no defects occur. For example, "320°C" means that no defects were confirmed when evaluating in a solder bath at 320°C.

[Solder heat resistance test (moisture absorption)] Prepare the following printed circuit board: Process the circuit of polyimide copper-clad laminate (manufactured by Nippon Steel Chemicals & Materials Co., Ltd., trade name: Espanex MB12-25-12UEG) to form a circuit with a wiring width/wiring spacing (L/S) = 1 mm/1 mm. Place a resin film on the wiring of the printed circuit board, and laminate a polyimide film (manufactured by DuPont Toray Co., Ltd., trade name: Kapton 50EN-S) on the opposite side of the resin film that contacts the printed circuit board, and then press at a temperature of 160°C, a pressure of 3.5 MPa, and a time of 60 minutes. After the copper foil test piece was placed at 40°C and 80% relative humidity for 72 hours, it was immersed in a solder bath set at each evaluation temperature for 10 seconds and its bonding state was observed to confirm whether there were any defects such as blistering, expansion, and peeling. Heat resistance is expressed by the upper limit temperature at which no defects occur. For example, "260°C" means that no defects were confirmed when the evaluation was performed in a solder bath at 260°C.

[Peel strength measurement] Peel strength was measured using the following method. A copper foil on one side of a double-sided polyimide copper-clad laminate (Espanex MB12-25-12UEG, manufactured by Nippon Steel Chemicals & Materials Co., Ltd.) cut into pieces with a width of 50 mm and a length of 100 mm was etched, a resin film was placed on the remaining copper foil side, and a polyimide film (Kapton 50EN-S, manufactured by DuPont Toray Co., Ltd.) was laminated on the resin film on the side opposite to the copper-clad laminate, and pressed at a temperature of 160°C, a pressure of 3.5 MPa, and a time of 60 minutes. The laminate was cut into test pieces with a width of 5 mm, and the test piece was stretched in the 90° direction at a speed of 50 mm/min using a tensile testing machine (Strograph VE, manufactured by Toyo Seiki Seisaku-sho, Ltd.), and the peel strength between the resin film as the adhesive layer and the copper foil was measured.

[Evaluation method of flame retardancy] The flame retardancy was evaluated by the following method. Polyimide film (manufactured by DuPont Toray Co., Ltd., trade name: Kapton 50EN-S) was laminated on both sides of a resin film in which four sheets were laminated to form a thickness of 100 μm, and pressed at a temperature of 160°C, a pressure of 3.5 MPa, and a time of 60 minutes. The sample was cut into 200 mm ± 5 mm × 50 mm ± 1 mm, rounded to a cylindrical shape with a diameter of about 12.7 mm and a length of 200 mm ± 5 mm, and a test piece was made according to the UL94VTM standard and a combustion test was performed. If the time until the fire was extinguished was 0 to 5 seconds, it was rated as "◎" (excellent), if it was 6 to 10 seconds, it was rated as "○" (good), if it was 11 to 20 seconds, it was rated as "△" (acceptable), and if it exceeded 21 seconds, it was rated as "×" (unacceptable).

[Synthesis Example 3-1] 55.51 g of BTDA (0.1721 mol), 94.49 g of DDA2 (0.1735 mol), 210 g of NMP and 140 g of xylene were placed in a 1000 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, stirred for 10 hours, and 125 g of xylene was added to prepare a polyimide solution 3-1 (solid content: 30% by weight, weight average molecular weight: 80,900) that had been imidized.

[Example 3-1] 1.09 g of N-12 and 7.50 g of LCP filler were mixed into 100 g of the polyimide solution 3-1 prepared in Synthesis Example 3-1, and xylene was added to dilute and stir in such a way that the solid content became 30% by weight, thereby preparing a polyimide varnish 3-1a.

[Example 3-2 to Example 3-4] Polyimide varnish 3-2a to Polyimide varnish 3-4a were prepared in the same manner as Example 3-1 except that the amount of LCP filler was changed as shown in Table 3-1.

[Example 3-5] 1.09 g of N-12, 7.50 g of LCP filler, and 7.50 g of flame retardant 1 were mixed with 100 g of the polyimide solution 3-1 prepared in Synthesis Example 3-1, and xylene was added to dilute and stir in such a way that the solid content became 30% by weight, thereby preparing a polyimide varnish 3-5a.

[Example 3-6 to Example 3-7] Polyimide varnish 3-6a to Polyimide varnish 3-7a were prepared in the same manner as Example 3-5 except that the amount of LCP filler was changed as shown in Table 3-1.

[Example 3-8 to Example 3-10] Instead of flame retardant 1, flame retardant 2 was used in the amount of Table 3-1, and LCP filler was formulated as in Table 3-1. Polyimide varnish 3-8a to polyimide varnish 3-10a were prepared in the same manner as in Example 3-5.

[Comparative Example 3-1] Polyimide varnish 3-11a was prepared in the same manner as Example 3-1 except that LCP filler was not added.

[Comparative Example 3-2] Polyimide varnish 3-12a was prepared in the same manner as Example 3-5 except that LCP filler was not added.

[Table 3-1] Polyimide varnish Embodiment Comparison Example 3-1 3-2 3-3 3-4 3-5 3-6 3-7 3-8 3-9 3-10 3-1 3-2 Type 3-1a 3-2a 3-3a 3-4a 3-5a 3-6a 3-7a 3-8a 3-9a 3-10a 3-11a 3-12a Polyimide solution[g] 100 100 100 100 100 100 100 100 100 100 100 100 A Solid content of polyimide solution [g] 30 30 30 30 30 30 30 30 30 30 30 30 B LCP filler [g] 7.5 15.0 22.5 30.0 7.5 15.0 22.5 7.5 15.0 22.5 0 0 B/(A+B) [volume %] 17.6 30.0 39.1 46.2 17.6 30.0 39.1 17.6 30.0 39.1 0 0 N-12[g] 1.09 1.09 1.09 1.09 1.09 1.09 1.09 1.09 1.09 1.09 1.09 1.09 Flame retardant 1 0 0 0 0 7.5 7.5 7.5 0 0 0 0 7.5 Flame retardant 2 0 0 0 0 0 0 0 7.5 7.5 7.5 0 0 Xylene[g] 20 38 55 73 38 55 73 38 55 73 3 20 Solid content concentration [weight %] 30 30 30 30 30 30 30 30 30 30 30 30

[Example 3-11] The polyimide varnish 3-1a prepared in Example 3-1 was applied to one side of a PET film subjected to a mold release treatment, dried at 80°C for 15 minutes, and then peeled off to prepare a resin film 3-1b (thickness: 25 μm). The various evaluation results of the resin film 3-1b are as follows. Relative dielectric constant: 2.7, dielectric loss tangent: 0.0015, tensile modulus: 0.6 GPa, maximum elongation: 131%, Tg: 54°C, film retention: good, solder heat resistance test (dry): 320°C, solder heat resistance test (moisture absorption): 260°C, peel strength: 1.6 kN/m, flame retardancy: ○

[Example 3-12] Using polyimide varnish 3-2a, a resin film 3-2b was prepared in the same manner as in Example 3-11. The various evaluation results of the resin film 3-2b are as follows. Relative dielectric constant: 2.7, dielectric loss tangent: 0.0014, tensile modulus of elasticity: 0.7 GPa, maximum elongation: 80%, Tg: 54°C, film retention: good, solder heat resistance test (dry): 320°C, solder heat resistance test (moisture absorption): 260°C, peel strength: 1.5 kN/m, flame retardancy: ○

[Example 3-13] Using polyimide varnish 3-3a, a resin film 3-3b was prepared in the same manner as in Example 3-11. The various evaluation results of the resin film 3-3b are as follows. Relative dielectric constant: 2.8, dielectric loss tangent: 0.0014, tensile modulus of elasticity: 0.7 GPa, maximum elongation: 38%, Tg: 58°C, film retention: good, solder heat resistance test (dry): 320°C, solder heat resistance test (moisture absorption): 270°C, peel strength: 1.2 kN/m, flame retardancy: ○

[Example 3-14] Using polyimide varnish 3-4a, a resin film 3-4b was prepared in the same manner as in Example 3-11. The various evaluation results of the resin film 3-4b are as follows. Relative dielectric constant: 2.9, dielectric loss tangent: 0.0013, tensile modulus of elasticity: 0.8 GPa, maximum elongation: 18%, Tg: 58°C, film retention: good, solder heat resistance test (dry): 320°C, solder heat resistance test (moisture absorption): 270°C, peel strength: 1.2 kN/m, flame retardancy: ○

[Example 3-15] Using polyimide varnish 3-5a, a resin film 3-5b was prepared in the same manner as in Example 3-11. The various evaluation results of the resin film 3-5b are as follows. Relative dielectric constant: 2.7, dielectric loss tangent: 0.0016, tensile modulus of elasticity: 0.5 GPa, maximum elongation: 100%, Tg: 54°C, film retention: good, solder heat resistance test (dry): 320°C, solder heat resistance test (moisture absorption): 270°C, peel strength: 2.0 kN/m, flame retardancy: ◎

[Example 3-16] Using polyimide varnish 3-6a, a resin film 3-6b was prepared in the same manner as in Example 3-11. The various evaluation results of the resin film 3-6b are as follows. Relative dielectric constant: 2.8, dielectric loss tangent: 0.0015, tensile modulus of elasticity: 0.7 GPa, maximum elongation: 33%, Tg: 58°C, film retention: good, solder heat resistance test (dry): 320°C, solder heat resistance test (moisture absorption): 270°C, peel strength: 1.3 kN/m, flame retardancy: ◎

[Example 3-17] Using polyimide varnish 3-7a, a resin film 3-7b was prepared in the same manner as in Example 3-11. The various evaluation results of the resin film 3-7b are as follows. Relative dielectric constant: 2.8, dielectric loss tangent: 0.0014, tensile modulus of elasticity: 0.7 GPa, maximum elongation: 11%, Tg: 58°C, film retention: good, solder heat resistance test (dry): 320°C, solder heat resistance test (moisture absorption): 280°C, peel strength: 0.9 kN/m, flame retardancy: ◎

[Example 3-18] Using polyimide varnish 3-8a, a resin film 3-8b was prepared in the same manner as in Example 3-11. The various evaluation results of the resin film 3-8b are as follows. Relative dielectric constant: 2.7, dielectric loss tangent: 0.0015, tensile modulus of elasticity: 0.5 GPa, maximum elongation: 114%, Tg: 54°C, film retention: good, solder heat resistance test (dry): 320°C, solder heat resistance test (moisture absorption): 280°C, peel strength: 1.4 kN/m, flame retardancy: ◎

[Example 3-19] Using polyimide varnish 3-9a, a resin film 3-9b was prepared in the same manner as in Example 3-11. The various evaluation results of the resin film 3-9b are as follows. Relative dielectric constant: 2.8, dielectric loss tangent: 0.0014, tensile modulus of elasticity: 0.6 GPa, maximum elongation: 52%, Tg: 56°C, film retention: good, solder heat resistance test (dry): 320°C, solder heat resistance test (moisture absorption): 280°C, peel strength: 1.0 kN/m, flame retardancy: ◎

[Example 3-20] Using polyimide varnish 3-10a, a resin film 3-10b was prepared in the same manner as in Example 3-11. The various evaluation results of the resin film 3-10b are as follows. Relative dielectric constant: 2.9, dielectric loss tangent: 0.0013, tensile modulus of elasticity: 0.6 GPa, maximum elongation: 22%, Tg: 56°C, film retention: good, solder heat resistance test (dry): 320°C, solder heat resistance test (moisture absorption): 290°C, peel strength: 0.7 kN/m, flame retardancy: ◎

[Comparative Example 3-3] Using polyimide varnish 3-11a, a resin film 3-11b was prepared in the same manner as in Example 3-11. The various evaluation results of the resin film 3-11b are as follows. Relative dielectric constant: 2.6, dielectric loss tangent: 0.0017, tensile modulus of elasticity: 0.4 GPa, maximum elongation: 197%, Tg: 56°C, film retention: good, solder heat resistance test (dry): 320°C, solder heat resistance test (moisture absorption): 220°C, peel strength: 1.6 kN/m, flame retardancy: ×

[Comparative Example 3-4] Using polyimide varnish 3-12a, a resin film 3-12b was prepared in the same manner as in Example 3-11. The various evaluation results of the resin film 3-12b are as follows. Relative dielectric constant: 2.6, dielectric loss tangent: 0.0018, tensile modulus of elasticity: 0.8 GPa, maximum elongation: 226%, Tg: 56°C, film retention: good, solder heat resistance test (dry): 320°C, solder heat resistance test (moisture absorption): 280°C, peel strength: 1.7 kN/m, flame retardancy: △

The above results are summarized and shown in Table 3-2.

[Table 3-2] Resin film Embodiment Comparison Example 3-11 3-12 3-13 3-14 3-15 3-16 3-17 3-18 3-19 3-20 3-3 3-4 Type 3-1b 3-2b 3-3b 3-4b 3-5b 3-6b 3-7b 3-8b 3-9b 3-10b 3-11b 3-12b Relative dielectric constant 2.7 2.7 2.8 2.9 2.7 2.8 2.8 2.7 2.8 2.9 2.6 2.6 Dielectric loss tangent 0.0015 0.0014 0.0014 0.0013 0.0016 0.0015 0.0014 0.0015 0.0014 0.0013 0.0017 0.0018 Tensile modulus of elasticity [GPa] 0.6 0.7 0.7 0.8 0.5 0.7 0.7 0.5 0.6 0.6 0.4 0.8 Maximum elongation [%] 131 80 38 18 100 33 11 114 52 twenty two 197 226 Tg[℃] 54 54 58 58 54 58 58 54 56 56 56 56 Film retention good good good good good good good good good good good good Solder heat resistance test (dry) [℃] 320 320 320 320 320 320 320 320 320 320 320 320 Solder heat resistance test (moisture absorption) [℃] 260 260 270 280 270 270 280 280 280 290 220 280 Peel strength [kN/m] 1.6 1.5 1.2 1.2 2.0 1.3 0.9 1.4 1.0 0.7 1.6 1.7 Flame retardant ○ ○ ○ ○ ◎ ◎ ◎ ◎ ◎ ◎ × △

According to Table 3-2, it is confirmed that the dielectric loss tangent, flame retardancy, and solder heat resistance temperature (moisture absorption) of resin films 3-1b to 3-4b of Examples 3-11 to 3-14 to which LCP fillers are added are improved compared to the resin film 3-11b of Comparative Example 3-3. As the amount of LCP filler added, which has a lower dielectric loss tangent than DDA-based thermoplastic polyimide, increases, the dielectric loss tangent of the resin film decreases. In addition, by blending LCP fillers with a high aromatic ring concentration in the easily flammable DDA-based thermoplastic polyimide, an excellent flame retardant effect is exhibited. Furthermore, it is considered that by adding the LCP filler, the hygroscopic component is reduced and the elastic modulus is increased, thereby improving the solder heat resistance.

In addition, the resin films 3-1b to 3-4b maintain film properties, and the bonding strength exceeds 0.6 kN/m which is generally required for the production of flexible printed wiring boards, so the resin film of this embodiment is preferably used to produce flexible printed wiring boards using high-frequency bands of 10 GHz or more. DDA-based thermoplastic polyimide has a large elongation, so film properties can be maintained even when LCP fillers are added. Furthermore, Tg is sufficiently low for the pressing temperature, so it is believed that the resin follows the fine unevenness of the copper foil surface and utilizes the carbonyl group of BTDA used as an acid anhydride to ensure adhesion.

In addition, according to Table 3-2, compared with the resin film 3-12b of the comparative example 3-4, the dielectric loss tangent of the resin films 3-5b to 3-10b of the examples 3-15 to 3-20 to which the LCP filler is added is reduced, and the flame retardancy is greatly improved, and they are preferably used as flexible printed wiring board materials corresponding to high frequencies where the thick film of the dielectric layer is continuously developing. It is believed that in the combination of only DDA-based thermoplastic polyimide and phosphorus-based flame retardant, the carbon formation effect of the phosphorus-based flame retardant cannot be fully demonstrated in most cases because the aromatic ring concentration in the DDA-based thermoplastic polyimide is low. In contrast, as shown in Examples 3-15 to 3-20, by setting the combination of DDA-based thermoplastic polyimide, LCP filler and phosphorus-based flame retardant, the aromatic ring concentration in the composition becomes higher, and as a result, the flame retardant effect of the phosphorus-based flame retardant becomes greater.

Although the embodiments of the present invention have been described in detail for the purpose of illustration, the present invention is not limited to the embodiments described above and various modifications are possible.

This application claims priority based on Japanese Patent Application No. 2019-196671 filed in Japan on October 29, 2019, and Japanese Patent Application No. 2019-238107 and Japanese Patent Application No. 2019-238108 filed in Japan on December 27, 2019, and all the contents of those applications are hereby incorporated by reference.

without

without

Claims (7)

A resin composition characterized by containing the following (A) components and (B) components; (A) component: a thermoplastic polyimide containing tetracarboxylic acid residues derived from tetracarboxylic anhydride and diamine residues derived from diamine compounds, and containing 40 mol% or more of diamine residues derived from a dimer diamine composition mainly composed of a dimer diamine in which both terminal carboxylic acid groups of a dimer acid are substituted with primary aminomethyl or amino groups, and (B) component: a liquid crystalline polymer filler, and relative to the total of the (A) component and the (B) component, the (B) component is in the range of 15 volume % to 50 volume % The resin composition as described in claim 1, wherein when the dielectric loss tangent of the component (A) at 10 GHz is set to Dfa and the dielectric loss tangent of the component (B) at 10 GHz is set to Dfb, Dfb is less than 0.0019, and Dfa＞Dfb. The resin composition according to claim 1, wherein the component (A) contains 90 mol parts or more of tetracarboxylic acid residues derived from tetracarboxylic anhydride represented by the following general formula (1) and/or general formula (2) relative to 100 mol parts of the tetracarboxylic anhydride residues, In the general formula (1), X represents a single bond or a divalent group selected from the following formulas; in the general formula (2), the cyclic moiety represented by Y represents a cyclic saturated hydrocarbon group selected from a four-membered ring, a five-membered ring, a six-membered ring, a seven-membered ring or an eight-membered ring; In the above formula, Z represents -C ₆ H ₄ -, -(CH ₂ )n- or -CH ₂ -CH(-OC(=O)-CH ₃ )-CH ₂ -, and n represents an integer of 1-20. The resin composition as claimed in claim 1, wherein 15% to 30% by weight of a phosphorus-based flame retardant is further added relative to 100% by weight of the non-volatile organic compound component of the resin composition. A resin film comprising a thermoplastic resin layer, wherein the thermoplastic resin layer is a thermoplastic resin layer obtained by forming the resin composition according to any one of claims 1 to 4 into a film. The resin film as described in claim 5, wherein the thickness is in the range of 15 μm to 100 μm. The resin film according to claim 5, wherein the component (B) is in a range of 15 volume % to 40 volume % based on the total of the component (A) and the component (B).