Resin composition, adhesive film, laminate, printed wiring board

Abstract

This application provides a resin composition that has heat resistance, good embeddability into the unevenness of the wiring substrate, and flame retardancy. This application provides an adhesive film comprising the above-described resin composition, a laminate comprising the adhesive film and a substrate, and a printed wiring board comprising the laminate. A resin composition comprises a crosslinked polyester resin (C), a transesterification catalyst (D), and a flame retardant (E), wherein the crosslinked polyester resin (C) has a structure formed by crosslinking the side chain carboxyl groups of a polyester resin (A) having carboxyl groups on the side chain with an epoxy crosslinking agent (B), wherein the epoxy crosslinking agent (B) comprises an epoxy compound (b1) having two epoxy groups and no tertiary amino groups in the molecule, and an epoxyamine compound (b2) having two or more epoxy groups and one or more tertiary amino groups in the molecule.

Description

Technical Field

[0001] The present invention relates to a resin composition, an adhesive film comprising the resin composition, a laminate comprising the adhesive film and a substrate, and a printed circuit board comprising the laminate. Background Technology

[0002] Epoxy-based adhesives are being researched as bonding agents traditionally used for electronic circuit boards and flexible printed wiring boards (hereinafter sometimes referred to as FPCs). For adhesives used in these applications, in addition to good adhesion to the substrate material, heat resistance is required to withstand temperatures above 220°C (especially above 260°C) under solder reflow conditions when used as mounting components.

[0003] In recent years, adhesive films made by forming adhesives into a film form have begun to be used in this application. For adhesive films used in this application, it is required to suppress the decrease in connection reliability caused by thermal stress resulting from the use of various materials with different coefficients of thermal expansion, and to improve the embedding performance into the unevenness of the wiring substrate. As an adhesive film that meets these requirements, Patent Document 1 proposes an adhesive film in which an aliphatic or alicyclic epoxy resin is mixed into acrylic rubber. Furthermore, Patent Document 2 proposes a cross-linked polyester resin that has high adhesion to metal substrates and can achieve high heat resistance.

[0004] Existing technical documents

[0005] Patent documents

[0006] Patent Document 1: Japanese Patent Application Publication No. 2011-159693

[0007] Patent Document 2: International Publication No. 2023 / 063386 Summary of the Invention

[0008] The problem that the invention aims to solve

[0009] That said, depending on the application of the adhesive film, flame retardancy is sometimes desired. However, while Patent Documents 1 and 2 investigated the heat resistance and embeddability of the adhesive film into the unevenness of the wiring substrate, flame retardancy was not studied. According to the inventors' research, adding a flame retardant tends to reduce heat resistance. Attempting to improve heat resistance tends to reduce embeddability. Therefore, it is difficult to consistently satisfy flame retardancy, heat resistance, and embeddability.

[0010] The present invention aims to provide a resin composition that is heat-resistant, has good embeddability into the unevenness of the wiring substrate, and is flame-retardant. Furthermore, another objective of the present invention is to provide an adhesive film comprising the above-described resin composition, a laminate comprising the adhesive film and a substrate, and a printed wiring board comprising the laminate.

[0011] Methods for solving problems

[0012] The present invention is described below.

[0013] [1] A resin composition comprising a crosslinked polyester resin (C), an ester exchange catalyst (D), and a flame retardant (E), wherein the crosslinked polyester resin (C) has a structure formed by crosslinking the side chain carboxyl groups of a polyester resin (A) having carboxyl groups in its side chain with an epoxy crosslinking agent (B), wherein the epoxy crosslinking agent (B) comprises an epoxy compound (b1) having two epoxy groups in the molecule and no tertiary amino group, and an epoxy amine compound (b2) having two or more epoxy groups and one or more tertiary amino groups in the molecule.

[0014] [2] According to the resin composition of [1], wherein the number of epoxy groups in the molecule of the epoxy amine compound (b2) is 2 to 4.

[0015] [3] The resin composition according to [1] or [2], wherein the epoxyamine compound (b2) has one or more epoxides formed by the bonding of the tertiary amino group to the epoxy group via an alkylene group having 1 to 4 carbon atoms.

[0016] [4] The resin composition according to any one of [1] to [3], wherein the epoxy compound (b1) is an aliphatic epoxy compound.

[0017] [5] The resin composition according to any one of [1] to [4], wherein the flame retardant (E) is an inorganic flame retardant filler and / or an organic flame retardant filler.

[0018] [6] The resin composition according to any one of [1] to [5], wherein the flame retardant (E) is a phosphorus compound.

[0019] [7] The resin composition according to any one of [1] to [6] further comprises an inorganic filler (F).

[0020] [8] The resin composition according to [7], wherein the inorganic filler (F) is a silica filler.

[0021] [9] The resin composition according to [7], wherein the inorganic filler (F) is hydrophobic silica.

[0022]

[10] The resin composition according to any one of [7] to [9], wherein, relative to 100 parts by weight of the polyester resin (A), it contains 2 to 50 parts by weight of the inorganic filler (F).

[0023]

[11] An adhesive film comprising any one of the resin compositions described in [1] to

[10] .

[0024]

[12] A laminate comprising the adhesive film and substrate described in

[11] .

[0025]

[13] A printed wiring board comprising the laminate described in

[12] .

[0026]

[14] The resin composition according to any one of [1] to

[10] , wherein the flame retardant (E) is a flame retardant that is insoluble in organic solvents.

[0027] Invention Effects

[0028] According to the present invention, a resin composition having heat resistance, good embeddability into the unevenness of the wiring substrate, and flame retardancy can be provided. Furthermore, according to the present invention, an adhesive film comprising the above-described resin composition, a laminate comprising the adhesive film and a substrate, and a printed wiring board comprising the laminate can be provided. Detailed Implementation

[0029] The main point of the resin composition involved in this invention is that it comprises a crosslinked polyester resin (C), an ester exchange catalyst (D), and a flame retardant (E). The crosslinked polyester resin (C) has a structure formed by crosslinking the side chain carboxyl groups of a polyester resin (A) with carboxyl groups on the side chain using an epoxy crosslinking agent (B). The epoxy crosslinking agent (B) comprises an epoxy compound (b1) having two epoxy groups and no tertiary amino groups in the molecule, and an epoxy amine compound (b2) having two or more epoxy groups and one or more tertiary amino groups in the molecule. The addition of the flame retardant (E) can easily have an adverse effect on the heat resistance and embeddability of the resin composition. However, it has been found that if the side chain carboxyl groups of the polyester resin (A) are crosslinked using an epoxy crosslinking agent (B) composed of epoxy compounds (b1) and epoxy amine compounds (b2), then in the presence of the ester exchange catalyst (D), it is possible to balance high crosslinking density and the characteristic of softening upon heating. This improves the flame retardancy without reducing the heat resistance and embeddability of the resin composition, thus completing this invention. The present invention will be described below.

[0030] (A) Polyester resins with carboxyl groups on the side chains

[0031] Polyester resin (A) has carboxyl groups in its side chains (hereinafter sometimes referred to as branched structures). In addition, polyester resin (A) has ester bonds within its molecule.

[0032] The structure of a polyester resin (A) with a carboxyl group in the side chain [hereinafter sometimes simply referred to as polyester resin (A)] can also be a structure in which the substituents branching from the main chain of the polyester resin (e.g., aliphatic hydrocarbon groups, aromatic hydrocarbon groups, alicyclic hydrocarbon groups, etc.) have carboxyl groups, or a structure in which the main chain of the polyester resin has carboxyl groups directly, preferably a structure in which the main chain of the polyester resin has carboxyl groups directly.

[0033] The number average molecular weight (Mn) of the polyester resin (A) is preferably, for example, 5,000 to 50,000. Since the number average molecular weight (Mn) of the polyester resin (A) is within the above range, the acid value of the polyester resin (A) is easily controlled. The number average molecular weight (Mn) of the polyester resin (A) is more preferably 10,000 to 25,000, and even more preferably 12,000 to 20,000.

[0034] The acid value of the polyester resin (A) is preferably, for example, 5 to 40 mg KOH / g. Because the acid value of the polyester resin (A) is 5 mg KOH / g or higher, sufficient crosslinking occurs between it and the epoxy crosslinking agent (B), improving the heat resistance of the resin composition. Because the acid value of the polyester resin (A) is 40 mg KOH / g or lower, the crosslinking density is optimized, the molecular motion is not inhibited, ester bond exchange easily occurs, softening becomes sufficient, and adhesion becomes good. The acid value of the polyester resin (A) is more preferably 7 to 30 mg KOH / g, and even more preferably 10 to 20 mg KOH / g.

[0035] The glass transition temperature of the polyester resin (A) is preferably 0 to 110°C, more preferably 5 to 85°C, even more preferably 10 to 65°C, and particularly preferably 10 to 45°C.

[0036] The number of carboxyl groups (N) in each polymer chain of polyester resin (A) COOH For example, in the polyester resin (A) before crosslinking, each molecule contains approximately 2 to 60 carboxyl groups, preferably 3 to 40, and more preferably 4 to 20. The more carboxyl groups there are, the more crosslinking points there are, and the better the heat resistance. Furthermore, since the number of carboxyl groups is not excessive, the toughness or elasticity becomes good. The number of carboxyl groups in each polymer chain of the polyester resin (A) can be determined by proton nuclear magnetic resonance (1H NMR).

[0037] In order to give polyester resin (A) a branched structure and make it a substance with side chains, the copolymer components that are its raw materials can also have a branched structure.

[0038] Polyester resin (A) can be manufactured by reacting a polycarboxylic acid component with a polyol component, or it can be a substance obtained by adding a monomer with a carboxyl group to a polyester with a reaction site obtained by reacting a polycarboxylic acid component with a polyol component. However, it is preferred to be a substance that imparts a carboxyl group by reacting a high molecular weight polyol (a) obtained by reacting a polycarboxylic acid component with a polyol component with three or more functions (copolymerization).

[0039] Polyester resin (A) is preferably included as a main agent in the resin composition. In this specification, the main agent in the resin composition specifically refers to the component with the highest content in the solid components of the resin composition. The content of polyester resin (A) in the resin composition of the present invention is preferably 50% by mass or more, more preferably 60% by mass or more, and even more preferably 70% by mass or more, out of 100% by mass of the solid components of the adhesive composition. Furthermore, the content of polyester resin (A) in the resin composition is preferably 99.0% by mass or less, more preferably 98.0% by mass or less, and even more preferably 97.5% by mass or less, out of 100% by mass of the solid components of the adhesive composition. That is, the content of polyester resin (A) in the resin composition is preferably 50 to 99.0% by mass, more preferably 60 to 98.0% by mass, and even more preferably 70 to 97.5% by mass, out of 100% by mass of the solid components of the adhesive composition. Since adhesion or heat resistance becomes good within the range described above, this is preferred.

[0040] (a) Polyols

[0041] Polymer polyol (a) can also be a polymer of polycarboxylic acid components and polyol components (polymer polyester polyol). In addition, polymer polyol (a) can also contain polycarboxylic acid components with more than three functions or polyol components with more than three functions.

[0042] (Polycarboxylic acid components)

[0043] As a polycarboxylic acid component for use in high molecular weight polyols (a), aromatic dicarboxylic acid components and / or polycarboxylic acid components other than aromatic dicarboxylic acid components may also be used, with at least aromatic dicarboxylic acid components preferred.

[0044] From the viewpoint of improving the cohesive force and strength of the resin, aromatic dicarboxylic acid components are preferred as polycarboxylic acid components for polymeric polyols (a). Examples of aromatic dicarboxylic acid components include terephthalic acid, isophthalic acid, phthalic acid, naphthalenedicarboxylic acid, biphenyl dicarboxylic acid, and dibenzoic acid. Additionally, aromatic dicarboxylic acids having sulfonic acid groups, such as sulfoterephthalic acid, 5-sulfoisophthalic acid, 4-sulfophthalic acid, 4-sulfonnaphthalene-2,7-dicarboxylic acid, and 5-(4-sulfophenoxy)isophthalic acid, and aromatic dicarboxylic acids having sulfonate groups such as their metal salts or ammonium salts, can also be used. These can be used alone or in mixtures of two or more. Among these, terephthalic acid, isophthalic acid, and mixtures thereof are preferred.

[0045] Examples of polycarboxylic acid components other than aromatic dicarboxylic acids include alicyclic dicarboxylic acids such as 1,4-cyclohexanedicarboxylic acid, 1,3-cyclohexanedicarboxylic acid, 1,2-cyclohexanedicarboxylic acid and their anhydrides; aliphatic dicarboxylic acids such as succinic acid, adipic acid, azelaic acid, sebacic acid, dodecanoic acid, and dimer acids; and dicarboxylic acids containing unsaturated bonds such as fumaric acid, maleic acid and their anhydrides. Additionally, thiomalic acid, which has a thiol group in its molecular structure, and 2,5-furandicarboxylic acid (FDCA) derived from biomass can also be used. These can be used alone or in combination of two or more.

[0046] (Polyol components)

[0047] As the polyol component used in the high molecular weight polyol (a), a diol component is preferred. Examples of diol components include aliphatic diols, alicyclic diols, aromatic diols, or diols containing ether bonds.

[0048] Examples of aliphatic diols include ethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,4-butanediol, 2-methyl-1,3-propanediol, 2-methyl-1,3-butanediol, 1,5-pentanediol, 2,2-dimethyl-1,3-propanediol, 1,6-hexanediol, 3-methyl-1,5-pentanediol, 1,9-nonanediol, 2-ethyl-2-butylpropanediol (DMH), neopentyl hydroxypentanoate, dimethylolheptane, and 2,2,4-trimethyl-1,3-pentanediol.

[0049] Examples of alicyclic diols include 1,4-cyclohexanediol, 1,4-cyclohexanediethanol, tricyclodecanediol, tricyclodecanediol, spirodiol, hydrogenated bisphenol A, ethylene oxide adducts and propylene oxide adducts of hydrogenated bisphenol A, and dimerized diols.

[0050] Examples of aromatic diols include p-xylene glycol, m-xylene glycol, o-xylene glycol, p-hydroxyphenylethanol, 1,4-benzene glycol, ethylene oxide adducts of 1,4-benzene glycol, and diols obtained by adding ethylene oxide or propylene oxide to two phenolic hydroxyl groups of bisphenols such as bisphenol A, ethylene oxide adducts of bisphenol A, and propylene oxide adducts, in 1 to several molar amounts. Alternatively, diol-modified aromatic dicarboxylic acids can be used. Specific examples include bis-2-hydroxyethyl terephthalate (BHET), a ethylene glycol-modified terephthalic acid, a propylene glycol-modified terephthalic acid, an ethylene glycol-modified isophthalic acid, a propylene glycol-modified isophthalic acid, an ethylene glycol-modified phthalic acid, and a propylene glycol-modified phthalic acid. Other examples of diol-modified aromatic dicarboxylic acids include diol-modified aromatic dicarboxylic acids such as naphthalenedicarboxylic acid, biphenyl dicarboxylic acid, dibenzoic acid, 5-hydroxyisophthalic acid, sulfoterephthalic acid, 5-sulfoisophthalic acid, 4-sulfophthalic acid, 4-sulfonnaphthal-2,7-dicarboxylic acid, 5-(4-sulfophenoxy)isophthalic acid, sulfoterephthalic acid and / or their metal salts, ammonium salts, etc., having sulfonic acid groups or sulfonate groups.

[0051] Examples of diols containing ether bonds include diethylene glycol, triethylene glycol, dipropylene glycol, polyethylene glycol, polypropylene glycol, polytetramethylene glycol, neopentyl glycol ethylene oxide adduct, and neopentyl glycol propylene oxide adduct.

[0052] These can be used alone or in combination of two or more. Among these, aliphatic diols are preferred, and ethylene glycol, 2-methyl-1,3-butanediol, 2,2-dimethyl-1,3-propanediol, and 1,6-hexanediol are more preferred.

[0053] (Polycarboxylic acid components with 3 or more functions)

[0054] Examples of polycarboxylic acid components with three or more functions used in high molecular weight polyols (a) include trimellitic acid, pyromellitic acid, ethylene glycol bis(dehydrated trimellitic acid ester), glyceryl tri(dehydrated trimellitic acid ester), trimellitic anhydride, pyromellitic tetracarboxylic anhydride (PMDA), oxydiphthalic dianhydride (ODPA), 3,3',4,4'-benzophenone tetracarboxylic dianhydride (BTDA), 3,3',4,4'-biphenyl tetracarboxylic dianhydride (BPDA), 3,3',4,4'-diphenyl sulfone tetracarboxylic dianhydride (DSDA), 4,4'-(hexafluoroisopropylidene)diphthalic dianhydride (6FDA), and 2,2'-bis[(dicarboxyphenoxy)phenyl]propane dianhydride (BSAA). These can be used alone or in mixtures of two or more. Among these, trimellitic anhydride is preferred.

[0055] (Polyols with 3 or more functions)

[0056] Examples of polyols with three or more functions used in high molecular weight polyols (a) include glycerol, trimethylolethane, trimethylolpropane, and pentaerythritol. These can be used alone or in combination of two or more.

[0057] As other components, high molecular weight polyols (a) may also include oxocarboxylic acid compounds with hydroxyl and carboxyl groups in their molecular structures, such as 5-hydroxyisophthalic acid, p-hydroxybenzoic acid, p-hydroxyphenylpropionic acid, p-hydroxyphenylacetic acid, 6-hydroxy-2-naphthoic acid, and 4,4-bis(p-hydroxyphenyl)valeric acid.

[0058] The number average molecular weight (Mn) of the high molecular weight polyol (a) is preferably 1,000 to 30,000, more preferably 2,000 to 25,000, and even more preferably 3,000 to 20,000.

[0059] The polymeric polyol (a) may also contain two or more polymeric polyols with different number-average molecular weights (Mn). When the polymeric polyol (a) contains two or more polymeric polyols with different number-average molecular weights (Mn), it may also contain a long-chain polymeric polyol (a1) with a number-average molecular weight (Mn) of 7000 or more and a short-chain polymeric polyol (a2) with a number-average molecular weight (Mn) of 1000 or more and less than 7000. By containing two or more polymeric polyols with different number-average molecular weights (Mn), the heat resistance of the resin composition can be further improved. For example, the long-chain molecules of the long-chain polymeric polyol (a1) block contribute to heat resistance, while the introduction of the short-chain polymeric polyol (a2) block allows for the introduction of a sufficient amount of carboxylic acid to impart heat resistance. Furthermore, there is no particular upper limit to the number-average molecular weight (Mn) of the long-chain polymeric polyol (a1), for example, it may be 20000 or less.

[0060] When the polymeric polyol (a) comprises a long-chain polymeric polyol (a1) and a short-chain polymeric polyol (a2), the polymerization ratio of the long-chain polymeric polyol (a1) to the short-chain polymeric polyol (a2) is such that, relative to 100 parts by mass of the total long-chain polymeric polyol (a1) and short-chain polymeric polyol (a2), the amount of short-chain polymeric polyol (a2) is preferably 5 to 50 parts by mass. Since the polymerization ratio of the long-chain polymeric polyol (a1) to the short-chain polymeric polyol (a2) is within the above range, the heat resistance of the resin composition can be improved. The amount of short-chain polymeric polyol (a2) is more preferably 10 to 40 parts by mass, and even more preferably 20 to 30 parts by mass, relative to 100 parts by mass of the total long-chain polymeric polyol (a1) and short-chain polymeric polyol (a2).

[0061] When the polymeric polyol (a) comprises a long-chain polymeric polyol (a1) and a short-chain polymeric polyol (a2), the polymerization amount of the long-chain polymeric polyol (a1) is preferably 50 to 90% by mass when the polymeric polyol (a) is set to 100% by mass. Since the polymerization amount of the long-chain polymeric polyol (a1) in the polymeric polyol (a) is within the above range, the heat resistance and adhesion of the resin composition are good based on the balance with the polymerization amount of the short-chain polymeric polyol (a2) or the polycarboxylic acid component with more than three functions. The polymerization amount of the long-chain polymeric polyol (a1) is more preferably 60 to 85% by mass when the polymeric polyol (a) is set to 100% by mass, and even more preferably 70 to 80% by mass.

[0062] (Polycarboxylic acid components with 3 or more functions)

[0063] There are no particular limitations on polycarboxylic acid components with three or more functions that react (polymerize) with high molecular weight polyols (a), as long as they are compounds with three or more carboxyl groups within the molecule. Carboxyl groups can also form anhydride groups within the molecule; in that case, one anhydride group is counted as two carboxyl groups.

[0064] Examples of polycarboxylic acid components with three or more functions include trimellitic acid, pyromellitic acid, ethylene glycol bis(dehydrated trimellitic acid ester), glyceryl tri(dehydrated trimellitic acid ester), trimellitic anhydride, pyromellitic tetracarboxylic anhydride (PMDA), oxydiphthalic dianhydride (ODPA), 3,3',4,4'-benzophenone tetracarboxylic dianhydride (BTDA), 3,3',4,4'-biphenyl tetracarboxylic dianhydride (BPDA), 3,3',4,4'-diphenyl sulfone tetracarboxylic dianhydride (DSDA), 4,4'-(hexafluoroisopropylidene)diphthalic dianhydride (6FDA), and 2,2'-bis[(dicarboxyphenoxy)phenyl]propane dianhydride (BSAA). These can be used alone or in combination of two or more. Among these, pyromellitic tetracarboxylic anhydride is preferred.

[0065] Regarding the amount of polycarboxylic acid components with three or more functions in the resin composition, relative to 100 moles of polyester resin (A), the polycarboxylic acid components with three or more functions may be 0.1 to 3 moles, more preferably 0.3 to 2 moles, and even more preferably 0.5 to 1.5 moles.

[0066] The polymerization ratio of the high-molecular-weight polyol (a) to the polycarboxylic acid component with three or more functions in the polyester resin (A) is preferably 0.5 to 10 parts by mass of the polycarboxylic acid component with three or more functions, more preferably 1 to 8 parts by mass, and even more preferably 2 to 5 parts by mass, relative to 100 parts by mass of the high-molecular-weight polyol (a). Since the polymerization ratio of the polycarboxylic acid component with three or more functions is above the lower limit, the crosslinking amount becomes sufficient, and the heat resistance of the resin composition is improved. Since the polymerization ratio of the polycarboxylic acid component with three or more functions is below the upper limit, the crosslinking density does not become too high, ester bond exchange easily occurs, softening becomes sufficient, and the adhesion is improved.

[0067] The acid value of the high molecular weight polyol (a) is preferably 0.1 to 20 mg KOH / g, more preferably 0.2 to 15 mg KOH / g, and even more preferably 0.3 to 10 mg KOH / g.

[0068] When the polyol (a) comprises a long-chain polyol (a1) and a short-chain polyol (a2), the acid value of the long-chain polyol (a1) is preferably 1 to 20 mg KOH / g, more preferably 2 to 15 mg KOH / g, and even more preferably 3 to 10 mg KOH / g. The acid value of the short-chain polyol (a2) is preferably 0.1 to 10 mg KOH / g, more preferably 0.2 to 8 mg KOH / g, and even more preferably 0.3 to 5 mg KOH / g.

[0069] The glass transition temperature of the polymeric polyol (a) is preferably -10 to 100°C, more preferably 0 to 80°C, and even more preferably 5 to 60°C.

[0070] When the polyol (a) comprises a long-chain polyol (a1) and a short-chain polyol (a2), the glass transition temperature of the long-chain polyol (a1) is preferably, for example, -10 to 60°C, more preferably -5 to 30°C, and even more preferably 0 to 15°C. The glass transition temperature of the short-chain polyol (a2) is preferably, for example, 5 to 100°C, more preferably 20 to 90°C, and even more preferably 30 to 80°C.

[0071] (Chain extender)

[0072] The polyester resin (A) may optionally contain a chain extender as a copolymer component, to the extent that the aforementioned effects are not impaired. By using a chain extender, an acid value can be efficiently imparted. For example, a low molecular weight diol with a molecular weight of 1000 or less can be used as a chain extender. However, aliphatic diols are not included among low molecular weight diols with a molecular weight of 1000 or less. Examples of low molecular weight diols with a molecular weight of 1000 or less include dimethylolbutyric acid (DMPO).

[0073] The amount of chain extender polymerized in the polyester resin (A) is preferably 0.1 to 5 parts by mass relative to 100 parts by mass of the high molecular weight polyol (a), more preferably 0.5 to 4 parts by mass, and even more preferably 1 to 3 parts by mass. If the amount of chain extender polymerized is too high, phenomena such as difficulty in increasing the molecular weight and reaction between the chain extenders may occur, resulting in the varnish turning cloudy.

[0074] (Reaction catalyst)

[0075] In the manufacture of polyester resin (A), reaction catalysts such as quaternary ammonium salts or tertiary amines can be used within a range that does not impair the aforementioned effects. Examples of reaction catalysts include, for instance, imidazole compounds such as 2-methylimidazole, 1,2-dimethylimidazole, 2-ethyl-4-methylimidazole, 2-phenyl-4-methylimidazole, or 1-cyanoethyl-2-ethyl-4-methylimidazole; triethylamine, triethylenediamine, N'-methyl-N-(2-dimethylaminoethyl)piperazine, N,N-diisopropylethylamine, N,N-dimethylaminopyridine, 1,8-diazabicyclo(5,4,0)-undecene-7, 1,5-diazabicyclo(5,4,0)-undecene-7, and 1,5-diazabicyclo(5,4,0)-undecene-7. Tertiary amines such as bicyclo(4,3,0)-nonene-5 or 6-dibutylamino-1,8-diazabicyclo(5,4,0)-undecene-7, and compounds that form amine salts of these tertiary amines using phenol, octanoic acid, or quaternized tetraphenylborate; quaternary ammonium salts such as tetramethylammonium bromide, tetraethylammonium bromide, tetra-n-butylammonium bromide, tetramethylammonium chloride, trimethylbenzylammonium chloride, triethylbenzylammonium chloride, tetramethylammonium hydroxide, trimethylbenzylammonium hydroxide, and tetra-n-butylammonium hydroxide. These can be used alone or in mixtures of two or more.

[0076] (B) Epoxy crosslinking agent

[0077] The epoxy crosslinking agent (B) comprises an epoxy compound (b1) having two epoxy groups and no tertiary amino groups in the molecule, and an epoxy amine compound (b2) having two or more epoxy groups and one or more tertiary amino groups in the molecule. Because it contains both epoxy compound (b1) and epoxy amine compound (b2), even if the resin composition contains a flame retardant, its heat resistance is not easily deteriorated, and its embedding properties are also improved.

[0078] (b1) Epoxy compound

[0079] Epoxy compounds (b1) are compounds having two epoxy groups within the molecule. However, compounds with two epoxy groups within the molecule do not include those that also simultaneously have a tertiary amine group within the molecule. By using epoxy compounds (b1), three-dimensional crosslinking is easily formed, thus improving the heat resistance of the resin composition.

[0080] Aliphatic epoxides (b1) can also be used as epoxides. Aliphatic epoxides are compounds composed of aliphatic saturated hydrocarbon groups and epoxy groups, and may also contain oxygen or sulfur atoms within the molecule as needed. Examples of aliphatic epoxides include compounds in which multiple epoxy-containing groups are bonded to aliphatic saturated hydrocarbon groups via oxygen or sulfur atoms. Examples of epoxy-containing groups include epoxy groups and glycidyl groups.

[0081] Examples of epoxy compounds (b1) include polytetramethylene glycol diglycidyl ether, polypropylene glycol diglycidyl ether, 1,4-butanediol diglycidyl ether, neopentyl glycol diglycidyl ether, 1,6-hexanediol diglycidyl ether, bisphenol A diglycidyl ether, and bisphenol S diglycidyl ether. These can be used alone or in combination of two or more. Among these, 1,4-butanediol diglycidyl ether is preferred.

[0082] Regarding the molar ratio of epoxy compound (b1) in the resin composition, the epoxy groups of epoxy compound (b1) can also be 10 to 200 molar parts relative to 100 molar parts of carboxyl groups in polyester resin (A). Since the molar ratio of epoxy groups of epoxy compound (b1) in the resin composition is within the above range, the crosslinking density becomes appropriate, and softening can be promoted by heating the resin composition. The molar ratio of epoxy groups of epoxy compound (b1) in the resin composition is more preferably 80 to 150 molar parts relative to 100 molar parts of carboxyl groups in polyester resin (A), and even more preferably 80 to 120 molar parts.

[0083] (b2) Epoxyamine compounds

[0084] Epoxyamine compounds (b2) are compounds that have two or more epoxy groups and one or more tertiary amino groups in their molecules. They may also contain oxygen atoms and sulfur atoms in their molecules as needed.

[0085] By using the epoxy amine compound (b2), the heat resistance of the resin composition can be improved even with the addition of a flame retardant (E). By crosslinking the side chain carboxyl groups of the polyester resin (A) with an epoxy crosslinking agent (B) composed of the epoxy amine compound (b2) and the aforementioned epoxy compound (b1), both high crosslinking density and the softening property upon heating can be achieved. Therefore, even with the addition of a flame retardant, both the heat resistance and embedding properties of the resin composition can be maintained. Furthermore, the tertiary amino group of the epoxy amine compound (b2) also exhibits transesterification catalysis with the transesterification catalyst (D). By heating the resin composition, the hydroxyl groups contained in the resin composition, due to the action of the tertiary amino group, attack the C=O bonds of the ester groups present near the hydroxyl groups, resulting in bond exchange based on the transesterification reaction, which can exhibit softening behavior.

[0086] The number of epoxy groups in the epoxide amine compound (b2) is preferably 2 to 4, more preferably 3 or 4. The number of tertiary amino groups in the epoxide amine compound (b2) may also be 2 or more, preferably 3 or less.

[0087] The epoxide amine compound (b2) may also have one or more epoxide amines formed by bonding a tertiary amino group to an alkylene group with an epoxy group via an alkylene group having 1 to 4 carbon atoms. The number of carbon atoms in the alkylene group bonded to the tertiary amino group and the epoxy group is more preferably 3 or less, further preferably 2 or less, and particularly preferably 1. One epoxy group may be bonded to the nitrogen atom of the tertiary amino group via an alkylene group having 1 to 4 carbon atoms, or two epoxy groups may be bonded to the alkylene group having 1 to 4 carbon atoms, preferably a diepoxide amine with two epoxy groups bonded to the alkylene group having 1 to 4 carbon atoms.

[0088] The number of epoxidized amino groups in the molecule of the epoxidized amine compound (b2) can be 2 or more, 3 or more, 5 or less, or 4 or less. That is, the number of epoxidized amino groups in the molecule of the epoxidized amine compound (b2) can be 2 to 5, or 3 or 4. The number of diepoxidized amino groups in the molecule of the epoxidized amine compound (b2) can be 1, 2, or 3, preferably 1 or 2, and more preferably 2 diglycidylamino groups.

[0089] The epoxide amine compound (b2) has an aromatic ring, and may also have a dicyclic amino group bonded to the aromatic ring. The number of dicyclic amino groups bonded to the aromatic ring may be one or two, preferably three or less. When the epoxide amine compound (b2) has an aromatic ring, the aromatic ring may also have a dicyclic amino group bonded to it via an alkylene group having 1 to 4 carbon atoms. The number of carbon atoms in the alkylene group bonded to the aromatic ring and the dicyclic amino group is more preferably 3 or less, further preferably 2 or less, and particularly preferably 1. When the epoxide amine compound (b2) has an aromatic ring, the number of the aromatic ring may be one or two, preferably three or less. When the epoxide amine compound (b2) has two or more aromatic rings, the aromatic rings may be directly bonded to each other, or two or more aromatic rings may be bonded to each other via an alkylene group having 1 to 4 carbon atoms.

[0090] Examples of epoxide amine compounds (b2) include 4-(ethylene oxide-2-ylmethoxy)-N,N-bis(ethylene oxide-2-ylmethyl)aniline (hereinafter sometimes referred to as triglycidyl-p-aminophenol), N,N,N',N'-tetraglycidyl-m-xylenediamine, and 4,4'-methylenebis(N,N-diglycidylaniline). These can be used alone or in mixtures of two or more. Among these, triglycidyl-p-aminophenol or N,N,N',N'-tetraglycidyl-m-xylenediamine are preferred.

[0091] Regarding the molar ratio of the epoxy amine compound (b2) in the resin composition, the epoxy groups of the epoxy amine compound (b2) can also be 1 to 30 molar parts relative to 100 molar parts of carboxyl groups in the polyester resin (A). Since the molar ratio of the epoxy groups of the epoxy amine compound (b2) in the resin composition is within the above range, the crosslinking density becomes appropriate, and softening can be promoted when the resin composition is heated. The molar ratio of the epoxy groups of the epoxy amine compound (b2) in the resin composition is more preferably 1 to 20 molar parts relative to 100 molar parts of carboxyl groups in the polyester resin (A), and even more preferably 2 to 10 molar parts.

[0092] The mixing ratio of the epoxy groups of the epoxy compound (b1) to the epoxy groups of the epoxide compound (b2) in the resin composition [epoxide groups of epoxy compound (b1) / epoxy groups of epoxide compound (b2)], in molar ratio relative to 100 molar parts of carboxyl groups in the polyester resin (A), is preferably 2 to 70. The mixing ratio [epoxide groups of epoxy compound (b1) / epoxy groups of epoxide compound (b2)] is more preferably 4 to 65, and even more preferably 8 to 60.

[0093] (C) Cross-linked polyester resin

[0094] Crosslinked polyester resin (C) is a resin having a structure formed by crosslinking the side chain carboxyl groups of polyester resin (A) with carboxyl groups in the side chain with an epoxy crosslinking agent (B), wherein the epoxy crosslinking agent (B) comprises an epoxy compound (b1) having two epoxy groups in the molecule and no tertiary amino group, and an epoxy amine compound (b2) having two or more epoxy groups and one or more tertiary amino groups in the molecule.

[0095] (D) Ester exchange catalyst

[0096] The transesterification catalyst (D) is a transesterification catalyst for the ester groups in a polyester resin (A) with carboxyl groups in its side chains. By including the transesterification catalyst (D), the crosslinked polyester resin (C) is subjected to dynamic covalent crosslinking that enables bond exchange at high temperatures, thereby exhibiting high strength at room temperature. Above the transesterification activation temperature, in addition to being able to adhere to or embed into substrates, films, and wiring, it also softens and can suppress problems of cracking or circuit deformation caused by the difference in thermal expansion between the insulating layer and the conductor layer, resulting in good embeddability of the resin composition.

[0097] Examples of transesterification catalysts (D) include zinc acetate, anhydrous zinc acetate, zinc acetylacetonate, triphenylphosphine, 1,5,7-triazabicyclo[4.4.0]dec-5-ene, and 1,8-diazabicyclo[5.4.0]undecene-7. These can be used alone or in mixtures of two or more. Among these, anhydrous zinc acetate is preferred.

[0098] Regarding the molar ratio of the transesterification catalyst (D) in the resin composition, the transesterification catalyst (D) is preferably 5 to 40 molar parts relative to 100 molar parts of carboxyl groups in the polyester resin (A). Since the molar ratio of the transesterification catalyst (D) in the resin composition is within the above range, softening can be promoted when the resin composition is heated. The molar ratio of the transesterification catalyst (D) in the resin composition is more preferably 10 to 30 molar parts relative to 100 molar parts of carboxyl groups in the polyester resin (A), and even more preferably 10 to 20 molar parts.

[0099] (E) Flame retardant

[0100] By including a flame retardant (E), flame retardancy can be imparted to the resin composition. The flame retardant (E) is not particularly limited to any flame retardant that causes the resin composition to exhibit flame retardancy by being added to it, but a flame retardant that is insoluble in organic solvents is preferred.

[0101] As a flame retardant (E), flame-retardant fillers can also be used, such as inorganic and organic flame-retardant fillers. Inorganic and organic flame-retardant fillers can be used alone or in combination.

[0102] Examples of inorganic flame-retardant fillers include metal oxides such as magnesium oxide, molybdenum oxide, zirconium oxide, tin oxide, tin oxide hydrate, and antimony oxide; metal hydroxide compounds such as aluminum hydroxide, magnesium hydroxide, zirconium hydroxide, calcium hydroxide, and barium hydroxide; metal carbonate compounds such as basic magnesium carbonate, zinc carbonate, magnesium-calcium carbonate (a mixture of magnesium carbonate and calcium carbonate), calcium carbonate, and barium carbonate; metal borate compounds such as zinc borate, zinc metaborate, and barium metaborate; inorganic metal compounds such as dolomite, hydrotalcite, and borax; and inorganic phosphorus compounds such as red phosphorus. These can be used individually or in combination of two or more.

[0103] Examples of organic flame-retardant fillers include melamine phosphate, melamine polyphosphate, guanidine phosphate, guanidine polyphosphate, ammonium phosphate, ammonium polyphosphate, ammonium phosphate amide, ammonium polyphosphate amide, urethane phosphate, urethane polyphosphate, tris(diethylphosphine)aluminum, tris(methylethylphosphine)aluminum, tris(diphenylphosphine)aluminum, bis(diethylphosphine)zinc, bis(methylethylphosphine)zinc, bis(diphenylphosphine)zinc, and bis(diethylphosphine)titanium oxide. Phosphorus compounds such as tetra(diethylphosphonic acid)titanium, bis(methylethylphosphonic acid)titanium oxide, tetra(methylethylphosphonic acid)titanium, bis(diphenylphosphonic acid)titanium oxide, and tetra(diphenylphosphonic acid)titanium; nitrogen compounds such as triazine compounds (e.g., melamine, melamine cyanurate), cyanuric acid compounds, isocyanuric acid compounds, triazole compounds, tetraazole compounds, diazo compounds, and urea; silicon compounds such as organosilicon compounds and silane compounds; etc. These can be used alone or in combination of two or more.

[0104] Among these, metal hydroxide compounds or phosphorus compounds are preferred, with phosphorus compounds being more preferred. Among phosphorus compounds, aluminum tris(diethylphosphonic acid)aluminum, aluminum tris(methylethylphosphonic acid)aluminum, aluminum tris(diphenylphosphonic acid)aluminum, and other aluminum phosphonates are more preferred. Phosphorus compounds are, for example, commercially available from Clariant Chemicals Co., Ltd. as "EXOLIT (registered trademark) OP-935". Furthermore, phosphorus compounds are available in types that are insoluble in organic solvents (phosphorus-based flame-retardant fillers) and types that are soluble in organic solvents (phosphorus-based flame-retardant non-fillers), but types that are insoluble in organic solvents (phosphorus-based flame-retardant fillers) are preferred.

[0105] The average particle size of the flame retardant (E) may be, for example, 1 to 50 μm, more preferably 2 to 30 μm, and even more preferably 3 to 10 μm. The maximum particle size of the flame retardant (E) may be, for example, 100 μm or less, more preferably 90 μm or less, and even more preferably 80 μm or less. The particle size (median diameter) of the flame retardant (E) can be determined on a volume basis using a laser diffraction-scattering particle size distribution measuring device.

[0106] Regarding the amount of flame retardant (E) in the resin composition, the amount of flame retardant (E) is preferably 1 to 50 parts by weight relative to 100 parts by weight of polyester resin (A). By keeping the amount of flame retardant (E) in the resin composition within the range described above, the flame retardancy of the resin composition can be improved. The amount of flame retardant (E) in the resin composition is more preferably 5 to 40 parts by weight relative to 100 parts by weight of polyester resin (A), and even more preferably 10 to 40 parts by weight.

[0107] (F) Inorganic fillers

[0108] The resin composition may further include an inorganic filler (F). Including an inorganic filler (F) improves heat resistance under humidified conditions. The inorganic filler (F) need not exhibit flame retardancy, and is not included in the list of inorganic fillers exhibiting flame retardancy.

[0109] As an inorganic filler (F), fillers can also be used, for example. Examples of fillers include silica fillers (hereinafter sometimes simply referred to as silica). As silica, hydrophilic silica and hydrophobic silica are known. Examples of hydrophilic silica include untreated silica, and silica with silanol groups or siloxanes on its surface can also be used. Examples of hydrophobic silica include silica treated with dimethyldichlorosilane, hexamethyldisilazane, octylsilane, etc. By using hydrophobic silica, moisture resistance can be imparted to the resin composition. Hydrophobic silica is preferred among these. Hydrophobic silica is, for example, commercially available from AEROSIL Corporation of Japan as "AEROSIL (registered trademark) R972".

[0110] The average particle size of the inorganic filler (F) may be, for example, 0.001 to 10 μm, more preferably 0.002 to 0.5 μm, and even more preferably 0.01 to 0.1 μm. The average particle size (median diameter) of the inorganic filler (F) can be determined using a laser diffraction-scattering particle size distribution measuring device on a volume basis.

[0111] The proportion of inorganic filler (F) in the resin composition is not particularly limited, but is preferably 2 to 50 parts by mass relative to 100 parts by mass of polyester resin (A), more preferably 4 to 40 parts by mass, further preferably 6 to 30 parts by mass, particularly preferably 6 to 20 parts by mass, and most preferably 6 to 15 parts by mass.

[0112] The resin composition can be obtained by mixing and heating a polyester resin (A) with carboxyl groups on its side chains, an epoxy crosslinking agent (B), an ester exchange catalyst (D), and a flame retardant (E) to carry out a crosslinking reaction via an epoxy ring-opening reaction. The heating temperature is preferably 80–200°C, more preferably 85–180°C, and even more preferably 90–150°C. The heating time, while also depending on the heating temperature, is preferably 30 minutes to 10 hours, more preferably 1–8 hours, and even more preferably 2–5 hours.

[0113] The reaction between polyester resin (A) and epoxy crosslinking agent (B) can be carried out in the absence of solvent or in the presence of an organic solvent. When using an organic solvent, there are no particular limitations as long as it does not react with either polyester resin (A) or epoxy crosslinking agent (B). Examples include aromatic organic solvents such as toluene and xylene, aliphatic organic solvents such as heptane and octane, ketone solvents such as methyl ethyl ketone, ether solvents such as tetrahydrofuran and diethyl ether, and amide solvents such as dimethylformamide, N-methylpyrrolidone, and N,N-dimethylformamide. These can be used alone or in mixtures of two or more. Among these, aromatic organic solvents, ketone solvents, and amide solvents are preferred.

[0114] The ratio of polyester resin (A) with carboxyl groups on its side chains to epoxy crosslinking agent (B) in crosslinked polyester resin (C) can be determined based on the molar ratio of functional groups between the carboxyl groups on the side chains of polyester resin (A) and the epoxy groups on the epoxy crosslinking agent (B). From the viewpoint of crosslinking reaction efficiency and softening of crosslinked polyester resin (C), the ratio of epoxy groups in epoxy crosslinking agent (B) to carboxyl groups in polyester resin (A) (carboxyl groups:epoxy groups) is preferably 100:50 to 100:150 (molar parts), more preferably 100:80 to 100:120 (molar parts).

[0115] (Adhesive film)

[0116] This invention also includes an adhesive film containing the above-described resin composition. The adhesive film may have an adhesive layer composed of the above-described resin composition, and may be a single-layer film formed by processing the above-described resin composition into a film-like structure, or a film having two or more layers, including an adhesive layer composed of the above-described resin composition and other layers such as a substrate layer or a release layer. The adhesive film may also have two or more adhesive layers composed of the above-described resin composition.

[0117] For adhesive films, for example, by applying a resin composition to a release substrate and drying it using conventional methods, an adhesive film with an adhesive layer composed of the resin composition laminated on the surface of the release substrate can be obtained. Furthermore, if a second release substrate is adhered to the adhesive layer after drying, it can be wound without causing transfer to the back of the release substrate, resulting in excellent operability. Moreover, since the adhesive layer is protected, its preservation is excellent, and its use becomes easy. Additionally, after being applied to and dried on the release substrate, the adhesive layer can be adhered to other substrates, and the adhesive layer itself can be transferred to those other substrates.

[0118] Examples of release agents include materials with a coating layer containing a pore-filling agent such as clay, polyethylene, or polypropylene on one or both sides of the surface of high-quality paper, kraft paper, roll paper, glassine paper, etc., and further coated with a silicone-based, fluorine-based, or alkyd-based release agent. Alternatively, materials coated with the aforementioned release agents can be used individually on various olefin films such as polyethylene, polypropylene, ethylene-α-olefin copolymer, and propylene-α-olefin copolymer, as well as on films such as polyethylene terephthalate and polyethylene naphthalate. Considering the release force between the release agent and the adhesive layer, and the adverse effects of silicone on electrical properties, materials obtained by filling pores with polypropylene on the surface of high-quality paper (especially on both sides) and then coating it with an alkyd-based release agent, or materials obtained by coating an alkyd-based release agent onto a polyethylene terephthalate film, are preferred.

[0119] There are no particular limitations on the method of coating the resin composition onto the release substrate; examples include comma coaters and reverse roller coaters. Depending on the requirements, the adhesive layer can also be applied directly or by transfer onto the rolled copper foil or polyimide film, which are materials constituting the printed wiring board.

[0120] The thickness of the adhesive layer can be varied as needed, but is preferably 5 to 200 μm. Because the thickness of the adhesive layer is 5 μm or more, sufficient adhesive strength can be obtained.

[0121] (Layered structure)

[0122] This invention also includes laminates containing the aforementioned adhesive film and substrate. Examples of laminates include a two-layer laminate (substrate / adhesive film) where an adhesive film is laminated on a substrate, or a three-layer laminate (substrate / adhesive film / substrate) where a substrate is further bonded. An adhesive film refers to an adhesive layer composed of a resin composition after the resin composition is coated onto and dried on a substrate, or an adhesive layer composed of a resin composition after the adhesive layer of an adhesive film made using a resin composition is bonded to a substrate and laminated.

[0123] Examples of substrates include resin substrates such as film-like resins, metal substrates such as metal plates or foils, paper, and composite materials. Resin substrates are preferred, and film-like resins (hereinafter sometimes referred to as substrate films) are even more preferred. By using resin substrates, the adhesion and durability to the adhesive layer constituting the adhesive film can be improved.

[0124] Materials used as resin base materials include, for example, polyester resins, polyamide resins, polyimide resins, polyamide-imide resins, liquid crystal polymers, polyphenylene sulfide, syndiotactic polystyrene, polyolefin resins, and fluoropolymers.

[0125] As the metal substrate material, any conventionally known conductive material that can be used in the circuit board can be used. Examples of conductive materials include various metals such as SUS, copper, aluminum, iron, steel, zinc, and nickel, as well as their respective alloys, platings, and metals treated with zinc or chromium compounds. Among these, SUS, copper, and aluminum are preferred from the viewpoint of adhesion strength and durability to the adhesive layer of the adhesive film. As the metal substrate, a foil of the above-mentioned conductive material is preferred, and copper foil is more preferred. As the copper foil, any copper foil manufactured by rolling or electrolysis can be used. To ensure adhesion to the adhesive film, the conductive material foil may be subjected to physical surface treatments such as roughening or chemical surface treatments such as pickling. The thickness of the conductive material foil is not particularly limited, but is preferably 1 to 50 μm, more preferably 3 to 30 μm, and even more preferably 10 to 20 μm. When the thickness of the conductive material foil is too thin, it is sometimes difficult to obtain sufficient electrical performance of the circuit. When the thickness of the conductive material foil is too thick, the processing efficiency during circuit fabrication may sometimes decrease.

[0126] Examples of paper types include premium paper, kraft paper, roll paper, and glassine paper.

[0127] Examples of composite materials include glass epoxy.

[0128] (Printed wiring board)

[0129] The present invention also includes a printed wiring board containing the above-described laminate. The printed wiring board comprises, as a component, a laminate formed of a foil of a conductive material forming a conductor circuit and a resin substrate.

[0130] Printed wiring boards are manufactured, for example, using metal-clad laminates via subtractive processing and other well-known methods. Depending on the requirements, they are collectively referred to as flexible circuit boards (FPCs), flat cables, and circuit boards for tape-on-board (TAB) applications, which partially or completely cover the conductor circuit formed by a foil of conductive material using a cover film or screen-printed ink.

[0131] The printed circuit board (PCB) can be configured with any layered structure suitable for use as a PCB. For example, it can be configured as a PCB consisting of four layers: a substrate film layer, a conductive material layer, an adhesive layer, and a cover film layer. Alternatively, it can be configured as a PCB consisting of five layers: a substrate film layer, an adhesive layer, a conductive material layer, an adhesive layer, and a cover film layer. Furthermore, depending on the requirements, it can also be configured by stacking two or three or more of the above-mentioned PCBs.

[0132] Printed wiring boards can be manufactured, for example, by a process that includes heating an adhesive film containing a resin composition to a substrate and then bonding them together. That is, for example, after overlapping the aforementioned layers of material, heating to above the softening temperature of the resin composition and then bonding them together, thereby enabling the lamination of components based on the properties of polyester resin (A) without curing, thus obtaining a printed wiring board.

[0133] As a printed circuit board, examples include articles in which a conductive material layer is laminated on a substrate film layer to form a desired loop pattern (hereinafter referred to as "substrate film-side 2-layer articles") or articles in which a resin composition layer is laminated on a substrate film layer and a conductive material layer is laminated thereon to form a desired loop pattern (hereinafter referred to as "substrate film-side 3-layer articles"). Hereinafter, "substrate film-side 2-layer articles" and "substrate film-side 3-layer articles" are sometimes collectively referred to as "substrate film-side articles". By laminating the substrate film-side articles obtained in this way, a 4-layer or 5-layer printed circuit board can be obtained. In forming the loop pattern, conventionally known methods can be used, such as additive methods and subtractive methods, with subtractive methods being preferred.

[0134] As a printed circuit board, it can also be a reinforcing material side product manufactured by coating a resin composition onto a flexible, rollable reinforcing material such as polyimide film. When the reinforcing material is a rigid and non-rollable material such as a metal plate such as SUS or aluminum, or a plate made by curing glass fiber with epoxy resin, it is suitable to manufacture it by transferring a resin composition pre-coated to a release substrate. In addition, a crosslinking reaction can be carried out in the coated resin composition as needed. The resulting reinforcing material side product can be directly used for bonding to the back of the printed circuit board, or it can be used for bonding to a substrate film side product after bonding and storing the release film.

[0135] This application claims the benefit of priority based on Japanese Patent Application No. 2024-029461, filed on February 29, 2024. The entire description of the aforementioned Japanese Patent Application No. 2024-029461 is incorporated herein by reference.

[0136]

Example

[0137] The following examples are provided to illustrate the invention in more detail, but the invention is not limited to the examples described below. It is of course possible to implement the invention by making changes that are suitable for the spirit described above and below, and all of these are included within the technical scope of the invention.

[0138] First, long-chain high-molecular-weight polyols (a1) and short-chain high-molecular-weight polyols (a2) are polymerized with polycarboxylic acid components with more than three functions to produce polyester resin (A) with carboxyl groups on the side chain.

[0139] (a1) Long-chain high molecular weight polyols

[0140] In a reaction vessel equipped with a stirrer, thermometer, and distillation cooler, 30 moles of terephthalic acid, 69 moles of isophthalic acid, and 1 mole of trimellitic anhydride were added as polycarboxylic acid components. 15 moles of 2-methyl-1,3-butanediol and 85 moles of 1,6-hexanediol were added as polyol components. 0.2 moles of tetrabutyl titanate were further added. The temperature was gradually raised to 250°C, and esterification was carried out while removing distilled water from the system. After esterification, the pressure was gradually reduced to 10 mmHg while initial polymerization was carried out and the temperature was raised to 250°C. Later polymerization was then carried out at below 1 mmHg until the specified torque was reached. Subsequently, atmospheric pressure was restored with nitrogen, and 1 mole of trimellitic anhydride, a polycarboxylic acid component with more than three functionalities, was added. The reaction was carried out at 220°C for 30 minutes, thereby obtaining a long-chain high-molecular-weight polyol (a1-1). The composition of the obtained long-chain high molecular weight polyol (a1-1) is shown in Table 1.

[0141] (a2) Short-chain high molecular weight polyols

[0142] In a reaction vessel equipped with a stirrer, thermometer, and distillation cooler, 50 moles of terephthalic acid and 50 moles of isophthalic acid were added as polycarboxylic acids, and 55 moles of ethylene glycol and 45 moles of 2,2-dimethyl-1,3-propanediol were added as polyols. 0.2 moles of tetrabutyl titanate were further added. The temperature was gradually raised to 250°C, and esterification was carried out while removing distilled water from the system. After esterification, the pressure was gradually reduced to 10 mmHg while initial polymerization was carried out and the temperature was raised to 250°C. Further polymerization was then carried out at a pressure below 1 mmHg until the specified torque was reached, thus obtaining a short-chain high-molecular-weight polyol (a2-1). The composition of the obtained short-chain high-molecular-weight polyol (a2-1) is shown in Table 1.

[0143] For the obtained long-chain high-molecular-weight polyols (a1-1) and short-chain high-molecular-weight polyols (a2-1), the number-average molecular weight (Mn), acid value, and glass transition temperature were determined using the following steps. These properties are shown in Table 1.

[0144] (i) Number-average molecular weight (Mn)

[0145] The obtained long-chain polyol (a1-1) or short-chain polyol (a2-1) was dissolved or diluted in tetrahydrofuran to a concentration of approximately 0.5% by mass. The substance filtered through a 0.5 μm PTFE membrane filter was used as the sample for analysis. The number-average molecular weight was determined by gel permeation chromatography using tetrahydrofuran as the mobile phase and a differential refractometer as the detector. The flow rate was set to 1 mL / min, and the column temperature was set to 30 °C. Monodisperse polystyrene was used as the molecular weight standard. The number-average molecular weight was calculated by omitting the portion of the molecular weight less than 1000.

[0146] (ii) Acid value

[0147] 0.2 g of the obtained long-chain polyol (a1-1) or short-chain polyol (a2-1) was dissolved in 20 ml of chloroform. Using phenolphthalein as an indicator, neutralization titration was performed with 0.1 N potassium hydroxide (KOH) ethanol solution. Based on the titration volume, the mg of KOH consumed in the neutralization was converted to the amount per 1 g of long-chain polyol (a1-1) or short-chain polyol (a2-1), and the acid value (mgKOH / g) was calculated.

[0148] (iii) Glass transition temperature

[0149] Five mg of either the long-chain polyol (a1-1) or the short-chain polyol (a2-1) was placed in an aluminum pan, and the sealed mixture was used as the sample for analysis. The sample was first held at 250°C for 5 minutes in a differential scanning calorimeter (DSC220 type) manufactured by Seiko Electronics Industries, Ltd., then rapidly cooled with liquid nitrogen. Subsequently, the sample was heated from -100°C to 300°C at a heating rate of 20°C / min and the temperature was measured. The inflection point of the obtained curve was taken as the glass transition temperature.

[0150] Table 1

[0151]

[0152] (A) Polyester resins with carboxyl groups on the side chains

[0153] In a reaction vessel equipped with a stirrer, thermometer, and reflux pipe, 80 parts by mass of long-chain polyol (a1-1), 20 parts by mass of short-chain polyol (a2-1), 2.6 parts by mass of pyromellitic anhydride (a polycarboxylic acid component with more than three functions), and 100 parts by mass of toluene were added. The mixture was gradually heated to 80°C while being dissolved in toluene. After dissolution, 0.05 parts by mass of triethylamine was added as a reaction catalyst, and the temperature was gradually increased to 105°C and the reaction was carried out for 24 hours. After the reaction was confirmed to be complete by infrared spectroscopy (IR), the mixture was diluted with 54 parts by mass of toluene to obtain a 40% by mass solution of a polyester resin (A-1) with carboxyl groups in its side chains. The composition of the obtained polyester resin (A-1) with carboxyl groups in its side chains is shown in Table 2.

[0154] For the obtained polyester resin (A-1), the number-average molecular weight (Mn), acid value, and glass transition temperature were determined using the steps described in (i) to (iii) above. These properties are shown in Table 2. Additionally, for the obtained polyester resin (A-1), the number of carboxyl groups per polymer chain was determined by proton nuclear magnetic resonance (¹H NMR). The measuring apparatus used was a Bruker Analytik DPX400 spectrometer (400 MHz), the measuring solvent was heavy DMSO, and the measuring temperature was set to 25 °C. The results are shown in Table 2.

[0155] Table 2

[0156]

[0157] Next, a mixture (resin composition before crosslinking) was prepared using the obtained polyester resin (A-1), epoxy crosslinking agent (B), transesterification catalyst (D-1), and flame retardant (E-1). The epoxy crosslinking agent (B) comprises an epoxy compound (b1) having two epoxy groups and no tertiary amino groups within its molecule, and an epoxy amine compound (b2) having two or more epoxy groups and one or more tertiary amino groups within its molecule. Additionally, an inorganic filler (F-1) was used as needed. The following compounds were used as the epoxy compound (b1) constituting the epoxy crosslinking agent (B), the epoxy amine compound (b2), the transesterification catalyst (D-1), the flame retardant (E-1), and the inorganic filler (F-1). The compounds used for comparative examples are also shown below.

[0158] Epoxide (b1-1): As 1,4-butanediol diglycidyl ether (hereinafter sometimes referred to as BDE), it uses "epogosey (registered trademark) BD" manufactured by Yokkaichi Synthetic Co., Ltd. 1,4-Butanediol diglycidyl ether (BDE) is classified under epoxide (b1). The number of epoxy groups within the molecule is two.

[0159] Epoxidamine compound (b2-1): As triglycidyl-p-aminophenol, "jER630" manufactured by Mitsubishi Chemical Corporation was used. Triglycidyl-p-aminophenol is classified as epoxidamine compound (b2). The number of epoxy groups in the molecule is 3, and the number of tertiary amino groups in the molecule is 1.

[0160] Epoxidized amine compound (b2-2): As N,N,N',N'-tetraglycidyl-m-xylenediamine, the multifunctional epoxy compound "TETRAD-X" manufactured by Mitsubishi Gas Chemical Co., Ltd. was used. N,N,N',N'-tetraglycidyl-m-xylenediamine is classified as epoxidized amine compound (b2). It has four epoxy groups and two tertiary amino groups within the molecule.

[0161] "Denacol EX-321" manufactured by Nagase ChemteX Co., Ltd.: "Denacol EX-321" is a mixture of aliphatic epoxy compounds having two epoxy groups in the molecule and no tertiary amino group and aliphatic epoxy compounds having three epoxy groups in the molecule and no tertiary amino group, and is not classified as either epoxy compound (b1) or epoxy amine compound (b2).

[0162] The transesterification catalyst (D-1) used was "zinc acetate anhydride (Zn(OAc)2)" manufactured by Fujifilm and Kojun Pharmaceutical Co., Ltd.

[0163] Flame retardant (E-1): "EXOLIT (registered trademark) OP-935" manufactured by Clariant Japan Co., Ltd. was used. "EXOLIT (registered trademark) OP-935" is a phosphorus-based compound and is insoluble in organic solvents.

[0164] Inorganic filler (F-1): "AEROSIL (registered trademark) R972" manufactured by AEROSIL Corporation of Japan was used. "AEROSIL (registered trademark) R972" is hydrophobic silica with an average particle size of 0.016 μm.

[0165] (Example 1)

[0166] Solution 1 was prepared by dissolving 100 parts by mass of polyester resin (A-1), 9.1 parts by mass of flame retardant (E-1), and 8.3 parts by mass of inorganic filler (F-1) in a mixed solvent of methyl ethyl ketone and toluene; and solution 2 was prepared by dissolving 1.1 parts by mass of transesterification catalyst (D) relative to 100 parts by mass of polyester resin (A-1) in N,N-dimethylformamide. Mixture 1 was prepared by mixing solutions 1 and 2, 3 parts by mass of epoxy compound (b1-1) relative to 100 parts by mass of polyester resin (A-1), and 0.06 parts by mass of epoxyamine compound (b2-1) relative to 100 parts by mass of polyester resin (A-1). The amount of transesterification catalyst (D) was 20 moles relative to 100 moles of carboxyl groups in polyester resin (A-1). The amount of epoxy groups in the epoxy compound (b1-1) is 98 moles relative to 100 moles of carboxyl groups in the polyester resin (A-1). The amount of epoxy groups in the epoxy amine compound (b2-1) is 2 moles relative to 100 moles of carboxyl groups in the polyester resin (A-1). The content of polyester resin (A) is 82.3% by mass in 100% by weight of the solids component of the adhesive composition.

[0167] (Example 2)

[0168] In Example 1, mixture 2 was prepared under the same conditions as in Example 1, except that the amount of epoxy compound (b1-1) relative to 100 parts by mass of polyester resin (A-1) was changed from 3 parts by mass to 2.9 parts by mass, and the amount of epoxy amine compound (b2-1) relative to 100 parts by mass of polyester resin (A-1) was changed from 0.06 parts by mass to 0.14 parts by mass. The amount of epoxy groups in epoxy compound (b1-1) was 95 moles relative to 100 moles of carboxyl groups in polyester resin (A-1). The amount of epoxy groups in epoxy amine compound (b2-1) was 5 moles relative to 100 moles of carboxyl groups in polyester resin (A-1). The content of polyester resin (A) was 82.3% by mass in 100% by mass of the solids component of the adhesive composition.

[0169] (Example 3)

[0170] In Example 1, mixture 3 was prepared under the same conditions as in Example 1, except that the amount of epoxy compound (b1-1) relative to 100 parts by mass of polyester resin (A-1) was changed from 3 parts by mass to 2.7 parts by mass, and 0.27 parts by mass of epoxy amine compound (b2-2) was used instead of epoxy amine compound (b2-1) relative to 100 parts by mass of polyester resin (A-1). The amount of epoxy groups in epoxy compound (b1-1) was 90 moles relative to 100 moles of carboxyl groups in polyester resin (A-1). The amount of epoxy groups in epoxy amine compound (b2-2) was 10 moles relative to 100 moles of carboxyl groups in polyester resin (A-1). The content of polyester resin (A) was 82.3% by mass in 100% by mass of the solids component of the adhesive composition.

[0171] (Example 4)

[0172] In Example 1, mixture 4 was prepared under the same conditions as in Example 1, except that solution 3, prepared by dissolving 100 parts by weight of polyester resin (A-1) and 9.1 parts by weight of flame retardant (E-1) in a mixed solvent of methyl ethyl ketone and toluene, was used instead of solution 1. The content of polyester resin (A) in the 100% by weight solids of the adhesive composition was 88.3% by weight.

[0173] (Comparative Example 11)

[0174] Solution 11, prepared by dissolving 100 parts by mass of polyester resin (A-1) in a mixed solvent of methyl ethyl ketone and toluene, and solution 2, prepared by dissolving 1.1 parts by mass of transesterification catalyst (D) relative to 100 parts by mass of polyester resin (A-1) in N,N-dimethylformamide, were prepared. Mixture 11 was prepared by mixing solutions 11 and 2 with 3 parts by mass of epoxy compound (b1-1) relative to 100 parts by mass of polyester resin (A-1). The content of polyester resin (A) in the 100% by mass solids component of the adhesive composition is 96.1% by mass.

[0175] (Comparative Example 12)

[0176] Solution 12, prepared by dissolving 100 parts by weight of polyester resin (A-1) and 9.1 parts by weight of flame retardant (E-1) in a mixed solvent of methyl ethyl ketone and toluene, and solution 2, prepared by dissolving 1.1 parts by weight of transesterification catalyst (D) relative to 100 parts by weight of polyester resin (A-1) in N,N-dimethylformamide, were prepared. Mixture 12 was prepared by mixing solutions 12 and 2 with 3 parts by weight of epoxy compound (b1-1) relative to 100 parts by weight of polyester resin (A-1). The content of polyester resin (A) in the 100% by weight solids component of the adhesive composition is 88.3% by weight.

[0177] (Comparative Example 13)

[0178] Solution 12, prepared by dissolving 100 parts by weight of polyester resin (A-1) and 9.1 parts by weight of flame retardant (E-1) in a mixed solvent of methyl ethyl ketone and toluene, and solution 2, prepared by dissolving 1.1 parts by weight of transesterification catalyst (D) relative to 100 parts by weight of polyester resin (A-1) in N,N-dimethylformamide, were prepared. Mixture 13 was prepared by mixing solutions 12 and 2 with 3.9 parts by weight of "Denacol EX-321" relative to 100 parts by weight of polyester resin (A-1). The content of polyester resin (A) in the 100% by weight solids component of the adhesive composition is 87.6% by weight.

[0179] (Comparative Example 14)

[0180] Solution 12, prepared by dissolving 100 parts by weight of polyester resin (A-1) and 9.1 parts by weight of flame retardant (E-1) in a mixed solvent of methyl ethyl ketone and toluene, and solution 2, prepared by dissolving 1.1 parts by weight of transesterification catalyst (D) relative to 100 parts by weight of polyester resin (A-1) in N,N-dimethylformamide, were prepared. Mixture 14 was prepared by mixing solutions 12 and 2 with 2.9 parts by weight of epoxyamine compound (b2-1) relative to 100 parts by weight of polyester resin (A-1). The content of polyester resin (A) in the 100% by weight solids component of the adhesive composition is 88.4% by weight.

[0181] The compositions of mixtures 1–4 and 11–14 are shown in Table 3 below. In Table 3, the mixing ratio of the epoxy groups of the epoxy compound (b1) to the epoxy groups of the epoxide compound (b2) in the mixture [epoxide group of epoxy compound (b1) / epoxy group of epoxide compound (b2)] is calculated and shown together.

[0182] Table 3

[0183]

[0184] Next, the obtained mixture was coated onto a substrate and dried to create a laminate consisting of an adhesive film (adhesive layer) and a substrate. Specifically, the obtained mixture was coated onto a 12.5 μm thick polyimide film (Apical, manufactured by KANEKA Co., Ltd., a registered trademark) to achieve a dried thickness of 25 μm. The film was then heated at 80°C for 1 minute, followed by heating at 140°C for 2 minutes to dry, and finally cured at 150°C for 3 hours to obtain a laminate consisting of an adhesive film containing a resin composition and a substrate.

[0185] The flame retardancy of the adhesive film was evaluated using the obtained laminate. Regarding the flame retardancy of the adhesive film, test pieces based on UL94 specifications were prepared from the obtained laminate, and flammability tests were conducted using the VTM method for evaluation. The results of the flammability tests were categorized as follows: those meeting VTM-0 conditions were considered acceptable and rated A; those meeting VTM-1 or VTM-2 conditions were considered unacceptable and rated B. The evaluation results are shown in Table 3.

[0186] Next, the heat resistance of the adhesive film was evaluated using the obtained laminate. Specifically, in the obtained laminate, a 49 μm thick copper-clad laminate (manufactured by Nippon Steel Chemicals & Materials Co., Ltd., ESPANEX series, Cu / polyimide / Cu=12μm / 25μm / 12μm) was bonded to the surface of the adhesive film (adhesive layer), and tested at 170°C and 20.4 kgf / cm². 2 A heat resistance evaluation test piece was manufactured by applying pressure of 2 MPa for 280 seconds to bond the polyimide film. The resulting test piece was placed in an oven and dried at 120°C for 30 minutes. The dry test piece (freshly removed from the oven with minimal moisture) was then floated on a solder bath, and any expansion was visually observed. The dry test piece was floated on the solder bath in such a way that the Cu of the copper-clad laminate was in contact with the solder. The initial temperature of the solder bath was set to 260°C. Even after holding the dry test piece on the 260°C solder bath for 1 minute, without any expansion on the surface of the polyimide film, the temperature of the solder bath was increased by 10°C and held for 1 minute. The temperature of the solder bath was increased in increments of 10°C until the surface of the polyimide film expanded, and the upper limit temperature at which the surface of the polyimide film did not expand was determined. Based on the determined upper limit temperature at which the surface of the polyimide film did not expand, the heat resistance of the adhesive film was evaluated according to the following criteria. The evaluation results are shown in Table 3.

[0187] (Evaluation Criteria)

[0188] The upper limit of the temperature at which the surface of the polyimide film will not expand is 280℃: Qualified, Evaluation A

[0189] The upper limit of the temperature at which the surface of the polyimide film will not expand is 270℃: Qualified, Evaluation B

[0190] The upper limit of the temperature at which the surface of the polyimide film will not expand is 260℃: Qualified, Evaluation C

[0191] The surface of the polyimide film expanded at 260℃: Unacceptable, Evaluation D

[0192] Next, the heat resistance of the adhesive film under humidified conditions was evaluated using the obtained laminate. Specifically, the heat resistance evaluation test piece was placed in a thermo-humidifier humidified to 80% RH at 40°C. The test piece, still heavily moist when removed from the thermo-humidifier (humidified test piece), was then floated on a solder bath, and the occurrence of expansion was visually observed. The humidified test piece was floated on the solder bath such that the Cu of the copper-clad laminate was in contact with the solder. The initial temperature of the solder bath was set to 220°C. When no expansion occurred on the surface of the polyimide film even after floating the humidified test piece on the 220°C solder bath for 1 minute, the temperature of the solder bath was increased by 10°C and maintained for 1 minute. The temperature of the solder bath was increased in increments of 10°C until the surface of the polyimide film expanded, and the upper limit temperature at which the surface of the polyimide film did not expand was determined. Based on the measured upper limit temperature at which the surface of the polyimide film does not expand, the heat resistance of the adhesive film under humidified conditions was evaluated according to the following criteria. The evaluation results are shown in Table 3.

[0193] (Evaluation Criteria)

[0194] The upper limit of the temperature at which the surface of the polyimide film will not expand is 240℃: Qualified, Evaluation A

[0195] The upper limit of the temperature at which the surface of the polyimide film will not expand is 230℃: Qualified, Evaluation B

[0196] The upper limit of the temperature at which the surface of the polyimide film will not expand is 220℃: Qualified, Evaluation C

[0197] The surface of the polyimide film swells below 220°C: Unacceptable, Evaluation D

[0198] Next, the embedding properties of the adhesive film were evaluated using the obtained laminate. Specifically, in the obtained laminate, a sample simulating the comb pattern of a flexible substrate (manufactured by OHYO Corporation, a sample with a Cu wiring loop of 50 μm / 50 μm formed on the surface of a polyimide film) was bonded to the surface of the adhesive film (adhesive layer), and tested at 170°C and 20.4 kgf / cm². 2 The pressure was applied at 2 MPa for 280 seconds. After pressurization, the cross-section of the test piece formed by bonding the laminated body and the comb-shaped sample was observed using a scanning electron microscope (SU1510) manufactured by Hitachi High Technology Co., Ltd., to confirm whether the adhesive layer was embedded in the loops. If the adhesive layer was embedded in the loops, it was considered to have satisfactory embedding and was rated A. If there were gaps in the loops, it was considered to have unsatisfactory embedding and was rated B. The evaluation results are shown in Table 3.

[0199] As shown in Table 3, Examples 1-4 are examples of resin compositions that meet the requirements specified in this invention, which can improve flame retardancy without reducing heat resistance and embedment properties. In particular, in Examples 1-3, since hydrophobic silica was mixed in as an inorganic filler (F), the heat resistance under humidified conditions was also good. On the other hand, Comparative Example 11 did not show flame retardancy because it did not contain flame retardant (E-1). Comparative Example 12 is an example of adding flame retardant (E-1) to Comparative Example 11. Although the flame retardancy was improved, the heat resistance deteriorated. Comparative Example 13 is an example of using Denacol EX-321 instead of the epoxy compound (b1-1) used in Comparative Example 12. Although the heat resistance was improved while the flame retardancy was improved, the softening temperature was increased and the embedment properties deteriorated. Comparative Example 14 is an example in which an epoxy amine compound (b2-1) was used instead of the epoxy compound (b1-1) used in Comparative Example 12. Similar to Comparative Example 13, although the flame retardancy was improved while the heat resistance was also improved, the softening temperature was higher and the embedment performance was worse.

Claims

1. A resin composition comprising a crosslinked polyester resin (C), an ester exchange catalyst (D), and a flame retardant (E). The crosslinked polyester resin (C) has a structure formed by crosslinking the carboxyl groups of the side chains of a polyester resin (A) with carboxyl groups in the side chains with an epoxy crosslinking agent (B), wherein the epoxy crosslinking agent (B) comprises an epoxy compound (b1) having two epoxy groups in the molecule and no tertiary amino group, and an epoxy amine compound (b2) having two or more epoxy groups and one or more tertiary amino groups in the molecule.

2. The resin composition according to claim 1, wherein, The epoxide amine compound (b2) has 2 to 4 epoxy groups in its molecule.

3. The resin composition according to claim 1, wherein, The epoxide amine compound (b2) has one or more epoxide amino groups, wherein the epoxide amino group is formed by bonding the tertiary amino group to the epoxy group via an alkylene group having 1 to 4 carbon atoms.

4. The resin composition according to claim 1, wherein, The epoxy compound (b1) is an aliphatic epoxy compound.

5. The resin composition according to claim 1, wherein, The flame retardant (E) is an inorganic flame retardant filler and / or an organic flame retardant filler.

6. The resin composition according to claim 1, wherein, The flame retardant (E) is a phosphorus-based compound.

7. The resin composition according to claim 1, wherein, It also contains inorganic filler (F).

8. The resin composition according to claim 7, wherein, The inorganic filler (F) is a silica filler.

9. The resin composition according to claim 7, wherein, The inorganic filler (F) is hydrophobic silica.

10. The resin composition according to claim 7, wherein, The inorganic filler (F) is contained in 2 to 50 parts by weight relative to 100 parts by weight of the polyester resin (A).

11. An adhesive film comprising the resin composition according to any one of claims 1 to 10.

12. A laminate comprising the adhesive film and substrate of claim 11.

13. A printed wiring board comprising the laminate of claim 12.

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