Resin composition, prepreg, resin-attached film, resin-attached metal foil, metal-clad laminate, and wiring board

Abstract

One aspect of the present invention relates to a resin composition comprising an epoxy resin (A), a curing agent (B), and an inorganic filler (C). The epoxy resin (A) includes an epoxy resin (A-1) having an aromatic ring in the molecule. The curing agent (B) includes tannic acid (B-1) and a phenolic resin (B-2), and the ratio of (hydroxyl equivalent of tannic acid (B-1)) / (epoxy equivalent of epoxy resin (A)) is 0.8 or less. The inorganic filler (C) contains aluminum hydroxide, and the content of the inorganic filler (C) is 60-200 parts by weight inclusive relative to the total amount of the epoxy resin (A) and the curing agent (B).

Description

Resin Composition, Prepreg, Resin-Coated Film, Resin-Coated Metal Foil, Metal-Clad Laminate, and Wiring Board

[0001] The present invention relates to a resin composition, a prepreg, a resin-coated film, a resin-coated metal foil, a metal-clad laminate, and a wiring board.

[0002] With the growing interest in environmental issues in recent years, plant-based biomass materials, which are sustainable resources and carbon stock materials, have attracted attention in various fields as an alternative to petroleum-derived resources.

[0003] Technical development is also underway for substrate materials for constituting base materials of printed wiring boards used in various electronic devices, to utilize biomass materials while reducing the use of petroleum-derived resources as much as possible. For example, Patent Document 1 discloses a resin composition obtained by replacing conventionally used resins with biologically derived materials such as tannin and lignin, and a printed circuit board using the resin composition. In addition, Patent Document 2 discloses a resin composition containing an epoxy resin, a catechol-based curing agent, and an inorganic filler as a material used for an insulating layer of a printed wiring board. It is described that this catechol-based curing agent can be synthesized using plant-derived raw materials, and for example, tannic acid can be used.

[0004] As described in Patent Document 1 and Patent Document 2, conventionally, mechanical properties (elastic modulus), thermal properties (glass transition temperature, decomposition temperature), processability, and the like of cured products of resin compositions containing a polyphenol analog or a compound having a catechol structure as a biomass material and an epoxy resin have been studied.

[0005] However, for substrate materials (resin compositions) for constituting base materials of printed wiring boards used in various electronic devices, it is also required that the cured product thereof has excellent adhesion to metal foil and excellent flame retardancy.

[0006] In this regard, the resin compositions described in Patent Documents 1 and 2 made it difficult to ensure excellent adhesion (peel strength) and flame retardancy of the cured resin composition to metal foil due to the following factors. Specifically, for example, lignin dissolves only in highly polar solvents, which posed a problem of low versatility when producing varnishes and ultimately prepregs. Furthermore, although tannic acid dissolves in general-purpose solvents, it was difficult to achieve both adhesion to metal foil and flame retardancy in the cured resin composition due to the following factors. First, because tannic acid has a complex three-dimensional structure, if a certain amount of tannic acid is added to the resin, curing failure or uneven curing occurs. This lowers the glass transition temperature of the resin composition and weakens the anchoring effect, resulting in the problem of not being able to obtain high adhesion. In addition, when inorganic fillers are added to impart flame retardancy, the relative proportion of resin components decreases, weakening the anchoring effect and thus reducing adhesion.

[0007] Therefore, the present invention has been made in response to these circumstances and aims to provide a resin composition that can reduce environmental impact and yield a cured product having excellent adhesion (peel strength) to metal foil and excellent flame retardancy. Furthermore, the present invention aims to provide a prepreg, resin-coated film, resin-coated metal foil, metal-clad laminate, and wiring board obtained using the above resin composition.

[0008] Japanese Patent Publication No. 2002-53699 Japanese Patent Publication No. 2024-75417

[0009] As a result of diligent research to solve the above problems, the inventors have found that the above problems can be solved by the following means.

[0010] A resin composition according to one aspect of the present invention comprises an epoxy resin (A), a curing agent (B), and an inorganic filler (C), wherein the epoxy resin (A) comprises an epoxy resin (A-1) having an aromatic ring in its molecule, the curing agent (B) comprises tannic acid (B-1) and a phenolic resin (B-2), and the ratio of (hydroxyl group equivalent of tannic acid (B-1)) / (epoxy equivalent of epoxy resin (A)) is 0.8 or less, and the inorganic filler (C) comprises aluminum hydroxide, and the content of the inorganic filler (C) is 60 parts by weight or more and 200 parts by weight or less relative to the total amount of epoxy resin (A) and curing agent (B).

[0011] Figure 1 is a schematic cross-sectional view showing an example of a prepreg according to an embodiment of the present invention. Figure 2A is a schematic cross-sectional view showing an example of a resin-coated film according to an embodiment of the present invention. Figure 2B is a schematic cross-sectional view showing an example of a resin-coated film according to an embodiment of the present invention. Figure 3 is a schematic cross-sectional view showing an example of a resin-coated metal foil according to an embodiment of the present invention. Figure 4 is a schematic cross-sectional view showing an example of a metal-clad laminate according to an embodiment of the present invention. Figure 5 is a schematic cross-sectional view showing an example of a wiring board according to an embodiment of the present invention.

[0012] The embodiments of the present invention will be described below, but the present invention is not limited thereto.

[0013] [Resin Composition] The resin composition according to this embodiment comprises an epoxy resin (A), a curing agent (B), and an inorganic filler (C). The epoxy resin (A) contains an epoxy resin (A-1) having an aromatic ring in its molecule. The curing agent (B) contains tannic acid (B-1) and a phenolic resin (B-2). The ratio of (hydroxyl group equivalent of tannic acid (B-1)) / (epoxy equivalent of epoxy resin (A)) is 0.8 or less. Furthermore, the inorganic filler (C) contains aluminum hydroxide. The content of the inorganic filler (C) is 60 parts by weight or more and 200 parts by weight or less relative to the total amount of epoxy resin (A) and curing agent (B).

[0014] This configuration reduces environmental impact and provides a resin composition that yields a cured product with excellent adhesion (peel strength) to metal foil and excellent flame retardancy. Furthermore, the resin composition can be used to provide prepregs, resin-coated films, resin-coated metal foils, metal-clad laminates, and wiring boards with excellent properties.

[0015] (Epoxy resin (A)) The epoxy resin (A) in this embodiment is not particularly limited as long as it contains epoxy resin (A-1) having an aromatic ring in its molecule, and may also contain epoxy resins other than epoxy resin (A-1), i.e., epoxy resins that do not have an aromatic ring in their molecule.

[0016] Epoxy resins (A-1) having aromatic rings in their molecules generally exhibit high rigidity and have a higher glass transition temperature compared to epoxy resins primarily composed of aliphatic skeletons. Therefore, by including epoxy resin (A) (A-1) in epoxy resin (A), excellent adhesion (peel strength) to metal foil can be achieved. In this specification, "having aromatic rings in their molecules" means having aromatic rings in the main chain or side chains.

[0017] The epoxy resin (A-1) is preferably an epoxy resin whose glass transition temperature (Tg) of the cured resin product obtained by phenol curing with a phenol novolac resin is 100°C or higher. The glass transition temperature is more preferably 120°C or higher, and even more preferably 140°C or higher. The glass transition temperature is measured by the method described in the examples below. Specifically, TD-2131 (manufactured by DIC Corporation) is used as the phenol novolac resin, and the epoxy equivalent of epoxy resin (A-1) and the hydroxyl group equivalent of the phenol novolac resin are blended in a stoichiometric ratio of 1:1. Furthermore, 1 phr of imidazole is added as a curing accelerator. The cured product obtained by heating this composition at 150°C for 2 hours can be measured by the measurement method described in the examples below.

[0018] Examples of epoxy resins (A-1) include bisphenol A type epoxy resin, bisphenol F type epoxy resin, bisphenol S type epoxy resin, novolac type epoxy resin, cresol novolac type epoxy resin, dicyclopentadienephenol type epoxy resin, triphenylmethane type epoxy resin, biphenyl type epoxy resin, and naphthalene type epoxy resin. These may be used individually or in combination of two or more types.

[0019] The content of epoxy resin (A-1) is preferably 10% by weight or more relative to the total weight (100% by weight) of epoxy resin (A). This ensures that excellent adhesion to the metal foil is more reliably achieved. The content of epoxy resin (A-1) is more preferably 25% by weight or more, and even more preferably 50% by weight or more, relative to the total weight of epoxy resin (A). As mentioned above, epoxy resin (A) may contain epoxy resins other than epoxy resin (A-1), or it may be entirely epoxy resin (A-1). Therefore, there is no particular upper limit to the content of epoxy resin (A-1) relative to the total weight of epoxy resin (A) (i.e., it may be 100% by weight).

[0020] Specific examples of epoxy resins other than epoxy resin (A-1) that epoxy resin (A) may contain include alicyclic epoxy resins, polyol-derived polyglycidyl ether (sorbitol, trimethylolpropane, pentaerythritol, etc.) type epoxy resins, fatty acid glycidyl ester type epoxy resins, hydrogenated BisA type epoxy resins, and even epoxidized vegetable oils (soybean oil, linseed oil, etc.). These may be used individually or in combination of two or more. Since none of these contain aromatic rings, they can be used to lower the viscosity of the resin varnish and to impart properties such as increased flexibility and pliability. Furthermore, using plant-derived materials can contribute to reducing environmental impact. As plant-derived materials, commercially available products such as "GEX-622" (sorbitol polyglycidyl ether type (SGE type) epoxy resin) and "GEX-252" (hydrogenated BisA type epoxy resin) manufactured by Nagase ChemteX Corporation can be used.

[0021] When epoxy resin (A) contains epoxy resins other than epoxy resin (A-1), the content of epoxy resins other than epoxy resin (A-1) is preferably 25% by weight or more and 90% by weight or less, and more preferably 50% by weight or more and 80% by weight or less, relative to the total weight (100% by weight) of epoxy resin (A). By having an epoxy resin content of 25% by weight or more relative to the total weight of epoxy resin (A), it is possible to impart properties such as lower viscosity, flexibility, and pliability to the resin varnish. By having an epoxy resin content of 95% by weight or less relative to the total weight of epoxy resin (A), excellent adhesion to metal foil can be more reliably ensured.

[0022] The total amount of epoxy equivalents of epoxy resin contained in epoxy resin (A) is preferably 100 to 600 g / eq. Within this range, the cured resin exhibits a high glass transition temperature and excellent mechanical properties, and the viscosity does not become excessively high, which is also preferable in terms of workability. The total amount of epoxy equivalents of epoxy resin contained in epoxy resin (A) is more preferably 100 to 500 g / eq, and even more preferably 150 to 300 g / eq.

[0023] (Curing agent (B)) In this embodiment, the curing agent (B) comprises tannic acid (B-1) and phenolic resin (B-2). By including tannic acid (B-1) in the cured product (B), a resin composition that can reduce environmental impact can be obtained.

[0024] Tannic acid (B-1) is usually derived from biomass. Specifically, tannic acid (B-1) is found in the bark, trunk, stem, branches, and leaves of woody plants (conifers and broad-leaved trees such as pine, cypress, and cedar families) and herbaceous plants, and is classified into two types: condensed tannins, which are polymerized compounds with a flavanol skeleton, and hydrolyzable tannins, which are formed by ester bonds between aromatic compounds such as gallic acid and ellagic acid and sugars such as glucose. Condensed tannins are distributed in both conifers and broad-leaved trees. They are more abundant in the bark than in the trunk, with the bark tannin content of acacia trees reaching 20-30%. Hydrolyzable tannins are localized and distributed in dicotyledonous polypetalous plants. Examples include gallotannins found in galls (called quinquefoliate galls) formed when the sumac aphid infests the leaves of the sumac plant (Araliaceae family), and ellagitannins found in geranium thunbergii (Geraniaceae family).

[0025] Tannic acid (B-1) can be obtained, for example, by extracting it from a tannic acid-containing material such as gallnuts with hot water and removing impurities with an organic solvent. However, commercially available products can also be purchased and used. For example, "Tannic Acid AL" manufactured by Fuji Chemical Industry Co., Ltd. can be used as a commercially available product.

[0026] In this embodiment, the ratio of (hydroxyl group equivalent of tannic acid (B-1)) / (epoxy equivalent of epoxy resin (A)) is 0.8 or less. Within this range, it is possible to reduce the environmental burden and provide a resin composition that yields a cured product with excellent adhesion (peel strength) to metal foil and excellent flame retardancy. The ratio of (hydroxyl group equivalent of tannic acid (B-1)) / (epoxy equivalent of epoxy resin (A)) is preferably 0.78 or less, and more preferably 0.75 or less. In this specification, the epoxy equivalent of epoxy resin (A) refers to the total amount of epoxy equivalent of epoxy resin contained in epoxy resin (A). In this specification, the hydroxyl group equivalent of tannic acid (B-1) refers to the phenolic hydroxyl group equivalent derived from tannic acid.

[0027] In this embodiment, the hydroxyl group equivalent of tannic acid (B-1) (the total amount of hydroxyl group equivalents of tannic acid contained in tannic acid (B-1)) is preferably 30 g / eq or more and 400 g / eq or less. By having a hydroxyl group equivalent of tannic acid (B-1) of 30 g / eq or more, the progress of local curing reactions between phenolic hydroxyl groups derived from tannic acid and epoxy groups derived from epoxy resin is suppressed, thereby suppressing the unevenness of thermal stress and mechanical stress, and enabling more reliable acquisition of excellent copper peel strength and quality stability in the cured product of the resin composition. On the other hand, by having a hydroxyl group equivalent of tannic acid (B-1) of 400 g / eq or less, a sufficient crosslinking density is obtained, and high glass transition temperature, mechanical strength, and heat resistance are obtained in the cured product of the resin composition. The hydroxyl group equivalent of tannic acid (B-1) is more preferably 40 g / eq or more and 300 g / eq or less, and even more preferably 50 g / eq or more and 150 g / eq or less.

[0028] The hydroxyl equivalent of tannic acid (B-1) can be measured as follows: Based on the analytical method described in "Xianzhi Meng et alten Nature Protocols 2019, 14, 2627-2647", tannic acid is mixed with a solvent of pyridine and deuterated chloroform and stirred, left at room temperature for 24 hours to dissolve as much as possible, then 2-chloro-4,4,5,5-tetramethyl-1,3,2-dioxaphosphorane is added under a nitrogen atmosphere and reacted at room temperature for more than 1 hour, and then measured using ECZL400s (JEOL Ltd.), ３１ Measurement is performed by P-NMR. 2-chloro-4,4,5,5-tetramethyl-1,3,2-dioxaphosphorane reacts with the hydroxyl groups in the compound, and the phosphorus atoms reacting with the alcoholic hydroxyl group and the phenolic hydroxyl group are detected as characteristic peaks. Then, using cyclohexanol as an internal standard, the hydroxyl group equivalent (phenolic hydroxyl group equivalent) of tannic acid can be calculated.

[0029] Examples of phenolic resins (B-2) include, for example, phenol novolac resins, cresol novolac resins, phenol / cresol mixed novolac resins, alkyl-modified phenol novolac resins, cardanol-based novolac resins, phenolic resins having multiple phenolic hydroxyl groups, and lignin derivatives. Furthermore, phenolic resins (B-2) are not limited to these, and resol type, naphthalene novolac type, and biphenyl novolac type can also be used.

[0030] Furthermore, as the phenolic resin (B-2), a phenolic resin containing a phosphorus atom can also be used. For example, a phenol derivative (DOPO-BQ) using 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) can be used, but is not limited to this. By using a phosphorus-containing phenolic resin, it is expected that the flame retardancy of the cured product of the resin composition will be improved.

[0031] The phenolic resin (B-2) described above may be used alone or in combination of two or more types.

[0032] In this embodiment, the phenolic resin (B-2) does not contain tannic acid (B-1).

[0033] In this embodiment, the hydroxyl group equivalent of the phenol resin (B-2) (the total amount of hydroxyl group equivalents of the phenol resin contained in the phenol resin (B-2)) is preferably 50 g / eq or more and 150 g / eq or less. By having a hydroxyl group equivalent of phenol resin (B-2) of 50 g / eq or more, the progress of local curing reactions between phenolic hydroxyl groups derived from the phenol resin and epoxy groups derived from the epoxy resin is suppressed, thereby suppressing the unevenness of thermal stress and mechanical stress, and making it possible to more reliably obtain excellent copper peel strength and quality stability in the cured product of the resin composition. On the other hand, by having a hydroxyl group equivalent of phenol resin (B-2) of 150 g / eq or less, a sufficient crosslinking density is obtained, and a high glass transition temperature, mechanical strength, and heat resistance are obtained in the cured product of the resin composition. The hydroxyl group equivalent of phenol resin (B-2) is more preferably 60 g / eq or more and 130 g / eq or less, and even more preferably 70 g / eq or more and 120 g / eq or less. In this specification, the hydroxyl group equivalent of phenol resin (B-2) refers to the phenolic hydroxyl group equivalent derived from the phenol resin.

[0034] Furthermore, in this embodiment, it is preferable that (total amount of hydroxyl group equivalents of tannic acid (B-1) and phenol resin (B-2)) / (epoxy equivalent of epoxy resin (A)) is 0.5 or more and less than 1.5. Within this range, unreacted tannic acid (B-1), epoxy resin (A), or phenol resin (B-2) is less likely to remain. Therefore, a cured product with excellent adhesion to metal foil and excellent flame retardancy can be obtained more reliably.

[0035] The ratio (total amount of hydroxyl group equivalents of tannic acid (B-1) and phenol resin (B-2)) / (epoxy equivalent of epoxy resin (A)) is more preferably 0.5 or more and 1.5 or less, and even more preferably 0.7 or more and 1.3 or less.

[0036] (Inorganic filler (C)) The inorganic filler (C) in this embodiment contains aluminum hydroxide. Here, aluminum hydroxide decomposes and reacts at high temperatures, releasing water vapor and absorbing thermal energy from the surroundings. This suppresses the rise in combustion temperature and effectively inhibits the continuation of combustion and the spread of flames. For these reasons, by including aluminum hydroxide in the resin composition, a cured product with higher flame retardancy can be obtained.

[0037] The aluminum hydroxide is not particularly limited, but from the viewpoint of uniform dispersibility and suppression of varnish viscosity increase, it is preferable that the average particle size is 1 μm or more and 10 μm or less, and more preferably 2 μm or more and 7 μm or less. The average particle size is measured using SALD-2300 (manufactured by Shimadzu Corporation) and represents the particle size at 50% of the cumulative value in the particle size distribution. Furthermore, from the viewpoint of uniform dispersibility and the smoothness of the cured resin composition, the shape of the aluminum hydroxide is preferably spherical or approximately spherical.

[0038] The inorganic filler (C) may contain inorganic fillers other than aluminum hydroxide. For example, it may further contain fillers made of at least one material selected from the group consisting of silica such as spherical silica, alumina, titanium oxide, metal oxides such as mica, metal hydroxides such as magnesium hydroxide, talc, aluminum borate, barium sulfate, and calcium carbonate. The inorganic filler (C) may be used alone or in combination of two or more materials. The inorganic filler (C) may be used as is or surface-treated with a silane coupling agent. Furthermore, from the viewpoint of reducing the burden on the environment, biomass-derived silica may be used as the silica.

[0039] The inorganic filler (C) content is 60 parts by weight or more and 200 parts by weight or less relative to the total amount (100 parts by weight) of the epoxy resin (A) and curing agent (B). If the inorganic filler (C) content is too low, it may not be possible to obtain sufficient flame retardancy in the cured resin composition. Conversely, if the inorganic filler (C) content is too high, it may result in poor adhesion of the cured resin composition to the metal foil. Therefore, if the inorganic filler (C) content is within the above range, a cured product with excellent adhesion to the metal foil and excellent flame retardancy can be obtained. The inorganic filler (C) content is more preferably 65 parts by weight or more and 200 parts by weight or less, and even more preferably 70 parts by weight or more and 180 parts by weight or less, relative to the total amount (100 parts by weight) of the epoxy resin (A) and curing agent (B).

[0040] The aluminum hydroxide content in the inorganic filler (C) is preferably 10% by weight or more and 100% by weight or less based on the total weight (100% by weight) of the inorganic filler (C). This provides sufficient flame retardancy. The aluminum hydroxide content is more preferably 30% by weight or more and 100% by weight or less based on the total weight of the inorganic filler (C), and even more preferably 50% by weight or more and 100% by weight or less.

[0041] (Other Components) The resin composition may further contain components other than those described above (other components) as necessary, to the extent that it does not impair the adhesion to the metal foil and flame retardancy effects according to this embodiment. Examples of other components include organic components other than those described above, flame retardants, organic peroxides, crosslinking agents, organic fillers, reaction initiators, curing accelerators, catalysts, polymerization retarders, polymerization inhibitors, dispersants, leveling agents, coupling agents, defoaming agents, antioxidants, heat stabilizers, antistatic agents, ultraviolet absorbers, dyes and pigments, and additives such as lubricants.

[0042] As the curing accelerator, any curing accelerator that can accelerate the curing reaction between the epoxy resin (A) and the curing agent (B) can be used without particular limitation. Specific examples thereof include imidazoles such as 2-ethyl-4-methylimidazole and cyanoethyl-2-ethyl-4-methylimidazole; amines such as dimethylbenzylamine, triethylenediamine, benzyldimethylamine and triethanolamine; and organic phosphines such as triphenylphosphine, diphenylphosphine and phenylphosphine. These may be used alone or in combination of two or more kinds thereof.

[0043] In the present embodiment, when the curing accelerator is contained, the content of the curing accelerator is preferably about 0.01% by weight or more and 1% by weight or less based on the total weight (100% by weight) of the resin component (organic component) in the resin composition.

[0044] The glass transition temperature (Tg) of a cured product of the resin composition according to the present embodiment is preferably 80°C or higher. When this condition is satisfied, a cured product excellent in adhesion to metal foil can be obtained more reliably. The glass transition temperature (Tg) of a cured product of the resin composition is more preferably 80°C or higher, and still more preferably 100°C or higher. The glass transition temperature (Tg) of a cured product of the resin composition can be measured by the method described in the Examples mentioned later.

[0045] (Production Method) The method for producing the resin composition in the present embodiment is not particularly limited, and examples thereof include a method of mixing an epoxy resin (A), a curing agent (B), an inorganic filler (C), and other components as necessary. Specifically, when obtaining a varnish-like composition containing an organic solvent, it is prepared, for example, as follows. Among the components of the resin composition, each component soluble in an organic solvent is added to the organic solvent and dissolved. At this time, heating may be performed as necessary. Thereafter, components insoluble in the organic solvent (e.g., the inorganic filler (C), etc.) that are used as needed are added, and the mixture is dispersed using a ball mill, bead mill, planetary mixer, roll mill, or the like until a predetermined dispersion state is achieved, whereby a varnish-like resin composition is prepared. The organic solvent used herein is not particularly limited as long as it can dissolve the epoxy resin (A), the curing agent (B), etc., and does not inhibit the curing reaction. Specific examples thereof include toluene, methyl ethyl ketone (MEK), and the like.

[0046] (Applications) By using the resin composition in the present embodiment, a prepreg, a metal foil with resin, a metal-clad laminate, a film with resin, and a wiring board can be obtained, and the prepreg, the metal foil with resin, the metal-clad laminate, the film with resin, and the wiring board are also encompassed in the present invention.

[0047] That is, by using the resin composition according to the present embodiment, a prepreg, a metal-clad laminate, a wiring board, a metal foil with resin, and a film with resin can be obtained as follows.

[0048] [Prepreg] FIG. 1 is a schematic cross-sectional view showing an example of the prepreg 1 according to an embodiment of the present invention. In the following description, each reference numeral in the description of the figures respectively denotes: 1, prepreg; 2, film with resin; 3, metal foil with resin; 4, metal-clad laminate; 5, wiring board; 11, 21, 31, resin layer; 12, base material; 22, support film; 23, protective film; 32, 42, metal foil; 41, 51, insulating layer; 52, wiring.

[0049] The prepreg 1 is in the form of a sheet. The prepreg 1 comprises at least one sheet-like substrate 12 and a resin layer 11. The substrate 12 is impregnated with the resin composition. The resin layer 11 contains the resin composition or a semi-cured product of the resin composition.

[0050] A semi-cured product is a resin composition that has been partially cured to the point where it can be further cured. In other words, a semi-cured product is a resin composition that has been partially cured (B-staged). For example, when a resin composition is heated, its viscosity gradually decreases at first, then curing begins, and the viscosity gradually increases. In such a case, a semi-cured product would be the state between the point where the viscosity begins to increase and before it is completely cured.

[0051] The base material 12 is a reinforcing material and is not particularly limited. The thickness of the base material 12 is not particularly limited, but is preferably in the range of 10 μm to 300 μm, and more preferably in the range of 30 μm to 200 μm.

[0052] Specific examples of the base material 12 include glass cloth, aramid cloth, polyester cloth, glass nonwoven fabric, aramid nonwoven fabric, polyester nonwoven fabric, pulp paper, and linter paper. Preferred types of glass cloth are, for example, #7628, #1501, #2116, #1080, #1078, and #106.

[0053] In manufacturing prepreg 1, it is preferable that the glass cloth is treated with a coupling agent before impregnation with the A-stage resin composition. Treating the glass cloth with a coupling agent in this way improves the adhesion between the glass cloth and the resin composition.

[0054] Preferably, the coupling agent has a reactant group that chemically bonds with an inorganic material and a reactant group that chemically bonds with an organic material within one molecule. Specific examples of reactants that chemically bond with inorganic materials include ethoxy groups and methoxy groups. Specific examples of reactants that chemically bond with organic materials include epoxy groups, amino groups, isocyanate groups, hydroxyl groups, and acid anhydride groups.

[0055] Specifically, the coupling agent is, for example, a silane coupling agent. Silane coupling agents include, for example, epoxysilanes, aminosilanes, isocyanatesilanes, and acid anhydride silanes. A specific example of an epoxysilane is 3-glycidoxypropyltrimethoxysilane. A specific example of an aminosilane is 3-aminopropyltriethoxysilane. A specific example of an isocyanatesilane is 3-isocyanatetopropyltriethoxysilane.

[0056] The method for manufacturing the prepreg 1 is not particularly limited, but one method involves impregnating the substrate 12 with an A-stage resin composition and then drying it. The resin composition is impregnated into the substrate 12 by immersion, coating, etc. Impregnation can be repeated multiple times as needed. In this case, it is also possible to adjust to the desired composition and impregnation amount by repeating the impregnation using multiple resin compositions with different compositions and concentrations. Here, A-stage refers to the initial stage in which the resin composition is soluble in a certain liquid and is fusible. In other words, the A-stage resin composition is a resin varnish. The resin varnish can be obtained, for example, by the method described above.

[0057] The substrate 12 impregnated with the resin composition (resin varnish) is heated under desired heating conditions, for example, at 80°C to 180°C for 1 minute to 10 minutes. Heating yields a prepreg in either a pre-cured state (A-stage) or a semi-cured state (B-stage). Heating can also cause organic solvents to volatilize from the resin varnish, reducing or removing them.

[0058] The prepreg of this embodiment can reduce environmental impact and possesses excellent adhesion to metal foil and excellent flame retardancy. Therefore, a wiring board equipped with an insulating layer formed using the prepreg of this embodiment can reduce environmental impact and has an insulating layer with excellent adhesion (peel strength) to metal foil and flame retardancy. Thus, the prepreg of this embodiment can be suitably used when forming insulating layers provided in metal-clad laminates and wiring boards.

[0059] [Resin-Coated Film] Figures 2A and 2B show the resin-coated film 2 according to this embodiment. The resin-coated film 2 is used for multilayering (build-up method) of the wiring board 5, etc. The resin-coated film 2 is a film as a whole. The resin-coated film 2 comprises a resin layer 21 and a support film 22. Figure 2A is a resin-coated film 2 without a protective film 23. Figure 2B is a resin-coated film 2 further comprising a protective film 23. If the protective film 23 is peeled off from the resin-coated film 2 shown in Figure 2B, it can become the resin-coated film 2 shown in Figure 2A. In addition, the resin-coated film 2 may have other layers between the resin layer 21 and the support film 22.

[0060] The resin layer 21 contains the resin composition or a semi-cured product of the resin composition. The semi-cured product becomes a cured product when heated. In this way, the resin layer 21 can form an insulating layer. The resin layer 21 may also contain a substrate, and the same substrate as the substrate 12 of the prepreg 1 can be used.

[0061] The thickness of the resin layer 21 is not particularly limited, but is preferably 120 μm or less, more preferably 100 μm or less, even more preferably 60 μm or less, and even more preferably 40 μm or less. This allows for a thinner insulating layer, enabling a thinner substrate. The thickness of the resin layer 21 is preferably 10 μm or more.

[0062] The support film 22 supports the resin layer 21. This support film 22 provides with the resin layer 21, making it easier to handle.

[0063] The support film 22 is, for example, an electrically insulating film. The support film 22 is not particularly limited, but examples include polyethylene terephthalate (PET) film, polyimide film, polyester film, polyparabanic acid film, polyether ether ketone film, polyphenylene sulfide film, aramid film, polycarbonate film, and polyarylate film.

[0064] A release agent layer (not shown) may be provided on the surface of the support film 22 that supports the resin layer 21. The release agent layer allows the support film 22 to be peeled off from the resin layer 21 as needed. Preferably, after the resin layer 21 is cured to form an insulating layer, the support film 22 is peeled off from this insulating layer.

[0065] In Figure 2A, one side of the resin layer 21 is covered by the support film 22, but as shown in Figure 2B, the other side of the resin layer 21 may be covered by the protective film 23. By covering both sides of the resin layer 21 with the support film 22 and the protective film 23 in this way, the resin layer 21 becomes easier to handle. In addition, it is possible to suppress the adhesion of foreign matter to the resin layer 21.

[0066] The protective film 23 is, for example, an electrically insulating film. The protective film 23 is not particularly limited, but examples include polyethylene terephthalate (PET) film, polyolefin film, polyester film, and polymethylpentene film.

[0067] A release agent layer (not shown) may be provided on the surface of the protective film 23 that is superimposed on the resin layer 21. The release agent layer allows the protective film 23 to be peeled off from the resin layer 21 as needed.

[0068] The support film 22 and protective film 23 may be subjected to surface treatments such as matte finish, corona treatment, release treatment, and roughening treatment, as needed.

[0069] The method for manufacturing the resin-coated film 2 is not particularly limited, but examples include a method of manufacturing by applying the above-mentioned varnish-like resin composition (resin varnish) onto a support film 22 and heating it. The varnish-like resin composition is applied onto the support film 22, for example, by using a bar coater. The applied resin composition is heated under conditions that vary depending on the resin composition, for example, 40°C to 180°C for 0.1 minutes to 10 minutes. The heated resin composition is formed on the support film 22 as an uncured resin layer 21. Note that the heating can cause organic solvents to volatilize from the resin varnish, thereby reducing or removing the organic solvents.

[0070] The resin-coated film of the aforementioned resin composition is a resin-coated film having a resin layer that can reduce environmental impact and yield a cured product with excellent adhesion (peel strength) to metal foil and excellent flame retardancy.

[0071] [Resin-coated metal foil] Figure 3 shows the resin-coated metal foil 3 according to this embodiment. The resin-coated metal foil 3 is in the form of a film overall. The resin-coated metal foil 3 comprises a resin layer 31 and a metal foil 32. The resin-coated metal foil 3 is used for multilayering (build-up method) of wiring boards 5, etc. The resin-coated metal foil 3 may have other layers between the resin layer 31 and the metal foil 32.

[0072] The resin layer 31 contains the resin composition or a semi-cured product of the resin composition. The semi-cured product can be cured by heating. In this way, the resin layer 31 can form an insulating layer. The resin layer 31 may also contain a substrate, and the same substrate as the substrate 12 of the prepreg 1 can be used.

[0073] The thickness of the resin layer 31 is not particularly limited, but is preferably 120 μm or less, more preferably 100 μm or less, even more preferably 60 μm or less, and even more preferably 40 μm or less. This makes it possible to reduce the thickness of the insulating layer formed when the resin layer 31 hardens, thereby enabling a thinner substrate. The thickness of the resin layer 31 is preferably 10 μm or more.

[0074] The metal foil 32 is bonded to the resin layer 31. A specific example of the metal foil 32 is copper foil, but it is not limited to this. Conductor wiring can be formed from the metal foil 32 by removing unwanted portions by etching using a subtractive method or the like.

[0075] The thickness of the metal foil 32 is not particularly limited, but is preferably 35 μm or less, and more preferably 18 μm or less. It is preferable that the thickness of the metal foil 32 is 5 μm or more.

[0076] Incidentally, the metal foil 32 may be composed of an ultrathin metal foil (for example, an ultrathin copper foil) of a so-called carrier-attached ultrathin metal foil (not shown). The carrier-attached ultrathin metal foil has a three-layer structure. That is, the carrier-attached ultrathin metal foil comprises a carrier, a release layer provided on the surface of the carrier, and an ultrathin metal foil provided on the surface of the release layer. The ultrathin metal foil is so thin that it is difficult to handle on its own, and of course it is thinner than the carrier. The carrier is a metal foil (for example, a copper foil) that serves to protect and support the ultrathin metal foil. The carrier-attached ultrathin metal foil has a certain thickness, making it easy to handle. The thickness of the ultrathin metal foil and the carrier are not particularly limited, but for example, the thickness of the ultrathin metal foil is in the range of 1 μm to 10 μm, and the thickness of the carrier is in the range of 18 μm to 35 μm. The ultrathin metal foil can be peeled off from the release layer as needed.

[0077] When using a carrier-attached ultrathin metal foil, the resin-coated metal foil 3 can be manufactured as follows: A resin composition is applied to the surface of the carrier-attached ultrathin metal foil and heated to form a resin layer 31. Then, the carrier is peeled off from the ultrathin metal foil. The ultrathin metal foil is adhered to the surface of the resin layer 31 as a metal foil 32. Preferably, the release layer is peeled off together with the carrier and does not remain on the surface of the ultrathin metal foil, but even if it remains, it can be easily removed. The ultrathin metal foil adhered to the surface of the resin layer 31 can be used as a seed layer in the Modified Semi-Additive Process (MSAP), and conductive wiring can be formed by electroplating this seed layer.

[0078] The resin-coated metal foil 3 may be equipped with a protective film or the like, if necessary. By providing a protective film, it is possible to suppress the adhesion of foreign matter to the resin layer 31. The protective film can be the same as the protective film 23 of the resin-coated film 2.

[0079] The resin-coated metal foil of the aforementioned resin composition is a resin-coated metal foil having a resin layer that can reduce environmental impact and yield a cured product with excellent adhesion (peel strength) to the metal foil and excellent flame retardancy.

[0080] [Metal-clad laminate] Figure 4 shows a metal-clad laminate 4 according to this embodiment. The metal-clad laminate 4 comprises an insulating layer 41 and a metal foil 42. The insulating layer 41 includes a cured product of the resin composition or a cured product of at least one prepreg 1. Thus, the metal-clad laminate 4 can be manufactured using the prepreg 1 as the material. The insulating layer 41 is an electrically insulating, insoluble and infusible layer. The metal foil 42 is bonded to the insulating layer 41. Figure 4 shows a metal-clad laminate 4 with metal foil 42 on both sides of the insulating layer 41.

[0081] The metal foil 42 is not particularly limited, but examples include copper foil, aluminum foil, etc. If the metal foil 42 is thin, it may be a carrier-equipped copper foil with a release layer and carrier to improve handling. The thickness of the metal foil 42 is preferably in the range of 18 μm to 210 μm.

[0082] A method for manufacturing the metal-clad laminate 4 includes, for example, a method of overlapping a metal foil 42 on one or both sides of a laminate consisting of one prepreg 1 or two or more prepreg 1, and then heating and pressing it. Preferably, before overlapping the metal foil 42 on the laminate, the surface of the metal foil 42 (at least the side overlapping the laminate) is treated with a coupling agent. When the metal foil 42 is surface-treated with a coupling agent in this way, the coupling agent bonds the organic material in the prepreg 1 with the metal foil 42, thereby further improving the adhesion between the insulating layer 41 and the metal foil 42. The coupling agent can be any of the above-mentioned ones. The heating and pressing conditions are not particularly limited.

[0083] The metal-clad laminate of this embodiment is a metal-clad laminate that can reduce environmental impact and has an insulating layer that combines excellent adhesion (peel strength) to metal foil and excellent flame retardancy.

[0084] In this embodiment, the metal-clad laminate preferably has a peel strength of 0.8 N / mm or more between the insulating layer and the metal foil. If this is the case, the adhesion between the insulating layer and the metal foil is high. The peel strength is more preferably 0.8 N / mm or more, and even more preferably 1.0 N / mm or more. The peel strength can be measured by the method described in "Copper Foil Peel Strength" in the embodiments described later.

[0085] [Wiring Board] Figure 5 shows a wiring board 5 according to this embodiment. The wiring board 5 comprises at least one insulating layer 51 and at least one wiring layer 52. The insulating layer 51 includes a cured product of the resin composition or at least one cured product of prepreg 1. The insulating layer 51 is an electrically insulating, insoluble and infusible layer. The wiring 52 is laminated on the insulating layer 51. The wiring board 5 is a concept that includes multilayer wiring boards having three or more wiring layers 52. Note that Figure 5 shows a wiring board having two wiring layers 52 and one insulating layer 51.

[0086] The method for manufacturing the wiring board 5 is not particularly limited as long as it can be manufactured. Specifically, one example is a method of manufacturing the wiring board 5 using the prepreg 1. This method includes, for example, a method of manufacturing a wiring board 5 in which wiring is provided as a circuit on the surface of the insulating layer 41 by etching the metal foil 42 on the surface of the metal-clad laminate 4 manufactured as described above to form wiring. That is, the wiring board 5 is obtained by partially removing the metal foil 42 on the surface of the metal-clad laminate 4 to form a circuit. In addition to the above method, other methods for circuit formation include, for example, circuit formation by the semi-additive process (SAP) or the modified semi-additive process (MSAP). Furthermore, the wiring board 5 may be multilayered by a build-up method using the resin-coated film 2 and the resin-coated metal foil 3.

[0087] A wiring board having an insulating layer containing a cured product of the aforementioned resin composition can reduce environmental impact and has an insulating layer with excellent adhesion (peel strength) to metal foil and excellent flame retardancy.

[0088] This specification discloses various aspects of technology as described above, but the main technologies are summarized below.

[0089] The resin composition in the first aspect of the present invention comprises an epoxy resin (A), a curing agent (B), and an inorganic filler (C), wherein the epoxy resin (A) comprises an epoxy resin (A-1) having an aromatic ring in its molecule, the curing agent (B) comprises tannic acid (B-1) and a phenolic resin (B-2), and the ratio of (hydroxyl group equivalent of tannic acid (B-1)) / (epoxy equivalent of epoxy resin (A)) is 0.8 or less, and the inorganic filler (C) comprises aluminum hydroxide, with the content of the inorganic filler (C) being 60 parts by weight or more and 200 parts by weight or less relative to the total amount of epoxy resin (A) and curing agent (B).

[0090] The resin composition in the second aspect of the present invention is the resin composition in the first aspect wherein the glass transition temperature of the cured product of the resin composition is 80°C or higher.

[0091] In the third aspect of the present invention, the resin composition is such that in the first or second resin composition, the content of epoxy resin (A-1) is 10% by weight or more relative to the total weight of epoxy resin (A).

[0092] The resin composition in the fourth aspect of the present invention is such that, in the resin composition in any one of the first to third aspects, (total amount of hydroxyl group equivalents of tannic acid (B-1) and phenol resin (B-2)) / (epoxy equivalent of epoxy resin (A)) is 0.5 or more and less than 1.5.

[0093] The prepreg in the fifth aspect of the present invention comprises a resin composition according to any one of the first to fourth aspects or a semi-cured product of the resin composition, and a fibrous substrate.

[0094] A resin-coated film according to a sixth aspect of the present invention comprises a resin layer containing a resin composition according to any one of the first to fourth aspects or a semi-cured product of the resin composition, and a support film.

[0095] The resin-coated metal foil in the seventh aspect of the present invention comprises a resin layer containing a resin composition according to any one of the first to fourth aspects or a semi-cured product of the resin composition, and a metal foil.

[0096] The metal-clad laminate according to the eighth aspect of the present invention comprises an insulating layer containing a cured product of the resin composition according to any one of the first to fourth aspects, and a metal foil.

[0097] A metal-clad laminate according to the ninth aspect of the present invention comprises an insulating layer containing a cured product of the prepreg according to the fifth aspect, and a metal foil.

[0098] A wiring board in the tenth aspect of the present invention comprises an insulating layer containing a cured resin composition according to any one of the first to fourth aspects, and wiring.

[0099] The wiring board in the eleventh aspect of the present invention comprises an insulating layer containing a cured prepreg in the fifth aspect, and wiring.

[0100] The present invention will be described in more detail below with reference to examples, but the scope of the present invention is not limited thereto.

[0101] First, the components used in preparing the resin composition in this embodiment will be described.

[0102] [Epoxy Resin (A)] (Epoxy Resin (A-1)) ・Epoxy Resin 1: Phenol novolac type epoxy resin ("EPICLON-N775" epoxy equivalent: 190 g / eq, manufactured by DIC Corporation) ・Epoxy Resin 2: Dicyclopentadiene type (DCPD type) epoxy resin ("HP-7200H" epoxy equivalent: 285 g / eq, manufactured by DIC Corporation) ・Epoxy Resin 3: Triphenolmethane type (TPM type) epoxy resin ("HP-7241" epoxy equivalent: 173 g / eq, manufactured by DIC Corporation) (Epoxy resins other than Epoxy Resin (A-1)) ・Epoxy Resin 4: Sorbitol polyglycidyl ether type (SGE type) epoxy resin ("GEX-252" epoxy equivalent: 212 g / eq, manufactured by Nagase ChemteX Corporation) Epoxy resin 5: Hydrogenated BisA type epoxy resin ("GEX-622" epoxy equivalent: 188 g / eq, manufactured by Nagase ChemteX Corporation)

[0103] [Curing agent (B)] (Tannic acid (B-1)) ・Tannic acid ("Tannic acid-AL", hydroxyl group equivalent: 70 g / eq, manufactured by Fuji Chemical Industry Co., Ltd.) (Phenol resin (B-2)) ・Phenol novolac ("TD-2090", hydroxyl group equivalent: 105 g / eq, manufactured by DIC Corporation)

[0104] [Inorganic filler (C)] - Aluminum hydroxide ("ALH-F" manufactured by Kawai Lime Industry Co., Ltd.)

[0105] [Curing accelerator] ・Imidazole catalyst ("2E4MZ (2-ethyl-4-methylimidazole)" manufactured by Shikoku Chemicals Co., Ltd.)

[0106] The hydroxyl equivalent of tannic acid was calculated as follows: Based on the analytical method described in "Xianzhi Meng et alten Nature Protocols 2019, 14, 2627-2647", tannic acid was mixed with a solvent of pyridine and deuterated chloroform and stirred, left at room temperature for 24 hours to dissolve as much as possible, and then 2-chloro-4,4,5,5-tetramethyl-1,3,2-dioxaphosphorane was added under a nitrogen atmosphere and reacted at room temperature for more than 1 hour, after which ECZL400s (JEOL Ltd.) was used. ３１The reaction was measured by P-NMR. 2-chloro-4,4,5,5-tetramethyl-1,3,2-dioxaphosphorane reacts with the hydroxyl groups in the compound, and the phosphorus atoms reacting with the alcoholic hydroxyl group and the phenolic hydroxyl group are detected as characteristic peaks. Therefore, cyclohexanol was used as an internal standard to calculate the hydroxyl group equivalent (phenolic hydroxyl group equivalent) of tannic acid.

[0107] <Examples 1-13, Comparative Examples 1-5> [Resin Varnish] First, epoxy resin (A), curing agent (B), inorganic filler (C), and curing accelerator were mixed in the proportions (parts by weight) shown in Table 1, so that the solid content concentration was 70% by weight relative to the solvent, methyl ethyl ketone. The mixture was then stirred in a disperser at room temperature for 2 hours to disperse and dissolve the mixture, thereby obtaining a varnish-like resin composition.

[0108] [Prepreg] The resin compositions (resin varnishes) of each example and comparative example prepared above were impregnated into glass cloth (manufactured by Nitto Boseki Co., Ltd., WEA7628), and then heated and dried in a dryer at 160°C for 3 minutes to prepare a prepreg in a semi-cured B-stage state. At that time, the content of the resin composition relative to the weight of the prepreg (resin content) was adjusted to approximately 40% by weight.

[0109] [Copper-clad laminate] Four sheets of the above prepreg were laminated together, sandwiched between two sheets of copper foil (manufactured by Fukuda Metal Foil Powder Co., Ltd., 35 μm thick, product number CF-T8G-UN-35), and heated and pressed for 120 minutes at 220°C and 3 MPa to produce a copper-clad laminate with a thickness of approximately 0.8 mm.

[0110] [Evaluation] (Glass transition temperature (Tg) measurement) The outer copper foil of the copper-clad laminates prepared as described above in Examples 1 to 13 and Comparative Examples 1 to 5 was etched across the entire surface, and the Tg of the obtained samples was measured using a viscoelastic spectrometer "DMS6100" manufactured by Seiko Instruments Inc. Dynamic viscoelasticity measurement (DMA) was performed in three-point bending mode at a frequency of 10 Hz, and the temperature at which tanδ showed a maximum when the temperature was raised from room temperature to 260°C at a heating rate of 5°C / min was defined as Tg. If multiple maximum peaks were observed, the temperature at which the peak observed on the lowest temperature side showed a maximum was adopted as the Tg value. In this test, a Tg of 80°C or higher was evaluated as acceptable.

[0111] (Copper foil peel strength) Test pieces measuring 100 mm in length and 10 mm in width were cut from the copper-clad laminates of Examples 1 to 13 and Comparative Examples 1 to 5, which were prepared as described above. Using these test pieces, the 90° peel strength was measured at 25°C and a tensile speed of 50 mm / min using a peel tester (EZtest, manufactured by Shimadzu Corporation). The curve of the test force and stroke consists of (A) the rising region, (B) the steady-state region, and (C) the peeling completion region. In this test, measurements were performed with N=5, and the average value of the peeling force in the steady-state peeling region (B) was calculated to determine the average peel strength F (N / mm). This average peel strength F is the copper foil peel strength. It was found that the higher this value, the higher the adhesion to the metal foil (copper foil). A copper foil peel strength of 0.8 N / mm or higher was considered a pass, and a value less than 0.8 N / mm was considered a fail.

[0112] (Combustion Test) The outer layer copper foil of the copper-clad laminates prepared as described above (Examples 1-13, Comparative Examples 1-5) was completely etched, and the samples obtained by cutting them to a size of 12 cm in length and 1 cm in width were brought into contact with the bottom of the sample for 10 seconds with a burner flame height of 20 mm. If the flame was extinguished within 30 seconds after being removed from the flame, it was considered a pass; if it continued to burn for more than 30 seconds or did not extinguish, it was considered a fail.

[0113]

[0114] (Discussion) The resin compositions of Examples 1 to 13 contain tannic acid, thus reducing the environmental impact. Furthermore, it was found that the resin compositions of Examples 1 to 13 yield cured products with excellent adhesion to metal foil (copper foil) (copper foil peel strength) and excellent flame retardancy.

[0115] On the other hand, the resin compositions of Comparative Examples 1 and 2 do not contain phenolic resin, and furthermore, the ratio of (hydroxyl group equivalent of tannic acid) / (epoxy equivalent of epoxy resin) is high, resulting in low copper foil peel strength. Also, the resin composition of Comparative Example 3 does not contain epoxy resin having aromatic rings, resulting in low copper foil peel strength. Furthermore, the resin composition of Comparative Example 4 has a low aluminum hydroxide content, resulting in poor combustion test results. Furthermore, the resin composition of Comparative Example 5 contains an excess of aluminum hydroxide, resulting in low copper foil peel strength.

[0116] This application is based on Japanese Patent Application No. 2025-50518, filed on March 25, 2025, the contents of which are included in this application.

[0117] In order to express the present invention, the invention has been adequately and sufficiently described above through embodiments with reference to specific examples and drawings, etc. However, those skilled in the art should recognize that it is easy to modify and / or improve the embodiments described above. Therefore, unless the modifications or improvements implemented by those skilled in the art fall outside the scope of the claims described in the claims, such modifications or improvements shall be interpreted as being included within the scope of the claims.

[0118] The present invention has broad industrial applicability in the technical fields related to electronic materials, electronic devices, optical devices, and the like.

Claims

1. A resin composition comprising an epoxy resin (A), a curing agent (B), and an inorganic filler (C), wherein the epoxy resin (A) comprises an epoxy resin (A-1) having an aromatic ring in its molecule, the curing agent (B) comprises tannic acid (B-1) and a phenolic resin (B-2), the ratio of (hydroxyl group equivalent of tannic acid (B-1)) to (epoxy equivalent of epoxy resin (A)) is 0.8 or less, and the inorganic filler (C) comprises aluminum hydroxide, with the content of the inorganic filler (C) being 60 parts by weight or more and 200 parts by weight or less relative to the total amount of epoxy resin (A) and curing agent (B).

2. The resin composition according to claim 1, wherein the glass transition temperature of the cured product of the resin composition is 80°C or higher.

3. The resin composition according to claim 1, wherein the content of epoxy resin (A-1) is 10% by weight or more relative to the total weight of epoxy resin (A).

4. The resin composition according to claim 1, wherein (total amount of hydroxyl group equivalents of tannic acid (B-1) and phenol resin (B-2)) / (epoxy equivalent of epoxy resin (A)) is 0.5 or more and less than 1.

5.

5. A prepreg comprising a resin composition according to any one of claims 1 to 4 or a semi-cured product of the resin composition, and a fibrous substrate.

6. A resin-coated film comprising a resin layer containing the resin composition described in any one of claims 1 to 4 or a semi-cured product of the resin composition, and a support film.

7. A resin-coated metal foil comprising a resin layer containing the resin composition according to any one of claims 1 to 4 or a semi-cured product of the resin composition, and a metal foil.

8. A metal-clad laminate comprising an insulating layer containing a cured product of the resin composition according to any one of claims 1 to 4, and a metal foil.

9. A metal-clad laminate comprising an insulating layer containing a cured prepreg according to claim 5, and a metal foil.

10. A wiring board comprising an insulating layer containing a cured resin composition according to any one of claims 1 to 4, and wiring.

11. A wiring board comprising an insulating layer containing a cured prepreg according to claim 5, and wiring.

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