Curable resin composition, resin sheet and its cured product

Abstract

The object of this invention is to provide a resin composition that yields a curable material with high heat resistance and low dielectric properties. A curable resin composition contains (A) a compound having at least two styrene structures within its molecule, (B) a maleimide compound, and (C) a cyanate ester compound.

Description

Curable resin composition, resin sheet and its cured product In recent years, multilayer boards carrying electrical and electronic components have been required to have a wide range of high-performance characteristics due to the expansion of their application fields. The mainstream of existing semiconductor chips is mounted on metal lead frames, but high-processing-capacity semiconductor chips such as central processing units (hereinafter referred to as CPUs) are mostly mounted on multilayer boards made of polymer materials. In particular, semiconductor packages (PKGs) used in smartphones and other devices require thinner substrates to meet the demands for miniaturization, thinning, and high density. However, thinner PKG substrates result in reduced rigidity, leading to significant warping and other defects caused by the heating process during soldering and mounting of the PKG onto the motherboard (printed circuit board, PCB). To mitigate this, PKG substrate materials with high Tg (heat resistance) above the soldering and mounting temperature are required. Furthermore, the fifth-generation communication system "5G," which is currently under accelerated development, is expected to further promote high-capacity and high-speed communication. The demand for low dielectric loss tangent materials is increasing, requiring at least a dielectric loss tangent of less than 0.005 at 10 GHz. Furthermore, with the development of electrification in the automotive industry, and the occasional placement of sophisticated electronic devices near the engine drive unit, higher levels of heat and moisture resistance are required. The use of SiC semiconductors in electric vehicles and air conditioning systems places extremely high demands on the sealing materials for these semiconductor components, rendering existing epoxy resin sealants inadequate. Against this backdrop, research is underway on polymer materials that combine high heat resistance with low dielectric properties. For example, Patent Document 1 proposes a composition comprising maleimide resin and a phenolic resin containing propylene groups. However, on the other hand, since phenolic hydroxyl groups that do not participate in the curing reaction remain, the electrical properties cannot be considered sufficient. Furthermore, Patent Document 2 discloses an allyl ether resin utilizing allyl-substituted hydroxyl groups. However, it shows that a Claisen rearrangement occurs at 190°C, and at the typical substrate molding temperature of 200°C, phenolic hydroxyl groups are generated that do not contribute to the curing reaction, thus failing to meet the electrical property requirements. [Prior Art Documents] [Patent Documents] [Patent Document 1] Japanese Patent Publication No. 04-359911 [Patent Document 2] International Publication No. 2016 / 002704 [The problem that the invention aims to solve] The present invention has been made in view of the aforementioned aspects, and its object is to provide a resin composition that yields a cured material with high heat resistance and low dielectric properties. [Means for Solving the Problem] The inventors conducted intensive research to solve the aforementioned problem and discovered that the cured resin composition containing compounds having at least two styrene structures, maleimide compounds, and cyanate ester compounds exhibits excellent high heat resistance and low dielectric properties, thus completing the present invention. That is, this invention relates to the following [1] to [8]. Furthermore, in this invention, "(numerical value 1) to (numerical value 2)" indicates that it includes upper and lower limits. [1] A curable resin composition comprising (A) a compound having at least two styrene structures in its molecule, (B) a maleimide compound, and (C) a cyanate compound. [2] The curable resin composition as described in the preceding item [1], wherein the component (A) is a compound represented by the following formula (1), [Chemistry 1] (In formula (1), there are multiple Rs that exist independently, representing hydrocarbon groups or halogenated alkyl groups with 1 to 10 carbon atoms; p and r represent integers from 0 to 4, q represents integers from 0 to 3, n is the average of the number of repetitions, 1 ≦ n ≦ 20) [3] The curable resin composition as described in the preceding item [1] or [2], wherein the component (B) is a compound represented by the following formula (3). [Chemistry 2] (In formula (3), multiple Rs exist independently, representing hydrocarbon groups or halogenated alkyl groups with 1 to 10 carbon atoms; p and r represent integers from 0 to 4, q represents integers from 0 to 3, n is the average of the number of repetitions, 1 ≦ n ≦ 20) [4] The curing resin composition as described in any one of the preceding items [1] to [3] further comprises a curing accelerator. [5] The curing resin composition as described in any one of the preceding items [1] to [4] further comprises an inorganic filler. [6] The curing resin composition as described in any one of the preceding items [1] to [5] further comprises a polymerization initiator. [7] A resin sheet comprising the resin composition as described in any one of the preceding items [1] to [6] and a support. [8] A cured product, which is a cured product of the curing resin composition as described in any one of the preceding items [1] to [6] or the resin sheet as described in the preceding item [7]. [Effects of the Invention] The present invention provides a resin composition with high heat resistance and excellent low dielectric properties, a cured product thereof, and a resin sheet containing the resin composition. The curable resin composition of the present invention contains (A) a compound having at least two styrene structures in the molecule (hereinafter also referred to as component (A)), (B) a maleimide compound (hereinafter also referred to as component (B)), and (C) a cyanate compound (hereinafter also referred to as component (C)). As component (A), any known component may be used, as long as it is a compound having at least two styrene structures within its molecule. Examples include: OPE-2St (manufactured by Mitsubishi Gas Chemical Co., Ltd.), oligodivinyl copolymer (ODV, manufactured by Nippon Steel Chemical & Materials Co., Ltd.), 1,2-bis(vinylphenyl)ethane (BVPE: a group of compounds such as 4,4'-vinylbistyrene, 3,4'-vinylbistyrene, and 3,3'-vinylbistyrene), divinylfluorene, divinylbiphenyl, divinylnaphthalene, divinylbenzene, and compounds represented by the following formula (1). Component (A) may be used in one or more forms. Among these, from the viewpoints of heat resistance, dielectric properties, compatibility with other curable resins (epoxy resins or reactive ester resins, etc.), and circuit embedding, component (A) is preferably a compound represented by the following formula (1). [Chemistry 2] (In formula (1), there are multiple Rs that exist independently, representing hydrocarbon groups or alkyl halides with 1 to 10 carbon atoms; p and r represent integers from 0 to 4, q represents integers from 0 to 3, n is the average of the number of repetitions, 1 ≦ n ≦ 20) In the formula (1), p and r are 0 to 4, preferably 0 to 2, and even more preferably 0. q is 0 to 3, preferably 0 to 2, and even more preferably 0. n is 1 ≤ n ≤ 20, preferably 1.1 ≤ n ≤ 20, even more preferably 1.1 ≤ n ≤ 10, and particularly preferably 1.1 ≤ n ≤ 5. The value of n can be calculated based on the number average molecular weight (Mn) of the compound in formula (1) determined by gel permeation chromatography (GPC). The number average molecular weight is preferably 200 or more and less than 5000, even more preferably 300 or more and less than 3000, and particularly preferably 400 or more and less than 2000. If the weight average molecular weight is less than 5000, purification by washing with water becomes easier; if it is 200 or more, the target compound will not volatilize during the solvent distillation step. In the formula (1), R is a hydrocarbon group or a haloalkyl group having 1 to 10 carbon atoms, preferably a hydrocarbon group having 1 to 10 carbon atoms, more preferably a hydrocarbon group having 1 to 5 carbon atoms, and most preferably a hydrocarbon group having 1 to 3 carbon atoms. Hydrocarbons with R having 3 or fewer carbon atoms are less likely to undergo molecular vibrations when exposed to high frequencies, thus exhibiting particularly excellent electrical properties. The compound represented by formula (1) is derived from the compound represented by formula (2) below. [Chemistry 3] (In formula (2), there are multiple Rs that exist independently, representing hydrocarbon groups or alkyl halides with 1 to 10 carbon atoms; p and r represent integers from 0 to 4, q represents integers from 0 to 3, n is the average of the number of repetitions, 1 ≤ n ≤ 20; X represents halogen atoms) The preferred ranges of R, p, r, q, and n in equation (2) are the same as those in equation (1). From the viewpoint of reactivity and the stability of the raw materials, X is preferably a bromine atom or a chlorine atom, and particularly preferably a bromine atom. The compound represented by formula (1) can be obtained, for example, by carrying out a dehydrohalogenation reaction of the compound represented by formula (2) in a solvent in the presence of an alkaline catalyst. Examples of solvents used include: aromatic solvents such as toluene and xylene; aliphatic solvents such as cyclohexane and n-hexane; ethers such as diethyl ether and diisopropyl ether; ester solvents such as ethyl acetate and butyl acetate; and ketone solvents such as methyl isobutyl ketone and cyclopentanone, etc., but are not limited to these, and two or more may be used together. In addition to the aforementioned non-water-soluble solvents, aprotic polar solvents may also be used. Examples include: dimethyl sulfone, dimethyl sulfoxide, dimethylformamide, dimethyl acetamide, 1,3-dimethyl-2-imidazolidineone, N-methylpyrrolidone, etc., and two or more may be used together. When using aprotic polar solvents, it is preferable to use a solvent with a higher boiling point than the non-water-soluble solvent used. The catalyst is not particularly limited, and alkaline catalysts such as sodium hydroxide, potassium hydroxide, and potassium carbonate can be listed. Since the dehydrohalogenation reaction is difficult to complete, aprotic polar solvents can be used in excess relative to the matrix, and the dehydrohalogenation reaction can be repeated two or three times or more. For example, the solution obtained by performing the dehydrohalogenation reaction of the compound represented by formula (2) in an organic solvent in the presence of an alkaline catalyst can be washed with water and then returned to the reaction vessel, where an alkaline catalyst is added to allow the reaction to proceed again. This can increase the degree of progress of the dehydrohalogenation reaction. That is, it can reduce the amount of residual halogen contained in the target compound. The amount of residual halogen in the target compound is preferably 1 ppm to 10,000 ppm, more preferably 1 ppm to 1,000 ppm, and even more preferably 1 ppm to 750 ppm. If the compound represented by formula (1) contains a large amount of residual halogen, it will cause molecular vibrations when exposed to high frequencies, which will have an adverse effect on electrical properties such as dielectric loss tangent. In addition, with a large amount of residual halogen, the risk of adverse conditions such as metal corrosion or ion migration increases in environmental tests such as HAST test (High Accelerated Stress Test). Therefore, the halogen content is preferred. The preparation method of the compound represented by formula (2) is not particularly limited. For example, a compound having a 2-bromoethylbenzene structure can be reacted with a dihalogenated methyl aryl compound (or a dihydroxymethyl aryl compound, etc.) under an acid catalyst such as hydrochloric acid, sulfonic acid, or activated clay. Alternatively, a compound having a 2-bromoethylbenzene structure can be reacted with a dihydroxymethyl aryl compound under an acid catalyst such as hydrochloric acid, sulfonic acid, or activated clay. When sulfonic acid or the like is used as a catalyst, it can also be neutralized using an alkali metal such as sodium hydroxide or potassium hydroxide before proceeding to the extraction step. Regarding the extraction step, aromatic hydrocarbon solvents such as toluene or xylene can be used alone, or non-aromatic hydrocarbons such as cyclohexane or toluene can be used in combination. After extraction, the organic layer is washed with water until the water becomes neutral, and the solvent and the compound having an excess of the 2-bromoethylbenzene structure are removed by distillation using an evaporator or the like, thereby obtaining the target compound having at least two or more 2-bromoethylbenzene structures within its molecule. Examples of compounds having the 2-bromoethylbenzene structure include, but are not limited to, 2-bromoethylbenzene, 1-(2-bromoethyl)-2-methylbenzene, 1-(2-bromoethyl)-3-methylbenzene, 1-(2-bromoethyl)-4-methylbenzene, 1-(2-bromoethyl)-2,3-dimethylbenzene, 1-(2-bromoethyl)-2,4-dimethylbenzene, 1-(2-bromoethyl)-2,5-dimethylbenzene, and 1-(2-bromoethyl)-2,6-dimethylbenzene. These compounds can be used alone or in combination of two or more. A higher carbon number increases solvent solubility but decreases heat resistance; therefore, unsubstituted or alkyl-substituted compounds with 1 to 3 carbons are preferred, more preferably unsubstituted or alkyl-substituted compounds with 1 to 2 carbons, and most preferably unsubstituted or methyl-substituted compounds. Examples of dihalogenated methyl aryl compounds include, but are not limited to, o-xylene difluoride, m-xylene difluoride, p-xylene difluoride, o-xylene dichloride, m-xylene dichloride, p-xylene dichloride, o-xylene dibromide, m-xylene dibromide, p-xylene dibromide, o-xylene diiodide, m-xylene diiodide, and p-xylene diiodide. These compounds can be used alone or in combination of two or more. From the viewpoint of the reactivity of the starting materials during synthesis, chloride-based compounds, bromide-based compounds, and iodide-based compounds are preferred, and chloride-based compounds and bromide-based compounds are more preferred. Examples of dihydroxymethyl aryl compounds include, but are not limited to, o-phthalimethanol, m-phthalimethanol, and terephthalimethanol. These compounds can be used alone or in combination of two or more. The amount of these compounds used is preferably 0.05 to 0.8 parts by mass, and more preferably 0.1 to 0.6 parts by mass, relative to 1 part by mass of a compound having the 2-bromoethylbenzene structure. When compounds with the 2-bromoethylbenzene structure react with halogenated methyl aryl compounds, catalysts can be used as follows, including hydrochloric acid, phosphoric acid, sulfuric acid, formic acid, p-toluenesulfonic acid, methanesulfonic acid, Lewis acids such as aluminum chloride and zinc chloride, activated clay, acid clay, white carbon, zeolite, silica alumina, and acidic ion exchange resins, depending on the need. These can be used alone or in combination of two or more. The amount of catalyst used is 0.05 mol to 0.8 mol relative to 1 mol of the compound with the 2-bromoethylbenzene structure used, preferably 0.1 mol to 0.7 mol. If too much catalyst is used, the viscosity of the reaction solution will be too high, making stirring difficult; if too little catalyst is used, the reaction may slow down. The reaction can be carried out using organic solvents such as hexane, cyclohexane, octane, toluene, and xylene, depending on the need, or it can be carried out in a solvent-free environment. For example, an acidic catalyst is added to a mixed solution of a compound having a 2-bromoethylbenzene structure, a halogenated methyl aryl compound, and a solvent. Water is then removed from the system via azeotropic extraction, provided the catalyst contains water. The reaction is then carried out at 40°C to 180°C, preferably 50°C to 170°C, for 0.5 to 20 hours. After the reaction, the acidic catalyst can be neutralized with an alkaline aqueous solution, but it can also proceed to the water washing step without neutralization. Regarding the water washing step, a non-water-soluble organic solvent is added to the oil layer, and repeated water washing is performed until the wastewater becomes neutral. The softening point of the compound represented by formula (2) is preferably below 80°C, and more preferably below 70°C. If the softening point is below 80°C, the viscosity when deriving the compound represented by formula (1) becomes lower. This makes it easier to ensure flowability, without impairing the impregnation of glass cloth or carbon fiber, and facilitates B-stage processes such as prepreg forming. When increasing the diluent to reduce viscosity, the resin may not adhere sufficiently to the fibrous material during the impregnation step. The curable resin composition of the present invention contains a maleimide compound as component (B). A maleimide compound refers to a compound having one or more maleimide groups within its molecule. As component (B), examples include: 4,4'-diphenylmethane bismaleimide, polyphenylmethane maleimide, m-phenyl bismaleimide, 2,2'-bis[4-(4-maleimidephenoxy)phenyl]propane, 3,3'-dimethyl-5,5'-diethyl-4,4'-diphenylmethane bismaleimide, 4-methyl-1,3-phenyl bismaleimide, 4,4'-diphenyl ether bismaleimide, 4,4'-diphenyl bismaleimide, 1,3-bis(3-maleimidephenoxy)benzene, 1,3-bis(4-maleimidephenoxy)benzene, and Xyloc type maleimide compounds (Annilius ( Anilix maleimide (manufactured by Mitsui Chemicals Fine Chemicals Co., Ltd.), biphenyl aralkyl maleimide compounds (solidified by removing the resin solution containing maleimide compound (M2) described in Example 4 of Japanese Patent Application Publication No. 2009-001783 by vacuum distillation), diaminocumylbenzene maleimide (maleimide compounds described in International Publication No. 2020 / 054601 and compounds represented by the following formula (3)), maleimide compounds having an indane structure described in Japanese Patent No. 6629692 or International Publication No. 2020 / 217679, "Material Stage (MATERIAL) The maleimide compounds described in "Epoxy Resin CAS Number Story - Hardener CAS Number Memorandum No. 31 Bismaleimide (1)" or "Material Stage" Vol. 19, No. 2, 2019 "Epoxy Resin CAS Number Story - Hardener CAS Number Memorandum No. 32 Bismaleimide (2)" are not limited to these. Furthermore, one or more of these compounds may be used.Of these, from the viewpoints of solvent solubility, dielectric properties, and heat resistance, 2,2'-bis[4-(4-maleimidephenoxy)phenyl]propane, 3,3'-dimethyl-5,5'-diethyl-4,4'-diphenylmethane bismaleimide, and biphenyl aralkyl-type maleimide compounds (the maleimide compound (M2) described in Example 4 of Japanese Patent Application Publication No. 2009-001783 is removed by vacuum distillation) The compounds that are solidified from resin solutions, diaminocumylbenzene type maleimides (maleimide compounds disclosed in International Publication No. 2020 / 054601 and compounds represented by the following formula (3), maleimide compounds with indane structure disclosed in International Publication No. 2020 / 217679, are preferably compounds represented by the following formula (3) in view of their compatibility with low polarity resins such as styrene-butadiene rubber or polybutadiene, polyphenylene ether compounds. [Chemistry 3] (In formula (3), there are multiple Rs that exist independently, representing hydrocarbon groups or alkyl halides with 1 to 10 carbon atoms; p and r represent integers from 0 to 4, q represents integers from 0 to 3, n is the average of the number of repetitions, 1 ≦ n ≦ 20) The optimal ranges of R, p, r, q, and n in equation (3) are the same as those in equation (1). The curable resin composition of the present invention contains a cyanate ester compound as component (C). Component (C) is a compound obtained by reacting a phenolic resin with a cyanide halide. Specific examples include: dicyanatobenzene, tricyanoxybenzene, dicyanoxynaphthalene, dicyanoxybiphenyl, 2,2'-bis(4-cyanoxyphenyl)propane, bis(4-cyanoxyphenyl)methane, bis(3,5-dimethyl-4-cyanoxyphenyl)methane, 2,2'-bis(3,5-dimethyl-4-cyanoxyphenyl)propane, 2,2'-bis(4-cyanoxyphenyl)ethane, 2,2'-bis(4-cyanoxyphenyl)hexafluoropropane, bis(4-cyanoxyphenyl) sulfide, bis(4-cyanoxyphenyl) varnish cyanate, and compounds in which the hydroxyl groups of a phenol-dicyclopentadiene cocondensate are converted to cyanate ester groups, etc., but are not limited to these. Furthermore, one or more of these compounds may be used. Furthermore, the cyanate ester compound described in Japanese Patent Application Publication No. 2005-264154 is particularly suitable as a cyanate ester compound due to its excellent low hygroscopicity, flame retardancy, and dielectric properties. To trimerize the cyanate ester groups and form a sym-triazine ring as needed, the cyanate ester resin may also contain catalysts such as zinc naphthenate, cobalt naphthenate, copper naphthenate, lead naphthenate, zinc octanoate, tin octanoate, lead acetone, and dibutyltin maleate. The catalyst is preferably used in amounts of 0.0001 to 0.10 parts by mass, and more preferably 0.00015 to 0.0015 parts by mass, relative to 100 parts by mass of the total mass of the cyanate ester resin and components (A) to (C). In the curable resin composition of the present invention, when the total amount of components (B) and (C) is set to 100 parts by mass, the content of component (A) is preferably 1 part by mass or more and 300 parts by mass or less, more preferably 5 parts by mass or more and 200 parts by mass or less, and even more preferably 10 parts by mass or more and 150 parts by mass or less. When the content of component (A) is less than 1 part by mass, there is a risk of deterioration of dielectric properties or easy water absorption, and when it is more than 100 parts by mass, it is sometimes difficult to exhibit good adhesion to copper foil, etc. The amount of component (B) added is preferably 1 to 300 parts by mass relative to 100 parts by mass of component (A), more preferably 5 to 250 parts by mass, and even more preferably 10 to 200 parts by mass. When the amount of component (B) added is less than 1 part by mass, the adhesion of the copper foil may be reduced, and when it is more than 300 parts by mass, the hardening properties or water absorption properties may be deteriorated. The amount of component (C) added is preferably 1 to 300 parts by mass relative to 100 parts by mass of component (B), more preferably 5 to 250 parts by mass, and even more preferably 10 to 200 parts by mass. When the amount of component (C) added is less than 1 part by mass, the curing properties or copper foil adhesion may decrease, and when it is more than 300 parts by mass, the water absorption properties may deteriorate. [Curing Accelerator] The curing properties of the curable resin composition of the present invention can also be improved by adding a curing accelerator. Preferably, the curing accelerator is an anionic curing accelerator that promotes the curing reaction by generating anions through irradiation or heating with ultraviolet or visible light, or a cationic curing accelerator that promotes the curing reaction by generating cations through irradiation or heating with ultraviolet or visible light. Examples of anionic hardening accelerators include: imidazoles such as 2-methylimidazole, 2-ethylimidazole, and 2-ethyl-4-methylimidazole; trialkylamines such as triethylamine and tributylamine; 4-dimethylaminopyridine, benzyldimethylamine, 2,4,6-tris(dimethylaminomethyl)phenol, and 1,8-diazabicyclo(5,4,0)-undecene, with 4-dimethylaminopyridine and 1,8-diazabicyclo(5,4,0)-undecene being preferred. Other examples include phosphines such as triphenylphosphine, tetrabutylammonium salts, triisopropylmethylammonium salts, trimethyldecylammonium salts, hexadecyltrimethylammonium salts, and hexadecyltrimethylammonium hydroxide, but these are not limited to these. Furthermore, one or more of these may be used. Examples of cationic hardening accelerators include: quaternary phosphonium salts such as triphenylbenzylphosphonium salt, triphenylethylphosphonium salt, and tetrabutylphosphonium salt (the counter ions of quaternary salts are halogens, organic acid anions, hydroxide ions, etc., without specific designation, but preferably organic acid anions and hydroxide ions), tin octoate, zinc carboxylate (zinc 2-ethylhexanoate, zinc stearate, zinc betaine, zinc myristate), zinc phosphate esters (zinc octyl phosphate, zinc stearyl phosphate), and other transition metal compounds (transition metal salts), but are not limited to these. Furthermore, one or more of these can be used. When the total of components (B) and (C) is set to 100 parts by mass, the amount of hardening accelerator used is 0.01 to 5.0 parts by mass as needed. [Inorganic Fillers] The curable resin composition of the present invention may contain inorganic fillers. Examples of inorganic fillers include: fused silica, crystalline silica, porous silica, alumina, zircon, calcium silicate, calcium carbonate, quartz powder, silicon carbide, silicon nitride, boron nitride, zirconium oxide, aluminum nitride, graphite, forsterite, steatite, spinel, mullite, titanium dioxide, talc, clay, iron oxide, asbestos, glass powder, etc., or these can be formed into spherical or fragmented inorganic fillers, but are not limited to these. Furthermore, one or more of these fillers may be used. Regarding the inorganic filler, when obtaining a curable resin composition for semiconductor sealing, the amount of inorganic filler used is preferably 80 to 92 parts by weight, and more preferably 83 to 90 parts by weight, out of 100 parts by weight of the curable resin composition. Furthermore, when obtaining a curable resin composition for interlayer insulating layer forming materials, copper laminates or prepregs, RCC and other substrate materials, the amount of the inorganic filler used is preferably 5 to 80 parts by weight, and more preferably 10 to 60 parts by weight, out of 100 parts by weight of the curable resin composition. [Polymerization Initiator] The curable resin composition of the present invention can also have its curability improved by adding a polymerization initiator. A polymerization initiator is a compound capable of polymerizing olefin functional groups such as ethylene unsaturated bonds, and examples include olefin metathesis polymerization initiators, anionic polymerization initiators, cationic polymerization initiators, and free radical polymerization initiators. Preferably, a free radical polymerization initiator with curability and moderate stability is used. A free radical polymerization initiator is a compound that generates free radicals and initiates a chain polymerization reaction by irradiation with ultraviolet or visible light or heating. Examples of usable free radical polymerization initiators include organic peroxides, azo compounds, and benzopinnatols. Since organic peroxides have less impact on curing temperature control, exhaust gas suppression, and the electrical properties of decomposition products, they are preferred. Examples of such organic peroxides include: ketone peroxides such as methyl ethyl ketone peroxide and acetyl acetone peroxide; diacyl peroxides such as benzoyl peroxide; dialkyl peroxides such as dicumyl peroxide and 1,3-bis(tert-butylperoxyisopropyl)benzene; peroxy ketals such as tert-butyl peroxybenzoate and 1,1-di-tert-butylperoxycyclohexane; α-cumyl peroxyneodecanate, tert-butyl peroxyneodecanate, tert-butyl peroxytrimethylacetate, 1,1,3,3-tetramethylbutylperoxy-2-ethylhexanoate, and tert-pentylperoxy-2-ethyl Alkyl peroxy esters such as hexanoates, tert-butylperoxy-2-ethylhexanoate, tert-pentylperoxy-3,5,5-trimethylhexanoate, tert-butylperoxy-3,5,5-trimethylhexanoate, and tert-pentylperoxybenzoate; peroxy carbonates such as di-2-ethylhexyl peroxydicarbonate, bis(4-tert-butylcyclohexyl)peroxydicarbonate, tert-butylperoxyisopropyl carbonate, and 1,6-bis(tert-butylperoxycarbonyloxy)hexane; tert-butyl hydroperoxide, cumene hydroperoxide, tert-butyl peroxyoctanoate, and lauryl peroxide, but not limited to these. Furthermore, one or more of these may be used. Among the organic peroxides, ketone peroxides, diacyl peroxides, hydroperoxides, dialkyl peroxides, peroxy ketals, alkyl peroxy esters, percarbonates, etc., are preferred, and dialkyl peroxides are even more preferred. Examples of the azo compounds include, but are not limited to, azobisisobutyronitrile, 4,4'-azobis(4-cyanopentaic acid), and 2,2'-azobis(2,4-dimethylpentanonitrile). Furthermore, one or more of these compounds may be used. The amount of polymerization initiator added is preferably 0.01 to 5 parts by mass, and more preferably 0.01 to 3 parts by mass, relative to 100 parts by mass of the curable resin composition. If the amount of polymerization initiator used is less than 0.01 parts by mass, there is a risk of insufficient molecular weight elongation during the polymerization reaction; if it is more than 5 parts by mass, there is a risk of impairing dielectric properties such as dielectric constant and dielectric loss tangent. [Polymerization Inhibitor] The curable resin composition of the present invention may also contain a polymerization inhibitor. By containing a polymerization inhibitor, storage stability can be improved, and the reaction start temperature can be controlled. By controlling the reaction start temperature, flowability can be easily ensured, and B-stage processes such as prepreg formation become easier without compromising impregnation in glass fiber cloth, etc. If the polymerization reaction proceeds excessively during prepreg formation, adverse conditions such as difficulty in lamination can easily occur during the lamination step. The polymerization inhibitor may be added during the synthesis of component (A) or after synthesis. The amount of polymerization inhibitor used relative to 100 parts by weight of component (A) is 0.008 parts by weight to 1 part by weight, preferably 0.01 parts by weight to 0.5 parts by weight. Examples of polymerization inhibitors include phenolic, sulfur-based, phosphorus-based, hindered amine-based, nitroso-based, and nitrocellulose-based inhibitors. Furthermore, one or more polymerization inhibitors may be used. Of these, phenolic, hindered amine, nitroso-based, and nitrocellulose-based inhibitors are preferred in this invention. Examples of phenolic polymerization inhibitors include: 2,6-di-tert-butyl-p-cresol, butylated hydroxyanisole, 2,6-di-tert-butyl-p-ethylphenol, stearyl-β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, isooctyl-3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, 2,4-bis-(n-octylthio)-6-(4-hydroxy-3,5-di-tert-butylaniline)-1,3,5-triazine, 2,4-bis[(octylthio)methyl]-o-cresol, and other monophenols, as well as 2,2'-methylenebis(4-methyl- 6-tert-butylphenol), 2,2'-methylenebis(4-ethyl-6-tert-butylphenol), 4,4'-thiobis(3-methyl-6-tert-butylphenol), 4,4'-butylenebis(3-methyl-6-tert-butylphenol), triethylene glycol-bis[3-(3-tert-butyl-5-methyl-4-hydroxyphenyl)propionate], 1,6-hexanediol-bis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], N,N'-hexamethylenebis(3,5-di-tert-butyl-4-hydroxy-hydrogenated cinnamylamine), 2,2-thio-diethylethylene Bisphenols such as bis(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, 3,5-di-tert-butyl-4-hydroxybenzyl phosphate-diethyl ester, 3,9-bis[1,1-dimethyl-2-{β-(3-tert-butyl-4-hydroxy-5-methylphenyl)propoxy}ethyl]2,4,8,10-tetraoxaspiro[5,5]undecane, and bis(3,5-di-tert-butyl-4-hydroxybenzyl sulfonate ethyl ester) calcium; 1,1,3-tris(2-methyl-4-hydroxy-5-tert-butylphenyl)butane, 1,3,5-trimethyl-2,4,6 The list includes, but is not limited to, high molecular weight phenols such as tris(3,5-di-tert-butyl-4-hydroxybenzyl)benzene, tetra-[methylene-3-(3',5'-di-tert-butyl-4'-hydroxyphenyl)propionate]methane, bis[3,3'-bis-(4'-hydroxy-3'-tert-butylphenyl)butyrate]ethylene glycol ester, tris(3,5-di-tert-butyl-4-hydroxybenzyl)-isocyanurate, 1,3,5-tris(3',5'-di-tert-butyl-4'-hydroxybenzyl)-S-triazine-2,4,6-(1H,3H,5H)trione, and tocopherol. Examples of sulfur-based polymerization inhibitors include, but are not limited to, dilauryl 3,3'-thiodipropionate, dimyristyl 3,3'-thiodipropionate, and distearate 3,3'-thiodipropionate. Examples of phosphorus-based polymerization inhibitors include: triphenyl phosphite, diphenyl isodecanyl phosphite, phenyl diisodecyl phosphite, tris(nonylphenyl) phosphite, pentaerythritol diisodecyl phosphite, tris(2,4-di-tert-butylphenyl) phosphite, cyclic neopentanetetrayl bis(octadecyl) phosphite, cyclic neopentanetetrayl bis(2,4-di-tert-butylphenyl) phosphite, cyclic neopentanetetrayl bis(2,4-di-tert-butyl-4-methylphenyl) phosphite, bis[2] Phosphites such as tributyl-6-methyl-4-{2-(octadecyloxycarbonyl)ethyl}phenyl]hydrophosphite, 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, 10-(3,5-di-tert-butyl-4-hydroxybenzyl)-9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, 10-decoxy-9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, and oxaphosphaphenanthrene oxides, but not limited to these. Examples of hindered amine polymerization inhibitors include: Adekastab LA-40MP, Adekastab LA-40Si, Adekastab LA-402AF, Adekastab LA-87, Adekastab LA-82, Adekastab LA-81, Adekastab LA-77Y, Adekastab LA-77G, Adekastab LA-72, Adekastab LA-68, and Adekastab. LA-63P, Adekastab LA-57, Adekastab LA-52, Chimassorb 2020FDL, Chimassorb 944FDL, Chimassorb 944LD, Tinuvin 622SF, Tinuvin PA144, Tinuvin 765, Tinuvin 770DF, Tinuvin XT55FB, Tinuvin 111FDL, Tinuvin 783FDL, Tinuvin 791FB, etc., but not limited to these. Examples of nitrosyl polymerization inhibitors include, but are not limited to, p-nitrosophenol, N-nitrosodiphenylamine, and ammonium salts of N-nitrosophenylhydroxyamine (cupferron). Among these, the ammonium salt of N-nitrosophenylhydroxyamine (cupferron) is preferred. Examples of nitroradical polymerization inhibitors include, but are not limited to, di-tert-butyl nitroxide, 2,2,6,6-tetramethylpiperidine-1-oxy, 4-hydroxy-2,2,6,6-tetramethylpiperidine-1-oxy, 4-oxo-2,2,6,6-tetramethylpiperidine-1-oxy, 4-amino-2,2,6,6-tetramethylpiperidine-1-oxy, 4-methoxy-2,2,6,6-tetramethylpiperidine-1-oxy, 4-acetoxy-2,2,6,6-tetramethylpiperidine-1-oxy, and 4-benzoxoxy-2,2,6,6-tetramethylpiperidine-1-oxy. [Flame Retardant] A flame retardant can be used in the curable resin composition of the present invention. Examples of flame retardants include halogen-based flame retardants, inorganic flame retardants (antimony compounds, metal hydroxides, nitrogen compounds, boron compounds, etc.), and phosphorus-based flame retardants. From the viewpoint of achieving halogen-free flame retardancy, phosphorus-based flame retardants are preferred. The phosphorus-based flame retardant can be either reactive or additive. Specific examples include: trimethyl phosphate, triethyl phosphate, trimethylol phosphate, tri(xylyl) phosphate, tolyl diphenyl phosphate, tolyl-2,6-di(xylyl) phosphate, 1,3-epoxyphenylbis(xylyl) phosphate, 1,4-epoxyphenylbis(xylyl) phosphate, 4,4'-biphenyl(xylyl) phosphate, and other phosphate esters; phosphanes such as 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide and 10-(2,5-dihydroxyphenyl)-10H-9-oxa-10-phosphaphenanthrene-10-oxide; and phosphorus-containing epoxy compounds obtained by reacting epoxy resin with the active hydrogen of the aforementioned phosphanes, as well as red phosphorus, etc., but are not limited to these. Furthermore, one or more of these may be used. The exemplary substances are preferably phosphate esters, phosphine derivatives, or phosphorus-containing epoxy compounds, particularly 1,3-epoxyphenylbis(di(xylyl)phosphate), 1,4-epoxyphenylbis(di(xylyl)phosphate), 4,4'-biphenyl(di(xylyl)phosphate), or phosphorus-containing epoxy compounds. When the total amount of components (A) to (C) is set to 100 parts by mass, the flame retardant content is preferably in the range of 0.1 parts by mass to 0.6 parts by mass. If it is less than 0.1 parts by mass, the flame retardancy may become insufficient; if it is more than 0.6 parts by mass, it may adversely affect the hygroscopicity and dielectric properties of the cured material. [Light Stabilizer] A light stabilizer can be used in the curable resin composition of the present invention. As a light stabilizer, a hindered amine-based light stabilizer is preferred, and a hindered amine light stabilizer (HALS) is particularly preferred. Examples of HALS include: the reaction product of dibutylamine-1,3,5-triazine-N,N'-bis(2,2,6,6-tetramethyl-4-piperidinyl)-1,6-hexamethylenediamine with N-(2,2,6,6-tetramethyl-4-piperidinyl)butylamine, the reaction product of dimethyl-1-(2-hydroxyethyl)-4-hydroxy-2,2,6,6-tetramethylpiperidinyl succinate, and poly[{6-(1,1,3,3-tetramethylbutyl)amino-1,3,5-triazine-2,4-diyl}{(2,2,6,6-tetramethyl-4-piperidinyl)imino}hexamethylene{(2,2,6,6-tetramethyl-4-diyl ... The following are examples of bis(1,2,2,6,6-pentamethyl-4-piperidinyl)[[3,5-bis(1,1-dimethylethyl)-4-hydroxyphenyl]methyl]butyl malonate, bis(2,2,6,6-tetramethyl-4-piperidinyl) sebacate, bis(1,2,2,6,6-pentamethyl-4-piperidinyl) sebacate, bis(1-octoxy-2,2,6,6-tetramethyl-4-piperidinyl) sebacate, 2-(3,5-di-tert-butyl-4-hydroxybenzyl)-2-n-butylmalonate bis(1,2,2,6,6-pentamethyl-4-piperidinyl) ester, but are not limited to these. Furthermore, one or more of these may be used. When the total amount of components (A) to (C) is set to 100 parts by mass, the content of the light stabilizer is preferably in the range of 0.001 parts by mass to 0.1 parts by mass. If it is less than 0.001 parts by mass, there is a risk that the light stabilizing effect may not be apparent, and if it is more than 0.1 parts by mass, there is a risk that it may have an adverse effect on the hygroscopicity and dielectric properties of the cured material. [Adhesive Resin] The curable resin composition of the present invention may use an adhesive resin. Examples of adhesive resins include, butyral resins, acetal resins, acrylic resins, epoxy-nylon resins, nitrile butadiene rubber (NBR)-phenol resins, epoxy-NBR resins, silicone resins, etc., but are not limited to these. Furthermore, one or more of these resins may be used. The amount of adhesive resin used is preferably within the range that does not impair the flame retardancy and heat resistance of the hardened material. When the total amount of components (A) to (C) is set to 100 parts by weight, it is preferably 0.05 parts by weight to 50 parts by weight, and even more preferably 0.05 parts by weight to 20 parts by weight as needed. [Additives] Additives may be used in the curable resin composition of the present invention. Examples of additives include modified acrylonitrile copolymers, polyethylene, fluororesins, silicone gels, silicone oils, surface treatment agents for fillers such as silane coupling agents, release agents, carbon black, phthalocyanine blue, phthalocyanine green, and other colorants. The amount of additives is preferably 1,000 parts by weight or less, and more preferably 700 parts by weight or less, relative to 100 parts by weight of the curing resin composition. The curable resin composition of the present invention may further utilize epoxy resin, reactive ester compound, phenolic resin, polyphenylene ether compound, amine resin, compound having vinyl unsaturated bonds, isocyanate resin, polyamide resin, polyimide resin, polybutadiene and its modified forms, polystyrene and its modified forms, etc., and may use one or more of these. Among these compounds, in terms of the balance of heat resistance, adhesion, and dielectric properties, it is preferable to contain polyphenylene ether compound, compound having vinyl unsaturated bonds, cyanate resin, polybutadiene and its modified forms, and polystyrene and its modified forms. By containing these compounds, the brittleness of the cured product can be improved and the adhesion to metals can be enhanced, and cracks in the encapsulation during reflow soldering or reliability tests such as thermal cycling can be suppressed. Regarding the amount of the compound used, unless otherwise specified, it is preferably 10 parts by mass or less, more preferably 5 parts by mass or less, and particularly preferably 3 parts by mass or less, relative to component (A). Furthermore, the lower limit is preferably 0.1 parts by mass or more, more preferably 0.25 parts by mass or more, and more preferably 0.5 parts by mass or more. By setting it within the aforementioned range, the effects of the heat resistance or dielectric properties of component (A) can be effectively utilized while also incorporating the effects of the added compounds. Examples of these components can be used as follows. [Epoxy Resin] The following are examples of preferred epoxy resins, but are not limited to these. Furthermore, epoxy resins can be in liquid or solid form, and one type or multiple types can be used. Examples of liquid epoxy resins include: bisphenol A type epoxy resin, bisphenol F type epoxy resin, bisphenol AF type epoxy resin, naphthalene type epoxy resin, glycidyl ester type epoxy resin, glycidylamine type epoxy resin, phenolic varnish type epoxy resin, alicyclic epoxy resin with ester skeleton, cyclohexane type epoxy resin, cyclohexanediethanol type epoxy resin, and epoxy resin with butadiene structure. Specific examples include: "RE310S", "RE410S" (manufactured by Nippon Kayaku Co., Ltd., bisphenol A type epoxy resin), "RE303S", "RE304S", "RE403S", "RE404S" (manufactured by Nippon Kayaku Co., Ltd., bisphenol F type epoxy resin), "HP4032", "HP4032D", "HP4032SS" (manufactured by DIC Corporation, naphthalene type epoxy resin), "828US", "jER828EL", "825", and "828EL". (The above are bisphenol A type epoxy resins manufactured by Mitsubishi Chemical Corporation), "jE807", "1750" (the above are bisphenol F type epoxy resins manufactured by Mitsubishi Chemical Corporation), "jER152" (phenolic varnish type epoxy resin manufactured by Mitsubishi Chemical Corporation), "630", "630LSD" (the above are glycidyl amine type epoxy resins manufactured by Mitsubishi Chemical Corporation), "ZX1059" (a mixture of bisphenol A type epoxy resin and bisphenol F type epoxy resin manufactured by Nippon Steel & Sumitomo Metal Chemicals Co., Ltd.), "EX-721" (Nagase Chemicals Co., Ltd.) The following epoxy resins are manufactured by ChemteX: glycidyl ester type epoxy resin, Celloxide 2021P (manufactured by Daicel, an alicyclic epoxy resin with an ester backbone), PB-3600 (manufactured by Daicel, an epoxy resin with a butadiene structure), ZX1658, and ZX1658GS (manufactured by Nippon Steel & Sumitomo Chemical Co., Ltd., liquid 1,4-glycidylcyclohexane type epoxy resin). These can be used individually or in combination of two or more. As a solid epoxy resin, preferred types include, for example, xylenol-type epoxy resin, naphthalene-type epoxy resin, naphthalene-type tetrafunctional epoxy resin, cresol-phenolic varnish-type epoxy resin, dicyclopentadiene-type epoxy resin, triphenol-type epoxy resin, naphthol-type epoxy resin, biphenyl-type epoxy resin, naphthyl ether-type epoxy resin, anthracene-type epoxy resin, bisphenol A-type epoxy resin, bisphenol AF-type epoxy resin, and tetraphenylethane-type epoxy resin. Examples include naphthol-type epoxy resin, bisphenol AF-type epoxy resin, naphthalene-type epoxy resin, and biphenyl-type epoxy resin.Specific examples include: "HP4032H" (manufactured by DIC, a naphthalene-type epoxy resin), "HP-4700", "HP-4710" (both manufactured by DIC, naphthalene-type tetrafunctional epoxy resins), "N-690" (manufactured by DIC, a cresol-phenolic varnish type epoxy resin), "N-695" (manufactured by DIC, a cresol-phenolic varnish type epoxy resin), "HP-7200", "HP-7200HH", and "HP-7 "200H" (manufactured by DIC Corporation, dicyclopentadiene type epoxy resin), "EXA-7311", "EXA-7311-G3", "EXA-7311-G4", "EXA-7311-G4S", "HP-6000" (manufactured by DIC Corporation, naphthyl ether type epoxy resin), "EPPN-502H" (manufactured by Nippon Kayaku Co., Ltd., pyrrolidone type epoxy resin), "NC-7000L", "NC-730 ...200H" (manufactured by DIC Corporation, dicyclopentadiene type epoxy resin), "EXA-7311", "EXA-7311-G3", "EXA-7311-G4", "EXA-7311-G4S", "HP-6000" (manufactured by DIC Corporation, naphthyl ether type epoxy resin), "EPPN-502H" (manufactured by Nippon Kayaku Co., Ltd., pyrrolidone type epoxy resin), "NC-7000L", "NC-7300" (manufactured by Nippon Kayaku Co., Ltd., pyrrolidone type epoxy resin), "200H" (manufactured by DIC Corporation, dicyclopentadiene type epoxy resin), "EXA-7311", "EXA-7311-G3", "EXA-7311-G4", "EXA-7311-G4S", "HP-6000" (manufactured by DIC Corporation, naphthyl The company manufactures the following epoxy resins: Naphthol-cresol phenolic resin (varnish type), "NC-3000H", "NC-3000", "NC-3000L", "NC-3100" (manufactured by Nippon Kayaku Co., Ltd., biphenyl aralkyl type epoxy resin), "XD-1000-2L", "XD-1000-L", "XD-1000-H", "XD-1000-H" (manufactured by Nippon Kayaku Co., Ltd., dicyclopentadiene type epoxy resin), and "ESN475V" (manufactured by Nippon Steel & Sumitomo Chemical Co., Ltd.). Naphthol-type epoxy resin), "ESN485" (manufactured by Nippon Steel & Sumitomo Chemical Co., Ltd., naphthol phenolic varnish type epoxy resin), "YX-4000H", "YX-4000", "YL6121" (manufactured by Mitsubishi Chemical Co., Ltd., biphenyl-type epoxy resin), "YX-4000HK" (manufactured by Mitsubishi Chemical Co., Ltd., bixylenol-type epoxy resin), "YX-8800" (manufactured by Mitsubishi Chemical Co., Ltd., anthracene-type epoxy resin), "PG-100", "CG-500" (manufactured by Osaka Gas Chemical Co., Ltd.), "Osaka Gas Chemical Co., Ltd." Gas Chemicals manufactures a variety of epoxy resins, including fluorene-based epoxy resins, "YL-7760" (manufactured by Mitsubishi Chemical Corporation, bisphenol AF type epoxy resin), "YL-7800" (manufactured by Mitsubishi Chemical Corporation, fluorene type epoxy resin), "jER1010" (manufactured by Mitsubishi Chemical Corporation, solid bisphenol A type epoxy resin), and "jER1031S" (manufactured by Mitsubishi Chemical Corporation, tetraphenylethane type epoxy resin). These resins can be used individually or in combination of two or more. [Reactive Ester Compounds] Reactive ester compounds are compounds whose structure contains at least one ester bond and on both sides of the ester bond are aliphatic chains, aliphatic rings, or aromatic rings. Examples of reactive ester compounds include phenolic esters, thiophenolic esters, N-hydroxyamine esters, and esters of heterocyclic hydroxyl compounds—compounds having two or more highly reactive ester groups per molecule. These compounds can be obtained by condensation reactions of at least one carboxylic acid compound, acid chloride, or thiocarboxylic acid compound with at least one hydroxyl compound or thiol compound. In particular, from the viewpoint of improved heat resistance, it is preferable to obtain them from a carboxylic acid compound or acid chloride and a hydroxyl compound; the hydroxyl compound is preferably a phenolic compound or a naphthol compound. Reactive ester compounds can be used alone or in combination of two or more. Examples of carboxylic acid compounds include benzoic acid, acetic acid, succinic acid, maleic acid, itaconic acid, phthalic acid, isophthalic acid, terephthalic acid, and pyromellitic acid. Examples of such acid chlorides include: acetyl chloride, acrylamide chloride, methacrylamide chloride, malondichlorochloride, succinic dichlorochloride, diglycolyl chloride, pentyl dichlorochloride, octyl dichlorochloride, decandichlorochloride, hexadichlorochloride, dodecanedioyl dichloride, nonadichlorochloride, 2,5-furan dicarbonyl dichloride, phthalic acid chloride, isophthalic acid chloride, terephthalic acid chloride, pyromellitic trimethylol chloride, bis(4-chlorocarbonylphenyl) ether, 4,4'-diphenyl dicarbonyl chloride, 4,4'-azodiphenyl phthalic acid dichloride, etc. Examples of the phenolic compounds and naphthol compounds include, for example: hydroquinone, resorcinol, bisphenol A, bisphenol F, bisphenol S, acid phenolphthalein, methylated bisphenol A, methylated bisphenol F, methylated bisphenol S, phenol, o-cresol, m-cresol, p-cresol, catechol, α-naphthol, β-naphthol, 1,5-dihydroxynaphthol, 1,6-dihydroxynaphthol, 2,6-dihydroxynaphthol, dihydroxybenzophenone, trihydroxybenzophenone, tetrahydroxybenzophenone, phloroglucin, pyroglucinol, dicyclopentadiene-type diphenol compounds, phenolic varnishes, and phenolic resins described later. Here, "dicyclopentadiene-type diphenol compounds" refers to diphenol compounds obtained by the condensation of two molecules of phenol in one molecule of dicyclopentadiene. Preferred examples of active ester compounds include active ester compounds containing a dicyclopentadiene-type diphenol structure, active ester compounds containing a naphthalene structure, active ester compounds containing an acetylated compound of phenolic varnish, active ester compounds containing a benzoylated compound of phenolic varnish, compounds described in Example 2 of International Publication No. 2020 / 095829, and compounds disclosed in International Publication No. 2020 / 059625. Among these, active ester compounds containing a naphthalene structure and active ester compounds containing a dicyclopentadiene-type diphenol structure are more preferred. The term "dicyclopentadiene-type diphenol structure" refers to a divalent structural unit containing a pentylenyl-dicyclopentyl-pentylphenyl group. Commercially available examples of active ester compounds include: "EXB9451", "EXB9460", "EXB9460S", "HPC-8000-65T", "HPC-8000H-65TM", "EXB-8000L-65TM", and "EXB-8150-65T" (manufactured by DIC), which are active ester compounds containing a dicyclopentadiene-type diphenol structure; and "EXB9416-70BK" (manufactured by DIC), which is an active ester compound containing a naphthalene structure. "DC808" (manufactured by Mitsubishi Chemical Corporation), an active ester compound containing phenolic varnishes and acetylated compounds; "YLH1026", "YLH1030", and "YLH1048" (manufactured by Mitsubishi Chemical Corporation), active ester compounds containing phenolic varnishes and acetylated compounds; "DC808" (manufactured by Mitsubishi Chemical Corporation), an active ester curing agent for phenolic varnishes and acetylated compounds; and "EXB-9050L-62M" manufactured by DIC Corporation, an active ester curing agent containing phosphorus atoms. [Phenolic Resins] Phenolic resins are compounds with two or more phenolic hydroxyl groups within their molecules. Examples of phenolic resins include: reaction products of phenols and aldehydes, reaction products of phenols and dienes, reaction products of phenols and ketones, reaction products of phenols and substituted biphenyls, reaction products of phenols and substituted phenyl compounds, reaction products of bisphenols and aldehydes, etc., but are not limited to these. Furthermore, one or more of these can be used. Specific examples of the raw materials described are given below, but are not limited to these. <Phenolics> Phenol, alkyl-substituted phenols, aromatic-substituted phenols, hydroquinone, resorcinol, naphthol, alkyl-substituted naphthol, dihydroxybenzene, alkyl-substituted dihydroxybenzene, dihydroxynaphthalene, etc. <Aldehydes> Formaldehyde, acetaldehyde, alkyl aldehydes, benzaldehyde, alkyl-substituted benzaldehyde, hydroxybenzene, naphthal, glutaraldehyde, o-phthalaldehyde, crotonaldehyde, cinnamaldehyde, furfural, etc. <Diene Compounds> Dicyclopentadiene, terpenes, vinylcyclohexene, norbornene, vinylnorbornene, tetrahydroindene, divinylbenzene, divinylbiphenyl, diisopropenylbiphenyl, butadiene, isoprene, etc. <Ketones> Acetone, methyl ethyl ketone, methyl isobutyl ketone, acetophenone, benzophenone, fluorenone, etc. <Substituted Biphenyls> 4,4'-bis(chloromethyl)-1,1'-biphenyl, 4,4'-bis(methoxymethyl)-1,1'-biphenyl, 4,4'-bis(hydroxymethyl)-1,1'-biphenyl, etc. <Substituted Phenyls> 1,4-bis(chloromethyl)benzene, 1,4-bis(methoxymethyl)benzene, 1,4-bis(hydroxymethyl)benzene, etc. [Polyphenylene ether compounds] From the viewpoint of heat resistance and electrical properties, polyphenylene ether compounds with vinyl unsaturated bonds are preferred, and more preferably polyphenylene ether compounds with acrylic, methacrylic, or styrene structures. Commercially available examples include SA-9000 (manufactured by SABIC, a polyphenylene ether compound with methacrylic groups) and OPE-2St 1200 (manufactured by Mitsubishi Gas Chemical, a polyphenylene ether compound with a styrene structure). The number average molecular weight (Mn) of the polyphenylene ether compound is preferably 500–5000, more preferably 2000–5000, and even more preferably 2000–4000. If the molecular weight is less than 500, the heat resistance of the cured material tends to be insufficient. Furthermore, if the molecular weight is greater than 5000, the melt viscosity becomes high, resulting in insufficient flowability and a tendency for poor molding. Furthermore, reactivity decreases, the curing reaction requires a longer time, the amount of unreacted substances that do not enter the curing system increases, the glass transition temperature of the cured product decreases, and the heat resistance of the cured product tends to decrease. If the number-average molecular weight of the polyphenylene ether compound is 500–5000, it can exhibit excellent heat resistance and formability while maintaining excellent dielectric properties. Moreover, the number-average molecular weight can be specifically determined using methods such as gel permeation chromatography. Polyphenylene ether compounds can be obtained through polymerization or by redistributing high molecular weight polyphenylene ether compounds with a number average molecular weight of approximately 10,000 to 30,000. Alternatively, they can be given free radical polymerization properties by reacting these compounds with compounds containing vinyl unsaturated bonds, such as methacryl chloride, acrylonitrile chloride, and chloromethylstyrene. Polyphenylene ether compounds obtained through redistribution reactions can be obtained, for example, by heating high molecular weight polyphenylene ether compounds in a solvent such as toluene in the presence of phenolic compounds and free radical initiators. Polyphenylene ether compounds obtained through redistribution reactions thus possess hydroxyl groups derived from phenolic compounds that contribute to curing at both ends of the molecular chain, thus maintaining higher heat resistance. Furthermore, they are superior in that functional groups can be introduced at both ends of the molecular chain after modification with compounds containing vinyl unsaturated bonds. Additionally, polyphenylene ether compounds obtained through polymerization reactions exhibit excellent flowability, which is also advantageous. In the case of polyphenylene ether compounds obtained by polymerization, the molecular weight of the polyphenylene ether compound can be adjusted by adjusting the polymerization conditions, etc. Furthermore, in the case of polyphenylene ether compounds obtained by redistribution reactions, the molecular weight of the obtained polyphenylene ether compound can be adjusted by adjusting the conditions of the redistribution reaction, etc. More specifically, this takes into account adjusting the amount of phenolic compound used in the redistribution reaction, etc. That is, the more phenolic compound used, the lower the molecular weight of the obtained polyphenylene ether compound. In this case, poly(2,6-dimethyl-1,4-phenylene ether) and the like can be used as the high molecular weight polyphenylene ether compound subjected to the redistribution reaction. Furthermore, there are no particular limitations on the phenolic compound used in the redistribution reaction; preferably, polyfunctional phenolic compounds having two or more phenolic hydroxyl groups in their molecules, such as bisphenol A, phenolic varnish, cresol varnish, etc., can be used. These can be used alone or in combination of two or more. The content of the polyphenylene ether compound is not particularly limited, but when the total mass of components (A) to (C) is set to 100 parts by mass, it is preferably 5 parts by mass to 1000 parts by mass, and more preferably 10 parts by mass to 750 parts by mass. If the content of the polyphenylene ether compound is within the aforementioned range, a cured product that not only has excellent heat resistance but also fully utilizes the excellent dielectric properties of the polyphenylene ether compound can be obtained, which is preferred in this respect. [Amine Resins] Amine resins are compounds with two or more amine groups within their molecules. Examples of amine resins include: diaminodiphenylmethane, diaminodiphenylmethane, isophorone diamine, naphthyldiamine, aniline phenolic varnish (the product of the reaction of aniline and formalin), N-methylaniline phenolic varnish (the product of the reaction of N-methylaniline and formalin), n-ethylaniline phenolic varnish (the product of the reaction of n-ethylaniline and formalin), 2-methylaniline reacting with formalin, 2,6-diisopropylaniline reacting with formalin, 2,6-diethylaniline reacting with formalin, 2-ethyl-6-ethylaniline reacting with formalin, 2,6-dimethylaniline reacting with formalin, and amine resins produced by the reaction of aniline with xylylene. Aniline resins obtained by reacting aniline with chloride, reaction products of aniline with substituted biphenyls (such as 4,4'-bis(chloromethyl)-1,1'-biphenyl and 4,4'-bis(methoxymethyl)-1,1'-biphenyl, as described in Japanese Patent No. 6429862, reaction products of aniline with substituted phenyls (such as 1,4-bis(chloromethyl)benzene, 1,4-bis(methoxymethyl)benzene and 1,4-bis(hydroxymethyl)benzene, 4,4'-(1,3-epoxyphenyldiisopropylidene)bisaniline, reaction products of aniline with diisopropylbenzene, dimerized diamines, etc., are not limited to these. Furthermore, one or more of these may be used. [Compounds containing vinyl unsaturated bonds] Compounds containing vinyl unsaturated bonds are compounds in which there is one or more vinyl unsaturated bonds in the molecule that can be polymerized by heat or light, with or without a polymerization initiator. Examples of compounds containing vinyl unsaturated bonds include, for instance, the reaction products of the aforementioned phenolic resins with halogenated compounds containing vinyl unsaturated bonds (chloromethylstyrene, allyl chloride, methylallyl chloride, acrylamide chloride, methacrylamide chloride, etc.); reaction products of phenols containing vinyl unsaturated bonds (2-allylphenol, 2-propenylphenol, 4-allylphenol, 4-propenylphenol, eugenol, isoeugenol, etc.) with halogenated compounds (1,4-bis(chloromethyl)benzene, 4,4'-bis(chloromethyl)biphenyl, 4,4'-difluorobenzophenone, 4,4'-dichlorobenzophenone, 4,4'-dibromobenzophenone, cyanuric chloride, etc.); reaction products of epoxy resins or alcohols with (meth)acrylic acids (acrylic acid, methacrylic acid, etc.); and acid-modified products of these compounds, but are not limited to these. Furthermore, one of these can be used, or multiple can be used together. [Isocyanate resin] Isocyanate resin is a compound with two or more isocyanate groups in its molecule. Examples of isocyanate resins include, but are not limited to, aromatic diisocyanates such as terephthalic diisocyanate, isophthalic diisocyanate, p-xylene diisocyanate, m-xylene diisocyanate, 2,4-toluene diisocyanate, 2,6-toluene diisocyanate, 4,4'-diphenylmethane diisocyanate, and naphthalene diisocyanate; aliphatic or alicyclic diisocyanates such as isophorone diisocyanate, hexamethylene diisocyanate, 4,4'-dicyclohexylmethane diisocyanate, hydrogenated xylene diisocyanate, norbornene diisocyanate, and lysine diisocyanate; biuret forms of one or more isocyanate monomers; isocyanates formed by trimerization of the aforementioned diisocyanate compounds; and polyisocyanates obtained by the aminoformation reaction of the aforementioned isocyanate compounds with polyol compounds. Furthermore, one or more of these resins may be used, or multiple resins may be used in combination. [Polyamide Resin] Examples of polyamide resins include reaction products of diamines, diisocyanates, oxazolines, and dicarboxylic acids; reaction products of diamines and acid chlorides; and ring-opening polymers of amide compounds. Furthermore, one or more of these can be used. Specific examples of the raw materials are given below, but the use is not limited to these. <Diamines> Ethylenediamine, trimethylenediamine, tetramethylenediamine, pentamethylenediamine, hexamethylenediamine, heptamethylenediamine, octamethylenediamine, nonamethylenediamine, decanediamine, undecanediamine, dodecanediamine, tridecanediamine, tetradecanediamine, pentadecanediamine, hexadecanediamine, heptadecananediamine, octadecanediamine, nonadecananediamine, eicosanediamine, 2-methyl-1,5-diaminopentane, 2-methyl-1,8-diaminooctane, dimers Diamine, cyclohexanediamine, bis-(4-aminocyclohexyl)methane, bis(3-methyl-4-aminocyclohexyl)methane, xylenediamine, norbornenediamine, isophoronediamine, diaminomethyltricyclodecane, phenylenediamine, diethyltoluenediamine, naphthyldiamine, diaminodiphenylmethane, bis(4-amino-3,5-dimethylphenyl)methane, bis(4-amino-3,5-diethylphenyl)methane, 4,4'-methylenebis-o-toluidine, 4,4'-Methylenebis-o-ethylaniline, 4,4'-Methylenebis-2-ethyl-6-methylaniline, 4,4'-Methylenebis-2,6-diisopropylaniline, 4,4-Ethylenediphenylamine, Diaminodiphenyl ether, 1,3-bis(3-aminophenoxy)benzene, 1,3-bis(4-aminophenoxy)benzene, 4,4-bis(4-aminophenoxy)biphenyl, 2,2-bis[4-(4-aminophenoxy) [4-(4-aminophenoxy)phenyl]propane, bis[4-(4-aminophenoxy)phenyl]phenyl, 2,2-bis(3-amino-4-hydroxyphenyl)propane, 2,2-bis(4-aminophenyl)hexafluoropropane, 4,4'-(1,3-aminophenyldiisopropylidene)bisaniline, 4,4'-(1,4-aminophenyldiisopropylidene)bisaniline, 9,9-bis(4-aminophenyl)fluorene, 2,7-diaminofluorene, aminobenzylamine, diaminobenzophenone, etc. <Diisocyanates> Benzene diisocyanate, toluene diisocyanate, 1,3-bis(isocyanomethyl)benzene, 1,3-bis(isocyanomethyl)cyclohexane, bis(4-isocyanophenyl)methane, isophorone diisocyanate, 1,3-bis(2-isocyano-2-propyl)benzene, 2,2-bis(4-isocyanophenyl)hexafluoropropane, dicyclohexylmethane-4,4'-diisocyanate, etc.<Dicarboxylic Acids> Oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, octanoic acid, azelaic acid, sebacic acid, undecanoic acid, dodecanoic acid, terephthalic acid, isophthalic acid, 5-hydroxyisophthalic acid, 2-chloroterephthalic acid, 2-methylterephthalic acid, 5-methylisophthalic acid, sodium isophthalate-5-sulfonate, hexahydroterephthalic acid, hexahydroisophthalic acid, cyclohexanedicarboxylic acid, biphenyl dicarboxylic acid, naphthalenedicarboxylic acid, benzophenone dicarboxylic acid, furan dicarboxylic acid, 4,4'-dicarboxylic acid diphenyl ether, 4,4'-dicarboxylic acid diphenyl sulfide, etc. <Lactamines> ε-caprolactam, ω-undecanoyllactone, ω-laurylamide, etc. [Polyimide Resin] Examples of polyimide resins include the reaction products of the diamine and the tetracarboxylic dianhydrides listed below, but are not limited to these. Furthermore, one or more of these can be used. <Tetracarboxylic Dianhydride> 4,4'-(hexafluoroisopropylidene) phthalic anhydride, 5-(2,5-dioxotetrahydro-3-furanyl)-3-methyl-cyclohexene-1,2-dicarboxylic anhydride, pyromellitic dianhydride, 1,2,3,4-benzenetetracarboxylic anhydride, 3,3',4,4'-benzophenonetetracarboxylic anhydride, 2,2',3,3'-benzophenonetetracarboxylic anhydride, 3,3',4,4'-biphenyltetracarboxylic anhydride, 3,3',4,4'-diphenyltetracarboxylic anhydride, 2,2',3,3'-biphenyltetracarboxylic anhydride, methylene-4,4'-phthalic anhydride, 1,1-ethylidene-4,4'-phthalic anhydride, 2,2'-propylidene -4,4'-Diphthalic anhydride, 1,2-Ethyl-4,4'-Diphthalic anhydride, 1,3-Trimethylene-4,4'-Diphthalic anhydride, 1,4-Tetramethylene-4,4'-Diphthalic anhydride, 1,5-Pentamethylene-4,4'-Diphthalic anhydride, 4,4'-Oxyphthalic anhydride, Thio-4,4'-Diphthalic anhydride, Sulfo-4,4'-Diphthalic anhydride, 1,3-Bis(3,4-dicarboxyphenyl)phthalic anhydride, 1,3-Bis(3,4-dicarboxyphenoxy)phthalic anhydride, 1,4-Bis(3,4-dicarboxyphenoxy)phthalic anhydride, 1,3-Bis[2-(3 [3,4-dicarboxyphenyl)-2-propyl]phenyl dianhydride, 1,4-bis[2-(3,4-dicarboxyphenyl)-2-propyl]phenyl dianhydride, bis[3-(3,4-dicarboxyphenoxy)phenyl]methane dianhydride, bis[4-(3,4-dicarboxyphenoxy)phenyl]methane dianhydride, 2,2-bis[3-(3,4-dicarboxyphenoxy)phenyl]propane dianhydride, 2,2-bis[4-(3,4-dicarboxyphenoxy)phenyl]propane dianhydride, bis(3,4-dicarboxyphenoxy)dimethylsilane dianhydride, 1,3-bis(3,4-dicarboxyphenyl)-1,1,3,3-tetramethyldisiloxane dianhydride, 2,3,6,7-naphthalenetetracarboxylic acid dianhydride, 1,4,5, 8-Naphthalenetetracarboxylic acid dianhydride, 1,2,5,6-Naphthalenetetracarboxylic acid dianhydride, 3,4,9,10-Perylenetetracarboxylic acid dianhydride, 2,3,6,7-Anthracenetetracarboxylic acid dianhydride, 1,2,7,8-Phenylenitetetracarboxylic acid dianhydride, Ethylenetetracarboxylic acid dianhydride, 1,2,3,4-Butanetetracarboxylic acid dianhydride, 1,2,3,4-Cyclobutanetetracarboxylic acid dianhydride, Cyclopentanetetracarboxylic acid dianhydride, Cyclohexane-1,2,3,4-Tetracarboxylic acid dianhydride, Cyclohexane-1,2,4,5-Tetracarboxylic acid dianhydride, 3,3',4,4'-Dicyclohexyltetracarboxylic acid dianhydride, Carbonyl-4,4'-Bis(cyclohexane-1,2-dicarboxylic acid) dianhydride, Methylene-4,4'-Bis(cyclohexane-1,2-dicarboxylic acid) dianhydride, 1,2-Ethyl-4,4'-bis(cyclohexane-1,2-dicarboxylic acid) dianhydride, 1,1-Ethylene-4,4'-bis(cyclohexane-1,2-dicarboxylic acid) dianhydride, 2,2-Propylene-4,4'-bis(cyclohexane-1,2-dicarboxylic acid) dianhydride, Oxy-4,4'-bis(cyclohexane-1,2-dicarboxylic acid) dianhydride, Thio-4,4'-bis(cyclohexane-1,2-dicarboxylic acid) dianhydride, Sulfo-4,4'-bis(cyclohexane-1,2-dicarboxylic acid) dianhydride, Bicyclo[2,2,2]octyl-7-ene 2,3,5,6-Tetracarboxylic acid dianhydride, rel-[1S,5R,6R]-3-oxabicyclo[3,2,1]octane-2,4-dione-6-spiro-3'-(tetrahydrofuran-2',5'-dione), 4-(2,5-dioxotetrahydrofuran-3-yl)-1,2,3,4-tetrahydronaphthalene-1,2-dicarboxylic acid anhydride, ethylene glycol-bis-(3,4-dicarboxylic acid anhydride phenyl) ether, 4,4'-biphenylbis(triphenyltriacrylic acid monoester anhydride), 9,9'-bis(3,4-dicarboxyphenyl)fluorene dianhydride, etc. [Polybutadiene and its modified derivatives] Polybutadiene and its modified derivatives are compounds that have a polybutadiene structure or a structure derived from polybutadiene within their molecules. The polybutadiene-derived structure can be converted from unsaturated bonds to single bonds by hydrogenation. Examples of polybutadiene and its modified derivatives include, but are not limited to, polybutadiene, hydroxyl-terminated polybutadiene, terminal (meth)acrylated polybutadiene, carboxylic acid-terminated polybutadiene, amine-terminated polybutadiene, and styrene-butadiene rubber. Furthermore, one or more of these can be used. From the viewpoint of dielectric properties, polybutadiene or styrene-butadiene rubber is preferred. Examples of styrene butadiene rubber (SBR) include RICON-100, RICON-181, RICON-184 (all manufactured by Cray Valley Corporation), and 1,2-SBS (manufactured by Nippon Soda Corporation). Examples of polybutadiene include B-1000, B-2000, and B-3000 (all manufactured by Nippon Soda Corporation). The molecular weight of both polybutadiene and styrene butadiene rubber is preferably 500 to 10,000 by weight average, more preferably 750 to 7,500, and even more preferably 1,000 to 5,000. Below the lower limit of these ranges, the volatile content is high, making it difficult to adjust the solids composition during prepreg production; above the upper limit of these ranges, compatibility with other curing resins deteriorates. Generally, in the case of compounds containing heteroatoms such as bismaleimide or polymaleimide, it is difficult to ensure compatibility with low-polarity compounds such as compounds mainly containing hydrocarbons or compounds containing only hydrocarbons due to their polarity. On the other hand, the component (A) of the present invention, because it is not designed to actively introduce heteroatoms such as oxygen or nitrogen, also exhibits excellent compatibility with materials having low polarity and low dielectric properties, or compounds containing only hydrocarbons. [Polystyrene and its modified compounds] Polystyrene and its modified compounds are compounds that have a polystyrene structure or a structure derived from polystyrene within their molecules. Examples of polystyrene and its modified compounds include: polystyrene, styrene-2-isopropenyl-2-oxazoline copolymer (Epocros RPS-1005 and RP-61, both manufactured by Nippon Shokubai Co., Ltd.), SEP (styrene-ethylene-propylene copolymer: Septon 1020, manufactured by Kuraray Co., Ltd.), and SEPS (styrene-ethylene-propylene-styrene copolymer: Septon 2002, Septon 2004F, Septon 2005, Septon 2006, Septon 2063, Septon 2104). All are manufactured by Kuraray Corporation. SEEPS (styrene-ethylene / ethylene-propylene-styrene block copolymers: Septon 4003, Septon 4044, Septon 4055, Septon 4077, Septon 4099, all manufactured by Kuraray Corporation), SEBS (styrene-ethylene-butene-styrene block copolymers: Septon 8004, Septon 8006, Septon 8007L, all manufactured by Kuraray Corporation), SEEPS-OH (a compound with hydroxyl groups at the end of the styrene-ethylene / ethylene-propylene-styrene block copolymer: Septon HG252) The products used include, but are not limited to, those manufactured by Kuraray Corporation, such as SIS (styrene-isoprene-styrene block copolymers: Septon 5125 and Septon 5127, both manufactured by Kuraray Corporation), hydrogenated SIS (hydrogenated styrene-isoprene-styrene block copolymers: Hybrar 7125F and Hybrar 7311F, both manufactured by Kuraray Corporation), SIBS (styrene-isobutylene-styrene block copolymers: SIBSTAR073T, SIBSTAR102T, and SIBSTAR103T, all manufactured by Kaneka Corporation, and Septon V9827, manufactured by Kuraray Corporation). Furthermore, one or more of these products may be used. Polystyrene and its modified products have higher heat resistance and are not easily oxidized and deteriorated, so it is preferable that they do not have unsaturated bonds.In addition, there are no particular restrictions on the weight average molecular weight of polystyrene and its modified products if it is above 10,000. However, if it is too large, the compatibility with low molecular weight components with a weight average molecular weight of about 50 to 1,000 and oligomer components with a weight average molecular weight of about 1,000 to 5,000 will become poor, except for polyphenylene ether compounds. Ensuring mixing and solvent stability will become difficult. Therefore, it is better to have a weight average molecular weight of about 10,000 to 300,000. The curable resin composition of the present invention can be obtained by preparing the components in a prescribed ratio, pre-curing at 130°C to 180°C for 30 to 500 seconds, and then post-curing at 150°C to 200°C for 2 to 15 hours to achieve a sufficient curing reaction and obtain the cured product of the present invention. Alternatively, the components of the curable resin composition can be uniformly dispersed or dissolved in a solvent or the like, and then cured after removing the solvent. The method for preparing the curable resin composition of the present invention is not particularly limited; the components may simply be uniformly mixed, or prepolymerization may be performed. For example, prepolymerization can be carried out by heating a mixture containing components (A) to (C) in the presence or absence of a curing accelerator or polymerization initiator, and in the presence or absence of a solvent. Similarly, prepolymerization can be performed by adding amine compounds, compounds having ethylene unsaturated bonds, maleimide compounds, cyanate compounds, polybutadiene and its modified forms, polystyrene and its modified forms, inorganic fillers, and other additives. Regarding the mixing or prepolymerization of the components, in the absence of a solvent, an extruder, kneader, roller, etc., may be used; in the presence of a solvent, a reaction vessel equipped with a stirring device, etc., may be used. As a method for uniform mixing, the resin composition is prepared by mixing using devices such as kneaders, rollers, or planetary mixers at a temperature ranging from 50°C to 100°C. The obtained resin composition can also be pulverized and molded into cylindrical ingots, granular powders, or powdered molded bodies using a tablet machine or similar molding machine. Alternatively, these compositions can be melted onto a surface support to form sheets with a thickness of 0.05 mm to 10 mm, thus creating a curable resin composition molded body. The resulting molded body is non-sticky at 0°C to 20°C and maintains almost no decrease in fluidity or curability even after storage at -25°C to 0°C for more than one week. The obtained molded body can be cured using a transfer molding machine or a compression molding machine. The curable resin composition of the present invention can also be configured as a varnish-like composition (hereinafter referred to as varnish) by adding organic solvents. As needed, the curable resin composition of the present invention can be dissolved in solvents such as toluene, xylene, acetone, methyl ethyl ketone, methyl isobutyl ketone, dimethylformamide, dimethyl acetamide, and N-methylpyrrolidone to prepare a varnish. This varnish is then impregnated in substrates such as glass fiber, carbon fiber, polyester fiber, polyamide fiber, alumina fiber, and paper, and dried by heating. The resulting prepreg is then hot-pressed to produce a cured product of the curable resin composition of the present invention. The solvent used in this case accounts for 10% to 70% by weight, preferably 15% to 70% by weight, in the mixture of the curable resin composition of the present invention and the solvent. Alternatively, if it is a liquid composition, a cured product containing carbon fibers can also be obtained directly, for example, by resin transfer molding (RTM). Furthermore, the curable composition of the present invention can also be used as a modifier for film-type compositions. Specifically, it can be used to improve the flexibility of the B-stage, etc. This type of film-type resin composition is obtained by preparing a curable resin composition varnish from the curable resin composition of the present invention, coating it onto a release film, removing the solvent under heat, and then performing B-stage modification, thereby obtaining a sheet-like adhesive. This sheet-like adhesive can be used as an interlayer insulating layer in multilayer substrates, etc. The curable resin composition of the present invention can also be heated, melted, and reduced in viscosity to impregnate reinforcing fibers such as glass fibers, carbon fibers, polyester fibers, polyamide fibers, and alumina fibers, thereby obtaining a prepreg. Specific examples include glass fibers such as E-glass cloth, D-glass cloth, S-glass cloth, Q-glass cloth, spherical glass cloth, NE-glass cloth, and T-glass cloth; further examples include inorganic fibers other than glass, or organic fibers such as polyparaphenylene terephthalamide (Kevlar (registered trademark), manufactured by DuPont), fully aromatic polyamide, polyester, polyparaphenylene benzoxazole, polyimide, and carbon fibers, but are not particularly limited to these. The shape of the substrate is not particularly limited; examples include woven fabrics, non-woven fabrics, roving, and chopped strand mat. In addition, known weaving methods include plain weave, basket weave, and twill weave, and the appropriate method can be selected from these known weaving methods according to the target application or performance. Furthermore, glass fabrics that have undergone fiber opening treatment or surface treatment using silane coupling agents are preferred. The thickness of the substrate is not particularly limited, but is preferably around 0.01 mm to 0.4 mm. Alternatively, a prepreg can be obtained by impregnating the varnish into reinforcing fibers and then heating and drying it. Alternatively, the prepreg can be used to manufacture laminates. There is no particular limitation as long as the laminate includes one or more prepregs, and it may have any other layers. Commonly known methods can be appropriately applied as methods for manufacturing the laminate, and there are no particular limitations. For example, in forming a laminate with metal foil, a multi-stage press, a multi-stage vacuum press, a continuous forming machine, or an autoclave forming machine can be used. The laminate can be obtained by stacking the prepregs together and then heating and pressurizing them. The heating temperature is not particularly limited, but preferably 65°C to 300°C, more preferably 120°C to 270°C. Furthermore, the pressure is not particularly limited. If the pressure is too high, it will be difficult to adjust the solid composition of the resin in the laminate, resulting in unstable quality. Conversely, if the pressure is too low, bubbles or poor adhesion between layers will occur. Therefore, a pressure of 2.0 MPa to 5.0 MPa, more preferably 2.5 MPa to 4.0 MPa, is preferred. The laminated board of this embodiment, by including a layer with metal foil, can be preferably used as a laminated board with metal foil as described later. The prepreg is cut into the desired shape, and after being laminated with copper foil or the like as needed, pressure is applied to the laminate using a pressing method, autoclave forming method, sheet winding method, etc., while the curable resin composition is heated and cured, thereby obtaining an electrical and electronic laminated board (printed wiring board) or carbon fiber reinforced material. The curable resin composition of the present invention can also be made into resin sheets. As a method for obtaining resin sheets from the curable resin composition of the present invention, for example, a method can be described by coating the curable resin composition onto a support film (support), drying it, and forming a resin composition layer on the support film. When using the curable resin composition of the present invention for resin sheets, it is important that the film softens under the lamination temperature conditions (70°C to 140°C) in a vacuum lamination process, and that the lamination of the circuit board exhibits fluidity (resin flow) capable of filling the vias or through holes present in the circuit board. It is preferable that the components are formulated to exhibit this characteristic. Furthermore, in the obtained resin sheet or circuit board (copper laminate, etc.), phenomena such as locally different characteristic values ​​due to phase separation or the like do not occur; certain properties are exhibited at any location, therefore, uniform appearance is required. Here, the diameter of the through-hole in the circuit board is 0.1 mm to 0.5 mm, and the depth is 0.1 mm to 1.2 mm, preferably within this range to allow for resin filling. Furthermore, when laminating both sides of the circuit board, it is ideal to fill approximately half of the through-hole. As a specific method for manufacturing the resin sheet, the following method can be listed: after preparing a varnished resin composition by mixing an organic solvent, the varnished resin composition is coated on the surface of a support film (Y), and then the organic solvent is dried by heating or hot air blowing to form a resin composition layer (X). The preferred organic solvents used here are ketones such as acetone, methyl ethyl ketone, and cyclohexanone; ethyl acetate, butyl acetate, cellolytic acetate, propylene glycol monomethyl ether acetate, carbitol acetate, etc.; cellolytic agents, carbitols such as butyl carbitol; aromatic hydrocarbons such as toluene and xylene; dimethylformamide, dimethylacetamide, N-methylpyrrolidone, etc. Furthermore, it is preferred that the non-volatile components be used at a ratio of 30% to 60% by mass. Furthermore, the thickness of the formed resin composition layer (X) must be greater than or equal to the thickness of the conductor layer. The conductor layer of the circuit board has a thickness ranging from 5 μm to 70 μm; therefore, the thickness of the resin composition layer (X) is preferably 10 μm to 100 μm. Furthermore, the resin composition layer (X) in this invention can also be protected using the protective film described later. By using a protective film, dust or other contaminants can be prevented from adhering to the surface of the resin composition layer, or damage can be caused. The supporting film and protective film can be made of various materials, including polyethylene, polypropylene, polyvinyl chloride and other polyolefins, polyethylene terephthalate (PET), polyethylene naphthalate and other polyesters, polycarbonate, polyimide, and release paper or metal foils such as copper foil and aluminum foil. Furthermore, in addition to matte treatment and corona treatment, the supporting film and protective film can also undergo release treatment. The thickness of the supporting film is not particularly limited, ranging from 10 μm to 150 μm, but preferably within the range of 25 μm to 50 μm. The thickness of the protective film is preferably set to 1 μm to 40 μm. The support film (Y) is peeled off after being laminated to the circuit board or after forming an insulating layer by heat curing. If the support film (Y) is peeled off after the resin composition layer constituting the resin sheet has been heat-cured, the adhesion of dust and other contaminants during the curing process can be prevented. In the case of peeling off after curing, a pre-molding treatment is performed on the support film. Furthermore, a multilayer printed circuit board can be manufactured from the resin sheet obtained as described above. For example, when the resin composition layer (X) is protected by a protective film, after peeling these films off, the resin composition layer (X) is laminated onto one or both sides of the circuit board by, for example, vacuum lamination, so that the resin composition layer (X) is in direct contact with the circuit board. The lamination method can be batch or continuous using rollers. Additionally, the resin sheet and circuit board can be heated (preheated) as needed before lamination. Regarding the lamination conditions, it is preferable to set the lamination temperature to 70°C to 140°C, and preferably to set the lamination pressure to 1 kgf / cm². 2 ~11 kgf / cm 2 (9.8×10) 4 N / m 2 ~107.9×10 4 N / m 2 Lamination is preferably performed under reduced pressure of 20 mmHg (26.7 hPa) or less. Furthermore, the curable resin composition of the present invention can be used to manufacture semiconductor devices. Examples of semiconductor devices include: dual in-line package (DIP), quad flat package (QFP), ball grid array (BGA), chip size package (CSP), small outline package (SOP), thin small outline package (TSOP), and thin quad flat package (TQFP). The curable resin composition and its cured product of the present invention can be used in a wide range of fields. Specifically, it can be used in molding materials, adhesives, composite materials, coatings, and various other applications. Because the cured product of the curable resin composition described in this invention exhibits excellent heat resistance and dielectric properties, it is preferably used as a sealing material for semiconductor components, a sealing material for liquid crystal display components, a sealing material for organic electroluminescent (EL) components, a composite material for electrical-electronic parts such as multilayer boards (printed wiring boards, ball grid array (BGA) substrates, and build-up substrates), or a lightweight, high-strength structural material such as carbon fiber reinforced plastics and glass fiber reinforced plastics, and in three-dimensional (3D) printing, etc. [Examples] The present invention will now be described in more detail with reference to specific embodiments. Unless otherwise specified, all parts are parts by weight. Furthermore, the present invention is not limited to these embodiments. The following describes the various analytical methods used in the examples. <Weight-average molecular weight (Mw), Number-average molecular weight (Mn)> were calculated using polystyrene standard solutions and converted from polystyrene values. Gel permeation chromatography (GPC): DGU-20A3R, LC-20AD, SIL-20AHT, RID-20A, SPD-20A, CTO-20A, CBM-20A (all manufactured by Shimadzu Corporation) Columns: Shodex KF-603, KF-602×2, KF-601×2 Connecting solution: Tetrahydrofuran Flow rate: 0.5 ml / min Column temperature: 40°C Detector: RI (Differential Refractive Index Detector) [Synthesis Example 1] A getter and an alkali trap were installed in a flask equipped with a thermometer, a cooling pipe, and a stirrer. 370.1 parts of 2-bromoethylbenzene (manufactured by Tokyo Chemical Co., Ltd.), 175.1 parts of α,α'-dichloro-p-xylene (manufactured by Tokyo Chemical Co., Ltd.), and 27.3 parts of methanesulfonic acid (manufactured by Tokyo Chemical Co., Ltd.) were added to the flask. The reaction was carried out at 130°C for 6 hours while the generated hydrogen chloride was collected using the alkali trap. 100 parts of toluene and 600 parts of cyclohexane were added and extracted. The organic layer was washed 5 times with 100 parts of water. The solvent and excess 2-bromoethylbenzene were removed by distillation under reduced pressure, yielding 380 parts of a compound (BEB-1) with the 2-bromoethylbenzene structure represented by formula (4) as a liquid resin (Mn: 938, Mw: 1290). The GPC diagram of the obtained compound is shown in Figure 1. The average value n of the repeating units, calculated based on the area % of the GPC chart, is 2.2. [Chemistry 5] [Synthesis Example 2] 300 parts of BEB-1 obtained in Synthesis Example 1, 245 parts of toluene, 735 parts of dimethyl sulfoxide, 0.15 parts of 4-hydroxy-2,2,6,6-tetramethylpiperidine-1-oxy radical, and 146.4 parts of 50 wt% sodium hydroxide aqueous solution were added to a flask equipped with a thermometer, cooling pipe, and stirrer. The reaction was continued at 40°C for 6 hours. 100 parts of water were added, and after washing the organic layer, the organic layer was returned to the reaction vessel. 735 parts of dimethyl sulfoxide and 9.8 parts of 50 wt% sodium hydroxide aqueous solution were added, and the reaction was carried out again at 40°C for 1 hour. 300 parts of toluene were added, and the organic layer was repeatedly washed with 100 parts of water until the water was neutral. The mixture was concentrated under reduced pressure using an evaporator to obtain 180 parts of compound (O-1) with two or more styrene structures in the molecule, as represented by the following formula (5). The GPC diagram of the obtained compound is shown in Figure 2. In addition, the obtained compounds 1 H-NMR ( 1 H-nuclear magnetic resonance, 1 The H-NMR data (dichloroform) is shown in Figure 3. 1 Vinyl-derived signals were observed at 5.10 ppm–5.30 ppm, 5.50 ppm–5.85 ppm, and 6.60 ppm–6.80 ppm in the H-NMR chart. The average n of the repeating units, calculated from the area % of the GPC chart, was 2.2 (molecular weights of the resin components: Mn: 797, Mw: 1187). [Chemistry 6] [Synthesis Example 3] A resin solution containing a maleimide compound represented by the following formula (6) synthesized according to the method described in International Publication No. 2020 / 054601 was concentrated under reduced pressure and heating to obtain a solidified maleimide compound (M-1). [Chemistry 7] [Example 1, Comparative Example 1] Materials were dissolved and mixed in acetone according to the proportions shown in Table 1 to achieve a solid content of 66% by mass. This was then applied to a mirror-finished copper foil to achieve a wet film thickness of 200 μm. After pre-drying in a vacuum oven at 60°C for 30 minutes, the film was cured at 220°C for 1 hour. Following curing, the copper foil was etched using ferric chloride to obtain a cured film (for Comparative Example 1, curing was performed at 175°C for 2 hours). For evaluation, the test pieces were cut to the desired dimensions using a laser cutter as needed. <Dielectric Constant Test / Dielectric Loss Tangent Test> Tests were conducted using a 10 GHz cavity resonator manufactured by ATE Corporation, employing the cavity resonator perturbation method. The test was performed on a sample measuring 1.7 mm wide × 100 mm long and 0.1 mm thick. <Heat Resistance (Differential Scanning Calorimeter (DSC))> Differential Scanning Calorimeter: DSC6220 (manufactured by SII NanoTechnology) Measurement Temperature Range: 30℃~330℃ Heating Rate: 10℃ / min Environment: Nitrogen (30 mL / min) Sample Amount: 5 mg Tg: Set the inflection point of the DSC graph as Tg. [Table 1] • CYTESTER TA: Bisphenol A type cyanate compound (manufactured by Mitsubishi Gas Chemical Co., Ltd.) • NC-3000-L: Biphenyl aralkyl type epoxy resin (manufactured by Nippon Kayaku Co., Ltd.) • 18% Octope Zn: Zinc 2-ethylhexanoate (curing accelerator, manufactured by Hope Pharmaceutical Co., Ltd.) • TPP-K: Tetraphenylphosphonium tetraphenylborate (curing accelerator, manufactured by Hokukoku Chemical Co., Ltd.) • 2E4MZ: 2-Ethyl-4-methylimidazole (curing accelerator, manufactured by Shikoku Chemical Co., Ltd.) Based on the results in Table 1, it was confirmed that Example 1 exhibits superior high heat resistance and low dielectric properties compared to the previously used epoxy resin composition. [Example 2] The materials were dissolved and mixed in acetone according to the proportions shown in Table 2, so that the solid content was 66% by mass. The mixture was then coated onto a mirror copper foil to make the wet film thickness 200 μm. After pre-drying in a vacuum oven at 60°C for 30 minutes, it was cured at 220°C for 1 hour. After curing, the copper foil was etched with ferric chloride to obtain a cured film. <Compatibility Test> The results of the evaluation based on the following criteria are shown in Table 2. After mixing each material into a polymer bottle (I-boy: manufactured by ASONE) according to the proportions shown in Table 2, the mixture was stirred for 1 hour at 100 rpm and 25°C using a roller mixer (MIX-ROTAR VMR-5: manufactured by ASONE). The evaluation was then performed based on the following criteria. The results are shown in Table 2. • When all materials except the inorganic filler are prepared into a resin solution, a homogeneous solution is formed: ○ • When all materials except the inorganic filler are prepared into a resin solution, a homogeneous solution cannot be formed: × <Film Formation Test> The results of the evaluation based on the following criteria are shown in Table 2. • No cracks or fissures formed in the hardened film after etching: ○ • Cracks or fissures formed in the hardened film after etching: × [Table 2] • CYTESTER TA: Bisphenol A cyanate compound (manufactured by Mitsubishi Gas Chemical Co., Ltd.) • 18% Octope Zn: Zinc 2-ethylhexanoate (curing accelerator, manufactured by Hope Pharmaceutical Co., Ltd.) • TPP-K: Tetraphenylphosphonium tetraphenylborate (curing accelerator, manufactured by Hokko Chemical Co., Ltd.) • DCP: Dicumyl peroxide (manufactured by Kayaku Akzo Co., Ltd.) • MSR-2212: Silicon dioxide filler (manufactured by Ryusei Co., Ltd.) Based on the results in Table 2, it was confirmed that Example 2 has excellent compatibility and sufficient flexibility for film formation. The curable resin composition, resin sheet and cured product of the present invention are preferably used in electrical and electronic components such as semiconductor sealing materials, printed wiring boards, and multilayer laminates. none Figure 1 shows the GPC chart for Synthesis Example 1. Figure 2 shows the GPC chart for Synthesis Example 2. Figure 3 shows the GPC chart for Synthesis Example 2. 1 H-NMR chart.

Claims

1. A curable resin composition comprising (A) a compound having at least two styrene structures within its molecule, (B) a maleimide compound, and (C) a cyanate compound, wherein the component (A) is selected from at least one group consisting of oligodivinyl copolymers, 4,4'-vinylbistyrene, 3,4'-vinylbistyrene, 3,3'-vinylbistyrene, divinylfluorene, divinylbiphenyl, divinylnaphthalene, divinylbenzene, and compounds represented by the following formula (1), wherein in formula (1), a plurality of Rs are present independently, representing a hydrocarbon group having 1 to 10 carbon atoms or a halogenated alkyl group having 1 to 10 carbon atoms; p and r represent integers from 0 to 4, q represents integers from 0 to 3, n is the average of the number of repetitions, and 1 ≤ n ≤ 20.

2. The curable resin composition as claimed in claim 1, wherein, The component (A) is the compound represented by formula (1).

3. The curable resin composition as described in claim 1 or claim 2, wherein, The component (B) is a compound represented by the following formula (3); In formula (3), there are multiple Rs that exist independently, representing a hydrocarbon group with 1 to 10 carbon atoms or a halogenated alkyl group with 1 to 10 carbon atoms; p and r represent integers from 0 to 4, q represents integers from 0 to 3, n is the average of the number of repetitions, and 1 ≦ n ≦ 20.

4. The curable resin composition as described in claim 1 or claim 2 further comprises a curing accelerator.

5. The curable resin composition as described in claim 1 or claim 2 further comprises an inorganic filler.

6. The curable resin composition as described in claim 1 or claim 2 further comprises a polymerization initiator.

7. A resin sheet comprising a resin composition as described in any one of claims 1 to 6 and a support.

8. A cured material, which is a cured resin composition as described in any one of claims 1 to 6 or a cured resin sheet as described in claim 7.

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