Curable resin composition and cured product thereof

Abstract

To provide a curable resin composition which is excellent in high heat resistance and low dielectric characteristics.SOLUTION: A curable resin composition contains (A) a compound having at least two or more styrene structures in the molecule, and (B) a thermal cationic polymerization initiator.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] In recent years, the required characteristics of laminates for mounting electrical and electronic components have become more widespread and sophisticated due to the expansion of their fields of use. Conventional semiconductor chips were mainly mounted on metal lead frames, but semiconductor chips with high processing power, such as central processing units (hereinafter referred to as CPUs), are increasingly being mounted on laminates made of polymer materials.

[0002] In particular, semiconductor packages (hereafter referred to as PKG) used in smartphones and other devices require thinner PKG substrates to meet the demand for smaller size, thinner thickness, and higher density. However, as the PKG substrate becomes thinner, its rigidity decreases, and defects such as large warping can occur due to the heat generated when soldering the PKG to the motherboard (PCB). To reduce this, there is a demand for PKG substrate materials with a high Tg above the soldering temperature.

[0003] In addition, the fifth-generation communication system "5G," currently under development, is expected to further increase capacity and speed, which is driving an ever-increasing need for low dielectric loss tangent materials, with a dielectric loss tangent of at least 0.005 or less at 10 GHz.

[0004] Furthermore, with the advancement of electronics in the automotive field, precision electronic devices are sometimes placed near engine drive units, requiring even higher levels of heat and moisture resistance. SiC semiconductors are beginning to be used in trains, air conditioners, etc., and the encapsulation materials for semiconductor elements require extremely high heat resistance, making it impossible to meet the requirements of conventional epoxy resin encapsulation materials.

[0005] In light of this background, polymeric materials that can achieve both heat resistance and low dielectric loss tangent characteristics are being investigated. For example, Patent Document 1 proposes a composition containing a maleimide resin and a propenyl group-containing phenolic resin. However, the electrical properties are not sufficient because phenolic hydroxyl groups that do not participate in the curing reaction remain. Patent Document 2 also discloses an allyl ether resin in which hydroxyl groups are substituted with allyl groups. However, it has been shown that Claisen rearrangement occurs at 190°C, and at 200°C, the molding temperature for general substrates, phenolic hydroxyl groups that do not participate in the curing reaction are generated, resulting in insufficient electrical properties. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Publication No. 04-359911 [Patent Document 2] International Publication No. 2016 / 002704 Summary of the Invention [Problem to be solved by the invention]

[0007] The present invention has been made in view of the above points, and an object of the present invention is to provide a curable resin composition that is excellent in high heat resistance and low dielectric properties. [Means for solving the problem]

[0008] As a result of intensive research to solve the above problems, the present inventors have found that a cured product of a curable resin composition containing a compound having at least two styrene structures in the molecule and a thermal cationic polymerization initiator has excellent heat resistance and low dielectric properties, and have thus completed the present invention.

[0009] That is, the present invention relates to the following [1] to [5]. In the present invention, "(Numerical value 1) to (Numerical value 2)" indicates that the upper and lower limit values ​​are included. [1] A curable resin composition comprising: (A) a compound having at least two styrene structures in the molecule; and (B) a thermal cationic polymerization initiator. [2] The curable resin composition according to item [1] above, wherein the component (A) is a compound represented by the following formula (1):

[0010] [ka]

[0011] (In formula (1), each R independently represents a hydrocarbon group or a halogenated alkyl group having 1 to 10 carbon atoms. p and r represent integers of 0 to 4, q represents an integer of 0 to 3, and n represents the average number of repetitions, and 1≦n≦20.) [3] The curable resin composition according to the above item [1] or [2], further comprising an inorganic filler. [4] A resin sheet comprising the curable resin composition according to any one of the above items [1] to [3] and a support. [5] A curable resin composition according to any one of the preceding items [1] to [3] or a cured product of the resin sheet according to the preceding item [4]. [Effects of the Invention]

[0012] According to the present invention, it is possible to provide a curable resin composition, a resin sheet, and a cured product thereof, which are excellent in high heat resistance and low dielectric properties. [Brief explanation of the drawings]

[0013] [Figure 1] 1 shows a GPC chart of Synthesis Example 1. [Figure 2] 1 shows a GPC chart of Synthesis Example 2. [Figure 3] 1H-NMR chart of Synthesis Example 2 is shown. DETAILED DESCRIPTION OF THE INVENTION

[0014] 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)), and (B) a thermal cationic polymerization initiator (hereinafter also referred to as component (B)).

[0015] Component (A) may be any known compound having at least two styrene structures in the molecule. Examples include OPE-2St (manufactured by Mitsubishi Gas Chemical Co., Inc.), ODV (oligodivinyl copolymer, manufactured by Nippon Steel Chemical & Materials Co., Ltd.), 1,2-bis(vinylphenyl)ethane (BVPE: a group of compounds such as 4,4'-ethylenebisstyrene, 3,4'-ethylenebisstyrene, and 3,3'-ethylenebisstyrene), divinylfluorene, divinylbiphenyl, divinylnaphthalene, divinylbenzene, and compounds represented by the following formula (1). Component (A) may be used alone or in combination. Among these, compounds represented by the following formula (1) are preferred as component (A) from the viewpoints of heat resistance, dielectric properties, compatibility with other curable resins (such as epoxy resins and active ester resins), circuit embedding properties, and the like.

[0016] [ka]

[0017] (In formula (1), each R independently represents a hydrocarbon group or a halogenated alkyl group having 1 to 10 carbon atoms. p and r represent integers of 0 to 4, q represents an integer of 0 to 3, and n represents the average number of repetitions, and 1≦n≦20.)

[0018] In the formula (1), p and r are 0 to 4, preferably 0 to 2, and more preferably 0. q is 0 to 3, preferably 0 to 2, and more preferably 0. n is 1≦n≦20, preferably 1.1≦n≦20, more preferably 1.1≦n≦10, and particularly preferably 1.1≦n≦5. The value of n can be calculated from the number average molecular weight (Mn) of the compound of formula (1) determined by gel permeation chromatography (GPC). The number average molecular weight is preferably 200 or more and less than 5000, more preferably 300 or more and less than 3000, and particularly preferably 400 or more and less than 2000. A weight average molecular weight of less than 5000 facilitates purification by washing with water, while a weight average molecular weight of 200 or more prevents the target compound from volatilizing during the solvent distillation step.

[0019] In the formula (1), R is a hydrocarbon group or halogenated alkyl 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 particularly preferably a hydrocarbon group having 1 to 3 carbon atoms. Hydrocarbons having R of 3 or less carbon atoms are less likely to undergo molecular vibration when exposed to high frequency waves, and therefore have particularly excellent electrical properties.

[0020] The compound represented by the formula (1) is derived from a compound represented by the following formula (2).

[0021] [ka]

[0022] (In formula (2), multiple R's each independently represent a hydrocarbon group or a halogenated alkyl group having 1 to 10 carbon atoms. p and r represent integers of 0 to 4, q represents an integer of 0 to 3, n represents the average number of repetitions, and 1≦n≦20. X represents a halogen atom.)

[0023] The preferred ranges of R, p, r, q, and n in the formula (2) are the same as those in the formula (1). From the viewpoints 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.

[0024] The compound represented by formula (1) can be obtained, for example, by subjecting the compound represented by formula (2) to a dehydrohalogenation reaction in a solvent in the presence of a basic catalyst. Examples of solvents that can be used include, but are not limited to, water-insoluble solvents such as 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. These solvents are not limited to these, and two or more of these solvents may be used in combination. Furthermore, aprotic polar solvents can also be used in combination with the water-insoluble solvents. Examples include dimethyl sulfone, dimethyl sulfoxide, dimethylformamide, dimethylacetamide, 1,3-dimethyl-2-imidazolidinone, and N-methylpyrrolidone, and two or more of these solvents may be used in combination. When using an aprotic polar solvent, it is preferable to use one with a higher boiling point than the water-insoluble solvent used in combination. The catalyst is not particularly limited, but examples include basic catalysts such as sodium hydroxide, potassium hydroxide, and potassium carbonate. Because it is difficult to completely complete the dehydrohalogenation reaction, a large excess of aprotic polar solvent relative to the substrate may be used, or the dehydrohalogenation reaction may be repeated two or more times. For example, the dehydrohalogenation reaction of the compound represented by formula (2) may be carried out in an organic solvent in the presence of a base catalyst, and the resulting solution may be washed with water and then returned to the reaction vessel, where the base catalyst is added and the reaction may be carried out again. This can increase the progress of the dehydrohalogenation reaction. This means that the amount of residual halogen in the target compound can be reduced. The amount of residual halogen is preferably 1 to 10,000 ppm, more preferably 1 to 1,000 ppm, and even more preferably 1 to 750 ppm. A high amount of residual halogen in the compound represented by formula (1) can cause molecular vibration when exposed to high frequency waves, adversely affecting electrical properties, particularly dielectric loss tangent. Furthermore, a high amount of residual halogen increases the risk of problems such as metal corrosion and ion migration in environmental tests such as HAST (High Accelerated Stress Test). Therefore, the above halogen content is preferred.

[0025] The method for producing the compound represented by formula (2) is not particularly limited. For example, a compound having a 2-bromoethylbenzene structure may be reacted with a bis(halogenated methylaryl) compound (or a bis(hydroxymethylaryl) compound, etc.) in the presence of an acid catalyst such as hydrochloric acid, sulfonic acid, or activated clay, or a compound having a 2-bromoethylbenzene structure may be reacted with a bis(hydroxymethylaryl) compound in the presence of an acid catalyst such as hydrochloric acid, sulfonic acid, or activated clay. When using a catalyst such as sulfonic acid, the reaction may be neutralized with an alkali metal such as sodium hydroxide or potassium hydroxide before proceeding to the extraction step. For the extraction step, an aromatic hydrocarbon solvent such as toluene or xylene may be used alone, or a non-aromatic hydrocarbon such as cyclohexane or toluene may be used in combination. After extraction, the organic layer is washed with water until the wastewater becomes neutral, and the solvent and excess compounds having a 2-bromoethylbenzene structure are distilled off using an evaporator or the like to obtain the target compound having at least two 2-bromoethylethylbenzene structures in the molecule.

[0026] Examples of compounds having a 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 may be used alone or in combination of two or more. A larger carbon number improves solvent solubility but reduces heat resistance. Therefore, the compound is preferably unsubstituted or substituted with an alkyl group having 1 to 3 carbon atoms, more preferably unsubstituted or substituted with an alkyl group having 1 to 2 carbon atoms, and most preferably unsubstituted or substituted with a methyl group.

[0027] Examples of bishalogenated methylaryl compounds include, but are not limited to, o-xylylene difluoride, m-xylylene difluoride, p-xylylene difluoride, o-xylylene dichloride, m-xylylene dichloride, p-xylylene dichloride, o-xylylene dibromide, m-xylylene dibromide, p-xylylene dibromide, o-xylylene diiodide, m-xylylene diiodide, and p-xylylene diiodide. These compounds may be used alone or in combination of two or more. From the viewpoint of the reactivity of the raw 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.

[0028] Examples of bishydroxymethylaryl compounds include, but are not limited to, o-benzenedimethanol, m-benzenedimethanol, and p-benzenedimethanol. These compounds may 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, more preferably 0.1 to 0.6 parts by mass, per part by mass of the compound having a 2-bromoethylbenzene structure.

[0029] When reacting a compound having a 2-bromoethylbenzene structure with a halogenated methylaryl compound or the like, a catalyst such as hydrochloric acid, phosphoric acid, sulfuric acid, formic acid, p-toluenesulfonic acid, or methanesulfonic acid may be used, as needed. In addition, Lewis acids such as aluminum chloride and zinc chloride, activated clay, acid clay, white carbon, zeolite, and silica alumina may also be used, or acidic ion exchange resins may be used in combination. The amount of catalyst used is 0.05 to 0.8 mol, preferably 0.1 to 0.7 mol, per mol of the compound having a 2-bromoethylbenzene structure used. Using too much catalyst can result in a reaction solution with too high a viscosity, making stirring difficult; using too little can slow the reaction. The reaction can be carried out using an organic solvent such as hexane, cyclohexane, octane, toluene, or xylene, as needed, or it can be carried out solvent-free. For example, an acidic catalyst is added to a mixed solution of a compound having a 2-bromoethylbenzene structure, a halogenated methylaryl compound, and a solvent, and if the catalyst contains water, the water is removed from the system by azeotropy. The reaction is then carried out at 40 to 180°C, preferably 50 to 170°C, for 0.5 to 20 hours. After the reaction is complete, the acidic catalyst may be neutralized with an aqueous alkali solution, but the process can proceed to a water-washing step without neutralization. In the water-washing step, a water-insoluble organic solvent is added to the oil layer, and washing is repeated until the wastewater becomes neutral.

[0030] The softening point of the compound represented by formula (2) is preferably 80°C or lower, more preferably 70°C or lower. If the softening point is 80°C or lower, the viscosity when converted into the compound represented by formula (1) is low. This makes it easier to ensure fluidity, does not impair the impregnation ability into glass cloth, carbon fiber, etc., and facilitates B-stage formation, such as prepreg formation. If the viscosity is reduced by increasing the dilution solvent, there is a possibility that the resin will not adhere sufficiently to the fibrous material during the impregnation process.

[0031] In the curable resin composition of the present invention, the content of component (A) is preferably 1 part by mass or more and 99 parts by mass or less, more preferably 5 parts by mass or more and 90 parts by mass or less, and even more preferably 10 parts by mass or more and 80 parts by mass or less, where the total nonvolatile content excluding inorganic fillers in the curable resin composition is 100 parts by mass. If the content of component (A) is less than 1 part by mass, there is a concern that the dielectric properties may deteriorate and the composition may be more likely to absorb water, and if it is more than 99 parts by mass, it may be difficult to achieve adhesion to copper foil, etc.

[0032] The curable resin composition of the present invention contains a thermal cationic polymerization initiator as component (B). A thermal cationic polymerization initiator is a compound that generates a cationic species such as a Bronsted acid or a Lewis acid upon heating. Preferred examples of component (B) are listed below, but the present invention is not limited to these. These may be used alone or in combination of two or more. Component (B) is preferably an organic onium salt compound in which a cationic component and an anionic component are paired. Examples of the cationic component include organic sulfonium, organic oxonium, organic ammonium, organic phosphonium, and organic iodonium. Examples of the anionic component include BF4 - , B(C6F5)4 - , SbF4 - , Sb(C6F5)4 - , AsF6 - , PF6 - , PF6 - , CF3SO3 - , C4F9SO3 - or (CF3SO2)3C -Examples of commercially available thermal cationic polymerization initiators include TA-60, TA-60B, TA-100, TA-120, and TA-160 (all manufactured by San-Apro Co., Ltd.), K-PURE (registered trademark) TAG-2678, TAG-2681, TAG-2689, TAG-2690, TAG-2700, CXC-1612, CXC-1614, CXC-1615, CXC-1616, CXC-1733, CXC-1738, CXC-1742, CXC-1802, and CXC-1821 (all manufactured by King Chemical Industries, Ltd.). Examples include San-Aid SI-45, SI-45L, SI-60, SI-60L, SI-80, SI-80L, SI-100, SI-100L, SI-110, SI-110L, SI-150, SI-150L, ​​SI-180, SI-180L, SI-B2, SI-B2A, SI-B3, SI-B3A, SI-B4, SI-B5, SI-200, SI-210, SI-220, SI-300, and SI-360 (all manufactured by Sanshin Chemical Industry Co., Ltd.). Among these, salts having a quaternary ammonium cation are preferred, and salts having a quaternary ammonium cation and a borate anion (BF4 - , B(C6F5)4 - etc.), salts consisting of quaternary ammonium cations and antimony anions (SbF4 - , Sb(C6F5)4 - etc.), and particularly preferred are salts consisting of a quaternary ammonium cation and a borate anion (BF4 - , B(C6F5)4 - etc.) Specific examples of salts composed of a quaternary ammonium cation and a borate anion include dimethylphenyl(4-methoxybenzyl)ammonium tetrakis(pentafluorophenyl)borate, dimethylphenyl(4-methylbenzyl)ammonium hexafluorotetrakis(pentafluorophenyl)borate, methylphenyldibenzylammonium tetrakis(pentafluorophenyl)borate, phenyltribenzylammonium tetrakis(pentafluorophenyl)borate, dimethylphenyl(3,4-dimethylbenzyl)ammonium tetrakis(pentafluorophenyl)borate, and N,N-diethyl-N-benzylanilinium boron tetrafluoride.

[0033] The amount of component (B) added is preferably 0.001 to 10 parts by mass, more preferably 0.01 to 5 parts by mass, and even more preferably 0.1 to 2.5 parts by mass, per 100 parts by mass of component (A). If the amount of component (B) added is less than 0.001 part by mass, curability may decrease, while if it is more than 10 parts by mass, wiring may corrode when used in electronic materials (copper-clad laminates, resin-coated copper foils, interlayer insulating materials, and semiconductor encapsulants).

[0034] [Inorganic filler] The curable resin composition of the present invention may contain an inorganic filler. Examples of inorganic fillers include, but are not limited to, powders such as fused silica, crystalline silica, porous silica, alumina, zircon, calcium silicate, calcium carbonate, quartz powder, silicon carbide, silicon nitride, boron nitride, zirconia, aluminum nitride, graphite, forsterite, steatite, spinel, mullite, titania, talc, clay, iron oxide asbestos, and glass powder, as well as inorganic fillers obtained by making these into spherical or crushed shapes. These fillers may be used alone or in combination.

[0035] When a curable resin composition for semiconductor encapsulation is obtained, the amount of inorganic filler used is preferably 80 to 92 parts by mass, and more preferably 83 to 90 parts by mass, per 100 parts by mass of the curable resin composition. When a curable resin composition for interlayer insulating layer formation, or a substrate material such as a copper-clad laminate, prepreg, or RCC is obtained, the amount of inorganic filler used is preferably 5 to 80 parts by mass, and more preferably 10 to 60 parts by mass, per 100 parts by mass of the curable resin composition.

[0036] [Curing accelerator] The curability of the curable resin composition of the present invention can be improved by adding a curing accelerator. As the curing accelerator, an anionic curing accelerator that accelerates the curing reaction by generating anions upon irradiation with ultraviolet light or visible light or heating, or a cationic curing accelerator that accelerates the curing reaction by generating cations upon irradiation with ultraviolet light or visible light or heating, is preferred.

[0037] Examples of anionic curing 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; and quaternary ammonium salts such as tetrabutylammonium salt, triisopropylmethylammonium salt, trimethyldecanylammonium salt, cetyltrimethylammonium salt, and hexadecyltrimethylammonium hydroxide, but are not limited thereto. These may be used alone or in combination.

[0038] Examples of cationic curing accelerators include quaternary phosphonium salts such as triphenylbenzylphosphonium salt, triphenylethylphosphonium salt, and tetrabutylphosphonium salt (the counter ion of the quaternary salt may be a halogen, an organic acid ion, a hydroxide ion, or the like, and is not particularly specified, but organic acid ions and hydroxide ions are particularly preferred), and transition metal compounds (transition metal salts) such as tin octoate, zinc carboxylate (zinc 2-ethylhexanoate, zinc stearate, zinc behenate, zinc myristate), and zinc phosphate ester (zinc octylphosphate, zinc stearylphosphate), but are not limited to these. These may be used alone or in combination.

[0039] The amount of the curing accelerator to be added is 0.01 to 5.0 parts by mass, if necessary, based on 100 parts by mass of the nonvolatile content excluding the inorganic filler in the curable resin composition.

[0040] [Polymerization initiators other than thermal cationic polymerization initiators] The curable resin composition of the present invention can also have improved curability by using a polymerization initiator other than a thermal cationic polymerization initiator in combination. It is preferable to use a radical polymerization initiator as the polymerization initiator to be used in combination. A radical polymerization initiator is a compound that generates radicals upon irradiation with ultraviolet light or visible light or upon heating, thereby initiating a chain polymerization reaction. Usable radical polymerization initiators include organic peroxides, azo compounds, and benzopinacols. Organic peroxides are preferred because they are effective in controlling the curing temperature, suppressing outgassing, and minimizing the impact of decomposition products on electrical properties. Examples of the organic peroxides include ketone peroxides such as methyl ethyl ketone peroxide and acetylacetone peroxide, diacyl peroxides such as benzoyl peroxide, dialkyl peroxides such as dicumyl peroxide and 1,3-bis-(t-butylperoxyisopropyl)-benzene, peroxyketals such as t-butyl peroxybenzoate and 1,1-di-t-butylperoxycyclohexane, α-cumylperoxyneodecanoate, t-butylperoxyneodecanoate, t-butylperoxypivalate, 1,1,3,3-tetramethylbutylperoxy-2-ethylhexanoate, t-amylperoxy-2-ethylhexanoate, t-butylperoxymethyl ... Examples of the peroxycarbonates include, but are not limited to, alkyl peresters such as di-2-ethylhexyl peroxydicarbonate, t-amylperoxy-3,5,5-trimethylhexanoate, t-butylperoxy-3,5,5-trimethylhexanoate, and t-amylperoxybenzoate, peroxycarbonates such as di-2-ethylhexyl peroxydicarbonate, bis(4-t-butylcyclohexyl)peroxydicarbonate, t-butylperoxyisopropyl carbonate, and 1,6-bis(t-butylperoxycarbonyloxy)hexane, t-butyl hydroperoxide, cumene hydroperoxide, t-butyl peroxyoctoate, and lauroyl peroxide. These peroxycarbonates may be used alone or in combination. Among the above organic peroxides, ketone peroxides, diacyl peroxides, hydroperoxides, dialkyl peroxides, peroxyketals, alkyl peresters, peroxycarbonates, etc. are preferred, with dialkyl peroxides being more preferred. Examples of the azo compounds include, but are not limited to, azobisisobutyronitrile, 4,4'-azobis(4-cyanovaleric acid), 2,2'-azobis(2,4-dimethylvaleronitrile), etc. These compounds may be used alone or in combination.

[0041] The amount of polymerization initiator other than the thermal cationic polymerization initiator added is preferably 0.01 to 5 parts by mass, and particularly preferably 0.01 to 3 parts by mass, relative to 100 parts by mass of the curable resin composition. If the amount is less than 0.01 part by mass, the molecular weight may not be sufficiently elongated during the polymerization reaction, and if the amount is more than 5 parts by mass, the dielectric properties such as the dielectric constant and the dielectric loss tangent may be impaired.

[0042] [Polymerization inhibitor] The curable resin composition of the present invention may contain a polymerization inhibitor. The inclusion of a polymerization inhibitor improves storage stability and enables control of the reaction initiation temperature. Controlling the reaction initiation temperature makes it easier to ensure fluidity, prevents impregnation into glass cloth and the like, and facilitates B-staging, such as prepreg formation. If the polymerization reaction proceeds too much during prepreg formation, problems such as difficulty in lamination during the lamination process are likely to occur.

[0043] The polymerization inhibitor may be added during or after the synthesis of component (A). The amount of the polymerization inhibitor used is 0.008 to 1 part by weight, preferably 0.01 to 0.5 parts by weight, per 100 parts by weight of component (A).

[0044] Examples of the polymerization inhibitor include phenol-based, sulfur-based, phosphorus-based, hindered amine-based, nitroso-based, and nitroxyl radical-based inhibitors. One type of polymerization inhibitor may be used alone, or multiple types may be used in combination. Among these, phenol-based, hindered amine-based, nitroso-based, and nitroxyl radical-based inhibitors are preferred in the present invention.

[0045] Examples of the phenolic polymerization inhibitor include 2,6-di-t-butyl-p-cresol, butylated hydroxyanisole, 2,6-di-t-butyl-p-ethylphenol, stearyl-β-(3,5-di-t-butyl-4-hydroxyphenyl)propionate, isooctyl-3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate, 2,4-bis-(n-octylthio)-6-(4-hydroxy-3,5-di-t-butylanilino)-1,3,5-triazine, 2,4-bis[(octylthio)methyl]-o ...butylated hydroxyanisole, butylated hydroxyanisole, butylated hydroxyanisole, butylated hydroxyanisole, butylated hydroxyanisole, butylated hydroxyanisole, butylated hydroxyanisole, butylated hydroxyanisole, butylated hydroxyanisole, butylated hydroxyanisole, butylated hydroxyanisole, butylated hydroxyanisole, butylated hydroxyanisole, butylated hydroxyanisole, butylated hydroxyanisole, butylated hydroxyanisole, butylated hydroxyanisole, butylated hydroxyanisole, butylated hydroxyani Monophenols such as resol, 2,2'-methylenebis(4-methyl-6-t-butylphenol), 2,2'-methylenebis(4-ethyl-6-t-butylphenol), 4,4'-thiobis(3-methyl-6-t-butylphenol), 4,4'-butylidenebis(3-methyl-6-t-butylphenol), triethylene glycol-bis[3-(3-t-butyl-5-methyl-4-hydroxyphenyl)propionate], 1,6-hexanediol-bis[3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate] N,N'-Hexamethylenebis(3,5-di-t-butyl-4-hydroxy-hydrocinnamamide), 2,2-thio-diethylenebis[3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate], 3,5-di-t-butyl-4-hydroxybenzylphosphonate-diethyl ester, 3,9-bis[1,1-dimethyl-2-{β-(3-t-butyl-4-hydroxy-5-methylphenyl)propionyloxy}ethyl]2,4,8,10-tetraoxaspiro[5,5]undecane, bis(3,5-di-t-butyl Bisphenols such as calcium ethyl-4-hydroxybenzylsulfonate, 1,1,3-tris(2-methyl-4-hydroxy-5-t-butylphenyl)butane, 1,3,5-trimethyl-2,4,6-tris(3,5-di-t-butyl-4-hydroxybenzyl)benzene, tetrakis-[methylene-3-(3',5'-di-t-butyl-4'-hydroxyphenyl)propionate]methane, bis[3,3'-bis-(4'-hydroxy-3'-t-butylphenyl)butyric acid]glycol ester, tris-(3,Examples of the phenolic compound include, but are not limited to, polymeric phenols such as 5-di-t-butyl-4-hydroxybenzyl)isocyanurate, 1,3,5-tris(3',5'-di-t-butyl-4'-hydroxybenzyl)-S-triazine-2,4,6-(1H,3H,5H)trione, and tocopherol.

[0046] Examples of the sulfur-based polymerization inhibitor include, but are not limited to, dilauryl-3,3'-thiodipropionate, dimyristyl-3,3'-thiodipropionate, and distearyl-3,3'-thiodipropionate.

[0047] Examples of the phosphorus-based polymerization inhibitor include triphenyl phosphite, diphenyl isodecyl phosphite, phenyl diisodecyl phosphite, tris(nonylphenyl) phosphite, diisodecyl pentaerythritol phosphite, tris(2,4-di-t-butylphenyl) phosphite, cyclic neopentane tetrayl bis(octadecyl) phosphite, cyclic neopentane tetrayl bi(2,4-di-t-butylphenyl) phosphite, cyclic neopentane tetrayl bi(2,4-di-t-butyl-4-methylphenyl) phosphite, bis[2-t 10-(3,5-di-t-butyl-4-hydroxybenzyl)-9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, 10-(3,5-di-t-butyl-4-hydroxybenzyl)-9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, 10-decyloxy-9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, and the like, but are not limited to these.

[0048] Examples of the hindered amine polymerization inhibitor include, but are not limited to, ADK STAB LA-40MP, ADK STAB LA-40Si, ADK STAB LA-402AF, ADK STAB LA-87, DECASTAB LA-82, DECASTAB LA-81, ADK STAB LA-77Y, ADK STAB LA-77G, ADK STAB LA-72, ADK STAB LA-68, ADK STAB LA-63P, ADK STAB LA-57, ADK STAB LA-52, Chimassorb 2020FDL, Chimassorb 944FDL, Chimassorb 944LD, Tinuvin 622SF, Tinuvin PA144, Tinuvin 765, Tinuvin 770DF, Tinuvin XT55FB, Tinuvin 111FDL, Tinuvin 783FDL, and Tinuvin 791FB.

[0049] Examples of the nitroso-based polymerization inhibitor include, but are not limited to, p-nitrosophenol, N-nitrosodiphenylamine, ammonium salt of N-nitrosophenylhydroxyamine, (cupferron), etc. Among these, the ammonium salt of N-nitrosophenylhydroxyamine (cupferron) is preferred.

[0050] Examples of the nitroxyl radical polymerization inhibitor include di-tert-butyl nitroxide, 2,2,6,6-tetramethylpiperidine-1-oxyl, 4-hydroxy-2,2,6,6-tetramethylpiperidine-1-oxyl, 4-oxo-2,2,6,6-tetramethylpiperidine-1-oxyl, 4-amino-2,2,6,6-tetramethylpiperidine-1-oxyl, 4-methoxy-2,2,6,6-tetramethylpiperidine-1-oxyl, 4-acetoxy-2,2,6,6-tetramethylpiperidine-1-oxyl, and 4-benzoyloxy-2,2,6,6-tetramethylpiperidine-1-oxyl, but are not limited to these.

[0051] [Flame retardant] The curable resin composition of the present invention may contain a flame retardant. Examples of the flame retardant 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 may be either a reactive type or an additive type. Specific examples include phosphate esters such as trimethyl phosphate, triethyl phosphate, tricresyl phosphate, trixylenyl phosphate, cresyl diphenyl phosphate, cresyl-2,6-dixylenyl phosphate, 1,3-phenylenebis(dixylenyl phosphate), 1,4-phenylenebis(dixylenyl phosphate), and 4,4'-biphenyl(dixylenyl phosphate); phosphanes such as 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide and 10(2,5-dihydroxyphenyl)-10H-9-oxa-10-phosphaphenanthrene-10-oxide; phosphorus-containing epoxy compounds obtained by reacting epoxy resins with the active hydrogen of the phosphanes; and red phosphorus. These may be used alone or in combination. Of the above-mentioned exemplified substances, phosphate esters, phosphanes, and phosphorus-containing epoxy compounds are preferred, and 1,3-phenylenebis(dixylenyl phosphate), 1,4-phenylenebis(dixylenyl phosphate), 4,4'-biphenyl(dixylenyl phosphate), and phosphorus-containing epoxy compounds are particularly preferred.

[0052] The content of the flame retardant is preferably in the range of 0.1 to 0.6 parts by mass, assuming that the total nonvolatile content excluding inorganic fillers in the curable resin composition is 100 parts by mass. If the content is less than 0.1 part by mass, the flame retardancy may be insufficient, and if the content is more than 0.6 part by mass, the moisture absorption and dielectric properties of the cured product may be adversely affected.

[0053] [Light stabilizer] The curable resin composition of the present invention may contain a light stabilizer, and as the light stabilizer, a hindered amine light stabilizer, particularly HALS, etc., is preferred. Examples of HALS include reaction products of dibutylamine, 1,3,5-triazine, N,N'-bis(2,2,6,6-tetramethyl-4-piperidyl-1,6-hexamethylenediamine and N-(2,2,6,6-tetramethyl-4-piperidyl)butylamine, reaction products of dimethyl succinate and 1-(2-hydroxyethyl)-4-hydroxy-2,2,6,6-tetramethylpiperidine, poly[{6-(1,1,3,3-tetramethylbutyl)amino-1,3,5-triazine-2,4-diyl}{(2,2,6,6-tetramethyl-4-piperidyl)imino}hexamethylene{(2,2,6,6-tetramethyl-4-piperidyl)imino}], bis(1,2 ,2,6,6-pentamethyl-4-piperidyl)[[3,5-bis(1,1-dimethylethyl)-4-hydroxyphenyl]methyl]butyl malonate, bis(2,2,6,6-tetramethyl-4-piperidyl)sebacate, bis(1,2,2,6,6-pentamethyl-4-piperidyl)sebacate, bis(1-octyloxy-2,2,6,6-tetramethyl-4-piperidyl)sebacate, bis(1,2,2,6,6-pentamethyl-4-piperidyl)2-(3,5-di-t-butyl-4-hydroxybenzyl)-2-n-butylmalonate, etc., but are not limited thereto. These may be used alone or in combination.

[0054] The content of the light stabilizer is preferably in the range of 0.001 to 10 parts by mass, assuming that the total nonvolatile content excluding inorganic fillers in the curable resin composition is 100 parts by mass. If the content is less than 0.001 part by mass, it may be insufficient to exhibit a light stabilizing effect, and if it is more than 10 parts by mass, it may have an adverse effect on the moisture absorption and dielectric properties of the cured product.

[0055] [Binder resin] The curable resin composition of the present invention may contain a binder resin. Examples of binder resins include, but are not limited to, butyral resins, acetal resins, acrylic resins, epoxy-nylon resins, NBR-phenol resins, epoxy-NBR resins, and silicone resins. These may be used alone or in combination.

[0056] The amount of binder resin blended is preferably within a range that does not impair the flame retardancy and heat resistance of the cured product, and is preferably 0.05 to 50 parts by mass, and more preferably 0.05 to 20 parts by mass, where the total nonvolatile content excluding inorganic fillers in the curable resin composition is 100 parts by mass.

[0057] [Additives] The curable resin composition of the present invention may contain additives, such as modified acrylonitrile copolymers, polyethylene, fluororesins, silicone gels, silicone oils, surface treatment agents for fillers such as silane coupling agents, release agents, and colorants such as carbon black, phthalocyanine blue, and phthalocyanine green.

[0058] The amount of the additive to be added is preferably 1,000 parts by mass or less, more preferably 700 parts by mass or less, per 100 parts by mass of the curable resin composition.

[0059] The curable resin composition of the present invention may further contain epoxy resins, active ester compounds, phenolic resins, polyphenylene ether compounds, amine resins, maleimide compounds, compounds having an ethylenically unsaturated bond, isocyanate resins, polyamide resins, polyimide resins, cyanate ester resins, polybutadiene and its modified products, polystyrene and its modified products, etc., and these may be used alone or in combination. Among these compounds, polyphenylene ether compounds, compounds having an ethylenically unsaturated bond, cyanate ester resins, polybutadiene and its modified products, and polystyrene and its modified products are preferred in terms of the balance of heat resistance, adhesion, and dielectric properties. The inclusion of these compounds can improve the brittleness of the cured product and adhesion to metals, thereby suppressing package cracking during solder reflow and reliability tests such as thermal cycling.

[0060] Unless otherwise specified, the amount of the above compounds used is preferably 10 times by mass or less, more preferably 5 times by mass or less, and particularly preferably 3 times by mass or less, relative to the amount of component (A). The lower limit is preferably 0.1 times by mass or more, more preferably 0.25 times by mass or more, and even more preferably 0.5 times by mass or more. By keeping the amount within the above range, the effects of each compound added can be enhanced while utilizing the heat resistance and dielectric properties of component (A). The following examples of these components can be used.

[0061] [Epoxy resin] Preferred examples of epoxy resins include, but are not limited to, the following. The epoxy resin may be liquid or solid, and may be used alone or in combination.

[0062] Examples of liquid epoxy resins include bisphenol A type epoxy resins, bisphenol F type epoxy resins, bisphenol AF type epoxy resins, naphthalene type epoxy resins, glycidyl ester type epoxy resins, glycidyl amine type epoxy resins, phenol novolac type epoxy resins, alicyclic epoxy resins having an ester skeleton, cyclohexane type epoxy resins, cyclohexanedimethanol type epoxy resins, glycidyl amine type epoxy resins, and epoxy resins having a butadiene structure. Specific examples include "RE310S" and "RE410S" (all manufactured by Nippon Kayaku Co., Ltd., bisphenol A type epoxy resin), "RE303S", "RE304S", "RE403S", and "RE404S" (all manufactured by Nippon Kayaku Co., Ltd., bisphenol F type epoxy resin), "HP4032", "HP4032D", and "HP4032SS" (all manufactured by DIC Corporation, naphthalene type epoxy resin), "828US", "jER828EL", "825", and "828EL" (all manufactured by Mitsubishi Chemical Corporation, bisphenol A type epoxy resin), "jE807", and "1750" (all manufactured by Mitsubishi Chemical Corporation, bisphenol F type epoxy resin), and "jER152" (manufactured by Mitsubishi Chemical Corporation, phenol Novolac epoxy resin), "630", "630LSD" (all manufactured by Mitsubishi Chemical Corporation, glycidylamine epoxy resin), "ZX1059" (manufactured by Nippon Steel & Sumitomo Metal Chemical Co., Ltd., a mixture of bisphenol A epoxy resin and bisphenol F epoxy resin), "EX-721" (manufactured by Nagase ChemteX Corporation, glycidyl ester epoxy resin), "Celloxide 2021P" (manufactured by Daicel Corporation, alicyclic epoxy resin having an ester skeleton), "PB-3600" (manufactured by Daicel Corporation, epoxy resin having a butadiene structure), "ZX1658", "ZX1658GS" (all manufactured by Nippon Steel & Sumitomo Metal Chemical Co., Ltd., liquid 1,4-glycidylcyclohexane epoxy resin), etc. These may be used alone or in combination of two or more.

[0063] Preferred examples of solid epoxy resins include bixylenol-type epoxy resins, naphthalene-type epoxy resins, naphthalene-type tetrafunctional epoxy resins, cresol novolac-type epoxy resins, dicyclopentadiene-type epoxy resins, trisphenol-type epoxy resins, naphthol-type epoxy resins, biphenyl-type epoxy resins, naphthylene ether-type epoxy resins, anthracene-type epoxy resins, bisphenol A-type epoxy resins, bisphenol AF-type epoxy resins, and tetraphenylethane-type epoxy resins, and examples of such solid epoxy resins include naphthol-type epoxy resins, bisphenol AF-type epoxy resins, naphthalene-type epoxy resins, and biphenyl-type epoxy resins.Specific examples include "HP4032H" (manufactured by DIC Corporation, naphthalene-type epoxy resin), "HP-4700", "HP-4710" (all manufactured by DIC Corporation, naphthalene-type tetrafunctional epoxy resin), "N-690" (manufactured by DIC Corporation, cresol novolac-type epoxy resin), "N-695" (manufactured by DIC Corporation, cresol novolac-type epoxy resin), "HP-7200" (manufactured by DIC Corporation, dicyclopentadiene-type epoxy resin), "HP-7200", "HP-7200HH", "HP-7200H" (all manufactured by DIC Corporation, dicyclopentadiene-type epoxy resin). epoxy resin), "EXA-7311", "EXA-7311-G3", "EXA-7311-G4", "EXA-7311-G4S", "HP-6000" (all manufactured by DIC Corporation, naphthylene ether type epoxy resin), "EPPN-502H" (manufactured by Nippon Kayaku Co., Ltd., trisphenol type epoxy resin), "NC-7000L", "NC-7300" (all manufactured by Nippon Kayaku Co., Ltd., naphthol-cresol novolac type epoxy resin), "NC-3000H", "NC-3000", "NC-3000L", "NC-3100" (all manufactured by Nippon Kayaku Co., Ltd., biphenyl ether type epoxy resin), raryl-type epoxy resin), "XD-1000-2L", "XD-1000-L", "XD-1000-H", "XD-1000-H" (all manufactured by Nippon Kayaku Co., Ltd., dicyclopentadiene-type epoxy resin), "ESN475V" (manufactured by Nippon Steel & Sumikin Chemical Co., Ltd., naphthol-type epoxy resin), "ESN485" (manufactured by Nippon Steel & Sumikin Chemical Co., Ltd., naphthol novolac-type epoxy resin), "YX-4000H", "YX-4000", "YL6121" (all manufactured by Mitsubishi Chemical Corporation, biphenyl-type epoxy resin), "YX-4000HK" (manufactured by Mitsubishi Chemical Corporation, biphenyl-type epoxy resin) Examples of epoxy resins that can be used include "YX-8800" (manufactured by Mitsubishi Chemical Corporation, anthracene-type epoxy resin), "PG-100" and "CG-500" (manufactured by Osaka Gas Chemicals Co., Ltd., fluorene-based epoxy resin), "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 may be used alone or in combination of two or more.

[0064] [Active ester compounds] An active ester compound refers to a compound containing at least one ester bond in its structure, with an aliphatic chain, an aliphatic ring, or an aromatic ring bonded to both sides of the ester bond. Examples of active ester compounds include phenol esters, thiophenol esters, N-hydroxyamine esters, and esters of heterocyclic hydroxy compounds, which have two or more highly reactive ester groups per molecule. These compounds are obtained by a condensation reaction between at least one of a carboxylic acid compound, an acid chloride, or a thiocarboxylic acid compound and at least one of a hydroxy compound or a thiol compound. From the viewpoint of improving heat resistance, active ester compounds are preferably obtained from a carboxylic acid compound or an acid chloride and a hydroxy compound, with phenol compounds or naphthol compounds being preferred as the hydroxy compound. Active ester compounds may be used singly or in combination of two or more.

[0065] Examples of the carboxylic acid compound include benzoic acid, acetic acid, succinic acid, maleic acid, itaconic acid, phthalic acid, isophthalic acid, terephthalic acid, and pyromellitic acid.

[0066] Examples of the acid chloride include acetyl chloride, acrylic acid chloride, methacrylic acid chloride, malonyl chloride, succinic acid dichloride, diglycolyl chloride, glutaric acid dichloride, suberic acid dichloride, sebacic acid dichloride, adipic acid dichloride, dodecandioyl dichloride, azelaic acid chloride, 2,5-furandicarbonyl dichloride, phthaloyl chloride, isophthaloyl chloride, terephthaloyl chloride, trimesic acid chloride, bis(4-chlorocarbonylphenyl) ether, 4,4'-diphenyldicarbonyl chloride, and 4,4'-azodibenzoyl dichloride.

[0067] Examples of the phenol compound and naphthol compound include hydroquinone, resorcinol, bisphenol A, bisphenol F, bisphenol S, phenolphthalene, methylated bisphenol A, methylated bisphenol F, methylated bisphenol S, phenol, o-cresol, m-cresol, p-cresol, catechol, α-naphthol, β-naphthol, 1,5-dihydroxynaphthalene, 1,6-dihydroxynaphthalene, 2,6-dihydroxynaphthalene, dihydroxybenzophenone, trihydroxybenzophenone, tetrahydroxybenzophenone, phloroglucinol, benzenetriol, dicyclopentadiene-type diphenol compounds, phenol novolak, and the phenolic resins described below. Here, the term "dicyclopentadiene-type diphenol compound" refers to a diphenol compound obtained by condensing one dicyclopentadiene molecule with two phenol molecules.

[0068] Preferred specific examples of the active ester compound include active ester compounds containing a dicyclopentadiene-type diphenol structure, active ester compounds containing a naphthalene structure, active ester compounds containing an acetylated product of phenol novolac, active ester compounds containing a benzoylated product of phenol novolac, the compound described in Example 2 of WO 2020 / 095829, and the compounds disclosed in WO 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 dicyclopentadiene-type diphenol structure refers to a divalent structural unit consisting of phenylene-dicyclopentylene-phenylene.

[0069] Commercially available active ester compounds include, for example, "EXB9451," "EXB9460," "EXB9460S," "HPC-8000-65T," "HPC-8000H-65TM," "EXB-8000L-65TM," and "EXB-8150-65T" (manufactured by DIC Corporation) as active ester compounds containing a dicyclopentadiene-type diphenol structure, "EXB9416-70BK" (manufactured by DIC Corporation) as an active ester compound containing a naphthalene structure, and "EXB9416-70BK" (manufactured by DIC Corporation) as a phenolic compound. Examples of active ester compounds containing acetylated volac include "DC808" (manufactured by Mitsubishi Chemical Corporation); active ester compounds containing benzoylated phenol novolac include "YLH1026," "YLH1030," and "YLH1048" (manufactured by Mitsubishi Chemical Corporation); an active ester curing agent that is an acetylated phenol novolac is "DC808" (manufactured by Mitsubishi Chemical Corporation); and an active ester curing agent containing a phosphorus atom is "EXB-9050L-62M" (manufactured by DIC Corporation).

[0070] [Phenol resin] Examples of phenolic resins include, but are not limited to, reaction products of phenols and aldehydes, reaction products of phenols and diene compounds, reaction products of phenols and ketones, reaction products of phenols and substituted biphenyls, reaction products of phenols and substituted phenyls, reaction products of bisphenols and aldehydes, etc. These may be used alone or in combination. Specific examples of the above raw materials are given below, but are not limited to these. <Phenols> Phenol, alkyl-substituted phenol, aromatic-substituted phenol, hydroquinone, resorcinol, naphthol, alkyl-substituted naphthol, dihydroxybenzene, alkyl-substituted dihydroxybenzene, dihydroxynaphthalene, etc. <Aldehydes> Formaldehyde, acetaldehyde, alkyl aldehyde, benzaldehyde, alkyl-substituted benzaldehyde, hydroxybenzaldehyde, naphthaldehyde, glutaraldehyde, phthalaldehyde, crotonaldehyde, cinnamaldehyde, furfural, and the like. <Diene compounds> Dicyclopentadiene, terpenes, vinylcyclohexene, norbornadiene, vinylnorbornene, tetrahydroindene, divinylbenzene, divinylbiphenyl, diisopropenylbiphenyl, butadiene, isoprene, and the like. <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 and the like. <Substituted phenyls> 1,4-bis(chloromethyl)benzene, 1,4-bis(methoxymethyl)benzene, 1,4-bis(hydroxymethyl)benzene and the like.

[0071] [Polyphenylene ether compounds] From the viewpoints of heat resistance and electrical properties, the polyphenylene ether compound is preferably a polyphenylene ether compound having an ethylenically unsaturated bond, and more preferably a polyphenylene ether compound having an acrylic group, a methacrylic group, or a styrene structure. Commercially available products include SA-9000 (manufactured by SABIC, a polyphenylene ether compound having a methacrylic group) and OPE-2St 1200 (manufactured by Mitsubishi Gas Chemical Company, a polyphenylene ether compound having a styrene structure). The number average molecular weight (Mn) of the polyphenylene ether compound is preferably 500 to 5000, more preferably 2000 to 5000, and even more preferably 2000 to 4000. If the molecular weight is less than 500, the heat resistance of the cured product tends to be insufficient. On the other hand, if the molecular weight is more than 5000, the melt viscosity increases and sufficient fluidity cannot be obtained, which tends to result in molding defects. In addition, the reactivity decreases, the curing reaction takes a long time, and the amount of unreacted material not incorporated into the curing system increases, which tends to lower the glass transition temperature of the cured product and reduce the heat resistance of the cured product. When the number average molecular weight of the polyphenylene ether compound is 500 to 5000, it is possible to maintain excellent dielectric properties while exhibiting excellent heat resistance, moldability, etc. The number average molecular weight here can be specifically measured using gel permeation chromatography, etc.

[0072] The polyphenylene ether compound may be obtained by a polymerization reaction or by a redistribution reaction of a high-molecular-weight polyphenylene ether compound having a number-average molecular weight of approximately 10,000 to 30,000. Alternatively, these compounds may be used as raw materials and reacted with a compound having an ethylenically unsaturated bond, such as methacryl chloride, acrylic chloride, or chloromethylstyrene, to impart radical polymerizability. The polyphenylene ether compound obtained by the redistribution reaction may be obtained, for example, by heating a high-molecular-weight polyphenylene ether compound in a solvent such as toluene in the presence of a phenolic compound and a radical initiator to cause a redistribution reaction. The polyphenylene ether compound obtained by the redistribution reaction thus has hydroxyl groups derived from the phenolic compound at both ends of the molecular chain that contribute to curing, thereby maintaining even higher heat resistance. Furthermore, functional groups can be introduced at both ends of the molecular chain even after modification with a compound having an ethylenically unsaturated bond. Furthermore, the polyphenylene ether compound obtained by the polymerization reaction is preferred because it exhibits excellent flowability.

[0073] 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. In the case of polyphenylene ether compounds obtained by redistribution, the molecular weight of the resulting polyphenylene ether compound can be adjusted by adjusting the conditions, etc. of the redistribution reaction. More specifically, adjusting the amount of the phenolic compound used in the redistribution reaction can be considered. That is, the greater the amount of the phenolic compound, the lower the molecular weight of the resulting polyphenylene ether compound. In this case, poly(2,6-dimethyl-1,4-phenylene ether) or the like can be used as the high-molecular-weight polyphenylene ether compound that undergoes the redistribution reaction. The phenolic compound used in the redistribution reaction is not particularly limited, but preferred are, for example, polyfunctional phenolic compounds having two or more phenolic hydroxyl groups per molecule, such as bisphenol A, phenol novolac, and cresol novolac. These compounds may be used alone or in combination of two or more.

[0074] The content of the polyphenylene ether compound is not particularly limited, but is preferably 5 to 1,000 parts by mass, and more preferably 10 to 750 parts by mass, where the nonvolatile content excluding inorganic fillers in the curable resin composition is 100 parts by mass. A content of the polyphenylene ether compound within the above range is preferable in that it not only has excellent heat resistance, etc., but also allows a cured product to fully exhibit the excellent dielectric properties of the polyphenylene ether compound.

[0075] [Amine resin] Amine resins are compounds having two or more amino groups in the molecule. Examples of amine resins include diaminodiphenylmethane, diaminodiphenylsulfone, isophoronediamine, naphthalenediamine, aniline novolak (a reaction product of aniline and formalin), N-methylaniline novolak (a reaction product of N-methylaniline and formalin), orthoethylaniline novolak (a reaction product of orthoethylaniline and formalin), a reaction product of 2-methylaniline and formalin, a reaction product of 2,6-diisopropylaniline and formalin, a reaction product of 2,6-diethylaniline and formalin, a reaction product of 2-ethyl-6-ethylaniline and formalin, a reaction product of 2,6-dimethylaniline and formalin, and a reaction product obtained by the reaction of aniline and xylylene chloride. Examples of suitable aniline resins include, but are not limited to, aniline resins disclosed in Japanese Patent No. 6429862, reaction products of aniline and substituted biphenyls (such as 4,4'-bis(chloromethyl)-1,1'-biphenyl and 4,4'-bis(methoxymethyl)-1,1'-biphenyl), reaction products of aniline and substituted phenyls (such as 1,4-bis(chloromethyl)benzene, 1,4-bis(methoxymethyl)benzene and 1,4-bis(hydroxymethyl)benzene), 4,4'-(1,3-phenylenediisopropylidene)bisaniline, 4,4'-(1,4-phenylenediisopropylidene)bisaniline, reaction products of aniline and diisopropenylbenzene, and dimer diamine. These may be used singly or in combination.

[0076] [Maleimide compounds] A maleimide compound is a compound having one or more maleimide groups in the molecule. Examples of maleimide compounds include 4,4'-diphenylmethane bismaleimide, polyphenylmethane maleimide, m-phenylene bismaleimide, 2,2'-bis[4-(4-maleimidophenoxy)phenyl]propane, 3,3'-dimethyl-5,5'-diethyl-4,4'-diphenylmethane bismaleimide, 4-methyl-1,3-phenylene bismaleimide, 4,4'-diphenylether bismaleimide, 4,4'-diphenylsulfone bismaleimide, 1,3-bis(3-maleimidophenoxy)benzene, 1,3-bis(4-maleimidophenoxy)benzene), and Xyloc-type maleimide compounds (anilix). Maleimide, manufactured by Mitsui Chemicals Fine Co., Ltd.), biphenylaralkyl-type maleimide compounds (solidified by distilling off the solvent under reduced pressure from a resin solution containing the maleimide compound (M2) described in Example 4 of JP 2009-001783 A), bisaminocumylbenzene-type maleimide (maleimide compounds described in WO 2020 / 054601 A), maleimide compounds having an indane structure described in Japanese Patent No. 6629692 or WO 2020 / 217679, MATERIAL STAGE Vol. 18, No. 12 2019 "Continued Story of Epoxy Resin CAS Numbers - Hardener CAS Number Memorandum No. 31 Bismaleimide (1)" and MATERIAL STAGE Vol. 19, No. 2 2019 "Continued Story of Epoxy Resin CAS Numbers - Hardener CAS Number Memorandum No. 32" Examples of suitable maleimide compounds include, but are not limited to, the maleimide compounds described in "Bismaleimide (2)." These compounds may be used alone or in combination.

[0077] The amount of the maleimide compound added is preferably 10 times by mass or less, more preferably 5 times by mass or less, and particularly preferably 3 times by mass or less, relative to the amount of component (A). The lower limit is preferably 0.01 times by mass or more, more preferably 0.1 times by mass or more. Within this range, the effects of heat resistance, dielectric properties, and low water absorption of component (A) can be utilized.

[0078] [Compounds containing ethylenically unsaturated bonds] A compound containing an ethylenically unsaturated bond is a compound that has one or more ethylenically unsaturated bonds in the molecule that can be polymerized by heat or light, regardless of whether a polymerization initiator is used or not. Examples of compounds containing ethylenically unsaturated bonds include, but are not limited to, reaction products of the phenolic resins with ethylenically unsaturated bond-containing halogenated compounds (e.g., chloromethylstyrene, allyl chloride, methallyl chloride, acrylic acid chloride, methacrylic acid chloride), reaction products of ethylenically unsaturated bond-containing phenols (e.g., 2-allylphenol, 2-propenylphenol, 4-allylphenol, 4-propenylphenol, eugenol, isoeugenol) with halogenated compounds (e.g., 1,4-bis(chloromethyl)benzene, 4,4'-bis(chloromethyl)biphenyl, 4,4'-difluorobenzophenone, 4,4'-dichlorobenzophenone, 4,4'-dibromobenzophenone, cyanuric chloride), reaction products of epoxy resins or alcohols with (meth)acrylic acids (e.g., acrylic acid, methacrylic acid), and acid-modified products thereof. These compounds may be used singly or in combination.

[0079] [Isocyanate resin] An isocyanate resin is a compound that has two or more isocyanate groups in its molecule. Examples of the isocyanate resin include, but are not limited to, aromatic diisocyanates such as p-phenylene diisocyanate, m-phenylene diisocyanate, p-xylene diisocyanate, m-xylene diisocyanate, 2,4-tolylene diisocyanate, 2,6-tolylene 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; polyisocyanates such as one or more biuret forms of isocyanate monomers or isocyanate forms obtained by trimerizing the above-mentioned diisocyanate compounds; and polyisocyanates obtained by a urethanization reaction between the above-mentioned isocyanate compounds and polyol compounds. These may be used alone or in combination.

[0080] [Polyamide resin] Examples of polyamide resins include reaction products of one or more of diamines, diisocyanates, and oxazolines with dicarboxylic acids, reaction products of diamines with acid chlorides, and ring-opening polymerization products of lactam compounds. These may be used alone or in combination. Specific examples of the above raw materials are given below, but are not limited to these. <Diamine> Ethylenediamine, trimethylenediamine, tetramethylenediamine, pentamethylenediamine, hexamethylenediamine, heptamethylenediamine, octamethylenediamine, nonamethylenediamine, decanediamine, undecanediamine, dodecanediamine, tridecanediamine, tetradecanediamine, pentadecanediamine, hexadecanediamine, heptadecanediamine, octadecanediamine, nonadecanediamine, eicosanediamine, 2-methyl-1,5-diaminopentane, 2-methyl 1,8-diaminooctane, dimer diamine, cyclohexanediamine, bis-(4-aminocyclohexyl)methane, bis(3-methyl-4-aminocyclohexyl)methane, xylylenediamine, norbornanediamine, isophoronediamine, bisaminomethyltricyclodecane, phenylenediamine, diethyltoluenediamine, naphthalenediamine, 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-ethylenedianiline, diaminodiphenyl sulfone, 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-amino 4,4'-(1,3-phenylenediisopropylidene)bisaniline, 4,4'-(1,4-phenylenediisopropylidene)bisaniline, 9,9-bis(4-aminophenyl)fluorene, 2,7-diaminofluorene, aminobenzylamine, diaminobenzophenone, and the like. <Diisocyanate> Benzene diisocyanate, toluene diisocyanate, 1,3-bis(isocyanatomethyl)benzene, 1,3-bis(isocyanatomethyl)cyclohexane, bis(4-isocyanatophenyl)methane, isophorone diisocyanate, 1,3-bis(2-isocyanato-2-propyl)benzene, 2,2-bis(4-isocyanatophenyl)hexafluoropropane, dicyclohexylmethane-4,4'-diisocyanate, and the like. <Dicarboxylic acid> Oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, suberic acid, azelaic acid, sebacic acid, undecanedioic acid, dodecanedioic acid, terephthalic acid, isophthalic acid, 5-hydroxyisophthalic acid, 2-chloroterephthalic acid, 2-methylterephthalic acid, 5-methylisophthalic acid, 5-sodium sulfoisophthalic acid, hexahydroterephthalic acid, hexahydroisophthalic acid, cyclohexanedicarboxylic acid, biphenyldicarboxylic acid, naphthalenedicarboxylic acid, benzophenonedicarboxylic acid, furandicarboxylic acid, 4,4'-dicarboxydiphenyl ether, 4,4'-dicarboxydiphenyl sulfide, etc. <Lactam> ε-caprolactam, ω-undecanelactam, ω-laurolactam, and the like.

[0081] [Polyimide resin] Examples of polyimide resins include, but are not limited to, reaction products of the above diamines with the following tetracarboxylic dianhydrides. These may be used alone or in combination. <Tetracarboxylic acid dianhydride> 4,4'-(Hexafluoroisopropylidene)diphthalic anhydride, 5-(2,5-dioxotetrahydro-3-furanyl)-3-methyl-cyclohexene-1,2dicarboxylic anhydride, pyromellitic dianhydride, 1,2,3,4-benzenetetracarboxylic dianhydride, 3,3',4,4'-benzophenonetetracarboxylic dianhydride, 2,2',3,3'-benzophenonetetracarboxylic dianhydride, 3,3',4,4'-biphenyltetracarboxylic dianhydride, 3,3',4,4'-diphenylsulfonetetracarboxylic dianhydride, 2,2',3, 3'-Biphenyltetracarboxylic dianhydride, methylene-4,4'-diphthalic dianhydride, 1,1-ethylidene-4,4'-diphthalic dianhydride, 2,2'-propylidene-4,4'-diphthalic dianhydride, 1,2-ethylene-4,4'-diphthalic dianhydride, 1,3-trimethylene-4,4'-diphthalic dianhydride, 1,4-tetramethylene-4,4'-diphthalic dianhydride, 1,5-pentamethylene-4,4'-diphthalic dianhydride, 4,4'-oxydiphthalic dianhydride, thio-4,4'-diphthalic dianhydride, sulfonyl-4,4'-diphthalic acid Dianhydride, 1,3-bis(3,4-dicarboxyphenyl)benzene dianhydride, 1,3-bis(3,4-dicarboxyphenoxy)benzene dianhydride, 1,4-bis(3,4-dicarboxyphenoxy)benzene dianhydride, 1,3-bis[2-(3,4-dicarboxyphenyl)-2-propyl]benzene dianhydride, 1,4-bis[2-(3,4-dicarboxyphenyl)-2-propyl]benzene dianhydride, bis[3-(3,4-dicarboxyphenoxy)phenyl]methane dianhydride, bis[4-(3,4-dicarboxyphenoxy)phenyl]meth 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 dianhydride, 1,4,5,8-naphthalenetetracarboxylic dianhydride, 1,2,5,6-naphthalenetetracarboxylic dianhydride, 3,4,9,10-Perylenetetracarboxylic dianhydride, 2,3,6,7-anthracenetetracarboxylic dianhydride, 1,2,7,8-phenanthrenetetracarboxylic dianhydride, ethylenetetracarboxylic dianhydride, 1,2,3,4-butanetetracarboxylic dianhydride, 1,2,3,4-cyclobutanetetracarboxylic dianhydride, cyclopentanetetracarboxylic dianhydride, cyclohexane-1,2,3,4-tetracarboxylic dianhydride, cyclohexane-1,2,4,5-tetracarboxylic dianhydride tetracarboxylic dianhydride, 3,3',4,4'-bicyclohexyltetracarboxylic dianhydride, carbonyl-4,4'-bis(cyclohexane-1,2-dicarboxylic) dianhydride, methylene-4,4'-bis(cyclohexane-1,2-dicarboxylic) dianhydride, 1,2-ethylene-4,4'-bis(cyclohexane-1,2-dicarboxylic) dianhydride, 1,1-ethylidene-4,4'-bis(cyclohexane-1,2-dicarboxylic) dianhydride, 2,2-propylidene -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, sulfonyl-4,4'-bis(cyclohexane-1,2-dicarboxylic acid) dianhydride, bicyclo[2,2,2]oct-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'-biphenyl bis(trimellitic acid monoester acid anhydride), 9,9'-bis(3,4-dicarboxyphenyl)fluorene dianhydride, etc.,

[0082] [Cyanate ester resin] Cyanate ester resins are cyanate ester compounds obtained by reacting phenolic resins with cyanogen halides. Specific examples include, but are not limited to, dicyanatobenzene, tricyanatobenzene, dicyanatonaphthalene, dicyanatobiphenyl, 2,2'-bis(4-cyanatophenyl)propane, bis(4-cyanatophenyl)methane, bis(3,5-dimethyl-4-cyanatophenyl)methane, 2,2'-bis(3,5-dimethyl-4-cyanatophenyl)propane, 2,2'-bis(4-cyanatophenyl)ethane, 2,2'-bis(4-cyanatophenyl)hexafluoropropane, bis(4-cyanatophenyl)sulfone, bis(4-cyanatophenyl)thioether, phenol novolac cyanate, and phenol-dicyclopentadiene co-condensates in which the hydroxyl groups have been converted to cyanate groups. These compounds may be used alone or in combination. Furthermore, the cyanate ester compound, the synthesis method of which is described in JP-A-2005-264154, is particularly preferred as the cyanate ester compound because it has low moisture absorption, flame retardancy, and excellent dielectric properties. The cyanate ester resin may optionally contain a catalyst such as zinc naphthenate, cobalt naphthenate, copper naphthenate, lead naphthenate, zinc octoate, tin octoate, lead acetylacetonate, or dibutyltin maleate to trimerize the cyanate group to form a sym-triazine ring.

[0083] The catalyst is preferably used in an amount of 0.0001 to 0.10 parts by mass, and more preferably 0.00015 to 0.0015 parts by mass, per 100 parts by mass of the cyanate ester resin.

[0084] [Polybutadiene and its modified products] Polybutadiene and its modified products are polybutadiene or compounds having a structure derived from polybutadiene in the molecule. The unsaturated bonds in the polybutadiene-derived structure may be partially or entirely converted to single bonds by hydrogenation. Examples of polybutadiene and its modified products include, but are not limited to, polybutadiene, hydroxyl-terminated polybutadiene, (meth)acrylate-terminated polybutadiene, carboxylic acid-terminated polybutadiene, amine-terminated polybutadiene, and styrene-butadiene rubber. These may be used alone or in combination. Among these, polybutadiene or styrene-butadiene rubber is preferred from the viewpoint of dielectric properties. Examples of styrene-butadiene rubber (SBR) include RICON-100, RICON-181, and RICON-184 (all manufactured by Cray Valley Corporation), and 1,2-SBS (manufactured by Nippon Soda Co., Ltd.). Examples of polybutadiene include B-1000, B-2000, and B-3000 (all manufactured by Nippon Soda Co., Ltd.). The molecular weight of polybutadiene and styrene-butadiene rubber is preferably a weight-average molecular weight of 500 to 10,000, more preferably 750 to 7,500, and even more preferably 1,000 to 5,000. Below the lower limit of the above range, the amount of evaporation is high, making it difficult to adjust the solids content during prepreg production, while above the upper limit of the above range, compatibility with other curable resins deteriorates. Generally, in the case of compounds containing heteroatoms such as oxygen or nitrogen, such as bismaleimides and polymaleimides, it is difficult to ensure compatibility with low-polarity compounds, such as compounds composed mainly of hydrocarbons or compounds composed only of hydrocarbons, due to their polarity. On the other hand, component (A) of the present invention has a skeletal design that does not actively incorporate heteroatoms such as oxygen or nitrogen, and therefore has excellent compatibility with materials with low polarity and low dielectric properties, as well as compounds composed only of hydrocarbons.

[0085] [Polystyrene and its modified products] Polystyrene and its modified products are polystyrene or compounds having a structure derived from polystyrene in the molecule. Examples of polystyrene and modified products thereof include polystyrene, styrene-2-isopropenyl-2-oxazoline copolymer (Epocross RPS-1005, RP-61, both manufactured by Nippon Shokubai Co., Ltd.), SEP (styrene-ethylene-propylene copolymer: Septon 1020, manufactured by Kuraray Co., Ltd.), SEPS (styrene-ethylene-propylene-styrene copolymer: Septon 2002, Septon 2004F, Septon 2005, Septon 2006, Septon 2063, Septon 2104, all manufactured by Kuraray Co., Ltd.), SEEPS (styrene-ethylene / ethylene-propylene-styrene block copolymer: Septon 4003, Septon 4044, Septon 4055, Septon 4077, Septon 4099, all manufactured by Kuraray Co., Ltd.), SEBS (styrene-ethylene-butylene-styrene copolymer: Septon 4003, Septon 4044, Septon 4055, Septon 4077, Septon 4099, all manufactured by Kuraray Co., Ltd.), Examples of suitable block copolymers include Septon 8004, Septon 8006, and Septon 8007L (all manufactured by Kuraray Co., Ltd.), SEEPS-OH (a styrene-ethylene / ethylene-propylene-styrene block copolymer having a terminal hydroxyl group: Septon HG252, manufactured by Kuraray Co., Ltd.), SIS (styrene-isoprene-styrene block copolymer: Septon 5125 and Septon 5127, both manufactured by Kuraray Co., Ltd.), hydrogenated SIS (hydrogenated styrene-isoprene-styrene block copolymer: Hybrar 7125F and Hybrar 7311F, both manufactured by Kuraray Co., Ltd.), and SIBS (styrene-isobutylene-styrene block copolymer: SIBSTAR 073T, SIBSTAR 102T, and SIBSTAR 103T (all manufactured by Kaneka Corporation), and Septon V9827 (manufactured by Kuraray Co., Ltd.)), but are not limited to these. These may be used alone or in combination. Polystyrene and its modified products are preferably free of unsaturated bonds, since they have higher heat resistance and are less susceptible to oxidative degradation. The weight-average molecular weight of polystyrene and its modified products is not particularly limited as long as it is 10,000 or more, but if it is too large, compatibility with not only polyphenylene ether compounds but also 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 deteriorates, making it difficult to ensure mixing and solvent stability. Therefore, the weight-average molecular weight is preferably about 10,000 to 300,000.

[0086] The curable resin composition of the present invention can be obtained by preparing the above-mentioned components in a predetermined ratio, pre-curing the composition at 130 to 180°C for 30 to 500 seconds, and then post-curing the composition at 150 to 200°C for 2 to 15 hours, thereby allowing the curing reaction to proceed sufficiently and producing 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.

[0087] The method for preparing the curable resin composition of the present invention is not particularly limited. The components may be simply mixed uniformly, or prepolymerized. For example, a mixture of components (A), (B), and other compounds may be heated in the presence or absence of a curing accelerator or polymerization initiator, and in the presence or absence of a solvent, to form a prepolymer. Similarly, compounds such as amine compounds, compounds having ethylenically unsaturated bonds, maleimide compounds, cyanate ester compounds, polybutadiene and its modified products, polystyrene and its modified products, inorganic fillers, and other additives may be added to form a prepolymer. Mixing or prepolymerization of the components may be performed using, for example, an extruder, kneader, or rolls in the absence of a solvent, or using a reactor equipped with a stirrer in the presence of a solvent.

[0088] To achieve uniform mixing, the materials are kneaded at a temperature in the range of 50 to 100°C using a device such as a kneader, roll, or planetary mixer to obtain a uniform resin composition. The resulting resin composition is then pulverized and molded into cylindrical tablets using a molding machine such as a tablet machine, or into granular powder or powder-like molded products. Alternatively, these compositions can be melted on a surface support and molded into a sheet with a thickness of 0.05 mm to 10 mm to obtain a molded curable resin composition. The resulting molded product is non-sticky at 0 to 20°C, and exhibits little loss of fluidity or curability even when stored at -25 to 0°C for one week or more. The resulting molded article can be molded into a cured product using a transfer molding machine or a compression molding machine.

[0089] The curable resin composition of the present invention can also be converted into a varnish-like composition (hereinafter simply referred to as varnish) by adding an organic solvent. The curable resin composition of the present invention can be dissolved in a solvent such as toluene, xylene, acetone, methyl ethyl ketone, methyl isobutyl ketone, dimethylformamide, dimethylacetamide, or N-methylpyrrolidone, as needed, to form a varnish. This varnish can then be impregnated into a substrate such as glass fiber, carbon fiber, polyester fiber, polyamide fiber, alumina fiber, or paper, and heated and dried to obtain a prepreg. This prepreg can then be hot-press molded to form a cured product of the curable resin composition of the present invention. The solvent used in this process accounts for 10 to 70 wt %, preferably 15 to 70 wt %, of the mixture of the curable resin composition of the present invention and the solvent. Furthermore, if the composition is in liquid form, a cured curable resin containing carbon fiber can also be obtained directly, for example, by the RTM method.

[0090] 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 flexibility in the B-stage. Such a film-type resin composition can be obtained as a sheet-like adhesive by applying the curable resin composition of the present invention as a varnish onto a release film, removing the solvent under heating, and then performing B-stage formation. This sheet-like adhesive can be used as an interlayer insulating layer in a multilayer substrate or the like.

[0091] The curable resin composition of the present invention can also be used to obtain a prepreg by heating and melting it to reduce its viscosity and impregnating it into reinforcing fibers such as glass fibers, carbon fibers, polyester fibers, polyamide fibers, and alumina fibers. Specific examples include, but are not limited to, 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; inorganic fibers other than glass; and organic fibers such as polyparaphenylene terephthalamide (Kevlar®, manufactured by DuPont), wholly aromatic polyamide, polyester, polyparaphenylene benzoxazole, polyimide, and carbon fiber. The shape of the substrate is not particularly limited, but examples include woven fabric, nonwoven fabric, roving, and chopped strand mat. Known weaving methods for woven fabrics include plain weave, saddle weave, and twill weave, and these known methods can be appropriately selected depending on the intended application and performance. Also suitable are woven fabrics that have been subjected to fiber-opening treatment and glass woven fabrics that have been surface-treated with a silane coupling agent or the like. The thickness of the substrate is not particularly limited, but is preferably about 0.01 to 0.4 mm. Also, a prepreg can be obtained by impregnating reinforcing fibers with the varnish and drying them by heating.

[0092] A laminate can also be manufactured using the prepreg. The laminate is not particularly limited as long as it includes one or more prepregs, and may also include any other layers. The method for manufacturing the laminate can be any generally known method, and is not particularly limited. For example, when molding a metal foil-clad laminate, a multi-stage press, a multi-stage vacuum press, a continuous molding machine, an autoclave molding machine, or the like can be used. The prepregs are laminated together and then heated and pressure molded to obtain a laminate. The heating temperature is not particularly limited, but is preferably 65 to 300°C, more preferably 120 to 270°C. The pressure applied is also not particularly limited, but if the pressure is too high, it becomes difficult to adjust the resin solid content of the laminate, resulting in unstable quality. If the pressure is too low, air bubbles will form and adhesion between the laminate layers will be poor. Therefore, a pressure of 2.0 to 5.0 MPa is preferred, and 2.5 to 4.0 MPa is more preferred. The laminate of this embodiment, having a layer made of metal foil, can be suitably used as a metal foil-clad laminate, as described below. The prepreg is cut into a desired shape and laminated with copper foil or the like as needed. The laminate is then heated and cured while applying pressure by press molding, autoclave molding, sheet winding molding, or the like, to obtain an electrical and electronic laminate (printed wiring board) or a carbon fiber reinforced material.

[0093] The curable resin composition of the present invention can also be made into a resin sheet. For example, a method for obtaining a resin sheet from the curable resin composition of the present invention includes applying the curable resin composition to a support film (support) and then drying the composition to form a resin composition layer on the support film. When the curable resin composition of the present invention is used for a resin sheet, it is essential that the film softens under the lamination temperature conditions (70°C to 140°C) in a vacuum lamination method and exhibits fluidity (resin flow) that allows resin filling of via holes or through holes present in the circuit board simultaneously with lamination of the circuit board. It is preferable to blend the above-mentioned components so as to exhibit such properties. The resulting resin sheet or circuit board (e.g., copper-clad laminate) is required to have a uniform appearance in order to exhibit consistent performance at any location without causing phenomena such as locally varying property values ​​due to phase separation.

[0094] Here, the diameter of the through-holes in the circuit board is 0.1 to 0.5 mm, and the depth is 0.1 to 1.2 mm, and it is preferable to make it possible to fill the resin within this range. When laminating both sides of the circuit board, it is desirable to fill about half of the through-holes.

[0095] A specific method for producing the resin sheet includes preparing a resin composition varnished by blending an organic solvent, applying the varnished resin composition to the surface of a support film (Y), and then drying the organic solvent by heating or blowing hot air, etc., to form a resin composition layer (X).

[0096] The organic solvent used here is preferably, for example, a ketone such as acetone, methyl ethyl ketone, or cyclohexanone; an acetate ester such as ethyl acetate, butyl acetate, cellosolve acetate, propylene glycol monomethyl ether acetate, or carbitol acetate; a carbitol such as cellosolve or butyl carbitol; an aromatic hydrocarbon such as toluene or xylene; dimethylformamide, dimethylacetamide, or N-methylpyrrolidone; and it is preferably used in a proportion such that the nonvolatile content is 30 to 60% by mass.

[0097] The thickness of the resin composition layer (X) to be formed must be equal to or greater than the thickness of the conductor layer. Since the thickness of the conductor layer of the circuit board is in the range of 5 to 70 μm, the thickness of the resin composition layer (X) is preferably 10 to 100 μm. The resin composition layer (X) in the present invention may be protected with a protective film, which will be described later. Protection with a protective film can prevent the adhesion of dust and the like to the surface of the resin composition layer and scratches.

[0098] Examples of the support film and protective film include polyolefins such as polyethylene, polypropylene, and polyvinyl chloride; polyesters such as polyethylene terephthalate (PET) and polyethylene naphthalate; polycarbonate; polyimide; and release paper and metal foils such as copper foil and aluminum foil. The support film and protective film may be subjected to a mud treatment, corona treatment, or release treatment. The thickness of the support film is not particularly limited, but is generally in the range of 10 to 150 μm, preferably 25 to 50 μm. The thickness of the protective film is preferably 1 to 40 μm.

[0099] The support film (Y) is peeled off after laminating it onto a 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, adhesion of dust and the like during the curing process can be prevented. When peeling off after curing, the support film is previously subjected to a release treatment.

[0100] A multilayer printed circuit board can be produced from the resin sheet obtained as described above. For example, when the resin composition layer (X) is protected by a protective film, the film is peeled off, and then the resin composition layer (X) is laminated onto one or both sides of the circuit board so as to be in direct contact with the circuit board, for example, by a vacuum lamination method. The lamination method may be a batch method or a continuous method using a roll. If necessary, the resin sheet and the circuit board may be heated (preheated) before lamination. The lamination conditions are preferably a pressure bonding temperature (lamination temperature) of 70 to 140°C and a pressure bonding pressure of 1 to 11 kgf / cm. 2 (9.8×10 4 ~107.9×10 4 N / m 2 ), and lamination is preferably carried out under reduced air pressure of 20 mmHg (26.7 hPa) or less.

[0101] The curable resin composition of the present invention can be used to manufacture semiconductor devices, such as DIP (dual in-line package), QFP (quad flat package), BGA (ball grid array), CSP (chip size package), SOP (small outline package), TSOP (thin small outline package), and TQFP (thin quad flat package).

[0102] The curable resin composition and its cured product of the present invention can be used in a wide range of fields. Specifically, they can be used in various applications such as molding materials, adhesives, composite materials, and paints. Because the cured product of the curable resin composition of the present invention exhibits excellent heat resistance and dielectric properties, it is suitable for use in electrical and electronic components such as encapsulants for semiconductor devices, encapsulants for liquid crystal display devices, encapsulants for organic EL devices, laminates (printed wiring boards, BGA substrates, build-up substrates, etc.), lightweight, high-strength structural composite materials such as carbon fiber reinforced plastics and glass fiber reinforced plastics, 3D printing, etc. [Example]

[0103] The present invention will now be described in more detail with reference to examples. Unless otherwise specified, all parts are by weight. It should be noted that the present invention is not limited to these examples.

[0104] The various analytical methods used in the examples are described below. <Weight average molecular weight (Mw), number average molecular weight (Mn)> Calculation was performed in terms of polystyrene using a polystyrene standard solution. GPC: DGU-20A3R, LC-20AD, SIL-20AHT, RID-20A, SPD-20A, CTO-20A, CBM-20A (all manufactured by Shimadzu Corporation) Column: Shodex KF-603, KF-602x2, KF-601x2) Coupled eluent: tetrahydrofuran Flow rate: 0.5ml / min. Column temperature: 40℃ Detection: RI (differential refractive index detector)

[0105] [Synthesis Example 1] A flask equipped with a thermometer, condenser, and stirrer was equipped with an aspirator and a base trap. 370.1 parts of 2-bromoethylbenzene (Tokyo Chemical Industry Co., Ltd.), 175.1 parts of α,α'-dichloro-p-xylene (Tokyo Chemical Industry Co., Ltd.), and 27.3 parts of methanesulfonic acid (Tokyo Chemical Industry Co., Ltd.) were charged to the flask and reacted at 130°C for 6 hours while collecting the evolved hydrogen chloride with a base trap. 100 parts of toluene and 600 parts of cyclohexane were added for extraction, and the organic layer was washed five times with 100 parts of water. The solvent and excess 2-bromoethylbenzene were distilled off under reduced pressure with heating to obtain 380 parts of a compound (BEB-1) having a 2-bromoethylbenzene structure represented by formula (3) below as a liquid resin (Mn: 938, Mw: 1290). The GPC chart of the resulting compound is shown in Figure 1. The average repeating unit value (n), calculated from the area percentage of the GPC chart, was 2.2.

[0106] [ka]

[0107] [Synthesis Example 2] A flask equipped with a thermometer, condenser, and stirrer was charged with 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-oxyl free radical, and 146.4 parts of 50 wt% aqueous sodium hydroxide solution, and the reaction was continued at 40°C for 6 hours. 100 parts of water was added, and the organic layer was washed, and then returned to the reaction vessel. 735 parts of dimethyl sulfoxide and 9.8 parts of 50 wt% aqueous sodium hydroxide solution were added, and the reaction was continued for another hour at 40°C. 300 parts of toluene was added, and the organic layer was repeatedly washed with 100 parts of water until the wastewater became neutral. The mixture was concentrated under reduced pressure using an evaporator to obtain 180 parts of compound (O-1) having two or more styrene structures in the molecule, as represented by the following formula (4). The GPC chart of the obtained compound is shown in Figure 2. The obtained compound 1 The H-NMR data (deuterated chloroform) is shown in Figure 3. 1 Signals derived from vinyl groups were observed at 5.10-5.30 ppm, 5.50-5.85 ppm, and 6.60-6.80 ppm in the H-NMR chart. The average value n of the repeating units calculated from the area % of the GPC chart was 2.2 (the molecular weight of the resin component was Mn: 797, Mw: 1187).

[0108] [ka]

[0109] [Example 1, Comparative Example 1] The materials shown in Table 1 were dissolved in acetone at the proportions shown in Table 1 to a solid content of 66% by mass, and then mixed. The mixture was applied to a mirror-finished copper foil to a wet film thickness of 200 μm, pre-dried in a vacuum oven at 60°C for 30 minutes, and then cured at 220°C for 1 hour. After curing, the copper foil was etched using ferric chloride to obtain a cured film. (For Comparative Example 1, the film was cured at 175°C for 2 hours.) For evaluation, test pieces were cut to the desired size using a laser cutter as needed, and evaluation was performed.

[0110] <Dielectric constant test / dielectric loss tangent test> The test was performed using a cavity resonator perturbation method using a 10GHz cavity resonator manufactured by ATE Co., Ltd. The sample size was 1.7mm wide x 100mm long, and the thickness was 0.1mm.

[0111] <Heat resistance (DSC)> Differential scanning calorimeter: DSC6220 (SII NanoTechnology) Measurement temperature range: 30 to 330°C Heating rate: 10°C / min Atmosphere: Nitrogen (30 mL / min) Sample amount: 5 mg Tg: The inflection point on the DSC chart was taken as Tg.

[0112] [Table 1] SI-B5: Thermal cationic polymerization initiator (manufactured by Sanshin Chemical Industry Co., Ltd.) NC-3000-L: Biphenyl aralkyl epoxy resin (manufactured by Nippon Kayaku Co., Ltd.) 2E4MZ: 2-ethyl-4-methylimidazole (curing accelerator, manufactured by Shikoku Chemicals Co., Ltd.)

[0113] From the results in Table 1, it was confirmed that Example 1 was superior in high heat resistance and low dielectric properties compared to conventionally used epoxy resin compositions.

[0114] The curable resin composition, resin sheet and cured product thereof of the present invention are suitable for use in electric and electronic parts such as semiconductor encapsulants, printed wiring boards and build-up laminates.

Claims

1. A curable resin composition containing (A) a compound having at least two styrene structures in the molecule and (B) a thermal cationic polymerization initiator, The curable resin composition, wherein the component (A) is a compound represented by the following formula (1), and the component (B) is an organic sulfonium salt compound: 【Chemistry 1】 (In formula (1), each R independently represents a hydrocarbon group or a halogenated alkyl group having 1 to 10 carbon atoms; p and r represent integers of 0 to 4; q represents an integer of 0 to 3; n represents the average number of repetitions, and 1≦n≦20.)

2. The curable resin composition according to claim 1 , further comprising an inorganic filler.

3. A resin sheet comprising the curable resin composition according to claim 1 or 2 and a support.

4. A cured product of the curable resin composition according to claim 1 or 2 or the resin sheet according to claim 3.

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