Curable composition, prepreg, metal-clad laminate, printed circuit board and semiconductor package

Abstract

Provided is a curable composition comprising: a compound (A) containing an indene ring and a vinylbenzyl group; and a hollow filler (B).

Description

Curable compositions, prepregs, metal-clad laminates, printed circuit boards, and semiconductor packages 【0001】 This disclosure relates to curable compositions, prepregs, metal-clad laminates, printed circuit boards, and semiconductor packages. 【0002】 Metal-clad laminates, such as copper-clad laminates, prepregs that can be used for metal-clad laminates, and semiconductor packages using metal-clad laminates are used in a wide variety of electronic devices, including mobile communication devices such as smartphones, their base station equipment, network infrastructure equipment such as servers, routers, and large servers, large computers, personal computers, and industrial computers. They are also used in electronic devices installed in home appliances, automobiles, and other similar products. 【0003】 In electronic devices, when processing vast amounts of data at high speed, substrate materials with low transmission loss in the high-frequency range are required. Low dielectric constant and low dielectric loss tangent resins are used as substrate materials to provide substrates with low transmission loss, but with the recent advancements in communication technology, there is a need for the development of resins with even lower dielectric constant and low dielectric loss tangent. 【0004】 Patent Document 1 discloses a curable vinylbenzyl compound having an indene ring structure into which vinylbenzyl groups are introduced, which can be used to make a cured product with excellent dielectric properties, high heat resistance, and low water absorption. 【0005】 Japanese Patent Publication No. 2003-277440 【0006】 One of the objectives of this disclosure is to provide a curable composition, prepreg, metal-clad laminate, printed circuit board, and semiconductor package that exhibit excellent flame retardancy in the cured product. 【0007】 This disclosure includes, but is not limited to, the following embodiments. One embodiment relates to a curable composition comprising a compound (A) comprising an indene ring and a vinylbenzyl group, and a hollow filler (B). 【0008】 This disclosure makes it possible to provide curable compositions, prepregs, metal-clad laminates, printed circuit boards, and semiconductor packages that exhibit excellent flame retardancy in the cured products. 【0009】 The embodiments of this disclosure are described in detail below. This disclosure is not limited to the embodiments described below. 【0010】 In this disclosure, numerical ranges indicated using "~" represent a range that includes the numbers before and after "~" as the minimum and maximum values, respectively. In numerical ranges described stepwise in this disclosure, the upper or lower limit of one numerical range may be replaced with the upper or lower limit of another numerical range. Furthermore, the upper or lower limits of numerical ranges described in this disclosure may be replaced with the values ​​shown in the examples. In this disclosure, each component may contain one or more of the corresponding substances unless otherwise specified. In this disclosure, the content of each component in the curable composition means the total amount of the multiple substances present in the curable composition if there are multiple substances corresponding to each component in the curable composition, unless otherwise specified. 【0011】 In this disclosure, unless otherwise specified, the number-average molecular weight (Mn) and weight-average molecular weight (Mw) are values ​​measured by the following procedure. The number-average molecular weight (Mn) and weight-average molecular weight (Mw) are converted from a calibration curve using standard polystyrene by gel permeation chromatography (GPC). The calibration curve is approximated by a cubic equation using standard polystyrene: TSK standard POLYSTYRENE (Type; A-2500, A-5000, F-20, F-80) (manufactured by Tosoh Corporation, trade name). The GPC conditions are shown below. 【0012】Instrument: High-speed GPC instrument "HLC-8320GPC" (Tosoh Corporation, product name) Detector: Ultraviolet absorption detector "UV-8320" (Tosoh Corporation, product name) Columns: Guard column; TSKgel guardcolumn Super(HZ)-M+, Column; TSKgel SuperMultipore HZ-M (2), Reference column; TSKgel SuperH-RC (2) (all Tosoh Corporation, product names) Column size: 4.6 × 20 mm (guard column), 4.6 × 150 mm (column), 6.0 × 150 mm (reference column) Eluent: Tetrahydrofuran Sample concentration: 10 mg / 1 mL Injection volume: 20 μL or 2 μL Flow rate: 0.35 mL / min Measurement temperature: 40°C 【0013】 One embodiment of the present disclosure is a curable composition comprising a compound (A) containing an indene ring and a vinylbenzyl group, and a hollow filler (B). 【0014】 Compound (A) is not limited in terms of other specific structures, molecular weight, etc., as long as it contains an indene ring and a vinylbenzyl group, and a wide variety of compounds can be used. Compound (A) may be a compound having a single molecular structure, or it may be a resin containing multiple compounds with a molecular weight distribution and partially different structures. If compound (A) is a resin, not all molecules in the resin have to have a vinylbenzyl group; it is sufficient that the resin as a whole contains a vinylbenzyl group. Compound (A) may be used alone, or two or more may be used in combination. 【0015】Regarding the vinylbenzyl groups contained in compound (A), the vinylbenzyl groups may be o-vinylbenzyl groups, m-vinylbenzyl groups, or p-vinylbenzyl groups. Among these, p-vinylbenzyl groups are preferred because they result in a compound with excellent dielectric properties in the cured product. The proportion of p-vinylbenzyl groups in the total vinylbenzyl groups contained in compound (A) may be 10 mol% or more, 20 mol% or more, or 30 mol% or more. It may also be 100 mol% or less, 80 mol% or less, or 70 mol% or less. The proportion of p-vinylbenzyl groups in the total vinylbenzyl groups contained in compound (A) may be in the range of 10 to 100 mol%. If the proportion of p-vinylbenzyl groups is less than 100 mol%, the remaining vinylbenzyl groups may be m-vinylbenzyl groups. 【0016】 Compound (A) may contain, in addition to the indene ring and vinylbenzyl group, an arylalkyl group other than the vinylbenzyl group (hereinafter also referred to as "arylalkyl group"). The arylalkyl group in compound (A) is an optional component and is not essential. The number of carbon atoms in the alkyl group within the arylalkyl group is not particularly limited, but may be in the range of 1 to 6, for example. The alkyl group may be linear or have a branched structure. Specific examples of alkyl groups include methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, isobutyl group, sec-butyl group, t-butyl group, n-pentyl group, isopentyl group, neopentyl group, t-pentyl group, n-hexyl group, isohexyl group, etc. Among these, it is preferable that the alkyl group in the arylalkyl group has a relatively small number of carbon atoms, as this results in a compound with excellent dielectric properties. For example, the alkyl group in the arylalkyl group may be a methyl group or an ethyl group, or it may be a methyl group. 【0017】The aryl group in the arylalkyl group is not particularly limited as long as it is other than a styryl group, and examples thereof include a phenyl group, a naphthyl group, and a structural moiety having one or more substituents on these aromatic rings. Examples of the substituent on the aromatic ring include a halogen atom such as a fluorine atom, a chlorine atom, a bromine atom, or an iodine atom; an alkyl group having 1 to 6 carbon atoms such as a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a sec-butyl group, a t-butyl group, an n-pentyl group, an isopentyl group, a neopentyl group, a t-pentyl group, an n-hexyl group, or an isohexyl group; an alkoxy group represented by RO—, where R is the aforementioned alkyl group; a polymerizable unsaturated bond-containing group such as a vinyl group, a vinyloxy group, an allyl group, an allyloxy group, a (meth)acryloyl group, or a (meth)acryloyloxy group; an aryl group such as a phenyl group, a tolyl group, a xylyl group, a mesityl group, or a naphthyl group; an aryloxy group such as a phenyloxy group, a tolyloxy group, a xylyloxy group, a mesityloxy group, or a naphthyloxy group. 【0018】 The arylalkyl group may not have a polymerizable unsaturated bond. The aryl group in the arylalkyl group may be a phenyl group, a naphthyl group, or a group having 1 to 3 alkyl groups having 1 to 3 carbon atoms on these aromatic rings. 【0019】 As an example of the compound (A), for example, in the above general formula (1), R １ , R ２ and R ３ at least one of which is a vinylbenzyl group, a compound (A1), at least two compounds having different structures among the compounds represented by the following general formula (1), and R １ , R ２ and R ３ in the resin, at least one of which is a vinylbenzyl group, a resin (A2), etc. may be mentioned. 【0020】 【0021】 [In the general formula (1), R １ , R ２ and R ３Each of these is independently a hydrogen atom, a vinylbenzyl group, or an arylalkyl group other than a vinylbenzyl group. ４ is a hydrogen atom, a halogen atom, or a monovalent organic group, and has four R ４ All of them may be different from each other, and there are four R's. ４ Two or more of them may be identical. 【0022】 R in general formula (1) １ , R ２ and R ３ Each of these is independently a hydrogen atom, a vinylbenzyl group, or an arylalkyl group other than a vinylbenzyl group. Details of the arylalkyl group are as described above. Note that in resin (A1), the arylalkyl group is an optional component and not an essential component. 【0023】 R in general formula (1) ４ is a hydrogen atom, a halogen atom, or a monovalent organic group. Specific examples of halogen atoms include fluorine, chlorine, bromine, and iodine atoms. Examples of monovalent organic groups include alkyl groups with 1 to 6 carbon atoms, such as methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, t-butyl, n-pentyl, isopentyl, neopentyl, t-pentyl, n-hexyl, and isohexyl groups; alkoxy groups represented as RO-, where R is one of the aforementioned alkyl groups; polymerizable unsaturated bond-containing groups, such as vinyl, vinyloxy, allyl, allyloxy, (meth)acryloyl, and (meth)acryloyloxy groups; aryl groups, such as phenyl, tolyl, xylyl, mesityl, and naphthyl groups; and aryloxy groups, such as phenyloxy, tolyloxy, xylyloxy, mesityloxy, and naphthyloxy groups. R in general formula (1) ４ All of them may be hydrogen atoms. 【0024】 Compound (A1) is R in the above general formula (1). １ , R ２ and R ３ The compound is one in which at least one of the groups is a vinylbenzyl group. Compound (A1) is R １ , R ２ and R３ A compound in which one of the groups is a vinylbenzyl group and the other two are hydrogen atoms, R １ , R ２ and R ３ A compound in which two of the groups are vinylbenzyl groups and the other one is a hydrogen atom, R １ , R ２ and R ３ It may be any compound in which all of the groups are vinylbenzyl groups. 【0025】 Furthermore, compound (A1) has R in the above general formula (1). １ , R ２ and R ３ At least one of them is a vinylbenzyl group, and further, R １ , R ２ and R ３ The compound may be one in which at least one of the groups is an arylalkyl group other than a vinylbenzyl group. １ , R ２ and R ３ A compound in which one of the components is a vinylbenzyl group, one is an arylalkyl group, and one is a hydrogen atom, R １ , R ２ and R ３ A compound in which two of the groups are vinylbenzyl groups and one is an arylalkyl group, R １ , R ２ and R ３ A compound in which one of the groups is a vinylbenzyl group and the other two are arylalkyl groups, R １ , R ２ and R ３ A compound in which 1 to 3 of the groups are vinylbenzyl groups and the others are hydrogen atoms, R １ , R ２ and R ３ It may be any compound in which one to three of the atoms are arylalkyl groups and the others are hydrogen atoms. 【0026】 In resin (A2), R present in the resin １ , R ２ and R ３ At least one of them is a vinylbenzyl group. The resin (A2) is R １ , R ２ and R３ A compound in which one of the groups is a vinylbenzyl group and the other two are hydrogen atoms, R １ , R ２ and R ３ A compound in which two of the groups are vinylbenzyl groups and the other is a hydrogen atom, R １ , R ２ and R ３ A compound in which all are vinylbenzyl groups, R １ , R ２ and R ３ It may contain at least two types of compounds in which all atoms are hydrogen atoms. 【0027】 Furthermore, in resin (A2), R present in the resin １ , R ２ and R ３ At least one of them is a vinylbenzyl group, but furthermore, R present in the resin １ , R ２ and R ３ At least one of them may be an arylalkyl group other than a vinylbenzyl group. In this case, the resin (A1) is R １ , R ２ and R ３ A compound in which one of the components is a vinylbenzyl group, one is an arylalkyl group, and one is a hydrogen atom, R １ , R ２ and R ３ A compound in which two of the groups are vinylbenzyl groups and one is an arylalkyl group, R １ , R ２ and R ３ A compound in which one of the groups is a vinylbenzyl group and the other two are arylalkyl groups, R １ , R ２ and R ３ A compound in which 1 to 3 of the groups are vinylbenzyl groups and the others are hydrogen atoms, R １ , R ２ and R ３ A compound in which one to three of the atoms are arylalkyl groups and the others are hydrogen atoms, R １ , R ２ and R ３The compound may contain at least two types of compounds in which all atoms are hydrogen atoms. In a compound having multiple arylalkyl groups in one molecule, the arylalkyl groups may all be different, or some or all of them may be the same. 【0028】 In resin (A2), the average of the total number of vinylbenzyl groups and arylalkyl groups in one molecule is preferably 1.5 or higher, more preferably 1.8 or higher, and particularly preferably 2.0 or higher, as this results in excellent curability. It may also be 3.0 or lower, 2.8 or lower, or 2.5 or lower. The average of the total number of vinylbenzyl groups and arylalkyl groups in one molecule may be in the range of 1.5 to 3.0. Note that in resin (A1), the arylalkyl group is an optional component and is not an essential component. 【0029】 When resin (A2) contains an arylalkyl group, the ratio of vinylbenzyl groups to the total number of vinylbenzyl groups and arylalkyl groups present in resin (A2) may be 30 mol% or more, 60 mol% or more, or 85 mol% or more. It may also be 99 mol% or less, 95 mol% or less, or 80 mol% or less. The ratio of vinylbenzyl groups to the total number of vinylbenzyl groups and arylalkyl groups may be in the range of 30 to 99 mol%. 【0030】 Compound (A1) and resin (A2) are compounds identified by their molecular structure, and their preparation method is not particularly limited. One example of a method for producing compound (A1) and resin (A2) is to react indene and styrene having a methyl halide group in the presence of a basic compound. If compound (A1) and resin (A2) contain an arylalkyl group, an aromatic compound having a halide alkyl group corresponding to the arylalkyl group may be added as a reaction material as an optional component. 【0031】Examples of styrenes having a methyl halide group include o-chloromethylstyrene, m-chloromethylstyrene, and p-chloromethylstyrene. These may be used individually or in combination of two or more. Examples of aromatic compounds having an alkyl halide include α-chlorotoluene, α-chloroxylene, and 1-(chloromethyl)naphthalene. These may be used individually or in combination of two or more. 【0032】 The total number of moles of styrene having a methyl halide group and an aromatic compound having an alkyl halide per mole of indene may be 1.5 moles or more, 1.8 moles or more, or 2.0 moles or more. It may also be 3.0 moles or less, 2.8 moles or less, or 2.5 moles or less. The total number of moles of styrene having a methyl halide group and an aromatic compound having an alkyl halide per mole of indene may be in the range of 1.5 to 3.0 moles. 【0033】 When using an aromatic compound having an alkyl halogenate, the ratio of styrene having a methyl halogenate to the total number of moles of styrene having a methyl halogenate and the aromatic compound having an alkyl halogenate may be 30 mol% or more, 60 mol% or more, or 85 mol% or more. It may also be 99 mol% or less, 95 mol% or less, or 80 mol% or less. The ratio of styrene having a methyl halogenate to the total number of moles of styrene having a methyl halogenate and the aromatic compound having an alkyl halogenate may be in the range of 30 to 99 mol%. 【0034】 Examples of basic compounds include alkali metal hydroxides and alkali metal alkoxides. These may be used individually or in combination of two or more. 【0035】A phase-transfer catalyst may be used in the above reaction. Examples of phase transfer catalysts include quaternary ammonium salts such as tetra-n-butylammonium chloride, tetra-n-butylammonium bromide (tetra-n-butylammonium bromide), tetraethylammonium chloride, tetraethylammonium bromide, tetrapropylammonium chloride, tetrapropylammonium bromide, benzyltrimethylammonium chloride, benzyltrimethylammonium bromide, benzyltributylammonium chloride, benzyltributylammonium bromide, benzyldimethyltetradecylammonium chloride, tricaprylmethylammonium chloride, tetradecyltrimethylammonium bromide, hexadecyltrimethylammonium bromide, trioctylmethylammonium chloride, and tetra-n-butylammonium bisulfate; and quaternary phosphonium salts such as tetra-n-butylphosphonium chloride, tetra-n-butylphosphonium bromide, tetraphenylphosphonium chloride, tetraphenylphosphonium bromide, benzyltriphenylphosphonium chloride, and benzyltriphenylphosphonium bromide. These may be used individually or in combination of two or more types. 【0036】 The above reaction may be carried out, for example, under heating and stirring conditions. The heating temperature may be around 50 to 100°C. The above reaction can also be carried out by solution polymerization. The solvent used is not particularly limited as long as it can dissolve the reaction raw materials and has a boiling point above the reaction temperature, but examples include aromatic hydrocarbon solvents such as toluene, xylene, and mesitylene. These may be used individually or in combination of two or more. 【0037】Polymerization inhibitors may be used in the reaction system as needed. Examples of polymerization inhibitors include hydroquinone, methylhydroquinone, t-butylhydroquinone, 2,6-di-t-butylhydroquinone, 2,5-di-t-butylhydroquinone, hydroquinone monomethyl ether, 1,4-benzoquinone, 2-t-butyl-1,4-benzoquinone, 2-t-butylphenol, 2,4-di-t-butylphenol, 2,6-di-t-butylphenol, cresol, catechol, 4-t-butylcatechol, pyrogallol, and 4 Examples include methoxyphenol, thiodiphenylamine, phenothiazine, 3,7-dioctylphenothiazine, 3,7-dicumylphenothiazine, 2,2,6,6-tetramethylpiperidine-1-oxyl, 4-hydroxy-2,2,6,6-tetramethylpiperidine-1-oxyl, 4-benzoyloxy-2,2,6,6-tetramethylpiperidine-1-oxyl, and bis(2,2,6,6-tetramethyl-1-piperidinyloxy-4-yl) sebacate. These may be used individually or in combination of two or more. 【0038】 The product obtained from the above reaction may be purified by known methods such as concentration, reprecipitation, and washing, if necessary. 【0039】 Another example of compound (A) is a prepolymer (A3) obtained by polymerizing a portion of the vinyl groups in at least one selected from the group consisting of compound (A1) and resin (A2) (hereinafter also referred to as "compound (A1) / resin (A2)"). In this disclosure, a prepolymer is a polymer in which a portion of the polymerizable groups in the raw material remain without undergoing a polymerization reaction, and which has curability due to the remaining polymerizable groups. 【0040】 The prepolymer (A3) may also be prepared using compound (A1) / resin (A2) in combination with other reaction materials. The proportion of compound (A1) / resin (A2) in the total reaction materials of the prepolymer (A3) may be 50 mol% or more, 80 mol% or more, or 100 mol%. 【0041】The method for producing the prepolymer (A3) is not particularly limited, and it can be produced by polymerizing reaction materials containing compound (A1) / resin (A2) in a general manner. One example of this is radical polymerization. The polymerization initiator used in radical polymerization is not particularly limited, and known ones such as azo polymerization initiators and organic peroxide polymerization initiators can be used. The polymerization reaction may be carried out in a solvent. Examples of solvents that can be used include toluene and xylene. These may be used individually or in combination of two or more. 【0042】 The weight-average molecular weight (Mw) of prepolymer (A3) is not particularly limited, but may be 1,000 or more, 2,000 or more, or 3,000 or more, from the viewpoint of ease of manufacture and ease of handling of the curable resin material. It may also be 15,000 or less, 10,000 or less, or 8,000 or less. The weight-average molecular weight (Mw) of prepolymer (A1-2) may be in the range of 1,000 to 15,000. 【0043】 The proportion of resin (A2) in compound (A) is not particularly limited and can be adjusted as appropriate depending on the application of the curable composition, desired performance, etc., but for example it may be 50% by mass or more, 70% by mass or more, 90% by mass or more, or 100% by mass or more. 【0044】 The hollow filler (B) can be either an organic hollow filler or an inorganic hollow filler. One type of hollow filler (B) may be used alone, or two or more types may be used in combination. Examples of organic hollow fillers include hollow resin fillers having a resin-containing shell and a hollow part covered by the shell. In hollow resin fillers, the type of resin contained in the shell is not particularly limited, and any resin known as a hollow resin filler can be widely used. Examples of resins contained in the shell include acrylic resin, styrene resin, polyarylene ether resin, etc. 【0045】Examples of inorganic hollow fillers include silica, various metal silicates, aluminum oxide, aluminum hydroxide, aluminum nitride, boehmite, barium sulfate, barium carbonate, talc, clay, mica powder, zinc oxide, hydrotalcite, magnesium hydroxide, magnesium carbonate, magnesium oxide, calcium carbonate, manganese nitride, aluminum borate, strontium carbonate, strontium titanate, calcium titanate, magnesium titanate, bismuth titanate, titanium oxide, zirconium oxide, barium titanate, barium zirconate titanate, barium zirconate, calcium zirconate, zirconium phosphate, zirconium tungstate phosphate, etc. Examples of metal silicates include aluminum, lead, nickel, cobalt, copper, zinc, zirconium, iron, lithium, magnesium, barium, potassium, calcium, titanium, boron, sodium, etc. 【0046】 The porosity of the hollow filler (B) is not particularly limited, but may be, for example, 5 volume% or more, 20 volume% or more, or 50 volume% or more. It may also be 90 volume% or less, or 80 volume% or less. The porosity of the hollow filler (B) may be in the range of 5 to 90 volume%. The porosity of the hollow filler (B) can be calculated by known methods, for example, from the density of the hollow filler (B) and the material density of the material forming the hollow filler (B). 【0047】 The particle size of the hollow filler (B) is not particularly limited, but for example, the volume-based median system (D50) value measured by a laser diffraction / scattering particle size distribution analyzer may be in the range of 0.01 to 10 μm. 【0048】The content of hollow filler (B) in the curable composition is not particularly limited, but for example, it may be 5 parts by mass or more, or 10 parts by mass or more, per 100 parts by mass of the total resin components in the curable composition. Alternatively, it may be 50 parts by mass or less, 20 parts by mass or less, or 15 parts by mass or less. The amount of hollow filler (B) per 100 parts by mass of the total resin components in the curable composition may be in the range of 5 to 50 parts by mass. The resin components of the curable composition refer to the total of compound (A), other polymerizable group-containing compounds (D) described later, and elastomers. 【0049】 The curable composition may contain a hollow filler (B) as well as other fillers (C) other than the hollow filler (B). Specifically, the other fillers (C) may be so-called solid fillers that do not have a hollow structure. Both organic and inorganic fillers can be used for the other fillers (C). One type of other filler (C) may be used alone, or two or more types may be used in combination. 【0050】 Other fillers include, for example, silica, alumina, titanium oxide, barium titanate, strontium titanate, potassium titanate, calcium titanate, aluminum carbonate, magnesium hydroxide, aluminum silicate, calcium carbonate, calcium silicate, magnesium silicate, silicon nitride, boron nitride, aluminum borate, silicon carbide, mica, beryllia, clay, and talc. Among these, silica is preferred from the viewpoint of dielectric properties. The type of silica is not particularly limited and may be crystalline silica or amorphous silica, and may be natural silica or synthetic silica. The method of producing synthetic silica is also not particularly limited and may be any of the following: wet silica such as colloidal silica, fumed silica (dry silica), fused silica, etc. The shape of the silica is also not particularly limited and may be any of the following: spherical silica, crushed silica, etc. 【0051】The particle size of the other filler (C) is not particularly limited, but for example, the volume-based median system (D50) value measured by a laser diffraction / scattering particle size distribution analyzer may be in the range of 0.01 to 20 μm. 【0052】 When other fillers (C) are used, the proportion of hollow filler (B) in the total of 100 parts by mass of hollow filler (B) and other fillers (C) is not particularly limited, but may be, for example, 3% by mass or more, 5% by mass or more, or 8% by mass or more. It may also be 50% by mass or less, 30% by mass or less, or 20% by mass or less. The proportion of hollow filler (B) in the total of 100 parts by mass of hollow filler (B) and other fillers (C) may be in the range of 3 to 50 parts by mass. 【0053】 The curable composition may contain compound (A) as well as other polymerizable group-containing compounds (D) other than compound (A). Specific examples of other polymerizable group-containing compounds (D) (hereinafter also referred to as "compound (D)") include, for example, compounds having a maleimide group, polyarylene ether compounds having a polymerizable group, aromatic compounds having a vinyl group, triallyl isocyanurate, and the like. 【0054】 Examples of compounds having a maleimide group include bismaleimide compounds and maleimide resins. 【0055】Specific examples of bismaleimide compounds include, for example, N,N'-ethylenebismaleimide, N,N'-hexamethylenebismaleimide, N,N'-(1,3-phenylene)bismaleimide, N,N'-[1,3-(2-methylphenylene)]bismaleimide, N,N'-[1,3-(4-methylphenylene)]bismaleimide, N,N'-(1,4-phenylene)bismaleimide, bis(4-maleimidophenyl)methane, bis(3-methyl-4-maleimidophenyl)methane, and 3,3'-dimethyl-5,5'-die Tyl-4,4'-diphenylmethanebismaleimide, bis(4-maleimidophenyl)ether, bis(4-maleimidophenyl)sulfone, bis(4-maleimidophenyl)sulfide, bis(4-maleimidophenyl)ketone, bis(4-maleimidocyclohexyl)methane, 1,4-bis(4-maleimidophenyl)cyclohexane, 1,4-bis(maleimidomethyl)cyclohexane, 1,4-bis(maleimidomethyl)benzene, 1,3-bis(4-maleimidophenoxy)benzene, 1,3-bis(3- Maleimidophenoxy)benzene, bis[4-(3-maleimidophenoxy)phenyl]methane, bis[4-(4-maleimidophenoxy)phenyl]methane, 1,1-bis[4-(3-maleimidophenoxy)phenyl]ethane, 1,1-bis[4-(4-maleimidophenoxy)phenyl]ethane, 1,2-bis[4-(3-maleimidophenoxy)phenyl]ethane, 1,2-bis[4-(4-maleimidophenoxy)phenyl]ethane, 2,2-bis[4-(3-maleimidophenoxy)phenyl]propane , 2,2-bis[4-(4-maleimidophenoxy)phenyl]propane, 2,2-bis[4-(3-maleimidophenoxy)phenyl]butane, 2,2-bis[4-(4-maleimidophenoxy)phenyl]butane, 2,2-bis[4-(3-maleimidophenoxy)phenyl]-1,1,1,3,3,3-hexafluoropropane, 2,2-bis[4-(4-maleimidophenoxy)phenyl]-1,1,1,3,3,3-hexafluoropropane, 4,4-bis(3-maleimidophenoxy)biphenyl, 4,4-bis(4-maleimidophenoxy)biphenyl, bis[4-(3-maleimidophenoxy)phenyl]ketone, bis[4-(4-maleimidophenoxy)phenyl]ketone, bis(4-maleimidophenoxy)disulfide, bis[4-(3-maleimidophenoxy)phenyl]sulfide, bis[4-(4-maleimidophenoxy)phenyl]sulfide, bis[4-(3-maleimidophenoxy)phenyl ] sulfoxide, bis[4-(4-maleimidophenoxy)phenyl] sulfoxide, bis[4-(3-maleimidophenoxy)phenyl] sulfone, bis[4-(4-maleimidophenoxy)phenyl] sulfone, bis[4-(3-maleimidophenoxy)phenyl] ether, bis[4-(4-maleimidophenoxy)phenyl] ether, 1,4-bis[4-(4-maleimidophenoxy)-α,α-dimethicone Rubenzyl]benzene, 1,3-bis[4-(4-maleimidophenoxy)-α,α-dimethylbenzyl]benzene, 1,4-bis[4-(3-maleimidophenoxy)-α,α-dimethylbenzyl]benzene, 1,3-bis[4-(3-maleimidophenoxy)-α,α-dimethylbenzyl]benzene, 1,4-bis[4-(4-maleimidophenoxy)-3,5-dimethyl-α,α-dimethylbenzyl]benzene Examples include 1,3-bis[4-(4-maleimidophenoxy)-3,5-dimethyl-α,α-dimethylbenzyl]benzene, 1,4-bis[4-(3-maleimidophenoxy)-3,5-dimethyl-α,α-dimethylbenzyl]benzene, 1,3-bis[4-(3-maleimidophenoxy)-3,5-dimethyl-α,α-dimethylbenzyl]benzene, and aromatic bismaleimide compounds having an indane skeleton. 【0056】 Specific examples of maleimide resins include, for example, polyphenylmethane maleimide, maleimide resins having an indan skeleton, biphenyl aralkyl type maleimide resins, and long-chain alkyl group-containing maleimide resins. 【0057】 Maleimide resins having an indan skeleton include, for example, those represented by the following general formula (2). 【0058】 [R in general formula (2)]５ is a hydrogen atom or a methyl group, and a is an integer of 1 or more.] 【0059】 The biphenyl aralkyl type maleimide resin includes, for example, those represented by the following general formula (3). 【0060】 【0061】 [In the general formula (3), b is an integer of 1 or more.] 【0062】 The long-chain alkyl group-containing maleimide resin includes, for example, those represented by the following general formula (4). 【0063】 【0064】 [In the general formula (4), R ６ are each independently an alkylene group having 1 to 50 carbon atoms, and c is an integer of 1 to 10.] 【0065】 For the polyarylene ether compound having a polymerizable group, the arylene group is not particularly limited. For example, a phenylene group, a naphthylene group, and a structure in which an alkyl group, an alkyloxy group, a halogen atom, etc. are substituted 1 to a plurality of times on these aromatic carbons can be mentioned. The polymerizable group may be included, for example, as a vinyl group, a vinyloxy group, an allyl group, an allyloxy group, a (meth)acryloyl group, a (meth)acryloyloxy group, a vinylbenzyl group, a vinylbenzyloxy group, etc. The polyarylene ether compound having a polymerizable group may have a structural part other than the polyarylene ether structure. Specifically, it may have an acrylic polymerization site, a (poly)urethane site, a (poly)ester site, etc. in the molecular chain. The number of polymerizable groups in one molecule of the polyarylene ether compound is not particularly limited, and the substitution position of the polymerizable group is also not particularly limited. For example, the polyarylene ether compound may have a polymerizable group at the molecular end, or may have polymerizable groups at both ends. 【0066】 Specific examples of the polyarylene ether compound having a polymerizable group include, for example, resins represented by the following general formula (4). 【0067】 【0068】 [In general formula (5), R ７ Each of these is independently either a hydrogen atom or a methyl group. ８ [x] is one of the following: vinylbenzyl group, acryloyl group, or methacryloyl group. d and e are integers greater than or equal to 1. X is a divalent organic group. 【0069】 In general formula (4), X is a divalent organic group, and its specific structure is not particularly limited, but examples include hydrocarbon groups having 1 to 6 carbon atoms, halogenated hydrocarbon groups, oxygen atoms, sulfur atoms, carbonyl groups, sulfonyl groups, etc. 【0070】 The molecular weight of the polyarylene ether compound having polymerizable groups is not particularly limited, but for example, the number average molecular weight (Mn) may be in the range of 1,000 to 5,000. 【0071】 Aromatic compounds having a vinyl group include, for example, styrene, divinylbenzene, and 1,2-bis(4-vinylphenyl)ethane. 【0072】 The proportion of compound (A) in the total 100 parts by mass of compound (A) and compound (D) is not particularly limited, but may be, for example, 10 parts by mass or more, 20 parts by mass or more, or 30 parts by mass or more. It may also be 80 parts by mass or less, 70 parts by mass or less, or 60 parts by mass or less. The proportion of compound (A) in the total 100 parts by mass of compound (A) and compound (D) may be in the range of 10 to 80 parts by mass. 【0073】 Other optional components that the curable composition may contain include, for example, other thermosetting compounds other than compounds (A) and (D), elastomers, polymerization initiators, flame retardants, coupling agents, heat stabilizers, antistatic agents, ultraviolet absorbers, pigments, colorants, lubricants, fillers, solvents, and the like. Each of these other components may be used individually or in combination of two or more types. 【0074】 Other thermosetting compounds include, for example, epoxy resins, phenolic resins, cyanate resins, benzoxazine resins, oxetane resins, amino resins, silicone resins, triazine resins, and melamine resins. 【0075】 The ratio of the total mass of compound (A) and compound (D) to the total mass of curable components contained in the curable composition may be 50% by mass or more, 80% by mass or more, 90% by mass or more, or 100% by mass. The curable components contained in the curable composition refer to compound (A), compound (D), and other thermosetting compounds. 【0076】 Examples of elastomers include polyether-based elastomers, styrene-based elastomers, conjugated diene-based elastomers, urethane-based elastomers, polyester-based elastomers, polyamide-based elastomers, acrylic-based elastomers, and silicone-based elastomers. 【0077】 The weight-average molecular weight (Mw) of the elastomer is not particularly limited and may be, for example, 100,000 or less, 60,000 or less, or 30,000 or less. It may also be 1,000 or more, 3,000 or more, or 5,000 or more. The weight-average molecular weight (Mw) of the elastomer may be in the range of 1,000 to 100,000. 【0078】 If the curable composition contains an elastomer, its content may be 3% by mass or more, 5% by mass or more, or 10% by mass or more, relative to the total mass of the resin components contained in the curable composition. It may also be 40% by mass or less, 30% by mass or less, or 20% by mass or less. The ratio of elastomer to the total mass of the resin components contained in the curable composition may be in the range of 3 to 40% by mass. The resin components contained in the curable composition refer to compound (A), compound (D), other thermosetting compounds, and elastomers. 【0079】The polymerization initiator may be a thermal radical polymerization initiator or a photoradical polymerization initiator, but a thermal radical polymerization initiator is preferred. Specific examples of polymerization initiators include azo polymerization initiators and organic peroxide polymerization initiators. Examples of azo polymerization initiators include 2,2'-azobis(2,4,4-trimethylpentane), dimethyl-2,2'-azobis(2-methylpropionate), 2,2'-azobis(N-butyl-2-methylpropionamide), 2,2'-azobis[N-(2-propenyl)-2-methylpropionamide], 1,1'-azobis(cyclohexane-1-carbonitride), and dimethyl-1,1'-azobis(1-cyclohexanecarboxylate). Examples include 2,2'-azobis(isobutyronitrile), 2,2'-azobis(2-methylpropanenitrile), 2,2'-azobis(2-methylbutyronitrile), 2,2'-azobis(4-methoxy-2,4-dimethylvaleronitrile), 2,2'-azobis(2,4-dimethylvaleronitrile), and 4,4'-azobis(3,3,4,4,5,5,6,6,7,7,8,8,8-tridecafluorooctyl4-cyanopentanoate). Examples of organic peroxide polymerization initiators include dicumyl peroxide, dibenzoyl peroxide, 2-butanone peroxide, tert-butyl perbenzoate, di-tert-butyl peroxide, 2,5-dimethyl-2,5-di(t-butylperoxy)hexane, α,α'-di(t-butylperoxy)diisopropylbenzene, and tert-butyl hydroperoxide. 【0080】 If the curable composition contains a polymerization initiator, the amount of polymerization initiator added may be in the range of 0.01 to 5 parts by mass per 100 parts by mass of the total of compound (A) and compound (D). 【0081】Examples of flame retardants include halogen-based flame retardants, phosphorus-based flame retardants, nitrogen-based flame retardants, silicone-based flame retardants, and inorganic flame retardants. The amount of flame retardant added is adjusted as appropriate depending on the type of flame retardant, the intended use of the curable composition, and the desired physical properties. For example, when using a phosphorus-based flame retardant, the amount may be adjusted by the phosphorus atom content in the curable composition. Specifically, the phosphorus atom content relative to the total mass of the components of the curable composition excluding the solvent may be in the range of 0.1 to 20% by mass. 【0082】 The coupling agents include, for example, epoxy group-containing silanes such as 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropylmethyldimethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, 3-glycidoxypropyltriethoxysilane, and 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane; 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, N-(2-aminoethyl)-3-aminopropyltrimethoxysilane, N-(2-aminoethyl)-3-aminopropylmethyldimethoxysilane, 3-triethoxysilyl-n-(1,3-dimethylbutylidene)propylamine, and N-phenyl-3-aminopropyl Examples include amino group-containing silanes such as ropiltrimethoxysilane; cationic silanes such as 3-(trimethoxylyl)propyltetramethylammonium chloride; vinyl group-containing silanes such as vinyltrimethoxysilane and vinyltriethoxysilane; (meth)acryloyl group-containing silanes such as 3-acryloxypropyltrimethoxysilane, 3-methacryloxypropylmethyldimethoxysilane, 3-methacryloxypropyltrimethoxysilane, 3-methacryloxypropylmethyldiethoxysilane, and 3-methacryloxypropyltriethoxysilane; and mercapto group-containing silanes such as 3-mercaptopropylmethyldimethoxysilane and 3-mercaptopropyltrimethoxysilane. When the curable composition contains a coupling agent, the amount of coupling agent added may be in the range of 0.1 to 5 parts by mass per 100 parts by mass of the total resin components in the curable composition. 【0083】The curable composition may be solvent-free or may contain a solvent. The solvent can adjust the viscosity of the curable composition and further improve its coating properties. Organic solvents are preferred as the solvent. 【0084】 Examples of organic solvents include alcohol-based solvents such as ethanol, propanol, butanol, methyl cellosolve, ethylene glycol monobutyl ether, and propylene glycol monomethyl ether; ketone-based solvents such as acetone, methyl ethyl ketone, methyl isobutyl ketone, and cyclohexanone; ether-based solvents such as tetrahydrofuran; aromatic hydrocarbon-based solvents such as toluene, xylene, and mesitylene; nitrogen-containing solvents such as dimethylformamide, dimethylacetamide, and N-methylpyrrolidone; sulfur-containing solvents such as dimethyl sulfoxide; and ester-based solvents such as γ-butyrolactone. 【0085】 If the curable composition contains a solvent, the solid content of the curable composition may be, for example, in the range of 30 to 95% by mass. 【0086】 The method for producing the curable composition is not particularly limited. One example of a method for producing the curable composition is to add and mix compound (A), hollow filler (B), and optional components as needed. More specifically, for example, compound (A), hollow filler (B), and optional components as needed can be dissolved or dispersed in a solvent and mixed to obtain a curable composition. The mixing order of each component, temperature, time, and other conditions are not particularly limited and can be appropriately adjusted according to the type of raw materials, production scale, production equipment, etc. 【0087】[Prepreg] According to one embodiment, a prepreg containing a curable composition or a semi-cured product of a curable composition can be provided. This prepreg can be formed, for example, using a curable composition and a fibrous substrate. With respect to the semi-cured product of a curable composition, in this disclosure, the state of B-stage in JIS K 6800 (1985) can be cited as one indicator of the semi-cured state. The prepreg may contain, for example, a curable composition or a semi-cured product of a curable composition and a fibrous substrate such as a sheet-like fibrous substrate. In the prepreg, the curable composition may be in an uncured state, or it may be in a partially or entirely semi-cured state. 【0088】 A prepreg can be obtained, for example, by impregnating a fibrous substrate with a curable composition and drying the fibrous substrate impregnated with the curable composition. Drying is preferably carried out at a temperature above which volatile components such as solvents that may be contained in the curable composition are removed, and may also be carried out at a temperature above which the curable components contained in the curable composition are partially cured, depending on the application. Furthermore, it is preferable that the drying is adjusted so that the thermosetting resin contained in the curable composition is not completely cured. From this viewpoint, the drying temperature may be, for example, 80 to 200°C, and the drying time may be, for example, 1 to 30 minutes, depending on the drying temperature, drying equipment, and its scale. 【0089】 The fibrous base material may be woven, knitted, or nonwoven fabric. The fibrous base material may be provided in the form of chopped strand mat, roving, etc. The fiber material may be either inorganic or organic fiber. Examples of inorganic fibers include glass fiber and carbon fiber. Examples of glass fiber include E glass, NE glass, D glass, S glass, and Q glass. Examples of organic fibers include polyimide, polyester, and tetrafluoroethylene. The fibrous base material may use one of these fibers alone, or it may use two or more of these fibers in combination. From the viewpoint of dielectric properties and thermal expansion resistance, inorganic fibers are preferred for the fibrous base material, and glass fibers are more preferred. 【0090】The fibrous substrate can be appropriately selected depending on the application of the prepreg, but a sheet-like fibrous substrate is preferred. The sheet-like fibrous substrate may be, for example, various sheet-like fibrous substrates used in known laminates for electrical insulating materials. The thickness of the sheet-like fibrous substrate is not particularly limited, but for example, 0.01 to 0.1 mm is preferred. Here, the thickness is determined by measuring the thickness at five points at equal distances across the entire surface of the sheet-like fibrous substrate and taking the arithmetic mean of the five points. 【0091】 [Resin Film] According to one embodiment, a resin film comprising a curable composition or a semi-cured product of a curable composition can be provided. The resin film can be obtained, for example, by coating a material to be coated with a curable composition and drying or semi-curing it. Drying or semi-curing may be carried out in the same manner as the method for manufacturing the prepreg described above. After drying the resin film on the material to be coated, the product may be provided as a combination of the resin film and the material to be coated. For example, in this method, the resin film can be provided as a surface protective film, an interlayer insulating film, etc., in a printed circuit board. In another method, after drying the resin film on the material to be coated, the resin film may be peeled off the material to provide the resin film as a product. 【0092】 The material to be coated may be either an inorganic or organic substrate, and examples include glass substrates, metal foils, metal plates and other metal substrates, plastic plates, plastic films and other plastic substrates, paper substrates, and even fibrous substrates as described in the prepreg section above. In order to peel the resin film from the material to be coated and provide it, a material to be coated that has a release layer formed on its surface may be used. 【0093】 [Metal-clad laminate] According to one embodiment, a metal-clad laminate can be provided that includes a cured product of a curable composition and a metal foil. With respect to the cured product, in this disclosure, the state of the C-stage in JIS K 6800 (1985) can be cited as one indicator of the cured product. 【0094】In a metal-clad laminate, the cured product of the curable composition may be included as the cured product of the curable composition itself, or it may be included in the form of a prepreg. The metal-clad laminate may include a prepreg layer and a metal foil placed on at least one surface of the prepreg layer. The prepreg layer is the cured product of the prepreg described above, and may consist of a single prepreg or multiple prepregs laminated together. Furthermore, the metal-clad laminate may have the metal foil placed on one surface of the curable composition or the cured product of the prepreg, or it may have the metal foil placed on both surfaces of the curable composition or the cured product of the prepreg. The metal-clad laminate may be manufactured by placing the metal foil on at least one surface of a single sheet-like prepreg, or by laminating two or more sheet-like prepregs and placing the metal foil on at least one surface of the outermost layer of the laminate. The metal-clad laminate may be manufactured by laminating two or more sheet-like prepregs and placing the metal foil on both surfaces of this laminate. 【0095】 The following describes a specific method for manufacturing metal-clad laminates, which involves arranging metal foil on a laminate of two or more sheet-like prepregs. 【0096】 First, two or more sheet-like prepregs are laminated to obtain a laminate. In this laminate, the two or more sheet-like prepregs may be identical, or some or all of them may be different. In the laminate, it is sufficient that at least one of the two or more sheet-like prepregs is obtained using the curable composition according to one embodiment. 【0097】Next, a metal foil is placed on at least one surface of the laminate. The laminate with the metal foil is then heated and pressurized. This causes the sheet-like prepreg to harden, and a hardened prepreg product can be obtained. Adjacent sheet-like prepregs can also be bonded together. The heating and pressurizing conditions are not particularly limited, but for example, the temperature can be 100 to 300°C, the time 10 to 300 minutes, and the pressure 0.5 to 50 MPa. After heating and pressurizing, reheating may be performed to further harden the prepreg. In this case, the reheating temperature can be 100 to 300°C. As for the pressurizing method, for example, an autoclave molding machine, a multi-stage press machine, a multi-stage vacuum press machine, a continuous molding machine, etc., can be used. 【0098】 The metal used for the metal foil is not particularly limited and can include, for example, copper, nickel, aluminum, gold, silver, platinum, molybdenum, ruthenium, tungsten, iron, titanium, chromium, and alloys containing two or more of these metal elements. Industrially, it is preferable to use elemental copper, nickel, or aluminum. By using copper as the metal foil, a copper-clad laminate can be provided. 【0099】 [Printed Wiring Board] According to one embodiment, a printed wiring board containing a cured product of a curable composition can be provided. In the printed wiring board, the cured product of the curable composition may be included as the cured product of the curable composition itself, or it may be included in the form of a prepreg. The printed wiring board can be manufactured using a curable composition, a prepreg, a metal-clad laminate, or a combination thereof. For example, a printed wiring board can be provided by forming wiring using a metal-clad laminate by a known method. Details of the prepreg and metal-clad laminate are as described above. The printed wiring board may be either a single-layer printed wiring board or a multi-layer printed wiring board. 【0100】[Semiconductor Package] According to one embodiment, a semiconductor package including a printed wiring board and a semiconductor element can be provided. More specifically, for example, a semiconductor package including a printed wiring board containing a cured product of a curable composition and a semiconductor element can be provided. The semiconductor package can be manufactured, for example, by mounting a semiconductor element, a memory, etc. on the printed wiring board by a known method. 【0101】 The curable composition according to one embodiment can be used for prepregs, resin films, and metal-clad laminates. The curable composition according to one embodiment can be used for encapsulants, surface protection films, and interlayer insulation films. For example, as a cured product for encapsulating a semiconductor element, a semiconductor package including a cured product of the curable composition according to one embodiment can be provided. In another example, a printed wiring board including at least one of a surface protection film and an interlayer insulation film formed by the curable composition according to one embodiment can be provided. Since these articles have a low dielectric constant and a low dielectric tangent while being excellent in flame retardancy, the product reliability can be further enhanced. 【0102】 Examples of the embodiments are given below. The present invention is not limited to the following embodiments. <1> A curable composition containing a compound (A) containing an indene ring and a vinylbenzyl group, and a hollow filler (B). 【0103】 <2> The curable composition according to <1> above, wherein the compound (A) contains at least two compounds having different structures among the compounds represented by the following general formula (1), and at least one of R １ , R ２ and R ３ in the resin is a vinylbenzyl group, and includes a resin (A2). 【0104】 【0105】 [In general formula (1), R １ , R ２ and R ３ are each independently a hydrogen atom, a vinylbenzyl group, or an arylalkyl group other than a vinylbenzyl group. R ４is a hydrogen atom, a halogen atom, or a monovalent organic group, and has four R ４ All of them may be different from each other, and there are four R's. ４ Two or more of them may be identical. 【0106】 <3> The curable composition according to <1> or <2>, further comprising other fillers (C) other than the hollow filler. 【0107】 <4> The curable composition according to <3>, wherein the proportion of the hollow filler (B) in a total of 100 parts by mass of the hollow filler (B) and the other filler (C) is in the range of 3 to 50 parts by mass. 【0108】 <5> A prepreg comprising a curable composition or a semi-cured product of a curable composition as described in any one of <1> to <4> above. 【0109】 <6> A resin film comprising a curable composition or a semi-cured product of a curable composition as described in any one of <1> to <4> above. 【0110】 <7> A metal-clad laminate comprising a cured product of any one of the curable compositions described in <1> to <4> above, and a metal foil. 【0111】 <8> A metal-clad laminate comprising a cured product of any one of the curable compositions described in <1> to <4> above. 【0112】 <9> A semiconductor package comprising the printed circuit board described in <8> above and a semiconductor element. 【0113】 <10> A semiconductor package comprising a semiconductor element and a cured product of any one of <1> to <4> that encapsulates the semiconductor element. 【0114】 <11> A printed circuit board comprising at least one of a surface protective film and an interlayer insulating film formed by any one of the curable compositions described in <1> to <4> above. 【0115】 The present invention will be described in more detail below with reference to examples, but the present invention is not limited to the following examples. 【0116】Measurement Method of Number-Average Molecular Weight (Mn) and Weight-Average Molecular Weight (Mw) The number-average molecular weight (Mn) and weight-average molecular weight (Mw) were calculated from a calibration curve using standard polystyrene by gel permeation chromatography (GPC). The calibration curve was approximated by a cubic equation using standard polystyrene: TSK standard POLYSTYRENE (Type; A-2500, A-5000, F-20, F-80) (manufactured by Tosoh Corporation, trade name). The GPC conditions are shown below. 【0117】 Instrument: High-speed GPC instrument "HLC-8320GPC" (Tosoh Corporation, product name) Detector: Ultraviolet absorption detector "UV-8320" (Tosoh Corporation, product name) Columns: Guard column; TSKgel guardcolumn Super(HZ)-M+, Column; TSKgel SuperMultipore HZ-M (2), Reference column; TSKgel SuperH-RC (2) (all Tosoh Corporation, product names) Column size: 4.6 × 20 mm (guard column), 4.6 × 150 mm (column), 6.0 × 150 mm (reference column) Eluent: Tetrahydrofuran Sample concentration: 10 mg / 1 mL Injection volume: 20 μL or 2 μL Flow rate: 0.35 mL / min Measurement temperature: 40°C 【0118】 [Production of resin (A2-1)] A 500 mL reaction vessel equipped with a stirrer, thermometer, reflux tubing, and nitrogen inlet was charged with 35.6 parts by mass of indene, 124.9 parts by mass of chloromethylstyrene (*1), 6.5 parts by mass of α-chloro-p-xylene, 7.1 parts by mass of tetra-n-butylammonium bromide as a phase transfer catalyst, 0.1 parts by mass of phenothiazine as a polymerization inhibitor, and 94.5 parts by mass of toluene as a solvent. The mixture was heated and stirred at 40°C while blowing in nitrogen at a flow rate of 50 mL / min. 【0119】 Next, 125 parts by mass of a 48% sodium hydroxide aqueous solution were added dropwise over 20 minutes, and the mixture was stirred at 60°C for 9 hours. Nitrogen was continuously blown in during the reaction. After cooling to room temperature (25°C) and neutralizing with a 10% hydrochloric acid aqueous solution, the mixture was washed twice with pure water. After removing toluene by vacuum distillation, the resulting viscous liquid was washed with methanol and vacuum-dried to obtain resin (A2-1). 【0120】 Chloromethylstyrene (*1): AGC Seimi Chemical Co., Ltd. "CMS-P", a mixture of m-isomer and p-isomer, m-isomer content approximately 50% by mass, p-isomer content approximately 50% by mass. 【0121】 [Preparation of Flame Retardant 2] 432 parts by mass of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO), 251 parts by mass of bis(chloromethyl)biphenyl, and 2400 parts by mass of toluene were added to a reaction vessel equipped with a stirrer, thermometer, reflux tubing, and nitrogen inlet. The reaction was then continued at 170°C for 16 hours while stirring the contents of the reaction vessel. After the reaction mixture was cooled to room temperature, hexane was added to precipitate the product, which was then filtered. The resulting white crystals were dried at 120°C to obtain a compound represented by the following structural formula. This compound is designated as Flame Retardant 2. 【0122】 【0123】 [Examples 1-14 and Comparative Example 1] Each component was blended in the proportions shown in Tables 1-3, and the solid content was adjusted to approximately 65% ​​by mass with toluene to produce a curable composition. For the components blended in Tables 1-3, the values ​​for components that are solutions are calculated on a solid content basis. The amount of flame retardant added is calculated as the phosphorus atom content relative to the total mass of the components excluding the filler and solvent from the curable composition. The following evaluation tests were performed on the obtained curable compositions. The results are shown in Table 1. 【0124】 Details of each component listed in Table 1 are as follows: • Resin (A2-1): Resin (A2-1) obtained earlier • Compound (D-1): Polymerizable group-containing aromatic polyether compound, "HC-G0037" manufactured by JSR Corporation • Compound (D-2): Maleimide resin (long-chain alkyl group-containing bismaleimide resin) with the following general formula, "SFR-2300" manufactured by Hitachi Chemical Co., Ltd. 【0125】 【0126】[c is an integer from 1 to 10.] • Compound (D-3): SA9000 manufactured by SABIC Corporation, a polyphenylene ether resin with methacryloyl groups at the terminals, number average molecular weight (Mn) 1700. • Elastomer: SEPS2002 manufactured by Kuraray Co., Ltd., styrene-ethylene-propylene-styrene elastomer 【0127】 • Polymerization initiator: 2,2'-azobis(2,4,4-trimethylpentane), "VR-110" manufactured by Fujifilm Wako Pure Chemical Industries, Ltd. • Flame retardant 1: A phosphorus atom-containing compound represented by the following general formula ("Rabitol FP-72 (TP)" manufactured by Fushimi Pharmaceutical Co., Ltd.) 【0128】 【0129】 [f is an integer between 3 and 8.] 【0130】 • Flame retardant 2: Flame retardant 2 obtained above • Coupling agent: 3-methacryloxypropyltrimethoxysilane, manufactured by Shin-Etsu Chemical Co., Ltd. "KBM-503" • Inorganic hollow filler (B-1): Average particle size (D ５０ ) 2.0 μm hollow silica / organic hollow filler (B-2): average particle size (D ５０ ) 4.0 μm hollow resin filler / organic hollow filler (B-3): average particle size (D ５０ ) 2.4 μm hollow resin filler / inorganic solid filler (C-1): average particle size (D ５０ ) 1.0 μm solid silica 【0131】 [Prepreg Preparation] The curable composition was impregnated and coated onto glass cloth conforming to IPC standard #1078, and then heated and dried at 120°C for 10 minutes to obtain a prepreg. The solid content of the prepreg derived from the curable composition was approximately 80% by mass. 【0132】 [Preparation of double-sided copper-clad laminate] Multiple prepregs were stacked, and 18 μm thick electrolytic copper foil (SI-VSP-18, manufactured by Mitsui Mining & Smelting Co., Ltd.) was placed on both sides with the matte side facing the prepreg. This was then subjected to a load of 3 kg / cm². ２A double-sided copper-clad laminate was obtained by heating and pressurizing at 230°C for 80 minutes under vacuum pressing conditions. For the flame retardancy test, the thickness of the cured prepreg was 1.6 mm, and for the dielectric loss tangent (Df) measurement, the thickness of the cured prepreg was 0.2 mm. 【0133】 [Evaluation of Flame Retardancy] Double-sided copper-clad laminates were immersed in the copper etching solution (*3) described below to remove the copper foil, and five pieces measuring 125 mm in length and 13 mm in width were prepared as test specimens. A vertical combustion test in accordance with UL94-V was performed using these test specimens. Specifically, the upper end of the test specimen was held, and the flame of a gas burner was applied vertically to the lower end of the test specimen for 10 seconds, after which the flame of the gas burner was removed. After confirming that the flame had gone out, the flame of the gas burner was applied vertically to the lower end of the test specimen again for 10 seconds. The burning time after the flame was removed was measured. The first and second burning times of each test specimen were added together to calculate the average burning time for the five test specimens, and they were evaluated according to the following criteria: A: 15 seconds or less B: 16 seconds or more and 20 seconds or less C: 21 seconds or more and 25 seconds or less D: 25 seconds or more 【0134】 (*3) Copper etching solution: 10% by mass solution of ammonium persulfate (manufactured by Mitsubishi Gas Chemical Company, Inc.) 【0135】 [Measurement of Dielectric Loss Tangent (Df)] Only Examples 1 and 2 were evaluated. The copper foil on both sides of the double-sided copper-clad laminate obtained earlier was removed by immersion in a copper etching solution (*3) to prepare a 100 mm x 40 mm test specimen. The obtained test specimen was dried at 105°C for 1 hour, and then left to stand for 24 hours in an ambient temperature of 24.2°C and humidity of 54% RH. Next, the dielectric loss tangent (Df) was measured in the 10 GHz band at an ambient temperature of 25°C in accordance with the split-post dielectric resonator method. The measuring instrument used was the "PNA Network Analyzer N5222B" from agilent technologies. The measured value in Comparative Example 1 was set to 100, and the values ​​in Examples 1 and 2 were evaluated. 【0136】 【0137】 【0138】 【0139】 In the curable compositions of Examples 1 to 14, which contained compound (A) and hollow filler (B), highly flame-retardant cured products were obtained, as shown in Tables 1 to 3. On the other hand, the curable composition of Comparative Example 1, which did not contain compound (A), had significantly lower flame retardancy in the cured product compared to the examples. 【0140】 The disclosures of this application are related to the subject matter described in Japanese Patent Application No. 2024-217552, filed on 12 December 2024, the disclosures of which are incorporated herein by reference.

Claims

1. A curable composition comprising a compound (A) containing an indene ring and a vinylbenzyl group, and a hollow filler (B).

2. The compound (A) contains at least two compounds having different structures among the compounds represented by the following general formula (1), and R present in the resin １ , R ２ and R ３ The curable composition according to claim 1, comprising a resin (A2) in which at least one of them is a vinylbenzyl group. [In the general formula (1), R １ , R ２ and R ３ are each independently a hydrogen atom, a vinylbenzyl group, or an arylalkyl group other than a vinylbenzyl group. R ４ is a hydrogen atom, a halogen atom or a monovalent organic group, and all of the four R ４ may be different from each other, and two or more of the four R ４ may be the same as each other. ] 3. The curable composition according to claim 1, further comprising other fillers (C) other than the hollow filler (B).

4. The curable composition according to claim 3, wherein the proportion of the hollow filler (B) in a total of 100 parts by mass of the hollow filler (B) and the other filler (C) is in the range of 3 to 50 parts by mass.

5. A prepreg comprising a curable composition according to any one of claims 1 to 4 or a semi-cured product of the curable composition.

6. A resin film comprising a curable composition according to any one of claims 1 to 4 or a semi-cured product of the curable composition.

7. A metal-clad laminate comprising a cured product of a curable composition according to any one of claims 1 to 4 and a metal foil.

8. A printed circuit board comprising a cured product of a curable composition according to any one of claims 1 to 4.

9. A semiconductor package comprising a printed circuit board according to claim 8 and a semiconductor element.

10. A semiconductor package comprising a semiconductor element and a cured product of a curable composition according to any one of claims 1 to 4 for sealing the semiconductor element.

11. A printed circuit board comprising at least one of a surface protective film and an interlayer insulating film formed by the curable composition according to any one of claims 1 to 4.

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