Curable composition and cured product

Abstract

The present invention provides: a curable composition that provides a cured product having both a low dielectric loss tangent and excellent adhesion to a copper foil; a cured product of the curable composition; a metal-clad laminate provided with a metal layer and a substrate containing the cured product; and a method for producing the curable composition.　This curable composition contains a modifier (A), a modified polyphenylene ether (B), and a radically polymerizable compound (C). The modifier (A) includes core-shell polymer particles (A2) and a modified styrene-based elastomer (A1-1) as a modified resin (A1). A common polar group is included in the modified resin (A) and the core-shell polymer particles (A2). The used modified polyphenylene ether (B) has a carbon-carbon unsaturated double bond-containing group that is bound to an oxygen atom at a terminal of the molecule chain.

Description

Curable composition and cured product

[0001] The present invention relates to a curable composition that gives a cured product that has both excellent adhesion to copper foil and a low dielectric tangent, a cured product of the curable composition, a metal-clad laminate comprising a substrate containing the cured product and a metal layer, and a method for producing the curable composition.

[0002] In recent years, there has been a demand for communication devices such as smartphones and electronic devices such as next-generation televisions to transmit and receive large amounts of data at high speeds. Accordingly, the frequencies of electrical signals are becoming increasingly higher. Specifically, in the field of wireless communications, the use of high-frequency bands of 10 GHz or higher is being considered for the introduction of fifth-generation mobile communication systems.

[0003] However, as the frequency of the signal used increases, transmission loss increases, which can lead to erroneous recognition of information. To reduce this transmission loss, low-dielectric materials with low relative permittivity and dielectric loss tangent, which are factors related to the dielectric loss caused by insulating resins that constitute electronic components such as circuit boards, are needed. Under these circumstances, in order to obtain low-dielectric materials that can be used in high-frequency bands, a technology has been proposed in which a styrene-based thermoplastic elastomer is added as a resin modifier to a modified polyphenylene ether base resin in order to improve the dielectric properties (see Patent Document 1).

[0004] JP 2023-001134 A

[0005] A preferred application of the material having excellent low dielectric properties is a wiring board. The wiring board is usually a copper-clad laminate (CCL). However, a wiring board including a film or sheet made of a resin composition as described in Patent Document 1, or a wiring board impregnated with a resin composition as described in Patent Document 1, does not necessarily have good adhesion to copper foil.

[0006] The present invention has been made in view of the above-mentioned problems, and aims to provide a curable composition that gives a cured product that has both excellent adhesion to copper foil and a low dielectric tangent; a cured product of the curable composition; a metal-clad laminate comprising a substrate containing the cured product and a metal layer; and a method for producing the curable composition.

[0007] The present inventors have conducted extensive research to solve the above problems and have completed the present invention.

[0008] That is, the present invention provides the following (1) to (15): (1) A polymerizable composition comprising a modifier (A), a modified polyphenylene ether (B), and a radically polymerizable compound (C), wherein the modifier (A) comprises a modified resin (A1) and core-shell polymer particles (A2), wherein the modified resin (A1) comprises a modified styrene-based elastomer (A1-1), wherein the modified resin (A1) and the core-shell polymer particles (A2) are modified with a monomer having one or more polar groups selected from the group consisting of an epoxy group, an amino group, an acid anhydride group, a hydroxy group, and a carboxy group, wherein the type of the group present in the largest amount among the one or more polar groups present in the modified resin (A1) is the same as the type of the group present in the largest amount among the one or more polar groups present in the core-shell polymer particles (A2), and wherein the modified polyphenylene ether (B) has a carbon-carbon unsaturated double bond-containing group bonded to an oxygen atom at a molecular chain terminal, A curable composition, wherein the radically polymerizable compound (C) has two or more radically polymerizable carbon-carbon unsaturated double bonds. (2) The curable composition according to (1), wherein the modified polyphenylene ether (B) has, as the carbon-carbon unsaturated double bond-containing group, one or more selected from a vinylbenzyl group, a vinyl group, an allyl group, and a (meth)acryloyl group. (3) The curable composition according to (1) or (2), wherein the most abundant group among the one or more polar groups possessed by the modified resin (A1) and the most abundant group among the one or more polar groups possessed by the core-shell polymer particles (A2) are epoxy groups. (4) The curable composition according to any one of (1) to (3), comprising 25 to 90 parts by mass of the modified resin (A1) and 10 to 75 parts by mass of the core-shell polymer particles (A2) per 100 parts by mass of the modifier (A). (5) The curable composition according to any one of (1) to (4), wherein the content of polar groups in the modified resin (A1) is 0.1% by mass or more and 8% by mass or less, based on the mass of the modified resin (A1). (6) The curable composition according to any one of (1) to (5), wherein the content of polar groups in the core-shell polymer particles (A2) is 0.5% by mass or more and 10% by mass or less, based on the mass of the core-shell polymer particles (A2).(7) The curable composition according to any one of (1) to (6), wherein the amount of the radically polymerizable compound (C) is 10 parts by mass or more and 80 parts by mass or less per 100 parts by mass of the modified polyphenylene ether (B). (8) The curable composition according to any one of (1) to (7), wherein the amount of the core-shell polymer particles (A2) is 0.1 parts by mass or more and 30 parts by mass or less per 100 parts by mass of the modified polyphenylene ether (B). (9) The curable composition according to any one of (1) to (8), wherein the amount of the modified resin (A1) is 5 parts by mass or more and 50 parts by mass or less per 100 parts by mass of the modified polyphenylene ether (B). (10) A cured product of the curable composition according to any one of (1) to (9). (11) The cured product according to (10), wherein the dielectric loss tangent measured at 40 GHz is less than 0.0050. (12) A metal-clad laminate comprising a substrate containing the cured product according to (10) and a metal layer. (13) The metal-clad laminate according to (12), in which the peel strength measured by peeling the metal layer according to JIS C6471-1995 is 4.0 N / cm or more. (14) The metal-clad laminate according to (12) or (13), in which Rz on the main surface side of the metal layer is 0.3 μm or more and 2.0 μm or less before the metal layer is bonded to the substrate. (15) A method for producing the curable composition according to any one of (1) to (9), comprising: obtaining a first stock solution (a) containing a modifier (A) and a modified polyphenylene ether (B); obtaining a second stock solution (b) containing a radical-polymerizable compound (C); and mixing the first stock solution (a) and the second stock solution (b).

[0009] According to the present invention, it is possible to provide a curable composition that gives a cured product that has both excellent adhesion to copper foil and a low dielectric tangent, a cured product of the curable composition, a metal-clad laminate comprising a substrate containing the cured product and a metal layer, and a method for producing the curable composition.

[0010] <Curable Composition> The curable composition contains a modifier (A), a modified polyphenylene ether (B), and a radically polymerizable compound (C). The modifier (A) contains a modified resin (A1) and core-shell polymer particles (A2). The modified resin (A1) contains a modified styrene-based elastomer (A1-1). The modified resin (A1) and the core-shell polymer particles (A2) are modified with a monomer having one or more polar groups selected from the group consisting of an epoxy group, an amino group, an acid anhydride group, a hydroxy group, and a carboxy group. The type of the most abundant group among the one or more polar groups contained in the modified resin (A1) is the same as the type of the most abundant group among the one or more polar groups contained in the core-shell polymer particles (A2). The modified polyphenylene ether (B) has a carbon-carbon unsaturated double bond-containing group bonded to an oxygen atom at the molecular chain terminal. The radically polymerizable compound (C) has two or more radically polymerizable carbon-carbon unsaturated double bonds. The curable composition provides a cured product that has both excellent adhesion to copper foil and a low dielectric loss tangent. The curable composition also provides a cured product that has excellent heat resistance.

[0011] The form of the curable composition is not particularly limited. The curable composition is preferably a varnish-like composition containing the modified resin (A1), the modified polyphenylene ether (B), and the radical polymerizable compound (C) in a state of being dissolved in an organic solvent, and the core-shell polymer particles (A2) in a state of being dispersed in an organic solvent.

[0012] The organic solvent that the curable composition may contain is the same as the organic solvent that the modifier (A) may contain, which will be described later.

[0013] When the curable composition is a varnish-like composition containing an organic solvent, the solids concentration of the curable composition is preferably 20% by mass or more and 80% by mass or less, and more preferably 30% by mass or more and 70% by mass or less.

[0014] Essential and optional components contained in the curable composition will be described below.

[0015] <Modifier (A)> The curable composition contains a modifier (A). The modifier contains a modified resin (A1) and core-shell polymer particles (A2). The modified resin (A1) contains a modified styrene-based elastomer (A1-1). The modified resin (A1) and the core-shell polymer particles (A2) are modified with a monomer having one or more polar groups selected from the group consisting of an epoxy group, an amino group, an acid anhydride group, a hydroxy group, and a carboxy group. The type of the group that is most abundant among the one or more polar groups contained in the modified resin (A1) is the same as the type of the group that is most abundant among the one or more polar groups contained in the core-shell polymer particles (A2).

[0016] The modifier (A) is blended with the modified polyphenylene ether (B) described below. When the modifier (A) is blended with the modified polyphenylene ether (B), the adhesion of the cured product of the curable composition containing the modified polyphenylene ether (B) to copper foil can be improved without significantly deteriorating the dielectric properties of the modified polyphenylene ether (B).

[0017] The modifier (A) preferably contains 25 to 90 parts by mass of the modified resin (A1) and 10 to 75 parts by mass of the core-shell polymer particles (A2) relative to 100 parts by mass of the modifier (A).

[0018] The lower limit of the content of the modified resin (A1) in the modifier (A) may be 30 parts by mass or more, 40 parts by mass or more, or 50 parts by mass or more, relative to 100 parts by mass of the modifier (A). The upper limit of the content of the modified resin (A1) may be 80 parts by mass or less, 70 parts by mass or less, or 60 parts by mass or less, relative to 100 parts by mass of the modifier (A). Therefore, the content of the modified resin (A1) in the modifier (A) may be 30 parts by mass or more and 80 parts by mass or less, 40 parts by mass or more and 70 parts by mass or less, or 50 parts by mass or more and 60 parts by mass or less, relative to 100 parts by mass of the modifier (A).

[0019] The lower limit of the content of the core-shell polymer particles (A2) in the modifier (A) may be 20 parts by mass or more, 30 parts by mass or more, or 40 parts by mass or more, relative to 100 parts by mass of the modifier (A). The upper limit of the content of the core-shell polymer particles (A2) may be 70 parts by mass or less, 60 parts by mass or less, or 50 parts by mass or less, relative to 100 parts by mass of the modifier (A). Therefore, the content of the core-shell polymer particles (A2) in the modifier (A) may be 20 parts by mass or more and 70 parts by mass or less, 30 parts by mass or more and 60 parts by mass or less, or 40 parts by mass or more and 50 parts by mass or less, relative to 100 parts by mass of the modifier (A).

[0020] In the curable composition, the amount of the modified resin (A1) derived from the modifier (A) is preferably 5 to 50 parts by mass, more preferably 7 to 40 parts by mass, and even more preferably 10 to 30 parts by mass, relative to 100 parts by mass of the modified polyphenylene ether (B). In the curable composition, the amount of the core-shell polymer particles (A2) derived from the modifier (A) is preferably 0.1 to 30 parts by mass, more preferably 0.5 to 25 parts by mass, and even more preferably 1 to 18 parts by mass, relative to 100 parts by mass of the modified polyphenylene ether (B).

[0021] The essential and optional components contained in the modifier (A) will be described below.

[0022] [Modified Resin (A1)] The modified resin (A1) is a resin modified with a monomer having one or more polar groups selected from the group consisting of an epoxy group, an amino group, an acid anhydride group, a hydroxy group, and a carboxy group. The structural unit derived from the monomer having the polar group may be bonded to the main chain of the resin as a side chain of the resin by graft polymerization, or may be bonded to the main chain of the resin as a structural unit constituting the main chain of the resin.

[0023] The content of polar groups in the modified resin (A1) is not particularly limited as long as the desired effect is not impaired. The content of polar groups in the modified resin (A1) is preferably 0.1% by mass or more and 8% by mass or less, more preferably 0.1% by mass or more and 5% by mass or less, and even more preferably 0.1% by mass or more and 3% by mass or less, relative to the mass of the modified resin (A1). The content of polar groups in the modified resin (A1) can be measured by various methods depending on the type of polar group. When the polar group is an epoxy group, the content of epoxy groups in the modified resin (A1) can be measured, for example, using a potentiometric titrator in accordance with JIS K7236.

[0024] The ratio of the mass of the polar group having the largest amount to the total mass of the polar groups in the modified resin (A1) is preferably 50% by mass to 100% by mass, more preferably 75% by mass to 100% by mass, even more preferably 90% by mass to 100% by mass, and particularly preferably 100% by mass. The ratio of the mass of the polar group having the largest amount to the total mass of the polar groups in the core-shell polymer particles (A2) is preferably 50% by mass to 100% by mass, more preferably 75% by mass to 100% by mass, even more preferably 90% by mass to 100% by mass, and particularly preferably 100% by mass.

[0025] The modified resin (A1) includes a modified styrene-based elastomer (A1-1). The modified resin (A1) may include a modified resin other than the modified styrene-based elastomer (A1-1) as long as the desired effect is not impaired. Examples of modified resins other than the modified styrene-based elastomer (A1-1) include modified polyolefin-based resins, modified (meth)acrylic resins, modified polystyrene resins, modified polyphenylene ether resins other than the modified polyphenylene ether (B), modified silicone resins, modified polyester resins, and modified fluororesins. Among these, modified polyolefin-based resins are preferred. These modified resins other than the modified styrene-based elastomer (A1-1) can be obtained by using a monomer having the specific polar group described above when producing the modified resin, or by reacting a monomer having the specific polar group described above with the main chain of the resin to introduce a branch having a polar group into the main chain.

[0026] The content of the modified styrene-based elastomer (A1-1) is preferably 70% by mass or more and 100% by mass or less, more preferably 80% by mass or more and 100% by mass or less, still more preferably 90% by mass or more and 100% by mass or less, and particularly preferably 100% by mass, based on the mass of the modified resin (A1).

[0027] [Modified Styrenic Elastomer (A1-1)] The styrene elastomer is a block copolymer containing a polystyrene block derived from a styrene monomer consisting of styrene and a styrene derivative. The modified styrene elastomer (A1-1) is a modified resin obtained by modifying the above styrene elastomer with a monomer having one or more polar groups selected from the group consisting of an epoxy group, an amino group, an acid anhydride group, a hydroxyl group, and a carboxyl group.

[0028] The styrene monomer used as a raw material for the styrene elastomer is not particularly limited. Suitable examples of the styrene monomer include styrene, 4-methylstyrene, α-methylstyrene, 2,4-dimethylstyrene, α-methyl-4-methylstyrene, 4-chlorostyrene, α-chloro-4-chlorostyrene, 4-tert-butylstyrene, 4-methoxystyrene, 4-chloromethylstyrene, and styrene derivatives substituted with a silyl group. Of the above styrene monomers, styrene, α-methylstyrene, and 4-methylstyrene are preferred, and styrene and α-methylstyrene are more preferred from the standpoint of cost.

[0029] The blocks other than the polystyrene block in the styrene elastomer may be any of various known blocks used in styrene elastomers. Preferred styrene elastomers include styrene / isoprene / styrene elastomer, styrene / isobutylene / styrene elastomer, styrene / ethylenebutylene / styrene elastomer, hydrogenated styrene / isoprene / styrene elastomer, and hydrogenated styrene / (butadiene / isoprene) / styrene elastomer. The polystyrene block in the styrene elastomer may be a block made of polystyrene, a block made of a homopolymer of a styrene derivative, or a block made of a copolymer of two or more styrene monomers. The polystyrene block in the styrene elastomer is preferably a block made of polystyrene.

[0030] Among the polar groups possessed by the monomers used for modification, epoxy groups are preferred because they have an excellent effect of improving the adhesion of the cured product of the curable composition to the copper foil. The monomer having a polar group may have two or more polar groups. As the monomer having a polar group, a compound having one or two polar groups is preferred, and a compound having one polar group is more preferred.

[0031] Examples of the polar group-containing monomer include unsaturated group-containing epoxy compounds such as glycidyl (meth)acrylate, monoglycidyl maleate, monoglycidyl itaconate, monoglycidyl allyl succinate, allyl glycidyl ether, 3,4-epoxy-1-butene, and vinylcyclohexene monoxide; unsaturated amines such as allylamine, methallylamine, 1-amino-4-pentene, and 4-vinylaniline; unsaturated group-containing acid anhydrides such as maleic anhydride; hydroxyl group-containing unsaturated compounds such as 2-hydroxyethyl (meth)acrylate, allyl alcohol, methallyl alcohol, 1-butenyl alcohol, and 4-hydroxystyrene; and unsaturated carboxylic acids such as (meth)acrylic acid, maleic acid, fumaric acid, itaconic acid, and crotonic acid. Among these, glycidyl (meth)acrylate is preferred due to its excellent adhesion-improving effect. When producing the modified styrene-based elastomer (A1), two or more polar group-containing monomers may be used in combination.

[0032] The modification with a monomer having a polar group may be graft modification, or may be modification in which a monomer having a polar group is incorporated into a block constituting the styrene-based elastomer by copolymerization.

[0033] The graft-modified styrene-based elastomer (A1-1) is preferably graft-modified with a monomer having a polar group and an aromatic vinyl monomer not having a polar group. By using a monomer having a polar group in combination with an aromatic vinyl monomer not having a polar group, the graft reaction is stabilized, making it easier to graft a desired amount of the vinyl monomer having a polar group.

[0034] Specific examples of aromatic vinyl monomers having no polar group include styrene, 4-methylstyrene, α-methylstyrene, 4-chlorostyrene, α-chlorostyrene, dichlorostyrene, and 4-nitrostyrene. Among these, styrene, α-methylstyrene, and 4-methylstyrene are preferred because of their low cost, and styrene is particularly preferred. The aromatic vinyl monomers having no polar group can be used alone or in combination of two or more.

[0035] Examples of radical polymerization initiators that can be used when graft-modifying a styrene-based elastomer include 2,2-bis(tert-butylperoxy)butane, α,α'-bis(tert-butylperoxy-m-isopropyl)benzene, benzoyl peroxide, di(3-methyl-3-methoxybutyl)peroxydicarbonate, and di-tert-butylperoxyisophthalate. The above radical polymerization initiators can be used alone or in combination of two or more.

[0036] The amount of the radical polymerization initiator used is not particularly limited as long as the graft modification reaction proceeds smoothly, and is preferably 0.01 parts by mass or more and 10 parts by mass or less, and more preferably 0.2 parts by mass or more and 5 parts by mass or less, relative to 100 parts by mass of the styrene-based elastomer.

[0037] The amount of the monomer having a polar group used for graft modification of the styrene-based elastomer to be added is preferably 0.1 parts by mass or more and 12 parts by mass or less, more preferably 0.5 parts by mass or more and 10 parts by mass or less, and particularly preferably 1 part by mass or more and 8 parts by mass or less, relative to 100 parts by mass of the styrene-based elastomer.

[0038] By using a modified styrene-based elastomer (A1-1) modified with a monomer having a polar group in an amount within this range, the cured product of the curable composition has an excellent effect of improving adhesion to copper foil.

[0039] The amount of the aromatic vinyl monomer having no polar group used for graft modification of the styrene-based elastomer is preferably 0.1 parts by mass or more and 12 parts by mass or less, more preferably 0.5 parts by mass or more and 10 parts by mass or less, and particularly preferably 1 part by mass or more and 8 parts by mass or less, relative to 100 parts by mass of the styrene-based elastomer.

[0040] When the modified styrene elastomer (A1-1) contains a structural unit derived from a monomer having a polar group in the main chain, the modified styrene elastomer (A1-1) can be obtained by copolymerizing a monomer that gives a block constituting the styrene elastomer with a monomer having a polar group according to a well-known method. In this case, the preferred styrene elastomer is the same as that used in producing the modified styrene elastomer (A1-1) by graft modification.

[0041] <Core-shell polymer particles (A2)> The core-shell polymer particles (A2) have a core-shell structure and are polymer particles modified with a monomer having one or more polar groups selected from the group consisting of an epoxy group, an amino group, an acid anhydride group, a hydroxy group, and a carboxy group. The monomer having a polar group is as described above for the modified resin (A1). The core and the shell may each be composed of two or more layers. In the case of a multilayer structure, the polymer compositions of the layers may be different. The shell is a layer formed by graft polymerizing a graft-copolymerizable monomer (shell-forming monomer) onto the core, and at least a portion of the shell is the outermost layer of the core-shell polymer particle (A2). The entire shell need not necessarily be present on the outermost side of the core-shell polymer particle (A2). In the core-shell polymer particles (A2), the outermost layer of the shell is usually modified with the above-mentioned monomer having a polar group.

[0042] The content of polar groups in the core-shell polymer particles (A2) is not particularly limited as long as the desired effect is not impaired. The content of polar groups in the core-shell polymer particles (A2) is preferably 0.5% by mass or more and 10% by mass or less, more preferably 0.7% by mass or more and 8% by mass or less, and even more preferably 1% by mass or more and 6% by mass or less, relative to the mass of the core-shell polymer particles (A2). The content of polar groups in the core-shell polymer particles (A2) can be measured by various methods depending on the type of polar group. When the polar group is an epoxy group, for example, the content of epoxy groups in the core-shell polymer particles (A2) can be measured using a potentiometric titrator in accordance with JIS K7236.

[0043] The ratio of the mass of the core to the mass of the shell in the core-shell polymer particles, in terms of core / shell, is preferably from 50 / 50 to 99 / 1, more preferably from 60 / 40 to 95 / 5, and even more preferably from 70 / 30 to 90 / 10.

[0044] The core is preferably made of a crosslinked polymer. The crosslinked polymer is substantially insoluble in a solvent. The gel content of the core is preferably 60% by mass or more, more preferably 80% by mass or more, even more preferably 90% by mass or more, and particularly preferably 95% by mass or more.

[0045] The core is preferably a rubbery elastomer which is a polymer of monomers consisting of 50% by mass to 100% by mass of one or more monomers selected from the group consisting of diene monomers and (meth)acrylic acid ester monomers and 0% by mass to 50% by mass of other copolymerizable vinyl monomers, more preferably a rubbery elastomer which is a polymer of monomers consisting of 60% by mass to 100% by mass of one or more monomers selected from the group consisting of diene monomers and (meth)acrylic acid ester monomers and 0% by mass to 40% by mass of other copolymerizable vinyl monomers, and even more preferably a rubbery elastomer which is a polymer of monomers consisting of 70% by mass to 100% by mass of one or more monomers selected from the group consisting of diene monomers and (meth)acrylic acid ester monomers and 0% by mass to 30% by mass of other copolymerizable vinyl monomers.

[0046] Hereinafter, "a monomer selected from the group consisting of a diene monomer and a (meth)acrylic acid ester monomer" will be referred to as "monomer A." The other copolymerizable vinyl monomer is a vinyl monomer copolymerizable with monomer A. Furthermore, "(meth)acrylic" means both acrylic and methacrylic.

[0047] Examples of diene monomers include butadiene, isoprene, and chloroprene, with butadiene being preferred. Examples of (meth)acrylic acid ester monomers include butyl acrylate, 2-ethylhexyl acrylate, and lauryl methacrylate, with butyl acrylate and 2-ethylhexyl acrylate being preferred. These monomers may be used alone or in combination of two or more.

[0048] Examples of vinyl monomers copolymerizable with monomer A include one or more monomers selected from the group consisting of aromatic vinyl compounds, vinyl cyanide compounds, unsaturated carboxylic acid derivatives, (meth)acrylamide derivatives, and maleimide derivatives. Examples of aromatic vinyl compounds include styrene, α-methylstyrene, and vinylnaphthalene. Examples of vinyl cyanide compounds include (meth)acrylonitrile and substituted acrylonitrile. Examples of unsaturated carboxylic acid derivatives include (meth)acrylic acid, itaconic acid, crotonic acid, and maleic anhydride. Examples of (meth)acrylamide derivatives include (meth)acrylamide and N-substituted (meth)acrylamide. Examples of maleimide derivatives include maleimide and N-substituted maleimide. These monomers may be used alone or in combination of two or more.

[0049] When preparing the polymer constituting the core, a crosslinkable monomer may be used for the purpose of suppressing swelling of the core due to a solvent. Examples of the crosslinkable monomer include divinylbenzene, butanediol di(meth)acrylate, triallyl (iso)cyanurate, allyl (meth)acrylate, diallyl itaconate, and diallyl phthalate. The amount of the crosslinkable monomer used is preferably 0.2% by mass or more and 7% by mass or less, more preferably 0.5% by mass or more and 5% by mass or less, and even more preferably 1% by mass or more and 3% by mass or less, based on the mass of the core-shell polymer particles (A2).

[0050] In addition, coating the core with a crosslinkable monomer and forming an intermediate layer between the core and the shell is effective in suppressing fusion between the core-shell polymer particles (A2). The crosslinkable monomer used to form the intermediate layer is not particularly limited, but a trialkenyl isocyanurate compound such as triallyl isocyanurate (TAIC) is preferred.

[0051] In order to adjust the molecular weight and / or degree of crosslinking of the polymer constituting the core layer, a chain transfer agent may be used in the polymerization of the core. Examples of the chain transfer agent include alkyl mercaptans having 5 to 20 carbon atoms. The amount of the chain transfer agent used is preferably 5% by mass or less, more preferably 3% by mass or less, based on the mass of the core.

[0052] The core may contain a crosslinked aromatic vinyl. Examples of the crosslinked aromatic vinyl include copolymers of aromatic vinyl compounds and the above-mentioned crosslinkable monomers. Examples of the aromatic vinyl compounds include styrene, 2-vinylnaphthalene, α-methylstyrene, 4-methylstyrene, 2,4-dimethylstyrene, 3,5-dimethylstyrene, 2,4,6-trimethylstyrene, 4-methoxystyrene, and 2-chlorostyrene.

[0053] The type of polymer constituting the shell is not particularly limited, and the polymer constituting the shell is preferably a polymer of one or more monomers selected from a (meth)acrylic acid ester monomer, an aromatic vinyl monomer, a vinyl cyanide monomer, an unsaturated carboxylic acid derivative, a (meth)acrylamide derivative, and a maleimide derivative.

[0054] As the (meth)acrylic acid ester-based monomer, aromatic vinyl-based monomer, vinyl cyanide-based monomer, unsaturated carboxylic acid derivative, (meth)acrylamide derivative, and maleimide derivative, the compounds described above as specific examples of the monomer A and the vinyl monomer copolymerizable with the monomer A can be used.

[0055] The core-shell polymer particles (A2) preferably contain styrene units in an amount of 30% by mass or more, more preferably 40% by mass or more, and even more preferably 50% by mass or more.

[0056] The core-shell polymer particles (A2) are modified with a monomer having one or more polar groups selected from the group consisting of an epoxy group, an amino group, an acid anhydride group, a hydroxy group, and a carboxy group. Therefore, in the core-shell polymer particles (A2), it is preferred that the resin constituting the shell contains a structural unit derived from the monomer having the polar group, or that the monomer having the polar group is graft-polymerized onto the resin constituting the shell.

[0057] When modifying the core-shell polymer particles, a monomer having a polar group is used so that the ratio of the mass of the polar group to the mass of the core-shell polymer particles (A2) falls within the above-mentioned preferred range.

[0058] The volume average particle diameter of the core-shell polymer particles (A2) is preferably 10 nm to 400 nm, more preferably 50 nm to 300 nm, and even more preferably 80 nm to 250 nm. The volume average particle diameter of the core-shell polymer particles (A2) can be measured using a laser diffraction / scattering particle size distribution analyzer such as Microtrac (Microtrac UPA, manufactured by Nikkiso Co., Ltd.).

[0059] The method for producing the core-shell polymer particles (A2) is not particularly limited. For example, well-known methods such as emulsion polymerization, suspension polymerization, and microsuspension polymerization can be used. Among them, multistage emulsion polymerization is preferred.

[0060] <Other Components> The modifier (A) may contain other components in addition to the modified resin (A1) and the core-shell polymer particles (A2) depending on the intended use of the curable composition.

[0061] Examples of other components include various additives such as compatibilizers, fillers, antioxidants, heat stabilizers, light stabilizers, flame retardants, lubricants, antistatic agents, colorants, rust inhibitors, crosslinking agents, foaming agents, fluorescent agents, surface smoothing agents, surface gloss improvers, and mold release improvers.

[0062] In addition, the modifier (A) may contain an organic solvent if necessary.Preferred examples of organic solvents include ketones such as methyl ethyl ketone and methyl isobutyl ketone; aliphatic hydrocarbons such as pentane, hexane, cyclohexane, octane, and decane; aromatic hydrocarbons such as benzene, toluene, and xylene; ethers such as diethyl ether, diisopropyl ether, and tetrahydrofuran; halogenated hydrocarbons such as methylene chloride, methyl chloroform, carbon tetrachloride, dichlorodifluoromethane, and perchloroethylene.Two or more of these organic solvents may be used in combination.

[0063] When the modifier (A) contains an organic solvent, the solid content concentration of the modifier (A) is not particularly limited. The solid content concentration of the modifier (A) is preferably 5% by mass or more and 50% by mass or less, and more preferably 10% by mass or more and 40% by mass or less.

[0064] The modified resin (A1) and the core-shell polymer particles (A2) described above are uniformly mixed together, if necessary, with other additives to obtain the modifier (A). Preferably, the modifier (A) is prepared by mixing a solution of the modified resin (A1) in an organic solvent with a dispersion of the core-shell polymer particles (A2) dispersed in an organic solvent.

[0065] [Modified Polyphenylene Ether (B)] The curable composition contains a modified polyphenylene ether (B). The modified polyphenylene ether (B) has a carbon-carbon unsaturated double bond-containing group bonded to an oxygen atom at the molecular chain terminal. The polyphenylene ether usually has a hydroxyl group bonded to an aromatic ring at the molecular chain terminal. The modified polyphenylene ether (B) is obtained by substituting the hydrogen atom in this terminal hydroxyl group with the carbon-carbon unsaturated double bond-containing group.

[0066] The carbon-carbon unsaturated double bond-containing group is preferably one or more selected from a vinylbenzyl group, a vinyl group, an allyl group, and a (meth)acryloyl group. When the carbon-carbon unsaturated double bond-containing group is a vinylbenzyl group, an allyl group, or a (meth)acryloyl group, the terminal hydroxyl groups of the polyphenylene ether can be converted to vinylbenzyloxy groups, allyloxy groups, or (meth)acryloyloxy groups using a corresponding halide according to a conventional method. When the carbon-carbon unsaturated double bond-containing group is a vinyl group, the terminal hydroxyl groups of the polyphenylene ether can be converted to vinyloxy groups by methods such as an ether exchange reaction between a vinyl ether compound, such as an alkyl vinyl ether (e.g., methyl vinyl ether), and the terminal hydroxyl groups; a vinylation reaction using a vinyl ester compound (e.g., vinyl acetate); or the addition of acetylene to the terminal hydroxyl groups.

[0067] Alternatively, commercially available products may be used as the modified polyphenylene ether (B). Specific examples of commercially available products include vinylbenzyl-terminated polyphenylene ethers such as OPE-2St-2200 and OPE-2st-1200 (both manufactured by Mitsubishi Gas Chemical Company, Inc.) and methacryloyl-terminated polyphenylene ethers such as Noryl (registered trademark) SA9000 (manufactured by SABIC).

[0068] The molecular weight of the modified polyphenylene ether (B) is not particularly limited as long as the desired effect is not impaired. The molecular weight of the modified polyphenylene ether (B) is preferably 1,000 or more, more preferably 2,000 or more, in terms of number average molecular weight (Mn). The molecular weight of the modified polyphenylene ether (B) is preferably 1,000 or more and 10,000 or less, more preferably 2,000 or more and 5,000 or less, in terms of number average molecular weight (Mn).

[0069] [Radical polymerizable compound (C)] The curable composition contains a radical polymerizable compound (C). The radical polymerizable compound (C) is a compound having two or more radically polymerizable carbon-carbon unsaturated double bonds. Note that the radical polymerizable compound (C) is a compound that does not fall under the category of the modified polyphenylene ether (B).

[0070] The molecular weight of the radical polymerizable compound (C) is not particularly limited. When the radical polymerizable compound (C) is not a polymer, the molecular weight of the radical polymerizable compound (C) is preferably 10,000 or less.

[0071] The radical polymerizable compound (C) has a radical polymerizable group containing a carbon-carbon unsaturated double bond. The radical polymerizable group is not particularly limited, but is typically a carbon-carbon double bond-containing group. Suitable examples of the carbon-carbon double bond-containing group include alkenyl groups such as a vinyl group, an allyl group, and a methallyl group; unsaturated acyl groups such as a (meth)acryloyl group (an acryloyl group or a methacryloyl group); and a maleimide group.

[0072] Specific preferred examples of the radically polymerizable compound (C) include divinylbenzene, triallyl cyanurate, triallyl isocyanurate, trimethallyl isocyanurate, trimethylolpropane tri(meth)acrylate, 1,3,5-triacryloylhexahydro-1,3,5-triazine, triallyl trimellitate, 1,3-phenylenediamine bismaleimide, dipropargyl terephthalate, diallyl phthalate, and N,N',N'',N'''-tetraallyl terephthalamide.

[0073] Among these, one or more selected from the group consisting of divinylbenzene, triallyl cyanurate, triallyl isocyanurate, trimethallyl isocyanurate, and trimethylolpropane tri(meth)acrylate are more preferred.

[0074] Furthermore, a bismaleimide compound obtained by reacting a terminal amino group of an oligomer, which is obtained by reacting dimer diamine with tetracarboxylic dianhydride, with maleic anhydride is also preferred as the radical polymerizable compound (C) because the dielectric loss tangent of the cured product is low. A specific example of the bismaleimide compound is MIZ-001 (manufactured by Nippon Kayaku Co., Ltd.).

[0075] The content of the radically polymerizable compound (C) in the curable composition is preferably 10 parts by mass or more and 80 parts by mass or less, and more preferably 20 parts by mass or more and 50 parts by mass or less, relative to 100 parts by mass of the resin.

[0076] [Radical Polymerization Initiator (D)] As described above, the curable composition contains a radically polymerizable compound (C). Therefore, the curable composition may contain a radical polymerization initiator (D) for the purpose of promoting the reaction between the radically polymerizable compounds (C) and the reaction between the modified polyphenylene ether (B) and the radically polymerizable compound (C). As the radical polymerization initiator (D), any conventionally known radical polymerization initiator can be used without any particular limitation. Specific examples are the same as the specific examples of radical polymerization initiators that can be used when graft-modifying a styrene-based elastomer, and these can be used alone or in combination of two or more.

[0077] The amount of the radical polymerization initiator (D) used is not particularly limited as long as the curable composition is capable of radical polymerization by heating or exposure to light. The amount of the radical polymerization initiator (D) used is, for example, preferably 1 part by mass or more and 10 parts by mass or less, more preferably 1.5 parts by mass or more and 9 parts by mass or less, and even more preferably 2 parts by mass or more and 8 parts by mass or less, relative to 100 parts by mass of the radical polymerizable compound (C).

[0078] [Inorganic Filler] The curable composition may contain an inorganic filler as needed. Examples of inorganic fillers include calcium carbonate, talc, clay, silica, magnesium carbonate, barium sulfate, titanium oxide, alumina, montmorillonite, gypsum, glass flakes, glass fiber, milled glass fiber, carbon fiber, alumina fiber, silica-alumina fiber, aluminum borate whisker, and potassium titanate fiber. The inorganic fillers may be used alone or in combination of two or more.

[0079] The amount of the inorganic filler used is not particularly limited as long as the desired effect is not impaired. The amount of the base-free filler used is preferably 10 parts by mass or more and 200 parts by mass or less, and more preferably 20 parts by mass or more and 100 parts by mass or less, per 100 parts by mass of the modified polyphenylene ether (B).

[0080] [Other Additives] The curable composition may contain various additives, as needed, that may be contained in the modifier (A). These additives may be used alone or in combination of two or more.

[0081] [Method for producing curable composition] The method for producing the curable composition is not particularly limited as long as it is a method that can uniformly mix the modifier (A), the modified polyphenylene ether (B), and the radical polymerizable compound (C). Since this method can uniformly mix the modifier (A), the modified polyphenylene ether (B), and the radical polymerizable compound (C) while avoiding curing by heating, it is preferable to prepare the curable composition by mixing the modifier (A), the modified polyphenylene ether (B), and the radical polymerizable compound (C) in the above-mentioned organic solvent.

[0082] A preferred method for producing the curable composition is to mix an organic solvent-containing modifier (A) with an organic solvent solution of a modified polyphenylene ether (B) and a radically polymerizable compound (C). Such a method preferably includes obtaining a first stock solution (a) containing the modifier (A) and the modified polyphenylene ether (B), obtaining a second stock solution (b) containing the radically polymerizable compound (C), and mixing the first stock solution (a) and the second stock solution (b).

[0083] The first stock solution (a) and the second stock solution (b) usually contain an organic solvent. Suitable examples of the organic solvent that the first stock solution (a) and the second stock solution (b) may contain are the same as the suitable examples of the organic solvent that the modifier (A) may contain.

[0084] When the curable composition contains a radical polymerization initiator (D), the radical polymerization initiator (D) may be contained in either the first stock solution (a) or the second stock solution (b). However, in terms of the stability of the radical polymerizable compound (C), it is preferable that the radical polymerization initiator (D) be added to a mixed solution of the first stock solution (a) and the second stock solution (b). The radical polymerization initiator (D) can be added as a solution, a slurry, or a solid to a mixed solution of the first stock solution (a) and the second stock solution (b).

[0085] By applying energy to the curable composition described above by a method such as heating or exposure to light, the curable composition is cured to form a cured product. The dielectric loss tangent of the cured product measured under conditions of 28 to 40 GHz is preferably less than 0.0050. In particular, the dielectric loss tangent measured under conditions of 40 GHz is preferably less than 0.0050. A cured product exhibiting such a dielectric loss tangent is suitable as a material for semiconductor package substrates for smartphones, etc.

[0086] As described above, the cured product of the curable composition is preferably used as a material for a wiring board. Specifically, a metal-clad laminate including a substrate containing the cured product of the curable composition and a metal layer serving as a wiring material is preferably used.

[0087] In a wiring board including a substrate containing the cured product of the curable composition and a metal layer serving as a wiring material, the substrate and the metal layer made of a metal foil such as copper foil are well adhered to each other. In particular, when the metal layer is in contact with the cured product of the curable composition, the metal layer is well adhered to the substrate. When the metal layer is in contact with the cured product of the curable composition, the metal-clad laminate has a peel strength of 4.0 N / cm or more, preferably 4.5 N / cm or more, and more preferably 5.0 N / cm or more, as measured by peeling the metal layer according to, for example, JIS C6471-1995.

[0088] As described above, the metal layer adheres well to the cured product of the curable composition on the substrate. Therefore, the roughness of the main surface of the metal layer may be low. In a metal-clad laminate, when the metal layer is in contact with the cured product of the curable composition, the Rz on the main surface side of the metal layer is preferably 2.5 μm or less, more preferably 1.0 μm or less, and even more preferably 0.5 μm or less, before the metal layer is bonded to the substrate. The lower limit of Rz is not particularly limited, but may be, for example, 0.1 μm or more, or 0.3 μm or more.

[0089] Preferred substrate materials include a sheet made of a curable composition or a cured product of the curable composition, and a prepreg made of a fiber sheet and a cured product of the curable composition composited with the fiber sheet. The method for forming the sheet made of the curable composition is not particularly limited. When the curable composition is a varnish-like composition, a sheet made of the curable composition can be formed by a solution casting method. Furthermore, a sheet made of the cured product of the curable composition can be obtained by curing the sheet made of the curable composition. The sheet obtained in this manner is suitable for use as at least one layer constituting a laminate. Furthermore, the prepreg can be formed by impregnating a fiber sheet such as a glass fiber sheet with a radically polymerizable curable composition, and then curing the curable composition impregnated into the fiber sheet by a method such as heating or exposure to light.

[0090] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples.

[0091] [Production Example 1] (Production of Modified Styrenic Elastomer A1-1) 100 parts by mass of styrene / ethylene butylene / styrene elastomer (SEPTON 8007L, manufactured by Kuraray) and 0.15 parts by mass of 1,3-di(tert-butylperoxyisopropyl)benzene (PERBUTYL P, manufactured by NOF Corp.) were supplied from the hopper port to a twin-screw extruder (46 mmφ, L / D=63, manufactured by Kobe Steel, Ltd., KTX46) set at a cylinder temperature of 230°C and a screw rotation speed of 150 rpm, and melt-kneaded. 1 part by mass of styrene and 1 part by mass of glycidyl methacrylate were added midway through the cylinder. Subsequently, pellets of modified styrenic elastomer A1-1 were obtained by vacuum devolatilization through a vent port.

[0092] The obtained resin pellets were dissolved in xylene at 130°C and then cooled to room temperature again to precipitate a recrystallized resin, which was used to measure the epoxy group content using an automatic potentiometric titrator (AT700 manufactured by Kyoto Electronics Manufacturing Co., Ltd.) in accordance with JIS K 7236. The epoxy group content of the modified styrene-based elastomer A1-1 was 0.21% by mass.

[0093] [Production Example 2] (Production of Modified Styrenic Elastomer A1-2) A modified styrene-based elastomer A1-2 was obtained in the same manner as in Production Example A1, except that SEPTON 8007L was replaced with a styrene / isobutylene / styrene elastomer (SIBSTAR 103T, manufactured by Kaneka). The epoxy group content of the modified styrene-based elastomer A1-2 was 0.34 mass%.

[0094] [Production Example 3] 200 parts by mass of water, 0.03 parts by mass of tripotassium phosphate, 0.25 parts by mass of potassium dihydrogen phosphate, 0.002 parts by mass of ethylenediaminetetraacetic acid (EDTA), 0.001 parts by mass of ferrous sulfate heptahydrate, and 1.5 parts by mass of sodium dodecylbenzenesulfonate (SDBS) were added to a 100 L pressure polymerization vessel. While stirring the mixture in the pressure polymerization vessel, oxygen in the vessel was thoroughly removed by nitrogen substitution. Subsequently, 75 parts by mass of butadiene (Bd) and 25 parts by mass of styrene were added to the pressure polymerization vessel. Next, the temperature in the pressure polymerization vessel was raised to 45°C. Subsequently, 0.015 parts by mass of paramenthane hydroperoxide (PHP) was added to the pressure polymerization vessel. Next, 0.04 parts by mass of sodium formaldehyde sulfoxylate (SFS) was added to the pressure polymerization vessel to initiate polymerization. Four hours after the start of polymerization, 0.01 parts by mass of PHP, 0.0015 parts by mass of EDTA, and 0.001 parts by mass of ferrous sulfate heptahydrate were added to the pressure-resistant polymerization vessel. Ten hours after the start of polymerization, the reaction solution in the pressure-resistant polymerization vessel was depressurized to remove volatile components such as remaining monomers, thereby terminating the polymerization. In this manner, a styrene-butadiene rubber latex was obtained. The volume-average particle size of the styrene-butadiene rubber particles contained in the obtained styrene-butadiene rubber latex was 100 nm.

[0095] 241 parts by mass of the obtained styrene-butadiene rubber latex (80 parts by mass of styrene-butadiene rubber particles) and 65 parts by mass of water were added to a glass reaction vessel equipped with a thermometer, a stirrer, a reflux condenser, a nitrogen inlet, and a monomer addition device. The gas in the glass reaction vessel was replaced with nitrogen. The contents of the glass reaction vessel were then stirred at 60°C. 0.004 parts by mass of EDTA, 0.001 parts by mass of ferrous sulfate heptahydrate, and 0.2 parts by mass of SFS were then added to the glass reaction vessel. 2 parts by mass of triallyl isocyanurate (TAIC) and 0.07 parts by mass of cumene hydroperoxide (CHP) were then added to the glass reaction vessel. The contents of the glass reaction vessel were then stirred for 60 minutes. Thereafter, a mixture of 12 parts by mass of styrene, 4 parts by weight of acrylonitrile, 4 parts by mass of glycidyl methacrylate, and 0.08 parts by mass of tert-butyl hydroperoxide (TBP) was continuously added to a glass reaction vessel over a period of 110 minutes. Thereafter, 0.04 parts by mass of TBP was added to the glass reaction vessel, and stirring was continued for another hour to complete the polymerization. In this way, an aqueous latex containing core-shell polymer particles B1 was obtained. The volume average particle diameter of the core-shell polymer particles B1 contained in the aqueous latex was 110 nm. Furthermore, the ratio of the mass of the epoxy groups to the mass of the core-shell polymer particles B1 was 1.2% by mass. Using the obtained aqueous latex, a dispersion of core-shell polymer A2-1 was obtained in which the core-shell polymer particles B1 were dispersed in methyl ethyl ketone (MEK) at a solids concentration of 25% by mass according to the method described in Production Example 1 of WO 2020 / 027189.

[0096] [Production Example 4] 7.2 g of the modified styrene-based elastomer A1-1 obtained in Production Example A1 was dissolved in 28.8 g of toluene. Next, 11.2 g of a methyl ethyl ketone (MEK) dispersion of the core-shell polymer particles A2-1 (solid content concentration: 25% by mass) was added to the toluene solution of the modified styrene-based elastomer A1-1 to obtain 47.2 g of Modifier 1. The obtained 47.2 g of Modifier 1 contained 2.8 g of core-shell polymer particles A2-1.

[0097] [Production Example 5] Modifier 2 was obtained in the same manner as in Production Example 4, except that the amount of modified styrene-based elastomer A1-1 was changed from 7.2 g to 7.0 g and the amount of core-shell polymer particles A2-1 was changed from 2.8 g to 5.4 g.

[0098] [Production Example 6] Modifier 3 was obtained in the same manner as in Production Example 4, except that 7.2 g of modified styrene elastomer A1-1 was changed to 7.2 g of modified styrene elastomer A1-2.

[0099] [Production Example 7] Modifier 4 was obtained in the same manner as in Production Example 5, except that 7.0 g of modified styrene elastomer A1-1 was changed to 7.0 g of modified styrene elastomer A1-2.

[0100] [Production Example 8] Modifier 5 was obtained in the same manner as in Production Example 4, except that the amount of modified styrene elastomer A1-1 was changed from 7.2 g to 3.0 g.

[0101] [Production Example 9] Modifier 6 was obtained in the same manner as in Production Example 4, except that the amount of modified styrene elastomer A1-1 was changed from 7.2 g to 18.0 g and the amount of toluene was changed from 28.8 g to 48.0 g.

[0102] [Production Example 10] Modifier 7 was obtained in the same manner as in Production Example 4, except that the amount of core-shell polymer particles A2-1 was changed from 2.8 g to 0.15 g.

[0103] [Production Example 11] Modifier 8 was obtained in the same manner as in Production Example 4, except that the amount of core-shell polymer particles A2-1 was changed from 2.8 g to 9.0 g and the amount of toluene was changed from 28.8 g to 35.0 g.

[0104] In the comparative examples, the following A1-3, A1-4, and A1-5 were used as other elastomers (A'1): A1-3: Unmodified styrene-based elastomer (styrene / ethylenebutylene / styrene elastomer, manufactured by Kuraray, SEPTON 8007L) A1-4: Polyolefin-based elastomer containing 4-methyl-1-pentene units (ABSOTOMER (registered trademark) EP-1013, manufactured by Mitsui Chemicals) A1-5: Unmodified styrene-based elastomer (hydrogenated styrene-butadiene block copolymer, manufactured by JSR Corporation, DYNARON (registered trademark) 8903P)

[0105] In the examples, the following B1 to B3 were used as the modified polyphenylene ether (B). B1: Modified polyphenylene ether modified at both ends with methacrylate (manufactured by SABIC, Noryl (registered trademark) SA9000, number average molecular weight: 1700, carbon-carbon unsaturated double bond equivalent weight 850 g / eq) B2: Modified polyphenylene ether modified at both ends with vinylbenzyl groups (manufactured by Mitsubishi Gas Chemical Company, Inc., OPE-2St-2200, number average molecular weight: 2070, carbon-carbon unsaturated double bond equivalent weight 1090 g / eq) B3: Modified polyphenylene ether modified at both ends with vinylbenzyl groups (manufactured by Mitsubishi Gas Chemical Company, Inc., OPE-2St-1200, number average molecular weight: 1100, carbon-carbon unsaturated double bond equivalent weight 660 g / eq) In addition, in the comparative examples, the following B4 was used as unmodified polyphenylene ether (B'). B4: Unmodified polyphenylene ether having hydroxyl groups at both ends (manufactured by SABIC, Noryl (registered trademark) SA90)

[0106] In the examples and comparative examples, the following C1 to C3 were used as the radical polymerizable compound (C). The following were used as the silica and radical polymerization initiator (D): C1: triallyl isocyanurate (TAIC, manufactured by Mitsubishi Chemical Corporation) C2: divinylbenzene (mixture of meta- and para-isomers, Tokyo Chemical Industry Co., Ltd.) C3: bismaleimide compound (MIZ-001, manufactured by Nippon Kayaku Co., Ltd.) Silica: SC2300-SVJ (manufactured by Admatechs Co., Ltd., average particle size 0.5 μm) Radical polymerization initiator (D): Perbutyl P (PBP) (manufactured by NOF Corporation)

[0107] [Examples 1 to 14] In Example 1, Examples 5 to 8, Example 13, and Example 14, the above-mentioned Modifier 1 was used. In Example 2, the above-mentioned Modifier 2 was used. In Example 3, the above-mentioned Modifier 3 was used. In Example 4, the above-mentioned Modifier 4 was used. In Example 9, the above-mentioned Modifier 5 was used. In Example 10, the above-mentioned Modifier 6 was used. In Example 11, the above-mentioned Modifier 7 was used. In Example 12, the above-mentioned Modifier 8 was used.

[0108] The amount and type of modified polyphenylene ether (B) shown in Table 1, the amount and type of radical polymerizable compound (C) shown in Table 1, the amount of silica shown in Table 1, and 1.1 g of radical polymerization initiator (D) were dissolved and dispersed in the amount of toluene shown in Table 1 to obtain a toluene dispersion. The above-mentioned modifier was added to the toluene dispersion and stirred uniformly to obtain a curable composition of each example. Note that in Examples 5 to 8, the radical polymerization initiator (D) was not used.

[0109] Comparative Example 1 The modified polyphenylene ether (B) in the amount and type shown in Table 2, silica in the amount shown in Table 2, and 2.5 g of the radical polymerization initiator (D) were dissolved and dispersed in the amount of toluene shown in Table 2 to obtain a curable composition.

[0110] [Comparative Example 2] A toluene dispersion was obtained by dissolving and dispersing the modified polyphenylene ether (B) in the amount and type shown in Table 2, the silica in the amount shown in Table 2, and 1.1 g of the radical polymerization initiator (D) in the toluene amount shown in Table 2. The above-mentioned modifier 1 was added to the toluene dispersion, and the mixture was stirred uniformly to obtain a curable composition.

[0111] Comparative Example 3 70.0 g of unmodified polyphenylene ether having hydroxyl groups at both ends (Noryl (registered trademark) SA90, manufactured by SABIC Corporation), the amount and type of radical polymerizable compound (C) shown in Table 2, silica shown in Table 2, and 2.5 g of radical polymerization initiator (D) were dissolved and dispersed in the amount of toluene shown in Table 2 to obtain a curable composition.

[0112] Comparative Example 4 A toluene dispersion was obtained by dissolving and dispersing the unmodified polyphenylene ether (B') in the amount and type shown in Table 2, the radical polymerizable compound (C) in the amount and type shown in Table 2, silica in the amount shown in Table 2, and 1.1 g of radical polymerization initiator (D) in the amount of toluene shown in Table 2. The above-mentioned modifier 1 was added to the toluene dispersion, and the mixture was stirred uniformly to obtain a curable composition.

[0113] Comparative Example 5 The modified polyphenylene ether (B) in the amount and type shown in Table 2, the radical polymerizable compound (C) in the amount and type shown in Table 2, silica in the amount shown in Table 2, and 1.1 g of the radical polymerization initiator (D) were dissolved and dispersed in the amount of toluene shown in Table 2 to obtain a curable composition.

[0114] Comparative Example 6 A modifier (A') not corresponding to the modifier (A) was obtained in the same manner as in Production Example 4, except that 7.2 g of the modified styrene-based elastomer A1-1 was replaced with another elastomer (A'1) in the amount and type shown in Table 2. The modified polyphenylene ether (B) in the amount and type shown in Table 2, the radical polymerizable compound (C) in the amount and type shown in Table 2, silica in the amount shown in Table 2, and 1.1 g of radical polymerization initiator (D) were dissolved and dispersed in the amount of toluene shown in Table 2 to obtain a toluene dispersion. The modifier (A') was added to the toluene dispersion and stirred uniformly to obtain a curable composition.

[0115] Comparative Example 7 A modifier (A') not corresponding to the modifier (A) was obtained in the same manner as in Production Example 4, except that 7.2 g of the modified styrene-based elastomer A1-1 was replaced with another elastomer (A'1) in the amount and type shown in Table 2, and the amount of 2.8 g of core-shell polymer particles B1 was changed from 2.8 g to 2.6 g. The amount and type of modified polyphenylene ether (B) shown in Table 2, the amount and type of radical polymerizable compound (C) shown in Table 2, the amount of silica shown in Table 2, and 1.1 g of radical polymerization initiator (D) were dissolved and dispersed in the amount of toluene shown in Table 2 to obtain a toluene dispersion. The above modifier (A') was added to the toluene dispersion and stirred uniformly to obtain a curable composition.

[0116] Comparative Example 8 12.0 g of a methyl ethyl ketone (MEK) dispersion of the core-shell polymer particles A2-1 (solid content concentration: 25% by mass) containing 3.0 g of the core-shell polymer particles A2-1, the amount and type of modified polyphenylene ether (B) shown in Table 2, the amount and type of radical polymerizable compound (C) shown in Table 2, silica shown in Table 2, and 1.2 g of the radical polymerization initiator (D) were dissolved and dispersed in the amount of toluene shown in Table 2 to obtain a curable composition.

[0117] Comparative Example 9 The modified styrene-based elastomer (A) in the amount and type shown in Table 2, the modified polyphenylene ether (B) in the amount and type shown in Table 2, the radical polymerizable compound (C) in the amount and type shown in Table 2, silica in the amount shown in Table 2, and 1.1 g of the radical polymerization initiator (D) were dissolved and dispersed in the amount of toluene shown in Table 2 to obtain a curable composition.

[0118] [Comparative Example 10] The modified polyphenylene ether (B) in the amount and type shown in Table 2, the radical polymerizable compound (C) in the amount and type shown in Table 2, silica in the amount shown in Table 2, and 2.5 g of the radical polymerization initiator (D) were dissolved and dispersed in the amount of toluene shown in Table 2 to obtain a curable composition.

[0119] Prepregs were obtained using the curable compositions obtained in each Example and Comparative Example according to the following method. Specifically, a glass cloth (manufactured by Nitto Boseki Co., Ltd., product name: NE-1078, size: 100 mm x 200 mm) was impregnated with the curable composition. The glass cloth impregnated with the curable composition was passed through two Teflon rods arranged in parallel with a 0.4 mm gap between them to remove excess curable composition. The glass cloth impregnated with the curable composition was heated at 60°C for 100 minutes, 100°C for 10 minutes, and 120°C for 50 minutes in this order to obtain prepregs.

[0120] Using the obtained prepreg, the adhesion of the electrolytic copper foil, the dielectric loss tangent, and the heat resistance were evaluated according to the following methods.

[0121] [Measurement of Dielectric Loss Tangent (Df)] Cured sheets were formed using prepregs obtained using the curable compositions of each Example and Comparative Example. The dielectric loss tangent was measured using test pieces cut out from the cured sheets. The specific method is described below. The measurement results of the dielectric loss tangent are shown in Tables 1 and 2.

[0122] <Preparation of Cured Sheet> Cured sheets were prepared using the prepregs obtained in each Example and Comparative Example according to the following method. First, the prepreg was sandwiched between two Teflon sheets (manufactured by Nitto Denko Corporation, product name: Nitoflon (registered trademark), thickness 50 μm). The prepreg sandwiched between the two Teflon sheets was set in a press at a press temperature of 100°C and a press pressure of 0.5 MPa (G), and then the press temperature was increased at a rate of 3°C / min. When the press temperature reached 140°C, the press pressure was increased to 3.0 MPa (G). Next, the press temperature was increased to 200°C at a rate of 3°C / min. After the press temperature reached 200°C, pressing was continued for 75 minutes to obtain a cured sheet in which the cured product of the curable composition and the glass sheet were combined.

[0123] <Measurement of Dielectric Loss Tangent> The dielectric loss tangent was measured using a network analyzer (N5222B, manufactured by KEYSIGHT) and a split cylinder resonator (CR-740, manufactured by EM Labs) as measuring devices. A 30 mm x 40 mm test piece cut out from the cured sheet was used to measure the dielectric loss tangent. Before measuring the dielectric loss tangent, the test piece was left to stand for 24 hours under conditions of 23°C and 50% RH. The measurement conditions were as follows: Measurement frequency: 40 GHz, Temperature: 23°C, Humidity: 50% RH

[0124] [Evaluation of Adhesion of Electrodeposited Copper Foil] Prepregs obtained using the curable compositions of each Example and Comparative Example were used. Metal laminates were formed by laminating electrolytic copper foils on both sides of the cured prepreg sheets. The peel strength of the metal foils was measured using the resulting metal laminates. The specific method is described below. The peel strength measurement results are shown in Tables 1 and 2.

[0125] <Preparation of Metal Laminate> A metal laminate was prepared using the prepreg obtained in each Example and Comparative Example according to the following method. First, the prepreg was sandwiched between the laminated (matte) surfaces of two identical electrolytic copper foils. The prepreg sandwiched between the two electrolytic copper foils was set in a press at a press temperature of 100°C and a press pressure of 0.5 MPa (G), and then the press temperature was increased at a rate of 3°C / min. When the press temperature reached 140°C, the press pressure was increased to 3.0 MPa (G). Next, the press temperature was increased to 200°C at a rate of 3°C / min. After the press temperature reached 200°C, pressing was continued for 75 minutes to obtain a metal laminate. In the metal laminate, electrolytic copper foil was laminated on both main surfaces of a cured sheet formed by combining a cured product of the curable composition and a glass sheet. The following three types of copper foil were used. Copper foil 1: Electrolytic copper foil manufactured by Mitsui Mining & Smelting Co., Ltd., trade name: HS1-VSP, thickness: 18 μm, laminate surface roughness Rz: 1.52 μm, Ra: 0.24 μm Copper foil 2: Electrolytic copper foil manufactured by Mitsui Smelting & Mining Co., Ltd., trade name: SI-VSP, thickness: 18 μm, laminate surface roughness Rz: 0.56 μm, Ra: 0.07 μm Copper foil 3: Electrolytic copper foil manufactured by Fukuda Metal Foil & Powder Co., Ltd., trade name: CF-T49A-DS-HD2-18, thickness: 18 μm, laminate surface roughness Rz: 0.42 μm, Ra: 0.06 μm

[0126] <Measurement of Rz and Ra of Copper Foil Laminate Surface> Using a scanning probe microscope (device name: Dimension Icon) manufactured by Bruker AXS as the measuring device, Rz and Ra of the copper foil laminate surface were measured as follows: Measurement mode: Tapping Measurement range: 50 μm × 50 μm Number of data: 512 × 512 Probe: HQ: NSC15 / AI BS

[0127] Using the obtained metal laminate, the peel strength of the electrolytic copper foil was measured in accordance with "6.5 Peel Strength" of JIS C6471-1995. Specifically, a 1 mm wide metal foil portion was peeled at a peel angle of 90° and a peel rate of 100 mm / min. The load during peeling was measured, and the measured value of the load was taken as the peel strength. The measured values ​​of the peel strength are shown in Tables 1 and 2.

[0128] [Evaluation of Heat Resistance] A 50 mm x 50 mm test piece was cut out from the metal laminate prepared according to the method for preparing a metal laminate. The test piece was placed in a hot air oven at 260°C for 1 hour. The test piece heated in the oven was visually inspected for defects in appearance such as swelling or peeling of the metal laminate. Before the heat resistance test, the test piece was left to stand for 24 hours under conditions of 23°C and 50% RH. ⊚: No change in appearance such as swelling or peeling of the metal laminate. ○: Blistering of the metal laminate in one place. ×: Blistering or peeling of the metal laminate in two or more places.

[0129] In Table 1 below, component (A1) is a modified styrene-based elastomer (A1-1). Component (A2) is a core-shell polymer particle (A2). Component (B) is a modified polyphenylene ether. Component (C) is a radically polymerizable compound (C). Component (D) is a radical polymerization initiator (D).

[0130] In Table 2 below, component (A1) is a modified styrene-based elastomer (A1-1). Component (A'1) is an elastomer (A'1) other than a modified styrene-based elastomer. Component (A2) is a core-shell polymer particle (A2). Component (B) is a modified polyphenylene ether. Component (B') is an unmodified polyphenylene ether (B'). Component (C) is a radically polymerizable compound (C). Component (D) is a radical polymerization initiator (D).

[0131] Table 1 shows that the curable compositions of the examples, which include a modifier (A) containing a modified resin (A1) that satisfies the above-mentioned specified conditions and core-shell polymer particles (A2) that satisfy the above-mentioned specified conditions, a modified polyphenylene ether (B) having a carbon-carbon unsaturated double bond-containing group bonded to an oxygen atom at the molecular chain terminal, and a radically polymerizable compound (C), provide cured products that combine excellent adhesion to copper foil and a low dielectric dissipation factor. Furthermore, the cured products of the curable compositions of the examples also had excellent heat resistance. On the other hand, the comparative examples show that cured products of curable compositions lacking at least one of the essential components either exhibit poor adhesion to copper foil or have a high dielectric dissipation factor.

Claims

1. A polymerizable composition comprising a modifier (A), a modified polyphenylene ether (B), and a radical polymerizable compound (C), wherein the modifier (A) comprises a modified resin (A1) and a core-shell polymer particle (A2), the modified resin (A1) comprises a modified styrene-based elastomer (A1-1), the modified resin (A1) and the core-shell polymer particle (A2) are modified with a monomer having one or more polar groups selected from the group consisting of an epoxy group, an amino group, an acid anhydride group, a hydroxyl group, and a carboxyl group, the type of the group that is most abundant among the one or more polar groups possessed by the modified resin (A1) is the same as the type of the group that is most abundant among the one or more polar groups possessed by the core-shell polymer particle (A2), the modified polyphenylene ether (B) has a carbon-carbon unsaturated double bond-containing group bonded to an oxygen atom at a molecular chain terminal, The curable composition, wherein the radically polymerizable compound (C) has two or more radically polymerizable carbon-carbon unsaturated double bonds.

2. The curable composition according to claim 1, wherein the modified polyphenylene ether (B) has, as the carbon-carbon unsaturated double bond-containing group, at least one selected from a vinylbenzyl group, a vinyl group, an allyl group, and a (meth)acryloyl group.

3. The curable composition according to claim 1, wherein the largest group among the one or more polar groups contained in the modified resin (A1) and the largest group among the one or more polar groups contained in the core-shell polymer particles (A2) are epoxy groups.

4. The curable composition according to claim 1, comprising 25 parts by mass or more and 90 parts by mass or less of the modified resin (A1) and 10 parts by mass or more and 75 parts by mass or less of the core-shell polymer particles (A2) relative to 100 parts by mass of the modifier (A).

5. The curable composition according to claim 1, wherein the content of the polar group in the modified resin (A1) is 0.1 mass % or more and 8 mass % or less relative to the mass of the modified resin (A1).

6. The curable composition according to claim 1, wherein the content of the polar group in the core-shell polymer particles (A2) is 0.5 mass % or more and 10 mass % or less, based on the mass of the core-shell polymer particles (A2).

7. The curable composition according to claim 1, wherein the amount of the radically polymerizable compound (C) is 10 parts by mass or more and 80 parts by mass or less per 100 parts by mass of the modified polyphenylene ether (B).

8. The curable composition according to claim 1, wherein the amount of the core-shell polymer particles (A2) is 0.1 parts by mass or more and 30 parts by mass or less per 100 parts by mass of the modified polyphenylene ether (B).

9. The curable composition according to claim 1, wherein the amount of the modified resin (A1) is 5 parts by mass or more and 50 parts by mass or less per 100 parts by mass of the modified polyphenylene ether (B).

10. A cured product of the curable composition according to any one of claims 1 to 9.

11. The cured product according to claim 10, having a dielectric loss tangent measured at 40 GHz of less than 0.0050.

12. A metal-clad laminate comprising a substrate comprising the cured product according to claim 10 and a metal layer.

13. The metal-clad laminate according to claim 12, wherein the metal layer is in contact with the cured product, and the peel strength measured by peeling the metal layer in accordance with JIS C6471-1995 is 4.0 N / cm or more.

14. The method for producing a metal-clad laminate according to claim 13, wherein Rz on the main surface side of the metal layer is 0.3 μm or more and 2.0 μm or less before the metal layer is bonded to the substrate.

15. A method for producing a curable composition according to claim 1 or 2, comprising: obtaining a first stock solution (a) containing the modifier (A) and the modified polyphenylene ether (B); obtaining a second stock solution (b) containing the radical polymerizable compound (C); and mixing the first stock solution (a) and the second stock solution (b).

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