WO2025164387A1 - Resin composition, prepreg, resin-attached film, resin-attached metal foil, metal-clad laminate, and wiring board - Google Patents

Abstract

One aspect of the present invention pertains to a resin composition comprising: a maleimide compound (A) having, per molecule, an indane structure and/or an arylene structure which is oriented and bonded to the meta position; a curing agent (B) having a carbon-carbon unsaturated bond in the molecule; and a styrene-based polymer (C) which is solid at 25°C and has an ethylene structural unit and a butylene structural unit in each molecule, the butylene structural unit comprising 50 mol% or more of the total of the ethylene structural units and the butylene structural units. The contained amount of the styrene-based polymer (C) is 12 mass% or more.

Description

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

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

In response to the increasing volume of information processed and the increasing speed of information communication, various electronic devices are undergoing advances in packaging technologies, such as higher integration, higher density wiring, and multi-layering of the semiconductor devices installed. Furthermore, the wiring boards used in various electronic devices are required to be high-frequency compatible, such as server boards for communication infrastructure equipment applications such as network equipment, servers, and AI (artificial intelligence) processors, and millimeter-wave radar boards for automotive applications. The substrate materials used to form the insulating layers of wiring boards used in various electronic devices are required to have low relative permittivity and dielectric dissipation factor in order to increase signal transmission speeds and reduce loss during signal transmission. Examples of substrate materials used to form the insulating layers of such wiring boards include the resin compositions described in Patent Documents 1 and 2.

Patent Document 1 describes a resin composition containing high-molecular-weight components such as a maleimide compound, an allyl group-containing benzoxazine compound, and a thermoplastic resin. Patent Document 1 discloses that it is possible to obtain a cured product that has a small dielectric tangent value, excellent adhesion to conductive materials after environmental resistance testing, and improved brittleness.

Patent Document 2 describes a resin composition containing a maleimide compound having an indane structure in the molecule and a styrene-based polymer that is solid at 25°C. Patent Document 2 discloses that a cured product can be obtained that has low dielectric properties, excellent adhesion to metal foil, a high glass transition temperature, and in which increases in the relative dielectric constant and dielectric loss tangent due to temperature are sufficiently suppressed.

Wiring boards are also required to be free of warping. For this reason, it is necessary to suppress warping of the insulating layers provided on wiring boards. Therefore, resin compositions used as substrate materials for forming the insulating layers of wiring boards are required to produce cured products with a low coefficient of thermal expansion.

Japanese Patent Application Laid-Open No. 2020-158705 International Publication No. 2022/054864

The present invention was made in light of these circumstances, and aims to provide a resin composition that produces a cured product with a low coefficient of thermal expansion. It also aims to provide prepregs, resin-coated films, resin-coated metal foils, metal-clad laminates, and wiring boards that are obtained using the resin composition.

One aspect of the present invention is a resin composition comprising: a maleimide compound (A) having in its molecule at least one of an indane structure and an arylene structure bonded in a meta-oriented manner; a curing agent (B) having in its molecule a carbon-carbon unsaturated bond; and a styrene-based polymer (C) that has in its molecule ethylene structural units and butylene structural units, the butylene structural units accounting for 50 mol % or more of the total of the ethylene structural units and the butylene structural units, and that is solid at 25°C, the content of the styrene-based polymer (C) being 12 mass % or more.

These and other objects, features, and advantages of the present invention will become apparent from the following detailed description and accompanying drawings.

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

Electronic devices, particularly small portable devices such as mobile communication terminals and notebook PCs, are rapidly becoming more multifunctional, high-performance, thin, and compact. Accordingly, the wiring boards used in these products are also required to have finer conductor wiring, more multi-layered conductor wiring layers, thinner surfaces, and higher performance mechanical properties. In particular, as wiring boards become thinner and larger, warping occurs in semiconductor packages that mount semiconductor chips on wiring boards, making them more susceptible to mounting defects. To prevent warping in semiconductor packages that mount semiconductor chips on wiring boards, the insulating layer must have a low thermal expansion coefficient (coefficient of thermal expansion). Therefore, substrate materials used to form the insulating layers of wiring boards must be able to produce cured products with a low thermal expansion coefficient.

After extensive investigation, the inventors have discovered that the above-mentioned object of providing a resin composition that produces a cured product with a low coefficient of thermal expansion can be achieved by the present invention described below.

The following describes embodiments of the present invention, but the present invention is not limited to these.

[Resin composition]
A resin composition according to an embodiment of the present invention comprises a maleimide compound (A) having in its molecule at least one of an indane structure and an arylene structure bonded in a meta-oriented manner; a curing agent (B) having in its molecule a carbon-carbon unsaturated bond; and a styrene-based polymer (C) having in its molecule ethylene structural units and butylene structural units, the butylene structural units accounting for 50 mol % or more of the total of the ethylene structural units and the butylene structural units, which is solid at 25°C, the content of the styrene-based polymer (C) being 12 mass % or more. When the resin composition is cured, a cured product having a low coefficient of thermal expansion is obtained. This is believed to be due to the fact that the inclusion of the styrene-based polymer (C) in a resin composition comprising the maleimide compound (A) and the curing agent (B) can reduce the coefficient of thermal expansion of the cured product obtained by curing the resin composition.

(Maleimide Compound (A))
As described above, the maleimide compound (A) has at least one of an indane structure and an arylene structure bonded to a meta-position in the molecule, and specifically includes at least one selected from the group consisting of a maleimide compound (A1) having an indane structure in the molecule, a maleimide compound (A2) having an arylene structure bonded to a meta-position in the molecule, and a maleimide compound (A3) having an indane structure and an arylene structure bonded to a meta-position in the molecule.

(Maleimide compound (A1) having an indane structure in the molecule)
The maleimide compound (A1) is not particularly limited as long as it is a maleimide compound having an indane structure in the molecule. The maleimide compound (A1) has not only the indane structure but also a maleimide group in the molecule. Examples of the indane structure include an indane structure represented by the following formula (1). That is, specific examples of the maleimide compound (A1) include a maleimide compound (A1-1) having a structure represented by the following formula (1) in the molecule as the indane structure, and more specific examples include a maleimide compound (A1-1-1) represented by the following formula (4).

In formula (1), each Rb is independent. That is, each Rb may be the same group or different groups. For example, when r is 2 or 3, two or three Rb's bonded to the same benzene ring may be the same group or different groups. Rb represents an alkyl group having 1 to 10 carbon atoms, an alkyloxy group (alkoxy group) having 1 to 10 carbon atoms, an alkylthio group having 1 to 10 carbon atoms, an aryl group having 6 to 10 carbon atoms, an aryloxy group having 6 to 10 carbon atoms, an arylthio group having 6 to 10 carbon atoms, a cycloalkyl group having 3 to 10 carbon atoms, a halogen atom, a nitro group, a hydroxyl group, or a mercapto group (thiol group). r represents an integer of 0 to 3.

In formula (4), each Ra is independent. That is, each Ra may be the same group or different groups. For example, when q is 2 to 4, 2 to 4 Ra bonded to the same benzene ring may be the same group or different groups. Ra represents an alkyl group having 1 to 10 carbon atoms, an alkyloxy group having 1 to 10 carbon atoms, an alkylthio group having 1 to 10 carbon atoms, an aryl group having 6 to 10 carbon atoms, an aryloxy group having 6 to 10 carbon atoms, an arylthio group having 6 to 10 carbon atoms, a cycloalkyl group having 3 to 10 carbon atoms, a halogen atom, a nitro group, a hydroxyl group, or a mercapto group. Rb's are the same as Rb's in formula (1), and each independently represents an alkyl group having 1 to 10 carbon atoms, an alkyloxy group having 1 to 10 carbon atoms, an alkylthio group having 1 to 10 carbon atoms, an aryl group having 6 to 10 carbon atoms, an aryloxy group having 6 to 10 carbon atoms, an arylthio group having 6 to 10 carbon atoms, a cycloalkyl group having 3 to 10 carbon atoms, a halogen atom, a nitro group, a hydroxyl group, or a mercapto group. q represents 0 to 4. r represents 0 to 3. n represents 0.95 to 10.

r is the average value of the degree of substitution of Rb, and a smaller value is preferable, specifically 0. In other words, it is preferable that a hydrogen atom be bonded to a position on the benzene ring where Rb can be bonded. The maleimide compound (A1) having such an r is easy to synthesize. This is thought to be due to reduced steric hindrance and increased electron density in the aromatic ring. Furthermore, when r is 1 to 3, Rb is preferably at least one selected from the group consisting of an alkyl group having 1 to 4 carbon atoms, a cycloalkyl group having 3 to 6 carbon atoms, and an aryl group having 6 to 10 carbon atoms. Furthermore, Ra is preferably at least one selected from the group consisting of an alkyl group having 1 to 4 carbon atoms, a cycloalkyl group having 3 to 6 carbon atoms, and an aryl group having 6 to 10 carbon atoms. Being an alkyl group having 1 to 4 carbon atoms, a cycloalkyl group having 3 to 6 carbon atoms, or an aryl group having 6 to 10 carbon atoms improves solubility in solvents and suppresses a decrease in the reactivity of the maleimide group, resulting in a suitable cured product. This is thought to be due to a decrease in planarity near the maleimide group and a decrease in crystallinity.

Specific examples of groups represented by Ra and Rb include the following groups:

The alkyl group having 1 to 10 carbon atoms is not particularly limited, and examples include a methyl group, an ethyl group, a propyl group, a hexyl group, and a decyl group.

The alkyloxy group having 1 to 10 carbon atoms is not particularly limited, and examples include a methyloxy group, an ethyloxy group, a propyloxy group, a hexyloxy group, and a decyloxy group.

The alkylthio group having 1 to 10 carbon atoms is not particularly limited, and examples include a methylthio group, an ethylthio group, a propylthio group, a hexylthio group, and a decylthio group.

The aryl group having 6 to 10 carbon atoms is not particularly limited, and examples include a phenyl group and a naphthyl group.

The aryloxy group having 6 to 10 carbon atoms is not particularly limited, and examples include a phenyloxy group and a naphthyloxy group.

The arylthio group having 6 to 10 carbon atoms is not particularly limited, and examples include a phenylthio group and a naphthylthio group.

The cycloalkyl group having 3 to 10 carbon atoms is not particularly limited, and examples include a cyclopropyl group, a cyclobutyl group, a cyclohexyl group, and a cyclooctyl group.

Examples of the halogen atom include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom.

q is the average value of the degree of substitution of Ra, and is preferably 2 to 3, and more preferably 2. The maleimide compound (A1) with such a q is easy to synthesize. This is thought to be because, particularly when q is 2, steric hindrance is reduced and the electron density of the aromatic ring is increased.

n is the average number of repeats, and as described above, is 0.95 to 10, preferably 0.98 to 8, more preferably 1 to 7, and even more preferably 1.1 to 6. In the maleimide compound (A1-1) having an indane structure represented by formula (1) in the molecule and the maleimide compound (A1-1-1) represented by formula (4), the content of the maleimide compound in which n, the average number of repeats (degree of polymerization), is 0, is preferably 32 mass% or less based on the total amount of the maleimide compound (A1).

The molecular weight distribution (Mw/Mn) of the maleimide compound (A1) obtained by GPC measurement is preferably 1 to 4, more preferably 1.1 to 3.8, even more preferably 1.2 to 3.6, and particularly preferably 1.3 to 3.4. The molecular weight distribution is obtained by gel permeation chromatography (GPC) measurement.

As the maleimide compound (A1), commercially available products can be used, such as the solid content of NE-X-9470S manufactured by DIC Corporation.

(Maleimide Compound (A2) Having an Arylene Structure in the Molecule Oriented at the Meta Position)
The maleimide compound (A2) is not particularly limited as long as it is a maleimide compound having an arylene structure in the molecule that is bonded in a meta-oriented manner. The maleimide compound (A2) has not only the arylene structure but also a maleimide group in the molecule. Examples of the arylene structure include an arylene structure in which a structure containing a maleimide group is bonded in the meta-position (an arylene structure in which a structure containing a maleimide group is substituted at the meta-position). The arylene structure is an arylene group bonded in a meta-oriented manner, such as a group represented by the following formula (5). Examples of the arylene structure include m-arylene groups such as m-phenylene and m-naphthylene groups, and more specifically, a group represented by the following formula (5):

Examples of the maleimide compound (A2) include a maleimide compound (A2-1) represented by the following formula (2), and more specifically, a maleimide compound (A2-1-2) represented by the following formula (6):

In formula (2), Ar represents an arylene group oriented and bonded at the meta position. R _A , R _B , R _C , and R _D are each independent. That is, R _A , R _B , R _C , and R _D may be the same group or different groups. R _A , R _B , R _C , and R _D represent a hydrogen atom, an alkyl group having 1 to 5 carbon atoms, or a phenyl group, and preferably a hydrogen atom. R _E and R _F are each independent. That is, R _E and R _F may be the same group or different groups. R _E and R _F represent an aliphatic hydrocarbon group. s represents 1 to 5.

The arylene group is not particularly limited as long as it is an arylene group oriented and bonded at the meta position, and examples include m-arylene groups such as m-phenylene and m-naphthylene, and more specifically, groups represented by formula (5) above.

Examples of the alkyl group having 1 to 5 carbon atoms include a methyl group, an ethyl group, a propyl group, an isopropyl group, an n-butyl group, a sec-butyl group, an isobutyl group, a tert-butyl group, a pentyl group, and a neopentyl group.

The aliphatic hydrocarbon group is a divalent group and may be acyclic or cyclic. Examples of the aliphatic hydrocarbon group include alkylene groups, and more specifically, methylene groups, methylmethylene groups, and dimethylmethylene groups. Among these, the dimethylmethylene group is preferred.

In the maleimide compound (A2-1) represented by the formula (2), the repeating number s is preferably 1 to 5. This s is the average value of the repeating number (degree of polymerization).

In formula (6), s represents 1 to 5. This s is the same as s in formula (2) and is the average value of the number of repetitions (degree of polymerization).

The maleimide compound (A2-1) represented by formula (2) and the maleimide compound (A2-1-1) represented by formula (6) may contain a monofunctional compound where s is 0, as long as s, the average number of repeating units (degree of polymerization), is 1 to 5, or may contain a polyfunctional compound such as a heptafunctional or octafunctional compound where s is 6 or more.

As the maleimide compound (A2), commercially available products can be used, such as the solid content of MIR-5000-60T manufactured by Nippon Kayaku Co., Ltd.

As the maleimide compound (A2), the maleimide compounds exemplified above may be used alone or in combination of two or more. For example, as the maleimide compound (A2), the maleimide compound (A2-1) represented by formula (2) may be used alone, or two or more types of the maleimide compound (A2-1) represented by formula (2) may be used in combination. When two or more types of the maleimide compound (A2-1) represented by formula (2) are used in combination, for example, a maleimide compound (A1) represented by formula (2) other than the maleimide compound (A2-1-1) represented by formula (6) may be used in combination with the maleimide compound (A2-1-1) represented by formula (6).

(Maleimide Compound (A3) Having an Indane Structure and an Arylene Structure Bonded at the Meta Position in the Molecule)
The maleimide compound (A3) is not particularly limited as long as it is a maleimide compound having an indane structure and an arylene structure bonded in a meta-oriented manner in the molecule. The maleimide compound (A3) has not only the arylene structure and the indane structure, but also a maleimide group in the molecule. The indane structure is the same as the indane structure in the maleimide compound (A1), and the arylene structure is the same as the arylene structure bonded in a meta-oriented manner in the maleimide compound (A2). Specific examples of the maleimide compound (A3) include maleimide compounds represented by the following formulas (7) to (9):

In formula (7), n represents 0.95 to 10.

In formula (8), n represents 0.95 to 10.

In formula (9), n represents 0.95 to 10.

The maleimide compound (A) may be used alone or in combination of two or more. The content of the maleimide compound (A1) is preferably 40 to 100 parts by mass, more preferably 50 to 100 parts by mass, per 100 parts by mass of the maleimide compound (A). The content of the maleimide compound (A2) is preferably 40 to 100 parts by mass, more preferably 50 to 100 parts by mass, per 100 parts by mass of the maleimide compound (A). The content of the maleimide compound (A3) is preferably 40 to 100 parts by mass, more preferably 50 to 100 parts by mass, per 100 parts by mass of the maleimide compound (A).

(Curing agent (B))
The curing agent (B) is not particularly limited as long as it is a curing agent having a carbon-carbon unsaturated bond in the molecule. For example, it may be a compound different from the maleimide compound (A) that can react with the maleimide compound (A) to cure the resin composition. Specific examples of the curing agent (B) include benzoxazine compounds (B1) having an alkenyl group in the molecule, hydrocarbon compounds (B2) having a carbon-carbon unsaturated double bond in the molecule, polybutadiene compounds (B3) having an epoxy group in the molecule, and other curing agents (B4) [curing agents (B4) having a carbon-carbon unsaturated bond in the molecule other than the benzoxazine compounds (B1), the hydrocarbon compounds (B2), and the polybutadiene compounds (B3) having an epoxy group in the molecule]. These curing agents (B) may be used alone or in combination of two or more.

(Benzoxazine Compound (B1) Having an Alkenyl Group in the Molecule)
The benzoxazine compound (B1) is not particularly limited as long as it is a benzoxazine compound having an alkenyl group in the molecule. The benzoxazine compound (B1) contains not only an alkenyl group but also a benzoxazine group in the molecule. The alkenyl group is not particularly limited, but examples thereof include alkenyl groups having 2 to 6 carbon atoms. Specific examples of the alkenyl group include vinyl groups, allyl groups, propenyl groups, and butenyl groups. Of these, allyl groups and propenyl groups are preferred, and allyl groups are more preferred. The curing agent (B) is preferably a benzoxazine compound having an allyl group in the molecule. Examples of the benzoxazine group include a benzoxazine group represented by the following formula (10) and a benzoxazine group represented by the following formula (11). Examples of the benzoxazine compound (B1) include not only a benzoxazine compound (B1-1) having a benzoxazine group represented by the following formula (10) in the molecule, and a benzoxazine compound (B1-2) having a benzoxazine group represented by the following formula (11) in the molecule, but also a benzoxazine compound (B1-3) having a benzoxazine group represented by the following formula (10) and a benzoxazine group represented by the following formula (11) in the molecule.

In formula (10), _R1 represents an allyl group, and a represents 1 to 4. a represents the average value of the degree of substitution of _R1 , and is 1 to 4, and is preferably 1.

In formula (11), _R2 represents an allyl group.

Specific examples of the benzoxazine compound (B1) include the benzoxazine compound (B1-1) represented by the following formula (12):

In formula (12), R ₃ and R ₄ represent an allyl group, Y represents an alkylene group, and b and c each independently represent 1 to 4.

The alkylene group is not particularly limited, and examples include methylene, ethylene, propylene, butylene, pentylene, hexylene, heptylene, octane, icosane, and hexatriacontane groups. Of these, the methylene group is preferred.

b is the average value of the degree of substitution of _R3 and is 1 to 4, preferably 1. Furthermore, c is the average value of the degree of substitution of _R4 and is 1 to 4, preferably 1.

As the benzoxazine compound (B1), commercially available products can be used, such as ALPd manufactured by Shikoku Chemicals Corporation.

As the benzoxazine compound (B1), the benzoxazine compounds exemplified above may be used alone or in combination of two or more.

(Hydrocarbon Compound (B2) Having a Carbon-Carbon Unsaturated Double Bond in the Molecule)
The hydrocarbon compound (B2) is not particularly limited as long as it is a hydrocarbon compound having a carbon-carbon unsaturated double bond in the molecule. The carbon-carbon unsaturated group is not particularly limited, but examples thereof include alkenyl groups. Examples of the alkenyl group include alkenyl groups having 2 to 6 carbon atoms, specifically vinyl groups, allyl groups, propenyl groups, and butenyl groups, with allyl groups and propenyl groups being preferred. Examples of the hydrocarbon compound (B2) include divinylbenzenes such as o-divinylbenzene, m-divinylbenzene, and p-divinylbenzene, hydrocarbon compounds (B2-1) represented by the following formula (3), and hydrocarbon compounds (B2-2) represented by the following formula (14).

In formula (3), X represents a hydrocarbon group having 6 or more carbon atoms and containing at least one selected from an aromatic cyclic group and an aliphatic cyclic group, and m represents 1 to 10.

The aromatic cyclic group is not particularly limited, but examples thereof include a phenylene group, a xylylene group, a naphthylene group, a tolylene group, and a biphenylene group. The aliphatic cyclic group is not particularly limited, but examples thereof include a group containing an indane structure and a group containing a cycloolefin structure. Among these, X is preferably an aromatic cyclic group, and more preferably a xylylene group. The number of carbon atoms in the hydrocarbon group is not particularly limited as long as it is 6 or more, but is preferably 6 to 20. More specific examples of the hydrocarbon compound (B2-1) include hydrocarbon compounds (B2-1-1) represented by the following formula (13).

In formula (13), m represents 1 to 10.

In formula (14), e represents 1 to 20.

In the hydrocarbon compound (B2-2), e is preferably 1 to 20, more preferably 1 to 12, and even more preferably 1 to 6. Specific examples of the hydrocarbon compound (B2-2) include a compound represented by formula (14) where e is 1 [bis-(4-vinylphenyl)methane (BVPM)], a compound represented by formula (14) where e is 2 [1,2-bis(vinylphenyl)ethane (BVPE)], and a compound represented by formula (14) where e is 6 [1,6-bis(4-vinylphenyl)hexane (BVPH)].

Among the above examples, the hydrocarbon compound (B2) is preferably the hydrocarbon compound (B2-1) represented by formula (3), and more preferably the hydrocarbon compound (B2-1-1) represented by formula (13).

(Polybutadiene compound (B3) having epoxy groups in the molecule)
The polybutadiene compound (B3) having an epoxy group in the molecule is not particularly limited, and examples thereof include epoxidized polybutadiene, i.e., a compound in which epoxy groups have been introduced into the molecule by epoxidizing at least a portion of the carbon-carbon double bonds contained in polybutadiene, and a compound in which both terminals of polybutadiene have been glycidyl-etherified. The epoxidation is carried out, for example, by adding one oxygen atom to the carbon-carbon double bond contained in polybutadiene (polybutadiene before epoxidation) using an epoxidizing agent to form a three-membered ring epoxy group. A compound in which both terminals of polybutadiene have been glycidyl-etherified can be obtained by adding epichlorohydrin to polybutadiene having hydroxyl groups at both terminals.

The carbon-carbon double bond configuration of the polybutadiene (before epoxidation) may be any of cis-1,4, trans-1,4, cis-1,2, and trans-1,2. Furthermore, there are no particular limitations on the ratio of these.

The epoxidizing agent is not particularly limited as long as it can epoxidize the carbon-carbon double bonds contained in polybutadiene. Examples of the epoxidizing agent include percarboxylic acids such as peracetic acid, performic acid, perbenzoic acid, trifluoroperacetic acid, and perpropionic acid, organic hydroperoxides such as t-butyl hydroperoxide and cumene hydroperoxide, and hydrogen peroxide.

The polybutadiene compound having epoxy groups in its molecule preferably has an oxirane oxygen concentration of 1 to 10% by mass, and more preferably 5 to 9% by mass. If the oxirane oxygen concentration is too low, the effect of adding the polybutadiene compound having epoxy groups in its molecule, namely, the effect of improving the adhesion of the cured resin composition to metal foil, tends to be insufficient. Furthermore, if the oxirane oxygen concentration is too high, the epoxy groups tend to become too numerous, which tends to deteriorate the low dielectric properties. By using a polybutadiene compound having epoxy groups in its molecule whose oxirane oxygen concentration is within the above range, a resin composition can be obtained that, when cured, results in a cured product with low dielectric properties and high adhesion to metal foil.

The concentration of oxirane oxygen is an indicator of the content of epoxy groups contained in the polybutadiene compound having epoxy groups in its molecules, and can be measured, for example, by the hydrogen bromide-glacial acetic acid solution method.

(Other curing agents (B4))
The other curing agent (B4) is not particularly limited as long as it is a curing agent having a carbon-carbon unsaturated bond in the molecule other than the benzoxazine compound (B1), the hydrocarbon compound (B2), and the polybutadiene compound (B3) having an epoxy group in the molecule. Examples of the other curing agent (B4) include polyphenylene ether compounds, methacrylate compounds, acrylate compounds, vinyl compounds, and allyl compounds, each of which has a carbon-carbon unsaturated double bond in the molecule.

The polyphenylene ether compound is not particularly limited as long as it is a polyphenylene ether compound having a carbon-carbon unsaturated double bond in the molecule. Examples of the polyphenylene ether compound include polyphenylene ether compounds having a terminal carbon-carbon unsaturated double bond. More specifically, examples include polyphenylene ether compounds having a substituent having a carbon-carbon unsaturated double bond at the molecular end, such as modified polyphenylene ether compounds whose ends have been modified with a substituent having a carbon-carbon unsaturated double bond. Examples of the substituent having a carbon-carbon unsaturated double bond include a vinylbenzyl group (ethenylbenzyl group), an acryloyl group, and a methacryloyl group.

The methacrylate compound is a compound having a methacryloyl group in the molecule, and examples thereof include monofunctional methacrylate compounds having one methacryloyl group in the molecule, and polyfunctional methacrylate compounds having two or more methacryloyl groups in the molecule. Examples of the monofunctional methacrylate compounds include methyl methacrylate, ethyl methacrylate, propyl methacrylate, and butyl methacrylate. Examples of the polyfunctional methacrylate compounds include dimethacrylate compounds such as tricyclodecane dimethanol dimethacrylate (DCP).

The acrylate compound is a compound having an acryloyl group in the molecule, and examples thereof include monofunctional acrylate compounds having one acryloyl group in the molecule, and polyfunctional acrylate compounds having two or more acryloyl groups in the molecule. Examples of monofunctional acrylate compounds include methyl acrylate, ethyl acrylate, propyl acrylate, and butyl acrylate. Examples of polyfunctional acrylate compounds include diacrylate compounds such as tricyclodecane dimethanol diacrylate.

The vinyl compound is a compound that has a vinyl group in its molecule, and examples include monofunctional vinyl compounds (monovinyl compounds) that have one vinyl group in their molecule, and polyfunctional vinyl compounds that have two or more vinyl groups in their molecule. Examples of monofunctional vinyl compounds include vinylbenzene compounds that have a skeleton containing a phosphorus atom in their molecule, such as 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO).

The allyl compound is a compound having an allyl group in the molecule, and examples include triallyl isocyanurate compounds such as triallyl isocyanurate (TAIC), diallyl bisphenol compounds, and diallyl phthalate (DAP).

As the curing agent (B), the curing agents exemplified above may be used alone or in combination of two or more.

(Styrene-based polymer (C))
The styrene-based polymer (C) is not particularly limited as long as it has an ethylene structural unit and a butylene structural unit in its molecule, the butylene structural unit accounts for 50 mol% or more of the total of the ethylene structural units and the butylene structural units, and is a solid styrene-based polymer at 25°C. Examples of the styrene-based polymer (C) include a styrene-based polymer that has the ethylene structural unit and the butylene structural unit in its molecule as described above, is solid at 25°C, and can be used as a resin contained in a resin composition used to form an insulating layer provided in a metal-clad laminate, a wiring board, or the like. The resin composition used to form an insulating layer provided in a metal-clad laminate, a wiring board, or the like may be a resin composition used to form a resin layer provided in a resin-coated film, a resin-coated metal foil, or the like, or may be a resin composition contained in a prepreg. The content of the butylene structural unit is 50 mol% or more, preferably 50 to 80 mol%, and more preferably 60 to 75 mol%, of the total of the ethylene structural units and the butylene structural units. When the content of the butylene structural unit is within the above range, the effect of the styrene-based polymer (C), i.e., the effect of reducing the thermal expansion coefficient of the cured product of the resin composition, can be more suitably exhibited. Examples of the styrene-based polymer (C) include a styrene-based polymer further containing a structural unit derived from a monomer containing styrene in the molecule.

Examples of the styrene-based copolymer include copolymers obtained by copolymerizing one or more of the styrene-containing monomers (styrene-based monomers) with one or more other monomers copolymerizable with the styrene-based monomer. The styrene-based copolymer may be a random copolymer or a block copolymer. Examples of the block copolymer include a binary copolymer of a structural unit (repeating unit) derived from the styrene-based monomer and a structural unit (repeating unit) derived from the other copolymerizable monomer, and a terpolymer of a structural unit (repeating unit) derived from the styrene-based monomer, a structural unit (repeating unit) derived from the other copolymerizable monomer, and a structural unit (repeating unit) derived from the styrene-based monomer. The styrene-based polymer (C) may be a hydrogenated styrene-based copolymer obtained by hydrogenating the styrene-based copolymer. Preferably, the styrene-based polymer (C) is at least partially hydrogenated. By including an at least partially hydrogenated styrene-based polymer, a resin composition can be obtained that exhibits a low dielectric loss tangent and thermal expansion coefficient and exhibits excellent toughness as a cured product.

The styrene-based monomer is not particularly limited, but examples include styrene, styrene derivatives, styrene in which some of the hydrogen atoms on the benzene ring have been substituted with alkyl groups, styrene in which some of the hydrogen atoms on the vinyl group have been substituted with alkyl groups, vinyltoluene, α-methylstyrene, butylstyrene, dimethylstyrene, and isopropenyltoluene. These styrene-based monomers may be used alone or in combination of two or more.

The structural unit derived from the styrene-based monomer is not particularly limited, and examples thereof include a structural unit (repeating unit) represented by the following formula (15). That is, examples of the styrene-based polymer (C) include polymers having a structural unit represented by the following formula (15) in the molecule.

In formula (15), R ₅ to R ₇ each independently represent a hydrogen atom or an alkyl group, and R ₈ represents any group selected from the group consisting of a hydrogen atom, an alkyl group, an alkenyl group, and an isopropenyl group. The alkyl group is not particularly limited, and is preferably, for example, an alkyl group having 1 to 18 carbon atoms, and more preferably an alkyl group having 1 to 10 carbon atoms. Specific examples include a methyl group, an ethyl group, a propyl group, a hexyl group, and a decyl group. The alkenyl group is preferably an alkenyl group having 1 to 10 carbon atoms.

The styrene-based polymer (C) preferably contains at least one structural unit represented by formula (15), and may contain a combination of two or more different structural units represented by formula (15). The styrene-based polymer (C) may also contain a combination of a structural unit represented by formula (15) and a structural unit other than the structural unit represented by formula (15).

The content of the structural units derived from the styrene-containing monomer is preferably 20% by mass or less, and more preferably 5 to 20% by mass, relative to the styrene-based polymer (C). When the content of the structural units derived from the styrene-containing monomer is within this range, the effect of the styrene-based polymer (C), i.e., the effect of reducing the thermal expansion coefficient of the cured product of the resin composition, can be more effectively achieved. This is thought to be due to the following: If the content of the structural units derived from the styrene-containing monomer is too high, it is thought that the reduction in the thermal expansion coefficient of the cured product of the resin composition cannot be fully achieved. Therefore, when the content of the structural units derived from the styrene-containing monomer is within the above range, it is thought that the effect of the styrene-based polymer (C) can be effectively achieved. Furthermore, it is preferable that the content of the structural units derived from the styrene-containing monomer be 20% by mass or less relative to the styrene-based polymer (C); however, if the content of the structural units derived from the styrene-containing monomer is too low, the ethylene structural units and butylene structures will be too high, making it difficult to achieve the effects of the styrene-based polymer (C), and therefore it is more preferable that the content be 5% by mass or more.

The ethylene structural unit is not particularly limited, and examples thereof include those having an ethylene structure among the structural units (repeating units) derived from the other copolymerizable monomers. The ethylene structural unit is a structure derived from a 1,4-bond of a conjugated diene monomer (conjugated dienes), and the atom or group bonded to the carbon of the -C-C- bond of the main chain is a hydrogen atom or a methyl group. Specific examples of the conjugated diene monomer include 1,3-butadiene, 2-methyl-1,3-butadiene (isoprene), 2,3-dimethyl-1,3-butadiene, 1,3-pentadiene, 2-methyl-1,3-pentadiene, 1,3-hexadiene, and 1,3-cyclohexadiene. Therefore, specific examples of the ethylene structural unit include structural units having an ethylene structure among the structural units derived from the conjugated dienes, and more specific examples include structural units (1,4-addition structural units) having an ethylene structure among structural units (repeating units) derived from 1,3-butadiene. Examples of the ethylene structural unit include structural units represented by the following formula (16) in which all of R ₉ to R ₁₂ are hydrogen atoms or methyl groups, structural units represented by the following formula (17) in which all of R ₁₃ to R ₂₀ are hydrogen atoms or methyl groups, and structural units represented by the following formula (18) in which all of R ₂₁ to R ₂₆ are hydrogen atoms or methyl groups. More specific examples of the ethylene structural unit include structural units represented by the following formula (22) and formulas (29) to (32).

The butylene structural unit is not particularly limited, and examples thereof include those having a butylene structure among the structural units (repeating units) derived from the other copolymerizable monomers. The butylene structural unit is at least one of a structure derived from a 1,2-bond of a conjugated diene monomer (conjugated dienes) and a structure derived from a 3,4-bond of a conjugated diene monomer (conjugated dienes), and at least one of the atoms or groups bonded to the carbon of the -C-C- bond of the main chain is a side chain having two or more carbon atoms. Therefore, specific examples of the butylene structural unit include structural units having a butylene structure among the structural units derived from the conjugated dienes, and more specific examples include structural units having a butylene structure (at least one of a 1,2-addition structural unit and a 3,4-addition structural unit) among the structural units (repeating units) derived from 1,3-butadiene. The butylene structural unit may be, for example, a hydrogenated structural unit. Examples of the butylene structural unit include a structural unit represented by the following formula (16) in which at least one of R ₉ to R ₁₂ is a side chain having 2 or more carbon atoms, a structural unit represented by the following formula (17) in which at least one of R ₁₃ to R ₂₀ is a side chain having 2 or more carbon atoms, and a structural unit represented by the following formula (18) in which at least one of R ₂₁ to R ₂₆ is a side chain having 2 or more carbon atoms. More specific examples of the ethylene structural unit include structural units represented by the following formulas (23) to (28).

The styrene-based polymer (C) contains, in its molecule, a first structural unit (ethylene structural unit) derived from a 1,4-bond of a conjugated diene monomer, and a second structural unit (butylene structural unit) of at least one of a structural unit derived from a 1,2-bond of a conjugated diene monomer and a structural unit derived from a 3,4-bond of a conjugated diene monomer, and the second structural unit accounts for 50 mol % or more of the total of the first structural unit and the second structural unit.

In the formula (16), R ₉ to R ₁₂ each independently represent a group selected from the group consisting of a hydrogen atom, an alkyl group, an alkenyl group, and an isopropenyl group. The alkyl group is not particularly limited, and is preferably, for example, an alkyl group having 1 to 18 carbon atoms, and more preferably an alkyl group having 1 to 10 carbon atoms. Specific examples include a methyl group, an ethyl group, a propyl group, a hexyl group, and a decyl group. The alkenyl group is preferably an alkenyl group having 1 to 10 carbon atoms. Among the structural units represented by the formula (16), in the ethylene structural unit, R ₉ to R ₁₂ each independently represent a hydrogen atom or a methyl group. In the butylene structural unit, at least one of R ₉ to R ₁₂ represents a side chain having two or more carbon atoms, specifically, a group selected from the group consisting of an alkyl group, an alkenyl group, and an isopropenyl group having two or more carbon atoms.

In the formula (17), R ₁₃ to R ₂₀ each independently represent a group selected from the group consisting of a hydrogen atom, an alkyl group, an alkenyl group, and an isopropenyl group. The alkyl group is not particularly limited, and is preferably, for example, an alkyl group having 1 to 18 carbon atoms, and more preferably an alkyl group having 1 to 10 carbon atoms. Specific examples include a methyl group, an ethyl group, a propyl group, a hexyl group, and a decyl group. The alkenyl group is preferably an alkenyl group having 1 to 10 carbon atoms. Among the structural units represented by the formula (17), in the ethylene structural unit, R ₁₃ to R ₂₀ each independently represent a hydrogen atom or a methyl group. In addition, in the butylene structural unit, at least one of R ₁₃ to R ₂₀ represents a side chain having two or more carbon atoms, specifically, a group selected from the group consisting of an alkyl group, an alkenyl group, and an isopropenyl group having two or more carbon atoms.

In the formula (18), R ₂₁ to R ₂₆ each independently represent a group selected from the group consisting of a hydrogen atom, an alkyl group, an alkenyl group, and an isopropenyl group. The alkyl group is not particularly limited, and is preferably, for example, an alkyl group having 1 to 18 carbon atoms, and more preferably an alkyl group having 1 to 10 carbon atoms. Specific examples include a methyl group, an ethyl group, a propyl group, a hexyl group, and a decyl group. The alkenyl group is preferably an alkenyl group having 1 to 10 carbon atoms. Among the structural units represented by the formula (18), in the ethylene structural unit, R ₂₁ to R ₂₆ each independently represent a hydrogen atom or a methyl group. In the butylene structural unit, at least one of R ₂₁ to R ₂₆ represents a side chain having two or more carbon atoms, specifically, a group selected from the group consisting of an alkyl group, an alkenyl group, and an isopropenyl group having two or more carbon atoms.

More specifically, examples of the structural unit represented by formula (15) include structural units represented by the following formulas (19) to (21). Furthermore, the structural unit represented by formula (15) may also be a structure in which the structural units represented by formulas (19) to (21) below are respectively repeated.

More specifically, the structural unit represented by the formula (16) includes structural units represented by the following formulas (22) to (28). The structural unit represented by the formula (16) may also be a structure in which the structural units represented by the following formulas (22) to (28) are respectively repeated.

More specifically, the structural unit represented by the formula (17) includes structural units represented by the following formulas (29) and (30). The structural unit represented by the formula (17) may also be a structure in which structural units represented by the following formulas (31) and (32) are respectively repeated. The structural unit represented by the formula (17) may be one of these alone or a combination of two or more different types.

More specifically, examples of the structural unit represented by formula (18) include structural units represented by the following formulas (31) and (32). The structural unit represented by formula (18) may also be a structure in which the structural units represented by formula (31) and formula (32) are respectively repeated. The structural unit represented by formula (18) may be one of these alone or a combination of two or more different types.

The styrene polymer (C) may contain a structural unit derived from another copolymerizable monomer other than the ethylene structural unit and the butylene structural unit as the structural unit (repeating unit) derived from the other copolymerizable monomer. Examples of such another copolymerizable monomer include, but are not limited to, olefins such as α-pinene, β-pinene, and dipentene, and non-conjugated dienes such as 1,4-hexadiene and 3-methyl-1,4-hexadiene.

Examples of the styrene-based polymer (C) include methylstyrene (ethylene/butylene) methylstyrene copolymer, methylstyrene (ethylene-ethylene/propylene) methylstyrene copolymer, styrene-isoprene copolymer, styrene-isoprene styrene copolymer, styrene (ethylene/butylene) styrene copolymer, styrene (ethylene-ethylene/propylene) styrene copolymer, styrene-butadiene styrene copolymer, and styrene (butadiene/butylene) styrene copolymer. The styrene-based polymer (C) may be a styrene-based polymer in which at least a portion of the styrene-based copolymer is hydrogenated. The styrene-based polymer (C) is preferably a styrene-based polymer in which at least a portion of the styrene-based polymer is acid-modified, and more preferably a styrene-based polymer in which at least a portion of the styrene-based polymer is acid-modified with maleic anhydride. The use of such an acid-modified styrene-based polymer can increase the glass transition temperature. This is thought to be due to the increased compatibility of the styrene-based polymer (C) with the maleimide compound (A). The acid value of the styrene-based polymer (C) is preferably 2 mg CH ₃ ONa/g or more, more preferably 2 to 10 mg _{CH 3} ONa/g. Specifically, the styrene-based polymer (C) is preferably a styrene-based polymer acid-modified with maleic anhydride so as to have an acid value of 2 mg _{CH 3} ONa/g or more, and more preferably a styrene-based polymer acid-modified with maleic anhydride so as to have an acid value of 2 to 10 mg CH 3 ONa/g. When the acid value of the styrene-based polymer (C) is within the above range, the effect of the styrene-based polymer (C), i.e., the effect of reducing the thermal expansion coefficient of the cured product of the resin composition, can be more suitably exhibited. More specifically, the effect of reducing the thermal expansion coefficient in a high temperature range (e.g., 210 to 260°C) can be more suitably exhibited. This is thought to be due to the increased compatibility of the styrene-based polymer (C) with the maleimide compound (A). Therefore, even if the content of structural units derived from the styrene-containing monomer is relatively low, for example, 5 to 20 mass %, the effect of reducing the thermal expansion coefficient of the cured product of the resin composition can be more suitably achieved. Here, the acid value is the amount (mg) of sodium methoxide (CH ₃ ONa) required to neutralize the free acid in 1 g of sample.

The styrene polymer (C) preferably has a weight-average molecular weight of 10,000 to 300,000, and more preferably 10,000 to 200,000. If the molecular weight is too low, the glass transition temperature of the cured product of the resin composition tends to decrease, and the heat resistance tends to decrease. If the molecular weight is too high, the viscosity of the resin composition when made into a varnish or when heated and molded tends to become too high. The weight-average molecular weight may be measured using a general molecular weight measurement method, and specific examples include values measured using gel permeation chromatography (GPC).

The styrene-based polymer (C) may be any of the above-exemplified styrene-based polymers used alone or in combination of two or more.

(Maleimide Compound (D))
The resin composition may contain a maleimide compound (D) other than the maleimide compound (A). The maleimide compound (D) is not particularly limited as long as it is a maleimide compound other than the maleimide compound (A1), the maleimide compound (A2), and the maleimide compound (A3). The maleimide compound (D) is a maleimide compound that has a maleimide group in the molecule and does not have either the arylene structure bonded to the meta position or the indane structure in the molecule. Examples of the maleimide compound (D) include maleimide compounds having one or more maleimide groups in the molecule, and modified maleimide compounds. Examples of the maleimide compound (D) include phenylmaleimide compounds such as 4,4'-diphenylmethane bismaleimide, phenylmethane maleimide, m-phenylene bismaleimide, bisphenol A diphenyl ether bismaleimide, 3,3'-dimethyl-5,5'-diethyl-4,4'-diphenylmethane bismaleimide, 4-methyl-1,3-phenylene bismaleimide, and biphenylaralkyl polymaleimide compounds, as well as N-alkyl bismaleimide compounds having an aliphatic skeleton. Examples of the modified maleimide compound include modified maleimide compounds in which a portion of the molecule is modified with an amine compound, and modified maleimide compounds in which a portion of the molecule is modified with a silicone compound. As the maleimide compound (D), commercially available products may be used. For example, the solid content of MIR-3000-70MT manufactured by Nippon Kayaku Co., Ltd., BMI-2300, BMI-4000, and BMI-5100 manufactured by Daiwa Kasei Kogyo Co., Ltd., BMI, BMI-70, and BMI-80 manufactured by K.I. Kasei Co., Ltd., and BMI-689, BMI-1500, BMI-3000J, and BMI-5000 manufactured by Designer Molecules Inc. may be used.

(Inorganic filler (E))
The resin composition may contain an inorganic filler (E) as needed, as long as the effects of the present invention are not impaired. Furthermore, it is preferable to contain the inorganic filler (E) in order to improve the heat resistance, etc., of the cured product of the resin composition. The inorganic filler (E) is not particularly limited as long as it is an inorganic filler that can be used as an inorganic filler contained in a resin composition. Examples of the inorganic filler (E) include metal oxide fillers, metal hydroxide fillers, molybdate fillers, nitride fillers, titanate fillers, magnesium carbonate fillers such as anhydrous magnesium carbonate fillers, calcium carbonate fillers, quartz glass fillers, talc fillers, aluminum borate fillers, and barium sulfate fillers. Examples of the metal oxide fillers include silica fillers, alumina fillers, titanium oxide fillers, magnesium oxide fillers, and mica fillers. Examples of the silica fillers include crushed silica, spherical silica such as fused spherical silica, and silica particles. Examples of the metal hydroxide filler include magnesium hydroxide filler and aluminum hydroxide filler. Examples of the molybdate filler include zinc molybdate filler, calcium molybdate filler, and magnesium molybdate filler. Examples of the nitride filler include aluminum nitride filler and boron nitride filler. Examples of the titanate filler include barium titanate filler, strontium titanate filler, calcium titanate filler, and aluminum titanate filler. Among these, metal hydroxide fillers such as silica filler, magnesium hydroxide filler, and aluminum hydroxide filler, aluminum oxide filler, boron nitride filler, strontium titanate filler, calcium titanate filler, and zinc molybdate filler are preferred, with silica filler being more preferred. The inorganic fillers may be used alone or in combination of two or more. When two or more kinds of the inorganic fillers are used in combination, a silica filler may be used in combination with one or more inorganic fillers other than the silica filler, and a silica filler and a zinc molybdate filler are preferably used in combination. In addition, the inorganic filler may be, for example, a talc filler carrying molybdate in the molybdate filler.

The inorganic filler (E) may be a surface-treated or untreated inorganic filler. Examples of the surface treatment include treatment with a silane coupling agent.

The silane coupling agent is not particularly limited, and examples include silane coupling agents having at least one functional group selected from the group consisting of vinyl groups, styryl groups, methacryloyl groups, acryloyl groups, phenylamino groups, isocyanurate groups, ureido groups, mercapto groups, isocyanate groups, epoxy groups, and acid anhydride groups. In other words, this silane coupling agent has at least one reactive functional group selected from vinyl groups, styryl groups, methacryloyl groups, acryloyl groups, phenylamino groups, isocyanurate groups, ureido groups, mercapto groups, isocyanate groups, epoxy groups, and acid anhydride groups, and further includes compounds having a hydrolyzable group such as a methoxy group or an ethoxy group.

The silane coupling agent has a vinyl group, and examples thereof include vinyltriethoxysilane and vinyltrimethoxysilane. The silane coupling agent has a styryl group, and examples thereof include p-styryltrimethoxysilane and p-styryltriethoxysilane. The silane coupling agent has a methacryloyl group, and examples thereof include 3-methacryloxypropyltrimethoxysilane, 3-methacryloxypropylmethyldimethoxysilane, 3-methacryloxypropyltriethoxysilane, 3-methacryloxypropylmethyldiethoxysilane, and 3-methacryloxypropylethyldiethoxysilane. The silane coupling agent has an acryloyl group, and examples thereof include 3-acryloxypropyltrimethoxysilane and 3-acryloxypropyltriethoxysilane. Examples of the silane coupling agent include those having a phenylamino group, such as N-phenyl-3-aminopropyltrimethoxysilane and N-phenyl-3-aminopropyltriethoxysilane.

The average particle size of the inorganic filler (E) is not particularly limited, but is preferably 0.05 to 10 μm, and more preferably 0.1 to 8 μm. Note that the average particle size here refers to the volume average particle size. The volume average particle size can be measured, for example, by laser diffraction.

(Content)
The content of the styrene polymer (C) is 12% by mass or more, preferably 12 to 40% by mass, more preferably 12 to 30% by mass, and even more preferably 12 to 25% by mass, based on the total amount of the maleimide compound (A), the curing agent (B), and the styrene polymer (C), ...

The content of the maleimide compound (A) is preferably 20 to 50 mass %, and more preferably 25 to 45 mass %, of the total of the maleimide compound (A), the curing agent (B), and the styrene-based polymer (C).

The content of the curing agent (B) is preferably 5 to 40 mass% and more preferably 5 to 30 mass% based on the total of the maleimide compound (A), the curing agent (B), and the styrene-based polymer (C).

By incorporating the maleimide compound (A), the radical polymerizable compound (B), and the styrene-based polymer (C) in amounts within the above ranges, a resin composition can be obtained that will result in a cured product with a lower thermal expansion coefficient.

As described above, the resin composition may contain the maleimide compound (D). When the resin composition contains the maleimide compound (D), the total content of the maleimide compound (A) and the maleimide compound (D) is preferably 20 to 60% by mass, and more preferably 30 to 55% by mass, based on the total of the maleimide compound (A), the curing agent (B), the styrene-based polymer (C), and the maleimide compound (D).

As described above, the resin composition may contain the inorganic filler (E). When the resin composition contains the inorganic filler (E), the content of the inorganic filler (E) is preferably 100 to 300 parts by mass, and more preferably 100 to 250 parts by mass, per 100 parts by mass of the organic components (other than the inorganic filler (E) in the resin composition). Furthermore, the content of the inorganic filler (E) is preferably 100 to 300 parts by mass, and more preferably 100 to 250 parts by mass, per 100 parts by mass of the total of the maleimide compound (A), the curing agent (B), and the styrene-based polymer (C). The inclusion of the inorganic filler is preferable in terms of increasing the glass transition temperature and storage modulus of the resin composition.

(Other ingredients)
The resin composition may contain components (other components) other than the maleimide compound (A), the curing agent (B), and the styrene-based polymer (C), as long as the effects of the present invention are not impaired. As described above, the resin composition may contain the maleimide compound (D) and the inorganic filler (E) as the other components. Examples of the other components include, in addition to the maleimide compound (D) and the inorganic filler (E), organic components other than the maleimide compound (A), the curing agent (B), the styrene-based polymer (C), and the maleimide compound (D), flame retardants, reaction initiators, curing accelerators, catalysts, polymerization retarders, polymerization inhibitors, dispersants, leveling agents, coupling agents, defoamers, antioxidants, heat stabilizers, antistatic agents, UV absorbers, dyes and pigments, and additives such as lubricants.

As described above, the resin composition according to this embodiment may contain organic components other than the maleimide compound (A), the curing agent (B), the styrene-based polymer (C), and the maleimide compound (D). The organic components may be, for example, compounds that react with at least one of the maleimide compound (A), the curing agent (B), and the styrene-based polymer (C), or compounds that do not react with them. Specific examples of the organic components include oxazine compounds other than the oxazine compound (B1) (other oxazine compounds), epoxy compounds, cyanate ester compounds, and active ester compounds.

The other oxazine compounds are not particularly limited as long as they have an oxazine group in the molecule and are oxazine compounds other than the oxazine compound (B1). Examples of the other oxazine compounds include benzoxazine compounds having a phenolphthalein structure in the molecule (phenolphthalein-type benzoxazine compounds), bisphenol F-type benzoxazine compounds, and diaminodiphenylmethane (DDM)-type benzoxazine compounds. More specific examples of the other oxazine compounds include 3,3'-(methylene-1,4-diphenylene)bis(3,4-dihydro-2H-1,3-benzoxazine) (P-d-type benzoxazine compound) and 2,2-bis(3,4-dihydro-2H-3-phenyl-1,3-benzoxazine)methane (F-a-type benzoxazine compound).

The epoxy compound is a compound that has an epoxy group in its molecule, and specific examples include bisphenol-type epoxy compounds such as bisphenol A-type epoxy compounds, phenol novolac-type epoxy compounds, cresol novolac-type epoxy compounds, dicyclopentadiene-type epoxy compounds, bisphenol A novolac-type epoxy compounds, biphenyl aralkyl-type epoxy compounds, polybutadiene compounds that have an epoxy group in their molecule, and naphthalene ring-containing epoxy compounds. The epoxy compound also includes epoxy resins, which are polymers of the above epoxy compounds.

The cyanate ester compound is a compound having a cyanate group in the molecule, and examples include 2,2-bis(4-cyanatephenyl)propane, bis(3,5-dimethyl-4-cyanatephenyl)methane, and 2,2-bis(4-cyanatephenyl)ethane.

The active ester compound is a compound having a highly reactive ester group in the molecule, and examples include benzenecarboxylic acid active ester, benzenedicarboxylic acid active ester, benzenetricarboxylic acid active ester, benzenetetracarboxylic acid active ester, naphthalenecarboxylic acid active ester, naphthalenedicarboxylic acid active ester, naphthalenetricarboxylic acid active ester, naphthalenetetracarboxylic acid active ester, fluorenecarboxylic acid active ester, fluorenedicarboxylic acid active ester, fluorenetricarboxylic acid active ester, and fluorenetetracarboxylic acid active ester.

As described above, the resin composition according to this embodiment may contain a flame retardant. By including a flame retardant, the flame retardancy of the cured resin composition can be enhanced. The flame retardant is not particularly limited. Specifically, in fields where halogen-based flame retardants such as bromine-based flame retardants are used, preferred examples include ethylene dipentabromobenzene, ethylene bistetrabromoimide, decabromodiphenyl oxide, tetradecabromodiphenoxybenzene, and bromostyrene-based compounds that react with the polymerizable compounds, all of which have melting points of 300°C or higher. It is believed that the use of a halogen-based flame retardant can suppress the elimination of halogens at high temperatures, thereby preventing a decrease in heat resistance. Furthermore, in fields where halogen-free materials are required, phosphorus-containing flame retardants (phosphorus-based flame retardants) are sometimes used. The phosphorus-based flame retardant is not particularly limited, but examples thereof include phosphate ester-based flame retardants, phosphazene-based flame retardants, bisdiphenylphosphine oxide-based flame retardants, 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO)-based flame retardants, and phosphinate-based flame retardants. Specific examples of phosphate ester-based flame retardants include condensed phosphate esters of dixylenyl phosphate. Specific examples of phosphazene-based flame retardants include phenoxyphosphazene. Specific examples of bisdiphenylphosphine oxide-based flame retardants include xylylenebisdiphenylphosphine oxide. Specific examples of DOPO-based flame retardants include hydrocarbons having two DOPO groups in the molecule (DOPO derivative compounds) and DOPO having a reactive functional group. Specific examples of phosphinate-based flame retardants include metal phosphinates of aluminum dialkylphosphinates. As the flame retardant, each of the exemplified flame retardants may be used alone or in combination of two or more.

As described above, the resin composition according to this embodiment may contain a reaction initiator. The reaction initiator is not particularly limited as long as it can accelerate the curing reaction of the resin composition, and examples thereof include peroxides and organic azo compounds. Examples of peroxides include α,α'-di(t-butylperoxy)diisopropylbenzene (PBP), 2,5-dimethyl-2,5-di(t-butylperoxy)-3-hexyne, and benzoyl peroxide. Examples of organic azo compounds include azobisisobutyronitrile. If necessary, a metal carboxylate or the like can be used in combination. This further accelerates the curing reaction. Among these, α,α'-di(t-butylperoxy)diisopropylbenzene is preferred. Because α,α'-di(t-butylperoxy)diisopropylbenzene has a relatively high reaction initiation temperature, it can suppress acceleration of the curing reaction when curing is not required, such as during prepreg drying, thereby suppressing a decrease in the shelf life of the resin composition. Furthermore, α,α'-di(t-butylperoxy)diisopropylbenzene has low volatility and does not evaporate during prepreg drying or storage, providing good stability. Furthermore, the reaction initiators may be used alone or in combination of two or more.

As described above, the resin composition according to this embodiment may contain a curing accelerator. The curing accelerator is not particularly limited as long as it can accelerate the curing reaction of the resin composition. Specific examples of the curing accelerator include imidazoles and their derivatives, organophosphorus compounds, amines such as secondary amines and tertiary amines, quaternary ammonium salts, organoboron compounds, and metal soaps. Examples of the imidazoles include 2-ethyl-4-methylimidazole (2E4MZ), 2-methylimidazole, 2-phenyl-4-methylimidazole, 2-phenylimidazole, and 1-benzyl-2-methylimidazole. Examples of the organophosphorus compounds include triphenylphosphine, diphenylphosphine, phenylphosphine, tributylphosphine, and trimethylphosphine. Examples of the amines include dimethylbenzylamine, triethylenediamine, triethanolamine, and 1,8-diaza-bicyclo(5,4,0)undecene-7 (DBU). Examples of the quaternary ammonium salts include tetrabutylammonium bromide. Examples of the organoboron compounds include tetraphenylboron salts such as 2-ethyl-4-methylimidazole tetraphenylborate, and tetra-substituted phosphonium tetra-substituted borates such as tetraphenylphosphonium ethyltriphenylborate. The metal soap refers to a fatty acid metal salt, and may be either a linear fatty acid metal salt or a cyclic fatty acid metal salt. Specific examples of the metal soap include linear fatty acid metal salts and cyclic fatty acid metal salts having 6 to 10 carbon atoms. More specifically, examples include aliphatic metal salts composed of linear fatty acids such as stearic acid, lauric acid, ricinoleic acid, and octylic acid, or cyclic fatty acids such as naphthenic acid, and metals such as lithium, magnesium, calcium, barium, copper, and zinc. For example, zinc octylate is one example. The curing accelerators may be used alone or in combination of two or more.

As described above, the resin composition according to this embodiment may contain a silane coupling agent. The silane coupling agent may be contained in the resin composition, or may be contained as a silane coupling agent that has been pre-surface-treated on an inorganic filler contained in the resin composition. Among these, the silane coupling agent is preferably contained as a silane coupling agent that has been pre-surface-treated on an inorganic filler. It is more preferable to contain the silane coupling agent as a silane coupling agent that has been pre-surface-treated on an inorganic filler, and further to contain the silane coupling agent in the resin composition. Furthermore, in the case of a prepreg, the silane coupling agent may be contained as a silane coupling agent that has been pre-surface-treated on a fibrous base material. Examples of the silane coupling agent include the same silane coupling agents as those used to surface-treat the inorganic filler, as described above.

The resin composition according to this embodiment is a resin composition that produces a cured product with a low coefficient of thermal expansion. As a result, wiring boards equipped with an insulating layer formed using the resin composition according to this embodiment are less likely to warp.

(Application)
The resin composition is used to produce a prepreg, as described below, and also to form a resin layer provided in a resin-coated metal foil and a resin-coated film, and an insulating layer provided in a metal-clad laminate and a wiring board.

(Manufacturing method)
The method for producing the resin composition is not particularly limited, and examples thereof include a method of mixing the maleimide compound (A), the curing agent (B), the styrene-based polymer (C), and, if necessary, components other than the maleimide compound (A), the curing agent (B), and the styrene-based polymer (C) so as to achieve a predetermined content, etc. In addition, in the case of obtaining a varnish-like composition containing an organic solvent, the method described below, etc. can be used.

By using the resin composition according to this embodiment, prepregs, metal-clad laminates, wiring boards, resin-coated metal foils, and resin-coated films can be obtained as follows.

[Prepreg]
FIG. 1 is a schematic cross-sectional view showing an example of a prepreg 1 according to an embodiment of the present invention.

As shown in Figure 1, the prepreg 1 according to this embodiment comprises the resin composition or a semi-cured resin composition 2, and a fibrous base material 3. This prepreg 1 comprises the resin composition or a semi-cured resin composition 2, and the fibrous base material 3 present in the resin composition or the semi-cured resin composition 2.

In this embodiment, a semi-cured product refers to a resin composition that has been partially cured to the extent that it can be further cured. In other words, a semi-cured product is a resin composition that has been semi-cured (B-staged). For example, when a resin composition is heated, the viscosity initially gradually decreases, and then curing begins, causing the viscosity to gradually increase. In such a case, semi-cured refers to the state between when the viscosity begins to increase and when the composition is completely cured.

The prepreg obtained using the resin composition according to this embodiment may comprise a semi-cured product of the resin composition as described above, or may comprise the uncured resin composition itself. That is, it may be a prepreg comprising a semi-cured product of the resin composition (the resin composition in B stage) and a fibrous base material, or a prepreg comprising the resin composition before curing (the resin composition in A stage) and a fibrous base material. Furthermore, the resin composition or semi-cured product of the resin composition may be the resin composition that has been dried or heat-dried.

When producing the prepreg, the resin composition 2 is often prepared in a varnish form and used to impregnate the fibrous base material 3, which is the base material for forming the prepreg. In other words, the resin composition 2 is usually a resin varnish prepared in a varnish form. Such a varnish-like resin composition (resin varnish) is prepared, for example, as follows.

First, each component that is soluble in an organic solvent is added to the organic solvent and dissolved. Heating may be used if necessary. Then, any components that are insoluble in the organic solvent are added as needed, and the mixture is dispersed using a ball mill, bead mill, planetary mixer, roll mill, or the like until the desired dispersion state is achieved, thereby preparing a varnish-like resin composition. The organic solvent used here is not particularly limited, as long as it dissolves the organic components and resin components in the resin composition and does not inhibit the curing reaction. Specific examples include toluene and methyl ethyl ketone (MEK).

Specific examples of the fibrous substrate include glass cloth, aramid cloth, polyester cloth, glass nonwoven fabric, aramid nonwoven fabric, polyester nonwoven fabric, pulp paper, and linter paper. Using glass cloth results in a laminate with excellent mechanical strength, and flattened glass cloth is particularly preferred. Specific examples of the flattening process include a method in which glass cloth is continuously pressed with a press roll at an appropriate pressure to compress the yarns flat. The thickness of commonly used fibrous substrates is, for example, 0.01 mm or more and 0.3 mm or less. The glass fibers constituting the glass cloth are not particularly limited, but examples include Q glass, NE glass, E glass, S glass, T glass, L glass, and L2 glass. The surface of the fibrous substrate may be treated with a silane coupling agent. The silane coupling agent is not particularly limited, but examples include silane coupling agents having at least one group selected from the group consisting of vinyl groups, acryloyl groups, methacryloyl groups, styryl groups, amino groups, and epoxy groups in the molecule.

The method for producing the prepreg is not particularly limited, as long as it is capable of producing the prepreg. Specifically, when producing the prepreg, the resin composition according to the present embodiment described above is often prepared in the form of a varnish, as described above, and used as a resin varnish.

Specific methods for producing prepreg 1 include impregnating fibrous base material 3 with resin composition 2, for example, resin composition 2 prepared in the form of a varnish, and then drying. The resin composition 2 is impregnated into the fibrous base material 3 by immersion, coating, or the like. Impregnation can be repeated multiple times as needed. Furthermore, by repeating the impregnation process using multiple resin compositions with different compositions and concentrations, it is possible to adjust the final composition and impregnation amount to the desired level.

The fibrous substrate 3 impregnated with the resin composition (resin varnish) 2 is heated under the desired heating conditions, for example, at 40°C to 180°C for 1 minute to 10 minutes. By heating, a prepreg 1 in an uncured (A-stage) or semi-cured (B-stage) state is obtained. Furthermore, by heating, the organic solvent can be volatilized from the resin varnish, reducing or eliminating the organic solvent.

[Metal-clad laminate]
FIG. 2 is a schematic cross-sectional view showing an example of a metal-clad laminate 11 according to an embodiment of the present invention.

As shown in FIG. 2, the metal-clad laminate 11 according to this embodiment has an insulating layer 12 containing a cured product of the resin composition and a metal foil 13 disposed on the insulating layer 12. Examples of the metal-clad laminate 11 include a metal-clad laminate composed of an insulating layer 12 containing a cured product of the prepreg 1 shown in FIG. 1 and a metal foil 13 laminated together with the insulating layer 12. The insulating layer 12 may be composed of either a cured product of the resin composition or a cured product of the prepreg. The thickness of the metal foil 13 varies depending on the performance required of the final wiring board and is not particularly limited. The thickness of the metal foil 13 can be appropriately set depending on the desired purpose, and is preferably 0.2 to 70 μm, for example. Examples of the metal foil 13 include copper foil and aluminum foil. If the metal foil is thin, it may be a carrier-supported copper foil equipped with a release layer and carrier to improve handling.

The method for manufacturing the metal-clad laminate 11 is not particularly limited, as long as it can be used to manufacture the metal-clad laminate 11. Specifically, a method for manufacturing the metal-clad laminate 11 using the prepreg 1 is exemplified. This method involves stacking one or more prepregs 1, then stacking a metal foil 13 such as copper foil on both sides or one side of the prepreg 1, and then heat-pressing and molding the metal foil 13 and the prepreg 1 to form an integrated laminate. In other words, the metal-clad laminate 11 is obtained by laminating the metal foil 13 on the prepreg 1 and then heat-pressing and molding the laminate. The heat-pressing conditions can be appropriately set depending on the thickness of the metal-clad laminate 11, the type of resin composition contained in the prepreg 1, and other factors. For example, the temperature can be 170 to 230°C, the pressure can be 2 to 7 MPa, and the time can be 60 to 150 minutes. The metal-clad laminate may also be manufactured without using a prepreg. For example, a method may be used in which a varnish-like resin composition is applied to a metal foil, a layer containing the resin composition is formed on the metal foil, and then heating and pressurizing is performed.

[Wiring board]
FIG. 3 is a schematic cross-sectional view showing an example of a wiring board 21 according to an embodiment of the present invention.

As shown in FIG. 3, the wiring board 21 according to this embodiment has an insulating layer 12 containing a cured product of the resin composition, and wiring 14 provided on the insulating layer 12. Examples of the wiring board 21 include a wiring board composed of an insulating layer 12 formed by curing the prepreg 1 shown in FIG. 1, and wiring 14 laminated together with the insulating layer 12 and formed by partially removing the metal foil 13. Furthermore, the insulating layer 12 may be made of a cured product of the resin composition, or a cured product of the prepreg.

The method for manufacturing the wiring board 21 is not particularly limited, as long as it can be used to manufacture the wiring board 21. Specific examples include a method of manufacturing the wiring board 21 using the prepreg 1. Examples of this method include a method of manufacturing the wiring board 21 in which wiring is provided as a circuit on the surface of the insulating layer 12 by etching the metal foil 13 on the surface of the metal-clad laminate 11 manufactured as described above. That is, the wiring board 21 is obtained by forming a circuit by partially removing the metal foil 13 on the surface of the metal-clad laminate 11. In addition to the above methods, other methods for forming circuits include circuit formation using a semi-additive process (SAP) or a modified semi-additive process (MSAP).

[Metal foil with resin]
FIG. 4 is a schematic cross-sectional view showing an example of a resin-coated metal foil 31 according to this embodiment.

As shown in FIG. 4, the resin-coated metal foil 31 according to this embodiment comprises a resin layer 32 containing the resin composition or a semi-cured product of the resin composition, and a metal foil 13. This resin-coated metal foil 31 has the metal foil 13 on the surface of the resin layer 32. That is, this resin-coated metal foil 31 comprises the resin layer 32 and the metal foil 13 laminated together with the resin layer 32. The resin-coated metal foil 31 may also comprise another layer between the resin layer 32 and the metal foil 13.

The resin layer 32 may contain a semi-cured product of the resin composition as described above, or may contain the uncured resin composition. That is, the resin-coated metal foil 31 may comprise a resin layer containing a semi-cured product of the resin composition (the resin composition in B stage) and a metal foil, or may be a resin-coated metal foil comprising a resin layer containing the resin composition before curing (the resin composition in A stage) and a metal foil. Furthermore, the resin layer only needs to contain the resin composition or a semi-cured product of the resin composition, and may or may not contain a fibrous substrate. Furthermore, the resin composition or the semi-cured product of the resin composition may be the resin composition that has been dried or heat-dried. Furthermore, the fibrous substrate can be the same as the fibrous substrate of a prepreg.

The metal foil can be any metal foil used in metal-clad laminates or resin-coated metal foils, without limitation. Examples of the metal foil include copper foil and aluminum foil.

The resin-coated metal foil 31 may be provided with a cover film or the like, if necessary. By providing a cover film, it is possible to prevent the intrusion of foreign matter. The cover film is not particularly limited, but examples include polyolefin film, polyester film, polymethylpentene film, and films formed by providing these films with a release agent layer.

The method for producing the resin-coated metal foil 31 is not particularly limited, as long as it can produce the resin-coated metal foil 31. Examples of methods for producing the resin-coated metal foil 31 include a method in which the varnish-like resin composition (resin varnish) is applied to the metal foil 13 and heated. The varnish-like resin composition is applied to the metal foil 13 using, for example, a bar coater. The applied resin composition is heated, for example, at a temperature of 40°C to 180°C for 0.1 to 10 minutes. The heated resin composition is formed on the metal foil 13 as an uncured resin layer 32. Note that the heating volatilizes the organic solvent from the resin varnish, thereby reducing or removing the organic solvent.

[Resin-coated film]
FIG. 5 is a schematic cross-sectional view showing an example of a resin-coated film 41 according to this embodiment.

As shown in FIG. 5, the resin-coated film 41 according to this embodiment comprises a resin layer 42 containing the resin composition or a semi-cured product of the resin composition, and a support film 43. This resin-coated film 41 comprises the resin layer 42 and the support film 43 laminated together with the resin layer 42. The resin-coated film 41 may also comprise another layer between the resin layer 42 and the support film 43.

The resin layer 42 may contain a semi-cured product of the resin composition as described above, or may contain the uncured resin composition. That is, the resin-coated film 41 may comprise a resin layer containing a semi-cured product of the resin composition (the resin composition in B-stage) and a support film, or may be a resin-coated film comprising a resin layer containing the resin composition before curing (the resin composition in A-stage) and a support film. The resin layer may contain the resin composition or a semi-cured product of the resin composition, and may or may not contain a fibrous substrate. The resin composition or the semi-cured product of the resin composition may be the resin composition that has been dried or heat-dried. The fibrous substrate may be the same as the fibrous substrate of a prepreg.

The support film 43 can be any support film used for resin-coated films, without limitation. Examples of such support films include electrically insulating films such as polyester film, polyethylene terephthalate (PET) film, polyimide film, polyparabanic acid film, polyether ether ketone film, polyphenylene sulfide film, polyamide film, polycarbonate film, and polyarylate film.

The resin-coated film 41 may be provided with a cover film or the like, if necessary. By providing a cover film, it is possible to prevent the intrusion of foreign matter. The cover film is not particularly limited, but examples include polyolefin film, polyester film, and polymethylpentene film.

The support film and cover film may be subjected to surface treatments such as matte treatment, corona treatment, release treatment, and roughening treatment, as needed.

The method for producing the resin-coated film 41 is not particularly limited as long as it can produce the resin-coated film 41. Examples of methods for producing the resin-coated film 41 include a method in which the varnish-like resin composition (resin varnish) is applied to a support film 43 and heated. The varnish-like resin composition is applied to the support film 43 using, for example, a bar coater. The applied resin composition is heated, for example, at a temperature of 40°C to 180°C for 0.1 minutes to 10 minutes. The heated resin composition is formed on the support film 43 as an uncured resin layer 42. The heating volatilizes the organic solvent from the resin varnish, thereby reducing or eliminating the organic solvent.

The resin composition according to this embodiment is a resin composition that yields a cured product with a low thermal expansion coefficient. In other words, when the resin composition is cured, it yields a cured product with a low thermal expansion coefficient. Therefore, a prepreg comprising the resin composition or a semi-cured product of the resin composition is a prepreg that yields a cured product with a low thermal expansion coefficient. Resin-coated metal foils and resin-coated films that include a resin layer containing the resin composition or a semi-cured product of the resin composition are resin-coated metal foils and resin-coated films that include a resin layer that yields an insulating layer containing a cured product with a low thermal expansion coefficient. Metal-clad laminates and wiring boards that include an insulating layer containing a cured product of the resin composition are metal-clad laminates and wiring boards that include an insulating layer containing a cured product with a low thermal expansion coefficient. The prepregs, resin-coated metal foils, resin-coated films, and metal-clad laminates can be suitably used to manufacture wiring boards that include an insulating layer containing a cured product with a low thermal expansion coefficient. The prepregs, resin-coated metal foils, resin-coated films, and metal-clad laminates can also be used, for example, to manufacture multilayer wiring boards. In the case of the resin-coated film, a multilayer wiring board can be produced, for example, by laminating it on a wiring board and then peeling off the support film, or by laminating it on a wiring board after peeling off the support film. In the case of the resin-coated metal foil, a multilayer wiring board can be produced, for example, by laminating it on a wiring board. In this way, by using the resin-coated film and resin-coated metal foil, etc., a multilayer wiring board having an insulating layer containing a cured material with a low thermal expansion coefficient can be produced. A wiring board obtained using the prepreg, the resin-coated metal foil, the resin-coated film, and a metal-clad laminate has an insulating layer containing a cured material with a low thermal expansion coefficient.

As mentioned above, this specification discloses various aspects of technology, the main technologies of which are summarized below.

The resin composition according to a first aspect of the present invention comprises a maleimide compound (A) having in its molecule at least one of an indane structure and an arylene structure bonded in a meta-oriented manner; a curing agent (B) having in its molecule a carbon-carbon unsaturated bond; and a styrene-based polymer (C) that has in its molecule ethylene structural units and butylene structural units, the butylene structural units accounting for 50 mol % or more of the total of the ethylene structural units and the butylene structural units, and is solid at 25°C, the content of the styrene-based polymer (C) being 12 mass % or more.

The resin composition according to the second aspect of the present invention is the resin composition according to the first aspect of the present invention, wherein the styrene-based polymer (C) contains 20% by mass or less of structural units derived from a monomer containing styrene.

The resin composition according to the third aspect of the present invention is the resin composition according to the first or second aspect of the present invention, further comprising a maleimide compound (D) other than the maleimide compound (A).

A resin composition according to a fourth aspect of the present invention is a resin composition according to any one of the first to third aspects of the present invention, in which the content of the styrene polymer (C) is 20 to 60 mass% based on the total of the maleimide compound (A), the curing agent (B), and the styrene polymer (C).

A resin composition according to a fifth aspect of the present invention is a resin composition according to any one of the first to fourth aspects of the present invention, in which the content of the maleimide compound (A) is 20 to 50 mass% based on the total of the maleimide compound (A), the curing agent (B), and the styrene-based polymer (C).

A resin composition according to a sixth aspect of the present invention is a resin composition according to any one of the first to fifth aspects of the present invention, in which the content of the curing agent (B) is 5 to 40 mass% based on the total of the maleimide compound (A), the curing agent (B), and the styrene-based polymer (C).

A resin composition according to a seventh aspect of the present invention is the resin composition according to any one of the first to sixth aspects of the present invention, wherein the styrene polymer (C) has an acid value of 2 mg CH ₃ ONa/g or more.

The resin composition according to an eighth aspect of the present invention is a resin composition according to any one of the first to seventh aspects of the present invention, wherein the maleimide compound (A) contains a maleimide compound (A1-1) having a structure represented by formula (1) in the molecule as the indane structure.

A resin composition according to a ninth aspect of the present invention is a resin composition according to any one of the first to seventh aspects of the present invention, in which the maleimide compound (A) contains a maleimide compound (A2-1) represented by the formula (2).

A resin composition according to a tenth aspect of the present invention is a resin composition according to any one of the first to ninth aspects of the present invention, wherein the curing agent (B) includes at least one selected from the group consisting of a benzoxazine compound (B1) having an alkenyl group in the molecule, a hydrocarbon compound (B2) having a carbon-carbon unsaturated double bond in the molecule, and a polybutadiene compound (B3) having an epoxy group in the molecule.

The resin composition according to an eleventh aspect of the present invention is the resin composition according to the tenth aspect of the present invention, wherein the hydrocarbon compound (B2) contains a hydrocarbon compound (B-2) represented by the formula (3).

The resin composition according to the twelfth aspect of the present invention is a resin composition according to any one of the first to eleventh aspects of the present invention, further comprising an inorganic filler (E).

The prepreg according to the thirteenth aspect of the present invention is a prepreg comprising a resin composition according to any one of the first to twelfth aspects of the present invention or a semi-cured product of the resin composition, and a fibrous base material.

The resin-coated film according to the fourteenth aspect of the present invention is a resin-coated film comprising a resin layer containing the resin composition according to any one of the first to twelfth aspects of the present invention or a semi-cured product of the resin composition, and a support film.

The resin-coated metal foil according to the fifteenth aspect of the present invention is a resin-coated metal foil comprising a resin layer containing the resin composition according to any one of the first to twelfth aspects of the present invention or a semi-cured product of the resin composition, and a metal foil.

The metal-clad laminate according to the sixteenth aspect of the present invention is a metal-clad laminate comprising an insulating layer containing a cured product of the resin composition according to any one of the first to twelfth aspects of the present invention, and a metal foil.

The metal-clad laminate according to the seventeenth aspect of the present invention is a metal-clad laminate comprising an insulating layer containing a cured product of the prepreg according to the thirteenth aspect of the present invention and a metal foil.

The wiring board according to the eighteenth aspect of the present invention is a wiring board comprising an insulating layer containing a cured product of the resin composition according to any one of the first to twelfth aspects of the present invention, and wiring.

The wiring board according to the 19th aspect of the present invention is a wiring board comprising an insulating layer containing a cured product of the prepreg according to the 13th aspect of the present invention, and wiring.

The present invention provides a resin composition that produces a cured product with a low coefficient of thermal expansion. The present invention also provides prepregs, resin-coated films, resin-coated metal foils, metal-clad laminates, and wiring boards that are produced using the resin composition.

The present invention will be explained in more detail below using examples, but the scope of the present invention is not limited to these examples.

[Examples 1 to 5 and Comparative Examples 1 to 6]
In this example, each component used in preparing the resin composition will be described.

(Maleimide Compound (A))
Maleimide compound 1: A maleimide compound having an arylene structure substituted at the meta position in the molecule (solid content in MIR-5000-60T (a toluene solution of a maleimide compound) manufactured by Nippon Kayaku Co., Ltd., a maleimide compound represented by the formula (6) above, maleimide equivalent: 260 g/mol)
Maleimide compound 2: A maleimide compound having an indane structure and an arylene structure bonded to the meta position in the molecule (solid content in NE-X-9470S manufactured by DIC Corporation, a maleimide compound represented by the formula (7)).

(Curing agent (B))
Hydrocarbon compound: A hydrocarbon compound represented by the formula (13).

Specifically, it is a hydrocarbon compound synthesized as follows:

(Synthesis Example 1)
A flask equipped with a thermometer, a condenser, and a stirrer was charged with 296 parts by mass of 2-bromoethylbenzene (manufactured by Tokyo Chemical Industry Co., Ltd.), 70 parts by mass of α,α'-dichloro-p-xylene (manufactured by Tokyo Chemical Industry Co., Ltd.), and 18.4 parts by mass of methanesulfonic acid (manufactured by Tokyo Chemical Industry Co., Ltd.), and the mixture was allowed to react at 130 ° C. for 8 hours. After the reaction, the mixture was allowed to cool, and the reaction liquid obtained by the reaction was neutralized with an aqueous sodium hydroxide solution, extracted with 1,200 parts by mass of toluene, and the organic layer was washed five times with 100 parts by mass of water. By distilling off the solvent and excess 2-bromoethylbenzene under heating and reduced pressure, 160 parts by mass of an olefin compound precursor (BEB-1) having a 2-bromoethylbenzene structure was obtained as a liquid resin (Mn: 538, Mw: 649). The repeating unit d was 1.7. Furthermore, in the ¹ H-NMR chart (DMSO-d ₆ ) of the obtained compound, signals derived from bromoethyl groups were observed at 2.95-3.15 ppm and 3.60-3.75 ppm.

(Synthesis Example 2)
Next, 22 parts by mass of BEB-1 obtained in Synthesis Example 1, 50 parts by mass of toluene, 150 parts by mass of dimethyl sulfoxide, 15 parts by mass of water, and 5.4 parts by mass of sodium hydroxide were added to a flask equipped with a thermometer, a condenser, and a stirrer, and the mixture was reacted at 40°C for 5 hours. After the reaction, the mixture was allowed to cool, and then 100 parts by mass of toluene was added, and the organic layer was washed five times with 100 parts by mass of water. The solvent was distilled off under heating and reduced pressure to obtain 13 parts by mass of a liquid olefin compound having a styrene structure as a functional group (Mn: 432, Mw: 575). The repeating unit d was 1.7. Furthermore, in ^{the 1} H-NMR data (DMSO-d ₆ ) of the obtained compound, signals derived from vinyl groups were observed at 5.10-5.30 ppm, 5.50-5.85 ppm, and 6.60-6.80 ppm.

The resulting compound (liquid olefin compound) was the hydrocarbon compound represented by formula (13).

The weight average molecular weight (Mw) and number average molecular weight (Mn) used in Synthesis Example 1 and Synthesis Example 2 were determined by the following analytical method.

(Analysis method)
Calculation was performed in terms of polystyrene using a polystyrene standard solution.

GPC: DGU-20A3R, LC-20AD, SIL-20AHT, RID-20A, SPD-20A, CTO-2, CBM-20A (all manufactured by Shimadzu Corporation)
Column: Shodex KF-603, KF-602x2, KF-601x2)
Eluent for coupling: tetrahydrofuran Flow rate: 0.5 ml/min.
Column temperature: 40°C
Detection: RI (differential refractive index detector)
Benzoxazine compound: a benzoxazine compound having an allyl group in the molecule (a benzoxazine compound represented by the formula (12) above, in which _R3 and _R4 are allyl groups, X is a methylene group, and b and c are 1, ALPd manufactured by Shikoku Chemicals Corporation).
Epoxidized polybutadiene: a polybutadiene compound having an epoxy group in the molecule (JP-100 manufactured by Nippon Soda Co., Ltd., an epoxidized polybutadiene in which an epoxy group has been introduced by oxidizing the vinyl group of 1,2-polybutadiene; oxirane oxygen concentration: 7.7% by mass)

(Styrene-based polymer (C))
C5025: styrene-based polymer acid-modified with maleic anhydride (C5025 manufactured by Asahi Kasei Corporation, molar ratio of ethylene structural units to the butylene structure (ethylene structural units:butylene structure) = 27:73, structural units derived from monomers including styrene 12% by mass, weight average molecular weight Mw 160,000, acid value 4 mg CH ₃ ONa/g, solid at 25°C)
H1221: styrene-based polymer (Tuftec H1221 manufactured by Asahi Kasei Corporation, molar ratio of ethylene structural units to the butylene structure (ethylene structural units:butylene structure) = 23:77, structural units derived from monomers including styrene 12% by mass, acid value less than 0.03 mg CH ₃ ONa/g (below detection limit), weight average molecular weight Mw 150,000, solid at 25°C)

(Styrene-based polymer other than styrene-based polymer (C))
H1041: styrene-based polymer (Tuftec H1041 manufactured by Asahi Kasei Corporation, molar ratio of ethylene structural units to the butylene structure (ethylene structural units:butylene structure) = 65:35, structural units derived from monomers including styrene 28% by mass, weight average molecular weight Mw 75,000, solid at 25°C)
S1609: styrene-based polymer (S1609 manufactured by Asahi Kasei Corporation, molar ratio of ethylene structural units to the butylene structures (ethylene structural units:butylene structures) = 75:25, structural units derived from monomers including styrene 66% by mass, weight-average molecular weight Mw 220,000, solid at 25°C)
P1500: styrene-based polymer (Tuftec P1500 manufactured by Asahi Kasei Corporation, molar ratio of ethylene structural units to the butylene structure (ethylene structural units:butylene structure) = 62:38, structural units derived from monomers including styrene 29% by mass, weight average molecular weight Mw 72,000, solid at 25°C)
M1913: styrene-based polymer acid-modified with maleic anhydride (Tuftec M1913 manufactured by Asahi Kasei Corporation, molar ratio of ethylene structural units to the butylene structure (ethylene structural units:butylene structure) = 64:36, structural units derived from monomers including styrene 30% by mass, weight average molecular weight Mw 42,000, acid value 10 mg CH ₃ ONa/g, solid at 25°C)

(Maleimide Compound (D))
Maleimide compound 3: 3,3'-dimethyl-5,5'-diethyl-4,4'-diphenylmethane bismaleimide (BMI-5100, manufactured by Daiwa Chemical Industry Co., Ltd., bismaleimide compound, maleimide equivalent: 221 g/mol)

(Reaction initiator)
PBP: α,α'-di(t-butylperoxy)diisopropylbenzene (PBP) (Perbutyl P manufactured by NOF Corporation)

(Curing accelerator)
2E4MZ: 2-ethyl-4-methylimidazole (2E4MZ) (2E4MZ manufactured by Shikoku Chemicals Corporation)

(Inorganic filler)
Silica: Silica particles surface-treated with a silane coupling agent having a phenylamino group in the molecule (SC2500-SXJ manufactured by Admatechs Co., Ltd.)
Zinc molybdate: Zinc molybdate filler (Z4SX-A1 manufactured by Admatechs Co., Ltd.)

[Preparation method]
First, the components other than the inorganic filler were added to a mixed solvent of toluene and methyl ethyl ketone (MEK) (mass ratio of approximately 2:1) so that the solids concentration was 40 to 50% by mass, in the composition (parts by mass) shown in Table 1, and mixed. The resulting mixture was stirred for 60 minutes. Thereafter, if an inorganic filler was included, the inorganic filler was added to the resulting mixture in the composition (parts by mass) shown in Table 1, and dispersed using a bead mill. This resulted in a varnish-like resin composition (varnish).

Next, prepreg was obtained as follows:

The resulting varnish was impregnated into a fibrous substrate (glass cloth: #2118 type T-glass manufactured by Nitto Boseki Co., Ltd.), which was then heated and dried at 130°C for 3 minutes to produce a prepreg. The content of the components that make up the resin through the curing reaction (resin content) relative to the prepreg was adjusted to approximately 43% by mass. Furthermore, the thickness after curing was adjusted to be 103 μm.

The evaluation substrate (metal-clad laminate) was obtained as follows.

Twelve sheets of the resulting prepreg were stacked together, and 12 μm thick copper foil (3EC-VLP manufactured by Mitsui Mining & Smelting Co., Ltd.) was placed on both sides. This was used as a pressure body and heated to 220°C at a temperature increase rate of 3°C/min, and then heated and pressurized at 220°C for 120 minutes at a pressure of 3 MPa, resulting in an evaluation substrate (metal-clad laminate) with copper foil adhered to both sides and a resin layer thickness of approximately 1,236 μm.

The evaluation substrate prepared as described above was evaluated using the method described below.

[Glass transition temperature (Tg)]
The copper foil was removed from the evaluation substrate (metal-clad laminate) by etching to prepare an unclad plate, which was used as a test specimen. The Tg of the cured resin composition was measured using a Seiko Instruments Inc. viscoelasticity spectrometer "DMS6100." Dynamic mechanical analysis (DMA) was performed using a bending module at a frequency of 10 Hz. The temperature at which tan δ reached a maximum when the temperature was increased from room temperature to 340°C at a heating rate of 5°C/min was defined as Tg (°C). A glass transition temperature of 270°C or higher was deemed to be "passed."

[Storage modulus]
In the dynamic mechanical analysis (DMA) performed when measuring the glass transition temperature, the storage modulus at 30° C. was also measured.

[Thermal expansion coefficient (50 to 100°C)]
An unclad plate obtained by etching the copper foil from the evaluation substrate (metal-clad laminate) was used as a test specimen. The thermal expansion coefficient in the plane direction (tensile direction, Y direction) of the evaluation substrate at a temperature below the glass transition temperature of the cured resin composition was measured by the TMA method (thermo-mechanical analysis). Specifically, a TMA device ("TMA6000" manufactured by SII NanoTechnology Inc.) was used for the measurement in compression mode. To eliminate the influence of thermal distortion of the test specimen, the test specimen was pulled in the Y direction with a load of 10 g, and the temperature was raised from 30 ° C to 320 ° C at a heating rate of 10 ° C / min, and then cooled to room temperature. Then, the test specimen was pulled in the Y direction with a load of 10 g, and the temperature was raised from 30 ° C to 320 ° C at a heating rate of 10 ° C / min. A temperature displacement chart was obtained during this temperature increase. The average thermal expansion coefficient from 50 to 100 ° C was calculated from the temperature displacement chart obtained at this time. The lower this average coefficient of thermal expansion (Y-CTE 50-100°C), the better the result. In this test, a value of 4.0 ppm/°C or less was judged to be "pass."

[Copper foil peel strength]
The metal foil (copper foil) was peeled off from the evaluation substrate (metal-clad laminate), and the peel strength at this time was measured in accordance with JIS C 6481 (1996). Specifically, the copper foil was peeled off from the evaluation substrate at a rate of 50 mm/min using a tensile tester, and the peel strength at this time (N/mm) was measured.

The results of each of the above evaluations, along with the composition of the resin composition, are shown in Table 1.

In Table 1, ">310" in the glass transition temperature column indicates a temperature above 310°C. Furthermore, when the average thermal expansion coefficient (Y-CTE 50-100°C) is 4.0 ppm/°C or less, the average thermal expansion coefficient from 210 to 260°C (Y-CTE 50-260°C) and the average thermal expansion coefficient from 50 to 260°C (Y-CTE 50-260°C) were calculated from the temperature change chart for reference. These results are also shown in Table 1.

As can be seen from Table 1, when the resin compositions (Examples 1 to 5) contained the maleimide compound (A), the curing agent (B), and 12% by mass or more of the styrene-based polymer (C), a resin composition was obtained that gave a cured product with a low coefficient of thermal expansion, compared to the cases where the styrene-based polymer (C) was not contained (Comparative Examples 1, 2, 4, and 6) and the cases where the styrene-based polymer (C) was contained but its content was as low as less than 12% by mass (Comparative Examples 3 and 5).

When a styrene polymer having an acid value of 2 mg CH ₃ ONa/g or more was used as the styrene polymer (C), that is, when a styrene polymer acid-modified with maleic anhydride so as to have an acid value of 2 mg CH ₃ ONa/g or more was used (Example 1 and Examples 3 to 5), the thermal expansion coefficient was lower even in the high temperature range (210 to 260° C.) than when a non-acid-modified styrene polymer was used (Example 2). Note that when an inorganic filler was included (Examples 1 and 2), the storage modulus was higher than when no inorganic filler was included (Examples 3 to 5).

This application is based on Japanese Patent Application No. 2024-014384, filed on February 1, 2024, the contents of which are incorporated herein by reference.

In order to express the present invention, the present invention has been appropriately and sufficiently described above through the embodiments, but it should be recognized that those skilled in the art could easily modify and/or improve the above-described embodiments. Therefore, unless modifications or improvements made by those skilled in the art are at a level that would cause them to depart from the scope of the claims set forth in the claims, such modifications or improvements are construed as being encompassed within the scope of the claims.

The present invention provides a resin composition that produces a cured product with a low coefficient of thermal expansion. The present invention also provides prepregs, resin-coated films, resin-coated metal foils, metal-clad laminates, and wiring boards that are produced using the resin composition.

Claims (19)

a maleimide compound (A) having, in the molecule, at least one of an indane structure and an arylene structure bonded to a meta position;
a curing agent (B) having a carbon-carbon unsaturated bond in the molecule;
a styrene-based polymer (C) that has ethylene structural units and butylene structural units in its molecule, the butylene structural units accounting for 50 mol % or more of the total of the ethylene structural units and the butylene structural units, and is solid at 25°C;
The resin composition has a content of the styrene polymer (C) of 12 mass% or more. The resin composition according to claim 1, wherein the styrene-based polymer (C) contains 20% by mass or less of structural units derived from a monomer containing styrene. The resin composition according to claim 1, further comprising a maleimide compound (D) other than the maleimide compound (A). The resin composition according to claim 1, wherein the content of the styrene polymer (C) is 20 to 60 mass% based on the total of the maleimide compound (A), the curing agent (B), and the styrene polymer (C). The resin composition according to claim 1, wherein the content of the maleimide compound (A) is 20 to 50 mass% based on the total of the maleimide compound (A), the curing agent (B), and the styrene-based polymer (C). The resin composition according to claim 1, wherein the content of the curing agent (B) is 5 to 40 mass% based on the total of the maleimide compound (A), the curing agent (B), and the styrene-based polymer (C). The resin composition according to claim 1, wherein the styrene-based polymer (C) has an acid value of 2 mg CH ₃ ONa/g or more. The resin composition according to claim 1, wherein the maleimide compound (A) includes a maleimide compound (A1-1) having a structure represented by the following formula (1) in the molecule as the indane structure:
[In formula (1), each Rb independently represents an alkyl group having 1 to 10 carbon atoms, an alkyloxy group having 1 to 10 carbon atoms, an alkylthio group having 1 to 10 carbon atoms, an aryl group having 6 to 10 carbon atoms, an aryloxy group having 6 to 10 carbon atoms, an arylthio group having 6 to 10 carbon atoms, a cycloalkyl group having 3 to 10 carbon atoms, a halogen atom, a hydroxyl group, or a mercapto group, and r represents 0 to 3.] The resin composition according to claim 1, wherein the maleimide compound (A) includes a maleimide compound (A2-1) represented by the following formula (2):
[In formula (2), Ar represents an arylene group oriented and bonded at the meta position; R _A , R _B , R _C , and R _D each independently represent a hydrogen atom, an alkyl group having 1 to 5 carbon atoms, or a phenyl group; R _E and R _F each independently represent an aliphatic hydrocarbon group; and s represents an integer of 1 to 5.] The resin composition according to claim 1, wherein the curing agent (B) comprises at least one compound selected from the group consisting of a benzoxazine compound (B1) having an alkenyl group in the molecule, a hydrocarbon compound (B2) having a carbon-carbon unsaturated double bond in the molecule, and a polybutadiene compound (B3) having an epoxy group in the molecule. The resin composition according to claim 10, wherein the hydrocarbon compound (B2) includes a hydrocarbon compound (B2-1) represented by the following formula (3):
[In formula (3), X represents a hydrocarbon group having 6 or more carbon atoms and containing at least one selected from an aromatic cyclic group and an aliphatic cyclic group, and m represents 1 to 10.] The resin composition according to claim 1, further comprising an inorganic filler (E). A prepreg comprising the resin composition or a semi-cured product of the resin composition according to any one of claims 1 to 12, and a fibrous base material. A resin-coated film comprising a resin layer containing the resin composition according to any one of claims 1 to 12 or a semi-cured product of the resin composition, and a support film. A resin-coated metal foil comprising a resin layer containing the resin composition according to any one of claims 1 to 12 or a semi-cured product of the resin composition, and a metal foil. A metal-clad laminate comprising an insulating layer containing a cured product of the resin composition described in any one of claims 1 to 12 and a metal foil. A metal-clad laminate comprising an insulating layer containing a cured product of the prepreg described in claim 13 and metal foil. A wiring board comprising an insulating layer containing a cured product of the resin composition described in any one of claims 1 to 12, and wiring. A wiring board comprising an insulating layer containing a cured product of the prepreg described in claim 13 and wiring.