Resin composition, prepreg, film attached to resin, metal foil attached to resin, metal-clad laminated board, and wiring board

Abstract

One aspect of the present invention is a resin composition comprising: a (meth)acrylate compound (A) having an indane skeleton and represented by general formula (1); and hollow silica particles (B).　In formula (1), X represents a (meth)acryloyloxy group, Ra and Rb each independently represent a C1-12 alkyl group, an aryl group, an aralkyl group, or a cycloalkyl group, j represents an integer of 1-3, k and l each independently represent an integer of 0-4, n is an average repeating unit and represents a numerical value of 0.5-20, and m represents an integer of 0-2.

Description

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

[0001] 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.

[0002] With the increase in the amount of information processed and the increase in the speed of information communication, various electronic devices are undergoing advances in packaging technologies, such as higher integration of semiconductor devices, higher density wiring, and multi-layering. Furthermore, 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 in-vehicle applications. Substrate materials for constituting the insulating layers of wiring boards used in various electronic devices are required to have low relative permittivity and dielectric loss tangent in order to increase signal transmission speed and reduce loss during signal transmission.

[0003] Examples of substrate materials for forming the insulating layer of such wiring boards include resin compositions described in Patent Documents 1 and 2.

[0004] Patent Document 1 describes a low dielectric resin composition containing hollow particles each having a shell and a hollow portion, and a thermosetting resin, in which the hollow particles have a shell whose total shell is 98 mass % or more formed of silica, an average porosity of 30 to 80 volume %, and an average particle size of 0.1 to 20 μm. Patent Document 1 discloses that the dielectric constant, dielectric loss tangent, and thermal expansion coefficient can all be reduced, and high insulation reliability can be obtained.

[0005] Patent Document 2 describes a resin composition that includes a thermosetting resin and a filler, wherein the filler contains hollow particles having an average particle size of 0.01 to 10 μm and a number of bubbles of 1 to 10. Patent Document 2 discloses that it is now possible to provide a resin composition that has an excellent appearance when processed and an even lower dielectric constant.

[0006] Substrate materials for forming insulating layers of wiring boards are required to have low relative dielectric constants and low dielectric loss tangents for the cured products obtained by curing.

[0007] JP 2008-31409 A International Publication No. 2019 / 230661

[0008] The present invention has been made in view of the above circumstances, and aims to provide a resin composition that can give a cured product with a low dielectric constant and dielectric loss tangent. Another aim of the present invention is to provide a prepreg, a resin-coated film, a resin-coated metal foil, a metal-clad laminate, and a wiring board that can be obtained using the resin composition.

[0009] One aspect of the present invention is a resin composition containing (A) a (meth)acrylate compound having an indane skeleton represented by the following general formula (1) and (B) hollow silica particles.

[0010] In the above formula (1), X represents a (meth)acryloyloxy group; Ra and Rb each independently represent an alkyl group, aryl group, aralkyl group, or cycloalkyl group having 1 to 12 carbon atoms; j represents an integer of 1 to 3; k and l each independently represent an integer of 0 to 4; n is an average repeating unit and represents a number of 0.5 to 20; and m represents an integer of 0 to 2.

[0011] These and other objects, features, and advantages of the present invention will become apparent from the following detailed description and the accompanying drawings.

[0012] 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.

[0013] When hollow particles such as hollow silica particles are added to a thermosetting compound such as a polyphenylene ether compound or a maleimide compound, it is possible to reduce dielectric properties such as the relative permittivity, as in the resin compositions described in Patent Documents 1 and 2, for example. However, in applications where higher speed communication and the like are required, there is a need for a substrate material for constituting an insulating layer of a wiring board to have lower dielectric properties such as the relative permittivity.

[0014] 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, wiring boards used in these products are also required to have finer conductor wiring, more multi-layered conductor wiring layers, thinner wiring, and higher performance in terms of mechanical properties. In particular, as wiring boards become thinner and larger, thinner insulating layers are also increasingly required. When insulating layers are thin, the effect of reducing conductor loss due to a low dielectric constant can be more effectively exerted, and it is expected that transmission loss can be further reduced. This also leads to a greater demand for lower dielectric properties, such as the dielectric constant.

[0015] As a result of extensive investigations, the present inventors have found that the above-mentioned object of providing a resin composition that gives a cured product with a low relative dielectric constant and dielectric loss tangent can be achieved by the present invention described below.

[0016] Hereinafter, embodiments of the present invention will be described, but the present invention is not limited to these.

[0017] [Resin Composition] A resin composition according to an embodiment of the present invention is a resin composition comprising (A) a (meth)acrylate compound having an indane skeleton, and (B) hollow silica particles, each of which is represented by the following general formula (1): By curing the resin composition, a cured product having a low dielectric constant and a low dielectric loss tangent can be obtained.

[0018] ((Meth)acrylate Compound (A)) The (meth)acrylate compound (A) is not particularly limited as long as it is a (meth)acrylate compound having an indane skeleton represented by the following general formula (1).

[0019] In the above formula (1), X represents a (meth)acryloyloxy group. Ra and Rb each independently represent an alkyl group, aryl group, aralkyl group, or cycloalkyl group having 1 to 12 carbon atoms. j represents an integer of 1 to 3. k and l each independently represent an integer of 0 to 4. n is an average repeating unit and represents a number of 0.5 to 20. m represents an integer of 0 to 2. The straight lines from each of Ra, X, and the carbon atom to the aromatic ring indicate that Ra, X, and the carbon atom may each be bonded to any carbon atom of the aromatic ring.

[0020] The (meth)acrylate compound (A) has a low-polarity indane skeleton, which reduces the proportion of polar functional groups in the structure of the (meth)acrylate compound (A). As a result, a cured product produced using the (meth)acrylate compound (A) has excellent low dielectric properties. For this reason, it is preferable to include the (meth)acrylate compound (A) in the resin composition. Furthermore, the (meth)acrylate compound (A) is preferable because it has the indane skeleton, which provides excellent flexibility and pliability and is expected to improve brittleness resistance.

[0021] In the above formula (1), X is a (meth)acryloyloxy group, that is, an acryloyloxy group or a methacryloyloxy group, and preferably a methacryloyloxy group. X is a crosslinking group. The (meth)acrylate compound (A) is preferred because it has a (meth)acryloyloxy group in it, and thus a cured product having a low dielectric tangent can be obtained compared to compounds having other crosslinking groups [e.g., vinylbenzyl ether groups (styryl groups), dihydroxybenzene groups, etc.].

[0022] Although the detailed reason why the (meth)acrylate compound (A) containing the (meth)acryloyloxy group results in a cured product exhibiting low dielectric properties is unclear, it is speculated that the low molecular mobility of the ester group based on the (meth)acryloyloxy group contributes to this. For example, a curable compound containing a vinylbenzyl ether group (styryl group) as a conventionally used curable compound will have an ether group, which is a polar group. Furthermore, a curable compound containing a dihydroxybenzene group will have multiple hydroxyl groups, which are polar groups. The ester group based on the (meth)acryloyloxy group has lower molecular mobility than the polar groups of conventionally used curable compounds. Therefore, it is speculated that the lower molecular mobility of the ester group based on the (meth)acryloyloxy group contributes to this. The presence of a highly polar polar group, such as an ether group or a hydroxyl group, tends to increase the relative dielectric constant and dielectric loss tangent.

[0023] When the crosslinking group X is a methacryloyloxy group, a cured product with a lower dielectric loss tangent can be obtained, which is preferable. The reason why a cured product with a lower dielectric loss tangent can be obtained when the crosslinking group X is a methacryloyloxy group is presumably because the methacryloyloxy group contains a methyl group in its structure, which increases steric hindrance and further reduces molecular mobility. Furthermore, when there are multiple crosslinking groups, the crosslinking density increases and heat resistance improves.

[0024] In the above formula (1), each Ra independently represents an alkyl group, aryl group, aralkyl group, or cycloalkyl group having 1 to 12 carbon atoms, and is preferably an alkyl group, aryl group, or cycloalkyl group having 1 to 4 carbon atoms. The (meth)acrylate compound (A) is preferably such a group as an alkyl group having 1 to 12 carbon atoms, because the planarity near any of the benzene ring, naphthalene ring, and anthracene ring, as described below, is reduced, and the reduced crystallinity improves solvent solubility and lowers the melting point. Furthermore, the (meth)acrylate compound (A) is preferably such a group because the Ra acts as a steric hindrance, further reducing molecular mobility, thereby enabling a cured product with a lower dielectric tangent to be obtained.

[0025] In the formula (1), each Rb independently represents an alkyl group, aryl group, aralkyl group, or cycloalkyl group having 1 to 12 carbon atoms, and is preferably an alkyl group, aryl group, or cycloalkyl group having 1 to 4 carbon atoms. In the (meth)acrylate compound (A), when Rb is the group such as an alkyl group having 1 to 12 carbon atoms, the planarity in the vicinity of any one of a benzene ring, a naphthalene ring, and an anthracene ring, which will be described later, is reduced, and the reduced crystallinity improves solvent solubility and lowers the melting point, which is preferable.

[0026] In the above formula (1), j represents an integer of 1 to 3, preferably an integer of 1 to 2. It is preferable that j is within the above range, since the flexibility of the (meth)acrylate compound (A) is ensured. Note that it is preferable that a plurality of Xs serving as crosslinking groups are introduced into the same benzene ring or the like, since the plurality of crosslinking groups inhibit (suppress) each other's molecular mobility, and a cured product exhibiting a low dielectric tangent can be obtained even in the absence of the substituent Ra.

[0027] In the formula (1), k and l each independently represent an integer of 0 to 4, and preferably an integer of 0 to 2. It is preferable that each of k and l is within the above range, since the reactivity of the (meth)acrylate compound (A) is excellent.

[0028] In the above formula (1), m represents an integer of 0 to 2. Specifically, in the (meth)acrylate compound (A), the aromatic ring in parentheses with m is a benzene ring when m is 0, a naphthalene ring when m is 1, and an anthracene ring when m is 2, and is preferably a benzene ring with m being 0. It is preferable that m is within the above range from the viewpoint of improving the solvent solubility of the (meth)acrylate compound (A).

[0029] In the above formula (1), n ​​represents the average number of repeating units and is a value between 0.5 and 20, preferably between 0.5 and 5, and more preferably between 0.95 and 2.5. It is preferable that n is within the above range (that the indane skeleton is present within the above range) because this improves the solvent solubility of the (meth)acrylate compound (A). If n is less than 0.5, the proportion of high-melting-point substances in the structure of the (meth)acrylate compound having an indane skeleton will be high, resulting in poor solvent solubility. Furthermore, the proportion of high-molecular-weight components that contribute to flexibility will be low, resulting in poor brittle resistance of the resulting cured product. Furthermore, flexibility and pliability may also be reduced. For these reasons, it is not preferable for n to be less than 0.5. Furthermore, if n exceeds 20, the viscosity of the (meth)acrylate compound having an indane skeleton will increase when dissolved in a solvent. Furthermore, there is a concern that the heat resistance of the resulting cured product will be poor. Furthermore, there is a concern that the amount of high molecular weight components will be too high, resulting in reduced fluidity and poor handleability when molding the cured product. For these reasons, it is not preferable for n to exceed 20. Furthermore, from the viewpoint of a high heat distortion temperature, a high glass transition temperature, etc. of the cured product, the value of n is particularly preferably 0.95 to 2.5.

[0030] The (meth)acrylate compound (A) has the indane skeleton, which introduces an alicyclic structure into the structure of the (meth)acrylate compound, which has an excellent balance between heat resistance and dielectric properties. Therefore, a cured product produced using the (meth)acrylate compound (A) has an excellent balance between heat resistance and dielectric properties (particularly a low dielectric tangent), and further has a (meth)acryloyloxy group, which serves as a crosslinking group, in the molecular structure, which allows it to exhibit even lower dielectric properties, which is preferable.

[0031] Examples of the (meth)acrylate compound (A) include a (meth)acrylate compound (a) having an indane skeleton represented by the following general formula (2): The (meth)acrylate compound (A) preferably contains the (meth)acrylate compound (a).

[0032] In the above formula (2), R １ and R ２ each independently represents a hydrogen atom, an alkyl group having 1 to 12 carbon atoms, an aryl group, an aralkyl group, or a cycloalkyl group, and R １ and R ２ are not simultaneously hydrogen atoms, and n is the average repeating unit and is a value of 0.5 to 20.

[0033] In the above formula (2), R １ and R ２ are each independently a hydrogen atom, an alkyl group having 1 to 12 carbon atoms, an aryl group, an aralkyl group, or a cycloalkyl group, and are not both hydrogen atoms at the same time, and are preferably an alkyl group, an aryl group, or a cycloalkyl group having 1 to 4 carbon atoms. １ and R ２ are the above-mentioned groups such as alkyl groups having 1 to 12 carbon atoms, the planarity in the vicinity of the benzene ring is reduced, and the reduced crystallinity improves the solvent solubility and lowers the melting point, which is preferable. １ and the R ２ and R １ and the R２ Since both of the groups cannot be hydrogen atoms at the same time, it is presumed that steric hindrance increases and molecular mobility further decreases, which is preferable because a cured product with a lower dielectric loss tangent can be obtained.

[0034] In the above formula (2), n represents the average number of repeating units and is a value between 0.5 and 20, preferably between 0.5 and 5, and more preferably between 0.95 and 2.5. It is preferable that n is within the above range (that the indane skeleton is present within the above range) because this improves the solvent solubility of the (meth)acrylate compound (a). If n is less than 0.5, the proportion of high-melting-point substances in the structure of the (meth)acrylate compound having an indane skeleton will be high, resulting in poor solvent solubility. Furthermore, the proportion of high-molecular-weight components that contribute to flexibility will be low, resulting in poor brittle resistance of the resulting cured product. Furthermore, flexibility and pliability may also be reduced. For these reasons, it is not preferable for n to be less than 0.5. Furthermore, if n exceeds 20, the viscosity of the (meth)acrylate compound having an indane skeleton will increase when dissolved in a solvent. Furthermore, there is a concern that the heat resistance of the resulting cured product will be poor. Furthermore, there is a concern that the amount of high molecular weight components will be too high, resulting in reduced fluidity and poor handleability when molding the cured product. For these reasons, it is not preferable for n to exceed 20. Furthermore, from the viewpoint of achieving a high heat distortion temperature and a high glass transition temperature of the cured product, the value of n is particularly preferably 0.95 to 2.5.

[0035] The (meth)acrylate compound (a) has the indane skeleton, which introduces an alicyclic structure into the structure of the (meth)acrylate compound (a), which exhibits an excellent balance between heat resistance and dielectric properties. A cured product produced using the (meth)acrylate compound (a) exhibits an excellent balance between heat resistance and dielectric properties (particularly a low dielectric tangent), and the presence of a methacryloyloxy group at the end of the molecular structure increases steric hindrance compared to an acryloyloxy group, thereby enabling the development of even lower dielectric properties, which is preferable.

[0036] (Hollow Silica Particles (B)) The hollow silica particles (B) are not particularly limited, and examples thereof include silica particles having an outer shell layer and a porous or hollow interior.

[0037] The volume average particle diameter of the hollow silica particles (B) is not particularly limited, but is preferably 1 μm or less, and more preferably 0.1 to 0.8 μm. The volume average particle diameter here may be, for example, the volume-based cumulative 50% particle diameter (D50). Specifically, the volume average particle diameter may be the particle diameter (D50) at which the cumulative particle size distribution from the small particle diameter side reaches 50% (volume basis) in a particle size distribution measured by a general laser diffraction / scattering method or the like.

[0038] The hollow ratio of the hollow silica particles (B) is not particularly limited, but is preferably, for example, 20 to 80%, and more preferably 40 to 60%.

[0039] Here, the void ratio of the hollow silica particles (B) is a value calculated from the specific gravity of the hollow silica particles (B) and the specific gravity of solid silica particles (silica particles without voids). Specifically, since the specific gravity of solid silica particles is 2.2, the void ratio of the hollow silica particles (B) is calculated by the following formula:

[0040] Hollow ratio (%)=(1−specific gravity of hollow silica particles / 2.2)×100 The specific gravity of the hollow silica particles (B) is not particularly limited, but is preferably a specific gravity that satisfies the hollow ratio of the hollow silica particles (B), specifically, it is preferably 0.4 to 1.8, and more preferably 0.9 to 1.3.

[0041] The specific surface area of ​​the hollow silica particles (B) is 100 m2 in terms of BET specific surface area. ２ / g or less, and 10 to 50m ２ / g. The BET specific surface area is a specific surface area measured by the BET method and can be measured by a known method. Examples of methods for measuring the BET specific surface area include a method in which a nitrogen adsorption isotherm is measured and the BET specific surface area is calculated from the obtained adsorption isotherm.

[0042] The dielectric constant of the hollow silica particles (B) at 10 GHz is not particularly limited, but is preferably, for example, 2.5 or less, and more preferably 1.3 to 2. The dielectric dissipation factor of the hollow silica particles (B) at 10 GHz is not particularly limited, but is, for example, preferably 0.006 or less, and more preferably 0.0005 to 0.003. The dielectric constant and dielectric dissipation factor here refer to the dielectric constant and dielectric dissipation factor at a frequency of 10 GHz, and examples thereof include the dielectric constant and dielectric dissipation factor at a frequency of 10 GHz measured by a cavity resonator perturbation method.

[0043] The hollow silica particles (B) may be surface-treated hollow silica particles or may be non-surface-treated hollow silica particles.

[0044] The silane coupling agent is not particularly limited, and examples thereof include silane coupling agents having at least one functional group selected from the group consisting of vinyl group, styryl group, methacryloyl group, acryloyl group, phenylamino group, isocyanurate group, ureido group, mercapto group, isocyanate group, epoxy group, and acid anhydride group. That is, the silane coupling agent has at least one reactive functional group selected from vinyl group, styryl group, methacryloyl group, acryloyl group, phenylamino group, isocyanurate group, ureido group, mercapto group, isocyanate group, epoxy group, and acid anhydride group, and further includes compounds having a hydrolyzable group such as a methoxy group or an ethoxy group.

[0045] Examples of the silane coupling agent include those having a vinyl group, such as vinyltriethoxysilane and vinyltrimethoxysilane. Examples of the silane coupling agent include those having a styryl group, such as p-styryltrimethoxysilane and p-styryltriethoxysilane. Examples of the silane coupling agent include those having a methacryloyl group, such as 3-methacryloxypropyltrimethoxysilane, 3-methacryloxypropylmethyldimethoxysilane, 3-methacryloxypropyltriethoxysilane, 3-methacryloxypropylmethyldiethoxysilane, and 3-methacryloxypropylethyldiethoxysilane. Examples of the silane coupling agent include those having an acryloyl group, such as 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.

[0046] (Styrene-Based Polymer (C)) The resin composition may further contain a styrene-based polymer (C), and preferably contains the styrene-based polymer (C). The styrene-based polymer (C) is not particularly limited, and examples thereof include styrene-based polymers that can be used as resins contained in resin compositions used to form insulating layers provided in metal-clad laminates, wiring boards, and the like. The resin compositions used to form insulating layers provided in metal-clad laminates, wiring boards, and the like may be resin compositions used to form resin layers provided in resin-coated films, resin-coated metal foils, and the like, or may be resin compositions contained in prepregs. Examples of the styrene-based polymer include styrene-based polymers having an unsaturated double bond in the molecule, and more specifically, styrene-based polymers containing 40 mol% or more of structural units having a 1,2-vinyl group in the side chain relative to all structural units. The styrene-based polymer (C) preferably has a content of structural units having a 1,2-vinyl group in the side chain of 40 mol% or more, more preferably 60 to 80 mol%, relative to all structural units. The structural unit having a 1,2-vinyl group in a side chain is not particularly limited, and examples thereof include a structural unit represented by the following formula (12), a structural unit represented by the following formula (13), and a structural unit represented by the following formula (16). When the content of the structural unit having a 1,2-vinyl group in a side chain is within the above range, the effects of adding the styrene-based polymer (C), for example, the effects of reducing the dielectric properties such as the dielectric constant and the thermal expansion coefficient of the cured product of the resin composition, can be suitably exhibited. Examples of the styrene-based polymer (C) include styrene-based polymers further containing a structural unit derived from a monomer containing styrene (styrene-based monomer) in the molecule.

[0047] Examples of the styrene-based copolymer include copolymers obtained by copolymerizing one or more of the 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 as long as it has a structure derived from the styrene-based monomer in the molecule. Examples of the block copolymer include a binary copolymer of a structure (repeating unit) derived from the styrene-based monomer and the other copolymerizable monomer (repeating unit), and a terpolymer of a structure (repeating unit) derived from the styrene-based monomer, the other copolymerizable monomer (repeating unit), and a structure (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, but examples include partially hydrogenated styrene-based copolymers having unsaturated double bonds in the molecule. The styrene-based polymer (C) may be the styrene-based copolymer, the at least partially hydrogenated styrene-based polymer, or the hydrogenated styrene-based copolymer in which a portion of the copolymer is modified with maleic anhydride.

[0048] The styrene-based monomer is not particularly limited, but examples thereof 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. Furthermore, the copolymerizable other monomer is not particularly limited, but examples thereof include olefins such as α-pinene, β-pinene, and dipentene, non-conjugated dienes such as 1,4-hexadiene and 3-methyl-1,4-hexadiene, and conjugated dienes such as 1,3-butadiene and 2-methyl-1,3-butadiene (isoprene). These copolymerizable other monomers may be used alone or in combination of two or more.

[0049] Examples of the styrene-based polymer (C) include polymers having a structural unit represented by the following formula (3) (a structure derived from the styrene-based monomer) in the molecule.

[0050] In formula (3), R ３ ~R ５ each independently represents a hydrogen atom or an alkyl group, and R ６ 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.

[0051] The content of the structural units derived from the styrene-containing monomer is preferably 50% by mass or less, and more preferably 5 to 40% by mass, relative to the styrene-based polymer (C). When the content of the structural units derived from the styrene-containing monomer 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. This is thought to be due to the following. When 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 sufficiently exhibited. 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 suitably exhibited. Furthermore, the content of the structural units derived from the styrene-containing monomer is preferably 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 small, the ethylene structural units and the butylene structures become too large, making it difficult to obtain the effects of the styrene-based polymer (C). From this point of view, the content is more preferably 5% by mass or more.

[0052] The styrene-based polymer (C) preferably contains at least one structural unit represented by the formula (3), and may contain two or more different structural units in combination. The styrene-based polymer (C) may also contain a structure in which the structural unit represented by the formula (3) is repeated.

[0053] The styrene-based polymer (C) may have, in addition to the structural unit represented by formula (3), at least one of structural units represented by formula (4), formula (5), and formula (6) below, and structures in which the structural units represented by formula (4), formula (5), and formula (6) below are repeated, as structural units derived from other monomers copolymerizable with the styrene-based monomer:

[0054] Examples of the styrene-based polymer (C) include a styrene-based polymer that has ethylene structural units and butylene structural units in its molecule, the butylene structural units being 40 mol% or more relative to the total of the ethylene structural units and the butylene structural units, and that is solid at 25°C. The content of the butylene structural units is 40 mol% or more, preferably 40 to 80 mol%, and more preferably 60 to 75 mol%, relative to the total of the ethylene structural units and the butylene structural units. When the content of the butylene structural units 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.

[0055] 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 having an ethylene structure (1,4-addition structural units) among structural units (repeating units) derived from 1,3-butadiene. Examples of the ethylene structural unit include structural units represented by the following formula (4): ７ ~R １０ a structural unit in which all of R are hydrogen atoms or methyl groups; a structural unit represented by the following formula (5), １１ ~R １８ In the structural unit in which all of R are hydrogen atoms or methyl groups, and in the structural unit represented by the following formula (6), １９ ~R ２４ are all hydrogen atoms or methyl groups. More specific examples of the ethylene structural unit include structural units represented by the following formula (10) and formulas (17) to (20):

[0056] 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, but the styrene-based polymer (C) also includes a structural unit that is not hydrogenated so that a 1,2-vinyl group remains. The butylene structural unit may be, for example, a structural unit represented by the following formula (4), in which R ７ ~R １０ At least one of the structural units is a structural unit having a side chain with two or more carbon atoms, and among the structural units represented by the following formula (5), R １１ ~R １８ At least one of the structural units is a structural unit having a side chain with two or more carbon atoms, and at least one of the structural units represented by the following formula (6) is R １９ ~R ２４ and the like, in which at least one of the structural units is a side chain having two or more carbon atoms. More specific examples of the butylene structural unit include structural units represented by the following formulas (11) to (16). The styrene-based polymer (C) preferably 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) which is 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.

[0057] In the formula (4), R ７ ~R １０ are each independently 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, 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 formula (4), the ethylene structural unit is ７ ~R １０ are each independently a hydrogen atom or a methyl group. ７ ~R １０ At least one of the groups represents a side chain having two or more carbon atoms, specifically, any group selected from the group consisting of an alkyl group, an alkenyl group, and an isopropenyl group having two or more carbon atoms.

[0058] In the formula (5), R １１ ~R １８ are each independently 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, 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 formula (5), the ethylene structural unit is １１ ~R １８ are each independently a hydrogen atom or a methyl group. １３ ~R ２０ At least one of the groups represents a side chain having two or more carbon atoms, specifically, any group selected from the group consisting of an alkyl group, an alkenyl group, and an isopropenyl group having two or more carbon atoms.

[0059] In the formula (6), R １９ ~R ２４ are each independently 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, 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 formula (6), the ethylene structural unit is １９ ~R ２４ are each independently a hydrogen atom or a methyl group. １９ ~R ２４ At least one of the groups represents a side chain having two or more carbon atoms, specifically, any group selected from the group consisting of an alkyl group, an alkenyl group, and an isopropenyl group having two or more carbon atoms.

[0060] The styrene-based polymer (C) preferably contains at least one structural unit represented by the formula (4), the formula (5), or the formula (6), and may contain two or more different structural units in combination. The styrene-based polymer may also have at least one structure in which the structural units represented by the formula (4), the formula (5), or the formula (6) are repeated.

[0061] More specifically, the structural unit represented by formula (3) includes structural units represented by the following formulas (7) to (9). The structural unit represented by formula (3) may also be a structure in which the structural units represented by formulas (7) to (9) are respectively repeated. The structural unit represented by formula (3) may be one of these alone or a combination of two or more different types.

[0062]

[0063]

[0064]

[0065] More specifically, examples of the structural unit represented by formula (4) include structural units represented by the following formulas (10) to (16). The structural unit represented by formula (4) may also be a structure in which the structural units represented by formulas (10) to (16) are respectively repeated. The structural unit represented by formula (4) may be one of these alone or a combination of two or more different types.

[0066]

[0067]

[0068]

[0069]

[0070]

[0071]

[0072]

[0073] More specifically, the structural unit represented by the formula (5) includes structural units represented by the following formulas (17) and (18). The structural unit represented by the formula (5) may also be a structure in which the structural units represented by the following formulas (17) and (18) are respectively repeated. The structural unit represented by the formula (5) may be one of these alone or a combination of two or more different types.

[0074]

[0075]

[0076] More specifically, the structural unit represented by the formula (6) includes structural units represented by the following formulas (19) and (20). The structural unit represented by the formula (6) may also be a structure in which the structural units represented by the following formulas (19) and (20) are respectively repeated. The structural unit represented by the formula (6) may be one of these alone or a combination of two or more different types.

[0077]

[0078]

[0079] Preferred examples of the styrene copolymer (C) include polymers or copolymers obtained by polymerizing or copolymerizing one or more styrene monomers such as styrene, vinyltoluene, α-methylstyrene, isopropenyltoluene, divinylbenzene, and allylstyrene.

[0080] More specific examples of the styrene polymer (C) include styrene-butadiene block copolymers such as methylstyrene (ethylene / butylene) methylstyrene block copolymer, methylstyrene (ethylene-ethylene / propylene) methylstyrene block copolymer, styrene-isoprene block copolymer, hydrogenated styrene-isoprene-styrene block copolymer, styrene (ethylene / butylene) styrene block copolymer, styrene (ethylene-ethylene / propylene) styrene block copolymer, methylstyrene (styrene / butadiene random copolymer block) methylstyrene copolymer, styrene (styrene / butadiene random copolymer block) styrene copolymer, styrene-butadiene-styrene block copolymer, styrene-isobutylene-styrene block copolymer, styrene (butadiene / butylene) styrene block copolymer, and hydrogenated products of at least a portion of these.

[0081] As the styrene-based polymer (C), commercially available products may be used, such as Tuftec P1500, Tuftec H1221, Tuftec H1041, Tuftec H1517, Tuftec M1913, and SOE1605 manufactured by Asahi Kasei Corporation, and Asaprene T437 manufactured by Asahi Kasei Corporation.

[0082] As the styrene-based polymer (C), the above-exemplified styrene-based polymers may be used alone or in combination of two or more.

[0083] The styrene polymer (C) preferably has a vinyl group equivalent of 150 g / mol or less, more preferably 50 to 130 g / mol. When the vinyl group equivalent is within this range, the effects of adding the styrene polymer (C), such as reducing the dielectric properties such as the relative permittivity and the thermal expansion coefficient of the cured product of the resin composition, can be suitably exhibited. The vinyl group equivalent can be, for example, a value calculated by measuring the iodine value by the Wiess method.

[0084] The styrene polymer (C) preferably has a weight-average molecular weight of 1,000 to 300,000, 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 during heat molding tends to become too high. The weight-average molecular weight may be measured by a general molecular weight measurement method, and specific examples include values ​​measured using gel permeation chromatography (GPC).

[0085] (Curing Agent (D)) The resin composition may further contain a curing agent (D), and preferably contains the curing agent (D). The curing agent (D) is not particularly limited, and examples thereof include a cross-linking curing agent having a molecular weight of less than 300 and having two or more unsaturated double bonds in the molecule. Examples of the curing agent (D) include a compound that is different from the (meth)acrylate compound (A) and different from the styrene-based polymer (C), and that can react with the (meth)acrylate compound (A) to cure the resin composition. Examples of the curing agent (D) include an allyl compound, a vinyl compound, a maleimide compound, and a (meth)acrylate compound (d) other than the (meth)acrylate compound (A).

[0086] The allyl compound is a compound having an allyl group in the molecule, and examples of the allyl compound include triallyl isocyanurate (TAIC), diallyl bisphenol compounds, and diallyl phthalate (DAP).

[0087] The vinyl compound is a compound having a vinyl group in its molecule. Examples of the vinyl compound include monofunctional vinyl compounds having one vinyl group in its molecule and polyfunctional vinyl compounds having two or more vinyl groups in its molecule. Examples of the monofunctional vinyl compound include vinylbenzene compounds having a phosphorus atom-containing skeleton in its molecule, such as 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO). Examples of the polyfunctional vinyl compound include divinylbenzene and polybutadiene compounds. Examples of the polybutadiene compound include polybutadiene and hydrogenated styrene-butadiene copolymers, and more specifically, B-1000, B-2000, and B-3000 manufactured by Nippon Soda Co., Ltd., and Ricon manufactured by Cray Valley Chemical Industries, Ltd.

[0088] The maleimide compound is a compound having a maleimide group in the molecule. Examples of the maleimide compound include monofunctional maleimide compounds having one maleimide group in the molecule and polyfunctional maleimide compounds having two or more maleimide groups in the molecule. Examples of the modified maleimide compound include modified maleimide compounds in which a portion of the molecule is amine-modified, modified maleimide compounds in which a portion of the molecule is silicone-modified, and modified maleimide compounds in which a portion of the molecule is both amine-modified and silicone-modified.

[0089] The (meth)acrylate compound (d) is not particularly limited as long as it is a (meth)acrylate compound other than the (meth)acrylate compound (A). The (meth)acrylate compound (d) is a methacrylate compound and an acrylate compound different from the (meth)acrylate compound (A).

[0090] Examples of the methacrylate compound include a monofunctional methacrylate compound having one methacryloyl group in the molecule and a polyfunctional methacrylate compound having two or more methacryloyl groups in the molecule. Examples of the monofunctional methacrylate compound include methyl methacrylate, ethyl methacrylate, propyl methacrylate, and butyl methacrylate. Examples of the polyfunctional methacrylate compound include a dimethacrylate compound such as tricyclodecane dimethanol dimethacrylate (DCP).

[0091] Examples of the acrylate compound include a monofunctional acrylate compound having one acryloyl group in the molecule and a polyfunctional acrylate compound having two or more acryloyl groups in the molecule. Examples of the monofunctional acrylate compound include methyl acrylate, ethyl acrylate, propyl acrylate, and butyl acrylate. Examples of the polyfunctional acrylate compound include a diacrylate compound such as tricyclodecane dimethanol diacrylate.

[0092] Among the above-mentioned curing agents (D), for example, the allyl compounds etc. are preferable, and triallyl isocyanurate (TAIC) etc. are more preferable. As the curing agent (D), the above-mentioned curing agents may be used alone or in combination of two or more kinds.

[0093] The molecular weight of the curing agent (D) is preferably less than 300, more preferably 200 to 280. Using the curing agent (C) with such a molecular weight allows for favorable curing of a resin composition containing the (meth)acrylate compound (A) and the styrene-based polymer (B). Therefore, by curing, a cured product having a low relative dielectric constant and dielectric dissipation factor (excellent low dielectric properties) and a low coefficient of thermal expansion can be favorably obtained. Since the curing agent (D) is not a polymeric substance, the molecular weight of the curing agent (D) may simply be the molecular weight, but it may also be the weight-average molecular weight Mw. This weight-average molecular weight may be measured by a general molecular weight measurement method, and specifically, a value measured using gel permeation chromatography (GPC) may be used.

[0094] The resin composition may contain, as necessary, inorganic fillers other than the hollow silica particles (B) (other inorganic fillers) as long as the effects of the present invention are not impaired. The other inorganic fillers are not particularly limited as long as they are inorganic fillers other than the hollow silica particles (B) and can be used as inorganic fillers contained in the resin composition. Examples of the other inorganic fillers include metal oxide fillers other than the hollow silica particles (B), 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 other than the hollow silica particles (B), alumina fillers, titanium oxide fillers, magnesium oxide fillers, and mica fillers. Examples of the silica fillers include solid 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. The other inorganic fillers may be used alone or in combination of two or more.

[0095] Said other inorganic filler can be surface-treated inorganic filler or can be surface-untreated inorganic filler.In addition, said surface treatment can be for example, treatment with silane coupling agent.Said silane coupling agent is not particularly limited, and for example, can be the same as the silane coupling agent used when surface-treating said hollow silica particle (B) as mentioned above.

[0096] The average particle size of the other inorganic filler is not particularly limited, and is preferably 0.05 to 10 μm, and more preferably 0.1 to 8 μm. Here, the average particle size refers to the volume average particle size. The volume average particle size can be measured, for example, by a laser diffraction method.

[0097] (Content) The content of the (meth)acrylate compound (A) is preferably 10 to 80% by mass, and more preferably 20 to 50% by mass, relative to the resin composition. Furthermore, when the resin composition contains the styrene-based polymer (C), the content of the (meth)acrylate compound (A) is preferably 40 to 60% by mass, relative to the total of the (meth)acrylate compound (A) and the styrene-based polymer (C). Furthermore, when the resin composition contains the styrene-based polymer (C) and the curing agent (D), the content of the (meth)acrylate compound (A) is preferably 20 to 80% by mass, and more preferably 40 to 60% by mass, relative to the total of the (meth)acrylate compound (A), the styrene-based polymer (C), and the curing agent (D).

[0098] The content of the hollow silica particles (B) is preferably 5 to 60% by mass, more preferably 5 to 40% by mass, and even more preferably 10 to 40% by mass, relative to the resin composition. The content of the hollow silica particles (B) is preferably 5 to 150 parts by mass, more preferably 15 to 120 parts by mass, relative to 100 parts by mass of the (meth)acrylate compound (A). Furthermore, when the resin composition contains the styrene-based polymer (C), the content of the hollow silica particles (B) is preferably 1 to 80 parts by mass, more preferably 5 to 60 parts by mass, relative to 100 parts by mass of the (meth)acrylate compound (A) and the styrene-based polymer (C) combined. Furthermore, when the resin composition contains the styrene-based polymer (C) and the curing agent (D), the content of the hollow silica particles (B) is preferably 5 to 60 parts by mass, and more preferably 10 to 40 parts by mass, relative to 100 parts by mass of the total of the (meth)acrylate compound (A), the styrene-based polymer (C), and the curing agent (D). The content of the hollow silica particles (B) is preferably 1 to 80 parts by mass, and more preferably 5 to 60 parts by mass, relative to 100 parts by mass of organic components (other than the hollow silica particles (B) and the other inorganic fillers in the resin composition).

[0099] By containing the (meth)acrylate compound (A) and the hollow silica particles (B) so that their respective contents fall within the above ranges, the resulting resin composition can be cured to suitably give a cured product having a low relative dielectric constant and dielectric loss tangent.

[0100] When the resin composition contains the other inorganic filler, the content of the hollow silica particles (B) is preferably 1 to 60 mass%, more preferably 5 to 40 mass%, based on the total amount of the hollow silica particles (B) and the other inorganic filler.

[0101] When the resin composition contains the styrene-based polymer (C), the content of the styrene-based polymer (C) is preferably 10 to 60% by mass, and more preferably 20 to 40% by mass, relative to the resin composition. The content of the styrene-based polymer (C) is preferably 20 to 60% by mass, and more preferably 30 to 50% by mass, relative to the total of the (meth)acrylate compound (A) and the styrene-based polymer (C). When the resin composition contains the styrene-based polymer (C) and the curing agent (D), the content of the styrene-based polymer (C) is preferably 20 to 60% by mass, and more preferably 30 to 50% by mass, relative to the total of the (meth)acrylate compound (A), the styrene-based polymer (C), and the curing agent (D).

[0102] When the resin composition contains the curing agent (D), the content of the curing agent (D) is preferably 1 to 30% by mass, and more preferably 5 to 20% by mass, relative to the resin composition. The content of the curing agent (D) is preferably 5 to 50% by mass, and more preferably 10 to 40% by mass, relative to the total of the (meth)acrylate compound (A) and the curing agent (D). When the resin composition contains the styrene-based polymer (C) and the curing agent (D), the content of the curing agent (D) is preferably 1 to 50% by mass, and more preferably 5 to 30% by mass, and more preferably 8 to 25% by mass, relative to the total of the (meth)acrylate compound (A), the styrene-based polymer (C), and the curing agent (D).

[0103] (Other Components) The resin composition may contain components (other components) other than the (meth)acrylate compound (A) and the hollow silica particles (B) within a range that does not impair the effects of the present invention. As described above, the resin composition may contain the styrene-based polymer (C), the curing agent (D), and the other inorganic fillers as the other components. In addition to these, examples of the other components include organic components other than the (meth)acrylate compound (A), the styrene-based polymer (C), and the curing agent (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.

[0104] As described above, the resin composition according to this embodiment may contain an organic component other than the (meth)acrylate compound (A), the styrene-based polymer (C), and the curing agent (D). The organic component may be, for example, a compound that reacts with or does not react with at least one of the (meth)acrylate compound (A), the styrene-based polymer (C), and the curing agent (D). Specific examples of the organic component include oxazine compounds, epoxy compounds, cyanate ester compounds, and active ester compounds.

[0105] The oxazine compound is not particularly limited as long as it is a compound having an oxazine group in the molecule. Examples of the oxazine compound 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 oxazine compound 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).

[0106] The epoxy compound is a compound having an epoxy group in the molecule, and specific examples thereof 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 having an epoxy group in the molecule, and naphthalene ring-containing epoxy compounds. The epoxy compound also includes epoxy resins, which are polymers of the above-mentioned epoxy compounds.

[0107] The cyanate ester compound is a compound having a cyanate group in the molecule, and examples thereof include 2,2-bis(4-cyanatephenyl)propane, bis(3,5-dimethyl-4-cyanatephenyl)methane, and 2,2-bis(4-cyanatephenyl)ethane.

[0108] The active ester compound is a compound having an ester group with high reactivity in the molecule, and examples thereof 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.

[0109] 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 improved. The flame retardant is not particularly limited. Specifically, in fields where halogen-based flame retardants such as bromine-based flame retardants are used, for example, ethylene dipentabromobenzene, ethylene bistetrabromoimide, decabromodiphenyl oxide, tetradecabromodiphenoxybenzene, and bromostyrene-based compounds that react with the polymerizable compounds, which have melting points of 300°C or higher, are preferred. It is believed that the use of a halogen-based flame retardant can suppress halogen elimination at high temperatures and thus suppress 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 kinds.

[0110] 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 deterioration in the shelf life of the resin composition. Furthermore, since α,α'-di(t-butylperoxy)diisopropylbenzene has low volatility, it does not volatilize during drying or storage of the prepreg, and has good stability. The reaction initiators may be used alone or in combination of two or more.

[0111] As described above, the resin composition according to this embodiment may contain a reaction initiator other than the organic peroxide (D). The reaction initiator other than the organic peroxide (D) is not particularly limited as long as it can accelerate the curing reaction of the resin composition, and examples thereof include organic azo compounds. Examples of the organic azo compounds include azobisisobutyronitrile. Furthermore, if necessary, a metal carboxylate or the like can be used in combination. This can further accelerate the curing reaction. The reaction initiator other than the organic peroxide (D) may be used alone or in combination of two or more.

[0112] 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 of the curing accelerator 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 included. The curing accelerators may be used alone or in combination of two or more.

[0113] 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 previously 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 previously surface-treated on an inorganic filler, and it is more preferable to contain the silane coupling agent in the inorganic filler as a silane coupling agent that has been previously surface-treated, and further to contain the silane coupling agent in the resin composition. In addition, in the case of a prepreg, the prepreg may contain the silane coupling agent that has been previously surface-treated on a fibrous substrate. Examples of the silane coupling agent include the same silane coupling agents as those used when surface-treating the hollow silica particles (B) described above.

[0114] The resin composition according to the present embodiment is a resin composition that can give a cured product having excellent low dielectric properties such as a low relative dielectric constant, etc. Therefore, a wiring board having an insulating layer formed using the resin composition according to the present embodiment is a wiring board having an insulating layer having excellent low dielectric properties.

[0115] (Uses) The resin composition is used to produce a prepreg, as described below, and to form a resin layer provided in a resin-coated metal foil or a resin-coated film, and an insulating layer provided in a metal-clad laminate or a wiring board.

[0116] (Production method) The method for producing the resin composition is not particularly limited, and examples thereof include a method of mixing the (meth)acrylate compound (A), the hollow silica particles (B), and, if necessary, components other than the (meth)acrylate compound (A) and the hollow silica particles (B) to a predetermined content. In addition, in the case of obtaining a varnish-like composition containing an organic solvent, the method described below can be used.

[0117] [Prepreg, metal-clad laminate, wiring board, resin-coated metal foil, and resin-coated film] By using the resin composition according to this embodiment, a prepreg, a metal-clad laminate, a wiring board, a resin-coated metal foil, and a resin-coated film can be obtained as follows.

[0118] (Prepreg) FIG. 1 is a schematic cross-sectional view showing an example of a prepreg 1 according to an embodiment of the present invention.

[0119] 1, the prepreg 1 according to this embodiment comprises the resin composition or a semi-cured product of the resin composition 2, and a fibrous base material 3. This prepreg 1 comprises the resin composition or a semi-cured product of the resin composition 2, and the fibrous base material 3 present in the resin composition or the semi-cured product of the resin composition 2.

[0120] In this embodiment, the semi-cured product refers to a resin composition that has been partially cured to the extent that it can be further cured. That is, the semi-cured product refers to 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, and the viscosity gradually increases. In such a case, the semi-cured state may refer to a state between when the viscosity starts to increase and when the composition is completely cured.

[0121] 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 the semi-cured product of the resin composition may be the resin composition that has been dried or heat-dried.

[0122] 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 a base material for forming the prepreg. That is, the resin composition 2 is usually often a resin varnish prepared in a varnish form. Such a varnish-like resin composition (resin varnish) is prepared, for example, as follows.

[0123] First, each component that is soluble in an organic solvent is added to the organic solvent and dissolved. Heating may be performed as necessary. Then, 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 a predetermined 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 (meth)acrylate compound (A) and the like and does not inhibit the curing reaction. Specific examples include toluene and methyl ethyl ketone (MEK).

[0124] 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. Glass cloth can be used to obtain a laminate with excellent mechanical strength, and flattened glass cloth is particularly preferred. A specific example of the flattening process is 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, and 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 thereof include silane coupling agents having at least one group selected from the group consisting of a vinyl group, an acryloyl group, a methacryloyl group, a styryl group, an amino group, and an epoxy group in the molecule.

[0125] The method for producing the prepreg is not particularly limited as long as it can produce the prepreg. Specifically, when producing the prepreg, the resin composition according to the present embodiment is often prepared in the form of a varnish, as described above, and used as a resin varnish.

[0126] Specific examples of methods for producing the prepreg 1 include a method in which the resin composition 2, for example, a resin composition 2 prepared in a varnish form, is impregnated into a fibrous substrate 3, followed by drying. The resin composition 2 is impregnated into the fibrous substrate 3 by immersion, coating, or the like. Impregnation can be repeated multiple times as necessary. In this case, by repeating the impregnation using multiple resin compositions with different compositions and concentrations, it is also possible to adjust the final composition and impregnation amount to the desired one.

[0127] The fibrous substrate 3 impregnated with the resin composition (resin varnish) 2 is heated under desired conditions, for example, at 40°C to 180°C for 1 minute to 10 minutes. This heating process results in a prepreg 1 in an uncured (A-stage) or semi-cured (B-stage) state. The heating process also volatilizes the organic solvent from the resin varnish, reducing or eliminating the organic solvent.

[0128] (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.

[0129] As shown in FIG. 2 , the metal-clad laminate 11 according to this embodiment includes 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 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, for example, 0.2 to 70 μm. Examples of the metal foil 13 include copper foil and aluminum foil. When the metal foil is thin, it may be a carrier-attached copper foil equipped with a release layer and a carrier to improve handling.

[0130] The method for producing the metal-clad laminate 11 is not particularly limited as long as it can produce the metal-clad laminate 11. Specifically, a method for producing the metal-clad laminate 11 using the prepreg 1 can be used. Examples of such a method include stacking one or more prepregs 1, placing 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. That is, the metal-clad laminate 11 can be 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 0.5 to 5 MPa, and the time can be 60 to 150 minutes. The metal-clad laminate can also be produced without using a prepreg. For example, a method may be used in which a varnish-like resin composition is applied onto a metal foil to form a layer containing the resin composition on the metal foil, and then the layer is heated and pressed.

[0131] (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.

[0132] As shown in Fig. 3, wiring board 21 according to this embodiment has insulating layer 12 containing a cured product of the resin composition, and wiring 14 provided on insulating layer 12. Examples of wiring board 21 include a wiring board configured from insulating layer 12 used by curing prepreg 1 shown in Fig. 1, and wiring 14 laminated together with insulating layer 12 and formed by partially removing metal foil 13. Furthermore, insulating layer 12 may be made of a cured product of the resin composition, or may be made of a cured product of the prepreg.

[0133] The method for manufacturing the wiring board 21 is not particularly limited as long as the wiring board 21 can be manufactured. 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, examples of the method for forming a circuit include circuit formation by a semi-additive process (SAP) or a modified semi-additive process (MSAP).

[0134] (Resin-Coated Metal Foil) FIG. 4 is a schematic cross-sectional view showing an example of a resin-coated metal foil 31 according to this embodiment.

[0135] 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. The resin-coated metal foil 31 has the metal foil 13 on the surface of the resin layer 32. That is, the 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.

[0136] 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 a resin layer containing the resin composition before curing (the resin composition in A-stage) and a metal foil. 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.

[0137] The metal foil may be any metal foil used in a metal-clad laminate or a resin-coated metal foil, and examples of the metal foil include copper foil and aluminum foil.

[0138] The resin-coated metal foil 31 may be provided with a cover film or the like as necessary. By providing a cover film, it is possible to prevent the inclusion of foreign matter, etc. The cover film is not particularly limited, but examples thereof include polyolefin films, polyester films, polymethylpentene films, and films formed by providing these films with a release agent layer.

[0139] The method for producing the resin-coated metal foil 31 is not particularly limited as long as the resin-coated metal foil 31 can be produced. Examples of the method for producing the resin-coated metal foil 31 include a method of applying the varnish-like resin composition (resin varnish) to the metal foil 13 and heating the applied resin composition. 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 40°C or higher and 180°C or lower for 0.1 minutes or longer and 10 minutes or shorter. The heated resin composition is formed on the metal foil 13 as an uncured resin layer 32. The heating volatilizes the organic solvent from the resin varnish, thereby reducing or removing the organic solvent.

[0140] (Resin-Coated Film) FIG. 5 is a schematic cross-sectional view showing an example of a resin-coated film 41 according to this embodiment.

[0141] 5 , the resin-coated film 41 according to this embodiment includes a resin layer 42 containing the resin composition or a semi-cured product of the resin composition, and a support film 43. The resin-coated film 41 includes the resin layer 42 and the support film 43 laminated together with the resin layer 42. The resin-coated film 41 may also include another layer between the resin layer 42 and the support film 43.

[0142] 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 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 obtained by drying or heat-drying the resin composition. The fibrous substrate may be the same as the fibrous substrate of a prepreg.

[0143] Any support film used for a resin-coated film can be used without limitation as the support film 43. Examples of the support film 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.

[0144] The resin-coated film 41 may be provided with a cover film or the like as necessary. By providing a cover film, it is possible to prevent the inclusion of foreign matter, etc. The cover film is not particularly limited, but examples thereof include a polyolefin film, a polyester film, and a polymethylpentene film.

[0145] The support film and the cover film may be subjected to surface treatment such as matte treatment, corona treatment, release treatment, and roughening treatment, if necessary.

[0146] 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 40°C or higher and 180°C or lower for 0.1 minutes or longer and 10 minutes or shorter. 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 removing the organic solvent.

[0147] When cured, the resin composition according to this embodiment forms a cured product with a low dielectric constant and dielectric loss tangent. Therefore, when cured, the prepreg forms a cured product with a low dielectric constant and dielectric loss tangent. The resin-coated metal foil and the resin-coated film are, respectively, resin-coated metal foil and resin-coated film, each having a resin layer that becomes an insulating layer containing the cured product upon curing. The metal-clad laminate and the wiring board are, respectively, metal-clad laminate and wiring board, each having an insulating layer containing the cured product. The prepreg, the resin-coated film, the resin-coated metal foil, and the metal-clad laminate can be suitably used to manufacture the wiring board, for example, and can also be used to manufacture a multilayer wiring board. For example, a multilayer wiring board can be manufactured by laminating the resin-coated film on a wiring board and then peeling off the support film, or by laminating the resin-coated film on a wiring board after peeling off the support film. The resin-coated metal foil can be, for example, laminated on a wiring board, to manufacture a multilayer wiring board. In this way, by using the resin-coated film and the resin-coated metal foil, etc., it is possible to manufacture a multi-layer wiring board having an insulating layer containing the cured product.

[0148] As described above, this specification discloses various aspects of the technology, the main technologies of which are summarized below.

[0149] The resin composition according to the first aspect of the present invention is a resin composition containing (A) a (meth)acrylate compound having an indane skeleton represented by the general formula (1) and (B) hollow silica particles.

[0150] A resin composition according to a second aspect of the present invention is the resin composition according to the first aspect of the present invention, wherein X is a methacryloyloxy group.

[0151] A resin composition according to a third aspect of the present invention is the resin composition according to the first or second aspect of the present invention, wherein the (meth)acrylate compound (A) comprises a methacrylate compound (a) having an indane skeleton represented by the general formula (2).

[0152] A resin composition according to a fourth aspect of the present invention is the resin composition according to any one of the first to third aspects of the present invention, wherein the hollow silica particles (B) have a volume average particle diameter of 1 μm or less.

[0153] A resin composition according to a fifth aspect of the present invention is the resin composition according to any one of the first to fourth aspects of the present invention, wherein the content of the hollow silica particles (B) is 5 to 40 mass% relative to the resin composition.

[0154] A resin composition according to a sixth aspect of the present invention is the resin composition according to any one of the first to fifth aspects of the present invention, further comprising a styrene-based polymer (C).

[0155] A resin composition related to a seventh aspect of the present invention is the resin composition related to the sixth aspect of the present invention, wherein the content of the (meth)acrylate compound (A) is 40 to 60 mass% with respect to the total of the (meth)acrylate compound (A) and the styrene-based polymer (C).

[0156] A resin composition according to an eighth aspect of the present invention is the resin composition according to any one of the first to seventh aspects of the present invention, further comprising a curing agent (D).

[0157] A resin composition according to a ninth aspect of the present invention is the resin composition according to the eighth aspect of the present invention, wherein the curing agent (D) comprises at least one selected from the group consisting of an allyl compound, a vinyl compound, a maleimide compound, and a (meth)acrylate compound (d) other than the (meth)acrylate compound (A).

[0158] A resin composition according to a tenth aspect of the present invention is the resin composition according to any one of the first to ninth aspects of the present invention, further comprising a styrene-based polymer (C) and a curing agent (D), and the content of the (meth)acrylate compound (A) is 20 to 80 mass % with respect to the total of the (meth)acrylate compound (A), the styrene-based polymer (C), and the curing agent (D).

[0159] A resin composition according to an eleventh aspect of the present invention is the resin composition according to any one of the first to tenth aspects of the present invention, further comprising a styrene-based polymer (C) and a curing agent (D), and the content of the styrene-based polymer (C) is 20 to 60 mass% with respect to the total of the (meth)acrylate compound (A), the styrene-based polymer (C), and the curing agent (D).

[0160] A resin composition according to a twelfth aspect of the present invention is the resin composition according to any one of the first to eleventh aspects of the present invention, further comprising a styrene-based polymer (C) and a crosslinking curing agent (D), and the content of the curing agent (D) is 5 to 30 mass % with respect to the total of the (meth)acrylate compound (A), the styrene-based polymer (C), and the curing agent (D).

[0161] A prepreg according to a thirteenth aspect of the present invention is a prepreg comprising 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 fibrous base material.

[0162] 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.

[0163] A resin-coated metal foil according to a 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.

[0164] A metal-clad laminate according to a 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.

[0165] A metal-clad laminate according to a 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.

[0166] A wiring board according to an 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.

[0167] A metal-clad laminate according to a nineteenth aspect of the present invention is a wiring board comprising an insulating layer containing a cured product of the prepreg according to the thirteenth aspect of the present invention and wiring.

[0168] According to the present invention, there is provided a resin composition that can give a cured product having a low dielectric constant and a low dielectric loss tangent. Furthermore, according to the present invention, there are provided a prepreg, a resin-coated film, a resin-coated metal foil, a metal-clad laminate, and a wiring board that can be obtained using the resin composition.

[0169] The present invention will be explained in more detail below with reference to examples, but the scope of the present invention is not limited to these examples.

[0170] Examples 1 to 3 and Comparative Example In these examples, each component used in preparing the resin composition will be described.

[0171] ((Meth)acrylate compound (A)) Methacrylate compound: represented by the formula (2), R １ and R ２ is a methyl group and n is 1.6 (NE-V-RD004 manufactured by DIC Corporation)

[0172] (Modified PPE) Modified PPE: polyphenylene ether compound having a methacryloyl group at the end (SA9000 manufactured by SABIC Innovative Plastics, a modified polyphenylene ether in which the terminal hydroxyl group of polyphenylene ether is modified with a methacryloyl group, weight average molecular weight Mw 2000)

[0173] (Styrene-based polymer (B)) H1041: Hydrogenated styrene (ethylene / butylene) styrene block copolymer (Tuftec H1041 manufactured by Asahi Kasei Corporation)

[0174] (Curing agent (D)) TAIC: triallyl isocyanurate (TAIC manufactured by Nippon Kasei Chemical Co., Ltd.)

[0175] (Reaction initiator) PBP: α,α'-bis(t-butylperoxy-m-isopropyl)benzene (Perbutyl P manufactured by NOF Corporation)

[0176] (Hollow Silica Particles (B)) Hollow Silica Particles 1: Hollow silica particles (manufactured by Fuso Chemical Co., Ltd., volume average particle diameter D50: 0.5 μm, specific gravity: 1.1) Hollow Silica Particles 2: Hollow silica particles (manufactured by Admatechs Co., Ltd., volume average particle diameter D50: 0.6 μm, specific gravity: 1.39) Hollow Silica Particles 3: Hollow silica particles (manufactured by AGC Inc., volume average particle diameter D50: 2 μm, specific gravity: 0.48)

[0177] (Inorganic fillers other than hollow silica particles) Solid silica particles: solid silica particles (K180SV-C2 manufactured by Admatechs Co., Ltd., volume average particle size: 0.18 μm, specific gravity: 2.2)

[0178] [Preparation Method] First, components other than the inorganic filler (hollow silica particles and inorganic fillers other than hollow silica particles) were added to a mixed solvent of toluene and methyl ethyl ketone (MEK) (mass ratio of approximately 2:1) so as to have a solids concentration of 40 to 50 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 produced a varnish-like resin composition (varnish).

[0179] Next, a resin film was obtained as follows.

[0180] The obtained varnish was applied to a polyethylene terephthalate (PET) film (SP-PET manufactured by Mitsui Chemicals Tohcello Co., Ltd.) so that the thickness after drying would be 25 μm, and a resin film was formed on the PET film by heating and drying at 100° C. for 3 minutes. This resin film was peeled off from the PET film to obtain a resin film with a thickness of 25 μm.

[0181] An evaluation substrate (metal-clad laminate) was obtained as follows.

[0182] Four sheets of the obtained resin film were stacked, 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 a temperature of 220°C at a temperature increase rate of 3°C / min, and then heated and pressed at 220°C for 120 minutes under a pressure of 3 MPa, thereby obtaining an evaluation substrate (metal-clad laminate) with copper foil adhered to both sides and an insulating layer thickness of approximately 100 μm.

[0183] The evaluation substrate prepared as described above was evaluated by the following method.

[0184] [Dielectric Properties (Dielectric Constant Dk and Dielectric Loss Tangent Df)] The copper foil was removed from the evaluation substrate by etching. The substrate thus obtained was used as a test specimen, and the dielectric constant and dielectric loss tangent at 10 GHz were measured using a cavity resonator perturbation method. Specifically, the dielectric constant (Dk) and dielectric loss tangent (Df) of the test specimen at 10 GHz were measured using a network analyzer (Keysight Technologies, Inc. N5230A).

[0185] [Thermal expansion coefficient (25 to 150 ° 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) 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 tensile mode. In order to eliminate the influence of thermal distortion of the test specimen, the test specimen was heated from 20 ° C to 320 ° C at a heating rate of 10 ° C / min while pulled with a load of 10 g, and then cooled to room temperature. Then, the test specimen was heated from 20 ° C to 320 ° C at a heating rate of 10 ° C / min while pulled with a load of 10 g. A temperature displacement chart was obtained during this heating period. From the temperature change chart obtained at this time, the average coefficient of thermal expansion from 25 to 150° C. was calculated. The smaller this average coefficient of thermal expansion (CTE 25-150° C.), the more preferable the result.

[0186] The results of the above evaluations are shown in Table 1 together with the formulations of the resin compositions.

[0187] As can be seen from Table 1, in the case of the resin composition containing the (meth)acrylate compound (A) having an indane skeleton represented by the general formula (1) and the hollow silica particles (B) (Examples 1 to 3), a cured product having a lower dielectric constant and dielectric loss tangent was obtained compared to the case (Comparative Example) which did not contain these compounds and contained a modified PPE and an inorganic filler other than the hollow silica particles (B).

[0188] This application is based on Japanese Patent Application No. 2024-121161 filed on July 26, 2024, the contents of which are incorporated herein by reference.

[0189] In order to express the present invention, the present invention has been properly and sufficiently described through the embodiments in the above, but it should be recognized that those skilled in the art can easily change and / or improve the above-mentioned embodiments. Therefore, unless the changes or improvements made by those skilled in the art are at a level that causes departure from the scope of the claims described in the claims, such changes or improvements are interpreted as being included in the scope of the claims.

[0190] According to the present invention, there is provided a resin composition that can give a cured product having a low dielectric constant and a low dielectric loss tangent. Also, according to the present invention, there are provided a prepreg, a resin-coated film, a resin-coated metal foil, a metal-clad laminate, and a wiring board that can be obtained using the resin composition.

Claims

1. A resin composition comprising (A) a (meth)acrylate compound having an indane skeleton represented by the following general formula (1) and (B) hollow silica particles: [In the above formula (1), X represents a (meth)acryloyloxy group; Ra and Rb each independently represent an alkyl group, aryl group, aralkyl group, or cycloalkyl group having 1 to 12 carbon atoms; j represents an integer of 1 to 3; k and l each independently represent an integer of 0 to 4; n is an average repeating unit and represents a number of 0.5 to 20; and m represents an integer of 0 to 2.] 2. The resin composition according to claim 1, wherein X is a methacryloyloxy group.

3. The resin composition according to claim 1, wherein the (meth)acrylate compound (A) comprises a methacrylate compound (a) having an indane skeleton represented by the following general formula (2): [In the above formula (2), R １ and R ２ each independently represents a hydrogen atom, an alkyl group having 1 to 12 carbon atoms, an aryl group, an aralkyl group, or a cycloalkyl group, and R １ and R ２ are not both hydrogen atoms at the same time, and n is the average repeating unit and is a value of 0.5 to 20.

4. The resin composition according to claim 1, wherein the hollow silica particles (B) have a volume average particle size of 1 μm or less.

5. The resin composition according to claim 1, wherein the content of the hollow silica particles (B) is 5 to 40% by mass based on the resin composition.

6. The resin composition according to claim 1, further comprising a styrene polymer (C).

7. The resin composition according to claim 6, wherein the content of the (meth)acrylate compound (A) is 40 to 60 mass % based on the total of the (meth)acrylate compound (A) and the styrene-based polymer (C).

8. The resin composition according to claim 1, further comprising a curing agent (D).

9. The resin composition according to claim 8, wherein the curing agent (D) comprises at least one selected from the group consisting of allyl compounds, vinyl compounds, maleimide compounds, and (meth)acrylate compounds (d) other than the (meth)acrylate compound (A).

10. The resin composition according to claim 1, further comprising a styrene-based polymer (C) and a curing agent (D), wherein the content of the (meth)acrylate compound (A) is 20 to 80 mass % based on the total of the (meth)acrylate compound (A), the styrene-based polymer (C), and the curing agent (D).

11. The resin composition according to claim 1, further comprising a styrene polymer (C) and a curing agent (D), wherein the content of the styrene polymer (C) is 20 to 60 mass% based on the total of the (meth)acrylate compound (A), the styrene polymer (C), and the curing agent (D).

12. The resin composition according to claim 1, further comprising a styrene-based polymer (C) and a curing agent (D), wherein the content of the curing agent (D) is 5 to 30 mass% based on the total of the (meth)acrylate compound (A), the styrene-based polymer (C), and the curing agent (D).

13. A prepreg comprising the resin composition according to any one of claims 1 to 12 or a semi-cured product of said resin composition and a fibrous base material.

14. 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 said resin composition, and a support film.

15. 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 said resin composition, and a metal foil.

16. A metal-clad laminate comprising an insulating layer containing a cured product of the resin composition according to any one of claims 1 to 12 and a metal foil.

17. A metal-clad laminate comprising an insulating layer containing a cured product of the prepreg according to claim 13 and a metal foil.

18. A wiring board comprising an insulating layer containing a cured product of the resin composition according to any one of claims 1 to 12, and wiring.

19. A wiring board comprising an insulating layer containing the cured product of the prepreg according to claim 13 and wiring.

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