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

Abstract

The present disclosure addresses the problem of providing a resin composition in which uneven distribution of an inorganic filler contained in a cured product is suppressed, and a cured product of which is highly flame retardant. The resin composition comprises an epoxy compound (A), a maleimide compound (B), a curing agent (C), a phosphorus-based flame retardant (D), and an inorganic filler (E). The resin composition does not comprise a hydrated metal compound. The phosphorus-based flame retardant (D) includes at least one compound selected from the group consisting of phosphoric acid ester compounds (D1) and phosphine compounds (D2). The content of the phosphorus-based flame retardant (D) is 3.0-20.0 parts by mass with respect to 100 parts by mass of the total of the epoxy compound (A), the maleimide compound (B), and the curing agent (C). The inorganic filler (E) includes silica particles (E1) having, in a volume-based particle size distribution based on laser diffraction scattering, an average particle size (D50) of not less than 0.1 μm but less than 2.5 μm.

Description

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

[0001] This disclosure generally relates to resin compositions, prepregs, resin films, metal foils with resin, metal-clad laminates, and printed wiring boards. More specifically, this disclosure relates to resin compositions, prepregs, resin films, metal foils with resin, metal-clad laminates, and printed wiring boards containing epoxy resins.

[0002] Patent Document 1 discloses a resin composition containing an epoxy compound (A), a maleimide compound (B), a curing agent (C), and an inorganic filler (D), wherein the inorganic filler (D) includes a silica filler (D1) and silica-treated magnesium hydroxide (D2) obtained by surface-treating magnesium hydroxide with silica. Patent Document 1 discloses that the resin composition can suppress the occurrence of ion migration and achieve a low coefficient of thermal expansion.

[0003] Regarding resin compositions such as those described above, it is required that the uneven distribution of the inorganic filler contained in the cured product be suppressed and that the cured product have high flame retardancy.

[0004] International Publication No. 2024 / 195732

[0005] An object of this disclosure is to provide a resin composition, prepreg, resin film, metal foil with resin, metal-clad laminate, and printed wiring board in which the uneven distribution of the inorganic filler contained in the cured product is suppressed and the cured product has high flame retardancy.

[0006] The resin composition according to one aspect of this disclosure contains an epoxy compound (A), a maleimide compound (B), a curing agent (C), a phosphorus-based flame retardant (D), and an inorganic filler (E). The resin composition does not contain a hydrated metal compound. The phosphorus-based flame retardant (D) includes at least one selected from the group consisting of a phosphate ester compound (D1) and a phosphine compound (D2) represented by formula (1).

[0007]

[0008] In formula (1), each of R1, R2, and R3 is independently a monovalent organic group containing a carbon atom, a hydrogen atom, a halogen atom, or a hydroxyl group. The content of the phosphorus-based flame retardant (D) is 3.0 parts by mass or more and 20.0 parts by mass or less, based on 100 parts by mass of the total of the epoxy compound (A), the maleimide compound (B), and the curing agent (C). The inorganic filler (E) contains silica particles (E1) having an average particle diameter (D50) of 0.1 μm or more and less than 2.5 μm in a volume-based particle size distribution based on laser diffraction scattering.

[0009] A prepreg according to one aspect of the present disclosure comprises the resin composition or a semi-cured product of the resin composition and a fibrous substrate.

[0010] A resin-coated film according to one aspect of the present disclosure comprises a resin layer containing the resin composition or a semi-cured product of the resin composition, and a support film.

[0011] A resin-coated metal foil according to one aspect of the present disclosure comprises a resin layer containing the resin composition or a semi-cured product of the resin composition, and a metal foil.

[0012] A metal-clad laminate according to one aspect of the present disclosure comprises an insulating layer containing a cured product of the resin composition and a metal layer.

[0013] A printed circuit board according to one aspect of the present disclosure comprises an insulating layer containing a cured product of the resin composition and wiring.

[0014] Figure 1 is a schematic cross-sectional view showing a prepreg according to one embodiment of the present disclosure. Figure 2 is a schematic cross-sectional view showing a resin-coated film (without protective film) according to one embodiment of the present disclosure. Figure 3 is a schematic cross-sectional view showing a resin-coated film (with protective film) according to one embodiment of the present disclosure. Figure 4 is a schematic cross-sectional view showing a resin-coated metal foil according to one embodiment of the present disclosure. Figure 5 is a schematic cross-sectional view showing a metal-clad laminate according to one embodiment of the present disclosure. Figure 6 is a schematic cross-sectional view showing a printed circuit board according to one embodiment of the present disclosure.

[0015] 1. Overview Insulating substrates in metal-clad laminates or printed circuit boards may contain embedded electronic components. For example, recesses may be formed in the insulating substrate, and electronic components may be placed in these recesses. In this case, after placing the electronic components, the entire recess may be filled with a resin composition and cured, thereby protecting the placed electronic components with the cured resin composition. To adequately protect the electronic components placed in the recesses, the resin composition is required to suppress the uneven distribution of inorganic fillers contained in the cured product, and for the cured product to have high flame retardancy. Therefore, the inventors have diligently researched and developed this invention.

[0016] The resin composition (M) according to the embodiment contains an epoxy compound (A), a maleimide compound (B), a curing agent (C), a phosphorus-based flame retardant (D), and an inorganic filler (E). However, the resin composition (M) does not contain a hydrated metal compound. The phosphorus-based flame retardant (D) includes at least one selected from the group consisting of a phosphate ester compound (D1) and a phosphine compound (D2) represented by formula (1).

[0017]

[0018] In formula (1), each of R1, R2, and R3 is independently a monovalent organic group containing a carbon atom, a hydrogen atom, a halogen atom, or a hydroxyl group. The content of the phosphorus-based flame retardant (D) is 3.0 parts by mass or more and 20.0 parts by mass or less per 100 parts by mass of the total of the epoxy compound (A), maleimide compound (B), and curing agent (C). The inorganic filler (E) contains silica particles (E1) having an average particle size (D50) of 0.1 μm or more and less than 2.5 μm in the volume-based particle size distribution based on laser diffraction scattering.

[0019] According to the above configuration, the uneven distribution of inorganic fillers contained in the cured product is suppressed, and a resin composition (M) having high flame retardancy in the cured product is obtained. The exact reason why the resin composition (M) according to the embodiment can exhibit the above effect has not been precisely clarified, but it is presumed to be due to the following reasons.

[0020] In this embodiment, the resin composition (M) contains a phosphorus-based flame retardant (D) comprising at least one selected from the group consisting of phosphate ester compounds (D1) and phosphine compounds (D2). A phosphorus-based flame retardant (D) containing such specific components can suppress the aggregation of the inorganic filler (E). The content of the phosphorus-based flame retardant (D) is 3.0 parts by mass or more and 20.0 parts by mass or less, based on 100 parts by mass of the total of the epoxy compound (A), maleimide compound (B), and curing agent (C). Thus, in this embodiment, the resin composition (M) contains a phosphorus-based flame retardant (D) containing specific components in a specific content. In this case, the phosphorus-based flame retardant (D), which can suppress the aggregation of the inorganic filler (E), can efficiently mix with the epoxy compound (A) and the maleimide compound (B). Therefore, the dispersibility of the inorganic filler (E) in the resin composition (M) is efficiently improved. This makes it less likely for the inorganic filler (E) to separate from the epoxy compound (A) and maleimide compound (B) when the resin composition (M) flows. As a result, when the resin composition (M) hardens, the uneven distribution of the inorganic filler (E) contained in the hardened product is suppressed.

[0021] In this embodiment, the resin composition (M) does not contain a hydrated metal compound. When the cured product of the resin composition (M) burns, char may be formed. Since the hydrated metal compound combines with the phosphorus in the phosphorus-based flame retardant (D), the proportion of phosphorus that forms char is insufficient, and as a result, char formation is not easily promoted.

[0022] In contrast, in this embodiment, the resin composition (M) does not contain a hydrated metal compound. This enhances the char formation effect of the phosphorus-based flame retardant (D). As a result, the cured product has high flame retardancy.

[0023] 2. Details 2.1 Components The components contained in the resin composition (M) will be described below.

[0024] (Epoxy compound (A)) The resin composition (M) contains epoxy compound (A). The form of epoxy compound (A) is not particularly limited, but it is preferably a prepolymer.

[0025] The number of epoxy groups in epoxy compound (A) is not particularly limited, but it is preferable that epoxy compound (A) has at least two or more epoxy groups in one molecule.

[0026] The epoxy compound (A) may include, for example, at least one selected from the group consisting of naphthalene-type epoxy compounds, cresol-type epoxy compounds, bisphenol A-type epoxy compounds, bisphenol F-type epoxy compounds, bosphenol S-type epoxy compounds, phenol novolac-type epoxy compounds, biphenol-type epoxy compounds, dicyclopentadiene-type epoxy compounds, epoxy compounds of condensates of phenols and aromatic aldehydes having a phenolic hydroxyl group, triglycidyl isocyanurates, and alicyclic epoxy compounds. It is particularly preferable that the epoxy compound (A) includes at least one selected from the group consisting of naphthalene-type epoxy compounds and biphenyl-type epoxy compounds. Naphthalene-type epoxy compounds have a naphthalene structure in one molecule. The molecular motion of compounds having a naphthalene structure is easily suppressed. Therefore, the glass transition temperature (Tg) of the cured product is increased, and as a result, the heat resistance of the cured product is improved. Biphenyl-type epoxy compounds have a biphenyl structure in one molecule. Compounds having a biphenyl skeleton may have high polarity. Therefore, when a metal foil treated with a silane coupling agent comes into contact with a cured product, an attractive force is generated between the biphenyl skeleton and the silane coupling agent, resulting in improved adhesion between the cured product and the metal foil.

[0027] The content of epoxy compound (A) is preferably 25.0% by mass or more and 45.0% by mass or less, relative to the total amount of epoxy compound (A), maleimide compound (B), and curing agent (C).

[0028] If the epoxy compound (A) content is 25.0% by mass or more, the decrease in adhesion of the cured product can be suppressed, and the water absorption rate of the cured product is less likely to increase. Here, in this disclosure, "adhesion" means the adhesion between the insulating layer 41 and the metal layer 43 in the metal-clad laminate 4, and the adhesion between the insulating layer 51 and the wiring 53 in the printed wiring board 5. That is, by having an epoxy compound (A) content above a certain value, the adhesion between the insulating layer 41 and the metal layer 43 in the metal-clad laminate 4 is improved. And the adhesion between the insulating layer 51 and the wiring 53 in the printed wiring board 5 is improved. The epoxy compound (A) content is more preferably 30.0% by mass or more, and even more preferably 35.0% by mass or more.

[0029] If the content of epoxy compound (A) is 45.0% by mass or less, the decrease in the glass transition temperature (Tg) of the cured product is suppressed, and the coefficient of thermal expansion (CTE) of the cured product is less likely to increase. The content of epoxy compound (A) is more preferably 42.0% by mass or less, and even more preferably 40.0% by mass or less.

[0030] (Maleimide Compound (B)) The resin composition (M) contains a maleimide compound (B). The number of maleimide groups in the maleimide compound (B) is not particularly limited, but it is preferable that the maleimide compound (B) has two or more maleimide groups in one molecule. It is preferable that the maleimide compound (B) contains a bismaleimide compound. Bismaleimide compounds can have a rigid chemical structure and high reactivity. Therefore, when the resin composition (M) contains a bismaleimide compound, the elastic modulus and glass transition temperature (Tg) of the cured product are increased. It is also preferable that the maleimide compound (B) contains a phenylmaleimide compound.

[0031] The maleimide compound (B) is not particularly limited, but examples include the following. Commercially available products are listed in parentheses.

[0032] • 4,4'-Diphenylmethanebismaleimide (manufactured by Yamato Kasei Kogyo Co., Ltd., product name "BMI-1000") • Polyphenylmethanebismaleimide (manufactured by Yamato Kasei Kogyo Co., Ltd., product name "BMI-2300") • m-Phenylenebismaleimide (manufactured by Yamato Kasei Kogyo Co., Ltd., product name "BMI-3000") • Bisphenol A diphenyl ether bismaleimide (manufactured by Yamato Kasei Kogyo Co., Ltd., product name "BMI-4000") • 3,3'-Dimethyl-5,5'-Diethyl-4,4'-Diphenylmethanebismaleimide (manufactured by Yamato Kasei Kogyo Co., Ltd., product name "BMI-5100") • 4-Methyl-1,3-Phenylenebismaleimide (manufactured by Yamato Kasei Kogyo Co., Ltd., product name "BMI-7000") - 1,6'-bismaleimide-(2,2,4-trimethyl)hexane (manufactured by Yamato Chemical Industries, Ltd., product name "BMI-TMH") - Biphenylaralkyl type maleimide compound (manufactured by Nippon Kayaku Co., Ltd., product name "MIR-3000-70T") - Compounds having a phenylmaleimide group and an arylene structure substituted at the meta position in the molecule.

[0033] The maleimide compound (B) may be present in the resin composition (M) as a single type or as two or more types.

[0034] The content of maleimide compound (B) is preferably 25.0% by mass or more and 45.0% by mass or less, based on 100 parts by mass of the total of epoxy compound (A), maleimide compound (B), and curing agent (C).

[0035] If the maleimide compound (B) content is 25.0% by mass or more, the decrease in the glass transition temperature (Tg) of the cured product is suppressed, and the coefficient of thermal expansion (CTE) of the cured product is less likely to increase. The maleimide compound (B) content is more preferably 30.0% by mass or more, and even more preferably 32.0% by mass or more.

[0036] If the maleimide compound (B) content is 45.0% by mass or less, the decrease in adhesion of the cured product is suppressed, and the water absorption rate of the cured product is less likely to increase. The maleimide compound (B) content is more preferably 40.0% by mass or less, and even more preferably 35.0% by mass or less.

[0037] (Hardening Agent (C)) The resin composition (M) contains a hardening agent (C). The hardening agent (C) may include, for example, at least one selected from the group consisting of a phenolic compound (C1), dicyandiamide, polyisocyanate, polyol hardening agent, silicone-based hardening agent, and acid anhydride compound. The hardening agent (C) preferably contains a phenolic compound (C1). In this case, the flame retardancy of the cured product is enhanced.

[0038] The phenolic compound (C1) preferably has, for example, two or more phenolic hydroxyl groups in one molecule. In this case, the adhesion and flame retardancy of the cured product are enhanced.

[0039] The phenolic compound (C1) preferably contains a phosphorus-containing phenolic compound (C11) containing a phosphorus atom. In this case, the flame retardancy of the cured product is further enhanced.

[0040] The phosphorus-containing phenolic compound (C11) is not particularly limited, but preferably has a structure represented by formula (2) in one molecule. Further, the phosphorus-containing phenolic compound (C11) preferably has a bisphenol A type structure in one molecule. That is, the phosphorus-containing phenolic compound (C11) more preferably has a structure represented by formula (2) in one molecule and a bisphenol A type structure. In this case, the cured product may have higher flame retardancy.

[0041] As an example of the phosphorus-containing phenolic compound (C11) having a structure represented by formula (2) and a bisphenol A type structure, the product name "XZ92741.00" manufactured by Dow Chemical Japan Co., Ltd. can be mentioned.

[0042]

[0043] (In the formula, * represents a bond) The content of the phosphorus-containing phenolic compound (C11) is preferably 5% by mass or more and 30% by mass or less with respect to 100 parts by mass in total of the epoxy compound (A), the maleimide compound (B), and the curing agent (C). When the content of the phosphorus-containing phenolic compound (C11) is 10% by mass or more, the flame retardancy of the cured product is enhanced. When the content of the phosphorus-containing phenolic compound (C11) is 20% by mass or less, the heat resistance can be maintained.

[0044] The phenolic compound (C1) preferably contains a phosphorus-free phenolic compound (C12) that does not contain a phosphorus atom. The phosphorus-free phenolic compound (C12) preferably has a biphenyl structure. Examples of such a phosphorus-free phenolic compound (C12) include biphenyl aralkyl type phenolic compounds.

[0045] When the phenolic compound (C1) contains a phosphorus-containing phenolic compound (C11) and a phosphorus-free phenolic compound (C12), the mass ratio (C11 / C12) of the phosphorus-containing phenolic compound (C11) to the phosphorus-free phenolic compound (C12) is preferably 0.1 or more and 0.5 or less, more preferably 0.2 or more and 0.4 or less.

[0046] When the curing agent (C) has an active hydrogen group, the total amount of the active hydrogen groups of the curing agent (C) is preferably 0.2 equivalents or more with respect to 1 equivalent of the epoxy groups of the epoxy compound (A). When the total amount of the active hydrogen groups of the curing agent (C) is 0.2 equivalents or more, a decrease in the heat resistance and adhesion of the cured product can be suppressed. The total amount of the active hydrogen groups of the curing agent (C) is preferably 0.5 equivalents or less with respect to 1 equivalent of the epoxy groups of the epoxy compound (A). When the total amount of the active hydrogen groups of the curing agent (C) is 0.5 equivalents or less, a decrease in the adhesion and flame retardancy of the cured product and the moldability of the resin composition (M) can be suppressed. Suppression of a decrease in the moldability of the resin composition (M) means that the gel time of the resin composition (M) does not become too short.

[0047] (Phosphorus-based flame retardant (D)) The resin composition (M) contains a phosphorus-based flame retardant (D). In the embodiment, the phosphorus-based flame retardant (D) includes at least one selected from the group consisting of phosphate ester compounds (D1) and phosphine compounds represented by formula (1) (D2).

[0048] The structure of the phosphate ester compound (D1) is not particularly limited, but it is preferable that the phosphate ester compound (D1) has an aromatic ring. Furthermore, the number of phosphorus atoms in one molecule of the phosphate ester compound (D1) is not particularly limited, but it is preferable that the phosphate ester compound (D1) has two or more phosphorus atoms in one molecule. In other words, it is preferable that the phosphate ester compound (D1) includes an aromatic condensed phosphate ester compound (D11). In this case, the cured product may have higher flame retardancy. Furthermore, it is preferable that the aromatic ring of the phosphate ester compound (D1) has substituents. Examples of substituents include methyl groups. When the aromatic ring has substituents, the heat resistance of the cured product tends to increase.

[0049] For example, the aromatic condensed phosphate ester compound (D11) is represented by formula (3).

[0050]

[0051] In formula (3), Ar represents an aryl group. X represents a divalent organic group having an aromatic ring. The aryl group may have substituents. Examples of substituents include methyl groups.

[0052] More specifically, the aromatic condensed phosphate ester compound (D11) preferably contains at least one selected from the group consisting of the compound represented by formula (4), the compound represented by formula (5), and the compound represented by formula (6). In this case, the uneven distribution of inorganic fillers contained in the cured product is further suppressed, and the cured product has higher flame retardancy.

[0053]

[0054]

[0055]

[0056] For example, the phosphine compound (D2) is represented by formula (1).

[0057]

[0058] In formula (1), each of R1, R2, and R3 is independently a monovalent organic group containing a carbon atom, a hydrogen atom, a halogen atom, or a hydroxyl group.

[0059] The monovalent organic group containing a carbon atom may be an aromatic hydrocarbon group or an aliphatic hydrocarbon group.

[0060] A monovalent organic group containing a carbon atom may further contain at least one of the following: a phenyl group, a phenylene group, a phosphoryl group, an alkoxy group, an ester bond, a cyano group, a carboxyl group, and a vinyl group.

[0061] The phosphine compound (D2) represented by formula (1) more preferably contains xylylene bisdiphenylphosphine oxide represented by formula (7). That is, the phosphorus-based flame retardant (D) more preferably contains xylylene bisdiphenylphosphine oxide (para-xylylene bisdiphenylphosphine oxide) represented by formula (7). In this case, the cured product may have higher flame retardancy.

[0062]

[0063] The phosphine compound (D2) may include at least one selected from the group consisting of diphenylphosphine oxide, dimethyl phosphonate, trimethyl phosphonoacetate, diethyl cyanomethylphosphonate, 2-phosphonobutane-1,2,4-tricarboxylic acid, 3-methyl-1-phenyl-2-phosphorene-1-oxide, phenylphosphonic acid dichloride, diethylphosphonoacetate tert-butyl, tetraisopropyl methylenediphosphonate, diphenylphosphinic acid chloride, triphenylphosphine oxide, triethyl 2-fluoro-2-phosphonoacetate, vinylphosphonic acid, diethylphosphonoacetate methyl, and phenylphosphinic acid.

[0064] Furthermore, the phosphorus-based flame retardant (D) may include, for example, a phosphate ester compound (D1) and a phosphine compound (D2) represented by formula (1), as well as at least one selected from the group consisting of a phosphine compound including a phosphine metal salt compound, a phosphine compound different from phosphine compound (D2), and a phosphazene compound. Specific examples of phosphazene compounds include phenoxyphosphazene. Specific examples of phosphine compounds include phosphine metal salts of aluminum dialkylphosphinate salts.

[0065] In the embodiment, the content of the phosphorus-based flame retardant (D) is 3.0 parts by mass or more and 20.0 parts by mass or less, based on 100 parts by mass of the total of the epoxy compound (A), maleimide compound (B), and curing agent (C). From the viewpoint of suppressing the inorganic filler (E) in the cured product and improving the flame retardancy of the cured product, the content of the phosphorus-based flame retardant (D) is preferably 5 parts by mass or more, and more preferably 7 parts by mass or more. From the viewpoint of heat resistance, the content of the phosphorus-based flame retardant (D) is preferably 15 parts by mass or less, and more preferably 10 parts by mass or less.

[0066] (Inorganic Filler (E)) The resin composition (M) contains an inorganic filler (E). For example, the inorganic filler (E) includes silica filler from the viewpoint of reducing the thermal expansion coefficient of the cured product. In the embodiment, the inorganic filler (E) includes silica particles (E1) having an average particle diameter (D50) of 0.1 μm or more and 2.5 μm or less in a volume-based particle size distribution based on laser diffraction scattering. The silica particles (E1) can maintain the enhanced moldability of the resin composition (M). The average particle diameter (D50) of the silica particles (E1) is preferably 0.5 μm or more. The average particle diameter (D50) of the silica particles (E1) is preferably 2.3 μm or less. In this case, the enhanced moldability of the resin composition (M) can be better maintained.

[0067] The silica particles (E1) may include at least one selected from the group consisting of fused silica and crystalline silica. Examples of the morphology of the silica particles (E1) include spherical or crushed forms, but the spherical form is preferred. If the silica particles (E1) are spherical, their specific surface area tends to be smaller. In this case, the fluidity of the resin composition (M) may be improved, thereby improving the moldability of the resin composition (M).

[0068] The inorganic filler (E) may be surface-treated with a coupling agent. Preferably, the coupling agent has a reactive group that chemically bonds with the inorganic material and a reactive group that chemically bonds with the organic material within one molecule. Specific examples of reactive groups that chemically bond with the inorganic material include ethoxy groups and methoxy groups. Specific examples of reactive groups that chemically bond with the organic material include epoxy groups, amino groups, isocyanate groups, hydroxyl groups, and acid anhydride groups. The coupling agent is not particularly limited, but examples include silane coupling agents. Silane coupling agents include, for example, epoxy silanes, aminosilanes, isocyanate silanes, and acid anhydride silanes. Specific examples of epoxy silanes include 3-glycidoxypropyltrimethoxysilane. Specific examples of aminosilanes include 3-aminopropyltriethoxysilane. Specific examples of isocyanate silanes include 3-isocyanatetopropyltriethoxysilane. The silica particles (E1) are preferably surface-treated with an epoxy silane compound. In other words, it is preferable that the silica particles (E1) include spherical silica (E11) surface-treated with an epoxysilane compound. In this case, the uneven distribution of inorganic filler (E) contained in the cured product is further suppressed.

[0069] The silica particle (E1) content is preferably 50% by mass or more and 100% by mass or less relative to the total amount of inorganic filler (E). In this case, the fluidity of the resin composition (M) may be improved, and the moldability may be improved. The silica particle (E1) content is more preferably 60% by mass or more, and even more preferably 70% by mass or more. The silica particle (E1) content is more preferably 98% by mass or less, and even more preferably 96% by mass or less.

[0070] Furthermore, the inorganic filler (E) may include, in addition to silica particles (E1), at least one selected from the group consisting of molybdate compound particles (E2), talc, alumina, and glass. In the embodiment, it is preferable that the inorganic filler (E) includes molybdate compound particles (E2) in addition to silica particles (E1). For example, when manufacturing a metal-clad laminate or printed circuit board, an insulating substrate may be processed with a drill. If the insulating substrate contains a cured product of a resin composition (M) containing molybdate compound particles (E2), drill wear is suppressed. In other words, the molybdate compound particles (E2) can improve the drillability of the cured product. The molybdate compound particles (E2) may include, for example, at least one selected from the group consisting of zinc molybdate, calcium zinc molybdate compounds, and calcium molybdate compounds. The molybdate compound particles (E2) may be attached to a component different from the molybdate compound particles (E2). To put it more specifically, the inorganic filler (E) may contain zinc molybdate talc, in which zinc molybdate is attached to the surface of talc particles.

[0071] The content of molybdate compound particles (E2) is preferably 2% by mass or more and 10% by mass or less relative to the total amount of inorganic filler (E). In this case, the drillability of the cured product may be further improved. The content of molybdate compound particles (E2) is more preferably 3% by mass or more, and even more preferably 4% by mass or more. The content of molybdate compound particles (E2) is more preferably 8% by mass or less, and even more preferably 6% by mass or less.

[0072] (Additive (F)) The resin composition (M) may contain, in addition to the epoxy compound (A), maleimide compound (B), curing agent (C), phosphorus-based flame retardant (D), and inorganic filler (E), components different from the epoxy compound (A), maleimide compound (B), curing agent (C), phosphorus-based flame retardant (D), and inorganic filler (E) (hereinafter also referred to as additive (F)). For example, additive (F) may include at least one selected from the group consisting of curing accelerators, halogen-based flame retardants, dispersants, coupling agents, dyes, surfactants, and leveling agents.

[0073] The curing accelerator is not particularly limited, but examples include imidazoles such as 2-ethyl-4-methylimidazole, 2-methylimidazole, and 2-phenyl-4-methylimidazole; amines such as dimethylbenzylamine, triethylenediamine, benzyldimethylamine, and triethanolamine; and tetraphenylboron salts such as 2-ethyl-4-methylimidazole tetraphenylborate. When the resin composition (M) contains a curing accelerator, the content of the curing accelerator is preferably 0.01 parts by mass or more and 0.1 parts by mass or less, based on 100 parts by mass of the total of the epoxy compound (A) and the curing agent (C).

[0074] Examples of halogenated flame retardants include ethylenedipentabromobenzene, ethylenebistetrabromoimide, decabromodiphenyl oxide, and tetradecabromodifenoxybenzene.

[0075] (Other) In the embodiment, the resin composition (M) does not contain a hydrated metal compound. The hydrated metal compound may include, for example, at least one selected from the group consisting of magnesium hydroxide, aluminum hydroxide, iron hydroxide, cobalt hydroxide, zinc hydroxide, and nickel hydroxide. Note that "the resin composition (M) does not contain a hydrated metal compound" means that the resin composition (M) does not contain any hydrated metal compounds other than those inevitably mixed in. For example, the content of the hydrated metal compound that is inevitably mixed in is 0.001% by mass or less of the total amount of the resin composition (M). By having a hydrated metal compound content of 0.001% by mass or less, the decrease in the flame retardancy of the cured product can be suppressed.

[0076] 2.2 Uses The uses of the resin composition (M) will be described below.

[0077] (Prepreg) In the embodiment, the resin composition (M) is for the production of a prepreg (see Figure 1). The prepreg 1 according to the embodiment comprises the resin composition (M) or a semi-cured product of the resin composition (M) and a fibrous substrate 12. The fibrous substrate 12 is impregnated with the resin composition (M). For example, the prepreg 1 comprises a resin layer 11. When the prepreg 1 comprises a resin layer 11, the resin layer 11 contains the resin composition (M) or a semi-cured product of the resin composition (M). Also, as shown in Figure 1, the prepreg 1 may have one fibrous substrate 12, or it may have two or more fibrous substrates 12.

[0078] The thickness of the fibrous base material 12 is not particularly limited, but is preferably 5 μm or more. In this case, since the fibrous base material 12 has sufficient thickness, it is possible to easily manufacture an electronic component embedded substrate from the prepreg 1. The thickness of the fibrous base material 12 is preferably 300 μm or less. The fibrous base material 12 is a reinforcing material, and its material is not particularly limited. Specific examples of the fibrous base material 12 include glass cloth, aramid cloth, polyester cloth, glass nonwoven fabric, aramid nonwoven fabric, polyester nonwoven fabric, pulp paper, or linter paper. Preferred types of glass cloth are #7628, #1501, #2116, #1080, #1078, and #106. When manufacturing the prepreg 1, it is preferable that the glass cloth is treated with a coupling agent before impregnation with the resin composition (M) of the A stage. When the glass cloth is treated with a coupling agent, the adhesion between the glass cloth and the resin composition (M) may be improved. The coupling agent is not particularly limited, but examples include those that can be used for surface treatment of inorganic fillers (E).

[0079] The prepreg 1 is manufactured by impregnating a fibrous substrate 12 with a resin composition (M). In this case, the fibrous substrate 12 may be impregnated with the resin composition (M) by immersing it in a varnish (hereinafter also referred to as varnish (V)) containing the resin composition (M) and an organic solvent, or by applying varnish (V) to the fibrous substrate 12.

[0080] Furthermore, when using varnish (V), the fibrous substrate 12 impregnated with the resin composition (M) may be heated to remove the organic solvent. For example, the heating temperature is 100°C to 150°C, and the heating time is 3 minutes to 5 minutes. Note that the method for producing the prepreg 1 according to the embodiment is not limited to the above method and may be produced by any appropriate method.

[0081] (Resin-coated film) In this embodiment, the resin composition (M) is for making a resin-coated film (see Figure 2). The resin-coated film 2 according to this embodiment comprises a resin layer 21 and a support film 22. The resin layer 21 contains the resin composition (M) or a semi-cured product of the resin composition (M). When the resin layer 21 is heated, an insulating substrate can be formed.

[0082] The thickness of the resin layer 21 is, for example, 40 μm to 120 μm. In this case, it becomes easier to form an insulating substrate of appropriate thickness from the resin layer 21.

[0083] The support film 22 is a layer that supports the resin layer 21. The support film 22 may have electrical insulating properties. Specifically, the support film 22 may include, for example, at least one selected from the group consisting of polyethylene terephthalate (PET) film, polyimide film, polyester film, polyparabanic acid film, polyether ether ketone film, polyphenylene sulfide film, aramid film, polycarbonate film, and polyarylate film.

[0084] The surface of the support film 22 that supports the resin layer 21 may be treated with a release agent. If a release agent is applied, the insulating layer formed from the resin layer 21 will be easier to peel off from the support film 22.

[0085] A protective film 23 may be placed on the side of the resin layer 21 opposite to the side where the support film 22 is placed (see Figure 3). The presence of the protective film 23 makes it more difficult for foreign matter to adhere to the resin layer 21. The protective film 23 is, for example, an electrically insulating film. The protective film 23 may include at least one selected from the group consisting of polyethylene terephthalate (PET) film, polyolefin film, polyester film, and polymethylpentene film. A release treatment may be applied to the surface of the protective film 23 that overlaps with the resin layer 21. In this case, the protective film becomes easier to peel off from the resin layer 21.

[0086] (Resin-coated metal foil) In this embodiment, the resin composition (M) is for producing resin-coated metal foil (see Figure 4). The resin-coated metal foil 3 according to this embodiment comprises a resin layer 31 and a metal foil 32. The resin layer 31 contains the resin composition (M) or a semi-cured product of the resin composition (M). Therefore, when the resin layer 31 is heated, an insulating substrate can be formed.

[0087] The thickness of the resin layer 31 is, for example, 40 μm to 120 μm. In this case, an insulating substrate of appropriate thickness is easily formed from the resin layer 31.

[0088] The metal foil 32 is arranged on one surface of the resin layer 31. A specific example of the metal foil 32 is, but is not limited to, copper foil. For example, if the metal foil 32 is partially removed, a conductive wiring can be formed.

[0089] The thickness of the metal foil 32 is, for example, 5 μm or more and 35 μm or less. Preferably, the thickness of the metal foil 32 is 18 μm or less.

[0090] For example, a resin-coated metal foil 3 can be manufactured by applying a resin composition (M) to one or both sides of a metal foil 32. In this case, the applied resin composition (M) may be heated as needed. In this case, the resin composition (M) may partially harden.

[0091] The metal foil 32 may be formed from a carrier-attached metal foil. For example, the carrier-attached metal foil has a two-layer structure. In this case, the carrier-attached metal foil comprises a carrier and an ultrathin metal foil placed on the surface of the carrier. The ultrathin metal foil constitutes the metal foil 32. The carrier is a metal foil that protects and supports the ultrathin metal foil. When the metal foil 32 has a carrier, the metal foil 32 becomes easier to handle even if the ultrathin metal foil is thinner than the carrier. The thickness of the ultrathin metal foil and the carrier is not particularly limited, but for example, the thickness of the ultrathin metal foil is 1 μm or more and 10 μm or less, and the thickness of the carrier is 18 μm or more and 35 μm or less. The surface of the carrier that overlaps with the ultrathin metal foil may be subjected to a release treatment. In this case, the ultrathin metal foil becomes easier to peel off from the carrier. Furthermore, when a carrier-attached metal foil is used, the resin-coated metal foil 3 can be manufactured as follows. First, a resin composition (M) is applied to the surface of the ultrathin metal foil, and if necessary, it is heated to form a resin layer 31. Next, by peeling the carrier from the ultrathin metal foil, a resin-coated metal foil 3 can be manufactured. The ultrathin metal foil adhered to the surface of the resin layer 31 can be used as a seed layer in the Modified Semi-Additive Process (MSAP). If this seed layer is subjected to electroplating, a conductive wiring can be formed.

[0092] (Metal-clad laminate) In this embodiment, the resin composition (M) is for manufacturing a metal-clad laminate (see Figure 5). The metal-clad laminate 4 according to this embodiment comprises an insulating layer 41 and a metal layer 43. The insulating layer 41 in the metal-clad laminate 4 may be one or more. The insulating layer 41 contains a cured product of the resin composition (M). The uneven distribution of inorganic filler (E) contained in the cured product is suppressed. Therefore, even if the insulating layer 41 is heated, deformation of the insulating layer 41 is less likely to occur. As a result, blistering of the insulating layer 41 is suppressed, and the reliability of the metal-clad laminate 4 is improved. Note that "blistering" refers to a partially raised peeling that occurs between insulating layers 41 or between the insulating layer 41 and the metal layer 43, and is a form of delamination.

[0093] The insulating layer 41 may be formed from the prepreg 1. That is, the insulating layer 41 may include a cured product of the prepreg 1. When the insulating layer 41 is manufactured using the prepreg 1, the insulating layer 41 includes a fibrous substrate 42. The fibrous substrate 42 is the same as the fibrous substrate 12 described above. In this way, the metal-clad laminate 4 can be manufactured using the prepreg 1 as the material. The insulating layer 41 is an electrically insulating, insoluble and infusible layer. The metal layer 43 is in close contact with the insulating layer 41. The metal layer 43 is a layer containing metal. The metal layer 43 may be copper foil. The thickness of the metal layer 43 is preferably 18 μm or more and 210 μm or less. The ten-point average roughness Rzjis of the metal layer 43 is preferably 5.0 μm or more. In this case, the adhesion between the insulating layer 41 and the metal layer 43 is improved.

[0094] For example, a metal-clad laminate 4 according to the embodiment can be manufactured by placing a metal foil on one or both sides of a laminate consisting of one prepreg 1 or two or more prepreg 1 to form a metal layer 43, and then heating and pressurizing the laminate and the metal foil. It is preferable that the surface of the metal foil that overlaps with the laminate is treated with a coupling agent before placing the metal foil on the laminate. In this case, the coupling agent can bond the organic material in the prepreg 1 with the metal layer 43. This can improve the adhesion between the insulating layer 41 and the metal layer 43.

[0095] The insulating layer 41 is suitable as a substrate for embedding electronic components. For example, if the insulating layer 41 has recesses, the insulating layer 41 can become a substrate for embedding electronic components. Electronic components can be placed in the recesses. Recesses can be formed by processing the insulating layer 41 using a drill. In this embodiment, after electronic components are placed in the recesses of the insulating layer 41, the entire recess is filled with a resin composition (M) or its semi-cured product to protect the electronic components placed in the recess with the cured resin composition (M). Specifically, a prepreg 1 is placed on top of the insulating layer 41 in which electronic components are placed in the recesses. Subsequently, the insulating layer 41 and the prepreg 1 placed on top of the insulating layer 41 are heated. As a result, the resin composition (M) or its semi-cured product contained in the prepreg 1 flows into the recesses of the insulating layer 41, and the recesses of the insulating layer 41 are filled with the resin composition (M) or its semi-cured product. Furthermore, by curing the resin composition (M) or its semi-cured product filled into the recess, the electronic components placed in the recess can be protected by covering them with the cured resin composition (M).

[0096] As described above, the uneven distribution of the inorganic filler (E) contained in the cured resin composition (M) is suppressed, and the enhanced heat resistance of the cured material interposed between the electronic component and the recess is maintained. Therefore, even when the insulating layer 41 is heated, deformation of the cured material interposed between the electronic component and the recess is less likely to occur. This helps maintain the reliability of the electronic component. In addition, in this embodiment, the effect of char formation by the phosphorus flame retardant (D) when the cured resin composition (M) burns is enhanced. Therefore, the cured material interposed between the electronic component and the recess has high flame retardancy. This makes it less likely for the electronic component to burn. In this way, the electronic component placed in the recess of the insulating layer 41 can be adequately protected.

[0097] (Printed Wiring Board) In this embodiment, the resin composition (M) is for manufacturing a printed wiring board (see Figure 6). The printed wiring board 5 according to this embodiment comprises an insulating layer 51 and wiring 53. The insulating layer 51 of the printed wiring board 5 may be one or more. The insulating layer 51 contains a cured product of the resin composition (M). The uneven distribution of inorganic filler (E) contained in the cured product is suppressed. As a result, even if the insulating layer 51 is heated, deformation of the insulating layer 51 is less likely to occur. This suppresses swelling of the insulating layer 51, thereby increasing the reliability of the printed wiring board 5.

[0098] The printed circuit board 5 can be manufactured using prepreg 1 as the material. The insulating layer 51 may be formed from prepreg 1. That is, the insulating layer 51 may include a cured product of prepreg 1. When the insulating layer 51 is manufactured using prepreg 1, the insulating layer 51 includes a fibrous substrate 52. The fibrous substrate 52 is the same as the fibrous substrate 12 described above. The insulating layer 51 is an electrically insulating, insoluble and infusible layer.

[0099] The printed circuit board 5 includes a conductor layer 530. The conductor layer 530 is arranged on an insulating layer 51. In this disclosure, "conductor layer" means a conductive layer such as a signal layer, power layer, or ground layer. The conductor layer 530 includes wiring 53.

[0100] The printed circuit board 5 is a concept that includes circuit boards having two or fewer conductor layers 530 and multilayer circuit boards having three or more conductor layers 530. Figure 6 shows a circuit board having two conductor layers 530 and one insulating layer 51.

[0101] The printed circuit board 5 can be manufactured, for example, from a metal-clad laminate 4. Furthermore, the printed circuit board 5 may be multilayered using a build-up method with a resin-coated film 2 and a resin-coated metal foil 3. The printed circuit board 5 may have one or more through-hole platings 54. The through-hole platings 54 are formed, for example, by drilling holes in the insulating layer 51, performing a desmear treatment, and then applying copper plating or the like to the inner walls of these holes. The desmear treatment can be performed, for example, by the permanganate method. Although not shown in the figures, the printed circuit board 5 may also have one or more blind via holes. The holes may be through holes or non-through holes.

[0102] The insulating layer 51 is suitable as a substrate for embedding electronic components. For example, if the insulating layer 51 has recesses, the insulating layer 51 can become a substrate for embedding electronic components. Electronic components can be placed in the recesses. The method for forming the recesses in the insulating layer 51 and the method for forming the recesses in the insulating layer 41 may be the same. In this embodiment, after electronic components are placed in the recesses of the insulating layer 51, the entire recess is filled with a resin composition (M) or a semi-cured product thereof, thereby protecting the electronic components placed in the recesses with a cured product of the resin composition (M). For example, a prepreg 1 is placed on top of the insulating layer 51 in which electronic components are placed in the recesses. Subsequently, the insulating layer 51 and the prepreg 1 placed on top of the insulating layer 51 are heated. As a result, the resin composition (M) or a semi-cured product thereof contained in the prepreg 1 flows into the recesses of the insulating layer 51, and the recesses of the insulating layer 51 are filled with the resin composition (M) or a semi-cured product thereof. Furthermore, by curing the resin composition (M) or its semi-cured product filled into the recess, the electronic components placed in the recess can be protected by covering them with the cured resin composition (M).

[0103] As described above, the uneven distribution of the inorganic filler (E) contained in the cured product of the resin composition (M) is suppressed, and the enhanced heat resistance of the cured product interposed between the electronic component and the recess is maintained. Therefore, even if the insulating layer 51 is heated, deformation of the cured product interposed between the electronic component and the recess is less likely to occur. This helps to maintain the reliability of the electronic component. In addition, in this embodiment, the effect of char formation by the phosphorus flame retardant (D) when the cured product of the resin composition (M) burns is enhanced. Therefore, the cured product interposed between the electronic component and the recess has high flame retardancy. This makes it less likely for the electronic component to burn. In this way, the electronic component contained in the cured product of the prepreg 1 can be adequately protected.

[0104] 3. Embodiments As is clear from the above embodiments, this disclosure includes the following embodiments. In the following embodiments, reference numerals are enclosed in parentheses solely to indicate the correspondence with the embodiments.

[0105] A resin composition according to a first aspect of this disclosure contains an epoxy compound (A), a maleimide compound (B), a curing agent (C), a phosphorus-based flame retardant (D), and an inorganic filler (E). The resin composition does not contain a hydrated metal compound. The phosphorus-based flame retardant (D) includes at least one selected from the group consisting of phosphate ester compounds (D1) and phosphine compounds represented by formula (1) (D2).

[0106]

[0107] In formula (1), each of R1, R2, and R3 is independently a monovalent organic group containing a carbon atom, a hydrogen atom, a halogen atom, or a hydroxyl group. The content of the phosphorus-based flame retardant (D) is 3.0 parts by mass or more and 20.0 parts by mass or less per 100 parts by mass of the total of the epoxy compound (A), maleimide compound (B), and curing agent (C). The inorganic filler (E) contains silica particles (E1) having an average particle size (D50) of 0.1 μm or more and less than 2.5 μm in the volume-based particle size distribution based on laser diffraction scattering.

[0108] According to this embodiment, a resin composition is obtained in which the uneven distribution of inorganic fillers contained in the cured product is suppressed, and the cured product has high flame retardancy.

[0109] In the second aspect of the present disclosure, the resin composition, in the first aspect, comprises an aromatic condensed phosphate ester compound (D11) as the phosphate ester compound (D11).

[0110] In the third aspect of the present disclosure, the resin composition, in the first or second aspect, comprises at least one epoxy compound (A) selected from the group consisting of naphthalene-type epoxy compounds and biphenyl-type epoxy compounds.

[0111] In a fourth aspect of the present disclosure, the resin composition, in any one of the first to third aspects, comprises a phenol compound (C1) as the curing agent (C).

[0112] In the fifth aspect of the present disclosure, the resin composition, in any one of the first to fourth aspects, comprises a phosphorus-containing phenol compound (C11) as the phenol compound (C1).

[0113] In the sixth aspect of the present disclosure, the resin composition, in any one of the first to fifth aspects, comprises an inorganic filler (E) containing molybdate compound particles (E2).

[0114] In the seventh aspect of the present disclosure, the resin composition, in any one of the first to sixth aspects, has an epoxy compound (A) content of 25.0% by mass or more and 45.0% by mass or less, relative to the total amount of epoxy compound (A), maleimide compound (B), and curing agent (C).

[0115] In the eighth aspect of the present disclosure, the resin composition, in any one of the first to seventh aspects, comprises silica particles (E1) that are surface-treated with an epoxysilane compound (E11).

[0116] In any one of the first to eighth embodiments, the resin composition comprises a phosphine compound (D2) represented by formula (1) and xylylene bis-diphenylphosphine oxide represented by formula (7).

[0117]

[0118] A prepreg (1) according to the tenth aspect of the present disclosure comprises a resin composition according to any one of the first to ninth aspects, or a semi-cured product of a resin composition, and a fibrous substrate.

[0119] A resin-coated film (2) according to the eleventh aspect of the present disclosure comprises a resin layer (21) containing a resin composition according to any one of the first to ninth aspects, or a semi-cured product of the resin composition, and a support film (22).

[0120] A resin-coated metal foil (3) according to a twelfth aspect of the present disclosure comprises a resin layer (31) containing a resin composition according to any one of the first to ninth aspects, or a semi-cured product of the resin composition, and a metal foil (32).

[0121] A metal-clad laminate (4) according to a thirteenth aspect of the present disclosure comprises an insulating layer (41) containing a cured product of a resin composition according to any one of the first to ninth aspects, and a metal layer (43).

[0122] A printed circuit board (5) according to a fourteenth aspect of the present disclosure comprises an insulating layer (51) containing a cured product of a resin composition according to any one of the first to ninth aspects, and wiring (53).

[0123] The present disclosure will be described in detail below with reference to examples. However, the present disclosure is not limited to the following examples.

[0124] 1. Preparation of Resin Composition The components shown in Table 1 were mixed in the amounts shown in Table 1, and then diluted with MEK (methyl ethyl ketone) and DMF (N,N'-dimethylformamide) to homogenize the mixture, thereby preparing a varnish consisting of a resin composition and an organic solvent. The varnish was prepared so that the proportion of the resin composition in the varnish was 92% by mass. Details of the components are as follows.

[0125] <Epoxy Compound (A)> - Epoxy Compound #1: Manufactured by DIC Corporation, product name "HP-9500", naphthalene-type epoxy compound, epoxy equivalent: 230 g / eq. <Maleimide Compound (B)> - Maleimide Compound #1: Manufactured by Yamato Chemical Industries, Ltd., product name "BMI-2300", bismaleimide compound <Curing Agent (C)> - Curing Agent #1 (C12): Manufactured by Meiwa Chemicals, Ltd., product name "MEHC-7403H", biphenylaralkyl-type phenol compound, hydroxyl equivalent: 132 g / eq. - Curing Agent #2 (C11): Manufactured by Dow Chemical Japan Ltd., product name "XZ92741.00", phosphorus-containing phenol compound, phosphorus atom content 9.6% by mass, hydroxyl equivalent: 550 g / eq. <Phosphorus-based flame retardants (D)> - Phosphorus-based flame retardant #1 (D1): Manufactured by Daihachi Chemical Industry Co., Ltd., product name "SR-3000", phosphate ester, phosphorus atom content approximately 7% by mass - Phosphorus-based flame retardant #2 (D11): Manufactured by Daihachi Chemical Industry Co., Ltd., product name "PX-200" (compound shown in formula (6)), aromatic condensed phosphate ester (non-halogen condensed phosphate ester), phosphorus atom content approximately 9% by mass - Phosphorus-based flame retardant #3: Manufactured by Clariant Chemicals Co., Ltd., product name "OP935", phosphinate metal salt, phosphorus atom content approximately 23% by mass - Phosphorus-based flame retardant #4 (D2): Manufactured by Daiichi Kogyo Seiyaku Co., Ltd., product name "PQ-60" (compound shown in formula (7)), xylylene bis-diphenylphosphine oxide (para-xylylene bis-diphenylphosphine oxide), phosphorus atom content approximately 12% by mass <Inorganic fillers (E)> - Inorganic filler #1 (E1): Manufactured by Novoray Co., Ltd., product name "NQ2022B", phenylamino-treated silica, average particle size (D50) 2.1 μm - Inorganic filler #2 (E11): Manufactured by Admatex Co., Ltd., product name "SC2500-SEJZ", epoxysilane-treated silica, average particle size (D50) 0.6 μm - Inorganic filler #3 (E1): Manufactured by SIBELCO Co., Ltd., product name "MEGASIL 525", untreated silica, average particle size (D50) 2.5 μm - Inorganic filler #4 (E2): Manufactured by Huber Engineered Materials, product name "Kemgard911C", zinc molybdate talc <Additives (F)> - Additive #1: Manufactured by Shikoku Chemicals Co., Ltd., product name "2E4MZ", imidazole catalyst (2-ethyl-4-methylimidazole)<Other> - Hydrated metal compound: Manufactured by Kamishima Chemical Industry Co., Ltd., product name "Magsees EP1-S", silica-treated magnesium hydroxide, average particle size (D50) 2 μm.

[0126] 2. Evaluation 2.1 As the manufacturing base material for the prepreg, glass cloth (Nanya "#7628") was used. The glass cloth was impregnated with the above-mentioned varnish at room temperature, and then heated at approximately 150°C for 4 to 5 minutes using a non-contact type heating unit to dry out and remove the solvent in the varnish, thereby partially curing the resin composition and producing the prepreg. The proportion of the resin composition contained in the prepreg was adjusted to 46% by mass.

[0127] 2.2 Manufacturing of copper-clad laminates Four sheets of the above prepreg are stacked, and these prepregs are sandwiched between the roughened surfaces of two copper foils (35 μm thick) and heated at 220°C and 2.94 MPa (30 kgf / cm²). ２ By heating and pressurizing the material for 90 minutes, a copper-clad laminate (CCL) with an overall insulating layer thickness of 800 μm was manufactured.

[0128] 2.3 Evaluation (Glass Transition Temperature (Tg)) The copper foil of the above copper-clad laminate was removed by etching to obtain an insulating substrate (so-called unclad board) that was not covered with copper foil, and a disc-shaped sample was cut out from this insulating substrate. After drying this sample, dynamic viscoelasticity measurement (DMA) was performed to measure the glass transition temperature (Tg). Specifically, dynamic viscoelasticity measurement (DMA) was performed on a bending module at a frequency of 10 Hz, and the temperature at which tanδ showed a maximum when the temperature was raised from room temperature to 380°C under the condition of a heating rate of 5°C / min was defined as the glass transition temperature (Tg).

[0129] (Oven Heat Resistant) The above copper-clad laminate was cut into 5 cm squares to serve as samples. These samples were placed in a 270°C oven for 1 hour, and the presence or absence of blistering was visually checked. Blistering refers to a partially raised peeling that occurs between insulating layers or between the insulating layer and the copper foil in the sample, and is a form of delamination. The following criteria were used for evaluation.

[0130] A: No swelling. B: One or more swellings present.

[0131] (Copper foil adhesion) The copper foil adhesion (peel strength) of the above copper-clad laminate was measured in accordance with JIS C6481.

[0132] (Degree of separation of inorganic filler in the cured product) The above copper-clad laminate was processed with a drill to create a recess that reached the insulating layer. The copper-clad laminate was then cut across the recess. Subsequently, the insulating layer portion of the cross-section of the recess was observed under a microscope and evaluated according to the following criteria.

[0133] A: No unevenness caused by the separation of inorganic filler is observed in the cured resin composition present in the cross-section of the recess. B: Unevenness caused by the separation of inorganic filler is observed in the cured resin composition present in the cross-section of the recess.

[0134] In Comparative Example 4, while no unevenness caused by the separation of the inorganic filler was observed in the cured product, voids were found within the cured product. This is presumed to be because the inorganic filler contained crushed silica.

[0135] (Flame Retardancy) Flame retardancy was evaluated by performing a UL94 combustion test. Specifically, the copper foil of the above-mentioned copper-clad laminate was removed by etching to create an unclad plate, and strip-shaped samples measuring 125 mm in length and 12.5 mm in width were cut from this unclad plate. These samples were mounted vertically in a clamp, and two 10-second indirect flame tests were performed using a 20 mm flame. Based on the combustion behavior, a rating of V-0, V-1, V-2, or Not was determined.

[0136]

[0137]

Claims

1. A resin composition comprising: an epoxy compound (A), a maleimide compound (B), a curing agent (C), a phosphorus-based flame retardant (D), and an inorganic filler (E); the resin composition not containing a hydrated metal compound; and the phosphorus-based flame retardant (D) comprising at least one selected from the group consisting of a phosphate ester compound (D1) and a phosphine compound represented by formula (1) (D2). In formula (1), each of R1, R2, and R3 is independently a monovalent organic group containing a carbon atom, a hydrogen atom, a halogen atom, or a hydroxyl group; the content of the phosphorus-based flame retardant (D) is 3.0 parts by mass or more and 20.0 parts by mass or less with respect to 100 parts by mass of the total of the epoxy compound (A), the maleimide compound (B), and the curing agent (C); and the inorganic filler (E) comprises silica particles (E1) having an average particle diameter (D50) of 0.1 μm or more and less than 2.5 μm in a volume-based particle size distribution based on laser diffraction scattering method.

2. The resin composition according to claim 1, wherein the phosphate ester compound (D1) comprises an aromatic condensed phosphate ester compound (D11).

3. The resin composition according to claim 1, wherein the epoxy compound (A) comprises at least one selected from the group consisting of naphthalene-type epoxy compounds and biphenyl-type epoxy compounds.

4. The resin composition according to claim 1, wherein the curing agent (C) comprises a phenol compound (C1).

5. The resin composition according to claim 4, wherein the phenol compound (C1) comprises a phosphorus-containing phenol compound (C11).

6. The resin composition according to claim 1, wherein the inorganic filler (E) comprises molybdate compound particles (E2).

7. The resin composition according to claim 1, wherein the content of the epoxy compound (A) is 25.0% by mass or more and 45.0% by mass or less, based on the total amount of the epoxy compound (A), the maleimide compound (B), and the curing agent (C).

8. The resin composition according to claim 1, wherein the silica particles (E1) include spherical silica surface-treated with an epoxysilane compound.

9. The resin composition according to claim 1, wherein the phosphine compound (D2) represented by formula (1) comprises xylylene bis-diphenylphosphine oxide represented by formula (7).

10. A prepreg comprising a resin composition according to any one of claims 1 to 9, or a semi-cured product of the resin composition, and a fibrous substrate.

11. A resin-coated film comprising a resin layer containing a resin composition according to any one of claims 1 to 9, or a semi-cured product of the resin composition, and a support film.

12. A resin-coated metal foil comprising a resin layer containing a resin composition according to any one of claims 1 to 9, or a semi-cured product of the resin composition, and a metal foil.

13. A metal-clad laminate comprising an insulating layer containing a cured product of a resin composition according to any one of claims 1 to 9, and a metal layer.

14. A printed circuit board comprising an insulating layer containing a cured resin composition according to any one of claims 1 to 9, and wiring.

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