Resin composition

Abstract

To provide a resin composition or the like capable of giving a cured product having a high relative magnetic permeability, a low loss coefficient, and excellent mechanical strength.SOLUTION: The resin composition contains (A) a resin having a weight average molecular weight of 600 or more, (B) an epoxy resin (excluding those corresponding to the component (A)), (C) an amine-based dispersant, and (D) a magnetic powder.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a resin composition, and a resin sheet, a circuit board, and an inductor component that use the resin composition. [Background technology]

[0002] Inductor-embedded substrates, which incorporate an inductor into a circuit board such as a printed wiring board, are generally formed using a magnetic layer that is a cured product of a resin composition containing magnetic powder in order to increase inductance.

[0003] For example, Patent Document 1 describes forming an inductor using a resin sheet. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2022-120452 Summary of the Invention [Problem to be solved by the invention]

[0005] When producing a resin sheet having a resin composition layer containing a resin composition, from the viewpoint of forming the sheet, it has generally been required that the resin composition contain a polymer compound having a weight average molecular weight of about 30,000. However, when a polymer compound is contained in a resin composition, the mechanical strength of the resin composition layer in the resin sheet may decrease.

[0006] 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 having high relative permeability, a low loss factor, and excellent mechanical strength; and a resin sheet, a circuit board, and an inductor substrate that can be obtained using the resin composition. [Means for solving the problem]

[0007] As a result of intensive research conducted by the present inventors to achieve the above object, they discovered that by using a resin composition containing a combination of a resin having a weight-average molecular weight of 600 or more, an epoxy resin, an amine-based dispersant, a solvent, and a magnetic powder, the cured product of the resin composition layer has a high relative permeability, a low loss factor, and excellent mechanical strength, and they have completed the present invention.

[0008] That is, the present invention includes the following. [1] (A) a resin having a weight average molecular weight of 600 or more; (B) Epoxy resin (excluding those corresponding to component (A)), (C) an amine-based dispersant, and (D) A resin composition containing magnetic powder. [2] The resin composition according to [1], wherein the component (A) contains (A-1) a resin oligomer having a weight-average molecular weight of 600 or more and less than 8,000. [3] The resin composition according to [1] or [2], wherein the component (A) comprises either (A-1) a resin oligomer having a weight-average molecular weight of 600 or more but less than 8000, or (A-2) a resin having a weight-average molecular weight of 8000 or more. [4] The resin composition according to [3], wherein A2 / (A1+A2) is 0 or more and 0.7 or less, where A1 is the content of component (A-1) and A2 is the content of component (A-2) when the nonvolatile components in the resin composition are 100% by mass. [5] The resin composition according to any one of [2] to [4], wherein the component (A-1) contains an epoxy group-containing oligomer. [6] The resin composition according to any one of [1] to [5], wherein Am / (Am+Bm) is 0.1 or more and 0.8 or less, where Am is the content of component (A) and Bm is the content of component (B) when the nonvolatile components in the resin composition are 100% by mass. [7] The resin composition according to any one of [1] to [6], wherein the component (C) contains a polyester skeleton. [8] The resin composition according to any one of [1] to [7], wherein the component (C) contains a polyester skeleton represented by formula (1). [ka] (In general formula (1), each R independently represents a divalent hydrocarbon group having 2 to 10 carbon atoms, and n represents an integer of 2 to 1000.) [9] The resin composition according to any one of [1] to [8], wherein the content (vol %) of component (D) is 70 vol % or more relative to 100 vol % of the nonvolatile components of the resin composition.

[10] The resin composition according to any one of [1] to [9], further comprising (E) a solvent.

[11] A resin sheet comprising a support and a resin composition layer formed on the support from the resin composition according to any one of [1] to

[10] .

[12] A circuit board comprising: a substrate having a through-hole; and a cured product of the resin composition according to any one of [1] to

[10] filled in the through-hole.

[13] A circuit board comprising a magnetic layer which is a cured product of the resin composition according to any one of [1] to

[10] .

[14] An inductor substrate comprising the circuit board according to

[12] .

[15] An inductor substrate comprising the circuit board according to

[13] . [Effects of the Invention]

[0009] According to the present invention, it is possible to provide a resin sheet from which a cured product having high relative permeability, low loss factor, and excellent mechanical strength can be obtained, as well as a circuit board and an inductor component using the resin sheet. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 1 is a cross-sectional view schematically showing a core substrate before through holes are formed in the method for manufacturing a circuit board according to the first embodiment. [Figure 2] FIG. 2 is a cross-sectional view schematically showing a core substrate in which a through hole is formed in the method for manufacturing a circuit board according to the first embodiment. [Figure 3]FIG. 3 is a cross-sectional view schematically showing a core substrate having a plating layer formed in a through-hole in the method for manufacturing a circuit board according to the first embodiment. [Figure 4] FIG. 4 is a cross-sectional view that schematically shows how a core substrate and a resin sheet are laminated together in the method for manufacturing a circuit board according to the first embodiment. [Figure 5] FIG. 5 is a cross-sectional view that schematically shows a state in which a core substrate and a resin sheet are laminated together in the method for manufacturing a circuit board according to the first embodiment. [Figure 6] FIG. 6 is a schematic cross-sectional view for explaining step (2) of the method for manufacturing the circuit board according to the first embodiment. [Figure 7] FIG. 7 is a schematic cross-sectional view for explaining step (3) of the method for manufacturing the circuit board according to the first embodiment. [Figure 8] FIG. 8 is a schematic cross-sectional view for explaining step (5) of the method for manufacturing the circuit board according to the first embodiment. [Figure 9] FIG. 9 is a schematic cross-sectional view for explaining step (5) of the method for manufacturing the circuit board according to the first embodiment. [Figure 10] FIG. 10 is a schematic cross-sectional view illustrating step (A) of the method for manufacturing a circuit board according to the second embodiment. [Figure 11] FIG. 11 is a schematic cross-sectional view illustrating step (A) of the method for manufacturing a circuit board according to the second embodiment. [Figure 12] FIG. 12 is a schematic cross-sectional view illustrating step (B) of the method for manufacturing a circuit board according to the second embodiment. [Figure 13] FIG. 13 is a schematic cross-sectional view illustrating step (D) of the method for producing a circuit board according to the second embodiment. [Figure 14] FIG. 14 is a schematic plan view of an inductor component including a circuit board obtained by the method for manufacturing a circuit board according to the second embodiment, viewed from one side in the thickness direction. [Figure 15] FIG. 15 is a schematic diagram showing a cut end surface of an inductor component including a circuit board obtained by the method for manufacturing a circuit board according to the second embodiment, cut at the position indicated by the dashed dotted line II-II. [Figure 16] FIG. 16 is a schematic plan view illustrating the configuration of a first conductor layer in an inductor component including a circuit board obtained by the method for manufacturing a circuit board according to the second embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0011] Hereinafter, embodiments of the present invention will be described with reference to the drawings. Note that each drawing merely shows the shape, size, and arrangement of components in a schematic manner to the extent that the invention can be understood. The present invention is not limited by the following description, and each component can be modified as appropriate. In the drawings used in the following description, similar components are denoted by the same reference numerals, and redundant explanations may be omitted. Furthermore, the configuration according to the embodiments of the present invention may not necessarily be manufactured or used in the arrangement shown in the drawings.

[0012] [Resin composition] The resin composition of the present invention contains (A) a resin having a weight-average molecular weight of 600 or more, (B) an epoxy resin (excluding those corresponding to component (A)), (C) an amine-based dispersant, and (D) a magnetic powder. By using such a resin composition, it is possible to obtain a cured product having high relative permeability, low loss factor, and excellent mechanical strength.

[0013] The resin composition may further contain optional components such as (E) a solvent, (F) a curing agent, and (G) other additives, as needed.

[0014] Each component that may be contained in the resin composition will be described below. In the present invention, unless otherwise specified, the content of each component in the resin composition is a value when the nonvolatile components in the resin composition are taken as 100 mass %, and the nonvolatile components refer to all nonvolatile components in the resin composition excluding the solvent.

[0015] <(A) Resin with a weight-average molecular weight of 600 or more> The resin composition contains, as component (A), a resin (A) having a weight-average molecular weight of 600 or more. By including a resin (A) having a weight-average molecular weight of 600 or more in the resin composition, the mechanical strength of the cured product of the resin composition can be increased. The component (A) may be used alone or in combination of two or more.

[0016] From the viewpoint of increasing the mechanical strength of the cured product of the resin composition, the weight average molecular weight of component (A) is 600 or more, preferably 700 or more, and more preferably 800 or more. The upper limit is preferably 100,000 or less, more preferably 50,000 or less, and even more preferably 40,000 or less, 30,000 or less, 20,000 or less, 10,000 or less, 9,000 or less, 8,000 or less, 7,500 or less, or 7,000 or less. The weight average molecular weight of the resin is the weight average molecular weight in terms of polystyrene measured by gel permeation chromatography (GPC).

[0017] From the viewpoint of significantly achieving the effects of the present invention, the component (A) preferably contains either (A-1) a resin oligomer having a weight-average molecular weight of 600 or more and less than 8000, or (A-2) a resin having a weight-average molecular weight of 8000 or more. Therefore, the component (A) may contain only (A-1) a resin oligomer having a weight-average molecular weight of 600 or more and less than 8000, or may contain only (A-2) a resin having a weight-average molecular weight of 8000 or more, or may contain a combination of (A-1) a resin oligomer having a weight-average molecular weight of 600 or more and less than 8000 and (A-2) a resin having a weight-average molecular weight of 8000 or more. The component (A) preferably contains (A-1) a resin oligomer having a weight-average molecular weight of 600 or more and less than 8000.

[0018] From the viewpoint of achieving the effects of the present invention significantly, the weight average molecular weight of the component (A-1) is at least 600, preferably at least 700, and more preferably at least 800. The upper limit is preferably less than 8000, and is preferably 7500 or less, and more preferably 7000 or less.

[0019] From the viewpoint of achieving the effects of the present invention significantly, the weight average molecular weight of the (A-2) component is at least 8000, preferably at least 9000, and more preferably at least 10000. The upper limit is preferably at most 100000, more preferably at most 50000, and even more preferably at most 40000.

[0020] As the component (A-1), a resin oligomer having a weight-average molecular weight of 600 or more and less than 8000 can be used. Such a component is preferably either a thermosetting resin oligomer or a thermoplastic resin oligomer having a thermosetting functional group such as an epoxy group, with a thermosetting resin oligomer being more preferred. Examples of thermosetting resin oligomers include epoxy group-containing oligomers and phenolic resin oligomers. Here, "epoxy group-containing oligomer" refers to an oligomer having an epoxy group. Of these, epoxy group-containing oligomers are preferred as the component (A-1). The component (A-1) may be used alone or in combination of two or more.

[0021] The epoxy group-containing oligomer preferably contains two or more epoxy groups per molecule. The epoxy group-containing oligomer preferably has an aromatic structure, and when two or more epoxy group-containing oligomers are used, it is more preferable that at least one of them has an aromatic structure. The aromatic structure is a chemical structure generally defined as aromatic, and includes polycyclic aromatics and aromatic heterocycles. The proportion of the epoxy group-containing oligomer having two or more epoxy groups per molecule is preferably 50% by mass or more, more preferably 60% by mass or more, and particularly preferably 70% by mass or more, based on 100% by mass of the non-volatile components of the epoxy group-containing oligomer.

[0022] The epoxy group-containing oligomer is preferably a bisphenol-type epoxy group-containing oligomer, more preferably a bisphenol A-type epoxy group-containing oligomer, a bisphenol F-type epoxy group-containing oligomer, or a bisphenol AF-type epoxy group-containing oligomer, and more preferably a bisphenol A-type epoxy group-containing oligomer or a bisphenol F-type epoxy group-containing oligomer. Specific examples of epoxy group-containing oligomers include Mitsubishi Chemical Corporation's "jER1001" (bisphenol A-type epoxy group-containing oligomer), "jER4005P" (bisphenol F-type epoxy group-containing oligomer), "jER1004AF" (a polyether-type epoxy group-containing oligomer produced from bisphenol), "jER4005P" (bisphenol F-type epoxy group-containing oligomer), and "jER1010" (bisphenol A-type epoxy resin), and DIC Corporation's "EXA-4850-150" (modified bisphenol-type epoxy resin). These may be used alone or in combination of two or more.

[0023] The epoxy equivalent of the epoxy group-containing oligomer is preferably 50 g / eq to 5000 g / eq, more preferably 50 g / eq to 3000 g / eq, even more preferably 80 g / eq to 2000 g / eq, and even more preferably 110 g / eq to 1000 g / eq. Within this range, the crosslink density of the cured product is sufficient, resulting in a magnetic layer with low surface roughness. The epoxy equivalent can be measured according to JIS K7236 and is the mass of the resin containing one equivalent of epoxy groups.

[0024] As the phenolic resin oligomer, commercially available products can be used, such as "S-1P" and "S-1P" manufactured by Maruzen Petrochemical Co., Ltd.

[0025] When the non-volatile components in the resin composition are taken as 100% by mass, the content of the (A-1) component is preferably 0.1% by mass or more, more preferably 0.2% by mass or more, and even more preferably 0.3% by mass or more, from the viewpoint of significantly obtaining the effects of the present invention, and is preferably 5% by mass or less, more preferably 3% by mass or less, and even more preferably 1% by mass or less.

[0026] As the component (A-2), a resin having a weight-average molecular weight of 8,000 or more can be used. Such a component is preferably either a thermosetting resin or a thermoplastic resin, with a thermoplastic resin being more preferred. Examples of thermoplastic resins include phenoxy resin, polyvinyl acetal resin, polyolefin resin, polyimide resin, polybutadiene resin, polyamideimide resin, polyetherimide resin, polysulfone resin, polyethersulfone resin, polyphenylene ether resin, polyetheretherketone resin, and polyester resin, with a phenoxy resin being preferred. The component (A-2) may be used alone or in combination of two or more.

[0027] Examples of phenoxy resins include phenoxy resins having one or more skeletons selected from the group consisting of bisphenol A, bisphenol F, bisphenol S, bisphenolacetophenone, novolac, biphenyl, fluorene, dicyclopentadiene, norbornene, naphthalene, anthracene, adamantane, terpene, and trimethylcyclohexane. The terminal of the phenoxy resin may be any functional group such as a phenolic hydroxyl group or an epoxy group. Specific examples of phenoxy resins include "1256" and "4250" manufactured by Mitsubishi Chemical Corporation (both of which are phenoxy resins containing a bisphenol A skeleton); "YX8100" manufactured by Mitsubishi Chemical Corporation (phenoxy resin containing a bisphenol S skeleton); "YX6954" manufactured by Mitsubishi Chemical Corporation (phenoxy resin containing a bisphenol acetophenone skeleton); "FX280" and "FX293" manufactured by Nippon Steel & Sumikin Chemical Co., Ltd.; and "YL7500BH30," "YX6954BH30," "YX7553," "YX7553BH30," "YL7769BH30," "YL6794," "YL7213," "YL7290," "YL7482," and "YL7891BH30" manufactured by Mitsubishi Chemical Corporation.

[0028] Examples of polyvinyl acetal resins include polyvinyl formal resins and polyvinyl butyral resins, with polyvinyl butyral resins being preferred. Specific examples of polyvinyl acetal resins include Denka Butyral 4000-2, Denka Butyral 5000-A, Denka Butyral 6000-C, and Denka Butyral 6000-EP, manufactured by Denki Kagaku Kogyo Co., Ltd.; and S-LEC BH series, BX series (e.g., BX-5Z), KS series (e.g., KS-1), BL series, and BM series, manufactured by Sekisui Chemical Co., Ltd.

[0029] Examples of polyolefin resins include ethylene copolymer resins such as low-density polyethylene, very low-density polyethylene, high-density polyethylene, ethylene-vinyl acetate copolymer, ethylene-ethyl acrylate copolymer, and ethylene-methyl acrylate copolymer; and polyolefin polymers such as polypropylene and ethylene-propylene block copolymer.

[0030] Specific examples of polyimide resins include "SLK-6100" manufactured by Shin-Etsu Chemical Co., Ltd., and "Rikacoat SN20" and "Rikacoat PN20" manufactured by New Japan Chemical Co., Ltd. Specific examples of polyimide resins also include modified polyimides such as linear polyimides obtained by reacting bifunctional hydroxyl group-terminated polybutadiene, a diisocyanate compound, and a tetrabasic acid anhydride (polyimides described in JP-A No. 2006-37083), and polysiloxane skeleton-containing polyimides (polyimides described in JP-A Nos. 2002-12667 and 2000-319386).

[0031] Examples of polybutadiene resins include hydrogenated polybutadiene skeleton-containing resins, hydroxy group-containing polybutadiene resins, phenolic hydroxy group-containing polybutadiene resins, carboxy group-containing polybutadiene resins, acid anhydride group-containing polybutadiene resins, epoxy group-containing polybutadiene resins, isocyanate group-containing polybutadiene resins, urethane group-containing polybutadiene resins, and polyphenylene ether-polybutadiene resins.

[0032] Specific examples of polyamide-imide resins include "Vylomax HR11NN" and "Vylomax HR16NN" manufactured by Toyobo Co., Ltd. Specific examples of polyamide-imide resins also include modified polyamide-imides such as "KS9100" and "KS9300" (polysiloxane skeleton-containing polyamide-imides) manufactured by Hitachi Chemical Co., Ltd.

[0033] A specific example of the polyethersulfone resin is "PES5003P" manufactured by Sumitomo Chemical Co., Ltd.

[0034] Specific examples of polysulfone resins include polysulfones "P1700" and "P3500" manufactured by Solvay Advanced Polymers.

[0035] A specific example of the polyphenylene ether resin is NORYL SA90 manufactured by SABIC, etc. A specific example of the polyetherimide resin is ULTEM manufactured by GE, etc.

[0036] Examples of polycarbonate resins include hydroxyl group-containing carbonate resins, phenolic hydroxyl group-containing carbonate resins, carboxyl group-containing carbonate resins, acid anhydride group-containing carbonate resins, isocyanate group-containing carbonate resins, and urethane group-containing carbonate resins. Specific examples of polycarbonate resins include "FPC0220" manufactured by Mitsubishi Gas Chemical Company, Inc., "T6002" and "T6001" (polycarbonate diols) manufactured by Asahi Kasei Chemicals Corporation, and "C-1090," "C-2090," and "C-3090" (polycarbonate diols) manufactured by Kuraray Co., Ltd. Specific examples of polyether ether ketone resins include "Sumiploy K" manufactured by Sumitomo Chemical Co., Ltd.

[0037] Examples of polyester resins include polyethylene terephthalate resin, polyethylene naphthalate resin, polybutylene terephthalate resin, polybutylene naphthalate resin, polytrimethylene terephthalate resin, polytrimethylene naphthalate resin, and polycyclohexane dimethyl terephthalate resin.

[0038] The content of component (A-2) is preferably 0.5% by mass or more, more preferably 1% by mass or more, or 1.5% by mass or more, based on 100% by mass of the non-volatile components in the resin composition. From the viewpoint of significantly achieving the effects of the present invention, the content is preferably 5% by mass or less, more preferably 3% by mass or less, even more preferably 2% by mass or less, and particularly preferably 0% by mass.

[0039] The content of component (A-2) is preferably small from the viewpoint of achieving the remarkable effects of the present invention. When the content of component (A-1) is A1 and the content of component (A-2) is A2, assuming that the nonvolatile components in the resin composition are 100 mass%, from the viewpoint of achieving the remarkable effects of the present invention, A2 / (A1+A2) is preferably 0 or more, more preferably 0.2 or more, even more preferably 0.4 or more, 0.6 or more, and preferably 0.7 or less.

[0040] The content of component (A) (the total content of components (A-1) and (A-2)), when the non-volatile components in the resin composition are taken as 100% by mass, is preferably 0.1% by mass or more, more preferably 0.2% by mass or more, and even more preferably 0.3% by mass or more, and is preferably 5% by mass or less, more preferably 3% by mass or less, and even more preferably 2% by mass or less, from the viewpoint of significantly achieving the effects of the present invention.

[0041] <(B) Epoxy resin> The resin composition contains a (B) epoxy resin as the (B) component. The (B) epoxy resin as the (B) component does not include those corresponding to the above-mentioned (A) component. By including the (B) epoxy resin in the resin composition, it becomes possible to obtain a cured resin composition having excellent mechanical strength. The (B) epoxy resin may be used alone or in combination of two or more types.

[0042] Examples of (B) epoxy resins include bisphenol A epoxy resins, bisphenol F epoxy resins, bisphenol S epoxy resins, bisphenol AF epoxy resins, dicyclopentadiene epoxy resins, trisphenol epoxy resins, phenol novolac epoxy resins, tert-butyl-catechol epoxy resins, epoxy resins having a condensed ring structure such as naphthol novolac epoxy resins, naphthalene epoxy resins, naphthol epoxy resins, and anthracene epoxy resins, glycidylamine epoxy resins, glycidyl ester epoxy resins, cresol novolac epoxy resins, biphenyl epoxy resins, linear aliphatic epoxy resins, epoxy resins having a butadiene structure, alicyclic epoxy resins, heterocyclic epoxy resins, spiro ring-containing epoxy resins, cyclohexanedimethanol epoxy resins, trimethylol epoxy resins, tetraphenylethane epoxy resins, and alicyclic diglycidyl ether epoxy resins. The epoxy resins may be used alone or in combination of two or more. The (B) epoxy resin is preferably at least one selected from bisphenol A type epoxy resins and bisphenol F type epoxy resins, and more preferably contains bisphenol A type epoxy resins and bisphenol F type epoxy resins.

[0043] The (B) epoxy resin preferably contains an epoxy resin having two or more epoxy groups per molecule. The (B) epoxy resin preferably has an aromatic structure, and when two or more epoxy resins are used, it is more preferable that at least one of them has an aromatic structure. The aromatic structure is a chemical structure generally defined as aromatic, and also includes polycyclic aromatics and aromatic heterocycles. The proportion of the epoxy resin having two or more epoxy groups per molecule is preferably 50% by mass or more, more preferably 60% by mass or more, and particularly preferably 70% by mass or more, based on 100% by mass of the nonvolatile components of the epoxy resin.

[0044] Epoxy resins include epoxy resins that are liquid at a temperature of 25°C (hereinafter sometimes referred to as "liquid epoxy resins") and epoxy resins that are solid at a temperature of 25°C (hereinafter sometimes referred to as "solid epoxy resins"). The resin composition may contain, as the (B) epoxy resin, only a liquid epoxy resin, only a solid epoxy resin, or a combination of a liquid epoxy resin and a solid epoxy resin; however, from the viewpoint of reducing the viscosity of the resin composition, it is preferable to contain only a liquid epoxy resin.

[0045] Preferred liquid epoxy resins include glycerol-type epoxy resins, bisphenol A-type epoxy resins, bisphenol F-type epoxy resins, bisphenol AF-type epoxy resins, naphthalene-type epoxy resins, glycidyl ester-type epoxy resins, glycidyl amine-type epoxy resins, phenol novolac-type epoxy resins, alicyclic epoxy resins having an ester skeleton, cyclohexanedimethanol-type epoxy resins, alicyclic diglycidyl ether-type epoxy resins, alicyclic glycidyl ether-type epoxy resins, alicyclic glycidyl ether-type epoxy resins, and epoxy resins having a butadiene structure, with bisphenol A-type epoxy resins and bisphenol F-type epoxy resins being more preferred. Specific examples of liquid epoxy resins include "HP4032", "HP4032D", and "HP4032SS" (naphthalene type epoxy resins) manufactured by DIC Corporation; "828US", "jER828EL" (bisphenol A type epoxy resin), "jER807" (bisphenol F type epoxy resin), and "jER152" (phenol novolac type epoxy resin) manufactured by Mitsubishi Chemical Corporation; "630" and "630LSD" manufactured by Mitsubishi Chemical Corporation; "ED-523T" (glycirol type epoxy resin (ADEKA glycirol)), "EP-3980S" (glycidylamine type epoxy resin), and "EP-4088S" ( dicyclopentadiene-type epoxy resins); "ZX1059" (a mixture of bisphenol A-type epoxy resin and bisphenol F-type epoxy resin), "EX-201" (alicyclic glycidyl ether-type epoxy resin), "ZX1658" and "ZX1658GS" (alicyclic diglycidyl ether-type epoxy resin) manufactured by Nippon Steel Chemical & Material Co., Ltd.; "EX-721" (glycidyl ester-type epoxy resin) manufactured by Nagase ChemteX Corporation; "Celloxide 2021P" (alicyclic epoxy resin having an ester skeleton) and "PB-3600" (epoxy resin having a butadiene structure) manufactured by Daicel Corporation. These may be used alone or in combination of two or more.

[0046] Preferred examples of solid epoxy resins include naphthalene-type tetrafunctional epoxy resins, cresol novolac-type epoxy resins, dicyclopentadiene-type epoxy resins, trisphenol-type epoxy resins, naphthol-type epoxy resins, biphenyl-type epoxy resins, naphthylene ether-type epoxy resins, anthracene-type epoxy resins, bisphenol A-type epoxy resins, and tetraphenylethane-type epoxy resins. Specific examples of solid epoxy resins include "HP4032H" (naphthalene-type epoxy resin) manufactured by DIC Corporation. Resin), "HP -4710 (Naphthalene-type tetrafunctional epoxy Resin); Mitsubishi "YX4000H", "YL6121" (biphenyl-type epoxy resin), "YX4000HK" (bixylenol-type epoxy resin), and "YX8800" (anthracene-type epoxy resin) manufactured by Osaka Gas Chemicals Co., Ltd.; "PG-10" manufactured by Osaka Gas Chemicals Co., Ltd. 0", Mitsubishi Chemical Co.'s "YL7760" (bisphenol AF type epoxy) Resin), etc. These may be used alone or in combination of two or more.

[0047] When a liquid epoxy resin and a solid epoxy resin are used in combination as the (B) epoxy resin, the ratio thereof (liquid epoxy resin:solid epoxy resin) is preferably in the range of 1:0.1 to 1:4 by mass. By setting the ratio of the liquid epoxy resin to the solid epoxy resin in this range, effects such as the ability to obtain a cured product with sufficient breaking strength can be obtained. From the viewpoint of the above effects, the ratio of the liquid epoxy resin to the solid epoxy resin (liquid epoxy resin:solid epoxy resin) is more preferably in the range of 1:0.3 to 1:3.5 by mass, even more preferably in the range of 1:0.6 to 1:3, and particularly preferably in the range of 1:0.8 to 1:2.5.

[0048] The epoxy equivalent of the (B) epoxy resin is preferably 50 g / eq to 5000 g / eq, more preferably 50 g / eq to 3000 g / eq, even more preferably 80 g / eq to 2000 g / eq, and even more preferably 110 g / eq to 1000 g / eq. This range ensures sufficient crosslink density in the cured product, resulting in a magnetic layer with low surface roughness. The epoxy equivalent can be measured according to JIS K7236 and is the mass of the resin containing one equivalent of epoxy groups.

[0049] The weight average molecular weight of the (B) epoxy resin is preferably less than 600, more preferably 500 or less, and even more preferably 400 or less. There is no particular lower limit, but it is 100 or more, more preferably 150 or more, and even more preferably 200 or more.

[0050] From the viewpoint of obtaining a magnetic layer exhibiting good mechanical strength, the content (mass %) of (B) epoxy resin is preferably 0.1 mass % or more, more preferably 0.3 mass % or more, even more preferably 0.5 mass % or more, and even more preferably 1 mass % or more, when the nonvolatile components in the resin composition are taken as 100 mass %. The upper limit of the epoxy resin content is not particularly limited as long as the effects of the present invention are achieved, but is preferably 5 mass % or less, more preferably 3 mass % or less, and even more preferably 2 mass % or less.

[0051] The content (vol %) of the (B) epoxy resin is preferably 1% by mass or more, more preferably 3% by mass or more, and even more preferably 5% by mass or more, when the nonvolatile components in the resin composition are taken as 100% by volume. The upper limit is not particularly limited as long as the effects of the present invention are achieved, but is preferably 25% by mass or less, more preferably 20% by mass or less, and even more preferably 15% by mass or less.

[0052] When the nonvolatile components in the resin composition are taken as 100% by mass, the content of component (A) (the total content of components (A-1) and (A-2)) is Am and the content of epoxy resin (B) is Bm. From the viewpoint of significantly achieving the effects of the present invention, Am / (Am+Bm) is preferably 0.1 or more, more preferably 0.15 or more, even more preferably 0.2 or more, and is preferably 0.8 or less, more preferably 0.4 or less, even more preferably 0.3 or less.

[0053] <(C) Amine-based dispersant> The resin composition contains an amine-based dispersant (C) as component (C). This amine-based dispersant (C) does not include those corresponding to the aforementioned components (A) and (B). As mentioned above, if a polymer compound is added to a resin composition from the viewpoint of forming a sheet, the mechanical strength of the cured resin composition decreases. In the present invention, by including component (C) in combination with component (A) in the resin composition, it is possible to improve the relative permeability and mechanical strength compared to a resin composition that does not contain components (A) and (C) (i.e., a resin composition having the same composition as the resin composition except that a polymer compound having a higher molecular weight than component (A) is included instead of components (A) and (C)). The amine-based dispersant (C) may be used alone or in combination of two or more.

[0054] The amine dispersant (C) of the present invention refers to a dispersant having an amine skeleton, preferably a polyamine skeleton. The amine value of component (C) is preferably 1 mgKOH / g or more, more preferably 5 mgKOH / g or more, even more preferably 10 mgKOH / g or more, and preferably 45 mgKOH / g or less, more preferably 40 mgKOH / g or less, even more preferably 35 mgKOH / g or less. The amine value can be measured by neutralization titration. Specifically, it can be measured by the following method.

[0055] Measurement of the amine value of amine-based dispersants Weigh 15 g of sample (solid content) into a 200 mL conical beaker, add 75 mL of toluene, and then add 50 mL of ethanol. Heat as necessary to dissolve the sample uniformly to obtain a solution.

[0056] Add 10 drops of thymol blue test solution to this solution, mix evenly, and shake with 0.5 mol / L hydrochloric acid. The titration was stopped when the solution turned pink, and the weight of the solution was calculated using the following formula: The value was calculated. Amine value (mgKOH / g) = (A × f × 56.106 × 0.5) / sample weight (g) A: Amount (mL) of 0.5 mol / L hydrochloric acid f: Factor (potency) of 0.5 mol / L hydrochloric acid

[0057] Component (C) may have an acid functional group such as a carboxyl group. The acid value of component (C) is preferably 1 mgKOH / g or more, more preferably 3 mgKOH / g or more, even more preferably 5 mgKOH / g or more, and preferably 30 mgKOH / g or less, more preferably 28 mgKOH / g or less, even more preferably 25 mgKOH / g or less. The acid value can be measured by neutralization titration, specifically, according to JIS K 0070.

[0058] As an embodiment of the (C) amine-based dispersant, a dispersant containing a polyester skeleton derived from a polyester can be used. Specifically, a dispersant having a polyester skeleton derived from a polyester and an amine skeleton derived from an amine, preferably a polyamine skeleton, can be used. Component (A) has a lower weight-average molecular weight than conventional polymer compounds, and therefore is highly compatible with polyester skeletons. Furthermore, polymer compounds have long molecular lengths, which increase the distance between magnetic powder particles in the resin composition, resulting in a decrease in relative permeability. However, the component (A) used in the present invention has a shorter molecular length than polymer compounds, which reduces the distance between magnetic powder particles in the resin composition. This is believed to result in an increased magnetic moment and improved relative permeability. Furthermore, the nitrogen atoms in the amine skeleton adsorb to the magnetic powder, resulting in a core encapsulating the magnetic powder with the amine skeleton acting as a shell. This is believed to improve the mechanical strength of the cured resin composition.

[0059] The polyester skeleton is a skeleton derived from a polyester, and the polyester skeleton is preferably represented by general formula (1). [ka] (In general formula (1), R each independently represents a divalent hydrocarbon group having 2 to 10 carbon atoms which may have a substituent, and n represents an integer of 2 to 1000.)

[0060] In general formula (1), R represents a divalent hydrocarbon group having 2 to 10 carbon atoms. The hydrocarbon group has 2 or more carbon atoms, preferably 3 or more, and more preferably 4 or more. The upper limit of the number of carbon atoms is 10 or less, preferably 8 or less, and more preferably 6 or less. The hydrocarbon group may be linear, branched, or cyclic, with linear or branched hydrocarbon groups being preferred. Examples of the hydrocarbon group include aliphatic hydrocarbon groups and aromatic hydrocarbon groups, with aliphatic hydrocarbon groups being preferred. The hydrocarbon group may be either saturated or unsaturated, with saturated hydrocarbon groups being preferred. Specific examples of the hydrocarbon group include alkylene groups, alkenylene groups, alkynylene groups, and arylene groups. Among these, alkylene groups are particularly preferred as the hydrocarbon group.

[0061] Examples of alkylene groups include ethylene, propylene, butylene, pentylene, hexylene, heptylene, octylene, nonylene, and decylene groups. Examples of alkenylene groups include ethenylene, propenylene, butenylene, pentenylene, hexenylene, heptenylene, octenylene, nonenylene, and decenylene groups. Examples of alkynylene groups include ethynylene, propenylene, butynylene, pentynylene, hexynylene, heptynylene, octynylene, nonenylene, and decynylene groups. Examples of arylene groups include phenylene and naphthylene groups. Among these, butylene and pentylene groups are preferred as R.

[0062] The divalent hydrocarbon group represented by R in the general formula (1) may or may not have a substituent. The substituent is not particularly limited, and examples thereof include a halogen atom, -OH, -OC 1-6 Alkyl group, -N(C 1-10 Alkyl group)2, C 1-10 Alkyl group, C 6-10 Aryl groups, -NH2, -CN, -C(O)OC 1-10 Examples of the alkyl group include alkyl groups, -COOH, -C(O)H, and -NO2. p-qThe term “(where p and q are positive integers and p < q)” indicates that the number of carbon atoms in the organic group described immediately after this term is p to q. For example, “C 1-10 alkyl group” indicates an alkyl group having 1 to 10 carbon atoms. These substituents may be bonded to each other to form a ring, and the ring structure includes spiro rings and fused rings.

[0063] The above-mentioned substituents may further have substituents (hereinafter sometimes referred to as “secondary substituents”). Unless otherwise specified, the same substituents as those described above may be used as the secondary substituents.

[0064] ]In the general formula (1), n represents an integer of 2 to 1000. n is 2 or more, preferably 5 or more, more preferably 10 or more. The upper limit is 1000 or less, preferably 500 or less, more preferably 100 or less, 50 or less.

[0065] The amine skeleton is a skeleton derived from an amine. Examples of the amine include polyallylamine, polyvinylamine, etc. Among them, polyallylamine is preferred.

[0066] In addition to the amine skeleton and the polyester skeleton, the component (C) may contain any skeleton. Examples of the arbitrary skeleton include a polyester skeleton in which R in the general formula (1) is a divalent hydrocarbon group having 1 or 11 or more carbon atoms (n is the same as in the formula (1)). The terminal of this polyester skeleton is not particularly limited.

[0067] Examples of the terminal of the component (C) include a residue of a carboxylic acid, a hydroxy group, a hydrogen atom, etc., which will be described later.

[0068] The component (C) can be produced, for example, by reacting a polyamine with a polyester. Examples of the polyamine include polyallylamine, polyvinylamine, etc., and polyallylamine is preferred.

[0069] Polyamines can be obtained by polymerizing monomeric amines in the presence of a polymerization initiator and / or a chain transfer catalyst. For example, polyallylamine can be obtained by polymerizing allylamine in the presence of a polymerization initiator and / or a chain transfer catalyst.

[0070] The polymerization initiator is not particularly limited, and examples thereof include ketone peroxides such as methyl ethyl ketone, diacyl peroxides such as benzoyl peroxide, peroxydicarbonates such as diisopropyl peroxydicarbonate, peroxyketals such as 1,1-bis(t-butylperoxy)cyclohexane, hydroperoxides such as t-butyl hydroperoxide, peroxyesters such as t-butyl peroxypivalate, and also azobisisobutyronitrile, hydrogen peroxide, and ferrous salts. Furthermore, the polymerization initiators described in JP-B-2-14364 may also be used. These may be used alone or in combination of two or more.

[0071] The chain transfer catalyst is not particularly limited, and examples thereof include alkyl mercaptans such as lauryl mercaptan, thiocarboxylic acids such as mercaptoacetic acid, 2-mercaptopropionic acid, and 3-mercaptopropionic acid, and thiocarboxylic acid esters such as butyl thioglycolate and 2-ethylhexyl thioglycolate. These may be used alone or in combination of two or more.

[0072] The weight-average molecular weight of the polyamine is preferably 150 to 100,000, and more preferably 600 to 20,000. When the weight-average molecular weight of the polyamine is 150 or more, the adsorptive power to particles is improved, improving particle dispersibility, while when the weight-average molecular weight of the polyamine is 100,000 or less, particle aggregation can be suppressed, improving particle dispersibility. Note that polyamines of any weight-average molecular weight may be produced using the method described in JP-B-2-14364.

[0073] Commercially available polyamines can be used, such as "PAA-01," "PAA-03," "PAA-05," "PAA-08," "PAA-15," "PAA-15C," and "PAA-25," all manufactured by Nittobo Medical Co., Ltd.

[0074] The polyester can be produced, for example, by reacting a lactone represented by general formula (2) with a carboxylic acid. [ka] (In general formula (2), R 2 is the same as R in general formula (1).

[0075] Examples of lactones represented by general formula (2) include ε-caprolactone, β-propiolactone, γ-butyrolactone, δ-valerolactone, β-methyl-δ-valerolactone, 4-methylcaprolactone, and 2-methylcaprolactone.

[0076] The carboxylic acid can be one that functions as an initiator for ring-opening polymerization of the lactone represented by general formula (2). Examples of such carboxylic acids include hydroxycarboxylic acids such as ricinoleic acid, ricinoleic acid, 9- and 10-hydroxystearic acid, castor oil fatty acid, hydrogenated castor oil fatty acid, lactic acid, 12-hydroxystearic acid, and glycolic acid; dodecanoic acid, and stearic acid. Among these, hydroxycarboxylic acids are preferred.

[0077] The reaction temperature is preferably 120 to 220° C., more preferably 160 to 210° C. The reaction time is preferably 0.5 to 72 hours. When the reaction is carried out under a nitrogen stream, a polyester with a high degree of polymerization can be obtained.

[0078] In addition, the reaction may be carried out in the presence of a polymerization catalyst or a polymerization initiator, if necessary, in order to control the reaction.

[0079] Examples of the polymerization catalyst include quaternary ammonium salts such as tetramethylammonium chloride, tetrabutylammonium chloride, tetramethylammonium bromide, tetrabutylammonium bromide, tetramethylammonium iodide, tetrabutylammonium iodide, benzyltrimethylammonium chloride, benzyltrimethylammonium bromide, and benzyltrimethylammonium iodide; tetramethylphosphonium chloride, tetrabutylphosphonium chloride, tetramethylphosphonium bromide, tetrabutylphosphonium bromide, tetramethylphosphonium iodide, tetrabutylphosphonium iodide, and benzyltrimethylammonium iodide; Examples of suitable phosphonium compounds include quaternary phosphonium salts such as methylphosphonium chloride, benzyltrimethylphosphonium bromide, benzyltrimethylphosphonium iodide, tetraphenylphosphonium chloride, tetraphenylphosphonium bromide, and tetraphenylphosphonium iodide; phosphorus compounds such as triphenylphosphine; organic carboxylates such as potassium acetate, sodium acetate, potassium benzoate, and sodium benzoate; alkali metal alcoholates such as sodium alcoholate and potassium alcoholate; tertiary amines; organic tin compounds; organic aluminum compounds; organic titanate compounds such as tetrabutyl titanate; and zinc compounds such as zinc chloride.

[0080] Examples of the polymerization initiator include aliphatic monocarboxylic acids such as acetic acid, propionic acid, caprylic acid, nonanoic acid, capric acid, octylic acid, lauric acid, myristic acid, palmitic acid, stearic acid, isononanoic acid, and arachic acid; and aromatic monocarboxylic acids such as benzoic acid and p-butylbenzoic acid.

[0081] The weight-average molecular weight of the polyester is preferably 1000 or more, more preferably 1500 or more, and even more preferably 2000 or more, and is preferably 50000 or less, more preferably 40000 or less, and even more preferably 30000 or less. The weight-average molecular weight is a weight-average molecular weight in terms of polystyrene measured by gel permeation chromatography (GPC).

[0082] The reaction temperature and reaction time in the reaction between the polyamine and the polyester are the same as those in the reaction between the lactone represented by the general formula (2) and the carboxylic acid.

[0083] In producing component (C), in addition to the polyamine and polyester, any other monomer may be used as long as it does not impair the effects of the present invention. Examples of such optional monomers include polyesters in which R in general formula (1) is a divalent hydrocarbon group having 1 or 11 or more carbon atoms.

[0084] The pH of component (C) can usually be 4 or more and less than 7. The pH can be measured by the indicator method. Specifically, the pH can be measured by immersing a measurement sample (22°C) with a dispersant concentration of 0.1 g / mL, prepared by dissolving the dispersant in acetone, into a pH test paper. The pH test paper can be one that can measure pH in the acidic range (for example, one with a measurement range of pH 0.0 to 14.0, pH 1.0 to 14.0, or pH 0.5 to 5.0), such as the pH test paper "pH Test Paper pH 1-14" (pH measurement range pH 1.0 to 14.0) manufactured by AS ONE Corporation.

[0085] The weight average molecular weight of component (C) is preferably at least 1000, more preferably at least 1500, and even more preferably at least 2000, and is preferably at most 50000, more preferably at most 40000, and even more preferably at most 30000. The weight average molecular weight is the weight molecular weight in terms of polystyrene measured by gel permeation chromatography (GPC).

[0086] Component (C) can be a commercially available product, such as Solsverse 24000GR manufactured by Lubrizol Japan.

[0087] From the viewpoint of achieving a significant effect of the present invention, the content of component (C) is preferably 0.01% by mass or more, more preferably 0.05% by mass or more, and even more preferably 0.1% by mass or more, based on 100% by mass of the non-volatile components in the resin composition, and the upper limit is preferably 5% by mass or less, more preferably 3% by mass or less, and even more preferably 1% by mass or less.

[0088] The content of component (C) when the nonvolatile components in the resin composition are taken as 100% by mass is defined as Cm. From the viewpoint of achieving a significant effect of the present invention, Am / Cm is preferably 0.1 or more, more preferably 0.5 or more, and even more preferably 1 or more, and is preferably 10 or less, more preferably 8 or less, and even more preferably 5 or less.

[0089] <(D) Magnetic powder> The resin composition contains a magnetic powder (D) as component (D). By adding the magnetic powder (D) to the resin composition, the relative permeability of the cured product of the resin composition can be increased and the loss factor can be reduced. The magnetic powder (D) may be used alone or in combination of two or more types.

[0090] The (D) magnetic powder can be particles of a material having a relative magnetic permeability of greater than 1. One embodiment of the (D) magnetic powder preferably includes either a nanocrystalline magnetic powder or a small-diameter magnetic powder, and more preferably includes a nanocrystalline magnetic powder.

[0091] The term "nanocrystalline magnetic powder" refers to a magnetic powder containing crystal grains with a particle size of 100 nm or less. There is no particular lower limit on the particle size of the crystal grains, but it is preferably 1 nm or more. In particular, it is preferable that the maximum particle size of the crystal grains in the nanocrystalline magnetic powder is 100 nm or less. Typically, one particle of nanocrystalline magnetic powder contains multiple crystal grains, and therefore the nanocrystalline magnetic powder particles can be polycrystalline. The size of the crystal grains can be observed, for example, using a TEM (transmission electron microscope). Since nanocrystalline magnetic powder contains crystal grains, it can generally show peaks indicating crystallinity in an X-ray diffraction pattern. The crystal structure of the crystal grains can be, for example, a bcc crystal structure (body-centered cubic lattice structure), but other crystal structures are also possible.

[0092] The nanocrystalline magnetic powder is usually contained in the resin composition in the form of particles. The nanocrystalline magnetic powder may contain crystal grains in at least a portion of the particles, preferably in the surface layer of the particles, more preferably in the entire particles, and particularly preferably consisting of only crystal grains.

[0093] Nanocrystalline magnetic powders typically have particle sizes in the range of 5.5 μm to 20 μm. The particle size of nanocrystalline magnetic powders can be measured using a laser diffraction / scattering method based on Mie scattering theory. Specifically, a volumetric particle size distribution of nanocrystalline magnetic powders can be created using a laser diffraction / scattering particle size distribution analyzer, and the particle size can then be measured from that distribution. A preferred measurement sample is magnetic powder dispersed in pure water using ultrasonic waves. Examples of laser diffraction / scattering particle size distribution analyzers that can be used include the Microtrackbell "MT3000II," the Horiba "LA-960," and the Shimadzu "SALD-2200."

[0094] Average particle size D of nanocrystalline magnetic powder 50 is usually 5.5 μm or more, preferably 5.7 μm or more, more preferably 5.9 μm or more, and is usually 20 μm or less, preferably 18 μm or less, more preferably 16 μm or less. 50By using nanocrystalline magnetic powder having an average particle size D, it is possible to improve the relative permeability, loss factor, and mechanical strength. 50 represents the volume-based median diameter, which can be determined from the volume-based particle size distribution measured by the laser diffraction / scattering method described above.

[0095] The volumetric particle size distribution of nanocrystalline magnetic powder usually follows a normal distribution. Therefore, the nanocrystalline magnetic powder has an average particle size D 50 10% smaller particle size D 10 , and the average particle size D of the nanocrystalline magnetic powder 50 Larger 90% particle size D 90 Here, the 10% particle size D 10 90% particle size D is the particle size at which the cumulative volume from the smallest particle size in the particle size distribution on a volume basis reaches 10%. 90 This refers to the particle size at which the cumulative volume from the smallest particle size is 90% in the particle size distribution based on volume. 10 and 90% particle size D 90 can be measured from the volume-based particle size distribution measured by the laser diffraction / scattering method described above.

[0096] 10% particle size D of nanocrystalline magnetic powder 10 is preferably greater than 2.0 μm, more preferably 2.4 μm or more, and particularly preferably 2.8 μm or more. 50 The 10% particle size D of the nanocrystalline magnetic powder is, for example, 10 μm or less, 8 μm or less, 6 μm or less, etc. 10 When is in the above range, the relative permeability, loss factor and mechanical strength can be improved.

[0097] 90% particle size D of nanocrystalline magnetic powder 90 is preferably 60 μm or less, more preferably 50 μm or less, and particularly preferably 40 μm or less. 50 The 90% particle diameter D of the nanocrystalline magnetic powder is, for example, 6 μm or more, 8 μm or more, 10 μm or more, etc. 90When is in the above range, the relative permeability, loss factor and mechanical strength can be improved.

[0098] 10% particle size D of nanocrystalline magnetic powder 10 and 90% particle size D 90 Difference D 90 -D 10 is preferably 1 μm or more, more preferably 3 μm or more, particularly preferably 5 μm or more, and is preferably 40 μm or less, more preferably 35 μm or less, particularly preferably 30 μm or less. 90 -D 10 When is in the above range, the relative permeability, loss factor and mechanical strength can be improved.

[0099] 10% particle size D of nanocrystalline magnetic powder 10 and 90% particle size D 90 Relative to D 90 / D 10 is preferably 1.1 or more, more preferably 2 or more, particularly preferably 3 or more, and is preferably 10 or less, more preferably 8 or less, particularly preferably 6 or less. 90 / D 10 When is in the above range, the relative permeability, loss factor and mechanical strength can be improved.

[0100] The nanocrystalline magnetic powder can be particles of a magnetic material having a relative magnetic permeability greater than 1. This magnetic material is usually an inorganic material, and may be a soft magnetic material or a hard magnetic material. Furthermore, one type of magnetic material may be used alone, or two or more types may be used in combination. Among these, from the viewpoint of suppressing uneven distribution of the nanocrystalline magnetic powder, a soft magnetic material is preferred as the magnetic material contained in the nanocrystalline magnetic powder.

[0101] Examples of magnetic materials contained in the nanocrystalline magnetic powder include magnetic metal oxides and magnetic metals. Among these, the magnetic material contained in the nanocrystalline magnetic powder preferably contains iron (Fe). Therefore, examples of magnetic materials contained in the nanocrystalline magnetic powder include crystalline iron alloy magnetic materials and crystalline ferrite magnetic materials. From the viewpoint of magnetic permeability and loss factor, the magnetic material contained in the nanocrystalline magnetic powder preferably has a composition that further contains one or more elements selected from the group consisting of Nb, Hf, Zr, Ta, Mo, W, and V in combination with Fe.

[0102] Preferred examples of magnetic materials contained in the nanocrystalline magnetic powder include magnetic materials described in JP 2021-158343 A, JP 2021-141267 A, JP 2019-31463 A, JP 2021-11602 A, etc.

[0103] Among the above examples, Fe-Si-Nb-B alloy powder is preferred from the viewpoints of magnetic permeability and loss factor. Fe-Si-Nb-B alloy powder refers to magnetic powder formed from an alloy containing Fe, Si, Nb, and B.

[0104] The nanocrystalline magnetic powder preferably contains the above-mentioned magnetic material, and preferably contains only the above-mentioned magnetic material. The nanocrystalline magnetic powder may be used alone or in combination of two or more types.

[0105] Nanocrystalline magnetic powder can be manufactured, for example, by an atomization method. Specific examples of methods for manufacturing nanocrystalline magnetic powder include those described in JP 2021-141267 A and JP 2021-158343 A.

[0106] Furthermore, commercially available nanocrystalline magnetic powders may be used. Examples of commercially available magnetic powders containing nanocrystalline magnetic powder include "KUAMET NC1-53 μm," "KUAMET NC1-38 μm," and "ATFINE-NC1 PF10FA" manufactured by Epson Atmix Corporation. When purchasing nanocrystalline magnetic powders from the market, the commercially available magnetic powders may be classified as necessary.

[0107] The nanocrystalline magnetic powder is preferably spherical. The aspect ratio, calculated by dividing the length of the long axis of each nanocrystalline magnetic powder particle by the length of the short axis, is preferably 2 or less, more preferably 1.5 or less, and even more preferably 1.2 or less, and is usually 1 or more, preferably greater than 1, and more preferably 1.05 or more.

[0108] The content (mass%) of the nanocrystalline magnetic powder is preferably 30 mass% or more, more preferably 40 mass% or more, and even more preferably 50 mass% or more, relative to 100 mass% of the nonvolatile components of the resin composition, and is preferably 90 mass% or less, more preferably 85 mass% or less, and even more preferably 80 mass% or less. When the content of the nanocrystalline magnetic powder is within the above range, the relative permeability, loss factor, and mechanical strength can be improved.

[0109] The content (volume %) of the nanocrystalline magnetic powder is preferably 23% by volume or more, more preferably 25% by volume or more, even more preferably 28% by volume or more, and is preferably 60% by volume or less, more preferably 50% by volume or less, even more preferably 40% by volume or less, based on 100% by volume of the nonvolatile components of the resin composition. When the content of the nanocrystalline magnetic powder is within the above range, the relative permeability, loss factor, and mechanical strength can be improved.

[0110] The small-diameter magnetic powder is usually contained in the resin composition in the form of particles. This small-diameter magnetic powder usually has a particle size of 2 μm or less. The particle size of the small-diameter magnetic powder can be measured by the same method as that for the particle size of the nanocrystalline magnetic powder.

[0111] Average particle size D of small-diameter magnetic powder 50 is usually 2 μm or less, preferably 1.5 μm or less, and more preferably 1 μm or less. The lower limit can be, for example, 0.01 μm or more, 0.1 μm or more, etc. The average particle size D in such a range 50 By using small-diameter magnetic powder having an average particle diameter D, it is possible to improve the relative permeability, loss factor, and mechanical strength. 50represents the volume-based median diameter, and the average particle size D of the nanocrystalline magnetic powder 50 can be measured by the same method.

[0112] The particle size distribution of small-diameter magnetic powder on a volume basis usually follows a normal distribution. Therefore, the average particle size D 50 10% smaller particle size D 10 , and the average particle size D of the small-diameter magnetic powder 50 Larger 90% particle size D 90 The 10% particle size D of the small-diameter magnetic powder 10 and 90% particle size D 90 is the 10% particle size D of the nanocrystalline magnetic powder 10 and 90% particle size D 90 can be measured in the same way.

[0113] 10% particle size D of small diameter magnetic powder 10 is preferably 0.01 μm or more, more preferably 0.02 μm or more, and particularly preferably 0.03 μm or more. 50 The 10% particle diameter D of the small-diameter magnetic powder is, for example, 1 μm or less, 0.7 μm or less, or 0.5 μm or less. 10 When is in the above range, the relative permeability, loss factor and mechanical strength can be improved.

[0114] 90% particle size D of small diameter magnetic powder 90 is preferably less than 5.5 μm, more preferably 4 μm or less, and particularly preferably 2 μm or less. 50 The 90% particle diameter D of the small-diameter magnetic powder is, for example, 0.5 μm or more, 0.8 μm or more, or 1 μm or more. 90 When is in the above range, the relative permeability, loss factor and mechanical strength can be improved.

[0115] 10% particle size D of small diameter magnetic powder 10 and 90% particle size D 90 Difference D 90 -D 10is preferably 0.1 μm or more, more preferably 0.3 μm or more, particularly preferably 0.5 μm or more, and is preferably 5 μm or less, more preferably 4 μm or less, particularly preferably 3 μm or less. 90 -D 10 When is in the above range, the relative permeability, loss factor and mechanical strength can be improved.

[0116] 10% particle size D of small diameter magnetic powder 10 and 90% particle size D 90 Relative to D 90 / D 10 is preferably 1.1 or more, more preferably 1.5 or more, particularly preferably 2 or more, and is preferably 50 or less, more preferably 40 or less, particularly preferably 30 or less. 90 / D 10 When is in the above range, the relative permeability, loss factor and mechanical strength can be improved.

[0117] The small-diameter magnetic powder may be a nanocrystalline magnetic powder containing crystal grains, an amorphous magnetic powder containing no crystal grains, a crystalline magnetic powder other than nanocrystalline magnetic powder, or a combination of these. Nanocrystalline magnetic powders are as described above. On the other hand, amorphous magnetic materials are non-crystalline, so they usually do not show specific peaks indicating crystallinity in their X-ray diffraction patterns. Generally, the X-ray diffraction pattern of amorphous magnetic powders shows a broad pattern without peaks indicating crystallinity.

[0118] The small-diameter magnetic powder can be particles of a magnetic material having a relative magnetic permeability greater than 1. This magnetic material is usually an inorganic material, and may be a soft magnetic material or a hard magnetic material. Furthermore, one type of magnetic material may be used alone, or two or more types may be used in combination. Among these, from the viewpoint of suppressing uneven distribution of the small-diameter magnetic powder, a soft magnetic material is preferred as the magnetic material contained in the small-diameter magnetic powder.

[0119] Examples of the magnetic material contained in the small diameter magnetic powder include magnetic metal oxide materials and magnetic metal materials.

[0120] Examples of magnetic metal oxide materials include ferrite-based magnetic materials and iron oxide materials such as iron oxide powder (III) and triiron tetroxide powder. Among these, ferrite-based magnetic materials are preferred. Ferrite-based magnetic materials are usually composite oxides whose main component is iron oxide and are chemically stable. Therefore, when ferrite-based magnetic materials are used, advantages such as high corrosion resistance, low risk of fire, and resistance to demagnetization can be obtained.

[0121] Examples of ferrite-based magnetic materials include Fe-Mn ferrite, Fe-Mn-Mg ferrite, Fe-Mn-Mg-Sr ferrite, Fe-Mg-Zn ferrite, Fe-Mg-Sr ferrite, Fe-Zn-Mn ferrite, Fe-Cu-Zn ferrite, Fe-Ni-Zn ferrite, Fe-Ni-Zn-Cu ferrite, Fe-Ba-Zn ferrite, Fe-Ba-Mg ferrite, Fe-Ba-Ni ferrite, Fe-Ba-Co ferrite, Fe-Ba-Ni-Co ferrite, and Fe-Y ferrite.

[0122] Among ferrite-based magnetic materials, from the viewpoint of significantly achieving the desired effects of the present invention, ferrites containing at least one element selected from the group consisting of Mn, Zn, Ni, and Cu are preferred, with ferrites containing Mn being particularly preferred. Therefore, preferred ferrite-based magnetic materials include, for example, Fe-Mn-based ferrites, Fe-Mn-Mg-based ferrites, Fe-Mn-Mg-Sr-based ferrites, Fe-Mg-Zn-based ferrites, Fe-Zn-Mn-based ferrites, Fe-Cu-Zn-based ferrites, Fe-Ni-Zn-based ferrites, Fe-Ni-Zn-Cu-based ferrites, Fe-Ba-Zn-based ferrites, Fe-Ba-Ni-based ferrites, and Fe-Ba-Ni-Co-based ferrites. Among these, Fe-Mn-based ferrites, Fe-Mn-Mg-based ferrites, Fe-Mn-Mg-Sr-based ferrites, and Fe-Zn-Mn-based ferrites are preferred, with Fe-Mn-based ferrites being particularly preferred. Fe-Mn ferrite refers to ferrite containing Fe and Mn.

[0123] Examples of magnetic metal materials include pure iron; crystalline or amorphous alloy magnetic materials such as Fe-Si alloys, Fe-Si-Al alloys, Fe-Cr alloys, Fe-Cr-Si alloys, Fe-Ni-Cr alloys, Fe-Cr-Al alloys, Fe-Ni alloys, Fe-Ni-B alloys, Fe-Ni-Mo alloys, Fe-Ni-Mo-Cu alloys, Fe-Co alloys, Fe-Ni-Co alloys, and Co-based amorphous alloys. Among magnetic metal materials, iron alloy magnetic materials are more preferred. From the viewpoint of significantly achieving the desired effects of the present invention, iron alloy magnetic materials containing Fe and at least one element selected from the group consisting of Si, Cr, Al, Ni, and Co are preferred, and Fe-Si-Cr alloys are particularly preferred. The Fe-Si-Cr alloy material refers to an alloy containing Fe, Si, and Cr.

[0124] The magnetic material contained in the small-diameter magnetic powder may be the same as or different from the magnetic material described as the magnetic material of the nanocrystalline magnetic powder.

[0125] The small-diameter magnetic powder preferably contains the above-mentioned magnetic material, and preferably contains only the above-mentioned magnetic material. The small-diameter magnetic powder may be used alone or in combination of two or more types.

[0126] As the small-diameter magnetic powder, commercially available magnetic powders may be used. Specific examples of commercially available magnetic powders include "MZ03S", "M05S", "M001", and "MZ05S" manufactured by Powder Tech Co., Ltd.; "PST-S" manufactured by Sanyo Special Steel Co., Ltd.; and "AW2-08", "AW2-08PF20F", "AW2-08PF10F", "AW2-08PF3F", "Fe-3.5Si-4.5CrPF20F", "Fe-50NiPF20F", "Fe-80Ni-4MoPF20F", "ATFINE-NC1 PF5FA", and "ATFINE-NC1" manufactured by Epson Atmix Corporation. PF3FA"; "CVD iron powder (0.7 μm)", "LD-M", "LD-MH", "KNI-106", "KNI-106GSM", "KNI-106GS", "KNI-109", "KNI-109GSM", "KNI-109GS" manufactured by JFE Chemical Corporation; "KNS-415", "BSF-547", "BSF-029", "BSN-125", "BSN-125", "BSN-714", "BSN-828", "S-1281", "S-1641", "S-1651", "S-1470", "S-1511", "S-2430" manufactured by Toda Kogyo Co., Ltd.; "JR09P2" manufactured by Japan Metals and Chemical Industries, Ltd.; "Nanotek" manufactured by CIK Nanotech; "JEMK-S" and "JEMK-H" manufactured by Kinseimatec Co., Ltd.; "Yttrium iron" manufactured by Aldrich oxide" manufactured by DOWA Electronics Co., Ltd.; and "MA-RCO-5" manufactured by DOWA Electronics Co., Ltd. When small-diameter magnetic powder is purchased from the market, commercially available magnetic powder may be classified as necessary.

[0127] The small-diameter magnetic powder is preferably spherical. The aspect ratio of the particles of the small-diameter magnetic powder can be in the same range as the aspect ratio of the nanocrystalline magnetic powder. The aspect ratio of the small-diameter magnetic powder and the aspect ratio of the nanocrystalline magnetic powder can be the same or different.

[0128] The content (mass%) of the small-diameter magnetic powder is preferably 1 mass% or more, more preferably 5 mass% or more, and particularly preferably 8 mass% or more, relative to 100 mass% of the nonvolatile components of the resin composition, and is preferably 20 mass% or less, preferably 15 mass% or less, and more preferably 10 mass% or less. When the content of the small-diameter magnetic powder is within the above range, the relative permeability, loss factor, and mechanical strength can be improved.

[0129] The content (vol %) of the small-diameter magnetic powder is preferably 5% by volume or more, more preferably 6% by volume or more, and even more preferably 7% by volume or more, relative to 100% by volume of the nonvolatile components of the resin composition, and is preferably 30% by volume or less, more preferably 26% by volume or less, and even more preferably 22% by volume or less. When small-diameter magnetic powder with such a content is used, the relative permeability, loss factor, and mechanical strength can be improved.

[0130] The content (volume %) of nanocrystalline magnetic powder is represented by "V(A)" and the content (volume %) of small-diameter magnetic powder is represented by "V(B)" relative to 100% by volume of the nonvolatile components of the resin composition. In this case, the volume ratio of the nanocrystalline magnetic powder to the small-diameter magnetic powder contained in the resin composition (nanocrystalline magnetic powder / small-diameter magnetic powder) can be expressed as "V(A) / V(B)". This volume ratio V(A) / V(B) is usually 0.8 or more, preferably 1 or more, more preferably 1.2 or more, and particularly preferably 1.4 or more, and usually 12 or less, preferably 8.4 or less, more preferably 7.0 or less, even more preferably 6.0 or less, and particularly preferably 5.0 or less. When the volume ratio V(A) / V(B) is within the above range, the relative permeability, loss factor, and mechanical strength can be improved.

[0131] Furthermore, the total volume % of the nanocrystalline magnetic powder and small-diameter magnetic powder contained in the resin composition, relative to 100% by volume of the nonvolatile components of the resin composition, can be expressed as "V(A) + V(B)". This total volume % V(A) + V(B) is usually 28% by volume or more, preferably 34% by volume or more, more preferably 38% by volume or more, and particularly preferably 40% by volume or more, and is preferably 72% by volume or less, more preferably 68% by volume or less, even more preferably 64% by volume or less, and particularly preferably 60% by volume or less. When the total volume % V(A) + V(B) of the nanocrystalline magnetic powder and small-diameter magnetic powder is within the above range, the relative permeability, loss factor, and mechanical strength can be improved.

[0132] The content (mass%) of nanocrystalline magnetic powder relative to 100% by mass of the nonvolatile components of the resin composition is represented by "M(A)," and the content (mass%) of small-diameter magnetic powder is represented by "M(B)." In this case, the mass ratio of the nanocrystalline magnetic powder to the small-diameter magnetic powder contained in the resin composition ((A) nanocrystalline magnetic powder / (B) small-diameter magnetic powder) can be represented by "M(A) / M(B)." This mass ratio M(A) / M(B) is preferably 1 or more, more preferably 3 or more, and particularly preferably 5 or more, and is preferably 15 or less, more preferably 10 or less, and particularly preferably 9 or less. When the mass ratio M(A) / M(B) is within the above range, the relative permeability, loss factor, and mechanical strength can be improved.

[0133] Furthermore, the total amount (mass%) of the nanocrystalline magnetic powder and small-diameter magnetic powder contained in the resin composition relative to 100% by mass of the nonvolatile components of the resin composition can be expressed as "M(A) + M(B)". This total amount (mass%) M(A) + M(B) is preferably 40% by mass or more, more preferably 45% by mass or more, even more preferably 50% by mass or more, and particularly preferably 53% by mass or more, and is preferably 95% by mass or less, more preferably 90% by mass or less, and particularly preferably 88% by mass or less. When the total amount (mass%) M(A) + M(B) is within the above range, the relative permeability, loss factor, and mechanical strength can be improved.

[0134] (D) The magnetic powder may further contain a magnetic powder different from the nanocrystalline magnetic powder and the small diameter magnetic powder. The magnetic powder different from the nanocrystalline magnetic powder and the small diameter magnetic powder is sometimes referred to as an "intermediate magnetic powder."

[0135] The intermediate magnetic powder includes the following magnetic powders (D1) and (D2). (D1) Nanocrystalline magnetic powder having a particle size of more than 2 μm and less than 5.5 μm. (D2) A magnetic powder other than nanocrystalline magnetic powder, which has a particle size of more than 2 μm and not more than 20 μm.

[0136] By incorporating an intermediate magnetic powder into a resin composition, the proportion of magnetic powder in the resin composition can be increased, thereby increasing the relative permeability of the cured resin composition. While the loss factor of the cured resin composition can usually be increased by incorporating an intermediate magnetic powder, the small particle size of the intermediate magnetic powder can suppress the increase in the loss factor. Therefore, the intermediate magnetic powder can usually improve the relative permeability while suppressing the increase in the loss factor.

[0137] Average particle size D of medium magnetic powder 50 Specifically, the average particle diameter D is usually larger than 2 μm, preferably 2.5 μm or more, more preferably 3 μm or more, and is usually less than the average particle diameter of the nanocrystalline magnetic powder, preferably less than 5.5 μm, more preferably 5 μm or less. 50 When using an intermediate magnetic powder having an average particle diameter D, the relative permeability, loss factor, and mechanical strength can be improved. 50 represents the volume-based median diameter, and the average particle size D of the nanocrystalline magnetic powder 50 can be measured by the same method.

[0138] The particle size distribution of the intermediate magnetic powder on a volume basis usually follows a normal distribution. Therefore, the intermediate magnetic powder has an average particle size D 50 10% smaller particle size D 10 , and the average particle size D of the intermediate magnetic powder 50 Larger 90% particle size D 90The 10% particle size D of the intermediate magnetic raw powder 10 and 90% particle size D 90 is the 10% particle size D of the nanocrystalline magnetic powder 10 and 90% particle size D 90 can be measured in the same way.

[0139] 10% particle size D of medium magnetic powder 10 is preferably 1 μm or more, more preferably 1.3 μm or more, and even more preferably 1.5 μm or more. 50 The 10% particle size D of the intermediate magnetic powder is, for example, 5 μm or less, 4 μm or less, 3 μm or less, etc. 10 When is in the above range, the relative permeability, loss factor and mechanical strength can be improved.

[0140] 90% particle size D of medium magnetic powder 90 is preferably less than 10 μm, more preferably 9 μm or less, and particularly preferably 8 μm or less. 50 The 90% particle size D of the intermediate magnetic powder is, for example, 3 μm or more, 4 μm or more, 5 μm or more, etc. 90 When is in the above range, the relative permeability, loss factor and mechanical strength can be improved.

[0141] 10% particle size D of medium magnetic powder 10 and 90% particle size D 90 Difference D 90 -D 10 is preferably 0.1 μm or more, more preferably 1 μm or more, particularly preferably 2 μm or more, and is preferably 9 μm or less, more preferably 7 μm or less, particularly preferably 5 μm or less. 90 -D 10 When is in the above range, the relative permeability, loss factor and mechanical strength can be improved.

[0142] 10% particle size D of medium magnetic powder 10 and 90% particle size D 90 Relative to D 90 / D 10is preferably 1.1 or more, more preferably 1.5 or more, particularly preferably 2 or more, and is preferably 10 or less, more preferably 8 or less, particularly preferably 6 or less. 90 / D 10 When is in the above range, the relative permeability, loss factor and mechanical strength can be improved.

[0143] The intermediate magnetic powder may be a nanocrystalline magnetic powder containing crystal grains, an amorphous magnetic powder containing no crystal grains, a crystalline magnetic powder other than nanocrystalline magnetic powder, or a combination of these. This intermediate magnetic powder may be particles of a magnetic material having a relative permeability greater than 1. The magnetic material contained in the intermediate magnetic powder may be the same as or different from the magnetic material contained in the small-diameter magnetic powder. The intermediate magnetic powder preferably contains the above-mentioned magnetic material, and more preferably contains only the above-mentioned magnetic material. Furthermore, one type of intermediate magnetic powder may be used alone, or two or more types may be used in combination.

[0144] As the medium-sized magnetic powder, commercially available magnetic powder may be used. Specific examples of commercially available magnetic powder include the same examples as those of the small-sized magnetic powder. When the medium-sized magnetic powder is purchased from the market, the commercially available magnetic powder may be classified as necessary.

[0145] The medium magnetic powder is preferably spherical. The aspect ratio range of the medium magnetic powder particles can be the same as the aspect ratio range of the nanocrystalline magnetic powder. The aspect ratio of the medium magnetic powder and the aspect ratio of the nanocrystalline magnetic powder can be the same or different. Furthermore, the aspect ratio of the medium magnetic powder and the aspect ratio of the small diameter magnetic powder can be the same or different.

[0146] The content (vol %) of the intermediate magnetic powder may be 0% or more, and is preferably 1% or more, more preferably 3% or more, and particularly preferably 5% or more, and is preferably 25% or less, more preferably 15% or less, and particularly preferably 13% or less, based on 100% by volume of the nonvolatile components of the resin composition. When the content of the intermediate magnetic powder is within the above range, the relative permeability, loss factor, and mechanical strength can be improved.

[0147] The content (mass %) of the intermediate magnetic powder may be 0 mass % or more, and is preferably 1 mass % or more, more preferably 5 mass % or more, and particularly preferably 8 mass % or more, and is preferably 20 mass % or less, preferably 15 mass % or less, and more preferably 10 mass % or less, relative to 100 mass % of the nonvolatile components of the resin composition. When the content of the intermediate magnetic powder is within the above range, the relative permeability, loss factor, and mechanical strength can be improved.

[0148] The amount (volume %) of the intermediate magnetic powder relative to 100% by volume of the nonvolatile components of the resin composition is represented by "V(C)." In this case, the volume ratio of the nanocrystalline magnetic powder to the intermediate magnetic powder contained in the resin composition (intermediate magnetic powder / nanocrystalline magnetic powder) can be represented by "V(C) / V(A)." This volume ratio V(C) / V(A) may be 0 or greater than 0, and is preferably 0.01 or greater, more preferably 0.1 or greater, and is preferably 1.0 or less, more preferably 0.9 or less, and particularly preferably 0.8 or less. When the volume ratio V(C) / V(A) is within the above range, the relative permeability, loss factor, and mechanical strength can be improved.

[0149] Furthermore, the volume ratio of the small-diameter magnetic powder to the medium-diameter magnetic powder contained in the resin composition (medium-diameter magnetic powder / small-diameter magnetic powder) can be expressed as "V(C) / V(B)". This volume ratio V(C) / V(B) may be 0 or greater than 0, and is preferably 0.01 or greater, more preferably 0.1 or greater, and is preferably 8 or less, more preferably 5 or less, and particularly preferably 2 or less. When the volume ratio V(C) / V(B) is within the above range, the relative permeability, loss factor, and mechanical strength can be improved.

[0150] The total volume % of the nanocrystalline magnetic powder, small diameter magnetic powder, and medium-sized magnetic powder is preferably 70% by volume or more, preferably 75% by volume or more, particularly preferably 80% by volume or more, and is preferably 95% by volume or less, more preferably 90% by volume or less, particularly preferably 85% by volume or less, based on 100% by volume of the nonvolatile components of the resin composition. When the total volume % of the nanocrystalline magnetic powder, small diameter magnetic powder, and medium-sized magnetic powder is within the above range, the relative permeability, loss factor, and mechanical strength can be improved.

[0151] The total volume percent of the nanocrystalline magnetic powder, small-diameter magnetic powder, and medium-sized magnetic powder is preferably 50% by volume or more, more preferably 60% by volume or more, and particularly preferably 70% by volume or more, based on 100% by volume of the total amount of all magnetic powders in the resin composition. A large value indicates that the resin composition contains fewer large magnetic powders with particle sizes larger than 20 μm. When the total volume percent of the nanocrystalline magnetic powder, small-diameter magnetic powder, and medium-sized magnetic powder is within the above range, the relative permeability, loss factor, and mechanical strength can be improved.

[0152] The content (mass %) of the intermediate magnetic powder relative to 100 mass % of the nonvolatile components of the resin composition is represented by "M(C)." In this case, the mass ratio of the nanocrystalline magnetic powder to the intermediate magnetic powder contained in the resin composition (intermediate magnetic powder / nanocrystalline magnetic powder) can be represented by "M(C) / M(A)." This mass ratio M(C) / M(A) may be 0 or greater than 0, and is preferably 1 or greater, more preferably 3 or greater, and particularly preferably 5 or greater, and is preferably 15 or less, more preferably 10 or less, and particularly preferably 9 or less. When the mass ratio M(C) / M(A) is within the above range, the relative permeability, loss factor, and mechanical strength can be improved.

[0153] Furthermore, the mass ratio of the small-diameter magnetic powder to the medium-diameter magnetic powder contained in the resin composition (medium-diameter magnetic powder / small-diameter magnetic powder) can be expressed as "M(C) / M(B)". This mass ratio M(C) / M(B) may be 0 or greater than 0, and is preferably 0.01 or greater, more preferably 0.1 or greater, even more preferably 0.5 or greater, and is preferably 8 or less, more preferably 5 or less, and particularly preferably 1.5 or less. When the mass ratio M(C) / M(B) is within the above range, the relative permeability, loss factor, and mechanical strength can be improved.

[0154] The total amount (mass%) of the nanocrystalline magnetic powder, small diameter magnetic powder, and medium-sized magnetic powder is preferably 40 mass% or more, preferably 50 mass% or more, particularly preferably 60 mass% or more, and preferably 99 mass% or less, more preferably 98 mass% or less, relative to 100 mass% of the nonvolatile components of the resin composition. When the total amount (mass%) of the nanocrystalline magnetic powder, small diameter magnetic powder, and medium-sized magnetic powder is within the above range, the relative permeability, loss factor, and mechanical strength can be improved.

[0155] The total amount (mass%) of the nanocrystalline magnetic powder, small-diameter magnetic powder, and medium-sized magnetic powder is preferably 50% by mass or more, more preferably 60% by mass or more, and particularly preferably 70% by mass or more, based on 100% by mass of the total amount of all magnetic powders in the resin composition. A large value indicates that there are fewer giant magnetic powders with particle sizes larger than 20 μm in the resin composition. When the total amount (mass%) of the nanocrystalline magnetic powder, small-diameter magnetic powder, and medium-sized magnetic powder is within the above range, the relative permeability, loss factor, and mechanical strength can be improved.

[0156] The content of the magnetic powder (D) is defined as Dm, and the content of the component (C) is defined as Cm, relative to 100% by mass of the nonvolatile components of the resin composition. Dm / Cm is preferably 100 or more, more preferably 130 or more, and even more preferably 150 or more, and is preferably 800 or less, more preferably 600 or less, and even more preferably 550 or less.

[0157] The content (vol %) of the (D) magnetic powder is preferably 70% by volume or more, preferably 75% by volume or more, particularly preferably 80% by volume or more, and preferably 95% by volume or less, more preferably 90% by volume or less, particularly preferably 85% by volume or less, based on 100% by volume of the nonvolatile components of the resin composition. When the content of the (D) magnetic powder is within the above range, the relative permeability, loss factor, and mechanical strength can be improved.

[0158] The content (mass %) of the (D) magnetic powder is preferably 40 mass % or more, preferably 50 mass % or more, particularly preferably 60 mass % or more, and preferably 99 mass % or less, more preferably 98 mass % or less, based on 100 mass % of the nonvolatile components of the resin composition. When the content of the (D) magnetic powder is within the above range, the relative permeability, loss factor, and mechanical strength can be improved.

[0159] <(E) Solvent> The resin composition may further contain a solvent (E) as a volatile component in addition to the nonvolatile components (A) to (D) described above.

[0160] (E) As the solvent, an organic solvent is usually used, for example, ketone-based solvents such as acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, etc.; ester-based solvents such as methyl acetate, ethyl acetate, butyl acetate, isobutyl acetate, isoamyl acetate, methyl propionate, ethyl propionate, γ-butyrolactone, etc.; ether-based solvents such as tetrahydropyran, tetrahydrofuran, 1,4-dioxane, diethyl ether, diisopropyl ether, dibutyl ether, diphenyl ether, etc.; alcohol-based solvents such as methanol, ethanol, propanol, butanol, ethylene glycol, etc.; 2-ethoxyethyl acetate, propylene glycol monomethyl ether acetate, diethylene glycol monoethyl ether acetate, ethyl diglycol acetate, γ-butyrolactone, methyl methoxypropionate, etc. Examples of the solvent include ether ester solvents such as methyl lactate, ethyl lactate, and methyl 2-hydroxyisobutyrate; ether alcohol solvents such as 2-methoxypropanol, 2-methoxyethanol, 2-ethoxyethanol, propylene glycol monomethyl ether, and diethylene glycol monobutyl ether (butyl carbitol); amide solvents such as N,N-dimethylformamide, N,N-dimethylacetamide, and N-methyl-2-pyrrolidone; sulfoxide solvents such as dimethyl sulfoxide; nitrile solvents such as acetonitrile and propionitrile; aliphatic hydrocarbon solvents such as hexane, cyclopentane, cyclohexane, and methylcyclohexane; and aromatic hydrocarbon solvents such as benzene, toluene, xylene, ethylbenzene, and trimethylbenzene. Among these, preferred solvents for (E) are aliphatic hydrocarbon solvents and ketone solvents. The solvents for (E) may be used singly or in combination.

[0161] The amount of (E) solvent is preferably 0.5% by mass or more, more preferably 1% by mass or more, and even more preferably 1.5% by mass or more, based on the total mass of the resin composition, from the viewpoints of improving the peelability of the resin sheet from the support and reducing the tackiness of the resin composition layer. The upper limit is preferably 15% by mass or less, more preferably 10% by mass or less, and even more preferably 8% by mass or less, from the viewpoints of reducing the viscosity of the resin varnish to facilitate application in the production of the resin sheet.

[0162] <(F) Hardener> The resin composition may contain a (F) curing agent as component (F) in combination with components (A) to (D). This (F) curing agent as component (F) does not include those corresponding to the above-mentioned components (A) to (E). The (F) curing agent includes an epoxy resin curing agent having the function of curing the (B) epoxy resin, and a curing accelerator having the function of accelerating the curing rate of the (B) epoxy resin. The curing accelerator is usually used in combination with the epoxy resin curing agent. The resin composition preferably contains an epoxy resin curing agent as the (F) curing agent.

[0163] (epoxy resin hardener) The epoxy resin curing agent typically reacts with the (B) epoxy resin to cure the resin composition. Examples of epoxy resin curing agents include phenol-based epoxy resin curing agents, naphthol-based epoxy resin curing agents, active ester-based epoxy resin curing agents, acid anhydride-based epoxy resin curing agents, benzoxazine-based epoxy resin curing agents, cyanate ester-based epoxy resin curing agents, and imidazole-based epoxy resin curing agents. The epoxy resin curing agent is preferably one or more selected from phenol-based epoxy resin curing agents and naphthol-based epoxy resin curing agents, with phenol-based epoxy resin curing agents being more preferred. The epoxy resin curing agents may be used alone or in combination of two or more.

[0164] As the phenolic epoxy resin curing agent and naphthol epoxy resin curing agent, from the viewpoint of heat resistance and water resistance, a phenolic epoxy resin curing agent having a novolac structure or a naphthol epoxy resin curing agent having a novolac structure is preferred. As the phenolic epoxy resin curing agent, a nitrogen-containing phenolic epoxy resin curing agent is preferred, a triazine skeleton-containing phenolic epoxy resin curing agent is more preferred, and a triazine skeleton-containing phenolic novolac epoxy resin curing agent is even more preferred.

[0165] Specific examples of phenol-based epoxy resin curing agents and naphthol-based epoxy resin curing agents include "MEH-7700," "MEH-7810," and "MEH-7851" manufactured by Meiwa Chemical Industry Co., Ltd.; "NHN," "CBN," and "GPH" manufactured by Nippon Kayaku Co., Ltd.; "SN170," "SN180," "SN190," "SN475," "SN485," "SN495V," "SN375," and "SN395" manufactured by Nippon Steel & Sumikin Chemical Co., Ltd.; "TD-2090," "LA-7052," "LA-7054," "LA-1356," "LA-3018-50P," "EXB-9500," "HPC-9500," "KA-1160," "KA-1163," and "KA-1165" manufactured by DIC Corporation; and "GDP-6115L" and "GDP-6115H" manufactured by Gun-ei Chemical Co., Ltd.

[0166] The active ester-based epoxy resin curing agent is not particularly limited, but compounds having two or more highly reactive ester groups per molecule, such as phenol esters, thiophenol esters, N-hydroxyamine esters, and esters of heterocyclic hydroxy compounds, are generally preferred. The active ester-based epoxy resin curing agent is preferably one obtained by the condensation reaction of a carboxylic acid compound and / or a thiocarboxylic acid compound with a hydroxy compound and / or a thiol compound. From the viewpoint of improving heat resistance, active ester-based epoxy resin curing agents obtained from a carboxylic acid compound and a hydroxy compound are preferred, and active ester-based epoxy resin curing agents obtained from a carboxylic acid compound and a phenol compound and / or a naphthol compound are more preferred. Examples of carboxylic acid compounds include benzoic acid, acetic acid, succinic acid, maleic acid, itaconic acid, phthalic acid, isophthalic acid, terephthalic acid, and pyromellitic acid. Examples of phenol compounds or naphthol compounds include hydroquinone, resorcinol, bisphenol A, bisphenol F, bisphenol S, phenolphthalene, methylated bisphenol A, methylated bisphenol F, methylated bisphenol S, phenol, o-cresol, m-cresol, p-cresol, catechol, α-naphthol, β-naphthol, 1,5-dihydroxynaphthalene, 1,6-dihydroxynaphthalene, 2,6-dihydroxynaphthalene, dihydroxybenzophenone, trihydroxybenzophenone, tetrahydroxybenzophenone, phloroglucin, benzenetriol, dicyclopentadiene-type diphenol compounds, and phenol novolak. Here, "dicyclopentadiene-type diphenol compounds" refers to diphenol compounds obtained by condensing one dicyclopentadiene molecule with two phenol molecules.

[0167] Specifically, active ester-based epoxy resin curing agents containing a dicyclopentadiene-type diphenol structure, active ester-based epoxy resin curing agents containing a naphthalene structure, active ester-based epoxy resin curing agents containing an acetylated product of phenol novolac, and active ester-based epoxy resin curing agents containing a benzoylated product of phenol novolac are preferred. The "dicyclopentadiene-type diphenol structure" refers to a divalent structure consisting of phenylene-dicyclopentylene-phenylene.

[0168] Commercially available active ester epoxy resin curing agents include DIC Corporation's "EXB9451," "EXB9460," "EXB9460S," "HPC-8000-65T," "HPC-8000H-65™," and "EXB-8000L-65™," which are active ester epoxy resin curing agents containing a dicyclopentadiene-type diphenol structure; DIC Corporation's "EXB9416-70BK," which is an active ester compound containing a naphthalene structure; Mitsubishi Chemical Corporation's "DC808," which is an active ester epoxy resin curing agent containing an acetylated phenol novolac; Mitsubishi Chemical Corporation's "YLH1026," "YLH1030," and "YLH1048," which are active ester epoxy resin curing agents containing a benzoylated phenol novolac; and Mitsubishi Chemical Corporation's "DC808," which is an active ester epoxy resin curing agent that is an acetylated phenol novolac.

[0169] Acid anhydride-based epoxy resin curing agents include epoxy resin curing agents having one or more acid anhydride groups in one molecule. Specific examples of acid anhydride-based epoxy resin curing agents include phthalic anhydride, tetrahydrophthalic anhydride, hexahydrophthalic anhydride, methyltetrahydrophthalic anhydride, methylhexahydrophthalic anhydride, methylnadic anhydride, hydrogenated methylnadic anhydride, trialkyltetrahydrophthalic anhydride, dodecenyl succinic anhydride, 5-(2,5-dioxotetrahydro-3-furanyl)-3-methyl-3-cyclohexene-1,2-dicarboxylic anhydride, trimellitic anhydride, pyromellitic anhydride, benzophenone tetracarboxylic anhydride, methyl tetrahydrophthalic anhydride, methyl hexahydrophthalic anhydride, methyl hexahydrophthalic anhydride, methyl hexahydrophthalic anhydride, methyl hexahydrophthalic anhydride, trialkyltetrahydrophthalic anhydride, dodecenyl succinic anhydride, 5-(2,5-dioxotetrahydro-3-furanyl)-3-methyl-3-cyclohexene-1,2-dicarboxylic anhydride, trimellitic anhydride, pyromellitic anhydride, benzophenone tetracarboxylic anhydride, methyl hexahydrophthalic anhydride, methyl hexahydrophthalic anhydride, trialkyl tetrahydrophthalic anhydride, dodecenyl succinic anhydride, 5-(2,5-dioxotetrahydro-3-furanyl)-3-methyl-3-cyclohexene-1,2-dicarboxylic ... Examples of suitable anhydrides include carboxylic acid dianhydride, biphenyltetracarboxylic acid dianhydride, naphthalenetetracarboxylic acid dianhydride, oxydiphthalic dianhydride, 3,3'-4,4'-diphenylsulfonetetracarboxylic acid dianhydride, 1,3,3a,4,5,9b-hexahydro-5-(tetrahydro-2,5-dioxo-3-furanyl)-naphtho[1,2-C]furan-1,3-dione, ethylene glycol bis(anhydrotrimellitate), and polymeric anhydrides such as styrene-maleic acid resin, which is a copolymer of styrene and maleic acid.

[0170] Commercially available acid anhydride epoxy resin curing agents include "HNA-100" and "MH-700" manufactured by New Japan Chemical Co., Ltd.

[0171] Specific examples of benzoxazine-based epoxy resin curing agents include "HFB2006M" manufactured by Showa Polymer Co., Ltd., and "Pd" and "Fa" manufactured by Shikoku Chemical Industry Co., Ltd.

[0172] Examples of cyanate ester-based epoxy resin curing agents include bifunctional cyanate resins such as bisphenol A dicyanate, polyphenol cyanate, oligo(3-methylene-1,5-phenylene cyanate), 4,4'-methylenebis(2,6-dimethylphenyl cyanate), 4,4'-ethylidene diphenyl dicyanate, hexafluorobisphenol A dicyanate, 2,2-bis(4-cyanate)phenylpropane, 1,1-bis(4-cyanate phenylmethane), bis(4-cyanate-3,5-dimethylphenyl)methane, 1,3-bis(4-cyanate phenyl-1-(methylethylidene))benzene, bis(4-cyanate phenyl)thioether, and bis(4-cyanate phenyl)ether; multifunctional cyanate resins derived from phenol novolac and cresol novolac; and prepolymers in which these cyanate resins are partially converted to triazine. Specific examples of cyanate ester-based epoxy resin curing agents include "PT30" and "PT60" (both phenol novolac-type multifunctional cyanate ester resins) manufactured by Lonza Japan Co., Ltd., "BA230" and "BA230S75" (prepolymers in which part or all of bisphenol A dicyanate has been triazine-converted to form a trimer).

[0173] Examples of imidazole-based epoxy resin curing agents include 2-methylimidazole, 2-undecylimidazole, 2-heptadecylimidazole, 1,2-dimethylimidazole, 2-ethyl-4-methylimidazole, 1,2-dimethylimidazole, 2-ethyl-4-methylimidazole, 2-phenylimidazole, 2-phenyl-4-methylimidazole, 1-benzyl-2-methylimidazole, and 1-benzyl-2-phenylimidazoline. 1-cyanoethyl-2-methylimidazole, 1-cyanoethyl-2-undecylimidazole, 1-cyanoethyl-2-ethyl-4-methylimidazole, 1-cyanoethyl-2-phenylimidazole, 1-cyanoethyl-2-undecylimidazole, 1-cyanoethyl-2-phenylimidazolium trimellitate, 1-cyanoethyl-2-phenylimidazolium trimellitate, 2,4-diamino-6-[2'-methylimidazolyl-(1')]-ethyl-s-triazine, 2,4-Diamino-6-[2'-undecylimidazolyl-(1')]-ethyl-s-triazine, 2,4-diamino-6-[2'-ethyl-4'-methylimidazolyl-(1')]-ethyl-s-triazine, 2,4-diamino-6-[2'-methylimidazolyl-(1')]-ethyl-s-triazine isocyanuric acid adduct, 2-phenylimidazole isocyanuric acid adduct, 2-phenyl-4,5-dihydroxymethylimidazole, 2- Examples thereof include imidazole compounds such as phenyl-4-methyl-5-hydroxymethylimidazole, 2,3-dihydro-1H-pyrrolo[1,2-a]benzimidazole, 1-dodecyl-2-methyl-3-benzylimidazolium chloride, 2-methylimidazoline, and 2-phenylimidazoline, as well as adducts of imidazole compounds with epoxy resins, with 2-ethyl-4-methylimidazole and 1-benzyl-2-phenylimidazole being preferred.

[0174] As the imidazole-based epoxy resin curing agent, commercially available products may be used, such as "2MZA-PW" and "2PHZ-PW" manufactured by Shikoku Chemical Industry Co., Ltd., and "P200-H50" manufactured by Mitsubishi Chemical Corporation.

[0175] The ratio of the amount of epoxy resin to the amount of epoxy resin curing agent, expressed as the ratio of [total number of epoxy groups in the epoxy resin] to [total number of reactive groups in the epoxy resin curing agent], is preferably in the range of 1:0.2 to 1:2, more preferably in the range of 1:0.3 to 1:1.5, and even more preferably in the range of 1:0.4 to 1:1. Here, the reactive groups in the epoxy resin curing agent are active hydroxyl groups, active ester groups, etc., and vary depending on the type of epoxy resin curing agent. The total number of epoxy groups in the epoxy resin is the sum of the values ​​obtained by dividing the mass of the nonvolatile components of each epoxy resin by the epoxy equivalent weight for all epoxy resins, and the total number of reactive groups in the epoxy resin curing agent is the sum of the values ​​obtained by dividing the mass of the nonvolatile components of each epoxy resin curing agent by the reactive group equivalent weight for all epoxy resin curing agents. By maintaining the ratio of epoxy resin to epoxy resin curing agent within this range, the heat resistance of the cured product is further improved.

[0176] The content of the epoxy resin curing agent is preferably 0.1% by mass or more, more preferably 0.5% by mass or more, and even more preferably 0.8% by mass or more, based on 100% by mass of the non-volatile components in the resin composition, and the upper limit is preferably 8% by mass or less, more preferably 3% by mass or less, and even more preferably 2% by mass or less.

[0177] (curing accelerator) The curing accelerator typically acts as a catalyst in the curing reaction of the (B) epoxy resin, thereby accelerating the curing reaction. Examples of the curing accelerator include amine-based curing accelerators, imidazole-based curing accelerators, phosphorus-based curing accelerators, guanidine-based curing accelerators, and metal-based curing accelerators. From the viewpoint of reducing the viscosity of the resin composition, preferred curing accelerators are amine-based curing accelerators, imidazole-based curing accelerators, and guanidine-based curing accelerators. Furthermore, from the viewpoint of improving the mechanical strength of the resulting cured product, imidazole-based curing accelerators are more preferred. One type of curing accelerator may be used alone, or two or more types may be used in combination. The curing accelerator is generally used in combination with an epoxy resin curing agent.

[0178] Examples of the amine curing accelerator include trialkylamines such as triethylamine and tributylamine, 4-dimethylaminopyridine, benzyldimethylamine, 2,4,6-tris(dimethylaminomethyl)phenol, and 1,8-diazabicyclo(5,4,0)-undecene, with 4-dimethylaminopyridine and 1,8-diazabicyclo(5,4,0)-undecene being preferred.

[0179] As the amine-based curing accelerator, commercially available products may be used, such as "PN-50," "PN-23," and "MY-25" manufactured by Ajinomoto Fine-Techno Co., Ltd.

[0180] The imidazole-based curing accelerator is the same as the imidazole-based epoxy resin curing agent described above. When used in combination with other epoxy resin curing agents, the imidazole-based epoxy resin curing agent may function as a curing accelerator.

[0181] Examples of phosphorus-based curing accelerators include triphenylphosphine, phosphonium borate compounds, tetraphenylphosphonium tetraphenylborate, n-butylphosphonium tetraphenylborate, tetrabutylphosphonium decanoate, (4-methylphenyl)triphenylphosphonium thiocyanate, tetraphenylphosphonium thiocyanate, and butyltriphenylphosphonium thiocyanate, with triphenylphosphine and tetrabutylphosphonium decanoate being preferred.

[0182] As the phosphorus-based curing accelerator, commercially available products may be used, for example, "TBP-DA" manufactured by Hokko Chemical Industry Co., Ltd.

[0183] Examples of guanidine-based curing accelerators include dicyandiamide, 1-methylguanidine, 1-ethylguanidine, 1-cyclohexylguanidine, 1-phenylguanidine, 1-(o-tolyl)guanidine, dimethylguanidine, diphenylguanidine, trimethylguanidine, tetramethylguanidine, pentamethylguanidine, 1,5,7-triazabicyclo[4.4.0]dec-5-ene, and 7-methyl-1,5,7-triazabicyclo[4.4.0]dec-5-ene. Examples of suitable biguanide include 1-methylbiguanide, 1-ethylbiguanide, 1-n-butylbiguanide, 1-n-octadecylbiguanide, 1,1-dimethylbiguanide, 1,1-diethylbiguanide, 1-cyclohexylbiguanide, 1-allylbiguanide, 1-phenylbiguanide, and 1-(o-tolyl)biguanide. Of these, dicyandiamide and 1,5,7-triazabicyclo[4.4.0]dec-5-ene are preferred.

[0184] Examples of metal-based curing accelerators include organometallic complexes or organometallic salts of metals such as cobalt, copper, zinc, iron, nickel, manganese, and tin. Specific examples of organometallic complexes include organic cobalt complexes such as cobalt(II) acetylacetonate and cobalt(III) acetylacetonate, organic copper complexes such as copper(II) acetylacetonate, organic zinc complexes such as zinc(II) acetylacetonate, organic iron complexes such as iron(III) acetylacetonate, organic nickel complexes such as nickel(II) acetylacetonate, and organic manganese complexes such as manganese(II) acetylacetonate. Examples of organometallic salts include zinc octoate, tin octoate, zinc naphthenate, cobalt naphthenate, tin stearate, and zinc stearate.

[0185] The content of the curing accelerator is preferably 0.001% by mass or more, more preferably 0.005% by mass or more, and even more preferably 0.01% by mass or more, where the non-volatile components in the resin composition are taken as 100% by mass, and the upper limit is preferably 2% by mass or less, more preferably 0.1% by mass or less, and even more preferably 0.05% by mass or less.

[0186] The content of the (F) curing agent is preferably 0.1% by mass or more, more preferably 0.5% by mass or more, and even more preferably 0.8% by mass or more, based on 100% by mass of the non-volatile components in the resin composition, and the upper limit is preferably 8% by mass or less, more preferably 4% by mass or less, and even more preferably 3% by mass or less.

[0187] <(G) Other additives> The resin composition may contain (G) other additives as an optional non-volatile component. Examples of (G) other additives include radical polymerizable compounds; polymerization initiators; organometallic compounds such as organic copper compounds, organic zinc compounds, and organic cobalt compounds; colorants such as phthalocyanine blue, phthalocyanine green, iodine green, diazo yellow, crystal violet, titanium oxide, and carbon black; polymerization inhibitors such as hydroquinone, catechol, pyrogallol, and phenothiazine; leveling agents such as silicone-based leveling agents and acrylic polymer-based leveling agents; thickeners such as bentone and montmorillonite; antifoaming agents such as silicone-based antifoaming agents, acrylic-based antifoaming agents, fluorine-based antifoaming agents, and vinyl resin-based antifoaming agents; ultraviolet absorbers such as benzotriazole-based ultraviolet absorbers; adhesion improvers such as urea silane; adhesion promoters such as triazole-based adhesion promoters, tetrazole-based adhesion promoters, and triazine-based adhesion promoters; and antioxidants such as hindered phenol-based antioxidants. surfactants such as fluorine-based surfactants and silicone-based surfactants; flame retardants such as phosphorus-based flame retardants (e.g., phosphate ester compounds, phosphazene compounds, phosphinic acid compounds, and red phosphorus), nitrogen-based flame retardants (e.g., melamine sulfate), halogen-based flame retardants, and inorganic flame retardants (e.g., antimony trioxide); optional dispersants (excluding those corresponding to component (C)) such as phosphate ester-based dispersants, polyoxyalkylene-based dispersants, acetylene-based dispersants, silicone-based dispersants, anionic dispersants, and cationic dispersants; stabilizers such as borate-based stabilizers, titanate-based stabilizers, aluminate-based stabilizers, zirconate-based stabilizers, isocyanate-based stabilizers, carboxylic acid-based stabilizers, and carboxylic anhydride-based stabilizers; photopolymerization initiation aids such as tertiary amines; and photosensitizers such as pyrarizones, anthracenes, coumarins, xanthones, and thioxanthones. (G) Other additives may be used singly or in combination of two or more.

[0188] <Physical properties of resin composition> The cured product obtained by heating the resin composition at 190°C for 90 minutes exhibits excellent mechanical strength. Therefore, the cured product provides a magnetic layer with excellent tensile strength. The tensile strength is preferably 70 MPa or more, more preferably 71 MPa or more, and even more preferably 72 MPa or more. There is no particular upper limit, but it can be 150 MPa or less. Mechanical strength (tensile strength) can be measured by the method described in the examples below.

[0189] The cured product obtained by heating the resin composition at 190°C for 90 minutes exhibits excellent mechanical strength. Therefore, the cured product provides a magnetic layer with excellent elongation at break. The elongation at break is preferably 0.5% or more, more preferably 0.55% or more, and even more preferably 0.6% or more. There is no particular upper limit, but it can be 10% or less. The mechanical strength (elongation at break) can be measured by the method described in the examples below.

[0190] The cured product obtained by heating the resin composition at 190°C for 90 minutes exhibits excellent mechanical strength. Therefore, the cured product provides a magnetic layer with excellent Young's modulus. The Young's modulus is preferably 10 GPa or more, more preferably 11 GPa or more, and even more preferably 12 GPa or more. There is no particular upper limit, but it can be 50 GPa or less, for example. The mechanical strength (Young's modulus) can be measured by the method described in the Examples below.

[0191] A cured product obtained by heating the resin composition at 190°C for 90 minutes exhibits the characteristic of high relative magnetic permeability at a frequency of 10 MHz. Therefore, the cured product provides a magnetic layer with high relative magnetic permeability. The relative magnetic permeability of this cured product at a frequency of 10 MHz is preferably 40 or higher, more preferably 43 or higher, and even more preferably 45 or higher. The upper limit is not particularly limited, but may be 100 or lower. The relative magnetic permeability can be measured by the method described in the Examples below.

[0192] A cured product obtained by heating a resin composition at 190°C for 90 minutes typically exhibits the characteristic of a low loss factor at a frequency of 10 MHz. Therefore, the cured product provides a magnetic layer with a low loss factor. The loss factor of this cured product at a frequency of 10 MHz is preferably 0.3 or less, more preferably 0.3 or less, and even more preferably 0.2 or less. The lower limit is not particularly limited, but may be 0.001 or more. The loss factor can be measured by the method described in the Examples below.

[0193] From the viewpoint of utilizing the above-mentioned advantages, the resin composition is preferably used for forming a magnetic layer of a circuit board. Also, from the viewpoint of utilizing the above-mentioned advantages, the resin composition is preferably used for filling through holes in a core substrate.

[0194] [Resin sheet] The resin sheet includes a support and a resin composition layer formed from the resin composition of the present invention provided on the support.

[0195] From the viewpoint of thinning, the thickness of the resin composition layer is preferably 5 μm or more, more preferably 10 μm or more, particularly preferably 50 μm or more, and preferably 600 μm or less, more preferably 300 μm or less, particularly preferably 200 μm or less.

[0196] Examples of the support include films made of plastic materials, metal foils, and release papers, with films made of plastic materials and metal foils being preferred.

[0197] When a film made of a plastic material is used as the support, examples of the plastic material include polyesters such as polyethylene terephthalate (hereinafter sometimes abbreviated as "PET") and polyethylene naphthalate (hereinafter sometimes abbreviated as "PEN"), polycarbonate (hereinafter sometimes abbreviated as "PC"), acrylic polymers such as polymethyl methacrylate (PMMA), cyclic polyolefins, triacetyl cellulose (TAC), polyether sulfide (PES), polyether ketone, polyimide, etc. Among these, polyethylene terephthalate and polyethylene naphthalate are preferred, with inexpensive polyethylene terephthalate being particularly preferred.

[0198] When a metal foil is used as the support, examples of the metal foil include copper foil and aluminum foil, with copper foil being preferred. The copper foil may be a foil made of a single metal, copper, or an alloy of copper and another metal (e.g., tin, chromium, silver, magnesium, nickel, zirconium, silicon, titanium, etc.).

[0199] The surface of the support that is to be bonded to the resin composition layer may be subjected to a matte treatment or a corona treatment.

[0200] The support may also be a support with a release layer, which has a release layer on the surface that bonds to the resin composition layer. Examples of the release agent used in the release layer of the support with a release layer include one or more release agents selected from the group consisting of alkyd resins, polyolefin resins, urethane resins, and silicone resins. Commercially available products may also be used as the support with a release layer, including, for example, "PET501010," "SK-1," "AL-5," and "AL-7" manufactured by Lintec Corporation; "Lumirror T60" manufactured by Toray Industries, Inc.; "Purex" manufactured by Teijin Limited; and "Uni-Peel" manufactured by Unitika Limited, which are PET films having a release layer primarily composed of an alkyd resin-based release agent.

[0201] The thickness of the support is not particularly limited, but is preferably in the range of 5 μm to 75 μm, more preferably 10 μm to 60 μm. When a support with a release layer is used, it is preferable that the thickness of the entire support with a release layer is in the above range.

[0202] The resin sheet can be produced, for example, by applying the resin composition to a support using a die coater or the like to form a resin composition layer. If necessary, a resin varnish dissolved in a solvent may be prepared, and this resin varnish may be applied to the support. When a solvent is used, drying may be performed after application if necessary.

[0203] Drying may be carried out by heating, blowing hot air, or the like. Drying conditions are not particularly limited, but drying is carried out so that the content of organic solvent in the resin composition layer becomes 10% by mass or less, preferably 5% by mass or less. Although it varies depending on the components contained in the resin composition, a resin composition layer can be formed by drying at 50°C to 150°C for 3 to 10 minutes.

[0204] In the resin sheet, a protective film conforming to the support can be further laminated on the surface of the resin composition layer not bonded to the support (i.e., the surface opposite to the support). The thickness of the protective film is not particularly limited, but is, for example, 1 μm to 40 μm. By laminating the protective film, it is possible to prevent adhesion of dust and the like to the surface of the resin composition layer and scratches. The resin sheet can be stored in a roll shape. When the resin sheet has a protective film, it can be used by peeling off the protective film.

[0205] [Circuit board and its manufacturing method] A circuit board according to one embodiment of the present invention includes a magnetic layer. This magnetic layer includes the resin composition described above or a cured product of the resin composition layer of a resin sheet, and preferably includes only the cured product of the resin composition described above. The specific structure of the circuit board is not limited as long as it includes a magnetic layer including the cured product of the resin composition described above. The circuit board of the first embodiment is a circuit board including a core substrate as a substrate having through holes formed therein and a magnetic layer filled in the through holes. The circuit board of the second embodiment is a circuit board including a magnetic layer formed from the cured product of the resin composition layer of a resin sheet. In these circuit boards, the magnetic layer may be a layer formed by curing a resin composition layer, or may be a layer formed by curing a resin composition. First and second embodiments of a circuit board manufacturing method will be described below. However, the circuit board manufacturing method according to the present invention is not limited to the first and second embodiments exemplified below.

[0206] First Embodiment The circuit board of the first embodiment includes a core substrate having through holes formed therein and a magnetic layer filled in the through holes. (1) a step of laminating a core substrate having through holes formed therein and a resin sheet so that the through holes are filled with a resin composition layer; (2) curing the resin composition layer to form a magnetic layer; Contains, in this order:

[0207] Furthermore, the method for manufacturing a circuit board according to the first embodiment may include any step in combination with the steps (1) and (2). For example, the method for manufacturing a circuit board may include the following steps: (3) polishing the magnetic layer; (4) a step of roughening the magnetic layer; and (5) forming a conductor layer on the magnetic layer; Typically, steps (3), (4) and (5) are carried out in this order.

[0208] <Process (1)> Step (1) typically includes preparing a core substrate having through holes formed therein. The core substrate may be purchased from the market or may be manufactured using an appropriate material. An example method for manufacturing the core substrate will now be described.

[0209] Fig. 1 is a cross-sectional view schematically showing a core substrate 10 before through holes are formed in the method for manufacturing a circuit board according to the first embodiment of the present invention. The step of preparing the core substrate 10 may include preparing a core substrate 10 in which no through holes to be filled with a magnetic layer are formed, as in the example shown in Fig. 1. This core substrate 10 is a substrate in which through holes are not formed, and may be a plate-shaped member.

[0210] The core substrate 10 typically includes a support substrate 11. Examples of the support substrate 11 include insulating substrates such as a glass epoxy substrate, a metal substrate, a polyester substrate, a polyimide substrate, a BT resin substrate, and a thermosetting polyphenylene ether substrate. A metal layer may be provided on the support substrate 11. The metal layer may be provided on one side or both sides of the support substrate 11. Here, an example is shown in which metal layers 12 and 13 are provided on both surfaces of the support substrate 11. Examples of the metal layers 12 and 13 include layers formed of a metal such as copper. The metal layers 12 and 13 may be, for example, copper foil such as a carrier-attached copper foil, or may be metal layers formed from the material of the conductor layer described below.

[0211] FIG. 2 is a cross-sectional view schematically showing a core substrate 10 having a through hole 14 formed therein in the method for manufacturing a circuit board according to the first embodiment of the present invention. The step of preparing the core substrate 10 may include forming the through hole 14 in the core substrate 10, as in the example shown in FIG. 2. The through hole 14 can be formed by, for example, drilling, laser irradiation, plasma irradiation, or the like. Typically, the through hole 14 can be formed by drilling a through hole in the core substrate 10. As a specific example, the through hole 14 can be formed using a commercially available drilling device. An example of a commercially available drilling device is the "ND-1S211" manufactured by Hitachi Via Mechanics, Ltd.

[0212] FIG. 3 is a cross-sectional view schematically illustrating a core substrate 10 having a plating layer 20 formed in a through-hole 14 in the circuit board manufacturing method according to the first embodiment of the present invention. The process of preparing the core substrate 10 may include, if necessary, roughening the core substrate 10 and then forming the plating layer 20 as shown in FIG. 3 . The roughening process may be either a dry or wet roughening process. An example of a dry roughening process is plasma treatment. An example of a wet roughening process is a method in which a swelling process using a swelling liquid, a roughening process using an oxidizing agent, and a neutralization process using a neutralizing liquid are performed in this order. The plating layer 20 may be formed by a plating method. The procedure for forming the plating layer 20 by a plating method may be the same as that for forming the conductor layer in step (5) described below. Here, an example is shown in which the plating layer 20 is formed in the through-hole 14 and on the surfaces of the metal layer 12 and the metal layer 13. In this example, the core substrate provided with the plating layer 20 will be described by assigning the same reference numeral "10" as the core substrate 10 before the plating layer 20 is formed.

[0213] FIG. 4 is a cross-sectional view schematically illustrating lamination of a core substrate 10 and a resin sheet 30 in a method for manufacturing a circuit board according to the first embodiment of the present invention. Step (1) includes preparing a core substrate 10 having through holes 14 formed therein, and then laminating the core substrate 10 and the resin sheet 30, as shown in FIG. 4. In this embodiment, an example will be described in which a resin sheet 30 including a resin composition layer 31 and a support 32 is laminated on one surface 10U of the core substrate 10. In the following description, the surface 10U of the core substrate 10 that is bonded to the resin sheet 30 will be referred to as the "first surface 10U," and the opposite surface will be referred to as the "second surface 10D."

[0214] The core substrate 10 and the resin sheet 30 are laminated together so that the resin composition layer 31 fills the through-holes 14 partially or entirely. Therefore, lamination is typically performed so that the resin composition layer 31 and the core substrate 10 are bonded together. Specifically, the lamination can be performed by thermocompression bonding the resin sheet 30 to the core substrate 10, thereby bonding the resin composition layer 31 to the core substrate 10. When the resin sheet 30 includes a support 32, as in the example shown in FIG. 4 , the lamination can be performed by pressing the resin sheet 30 against the core substrate 10 from the support 32 side. Examples of members used for thermocompression bonding (hereinafter sometimes referred to as "thermocompression bonding member"; not shown) include a heated metal plate (e.g., a stainless steel plate) or a metal roll (e.g., a stainless steel roll). The thermocompression bonding member may be directly pressed against the resin sheet 30; however, it is preferable to press the resin sheet 30 through an elastic material such as heat-resistant rubber so that the resin sheet 30 can adequately conform to the surface irregularities of the core substrate 10.

[0215] The lamination of the core substrate 10 and the resin sheet 30 may be carried out, for example, by a vacuum lamination method. The lamination conditions may be, for example, as follows: The thermocompression temperature is preferably in the range of 60°C to 160°C, more preferably 80°C to 140°C. The thermocompression pressure is preferably in the range of 0.098 MPa to 1.77 MPa, more preferably 0.29 MPa to 1.47 MPa. The thermocompression time is preferably in the range of 20 seconds to 400 seconds, more preferably 30 seconds to 300 seconds. The lamination is preferably carried out under reduced pressure conditions of 13 hPa or less.

[0216] After lamination, the laminated resin sheet 30 may be smoothed under normal pressure (atmospheric pressure), for example, by pressing a thermocompression member from the support 32 side. The pressing conditions for the smoothing treatment may be the same as the thermocompression conditions for the lamination. Note that the lamination and smoothing treatment may be performed consecutively using a vacuum laminator.

[0217] FIG. 5 is a cross-sectional view schematically illustrating lamination of a core substrate 10 and a resin sheet 30 in the method for manufacturing a circuit board according to the first embodiment of the present invention. By laminating the core substrate 10 and the resin sheet 30, as shown in FIG. 5, the resin composition layer 31 of the resin sheet 30 penetrates into the through-holes 14, thereby filling the through-holes 14. Here, an example will be described in which a portion of the resin composition layer 31 penetrates into the through-holes 14, while another portion adheres to the first surface 10U of the core substrate 10 without penetrating the through-holes 14. Thus, the resin composition layer 31 can be formed on the first surface 10U of the core substrate 10. Furthermore, another portion of the resin composition layer 31 that penetrates into the through-holes 14 can pass through the through-holes 14 and be discharged from the opening on the second surface 10D of the core substrate 10. Thus, the resin composition layer 31 can be formed on the second surface 10D of the core substrate 10.

[0218] Typically, the support 32 is peeled off after laminating the core substrate 10 and the resin sheet 30. In this embodiment, an example will be described in which the support 32 is peeled off after laminating the core substrate 10 and the resin sheet 30 and before step (2). However, the peeling of the support 32 may be performed after step (2).

[0219] <Process (2)> 6 is a schematic cross-sectional view illustrating step (2) of the method for manufacturing a circuit board according to the first embodiment of the present invention. Step (2) includes, after laminating the core substrate 10 and the resin sheet 30, curing the resin composition layer 31, as shown in FIG. 6. Curing the resin composition layer 31 forms a magnetic layer 40 containing a cured product of the resin composition. The magnetic layer 40 is formed in the through-holes 14, and can also typically be formed on the first surface 10U and second surface 10D of the core substrate 10.

[0220] The resin composition layer 31 is usually cured by thermal curing. The thermal curing conditions for the resin composition layer 31 can be appropriately set within a range in which the curing of the resin composition layer 31 proceeds. The curing temperature is preferably 60°C or higher, more preferably 70°C or higher, and even more preferably 80°C or higher, and preferably 245°C or lower, more preferably 220°C or lower, and even more preferably 200°C or lower. The curing time is preferably 5 minutes or longer, more preferably 10 minutes or longer, and even more preferably 15 minutes or longer, and preferably 120 minutes or shorter, more preferably 110 minutes or shorter, and even more preferably 100 minutes or shorter.

[0221] The degree of hardening of the magnetic layer 40 obtained in step (2) is preferably 80% or more, more preferably 85% or more, and even more preferably 90% or more. The degree of hardening can be measured using, for example, a differential scanning calorimeter.

[0222] The method for manufacturing a circuit board may include a step (preheating step) of heating the resin composition layer 31 at a temperature lower than the curing temperature after laminating the core substrate 10 and the resin sheet 30 and before curing the resin composition layer 31. For example, prior to curing the resin composition layer 31, the resin composition layer 31 may be preheated at a temperature of typically 50°C or higher and lower than 120°C (preferably 60°C or higher and 110°C or lower, more preferably 70°C or higher and 100°C or lower) for typically 5 minutes or longer (preferably 5 to 150 minutes, more preferably 15 to 120 minutes).

[0223] <Process (3)> FIG. 7 is a schematic cross-sectional view illustrating step (3) of the method for manufacturing a circuit board according to the first embodiment of the present invention. Step (3) may include polishing the magnetic layer 40. Specifically, step (3) may include polishing the magnetic layer 40 located outside the through-holes 14. In the example shown in this embodiment, the magnetic layer 40 is formed on the first surface 10U and the second surface 10D of the core substrate 10, and therefore the magnetic layer 40 located on these first surface 10U and second surface 10D can be polished. The magnetic layer 40 located outside the through-holes 14 is generally an excess portion not required for the final product. By polishing, the excess portion can be removed, as shown in FIG. 7. Furthermore, polishing can flatten the polished surfaces 40U and 40D, which serve as the surfaces of the magnetic layer 40.

[0224] The polishing method may be any method capable of removing unnecessary portions of the magnetic layer 40. Examples of such polishing methods include buff polishing, belt polishing, ceramic polishing, etc. Commercially available buff polishing devices include the "NT-700IM" manufactured by Ishii Hyoki Co., Ltd.

[0225] The arithmetic mean roughness (Ra) of the polished surfaces 40U and 40D of the magnetic layer 40 is preferably 300 nm or more, more preferably 350 nm or more, and even more preferably 400 nm or more, from the viewpoint of improving adhesion with the conductor layer (not shown in FIG. 7). The upper limit is preferably 1000 nm or less, more preferably 900 nm or less, and even more preferably 800 nm or less. The surface roughness (Ra) can be measured, for example, using a non-contact surface roughness meter.

[0226] After step (2) and before step (3), magnetic layer 40 may be subjected to a heat treatment to further increase the degree of hardening of magnetic layer 40. The temperature in the heat treatment may be the same as the hardening temperature described above. Specific heat treatment temperatures are preferably 120°C or higher, more preferably 130°C or higher, and even more preferably 150°C or higher, and are preferably 245°C or lower, more preferably 220°C or lower, and even more preferably 200°C or lower. The heat treatment time is preferably 5 minutes or longer, more preferably 10 minutes or longer, and even more preferably 15 minutes or longer, and is preferably 150 minutes or shorter, more preferably 120 minutes or shorter, and even more preferably 100 minutes or shorter.

[0227] By carrying out the above-described steps (1) and (2) and further carrying out step (3) as needed, it is possible to obtain a circuit board 100 including a core substrate 10 and a magnetic layer 40 filling the through-holes 14 of the core substrate 10. The circuit board 100 thus obtained may be subjected to steps (4) and (5) as needed to form a conductor layer.

[0228] <Process (4)> Step (4) includes subjecting the magnetic layer to a roughening treatment. Typically, the roughening treatment is applied to the polished surface of the magnetic layer. In step (4), the roughening treatment may be applied not only to the polished surface of the magnetic layer but also to surfaces 10U and 10D of core substrate 10.

[0229] The procedure and conditions for the roughening treatment are not particularly limited, and may be, for example, the procedure and conditions used in the manufacturing method of a multilayer printed wiring board. As a specific example, the roughening treatment may be performed by a method including, in this order, a swelling treatment with a swelling liquid, a roughening treatment with an oxidizing agent, and a neutralization treatment with a neutralizing liquid.

[0230] Examples of swelling liquids used in the swelling treatment include alkaline solutions and surfactant solutions, with alkaline solutions being preferred. As alkaline solutions serving as swelling liquids, sodium hydroxide solutions and potassium hydroxide solutions are more preferred. Examples of commercially available swelling liquids include "Swelling Dip Securigans P" and "Swelling Dip Securigans SBU" manufactured by Atotech Japan.

[0231] Swelling treatment with a swelling liquid can be carried out, for example, by immersing the magnetic layer for 1 to 20 minutes in swelling liquid at 30 to 90° C. To keep swelling of the resin contained in the magnetic layer to an appropriate level, it is preferable to immerse the magnetic layer in swelling liquid at 40 to 80° C. for 5 to 15 minutes.

[0232] Examples of oxidizing agents used in roughening treatment include alkaline permanganate solutions prepared by dissolving potassium permanganate or sodium permanganate in an aqueous solution of sodium hydroxide. Roughening treatment using an oxidizing agent such as alkaline permanganate solution is preferably carried out by immersing the magnetic layer in an oxidizing agent solution heated to 60°C to 80°C for 10 to 30 minutes. The concentration of permanganate in the alkaline permanganate solution is preferably 5% to 10% by mass. Commercially available oxidizing agents include alkaline permanganate solutions such as "Concentrate Compact P" and "Dosing Solution Securigance P" manufactured by Atotech Japan.

[0233] The neutralizing solution used in the neutralization treatment is preferably an acidic aqueous solution. An example of a commercially available neutralizing solution is "Reduction Solution Securigance P" manufactured by Atotech Japan. Neutralization treatment using a neutralizing solution can be carried out by immersing the surface that has been roughened with an oxidizing solution in the neutralizing solution at 30°C to 80°C for 5 to 30 minutes. From the standpoint of workability, etc., a preferred method is to immerse the magnetic layer that has been roughened with an oxidizing solution in the neutralizing solution at 40°C to 70°C for 5 to 20 minutes.

[0234] The arithmetic mean roughness (Ra) of the magnetic layer surface after roughening treatment is preferably 300 nm or more, more preferably 350 nm or more, and even more preferably 400 nm or more, from the viewpoint of improving adhesion with the conductor layer. The upper limit is preferably 1500 nm or less, more preferably 1200 nm or less, and even more preferably 1000 nm or less. The surface roughness (Ra) can be measured, for example, using a non-contact surface roughness meter.

[0235] <Process (5)> FIG. 8 is a schematic cross-sectional view illustrating step (5) of the method for manufacturing the circuit board 100 according to the first embodiment of the present invention. Step (5), as shown in FIG. 8, includes forming a conductor layer 50 on the polished surfaces 40U and 40D of the magnetic layer 40. This embodiment shows an example in which the conductor layer 50 is formed not only on the polished surfaces 40U and 40D of the magnetic layer 40 but also on the surrounding surfaces (for example, the first surface 10U and second surface 10D of the core substrate 10). Also, while FIG. 8 shows an example in which the conductor layer 50 is formed on both sides of the core substrate 10, the conductor layer 50 may be formed on only one side of the core substrate 10.

[0236] 9 is a schematic cross-sectional view illustrating step (5) of the method for manufacturing the circuit board 100 according to the first embodiment of the present invention. As shown in FIG. 9, step (5) may include forming a conductor layer 50, and then removing the conductor layer 50, the metal layers 12 and 13, and a portion of the plating layer 20 by a process such as etching to form a patterned conductor layer 51.

[0237] The conductor layer 50 can be formed by, for example, plating, sputtering, vapor deposition, etc., with plating being preferred. In a preferred embodiment, the surface of the magnetic layer 40 (and, if necessary, the core substrate 10) can be plated by an appropriate method such as a semi-additive method or a full-additive method to form a patterned conductor layer 51 having a desired wiring pattern. Examples of materials for the conductor layer 50 include simple metals such as gold, platinum, palladium, silver, copper, aluminum, cobalt, chromium, zinc, nickel, titanium, tungsten, iron, tin, and indium; and alloys of two or more metals selected from the group consisting of gold, platinum, palladium, silver, copper, aluminum, cobalt, chromium, zinc, nickel, titanium, tungsten, iron, tin, and indium. Among these, from the viewpoints of versatility, cost, ease of patterning, and the like, it is preferable to use chromium, nickel, titanium, aluminum, zinc, gold, palladium, silver, or copper, or a nickel-chromium alloy, a copper-nickel alloy, or a copper-titanium alloy, it is more preferable to use chromium, nickel, titanium, aluminum, zinc, gold, palladium, silver, or copper, or a nickel-chromium alloy, and it is even more preferable to use copper.

[0238] An example of a method for forming the patterned conductor layer 51 will now be described in detail. A plating seed layer is formed on the polished surfaces 40U and 40D of the magnetic layer 40 by electroless plating. Next, a mask pattern is formed on the formed plating seed layer as needed, and then an electroplated layer is formed by electrolytic plating. Thereafter, the mask pattern is removed as needed, and any unnecessary plating seed layer is removed by etching or other process, thereby forming the patterned conductor layer 51 having the desired wiring pattern. After forming the patterned conductor layer 51, an annealing treatment may be performed as needed to improve the adhesion strength of the patterned conductor layer 51. The annealing treatment can be performed, for example, by heating at 150°C to 200°C for 20 to 90 minutes.

[0239] The thickness of the patterned conductor layer 51 is preferably 1 μm or more, more preferably 3 μm or more, even more preferably 5 μm or more, and is preferably 70 μm or less, more preferably 50 μm or less, even more preferably 40 μm or less, and particularly preferably 10 μm or less.

[0240] The above method produces a circuit board 100 equipped with a magnetic layer 40. The magnetic layer 40 is obtained by curing the resin composition layer 31, and therefore contains a cured product of the resin composition. Therefore, the magnetic layer 40 can contain a large amount of magnetic powder (not shown), and can therefore have excellent magnetic properties.

[0241] Second Embodiment The circuit board of the second embodiment includes a magnetic layer formed from a cured product of a resin composition layer of a resin sheet. (A) a step of laminating a resin sheet onto an inner layer substrate so that the resin composition layer is bonded to the inner layer substrate, thereby forming a magnetic layer; Includes.

[0242] Furthermore, the method for manufacturing a circuit board according to the second embodiment may include any step in addition to step (A). For example, the method for manufacturing a circuit board may include the following steps: (B) a step of drilling holes in the magnetic layer; (C) a step of roughening the magnetic layer; and (D) forming a conductor layer on the magnetic layer; This production method preferably includes steps (A) to (D) in this order.

[0243] <Process (A)> Step (A) is a step of forming a magnetic layer by laminating a resin sheet on an inner layer substrate so that the resin composition layer is bonded to the inner layer substrate. In one embodiment of step (A), the resin sheet is laminated on the inner layer substrate so that the resin composition layer is bonded to the inner layer substrate, and the resin composition layer is thermally cured to form the magnetic layer.

[0244] 10 is a schematic cross-sectional view illustrating step (A) of the method for manufacturing a circuit board according to the second embodiment of the present invention. In step (A), a resin sheet 310 including a support 330 and a resin composition layer 320a provided on the support 330 is laminated on an inner substrate 200 so that the resin composition layer 320a is bonded to the inner substrate 200.

[0245] The inner substrate 200 is an insulating substrate. Examples of materials for the inner substrate 200 include insulating base materials such as a glass epoxy substrate, a metal substrate, a polyester substrate, a polyimide substrate, a BT resin substrate, and a thermosetting polyphenylene ether substrate. The inner substrate 200 may be an inner circuit board having wiring and the like built into its thickness.

[0246] As shown in FIG. 10 as an example, the inner layer substrate 200 has a first conductor layer 420 provided on the first main surface 200a and an external terminal 240 provided on the second main surface 200b. The first conductor layer 420 may include multiple wirings. In the illustrated example, only the wirings constituting the coil-shaped conductive structure 400 of the inductor element are shown. The external terminal 240 is a terminal for electrically connecting to an external device or the like (not shown). The external terminal 240 can be configured as part of the conductor layer provided on the second main surface 200b.

[0247] The conductive material that can form the first conductive layer 420 and the external terminals 240 is the same as the material of the conductive layer explained in the section "<Step (5)>" of the first embodiment.

[0248] The first conductor layer 420 and the external terminal 240 may have a single-layer structure or a multi-layer structure in which two or more single metal layers or alloy layers made of different types of metals or alloys are stacked. The thickness of the first conductor layer 420 and the external terminal 240 is the same as that of the second conductor layer 440 described below.

[0249] The line (L) / space (S) ratio of the first conductor layer 420 and the external terminal 240 is not particularly limited, but from the viewpoint of reducing surface irregularities and obtaining a magnetic layer with excellent smoothness, it is usually 900 / 900 μm or less, preferably 700 / 700 μm or less, more preferably 500 / 500 μm or less, even more preferably 300 / 300 μm or less, and even more preferably 200 / 200 μm or less. The lower limit of the line / space ratio is not particularly limited, but from the viewpoint of improving the embedding of the resin composition layer in the spaces, it is preferably 1 / 1 μm or more.

[0250] The inner substrate 200 may have a plurality of through holes 220 that penetrate the inner substrate 200 from the first main surface 200a to the second main surface 200b. The through holes 220 are provided with internal through-hole wiring 220a. The internal through-hole wiring 220a electrically connects the first conductor layer 420 and the external terminal 240.

[0251] The resin composition layer 320a and the inner substrate 200 are joined together in the same manner as the lamination method of the core substrate and the resin sheet described in the section "<Step (1)>" of the first embodiment.

[0252] After the resin sheet is laminated on the inner substrate, the resin composition layer is thermally cured to form the magnetic layer. As shown in an example in Figure 11, the resin composition layer 320a bonded to the inner substrate 200 is thermally cured to form the first magnetic layer 320.

[0253] The conditions for thermally curing the resin composition layer 320a are the same as those for thermally curing the resin composition layer described in the section "<Step (2)>" of the first embodiment.

[0254] The support 330 may be removed between the end of the thermal curing in step (A) and step (B), or may be peeled off after step (B).

[0255] <Process (B)> 12 is a schematic cross-sectional view illustrating step (B) of the method for manufacturing a circuit board according to the second embodiment of the present invention. In step (B), the first magnetic layer 320 is drilled to form via holes 360.

[0256] The via holes 360 serve as paths for electrically connecting the first conductor layer 420 and the second conductor layer 440 described below. The via holes 360 may be formed using, for example, a drill, a laser, plasma, or the like, depending on the composition of the resin composition used to form the magnetic layer. The dimensions and shape of the via holes may be determined appropriately depending on the design of the circuit board.

[0257] <Process (C)> Step (C) includes subjecting the magnetic layer with the via holes formed therein to a roughening treatment, which can be carried out by the same method as that described in the "<Step (4)>" section of the first embodiment.

[0258] The roughening treatment in step (C) may be a treatment for polishing the surface of the insulating layer, which may be performed by the same polishing method as described in the section "<Step (3)>" of the first embodiment.

[0259] The arithmetic mean roughness (Ra) of the roughened surface of the magnetic layer is preferably 300 nm or more, more preferably 350 nm or more, and even more preferably 400 nm or more, from the viewpoint of improving plating adhesion. The upper limit is preferably 1000 nm or less, more preferably 900 nm or less, and even more preferably 800 nm or less. The surface roughness (Ra) can be measured, for example, using a non-contact surface roughness meter.

[0260] <Process (D)> 13 is a schematic cross-sectional view illustrating step (D) of the method for manufacturing a circuit board according to the second embodiment of the present invention. Step (D) includes forming a second conductor layer 440 on the first magnetic layer 320, as shown in an example in FIG.

[0261] The conductive material that can be used to form the second conductive layer 440 is the same as the material for the conductive layer described in the section "<Step (5)>" of the first embodiment.

[0262] From the viewpoint of thinning, the thickness of the second conductor layer 440 is preferably 70 μm or less, more preferably 60 μm or less, even more preferably 50 μm or less, still more preferably 40 μm or less, particularly preferably 30 μm or less, 20 μm or less, 15 μm or less, or 10 μm or less. The lower limit is preferably 1 μm or more, more preferably 3 μm or more, and even more preferably 5 μm or more.

[0263] The second conductor layer 440 can be formed by plating. The second conductor layer 440 is preferably formed by a wet plating method such as a semi-additive method or a full-additive method including an electroless plating process, a mask pattern formation process, an electrolytic plating process, and a flash etching process. By forming the second conductor layer 440 using a wet plating method, it is possible to form the second conductor layer 440 including a desired wiring pattern. Note that this process also forms via-hole wiring 360a in the via hole 360.

[0264] The first conductor layer 420 and the second conductor layer 440 may be provided in a spiral shape, for example, as shown in Figures 14 to 16 described later. In one example, one end of the spiral wiring portion of the second conductor layer 440 on the central side is electrically connected to one end of the spiral wiring portion of the first conductor layer 420 on the central side by via-hole wiring 360a. The other end of the spiral wiring portion of the second conductor layer 440 on the outer periphery is electrically connected to land 420a of the first conductor layer 42 by via-hole wiring 360a. Therefore, the other end of the spiral wiring portion of the second conductor layer 440 on the outer periphery is electrically connected to external terminal 240 via via-hole wiring 360a, land 420a, and through-hole wiring 220a.

[0265] The coil-shaped conductive structure 400 is composed of a spiral wiring portion that is part of the first conductor layer 420, a spiral wiring portion that is part of the second conductor layer 440, and via-hole wiring 360a that electrically connects the spiral wiring portion of the first conductor layer 420 and the spiral wiring portion of the second conductor layer 440.

[0266] After step (D), a step of forming a magnetic layer on the conductor layer may be performed. More specifically, as shown in an example in Fig. 15, the second magnetic layer 340 is formed on the first magnetic layer 320 on which the second conductor layer 440 and the via-hole wiring 360a are formed. The second magnetic layer may be formed by the same steps as those already described.

[0267] [Inductor board] The inductor substrate includes the circuit board of the present invention. When such an inductor component includes a circuit board obtained by the circuit board manufacturing method of the first embodiment, it has an inductor pattern formed of a conductor around at least a portion of the periphery of the cured resin composition layer. For example, an inductor substrate such as that described in JP 2016-197624 A can be used.

[0268] Furthermore, when including a circuit board obtained by the circuit board manufacturing method of the second embodiment, the inductor substrate has a magnetic layer and a conductive structure at least partially embedded in the magnetic layer, and includes an inductor element formed by the conductive structure and a portion of the magnetic layer extending in the thickness direction of the magnetic layer and surrounded by the conductive structure. Fig. 14 is a schematic plan view of the inductor substrate incorporating the inductor element, as viewed from one side in the thickness direction. Fig. 15 is a schematic view showing a cut end surface of the inductor substrate cut at the position indicated by the dashed dotted line II-II in Fig. 14. Fig. 16 is a schematic plan view illustrating the configuration of a first conductor layer in the inductor substrate.

[0269] 14 and 15, the circuit board 100 is a build-up wiring board having multiple magnetic layers (first magnetic layer 320, second magnetic layer 340) and multiple conductor layers (first conductor layer 420, second conductor layer 440), i.e., having build-up magnetic layers and build-up conductor layers. The inductor substrate 100 also includes an inner layer substrate 200.

[0270] 15, the first magnetic layer 320 and the second magnetic layer 340 constitute the magnetic part 300, which can be seen as an integrated magnetic layer. Therefore, the coiled conductive structure 400 is provided so that at least a portion thereof is embedded in the magnetic part 300. That is, in the inductor substrate 100 of this embodiment, the inductor element is constituted by the coiled conductive structure 400 and a core portion that extends in the thickness direction of the magnetic part 300 and is a portion of the magnetic part 300 surrounded by the coiled conductive structure 400.

[0271] 16, the first conductor layer 420 includes a spiral wiring portion for constituting the coil-shaped conductive structure 400 and a rectangular land 420a electrically connected to the through-hole wiring 220a. In the illustrated example, the spiral wiring portion includes a straight portion, a bent portion that bends at a right angle, and a detour portion that detours around the land 420a. In the illustrated example, the spiral wiring portion of the first conductor layer 420 has an overall outline that is approximately rectangular, and has a shape that winds counterclockwise from the center toward the outside.

[0272] Similarly, a second conductor layer 440 is provided on the first magnetic layer 320. The second conductor layer 440 includes a spiral wiring portion for configuring the coil-shaped conductive structure 400. In Fig. 14 or 15, the spiral wiring portion includes a straight portion and a bent portion bent at a right angle. In Fig. 14 or 15, the spiral wiring portion of the second conductor layer 440 has an overall outline that is approximately rectangular, and has a shape that winds clockwise from the center toward the outside.

[0273] Such an inductor substrate can be used as a wiring board for mounting electronic components such as semiconductor chips, or as a (multilayer) printed wiring board using such a wiring board as an inner layer substrate.Furthermore, such a wiring board can be singulated and used as a chip inductor substrate, or as a surface-mounted printed wiring board.

[0274] Furthermore, various types of semiconductor devices can be manufactured using such a wiring board. Semiconductor devices including such wiring boards can be suitably used in electrical appliances (e.g., computers, mobile phones, digital cameras, televisions, etc.) and vehicles (e.g., motorcycles, automobiles, trains, ships, aircraft, etc.). [Example]

[0275] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples. In the following description, "parts" and "%" representing amounts mean "parts by mass" and "% by mass", respectively, unless otherwise specified.

[0276] <Synthesis Example 1: Synthesis of Polyester Solution 1> A reaction flask equipped with a thermometer, stirrer, nitrogen inlet, and reflux condenser was charged with 10.0 parts of 12-hydroxystearic acid (manufactured by Junsei Chemical Co., Ltd.) and 190 parts of ε-caprolactone (manufactured by Junsei Chemical Co., Ltd.). The mixture was heated to 160°C over 4 hours under a nitrogen stream, heated at 160°C for 2 hours, and then heated until the remaining amount of ε-caprolactone was 1% or less. The mixture was then cooled to room temperature. Hereinafter, this reaction solution will be referred to as Polyester Solution 1.

[0277] <Synthesis Example 2: Synthesis of Amine Dispersant 1> A mixture of 25.0 parts xylene and 70 parts 10% aqueous polyallylamine solution ("PAA-1LV" manufactured by Nitto Boseki Co., Ltd., number-average molecular weight approximately 3,000) was stirred at 160°C in a reaction flask equipped with a thermometer, stirrer, nitrogen inlet, and reflux condenser. Water was distilled off using a separator, and while the xylene was returned to the reaction solution, 114.21 parts of the polyester solution obtained in Synthesis Example 1, heated to 160°C, was added and the reaction was carried out at 160°C for 2 hours. The mixture was further heated at 160°C for 4 hours, and the xylene was distilled off at 160°C to obtain Amine Dispersant 1. Amine Dispersant 1 had a polyester skeleton represented by the general formula (1), where R was an alkylene group containing 5 carbon atoms, and had an amine value of 20.0 mgKOH / g and an acid value of 16.0 mgKOH / g. The pH was 6 using the indicator method.

[0278] <Synthesis Example 3: Synthesis of Amine Dispersant 2> A mixture of 25.0 parts xylene and 70 parts 10% aqueous polyallylamine solution ("PAA-1LV" manufactured by Nitto Boseki Co., Ltd., number-average molecular weight approximately 3,000) was stirred at 160°C in a reaction flask equipped with a thermometer, stirrer, nitrogen inlet, and reflux condenser. Water was distilled off using a separator, and while the xylene was returned to the reaction solution, 114.21 parts of the polyester solution obtained in Synthesis Example 1, heated to 160°C, was added and the reaction was carried out at 160°C for 3 hours. The mixture was further heated at 160°C for 4 hours, and the xylene was distilled off at 160°C to obtain Amine Dispersant 2. Amine Dispersant 2 had a polyester skeleton represented by the general formula (1), where R was an alkylene group containing 5 carbon atoms, and had an amine value of 11.0 mgKOH / g and an acid value of 17.5 mgKOH / g. The pH was 6 using the indicator method.

[0279] Example 1 Resin oligomer with a weight average molecular weight of 600 or more and less than 8000 ("jER1001" manufactured by Mitsubishi Chemical Corporation, bisphenol A type epoxy resin, epoxy equivalent (EPW) 475 g / eq., softening point 64°C, bifunctional (2B), weight average molecular weight 900) 0.21 parts, epoxy resin ("ZX-1059" manufactured by Nippon Steel Chemical & Material Co., Ltd., a mixture of bisphenol A type epoxy resin and bisphenol F type epoxy resin) 0.65 parts, amine dispersant 1 0.18 parts, cyclohexanone 1.00 parts, methyl ethyl ketone 1.00 parts, magnetic powder ("KUAMET NC1-53 μm" manufactured by Epson Atmix Corporation, nanocrystals made of Fe-Si-Nb-B alloy, average particle size (D 50 ) 27.3 μm) 34.90 parts, magnetic powder (Epson Atmix "AW2-08PF3F", Fe-Si-Cr alloy powder, amorphous powder, average particle size (D 50 ) 3.1 μm) 4.32 parts, magnetic powder (JFE Mineral Co., Ltd. "CVD iron powder (0.7 μm)", average particle size (D 50 ) 0.7 μm) and 0.84 parts of phenolic resin (DIC Corporation's "LA-7054", a methyl ethyl ketone solution with a solids content of 60% and a hydroxyl group equivalent of approximately 125) were mixed and uniformly dispersed in a high-speed rotating mixer to prepare a resin composition.

[0280] <Example 2> In Example 1, 1) 0.21 parts of a resin oligomer having a weight-average molecular weight of 600 or more and less than 8000 ("jER1001" manufactured by Mitsubishi Chemical Corporation, bisphenol A type epoxy resin, epoxy equivalent (EPW) 475 g / eq., softening point 64°C, bifunctional (2B), weight-average molecular weight 900) was replaced with 0.21 parts of a resin oligomer having a weight-average molecular weight of 600 or more and less than 8000 ("jER4005P" manufactured by Mitsubishi Chemical Corporation, bisphenol F type epoxy resin, weight-average molecular weight: 6200), 2) 0.18 parts of amine dispersant 1 was changed to 0.18 parts of amine dispersant 2. A resin composition was prepared in the same manner as in Example 1 except for the above points.

[0281] Example 3 In Example 1, 0.21 parts of a resin oligomer having a weight-average molecular weight of 600 or more and less than 8000 ("jER1001" manufactured by Mitsubishi Chemical Corporation, bisphenol A type epoxy resin, epoxy equivalent (EPW) 475 g / eq., softening point 64°C, bifunctional (2B), weight-average molecular weight 900) was replaced with 0.21 parts of a resin oligomer having a weight-average molecular weight of 600 or more and less than 8000 ("jER4005P" manufactured by Mitsubishi Chemical Corporation, bisphenol F type epoxy, weight-average molecular weight: 6200). A resin composition was prepared in the same manner as in Example 1 except for the above points.

[0282] Example 4 In Example 1, 1) 0.21 parts of a resin oligomer having a weight-average molecular weight of 600 or more and less than 8000 ("jER1001" manufactured by Mitsubishi Chemical Corporation, bisphenol A type epoxy resin, epoxy equivalent (EPW) 475 g / eq., softening point 64°C, bifunctional (2B), weight-average molecular weight 900) was replaced with 0.23 parts of a resin oligomer having a weight-average molecular weight of 600 or more and less than 8000 ("jER4005P" manufactured by Mitsubishi Chemical Corporation, bisphenol F type epoxy, weight-average molecular weight: 6200), 2) The amount of epoxy resin (Nippon Steel Chemical & Material Co., Ltd. "ZX-1059", a mixture of bisphenol A epoxy resin and bisphenol F epoxy resin) was changed from 0.65 parts to 0.74 parts. 3) 0.18 parts of amine dispersant 1 was replaced with 0.09 parts of amine dispersant 2, 4) The amount of methyl ethyl ketone was changed from 1.00 parts to 1.30 parts. 5) 0.84 parts of phenolic resin (DIC Corporation's "LA-7054," a methyl ethyl ketone solution with a solids content of 60% and a hydroxyl equivalent of approximately 125) was replaced with 0.48 parts of phenolic resin (DIC Corporation's "Phenolite TD-2090," a hydroxyl equivalent of 105 g / eq. and a softening point of 120°C). A resin composition was prepared in the same manner as in Example 1 except for the above.

[0283] <Example 5> In Example 4, 1) The amount of amine dispersant 2 was changed from 0.09 parts to 0.08 parts. 2) 0.01 parts of a curing accelerator ("TBP-DA" manufactured by Hokko Chemical Industry Co., Ltd.) was used. A resin composition was prepared in the same manner as in Example 4 except for the above.

[0284] Example 6 In Example 1, 1) 0.21 parts of a resin oligomer with a weight-average molecular weight of 600 or more but less than 8000 ("jER1001" manufactured by Mitsubishi Chemical Corporation, bisphenol A type epoxy resin, epoxy equivalent (EPW) 475 g / eq., softening point 64°C, bifunctional (2B), weight-average molecular weight 900) was replaced with 0.9 parts of a resin with a weight-average molecular weight of 8000 or more ("YX7553H30" manufactured by Mitsubishi Chemical Corporation, special skeleton phenoxy resin, 30% solution of methyl ethyl ketone: cyclohexanone = 1:1, weight-average molecular weight: 35000), 2) The amount of epoxy resin (Nippon Steel Chemical & Material Co., Ltd. "ZX-1059", a mixture of bisphenol A epoxy resin and bisphenol F epoxy resin) was changed from 0.65 parts to 0.56 parts. 3) The amount of amine dispersant 1 was changed from 0.18 parts to 0.27 parts. 4) The amount of methyl ethyl ketone was changed from 1.00 parts to 0.05 parts. 5) The amount of phenolic resin (DIC Corporation "LA-7054", a methyl ethyl ketone solution with a hydroxyl equivalent of approximately 125 and a solid content of 60%) was changed from 0.84 parts to 0.73 parts. 6) 0.01 parts of a curing accelerator ("TBP-DA" manufactured by Hokko Chemical Industry Co., Ltd.) was used. A resin composition was prepared in the same manner as in Example 1 except for the above.

[0285] Example 7 In Example 1, 1) 0.18 parts of the amine-based dispersant 1 was changed to 0.18 parts of an amine-based dispersant (Solsperse 24000GR (amine value 40 mg KOH / g, acid value 25 mg KOH / g, polyester) manufactured by Lubrizol Japan Corporation). A resin composition was prepared in the same manner as in Example 1 except for the above.

[0286] <Comparative Example 1> In Example 6, 0.27 parts of the amine-based dispersant 2 was changed to 0.27 parts of a dispersant (NOF Corporation's "SC-1015F", a polyoxyalkylene-based dispersant). A resin composition was prepared in the same manner as in Example 6 except for the above.

[0287] <Comparative Example 2> In Example 6, 0.27 parts of the amine-based dispersant 2 was changed to 0.27 parts of a dispersant ("KBM-103" manufactured by Shin-Etsu Chemical Co., Ltd., a phenyl silane coupling agent). A resin composition was prepared in the same manner as in Example 6 except for the above.

[0288] <Comparative Example 3> In Example 6, 0.27 parts of the amine-based dispersant 2 was changed to 0.27 parts of a dispersant ("KBM-573" manufactured by Shin-Etsu Chemical Co., Ltd., an aminosilane-based coupling agent). A resin composition was prepared in the same manner as in Example 6 except for the above.

[0289] <Measurement of relative permeability and loss factor> (1) Preparation of the cured product A polyethylene terephthalate (PET) film ("PET501010" manufactured by Lintec Corporation, thickness 50 μm) treated with a silicone-based release agent was prepared as a support. Each resin composition was uniformly applied to the release surface of the PET film using a doctor blade so that the thickness of the resin composition layer after drying would be 100 μm, thereby obtaining a resin sheet. The obtained resin sheet was heated at 190°C for 90 minutes to thermally cure the resin composition layer, and the support was peeled off to obtain a sheet-like cured product. Hereinafter, this sheet-like cured product will sometimes be referred to as Sample A.

[0290] (2) Measurement of relative permeability and loss factor The obtained sample A was cut to obtain a doughnut-shaped evaluation sample with an outer diameter of 19.2 mm and an inner diameter of 8.2 mm. The relative permeability (μ'), imaginary component of complex permeability (μ''), and loss factor (tanδ) of this evaluation sample were measured at a measurement frequency of 10 MHz and room temperature of 23°C using a Keysight magnetic material test fixture "16454A" and a Keysight impedance analyzer "E4991B." The loss factor tanδ was calculated using the formula "tanδ = μ'' / μ'." The relative permeability was evaluated according to the following criteria. 〇: Relative permeability is 40 or more. ×: Relative permeability is less than 40.

[0291] <Evaluation of tensile strength of cured resin composition> The tensile strength of Sample A was evaluated. The tensile strength was measured using an Orientec tensile testing machine "RTC-1250A" to measure the strength at break at 23°C. The measurement was carried out in accordance with JIS K7127. The tensile strength was evaluated according to the following criteria. 〇: Tensile strength is 70 MPa or more. ×: Tensile strength is less than 70 MPa.

[0292] <Evaluation of elongation> Elongation was evaluated using Sample A. Tensile strength was measured using a tensile testing machine "RTC-1250A" manufactured by Orientec Co., Ltd., and the breaking elongation was measured at 23°C. The measurement was carried out in accordance with JIS K6251.

[0293] <Measurement of Young's modulus> Young's modulus was evaluated using Sample A. Tensile strength was measured using a tensile testing machine "RTC-1250A" manufactured by Orientec Co., Ltd., and Young's modulus was measured at 23°C. The measurement was carried out in accordance with JIS K6253.

[0294] [Table 1] [Explanation of symbols]

[0295] 10 Core substrate 10U front page 10D second side 11 Support substrate 12 metal layer 13 Metal layer 14 through holes 20 plating layer 30 Resin sheet 31 Resin composition layer 32 Support 40 Magnetic layer 40U polished surface 40D polished surface 50 Conductor Layer 51 Patterned conductor layer 100 Circuit Boards 200 inner layer board 200a 1st main surface 200b 2nd main surface 220 through hole 220a Through-hole wiring 240 External terminal 300 Magnetic part 310 Resin Sheet 320a Resin composition layer 320 First insulating layer 330 Support 340 Second insulating layer 360 Beer Hall 360a via hole wiring 400 Coil-shaped conductive structure 420 First conductor layer 420a Land 440 Second conductor layer

Claims

1. (A) a resin having a weight average molecular weight of 600 or more; (B) epoxy resin (excluding those corresponding to component (A)), (C) an amine-based dispersant, and (D) magnetic powder, The component (A) contains (A-1) a bisphenol-type epoxy group-containing oligomer and / or a phenol resin oligomer having a weight average molecular weight of 800 or more and less than 8,000, The component (C) contains a polyester skeleton represented by formula (1) and a polyamine skeleton derived from polyallylamine, the content of the component (A-1) is 0.1 to 5% by mass, based on 100% by mass of the nonvolatile components in the resin composition; A resin composition, wherein the content (vol %) of component (D) is 70% by volume or more relative to 100% by volume of the nonvolatile components of the resin composition. 【Chemical 1】 (In general formula (1), each R independently represents a divalent hydrocarbon group having 2 to 10 carbon atoms, and n represents an integer of 2 to 1,000.)

2. 2. The resin composition according to claim 1, wherein A2 / (A1+A2) is 0 or more and 0.7 or less, where A1 is the content of the component (A-1) and A2 is the content of the component (A-2) when the total amount of nonvolatile components in the resin composition is 100% by mass.

3. 2. The resin composition according to claim 1, wherein Am / (Am+Bm) is 0.1 or more and 0.8 or less, where Am is the content of component (A) and Bm is the content of component (B) when the nonvolatile components in the resin composition are 100% by mass.

4. A resin composition as described in claim 1, wherein component (D) includes nanocrystalline magnetic powder.

5. The resin composition according to claim 1 , further comprising (E) a solvent.

6. A resin sheet comprising a support and a resin composition layer formed on the support using the resin composition according to any one of claims 1 to 5.

7. A circuit board comprising: a substrate having a through-hole; and a cured product of the resin composition according to any one of claims 1 to 5, filled in the through-hole.

8. A circuit board comprising a magnetic layer which is a cured product of the resin composition according to any one of claims 1 to 5.

9. An inductor substrate comprising the circuit board of claim 7 .

10. An inductor substrate comprising the circuit board of claim 8 .

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