Resin composition

Abstract

Provided is a resin composition capable of yielding a cured product having a high relative permeability, a low loss factor, and excellent chemical resistance. This resin composition comprises: (A) an epoxy resin; (B) a magnetic powder; and (C) an organic filler. If a nonvolatile component in the resin composition is taken as 100 mass% the content of component (B) is Bm. When the content of component (C) is Cm if a nonvolatile component in the resin composition is taken as 100 mass%, Bm / Cm is 50 to 500.

Description

resin composition

[0001] The present invention relates to a resin composition, a method for producing the same, and a cured product, a magnetic sheet, a circuit board, and an inductor board using the resin composition.

[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.

[0004] International Publication No. 2023 / 095466

[0005] In recent years, there has been a demand for further improvement in the inductor performance of inductor-embedded substrates. To improve inductor performance, it is important to improve the magnetic properties of the cured resin composition, i.e., the relative permeability, and to reduce the loss factor. One possible method for improving the magnetic properties of the cured resin composition is to include a large amount of magnetic powder in the resin composition.

[0006] However, magnetic powder is easily dissolved by acid chemicals. Therefore, when a conductor layer is formed by plating on a magnetic layer formed using a resin composition containing a large amount of magnetic powder or a magnetic sheet containing such a resin composition, the magnetic powder is dissolved by the acid chemicals used in the plating process. This can lead to a deterioration in strength and cracking of the magnetic layer and substrate. Hereinafter, resistance to acid chemicals may be referred to as chemical resistance.

[0007] On the other hand, if the content of magnetic powder is reduced to suppress dissolution by the acid chemical solution, the magnetic properties will be deteriorated. Therefore, it is difficult to achieve both improved magnetic properties and improved chemical resistance at the same time.

[0008] The present invention has been made in view of the above circumstances, and aims to provide a resin composition that can give a cured product having a high relative magnetic permeability, a low loss factor, and excellent chemical resistance; a method for producing the same; a cured product of the resin composition; a magnetic sheet containing the resin composition; and a circuit board and an inductor board that contain a cured product of the resin composition.

[0009] The present inventors have conducted extensive research to solve the above-mentioned problems, and as a result, have found that the above-mentioned problems can be solved by incorporating a magnetic powder and an organic filler in a specific ratio, thereby completing the present invention.

[0010] That is, the present invention includes the following: [1] A resin composition containing (A) an epoxy resin, (B) a magnetic powder, and (C) an organic filler, wherein the content of component (B) is B when the nonvolatile components in the resin composition are 100 mass %. ｍ The content of the (C) component when the nonvolatile components in the resin composition are taken as 100% by mass is defined as C ｍ When this is done, B ｍ / C ｍ is 50 or more and 500 or less. [2] The resin composition according to [1], further comprising a dispersant (D). [3] The resin composition according to [2], wherein the component (D) comprises any one of a polyester skeleton, a polyoxyalkylene skeleton, and a phosphate ester skeleton represented by formula (D-1). In formula (D-1), R １１ each independently represents a divalent hydrocarbon group having 2 to 10 carbon atoms which may have a substituent, n １ represents an integer of 2 to 1000. [4] The content of component (C) when the nonvolatile components in the resin composition are 100 mass % is ｍ The content of the (D) component when the nonvolatile components in the resin composition are taken as 100% by mass is defined as D ｍ When this is done, C ｍ / D ｍ The resin composition according to [2] or [3], wherein the component (B) is (B-1)D ５０ Magnetic powder having a particle size of 1 μm or more, and (B-2) D ５０[6] The resin composition according to any one of [1] to [4], which contains magnetic powder having a particle size of less than 1 μm. [6] The content of component (B-1) when the nonvolatile components in the resin composition are 100 mass % is B ｍ１ When the content of the nonvolatile components in the resin composition is 100% by mass, and the content of the component (C) is Cm, B ｍ１ / C ｍ [7] The resin composition according to [5], wherein the content of the (B-2) component when the nonvolatile components in the resin composition are 100% by mass is defined as Bm2, and the content of the (C) component when the nonvolatile components in the resin composition are 100% by mass is defined as Cm, ｍ２ / C ｍ The resin composition according to [5] or [6], wherein D of the whole particles is 5 or more and 100 or less. １０ The resin composition according to any one of [1] to [7], wherein the thickness of the resin composition is 0.1 μm or more and less than 4 μm. [9] The resin composition according to any one of [1] to [8], further comprising (H) an amphiphilic copolymer.

[10] The resin composition according to any one of [1] to [9], wherein the content (volume %) of the (B) component is 50 vol% or more, when the total volume of the nonvolatile components in the resin composition is 100 vol%.

[11] The resin composition according to any one of [1] to

[10] , wherein the content (volume %) of the (C) component is 0.1 vol% or more, when the total volume of the nonvolatile components in the resin composition is 100 vol%.

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

[11] .

[13] A circuit board comprising a substrate having through holes and a cured product of the resin composition according to any one of [1] to

[11] , filled in the through holes.

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

[11] .

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

[13] .

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

[14] .

[17] A method for producing the resin composition according to any one of [1] to

[11] , comprising: (A) an epoxy resin; (B-1) D ５０ Magnetic powder having a particle size of 1 μm or more, (B-2) D ５０(C) an organic filler; and (B) a magnetic powder having a particle size of less than 1 μm. The content of the component (B) is B when the nonvolatile components in the resin composition are taken as 100% by mass. ｍ The content of the (C) component when the nonvolatile components in the resin composition are taken as 100% by mass is defined as C ｍ When this is done, B ｍ / C ｍ is 50 or more and 500 or less.

[0011] According to the present invention, it is possible to provide a resin composition that can give a cured product having a high relative magnetic permeability, a low loss factor, and excellent chemical resistance; a method for producing the same; a cured product of the resin composition; a magnetic sheet containing the resin composition; and a circuit board and an inductor board that contain the cured product of the resin composition.

[0012] FIG. 1 is a cross-sectional view schematically showing a core substrate prepared in a method for manufacturing a circuit board according to a first embodiment of the present invention. FIG. 2 is a cross-sectional view schematically showing a core substrate having through holes formed therein in the method for manufacturing a circuit board according to a first embodiment of the present invention. FIG. 3 is a cross-sectional view schematically showing a core substrate having plating layers formed in the through holes in the method for manufacturing a circuit board according to a first embodiment of the present invention. FIG. 4 is a cross-sectional view schematically showing a state in which a resin composition has been filled into the through holes of the core substrate in the method for manufacturing a circuit board according to a first embodiment of the present invention. FIG. 5 is a cross-sectional view schematically showing step (2) of the method for manufacturing a circuit board according to a first embodiment of the present invention. FIG. 6 is a cross-sectional view schematically showing step (3) of the method for manufacturing a circuit board according to a first embodiment of the present invention. FIG. 7 is a cross-sectional view schematically showing step (5) of the method for manufacturing a circuit board according to a first embodiment of the present invention. FIG. 8 is a cross-sectional view schematically showing step (5) of the method for manufacturing a circuit board according to a first embodiment of the present invention. FIG. 9 is a cross-sectional view schematically showing step (i) of the method for manufacturing a circuit board according to a second embodiment of the present invention. FIG. 10 is a schematic cross-sectional view illustrating step (i) in a method for manufacturing a circuit board according to a second example of one embodiment of the present invention. FIG. 11 is a schematic cross-sectional view illustrating step (ii) in a method for manufacturing a circuit board according to a second example of one embodiment of the present invention. FIG. 12 is a schematic cross-sectional view illustrating step (iv) in a method for manufacturing a circuit board according to a second example of one embodiment of the present invention. FIG. 13 is a schematic plan view of a circuit board included in an inductor substrate, viewed from one side in its thickness direction. FIG. 14 is a schematic view showing a cut end surface of the circuit board cut at the position indicated by the dashed dotted line II-II in FIG. 13. FIG. 15 is a schematic plan view illustrating the configuration of a first conductor layer of a circuit board included in an inductor substrate.

[0013] The present invention will be described in detail below with reference to preferred embodiments thereof. However, the present invention is not limited to the following embodiments and examples, and can be implemented with any modifications within the scope of the claims and their equivalents.

[0014] [Resin Composition] The resin composition of the present invention contains (A) an epoxy resin, (B) a magnetic powder, and (C) an organic filler, and the content of component (B) is B when the nonvolatile components in the resin composition are 100 mass %. ｍ The content of the (C) component when the nonvolatile components in the resin composition are taken as 100% by mass is defined as C ｍ When this is done, B ｍ / C ｍ is 50 or more and 500 or less. By using such a resin composition, it is possible to achieve both improvement in magnetic properties and improvement in chemical resistance.

[0015] The resin composition may further contain optional components such as (D) a dispersant, (E) a curing agent, (F) a thermoplastic resin, (G) a curing accelerator, (H) an amphiphilic copolymer, (I) optional additives, and (J) a solvent, as necessary. Each component that may be contained in the resin composition will be described below.

[0016] <(A) Epoxy Resin> The resin composition contains an epoxy resin (A) as component (A). The epoxy resin (A) typically reacts with heat to form bonds and cure. Therefore, a cured product can be obtained by curing a resin composition containing a combination of components (A) to (C). One type of epoxy resin (A) may be used alone, or two or more types may be used in combination.

[0017] Examples of the epoxy resin (A) include bixylenol type epoxy resins, bisphenol A type epoxy resins, bisphenol F type epoxy resins, bisphenol S type epoxy resins, bisphenol AF type epoxy resins, bisphenol E type epoxy resins, dicyclopentadiene type epoxy resins, trisphenol type epoxy resins, phenol novolac type epoxy resins, glycidyl amine type epoxy resins, glycidyl ester type epoxy resins, cresol novolac type epoxy resins, biphenyl type epoxy resins, linear aliphatic epoxy resins, epoxy resins having a butadiene structure, alicyclic epoxy resins, and alicyclic epoxy resins having an ester skeleton. Examples of epoxy resins include epoxy resins; heterocyclic epoxy resins; spiro ring-containing epoxy resins; cyclohexane-type epoxy resins; cyclohexanedimethanol-type epoxy resins; trimethylol-type epoxy resins; tetraphenylethane-type epoxy resins; epoxy resins containing a condensed ring skeleton such as naphthylene ether-type epoxy resins, tert-butyl-catechol-type epoxy resins, naphthalene-type epoxy resins, naphthol-type epoxy resins, anthracene-type epoxy resins, and naphthol novolac-type epoxy resins; isocyanurate-type epoxy resins; epoxy resins containing an alkyleneoxy skeleton and a butadiene skeleton; and epoxy resins containing a fluorene structure.

[0018] The epoxy resin (A) preferably contains an epoxy resin having two or more epoxy groups per molecule, and the proportion of the epoxy resin having two or more epoxy groups per molecule relative to the total amount (100 mass%) of the epoxy resin (A) is preferably 50 mass% or more, more preferably 60 mass% or more, and even more preferably 70 mass% or more.

[0019] The epoxy resin (A) preferably has an aromatic structure. When two or more types of epoxy resins are used, it is preferred that at least one of the epoxy resins has an aromatic structure. The aromatic structure is a chemical structure generally defined as aromatic, and includes polycyclic aromatic rings and aromatic heterocycles.

[0020] (A) Epoxy resins include epoxy resins that are liquid at a temperature of 20°C (hereinafter sometimes referred to as "liquid epoxy resins") and epoxy resins that are solid at a temperature of 20°C (hereinafter sometimes referred to as "solid epoxy resins"). (A) Epoxy resins may be liquid epoxy resins only, solid epoxy resins only, or a combination of liquid epoxy resins and solid epoxy resins.

[0021] The liquid epoxy resin is preferably a liquid epoxy resin having two or more epoxy groups per molecule.As the liquid epoxy resin, bisphenol A type epoxy resin, bisphenol F type epoxy resin, bisphenol AF type epoxy resin, bisphenol E type epoxy resin, naphthalene type epoxy resin, glycidyl ester type epoxy resin, glycidyl amine type epoxy resin, phenol novolac type epoxy resin, alicyclic epoxy resin having an ester skeleton, cyclohexane type epoxy resin, cyclohexane dimethanol type epoxy resin, epoxy resin having a butadiene structure, epoxy resin containing an alkyleneoxy skeleton and a butadiene skeleton, epoxy resin containing a fluorene structure, and dicyclopentadiene type epoxy resin are preferred.Among these, bisphenol A type epoxy resin and bisphenol F type epoxy resin are particularly preferred.

[0022] Specific examples of liquid epoxy resins include "YX7400" manufactured by Mitsubishi Chemical Corporation; "HP4032", "HP4032D", and "HP4032SS" (naphthalene-type epoxy resins) manufactured by DIC Corporation; "828US", "828EL", "jER828EL", "825", and "Epikote 828EL" (bisphenol A-type epoxy resins) manufactured by Mitsubishi Chemical Corporation; and "jER807" and "1750" (bisphenol F-type epoxy resins) manufactured by Mitsubishi Chemical Corporation. Mitsubishi Chemical Corporation's "jER152" (phenol novolac type epoxy resin); Mitsubishi Chemical Corporation's "630", "630LSD", and "604" (glycidylamine type epoxy resin); ADEKA Corporation's "ED-523T" (glycilol type epoxy resin); ADEKA Corporation's "EP-3950L" and "EP-3980S" (glycidylamine type epoxy resin); ADEKA Corporation's "EP-4088S" (dicyclopentasiloxane type epoxy resin). bisphenol A type 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); "EX-721" manufactured by Nagase ChemteX Corporation (glycidyl ester type epoxy resin); "EX-991L" manufactured by Nagase ChemteX Corporation (an alkyleneoxy skeleton-containing epoxy resin); "Celloxide 2021P" and "Celloxide 2081" manufactured by Daicel Corporation Examples of suitable liquid epoxy resins include "PB-3600" manufactured by Daicel Corporation, "JP-100" and "JP-200" manufactured by Nippon Soda Co., Ltd. (epoxy resins having a butadiene structure); "ZX-1658" and "ZX-1658GS" manufactured by Nippon Steel Chemical & Material Co., Ltd. (liquid 1,4-glycidylcyclohexane-type epoxy resins); "EG-280" manufactured by Osaka Gas Chemicals Co., Ltd. (fluorene structure-containing epoxy resin), and "EPOX MK R710" and "EPOX MK R1710" manufactured by Printec Co., Ltd. (bisphenol E-type epoxy resins). One type of liquid epoxy resin may be used alone, or two or more types may be used in combination.

[0023] The solid epoxy resin is preferably a solid epoxy resin having three or more epoxy groups per molecule, and more preferably an aromatic solid epoxy resin having three or more epoxy groups per molecule.Preferred solid epoxy resins include bixylenol-type epoxy resins, naphthalene-type epoxy resins, 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, bisphenol AF-type epoxy resins, and tetraphenylethane-type epoxy resins.

[0024] Specific examples of solid epoxy resins include "HP4032H" (naphthalene type epoxy resin) manufactured by DIC Corporation; "HP-4700" and "HP-4710" (naphthalene type tetrafunctional epoxy resins) manufactured by DIC Corporation; "N-690" (cresol novolac type epoxy resin) manufactured by DIC Corporation; "N-695" (cresol novolac type epoxy resin) manufactured by DIC Corporation; and "HP-7200", "HP-7200HH", and "HP-7200H" (dicyclopentadiene type epoxy resins) manufactured by DIC Corporation. "EXA-7311", "EXA-7311-G3", "EXA-7311-G4", "EXA-7311-G4S", and "HP6000" (naphthylene ether type epoxy resins) manufactured by DIC Corporation; "EPPN-502H" (trisphenol type epoxy resin) manufactured by Nippon Kayaku Co., Ltd.; "NC7000L" (naphthol novolac type epoxy resin) manufactured by Nippon Kayaku Co., Ltd.; "NC3000H", "NC3000", "NC3000L", and "NC3100" (biphenyl type epoxy resins) manufactured by Nippon Kayaku Co., Ltd. resin); "ESN475V" (naphthol-type epoxy resin) manufactured by Nippon Steel Chemical & Material Co., Ltd.; "ESN485" (naphthol novolac-type epoxy resin) manufactured by Nippon Steel Chemical & Material Co., Ltd.; "YX4000H", "YX4000", and "YL6121" (biphenyl-type epoxy resins) manufactured by Mitsubishi Chemical Corporation; "YX4000HK" (bixylenol-type epoxy resin) manufactured by Mitsubishi Chemical Corporation; "YX8800" (anthracene-type epoxy resin) manufactured by Mitsubishi Chemical Corporation; Examples of the solid epoxy resin include "YX7700" manufactured by Mitsubishi Chemical Corporation (xylene structure-containing novolac type epoxy resin); "PG-100" and "CG-500" manufactured by Osaka Gas Chemicals Co., Ltd.; "YL7760" manufactured by Mitsubishi Chemical Corporation (bisphenol AF type epoxy resin); "YL7800" manufactured by Mitsubishi Chemical Corporation (fluorene type epoxy resin); "jER1010" manufactured by Mitsubishi Chemical Corporation (solid bisphenol A type epoxy resin); and "jER1031S" manufactured by Mitsubishi Chemical Corporation (tetraphenylethane type epoxy resin). One type of solid epoxy resin may be used alone, or two or more types may be used in combination.

[0025] When a liquid epoxy resin and a solid epoxy resin are used in combination as the epoxy resin, the mass ratio of the liquid epoxy resin to the solid epoxy resin (liquid epoxy resin / solid epoxy resin) is preferably 0.5 or more, more preferably 1 or more, even more preferably 5 or more, and particularly preferably 10 or more.

[0026] The epoxy equivalent of the (A) 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. The epoxy equivalent is the mass of a resin containing one equivalent of epoxy groups. This epoxy equivalent can be measured in accordance with JIS K7236.

[0027] The weight average molecular weight (Mw) of the epoxy resin (A) is preferably 100 to 5000, more preferably 250 to 3000, and even more preferably 400 to 1500. The weight average molecular weight of the resin can be measured by gel permeation chromatography (GPC) as a polystyrene-equivalent value.

[0028] The content (mass %) of component (A), when the non-volatile components of the resin composition are taken as 100 mass %, is preferably 0.1 mass % or more, more preferably 0.5 mass % or more, and even more preferably 1 mass % or more, and is preferably 10 mass % or less, more preferably 5 mass % or less, and even more preferably 3 mass % or less.

[0029] The content (mass %) of component (A) is preferably 10 mass % or more, more preferably 15 mass % or more, and even more preferably 20 mass % or more, and is preferably 55 mass % or less, more preferably 50 mass % or less, and even more preferably 45 mass % or less, when the resin component of the resin composition is taken as 100 mass %.

[0030] 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 100 mass %, and the nonvolatile components refer to all components constituting the resin composition other than the solvent described below. Furthermore, the "resin components" of the resin composition refer to all nonvolatile components contained in the resin composition excluding component (B), magnetic powder not corresponding to component (B), and inorganic particles such as inorganic fillers such as silica.

[0031] <(B) Magnetic Powder> The resin composition contains (B) magnetic powder as component (B). By including component (B) in the resin composition, it is possible to improve the relative permeability of the cured product and reduce the loss factor. One type of (B) magnetic powder may be used alone, or two or more types may be used in combination.

[0032] As the (B) magnetic powder, particles of a material having a relative magnetic permeability greater than 1 can be used. The material of the (B) magnetic powder is usually an inorganic material, and may be a soft magnetic material, a hard magnetic material, or a combination of a soft magnetic powder and a hard magnetic powder. In particular, from the viewpoint of significantly obtaining the effects of the present invention, it is preferable that the (B) magnetic powder contains a soft magnetic powder, and it is more preferable that it contains only a soft magnetic powder. Furthermore, the material of the (B) magnetic powder may be used alone or in combination of two or more types.

[0033] (B) Examples of materials contained in the magnetic powder include magnetic metal materials and magnetic metal oxide materials. Among these, magnetic metal materials are preferred in the present invention.

[0034] 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, alloy magnetic materials are more preferred. Here, the term "Fe—Si alloy" refers to a magnetic metal material containing the elements Fe and Si. The same applies to magnetic metal materials containing three or more elements.

[0035] From the viewpoint of significantly achieving the desired effects of the present invention, the alloy magnetic material is preferably an iron alloy magnetic material containing Fe and at least one element selected from the group consisting of Si, Cr, Al, Ni, and Co, and more preferably an Fe—Si—Cr alloy. The Fe—Si—Cr alloy material refers to an alloy containing Fe, Si, and Cr. The same applies to alloy magnetic materials containing three or more elements.

[0036] 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.

[0037] 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.

[0038] As a ferrite-based magnetic material, for example, the term "Fe-Mn-based ferrite" refers to a ferrite containing divalent Fe and Mn as elements. The same applies to ferrites containing three or more elements.

[0039] (B) Magnetic powder D ５０ is preferably 1.6 μm or more, more preferably 2 μm or more, even more preferably 2.5 μm or more, and is preferably 5 μm or less, more preferably 4.5 μm or less, even more preferably 4 μm or less. ５０ represents the average particle size of all the magnetic powder (B) contained in the resin composition, including the components (B-1) and (B-2) described below, and is the value at which the integrated value of the volume-based particle size distribution is 50% when measured using the method described below.

[0040] The particle size of component (B) can be measured by a laser diffraction / scattering method based on Mie scattering theory. Specifically, a particle size distribution of the nanocrystalline magnetic powder is created on a volume basis using a laser diffraction / scattering particle size distribution measuring device, and the particle size can be measured from that particle size distribution. A measurement sample that is preferably used is one in which magnetic powder is dispersed in pure water using ultrasonic waves. Examples of laser diffraction / scattering particle size distribution measuring devices that can be used include the "MT3000II" manufactured by Microtrackbell, the "LA-960" manufactured by Horiba, Ltd., and the "SALD-2200" manufactured by Shimadzu Corporation.

[0041] The particle size distribution of the component (B) on a volume basis usually follows a normal distribution. ５０ Smaller D １０ and D of the component (B). ５０ Bigger D ９０ where D １０ D refers to the so-called 10% particle size, which represents the particle size when the cumulative volume from the small particle size side in the volume-based particle size distribution is 10%. ９０ This refers to the so-called 90% particle size, and represents the particle size when the cumulative volume from the smallest particle size in the volume-based particle size distribution is 90%. １０ and D ９０ can be measured from the particle size distribution on a volume basis measured by the laser diffraction / scattering method. １０ and D ９０ (B) D of magnetic powder ５０Similarly, the D of the entire magnetic powder (B) contained in the resin composition, including the components (B-1) and (B-2) described below. １０ and D ９０ Represents.

[0042] (B) Component D １０ is preferably 0.1 μm or more, more preferably 0.3 μm or more, and even more preferably 0.5 μm or more. ５０ The thickness is preferably 1.5 μm or less, more preferably 1.3 μm or less, and even more preferably 1.2 μm or less.

[0043] (B) Component D ９０ is preferably 3 μm or more, more preferably 3.5 μm or more, and even more preferably 4 μm or more. The upper limit is preferably 10 μm or less, more preferably 8 μm or less, and even more preferably 6 μm or less.

[0044] (B) Component D １０ and D ５０ Difference D ５０ -D １０ is preferably 0.1 μm or more, more preferably 0.5 μm or more, even more preferably 1 μm or more, and is preferably 8 μm or less, more preferably 5 μm or less, even more preferably 3 μm or less.

[0045] (B) Component D ５０ and D ９０ Difference D ９０ -D ５０ is preferably 0.1 μm or more, more preferably 0.5 μm or more, even more preferably 1 μm or more, and is preferably 8 μm or less, more preferably 5 μm or less, even more preferably 3 μm or less.

[0046] (B) Component D １０ and D ９０ Difference D ９０ -D １０ is preferably 1 μm or more, more preferably 2 μm or more, and even more preferably 3 μm or more, and is preferably 10 μm or less, more preferably 8 μm or less, and even more preferably 5 μm or less.

[0047] (B) Component D １０ and D ５０Relative to D ５０ / D １０ is preferably 1.1 or more, more preferably 1.3 or more, even more preferably 1.5 or more, and is preferably 10 or less, more preferably 8 or less, even more preferably 5 or less.

[0048] (B) Component D ５０ and D ９０ Relative to D ９０ / D ５０ is preferably 1.1 or more, more preferably 1.2 or more, and even more preferably 1.3 or more, and is preferably 10 or less, more preferably 8 or less, and even more preferably 5 or less.

[0049] (B) Component D １０ and D ９０ Relative to D ９０ / D １０ is preferably 1.1 or more, more preferably 3 or more, even more preferably 5 or more, and is preferably 20 or less, more preferably 15 or less, even more preferably 10 or less.

[0050] The specific surface area of ​​component (B) is preferably 0.05 m ２ / g or more, more preferably 0.1 m ２ / g or more, more preferably 0.5m ２ / g or more, preferably 20m ２ / g or less, more preferably 10m ２ / g or less, more preferably 5m ２ The specific surface area of ​​component (B) can be measured by the BET method. Specifically, the specific surface area can be measured according to the BET method by adsorbing nitrogen gas onto the surface of a sample using a specific surface area measuring device (Macsorb HM Model 1210 manufactured by Mountech Co., Ltd.) and using the BET multipoint method.

[0051] (B) As the 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", "B" manufactured by Toda Kogyo Co., Ltd. Examples of magnetic powders include "SN-125", "BSN-714", "BSN-828", "S-1281", "S-1641", "S-1651", "S-1470", "S-1511", and "S-2430" manufactured by Japan Metals and Chemical Industries, Ltd., "JR09P2" manufactured by CIK Nanotech Co., Ltd., "Nanotek" manufactured by CIK Nanotech Co., Ltd., "JEMK-S" and "JEMK-H" manufactured by Kinsei Matec Co., Ltd., "Yttrium iron oxide" manufactured by ALDRICH Corporation, and "MA-RCO-5" manufactured by DOWA Electronics Co., Ltd. When component (B) is purchased from the market, commercially available magnetic powder may be classified as necessary.

[0052] (B) The specific gravity of the magnetic powder is, for example, 4 g / cm ３ ~10g / cm ３ It is possible.

[0053] The particles of the (B) magnetic powder are preferably spherical or ellipsoidal. The ratio (aspect ratio) of the length of the major axis of the (B) magnetic powder particle divided by the length of the minor axis is preferably 2 or less, more preferably 1.5 or less, even more preferably 1.2 or less, and is usually 1.0 or more. In general, when the shape of the magnetic powder particle is flat rather than spherical, it is easy to improve the relative permeability. On the other hand, when the shape of the magnetic powder particle is close to spherical, it is easy to lower the loss factor.

[0054] There are no limitations on the method for producing component (B). Component (B) can be produced, for example, by atomization. This atomization method typically involves dropping a bath of molten iron and nickel while spraying high-pressure water or gas onto it to rapidly cool and solidify it, thereby obtaining component (B). Among the atomization methods described above, water atomization, in which water is sprayed onto the dropping bath, is preferred. For example, the method described in JP 2018-178254 A can be used as such an atomization method.

[0055] The component (B) is (B-1)D ５０ Magnetic powder having a particle size of 1 μm or more, and (B-2) D ５０ It is preferable that the resin composition contains magnetic powder having a particle size of less than 1 μm. ５０ Since the component (B-2) can enter the gaps between particles of the component (B-1) which has a large D, a high filling rate of the component (B) is possible, and the relative permeability and loss factor can be improved. ５０ , D １０ , and D ９０ is the D of component (B). ５０ It can be measured in the same manner as above.

[0056] The components (B-1) and (B-2) may be the same material or different materials, as described above.

[0057] D of component (B-1) ５０ is 1 μm or more, preferably 1.5 μm or more, more preferably 2 μm or more, and even more preferably 2.5 μm or more. The upper limit is 30 μm or less, preferably 10 μm or less, more preferably 8 μm or less, and even more preferably 4 μm or less. ５０ This refers to the average particle size of the component (B-1), which is the value at which the integrated value of the particle size distribution on a volume basis becomes 50%. ５０ The measurement method is (B) D of magnetic powder ５０ The measurement method is the same as that of

[0058] D of component (B-1) １０ is preferably 0.5 μm or more, more preferably 1.0 μm or more, and even more preferably 1.5 μm or more. The upper limit is preferably 10 μm or less, more preferably 5 μm or less, and even more preferably 3 μm or less. １０ This refers to the so-called 10% particle size of component (B-1), and represents the particle size when the cumulative volume from the smallest particle size in the volume-based particle size distribution is 10%. １０ The measurement method is (B) D of magnetic powder １０ The measurement method is the same as that of

[0059] D of component (B-1) ９０ is preferably 2.0 μm or more, more preferably 3.0 μm or more, and even more preferably 4.0 μm or more. The upper limit is preferably 50 μm or less, more preferably 30 μm or less, and even more preferably 10 μm or less. ９０ This refers to the 90% particle size of the component (B-1), and represents the particle size when the cumulative volume from the smallest particle size in the volume-based particle size distribution is 90%. ９０ The measurement method is (B) D of magnetic powder ９０ The measurement method is the same as that of

[0060] D of component (B-2) ５０ is less than 1 μm, preferably 0.9 μm or less, more preferably 0.8 μm or less. The lower limit is 0.01 μm or more, more preferably 0.05 μm or more, and even more preferably 0.1 μm or more. ５０ This refers to the average particle size of the component (B-2), which is the value at which the integrated value of the particle size distribution on a volume basis becomes 50%. ５０ The measurement method is (B) D of magnetic powder ５０ The measurement method is the same as that of

[0061] D of component (B-2) １０is preferably 0.05 μm or more, more preferably 0.1 μm or more, and even more preferably 0.3 μm or more. The upper limit is preferably 0.8 μm or less, more preferably 0.6 μm or less, and even more preferably 0.5 μm or less. １０ This refers to the so-called 10% particle size of component (B-2), and represents the particle size when the cumulative volume from the smaller particle size side in the volume-based particle size distribution is 10%. １０ The measurement method is (B) D of magnetic powder １０ The measurement method is the same as that of

[0062] D of component (B-2) ９０ is preferably 0.5 μm or more, more preferably 0.7 μm or more, and even more preferably 1.0 μm or more. The upper limit is preferably 4.0 μm or less, more preferably 3.0 μm or less, and even more preferably 2.0 μm or less. ９０ This refers to the 90% particle size of the component (B-2), and represents the particle size when the cumulative volume from the smaller particle size side in the volume-based particle size distribution is 90%. ９０ The measurement method is (B) D of magnetic powder ９０ The measurement method is the same as that of

[0063] The content (mass%) of the component (B-1), when the total amount of non-volatile components in the resin composition is taken as 100 mass%, is preferably 35 mass% or more, more preferably 45 mass% or more, even more preferably 55 mass% or 65 mass% or more, and is preferably 98 mass% or less, more preferably 95 mass% or less, even more preferably 93 mass% or less.

[0064] The content (vol %) of the component (B-1) is preferably 9 vol % or more, more preferably 11 vol % or more, and even more preferably 13 vol % or more, and is preferably 75 vol % or less, more preferably 70 vol % or less, and even more preferably 60 vol % or less, when the total volume of non-volatile components in the resin composition is 100 vol %.

[0065] The volumetric content (vol %) of each component contained in the resin composition can be calculated from the mass of the component contained in the resin composition. Specifically, the mass is divided by the specific gravity to determine the volume of each component, and the volumetric content (vol %) can be calculated from the volume of each component thus determined.

[0066] The content (mass %) of the component (B-2) is preferably 1 mass % or more, more preferably 5 mass % or more, and even more preferably 8 mass % or more, and is preferably 50 mass % or less, more preferably 45 mass % or less, and even more preferably 40 mass % or less, 35 mass % or less, 30 mass % or less, or 25 mass % or less, when the total amount of non-volatile components in the resin composition is 100 mass %.

[0067] The content (vol %) of the component (B-2) is preferably 1 vol % or more, more preferably 5 vol % or more, and even more preferably 9 vol % or more, and is preferably 25 vol % or less, more preferably 20 vol % or less, and even more preferably 15 vol % or less, when the non-volatile components in the resin composition are taken as 100 vol %.

[0068] The content (mass %) of component (B) is preferably 50 mass % or more, more preferably 60 mass % or more, even more preferably 70 mass % or more, or 80 mass % or more, and is preferably 98 mass % or less, more preferably 95 mass % or less, even more preferably 94 mass % or less, or 93 mass % or less, when the non-volatile components in the resin composition are taken as 100 mass %.

[0069] The content (vol %) of component (B) is preferably 50 vol % or more, more preferably 55 vol % or more, and even more preferably 60 vol % or more, and is preferably 90 vol % or less, more preferably 80 vol % or less, and even more preferably 75 vol % or less, when the non-volatile components in the resin composition are taken as 100 vol %.

[0070] <(C) Organic Filler> The resin composition contains an organic filler (C) as component (C). This organic filler (C) as component (C) does not include any of the aforementioned components (A) and (B). While the inclusion of component (B) in a resin composition can increase the relative magnetic permeability and produce a cured product with a low loss factor, it also makes it difficult to maintain chemical resistance. However, the resin composition of the present invention contains a combination of component (B) and component (C) in a predetermined content ratio, thereby achieving both improved relative magnetic permeability and loss factor, as well as improved chemical resistance. The component (C) may be used alone or in combination of two or more.

[0071] The content (mass %) of component (C) is preferably 0.01 mass % or more, more preferably 0.05 mass % or more, and even more preferably 0.1 mass % or more, and is preferably 5 mass % or less, more preferably 4 mass % or less, and more preferably 3 mass % or less, based on 100 mass % of the non-volatile components in the resin composition.

[0072] The content (mass %) of component (C) is preferably 0.1 mass % or more, more preferably 0.5 mass % or more, and even more preferably 1 mass % or more, and is preferably 30 mass % or less, more preferably 25 mass % or less, and even more preferably 20 mass % or less, when the resin component of the resin composition is taken as 100 mass %.

[0073] The content of component (B) when the nonvolatile components in the resin composition are 100% by mass is defined as B ｍ The content of the (C) component when the nonvolatile components in the resin composition are taken as 100% by mass is defined as C ｍ When this is done, B ｍ / C ｍ is 50 or more, preferably 51 or more, more preferably 55 or more, even more preferably 60 or more, 65 or more, or 70 or more. The upper limit is 500 or less, preferably 480 or less, more preferably 460 or less, and even more preferably 450 or less. By adjusting the contents of components (B) and (C) so that the content ratio of component (B) to component (C) falls within the above range, it is possible to obtain a cured product that has a high relative permeability, a low loss factor, and excellent chemical resistance.

[0074] The content of the (B-1) component when the nonvolatile components in the resin composition are 100% by mass is defined as B ｍ１ When this is done, B ｍ１ / C ｍ is preferably 40 or more, more preferably 41 or more, even more preferably 43 or more, 45 or more, 50 or more, or 60 or more, and is preferably 400 or less, more preferably 380 or less, even more preferably 360 or less.

[0075] The content of the (B-2) component when the nonvolatile components in the resin composition are 100% by mass is B ｍ２ When this is done, B ｍ２ / C ｍ is preferably 5 or more, more preferably 6 or more, even more preferably 8 or more, 10 or more, or 15 or more, and is preferably 100 or less, more preferably 95 or less, even more preferably 93 or less.

[0076] The content (vol %) of component (C) is preferably 0.1 vol % or more, more preferably 0.3 vol % or more, even more preferably 0.5 vol % or more, 0.7 vol % or more, or 2 vol % or more, and is preferably 20 vol % or less, more preferably 15 vol % or less, more preferably 10 vol % or less, and even more preferably 8 vol % or less, assuming that the non-volatile components in the resin composition are 100 vol %.

[0077] The content of component (B) when the nonvolatile components in the resin composition are 100% by volume is defined as B ｖ The content of component (C) when the nonvolatile components in the resin composition are 100% by volume is defined as C ｖ When this is done, B ｖ / C ｖ is preferably 5 or more, more preferably 8 or more, even more preferably 10 or more, and is preferably 100 or less, more preferably 90 or less, even more preferably 80 or less, 70 or less, 60 or less, or 50 or less.

[0078] Component (C) is present in the resin composition in the form of particles. Examples of component (C) include rubber particles, silicone particles, and core-shell rubber particles. From the viewpoint of significantly achieving the desired effects of the present invention, it is preferable to use any of rubber particles, silicone particles, and core-shell rubber particles. From the viewpoint of facilitating uniform dispersion of component (B) in the resin composition, it is more preferable to use core-shell rubber particles.

[0079] Examples of the rubber component contained in the rubber particles include olefin-based thermoplastic elastomers such as polybutadiene, polyisoprene, polychlorobutadiene, ethylene-vinyl acetate copolymer, styrene-butadiene copolymer, styrene-isoprene copolymer, styrene-isobutylene copolymer, acrylonitrile-butadiene copolymer, isoprene-isobutylene copolymer, isobutylene-butadiene copolymer, ethylene-propylene-diene terpolymer, and ethylene-propylene-butene terpolymer; and acrylic-based thermoplastic elastomers such as poly(propyl meth)acrylate, poly(butyl meth)acrylate, poly(cyclohexyl meth)acrylate, and poly(octyl meth)acrylate. Olefin-based thermoplastic elastomers are preferred, and styrene-butadiene copolymers are more preferred. Furthermore, silicone-based rubbers such as polyorganosiloxane rubbers may be mixed into the rubber component. The rubber component contained in the rubber particles has a glass transition temperature of, for example, 0°C or lower, preferably -10°C or lower, more preferably -20°C or lower, and even more preferably -30°C or lower.

[0080] Examples of the silicone material contained in the silicone particles include polysiloxane compounds. Examples of the polysiloxane compounds include polydialkylsiloxanes such as polydimethylsiloxane; polydiarylsiloxanes such as polydiphenylsiloxane; polyalkylarylsiloxanes such as polymethylphenylsiloxane; polydialkyl-diarylsiloxanes such as polydimethyl-diphenylsiloxane; polydialkyl-alkylarylsiloxanes such as polydimethyl-methylphenylsiloxane; and polydiaryl-alkylarylsiloxanes such as polydiphenyl-methylphenylsiloxane. The polysiloxane compound may have a crosslinked structure.

[0081] Examples of commercially available silicone particles include "KMP-600," "KMP-601," "KMP-602," "KMP-605," and "X-52-7030" (silicone rubber particles coated with silicone resin) manufactured by Shin-Etsu Chemical Co., Ltd.; and "KMP-597," "KMP-598," "KMP-594," and "X-52-875" (uncoated silicone rubber particles) manufactured by Shin-Etsu Chemical Co., Ltd.

[0082] The core-shell rubber particles are particulate organic fillers consisting of core particles containing a rubber component as described above and one or more shell layers covering the core particles. Furthermore, the core-shell rubber particles are preferably core-shell graft copolymer particles consisting of core particles containing a rubber component as described above and a shell formed by graft copolymerization of a monomer component copolymerizable with the rubber component contained in the core particles. The term "core-shell" as used herein does not necessarily refer only to particles in which the core particle and the shell portion are clearly distinguishable, but also includes particles in which the boundary between the core particle and the shell portion is unclear, and the core particle does not necessarily have to be completely covered by the shell portion.

[0083] The rubber component is preferably contained in the core-shell graft copolymer particles in an amount of 40% by mass or more, more preferably 50% by mass or more, and even more preferably 60% by mass or more. The upper limit of the rubber component content in the core-shell graft copolymer particles is not particularly limited, but from the viewpoint of sufficiently covering the core particles with the shell portion, it is preferably 95% by mass or less, for example, 90% by mass or less.

[0084] Examples of the monomer component forming the shell portion of the core-shell graft copolymer particles include (meth)acrylic acid esters such as methyl (meth)acrylate, ethyl (meth)acrylate, butyl (meth)acrylate, cyclohexyl (meth)acrylate, octyl (meth)acrylate, and glycidyl (meth)acrylate; (meth)acrylic acid; N-substituted maleimides such as N-methylmaleimide and N-phenylmaleimide; maleimide; α,β-unsaturated carboxylic acids such as maleic acid and itaconic acid; aromatic vinyl compounds such as styrene, 4-vinyltoluene, and α-methylstyrene; and (meth)acrylonitrile, among which (meth)acrylic acid esters are preferred, and methyl (meth)acrylate is more preferred.

[0085] Commercially available core-shell type graft copolymer particles include, for example, "AC3401N" and "Staphyloid AC3816N" manufactured by Aica Kogyo Co., Ltd.; "Metablen SX-006" manufactured by Mitsubishi Chemical Corporation; "CHT" manufactured by Samsung SDI; "B602" manufactured by Techno UMG Co., Ltd.; and "Paraloid EXL2602," "Paraloid EXL2603," "Paraloid EXL2655 (EXL2655)," "Paraloid EXL2311," and "Paraloid EXL231" manufactured by Dow Chemical Japan. 3," "Paraloid EXL2315," "Paraloid KM330," "Paraloid KM336P," "Paraloid KCZ201," "Metablen C-223A," "Metablen E-901," "Metablen S-2001," "Metablen W-450A," and "Metablen SRK-200" manufactured by Mitsubishi Rayon Co., Ltd., and "Kane Ace M-511," "Kane Ace M-600," "Kane Ace M-400," "Kane Ace M-580," and "Kane Ace MR-01" manufactured by Kaneka Corporation.

[0086] The average particle size (average primary particle size) of the core-shell graft copolymer particles is not particularly limited, but is preferably 20 nm or more, more preferably 50 nm or more, even more preferably 80 nm or more, particularly preferably 100 nm or more, and preferably 5,000 nm or less, more preferably 2,000 nm or less, even more preferably 1,000 nm or less, particularly preferably 500 nm or less. The average particle size (average primary particle size) of the core-shell graft copolymer particles can be measured using a zeta potential particle size distribution analyzer or the like.

[0087] (C) Component D ５０ is preferably 20 nm or more, more preferably 50 nm or more, and even more preferably 100 nm or more. The upper limit is preferably 5,000 nm or less, more preferably 1,000 nm or less, and even more preferably 700 nm or less. ５０ This refers to the average particle size of the component (C), which is the value at which the integrated value of the particle size distribution on a volume basis becomes 50%. ５０ The measurement method is (B) D of magnetic powder ５０ The measurement method is the same as that of

[0088] (C) Component D １０ is preferably 5 nm or more, more preferably 10 nm or more, and even more preferably 20 nm or more. The upper limit is preferably 1,000 nm or less, more preferably 700 nm or less, and even more preferably 500 nm or less. １０ This refers to the so-called 10% particle size of component (C), and represents the particle size when the integrated volume accumulated from the smallest particle size side in the volume-based particle size distribution is 10%. １０ The measurement method is (B) D of magnetic powder １０ The measurement method is the same as that of

[0089] (C) Component D ９０ is preferably 50 nm or more, more preferably 100 nm or more, and even more preferably 200 nm or more. The upper limit is preferably 10,000 nm or less, more preferably 7,500 nm or less, and even more preferably 5,000 nm or less. ９０This refers to the so-called 90% particle size of component (C), and represents the particle size when the integrated volume accumulated from the smallest particle size side in the volume-based particle size distribution is 90%. ９０ The measurement method is (B) D of magnetic powder ９０ The measurement method is the same as that of

[0090] D of the whole particle ５０ is preferably 1.6 μm or more, more preferably 2 μm or more, even more preferably 2.5 μm or more, and is preferably 5 μm or less, more preferably 4.5 μm or less, even more preferably 4 μm or less. ５０ "Particles" in "" refers to components that do not dissolve in a solvent, and in addition to components (B) and (C), if the composition contains magnetic powder that does not fall under component (B), or a filler with a relative magnetic permeability of 1 or less, such as an inorganic filler such as silica, the concept also includes the magnetic powder and the inorganic filler. ５０ D is the average particle size of all particles, and is the value at which the integrated value of the particle size distribution on a volume basis becomes 50%. ５０ The measurement method is (B) D of magnetic powder ５０ The measurement method is the same as that of

[0091] D of the whole particle １０ is preferably 0.1 μm or more, more preferably 0.3 μm or more, and even more preferably 0.5 μm or more. ５０ The D of the whole particles is less than 4 μm, preferably 1.5 μm or less, more preferably 1.3 μm or less, and further preferably 1.2 μm or less. １０ D refers to the so-called 10% particle size of all particles, and represents the particle size when the integrated volume accumulated from the small particle size side in the volume-based particle size distribution is 10%. １０ The measurement method is (B) D of magnetic powder １０ The measurement method is the same as that of

[0092] D of the whole particle ９０ is preferably 3 μm or more, more preferably 3.5 μm or more, and even more preferably 4 μm or more. The upper limit is preferably 10 μm or less, more preferably 8 μm or less, and even more preferably 6 μm or less.９０ D refers to the so-called 90% particle size of all particles, and represents the particle size when the integrated volume accumulated from the smallest particle size side in the volume-based particle size distribution is 90%. ９０ The measurement method is (B) D of magnetic powder ９０ The measurement method is the same as that of

[0093] D of the whole particle １０ and D ５０ Difference D ５０ -D １０ is preferably 0.1 μm or more, more preferably 0.5 μm or more, even more preferably 1 μm or more, and is preferably 8 μm or less, more preferably 5 μm or less, even more preferably 3 μm or less.

[0094] D of the whole particle ５０ and D ９０ Difference D ５０ -D １０ is preferably 0.1 μm or more, more preferably 0.5 μm or more, even more preferably 1 μm or more, and is preferably 8 μm or less, more preferably 5 μm or less, even more preferably 3 μm or less.

[0095] D of the whole particle １０ and D ９０ Difference D ９０ -D １０ is preferably 1 μm or more, more preferably 2 μm or more, and even more preferably 3 μm or more, and is preferably 10 μm or less, more preferably 8 μm or less, and even more preferably 5 μm or less.

[0096] D of the whole particle １０ and D ５０ Relative to D ５０ / D １０ is preferably 1 or more, more preferably 2 or more, even more preferably 3 or more, and is preferably 10 or less, more preferably 8 or less, even more preferably 5 or less.

[0097] D of the whole particle ５０ and D ９０ Relative to D ９０ / D ５０is preferably 1.1 or more, more preferably 1.2 or more, and even more preferably 1.3 or more, and is preferably 10 or less, more preferably 8 or less, and even more preferably 5 or less.

[0098] D of the whole particle １０ and D ９０ Relative to D ９０ / D １０ is preferably 1.1 or more, more preferably 1.2 or more, and even more preferably 1.3 or more, and is preferably 10 or less, more preferably 8 or less, and even more preferably 5 or less.

[0099] <(D) Dispersant> The resin composition may contain a (D) dispersant as an optional component in combination with the above-described (A) to (C) components. The (D) dispersant as this (D) component does not include those that fall under the above-described (A) to (C) components. By including the (D) component in the resin composition, it is possible to further improve the relative magnetic permeability. One type of (D) dispersant may be used alone, or two or more types may be used in combination.

[0100] The (D) dispersant may be, for example, one that contains a functional group capable of adsorbing to particles of the (B) magnetic powder, and that disperses the particles of the (B) magnetic powder due to repulsion between the (D) dispersants (e.g., electrostatic repulsion, steric repulsion, etc.) when adsorbed to the (B) magnetic powder. Examples of such (D) dispersants include dispersants containing acidic ionic groups and dispersants containing basic ionic groups.

[0101] The basic ionic group-containing dispersant typically contains a basic ionic group such as a primary, secondary, or tertiary amino group; an ammonium group; an imino group; or a nitrogen-containing heterocyclic group such as pyridine, pyrimidine, pyrazine, imidazole, or triazole. The basic ionic group may be neutralized with an acid such as an organic acid or an inorganic acid. Preferred examples of the basic ionic group-containing dispersant include basic ionic group-containing polymer dispersants containing a polymer chain such as a polyester skeleton represented by formula (D-1) described below.

[0102] The acidic ionic group-containing dispersant usually contains a carboxyl group, a sulfo group (-SO ３H), sulfate group (-OSO ３ H), phosphono group (-PO(OH) ２ ), a phosphonooxy group (—OPO(OH) ２ The acidic ionic group contains an acidic ionic group such as a hydroxyphosphoryl group (-PO(OH)), a sulfanyl group (-SH), or the like. The acidic ionic group usually has a dissociable proton, and may be neutralized with a base such as an amine or a hydroxide ion. Preferred examples of the acidic ionic group-containing dispersant include dispersants having a polyoxyalkylene skeleton, which will be described later, dispersants having a phosphate ester skeleton, which will be described later, and acidic ionic group-containing polymer dispersants containing a polymer chain such as a polyether chain.

[0103] From the viewpoint of significantly achieving the effects of the present invention, the dispersant (D) preferably contains any one of a polyester skeleton, a polyoxyalkylene skeleton, and a phosphate skeleton represented by the following formula (D-1): In formula (D-1), R １１ each independently represents a divalent hydrocarbon group having 2 to 10 carbon atoms which may have a substituent, n １ represents an integer of 2 to 1000.

[0104] R in formula (D-1) １１ each independently represents a divalent hydrocarbon group having 2 to 10 carbon atoms. The divalent 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 divalent hydrocarbon groups being preferred. Examples of divalent hydrocarbon groups include aliphatic hydrocarbon groups and aromatic hydrocarbon groups, with aliphatic hydrocarbon groups being preferred. The divalent hydrocarbon group may be either a divalent saturated hydrocarbon group or a divalent unsaturated hydrocarbon group, with divalent saturated hydrocarbon groups being preferred. Specific examples of divalent hydrocarbon groups include alkylene groups, alkenylene groups, alkynylene groups, and arylene groups. Of these, alkylene groups are particularly preferred as divalent hydrocarbon groups.

[0105] 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 for R.

[0106] R in formula (D-1) １１ The divalent hydrocarbon group represented by may or may not have a substituent. The substituent is not particularly limited, and examples thereof include a halogen atom, —OH, —O—C １－６ alkyl group, —N(C １－１０ alkyl group) ２ , C １－１０ Alkyl group, C ６－１０ Aryl group, —NH ２ , -CN, -C(O)OC １－１０ Alkyl group, —COOH, —C(O)H, —NO ２ Here, "C ｐ－ｑ The term "(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 The expression "alkyl group" refers to an alkyl group having 1 to 10 carbon atoms. These substituents may be bonded to each other to form a ring, and ring structures include spiro rings and fused rings.

[0107] The above-mentioned substituents may further have a substituent (hereinafter, sometimes referred to as a "secondary substituent"). Unless otherwise specified, the secondary substituent may be the same as the above-mentioned substituent.

[0108] n in formula (D-1) １ represents an integer of 2 to 1000. １is 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.

[0109] The polyoxyalkylene skeleton is —O—(CH ２ ) ｎ In the formula, n is preferably 10 or less, more preferably 6 or less, and even more preferably 3 or less, and is preferably 1 or more, and more preferably 2 or more.

[0110] Examples of dispersants having a polyoxyalkylene skeleton in component (D) include polyoxyethylene alkyl ethers, polyoxyethylene alkyl esters, polyoxyethylene sorbitan fatty acid esters, polyoxyethylene alkyl phenyl ethers, polyoxyethylene alkyl amines, and polyoxyethylene alkyl amides.

[0111] The phosphate ester skeleton refers to a structure in which one or more of the three hydrogen atoms of phosphoric acid are substituted with an organic group. As the dispersant having a phosphate ester skeleton in component (D), for example, a dispersant having a polyether-type phosphate ester structure is preferred. The dispersant having a polyether-type phosphate ester structure is a dispersant having a phosphate ester structure containing a poly(alkyleneoxy) structure in the molecule. Examples of dispersants having a polyether-type phosphate ester structure include polyoxyalkylene alkyl ether phosphate esters and polyoxyalkylene alkylphenyl ether phosphate esters.

[0112] The polyester skeleton, polyoxyalkylene skeleton, and phosphate skeleton represented by formula (D-1) may be present as a main chain or as a side chain, but from the viewpoint of achieving the remarkable effects of the present invention, it is preferable that they be present as a side chain. Furthermore, the polyester skeleton, polyoxyalkylene skeleton, and phosphate skeleton represented by formula (D-1) may have either a basic ionic group or an acidic ionic group. In particular, from the viewpoint of achieving the remarkable effects of the present invention, it is preferable that the polyoxyalkylene skeleton has an acidic ionic group. The basic ionic group and the acidic ionic group are as described above.

[0113] The component (D) may contain an optional skeleton in addition to any one of the polyester skeleton, polyoxyalkylene skeleton, and phosphate skeleton represented by formula (D-1), as long as the effects of the present invention are not impaired. Examples of the optional skeleton include a structural unit derived from polymaleic acid; a polystyrene structural unit; and an amine skeleton such as a structural unit derived from polyallylamine or a structural unit derived from polyvinylamine. When the component (D) has an optional skeleton, it is preferable that the optional skeleton is any one of a block copolymer, a random copolymer, an alternating copolymer, and a graft copolymer with any one of the polyester skeleton, polyoxyalkylene skeleton, and phosphate skeleton represented by formula (D-1).

[0114] Examples of the terminal group of component (D) include a carboxylic acid residue, an alkoxy group, a hydroxy group, and a hydrogen atom.

[0115] The pH of component (D) can usually be 4 or more and less than 7. The pH can be measured by an indicator method. Specifically, the pH can be measured by immersing a measurement sample (22°C) prepared by dissolving the dispersant in acetone and having a dispersant concentration of 0.1 g / mL into a pH test paper. As the pH test paper, a pH test paper capable of measuring pH in the acidic range (for example, a pH test paper with a measurement range of pH 0.0 to 14.0, pH 1.0 to 14.0, or pH 0.5 to 5.0) can be used, 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.

[0116] The component (D) may have an acid value within a specific range. From the viewpoint of significantly achieving the effects of the present invention, the acid value of the component (D) is preferably 1 mgKOH / g or more, more preferably 5 mgKOH / g or more, even more preferably 10 mgKOH / g, 20 mgKOH / g, or 30 mgKOH / g, and is preferably 100 mgKOH / g or less, more preferably 90 mgKOH / g or less, even more preferably 80 mgKOH / g or less. The acid value can be measured by neutralization titration.

[0117] Component (D) may have an amine value within a specific range. The amine value of component (D) is preferably 1 mgKOH / g or more, more preferably 5 mgKOH / g or more, and even more preferably 10 mgKOH / g or more, and is preferably 45 mgKOH / g or less, more preferably 40 mgKOH / g or less, and even more preferably 35 mgKOH / g or less. The amine value can be measured by neutralization titration.

[0118] The weight average molecular weight of component (D) is preferably at least 1,000, more preferably at least 1,500, and even more preferably at least 2,000, and is preferably at most 50,000, more preferably at most 40,000, and even more preferably at most 30,000. The weight average molecular weight is the weight molecular weight in terms of polystyrene measured by gel permeation chromatography (GPC).

[0119] The component (D) having a polyester skeleton represented by formula (D-1) can be produced, for example, by the method described in JP-A-2022-064864.

[0120] Component (D) can be a commercially available product, such as "SC-1015F" manufactured by NOF Corporation, "PB-821" and "PB-881" manufactured by Ajinomoto Fine-Techno Co., Inc., and "ED-152" and "ED400" manufactured by Kusumoto Chemicals Co., Ltd.

[0121] The content (mass %) of component (D) is preferably 0.01 mass % or more, more preferably 0.05 mass % or more, and even more preferably 0.1 mass % or more, based on 100 mass % of the non-volatile components in the resin composition. The upper limit is preferably 5 mass % or less, more preferably 1 mass % or less, and even more preferably 0.5 mass % or less.

[0122] The content (mass %) of component (D) is preferably 0.1 mass % or more, more preferably 0.5 mass % or more, and even more preferably 0.8 mass % or more, when the resin component of the resin composition is taken as 100 mass %, and is preferably 10 mass % or less, more preferably 5 mass % or less, and even more preferably 3 mass % or less.

[0123] The content of component (D) when the nonvolatile components in the resin composition are 100% by mass is D ｍ The content of the (C) component when the nonvolatile components in the resin composition are taken as 100% by mass is defined as C ｍ When this is done, C ｍ / D ｍ is preferably 1 or more, more preferably 3 or more, and even more preferably 5 or more. The upper limit is preferably 12 or less, more preferably 10 or less, and even more preferably 9 or less.

[0124] <(E) Curing Agent> The resin composition may further contain a (E) curing agent as an optional component in combination with the above-described components (A) to (D). The (E) curing agent has the function of curing the (A) epoxy resin. The (E) curing agent as component (E) does not include those corresponding to the above-described components (A) to (D). The (E) curing agent may be used alone, or two or more types may be used in combination.

[0125] Examples of the (E) curing agent include phenol-based curing agents, active ester-based curing agents, amine-based curing agents, carbodiimide-based curing agents, acid anhydride-based curing agents, benzoxazine-based curing agents, cyanate ester-based curing agents, thiol-based curing agents, etc. The (E) curing agent is preferably at least one selected from phenol-based epoxy resin curing agents and naphthol-based curing agents.

[0126] As the phenolic curing agent, a resin having one or more, preferably two or more, hydroxyl groups bonded to an aromatic ring such as a benzene ring or a naphthalene ring per molecule can be used. From the viewpoint of heat resistance and water resistance, a phenolic curing agent having a novolac structure is preferred. From the viewpoint of adhesion, a nitrogen-containing phenolic curing agent is preferred, and a triazine skeleton-containing phenolic curing agent is more preferred. Among them, from the viewpoint of highly satisfying heat resistance, water resistance, and adhesion, a triazine skeleton-containing phenolic novolac resin is preferred.

[0127] Specific examples of phenol-based curing agents include "MEH-7700", "MEH-7810", "MEH-7851", and "MEH-8000H" manufactured by Meiwa Chemical Industry Co., Ltd.; "NHN", "CBN", and "GPH" manufactured by Nippon Kayaku Co., Ltd.; and "SN-170", "SN-180", "SN-190", "SN-475", "SN-485", "SN-495", "SN-495V", "SN-375", and "SN-375V" manufactured by Nippon Steel Chemical & Material Co., Ltd. N-395"; "TD-2090", "TD-2090-60M", "LA-7052", "LA-7054", "LA-1356", "LA-3018", "LA-3018-50P", "EXB-9500", "HPC-9500", "KA-1160", "KA-1163", and "KA-1165" manufactured by DIC Corporation; and "GDP-6115L", "GDP-6115H", and "ELPC75" manufactured by Gun-ei Chemical Co., Ltd.

[0128] As the active ester curing agent, a compound having one or more, preferably two or more, active ester groups per molecule can be used. Among these, preferred active ester curing agents are 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. The active ester curing agent is preferably one obtained by a condensation reaction between a carboxylic acid compound and / or a thiocarboxylic acid compound and a hydroxy compound and / or a thiol compound. In particular, from the viewpoint of improving heat resistance, active ester curing agents obtained from a carboxylic acid compound and a hydroxy compound are preferred, and active ester 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, phenol novolak, etc. Here, "dicyclopentadiene-type diphenol compounds" refers to diphenol compounds obtained by condensing one dicyclopentadiene molecule with two phenol molecules.

[0129] Specific preferred examples of the active ester curing agent include active ester curing agents containing a dicyclopentadiene-type diphenol structure, active ester curing agents containing a naphthalene structure, active ester curing agents containing an acetylated product of phenol novolac, and active ester curing agents containing a benzoylated product of phenol novolac. Among these, active ester curing agents containing a naphthalene structure and active ester curing agents containing a dicyclopentadiene-type diphenol structure are more preferred. The "dicyclopentadiene-type diphenol structure" refers to a divalent structural unit consisting of phenylene-dicyclopentylene-phenylene.

[0130] Commercially available active ester curing agents include "EXB9451", "EXB9460", "EXB9460S", "HPC-8000L-65TM", "HPC-8000-65T", "EXB-8000H", and "EXB-8000L-65TM" (manufactured by DIC Corporation) as active ester curing agents containing a dicyclopentadiene-type diphenol structure; and "EXB-9416-70BK", "EXB-8100L-65T", "HPC-8150-62T", "EXB-8150L-65T", "EXB-8100L-65T", and "EXB-8" (manufactured by DIC Corporation) as active ester curing agents containing a naphthalene structure. Examples of such curing agents include "EXB9401" (manufactured by DIC Corporation) as a phosphorus-containing active ester curing agent, "DC808" (manufactured by Mitsubishi Chemical Corporation) as an active ester curing agent containing an acetylated product of phenol novolac, "YLH1026," "YLH1030," and "YLH1048" (manufactured by Mitsubishi Chemical Corporation) and "EXB-8500-65T" (manufactured by DIC Corporation) as active ester curing agents containing a benzoylated product of phenol novolac, and "PC1300-02-65T" and "PC1300-02-65MA" (manufactured by Air Water Inc.) as active ester curing agents containing a styryl group and a naphthalene structure.

[0131] As the amine-based curing agent, a resin having one or more, preferably two or more, amino groups per molecule can be used. Examples of the amine-based curing agent include aliphatic amines, polyether amines, alicyclic amines, and aromatic amines. Among these, aromatic amines are preferred. The amine-based curing agent is preferably a primary amine or a secondary amine, and more preferably a primary amine. Specific examples of the amine-based curing agent include 4,4'-methylenebis(2,6-dimethylaniline), diphenyldiaminosulfone, 4,4'-diaminodiphenylmethane, 4,4'-diaminodiphenylsulfone, 3,3'-diaminodiphenylsulfone, m-phenylenediamine, m-xylylenediamine, diethyltoluenediamine, 4,4'-diaminodiphenyl ether, 3,3'-dimethyl-4,4'-diaminobiphenyl, 2,2'-dimethyl-4,4'-diaminobiphenyl, 3,3'-dihydroxybenzidine, 2,2-bis(3-amino-4-hydroxybenzidine), and 2,2-bis(3-amino-4-hydroxybenzidine). bis(4-aminophenoxy)biphenyl)propane, 3,3-dimethyl-5,5-diethyl-4,4-diphenylmethanediamine, 2,2-bis(4-aminophenyl)propane, 2,2-bis(4-(4-aminophenoxy)phenyl)propane, 1,3-bis(3-aminophenoxy)benzene, 1,3-bis(4-aminophenoxy)benzene, 1,4-bis(4-aminophenoxy)benzene, 4,4'-bis(4-aminophenoxy)biphenyl, bis(4-(4-aminophenoxy)phenyl)sulfone, bis(4-(3-aminophenoxy)phenyl)sulfone, and the like. Commercially available amine-based curing agents may be used, and examples thereof include "KAYABOND C-200S," "KAYABOND C-100," "KAYAHARD A-A," "KAYAHARD A-B," and "KAYAHARD A-S" manufactured by Nippon Kayaku Co., Ltd., and "Epicure W" manufactured by Mitsubishi Chemical Corporation.

[0132] As the carbodiimide curing agent, a resin having one or more, preferably two or more, carbodiimide structures in one molecule can be used. Specific examples of the carbodiimide curing agent include aliphatic biscarbodiimides such as tetramethylene-bis(t-butylcarbodiimide) and cyclohexanebis(methylene-t-butylcarbodiimide); aromatic biscarbodiimides such as phenylene-bis(xylylcarbodiimide); aliphatic polycarbodiimides such as polyhexamethylenecarbodiimide, polytrimethylhexamethylenecarbodiimide, polycyclohexylenecarbodiimide, poly(methylenebiscyclohexylenecarbodiimide), and poly(isophoronecarbodiimide); poly(phenylenecarbodiimide), poly(

[0039] Examples of polycarbodiimides include aromatic polycarbodiimides such as poly(naphthylenecarbodiimide), poly(tolylenecarbodiimide), poly(methyldiisopropylphenylenecarbodiimide), poly(triethylphenylenecarbodiimide), poly(diethylphenylenecarbodiimide), poly(triisopropylphenylenecarbodiimide), poly(diisopropylphenylenecarbodiimide), poly(xylylenecarbodiimide), poly(tetramethylxylylenecarbodiimide), poly(methylenediphenylenecarbodiimide), and poly[methylenebis(methylphenylene)carbodiimide]. Commercially available carbodiimide curing agents include, for example, "Carbodilite V-02B," "Carbodilite V-03," "Carbodilite V-04K," "Carbodilite V-07," and "Carbodilite V-09," manufactured by Nisshinbo Chemical Inc.; and "Stavaxol P," "Stavaxol P400," and "Hykasil 510," manufactured by Lanxess AG.

[0133] As the acid anhydride curing agent, a resin having one or more acid anhydride groups per molecule can be used, and a resin having two or more acid anhydride groups per molecule is preferred. Specific examples of the acid anhydride curing agent 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, and benzophenonetetracarboxylic dianhydride. anhydride, biphenyltetracarboxylic dianhydride, naphthalenetetracarboxylic dianhydride, oxydiphthalic dianhydride, 3,3'-4,4'-diphenylsulfonetetracarboxylic 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), polymeric acid anhydrides such as styrene-maleic acid resins in which styrene and maleic acid are copolymerized, and the like. Examples of commercially available acid anhydride curing agents include "HNA-100", "MH-700", "MTA-15", "DDSA", and "OSA" manufactured by New Japan Chemical Co., Ltd.; "YH-306" and "YH-307" manufactured by Mitsubishi Chemical Corporation; "HN-2200" and "HN-5500" manufactured by Resonac Corporation; and "EF-30", "EF-40", "EF-60", and "EF-80" manufactured by Clay Valley Corporation.

[0134] Specific examples of benzoxazine-based curing agents include "JBZ-OD100", "JBZ-OP100D", and "ODA-BOZ" manufactured by JFE Chemical Corporation; "P-d" and "F-a" manufactured by Shikoku Chemicals Corporation; and "HFB2006M" manufactured by Showa Polymer Co., Ltd.

[0135] Examples of cyanate ester 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-cyanatephenylmethane), bis(4-cyanate-3,5-dimethylphenyl)methane, 1,3-bis(4-cyanatephenyl-1-(methylethylidene))benzene, bis(4-cyanatephenyl)thioether, and bis(4-cyanatephenyl)ether; polyfunctional cyanate resins derived from phenol novolac and cresol novolac; and prepolymers in which these cyanate resins are partially triazine converted. Specific examples of cyanate ester curing agents include "PT30" and "PT60" (phenol novolac type multifunctional cyanate ester resins), "ULL-950S" (multifunctional cyanate ester resin), "BA230" and "BA230S75" (prepolymers in which part or all of bisphenol A dicyanate has been triazinated to form a trimer), all of which are manufactured by Arxada.

[0136] Examples of thiol-based curing agents include trimethylolpropane tris(3-mercaptopropionate), pentaerythritol tetrakis(3-mercaptobutyrate), and tris(3-mercaptopropyl)isocyanurate.

[0137] The active group equivalent of the (E) curing agent is preferably 50 g / eq. to 3000 g / eq., more preferably 100 g / eq. to 1000 g / eq., even more preferably 100 g / eq. to 500 g / eq., and particularly preferably 100 g / eq. to 300 g / eq. The active group equivalent represents the mass of the (E) curing agent per equivalent of the active group.

[0138] When the number of epoxy groups in the (A) epoxy resin is taken as 1, the number of active groups in the (E) curing agent is preferably 0.01 or more, more preferably 0.1 or more, particularly preferably 0.5 or more, and preferably 10 or less, more preferably 5 or less, particularly preferably 3 or less. The active groups in the (E) curing agent are active hydroxyl groups, etc., and vary depending on the type of curing agent. The number of epoxy groups in the (A) epoxy resin is the total value for all epoxy resins obtained by dividing the mass of the nonvolatile components of each epoxy resin by the epoxy equivalent. The number of active groups in the (E) curing agent is the total value for all curing agents obtained by dividing the mass of the nonvolatile components of each curing agent by the active group equivalent.

[0139] The content (mass%) of the (E) curing agent, when the total amount of non-volatile components in the resin composition is taken as 100 mass%, is preferably 0.1 mass% or more, more preferably 0.5 mass% or more, and even more preferably 1 mass% or more, and the upper limit is preferably 5 mass% or less, more preferably 4 mass% or less, and even more preferably 3 mass% or less.

[0140] The content (mass %) of the (E) curing agent, when the resin component of the resin composition is taken as 100 mass %, is preferably 25 mass % or more, more preferably 30 mass % or more, even more preferably 35 mass % or more, and is preferably 50 mass % or less, more preferably 45 mass % or less, even more preferably 40 mass % or less.

[0141] <(F) Thermoplastic Resin> The resin composition may further contain a (F) thermoplastic resin as an optional component in combination with the above-described (A) to (E) components. The (F) thermoplastic resin as the (F) component does not include those corresponding to the above-described (A) to (E) components. By including the (F) thermoplastic resin in the resin composition, the film-forming properties of the magnetic sheet can be further improved. The (F) thermoplastic resin may be used alone or in combination of two or more types.

[0142] Examples of the thermoplastic resin (F) include phenoxy resin, polyimide resin, polyvinyl acetal resin, polyolefin resin, polybutadiene resin, polyamideimide resin, polyetherimide resin, polysulfone resin, polyethersulfone resin, polyphenylene ether resin, polycarbonate resin, polyetheretherketone resin, and polyester resin, with phenoxy resin being preferred.

[0143] Examples of the phenoxy resin 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 Chemical & Material Co., Ltd.; and "YL7500BH30," "YX6954BH30," "YX7553," "YX7553BH30," "YL7769BH30," "YL6794," "YL7213," "YL7290," "YL7482," and "YL7891BH30" manufactured by Mitsubishi Chemical Corporation.

[0144] 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).

[0145] 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 the 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.

[0146] 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.

[0147] 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.

[0148] 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 Resonac Corporation.

[0149] A specific example of the polyethersulfone resin is "PES5003P" manufactured by Sumitomo Chemical Co., Ltd.

[0150] Specific examples of polysulfone resins include polysulfones "P1700" and "P3500" manufactured by Solvay Advanced Polymers.

[0151] 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.

[0152] Examples of polycarbonate resins include hydroxy group-containing carbonate resins, phenolic hydroxy group-containing carbonate resins, carboxy 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 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.

[0153] 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.

[0154] The weight average molecular weight (Mw) of the thermoplastic resin (F) is preferably greater than 5,000, more preferably at least 8,000, even more preferably at least 10,000, and particularly preferably at least 20,000. There is no particular upper limit, and it can be, for example, 1,000,000 or less, 500,000 or less, or 100,000 or less.

[0155] The content (mass%) of the (F) thermoplastic resin, when the non-volatile components of the resin composition are taken as 100 mass%, is preferably 0.1 mass% or more, more preferably 0.3 mass% or more, particularly preferably 0.5 mass% or more, and is preferably 5 mass% or less, more preferably 3 mass% or less, and even more preferably 2 mass% or less.

[0156] The content (mass %) of the (F) thermoplastic resin, when the resin component of the resin composition is taken as 100 mass %, is preferably 1 mass % or more, more preferably 3 mass % or more, even more preferably 5 mass % or more, and is preferably 35 mass % or less, more preferably 30 mass % or less, even more preferably 25 mass % or less.

[0157] <(G) Curing Accelerator> The resin composition may further contain a (G) curing accelerator as an optional component in combination with the above-described components (A) to (F). The (G) curing accelerator as component (G) does not include those corresponding to the above-described components (A) to (F). The (G) curing accelerator functions as a catalyst for the reaction of the (A) epoxy resin, and therefore can accelerate the curing of the resin composition. One type of (G) curing accelerator may be used alone, or two or more types may be used in combination.

[0158] Examples of the (G) curing accelerator include phosphorus-based curing accelerators, imidazole-based curing accelerators, amine-based curing accelerators, guanidine-based curing accelerators, metal-based curing accelerators, and urea-based curing accelerators. One type of (G) curing accelerator may be used alone, or two or more types may be used in combination. Among these, imidazole-based curing accelerators are preferred as the (G) curing accelerator.

[0159] Examples of the phosphorus-based curing accelerator include phosphonium salts and phosphines. Examples of the phosphonium salt include aliphatic phosphonium salts such as tetrabutylphosphonium bromide, tetrabutylphosphonium chloride, tetrabutylphosphonium acetate, tetrabutylphosphonium decanoate, tetrabutylphosphonium laurate, n-butylphosphonium tetraphenylborate, bis(tetrabutylphosphonium)pyromellitate, tetrabutylphosphonium hydrogenhexahydrophthalate, tetrabutylphosphonium 2,6-bis[(2-hydroxy-5-methylphenyl)methyl]-4-methylphenolate, and di-tert-butylmethylphosphonium tetraphenylborate; methyltriphenylphosphonium bromide, ethyltriphenylphosphonium bromide, and propyltriphenylphosphonium. bromide, butyltriphenylphosphonium bromide, benzyltriphenylphosphonium chloride, tetraphenylphosphonium bromide, p-tolyltriphenylphosphonium tetra-p-tolylborate, tetraphenylphosphonium tetraphenylborate, tetraphenylphosphonium tetra-p-tolylborate, triphenylethylphosphonium tetraphenylborate, tris(3-methylphenyl)ethylphosphonium tetraphenylborate, tris(2-methoxyphenyl)ethylphosphonium tetraphenylborate, (4-methylphenyl)triphenylphosphonium thiocyanate, tetraphenylphosphonium thiocyanate, and aromatic phosphonium salts such as butyltriphenylphosphonium thiocyanate.

[0160] Examples of phosphines include aliphatic phosphines such as tributylphosphine, tri-tert-butylphosphine, trioctylphosphine, di-tert-butyl(2-butenyl)phosphine, di-tert-butyl(3-methyl-2-butenyl)phosphine, and tricyclohexylphosphine; dibutylphenylphosphine, di-tert-butylphenylphosphine, methyldiphenylphosphine, ethyldiphenylphosphine, butyldiphenylphosphine, diphenylcyclohexylphosphine, triphenylphosphine, tri-o-tolylphosphine, tri-m-tolylphosphine, tri-p-tolylphosphine, tris(4-ethylphenyl)phosphine, tris(4-propylphenyl)phosphine, tris(4-isopropylphenyl)phosphine, tris(4-butylphenyl)phosphine, tris(4-tert-butylphenyl)phosphine, tris(2,4-dimethylphenyl)phosphine, and tris(2,5-dimethylphenyl)phosphine. tris(2,6-dimethylphenyl)phosphine, tris(3,5-dimethylphenyl)phosphine, tris(2,4,6-trimethylphenyl)phosphine, tris(2,6-dimethyl-4-ethoxyphenyl)phosphine, tris(2-methoxyphenyl)phosphine, tris(4-methoxyphenyl)phosphine, tris(4-ethoxyphenyl)phosphine, tris(4-tert-butoxyphenyl)phosphine, diphenyl-2-pyridylphosphine, 1,2- Examples thereof include aromatic phosphines such as bis(diphenylphosphino)ethane, 1,3-bis(diphenylphosphino)propane, 1,4-bis(diphenylphosphino)butane, 1,2-bis(diphenylphosphino)acetylene, and 2,2′-bis(diphenylphosphino)diphenyl ether; aromatic phosphine-borane complexes such as triphenylphosphine-triphenylborane; and aromatic phosphine-quinone addition products such as triphenylphosphine-p-benzoquinone addition products.

[0161] As the phosphorus-based curing accelerator, commercially available products may be used, for example, "TBP-DA" manufactured by Hokko Chemical Industry Co., Ltd.

[0162] Examples of the imidazole curing accelerator 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-phenylimidazole. 1-cyanoethyl-2-methylimidazole, 1-cyanoethyl-2-undecylimidazole, 1-cyanoethyl-2-ethyl-4-methylimidazole, 1-cyanoethyl-2-phenylimidazole, 1-cyanoethyl-2-undecylimidazolium 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-phenyl-4,5-dihydroxymethylimidazole,

[0039] Examples of the imidazole compound include imidazole compounds such as 2-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.As the imidazole-based curing accelerator, commercially available products may be used, and examples thereof include "P200-H50" manufactured by Mitsubishi Chemical Corporation; and "Curezol 2MZ", "2E4MZ", "Cl1Z", "Cl1Z-CN", "Cl1Z-CNS", "Cl1Z-A", "2MZ-OK", "2MA-OK", "2MA-OK-PW", "2MZA-PW", "2PHZ", "2PHZ-PW", "1B2PZ", and "1B2PZ-10M" manufactured by Shikoku Chemicals Corporation.

[0163] Examples of the amine curing accelerator include trialkylamines such as triethylamine and tributylamine, 4-dimethylaminopyridine, benzyldimethylamine, 2,4,6-tris(dimethylaminomethyl)phenol, 1,8-diazabicyclo(5,4,0)-undecene, 1,8-diazabicyclo[5,4,0]undecene-7,4-dimethylaminopyridine, and 2,4,6-tris(dimethylaminomethyl)phenol, with 4-dimethylaminopyridine being preferred. Commercially available amine curing accelerators may be used, such as "PN-50," "PN-23," and "MY-25" manufactured by Ajinomoto Fine-Techno Co., Inc.

[0164] Examples of guanidine 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.

[0165] 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.

[0166] Examples of the urea-based curing accelerator include 1,1-dimethylurea; aliphatic dimethylureas such as 1,1,3-trimethylurea, 3-ethyl-1,1-dimethylurea, 3-cyclohexyl-1,1-dimethylurea, and 3-cyclooctyl-1,1-dimethylurea; 3-phenyl-1,1-dimethylurea, 3-(4-chlorophenyl)-1,1-dimethylurea, 3-(3,4-dichlorophenyl)-1,1-dimethylurea, 3-(3-chloro-4-methylphenyl)-1,1-dimethylurea, 3-(2-methylphenyl)-1,1-dimethylurea, 3-(4-methylphenyl)-1,1-dimethylurea, and 3-(3,4-dimethylphenyl)-1,1-dimethylurea. aromatic dimethylureas such as N,N-(1,4-phenylene)bis(N',N'-dimethylurea), N,N-(4-methyl-1,3-phenylene)bis(N',N'-dimethylurea) [toluene bisdimethylurea], and the like.

[0167] The content (mass%) of the (G) curing accelerator, when the non-volatile components of the resin composition are taken as 100 mass%, is preferably 0.001 mass% or more, more preferably 0.005 mass% or more, even more preferably 0.01 mass% or more, and is preferably 3 mass% or less, more preferably 2 mass% or less, particularly preferably 1 mass% or less.

[0168] The content (mass%) of the (G) curing accelerator, when the resin component of the resin composition is taken as 100 mass%, is preferably 0.05 mass% or more, more preferably 0.1 mass% or more, even more preferably 0.2 mass% or more, and is preferably 5 mass% or less, more preferably 1.5 mass% or less, even more preferably 1 mass% or less.

[0169] <(H) Amphiphilic Copolymer> The resin composition may further contain an amphiphilic copolymer (H) as an optional component in combination with the above-described components (A) to (G). The amphiphilic copolymer (H) as component (H) does not include components (A) to (G). By including an amphiphilic copolymer (H) in the resin composition, the relative magnetic permeability of the cured resin composition can be improved. The amphiphilic copolymer (H) may be used alone or in combination of two or more types. Herein, the term "amphiphilic copolymer" refers to a block copolymer containing at least one epoxy resin-miscible polyether block segment and at least one epoxy resin-immiscible polyether block segment.

[0170] Examples of epoxy resin-compatible polyether block segments include those derived from alkylene oxides. The epoxy resin-compatible polyether block segments derived from alkylene oxides are preferably one or more polyalkylene oxide blocks selected from polyethylene oxide blocks, polypropylene oxide blocks, poly(ethylene oxide-co-propylene oxide) blocks, poly(ethylene oxide-ran-propylene oxide) blocks, and mixtures thereof, more preferably polyethylene oxide blocks or polypropylene oxide blocks, and even more preferably polyethylene oxide blocks or polypropylene oxide blocks.

[0171] The epoxy resin-immiscible block segment may, for example, be at least one epoxy resin-immiscible polyether block segment derived from an alkylene oxide. As the at least one epoxy resin-immiscible polyether block segment derived from an alkylene oxide, for example, one or more polyalkylene oxide blocks selected from polybutylene oxide blocks, polyhexylene oxide blocks derived from 1,2-epoxyhexane, polydodecylene oxide blocks derived from 1,2-epoxydodecane, and mixtures thereof are preferred, with polybutylene oxide blocks being more preferred.

[0172] Component (H) preferably has one or more epoxy resin-compatible block segments, more preferably two or more epoxy resin-compatible block segments. Similarly, it preferably has one or more epoxy resin-immiscible block segments, more preferably two or more epoxy resin-immiscible block segments. Therefore, component (H) preferably has an epoxy resin-compatible block segment or an epoxy resin-immiscible block segment selected from the group consisting of a diblock, linear triblock, linear tetrablock, higher-order multiblock structure, branched block structure, star block structure, and combinations thereof.

[0173] Component (H) may contain other segments in the molecule to the extent that the effect of the component (H) is not impaired. Examples of other segments include segments derived from polyethylene propylene (PEP), polybutadiene, polyisoprene, polydimethylsiloxane, polybutylene oxide, polyhexylene oxide, polyalkylmethyl methacrylates such as polyethylhexyl methacrylate, and mixtures thereof.

[0174] The number average molecular weight of component (H) is preferably 3,000 to 20,000. The number average molecular weight can be measured by gel permeation chromatography (GPC) as a polystyrene equivalent value.

[0175] The weight average molecular weight (Mw) of component (H) is preferably 1,000 to 10,000, more preferably 1,500 to 8,000, and even more preferably 2,000 to 7,500. The weight average molecular weight of the resin can be measured by gel permeation chromatography (GPC) as a polystyrene-equivalent value.

[0176] Examples of component (H) include amphiphilic polyether triblock copolymers such as poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) (PEO-PPO-OEO); poly(ethylene oxide)-poly(butylene oxide)-poly(propylene oxide) (PEO-PBO-PPO); poly(ethylene oxide)-poly(butylene oxide) (PEO-PBO); poly(ethylene oxide)-poly(propylene oxide) (PEO-PPO); poly(ethylene oxide)-b-poly(butylene oxide) (PEO-PBO); and poly(ethylene oxide)-b-poly(butylene oxide)-b-poly(ethylene oxide) (PEO-PBO-PEO), with poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) being preferred.

[0177] Component (H) may also be a commercially available product. Examples of commercially available products include "P-0803N", "P-0403N", and "P-0303N" manufactured by NOF Corporation; "L-23", "L-31", "L-44", "L-61", "L-62", "L-64", "L-71", "L-72", "L-101", "L-121", "P-84", "P-5", "P-103", "F-68", "F-88", "F-108", "25R-1", "25R-2", "17R-2", "17R-3", and "17R-4" manufactured by ADEKA Corporation; and "Fortegra 100" manufactured by The Dow Chemical Company.

[0178] The content of component (H) when the nonvolatile components in the resin composition are 100% by mass is H ｍ The content of the (C) component when the nonvolatile components in the resin composition are taken as 100% by mass is defined as C ｍ When this is done, H ｍ / C ｍ is preferably 0.1 or more, more preferably 0.2 or more, and even more preferably 0.3 or more. The upper limit is preferably 1.5 or less, more preferably 1.2 or less, and even more preferably 1.0 or less.

[0179] The content of component (H) when the nonvolatile components in the resin composition are 100% by mass is H ｍ The content of the (D) component when the nonvolatile components in the resin composition are taken as 100% by mass is defined as D ｍ When this is done, H ｍ / D ｍ is preferably 1 or more, more preferably 2 or more, and even more preferably 2.5 or more. The upper limit is preferably 15 or less, more preferably 12 or less, and even more preferably 10 or less.

[0180] The content (mass %) of component (H) is preferably 0.1 mass % or more, more preferably 0.2 mass % or more, even more preferably 0.3 mass % or more, or 0.4 mass % or more, and is preferably 1.5 mass % or less, more preferably 1.2 mass % or less, even more preferably 0.8 mass % or less, or 0.6 mass % or less, based on 100 mass % of the non-volatile components in the resin composition.

[0181] The content (mass %) of component (H) is preferably 1 mass % or more, more preferably 2 mass % or more, even more preferably 3 mass % or more, 4 mass % or more, 5 mass % or more, or 6 mass % or more, when the resin component of the resin composition is taken as 100 mass %, and is preferably 10 mass % or less, more preferably 9 mass % or less, even more preferably 8 mass % or less, or 7 mass % or less.

[0182] <(I) Optional Additives> The resin composition may further contain (I) optional additives as an optional component in combination with the above-described components (A) to (H). The optional additives (I) as component (I) do not include those corresponding to the above-described components (A) to (H).

[0183] (I) Examples of optional additives include inorganic fillers having a relative magnetic permeability of less than 1, such as alumina and silica; radical polymerizable compounds such as maleimide-based radical polymerizable compounds, vinylphenyl-based radical polymerizable compounds, (meth)acrylic-based radical polymerizable compounds, allyl-based radical polymerizable compounds, and polybutadiene-based radical polymerizable compounds; radical polymerization initiators such as peroxide-based radical polymerization initiators and azo-based radical polymerization initiators; inorganic fillers such as silica particles; organic fillers such as rubber particles; organometallic compounds such as organocopper compounds and organozinc compounds; 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; and silicone-based Examples of the additives include antifoaming agents such as antifoaming agents, acrylic 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 silanes; adhesion imparting agents such as triazole-based adhesion imparting agents, tetrazole-based adhesion imparting agents, and triazine-based adhesion imparting agents; antioxidants such as hindered phenol-based antioxidants; 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); and 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. (I) The optional additives may be used alone or in combination of two or more.

[0184] The total content (mass%) of the resin components is preferably 1 mass% or more, more preferably 3 mass% or more, and even more preferably 5 mass% or more, and is preferably 25 mass% or less, more preferably 20 mass% or less, and even more preferably 15 mass% or less, when the non-volatile components of the resin composition are taken as 100 mass%.

[0185] The total content (vol %) of the resin components is preferably 10 vol % or more, more preferably 15 vol % or more, and even more preferably 20 vol %, and is preferably 45 vol % or less, more preferably 40 vol % or less, and even more preferably 35 vol % or less, when the non-volatile components of the resin composition are taken as 100 vol %.

[0186] <(J) Solvent> The resin composition may further contain (J) a solvent as a volatile component in addition to the non-volatile components (A) to (I) described above.

[0187] As the (J) solvent, an organic solvent is usually used. Examples of the (J) solvent include ketone-based solvents such as acetone, methyl ethyl ketone, methyl isobutyl ketone, and cyclohexanone; ester-based solvents such as methyl acetate, ethyl acetate, butyl acetate, isobutyl acetate, isoamyl acetate, methyl propionate, ethyl propionate, and γ-butyrolactone; ether-based solvents such as tetrahydropyran, tetrahydrofuran, 1,4-dioxane, diethyl ether, diisopropyl ether, dibutyl ether, and diphenyl ether; alcohol-based solvents such as methanol, ethanol, propanol, butanol, and ethylene glycol; and ether-based solvents such as 2-ethoxyethyl acetate, propylene glycol monomethyl ether acetate, diethylene glycol monoethyl ether acetate, ethyl diglycol acetate, γ-butyrolactone, and methyl methoxypropionate. Examples of the solvent include ester-based solvents; ester alcohol-based solvents such as methyl lactate, ethyl lactate, and methyl 2-hydroxyisobutyrate; ether alcohol-based solvents such as 2-methoxypropanol, 2-methoxyethanol, 2-ethoxyethanol, propylene glycol monomethyl ether, and diethylene glycol monobutyl ether (butyl carbitol); amide-based solvents such as N,N-dimethylformamide, N,N-dimethylacetamide, and N-methyl-2-pyrrolidone; sulfoxide-based solvents such as dimethyl sulfoxide; nitrile-based solvents such as acetonitrile and propionitrile; aliphatic hydrocarbon-based solvents such as hexane, cyclopentane, cyclohexane, and methylcyclohexane; and aromatic hydrocarbon-based solvents such as benzene, toluene, xylene, ethylbenzene, trimethylbenzene, and solvent naphtha. The (J) solvent may be used alone or in combination of two or more.

[0188] The amount of (J) solvent is preferably set so as to adjust the melt viscosity of the resin composition within an appropriate range. The amount of (J) solvent may be, for example, 3% by mass or less, 1% by mass or less, 0.5% by mass or less, 0.1% by mass or less, or 0.01% by mass or less, relative to 100% by mass of nonvolatile components in the resin composition. It is particularly preferable that the resin composition does not contain (J) solvent. When the amount of (J) solvent is small, the generation of voids due to evaporation of the (J) solvent can be suppressed. Furthermore, the handleability and workability of the resin composition can be improved.

[0189] <Characteristics of Resin Composition> The above-described resin composition can be cured by heat. Therefore, a cured product of the resin composition can be obtained by thermally curing the resin composition. Generally, among the components contained in the resin composition, volatile components such as solvent (J) can be volatilized by the heat during thermal curing, but non-volatile components such as components (A) to (I) do not volatilize by the heat during thermal curing. Therefore, a cured product of the resin composition can contain the non-volatile components of the resin composition or their reaction products.

[0190] According to the resin composition of this embodiment, by combining and containing the components (B) and (C) in a predetermined ratio, it is possible to achieve both improved magnetic properties and improved chemical resistance.

[0191] A cured product obtained by thermally curing a resin composition at 190°C for 90 minutes exhibits excellent chemical resistance. For example, the cured product is immersed in 5N hydrochloric acid for 10 minutes, washed with water, and then dried at 130°C for 15 minutes to obtain a cured product after chemical immersion. The Young's modulus of the cured product before and after chemical immersion is measured, and the change in Young's modulus is calculated. A higher Young's modulus change indicates better chemical resistance. The Young's modulus change is preferably 90% or more, more preferably 95% or more. There is no particular upper limit, but it can be 100% or less. Chemical resistance can be evaluated by the method described in the examples below.

[0192] A cured product obtained by thermally curing the resin composition at 190°C for 90 minutes exhibits the characteristic of high relative magnetic permeability. For example, when the relative magnetic permeability is measured under conditions of a measurement frequency of 10 MHz and a room temperature of 23°C, the relative magnetic permeability is preferably 8 or more, more preferably 9 or more. There is no particular limit on the upper limit of the relative magnetic permeability, and it can be, for example, 100 or less. The relative magnetic permeability can be measured by the method described in the examples below.

[0193] A cured product obtained by thermally curing the resin composition at 190°C for 90 minutes exhibits the characteristic of a small loss factor tanδ. The smaller the loss factor, the smaller the magnetic loss. For example, when the loss factor tanδ is measured under conditions of a measurement frequency of 10 MHz and a room temperature of 23°C, the loss factor tanδ is preferably 0.047 or less, more preferably 0.045 or less. There is no particular restriction on the lower limit of the loss factor, and it can be, for example, 0.00001 or more. The loss factor tanδ can be measured by the method described in the examples below.

[0194] Taking advantage of the excellent properties described above, the resin composition is preferably used as a resin composition for manufacturing an inductor. For example, the resin composition described above is preferably used as a hole-filling resin composition for filling holes in a substrate provided in a circuit board. Furthermore, for example, the resin composition described above is also preferably used to form a cured product layer on a circuit board. To facilitate application to these uses, the resin composition may be used in the form of a paste or in the form of a magnetic sheet including a layer of the resin composition.

[0195] [Method of Producing Resin Composition] The method of producing the resin composition comprises: (A) an epoxy resin; (B-1) D ５０ Magnetic powder having a particle size of 1 μm or more, (B-2) D ５０ The method includes a step of mixing magnetic powder having a particle size of less than 1 μm and (C) an organic filler, and the content of component (B) is set to B when the nonvolatile components in the resin composition are taken as 100 mass %. ｍ The content of the (C) component when the nonvolatile components in the resin composition are taken as 100% by mass is defined as C ｍ When this is done, B ｍ / C ｍis 50 or more and 500 or less. The resin composition and the components (A) to (C) contained in the resin composition are as described above.

[0196] The resin composition can be produced, for example, by adding and mixing the ingredients in any order and / or all or some of them simultaneously to any preparation vessel. The temperature can be appropriately set during the process of adding and mixing each ingredient, and heating and / or cooling may be performed temporarily or throughout the process. Stirring or shaking may be performed during the process of adding and mixing each ingredient. During or after the addition and mixing, the resin composition may be stirred or shaken using a stirring or shaking device such as a mixer to uniformly disperse the ingredients. Simultaneously with the stirring or shaking, degassing may be performed under low-pressure conditions, such as under vacuum. The mixing temperature may be, for example, 10 to 40°C. The stirring speed during mixing may be, for example, 100 to 10,000 rpm. The mixing time may be, for example, 10 seconds to 10 minutes.

[0197] [Cured Product] The cured product of the present invention can be obtained by curing the resin composition of the present invention. The curing conditions for the resin composition may be the conditions for step (2) described below. In addition, the resin composition may be preheated before being thermally cured, and heating may be performed multiple times, including preheating.

[0198] [Magnetic Sheet] The magnetic sheet includes a support and a resin composition layer provided on the support. The resin composition layer includes the above-described resin composition, and preferably includes only the resin composition.

[0199] From the viewpoint of thinning, the thickness of the resin composition layer is preferably 250 μm or less, more preferably 200 μm or less. The lower limit of the thickness of the resin composition layer may be, for example, 5 μm or more, or 10 μm or more.

[0200] Examples of the support include a film made of a plastic material, a metal foil, and release paper, with a film made of a plastic material and a metal foil being preferred.

[0201] When a film 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.

[0202] 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, such as copper, or a foil made of an alloy of copper and another metal (e.g., tin, chromium, silver, magnesium, nickel, zirconium, silicon, titanium, etc.).

[0203] 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.

[0204] The support may also be a support with a release layer, which has a release layer on the surface that bonds with 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-based release agents, polyolefin-based release agents, urethane-based release agents, and silicone-based release agents. Commercially available products may be used as the support with a release layer, and examples include "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 Ltd., which are PET films having a release layer primarily composed of a silicone-based release agent or an alkyd resin-based release agent.

[0205] The thickness of the support is not particularly limited, but is preferably in the range of 5 μm to 75 μm, and more preferably in the range of 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.

[0206] In the magnetic sheet, a protective film similar to that of the support may be provided on the surface of the resin composition layer that is not bonded to the support (i.e., the surface opposite the support). The thickness of the protective film is not particularly limited, but is, for example, 1 μm to 40 μm. By providing the protective film, it is possible to prevent adhesion of dust and scratches to the surface of the resin composition layer.

[0207] The magnetic 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, an organic solvent may be mixed with the resin composition and then applied to the support. When an organic solvent is used, drying may be performed after application if necessary.

[0208] Drying may be carried out by, for example, 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.

[0209] The magnetic sheet can be stored in a roll. When the magnetic sheet has a protective film, it can usually be used by peeling off the protective film.

[0210] [Circuit board and manufacturing method thereof] The circuit board includes a cured product of the resin composition described above. The specific structure of the circuit board is not limited as long as it includes a cured product of the resin composition. A circuit board according to a first example includes a substrate having holes and a cured product of the resin composition filled in the holes. A circuit board according to a second example includes a cured product layer including a cured product of the resin composition. Manufacturing methods for the circuit boards according to the first and second examples will be described below. However, the circuit board and its manufacturing method are not limited to the first and second examples illustrated below.

[0211] <First Example of Circuit Board> The first example of the circuit board includes a substrate having holes formed therein and a cured product of a resin composition filled in the holes. This circuit board can be manufactured by a manufacturing method including, for example, (1) a step of filling the holes in the substrate with a resin composition, and (2) a step of thermally curing the resin composition to obtain a cured product. The first example of the circuit board manufacturing method may further include: (3) a step of polishing the surface of the cured product or the resin composition; (4) a step of roughening the cured product; and (5) a step of forming a conductor layer on the cured product. Typically, steps (1) to (5) may be performed in the order of step (1), step (2), step (3), step (4), and step (5), or step (2) may be performed after step (3). In the first example of the circuit board manufacturing method, it is preferable to form a cured product using a resin composition. The following description will be given using an example using a substrate having through-holes formed therein as holes penetrating the substrate in the thickness direction.

[0212] Step (1) Step (1) typically includes preparing a substrate with through holes formed therein. The substrate may be purchased from the market. Alternatively, the substrate may be manufactured using an appropriate material. An example method for manufacturing a substrate will be described below.

[0213] FIG. 1 is a cross-sectional view schematically illustrating a core substrate 10 prepared in a circuit board manufacturing method according to a first embodiment of the present invention. The substrate preparation step may include a step of preparing a core substrate 10, as in the example illustrated in FIG. 1 . The core substrate 10 typically includes a support substrate 11. Examples of the support substrate 11 include insulating substrates such as glass epoxy substrates, metal substrates, polyester substrates, polyimide substrates, BT resin substrates, and thermosetting polyphenylene ether substrates. A metal layer may also be provided on the support substrate 11. The metal layer may be provided on one or both surfaces 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.

[0214] FIG. 2 is a cross-sectional view schematically showing a core substrate 10 having a through hole 14 formed therein, in a method for manufacturing a circuit board according to a first example of one embodiment of the present invention. The step of preparing a substrate may include a step of 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.

[0215] 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 a circuit board manufacturing method according to a first embodiment of the present invention. The substrate preparation process may include a process of, 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 in which the plating layer 20 is formed in the through-hole 14 and on the surface of the metal layer 12 and the surface of the metal layer 13 is shown and described.

[0216] 4 is a cross-sectional view schematically illustrating a state in which a resin composition 30a is filled into through holes in a core substrate 10 in a method for manufacturing a circuit board according to a first example of one embodiment of the present invention. Step (1) includes preparing a core substrate 10 having through holes 14 formed therein as described above, and then filling the through holes 14 in the core substrate 10 with the resin composition 30a, as shown in FIG. 4. The filling can be performed by, for example, a printing method. Examples of printing methods include a method of printing the resin composition 30a into the through holes 14 using a squeegee, a method of printing the resin composition 30a using a cartridge, a method of printing the resin composition 30a by mask printing, a roll coating method, an inkjet method, and the like.

[0217] 5 is a schematic cross-sectional view illustrating step (2) of the method for manufacturing a circuit board according to a first embodiment of the present invention. Step (2) includes filling through-hole 14 with resin composition 30a and then curing resin composition 30a to form cured product 30 as shown in FIG.

[0218] The resin composition 30a is typically cured by thermal curing. The thermal curing conditions for the resin composition 30a can be appropriately set within a range in which the curing of the resin composition 30a proceeds. The curing temperature is preferably 120°C or higher, more preferably 130°C or higher, and even more preferably 150°C or higher, and is 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 is preferably 120 minutes or shorter, more preferably 110 minutes or shorter, and even more preferably 100 minutes or shorter.

[0219] The degree of cure of the cured product 30 obtained in step (2) is preferably 80% or more, more preferably 85% or more, and even more preferably 90% or more. The degree of cure can be measured using, for example, a differential scanning calorimeter.

[0220] The method for manufacturing a circuit board according to the first example may include a step (preheating step) of heating the resin composition 30a at a temperature lower than the curing temperature after filling the through-holes 14 with the resin composition 30a and before curing the resin composition 30a. For example, prior to curing the resin composition 30a, the resin composition 30a 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 minutes to 150 minutes, more preferably 15 minutes to 120 minutes).

[0221] Step (3)—FIG. 6 is a schematic cross-sectional view illustrating step (3) of the method for manufacturing a circuit board according to a first example of one embodiment of the present invention. When resin composition 30a is filled into through-hole 14 in step (1), excess resin composition 30a may protrude or adhere to the outside of through-hole 14. Therefore, resin composition 30a may be provided not only within through-hole 14 but also outside through-hole 14. Therefore, step (3) includes polishing the excess cured material 30 protruding from or adhering to core substrate 10, as shown in FIG. By polishing, the excess cured material 30 is removed, thereby flattening the surface of cured material 30. Furthermore, the surface (polished surface) 31 of cured material 30 flattened by polishing typically forms a plane flush with the surface 21 surrounding polished surface 31 (e.g., the surface of core substrate 10, the surface of plating layer 20).

[0222] The cured product 30 can be polished by any method capable of removing excess cured product 30 protruding from or adhering to the core substrate 10. Examples of such polishing methods include buff polishing, belt polishing, and ceramic polishing. An example of a commercially available buff polishing device is the "NT-700IM" manufactured by Ishii Hyoki Co., Ltd.

[0223] The arithmetic mean roughness (Ra) of the polished surface 31 (the surface after curing) of the cured product 30 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 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.

[0224] The method for producing a circuit board according to the first example may include a step of subjecting the cured product 30 to a heat treatment after step (3) in order to further increase the degree of cure of the cured product 30. The temperature in the heat treatment may be the same as the curing 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 90 minutes or shorter, more preferably 70 minutes or shorter, and even more preferably 60 minutes or shorter.

[0225] Furthermore, when step (3) is performed before step (2), a preheating treatment may be performed before step (3), in which the resin composition is heated at a temperature lower than the curing temperature. The temperature in the preheating treatment is preferably 100°C or higher, more preferably 110°C or higher, even more preferably 120°C or higher, and preferably 245°C or lower, more preferably 220°C or lower, even more preferably 200°C or lower. The heat treatment time is preferably 5 minutes or longer, more preferably 10 minutes or longer, even more preferably 15 minutes or longer, and preferably 90 minutes or shorter, more preferably 70 minutes or shorter, even more preferably 60 minutes or shorter.

[0226] Step (4) Step (4) includes subjecting the cured product 30 to a roughening treatment (desmear treatment). The roughening treatment roughens the surface of the cured product 30. When the surface of the cured product 30 is polished, step (4) typically includes subjecting the polished surface 31 to a roughening treatment (desmear treatment). The procedure and conditions for the roughening treatment are not particularly limited, and for example, the procedure and conditions used in the manufacturing method of a multilayer printed wiring board can be adopted. As a specific example, the cured product 30 can be roughened by performing a swelling treatment with a swelling liquid, a roughening treatment with an oxidizing agent, and a neutralization treatment with a neutralizing liquid in this order.

[0227] Examples of swelling solutions that can be used in the roughening step include alkaline solutions and surfactant solutions, with alkaline solutions being preferred. As alkaline solutions serving as swelling solutions, sodium hydroxide solutions and potassium hydroxide solutions are more preferred. Examples of commercially available swelling solutions include "Swelling Dip Securigans P" and "Swelling Dip Securigans SBU" manufactured by Atotech Japan.

[0228] The swelling treatment with a swelling liquid can be carried out, for example, by immersing the cured product 30 for 1 to 20 minutes in a swelling liquid at 30 to 90° C. From the viewpoint of suppressing swelling of the resin contained in the cured product 30 to an appropriate level, it is preferable to immerse the cured product 30 in a swelling liquid at 40 to 80° C. for 5 to 15 minutes.

[0229] Examples of oxidizing agents that can be used in the roughening treatment with an oxidizing agent include alkaline permanganate solutions prepared by dissolving potassium permanganate or sodium permanganate in an aqueous solution of sodium hydroxide. Roughening treatment with an oxidizing agent such as alkaline permanganate solution is preferably carried out by immersing the cured material 30 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% by mass to 10% by mass. Commercially available oxidizing agents include alkaline permanganate solutions such as "Concentrate Compact P" and "Dosing Solution Securigans P" manufactured by Atotech Japan.

[0230] The neutralizing liquid used in the neutralization treatment is preferably an acidic aqueous solution. An example of a commercially available neutralizing liquid is "Reduction Solution Securigance P" manufactured by Atotech Japan. The neutralization treatment using a neutralizing liquid can be carried out by immersing the surface that has been roughened with an oxidizing solution in the neutralizing liquid at 30°C to 80°C for 5 to 30 minutes. From the standpoint of workability, etc., a method in which the cured product 30 that has been roughened with an oxidizing solution is immersed in the neutralizing liquid at 40°C to 70°C for 5 to 20 minutes is preferred.

[0231] The arithmetic mean roughness (Ra) of the surface of the cured product 30 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.

[0232] -Step (5)- Figure 7 is a schematic cross-sectional view illustrating step (5) of the method for manufacturing a circuit board according to a first example of one embodiment of the present invention. Step (5), as shown in Figure 7, involves forming a conductor layer 40 on the polished surface 31 of the cured product 30. Here, an example is shown in which the conductor layer 40 is formed not only on the polished surface 31 of the cured product 30 but also on the surrounding surfaces 21 (e.g., the surface of the core substrate 10, the surface of the plating layer 20). Also, although Figure 7 shows an example in which the conductor layer 40 is formed on both sides of the core substrate 10, the conductor layer 40 may be formed on only one side of the core substrate 10.

[0233] 8 is a schematic cross-sectional view illustrating step (5) of the method for manufacturing a circuit board according to a first example of one embodiment of the present invention. As shown in Fig. 8, step (5) may include forming a conductor layer 40, and then removing parts of the conductor layer 40, the metal layer 12, the metal layer 13, and the plating layer 20 by a process such as etching to form a patterned conductor layer 41.

[0234] Examples of methods for forming the conductor layer 40 include plating, sputtering, and vapor deposition, with plating being preferred. In a preferred embodiment, the surface of the cured product 30 (and the plating layer 20) can be plated by an appropriate method such as a semi-additive method or a full-additive method to form a patterned conductor layer 41 having a desired wiring pattern. Examples of materials for the conductor layer 40 include single 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.

[0235] Here, an example of a method for forming a patterned conductor layer 41 on the polished surface 31 of the cured product 30 will be described in detail. A plating seed layer is formed on the polished surface 31 of the cured product 30 by electroless plating. Next, an electrolytic plating layer is formed on the formed plating seed layer by electrolytic plating. Thereafter, if necessary, unnecessary plating seed layer is removed by a process such as etching, thereby forming a patterned conductor layer 41 having a desired wiring pattern. After forming the patterned conductor layer 41, an annealing treatment may be performed as necessary to improve the adhesion strength of the patterned conductor layer 41. The annealing treatment can be performed, for example, by heating at 150 to 200°C for 20 to 90 minutes.

[0236] From the viewpoint of thinning, the thickness of the patterned conductor layer 41 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.

[0237] By the above method, the circuit board 1 including the cured product 30 of the resin composition 30a can be manufactured.

[0238] <Circuit Board According to Second Example> The circuit board according to the second example includes a cured material layer containing a cured material of a resin composition. The cured material layer preferably contains only a cured material of the resin composition. The cured material layer is preferably formed using a magnetic sheet. This circuit board can be produced, for example, by a production method including: (i) a step of forming a cured material layer on an inner layer substrate; (ii) a step of drilling holes in the cured material layer; (iii) a step of roughening the surface of the cured material layer; and (iv) a step of forming a conductor layer on the surface of the cured material layer.

[0239] -Step (i)-Step (i) includes forming a cured material layer on an inner layer substrate. Preferably, step (i) includes laminating a magnetic sheet on the inner layer substrate such that the resin composition layer is bonded to the inner layer substrate, thereby forming a cured material layer. For example, the magnetic sheet is laminated on the inner layer substrate such that the resin composition layer is bonded to the inner layer substrate, and the resin composition layer is thermally cured to form a cured material layer.

[0240] 9 is a schematic cross-sectional view illustrating step (i) in a method for manufacturing a circuit board according to a second embodiment of the present invention. As shown in FIG. 9, a magnetic sheet 310 is prepared, which includes a support 330 and a resin composition layer 320a provided on the support 330. Then, the magnetic sheet 310 and the inner substrate 200 are laminated together so that the resin composition layer 320a is bonded to the inner substrate 200.

[0241] An insulating substrate can be used as the inner layer substrate 200. Examples of the inner layer 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 layer substrate 200 may be an inner layer circuit board having wiring and the like formed within its thickness.

[0242] The inner substrate 200 shown in this example includes 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. However, in the example shown in FIG. 9, only the wirings constituting the coil-shaped conductive structure 400 (see FIG. 12) of the inductor element are shown. The external terminal 240 may be a terminal for electrically connecting to an external device or the like (not shown). The external terminal 240 may be configured as a part of the conductor layer provided on the second main surface 200b.

[0243] Conductive materials that can form the first conductor layer 420 and the external terminals 240 include, for example, the same materials as those for the conductor layers described in the first example.

[0244] 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 may be the same as that of the second conductor layer 440 described below.

[0245] 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 cured product 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 still 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.

[0246] 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 terminals 240.

[0247] The resin composition layer 320a and the inner substrate 200 can be bonded, for example, by thermocompression bonding the magnetic sheet 310 to the inner substrate 200 from the support 330 side. Examples of a member for thermocompression bonding the magnetic sheet 310 to the inner substrate 200 (hereinafter also referred to as a "thermocompression bonding member") include a heated metal plate (such as a stainless steel (SUS) plate) or a metal roll (SUS roll). Note that rather than pressing the magnetic sheet 310 by directly contacting it with the thermocompression bonding member, it is preferable to press the magnetic sheet 310 via a sheet made of an elastic material such as heat-resistant rubber so that the magnetic sheet 310 can sufficiently conform to the irregularities on the surface of the inner substrate 200.

[0248] The temperature during thermocompression bonding is preferably in the range of 80°C to 160°C, more preferably 90°C to 140°C, and even more preferably 100°C to 120°C, the pressure during thermocompression bonding is preferably in the range of 0.098 MPa to 1.77 MPa, more preferably 0.29 MPa to 1.47 MPa, and the time during thermocompression bonding is preferably in the range of 20 seconds to 400 seconds, more preferably 30 seconds to 300 seconds. The bonding of the magnetic sheet and the inner layer substrate is preferably carried out under reduced pressure conditions of 26.7 hPa or less.

[0249] The resin composition layer 320a of the magnetic sheet 310 can be bonded to the inner layer substrate 200 using a commercially available vacuum laminator. Examples of commercially available vacuum laminators include a vacuum pressure laminator manufactured by Meiki Seisakusho Co., Ltd. and a vacuum applicator manufactured by Nikko Materials Co., Ltd.

[0250] After bonding the magnetic sheet 310 and the inner layer substrate 200, the laminated magnetic sheet 310 may be smoothed under normal pressure (atmospheric pressure), for example, by pressing a thermocompression member from the support 330 side. The pressing conditions for the smoothing treatment may be the same as the thermocompression conditions for the lamination. The smoothing treatment may be performed using a commercially available laminator. Note that the lamination and smoothing treatment may be performed consecutively using the commercially available vacuum laminator.

[0251] 10 is a schematic cross-sectional view illustrating step (i) in a method for manufacturing a circuit board according to a second embodiment of the present invention. After laminating the magnetic sheet 310 on the inner substrate 200, the resin composition layer 320a is cured to form a cured layer. In this example, as shown in FIG. 10, the resin composition layer 320a bonded to the inner substrate 200 is thermally cured to form the first cured layer 320.

[0252] The thermal curing conditions for the resin composition layer 320a can be appropriately set within a range in which the curing of the resin composition proceeds. The curing temperature is preferably 120°C or higher, more preferably 130°C or higher, and even more preferably 150°C or higher, and is 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 is preferably 120 minutes or shorter, more preferably 110 minutes or shorter, and even more preferably 100 minutes or shorter.

[0253] The support 330 may be removed between the end of the thermal curing in step (i) and the step (ii), or may be peeled off after the step (ii).

[0254] The arithmetic mean roughness (Ra) of the cured layer before 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 plating. 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.

[0255] In step (i), instead of using a magnetic sheet, a resin composition may be applied to the inner layer substrate 200 using a die coater or the like, and then thermally cured to form a cured layer.

[0256] -Step (ii)- Figure 11 is a schematic cross-sectional view illustrating step (ii) in a method for producing a circuit board according to a second example of one embodiment of the present invention. As shown in Figure 11, step (ii) includes drilling the first cured material layer 320 to form via holes 360. The via holes 360 form paths for electrically connecting the first conductor layer 420 and the second conductor layer 440, which will be described later. The via holes 360 may be formed using, for example, a drill, a laser, plasma, or the like. The dimensions and shape of the holes may be determined appropriately depending on the design of the printed wiring board.

[0257] Step (iii) In step (iii), the surface of the cured material layer having the via holes formed therein is roughened. The roughening treatment in step (iii) can be performed by the same method as described in step (4) of the first example.

[0258] The arithmetic mean roughness (Ra) of the cured layer 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 plating. 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.

[0259] 12 is a schematic cross-sectional view illustrating step (iv) in the method for producing a circuit board according to a second embodiment of the present invention. As shown in FIG. 12, in step (iv), a second conductor layer 440 is formed on the first cured material layer 320.

[0260] Examples of conductive materials that can form the second conductor layer 440 include the same materials as those of the conductor layer described in the first example.

[0261] 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.

[0262] 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.

[0263] The first conductor layer 420 and the second conductor layer 440 may be provided in a spiral shape, for example, as shown in Figures 13 to 15 (described later). In one example, one central end of the spiral wiring portion of the second conductor layer 440 is electrically connected to one central end of the spiral wiring portion of the first conductor layer 420 by via-hole wiring 360a. The other outer peripheral end of the spiral wiring portion of the second conductor layer 440 is electrically connected to land 420a of the first conductor layer 420 by via-hole wiring 360a. Therefore, the other outer peripheral end of the spiral wiring portion of the second conductor layer 440 is electrically connected to external terminal 240 via via-hole wiring 360a, land 420a, and through-hole wiring 220a.

[0264] 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.

[0265] After step (iv), a step of forming a cured material layer on the conductor layer may be further performed. Specifically, as shown in an example in FIG. 14 , a second cured material layer 340 is formed on a first cured material layer 320 on which a second conductor layer 440 and via-hole wiring 360a have been formed. The second cured material layer may be formed by a process similar to the process already described. By the above method, a circuit board 100 including a first cured material layer 320 and a second cured material layer 340 formed from a cured product of the resin composition can be manufactured.

[0266] [Inductor Substrate] The inductor substrate includes the circuit board described above. When such an inductor substrate includes a circuit board obtained by the circuit board manufacturing method according to the first example described above, it may have an inductor pattern formed of a conductor around at least a portion of the periphery of the cured product of the resin composition. In this case, the inductor substrate may include, for example, an inductor element configured by an inductor pattern formed of at least a portion of the metal layer 12, the metal layer 13, the plating layer 20, and the patterned conductor layer 41, and a core formed of the cured product 30 surrounded by this inductor pattern. For example, an inductor substrate such as that described in JP 2016-197624 A can be used.

[0267] Furthermore, when the inductor substrate includes a circuit board obtained by the circuit board manufacturing method according to the second example, the inductor substrate may have a cured material layer and a conductive structure at least partially embedded in the cured material layer, and the inductor substrate may include an inductor element constituted by the conductive structure and a portion of the cured material layer that extends in the thickness direction of the cured material layer and is surrounded by the conductive structure.

[0268] Fig. 13 is a schematic plan view of the circuit board 100 included in the inductor substrate, viewed from one side in the thickness direction. Fig. 14 is a schematic view showing a cut end surface of the circuit board 100 cut at the position indicated by the dashed dotted line II-II in Fig. 13. Fig. 15 is a schematic plan view for explaining the configuration of the first conductor layer 420 of the circuit board 100 included in the inductor substrate.

[0269] As shown in Figures 13 and 14 as an example, the circuit board 100 may be a board having multiple cured material layers (first cured material layer 320, second cured material layer 340) and multiple conductor layers (first conductor layer 420, second conductor layer 440). Thus, in the example shown here, the circuit board 100 may be a build-up wiring board having build-up cured material layers and build-up conductor layers. The circuit board 100 also includes an inner layer board 200.

[0270] 14 , the first cured material layer 320 and the second cured material layer 340 constitute the magnetic part 300, which can be seen as an integrated cured material 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 circuit board 100 shown in this example, 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] 15, 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 example shown here, the spiral wiring portion includes a straight portion, a bent portion bent at a right angle, and a detour portion that detours around the land 420a. 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 to the outside.

[0272] Similarly, a second conductor layer 440 is provided on the first cured material layer 320. The second conductor layer 440 includes a spiral wiring portion for configuring the coil-shaped conductive structure 400. In Fig. 13 or 14, the spiral wiring portion includes a straight portion and a bent portion bent at a right angle. In Fig. 13 or 14, the spiral wiring portion of the second conductor layer 440 has an overall outline that is approximately rectangular, and has a shape that is wound clockwise from the center toward the outside.

[0273] The inductor substrate described above 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 used as an individual chip inductor component, or as a printed wiring board on which the chip inductor component is surface-mounted.

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

[0275] The present invention will be specifically described below with reference to examples. The present invention is not limited to these examples. In the following, "%" and "parts" representing amounts mean "% by mass" and "parts by mass" unless otherwise specified. Furthermore, unless a temperature is specifically specified, the temperature condition is room temperature (23°C). Furthermore, unless a pressure is specifically specified, the pressure condition is normal pressure (1 atm).

[0276] Synthesis Example 1: Synthesis of Dispersant 1 In a reaction flask equipped with a thermometer, a stirrer, a nitrogen inlet, and a reflux condenser, 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.) were charged, and the temperature was raised to 160°C over 4 hours under a nitrogen stream. After heating at 160°C for 2 hours, heating was continued until the remaining amount of ε-caprolactone was 1% or less. The mixture was then cooled to room temperature. Hereinafter, this reaction liquid is referred to as Reaction Liquid 1.

[0277] In a reaction flask equipped with a thermometer, a stirrer, a nitrogen inlet and a reflux condenser, a mixture consisting of 25.0 parts of xylene and 70 parts of a 10% aqueous solution of polyallylamine ("PAA-1LV", manufactured by Nitto Boseki Co., Ltd., number average molecular weight approximately 3,000) was stirred at 160 ° C., and water was distilled off using a separator, and while the xylene was returned to the reaction solution, 14.21 parts of reaction solution 1 heated to 160 ° C. was added thereto, and the reaction was carried out at 160 ° C. for 3 hours. Further heating was carried out at 160 ° C. for 4 hours, and xylene was distilled off at 160 ° C. to obtain Dispersant 1. Dispersant 1 is a compound represented by the general formula (D-1) R １１ The polyester skeleton was an alkylene group having 5 carbon atoms, and the amine value was 11.0 mg KOH / g and the acid value was 17.5 mg KOH / g. The pH was 6 as measured by the indicator method.

[0278] Example 1 Preparation of Resin Composition 2.61 parts by mass of epoxy resin ("ZX-1059", a mixture of bisphenol A type epoxy resin and bisphenol F type epoxy resin, manufactured by Nippon Steel Chemical & Material Co., Ltd.), magnetic powder ("AW2-08PF3F", manufactured by Epson Atmix Corporation, Fe-Si-Cr alloy powder, amorphous powder, D ５０ 96.67 parts by mass of magnetic powder ("CVD iron powder (0.7 μm)" manufactured by JFE Mineral Co., Ltd.), D ５０ 0.7 μm) 24.17 parts by mass, organic filler ("Staphyloid AC3816N" manufactured by Aica Kogyo Co., Ltd., D ５０ 0.5 μm), 2.32 parts by mass of dispersant 1 (the dispersant synthesized in Synthesis Example 1, a polyester dispersant having 5 carbon atoms), 0.19 parts by mass of triazine skeleton-containing phenolic resin (DIC Corporation's "LA-7054," a MEK solution with a hydroxyl group equivalent of approximately 125 and a solid content of 60%), 5.11 parts by mass of phenoxy resin (Mitsubishi Chemical Corporation's "YX7553BH30," a 1:1 mixture of MEK and cyclohexanone with a solid content of 30%), Magnetic varnish 1 was prepared by mixing 2.33 parts by mass of a curing accelerator ("2E4MZ", 2-ethyl-4-methylimidazole, manufactured by Shikoku Chemical Industry Co., Ltd.), 0.04 parts by mass of an imidazole curing accelerator ("2E4MZ", 2-ethyl-4-methylimidazole, manufactured by Shikoku Chemical Industry Co., Ltd.), 2.67 parts by mass of a solvent (solvent naphtha, "IP150", manufactured by Idemitsu Kosan Co., Ltd.), 0.19 parts by mass of a solvent (toluene), 4.16 parts by mass of a solvent (methyl ethyl ketone), and 1.21 parts by mass of a solvent (cyclohexanone).

[0279] Examples 2 to 17 and Comparative Examples 1 to 4: Preparation of Resin Compositions In Example 1, the types of each component were changed in the parts by mass shown in the table below. Resin compositions were prepared in the same manner as in Example 1, except for the above points.

[0280]

[0281] The details of each component listed in the table are as follows: (A) Component ZX-1059: 1:1 mixture of bisphenol A epoxy resin and bisphenol F epoxy resin, manufactured by Nippon Steel Chemical & Material Co., Ltd., functional group equivalent 169 g / eq. (B) Component AW02-08PF3F: Fe-Si-Cr alloy powder, manufactured by Epson Atmix Corporation, amorphous powder, D ５０ = 3.1 μm CVD iron powder: "CVD iron powder (0.7 μm)" manufactured by JFE Mineral Co., Ltd., D ５０ = 0.7 μm (C) Component AC3816N: Core-shell type rubber particles, "Staphyloid AC3816N" manufactured by Aica Kogyo Co., Ltd., D ５０= 0.5 μm EXL2655: Core-shell type rubber particles, "EXL2655" manufactured by Dow Chemical Japan SX-006: Core-shell type rubber particles, "Metablen SX-006" manufactured by Mitsubishi Chemical Corporation (D) Component Dispersant 1: Dispersant synthesized in Synthesis Example 1 SC-1015F: "SC-1015F" manufactured by NOF Corporation, an acidic polyfunctional comb-type dispersant having an ionic group in the main chain and a polyoxyalkylene chain in the graft chain ED-152: "ED-152" manufactured by Kusumoto Chemicals Co., Ltd., a polyether phosphate ester-based dispersant (E) Component LA-7054: Triazine skeleton-containing phenolic resin, manufactured by DIC Corporation, hydroxyl group equivalent of approximately 125 g / eq. Component (F): YX7553BH30: Phenoxy resin, 1:1 solution of MEK and cyclohexanone with a non-volatile content of 30% by mass, manufactured by Mitsubishi Chemical Corporation. Component (G): 2E4MZ: Imidazole curing accelerator (2-ethyl-4-methylimidazole), manufactured by Shikoku Chemical Industry Co., Ltd. Component (H): P-0803N: Block copolymer of butylene oxide and ethylene oxide, manufactured by NOF Corporation. L-44: Block copolymer of ethylene oxide and propylene oxide, weight average molecular weight 2,200, manufactured by ADEKA Corporation. P-85: Block copolymer of ethylene oxide and propylene oxide, weight average molecular weight 4,600, manufactured by ADEKA Corporation. (I) Component Inorganic Filler 1: Spherical silica ("SO-C2" manufactured by Admatechs Co., Ltd.) surface-treated with an aminosilane coupling agent ("KBM573" manufactured by Shin-Etsu Chemical Co., Ltd.). ５０ =0.5μm, specific surface area 5.8m ２ / g

[0282] <Measurement of particle size distribution> 100 mg of component (B) used in each example and 10 g of methyl ethyl ketone were weighed into a vial and dispersed by ultrasonic waves for 10 minutes. Using a laser diffraction particle size distribution analyzer ("LA-960" manufactured by Horiba, Ltd.), blue and red wavelength light sources were used, and the particle size distribution of the particles contained in the resin composition was measured on a volume basis using a flow cell method. From the obtained particle size distribution, the D of component (B) was determined as the median diameter. １０ , D ５０ and D ９０ The particle size distribution of all particles was also measured in the same manner.

[0283] <Preparation of Sample A> 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 was 100 μm, thereby obtaining a magnetic sheet. The obtained magnetic 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 may be referred to as Sample A.

[0284] <Measurement of relative permeability and loss factor> The obtained sample A was cut to obtain a doughnut-shaped evaluation sample having 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 100 MHz and a room temperature of 23°C using a magnetic material test fixture "16454A" manufactured by Keysight and an impedance analyzer "E4991B" manufactured by Keysight. The loss factor tanδ was calculated using the formula "tanδ = μ'' / μ'". The relative permeability was evaluated according to the following criteria: ◯: Relative permeability is 9.0 or more Δ: Relative permeability is 8.0 or more and less than 9.0 ×: Relative permeability is less than 8.0. The loss factor was evaluated according to the following criteria. ◯: Loss factor is 0.045 or less △: Loss factor is greater than 0.045 and less than 0.047 ×: Loss factor is greater than 0.047

[0285] <Evaluation of change in Young's modulus after chemical immersion (evaluation of chemical resistance)> (1) A part of the chemical immersion sample A was immersed in 5N hydrochloric acid for 10 minutes, washed with water, and then dried at 130°C for 15 minutes to remove moisture from the cured product, thereby obtaining a cured product after chemical immersion.

[0286] (2) Measurement of Young's modulus before and after immersion in chemical solution Young's modulus was evaluated using Sample A before and after immersion in chemical solution. Tensile strength was measured using a tensile testing machine "RTC-1250A" manufactured by Orientec Co., Ltd., and Young's modulus at 23°C was measured. The measurement was carried out in accordance with JIS K6253.

[0287] (3) Calculation of change in Young's modulus after chemical immersion Using the results of the Young's modulus of sample A before and after chemical immersion in (2), the change in Young's modulus after chemical immersion was calculated using the formula "(change in Young's modulus after chemical immersion) = (Young's modulus after chemical immersion) / (Young's modulus before chemical immersion) × 100". The change in Young's modulus after chemical immersion was evaluated according to the following criteria. A higher value for the change in Young's modulus indicates better chemical resistance. ◯: The change in Young's modulus after chemical immersion is 95% or more. △: The change in Young's modulus after chemical immersion is 90% or more but less than 95%. ×: The change in Young's modulus after chemical immersion is less than 90%.

[0288]

[0289] B ｍ / C ｍ In Examples 1 to 17, where the value is in the range of 50 to 500, the component (C) is contained in a predetermined amount, and therefore the component (B) is easily dispersed uniformly in the resin composition, and as a result, the relative permeability is high and the loss factor is low. ｍ / C ｍ In Examples 1 to 17, in which the value is in the range of 50 or more and 500 or less, the (C) component is contained in a predetermined amount, and therefore it is considered that improvements in relative permeability and loss factor as well as improvements in chemical resistance can be achieved at the same time.

[0290] On the other hand, in Comparative Examples 1, 3, and 4, which do not contain the component (C), the component (B) is not uniformly dispersed in the resin composition, and it is thought that the presence of the component (B) in the resin composition is uneven. As a result, although the relative permeability is high, the loss factor is low. ｍ / C ｍ In Comparative Example 2, where the value is less than 50, the content of the (B) component in the resin composition is relatively small compared to Examples 1 to 17, so the relative permeability is low, and the content of the (C) component is relatively large compared to Examples 1 to 17, so it is thought that this results in poor chemical resistance.

[0291] REFERENCE SIGNS LIST 1 Circuit board 10 Core board 11 Support board 12 Metal layer 13 Metal layer 14 Through hole 20 Plated layer 21 Surface surrounding the polished surface 30 Cured product 30a Resin composition 31 Polished surface of the cured product (polished surface) 40 Conductive layer 41 Patterned conductor layer 100 Circuit board 200 Inner layer board 200a First main surface 200b Second main surface 220 Through hole 220a Wiring inside the through hole 240 External terminal 310 Magnetic sheet 320 First cured product layer 320a Resin composition layer 330 Support 360 Via hole 360a Wiring inside the via hole 400 Coil-shaped conductive structure 420 First conductor layer 420a Land 440 Second conductor layer

Claims

1. A resin composition comprising (A) an epoxy resin, (B) a magnetic powder, and (C) an organic filler, wherein the content of component (B) is B when the nonvolatile components in the resin composition are 100% by mass. ｍ The content of the (C) component when the nonvolatile components in the resin composition are taken as 100% by mass is defined as C ｍ When this is done, B ｍ / C ｍ is 50 or more and 500 or less.

2. The resin composition according to claim 1, further comprising (D) a dispersant.

3. The resin composition according to claim 2, wherein component (D) contains any one of a polyester skeleton, a polyoxyalkylene skeleton, and a phosphate ester skeleton represented by formula (D-1). In formula (D-1), R １１ each independently represents a divalent hydrocarbon group having 2 to 10 carbon atoms which may have a substituent, n １ represents an integer of 2 to 1000.

4. The content of component (C) when the nonvolatile components in the resin composition are 100% by mass is C ｍ The content of the (D) component when the nonvolatile components in the resin composition are taken as 100% by mass is defined as D ｍ When this is done, C ｍ / D ｍ The resin composition according to claim 2, wherein is 1 or more and 12 or less.

5. (B) component is (B-1)D ５０ Magnetic powder having a particle size of 1 μm or more, and (B-2) D ５０ The resin composition according to claim 1, which contains magnetic powder having a particle size of less than 1 μm.

6. The content of component (B-1) when the nonvolatile components in the resin composition are 100% by mass is B ｍ１ When the content of the nonvolatile components in the resin composition is 100% by mass, and the content of the component (C) is Cm, B ｍ１ / C ｍ The resin composition according to claim 5, wherein the molecular weight is 40 or more and 400 or less.

7. When the content of the (B-2) component when the nonvolatile components in the resin composition are 100% by mass is defined as Bm2, and when the content of the (C) component when the nonvolatile components in the resin composition are 100% by mass is defined as Cm, then B ｍ２ / C ｍ The resin composition according to claim 5, wherein the σ is 5 or more and 100 or less.

8. D of the whole particle １０ The resin composition according to claim 1, wherein the particle size is 0.1 μm or more and less than 4 μm.

9. The resin composition according to claim 1, further comprising (H) an amphiphilic copolymer.

10. A resin composition according to claim 1, wherein the content (volume %) of component (B) is 50% by volume or more when the non-volatile components in the resin composition are taken as 100% by volume.

11. A resin composition according to claim 1, in which the content (vol %) of component (C) is 0.1 vol % or more when the non-volatile components in the resin composition are taken as 100 vol %.

12. A magnetic sheet comprising a support and a resin composition layer formed on the support from the resin composition according to any one of claims 1 to 11.

13. 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 11 filled in the through-hole.

14. A circuit board comprising a magnetic layer which is a cured product of the resin composition according to any one of claims 1 to 11.

15. An inductor substrate comprising the circuit board of claim 13.

16. An inductor substrate comprising the circuit board of claim 14.

17. A method for producing the resin composition according to any one of claims 1 to 11, comprising: (A) an epoxy resin; (B-1) D ５０ Magnetic powder having a particle size of 1 μm or more, (B-2) D ５０ (C) an organic filler; and (B) a magnetic powder having a particle size of less than 1 μm. The content of the component (B) is B when the nonvolatile components in the resin composition are taken as 100% by mass. ｍ The content of the (C) component when the nonvolatile components in the resin composition are taken as 100% by mass is defined as C ｍ When this is done, B ｍ / C ｍ is 50 or more and 500 or less.

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