Resin composition

Abstract

Provided is a resin composition or the like that facilitates acquisition of a cured product having excellent coatability and high relative permeability. This resin composition contains (A) nanocrystalline magnetic powder, (B) magnetic powder containing Fe and Ni, and (C) a thermosetting resin. The content ratio of Fe and Ni (Fe content / Ni content) contained in the component (B) is 0.85-1.25, the content of oxygen atoms contained in the component (B) is 0.3 mass% or greater with respect to 100 mass% of the component (B), and the 10% particle diameter (D10) of the particles as a whole contained in the resin composition is 0.2-4 μm.

Description

resin composition

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

[0002] Many inductor elements are mounted on information terminals such as mobile phones and smartphones. Recently, a method has been developed in which a coil is formed using a conductor pattern on a substrate, and the inductor element is provided inside the substrate. Known methods for forming these inductor elements include using a resin composition containing magnetic powder. For example, paste-like resin compositions for filling holes such as through-holes, and film-like resin compositions for forming magnetic layers are known (see Patent Documents 1 and 2).

[0003] In recent years, there has been a demand for further improving the magnetic properties of magnetic materials in order to further improve the performance of inductor elements. One method for improving the magnetic properties of magnetic materials is to increase the content of magnetic powder in the material. For example, a technology is known in which two or more types of magnetic metal powders with different average particle sizes are used to increase the powder packing rate and improve the magnetic properties (Patent Document 3).

[0004] International Publication No. 2019 / 181463 Japanese Patent Application Laid-Open No. 2015-187260 Japanese Patent Application Laid-Open No. 2019-220609

[0005] In conventional resin compositions, increasing the filling rate of magnetic powder increases the viscosity of the resin composition. Therefore, when a magnetic sheet is formed using the resin composition, it becomes difficult to apply the resin composition to a support, which can hinder the production of the magnetic sheet. Hereinafter, the ease of application of a resin composition may be referred to as "applicability."

[0006] The present invention has been devised in view of the above-mentioned problems, and aims to provide a resin composition and a method for producing the same that are excellent in coatability and can give a cured product with high relative magnetic permeability; a cured product of the resin composition; a magnetic paste and a magnetic sheet containing the resin composition; and a circuit board and an inductor board that contain a cured product of the resin composition.

[0007] 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 a resin composition containing a magnetic powder containing specific amounts of Fe, Ni, and oxygen atoms in combination with a nanocrystalline magnetic powder, and the average particle size and 10% particle size of these particles are within a specific range, thereby completing the present invention.

[0008] That is, the present invention includes the following: [1] A resin composition comprising: (A) nanocrystalline magnetic powder, (B) magnetic powder containing Fe and Ni, and (C) a thermosetting resin, wherein the content ratio of Fe and Ni contained in component (B) (Fe content / Ni content) is 0.85 or more and 1.25 or less, the content of oxygen atoms contained in component (B) is 0.3 mass% or more relative to 100 mass% of component (B), and the 10% particle diameter (D １０ [2] The resin composition according to [1], wherein the average particle size (D) of the component (B) is 0.2 μm or more and 4 μm or less. [3] The resin composition according to [1], wherein the average particle size (D) of the component (B) is 0.2 μm or more and 4 μm or less. ５０ [4] The resin composition according to [1] or [2], wherein the average particle size (D ５０) is more than 15 μm and less than 50 μm. [5] The resin composition according to any one of [1] to [4], wherein the component (C) comprises an epoxy resin (C-1). [6] The resin composition according to any one of [1] to [5], wherein the component (C) comprises a curing agent (C-2). [7] The resin composition according to any one of [1] to [6], further comprising a dispersant (E). [8] The resin composition according to [7], wherein the component (E) comprises a cationic dispersant. [9] The resin composition according to any one of [1] to [8], further comprising a curing accelerator (F).

[10] The resin composition according to any one of [1] to [9], wherein the volume ratio of the component (A) is 0.60 or more and 0.92 or less when the total content (volume %) of the components (A) and (B) is taken as 1.

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

[10] , wherein the content of oxygen atoms contained in component (B) is 27% by mass or less, relative to 100% by mass of component (B).

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

[11] , which is for hole filling.

[13] A cured product of the resin composition according to any one of [1] to

[12] .

[14] A magnetic paste comprising the resin composition according to any one of [1] to

[12] .

[15] A magnetic sheet comprising a support and a resin composition layer provided on the support, wherein the resin composition layer comprises the resin composition according to any one of [1] to

[12] .

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

[12] , the cured product being filled in the holes.

[17] A circuit board comprising a cured product layer containing a cured product of the resin composition according to any one of [1] to

[12] .

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

[16] .

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

[17] .

[20] A method for producing a resin composition according to any one of [1] to

[12] , comprising: (A) nanocrystalline magnetic powder; (B) magnetic powder containing Fe and Ni; and (C) a thermosetting resin, wherein the average particle size (D ５０ ) is more than 15 μm and less than 50 μm, the content ratio of Fe and Ni contained in component (B) (Fe content / Ni content) is 0.85 or more and 1.25 or less, and the average particle size (D ５０) is more than 0.8 μm and less than 1.5 μm, the content of oxygen atoms contained in component (B) is 0.3 mass% or more relative to 100 mass% of component (B), and 10% particle diameter (D １０ ) is 0.2 μm or more and 4 μm or less.

[0009] According to the present invention, it is possible to provide a resin composition and a method for producing the same that are excellent in coatability and can give a cured product with high relative magnetic permeability; a cured product of the resin composition; a magnetic paste and a magnetic sheet containing the resin composition; and a circuit board and an inductor board that contain the cured product of the resin composition.

[0010] 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.

[0011] 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.

[0012] <Resin Composition> The resin composition of the present invention is a resin composition containing (A) nanocrystalline magnetic powder, (B) magnetic powder containing Fe and Ni, and (C) a thermosetting resin, wherein the content ratio of Fe and Ni contained in component (B) (Fe content / Ni content) is 0.85 or more and 1.25 or less, the content of oxygen atoms contained in component (B) is 0.3 mass% or more relative to 100 mass% of component (B), and the 10% particle diameter (D １０ ) is 0.2 μm or more and 4 μm or less, and the average particle size (D ５０ ) is 10 μm or more and 40 μm or less. Such a resin composition has excellent coatability and can increase the relative permeability of a cured product of the resin composition. In addition, a cured product can be obtained that usually has a low loss factor and excellent maximum strength and elongation.

[0013] In conventional resin compositions, increasing the filling rate of magnetic powder increases the relative permeability of the cured resin composition, but also increases the viscosity of the resin composition, tending to result in poor coatability. For this reason, it has been difficult to achieve both improved relative permeability and coatability. However, in the resin composition of the present invention, by incorporating a combination of components (A) and (B) and adjusting the particle size of the entire particles contained in the resin composition, it is possible to achieve both improved relative permeability and improved coatability.

[0014] Here, "10% particle size of all particles (D １０ ") and "average particle size of the whole particle (D ５０ "Particles" in "components (A) and (B)" refer to components that do not dissolve in a solvent, and in the case where the composition contains, in addition to components (A) and (B), magnetic powder that does not fall under components (A) and (B), and organic fillers such as rubber particles, and inorganic fillers such as silica, whose relative permeability is 1 or less, the concept also includes the magnetic powder and the fillers.

[0015] 10% particle diameter of all particles (D１０ ) is 0.2 μm or more, preferably 0.5 μm or more, more preferably 0.6 μm or more, even more preferably 0.8 μm or more, or 1 μm or more. The upper limit is 4 μm or less, preferably 3.5 μm or less, more preferably 3 μm or less, even more preferably 2.8 μm or less. 10% particle diameter (D １０ By setting the value of the magnetic permeability (%) within this range, it is possible to improve both the relative permeability and the coatability.

[0016] The average particle size of all particles (D ５０ ) is preferably 10 μm or more, more preferably 12 μm or more, even more preferably 13 μm or more, or 14 μm or more. The upper limit is preferably 40 μm or less, more preferably 35 μm or less, even more preferably 30 μm or less, or 25 μm or less. ５０ By setting the value of the magnetic permeability within this range, it is possible to improve both the relative magnetic permeability and the coatability.

[0017] 90% particle diameter of all particles (D ９０ The upper limit of the thickness is preferably 60 μm or less, more preferably 50 μm or less, and even more preferably 45 μm or less.

[0018] 10% particle diameter of all particles (D １０ ) and average particle size (D ５０ ) and the difference D ５０ -D １０ is preferably 3 μm or more, more preferably 5 μm or more, and even more preferably 10 μm or more, and is preferably 40 μm or less, more preferably 35 μm or less, and even more preferably 30 μm or less.

[0019] The average particle size of all particles (D ５０ ) and 90% particle size (D ９０ ) and the difference D ９０ -D ５０ is preferably 7 μm or more, more preferably 10 μm or more, even more preferably 13 μm or more, or 14 μm or more, and is preferably 30 μm or less, more preferably 25 μm or less, even more preferably 20 μm or less.

[0020] 10% particle diameter of all particles (D １０ ) and 90% particle size (D ９０ ) and the difference D ９０ -D １０ is preferably 20 μm or more, more preferably 25 μm or more, and even more preferably 30 μm or more, and is preferably 55 μm or less, more preferably 50 μm or less, and even more preferably 45 μm or less.

[0021] 10% particle diameter of all particles (D １０ ) and average particle size (D ５０ ) ratio D ５０ / D １０ is preferably 1.1 or more, more preferably 3 or more, even more preferably 5 or more, or 7 or more, and is preferably 40 or less, more preferably 35 or less, even more preferably 30 or less.

[0022] The average particle size of all particles (D ５０ ) and 90% particle size (D ９０ ) ratio D ９０ / D ５０ is preferably 0.8 or more, more preferably 1.0 or more, even more preferably 1.2 or more, and is preferably 3.0 or less, more preferably 2.8 or less, even more preferably 2.6 or less.

[0023] 10% particle diameter of all particles (D １０ ) and 90% particle size (D ９０ ) ratio D ９０ / D １０ is preferably 8 or more, more preferably 10 or more, and even more preferably 12 or more, and is preferably 55 or less, more preferably 45 or less, and even more preferably 40 or less.

[0024] Since the resin composition contains at least the components (A) and (B) as particles, it is preferable that the particle size distribution on a volume basis has two or more peak tops. Of the two or more peak tops, one of the two or more peak tops is usually the average particle size D of the component (A). ５０ and the other is the average particle size (D ５０ Therefore, the range of particle diameters at two or more peak tops is the average particle diameter (D ５０) The average particle size (D ５０ ) will be discussed later.

[0025] The resin composition may further contain optional components such as (D) a thermoplastic resin, (E) a dispersant, (F) a curing accelerator, (G) other additives, and (H) a solvent, as necessary. Each component that can be contained in the resin composition will be described below.

[0026] <(A) Nanocrystalline Magnetic Powder> The resin composition contains (A) nanocrystalline magnetic powder as component (A). By incorporating (A) nanocrystalline magnetic powder into the resin composition, it is possible to obtain a cured product with high relative magnetic permeability. (A) Nanocrystalline magnetic powder may be used singly or in combination of two or more types. Nanocrystalline magnetic powder refers to a magnetic powder containing crystal grains with a particle size of 100 nm or less. The lower limit of the particle size of the crystal grains is not particularly limited, but is preferably 1 nm or more. In particular, nanocrystalline magnetic powders preferably have a maximum particle size of 100 nm or less. Typically, each nanocrystalline magnetic powder particle contains multiple crystal grains, and therefore, the nanocrystalline magnetic powder particles can be polycrystalline. The size of the crystal grains can be observed, for example, using a transmission electron microscope (TEM). Because nanocrystalline magnetic powders contain crystal grains, they generally exhibit peaks indicating crystallinity in X-ray diffraction patterns. The crystal structure of the crystal grains may be, for example, a bcc crystal structure (body-centered cubic lattice structure), but may be any other crystal structure.

[0027] Component (A) is usually contained in the resin composition in the form of particles. Component (A) may contain crystal grains in at least a portion of its particles, preferably containing crystal grains in the surface layer of the particles, more preferably containing crystal grains throughout the particles, and particularly preferably consisting of only crystal grains.

[0028] (A) Average particle size (D ５０ ) is the average particle size (D) of the magnetic powder containing (B) Fe and Ni ５０ It is preferable that the average particle size (D ５０The average particle diameter (D) of component (A) is preferably greater than 15 μm, more preferably 15.2 μm or more, even more preferably 15.3 μm or more, or 15.5 μm or more, and is preferably 50 μm or less, more preferably 45 μm or less, even more preferably 40 μm or less, 35 μm or less, or 30 μm or less. ５０ When the average particle diameter D of the nanocrystalline magnetic powder is within this range, it is possible to improve both the relative permeability and the coatability. ５０ represents the volume-based median diameter.

[0029] The particle size of component (A) 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 can be preferably used is one in which the 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.

[0030] The particle size distribution of the component (A) on a volume basis usually follows a normal distribution. Therefore, the nanocrystalline magnetic powder (A) has an average particle size (D ５０ 10% particle size (D １０ ), and the average particle size (D ５０ ) larger than 90% particle size (D ９０ ), where 10% particle size (D １０ ) represents the particle size at which the cumulative volume from the smaller particle size side reaches 10% in the particle size distribution based on volume. ９０ ) represents the particle size at which the cumulative volume from the smallest particle size side reaches 90% in the particle size distribution based on volume. １０ ) and 90% particle size (D ９０ ) can be measured from the volume-based particle size distribution measured by the laser diffraction / scattering method.

[0031] 10% particle size (D１０ ) is preferably greater than 4 μm, more preferably 5 μm or more, and even more preferably 6 μm or more. ５０ ) or less, preferably 15 μm or less, more preferably 14 μm or less, and even more preferably 13 μm or less.

[0032] (A) 90% particle size (D ９０ The upper limit of the thickness is preferably 70 μm or less, more preferably 75 μm or less, and even more preferably 70 μm or less.

[0033] 10% particle size (D １０ ) and average particle size (D ５０ ) and the difference D ５０ -D １０ is preferably 1 μm or more, more preferably 5 μm or more, and even more preferably 8 μm or more, and is preferably 30 μm or less, more preferably 25 μm or less, and even more preferably 20 μm or less.

[0034] (A) Average particle size (D ５０ ) and 90% particle size (D ９０ ) and the difference D 9０ -D １０ is preferably 10 μm or more, more preferably 15 μm or more, and even more preferably 20 μm or more, and is preferably 45 μm or less, more preferably 40 μm or less, and even more preferably 35 μm or less.

[0035] 10% particle size (D １０ ) and 90% particle size (D ９０ ) and the difference D ９０ -D １０ is preferably 20 μm or more, more preferably 25 μm or more, even more preferably 30 μm or more, and is preferably 60 μm or less, more preferably 55 μm or less, even more preferably 50 μm or less.

[0036] 10% particle size (D １０ ) and average particle size (D ５０ ) ratio D ５０ / D １０is preferably 1.1 or more, more preferably 1.5 or more, even more preferably 2 or more, and is preferably 10 or less, more preferably 5 or less, even more preferably 3 or less.

[0037] (A) Average particle size (D ５０ ) and 90% particle size (D ９０ ) ratio D ９０ / D ５０ is preferably 1.1 or more, more preferably 1.5 or more, even more preferably 2 or more, and is preferably 10 or less, more preferably 5 or less, even more preferably 3 or less.

[0038] 10% particle size (D １０ ) and 90% particle size (D ９０ ) ratio D ９０ / D １０ is preferably 1.1 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 6 or less.

[0039] The specific surface area of ​​component (A) is preferably 0.2 m ２ / g or more, more preferably 0.25m ２ / g or more, more preferably 0.3m ２ / g or more, preferably 1.0m ２ / g or less, more preferably 0.9m ２ / g or less, more preferably 0.8m ２ The specific surface area of ​​component (A) 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 then using the BET multipoint method.

[0040] The component (A) may be particles of a magnetic material having a relative magnetic permeability greater than 1. The component (A) is usually an inorganic material, and may be a soft magnetic material or a hard magnetic material. Among these, from the viewpoint of suppressing uneven distribution of the component (A) contained in the resin composition, a soft magnetic material is preferred as the component (A).

[0041] Examples of the magnetic material contained in the (A) nanocrystalline magnetic powder include magnetic metal oxides and magnetic metals. Among these, the magnetic material contained in the (A) nanocrystalline magnetic powder preferably contains iron (Fe). Therefore, examples of the magnetic material contained in the (A) nanocrystalline magnetic powder include crystalline iron alloy magnetic materials and crystalline ferrite magnetic materials. From the viewpoint of improving the magnetic permeability and loss factor, the magnetic material contained in the (A) nanocrystalline magnetic powder preferably has a composition further containing one or more elements selected from the group consisting of Nb, Hf, Zr, Ta, Mo, W, and V in combination with Fe.

[0042] (A) Preferred examples of the magnetic material contained in the nanocrystalline magnetic powder include the magnetic materials described in JP-A-2021-158343, JP-A-2021-141267, JP-A-2019-31463, JP-A-2021-11602, etc.

[0043] Among the above examples, Fe—Si—Nb—B alloy powder is preferred from the viewpoints of magnetic permeability and loss factor. The Fe—Si—Nb—B alloy powder refers to a magnetic powder formed from an alloy containing Fe, Si, Nb, and B.

[0044] (A) The nanocrystalline magnetic powder preferably contains the above-mentioned magnetic material, and preferably contains only the above-mentioned magnetic material.

[0045] (A) Nanocrystalline magnetic powder can be produced, for example, by an atomization method. Specific examples of methods for producing nanocrystalline magnetic powder include those described in JP 2021-141267 A and JP 2021-158343 A.

[0046] (A) The nanocrystalline magnetic powder may be a commercially available product. Examples of commercially available products include "KUAMET NC1-53 μm," "KUAMET NC1-38 μm," "ATFINE-NC1 PF10FA," and "KUAMET NC-V1 038CO3A," manufactured by Epson Atmix Corporation. When nanocrystalline magnetic powder is purchased from the market, the commercially available magnetic powder may be classified as necessary.

[0047] The nanocrystalline magnetic powder (A) is preferably spherical. The aspect ratio, calculated by dividing the length of the major axis of a particle of the nanocrystalline magnetic powder (A) by the length of the minor axis, is preferably 2 or less, more preferably 1.5 or less, and even more preferably 1.2 or less, and is usually 1 or more, preferably greater than 1, and more preferably 1.05 or more.

[0048] The true density of the component (A) is, for example, 4 g / cm ３ ~10g / cm ３ The range may be:

[0049] The content (mass %) of (A) nanocrystalline magnetic powder is preferably 50 mass % or more, more preferably 60 mass % or more, even more preferably 70 mass % or more, and is preferably 95 mass % or less, more preferably 90 mass % or less, even more preferably 85 mass % or less, when the non-volatile components of the resin composition are taken as 100 mass %.

[0050] The content (volume %) of (A) nanocrystalline magnetic powder is preferably 40 volume % or more, more preferably 50 volume % or more, and even more preferably 60 volume % or more, when the nonvolatile components of the resin composition are taken as 100 volume %, and is preferably 90 volume % or less, more preferably 85 volume % or less, and even more preferably 80 volume % or less.

[0051] 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% by mass, and the nonvolatile components refer to all nonvolatile components in the resin composition excluding the solvent. The volumetric amount (vol %) of each component contained in the resin composition is calculated from the mass of the component contained in the resin composition. Specifically, the volume of each component is calculated by dividing the mass by the specific gravity, and the volumetric amount (vol %) can be calculated from the volume of each component thus calculated.

[0052] The content (mass %) of the (A) nanocrystalline magnetic powder is preferably 50 mass % or more, more preferably 60 mass % or more, and even more preferably 70 mass % or more, when the total amount of the (A) component and the (B) component is taken as 100 mass %, and is preferably 95 mass % or less, more preferably 90 mass % or less, and even more preferably 88 mass % or less.

[0053] When the total content (volume %) of components (A) and (B) is taken as 1, the volume ratio of component (A) is preferably 0.60 or more, more preferably 0.65 or more, even more preferably 0.7 or more, and preferably 0.92 or less, more preferably 0.9 or less, even more preferably 0.89 or less. When the resin composition contains, in addition to components (A) and (B), a magnetic powder in component (G) that does not fall under components (A) and (B), it is sufficient that the volume ratio of component (A) is within the above range when the total content (volume %) of components (A), (B), and the magnetic powder is taken as 1. By setting the volume ratio of component (A) within this range, the relative permeability can be improved.

[0054] When the total content (vol %) of all components contained in the resin composition is taken as 1, the volume ratio of component (A) is preferably 0.1 or more, more preferably 0.3 or more, even more preferably 0.4, and is preferably 0.9 or less, more preferably 0.8 or less, even more preferably 0.7 or less, or 0.6 or less.

[0055] <(B) Magnetic Powder Containing Fe and Ni> The resin composition contains (B) a magnetic powder containing Fe and Ni as component (B). This (B) magnetic powder containing Fe and Ni as component (B) does not include anything that corresponds to component (A). Furthermore, (B) magnetic powder containing Fe and Ni as component (B) does not include nanocrystalline magnetic powder containing Fe and Ni. By incorporating a combination of components (A) and (B) as the magnetic powder contained in the resin composition, it is possible to obtain a cured product with a high relative permeability and a low loss factor. One type of component (B) may be used alone, or two or more types may be used in combination.

[0056] Component (B) can be formed by oxidizing the surface of magnetic powder particles. The content of oxygen atoms contained in component (B) is 0.3% by mass or more, preferably 0.31% by mass or more, more preferably 0.32% by mass or more, and even more preferably 0.33% by mass or more, based on 100% by mass of component (B). If the content of oxygen atoms contained in component (B) is less than 0.3% by mass, the electrical resistivity may decrease. As a result, eddy currents generated by the flow of current may prevent the magnetic field from entering the resin composition, adversely affecting the relative permeability. The upper limit of the content of oxygen atoms contained in component (B) is preferably 27% by mass or less, more preferably 25% by mass or less, even more preferably 23% by mass or less, 20% by mass or less, 18% by mass or less, 15% by mass or less, 13% by mass or less, 10% by mass or less, 8% by mass or less, 5% by mass or less, 3% by mass or less, or 2% by mass or less. If the content of oxygen atoms contained in component (B) exceeds 27% by mass, the content of Fe and Ni per weight decreases, which may result in a low relative permeability. The content of oxygen atoms can be measured using an inductively coupled plasma optical emission spectrometer (e.g., Agilent Technologies' "ICP-OES 720ES"). The content of oxygen atoms contained in ferrite is typically about 28% by mass. Therefore, component (B) is a different component from ferrite containing Fe and Ni.

[0057] The mass ratio of the Fe content to the Ni content contained in the (B) component (Fe content / Ni content) is 0.85 or more, preferably 0.9 or more, more preferably 0.93 or more, even more preferably 0.95 or more, or 0.97 or more. The upper limit is 1.25 or less, preferably 1.1 or less, more preferably 1.05 or less, even more preferably 1.0 or less, or 0.99 or less. By having the Fe content / Ni content within this range, the relative permeability can be improved.

[0058] The content of Fe in component (B), relative to 100% by mass of component (B), is preferably 25% by mass or more, more preferably 35% by mass or more, and even more preferably 45% by mass or more, and is preferably 75% by mass or less, more preferably 65% ​​by mass or less, and even more preferably 55% by mass or less.

[0059] The content of Ni contained in component (B), relative to 100 mass% of component (B), is preferably 25 mass% or more, more preferably 35 mass% or more, even more preferably 45 mass% or more, and is preferably 75 mass% or less, more preferably 65 mass% or less, even more preferably 55 mass% or less.

[0060] The total amount of Fe and Ni contained in component (B), relative to 100% by mass of component (B), is preferably 50% by mass or more, more preferably 70% by mass or more, and even more preferably 90% by mass or more, and is preferably 99.7% by mass or less, more preferably 99% by mass or less, and even more preferably 98% by mass or less.

[0061] The amount of each element contained in component (B) can be measured using an inductively coupled plasma optical emission spectrometer (ICP-OES 720ES, manufactured by Agilent Technologies).

[0062] A preferred embodiment of component (B) is an Fe—Ni-based alloy magnetic powder in which the oxygen atom content is 0.3 mass% or more relative to 100 mass% of component (B), and the mass ratio of the Fe content to the Ni content (Fe content / Ni content) is 0.85 to 1.25. The term "Fe—Ni alloy magnetic powder" refers to an alloy magnetic powder containing the elements Fe and Ni. The same applies to an alloy magnetic powder containing three or more elements.

[0063] Component (B) may contain any element other than Fe, Ni, and oxygen atoms within a range that does not impair the effects of the present invention. Thus, component (B) may be an Fe—Ni—Cr based alloy magnetic powder, an Fe—Ni—Si based alloy magnetic powder, an Fe—Ni—B based alloy magnetic powder, an Fe—Ni—Mo based alloy magnetic powder, an Fe—Ni—Si—Cr based alloy magnetic powder, or an Fe—Ni—Mo—Cu based alloy magnetic powder.

[0064] Examples of optional elements that may be contained in component (B) include elements derived from impurities that may be inevitably mixed in depending on the manufacturing method of component (B). Specific examples of elements derived from impurities that may be inevitably mixed in include P, S, Mn, Mo, Cu, and Co. However, from the viewpoint of significantly achieving the effects of the present invention, the amount of elements derived from impurities contained in component (B) is preferably less than 1.00% by mass relative to 100% by mass of component (B).

[0065] The component (B) preferably has a smaller average particle size than the component (A) from the viewpoint of allowing the component (B) to enter the gaps between the particles of the component (A) and highly filling the components (A) and (B). ５０ The average particle size (D) of component (B) is preferably greater than 0.8 μm, more preferably 0.9 μm or more, and even more preferably 0.95 μm or more. The upper limit is preferably less than 1.5 μm, more preferably 1.45 μm or less, and even more preferably 1.42 μm or less. ５０ When the average particle diameter (D) is within this range, the component (B) can enter the gaps between the particles of the component (A), which allows for high packing of the components (A) and (B), thereby improving the magnetic properties such as the relative permeability and loss factor. ５０ ) can be measured in the same manner as for the average particle size of component (A).

[0066] The particle size distribution of the component (B) on a volume basis usually follows a normal distribution. Therefore, the average particle size (D ５０ ) 10% particle size D １０ and the average particle size of the component (B) (D ５０ ) larger than 90% particle size (D ９０ ) may be present.

[0067] (B) 10% particle size (D １０ ) is preferably 0.1 μm or more, more preferably 0.15 μm or more, and even more preferably 0.2 μm or more. ５０ ) or less, preferably 2.5 μm or less, more preferably 2 μm or less, and even more preferably 1.5 μm or less.

[0068] (B) 90% particle size (D ９０ The upper limit of the thickness is preferably 10 μm or less, more preferably 5 μm or less, and even more preferably 3 μm or less.

[0069] (B) 10% particle size (D １０ ) and average particle size (D ５０ ) and the difference D ５０ -D １０ is preferably 0.05 μm or more, more preferably 0.1 μm or more, and even more preferably 0.15 μm or more, and is preferably 1.5 μm or less, more preferably 1 μm or less, and even more preferably 0.8 μm or less.

[0070] (B) Average particle size of component (D ５０ ) and 90% particle size (D ９０ ) and the difference D ５０ -D １０ is preferably 0.05 μm or more, more preferably 0.1 μm or more, and even more preferably 0.15 μm or more, and is preferably 2.5 μm or less, more preferably 2 μm or less, and even more preferably 1.5 μm or less.

[0071] (B) 10% particle size (D １０ ) and 90% particle size (D ９０ ) and the difference D ９０ -D １０ is preferably 0.3 μm or more, more preferably 0.5 μm or more, and even more preferably 0.8 μm or more, and is preferably 3 μm or less, more preferably 2 μm or less, and even more preferably 1.5 μm or less.

[0072] (B) 10% particle size (D １０ ) and average particle size (D ５０ ) ratio D ５０ / D １０ is preferably 1.1 or more, more preferably 1.13 or more, even more preferably 1.15 or more, and is preferably 10 or less, more preferably 8 or less, even more preferably 5 or less.

[0073] (B) Average particle size of component (D ５０ ) and 90% particle size (D ９０ ) ratio D９０ / D ５０ is preferably 1.1 or more, more preferably 1.13 or more, even more preferably 1.15 or more, and is preferably 10 or less, more preferably 8 or less, even more preferably 5 or less.

[0074] (B) 10% particle size (D １０ ) and 90% particle size (D ９０ ) ratio D ９０ / D １０ is preferably 1.1 or more, more preferably 1.5 or more, even more preferably 2 or more, and is preferably 15 or less, more preferably 10 or less, even more preferably 8 or less.

[0075] 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.

[0076] In another embodiment, component (B) may have a core-shell structure in which a magnetic powder containing Fe and Ni is coated with a coating layer. Component (B) having such a core-shell structure may have a two-layer structure consisting of a magnetic powder containing Fe and Ni and a coating layer, or may have a three-layer or greater structure including an optional layer. The average particle size, 10% particle size, 90% particle size, and specific surface area of ​​component (B) having a core-shell structure are preferably within the above-described ranges.

[0077] The material constituting the coating layer is preferably a silicon oxide capable of forming a coating on the surface of the magnetic powder containing Fe and Ni. Examples of silicon oxide include SiO such as silicon dioxide. ｘ(x is a number of 1 to 2); water-soluble alkali metal silicates such as sodium silicate; and SiO ｘ (where x is a number of 1 or 2) is preferred, and silicon dioxide is more preferred.

[0078] Silicon oxide can be obtained by the so-called sol-gel method, in which a silica precursor is hydrolyzed and polycondensed under acidic or basic conditions. Examples of silica precursors include silicate esters such as tetraethyl orthosilicate and silicates such as sodium silicate. These may be used alone or in combination to form a sol of two or more types.

[0079] The mass ratio of the magnetic powder containing Fe and Ni to the coating layer (magnetic powder containing Fe and Ni / coating layer) is preferably 0.1 or more, more preferably 0.5 or more, and even more preferably 1 or more, and is preferably 20 or less, more preferably 15 or less, and even more preferably 10 or less. The mass ratio can be calculated from the ratio of the amount of magnetic powder containing Fe and Ni charged when producing component (B) having a core-shell structure to the total amount of monomers and silica precursors that form the coating layer charged.

[0080] The thickness of the coating layer is preferably 5 nm or less, more preferably 4 nm or less, and even more preferably 3 nm or less, and is preferably 0.1 nm or more, more preferably 0.5 nm or more, and even more preferably 1 nm or more. The thickness of the coating layer can be calculated from the amount of material used to form the coating layer and the specific surface area of ​​the magnetic powder containing Fe and Ni.

[0081] The core-shell structured component (B) can be produced, for example, by mixing a magnetic powder containing Fe and Ni with a material that constitutes the coating layer, or a precursor thereof, and then subjecting the mixture to reactions such as hydrolysis and polymerization as necessary.

[0082] The component (B) may be surface-treated with a surface treatment agent as needed. Examples of the surface treatment agent include silane coupling agents such as vinylsilane coupling agents, (meth)acrylic coupling agents, fluorine-containing silane coupling agents, aminosilane coupling agents, epoxysilane coupling agents, mercaptosilane coupling agents, and silane coupling agents; alkoxysilanes; organosilazane compounds; titanate coupling agents; surfactants; and polymer compounds such as vinyl polymers. One type of surface treatment agent may be used alone, or two or more types may be used in any combination.

[0083] Commercially available surface treatment agents may be used. Examples of commercially available surface treatment agents include "KBM1003" (vinyltriethoxysilane), "KBM503" (3-methacryloxypropyltriethoxysilane), "KBM103" (phenyltrimethoxysilane), "KBM403" (3-glycidoxypropyltrimethoxysilane), "KBM803" (3-mercaptopropyltrimethoxysilane), and "KBE903" (all manufactured by Shin-Etsu Chemical Co., Ltd.). " (3-aminopropyltriethoxysilane), "KBM573" (N-phenyl-3-aminopropyltrimethoxysilane), "SZ-31" (hexamethyldisilazane), "KBM103" (phenyltrimethoxysilane), "KBM-4803" (long-chain epoxy-type silane coupling agent), "KBM-7103" (3,3,3-trifluoropropyltrimethoxysilane), and "ALM" and "TTM" manufactured by Ajinomoto Fine-Techno Co., Ltd. are examples thereof.

[0084] From the viewpoint of improving the dispersibility of component (B), the surface treatment is preferably carried out at a level of 0.01 parts by mass or more, more preferably 0.03 parts by mass or more, and even more preferably 0.05 parts by mass or more, per 100 parts by mass of component (B).The upper limit is preferably 3 parts by mass or less, more preferably 2 parts by mass or less, and even more preferably 1 part by mass or less.

[0085] The degree of surface treatment with the surface treatment agent can be evaluated by the amount of carbon per unit surface area of ​​component (B). From the viewpoint of improving the dispersibility of component (B), the amount of carbon per unit surface area of ​​component (B) is 0.02 mg / m ２ More than 0.1 mg / m ２ More preferably, 0.2 mg / m or more ２ On the other hand, from the viewpoint of suppressing an increase in the viscosity of the resin composition, it is more preferable that the content is 1 mg / m ２ Preferably, 0.8 mg / m or less ２ More preferably, 0.5 mg / m or less ２ The following is even more preferred:

[0086] The carbon amount per unit surface area of ​​component (B) can be measured after component (B) has been surface-treated with a surface treatment agent and then washed with a solvent (e.g., methyl ethyl ketone (MEK)). Specifically, a sufficient amount of MEK as a solvent is added to component (B) that has been surface-treated with a surface treatment agent, and ultrasonic washing is performed at 25°C for 5 minutes. The supernatant is removed, and the solid content is dried. Then, the carbon amount per unit surface area of ​​component (B) can be measured using a carbon analyzer. An "EMIA-320V" manufactured by Horiba, Ltd. or the like can be used as the carbon analyzer.

[0087] Component (B) may be a commercially available product. Examples of commercially available products include "NiFe-GB1001" and "NiFe-GB0501" manufactured by Guangbo Co., Ltd. When component (B) is purchased from the market, the commercially available magnetic powder may be classified as necessary.

[0088] The particles of component (B) are preferably spherical or ellipsoidal. The value obtained by dividing the length of the major axis of the particles of component (B) by the length of the minor axis (aspect ratio) is preferably 2 or less, more preferably 1.6 or less, and even more preferably 1.4 or less. When the aspect ratio of component (B) is within the above range, the viscosity of the resin composition can be reduced.

[0089] The true density of the component (B) is, for example, 4 g / cm ３ ~10g / cm ３ The range may be:

[0090] 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.

[0091] The content (mass %) of component (B) is preferably 6 mass % or more, more preferably 8 mass % or more, and even more preferably 10 mass % or more, when the non-volatile components in the resin composition are taken as 100 mass %, and is preferably 60 mass % or less, more preferably 50 mass % or less, and even more preferably 40 mass % or less, or 30 mass % or less.

[0092] The content (vol %) of component (B) is preferably 4 vol % or more, more preferably 6 vol % or more, and even more preferably 8 vol % or more, and is preferably 35 vol % or less, more preferably 25 vol % or less, and even more preferably 20 vol % or less, when the non-volatile components in the resin composition are taken as 100 vol %.

[0093] The content (vol %) of component (B), when the total content of component (A) and component (B) is taken as 100 vol %, is preferably 3 vol % or more, more preferably 5 vol % or more, even more preferably 10 vol % or more, and is preferably 40 vol % or less, more preferably 35 vol % or less, even more preferably 30 vol % or less.

[0094] The content (mass%) of component (B), when the total content of component (A) and component (B) is taken as 100 mass%, is preferably 5 mass% or more, more preferably 8 mass% or more, even more preferably 10 mass% or more, and is preferably 45 mass% or less, more preferably 40 mass% or less, even more preferably 35 mass% or less.

[0095] The total content (vol %) of the (A) component and the (B) component is preferably 50 vol % or more, more preferably 60 vol % or more, even more preferably 70 vol % or more, or 75 vol % or more, relative to 100 vol % of the nonvolatile components in the resin composition, and is preferably 95 vol % or less, more preferably 90 vol % or less, and even more preferably 85 vol % or less.

[0096] The total content (mass%) of the (A) component and the (B) component is preferably 70 mass% or more, more preferably 80 mass% or more, and even more preferably 90 mass% or more, relative to 100 mass% of the nonvolatile components in the resin composition, and is preferably 98 mass% or less, more preferably 97 mass% or less, and even more preferably 96 mass% or less.

[0097] The volume ratio of component (B) is preferably 0.03 or more, more preferably 0.05 or more, even more preferably 0.1 or more, and is preferably 0.4 or less, more preferably 0.35 or less, and even more preferably 0.3 or less, when the total content (volume %) of components (A) and (B) is taken as 1. When the resin composition contains, in addition to components (A) and (B), a magnetic powder in component (G) that does not fall under components (A) and (B), it is sufficient that the volume ratio of component (B) when the total content (volume %) of components (A), (B), and the magnetic powder is taken as 1 is within the above range.

[0098] <(C) Thermosetting Resin> The resin composition contains a (C) thermosetting resin as the (C) component. The (C) thermosetting resin as the (C) component does not include those corresponding to the above-mentioned (A) to (B) components. The (C) thermosetting resin can usually bind the (A) component and the (B) component. Furthermore, the (C) thermosetting resin can usually react with heat to form bonds and harden. Therefore, a cured product can be obtained by hardening a resin composition containing a combination of the (A) to (C) components. One type of (C) thermosetting resin may be used alone, or two or more types may be used in combination.

[0099] Examples of the thermosetting resin (C) include epoxy resins, phenolic resins, active ester resins, amine resins, acid anhydride resins, benzoxazine resins, cyanate ester resins, and carbodiimide resins.

[0100] The (C) thermosetting resin preferably contains a (C-1) epoxy resin. The (C-1) epoxy resin refers to a resin having one or more epoxy groups in its molecule. When the (C) thermosetting resin contains a (C-1) epoxy resin, the dispersibility of the (A) component and the (B) component can be improved, and the relative permeability and loss factor of the cured product of the resin composition can be effectively improved.

[0101] Examples of the epoxy resin (C-1) 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 the epoxy resins include: epoxy resins containing a condensed ring skeleton, such as cyclohexane-type epoxy resins, heterocyclic epoxy resins, spiro ring-containing epoxy resins, cyclohexane dimethanol-type epoxy resins, trimethylol-type epoxy resins, tetraphenylethane-type epoxy resins, 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. The (B-1) epoxy resin may be used alone or in combination of two or more.

[0102] The epoxy resin (C-1) 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 of the epoxy resin (C-1) (100% by mass) is preferably 50% by mass or more, more preferably 60% by mass or more, and even more preferably 70% by mass or more.

[0103] The epoxy resin (C-1) preferably has an aromatic structure. When two or more types of epoxy resins are used, it is preferable that at least one type of epoxy resin has an aromatic structure. An aromatic structure is a chemical structure generally defined as aromatic, and also includes polycyclic aromatic rings and aromatic heterocycles.

[0104] The (C-1) epoxy resin includes an epoxy resin that is liquid at a temperature of 20°C (hereinafter sometimes referred to as a "liquid epoxy resin") and an epoxy resin that is solid at a temperature of 20°C (hereinafter sometimes referred to as a "solid epoxy resin"). The (C-1) epoxy resin may be a liquid epoxy resin alone, a solid epoxy resin alone, or a combination of a liquid epoxy resin and a solid epoxy resin. Of these, the (C-1) epoxy resin preferably contains a combination of a liquid epoxy resin and a solid epoxy resin.

[0105] 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.

[0106] 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 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.

[0107] The solid epoxy resin is preferably a solid epoxy resin having three or more epoxy groups per molecule, more preferably an aromatic solid epoxy resin having three or more epoxy groups per molecule.As the solid epoxy resin, bixylenol type epoxy resin, naphthalene type epoxy resin, naphthalene type tetrafunctional epoxy resin, cresol novolac type epoxy resin, dicyclopentadiene type epoxy resin, trisphenol type epoxy resin, naphthol type epoxy resin, biphenyl type epoxy resin, naphthylene ether type epoxy resin, anthracene type epoxy resin, bisphenol A type epoxy resin, bisphenol AF type epoxy resin, tetraphenylethane type epoxy resin is preferred, and naphthalene type epoxy resin is more preferred.

[0108] 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.

[0109] 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.

[0110] The epoxy equivalent of the (C-1) 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.

[0111] The weight average molecular weight (Mw) of the epoxy resin (C-1) 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.

[0112] The content (mass%) of the epoxy resin (C-1) as the component (C), when the total non-volatile components of the resin composition is taken as 100 mass%, is preferably 0.1 mass% or more, more preferably 0.5 mass% or more, even more preferably 1 mass% or more, and is preferably 10 mass% or less, more preferably 5 mass% or less, even more preferably 3 mass% or less.

[0113] The content (mass%) of the epoxy resin (C-1) as the component (C), when the resin component of the resin composition is taken as 100 mass%, is preferably 15 mass% or more, more preferably 20 mass% or more, even more preferably 25 mass% or more, or 30 mass% or more, and is preferably 60 mass% or less, more preferably 50 mass% or less, and even more preferably 45 mass% or less.

[0114] The "resin component" of the resin composition refers to the non-volatile components contained in the resin composition, excluding components (A) and (B), as well as magnetic powder that does not fall under components (A) and (B), and inorganic particles such as inorganic fillers such as silica.

[0115] When the (C) thermosetting resin contains the (C-1) epoxy resin, the (C) thermosetting resin may contain a resin capable of reacting with the (C-1) epoxy resin to form a bond. Hereinafter, the resin capable of reacting with the (C-1) epoxy resin to form a bond may be referred to as the "(C-2) curing agent." Examples of the (C-2) curing agent include phenolic resins, active ester resins, amine resins, carbodiimide resins, acid anhydride resins, benzoxazine resins, cyanate ester resins, and thiol resins. One type of (C-2) curing agent may be used alone, or two or more types may be used in combination. A phenolic resin is preferred as the curing agent.

[0116] As the phenolic resin, 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 resin having a novolac structure is preferred. From the viewpoint of adhesion, a nitrogen-containing phenolic resin is preferred, and a triazine skeleton-containing phenolic resin is more preferred. Among them, a triazine skeleton-containing phenolic novolac resin is preferred from the viewpoint of highly satisfying heat resistance, water resistance, and adhesion.

[0117] Specific examples of phenolic resins 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" manufactured by Nippon Steel Chemical & Material Co., Ltd. -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.

[0118] As the activated ester resin, a compound having one or more, preferably two or more, activated ester groups per molecule can be used. Among these, preferred activated ester resins 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 activated ester resin 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, activated ester resins obtained from a carboxylic acid compound and a hydroxy compound are preferred, and activated ester resins 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.

[0119] Specific preferred examples of the active ester resin include active ester resins containing a dicyclopentadiene-type diphenol structure, active ester resins containing a naphthalene structure, active ester resins containing an acetylated product of phenol novolac, and active ester resins containing a benzoylated product of phenol novolac. Among these, active ester resins containing a naphthalene structure and active ester resins 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.

[0120] Commercially available activated ester resins include activated ester resins containing a dicyclopentadiene-type diphenol structure such as "EXB9451", "EXB9460", "EXB9460S", "HPC-8000-65T", "HPC-8000H-65TM", and "EXB-8000L-65TM" (manufactured by DIC Corporation); activated ester resins containing a naphthalene structure such as "EXB-9416-70BK", "EXB-8150-65T", "EXB-8100L-65T", and "EXB-8150L-65T" (manufactured by DIC Corporation); and phenol novolac resins such as "EXB-9416-70BK", "EXB-8150-65T", "EXB-8100L-65T", and "EXB-8150L-65T" (manufactured by DIC Corporation). Examples of active ester resins containing acetylated products include "DC808" (manufactured by Mitsubishi Chemical Corporation); examples of active ester resins containing benzoylated phenol novolac include "YLH1026" (manufactured by Mitsubishi Chemical Corporation); examples of active ester resins that are acetylated phenol novolac include "DC808" (manufactured by Mitsubishi Chemical Corporation); and examples of active ester resins that are benzoylated phenol novolac include "YLH1026" (manufactured by Mitsubishi Chemical Corporation), "YLH1030" (manufactured by Mitsubishi Chemical Corporation), and "YLH1048" (manufactured by Mitsubishi Chemical Corporation).

[0121] As the amine-based resin, a resin having one or more, preferably two or more amino groups in one molecule can be used. Examples of the amine-based resin include aliphatic amines, polyether amines, alicyclic amines, and aromatic amines. Among these, aromatic amines are preferred. The amine-based resin is preferably a primary amine or a secondary amine, and more preferably a primary amine. Specific examples of the amine-based resin 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-hydroxybenzoyl) phenyl)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 resins 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.

[0122] As the carbodiimide resin, a resin having one or more, preferably two or more, carbodiimide structures in one molecule can be used. Specific examples of the carbodiimide resin 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(naphthalenecarbodiimide); Examples of polycarbodiimides include aromatic polycarbodiimides such as poly(methylenebis(methylphenylene)carbodiimide), 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 resins 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.

[0123] As the acid anhydride resin, a resin having one or more acid anhydride groups in one molecule can be used, and a resin having two or more acid anhydride groups in one molecule is preferred. Specific examples of the acid anhydride resin 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 resins 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 Cray Valley Chemical Industries, Ltd.

[0124] Specific examples of benzoxazine resins 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.

[0125] Examples of cyanate ester resins 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, cresol novolac, etc.; and prepolymers in which these cyanate resins are partially triazine-converted. Specific examples of cyanate ester resins 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 is triazine-converted to form a trimer), all of which are manufactured by Arxada.

[0126] Examples of thiol-based resins include trimethylolpropane tris(3-mercaptopropionate), pentaerythritol tetrakis(3-mercaptobutyrate), and tris(3-mercaptopropyl)isocyanurate.

[0127] The active group equivalent of the (C-2) 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 (C-2) curing agent per equivalent of the active group.

[0128] When the number of epoxy groups in the (C-1) epoxy resin is taken as 1, the number of active groups in the (C-2) 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 (C-2) curing agent are active hydroxyl groups or the like, and vary depending on the type of curing agent. The number of epoxy groups in the (C-1) 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 (C-2) 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.

[0129] The content (mass %) of the (C-2) curing agent as the component (C), 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, even more preferably 1 mass % or more, and is preferably 10 mass % or less, more preferably 5 mass % or less, even more preferably 3 mass % or less.

[0130] The content (mass %) of the (C-2) curing agent as the component (C) is preferably 15 mass % or more, more preferably 20 mass % or more, even more preferably 25 mass % or more, or 30 mass % or more, and is preferably 60 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 %.

[0131] The range of the weight average molecular weight (Mw) of the thermosetting resin (C) can usually be the same as the range of the weight average molecular weight of the epoxy resin (C-1) described above.

[0132] The content (mass%) of the (C) thermosetting resin is preferably 0.2 mass% or more, more preferably 1 mass% or more, and even more preferably 2 mass% or more, and is preferably 20 mass% or less, more preferably 10 mass% or less, and even more preferably 6 mass% or less, when the non-volatile components of the resin composition are taken as 100 mass%.

[0133] The content (mass%) of the (C) thermosetting resin, when the resin component of the resin composition is taken as 100 mass%, is preferably 30 mass% or more, more preferably 40 mass% or more, even more preferably 50 mass% or more, or 60 mass% or more, and is preferably 95 mass% or less, more preferably 90 mass% or less, even more preferably 88 mass% or less.

[0134] <(D) Thermoplastic Resin> The resin composition may further contain a (D) thermoplastic resin as an optional component in combination with the above-described (A) to (C) components. The (D) thermoplastic resin as the (D) component does not include those corresponding to the above-described (A) to (C) components. The (D) thermoplastic resin may be used alone, or two or more types may be used in combination.

[0135] Examples of the thermoplastic resin (D) 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.

[0136] 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.

[0137] 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).

[0138] 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.

[0139] 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.

[0140] 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.

[0141] 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.

[0142] A specific example of the polyethersulfone resin is "PES5003P" manufactured by Sumitomo Chemical Co., Ltd.

[0143] Specific examples of polysulfone resins include polysulfone "P1700" and "P3500" manufactured by Solvay Advanced Polymers.

[0144] 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.

[0145] 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.

[0146] 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.

[0147] The weight average molecular weight (Mw) of the thermoplastic resin (D) 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.

[0148] The content (mass%) of the (D) 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 0.4 mass% or more, and is preferably 5 mass% or less, more preferably 3 mass% or less, and even more preferably 2 mass% or less.

[0149] The content (mass%) of the (D) thermoplastic resin, when the resin component of the resin composition is taken as 100 mass%, is preferably 3 mass% or more, more preferably 5 mass% or more, even more preferably 8 mass% or more, or 10 mass% or more, and is preferably 45 mass% or less, more preferably 40 mass% or less, even more preferably 35 mass% or less.

[0150] <(E) Dispersant> The resin composition may further contain an optional (E) dispersant in combination with the above-described (A) to (C) components. The (E) dispersant as the (E) component does not include those corresponding to the above-described (A) to (D) components. The (E) dispersant can improve the dispersibility of the (A) and (B) components. Furthermore, by including the (E) dispersant in the resin composition, it is possible to obtain a cured product with excellent maximum strength and elongation. The (E) dispersant may be used alone, or two or more types may be used in combination.

[0151] The (E) dispersant may be a compound capable of reducing the viscosity of the resin composition. Examples of the (E) dispersant include phosphate ester dispersants, polyoxyalkylene dispersants, acetylene dispersants, silicone dispersants, anionic dispersants, and cationic dispersants. Among these, the (E) dispersant preferably contains a cationic dispersant, from the viewpoint of significantly achieving the effects of the present invention.

[0152] Among phosphate ester-based dispersants, polyether-type phosphate ester-based dispersants are preferred. Polyether-type phosphate ester-based dispersants are phosphate ester-based dispersants that contain a poly(alkyleneoxy) structure in the molecule. Examples of polyether-type phosphate ester-based dispersants include polyoxyalkylene alkyl ether phosphate esters and polyoxyalkylene alkylphenyl ether phosphate esters.

[0153] The polyoxyalkylene alkyl ether phosphate ester may have a structure in which 1 to 3 alkyl-oxy-poly(alkyleneoxy) groups are bonded to the phosphorus atom of the phosphate. The number of alkyleneoxy units (repeating units) in the poly(alkyleneoxy) moiety in the alkyl-oxy-poly(alkyleneoxy) group is preferably 2 to 30, more preferably 3 to 20. The alkylene group in the poly(alkyleneoxy) moiety is preferably an alkylene group having 2 to 4 carbon atoms. Examples of such alkylene groups include an ethylene group, a propylene group, an isopropylene group, a butylene group, and an isobutyl group. Furthermore, the alkyl group in the alkyl-oxy-poly(alkyleneoxy) group is preferably an alkyl group having 6 to 30 carbon atoms, more preferably an alkyl group having 8 to 20 carbon atoms. Examples of such alkyl groups include decyl, undecyl, dodecyl, tridecyl, tetradecyl, pentadecyl, hexadecyl, heptadecyl, and octadecyl groups. When the polyoxyalkylene alkyl ether phosphate ester has multiple alkyl-oxy-poly(alkyleneoxy) groups, the multiple alkyl groups may be the same or different. Furthermore, the multiple alkylene groups may be the same or different.

[0154] Examples of commercially available phosphate ester dispersants include polyether phosphate ester dispersants manufactured by Kusumoto Chemical Industries Co., Ltd. (for example, HIPLAAD series "ED152", "ED153", "ED154", "ED118", "ED174", "ED251", etc.); and Phosphanol series "RS-410", "RS-610", "RS-710" manufactured by Toho Chemical Industry Co., Ltd.

[0155] Examples of polyoxyalkylene dispersants include polyoxyethylene alkyl ethers, polyoxyethylene alkyl esters, polyoxyethylene sorbitan fatty acid esters, polyoxyethylene alkylphenyl ethers, polyoxyethylene alkylamines, polyoxyethylene alkylamides, etc. Commercially available examples of polyoxyalkylene dispersants include "AKM-0531," "AFB-1521," "SC-0505K," "SC-1015F," and "SC-0708A," as well as "HKM-50A," from the "Marialim" series manufactured by NOF Corporation.

[0156] An example of an acetylene-based dispersant is acetylene glycol. Examples of commercially available acetylene-based dispersants include "82", "104", "440", "465", and "485" from the "Surfynol" series manufactured by Air Products and Chemicals Inc., as well as "Olefin Y".

[0157] Examples of silicone-based dispersants include polyether-modified polydimethylsiloxane, polyether-modified siloxane, polyester-modified polydimethylsiloxane, etc. Examples of commercially available silicone-based dispersants include "BYK347" and "BYK348" manufactured by BYK-Chemie.

[0158] Examples of anionic dispersants include sodium polyacrylate, sodium dodecyl benzelsulfonate, sodium laurate, polyoxyethylene alkyl ether ammonium sulfate, carboxymethyl cellulose sodium salt, etc. Examples of commercially available anionic dispersants include "PN-411" and "PA-111" manufactured by Ajinomoto Fine-Techno Co., Ltd., and "A-550" and "PS-1900" manufactured by Lion Corporation.

[0159] Examples of cationic dispersants include amino group-containing polyacrylate resins, amino group-containing polystyrene resins, etc. Commercially available examples of cationic dispersants include "161", "162", "164", "182", "2000", and "2001" manufactured by BYK-Chemie; "PB-821", "PB-822", and "PB-824" manufactured by Ajinomoto Fine-Techno Co., Ltd.; "V-216" and "V-220" manufactured by ISP Japan; and "Solsperse 13940", "Solsperse 24000", and "Solsperse 32000" manufactured by Lubrizol Corporation.

[0160] The content (mass%) of the (E) dispersant, when the non-volatile components of the resin composition are taken as 100 mass%, is preferably 0.01 mass% or more, more preferably 0.05 mass% or more, even more preferably 0.1 mass% or more, and is preferably 5 mass% or less, more preferably 4 mass% or less, even more preferably 3 mass% or less, 2 mass% or less, 1 mass% or less, or 0.5 mass% or less.

[0161] The content (mass%) of the (E) dispersant, when the resin component of the resin composition is taken as 100 mass%, is preferably 0.5 mass% or more, more preferably 1 mass% or more, and even more preferably 1.5 mass% or more, and is preferably 50 mass% or less, more preferably 40 mass% or less, and even more preferably 30 mass% or less, 20 mass% or less, 10 mass% or less, 8 mass% or less, 5 mass% or less, or 3 mass% or less.

[0162] <(F) Curing Accelerator> The resin composition may further contain a (F) curing accelerator as an optional component in combination with the above-described components (A) to (E). The (F) curing accelerator as component (F) does not include those corresponding to the above-described components (A) to (E). The (F) curing accelerator functions as a catalyst for the reaction of the (C) thermosetting resin, and therefore can accelerate the curing of the resin composition. One type of (F) curing accelerator may be used alone, or two or more types may be used in combination.

[0163] Examples of the (F) 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 (F) 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 (F) curing accelerator.

[0164] 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.

[0165] 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.

[0166] As the phosphorus-based curing accelerator, commercially available products may be used, for example, "TBP-DA" manufactured by Hokko Chemical Industry Co., Ltd.

[0167] 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.

[0168] 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.

[0169] 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.

[0170] 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.

[0171] 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.

[0172] The content (mass%) of the (F) 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.

[0173] The content (mass%) of the (F) curing accelerator, when the resin component of the resin composition is taken as 100 mass%, is preferably 0.1 mass% or more, more preferably 0.2 mass% or more, even more preferably 0.3 mass% or more, and is preferably 5 mass% or less, more preferably 1.5 mass% or less, even more preferably 1 mass% or less.

[0174] <(G) Optional Additives> The resin composition may further contain (G) optional additives as an optional component in combination with the above-described components (A) to (F). The optional additives (G) as component (G) do not include those corresponding to the above-described components (A) to (F).

[0175] Examples of the optional additives (G) include magnetic powders that do not fall under the category of components (A) and (B); organic fillers such as rubber particles; 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; bentone, monmo Examples of the additives include thickeners such as lilonite; antifoaming agents such as silicone antifoaming agents, acrylic antifoaming agents, fluorine antifoaming agents, and vinyl resin antifoaming agents; ultraviolet absorbers such as benzotriazole ultraviolet absorbers; adhesion improvers such as urea silane; adhesion promoters such as triazole adhesion promoters, tetrazole adhesion promoters, and triazine adhesion promoters; antioxidants such as hindered phenol 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. (G) Optional additives may be used alone or in combination of two or more.

[0176] The total content (mass%) of the resin components is preferably 1 mass% or more, more preferably 2 mass% or more, and even more preferably 3 mass% or more, and is preferably 10 mass% or less, more preferably 8 mass% or less, and even more preferably 5 mass% or less, when the non-volatile components of the resin composition are taken as 100 mass%.

[0177] 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 35 vol % or less, more preferably 30 vol % or less, and even more preferably 25 vol % or less, when the non-volatile components of the resin composition are taken as 100 vol %.

[0178] <(H) Solvent> The resin composition may further contain (H) solvent as a volatile component in addition to the non-volatile components (A) to (G) described above.

[0179] As the (H) solvent, an organic solvent is usually used, for example, ketone-based solvents such as acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, etc.; ester-based solvents such as methyl acetate, ethyl acetate, butyl acetate, isobutyl acetate, isoamyl acetate, methyl propionate, ethyl propionate, γ-butyrolactone, etc.; ether-based solvents such as tetrahydropyran, tetrahydrofuran, 1,4-dioxane, diethyl ether, diisopropyl ether, dibutyl ether, diphenyl ether, etc.; alcohol-based solvents such as methanol, ethanol, propanol, butanol, ethylene glycol, etc.; 2-ethoxyethyl acetate, propylene glycol monomethyl ether acetate, diethylene glycol monoethyl ether acetate, ethyl diglycol acetate, γ-butyrolactone, methyl methoxypropionate, etc. ether ester-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, and trimethylbenzene. The (H) solvent may be used alone or in combination of two or more.

[0180] The amount of (H) solvent is preferably set so as to adjust the melt viscosity of the resin composition within an appropriate range. With respect to 100% by mass of all components in the resin composition, the content of (H) solvent is preferably 10% by mass or less, more preferably 8% by mass or less, even more preferably 6% by mass or less, 5% by mass or less, or 4% by mass or less, and is preferably 0.01% by mass or more, more preferably 0.05% by mass or more, and even more preferably 0.1% by mass or more. By adjusting the content of (H) solvent to fall within this range, it is possible to suppress the generation of voids due to the evaporation of (H) solvent. Furthermore, it is possible to improve the handleability and workability of the resin composition.

[0181] <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 (H) can be volatilized by the heat during thermal curing, but non-volatile components such as components (A) to (G) 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.

[0182] The resin composition according to the present embodiment contains a combination of components (A) and (B) and adjusts the particle size of the entire particles contained in the resin composition, thereby achieving both improved relative permeability and improved coatability. Furthermore, a cured product can be obtained that typically has a low loss factor, excellent peak strength, and excellent elongation.

[0183] The resin composition exhibits excellent applicability. Therefore, even if the amount of solvent contained in the resin composition is small, the resin composition has high fluidity, allowing for smooth application. Therefore, the resin composition can preferably have a small solvent content, and more preferably can be solvent-free.

[0184] Although there are no particular limitations on the properties of the resin composition, it is preferable that the resin composition be in a paste form with fluidity. For example, the resin composition may be made into a paste-like resin composition using a solvent. Furthermore, for example, the resin composition may be made into a solvent-free paste-like resin composition by using a liquid thermosetting resin such as a liquid epoxy resin. When the solvent content in the resin composition is low or when no solvent is included, the generation of voids due to solvent evaporation can be suppressed, and the resin composition can also be made easy to handle and work with.

[0185] 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 35 or more, more preferably 35.5 or more, and even more preferably 36 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.

[0186] A cured product obtained by thermally curing a resin composition at 190°C for 90 minutes typically exhibits the characteristic of a small loss factor tan δ. For example, when the loss factor tan δ is measured at a measurement frequency of 10 MHz and a room temperature of 23°C, the loss factor tan δ is preferably 0.1 or less, more preferably 0.095 or less, and even more preferably 0.09 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 tan δ can be measured by the method described in the examples below.

[0187] A cured product obtained by thermally curing a resin composition at 190°C for 90 minutes usually exhibits the characteristic of having a high maximum point strength. The maximum point strength can be determined by a tensile strength test in accordance with JIS K7127. The maximum point strength measured under conditions of 25°C is preferably 20 MPa or more, more preferably 30 MPa or more, and even more preferably 35 MPa or more. There is no particular limit on the upper limit of the maximum point strength, and it can be, for example, 100 MPa or less. The maximum point strength can be measured by the method described in the examples below.

[0188] A cured product obtained by thermally curing a resin composition at 190°C for 90 minutes usually exhibits the characteristic of a large elongation percentage. The elongation percentage can be determined by a tensile strength test in accordance with JIS K7127. The elongation percentage measured under conditions of 25°C is preferably 0.2% or more, more preferably 0.25% or more, and even more preferably 0.3% or more. There is no particular restriction on the upper limit of the elongation percentage, and it can be, for example, 10% or less. The elongation percentage can be measured by the method described in the examples below.

[0189] 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.

[0190] <Method for producing resin composition> The resin composition can be produced, for example, by mixing the above-mentioned components. The above-mentioned components may be mixed partially or entirely at the same time, or may be mixed sequentially. In the process of mixing each component, the temperature may be set appropriately, and thus heating and / or cooling may be performed temporarily or throughout. Furthermore, stirring or shaking may be performed in the process of mixing each component. Furthermore, degassing may be performed under low-pressure conditions, such as under vacuum.

[0191] [Magnetic Paste] The magnetic paste contains the resin composition described above. The magnetic paste is usually a fluid paste containing the resin composition, and can therefore be preferably used to fill holes by printing. This magnetic paste may contain only the resin composition described above, or may contain any component in combination with the resin composition. Preferably, the paste-like resin composition itself can be used as the magnetic paste.

[0192] The magnetic paste is preferably in a paste form at 23°C. The viscosity of this magnetic paste at 23°C is preferably 20 Pa·s or more, more preferably 25 Pa·s or more, even more preferably 30 Pa·s or more, and particularly preferably 50 Pa·s or more, and is preferably 200 Pa·s or less, more preferably 180 Pa·s or less, and even more preferably 160 Pa·s or less. The viscosity can be measured using an E-type viscometer ("RE-80U" manufactured by Toki Sangyo Co., Ltd., 3° ​​x R9.7 rotor) under measurement conditions of a measurement sample volume of 0.22 ml and a rotation speed of 5 rpm.

[0193] [Cured Product] The cured product of the present invention is obtained by curing the resin composition or magnetic paste of the present invention. The curing conditions for the resin composition and the magnetic paste may be the conditions of step (2) described below. In addition, the magnetic paste may be preheated before being thermally cured, and heating may be performed multiple times, including preheating.

[0194] [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.

[0195] 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.

[0196] 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.

[0197] 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.

[0198] When a metal foil is used as the support, examples of the metal foil include copper foil and aluminum foil, with copper foil being preferred. The copper foil may be a foil made of a single metal, 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.).

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

[0200] The support may also be a support with a release layer, which has a release layer on the surface that bonds 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.

[0201] 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.

[0202] 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.

[0203] 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.

[0204] The content of the (H) solvent in the resin composition at the time of application before drying is preferably 10% by mass or less, more preferably 8% by mass or less, even more preferably 6% by mass or less, 5% by mass or less, or 4% by mass or less, and is preferably 0.01% by mass or more, more preferably 0.05% by mass or more, and even more preferably 0.1% by mass or more, relative to 100% by mass of all components in the resin composition. By adjusting the amount of the (H) solvent so that it falls within this range, it is possible to suppress the generation of voids due to the evaporation of the (H) solvent.

[0205] 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.

[0206] The content of the (H) solvent in the resin composition layer after drying can 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 all components in the resin composition layer. It is particularly preferable that the resin composition does not contain the (H) solvent. When the amount of the (H) solvent is small, the generation of voids due to the evaporation of the (H) solvent can be suppressed. Furthermore, the handleability and workability of the resin composition layer can be improved.

[0207] 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.

[0208] [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.

[0209] <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, the cured product is preferably formed using a paste-like resin composition. The following description will be given using an example of a substrate having through-holes formed therein as holes penetrating the substrate in the thickness direction.

[0210] 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.

[0211] 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.

[0212] 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.

[0213] 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.

[0214] 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.

[0215] 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.

[0216] 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.

[0217] 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.

[0218] 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).

[0219] 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).

[0220] 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.

[0221] 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 arithmetic mean roughness (Ra) can be measured using a non-contact surface roughness meter.

[0222] 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.

[0223] 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.

[0224] 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.

[0225] 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.

[0226] 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.

[0227] 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.

[0228] 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.

[0229] 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 arithmetic mean roughness (Ra) can be measured using a non-contact surface roughness meter.

[0230] -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.

[0231] 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.

[0232] 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.

[0233] 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.

[0234] 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.

[0235] By the above method, the circuit board 1 including the cured product 30 of the resin composition 30a can be manufactured.

[0236] <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.

[0237] -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.

[0238] 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.

[0239] 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.

[0240] 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.

[0241] Examples of conductive materials that can form the first conductor layer 420 and the external terminals 240 include the same materials as those for the conductor layers described in the first example.

[0242] 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.

[0243] 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.

[0244] 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.

[0245] 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.

[0246] 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.

[0247] 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.

[0248] 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.

[0249] 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.

[0250] 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.

[0251] 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).

[0252] 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 arithmetic mean roughness (Ra) can be measured using a non-contact surface roughness meter.

[0253] 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.

[0254] -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.

[0255] 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.

[0256] 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 arithmetic mean roughness (Ra) can be measured using a non-contact surface roughness meter.

[0257] 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.

[0258] 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.

[0259] 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.

[0260] 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.

[0261] 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.

[0262] 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.

[0263] 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.

[0264] [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.

[0265] 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.

[0266] 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.

[0267] 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.

[0268] 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.

[0269] 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.

[0270] 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 Figure 13 or 14, the spiral wiring portion includes a straight portion and a bent portion bent at a right angle. In Figure 13 or 14, the spiral wiring portion of the second conductor layer 44 has an overall outline that is approximately rectangular, and has a shape that is wound clockwise from the center toward the outside.

[0271] 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.

[0272] 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.).

[0273] The present invention will be described in more detail 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). Furthermore, the amount of each element contained in component (B) was measured using an inductively coupled plasma optical emission spectrometer.

[0274] Example 1 Preparation of Resin Composition 1 A resin composition was prepared by mixing 85.11 parts by mass of nanocrystalline magnetic powder ("KUAMET NC1-V1 038CO3A" manufactured by Epson Atmix Corporation), 12.62 parts by mass of Fe—Ni alloy magnetic powder ("NiFe-GB1001" manufactured by Guangbo Co., Ltd.), and 1.22 parts by mass of liquid epoxy resin ("ZX-1059" manufactured by Nippon Steel Chemical & Material Co., Ltd., a mixture of bisphenol A epoxy resin and bisphenol F epoxy resin, true density 1.2 g / cm). ３ 1.11 parts by mass of a biphenyl-skeleton phenol-based curing agent ("GPH-65" manufactured by Nippon Kayaku Co., Ltd., true density 1.2 g / cm ３ ) 1.56 parts by mass, a solid epoxy resin (DIC Corporation "HP-4700", a naphthalene-type tetrafunctional epoxy resin, true density 1.2 g / cm ３) 0.48 parts by mass, phenoxy resin ("YX7553BH30" manufactured by Mitsubishi Chemical Corporation, a solution of methyl ethyl ketone:cyclohexanone = 1:1 with 30% non-volatile components, a special skeleton phenoxy resin, true density of the non-volatile components 1.2 g / cm ３ ) 1.42 parts by mass, a curing accelerator ("2PHZ-PW" manufactured by Shikoku Chemicals Corporation, an imidazole-based curing accelerator, true density 1.2 g / cm ３ ) 0.02 parts by mass, a dispersant ("PB-821" manufactured by Ajinomoto Fine-Techno Co., Inc., cationic dispersant, true density 1.2 g / cm ３ 0.11 parts by mass of toluene, 0.11 parts by mass of methyl ethyl ketone (MEK) as a solvent, and 0.70 parts by mass of cyclohexanone (Anone) as a solvent were mixed and uniformly dispersed in a high-speed rotating mixer to prepare resin composition 1.

[0275] Examples 2 to 10 and Comparative Examples 1 to 4: Preparation of Resin Compositions 2 to 14 In Example 1, the type of each component was changed in the parts by mass shown in the table below. Resin compositions 2 to 14 were prepared in the same manner as in Example 1 except for the above.

[0276] *1: Indicates the content when the non-volatile components in the resin composition are taken as 100% by volume.

[0277] Details of each component listed in the table are as follows: Component (A) KUAMET NC1-53 μm: Epson Atmix Corporation, average particle size (D ５０ ) is 27 μm, 10% particle size (D １０ ) is 11 μm, 90% particle size (D ９０ ) is 57 μm. KUAMET NC-V1 038CO3A: Epson Atmix Corporation, average particle size (D ５０ ) is 16 μm, 10% particle size (D １０ ) is 6.8 μm, 90% particle size (D ９０ ) is 38 μm (B) Component NiFe-GB0501, Fe-Ni alloy magnetic powder, manufactured by Guangbo Co., Ltd., oxygen atom content 0.46 mass%, Fe and Ni content ratio (Fe content:Ni content) = 1.01:1, 1, average particle size (D ５０ ) is 1 μm, 10% particle size (D １０) is 0.3 μm, 90% particle size (D ９０ ) is 1.3 μm. NiFe-GB1001, Fe-Ni alloy magnetic powder, manufactured by Guangbo Co., Ltd., oxygen atom content 0.34 mass %, Fe and Ni content ratio (Fe content:Ni content) = 1.01:1, average particle size (D ５０ ) is 1.4 μm, 10% particle size (D １０ ) is 1.2 μm, 90% particle size (D ９０ ) is 2.7 μm. Component (C) ZX-1059: a 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., true density 1.2 g / cm ３ HP-4700: naphthalene-type tetrafunctional epoxy resin, manufactured by DIC Corporation, functional group equivalent weight 162 g / eq., true density 1.2 g / cm ３ GPH-65: biphenyl skeleton phenolic curing agent, manufactured by Nippon Kayaku Co., Ltd., true density 1.2 g / cm ３ Component (D) YX7553BH30: phenoxy resin, 1:1 solution of MEK and cyclohexanone with a nonvolatile content of 30% by mass, manufactured by Mitsubishi Chemical Corporation Component (E) PB-821: cationic dispersant, manufactured by Ajinomoto Fine-Techno Co., Inc., true density 1.2 g / cm ３ 161: Cationic dispersant, manufactured by BYK-Chemie, true density 1.2 g / cm ３ PA-111: Anionic dispersant, manufactured by Ajinomoto Fine-Techno Co., Inc., true density 1.2 g / cm ３ Component (F) 2PHZ-PW: Imidazole curing accelerator, manufactured by Shikoku Chemicals Corporation, true density 1.2 g / cm ３ ) (G) Component NiFe-GB1501: FeNi magnetic powder having a composition ratio of Fe:Ni of 0.85:1 to 1.25:1 and an oxygen atom content of less than 0.3 mass%, manufactured by Guangbo Co., Ltd., oxygen atom content 0.26 mass%, Fe to Ni content ratio (Fe content:Ni content) = 1.01:1, average particle size (D ５０ ) is 2.8 μm, 10% particle size (D １０ ) is 2.1 μm, 90% particle size (D ９０) is 3.4 μm. MA-RCO-40: FeNi magnetic powder with a composition ratio of Fe:Ni of 0.001 to 0.85:1 or 1.25 to 99:1, and an oxygen atom content of 0.3 mass% or more, manufactured by Mitsubishi Steel Corporation, oxygen atom content 0.34 mass%, Fe to Ni content ratio (Fe content:Ni content) = 0.25:1, average particle size (D ５０ ) is 3.1 μm, 10% particle size (D １０ ) is 1.1 μm, 90% particle size (D ９０ ) is 5.9 μm CVD iron powder (0.7 μm): Product name "CVD iron powder (0.7 μm)", manufactured by JFE Mineral Co., Ltd., average particle size (D ５０ ) is 0.7 μm, 10% particle size (D １０ ) is 0.42 μm, 90% particle size (D ９０ ) is 1.18 μm (H) Component Toluene: toluene MEK: methyl ethyl ketone Anone: cyclohexanone

[0278] <Measurement of particle size distribution of all particles> 100 mg of the particles used in each example and 10 g of methyl ethyl ketone were weighed into a vial and dispersed by ultrasonic waves for 10 minutes. The particle size distribution of the particles was measured on a volume basis using a laser diffraction particle size distribution measuring device ("LA-960" manufactured by Horiba, Ltd.). From the obtained particle size distribution, the D of the particles was determined as the median diameter. １０ , D ５０ and D ９０ was calculated.

[0279] <Evaluation of Coatability of Resin Composition> Coatability was evaluated for resin compositions 1 to 14. 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 with a doctor blade so that the thickness of the resin composition layer after drying would be 100 μm, thereby obtaining a magnetic sheet. The fluidity of the resin composition was confirmed, and the presence or absence of coatability was evaluated according to the following evaluation criteria: ∘: The resin composition was in a paste state with fluidity and was coatable. ×: The resin composition lacked fluidity and could not be coated. Alternatively, the resin composition was in a paste state with fluidity, but streaks occurred during coating, making it impossible to coat.

[0280] <Measurement of Relative Permeability and Loss Factor> The magnetic sheet prepared for evaluating the coatability of the resin composition 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. The obtained sheet-like cured product was cut to obtain a doughnut-shaped evaluation sample with an outer diameter of 19.2 mm and an inner diameter of 8.2 mm. The relative permeability (μ'), magnetic loss (μ''), and loss factor (tan δ) of this evaluation sample were measured at a measurement frequency of 10 MHz and a room temperature of 23°C using a Keysight magnetic material test fixture "16454A" and a Keysight impedance analyzer "E4991B". The loss factor tan δ was calculated using the following formula, "tan δ = μ'' / μ'", and the relative permeability and loss factor were evaluated according to the following criteria: ◯: Relative permeability of 35 or more. ×: Relative permeability of less than 35. Good: Loss factor tan δ is 0.10 or less. Bad: Loss factor tan δ is more than 0.10.

[0281] <Measurement of Maximum Point Strength and Elongation> The magnetic sheet prepared for evaluating the resin composition coatability 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. Using the obtained sheet-like cured product, tensile strength measurements were performed in accordance with Japanese Industrial Standards (JIS K7127), and the maximum point strength and elongation at 25°C were measured. For the measurements, an Orientec RTC-1250A tensile tester was used, and five measurements were performed, and the average values ​​were calculated. The maximum point strength and elongation were evaluated according to the following criteria: ⊚: Maximum point strength was 30 MPa or more; 〇: Maximum point strength was 20 MPa or more and less than 30 MPa; ×: Maximum point strength was less than 20 MPa; ⊚: Elongation was 0.25% or more; 〇: Elongation was 0.15% or more and less than 0.25%; ×: Elongation was less than 0.15%.

[0282]

[0283] It has been confirmed that the resin compositions according to Examples 1 to 10 have two or more peak tops in the particle size distribution.

[0284] REFERENCE SIGNS LIST 1 Circuit board 10 Core board 11 Support board 12 Metal layer 13 Metal layer 14 Through hole 20 Plating 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) nanocrystalline magnetic powder, (B) magnetic powder containing Fe and Ni, and (C) a thermosetting resin, wherein the content ratio of Fe and Ni contained in component (B) (Fe content / Ni content) is 0.85 or more and 1.25 or less, the content of oxygen atoms contained in component (B) is 0.3 mass% or more relative to 100 mass% of component (B), and the 10% particle diameter (D １０ ) is 0.2 μm or more and 4 μm or less.

2. The resin composition according to claim 1, which has two or more peak tops in its particle size distribution.

3. Average particle size of component (B) (D ５０ 2. The resin composition according to claim 1, wherein the particle size is greater than 0.8 μm and less than 1.5 μm.

4. Average particle size of component (A) (D ５０ 2. The resin composition according to claim 1, wherein the particle size is greater than 15 μm and less than 50 μm.

5. The resin composition according to claim 1, wherein component (C) comprises epoxy resin (C-1).

6. The resin composition according to claim 1, wherein component (C) includes a curing agent (C-2).

7. The resin composition according to claim 1, further comprising (E) a dispersant.

8. The resin composition according to claim 7, wherein component (E) comprises a cationic dispersant.

9. The resin composition according to claim 1, further comprising (F) a curing accelerator.

10. A resin composition according to claim 1, wherein the volume ratio of component (A) is 0.60 or more and 0.92 or less when the total content (volume %) of components (A) and (B) is 1.

11. The resin composition according to claim 1, wherein the content of oxygen atoms contained in component (B) is 27% by mass or less based on 100% by mass of component (B).

12. The resin composition according to claim 1, which is used for filling holes.

13. A cured product of the resin composition according to any one of claims 1 to 12.

14. A magnetic paste comprising the resin composition according to any one of claims 1 to 12.

15. A magnetic sheet comprising a support and a resin composition layer provided on the support, wherein the resin composition layer contains the resin composition according to any one of claims 1 to 12.

16. A circuit board comprising a substrate having a hole, and a cured product of the resin composition according to any one of claims 1 to 12 filled in the hole.

17. A circuit board comprising a cured layer containing a cured product of the resin composition according to any one of claims 1 to 12.

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

19. An inductor substrate comprising the circuit board of claim 17.

20. A method for producing a resin composition according to claim 1, comprising: (A) nanocrystalline magnetic powder; (B) magnetic powder containing Fe and Ni; and (C) a thermosetting resin, wherein the average particle size (D) of the component (A) is ５０ ) is more than 15 μm and less than 50 μm, the content ratio of Fe and Ni contained in component (B) (Fe content / Ni content) is 0.85 or more and 1.25 or less, and the average particle size (D ５０ ) is more than 0.8 μm and less than 1.5 μm, the content of oxygen atoms contained in component (B) is 0.3 mass% or more relative to 100 mass% of component (B), and 10% particle diameter (D １０ ) is 0.2 μm or more and 4 μm or less.

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