Resin composition and method for producing same

Abstract

According to the present invention, a resin composition includes (A) a nanocrystal magnetic powder that has a particle diameter of 5.5–20 μm, (B) a magnetic powder that has a particle diameter of no more than 2 μm, and (D) a thermosetting resin. The (A) component is 23–60 vol% of the 100 vol% of the non-volatile components of the resin composition, and the (B) component is 5–30 vol% of the 100 vol% of the non-volatile components of the resin composition.

Description

[Technical Field]

[0001] The present invention relates to a resin composition and a method for producing the same, and further to a cured product obtained from the resin composition, a resin sheet and a method for producing the same, a circuit board, and an inductor board. [Background technology]

[0002] With the recent trend toward smaller and lighter electronic devices and the widespread use of portable devices, switching power supply circuits have been made smaller and more powerful. Switching power supply circuits usually include an inductor (Patent Documents 1 to 3). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2017-69523 [Patent Document 2] International Publication No. 2006 / 54749 [Patent Document 3] Japanese Patent Application Publication No. 2019-192920 Summary of the Invention [Problem to be solved by the invention]

[0004] In order to miniaturize switching power supplies, miniaturization of inductors is required (Patent Document 1). Increasing the switching frequency is advantageous for miniaturizing inductors. However, the magnetic materials used to form inductors generally have large magnetic losses due to eddy current losses inside the magnetic powder at high frequencies, resulting in a decrease in the efficiency of the switching power supply (Patent Document 2). Furthermore, when the size of the metal magnetic powder is large, the eddy current loss inside the metal magnetic powder increases. Therefore, high-speed switching operations such as those from 50 MHz to 100 MHz result in large losses, making it difficult to support high frequencies (Patent Document 3).

[0005] Given this background, there has been a recent demand for inductors that can operate in a relatively low frequency band of around 10 MHz, which is lower than conventional inductors. Therefore, in order to simultaneously achieve high functionality and miniaturization of inductors, there is a demand for magnetic materials that can achieve high relative permeability and low magnetic loss in the low frequency band.

[0006] In addition, the resin composition may be applied when used. For example, when producing a resin sheet having a resin composition layer containing the resin composition, the resin composition may be applied onto a support. In addition, for example, when filling holes formed in a substrate with the resin composition, the resin composition may be applied onto the substrate to fill the holes. Therefore, the resin composition is required to have excellent application properties.

[0007] The present invention has been made in view of the above-mentioned problems, and aims to provide a resin composition and a method for producing the same, which can give a cured product that can achieve high relative permeability and low magnetic loss in the low frequency band and has excellent coatability; a cured product of the resin composition; a resin sheet containing the resin composition and a method for producing the same; and a circuit board and an inductor board each containing a cured product of the resin composition. [Means for solving the problem]

[0008] The present inventors have conducted extensive research to solve the above-mentioned problems. As a result, the present inventors have found that the above-mentioned problems can be solved by a resin composition containing a nanocrystalline magnetic powder having a particle size within a specific range, a magnetic powder having a particle size within another specific range, and a thermosetting resin. The present inventors have also found that the above-mentioned problems can be solved by a resin composition containing a nanocrystalline magnetic powder having an average particle size within a specific range, a magnetic powder having an average particle size within another specific range, and a thermosetting resin. The present invention was completed based on these findings. That is, the present invention includes the following.

[0009] [1] (A) a nanocrystalline magnetic powder having a particle size of 5.5 μm or more and 20 μm or less; (B) a magnetic powder having a particle size of 2 μm or less; (D) a thermosetting resin, The amount of component (A) is 23% by volume or more and 60% by volume or less, based on 100% by volume of the nonvolatile components of the resin composition; A resin composition, wherein the amount of component (B) is 5% by volume or more and 30% by volume or less, based on 100% by volume of the nonvolatile components of the resin composition. [2] The resin composition according to [1], wherein the volume ratio of component (A) to component (B) (component (A) / component (B)) is 1 or more and 12 or less. [3] (C) further containing magnetic powder, The resin composition according to [1] or [2], wherein the magnetic powder (C) is a magnetic powder other than the component (A) and has a particle size of more than 2 μm and not more than 20 μm. [4] The resin composition according to any one of [1] to [3], wherein the component (D) comprises an epoxy resin. [5] The resin composition according to any one of [1] to [4], further comprising (E) a curing accelerator. [6] (a) a nanocrystalline magnetic powder having an average particle size of 5.5 μm or more and 20 μm or less; (b) a magnetic powder having an average particle size of 2 μm or less; (D) a thermosetting resin. [7] (a) a nanocrystalline magnetic powder having an average particle size of 5.5 μm or more and 20 μm or less; (b) a magnetic powder having an average particle size of 2 μm or less; (D) a thermosetting resin. [8] The method for producing a resin composition according to [6] or [7], wherein the amount of component (a) is 30% by volume or more and 80% by volume or less, based on 100% by volume of the nonvolatile components of the resin composition. [9] (a) 10% particle size of component D 10 The method for producing a resin composition according to any one of [6] to [8], wherein the average particle diameter is greater than 2 μm.

[10] The method for producing a resin composition according to any one of [6] to [9], wherein the amount of component (b) is 5% by volume or more and 50% by volume or less relative to 100% by volume of the non-volatile components of the resin composition.

[11] (b) 90% particle size of component D 90 The method for producing a resin composition according to any one of [6] to

[10] , wherein the average particle size is less than 5.5 μm.

[12] (c) further mixing with magnetic powder; The method for producing a resin composition according to any one of [6] to

[11] , wherein the (c) magnetic powder has an average particle size of more than 2 μm and not more than 20 μm, and smaller than the average particle size of the (a) component.

[13] The method for producing a resin composition according to

[12] , wherein (c) the amount of magnetic powder is 34% by volume or less relative to 100% by volume of the nonvolatile components of the resin composition.

[14] A cured product of the resin composition according to any one of [1] to [5].

[15] A support and a resin composition layer formed on the support, A resin sheet, wherein a resin composition layer contains the resin composition according to any one of [1] to [5].

[16] A step of producing a resin composition by the production method according to any one of [6] to

[13] ; and applying the resin composition onto a support.

[17] A circuit board comprising a cured product of the resin composition according to any one of [1] to [5].

[18] The circuit board according to

[17] , comprising a substrate having through holes formed therein and a cured product of the resin composition filled in the through holes.

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

[17] or

[18] . [Effects of the Invention]

[0010] According to the present invention, it is possible to provide a resin composition and a method for producing the same, which can give a cured product that can achieve high relative permeability and low magnetic loss in the low frequency band and has excellent coatability; a cured product of the resin composition; a resin sheet containing the resin composition and a method for producing the same; and a circuit board and an inductor board each containing a cured product of the resin composition. [Brief explanation of the drawings]

[0011] [Figure 1] 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 example of a fourth embodiment of the present invention. [Figure 2] FIG. 2 is a cross-sectional view schematically showing a core substrate in which a through-hole is formed, in a method for manufacturing a circuit board according to a first example of the fourth embodiment of the present invention. [Figure 3] FIG. 3 is a cross-sectional view that schematically shows a core substrate in which a plating layer has been formed in a through-hole in a method for manufacturing a circuit board according to a first example of the fourth embodiment of the present invention. [Figure 4] FIG. 4 is a cross-sectional view that schematically shows a state in which a resin composition is filled into a through-hole in a core substrate in a method for manufacturing a circuit board according to a first example of the fourth embodiment of the present invention. [Figure 5] FIG. 5 is a schematic cross-sectional view for explaining step (2) of the method for manufacturing a circuit board according to the first example of the fourth embodiment of the present invention. [Figure 6] FIG. 6 is a schematic cross-sectional view for explaining step (3) of the method for manufacturing a circuit board according to the first example of the fourth embodiment of the present invention. [Figure 7] FIG. 7 is a schematic cross-sectional view for explaining step (5) of the method for manufacturing a circuit board according to the first example of the fourth embodiment of the present invention. [Figure 8] FIG. 8 is a schematic cross-sectional view for explaining step (5) of the method for manufacturing a circuit board according to the first example of the fourth embodiment of the present invention. [Figure 9] FIG. 9 is a schematic cross-sectional view illustrating step (i) in the method for manufacturing a circuit board according to the second example of the fourth embodiment of the present invention. [Figure 10] FIG. 10 is a schematic cross-sectional view illustrating step (i) in the method for manufacturing a circuit board according to the second example of the fourth embodiment of the present invention. [Figure 11] FIG. 11 is a schematic cross-sectional view illustrating step (ii) in the method for manufacturing a circuit board according to the second example of the fourth embodiment of the present invention. [Figure 12]FIG. 12 is a schematic cross-sectional view illustrating step (iv) in the method for manufacturing a circuit board according to the second example of the fourth embodiment of the present invention. [Figure 13] FIG. 13 is a schematic plan view of the circuit board of the inductor substrate as viewed from one side in the thickness direction. [Figure 14] FIG. 14 is a schematic diagram showing a cut end surface of the circuit board cut at the position indicated by the dashed line II-II in FIG. [Figure 15] FIG. 15 is a schematic plan view illustrating the configuration of a first conductor layer of a circuit board included in the inductor substrate. DETAILED DESCRIPTION OF THE INVENTION

[0012] The present invention will be described in detail below based on preferred embodiments. 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. In the following description, "magnetic permeability" refers to "relative magnetic permeability" unless otherwise specified.

[0013] <Outline of Resin Composition According to First Embodiment> The resin composition according to the first embodiment of the present invention comprises (A) nanocrystalline magnetic powder having a particle size of 5.5 μm or more and 20 μm or less, (B) magnetic powder having a particle size of 2 μm or less, and (D) a thermosetting resin. In the following description, "(A) nanocrystalline magnetic powder having a particle size of 5.5 μm or more and 20 μm or less" may be referred to as "(A) nanocrystalline magnetic powder." Furthermore, "(B) magnetic powder having a particle size of 2 μm or less" may be referred to as "(B) small-diameter magnetic powder." The resin composition according to the first embodiment of the present invention comprises the (A) nanocrystalline magnetic powder and the (B) small-diameter magnetic powder in amounts within specific ranges.

[0014] The resin composition according to the first embodiment of the present invention can be cured by thermally curing the thermosetting resin (D) to provide a cured product. The cured product thus obtained can have high relative permeability and low magnetic loss in the low frequency band (e.g., 10 MHz). Furthermore, the resin composition according to the first embodiment of the present invention can usually have excellent coatability.

[0015] The present inventors speculate as follows about the mechanism by which the resin composition according to the first embodiment of the present invention provides the above-described effects, although the technical scope of the present invention is not limited to the mechanism below. The nanocrystalline magnetic powder (A) has the effect of improving the relative permeability and magnetic loss of the cured resin composition. Specifically, nanocrystalline magnetic powder with a particle size of 5.5 μm or more can have a high relative permeability, and nanocrystalline magnetic powder with a particle size of 20 μm or less can have a low magnetic loss. Therefore, a cured resin composition containing the nanocrystalline magnetic powder (A) with a particle size in the above range can have good relative permeability and magnetic loss. Furthermore, (B) small-diameter magnetic powder improves the coatability of the resin composition and also improves the relative magnetic permeability and magnetic loss of the cured resin composition. Specifically, magnetic powder having a particle size of 2 μm or less can reduce the viscosity of the resin composition. Furthermore, magnetic powder having a particle size of 2 μm or less has low magnetic loss. Therefore, (B) small-diameter magnetic powder can increase the amount of magnetic powder in the resin composition to improve the relative magnetic permeability, while suppressing an increase in magnetic loss relative to the improvement in relative magnetic permeability. The mechanism by which the effects of this embodiment are obtained is thought to include the action of the combination of the (A) nanocrystalline magnetic powder and (B) small-diameter magnetic powder.

[0016] <(A) Nanocrystalline Magnetic Powder According to the First Embodiment> The resin composition according to the first embodiment of the present invention contains, as component (A), nanocrystalline magnetic powder (A) having a particle size within a specific range. In the specification, the term "nanocrystalline magnetic powder" refers to a magnetic powder containing crystal grains with a particle size of 100 nm or less. While there is no particular lower limit on the particle size of the crystal grains, it is preferably 1 nm or more. In particular, it is preferable that the maximum particle size of the nanocrystalline magnetic powder is 100 nm or less. Typically, each nanocrystalline magnetic powder particle contains multiple crystal grains, and thus 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 powder contains crystal grains, it generally exhibits peaks indicating crystallinity in an X-ray diffraction pattern. The crystal structure of the crystal grains can be, for example, a bcc crystal structure (body-centered cubic lattice structure), but other crystal structures are also possible.

[0017] The (A) nanocrystalline magnetic powder is usually contained in the resin composition in the form of particles. The (A) nanocrystalline magnetic powder may contain crystal grains in at least a portion of the 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.

[0018] The (A) nanocrystalline magnetic powder has a particle size in the range of 5.5 μm to 20 μm. The particle size of the (A) nanocrystalline magnetic powder can be measured by a laser diffraction / scattering method based on Mie scattering theory. Specifically, a particle size distribution of the (A) nanocrystalline magnetic powder is created on a volume basis using a laser diffraction / scattering particle size distribution analyzer, and the particle size can be measured from that particle size distribution. A preferable measurement sample is magnetic powder dispersed in pure water using ultrasonic waves. Examples of laser diffraction / scattering particle size distribution analyzers that can be used include the Microtrackbell "MT3000II," the Horiba "LA-960," and the Shimadzu "SALD-2200."

[0019] The resin composition according to the first embodiment of the present invention contains a specific amount of nanocrystalline magnetic powder (A) having a particle size within the above-mentioned range. Specifically, the amount (volume %) of the nanocrystalline magnetic powder (A) is typically 23% by volume or more, preferably 25% by volume or more, and more preferably 28% by volume or more, relative to 100% by volume of the nonvolatile components of the resin composition, and is typically 60% by volume or less, preferably 50% by volume or less, and more preferably 40% by volume or less. When using such an amount of nanocrystalline magnetic powder (A), it is possible to improve both the relative permeability and magnetic loss in the low frequency band, and further improve the coatability of the resin composition.

[0020] The (A) nanocrystalline magnetic powder can be particles of a magnetic material having a relative magnetic permeability greater than 1. This magnetic material is usually an inorganic material, and may be a soft magnetic material or a hard magnetic material. Furthermore, one type of magnetic material may be used alone, or two or more types may be used in combination. Among these, from the viewpoint of suppressing uneven distribution of the (A) nanocrystalline magnetic powder, a soft magnetic material is preferred as the magnetic material contained in the (A) nanocrystalline magnetic powder.

[0021] 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. To achieve the most significant effects of the present invention, the magnetic material contained in the (A) nanocrystalline magnetic powder preferably has a composition that further contains one or more elements selected from the group consisting of Nb, Hf, Zr, Ta, Mo, W, and V in combination with Fe.

[0022] (A) Preferred examples of the magnetic material contained in the nanocrystalline magnetic powder include the magnetic materials described in JP 2021-158343 A, JP 2021-141267 A, JP 2019-31463 A, JP 2021-11602 A, etc.

[0023] Among the above examples, Fe-Si-Nb-B alloy powder is preferred from the viewpoint of significantly achieving the desired effects of the present invention. Fe-Si-Nb-B alloy powder refers to a magnetic powder formed from an alloy containing Fe, Si, Nb, and B.

[0024] The nanocrystalline magnetic powder (A) preferably contains the above-mentioned magnetic material, and preferably contains only the above-mentioned magnetic material. The nanocrystalline magnetic powder (A) may be used alone or in combination of two or more types.

[0025] (A) Nanocrystalline magnetic powder can be produced, for example, by atomization. Specific examples of methods for producing (A) nanocrystalline magnetic powder include the methods described in JP 2021-141267 A and JP 2021-158343 A. Commercially available (A) nanocrystalline magnetic powders may also be used. Examples of commercially available magnetic powders containing (A) nanocrystalline magnetic powder include "KUAMET NC1-38um" and "ATFINE-NC1 PF10FA" manufactured by Epson Atmix. However, commercially available magnetic powders generally have a wide particle size distribution and may contain particles with particle sizes outside the range of 5.5 μm to 20 μm. Therefore, when purchasing (A) nanocrystalline magnetic powder from the market, the commercially available magnetic powder may be classified as needed.

[0026] The (A) nanocrystalline magnetic powder is preferably spherical. The aspect ratio, calculated by dividing the length of the long axis of a particle of the (A) nanocrystalline magnetic powder by the length of the short axis, is preferably 2 or less, more preferably 1.5 or less, and even more preferably 1.2 or less, and is usually 1 or more, preferably greater than 1, and more preferably 1.05 or more.

[0027] The amount (volume %) of the (A) nanocrystalline magnetic powder is represented by "V(A)" and the amount (volume %) of the (B) small-diameter magnetic powder is represented by "V(B)" relative to 100% by volume of the nonvolatile components of the resin composition. In this case, the volume ratio of the (A) nanocrystalline magnetic powder to the (B) small-diameter magnetic powder ((A) nanocrystalline magnetic powder / (B) small-diameter magnetic powder) contained in the resin composition can be represented by "V(A) / V(B)." This volume ratio V(A) / V(B) is usually 0.8 or more, preferably 1 or more, more preferably 1.2 or more, and particularly preferably 1.4 or more, and usually 12 or less, preferably 8.4 or less, more preferably 7.0 or less, even more preferably 6.0 or less, and particularly preferably 5.0 or less. When the volume ratio V(A) / V(B) is within the above range, both the relative permeability and magnetic loss can be effectively improved in the low-frequency band, and the coatability of the resin composition can be further improved.

[0028] Furthermore, the total volume % of the (A) nanocrystalline magnetic powder and (B) small-diameter magnetic powder contained in the resin composition, relative to 100% by volume of the nonvolatile components of the resin composition, can be expressed as "V(A) + V(B)." This total volume % V(A) + V(B) is usually 28% by volume or more, preferably 34% by volume or more, more preferably 38% by volume or more, and particularly preferably 40% by volume or more, and is preferably 72% by volume or less, more preferably 68% by volume or less, even more preferably 64% by volume or less, and particularly preferably 60% by volume or less. When the total volume % V(A) + V(B) of the (A) nanocrystalline magnetic powder and (B) small-diameter magnetic powder is within the above range, both the relative permeability and magnetic loss can be effectively improved in the low-frequency band, and the coatability of the resin composition can be further improved.

[0029] The total amount (vol %) of all magnetic powders in the resin composition is preferably 30% by volume or more, more preferably 40% by volume or more, and particularly preferably 50% by volume or more, relative to 100% by volume of the nonvolatile components of the resin composition, and is preferably 95% by volume or less, more preferably 90% by volume or less, and particularly preferably 85% by volume or less. When the total amount (vol %) of magnetic powders is within the above range, it is possible to effectively improve both the relative permeability and magnetic loss in the low frequency band, and also to further improve the coatability of the resin composition.

[0030] The total amount (volume %) of the (A) nanocrystalline magnetic powder and the (B) small-diameter magnetic powder is preferably 40% by volume or more, more preferably 50% by volume or more, and particularly preferably 54% by volume or more, relative to 100% by volume of the total amount of all magnetic powders in the resin composition, and may be, for example, 100% by volume or less, 90% by volume or less, 80% by volume or less, etc. When the total amount (volume %) of the (A) nanocrystalline magnetic powder and the (B) small-diameter magnetic powder is within the above range, it is possible to effectively improve both the relative magnetic permeability and magnetic loss in the low-frequency band, and further improve the coatability of the resin composition.

[0031] The amount (mass%) of the (A) nanocrystalline magnetic powder is preferably 30% by mass or more, more preferably 34% by mass or more, and particularly preferably 38% by mass or more, relative to 100% by mass of the nonvolatile components of the resin composition, and is preferably 60% by mass or less, preferably 56% by mass or less, and even more preferably 52% by mass or less. When the amount (mass%) of the (A) nanocrystalline magnetic powder is within the above range, it is possible to effectively improve both the relative permeability and magnetic loss in the low frequency band, and also to further improve the coatability of the resin composition.

[0032] The amount (mass%) of the (A) nanocrystalline magnetic powder relative to 100% by mass of the nonvolatile components of the resin composition is represented by "M(A)," and the amount (mass%) of the (B) small-diameter magnetic powder is represented by "M(B)." In this case, the mass ratio of the (A) nanocrystalline magnetic powder to the (B) small-diameter magnetic powder ((A) nanocrystalline magnetic powder / (B) small-diameter magnetic powder) contained in the resin composition can be represented by "M(A) / M(B)." This mass ratio M(A) / M(B) is preferably 1.0 or more, more preferably 1.2 or more, and particularly preferably 1.4 or more, and is preferably 10 or less, more preferably 8 or less, and particularly preferably 6 or less. When the mass ratio M(A) / M(B) is within the above range, both the relative permeability and magnetic loss can be effectively improved in the low-frequency band, and the coatability of the resin composition can be further improved.

[0033] Furthermore, the total mass % of the (A) nanocrystalline magnetic powder and (B) small-diameter magnetic powder contained in the resin composition, relative to 100% by mass of the nonvolatile components of the resin composition, can be expressed as "M(A) + M(B)." This total mass % M(A) + M(B) is preferably 40% by mass or more, more preferably 45% by mass or more, even more preferably 50% by mass or more, and particularly preferably 53% by mass or more, and is preferably 90% by mass or less, more preferably 80% by mass or less, and particularly preferably 70% by mass or less. When the total mass % M(A) + M(B) is within the above range, both the relative permeability and magnetic loss can be effectively improved in the low-frequency band, and the coatability of the resin composition can be further improved.

[0034] The total amount (mass%) of all magnetic powders in the resin composition is preferably 80 mass% or more, more preferably 85 mass% or more, and particularly preferably 90 mass% or more, relative to 100 mass% of the nonvolatile components of the resin composition, and is preferably 99 mass% or less, more preferably 98 mass% or less, and particularly preferably 97 mass% or less. When the total amount (mass%) of magnetic powders is within the above range, it is possible to effectively improve both the relative permeability and magnetic loss in the low frequency band, and also to further improve the coatability of the resin composition.

[0035] The total amount (mass%) of the (A) nanocrystalline magnetic powder and the (B) small-diameter magnetic powder is preferably 50% by mass or more, more preferably 53% by mass or more, and particularly preferably 55% by mass or more, relative to 100% by mass of the total amount of all magnetic powders in the resin composition, and may be, for example, 100% by mass or less, 90% by mass or less, 80% by mass or less, 70% by mass or less, etc. When the total amount (mass%) of the (A) nanocrystalline magnetic powder and the (B) small-diameter magnetic powder is within the above range, it is possible to effectively improve both the relative magnetic permeability and magnetic loss in the low-frequency band, and further improve the coatability of the resin composition.

[0036] <(B) Small Diameter Magnetic Powder According to the First Embodiment> The resin composition according to the first embodiment of the present invention contains, as component (B), a small-diameter magnetic powder (B) having a particle size within a specific range. The small-diameter magnetic powder (B) is usually contained in the resin composition in the form of particles. This small-diameter magnetic powder (B) has a particle size of 2 μm or less. The particle size of the small-diameter magnetic powder (B) can be measured by the same method as that for the particle size of the nanocrystalline magnetic powder (A).

[0037] The resin composition according to the first embodiment of the present invention contains a specific amount of small-diameter magnetic powder (B) having a particle size within the above-mentioned range. Specifically, the amount (vol %) of the small-diameter magnetic powder (B) is typically 5% by volume or more, preferably 6% by volume or more, and more preferably 7% by volume or more, relative to 100% by volume of the nonvolatile components of the resin composition, and is typically 30% by volume or less, preferably 26% by volume or less, and more preferably 22% by volume or less. When such an amount of small-diameter magnetic powder (B) is used, it is possible to improve both the relative permeability and magnetic loss in the low-frequency band, and also to improve the coatability of the resin composition.

[0038] (B) Small-diameter magnetic powder may be nanocrystalline magnetic powder containing crystal grains, amorphous magnetic powder containing no crystal grains, crystalline magnetic powder other than nanocrystalline magnetic powder, or a combination of these. Nanocrystalline magnetic powder is as explained in the section on (A) nanocrystalline magnetic powder. On the other hand, amorphous magnetic materials are non-crystalline, so they do not usually show specific peaks indicating crystallinity in their X-ray diffraction patterns. Generally, the X-ray diffraction pattern of amorphous magnetic powder shows a broad pattern without peaks indicating crystallinity.

[0039] The (B) small-diameter magnetic powder can be particles of a magnetic material having a relative magnetic permeability greater than 1. This magnetic material is usually an inorganic material, and may be a soft magnetic material or a hard magnetic material. Furthermore, one type of magnetic material may be used alone, or two or more types may be used in combination. Among these, from the viewpoint of suppressing uneven distribution of the (B) small-diameter magnetic powder, a soft magnetic material is preferred as the magnetic material contained in the (B) small-diameter magnetic powder.

[0040] (B) Examples of the magnetic material contained in the small-diameter magnetic powder include magnetic metal oxide materials and magnetic metal materials.

[0041] Examples of magnetic metal oxide materials include ferrite-based magnetic materials and iron oxide materials such as iron oxide powder (III) and triiron tetroxide powder. Among these, ferrite-based magnetic materials are preferred. Ferrite-based magnetic materials are usually composite oxides whose main component is iron oxide and are chemically stable. Therefore, when ferrite-based magnetic materials are used, advantages such as high corrosion resistance, low risk of fire, and resistance to demagnetization can be obtained.

[0042] Examples of ferrite-based magnetic materials include Fe-Mn ferrite, Fe-Mn-Mg ferrite, Fe-Mn-Mg-Sr ferrite, Fe-Mg-Zn ferrite, Fe-Mg-Sr ferrite, Fe-Zn-Mn ferrite, Fe-Cu-Zn ferrite, Fe-Ni-Zn ferrite, Fe-Ni-Zn-Cu ferrite, Fe-Ba-Zn ferrite, Fe-Ba-Mg ferrite, Fe-Ba-Ni ferrite, Fe-Ba-Co ferrite, Fe-Ba-Ni-Co ferrite, and Fe-Y ferrite.

[0043] Among ferrite-based magnetic materials, from the viewpoint of significantly achieving the desired effects of the present invention, ferrites containing at least one element selected from the group consisting of Mn, Zn, Ni, and Cu are preferred, with ferrites containing Mn being particularly preferred. Therefore, preferred ferrite-based magnetic materials include, for example, Fe-Mn-based ferrites, Fe-Mn-Mg-based ferrites, Fe-Mn-Mg-Sr-based ferrites, Fe-Mg-Zn-based ferrites, Fe-Zn-Mn-based ferrites, Fe-Cu-Zn-based ferrites, Fe-Ni-Zn-based ferrites, Fe-Ni-Zn-Cu-based ferrites, Fe-Ba-Zn-based ferrites, Fe-Ba-Ni-based ferrites, and Fe-Ba-Ni-Co-based ferrites. Among these, Fe-Mn-based ferrites, Fe-Mn-Mg-based ferrites, Fe-Mn-Mg-Sr-based ferrites, and Fe-Zn-Mn-based ferrites are preferred, with Fe-Mn-based ferrites being particularly preferred. Fe-Mn ferrite refers to ferrite containing Fe and Mn.

[0044] Examples of magnetic metal materials include pure iron; crystalline or amorphous alloy magnetic materials such as Fe-Si alloys, Fe-Si-Al alloys, Fe-Cr alloys, Fe-Cr-Si alloys, Fe-Ni-Cr alloys, Fe-Cr-Al alloys, Fe-Ni alloys, Fe-Ni-B alloys, Fe-Ni-Mo alloys, Fe-Ni-Mo-Cu alloys, Fe-Co alloys, Fe-Ni-Co alloys, and Co-based amorphous alloys. Among magnetic metal materials, iron alloy magnetic materials are more preferred. From the viewpoint of significantly achieving the desired effects of the present invention, iron alloy magnetic materials containing Fe and at least one element selected from the group consisting of Si, Cr, Al, Ni, and Co are preferred, and Fe-Si-Cr alloys are particularly preferred. The Fe-Si-Cr alloy material refers to an alloy containing Fe, Si, and Cr.

[0045] The magnetic material contained in the (B) small-diameter magnetic powder may be the same as or different from the magnetic material described as the magnetic material of the (A) nanocrystalline magnetic powder.

[0046] The (B) small-diameter magnetic powder preferably contains the above-mentioned magnetic material, and preferably contains only the above-mentioned magnetic material. The (B) small-diameter magnetic powder may be used alone or in combination of two or more types.

[0047] (B) As the small-diameter magnetic powder, commercially available magnetic powders may be used. Specific examples of commercially available magnetic powders include "MZ03S", "M05S", "M001", and "MZ05S" manufactured by Powder Tech Co., Ltd.; "PST-S" manufactured by Sanyo Special Steel Co., Ltd.; and "AW2-08", "AW2-08PF20F", "AW2-08PF10F", "AW2-08PF3F", "Fe-3.5Si-4.5CrPF20F", "Fe-50NiPF20F", "Fe-80Ni-4MoPF20F", "ATFINE-NC1 PF5FA", and "ATFINE-NC1" manufactured by Epson Atmix Corporation. PF3FA"; "CVD iron powder (0.7 μm)", "LD-M", "LD-MH", "KNI-106", "KNI-106GSM", "KNI-106GS", "KNI-109", "KNI-109GSM", "KNI-109GS" manufactured by JFE Chemical Corporation; "KNS-415", "BSF-547", "BSF-029", "BSN-125", "BSN-125", "BSN-714", "BSN-828", "S-1281", "S-1641", "S-1651", "S-1470", "S-1511", "S-2430" manufactured by Toda Kogyo Co., Ltd.; "JR09P2" manufactured by Japan Metals and Chemical Industries, Ltd.; "Nanotek" manufactured by CIK Nanotech; "JEMK-S" and "JEMK-H" manufactured by Kinseimatec Co., Ltd.; "Yttrium iron" manufactured by Aldrich oxide" manufactured by DOWA Electronics Co., Ltd.; and "MA-RCO-5" manufactured by DOWA Electronics Co., Ltd. However, commercially available magnetic powders generally have a wide particle size distribution and may contain particles with particle sizes outside the range of 2 μm or less. Therefore, when purchasing (B) small-diameter magnetic powder from the market, the commercially available magnetic powder may be classified as necessary.

[0048] The (B) small-diameter magnetic powder is preferably spherical. The aspect ratio range of the (B) small-diameter magnetic powder particles can be the same as the aspect ratio range of the (A) nanocrystalline magnetic powder. The aspect ratio of the (B) small-diameter magnetic powder and the aspect ratio of the (A) nanocrystalline magnetic powder may be the same or different.

[0049] The amount (mass %) of (B) small-diameter magnetic powder is preferably 5% by mass or more, more preferably 7% by mass or more, and particularly preferably 9% by mass or more, relative to 100% by mass of the nonvolatile components of the resin composition, and is preferably 40% by mass or less, preferably 35% by mass or less, and more preferably 30% by mass or less. When the amount (mass %) of (B) small-diameter magnetic powder is within the above range, it is possible to effectively improve both the relative permeability and magnetic loss in the low-frequency band, and also to further improve the coatability of the resin composition.

[0050] <(C) Intermediate Magnetic Powder According to the First Embodiment> The resin composition according to the first embodiment of the present invention may further contain (C) magnetic powder as an optional component. The (C) magnetic powder as the (C) component refers to a magnetic powder other than the (A) nanocrystalline magnetic powder, which has a particle size of more than 2 μm and not more than 20 μm. This (C) magnetic powder is sometimes referred to as "(C) intermediate magnetic powder." The particle size of the (C) intermediate magnetic powder can be measured by the same method as that of the (A) nanocrystalline magnetic powder. The (C) intermediate magnetic powder does not include the (A) nanocrystalline magnetic powder or the (B) small-diameter magnetic powder. In summary, the (C) intermediate magnetic powder includes the magnetic powders (C1) and (C2) below. (C1) Nanocrystalline magnetic powder having a particle size of more than 2 μm and less than 5.5 μm. (C2) A magnetic powder other than nanocrystalline magnetic powder, which has a particle size of more than 2 μm and not more than 20 μm.

[0051] The (C) intermediate magnetic powder allows the proportion of magnetic powder in the resin composition to be increased, thereby increasing the relative magnetic permeability of the cured resin composition. Normally, magnetic powder can increase the magnetic loss of the cured resin composition, but the (C) intermediate magnetic powder has a small particle size, so the degree of increase in magnetic loss can be suppressed. Therefore, the (C) intermediate magnetic powder usually allows the relative magnetic permeability to be improved while suppressing the increase in magnetic loss.

[0052] The (C) intermediate magnetic powder may be a nanocrystalline magnetic powder containing crystal grains, an amorphous magnetic powder containing no crystal grains, a crystalline magnetic powder other than nanocrystalline magnetic powder, or a combination of these. This (C) intermediate magnetic powder may be particles of a magnetic material having a relative permeability greater than 1. The magnetic material contained in the (C) intermediate magnetic powder may be the magnetic material described as the magnetic material of the (B) small-diameter magnetic powder. The magnetic material contained in the (C) intermediate magnetic powder and the magnetic material of the (B) small-diameter magnetic powder may be the same or different. The (C) intermediate magnetic powder preferably contains the above-mentioned magnetic material, and preferably contains only the above-mentioned magnetic material. Furthermore, one type of (C) intermediate magnetic powder may be used alone, or two or more types may be used in combination.

[0053] Commercially available magnetic powders may be used as the (C) medium-sized magnetic powder. Specific examples of commercially available magnetic powders include the same examples as those for the (B) small-sized magnetic powder. However, commercially available magnetic powders generally have a wide particle size distribution and may contain particles with particle sizes outside the range of more than 2 μm and less than 5.5 μm or more than 2 μm and less than 20 μm. Therefore, when purchasing the (C) medium-sized magnetic powder from the market, the commercially available magnetic powder may be classified as necessary.

[0054] The (C) medium magnetic powder is preferably spherical. The aspect ratio range of the particles of the (C) medium magnetic powder can be the same as the aspect ratio range of the (A) nanocrystalline magnetic powder. The aspect ratio of the (C) medium magnetic powder and the aspect ratio of the (A) nanocrystalline magnetic powder may be the same or different. Furthermore, the aspect ratio of the (C) medium magnetic powder and the aspect ratio of the (B) small diameter magnetic powder may be the same or different.

[0055] The amount (vol %) of the (C) intermediate magnetic powder may be 0% or more, and is preferably 1% or more, more preferably 3% or more, and particularly preferably 5% or more, and is preferably 25% or less, more preferably 15% or less, and particularly preferably 13% or less, based on 100% by volume of the nonvolatile components of the resin composition. When the amount (vol %) of the (C) intermediate magnetic powder is within the above range, it is possible to effectively improve both the relative permeability and magnetic loss in the low frequency band, and further improve the coatability of the resin composition.

[0056] The amount (volume %) of the (C) intermediate magnetic powder relative to 100% by volume of the nonvolatile components of the resin composition is represented by "V(C)." In this case, the volume ratio of the (A) nanocrystalline magnetic powder to the (C) intermediate magnetic powder contained in the resin composition ((C) intermediate magnetic powder / (A) nanocrystalline magnetic powder) can be represented by "V(C) / V(A)." This volume ratio V(C) / V(A) may be 0 or greater, and is preferably 0.01 or greater, more preferably 0.1 or greater, and is preferably 1.0 or less, more preferably 0.9 or less, and particularly preferably 0.8 or less. When the volume ratio V(C) / V(A) is within the above range, both the relative permeability and magnetic loss can be effectively improved in the low frequency band, and the coatability of the resin composition can be further improved.

[0057] Furthermore, the volume ratio of the (B) small-diameter magnetic powder to the (C) medium-diameter magnetic powder contained in the resin composition ((C) medium-diameter magnetic powder / (B) small-diameter magnetic powder) can be expressed as "V(C) / V(B)". This volume ratio V(C) / V(B) may be 0 or greater than 0, and is preferably 0.01 or greater, more preferably 0.1 or greater, and is preferably 8 or less, more preferably 5 or less, and particularly preferably 2 or less. When the volume ratio V(C) / V(B) is within the above range, it is possible to effectively improve both the relative permeability and magnetic loss in the low-frequency band, and further improve the coatability of the resin composition.

[0058] The total amount (volume %) of the (A) nanocrystalline magnetic powder, (B) small-diameter magnetic powder, and (C) medium-sized magnetic powder is preferably 30% by volume or more, preferably 40% by volume or more, particularly preferably 50% by volume or more, and is preferably 90% by volume or less, more preferably 80% by volume or less, and particularly preferably 70% by volume or less, based on 100% by volume of the nonvolatile components of the resin composition. When the total amount (volume %) of the (A) nanocrystalline magnetic powder, (B) small-diameter magnetic powder, and (C) medium-sized magnetic powder is within the above range, both the relative permeability and magnetic loss can be effectively improved in the low-frequency band, and the coatability of the resin composition can be further improved.

[0059] The total volume percent of the (A) nanocrystalline magnetic powder, (B) small-diameter magnetic powder, and (C) medium-sized magnetic powder is preferably 50% by volume or more, more preferably 60% by volume or more, and particularly preferably 70% by volume or more, based on 100% by volume of the total amount of all magnetic powders in the resin composition. A large volume percent indicates that the resin composition contains a small amount of giant magnetic powder with a particle size greater than 20 μm. When the total volume percent of the (A) nanocrystalline magnetic powder, (B) small-diameter magnetic powder, and (C) medium-sized magnetic powder falls within the above range, both the relative permeability and magnetic loss can be effectively improved in the low-frequency band, and the coatability of the resin composition can be further improved.

[0060] The amount (mass %) of the (C) intermediate magnetic powder may be 0% by mass or greater than 0% by mass, relative to 100% by mass of the nonvolatile components of the resin composition, and is preferably 1% by mass or greater, more preferably 3% by mass or greater, and particularly preferably 5% by mass or greater, and is preferably 40% by mass or less, more preferably 35% by mass or less, and particularly preferably 30% by mass or less. When the amount (mass %) of the (C) intermediate magnetic powder is within the above range, it is possible to effectively improve both the relative permeability and magnetic loss in the low frequency band, and also to further improve the coatability of the resin composition.

[0061] The amount (mass %) of the (C) intermediate magnetic powder relative to 100 mass % of the nonvolatile components of the resin composition is represented by "M(C)." In this case, the mass ratio of the (A) nanocrystalline magnetic powder to the (C) intermediate magnetic powder ((C) intermediate magnetic powder / (A) nanocrystalline magnetic powder) contained in the resin composition can be represented by "M(C) / M(A)." This mass ratio M(C) / M(A) may be 0 or greater, and is preferably 0.01 or greater, more preferably 0.1 or greater, and is preferably 1.0 or less, more preferably 0.9 or less, and particularly preferably 0.8 or less. When the mass ratio M(C) / M(A) is within the above range, both the relative permeability and magnetic loss can be effectively improved in the low frequency band, and the coatability of the resin composition can be further improved.

[0062] Furthermore, the mass ratio of the (B) small-diameter magnetic powder to the (C) medium-diameter magnetic powder contained in the resin composition ((C) medium-diameter magnetic powder / (B) small-diameter magnetic powder) can be expressed as "M(C) / M(B)". This mass ratio M(C) / M(B) may be 0 or greater than 0, and is preferably 0.01 or greater, more preferably 0.1 or greater, and is preferably 8 or less, more preferably 5 or less, and particularly preferably 2 or less. When the mass ratio M(C) / M(B) is within the above range, it is possible to effectively improve both the relative permeability and magnetic loss in the low-frequency band, and further improve the coatability of the resin composition.

[0063] The total amount (mass%) of the (A) nanocrystalline magnetic powder, (B) small-diameter magnetic powder, and (C) medium-sized magnetic powder is preferably 40% by mass or more, preferably 50% by mass or more, particularly preferably 60% by mass or more, and is preferably 99% by mass or less, and more preferably 98% by mass or less, relative to 100% by mass of the nonvolatile components of the resin composition. When the total amount (mass%) of the (A) nanocrystalline magnetic powder, (B) small-diameter magnetic powder, and (C) medium-sized magnetic powder is within the above range, it is possible to effectively improve both the relative magnetic permeability and magnetic loss in the low-frequency band, and further improve the coatability of the resin composition.

[0064] The total amount (mass%) of (A) nanocrystalline magnetic powder, (B) small-diameter magnetic powder, and (C) medium-sized magnetic powder is preferably 50% by mass or more, more preferably 60% by mass or more, and particularly preferably 70% by mass or more, based on 100% by mass of the total amount of all magnetic powders in the resin composition. A large value indicates that the resin composition contains less giant magnetic powder with a particle size of more than 20 μm. When the total amount (mass%) of (A) nanocrystalline magnetic powder, (B) small-diameter magnetic powder, and (C) medium-sized magnetic powder falls within the above range, both the relative permeability and magnetic loss can be effectively improved in the low-frequency band, and the coatability of the resin composition can be further improved.

[0065] <(D) Thermosetting Resin According to the First Embodiment> The resin composition according to the first embodiment of the present invention includes a thermosetting resin (D) as component (D). Examples of the thermosetting resin (D) include epoxy resins, phenolic resins, thiol resins, benzoxazine resins, active ester resins, cyanate ester resins, carbodiimide resins, amine resins, acid anhydride resins, epoxy acrylate resins, urethane acrylate resins, urethane resins, polyimide resins, unsaturated polyester resins, melamine resins, silicone resins, and phenoxy resins. The thermosetting resin (D) may be used singly or in combination of two or more.

[0066] The (D) thermosetting resin preferably contains an epoxy resin. Epoxy resin refers to a resin having an epoxy group. When the (D) thermosetting resin contains an epoxy resin, the resin composition can have particularly good coatability, and the cured product can have particularly excellent relative magnetic permeability and magnetic loss.

[0067] Examples of epoxy resins 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, dicyclopentadiene-type epoxy resins, trisphenol-type epoxy resins, naphthol novolac-type epoxy resins, phenol novolac-type epoxy resins, tert-butyl-catechol-type epoxy resins, naphthalene-type epoxy resins, naphthol-type epoxy resins, anthracene-type epoxy resins, glycidylamine-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, heterocyclic epoxy resins, spiro ring-containing epoxy resins, cyclohexane-type epoxy resins, cyclohexanedimethanol-type epoxy resins, naphthylene ether-type epoxy resins, trimethylol-type epoxy resins, tetraphenylethane-type epoxy resins, glycidyl ether-type aliphatic epoxy resins, and glycidyl ether-type aromatic epoxy resins. The epoxy resin may be used alone or in combination of two or more kinds.

[0068] The resin composition preferably contains an epoxy resin having two or more epoxy groups in one molecule as the epoxy resin. From the viewpoint of significantly achieving the desired effects of the present invention, the amount of the epoxy resin having two or more epoxy groups in one molecule is preferably 50% by mass or more, more preferably 60% by mass or more, and particularly preferably 70% by mass or more, relative to 100% by mass of the non-volatile components of the epoxy resin.

[0069] The epoxy resin preferably has an aromatic structure. When two or more epoxy resins are used, it is preferable that at least one of the epoxy resins has an aromatic structure. The aromatic structure is a chemical structure generally defined as aromatic, and includes polycyclic aromatic rings and aromatic heterocycles.

[0070] Epoxy resins include epoxy resins that are liquid at a temperature of 25°C (hereinafter sometimes referred to as "liquid epoxy resins") and epoxy resins that are solid at a temperature of 25°C (hereinafter sometimes referred to as "solid epoxy resins"). The resin composition may contain only liquid epoxy resins as the epoxy resin, only solid epoxy resins, or a combination of liquid epoxy resins and solid epoxy resins. Of these, preferably, the epoxy resin contains only liquid epoxy resins.

[0071] The amount of the liquid epoxy resin is preferably 60% by mass or more, more preferably 80% by mass or more, even more preferably 90% by mass or more, and particularly preferably 100% by mass, based on 100% by mass of the total epoxy resin.

[0072] The liquid epoxy resin is preferably a liquid epoxy resin having two or more epoxy groups in one molecule.

[0073] Preferred liquid epoxy resins include glycirol-type epoxy resins, bisphenol A-type epoxy resins, bisphenol F-type epoxy resins, bisphenol AF-type epoxy resins, naphthalene-type epoxy resins, glycidyl ether-type aliphatic epoxy resins, glycidyl ether-type aromatic epoxy resins, glycidyl ester-type epoxy resins, glycidyl amine-type epoxy resins, phenol novolac-type epoxy resins, alicyclic epoxy resins having an ester skeleton, cyclohexanedimethanol-type epoxy resins, dicyclopentadiene-type epoxy resins, and epoxy resins having a butadiene structure, and more preferred are bisphenol A-type epoxy resins, bisphenol F-type epoxy resins, glycidyl ether-type aliphatic epoxy resins, and glycidyl ether-type aromatic epoxy resins.

[0074] Specific examples of liquid epoxy resins include "HP4032," "HP4032D," and "HP4032SS" (naphthalene-type epoxy resins) manufactured by DIC Corporation; "828US," "jER828EL" (bisphenol A-type epoxy resin), "jER807" (bisphenol F-type epoxy resin), and "jER152" (phenol novolac-type epoxy resin) manufactured by Mitsubishi Chemical Corporation; "630" and "630LSD" (glycidyl ether-type aromatic epoxy resins) manufactured by Mitsubishi Chemical Corporation; and "ED-523T" (glycirol-type epoxy resin (ADEKA glycirol)) and "EP-3980S" (glycidyl amine epoxy resin) manufactured by ADEKA Corporation. type epoxy resin), "EP-4088S" (glycidyl ether type aliphatic epoxy resin); "ZX-1059" (a mixture of bisphenol A type epoxy resin and bisphenol F type epoxy resin) manufactured by Nippon Steel Chemical & Material Corporation; "EX-721" (glycidyl ester type epoxy resin) manufactured by Nagase ChemteX Corporation; "Celloxide 2021P" (alicyclic epoxy resin with an ester skeleton) and "PB-3600" (epoxy resin with a butadiene structure) manufactured by Daicel Corporation; and "ZX1658" and "ZX1658GS" (liquid 1,4-glycidylcyclohexane) manufactured by Nippon Steel Chemical & Material Corporation.

[0075] As the solid epoxy resin, a solid epoxy resin having three or more epoxy groups in one molecule is preferred, and an aromatic solid epoxy resin having three or more epoxy groups in one molecule is more preferred.

[0076] Preferred solid epoxy resins include bixylenol-type epoxy resins, naphthalene-type epoxy resins, naphthalene-type tetrafunctional epoxy resins, naphthol novolac-type epoxy resins, cresol novolac-type epoxy resins, dicyclopentadiene-type epoxy resins, trisphenol-type epoxy resins, naphthol-type epoxy resins, biphenyl-type epoxy resins, naphthylene ether-type epoxy resins, anthracene-type epoxy resins, bisphenol A-type epoxy resins, bisphenol AF-type epoxy resins, phenol aralkyl-type epoxy resins, tetraphenylethane-type epoxy resins, phenolphthalimidine-type epoxy resins, and phenolphthalein-type epoxy resins.

[0077] 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; "HP-7200", "HP-7200HH", "HP-7200H", and "HP-7200L" (dicyclopentadiene type epoxy resins) manufactured by DIC Corporation; and "EXA-73" manufactured by DIC Corporation. 11", "EXA-7311-G3", "EXA-7311-G4", "EXA-7311-G4S", "HP6000" (naphthylene ether type epoxy resin); "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", "NC3000FH", "NC3100" (biphenyl type epoxy resin) manufactured by Nippon Kayaku Co., Ltd.; "ESN475V" manufactured by Nippon Steel Chemical & Material Co., Ltd. (Naphthalene-type epoxy resin); "ESN485" (naphthol-type epoxy resin) manufactured by Nippon Steel Chemical & Material Co., Ltd.; "ESN375" (dihydroxynaphthalene-type epoxy resin) manufactured by Nippon Steel Chemical & Material Co., Ltd.; "YX4000H", "YX4000", "YX4000HK", and "YL7890" (bixylenol-type epoxy resin) manufactured by Mitsubishi Chemical Corporation; "YL6121" (biphenyl-type epoxy resin) manufactured by Mitsubishi Chemical Corporation; "YX8800" (anthracene-type epoxy resin) manufactured by Mitsubishi Chemical Corporation; "YX77" manufactured by Mitsubishi Chemical Corporation Examples of epoxy resins include "00" (phenol aralkyl type epoxy resin); "PG-100" and "CG-500" manufactured by Osaka Gas Chemicals Co., Ltd.; "YL7760" (bisphenol AF type epoxy resin) manufactured by Mitsubishi Chemical Corporation; "YL7800" (fluorene type epoxy resin) manufactured by Mitsubishi Chemical Corporation; "jER1010" (bisphenol A type epoxy resin) manufactured by Mitsubishi Chemical Corporation; "jER1031S" (tetraphenylethane type epoxy resin) manufactured by Mitsubishi Chemical Corporation; and "WHR991S" (phenolphthalimidine type epoxy resin) manufactured by Nippon Kayaku Co., Ltd. These may be used alone or in combination of two or more.

[0078] When a solid epoxy resin and a liquid epoxy resin are used in combination as the epoxy resin, the mass ratio of the solid epoxy resin to the liquid epoxy resin (solid epoxy resin / liquid epoxy resin) is not particularly limited, but is preferably 1 or less, more preferably 0.5 or less, even more preferably 0.1 or less, still more preferably 0.05 or less, and particularly preferably 0.01 or less.

[0079] The epoxy equivalent of the 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 the resin per equivalent of epoxy groups. This epoxy equivalent can be measured according to JIS K7236.

[0080] From the viewpoint of significantly achieving the desired effects of the present invention, the weight average molecular weight (Mw) of the epoxy resin 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 as a polystyrene-equivalent value by gel permeation chromatography (GPC).

[0081] The amount (vol %) of the epoxy resin is preferably 2.5% by volume or more, more preferably 4.0% by volume or more, and particularly preferably 4.5% by volume or more, relative to 100% by volume of the nonvolatile components in the resin composition, and is preferably 10.0% by volume or less, more preferably 9.0% by volume or less, and particularly preferably 8.0% by volume or less. When the amount (vol %) of the epoxy resin is within this range, both the relative permeability and magnetic loss can be effectively improved in the low frequency band, and the coatability of the resin composition can be further improved.

[0082] The amount (mass %) of the epoxy resin is preferably 0.1 mass % or more, more preferably 0.5 mass % or more, particularly preferably 1.0 mass % or more, and is preferably 20 mass % or less, more preferably 15 mass % or less, and even more preferably 10 mass % or less, relative to 100 mass % of the nonvolatile components in the resin composition. When the amount (mass %) of the epoxy resin is within the above range, it is possible to effectively improve both the relative magnetic permeability and magnetic loss in the low frequency band, and also to further improve the coatability of the resin composition.

[0083] When the (D) thermosetting resin contains an epoxy resin, the (D) thermosetting resin may further contain an epoxy curing agent. The epoxy curing agent refers to a thermosetting resin that can react with the epoxy resin to cure the resin composition. Examples of epoxy curing agents include phenolic resins, carbodiimide resins, acid anhydride resins, amine resins, benzoxazine resins, active ester resins, cyanate ester resins, and thiol resins. One type of epoxy curing agent may be used alone, or two or more types may be used in combination.

[0084] The phenolic resin may be 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. Preferred phenolic resins include biphenyl-type resins, naphthalene-type resins, phenol novolac-type resins, naphthylene ether-type resins, and triazine skeleton-containing phenolic resins. Specific examples include biphenyl-type resins such as "MEH-7700," "MEH-7810," and "MEH-7851" (manufactured by Meiwa Kasei Co., Ltd.); naphthalene-type resins such as "NHN," "CBN," and "GPH" (manufactured by Nippon Kayaku Co., Ltd.); "SN170," "SN180," "SN190," "SN475," "SN485," "SN495," "SN375," and "SN395" (manufactured by Nippon Steel Chemical Co., Ltd.); and "EXB9500" (manufactured by DIC Corporation). Specific examples of triazine skeleton-containing phenolic resins include "LA3018," "LA7052," "LA7054," and "LA1356" (manufactured by DIC Corporation). Naphthalene-type resins and triazine skeleton-containing phenolic resins are particularly preferred.

[0085] The carbodiimide resin may be a resin having one or more, preferably two or more, carbodiimide structures in one molecule. 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(methylenediphenylenecarbodiimide), 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 Rhein Chemie.

[0086] As the acid anhydride resin, a curing agent having one or more acid anhydride groups in one molecule may 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 benzophenone tetracarboxylic anhydride. Examples of suitable acid anhydrides include 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), and polymeric acid anhydrides such as styrene-maleic acid resins (copolymers of styrene and maleic acid). Commercially available acid anhydride resins include "HNA-100," "MH-700," "MTA-15," "DDSA," and "OSA" from New Japan Chemical Co., Ltd., "YH-306" and "YH-307" from Mitsubishi Chemical Corporation, and "HN-2200" and "HN-5500" from Hitachi Chemical Co., Ltd.

[0087] The amine resin may be a resin having one or more, preferably two or more, amino groups in one molecule. Examples of the amine resin include aliphatic amines, polyether amines, alicyclic amines, and aromatic amines, with aromatic amines being preferred. The amine resin is preferably a primary amine or secondary amine, with primary amines being more preferred. Specific examples of the amine resin include 4,4'-methylenebis(2,6-dimethylaniline), 4,4'-diaminodiphenylmethane, 4,4'-diaminodiphenyl sulfone, 3,3'-diaminodiphenyl sulfone, m-phenylenediamine, m-xylylenediamine, diethyltoluenediamine, 4,4'-diaminodiphenyl ether, 3,3'-dimethyl-4,4'-diaminobiphenyl, 2,2'-dimethyl-4,4'-diaminobiphenyl, 3,3'-dihydroxybenzidine, and 2,2-bis(3-amino-4-hydroxyphenyl)propanol. Examples of suitable bis(4-aminophenoxy)benzene include bis(4-aminophenyl)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, and bis(4-(3-aminophenoxy)phenyl)sulfone. Commercially available amine-based resins may be used, such as "SEIKACURE-S" manufactured by Seika Corporation, "KAYABOND C-200S", "KAYABOND C-100", "KAYAHARD AA", "KAYAHARD AB", and "KAYAHARD AS" manufactured by Nippon Kayaku Co., Ltd., and "Epicure W" manufactured by Mitsubishi Chemical Corporation.

[0088] Specific examples of benzoxazine resins include "JBZ-OP100D" and "ODA-BOZ" manufactured by JFE Chemical Corporation; "HFB2006M" manufactured by Showa Polymer Co., Ltd.; and "Pd" and "Fa" manufactured by Shikoku Chemical Industry Co., Ltd.

[0089] The active ester resin may be a resin having one or more, preferably two or more, active ester groups per molecule. Among these, preferred active ester resins are those having two or more highly reactive ester groups per molecule, such as phenol esters, thiophenol esters, N-hydroxyamine esters, and esters of heterocyclic hydroxy compounds. The active ester 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. From the viewpoint of improving heat resistance, active ester resins obtained from a carboxylic acid compound and a hydroxy compound are preferred, and active 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, and phenol novolak. Here, "dicyclopentadiene-type diphenol compounds" refers to diphenol compounds obtained by condensing one dicyclopentadiene molecule with two phenol molecules.

[0090] Specifically, preferred active ester resins include dicyclopentadiene-type active ester resins, naphthalene-type 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. Preferred dicyclopentadiene-type active ester resins include active ester resins containing a dicyclopentadiene-type diphenol structure. Commercially available active ester resins include, for example, active ester resins containing a dicyclopentadiene-type diphenol structure such as "EXB9451", "EXB9460", "EXB9460S", "EXB-8000L", "EXB-8000L-65M", "EXB-8000L-65TM", "HPC-8000L-65TM", "HPC-8000", "HPC-8000-65T", "HPC-8000H", and "HPC-8000H-65TM" (manufactured by DIC Corporation); active ester resins containing a naphthalene structure such as "HP-B-8151-62T", "HP-C-8151-62T", "EXB-8100L-65T", and "EXB-8150-60T"; Examples of such active ester resins include "EXB-8150-62T," "EXB-9416-70BK," "HPC-8150-60T," "HPC-8150-62T," and "EXB-8" (manufactured by DIC Corporation); "EXB9401" (manufactured by DIC Corporation) as a phosphorus-containing active ester resin; "DC808" (manufactured by Mitsubishi Chemical Corporation) as an active ester resin which is an acetylated product of phenol novolac; "YLH1026," "YLH1030," and "YLH1048" (manufactured by Mitsubishi Chemical Corporation) as active ester resins which are benzoylated products of phenol novolac; and "PC1300-02-65MA" (manufactured by Air Water Inc.) as an active ester resin containing a styryl group and a naphthalene structure.

[0091] 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; multifunctional cyanate resins derived from phenol novolac and cresol novolac; and prepolymers in which these cyanate resins are partially converted to triazine. Specific examples of cyanate ester resins include "PT30" and "PT60" manufactured by Lonza Japan Co., Ltd. (both of which are phenol novolac-type multifunctional cyanate ester resins), "BA230" and "BA230S75" (prepolymers in which part or all of bisphenol A dicyanate has been triazine-converted to form a trimer).

[0092] Examples of thiol-based resins include trimethylolpropane tris(3-mercaptopropionate), pentaerythritol tetrakis(3-mercaptobutyrate), and tris(3-mercaptopropyl)isocyanurate.

[0093] The reactive group equivalent of the epoxy 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 reactive group equivalent represents the mass of the epoxy curing agent per equivalent of the reactive group.

[0094] The amount of the epoxy curing agent is preferably 40% by mass or less, more preferably 30% by mass or less, even more preferably 20% by mass or less, and particularly preferably 10% by mass or less, relative to 100% by mass of the nonvolatile components in the resin composition. The lower limit can be, for example, 0% by mass or more, 0.01% by mass or more, or 0.1% by mass or more.

[0095] The amount (vol %) of the (D) thermosetting resin is preferably 2.5% by volume or more, more preferably 4.0% by volume or more, and particularly preferably 4.5% by volume or more, relative to 100% by volume of the nonvolatile components in the resin composition, and is preferably 10.0% by volume or less, more preferably 9.0% by volume or less, and particularly preferably 8.0% by volume or less. When the amount (vol %) of the (D) thermosetting resin is within this range, both the relative permeability and magnetic loss can be effectively improved in the low frequency band, and the coatability of the resin composition can be further improved.

[0096] The amount (mass %) of the (D) thermosetting resin is preferably at least 0.1 mass %, more preferably at least 0.5 mass %, and particularly preferably at least 1.0 mass %, relative to 100 mass % of the nonvolatile components in the resin composition, and is preferably at most 20 mass %, more preferably at most 15 mass %, and even more preferably at most 10 mass %. When the amount (mass %) of the (D) thermosetting resin is within the above range, both the relative permeability and magnetic loss can be effectively improved in the low frequency band, and the coatability of the resin composition can be further improved.

[0097] The amount of (D) thermosetting resin is preferably 50% by mass or more, more preferably 60% by mass or more, and particularly preferably 70% by mass or more, relative to 100% by mass of the resin components in the resin composition, and is preferably 100% by mass or less, more preferably 95% by mass or less, and particularly preferably 90% by mass or less. When the amount of (D) thermosetting resin is within this range, both the relative magnetic permeability and magnetic loss can be effectively improved in the low frequency band, and the coatability of the resin composition can be further improved. The resin components of the resin composition refer to the non-volatile components in the resin composition other than inorganic fillers such as magnetic powder.

[0098] <(E) Curing Accelerator According to the First Embodiment> The resin composition according to the first embodiment of the present invention may further contain a curing accelerator (E) as an optional component. The curing accelerator (E) as the component (E) does not include components (A) to (D) described above. The curing accelerator (E) functions as a catalyst for the reaction of the thermosetting resin (D), and can therefore accelerate the curing of the resin composition. For example, when the thermosetting resin (D) contains an epoxy resin, the curing accelerator (E) preferably accelerates the curing of the epoxy resin.

[0099] Examples of the (E) curing accelerator include imidazole-based curing accelerators, phosphorus-based curing accelerators, urea-based curing accelerators, guanidine-based curing accelerators, metal-based curing accelerators, and amine-based curing accelerators. Among these, the (E) curing accelerator preferably includes an imidazole-based curing accelerator. One type of (E) curing accelerator may be used alone, or two or more types may be used in combination.

[0100] 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-methylimidazole. Phenylimidazole, 1-cyanoethyl-2-methylimidazole, 1-cyanoethyl-2-undecylimidazole, 1-cyanoethyl-2-ethyl-4-methylimidazole, 1-cyanoethyl-2-phenylimidazole, 1-cyanoethyl-2-undecylimidazole, 1-cyanoethyl-2-phenylimidazolium trimellitate, 1-cyanoethyl-2-phenylimidazolium trimellitate, 2,4-diamino-6-[2'-methylimidazolyl -(1')]-ethyl-s-triazine, 2,4-diamino-6-[2'-undecylimidazolyl-(1')]-ethyl-s-triazine, 2,4-diamino-6-[2'-ethyl-4'-methylimidazolyl-(1')]-ethyl-s-triazine, 2,4-diamino-6-[2'-methylimidazolyl-(1')]-ethyl-s-triazine isocyanuric acid adduct, 2-phenylimidazole isocyanuric acid adduct Examples of imidazole compounds include 2-phenyl-4,5-dihydroxymethylimidazole, 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. Commercially available imidazole curing accelerators may also be used, such as "1B2PZ," "2MZA-PW," and "2PHZ-PW" manufactured by Shikoku Chemical Industry Co., Ltd., and "P200-H50" manufactured by Mitsubishi Chemical Corporation.

[0101] Examples of the phosphorus-based curing accelerator include aliphatic phosphonium salts such as tetrabutylphosphonium bromide, tetrabutylphosphonium chloride, tetrabutylphosphonium acetate, tetrabutylphosphonium decanoate, tetrabutylphosphonium laurate, 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, propyltriphenylphosphonium bromide, butyltriphenylphosphonium bromide, benzyltriphenylphosphonium chloride, tetraphenylphosphonium bromide, p-tolyltriphenylphosphonium tetra-p-tolylborate, and tetraphenylphosphonium bromide. aromatic phosphonium salts such as tetraphenylborate, tetraphenylphosphonium tetra-p-tolylborate, triphenylethylphosphonium tetraphenylborate, tris(3-methylphenyl)ethylphosphonium tetraphenylborate, tris(2-methoxyphenyl)ethylphosphonium tetraphenylborate, (4-methylphenyl)triphenylphosphonium thiocyanate, tetraphenylphosphonium thiocyanate, and butyltriphenylphosphonium thiocyanate; aromatic phosphine-borane complexes such as triphenylphosphine-triphenylborane; aromatic phosphine-quinone adducts such as triphenylphosphine-p-benzoquinone adduct; 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, tris(2,5-dimethylphenyl)phosphine, tris(2,6-dimethylphenyl)phosphine aromatic phosphines such as benzene, 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-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;

[0102] 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 toluene bis(dimethylurea), 3-(4-isopropylphenyl)-1,1-dimethylurea, 3-(4-methoxyphenyl)-1,1-dimethylurea, 3-(4-nitrophenyl)-1,1-dimethylurea, 3-[4-(4-methoxyphenoxy)phenyl]-1,1-dimethylurea, 3-[4-(4-chlorophenoxy)phenyl]-1,1-dimethylurea, 3-[3-(trifluoromethyl)phenyl]-1,1-dimethylurea, N,N-(1,4-phenylene)bis(N',N'-dimethylurea), and N,N-(4-methyl-1,3-phenylene)bis(N',N'-dimethylurea) [toluene bisdimethylurea].

[0103] 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, 7-methyl-1,5,7-triazabicyclo[4.4.0]dec-5-ene, 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.

[0104] 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.

[0105] 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, etc. Commercially available amine curing accelerators may be used, such as "MY-25" manufactured by Ajinomoto Fine-Techno Co., Inc.

[0106] The amount (vol %) of (E) the curing accelerator may be 0 vol % or more than 0 vol %, and is preferably 0.1 vol % or more, more preferably 0.2 vol % or more, and particularly preferably 0.3 vol % or more, and is preferably 2.0 vol % or less, more preferably 1.0 vol % or less, and particularly preferably 0.7 vol % or less, relative to 100 vol % of the non-volatile components in the resin composition.

[0107] The amount (mass %) of (E) curing accelerator may be preferably 0 mass % or more than 0 mass %, and is preferably 0.01 mass % or more, more preferably 0.05 mass % or more, particularly preferably 0.1 mass % or more, and is preferably 5 mass % or less, more preferably 3 mass % or less, particularly preferably 1 mass % or less, relative to 100 mass % of non-volatile components in the resin composition.

[0108] The range of the amount (mass%) of (E) curing accelerator, relative to 100 mass% of the resin component in the resin composition, may be preferably 0 mass% or more than 0 mass%, and is preferably 0.1 mass% or more, more preferably 1 mass% or more, particularly preferably 3 mass% or more, and is preferably 20 mass% or less, more preferably 15 mass% or less, particularly preferably 10 mass% or less.

[0109] <(F) Dispersant According to the First Embodiment> The resin composition according to the first embodiment of the present invention may further contain a dispersant (F) as an optional component. The dispersant (F) as the component (F) does not include those corresponding to the above-mentioned components (A) to (E). The dispersant (F) can improve the dispersibility of magnetic powders such as the nanocrystalline magnetic powder (A), the small-diameter magnetic powder (B), and the medium-sized magnetic powder (C).

[0110] There are no limitations on the type of (F) dispersant. For example, the (F) dispersant may contain a functional group capable of adsorbing to the magnetic powder, and when adsorbed to the magnetic powder, disperse the magnetic powder by repulsion between (F) dispersants (e.g., electrostatic repulsion, steric repulsion, etc.). Examples of such (F) dispersants include acidic dispersants and basic dispersants.

[0111] Acidic dispersants typically contain acidic functional groups such as carboxyl groups, sulfo groups (-SO3H), sulfate groups (-OSO3H), phosphono groups (-PO(OH)2), phosphonooxy groups (-OPO(OH)2), hydroxyphosphoryl groups (-PO(OH)-), and sulfanyl groups (-SH). The acidic functional groups typically have a dissociable proton and may be neutralized with a base such as an amine or hydroxide ion. Preferred acidic dispersants include, for example, acidic polymer dispersants containing a polymer chain such as a polyoxyalkylene chain or a polyether chain. Preferred examples of acidic dispersants include "C-2093I" and "SC-1015F (a multifunctional comb-type functional polymer having an ionic group in the main chain and a polyoxyalkylene chain in the graft chain)" manufactured by NOF Corporation; "ED152," "ED153," "ED154," "ED118," "ED174," "ED251," and "DA-375" (polyether-type phosphate ester dispersants) manufactured by Kusumoto Chemicals Co., Ltd.; "RS-410," "RS-610," and "RS-710" (pH 1.9) (phosphate ester dispersants) from the "Phosphanol" series manufactured by Toho Chemical Industry Co., Ltd.; and "AKM-0531," "AFB-1521," "SC-0505K," and "SC-0708A" from the "Marialim" series manufactured by NOF Corporation.

[0112] Basic dispersants typically contain basic functional groups such as primary, secondary, and tertiary amino groups; ammonium groups; imino groups; and nitrogen-containing heterocyclic groups such as pyridine, pyrimidine, pyrazine, imidazole, and triazole. The basic functional groups may be neutralized with an acid such as an organic acid or an inorganic acid. Preferred basic dispersants include, for example, basic polymer dispersants containing polymer chains such as polyester chains. Preferred examples of basic dispersants include "PB-881" (a dispersant containing polyester chains) manufactured by Ajinomoto Fine-Techno Co., Inc.

[0113] The (F) dispersant may be used alone or in combination of two or more.

[0114] The amount (vol %) of (F) dispersant may be 0 vol % or more, and is preferably 0.3 vol % or more, more preferably 0.6 vol % or more, and particularly preferably 1.2 vol % or more, and is preferably 6 vol % or less, more preferably 4 vol % or less, and particularly preferably 3 vol % or less, relative to 100 vol % of the nonvolatile components in the resin composition.

[0115] The amount (mass %) of the (F) dispersant may be preferably 0 mass % or more than 0 mass %, and is preferably 0.01 mass % or more, more preferably 0.05 mass % or more, particularly preferably 0.1 mass % or more, and is preferably 5 mass % or less, more preferably 3 mass % or less, particularly preferably 1 mass % or less, relative to 100 mass % of the non-volatile components in the resin composition.

[0116] The amount (mass %) of the (F) dispersant, relative to 100 mass % of the resin component in the resin composition, may preferably be 0 mass % or more, and may be preferably 0.1 mass % or more, more preferably 1 mass % or more, particularly preferably 5 mass % or more, and is preferably 30 mass % or less, more preferably 25 mass % or less, particularly preferably 20 mass % or less.

[0117] <(G) Optional Additive According to the First Embodiment> The resin composition according to the first embodiment of the present invention may further contain (G) optional additives in addition to the above-described components. Examples of optional additives (G) include radical polymerization initiators such as peroxide radical polymerization initiators and azo radical polymerization initiators; 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 leveling agents and acrylic polymer leveling agents; thickeners such as bentone and montmorillonite; antifoaming agents such as silicone antifoaming agents, acrylic antifoaming agents, fluorine-based antifoaming agents, and vinyl resin antifoaming agents; ultraviolet absorbers such as benzotriazole ultraviolet absorbers; adhesion improvers such as urea silanes; triazole adhesion promoters and tetrazole adhesion promoters. Examples of the optional additives (G) include adhesion promoters such as triazine-based adhesion promoters; antioxidants such as hindered phenol-based antioxidants and hindered amine-based antioxidants; fluorescent brighteners such as stilbene derivatives; surfactants such as fluorine-based surfactants and silicone-based surfactants; flame retardants such as phosphorus-based flame retardants (e.g., phosphate ester compounds, phosphazene compounds, phosphinic acid compounds, and red phosphorus), nitrogen-based flame retardants (e.g., melamine sulfate), halogen-based flame retardants, and inorganic flame retardants (e.g., antimony trioxide); 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. One or more of the optional additives (G) may be used alone or in combination.

[0118] <Solvent (H) according to the first embodiment> The resin composition according to the first embodiment of the present invention may further contain an optional solvent (H) as a volatile component in addition to the non-volatile components such as the components (A) to (G) described above.

[0119] As the (H) solvent, an organic solvent is usually used. It is preferable that this organic solvent be capable of dissolving the resin component contained in the non-volatile component. Examples of organic solvents include ketone-based solvents such as acetone, methyl ethyl ketone, methyl isobutyl ketone, and cyclohexanone; ester-based solvents such as methyl acetate, ethyl acetate, butyl acetate, isobutyl acetate, isoamyl acetate, methyl propionate, ethyl propionate, and γ-butyrolactone; ether-based solvents such as tetrahydropyran, tetrahydrofuran, 1,4-dioxane, diethyl ether, diisopropyl ether, dibutyl ether, and diphenyl ether; alcohol-based solvents such as methanol, ethanol, propanol, butanol, and ethylene glycol; 2-ethoxyethyl acetate, propylene glycol monomethyl ether acetate, diethylene glycol monoethyl ether acetate, ethyl diglycol acetate, γ-butyrolactone, and methyl methoxypropionate. Examples of the solvent include ether ester solvents such as methyl lactate, ethyl lactate, and methyl 2-hydroxyisobutyrate; ether alcohol solvents such as 2-methoxypropanol, 2-methoxyethanol, 2-ethoxyethanol, propylene glycol monomethyl ether, and diethylene glycol monobutyl ether (butyl carbitol); amide solvents such as N,N-dimethylformamide, N,N-dimethylacetamide, and N-methyl-2-pyrrolidone; sulfoxide solvents such as dimethyl sulfoxide; nitrile solvents such as acetonitrile and propionitrile; aliphatic hydrocarbon solvents such as hexane, cyclopentane, cyclohexane, and methylcyclohexane; and aromatic hydrocarbon solvents such as benzene, toluene, xylene, ethylbenzene, and trimethylbenzene. The solvent (H) may be used singly or in combination of two or more in any ratio.

[0120] The amount of (H) solvent is preferably small when a paste-like resin composition is to be prepared. For example, the amount of (H) solvent may be 5.5% by mass or less, 4% by mass or less, 3% by mass or less, 2% by mass or less, or 1% by mass or less, relative to 100% by mass of non-volatile components in the resin composition. Among these, it is preferable that the resin composition does not contain (H) solvent. That is, the amount of (H) solvent is preferably 0% by mass. When the content of (H) solvent in the resin composition is small or when no (H) solvent is contained, it is possible to suppress the generation of voids due to the evaporation of (H) solvent, and further, it is possible to achieve excellent handleability and workability.

[0121] <Characteristics of the resin composition according to the first embodiment> The resin composition according to the first embodiment of the present invention can be cured by heat. Therefore, a cured product of the resin composition can be obtained by thermally curing the resin composition. Among the components contained in the resin composition, volatile components such as (H) solvent can be volatilized by the heat during thermal curing, but nonvolatile components such as components (A) to (G) do not volatilize by the heat during thermal curing. Therefore, the cured product of the resin composition can contain the nonvolatile components of the resin composition or their reaction products.

[0122] The resin composition according to the first embodiment of the present invention can provide a cured product with improved relative magnetic permeability and magnetic loss. Specifically, the cured product of this resin composition can have high relative magnetic permeability and low magnetic loss in the low frequency band (e.g., 10 MHz).

[0123] In one example, when the relative magnetic permeability of a cured resin composition is measured at a measurement frequency of 10 MHz and a room temperature of 23°C, the range of the relative magnetic permeability is preferably 25 or more, more preferably 30 or more, and particularly preferably 35 or more. There is no particular upper limit, and it can be, for example, 80 or less, 75 or less, or 70 or less. The relative magnetic permeability of a cured resin composition can be measured by the method described in <Test Example 2: Measurement and evaluation of relative magnetic permeability> in the Examples below.

[0124] In one example, when the loss factor (tan δ) of a cured resin composition is measured at a measurement frequency of 10 MHz and a room temperature of 23°C, the loss factor is preferably in the range of 0.13 or more, more preferably 0.10 or less, and particularly preferably 0.07 or less. The lower limit may be, for example, 0.000 or more, 0.001 or more, etc. In general, the smaller the loss factor (tan δ), the lower the magnetic loss. The loss factor (tan δ) of a cured resin composition can be measured by the method described in <Test Example 3: Measurement and Evaluation of Loss Factor (tan δ)> in the Examples below.

[0125] The resin composition according to the first embodiment of the present invention can have excellent applicability. Specifically, even when the amount of solvent is small, the resin composition can have high fluidity, allowing for smooth application. Therefore, the resin composition can preferably have a small solvent content, and more preferably be solvent-free. Therefore, since the formation of voids due to the solvent can be suppressed, it is usually possible to obtain a cured product with excellent mechanical strength and uniformity.

[0126] 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.

[0127] 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 resin sheet including a layer of the resin composition.

[0128] <Method of manufacturing resin composition according to first embodiment> The resin composition according to the first embodiment of the present invention may be produced, for example, by a production method including 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 the components, the temperature may be adjusted appropriately, and thus heating and / or cooling may be performed temporarily or throughout. In addition, stirring or shaking may be performed in the process of mixing the components. Furthermore, degassing may be performed under low-pressure conditions, such as under vacuum. The resin composition according to the first embodiment of the present invention may be produced by the method for producing a resin composition according to the second embodiment described below.

[0129] <Outline of method for producing resin composition according to second embodiment> A method for producing a resin composition according to a second embodiment of the present invention includes: (a) a nanocrystalline magnetic powder having an average particle size of 5.5 μm or more and 20 μm or less; (b) a magnetic powder having an average particle size of 2 μm or less; (D) a thermosetting resin; In the following explanation, "(a) nanocrystalline magnetic powder having an average particle size of 5.5 μm or more and 20 μm or less" may be referred to as "(a) nanocrystalline magnetic raw material powder." Also, "(b) magnetic powder having an average particle size of 2 μm or less" may be referred to as "(b) small-diameter magnetic raw material powder."

[0130] The resin composition produced by the production method according to the second embodiment of the present invention can achieve the same effects as the resin composition according to the first embodiment. Therefore, the resin composition produced by the production method according to the second embodiment of the present invention can be cured by thermally curing the thermosetting resin (D) to provide a cured product. The cured product thus obtained can have high relative permeability and low magnetic loss in the low frequency band (e.g., 10 MHz). Furthermore, this resin composition usually has excellent applicability.

[0131] As can be seen from the range of average particle size, the (a) nanocrystalline magnetic raw powder includes the (A) nanocrystalline magnetic powder described in the first embodiment, and the (b) small-diameter magnetic raw powder can include the (B) small-diameter magnetic powder described in the first embodiment. Therefore, the inventors speculate that the mechanism by which the effects of this embodiment are obtained includes the action of the combination of the (A) nanocrystalline magnetic powder and the (B) small-diameter magnetic powder described in the first embodiment. However, the technical scope of the present invention is not limited to the mechanism described here.

[0132] <(a) Nanocrystalline Magnetic Raw Material Powder According to Second Embodiment> A manufacturing method according to a second embodiment of the present invention includes mixing (a) nanocrystalline magnetic raw powder as component (a) with (b) small-diameter magnetic raw powder and (D) thermosetting resin. The (a) nanocrystalline magnetic raw powder is a nanocrystalline magnetic powder having an average particle size within a specific range. The range of the nanocrystalline magnetic powder is as described in the first embodiment.

[0133] The (a) nanocrystalline magnetic raw powder is usually mixed in the form of particles. The (a) nanocrystalline magnetic raw powder may contain crystal grains in at least a portion of the particles, preferably in the surface layer of the particles, more preferably in the entire particles, and particularly preferably consisting of only crystal grains.

[0134] (a) The nanocrystalline magnetic raw powder has an average particle size D in the range of 5.5 μm to 20 μm. 50 More specifically, (a) the average particle size D of the nanocrystalline magnetic raw powder 50is usually 5.5 μm or more, preferably 5.7 μm or more, more preferably 5.9 μm or more, and is usually 20 μm or less, preferably 18 μm or less, more preferably 16 μm or less. 50 By using a manufacturing method including mixing (a) nanocrystalline magnetic raw material powder having the above formula with (b) small-diameter magnetic raw material powder and (D) a thermosetting resin, it is possible to improve both the relative permeability and magnetic loss in the low frequency band, and further to manufacture a resin composition with excellent coatability.

[0135] (a) Average particle size D of nanocrystalline magnetic raw powder 50 represents the volume-based median diameter. (a) Average particle diameter D of the nanocrystalline magnetic raw powder 50 can be measured by a laser diffraction and scattering method based on the Mie scattering theory. Specifically, a laser diffraction and scattering particle size distribution measuring device is used to (a) create a particle size distribution of the nanocrystalline magnetic raw material powder on a volume basis, and the median diameter is taken as the average particle size D 50 The measurement can be performed by the following method. A measurement sample can preferably be prepared by dispersing magnetic powder in water using ultrasonic waves. As a laser diffraction scattering particle size distribution measuring device, the "MT3000II" manufactured by Microtrackbell, the "LA-960" manufactured by Horiba, Ltd., the "SALD-2200" manufactured by Shimadzu Corporation, etc. can be used.

[0136] Usually, the volumetric particle size distribution of the (a) nanocrystalline magnetic raw powder follows a normal distribution. Therefore, the (a) nanocrystalline magnetic raw powder has an average particle size D 50 10% smaller particle size D 10 , and the average particle size D of the (a) nanocrystalline magnetic raw powder 50 Larger 90% particle size D 90 Here, the 10% particle size D 10 90% particle size D is the particle size at which the cumulative volume from the smallest particle size in the particle size distribution on a volume basis reaches 10%. 90 This refers to the particle size at which the cumulative volume from the smallest particle size in the volume-based particle size distribution reaches 90%. (a) 10% particle size D of nanocrystalline magnetic raw powder10 and 90% particle size D 90 can be measured from the volume-based particle size distribution measured by the laser diffraction / scattering method described above.

[0137] (a) 10% particle size D of nanocrystalline magnetic raw powder 10 is preferably greater than 2.0 μm, more preferably 2.4 μm or more, and particularly preferably 2.8 μm or more. 50 (a) The 10% particle diameter D of the nanocrystalline magnetic raw material powder is, for example, 10 μm or less, 8 μm or less, 6 μm or less, etc. 10 When the value of the relative magnetic permeability is within the above range, both the relative magnetic permeability and the magnetic loss can be effectively improved in the low frequency band, and a resin composition having particularly excellent coatability can be produced.

[0138] (a) 90% particle size D of nanocrystalline magnetic raw powder 90 is preferably 60 μm or less, more preferably 50 μm or less, and particularly preferably 40 μm or less. 50 (a) The 90% particle diameter D of the nanocrystalline magnetic raw material powder is, for example, 6 μm or more, 8 μm or more, 10 μm or more, etc. 90 When the value of the relative magnetic permeability is within the above range, both the relative magnetic permeability and the magnetic loss can be effectively improved in the low frequency band, and a resin composition having particularly excellent coatability can be produced.

[0139] (a) 10% particle size D of nanocrystalline magnetic raw powder 10 and 90% particle size D 90 Difference D 90 -D 10 is preferably 1 μm or more, more preferably 3 μm or more, particularly preferably 5 μm or more, and is preferably 40 μm or less, more preferably 35 μm or less, particularly preferably 30 μm or less. 90 -D 10 When the value of the relative magnetic permeability is within the above range, both the relative magnetic permeability and the magnetic loss can be effectively improved in the low frequency band, and a resin composition having particularly excellent coatability can be produced.

[0140] (a) 10% particle size D of nanocrystalline magnetic raw powder 10 and 90% particle size D90 Relative to D 90 / D 10 is preferably 1.1 or more, more preferably 2 or more, particularly preferably 3 or more, and is preferably 10 or less, more preferably 8 or less, particularly preferably 6 or less. 90 / D 10 When the value of the relative magnetic permeability is within the above range, both the relative magnetic permeability and the magnetic loss can be effectively improved in the low frequency band, and a resin composition having particularly excellent coatability can be produced.

[0141] The (a) nanocrystalline magnetic raw powder can be particles of a magnetic material having a relative magnetic permeability greater than 1. As the magnetic material contained in the (a) nanocrystalline magnetic raw powder, it is preferable to use the magnetic material described as the magnetic material of the (A) nanocrystalline magnetic powder.

[0142] The (a) nanocrystalline magnetic raw material powder preferably contains the above-mentioned magnetic material, and preferably contains only the above-mentioned magnetic material. The (a) nanocrystalline magnetic raw material powder may be used alone or in combination of two or more types.

[0143] (a) Nanocrystalline magnetic raw powder can be manufactured by, for example, an atomization method. Specific examples of methods for manufacturing (a) nanocrystalline magnetic raw powder include the methods described in JP 2021-141267 A and JP 2021-158343 A. Commercially available (a) nanocrystalline magnetic raw powder may also be used. Examples of commercially available magnetic powders containing (a) nanocrystalline magnetic raw powder include "KUAMET NC1-38um" and "ATFINE-NC1 PF10FA" manufactured by Epson Atmix. When (a) nanocrystalline magnetic raw powder is obtained from the market, commercially available magnetic powders may be classified as needed. For example, a magnetic powder having an average particle size D in the above-mentioned range may be used. 50 The commercially available magnetic powder having no average particle diameter D 50 The value of may be adjusted appropriately.

[0144] The (a) nanocrystalline magnetic raw powder is preferably spherical. The aspect ratio of the particles of the (a) nanocrystalline magnetic raw powder can be in the same range as the aspect ratio of the (A) nanocrystalline magnetic powder.

[0145] The amount (volume %) of the (a) nanocrystalline magnetic raw material powder used in the manufacturing method according to the second embodiment of the present invention is preferably 30% by volume or more, more preferably 40% by volume or more, and particularly preferably 50% by volume or more, relative to 100% by volume of the nonvolatile components of the resin composition to be manufactured, and is preferably 80% by volume or less, more preferably 75% by volume or less, and particularly preferably 70% by volume or less. When the amount (volume %) of the (a) nanocrystalline magnetic raw material powder is within the above range, it is possible to effectively improve both the relative permeability and magnetic loss in the low frequency band, and to manufacture a resin composition that has particularly excellent coatability.

[0146] The amount (volume %) of (a) nanocrystalline magnetic raw powder is represented by "V(a)," and the amount (volume %) of (b) small-diameter magnetic raw powder is represented by "V(b)," relative to 100% by volume of the nonvolatile components of the resin composition. In this case, the volume ratio of the (a) nanocrystalline magnetic raw powder to the (b) small-diameter magnetic raw powder ((a) nanocrystalline magnetic raw powder / (b) small-diameter magnetic raw powder) can be represented by "V(a) / V(b)." This volume ratio V(a) / V(b) is preferably 1.0 or more, more preferably 1.5 or more, even more preferably 2.0 or more, and particularly preferably 2.5 or more, and is preferably 20 or less, more preferably 16 or less, even more preferably 12 or less, and particularly preferably 8 or less. When the volume ratio V(a) / V(b) is within the above range, both the relative permeability and magnetic loss can be effectively improved in the low-frequency band, and a resin composition with particularly excellent coatability can be produced.

[0147] Furthermore, the total volume % of (a) nanocrystalline magnetic raw powder and (b) small-diameter magnetic raw powder, relative to 100% by volume of the nonvolatile components of the resin composition, can be expressed as "V(a) + V(b)." This total volume % V(a) + V(b) is preferably 40% by volume or more, more preferably 50% by volume or more, and particularly preferably 60% by volume or more, and is preferably 90% by volume or less, more preferably 86% by volume or less, and particularly preferably 82% by volume or less. When the total volume % V(a) + V(b) of (a) nanocrystalline magnetic raw powder and (b) small-diameter magnetic raw powder is within the above range, both the relative permeability and magnetic loss can be effectively improved in the low-frequency band, and a resin composition with particularly excellent coatability can be produced.

[0148] The total amount (vol %) of all magnetic powders mixed to produce the resin composition is preferably 40% by volume or more, more preferably 50% by volume or more, and particularly preferably 60% by volume or more, relative to 100% by volume of the nonvolatile components of the resin composition, and is preferably 95% by volume or less, more preferably 90% by volume or less, and particularly preferably 85% by volume or less. When the total amount (vol %) of magnetic powders is within the above range, both the relative permeability and magnetic loss can be effectively improved in the low frequency band, and a resin composition with particularly excellent coatability can be produced.

[0149] The total amount (volume %) of (a) nanocrystalline magnetic raw powder and (b) small-diameter magnetic raw powder is preferably 80% by volume or more, more preferably 85% by volume or more, and particularly preferably 90% by volume or more, relative to 100% by volume, the total amount of all magnetic powders mixed to produce the resin composition, and may be, for example, 100% by volume or less, 98% by volume or less, 95% by volume or less, etc. When the total amount (volume %) of (a) nanocrystalline magnetic raw powder and (b) small-diameter magnetic raw powder is within the above range, both the relative permeability and magnetic loss can be effectively improved in the low-frequency band, and a resin composition with particularly excellent coatability can be produced.

[0150] The amount (mass %) of the (a) nanocrystalline magnetic raw material powder used in the manufacturing method according to the second embodiment of the present invention is preferably 50 mass % or more, more preferably 60 mass % or more, and particularly preferably 70 mass % or more, relative to 100 mass % of the nonvolatile components of the resin composition to be manufactured, and is preferably 90 mass % or less, more preferably 86 mass % or less, and particularly preferably 82 mass % or less. When the amount (mass %) of the (a) nanocrystalline magnetic raw material powder is within the above range, it is possible to effectively improve both the relative permeability and magnetic loss in the low frequency band, and to manufacture a resin composition that has particularly excellent coatability.

[0151] Relative to 100% by mass of the nonvolatile components of the resin composition, the amount (mass%) of (a) nanocrystalline magnetic raw powder is represented by "M(a)," and the amount (mass%) of (b) small-diameter magnetic raw powder is represented by "M(b)." In this case, the mass ratio of the (a) nanocrystalline magnetic raw powder to the (b) small-diameter magnetic raw powder ((a) nanocrystalline magnetic raw powder / (b) small-diameter magnetic raw powder) can be represented by "M(a) / M(b)." This mass ratio M(a) / M(b) is preferably 1 or more, more preferably 2 or more, even more preferably 3 or more, and preferably 20 or less, more preferably 15 or less, and even more preferably 10 or less. When the mass ratio M(a) / M(b) is within the above range, both the relative permeability and magnetic loss can be effectively improved in the low-frequency band, and a resin composition with particularly excellent coatability can be produced.

[0152] Furthermore, the total mass % of (a) nanocrystalline magnetic raw powder and (b) small-diameter magnetic raw powder, relative to 100% by mass of the nonvolatile components of the resin composition, can be expressed as "M(a) + M(b)." This total mass % M(a) + M(b) is preferably 60% by mass or more, more preferably 70% by mass or more, and particularly preferably 80% by mass or more, and is preferably 98% by mass or less, more preferably 97% by mass or less, and particularly preferably 96% by mass or less. When the total mass % M(a) + M(b) of (a) nanocrystalline magnetic raw powder and (b) small-diameter magnetic raw powder is within the above range, both the relative permeability and magnetic loss can be effectively improved in the low-frequency band, and a resin composition with particularly excellent coatability can be produced.

[0153] The total amount (mass%) of all magnetic powders mixed to produce the resin composition is preferably 80 mass% or more, more preferably 85 mass% or more, and particularly preferably 90 mass% or more, relative to 100 mass% of the nonvolatile components of the resin composition, and is preferably 99 mass% or less, more preferably 98 mass% or less, and particularly preferably 97 mass% or less. When the total amount (mass%) of magnetic powders is within the above range, both the relative permeability and magnetic loss can be effectively improved in the low frequency band, and a resin composition with particularly excellent coatability can be produced.

[0154] The total amount (mass%) of (a) nanocrystalline magnetic raw powder and (b) small-diameter magnetic raw powder is preferably 80% by mass or more, more preferably 85% by mass or more, and particularly preferably 89.8% by mass or more, relative to 100% by mass, the total amount of all magnetic powders mixed to produce the resin composition. It may be, for example, 100% by mass or less, 98% by mass or less, 95% by mass or less, etc. When the total amount (mass%) of (a) nanocrystalline magnetic raw powder and (b) small-diameter magnetic raw powder is within the above range, it is possible to effectively improve both the relative permeability and magnetic loss in the low-frequency band, and to produce a resin composition that has particularly excellent coatability.

[0155] <(b) Small-diameter magnetic raw material powder according to the second embodiment> The resin composition according to the second embodiment of the present invention comprises mixing (b) small-diameter magnetic raw material powder as component (b) with (a) nanocrystalline magnetic raw material powder and (D) thermosetting resin. The (b) small-diameter magnetic raw material powder is usually mixed in the form of particles.

[0156] (b) The small-diameter magnetic raw powder has an average particle size D of 2 μm or less. 50 Specifically, (b) the average particle diameter D of the small-diameter magnetic raw material powder 50 is usually 2 μm or less, preferably 1.5 μm or less, and more preferably 1 μm or less. The lower limit can be, for example, 0.01 μm or more, 0.1 μm or more, etc. The average particle size D in such a range 50By using a manufacturing method including mixing (b) small-diameter magnetic raw material powder having an average particle diameter D of (b) with (a) nanocrystalline magnetic raw material powder and (D) thermosetting resin, it is possible to improve both the relative permeability and magnetic loss in the low frequency band, and further to manufacture a resin composition with excellent coatability. 50 represents the volume-based median diameter, and (a) the average particle size D of the nanocrystalline magnetic raw powder. 50 can be measured by the same method.

[0157] Usually, the particle size distribution of the (b) small-diameter magnetic raw material powder on a volume basis follows a normal distribution. Therefore, the (b) small-diameter magnetic raw material powder has an average particle size D 50 10% smaller particle size D 10 , and the average particle diameter D of the (b) small-diameter magnetic raw material powder 50 Larger 90% particle size D 90 (b) 10% particle diameter D of the small-diameter magnetic raw material powder 10 and 90% particle size D 90 is the 10% particle size D of (a) nanocrystalline magnetic raw powder 10 and 90% particle size D 90 can be measured in the same way.

[0158] (b) 10% particle size D of small-diameter magnetic raw powder 10 is preferably 0.01 μm or more, more preferably 0.02 μm or more, and particularly preferably 0.03 μm or more. 50 (b) The 10% particle diameter D of the small-diameter magnetic raw material powder is, for example, 1 μm or less, 0.7 μm or less, or 0.5 μm or less. 10 When the value of the relative magnetic permeability is within the above range, both the relative magnetic permeability and the magnetic loss can be effectively improved in the low frequency band, and a resin composition having particularly excellent coatability can be produced.

[0159] (b) 90% particle size D of small-diameter magnetic raw powder 90 is preferably less than 5.5 μm, more preferably 4 μm or less, and particularly preferably 2 μm or less. 50 (b) The 90% particle diameter D of the small-diameter magnetic raw material powder is, for example, 0.5 μm or more, 0.8 μm or more, 1 μm or more, etc.90 When the value of the relative magnetic permeability is within the above range, both the relative magnetic permeability and the magnetic loss can be effectively improved in the low frequency band, and a resin composition having particularly excellent coatability can be produced.

[0160] (b) 10% particle size D of small-diameter magnetic raw powder 10 and 90% particle size D 90 Difference D 90 -D 10 is preferably 0.1 μm or more, more preferably 0.3 μm or more, particularly preferably 0.5 μm or more, and is preferably 5 μm or less, more preferably 4 μm or less, particularly preferably 3 μm or less. 90 -D 10 When the value of the relative magnetic permeability is within the above range, both the relative magnetic permeability and the magnetic loss can be effectively improved in the low frequency band, and a resin composition having particularly excellent coatability can be produced.

[0161] (b) 10% particle size D of small-diameter magnetic raw powder 10 and 90% particle size D 90 Relative to D 90 / D 10 is preferably 1.1 or more, more preferably 1.5 or more, particularly preferably 2 or more, and is preferably 50 or less, more preferably 40 or less, particularly preferably 30 or less. 90 / D 10 When the value of the relative magnetic permeability is within the above range, both the relative magnetic permeability and the magnetic loss can be effectively improved in the low frequency band, and a resin composition having particularly excellent coatability can be produced.

[0162] (b) The small-diameter magnetic raw material powder may be a nanocrystalline magnetic powder, an amorphous magnetic powder, a crystalline magnetic powder other than a nanocrystalline magnetic powder, or a combination thereof.

[0163] The (b) small-diameter magnetic raw material powder can be particles of a magnetic material having a relative magnetic permeability greater than 1. As the magnetic material contained in the (b) small-diameter magnetic raw material powder, it is preferable to use the magnetic material described as the magnetic material of the (B) small-diameter magnetic powder.

[0164] The (b) small-diameter magnetic raw material powder preferably contains the above-mentioned magnetic material, and preferably contains only the above-mentioned magnetic material. The (b) small-diameter magnetic raw material powder may be used alone or in combination of two or more types.

[0165] As the (b) small-diameter magnetic raw powder, a commercially available magnetic powder may be used. Specific examples of commercially available magnetic powder include the same examples as the (B) small-diameter magnetic powder. When the (b) small-diameter magnetic raw powder is obtained from the market, the commercially available magnetic powder may be classified as necessary. For example, the magnetic powder having an average particle diameter D in the above-mentioned range may be used. 50 The commercially available magnetic powder having no average particle diameter D 50 The value of may be adjusted appropriately.

[0166] The (b) small-diameter magnetic raw powder is preferably spherical. The range of the aspect ratio of the particles of the (b) small-diameter magnetic raw powder can be the same as the range of the aspect ratio of the (B) small-diameter magnetic powder.

[0167] The amount (vol %) of the (b) small-diameter magnetic raw material powder used in the manufacturing method according to the second embodiment of the present invention is preferably 5% by volume or more, more preferably 6% by volume or more, and particularly preferably 7% by volume or more, relative to 100% by volume of the non-volatile components of the resin composition to be manufactured, and is preferably 50% by volume or less, more preferably 40% by volume or less, and particularly preferably 30% by volume or less. When the amount (vol %) of the (b) small-diameter magnetic raw material powder is within the above range, both the relative permeability and magnetic loss can be effectively improved in the low-frequency band, and a resin composition with particularly excellent coatability can be manufactured.

[0168] The amount (mass %) of the (b) small-diameter magnetic raw material powder used in the manufacturing method according to the second embodiment of the present invention is preferably 5 mass % or more, more preferably 6 mass % or more, and particularly preferably 7 mass % or more, relative to 100 mass % of the non-volatile components of the resin composition to be manufactured, and is preferably 50 mass % or less, more preferably 40 mass % or less, and particularly preferably 30 mass % or less. When the amount (mass %) of the (b) small-diameter magnetic raw material powder is within the above range, both the relative permeability and magnetic loss can be effectively improved in the low-frequency band, and a resin composition with particularly excellent coatability can be manufactured.

[0169] <(c) Intermediate Magnetic Raw Material Powder According to Second Embodiment> The manufacturing method according to the second embodiment of the present invention may include further mixing (c) magnetic powder as an optional component in combination with (a) nanocrystalline magnetic raw powder, (b) small-diameter magnetic raw powder, and (D) thermosetting resin. The (c) magnetic powder as the (c) component refers to magnetic powder having an average particle size greater than 2 μm and equal to or less than 20 μm, and smaller than the average particle size of the (a) nanocrystalline magnetic raw powder. This (c) magnetic powder is sometimes referred to as "(c) intermediate magnetic raw powder." The (c) intermediate magnetic raw powder does not include the (a) nanocrystalline magnetic raw powder or the (b) small-diameter magnetic raw powder. In summary, the (c) intermediate magnetic raw powder includes the magnetic powders (c1) and (c2) below. (c1) Nanocrystalline magnetic powder having an average particle size greater than 2 μm and less than 5.5 μm. (c2) A magnetic powder other than nanocrystalline magnetic powder, which has an average particle size greater than 2 μm and smaller than the average particle size of the (a) nanocrystalline magnetic raw powder.

[0170] As can be seen from the range of average particle size, the (c) intermediate magnetic raw powder can include the (C) intermediate magnetic powder described in the first embodiment. Therefore, the (c) intermediate magnetic raw powder can generally improve the relative permeability while suppressing an increase in magnetic loss, just like the (C) intermediate magnetic powder.

[0171] (c) Average particle size D of intermediate magnetic raw powder 50 Specifically, the average particle size D is usually larger than 2 μm, preferably 2.5 μm or more, more preferably 3 μm or more, and is usually less than the average particle size of the (a) nanocrystalline magnetic raw powder, preferably less than 5.5 μm, more preferably 5 μm or less. 50 When the (c) intermediate magnetic raw material powder having the average particle diameter D of (c) is used, it is possible to effectively improve both the relative magnetic permeability and the magnetic loss in the low frequency band, and it is possible to produce a resin composition that is particularly excellent in coatability. 50 represents the volume-based median diameter, and (a) the average particle size D of the nanocrystalline magnetic raw powder. 50can be measured by the same method.

[0172] Usually, the particle size distribution of the (c) intermediate magnetic raw powder on a volume basis follows a normal distribution. Therefore, the (c) intermediate magnetic raw powder has an average particle size D 50 10% smaller particle size D 10 , and the average particle size D of the (c) intermediate magnetic raw material powder 50 Larger 90% particle size D 90 (c) 10% particle diameter D of the intermediate magnetic raw material powder 10 and 90% particle size D 90 is the 10% particle size D of (a) nanocrystalline magnetic raw powder 10 and 90% particle size D 90 can be measured in the same way.

[0173] (c) 10% particle size D of intermediate magnetic raw powder 10 is preferably 1 μm or more, more preferably 1.3 μm or more, and particularly preferably 1.5 μm or more. 50 (c) The 10% particle size D of the intermediate magnetic raw material powder is, for example, 5 μm or less, 4 μm or less, 3 μm or less, etc. 10 When the value of the relative magnetic permeability is within the above range, both the relative magnetic permeability and the magnetic loss can be effectively improved in the low frequency band, and a resin composition having particularly excellent coatability can be produced.

[0174] (c) 90% particle size D of intermediate magnetic raw powder 90 is preferably less than 10 μm, more preferably 9 μm or less, and particularly preferably 8 μm or less. 50 (c) 90% particle diameter D of the intermediate magnetic raw material powder. 90 When the value of the relative magnetic permeability is within the above range, both the relative magnetic permeability and the magnetic loss can be effectively improved in the low frequency band, and a resin composition having particularly excellent coatability can be produced.

[0175] (c) 10% particle size D of intermediate magnetic raw powder 10 and 90% particle size D 90 Difference D 90 -D 10is preferably 0.1 μm or more, more preferably 1 μm or more, particularly preferably 2 μm or more, and is preferably 9 μm or less, more preferably 7 μm or less, particularly preferably 5 μm or less. 90 -D 10 When the value of the relative magnetic permeability is within the above range, both the relative magnetic permeability and the magnetic loss can be effectively improved in the low frequency band, and a resin composition having particularly excellent coatability can be produced.

[0176] (c) 10% particle size D of intermediate magnetic raw powder 10 and 90% particle size D 90 Relative to D 90 / D 10 is preferably 1.1 or more, more preferably 1.5 or more, particularly preferably 2 or more, and is preferably 10 or less, more preferably 8 or less, particularly preferably 6 or less. 90 / D 10 When the value of the relative magnetic permeability is within the above range, both the relative magnetic permeability and the magnetic loss can be effectively improved in the low frequency band, and a resin composition having particularly excellent coatability can be produced.

[0177] The (c) intermediate magnetic raw powder may be a nanocrystalline magnetic powder, an amorphous magnetic powder, a crystalline magnetic powder other than a nanocrystalline magnetic powder, or a combination of these. The (c) intermediate magnetic raw powder may be particles of a magnetic material having a relative permeability greater than 1. As the magnetic material contained in the (c) intermediate magnetic raw powder, it is preferable to use the magnetic material described as the magnetic material of the (C) intermediate magnetic powder.

[0178] The (c) intermediate magnetic raw material powder preferably contains the above-mentioned magnetic material, and preferably contains only the above-mentioned magnetic material. The (c) intermediate magnetic raw material powder may be used alone or in combination of two or more types.

[0179] As the (c) intermediate magnetic raw powder, a commercially available magnetic powder may be used. Specific examples of commercially available magnetic powder include the same examples as those of the (C) intermediate magnetic powder. When the (c) intermediate magnetic raw powder is obtained from the market, the commercially available magnetic powder may be classified as necessary. For example, the magnetic powder having an average particle diameter D in the above-mentioned range may be used.50 The commercially available magnetic powder having no average particle diameter D 50 The value of may be adjusted appropriately.

[0180] The (c) intermediate magnetic raw powder is preferably spherical. The range of the aspect ratio of the particles of the (c) intermediate magnetic raw powder may be the same as the range of the aspect ratio of the (C) intermediate magnetic powder.

[0181] The amount (vol %) of the (c) intermediate magnetic raw material powder used in the manufacturing method according to the second embodiment of the present invention may be 0 vol % or more, relative to 100 vol % of the nonvolatile components of the resin composition to be produced, and is preferably 1 vol % or more, more preferably 3 vol % or more, particularly preferably 5 vol % or more, and is preferably 34 vol % or less, more preferably 30 vol % or less, particularly preferably 20 vol % or less. When the amount (vol %) of the (c) intermediate magnetic raw material powder is within the above range, both the relative permeability and magnetic loss can be effectively improved in the low frequency band, and a resin composition with particularly excellent coatability can be produced.

[0182] The amount (volume %) of the (c) intermediate magnetic raw powder relative to 100% by volume of the nonvolatile components of the resin composition is represented by "V(c)." In this case, the volume ratio of the (a) nanocrystalline magnetic raw powder to the (c) intermediate magnetic raw powder ((c) intermediate magnetic raw powder / (a) nanocrystalline magnetic raw powder) can be represented by "V(c) / V(a)." This volume ratio V(c) / V(a) may be 0 or greater than 0, and is preferably 0.01 or greater, more preferably 0.05 or greater, particularly preferably 0.1 or greater, and is preferably 0.8 or less, more preferably 0.6 or less, and particularly preferably 0.4 or less. When the volume ratio V(c) / V(a) is within the above range, both the relative permeability and magnetic loss can be effectively improved in the low frequency band, and a resin composition with particularly excellent coatability can be produced.

[0183] Furthermore, the volume ratio of the (b) small-diameter magnetic raw powder to the (c) medium-diameter magnetic raw powder contained in the resin composition (((c) medium-diameter magnetic raw powder / b) small-diameter magnetic raw powder) can be expressed as "V(c) / V(b)". This volume ratio V(c) / V(b) may be 0 or greater than 0, and is preferably 0.01 or greater, more preferably 0.1 or greater, particularly preferably 0.2 or greater, and is preferably 9 or less, more preferably 7 or less, particularly preferably 5 or less. When the volume ratio V(c) / V(b) is within the above range, both the relative permeability and magnetic loss can be effectively improved in the low-frequency band, and a resin composition with particularly excellent coatability can be produced.

[0184] The total amount (volume %) of (a) nanocrystalline magnetic raw powder, (b) small-diameter magnetic raw powder, and (c) intermediate magnetic raw powder is preferably 40% by volume or more, more preferably 50% by volume or more, and particularly preferably 60% by volume or more, relative to 100% by volume of the nonvolatile components of the resin composition, and is preferably 95% by volume or less, more preferably 90% by volume or less, and particularly preferably 85% by volume or less. When the total amount (volume %) of (a) nanocrystalline magnetic raw powder, (b) small-diameter magnetic raw powder, and (c) intermediate magnetic raw powder is within this range, it is possible to effectively improve both the relative permeability and magnetic loss in the low-frequency band, and further improve the coatability of the resin composition.

[0185] The total amount (volume %) of (a) nanocrystalline magnetic raw powder, (b) small-diameter magnetic raw powder, and (c) medium-sized magnetic raw powder is preferably 90% by volume or more, more preferably 94% by volume or more, and particularly preferably 98% by volume or more, based on 100% by volume of the total amount of all magnetic powders mixed to produce the resin composition. A large value indicates that there is little giant magnetic powder with an average particle size of more than 20 μm. When the total amount (volume %) of (a) nanocrystalline magnetic raw powder, (b) small-diameter magnetic raw powder, and (c) medium-sized magnetic raw powder is within the above range, it is possible to effectively improve both the relative permeability and magnetic loss in the low-frequency band, and further improve the coatability of the resin composition.

[0186] The amount (mass %) of the (c) intermediate magnetic raw material powder used in the manufacturing method according to the second embodiment of the present invention may be 0 mass % or more, relative to 100 mass % of the non-volatile components of the resin composition to be produced, and is preferably 1 mass % or more, more preferably 3 mass % or more, particularly preferably 5 mass % or more, and is preferably 45 mass % or less, more preferably 30 mass % or less, particularly preferably 15 mass % or less. When the amount (mass %) of the (c) intermediate magnetic raw material powder is within the above range, both the relative permeability and magnetic loss can be effectively improved in the low frequency band, and a resin composition with particularly excellent coatability can be produced.

[0187] The amount (mass %) of the (c) intermediate magnetic raw powder relative to 100 mass % of the nonvolatile components of the resin composition is represented by "M(c)." In this case, the mass ratio of the (a) nanocrystalline magnetic raw powder to the (c) intermediate magnetic raw powder ((c) intermediate magnetic raw powder / (a) nanocrystalline magnetic raw powder) can be represented by "M(c) / M(a)." This mass ratio M(c) / M(a) may be 0 or greater than 0, and is preferably 0.01 or greater, more preferably 0.05 or greater, particularly preferably 0.1 or greater, and is preferably 0.8 or less, more preferably 0.6 or less, and particularly preferably 0.4 or less. When the mass ratio M(c) / M(a) is within the above range, both the relative permeability and magnetic loss can be effectively improved in the low frequency band, and a resin composition with particularly excellent coatability can be produced.

[0188] Furthermore, the mass ratio of the (b) small-diameter magnetic raw powder to the (c) medium-diameter magnetic raw powder contained in the resin composition (((c) medium-diameter magnetic raw powder / b) small-diameter magnetic raw powder) can be expressed as "M(c) / M(b)". This mass ratio M(c) / M(b) may be 0 or greater than 0, and is preferably 0.01 or greater, more preferably 0.1 or greater, particularly preferably 0.2 or greater, and is preferably 9 or less, more preferably 7 or less, particularly preferably 5 or less. When the mass ratio M(c) / M(b) is within the above range, both the relative permeability and magnetic loss can be effectively improved in the low-frequency band, and a resin composition with particularly excellent coatability can be produced.

[0189] The total amount (mass%) of (a) nanocrystalline magnetic raw powder, (b) small-diameter magnetic raw powder, and (c) intermediate magnetic raw powder is preferably 80% by mass or more, more preferably 85% by mass or more, and particularly preferably 90% by mass or more, relative to 100% by mass of the non-volatile components of the resin composition, and is preferably 99% by mass or less, more preferably 98% by mass or less, and particularly preferably 97% by mass or less. When the total amount (mass%) of (a) nanocrystalline magnetic raw powder, (b) small-diameter magnetic raw powder, and (c) intermediate magnetic raw powder is within the above range, it is possible to effectively improve both the relative permeability and magnetic loss in the low-frequency band, and further improve the coatability of the resin composition.

[0190] The total amount (mass%) of (a) nanocrystalline magnetic raw powder, (b) small-diameter magnetic raw powder, and (c) medium-sized magnetic raw powder is preferably 90% by mass or more, more preferably 94% by mass or more, and particularly preferably 98% by mass or more, based on 100% by mass of the total amount of all magnetic powders mixed to produce the resin composition. A large value indicates that there is little giant magnetic powder with an average particle size of more than 20 μm. When the total amount (mass%) of (a) nanocrystalline magnetic raw powder, (b) small-diameter magnetic raw powder, and (c) medium-sized magnetic raw powder falls within the above range, it is possible to effectively improve both the relative permeability and magnetic loss in the low-frequency band, and further improve the coatability of the resin composition.

[0191] <(D) Thermosetting Resin According to Second Embodiment> A manufacturing method according to a second embodiment of the present invention includes mixing a (D) thermosetting resin as component (D) with (a) nanocrystalline magnetic raw powder and (b) small-diameter magnetic raw powder. The (D) thermosetting resin according to the second embodiment can be the same as the (D) thermosetting resin according to the first embodiment. The amount of the (D) thermosetting resin used in the manufacturing method according to the second embodiment can be within the same range as described in the first embodiment. Therefore, in the manufacturing method according to the second embodiment, for example, the amount of the liquid epoxy resin, the amount of the epoxy resin, and the amount of the (D) thermosetting resin can be within the same range as described in the first embodiment, and the same effects as described in the first embodiment can be obtained.

[0192] <(E) Curing Accelerator According to Second Embodiment> In the production method according to the second embodiment of the present invention, a curing accelerator (E) may be further mixed as an optional component in combination with the above-described components. The curing accelerator (E) as the component (E) according to the second embodiment may be the same as the curing accelerator (E) according to the first embodiment. The amount of the curing accelerator (E) used in the production method according to the second embodiment may be in the same range as that described in the first embodiment. The curing accelerator (E) can provide the same effects as those described in the first embodiment.

[0193] <Dispersant (F) according to the second embodiment> In the production method according to the second embodiment of the present invention, a dispersant (F) may be further mixed as an optional component in combination with the above-described components. The dispersant (F) used as the component (F) according to the second embodiment may be the same as the dispersant (F) according to the first embodiment. The amount of the dispersant (F) used in the production method according to the second embodiment may be in the same range as that described in the first embodiment. The dispersant (F) can provide the same effects as those described in the first embodiment.

[0194] <(G) Optional Additive According to Second Embodiment> In the production method according to the second embodiment of the present invention, an optional additive (G) may be further mixed in addition to the above-mentioned components. The optional additive (G) according to the second embodiment may be the same as the optional additive (G) according to the first embodiment.

[0195] <Solvent (H) according to the second embodiment> The resin composition according to the second embodiment of the present invention may further contain an optional (H) solvent as a volatile component in addition to the non-volatile components such as the components (a) to (c) and components (D) to (G) described above. The (H) solvent according to the second embodiment may be the same as the (H) solvent according to the first embodiment. The amount of the (H) solvent used in the production method according to the second embodiment may be the same as that described in the first embodiment.

[0196] <Operation of the manufacturing method according to the second embodiment> The manufacturing method according to the second embodiment of the present invention includes mixing the above-mentioned (a) nanocrystalline magnetic raw powder, (b) small-diameter magnetic raw powder, and (D) thermosetting resin. If necessary, some or all of optional components such as (c) intermediate magnetic raw powder, (E) hardening accelerator, (F) dispersant, (G) optional additive, and (H) solvent may be mixed in combination with the (a) nanocrystalline magnetic raw powder, (b) small-diameter magnetic raw powder, and (D) thermosetting resin.

[0197] The above components may be mixed in part or in whole simultaneously or sequentially. The temperature may be appropriately set during the process of mixing the components. Therefore, heating and / or cooling may be performed temporarily or throughout the process. Furthermore, stirring or shaking may be performed during the process of mixing the components. Furthermore, degassing may be performed under low-pressure conditions, such as under vacuum.

[0198] <Resin composition produced by the production method according to the second embodiment> The resin composition produced by the manufacturing method according to the second embodiment of the present invention may contain the above-described components mixed together. Thus, the resin composition may contain (a) nanocrystalline magnetic raw powder, (b) small-diameter magnetic raw powder, and (D) thermosetting resin, and may further contain (c) intermediate magnetic raw powder, (E) curing accelerator, (F) dispersant, (G) optional additives, and (H) solvent, as needed. The resin composition may also contain the above-described components in their mixed amounts. Thus, the ranges of the amounts of (a) nanocrystalline magnetic raw powder, (b) small-diameter magnetic raw powder, (c) intermediate magnetic raw powder, (D) thermosetting resin, (E) curing accelerator, (F) dispersant, (G) optional additives, and (H) solvent contained in the resin composition may be as described above. The resin composition according to the first embodiment may also be produced by the manufacturing method according to the second embodiment of the present invention.

[0199] The resin composition produced by the production method according to the second embodiment of the present invention can be cured by heat. Therefore, a cured product of the resin composition can be obtained by thermally curing the resin composition. Among the components contained in the resin composition, volatile components such as (H) solvent can be volatilized by the heat during thermal curing, but non-volatile components such as components (a) to (c) and components (D) to (G) cannot be volatilized by the heat during thermal curing. Therefore, the cured product of the resin composition can contain the non-volatile components of the resin composition or their reaction products.

[0200] The resin composition produced by the production method according to the second embodiment of the present invention can provide a cured product with improved relative magnetic permeability and magnetic loss. Specifically, the cured product of this resin composition can have high relative magnetic permeability and low magnetic loss in the low-frequency band (e.g., 10 MHz). In one example, the range of relative magnetic permeability of the cured product of the resin composition produced by the production method according to the second embodiment of the present invention can be the same as the range of relative magnetic permeability of the cured product of the resin composition according to the first embodiment. In another example, the range of loss factor of the cured product of the resin composition produced by the production method according to the second embodiment of the present invention can be the same as the range of loss factor of the cured product of the resin composition according to the first embodiment. The relative magnetic permeability and loss factor can be measured by the same method as described in the first embodiment.

[0201] The resin composition produced by the production method according to the second embodiment of the present invention can have excellent coatability, similar to the resin composition according to the first embodiment.

[0202] There are no particular restrictions on the properties of the resin composition produced by the production method according to the second embodiment of the present invention, but it is preferably in the form of a paste having fluidity, similar to the resin composition according to the first embodiment.

[0203] The resin composition produced by the production method according to the second embodiment of the present invention can obtain the same advantages as the resin composition according to the first embodiment. Furthermore, the resin composition produced by the production method according to the second embodiment of the present invention can be used, for example, for the same applications as the resin composition according to the first embodiment.

[0204] <Resin sheet according to the third embodiment> A resin sheet according to a third embodiment of the present invention includes a support and a resin composition layer formed on the support. The resin composition layer contains a resin composition, preferably only a resin composition. The resin composition may be one of the resin composition according to the first embodiment and the resin composition produced by the production method according to the second embodiment, or a combination thereof.

[0205] 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 is not particularly limited, but may be, for example, 5 μm or more, 10 μm or more, etc.

[0206] Examples of the support include plastic film, metal foil, and release paper, with plastic film and metal foil being preferred.

[0207] When a film of a plastic material is used as the support, examples of the plastic material include polyesters such as polyethylene terephthalate (PET) and polyethylene naphthalate (PEN), acrylic polymers such as polycarbonate (PC) and 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.

[0208] When a metal foil is used as the support, examples of the metal foil include copper foil and aluminum foil, with copper foil being preferred. The copper foil may be a foil made of a single metal, copper, or an alloy of copper and another metal (e.g., tin, chromium, silver, magnesium, nickel, zirconium, silicon, titanium, etc.).

[0209] The surface of the support that is to be bonded to the resin composition layer may be subjected to a surface treatment such as matte treatment or corona treatment.

[0210] The support may also be a support with a release layer, which has a release layer on the surface that bonds to the resin composition layer. Examples of the release agent used in the release layer of the support with a release layer include one or more release agents selected from the group consisting of alkyd-based release agents, polyolefin-based release agents, urethane-based release agents, and silicone-based release agents. Commercially available products may also be used as the support with a release layer, including PET films having a release layer primarily composed of a silicone-based release agent or an alkyd resin-based release agent, such as "PET501010," "SK-1," "AL-5," and "AL-7" manufactured by Lintec Corporation; "Lumirror T60" manufactured by Toray Industries, Inc.; "Purex" manufactured by Teijin Limited; and "Uni-Peel" manufactured by Unitika Limited.

[0211] The thickness of the support is not particularly limited, but is preferably in the range of 5 μm to 75 μm, more preferably 10 μm to 60 μm. When a support with a release layer is used, it is preferable that the thickness of the entire support with a release layer is in the above range.

[0212] In the resin 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 to the support). The thickness of the protective film is not particularly limited, but is, for example, 1 μm to 40 μm. By laminating the protective film, it is possible to prevent dust from adhering to the surface of the resin composition layer and scratches.

[0213] The resin sheet can be produced, for example, by a production method including a step of applying a resin composition onto a support. The resin sheet production method may be a production method including a step of producing a resin composition by the production method described in the first embodiment or the second embodiment, and a step of applying the resin composition onto a support. The resin composition can be applied, for example, using a coating device such as a die coater. By applying the resin composition, a resin composition layer can be formed on the support, so that a resin sheet can be obtained.

[0214] If necessary, an organic solvent may be mixed with the resin composition and then applied onto the support. For example, the solvent (H) described in the first embodiment may be used as the organic solvent. When an organic solvent is used, drying may be performed after application, if necessary. Drying may be performed by heating, blowing hot air, or other methods. The drying conditions are not particularly limited, but drying is performed so that the content of the organic solvent in the resin composition layer is typically 10% by mass or less, preferably 5% by mass or less. Although this varies depending on the components contained in the resin composition, a resin composition layer can be formed, for example, by drying at 50°C to 150°C for 3 to 10 minutes.

[0215] The resin sheet can be stored in a rolled state. When the resin sheet has a protective film, it can usually be used by peeling off the protective film.

[0216] <Circuit board according to the fourth embodiment> A circuit board according to a fourth embodiment of the present invention includes a cured resin composition, which may be either the resin composition according to the first embodiment or the resin composition produced by the production method according to the second embodiment, or a combination thereof.

[0217] 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 formed therein 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 formed from the cured product of the resin composition. The circuit boards according to the first and second examples will be described below.

[0218] (First Example of Circuit Board) A circuit board according to a first example includes a substrate having holes formed therein and a cured product of a resin composition filled in the holes. (1) filling holes in a substrate with a resin composition; and (2) a step of thermally curing the resin composition to obtain a cured product; The method for manufacturing a circuit board according to the first example further includes the steps of: (3) a step of polishing the surface of the cured product or resin composition; (4) roughening the cured product; and (5) forming a conductive layer on the roughened surface of the cured product; The steps (1) to (5) are usually carried out in the order of step (1), step (2), step (3), step (4) and step (5), but step (2) may be carried out after step (3). In the method for producing a circuit board according to the first example, it is preferable to form a cured product using a paste-like resin composition. In the following explanation, an example will be given in which a board having through-holes formed therein as holes penetrating the board in the thickness direction is used.

[0219] -Process (1)- Step (1) typically includes preparing a substrate having through-holes formed therein. The substrate may be purchased from the market or may be manufactured using an appropriate material. An example method for manufacturing the substrate will now be described.

[0220] FIG. 1 is a cross-sectional view schematically illustrating a core substrate 10 prepared in a circuit board manufacturing method according to a first example of the fourth 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 be provided on the support substrate 11. The metal layer may be provided on one or both surfaces of the support substrate 11. In this example, a first metal layer 12 and a second metal layer 13 are provided on both surfaces of the support substrate 11. Examples of the first metal layer 12 and the second metal layer 13 include layers formed of a metal such as copper. The first metal layer 12 and the second metal layer 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.

[0221] FIG. 2 is a cross-sectional view schematically showing a core substrate 10 having through holes 14 formed therein in a method for manufacturing a circuit board according to a first example of the fourth embodiment of the present invention. The step of preparing a substrate may include a step of forming through holes 14 in the core substrate 10, as in the example shown in FIG. 2. The through holes 14 can be formed by, for example, drilling, laser irradiation, plasma irradiation, or the like. Typically, the through holes 14 can be formed by drilling through the core substrate 10. As a specific example, the through holes 14 can be formed using a commercially available drilling machine. An example of a commercially available drilling machine is the "ND-1S211" manufactured by Hitachi Via Mechanics, Ltd.

[0222] 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 example of the fourth embodiment of the present invention. The substrate preparation process may include a process of roughening the core substrate 10 as needed, followed by 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 the formation of 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 first metal layer 12 and the surface of the second metal layer 13 will be described.

[0223] FIG. 4 is a cross-sectional view schematically illustrating the state in which the through-holes 14 of the core substrate 10 are filled with the resin composition 30a in the method for manufacturing a circuit board according to a first example of the fourth embodiment of the present invention. Step (1) involves preparing the core substrate 10 having the through-holes 14 formed therein as described above, and then filling the through-holes 14 of the core substrate 10 with the resin composition 30a, as shown in FIG. 4 . The filling can be performed, for example, by a printing method. Examples of printing methods include printing the resin composition 30a into the through-holes 14 using a squeegee, printing the resin composition 30a using a cartridge, printing the resin composition 30a by mask printing, roll coating, and inkjet printing. Typically, excess resin composition 30a protrudes or adheres to the outside of the through-holes 14. Therefore, the resin composition 30a can be provided not only within the through-holes 14 but also outside the through-holes 14.

[0224] -Process (2)- 5 is a schematic cross-sectional view illustrating step (2) of the method for manufacturing a circuit board according to a first example of the fourth embodiment of the present invention. Step (2) includes filling through-holes 14 with resin composition 30a and then curing resin composition 30a to form a cured product 30 as shown in FIG.

[0225] 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.

[0226] 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.

[0227] The method for manufacturing a circuit board according to the first example may include a step of heating resin composition 30a at a temperature lower than the curing temperature (preheating step) after filling through-holes 14 with resin composition 30a and before curing resin composition 30a. For example, prior to curing resin composition 30a, 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 to 150 minutes, more preferably 15 to 120 minutes).

[0228] -Process (3)- 6 is a schematic cross-sectional view illustrating step (3) of the method for manufacturing a circuit board according to a first example of the fourth embodiment of the present invention. Step (3) includes polishing excess cured material 30 protruding from or adhering to core substrate 10, as shown in FIG. 6. By polishing, excess cured material 30 is removed, thereby flattening the surface of cured material 30. Surface 31 (polished surface) of cured material 30 flattened by polishing can usually form a flat surface that is flush with surfaces 21 surrounding polished surface 31 (e.g., the surface of core substrate 10, the surface of plating layer 20).

[0229] The polishing method may be any method capable of removing excess cured material 30 protruding from or adhering to core substrate 10. Examples of such polishing methods include buffing, belt polishing, and ceramic polishing. An example of a commercially available buffing machine is "NT-700IM" manufactured by Ishii Hyoki Co., Ltd.

[0230] The arithmetic mean roughness (Ra) of the polished surface 31 of the cured product 30 (after the cured product layer is thermally cured) is preferably 300 nm or more, more preferably 350 nm or more, and even more preferably 400 nm or more, from the viewpoint of improving adhesion with the conductor layer. The upper limit is preferably 1000 nm or less, more preferably 900 nm or less, and even more preferably 800 nm or less. The surface roughness (Ra) can be measured, for example, using a non-contact surface roughness meter.

[0231] When step (3) is performed after step (2), the method for producing a circuit board may include a step of heat treating the cured product 30 after step (2) and before 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 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 preferably 90 minutes or shorter, more preferably 70 minutes or shorter, and even more preferably 60 minutes or shorter.

[0232] Furthermore, when step (3) is performed before step (2), the method for producing a circuit board may include a step of subjecting the resin composition layer to a preheating treatment before step (3), in which the resin composition layer is heated at a temperature lower than the curing temperature of the resin composition. 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.

[0233] -Process (4)- Step (4) includes subjecting the surface of 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 has been polished, step (4) typically includes subjecting the polished surface 31 to a roughening treatment (desmear treatment). The procedure and conditions for the roughening step 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. For example, the roughening step may roughen the surface of the cured product 30 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.

[0234] Examples of swelling liquids that can be used in the roughening step include alkaline solutions and surfactant solutions, with alkaline solutions being preferred. Sodium hydroxide solution and potassium hydroxide solution are more preferred as alkaline solutions used as swelling liquids. Examples of commercially available swelling liquids include "Swelling Dip Securigance P" and "Swelling Dip Securigance SBU" manufactured by Atotech Japan. Swelling treatment using a swelling liquid can be performed, for example, by immersing the cured material 30 in the swelling liquid at 30°C to 90°C for 1 to 20 minutes. To keep swelling of the resin constituting the cured material 30 to an appropriate level, it is preferable to immerse the cured material 30 in the swelling liquid at 40°C to 80°C for 5 to 15 minutes.

[0235] 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 Securigance P" manufactured by Atotech Japan.

[0236] The neutralizing solution used in the neutralization treatment is preferably an acidic aqueous solution. An example of a commercially available neutralizing solution is "Reduction Solution Securigance P" manufactured by Atotech Japan. Neutralization treatment with a neutralizing solution can be performed by immersing the surface roughened with an oxidizing solution in the neutralizing solution at 30°C to 80°C for 5 to 30 minutes. From the standpoint of workability, a preferred method is to immerse the cured product 30 roughened with an oxidizing solution in the neutralizing solution at 40°C to 70°C for 5 to 20 minutes.

[0237] The arithmetic mean roughness (Ra) of the surface of the cured product 30 after roughening treatment is preferably 300 nm or more, more preferably 350 nm or more, and even more preferably 400 nm or more, from the viewpoint of improving adhesion with the conductor layer. The upper limit is preferably 1500 nm or less, more preferably 1200 nm or less, and even more preferably 1000 nm or less. The surface roughness (Ra) can be measured, for example, using a non-contact surface roughness meter.

[0238] -Process (5)- Fig. 7 is a schematic cross-sectional view illustrating step (5) of the method for manufacturing a circuit board according to a first example of the fourth embodiment of the present invention. Step (5) includes forming a conductor layer 40 on the polished surface 31 of the cured product 30, as shown in Fig. 7. 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, Fig. 7 shows an example in which the conductor layer 40 is formed on both sides of the core substrate 10, but the conductor layer 40 may be formed on only one side of the core substrate 10.

[0239] 8 is a schematic cross-sectional view illustrating step (5) of the method for manufacturing a circuit board according to a first example of the fourth 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 first metal layer 12, the second metal layer 13, and the plating layer 20 by etching or other processing to form a patterned conductor layer 41.

[0240] 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 simple metals such as gold, platinum, palladium, silver, copper, aluminum, cobalt, chromium, zinc, nickel, titanium, tungsten, iron, tin, and indium; and alloys of two or more metals selected from the group consisting of gold, platinum, palladium, silver, copper, aluminum, cobalt, chromium, zinc, nickel, titanium, tungsten, iron, tin, and indium. Among these, from the viewpoints of versatility, cost, ease of patterning, and the like, it is preferable to use chromium, nickel, titanium, aluminum, zinc, gold, palladium, silver, or copper, or a nickel-chromium alloy, a copper-nickel alloy, or a copper-titanium alloy, it is more preferable to use chromium, nickel, titanium, aluminum, zinc, gold, palladium, silver, or copper, or a nickel-chromium alloy, and it is even more preferable to use copper.

[0241] 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°C to 200°C for 20 to 90 minutes.

[0242] 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 still more preferably 5 μm or more.

[0243] By the above method, a circuit board 1 including a cured product 30 of the resin composition 30a can be produced.

[0244] (Second Example Circuit Board) The circuit board according to the second example includes a cured layer containing a cured resin composition. The cured layer preferably includes only a cured product of the resin composition. The cured layer is preferably formed using a resin sheet. This circuit board may be, for example, (i) forming a cured material layer on an inner layer substrate; (ii) drilling holes in the cured layer; (iii) roughening the surface of the cured layer; and (iv) forming a conductive layer on the surface of the cured material layer; It can be produced by a production method including the steps of:

[0245] -Process (i)- Step (i) includes forming a cured material layer on the inner layer substrate. Preferably, step (i) includes laminating a resin sheet on the inner layer substrate so that the resin composition layer is bonded to the inner layer substrate to form a cured material layer. For example, the resin sheet is laminated on the inner layer substrate so that the resin composition layer is bonded to the inner layer substrate, and the resin composition layer is thermally cured to form a cured material layer.

[0246] 9 is a schematic cross-sectional view illustrating step (i) in a method for manufacturing a circuit board according to a second example of the fourth embodiment of the present invention. As shown in FIG. 9, a resin sheet 310 is prepared, which includes a support 330 and a resin composition layer 320a provided on the support 330. Then, the resin sheet 310 and the inner substrate 200 are laminated together so that the resin composition layer 320a is bonded to the inner substrate 200.

[0247] 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 built into its thickness.

[0248] 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 of the inductor element (see FIG. 12) 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.

[0249] Conductive materials that can form the first conductor layer 420 and the external terminals 240 include, for example, the same materials as those for the conductor layers described in the first example.

[0250] 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.

[0251] 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 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.

[0252] The inner substrate 200 may have a plurality of through holes 220 that penetrate the inner substrate 200 from the first main surface 200a to the second main surface 200b. The through holes 220 are provided with internal through-hole wiring 220a. The internal through-hole wiring 220a electrically connects the first conductor layer 420 and the external terminal 240.

[0253] The resin composition layer 320a and the inner substrate 200 can be bonded, for example, by thermocompression bonding the resin sheet 310 to the inner substrate 200 from the support 330 side. Examples of a member for thermocompression bonding the resin 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 (such as a SUS roll). Note that rather than pressing the resin sheet 310 by directly contacting it with the thermocompression bonding member, it is preferable to press the resin sheet 310 via a sheet made of an elastic material such as heat-resistant rubber so that the resin sheet 310 can sufficiently conform to the irregularities on the surface of the inner substrate 200.

[0254] 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 0.098MPa to 1.77MPa, and more preferably 0.29MPa to 1.47MPa. The time for thermocompression bonding is preferably in the range of 20 seconds to 400 seconds, and more preferably 30 seconds to 300 seconds. The resin sheet and the inner layer substrate are preferably bonded under reduced pressure conditions of 26.7hPa or less.

[0255] The resin composition layer 320a of the resin 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.

[0256] After bonding the resin sheet 310 and the inner layer substrate 200, the laminated resin 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.

[0257] 10 is a schematic cross-sectional view illustrating step (i) in a method for manufacturing a circuit board according to a second example of the fourth embodiment of the present invention. After laminating the resin sheet 310 on the inner substrate 200, the resin composition layer 320a is thermally 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.

[0258] The thermal curing conditions for the resin composition layer 320a can be appropriately set within the 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.

[0259] 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).

[0260] The arithmetic mean roughness (Ra) of the cured layer before roughening treatment is preferably 300 nm or more, more preferably 350 nm or more, and even more preferably 400 nm or more, from the viewpoint of improving adhesion with the plating. The upper limit is preferably 1000 nm or less, more preferably 900 nm or less, and even more preferably 800 nm or less. The surface roughness (Ra) can be measured, for example, using a non-contact surface roughness meter.

[0261] Step (i) may include applying a resin composition, instead of a resin sheet, onto the inner layer substrate 200 using a coating device such as a die coater, and then thermally curing the composition to form a cured layer.

[0262] -Process (ii)- Fig. 11 is a schematic cross-sectional view illustrating step (ii) in the method for manufacturing a circuit board according to a second example of the fourth embodiment of the present invention. As shown in Fig. 11, step (ii) includes drilling the first cured material layer 320 to form via holes 360. The via holes 360 can serve as paths for electrically connecting the first conductor layer 420 and the second conductor layer 440 described below. The via holes 360 may be formed using, for example, a drill, a laser, plasma, or the like. The dimensions and shape of the holes may be determined appropriately depending on the design of the printed wiring board.

[0263] -Process (iii)- In step (iii), the surface of the cured material layer in which the via holes have been formed is roughened by the same method as that described in step (4) of the first example.

[0264] The arithmetic mean roughness (Ra) of the cured layer after roughening treatment is preferably 300 nm or more, more preferably 350 nm or more, and even more preferably 400 nm or more, from the viewpoint of improving adhesion with the plating. The upper limit is preferably 1500 nm or less, more preferably 1200 nm or less, and even more preferably 1000 nm or less. The surface roughness (Ra) can be measured, for example, using a non-contact surface roughness meter.

[0265] -Process (iv)- 12 is a schematic cross-sectional view illustrating step (iv) in the method for producing a circuit board according to the second example of the fourth 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.

[0266] Conductive materials that can be used to form the second conductor layer 440 include the same materials as those used to form the conductor layer described in the first example.

[0267] 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 still more preferably 5 μm or more.

[0268] 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 easily 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.

[0269] The first conductor layer 420 and the second conductor layer 440 may be provided in a spiral shape, for example, as shown in FIGS. 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 the 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 the external terminal 240 via the via-hole wiring 360a, the land 420a, and the through-hole wiring 220a.

[0270] 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.

[0271] After step (iv), a step of forming a cured material layer on the conductor layer may be performed. Specifically, as shown in FIG. 14, a second cured material layer 340 is formed on the first cured material layer 320 on which the second conductor layer 440 and the via-hole wiring 360a have been formed. The second cured material layer 340 may be formed by the same steps as those already described. By the above method, a circuit board 100 including the first cured material layer 320 and the second cured material layer 340 formed from the cured product of the resin composition can be manufactured.

[0272] <Inductor Substrate According to Fifth Embodiment> An inductor substrate according to a fifth embodiment of the present invention includes the circuit board according to the fourth embodiment described above. When such an inductor substrate includes the circuit board 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 resin composition. In this case, the inductor substrate may include, for example, an inductor element composed of an inductor pattern formed of at least a portion of the first metal layer 12, the second metal layer 13, the plating layer 20, and the patterned conductor layer 41, and a core formed of the cured material 30 surrounded by this inductor pattern. For example, an inductor substrate such as that described in JP 2016-197624 A can be used.

[0273] When including the circuit board 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.

[0274] 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.

[0275] 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.

[0276] 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 which is a portion of the magnetic part 300 that extends in the thickness direction of the magnetic part 300 and is surrounded by the coiled conductive structure 400.

[0277] 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 that bends 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 toward the outside.

[0278] Similarly, a second conductor layer 440 is provided on the first cured material layer 320. The second conductor layer 440 includes a spiral wiring portion for configuring the coil-shaped conductive structure 400. In Fig. 13 or 14, the spiral wiring portion includes a straight portion and a bent portion bent at a right angle. In Fig. 13 or 14, the spiral wiring portion of the second conductor layer 440 has an overall outline that is approximately rectangular and has a shape that is wound clockwise from the center toward the outside.

[0279] The inductor substrate described above can be used as a wiring board for mounting electronic components such as semiconductor chips, and can also be used 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, and can also be used as a printed wiring board with the chip inductor component surface-mounted.

[0280] Furthermore, various types of semiconductor devices can be manufactured using such a wiring board. Semiconductor devices including such wiring boards can be suitably used in electrical appliances (e.g., computers, mobile phones, digital cameras, televisions, etc.) and vehicles (e.g., motorcycles, automobiles, trains, ships, aircraft, etc.). [Example]

[0281] 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. Unless otherwise specified, the temperature condition is room temperature (23°C). Unless otherwise specified, the pressure condition is normal pressure (1 atm).

[0282] <(a) Nanocrystalline magnetic powder with an average particle size of 5.5 μm or more and 20 μm or less> Epson Atmix "KUAMET NC1-38um", nanocrystalline magnetic powder made of Fe-Si-Nb-B alloy, 10% particle size (D 10 )5.8μm, average particle size (D 50 )15.1μm, 90% particle size (D 90 ) 34.7 μm, the volume fraction of particles in this magnetic powder having a particle size of 2 μm or less is 0.0 vol%, the volume fraction of particles in this magnetic powder having a particle size of more than 2 μm but less than 5.5 μm is 8.6 vol%, the volume fraction of particles in this magnetic powder having a particle size of 5.5 μm or more but less than 20 μm is 56.4 vol%, and the volume fraction of particles in this magnetic powder having a particle size of more than 20 μm is 35.0 vol%. Epson Atmix "ATFINE-NC1 PF10FA", nanocrystalline magnetic powder made of Fe-Si-Nb-B alloy, 10% particle size (D 10 )3.0μm, average particle size (D 50 )6.0μm, 90% particle size (D 90) 10.7 μm, the volume fraction of particles in this magnetic powder having a particle size of 2 μm or less is 2.5 vol%, the volume fraction of particles in this magnetic powder having a particle size of more than 2 μm but less than 5.5 μm is 40.2 vol%, the volume fraction of particles in this magnetic powder having a particle size of 5.5 μm or more but less than 20 μm is 57.3 vol%, and the volume fraction of particles in this magnetic powder having a particle size of more than 20 μm is 0.0 vol%.

[0283] <(a') Nanocrystalline magnetic powder with an average particle size exceeding 20 μm> Epson Atmix "KUAMET NC1-53um", nanocrystalline Fe-Si-Nb-B alloy, 10% grain size (D 10 )9.8μm, average particle size (D 50 )27.3μm, 90% particle size (D 90 ) 59.7 μm, the volume fraction of particles in this magnetic powder having a particle size of 2 μm or less is 0.0 vol%, the volume fraction of particles in this magnetic powder having a particle size of more than 2 μm but less than 5.5 μm is 2.5 vol%, the volume fraction of particles in this magnetic powder having a particle size of 5.5 μm or more but less than 20 μm is 35.4 vol%, and the volume fraction of particles in this magnetic powder having a particle size of more than 20 μm is 62.1 vol%.

[0284] <(b) Magnetic powder with an average particle size of 2 μm or less> Powder Tech "M001", Fe-Mn ferrite powder (crystalline magnetic powder other than nanocrystalline magnetic powder), 10% particle size (D 10 )0.05μm, average particle size (D 50 )0.12μm, 90% particle size (D 90 ) 1.1 μm, the volume fraction of particles in this magnetic powder with a particle size of 2 μm or less is 97.0 vol%, the volume fraction of particles in this magnetic powder with a particle size of more than 2 μm but less than 5.5 μm is 3.0 vol%, the volume fraction of particles in this magnetic powder with a particle size of 5.5 μm or more but less than 20 μm is 0.0 vol%, and the volume fraction of particles in this magnetic powder with a particle size greater than 20 μm is 0.0 vol%. JFE Mineral Co., Ltd.'s "CVD iron powder (0.7 μm)", Fe-Si-Cr alloy powder (crystalline magnetic powder other than nanocrystalline magnetic powder), 10% particle size (D 10 )0.46μm, average particle size (D 50 )0.75μm, 90% particle size (D 90) 1.12 μm, the volume fraction of particles in this magnetic powder with a particle size of 2 μm or less is 100.0 vol%, the volume fraction of particles in this magnetic powder with a particle size of more than 2 μm but less than 5.5 μm is 0.0 vol%, the volume fraction of particles in this magnetic powder with a particle size of 5.5 μm or more but less than 20 μm is 0.0 vol%, and the volume fraction of particles in this magnetic powder with a particle size of more than 20 μm is 0.0 vol%.

[0285] <(c) Magnetic powder having an average particle size of more than 2 μm and not more than 20 μm and smaller than that of component (a)> Epson Atmix "ATFINE-NC1 PF5FA", Fe-Si-Nb-B alloy powder (nanocrystalline magnetic powder with an average particle size of less than 5.5 μm), 10% particle size (D 10 )2.3μm, average particle size (D 50 )4.3μm, 90% particle size (D 90 ) 7.1 μm, the volume fraction of particles in this magnetic powder having a particle size of 2 μm or less is 6.9 vol%, the volume fraction of particles in this magnetic powder having a particle size of more than 2 μm but less than 5.5 μm is 77.1 vol%, the volume fraction of particles in this magnetic powder having a particle size of 5.5 μm or more but less than 20 μm is 16.0 vol%, and the volume fraction of particles in this magnetic powder having a particle size of more than 20 μm is 0.0 vol%. Epson Atmix "ATFINE-NC1 PF3FA", Fe-Si-Nb-B alloy powder (nanocrystalline magnetic powder with an average particle size of less than 5.5 μm), 10% particle size (D 10 )2.0μm, average particle size (D 50 )3.5μm, 90% particle size (D 90 ) 5.8 μm, the volume fraction of particles in this magnetic powder having a particle size of 2 μm or less is 10.4 vol%, the volume fraction of particles in this magnetic powder having a particle size of more than 2 μm but less than 5.5 μm is 73.6 vol%, the volume fraction of particles in this magnetic powder having a particle size of 5.5 μm or more but less than 20 μm is 16.0 vol%, and the volume fraction of particles in this magnetic powder having a particle size of more than 20 μm is 0.0 vol%. Epson Atmix "AW2-08PF3F", Fe-Si-Cr alloy powder (amorphous powder), 10% particle size (D 10 )1.7μm, average particle size (D 50 )3.1μm, 90% particle size (D 90) 5.2 μm, the volume fraction of particles in this magnetic powder having a particle size of 2 μm or less is 13.9 vol%, the volume fraction of particles in this magnetic powder having a particle size of more than 2 μm but less than 5.5 μm is 72.1 vol%, the volume fraction of particles in this magnetic powder having a particle size of 5.5 μm or more but less than 20 μm is 14.0 vol%, and the volume fraction of particles in this magnetic powder having a particle size of more than 20 μm is 0.0 vol%.

[0286] Example 1 (a) Nanocrystalline magnetic powder with an average particle size of 5.5 μm or more and 20 μm or less (Epson Atmix "KUAMET NC1-38um", average particle size (D 50 (b) 103.5 parts by mass of magnetic powder having an average particle size of 2 μm or less ("M001" manufactured by Powder Tech Co., Ltd., average particle size (D 50 ) 0.12 μm) in 24.6 parts by mass, (c) magnetic powder (Epson Atmix "AW2-08PF3F" having an average particle size of more than 2 μm and not more than 20 μm and smaller than the average particle size of component (a), 50 A resin composition was prepared by mixing 11.8 parts by mass of (A) epoxy resin (Nippon Steel Chemical & Material Co., Ltd., "ZX-1059," a mixture of bisphenol A epoxy resin and bisphenol F epoxy resin), 0.9 parts by mass of (D) epoxy resin (Mitsubishi Chemical Corporation, "630," a glycidyl ether aromatic epoxy resin), 0.2 parts by mass of (E) curing accelerator (Shikoku Chemical Industries, Ltd., "2MZA-PW," an imidazole curing accelerator), 0.5 parts by mass of (F) dispersant (NOF Corporation, "SC-1015F," a polyoxyalkylene dispersant), and 3.8 parts by mass of (H) solvent (Tokyo Chemical Industry Co., Ltd., "butyl carbitol acetate," a solvent), and uniformly dispersing the mixture using a high-speed rotary mixer.

[0287] <Example 2> The amount of (a) nanocrystalline magnetic powder ("KUAMET NC1-38um" manufactured by Epson Atmix) having an average particle size of 5.5 μm or more and 20 μm or less was changed from 103.5 parts by mass to 120.8 parts by mass. The amount of (b) magnetic powder ("M001" manufactured by Powder Tech Co., Ltd.) having an average particle size of 2 μm or less was changed from 24.6 parts by mass to 21.3 parts by mass. Furthermore, 11.8 parts by mass of (c) magnetic powder ("AW2-08PF3F" manufactured by Epson Atmix) having an average particle size of more than 2 μm and 20 μm or less, and smaller than the average particle size of component (a), was not used. Aside from the above, the resin composition was prepared in the same manner as in Example 1.

[0288] Example 3 (a) The amount of nanocrystalline magnetic powder (KUAMET NC1-38um manufactured by Epson Atmix) with an average particle size of 5.5 μm to 20 μm was changed from 103.5 parts by mass to 120.8 parts by mass. (b) The amount of magnetic powder with an average particle size of 2 μm or less was changed from 24.6 parts by mass of Powdertech's M001 to 24.6 parts by mass of JFE Mineral's CVD iron powder (0.7 μm) (average particle size (D 50 ) 0.75 μm) was changed to 14.4 parts by mass. Furthermore, the amount of (c) magnetic powder ("AW2-08PF3F" manufactured by Epson Atmix Corporation) used, having an average particle size of more than 2 μm and not more than 20 μm and smaller than the average particle size of component (a), was changed from 11.8 parts by mass to 14.4 parts by mass. Aside from the above, a resin composition was prepared in the same manner as in Example 1.

[0289] Example 4 (a) Nanocrystalline magnetic powder with an average particle size of 5.5 μm or more and 20 μm or less (Epson Atmix "ATFINE-NC1 PF10FA", average particle size (D 50A resin composition was prepared by mixing 56.0 parts by mass of (b) a magnetic powder having an average particle size of 2 μm or less ("CVD iron powder (0.7 μm)" manufactured by JFE Mineral Co., Ltd.), 18.2 parts by mass of (D) an epoxy resin ("ZX-1059" manufactured by Nippon Steel Chemical & Material Co., Ltd.), 0.8 parts by mass of (D) an epoxy resin ("630" manufactured by Mitsubishi Chemical Corporation, glycidyl ether type aromatic epoxy resin), 0.2 parts by mass of (E) a curing accelerator ("2MZA-PW" manufactured by Shikoku Chemical Industries, Ltd., imidazole curing accelerator), 0.4 parts by mass of (F) a dispersant ("SC-1015F" manufactured by NOF Corporation, polyoxyalkylene dispersant), and 3.1 parts by mass of (H) a solvent ("Butyl Carbitol Acetate" manufactured by Tokyo Chemical Industry Co., Ltd., solvent), and uniformly dispersing the mixture using a high-speed rotary mixer.

[0290] <Example 5> (a) 53.1 parts by mass of nanocrystalline magnetic powder (KUAMET NC1-38um manufactured by Epson Atmix) having an average particle size of 5.5 μm or more and 20 μm or less, (b) 6.3 parts by mass of magnetic powder (CVD iron powder (0.7 μm) manufactured by JFE Mineral Co., Ltd.) having an average particle size of 2 μm or less, (c) 6.3 parts by mass of magnetic powder (ATFINE-NC1 PF5FA manufactured by Epson Atmix) having an average particle size of more than 2 μm and 20 μm or less and smaller than the average particle size of the component (a), 50 A resin composition was prepared by mixing 6.7 parts by mass of (A) nanocrystalline magnetic powder (having a particle size of 4.3 μm and an average particle size of less than 5.5 μm), 0.8 parts by mass of (D) epoxy resin (ZX-1059 manufactured by Nippon Steel Chemical & Material Co., Ltd.), 0.8 parts by mass of (D) epoxy resin (630 manufactured by Mitsubishi Chemical Corporation, a glycidyl ether-type aromatic epoxy resin), 0.1 parts by mass of (E) curing accelerator (2MZA-PW manufactured by Shikoku Chemical Industries, Ltd., an imidazole-based curing accelerator), 0.4 parts by mass of (F) dispersant (SC-1015F manufactured by NOF Corporation, a polyoxyalkylene-based dispersant), and 2.0 parts by mass of (H) solvent (butyl carbitol acetate manufactured by Tokyo Chemical Industry Co., Ltd., a solvent), and uniformly dispersing the mixture using a high-speed rotary mixer.

[0291] Example 6 (a) 49.1 parts by mass of nanocrystalline magnetic powder ("KUAMET NC1-38um" manufactured by Epson Atmix Corporation) having an average particle size of 5.5 μm or more and 20 μm or less, (b) 10.1 parts by mass of magnetic powder ("CVD iron powder (0.7 μm)" manufactured by JFE Mineral Co., Ltd.) having an average particle size of 2 μm or less, (c) 6.3 parts by mass of spherical magnetic powder ("AW2-08PF3F" manufactured by Epson Atmix Corporation) having an average particle size of more than 2 μm and 20 μm or less and smaller than the average particle size of component (a), (D) 0.8 parts by mass of epoxy resin ("ZX-1059" manufactured by Nippon Steel Chemical & Material Co., Ltd.), (E) 0.8 parts by mass of epoxy resin ( A resin composition was prepared by mixing 0.8 parts by mass of (E) a curing accelerator ("630" manufactured by Mitsubishi Chemical Corporation, a glycidyl ether-type aromatic epoxy resin), 0.1 parts by mass of (E) a curing accelerator ("2MZA-PW" manufactured by Shikoku Chemical Industries, Ltd., an imidazole-based curing accelerator), 0.4 parts by mass of (F) a dispersant ("SC-1015F" manufactured by NOF Corporation, a polyoxyalkylene-based dispersant), and 1.8 parts by mass of (H) a solvent ("Butyl Carbitol Acetate" manufactured by Tokyo Chemical Industry Co., Ltd., a solvent), and uniformly dispersing the mixture using a high-speed rotary mixer.

[0292] <Comparative Example 1> (b) A resin composition was prepared in the same manner as in Example 1, except that 24.6 parts by mass of magnetic powder ("M001" manufactured by Powder Tech Co., Ltd.) having an average particle size of 2 μm or less was not used.

[0293] <Comparative Example 2> (a') Nanocrystalline magnetic powder with an average particle size exceeding 20 μm (Epson Atmix "KUAMET NC1-53 μm", average particle size (D 50) 27.3 μm) 105.1 parts by mass, (b) 13.1 parts by mass of magnetic powder ("M001" manufactured by Powder Tech Co., Ltd.) having an average particle size greater than 2 μm and less than 20 μm and smaller than that of component (A), (c) 13.1 parts by mass of spherical magnetic powder ("AW2-08PF3F" manufactured by Epson Atmix Corporation) having an average particle size greater than 2 μm and less than that of component (a), (D) 1.0 part by mass of epoxy resin ("ZX-1059" manufactured by Nippon Steel Chemical & Material Co., Ltd.), (D) epoxy A resin composition was prepared by mixing 1.0 part by mass of resin ("630" manufactured by Mitsubishi Chemical Corporation, a glycidyl ether-type aromatic epoxy resin), 0.2 part by mass of (E) curing accelerator ("2MZA-PW" manufactured by Shikoku Chemical Industries, Ltd., an imidazole-based curing accelerator), 0.5 part by mass of (F) dispersant ("SC-1015F" manufactured by NOF Corporation, a polyoxyalkylene-based dispersant), and 4.0 parts by mass of (H) solvent ("Butyl Carbitol Acetate" manufactured by Tokyo Chemical Industry Co., Ltd., a solvent), and uniformly dispersing the mixture using a high-speed rotary mixer.

[0294] <Comparative Example 3> (a) 103.5 parts by mass of nanocrystalline magnetic powder ("KUAMET NC1-38um" manufactured by Epson Atmix) having an average particle size of 5.5 μm or more and 20 μm or less was not used, and (c) 103.5 parts by mass of magnetic powder ("ATFINE-NC1 PF3FA" manufactured by Epson Atmix) having an average particle size of more than 2 μm and 20 μm or less and smaller than the average particle size of the component (a) was not used. 50 A resin composition was prepared in the same manner as in Example 1, except that 103.5 parts by mass of ) nanocrystalline magnetic powder having an average particle size of less than 3.5 μm and 5.5 μm was used.

[0295] <Comparative Example 4> A resin composition was prepared in the same manner as in Comparative Example 1, except that the amount of (c) magnetic powder ("AW2-08PF3F" manufactured by Epson Atmix) having an average particle size greater than 2 μm and equal to or less than 20 μm and smaller than the average particle size of component (a) was changed from 11.8 parts by mass to 23.0 parts by mass.

[0296] The volume fraction of particles having a particle size of <5.5 μm or more and 20 μm or less, the volume fraction of magnetic powder having a particle size of 2 μm or less, the volume fraction of particles having a particle size of more than 2 μm but less than 5.5 μm, the volume fraction of particles having a particle size of more than 20 μm, the 10% particle size (D 10 ), average particle size (D 50 ), and 90% particle size (D 90 ) calculation> The magnetic powder was dispersed in pure water using ultrasonic waves and used as a measurement sample. The particle size distribution of the magnetic powder was measured on a volume basis using a laser diffraction scattering particle size distribution analyzer ("LA-960" manufactured by Horiba, Ltd.). From this particle size distribution, the volume fraction of magnetic powder having a particle size of 5.5 μm or more and 20 μm or less, the volume fraction of magnetic powder having a particle size of 2 μm or less, the volume fraction of particles having a particle size of 2 μm or more and less than 5.5 μm, the volume fraction of particles having a particle size of more than 20 μm, and the 10% particle size (D 10 ), 50% particle size (average particle size) (D 50 ), and 90% particle size (D 90 ) was calculated.

[0297] <Test Example 1: Evaluation of the coatability of the resin composition> The resin compositions prepared in the examples and comparative examples were evaluated for coatability. A polyethylene terephthalate (PET) film ("PET501010" manufactured by Lintec Corporation, thickness 50 μm) treated with a silicone-based release agent was prepared as a support. Each resin composition was uniformly applied to the release surface of the PET film using a doctor blade so that the thickness of the resin composition layer after drying was 100 μm, thereby obtaining a resin sheet. The fluidity of the resin composition was confirmed, and the presence or absence of coatability was evaluated according to the following evaluation criteria.

[0298] (Evaluation criteria for coating properties) "Good": The resin composition is in a paste form with fluidity and is easy to apply. "X": The resin composition had no fluidity and could not be applied.

[0299] <Test Example 2: Measurement and Evaluation of Relative Permeability> In the examples and comparative examples other than Comparative Example 1, the relative magnetic permeability (μ′) was measured by the following method. The resin sheet obtained in Test Example 1 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 cured product was cut into test pieces 5 mm wide and 18 mm long to obtain evaluation samples. The relative permeability (μ') of this evaluation sample was measured using a measuring device (Agilent Technologies, "HP8362B") using a 3-turn coil method at a measurement frequency of 10 MHz at room temperature of 23°C. The relative permeability was evaluated according to the following evaluation criteria.

[0300] The resin composition obtained in Comparative Example 1 had poor coatability, so a resin sheet could not be produced by the same method as in the other Examples and Comparative Examples. Therefore, in Comparative Example 1, the relative magnetic permeability (μ') was measured by the following method. A solvent (butyl carbitol acetate, manufactured by Tokyo Chemical Industry Co., Ltd.) was added in an amount of 3% by weight to the resin composition prepared in Comparative Example 1, and the mixture was uniformly dispersed using a high-speed rotating mixer to obtain a varnish. 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. The varnish was uniformly applied to the release surface of the PET film using a doctor blade so that the thickness of the resin composition layer after drying was 100 μm, obtaining a resin sheet. Using this resin sheet, a sheet-shaped cured product was produced using the same method as in the Examples and Comparative Examples other than Comparative Example 1, and the relative magnetic permeability (μ') was measured. The relative magnetic permeability was evaluated according to the following evaluation criteria.

[0301] (Evaluation criteria for relative permeability) "Good": Relative permeability is 25 or more. "×": Relative permeability is less than 25.

[0302] <Test Example 3: Measurement and Evaluation of Loss Factor (tan δ)> The sheet-like cured product obtained in Test Example 2 was cut into test pieces measuring 5 mm in width and 18 mm in length to obtain evaluation samples. The evaluation samples were measured for magnetic loss (μ'') at room temperature of 23°C using a measuring device (Agilent Technologies, "HP8362B") using a 3-turn coil method at a measurement frequency of 10 MHz. The loss factor tanδ was calculated using the formula "tanδ=μ'' / μ'". The loss factor (tanδ) was evaluated according to the following evaluation criteria.

[0303] (Evaluation criteria for loss factor (tanδ)) "Good": Loss coefficient (tanδ) is 0.1 or less. "X": Loss factor (tan δ) exceeds 0.1.

[0304] <Result> The components and their contents of the resin compositions of the examples and comparative examples, as well as the measurement and evaluation results of the test examples, are shown in the following table. In the table, the total contents (mass % and volume %) of components (a) to (c), components (A) to (C), and magnetic powder are values ​​when the nonvolatile components in the resin composition are taken as 100%.

[0305] [Table 1]

[0306] [Table 2] [Explanation of symbols]

[0307] 1 circuit board 10 Core Board 11 Support substrate 12 1st metal layer 13 Second metal layer 14 through holes 20 plating layer 21 Surface surrounding the polished surface 30 Cured product 30a Resin composition 31 Polished surface of hardened material (polished surface) 40 Conductor Layer 41 Patterned conductor layer 100 Circuit Boards 200 inner layer board 200a 1st main surface 200b 2nd main surface 220 through hole 220a Through-hole wiring 240 External terminal 310 Resin Sheet 320 1st cured material layer 320a Resin composition layer 330 Support 360 Beer Hall 360a via hole wiring 400 Coil-shaped conductive structure 420 First conductor layer 420a Land 440 Second conductor layer

Claims

1. (A) a nanocrystalline magnetic powder having a particle size of 5.5 μm or more and 20 μm or less; (B) a magnetic powder having a particle size of 2 μm or less; (D) a thermosetting resin, The amount of component (A) is 23% by volume or more and 60% by volume or less, based on 100% by volume of the non-volatile components of the resin composition; A resin composition, wherein the amount of component (B) is 5% by volume or more and 30% by volume or less, based on 100% by volume of the nonvolatile components of the resin composition.

2. 2. The resin composition according to claim 1, wherein the volume ratio of component (A) to component (B) (component (A) / component (B)) is 1 or more and 12 or less.

3. The resin composition according to claim 1 , wherein the component (B) comprises a ferrite-based magnetic material.

4. (C) further containing magnetic powder, 2. The resin composition according to claim 1, wherein the magnetic powder (C) is a magnetic powder other than the component (A) and has a particle size of more than 2 μm and not more than 20 μm.

5. 5. The resin composition according to claim 4, wherein the component (C) includes (C2) a magnetic powder other than the nanocrystalline magnetic powder and having a particle size of more than 2 μm and not more than 20 μm.

6. The resin composition according to claim 4, wherein the amount of component (C) is 1% by volume or more and 25% by volume or less, based on 100% by volume of the nonvolatile components of the resin composition.

7. The resin composition according to claim 4, wherein the volume ratio of the component (B) to the component (C) (component (C) / component (B)) is 0.01 or more and 8 or less.

8. The resin composition according to claim 1 , wherein component (D) comprises an epoxy resin.

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

10. The resin composition according to claim 1, further comprising (F) a dispersant.

11. (a) a nanocrystalline magnetic powder having an average particle size of 5.5 μm or more and 20 μm or less; (b) a magnetic powder having an average particle size of 2 μm or less; The method for producing the resin composition according to claim 1, comprising mixing (D) a thermosetting resin.

12. (a) a nanocrystalline magnetic powder having an average particle size of 5.5 μm or more and 20 μm or less; (b) a magnetic powder having an average particle size of 2 μm or less; (c) magnetic powder; (D) a thermosetting resin, (c) the magnetic powder is (c1) a nanocrystalline magnetic powder having an average particle size greater than 2 μm and less than 5.5 μm; and (c2) a magnetic powder other than nanocrystalline magnetic powder, the magnetic powder having an average particle size greater than 2 μm and smaller than the average particle size of the (a) nanocrystalline magnetic raw powder; Selected from The amount of component (a) is 30% by volume or more and 80% by volume or less, based on 100% by volume of the non-volatile components of the resin composition; A method for producing a resin composition, wherein the amount of component (b) is 5% by volume or more and 50% by volume or less, based on 100% by volume of the non-volatile components of the resin composition.

13. 10% particle size D of component (a) １０ The method for producing a resin composition according to claim 11 or 12, wherein the average particle diameter is greater than 2 μm.

14. (b) 90% particle size D of component ９０ The method for producing a resin composition according to claim 11 or 12, wherein the particle size is less than 5.5 μm.

15. (c) further mixing a magnetic powder; The method for producing a resin composition according to claim 11, wherein the magnetic powder (c) has an average particle size of more than 2 μm and not more than 20 μm, and smaller than the average particle size of the component (a).

16. The method for producing a resin composition according to claim 12 or 15, wherein the amount of (c) the magnetic powder is 34% by volume or less relative to 100% by volume of the nonvolatile components of the resin composition.

17. A cured product of the resin composition according to any one of claims 1 to 10.

18. A support and a resin composition layer formed on the support, A resin sheet, wherein the resin composition layer comprises the resin composition according to any one of claims 1 to 10.

19. A step of producing a resin composition by the production method according to claim 11 or 12; and applying the resin composition onto a support.

20. A circuit board comprising a cured product of the resin composition according to any one of claims 1 to 10.

21. 21. The circuit board according to claim 20, comprising: a substrate having through holes formed therein; and a cured product of a resin composition filled in the through holes.

22. An inductor substrate comprising the circuit board of claim 20.

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