Resin composition and method for producing the same

Abstract

To provide a resin composition which can achieve high relative magnetic permeability in a low frequency band and is excellent in appearance when applied.SOLUTION: A resin composition comprising a thermosetting resin and an iron alloy-based magnetic powder, wherein when a non-volatile component of the resin composition is 100% by volume, (a) a content of the iron alloy-based magnetic powder having a particle diameter of more than 20 μm and 50 μm or less is 26% by volume or more and 45% by volume or less, (b) a content of the iron alloy-based magnetic powder having a particle diameter of more than 2 μm and 20 μm or less is 28% by volume or more and 68% by volume or less, and (c) a content of the iron alloy-based magnetic powder having a particle diameter of 2 μm or less is 1% by volume or more and 41% by volume or less.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a resin composition, a method for producing the same, and a cured product, a magnetic paste, a resin sheet, a circuit board, and an inductor board using the resin composition. [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 4). [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 [Patent Document 4] International Publication No. 2023 / 176284 Summary of the Invention [Problem to be solved by the invention]

[0004] In recent years, in order to simultaneously achieve high functionality and miniaturization of inductors, there has been a demand for magnetic materials that can achieve high relative permeability in the low frequency band of around 10 MHz.

[0005] Furthermore, when used, the magnetic material may be applied as a resin composition containing magnetic powder. For example, when manufacturing a resin sheet having a magnetic material layer, a resin composition containing magnetic powder may be applied to a support. When filling holes formed in a substrate with magnetic material, a resin composition containing magnetic powder may be applied to the substrate to fill the holes. Furthermore, when manufacturing a circuit board having a magnetic material layer, a resin composition containing magnetic powder may be applied to a substrate having a wiring pattern on its surface to embed the wiring pattern. When applying a resin composition containing magnetic powder, the resin composition is required to have fluidity to ensure application properties.

[0006] However, according to the inventors' investigations, when a magnetic powder is blended into a resin composition to the extent that a high relative magnetic permeability is achieved, it has been found that even if such a resin composition has fluidity, streaks occur during application, resulting in a poor appearance. It has been confirmed that resin compositions with poor appearance during application induce problems such as the generation of voids and poor adhesion to the substrate during the process of filling holes or embedding wiring patterns. The generation of voids and poor adhesion to the substrate can cause, for example, a decrease in the inductance value of an inductor component, so resin compositions containing magnetic powder are required to have excellent appearance during application.

[0007] The present invention has been devised in view of the above-mentioned problems, and aims to provide a resin composition and a method for producing the same, which can give a cured product that can achieve high relative permeability in the low frequency band and has excellent appearance when applied; a cured product of the resin composition; a magnetic paste and resin sheet containing the resin composition; and a circuit board and inductor board containing the 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, and as a result have found that a resin composition containing an iron alloy magnetic powder having a particle size within a specific range, an iron alloy magnetic powder having a particle size within another specific range, an iron alloy magnetic powder having a particle size within yet another specific range, and a thermosetting resin can solve the above-mentioned problems, thereby completing the present invention.

[0009] That is, the present invention includes the following. <1> A resin composition containing a thermosetting resin and an iron alloy magnetic powder, When the non-volatile components of the resin composition are 100% by volume, (a) The content of iron alloy magnetic powder having a particle size of more than 20 μm and not more than 50 μm is 26% by volume or more and 45% by volume or less, (b) The content of iron alloy magnetic powder having a particle size of more than 2 μm and not more than 20 μm is 28% by volume or more and 68% by volume or less, (c) A resin composition in which the content of iron alloy magnetic powder having a particle size of 2 μm or less is 1% by volume or more and 41% by volume or less. <2> (a) The iron alloy magnetic powder having a particle size of more than 20 μm and not more than 50 μm includes a nanocrystalline magnetic powder made of an iron alloy, <1> The resin composition according to claim 1. <3> (b) The iron alloy magnetic powder having a particle size of more than 2 μm and not more than 20 μm includes at least one iron alloy magnetic powder selected from nanocrystalline magnetic powder made of iron alloy, iron alloy magnetic powder containing Ni, polycrystalline magnetic powder made of iron alloy, and amorphous magnetic powder; <1> or <2> The resin composition according to claim 1. <4> The thermosetting resin includes an epoxy resin. <1> ~ <3> The resin composition according to any one of the above. <5> The thermosetting resin includes a curing agent. <1> ~ <4> The resin composition according to any one of the above. <6> Further, the thermoplastic resin <1> ~ <5> The resin composition according to any one of the above. <7> Further, a curing accelerator is included. <1> ~ <6> The resin composition according to any one of the above. <8> Further comprising a dispersant, <1> ~ <7> The resin composition according to any one of the above. <9> For hole filling, <1> ~ <8> The resin composition according to any one of the above. <10> (A) an iron alloy magnetic powder having an average particle size of more than 20 μm and not more than 50 μm; (B) an iron alloy magnetic powder having an average particle size of more than 2 μm and not more than 20 μm; (C) an iron alloy magnetic powder having an average particle size of 2 μm or less; (D) a thermosetting resin, <1> ~ <9> 10. A method for producing the resin composition according to claim 9. <11> (A) an iron alloy magnetic powder having an average particle size of more than 20 μm and not more than 50 μm; (B) an iron alloy magnetic powder having an average particle size of more than 2 μm and not more than 20 μm; (C) an iron alloy magnetic powder having an average particle size of 2 μm or less; (D) a thermosetting resin. <12> (A) The iron alloy magnetic powder having an average particle size of more than 20 μm and not more than 50 μm includes a nanocrystalline magnetic powder made of an iron alloy, <10> or <11> A method for producing the resin composition described in claim 1. <13> The component (B) is at least one iron alloy-based magnetic powder selected from the group consisting of nanocrystalline magnetic powder made of iron alloy, iron alloy-based magnetic powder containing Ni, polycrystalline magnetic powder made of iron alloy, and amorphous magnetic powder. <10> ~ <12> 10. A method for producing the resin composition according to claim 9. <14> When the nonvolatile components of the resin composition to be produced are taken as 100% by volume, the blending amount of component (A) is 60% by volume or more and 75% by volume or less. <10> ~ <13> 10. A method for producing the resin composition according to claim 9. <15> <1> ~ <9> A cured product of the resin composition according to any one of claims 1 to 11. <16> <1> ~ <9> A magnetic paste comprising the resin composition according to any one of claims 1 to 4. <17> A support and a resin composition layer provided on the support, The resin composition layer is <1> ~ <9> A resin sheet comprising the resin composition according to any one of claims 1 to 11. <18> <1> ~ <9> 1. A circuit board comprising a cured product layer containing a cured product of the resin composition according to any one of claims 1 to 8. <19> The method comprises: forming a substrate having holes; and curing the resin composition filled in the holes. <18> The circuit board according to claim 1. <20> <18> or <19> An inductor substrate comprising the circuit board according to claim 1. [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 produce a cured product that can achieve high relative permeability in the low frequency band and has excellent appearance when applied; a cured product of the resin composition; a magnetic paste and resin sheet containing the resin composition; and a circuit board and inductor board containing the 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 one embodiment of the present invention. [Figure 2] FIG. 2 is a cross-sectional view that schematically shows a core substrate in which a through-hole is formed, in a method for manufacturing a circuit board according to a first example of one 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 one embodiment of the present invention. [Figure 4]FIG. 4 is a cross-sectional view that schematically shows how the through-holes of the core substrate are filled with a resin composition in a method for manufacturing a circuit board according to a first example of one embodiment of the present invention. [Figure 5] FIG. 5 is a schematic cross-sectional view illustrating step (2) of the method for manufacturing a circuit board according to a first example of one embodiment of the present invention. [Figure 6] FIG. 6 is a schematic cross-sectional view illustrating step (3) of the method for manufacturing a circuit board according to a first example of one embodiment of the present invention. [Figure 7] 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 one embodiment of the present invention. [Figure 8] FIG. 8 is a schematic cross-sectional view illustrating step (5) of the method for manufacturing a circuit board according to a first example of one embodiment of the present invention. [Figure 9] FIG. 9 is a schematic cross-sectional view illustrating step (i) in a method for producing a circuit board according to a second example of one embodiment of the present invention. [Figure 10] FIG. 10 is a schematic cross-sectional view illustrating step (i) in a method for producing a circuit board according to a second example of one embodiment of the present invention. [Figure 11] FIG. 11 is a schematic cross-sectional view illustrating step (ii) in a method for producing a circuit board according to a second example of one embodiment of the present invention. [Figure 12] FIG. 12 is a schematic cross-sectional view illustrating step (iv) in the method for producing a circuit board according to a second example of one 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 with reference to embodiments and examples. 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 of the present invention and their equivalents.

[0013] In the following description, the "resin component" of the resin composition refers to the non-volatile components contained in the resin composition excluding inorganic particles such as magnetic powder.

[0014] In the following description, "magnetic permeability" refers to "relative magnetic permeability" unless otherwise specified.

[0015] In the following description, the term "E1-E2 alloy" refers to an alloy containing elements E1 and E2, and the term "E1-E2-E3 alloy" refers to an alloy containing elements E1, E2, and E3, as well as alloys containing four or more elements.

[0016] In the following description, the term "E1-based ferrite" refers to ferrite containing element E1, the term "E1-E2-based ferrite" refers to ferrite containing elements E1 and E2, and the term "E1-E2-E3-based ferrite" refers to ferrite containing elements E1, E2, and E3. The same applies to ferrites containing four or more elements. In addition, when Fe is included in the elements E1 and E2 in a ferrite, the Fe refers to divalent iron, not trivalent iron derived from iron oxide (Fe2O3).

[0017] <Outline of Resin Composition According to First Embodiment> The resin composition according to the first embodiment of the present invention (hereinafter also referred to as "the resin composition of the present invention") contains a thermosetting resin and an iron alloy-based magnetic powder, and when the non-volatile components of the resin composition are 100% by volume, (a) The content of iron alloy magnetic powder having a particle size of more than 20 μm and not more than 50 μm is 26% by volume or more and 45% by volume or less, (b) The content of iron alloy magnetic powder having a particle size of more than 2 μm and not more than 20 μm is 28% by volume or more and 68% by volume or less, (c) The content of iron alloy magnetic powder having a particle size of 2 μm or less is 1% by volume or more and 41% by volume or less. In the following description, "(a) iron alloy magnetic powder having a particle size of more than 20 μm and not more than 50 μm" may be referred to as "(a) large diameter magnetic powder." Also, "(b) iron alloy magnetic powder having a particle size of more than 2 μm and not more than 20 μm" may be referred to as "(b) medium diameter magnetic powder." Also, "(c) iron alloy magnetic powder having a particle size of 2 μm or less" may be referred to as "(c) small diameter magnetic powder." The resin composition according to the first embodiment of the present invention contains a thermosetting resin as well as (a) large diameter magnetic powder, (b) medium diameter magnetic powder, and (c) small diameter magnetic powder in specific range amounts.

[0018] The resin composition of the present invention can be cured by thermal curing of the thermosetting resin to provide a cured product. The cured product thus obtained can have high relative magnetic permeability in the low frequency band (e.g., 10 MHz). Furthermore, the resin composition of the present invention can have excellent appearance when applied.

[0019] As mentioned above, the inventors discovered that when magnetic powder was blended into a resin composition to the extent that a high relative magnetic permeability was achieved, even if the resin composition had fluidity, streaks occurred during application, resulting in a deterioration in appearance.

[0020] Furthermore, the inventors have confirmed that resin compositions that have poor appearance when applied induce problems such as the generation of voids and poor adhesion to the substrate during the process of filling holes or embedding wiring patterns. The generation of voids and poor adhesion to the substrate can cause, for example, a decrease in the inductance value of an inductor component.

[0021] In contrast, a resin composition containing a thermosetting resin and an iron alloy-based magnetic powder, in which, when the nonvolatile components of the resin composition are taken as 100% by volume, (a) the content of the iron alloy-based magnetic powder having a particle size of more than 20 μm and not more than 50 μm is 26% by volume to 45% by volume, (b) the content of the iron alloy-based magnetic powder having a particle size of more than 2 μm and not more than 20 μm is 28% by volume to 68% by volume, and (c) the content of the iron alloy-based magnetic powder having a particle size of 2 μm or less is 1% by volume to 41% by volume, can produce a cured product that achieves high relative magnetic permeability in the low frequency band. Furthermore, such a resin composition can suppress the occurrence of streaks during application of the resin composition, resulting in an excellent appearance upon application. Therefore, the resin composition of the present invention significantly contributes to the realization of an inductor that simultaneously achieves high functionality and miniaturization.

[0022] <(a) Large-diameter magnetic powder according to the first embodiment (iron alloy-based magnetic powder having a particle size of more than 20 μm and not more than 50 μm)> The resin composition according to the first embodiment of the present invention contains (a) large-diameter magnetic powder (iron alloy-based magnetic powder having a particle size of more than 20 μm and not more than 50 μm).

[0023] From the viewpoint of obtaining the effects of the present invention more effectively, it is preferable that the (a) large-diameter magnetic powder contains nanocrystalline magnetic powder made of an iron alloy. In this specification, the term "nanocrystalline magnetic powder" refers to a magnetic powder containing crystal grains with a diameter of 100 nm or less. There is no particular lower limit on the diameter of the crystal grains, but it is preferably 1 nm or more. In particular, it is preferable that the maximum diameter of the crystal grains in the nanocrystalline magnetic powder is 100 nm or less. Generally, one particle of nanocrystalline magnetic powder contains multiple crystal grains, and therefore, the nanocrystalline magnetic powder particles can be polycrystalline. The size of the crystal grains can be observed, for example, using a transmission electron microscope (TEM). Since 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.

[0024] The (a) large-diameter magnetic powder is contained in the resin composition in the form of particles, for example. The (a) large-diameter magnetic powder may contain crystal grains in at least a portion of the particles, preferably contains crystal grains in the surface layer of the particles, more preferably contains crystal grains throughout the particles, and even more preferably consists of only crystal grains.

[0025] (a) Large-diameter magnetic powder refers to iron alloy magnetic powder contained in a resin composition with a particle size in the range of more than 20 μm to 50 μm. The presence and content of (a) large-diameter magnetic powder can be measured using a laser diffraction / scattering method based on Mie scattering theory. Specifically, a volumetric particle size distribution of the magnetic powder contained in the resin composition is created using a laser diffraction / scattering particle size distribution analyzer, and the particle size can be measured from that particle size distribution. A preferred measurement sample is magnetic powder dispersed in pure water using ultrasonic waves. Examples of laser diffraction / scattering particle size distribution analyzers that can be used include the Microtrackbell "MT3000II," the Horiba "LA-960," and the Shimadzu "SALD-2200."

[0026] The resin composition of the present invention contains (a) large-diameter magnetic powder in a specific amount. Specifically, the content of (a) large-diameter magnetic powder is 26% by volume or more, preferably 27% by volume or more, and more preferably 28% by volume or more, assuming that the non-volatile components of the resin composition are 100% by volume. The upper limit of the content of (a) large-diameter magnetic powder is 45% by volume or less, preferably 40% by volume or less, more preferably 35% by volume or less, 34% by volume or less, or 32% by volume or less. When such an amount of (a) large-diameter magnetic powder is used, the relative permeability can be improved in the low-frequency band.

[0027] The magnetic material contained in the (a) large-diameter magnetic powder may be, for example, a magnetic metal. Among these, the magnetic material contained in the (a) large-diameter magnetic powder preferably contains iron (Fe). Therefore, the magnetic material contained in the (a) large-diameter magnetic powder may be, for example, a crystalline iron alloy magnetic material. To achieve the most significant effects of the present invention, the magnetic material contained in the (a) large-diameter magnetic powder preferably has a composition that further contains, in addition to Fe, one or more elements selected from the group consisting of Nb, Hf, Zr, Ta, Mo, W, and V.

[0028] (a) Preferred examples of magnetic materials contained in the large-diameter magnetic powder include magnetic materials described in JP 2021-158343 A, JP 2021-141267 A, WO 2019-31463 A, JP 2021-11602 A, etc.

[0029] Among the above examples, (a) the large-diameter magnetic powder preferably contains nanocrystalline magnetic powder made of an Fe—Si—Nb—B alloy, from the viewpoint of significantly achieving the desired effects of the present invention.

[0030] (a) The large-diameter magnetic powder may contain one type of powder alone, or may contain a combination of two or more types of powders with different alloy compositions.

[0031] (a) Large-diameter magnetic powder can be manufactured, for example, by atomization. Specific examples of methods for manufacturing (a) large-diameter magnetic powder include the methods described in JP 2021-141267 A and JP 2021-158343 A. Furthermore, (a) large-diameter magnetic powder may be a commercially available product. Examples of commercially available magnetic powders containing (a) large-diameter magnetic powder include "KUAMET NC1-53um," "KUAMET NC1-75um," "KUAMET NC1 053C03," "KUAMET NC1 075C03," and "KUAMET NC2-53um" manufactured by Epson Atmix Corporation. However, commercially available magnetic powders generally have a wide particle size distribution and may contain particles with a particle size of 20 μm or less or particles with a particle size of more than 50 μm. Therefore, when purchasing (a) large-diameter magnetic powder from the market, the commercially available magnetic powder may be classified as needed.

[0032] The (a) large-diameter magnetic powder is preferably spherical. The value obtained by dividing the length of the major axis of the (a) large-diameter magnetic powder particle by the length of the minor axis (aspect ratio) is preferably 2 or less, more preferably 1.5 or less, and even more preferably 1.2 or less, for example, 1 or more, preferably greater than 1, and more preferably 1.05 or more.

[0033] In the resin composition of the present invention, the content of (a) large-diameter magnetic powder is preferably 28% by volume or more, more preferably 30% by volume or more, and even more preferably 32% by volume or more, when the total volume of the magnetic powder contained in the resin composition is taken as 100% by volume, and is preferably 60% by volume or less, more preferably 55% by volume or less, and even more preferably 50% by volume or less, 45% by volume or less, or 40% by volume or less. When the content (volume %) of (a) large-diameter magnetic powder in the total magnetic powder is within the above range, the relative permeability can be effectively improved in the low-frequency band.

[0034] In the resin composition of the present invention, the content of (a) large-diameter magnetic powder is preferably 27% by mass or more, more preferably 30% by mass or more, and even more preferably 32% by mass or more, and is preferably 45% by mass or less, more preferably 55% by mass or less, and even more preferably 50% by mass or less, 45% by mass or less, 40% by mass or less, or 37% by mass or less, when the non-volatile components of the resin composition are taken as 100% by mass. When the content (mass%) of (a) large-diameter magnetic powder in the resin composition is within the above range, the relative permeability can be effectively improved in the low-frequency band.

[0035] <(b) Intermediate Magnetic Powder According to First Embodiment (Iron Alloy-Based Magnetic Powder Having a Particle Size of More than 2 μm and Not More than 20 μm)> The resin composition according to the first embodiment of the present invention contains (b) intermediate magnetic powder having a particle size within a specific range. The (b) intermediate magnetic powder is contained in the resin composition, for example, in the form of particles. This (b) intermediate magnetic powder refers to the iron alloy magnetic powder contained in the resin composition, whose particle size is in the range of more than 2 μm to 20 μm. The presence and content of the (b) intermediate magnetic powder can be determined and measured in the same manner as for the (a) large diameter magnetic powder. The (b) intermediate magnetic powder is an iron alloy magnetic powder. One type of (b) intermediate magnetic powder may be used alone, or two or more types may be used in combination.

[0036] (b) It is preferable that the intermediate magnetic powder contains at least one type of iron alloy magnetic powder selected from nanocrystalline magnetic powder made of iron alloy, iron alloy-based magnetic powder containing Ni, polycrystalline magnetic powder made of iron alloy, and amorphous magnetic powder.

[0037] In a preferred embodiment, the (b) medium magnetic powder includes a nanocrystalline magnetic powder having a particle size of more than 2 μm and not more than 20 μm and made of an iron alloy. The nanocrystalline magnetic powder made of an iron alloy is as described in the section (a) Large-diameter magnetic powder. The nanocrystalline magnetic powder used as the (b) medium magnetic powder may contain one type of powder alone, or may contain a combination of two or more types with different alloy compositions.

[0038] In another preferred embodiment, the (b) intermediate magnetic powder includes an iron alloy-based magnetic powder having a particle size of more than 2 μm and not more than 20 μm and containing Ni. Examples of iron alloys containing Ni include Fe-Ni alloys, Fe-Ni-Si alloys, Fe-Ni-Cr alloys, Fe-Ni-B alloys, Fe-Si-Nb-B alloys, Fe-Ni-Mo alloys, Fe-Ni-Mo-Cu alloys, Fe-Ni-Si-Cr alloys, and Fe-Ni-Co alloys. The iron alloys containing Ni may be used singly or in combination of two or more types with different alloy compositions. The iron alloy-based magnetic powder containing Ni as the (b) intermediate magnetic powder preferably includes a magnetic powder made of at least one iron alloy selected from the group consisting of an Fe-Ni alloy and an Fe-Ni-Si alloy. Therefore, in a preferred embodiment, (b) the iron alloy magnetic powder containing Ni as the intermediate magnetic powder comprises one or more magnetic powders selected from the group consisting of Fe-Ni alloy magnetic powders and Fe-Ni-Si alloy magnetic powders.

[0039] In yet another preferred embodiment, the (b) intermediate magnetic powder includes a polycrystalline magnetic powder made of an iron alloy and having a particle size of more than 2 μm and not more than 20 μm. Polycrystalline magnetic powder made of an iron alloy has multiple crystalline structures per particle, and therefore has grain boundaries. Distinguishing between a single crystal structure and a polycrystalline structure can be achieved by observing the crystal lattice with a transmission electron microscope (TEM) or observing the grain boundaries with a scanning electron microscope (SEM). The composition of the iron alloy in the polycrystalline magnetic powder is not particularly limited, and examples include 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-Si alloys, Fe-Ni-Si-Cr alloys, Fe-Ni-Mo alloys, Fe-Ni-Mo-Cu alloys, Fe-Co alloys, and Fe-Ni-Co alloys. (b) The polycrystalline magnetic powder made of an iron alloy as the intermediate magnetic powder may be used singly or in combination of two or more types with different alloy compositions.

[0040] In yet another preferred embodiment, the (b) intermediate magnetic powder comprises an amorphous magnetic powder having a particle size of more than 2 μm and not more than 20 μm. Because amorphous magnetic materials are non-crystalline, they generally do not exhibit specific peaks indicating crystallinity in their X-ray diffraction patterns. Therefore, the X-ray diffraction pattern of amorphous magnetic powder appears as a broad pattern without peaks indicating crystallinity. The (b) intermediate magnetic powder may be of one type, or two or more types with different alloy compositions may be used in combination.

[0041] The resin composition of the present invention contains (b) intermediate magnetic powder in a specific amount. Specifically, the content of component (b) is 28% by volume or more and 68% by volume or less, assuming that the non-volatile components of the resin composition are 100% by volume. The upper limit of the content of component (b) is preferably 60% by volume or less, more preferably 50% by volume or less, and even more preferably 40% by volume or less or 38% by volume or less. When such an amount of (b) intermediate magnetic powder is contained, the relative permeability can be improved in the low frequency band, and further, the appearance of the resin composition when applied can be improved.

[0042] (b) The intermediate magnetic powder may be a commercially available product. (b) Examples of commercially available magnetic powders including intermediate magnetic powders include "KUAMET NC1-V1-38um," "ATFINE-NC1 PF3FA," "ATFINE-NC1 PF5FA," "ATFINE-NC1 PF10FA," "ATFINE-NC1 PF3FC124A," "ATFINE-NC1 PF5FC124A," and "ATFINE-NC1 PF10FC124A" manufactured by Epson Atmix (nanocrystalline magnetic powders made of iron alloys); "AKT-PB-3Si(3)" and "AKT-PB(5)" manufactured by Mitsubishi Steel; "50%FE-50%NI PF-5F," "50%FE-50%NI PF-10F," and "50%FE-50%NI PF-20F" manufactured by Epson Atmix (iron alloy magnetic powders containing Ni); and "EA-SMP-10" manufactured by Epson Atmix. Examples include "AW02-08 PF3K," "EA-SMP-10 PF5F," and "EA-SMP-10 PF10F" (polycrystalline magnetic powders made of iron alloys); and "AW02-08 PF3F," "AW02-08 PF5F," "AW02-08 PF8F," and "AW02-08 PF10F" (amorphous magnetic powders) manufactured by Epson Atmix. However, commercially available magnetic powders generally have a wide particle size distribution and may contain particles with a particle size of 2 μm or less or particles with a particle size of more than 20 μm. Therefore, when purchasing (b) intermediate magnetic powder from the market, the commercially available magnetic powder may be classified as necessary.

[0043] The (b) medium magnetic powder is preferably spherical. The aspect ratio range of the particles of the (b) medium magnetic powder may be the same as the aspect ratio range of the (a) large diameter magnetic powder. The aspect ratio of the (b) medium magnetic powder and the aspect ratio of the (a) large diameter magnetic powder may be the same or different.

[0044] In the resin composition of the present invention, the content of (b) intermediate magnetic powder is preferably 30% by volume or more, more preferably 32% by volume or more, and even more preferably 34% by volume or more, and is preferably 55% by volume or less, more preferably 50% by volume or less, and even more preferably 45% by volume or less, when the total magnetic powder contained in the resin composition is taken as 100% by volume. When the content (volume %) of (b) intermediate magnetic powder in the total magnetic powder is within the above range, it is possible to effectively improve the relative magnetic permeability in the low frequency band, and further to improve the appearance when the resin composition is applied.

[0045] In the resin composition of the present invention, the content of (b) intermediate magnetic powder is preferably 27% by mass or more, more preferably 30% by mass or more, and even more preferably 33% by mass or more, and is preferably 55% by mass or less, more preferably 48% by mass or less, and even more preferably 44% by mass or less, when the non-volatile components of the resin composition are taken as 100% by mass. When the content (% by mass) of (b) intermediate magnetic powder in the resin composition is within the above range, the relative magnetic permeability can be effectively improved in the low frequency band, and further, the appearance of the resin composition when applied can be improved.

[0046] In the resin composition of the present invention, the content (volume %) of the (a) large-diameter magnetic powder is represented by "V(a)," and the content (volume %) of the (b) medium-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) large-diameter magnetic powder to the (b) medium-diameter magnetic powder ((a) large-diameter magnetic powder / (b) medium-diameter magnetic powder) contained in the resin composition can be represented by "V(a) / V(b)." This volume ratio V(a) / V(b) is preferably 0.4 or more, more preferably 0.6 or more, even more preferably 0.7 or more, and preferably 1.1 or less. When the volume ratio V(a) / V(b) is within the above range, the relative magnetic permeability can be effectively improved in the low-frequency band, and further, the appearance of the resin composition when applied can be improved.

[0047] Furthermore, in the resin composition of the present invention, the total amount (volume %) of (a) the large-diameter magnetic powder and (b) the medium-sized magnetic powder can be expressed as "V(a) + V(b)." This total amount (volume %) V(a) + V(b) is preferably 55% by volume or more, more preferably 56% by volume or more, and is preferably 90% by volume or less, more preferably 80% by volume or less, and even more preferably 70% by volume or less or 65% by volume or less. When the total amount (volume %) V(a) + V(b) is within the above range, the relative permeability can be effectively improved in the low-frequency band, and further, the appearance of the resin composition when applied can be improved.

[0048] <(c) Small-diameter magnetic powder (iron alloy-based magnetic powder having a particle size of 2 μm or less) according to the first embodiment> The resin composition according to the first embodiment of the present invention contains (c) small-diameter magnetic powder having a particle size within a specific range. The (c) small-diameter magnetic powder is contained in the resin composition, for example, in the form of particles. This (c) small-diameter magnetic powder refers to iron alloy-based magnetic powder contained in the resin composition having a particle size within a range of 2 μm or less. The particle size of the (c) small-diameter magnetic powder can be determined and measured in the same manner as the (a) large-diameter magnetic powder. The (c) small-diameter magnetic powder is an iron alloy-based magnetic powder. One type of (c) small-diameter magnetic powder may be used alone, or two or more types may be used in combination.

[0049] (c) The small-diameter magnetic powder may be a nanocrystalline magnetic powder containing crystal grains, a polycrystalline magnetic powder, an amorphous magnetic powder containing no crystal grains, a crystalline magnetic powder other than a nanocrystalline magnetic powder, or a combination of these.

[0050] Examples of iron alloys that form the (c) small-diameter magnetic powder include pure iron, crystalline or amorphous alloys such as Fe-Si alloys, Fe-Si-Cr alloys, Fe-Si-Al alloys, Fe-Si-Nb-B alloys, Fe-Cr alloys, Fe-Ni-Cr alloys, Fe-Cr-Al alloys, Fe-Ni alloys, Fe-Ni-Si alloys, Fe-Ni-B alloys, Fe-Ni-Mo alloys, Fe-Ni-Mo-Cu alloys, Fe-Ni-Si-Cr alloys, Fe-Co alloys, Fe-Ni-Co alloys, and Co-based amorphous alloys. Among these, the (c) small-diameter magnetic powder preferably contains magnetic powder made of at least one iron alloy selected from the group consisting of Fe-Si-Cr alloys, Fe-Si-Nb-B alloys, Fe-Ni alloys, and Fe-Ni-Si alloys. Therefore, in a preferred embodiment, (c) the iron alloy magnetic powder as the small-diameter magnetic powder comprises one or more magnetic powders selected from the group consisting of Fe-Si-Cr alloy magnetic powder, Fe-Si-Nb-B alloy magnetic powder, Fe-Ni alloy magnetic powder, and Fe-Ni-Si alloy magnetic powder.

[0051] The resin composition of the present invention contains a specific amount of (c) small-diameter magnetic powder having a particle size within the above range. Specifically, the content of the (c) small-diameter magnetic powder is 1% by volume or more, preferably 2% by volume or more, more preferably 3% by volume or more, and even more preferably 4% by volume or more, based on 100% by volume of the nonvolatile components of the resin composition. Furthermore, the upper limit of the amount (volume %) of the (c) small-diameter magnetic powder is 41% by volume or less, preferably 30% by volume or less, more preferably 20% by volume or less, and even more preferably 15% by volume or less or 14% by volume or less. When the resin composition contains such an amount of (c) small-diameter magnetic powder, the relative permeability can be improved in the low-frequency band, and the appearance of the resin composition when applied can be improved.

[0052] The (c) small-diameter magnetic powder may be a commercially available product. Examples of commercially available magnetic powders containing the (c) small-diameter magnetic powder include "G00129R" and "CVD iron powder (0.7 μm)" manufactured by JFE Mineral Co., Ltd. However, commercially available magnetic powders generally have a wide particle size distribution and may contain particles with a particle size of more than 2 μm. Therefore, when purchasing the (c) small-diameter magnetic powder from the market, the commercially available magnetic powder may be classified as necessary.

[0053] The (c) small-diameter magnetic powder is preferably spherical. The aspect ratio range of the particles of the (c) small-diameter magnetic powder may be the same as the aspect ratio range of the (a) large-diameter magnetic powder. The aspect ratio of the (c) small-diameter magnetic powder and the aspect ratio of the (a) large-diameter magnetic powder may be the same or different.

[0054] In the resin composition of the present invention, the content of (c) small-diameter magnetic powder is preferably 1% by volume or more, more preferably 3% by volume or more, and even more preferably 5% by volume or more, and is preferably 23% by volume or less, more preferably 20% by volume or less, and even more preferably 17% by volume or less, when the total magnetic powder contained in the resin composition is taken as 100% by volume. When the content (volume %) of (c) small-diameter magnetic powder in the total magnetic powder is within the above range, it is possible to effectively improve the relative magnetic permeability in the low-frequency band, and further to improve the appearance of the resin composition when applied.

[0055] In the resin composition of the present invention, the content of the (c) small-diameter magnetic powder is preferably 1% by mass or more, more preferably 3% by mass or more, and even more preferably 5% by mass or more, and is preferably 30% by mass or less, more preferably 20% by mass or less, and even more preferably 16% by mass or less, when the non-volatile components of the resin composition are taken as 100% by mass. When the content (mass %) of the (c) small-diameter magnetic powder in the resin composition is within the above range, the relative magnetic permeability can be effectively improved in the low-frequency band, and further, the appearance of the resin composition when applied can be improved.

[0056] In the resin composition of the present invention, the content (volume %) of the (c) small-diameter 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) large-diameter magnetic powder to the (c) small-diameter magnetic powder contained in the resin composition ((a) large-diameter magnetic powder / (c) small-diameter magnetic powder) can be represented by "V(a) / V(c)." This volume ratio V(a) / V(c) is preferably 1 or more, more preferably 1.5 or more, and even more preferably 2 or more, and is preferably 30 or less, more preferably 15 or less, and even more preferably 10 or less or 7 or less. When the volume ratio V(a) / V(c) is within the above range, the relative magnetic permeability can be effectively improved in the low-frequency band, and further, the appearance of the resin composition when applied can be improved.

[0057] Furthermore, in the resin composition of the present invention, the total amount (volume %) of (a) the large-diameter magnetic powder and (c) the small-diameter magnetic powder can be expressed as "V(a) + V(c)." This total amount (volume %) V(a) + V(c) is preferably 28% by volume or more, more preferably 30% by volume or more, even more preferably 32% by volume or more, and is preferably 60% by volume or less, more preferably 50% by volume or less, and even more preferably 45% by volume or less. When the total amount (volume %) V(a) + V(c) is within the above range, the relative permeability can be effectively improved in the low-frequency band, and further, the appearance of the resin composition when applied can be improved.

[0058] <(D) Thermosetting Resin According to the First Embodiment> The resin composition according to the first embodiment of the present invention contains a thermosetting resin (also referred to as "(D) thermosetting resin" or "(D) component"). The (D) thermosetting resin can bind magnetic powders including (a) large-diameter magnetic powder, (b) medium-diameter magnetic powder, and (c) small-diameter magnetic powder. The (D) thermosetting resin can react with heat to form bonds and harden. Therefore, a cured product can be obtained by hardening a resin composition containing a combination of (a) large-diameter magnetic powder, (b) medium-diameter magnetic powder, (c) small-diameter magnetic powder, and the (D) thermosetting resin.

[0059] Examples of the (D) thermosetting resin include epoxy resins, phenolic resins, active ester resins, amine resins, acid anhydride resins, benzoxazine resins, cyanate ester resins, carbodiimide resins, etc. One type of (D) thermosetting resin may be used alone, or two or more types may be used in combination.

[0060] The (D) thermosetting resin preferably contains an epoxy resin (also referred to as "(D-1) epoxy resin" or "(D-1) component"). The (D-1) epoxy resin refers to a resin having one or more epoxy groups in its molecule. When the (D) thermosetting resin contains the (D-1) epoxy resin, it is possible to improve the dispersibility of the magnetic powders (a) to (c) and effectively improve the relative magnetic permeability of the cured product of the resin composition.

[0061] Examples of the (D-1) epoxy resin 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, phenol novolac-type epoxy resins, glycidyl amine-type epoxy resins, glycidyl ester-type epoxy resins, cresol novolac-type epoxy resins, biphenyl-type epoxy resins, linear aliphatic epoxy resins, epoxy resins having a butadiene structure, alicyclic epoxy resins, and alicyclic epoxy resins having an ester skeleton. Examples of the epoxy resin (D-1) include heterocyclic epoxy resins, spiro ring-containing epoxy resins, cyclohexane epoxy resins, cyclohexanedimethanol epoxy resins, trimethylol epoxy resins, tetraphenylethane epoxy resins, epoxy resins containing a condensed ring skeleton such as naphthylene ether epoxy resins, tert-butyl-catechol epoxy resins, naphthalene epoxy resins, naphthol epoxy resins, anthracene epoxy resins, and naphthol novolac epoxy resins, isocyanurate epoxy resins, alkyleneoxy and butadiene skeleton-containing epoxy resins, and fluorene structure-containing epoxy resins. One type of epoxy resin (D-1) may be used alone, or two or more types may be used in combination.

[0062] The epoxy resin (D-1) preferably contains an epoxy resin having two or more epoxy groups per molecule, and the proportion of the epoxy resin having two or more epoxy groups per molecule relative to the total amount of the epoxy resin (D-1) (100% by mass) is preferably 50% by mass or more, more preferably 60% by mass or more, and even more preferably 70% by mass or more.

[0063] (D-1) epoxy resins include epoxy resins that are liquid at a temperature of 20°C (hereinafter sometimes referred to as "liquid epoxy resins") and epoxy resins that are solid at a temperature of 20°C (hereinafter sometimes referred to as "solid epoxy resins"). The (D-1) epoxy resin may be a liquid epoxy resin alone, a solid epoxy resin alone, or a combination of a liquid epoxy resin and a solid epoxy resin. When a combination of a liquid epoxy resin and a solid epoxy resin is used as the (D-1) epoxy resin, the ratio by mass between them (liquid epoxy resin:solid epoxy resin) is preferably 1:0.01 to 1:50, more preferably 1:0.05 to 1:20, and even more preferably 1:0.1 to 1:10.

[0064] The liquid epoxy resin is preferably a liquid epoxy resin having two or more epoxy groups per molecule. Examples of the liquid epoxy resin include bisphenol A epoxy resin, bisphenol F epoxy resin, bisphenol AF epoxy resin, naphthalene epoxy resin, glycidyl ester epoxy resin, glycidyl amine epoxy resin, phenol novolac epoxy resin, alicyclic epoxy resin having an ester skeleton, cyclohexane epoxy resin, cyclohexanedimethanol epoxy resin, epoxy resin having a butadiene structure, epoxy resin containing an alkyleneoxy skeleton and a butadiene skeleton, epoxy resin containing a fluorene structure, and dicyclopentadiene epoxy resin. Among these, bisphenol A epoxy resin and bisphenol F epoxy resin are more preferred.

[0065] Specific examples of liquid epoxy resins include "YX7400" manufactured by Mitsubishi Chemical Corporation; "HP4032", "HP4032D", and "HP4032SS" (naphthalene-type epoxy resins) manufactured by DIC Corporation; "828US", "828EL", "jER828EL", "825", and "Epikote 828EL" (bisphenol A-type epoxy resins) manufactured by Mitsubishi Chemical Corporation; "jER807" and "1750" (bisphenol F-type epoxy resins) manufactured by Mitsubishi Chemical Corporation; "jER152" (phenol novolac-type epoxy resin) manufactured by Mitsubishi Chemical Corporation; "630", "630LSD", and "604" (glycidylamine-type epoxy resins) manufactured by Mitsubishi Chemical Corporation; "ED-523T" (glycirol-type epoxy resin) manufactured by ADEKA Corporation; "EP-3950L" and "EP-3980S" (glycidylamine-type epoxy resins) manufactured by ADEKA Corporation; and "EP-4088S" (glycidylamine-type epoxy resins) manufactured by ADEKA Corporation. peropentadiene-type epoxy resins); "ZX-1059" manufactured by Nippon Steel Chemical & Material Co., Ltd. (a mixture of bisphenol A-type epoxy resin and bisphenol F-type epoxy resin); "EX-721" manufactured by Nagase ChemteX Corporation (glycidyl ester-type epoxy resin); "EX-991L" manufactured by Nagase ChemteX Corporation (an epoxy resin containing an alkyleneoxy skeleton); "Celloxide 2021P" and "Celloxide 2081" manufactured by Daicel Corporation (alicyclic epoxy resins with an ester skeleton); "PB-3600" manufactured by Daicel Corporation, "JP-100" and "JP-200" manufactured by Nippon Soda Co., Ltd. (epoxy resins with a butadiene structure); "ZX-1658" and "ZX-1658GS" manufactured by Nippon Steel Chemical & Material Co., Ltd. (liquid 1,4-glycidylcyclohexane-type epoxy resin); and "EG-280" manufactured by Osaka Gas Chemicals Co., Ltd. (an epoxy resin containing a fluorene structure). The liquid epoxy resin may be used alone or in combination of two or more.

[0066] The solid epoxy resin is preferably a solid epoxy resin having three or more epoxy groups per molecule, more preferably an aromatic solid epoxy resin having three or more epoxy groups per molecule.The solid epoxy resin is preferably a bixylenol type epoxy resin, a naphthalene type epoxy resin, a naphthalene type tetrafunctional epoxy resin, a cresol novolac type epoxy resin, a dicyclopentadiene type epoxy resin, a trisphenol type epoxy resin, a naphthol type epoxy resin, a biphenyl type epoxy resin, a naphthylene ether type epoxy resin, an anthracene type epoxy resin, a bisphenol A type epoxy resin, a bisphenol AF type epoxy resin, or a tetraphenylethane type epoxy resin, and more preferably a dicyclopentadiene type epoxy resin.

[0067] Specific examples of solid epoxy resins include DIC Corporation's "HP4032H" (naphthalene-type epoxy resin); DIC Corporation's "HP-4700" and "HP-4710" (naphthalene-type tetrafunctional epoxy resins); DIC Corporation's "N-690" (cresol novolac-type epoxy resin); DIC Corporation's "N-695" (cresol novolac-type epoxy resin); and DIC Corporation's "HP-7200," "HP-7200HH," and "HP-7200H" (dicyclopentadiene-type epoxy resins). DIC's "EXA-7311", "EXA-7311-G3", "EXA-7311-G4", "EXA-7311-G4S", and "HP6000" (naphthylene ether type epoxy resins); Nippon Kayaku's "EPPN-502H" (trisphenol type epoxy resin); Nippon Kayaku's "NC7000L" (naphthol novolac type epoxy resin); Nippon Kayaku's "NC3000H", "NC3000", "NC3000L", and "NC3100" (biphenyl type epoxy resins). resin); "ESN475V" (naphthol-type epoxy resin) manufactured by Nippon Steel Chemical & Material Co., Ltd.; "ESN485" (naphthol novolac-type epoxy resin) manufactured by Nippon Steel Chemical & Material Co., Ltd.; "YL6121" (biphenyl-type epoxy resin) manufactured by Mitsubishi Chemical Corporation; "YX4000H", "YX4000", and "YX4000HK" (bixylenol-type epoxy resin) manufactured by Mitsubishi Chemical Corporation; "YX8800" (anthracene-type epoxy resin) manufactured by Mitsubishi Chemical Corporation Examples of suitable solid epoxy resins include "YX7700" (xylene structure-containing novolac epoxy resin) manufactured by Mitsubishi Chemical Corporation; "PG-100" and "CG-500" manufactured by Osaka Gas Chemicals Co., Ltd.; "YL7760" (bisphenol AF epoxy resin) manufactured by Mitsubishi Chemical Corporation; "YL7800" (fluorene epoxy resin) manufactured by Mitsubishi Chemical Corporation; "jER1010" (solid bisphenol A epoxy resin) manufactured by Mitsubishi Chemical Corporation; and "jER1031S" (tetraphenylethane epoxy resin) manufactured by Mitsubishi Chemical Corporation. One type of solid epoxy resin may be used alone, or two or more types may be used in combination.

[0068] The epoxy equivalent of the (D-1) epoxy resin is preferably 50 g / eq. to 5,000 g / eq., more preferably 50 g / eq. to 3,000 g / eq., even more preferably 80 g / eq. to 2,000 g / eq., and even more preferably 110 g / eq. to 1,000 g / eq. The epoxy equivalent is the mass of an epoxy resin containing one equivalent of epoxy groups. This epoxy equivalent can be measured according to JIS K7236.

[0069] The weight average molecular weight (Mw) of the epoxy resin (D-1) is preferably 100 to 5,000, more preferably 250 to 3,000, and even more preferably 400 to 1,500. The weight average molecular weight of the resin can be measured by gel permeation chromatography (GPC) as a polystyrene-equivalent value.

[0070] In the resin composition of the present invention, the content of component (D-1) is preferably 0.5% by mass or more, more preferably 1% by mass or more, and even more preferably 1.3% by mass or more, and is preferably 3% by mass or less, more preferably 2% by mass or less, and even more preferably 1.6% by mass or less, when the non-volatile components of the resin composition are taken as 100% by mass. When the content (mass%) of epoxy resin (D-1) is within the above range, the relative magnetic permeability of the cured product of the resin composition can be effectively improved.

[0071] In the resin composition of the present invention, the content of component (D-1) is preferably 30% by mass or more, more preferably 35% by mass or more, and even more preferably 40% by mass or more, and is preferably 60% by mass or less, more preferably 50% by mass or less, and even more preferably 45% by mass or less, when the resin components of the resin composition are taken as 100% by mass. When the content (mass%) of epoxy resin (D-1) is within the above range, the relative magnetic permeability of the cured product of the resin composition can be effectively improved.

[0072] When the (D) thermosetting resin contains a (D-1) epoxy resin, the (D) thermosetting resin may contain a resin capable of reacting with and bonding to the (D-1) epoxy resin. The resin capable of reacting with and bonding to the (D-1) epoxy resin may be referred to as the "(D-2) curing agent" below. Examples of the (D-2) curing agent include phenolic resins, active ester resins, amine resins, carbodiimide resins, acid anhydride resins, benzoxazine resins, cyanate ester resins, and thiol resins. The (D-2) curing agent may be used alone or in combination of two or more. Among these, phenolic resins are preferred.

[0073] As the phenolic resin, a resin having one or more, preferably two or more, hydroxyl groups bonded to an aromatic ring such as a benzene ring or a naphthalene ring per molecule can be used. From the viewpoint of heat resistance and water resistance, a phenolic resin having a novolac structure is preferred. From the viewpoint of adhesion, a nitrogen-containing phenolic resin is preferred, and a triazine skeleton-containing phenolic resin is more preferred. Among them, a triazine skeleton-containing phenolic novolac resin is preferred from the viewpoint of highly satisfying heat resistance, water resistance, and adhesion.

[0074] Specific examples of phenolic resins include "MEH-7700", "MEH-7810", "MEH-7851", and "MEH-8000H" manufactured by Meiwa Chemical Industry Co., Ltd.; "NHN", "CBN", and "GPH" manufactured by Nippon Kayaku Co., Ltd.; and "SN-170", "SN-180", "SN-190", "SN-475", "SN-485", "SN-495", "SN-495V", "SN-375", and "SN" manufactured by Nippon Steel Chemical & Material Co., Ltd. -395"; "TD-2090", "TD-2090-60M", "LA-7052", "LA-7054", "LA-1356", "LA-3018", "LA-3018-50P", "EXB-9500", "HPC-9500", "KA-1160", "KA-1163", and "KA-1165" manufactured by DIC Corporation; and "GDP-6115L", "GDP-6115H", and "ELPC75" manufactured by Gun-ei Chemical Co., Ltd.

[0075] The active ester resin may be a compound having one or more, preferably two or more, active ester groups per molecule. Among these, preferred active ester resins are compounds having two or more highly reactive ester groups per molecule, such as phenol esters, thiophenol esters, N-hydroxyamine esters, and esters of heterocyclic hydroxy compounds. The 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. Among these, 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.

[0076] Preferred examples of the active ester resin include active ester resins containing a dicyclopentadiene-type diphenol structure, active ester resins containing a naphthalene structure, active ester resins containing an acetylated product of phenol novolac, and active ester resins containing a benzoylated product of phenol novolac. Among these, active ester resins containing a naphthalene structure and active ester resins containing a dicyclopentadiene-type diphenol structure are more preferred. The "dicyclopentadiene-type diphenol structure" refers to a divalent structural unit consisting of phenylene-dicyclopentylene-phenylene.

[0077] Commercially available activated ester resins include activated ester resins containing a dicyclopentadiene-type diphenol structure, such as "EXB9451," "EXB9460," "EXB9460S," "HPC-8000-65T," "HPC-8000H-65TM," and "EXB-8000L-65TM" (manufactured by DIC Corporation); activated ester resins containing a naphthalene structure, such as "EXB-9416-70BK," "EXB-8150-65T," "EXB-8100L-65T," and "EXB-8150L-65T" (manufactured by DIC Corporation); and phenol novolac resins. Examples of active ester resins containing acetylated compounds include "DC808" (manufactured by Mitsubishi Chemical Corporation); active ester resins containing benzoylated phenol novolac include "YLH1026" (manufactured by Mitsubishi Chemical Corporation); active ester resins that are acetylated phenol novolac include "DC808" (manufactured by Mitsubishi Chemical Corporation); and active ester resins that are benzoylated phenol novolac include "YLH1026" (manufactured by Mitsubishi Chemical Corporation), "YLH1030" (manufactured by Mitsubishi Chemical Corporation), and "YLH1048" (manufactured by Mitsubishi Chemical Corporation).

[0078] As the amine-based resin, a resin having one or more, preferably two or more amino groups in one molecule can be used. Examples of the amine-based resin include aliphatic amines, polyether amines, alicyclic amines, and aromatic amines. Among these, aromatic amines are preferred. The amine-based resin is preferably a primary amine or a secondary amine, and more preferably a primary amine. Specific examples of the amine-based resin include 4,4'-methylenebis(2,6-dimethylaniline), diphenyldiaminosulfone, 4,4'-diaminodiphenylmethane, 4,4'-diaminodiphenylsulfone, 3,3'-diaminodiphenylsulfone, m-phenylenediamine, m-xylylenediamine, diethyltoluenediamine, 4,4'-diaminodiphenyl ether, 3,3'-dimethyl-4,4'-diaminobiphenyl, 2,2'-dimethyl-4,4'-diaminobiphenyl, 3,3'-dihydroxybenzidine, 2,2-bis(3-amino-4-hydroxybenzoyl) Examples of suitable amine resins include 4,4'-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 resins may be used, such as "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.

[0079] As the carbodiimide resin, a resin having one or more, preferably two or more, carbodiimide structures in one molecule can be used. Specific examples of the carbodiimide resin include aliphatic biscarbodiimides such as tetramethylene-bis(t-butylcarbodiimide) and cyclohexanebis(methylene-t-butylcarbodiimide); aromatic biscarbodiimides such as phenylene-bis(xylylcarbodiimide); aliphatic polycarbodiimides such as polyhexamethylenecarbodiimide, polytrimethylhexamethylenecarbodiimide, polycyclohexylenecarbodiimide, poly(methylenebiscyclohexylenecarbodiimide), and poly(isophoronecarbodiimide); poly(phenylenecarbodiimide), poly(naphthalenecarbodiimide); Examples of polycarbodiimides include aromatic polycarbodiimides such as poly(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 Lanxess AG.

[0080] As the acid anhydride resin, a resin having one or more acid anhydride groups in one molecule can be used, and a resin having two or more acid anhydride groups in one molecule is preferred. Specific examples of the acid anhydride resin include phthalic anhydride, tetrahydrophthalic anhydride, hexahydrophthalic anhydride, methyltetrahydrophthalic anhydride, methylhexahydrophthalic anhydride, methylnadic anhydride, hydrogenated methylnadic anhydride, trialkyltetrahydrophthalic anhydride, dodecenyl succinic anhydride, 5-(2,5-dioxotetrahydro-3-furanyl)-3-methyl-3-cyclohexene-1,2-dicarboxylic anhydride, trimellitic anhydride, pyromellitic anhydride, and benzophenonetetracarboxylic dianhydride. Examples of suitable anhydrides include anhydrides, 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 anhydrides such as styrene-maleic acid resins, which are copolymers of styrene and maleic acid. Commercially available acid anhydride resins include, for example, "HNA-100," "MH-700," "MTA-15," "DDSA," and "OSA" manufactured by New Japan Chemical Co., Ltd.; "YH-306" and "YH-307" manufactured by Mitsubishi Chemical Corporation; "HN-2200" and "HN-5500" manufactured by Resonac Corporation; and "EF-30," "EF-40," "EF-60," and "EF-80" manufactured by Cray Valley Chemical Industries, Ltd.

[0081] Specific examples of benzoxazine resins include "JBZ-OD100," "JBZ-OP100D," and "ODA-BOZ" manufactured by JFE Chemical Corporation; "Pd" and "Fa" manufactured by Shikoku Chemical Industry Co., Ltd.; and "HFB2006M" manufactured by Showa Polymer Co., Ltd.

[0082] Examples of cyanate ester resins include bifunctional cyanate resins such as bisphenol A dicyanate, polyphenol cyanate, oligo(3-methylene-1,5-phenylene cyanate), 4,4'-methylenebis(2,6-dimethylphenyl cyanate), 4,4'-ethylidene diphenyl dicyanate, hexafluorobisphenol A dicyanate, 2,2-bis(4-cyanate)phenylpropane, 1,1-bis(4-cyanatephenylmethane), bis(4-cyanate-3,5-dimethylphenyl)methane, 1,3-bis(4-cyanatephenyl-1-(methylethylidene))benzene, bis(4-cyanatephenyl)thioether, and bis(4-cyanatephenyl)ether; polyfunctional cyanate resins derived from phenol novolac, cresol novolac, etc.; and prepolymers in which these cyanate resins are partially triazine converted. Specific examples of cyanate ester resins include Lonza's "PT30" and "PT60" (phenol novolac-type multifunctional cyanate ester resins), "ULL-950S" (multifunctional cyanate ester resin), "BA230" and "BA230S75" (prepolymers in which part or all of bisphenol A dicyanate has been triazine-converted to form a trimer).

[0083] Examples of thiol-based resins include trimethylolpropane tris(3-mercaptopropionate), pentaerythritol tetrakis(3-mercaptobutyrate), and tris(3-mercaptopropyl)isocyanurate.

[0084] The active group equivalent of the (D-2) curing agent is preferably 50 g / eq. to 3,000 g / eq., more preferably 100 g / eq. to 1,000 g / eq., even more preferably 100 g / eq. to 500 g / eq., and still more preferably 100 g / eq. to 300 g / eq. The active group equivalent represents the mass of the (D-2) curing agent per equivalent of the active group.

[0085] When the number of epoxy groups in the (D-1) epoxy resin is taken as 1, the number of active groups in the (D-2) curing agent is preferably 0.01 or more, more preferably 0.1 or more, even more preferably 0.5 or more, and preferably 10 or less, more preferably 5 or less, and even more preferably 3 or less. The active groups in the (D-2) curing agent are active hydroxyl groups, etc., and vary depending on the type of curing agent. The number of epoxy groups in the (D-1) epoxy resin is the total value for all epoxy resins obtained by dividing the mass of the nonvolatile components of each epoxy resin by the epoxy equivalent. The number of active groups in the (D-2) curing agent is the total value for all curing agents obtained by dividing the mass of the nonvolatile components of each curing agent by the active group equivalent.

[0086] In the resin composition of the present invention, the content of component (D-2) is preferably 0.5% by mass or more, more preferably 1.0% by mass or more, and even more preferably 1.3% by mass or more, and is preferably 3.0% by mass or less, more preferably 2.0% by mass or less, and even more preferably 1.5% by mass or less, when the non-volatile components of the resin composition are taken as 100% by mass. When the amount (mass %) of the (D-2) curing agent is within the above range, the relative magnetic permeability of the cured product of the resin composition can be effectively improved.

[0087] In the resin composition of the present invention, the content of component (D-2) is preferably 30% by mass or more, more preferably 35% by mass or more, and even more preferably 40% by mass or more, and is preferably 60% by mass or less, more preferably 50% by mass or less, and even more preferably 45% by mass or less, when the resin components of the resin composition are taken as 100% by mass. When the content (mass %) of the (D-2) curing agent is within the above range, the relative magnetic permeability of the cured product of the resin composition can be effectively improved.

[0088] The range of the weight average molecular weight (Mw) of the (D) thermosetting resin can usually be the same as the range of the weight average molecular weight of the (D-1) epoxy resin described above.

[0089] In the resin composition of the present invention, the content of component (D) is preferably 2% by mass or more, more preferably 2.5% by mass or more, and even more preferably 2.8% by mass or more, and is preferably 5% by mass or less, more preferably 4% by mass or less, and even more preferably 3% by mass or less, when the non-volatile components of the resin composition are taken as 100% by mass. When the content (mass%) of the thermosetting resin (D) is within the above range, the relative magnetic permeability of the cured product of the resin composition can be effectively improved.

[0090] In the resin composition of the present invention, the content of component (D) is preferably 60% by mass or more, more preferably 70% by mass or more, and even more preferably 80% by mass or more, and is preferably 90% by mass or less, more preferably 88% by mass or less, and even more preferably 87% by mass or less, when the resin components of the resin composition are taken as 100% by mass. When the content (mass%) of the thermosetting resin (D) is within the above range, the relative magnetic permeability of the cured product of the resin composition can be effectively improved.

[0091] <(E) Other Magnetic Powders According to the First Embodiment> The resin composition according to the first embodiment of the present invention may further contain, as an optional component, a magnetic powder other than the magnetic powders (a) to (c) (also referred to as "(E) other magnetic powder" or "(E) component") in addition to the magnetic powders (a) to (c) and component (D) described above.

[0092] As the (E) other magnetic powder, particles of a material having a relative magnetic permeability greater than 1 can be used. The material of the (E) other magnetic powder is, for example, an inorganic material, and may be a soft magnetic material or a hard magnetic material. Furthermore, the material of the (E) other magnetic powder may be used alone or in combination of two or more types. Therefore, the (E) other magnetic powder may be a soft magnetic powder, a hard magnetic powder, or a combination of a soft magnetic powder and a hard magnetic powder. In particular, the (E) other magnetic powder preferably contains a soft magnetic powder, and more preferably contains only a soft magnetic powder.

[0093] (E) Other magnetic powders include, for example, magnetic metal oxide powders and magnetic metal powders.

[0094] Examples of magnetic metal oxide powders include ferrite-based magnetic powders, and iron oxide powders such as iron oxide powder (III) and triiron tetroxide powder.

[0095] Examples of ferrite-based magnetic materials include Mn-based ferrite, Mn-Mg-based ferrite, Mn-Mg-Sr-based ferrite, Mg-Zn-based ferrite, Mg-Sr-based ferrite, Zn-Mn-based ferrite, Cu-Zn-based ferrite, Ni-Zn-based ferrite, Ni-Zn-Cu-based ferrite, Ba-Zn-based ferrite, Ba-Mg-based ferrite, Ba-Ni-based ferrite, Ba-Co-based ferrite, Ba-Ni-Co-based ferrite, and Y-based ferrite.

[0096] 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.

[0097] When the resin composition of the present invention contains (E) other magnetic powders, it is preferable to adjust the amount of component (E) so that the magnetic powders (a) to (c) fall within the above-mentioned content ranges.

[0098] When the resin composition of the present invention contains (E) other magnetic powder, the content of component (E) may be 0 vol% or more than 0 vol%, based on 100 vol% of the non-volatile components of the resin composition, and is preferably 0.1 vol% or more, more preferably 1 vol% or more, even more preferably 3 vol% or more, and is preferably 25 vol% or less, more preferably 15 vol% or less, even more preferably 10 vol% or less.

[0099] When the resin composition of the present invention contains (E) other magnetic powder, the content of component (E) may be 0% by mass or more, and is preferably 0.1% by mass or more, more preferably 1% by mass or more, and even more preferably 3% by mass or more, and is preferably 25% by mass or less, more preferably 15% by mass or less, and even more preferably 10% by mass or less, when the non-volatile components of the resin composition are taken as 100% by mass.

[0100] <Thermoplastic resin (F) according to the first embodiment> The resin composition according to the first embodiment of the present invention may further contain a thermoplastic resin (also referred to as "(F) thermoplastic resin" or "(F) component") as an optional component in combination with the magnetic powders (a) to (c), component (D), and component (E) described above. The (F) thermoplastic resin does not include those corresponding to the above-mentioned component (D). The (F) thermoplastic resin can effectively improve the mechanical properties of the cured resin composition.

[0101] Examples of the (F) thermoplastic resin include phenoxy resin, polyimide resin, polyvinyl acetal resin, polyolefin resin, polybutadiene resin, polyamideimide resin, polyetherimide resin, polysulfone resin, polyethersulfone resin, polyphenylene ether resin, polycarbonate resin, polyetheretherketone resin, polyester resin, etc. The (F) thermoplastic resin may be used alone or in combination of two or more.

[0102] Examples of phenoxy resins include phenoxy resins having one or more skeletons selected from the group consisting of bisphenol A, bisphenol F, bisphenol S, bisphenolacetophenone, novolac, biphenyl, fluorene, dicyclopentadiene, norbornene, naphthalene, anthracene, adamantane, terpene, and trimethylcyclohexane. The terminal of the phenoxy resin may be any functional group such as a phenolic hydroxyl group or an epoxy group. Specific examples of phenoxy resins include "1256" and "4250" manufactured by Mitsubishi Chemical Corporation (both of which are phenoxy resins containing a bisphenol A skeleton); "YX8100" manufactured by Mitsubishi Chemical Corporation (phenoxy resin containing a bisphenol S skeleton); "YX6954" manufactured by Mitsubishi Chemical Corporation (phenoxy resin containing a bisphenol acetophenone skeleton); "FX280" and "FX293" manufactured by Nippon Steel Chemical & Material Co., Ltd.; "YL7500BH30," "YX6954BH30," "YX7553," "YX7553BH30," "YL7769BH30," "YL6794," "YL7213," "YL7290," "YL7482," and "YL7891BH30" manufactured by Mitsubishi Chemical Corporation; and the like.

[0103] Specific examples of polyimide resins include "SLK-6100" manufactured by Shin-Etsu Chemical Co., Ltd., and "Rikacoat SN20" and "Rikacoat PN20" manufactured by New Japan Chemical Co., Ltd. Specific examples of polyimide resins also include modified polyimides such as linear polyimides obtained by reacting bifunctional hydroxyl group-terminated polybutadiene, a diisocyanate compound, and a tetrabasic acid anhydride (polyimides described in JP-A No. 2006-37083), and polysiloxane skeleton-containing polyimides (polyimides described in JP-A Nos. 2002-12667 and 2000-319386).

[0104] Examples of polyvinyl acetal resins include polyvinyl formal resins and polyvinyl butyral resins, with polyvinyl butyral resins being preferred. Specific examples of polyvinyl acetal resins include S-LEC BH series, BX series (e.g., BX-5Z), KS series (e.g., KS-1), BL series, and BM series manufactured by Sekisui Chemical Co., Ltd.

[0105] Examples of polyolefin resins include ethylene copolymer resins such as low-density polyethylene, very low-density polyethylene, high-density polyethylene, ethylene-vinyl acetate copolymer, ethylene-ethyl acrylate copolymer, and ethylene-methyl acrylate copolymer; and polyolefin polymers such as polypropylene and ethylene-propylene block copolymer.

[0106] Examples of polybutadiene resins include hydrogenated polybutadiene skeleton-containing resins, hydroxy group-containing polybutadiene resins, phenolic hydroxy group-containing polybutadiene resins, carboxy group-containing polybutadiene resins, acid anhydride group-containing polybutadiene resins, epoxy group-containing polybutadiene resins, isocyanate group-containing polybutadiene resins, urethane group-containing polybutadiene resins, and polyphenylene ether-polybutadiene resins.

[0107] Specific examples of polyamide-imide resins include "Vylomax HR11NN" and "Vylomax HR16NN" manufactured by Toyobo Co., Ltd. Specific examples of polyamide-imide resins also include modified polyamide-imides such as "KS9100" and "KS9300" (polysiloxane skeleton-containing polyamide-imides) manufactured by Hitachi Chemical Co., Ltd.

[0108] A specific example of the polyethersulfone resin is "PES5003P" manufactured by Sumitomo Chemical Co., Ltd.

[0109] Specific examples of polysulfone resins include polysulfones "P1700" and "P3500" manufactured by Solvay Advanced Polymers.

[0110] A specific example of the polyphenylene ether resin is "NORYL SA90" manufactured by SABIC, etc. A specific example of the polyetherimide resin is "Ultem" manufactured by GE, etc.

[0111] Examples of polycarbonate resins include hydroxyl group-containing carbonate resins, phenolic hydroxyl group-containing carbonate resins, carboxyl group-containing carbonate resins, acid anhydride group-containing carbonate resins, isocyanate group-containing carbonate resins, and urethane group-containing carbonate resins. Specific examples of polycarbonate resins include "FPC0220" manufactured by Mitsubishi Gas Chemical Company, Inc., "T6002" and "T6001" (polycarbonate diols) manufactured by Asahi Kasei Corporation, and "C-1090," "C-2090," and "C-3090" (polycarbonate diols) manufactured by Kuraray Co., Ltd. Specific examples of polyether ether ketone resins include "Sumiploy K" manufactured by Sumitomo Chemical Co., Ltd.

[0112] Examples of polyester resins include polyethylene terephthalate resin, polyethylene naphthalate resin, polybutylene terephthalate resin, polybutylene naphthalate resin, polytrimethylene terephthalate resin, polytrimethylene naphthalate resin, and polycyclohexane dimethyl terephthalate resin.

[0113] The weight average molecular weight (Mw) of the (F) thermoplastic resin is preferably greater than 5,000, more preferably at least 8,000, even more preferably at least 10,000, and still more preferably at least 20,000. There is no particular upper limit, and it can be, for example, 1,000,000 or less, 500,000 or less, or 100,000 or less.

[0114] When the resin composition of the present invention contains a thermoplastic resin (F), the content of the component (F) is preferably 0.1% by mass or more, more preferably 0.2% by mass or more, and even more preferably 0.3% by mass or more, and is preferably 1% by mass or less, more preferably 0.7% by mass or less, and even more preferably 0.5% by mass or less, based on 100% by mass of the non-volatile components of the resin composition.

[0115] When the resin composition of the present invention contains a thermoplastic resin (F), the content of the component (F) is preferably 5% by mass or more, more preferably 8% by mass or more, and even more preferably 10% by mass or more, and is preferably 15% by mass or less, more preferably 13% by mass or less, and even more preferably 12% by mass or less, based on 100% by mass of the resin components of the resin composition.

[0116] <(G) 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 (also referred to as "(G) curing accelerator" or "(G) component") as an optional component in combination with the magnetic powders (a) to (c) and components (D) to (F) described above. The (G) curing accelerator does not include the magnetic powders (a) to (c) and components (D) to (F) described above. The (G) curing accelerator functions as a catalyst for the reaction of the (D) thermosetting resin, and can therefore accelerate the curing of the resin composition.

[0117] Examples of the (G) curing accelerator include imidazole-based curing accelerators, phosphorus-based curing accelerators, amine-based curing accelerators, guanidine-based curing accelerators, metal-based curing accelerators, and urea-based curing accelerators. One (G) curing accelerator may be used alone, or two or more (G) curing accelerators may be used in combination. Among these, imidazole-based curing accelerators and phosphorus-based curing accelerators are preferred, and imidazole-based curing accelerators are more preferred.

[0118] 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, 1-benzyl-2-phenylimidazole, 1-cyanoethyl-2-methylimidazole, 1-cyanoethyl-2-undecylimidazole, 1-cyanoethyl-2-ethyl-4-methylimidazole, 1-cyanoethyl-2-phenylimidazole, 1-cyanoethyl-2-undecylimidazole, 1-cyanoethyl-2-phenylimidazolium trimellitate, 1-cyanoethyl-2-phenylimidazolium trimellitate, 2,4-diamino-6-[2'-methylimidazolyl-(1')]-ethyl-s-triazine, 2, 4-Diamino-6-[2'-undecylimidazolyl-(1')]-ethyl-s-triazine, 2,4-diamino-6-[2'-ethyl-4'-methylimidazolyl-(1')]-ethyl-s-triazine, 2,4-diamino-6-[2'-methylimidazolyl-(1')]-ethyl-s-triazine isocyanuric acid adduct, 2-phenylimidazole isocyanuric acid adduct, 2-phenyl-4,5-dihydroxymethylimidazole, 2-phenyl-4,5-dihydroxymethylimidazole, Examples of the imidazole compound include imidazole compounds such as 2-phenyl-4-methyl-5-hydroxymethylimidazole, 2,3-dihydro-1H-pyrrolo[1,2-a]benzimidazole, 1-dodecyl-2-methyl-3-benzylimidazolium chloride, 2-methylimidazoline, and 2-phenylimidazoline, as well as adducts of imidazole compounds with epoxy resins, and 2-ethyl-4-methylimidazole and 1-benzyl-2-phenylimidazole are preferred. As the imidazole-based curing accelerator, commercially available products may be used, and examples thereof include "P200-H50" manufactured by Mitsubishi Chemical Corporation; "Curezol 2MZ", "2E4MZ", "Cl1Z", "Cl1Z-CN", "Cl1Z-CNS", "Cl1Z-A", "2MZ-OK", "2MA-OK", "2MA-OK-PW", "2MZA-PW", "2PHZ", "2PHZ-PW", "1B2PZ", and "1B2PZ-10M" manufactured by Shikoku Chemicals Corporation.

[0119] Examples of the phosphorus-based curing accelerator include phosphonium salts and phosphines. Examples of the phosphonium salt include aliphatic phosphonium salts such as tetrabutylphosphonium bromide, tetrabutylphosphonium chloride, tetrabutylphosphonium acetate, tetrabutylphosphonium decanoate, tetrabutylphosphonium laurate, n-butylphosphonium tetraphenylborate, bis(tetrabutylphosphonium)pyromellitate, tetrabutylphosphonium hydrogenhexahydrophthalate, tetrabutylphosphonium 2,6-bis[(2-hydroxy-5-methylphenyl)methyl]-4-methylphenolate, and di-tert-butylmethylphosphonium tetraphenylborate; methyltriphenylphosphonium bromide, ethyltriphenylphosphonium bromide, and propyltriphenylphosphonium. bromide, butyltriphenylphosphonium bromide, benzyltriphenylphosphonium chloride, tetraphenylphosphonium bromide, p-tolyltriphenylphosphonium tetra-p-tolylborate, tetraphenylphosphonium tetraphenylborate, tetraphenylphosphonium tetra-p-tolylborate, triphenylethylphosphonium tetraphenylborate, tris(3-methylphenyl)ethylphosphonium tetraphenylborate, tris(2-methoxyphenyl)ethylphosphonium tetraphenylborate, (4-methylphenyl)triphenylphosphonium thiocyanate, tetraphenylphosphonium thiocyanate, and aromatic phosphonium salts such as butyltriphenylphosphonium thiocyanate.

[0120] Examples of phosphines include aliphatic phosphines such as tributylphosphine, tri-tert-butylphosphine, trioctylphosphine, di-tert-butyl(2-butenyl)phosphine, di-tert-butyl(3-methyl-2-butenyl)phosphine, and tricyclohexylphosphine; dibutylphenylphosphine, di-tert-butylphenylphosphine, methyldiphenylphosphine, ethyldiphenylphosphine, butyldiphenylphosphine, diphenylcyclohexylphosphine, triphenylphosphine, tri-o-tolylphosphine, tri-m-tolylphosphine, tri-p-tolylphosphine, tris(4-ethylphenyl)phosphine, tris(4-propylphenyl)phosphine, tris(4-isopropylphenyl)phosphine, tris(4-butylphenyl)phosphine, tris(4-tert-butylphenyl)phosphine, tris(2,4-dimethylphenyl)phosphine, and tris(2,5-dimethylphenyl)phosphine. tris(2,6-dimethylphenyl)phosphine, tris(3,5-dimethylphenyl)phosphine, tris(2,4,6-trimethylphenyl)phosphine, tris(2,6-dimethyl-4-ethoxyphenyl)phosphine, tris(2-methoxyphenyl)phosphine, tris(4-methoxyphenyl)phosphine, tris(4-ethoxyphenyl)phosphine, tris(4-tert-butoxyphenyl)phosphine, diphenyl-2-pyridylphosphine, 1,2- Examples include aromatic phosphines such as bis(diphenylphosphino)ethane, 1,3-bis(diphenylphosphino)propane, 1,4-bis(diphenylphosphino)butane, 1,2-bis(diphenylphosphino)acetylene, and 2,2'-bis(diphenylphosphino)diphenyl ether; aromatic phosphine-borane complexes such as triphenylphosphine-triphenylborane; and aromatic phosphine-quinone adducts such as triphenylphosphine-p-benzoquinone adduct.

[0121] As the phosphorus-based curing accelerator, commercially available products may be used, for example, "TBP-DA" manufactured by Hokko Chemical Industry Co., Ltd.

[0122] Examples of the amine curing accelerator include trialkylamines such as triethylamine and tributylamine, 4-dimethylaminopyridine, benzyldimethylamine, 2,4,6-tris(dimethylaminomethyl)phenol, 1,8-diazabicyclo(5,4,0)-undecene, 1,8-diazabicyclo[5,4,0]undecene-7,4-dimethylaminopyridine, and 2,4,6-tris(dimethylaminomethyl)phenol, with 4-dimethylaminopyridine being preferred. Commercially available amine curing accelerators may also be used, such as "PN-50," "PN-23," and "MY-25" manufactured by Ajinomoto Fine-Techno Co., Inc.

[0123] Examples of guanidine-based curing accelerators include dicyandiamide, 1-methylguanidine, 1-ethylguanidine, 1-cyclohexylguanidine, 1-phenylguanidine, 1-(o-tolyl)guanidine, dimethylguanidine, diphenylguanidine, trimethylguanidine, tetramethylguanidine, pentamethylguanidine, 1,5,7-triazabicyclo[4.4.0]dec-5-ene, and 7-methyl-1,5,7-triazabicyclo[4.4.0]dec-5-ene. Examples of suitable biguanide include 1-methylbiguanide, 1-ethylbiguanide, 1-n-butylbiguanide, 1-n-octadecylbiguanide, 1,1-dimethylbiguanide, 1,1-diethylbiguanide, 1-cyclohexylbiguanide, 1-allylbiguanide, 1-phenylbiguanide, and 1-(o-tolyl)biguanide. Of these, dicyandiamide and 1,5,7-triazabicyclo[4.4.0]dec-5-ene are preferred.

[0124] 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.

[0125] 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].

[0126] When the resin composition of the present invention contains a (G) curing accelerator, the content of the (G) component is preferably 0.001% by mass or more, more preferably 0.01% by mass or more, and preferably 0.05% by mass or less, more preferably 0.03% by mass or less, based on 100% by mass of the non-volatile components of the resin composition.

[0127] When the resin composition of the present invention contains a (G) curing accelerator, the content of the (G) component, when the resin components of the resin composition are taken as 100% by mass, is preferably 0.1% by mass or more, more preferably 0.3% by mass or more, even more preferably 0.5% by mass or more, and is preferably 1.5% by mass or less, more preferably 1% by mass or less, even more preferably 0.7% by mass or less.

[0128] <(H) Dispersant According to the First Embodiment> The resin composition according to the first embodiment of the present invention may combine the magnetic powders (a) to (c) and components (D) to (G) described above, and may further contain a dispersant (also referred to as "(H) dispersant" or "(H) component") as an optional component. The (H) dispersant does not include those corresponding to the above-mentioned components (D) to (G). The (H) dispersant can improve the dispersibility of the magnetic powders (a) to (c).

[0129] As the (H) dispersant, a compound capable of reducing the viscosity of the resin composition can be used. Examples of the (H) dispersant include phosphate ester-based dispersants, polyoxyalkylene-based dispersants, acetylene-based dispersants, silicone-based dispersants, anionic dispersants, and cationic dispersants. One type of (H) dispersant may be used alone, or two or more types may be used in combination. Among these, phosphate ester-based dispersants are preferred.

[0130] Among phosphate ester-based dispersants, polyether-type phosphate ester-based dispersants are preferred. Polyether-type phosphate ester-based dispersants are phosphate ester-based dispersants containing a poly(alkyleneoxy) structure in the molecule. Examples of polyether-type phosphate ester-based dispersants include polyoxyalkylene alkyl ether phosphate esters and polyoxyalkylene alkylphenyl ether phosphate esters. Among these, polyoxyalkylene alkyl ether phosphate esters are preferred.

[0131] The polyoxyalkylene alkyl ether phosphate ester may have a structure in which 1 to 3 alkyl-oxy-poly(alkyleneoxy) groups are bonded to the phosphorus atom of the phosphate. The number of alkyleneoxy units (repeating units) in the poly(alkyleneoxy) moiety in the alkyl-oxy-poly(alkyleneoxy) group is preferably 2 to 30, more preferably 3 to 20. The alkylene group in the poly(alkyleneoxy) moiety is preferably an alkylene group having 2 to 4 carbon atoms. Examples of such alkylene groups include an ethylene group, a propylene group, an isopropylene group, a butylene group, and an isobutyl group. Furthermore, the alkyl group in the alkyl-oxy-poly(alkyleneoxy) group is preferably an alkyl group having 6 to 30 carbon atoms, more preferably an alkyl group having 8 to 20 carbon atoms. Examples of such alkyl groups include decyl, undecyl, dodecyl, tridecyl, tetradecyl, pentadecyl, hexadecyl, heptadecyl, and octadecyl groups. When the polyoxyalkylene alkyl ether phosphate ester has multiple alkyl-oxy-poly(alkyleneoxy) groups, the multiple alkyl groups may be the same or different. Furthermore, the multiple alkylene groups may be the same or different.

[0132] The acid value of the polyether phosphate ester dispersant is preferably 10 or more, more preferably 15 or more, and is preferably 200 or less, more preferably 150 or less. The acid value can be measured by neutralization titration.

[0133] Commercially available examples of phosphate ester dispersants include polyether phosphate ester dispersants manufactured by Kusumoto Chemical Industries Co., Ltd. (e.g., the HIPLAAD series "ED152," "ED153," "ED154," "ED118," "ED174," and "ED251"); and the Phosphanol series "RS-410," "RS-610," and "RS-710" manufactured by Toho Chemical Industry Co., Ltd.

[0134] Examples of polyoxyalkylene dispersants include polyoxyethylene alkyl ethers, polyoxyethylene alkyl esters, polyoxyethylene sorbitan fatty acid esters, polyoxyethylene alkylphenyl ethers, polyoxyethylene alkylamines, polyoxyethylene alkylamides, etc. Commercially available examples of polyoxyalkylene dispersants include "AKM-0531," "AFB-1521," "SC-0505K," "SC-1015F," "SC-0708A," and "HKM-50A" from the "Marialim" series manufactured by NOF Corporation.

[0135] An example of an acetylene-based dispersant is acetylene glycol. Examples of commercially available acetylene-based dispersants include "82," "104," "440," "465," "485," and "Olefin Y" from the "Surfynol" series manufactured by Air Products and Chemicals Inc.

[0136] Examples of silicone-based dispersants include polyether-modified polydimethylsiloxane, polyether-modified siloxane, polyester-modified polydimethylsiloxane, etc. Examples of commercially available silicone-based dispersants include "BYK347" and "BYK348" manufactured by BYK-Chemie.

[0137] Examples of anionic dispersants include sodium polyacrylate, sodium dodecyl benzyl sulfonate, sodium laurate, ammonium polyoxyethylene alkyl ether sulfate, sodium carboxymethyl cellulose, etc. Commercially available examples of anionic dispersants include "PN-411" and "PA-111" manufactured by Ajinomoto Fine-Techno Co., Ltd., and "A-550" and "PS-1900" manufactured by Lion Corporation.

[0138] Examples of cationic dispersants include amino group-containing polyacrylate resins and amino group-containing polystyrene resins. Commercially available cationic dispersants include "161," "162," "164," "182," "2000," and "2001" manufactured by BYK-Chemie; "PB-821," "PB-822," "PB-824," and "PB-881" manufactured by Ajinomoto Fine-Techno Co., Ltd.; "V-216" and "V-220" manufactured by ISP Japan; and "Solsperse 13940," "Solsperse 24000," and "Solsperse 32000" manufactured by Lubrizol Corporation.

[0139] The dispersant (H) may be used alone or in combination of two or more.

[0140] When the resin composition of the present invention contains a dispersant (H), the content of the component (H) is preferably 0.01% by mass or more, more preferably 0.05% by mass or more, and even more preferably 0.1% by mass or more, and is preferably 1% by mass or less, more preferably 0.5% by mass or less, and even more preferably 0.3% by mass or less, based on 100% by mass of the non-volatile components of the resin composition.

[0141] When the resin composition of the present invention contains a dispersant (H), the content of the component (H) is preferably 1% by mass or more, more preferably 2% by mass or more, and even more preferably 2.5% by mass or more, and is preferably 5% by mass or less, more preferably 4% by mass or less, and even more preferably 3% by mass or less, based on 100% by mass of the resin components of the resin composition.

[0142] In the resin composition of the present invention, the content (mass%) of the (a) large-diameter magnetic powder is represented by "M(a)" and the content (mass%) of the (H) dispersant is represented by "M(H)" relative to 100% by mass of the nonvolatile components of the resin composition. In this case, the mass ratio of the (H) dispersant to the (a) large-diameter magnetic powder contained in the resin composition ((H) dispersant / (a) large-diameter magnetic powder) as a percentage can be expressed as "M(H) / M(a) × 100." The value of M(H) / M(a) × 100 is preferably 0.15 or more, more preferably 0.2 or more, even more preferably 0.25 or more, and preferably 0.5 or less, more preferably 0.4 or less, even more preferably 0.35 or less or 0.33 or less. When the value of M(H) / M(a) × 100 is within the above range, the relative magnetic permeability can be effectively improved in the low-frequency band, and further, the appearance of the resin composition when applied can be improved.

[0143] Furthermore, in the resin composition of the present invention, the content (mass %) of the (b) intermediate magnetic powder relative to 100 mass % of the nonvolatile components of the resin composition is represented by "M(b)." In this case, the mass ratio of the (H) dispersant to the (b) intermediate magnetic powder contained in the resin composition ((H) dispersant / (b) intermediate magnetic powder) as a percentage can be represented by "M(H) / M(b) × 100." The value of M(H) / M(b) × 100 is preferably 0.15 or greater, more preferably 0.2 or greater, even more preferably 0.23 or greater, and preferably 0.31 or less. When the value of M(H) / M(b) × 100 is within the above range, the relative magnetic permeability can be effectively improved in the low frequency band, and further, the appearance of the resin composition when applied can be improved.

[0144] In the resin composition of the present invention, the content (mass%) of the (c) small-diameter 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 (H) dispersant to the (c) small-diameter magnetic powder contained in the resin composition ((H) dispersant / (c) small-diameter magnetic powder) as a percentage can be represented by "M(H) / M(c) × 100." The value of M(H) / M(c) × 100 is preferably 0.5 or more, more preferably 0.6 or more, and even more preferably 0.7 or more, and is preferably 5 or less, more preferably 3 or less, and even more preferably 2 or less or 1.9 or less. When the value of M(H) / M(c) × 100 is within the above range, the relative magnetic permeability can be effectively improved in the low-frequency band, and further, the appearance of the resin composition when applied can be improved.

[0145] Furthermore, in the resin composition of the present invention, the mass ratio of the (H) dispersant to the total amount of the (a) large-diameter magnetic powder, (b) medium-diameter magnetic powder, and (c) small-diameter magnetic powder contained in the resin composition ((H) dispersant / ((a) large-diameter magnetic powder + (b) medium-diameter magnetic powder + (c) small-diameter magnetic powder)) can be expressed as a percentage by "M(H) / (M(a)+M(b)+M(c))×100". The value of M(H) / (M(a)+M(b)+M(c))×100 is preferably 0.05 or more, more preferably 0.1 or more, even more preferably 0.11 or more, and preferably 0.2 or less, more preferably 0.15 or less, even more preferably 0.13 or less. When the value of M(H) / (M(a)+M(b)+M(c))×100 is within the above range, the relative permeability can be effectively improved in the low frequency band, and further, the appearance of the resin composition when applied can be improved.

[0146] <(I) Optional Additive According to the First Embodiment> The resin composition according to the first embodiment of the present invention may further contain (I) optional additives in addition to the above-described components. Examples of the optional additives 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 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, red phosphorus), nitrogen-based flame retardants (e.g., melamine sulfate), halogen-based flame retardants, and inorganic flame retardants (e.g., antimony trioxide), and stabilizers such as borate-based stabilizers, titanate-based stabilizers, aluminate-based stabilizers, zirconate-based stabilizers, isocyanate-based stabilizers, carboxylic acid-based stabilizers, and carboxylic anhydride-based stabilizers. (I) The optional additives may be used singly or in combination of two or more.

[0147] <Solvent (J) according to the first embodiment> The resin composition according to the first embodiment of the present invention may further contain an optional (J) solvent as a volatile component in addition to the non-volatile components such as the magnetic powders (a) to (c) and components (D) to (I) described above.

[0148] As the (J) 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 components. 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 (J) may be used singly or in combination of two or more in any ratio.

[0149] In the resin composition of the present invention, the amount of (J) solvent is preferably small when the resin composition is in a paste form. The content of (J) solvent can be, for example, 5% by mass or less, based on 100% by mass of all components in the resin composition. When the content (mass%) of (J) solvent in the resin composition is small, it is possible to suppress the generation of voids due to the evaporation of (J) solvent, and further, it is possible to improve the handleability and workability of the resin composition.

[0150] <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. Generally, among the components contained in the resin composition, volatile components such as the solvent (J) can be volatilized by the heat during thermal curing, but nonvolatile components such as the magnetic powders (a) to (c) and the components (D) to (I) 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.

[0151] The resin composition according to the first embodiment of the present invention can provide a cured product with improved relative magnetic permeability. Specifically, the cured product of this resin composition can have high relative magnetic permeability in the low frequency band (e.g., 10 MHz).

[0152] In one example, when the relative magnetic permeability of a cured product of the resin composition of the present invention is measured under conditions of a measurement frequency of 10 MHz and a room temperature of 23°C, the range of the relative magnetic permeability is preferably 39.0 or more, more preferably 39.5 or more, and even more preferably 40.0 or more. There is no particular upper limit, and it can be, for example, 80.0 or less, 75.0 or less, 70.0 or less, etc. The relative magnetic permeability of the cured product of the resin composition can be measured by the method described in <Test Example 2: Measurement and Evaluation of Relative Magnetic Permeability> in the Examples below.

[0153] The resin composition according to the first embodiment of the present invention can have an excellent appearance when applied. In one example, when the resin composition is applied uniformly with a doctor blade, the occurrence of streaks during application can be suppressed.

[0154] Although there are no particular limitations on the properties of the resin composition of the present invention, it is preferably 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 paste-like resin composition by using a liquid thermosetting resin such as a liquid epoxy resin. When the amount of (J) solvent in the resin composition is small, it is possible to suppress the generation of voids due to the evaporation of (J) solvent, and further, it is possible to achieve excellent handleability and workability.

[0155] Taking advantage of the excellent properties described above, the resin composition of the present invention 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 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.

[0156] <Method of manufacturing resin composition according to first embodiment> The method for producing a resin composition according to the first embodiment of the present invention is not particularly limited as long as it can achieve the above-mentioned configuration. As described above, the resin composition of the present invention is characterized by containing specific contents of (a) large-diameter magnetic powder, (b) medium-diameter magnetic powder, and (c) small-diameter magnetic powder, and the magnetic powder raw material containing (a) large-diameter magnetic powder, the magnetic powder raw material containing (b) medium-diameter magnetic powder, and the magnetic powder raw material containing (c) small-diameter magnetic powder are mixed together and used so that the contents of the (a) large-diameter magnetic powder, (b) medium-diameter magnetic powder, and (c) small-diameter magnetic powder in the resin composition fall within the above-mentioned predetermined range. Alternatively, a magnetic powder raw material containing (a) large-diameter magnetic powder and (b) medium-diameter magnetic powder may be mixed with a magnetic powder raw material containing (c) small-diameter magnetic powder. Alternatively, a magnetic powder raw material containing (a) large-diameter magnetic powder may be mixed with a magnetic powder raw material containing (b) medium-diameter magnetic powder and (c) small-diameter magnetic powder. Alternatively, a magnetic powder raw material containing (a) large-diameter magnetic powder, (b) medium-diameter magnetic powder, and (c) small-diameter magnetic powder may be used singly or in combination. The magnetic powder and the above-mentioned components (D) to (J) may be mixed partially or entirely simultaneously or sequentially. The temperature may be adjusted appropriately during the mixing process of each component, and thus heating and / or cooling may be performed temporarily or throughout the mixture. Furthermore, stirring or shaking may be performed during the mixing process of each component. 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.

[0157] <Outline of method for producing resin composition according to second embodiment> Below, an example of a method for producing a resin composition that is particularly suitable for producing a resin composition containing specific amounts of (a) large-diameter magnetic powder, (b) medium-diameter magnetic powder, and (c) small-diameter magnetic powder will be described.

[0158] The method for producing a resin composition according to the second embodiment of the present invention (hereinafter also referred to as the "production method of the present invention") is as follows: (A) an iron alloy magnetic powder having an average particle size of more than 20 μm and not more than 50 μm; (B) an iron alloy magnetic powder having an average particle size of more than 2 μm and not more than 20 μm; (C) an iron alloy magnetic powder having an average particle size of 2 μm or less; (D) a thermosetting resin; In the following explanation, "(A) iron alloy magnetic powder having an average particle size of more than 20 μm and not more than 50 μm" may be referred to as "(A) large-diameter magnetic raw powder." Also, "(B) iron alloy magnetic powder having an average particle size of more than 2 μm and not more than 20 μm" may be referred to as "(B) medium-diameter magnetic raw powder." Also, "(C) iron alloy magnetic powder having an average particle size of 2 μm or less" may be referred to as "(C) small-diameter magnetic raw powder."

[0159] The resin composition obtained by the production method of the present invention can be cured by thermally curing the (D) thermosetting resin to provide a cured product. The cured product thus obtained can have a high relative magnetic permeability in the low frequency band (e.g., 10 MHz). Furthermore, the resin composition obtained by the production method of the present invention can have an excellent appearance when applied.

[0160] As can be seen from the range of average particle diameters, the (A) large-diameter magnetic raw powder can include the (a) large-diameter magnetic powder described in the first embodiment. The (B) medium-diameter magnetic raw powder can include the (b) medium-diameter magnetic powder described in the first embodiment. The (C) small-diameter magnetic raw powder can include the (c) small-diameter magnetic powder described in the first embodiment. Therefore, the inventors believe that the mechanism by which the effects of this embodiment are obtained includes the combined action of the (a) large-diameter magnetic powder, (b) medium-diameter magnetic powder, and (c) 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.

[0161] <(A) Iron alloy magnetic powder having an average particle size of more than 20 μm and not more than 50 μm according to the second embodiment> A manufacturing method according to a second embodiment of the present invention includes mixing (A) large-diameter magnetic raw powder as component (A) with (B) medium-diameter magnetic raw powder, (C) small-diameter magnetic raw powder, and (D) thermosetting resin. The (A) large-diameter magnetic raw powder is an iron alloy-based magnetic powder having an average particle size within a specific range.

[0162] The (A) large-diameter magnetic raw powder is, for example, subjected to mixing in the form of particles. The (A) large-diameter magnetic raw powder may contain crystal grains in at least a portion of its particles, preferably contains crystal grains in the surface layer of the particles, more preferably contains crystal grains throughout the particles, and even more preferably consists of only crystal grains.

[0163] (A) The large-diameter magnetic raw powder has an average particle size D in the range of more than 20 μm and not more than 50 μm. 50 More specifically, (A) the average particle diameter D of the large-diameter magnetic raw powder 50 is preferably 21 μm or more, more preferably 23 μm or more, even more preferably 25 μm or more, and is preferably 60 μm or less, more preferably 50 μm or less, even more preferably 40 μm or less. 50 By using a manufacturing method including mixing (A) large-diameter magnetic raw powder having the above formula with (B) medium-diameter magnetic raw powder, (C) small-diameter magnetic raw powder, and (D) a thermosetting resin, it is possible to improve the relative permeability in the low frequency band and further to manufacture a resin composition that has excellent appearance when applied.

[0164] (A) Average particle size D of large-diameter magnetic raw powder 50 represents the volume-based median diameter. (A) Average particle diameter D of large-diameter magnetic raw powder 50 can be measured by a laser diffraction / scattering method based on the Mie scattering theory. Specifically, a laser diffraction / scattering particle size distribution analyzer is used to create (A) a particle size distribution of large-diameter 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.

[0165] In order to obtain the effects of the present invention more effectively, it is preferable that the (A) large-diameter magnetic raw powder contains nanocrystalline magnetic powder made of an iron alloy. The range of the nanocrystalline magnetic powder made of an iron alloy is as described in the first embodiment.

[0166] The (A) large-diameter magnetic raw material powder may be used alone or in combination of two or more.

[0167] (A) Large-diameter magnetic raw powder can be produced, for example, by an atomization method. Specific examples of methods for producing (A) large-diameter magnetic raw powder include the methods described in JP 2021-141267 A and JP 2021-158343 A. Commercially available (A) large-diameter magnetic raw powder may also be used. Examples of commercially available magnetic powders containing (A) large-diameter magnetic raw powder include "KUAMET NC1-53um," "KUAMET NC1-75um," "KUAMET NC1 053C03," "KUAMET NC1 075C03," and "KUAMET NC2-53um" manufactured by Epson Atmix. When (A) large-diameter magnetic raw powder is obtained from the market, commercially available magnetic powders may be classified as necessary. 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 that does not have the average particle diameter D 50 The value of may be adjusted appropriately.

[0168] The (A) large-diameter magnetic raw powder is preferably spherical. The aspect ratio of the particles of the (A) large-diameter magnetic raw powder may be in the same range as the aspect ratio of the (a) large-diameter magnetic powder.

[0169] The amount of (A) large-diameter magnetic raw material powder used in the manufacturing method of the present invention is preferably 60% by volume or more, more preferably 62% by volume or more, even more preferably 64% by volume or more or 65% by volume or more, and is preferably 75% by volume or less, more preferably 73% by volume or less, even more preferably 71% by volume or less or 70% by volume or less, assuming that the non-volatile components of the resin composition to be manufactured are 100% by volume. When the blending amount (volume %) of (A) large-diameter magnetic raw material powder is within the above range, the relative permeability can be effectively improved in the low-frequency band.

[0170] The amount of (A) large-diameter magnetic raw material powder used in the manufacturing method of the present invention is preferably 60% by mass or more, more preferably 70% by mass or more, even more preferably 75% by mass or more, and preferably 90% by mass or less, more preferably 85% by mass or less, even more preferably 82% by mass or less, when the non-volatile components of the resin composition to be manufactured are taken as 100% by mass. When the blending amount (mass %) of (A) large-diameter magnetic raw material powder is within the above range, the relative permeability can be effectively improved in the low frequency band.

[0171] The amount of (A) large-diameter magnetic raw powder used in the manufacturing method of the present invention is preferably 70% by volume or more, more preferably 75% by volume or more, even more preferably 78% by volume or more, and is preferably 90% by volume or less, more preferably 87% by volume or less, even more preferably 85% by volume or less, when the total magnetic powder mixed to manufacture the resin composition is taken as 100% by volume. When the amount (volume %) of (A) large-diameter magnetic raw powder in the total magnetic powder is within the above range, the relative permeability can be effectively improved in the low-frequency band.

[0172] The amount of (A) large-diameter magnetic raw powder used in the manufacturing method of the present invention is preferably 70% by mass or more, more preferably 75% by mass or more, even more preferably 78% by mass or more, and is preferably 90% by mass or less, more preferably 87% by mass or less, even more preferably 85% by mass or less, when the total magnetic powder mixed to manufacture the resin composition is taken as 100% by mass. When the amount (% by mass) of (A) large-diameter magnetic raw powder in the total magnetic powder is within the above range, the relative permeability can be effectively improved in the low-frequency band.

[0173] <(B) Iron alloy magnetic powder having an average particle size of more than 2 μm and 20 μm or less according to the second embodiment> A manufacturing method according to a second embodiment of the present invention includes mixing (B) intermediate magnetic raw powder as component (B) with (A) large-diameter magnetic raw powder, (C) small-diameter magnetic raw powder, and (D) thermosetting resin. The (B) intermediate magnetic raw powder is an iron alloy-based magnetic powder having an average particle size within a specific range. The (B) intermediate magnetic raw powder is, for example, subjected to mixing in the form of particles.

[0174] (B) The intermediate magnetic raw powder has an average particle size D in the range of more than 2 μm and not more than 20 μm. 50 More specifically, (B) the average particle diameter D of the intermediate magnetic raw material powder 50 is preferably 2.1 μm or more, more preferably 2.2 μm or more, even more preferably 2.3 μm or more, and is preferably 19 μm or less, more preferably 18 μm or less, even more preferably 17 μm or less. 50 By using a manufacturing method including mixing (B) intermediate magnetic raw powder having the average particle diameter D with (A) large-diameter magnetic raw powder, (C) small-diameter magnetic raw powder, and (D) a thermosetting resin, it is possible to improve the relative permeability in the low frequency band and to manufacture a resin composition that has an excellent appearance when applied. 50 represents the volume-based median diameter, and (A) the average particle diameter D of the large-diameter magnetic raw powder 50 can be measured by the same method.

[0175] (B) The intermediate magnetic raw powder is preferably at least one iron alloy magnetic powder selected from nanocrystalline magnetic powder made of iron alloy, iron alloy magnetic powder containing Ni, polycrystalline magnetic powder, and amorphous magnetic powder. The ranges of nanocrystalline magnetic powder made of iron alloy, iron alloy magnetic powder containing Ni, polycrystalline magnetic powder, and amorphous magnetic powder are as explained in the first embodiment.

[0176] The (B) intermediate magnetic raw material powder may be used alone or in combination of two or more kinds.

[0177] (B) The intermediate magnetic raw material powder may be a commercially available product. (B) Examples of commercially available magnetic powders including intermediate magnetic raw material powders include "KUAMET NC1-V1-38um," "ATFINE-NC1 PF3FA," "ATFINE-NC1 PF5FA," "ATFINE-NC1 PF10FA," "ATFINE-NC1 PF3FC124A," "ATFINE-NC1 PF5FC124A," and "ATFINE-NC1 PF10FC124A" manufactured by Epson Atmix (nanocrystalline magnetic powders); "AKT-PB-3Si(3)" and "AKT-PB(5)" manufactured by Mitsubishi Steel, Ltd.; "50%FE-50%NI PF-5F," "50%FE-50%NI PF-10F," and "50%FE-50%NI PF-20F" manufactured by Epson Atmix (iron alloy magnetic powders containing Ni); and "EA-SMP-10 PF3K" and "EA-SMP-10" manufactured by Epson Atmix. Examples of such magnetic powders include "AW02-08 PF5F", "EA-SMP-10 PF10F" (polycrystalline magnetic powders), and "AW02-08 PF3F", "AW02-08 PF5F", "AW02-08 PF8F", and "AW02-08 PF10F" (amorphous magnetic powders) manufactured by Epson Atmix Corporation. When (B) intermediate magnetic raw powders are purchased from the market, commercially available magnetic powders may be classified as necessary. For example, magnetic powders having an average particle size D in the above-mentioned range may be used. 50 The commercially available magnetic powder that does not have the average particle diameter D 50 The value of may be adjusted appropriately.

[0178] The (B) intermediate magnetic raw powder is preferably spherical. The range of aspect ratios of the particles of the (B) intermediate magnetic raw powder may be the same as the range of aspect ratios of the (b) intermediate magnetic powder.

[0179] The amount of (B) intermediate magnetic raw material powder used in the manufacturing method of the present invention is preferably 1 vol% or more, more preferably 2 vol% or more, and even more preferably 3 vol% or more, and is preferably 20 vol% or less, more preferably 16 vol% or less, and even more preferably 13 vol% or less, when the non-volatile components of the resin composition to be manufactured are taken as 100 vol%. When the blending amount (vol%) of (B) intermediate magnetic raw material powder is within the above range, it is possible to effectively improve the relative permeability in the low frequency band, and furthermore, it is possible to manufacture a resin composition that has excellent appearance when applied.

[0180] The amount of (B) intermediate magnetic raw material powder used in the production method of the present invention is preferably at least 1 mass%, more preferably at least 3 mass%, even more preferably at least 4 mass%, and is preferably at most 20 mass%, more preferably at most 17 mass%, even more preferably at most 15 mass%, assuming that the non-volatile components of the resin composition produced are 100 mass%. When the blending amount (mass%) of (B) intermediate magnetic raw material powder is within the above range, it is possible to effectively improve the relative permeability in the low frequency band, and further to produce a resin composition that has excellent appearance when applied.

[0181] The amount of (B) intermediate magnetic raw powder used in the manufacturing method of the present invention is preferably 1 vol% or more, more preferably 3 vol% or more, and even more preferably 4 vol% or more, and is preferably 20 vol% or less, more preferably 17 vol% or less, and even more preferably 15 vol% or less, when the total magnetic powder mixed to manufacture the resin composition is taken as 100 vol%. When the amount (vol%) of (B) intermediate magnetic raw powder in the total magnetic powder is within the above range, it is possible to effectively improve the relative magnetic permeability in the low frequency band, and furthermore, it is possible to manufacture a resin composition that has excellent appearance when applied.

[0182] The amount of (B) intermediate magnetic raw powder used in the manufacturing method of the present invention is preferably 1% by mass or more, more preferably 3% by mass or more, and even more preferably 4% by mass or more, relative to 100% by mass of the total amount of magnetic powder mixed to manufacture the resin composition, and is preferably 20% by mass or less, more preferably 17% by mass or less, and even more preferably 15% by mass or less. When the amount (mass %) of (B) intermediate magnetic raw powder in the total magnetic powder is within the above range, it is possible to effectively improve the relative magnetic permeability in the low frequency band, and further to manufacture a resin composition that has excellent appearance when applied.

[0183] The amount (volume %) of the (A) large-diameter magnetic raw powder is represented by "V(A)," and the amount (volume %) of the (B) medium-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) large-diameter magnetic raw powder to the (B) medium-diameter magnetic raw powder ((A) large-diameter magnetic raw powder / (B) medium-diameter magnetic raw powder) can be represented by "V(A) / V(B)." This volume ratio V(A) / V(B) is preferably 1 or more, more preferably 3 or more, and even more preferably 5 or more, and is preferably 25 or less, more preferably 20 or less, and even more preferably 17 or less. When the volume ratio V(A) / V(B) is within the above range, it is possible to effectively improve the relative permeability in the low-frequency band and produce a resin composition that has excellent appearance when applied.

[0184] The total volume % of the (A) large-diameter magnetic raw powder and the (B) medium-diameter magnetic raw powder can be expressed as "V(A) + V(B)." This total volume % V(A) + V(B) is preferably 70 volume % or more, more preferably 80 volume % or more, and even more preferably 84 volume % or more, and is preferably 97 volume % or less, and more preferably 95 volume % or less. When the total volume % V(A) + V(B) is within the above range, the relative permeability can be effectively improved in the low frequency band, and a resin composition with excellent appearance when applied can be produced.

[0185] <(C) Iron alloy magnetic powder having an average particle size of 2 μm or less according to the second embodiment> A manufacturing method according to a third embodiment of the present invention includes mixing (C) small-diameter magnetic raw powder as component (C) with (A) large-diameter magnetic raw powder, (B) medium-diameter magnetic raw powder, and (D) thermosetting resin. The (C) small-diameter magnetic raw powder is an iron alloy-based magnetic powder having a specific average particle size. The (C) small-diameter magnetic raw powder is, for example, in the form of particles, and is subjected to mixing.

[0186] (C) Small-diameter magnetic raw powder has an average particle size D of 2 μm or less. 50 More specifically, (C) the average particle diameter D of the small-diameter magnetic raw powder 50 (C) The average particle size D of the small-diameter magnetic raw material powder is preferably 1.9 μm or less, and more preferably 1.8 μm or less. 50 The lower limit of the average particle diameter D is not particularly limited, and may be, for example, 0.01 μm or more or 0.1 μm or more. 50 By using a manufacturing method including mixing (C) small-diameter magnetic raw powder having the average particle diameter D of (C) with (A) large-diameter magnetic raw powder, (B) medium-diameter magnetic raw powder, and (D) thermosetting resin, it is possible to improve the relative permeability in the low frequency band and to manufacture a resin composition that has excellent appearance when applied. 50 represents the volume-based median diameter, and (A) the average particle diameter D of the large-diameter magnetic raw powder 50 can be measured by the same method.

[0187] The range of the iron alloy forming the component (C), including the preferred range, is the same as the range of the iron alloy forming the small-diameter magnetic powder (c) according to the first embodiment.

[0188] The (C) small-diameter magnetic raw material powder may be used alone or in combination of two or more.

[0189] The (C) small-diameter magnetic raw powder may be a commercially available product. Examples of commercially available magnetic powders containing the (C) small-diameter magnetic raw powder include "G00129R" and "CVD iron powder (0.7 μm)" manufactured by JFE Mineral Co., Ltd. When the (C) 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 that does not have the average particle diameter D 50 The value of may be adjusted appropriately.

[0190] The (C) small-diameter magnetic raw powder is preferably spherical. The range of the aspect ratio of the particles of the (C) small-diameter magnetic raw powder may be the same as the range of the aspect ratio of the (c) small-diameter magnetic powder.

[0191] The amount of (C) small-diameter magnetic raw material powder used in the manufacturing method of the present invention is preferably 1 vol% or more, more preferably 2 vol% or more, and even more preferably 3 vol% or more, and is preferably 20 vol% or less, more preferably 16 vol% or less, and even more preferably 13 vol% or less, when the non-volatile components of the resin composition to be manufactured are taken as 100 vol%. When the blending amount (vol%) of (C) small-diameter magnetic raw material powder is within the above range, it is possible to effectively improve the relative permeability in the low frequency band, and further to manufacture a resin composition that has excellent appearance when applied.

[0192] The amount of (C) small-diameter magnetic raw material powder used in the production method of the present invention is preferably 1% by mass or more, more preferably 3% by mass or more, even more preferably 4% by mass or more, and preferably 20% by mass or less, more preferably 17% by mass or less, even more preferably 15% by mass or less, when the non-volatile components of the produced resin composition are taken as 100% by mass. When the blending amount (mass %) of (C) small-diameter magnetic raw material powder is within the above range, it is possible to effectively improve the relative permeability in the low frequency band, and further to produce a resin composition that has excellent appearance when applied.

[0193] The amount of (C) small-diameter magnetic raw powder used in the manufacturing method of the present invention is preferably 1% by volume or more, more preferably 3% by volume or more, even more preferably 4% by volume or more, and preferably 20% by volume or less, more preferably 18% by volume or less, even more preferably 16% by volume or less, when the total magnetic powder mixed to manufacture the resin composition is taken as 100% by volume. When the amount (volume %) of (C) small-diameter magnetic raw powder in the total magnetic powder is within the above range, it is possible to effectively improve the relative magnetic permeability in the low frequency band, and furthermore, it is possible to manufacture a resin composition that has excellent appearance when applied.

[0194] The amount of (C) small-diameter magnetic raw powder used in the manufacturing method of the present invention is preferably 1% by mass or more, more preferably 3% by mass or more, and even more preferably 4% by mass or more, relative to 100% by mass of the total amount of magnetic powder mixed to manufacture the resin composition, and is preferably 20% by mass or less, more preferably 18% by mass or less, and even more preferably 16% by mass or less. When the amount (mass %) of (C) small-diameter magnetic raw powder in the total magnetic powder is within the above range, it is possible to effectively improve the relative magnetic permeability in the low-frequency band, and further to manufacture a resin composition that has excellent appearance when applied.

[0195] The amount (volume %) of the (C) small-diameter 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) large-diameter magnetic raw powder to the (C) small-diameter magnetic raw powder ((A) large-diameter magnetic raw powder / (C) small-diameter magnetic raw powder) can be represented by "V(A) / V(C)." This volume ratio V(A) / V(C) is preferably 1 or more, more preferably 3 or more, even more preferably 4 or more, and is preferably 25 or less, more preferably 20 or less, and even more preferably 17 or less. When the volume ratio V(A) / V(C) is within the above range, it is possible to effectively improve the relative permeability in the low-frequency band, and furthermore, it is possible to produce a resin composition that has excellent appearance when applied.

[0196] The total volume % of the (A) large-diameter magnetic raw powder and the (C) small-diameter magnetic raw powder can be expressed as "V(A) + V(C)." This total volume % V(A) + V(C) is preferably 70 volume % or more, more preferably 80 volume % or more, and even more preferably 84 volume % or more, and is preferably 97 volume % or less, and more preferably 96 volume % or less. When the total volume % V(A) + V(C) is within the above range, the relative permeability can be effectively improved in the low frequency band, and a resin composition with excellent appearance when applied can be produced.

[0197] <(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) large-diameter magnetic raw powder, (B) medium-diameter magnetic raw powder, and (C) small-diameter magnetic raw powder. The (D) thermosetting resin according to the second embodiment may 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 may be the same as that described in the first embodiment. Therefore, in the manufacturing method according to the second embodiment, the amount of the (D-1) epoxy resin, the amount of the (D-2) curing agent, and the amount of the (D) thermosetting resin may be the same as that described in the first embodiment. The (D) thermosetting resin according to the second embodiment can achieve the same effects as the (D) thermosetting resin described in the first embodiment.

[0198] <(E) Other Magnetic Raw Material Powders According to the Second Embodiment> In the production method according to the second embodiment of the present invention, a magnetic raw material powder other than the components (A) to (C) (hereinafter also referred to as “(E) other magnetic raw material powder” or “component (E)”) may be further mixed as an optional component in combination with the components (A) to (D).

[0199] As the (E) other magnetic raw powder, particles of a material having a relative magnetic permeability greater than 1 can be used. The material of the (E) other magnetic raw powder is, for example, an inorganic material, and may be a soft magnetic material or a hard magnetic material. Furthermore, the material of the (E) other magnetic raw powder may be used alone or in combination of two or more types. Therefore, the (E) other magnetic raw powder may be a soft magnetic powder, a hard magnetic powder, or a combination of a soft magnetic powder and a hard magnetic powder. Furthermore, the (E) other magnetic raw powder may be used alone or in combination of two or more types. In particular, the (E) other magnetic raw powder preferably contains a soft magnetic powder, and more preferably contains only a soft magnetic powder.

[0200] (E) Examples of other magnetic powders include magnetic metal oxide powders and magnetic metal powders. The ranges of magnetic metal oxide powders and magnetic metal powders are as described above.

[0201] When (E) other magnetic raw material powder is mixed in the production method of the present invention, it is preferable to adjust the amount of component (E) so that the amounts of components (A) to (C) fall within the ranges described above.

[0202] The amount of component (E) used in the production method of the present invention may be 0% by volume or more than 0% by volume, and is preferably 0.1% by volume or more, more preferably 1% by volume or more, and even more preferably 3% by volume or more, relative to 100% by volume of the non-volatile components of the resin composition to be produced, and is preferably 25% by volume or less, more preferably 15% by volume or less, and even more preferably 10% by volume or less.

[0203] The amount of component (E) used in the production method of the present invention may be 0% by mass or more than 0% by mass, and is preferably 0.1% by mass or more, more preferably 1% by mass or more, and even more preferably 3% by mass or more, and is preferably 25% by mass or less, more preferably 15% by mass or less, and even more preferably 10% by mass or less, assuming that the non-volatile components of the resin composition to be produced are 100% by mass.

[0204] <Thermoplastic resin (F) according to the second embodiment> In the production method according to the second embodiment of the present invention, a thermoplastic resin (F) may be further mixed as an optional component in combination with the above-described components (A) to (E). The thermoplastic resin (F) according to the second embodiment may be the same as the thermoplastic resin (F) according to the first embodiment. The amount of the thermoplastic resin (F) used in the production method according to the second embodiment may be the same as that described in the first embodiment. The thermoplastic resin (F) according to the second embodiment can provide the same effects as the thermoplastic resin (F) described in the first embodiment.

[0205] <(G) Curing Accelerator According to Second Embodiment> In the production method according to the second embodiment of the present invention, a (G) curing accelerator may be further mixed as an optional component in combination with the above-described components (A) to (F). The (G) curing accelerator according to the second embodiment may be the same as the (G) curing accelerator according to the first embodiment. The amount of the (G) curing accelerator used in the production method according to the second embodiment may be the same as that described in the first embodiment. The (G) curing accelerator according to the second embodiment can provide the same effects as the (G) curing accelerator described in the first embodiment.

[0206] <(H) Dispersant According to the Second Embodiment> In the production method according to the second embodiment of the present invention, a dispersant (H) may be further mixed as an optional component in combination with the components (A) to (G). The dispersant (H) according to the second embodiment may be the same as the dispersant (H) according to the first embodiment. The amount of dispersant (H) used in the production method according to the second embodiment may be the same as that described in the first embodiment. The dispersant (H) according to the second embodiment can achieve the same effects as the dispersant (H) described in the first embodiment.

[0207] In the manufacturing method of the present invention, the blending amount (mass%) of the (A) large-diameter magnetic raw material powder is represented by "M(A)" and the blending amount (mass%) of the (H) dispersant is represented by "M(H)" relative to 100% by mass of the nonvolatile components of the resin composition produced. In this case, the mass ratio of the (H) dispersant to the (A) large-diameter magnetic raw material powder ((H) dispersant / (A) large-diameter magnetic raw material powder) can be expressed as "M(H) / M(A) x 100." The value of M(H) / M(A) x 100 is preferably 0.1 or more, more preferably 0.11 or more, even more preferably 0.12 or more, and preferably 0.17 or less, more preferably 0.15 or less, and even more preferably 0.14 or less. When the value of M(H) / M(A) x 100 is within the above range, the relative permeability can be effectively improved in the low-frequency band.

[0208] In the manufacturing method of the present invention, the blending amount (mass %) of the (B) intermediate magnetic raw powder relative to 100 mass % of the nonvolatile components of the resin composition produced is represented by "M(B)." In this case, the mass ratio of the (H) dispersant to the (B) intermediate magnetic raw powder ((H) dispersant / (B) intermediate magnetic raw powder) as a percentage can be expressed as "M(H) / M(B) × 100." The value of M(H) / M(B) × 100 is preferably 0.5 or more, more preferably 0.6 or more, and even more preferably 0.7 or more, and is preferably 5 or less, more preferably 3.5 or less, and even more preferably 2.5 or less or 2.3 or less. When the value of M(H) / M(B) × 100 is within the above range, the relative permeability can be effectively improved in the low frequency band, and a resin composition with excellent appearance when applied can be produced.

[0209] In the manufacturing method of the present invention, the blending amount (mass %) of the (C) small-diameter magnetic raw material powder relative to 100 mass % of the nonvolatile components of the resin composition produced is represented by "M(C)." In this case, the mass ratio of the (H) dispersant to the (C) small-diameter magnetic raw material powder ((H) dispersant / (C) small-diameter magnetic raw material powder) as a percentage can be expressed as "M(H) / M(C) × 100." The value of M(H) / M(C) × 100 is preferably 0.5 or more, more preferably 0.6 or more, and even more preferably 0.7 or more, and is preferably 5 or less, more preferably 3.5 or less, and even more preferably 2.5 or less or 2.3 or less. When the value of M(H) / M(C) × 100 is within the above range, the relative permeability can be effectively improved in the low-frequency band, and a resin composition with excellent appearance when applied can be produced.

[0210] Furthermore, in the manufacturing method of the present invention, the mass ratio of the (H) dispersant to the total amount of the (A) large-diameter magnetic raw powder, the (B) medium-diameter magnetic raw powder, and the (C) small-diameter magnetic raw powder ((H) dispersant / ((A) large-diameter magnetic raw powder + (B) medium-diameter magnetic raw powder + (C) small-diameter magnetic raw powder)) can be expressed as a percentage by "M(H) / (M(A)+M(B)+M(C))×100". The value of M(H) / (M(A)+M(B)+M(C))×100 is preferably 0.05 or more, more preferably 0.08 or more, even more preferably 0.1 or more, and is preferably 0.13 or less, more preferably 0.12 or less, even more preferably 0.11 or less. When the value of M(H) / (M(A)+M(B)+M(C))×100 is within the above range, the relative permeability can be effectively improved in the low frequency band, and a resin composition with excellent appearance when applied can be produced.

[0211] <(I) Optional Additives According to the Second Embodiment> In the production method according to the second embodiment of the present invention, an optional additive (I) may be further mixed as an optional component in combination with the components (A) to (H). The optional additive (I) according to the second embodiment may be the same as the optional additive (I) according to the first embodiment.

[0212] <Solvent (J) according to the second embodiment> In the production method according to the second embodiment of the present invention, a (J) solvent may be further mixed as an optional component in combination with the above-described components (A) to (I). The (J) solvent according to the second embodiment may be the same as the (J) solvent according to the first embodiment. The amount of the (J) solvent used in the production method according to the second embodiment may be in the same range as that described in the first embodiment.

[0213] <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) large-diameter magnetic raw powder, (B) medium-diameter magnetic raw powder, (C) small-diameter magnetic raw powder, and (D) thermosetting resin. If necessary, some or all of optional components such as (E) other magnetic powders, (F) thermoplastic resin, (G) curing accelerator, (H) dispersant, (I) optional additive, and (J) solvent may be mixed in combination with the (A) large-diameter magnetic raw powder, (B) medium-diameter magnetic raw powder, (C) small-diameter magnetic raw powder, and (D) thermosetting resin.

[0214] 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.

[0215] <Resin composition produced by the production method according to the second embodiment> The resin composition produced by the production method according to the second embodiment of the present invention may contain the above-described components mixed together. Therefore, the resin composition produced may contain (A) large-diameter magnetic raw powder, (B) medium-diameter magnetic raw powder, (C) small-diameter magnetic raw powder, and (D) thermosetting resin, and may further contain, as necessary, (E) other magnetic powder, (F) thermoplastic resin, (G) curing accelerator, (H) dispersant, (I) optional additive, and (J) solvent. Therefore, the amounts of the (A) large-diameter magnetic raw powder, (B) medium-diameter magnetic raw powder, (C) small-diameter magnetic raw powder, (D) thermosetting resin, (E) other magnetic powder, (F) thermoplastic resin, (G) curing accelerator, (H) dispersant, (I) optional additive, and (J) solvent contained in the resin composition may be within the ranges described above. The resin composition according to the first embodiment may also be produced by the production method according to the second embodiment of the present invention.

[0216] The resin composition obtained 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. Generally, among the components contained in the resin composition, volatile components such as the solvent (J) can be volatilized by the heat during thermal curing, but non-volatile components such as components (A) to (G) do not volatilize by the heat during thermal curing. Therefore, the cured product of the resin composition produced can contain the non-volatile components of the resin composition or their reaction products.

[0217] The resin composition obtained by the manufacturing method according to the second embodiment of the present invention can provide a cured product with improved relative magnetic permeability. Specifically, the cured product of this resin composition can have high relative magnetic permeability in the low frequency band (e.g., 10 MHz).

[0218] In one example, when the relative magnetic permeability of a cured product of the resin composition produced 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 39.0 or more, more preferably 39.5 or more, and even more preferably 40.0 or more, 41.0 or more, 42.0 or more, 43.0 or more, 44.0 or more, 45.0 or more, or 46.0 or more. There is no particular upper limit, and it can be, for example, 80.0 or less, 75.0 or less, 70.0 or less, etc.

[0219] The resin composition produced by the production method according to the second embodiment of the present invention can have an excellent appearance when applied, similar to the resin composition according to the first embodiment.

[0220] 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.

[0221] The resin composition obtained 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.

[0222] <Magnetic Paste According to Third Embodiment> The magnetic paste according to the third embodiment of the present invention contains at least one of the resin composition according to the first embodiment and the resin composition produced by the production method according to the second embodiment. The magnetic paste is generally a fluid paste containing a resin composition, and therefore can be preferably used for filling holes by printing. This magnetic paste may contain only the resin composition described above, or may contain optional components in combination with the resin composition. Preferably, the paste-like resin composition itself can be used as the magnetic paste.

[0223] The magnetic paste is preferably in a paste form at 23°C. The viscosity of this magnetic paste at 23°C is preferably 20 Pa·s or more, more preferably 25 Pa·s or more, even more preferably 30 Pa·s or more, and particularly preferably 50 Pa·s or more, and is preferably 200 Pa·s or less, more preferably 180 Pa·s or less, and even more preferably 160 Pa·s or less. The viscosity can be measured, for example, using an E-type viscometer (Toki Sangyo Co., Ltd. "RE-80U" with a 3° x R9.7 rotor) under measurement conditions of a measurement sample volume of 0.22 ml and a rotation speed of 5 rpm.

[0224] <Resin sheet according to the fourth embodiment> A resin sheet according to a fourth 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, and preferably contains only a resin composition. As the resin composition, at least one of the resin composition according to the first embodiment and the resin composition obtained by the manufacturing method according to the second embodiment can be used.

[0225] 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 can be, for example, 5 μm or more, 10 μm or more, etc.

[0226] Examples of the support include a film made of a plastic material, a metal foil, and release paper, with a film made of a plastic material and a metal foil being preferred.

[0227] When a film of a plastic material is used as the support, examples of the plastic material include polyesters such as polyethylene terephthalate (hereinafter sometimes abbreviated as "PET") and polyethylene naphthalate (hereinafter sometimes abbreviated as "PEN"), polycarbonate (hereinafter sometimes abbreviated as "PC"), acrylic polymers such as polymethyl methacrylate (PMMA), cyclic polyolefins, triacetyl cellulose (TAC), polyether sulfide (PES), polyether ketone, polyimide, etc. Among these, polyethylene terephthalate and polyethylene naphthalate are preferred, and inexpensive polyethylene terephthalate is more preferred.

[0228] 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.).

[0229] The surface of the support that is to be bonded to the resin composition layer may be subjected to a matte treatment or a corona treatment.

[0230] 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 release agents include alkyd resin-based release agents such as "SK-1," "AL-5," and "AL-7" manufactured by Lintec Corporation. Commercially available support with a release layer includes PET films having a release layer primarily composed of 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 Ltd.

[0231] 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.

[0232] 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 providing the protective film, adhesion of dust and the like to the surface of the resin composition layer and scratches can be suppressed.

[0233] The resin sheet can be produced, for example, by applying the resin composition to a support using a die coater or the like to form a resin composition layer. If necessary, the resin composition may be mixed with an organic solvent and then applied to the support. When an organic solvent is used, drying may be performed after application, if necessary.

[0234] Drying may be carried out by, for example, heating, blowing hot air, or the like. Drying conditions are not particularly limited, but drying is carried out so that the content of organic solvent in the resin composition layer becomes 10% by mass or less, preferably 5% by mass or less. Although it varies depending on the components contained in the resin composition, a resin composition layer can be formed by drying at 50°C to 150°C for 3 to 10 minutes.

[0235] 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.

[0236] <Circuit board according to the fifth embodiment> A circuit board according to a fifth embodiment of the present invention includes a cured resin composition, which may be at least one of the resin composition according to the first embodiment and the resin composition obtained by the production method according to the second embodiment.

[0237] 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.

[0238] <Circuit board according to the first example> 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) A step of subjecting the cured product to a roughening treatment; and (5) forming a conductive layer on the cured product; The steps (1) to (5) may be carried out in the order of step (1), step (2), step (3), step (4) and step (5), or 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.

[0239] <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.

[0240] FIG. 1 is a cross-sectional view schematically illustrating a core substrate 10 prepared in a circuit board manufacturing method according to a first embodiment of the present invention. The substrate preparation step may include a step of preparing a core substrate 10, as in the example illustrated in FIG. 1 . The core substrate 10 typically includes a support substrate 11. Examples of the support substrate 11 include insulating substrates such as glass epoxy substrates, metal substrates, polyester substrates, polyimide substrates, BT resin substrates, and thermosetting polyphenylene ether substrates. A metal layer may be provided on the support substrate 11. The metal layer may be provided on one or both surfaces of the support substrate 11. Here, an example is shown in which metal layers 12 and 13 are provided on both surfaces of the support substrate 11. Examples of the metal layers 12 and 13 include layers formed of a metal such as copper. The metal layers 12 and 13 may be, for example, copper foil such as a carrier-attached copper foil, or may be metal layers formed from the material of the conductor layer described below.

[0241] FIG. 2 is a cross-sectional view schematically showing a core substrate 10 having a through hole 14 formed therein, in a method for manufacturing a circuit board according to a first embodiment of the present invention. As in the example shown in FIG. 2, the step of preparing a substrate may include a step of forming the through hole 14 in the core substrate 10. The through hole 14 can be formed by, for example, drilling, laser irradiation, plasma irradiation, or the like. Typically, the through hole 14 can be formed by drilling a through hole in the core substrate 10. As a specific example, the through hole 14 can be formed using a commercially available drilling machine. An example of a commercially available drilling machine is the "ND-1S211" manufactured by Hitachi Via Mechanics, Ltd.

[0242] FIG. 3 is a cross-sectional view schematically illustrating a core substrate 10 having a plating layer 20 formed in a through-hole 14 in a circuit board manufacturing method according to a first embodiment of the present invention. The substrate preparation process may include a process of 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 that for forming the conductor layer in step (5) described below. Here, an example in which the plating layer 20 is formed in the through-hole 14 and on the surfaces of the metal layer 12 and the metal layer 13 will be described.

[0243] FIG. 4 is a cross-sectional view schematically illustrating how resin composition 30a is filled into through-holes in core substrate 10 in a method for manufacturing a circuit board according to a first example of one embodiment of the present invention. Step (1) includes preparing core substrate 10 having through-holes 14 formed therein as described above, and then filling through-holes 14 in core substrate 10 with resin composition 30a, as shown in FIG. 4. The filling can be performed by, for example, a printing method. Examples of printing methods include a method of printing resin composition 30a into through-holes 14 using a squeegee, a method of printing resin composition 30a using a cartridge, a method of printing resin composition 30a by mask printing, a roll coating method, an inkjet method, and the like.

[0244] <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 one 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.

[0245] 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.

[0246] 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.

[0247] 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).

[0248] <Process (3)> FIG. 6 is a schematic cross-sectional view illustrating step (3) of a method for manufacturing a circuit board according to a first example of one embodiment of the present invention. When resin composition 30a is filled into through-hole 14 in step (1), excess resin composition 30a may protrude from or adhere to the outside of through-hole 14. Therefore, resin composition 30a may be provided not only within through-hole 14 but also outside of through-hole 14. Therefore, step (3) includes polishing the excess cured material 30 protruding from or adhering to core substrate 10, as shown in FIG. 6. Polishing removes the excess cured material 30, thereby flattening the surface of cured material 30. Furthermore, surface 31 of cured material 30 flattened by polishing typically forms a plane flush with surfaces 21 surrounding polished surface 31 (e.g., the surface of core substrate 10, the surface of plating layer 20).

[0249] The cured product 30 can be polished by any method capable of removing excess cured product 30 protruding from or adhering to the core substrate 10. Examples of such polishing methods include buff polishing, belt polishing, and ceramic polishing. An example of a commercially available buff polishing device is the "NT-700IM" manufactured by Ishii Hyoki Co., Ltd.

[0250] The arithmetic mean roughness (Ra) of the polished surface 31 (surface after curing) of the cured product 30 is preferably 300 nm or more, more preferably 350 nm or more, and even more preferably 400 nm or more, from the viewpoint of improving adhesion with the conductor layer. The upper limit is preferably 1000 nm or less, more preferably 900 nm or less, and even more preferably 800 nm or less. The surface roughness (Ra) can be measured, for example, using a non-contact surface roughness meter.

[0251] The first example of the method for producing a circuit board may include a step of heat treating the cured product 30 after step (3) 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.

[0252] Furthermore, when step (3) is performed before step (2), a preheating treatment may be performed before step (3), in which the resin composition is heated at a temperature lower than the curing temperature. The temperature in the preheating treatment is preferably 100°C or higher, more preferably 110°C or higher, even more preferably 120°C or higher, and preferably 245°C or lower, more preferably 220°C or lower, even more preferably 200°C or lower. The heat treatment time is preferably 5 minutes or longer, more preferably 10 minutes or longer, even more preferably 15 minutes or longer, and preferably 90 minutes or shorter, more preferably 70 minutes or shorter, even more preferably 60 minutes or shorter.

[0253] <Process (4)> Step (4) includes subjecting the cured product 30 to a roughening treatment (desmear treatment). The roughening treatment roughens the surface of the cured product 30. When the surface of the cured product 30 is polished, step (4) typically includes subjecting the polished surface 31 to a roughening treatment (desmear treatment). The procedure and conditions for the roughening treatment are not particularly limited, and for example, the procedure and conditions used in the manufacturing method of a multilayer printed wiring board can be adopted. As a specific example, the roughening treatment can be applied to 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.

[0254] Examples of swelling solutions that can be used in the roughening step include alkaline solutions and surfactant solutions, with alkaline solutions being preferred. As alkaline solutions serving as swelling solutions, sodium hydroxide solutions and potassium hydroxide solutions are more preferred. Examples of commercially available swelling solutions include "Swelling Dip Securigans P" and "Swelling Dip Securigans SBU" manufactured by Atotech Japan.

[0255] The swelling treatment with a swelling liquid can be carried out, for example, by immersing the cured product 30 for 1 to 20 minutes in the swelling liquid at 30 to 90° C. From the viewpoint of suppressing swelling of the resin contained in the cured product 30 to an appropriate level, it is preferable to immerse the cured product 30 in the swelling liquid at 40 to 80° C. for 5 to 15 minutes.

[0256] 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% 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.

[0257] 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, etc., 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.

[0258] 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.

[0259] <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 one embodiment of the present invention. Step (5), as shown in Fig. 7, involves forming a conductor layer 40 on the polished surface 31 of the cured product 30. Here, an example is shown in which the conductor layer 40 is formed not only on the polished surface 31 of the cured product 30 but also on the surrounding surfaces 21 (e.g., the surface of the core substrate 10, the surface of the plating layer 20). Also, 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.

[0260] 8 is a schematic cross-sectional view illustrating step (5) of the method for manufacturing a circuit board according to a first example of one embodiment of the present invention. As shown in FIG. 8, step (5) may include forming a conductor layer 40, and then removing parts of the conductor layer 40, the metal layer 12, the metal layer 13, and the plating layer 20 by etching or other processing to form a patterned conductor layer 41.

[0261] 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.

[0262] Here, an example of a method for forming a patterned conductor layer 41 on the polished surface 31 of the cured product 30 will be described in detail. A plating seed layer is formed on the polished surface 31 of the cured product 30 by electroless plating. Next, an electrolytic plating layer is formed on the formed plating seed layer by electrolytic plating. Thereafter, if necessary, unnecessary plating seed layer is removed by a process such as etching, thereby forming a patterned conductor layer 41 having a desired wiring pattern. After forming the patterned conductor layer 41, an annealing treatment may be performed as necessary to improve the adhesion strength of the patterned conductor layer 41. The annealing treatment can be performed, for example, by heating at 150 to 200°C for 20 to 90 minutes.

[0263] From the viewpoint of thinning, the thickness of the patterned conductor layer 41 is preferably 70 μm or less, more preferably 60 μm or less, even more preferably 50 μm or less, still more preferably 40 μm or less, particularly preferably 30 μm or less, 20 μm or less, 15 μm or less, or 10 μm or less. The lower limit is preferably 1 μm or more, more preferably 3 μm or more, and even more preferably 5 μm or more.

[0264] By the above method, a circuit board 1 including a cured product 30 of the resin composition 30a can be produced.

[0265] <Circuit Board According to Second Example> The circuit board according to the second example includes a cured material layer containing a cured material of a resin composition. The cured material layer preferably contains only a cured material of the resin composition. The cured material layer is preferably formed using a resin sheet. This circuit board can 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:

[0266] <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.

[0267] 9 is a schematic cross-sectional view illustrating step (i) in a method for manufacturing a circuit board according to a second embodiment of the present invention. As shown in FIG. 9, a 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.

[0268] 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.

[0269] 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.

[0270] 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.

[0271] 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.

[0272] 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.

[0273] 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.

[0274] 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 member") include a heated metal plate (such as a stainless steel (SUS) plate) or a metal roll (SUS roll). Note that rather than pressing the resin sheet 310 by directly contacting it with the thermocompression 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.

[0275] 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, more preferably 0.29MPa to 1.47MPa, and the time during thermocompression bonding is preferably in the range of 20 seconds to 400 seconds, more preferably 30 seconds to 300 seconds. The resin sheet and the inner layer substrate are preferably bonded under reduced pressure conditions of 26.7hPa or less.

[0276] 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.

[0277] 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.

[0278] 10 is a schematic cross-sectional view illustrating step (i) in a method for manufacturing a circuit board according to a second embodiment of the present invention. After laminating the resin sheet 310 on the inner substrate 200, the resin composition layer 320a is cured to form a cured layer. In this example, as shown in FIG. 10, the resin composition layer 320a bonded to the inner substrate 200 is thermally cured to form the first cured layer 320.

[0279] 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.

[0280] 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).

[0281] 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.

[0282] In step (i), instead of using a resin sheet, a resin composition may be applied to the inner layer substrate 200 using a die coater or the like, and then thermally cured to form a cured layer.

[0283] <Process (ii)> Fig. 11 is a schematic cross-sectional view illustrating step (ii) in a method for manufacturing a circuit board according to a second example of one embodiment of the present invention. As shown in Fig. 11, step (ii) includes drilling the first cured material layer 320 to form via holes 360. The via holes 360 form paths for electrically connecting the first conductor layer 420 and the second conductor layer 440 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.

[0284] <Step (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.

[0285] 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.

[0286] <Process (iv)> 12 is a schematic cross-sectional view illustrating step (iv) in a method for producing a circuit board according to a second embodiment of the present invention. As shown in FIG. 12, in step (iv), a second conductor layer 440 is formed on a first cured material layer 320.

[0287] Conductive materials that can form the second conductor layer 440 include, for example, the same materials as those of the conductor layer described in the first example.

[0288] From the viewpoint of thinning, the thickness of the second conductor layer 440 is preferably 70 μm or less, more preferably 60 μm or less, even more preferably 50 μm or less, still more preferably 40 μm or less, particularly preferably 30 μm or less, 20 μm or less, 15 μm or less, or 10 μm or less. The lower limit is preferably 1 μm or more, more preferably 3 μm or more, and even more preferably 5 μm or more.

[0289] The second conductor layer 440 can be formed by plating. The second conductor layer 440 is preferably formed by a wet plating method such as a semi-additive method or a full-additive method including an electroless plating process, a mask pattern formation process, an electrolytic plating process, and a flash etching process. By forming the second conductor layer 440 using a wet plating method, it is possible to form the second conductor layer 440 including a desired wiring pattern. Note that this process also forms via-hole wiring 360a in the via hole 360.

[0290] The first conductor layer 420 and the second conductor layer 440 may be provided in a spiral shape, for example, as shown in Figures 13 to 15 described later. In one example, one end of the spiral wiring portion of the second conductor layer 440 on the central side is electrically connected to one end of the spiral wiring portion of the first conductor layer 420 on the central side by via-hole wiring 360a. The other end of the spiral wiring portion of the second conductor layer 440 on the outer periphery is electrically connected to land 420a of the first conductor layer 420 by via-hole wiring 360a. Therefore, the other end of the spiral wiring portion of the second conductor layer 440 on the outer periphery is electrically connected to external terminal 240 via via-hole wiring 360a, land 420a, and through-hole wiring 220a.

[0291] 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.

[0292] 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 a first cured material layer 320 on which a second conductor layer 440 and via-hole wiring 360a have been formed. The second cured material layer may be formed by a process similar to the process already described. By the above method, a circuit board 100 including a first cured material layer 320 and a second cured material layer 340 formed from a cured product of a resin composition can be manufactured.

[0293] <Inductor Substrate According to Sixth Embodiment> An inductor substrate according to a sixth embodiment of the present invention includes the circuit board according to the fifth 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 configured by 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.

[0294] Furthermore, when the inductor substrate includes a circuit board obtained by the circuit board manufacturing method according to the second example, the inductor substrate may have a cured material layer and a conductive structure at least partially embedded in the cured material layer, and the inductor substrate may include an inductor element constituted by the conductive structure and a portion of the cured material layer that extends in the thickness direction of the cured material layer and is surrounded by the conductive structure.

[0295] 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.

[0296] 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.

[0297] 14, the first cured material layer 320 and the second cured material layer 340 constitute the magnetic part 300, which can be seen as an integrated cured material layer. Therefore, the coiled conductive structure 400 is provided so that at least a portion thereof is embedded in the magnetic part 300. That is, in the circuit board 100 shown in this example, the inductor element is constituted by the coiled conductive structure 400 and a core portion that extends in the thickness direction of the magnetic part 300 and is a portion of the magnetic part 300 surrounded by the coiled conductive structure 400.

[0298] 15, the first conductor layer 420 includes a spiral wiring portion for constituting the coil-shaped conductive structure 400 and a rectangular land 420a electrically connected to the through-hole wiring 220a. In the example shown here, the spiral wiring portion includes a straight portion, a bent portion bent at a right angle, and a detour portion that detours around the land 420a. The spiral wiring portion of the first conductor layer 420 has an overall outline that is approximately rectangular, and has a shape that winds counterclockwise from the center toward the outside.

[0299] 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.

[0300] 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.

[0301] Furthermore, various types of semiconductor devices can be manufactured using such wiring boards. 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]

[0302] The present invention will be specifically described below with reference to examples. However, the present invention is not limited to these examples. In the following description, "parts" and "%" representing amounts mean "parts by mass" and "% by mass", respectively, unless otherwise specified. Furthermore, the temperature and pressure conditions were room temperature (23°C) and atmospheric pressure (1 atm), unless otherwise specified.

[0303] <(A) Iron alloy magnetic powder with an average particle size of more than 20 μm> Epson Atmix "KUAMET NC1-53um", nanocrystalline magnetic powder made of Fe-Si-Nb-B alloy, average particle size (D 50 )27.0μm, true density 7.2g / cm 3 The volume fraction of particles in this magnetic powder with a particle size of 2 μm or less is 0.0 vol%, the volume fraction of particles in this magnetic powder with a particle size of more than 2 μm but less than 20 μm is 37.9 vol%, and the volume fraction of particles in this magnetic powder with a particle size of more than 20 μm is 62.1 vol%. Epson Atmix "KUAMET NC1-75um", nanocrystalline magnetic powder made of Fe-Si-Nb-B alloy, average particle size (D 50 )35.0μm, true density 7.2g / cm 3 The volume fraction of particles in this magnetic powder with a particle size of 2 μm or less is 0.0 vol%, the volume fraction of particles in this magnetic powder with a particle size of more than 2 μm but less than 20 μm is 5.8 vol%, and the volume fraction of particles in this magnetic powder with a particle size of more than 20 μm is 94.2 vol%.

[0304] <(B) Iron alloy magnetic powder with an average particle size of more than 2 μm and not more than 20 μm> Epson Atmix "KUAMET NC1-V1-38um", nanocrystalline magnetic powder made of Fe-Si-Nb-B alloy, average particle size (D 50 )16.0μm, true density 7.2g / cm 3 The volume fraction of particles in this magnetic powder with a particle size of 2 μm or less is 0.0 vol%, the volume fraction of particles in this magnetic powder with a particle size of more than 2 μm and less than 20 μm is 65.0 vol%, and the volume fraction of particles in this magnetic powder with a particle size of more than 20 μm is 35.0 vol%. Epson Atmix "AW02-08 PF3F", amorphous magnetic powder made of Fe-Si-Cr alloy, average particle size (D 50 )3.4μm, true density 7.1g / cm 3 The volume fraction of particles in this magnetic powder with a particle size of 2 μm or less is 5.2 vol%, the volume fraction of particles in this magnetic powder with a particle size of more than 2 μm but less than 20 μm is 94.8 vol%, and the volume fraction of particles in this magnetic powder with a particle size of more than 20 μm is 0.0 vol%. Mitsubishi Steel "AKT-PB-3Si(3)", Fe-Ni-Si alloy magnetic powder, average particle size (D 50 )2.4μm, true density 8.0g / cm 3 The volume fraction of particles in this magnetic powder with a particle size of 2 μm or less is 39.0 vol%, the volume fraction of particles in this magnetic powder with a particle size of more than 2 μm but less than 20 μm is 61.0 vol%, and the volume fraction of particles in this magnetic powder with a particle size of more than 20 μm is 0.0 vol%. Mitsubishi Steel "AKT-PB(5)", Fe-Ni alloy magnetic powder, average particle size (D 50 )5.0μm, true density 8.2g / cm 3 The volume fraction of particles in this magnetic powder with a particle size of 2 μm or less is 21.0 vol%, the volume fraction of particles in this magnetic powder with a particle size of more than 2 μm but less than 20 μm is 79.0 vol%, and the volume fraction of particles in this magnetic powder with a particle size of more than 20 μm is 0.0 vol%. Epson Atmix "50%FE-50%NI PF-5F", Fe-Ni alloy magnetic powder, average particle size (D 50 )4.0μm, true density 8.2g / cm 3The volume fraction of particles in this magnetic powder with a particle size of 2 μm or less is 4.0 vol%, the volume fraction of particles in this magnetic powder with a particle size of more than 2 μm but less than 20 μm is 96.0 vol%, and the volume fraction of particles in this magnetic powder with a particle size of more than 20 μm is 0.0 vol%. Epson Atmix "EA-SMP-10 PF3K", polycrystalline magnetic powder made of Fe-Si-Cr alloy, average particle size (D 50 )4.0μm, true density 7.6g / cm 3 The volume fraction of particles in this magnetic powder with a particle size of 2 μm or less is 5.3 vol%, the volume fraction of particles in this magnetic powder with a particle size of more than 2 μm but less than 20 μm is 94.7 vol%, and the volume fraction of particles in this magnetic powder with a particle size of more than 20 μm is 0.0 vol%. Epson Atmix "ATFINE-NC1 PF5FA", nanocrystalline magnetic powder made of Fe-Si-Nb-B alloy, average particle size (D 50 )4.0μm, true density 7.2g / cm 3 The volume fraction of particles in this magnetic powder with a particle size of 2 μm or less is 3.8 vol%, the volume fraction of particles in this magnetic powder with a particle size of more than 2 μm but less than 20 μm is 96.2 vol%, and the volume fraction of particles in this magnetic powder with a particle size of more than 20 μm is 0.0 vol%. Epson Atmix "ATFINE-NC1 PF3FA", nanocrystalline magnetic powder made of Fe-Si-Nb-B alloy, average particle size (D 50 )3.0μm, true density 7.2g / cm 3 The volume fraction of particles in this magnetic powder with a particle size of 2 μm or less is 4.0 vol%, the volume fraction of particles in this magnetic powder with a particle size of more than 2 μm but less than 20 μm is 96.0 vol%, and the volume fraction of particles in this magnetic powder with a particle size of more than 20 μm is 0.0 vol%.

[0305] <(C) Iron alloy magnetic powder with an average particle size of 2 μm or less> JFE Mineral Co., Ltd. "G00129R", Fe-Si-Cr alloy magnetic powder, average particle size (D 50 )1.7μm, true density 7.0g / cm 3The volume fraction of particles in this magnetic powder with a particle size of 2 μm or less is 85.0 vol%, the volume fraction of particles in this magnetic powder with a particle size of more than 2 μm but less than 20 μm is 15.0 vol%, and the volume fraction of particles in this magnetic powder with a particle size of more than 20 μm is 0.0 vol%. JFE Mineral Co., Ltd. "CVD iron powder (0.7 μm)", Fe-Si-Cr alloy magnetic powder, average particle size (D 50 )0.7μm, true density 7.0g / cm 3 The volume fraction of particles in this magnetic powder with a particle size of 2 μm or less is 99.0 vol%, the volume fraction of particles in this magnetic powder with a particle size of more than 2 μm but less than 20 μm is 1.0 vol%, and the volume fraction of particles in this magnetic powder with a particle size of more than 20 μm is 0.0 vol%.

[0306] <(C') Magnetic powder other than iron alloy magnetic powder, with an average particle size of 2 μm or less> Powder Tech "M001", Mn-based ferrite powder, average particle size (D 50 )0.12μm, true density 5.0g / cm 3 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 20 μm is 3.0 vol%, and the volume fraction of particles in this magnetic powder with a particle size of more than 20 μm is 0.0 vol%.

[0307] Example 1: Preparation of resin composition 1 (A) 83.0 parts by mass of iron alloy magnetic powder having an average particle size of more than 20 μm ("KUAMET NC1-53um" manufactured by Epson Atmix), (B) 10.30 parts by mass of iron alloy magnetic powder having an average particle size of more than 2 μm and not more than 20 μm ("AW02-08 PF3F" manufactured by Epson Atmix), (C) 10.30 parts by mass of iron alloy magnetic powder having an average particle size of 2 μm or less ("CVD iron powder (0.7 μm)" manufactured by JFE Mineral Co., Ltd.), (D) liquid epoxy resin ("ZX-1059" manufactured by Nippon Steel Chemical & Material Co., Ltd., a mixture of bisphenol A epoxy resin and bisphenol F epoxy resin, true density 1.2 g / cm 3 ) 1.11 parts by mass, (D) biphenyl-skeleton phenol-based curing agent ("GPH-65" manufactured by Nippon Kayaku Co., Ltd., true density 1.2 g / cm 3) 1.56 parts by mass, (D) solid epoxy resin (DIC Corporation "HP-4700", naphthalene-type tetrafunctional epoxy resin, true density 1.2 g / cm 3 ) 0.48 parts by mass, (F) phenoxy resin ("YX7553BH30" manufactured by Mitsubishi Chemical Corporation, a solution of methyl ethyl ketone:cyclohexanone = 1:1 with 30% non-volatile components, a special skeleton phenoxy resin, true density of the non-volatile components 1.2 g / cm 3 ) 1.42 parts by mass, (G) curing accelerator ("2PHZ-PW" manufactured by Shikoku Chemicals Corporation, imidazole-based curing accelerator, true density 1.2 g / cm 3 ) 0.02 parts by mass, (H) dispersant (Ajinomoto Fine-Techno Co., Ltd. "PB-821", cationic dispersant, true density 1.2 g / cm 3 0.11 parts by mass of (J), 0.11 parts by mass of toluene as a solvent (J), 2.40 parts by mass of methyl ethyl ketone (MEK) as a solvent (J), and 0.74 parts by mass of cyclohexanone (Anone) as a solvent (J) were mixed and uniformly dispersed using a high-speed rotating mixer to prepare resin composition 1.

[0308] Example 2: Preparation of resin composition 2 In Example 1, (H) dispersant (NOF Corporation "SC-1015F", polyoxyalkylene dispersant, true density 1.2 g / cm 3 ) was changed to 0.11 parts by mass. Resin composition 2 was prepared in the same manner as in Example 1 except for the above.

[0309] Example 3: Preparation of resin composition 3 In Example 1, 1) (A) The amount of iron alloy magnetic powder having an average particle size of more than 20 μm (Epson Atmix's "KUAMET NC1-53um") was changed from 83.00 parts by mass to 87.00 parts by mass, 2) (B) The amount of iron alloy magnetic powder (Epson Atmix "AW02-08 PF3F") having an average particle size of more than 2 μm and not more than 20 μm was changed from 10.30 parts by mass to 5.60 parts by mass, 3) (C) The amount of iron alloy magnetic powder having an average particle size of 2 μm or less ("CVD iron powder (0.7 μm)" manufactured by JFE Mineral Co., Ltd.) was changed from 10.30 parts by mass to 10.50 parts by mass. Resin composition 3 was prepared in the same manner as in Example 1 except for the above.

[0310] Example 4: Preparation of resin composition 4 In Example 1, 1) (B) The amount of iron alloy magnetic powder (Epson Atmix Corporation's "AW02-08 PF3F") having an average particle size of more than 2 μm and not more than 20 μm was changed from 10.30 parts by mass to 5.00 parts by mass, 2) (C) The amount of iron alloy magnetic powder having an average particle size of 2 μm or less ("CVD iron powder (0.7 μm)" manufactured by JFE Mineral Co., Ltd.) was changed from 10.30 parts by mass to 15.50 parts by mass. Resin composition 4 was prepared in the same manner as in Example 1 except for the above.

[0311] Example 5: Preparation of resin composition 5 In Example 1, 1) (B) The amount of iron alloy magnetic powder (Epson Atmix "AW02-08 PF3F") having an average particle size of more than 2 μm and not more than 20 μm was changed from 10.30 parts by mass to 15.20 parts by mass, 2) (C) The amount of iron alloy magnetic powder having an average particle size of 2 μm or less ("CVD iron powder (0.7 μm)" manufactured by JFE Mineral Co., Ltd.) was changed from 10.30 parts by mass to 5.20 parts by mass. Resin composition 5 was prepared in the same manner as in Example 1 except for the above.

[0312] Example 6: Preparation of resin composition 6 In Example 1, 1) (A) The amount of iron alloy magnetic powder having an average particle size of more than 20 μm (Epson Atmix's "KUAMET NC1-53um") was changed from 83.00 parts by mass to 86.30 parts by mass, 2) (B) 10.30 parts by mass of an iron alloy magnetic powder having an average particle size of more than 2 μm and not more than 20 μm ("AW02-08 PF3F" manufactured by Epson Atmix) was replaced with 7.50 parts by mass of another (b) iron alloy magnetic powder having an average particle size of more than 2 μm and not more than 20 μm ("KUAMET NC1-V1-38um" manufactured by Epson Atmix). Resin composition 6 was prepared in the same manner as in Example 1 except for the above.

[0313] Example 7: Preparation of resin composition 7 In Example 1, 10.30 parts by mass of (B) iron alloy magnetic powder having an average particle size of more than 2 μm and not more than 20 μm ("AW02-08 PF3F" manufactured by Epson Atmix Corporation) was replaced with 7.50 parts by mass of another (B) iron alloy magnetic powder having an average particle size of more than 2 μm and not more than 20 μm ("AKT-PB-3Si(3)" manufactured by Mitsubishi Steel Corporation). Resin composition 7 was prepared in the same manner as in Example 1 except for the above.

[0314] Example 8: Preparation of resin composition 8 In Example 1, 10.30 parts by mass of (B) iron alloy magnetic powder having an average particle size of more than 2 μm and not more than 20 μm ("AW02-08 PF3F" manufactured by Epson Atmix Corporation) was replaced with 12.20 parts by mass of another (B) iron alloy magnetic powder having an average particle size of more than 2 μm and not more than 20 μm ("AKT-PB(5)" manufactured by Mitsubishi Steel Corporation). Resin composition 8 was prepared in the same manner as in Example 1 except for the above points.

[0315] Example 9: Preparation of resin composition 9 In Example 1, 10.30 parts by mass of (B) amorphous magnetic powder having an average particle size of more than 2 μm and not more than 20 μm ("AW02-08 PF3F" manufactured by Epson Atmix Corporation) was replaced with 12.00 parts by mass of another (B) iron alloy magnetic powder having an average particle size of more than 2 μm and not more than 20 μm ("50%FE-50%NI PF-5F" manufactured by Epson Atmix Corporation). Resin composition 9 was prepared in the same manner as in Example 1 except for the above points.

[0316] Example 10: Preparation of resin composition 10 In Example 1, 10.30 parts by mass of (B) iron alloy magnetic powder having an average particle size of more than 2 μm and not more than 20 μm ("AW02-08 PF3F" manufactured by Epson Atmix Corporation) was replaced with 11.40 parts by mass of another (B) iron alloy magnetic powder having an average particle size of more than 2 μm and not more than 20 μm ("EA-SMP-10 PF3K" manufactured by Epson Atmix Corporation). Resin composition 10 was prepared in the same manner as in Example 1 except for the above.

[0317] Example 11: Preparation of resin composition 11 In Example 1, 10.30 parts by mass of (B) iron alloy magnetic powder having an average particle size of more than 2 μm and not more than 20 μm ("AW02-08 PF3F" manufactured by Epson Atmix Corporation) was mixed with another (B) iron alloy magnetic powder having an average particle size of more than 2 μm and not more than 20 μm ("ATFINE-NC1 PF5FA" manufactured by Epson Atmix Corporation), an average particle size (D 50 ) 4.0 μm) was changed to 10.90 parts by mass. Resin composition 11 was prepared in the same manner as in Example 1 except for the above.

[0318] Example 12: Preparation of resin composition 12 In Example 1, 10.30 parts by mass of (B) iron alloy magnetic powder having an average particle size of more than 2 μm and not more than 20 μm ("AW02-08 PF3F" manufactured by Epson Atmix Corporation) was mixed with another (B) iron alloy magnetic powder having an average particle size of more than 2 μm and not more than 20 μm ("ATFINE-NC1 PF3FA" manufactured by Epson Atmix Corporation), an average particle size (D 50 ) 3.0 μm) was changed to 10.90 parts by mass. Resin composition 12 was prepared in the same manner as in Example 1 except for the above.

[0319] Example 13: Preparation of resin composition 13 In Example 1, 10.30 parts by mass of (C) iron alloy magnetic powder having an average particle size of 2 μm or less ("CVD iron powder (0.7 μm)" manufactured by JFE Mineral Co., Ltd.) was replaced with 10.30 parts by mass of another (C) iron alloy magnetic powder having an average particle size of 2 μm or less ("G00129R" manufactured by JFE Mineral Co., Ltd.). Resin composition 13 was prepared in the same manner as in Example 1 except for the above.

[0320] <Comparative Example 1: Preparation of Resin Composition 14> In Example 1, 83.00 parts by mass of (A) iron alloy magnetic powder having an average particle size of more than 20 μm ("KUAMET NC1-53um" manufactured by Epson Atmix) was changed to 83.00 parts by mass of (B) iron alloy magnetic powder having an average particle size of more than 2 μm and not more than 20 μm ("KUAMET NC1-V1-38um" manufactured by Epson Atmix). Resin composition 14 was prepared in the same manner as in Example 1 except for the above.

[0321] Comparative Example 2: Preparation of Resin Composition 15 In Example 1, the amount of (A) iron alloy magnetic powder having an average particle size of more than 20 μm (KUAMET NC1-53um manufactured by Epson Atmix Corporation) was changed from 83.00 parts by mass to 62.00 parts by mass. Resin composition 15 was prepared in the same manner as in Example 1 except for the above.

[0322] Comparative Example 3: Preparation of Resin Composition 16 In Example 1, 1) (A) 83.00 parts by mass of an iron alloy magnetic powder having an average particle size of more than 20 μm (Epson Atmix Corporation's "KUAMET NC1-53 μm") was replaced with 80.00 parts by mass of another (A) iron alloy magnetic powder having an average particle size of more than 20 μm (Epson Atmix Corporation's "KUAMET NC1-75 μm"); 2) (B) Iron alloy magnetic powder (Epson Atmix "AW02-08 PF3F") having an average particle size of more than 2 μm and less than 20 μm is not used, 3) (C) No iron alloy magnetic powder having an average particle size of 2 μm or less ("CVD iron powder (0.7 μm)" manufactured by JFE Mineral Co., Ltd.) was used. Resin composition 16 was prepared in the same manner as in Example 1 except for the above.

[0323] <Comparative Example 4: Preparation of Resin Composition 17> In Example 1, 1) (A) The amount of iron alloy magnetic powder (Epson Atmix Corporation's "KUAMET NC1-53um") having an average particle size of more than 20 μm was changed from 83.00 parts by mass to 92.50 parts by mass, 2) (B) Iron alloy magnetic powder (Epson Atmix "AW02-08 PF3F") having an average particle size of more than 2 μm and less than 20 μm is not used, 3) (C) The amount of iron alloy magnetic powder having an average particle size of 2 μm or less ("CVD iron powder (0.7 μm)" manufactured by JFE Mineral Co., Ltd.) was changed from 10.30 parts by mass to 11.44 parts by mass. Resin composition 17 was prepared in the same manner as in Example 1 except for the above points.

[0324] Comparative Example 5: Preparation of Resin Composition 18 In Example 1, 1) (A) The amount of iron alloy magnetic powder having an average particle size of more than 20 μm (Epson Atmix's "KUAMET NC1-53um") was changed from 83.00 parts by mass to 89.00 parts by mass, 2) (B) Iron alloy magnetic powder (Epson Atmix "AW02-08 PF3F") having an average particle size of more than 2 μm and less than 20 μm is not used, 3) (C) The amount of iron alloy magnetic powder having an average particle size of 2 μm or less ("CVD iron powder (0.7 μm)" manufactured by JFE Mineral Co., Ltd.) was changed from 10.30 parts by mass to 14.88 parts by mass. Resin composition 18 was prepared in the same manner as in Example 1 except for the above.

[0325] <Comparative Example 6: Preparation of Resin Composition 19> In Example 1, 1) (A) The amount of iron alloy magnetic powder (Epson Atmix Corporation's "KUAMET NC1-53um") having an average particle size of more than 20 μm was changed from 83.00 parts by mass to 92.90 parts by mass, 2) (B) The amount of iron alloy magnetic powder (Epson Atmix "AW02-08 PF3F") having an average particle size of more than 2 μm and not more than 20 μm was changed from 10.30 parts by mass to 11.50 parts by mass, 3) (C) No iron alloy magnetic powder having an average particle size of 2 μm or less ("CVD iron powder (0.7 μm)" manufactured by JFE Mineral Co., Ltd.) was used. Resin composition 19 was prepared in the same manner as in Example 1 except for the above.

[0326] Comparative Example 7: Preparation of Resin Composition 20 In Example 1, 10.30 parts by mass of (C) iron alloy magnetic powder having an average particle size of 2 μm or less ("CVD iron powder (0.7 μm)" manufactured by JFE Mineral Co., Ltd.) was replaced with 7.50 parts by mass of (C') magnetic powder other than iron alloy magnetic powder having an average particle size of 2 μm or less ("M001" manufactured by Powder Tech Co., Ltd.). Resin composition 20 was prepared in the same manner as in Example 1 except for the above.

[0327] <Test Example 1: Evaluation of Appearance of Resin Composition Upon Application> The resin compositions prepared in the examples and comparative examples were evaluated for their appearance when applied. 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 appearance of the resin composition when applied was evaluated according to the following evaluation criteria. [Evaluation criteria for appearance after application] "Good": No streaks were generated when the resin composition was applied. "X": Streaks occur when the resin composition is applied.

[0328] <Test Example 2: Measurement and Evaluation of Relative Permeability> 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.

[0329] [Evaluation criteria for relative permeability] "Good": Relative permeability is 39.0 or higher. "×": Relative permeability is less than 39.0.

[0330] <Result> The compositions of the resin compositions and the results of the examples and comparative examples are shown in Tables 1 to 3 below.

[0331] [Table 1]

[0332] [Table 2]

[0333] [Table 3] [Explanation of symbols]

[0334] 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 resin composition containing a thermosetting resin and an iron alloy magnetic powder, When the non-volatile components of the resin composition are 100% by volume, (a) the content of iron alloy magnetic powder having a particle size of more than 20 μm and not more than 50 μm is 26% by volume or more and 45% by volume or less; (b) the content of iron alloy magnetic powder having a particle size of more than 2 μm and not more than 20 μm is 28% by volume or more and 68% by volume or less; (c) A resin composition having an iron alloy magnetic powder content of 1% by volume or more and 41% by volume or less, the powder having a particle size of 2 μm or less.

2. 2. The resin composition according to claim 1, wherein (a) the iron alloy magnetic powder having a particle size of more than 20 μm and not more than 50 μm comprises a nanocrystalline magnetic powder made of an iron alloy.

3. (b) The resin composition according to claim 1, wherein the iron alloy magnetic powder having a particle size of more than 2 μm and not more than 20 μm comprises at least one iron alloy magnetic powder selected from the group consisting of nanocrystalline magnetic powder made of iron alloy, iron alloy magnetic powder containing Ni, polycrystalline magnetic powder made of iron alloy, and amorphous magnetic powder.

4. The resin composition according to claim 1 , wherein the thermosetting resin comprises an epoxy resin.

5. The resin composition of claim 1 , wherein the thermosetting resin comprises a curing agent.

6. The resin composition according to claim 1 , further comprising a thermoplastic resin.

7. The resin composition according to claim 1 , further comprising a curing accelerator.

8. The resin composition according to claim 1 , further comprising a dispersant.

9. The resin composition according to claim 1, which is used for hole filling.

10. (A) an iron alloy magnetic powder having an average particle size of more than 20 μm and not more than 50 μm; (B) an iron alloy magnetic powder having an average particle size of more than 2 μm and not more than 20 μm; (C) iron alloy magnetic powder having an average particle size of 2 μm or less; (D) a thermosetting resin.

11. (A) an iron alloy magnetic powder having an average particle size of more than 20 μm and not more than 50 μm; (B) an iron alloy magnetic powder having an average particle size of more than 2 μm and not more than 20 μm; (C) iron alloy magnetic powder having an average particle size of 2 μm or less; (D) a thermosetting resin.

12. The method for producing a resin composition according to claim 10 or 11, wherein (A) the iron alloy magnetic powder having an average particle size of more than 20 μm and not more than 50 μm includes a nanocrystalline magnetic powder made of an iron alloy.

13. 12. The method for producing a resin composition according to claim 10 or 11, wherein component (B) is at least one iron alloy-based magnetic powder selected from the group consisting of nanocrystalline magnetic powder made of an iron alloy, iron alloy-based magnetic powder containing Ni, polycrystalline magnetic powder made of an iron alloy, and amorphous magnetic powder.

14. 12. The method for producing a resin composition according to claim 10 or 11, wherein the blending amount of component (A) is 60% by volume or more and 75% by volume or less, when the nonvolatile components of the produced resin composition are 100% by volume.

15. A cured product of the resin composition according to any one of claims 1 to 9.

16. A magnetic paste comprising the resin composition according to any one of claims 1 to 9.

17. A support and a resin composition layer provided on the support, A resin sheet, wherein the resin composition layer comprises the resin composition according to any one of claims 1 to 9.

18. A circuit board comprising a cured product layer containing a cured product of the resin composition according to any one of claims 1 to 9.

19. The circuit board according to claim 18 , comprising: a substrate having holes; and a cured product of a resin composition filled in the holes.

20. An inductor substrate comprising the circuit board according to claim 18 or 19.

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