resin composition

Abstract

To provide a resin composition that allows for viscosity reduction. [Solution] A resin composition comprising (A) magnetic powder and (B) thermosetting resin, wherein component (A) comprises (A-1) magnetite powder with an average particle size of 1 μm or less and (A-2) magnetic powder with an average particle size of 1.5 μm or more, and the volume ratio of component (A-2) to component (A-1) ((A-2) component / (A-1) component) is 0.5 to 10.0.

Description

[Technical Field]

[0001] The present invention relates to a resin composition containing magnetic powder. Furthermore, it relates to a cured product, magnetic paste, resin sheet, circuit board, and inductor board obtained using the resin composition. [Background technology]

[0002] Inductor elements are widely used in information terminals such as mobile phones and smartphones. Traditionally, independent inductor components were mounted on the substrate, but in recent years, a method has emerged in which a coil is formed by the conductive pattern of the substrate and the inductor element is provided inside the substrate. One known method for providing an inductor element inside a substrate is to screen print a magnetic material containing magnetic powder onto a substrate including wiring to form a cured layer (Patent Documents 1 and 2).

[0003] In recent years, there has been a demand to further improve the performance of inductor elements by enhancing the magnetic properties of magnetic materials. One method for improving the magnetic properties of magnetic materials is to increase the magnetic powder content in the material. For example, a magnetic material is known in which the filling density of the powder is improved by using two or more types of magnetic metal powders having different average particle sizes, thereby enhancing the magnetic properties (Patent Document 3). [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 6-69058 [Patent Document 2] Japanese Patent Publication No. 2017-63100 [Patent Document 3] Japanese Patent Publication No. 2019-220609 [Overview of the project] [Problems that the invention aims to solve]

[0005] However, conventional resin compositions tended to have high viscosity. For example, to improve relative permeability, it is generally necessary to increase the content of magnetic powder, but increasing the content of magnetic powder easily increased the viscosity of the resin composition. High viscosity can prevent good coatability and fillability of the resin composition. Therefore, when trying to improve the handling properties such as coatability and fillability of conventional resin compositions, viscosity was a constraint, and thus the amount of magnetic powder that could be used was also limited.

[0006] Furthermore, generally speaking, increasing the content of magnetic powder tends to increase magnetic loss. Therefore, resin compositions are also required to reduce magnetic loss. Against this backdrop, there has been a demand for the development of resin compositions that can reduce both viscosity and magnetic loss in a balanced manner.

[0007] The present invention was devised in view of the above-mentioned problems, and aims to provide a resin composition capable of reducing both viscosity and magnetic loss; a magnetic paste containing the resin composition; a resin sheet comprising a resin composition layer containing the resin composition; a circuit board comprising a cured product of the resin composition; and an inductor board comprising the circuit board. [Means for solving the problem]

[0008] The inventors diligently studied to solve the aforementioned problems. As a result, the inventors found that the aforementioned problems can be solved when, in a resin composition comprising (A) magnetic powder and (B) thermosetting resin, component (A) contains (A-1) magnetite powder having an average particle size within a specific range and (A-2) magnetic powder having an average particle size within a specific range, in a volume ratio within a specific range, and thus completed the present invention. In other words, the present invention includes the following:

[0009] <1> A resin composition comprising (A) magnetic powder and (B) thermosetting resin, (A) Component comprises (A-1) magnetite powder with an average particle size of 1 μm or less, and (A-2) magnetic powder with an average particle size of 1.5 μm or more. A resin composition in which the volume ratio of component (A-2) to component (A-1) ((A-2) component / (A-1) component) is 0.5 to 10.0. <2> The resin composition according to <1>, wherein the average particle diameter of the component (A-2) is 10.0 μm or less. <3> The resin composition according to <1> or <2>, wherein the average particle diameter of the component (A-2) is 2.5 μm or more. <4> The resin composition according to any one of <1> to <3>, wherein the average particle diameter of the component (A-1) is 0.01 μm or more. <5> The resin composition according to any one of <1> to <4>, wherein the ratio of the average particle diameter of the component (A-2) to the average particle diameter of the component (A-1) ((A-2) component / (A-1) component) is 3 or more. <6> The resin composition according to any one of <1> to <5>, wherein the component (A-1) contains magnetite powder containing at least one element selected from the group consisting of Mn, Zn, Ni, Cu, Ti, Si, Al, Mg, and Ca in addition to Fe. <7> The resin composition according to any one of <1> to <6>, wherein the component (A-2) contains at least one selected from the group consisting of ferrite powder and magnetic alloy powder. <8> The resin composition according to any one of <1> to <7>, wherein the content of the component (A) is 50% by volume or more when the non-volatile components in the resin composition are 100% by volume. <9> The resin composition according to any one of <1> to <8>, wherein the content of the component (A) is 80% by volume or less when the non-volatile components in the resin composition are 100% by volume. <10> The resin composition according to any one of <1> to <9>, wherein the component (B) contains (B-1) epoxy resin. <11> The resin composition according to any one of <1> to <10>, wherein the viscosity under the measurement conditions of a temperature of 25 °C and a rotation speed of 5 rpm is 140 Pa·s or less. <12> A cured product of the resin composition according to any one of <1> to <11>. <13> A magnetic paste containing the resin composition according to any one of <1> to <11>. <14> A resin sheet comprising a support and a resin composition layer provided on the support and containing the resin composition according to any one of <1> to <11>. <15> A circuit board comprising a substrate having through-holes and a cured product of the resin composition according to any one of <1> to <11> filled in the through-holes. <16> A circuit board comprising a cured product layer containing a cured product of the resin composition according to any one of <1> to <11>. <17> An inductor board comprising the circuit board according to <15> or <16>.

Advantages of the Invention

[0010] According to the present invention, there can be provided a resin composition capable of reducing both viscosity and magnetic loss; a magnetic paste containing the resin composition; a resin sheet comprising a resin composition layer containing the resin composition; a circuit board containing a cured product of the resin composition; and an inductor board comprising the circuit board.

Brief Description of the Drawings

[0011] [Figure 1] FIG. 1 is a schematic cross-sectional view of a core substrate according to an example of a method for manufacturing a circuit board of the first embodiment. [Figure 2] FIG. 2 is a schematic cross-sectional view of a core substrate with through-holes formed according to an example of a method for manufacturing a circuit board of the first embodiment. [Figure 3] FIG. 3 is a schematic cross-sectional view showing the state of a core substrate with a plating layer formed in through-holes according to an example of a method for manufacturing a circuit board of the first embodiment. [Figure 4] FIG. 4 is a schematic cross-sectional view showing the state of a core substrate with a resin composition filled in through-holes according to an example of a method for manufacturing a circuit board of the first embodiment. [Figure 5] FIG. 5 is a schematic cross-sectional view showing the state of a core substrate with the filled resin composition thermally cured according to an example of a method for manufacturing a circuit board of the first embodiment. [Figure 6]Figure 6 is a schematic cross-sectional view showing the state of the core substrate after polishing the cured product according to an example of the manufacturing method of the circuit board according to the first embodiment. [Figure 7] Figure 7 is a schematic cross-sectional view showing a core substrate in which a conductive layer has been formed on a polished surface, according to an example of a circuit board manufacturing method of the first embodiment. [Figure 8] Figure 8 is a schematic cross-sectional view showing a core substrate on which a patterned conductor layer has been formed, according to an example of a circuit board manufacturing method of the first embodiment. [Figure 9] Figure 9 is a schematic cross-sectional view illustrating step (A) included in an example of a circuit board manufacturing method according to the second embodiment. [Figure 10] Figure 10 is a schematic cross-sectional view illustrating step (A) included in an example of a circuit board manufacturing method according to the second embodiment. [Figure 11] Figure 11 is a schematic cross-sectional view illustrating step (B) included in an example of a circuit board manufacturing method according to the second embodiment. [Figure 12] Figure 12 is a schematic cross-sectional view illustrating step (D) included in an example of a circuit board manufacturing method according to the second embodiment. [Figure 13] Figure 13 is a schematic plan view of a circuit board obtained by the manufacturing method of the second embodiment as an example, viewed from one side in the thickness direction. [Figure 14] Figure 14 is a schematic diagram showing the cut end face of a circuit board obtained by the manufacturing method of the circuit board of the second embodiment, cut at the position indicated by the dashed line II-II shown in Figure 13 as an example. [Figure 15] Figure 15 is a schematic plan view illustrating the configuration of the first conductor layer of a circuit board obtained by the manufacturing method of a circuit board according to a second embodiment as an example. [Modes for carrying out the invention]

[0012] The present invention will be described in detail below with reference to its preferred embodiments. However, the present invention is not limited to the embodiments and examples described below, and may be implemented with modifications as appropriate without departing from the scope of the claims and their equivalents.

[0013] <Resin composition> A resin composition according to one embodiment of the present invention comprises (A) magnetic powder and (B) thermosetting resin. The magnetic powder (A) comprises (A-1) magnetite powder with an average particle size of 1 μm or less and (A-2) magnetic powder with an average particle size of 1.5 μm or more. The volume ratio of the magnetic powder as component (A-2) to the magnetite powder as component (A-1) (component (A-2) / component (A-1)) is 0.5 to 10.0.

[0014] The resin composition of this embodiment can have low viscosity and produce a cured product with low magnetic loss. Therefore, the resin composition of this embodiment can reduce both viscosity and magnetic loss in a balanced manner. Preferably, the resin composition of this embodiment can improve not only viscosity and magnetic loss but also the relative permeability of the cured product. More specifically, the resin composition of this embodiment preferably has a low viscosity compared to the magnetic properties such as the relative permeability and magnetic loss of the cured product of the resin composition.

[0015] Therefore, for example, if the resin composition according to this embodiment has a composition that yields a cured product having magnetic properties comparable to those of a cured product of a conventional resin composition, the resin composition according to this embodiment can usually have a lower viscosity than a conventional resin composition. Thus, the resin composition of this embodiment can have a lower viscosity than a conventional resin composition and can yield a cured product having magnetic properties comparable to those of a cured product of a conventional resin composition.

[0016] Furthermore, for example, if the resin composition according to this embodiment has a viscosity similar to that of a conventional resin composition, the cured product of the resin composition according to this embodiment can have superior magnetic properties compared to the cured product of a conventional resin composition. Therefore, the resin composition of this embodiment can have a viscosity similar to that of a conventional resin composition, and a cured product with superior magnetic properties compared to the cured product of a conventional resin composition can be obtained.

[0017] The resin composition of the present invention may further contain any optional components in addition to (A) magnetic powder and (B) thermosetting resin. Examples of optional components include (C) any additive and (D) organic solvent. The components contained in the resin composition will be described in detail below.

[0018] <(A) Magnetic powder> A resin composition according to one embodiment of the present invention includes (A) magnetic powder as component (A). The (A) magnetic powder can impart magnetism to the resin composition and its cured product. In the resin composition according to this embodiment, the (A) magnetic powder comprises a combination of (A-1) magnetite powder with an average particle size of 1 μm or less and (A-2) magnetic powder with an average particle size of 1.5 μm or more. The (A-1) magnetite powder with an average particle size of 1 μm or less may hereinafter be referred to as "(A-1) small-diameter magnetite powder". The (A-2) magnetic powder with an average particle size of 1.5 μm or more may hereinafter be referred to as "(A-2) large-diameter magnetic powder".

[0019] <(A-1) Magnetite powder with an average particle size of 1 m or less> (A) The magnetic powder contains (A-1) small-diameter magnetite powder (i.e., magnetite powder with an average particle size of 1 μm or less) as component (A-1). Magnetite powder refers to powder of iron oxide material selected from the group consisting of triiron tetroxide (Fe3O4) and composite oxides mainly composed of triiron tetroxide. (A-1) Small-diameter magnetite powder may be used alone or in combination of two or more types.

[0020] (A-1) Small diameter magnetite powder is (FeO) x· It may have a composition represented by Fe2O3 (where 0 < x ≤ 1). (A-1) When the small-diameter magnetite powder is a composite oxide, the (A-1) small-diameter magnetite powder may contain one or more metal elements other than iron. Examples of these metal elements include Mn, Zn, Ni, Cu, Ti, Si, Al, Mg, and Ca. Therefore, the (A-1) small-diameter magnetite powder may contain a magnetite powder containing at least one element selected from the group consisting of Mn, Zn, Ni, Cu, Ti, Si, Al, Mg, and Ca in addition to Fe. The total amount of metal elements other than iron contained in the (A-1) small-diameter magnetite powder may be 0% by mass, but is usually greater than 0% by mass and usually 20% by mass or less with respect to 100% by mass of the mass of the (A-1) small-diameter magnetite powder.

[0021] The average particle diameter of the (A-1) small-diameter magnetite powder is usually 1 μm or less, preferably 0.8 μm or less, more preferably 0.6 μm or less. The lower limit of the average particle diameter of the (A-1) small-diameter magnetite powder is not particularly limited, but is preferably 0.01 μm or more, more preferably 0.05 μm or more, and particularly preferably 0.1 μm or more. When the (A-1) small-diameter magnetite powder has an average particle diameter within the above range, the viscosity of the resin composition and the magnetic loss of the cured product can be lowered, and usually the relative permeability of the cured product of the resin composition can be improved.

[0022] The average particle diameter of the (A-1) small-diameter magnetite powder represents the median diameter on a volume basis. This average particle diameter can be measured by a laser diffraction / scattering method based on the Mie scattering theory. Specifically, it can be measured by creating a particle size distribution on a volume basis with a laser diffraction scattering type particle size distribution measuring device and taking the median diameter thereof as the average particle diameter. As the measurement sample, a powder dispersed in water by ultrasonic waves can preferably be used. As the laser diffraction scattering type particle size distribution measuring device, "LA-500" manufactured by Horiba, Ltd., "SALD-2200" manufactured by Shimadzu Corporation, etc. can be used.

[0023] (A-1) The small-diameter magnetite powder is preferably in the form of substantially spherical particles. (A-1) When the particles of the small-diameter magnetite powder are substantially spherical, the viscosity of the resin composition and the magnetic loss of the cured product can be effectively reduced, and moreover, the relative permeability of the cured product of the resin composition can usually be made particularly good. (A-1) The aspect ratio of the particles of the small-diameter magnetite powder is preferably 2 or less, more preferably 1.5 or less, even more preferably 1.2 or less, and usually 1.0 or more. The aspect ratio of a particle represents the ratio (Lb / La) of the long axis (Lb) to the short axis (La) of the particle. Such substantially spherical magnetite powder can be produced, for example, by a method that suppresses the increase in aspect ratio associated with crystal growth by synthesizing magnetite powder while suppressing the increase in particle size due to crystal growth.

[0024] (A-1) The true specific gravity of small-diameter magnetite powder is, for example, 4.7 g / cm³. 3 ~5.5g / cm 3 It is possible.

[0025] (A-1) Small-diameter magnetite powder can be produced, for example, by a wet synthesis method. Specific production methods include, for example, the methods described in "Fine-particle iron oxide for soft ferrite raw materials" (Takahiro Kikuchi, Yukiko Okazaki, Koji Ikeda, JFE Technical Report No. 8, pp. 26-31, June 2005) and Japanese Patent Publication No. 2012-211054.

[0026] (A-1) Small diameter magnetite powder may be used as is from a commercially available product, or two or more types may be used in combination. (A-1) Specific examples of commercially available small diameter magnetite powder include "Magnetite A" manufactured by Toda Kogyo Co., Ltd.

[0027] (A-1) The content (volume %) of small-diameter magnetite powder is preferably 0.5 volume% or more, more preferably 1 volume% or more, even more preferably 5 volume% or more, even more preferably 10 volume% or more, and even more preferably 20 volume% or more, when the non-volatile components in the resin composition are taken as 100 volume%. (A-1) When the content of small-diameter magnetite powder is above the lower limit, the viscosity of the resin composition and the magnetic loss of the cured product can be effectively reduced, and moreover, the relative permeability of the cured product of the resin composition can usually be made particularly good. In particular, from the viewpoint of significantly reducing the magnetic loss of the cured product of the resin composition, the content (volume %) of small-diameter magnetite powder is particularly preferably 20.4 volume% or more. The upper limit is preferably 50 volume% or less, more preferably 40 volume% or less, even more preferably 30 volume% or less, and particularly preferably 25 volume% or less, when the non-volatile components in the resin composition are taken as 100 volume%. (A-1) When the content of small-diameter magnetite powder is below the above upper limit, the viscosity of the resin composition and the magnetic loss of the cured product can be effectively reduced, and furthermore, the relative permeability of the cured product of the resin composition can usually be made particularly good.

[0028] (A-1) The content (volume %) of small-diameter magnetite powder is preferably 1 volume % or more, more preferably 5 volume % or more, even more preferably 10 volume % or more, even more preferably 20 volume % or more, particularly preferably 25 volume % or more, preferably 55 volume % or less, more preferably 50 volume % or less, even more preferably 45 volume % or less, particularly preferably 40 volume % or less. (A-1) When the content of small-diameter magnetite powder is within the above range, the viscosity of the resin composition and the magnetic loss of the cured product can be effectively reduced, and furthermore, the relative permeability of the cured product of the resin composition can usually be made particularly good.

[0029] (A-1) The content (mass%) of small-diameter magnetite powder is preferably 0.5% by mass or more, more preferably 1% by mass or more, even more preferably 5% by mass or more, even more preferably 10% by mass or more, even more preferably 20% by mass or more, particularly preferably 25% by mass or more, preferably 70% by mass or less, more preferably 60% by mass or less, even more preferably 50% by mass or less, even more preferably 40% by mass or less, particularly preferably 35% by mass or less. (A-1) When the content of small-diameter magnetite powder is within the above range, the viscosity of the resin composition and the magnetic loss of the cured product can be effectively reduced, and furthermore, the relative permeability of the cured product of the resin composition can usually be made particularly good.

[0030] (A-1) The content (mass%) of small-diameter magnetite powder is preferably 1% by mass or more, more preferably 5% by mass or more, even more preferably 10% by mass or more, even more preferably 20% by mass or more, particularly preferably 25% by mass or more, preferably 55% by mass or less, more preferably 50% by mass or less, even more preferably 45% by mass or less, particularly preferably 40% by mass or less. (A-1) When the content of small-diameter magnetite powder is within the above range, the viscosity of the resin composition and the magnetic loss of the cured product can be effectively reduced, and furthermore, the relative permeability of the cured product of the resin composition can usually be made particularly good.

[0031] <(A-2) Magnetic powder with an average particle size of 1.5 μm or larger> (A) The magnetic powder contains (A-2) large-diameter magnetic powder (i.e., magnetic powder with an average particle size of 1.5 μm or more) as component (A-2). (A-2) The large-diameter magnetic powder may be used alone or in combination of two or more types.

[0032] (A-2) The large-diameter magnetic powder may be either soft magnetic powder or hard magnetic powder. In one embodiment, from the viewpoint of effectively lowering the viscosity of the resin composition and particularly improving the magnetic properties such as relative permeability and magnetic loss of the cured resin composition, (A-2) the large-diameter magnetic powder is preferably soft magnetic powder. (A-2) The large-diameter magnetic powder may be, for example, magnetic metal oxide powder, magnetic metal powder, etc.

[0033] The magnetic metal oxide powder is not particularly limited, but examples include ferrite powders such as Fe-Mn ferrite powder, Mg-Zn ferrite powder, Mn ferrite powder, Mn-Zn ferrite powder, Mn-Mg ferrite powder, Cu-Zn ferrite powder, Mg-Sr ferrite powder, Mn-Mg-Sr ferrite powder, Ni-Zn ferrite powder, Ni-Zn-Cu ferrite powder, Ba-Zn ferrite powder, Ba-Mg ferrite powder, Ba-Ni ferrite powder, Ba-Co ferrite powder, Ba-Ni-Co ferrite powder, and Y ferrite powder; iron oxide powders such as iron(III) oxide powder and triiron tetroxide powder; and so on.

[0034] The magnetic metal powder is not particularly limited, but examples include pure iron powder; crystalline or amorphous magnetic alloy powders such as Fe-Si alloy powder, Fe-Si-Al alloy powder, Fe-Cr alloy powder, Fe-Si-Cr alloy powder, Fe-Ni-Cr alloy powder, Fe-Cr-Al alloy powder, Fe-Ni alloy powder, Fe-Ni-Mo alloy powder, Fe-Ni-Mo-Cu alloy powder, Fe-Co alloy powder, Fe-Ni-Co alloy powder, and Co-based amorphous alloy powder.

[0035] (A-2) The large-diameter magnetic powder preferably contains at least one magnetic powder selected from ferrite powder and magnetic alloy powder. From the viewpoint of effectively reducing magnetic loss, (A-2) the large-diameter magnetic powder more preferably contains at least one magnetic alloy powder, even more preferably contains at least one magnetic alloy powder selected from Fe-Si-Cr alloy powder and Fe-Ni alloy powder, and particularly preferably contains Fe-Si-Cr alloy powder. Fe-Si-Cr alloy powder refers to an alloy powder containing Fe, Si, and Cr, and Fe-Ni alloy powder refers to an alloy powder containing Fe and Ni. Furthermore, (A-2) the large-diameter magnetic powder does not have to contain magnetite powder.

[0036] (A-2) The average particle size of the large-diameter magnetic powder is usually 1.5 μm or more, preferably 2.0 μm or more, more preferably 2.5 μm or more, and even more preferably 2.8 μm or more. (A-2) When the average particle size of the large-diameter magnetic powder is above the lower limit, the viscosity of the resin composition and the magnetic loss of the cured product can be reduced, and more normally, the relative permeability of the cured product of the resin composition can be improved. In particular, from the viewpoint of effectively reducing the viscosity of the resin composition, (A-2) the average particle size of the large-diameter magnetic powder is particularly preferably 3.5 μm or more. The upper limit is preferably 25 μm or less, more preferably 20 μm or less, even more preferably 15 μm or less, even more preferably 10 μm or less, and particularly preferably 7 μm or less. (A-2) When the average particle size of the large-diameter magnetic powder is below the upper limit, the viscosity of the resin composition and the magnetic loss of the cured product can be reduced, and more normally, the relative permeability of the cured product of the resin composition can be improved.

[0037] (A-2) The average particle size of large-diameter magnetic powder represents the median diameter based on volume. (A-2) The average particle size of large-diameter magnetic powder can be measured in the same way as (A-1) the average particle size of small-diameter magnetite powder.

[0038] (A-1) The ratio of the average particle size of the large-diameter magnetic powder ((A-2) component) to the average particle size of the small-diameter magnetite powder ((A-1) component) ((A-2) component / (A-1) component) is preferably 3 or more, more preferably 4 or more, particularly preferably 5 or more, and preferably 50 or less, more preferably 30 or less, particularly preferably 15 or less. When the ratio of the average particle sizes ((A-2) component / (A-1) component) is within the above range, the viscosity of the resin composition and the magnetic loss of the cured product can be effectively reduced, and usually, the relative permeability of the cured product of the resin composition can be made particularly good.

[0039] (A-2) The specific surface area of the large-diameter magnetic powder is not particularly limited, but is preferably 0.05 m 2 / g or more, more preferably 0.1 m 2 / g or more, still more preferably 0.3 m 2 / g or more, and preferably 30 m 2 / g or less, more preferably 20 m 2 / g or less, still more preferably 15 m 2 / g or less. The specific surface area of particles such as (A) magnetic powder can be measured by the BET method.

[0040] (A-2) The large-diameter magnetic powder is preferably composed of substantially spherical particles. The aspect ratio of the particles of the (A-2) large-diameter magnetic powder is preferably 4 or less, more preferably 3 or less, still more preferably 2 or less.

[0041] (A-2) The true specific gravity of the magnetic powder of the component can be, for example, 4 g / cm<00\00010>~10 g / cm 3 or so.

[0042] (A-2) As the large-diameter magnetic powder, commercially available magnetic powders may be used. Specific examples of commercially available magnetic powders that can be used include "M05S" and "MZ05S" manufactured by Powdertech Co., Ltd.; "AW2-08 PF8F" manufactured by Epson Atomics Co., Ltd., etc. The magnetic powder may be used alone or in combination of two or more.

[0043] The volume ratio of component (A-2) to component (A-1) ((A-2) component / (A-1) component) is usually within a specific range. The aforementioned volume ratio ((A-2) component / (A-1) component) represents the ratio of the total volume of large-diameter magnetic powder (A-2) contained in the resin composition to the total volume of small-diameter magnetite powder (A-1) contained in the resin composition. Specifically, this volume ratio ((A-2) component / (A-1) component) is usually 0.5 or more, preferably 0.8 or more, more preferably 1.0 or more, even more preferably 1.1 or more, even more preferably 1.2 or more, even more preferably 1.3 or more, and particularly even more preferably 1.4 or more. The upper limit of the volume ratio ((A-2) component / (A-1) component) is usually 10.0 or less, preferably 8.0 or less, more preferably 6.0 or less, even more preferably 5.0 or less, even more preferably 4.0 or less, even more preferably 3.0 or less, and particularly preferably 2.5 or less. When the volume ratio (component A-2 / component A-1) is within the above range, the viscosity of the resin composition and the magnetic loss of the cured product can be reduced, and the relative permeability of the cured product of the resin composition can usually be improved.

[0044] (A-2) The content (volume %) of large-diameter magnetic powder is preferably 10 volume% or more, more preferably 20 volume% or more, even more preferably 30 volume% or more, particularly preferably 40 volume% or more, preferably 80 volume% or less, more preferably 70 volume% or less, even more preferably 60 volume% or less, particularly preferably 55 volume% or less, when the non-volatile components in the resin composition are taken as 100 volume%. (A-2) When the content of large-diameter magnetic powder is within the above range, the viscosity of the resin composition and the magnetic loss of the cured product can be effectively reduced, and furthermore, the relative permeability of the cured product of the resin composition can usually be made particularly good.

[0045] (A-2) The content (volume %) of large-diameter magnetic powder is preferably 20 volume% or more, more preferably 30 volume% or more, even more preferably 40 volume% or more, particularly preferably 50 volume% or more, preferably 99 volume% or less, more preferably 95 volume% or less, even more preferably 80 volume% or less, and particularly preferably 75 volume% or less, when the total amount of magnetic powder (A) is taken as 100 volume%. (A-2) When the content of large-diameter magnetic powder is within the above range, the viscosity of the resin composition and the magnetic loss of the cured product can be effectively reduced, and furthermore, the relative permeability of the cured product of the resin composition can usually be made particularly good.

[0046] (A-2) The content (mass%) of large-diameter magnetic powder is preferably 20% by mass or more, more preferably 30% by mass or more, even more preferably 40% by mass or more, even more preferably 50% by mass or more, particularly preferably 60% by mass or more, preferably 95% by mass or less, more preferably 90% by mass or less, even more preferably 80% by mass or less, particularly preferably 70% by mass or less. (A-2) When the content of large-diameter magnetic powder is within the above range, the viscosity of the resin composition and the magnetic loss of the cured product can be effectively reduced, and furthermore, the relative permeability of the cured product of the resin composition can usually be made particularly good.

[0047] (A-2) The content (mass%) of large-diameter magnetic powder is preferably 30% by mass or more, more preferably 40% by mass or more, even more preferably 50% by mass or more, even more preferably 60% by mass or more, particularly preferably 65% ​​by mass or more, preferably 99% by mass or less, more preferably 95% by mass or less, even more preferably 90% by mass or less, even more preferably 80% by mass or less, particularly preferably 75% by mass or less. (A-2) When the content of large-diameter magnetic powder is within the above range, the viscosity of the resin composition and the magnetic loss of the cured product can be effectively reduced, and furthermore, the relative permeability of the cured product of the resin composition can usually be made particularly good.

[0048] <(A-3) Any magnetic powder> (A) The magnetic powder may include (A-3) any magnetic powder other than (A-1) small-diameter magnetite powder and (A-2) large-diameter magnetic powder. (A-3) Any magnetic powder may be, for example, magnetic metal oxide powder, magnetic metal powder, etc.

[0049] (A) The amount of any magnetic powder (A-3) in the magnetic powder is preferably as small as possible. The amount of any magnetic powder (A-3) (volume %) is preferably 5 volume % or less, more preferably 2 volume % or less, and even more preferably 1 volume % or less, when the total amount of magnetic powder (A) is 100 volume %. Also, the amount of any magnetic powder (A-3) (mass %) is preferably 5 mass % or less, more preferably 2 mass % or less, and even more preferably 1 mass % or less, when the total amount of magnetic powder (A) is 100 mass %. It is particularly preferable that the magnetic powder (A) does not contain any magnetic powder (A-3) (0 volume %, 0 mass %). That is, it is particularly preferable that the magnetic powder (A) contains only small-diameter magnetite powder and large-diameter magnetic powder.

[0050] <(A) Total amount of magnetic powder> (A) The magnetic powder content (volume %) is preferably 30% by volume or more, more preferably 40% by volume or more, even more preferably 50% by volume or more, even more preferably 55% by volume or more, even more preferably 60% by volume or more, particularly preferably 62% by volume or more, preferably 90% by volume or less, more preferably 85% by volume or less, even more preferably 80% by volume or less, particularly preferably 75% by volume or less. (A) When the magnetic powder content is within the above range, the viscosity of the resin composition and the magnetic loss of the cured product can be effectively reduced, and moreover, the relative permeability of the cured product of the resin composition can usually be made particularly good.

[0051] (A) The content (mass%) of magnetic powder is preferably 50% by mass or more, more preferably 60% by mass or more, even more preferably 70% by mass or more, even more preferably 75% by mass or more, even more preferably 80% by mass or more, even more preferably 85% by mass or more, particularly preferably 90% by mass or more, preferably 97% by mass or less, more preferably 95% by mass or less, even more preferably 94% by mass or less, particularly preferably 93% by mass or less. (A) When the content of magnetic powder is within the above range, the viscosity of the resin composition and the magnetic loss of the cured product can be effectively reduced, and furthermore, the relative permeability of the cured product of the resin composition can usually be made particularly good.

[0052] <(B) Thermosetting resin> A resin composition according to one embodiment of the present invention contains a thermosetting resin (B) as component (B). Examples of thermosetting resins (B) include epoxy resins, epoxy acrylate resins, urethane acrylate resins, urethane resins, cyanate resins, polyimide resins, benzoxazine resins, unsaturated polyester resins, phenolic resins, melamine resins, silicone resins, phenoxy resins, and the like. A single thermosetting resin (B) may be used alone, or two or more may be used in combination.

[0053] (B) The content (mass%) of the thermosetting resin is preferably 0.1% by mass or more, more preferably 1% by mass or more, even more preferably 3% by mass or more, particularly preferably 5% by mass or more, preferably 50% by mass or less, more preferably 30% by mass or less, even more preferably 20% by mass or less, particularly preferably 10% by mass or less, when the nonvolatile components in the resin composition are taken as 100% by mass. (B) When the content of the thermosetting resin is within the above range, the viscosity of the resin composition and the magnetic loss of the cured product can be effectively reduced, and furthermore, the relative permeability of the cured product of the resin composition can usually be made particularly good.

[0054] (B) The content (mass%) of the thermosetting resin is preferably 50% by mass or more, more preferably 60% by mass or more, even more preferably 70% by mass or more, particularly preferably 80% by mass or more, preferably 99% by mass or less, more preferably 95% by mass or less, particularly preferably 90% by mass or less, when the total resin components in the resin composition are considered as 100% by mass. (B) When the content of the thermosetting resin is within the above range, the viscosity of the resin composition and the magnetic loss of the cured product can be effectively reduced, and furthermore, the relative permeability of the cured product of the resin composition can usually be made particularly good. Unless otherwise specified, the resin components in the resin composition refer to the components of the resin composition excluding (A) inorganic particles such as magnetic powder from the nonvolatile components of the resin composition.

[0055] <(B-1) Epoxy resin> (B) The thermosetting resin preferably contains (B-1) epoxy resin as component (B-1). (B-1) epoxy resin means a resin having epoxy groups.

[0056] (B-1) Examples of epoxy resins include bixylenol-type epoxy resin, bisphenol A-type epoxy resin, bisphenol F-type epoxy resin, bisphenol S-type epoxy resin, bisphenol AF-type epoxy resin, dicyclopentadiene-type epoxy resin, trisphenol-type epoxy resin, naphthol novolac-type epoxy resin, phenol novolac-type epoxy resin, tert-butyl-catechol-type epoxy resin, naphthalene-type epoxy resin, naphthol-type epoxy resin, anthracene-type epoxy resin, glycidylamine-type epoxy resin, glycidyl ester-type epoxy resin, cresol novolac-type epoxy resin, biphenyl-type epoxy resin, linear aliphatic epoxy resin, epoxy resin having a butadiene structure, alicyclic epoxy resin, heterocyclic epoxy resin, spiro-ring-containing epoxy resin, cyclohexane-type epoxy resin, cyclohexanedimethanol-type epoxy resin, naphthylene ether-type epoxy resin, trimethylol-type epoxy resin, tetraphenylethane-type epoxy resin, etc. Epoxy resins may be used individually or in combination of two or more types.

[0057] The resin composition preferably contains an epoxy resin having two or more epoxy groups per molecule as the (B-1) epoxy resin. The proportion of the epoxy resin having two or more epoxy groups per molecule is preferably 50% by mass or more, more preferably 60% by mass or more, and particularly preferably 70% by mass or more, relative to 100% by mass of the nonvolatile component of the (B-1) epoxy resin.

[0058] (B-1) Epoxy resins include epoxy resins that are liquid at 25°C (hereinafter sometimes referred to as "liquid epoxy resins") and epoxy resins that are solid at 25°C (hereinafter sometimes referred to as "solid epoxy resins"). (B) The thermosetting resin may contain only liquid epoxy resin, only solid epoxy resin, or a combination of liquid epoxy resin and solid epoxy resin, but in a preferred embodiment, it contains only liquid epoxy resin.

[0059] The amount of liquid epoxy resin is preferably 60% by mass or more, more preferably 80% by mass or more, even more preferably 90% by mass or more, and particularly preferably 100% by mass, when the total amount of (B-1) epoxy resin is considered to be 100% by mass.

[0060] As the liquid epoxy resin, a liquid epoxy resin having two or more epoxy groups in one molecule is preferred.

[0061] Preferred liquid epoxy resins include glycirol-type epoxy resins, bisphenol A-type epoxy resins, bisphenol F-type epoxy resins, bisphenol AF-type epoxy resins, naphthalene-type epoxy resins, glycidyl ester-type epoxy resins, glycidylamine-type epoxy resins, phenol novolac-type epoxy resins, alicyclic epoxy resins having an ester skeleton, cyclohexanedimethanol-type epoxy resins, and epoxy resins having a butadiene structure, with glycirol-type epoxy resins, bisphenol A-type epoxy resins, and bisphenol F-type epoxy resins being more preferred.

[0062] Specific examples of liquid epoxy resins include DIC's "HP4032," "HP4032D," and "HP4032SS" (naphthalene-type epoxy resin); Mitsubishi Chemical's "828US," "jER828EL" (bisphenol A-type epoxy resin), "jER807" (bisphenol F-type epoxy resin), and "jER152" (phenol novolac-type epoxy resin); Mitsubishi Chemical's "630" and "630LSD," and ADEKA's "ED-523T" (glycirol-type epoxy resin (ADEKA glycirol)) and "EP-3980S" (glycidylamine-type epoxy resin). Examples include "EP-4088S" (dicyclopentadiene type epoxy resin); "ZX1059" (a mixture of bisphenol A type epoxy resin and bisphenol F type epoxy resin) from Nippon Steel Chemical & Material Co., Ltd.; "EX-721" (glycidyl ester type epoxy resin) from Nagase ChemteX Co., Ltd.; "Celoxide 2021P" (alicyclic epoxy resin with an ester skeleton) and "PB-3600" (epoxy resin with a butadiene structure) from Daicel Corporation; and "ZX1658" and "ZX1658GS" (1,4-glycidylcyclohexane) from Nippon Steel Chemical & Material Co., Ltd. These can be used individually or in combination of two or more types.

[0063] As the solid epoxy resin, a solid epoxy resin having three or more epoxy groups per molecule is preferred, and an aromatic solid epoxy resin having three or more epoxy groups per molecule is more preferred.

[0064] Preferred solid epoxy resins include bixylenol-type epoxy resin, naphthalene-type epoxy resin, naphthalene-type tetrafunctional epoxy resin, naphthol novolac-type epoxy resin, cresol novolac-type epoxy resin, dicyclopentadiene-type epoxy resin, trisphenol-type epoxy resin, naphthol-type epoxy resin, biphenyl-type epoxy resin, naphthylene ether-type epoxy resin, anthracene-type epoxy resin, bisphenol A-type epoxy resin, bisphenol AF-type epoxy resin, phenol aralkyl-type epoxy resin, tetraphenylethane-type epoxy resin, phenolphthalein-type epoxy resin, and phenolphthalein-type epoxy resin.

[0065] Specific examples of solid epoxy resins include DIC's "HP4032H" (naphthalene-type epoxy resin); DIC's "HP-4700" and "HP-4710" (naphthalene-type tetrafunctional epoxy resins); DIC's "N-690" (cresol novolac-type epoxy resin); DIC's "N-695" (cresol novolac-type epoxy resin); DIC's "HP-7200", "HP-7200HH", "HP-7200H", and "HP-7200L" (dicyclopentadiene-type epoxy resins); and DIC's "EXA-73 11", EXA-7311-G3, EXA-7311-G4, EXA-7311-G4S, HP6000 (naphthylene ether type epoxy resin); Nippon Kayaku Co., Ltd.'s EPPN-502H (trisphenol type epoxy resin); Nippon Kayaku Co., Ltd.'s NC7000L (naphthol novolac type epoxy resin); Nippon Kayaku Co., Ltd.'s NC3000H, NC3000, NC3000L, NC3000FH, NC3100 (biphenyl type epoxy resin); Nippon Steel Chemical & Material Co., Ltd.'s ESN475V (Naphthalene-type epoxy resin); "ESN485" (Naphthol-type epoxy resin) manufactured by Nippon Steel Chemical & Material Co., Ltd.; "ESN375" (Dihydroxynaphthalene-type epoxy resin) manufactured by Nippon Steel Chemical & Material Co., Ltd.; "YX4000H", "YX4000", "YX4000HK", "YL7890" (Bixylenol-type epoxy resin) manufactured by Mitsubishi Chemical Corporation; "YL6121" (Biphenyl-type epoxy resin) manufactured by Mitsubishi Chemical Corporation; "YX8800" (Anthracene-type epoxy resin) manufactured by Mitsubishi Chemical Corporation; "YX77" manufactured by Mitsubishi Chemical Corporation Examples include "00" (phenol aralkyl type epoxy resin); "PG-100" and "CG-500" manufactured by Osaka Gas Chemical Co., Ltd.; "YL7760" (bisphenol AF type epoxy resin) manufactured by Mitsubishi Chemical Corporation; "YL7800" (fluorene type epoxy resin) manufactured by Mitsubishi Chemical Corporation; "jER1010" (bisphenol A type epoxy resin) manufactured by Mitsubishi Chemical Corporation; "jER1031S" (tetraphenylethane type epoxy resin) manufactured by Mitsubishi Chemical Corporation; and "WHR991S" (phenolphthalein-imidine type epoxy resin) manufactured by Nippon Kayaku Co., Ltd. These can be used individually or in combination of two or more types.

[0066] (B-1) When using both a solid epoxy resin and a liquid epoxy resin as the epoxy resin, the mass ratio of the solid epoxy resin to the liquid epoxy resin (solid epoxy resin / liquid epoxy resin) is not particularly limited, but is preferably 1 or less, more preferably 0.5 or less, even more preferably 0.1 or less, even more preferably 0.05 or less, and particularly preferably 0.01 or less.

[0067] (B-1) The epoxy equivalent of the epoxy resin is preferably 50 g / eq. to 5000 g / eq., more preferably 50 g / eq. to 3000 g / eq., even more preferably 80 g / eq. to 2000 g / eq., and particularly preferably 110 g / eq. to 1000 g / eq. The epoxy equivalent is the mass of resin per equivalent of epoxy groups. This epoxy equivalent can be measured according to JIS K7236.

[0068] (B-1) The weight-average molecular weight (Mw) of the epoxy resin is preferably 100 to 5000, more preferably 250 to 3000, and even more preferably 400 to 1500. The weight-average molecular weight of the resin can be measured as a polystyrene equivalent by gel permeation chromatography (GPC).

[0069] (B-1) The epoxy resin content (mass%) is preferably 0.1% by mass or more, more preferably 1% by mass or more, even more preferably 3% by mass or more, particularly preferably 5% by mass or more, preferably 50% by mass or less, more preferably 30% by mass or less, even more preferably 20% by mass or less, particularly preferably 10% by mass or less, when the nonvolatile components in the resin composition are taken as 100% by mass. (B-1) When the epoxy resin content is within the above range, the viscosity of the resin composition and the magnetic loss of the cured product can be effectively reduced, and furthermore, the relative permeability of the cured product of the resin composition can usually be made particularly good.

[0070] (B-1) The epoxy resin content (mass%) is preferably 50% by mass or more, more preferably 60% by mass or more, even more preferably 70% by mass or more, particularly preferably 80% by mass or more, preferably 99% by mass or less, more preferably 95% by mass or less, particularly preferably 90% by mass or less, when the total resin components in the resin composition are considered as 100% by mass. (B-1) When the epoxy resin content is within the above range, the viscosity of the resin composition and the magnetic loss of the cured product can be effectively reduced, and furthermore, the relative permeability of the cured product of the resin composition can usually be made particularly good.

[0071] <(B-2) Epoxy hardener> (B) If the thermosetting resin contains (B-1) epoxy resin, (B) the thermosetting resin may also contain (B-2) epoxy curing agent. (B-2) The epoxy curing agent typically has the function of reacting with (B-1) epoxy resin to cure the resin composition.

[0072] (B-2) The epoxy curing agent is not particularly limited, but examples include phenolic curing agents, carbodiimide curing agents, acid anhydride curing agents, amine curing agents, benzoxazine curing agents, cyanate ester curing agents, thiol curing agents, etc. (B-2) The epoxy curing agent may be used alone or in combination of two or more types. (B-2) The epoxy curing agent preferably contains a phenolic curing agent.

[0073] As a phenol-type curing agent, a curing agent having one or more, preferably two or more, hydroxyl groups bonded to aromatic rings such as benzene rings and naphthalene rings per molecule can be used. Preferred phenol-type curing agents include biphenyl-type curing agents, naphthalene-type curing agents, phenol novolac-type curing agents, naphthylene ether-type curing agents, and triazine skeleton-containing phenol-based curing agents. Preferred examples include the biphenyl-type curing agents "MEH-7700," "MEH-7810," and "MEH-7851" (manufactured by Meiwa Kasei Co., Ltd.), the naphthalene-type curing agents "NHN," "CBN," and "GPH" (manufactured by Nippon Kayaku Co., Ltd.), "SN170," "SN180," "SN190," "SN475," "SN485," "SN495," "SN375," and "SN395" (manufactured by Nippon Steel Chemical Co., Ltd.), and "EXB9500" (manufactured by DIC Corporation), the phenol novolac-type curing agent "TD2090" (manufactured by DIC Corporation), and the naphthylene ether-type curing agent "EXB-6000" (manufactured by DIC Corporation). Specific examples of triazine skeleton-containing phenol-based curing agents include "LA3018," "LA7052," "LA7054," and "LA1356" (manufactured by DIC Corporation). Naphthalene-type curing agents and triazine skeleton-containing phenol-based curing agents are particularly preferred.

[0074] As a carbodiimide-based curing agent, a curing agent having one or more, preferably two or more, carbodiimide structures in one molecule may be used. Examples of carbodiimide-based curing agents include aliphatic biscarbodiimides such as tetramethylene-bis(t-butylcarbodiimide) and cyclohexanebis(methylene-t-butylcarbodiimide); biscarbodiimides such as aromatic biscarbodiimides such as phenylene-bis(xylylcarbodiimide); aliphatic polycarbodiimides such as polyhexamethylenecarbodiimide, polytrimethylhexamethylenecarbodiimide, polycyclohexylenecarbodiimide, poly(methylenebiscyclohexylenecarbodiimide), and poly(isophoronecarbodiimide); and poly(phenylenecarbodiimide), poly( Examples of polycarbodiimides include aromatic polycarbodiimides such as naphthylenecarbodiimide, poly(tylenecarbodiimide), poly(methyldiisopropylphenylenecarbodiimide), poly(triethylphenylenecarbodiimide), poly(diethylphenylenecarbodiimide), poly(triisopropylphenylenecarbodiimide), poly(diisopropylphenylenecarbodiimide), poly(xylylenecarbodiimide), poly(tetramethylxylylenecarbodiimide), poly(methylenediphenylenecarbodiimide), and poly[methylenebis(methylphenylene)carbodiimide].

[0075] Examples of commercially available carbodiimide-based curing agents include "Carbodilite V-02B," "Carbodilite V-03," "Carbodilite V-04K," "Carbodilite V-07," and "Carbodilite V-09" from Nisshinbo Chemical Co., Ltd., and "Stabaczol P," "Stabaczol P400," and "Hycazil 510" from Rhein Chemie Corporation.

[0076] As an acid anhydride-based curing agent, a curing agent having one or more acid anhydride groups in one molecule can be used, and a curing agent having two or more acid anhydride groups in one molecule is preferred. Examples of acid anhydride-based curing agents include phthalic anhydride, tetrahydrophthalic anhydride, hexahydrophthalic anhydride, methyltetrahydrophthalic anhydride, methylhexahydrophthalic anhydride, methylnadic anhydride, hydrogenated methylnadic anhydride, trialkyltetrahydrophthalic anhydride, dodecenyl succinic anhydride, 5-(2,5-dioxotetrahydro-3-furanyl)-3-methyl-3-cyclohexen-1,2-dicarboxylic acid anhydride, trimellitic anhydride, pyromellitic anhydride, and bensophenone tetracarboxylic acid di Examples of acid anhydrides include anhydrides, biphenyltetracarboxylic acid dianhydride, naphthalenetetracarboxylic acid dianhydride, oxydiphthalic acid dianhydride, 3,3'-4,4'-diphenylsulfonetetracarboxylic acid dianhydride, 1,3,3a,4,5,9b-hexahydro-5-(tetrahydro-2,5-dioxo-3-furanyl)-naphtho[1,2-C]furan-1,3-dione, ethylene glycol bis(anhydrotrimellitate), and polymer-type acid anhydrides such as styrene-maleic acid resin copolymerized with styrene and maleic acid. Commercially available acid anhydride-based curing agents include "HNA-100", "MH-700", "MTA-15", "DDSA", and "OSA" from Shin Nippon Rika Co., Ltd., "YH-306" and "YH-307" from Mitsubishi Chemical Corporation, and "HN-2200" and "HN-5500" from Hitachi Chemical Co., Ltd.

[0077] As the amine-based curing agent, a curing agent having one or more, preferably two or more, amino groups in one molecule may be used. Examples of amine-based curing agents include aliphatic amines, polyetheramines, alicyclic amines, aromatic amines, and the like, with aromatic amines being preferred. The amine-based curing agent is preferably a primary amine or a secondary amine, with primary amines being more preferred. Specific examples of amine-based curing agents include 4,4'-methylenebis(2,6-dimethylaniline), 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, and 2,2-bis(3-amino-4-hydroxyphenyl) Examples include propyl propane, 3,3-dimethyl-5,5-diethyl-4,4-diphenylmethanediamine, 2,2-bis(4-aminophenyl)propane, 2,2-bis(4-(4-aminophenoxy)phenyl)propane, 1,3-bis(3-aminophenoxy)benzene, 1,3-bis(4-aminophenoxy)benzene, 1,4-bis(4-aminophenoxy)benzene, 4,4'-bis(4-aminophenoxy)biphenyl, bis(4-(4-aminophenoxy)phenyl)sulfone, bis(4-(3-aminophenoxy)phenyl)sulfone, etc. Amine-based curing agents may be commercially available products, such as "SEIKACURE-S" from Seika Corporation, "KAYABOND C-200S," "KAYABOND C-100," "KAYAHARD AA," "KAYAHARD AB," and "KAYAHARD AS" from Nippon Kayaku Co., Ltd., and "Epicure W" from Mitsubishi Chemical Corporation.

[0078] Specific examples of benzoxazine-based curing agents include "JBZ-OP100D" and "ODA-BOZ" from JFE Chemical Corporation; "HFB2006M" from Showa Polymer Co., Ltd.; and "Pd" and "Fa" from Shikoku Chemicals Co., Ltd.

[0079] Examples of cyanate ester curing agents include bifunctional cyanate resins such as bisphenol A dicyanate, polyphenol cyanate (oligo(3-methylene-1,5-phenylene cyanate)), 4,4'-methylenebis(2,6-dimethylphenyl cyanate), 4,4'-ethylidene diphenyl dicyanate, hexafluorobisphenol A dicyanate, 2,2-bis(4-cyanate)phenylpropane, 1,1-bis(4-cyanatephenylmethane), bis(4-cyanate-3,5-dimethylphenyl)methane, 1,3-bis(4-cyanatephenyl-1-(methylethylidene))benzene, bis(4-cyanatephenyl) thioether, and bis(4-cyanatephenyl) ether; polyfunctional cyanate resins derived from phenol novolacs and cresol novolacs; and prepolymers in which these cyanate resins are partially triazined. Specific examples of cyanate ester-based curing agents include "PT30" and "PT60" (both phenol novolac type polyfunctional cyanate ester resins) manufactured by Lonza Japan, "BA230", and "BA230S75" (prepolymers in which part or all of bisphenol A dicyanate is triazined and trimerized).

[0080] Examples of thiol-based curing agents include trimethylolpropane tris(3-mercaptopropionate), pentaerythritol tetrakis(3-mercaptobutyrate), and tris(3-mercaptopropyl) isocyanurate.

[0081] (B-2) The reactive group equivalent of the epoxy curing agent is preferably 50 g / eq. to 3000 g / eq., more preferably 100 g / eq. to 1000 g / eq., even more preferably 100 g / eq. to 500 g / eq., and particularly preferably 100 g / eq. to 300 g / eq. The reactive group equivalent is the mass of the curing agent per equivalent of one reactive group.

[0082] (B-2) The content (mass%) of the epoxy curing agent is not particularly limited, but when the non-volatile components in the resin composition are taken as 100% by mass, it may be 0% by mass or more, preferably 0.01% by mass or more, more preferably 0.1% by mass or more, preferably 40% by mass or less, more preferably 30% by mass or less, even more preferably 20% by mass or less, and particularly preferably 10% by mass or less.

[0083] <(C) Any additives> The resin composition according to one embodiment of the present invention may further contain (C) any additive as a non-volatile component.

[0084] (C) Preferred examples of optional additives include (C-1) epoxy curing accelerators. (C-1) Epoxy curing accelerators have the function of accelerating the curing of (B-1) epoxy resins. Therefore, it is preferable to use (C-1) epoxy curing accelerators in combination with (B-1) epoxy resins.

[0085] Examples of (C-1) epoxy curing accelerators include imidazole-based curing accelerators, phosphorus-based curing accelerators, urea-based curing accelerators, guanidine-based curing accelerators, metal-based curing accelerators, and amine-based curing accelerators. In one embodiment, it is preferable that the (C-1) epoxy curing accelerator includes an imidazole-based curing accelerator. The (C-1) epoxy curing accelerator may be used alone or in combination of two or more types.

[0086] Examples of imidazole-based curing accelerators 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-undecylimidazolium trimellitate, 1-cyanoethyl-2-phenylimidazolium trimellitate, 2,4-diamino-6-[2'-methylimidazolyl -(1')]-ethyl-s-triazine, 2,4-diamino-6-[2'-undecylimidazolyl-(1')]-ethyl-s-triazine, 2,4-diamino-6-[2'-ethyl-4'-methylimidazolyl-(1')]-ethyl-s-triazine, 2,4-diamino-6-[2'-methylimidazolyl-(1')]-ethyl-s-triazine isocyanurate adduct, 2-phenylimidazole isocyanurate adduct Examples include imidazole compounds such as 2-phenyl-4,5-dihydroxymethylimidazole, 2-phenyl-4-methyl-5-hydroxymethylimidazole, 2,3-dihydro-1H-pyrrolo[1,2-a]benzimidazole, 1-dodecyl-2-methyl-3-benzylimidazolium chloride, 2-methylimidazoline, and 2-phenylimidazoline, as well as adducts of imidazole compounds with epoxy resins.

[0087] Commercially available imidazole-based curing accelerators may be used, such as "1B2PZ," "2MZA-PW," and "2PHZ-PW" from Shikoku Chemicals, and "P200-H50" from Mitsubishi Chemical Corporation.

[0088] Examples of phosphorus-based curing accelerators include aliphatic phosphonium salts such as tetrabutylphosphonium bromide, tetrabutylphosphonium chloride, tetrabutylphosphonium acetate, tetrabutylphosphonium decanoate, tetrabutylphosphonium laurate, bis(tetrabutylphosphonium) pyromelitate, tetrabutylphosphonium hydrogen hexahydrophthalate, tetrabutylphosphonium 2,6-bis[(2-hydroxy-5-methylphenyl)methyl]-4-methylphenolate, and di-tert-butylmethylphosphonium tetraphenylborate; methyltriphenylphosphonium bromide, ethyltriphenylphosphonium bromide, propyltriphenylphosphonium bromide, butyltriphenylphosphonium bromide, benzyltriphenylphosphonium chloride, tetraphenylphosphonium bromide, p-tolyltriphenylphosphonium tetra-p-tolylborate, and tetraphenylphosphonium bromide. Aromatic phosphonium salts such as tetraphenylborate, tetraphenylphosphonium tetra-p-tolylborate, triphenylethylphosphonium tetraphenylborate, tris(3-methylphenyl)ethylphosphonium tetraphenylborate, tris(2-methoxyphenyl)ethylphosphonium tetraphenylborate, (4-methylphenyl)triphenylphosphonium thiocyanate, tetraphenylphosphonium thiocyanate, and butyltriphenylphosphonium thiocyanate; aromatic phosphine-borane complexes such as triphenylphosphine-triphenylborane; aromatic phosphine-quinone addition products such as triphenylphosphine-p-benzoquinone addition products; aliphatic phosphines such as tributylphosphine, tri-tert-butylphosphine, trioctylphosphine, di-tert-butyl(2-butenyl)phosphine, di-tert-butyl(3-methyl-2-butenyl)phosphine, and tricyclohexylphosphine;Dibutylphenylphosphine, di-tert-butylphenylphosphine, methyldiphenylphosphine, ethyldiphenylphosphine, butyldiphenylphosphine, diphenylcyclohexylphosphine, triphenylphosphine, tri-o-tolylphosphine, tri-m-tolylphosphine, tri-p-tolylphosphine, tris(4-ethylphenyl)phosphine, tris(4-propylphenyl)phosphine, tris(4-isopropylphenyl)phosphine, tris(4-butylphenyl)phosphine, tris(4-tert-butylphenyl)phosphine, tris(2,4-dimethylphenyl)phosphine, tris(2,5-dimethylphenyl)phosphine, tris(2,6-dimethylphenyl)phosphine Examples include aromatic phosphines such as tris(3,5-dimethylphenyl)phosphine, tris(2,4,6-trimethylphenyl)phosphine, tris(2,6-dimethyl-4-ethoxyphenyl)phosphine, tris(2-methoxyphenyl)phosphine, tris(4-methoxyphenyl)phosphine, tris(4-ethoxyphenyl)phosphine, tris(4-tert-butoxyphenyl)phosphine, diphenyl-2-pyridylphosphine, 1,2-bis(diphenylphosphino)ethane, 1,3-bis(diphenylphosphino)propane, 1,4-bis(diphenylphosphino)butane, 1,2-bis(diphenylphosphino)acetylene, and 2,2'-bis(diphenylphosphino)diphenyl ether.

[0089] Examples of urea-based curing accelerators include aliphatic dimethylureas such as 1,1-dimethylurea, 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 toluenebisdimethylurea, 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) [toluenebisdimethylurea] are examples.

[0090] 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]deca-5-ene, 7-methyl-1,5,7-triazabicyclo[4.4.0]deca-5-ene, 1-methylbiguanide, 1-ethylbiguanide, 1-n-butylbiguanide, 1-n-octadecylbiguanide, 1,1-dimethylbiguanide, 1,1-diethylbiguanide, 1-cyclohexylbiguanide, 1-allylbiguanide, 1-phenylbiguanide, and 1-(o-tolyl)biguanide.

[0091] Examples of metal-based hardening 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 organocobalt complexes such as cobalt(II) acetylacetonate and cobalt(III) acetylacetonate, organocopper complexes such as copper(II) acetylacetonate, organozinc complexes such as zinc(II) acetylacetonate, organoiron complexes such as iron(III) acetylacetonate, organonickel complexes such as nickel(II) acetylacetonate, and organomanganese complexes such as manganese(II) acetylacetonate. Examples of organometallic salts include zinc octoate, tin octoate, zinc naphthenate, cobalt naphthenate, tin stearate, and zinc stearate.

[0092] Examples of amine-based curing accelerators include trialkylamines such as triethylamine and tributylamine, 4-dimethylaminopyridine, benzyldimethylamine, 2,4,6-tris(dimethylaminomethyl)phenol, and 1,8-diazabicyclo(5,4,0)-undecene. Commercially available amine-based curing accelerators may also be used, such as "MY-25" manufactured by Ajinomoto Fine Techno Co., Ltd.

[0093] (C-1) The content (mass%) of the epoxy curing accelerator may be 0% by mass or more than 0% by mass, when the non-volatile components in the resin composition are taken as 100% by mass, preferably 0.01% by mass or more, more preferably 0.1% by mass or more, particularly preferably 0.3% by mass or more, preferably 10% by mass or less, more preferably 5% by mass or less, even more preferably 2% by mass or less, particularly preferably 1% by mass or less. (C-1) When the content of the epoxy curing accelerator is within the above range, the viscosity of the resin composition and the magnetic loss of the cured product can be effectively reduced, and furthermore, the relative permeability of the cured product of the resin composition can usually be made particularly good.

[0094] (C-1) The content (mass%) of the epoxy curing accelerator may be 0 mass%, or more than 0 mass%, when the resin component in the resin composition is considered as 100 mass%, preferably 0.1 mass% or more, more preferably 1 mass% or more, particularly preferably 2 mass% or more, preferably 20 mass% or less, more preferably 15 mass% or less, even more preferably 10 mass% or less, particularly preferably 7 mass% or less. (C-1) When the content of the epoxy curing accelerator is within the above range, the viscosity of the resin composition and the magnetic loss of the cured product can be effectively reduced, and furthermore, the relative permeability of the cured product of the resin composition can usually be made particularly good.

[0095] (C) Another preferred example of an optional additive is (C-2) a dispersant. (C-2) A dispersant can improve the dispersibility of (A) the magnetic powder. (C-2) A dispersant may be used alone or in combination of two or more types.

[0096] (C-2) Examples of dispersants include phosphate ester dispersants, polyoxyalkylene dispersants, acetylene dispersants, silicone dispersants, anionic dispersants, cationic dispersants, and the like.

[0097] Among phosphate ester dispersants, polyether-type phosphate ester dispersants are preferred. Polyether-type phosphate ester dispersants are phosphate ester dispersants that contain a poly(alkylene oxy) structure in their molecules. Examples of polyether-type phosphate ester dispersants include polyoxyalkylene alkyl ether phosphate esters and polyoxyalkylene alkylphenyl ether phosphate esters. Among these, polyoxyalkylene alkyl ether phosphate esters are preferred.

[0098] Polyoxyalkylene alkyl ether phosphate esters may have a structure in which 1 to 3 alkyl-oxy-poly(alkyleneoxy) groups are bonded to the phosphorus atoms of the phosphate. The number of alkyleneoxy units (repeating units) in the poly(alkyleneoxy) moiety of the alkyl-oxy-poly(alkyleneoxy) group is preferably 2 to 30, and more preferably 3 to 20. Furthermore, 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 ethylene, propylene, isopropylene, butylene, and isobutyl. In addition, the alkyl group in the alkyl-oxy-poly(alkyleneoxy) group is preferably an alkyl group having 6 to 30 carbon atoms, and 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. Furthermore, if the polyoxyalkylene alkyl ether phosphate ester has multiple alkyl-oxy-poly(alkyleneoxy) groups, the multiple alkyl groups may be the same or different. Additionally, the multiple alkylene groups may be the same or different.

[0099] Examples of commercially available phosphate ester dispersants include polyether-type phosphate ester dispersants from Kusumoto Chemical Co., Ltd. (e.g., the HIPLAAD series such as "ED152", "ED153", "ED154", "ED118", "ED174", and "ED251"); and the Phosphanol series from Toho Chemical Industry Co., Ltd., such as "RS-410", "RS-610", and "RS-710".

[0100] Examples of polyoxyalkylene-based dispersants include polyoxyethylene alkyl ethers, polyoxyethylene alkyl esters, polyoxyethylene sorbitan fatty acid esters, polyoxyethylene alkylphenyl ethers, polyoxyethylene alkylamines, and polyoxyethylene alkylamides. Examples of commercially available polyoxyalkylene-based dispersants include NOF Corporation's "Marialim" series, such as "AKM-0531," "AFB-1521," "SC-0505K," "SC-1015F," and "SC-0708A," as well as "HKM-50A."

[0101] Examples of acetylene-based dispersants include acetylene glycol. Examples of commercially available acetylene-based dispersants include Air Products and Chemicals Inc.'s "Surfinol" series, specifically "82," "104," "440," "465," and "485," as well as "Olefin Y."

[0102] Examples of silicone-based dispersants include polyether-modified polydimethylsiloxane, polyether-modified siloxane, and polyester-modified polydimethylsiloxane. Examples of commercially available silicone-based dispersants include "BYK347" and "BYK348" manufactured by BIC Chemie.

[0103] Examples of anionic dispersants include sodium polyacrylate, sodium dodecylbenzylsulfonate, sodium lauryl sulfate, polyoxyethylene alkyl ether sulfate ammonium, and sodium carboxymethylcellulose salt. Examples of commercially available anionic dispersants include "PN-411" and "PA-111" from Ajinomoto Fine Techno Co., Ltd., and "A-550" and "PS-1900" from Lion Corporation.

[0104] Examples of cationic dispersants include amino group-containing polyacrylate resins and amino group-containing polystyrene resins. Examples of commercially available cationic dispersants include "161," "162," "164," "182," "2000," and "2001" from Bic Chemie; "PB-821," "PB-822," and "PB-824" from Ajinomoto Fine Techno; "V-216" and "V-220" from ISP Japan; and "Solspers 13940," "Solspers 24000," and "Solspers 32000" from Lubrizol.

[0105] (C-2) The content (mass%) of the dispersant may be 0% by mass or more than 0% by mass, when the non-volatile components in the resin composition are taken as 100% by mass, preferably 0.01% by mass or more, more preferably 0.1% by mass or more, even more preferably 0.2% by mass or more, particularly preferably 0.4% by mass or more, preferably 10% by mass or less, more preferably 5% by mass or less, even more preferably 2% by mass or less, particularly preferably 1% by mass or less. (C-2) When the content of the dispersant is within the above range, the viscosity of the resin composition and the magnetic loss of the cured product can be effectively reduced, and furthermore, the relative permeability of the cured product of the resin composition can usually be made particularly good.

[0106] (C-2) The content (mass%) of the dispersant may be 0% by mass or more than 0% by mass, when the resin component in the resin composition is considered as 100% by mass, preferably 0.1% by mass or more, more preferably 1% by mass or more, even more preferably 2% by mass or more, particularly preferably 5% by mass or more, preferably 20% by mass or less, more preferably 15% by mass or less, and even more preferably 10% by mass or less. (C-2) When the content of the dispersant is within the above range, the viscosity of the resin composition and the magnetic loss of the cured product can be effectively reduced, and furthermore, the relative permeability of the cured product of the resin composition can usually be made particularly good.

[0107] (C) Other examples of optional additives include: radical polymerizable compounds such as maleimide-based radical polymerizable compounds, vinylphenyl-based radical polymerizable compounds, (meth)acrylic-based radical polymerizable compounds, allyl-based radical polymerizable compounds, and polybutadiene-based radical polymerizable compounds; radical polymerizable initiators such as peroxide-based radical polymerizing initiators and azo-based radical polymerizing initiators; thermoplastic resins such as polyvinyl acetal resins, polyolefin resins, polysulfone resins, polyethersulfone resins, polyphenylene ether resins, polycarbonate resins, polyetheretherketone resins, and polyester resins; organic fillers such as rubber particles; organometallic compounds such as organocopper compounds and organozinc compounds; polymerization inhibitors such as hydroquinone, catechol, pyrogallol, and phenothiazine; leveling agents such as silicone-based leveling agents and acrylic polymer-based leveling agents; thickeners such as bentonite and montmorillonite; and silicones. Examples of antifoaming agents include: defoaming agents such as acrylic, fluorine, and vinyl resin defoaming agents; ultraviolet absorbers such as benzotriazole ultraviolet absorbers; adhesion improvers such as urea silane; adhesion improvers such as triazole, tetrazole, and triazine adhesion improvers; antioxidants such as hindered phenol and hindered amine antioxidants; fluorescent whitening agents such as stilbene derivatives; surfactants such as fluorine and silicone 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, titanate, aluminate, zirconate, isocyanate, carboxylic acid, and carboxylic acid anhydride stabilizers. The content of these (C) optional additives can be appropriately determined by a person skilled in the art.

[0108] <(D) Organic solvents> The resin composition according to one embodiment of the present invention may further contain any (D) organic solvent as a volatile component, in addition to the non-volatile components such as components (A) to (C) described above. The (D) organic solvent is preferably one capable of dissolving at least a portion of the non-volatile components. Examples of (D) organic solvents include: ketone solvents such as acetone, methyl ethyl ketone, methyl isobutyl ketone, and cyclohexanone; ester solvents such as methyl acetate, ethyl acetate, butyl acetate, isobutyl acetate, isoamyl acetate, methyl propionate, ethyl propionate, and γ-butyrolactone; ether solvents such as tetrahydropyran, tetrahydrofuran, 1,4-dioxane, diethyl ether, diisopropyl ether, dibutyl ether, and diphenyl ether; alcohol 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 include ether ester solvents such as: methyl lactate, ethyl lactate, methyl 2-hydroxyisobutyrate, etc.; ether alcohol solvents such as 2-methoxypropanol, 2-methoxyethanol, 2-ethoxyethanol, propylene glycol monomethyl ether, diethylene glycol monobutyl ether (butyl carbitol), etc.; amide solvents such as N,N-dimethylformamide, N,N-dimethylacetamide, N-methyl-2-pyrrolidone, etc.; sulfoxide solvents such as dimethyl sulfoxide, etc.; nitrile solvents such as acetonitrile, propionitrile, etc.; aliphatic hydrocarbon solvents such as hexane, cyclopentane, cyclohexane, methylcyclohexane, etc.; aromatic hydrocarbon solvents such as benzene, toluene, xylene, ethylbenzene, trimethylbenzene, etc. (D) Organic solvents may be used individually or in combination of two or more types.

[0109] There are no restrictions on the content of (D) organic solvent. In one embodiment, the lower the content of (D) organic solvent, the better. For example, if the nonvolatile components in the resin composition are 100% by mass, the content of (D) organic solvent may be 3% by mass or less, 1% by mass or less, 0.5% by mass or less, 0.1% by mass or less, 0.01% by mass or less, etc. It is particularly preferable that the resin composition does not contain (D) organic solvent (0% by mass).

[0110] <Properties of resin compositions> A resin composition according to one embodiment of the present invention can be cured by heat. Therefore, a cured product of the resin composition can be obtained by heat curing the resin composition. Normally, among the components contained in the resin composition, volatile components such as (D) organic solvents may volatilize due to the heat during heat curing, but non-volatile components such as components (A) to (C) do not volatilize due to the heat during heat curing. Therefore, the cured product of the resin composition may contain the non-volatile components of the resin composition or their reaction products.

[0111] A resin composition according to one embodiment of the present invention may have a low viscosity. A resin composition according to one embodiment of the present invention does not necessarily have a viscosity within a specific range, but preferably has the following viscosity. For example, the viscosity of the resin composition measured under the measurement conditions of a temperature of 25°C and a rotation speed of 5 rpm using the method described in <Test Example 1: Viscosity Measurement> below is preferably 140 Pa·s or less, more preferably 130 Pa·s or less, particularly preferably 120 Pa·s or less, preferably 10 Pa·s or more, more preferably 20 Pa·s or more, and particularly preferably 40 Pa·s or more. Furthermore, the viscosity of the resin composition measured under the measurement conditions of a temperature of 25°C and a rotation speed of 0.5 rpm using the method described in <Test Example 1: Viscosity Measurement> below is preferably 310 Pa·s or less, more preferably 300 Pa·s or less, even more preferably 290 Pa·s or less, particularly preferably 280 Pa·s or less, preferably 10 Pa·s or more, more preferably 20 Pa·s or more, and particularly preferably 40 Pa·s or more.

[0112] Generally, cured resin compositions containing magnetic powder can have higher relative permeability as the amount of magnetic powder increases. However, typically, the viscosity of the resin composition tends to increase as the amount of magnetic powder increases. Therefore, conventionally, it has been difficult to achieve both high relative permeability of the cured product and low viscosity of the resin composition. Consequently, it has been difficult to achieve high relative permeability of the cured product relative to the viscosity of the resin composition. In contrast, the resin composition according to this embodiment typically allows for a higher relative permeability of the cured product compared to the viscosity of the resin composition. Specifically, the ratio of the relative permeability of the cured product to the viscosity of the resin composition (relative permeability / viscosity) can be increased. Therefore, the resin composition according to this embodiment makes it possible to achieve both a high relative permeability of the cured product and a low viscosity of the resin composition.

[0113] A cured product of a resin composition according to one embodiment of the present invention may have low magnetic loss (μ'' / μ'). A cured product of a resin composition according to one embodiment of the present invention does not necessarily have a magnetic loss (μ'' / μ') within a specific range, but preferably has the following viscosity. For example, the magnetic loss (μ'' / μ') of a cured product of a resin composition measured under measurement conditions of a measurement frequency of 100 MHz and a temperature of 23°C using the method described in <Test Example 2: Measurement and Evaluation of Relative Permeability and Magnetic Loss> below is preferably 0.100 or less, more preferably 0.090 or less, and particularly preferably 0.080 or less.

[0114] Furthermore, the resin composition according to one embodiment of the present invention can reduce both viscosity and magnetic loss in a balanced manner. Therefore, the resin composition according to one embodiment of the present invention can effectively reduce the product of the magnetic loss of the cured product and the viscosity of the resin composition (magnetic loss × viscosity). For example, both magnetic loss and viscosity can be reduced compared to conventional methods, thereby reducing their product. Also, for example, the product can be reduced by lowering the viscosity while maintaining a similar level of magnetic loss to conventional methods. Moreover, for example, the product can be reduced by lowering the magnetic loss while maintaining a similar level of viscosity to conventional methods.

[0115] A cured resin composition according to one embodiment of the present invention can typically have a high relative permeability (μ'). For example, the relative permeability (μ') of a cured resin composition measured under the measurement conditions of a measurement frequency of 100 MHz and a temperature of 23°C using the method described later in <Test Example 2: Measurement and Evaluation of Relative Permeability and Magnetic Loss> is preferably 5.0 or higher, more preferably 6.0 or higher, even more preferably 7.0 or higher, and particularly preferably 8.0 or higher. There is no particular upper limit, and it may be, for example, 20 or less, 15 or less, 13 or less, etc.

[0116] The resin composition according to one embodiment of the present invention may be used in the form of a paste-like resin composition at room temperature (25°C), or in the form of a resin sheet containing a layer of the resin composition.

[0117] The resin composition according to one embodiment of the present invention may be a paste-like resin composition using an organic solvent, or it may be a paste-like resin composition that does not contain an organic solvent by using a liquid thermosetting resin such as a liquid epoxy resin. By having a low content of organic solvents in the resin composition, or by not containing any organic solvents at all, the generation of voids due to the volatilization of organic solvents can be suppressed, and the composition can also be made easier to handle and work with.

[0118] A resin composition according to one embodiment of the present invention can be suitably used, for example, as a resin composition for filling through-holes. Furthermore, a resin composition according to one embodiment of the present invention can be suitably used, for example, as a resin composition for forming inductor base elements for manufacturing inductor elements.

[0119] <Method for producing resin compositions> A resin composition according to one embodiment of the present invention can be produced, for example, by adding (A) magnetic powder, (B) thermosetting resin, optionally (C) any additive, and optionally (D) organic solvent in any order and / or partially or entirely simultaneously to any preparation container and mixing. The temperature can be set appropriately during the process of adding and mixing each component, and heating and / or cooling may be performed temporarily or throughout the process. Stirring or shaking may also be performed during the process of adding and mixing each component. The resin composition may also be stirred or shaken using, for example, a stirring device or shaking device such as a mixer to ensure uniform dispersion during or after adding and mixing. Degassing may also be performed simultaneously with stirring or shaking under low-pressure conditions such as vacuum.

[0120] <Magnetic paste> A magnetic paste (or magnetic ink) according to one embodiment of the present invention contains the resin composition described above. Since the magnetic paste is usually a fluid paste containing the resin composition, it can be preferably used for filling through-holes by printing. This magnetic paste may contain only the resin composition described above, or it may contain any other components in combination with the resin composition. Preferably, the paste-like resin composition itself can be used as the magnetic paste.

[0121] The viscosity of the magnetic paste measured under the measurement conditions of a temperature of 25°C and a rotation speed of 5 rpm using the method described in <Test Example 1: Viscosity Measurement> below is preferably 140 Pa·s or less, more preferably 130 Pa·s or less, particularly preferably 120 Pa·s or less, preferably 30 Pa·s or more, more preferably 40 Pa·s or more, and particularly preferably 50 Pa·s or more.

[0122] <Resin sheet> A resin sheet according to one embodiment of the present invention includes a support and a resin composition layer provided on the support. The resin composition layer includes the above-described resin composition, and preferably includes only the resin composition.

[0123] From the viewpoint of miniaturization, the thickness of the resin composition layer is preferably 250 μm or less, more preferably 200 μm or less. The lower limit of the thickness of the resin composition layer may be, for example, 5 μm or more, 10 μm or more, etc.

[0124] Examples of support materials include films made of plastic materials, metal foils, and release paper, with films made of plastic materials and metal foils being preferred.

[0125] When using a film made of plastic material as a support, examples of plastic materials 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, triacetylcellulose (TAC), polyether sulfide (PES), polyether ketone, and polyimide. Among these, polyethylene terephthalate and polyethylene naphthalate are preferred, and inexpensive polyethylene terephthalate is particularly preferred.

[0126] When using metal foil as a support, examples of metal foil include copper foil and aluminum foil, with copper foil being preferred. As for copper foil, foil made of single-metal copper may be used, or foil made of an alloy of copper with another metal (for example, tin, chromium, silver, magnesium, nickel, zirconium, silicon, titanium, etc.) may be used.

[0127] The support may have a matte finish or corona treatment applied to the surface that bonds with the resin composition layer.

[0128] Furthermore, as the support, a support with a release layer may be used, which has a release layer on the surface that is bonded to the resin composition layer. Examples of release agents used in the release layer of the support with a release layer include one or more release agents selected from the group consisting of alkyd-based release agents, polyolefin-based release agents, urethane-based release agents, and silicone-based release agents. Commercially available products may be used as the support with a release layer, for example, PET films having a release layer mainly composed of a silicone-based release agent or an alkyd resin-based release agent, such as "PET501010", "SK-1", "AL-5", and "AL-7" from Lintec Corporation; "Lumirror T60" from Toray Industries, Inc.; "Purex" from Teijin Ltd.; and "Unipeel" from Unitika Corporation.

[0129] The thickness of the support is not particularly limited, but is preferably in the range of 5 μm to 75 μm, and more preferably in the range of 10 μm to 60 μm. When using a support with a release layer, it is preferable that the overall thickness of the support with the release layer is within the above range.

[0130] In a resin sheet, a protective film similar to that of the support may be provided on the side of the resin composition layer that is not bonded to the support (i.e., the side opposite to the support). The thickness of the protective film is not particularly limited, but for example, it is 1 μm to 40 μm. By providing a protective film, it is possible to suppress the adhesion of dust and other debris and scratches to the surface of the resin composition layer.

[0131] A resin sheet can be manufactured, for example, by coating a resin composition onto a support using a die coater or the like to form a resin composition layer. If necessary, an organic solvent may be mixed with the resin composition before coating onto the support. If an organic solvent is used, drying may be performed after coating if necessary.

[0132] Drying may be carried out by methods such as heating or blowing hot air. The drying conditions are not particularly limited, but the resin composition layer should be dried so that the content of organic solvent in the resin composition layer is 10% by mass or less, preferably 5% by mass or less. Depending on the components contained in the resin composition, the resin composition layer can be formed by drying at 50°C to 150°C for 3 to 10 minutes.

[0133] Resin sheets can be stored by rolling them up. If the resin sheet has a protective film, it can usually be used after removing the protective film.

[0134] <Circuit board and method for manufacturing the same> The circuit board includes a cured product of the resin composition described above. The circuit board according to the first embodiment of the present invention comprises a substrate having through holes and a cured product of the resin composition filled in the through holes. The circuit board according to the second embodiment of the present invention comprises a cured product layer containing a cured product of the resin composition. The first and second embodiments relating to the circuit board will be described below. However, the method for manufacturing the circuit board is not limited to the first and second embodiments illustrated below.

[0135] <Circuit board according to the first embodiment> The circuit board according to the first embodiment can be manufactured, for example, by a manufacturing method including the following steps (1) to (5). In the first embodiment, it is preferable to form a cured product using a resin composition, and more preferable to form a cured product using a paste-like resin composition. (1) A step of filling through-holes of a substrate having through-holes with a resin composition, (2) A step of heat-curing the resin composition to obtain a cured product, (3) A step of polishing the surface of the cured product or resin composition. (4) A step of roughening the cured product, and (5) A step of forming a conductive layer on the surface of the cured material that has been roughened. In the method for manufacturing a circuit board of the present invention, steps (1) to (5) may be carried out in that order, or step (2) may be carried out after step (3).

[0136] <Process (1)> In carrying out step (1), the method for manufacturing the circuit board may include a step of preparing a resin composition. The resin composition is as described above.

[0137] Furthermore, the process (1) may include a step of preparing a core substrate 10 comprising a support substrate 11, and a first metal layer 12 and a second metal layer 13 made of metal such as copper foil provided on both surfaces of the support substrate 11, as shown in Figure 1 as an example. Examples of materials for 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. Examples of materials for the first and second metal layers include copper foil with carriers and materials for the conductive layer described later.

[0138] Furthermore, the method for manufacturing the circuit board may include a step of forming through-holes 14 in the core substrate 10, as shown in Figure 2 as an example. The through-holes 14 can be formed by, for example, drilling, laser irradiation, plasma irradiation, etc. Specifically, the through-holes 14 can be formed by creating through-holes in the core substrate 10 using a drill or the like.

[0139] The through-hole 14 can be formed using a commercially available drilling device. Examples of commercially available drilling devices include the "ND-1S211" manufactured by Hitachi Via Mechanics Co., Ltd.

[0140] After forming through-holes 14 in the core substrate 10, the process may include forming plating layers 20 inside the through-holes 14, on the surface of the first metal layer 12, and on the surface of the second metal layer 13, as shown in an example in Figure 3. Alternatively, the core substrate 10 may be roughened before forming the plating layers 20 if necessary.

[0141] The aforementioned roughening treatment may be either dry or wet. An example of a dry roughening treatment is plasma treatment. An example of a wet roughening treatment is a method in which swelling treatment with a swelling solution, roughening treatment with an oxidizing agent, and neutralization treatment with a neutralizing solution are performed in that order.

[0142] The plating layer 20 can be formed by a plating method. The procedure for forming the plating layer 20 by the plating method is the same as that for forming the conductive layer in step (5) described later.

[0143] After preparing the core substrate 10, the resin composition 30a is filled into the through-holes 14, as shown in Figure 4 as an example. Filling can be done, for example, by printing. Examples of printing methods include printing the resin composition 30a into the through-holes 14 via a squeegee, printing the resin composition 30a via a cartridge, printing the resin composition 30a using mask printing, roll coating, and inkjet printing.

[0144] <Process (2)> In step (2), after filling the through-hole 14 with the resin composition 30a, the resin composition 30a is heat-cured to form a cured product 30 in the through-hole 14, as shown in an example in Figure 5. The heat-curing conditions for the resin composition 30a may vary depending on the composition and type of the resin composition 30a, but the curing temperature is preferably 120°C or higher, more preferably 130°C or higher, even more preferably 150°C or higher, preferably 245°C or lower, more preferably 220°C or lower, and even more preferably 200°C or lower. The curing time for the resin composition 30a is preferably 5 minutes or more, more preferably 10 minutes or more, even more preferably 15 minutes or more, preferably 120 minutes or less, more preferably 110 minutes or less, and even more preferably 100 minutes or less.

[0145] The degree of hardening of the cured product 30 in step (2) is preferably 80% or more, more preferably 85% or more, and even more preferably 90% or more. The degree of hardening can be measured, for example, using a differential scanning calorimetry device.

[0146] Prior to thermal curing the resin composition 30a, a preheating treatment may be performed on the resin composition 30a by heating it at a temperature lower than the curing temperature. For example, prior to thermal curing the resin composition 30a, the resin composition 30a may be preheated at a temperature of 50°C or higher but less than 120°C (preferably 60°C or higher but 110°C or lower, more preferably 70°C or higher but 100°C or lower) for 5 minutes or more (preferably 5 minutes to 150 minutes, more preferably 15 minutes to 120 minutes).

[0147] <Process (3)> In step (3), as shown in Figure 6 as an example, excess hardened material 30 protruding from or adhering to the core substrate 10 is removed by polishing and flattened. As for the polishing method, a method that can polish away excess hardened material 30 protruding from or adhering to the core substrate 10 can be used. Examples of such polishing methods include buff polishing and belt polishing. A commercially available buff polishing device is the "NT-700IM" manufactured by Ishii Hyoki Co., Ltd.

[0148] The arithmetic mean roughness (Ra) of the polished surface of the cured product 30 (after the heat curing of the cured product layer) is preferably 300 nm or more, more preferably 350 nm or more, and even more preferably 400 nm or more, from the viewpoint of improving 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.

[0149] If step (3) is performed after step (2), heat treatment may be performed after step (2) and before step (3) if necessary, in order to further increase the degree of hardening of the cured product 30. The temperature in the heat treatment may be set in accordance with the curing temperature described above. The specific temperature for the heat treatment is preferably 120°C or higher, more preferably 130°C or higher, even more preferably 150°C or higher, 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 more, more preferably 10 minutes or more, even more preferably 15 minutes or more, preferably 90 minutes or less, more preferably 70 minutes or less, and even more preferably 60 minutes or less.

[0150] Furthermore, if 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 its 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, 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 more, more preferably 10 minutes or more, even more preferably 15 minutes or more, preferably 90 minutes or less, more preferably 70 minutes or less, and even more preferably 60 minutes or less.

[0151] <Process (4)> In step (4), the surface polished in step (3) is subjected to a roughening treatment (desmear treatment). The procedure and conditions of the roughening process are not particularly limited, and known procedures and conditions that are normally used in the manufacturing of multilayer printed circuit boards can be adopted. As a roughening process, for example, the cured product 30 can be roughened by performing a swelling treatment with a swelling liquid, a roughening treatment with an oxidizing agent, and a neutralization treatment with a neutralizing liquid in this order.

[0152] The swelling solution that can be used in the roughening process is not particularly limited, but examples include alkaline solutions and surfactant solutions, and an alkaline solution is preferred. As the alkaline solution used as the swelling solution, sodium hydroxide solution and potassium hydroxide solution are more preferred. Examples of commercially available swelling solutions include "Swelling Dip Securing P" and "Swelling Dip Securing SBU" manufactured by Atotech Japan Co., Ltd.

[0153] The swelling treatment with a swelling solution is not particularly limited, but for example, it can be carried out by immersing the core substrate 10 on which the cured product 30 is provided in a swelling solution at 30°C to 90°C for 1 to 20 minutes. From the viewpoint of suppressing the swelling of the resin constituting the cured product 30 to an appropriate level, it is preferable to immerse the cured product 30 in a swelling solution at 40°C to 80°C for 5 to 15 minutes.

[0154] The oxidizing agent that can be used for roughening treatment with an oxidizing agent is not particularly limited, but examples include an alkaline permanganate solution obtained by dissolving potassium permanganate or sodium permanganate in an aqueous solution of sodium hydroxide. The roughening treatment with an oxidizing agent such as an alkaline permanganate solution is preferably carried out by immersing the hardened material 30 in an oxidizing agent solution heated to 60°C to 80°C for 10 to 30 minutes. Furthermore, the concentration of permanganate in the alkaline permanganate solution is preferably 5% to 10% by mass. Examples of commercially available oxidizing agents include alkaline permanganate solutions such as "Concentrate Compact P" and "Dosing Solution Securigans P" manufactured by Attec Japan.

[0155] An acidic aqueous solution is preferred as the neutralizing solution that can be used for the neutralization treatment. A commercially available neutralizing solution is, for example, "Reduction Solution Securigans P" manufactured by Attec Japan. The neutralization treatment with the neutralizing solution can be carried out by immersing the treated surface, which has been roughened with an oxidizing agent solution, in a neutralizing solution at 30°C to 80°C for 5 to 30 minutes. From the viewpoint of workability, it is preferable to immerse the hardened product 30, which has been roughened with an oxidizing agent solution, in a neutralizing solution at 40°C to 70°C for 5 to 20 minutes.

[0156] The arithmetic mean roughness (Ra) 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 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.

[0157] <Process (5)> In step (5), as shown in Figure 7 as an example, a conductive layer 40 is formed on the polished surface of the cured product 30 and on the core substrate 10. Furthermore, after forming the conductive layer 40, as shown in Figure 8 as an example, the conductive layer 40, the first metal layer 12, the second metal layer 13, and a portion of the plating layer 20 may be removed by etching or other processes to form a pattern conductive layer 41. In Figure 7, the conductive layer 40 is formed on both sides of the core substrate 10, but the conductive layer 40 may be formed on only one side of the core substrate 10.

[0158] Methods for forming the conductor layer 40 include, for example, plating, sputtering, and vapor deposition, with plating being preferred. In a preferred embodiment, the surface of the hardened material 30 (and the plated layer 20) is plated by a suitable method such as a semi-additive method or a fully additive method to form a patterned conductor layer 41 having a desired wiring pattern. Examples of materials for the conductor layer 40 include single metals such as gold, platinum, palladium, silver, copper, aluminum, cobalt, chromium, zinc, nickel, titanium, tungsten, iron, tin, and indium; and alloys of two or more metals selected from the group consisting of gold, platinum, palladium, silver, copper, aluminum, cobalt, chromium, zinc, nickel, titanium, tungsten, iron, tin, and indium. In particular, from the viewpoint of versatility, cost, and ease of patterning, it is preferable to use chromium, nickel, titanium, aluminum, zinc, gold, palladium, silver, or copper, or nickel-chromium alloys, copper-nickel alloys, or copper-titanium alloys; it is more preferable to use chromium, nickel, titanium, aluminum, zinc, gold, palladium, silver, or copper, or nickel-chromium alloys; and it is even more preferable to use copper.

[0159] Here, an example of an embodiment in which a patterned conductor layer 41 is formed on the polished surface of the cured material 30 will be described in detail. A plating seed layer is formed on the polished surface of the cured material 30 by electroless plating. Next, an electroplated layer is formed on the formed plating seed layer by electroplating, and if necessary, the unnecessary plating seed layer can be removed by etching or other treatment to form a conductor layer 40 having a desired wiring pattern. After the formation of the conductor layer 40, annealing treatment may be performed as necessary for purposes such as improving the peel strength of the conductor layer 40. Annealing treatment can be performed, for example, by heating the circuit board at 150 to 200°C for 20 to 90 minutes.

[0160] From the viewpoint of miniaturization, the thickness of the pattern conductor layer is preferably 70 μm or less, more preferably 60 μm or less, even more preferably 50 μm or less, even more preferably 40 μm or less, and 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.

[0161] <Circuit board according to the second embodiment> The circuit board of the second embodiment comprises a cured layer containing a cured resin composition. Preferably, the cured layer contains only a cured resin composition. In the method for manufacturing the circuit board according to the second embodiment, preferably a resin sheet is used to form the cured layer. The method for manufacturing the circuit board according to the second embodiment will be described below. Sections that overlap with the description of the first embodiment will be omitted as appropriate.

[0162] The circuit board according to the second embodiment can be manufactured, for example, by a manufacturing method including the following steps (A) to (D). (A) A step of forming a cured material layer on an inner layer substrate, (B) A process of drilling holes in the hardened material layer. (C) A step of roughening the surface of the hardened layer, (D) A step of forming a conductive layer on the polished surface of the hardened material layer.

[0163] The following provides a detailed explanation of the above-mentioned processes (A) to (D) in the manufacturing of the circuit board.

[0164] <Process (A)> Step (A) is a step of forming a cured material layer on an inner layer substrate. Preferably, step (A) includes laminating a resin sheet onto an inner layer substrate such that the resin composition layer is bonded to the inner layer substrate, thereby forming a cured material layer. In step (A), for example, a resin sheet is laminated onto an inner layer substrate such that the resin composition layer is bonded to the inner layer substrate, and the resin composition layer is heat-cured to form a cured material layer.

[0165] In step (A), as shown in Figure 9 as an example, a resin sheet 310 including a support 330 and a resin composition layer 320a provided on the support 330 is laminated onto an inner layer substrate 200 such that the resin composition layer 320a is bonded to the inner layer substrate 200.

[0166] The inner layer substrate 200 may be an insulating substrate. Examples of materials for the inner layer substrate 200 include insulating substrates such as glass epoxy substrates, metal substrates, polyester substrates, polyimide substrates, BT resin substrates, and thermosetting polyphenylene ether substrates. The inner layer substrate 200 may also be an inner layer circuit board in which wiring and other structures are fabricated within its thickness.

[0167] As shown in Figure 9 as an example, the inner layer substrate 200 has a first conductor layer 420 provided on a first main surface 200a and an external terminal 240 provided on a second main surface 200b. The first conductor layer 420 may include multiple wirings. In the illustrated example, only the wiring constituting the coil-shaped conductive structure 400 of the inductor element is shown. The external terminal 240 is a terminal for electrically connecting to an external device or the like (not shown). The external terminal 240 can be configured as part of the conductor layer provided on the second main surface 200b.

[0168] The conductor material that can constitute the first conductor layer 420 and the external terminal 240 may be the same as the conductor layer material described in the "<Step (5)>" section of the first embodiment.

[0169] The first conductor layer 420 and the external terminal 240 may be a single-layer structure, or they may be a multi-layer structure in which two or more single-metal or alloy layers made of different types of metals or alloys are laminated. Furthermore, 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, which will be described later.

[0170] The line (L) / space (S) ratio of the first conductor layer 420 and the external terminal 240 is not particularly limited, but from the viewpoint of reducing surface irregularities and obtaining a cured product layer with excellent smoothness, it is usually 900 / 900 μm or less, preferably 700 / 700 μm or less, more preferably 500 / 500 μm or less, even more preferably 300 / 300 μm or less, and even more preferably 200 / 200 μm or less. The lower limit of the line / space ratio is not particularly limited, but from the viewpoint of good embedding of the resin composition layer into the space, it is preferably 1 / 1 μm or more.

[0171] The inner layer substrate 200 may have a plurality of through-holes 220 that penetrate the inner layer substrate 200 from the first main surface 200a to the second main surface 200b. Through-hole wiring 220a is provided in the through-holes 220. The through-hole wiring 220a electrically connects the first conductor layer 420 and the external terminal 240.

[0172] The resin composition layer 320a and the inner layer substrate 200 can be joined, for example, by heating and pressing the resin sheet 310 to the inner layer substrate 200 from the support 330 side. Examples of the member used to heat and press the resin sheet 310 to the inner layer substrate 200 (hereinafter also referred to as the "heat-pressing member") include a heated metal plate (such as a stainless steel (SUS) end plate) or a metal roll (SUS roll). It is preferable to press the resin sheet 310 via an elastic material such as heat-resistant rubber, rather than directly contacting and pressing the heat-pressing member to the resin sheet 310, so that the resin sheet 310 can adequately follow the irregularities on the surface of the inner layer substrate 200.

[0173] The temperature during heat 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 heat bonding is preferably in the range of 0.098 MPa to 1.77 MPa, more preferably 0.29 MPa to 1.47 MPa. The time during heat bonding is preferably in the range of 20 seconds to 400 seconds, more preferably 30 seconds to 300 seconds. The bonding of the resin sheet and the inner layer substrate is preferably carried out under reduced pressure conditions of 26.7 hPa or less.

[0174] The resin composition layer 320a of the resin sheet 310 and the inner layer substrate 200 can be bonded using a commercially available vacuum laminator. Examples of commercially available vacuum laminators include the vacuum pressure laminator manufactured by Meiki Seisakusho Co., Ltd. and the vacuum applicator manufactured by Nikko Materials Co., Ltd.

[0175] After bonding the resin sheet 310 and the inner layer substrate 200, the laminated resin sheet 310 may be smoothed by pressing a heat-pressure bonding member from the support 330 side under normal pressure (atmospheric pressure). The pressing conditions for the smoothing process can be the same as the heat-pressure bonding conditions for lamination. The smoothing process can be performed using a commercially available laminator. Lamination and smoothing may be performed continuously using the commercially available vacuum laminator described above.

[0176] After laminating the resin sheet 310 onto the inner layer substrate 200, the resin composition layer 320a is heat-cured to form a cured layer. As shown in Figure 10 as an example, the resin composition layer 320a bonded to the inner layer substrate 200 is heat-cured to form a first cured layer 320.

[0177] The thermal curing conditions for the resin composition layer 320a may vary depending on the composition and type of the resin composition, but the curing temperature is preferably 120°C or higher, more preferably 130°C or higher, even more preferably 150°C or higher, preferably 245°C or lower, more preferably 220°C or lower, and even more preferably 200°C or lower. The curing time for the resin composition layer 320a is preferably 5 minutes or more, more preferably 10 minutes or more, even more preferably 15 minutes or more, preferably 120 minutes or less, more preferably 110 minutes or less, and even more preferably 100 minutes or less.

[0178] The support 330 may be removed between the time of heat curing in step (A) and step (B), or it may be peeled off after step (B).

[0179] 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. Surface roughness (Ra) can be measured, for example, using a non-contact surface roughness meter.

[0180] In step (A), instead of a resin sheet, a resin composition may be applied onto the inner layer substrate 200 using a coating device such as a die coater, and a cured layer may be formed by heat curing.

[0181] <Process (B)> In step (B), as shown in Figure 11 as an example, holes are drilled in the first cured layer 320 to form via holes 360. The via holes 360 serve as pathways for electrically connecting the first conductor layer 420 and the second conductor layer 440, which will be described later. The via holes 360 may be formed using, for example, a drill, laser, plasma, etc., depending on the composition of the resin composition used to form the cured layer. The dimensions and shape of the holes may be determined as appropriate according to the design of the printed circuit board.

[0182] <Process (C)> In step (C), the surface of the hardened layer in which via holes have been formed is roughened. The roughening treatment in step (C) can be carried out as described in the "<Step (4)>" section of the first embodiment.

[0183] 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. Surface roughness (Ra) can be measured, for example, using a non-contact surface roughness meter.

[0184] <Process (D)> In step (D), a second conductive layer 440 is formed on the first cured material layer 320, as shown in Figure 12 as an example.

[0185] The conductive material that can constitute the second conductive layer 440 may be the same as the conductive layer material described in the "<Step (5)>" section of the first embodiment.

[0186] 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, even 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.

[0187] The second conductor layer 440 can be formed by plating. Preferably, the second conductor layer 440 is formed by a wet plating method such as a semi-additive method or a fully additive method, which includes an electroless plating step, a mask pattern formation step, an electrolytic plating step, and a flash etching step. By forming the second conductor layer 440 using a wet plating method, it is possible to form a second conductor layer 440 that includes a desired wiring pattern. In addition, this process also forms via hole wiring 360a within the via hole 360.

[0188] The first conductor layer 420 and the second conductor layer 440 may be arranged in a spiral shape, for example, as shown in Figures 13 to 15, which will be 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 by via hole wiring 360a. The other end of the spiral wiring portion of the second conductor layer 440, on the outer circumference side, is electrically connected to the land 420a of the first conductor layer 420 by via hole wiring 360a. Thus, the other end of the spiral wiring portion of the second conductor layer 440, on the outer circumference side, is electrically connected to the external terminal 240 via via hole wiring 360a, land 420a, and through-hole wiring 220a.

[0189] The coil-shaped conductive structure 400 is composed of a spiral wiring section which is part of the first conductor layer 420, a spiral wiring section which is part of the second conductor layer 440, and via-hole wiring 360a which electrically connects the spiral wiring section of the first conductor layer 420 and the spiral wiring section of the second conductor layer 440.

[0190] After step (D), a further step of forming a hardened material layer on the conductor layer may be performed. For example, as shown in Figure 14, a second hardened material layer 340 is formed on the first hardened material layer 320 on which the second conductor layer 440 and the via hole wiring 360a are formed. The second hardened material layer may be formed by the same process as described above.

[0191] <Inductor board> The inductor substrate includes the circuit board described above. When such an inductor substrate includes a circuit board obtained by the manufacturing method of the circuit board of the first embodiment, it has an inductor pattern formed by a conductor on at least a portion of the periphery of the cured resin composition. Such an inductor substrate can be, for example, the one described in Japanese Patent Application Publication No. 2016-197624.

[0192] Furthermore, when including a circuit board obtained by the circuit board manufacturing method of the second embodiment, the inductor substrate has a cured material layer and a conductive structure in which at least a portion is embedded in the cured material layer, and includes an inductor element composed of this 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. Here, Figure 13 is a schematic plan view of the circuit board 100 provided by the inductor substrate as seen from one side in its thickness direction. Figure 14 is a schematic diagram showing the cut end face of the circuit board cut at the position indicated by the dashed line II-II shown in Figure 13. Figure 15 is a schematic plan view for explaining the configuration of the first conductor layer of the circuit board provided by the inductor substrate.

[0193] The circuit board 100 may be a substrate having a plurality of cured material layers (first cured material layer 320, second cured material layer 340) and a plurality of conductor layers (first conductor layer 420, second conductor layer 440), as shown as an example in Figures 13 and 14. Therefore, 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 substrate 200.

[0194] As shown in Figure 14, the first cured layer 320 and the second cured layer 340 constitute a magnetic portion 300 that can be viewed as an integrated cured layer. Therefore, the coil-shaped conductive structure 400 is provided such that at least a portion of it is embedded in the magnetic portion 300. In other words, in the circuit board 100 of this embodiment, the inductor element is composed of a coil-shaped conductive structure 400 and a core portion which is a part of the magnetic portion 300 that extends in the thickness direction of the magnetic portion 300 and is surrounded by the coil-shaped conductive structure 400.

[0195] As shown in Figure 15 as an example, the first conductor layer 420 includes a spiral wiring section for forming a coil-shaped conductive structure 400 and a rectangular land 420a that is electrically connected to the through-hole wiring 220a. In the illustrated example, the spiral wiring section includes a straight section, a bent section that bends at a right angle, and a bypass section that bypasses the land 420a. In the illustrated example, the spiral wiring section of the first conductor layer 420 has an overall outline that is approximately rectangular and has a shape that is wound counterclockwise from the center outwards.

[0196] Similarly, a second conductor layer 440 is provided on the first cured material layer 320. The second conductor layer 440 includes a spiral wiring section for forming a coil-shaped conductive structure 400. In Figure 13 or Figure 14, the spiral wiring section includes a straight section and a bent section that bends at a right angle. In Figure 13 or Figure 14, the spiral wiring section of the second conductor layer 44 has an overall outline that is roughly rectangular and has a shape that is wound clockwise from the center outwards.

[0197] Such inductor substrates can be used as wiring boards for mounting electronic components such as semiconductor chips, and can also be used as (multilayer) printed wiring boards using such wiring boards as inner layer substrates. Furthermore, such wiring boards can be used as individual chip inductor components, and can also be used as printed wiring boards on which these chip inductor components are surface-mounted.

[0198] 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 products (e.g., computers, mobile phones, digital cameras, and televisions) and vehicles (e.g., motorcycles, automobiles, trains, ships, and aircraft). [Examples]

[0199] The present invention will be described in detail below with reference to examples. The present invention is not limited to these examples. In the following, "%" and "parts" representing quantities mean "mass%" and "parts by mass," respectively, unless otherwise specified. Unless otherwise specified, the temperature and pressure conditions are room temperature (25°C) and atmospheric pressure (1 atm), respectively.

[0200] <Example 1> Magnetite powder (Toda Kogyo Co., Ltd. "Magnetite A", average particle size (D 50 30.5 parts by mass of 0.5 μm (aspect ratio 1.1), ferrite powder (Powdertech Co., Ltd. "M05S", Mn-based ferrite, average particle size (D 50 71.2 parts by mass of (3 μm), 3.55 parts by mass of epoxy resin ("ZX-1059" manufactured by Nippon Steel & Sumitomo Metal Chemical Co., Ltd., a mixture of bisphenol A type epoxy resin and bisphenol F type epoxy resin, epoxy equivalent 169 g / eq.), 3.65 parts by mass of epoxy resin ("ZX-1658GS", cyclic aliphatic diglycidyl ether, manufactured by Nippon Steel Chemical & Material Co., Ltd., epoxy equivalent 135 g / eq.), polyfunctional epoxy 2.1 parts by mass of resin (Mitsubishi Chemical Corporation's "630," triglycidyl-p-aminophenol, epoxy equivalent 95 g / eq.), 0.64 parts by mass of curing accelerator (Shikoku Chemicals Co., Ltd.'s "2MZA-PW," imidazole-based curing accelerator), and 0.81 parts by mass of dispersant (Kusumoto Chemicals Co., Ltd.'s "ED-152," polyoxyalkylene-based dispersant) were added and uniformly dispersed in a high-speed rotary mixer to obtain a paste-like resin composition.

[0201] <Example 2> Magnetite powder (Toda Kogyo Co., Ltd. "Magnetite A", average particle size (D 50 A paste-like resin composition was obtained in the same manner as in Example 1, except that the amount of 0.5 μm material used was changed from 30.5 parts by mass to 36.6 parts by mass.

[0202] <Example 3> Magnetite powder (Toda Kogyo Co., Ltd. "Magnetite A", average particle size (D 50The amount of ferrite powder (0.5 μm) used was changed from 30.5 parts by mass to 36.6 parts by mass, and the ferrite powder (Powdertech Co., Ltd. "M05S", Mn-based ferrite, average particle size (D 50 A paste-like resin composition was obtained in the same manner as in Example 1, except that the amount of 3 μm material used was changed from 71.2 parts by mass to 85.4 parts by mass.

[0203] <Example 4> Ferrite powder (Powdertech Co., Ltd. "M05S", Mn-based ferrite, average particle size (D 50 )3μm) ferrite powder (Powdertech Co., Ltd. "MZ05S", MnZn-based ferrite, average particle size (D 50 A paste-like resin composition was obtained in the same manner as in Example 1, except that the particle size was changed to 4 μm.

[0204] <Example 5> Ferrite powder (Powdertech Co., Ltd. "M05S", Mn-based ferrite, average particle size (D 50 )3μm) Magnetic powder (Epson Atomics "AW2-08 PF8F", FeSiCr alloy (amorphous), average particle size (D 50 A paste-like resin composition was obtained in the same manner as in Example 1, except that the particle size was changed to 5 μm.

[0205] <Comparative Example 1> Magnetite powder (Toda Kogyo Co., Ltd. "Magnetite A", average particle size (D 50 )0.5μm,) ferrite powder (Powdertech Co., Ltd. "M03S", Mn-based ferrite, average particle size (D 50 A paste-like resin composition was obtained in the same manner as in Example 1, except that the particle size was changed to 0.4 μm.

[0206] <Comparative Example 2> Magnetite powder (Toda Kogyo Co., Ltd. "Magnetite A", average particle size (D 50 )0.5μm) ferrite powder (Powdertech Co., Ltd. "M03S", Mn-based ferrite, average particle size (D 50 A paste-like resin composition was obtained in the same manner as in Example 4, except that the particle size was changed to 0.4 μm.

[0207] <Comparative Example 3> Magnetite powder (Toda Kogyo Co., Ltd. "Magnetite A", average particle size (D 50 )0.5μm,) ferrite powder (Powdertech Co., Ltd. "M03S", Mn-based ferrite, average particle size (D 50 A paste-like resin composition was obtained in the same manner as in Example 5, except that the particle size was changed to 0.4 μm.

[0208] <Comparative Example 4> Magnetite powder (Toda Kogyo Co., Ltd. "Magnetite A", average particle size (D 50 )0.5μm) is not used, ferrite powder (Powdertech Co., Ltd. "M05S", Mn-based ferrite, average particle size (D 50 A paste-like resin composition was obtained in the same manner as in Example 1, except that the amount of 3 μm material used was changed from 71.2 parts by mass to 101.7 parts by mass.

[0209] <Comparative Example 5> Ferrite powder (Powdertech Co., Ltd. "M05S", Mn-based ferrite, average particle size (D 50 )3μm) is not used, magnetite powder (Toda Kogyo Co., Ltd. "Magnetite A", average particle size (D 50 A paste-like resin composition was obtained in the same manner as in Example 1, except that the amount of 0.5 μm material used was changed from 30.5 parts by mass to 101.7 parts by mass.

[0210] <Comparative Example 6> Magnetite powder (Toda Kogyo Co., Ltd. "Magnetite A", average particle size (D 50 )0.5μm,) magnetite powder (Toda Kogyo Co., Ltd. "Magnetite B", average particle size (D 50 A paste-like resin composition was obtained in the same manner as in Example 1, except that the particle size was changed to 1.3 μm.

[0211] <Comparative Example 7> Magnetite powder (Toda Kogyo Co., Ltd. "Magnetite A", average particle size (D 50 )0.5μm) magnetite powder (Toda Kogyo Co., Ltd.'s "Magnetite C", average particle size (D 50A paste-like resin composition was obtained in the same manner as in Example 1, except that the particle size was changed to 1.6 μm.

[0212] <Test Example 1: Viscosity Measurement> The resin compositions obtained in the examples and comparative examples were kept at a temperature of 25°C (±2°C), and their viscosity (Pa·s) was measured using an E-type viscometer (RE-80U, manufactured by Toki Sangyo Co., Ltd., with a 3°×R9.7 rotor). Measurements were performed using a 0.22 ml sample and a rotation speed of 5 rpm, and also using a 0.22 ml sample and a rotation speed of 0.5 rpm. However, for the resin compositions of Comparative Examples 5, 6, and 7, the viscosity (Pa·s) could not be measured because it exceeded the upper limit of the measurement range (specifically, the upper limit of the measurement range at 5 rpm was 300 Pa·s, and the upper limit of the measurement range at 0.5 rpm was 600 Pa·s).

[0213] The measured viscosity was evaluated based on the following evaluation criteria. However, the following viscosity evaluation criteria are for comparing the viscosities of the examples and comparative examples, and the resin compositions of the present invention may include resin compositions having viscosities in the range of evaluation "×". Viscosity (25℃, 5rpm): Values ​​of 130 Pa·s or less were rated "○", and values ​​exceeding 130 Pa·s were rated "×". Viscosity (25℃, 0.5rpm): 310 Pa·s or less was rated "○", and over 310 Pa·s was rated "×".

[0214] <Test Example 2: Measurement and Evaluation of Relative Permeability and Magnetic Loss> As a support, a polyethylene terephthalate (PET) film (Lintec Corporation, "PET501010", 50 μm thick) treated with a silicone-based release agent was prepared. The resin compositions obtained in the examples and comparative examples were uniformly applied to the release surface of the PET film using a doctor blade so that the thickness of the dried resin composition layer was 100 μm, thereby obtaining a resin sheet. The obtained resin sheet was heat-cured by heating it at 190°C for 90 minutes to heat-cur the resin composition layer, and a sheet-like cured product was obtained by peeling off the support. The obtained cured product was cut into test pieces with a width of 5 mm and a length of 18 mm to be used as evaluation samples. Using a measuring device (Agilent Technologies, "HP8362B"), the relative permeability (μ') and its imaginary component (μ'') were measured using the 3-turn coil method at a measurement frequency of 100 MHz and at room temperature of 23°C. Magnetic loss was calculated from μ'' / μ'.

[0215] (Evaluation criteria for relative permeability) "〇": Relative permeability of 8.0 or higher "×": Relative permeability is less than 8.0

[0216] (Evaluation criteria for magnetic loss) "〇": Magnetic loss is 0.08 or less "×": Magnetic loss exceeds 0.08

[0217] [result] The results of the above-mentioned examples and comparative examples are shown in Tables 1 and 2 below.

[0218] [Table 1]

[0219] [Table 2] [Explanation of Symbols]

[0220] 10 Core boards 11 Support substrate 12 1st metal layer 13 Second metal layer 14 Through Holes 20 Plating layer 30a Resin composition 30 Cured product 40 Conductor layer 41 Pattern Conductor Layers 100 Inductor Board 200 Inner layer substrate 200a 1st main surface 200b 2nd main surface 220 Through Hole 220a Through-hole wiring 240 External terminals 300 Magnetic part 310 Resin Sheet 320a Resin composition layer 320 1st cured material layer 330 Support 340 Second cured layer 360 Beer Hall 360a Wiring inside a via hall 400 Coil-shaped conductive structure 420 First Conductor Layer 420a Land 440 Second Conductor Layer

Claims

[Claim 1] A resin composition comprising (A) magnetic powder and (B) thermosetting resin, Component (A) comprises (A-1) magnetite powder with an average particle size of 1 μm or less, and (A-2) magnetic powder with an average particle size of 1.5 μm or more. A resin composition in which the volume ratio of component (A-2) to component (A-1) (component (A-2) / component (A-1)) is 0.5 to 10.0.

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