hardened body

Abstract

Provided is a cured body of a resin composition containing a thermosetting resin and a magnetic powder. With respect to the surface area of the cross section of the cured body, which is 100%, the ratio of the cured body surface area occupied by the magnetic powder is at least 70%. The average variation coefficient of the interparticle distance of the magnetic powder in the cured body when that distance is measured at three places is 85% or less.

Description

[Technical Field]

[0001] The present invention relates to a cured body of a resin composition containing a thermosetting resin and magnetic powder, and a method for producing the same. The present invention further relates to a circuit board and an inductor board containing the cured body. [Background technology]

[0002] Circuit boards used in electronic devices may have a layer containing magnetic material (hereinafter sometimes referred to as a "magnetic layer"). For example, a magnetic layer may be provided on a circuit board in order to form an inductor by combining it with coil-shaped wiring. Conventionally, there is a known technique for forming such a magnetic layer using a cured body obtained by curing a resin composition containing resin and magnetic powder (Patent Documents 1 and 2). [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Patent No. 6970786 [Patent Document 2] Japanese Patent Publication No. 2022-064864 [Overview of the Initiative] [Problems that the invention aims to solve]

[0004] Magnetic layers provided on circuit boards generally require high relative permeability. Therefore, the development of technologies to increase the relative permeability of the cured resin composition forming the magnetic layer is desirable.

[0005] The present invention was devised in view of the above-mentioned problems, and aims to provide a cured resin composition with high relative magnetic permeability and a method for manufacturing the same; and a circuit board and an inductor board containing the cured resin composition. [Means for solving the problem]

[0006] The inventors diligently studied to solve the aforementioned problems. As a result, the inventors discovered that the relative permeability can be improved in a cured resin composition containing a thermosetting resin and magnetic powder when the ratio of the area occupied by the magnetic powder to the area of ​​the cross-sectional area of ​​the cured resin, and the average of the coefficient of variation of the interparticle distance of the magnetic powder in the cured resin measured at three locations are within a specific range, and thus completed the present invention. In other words, the present invention includes the following:

[0007] [1] A cured body of a resin composition comprising a thermosetting resin and magnetic powder, The area occupied by magnetic powder is 70% or more of the total cross-sectional area of ​​the hardened body. A cured body in which the average coefficient of variation of the interparticle distance of magnetic powder in the cured body, measured at three locations, is 85% or less. [2] The cured product according to [1], wherein the amount of magnetic powder is 90% by mass or more relative to 100% by mass of the nonvolatile components of the resin composition. [3] The cured body according to [1] or [2], wherein the magnetic powder comprises particles having a particle size of 1 μm or less and particles having a particle size greater than 1 μm. [4] A cured body according to any one of [1] to [3], wherein the resin composition comprises a dispersant. [5] The cured product according to [4], wherein the dispersant contains a polyester skeleton. A method for producing a cured body according to any one of the items [6] [1] to [5], A step of mixing a thermosetting resin and magnetic powder to obtain a resin composition, A step of thermally curing the resin composition, A method for manufacturing a cured body, comprising the following in this order. [7] A circuit board comprising a cured body as described in any one of the items [1] to [5]. An inductor board, including the circuit board described in [8] [7]. [Effects of the Invention]

[0008] According to the present invention, it is possible to provide a cured product of a resin composition having a high relative permeability, a method for producing the same; and a circuit board and an inductor board including the cured product.

Brief Description of the Drawings

[0009] [Figure 1] FIG. 1 is a cross-sectional view schematically showing a core substrate prepared in the method for manufacturing a circuit board according to the first example of the present invention. [Figure 2] FIG. 2 is a cross-sectional view schematically showing a core substrate having through holes formed therein in the method for manufacturing a circuit board according to the first example of the present invention. [Figure 3] FIG. 3 is a cross-sectional view schematically showing a core substrate having a plating layer formed in through holes in the method for manufacturing a circuit board according to the first example of the present invention. [Figure 4] FIG. 4 is a cross-sectional view schematically showing a state where a resin composition is filled in through holes of a core substrate in the method for manufacturing a circuit board according to the first example of the present invention. [Figure 5] FIG. 5 is a schematic cross-sectional view for explaining step (2) of the method for manufacturing a circuit board according to the first example of the present invention. [Figure 6] FIG. 6 is a schematic cross-sectional view for explaining step (3) of the method for manufacturing a circuit board according to the first example of the present invention. [Figure 7] FIG. 7 is a schematic cross-sectional view for explaining step (5) of the method for manufacturing a circuit board according to the first example of the present invention. [Figure 8] FIG. 8 is a schematic cross-sectional view for explaining step (5) of the method for manufacturing a circuit board according to the first example of the present invention. [Figure 9] FIG. 9 is a schematic cross-sectional view for explaining step (i) in the method for manufacturing a circuit board according to the second example of the present invention. [Figure 10] FIG. 10 is a schematic cross-sectional view for explaining step (i) in the method for manufacturing a circuit board according to the second example of the present invention. [Figure 11]Figure 11 is a schematic cross-sectional view illustrating step (ii) in a method for manufacturing a circuit board according to a second example of the present invention. [Figure 12] Figure 12 is a schematic cross-sectional view illustrating step (v) in a method for manufacturing a circuit board according to a second example of the present invention. [Figure 13] Figure 13 is a schematic plan view of the circuit board of the inductor substrate, 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 cut at the position indicated by the dashed line II-II shown in Figure 13. [Figure 15] Figure 15 is a schematic plan view illustrating the configuration of the first conductor layer of the circuit board containing the inductor substrate. [Modes for carrying out the invention]

[0010] 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. In the following description, "permeability" refers to "relative permeability" unless otherwise specified.

[0011] In the following description, the term “may have substituents” with respect to a compound or group means both the case where the hydrogen atoms of the compound or group are not substituted with substituents, and the case where some or all of the hydrogen atoms of the compound or group are substituted with substituents.

[0012] <Overview of the hardened material> A cured body of a resin composition according to one embodiment of the present invention is a cured body of a resin composition comprising (A) a thermosetting resin and (B) magnetic powder. Therefore, the cured body according to this embodiment contains (B) magnetic powder. (B) magnetic powder is usually included in the cured body in granular form. When the cured body according to this embodiment is cut to form a cross-section, the ratio of the area occupied by (B) magnetic powder to 100% of the area of ​​the cross-section of the cured body is within a specific range. Furthermore, when the coefficient of variation of the interparticle distance of (B) magnetic powder in the cured body according to this embodiment is measured at three locations, the average of the coefficients of variation measured at those three locations is within a specific range.

[0013] The cured body according to this embodiment can have a high relative permeability. Furthermore, the cured body according to this embodiment can typically have a low loss coefficient.

[0014] Although not bound by any particular theory, the inventors deduce the reason for obtaining the above-mentioned effect as follows: When the area occupied by (B) magnetic powder in the cross-section of the hardened body is within a specific range, it indicates that the hardened body contains a large amount of (B) magnetic powder. Furthermore, when the coefficient of variation of the interparticle distance of (B) magnetic powder is within a specific range, it indicates that the interparticle distance of (B) magnetic powder is highly uniform, and therefore indicates that the particles of (B) magnetic powder are uniformly dispersed. In this regard, the inventors' investigations have shown that although the value of the coefficient of variation may change depending on the measurement point, the average of the coefficients of variation measured at multiple measurement points can represent the dispersion of (B) magnetic powder particles throughout the hardened body. Therefore, in this embodiment, the coefficient of variation is measured at three locations from the viewpoint of accurately identifying the dispersion of (B) magnetic powder particles throughout the hardened body, and the average of these coefficients of variation is evaluated. The fact that the average of the coefficients of variation is within a specific range indicates that the particles of (B) magnetic powder are uniformly dispersed throughout the hardened body. Therefore, in the cured body according to this embodiment, the uneven distribution of the resin component is suppressed while containing a large amount of (B) magnetic powder, thus improving magnetic properties such as relative permeability.

[0015] <Percentage of the area occupied by magnetic powder in the cross-section of the hardened body> In this embodiment, the ratio of the area occupied by the (B) magnetic powder to 100% of the cross-sectional area of ​​the cured body is within a specific range. Hereinafter, the ratio of the area occupied by the (B) magnetic powder to 100% of the cross-sectional area of ​​the cured body may be referred to as the "area ratio" of the (B) magnetic powder. Specifically, the area ratio of the (B) magnetic powder is usually 70% or more, preferably 72% or more, particularly preferably 74% or more, preferably 90% or less, more preferably 88% or less, and even more preferably 85% or less. When the area ratio of the (B) magnetic powder is within the above range, a high relative permeability can be obtained, and usually a low loss coefficient can be obtained.

[0016] (B) The area ratio of the magnetic powder (i.e., the ratio of the area occupied by the magnetic powder to 100% of the cross-sectional area of ​​the hardened body) can be calculated from images obtained by photographing the cross-section of the hardened body. In detail, it can be measured by the following method. The hardened body is cut to form a cross-section, and this cross-section is polished. The polished cross-section is photographed at a magnification of 5000x using a scanning electron microscope (SEM) to obtain an SEM cross-sectional image. The resolution of the SEM cross-sectional image can be 256 dpi horizontally and 256 dpi vertically. The imaging range of the SEM cross-sectional image can be 1280 pixels wide and 960 pixels high. The SEM cross-sectional image thus obtained is imported into the image analysis software "WinROOF2018" (manufactured by Mitani Corporation; hereinafter also referred to as "analysis software"). The analysis software is launched and the SEM cross-sectional image is displayed. Subsequently, the displayed image is subjected to automatic binarization using the modal method. After that, the area ratio of the particles extracted by the binarization process is calculated to calculate (B) the area ratio of the magnetic powder. The specific measurement method can be the method described in <Test 3. Measurement of the Area Ratio of Magnetic Powder> of the example described later.

[0017] (B) The area ratio of the magnetic powder can be adjusted, for example, by the amount of magnetic powder (B). In this case, it is preferable to use a combination of magnetic powders (B) having different average particle sizes to pack the magnetic powder (B) at a high density.

[0018] <Average coefficient of variation of interparticle distance in magnetic powder> The average coefficient of variation of the interparticle distance of the (B) magnetic powder in the cured body according to this embodiment, measured at three locations, is within a specific range. Here, the coefficient of variation represents the value obtained by dividing the standard deviation of the interparticle distance of the (B) magnetic powder by the average value of the interparticle distance of the (B) magnetic powder. Furthermore, the average coefficient of variation represents the average of the coefficients of variation measured at three locations in a measurement test in which the coefficient of variation of the interparticle distance of the (B) magnetic powder in the cured body is measured at three locations in the cured body. Specifically, the average coefficient of variation of the interparticle distance of the (B) magnetic powder is usually 85% or less, preferably 83% or less, more preferably 81% or less, and particularly preferably 80% or less. The lower limit is preferably as small as possible, for example, 40% or more, 50% or more, 60% or more, etc. When the average coefficient of variation of the interparticle distance of the (B) magnetic powder is within the above range, a high relative permeability can be obtained, and usually a low loss coefficient can be obtained.

[0019] (B) The average coefficient of variation of the interparticle distance of the magnetic powder can be calculated from images obtained by photographing three cross-sections of the hardened body. In detail, it can be measured by the following method. The hardened material is cut to form a cross-section, which is then polished. The polished cross-section is photographed at a magnification of 5000x using a scanning electron microscope (SEM) to obtain an SEM cross-sectional image. The resolution of the SEM cross-sectional image can be 256 dpi horizontally and 256 dpi vertically. The imaging range of the SEM cross-sectional image can be 1280 pixels wide and 960 pixels high. The acquired SEM cross-sectional image is imported into the image analysis software "WinROOF2018" (manufactured by Mitani Corporation; hereinafter also referred to as "analysis software"). The analysis software is launched and the SEM cross-sectional image is displayed. The displayed image is then automatically binarized using the modal method. After that, the inter-particle distance of the magnetic powder particles extracted by the binarization process (B) is measured. The measurement is performed by measuring the edge distance with a step angle of 20°. Then, from the obtained inter-particle distance measurement results, the mean and standard deviation of the inter-particle distance are calculated from the results between 0.1 μm and less than 5.0 μm. The coefficient of variation of the interparticle distance can be calculated by dividing the standard deviation of the obtained interparticle distance by the mean value of the interparticle distance.

[0020] The coefficient of variation is measured at three locations on the cross-section of the hardened body. The average of the coefficients of variation measured at these three locations can then be calculated. It is generally desirable to set the three cross-sections at a distance of 1 mm or more, but if the sample is small and it is not possible to set three cross-sections at a distance of 1 mm or more, they may be set at a distance of less than 1 mm. When the area occupied by the (B) magnetic powder is large in the cross-section of the hardened body as described above, the particles of the (B) magnetic powder become denser, so the coefficient of variation may be non-uniform at each measurement point. However, the average of the coefficients of variation measured at three different cross-sections accurately reflects the dispersibility of the (B) magnetic powder particles in the entire hardened body and has a high correlation with the magnetic properties such as the relative permeability of the hardened body. Therefore, in this embodiment, the range of the hardened body in which such excellent magnetic properties can be obtained is identified by the average of the coefficient of variation of the interparticle distance.

[0021] In the method for measuring the coefficient of variation described above, the "step angle" for measuring the distance between edges represents the angle between measurement points set on the edges of a particle in the SEM cross-sectional image. Here, the angle represents the angle with respect to the center of the particle. For example, in measuring the distance between edges, multiple measurement points are set at equal angular intervals along the edges of the particle. In this case, a first line segment is drawn from the center of the particle to the first measurement point on the edge of the particle. A second line segment is also drawn from the center of the particle to a second measurement point set next to the first measurement point on the edge of the particle. In this case, the angle between the first and second line segments corresponds to the step angle. Therefore, the smaller the step angle, the more measurement points can be set on the surface of the particle. For example, if the step angle is 20°, 360° / 20° = 18 measurement points can be set per particle.

[0022] Furthermore, in the aforementioned method for measuring the coefficient of variation, results outside the range of 0.1 μm to less than 5.0 μm are excluded; this is to eliminate noise. In other words, in the edge-to-edge distance measurement method described above, if the particle shape deviates significantly from a circle, the distance between measurement points set on the edge of the same particle may be measured. This distance is usually less than 0.1 μm. Since this distance between measurement points set on the edge of the same particle does not represent the distance between particles, it is excluded as noise. Furthermore, in the measurement of edge distance using the measurement method described above, the edge distance between a given particle and the closest particle is measured as the value corresponding to the inter-particle distance. However, depending on the particle distribution, the edge distance may be measured between two particles that are far apart. This distance is usually 5.0 μm or more in a hardened body where the area ratio of the magnetic powder is within the specific range described above. Since the edge distance between two particles that are far apart in this way does not represent the inter-particle distance that should be measured, it is excluded as noise.

[0023] (B) The specific method for measuring the average coefficient of variation of the interparticle distance of the magnetic powder can be the method described in <Test 2. Measurement of the coefficient of variation of the interparticle distance of the cured body> in the examples described later.

[0024] (B) The average coefficient of variation of the interparticle distance of the magnetic powder can be adjusted to the above range, for example, by making the dispersion of the magnetic powder in the resin composition uniform. For example, the dispersion of the magnetic powder can be made uniform by using a resin composition containing an appropriate dispersant or by appropriately adjusting the mixing order of each component in the method for manufacturing the resin composition.

[0025] Furthermore, the coefficient of variation values ​​measured at each of the three cross-sections to obtain the average of the coefficient of variation of the interparticle distance of the magnetic powder (B) described above are preferably 85% or less, more preferably 83% or less, even more preferably 81% or less, and particularly preferably 80% or less. The lower limit is preferable as small as possible, and can be, for example, 40% or more, 50% or more, 60% or more, etc. When not only the average of the coefficient of variation but also the values ​​of the coefficient of variation measured at the three cross-sections are all as small as described above, it is possible to significantly reduce the relative permeability.

[0026] <Resin composition> The resin composition for obtaining the cured product according to this embodiment comprises (A) a thermosetting resin and (B) magnetic powder. This resin composition can be cured by the thermosetting resin (A) reacting with heat to form bonds. In the resin composition, the magnetic powder (B) is usually included in granular form and is included in the cured product while maintaining that granular state.

[0027] -(A)Thermosetting resin- The resin composition according to this embodiment includes a thermosetting resin (A) as component (A). Examples of thermosetting resins (A) include epoxy resins, phenolic resins, thiol resins, benzoxazine resins, activated ester resins, cyanate ester resins, carbodiimide resins, amine resins, acid anhydride resins, epoxy acrylate resins, urethane acrylate resins, urethane resins, polyimide resins, unsaturated polyester resins, melamine resins, silicone resins, and the like. Furthermore, one type of thermosetting resin (A) may be used alone, or two or more types may be used in combination.

[0028] (A) The thermosetting resin preferably contains epoxy resin. Epoxy resin means a resin having epoxy groups. (A) When the thermosetting resin contains epoxy resin, the relative permeability and loss coefficient of the cured product can be made particularly excellent.

[0029] 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, glycidyl ether-type aliphatic epoxy resin, glycidyl ether-type aromatic epoxy resin, and the like. Epoxy resin may be used alone or in combination of two or more types.

[0030] The resin composition preferably contains an epoxy resin having two or more epoxy groups per molecule. From the viewpoint of significantly obtaining the desired effects of the present invention, the range of the amount of epoxy resin having two or more epoxy groups per molecule, relative to 100% by mass of the nonvolatile component of the epoxy resin, is preferably 50% by mass or more, more preferably 60% by mass or more, and even more preferably 70% by mass or more.

[0031] From the viewpoint of obtaining a cured product with excellent heat resistance, epoxy resins preferably have an aromatic structure. When using two or more epoxy resins, it is preferable that one or more epoxy resins have an aromatic structure. An aromatic structure is a chemical structure generally defined as aromatic, and includes polycyclic aromatics and aromatic heterocyclics.

[0032] 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"). The resin composition may contain only liquid epoxy resin, only solid epoxy resin, or a combination of liquid and solid epoxy resins. Preferably, the epoxy resin contains only liquid epoxy resin.

[0033] 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, based on 100% by mass of the total epoxy resin.

[0034] As the liquid epoxy resin, a liquid epoxy resin having two or more epoxy groups in one molecule is preferred.

[0035] Preferred liquid epoxy resins include glycirol-type epoxy resins, bisphenol A-type epoxy resins, bisphenol F-type epoxy resins, bisphenol AF-type epoxy resins, naphthalene-type epoxy resins, glycidyl ether-type aliphatic epoxy resins, glycidyl ether-type aromatic epoxy resins, glycidyl ester-type epoxy resins, glycidylamine-type epoxy resins, phenol novolac-type epoxy resins, alicyclic epoxy resins having an ester skeleton, cyclohexanedimethanol-type epoxy resins, dicyclopentadiene-type epoxy resins, and epoxy resins having a butadiene structure. Bisphenol A-type epoxy resins, bisphenol F-type epoxy resins, glycidyl ether-type aliphatic epoxy resins, and glycidyl ether-type aromatic epoxy resins are more preferred.

[0036] 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" (glycidyl ether-type aromatic epoxy resin); and ADEKA's "ED-523T" (glycirol-type epoxy resin (ADEKA glycirol)) and "EP-3980S" (glycidylamine). Examples include: type epoxy resins, "EP-4088S" (glycidyl ether type aliphatic epoxy resin); "ZX-1059" (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" (liquid 1,4-glycidylcyclohexane) from Nippon Steel Chemical & Material Co., Ltd.

[0037] 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.

[0038] 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.

[0039] 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.

[0040] When using both solid epoxy resin and liquid epoxy resin as the epoxy resin, the mass ratio of solid epoxy resin to 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.

[0041] The epoxy equivalent of the epoxy resin is preferably 50 g / eq. to 5000 g / eq., more preferably 50 g / eq. to 3000 g / eq., even more preferably 80 g / eq. to 2000 g / eq., and even more preferably 110 g / eq. to 1000 g / eq. The epoxy equivalent is the mass of resin per equivalent of epoxy groups. This epoxy equivalent can be measured according to JIS K7236.

[0042] 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, from the viewpoint of significantly obtaining the desired effects of the present invention. The weight-average molecular weight of the resin can be measured as a polystyrene equivalent value by gel permeation chromatography (GPC).

[0043] The amount of epoxy resin is preferably 0.1% by mass or more, more preferably 0.5% by mass or more, even more preferably 1.0% by mass or more, preferably 10% by mass or less, more preferably 8% by mass or less, and even more preferably 5% by mass or less, based on 100% by mass of the non-volatile components in the resin composition. When the amount of epoxy resin is within the above range, the relative permeability of the cured body can be effectively increased, and the loss coefficient can usually be effectively reduced.

[0044] The amount of epoxy resin is preferably 10% by mass or more, more preferably 20% by mass or more, even more preferably 30% by mass or more, preferably 70% by mass or less, more preferably 60% by mass or less, and even more preferably 50% by mass or less, based on 100% by mass of the resin components in the resin composition. The resin components in the resin composition refer to the components of the resin composition excluding (B) inorganic particles such as magnetic powder from the non-volatile components in the resin composition. When the amount of epoxy resin is within the above range, the relative permeability of the cured body can be effectively increased, and the loss coefficient can usually be effectively reduced.

[0045] (A) If the thermosetting resin contains an epoxy resin, it is preferable that (A) the thermosetting resin further contains an epoxy curing agent. The epoxy curing agent represents a thermosetting resin that reacts with the epoxy resin to form a bond and cure the resin composition. Examples of epoxy curing agents include phenolic resins, activated ester resins, carbodiimide resins, acid anhydride resins, amine resins, benzoxazine resins, cyanate ester resins, thiol resins, etc. Among these, phenolic resins are preferred. The epoxy curing agent may be used alone or in combination of two or more types.

[0046] As the phenolic resin, a resin having one or more, preferably two or more, phenolic hydroxyl groups per molecule can be used. A phenolic hydroxyl group refers to a hydroxyl group bonded to an aromatic ring such as a benzene ring or a naphthalene ring. As the phenolic resin, biphenyl-type phenolic resins, naphthalene-type phenolic resins, phenol novolac-type phenolic resins, naphthylene ether-type phenolic resins, and triazine skeleton-containing phenolic resins are preferred. Among these, nitrogen-containing phenolic resins are preferred from the viewpoint of adhesion of the cured product, and triazine skeleton-containing phenolic resins are more preferred.

[0047] Specific examples of phenolic resins include the biphenyl-type phenolic resins "MEH-7700," "MEH-7810," and "MEH-7851" (manufactured by Meiwa Kasei Co., Ltd.), the naphthalene-type phenolic resins "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 phenolic resin "TD2090" (manufactured by DIC Corporation), and the naphthylene ether-type phenolic resin "EXB-6000" (manufactured by DIC Corporation). Specific examples of triazine skeleton-containing phenolic resins include "LA3018," "LA7052," "LA7054," and "LA1356" (manufactured by DIC Corporation). In particular, naphthalene-type phenolic resins and triazine skeleton-containing phenolic resins are more preferred.

[0048] The amount of phenolic resin is preferably 0.01% by mass or more, more preferably 0.1% by mass or more, even more preferably 1.0% by mass or more, preferably 10% by mass or less, more preferably 8% by mass or less, and even more preferably 5% by mass or less, based on 100% by mass of the nonvolatile components in the resin composition. When the amount of phenolic resin is within the above range, the relative permeability of the cured product can be effectively increased, and the loss coefficient can usually be effectively reduced.

[0049] The amount of phenolic resin is preferably 0.1% by mass or more, more preferably 1% by mass or more, even more preferably 10% by mass or more, preferably 50% by mass or less, more preferably 40% by mass or less, and even more preferably 30% by mass or less, based on 100% by mass of the resin component in the resin composition. When the amount of phenolic resin is within the above range, the relative permeability of the cured product can be effectively increased, and the loss coefficient can usually be effectively reduced.

[0050] When the number of epoxy groups in the epoxy resin is set to 1, the number of phenolic hydroxyl groups in the phenolic resin is preferably 0.05 or more, more preferably 0.1 or more, even more preferably 0.2 or more, preferably 2.0 or less, more preferably 1.5 or less, and even more preferably 1.0 or less. "Number of epoxy groups in the epoxy resin" refers to the sum of all values ​​obtained by dividing the mass of the non-volatile components of the epoxy resin present in the resin composition by the epoxy equivalent. Similarly, "number of phenolic hydroxyl groups in the phenolic resin" refers to the sum of all values ​​obtained by dividing the mass of the non-volatile components of the phenolic resin present in the resin composition by the phenolic hydroxyl group equivalent. Furthermore, phenolic hydroxyl group equivalent refers to the mass of resin per equivalent of phenolic hydroxyl groups.

[0051] As the active ester resin, a resin having one or more active ester groups in one molecule can be used. Among these, compounds having two or more highly reactive ester groups in one molecule, such as phenol esters, thiophenol esters, N-hydroxyamine esters, and esters of heterocyclic hydroxy compounds, are preferred as the active ester resin. The active ester resin is preferably obtained by a condensation reaction between a carboxylic acid compound and / or a thiocarboxylic acid compound and a hydroxy compound and / or a thiol compound. Particularly from the viewpoint of improving heat resistance, an active ester resin obtained from a carboxylic acid compound and a hydroxy compound is preferred, and an active ester resin obtained from a carboxylic acid compound and a phenol compound and / or a naphthol compound is more preferred. Examples of carboxylic acid compounds include benzoic acid, acetic acid, succinic acid, maleic acid, itaconic acid, phthalic acid, isophthalic acid, terephthalic acid, and pyromellitic acid. Examples of phenol compounds or naphthol compounds include hydroquinone, resorcinol, bisphenol A, bisphenol F, bisphenol S, phenolphthalein, methylated bisphenol A, methylated bisphenol F, methylated bisphenol S, phenol, o-cresol, m-cresol, p-cresol, catechol, α-naphthol, β-naphthol, 1,5-dihydroxynaphthalene, 1,6-dihydroxynaphthalene, 2,6-dihydroxynaphthalene, dihydroxybenzophenone, trihydroxybenzophenone, tetrahydroxybenzophenone, phloroglucin, benzenetriol, dicyclopentadiene-type diphenol compounds, and phenol novolac. Here, "dicyclopentadiene-type diphenol compounds" refers to diphenol compounds obtained by the condensation of two phenol molecules with one dicyclopentadiene molecule.

[0052] Specifically, preferred active ester resins include dicyclopentadiene-type active ester resins, naphthalene-type active ester resins containing a naphthalene structure, active ester resins containing an acetylated phenol novolac, and active ester resins containing a benzoylated phenol novolac. More preferably, the active ester resin is at least one selected from dicyclopentadiene-type active ester resins and naphthalene-type active ester resins. As for dicyclopentadiene-type active ester resins, active ester resins containing a dicyclopentadiene-type diphenol structure are preferred.

[0053] Commercially available active ester resins include, for example, active ester resins containing a dicyclopentadiene-type diphenol structure such as "EXB9451", "EXB9460", "EXB9460S", "EXB-8000L", "EXB-8000L-65M", "EXB-8000L-65TM", "HPC-8000L-65TM", "HPC-8000", "HPC-8000-65T", "HPC-8000H", and "HPC-8000H-65TM" (manufactured by DIC Corporation); and active ester resins containing a naphthalene structure such as "HP-B-8151-62T", "HP-C-8151-62T", "EXB-8100L-65T", and "EXB-8150-60T". Examples include "EXB-8150-62T", "EXB-9416-70BK", "HPC-8150-60T", "HPC-8150-62T", and "EXB-8" (manufactured by DIC Corporation); as a phosphorus-containing active ester resin, "EXB9401" (manufactured by DIC Corporation); as an active ester resin that is an acetylated phenol novolac, "DC808" (manufactured by Mitsubishi Chemical Corporation); as an active ester resin that is a benzoylated phenol novolac, "YLH1026", "YLH1030", and "YLH1048" (manufactured by Mitsubishi Chemical Corporation); and as an active ester resin containing a styryl group and a naphthalene structure, "PC1300-02-65MA" (manufactured by Air Water Corporation). Active ester resins may be used individually or in combination of two or more types.

[0054] As carbodiimide resins, resins having one or more, preferably two or more, carbodiimide structures per molecule can be used. Examples of carbodiimide resins 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(na Examples of polycarbodiimides include aromatic polycarbodiimides such as phthalenecarbodiimide, poly(tylenecarbodiimide), poly(methyldiisopropylphenylenecarbodiimide), poly(triethylphenylenecarbodiimide), poly(diethylphenylenecarbodiimide), poly(triisopropylphenylenecarbodiimide), poly(diisopropylphenylenecarbodiimide), poly(xylylenecarbodiimide), poly(tetramethylxylylenecarbodiimide), poly(methylenediphenylenecarbodiimide), and poly[methylenebis(methylphenylene)carbodiimide]. Examples of commercially available carbodiimide resins include "Carbodilite V-02B," "Carbodilite V-03," "Carbodilite V-04K," "Carbodilite V-07," and "Carbodilite V-09" from Nisshinbo Chemical Co., Ltd., and "Stabaxol P," "Stabaxol P400," and "Hycazil 510" from Rhein Chemie Corporation. Carbodiimide resins may be used individually or in combination of two or more types.

[0055] As acid anhydride resins, resins having one or more, preferably two or more, acid anhydride groups per molecule can be used. Examples of acid anhydride resins 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 bensofenonetetracarboxylic 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, which is a copolymer of styrene and maleic acid. Examples of commercially available acid anhydride resins 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. Acid anhydride resins may be used individually or in combination of two or more types.

[0056] As the amine resin, a resin having one or more, preferably two or more, amino groups per molecule can be used. Examples of amine resins include aliphatic amines, polyetheramines, alicyclic amines, aromatic amines, etc., with aromatic amines being preferred. The amine resin is preferably a primary or secondary amine, with primary amines being more preferred. Specific examples of amine resins 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)propyl Examples include pan, 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. Commercially available amine resins may be used, 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. One type of amine resin may be used alone, or two or more types may be used in combination.

[0057] As the benzoxazine resin, a resin having one or more, preferably two or more, benzoxazine rings per molecule can be used. Specific examples of benzoxazine resins 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. Benzoxazine resins may be used individually or in combination of two or more types.

[0058] As the cyanate ester resin, a resin having one or more, preferably two or more cyanate groups in one molecule can be used. Examples of cyanate ester resins include bifunctional cyanate resins such as bisphenol A dicyanate, polyphenol cyanate (oligo(3-methylene-1,5-phenylene cyanate)), 4,4'-methylenebis(2,6-dimethylphenyl cyanate), 4,4'-ethylidene diphenyl dicyanate, hexafluorobisphenol A dicyanate, 2,2-bis(4-cyanate)phenylpropane, 1,1-bis(4-cyanatephenylmethane), bis(4-cyanate-3,5-dimethylphenyl)methane, 1,3-bis(4-cyanatephenyl-1-(methylethylidene))benzene, bis(4-cyanatephenyl) thioether, and bis(4-cyanatephenyl) ether; polyfunctional cyanate resins derived from phenol novolacs and cresol novolacs; and prepolymers in which these cyanate resins are partially triazined. Specific examples of cyanate ester resins 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). Cyanate ester resins may be used individually or in combination of two or more types.

[0059] Examples of thiol resins include trimethylolpropane tris(3-mercaptopropionate), pentaerythritol tetrakis(3-mercaptobutyrate), and tris(3-mercaptopropyl) isocyanurate. Thiol resins may be used individually or in combination of two or more types.

[0060] The reactive group equivalent of the epoxy curing agent is preferably 50 g / eq. to 3000 g / eq., more preferably 100 g / eq. to 1000 g / eq., even more preferably 100 g / eq. to 500 g / eq., and particularly preferably 100 g / eq. to 300 g / eq. The reactive group equivalent represents the mass of epoxy curing agent per equivalent of one reactive group.

[0061] The weight-average molecular weight (Mw) range of the epoxy curing agent may be the same as the weight-average molecular weight (Mw) range of the epoxy resin.

[0062] The amount of epoxy curing agent is preferably 0.01% by mass or more, more preferably 0.1% by mass or more, even more preferably 1.0% by mass or more, preferably 10% by mass or less, more preferably 6% by mass or less, and even more preferably 3% by mass or less, based on 100% by mass of the non-volatile components in the resin composition. When the amount of epoxy curing agent is within the above range, the relative permeability of the cured body can be effectively increased, and the loss coefficient can usually be effectively reduced.

[0063] The amount of epoxy curing agent is preferably 0.1% by mass or more, more preferably 1% by mass or more, even more preferably 10% by mass or more, preferably 50% by mass or less, more preferably 40% by mass or less, and even more preferably 30% by mass or less, based on 100% by mass of the resin component in the resin composition. When the amount of epoxy curing agent is within the above range, the relative permeability of the cured body can be effectively increased, and the loss coefficient can usually be effectively reduced.

[0064] When the number of epoxy groups in the epoxy resin is set to 1, the number of reactive groups in the epoxy curing agent is preferably 0.05 or more, more preferably 0.1 or more, even more preferably 0.2 or more, preferably 2.0 or less, more preferably 1.5 or less, and even more preferably 1.0 or less. The "number of reactive groups in the epoxy curing agent" refers to the sum of all values ​​obtained by dividing the mass of the nonvolatile components of the epoxy curing agent present in the resin composition by the equivalent amount of reactive groups.

[0065] (A) The range of the amount of thermosetting resin is preferably 0.1% by mass or more, more preferably 1% by mass or more, even more preferably 2% by mass or more, preferably 10% by mass or less, more preferably 8% by mass or less, and even more preferably 6% by mass or less, based on 100% by mass of the nonvolatile components in the resin composition. (A) When the amount of thermosetting resin is within the above range, the relative permeability of the cured body can be effectively increased, and the loss coefficient can usually be effectively reduced.

[0066] (A) The amount of thermosetting resin is preferably 30% by mass or more, more preferably 40% by mass or more, even more preferably 50% by mass or more, preferably 90% by mass or less, more preferably 80% by mass or less, and even more preferably 75% by mass or less, based on 100% by mass of the resin component in the resin composition. (A) When the amount of thermosetting resin is within the above range, the relative permeability of the cured body can be effectively increased, and the loss coefficient can usually be effectively reduced.

[0067] -(B) Magnetic powder- The resin composition according to this embodiment contains (B) magnetic powder as component (B). The (B) magnetic powder may be particles of a magnetic material having a relative permeability greater than 1. This magnetic material is usually an inorganic material and may be a soft magnetic material or a hard magnetic material. Furthermore, one type of magnetic material may be used alone, or two or more types may be used in combination. Among these, from the viewpoint of suppressing the uneven distribution of the (B) magnetic powder, a soft magnetic material is preferred as the magnetic material contained in the (B) magnetic powder.

[0068] (B) Examples of magnetic materials contained in the magnetic powder include magnetic metal oxide materials and magnetic metal materials. Furthermore, these magnetic materials are preferably iron-based magnetic materials containing iron (Fe).

[0069] Examples of magnetic metal oxide materials include ferrite materials, iron(III) oxide, and iron oxide materials such as triiron tetroxide. Among these, ferrite materials are preferred. Ferrite materials are usually composite oxides mainly composed of iron oxide and are chemically stable. Therefore, when using ferrite materials, advantages such as high corrosion resistance, low risk of ignition, and resistance to demagnetization can be obtained.

[0070] Examples of ferritic materials include Fe-Mn ferrite, Fe-Mn-Mg ferrite, Fe-Mn-Mg-Sr ferrite, Fe-Mg-Zn ferrite, Fe-Mg-Sr ferrite, Fe-Zn-Mn ferrite, Fe-Cu-Zn ferrite, Fe-Ni-Zn ferrite, Fe-Ni-Zn-Cu ferrite, Fe-Ba-Zn ferrite, Fe-Ba-Mg ferrite, Fe-Ba-Ni ferrite, Fe-Ba-Co ferrite, Fe-Ba-Ni-Co ferrite, and Fe-Y ferrite.

[0071] Among ferritic materials, ferrites containing at least one element selected from the group consisting of Mn, Zn, Ni, and Cu are preferred, and ferrites containing Mn are particularly preferred. Therefore, preferred ferritic materials include, for example, Fe-Mn ferrite, Fe-Mn-Mg ferrite, Fe-Mn-Mg-Sr ferrite, Fe-Mg-Zn ferrite, Fe-Zn-Mn ferrite, Fe-Cu-Zn ferrite, Fe-Ni-Zn ferrite, Fe-Ni-Zn-Cu ferrite, Fe-Ba-Zn ferrite, Fe-Ba-Ni ferrite, and Fe-Ba-Ni-Co ferrite. Among these, Fe-Mn ferrite, Fe-Mn-Mg ferrite, Fe-Mn-Mg-Sr ferrite, and Fe-Zn-Mn ferrite are preferred, and Fe-Mn ferrite is even more preferred. Fe-Mn ferrite refers to ferrite containing Fe and Mn.

[0072] Examples of magnetic metallic materials include pure iron; crystalline or amorphous alloy magnetic materials such as Fe-Si alloys, Fe-Si-Al alloys, Fe-Cr alloys, Fe-Si-Cr alloys, Fe-Ni-Cr alloys, Fe-Cr-Al alloys, Fe-Ni alloys, Fe-Ni-B alloys, Fe-Ni-Mo alloys, Fe-Ni-Mo-Cu alloys, Fe-Co alloys, Fe-Ni-Co alloys, Fe-Si-Nb-B alloys, and Co-based amorphous alloys. Among magnetic metallic materials, iron alloy magnetic materials are more preferred. Iron alloy magnetic materials containing Fe and at least one element selected from the group consisting of Si, Cr, Nb, and B are preferred, and Fe-Si-Cr alloys and Fe-Si-Nb-B alloys are even more preferred. Fe-Si-Cr alloy materials refer to alloys containing Fe, Si, and Cr. Furthermore, Fe-Si-Nb-B alloys refer to alloys containing Fe, Si, Nb, and B.

[0073] (B) The magnetic powder may be a crystalline magnetic powder containing crystal grains, or an amorphous magnetic powder without crystal grains, or a combination of these may be used. Since crystalline magnetic powder contains crystal grains, it can generally show peaks indicating crystallinity in its X-ray diffraction pattern. Examples of crystal structures of crystal grains include a bcc crystal structure (body-centered cubic lattice structure), but other crystal structures may also be used. On the other hand, amorphous magnetic materials are amorphous, so they usually do not show specific peaks indicating crystallinity in their X-ray diffraction pattern. Generally, the X-ray diffraction pattern of amorphous magnetic powder shows a broad pattern without peaks indicating crystallinity. Among these, (B) the magnetic powder preferably contains crystalline magnetic powder, and may contain only crystalline magnetic powder.

[0074] (B) As the magnetic powder, commercially available magnetic powder may be used. Specific examples of commercially available magnetic powders include Powdertec's "MZ03S", "M05S", "M001", "MZ05S"; Sanyo Special Steel's "PST-S"; Epson Atomics' "AW2-08", "AW2-08PF20F", "AW2-08PF10F", "AW2-08PF3F", "Fe-3.5Si-4.5CrPF20F", "Fe-50NiPF20F", "Fe-80Ni-4MoPF20F", "ATFINE-NC1 PF5FA", "ATFINE-NC1 PF3FA; JFE Chemical Co., Ltd. "CVD iron powder (0.7μm)", "LD-M", "LD-MH", "KNI-106", "KNI-106GSM", "KNI-106GS", "KNI-109", "KNI-109GSM", "KNI-109GS"; Toda Kogyo Co., Ltd. "KNS-415", "BSF-547", "BSF-029", "BSN-125", "BSN-125", "BSN-714", "BSN-828", "S-1281", "S-1641", "S-1651", "S-1470", "S-1511", "S-2430"; Nippon Heavy Chemical Industries Co., Ltd. "JR09P2"; CIK Nanotech Co., Ltd. "Nanotek"; Kinsei Matec Co., Ltd. "JEMK-S", "JEMK-H"; ALDRICH Co., Ltd. "Yttrium iron" Examples include "oxide"; "MA-RCO-5" manufactured by DOWA Electronics Corporation; etc. Alternatively, for example, the (B) magnetic powders described in Japanese Patent Publication No. 2021-158343, Japanese Patent Publication No. 2021-141267, Japanese Patent Publication No. 2019-31463, and Japanese Patent Publication No. 2021-11602 may be used. These magnetic powders may be classified as needed. Furthermore, one type of (B) magnetic powder may be used alone, or two or more types may be used in combination.

[0075] (B) The magnetic powder particles are preferably spherical. (B) The aspect ratio obtained by dividing the length of the major axis of the magnetic powder particles by the length of the minor axis is preferably 2 or less, more preferably 1.5 or less, even more preferably 1.2 or less, and usually 1 or more, preferably greater than 1, and more preferably 1.05 or more.

[0076] (B) The average particle size range of the magnetic powder is preferably 0.01 μm or more, more preferably 0.5 μm or more, even more preferably 1 μm or more, preferably 10 μm or less, more preferably 9 μm or less, and even more preferably 8 μm or less. (B) When the average particle size of the magnetic powder is within the above range, the relative permeability of the cured body can be effectively increased, and the loss coefficient can usually be effectively reduced.

[0077] (B) The average particle size of the magnetic powder represents the median diameter based on volume. The average particle size of the magnetic powder can be measured by the laser diffraction-scattering method based on Mie scattering theory. Specifically, the particle size distribution of the magnetic powder can be created based on volume using a laser diffraction-scattering particle size distribution analyzer, and the average particle size can be measured by taking its median diameter as the average particle size. The sample to be measured is preferably the magnetic powder dispersed in water using ultrasound. Suitable laser diffraction-scattering particle size distribution analyzers include the "MT3000II" from Microtrac-Bel, the "LA-500" from Horiba, Ltd., and the "SALD-2200" from Shimadzu Corporation.

[0078] (B) The specific surface area range of the magnetic powder is preferably 0.05 m². 2 / g or more, more preferably 0.1m 2 / g or more, more preferably 0.3m 2 / g or more, preferably 10m 2 / g or less, more preferably 8m 2 / g or less, more preferably 5m 2 (B) When the specific surface area of ​​the magnetic powder is within the above range, the relative permeability of the hardened body can be effectively increased, and the loss coefficient can usually be effectively reduced. (B) The specific surface area of ​​the magnetic powder can be measured by the BET method.

[0079] (B) The magnetic powder preferably contains a combination of (B-1) particles having a particle size of 1 μm or less and (B-2) particles having a particle size larger than 1 μm. In the following description, "(B-1) particles having a particle size of 1 μm or less" may be referred to as "(B-1) small-diameter magnetic particles" as appropriate. Also, "(B-2) particles having a particle size larger than 1 μm" may be referred to as "(B-2) large-diameter magnetic particles" as appropriate. When (B-1) small-diameter magnetic particles and (B-2) large-diameter magnetic particles are combined, (B-1) small-diameter magnetic particles can be inserted between the (B-2) large-diameter magnetic particles, so that the resin composition and its cured product can contain (B) magnetic powder at a high density.

[0080] The volume ratio ((B-1) / (B-2)) of (B-1) small-diameter magnetic particles to (B-2) large-diameter magnetic particles is preferably 0.1 / 9.9 or more, more preferably 0.5 / 9.5 or more, even more preferably 1 / 9 or more, preferably 6 / 4 or less, more preferably 5 / 5 or less, and even more preferably 4 / 6 or less. When the volume ratio ((B-1) / (B-2)) is within the above range, the relative permeability of the cured body can be effectively increased, and the loss coefficient can usually be effectively reduced. The volume ratio ((B-1) / (B-2)) can be measured from the volume-based particle size distribution of (B) magnetic powder measured by a laser diffraction scattering particle size distribution analyzer as described above.

[0081] (B) The amount of magnetic powder can be set within a range that keeps the area ratio of (B) magnetic powder within the specified range described above. Specifically, the range of the amount of (B) magnetic powder is preferably 90% by mass or more, more preferably 91% by mass or more, even more preferably 92% by mass or more, preferably 99% by mass or less, more preferably 98% by mass or less, and even more preferably 97% by mass or less, based on 100% by mass of the nonvolatile components in the resin composition. When the amount of (B) magnetic powder is above the lower limit of the above range, the amount of (B) magnetic powder can be increased, so the area ratio of the magnetic powder can be increased, and thus the relative permeability and loss coefficient can be made particularly good. Also, when the amount of (B) magnetic powder is below the upper limit of the above range, aggregation of (B) magnetic powder can be suppressed, so the coefficient of variation of the interparticle distance of the magnetic powder can be reduced, and thus the relative permeability and loss coefficient can be made particularly good.

[0082] -(C) Dispersant- The resin composition according to this embodiment may contain (C) a dispersant as an optional non-volatile component. As the (C) dispersant, a component that can improve the dispersibility of (B) magnetic powder may be used. However, components corresponding to (A) and (B) are not included in the (C) dispersant. The (C) dispersant can improve the uniformity of the dispersion of (B) magnetic powder in the resin composition and its cured product, thereby reducing the coefficient of variation of the interparticle distance of the magnetic powder. In addition, the (C) dispersant can usually lower the viscosity of the resin composition, thereby improving the coatability and fillability of the resin composition.

[0083] (C) As a dispersant, for example, one can be used that contains a functional group that has the ability to adsorb to the particles of (B) magnetic powder, and when adsorbed to the (B) magnetic powder, disperses the particles of (B) magnetic powder by repulsion between the (C) dispersants (e.g., electrostatic repulsion, steric repulsion, etc.). Examples of such (C) dispersants include acidic group-containing dispersants and basic group-containing dispersants. (C) Dispersants may be used individually or in combination of two or more types.

[0084] Acidic group-containing dispersants typically contain acidic functional groups such as carboxyl groups, sulfo groups (-SO3H), sulfate groups (-OSO3H), phosphono groups (-PO(OH)2), phosphonooxy groups (-OPO(OH)2), hydroxyphosphoryl groups (-PO(OH)-), and sulfanyl groups (-SH). Acidic functional groups usually have dissociable protons and may be neutralized by bases such as amines and hydroxide ions. Preferred acidic group-containing dispersants include, for example, acidic group-containing polymeric dispersants containing polymeric chains such as polyoxyalkylene chains and polyether chains.

[0085] Basic group-containing dispersants typically contain basic functional groups such as primary, secondary, and tertiary amino groups; ammonium groups; imino groups; and nitrogen-containing heterocyclic groups such as pyridine, pyrimidine, pyrazine, imidazole, and triazole. The basic functional groups may be neutralized with an acid such as an organic acid or an inorganic acid. Preferred basic group-containing dispersants include, for example, basic group-containing polymeric dispersants containing polymeric chains such as polyester chains.

[0086] (C) As the dispersant, an acidic dispersant is preferred. An acidic dispersant refers to a dispersant that is acidic. Furthermore, "acidic" in a dispersant means that its pH is 6 or less. In detail, the pH of the (C) dispersant is preferably 6 or less, more preferably 4 or less, even more preferably 3.8 or less, even more preferably 3.5 or less, even more preferably 3.3 or less, preferably 2 or more, more preferably 2.2 or more, and even more preferably 2.4 or more. When a (C) dispersant having a pH in this range is used, the relative permeability of the cured product can be effectively increased, and the loss coefficient can usually be effectively reduced.

[0087] (C) The pH of the dispersant can be measured by the indicator method. Specifically, the dispersant is dissolved in acetone to prepare a sample solution (22°C) with a dispersant concentration of 0.1 g / mL, and the pH can be measured by immersing pH test paper in this sample solution. As the pH test paper, pH test paper that can measure pH in the acidic range (for example, those with measurement ranges of pH 0.0 to 14.0, pH 1.0 to 14.0, pH 0.5 to 5.0, etc.) can be used. An example of pH test paper is the pH test paper "pH Test Paper pH1 to 14" (pH measurement range pH 1.0 to 14.0) manufactured by AS ONE Corporation. For the specific measurement method, the method described in <Method for measuring the pH of the dispersant (indicator method)> in the examples described later may be adopted.

[0088] Examples of commercially available acidic dispersants include NOF Corporation's "C-2093I" and "SC-1015F (a multifunctional comb-type functional polymer having ionic groups in the main chain and polyoxyalkylene chains in the graft chains)," Kusumoto Chemical Co., Ltd.'s "DA-375 (a polyether phosphate compound-based dispersant)," Toho Chemical Industry Co., Ltd.'s "Phosphanol" series "RS-410," "RS-610," and "RS-710" (pH 1.9) (phosphate ester-based dispersant), and NOF Corporation's "Marialim" series "AKM-0531," "AFB-1521," "SC-0505K," and "SC-0708A."

[0089] More preferably, the (C) dispersant contains a polyester skeleton. A (C) dispersant containing a polyester skeleton can effectively improve the dispersibility of the (B) magnetic powder. Among these, a (C) dispersant containing a polyester skeleton represented by the following formula (C1) is more preferred.

[0090] [ka]

[0091] (In formula (C1), R independently represents a divalent hydrocarbon group having 2 to 10 carbon atoms, which may have substituents, and n represents an integer from 2 to 1000.)

[0092] In formula (C1), R represents a divalent hydrocarbon group which may have substituents. The number of carbon atoms in this divalent hydrocarbon group is usually 2 or more, preferably 3 or more, more preferably 4 or more, and usually 10 or less, preferably 8 or less, more preferably 6 or less. The divalent hydrocarbon group may be linear, branched, or cyclic, with linear and branched being preferred. Examples of divalent hydrocarbon groups include aliphatic hydrocarbon groups and aromatic hydrocarbon groups, with aliphatic hydrocarbon groups being preferred. Examples of divalent hydrocarbon groups include alkylene groups, alkenylene groups, alkylylene groups, and arylene groups, with alkylene groups being preferred among them.

[0093] Examples of the alkylene group include an ethylene group, a propylene group, a butylene group, a pentylene group, a hexylene group, a heptylene group, an octylene group, a nonylene group, a decylene group, etc. Examples of the alkenylene group include an ethenylene group, a propenylene group, a butenylene group, a pentenylene group, a hexenylene group, a heptenylene group, an octenylene group, a nonenylene group, a decenylene group, etc. Examples of the alkynylene group include an ethynylene group, a propynylene group, a butynylene group, a pentynylene group, a hexynylene group, a heptynylene group, an octynylene group, a nonynylene group, a decynylene group, etc. Examples of the arylene group include a phenylene group, a naphthylene group, etc. Among them, as R, a butylene group and a pentylene group are preferable.

[0094] The divalent hydrocarbon group represented by R in formula (C1) may or may not have a substituent. Examples of the substituent include a halogen atom, -OH, -O-C 1-6 alkyl group, -N(C 1-10 alkyl group)2, C 1-10 alkyl group, C 6-10 aryl group, -NH2, -CN, -C(O)O-C 1-10 alkyl group, -COOH, -C(O)H, -NO2, etc. Here, the term "C p-q "(where p and q are positive integers and p < q) indicates that the number of carbon atoms of the organic group described immediately after this term is p to q. For example, the expression "C 1-10 alkyl group" indicates an alkyl group having 1 to 10 carbon atoms. These substituents may be bonded to each other to form a ring. The above-mentioned ring includes a spiro ring and a fused ring. Further, the above-mentioned substituent may have a further substituent (hereinafter sometimes referred to as a "secondary substituent"). Unless otherwise specified, the same substituents as those described above may be used as the secondary substituent.

[0095] In formula (C1), n represents an integer of 2 to 1000. Specifically, n is usually 2 or more, preferably 5 or more, more preferably 10 or more, and is usually 1000 or less, preferably 500 or less, more preferably 100 or less, and still more preferably 50 or less.

[0096] The dispersant (C) containing the polyester skeleton represented by formula (C1) may contain any skeleton in combination with the polyester skeleton represented by formula (C1), as long as it does not impede the effects of the present invention. Examples of any skeleton include a polyester skeleton in formula (C1) where R is a divalent hydrocarbon group having 1 or 11 or more carbon atoms, which may have substituents (n is the same as in formula (C1)), and a polyallylamine skeleton. The ends of the polyester skeleton are not particularly limited.

[0097] The terminal ends of the (C) dispersant containing a polyester skeleton are not particularly limited and include, for example, carboxylic acid residues, hydroxyl groups, hydrogen atoms, etc.

[0098] A dispersant (C) containing a polyester skeleton represented by formula (C1) can be produced, for example, by the method described in Japanese Patent Application Publication No. 2022-064864.

[0099] (C) The dispersant preferably has an acid value within a specific range. Specifically, the acid value range of the (C) dispersant is preferably 1 mg KOH / g or more, more preferably 3 mg KOH / g or more, even more preferably 5 mg KOH / g, preferably 30 mg KOH / g or less, more preferably 25 mg KOH / g or less, and even more preferably 20 mg KOH / g or less. When a (C) dispersant having an acid value within such a range is used, the relative permeability of the cured product can be effectively increased, and the loss coefficient can usually be effectively reduced. In particular, it is preferable that the (C) dispersant containing a polyester skeleton represented by formula (C1) has an acid value within the above range. The acid value can be measured by neutralization titration.

[0100] (C) The dispersant preferably has an amine value within a specific range. Specifically, the amine value of the (C) dispersant is preferably 1 mg KOH / g or more, more preferably 5 mg KOH / g or more, even more preferably 10 mg KOH / g or more, preferably 45 mg KOH / g or less, more preferably 40 mg KOH / g or less, and even more preferably 35 mg KOH / g or less. When a (C) dispersant having an amine value within such a range is used, the relative permeability of the cured product can be effectively increased, and the loss coefficient can usually be effectively reduced. In particular, it is preferable that the (C) dispersant containing a polyester skeleton represented by formula (C1) has an amine value within the above range. The amine value can be measured by neutralization titration.

[0101] (C) The weight-average molecular weight range of the dispersant is preferably 2000 or more, more preferably 3000 or more, even more preferably 5000 or more, preferably 50000 or less, more preferably 40000 or less, and even more preferably 30000 or less. The weight-average molecular weight is the weight molecular weight on a polystyrene basis measured by gel permeation chromatography (GPC).

[0102] (C) Dispersants include liquid dispersants at 25°C and solid dispersants at 25°C. (C) Dispersants may contain only liquid dispersants, only solid dispersants, or a combination of liquid and solid dispersants.

[0103] (C) The amount of dispersant is preferably 0.1% by mass or more, more preferably 0.3% by mass or more, even more preferably 0.5% by mass or more, preferably 5% by mass or less, more preferably 4% by mass or less, and even more preferably 3% by mass or less, based on 100% by mass of the nonvolatile components in the resin composition. (C) When the amount of dispersant is within the above range, the relative permeability of the cured body can be effectively increased, and the loss coefficient can usually be effectively reduced.

[0104] (C) The amount of dispersant is preferably 1% by mass or more, more preferably 5% by mass or more, even more preferably 10% by mass or more, preferably 30% by mass or less, more preferably 25% by mass or less, and even more preferably 20% by mass or less, based on 100% by mass of the resin component in the resin composition. (C) When the amount of dispersant is within the above range, the relative permeability of the cured body can be effectively increased, and the loss coefficient can usually be effectively reduced.

[0105] The mass ratio of (C) dispersant to (B) magnetic powder (component (C) / component (B)) is preferably 1.0 × 10 -3 The above is more 3.0 × 10 -3 More preferably 5.0 × 10 -3 The above, preferably 3.0 × 10 -2 The following is more preferable: 2.0 × 10 -2 More preferably 1.5 × 10 -2 The following applies: When the mass ratio (component C / component B) is within the aforementioned range, the relative permeability of the hardened body can be effectively increased, and the loss coefficient can usually be effectively reduced.

[0106] -(D) Polymer resin- The resin composition according to this embodiment may contain (D) polymer resin as an optional non-volatile component. However, components corresponding to (A) to (C) are not included in the (D) polymer resin. When (D) polymer resin is used, the film-forming properties of the resin composition can be improved to facilitate the formation of the resin composition layer, or the flexibility of the cured resin composition can be increased. The (D) polymer resin is usually compatible with resin components other than the (D) polymer resin and is included in the resin composition and its cured product. The (D) polymer resin may be used alone or in combination of two or more types.

[0107] (D) Polymer resins typically have a large molecular weight. Specifically, the weight-average molecular weight Mw of (D) polymer resins is usually greater than the weight-average molecular weight of (A) thermosetting resins, preferably greater than 5000, more preferably 8000 or more, even more preferably 10000 or more, even more preferably 20000 or more, preferably 100000 or less, more preferably 70000 or less, even more preferably 60000 or less, and even more preferably 50000 or less. The weight-average molecular weight Mw of (D) polymer resins is the weight-average molecular weight in terms of polystyrene, measured by gel permeation chromatography (GPC).

[0108] (D) Examples of polymer resins include phenoxy resin, polycarbonate resin, polyvinyl acetal resin, polyolefin resin, polyimide resin, polyamideimide resin, polyetherimide resin, polysulfone resin, polyethersulfone resin, polyphenylene ether resin, polyetheretherketone resin, polyester resin, etc. Among these, at least one selected from polyimide resin, polycarbonate resin, and phenoxy resin is preferred.

[0109] As the polyimide resin, a resin containing repeating units with imide bonds can be used. Examples of such resins include linear polyimides obtained by reacting a bifunctional hydroxyl-terminated polybutadiene, a diisocyanate compound, and a tetrabasic acid anhydride (polyimides described in Japanese Patent Publication No. 2006-37083), and modified polyimides containing a polysiloxane skeleton (polyimides described in Japanese Patent Publication No. 2002-12667 and Japanese Patent Publication No. 2000-319386, etc.). Commercially available polyimide resins can be used. Examples of commercially available products include "Ricacoat SN20" and "Ricacoat PN20" manufactured by Shin Nippon Rika Co., Ltd.

[0110] As the polycarbonate resin, a resin containing repeating units with a carbonate structure can be used. Examples of such resins include hydroxyl group-containing carbonate resins, phenolic hydroxyl group-containing carbonate resins, carboxyl group-containing carbonate resins, acid anhydride group-containing carbonate resins, isocyanate group-containing carbonate resins, and urethane group-containing carbonate resins. Commercially available carbonate resins can be used. Examples of commercially available products include "FPC0220" from Mitsubishi Gas Chemical Co., Ltd., "T6002" and "T6001" (polycarbonate diols) from Asahi Kasei Chemicals Corporation, and "C-1090," "C-2090," and "C-3090" (polycarbonate diols) from Kuraray Co., Ltd.

[0111] Examples of phenoxy resins include phenoxy resins having one or more skeletons selected from the group consisting of bisphenol A skeleton, bisphenol F skeleton, bisphenol S skeleton, bisphenolacetophenone skeleton, novolac skeleton, biphenyl skeleton, fluorene skeleton, dicyclopentadiene skeleton, norbornene skeleton, naphthalene skeleton, anthracene skeleton, adamantane skeleton, terpene skeleton, and trimethylcyclohexane skeleton. The terminal end of the phenoxy resin may be any functional group such as a phenolic hydroxyl group or an epoxy group. Specific examples of phenoxy resins include "1256" and "4250" (both phenoxy resins containing a bisphenol A skeleton) manufactured by Mitsubishi Chemical Corporation; "YX8100" (phenoxy resin containing a bisphenol S skeleton) manufactured by Mitsubishi Chemical Corporation; "YX6954" (phenoxy resin containing a bisphenol acetophenone skeleton) manufactured by Mitsubishi Chemical Corporation; "FX280" and "FX293" manufactured by Nippon Steel Chemical & Material Co., Ltd.; and "YL7500BH30", "YX6954BH30", "YX7553", "YX7553BH30", "YL7769BH30", "YL6794", "YL7213", "YL7290", "YL7553BH30", and "YL7482" manufactured by Mitsubishi Chemical Corporation.

[0112] Examples of polyvinyl acetal resins include polyvinyl formal resin and polyvinyl butyral resin, with polyvinyl butyral resin being preferred. Specific examples of polyvinyl acetal resins include S-Rec BH series, BX series (e.g., BX-5Z), KS series (e.g., KS-1), BL series, and BM series manufactured by Sekisui Chemical Co., Ltd.

[0113] Specific examples of polyamide-imide resins include "Viromax HR11NN" and "Viromax HR16NN" manufactured by Toyobo Co., Ltd. Other specific examples of polyamide-imide resins include modified polyamide-imides such as "KS9100" and "KS9300" (polysiloxane skeleton-containing polyamide-imide) manufactured by Hitachi Chemical Co., Ltd.

[0114] Specific examples of polyethersulfone resins include "PES5003P" manufactured by Sumitomo Chemical Co., Ltd.

[0115] Specific examples of polyphenylene ether resins include the oligophenylene ether styrene resin "OPE-2St 1200" manufactured by Mitsubishi Gas Chemical Company.

[0116] Specific examples of polysulfone resins include Solvay Advanced Polymers' polysulfones "P1700" and "P3500".

[0117] (D) The amount of polymer resin may be 0% by mass or more than 0% by mass, with respect to 100% by mass of the nonvolatile components of the resin composition, preferably 0.01% by mass or more, more preferably 0.1% by mass or more, even more preferably 0.2% by mass or more, preferably 5% by mass or less, more preferably 2% by mass or less, and even more preferably 1% by mass or less.

[0118] (D) The amount of polymer resin may be 0% by mass or more than 0% by mass, with respect to 100% by mass of the resin component of the resin composition, preferably 0.01% by mass or more, more preferably 0.1% by mass or more, even more preferably 1% by mass or more, preferably 30% by mass or less, more preferably 20% by mass or less, and even more preferably 15% by mass or less.

[0119] -(E) Any additives- The resin composition according to this embodiment may further include (E) any additive as an optional non-volatile component in combination with the components described above. Examples of optional additives (E) include: curing accelerators such as imidazole curing accelerators, phosphorus curing accelerators, urea curing accelerators, guanidine curing accelerators, metal curing accelerators, and amine curing accelerators; organic fillers such as rubber particles; organometallic compounds such as organic copper compounds and organic zinc compounds; polymerization inhibitors such as hydroquinone, catechol, pyrogallol, and phenothiazine; leveling agents such as silicone leveling agents and acrylic polymer leveling agents; thickeners such as bentonite and montmorillonite; defoaming agents such as silicone defoaming agents, acrylic defoaming agents, fluorine defoaming agents, and vinyl resin defoaming agents; ultraviolet absorbers such as benzotriazole ultraviolet absorbers; adhesion improvers such as urea silane; and triazole adhesion improvers. Examples of additives include: adhesion enhancers such as tetrazole-based adhesion enhancers and triazine-based adhesion enhancers; antioxidants such as hindered phenol-based antioxidants and hindered amine-based antioxidants; fluorescent whitening agents such as stilbene derivatives; surfactants such as fluorine-based surfactants and silicone-based surfactants; flame retardants such as phosphorus-based flame retardants (e.g., phosphate ester compounds, phosphazene compounds, phosphinic acid compounds, red phosphorus), nitrogen-based flame retardants (e.g., melamine sulfate), halogen-based flame retardants, and inorganic flame retardants (e.g., antimony trioxide); stabilizers such as borate-based stabilizers, titanate-based stabilizers, aluminate-based stabilizers, zirconate-based stabilizers, isocyanate-based stabilizers, carboxylic acid-based stabilizers, and carboxylic acid anhydride-based stabilizers; and so on. (E) Any additive may be used individually or in combination of two or more types.

[0120] -(F) Solvent- In addition to the non-volatile components such as components (A) to (E) described above, the resin composition according to this embodiment may further contain solvent (F) as a volatile component.

[0121] (F) As the solvent, an organic solvent is usually used. Preferably, this organic solvent is capable of dissolving the resin components contained in the non-volatile components. Examples of 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; and 2-ethoxyethyl acetate, propylene glycol monomethyl ether acetate, diethylene glycol monoethyl ether acetate, ethyl diglycol acetate, γ-butyrolactone, and methyl methoxypropionate. Examples of solvents include ether ester solvents; ester alcohol solvents such as methyl lactate, ethyl lactate, and methyl 2-hydroxyisobutyrate; ether alcohol solvents such as 2-methoxypropanol, 2-methoxyethanol, 2-ethoxyethanol, propylene glycol monomethyl ether, and diethylene glycol monobutyl ether (butyl carbitol); amide solvents such as N,N-dimethylformamide, N,N-dimethylacetamide, and N-methyl-2-pyrrolidone; sulfoxide solvents such as dimethyl sulfoxide; nitrile solvents such as acetonitrile and propionitrile; aliphatic hydrocarbon solvents such as hexane, cyclopentane, cyclohexane, and methylcyclohexane; and aromatic hydrocarbon solvents such as benzene, toluene, xylene, ethylbenzene, and trimethylbenzene. Furthermore, solvent (F) may be used alone or in combination of two or more types.

[0122] (F) The amount of solvent is preferably set so that the melt viscosity of the resin composition can be adjusted to an appropriate range. The amount of solvent (F) relative to 100% by mass of nonvolatile components in the resin composition may be, for example, 3% by mass or less, 1% by mass or less, 0.5% by mass or less, 0.1% by mass or less, or 0.01% by mass or less. The resin composition does not have to contain solvent (F). When the amount of solvent (F) is small, the generation of voids due to the evaporation of solvent (F) can be suppressed. Furthermore, the handling and workability of the resin composition can be improved.

[0123] -State of the resin composition- The resin composition according to this embodiment may be in solid or liquid form. The liquid resin composition may be a varnish containing a solvent, or a paste containing no solvent or a small amount of solvent. Regardless of the state of the resin composition, a cured body can be obtained by heating.

[0124] <Characteristics of the hardened material> The cured body according to this embodiment is a cured body of the resin composition described above. Specifically, a cured body can be obtained by thermal curing the resin composition. Normally, volatile components such as solvent (F) contained in the resin composition volatilize due to the heat during thermal curing, so a cured body containing non-volatile components such as components (A) to (E) or their reaction products can be obtained by thermal curing the resin composition.

[0125] The cured body according to this embodiment can have a high relative permeability. In one example, the relative permeability of the cured body is preferably 13.5 or higher, more preferably 14.0 or higher, even more preferably 15.0 or higher, and particularly preferably 16.0 or higher. There is no particular upper limit to the relative permeability, and it may be, for example, 30 or less, 20 or less, etc. The relative permeability of the cured body can be measured at a measurement frequency of 100 MHz and a room temperature of 23°C. The specific method for measuring the relative permeability can be the method described in <Test 1. Measurement of Relative Permeability and Loss Factor> of the Examples described later.

[0126] The cured body according to this embodiment can usually have a low loss coefficient tanδ. In one example, the loss coefficient tanδ of the cured body is preferably 0.15 or less, more preferably 0.10 or less, even more preferably 0.08 or less, and particularly preferably 0.06 or less. There is no particular limit to the lower limit of the loss coefficient tanδ, and it can be, for example, 0.01 or more. The loss coefficient tanδ of the cured body can be measured at a measurement frequency of 100 MHz and a room temperature of 23°C. The specific method for measuring the loss coefficient tanδ can be the method described in <Test 1. Measurement of relative permeability and loss coefficient> of the example described later.

[0127] The cured body is preferably used to form a magnetic layer on a circuit board, taking advantage of its excellent magnetic properties, such as relative permeability and loss coefficient tanδ. Examples of such magnetic layers include magnetic layers that fill holes in the substrate of a circuit board, and magnetic layers formed on the main surface of the substrate. However, the applications for which the cured resin composition is applied are not limited to those exemplified here.

[0128] <Method for manufacturing a hardened body> The method for manufacturing the cured body according to this embodiment is not particularly limited, as long as a cured body that satisfies the above-described requirements can be obtained. Typically, the cured body is (I) A step of mixing (A) a thermosetting resin and (B) magnetic powder to obtain a resin composition, The process of thermally curing the resin composition (II), It can be manufactured by a manufacturing method that includes these elements in this order.

[0129] In step (I), a resin composition is obtained by mixing (A) a thermosetting resin and (B) magnetic powder. When using a resin composition containing any component such as (C) a dispersant, there are no restrictions on the order in which the components are mixed. The components that may be included in the resin composition may be mixed some or all at the same time, or mixed sequentially. In addition, the temperature may be adjusted as appropriate during the mixing of each component, and thus heating and / or cooling may be performed temporarily or throughout the process. Furthermore, stirring or shaking may be performed during the mixing of each component.

[0130] In particular, step (I) of preparing the resin composition is (I-1) A step of mixing (A) a thermosetting resin and (B) magnetic powder to obtain an intermediate composition, (I-2) is a step of mixing the intermediate composition and (F) solvent, It is preferable that the components be included in this order. Here, the "intermediate composition" is included in the "resin composition" according to this embodiment because it includes (A) a thermosetting resin and (B) magnetic powder, but for the sake of explaining the method for manufacturing the cured product, it is referred to as the "intermediate composition". By mixing (A) a thermosetting resin and (B) a non-volatile component such as magnetic powder to obtain an intermediate composition, and then further mixing (F) a solvent into the intermediate composition, the dispersibility of the particles of (B) magnetic powder can be improved, and the average coefficient of variation of the interparticle distance of the magnetic powder can be easily reduced. The intermediate composition may contain (F) a solvent as needed.

[0131] In step (I-1), (A) a thermosetting resin and (B) magnetic powder are mixed to obtain an intermediate composition. When producing a resin composition containing any nonvolatile component such as (C) a dispersant, step (I-1) may include further mixing of any nonvolatile component in combination with (A) the thermosetting resin and (B) the magnetic powder. When any nonvolatile component is mixed, an intermediate composition containing any nonvolatile component in combination with (A) the thermosetting resin and (B) the magnetic powder can be obtained.

[0132] In process (I-1), there are no restrictions on the mixing order of each component. In particular, from the viewpoint of further effectively reducing the average coefficient of variation of the interparticle distance of the magnetic powder, process (I-1) is: (A) A step (I-1-1) to obtain a resin component composition by mixing a thermosetting resin with (C) any non-volatile component such as a dispersant, (I-1-2) is a step of mixing the resin component composition and (B) magnetic powder to obtain an intermediate composition. It is preferable to include them in this order.

[0133] According to step (I-1-1), a resin component composition is obtained that contains all nonvolatile components of the resin composition except for (B) magnetic powder. The resin component composition may optionally contain (F) solvent. Subsequently, in step (I-1-2), an intermediate composition is obtained by mixing the resin component composition with (B) magnetic powder. In the intermediate composition thus obtained, (B) magnetic powder can be dispersed with high uniformity. Therefore, the average coefficient of variation of the interparticle distance of the magnetic powder can be effectively reduced.

[0134] (B) From the viewpoint of increasing the content of magnetic powder, it is preferable that the (B) magnetic powder to be mixed contains a combination of (Bi) magnetic powder with an average particle size of 1 μm or less and (B-ii) magnetic powder with an average particle size greater than 1 μm. Therefore, in the method for manufacturing a cured body illustrated herein, it is preferable that the step of mixing (B) magnetic powder includes mixing a combination of (Bi) magnetic powder with an average particle size of 1 μm or less and (B-ii) magnetic powder with an average particle size greater than 1 μm. Typically, (Bi) magnetic powder with an average particle size of 1 μm or less contains (B-1) small-diameter magnetic particles, and (B-ii) magnetic powder with an average particle size greater than 1 μm contains (B-2) large-diameter magnetic particles, so the content of (B) magnetic powder can be increased. The average particle size can be measured by the method described above.

[0135] The average particle size of the (Bi) magnetic powder with an average particle size of 1 μm or less is 1 μm or less, preferably 0.8 μm or less, more preferably 0.5 μm or less, preferably 0.005 μm or more, more preferably 0.01 μm or more, and even more preferably 0.02 μm or more.

[0136] (B-ii) The average particle size of magnetic powder with an average particle size greater than 1 μm is greater than 1 μm, preferably 1.2 μm or more, more preferably 1.5 μm or more, preferably 10 μm or less, more preferably 9 μm or less, and even more preferably 8 μm or less.

[0137] The mass ratio ((Bi) / (B-ii)) of magnetic powder with an average particle size of 1 μm or less (Bi) and magnetic powder with an average particle size of greater than 1 μm (B-ii) is preferably 0.01 or more, more preferably 0.05 or more, even more preferably 0.10 or more, preferably 0.70 or less, more preferably 0.60 or less, and even more preferably 0.50 or less.

[0138] In step (I-2), (F) solvent is mixed with an intermediate composition containing (A) thermosetting resin and (B) magnetic powder. If (F) solvent is further mixed after mixing the non-volatile components in step (I-1), the dispersibility of the (B) magnetic powder particles can be improved. Typically, a resin varnish as a liquid resin composition can be obtained by step (I-2).

[0139] The amount of solvent (F) to be mixed can be appropriately set so that the average coefficient of variation of the interparticle distance of the magnetic powder falls within the specified range described above, and is preferably set according to the amount of solvent (F) in the resin composition obtained after mixing the solvent (F) in step (I-2). The amount of solvent (F) in the resin composition obtained in step (I-2) is usually greater than the total amount of resin components in the resin composition. In one example, the amount of solvent (F) in the resin composition obtained in step (I-2) is preferably 1% by mass or more, more preferably 3% by mass or more, even more preferably 5% by mass or more, preferably 50% by mass or less, more preferably 30% by mass or less, and even more preferably 10% by mass or less, based on 100% by mass of the entire resin composition.

[0140] Furthermore, the amount of solvent (F) mixed in step (I-2) is preferably 20% by mass or more, more preferably 30% by mass or more, even more preferably 40% by mass or more, preferably 100% by mass or less, more preferably 90% by mass or less, and even more preferably 80% by mass or less, relative to the total amount of solvent (F) in the resin composition obtained after mixing solvent (F).

[0141] Step (I) may optionally include a drying step (I-3). For example, if a resin composition containing solvent (F) is obtained by performing step (I-2), step (I-3) may include removing solvent (F) from the obtained resin composition by drying. Also, for example, if a solution or dispersion containing solvent (F) is used as a raw material for the resin composition, a resin composition containing solvent (F) is obtained, and step (I-3) may include removing solvent (F) from the resin composition by drying. Such drying may be performed, for example, after coating the resin composition onto a support in the resin sheet manufacturing process, or after coating the resin composition onto a substrate in the circuit board manufacturing process.

[0142] Drying may be carried out by drying methods such as heating or blowing hot air. The drying conditions are not particularly limited, but the amount of solvent (F) in the resin composition can be dried to a level of 10% by mass or less, preferably 5% by mass or less. Depending on the boiling point of solvent (F), drying may be carried out under conditions such as a drying temperature of 50°C to 150°C and a drying time of 3 to 10 minutes.

[0143] After preparing the resin composition in step (I), a cured body can be obtained by performing step (II) to heat-cur the resin composition. The heat-curing conditions for the resin composition can be appropriately set within the range in which the curing of the resin composition progresses. 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 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.

[0144] The degree of hardening of the cured product obtained in step (II) 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.

[0145] The method for manufacturing a cured body may include any additional steps in combination with the steps (I) and (II) described above. For example, the method for manufacturing a cured body may include a preheating step (III) in which, after preparing the resin composition, the resin composition is heated at a temperature lower than the curing temperature before the resin composition is heat-cured. For example, prior to curing the resin composition, the resin composition 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).

[0146] <Resin sheet> When a cured resin composition is used as the magnetic layer of a circuit board, the resin composition may be provided in the form of a resin sheet from the viewpoint of efficiently manufacturing the circuit board. This resin sheet comprises a support and a resin composition layer formed on the support. The resin composition layer contains the resin composition, preferably containing only the resin composition.

[0147] From the viewpoint of thinning, the thickness of the resin composition layer is preferably 250 μm or less, more preferably 200 μm or less, even more preferably 150 μm or less, and even more preferably 100 μm or less. The lower limit of the thickness of the resin composition layer is not particularly limited, but may be, for example, 5 μm or more, 10 μm or more, etc.

[0148] Examples of support materials include plastic film, metal foil, and release paper, with plastic film and metal foil being preferred.

[0149] When using a plastic film as a support, examples of plastic materials include polyesters such as polyethylene terephthalate (PET) and polyethylene naphthalate (PEN), polycarbonate (PC), acrylic polymers such as polymethyl methacrylate (PMMA), cyclic polyolefins, triacetylcellulose (TAC), polyether sulfide (PES), polyether ketones, and polyimides. Among these, polyethylene terephthalate and polyethylene naphthalate are preferred, and inexpensive polyethylene terephthalate is particularly preferred.

[0150] 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.

[0151] The support may have surface treatments such as matte finish or corona treatment applied to the surface that bonds with the resin composition layer.

[0152] 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.

[0153] 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.

[0154] 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. The protective film can suppress the adhesion of dust and scratches to the surface of the resin composition layer. When a resin sheet has a protective film, the resin sheet can usually be used by peeling off the protective film.

[0155] A resin sheet can be manufactured, for example, by a manufacturing method that includes a step of coating a resin composition onto a support. The coating of the resin composition can be carried out, for example, using a coating device such as a die coater. By coating the resin composition, a layer of the resin composition can be formed on the support, and a resin sheet can be obtained. The resin composition to be coated may or may not contain (F) solvent. Furthermore, if a resin composition containing (F) solvent is coated, drying may be carried out after coating as necessary. Drying can be carried out, for example, under the drying conditions described in the manufacturing method of the cured body. The manufactured resin sheet can usually be stored by winding it into a roll.

[0156] <Circuit board> The cured resin composition described above is preferably used to form a magnetic layer on a circuit board, taking advantage of its excellent magnetic properties. A circuit board using such a cured resin includes the cured resin. The specific structure of such a circuit board is not limited as long as it includes the cured resin composition. The circuit board according to the first example includes a substrate with holes formed on it and a cured resin composition filling these holes. In the circuit board according to the first example, a magnetic layer is formed by the cured resin in the holes. The circuit board according to the second example includes a substrate and a layer of cured resin formed on this substrate. In the circuit board according to the second example, a magnetic layer is formed by the layer of cured resin. The circuit boards according to the first and second examples will be described below. However, the circuit board and its manufacturing method are not limited to the first and second examples described below.

[0157] (Circuit board relating to the first example) The circuit board according to the first example includes a substrate in which holes are formed and a cured body of a resin composition filled in the holes. This circuit board is, for example, (1) A step of filling the holes in the substrate with a resin composition, and (2) A step of heat-curing the resin composition to obtain a cured body, It can be manufactured by a manufacturing method that includes the following. Furthermore, the manufacturing method of the circuit board according to the first example further includes the following: (3) A step of polishing the surface of the cured body or resin composition, (4) A step of roughening the hardened body, (5) A step of forming a conductive layer on the surface of the hardened body, It may include some or all of the above. Typically, steps (1) to (5) are performed in the order of steps (1), (2), (3), (4), and (5), but step (2) may be performed after step (3). The following explanation will use an example in which a substrate has through-holes formed as holes that penetrate the substrate in the thickness direction.

[0158] -Process (1)- Step (1) typically includes the step of preparing a substrate with through-holes formed on it. The substrate may be purchased from the market. Alternatively, the substrate may be manufactured using appropriate materials. The following describes an example of a substrate manufacturing method.

[0159] Figure 1 is a schematic cross-sectional view showing a core substrate 10 prepared in a method for manufacturing a circuit board according to a first example of the present invention. The step of preparing the substrate may include the step of preparing the core substrate 10, as shown in the example in Figure 1. The core substrate 10 usually includes a support substrate 11. Examples of the support substrate 11 include insulating substrates such as glass epoxy substrates, metal substrates, polyester substrates, polyimide substrates, BT resin substrates, and thermosetting polyphenylene ether substrates. A metal layer may also be provided on the support substrate 11. The metal layer may be provided on one side of the support substrate 11 or on both sides. Here, an example is shown in which a first metal layer 12 and a second metal layer 13 are provided on both surfaces of the support substrate 11. Examples of the first metal layer 12 and the second metal layer 13 include layers formed of a metal such as copper. The first metal layer 12 and the second metal layer 13 may be copper foil such as a carrier-attached copper foil, or metal layers formed of the material of the conductive layer described later.

[0160] Figure 2 is a schematic cross-sectional view showing a core substrate 10 with through-holes 14 formed in a method for manufacturing a circuit board according to the first example of the present invention. The step of preparing the substrate may include the step of forming through-holes 14 in the core substrate 10, as shown in the example in Figure 2. The through-holes 14 can be formed by methods such as drilling, laser irradiation, or plasma irradiation. Usually, the through-holes 14 can be formed by forming through holes in the core substrate 10. Specifically, the formation of through-holes 14 can be carried out using a commercially available drilling device. Examples of commercially available drilling devices include the "ND-1S211" manufactured by Hitachi Via Mechanics Co., Ltd.

[0161] Figure 3 is a schematic cross-sectional view showing a core substrate 10 in which a plating layer 20 is formed in through-holes 14 in a method for manufacturing a circuit board according to the first example of the present invention. The step of preparing the substrate may include, if necessary, a step of roughening the core substrate 10 and then forming the plating layer 20 as shown in Figure 3. The 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. The plating layer 20 can be formed by a plating method. The procedure for forming the plating layer 20 by a plating method may be the same as the procedure for forming the conductor layer in step (5) described later. Here, an example in which the plating layer 20 is formed in the through-holes 14, on the surface of the first metal layer 12, and on the surface of the second metal layer 13 will be shown and explained.

[0162] Figure 4 is a schematic cross-sectional view showing how the resin composition 30a is filled into the through-holes 14 of the core substrate 10 in a method for manufacturing a circuit board according to a first example of the present invention. Step (1) includes, after preparing a core substrate 10 with the through-holes 14 formed as described above, filling the through-holes 14 of the core substrate 10 with the resin composition 30a, as shown in Figure 4.

[0163] The resin composition 30a can be filled into the through-hole 14 by, for example, a printing method. Examples of printing methods include printing the resin composition 30a into the through-hole 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. Normally, excess resin composition 30a protrudes or adheres to the outside of the through-hole 14. Therefore, the resin composition 30a can be provided not only inside the through-hole 14 but also outside the through-hole 14. Figure 4 illustrates the state in which the resin composition 30a has been filled into the through-hole 14 by the printing method described above.

[0164] Furthermore, the filling of the through-holes 14 with the resin composition 30a may be carried out, for example, by laminating a resin sheet (not shown). Typically, the resin sheet and the core substrate 10 are laminated so that the resin composition layer is bonded to the core substrate 10, thereby filling the through-holes 14 with the resin composition 30a. Lamination can be carried out, for example, by heating and pressing the resin sheet to the core substrate 10 from the support side. Examples of a member for heating and pressing the resin sheet to the core substrate 10 (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 (such as a SUS roll). It is preferable to press the resin sheet via a sheet made of an elastic material such as heat-resistant rubber, rather than directly contacting and pressing the heat-pressing member to the resin sheet, so that the resin sheet can sufficiently follow the irregularities on the surface of the core substrate 10.

[0165] 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. Lamination of the resin sheet and the core substrate 10 is preferably carried out under reduced pressure conditions of 26.7 hPa or less.

[0166] Lamination of the resin sheet and the core substrate 10 can be performed 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.

[0167] When a resin sheet with a support is used, the support is usually peeled off after the lamination described above. The peeling off of the support may be performed before or after the curing of the resin composition, as described later. Some of the resin composition 30a contained in the resin composition layer may adhere to the outside of the through-hole 14. Therefore, when the resin composition 30a is filled into the through-hole 14 by lamination of resin sheets, the resin composition 30a may be provided not only inside the through-hole 14 but also outside the through-hole 14.

[0168] -Process (2)- Figure 5 is a schematic cross-sectional view illustrating step (2) of the method for manufacturing a circuit board according to a first example of the present invention. Step (2) includes filling the through-holes 14 with a resin composition 30a, and then curing the resin composition 30a to form a cured body 30 as shown in Figure 5. The cured body 30 can form a magnetic layer that fills the through-holes 14. The curing of the resin composition 30a is usually performed by thermal curing. The thermal curing conditions may be those described in the section on the method for manufacturing a cured body. Alternatively, a preheating step may be performed in which the resin composition 30a is heated at a temperature lower than the curing temperature before curing the resin composition 30a. The heating conditions in the preheating step may be those described in the section on the method for manufacturing a cured body.

[0169] -Process (3)- Figure 6 is a schematic cross-sectional view illustrating step (3) of a method for manufacturing a circuit board according to a first example of the present invention. Step (3) includes polishing excess hardened material 30 protruding from or adhering to the core substrate 10 as shown in Figure 6. Polishing removes the excess hardened material 30, so that the surface of the hardened material 30 can be flattened. The surface (polished surface) 31 of the hardened material 30 flattened by polishing can usually form a plane that is flush with the surrounding surface 21 (for example, the surface of the core substrate 10, the surface of the plating layer 20).

[0170] As a polishing method, a method that can remove excess hardened material 30 protruding from or adhering to the core substrate 10 may be employed. Examples of such polishing methods include buff polishing, belt polishing, and ceramic polishing. Examples of commercially available buff polishing equipment include the "NT-700IM" manufactured by Ishii Hyoki Co., Ltd.

[0171] If step (3) is performed after step (2), the method for manufacturing the circuit board may include a step of heat-treating the cured body 30 after step (2) and before step (3) for the purpose of further increasing the degree of curing of the cured body 30. The temperature in the heat treatment may be in accordance with the curing temperature described above. The specific heat treatment 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 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.

[0172] Furthermore, if step (3) is performed before step (2), the method for manufacturing the circuit board may include a step of performing a preheating treatment on the resin composition layer before step (3), which involves heating at a temperature lower than the curing temperature of the resin composition. The temperature in the preheating treatment is preferably 100°C or higher, more preferably 110°C or higher, even more preferably 120°C or higher, 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.

[0173] -Process (4)- Step (4) includes roughening the surface of the cured body 30 (desmear treatment). The roughening treatment roughens the surface of the cured body 30. If the surface of the cured body 30 is polished, the roughening treatment (desmear treatment) usually includes roughening the polished surface 31. The procedure and conditions of the roughening step are not particularly limited, and for example, the procedure and conditions used in the manufacturing method of multilayer printed circuit boards can be adopted. As a roughening step, for example, the surface of the cured body 30 may 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.

[0174] -Process (5)- Figure 7 is a schematic cross-sectional view illustrating step (5) of the method for manufacturing a circuit board according to a first example of the present invention. Step (5) includes forming a conductive layer 40 on the polished surface 31 of the hardened body 30, as shown in Figure 7. Here, an example is shown in which the conductive layer 40 is formed not only on the polished surface 31 of the hardened body 30 but also on the surrounding surface 21 (for example, the surface of the core substrate 10, the surface of the plating layer 20). Also, although Figure 7 shows an example in which the conductive layer 40 is formed on both sides of the core substrate 10, the conductive layer 40 may be formed on only one side of the core substrate 10.

[0175] Figure 8 is a schematic cross-sectional view illustrating step (5) of a method for manufacturing a circuit board according to a first example of the present invention. As shown in Figure 8, step (5) may include forming a conductive layer 40, and then removing a portion of the conductive layer 40, the first metal layer 12, the second metal layer 13, and the plating layer 20 by etching or other processes to form a patterned conductive layer 41.

[0176] 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 body 30 (and the plated layer 20) can be plated by a suitable method such as a semi-additive or 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.

[0177] Here, an example of a method for forming a patterned conductor layer 41 on the polished surface 31 of the hardened body 30 will be described in detail. A plating seed layer is formed on the polished surface 31 of the hardened body 30 by electroless plating. Next, an electroplated layer is formed on the formed plating seed layer by electroplating. After that, if necessary, the unnecessary plating seed layer can be removed by etching or other treatments to form a patterned conductor layer 41 having a desired wiring pattern. After the formation of the patterned conductor layer 41, annealing treatment may be performed if necessary to improve the adhesion strength of the patterned conductor layer 41. Annealing treatment can be performed, for example, by heating at 150°C to 200°C for 20 to 90 minutes.

[0178] From the viewpoint of thinning, the thickness of the pattern conductor layer 41 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.

[0179] By the above method, a circuit board 1 containing a cured body 30 of the resin composition 30a can be manufactured.

[0180] (Circuit board relating to the second example) The circuit board according to the second example comprises a magnetic layer as a layer of cured resin composition. Therefore, the magnetic layer includes cured resin composition, preferably only cured resin composition. This circuit board is, for example, (i) A step of forming a magnetic layer on an inner layer substrate, (ii) A process of drilling holes in the magnetic layer, (v) A step of forming a conductive layer on the surface of the magnetic layer, It can be manufactured by a manufacturing method that includes [the specified ingredient]. Furthermore, this manufacturing method can be further [details omitted]. (iii) A step of polishing the surface of the magnetic layer, (iv) A process of roughening the surface of the magnetic layer, This may include some or all of the above. Typically, steps (i) to (v) are performed in the order of steps (i), (ii), (iii), (iv), and (v).

[0181] -Process (i)- Step (i) includes forming a magnetic layer on an inner layer substrate. The formation of the magnetic layer in step (i) includes, for example, forming a resin composition layer on an inner layer substrate and forming a magnetic layer by thermal curing the formed resin composition layer. Preferably, step (i) includes laminating a resin sheet onto an inner layer substrate such that the resin composition layer is bonded to the inner layer substrate and forming a magnetic layer by thermal curing the resin composition layer. The preferred method for forming this magnetic layer will be described below.

[0182] Figure 9 is a schematic cross-sectional view illustrating step (i) in a method for manufacturing a circuit board according to a second example of the present invention. As shown in Figure 9, a resin sheet 310 is prepared, which includes a support 330 and a resin composition layer 320a provided on the support 330. The resin sheet 310 and the inner layer substrate 200 are then laminated together such that the resin composition layer 320a is bonded to the inner layer substrate 200.

[0183] An insulating substrate can be used as the inner layer substrate 200. Examples of insulating substrates for the inner layer substrate 200 include 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 the like are fabricated within its thickness.

[0184] The inner layer substrate 200 shown in this example comprises 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. However, in the example shown in Figure 9, only the wiring constituting the coil-shaped conductive structure 400 of the inductor element (see Figure 12) is shown. The external terminal 240 may be a terminal for electrically connecting to an external device or the like, which is not shown. The external terminal 240 can be configured as part of the conductor layer provided on the second main surface 200b.

[0185] Examples of conductor materials that can constitute the first conductor layer 420 and the external terminal 240 include the same materials as those described in the first example. The first conductor layer 420 and the external terminal 240 may be single-layer structures or multi-layer structures 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.

[0186] 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.

[0187] The lamination of the resin sheet 310 and the inner layer substrate 200 can be carried out in the same manner as the lamination of the resin sheet and the core substrate described in the first example. Furthermore, after lamination of the resin sheet 310 and the inner layer substrate 200, the laminated resin sheet 310 may be smoothed by, for example, 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 the lamination described above. The smoothing process can be carried out using a commercially available laminator. Lamination and smoothing may be carried out continuously using a commercially available vacuum laminator.

[0188] Figure 10 is a schematic cross-sectional view illustrating step (i) in a method for manufacturing a circuit board according to a second example of the present invention. After laminating the resin sheet 310 and the inner layer substrate 200, the resin composition layer 320a can be heat-cured to form a magnetic layer. In this example, as shown in Figure 10, the resin composition layer 320a bonded to the inner layer substrate 200 is heat-cured to form the first magnetic layer 320. The heat-curing conditions may be those described in the section on the method for manufacturing a cured body. Alternatively, a preheating step may be performed in which the resin composition layer 320a is heated at a temperature lower than the curing temperature before curing the resin composition layer 320a. The heating conditions in the preheating step may be those described in the section on the method for manufacturing a cured body.

[0189] The support 330 may be removed between the time of heat curing in step (i) and step (ii), or it may be peeled off after step (ii).

[0190] Step (i) may include, instead of laminating the resin sheets 310, applying a resin composition onto the inner layer substrate 200 using a coating device such as a die coater to form a resin composition layer, and then thermally curing the resin composition layer to form a magnetic layer 320.

[0191] -Process (ii)- Figure 11 is a schematic cross-sectional view illustrating step (ii) in a method for manufacturing a circuit board according to a second example of the present invention. As shown in Figure 11, step (ii) includes drilling holes in the first magnetic layer 320 to form via holes 360. The via holes 360 can serve as paths for electrically connecting the first conductor layer 420 and the second conductor layer 440, which will be described later. The via holes 360 may be formed using, for example, a drill, laser, plasma, etc. The dimensions and shape of the holes may be appropriately determined according to the design of the printed circuit board.

[0192] -Process (iii)- The method for manufacturing a circuit board according to the second example may optionally include a step (iii) of polishing the surface of the magnetic layer. For example, the surface of the first magnetic layer 320 may be polished. The polishing method in step (iii) may be the same as that described in the first example.

[0193] -Process (iv)- The method for manufacturing a circuit board according to the second example may include, if necessary, roughening the surface of the magnetic layer (desmearing). For example, the surface of the first magnetic layer 320 may be roughened. The roughening treatment roughens the surface of the first magnetic layer 320. In addition, if smear (resin residue; not shown) is formed in the via holes 360 of the first magnetic layer 320, the smear can be removed. The roughening treatment in step (iv) can be carried out in the same manner as the roughening treatment described in the first example.

[0194] -Process (v)- Figure 12 is a schematic cross-sectional view illustrating step (v) in a method for manufacturing a circuit board according to a second example of the present invention. As shown in Figure 12, in step (v), a second conductive layer 440 is formed on the first magnetic layer 320.

[0195] The conductor material that can constitute the second conductor layer 440 is the same as the material of the conductor layer described in the first example.

[0196] 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.

[0197] 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, a second conductor layer 440 containing a desired wiring pattern can be easily formed. In addition, this process also forms via hole wiring 360a within the via hole 360.

[0198] 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, on the central side, by via hole wiring 360a. The other end of the spiral wiring portion of the second conductor layer 440, on the outer circumference side, is electrically connected to the land 420a of the first conductor layer 420, by via hole wiring 360a. Therefore, the other end of the spiral wiring portion of the second conductor layer 440, on the outer circumference side, is electrically connected to the external terminal 240 via via hole wiring 360a, land 420a, and through-hole wiring 220a.

[0199] 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.

[0200] After step (v), a further step of forming a magnetic layer on the conductor layer may be performed. In detail, as shown in Figure 14 as an example, the second magnetic layer 340 is formed on the first magnetic layer 320 on which the second conductor layer 440 and via hole wiring 360a are formed. The second magnetic layer 340 may be formed by the same process as described above. By the above method, a circuit board 100 including the first magnetic layer 320 and the second magnetic layer 340 formed from a cured resin composition can be manufactured.

[0201] <Inductor board> The inductor substrate according to this embodiment includes the circuit board described above. When such an inductor substrate includes the circuit board according to the first example described above, it may have an inductor pattern formed of a conductor around at least a portion of the cured resin composition. In this case, the inductor substrate may include an inductor element composed of, for example, an inductor pattern formed of at least a portion of the first metal layer 12, the second metal layer 13, the plating layer 20, and the pattern conductor layer 41, and a core portion formed of the cured body 30 surrounded by this inductor pattern. Such an inductor substrate can be, for example, the one described in Japanese Patent Application Publication No. 2016-197624.

[0202] If the inductor substrate includes a circuit board according to the second example, the inductor substrate may have a magnetic layer including a hardened body and a conductive structure in which at least a portion is embedded in the magnetic layer. The inductor substrate may also include an inductor element composed of the conductive structure and a portion of the magnetic layer that extends in the thickness direction of the magnetic layer and is surrounded by the conductive structure.

[0203] Figure 13 is a schematic plan view of the circuit board 100 of the inductor substrate, viewed from one side in its thickness direction. Figure 14 is a schematic diagram showing the cut end face of the circuit board 100 cut at the position indicated by the dashed line II-II shown in Figure 13. Figure 15 is a schematic plan view illustrating the configuration of the first conductor layer 420 of the circuit board 100 included in the inductor substrate.

[0204] The circuit board 100 may be a substrate having a plurality of magnetic layers (first magnetic layer 320, second magnetic layer 340) and a plurality of conductive layers (first conductive layer 420, second conductive layer 440), as shown as an example in Figures 13 and 14. Therefore, in the example shown herein, the circuit board 100 may be a build-up wiring board having build-up magnetic layers and build-up conductive layers. The circuit board 100 also includes an inner layer substrate 200.

[0205] As shown in Figure 14, the first magnetic layer 320 and the second magnetic layer 340 constitute a magnetic portion 300 that can be viewed as an integrated magnetic 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 shown in this example, 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.

[0206] 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 this 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. Furthermore, 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.

[0207] Similarly, a second conductor layer 440 is provided on the first magnetic 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 440 has an overall outline that is approximately rectangular and has a shape that is wound clockwise from the center outwards.

[0208] The inductor substrate described above can be used as a wiring board for mounting electronic components such as semiconductor chips, and can also be used as a (multilayer) printed wiring board using such a wiring board as an inner layer substrate. Furthermore, such a wiring board can be used as individual chip inductor components, and can also be used as a printed wiring board on which these chip inductor components are surface-mounted.

[0209] 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]

[0210] The present invention will be described in detail below with reference to examples, but the present invention is not limited to these examples. In the following description, "parts" and "%" refer to "parts by mass" and "mass%" respectively, unless otherwise specified. Unless otherwise specified, the temperature conditions were room temperature (23°C) and the pressure conditions were atmospheric pressure (1 atm). Furthermore, "MEK" represents methyl ethyl ketone.

[0211] <Method for measuring the pH of dispersants (indicator method)> The pH of the dispersant was measured according to the following instructions. A dispersant was dissolved in acetone to prepare a sample solution (at 22°C) with a dispersant concentration of 0.1 g / mL. pH test paper was gently immersed in the sample solution, then removed and allowed to dry. The color of the damp part of the test paper was compared to a color chart, and the pH of the closest color was determined as the pH of each sample.

[0212] <Synthesis Example 1: Synthesis of Dispersant 1> In a reaction flask equipped with a thermometer, stirrer, nitrogen inlet, and reflux tubing, 10.0 parts of 12-hydroxystearic acid (manufactured by Junsei Chemical Co., Ltd.) and 190 parts of ε-caprolactone (manufactured by Junsei Chemical Co., Ltd.) were charged. The mixture was heated to 160°C over 4 hours under a nitrogen stream, then heated at 160°C for 2 hours, and finally heated until the amount of ε-caprolactone remaining was less than 1%. The mixture was then cooled to room temperature. This reaction solution will be referred to as reaction solution 1 below.

[0213] A reaction flask equipped with a thermometer, stirrer, nitrogen inlet, and reflux tubing contained a mixture of 25.0 parts xylene and 70 parts of a 10% aqueous solution of polyallylamine (PAA-1LV, manufactured by Nitto Boseki Co., Ltd., with a number average molecular weight of approximately 3,000), which was stirred at 160°C. Using a separation apparatus, the water was removed by distillation, and the xylene was returned to the reaction solution. 14.21 parts of reaction solution 1, heated to 160°C, were added to this mixture, and the reaction was carried out at 160°C for 2 hours. The mixture was further heated at 160°C for 4 hours, and the xylene was removed by distillation at 160°C to obtain dispersant 1.

[0214] Dispersant 1 has a polyester skeleton in which R in formula (C1) is an alkylene group with 5 carbon atoms, and had an amine value of 31.0 mg KOH / g and an acid value of 19.5 mg KOH / g. The pH of dispersant 1 using the indicator method was 6.

[0215] [ka]

[0216] <Example 1: Manufacturing of Magnetic Varnish 1> Composition A was obtained by mixing 2.41 parts by mass of epoxy resin ("ZX-1059", a mixture of bisphenol A type epoxy resin and bisphenol F type epoxy resin, manufactured by Nippon Steel Chemical & Material Co., Ltd., epoxy equivalent 169 g / eq.), 2.74 parts by mass of triazine skeleton-containing phenol resin (DIC Corporation, "LA-7054", hydroxyl group equivalent approximately 125 g / eq.; MEK solution with 60% solids), 2 parts by mass of phenoxy resin (Mitsubishi Chemical Corporation, "YL7553BH30", a 1:1 solution of MEK and cyclohexanone with 30% solids), and 1 part by mass of dispersant ("SC-0708A", polycarboxylic acid, manufactured by NOF Corporation, pH 3 by indicator method) at 1000 rpm for 20 seconds using a mixer (THINKY Corporation, "Awatori Rentaro").

[0217] Next, 79.5 parts by mass of magnetic powder (crystalline magnetic powder "ATFINE-NC1 PF5FA", Fe-Si-Nb-B alloy powder, average particle size 4.3 μm, manufactured by Epson Atomics) and 33.8 parts by mass of magnetic powder (crystalline magnetic powder, "CVD iron powder", Fe-Si-Cr alloy powder, average particle size 0.7 μm, manufactured by JFE Minerals) were added to composition A, and the mixture was mixed at 1000 rpm for 20 seconds using the mixer to obtain composition B.

[0218] Subsequently, 5.0 parts by mass of solvent (methyl ethyl ketone) were added to composition B, and the mixture was carried out using the mixer at 1000 rpm for 20 seconds to produce magnetic varnish 1. Of the total amount of magnetic powder contained in the obtained magnetic varnish 1 (100 volume%), small-diameter magnetic particles with a particle size of 1 μm or less accounted for 30 volume%, and large-diameter magnetic particles with a particle size greater than 1 μm accounted for 70 volume%.

[0219] <Example 2: Preparation of Magnetic Varnish 2> Magnetic varnish 2 was prepared by the same method as in Example 1, except that 1 part by mass of dispersant ("SC-0708A", polycarboxylic acid, manufactured by NOF Corporation, pH 3 by indicator method) was replaced with 1 part by mass of dispersant 1 prepared in Synthesis Example 1. The ratio of small-diameter magnetic particles and large-diameter magnetic particles to 100% by volume of the total amount of magnetic powder were the same as in Example 1.

[0220] <Example 3: Preparation of Magnetic Varnish 3> The amount of magnetic powder ("ATFINE-NC1 PF5FA", average particle size 4.3 μm, manufactured by Epson Atomics) was changed from 79.5 parts by mass to 90.64 parts by mass. In addition, the amount of magnetic powder (CVD iron powder, average particle size 0.7 μm, manufactured by JFE Minerals) was changed from 33.8 parts by mass to 22.66 parts by mass. Magnetic varnish 3 was manufactured by the same method as in Example 2, except for the above changes. Of the total amount of magnetic powder contained in the obtained magnetic varnish 3 (100 volume%), the proportion of small-diameter magnetic particles with a particle size of 1 μm or less was 20 volume%, and the proportion of large-diameter magnetic particles with a particle size greater than 1 μm was 80 volume%.

[0221] <Example 4: Preparation of Magnetic Varnish 4> The amount of magnetic powder ("ATFINE-NC1 PF5FA", average particle size 4.3 μm, manufactured by Epson Atomics) was changed from 79.5 parts by mass to 101.97 parts by mass. In addition, the amount of magnetic powder (CVD iron powder, average particle size 0.7 μm, manufactured by JFE Minerals) was changed from 33.8 parts by mass to 11.33 parts by mass. Magnetic varnish 4 was manufactured by the same method as in Example 2, except for the above changes. Of the total amount of magnetic powder contained in the obtained magnetic varnish 4 (100 volume%), the proportion of small-diameter magnetic particles with a particle size of 1 μm or less was 10 volume%, and the proportion of large-diameter magnetic particles with a particle size greater than 1 μm was 90 volume%.

[0222] <Example 5: Preparation of Magnetic Varnish 5> The amount of magnetic powder ("ATFINE-NC1 PF5FA", average particle size 4.3 μm, manufactured by Epson Atomics) was changed from 79.5 parts by mass to 59.63 parts by mass. In addition, the amount of magnetic powder (CVD iron powder, average particle size 0.7 μm, manufactured by JFE Minerals) was changed from 33.8 parts by mass to 25.35 parts by mass. Except for the above changes, magnetic varnish 5 was manufactured by the same method as in Example 1. Of the total amount of magnetic powder contained in the obtained magnetic varnish 5 (100 volume%), the proportion of small-diameter magnetic particles with a particle size of 1 μm or less was 30 volume%, and the proportion of large-diameter magnetic particles with a particle size greater than 1 μm was 70 volume%.

[0223] <Comparative Example 1: Preparation of Magnetic Varnish 6> Epoxy resin ("ZX-1059", a mixture of bisphenol A type epoxy resin and bisphenol F type epoxy resin, manufactured by Nippon Steel Chemical & Material Co., Ltd., epoxy equivalent 169 g / eq.) 2.41 parts by mass, triazine skeleton-containing phenol resin (DIC Corporation, "LA-7054", hydroxyl group equivalent approximately 125 g / eq.; MEK solution with 60% solids) 2.74 parts by mass, phenoxy resin (Mitsubishi Chemical Corporation, "YL7553BH30", a 1:1 solution of MEK and cyclohexanone with 30% solids) 2 parts by mass, dispersant 1 1 part by mass, magnetic powder ("ATFINE-NC1 79.5 parts by mass of PF5FA (average particle size 4.3 μm, manufactured by Epson Atomics), 33.8 parts by mass of magnetic powder (CVD iron powder, average particle size 0.7 μm, manufactured by JFE Minerals), and 5.0 parts by mass of solvent (methyl ethyl ketone) were placed together in a mixer (THINKY "Awatori Rentaro") and mixed at 1000 rpm for 20 seconds to produce magnetic varnish 6. The ratio of small-diameter magnetic particles and large-diameter magnetic particles relative to 100% of the total amount of magnetic powder were the same as in Example 1.

[0224] <Comparative Example 2: Preparation of Magnetic Varnish 7> Magnetic varnish 7 was prepared by the same method as in Example 1, except that 1 part by mass of the dispersant ("SC-0708A", polycarboxylic acid, manufactured by NOF Corporation, pH 3 by indicator method) was replaced with 1 part by mass of the dispersant ("AD-374M", basic polymer, manufactured by NOF Corporation, pH 9 by indicator method). The ratio of small-diameter magnetic particles and large-diameter magnetic particles to 100% by volume of the total amount of magnetic powder were the same as in Example 1.

[0225] <Comparative Example 3: Preparation of Magnetic Varnish 8> Magnetic varnish 8 was prepared by the same method as in Example 1, except that 1 part by mass of the dispersant ("SC-0708A", polycarboxylic acid, manufactured by NOF Corporation, pH 3 by indicator method) was replaced with 1 part by mass of the silane coupling agent ("KBM-103", manufactured by Shin-Etsu Chemical Co., Ltd.). The ratio of small-diameter magnetic particles and large-diameter magnetic particles to 100% by volume of the total amount of magnetic powder were the same as in Example 1.

[0226] <Manufacturing of resin sheets> A PET film (Toray Industries, Ltd., "Lumirror R80", 38 μm thick, softening point 130°C) treated with an alkyd resin-based release agent (Lintec Corporation, "AL-5") was prepared as a support. The resin varnish prepared in the examples and comparative examples was applied to the support using a die coater so that the thickness of the resin composition layer after drying was 100 μm, and a resin sheet was obtained by drying at 65°C to 115°C (average 100°C) for 7 minutes.

[0227] <Manufacturing of sheet-like hardened materials> The resin sheet was cut into 200mm squares. The cut resin sheet (200mm square) was laminated to one side of a polyimide film (Ube Industries, Ltd.'s "UPIREX 25S", 25μm thick, 240mm square) using a batch-type vacuum pressure laminator (Nikko Materials' 2-stage build-up laminator "CVP700") so that the resin composition layer was in contact with the center of the smooth surface of the polyimide film. Lamination was performed by reducing the pressure to 13hPa or less for 30 seconds, and then pressing at 100°C and a pressure of 0.74MPa for 30 seconds. This resulted in a multilayer film having a layer structure of support / resin composition layer / polyimide film. After peeling off the support, the resin composition layer was heat-cured by heating at 190°C for 90 minutes. Subsequently, the polyimide film was peeled off to obtain a sheet-like cured body of the resin composition.

[0228] <Test 1. Measurement of relative permeability and loss coefficient> The resulting sheet-like hardened material was cut to obtain a donut-shaped evaluation sample with an outer diameter of 19.2 mm and an inner diameter of 8.2 mm. The relative permeability (μ') and loss coefficient (tanδ) of this evaluation sample were measured using a Keysight magnetic material test fixture "16454A" and a Keysight impedance analyzer "E4991B" at a measurement frequency of 100 MHz and room temperature of 23°C. The loss coefficient tanδ was calculated using the following formula "tanδ = μ'' / μ'".

[0229] <Test 2. Measurement of the coefficient of variation of the interparticle distance in the hardened material> The following procedure was performed to obtain a cross-sectional SEM image of the resulting sheet-like hardened material. For the SEM, we used the "SU8200" manufactured by Hitachi High-Tech Corporation. First, the sheet-like hardened material was cut into 1cm x 3cm squares using a desktop hand cutter. Then, the 1cm cut surface was polished with 1200-grit sandpaper. After that, the polished surface was polished using the "IM4000" ion milling machine manufactured by Hitachi High-Tech Corporation. The ion beam irradiation speed during polishing was 3 reciprocations / min, the irradiation angle was 30°, and the processing time was 2 hours. Next, the obtained cross-section was observed using the SEM at a magnification of 5000x. As described above, the defined observation area was acquired as an SEM cross-sectional image (width 1280 pixels, height 960 pixels, horizontal resolution 256 dpi, vertical resolution 256 dpi).

[0230] The acquired SEM cross-sectional images were imported into the image analysis software "WinROOF2018" (hereinafter also referred to as "analysis software"), and image analysis was performed as follows. First, the analysis software was launched and the SEM cross-sectional image was displayed. Next, the displayed image was automatically binarized using the modal method. Subsequently, the inter-particle distances of the extracted particles were measured using a binarization process. The measurement was performed using an edge-to-edge distance with a step angle of 20°. Subsequently, the mean and standard deviation were calculated from the interparticle distance measurements between 0.1 μm and less than 5.0 μm. The coefficient of variation of the interparticle distance was calculated by dividing the obtained standard deviation by the mean.

[0231] The aforementioned procedure for measuring the coefficient of variation of the interparticle distance was performed three times, and the coefficient of variation was measured at each of the three cross-sections. The average of the coefficients of variation measured at the three cross-sections was then calculated.

[0232] <Test 3. Measurement of the area ratio of magnetic powder> The following procedure was performed to obtain a cross-sectional SEM image of the resulting sheet-like hardened material. As the SEM, "SU8200" manufactured by Hitachi High-Tech Corporation was used. First, the sheet-like cured body was cut into 1 cm squares. Then, for each cut piece, polishing was performed using the ion milling "IM4000" manufactured by Hitachi High-Tech Corporation. Subsequently, the obtained cross-section was observed at a magnification of 5000 times using the SEM. The observation region defined as described above was acquired as a SEM cross-sectional image (width 1280 pixels, height 960 pixels, horizontal resolution 256 dpi, vertical resolution 256 dpi).

[0233] The obtained SEM cross-sectional image was imported into the software "WinROOF2018" for image analysis (hereinafter also referred to as "analysis software"), and image analysis was performed as follows. First, the analysis software was launched, and the SEM cross-sectional image was displayed. Subsequently, automatic binarization processing was performed on the displayed image using the mode method. After that, the area ratio of the magnetic powder particles extracted by the binarization processing was calculated.

[0234] <Results> The results of the above-described examples and comparative examples are shown in the following table. In the following table, the meanings of the abbreviations are as follows. MEK: Methyl ethyl ketone tanδ: Loss coefficient Average of CV: Average of the coefficient of variation of the inter-particle distances measured at three cross-sections

[0235] [Table 1]

[0236] [Table 2] [Explanation of Signs]

[0237] 1 Circuit board 10 Core board 11 Support board 12 First metal layer 13 Second metal layer 14 Through-hole 20 Plating layer 21 Surface 30 Hardened body 30a Surface of the hardened body 40 Conductor layer 41 Pattern conductor layer 100 Circuit board 200 Inner layer substrate 200a First main surface 200b Second main surface 220 Through-hole 220a Through-hole internal wiring 240 External terminal 310 Resin sheet 320 First magnetic layer 320a Resin composition layer 330 Support 340 Second magnetic layer 360 Via hole 360a Via hole internal wiring 400 Coil-shaped conductive structure 420 First conductor layer 420a Land 440 Second conductor layer

Claims

1. A cured resin composition comprising a thermosetting resin, magnetic powder, and a dispersant containing a polyester skeleton, The area occupied by the magnetic powder is 70% or more of the total cross-sectional area of ​​the hardened body. A cured body in which the average coefficient of variation of the interparticle distance of magnetic powder in the cured body, measured at three locations, is 85% or less.

2. The cured body according to claim 1, wherein the amount of magnetic powder is 90% by mass or more relative to 100% by mass of the nonvolatile components of the resin composition.

3. The cured body according to claim 1, wherein the magnetic powder comprises (B-1) particles having a particle size of 1 μm or less and (B-2) particles having a particle size greater than 1 μm.

4. The cured product according to Claim 1, wherein the amount of dispersant is 0.1% by mass or more and 5% by mass or less with respect to 100% by mass of the nonvolatile components of the resin composition.

5. The cured body according to claim 3, wherein the volume ratio ((B-1) / (B-2)) of particles having a particle size of 1 μm or less (B-1) and particles having a particle size greater than 1 μm is 0.1 / 9.9 or more and 6 / 4 or less.

6. A method for manufacturing a cured product according to any one of claims 1 to 5, A step of mixing a thermosetting resin and magnetic powder to obtain a resin composition, A step of thermally curing the resin composition, A method for manufacturing a cured body, comprising the following in this order.

7. A circuit board comprising a cured body according to any one of claims 1 to 5.

8. An inductor board, including the circuit board described in claim 7.

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