Resin sheet

Abstract

The present application provides a resin sheet material and the like capable of obtaining a cured product having high relative magnetic permeability and excellent mechanical strength. A resin sheet material having a support and a resin composition layer formed of a resin composition provided on the support, the resin composition comprising: (A) a magnetic powder, (B) an epoxy resin, (C) a dispersing agent, (D) a curing agent, and (E) a thermoplastic resin, the (C) component having a polyester skeleton represented by the following general formula (1), in which R independently represents a divalent hydrocarbon group having 2 to 10 carbon atoms, and n represents an integer of 2 to 1000.

Description

Technical Field

[0001] This invention relates to resin sheets, resin compositions, and circuit boards and inductor components using the resin sheets or resin compositions. Background Technology

[0002] Inductor-embedded substrates, which house inductors on circuit boards such as printed wiring boards, are typically formed using resin compositions containing magnetic powder. Regarding the inductors contained in these substrates, methods are known to increase the content of magnetic powder in the resin composition or to improve the effective permeability of the magnetic layer, which is the cured resin composition, in order to increase their inductance.

[0003] For example, Patent Document 1 describes a resin sheet highly filled with magnetic filler with an average particle size of 10 μm or more.

[0004] Existing technical documents

[0005] Patent Document 1: Japanese Patent Application Publication No. 2014-127624 Summary of the Invention

[0006] The technical problem that the invention aims to solve

[0007] In recent years, there has been a demand for further increases in inductance. To improve the relative permeability of inductors, it is possible to increase the content of magnetic powder. However, if the content of magnetic powder is increased, the mechanical strength (tensile breaking strength) of the magnetic layer may sometimes decrease.

[0008] To improve relative permeability, it's possible to use magnetic powder with a large average particle size or a flat shape. However, using such powders increases magnetic loss, which can sometimes degrade inductor performance. Alternatively, using magnetic powder with a small average particle size can be considered, but this tends to reduce magnetic loss and consequently, relative permeability.

[0009] The present invention was made in view of the above circumstances, and its object is to provide resin sheets, resin compositions that can produce cured products with high relative permeability and excellent mechanical strength, as well as circuit boards and inductor components using the resin sheets or resin compositions.

[0010] Methods for solving technical problems

[0011] In order to achieve the above-mentioned objective, the inventors conducted in-depth research and found that by using a resin sheet containing a resin composition layer formed from a resin composition containing a dispersant with a polyester backbone, the cured resin composition layer can have a high relative magnetic permeability and thus excellent mechanical strength, thereby completing the present invention.

[0012] That is, the present invention includes the following contents.

[0013] [1] A resin sheet having a support and a resin composition layer formed of a resin composition disposed on the support.

[0014] The resin composition comprises:

[0015] (A) Magnetic powder,

[0016] (B) Epoxy resin,

[0017] (C) Dispersants,

[0018] (D) Curing agent, and

[0019] (E) Thermoplastic resins;

[0020] (C) The component has the polyester backbone shown in the following general formula (1):

[0021] [Chemical Formula 1]

[0022]

[0023] (In general formula (1), R independently represents divalent hydrocarbon groups with 2 to 10 carbon atoms, and n represents an integer from 2 to 1000).

[0024] [2] According to the resin sheet of [1], when the non-volatile component in the resin composition is set to 100% by mass, the content of component (C) is 0.1% by mass or more and 5% by mass or less.

[0025] [3] The resin sheet according to [1] or [2], wherein component (A) comprises magnetic powder with an average particle size of 1 μm or more (A-1) and magnetic powder with an average particle size of less than 1 μm (A-2).

[0026] [4] The resin sheet according to any one of [1] to [3], wherein the (A) component comprises (A-1) magnetic powder with an average particle size of 1 μm or more and 10 μm or less and (A-2) magnetic powder with an average particle size of 0.005 μm or more and less than 1 μm.

[0027] [5] The resin sheet according to any one of [1] to [4], wherein component (A) is at least one selected from iron oxide powder and ferroalloy metal powder.

[0028] [6] The resin sheet according to any one of [1] to [5], wherein component (A) comprises iron oxide powder, the iron oxide powder comprising ferrite, the ferrite comprising at least one selected from Ni, Cu, Mn and Zn.

[0029] [7] The resin sheet according to any one of [1] to [6], wherein when the non-volatile component in the resin composition is set to 100% by mass, the content of component (A) is 70% by mass or more and 98% by mass or less.

[0030] [8] The resin sheet according to any one of [1] to [7], wherein when the mass of the thermoplastic resin (E) when the non-volatile component in the resin composition is 100% by mass is set as E1 and the mass of the epoxy resin (B) when the non-volatile component in the resin composition is 100% by mass is set as B1, the ratio of B1 / E1 is 0.1 or more and 5 or less.

[0031] [9] The resin sheet according to any one of [1] to [8] is used to form a magnetic layer of a circuit board.

[0032]

[10] The resin sheet according to any one of [1] to [9] is used to fill through holes.

[0033]

[11] A circuit board comprising a magnetic layer, wherein the magnetic layer is a cured resin composition layer of the resin sheet as described in any one of [1] to

[10] .

[0034]

[12] A circuit board comprising a substrate having through holes and a magnetic layer filling the through holes.

[0035] The magnetic layer comprises a cured resin composition layer of the resin sheet as described in any one of [1] to

[10] .

[0036]

[13] An inductor component comprising the circuit board described in

[11] or

[12] .

[0037]

[14] A resin composition comprising:

[0038] (A) Magnetic powder,

[0039] (B) Epoxy resin,

[0040] (C) Dispersants,

[0041] (D) Curing agent, and

[0042] (E) Thermoplastic resin, wherein the mass of (E) thermoplastic resin when the non-volatile component in the resin composition is 100% by mass is set as E1, and the mass of (B) epoxy resin when the non-volatile component in the resin composition is 100% by mass is set as B1, wherein B1 / E1 is 0.1 or more and 5 or less.

[0043] (C) The component has the polyester backbone shown in the following general formula (1):

[0044] [Chemical Formula 2]

[0045]

[0046] (In general formula (1), R independently represents divalent hydrocarbon groups with 2 to 10 carbon atoms, and n represents an integer from 2 to 1000).

[0047]

[15] A circuit board comprising a magnetic layer, the magnetic layer being a cured product of the resin composition described in

[14] .

[0048]

[16] A circuit board comprising a substrate having through holes and a cured resin composition of

[14] filled in the through holes.

[0049]

[17] An inductor component comprising the circuit board described in

[15] or

[16] .

[0050] Invention Effects

[0051] According to the present invention, a resin sheet capable of producing a cured material with high relative magnetic permeability and excellent mechanical strength can be provided, as well as a circuit board and an inductor component using the resin sheet. Attached Figure Description

[0052] Figure 1 This is a schematic cross-sectional view of the core substrate before the formation of through-holes in the circuit board manufacturing method of the first embodiment.

[0053] Figure 2 This is a schematic cross-sectional view of a core substrate having through holes formed in the circuit board manufacturing method of the first embodiment.

[0054] Figure 3 This is a schematic cross-sectional view of a core substrate in which a plating layer is formed in a through-hole during the manufacturing method of the circuit board in the first embodiment.

[0055] Figure 4 This is a cross-sectional view schematically showing the state in which the core substrate and the resin sheet are laminated in the circuit board manufacturing method of the first embodiment.

[0056] Figure 5 This is a schematic cross-sectional view showing the state after the core substrate and resin sheet are laminated in the circuit board manufacturing method of the first embodiment.

[0057] Figure 6 This is a schematic cross-sectional view of step (2) of the method for manufacturing a circuit board according to the first embodiment.

[0058] Figure 7This is a schematic cross-sectional view of step (3) of the method for manufacturing a circuit board according to the first embodiment.

[0059] Figure 8 This is a schematic cross-sectional view of step (5) of the method for manufacturing a circuit board according to the first embodiment.

[0060] Figure 9 This is a schematic cross-sectional view of step (5) of the method for manufacturing a circuit board according to the first embodiment.

[0061] Figure 10 This is a schematic cross-sectional view illustrating step (A) of the method for manufacturing a circuit board according to the second embodiment.

[0062] Figure 11 This is a schematic cross-sectional view illustrating step (A) of the method for manufacturing a circuit board according to the second embodiment.

[0063] Figure 12 This is a schematic cross-sectional view illustrating step (B) of the method for manufacturing a circuit board according to the second embodiment.

[0064] Figure 13 This is a schematic cross-sectional view illustrating step (D) of the method for manufacturing a circuit board according to the second embodiment.

[0065] Figure 14 This is a schematic top view of an inductor component comprising a circuit board obtained by the manufacturing method of the circuit board of the second embodiment, viewed from one side of its thickness direction.

[0066] Figure 15 This is a schematic diagram showing the cut end face of an inductor component of a circuit board obtained by the manufacturing method of the circuit board according to the second embodiment, cut at the position indicated by the dotted line II-II.

[0067] Figure 16 This is a schematic top view illustrating the configuration of the first conductor layer in an inductor component comprising a circuit board obtained by the manufacturing method of the circuit board of the second embodiment. Detailed Implementation

[0068] Embodiments of the present invention will now be described with reference to the accompanying drawings. It should be noted that the drawings are merely schematic representations of the shape, size, and arrangement of the constituent elements to the extent that the invention can be understood. The present invention is not limited to the following description, and the constituent elements may be appropriately modified. In the drawings used for the following description, the same constituent elements are denoted by the same symbols, and repeated descriptions are sometimes omitted. Furthermore, the configurations involved in the embodiments of the present invention are not necessarily required to be manufactured or used according to the configurations shown in the drawings.

[0069] [Resin Sheets]

[0070] The resin sheet of the present invention is a resin sheet having a support and a resin composition layer formed of a resin composition disposed on the support, the resin composition comprising (A) magnetic powder, (B) epoxy resin, (C) dispersant, (D) curing agent and (E) thermoplastic resin, wherein component (C) has a polyester backbone as shown in the following general formula (1).

[0071] [Chemical Formula 3]

[0072]

[0073] (In general formula (1), R independently represents hydrocarbon groups with 2 to 10 carbon atoms, and n represents an integer from 2 to 1000.)

[0074] In this invention, by including dispersant (C) in the resin composition, a cured product with high relative magnetic permeability and excellent mechanical strength can be obtained. Furthermore, the cured product generally also reduces magnetic loss. Hereinafter, each layer constituting the resin sheet will be described in detail.

[0075] <Support Body>

[0076] Examples of supports include films made of plastic materials, metal foils, and release paper, with films and metal foils made of plastic materials being preferred, and films made of plastic materials being more preferred.

[0077] When a film formed of a plastic material is used as a support, examples of plastic materials include polyesters such as polyethylene terephthalate (hereinafter sometimes abbreviated as "PET") and polyethylene naphthalate (hereinafter sometimes abbreviated as "PEN"); acrylic polymers such as polycarbonate (hereinafter sometimes abbreviated as "PC"); polymethyl methacrylate (hereinafter sometimes abbreviated as "PMMA"); cyclic polyolefins; triacetyl cellulose (hereinafter sometimes abbreviated as "TAC"); polyether sulfide (hereinafter sometimes abbreviated as "PES"); polyether ketone; polyimide; etc. Among these, polyethylene terephthalate and polyethylene naphthalate are preferred, and inexpensive polyethylene terephthalate is particularly preferred.

[0078] When metal foil is used as a support, examples of metal foil include copper foil and aluminum foil. Among these, copper foil is preferred. As copper foil, foil formed from copper as a single metal can be used, or foil formed from an alloy of copper with other metals (such as tin, chromium, silver, magnesium, nickel, zirconium, silicon, titanium, etc.) can be used.

[0079] The support can also be treated with matte finish, corona treatment, antistatic treatment, etc. on the surface that bonds with the resin composition layer.

[0080] Alternatively, a support with a release layer can be used as the support body, on the surface that bonds 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 alkyd resins, polyolefin resins, polyurethane resins, and silicone resins. Commercially available release agents include, for example, "SK-1," "AL-5," and "AL-7" manufactured by Lintec Co., Ltd., which are alkyd resin-based release agents. Examples of supports with a release layer include, for example, "Lumirror T60" manufactured by Toray Industries, Ltd., "Purex" manufactured by Teijin Corporation, and "Unipeel" manufactured by Unitika Co., Ltd.

[0081] The thickness of the support is preferably in the range of 5 μm to 75 μm, more preferably in the range of 10 μm to 60 μm. It should be noted that when using a support with a release layer, the overall thickness of the support with the release layer is preferably within the above range.

[0082] <Resin Composition Layer>

[0083] In the resin sheet of the present invention, the resin composition layer disposed on the support is formed of a resin composition comprising (A) magnetic powder, (B) epoxy resin, (C) dispersant, (D) curing agent and (E) thermoplastic resin, wherein component (C) has a polyester backbone as shown in the following general formula (1).

[0084] [Chemical Formula 4]

[0085]

[0086] (In general formula (1), R independently represents hydrocarbon groups with 2 to 10 carbon atoms, and n represents an integer from 2 to 1000.)

[0087] The resin composition may be combined with components (A) to (E) to further contain any other components. Examples of such other components include (F) other additives and (G) solvents. The components contained in the resin composition will be described in detail below.

[0088] (A) Magnetic powder

[0089] The resin composition contains (A) magnetic powder as component (A). As the (A) magnetic powder, particles of a material having a relative magnetic permeability greater than 1 can be used. The material of the (A) magnetic powder is typically an inorganic material, and can be either a soft magnetic material or a hard magnetic material. One type of (A) magnetic powder can be used alone, or two or more types can be used in combination. Therefore, the (A) magnetic powder can be a soft magnetic powder, a hard magnetic powder, or a combination of soft and hard magnetic powders.

[0090] Examples of magnetic powders (A) include: pure iron powder; Mg-Zn ferrites, Fe-Mn ferrites, Mn-Zn ferrites, Mn-Mg ferrites, Cu-Zn ferrites, Mg-Mn-Sr ferrites, Ni-Zn ferrites, Ba-Zn ferrites, Ba-Mg ferrites, Ba-Ni ferrites, Ba-Co ferrites, Ba-Ni-Co ferrites, Y-based ferrites, iron oxide powder (III), and iron(III) oxide, etc. Iron powder; Fe-Si alloy powder, Fe-Si-Al alloy powder, Fe-Cr alloy powder, Fe-Cr-Si alloy powder, Fe-Ni-Cr alloy powder, Fe-Cr-Al alloy powder, Fe-Ni alloy powder, Fe-Ni-Mo alloy powder, Fe-Ni-Mo-Cu alloy powder, Fe-Co alloy powder, or Fe-Ni-Co alloy powder, etc., as well as amorphous alloys such as Co-based amorphous alloys.

[0091] Of which, (A) the magnetic powder is preferably selected from at least one of iron oxide powder and ferroalloy metal powder. The iron oxide powder is preferably ferrite containing at least one element selected from Ni, Cu, Mn, and Zn, and more preferably ferrite containing either Mn or Zn. Furthermore, the ferroalloy metal powder is preferably ferroalloy metal powder containing at least one element selected from Si, Cr, Al, Ni, and Co, and more preferably ferroalloy metal powder containing Ni.

[0092] As for (A) the magnetic powder, commercially available magnetic powders can be used. Specific examples of commercially available magnetic powders that can be used include: Powdertech's "M03S", "M05S", "MZ03S", and "M001"; DOWA Electronics' "MA-RCO-24"; Sanyo Special Steel's "PST-S"; EPSON ATMIX's "AW2-08", "AW2-08PF20F", "AW2-08PF10F", "AW2-08PF3F", "Fe-3.5Si-4.5CrPF20F", "Fe-50NiPF20F", and "Fe-80Ni-4MoPF20F"; and JFE Chemical's "LD-M", "LD-MH", "KNI-106", "KNI-106GSM", "KNI-106GS", and "KN". I-109, KNI-109GSM, KNI-109GS; KNS-415, BSF-547, BSF-029, BSN-125, BSN-714, BSN-828, S-1281, S-1641, S-1651, S-1470, S-1511, S-2430 manufactured by Toda Kogyo Co., Ltd.; JR09P2 manufactured by Nippon Heavy Chemical Industry Co., Ltd.; Nanotek manufactured by CIK NanoTek Co., Ltd.; JEMK-S and JEMK-H manufactured by KINSEI MATEC Co., Ltd.; Yttrium iron oxide manufactured by ALDRICH Co., Ltd., etc. (A) A single magnetic powder may be used, but from the viewpoint of significantly obtaining the effects of the present invention, it is preferable to use two or more powders together.

[0093] (A) The magnetic powder is preferably spherical. The aspect ratio (length-to-width ratio), obtained by dividing the length of the major axis of the magnetic powder by the length of the minor axis, is preferably 2 or less, more preferably 1.5 or less, and even more preferably 1.2 or less. Generally, it is easier to improve the relative permeability when the magnetic powder is a flat shape that is not spherical. However, especially when using spherical magnetic powder, it is generally preferred from the viewpoint of reducing magnetic loss.

[0094] From the viewpoint of improving relative permeability, the average particle size of the (A) magnetic powder is preferably 0.01 μm or more, more preferably 0.5 μm or more, and even more preferably 1 μm or more. Furthermore, it is preferably 10 μm or less, more preferably 9 μm or less, and even more preferably 8 μm or less. It should be noted that when two or more types of (A) magnetic powder are used together, the overall average particle size of the (A) component only needs to be within the aforementioned range.

[0095] The average particle size of magnetic powder can be measured using laser diffraction / scattering based on the Mie scattering theory. Specifically, a laser diffraction-scattering particle size distribution measuring device can be used to create a particle size distribution of the magnetic powder on a volume basis, and the median particle size can be used as the average particle size for measurement. The sample used for measurement is preferably a sample obtained by dispersing the magnetic powder in water using ultrasound. Suitable laser diffraction-scattering particle size distribution measuring devices include the Horiba Seisakusho "LA-500" and the Shimadzu Seisakusho "SALD-2200".

[0096] From the perspective of improving relative permeability, (A) the specific surface area of ​​the magnetic powder is preferably 0.05 m². 2 / g or more, more preferably 0.1m 2 / g or more, further preferably 0.3m 2 / g or more. Additionally, 10m is preferred. 2 / g or less, preferably 8m 2 / g or less, more preferably 5m 2 / g or less. The specific surface area of ​​(A) magnetic powder can be determined by the BET method. It should be noted that when using two or more (A) magnetic powders, the specific surface area of ​​the (A) component as a whole is sufficient as long as it is within the range described.

[0097] From the viewpoint of improving relative permeability, (A) the magnetic powder preferably includes (A-1) magnetic powder with an average particle size of 1 μm or more and (A-2) magnetic powder with an average particle size of less than 1 μm.

[0098] (A-1) The magnetic powder with an average particle size of 1 μm or more has an average particle size of 1 μm or more, preferably 1.2 μm or more, and more preferably 1.5 μm or more. (A-1) The upper limit of the average particle size of the component is preferably 10 μm or less, more preferably 9 μm or less, and even more preferably 8 μm or less. The average particle size of the component (A-1) can be determined by the method described above.

[0099] The specific surface area of ​​component (A-1) is preferably 0.01 m². 2 / g or more, preferably 0.05m 2 / g or more, further preferably 0.1m 2 / g or more. Additionally, 2m is preferred. 2 / g or less, more preferably 1.5m 2 / g or less, more preferably 1m 2 / g or less. The specific surface area of ​​component (A-1) can be determined by the method described above.

[0100] (A-2) The magnetic powder with an average particle size of less than 1 μm has an average particle size of less than 1 μm, preferably less than 0.8 μm, more preferably less than 0.5 μm. (A-2) The lower limit of the average particle size of the component is preferably 0.005 μm or more, more preferably 0.01 μm or more, and even more preferably 0.02 μm or more. The average particle size of the component (A-2) can be determined by the method described above.

[0101] The preferred specific surface area of ​​component (A-2) is 1 m². 2 / g or more, preferably 2m 2 / g or more, further preferably 3m 2 / g or more. Additionally, 500m is preferred. 2 / g or less, more preferably 400m 2 Below / g, 300m is further preferred. 2 / g or less. The specific surface area of ​​component (A-2) can be determined by the method described above.

[0102] As a preferred embodiment of component (A), it preferably includes magnetic powder with an average particle size of 1 μm or more and 10 μm or less (A-1) and magnetic powder with an average particle size of 0.005 μm or more and less than 1 μm (A-2). More preferably, it includes magnetic powder with an average particle size of 1.2 μm or more and 9 μm or less (A-1) and magnetic powder with an average particle size of 0.01 μm or more and less than 0.8 μm (A-2). Even more preferably, it includes magnetic powder with an average particle size of 1.5 μm or more and 8 μm or less (A-1) and magnetic powder with an average particle size of 0.02 μm or more and less than 0.5 μm (A-2).

[0103] Regarding the content (volume %) of magnetic powder in (A), from the viewpoint of improving relative permeability and reducing loss coefficient, when the non-volatile component in the resin composition is set to 100 vol%, it is preferably 40 vol% or more, more preferably 50 vol% or more, and even more preferably 60 vol% or more. Furthermore, it is preferably 85 vol% or less, more preferably 80 vol% or less, and even more preferably 70 vol% or less.

[0104] Regarding the content (mass%) of magnetic powder in (A), from the viewpoint of improving relative permeability and reducing loss coefficient, when the non-volatile component in the resin composition is set to 100% by mass, it is preferably 70% by mass or more, more preferably 75% by mass or more, and even more preferably 80% by mass or more or 90% by mass or more. Furthermore, it is preferably 98% by mass or less, more preferably 97% by mass or less, and even more preferably 96% by mass or less or 95% by mass or less.

[0105] It should be noted that, unless otherwise specified, the content of each component in the resin composition in this invention is the value when the non-volatile component in the resin composition is set to 100% by mass.

[0106] When component (A) includes components (A-1) and (A-2), regarding the content (mass%) of component (A-1), from the viewpoint of improving relative permeability and reducing loss coefficient, when the non-volatile component in the resin composition is set to 100% by mass, it is preferably 50% by mass or more, more preferably 60% by mass or more, and even more preferably 70% by mass or more. Furthermore, it is preferably 90% by mass or less, more preferably 85% by mass or less, and even more preferably 80% by mass or less.

[0107] When component (A) includes components (A-1) and (A-2), regarding the content (mass%) of component (A-2), from the viewpoint of improving relative permeability and reducing loss coefficient, when the non-volatile component in the resin composition is set to 100% by mass, it is preferably 10% by mass or more, more preferably 15% by mass or more, and even more preferably 20% by mass or more. Furthermore, it is preferably 50% by mass or less, more preferably 40% by mass or less, and even more preferably 30% by mass or less.

[0108] When the content of component (A-1) when the non-volatile component in the resin composition is set to 100% by mass is defined as a1 (by mass), and the content of component (A-2) when the non-volatile component in the resin composition is set to 100% by mass is defined as a2, a1 / a2 is preferably 10 or less, more preferably 8 or less, even more preferably 5 or less, preferably 1 or more, more preferably 2 or more, and even more preferably 3 or more. By adjusting the content of component (A) so that a1 / a2 is within the aforementioned range, the desired effect of the present invention can be obtained more significantly.

[0109] (B) Epoxy resin

[0110] The resin composition contains (B) epoxy resin as component (B). Examples of epoxy resins (B) include bisphenol A type epoxy resin; bisphenol F type epoxy resin; bisphenol S type epoxy resin; bisphenol AF type epoxy resin; dicyclopentadiene type epoxy resin; triphenol type epoxy resin; phenolic varnish type epoxy resin; tert-butyl-catechol type epoxy resin; naphthol varnish type epoxy resin, naphthalene type epoxy resin, naphthol type epoxy resin, anthracene type epoxy resin, etc., epoxy resins with fused ring structures; glycidylamine type epoxy resin; glycidyl ester type epoxy resin; cresol varnish type epoxy resin; biphenyl type epoxy resin; linear aliphatic epoxy resin; epoxy resin with butadiene structure; alicyclic epoxy resin; heterocyclic epoxy resin; epoxy resin containing spirocyclic ring; cyclohexanediol type epoxy resin; tris(hydroxymethyl) type epoxy resin; tetraphenylethane type epoxy resin; cyclic aliphatic diglycidyl ether type epoxy resin, etc. The epoxy resin can be used alone or in combination of two or more. (B) The epoxy resin is preferably selected from one or more of bisphenol A type epoxy resin and bisphenol F type epoxy resin, and more preferably includes bisphenol A type epoxy resin and bisphenol F type epoxy resin.

[0111] (B) The epoxy resin preferably comprises an epoxy resin having two or more epoxy groups in one molecule. Furthermore, (B) the epoxy resin preferably has an aromatic structure; when two or more epoxy resins are used, at least one has an aromatic structure. An aromatic structure is a chemical structure generally defined as aromatic, and also includes polycyclic aromatics and aromatic heterocycles. The proportion of epoxy resin having two or more epoxy groups in one molecule is preferably 50% by mass or more, more preferably 60% by mass or more, and particularly preferably 70% by mass or more, relative to 100% by mass of the non-volatile component of the epoxy resin.

[0112] 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"). In the resin composition, epoxy resin (B) may contain only liquid epoxy resin, only solid epoxy resin, or a combination of both; however, from the viewpoint of reducing the viscosity of the resin composition, it is preferable to contain only liquid epoxy resin.

[0113] As liquid epoxy resins, preferred types include Glycirol type epoxy resin, bisphenol A type epoxy resin, bisphenol F type epoxy resin, bisphenol AF type epoxy resin, naphthalene type epoxy resin, glycidyl ester type epoxy resin, glycidyl amine type epoxy resin, phenolic varnish type epoxy resin, alicyclic epoxy resin with an ester skeleton, cyclohexanediol type epoxy resin, cyclic aliphatic diglycidyl ether type epoxy resin, cyclic aliphatic glycidyl ether type epoxy resin, cyclic aliphatic glycidyl ether type epoxy resin, and epoxy resin with a butadiene structure; more preferably, bisphenol A type epoxy resin and bisphenol F type epoxy resin. 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" (phenolic varnish type epoxy resin); Mitsubishi Chemical's "630" and "630LSD"; and ADEKA's "ED-523T" (Gly Epoxy resins include: cirol type (ADEKAGLYCIROL), "EP-3980S" (glycidylamine type epoxy resin), "EP-4088S" (dicyclopentadiene type epoxy resin); Nippon Steel Chemical Materials Co., Ltd.'s "ZX1059" (a mixture of bisphenol A and bisphenol F type epoxy resins), "EX-201" (cyclic aliphatic glycidyl ether type epoxy resin), "ZX1658" and "ZX1658GS" (cyclic aliphatic diglycidyl ether type epoxy resin); Nagase ChemteX's "EX-721" (glycidyl ester type epoxy resin); and Daicel's "CELLOXIDE 2021P" (alicyclic epoxy resin with an ester skeleton) and "PB-3600" (an epoxy resin with a butadiene structure). These can be used individually or in combination.

[0114] As solid epoxy resins, the preferred types are naphthalene-type tetrafunctional epoxy resins, cresol-phenolic varnish-type epoxy resins, dicyclopentadiene-type epoxy resins, triphenol-type epoxy resins, naphthol-type epoxy resins, biphenyl-type epoxy resins, naphthalene ether-type epoxy resins, anthracene-type epoxy resins, bisphenol A-type epoxy resins, and tetraphenylethane-type epoxy resins. Specific examples of solid epoxy resins include DIC's "HP4032H" (naphthalene-type epoxy resin), "HP-4700", "HP-4710" (naphthalene-type tetrafunctional epoxy resin), "N-690" (cresol phenolic varnish type epoxy resin), "N-695" (cresol phenolic varnish type epoxy resin), "HP-7200", "HP-7200HH", "HP-7200H" (dicyclopentadiene type epoxy resin), "EXA-7311", "EXA-7311-G3", "EXA-7311-G4", "EXA-7311-G4S", and "HP6000" (naphthalene ether type epoxy resin); and Nippon Kayaku Co., Ltd.'s "EPPN-502H" (triphenol type epoxy resin), "NC7000L" (naphthalene phenolic varnish type epoxy resin), and "NC3" (naphthalene etheric varnish type epoxy resin). 000H, NC3000, NC3000L, NC3100 (biphenyl type epoxy resin); Nippon Steel Chemical Materials Co., Ltd.'s "ESN475V" (naphthalene type epoxy resin) and "ESN485" (naphthalene phenolic varnish type epoxy resin); Mitsubishi Chemical Co., Ltd.'s "YX4000H", "YL6121" (biphenyl type epoxy resin), "YX4000HK" (bixylenol type epoxy resin), and "YX8800" (anthracite type epoxy resin); Osaka Gas Chemical Co., Ltd.'s "PG-100" and "CG-500"; Mitsubishi Chemical Co., Ltd.'s "YL7760" (bisphenol AF type epoxy resin), "YL7800" (fluorene type epoxy resin), "jER1010" (solid bisphenol A type epoxy resin), and "jER1031S" (tetraphenylethane type epoxy resin), etc. They can be used individually or in combination of two or more.

[0115] When liquid epoxy resin and solid epoxy resin are used together as (B) epoxy resin, their mass ratio (liquid epoxy resin: solid epoxy resin) is preferably in the range of 1:0.1 to 1:4. By setting the mass ratio of liquid epoxy resin to solid epoxy resin within the aforementioned range, it is possible to obtain cured products with sufficient tensile strength. From the viewpoint of the above effects, the mass ratio of liquid epoxy resin to solid epoxy resin (liquid epoxy resin: solid epoxy resin) is more preferably in the range of 1:0.3 to 1:3.5, further preferably in the range of 1:0.6 to 1:3, and particularly preferably in the range of 1:0.8 to 1:2.5.

[0116] From the viewpoint of obtaining a magnetic layer exhibiting good mechanical strength, when the non-volatile component in the resin composition is set to 100% by mass, the content of epoxy resin (B) is preferably 0.1% by mass or more, more preferably 0.3% by mass or more, and even more preferably 0.5% by mass or more and 1% by mass or more. The upper limit of the epoxy resin content is not particularly limited as long as the effects of the present invention are achieved, but it is preferably 5% by mass or less, more preferably 3% by mass or less, and even more preferably 2% by mass or less.

[0117] When the non-volatile component in the resin composition is set to 100% by volume, the content (by volume) of epoxy resin (B) is preferably 1% by mass or more, more preferably 3% by mass or more, and even more preferably 5% by mass or more. There is no particular limitation on the upper limit as long as the effects of the present invention are achieved; it is preferably 25% by mass or less, more preferably 20% by mass or less, and even more preferably 15% by mass or less.

[0118] (B) 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. Within this range, the crosslinking density of the cured product becomes sufficient, and a magnetic layer with low surface roughness can be obtained. It should be noted that the epoxy equivalent can be determined according to JIS K 7236, and is the mass of the resin containing 1 equivalent of epoxy groups.

[0119] (B) The weight-average molecular weight of the epoxy resin is preferably 100 to 5000, more preferably 250 to 3000, and even more preferably 400 to 1500. Here, the weight-average molecular weight of the epoxy resin is the weight-average molecular weight converted from polystyrene as determined by gel permeation chromatography (GPC).

[0120] (C) Dispersant

[0121] The resin composition contains (C) a dispersant having a polyester backbone as shown in the following general formula (1) as component (C).

[0122] [Chemical Formula 5]

[0123]

[0124] (In general formula (1), R independently represents divalent hydrocarbon groups with 2 to 10 carbon atoms, and n represents an integer from 2 to 1000.)

[0125] As described above, if the content of magnetic powder (A) is increased to improve the relative permeability, the mechanical strength of the cured resin composition layer will decrease. In this invention, since component (C) is included in the resin composition as a dispersant, the relative permeability can be improved, and the mechanical strength can also be improved, compared to a resin composition that does not contain component (C) (i.e., a resin composition having the same composition as the resin composition except that it does not contain component (C)).

[0126] (C) component has a polyester skeleton as shown in general formula (1).

[0127] [Chemical Formula 6]

[0128]

[0129] (In general formula (1), R independently represents divalent hydrocarbon groups with 2 to 10 carbon atoms, and n represents an integer from 2 to 1000.)

[0130] In general formula (1), R represents a divalent hydrocarbon group with 2 to 10 carbon atoms. The hydrocarbon group has 2 or more carbon atoms, preferably 3 or more, and more preferably 4 or more. The upper limit of the number of carbon atoms is 10 or less, preferably 8 or less, and more preferably 6 or less. The hydrocarbon group can be any of straight-chain, branched, or cyclic, preferably straight-chain or branched. Examples of hydrocarbon groups include aliphatic hydrocarbon groups and aromatic hydrocarbon groups, preferably aliphatic hydrocarbon groups. The hydrocarbon group can be any of saturated hydrocarbon groups and unsaturated hydrocarbon groups, preferably saturated hydrocarbon groups. Specific examples of hydrocarbon groups include alkylene, alkenylene, ynylene, and arylene groups. Among these, from the viewpoint of significantly obtaining the effects of the present invention, alkylene groups are particularly preferred as hydrocarbon groups.

[0131] Examples of alkylene groups include ethylene, propylene, butylene, pentylene, hexylene, heptylene, octylene, nonylene, and decylene. Examples of alkenyl groups include vinylene, propenylene, butenylene, pentenylene, hexenylene, heptenylene, octylene, nonenylene, and decenylene. Examples of ynynyl groups include ethynylene, propynylene, butynylene, pentyynylene, hexynylene, heptynylene, octyynylene, nonynylene, and decynylene. Examples of aryl groups include phenylene and naphthylene. Butylene and pentylene are preferred as R.

[0132] In general formula (1), R represents a divalent hydrocarbon group, which may or may not have substituents. There are no particular restrictions on substituents; examples include halogen atoms, -OH, and -OC. 1-6 Alkyl, -N(C) 1-10 Alkyl)2, C 1-10 Alkyl, C 6-10Aryl, -NH₂, -CN, -C(O)O-C 1-10 alkyl, -COOH, -C(O)H, -NO₂, etc. Here, the term "C p-q " (where p and q are positive integers satisfying p<q) indicates that the number of carbon atoms in the organic group described immediately after this term is p to q. For example, the expression "C 1-10 alkyl" represents an alkyl group having 1 to 10 carbon atoms. These substituents may be bonded to each other to form a ring, and the ring structure also includes a spiro ring or a fused ring.

[0133] The above substituents may further have a substituent (hereinafter sometimes referred to as "secondary substituent"). As the secondary substituent, unless otherwise specified, the same groups as the above substituents can be used.

[0134] n in General Formula (1) represents an integer of 2 to 1000. n is 2 or more, preferably 5 or more, more preferably 10 or more. The upper limit is 1000 or less, preferably 500 or less, more preferably 100 or less, 50 or less.

[0135] As long as the effect of the present invention is not impaired, component (C) may contain any skeleton in addition to the polyester skeleton represented by General Formula (1). Examples of optional skeletons include a polyester skeleton in which R in General Formula (1) is a divalent hydrocarbon group having 1 or 11 or more carbon atoms (n is the same as in Formula (1)), and a polyallylamine skeleton. For example, the terminal of the polyester skeleton is not particularly limited.

[0136] Examples of the terminal of component (C) include residues of carboxylic acids described below, a hydroxyl group, a hydrogen atom, and the like.

[0137] Component (C) having a polyester skeleton represented by General Formula (1) can be produced, for example, by reacting a lactone represented by General Formula (2) with a carboxylic acid.

[0138] [Chemical Formula 7]

[0139]

[0140] (In General Formula (2), R 2 has the same meaning as R in General Formula (1).)

[0141] Examples of the lactone represented by General Formula (2) include ε-caprolactone, β-propiolactone, γ-butyrolactone, δ-valerolactone, β-methyl-δ-valerolactone, 4-methylcaprolactone, 2-methylcaprolactone, and the like.

[0142] Carboxylic acids can be those that function as initiators for the ring-opening polymerization of lactones represented by general formula (2). Examples of such carboxylic acids include ricinolic acid, ricinoleic acid, 9- and 10-hydroxystearic acid, castor oil fatty acids, hydrogenated castor oil fatty acids, lactic acid, 12-hydroxystearic acid, glycolic acid, and other hydroxycarboxylic acids; as well as dodecanoic acid and stearic acid. Among these, hydroxycarboxylic acids are preferred from the viewpoint of significantly obtaining the effects of the present invention.

[0143] The reaction temperature is preferably 120–220°C, more preferably 160–210°C. Furthermore, the reaction time is preferably 0.5–72 hours. When the reaction is carried out under a nitrogen flow, a polyester with a high degree of polymerization can be obtained.

[0144] In addition, depending on the needs and from the perspective of controlling the reaction, polymerization catalysts or polymerization initiators can be used in the above reactions.

[0145] Examples of polymerization catalysts include quaternary ammonium salts such as tetramethylammonium chloride, tetrabutylammonium chloride, tetramethylammonium bromide, tetrabutylammonium bromide, tetramethylammonium iodide, tetrabutylammonium iodide, benzyltrimethylammonium chloride, benzyltrimethylammonium bromide, and benzyltrimethylammonium iodide; and tetramethylphosphonium chloride, tetrabutylphosphonium chloride, tetramethylphosphonium bromide, tetrabutylphosphonium bromide, tetramethylphosphonium iodide, tetrabutylphosphonium iodide, and benzyltrimethylphosphonium chloride. Quaternary phosphonium salts such as benzyltrimethylphosphonium bromide, benzyltrimethylphosphonium iodide, tetraphenylphosphonium chloride, tetraphenylphosphonium bromide, and tetraphenylphosphonium iodide; phosphorus compounds such as triphenylphosphine; organic carboxylic acids such as potassium acetate, sodium acetate, potassium benzoate, and sodium benzoate; alkali metal alkoxides such as sodium alkoxide and potassium alkoxide; tertiary amines; organotin compounds; organoaluminum compounds; organotitanate compounds such as tetrabutyl titanate; zinc compounds such as zinc chloride; etc.

[0146] Examples of polymerization initiators include aliphatic monocarboxylic acids such as acetic acid, propionic acid, octanoic acid, nonanoic acid, decanoic acid, octanoic acid, lauric acid, myristic acid, palmitic acid, stearic acid, isononanoic acid, and arachidic acid; and aromatic monocarboxylic acids such as benzoic acid and p-butylbenzoic acid.

[0147] In the manufacture of component (C), any monomer may be used in addition to the lactone and carboxylic acid shown in general formula (2), provided that it does not impair the effects of the present invention. Examples of such monomers include polyallylamine. For example, when polyallylamine is used as an arbitrary monomer, component (C) containing a polyallylamine backbone in addition to the polyester backbone shown in general formula (1) can be manufactured. The reaction temperature and reaction time are the same as those in the manufacture of component (C) having the polyester backbone shown in general formula (1).

[0148] Polyallylamine can be obtained by polymerizing allylamine in the presence of a polymerization initiator and / or a chain transfer catalyst.

[0149] There are no particular limitations on polymerization initiators, and examples include: ketone peroxides such as methyl ethyl ketone, diacyl peroxides such as benzoyl peroxide, dicarbonate peroxides such as diisopropyl peroxide, ketal peroxides such as 1,1-bis(tert-butylperoxide)cyclohexane, hydroperoxides such as tert-butyl hydroperoxide, ester peroxides such as tert-butyl peroxypentanoate, other azobisisobutyronitrile, hydrogen peroxide, ferrous salts, etc. Furthermore, polymerization initiators described in Japanese Patent Publication No. 2-14364 can be used. One or more of them can be used alone.

[0150] There are no particular limitations on chain transfer catalysts, and examples include alkyl thiols such as dodecyl thiols, thiocarboxylic acids such as mercaptoacetic acid, 2-mercaptopropionic acid, and 3-mercaptopropionic acid, and thiocarboxylic acid esters such as butyl mercaptoacetate and 2-ethylhexyl mercaptoacetate. One or more of these catalysts can be used alone.

[0151] The weight-average molecular weight of polyallylamine is preferably 150 to 100,000, more preferably 600 to 20,000. When the weight-average molecular weight is 150 or higher, the adsorption force on particles such as component (A) is improved, and the particle dispersibility is improved. When the weight-average molecular weight is 100,000 or lower, the aggregation between particles can be suppressed, and the particle dispersibility is improved. It should be noted that polyallylamine with any weight-average molecular weight can be manufactured using the method described in Japanese Patent Publication No. 2-14364.

[0152] Commercially available polyallylamines can be used. Examples of commercially available polyallylamines include “PAA-01”, “PAA-03”, “PAA-05”, “PAA-08”, “PAA-15”, “PAA-15C”, and “PAA-25” manufactured by Nittobo Medical.

[0153] (C) The pH of component (C) is typically greater than 4 and less than 7. pH can be determined using an indicator method. Specifically, it can be determined by immersing pH test paper in a sample (22°C) prepared by dissolving the dispersant in acetone, with a dispersant concentration of 0.1 g / mL. As pH test paper, pH test paper capable of measuring the pH of acidic regions can be used (e.g., test paper with a measurement range of pH 0.0–14.0, pH 1.0–14.0, or pH 0.5–5.0). Examples include the pH test paper "pH 1–14" manufactured by AS ONE (pH measurement range of pH 1.0–14.0).

[0154] From the viewpoint of significantly obtaining the effects of the present invention, the acid value of component (C) is preferably 1 mg KOH / g or more, more preferably 3 mg KOH / g or more, even more preferably 5 mg KOH / g or more, 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. The acid value can be determined by neutralization titration.

[0155] (C) When the component is a dispersant obtained by reacting with polyallylamine, from the viewpoint of significantly obtaining the effects of the present invention, the amine value 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. The amine value can be determined by neutralization titration.

[0156] From the viewpoint of significantly obtaining the effects of the present invention, the weight-average molecular weight of component (C) is preferably 1000 or more, more preferably 1500 or more, further preferably 2000 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-average molecular weight converted from polystyrene as determined by gel permeation chromatography (GPC).

[0157] Regarding the content of component (C), from the viewpoint of significantly maximizing the effects of the present invention, when the non-volatile component in the resin composition is set to 100% by mass, it is preferably 0.1% by mass or more, more preferably 0.2% by mass or more, even more preferably 0.3% by mass or more, the upper limit is preferably 5% by mass or less, more preferably 3% by mass or less, and even more preferably 1% by mass or less.

[0158] When the mass (mass%) of component (C) is set to 100% by mass of the non-volatile component in the resin composition, and the mass (mass%) of magnetic powder (A) is set to A1 when the mass (mass%) of non-volatile component (A) in the resin composition is set to 100% by mass, (C1 / A1)×100 is preferably 0.1 or more, more preferably 0.2 or more, even more preferably 0.3 or more, preferably 10 or less, more preferably 5 or less, and even more preferably 1 or less. By adjusting the mass of component (A) and component (C) so that (C1 / A1)×100 is within the aforementioned range, the desired effect of the present invention can be obtained more significantly.

[0159] (D) Curing agent

[0160] The resin composition contains a curing agent (D) as component (D). The curing agent (D) includes an epoxy resin curing agent that functions to cure the epoxy resin (B), and a curing accelerator that functions to accelerate the curing speed of the epoxy resin (B). The curing accelerator is typically used in conjunction with the epoxy resin curing agent. Preferably, the resin composition contains an epoxy resin curing agent as curing agent (D), and more preferably, it contains both an epoxy resin curing agent and a curing accelerator as curing agent (D).

[0161] (Epoxy resin curing agent)

[0162] Epoxy resin curing agents typically react with epoxy resin (B) to cure the resin composition. Examples of epoxy resin curing agents include phenolic epoxy resin curing agents, naphthol-based epoxy resin curing agents, reactive ester-based epoxy resin curing agents, acid anhydride-based epoxy resin curing agents, benzoxazine-based epoxy resin curing agents, cyanate ester-based epoxy resin curing agents, and imidazole-based epoxy resin curing agents. From the viewpoint of significantly obtaining the effects of the present invention, it is preferable to use one or more epoxy resin curing agents selected from phenolic epoxy resin curing agents and naphthol-based epoxy resin curing agents. One epoxy resin curing agent may be used alone, or two or more may be used in combination.

[0163] From the viewpoint of heat resistance and water resistance, phenolic epoxy resin curing agents with a phenolic structure or naphthol-based epoxy resin curing agents with a phenolic structure are preferred as curing agents for phenolic and naphthol-based epoxy resins. As phenolic epoxy resin curing agents, nitrogen-containing phenolic epoxy resin curing agents are preferred, phenolic epoxy resin curing agents containing a triazine backbone are more preferred, and linear phenolic (Phenolic Novolac) epoxy resin curing agents containing a triazine backbone are even more preferred.

[0164] Specific examples of phenolic epoxy resin curing agents and naphthol-based epoxy resin curing agents include "MEH-7700", "MEH-7810", and "MEH-7851" manufactured by Meiwa Chemical Co., Ltd.; "NHN", "CBN", and "GPH" manufactured by Nippon Chemical Co., Ltd.; "SN170", "SN180", "SN190", "SN475", "SN485", "SN495V", "SN375", and "SN395" manufactured by Nippon Steel & Sumitomo Metal Chemical Co., Ltd.; "TD-2090", "LA-7052", "LA-7054", "LA-1356", "LA-3018-50P", "EXB-9500", "HPC-9500", "KA-1160", "KA-1163", and "KA-1165" manufactured by DIC Co., Ltd.; and "GDP-6115L" and "GDP-6115H" manufactured by Gunei Chemical Co., Ltd.

[0165] There are no particular limitations on the active ester-based epoxy resin curing agent used, but compounds with highly reactive ester groups, such as phenolic esters, thiophenolic esters, N-hydroxylamine esters, and heterocyclic hydroxyl compounds, are generally preferred. This active ester-based epoxy resin curing agent is preferably obtained through a condensation reaction of a carboxylic acid compound and / or a thiocarboxylic acid compound with a hydroxyl compound and / or a thiol compound. Particularly from the viewpoint of improving heat resistance, an active ester-based epoxy resin curing agent obtained from a carboxylic acid compound and a hydroxyl compound is preferred, and an active ester-based epoxy resin curing agent obtained from a carboxylic acid compound and a phenolic 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 phenolic 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-dihydroxynaphthol, 1,6-dihydroxynaphthol, 2,6-dihydroxynaphthol, dihydroxybenzophenone, trihydroxybenzophenone, tetrahydroxybenzophenone, phloroglucinol, pyroglucinol, dicyclopentadiene-type diphenol compounds, and linear phenolic resins (Phenolic Novolac). Here, "dicyclopentadiene-type diphenol compounds" refers to diphenol compounds obtained by condensing one molecule of dicyclopentadiene with two molecules of phenol.

[0166] Specifically, preferred active ester-based epoxy resin curing agents include those containing a dicyclopentadiene-type diphenol structure, those containing a naphthalene structure, those containing an acetylated linear phenolic resin, and those containing a benzoylated linear phenolic resin. "Dicyclopentadiene-type diphenol structure" refers to a divalent structural unit composed of phenylene-dicyclopentylene-phenylene.

[0167] Commercially available reactive ester-based epoxy resin curing agents, including those containing a dicyclopentadiene-type diphenol structure, are examples of DIC's "EXB9451", "EXB9460", "EXB9460S", "HPC-8000-65T", "HPC-8000H-65TM", and "HPC-8000L-65TM"; examples of reactive ester compounds containing a naphthalene structure are examples of DIC's "EXB9416-". 70BK”; as an active ester epoxy resin curing agent containing acetylated linear phenolic resin, examples include “DC808” manufactured by Mitsubishi Chemical Corporation; as an active ester epoxy resin curing agent containing benzoylation of linear phenolic resin, examples include “YLH1026”, “YLH1030”, and “YLH1048” manufactured by Mitsubishi Chemical Corporation; as an active ester epoxy resin curing agent containing acetylated linear phenolic resin, examples include “DC808” manufactured by Mitsubishi Chemical Corporation, etc.

[0168] Anhydride-based epoxy resin curing agents include epoxy resin curing agents having one or more anhydride groups per molecule. Specific examples of anhydride-based epoxy resin curing agents include phthalic anhydride, tetrahydrophthalic anhydride, hexahydrophthalic anhydride, methyltetrahydrophthalic anhydride, methylhexahydrophthalic anhydride, methylnadic anhydride, hydrogenated methylnadic anhydride, trialkyltetrahydrophthalic anhydride, dodecenylsuccinic anhydride, 5-(2,5-dioxotetrahydro-3-furanyl)-3-methyl-3-cyclohexene-1,2-dicarboxylic anhydride, trimellitic anhydride, and pyromellitic anhydride. Benzyl ketone tetracarboxylic dianhydride, biphenyl tetracarboxylic dianhydride, naphthalene tetracarboxylic dianhydride, oxophthalic dianhydride, 3,3'-4,4'-diphenyl sulfone tetracarboxylic 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(trimethoxybenzoic anhydride), styrene-maleic acid resin obtained by copolymerizing styrene and maleic acid, and other polymeric anhydrides.

[0169] Commercially available anhydride-based epoxy resin curing agents include "HNA-100" and "MH-700" manufactured by Shin Nippon Rikka Co., Ltd.

[0170] Specific examples of benzoxazine-based epoxy resin curing agents include "HFB2006M" manufactured by Showa Polymer Co., Ltd., and "Pd" and "Fa" manufactured by Shikoku Chemical Co., Ltd.

[0171] Examples of cyanate ester-based epoxy resin curing agents include bisphenol A dicyanate, polyphenol cyanate, oligomeric (3-methylene-1,5-phenylene cyanate), 4,4'-methylenebis(2,6-dimethylphenyl cyanate), 4,4'-ethoxydiphenyl dicyanate, hexafluorobisphenol A dicyanate, 2,2-bis(4-cyanoxy)phenylpropane, 1,1-bis(4-cyanoxyphenylmethane), bis(4-cyanoxy-3,5-dimethylphenyl)methane, 1,3-bis(4-cyanoxyphenyl-1-(methylethoxy))benzene, bis(4-cyanoxyphenyl)sulfide, and bis(4-cyanoxyphenyl) ether, as well as multifunctional cyanate ester resins derived from phenolic varnish resins and cresol varnish resins, and prepolymers obtained by triazineization of some of these cyanate ester resins. Specific examples of cyanate ester-based epoxy resin curing agents include "PT30" and "PT60" (both linear phenolic polyfunctional cyanate ester resins), "BA230", and "BA230S75" (prepolymers obtained by triazinizing part or all of bisphenol A dicyanate to form trimers).

[0172] Examples of imidazole-based epoxy resin curing agents include 2-methylimidazolium, 2-undecylimidazolium, 2-heptadecylimidazolium, 1,2-dimethylimidazolium, 2-ethyl-4-methylimidazolium, 2-phenylimidazolium, 2-phenyl-4-methylimidazolium, 1-benzyl-2-methylimidazolium, 1-benzyl-2-phenylimidazolium, 1-cyanoethyl-2-methylimidazolium, 1-cyanoethyl-2-undecylimidazolium, 1-cyanoethyl-2-ethyl-4-methylimidazolium, 1-cyanoethyl-2-phenylimidazolium, 1-cyanoethyl-2-undecylimidazolium trimellitate, 1-cyanoethyl-2-phenylimidazolium trimellitate, 2,4-diamino-6-[2'-methylimidazolyl-(1')]-ethyl-s-triazine, 2,4 -Diamino-6-[2'-undecylimidazolyl-(1')]-ethyl-s-triazine, 2,4-diamino-6-[2'-ethyl-4'-methylimidazolyl-(1')]-ethyl-s-triazine, 2,4-diamino-6-[2'-methylimidazolyl-(1')]-ethyl-s-triazine isocyanuric acid adduct, 2-phenylimidazolyl isocyanuric acid adduct, 2-phenyl-4,5-dihydroxymethylimidazolium, 2-phenyl-4-methyl-5-hydroxymethylimidazolium, 2,3-dihydro-1H-pyrrolo[1,2-a]benzimidazole, 1-dodecyl-2-methyl-3-benzylimidazolium chloride, 2-methylimidazoline, 2-phenylimidazoline and other imidazole compounds, as well as adducts of imidazole compounds with epoxy resins. Preferably, 2-ethyl-4-methylimidazolium or 1-benzyl-2-phenylimidazolium.

[0173] As an imidazole-based epoxy resin curing agent, commercially available products can be used, such as "2MZA-PW" and "2PHZ-PW" manufactured by Shikoku Chemical Industry Co., Ltd., and "P200-H50" manufactured by Mitsubishi Chemical Co., Ltd.

[0174] The ratio of epoxy resin to epoxy resin curing agent, expressed as the ratio of [total number of epoxy groups in the epoxy resin] to [total number of reactive groups in the epoxy resin curing agent], is preferably in the range of 1:0.2 to 1:2, more preferably in the range of 1:0.3 to 1:1.5, and even more preferably in the range of 1:0.4 to 1:1. Here, the reactive groups of the epoxy resin curing agent are active hydroxyl groups, active ester groups, etc., and vary depending on the type of epoxy resin curing agent. Furthermore, the total number of epoxy groups in the epoxy resin refers to the sum of the values ​​obtained by dividing the mass of the non-volatile components of each epoxy resin by the epoxy equivalent for all epoxy resins, and the total number of reactive groups in the epoxy resin curing agent refers to the sum of the values ​​obtained by dividing the mass of the non-volatile components of each epoxy resin curing agent by the reactive group equivalent for all epoxy resin curing agents. By keeping the ratio of epoxy resin to epoxy resin curing agent within the aforementioned range, the heat resistance of the cured product is further improved.

[0175] From the viewpoint of significantly obtaining the effects of the present invention, when the resin component in the resin composition is set to 100% by mass, the content of epoxy resin curing agent is preferably 0.1% by mass or more, more preferably 0.5% by mass or more, even more preferably 1% by mass or more, the upper limit is preferably 5% by mass or less, more preferably 4% by mass or less, and even more preferably 3% by mass or less.

[0176] (Curing accelerator)

[0177] Curing accelerators typically act as catalysts in the curing reaction of (B) epoxy resins, promoting the curing process. Examples of curing accelerators include amine-based, imidazole-based, phosphorus-based, guanidine-based, and metal-based curing accelerators. From the viewpoint of reducing the viscosity of the resin composition, amine-based, imidazole-based, and guanidine-based curing accelerators are preferred; from the viewpoint of further improving the mechanical strength of the cured product, imidazole-based curing accelerators are more preferred. A single curing accelerator can be used alone, or two or more can be used in combination. Curing accelerators are typically used in conjunction with epoxy resin curing agents.

[0178] Examples of amine-based curing accelerators include trialkylamines such as triethylamine and tributylamine, 4-dimethylaminopyridine, benzyl dimethylamine, 2,4,6-tris(dimethylaminomethyl)phenol, and 1,8-diazabicyclo(5,4,0)-undecene, with 4-dimethylaminopyridine and 1,8-diazabicyclo(5,4,0)-undecene being preferred.

[0179] As amine-based curing accelerators, commercially available products can be used, such as "PN-50", "PN-23", and "MY-25" manufactured by Ajinomoto Fine Technology Co., Ltd.

[0180] As an imidazole-based curing accelerator, it is the same as the imidazole-based epoxy resin curing agent described above. When the above-mentioned imidazole-based epoxy resin curing agent is used in combination with other epoxy resin curing agents, it sometimes functions as a curing accelerator.

[0181] Examples of phosphorus-based curing accelerators include triphenylphosphine, phosphonium borate compounds, tetraphenylphosphonium tetraphenylborate, n-butylphosphonium tetraphenylborate, tetrabutylphosphonium decanoate, (4-methylphenyl)triphenylphosphonium thiocyanate, tetraphenylphosphonium thiocyanate, and butyltriphenylphosphonium thiocyanate, with triphenylphosphine and tetrabutylphosphonium decanoate being preferred.

[0182] Examples of guanidine-based curing accelerators include dicyandiamide, 1-methylguanidine, 1-ethylguanidine, 1-cyclohexylguanidine, 1-phenylguanidine, 1-(o-tolyl)guanidine, dimethylguanidine, diphenylguanidine, trimethylguanidine, tetramethylguanidine, pentamethylguanidine, 1,5,7-triazabicyclo[4.4.0]dec-5-ene, 7-methyl-1,5,7-triazabicyclo[4.4.0]dec-5-ene, 1-methylbiguanidine, 1-ethylbiguanidine, 1-n-butylbiguanidine, 1-n-octadecylbiguanidine, 1,1-dimethylbiguanidine, 1,1-diethylbiguanidine, 1-cyclohexylbiguanidine, 1-allylbiguanidine, 1-phenylbiguanidine, and 1-(o-tolyl)biguanidine, with dicyandiamide and 1,5,7-triazabicyclo[4.4.0]dec-5-ene being preferred.

[0183] Examples of organometallic curing accelerators include organometallic complexes or organometallic salts of metals such as cobalt, copper, zinc, iron, nickel, manganese, and tin. Specific examples of organometallic complexes include organocobalt complexes such as cobalt(II) and cobalt(III) acetylacetone; organocopper complexes such as copper(II) acetylacetone; organozinc complexes such as zinc(II) acetylacetone; organoiron complexes such as iron(III) acetylacetone; organonickel complexes such as nickel(II) acetylacetone; and organomanganese complexes such as manganese(II) acetylacetone. Examples of organometallic salts include zinc octoate, tin octoate, zinc naphthenate, cobalt naphthenate, tin stearate, and zinc stearate.

[0184] From the viewpoint of significantly obtaining the effects of the present invention, when the resin component in the resin composition is set to 100% by mass, the content of the curing accelerator is preferably 0.001% by mass or more, more preferably 0.005% by mass or more, even more preferably 0.01% by mass or more, and the upper limit is preferably 1% by mass or less, more preferably 0.1% by mass or less, and even more preferably 0.05% by mass or less.

[0185] From the viewpoint of significantly obtaining the effects of the present invention, when the non-volatile component in the resin composition is set to 100% by mass, the content of (D) curing agent is preferably 0.1% by mass or more, more preferably 0.5% by mass or more, even more preferably 1% by mass or more, the upper limit is preferably 5% by mass or less, more preferably 4% by mass or less, and even more preferably 3% by mass or less.

[0186] When the mass (mass%) of the curing agent (D) is set to 100% by mass of the non-volatile component in the resin composition, and the mass (mass%) of the dispersant (C) is set to 100% by mass of the non-volatile component in the resin composition, the ratio of C1 to D1 is preferably 0.01 or more, more preferably 0.05 or more, even more preferably 0.1 or more, preferably 5 or less, more preferably 1.5 or less, and even more preferably 1 or less. By adjusting the mass of the (C) component and the (D) component to make C1 / D1 within the aforementioned range, the desired effect of the present invention can be obtained more significantly.

[0187] When the mass percentage of (A) magnetic powder is set to A1 (when the non-volatile component in the resin composition is 100% by mass), the mass percentage of (B) epoxy resin is set to B1 (when the non-volatile component in the resin composition is 100% by mass), the mass percentage of (C) dispersant is set to C1 (when the non-volatile component in the resin composition is 100% by mass), and the mass percentage of (D) curing agent is set to D1 (when the non-volatile component in the resin composition is 100% by mass), the ratio (B1+C1+D1) / A1 is preferably 0.001 or more, more preferably 0.005 or more, even more preferably 0.01 or more, preferably 1 or less, more preferably 0.5 or less, and even more preferably 0.3 or less. By adjusting the mass of components (A) to (D) so that (B1+C1+D1) / A1 is within the aforementioned range, the desired effect of the present invention can be obtained more significantly.

[0188] When the mass (mass%) of (A) magnetic powder is set to 100% by mass in the resin composition, the mass (mass%) of (C) dispersant is set to 100% by mass in the resin composition, and the mass (mass%) of (D) curing agent is set to 100% by mass in the resin composition, the mass (mass%) of (C1+D1)×100 is preferably 0.1 or more, more preferably 0.5 or more, further preferably 1 or more, preferably 10 or less, more preferably 5 or less, and further preferably 3 or less. By adjusting the mass of components (A), (C), and (D) to ensure that ((C1+D1) / A1)×100 is within the aforementioned range, the desired effect of the present invention can be obtained more significantly.

[0189] (E) Thermoplastic resin

[0190] The resin composition contains (E) thermoplastic resin as component (E). By including component (E) in the resin composition, the stress of the cured resin composition layer can be relaxed, thereby improving the mechanical strength of the cured product.

[0191] Examples of thermoplastic resins (E) include phenoxy resins, polyvinyl acetal resins, polyolefin resins, polyimide resins, polybutadiene resins, polyamide-imide resins, polyether-imide resins, polysulfone resins, polyethersulfone resins, polyphenylene ether resins, polyetheretherketone resins, and polyester resins, with phenoxy resins being preferred. One type of thermoplastic resin (E) may be used alone, or two or more may be used in combination.

[0192] Examples of phenoxy resins include those having one or more skeletons selected from the following: bisphenol A skeleton, bisphenol F skeleton, bisphenol S skeleton, bisphenol acetophenone skeleton, phenolic skeleton, biphenyl skeleton, fluorene skeleton, dicyclopentadiene skeleton, norbornene skeleton, naphthalene skeleton, anthracene skeleton, adamantane skeleton, terpene skeleton, and trimethylcyclohexane skeleton. The terminal group of the phenoxy resin can be any functional group such as a phenolic hydroxyl group or an epoxy group. Specific examples of phenoxy resins include Mitsubishi Chemical's "1256" and "4250" (both phenoxy resins containing a bisphenol A backbone); Mitsubishi Chemical's "YX8100" (a phenoxy resin containing a bisphenol S backbone); Mitsubishi Chemical's "YX6954" (a phenoxy resin containing a bisphenol acetophenone backbone); Nippon Steel & Sumitomo Metal Chemicals' "FX280" and "FX293"; and Mitsubishi Chemical's "YL7500BH30", "YX6954BH30", "YX7553", "YX7553BH30", "YL7769BH30", "YL6794", "YL7213", "YL7290", "YL7482", and "YL7891BH30", etc.

[0193] Examples of polyvinyl alcohol acetal resins include polyvinyl alcohol formal resin and polyvinyl alcohol butyral resin, with polyvinyl alcohol butyral resin being preferred. Specific examples of polyvinyl alcohol acetal resins include "Denka Butyral 4000-2", "Denka Butyral 5000-A", "Denka Butyral 6000-C", and "Denka Butyral 6000-EP" manufactured by Denka Kagaku Kogyo Co., Ltd.; and the S-LEC BH series, BX series (e.g., BX-5Z), KS series (e.g., KS-1), BL series, and BM series manufactured by Sekisui Chemicals Co., Ltd.

[0194] Examples of polyolefin resins include low-density polyethylene, ultra-low-density polyethylene, high-density polyethylene, ethylene-vinyl acetate copolymer, ethylene-ethyl acrylate copolymer, ethylene-methyl acrylate copolymer, and other ethylene-based copolymers; as well as polyolefin polymers such as polypropylene and ethylene-propylene block copolymers.

[0195] Specific examples of polyimide resins include "SLK-6100" manufactured by Shin-Etsu Chemical Industry Co., Ltd., and "RIKACOAT SN20" and "RIKACOAT PN20" manufactured by Shin Nippon Rikka Co., Ltd. Other specific examples of polyimide resins include linear polyimides (the polyimide described in Japanese Patent Application Publication No. 2006-37083) obtained by reacting difunctional hydroxyl-terminated polybutadiene, diisocyanate compounds, and tetrabasic anhydrides, and modified polyimides containing a polysiloxane backbone (the polyimides described in Japanese Patent Application Publication Nos. 2002-12667 and 2000-319386, etc.).

[0196] Examples of polybutadiene resins include resins containing a hydrogenated polybutadiene backbone, polybutadiene resins containing hydroxyl groups, polybutadiene resins containing phenolic hydroxyl groups, polybutadiene resins containing carboxyl groups, polybutadiene resins containing anhydride groups, polybutadiene resins containing epoxy groups, polybutadiene resins containing isocyanate groups, polybutadiene resins containing urethane groups, and polyphenylene ether-polybutadiene resins.

[0197] Specific examples of polyamide-imide resins include "VYLOMAX HR11NN" and "VYLOMAX HR16NN" manufactured by Toyobo Co., Ltd. Other specific examples of polyamide-imide resins include modified polyamide-imides such as "KS9100" and "KS9300" (polyamide-imide containing a polysiloxane backbone) manufactured by Hitachi Chemical Co., Ltd.

[0198] Specific examples of polyethersulfone resins include "PES5003P" manufactured by Sumitomo Chemical Co., Ltd.

[0199] Specific examples of polysulfone resins include polysulfones such as "P1700" and "P3500" manufactured by Solvay Performance Polymers.

[0200] Specific examples of polyphenylene ether resins include "NORYL SA90" manufactured by SABIC. Specific examples of polyetherimide resins include "Ultem" manufactured by GE.

[0201] Examples of polycarbonate resins include, for example, carbonate resins containing hydroxyl groups, carbonate resins containing phenolic hydroxyl groups, carbonate resins containing carboxyl groups, carbonate resins containing anhydride groups, carbonate resins containing isocyanate groups, and carbonate resins containing urethane groups. Specific examples of polycarbonate resins include "FPC0220" manufactured by Mitsubishi Gas Chemical Co., Ltd., "T6002" and "T6001" (polycarbonate diol) manufactured by Asahi Kasei Chemical Co., Ltd., and "C-1090," "C-2090," and "C-3090" (polycarbonate diol) manufactured by Kuraray Co., Ltd. Specific examples of polyetheretherketone (PEEK) resins include "Sumiploy K" manufactured by Sumitomo Chemical Co., Ltd.

[0202] Examples of polyester resins include polyethylene terephthalate resin, polyethylene naphthalate resin, polybutylene terephthalate resin, polybutylene naphthalate resin, polypropylene terephthalate resin, polypropylene naphthalate resin, and polycyclohexanedimethyl terephthalate resin.

[0203] (E) The weight-average molecular weight (Mw) of the thermoplastic resin is preferably greater than 5,000, more preferably 8,000 or more, further preferably 10,000 or more, and particularly preferably 20,000 or more. There is no particular upper limit; for example, it can be less than 1 million, less than 500,000, less than 100,000, etc. The weight-average molecular weight of the thermoplastic resin converted to polystyrene is determined by gel permeation chromatography (GPC). Specifically, the weight-average molecular weight of the thermoplastic resin converted to polystyrene can be determined using an LC-9A / RID-6A manufactured by Shimadzu Corporation, a Shodex K-800P / K-804L / K-804L manufactured by Showa Denko Corporation, and a mobile phase such as chloroform, with the column temperature set to 40°C. The determination is performed using a calibration curve of standard polystyrene.

[0204] Relative to 100% by mass of the non-volatile components of the resin composition, the content of (E) thermoplastic resin is preferably 0.1% by mass or more, more preferably 0.2% by mass or more, particularly preferably 0.3% by mass or more, preferably 5% by mass or less, more preferably 3% by mass or less, and particularly preferably 2% by mass or less. When the amount of (E) thermoplastic resin is within the above range, the cured resin composition can have particularly good magnetic properties.

[0205] When the mass (mass%) of the thermoplastic resin (E) with 100% by mass of the non-volatile component in the resin composition is set as E1, and the mass (mass%) of the epoxy resin (B) with 100% by mass of the non-volatile component in the resin composition is set as B1, the B1 / E1 ratio is preferably 0.1 or more, more preferably 0.3 or more, even more preferably 0.5 or more, preferably 5 or less, more preferably 1.5 or less, and even more preferably 1 or less. By adjusting the mass of the (B) component and the (E) component to bring the B1 / E1 within the aforementioned range, the desired effect of the present invention can be obtained more significantly.

[0206] When the mass (mass%) of the thermoplastic resin (E) when the non-volatile component in the resin composition is set to 100% by mass is set to E1, and the mass (mass%) of the dispersant (C) when the non-volatile component in the resin composition is set to 100% by mass is set to C1, C1 / E1 is preferably 0.01 or more, more preferably 0.05 or more, even more preferably 0.1 or more, preferably 5 or less, more preferably 1.5 or less, and even more preferably 1 or less. By adjusting the mass of the (C) component and the (E) component to make C1 / E1 within the aforementioned range, the desired effect of the present invention can be obtained more significantly.

[0207] When the non-volatile component in the resin composition is set to 100% by mass, the mass (mass%) of (A) magnetic powder is set to A1; the mass (mass%) of (B) epoxy resin is set to B1; the mass (mass%) of (C) dispersant is set to C1; the mass (mass%) of (D) curing agent is set to D1; and the mass (mass%) of (E) thermoplastic resin is set to E1, when the non-volatile component in the resin composition is set to 100% by mass, (B1+C1+D1+E1) / A1 is preferably 0.001 or more, more preferably 0.01 or more, further preferably 0.05 or more, preferably 1 or less, more preferably 0.5 or less, and further preferably 0.3 or less. By adjusting the quality of components (A) to (E) so that (B1+C1+D1+E1) / A1 is within the range described above, the desired effect of the present invention can be obtained more significantly.

[0208] When the mass (mass%) of (A) magnetic powder is set to 100% by mass in the resin composition, the mass (mass%) of (C) dispersant is set to 100% by mass in the resin composition, and the mass (mass%) of (E) thermoplastic resin is set to 100% by mass in the resin composition, ((C1+E1) / A1)×100 is preferably 0.1 or more, more preferably 0.5 or more, further preferably 1 or more, preferably 10 or less, more preferably 5 or less, and further preferably 3 or less. By adjusting the mass of components (A), (C), and (E) to ensure that ((C1+E1) / A1)×100 is within the aforementioned range, the desired effect of the present invention can be obtained more significantly.

[0209] (F) Other additives

[0210] As needed, the resin composition may further include (F) other additives. Examples of such other additives include, for instance, curing delay agents such as triethyl borate; inorganic fillers (excluding magnetic powders); flame retardants; organic fillers; organometallic compounds such as organocopper compounds, organozinc compounds, and organocobalt compounds; and resin additives such as thickeners; defoamers; leveling agents; adhesion promoters; and colorants.

[0211] (G) Solvent

[0212] The resin composition may be combined with non-volatile components such as components (A) to (F) above to further include solvent (G) as a volatile component.

[0213] Organic solvents are typically used as solvents for (G). 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, and carbitol acetate. Ether ester solvents such as acetate, γ-butyrolactone, and methyl methoxypropionate; 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. (G) A single solvent may be used alone, or two or more solvents may be used in combination.

[0214] The amount of solvent (G) is preferably set to adjust the melt viscosity of the resin composition or the resin composition layer containing the resin composition to an appropriate range. Alternatively, the resin composition may be free of solvent (G). For example, relative to the total mass of the resin composition, the content of organic solvent contained in the above-mentioned resin composition is preferably less than 1.0% by mass, more preferably 0.8% by mass or less, even more preferably 0.5% by mass or less, and particularly preferably 0.1% by mass or less. There is no particular limitation on the lower limit, which is 0.001% by mass or more, or none at all. By keeping the amount of solvent in the resin composition low, the formation of voids caused by solvent evaporation can be suppressed.

[0215] The thickness of the resin composition layer also depends on the thickness of the wiring, the thickness of the core substrate, and the size of the through-hole. It is preferably 5 μm or more, more preferably 10 μm or more, particularly preferably 50 μm or more, preferably 600 μm or less, more preferably 300 μm or less, and particularly preferably 200 μm or less.

[0216] <Manufacturing Method of Resin Sheets>

[0217] Resin sheets can be manufactured, for example, by a method involving coating a resin composition onto a support. Alternatively, a resin composition layer can be manufactured, for example, by preparing a resin varnish by dissolving or dispersing the resin composition in a solvent, coating the resin varnish onto a support using a die coater or the like, and then drying it to form a resin composition layer. It should be noted that a resin composition layer can also be manufactured by directly coating the resin composition onto the support using a die coater or the like to form a resin composition layer. The solvent described above (G) can be used as the solvent.

[0218] Drying can be carried out by known methods such as heating or hot air blowing. Drying conditions are not particularly limited, but drying is performed such that the content of organic solvent in the resin composition layer is 10% by mass or less, preferably 5% by mass or less. Depending on the boiling point of the organic solvent in the resin varnish, for example, when using a resin varnish containing 30% to 60% by mass of organic solvent, a resin composition layer can be formed by drying at 50°C to 150°C for 3 to 10 minutes.

[0219] In resin sheets, a protective film based on the support can be further laminated 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; for example, it can be 1 μm to 40 μm. By laminating the protective film, it is possible to suppress the adhesion of debris or other contaminants to the surface of the resin composition layer, or to prevent damage. The resin sheet can be stored in a rolled form. When the resin sheet has a protective film, it can be used by peeling off the protective film.

[0220] <Physical properties of the resin composition layer (resin composition), etc.>

[0221] The cured product obtained by heating the resin composition layer (resin composition) at 190°C for 90 minutes exhibits excellent mechanical strength (tensile breaking strength). Therefore, the cured product provides a magnetic layer with excellent tensile breaking strength. The tensile breaking strength is preferably 60 MPa or more, more preferably 70 MPa or more, and even more preferably 75 MPa or more. There is no particular upper limit, and it can be 150 MPa or less, etc. The mechanical strength (tensile breaking strength) can be measured by the method described in the examples below.

[0222] The cured product obtained by heating the resin composition layer (resin composition) at 190°C for 90 minutes exhibits a high relative permeability at a frequency of 50 MHz. Therefore, the cured product provides a magnetic layer with high relative permeability. The relative permeability of this cured product at a frequency of 50 MHz is preferably 20 or higher, more preferably 20.5 or higher, and even more preferably 21 or higher. Furthermore, there is no particular upper limit, and it can be 100 or lower, etc. The relative permeability can be measured by the method described in the examples described later.

[0223] A cured product obtained by heating a resin composition layer (resin composition) at 190°C for 90 minutes typically exhibits low magnetic loss at a frequency of 50 MHz. Therefore, the cured product provides a magnetic layer with low magnetic loss. The magnetic loss of this cured product at a frequency of 50 MHz is preferably 0.5 or less, more preferably 0.3 or less, and even more preferably 0.1 or less. The lower limit is not particularly limited, but can be 0.001 or more, etc. Magnetic loss can be measured by the method described in the examples described later.

[0224] From the viewpoint of utilizing the above advantages, the resin sheet preferably uses a resin composition layer (resin composition) as a magnetic layer for forming the circuit board. Furthermore, from the viewpoint of utilizing the above advantages, the resin sheet preferably uses a resin composition layer (resin composition) as a through-hole filler for the core substrate. When the core substrate and the resin sheet are laminated, part or all of the resin composition layer can be inserted into the through-hole, filling the through-hole with the resin composition. Moreover, by curing the resin composition, a magnetic layer can be formed within the through-hole.

[0225] [Resin Composition]

[0226] The resin composition of the present invention comprises (A) magnetic powder, (B) epoxy resin, (C) dispersant, (D) curing agent and (E) thermoplastic resin. When the mass (mass%) of (E) thermoplastic resin is set to 100% by mass of the non-volatile component in the resin composition, and the mass (mass%) of (B) epoxy resin is set to B1 when the mass (mass%) of (B) is set to 100% by mass of the non-volatile component in the resin composition, the ratio of B1 / E1 is 0.1 or more and 5 or less. Component (C) has a polyester backbone as shown in the following general formula (1).

[0227] [Chemical Formula 8]

[0228]

[0229] (In general formula (1), R independently represents hydrocarbon groups with 2 to 10 carbon atoms, and n represents an integer from 2 to 1000.)

[0230] The resin composition may also have states other than the state of a resin composition layer formed on a sheet, and may otherwise be the same composition as the resin composition layer described above. The components contained in the resin composition are as described above.

[0231] [cured material]

[0232] The cured product of the present invention is obtained by curing the resin composition layer of the present invention. Furthermore, the cured product of the present invention is obtained by curing the resin composition of the present invention. The curing conditions for the resin composition layer and the resin composition can use the conditions of step (2) described later. Alternatively, preheating may be performed before heat curing the resin composition layer and the resin composition, and the heating may include preheating multiple times.

[0233] [Circuit substrate and its manufacturing method]

[0234] One embodiment of the present invention relates to a circuit board comprising a magnetic layer. This magnetic layer comprises a cured product of the resin composition layer of the aforementioned resin sheet, preferably comprising only the cured product of the aforementioned resin composition. The specific structure of the circuit board is not limited as long as it includes a magnetic layer comprising the cured product of the aforementioned resin composition layer. The circuit board of the first embodiment is a circuit board comprising a core substrate as a substrate having through-holes and a magnetic layer filling the through-holes. Furthermore, the circuit board of the second embodiment is a circuit board comprising a magnetic layer formed from a cured product of the resin composition layer of the resin sheet. In these circuit boards, the magnetic layer may be a layer formed by curing the resin composition layer, or it may be a layer formed by curing the resin composition layer. Hereinafter, a first embodiment and a second embodiment of the circuit board manufacturing method will be described. However, the manufacturing method of the circuit board according to the present invention is not limited to the first and second embodiments described below.

[0235] <First Implementation Method>

[0236] The circuit board of the first embodiment includes a core substrate having through holes and a magnetic layer filling the through holes. The method for manufacturing this circuit board includes, for example, sequentially:

[0237] (1) A process of laminating a core substrate with through holes and a resin sheet by filling the through holes with a resin composition layer, and

[0238] (2) The process of curing the resin composition layer to form a magnetic layer.

[0239] Furthermore, the circuit board manufacturing method of the first embodiment can be combined with the above-described steps (1) to (2) to include any steps. For example, the circuit board manufacturing method may include:

[0240] (3) The process of grinding the magnetic layer.

[0241] (4) The process of roughening the magnetic layer, and

[0242] (5) The process of forming a conductor layer on the magnetic layer;

[0243] Typically, steps (3), (4), and (5) are performed in sequence.

[0244] <Process (1)>

[0245] Step (1) typically includes the process of preparing a core substrate with through-holes. The core substrate can be prepared from commercially available sources. Alternatively, the core substrate can be prepared by manufacturing it using suitable materials. Hereinafter, a method for manufacturing a core substrate in an example will be described.

[0246] Figure 1 This is a schematic cross-sectional view of the core substrate 10 before the formation of through-holes in the circuit board manufacturing method according to the first embodiment of the present invention. Figure 1 In the example shown, the process of preparing the core substrate 10 may include preparing a core substrate 10 before the formation of through-holes to be filled with a magnetic layer. This core substrate 10 is a substrate prior to the formation of the through-holes and may be a plate-like component.

[0247] The core substrate 10 typically includes a support substrate 11. Examples of the support substrate 11 include insulating substrates such as glass epoxy boards, metal substrates, polyester substrates, polyimide substrates, BT resin substrates, and thermosetting polyphenylene ether substrates. Additionally, a metal layer can be provided on the support substrate 11. The metal layer can be provided on one side or both sides of the support substrate 11. Here, an example is shown where metal layers 12 and 13 are provided on both surfaces of the support substrate 11. Examples of metal layers 12 and 13 include layers formed of metals such as copper. Metal layers 12 and 13 can be, for example, copper foil with a carrier, or metal layers formed of the material of the conductor layer described later.

[0248] Figure 2 This is a schematic cross-sectional view of a core substrate 10 having through-holes 14 formed in the circuit board manufacturing method according to the first embodiment of the present invention. Figure 2 In the example shown, the process of preparing the core substrate 10 may include forming a through hole 14 in the core substrate 10. The through hole 14 can be formed, for example, by drilling, laser irradiation, plasma irradiation, or other methods. Typically, the through hole 14 can be formed by forming a through-hole in the core substrate 10. Specifically, the formation of the through hole 14 can be performed using a commercially available drill bit. Examples of commercially available drill bits include, for instance, the "ND-1S211" manufactured by Hitachi ViaMechanics.

[0249] Figure 3This is a schematic cross-sectional view of a core substrate 10 in which a plating layer 20 is formed within a through-hole 14, as described in the manufacturing method of the circuit board according to the first embodiment of the present invention. The process of preparing the core substrate 10 may, as needed, include roughening the core substrate 10 afterward, such as... Figure 3 The plating layer 20 is formed as shown. As the roughening treatment described above, either dry or wet roughening treatment can be performed. Examples of dry roughening treatment include plasma treatment. Examples of wet roughening treatment include sequentially performing a swelling treatment using a swelling solution, a roughening treatment using an oxidizing agent, and a neutralization treatment using a neutralizing solution. The plating layer 20 can be formed by a plating method. The steps for forming the plating layer 20 by the plating method can be the same as the formation of the conductor layer in step (5) described later. Here, an example is shown where the plating layer 20 is formed inside the through-hole 14, on the surface of the metal layer 12, and on the surface of the metal layer 13. In this example, the core substrate having the plating layer 20 is labeled with the same symbol "10" as the core substrate 10 before the formation of the plating layer 20.

[0250] Figure 4 This is a cross-sectional view schematically showing the state in which the core substrate 10 and the resin sheet 30 are laminated in the circuit board manufacturing method according to the first embodiment of the present invention. Step (1) includes, after preparing the core substrate 10 with through holes 14 formed, as follows... Figure 4 As shown, the core substrate 10 and the resin sheet 30 are laminated. In this embodiment, an example is shown and described where the resin sheet 30, which includes a resin composition layer 31 and a support 32, is laminated onto a single surface 10U of the core substrate 10. In the following description, the surface 10U of the core substrate 10 that is bonded to the resin sheet 30 is sometimes referred to as the "first surface 10U", and the surface on the opposite side is referred to as the "second surface 10D".

[0251] The lamination of the core substrate 10 and the resin sheet 30 is performed such that part or all of the resin composition layer 31 fills the through-hole 14. Therefore, the lamination is typically performed by bonding the resin composition layer 31 to the core substrate 10. Specifically, the lamination can be performed by heating and pressing the resin sheet 30 onto the core substrate 10, thereby adhering the resin composition layer 31 to the core substrate 10. Figure 4In the example shown, when the resin sheet 30 has a support 32, the above-mentioned lamination can be performed by pressing the resin sheet 30 onto the core substrate 10 from the support 32 side. Examples of components for heat pressing (hereinafter sometimes referred to as "heat pressing components," not shown) include, for example, heated metal plates (SUS end plates, etc.) or metal rollers (SUS rollers, etc.). The heat pressing component can also be pressed directly onto the resin sheet 30, but it is preferable to press it using an elastic material such as heat-resistant rubber so that the resin sheet 30 fully follows the surface irregularities of the core substrate 10.

[0252] The lamination of the core substrate 10 and the resin sheet 30 can be performed, for example, by vacuum lamination. The lamination conditions can be as follows: The heating and pressing temperature is preferably in the range of 60°C to 160°C, more preferably in the range of 80°C to 140°C. The heating and pressing pressure is preferably in the range of 0.098 MPa to 1.77 MPa, more preferably in the range of 0.29 MPa to 1.47 MPa. The heating and pressing time is preferably in the range of 20 seconds to 400 seconds, more preferably in the range of 30 seconds to 300 seconds. Lamination is preferably performed under reduced pressure conditions of 13 hPa or less.

[0253] After lamination, the laminated resin sheet 30 can be smoothed under normal pressure (atmospheric pressure), for example, by pressing it from the support 32 side using a heated pressing member. The pressing conditions for smoothing can be the same as the heating and pressing conditions for lamination described above. It should be noted that lamination and smoothing can also be performed continuously using a vacuum laminator.

[0254] Figure 5 This is a schematic cross-sectional view illustrating the state after the core substrate 10 and the resin sheet 30 are laminated in the circuit board manufacturing method according to the first embodiment of the present invention. Through the lamination of the core substrate 10 and the resin sheet 30, as... Figure 5 As shown, the resin composition layer 31 of the resin sheet 30 enters the through-hole 14, thus filling the through-hole 14 with the resin composition layer 31. Here, an example is shown where a portion of the resin composition layer 31 enters the through-hole 14, while another portion does not enter the through-hole 14 and adheres to the first surface 10U of the core substrate 10. Therefore, the resin composition layer 31 can be formed on the first surface 10U of the core substrate 10. Furthermore, another portion of the resin composition layer 31 that has entered the through-hole 14 can pass through the through-hole 14 and exit from the opening on the second surface 10D side of the core substrate 10. Therefore, the resin composition layer 31 can be formed on the second surface 10D of the core substrate 10.

[0255] Typically, the support 32 is peeled off after the core substrate 10 and the resin sheet 30 are laminated. In this embodiment, an example is shown where the support 32 is peeled off after the core substrate 10 and the resin sheet 30 are laminated, but before step (2). However, the peeling off of the support 32 may also be performed after step (2).

[0256] <Process (2)>

[0257] Figure 6 This is a schematic cross-sectional view illustrating step (2) of the method for manufacturing a circuit board according to the first embodiment of the present invention. Step (2) includes, after laminating the core substrate 10 and the resin sheet 30, as follows: Figure 6 As shown, the resin composition layer 31 is cured. By curing the resin composition layer 31, a magnetic layer 40 containing the cured resin composition can be formed. The magnetic layer 40 is formed within the through-hole 14, and may also typically be formed on the first surface 10U and the second surface 10D of the core substrate 10.

[0258] The resin composition layer 31 is typically cured by heat curing. The heat curing conditions for the resin composition layer 31 can be appropriately set within the range of when the resin composition layer 31 is cured. The curing temperature is preferably 60°C or higher, more preferably 70°C or higher, even more preferably 80°C or higher, preferably 245°C or lower, more preferably 220°C or lower, 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, even more preferably 100 minutes or less.

[0259] The degree of curing of the magnetic layer 40 obtained in step (2) is preferably 80% or more, more preferably 85% or more, and even more preferably 90% or more. The degree of curing can be measured, for example, using a differential scanning calorimeter.

[0260] The method for manufacturing the circuit board may include a step of heating the resin composition layer 31 at a temperature lower than the curing temperature (preheating step) after the core substrate 10 and the resin sheet 30 are laminated and before the resin composition layer 31 is cured. For example, before curing the resin composition layer 31, the resin composition layer 31 may be preheated for 5 minutes or more (preferably 5 minutes to 150 minutes, more preferably 15 minutes to 120 minutes) at a temperature of 50°C or higher and lower than 120°C (preferably 60°C or higher and lower than 110°C, more preferably 70°C or higher and lower than 100°C).

[0261] <Process (3)>

[0262] Figure 7This is a schematic cross-sectional view illustrating step (3) of the method for manufacturing a circuit board according to the first embodiment of the present invention. Step (3) may include a step of polishing the magnetic layer 40. Specifically, step (3) may include a step of polishing the portion of the magnetic layer 40 located outside the through hole 14. In the example shown in this embodiment, since the magnetic layer 40 is formed on the first surface 10U and the second surface 10D of the core substrate 10, the portion of the magnetic layer 40 located on the first surface 10U and the second surface 10D can be polished. The portion of the magnetic layer 40 located outside the through hole 14 is usually a remaining portion that is not needed in the final product. Through the above-described polishing, as Figure 7 As shown, the remaining portion can be removed. Furthermore, by grinding, the polished surfaces 40U and 40D, which form the surface of the magnetic layer 40, can be planarized.

[0263] As a polishing method, a method capable of removing unwanted portions of the magnetic layer 40 can be employed. Examples of such polishing methods include polishing, belt polishing, and ceramic polishing. Commercially available polishing devices include, for example, the "NT-700IM" manufactured by Ishii Opto-Tech Co., Ltd.

[0264] The arithmetic mean roughness (Ra) of the polished surfaces 40U and 40D of the magnetic layer 40 is improved compared to the conductor layer. Figure 7 From the viewpoint of ensuring tightness between the surfaces (not shown), a depth of 300 nm or more is preferred, more preferably 350 nm or more, and even more preferably 400 nm or more. The upper limit is preferably 1000 nm or less, more preferably 900 nm or less, and even more preferably 800 nm or less. Surface roughness (Ra) can be measured using, for example, a non-contact surface roughness meter.

[0265] After step (2) and before step (3), in order to further improve the curing degree of the magnetic layer 40, heat treatment may be performed on the magnetic layer 40. The temperature in the aforementioned heat treatment may be based on the curing temperature described above. Specifically, the 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 150 minutes or lower, more preferably 120 minutes or lower, and even more preferably 100 minutes or lower.

[0266] By performing the above-described processes (1) to (2) and then performing process (3) as needed, a circuit board 100 having a core substrate 10 and a magnetic layer 40 filling the through holes 14 of the core substrate 10 can be obtained. The circuit board 100 thus obtained can be subjected to processes (4) and (5) as needed to form a conductor layer.

[0267] <Process (4)>

[0268] Step (4) includes a step of roughening the magnetic layer. Typically, the polished surface of the magnetic layer is roughened. In addition, in step (4), not only the polished surface of the magnetic layer can be roughened, but also the surfaces 10U and 10D of the core substrate 10 can be roughened.

[0269] There are no particular limitations on the order and conditions of the roughening treatment. For example, the order and conditions used in the manufacturing process of multilayer printed wiring boards can be adopted. As a specific example, the roughening treatment can be performed by sequentially including swelling treatment using a swelling liquid, roughening treatment using an oxidizing agent, and neutralization treatment using a neutralizing liquid.

[0270] Examples of swelling solutions used for swelling treatment include alkaline solutions and surfactant solutions, with alkaline solutions being preferred. Among the alkaline solutions used as swelling solutions, sodium hydroxide solutions and potassium hydroxide solutions are more preferred. Commercially available swelling solutions include, for example, "Swelling Dip Securiganth P" and "Swelling Dip Securiganth SBU" manufactured by Ammet Japan Co., Ltd.

[0271] Swelling treatment using a swelling solution can be performed, for example, by immersing the magnetic layer in a swelling solution at 30°C to 90°C for 1 to 20 minutes. From the viewpoint of suppressing the swelling of the resin contained in the magnetic layer at an appropriate level, it is preferable to immerse the magnetic layer in a swelling solution at 40°C to 80°C for 5 to 15 minutes.

[0272] Examples of oxidants used in roughening treatments include alkaline permanganate solutions, such as potassium permanganate or sodium permanganate dissolved in an aqueous solution of sodium hydroxide. Roughening treatment using an oxidant such as an alkaline permanganate solution is preferably performed by immersing the magnetic layer in an oxidant solution heated to 60°C to 80°C for 10 to 30 minutes. Furthermore, the concentration of permanganate in the alkaline permanganate solution is preferably 5% to 10% by mass. Commercially available oxidants include alkaline permanganate solutions such as "Concentrate Compact CP" and "Dosing Solution Securiganth P" manufactured by Ammet Japan Co., Ltd.

[0273] Acidic aqueous solutions are preferred as the neutralizing liquid used in the neutralization process. Commercially available neutralizing liquids include, for example, "Reduction Solution Securiganth P" manufactured by Ammet Japan Co., Ltd. Neutralization using the neutralizing liquid can be performed by immersing the roughened surface treated with an oxidizing agent solution in a neutralizing liquid at 30°C to 80°C for 5 to 30 minutes. From an operability perspective, immersing the magnetic layer roughened with an oxidizing agent solution in a neutralizing liquid at 40°C to 70°C for 5 to 20 minutes is preferable.

[0274] From the viewpoint of improving the adhesion between the magnetic layer and the conductor layer, the arithmetic mean roughness (Ra) of the surface after roughening treatment is preferably 300 nm or more, more preferably 350 nm or more, and even more preferably 400 nm or more. The upper limit is preferably 1500 nm or less, more preferably 1200 nm or less, and even more preferably 1000 nm or less. The surface roughness (Ra) can be measured, for example, using a non-contact surface roughness meter.

[0275] <Process (5)>

[0276] Figure 8 This is a schematic cross-sectional view illustrating step (5) of the manufacturing method of the circuit board 100 according to the first embodiment of the present invention. Figure 8 As shown, step (5) includes forming a conductor layer 50 on the polished surfaces 40U and 40D of the magnetic layer 40. This embodiment shows an example where the conductor layer 50 is formed not only on the polished surfaces 40U and 40D of the magnetic layer 40, but also on the surrounding surfaces (e.g., the first surface 10U and the second surface 10D of the core substrate 10). Additionally, in Figure 8 An example is shown in which conductor layers 50 are formed on both sides of the core substrate 10, but conductor layers 50 may also be formed on only one side of the core substrate 10.

[0277] Figure 9 This is a schematic cross-sectional view illustrating step (5) of the manufacturing method of the circuit board 100 according to the first embodiment of the present invention. Figure 9 As shown, step (5) can be included after forming conductor layer 50, by etching or other processes to remove conductor layer 50, metal layers 12 and 13, and a portion of plating layer 20 to form patterned conductor layer 51.

[0278] Methods for forming the conductor layer 50 include, for example, plating, sputtering, and vapor deposition, with plating being preferred. In a preferred embodiment, a patterned conductor layer 51 having a desired wiring pattern can be formed by plating on the surface of the magnetic layer 40 (and, if necessary, on the core substrate 10) using appropriate methods such as semi-additive or fully additive methods. Materials for the conductor layer 50 include, for example, 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 gold, platinum, palladium, silver, copper, aluminum, cobalt, chromium, zinc, nickel, titanium, tungsten, iron, tin, and indium. From the perspectives of versatility, cost, and ease of patterning, chromium, nickel, titanium, aluminum, zinc, gold, palladium, silver, or copper, or nickel-chromium alloys, copper-nickel alloys, or copper-titanium alloys, are preferred. Chromium, nickel, titanium, aluminum, zinc, gold, palladium, silver, or copper, or nickel-chromium alloys, are even more preferred. Copper is the most preferred material.

[0279] Here, an example of a method for forming the patterned conductor layer 51 is described in detail. A seed layer is formed on the polished surfaces 40U and 40D of the magnetic layer 40 by electroless plating. Next, a mask pattern is formed on the formed seed layer as needed, and an electroplated layer is formed by electroplating. Then, as needed, the mask pattern is removed, and the unwanted seed layer is removed by etching or other processes, thus forming the patterned conductor layer 51 with the desired wiring pattern. After forming the patterned conductor layer 51, an annealing process can be performed as needed to improve the adhesion strength of the patterned conductor layer 51. The annealing process can be performed, for example, by heating at 150°C to 200°C for 20 to 90 minutes.

[0280] The thickness of the patterned conductor layer 51 is preferably 1 μm or more, more preferably 3 μm or more, even more preferably 5 μm or more, preferably 70 μm or less, more preferably 50 μm or less, even more preferably 40 μm or less, and particularly preferably 10 μm or less.

[0281] By using the above method, a circuit board 100 having a magnetic layer 40 can be obtained. The magnetic layer 40 is obtained by curing the resin composition layer 31, and therefore contains a cured resin composition. As a result, the magnetic layer 40 can contain a large amount of magnetic powder (not shown), and therefore can have excellent magnetic properties.

[0282] <Second Implementation Method>

[0283] The circuit board of the second embodiment includes a magnetic layer formed from a cured resin composition layer of a resin sheet. A method for manufacturing this circuit board includes, for example:

[0284] (A) A process of laminating a resin sheet onto an inner substrate in such a way that the resin composition layer is bonded to the inner substrate to form a magnetic layer.

[0285] Furthermore, the circuit board manufacturing method of the second embodiment may include any steps other than step (A). For example, the circuit board manufacturing method may include:

[0286] (B) The process of creating openings in the magnetic layer.

[0287] (C) The process of roughening the magnetic layer, and

[0288] (D) The process of forming a conductor layer on a magnetic layer.

[0289] The manufacturing method preferably includes steps (A) to (D) in sequence.

[0290] <Process (A)>

[0291] Step (A) is a process of laminating a resin sheet onto an inner substrate in such a way that a resin composition layer is bonded to the inner substrate to form a magnetic layer. As one embodiment of step (A), a resin sheet is laminated onto an inner substrate in such a way that a resin composition layer is bonded to the inner substrate, and the resin composition layer is thermo-cured to form a magnetic layer.

[0292] Figure 10 This is a schematic cross-sectional view illustrating step (A) of the method for manufacturing a circuit board according to the second embodiment of the present invention. In step (A), a resin sheet 310 comprising a support 330 and a resin composition layer 320a disposed on the support 330 is laminated onto the inner layer substrate 200 in such a manner that the resin composition layer 320a is bonded to the inner layer substrate 200.

[0293] The inner layer substrate 200 is an insulating substrate. Examples of materials for the inner layer substrate 200 include insulating substrates such as glass epoxy boards, metal substrates, polyester substrates, polyimide substrates, BT resin substrates, and thermosetting polyphenylene ether substrates. The inner layer substrate 200 can be an inner circuit board with wiring or the like fabricated within its thickness.

[0294] like Figure 10 In one example shown, the inner substrate 200 has a first conductor layer 420 disposed on a first main surface 200a and an external terminal 240 disposed on a second main surface 200b. The first conductor layer 420 may include multiple wirings. In the example shown, only the wirings of the coil-shaped conductive structure 400 constituting the inductor element are shown. The external terminal 240 is a terminal for electrical connection to an external device, etc., not shown. The external terminal 240 may be configured as part of the conductor layer disposed on the second main surface 200b.

[0295] The conductor material that forms the first conductor layer 420 and the external terminal 240 is the same as the material of the conductor layer described in the “<process (5)>” column of the first embodiment.

[0296] The first conductor layer 420 and the external terminal 240 can be a single-layer structure, or a multi-layer structure obtained by stacking two or more single metal layers or alloy layers formed of different kinds of metals or alloys. In addition, the thickness of the first conductor layer 420 and the external terminal 240 is the same as that of the second conductor layer 440 described later.

[0297] The linewidth (L) / spacing (S) ratio of the first conductor layer 420 and the external terminal 240 is not particularly limited, but from the viewpoint of reducing surface unevenness to obtain a magnetic layer with excellent smoothness, it is generally 900 / 900 μm or less, preferably 700 / 700 μm or less, more preferably 500 / 500 μm or less, further preferably 300 / 300 μm or less, and even more preferably 200 / 200 μm or less. The lower limit of the linewidth / spacing ratio is not particularly limited, but from the viewpoint of ensuring good embedding of the resin composition layer in the space, it is preferably 1 / 1 μm or more.

[0298] The inner layer substrate 200 may have a plurality of through holes 220 extending through 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. Through-hole wiring 220a electrically connects the first conductor layer 420 to the external terminal 240.

[0299] The bonding of the resin composition layer 320a to the inner substrate 200 is the same as the lamination method of the core substrate and resin sheet described in the “<Process (1)>” column of the first embodiment.

[0300] After laminating a resin sheet onto an inner substrate, the resin composition layer is thermosetting to form a magnetic layer. For example... Figure 11 In one example shown, the resin composition layer 320a bonded to the inner substrate 200 is thermocured to form a first magnetic layer 320.

[0301] The thermosetting conditions of the resin composition layer 320a are the same as those of the resin composition layer described in the “<Step (2)>” column of the first embodiment.

[0302] The support 330 can be removed between process (B) and process (A) after thermosetting, or it can be peeled off after process (B).

[0303] <Process (B)>

[0304] Figure 12This is a schematic cross-sectional view illustrating step (B) of the method for manufacturing a circuit board according to the second embodiment of the present invention. In step (B), an opening is formed in the first magnetic layer 320 to create a via 360.

[0305] Via 360 is a path used to electrically connect the first conductor layer 420 to the second conductor layer 440, which will be described later. The via 360 can be formed using, for example, a drill bit, laser, plasma, etc., depending on the composition of the resin composition used in the formation of the magnetic layer. The size and shape of the via can be appropriately determined according to the design of the circuit board.

[0306] <Process (C)>

[0307] Step (C) includes a step of roughening the magnetic layer that has formed the via. As a method for roughening the magnetic layer in step (C), the same method as that described in the “<Step (4)>” column of the first embodiment can be used.

[0308] The roughening process in step (C) can be a process of grinding the surface of the insulating layer. As a grinding method, it can be performed by the same grinding as described in the "<Step (3)>" column of the first embodiment.

[0309] The arithmetic mean roughness (Ra) of the surface roughened as a magnetic layer is preferably 300 nm or more, more preferably 350 nm or more, and even more preferably 400 nm or more, from the viewpoint of improving coating adhesion. The upper limit is preferably 1000 nm or less, more preferably 900 nm or less, and even more preferably 800 nm or less. The surface roughness (Ra) can be measured, for example, using a non-contact surface roughness meter.

[0310] <Process (D)>

[0311] Figure 13 This is a schematic cross-sectional view illustrating step (D) of the method for manufacturing a circuit board according to the second embodiment of the present invention. In step (D), as... Figure 13 One example shown includes the step of forming a second conductor layer 440 on the first magnetic layer 320.

[0312] The conductor material that forms the second conductor layer 440 is the same as the material of the conductor layer described in the “<process (5)>” column of the first embodiment.

[0313] 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, 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.

[0314] The second conductor layer 440 can be formed by plating. The second conductor layer 440 is preferably formed, for example, by a wet plating method including a semi-additive method, a fully additive method, a semi-additive method, a photomask patterning method, an electrolytic plating method, and a flash etching method. By forming the second conductor layer 440 using a wet plating method, it can be formed as a second conductor layer 440 containing the desired wiring pattern. It should be noted that, through this process, the in-via wiring 360a is also formed within the via 360.

[0315] The first conductor layer 420 and the second conductor layer 440 are, for example, as described later. Figures 14-16 As shown in one example, it can be configured as a spiral. In one example, one end of the central side of the spiral wiring portion of the second conductor layer 440 is electrically connected to one end of the central side of the spiral wiring portion of the first conductor layer 420 via the via wiring 360a. The other end of the outer peripheral side of the spiral wiring portion of the second conductor layer 440 is electrically connected to the pad 420a of the first conductor layer 42 via the via wiring 360a. Therefore, the other end of the outer peripheral side of the spiral wiring portion of the second conductor layer 440 is electrically connected to the external terminal 240 via the via wiring 360a, the pad 420a, and the via wiring 220a.

[0316] The coil-shaped conductive structure 400 is composed of a spiral wiring portion that is part of a first conductor layer 420, a spiral wiring portion that is part of a second conductor layer 440, and a via wiring 360a that electrically connects the spiral wiring portion of the first conductor layer 420 and the spiral wiring portion of the second conductor layer 440.

[0317] Following step (D), a further step can be performed to form a magnetic layer on the conductor layer. Specifically, as follows... Figure 15 In one example shown, the second magnetic layer 340 is formed on the first magnetic layer 320, on which the second conductor layer 440 and the via wiring 360a are formed. The second magnetic layer can be formed by the same process as described.

[0318] [Inductor Components]

[0319] The inductor component includes the circuit board of the present invention. When such an inductor component includes a circuit board obtained by the manufacturing method of the circuit board of the first embodiment, at least a portion around the cured resin composition layer has an inductor pattern formed of conductors. Such an inductor component is applicable to, for example, the component described in Japanese Patent Application Publication No. 2016-197624.

[0320] Furthermore, in the case of a circuit board obtained by the manufacturing method of the circuit board according to the second embodiment, the inductor board has a magnetic layer and a conductive structure at least a portion of which is embedded in the magnetic layer, and includes an inductor element composed of the conductive structure and a portion of the magnetic layer extending along the thickness direction of the magnetic layer and surrounded by the conductive structure. Here, Figure 14 This is a schematic top view of an inductor substrate containing inductor elements, viewed from one side along its thickness direction. Figure 15 It means that by Figure 14 The diagram shows a cut end face of the inductor substrate, indicated by the dotted line II-II. Figure 16 This is a schematic top view used to illustrate the structure of the first conductor layer in an inductor substrate.

[0321] like Figure 14 and Figure 15 As shown as an example, the circuit board 100 is a stacked wiring board having multiple magnetic layers (first magnetic layer 320, second magnetic layer 340) and multiple conductor layers (first conductor layer 420, second conductor layer 440), that is, having stacked magnetic layers and stacked conductor layers. In addition, the inductor board 100 has an inner layer board 200.

[0322] according to Figure 15 The first magnetic layer 320 and the second magnetic layer 340 constitute a magnetic portion 300 that can be considered as an integral 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. That is, in the inductor substrate 100 of this embodiment, the inductor element is composed of the coil-shaped conductive structure 400 and a core portion of the magnetic portion 300 that extends along the thickness direction of the magnetic portion 300 and is surrounded by the coil-shaped conductive structure 400.

[0323] like Figure 16As illustrated in the figure, the first conductor layer 420 includes a spiral wiring portion for forming a coil-shaped conductive structure 400, and a rectangular pad 420a electrically connected to the wiring 220a within the via. In the example, the spiral wiring portion includes a straight portion, a curved portion bent at a right angle, and a detour portion meandering at the pad 420a. In the example, the spiral wiring portion of the first conductor layer 420 has an overall rectangular outline and is wound counterclockwise from the center outwards.

[0324] Similarly, a second conductor layer 440 is provided on the first magnetic layer 320. The second conductor layer 440 includes helical wiring portions for forming a coil-like conductive structure 400. Figure 14 or Figure 15 In this design, the spiral wiring section includes straight sections and curved sections bent at right angles. Figure 14 or Figure 15 In the second conductor layer 440, the spiral wiring portion has an overall outline that is roughly rectangular and is wound clockwise from the center to the outside.

[0325] Such inductor components can be used as wiring boards for mounting electronic components such as semiconductor chips, or as (multilayer) printed wiring boards in which the wiring board is used as an inner substrate. Furthermore, they can be used as chip inductor components formed by monolithically mounting the wiring board, or as printed wiring boards with the chip inductor component surface-mounted.

[0326] Furthermore, various types of semiconductor devices can be manufactured using the aforementioned wiring board. Semiconductor devices incorporating the wiring board are suitable for use in electrical products (e.g., computers, mobile phones, digital cameras, and televisions) and vehicles (e.g., motorcycles, automobiles, trams, ships, and aircraft).

[0327] Example

[0328] The present invention will now be specifically described through embodiments, but the present invention is not limited to these embodiments. It should be noted that, unless otherwise expressly stated, in the following description, "parts" and "%" refer to "parts by mass" and "% by mass," respectively.

[0329] <Determination of pH of Dispersant (Indicator Method)>

[0330] Dissolve the dispersant in acetone to prepare a sample (22℃) with a dispersant concentration of 0.1 g / mL. Immerse the pH test paper gently, then pull it up and dry off excess water. Compare the color of the wetted portion of the test paper with a standard color chart, and take the pH value of the closest color as the pH value of each sample.

[0331] <Synthesis Example 1: Synthesis of Dispersant 1>

[0332] In a reaction flask equipped with a thermometer, stirrer, nitrogen inlet, and reflux tube, 10.0 parts of 12-hydroxystearic acid (manufactured by Pure Chemical Industries, Inc.) and 190 parts of ε-caprolactone (manufactured by Pure Chemical Industries, Inc.) were added. The mixture was heated to 160°C over a nitrogen stream for 4 hours, and then heated at 160°C for 2 hours until the residual amount of ε-caprolactone was less than 1%. The mixture was then cooled to room temperature. Hereinafter, this reaction solution will be referred to as Dispersant 1. Dispersant 1 has a weight-average molecular weight of 23,000 and an acid value of 9.0 mg KOH / g. The pH value in the indicator method is 5.

[0333] <Synthesis Example 2: Synthesis of Dispersant 2>

[0334] In a reaction flask equipped with a thermometer, stirrer, nitrogen inlet, and reflux pipe, 10.0 parts of 12-hydroxystearic acid (manufactured by Pure Chemical Industries, Ltd.) and 180 parts of δ-valerolactone (manufactured by Tokyo Chemical Industry Co., Ltd.) were added. The mixture was heated to 160°C over a nitrogen atmosphere for 4 hours, and then heated at 160°C for 2 hours until the residual amount of δ-valerolactone was less than 1%. The mixture was then cooled to room temperature. Hereinafter, this reaction solution will be referred to as dispersant 2. Dispersant 2 has a weight-average molecular weight of 22,000 and an acid value of 8.9 mg KOH / g. The pH value in the indicator method is 5.

[0335] <Synthesis Example 3: Synthesis of Dispersant 3>

[0336] In a reaction flask equipped with a thermometer, stirrer, nitrogen inlet, and reflux pipe, a mixture of 25.0 parts xylene and 70 parts of a 10% aqueous solution of polyallylamine ("PAA-1LV" manufactured by Nitto Boshoku Co., Ltd., with a number average molecular weight of approximately 3,000) was stirred at 160°C. Water was removed by distillation using a separation apparatus. Simultaneously, while refluxing xylene into the reaction solution, a solution of dispersant 1 (14.21 parts) obtained in Synthesis Example 1, heated to 160°C, was added. The reaction was carried out at 160°C for 2 hours. Then, the mixture was heated at 160°C for 4 hours, and xylene was removed by distillation at 160°C to obtain dispersant 3. Dispersant 3 has an amine value of 31.0 mg KOH / g. The amine value immediately after mixing is 312.6 mg KOH / g. The pH value in the indicator method is 6.

[0337] <Synthesis Example 4: Synthesis of Dispersant 4>

[0338] In a reaction flask equipped with a thermometer, stirrer, nitrogen inlet, reflux tube, and water separator, 30.0 parts xylene (manufactured by Pure Chemical Industries, Inc.), 300.0 parts 12-hydroxystearic acid (manufactured by Pure Chemical Industries, Inc.), and 0.1 parts tetrabutyl titanate (manufactured by Tokyo Chemical Industry Co., Ltd.) were added. The mixture was heated to 160°C over a nitrogen flow for 4 hours. It was then heated at 160°C for another 4 hours, and the xylene was removed by distillation at 160°C to obtain dispersant 4. Dispersant 4 has a weight-average molecular weight of 6000 and an acid value of 23.0 mg KOH / g. The pH value in the indicator method is 5.

[0339] <Synthesis Example 5: Synthesis of Dispersant 5>

[0340] In a reaction flask equipped with a thermometer, stirrer, nitrogen inlet, reflux tube, and water separator, 30.0 parts xylene (manufactured by Pure Chemical Industries, Inc.), 300.0 parts 12-hydroxystearic acid (manufactured by Pure Chemical Industries, Inc.), and 0.1 parts tetrabutyl titanate (manufactured by Tokyo Chemical Industry Co., Ltd.) were added. The mixture was heated to 160°C over a nitrogen stream for 4 hours. It was then heated at 160°C for another 4 hours (at which point the acid value was approximately 20 mg KOH / g). The xylene was removed by distillation at 160°C. The mixture was then cooled to room temperature, and the water produced during the heating reaction was separated from the xylene in the distillate. The xylene was refluxed back into the reaction solution. This reaction solution was named polyester PE-1. In a reaction flask equipped with a thermometer, stirrer, nitrogen inlet, reflux tube, and water separator, a mixture of 25.0 parts xylene and 70 parts of a 10% aqueous solution of polyallylamine ("PAA-1LV" manufactured by Nitto Boshoku Co., Ltd., with a number average molecular weight of approximately 3,000) was stirred at 160°C. Water was removed by distillation using a separation device. Simultaneously, xylene was refluxed into the reaction solution while 2.5 parts of polyester PE-1 were added, and the reaction was carried out at 160°C for 2 hours. Then, the mixture was heated at 160°C for 4 hours, and xylene was removed by distillation at 160°C. Dispersant 5 has a polyester backbone of alkylene with 11 carbon atoms in general formula (1), and has an amine value of 38.5 mg KOH / g and an acid value of 23.5 mg KOH / g. The amine value of dispersant 5 after mixing is 317 mg KOH / g. The pH value of dispersant 5 in the indicator method is 6.

[0341] <Example 1: Manufacturing of Magnetic Varnish 1>

[0342] 2.41 parts by weight of epoxy resin (“ZX-1059”, a mixture of bisphenol A type epoxy resin and bisphenol F type epoxy resin, manufactured by Nippon Steel Chemical Materials Co., Ltd.), 2.74 parts by weight of phenolic resin containing a triazine skeleton (DIC Corporation “LA-7054”, a 60% solids MEK solution with a hydroxyl equivalent of approximately 125), phenoxy resin (Mitsubishi Chemical Corporation “YL7553BH30”, a 30% solids MEK solution) were prepared. 2.39 parts by mass of a 1:1 solution of cyclohexanone, 0.5 parts by mass of dispersant 1 (the dispersant synthesized in Synthesis Example 1, a polyester dispersant with 5 carbon atoms), 3.0 parts by mass of solvent (cyclohexanone), 0.02 parts by mass of imidazole-based curing accelerator ("2E4MZ", 2-ethyl-4-methylimidazolium, manufactured by Shikoku Chemical Industry Co., Ltd.), and magnetic powder ("MO3S", Fe-Mn ferrite, average particle size 0.4 μm, specific gravity 5.1 m). 2 Magnetic varnish 1 was prepared by mixing 27.91 parts by weight of Powdertech (manufactured by Powdertech) and 93.19 parts by weight of magnetic powder (MA-RCO-24 manufactured by DOWA Electronics, Fe-Ni alloy, average particle size 3.0 μm).

[0343] <Example 2: Preparation of Magnetic Varnish 2>

[0344] In Example 1, the content of dispersant 1 (the dispersant synthesized in Synthesis Example 1, a polyester dispersant with 5 carbon atoms) was changed from 0.5 parts by mass to 1 part by mass. Except for the above, magnetic varnish 2 was prepared in the same manner as in Example 1.

[0345] <Example 3: Preparation of Magnetic Varnish 3>

[0346] In Example 1, the content of dispersant 1 (the dispersant synthesized in Synthesis Example 1, a polyester dispersant with 5 carbon atoms) was changed from 0.5 parts by mass to 0.1 parts by mass. Except for the above, magnetic varnish 3 was prepared in the same manner as in Example 1.

[0347] <Example 4: Preparation of Magnetic Varnish 4>

[0348] In Example 1, 0.5 parts by mass of dispersant 1 (the dispersant synthesized in Synthesis Example 1, a polyester dispersant with 5 carbon atoms) was changed to 0.5 parts by mass of dispersant 2 (the dispersant synthesized in Synthesis Example 2, a polyester dispersant with 4 carbon atoms). Except for the above, magnetic varnish 4 was prepared in the same manner as in Example 1.

[0349] <Example 5: Preparation of Magnetic Varnish 5>

[0350] In Example 1, 0.5 parts by mass of dispersant 1 (the dispersant synthesized in Synthesis Example 1, a polyester dispersant with 5 carbon atoms) was changed to 0.5 parts by mass of dispersant 3 (the dispersant synthesized in Synthesis Example 3, a dispersant containing a polyester with 5 carbon atoms). Except for the above, magnetic varnish 5 was prepared in the same manner as in Example 1.

[0351] <Example 6: Preparation of Magnetic Varnish 6>

[0352] In Example 1, the magnetic powder (“MO3S”, Fe-Mn ferrite, average particle size 0.4 μm, specific gravity 5.1 m³) was used. 2 27.91 parts by weight ( / g, manufactured by Powdertech) were converted into magnetic powder ("MZ03S", Fe-Mn-Zn ferrite, average particle size 0.4μm, specific gravity 5.1m). 2 / g (manufactured by Powdertech) 27.91 parts by weight. Except as described above, magnetic varnish 6 was prepared in the same manner as in Example 1.

[0353] <Comparative Example 1: Preparation of Magnetic Varnish 7>

[0354] In Example 1, 0.5 parts by mass of dispersant 1 (the dispersant synthesized in Synthesis Example 1, a polyester dispersant with 5 carbon atoms) was changed to 0.5 parts by mass of dispersant 4 (the dispersant synthesized in Synthesis Example 4, a polyester dispersant with 11 carbon atoms, Synthesis Example 4). Except for the above, magnetic varnish 7 was prepared in the same manner as in Example 1.

[0355] <Comparative Example 2: Preparation of Magnetic Varnish 8>

[0356] In Example 1, 0.5 parts by mass of dispersant 1 (the dispersant synthesized in Synthesis Example 1, a polyester dispersant with 5 carbon atoms) was changed to 0.5 parts by mass of dispersant 5 (the dispersant synthesized in Synthesis Example 5, a dispersant containing a polyester with 11 carbon atoms). Except for the above, magnetic varnish 8 was prepared in the same manner as in Example 1.

[0357] <Comparative Example 3: Preparation of Magnetic Varnish 9>

[0358] In Example 1, 0.5 parts by mass of dispersant 1 (the dispersant synthesized in Synthesis Example 1, a polyester dispersant with 5 carbon atoms) was replaced with 0.5 parts by mass of dispersant (ED-152, a dispersant without a polyester backbone, manufactured by Kusunoki Chemical Co., Ltd.). Except for the above, magnetic varnish 9 was prepared in the same manner as in Example 1.

[0359] <Comparative Example 4: Preparation of Magnetic Varnish 10>

[0360] In Example 1, 0.5 parts by mass of dispersant 1 (the dispersant synthesized in Synthesis Example 1, a polyester dispersant with 5 carbon atoms) was replaced with 0.5 parts by mass of dispersant (SC-1015F, a dispersant without a polyester backbone, manufactured by Nippon Oil Company). Except for the above, magnetic varnish 10 was prepared in the same manner as in Example 1.

[0361] <Preparation of Resin Sheets>

[0362] On a PET film (Toray Industries' "Lumirror R80", thickness 38 μm, softening point 130°C, hereinafter sometimes referred to as "release PET") that had been treated with an alkyd resin-based release agent (Lintec Corporation's "AL-5"), a magnetic varnish prepared in the examples and comparative examples was applied using a die coater to make the thickness of the dried resin composition layer 100 μm. The film was then dried at 65°C to 115°C (average 100°C) for 7 minutes to obtain a resin sheet.

[0363] <Preparation of sheet-like cured materials>

[0364] Resin sheets were cut into 200mm squares. Using a batch vacuum pressure laminator (Nikko-materials CVP700, a 2-stage stacking laminator), the cut resin sheets (200mm squares) were laminated onto one side of a polyimide film (Ube Industries UPILEX 25S, 25μm thick, 240mm square) with the center of the smooth surface joined together. Lamination was performed by depressurizing for 30 seconds to a pressure below 13hPa, followed by pressing for 30 seconds at 100°C and 0.74MPa. This resulted in a multilayer film consisting of a support, a resin composition layer, and a polyimide film. After peeling off the support, the resin composition layer was thermocured by heating at 190°C for 90 minutes. Then, the polyimide film was peeled off, yielding a sheet-like cured product of the resin composition.

[0365] <Determination of relative permeability and magnetic loss>

[0366] The resulting sheet-like cured material was cut to obtain evaluation samples with a width of 5 mm and a length of 18 mm. For these evaluation samples, the relative permeability (μ') and magnetic loss (μ") were measured using a 3-turn coil method at a measurement frequency of 50 MHz and a room temperature of 23 °C, using an Agilent Technologies HP8362B instrument. Magnetic loss was calculated using the formula tanδ = μ' / μ". Furthermore, the relative permeability was evaluated according to the following criteria.

[0367] 〇: Relative permeability of 20 or higher

[0368] ×: Relative permeability less than 20

[0369] <Determination of Mechanical Strength (Tensive Breaking Strength)>

[0370] The tensile strength of the obtained sheet-like cured material was determined based on JIS K7127. The test results were evaluated according to the following criteria.

[0371] ○:60MPa or more

[0372] ×: Less than 60MPa

[0373] [Table 1]

[0374] (Table 1)

[0375]

[0376] Symbol Explanation

[0377] 10-core substrate

[0378] 10U First Side

[0379] 10D Second Side

[0380] 11Support base plate

[0381] 12 metal layers

[0382] 13 Metal Layers

[0383] 14 Through holes

[0384] 20 Coating Layers

[0385] 30 Resin Sheets

[0386] 31 Resin Composition Layer

[0387] 32 Support body

[0388] 40 magnetic layers

[0389] 40U Grinding Surface

[0390] 40D Grinding Surface

[0391] 50 Conductor Layer

[0392] 51 Patterned Conductor Layer

[0393] 100 Circuit Board

[0394] 200 Inner Layer Substrate

[0395] 200a First Main Surface

[0396] 200b Second Main Surface

[0397] 220 through hole

[0398] 220a Through-hole Wiring

[0399] 240 external terminals

[0400] 300 Magnetic Section

[0401] 310 Resin Sheets

[0402] 320a resin composition layer

[0403] 320 First magnetic layer

[0404] 330 Support

[0405] 340 Second magnetic layer

[0406] 360 via

[0407] 360a Wiring within Vias

[0408] 400 coil-shaped conductive structure

[0409] 420 First Conductor Layer

[0410] 420a pad

[0411] 440 Second conductor layer.

Claims

1. A resin sheet, the resin sheet having: Support body, and A resin composition layer formed of a resin composition is disposed on the support. The resin composition comprises: (A) Magnetic powder, (B) Epoxy resin, (C) Dispersants, (D) Curing agent, and (E) Thermoplastic resins, (C) The component has the polyester backbone shown in the following general formula (1): In general formula (1), R independently represents divalent hydrocarbon groups with 2 to 10 carbon atoms. n represents an integer from 2 to 1000. When the mass of the thermoplastic resin (E) in which the non-volatile component in the resin composition is 100% by mass is set as E1, and the mass of the epoxy resin (B) in which the non-volatile component in the resin composition is 100% by mass is set as B1, the ratio of B1 to E1 is 0.1 or more and 5 or less.

2. The resin sheet according to claim 1, wherein, (C) is produced by reacting a lactone and a hydroxycarboxylic acid, as shown in general formula (2), below. In general formula (2), R 2 Each of the 2 to 10 carbon atoms can be represented independently as a divalent hydrocarbon group.

3. The resin sheet according to claim 1, wherein, When the non-volatile component in the resin composition is set to 100% by mass, the content of component (C) is 0.1% by mass or more and 5% by mass or less.

4. The resin sheet according to claim 1, wherein, When the non-volatile component in the resin composition is set to 100% by mass, the content of component (C) is 0.3% by mass or more.

5. The resin sheet according to claim 1, wherein, When the non-volatile component in the resin composition is set to 100% by mass, the content of component (C) is less than 1% by mass.

6. The resin sheet according to claim 1, wherein, (A) Ingredients include: (A-1) Magnetic powder with an average particle size of 1 μm or larger, and (A-2) Magnetic powder with an average particle size of less than 1 μm.

7. The resin sheet according to claim 1, wherein, (A) Ingredients include: (A-1) Magnetic powders with an average particle size of 1 μm or more and 10 μm or less, and (A-2) Magnetic powder with an average particle size of 0.005 μm or more and less than 1 μm.

8. The resin sheet according to claim 6, wherein, The average particle size of component (A-1) is greater than 1.5 μm.

9. The resin sheet according to claim 6, wherein, The average particle size of component (A-1) is less than 8 μm.

10. The resin sheet according to claim 6, wherein, The average particle size of component (A-2) is above 0.02 μm.

11. The resin sheet according to claim 6, wherein, The average particle size of component (A-2) is less than 0.5 μm.

12. The resin sheet according to claim 1, wherein, (A) The component is selected from at least one of iron oxide powder and ferroalloy metal powder.

13. The resin sheet according to claim 1, wherein, (A) The composition includes iron oxide powder, which contains ferrite, which contains at least one element selected from Ni, Cu, Mn and Zn.

14. The resin sheet according to claim 1, wherein, When the non-volatile component in the resin composition is set to 100% by mass, the content of component (A) is 70% by mass or more and 98% by mass or less.

15. The resin sheet according to claim 1, wherein, When the non-volatile component in the resin composition is set to 100% by mass, the content of component (A) is 90% by mass or more.

16. The resin sheet according to claim 1, wherein, When the non-volatile component in the resin composition is set to 100% by mass, the content of component (A) is 95% by mass or less.

17. The resin sheet according to claim 1, wherein, When the mass of the thermoplastic resin (E) with 100% by mass of non-volatile components in the resin composition is set as E1, and the mass of the epoxy resin (B) with 100% by mass of non-volatile components in the resin composition is set as B1, the ratio of B1 to E1 is 0.5 or more.

18. The resin sheet according to claim 1, wherein, When the mass of the thermoplastic resin (E) with 100% by mass of non-volatile components in the resin composition is set as E1, and the mass of the epoxy resin (B) with 100% by mass of non-volatile components in the resin composition is set as B1, the ratio of B1 to E1 is 1 or less.

19. The resin sheet according to claim 1, wherein, When the non-volatile component in the resin composition is set to 100% by mass, the content of component (B) is 0.1% by mass or more.

20. The resin sheet according to claim 1, wherein, When the non-volatile component in the resin composition is set to 100% by mass, the content of component (B) is 1% by mass or more.

21. The resin sheet according to claim 1, wherein, When the non-volatile component in the resin composition is set to 100% by mass, the content of component (B) is less than 5% by mass.

22. The resin sheet according to claim 1, wherein, When the non-volatile component in the resin composition is set to 100% by mass, the content of component (B) is less than 2% by mass.

23. The resin sheet according to claim 1, wherein, When the non-volatile component in the resin composition is set to 100% by mass, the content of component (D) is 0.1% by mass or more.

24. The resin sheet according to claim 1, wherein, When the non-volatile component in the resin composition is set to 100% by mass, the content of component (D) is 1% by mass or more.

25. The resin sheet according to claim 1, wherein, When the non-volatile component in the resin composition is set to 100% by mass, the content of component (D) is less than 5% by mass.

26. The resin sheet according to claim 1, wherein, When the non-volatile component in the resin composition is set to 100% by mass, the content of component (D) is less than 3% by mass.

27. The resin sheet according to claim 1, wherein, When the non-volatile component in the resin composition is set to 100% by mass, the content of component (E) is 0.1% by mass or more.

28. The resin sheet according to claim 1, wherein, When the non-volatile component in the resin composition is set to 100% by mass, the content of component (E) is 0.3% by mass or more.

29. The resin sheet according to claim 1, wherein, When the non-volatile component in the resin composition is set to 100% by mass, the content of component (E) is less than 5% by mass.

30. The resin sheet according to claim 1, wherein, When the non-volatile component in the resin composition is set to 100% by mass, the content of component (E) is less than 2% by mass.

31. The resin sheet according to claim 1, used to form a magnetic layer of a circuit board.

32. The resin sheet according to claim 1, used for filling through holes.

33. A circuit board comprising a magnetic layer, the magnetic layer being a cured product of a resin composition layer of a resin sheet according to any one of claims 1 to 32.

34. A circuit board comprising: A substrate with through-holes is formed, and The magnetic layer filling the through hole, The magnetic layer comprises a cured resin composition layer of the resin sheet according to any one of claims 1 to 32.

35. An inductor component comprising the circuit board of claim 33.

36. A resin composition comprising: (A) Magnetic powder, (B) Epoxy resin, (C) Dispersants, (D) Curing agent, and (E) Thermoplastic resins, When the mass of the thermoplastic resin (E) in the resin composition is 100% by mass, and the mass of the epoxy resin (B) in the resin composition is 100% by mass, is defined as E1, the ratio of B1 to E1 is 0.1 or more and 5 or less. (C) The component has the polyester backbone shown in the following general formula (1): In general formula (1), R independently represents divalent hydrocarbon groups with 2 to 10 carbon atoms. n represents an integer from 2 to 1000.

37. The resin composition according to claim 36, wherein, When the mass of the thermoplastic resin (E) with 100% by mass of non-volatile components in the resin composition is set as E1, and the mass of the epoxy resin (B) with 100% by mass of non-volatile components in the resin composition is set as B1, the ratio of B1 to E1 is 0.5 or more.

38. The resin composition according to claim 36, wherein, When the mass of the thermoplastic resin (E) with 100% by mass of non-volatile components in the resin composition is set as E1, and the mass of the epoxy resin (B) with 100% by mass of non-volatile components in the resin composition is set as B1, the ratio of B1 to E1 is 1 or less.

39. The resin composition according to claim 36, wherein, When the non-volatile component in the resin composition is set to 100% by mass, the content of component (A) is 70% by mass or more.

40. The resin composition according to claim 36, wherein, When the non-volatile component in the resin composition is set to 100% by mass, the content of component (A) is 90% by mass or more.

41. The resin composition according to claim 36, wherein, When the non-volatile component in the resin composition is set to 100% by mass, the content of component (A) is 98% by mass or less.

42. The resin composition according to claim 36, wherein, When the non-volatile component in the resin composition is set to 100% by mass, the content of component (A) is 95% by mass or less.

43. The resin composition according to claim 36, wherein, When the non-volatile component in the resin composition is set to 100% by mass, the content of component (B) is 0.1% by mass or more.

44. The resin composition according to claim 36, wherein, When the non-volatile component in the resin composition is set to 100% by mass, the content of component (B) is 1% by mass or more.

45. The resin composition according to claim 36, wherein, When the non-volatile component in the resin composition is set to 100% by mass, the content of component (B) is less than 5% by mass.

46. ​​The resin composition according to claim 36, wherein, When the non-volatile component in the resin composition is set to 100% by mass, the content of component (B) is less than 2% by mass.

47. The resin composition according to claim 36, wherein, When the non-volatile component in the resin composition is set to 100% by mass, the content of component (C) is 0.1% by mass or more.

48. The resin composition according to claim 36, wherein, When the non-volatile component in the resin composition is set to 100% by mass, the content of component (C) is 0.3% by mass or more.

49. The resin composition according to claim 36, wherein, When the non-volatile component in the resin composition is set to 100% by mass, the content of component (C) is 0.1% by mass or more and 5% by mass or less.

50. The resin composition according to claim 36, wherein, When the non-volatile component in the resin composition is set to 100% by mass, the content of component (C) is less than 1% by mass.

51. The resin composition according to claim 36, wherein, When the non-volatile component in the resin composition is set to 100% by mass, the content of component (D) is 0.1% by mass or more.

52. The resin composition according to claim 36, wherein, When the non-volatile component in the resin composition is set to 100% by mass, the content of component (D) is 1% by mass or more.

53. The resin composition according to claim 36, wherein, When the non-volatile component in the resin composition is set to 100% by mass, the content of component (D) is less than 5% by mass.

54. The resin composition according to claim 36, wherein, When the non-volatile component in the resin composition is set to 100% by mass, the content of component (D) is less than 3% by mass.

55. The resin composition according to claim 36, wherein, When the non-volatile component in the resin composition is set to 100% by mass, the content of component (E) is 0.1% by mass or more.

56. The resin composition according to claim 36, wherein, When the non-volatile component in the resin composition is set to 100% by mass, the content of component (E) is 0.3% by mass or more.

57. The resin composition according to claim 36, wherein, When the non-volatile component in the resin composition is set to 100% by mass, the content of component (E) is less than 5% by mass.

58. The resin composition according to claim 36, wherein, When the non-volatile component in the resin composition is set to 100% by mass, the content of component (E) is less than 2% by mass.

59. A circuit board comprising a magnetic layer, the magnetic layer being a cured product of the resin composition of claim 36.

60. A circuit board having: Substrate with through holes, and The cured product of the resin composition of claim 36 filled in the through-hole.

61. An inductor component comprising the circuit board of claim 59 or 60.

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