resin sheet

Abstract

Providing resin sheets, etc., capable of obtaining a cured product with high relative permeability and excellent mechanical strength. A resin sheet having a support and a resin composition layer formed by a resin composition provided on the support, A resin composition, (A) Magnetic powder, (B) Epoxy resin, (C) Dispersant, (D) Curing agent and (E) Includes a thermoplastic resin, (C) A resin sheet having a polyester backbone represented by the following chemical formula (1). [Chemical Formula (1)] In chemical formula (1), R independently represents a divalent hydrocarbon group having 2 to 10 carbon atoms, and n represents an integer from 2 to 1,000.

Description

Technology Field

[0001] The present invention relates to a resin sheet, a resin composition, and a circuit board and an inductor component using said resin sheet or resin composition. Background Technology

[0002] Inductor-embedded substrates, which embed inductors in circuit boards such as printed circuit boards, are generally formed using a resin composition containing magnetic powder. Regarding the inductor included in the inductor-embedded substrate, methods are known to increase the content of magnetic powder in the resin composition or to increase the effective permeability of the magnetic layer, which is a cured product of the resin composition, in order to increase the inductance thereof.

[0003] For example, Patent Document 1 describes a resin sheet highly filled with magnetic fillers having an average particle diameter of 10 μm or more. Prior art literature

[0004] Japanese Patent Publication No. JP 2014-127624 The problem to be solved

[0005] Recently, there has been a demand to increase inductance. To increase the relative permeability of an inductor, one might consider increasing the content of magnetic powder; however, increasing the content of magnetic powder can sometimes lead to a decrease in the mechanical strength (tensile breaking strength) of the magnetic layer.

[0006] To increase relative permeability, one might consider using magnetic powder with a large average particle diameter or flattened magnetic powder, but using such magnetic powder can increase magnetic losses and degrade the performance of the inductor. Additionally, one might consider using magnetic powder with a small average particle diameter, but using such magnetic powder tends to reduce magnetic losses but tends to reduce relative permeability.

[0007] The present invention, made in consideration of the above circumstances, aims to provide a resin sheet, a resin composition, and a circuit board and an inductor component using said resin sheet or resin composition, which can obtain a cured product having high relative permeability and excellent mechanical strength. means of solving the problem

[0008] The inventors, having conducted diligent research to achieve the above objective, discovered that by using a resin sheet comprising a resin composition layer formed by a resin composition containing a dispersant having a polyester backbone, the relative permeability of the cured resin composition layer is high and the mechanical strength is excellent, thereby completing the present invention.

[0009] That is, the present invention includes the following contents.

[0010] [1] A resin sheet having a resin composition layer formed by a resin composition provided on the support, and a resin composition layer formed by a resin composition provided on the support,

[0011] A resin composition,

[0012] (A) Magnetic powder,

[0013] (B) Epoxy resin,

[0014] (C) Dispersant,

[0015] (D) Curing agent and

[0016] (E) Includes a thermoplastic resin,

[0017] (C) A resin sheet having a polyester backbone represented by the following chemical formula (1).

[0018] [Chemical Formula (1)]

[0019]

[0020] (In chemical formula (1), R each independently represents a divalent hydrocarbon group having 2 to 10 carbon atoms, and n represents an integer from 2 to 1,000.)

[0021] [2] (C) A resin sheet described in [1], wherein the content of the component is 0.1 mass% or more and 5 mass% or less when the non-volatile component in the resin composition is 100 mass%.

[0022] [3] A resin sheet described in [1] or [2], comprising (A) a magnetic powder with an average particle diameter of 1 μm or more and (A-2) a magnetic powder with an average particle diameter of less than 1 μm.

[0023] [4] A resin sheet described in any one of [1] to [3], comprising (A) a component, (A-1) a magnetic powder with an average particle diameter of 1 μm or more and 10 μm or less, and (A-2) a magnetic powder with an average particle diameter of 0.005 μm or more and less than 1 μm.

[0024] [5] (A) A resin sheet described in any one of [1] to [4], wherein the component is at least one selected from iron oxide powder and iron alloy metal powder.

[0025] [6] (A) A resin sheet described in any one of [1] to [5], comprising a ferrite in which the iron oxide is selected from at least one of Ni, Cu, Mn and Zn.

[0026] [7] (A) A resin sheet described in any one of [1] to [6], wherein the content of the component is 70 mass% or more and 98 mass% or less when the non-volatile component in the resin composition is 100 mass%.

[0027] [8] A resin sheet described in any one of [1] to [7], wherein the mass of (E) thermoplastic resin is E1 when the non-volatile component in the resin composition is 100 mass%, and the mass of (B) epoxy resin is B1 when the non-volatile component in the resin composition is 100 mass%, and B1 / E1 is 0.1 or more and 5 or less.

[0028] [9] A resin sheet described in any one of [1] to [8] for forming a magnetic layer of a circuit board.

[0029]

[10] A resin sheet for through-hole filling, described in any one of [1] to [9].

[0030]

[11] A circuit board comprising a magnetic layer which is a cured product of a resin composition layer of a resin sheet described in any one of [1] to

[10] .

[0031]

[12] A substrate having a through hole formed therein and a magnetic layer filled in the through hole, and

[0032] A circuit board in which the magnetic layer comprises a cured resin composition layer of a resin sheet described in any one of [1] to

[10] .

[0033]

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

[11] or

[12] .

[0034]

[14] (A) Magnetic powder,

[0035] (B) Epoxy resin,

[0036] (C) Dispersant,

[0037] (D) Curing agent and

[0038] (E) A resin composition comprising a thermoplastic resin,

[0039] When the non-volatile component in the resin composition is 100 mass%, let E1 be the mass of (E) thermoplastic resin, and when the non-volatile component in the resin composition is 100 mass%, let B1 be the mass of (B) epoxy resin, and B1 / E1 is 0.1 or greater and 5 or less, and

[0040] (C) A resin composition having a polyester backbone represented by the following chemical formula (1).

[0041] [Chemical Formula (1)]

[0042]

[0043] (In chemical formula (1), R each independently represents a divalent hydrocarbon group having 2 to 10 carbon atoms, and n represents an integer from 2 to 1,000.)

[0044]

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

[14] .

[0045]

[16] A circuit board having a through hole and a cured resin composition described in

[14] filled in the through hole.

[0046]

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

[15] or

[16] . Effects of the invention

[0047] According to the present invention, a resin sheet capable of obtaining a cured product having high relative permeability and excellent mechanical strength, and a circuit board and inductor component using said resin sheet can be provided. Brief explanation of the drawing

[0048] [Fig. 1] Fig. 1 is a cross-sectional view schematically showing a core substrate before a through-hole is formed in a method for manufacturing a circuit board of a first embodiment. [Fig. 2] Fig. 2 is a cross-sectional view schematically showing a core substrate with through holes formed therein in a method for manufacturing a circuit board of a first embodiment. [Fig. 3] Fig. 3 is a cross-sectional view schematically showing a core substrate in which a plating layer is formed in a through hole in a method for manufacturing a circuit board of a first embodiment. [Fig. 4] Fig. 4 is a cross-sectional view schematically showing the lamination of a core substrate and a resin sheet in a method for manufacturing a circuit board of the first embodiment. [Fig. 5] Fig. 5 is a cross-sectional view schematically showing a core substrate and a resin sheet laminated in a method for manufacturing a circuit board of the first embodiment. [Fig. 6] Fig. 6 is a schematic cross-sectional view for explaining the process (2) of the method for manufacturing a circuit board of the first embodiment. [Fig. 7] Fig. 7 is a schematic cross-sectional view for explaining the process (3) of the method for manufacturing a circuit board of the first embodiment. [Fig. 8] Fig. 8 is a schematic cross-sectional view for explaining the process (5) of the method for manufacturing a circuit board of the first embodiment. [Fig. 9] Fig. 9 is a schematic cross-sectional view for explaining the process (5) of the method for manufacturing a circuit board of the first embodiment. [Fig. 10] Fig. 10 is a schematic cross-sectional view illustrating process (A) of the method for manufacturing a circuit board of the second embodiment. [Fig. 11] Fig. 11 is a schematic cross-sectional view illustrating process (A) of the method for manufacturing a circuit board of the second embodiment. [Fig. 12] Fig. 12 is a schematic cross-sectional view illustrating process (B) of the method for manufacturing a circuit board of the second embodiment. [Fig. 13] Fig. 13 is a schematic cross-sectional view illustrating process (D) of the method for manufacturing a circuit board of the second embodiment. [Fig. 14] Fig. 14 is a schematic plan view of an inductor component including a circuit board obtained by the method of manufacturing a circuit board of the second embodiment, viewed from one side in the thickness direction. [Fig. 15] Fig. 15 is a schematic drawing showing a cross-section of an inductor component including a circuit board obtained by the method of manufacturing a circuit board of the second embodiment, cut at the position indicated by the dashed line II-II. [Fig. 16] Fig. 16 is a schematic plan view for explaining the configuration of a first conductor layer in an inductor component including a circuit board obtained by the method of manufacturing a circuit board of a second embodiment. Specific details for implementing the invention

[0049] Hereinafter, embodiments of the present invention will be described with reference to the drawings. Furthermore, each drawing merely illustrates the shape, size, and arrangement of components in a schematic manner to enable an understanding of the invention. The present invention is not limited to the description below, and each component may be appropriately modified. In the drawings used in the description below, identical components are indicated by the same reference numerals, and redundant descriptions may be omitted. Additionally, the configurations of the embodiments of the present invention are not necessarily manufactured or used in the arrangement of the illustrated examples.

[0050] [Resin Sheet]

[0051] The resin sheet of the present invention is a resin sheet having a support and a resin composition layer formed by a resin composition provided on the support, wherein the resin composition comprises (A) a magnetic powder, (B) an epoxy resin, (C) a dispersant, (D) a curing agent, and (E) a thermoplastic resin, and the component (C) has a polyester backbone represented by the following chemical formula (1).

[0052] [Chemical Formula (1)]

[0053]

[0054] (In chemical formula (1), R each independently represents a hydrocarbon group having 2 to 10 carbon atoms, and n represents an integer from 2 to 1,000.)

[0055] In the present invention, by incorporating (C) a dispersant into the resin composition, a cured product with high relative permeability and excellent mechanical strength can be obtained. In addition, the cured product can generally reduce magnetic loss. The above applies to each layer constituting the resin sheet.

[0056] Support structure

[0057] Examples of supports include a film made of plastic material, a metal foil, and a release liner; a film made of plastic material and a metal foil are preferred, and a film made of plastic material is more preferred.

[0058] When a film made of a plastic material is used as a support, the plastic material may be, for example, polyesters such as polyethylene terephthalate (hereinafter abbreviated as "PET") and polyethylene naphthalate (hereinafter abbreviated as "PEN"); polycarbonate (hereinafter abbreviated as "PC"); acrylic polymers such as polymethyl methacrylate (hereinafter abbreviated as "PMMA"); cyclic polyolefins; triacetylcellulose (hereinafter abbreviated as "TAC"); polyether sulfide (hereinafter abbreviated as "PES"); polyether ketones; polyimides, etc. Among these, polyethylene terephthalate and polyethylene naphthalate are preferred, and inexpensive polyethylene terephthalate is particularly preferred.

[0059] When using a metal foil as a support, examples of metal foils include copper foil and aluminum foil. Among these, copper foil is preferred. As for the copper foil, a foil made of copper may be used, or a foil made of an alloy of copper and other metals (e.g., tin, chromium, silver, magnesium, nickel, zirconium, silicon, titanium, etc.) may be used.

[0060] The support may have treatments such as mat treatment, corona treatment, and antistatic treatment performed on the surface bonded to the resin composition layer.

[0061] In addition, as a support, a support with a release layer attached having a release layer on the surface bonded to the resin composition layer may be used. As for the release agent used in the release layer of the support with the release layer attached, for example, one or more release agents selected from the group consisting of alkyd resin, polyolefin resin, urethane resin, and silicone resin may be used. As commercially available release agents, for example, alkyd resin-based release agents such as "SK-1," "AL-5," and "AL-7" manufactured by Lintec Co., Ltd. may be used. In addition, as a support with a release layer attached, for example, "Lumira T60" manufactured by Tore Co., Ltd.; "Purex" manufactured by Teijin Co., Ltd.; and "Unifil" manufactured by Unichika Co., Ltd. may be used.

[0062] The thickness of the support is preferably in the range of 5㎛ to 75㎛, and more preferably in the range of 10㎛ to 60㎛. In addition, when using a support with a release layer attached, it is preferable that the total thickness of the support with the release layer attached is within the above range.

[0063] <Resin composition layer>

[0064] In the resin sheet of the present invention, the resin composition layer provided on the support is formed by the resin composition, and the resin composition comprises (A) magnetic powder, (B) epoxy resin, (C) dispersant, (D) curing agent and (E) thermoplastic resin, and the component (C) has a polyester backbone represented by the following chemical formula (1).

[0065] [Chemical Formula (1)]

[0066]

[0067] (In chemical formula (1), R each independently represents a hydrocarbon group having 2 to 10 carbon atoms, and n represents an integer from 2 to 1,000.)

[0068] The resin composition may additionally include any component in combination with components (A) to (E). Examples of optional components include (F) other additives and (G) solvents. Each component included in the resin composition will be described in detail below.

[0069] -(A) Magnetic powder-

[0070] The resin composition contains (A) magnetic powder as (A) component. As (A) magnetic powder, particles of a material having a relative permeability greater than 1 may be used. The material of (A) magnetic powder is usually an inorganic material, and may be a soft magnetic material or a hard magnetic material. (A) magnetic powder may be used as a single type or two or more types may be used in combination. Accordingly, (A) magnetic powder may be a soft magnetic powder, a hard magnetic powder, or a combination of a soft magnetic powder and a hard magnetic powder.

[0071] (A) As a magnetic powder, for example, pure iron powder; Mg-Zn ferrite, Fe-Mn ferrite, Mn-Zn ferrite, Mn-Mg ferrite, Cu-Zn ferrite, Mg-Mn-Sr ferrite, Ni-Zn ferrite, Ba-Zn ferrite, Ba-Mg ferrite, Ba-Ni ferrite, Ba-Co ferrite, Ba-Ni-Co ferrite, Y ferrite, iron oxide (III), iron oxide such as triiron tetroxide; Examples include iron alloy-based metal powders such as 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; and amorphous alloys such as Co-based amorphous alloys.

[0072] Among these, (A) as the magnetic powder, it is preferable to have at least one selected from iron oxide powder and iron alloy-based metal powder. As the iron oxide powder, it is preferable to have a ferrite containing at least one selected from Ni, Cu, Mn and Zn, and more preferable to have a ferrite containing either Mn or Zn. In addition, as the iron alloy-based metal powder, it is preferable to have an iron alloy-based metal powder containing at least one selected from Si, Cr, Al, Ni and Co, and more preferable to have an iron alloy-based metal powder containing Ni.

[0073] (A) As the magnetic powder, commercially available magnetic powders may be used. Specific examples of commercially available magnetic powders that can be used include “M03S”, “M05S”, “MZ03S”, and “M001” manufactured by Powder Tech; “MA-RCO-24” manufactured by DOWA Electronics; “PST-S” manufactured by Sanyo Tokushu Seco; and “AW2-08”, “AW2-08PF20F”, “AW2-08PF10F”, “AW2-08PF3F”, “Fe-3.5Si-4.5CrPF20F”, “Fe-50NiPF20F”, and “Fe-80Ni-4MoPF20F” manufactured by Epson Atomics. "LD-M", "LD-MH", "KNI-106", "KNI-106GSM", "KNI-106GS", "KNI-109", "KNI-109GSM", "KNI-109GS" manufactured by JFE Chemicals; "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; "JR09P2" manufactured by Nippon Chukagaku Kogyo; "Nanotek" manufactured by CIK Nanotec; Examples include “JEMK-S” and “JEMK-H” manufactured by Kinsei Ematec Co., Ltd.; and “Yttrium iron oxide” manufactured by ALDRICH Co., Ltd.

[0074] (A) While a single type of magnetic powder may be used, it is preferable to use two or more types in combination to obtain the effects of the present invention significantly.

[0075] (A) It is preferable that the magnetic powder be spherical. The value obtained by dividing the length of the major axis of the magnetic powder by the length of the minor axis (aspect ratio) is preferably 2 or less, more preferably 1.5 or less, and even more preferably 1.2 or less. In general, it is easier to improve the relative permeability of the magnetic powder if it has a flat shape rather than a spherical shape. However, it is particularly preferable to use spherical magnetic powder from the perspective of generally lowering magnetic loss.

[0076] (A) The average particle diameter of the magnetic powder is preferably 0.01 μm or more, more preferably 0.5 μm or more, and even more preferably 1 μm or more, from the perspective of improving relative permeability. In addition, it is preferably 10 μm or less, more preferably 9 μm or less, and even more preferably 8 μm or less. In addition, when two or more types of (A) magnetic powder are used in combination, it is acceptable for the average particle diameter of the entire (A) component to be within this range.

[0077] The average particle diameter of magnetic powder can be measured by a laser diffraction scattering method based on the Mie scattering theory. Specifically, the average particle diameter can be measured by creating a particle diameter distribution of magnetic powder on a volume basis using a laser diffraction scattering type particle diameter distribution measuring device and taking the median diameter as the average particle diameter. Preferably, the measurement sample can be a magnetic powder dispersed in water by ultrasound. As a laser diffraction scattering type particle diameter distribution measuring device, the "LA-500" manufactured by Horiba Sesakusho Co., Ltd., the "SALD-2200" manufactured by Shimadzu Sesakusho Co., Ltd., etc., can be used.

[0078] (A) The specific surface area of ​​the magnetic powder is preferably 0.05 m² / g or more, more preferably 0.1 m² / g or more, and even more preferably 0.3 m² / g or more, from the perspective of improving relative permeability. In addition, it is preferably 10 m² / g or less, more preferably 8 m² / g or less, and even more preferably 5 m² / g or less. (A) The specific surface area of ​​the magnetic powder can be measured by the BET method. In addition, when two or more types of (A) magnetic powders are used in combination, it is preferable that the specific surface area of ​​the entire (A) component be within this range.

[0079] (A) In order to improve relative permeability, it is preferable that the magnetic powder comprises (A-1) a magnetic powder with an average particle diameter of 1 μm or more and (A-2) a magnetic powder with an average particle diameter of less than 1 μm.

[0080] (A-1) The average particle diameter of the magnetic powder having an average particle diameter of 1 μm or more is 1 μm or more, preferably 1.2 μm or more, more preferably 1.5 μm or more. (A-1) The upper limit of the average particle diameter of the component is preferably 10 μm or less, more preferably 9 μm or less, and even more preferably 8 μm or less. (A-1) The average particle diameter of the component can be measured by the above method.

[0081] (A-1) The specific surface area of ​​the component is preferably 0.01 m² / g or more, more preferably 0.05 m² / g or more, and even more preferably 0.1 m² / g or more. Additionally, it is preferably 2 m² / g or less, more preferably 1.5 m² / g or less, and even more preferably 1 m² / g or less. (A-1) The specific surface area of ​​the component can be measured by the above method.

[0082] (A-2) The average particle diameter of the magnetic powder with an average particle diameter of less than 1 μm is less than 1 μm, preferably 0.8 μm or less, more preferably 0.5 μm or less. (A-2) The lower limit of the average particle diameter 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. (A-2) The average particle diameter of the component can be measured by the above method.

[0083] (A-2) The specific surface area of ​​the component is preferably 1 m² / g or more, more preferably 2 m² / g or more, and even more preferably 3 m² / g or more. Additionally, it is preferably 500 m² / g or less, more preferably 400 m² / g or less, and even more preferably 300 m² / g or less. (A-2) The specific surface area of ​​the component can be measured by the above method.

[0084] (A) As a preferred embodiment of the component, it is preferable to include (A-1) a magnetic powder with an average particle diameter of 1 μm or more and 10 μm or less and (A-2) a magnetic powder with an average particle diameter of 0.005 μm or more and less than 1 μm, more preferable to include (A-1) a magnetic powder with an average particle diameter of 1.2 μm or more and 9 μm or less and (A-2) a magnetic powder with an average particle diameter of 0.01 μm or more and less than 0.8 μm, and even more preferable to include (A-1) a magnetic powder with an average particle diameter of 1.5 μm or more and 8 μm or less and (A-2) a magnetic powder with an average particle diameter of 0.02 μm or more and less than 0.5 μm.

[0085] (A) The content (volume%) of the magnetic powder is preferably 40 volume% or more, more preferably 50 volume% or more, and even more preferably 60 volume% or more, when the non-volatile component in the resin composition is 100 volume%, in order to improve relative permeability and reduce the loss factor. In addition, it is preferably 85 volume% or less, more preferably 80 volume% or less, and even more preferably 70 volume% or less.

[0086] (A) The content (mass%) of the magnetic powder is preferably 70 mass% or more, more preferably 75 mass% or more, even more preferably 80 mass% or more, and 90 mass% or more, when the non-volatile component in the resin composition is 100 mass%, in order to improve relative permeability and reduce the loss factor. In addition, it is preferably 98 mass% or less, more preferably 97 mass% or less, even more preferably 96 mass% or less, and 95 mass% or less.

[0087] In addition, in the present invention, the content of each component in the resin composition is, unless otherwise specified, the value when the non-volatile component in the resin composition is 100 mass%.

[0088] When component (A) includes components (A-1) and (A-2), the content (mass%) of component (A-1) is preferably 50 mass% or more, more preferably 60 mass% or more, and even more preferably 70 mass% or more, when the non-volatile component in the resin composition is 100 mass%, in order to improve relative permeability and reduce the loss factor. In addition, it is preferably 90 mass% or less, more preferably 85 mass% or less, and even more preferably 80 mass% or less.

[0089] When component (A) includes component (A-1) and component (A-2), the content (mass%) of component (A-2) is preferably 10 mass% or more, more preferably 15 mass% or more, and even more preferably 20 mass% or more, when the non-volatile component in the resin composition is 100 mass%, in order to improve relative permeability and reduce the loss factor. In addition, it is preferably 50 mass% or less, more preferably 40 mass% or less, and even more preferably 30 mass% or less.

[0090] When the content of component (A-1) is set to 100 mass% of the non-volatile component in the resin composition, the content of component (A-2) is set to a1 (mass%), and when the content of component (A-2) is set to 100 mass% of the non-volatile component in the resin composition, the content of component (A-2) is set to a2. In this case, 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 falls within this range, it becomes possible to obtain the desired effect of the present invention more significantly.

[0091] -(B) Epoxy Resin-

[0092] The resin composition contains (B) epoxy resin as component (B). As (B) epoxy resin, for example, bisphenol A type epoxy resin; bisphenol F type epoxy resin; bisphenol S type epoxy resin; bisphenol AF type epoxy resin; dicyclopentadiene type epoxy resin; trisphenol type epoxy resin; phenol novolak type epoxy resin; tert-butyl-catechol type epoxy resin; epoxy resin having a condensed ring structure such as naphthol novolak type epoxy resin, naphthalene type epoxy resin, naphthol type epoxy resin, anthracene type epoxy resin; glycidylamine type epoxy resin; glycidyl ester type epoxy resin; cresol novolak type epoxy resin; biphenyl type epoxy resin; linear aliphatic epoxy resin; epoxy resin having a butadiene structure; alicyclic epoxy resin; heterocyclic epoxy resin; spiro-ring containing epoxy resin; cyclohexanedimethanol type epoxy resin; trimethylol type epoxy resin; tetraphenylethane type epoxy resin; Examples include cyclic aliphatic diglycidyl ether-type epoxy resins. The epoxy resin may be used as a single type or in combination of two or more types. (B) The epoxy resin is preferably one or more selected from bisphenol A-type epoxy resin and bisphenol F-type epoxy resin, and it is more preferable to include bisphenol A-type epoxy resin and bisphenol F-type epoxy resin.

[0093] (B) It is preferable that the epoxy resin comprises an epoxy resin having two or more epoxy groups in one molecule. In addition, it is preferable that the epoxy resin (B) has an aromatic structure, and when two or more types of epoxy resins are used, it is more preferable that at least one type has an aromatic structure. An aromatic structure is a chemical structure generally defined as aromatic, and includes polycyclic aromatics and aromatic heterocyclic groups. With respect to 100 mass% of the non-volatile component of the epoxy resin, the proportion of the epoxy resin having two or more epoxy groups in one molecule is preferably 50 mass% or more, more preferably 60 mass% or more, and particularly preferably 70 mass% or more.

[0094] Epoxy resins include epoxy resins that are in a liquid state at a temperature of 25°C (hereinafter referred to as "liquid epoxy resin") and epoxy resins that are in a solid state at a temperature of 25°C (hereinafter referred to as "solid epoxy resin"). The resin composition may include only liquid epoxy resin as (B) epoxy resin, may include only solid epoxy resin, or may include a combination of liquid epoxy resin and solid epoxy resin, but it is preferable to include only liquid epoxy resin from the viewpoint of lowering the viscosity of the resin composition.

[0095] As for the liquid epoxy resin, 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, glycidylamine-type epoxy resin, phenol novolak-type resin, alicyclic epoxy resin having an ester backbone, cyclohexanedimethanol-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 having a butadiene structure are preferred, and bisphenol A-type epoxy resin and bisphenol F-type epoxy resin are more preferred. Specific examples of the liquid epoxy resin include “HP4032”, “HP4032D”, and “HP4032SS” (naphthalene-type epoxy resin) manufactured by DIC; "828US", "jER828EL" (Bisphenol A type epoxy resin), "jER807" (Bisphenol F type epoxy resin), "jER152" (Phenol novolak type epoxy resin) manufactured by Mitsubishi Chemical Corporation; "630", "630LSD" manufactured by Mitsubishi Chemical Corporation, "ED-523T" (Glycyrol type epoxy resin (Adecaglycyrol)), "EP-3980S" (Glycidylamine type epoxy resin), "EP-4088S" (Dicyclopentadiene type epoxy resin) manufactured by ADEKA Corporation; Examples include "ZX1059" (a mixture of bisphenol A type epoxy resin and bisphenol F type epoxy resin) and "EX-201" (cyclic aliphatic glycidyl ether type epoxy resin) manufactured by Nittetsu Chemical & Materials, "ZX1658" and "ZX1658GS" (cyclic aliphatic diglycidyl ether type epoxy resin); "EX-721" (glycidyl ester type epoxy resin) manufactured by Nagase Chemtex; and "Celoxide 2021P" (alicyclic epoxy resin having an ester backbone) and "PB-3600" (epoxy resin having a butadiene structure) manufactured by Daicel. These may be used individually or in combination of two or more types.

[0096] As for solid epoxy resins, naphthalene-type tetrafunctional epoxy resin, cresol novolak-type epoxy resin, dicyclopentadiene-type epoxy resin, trisphenol-type epoxy resin, naphthol-type epoxy resin, biphenyl-type epoxy resin, naphthylene ether-type epoxy resin, anthracene-type epoxy resin, bisphenol A-type epoxy resin, and tetraphenylethane-type epoxy resin are preferred. Specific examples of solid-phase epoxy resins include “HP4032H” (naphthalene-type epoxy resin), “HP-4700”, “HP-4710” (naphthalene-type tetrafunctional epoxy resin), “N-690” (cresol novolak-type epoxy resin), “N-695” (cresol novolak-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 “HP6,000” (naphtylene ether-type epoxy resin) manufactured by DIC. "EPPN-502H" (trisphenol-type epoxy resin), "NC7000L" (naphthol novolak-type epoxy resin), "NC3000H", "NC3000", "NC3000L", "NC3100" (biphenyl-type epoxy resin) manufactured by Nippon Kayaku Co., Ltd.; "ESN475V" (naphthalene-type epoxy resin); "ESN485" (naphthol novolak-type epoxy resin) manufactured by Nittetsu Chemical & Materials Co., Ltd.; "YX4000H", "YL6121" (biphenyl-type epoxy resin), "YX4000HK" (bicylenol-type epoxy resin), "YX8800" (anthracene-type epoxy resin) manufactured by Mitsubishi Chemical Co., Ltd.; Examples include “PG-100” and “CG-500” manufactured by Osaka Gas Chemical Co., Ltd., and “YL7760” (bisphenol AF type epoxy resin), “YL7800” (fluorene type epoxy resin), “jER1010” (solid bisphenol A type epoxy resin), and “jER1031S” (tetraphenylethane type epoxy resin) manufactured by Mitsubishi Chemical Co., Ltd. These may be used individually or in combination of two or more types.

[0097] (B) When liquid epoxy resin and solid epoxy resin are used together as epoxy resins, the ratio of liquid epoxy resin to solid epoxy resin is preferably in the range of 1:0.1 to 1:4 in terms of mass ratio. By setting the ratio of liquid epoxy resin to solid epoxy resin to this range, effects such as obtaining a cured product with sufficient rupture strength are obtained. In view of the above effects, the ratio of liquid epoxy resin to solid epoxy resin (liquid epoxy resin to solid epoxy resin) is more preferably in the range of 1:0.3 to 1:3.5 in terms of mass ratio, even more 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.

[0098] (B) The content of the epoxy resin is preferably 0.1 mass% or more, more preferably 0.3 mass% or more, even more preferably 0.5 mass% or more, and 1 mass% or more, when the non-volatile component in the resin composition is 100 mass%, in order to obtain a magnetic layer exhibiting good mechanical strength. The upper limit of the content of the epoxy resin is not particularly limited as long as the effects of the present invention are exhibited, but is preferably 5 mass% or less, more preferably 3 mass% or less, and even more preferably 2 mass% or less.

[0099] (B) The content of the epoxy resin (volume %) is preferably 1 mass% or more, more preferably 3 mass% or more, and even more preferably 5 mass% or more, when the non-volatile component in the resin composition is 100 volume%. The upper limit is not particularly limited as long as the effects of the present invention are observed, but is preferably 25 mass% or less, more preferably 20 mass% or less, and even more preferably 15 mass% or less.

[0100] (B) The epoxy equivalent of the epoxy resin is preferably 50 g / eq. to 5,000 g / eq., more preferably 50 g / eq. to 3,000 g / eq., even more preferably 80 g / eq. to 2,000 g / eq., and even more preferably 110 g / eq. to 1,000 g / eq. By being within this range, the crosslinking density of the cured product becomes sufficient, allowing for the formation of a magnetic layer with low surface roughness. Additionally, the epoxy equivalent can be measured according to JIS K7236 and is the mass of a resin containing 1 equivalent of an epoxy group.

[0101] (B) The weight average molecular weight of the epoxy resin is preferably 100 to 5,000, more preferably 250 to 3,000, and even more preferably 400 to 1,500. Here, the weight average molecular weight of the epoxy resin is the weight average molecular weight in polystyrene equivalent measured by gel permeation chromatography (GPC).

[0102] -(C) Dispersant-

[0103] The resin composition contains, as a component (C), a dispersant having a polyester backbone represented by the following chemical formula (1).

[0104] [Chemical Formula (1)]

[0105]

[0106] (In chemical formula (1), R each independently represents a divalent hydrocarbon group having 2 to 10 carbon atoms, and n represents an integer from 2 to 1,000.)

[0107] As mentioned above, if the content of (A) magnetic powder is increased to improve the relative permeability, the mechanical strength of the cured resin composition layer is reduced. In the present invention, since component (C) is included as a dispersant in the resin composition, it is possible to improve the relative permeability and mechanical strength compared to a resin composition that does not include component (C) (i.e., a resin composition having the same composition as the resin composition except that it does not include component (C)).

[0108] (C) The component has a polyester backbone represented by the chemical formula (1).

[0109] [Chemical Formula (1)]

[0110]

[0111] (In chemical formula (1), R each independently represents a divalent hydrocarbon group having 2 to 10 carbon atoms, and n represents an integer from 2 to 1,000.)

[0112] R in chemical formula (1) represents a divalent hydrocarbon group having 2 to 10 carbon atoms. The hydrocarbon group has 2 or more carbon atoms, preferably 3 or more, more preferably 4 or more. The upper limit of the number of carbon atoms is 10 or less, preferably 8 or less, more preferably 6 or less. The hydrocarbon group may be any of straight-chain, branched, or cyclic, and straight-chain or branched hydrocarbon groups are preferred. Examples of hydrocarbon groups include aliphatic hydrocarbon groups and aromatic hydrocarbon groups, and aliphatic hydrocarbon groups are preferred. Examples of hydrocarbon groups include saturated hydrocarbon groups and unsaturated hydrocarbon groups, and saturated hydrocarbon groups are preferred. Specific examples of hydrocarbon groups include alkylene groups, alkenylene groups, alkynylene groups, arylene groups, etc. Among them, as a hydrocarbon group, an alkylene group is particularly preferred from the perspective of significantly obtaining the effects of the present invention.

[0113] Examples of alkylene groups include ethylene, propylene, butylene, pentylene, hexylene, heptylene, octylene, nonylene, and decylene groups. Examples of alkenylene groups include ethenylene, propenylene, butylene, pentylene, hexenylene, heptylene, octylene, nonenylene, and decenylene groups. Examples of alkynylene groups include ethynylene, pyropylene, butylene, pentylene, hexylene, heptylene, octylene, nonenylene, and decenylene groups. Examples of arylene groups include phenylene and naphthylene groups. Among these, butylene and pentylene groups are preferred as R.

[0114] The divalent hydrocarbon group represented by R in chemical formula (1) may or may not have a substituent. There are no particular restrictions on the substituent, and examples include halogen atoms, -OH, and -OC 1-6 Alkyl group, -N(C 1-10 Alkyl group)2, C 1-10 Alkyl group, C 6-10 Aryl group, -NH2, -CN, -C(O)OC 1-10 Examples include alkyl groups, -COOH, -C(O)H, -NO2, etc. Here, "C p-q 」(p and q are positive integers, and p <q를 만족한다.)란 용어는, 이 용어의 바로 뒤에 기재된 유기 기의 탄소원자수가 p 내지 q인 것을 나타낸다. 예를 들면, 「C 1-10 The expression “alkyl group” indicates 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 includes a spiro ring or a condensed ring.

[0115] The above substituent may additionally have a substituent (hereinafter referred to as a “secondary substituent”). As for the secondary substituent, unless otherwise specifically noted, the same as the above substituent may be used.

[0116] n in chemical formula (1) represents an integer from 2 to 1,000. n is 2 or more, preferably 5 or more, more preferably 10 or more. The upper limit is 1,000 or less, preferably 500 or less, more preferably 100 or less, and 50 or less.

[0117] (C) The component may include any skeleton in addition to the polyester skeleton represented by Formula (1), provided that it does not impede the effects of the present invention. Examples of any skeletons include a polyester skeleton in which R in 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 ends of the polyester skeleton are not particularly limited.

[0118] (C) As terminals of the component, examples include residues of carboxylic acid, hydroxyl groups, hydrogen atoms, etc., as described below.

[0119] The component (C) having a polyester backbone represented by chemical formula (1) can be prepared, for example, by reacting a lactone represented by chemical formula (2) with a carboxylic acid.

[0120] [Chemical Formula (2)]

[0121]

[0122] (In chemical formula (2), R 2 is identical to R in chemical formula (1).

[0123] Examples of lactones represented by chemical formula (2) include ε-caprolactone, β-propiolactone, γ-butyrolactone, δ-valerolactone, β-methyl-δ-valerolactone, 4-methylcaprolactone, 2-methylcaprolactone, etc.

[0124] A carboxylic acid that functions as an initiator for ring-opening polymerization of a lactone represented by chemical formula (2) may be used. Examples of such carboxylic acids include hydroxycarboxylic acids such as ricinoleic acid, ricinoleic acid, 9- and 10-hydroxystearic acid, castor oil fatty acids, hydrogenated castor oil fatty acids, lactic acid, 12-hydroxystearic acid, and glycolic acid; dodecanoic acid; stearic acid, etc. Among these, hydroxycarboxylic acids are preferred from the viewpoint of significantly obtaining the effects of the present invention.

[0125] The reaction temperature is preferably 120 to 220°C, more preferably 160 to 210°C. In addition, the reaction time is preferably 0.5 to 72 hours. If the reaction is carried out under a nitrogen stream, a polyester with a high degree of polymerization can be obtained.

[0126] In addition, the above reaction may use a polymerization catalyst or a polymerization initiator to control the reaction, as needed.

[0127] As a polymerization catalyst, for example, quaternary ammonium salts such as tetramethylammonium chloride, tetrabutylammonium chloride, tetramethylammonium bromide, tetrabutylammonium bromide, tetramethylammonium iodine, tetrabutylammonium iodine, benzyltrimethylammonium chloride, benzyltrimethylammonium bromide, benzyltrimethylammonium iodine; Examples include quaternary phosphonium salts such as tetramethylphosphonium chloride, tetrabutylphosphonium chloride, tetramethylphosphonium bromide, tetrabutylphosphonium bromide, tetramethylphosphonium iodide, tetrabutylphosphonium iodide, benzyltrimethylphosphonium chloride, benzyltrimethylphosphonium bromide, benzyltrimethylphosphonium iodide, tetraphenylphosphonium chloride, tetraphenylphosphonium bromide, and tetraphenylphosphonium iodide; phosphorus compounds such as triphenylphosphine; organic carboxylates such as potassium acetate, sodium acetate, potassium benzoate, and sodium benzoate; alkali metal alcoholates such as sodium alcoholate and potassium alcoholate; tertiary amines; organotin compounds; organoaluminum compounds; organic titanate compounds such as tetrabutyl titanate; and zinc compounds such as zinc chloride.

[0128] Examples of polymerization initiators include aliphatic monocarboxylic acids such as acetic acid, propionic acid, caprylic acid, nonanoic acid, capric acid, octylic acid, lauryl acid, myristic acid, palmitic acid, stearic acid, isononanoic acid, and arachinic acid; and monocarboxylic acids such as aromatic monocarboxylic acids such as benzoic acid and p-butylbenzoic acid.

[0129] (C) In the preparation of component (C), any monomer may be additionally used in addition to the lactone and carboxylic acid represented by chemical formula (2), provided that it does not impede the effects of the present invention. Examples of any monomers include polyallylamine. For example, when polyallylamine is used as any monomer, component (C) containing a polyallylamine backbone can be prepared in addition to the polyester backbone represented by chemical formula (1). The reaction temperature and reaction time are the same as the reaction temperature and reaction time in the preparation of component (C) having the polyester backbone represented by chemical formula (1).

[0130] Polyallylamine is obtained by polymerizing allylamine in the presence of a polymerization initiator and / or a chain transfer catalyst.

[0131] Polymerization initiators are not particularly limited and may include, for example, ketone peroxides such as methyl ethyl ketone, diacyl peroxides such as benzoyl peroxide, peroxydicarbonates such as diisopropylperoxydicarbonate, peroxyketals such as 1,1-bis(t-butylperoxy)cyclohexane, hydroperoxides such as t-butylhydroperoxide, peroxyesters such as t-butylperoxypivalate, and other substances such as azobisisobutyronitrile, hydrogen peroxide, ferrous salts, etc. In addition, polymerization initiators described in Japanese Patent Publication No. JP 2-14364 may be used. These may be used individually or in combination of two or more.

[0132] The chain transfer catalyst is not particularly limited and examples include alkyl mercaptans such as lauryl mercaptan, thiocarboxylic acids such as mercaptoacetic acid, 2-mercaptopropionic acid, and 3-mercaptopropionic acid, and thiocarboxylic acid esters such as butyl thioglycolate and 2-ethylhexyl thioglycolate. These may be used individually or in combination of two or more types.

[0133] As for the weight average molecular weight of the polyallylamine, 150 to 100,000 is preferred, and 600 to 20,000 is more preferred. If the weight average molecular weight is 150 or higher, the adsorption capacity for particles such as component (A) is improved, and particle dispersibility is improved. If the weight average molecular weight is 100,000 or lower, aggregation between particles can be suppressed, and particle dispersibility is improved. In addition, a polyallylamine of any weight average molecular weight may be prepared using the method described in Japanese Patent Publication No. JP 2-14364.

[0134] Commercially available polyallylamines may 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 Nitto Bo Medical Co., Ltd.

[0135] (C) The pH of the component can typically be 4 or higher and less than 7. The pH can be measured by the indicator method. Specifically, the pH can be measured by immersing a pH test paper in a measurement sample (22°C) with a dispersant concentration of 0.1 g / mL, prepared by dissolving a dispersant in acetone. As the pH test paper, a pH test paper capable of measuring the pH in the acidic range (e.g., a measurement range of pH 0.0 to 14.0, pH 1.0 to 14.0, or pH 0.5 to 5.0, etc.) can be used, and examples include the pH test paper "pH test paper pH 1 to 14" manufactured by Azwan Co. (pH measurement range pH 1.0 to 14.0).

[0136] (C) As for the acid value of the component, in order to significantly obtain the effects of the present invention, it is preferably 1 mg KOH / g or more, more preferably 3 mg KOH / g or more, even more preferably 5 mg KOH / g, preferably 30 mg KOH / g or less, more preferably 25 mg KOH / g or less, and even more preferably 20 mg KOH / g or less. The acid value can be measured by a neutralization titration method.

[0137] (C) When the component is a dispersant reacted with polyallylamine, 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, from the view of significantly obtaining the effects of the present invention. The amine value can be measured by neutralization titration.

[0138] (C) As for the weight average molecular weight of the component, in order to significantly obtain the effects of the present invention, it is preferably 1,000 or more, more preferably 1,500 or more, even more preferably 2,000 or more, preferably 50,000 or less, more preferably 40,000 or less, and even more preferably 30,000 or less. The weight average molecular weight is the weight average molecular weight in polystyrene equivalent measured by gel permeation chromatography (GPC).

[0139] (C) The content of the component is preferably 0.1 mass% or more, more preferably 0.2 mass% or more, and even more preferably 0.3 mass% or more, when the non-volatile component in the resin composition is 100 mass%, in order to significantly exhibit the effects of the present invention, and the upper limit is preferably 5 mass% or less, more preferably 3 mass% or less, and even more preferably 1 mass% or less.

[0140] When the mass (mass%) of component (C) is 100 mass% of the non-volatile component in the resin composition, let C1 be the mass (mass%) of the magnetic powder (A) is 100 mass% of the non-volatile component in the resin composition, and let A1 be the mass (mass%) of the magnetic powder (A). (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 masses of component (A) and (C) so that (C1 / A1)×100 is within this range, it becomes possible to obtain the desired effect of the present invention more significantly.

[0141] -(D) Curing Agent-

[0142] The resin composition contains a curing agent (D) as component (D). The curing agent (D) includes an epoxy resin curing agent having the function of curing the epoxy resin (B) and a curing accelerator having the function of accelerating the curing speed of the epoxy resin (B). The curing accelerator is typically used in combination with the epoxy resin curing agent. It is preferable that the resin composition includes an epoxy resin curing agent as the curing agent (D), and it is more preferable that the curing accelerator be included together with the epoxy resin curing agent as the curing agent (D).

[0143] (Epoxy resin hardener)

[0144] The epoxy resin curing agent can typically react with (B) the epoxy resin to cure the resin composition. Examples of epoxy resin curing agents include phenolic epoxy resin curing agents, naphthol-based epoxy resin curing agents, active 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. As for the epoxy resin curing agent, one or more selected from phenolic epoxy resin curing agents and naphthol-based epoxy resin curing agents are preferred from the viewpoint of significantly obtaining the effects of the present invention. The epoxy resin curing agent may be used alone or two or more may be used in combination.

[0145] As a phenolic epoxy resin curing agent and a naphthol-based epoxy resin curing agent, a phenolic epoxy resin curing agent having a novolak structure or a naphthol-based epoxy resin curing agent having a novolak structure is preferred from the perspective of heat resistance and water resistance. As a phenolic epoxy resin curing agent, a nitrogen-containing phenolic epoxy resin curing agent is preferred, a triazine-frame-containing phenolic epoxy resin curing agent is more preferred, and a triazine-frame-containing phenolic novolak epoxy resin curing agent is even more preferred.

[0146] 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 Kasei Co., Ltd., “NHN”, “CBN”, and “GPH” manufactured by Nippon Kayaku Co., Ltd., “SN170”, “SN180”, “SN190”, “SN475”, “SN485”, “SN495V”, “SN375”, and “SN395” manufactured by Shin-Nippon Tetsu Sumikin Kagaku Co., Ltd., and “TD-2090”, “LA-7052”, “LA-7054”, “LA-1356”, “LA-3018-50P”, “EXB-9500”, “HPC-9500”, and “KA-1160” manufactured by DIC Co., Ltd. Examples include the “KA-1163”, “KA-1165”, and the “GDP-6115L” and “GDP-6115H” manufactured by Gunei Kagaku Co.

[0147] As for the active ester-based epoxy resin curing agent, there are no particular limitations, but generally, compounds having two or more highly reactive ester groups in one molecule, such as phenol esters, thiophenol esters, N-hydroxyamine esters, and esters of heterocyclic hydroxy compounds, are preferably used. The active ester-based epoxy resin curing agent is preferably obtained by a condensation reaction between a carboxylic acid compound and / or a thiocarboxylic acid compound and a hydroxy compound and / or a thiol compound. Particularly from the perspective of improving heat resistance, an active ester-based epoxy resin curing agent obtained from a carboxylic acid compound and a hydroxy compound is preferred, and an active ester-based epoxy resin curing agent obtained from a carboxylic acid compound and a phenol compound and / or 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, pyromellitic acid, etc. Examples of phenol compounds or naphthol compounds include hydroquinone, resorcinol, bisphenol A, bisphenol F, bisphenol S, phenolphthalein, methylated bisphenol A, methylated bisphenol F, methylated bisphenol S, phenol, o-cresol, m-cresol, p-cresol, catechol, α-naphthol, β-naphthol, 1,5-dihydroxynaphthalene, 1,6-dihydroxynaphthalene, 2,6-dihydroxynaphthalene, dihydroxybenzophenone, trihydroxybenzophenone, tetrahydroxybenzophenone, phloroglucine, benzenetriol, dicyclopentadiene-type diphenol compounds, phenol novolac, etc. Here, "dicyclopentadiene-type diphenol compound" refers to a diphenol compound obtained by condensing two molecules of phenol with one molecule of dicyclopentadiene.

[0148] Specifically, an active ester-based epoxy resin curing agent comprising a dicyclopentadiene-type diphenol structure, an active ester-based epoxy resin curing agent comprising a naphthalene structure, an active ester-based epoxy resin curing agent comprising an acetylated compound of phenol novolak, and an active ester-based epoxy resin curing agent comprising a benzoylated compound of phenol novolak are preferred. "Dicyclopentadiene-type diphenol structure" refers to a divalent structure composed of phenylene, dicyclopentylene, and phenylene.

[0149] As commercially available active ester-based epoxy resin curing agents, "EXB9451," "EXB9460," "EXB9460S," "HPC-8000-65T," "HPC-8000H-65TM," and "EXB-8000L-65TM" manufactured by DIC Corporation as active ester-based epoxy resin curing agents containing a dicyclopentadiene-type diphenol structure; "EXB9416-70BK" manufactured by DIC Corporation as an active ester compound containing a naphthalene structure; "DC808" manufactured by Mitsubishi Chemical Corporation as an active ester-based resin curing agent containing an acetylated compound of phenol novolak; and "YLH1026," "YLH1030," and "YLH1048" manufactured by Mitsubishi Chemical Corporation as active ester-based epoxy resin curing agents containing a benzoylated compound of phenol novolak; Examples of active ester-based epoxy resin curing agents that are acetylated compounds of phenol novolak include “DC808” manufactured by Mitsubishi Chemical.

[0150] Examples of acid anhydride-based epoxy resin curing agents include epoxy resin curing agents having one or more acid anhydride groups within one molecule. Specific examples of acid anhydride-based epoxy resin curing agents include phthalic anhydride, tetrahydrophthalic anhydride, hexahydrophthalic anhydride, methyltetrahydrophthalic anhydride, methylhexahydrophthalic anhydride, methylnadic anhydride, hydrogenated methylnadic anhydride, trialkyltetrahydrophthalic anhydride, dodecenyl succinic anhydride, 5-(2,5-dioxotetrahydro-3-furanyl)-3-methyl-3-cyclohexene-1,2-dicarboxylic anhydride, trimellitic anhydride, pyromellitic anhydride, benzophenonetetracarboxylic acid dihydride, biphenyltetracarboxylic acid dihydride, naphthalenetetracarboxylic acid dihydride, oxydiphthalic acid dihydride, and 3,3'-4,4'-diphenylsulfonetetracarboxylic acid Examples include dianhydrides, 1,3,3a,4,5,9b-hexahydro-5-(tetrahydro-2,5-dioxo-3-furanyl)-naphtho[1,2-C]furan-1,3-dione, ethylene glycolbis(anhydrotrimellitate), and polymeric acid anhydrides such as styrene-maleic acid resin copolymerized with styrene and maleic acid.

[0151] Examples of commercially available acid anhydride-based epoxy resin curing agents include "HNA-100" and "MH-700" manufactured by Shin Nippon Rika Co., Ltd.

[0152] Specific examples of benzoxazine-based epoxy resin curing agents include "HFB2006M" manufactured by Showa Kobunshi Co., Ltd., and "Pd" and "Fa" manufactured by Shikoku Kasei Kogyo Co., Ltd.

[0153] Examples of cyanate ester-based epoxy resin curing agents include bisphenol A dicyanate, polyphenol cyanate, oligo(3-methylene-1,5-phenylene cyanate), 4,4'-methylenebis(2,6-dimethylphenylcyanate), 4,4'-ethylidene diphenyl dicyanate, hexafluorobisphenol A dicyanate, 2,2-bis(4-cyanate)phenylpropane, 1,1-bis(4-cyanatephenylmethane), bis(4-cyanate-3,5-dimethylphenyl)methane, 1,3-bis(4-cyanatephenyl-1-(methylethylidene))benzene, bis(4-cyanatephenyl)thioether and bis(4-cyanatephenyl)ether, difunctional cyanate resins, polyfunctional cyanate resins derived from phenol novolac and cresol novolac, and prepolymers in which these cyanate resins are partially triazinated. Specific examples of cyanate ester-based epoxy resin curing agents include “PT30” and “PT60” manufactured by Lonza Japan (both are phenol novolak-type polyfunctional cyanate ester resins), “BA230”, and “BA230S75” (a prepolymer in which part or all of bisphenol A dicyanate is triazinated to form a trimer).

[0154] As an imidazole-based epoxy resin curing agent, for example, 2-methylimidazole, 2-undecylimidazole, 2-heptadecylimidazole, 1,2-dimethylimidazole, 2-ethyl-4-methylimidazole, 2-phenylimidazole, 2-phenyl-4-methylimidazole, 1-benzyl-2-methylimidazole, 1-benzyl-2-phenylimidazole, 1-cyanoethyl-2-methylimidazole, 1-cyanoethyl-2-undecylimidazole, 1-cyanoethyl-2-ethyl-4-methylimidazole, 1-cyanoethyl-2-phenylimidazole, 1-cyanoethyl-2-undecylimidazolium trimellitate, 1-cyanoethyl-2-phenylimidazole trimellitate, 2,4-diamino-6-[2'-methylimidazolyl-(1')]-ethyl-s-triazine, 2,4-diamino-6-[2'-undecylimidazolyl-(1')]-ethyl-s-triazine, 2,4-diamino-6-[2'-ethyl-4'-methylimidazolyl-(1')]-ethyl-s-triazine, 2,4-diamino-6-[2'-methylimidazolyl-(1')]-ethyl-s-triazine isocyanuric acid adduct, 2-phenylimidazole isocyanuric acid adduct, 2-phenyl-4,5-dihydroxymethylimidazole, 2-phenyl-4-methyl-5-hydroxymethylimidazole, 2,3-dihydro-1H-pyrrolo[1,2-a]benzimidazole, Examples include imidazole compounds such as 1-dodecyl-2-methyl-3-benzylimidazolium chloride, 2-methylimidazoline, and 2-phenylimidazoline, and adducts of imidazole compounds and epoxy resins, and 2-ethyl-4-methylimidazole and 1-benzyl-2-phenylimidazole are preferred.

[0155] As an imidazole-based epoxy resin curing agent, commercially available products may be used, for example, “2MZA-PW” and “2PHZ-PW” manufactured by Shikoku Kasei Kogyo, and “P200-H50” manufactured by Mitsubishi Chemical.

[0156] The ratio of the epoxy resin to the epoxy resin curing agent is [total number of epoxy groups of the epoxy resin] to [total number of reactive groups of the epoxy resin curing agent], 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. In addition, the total number of epoxy groups of the epoxy resin is 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 of the epoxy resin curing agent is the sum of the values ​​obtained by dividing the mass of the non-volatile components of each epoxy resin curing agent by the reactive equivalent for all epoxy resin curing agents. By keeping the ratio of the epoxy resin to the epoxy resin curing agent within this range, the heat resistance of the cured product is further improved.

[0157] The content of the epoxy resin curing agent is preferably 0.1 mass% or more, more preferably 0.5 mass% or more, and even more preferably 1 mass% or more, when the resin component in the resin composition is 100 mass%, in order to significantly obtain the effects of the present invention, and the upper limit is preferably 5 mass% or less, more preferably 4 mass% or less, and even more preferably 3 mass% or less.

[0158] (Curing accelerator)

[0159] A curing accelerator can typically act as a catalyst in the curing reaction of (B) the epoxy resin to accelerate the curing reaction. Examples of curing accelerators include amine-based curing accelerators, imidazole-based curing accelerators, phosphorus-based curing accelerators, guanidine-based curing accelerators, and metal-based curing accelerators. Regarding the curing accelerator, amine-based curing accelerators, imidazole-based curing accelerators, and guanidine-based curing accelerators are preferred from the perspective of lowering the viscosity of the resin composition, and imidazole-based curing accelerators are more preferred from the perspective of improving the mechanical strength of the resulting cured product. A single type of curing accelerator may be used alone, or two or more types may be used in combination. The curing accelerator is generally used in combination with the epoxy resin curing agent.

[0160] Examples of amine-based curing accelerators include trialkylamines such as triethylamine and tributylamine, 4-dimethylaminopyridine, benzyldimethylamine, 2,4,6-tris(dimethylaminomethyl)phenol, and 1,8-diazabicyclo(5,4,0)-undecene, and 4-dimethylaminopyridine and 1,8-diazabicyclo(5,4,0)-undecene are preferred.

[0161] As for amine-based curing accelerators, commercially available products may be used, for example, “PN-50”, “PN-23”, “MY-25” manufactured by Ajinomoto Fine Techno Co., Ltd.

[0162] As an imidazole-based curing accelerator, it is identical to the above-mentioned imidazole-based epoxy resin curing agent. When the above-mentioned imidazole-based epoxy resin curing agent is used in combination with other epoxy resin curing agents, it may function as a curing accelerator.

[0163] Examples of phosphorus-based curing accelerators include triphenylphosphine, phosphonium borate compounds, tetraphenylphosphonium tetraphenylborate, n-butylphosphonium tetraphenylborate, tetrabutylphosphonium decanate, (4-methylphenyl)triphenylphosphonium thiocyanate, tetraphenylphosphonium thiocyanate, butyltriphenylphosphonium thiocyanate, etc., and triphenylphosphine and tetrabutylphosphonium decanate are preferred.

[0164] As guanidine-based curing accelerators, for example, dicyandiamide, 1-methylguanidine, 1-ethylguanidine, 1-cyclohexylguanidine, 1-phenylguanidine, 1-(o-tolyl)guanidine, dimethylguanidine, diphenylguanidine, trimethylguanidine, tetramethylguanidine, pentamethylguanidine, 1,5,7-triazabicyclo[4.4.0]deca-5-ene, 7-methyl-1,5,7-triazabicyclo[4.4.0]deca-5-ene, 1-methylbiguanide, 1-ethylbiguanide, 1-n-butylbiguanide, 1-n-octadecylbiguanide, 1,1-dimethylbiguanide, 1,1-diethylbiguanide, 1-cyclohexylbiguanide, 1-allylbiguanide, Examples include 1-phenylbiguanide, 1-(o-tolyl)biguanide, etc., and dicyandiamide and 1,5,7-triazabicyclo[4.4.0]deca-5-ene are preferred.

[0165] Examples of metal-based hardening accelerators include organometallic complexes or organometallic salts of metals such as cobalt, copper, zinc, iron, nickel, manganese, and tin. Specific examples of organometallic complexes include organic cobalt complexes such as cobalt(II) acetylacetonate and cobalt(III) acetylacetonate, organic copper complexes such as copper(II) acetylacetonate, organic zinc complexes such as zinc(II) acetylacetonate, organic iron complexes such as iron(III) acetylacetonate, organic nickel complexes such as nickel(II) acetylacetonate, and organic manganese complexes such as manganese(II) acetylacetonate. Examples of organometallic salts include zinc octylate, tin octylate, zinc naphthenate, cobalt naphthenate, tin stearate, and zinc stearate.

[0166] The content of the curing accelerator is preferably 0.001 mass% or more, more preferably 0.005 mass% or more, and even more preferably 0.01 mass% or more, when the resin component in the resin composition is 100 mass%, in order to significantly obtain the effects of the present invention, and the upper limit is preferably 1 mass% or less, more preferably 0.1 mass% or less, and even more preferably 0.05 mass% or less.

[0167] (D) The content of the curing agent is preferably 0.1 mass% or more, more preferably 0.5 mass% or more, and even more preferably 1 mass% or more, when the non-volatile component in the resin composition is 100 mass%, in order to obtain the effect of the present invention, and the upper limit is preferably 5 mass% or less, more preferably 4 mass% or less, and even more preferably 3 mass% or less.

[0168] When the mass (mass%) of (D) curing agent is set to 100 mass% of the non-volatile component in the resin composition, and the mass (mass%) of (C) dispersant is set to C1 of the non-volatile component in the resin composition, C1 / 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 masses of component (C) and (D) so that C1 / D1 falls within this range, the desired effect of the present invention can be obtained more significantly.

[0169] When the non-volatile component in the resin composition is 100 mass%, the mass (mass%) of (A) magnetic powder is A1; when the non-volatile component in the resin composition is 100 mass%, the mass (mass%) of (B) epoxy resin is B1; when the non-volatile component in the resin composition is 100 mass%, the mass (mass%) of (C) dispersant is C1; and when the non-volatile component in the resin composition is 100 mass%, the mass (mass%) of (D) curing agent is D1. In this case, (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 component (A) to component (D) so that (B1 + C1 + D1) / A1 falls within this range, it becomes possible to obtain the desired effect of the present invention more significantly.

[0170] When the non-volatile component in the resin composition is 100 mass%, the mass (mass%) of (A) magnetic powder is denoted as A1; when the non-volatile component in the resin composition is 100 mass%, the mass (mass%) of (C) dispersant is denoted as C1; and when the non-volatile component in the resin composition is 100 mass%, the mass (mass%) of (D) curing agent is denoted as D1. Then, ((C1 + D1) / A1)×100 is preferably 0.1 or more, more preferably 0.5 or more, even more preferably 1 or more, preferably 10 or less, more preferably 5 or less, and even more preferably 3 or less. By adjusting the masses of component (A), component (C), and component (D) so that ((C1 + D1) / A1)×100 is within this range, it becomes possible to obtain the desired effect of the present invention more significantly.

[0171] -(E) Thermoplastic Resin-

[0172] The resin composition contains (E) a thermoplastic resin as (E) component. By including (E) component in the resin composition, the stress of the cured product in the resin composition layer is relieved, thereby improving the mechanical strength of the cured product.

[0173] (E) Examples of thermoplastic resins include phenoxy resin, polyvinyl acetal resin, polyolefin resin, polyimide resin, polybutadiene resin, polyamideimide resin, polyetherimide resin, polysulfone resin, polyethersulfone resin, polyphenylene ether resin, polyether ether ketone resin, polyester resin, etc., and phenoxy resin is preferred. (E) The thermoplastic resin may be used as a single type or in combination of two or more types.

[0174] Examples of phenoxy resins include phenoxy resins having one or more skeletons selected from the group consisting of bisphenol A skeleton, bisphenol F skeleton, bisphenol S skeleton, bisphenol acetophenone skeleton, novolac skeleton, biphenyl skeleton, fluorene skeleton, dicyclopentadiene skeleton, norbornene skeleton, naphthalene skeleton, anthracene skeleton, adamantane skeleton, terpene skeleton, and trimethylcyclohexane skeleton. The terminals of the phenoxy resin may be any functional group, such as phenolic hydroxyl groups or epoxy groups. Specific examples of phenoxy resins include "1256" and "4250" manufactured by Mitsubishi Chemical Corporation (both phenoxy resins containing a bisphenol A skeleton); and "YX8100" manufactured by Mitsubishi Chemical Corporation (phenoxy resin containing a bisphenol S skeleton). Examples include “YX6954” (bisphenol-acetophenone backbone containing phenoxy resin) manufactured by Mitsubishi Chemical Corporation; “FX280” and “FX293” manufactured by Shin Nippon Steel Sumitomo Metal Corporation; “YL7500BH30”, “YX6954BH30”, “YX7553”, “YX7553BH30”, “YL7769BH30”, “YL6794”, “YL7213”, “YL7290”, “YL7482”, and “YL7891BH30” manufactured by Mitsubishi Chemical Corporation.

[0175] Examples of polyvinyl acetal resins include polyvinyl formal resin and polyvinyl butyral resin, and polyvinyl butyral resin is preferred. Specific examples of polyvinyl acetal resins include "Denka Butyral 4000-2", "Denka Butyral 5000-A", "Denka Butyral 6000-C", and "Denka Butyral 6000-EP" manufactured by Denki Kagaku Kogyo Co., Ltd.; and the S-Rec BH series, BX series (e.g., BX-5Z), KS series (e.g., KS-1), BL series, BM series, etc. manufactured by Sekisui Kagaku Kogyo Co., Ltd.

[0176] Examples of polyolefin resins include, for instance, ethylene-based copolymer resins such as low-density polyethylene, ultra-low-density polyethylene, high-density polyethylene, ethylene-vinyl acetate copolymer, ethylene-ethyl acrylate copolymer, and ethylene-methyl acrylate copolymer; and polyolefin-based polymers such as polypropylene and ethylene-propylene block copolymer.

[0177] Specific examples of polyimide resins include "SLK-6100" manufactured by Shin-Etsu Kagaku Kogyo Co., Ltd., and "Ricacoat SN20" and "Ricacoat PN20" manufactured by Shin-Nippon Rica Co., Ltd. Specific examples of polyimide resins also include modified polyimides such as linear polyimide obtained by reacting a difunctional hydroxyl-terminated polybutadiene, a diisocyanate compound, and a tetrabasic acid anhydride (polyimide described in Japanese Patent Publication No. JP 2006-37083), and polyimide containing a polysiloxane backbone (polyimide described in Japanese Patent Publication No. JP 2002-12667 and Japanese Patent Publication No. JP 2000-319386, etc.).

[0178] Examples of polybutadiene resins include, for instance, a resin containing a hydrogenated polybutadiene backbone, a polybutadiene resin containing a hydroxyl group, a polybutadiene resin containing a phenolic hydroxyl group, a polybutadiene resin containing a carboxyl group, a polybutadiene resin containing an acid anhydride group, a polybutadiene resin containing an epoxy group, a polybutadiene resin containing an isocyanate group, a polybutadiene resin containing a urethane group, and a polyphenylene ether-polybutadiene resin.

[0179] Specific examples of polyamideimide resins include "Viromax HR11NN" and "Viromax HR16NN" manufactured by Toyobo Corporation. Specific examples of polyamideimide resins also include modified polyamideimides such as "KS9100" and "KS9300" (polyamideimide containing a polysiloxane backbone) manufactured by Hitachi Kasei Corporation.

[0180] Specific examples of polyethersulfone resins include "PES5003P" manufactured by Sumitomo Chemicals.

[0181] Specific examples of polysulfone resins include the polysulfones "P1700" and "P3500" manufactured by Solvay Advanced Polymers.

[0182] Specific examples of polyphenylene ether resins include "NORYL SA90" manufactured by SABIC. Specific examples of polyetherimide resins include "Ultem" manufactured by GE.

[0183] Examples of polycarbonate resins include hydroxyl group-containing carbonate resins, phenolic hydroxyl group-containing carbonate resins, carboxyl group-containing carbonate resins, acid anhydride group-containing carbonate resins, isocyanate group-containing carbonate resins, urethane group-containing carbonate resins, etc. Specific examples of polycarbonate resins include “FPC0220” manufactured by Mitsubishi Gas Chemicals, “T6002” and “T6001” (polycarbonate diol) manufactured by Asahi Kasei Chemicals, and “C-1090”, “C-2090” and “C-3090” (polycarbonate diol) manufactured by Kuraray. Specific examples of polyetheretherketone resins include “Sumiproi K” manufactured by Sumitomo Chemicals.

[0184] Examples of polyester resins include polyethylene terephthalate resin, polyethylene naphthalate resin, polybutylene terephthalate resin, polybutylene naphthalate resin, polytrimethylene terephthalate resin, polytrimethylene naphthalate resin, polycyclohexanedimethyl terephthalate resin, etc.

[0185] (E) The weight average molecular weight (Mw) of the thermoplastic resin is preferably greater than 5,000, more preferably 8,000 or more, even more preferably 10,000 or more, and particularly preferably 20,000 or more. There is no specific limit on the upper limit, and it may be, for example, 1 million or less, 500,000 or less, 100,000 or less, etc. (E) The weight average molecular weight of the thermoplastic resin in terms of polystyrene is measured by gel permeation chromatography (GPC). Specifically, (E) the weight average molecular weight of the thermoplastic resin equivalent to polystyrene can be calculated by using a measuring device, an LC-9A / RID-6A manufactured by Shimadzu Sesakusho, a column, a Shodex K-800P / K-804L / K-804L manufactured by Showa Denko, and a mobile phase such as chloroform, and measuring at a column temperature of 40°C, and using a calibration curve of standard polystyrene.

[0186] (E) The content of the thermoplastic resin is preferably 0.1 mass% or more, more preferably 0.2 mass% or more, particularly preferably 0.3 mass% or more, with respect to 100 mass% of the non-volatile component of the resin composition, and preferably 5 mass% or less, more preferably 3 mass% or less, and particularly preferably 2 mass% or less. (E) When the amount of the thermoplastic resin is within the above range, the magnetic properties of the cured product of the resin composition can be made particularly good.

[0187] When the mass (mass%) of (E) thermoplastic resin is 100 mass% of the non-volatile component in the resin composition, let E1 be the mass (mass%) of (B) epoxy resin is 100 mass% of the non-volatile component in the resin composition, let B1 be the mass (mass%) of (B). B1 / E1 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 masses of component (B) and (E) so that B1 / E1 falls within this range, it becomes possible to obtain the desired effect of the present invention more significantly.

[0188] When the mass (mass%) of (E) the thermoplastic resin is 100 mass% of the non-volatile component in the resin composition, let E1 be the mass (mass%) of (C) the dispersant is 100 mass% of the non-volatile component in the resin composition, and let C1 be the mass (mass%) of (C) the dispersant. 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 masses of component (C) and (E) so that C1 / E1 falls within this range, it becomes possible to obtain the desired effect of the present invention more significantly.

[0189] When the non-volatile component in the resin composition is 100 mass%, let A1 be the mass (mass%) of (A) magnetic powder; when the non-volatile component in the resin composition is 100 mass%, let B1 be the mass (mass%) of (B) epoxy resin; when the non-volatile component in the resin composition is 100 mass%, let C1 be the mass (mass%) of (C) dispersant; when the non-volatile component in the resin composition is 100 mass%, let D1 be the mass (mass%) of (D) curing agent; and when the non-volatile component in the resin composition is 100 mass%, let E1 be the mass (mass%) of (E) thermoplastic resin. In this case, (B1 + C1 + D1 + E1) / A1 is preferably 0.001 or more, more preferably 0.01 or more, even more preferably 0.05 or more, preferably 1 or less, and more preferably 0.5. Below, more preferably below 0.3. By adjusting the mass of component (A) to component (E) so that (B1 + C1 + D1 + E1) / A1 is within this range, it becomes possible to obtain the desired effect of the present invention more significantly.

[0190] When the non-volatile component in the resin composition is 100 mass%, the mass (mass%) of (A) magnetic powder is denoted as A1; when the non-volatile component in the resin composition is 100 mass%, the mass (mass%) of (C) dispersant is denoted as C1; and when the non-volatile component in the resin composition is 100 mass%, the mass (mass%) of (E) thermoplastic resin is denoted as E1. Then, ((C1 + E1) / A1)×100 is preferably 0.1 or more, more preferably 0.5 or more, even more preferably 1 or more, preferably 10 or less, more preferably 5 or less, and even more preferably 3 or less. By adjusting the masses of component (A), component (C), and component (E) so that ((C1 + E1) / A1)×100 is within this range, it becomes possible to obtain the desired effect of the present invention more significantly.

[0191] -(F) Other Additives-

[0192] The resin composition may additionally include (F) other additives as needed. Examples of such other additives include, for instance, curing retardants such as triethyl borate; inorganic fillers (except those corresponding to magnetic powders); flame retardants; organic fillers; organometallic compounds such as organocopper compounds, organozinc compounds, and organocobalt compounds; and resin additives such as thickeners; defoaming agents; leveling agents; adhesion-imparting agents and coloring agents.

[0193] -(G) Solvent-

[0194] The resin composition may additionally include a solvent (G) as a volatile component in combination with a non-volatile component such as components (A) to (F) above.

[0195] (G) As a solvent, organic solvents are typically used. Examples of organic solvents include ketone-based solvents such as acetone, methyl ethyl ketone, methyl isobutyl ketone, and cyclohexanone; ester-based solvents such as methyl acetate, ethyl acetate, butyl acetate, isobutyl acetate, isoamyl acetate, methyl propionate, ethyl propionate, and γ-butyrolactone; ether-based solvents such as tetrahydropyran, tetrahydrofuran, 1,4-dioxane, diethyl ether, diisopropyl ether, dibutyl ether, and diphenyl ether; and alcohol-based solvents such as methanol, ethanol, propanol, butanol, and ethylene glycol. Ether ester solvents such as 2-ethoxyethyl acetate, propylene glycol monomethyl ether acetate, diethylene glycol monoethyl ether acetate, ethyl diglycol acetate, γ-butyrolactone, methyl methoxypropionate, etc.; ester alcohol solvents such as methyl lactate, ethyl lactate, methyl 2-hydroxyisobutyrate, etc.; ether alcohol solvents such as 2-methoxypropanol, 2-methoxyethanol, 2-ethoxyethanol, propylene glycol monomethyl ether, diethylene glycol monobutyl ether (butyl carbitol), etc.; amide solvents such as N,N-dimethylformamide, N,N-dimethylacetamide, N-methyl-2-pyrrolidone, etc.; sulfoxide solvents such as dimethyl sulfoxide; nitrile solvents such as acetonitrile, propionitrile, etc.; Examples include aliphatic hydrocarbon solvents such as hexane, cyclopentane, cyclohexane, and methylcyclohexane; aromatic hydrocarbon solvents such as benzene, toluene, xylene, ethylbenzene, and trimethylbenzene. (G) One type of solvent may be used alone, or two or more types may be used in combination.

[0196] (G) It is preferable to set the amount of solvent so that the melt viscosity of the resin composition or the resin composition layer containing the resin composition can be adjusted to an appropriate range. Additionally, the resin composition may not include (G) solvent. For example, the content of the organic solvent included in the resin composition is preferably less than 1.0 mass%, more preferably 0.8 mass% or less, even more preferably 0.5 mass% or less, and particularly preferably 0.1 mass% or less, with respect to the total mass of the resin composition. The lower limit is not particularly restricted, but is 0.001 mass% or more or not contained. By keeping the amount of solvent in the resin composition low, the occurrence of voids due to the volatilization of the solvent can be suppressed.

[0197] The thickness of the resin composition layer depends on the thickness of the wiring, the thickness of the core substrate, and the dimensions of the through-hole, but 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.

[0198] Method for manufacturing resin sheets

[0199] A resin sheet can be manufactured by a method including, for example, applying a resin composition onto a support. Additionally, a resin composition layer can be manufactured by, for example, preparing a resin varnish by dissolving or dispersing a resin composition in a solvent, applying the resin varnish onto a support using a die coater or the like, and further drying it to form a resin composition layer. Alternatively, it can be manufactured by directly applying a resin composition onto a support using a die coater or the like to form a resin composition layer. As a solvent, the above (G) solvent may be used.

[0200] Drying may be carried out by known methods such as heating or hot air spraying. Although the drying conditions are not particularly limited, drying is performed so that the content of the organic solvent in the resin composition layer is 10 mass% or less, preferably 5 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 mass% to 60 mass% of an organic solvent, a resin composition layer can be formed by drying at 50°C to 150°C for 3 minutes to 10 minutes.

[0201] In the resin sheet, a protective film equivalent to the support may be additionally 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, but is, for example, 1 μm to 40 μm. By laminating the protective film, the adhesion of dust or the like to the surface of the resin composition layer and scratches can be suppressed. The resin sheet can be stored by winding it into a roll shape. If the resin sheet has a protective film, it can be used by peeling off the protective film.

[0202] <Physical properties of the resin composition layer (resin composition), etc.>

[0203] A cured product obtained by heating a resin composition layer (resin composition) at 190°C for 90 minutes exhibits the characteristic of having excellent mechanical strength (tensile breaking strength). Accordingly, the cured product forms a magnetic layer with excellent tensile breaking strength. As for the tensile breaking strength, it is preferably 60 MPa or higher, more preferably 70 MPa or higher, and even more preferably 75 MPa or higher. The upper limit is not particularly limited, but can be 150 MPa or lower. The mechanical strength (tensile breaking strength) can be measured by the method described in the examples described below.

[0204] A cured product obtained by heating a resin composition layer (resin composition) at 190°C for 90 minutes exhibits the characteristic of having a high relative permeability at a frequency of 50 MHz. Accordingly, the cured product forms a magnetic layer with a high relative permeability. The relative permeability of the 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. In addition, the upper limit is not particularly limited, but can be 100 or lower. The relative permeability can be measured by the method described in the examples described below.

[0205] A cured product obtained by heating a resin composition layer (resin composition) at 190°C for 90 minutes typically exhibits the characteristic of having low magnetic loss at a frequency of 50 MHz. Accordingly, the cured product forms a magnetic layer with low magnetic loss. The magnetic loss of the 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. The magnetic loss can be measured by the method described in the examples described below.

[0206] In order to utilize the above advantages, it is preferable to use the resin composition layer (resin composition) of the resin sheet for forming a magnetic layer of the circuit board. Additionally, in order to utilize the above advantages, it is preferable to use the resin composition layer (resin composition) of the resin sheet for filling through holes of the core substrate. When the core substrate and the resin sheet are laminated, a part or all of the resin composition layer can be introduced into the through hole to fill the through hole with the resin composition. Then, by curing the resin composition, a magnetic layer can be formed within the through hole.

[0207] [Resin Composition]

[0208] The resin composition of the present invention comprises (A) a magnetic powder, (B) an epoxy resin, (C) a dispersant, (D) a curing agent, and (E) a thermoplastic resin. When the non-volatile component in the resin composition is 100 mass%, the mass (mass%) of (E) the thermoplastic resin is denoted as E1, and when the non-volatile component in the resin composition is 100 mass%, the mass (mass%) of (B) the epoxy resin is denoted as B1. B1 / E1 is 0.1 or more and 5 or less, and the component (C) has a polyester backbone represented by the following chemical formula (1).

[0209] [Chemical Formula (1)]

[0210]

[0211] (In chemical formula (1), R each independently represents a hydrocarbon group having 2 to 10 carbon atoms, and n represents an integer from 2 to 1,000.)

[0212] The resin composition may be the same composition as the resin composition layer, except that it may have a state other than that of the resin composition layer formed on the sheet. Each component included in the resin composition is as described above.

[0213] [Hardened material]

[0214] The cured product of the present invention is obtained by curing the resin composition layer of the present invention. In addition, the cured product of the present invention is obtained by curing the resin composition of the present invention. The curing conditions of the resin composition layer and the resin composition may use the conditions of process (2) described later. In addition, preheating may be performed before heat curing the resin composition layer and the resin composition, and heating may be performed multiple times including preheating.

[0215] [Circuit board and method of manufacturing the same]

[0216] A circuit board according to one embodiment of the present invention includes a magnetic layer. The magnetic layer includes a cured product of a resin composition layer of the resin sheet, and preferably includes only the cured product of the resin composition. The specific structure of the circuit board is not limited as long as it comprises a magnetic layer including the cured product of the resin composition layer. A circuit board of the first embodiment is a circuit board comprising a core substrate having a through-hole formed therein and a magnetic layer filled in the through-hole. Furthermore, a circuit board of the second embodiment is a circuit board comprising a magnetic layer formed by the cured product of a 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. Hereinafter, the first and second embodiments of the method for manufacturing a circuit board will be described. However, the method for manufacturing a circuit board according to the present invention is not limited to the first and second embodiments exemplified below.

[0217] <First Embodiment>

[0218] A circuit board of the first embodiment comprises a core substrate having a through hole formed therein and a magnetic layer filled in the through hole. A method for manufacturing such a circuit board is, for example,

[0219] (1) A process of laminating a core substrate having a through hole and a resin sheet such that a layer of resin composition is filled into the through hole, and

[0220] (2) The process of curing the resin composition layer to form a magnetic layer is included in this order.

[0221] In addition, the method for manufacturing a circuit board of the first embodiment may include any process in combination with the above processes (1) and (2). For example, the method for manufacturing a circuit board is,

[0222] (3) Process of polishing the magnetic layer,

[0223] (4) A process for performing harmonic treatment on the magnetic layer and

[0224] (5) It may include a process of forming a conductive layer on the magnetic layer.

[0225] Typically, process (3), process (4) and process (5) are performed in this order.

[0226] <Process (1)>

[0227] Process (1) typically includes a process of preparing a core substrate having through holes formed therein. The core substrate may be prepared by purchasing it from the market. Additionally, the core substrate may be prepared by manufacturing it using a suitable material. Below, a method for manufacturing a core substrate according to an example is described.

[0228] FIG. 1 is a cross-sectional view schematically showing a core substrate (10) before a through-hole is formed in a method for manufacturing a circuit board according to a first embodiment of the present invention. The process of preparing the core substrate (10) may include preparing a core substrate (10) in which a through-hole to be filled with a magnetic layer is not formed, as shown in the example in FIG. 1. The core substrate (10) is a substrate before a through-hole is formed and may be a plate-shaped member.

[0229] The core substrate (10) typically includes a support substrate (11). As the support substrate (11), examples include insulating substrates such as a glass epoxy substrate, a metal substrate, a polyester substrate, a polyimide substrate, a BT resin substrate, or a thermosetting polyphenylene ether substrate. Additionally, a metal layer may be provided on the support substrate (11). The metal layer may be provided on one side of the support substrate (11) or on both sides. Here, an example is shown in which metal layers (12 and 13) are provided on both surfaces of the support substrate (11). As the metal layers (12 and 13), examples include layers formed by a metal such as copper. The metal layers (12 and 13) may be copper foil such as a carrier-attached copper foil, or metal layers formed from the material of the conductor layer described later.

[0230] FIG. 2 is a cross-sectional view schematically showing a core substrate (10) having a through hole (14) formed therein in a method for manufacturing a circuit board according to a first embodiment of the present invention. The process of preparing the core substrate (10) may include a step of forming a through hole (14) in the core substrate (10) as shown in FIG. 2. The through hole (14) can be formed by, for example, drilling, laser irradiation, plasma irradiation, etc. 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 carried out using a commercially available drilling device. Examples of commercially available drilling devices include the "ND-1S211" manufactured by Hitachi Via Mechanics Co., Ltd.

[0231] FIG. 3 is a cross-sectional view schematically showing a core substrate (10) having a plating layer (20) formed in a through hole (14) in a method for manufacturing a circuit board according to a first embodiment of the present invention. The process of preparing the core substrate (10) may include, if necessary, performing a conditioning treatment on the core substrate (10) and then forming a plating layer (20) as shown in FIG. 3. As for the conditioning treatment, either a dry or wet conditioning treatment may be performed. Examples of dry conditioning treatment include plasma treatment. In addition, examples of wet conditioning treatment include a method of performing swelling treatment with a swelling liquid, conditioning treatment with an oxidizing agent, and neutralization treatment with a neutralizing liquid in this order. The plating layer (20) may be formed by a plating method. The order in which the plating layer (20) is formed by the plating method may be the same as the formation of the conductor layer in the process (5) described later. Here, an example is shown in which a plating layer (20) is formed on the surface of the metal layer (12) and the surface of the metal layer (13) within the through hole (14). In addition, in this example, the core substrate having the plating layer (20) is described by attaching the same reference numeral "10" as the core substrate (10) before the plating layer (20) is formed.

[0232] FIG. 4 is a cross-sectional view schematically showing the stacking of a core substrate (10) and a resin sheet (30) in a method for manufacturing a circuit board according to a first embodiment of the present invention. Process (1) includes preparing a core substrate (10) having a through hole (14) formed therein, and then stacking the core substrate (10) and the resin sheet (30) as shown in FIG. 4. In this embodiment, an example is described in which a resin sheet (30) having a resin composition layer (31) and a support (32) is stacked on one side (10U) of the core substrate (10). In the following description, among the sides of the core substrate (10), the side (10U) that is bonded to the resin sheet (30) is referred to as the "first side (10U)," and the opposite side is referred to as the "second side (10D)."

[0233] Lamination of the core substrate (10) and the resin sheet (30) is performed such that part or all of the resin composition layer (31) is filled into the through hole (14). Accordingly, lamination is typically performed such that the resin composition layer (31) and the core substrate (10) are bonded together. Specifically, the lamination can be performed by bonding the resin composition layer (31) to the core substrate (10) by heat-pressing the resin sheet (30) onto the core substrate (10). As shown in the example illustrated in FIG. 4, when the resin sheet (30) is provided with a support (32), the lamination can be performed by pressing the resin sheet (30) onto the core substrate (10) from the side of the support (32). As for the member used for heat-pressing (hereinafter referred to as "heat-pressing member"; not illustrated), examples include a heated metal plate (SUS hard plate, etc.) or a metal roll (SUS roll, etc.). Although the heat-pressing member may be pressed directly onto the resin sheet (30), it is preferable to press by interposing an elastic material such as heat-resistant rubber so that the resin sheet (30) sufficiently follows the surface irregularities of the core substrate (10).

[0234] Lamination of the core substrate (10) and the resin sheet (30) may be carried out, for example, by a vacuum lamination method. Lamination conditions are, for example, as follows. The heat 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 heat 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 heat 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 carried out under reduced pressure conditions of 13 hPa or less.

[0235] After lamination, the laminated resin sheet (30) may be smoothed by pressing a heat-pressing member from the support (32) side, for example, under atmospheric pressure. The pressing conditions for the smoothing treatment may be the same as the heat-pressing conditions for the lamination. Additionally, the lamination and the smoothing treatment may be performed continuously using a vacuum laminator.

[0236] FIG. 5 is a cross-sectional view schematically showing a core substrate (10) and a resin sheet (30) laminated in a method for manufacturing a circuit board according to a first embodiment of the present invention. As shown in FIG. 5, the resin composition layer (31) of the resin sheet (30) enters the through hole (14) by the lamination of the core substrate (10) and the resin sheet (30), so the through hole (14) is filled by the resin composition layer (31). Here, an example is described in which a portion of the resin composition layer (31) enters the through hole (14), while another portion does not enter the through hole (14) and is attached to the first surface (10U) of the core substrate (10). Accordingly, the resin composition layer (31) can be formed on the first surface (10U) of the core substrate (10). Additionally, another portion of the resin composition layer (31) that has entered the through hole (14) may pass through the through hole (14) and be discharged from the opening on the second side (10D) of the core substrate (10). Thus, there may be cases where the resin composition layer (31) is formed on the second side (10D) of the core substrate (10).

[0237] 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 and explained in which the support (32) is peeled off after the core substrate (10) and the resin sheet (30) are laminated and before process (2). However, the peeling of the support (32) may be performed after process (2).

[0238] <Process (2)>

[0239] FIG. 6 is a schematic cross-sectional view for explaining the process (2) of the method for manufacturing a circuit board according to the first embodiment of the present invention. The process (2) includes laminating a core substrate (10) and a resin sheet (30), and then curing a resin composition layer (31) as shown in FIG. 6. 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 can also be formed on the first surface (10U) and the second surface (10D) of the core substrate (10).

[0240] The curing of the resin composition layer (31) is typically performed by thermal curing. The thermal curing conditions of the resin composition layer (31) can be appropriately set within the range in which the curing of the resin composition layer (31) proceeds. 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, and even more preferably 200°C or lower. The curing time is preferably 5 minutes or more, more preferably 10 minutes or more, even more preferably 15 minutes or more, preferably 120 minutes or less, more preferably 110 minutes or less, and even more preferably 100 minutes or less.

[0241] The degree of hardening of the magnetic layer (40) obtained in process (2) is preferably 80% or more, more preferably 85% or more, and even more preferably 90% or more. The degree of hardening can be measured, for example, using a differential scanning calorimeter.

[0242] A method for manufacturing a circuit board may include a process (preheating process) of heating the resin composition layer (31) at a temperature lower than the curing temperature after laminating the core substrate (10) and the resin sheet (30) and before curing the resin composition layer (31). For example, prior to curing the resin composition layer (31), the resin composition layer (31) may be preheated for at least 5 minutes (preferably 5 minutes to 150 minutes, more preferably 15 minutes to 120 minutes) at a temperature of typically 50°C or higher and less than 120°C (preferably 60°C or higher and less than 110°C, more preferably 70°C or higher and less than 100°C).

[0243] <Process (3)>

[0244] FIG. 7 is a schematic cross-sectional view for explaining process (3) of a method for manufacturing a circuit board according to a first embodiment of the present invention. Process (3) may include polishing a magnetic layer (40). In detail, process (3) may include polishing a portion of the magnetic layer (40) outside the through hole (14). In the example shown in this embodiment, since a 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) on the first surface (10U) and the second surface (10D) can be polished. The portion of the magnetic layer (40) outside the through hole (14) is generally an excess portion unnecessary for the final product. By the polishing, the excess portion can be removed as shown in FIG. 7. In addition, the polished surface (40U and 40D) as the surface of the magnetic layer (40) can be flattened by polishing.

[0245] As a polishing method, a method capable of removing unnecessary parts of the magnetic layer (40) may be adopted. Examples of such polishing methods include buff polishing, belt polishing, ceramic polishing, etc. Examples of commercially available buff polishing devices include the "NT-700IM" manufactured by Hyokki Ishii Co., Ltd.

[0246] The arithmetic mean roughness (Ra) of the polished surfaces (40U and 40D) of the magnetic layer (40) is preferably 300 nm or more, more preferably 350 nm or more, and even more preferably 400 nm or more, in order to improve adhesion with the conductor layer (not shown in FIG. 7). The upper limit is preferably 1,000 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.

[0247] Before process (3) after process (2), heat treatment may be performed on the magnetic layer (40) to further increase the degree of hardening of the magnetic layer (40). The temperature in the heat treatment may correspond to the hardening temperature. The specific heat treatment temperature is preferably 120°C or higher, more preferably 130°C or higher, more preferably 150°C or higher, preferably 245°C or lower, more preferably 220°C or lower, more preferably 200°C or lower. The heat treatment time is preferably 5 minutes or more, more preferably 10 minutes or more, more preferably 15 minutes or more, preferably 150 minutes or less, more preferably 120 minutes or less, more preferably 100 minutes or less.

[0248] By performing the above processes (1) and (2) and, if necessary, additionally performing process (3), a circuit board (100) having a core substrate (10) and a magnetic layer (40) that fills the through hole (14) of the core substrate (10) can be obtained. On the circuit board (100) obtained in this way, a conductive layer may be formed by performing processes (4) and (5) as necessary.

[0249] <Process (4)>

[0250] Process (4) includes performing a harmonizing treatment on the magnetic layer. Typically, the harmonizing treatment is performed on the polished surface of the magnetic layer. Additionally, in process (4), the harmonizing treatment may be performed not only on the polished surface of the magnetic layer but also on the surfaces (10U and 10D) of the core substrate (10).

[0251] The order and conditions of the harmonization treatment are not particularly limited, and, for example, the order and conditions used in the manufacturing method of a multilayer printed circuit board may be adopted. Specifically, the harmonization treatment may be performed by a method that includes swelling treatment with a swelling liquid, harmonization treatment with an oxidizing agent, and neutralization treatment with a neutralizing liquid in this order.

[0252] Examples of swelling solutions used for swelling treatment include alkaline solutions and surfactant solutions, and preferably alkaline solutions. As for alkaline solutions used as swelling solutions, sodium hydroxide solutions and potassium hydroxide solutions are more preferred. Examples of commercially available swelling solutions include "Swelling Deep Securigans P" and "Swelling Deep Securigans SBU" manufactured by Atotech Japan.

[0253] 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 minute to 20 minutes. In order to suppress the swelling of the resin contained in the magnetic layer to an appropriate level, it is preferable to immerse the magnetic layer in a swelling solution at 40°C to 80°C for 5 minutes to 15 minutes.

[0254] Examples of oxidizing agents used for oxidizing treatment include an alkaline permanganate solution in which potassium permanganate or sodium permanganate is dissolved in an aqueous solution of sodium hydroxide. It is preferable to perform oxidizing treatment using an oxidizing agent such as an alkaline permanganate solution by immersing the magnetic layer in a solution of the oxidizing agent heated to 60°C to 80°C for 10 to 30 minutes. In addition, it is preferable to set the concentration of permanganate in the alkaline permanganate solution to 5 mass% to 10 mass%. Examples of commercially available oxidizing agents include alkaline permanganate solutions such as "Concentrate Compact P" and "Dosing Solution Securigans P" manufactured by Atotech Japan.

[0255] An acidic aqueous solution is preferred as the neutralizing solution that can be used for the neutralization treatment. As a commercially available neutralizing solution, for example, "Reduction Solution Securigans P" manufactured by Atotech Japan Co., Ltd. Neutralization treatment using the neutralizing solution can be performed by immersing the treated surface, which has undergone harmonization treatment with an oxidizing agent solution, in a neutralizing solution at 30°C to 80°C for 5 to 30 minutes. In terms of workability, a method of immersing the magnetic layer, which has undergone harmonization treatment with an oxidizing agent solution, in a neutralizing solution at 40°C to 70°C for 5 to 20 minutes is preferred.

[0256] The arithmetic mean roughness (Ra) of the surface of the magnetic layer after surface harmonization treatment is preferably 300 nm or more, more preferably 350 nm or more, and even more preferably 400 nm or more, in order to improve adhesion with the conductor layer. The upper limit is preferably 1,500 nm or less, more preferably 1,200 nm or less, and even more preferably 1,000 nm or less. The surface roughness (Ra) can be measured, for example, using a non-contact surface roughness meter.

[0257] <Process (5)>

[0258] FIG. 8 is a schematic cross-sectional view for explaining a process (5) of a method for manufacturing a circuit board (100) according to a first embodiment of the present invention. The process (5) includes forming a conductive layer (50) on the polished surfaces (40U and 40D) of a magnetic layer (40) as shown in FIG. 8. In this embodiment, an example is shown in which the conductive layer (50) is formed not only on the polished surfaces (40U and 40D) of the magnetic layer (40) but also on surrounding surfaces (e.g., the first surface (10U) and the second surface (10D) of the core substrate (10). Additionally, FIG. 8 shows an example in which the conductive layer (50) is formed on both sides of the core substrate (10), but the conductive layer (50) may be formed only on one side of the core substrate (10).

[0259] FIG. 9 is a schematic cross-sectional view for explaining a process (5) of a method for manufacturing a circuit board (100) according to a first embodiment of the present invention. As shown in FIG. 9, the process (5) may include forming a conductor layer (50), and then removing a portion of the conductor layer (50), metal layers (12 and 13), and plating layer (20) by etching or other treatments to form a pattern conductor layer (51).

[0260] The method of forming the conductor layer (50) may include, for example, plating, sputtering, or deposition, and among these, plating is preferred. In a suitable embodiment, a pattern conductor layer (51) having a desired wiring pattern can be formed by plating the surface of the magnetic layer (40) (and, if necessary, the core substrate (10)) by a suitable method such as a semi-additive method or a full-additive method. As for the material of the conductor layer (50), examples include single metals such as gold, platinum, palladium, silver, copper, aluminum, cobalt, chromium, zinc, nickel, titanium, tungsten, iron, tin, and indium; and alloys of two or more metals selected from the group of gold, platinum, palladium, silver, copper, aluminum, cobalt, chromium, zinc, nickel, titanium, tungsten, iron, tin, and indium. Among them, from the perspective of versatility, cost, and ease of patterning, it is preferable to use chromium, nickel, titanium, aluminum, zinc, gold, palladium, silver, or copper, or nickel-chromium alloy, copper-nickel alloy, or copper-titanium alloy, it is more preferable to use chromium, nickel, titanium, aluminum, zinc, gold, palladium, silver, or copper, or nickel-chromium alloy, and it is even more preferable to use copper.

[0261] Here, an example of a method for forming a pattern conductor layer (51) is described in detail. A plating seed layer is formed by electroless plating on the polished surfaces (40U and 40D) of the magnetic layer (40). Then, if necessary, a mask pattern is formed on the formed plating seed layer, and then an electroplated layer is formed by electroplating. After that, if necessary, the mask pattern is removed, and an unnecessary plating seed layer is further removed by a process such as etching, so that a pattern conductor layer (51) having a desired wiring pattern can be formed. After the formation of the pattern conductor layer (51), an annealing treatment may be performed as necessary to improve the adhesion strength of the pattern conductor layer (51). The annealing treatment can be performed, for example, by heating at 150°C to 200°C for 20 to 90 minutes.

[0262] The thickness of the pattern 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, particularly preferably 10 μm or less.

[0263] By the above method, a circuit board (100) having a magnetic layer (40) can be obtained. Since the magnetic layer (40) is obtained by curing the resin composition layer (31), it contains a cured product of the resin composition. Therefore, the magnetic layer (40) can contain a large amount of magnetic powder (not shown), so it can have excellent magnetic properties.

[0264] <Second Embodiment>

[0265] The circuit board of the second embodiment includes a magnetic layer formed by a cured resin composition layer of a resin sheet. A method for manufacturing such a circuit board is, for example,

[0266] (A) A process of forming a magnetic layer by laminating a resin sheet onto an inner layer substrate such that a resin composition layer is bonded to the inner layer substrate.

[0267] In addition, the method for manufacturing a circuit board according to the second embodiment may include any process in addition to process (A). For example, the method for manufacturing a circuit board is,

[0268] (B) A process of performing drilling on the magnetic layer,

[0269] (C) A process for performing harmonic treatment on the magnetic layer and

[0270] (D) It may include a process of forming a conductive layer on a magnetic layer.

[0271] The above manufacturing method preferably includes processes (A) to (D) in this order.

[0272] <Process (A)>

[0273] Process (A) is a process of forming a magnetic layer by laminating a resin sheet onto an inner layer substrate such that a resin composition layer is bonded to the inner layer substrate. As one embodiment of process (A), a resin sheet is laminated onto an inner layer substrate such that a resin composition layer is bonded to the inner layer substrate, and the resin composition layer is heat-cured to form a magnetic layer.

[0274] FIG. 10 is a schematic cross-sectional view for explaining process (A) of a method for manufacturing a circuit board according to a second embodiment of the present invention. In process (A), a resin sheet (310) comprising a support (330) and a resin composition layer (320a) provided on the support (330) is laminated onto an inner layer substrate (200) such that the resin composition layer (320a) is bonded to the inner layer substrate (200).

[0275] The inner layer substrate (200) is an insulating substrate. As a material for the inner layer substrate (200), insulating substrates such as glass epoxy substrate, metal substrate, polyester substrate, polyimide substrate, BT resin substrate, and thermosetting polyphenylene ether substrate may be used. The inner layer substrate (200) may also be an inner layer circuit board in which wiring, etc., is formed and inserted within its thickness.

[0276] As illustrated in FIG. 10, the inner layer substrate (200) has a first conductor layer (420) provided on a first main surface (200a) and an external terminal (240) provided on a second main surface (200b). The first conductor layer (420) may include a plurality of wires. In the illustrated example, only the wires constituting the coil-shaped conductive structure (400) of the inductor element are illustrated. The external terminal (240) is a terminal for electrically connecting to an external device, etc., which is not illustrated. The external terminal (240) may be configured as part of the conductor layer provided on the second main surface (200b).

[0277] The conductor material capable of forming 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.

[0278] The first conductor layer (420) and the external terminal (240) may have a single-layer structure, or a multi-layer structure in which two or more single-metal layers or alloy layers made of different types of metals or alloys are stacked. 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.

[0279] The line (L) / space (S) ratio of the first conductor layer (420) and the external terminal (240) is not particularly limited, but in terms of reducing surface irregularities to obtain a magnetic layer with excellent smoothness, it is typically 900 / 900 μm or less, preferably 700 / 700 μm or less, more preferably 500 / 500 μm or less, even more preferably 300 / 300 μm or less, and even more preferably 200 / 200 μm or less. The lower limit of the line / space ratio is not particularly limited, but in terms of facilitating the embedding of the resin composition layer into the space, it is preferably 1 / 1 μm or more.

[0280] The inner layer substrate (200) may have a plurality of through holes (220) penetrating the inner layer substrate (200) from the first main surface (200a) to the second main surface (200b). Through holes (220) are provided with through-hole wiring (220a). Through-hole wiring (220a) electrically connects the first conductor layer (420) and the external terminal (240).

[0281] The bonding of the resin composition layer (320a) and the inner layer substrate (200) is the same as the method of laminating the core substrate and the resin sheet described in the “Process (1)” column of the first embodiment.

[0282] After laminating a resin sheet onto an inner layer substrate, a resin composition layer is heat-cured to form a magnetic layer. As shown in an example in FIG. 11, a resin composition layer (320a) bonded to an inner layer substrate (200) is heat-cured to form a first magnetic layer (320).

[0283] The heat curing conditions of the resin composition layer (320a) are the same as the heat curing conditions of the resin composition layer described in the “<Process (2)>” column of the first embodiment.

[0284] The support (330) may be removed between process (A) after heat curing and process (B), or peeled off after process (B).

[0285] <Process (B)>

[0286] FIG. 12 is a schematic cross-sectional view for explaining process (B) of a method for manufacturing a circuit board according to a second embodiment of the present invention. In process (B), a via hole (360) is formed by drilling a first magnetic layer (320).

[0287] The via hole (360) serves as a path for electrically connecting the first conductor layer (420) and the second conductor layer (440) described later. The formation of the via hole (360) may be carried out using, for example, a drill, a laser, plasma, etc., depending on the composition of the resin composition used to form the magnetic layer. The dimensions and shape of the via hole may be appropriately determined according to the design of the circuit board.

[0288] <Process (C)>

[0289] Process (C) includes performing a harmonic treatment on the magnetic layer in which the via holes are formed. As for the method of harmonic treatment in process (C), it can be performed by the same method as described in the “<Process (4)>” column of the first embodiment.

[0290] The harmonization treatment in process (C) may be a treatment that polishes the surface of the insulating layer. As for the polishing method, it may be performed by the same polishing as described in the “<Process (3)>” column of the first embodiment.

[0291] The arithmetic mean roughness (Ra) of the surface treated with the magnetic layer is preferably 300 nm or more, more preferably 350 nm or more, and even more preferably 400 nm or more, from the perspective of improving plating adhesion. The upper limit is preferably 1,000 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.

[0292] <Process (D)>

[0293] FIG. 13 is a schematic cross-sectional view to explain process (D) of a method for manufacturing a circuit board according to a second embodiment of the present invention. Process (D) includes forming a second conductor layer (440) on a first magnetic layer (320), as shown in FIG. 13 as an example.

[0294] The conductor material that can form the second conductor layer (440) is the same as the conductor layer material described in the “<Process (5)>” column of the first embodiment.

[0295] The thickness of the second conductor layer (440) is, in terms of thinning, preferably 70 μm or less, more preferably 60 μm or less, even more preferably 50 μm or less, even more preferably 40 μm or less, particularly preferably 30 μm or less, 20 μm or less, 15 μm or less, or 10 μm or less. The lower limit is preferably 1 μm or more, more preferably 3 μm or more, and even more preferably 5 μm or more.

[0296] The second conductor layer (440) can be formed by plating. The second conductor layer (440) is preferably formed by a wet plating method, such as a semi-additive method or a full-additive method, which includes, for example, an electroless plating process, a mask pattern forming process, an electrolytic plating process, and a flash etching process. By forming the second conductor layer (440) using a wet plating method, it can be formed as a second conductor layer (440) that includes a desired wiring pattern. In addition, by this process, wiring (360a) within the via hole (360) is formed together.

[0297] The first conductor layer (420) and the second conductor layer (440) may be provided in a spiral shape, for example, as shown in FIGS. 14 to 16 described later. 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) by a wiring inside a via hole (360a). The other end of the outer side of the spiral wiring portion of the second conductor layer (440) is electrically connected to the land (420a) of the first conductor layer (42) by a wiring inside a via hole (360a). Accordingly, the other end of the outer circumference of the spiral wiring portion of the second conductor layer (440) is electrically connected to an external terminal (240) via wiring inside a via hole (360a), a land (420a), and wiring inside a through hole (220a).

[0298] The coil-shaped conductive structure (400) is composed of a spiral wiring portion which is part of the first conductor layer (420), a spiral wiring portion which is part of the second conductor layer (440), and wiring (360a) inside a via hole that electrically connects the spiral wiring portion of the first conductor layer (420) and the spiral wiring portion of the second conductor layer (440).

[0299] After process (D), a process of forming a magnetic layer on the conductor layer may be performed additionally. In detail, as shown in FIG. 15, a second magnetic layer (340) is formed on the first magnetic layer (320) on which the second conductor layer (440) and wiring (360a) within the via hole are formed. The second magnetic layer may be formed by the same process as previously described.

[0300] [Inductor Components]

[0301] The inductor component comprises a circuit board of the present invention. When such an inductor component comprises a circuit board obtained by the method of manufacturing a circuit board of the first embodiment, it has an inductor pattern formed by a conductor on at least a portion of the periphery of the cured resin composition layer. Such an inductor component may be, for example, the one described in Japanese Patent Publication No. 2016-197624.

[0302] In addition, when including a circuit board obtained by the method for manufacturing a circuit board of the second embodiment, the inductor board comprises a magnetic layer and a conductive structure in which at least a portion is embedded in the magnetic layer, and an inductor element formed by the conductive structure and a portion of the magnetic layer that extends in the thickness direction of the magnetic layer and is surrounded by the conductive structure. Here, FIG. 14 is a schematic plan view of an inductor board containing an inductor element, viewed from one side in the thickness direction. FIG. 15 is a schematic drawing showing a cross-section of an inductor board cut at the position indicated by the dashed line II-II in FIG. 14. FIG. 16 is a schematic plan view for explaining the configuration of a first conductor layer in the inductor board.

[0303] The circuit board (100) is a build-up wiring board having a plurality of magnetic layers (first magnetic layer (320), second magnetic layer (340)) and a plurality of conductor layers (first conductor layer (420), second conductor layer (440)), as shown as an example in FIG. 14 and FIG. 15, that is, a build-up magnetic layer and a build-up conductor layer. In addition, the inductor board (100) is provided with an inner layer board (200).

[0304] From FIG. 15, the first magnetic layer (320) and the second magnetic layer (340) form a magnetic portion (300) that can be viewed as an integral magnetic layer. Accordingly, the coil-shaped conductive structure (400) is provided so that at least a portion of it is embedded in the magnetic portion (300). That is, in the inductor substrate (100) of the present embodiment, the inductor element is composed of the coil-shaped conductive structure (400) and a core that extends in the thickness direction of the magnetic portion (300) and is a part of the magnetic portion (300) surrounded by the coil-shaped conductive structure (400).

[0305] As shown as an example in FIG. 16, the first conductor layer (420) includes a spiral wiring portion for forming a coil-shaped conductive structure (400) and a rectangular land (420a) that is electrically connected to the wiring (220a) inside the through hole. In the illustrated example, the spiral wiring portion includes a curved portion that bends at a right angle to a straight portion and a bypass portion that bypasses the land (420a). In the illustrated example, the spiral wiring portion of the first conductor layer (420) has an overall outline that is approximately rectangular and has a shape that is wound counterclockwise from the center side toward the outside.

[0306] Likewise, a second conductor layer (440) is provided on the first magnetic layer (320). The second conductor layer (440) includes a spiral wiring portion for forming a coil-shaped conductive structure (400). In FIG. 14 or FIG. 15, the spiral wiring portion includes a curved portion that bends at a right angle to a straight portion. In FIG. 14 or FIG. 15, the spiral wiring portion of the second conductor layer (440) has an overall outline that is approximately rectangular and has a shape that is wound clockwise from the center side toward the outside.

[0307] These inductor components can be used as a wiring board for mounting electronic components such as semiconductor chips, and can also be used as a (multilayer) printed circuit board using these wiring boards as inner layer substrates. In addition, these wiring boards can be used as a chip inductor component that has been reorganized, and can also be used as a printed circuit board with the chip inductor component surface-mounted thereon.

[0308] In addition, various types of semiconductor devices can be manufactured using such a wiring board. Semiconductor devices including such a wiring board can be suitably used in electrical products (e.g., computers, mobile phones, digital cameras, and televisions) and vehicles (e.g., motorcycles, automobiles, trams, ships, and aircraft).

[0309] Examples

[0310] The present invention will be described in detail below by way of examples, but the present invention is not limited to these examples. Furthermore, in the following description, "parts" and "%" indicating amounts refer to "parts by mass" and "% by mass," respectively, unless otherwise specified.

[0311] <Measurement of pH of Dispersant (Indicator Method)>

[0312] A dispersant was dissolved in acetone to prepare a measurement sample (22°C) with a dispersant concentration of 0.1 g / mL. A pH test paper was gently immersed and then lifted to dry any excess moisture. The color of the wet part of the test paper was compared with a color sample, and the pH of the closest color was set as the pH of each sample.

[0313] <Synthesization Example 1: Synthesis of Dispersant 1>

[0314] 10.0 parts of 12-hydroxystearic acid (manufactured by Junsei Kagaku Co., Ltd.) and 190 parts of ε-caprolactone (manufactured by Junsei Kagaku Co., Ltd.) were injected into a reaction flask equipped with a thermometer, a stirrer, a nitrogen inlet, and a reflux tube. The temperature was raised to 160°C over 4 hours under a nitrogen stream, heated at 160°C for 2 hours, and then heated until the remaining amount of ε-caprolactone was 1% or less. Subsequently, the mixture was cooled to room temperature. Hereinafter, the above reaction solution is referred to as Dispersant 1. Dispersant 1 had the characteristics of a weight-average molecular weight of 23,000 and an acid value of 9.0 mg KOH / g. The pH in the indicator method was 5.

[0315] <Synthesization Example 2: Synthesis of Dispersant 2>

[0316] 10.0 parts of 12-hydroxystearic acid (manufactured by Junsei Kagaku Co., Ltd.) and 180 parts of δ-valerolactone (manufactured by Tokyo Kasei Kogyo) were injected into a reaction flask equipped with a thermometer, a stirrer, a nitrogen inlet, and a reflux tube. The temperature was raised to 160°C over 4 hours under a nitrogen stream, heated at 160°C for 2 hours, and then heated until the remaining amount of δ-valerolactone was 1% or less. Subsequently, it was cooled to room temperature. Hereinafter, the above reaction solution is referred to as Dispersant 2. Dispersant 2 had the characteristics of a weight-average molecular weight of 22,000 and an acid value of 8.9 mg KOH / g. The pH in the indicator method was 5.

[0317] <Synthesization Example 3: Synthesis of Dispersant 3>

[0318] A thermometer, a stirrer, a nitrogen inlet, and a reflux tube were provided, and a mixture consisting of 25.0 parts xylene and 70 parts of a 10% aqueous polyallylamine solution ("PAA-1LV" manufactured by Nitto Boseki Co., Ltd., number average molecular weight about 3,000) was stirred at 160°C in a reaction flask, and while water was distilled off using a separation device, xylene was flowed back into the reaction solution, and the dispersant 1 (14.21 parts) obtained in Synthesis Example 1, heated to 160°C, was added to it, and the reaction was carried out at 160°C for 2 hours.

[0319] Additionally, dispersant 3 was obtained by heating at 160°C for 4 hours and removing xylene by distillation at 160°C. Dispersant 3 had an amine value of 31.0 mg KOH / g. The amine value immediately after mixing was 312.6 mg KOH / g. The pH in the indicator method was 6.

[0320] <Synthesization Example 4: Synthesis of Dispersant 4>

[0321] 30.0 parts of xylene (manufactured by Junsei Kagaku Co.), 300.0 parts of 12-hydroxystearic acid (manufactured by Junsei Kagaku Co.), and 0.1 parts of tetrabutyl titanate (manufactured by Tokyo Kasei Co.) were injected into a reaction flask equipped with a thermometer, stirrer, nitrogen inlet, reflux tube, and water separator, and the temperature was raised to 160°C over 4 hours under a nitrogen stream. After heating at 160°C for an additional 4 hours, xylene was removed by distillation at 160°C to obtain dispersant 4. Dispersant 4 had a weight-average molecular weight of 6,000 and an acid value of 23.0 mg KOH / g. The pH in the indicator method was 5.

[0322] <Synthesization Example 5: Synthesis of Dispersant 5>

[0323] 30.0 parts of xylene (manufactured by Junsei Kagaku Co.), 300.0 parts of 12-hydroxystearic acid (manufactured by Junsei Kagaku Co.), and 0.1 parts of tetrabutyl titanate (manufactured by Tokyo Kasei Co.) were injected into a reaction flask equipped with a thermometer, a stirrer, a nitrogen inlet, a reflux tube, and a water separator, and the temperature was raised to 160°C over 4 hours under a nitrogen stream. Additionally, the mixture was heated at 160°C for 4 hours (at which time the acid value was approximately 20 mg KOH / g), and the xylene was removed by distillation at 160°C. Then, the mixture was cooled to room temperature, the water produced during the heating reaction was separated from the xylene in the effluent, and the xylene was returned to the reaction solution. This reaction solution is referred to as polyester PE-1.

[0324] In a reaction flask equipped with a thermometer, a stirrer, a nitrogen inlet, a reflux tube, and a water separator, a mixture consisting of 25.0 parts xylene and 70 parts of a 10% aqueous polyallylamine solution ("PAA-1LV" manufactured by Nitto Boseki Co., Ltd., number average molecular weight approximately 3,000) was stirred at 160°C, and water was distilled off using a separation device while simultaneously adding 2.5 parts of polyester PE-1 to the xylene while recirculating it into the reaction solution, and the reaction was carried out at 160°C for 2 hours. Additionally, the mixture was heated at 160°C for 4 hours, and xylene was distilled off at 160°C. Dispersant 5 had a polyester backbone in which R in chemical formula (1) was an alkylene group having 11 carbon atoms, and had the characteristics of 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 immediately after mixing was 317 mg KOH / g. The pH of dispersant 5 in the indicator method was 6.

[0325] <Example 1: Preparation of Magnetic Varnish 1>

[0326] 2.41 parts by mass of epoxy resin ("ZX-1059", a mixture of bisphenol A type epoxy resin and bisphenol F type epoxy resin, manufactured by Nittetsu Chemical & Materials Co., Ltd.), 2.74 parts by mass of triazine-backed phenol resin ("LA-7054" manufactured by DIC, a MEK solution with a hydroxyl equivalent of about 125 and a solid content of 60%), 2.39 parts by mass of phenoxy resin ("YL7553BH30" manufactured by Mitsubishi Chemical, a 1:1 solution of MEK and cyclohexanone with a solid content of 30%), 0.5 parts by mass of dispersant 1 (dispersant synthesized in Synthesis Example 1, a polyester dispersant with 5 carbon atoms), 3.0 parts by mass of solvent (cyclohexanone), imidazole-based curing accelerator ("2E4MZ", 2-ethyl tetramethylimidazole, Magnetic varnish 1 was prepared by mixing 0.02 parts by mass of (manufactured by Shikoku Kasei Kogyo Co., Ltd.), 27.91 parts by mass of magnetic powder ("M03S", Fe-Mn ferrite, average particle diameter 0.4 μm, specific gravity 5.1 m² / g, manufactured by Powder Tech Co., Ltd.), and 93.19 parts by mass of magnetic powder ("MA-RCO-24" manufactured by DOWA Electronics Co., Ltd., Fe-Ni alloy, average particle diameter 3.0 μm).

[0327] <Example 2: Preparation of Magnetic Varnish 2>

[0328] In Example 1, the content of dispersant 1 (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.

[0329] <Example 3: Preparation of Magnetic Varnish 3>

[0330] In Example 1, the content of dispersant 1 (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.

[0331] <Example 4: Preparation of Magnetic Varnish 4>

[0332] In Example 1, 0.5 parts by mass of dispersant 1 (dispersant synthesized in Synthesis Example 1, a polyester dispersant with 5 carbon atoms) was replaced with 0.5 parts by mass of dispersant 2 (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.

[0333] <Example 5: Preparation of Magnetic Varnish 5>

[0334] In Example 1, 0.5 parts by mass of dispersant 1 (dispersant synthesized in Synthesis Example 1, a polyester dispersant with 5 carbon atoms) was replaced with 0.5 parts by mass of dispersant 3 (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.

[0335] <Example 6: Preparation of Magnetic Varnish 6>

[0336] In Example 1, 27.91 parts by mass of magnetic powder ("MO3S", Fe-Mn-based ferrite, average particle diameter 0.4 μm, specific gravity 5.1 m² / g, manufactured by Powder Tech Co.) was replaced with 27.91 parts by mass of magnetic powder ("MZ03S", Fe-Mn-Zn-based ferrite, average particle diameter 0.4 μm, specific gravity 5.1 m² / g, manufactured by Powder Tech Co.). Except for the above, magnetic varnish 6 was prepared in the same manner as in Example 1.

[0337] <Comparative Example 1: Preparation of Magnetic Varnish 7>

[0338] In Example 1, 0.5 parts by mass of dispersant 1 (dispersant synthesized in Synthesis Example 1, a polyester dispersant with 5 carbon atoms) was replaced with 0.5 parts by mass of dispersant 4 (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.

[0339] <Comparative Example 2: Preparation of Magnetic Varnish 8>

[0340] In Example 1, 0.5 parts by mass of dispersant 1 (dispersant synthesized in Synthesis Example 1, a polyester dispersant with 5 carbon atoms) was replaced with 0.5 parts by mass of dispersant 5 (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.

[0341] <Comparative Example 3: Preparation of Magnetic Varnish 9>

[0342] In Example 1, 0.5 parts by mass of dispersant 1 (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 not having a polyester backbone, manufactured by Kusumoto Kasei Co., Ltd.). Except for the above, magnetic varnish 9 was prepared in the same manner as in Example 1.

[0343] <Comparative Example 4: Preparation of Magnetic Varnish 10>

[0344] In Example 1, 0.5 parts by mass of dispersant 1 (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 not having a polyester backbone, manufactured by Nichiyu Co., Ltd.). Except for the above, magnetic varnish 10 was prepared in the same manner as in Example 1.

[0345] Preparation of the resin sheet

[0346] A magnetic varnish prepared in the examples and comparative examples was applied with a die coater to a PET film (Torre Corporation’s “Lumira R80”, thickness 38 μm, softening point 130°C, hereinafter referred to as “release PET”) that had been treated with an alkyd resin-based release agent (“AL-5”), and the thickness of the resin composition layer after drying was 100 μm, and the resin sheet was obtained by drying at 65°C to 115°C (average 100°C) for 7 minutes.

[0347] <Production of Sheet-like Cured Materials>

[0348] A resin sheet was cut into 200 mm squares. The cut resin sheet (200 mm square) was laminated onto one side of a polyimide film (Ube Kosan Co., Ltd. “Upirex 25S”, 25 μm thickness, 240 mm square) using a batch-type vacuum pressure laminator (2-stage build-up laminator “CVP700” manufactured by Nikko Materials Co., Ltd.) so that the resin composition layer contacted the center of the smooth surface of the polyimide film. Lamination was performed by depressurizing the pressure for 30 seconds to reduce the atmospheric pressure to 13 hPa or less, and then pressing at 100°C and a pressure of 0.74 MPa for 30 seconds. In this way, a multilayer film having a layer configuration of a support / resin composition layer / polyimide film was obtained. After peeling off the support, the resin composition layer was heat-cured by heating at 190°C for 90 minutes. After that, the polyimide film was peeled off to obtain a sheet-like cured product of the resin composition.

[0349] Measurement of Relative Permeability and Magnetic Loss

[0350] The obtained sheet-like cured material was cut to obtain an evaluation sample with a width of 5 mm and a length of 18 mm. Using the HP8362B manufactured by Agilent Technologies, the relative permeability (μ') and magnetic loss (μ") of the evaluation sample were measured by the 3-turn coil method at a measurement frequency of 50 MHz and a room temperature of 23°C. The magnetic loss was calculated by the following equation “tanδ = μ' / μ"”. In addition, the relative permeability was evaluated according to the following criteria.

[0351] ○: Non-investment rate of 20 or higher

[0352] ×: Non-investment rate less than 20

[0353] Measurement of Mechanical Strength (Tensile Breaking Strength)

[0354] The tensile fracture strength of the obtained sheet-shaped hardened material was measured in accordance with JIS K7127. The measurement results were evaluated according to the following criteria.

[0355] ○: 60MPa or higher

[0356] ×: Less than 60MPa

[0357] Explanation of the symbols

[0358] 10 Core substrate 10U First surface 10D Second surface 11 Support substrate 12 Metal layer 13 Metal layer 14 Through hole 20 Plating layer 30 Resin sheet 31 Resin composition layer 32 Support 40 Magnetic layer 40U Polished surface 40D Polished surface 50 Conductor layer 51 Pattern conductor layer 100 Circuit board 200 Inner layer substrate 200a First main surface 200b Second main surface 220 Through hole 220a Wiring inside through hole 240 External terminal 300 Magnetic part 310 Resin sheet 320a Resin composition layer 320 First magnetic layer 330 Support 340 Second magnetic layer 360 Via hole 360a Wiring inside via hole 400 Coiled conductive structure 420 First conductor layer 420a Land 440 Second conductor layer

Claims

Claim 1 A resin sheet having a support and a resin composition layer formed by a resin composition provided on the support, wherein the resin composition comprises (A) a magnetic powder, (B) an epoxy resin, (C) a dispersant, (D) a curing agent, and (E) a thermoplastic resin, and (C) a component having a polyester backbone represented by the following chemical formula (1). [Chemical formula (1)] (In chemical formula (1), R each independently represents a divalent hydrocarbon group having 2 to 10 carbon atoms, and n represents an integer from 2 to 1,000.) Claim 2 A resin sheet according to claim 1, wherein the content of component (C) is 0.1 mass% or more and 5 mass% or less when the non-volatile component in the resin composition is 100 mass%. Claim 3 A resin sheet according to claim 1, wherein (A) the component comprises (A-1) a magnetic powder with an average particle diameter of 1 μm or more and (A-2) a magnetic powder with an average particle diameter of less than 1 μm. Claim 4 A resin sheet according to claim 1, wherein (A) the component comprises (A-1) a magnetic powder with an average particle diameter of 1 μm or more and 10 μm or less and (A-2) a magnetic powder with an average particle diameter of 0.005 μm or more and less than 1 μm. Claim 5 A resin sheet according to claim 1, wherein (A) the component is at least one selected from iron oxide powder and iron alloy-based metal powder. Claim 6 A resin sheet according to claim 1, wherein (A) a component comprises iron oxide, and the iron oxide comprises at least one selected from Ni, Cu, Mn and Zn. Claim 7 A resin sheet according to claim 1, wherein the content of component (A) is 70 mass% or more and 98 mass% or less when the non-volatile component in the resin composition is 100 mass%. Claim 8 A resin sheet according to claim 1, wherein when the non-volatile component in the resin composition is 100 mass%, the mass of (E) thermoplastic resin is E1, and when the non-volatile component in the resin composition is 100 mass%, the mass of (B) epoxy resin is B1, and B1 / E1 is 0.1 or more and 5 or less. Claim 9 A resin sheet for forming a magnetic layer of a circuit board in claim 1. Claim 10 In paragraph 1, a resin sheet for through-hole filling. Claim 11 A circuit board comprising a magnetic layer which is a cured product of a resin composition layer of a resin sheet described in any one of claims 1 to 10. Claim 12 A circuit board comprising a substrate having a through hole formed therein and a magnetic layer filled in the through hole, wherein the magnetic layer comprises a cured product of a resin composition layer of a resin sheet described in any one of claims 1 to 10. Claim 13 An inductor component comprising a circuit board as described in paragraph 11. Claim 14 A resin composition comprising (A) a magnetic powder, (B) an epoxy resin, (C) a dispersant, (D) a curing agent, and (E) a thermoplastic resin, wherein when the non-volatile component in the resin composition is 100 mass%, the mass of (E) the thermoplastic resin is E1, and when the non-volatile component in the resin composition is 100 mass%, the mass of (B) the epoxy resin is B1, so that B1 / E1 is 0.1 or more and 5 or less, and (C) the component has a polyester backbone represented by the following chemical formula (1). [Chemical formula (1)] (In chemical formula (1), R each independently represents a divalent hydrocarbon group having 2 to 10 carbon atoms, and n represents an integer from 2 to 1,000.) Claim 15 A circuit board comprising a magnetic layer which is a cured product of the resin composition described in paragraph 14. Claim 16 A circuit board having a substrate having a through hole and a cured product of the resin composition described in claim 14 filled in the through hole. Claim 17 An inductor component comprising a circuit board as described in paragraph 15 or 16.

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