resin sheets

Abstract

This invention provides resin sheets and the like that can be hardened to obtain materials with high relative magnetic permeability and excellent mechanical strength. The resin sheet of this invention has a support body and a resin composition layer formed of a resin composition disposed on the support body. The resin composition contains (A) magnetic powder, (B) epoxy resin, (C) dispersant, (D) hardener, and (E) thermoplastic resin. Component (C) has a polyester backbone as shown in the following general formula (1). In general formula (1), each R independently represents a divalent hydrocarbon group with 2 to 10 carbon atoms, and n represents an integer from 2 to 1000.

Description

Technical Field

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

[0002] Sensor-embedded substrates, which house sensors within circuit boards such as printed wiring boards, are generally formed using resin compositions containing magnetic powder. For sensors housed within sensor-embedded substrates, methods are known to increase the amount of magnetic powder in the resin composition or to improve the effective permeability of the magnetic layer, which is a cured component of the resin composition, in order to increase the inductance of the sensor.

[0003] For example, Patent Document 1 describes a resin sheet with a high filling of magnetic filler with an average particle size of 10 μm or more. [Previous Technical Documents] [Patent Literature]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 2014-127624 Summary of the Invention

[0005] [The problem solved by the invention]

[0006] In recent years, there has been a desire to further improve inductors. While increasing the relative permeability of an inductor can be considered by increasing the content of magnetic powder, this can reduce the mechanical strength (tensile strength) of the magnetic layer.

[0007] To improve relative permeability, the use of magnetic powder with a large average particle size or a flat shape has been considered. However, using such magnetic powder increases magnetic loss, which may reduce the performance of the sensor. Alternatively, magnetic powder with a small average particle size can also be considered. However, using such magnetic powder tends to reduce magnetic loss, which may also reduce the relative permeability.

[0008] The present invention is made in view of the above-mentioned matters, with the aim of providing resin sheets, resin compositions, and circuit boards and sensor components using the resin sheets or resin compositions that can produce hardened materials with high relative permeability and excellent mechanical strength. [Methods for solving the problem]

[0009] The inventors, through detailed research aimed at achieving the aforementioned objectives, discovered that by using the following resin sheet, the relative magnetic permeability of the cured resin composition layer can be increased, and excellent mechanical strength can be achieved, thus completing the present invention. The aforementioned resin sheet contains a resin composition layer formed from a resin composition containing a dispersant having a polyester backbone.

[0010] That is, the present invention contains the following content. [1] A resin sheet having a support and a resin composition layer formed of a resin composition disposed on the support, wherein the resin composition contains (A) magnetic powder, (B) epoxy resin, (C) dispersant, (D) hardener and (E) thermoplastic resin, and component (C) has a polyester skeleton as shown in the following general formula (1). (In general formula (1), each R independently represents a divalent hydrocarbon group with 2 to 10 carbon atoms, and n represents an integer from 2 to 1000.) [2] (C) The content of component is 0.1% to 5% by mass of the resin sheet as described in [1] when the non-volatile component in the resin composition is taken as 100% by mass. [3] (A) The resin flakes described in [1] or [2] contain magnetic powder with an average particle size of 1 μm or more (A-1) and magnetic powder with an average particle size of less than 1 μm (A-2). [4] (A) The component contains magnetic powder with an average particle size of 1 μm or more and 10 μm or less (A-1) and magnetic powder with an average particle size of 0.005 μm or more but less than 1 μm, as described in any of [1] to [3] resin flakes. [5] (A) The component is a resin sheet selected from at least one of iron oxide powder and ferroalloy metal powder as described in any of [1] to [4]. [6] (A) The component contains iron oxide powder, which contains resin flakes of at least one ferrite selected from Ni, Cu, Mn and Zn as described in any of [1] to [5]. [7] (A) The content of the component is 70% to 98% by mass or more when the non-volatile component in the resin composition is taken as 100% by mass, as in any of the resin sheets described in [1] to [6]. [8] When the non-volatile component in the resin composition is taken as 100% by mass, the mass of (E) thermoplastic resin is taken as E1, and the mass of (B) epoxy resin is taken as B1 when the non-volatile component in the resin composition is taken as 100% by mass, and the B1 / E1 is 0.1 to 5 or less, the resin sheet described in any of [1] to [7] is used. [9] A resin sheet as described in any of [1] to [8] used in the magnetic layer formation of a circuit board.

[10] Resin sheets as described in any of [1] to [9] for use in filling through holes.

[11] A circuit board containing a magnetic layer of a hardened material that is a resin composition layer as a resin sheet described in any of [1] to

[10] .

[12] A circuit board comprising a substrate having through holes and a magnetic layer filling the through holes, wherein the magnetic layer contains a hardened resin composition layer of a resin sheet as described in any of [1] to

[10] .

[13] A sensor component containing a circuit board as described in

[11] or

[12] .

[14] A resin composition comprising (A) magnetic powder, (B) epoxy resin, (C) dispersant, (D) curing agent and (E) thermoplastic resin, wherein when the non-volatile component in the resin composition is 100% by mass, the mass of (E) thermoplastic resin is E1, and when the non-volatile component in the resin composition is 100% by mass, the mass of (B) epoxy resin is B1, and B1 / E1 is 0.1 to 5 or less, and the (C) component has a polyester skeleton as shown in the following general formula (1). (In general formula (1), each R independently represents a divalent hydrocarbon group with 2 to 10 carbon atoms, and n represents an integer from 2 to 1000.)

[15] A circuit board containing a magnetic layer that is a hardened resin composition as described in

[14] .

[16] A circuit board containing a substrate having through holes and a hardened material of a resin composition as described in

[14] filling the aforementioned through holes.

[17] A sensor component containing a circuit board as described in

[15] or

[16] . [Effects of the Invention]

[0011] According to the present invention, a resin sheet with high relative permeability and excellent mechanical strength can be obtained, and a circuit board and sensor component using the resin sheet can be provided. Simple Explanation of the Diagram

[0012] [Figure 1] Figure 1 shows a cross-sectional view of the core substrate for forming through holes in the manufacturing method of the circuit board of the first embodiment. [Figure 2] Figure 2 shows a cross-sectional view of the core substrate for forming through holes in the manufacturing method of the circuit board of the first embodiment. [Figure 3] Figure 3 shows a cross-sectional view of a core substrate in which a plating layer is formed in a through hole during the manufacturing method of the circuit board of the first embodiment. [Figure 4] Figure 4 shows a cross-sectional view of the pattern of the laminated core substrate and the resin sheet in the manufacturing method of the circuit board of the first embodiment. [Figure 5] Figure 5 shows a cross-sectional view of the pattern of the laminated core substrate and the resin sheet in the manufacturing method of the circuit board of the first embodiment. [Figure 6] Figure 6 shows a cross-sectional view of step (2) of the method for manufacturing a circuit board in the first embodiment. [Fig. 7] Fig. 7 shows a cross-sectional view of step (3) of the method for manufacturing a circuit board in the first embodiment. [Fig. 8] Fig. 8 shows a cross-sectional view of step (5) of the method for manufacturing a circuit board in the first embodiment. [Fig. 9] Fig. 9 shows a cross-sectional view of step (5) of the method for manufacturing a circuit board in the first embodiment. [Fig. 10] Fig. 10 shows a schematic cross-sectional view of step (A) of the method for manufacturing a circuit board in the second embodiment. [Fig. 11] Fig. 11 shows a schematic cross-sectional view of step (A) of the method for manufacturing a circuit board in the second embodiment. [Fig. 12] Fig. 12 shows a schematic cross-sectional view of step (B) of the method for manufacturing a circuit board in the second embodiment. [Fig. 13] Fig. 13 shows a schematic cross-sectional view of step (D) of the manufacturing method of the circuit board used to illustrate the second embodiment. [Fig. 14] Fig. 14 shows a schematic plan view of a circuit board containing a sensor component of a circuit board obtained by the manufacturing method of the second embodiment of the circuit board, viewed from the thickness direction. [Fig. 15] Fig. 15 is a schematic diagram of the cut edge of the sensor component of the circuit board obtained by the manufacturing method of the circuit board of the second embodiment, which is cut at the position shown by the dashed line II-II. [Fig. 16] Fig. 16 is a schematic plan view used to illustrate the structure of the first conductor layer in a sensor component containing a circuit board obtained by the manufacturing method of the circuit board of the second embodiment. Implementation

[0013] [Types of Invention Implementation]

[0014] The embodiments of the present invention will be described below with reference to the drawings. The drawings are merely schematic representations of the shapes, dimensions, and arrangements of the constituent elements to an extent that the invention can be understood. The present invention is not limited by the following description, and the constituent elements may be suitably modified. In the drawings used in the following description, the same symbols are used to represent the same constituent elements, and omissions may occur when repeated descriptions are made. Furthermore, the configurations in the embodiments of the present invention are not necessarily manufactured or used according to the arrangements shown in the drawings.

[0015] [Resin flakes] The resin sheet of the present invention is a resin sheet having a support and a resin composition layer formed by the resin composition disposed on the support. The resin composition contains (A) magnetic powder, (B) epoxy resin, (C) dispersant, (D) hardener and (E) thermoplastic resin. Component (C) has a polyester skeleton as shown in the following general formula (1). (In general formula (1), each R independently represents a hydrocarbon group with 2 to 10 carbon atoms, and n represents an integer from 2 to 1000.)

[0016] In this invention, by incorporating dispersant (C) into the resin composition, a cured material with high relative magnetic permeability and excellent mechanical strength can be obtained. Furthermore, the aforementioned cured material generally also reduces magnetic loss. The layers constituting the resin sheet will be described in detail below.

[0017] <Support> Examples of support materials include films made of plastic materials, metal foils, and release paper, with films made of plastic materials and metal foils being preferred, and films made of plastic materials being even more desirable.

[0018] When a film made of plastic material is used as a support, examples of plastic materials include polyesters such as polyethylene terephthalate (hereinafter sometimes abbreviated as "PET") and polyethylene naphthalate (hereinafter sometimes abbreviated as "PEN"); acrylic polymers such as polycarbonate (hereinafter sometimes abbreviated as "PC"); polymethyl methacrylate (hereinafter sometimes abbreviated as "PMMA"); cyclic polyolefins; triacetin (hereinafter sometimes abbreviated as "TAC"); polyether sulfides (hereinafter sometimes abbreviated as "PES"); polyether ketones; polyimides; etc. Among these, polyethylene terephthalate and polyethylene naphthalate are preferred, and the simple polyethylene terephthalate is particularly preferred.

[0019] When using metal foil as a support, examples of metal foils include copper foil and aluminum foil. Among these, copper foil is preferred. As copper foil, foil made of copper alone can be used, or foil made of an alloy of copper with other metals (such as tin, chromium, silver, magnesium, nickel, zirconium, silicon, titanium, etc.) can be used.

[0020] For the support, matte treatment, corona treatment, anti-charge treatment, etc. can also be applied to the surface that bonds with the resin composition layer.

[0021] Furthermore, as a support, a support with a release layer can be used on the surface bonded to the resin composition layer. Examples of release agents for use in the release layer of a support with a release layer include one or more release agents selected from the group consisting of alkyd resins, polyolefin resins, urethane resins, and silicone resins. Commercially available release agents include, for example, "SK-1," "AL-5," and "AL-7" manufactured by Lintec Co., Ltd., which are alkyd resin-based release agents. Examples of supports with a release layer include "Lumirror T60" manufactured by Toray Co., Ltd.; "Purex" manufactured by Teijin Co., Ltd.; and "Unipeel" manufactured by Unitika Co., Ltd.

[0022] The thickness of the support is preferably in the range of 5μm to 75μm, and more preferably in the range of 10μm to 60μm. Furthermore, when using a support with a release layer, it is preferable that the total thickness of the support with the release layer falls within the above-mentioned range.

[0023] <Resin Composition Layer> In the resin sheet of the present invention, the resin composition layer disposed on the support is formed by the resin composition, which contains (A) magnetic powder, (B) epoxy resin, (C) dispersant, (D) hardener and (E) thermoplastic resin, and component (C) has a polyester skeleton as shown in the following general formula (1). (In general formula (1), each R independently represents a hydrocarbon group with 2 to 10 carbon atoms, and n represents an integer from 2 to 1000.)

[0024] The resin composition may further contain any components, including components (A) through (E). Examples of such arbitrary components include (F) other additives and (G) solvents. The components contained in the resin composition will be described in detail below.

[0025] -(A) Magnetic Powder- The resin composition contains (A) magnetic powder as component (A). As (A) magnetic powder, particles of a material having a relative magnetic permeability greater than 1 can be used. The material of (A) magnetic powder is generally an inorganic material, but it can also be a soft magnetic material or a hard magnetic material. (A) magnetic powder can be used alone, or two or more types can be used in combination. Therefore, (A) magnetic powder can be a soft magnetic powder, a hard magnetic powder, or a combination of soft and hard magnetic powders.

[0026] Examples of magnetic powders (A) include 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-based ferrite, iron oxide powder (III), and trioxide (III) Iron oxide powders, etc.; Fe-Si alloy powders, Fe-Si-Al alloy powders, Fe-Cr alloy powders, Fe-Cr-Si alloy powders, Fe-Ni-Cr alloy powders, Fe-Cr-Al alloy powders, Fe-Ni alloy powders, Fe-Ni-Mo alloy powders, Fe-Ni-Mo-Cu alloy powders, Fe-Co alloy powders, or Fe-Ni-Co alloy powders, etc., and other ferroalloy metal powders; Co-based amorphous alloys and other amorphous alloys.

[0027] Of which, (A) the magnetic powder is preferably selected from at least one of iron oxide powder and ferroalloy powder. As for the iron oxide powder, it is preferable to have at least one ferrite selected from Ni, Cu, Mn, and Zn, and even more preferably, it is preferable to have ferrite containing either Mn or Zn. Furthermore, as for the ferroalloy powder, it is preferable to have at least one ferroalloy powder selected from Si, Cr, Al, Ni, and Co, and even more preferably, it is preferable to have a ferroalloy powder containing Ni.

[0028] As for (A) magnetic powder, commercially available magnetic powders may be used. Specific examples of commercially available magnetic powders that may be used include: Powder Tech's "M03S", "M05S", "MZ03S", and "M001"; DOWA Electronics' "MA-RCO-24"; Sanyo Special Steel's "PST-S"; Epson Atomics' "AW2-08", "AW2-08PF20F", "AW2-08PF10F", "AW2-08PF3F", "Fe-3.5Si-4.5CrPF20F", "Fe-50NiPF20F", and "Fe-80Ni-4MoPF20F"; and JFE Chemical's "LD-M", "LD-MH", "KNI-106", "KNI-106GSM", "KNI-106GS", and "KNI-106GSM". 9”, “KNI-109GSM”, “KNI-109GS”; Toda Kogyo Co., Ltd.'s “KNS-415”, “BSF-547”, “BSF-029”, “BSN-125”, “BSN-125”, “BSN-714”, “BSN-828”, “S-1281”, “S-1641”, “S-1651”, “S-1470”, “S-1511”, “S-2430”; Nippon Heavy Chemical Industry Co., Ltd.'s “JR09P2”; CIK Nanotech Co., Ltd.'s “Nanotek”; Kinseimatec Co., Ltd.'s “JEMK-S”, “JEMK-H”; ALDRICH Co., Ltd.'s “Yttrium iron oxide”, etc. (A) One type of magnetic powder can be used alone, but from the viewpoint that the effects of the present invention can be significantly obtained, it is preferable to use two or more types together.

[0029] (A) Spherical magnetic powder is preferred. The aspect ratio (length of the major axis divided by the length of the minor axis) is preferably 2 or less, more preferably 1.5 or less, and even more preferably 1.2 or less. Generally, non-spherical, flat magnetic powders are more likely to improve relative permeability. However, spherical magnetic powders are particularly preferred from the viewpoint of generally reducing magnetic loss.

[0030] From the viewpoint of improving relative permeability, the average particle size of the magnetic powder (A) is preferably 0.01 μm or more, preferably 0.5 μm or more, and even more preferably 1 μm or more. Furthermore, it is preferably 10 μm or less, preferably 9 μm or less, and even more preferably 8 μm or less. When using two or more types of magnetic powder (A), the average particle size of the entire (A) component should be within this range.

[0031] The average particle size of magnetic powder can be determined using laser diffraction and scattering based on the Mie scattering theory. Specifically, using a laser diffraction and scattering particle size distribution measuring device, the particle size distribution of the magnetic powder is created on a volume basis, and the median diameter is used as the average particle size for measurement. It is preferable to use samples in which the magnetic powder is dispersed in water by ultrasonication. Suitable laser diffraction and scattering particle size distribution measuring devices include the "LA-500" manufactured by Horiba Corporation and the "SALD-2200" manufactured by Shimadzu Corporation.

[0032] (A) From the viewpoint of improving relative permeability, the specific surface area of ​​magnetic powder is preferably 0.05 m² / g or higher, more preferably 0.1 m² / g or higher, and even more preferably 0.3 m² / g or higher. Furthermore, it is preferably 10 m² / g or lower, more preferably 8 m² / g or lower, and even more preferably 5 m² / g or lower. The specific surface area of ​​(A) magnetic powder can be determined by the BET method. Moreover, when using two or more types of (A) magnetic powder, the overall specific surface area of ​​the (A) component within this range is acceptable.

[0033] (A) From the perspective of improving relative permeability, magnetic powder containing (A-1) magnetic powder with an average particle size of 1 μm or more and (A-2) magnetic powder with an average particle size of less than 1 μm is preferred.

[0034] (A-1) The average particle size of the magnetic powder with an average particle size of 1 μm or more is preferably 1.2 μm or more, and more preferably 1.5 μm or more. (A-1) The upper limit of the average particle size of the component is preferably 10 μm or less, more preferably 9 μm or less, and even more preferably 8 μm or less. (A-1) The average particle size of the component can be determined by the above method.

[0035] The specific surface area of ​​component (A-1) is preferably 0.01 m² / g or higher, more preferably 0.05 m² / g or higher, and even more preferably 0.1 m² / g or higher. Furthermore, it is preferably 2 m² / g or lower, more preferably 1.5 m² / g or lower, and even more preferably 1 m² / g or lower. The specific surface area of ​​component (A-1) can be determined by the method described above.

[0036] (A-2) The average particle size of the magnetic powder is less than 1 μm, preferably less than 0.8 μm, and more preferably less than 0.5 μm. (A-2) The lower limit of the average particle size of the component is preferably 0.005 μm or more, more preferably 0.01 μm or more, and even more preferably 0.02 μm or more. (A-2) The average particle size of the component can be determined by the above method.

[0037] The specific surface area of ​​component (A-2) is preferably 1 m² / g or higher, more preferably 2 m² / g or higher, and even more preferably 3 m² / g or higher. It is also preferably 500 m² / g or lower, more preferably 400 m² / g or lower, and even more preferably 300 m² / g or lower. The specific surface area of ​​component (A-2) can be determined by the method described above.

[0038] As a preferred embodiment of component (A), it is preferable to contain magnetic powder with an average particle size of 1 μm to 10 μm (A-1) and magnetic powder with an average particle size of 0.005 μm to 1 μm (A-2). It is even preferable to contain magnetic powder with an average particle size of 1.2 μm to 9 μm (A-1) and magnetic powder with an average particle size of 0.01 μm to 0.8 μm (A-2). It is even preferable to contain magnetic powder with an average particle size of 1.5 μm to 8 μm (A-1) and magnetic powder with an average particle size of 0.02 μm to 0.5 μm (A-2).

[0039] (A) The content (volume %) of magnetic powder: From the viewpoint of improving relative permeability and reducing loss coefficient, when the non-volatile component in the resin composition is taken as 100 vol%, it is preferably 40 vol% or more, more preferably 50 vol% or more, and even more preferably 60 vol% or more. Furthermore, it is preferably 85 vol% or less, more preferably 80 vol% or less, and even more preferably 70 vol% or less.

[0040] (A) The content (mass %) of magnetic powder: From the viewpoint of improving relative permeability and reducing loss coefficient, when the non-volatile component in the resin composition is taken as 100% by mass, it is preferably 70% by mass or more, more preferably 75% by mass or more, and even more preferably 80% by mass or more, or 90% by mass or more. Furthermore, it is preferably 98% by mass or less, more preferably 97% by mass or less, and even more preferably 96% by mass or less, or 95% by mass or less. Furthermore, in this invention, unless otherwise specified, the content of each component in the resin composition is the value when the non-volatile component in the resin composition is taken as 100% by mass.

[0041] (A) When the composition contains both components (A-1) and (A-2), from the viewpoint of improving relative permeability and reducing the loss coefficient, the content (mass %) of component (A-1) is preferably 50% or more, more preferably 60% or more, and even more preferably 70% or more. Furthermore, it is preferably 90% or less, more preferably 85% or less, and even more preferably 80% or less.

[0042] (A) When the composition contains both components (A-1) and (A-2), from the viewpoint of improving relative permeability and reducing the loss coefficient, the content (mass%) of component (A-2) is preferably 10% or more, more preferably 15% or more, and even more preferably 20% or more. Furthermore, it is preferably 50% or less, more preferably 40% or less, and even more preferably 30% or less.

[0043] When the content of component (A-1), representing 100% by mass of the non-volatile component in the resin composition, is defined as a1 (mass %), and the content of component (A-2), representing 100% by mass of the non-volatile component in the resin composition, is defined as a2, the ratio of 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) to bring a1 / a2 within this range, the desired effects of the present invention can be obtained more significantly.

[0044] -(B) Epoxy Resin- The resin composition contains epoxy resin as component (B). As (B) epoxy resins, examples include bisphenol A type epoxy resin; bisphenol F type epoxy resin; bisphenol S type epoxy resin; bisphenol AF type epoxy resin; dicyclopentadiene type epoxy resin; bisphenol type epoxy resin; phenolic varnish type epoxy resin; tert-butyl-catechol type epoxy resin; naphthol phenolic varnish type epoxy resin, naphthalene type epoxy resin, naphthol type epoxy resin, anthracene type epoxy resin, and other epoxy resins with condensation ring structures; glycidylamine type epoxy resin; glycidyl ester type epoxy resin; cresol phenolic varnish type epoxy resin; biphenyl type epoxy resin; linear aliphatic epoxy resin; epoxy resin with butadiene structure; alicyclic epoxy resin; heterocyclic epoxy resin; epoxy resin containing spirocyclic ring; cyclohexanediethanol type epoxy resin; tris(hydroxymethyl) type epoxy resin; tetraphenylethane type epoxy resin; cyclic aliphatic diglycidyl ether type epoxy resin, etc. Epoxy resin can be used alone or in combination of two or more types. (B) It is preferable that the epoxy resin is selected from one or more types of bisphenol A epoxy resin and bisphenol F epoxy resin, and it is even more preferable that it contains both bisphenol A epoxy resin and bisphenol F epoxy resin.

[0045] (B) Epoxy resins containing two or more epoxy groups per molecule are preferred. Furthermore, (B) epoxy resins with an aromatic structure are preferred, and when two or more epoxy resins are used, those with at least one aromatic structure are even more preferred. An aromatic structure is generally defined as an aromatic chemical structure, and may also contain polycyclic aromatics and aromatic heterocycles. The proportion of epoxy resins containing two or more epoxy groups per molecule, relative to 100% by mass of the non-volatile components, is preferably 50% by mass or more, more preferably 60% by mass or more, and particularly preferably 70% by mass or more.

[0046] Epoxy resins include those that are liquid at 25°C (hereinafter sometimes referred to as "liquid epoxy resin") and those that are solid at 25°C (hereinafter sometimes referred to as "solid epoxy resin"). The epoxy resin (B) in the resin composition may contain only liquid epoxy resin, only solid epoxy resin, or a combination of both. However, from the viewpoint of reducing the viscosity of the resin composition, those containing only liquid epoxy resin are preferred.

[0047] As liquid epoxy resins, mannitol epoxy resin, bisphenol A type epoxy resin, bisphenol F type epoxy resin, bisphenol AF type epoxy resin, naphthalene type epoxy resin, glycidyl ester type epoxy resin, glycidyl amine type epoxy resin, phenolic varnish type epoxy resin, alicyclic epoxy resin with ester skeleton, cyclohexanediethanol type epoxy resin, cyclic aliphatic diglycidyl ether type epoxy resin, cyclic aliphatic glycidyl ether type epoxy resin, cyclic aliphatic glycidyl ether type epoxy resin and epoxy resin with butadiene structure are preferred, with bisphenol A type epoxy resin and bisphenol F type epoxy resin being more preferred. Specific examples of liquid epoxy resins include DIC's "HP4032", "HP4032D", and "HP4032SS" (naphthalene-type epoxy resin); Mitsubishi Chemical's "828US", "jER828EL" (bisphenol A type epoxy resin), "jER807" (bisphenol F type epoxy resin), and "jER152" (phenolic varnish type epoxy resin); Mitsubishi Chemical's "630" and "630LSD"; and ADEKA's "ED-523T" (mannitol epoxy resin). Resins (adenosylglycerol), "EP-3980S" (glycidylamine type epoxy resin), "EP-4088S" (dicyclopentadiene type epoxy resin); "ZX1059" (a mixture of bisphenol A type epoxy resin and bisphenol F type epoxy resin) manufactured by Nippon Steel Chemical & Materials Co., Ltd., "EX-201" (cyclic aliphatic glycidyl ether type epoxy resin), "ZX1658" and "ZX1658GS" (cyclic aliphatic diglycidyl ether type epoxy resin); "EX-721" (glycidyl ester type epoxy resin) manufactured by Nagase Chemtex Co., Ltd.; "CELLOXIDE2021P" (alicyclic epoxy resin with ester skeleton) and "PB-3600" (epoxy resin with butadiene structure) manufactured by Daicel Chemical Industries, Ltd., etc. These can be used individually or in combination of two or more.

[0048] As solid epoxy resins, naphthalene-type tetrafunctional epoxy resins, cresol-phenolic varnish-type epoxy resins, dicyclopentadiene-type epoxy resins, succinate-type epoxy resins, naphthol-type epoxy resins, biphenyl-type epoxy resins, naphthylene ether-type epoxy resins, anthracene-type epoxy resins, bisphenol A-type epoxy resins, and tetraphenylethane-type epoxy resins are preferred. Specific examples of solid epoxy resins include DIC's "HP4032H" (naphthalene-type epoxy resin), "HP-4700", "HP-4710" (naphthalene-type tetrafunctional epoxy resin), "N-690" (cresol-phenolic varnish-type epoxy resin), "N-695" (cresol-phenolic varnish-type epoxy resin), "HP-7200", "HP-7200HH", and "HP-7200HH". "0H" (dicyclopentadiene type epoxy resin), "EXA-7311", "EXA-7311-G3", "EXA-7311-G4", "EXA-7311-G4S", "HP6000" (naphthyl ether type epoxy resin); "EPPN-502H" (phenol type epoxy resin), "NC7000L" (naphthol phenolic varnish type epoxy resin), "NC3" manufactured by Nippon Kayaku Co., Ltd. "000H", "NC3000", "NC3000L", "NC3100" (biphenyl type epoxy resin); "ESN475V" (naphthalene type epoxy resin) and "ESN485" (naphthol phenolic varnish type epoxy resin) manufactured by Nippon Steel Chemical & Materials Co., Ltd.; "YX4000H", "YL6121" (biphenyl type epoxy resin) and "YX4000HK" (biphenyl type epoxy resin) manufactured by Mitsubishi Chemical Co., Ltd. Epoxy resins include cresol-type epoxy resins, YX8800 (anthracene-type epoxy resin), PG-100 and CG-500 manufactured by Osaka Gas Chemical Co., Ltd., 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 can be used individually or in combination of two or more.

[0049] When using (B) epoxy resin, and combining liquid and solid epoxy resins, the mass ratio (liquid epoxy resin: solid epoxy resin) is preferably in the range of 1:0.1 to 1:4. By setting the mass ratio of liquid epoxy resin to solid epoxy resin within this range, an effect equivalent to obtaining a cured product with sufficient tensile strength can be achieved. From the viewpoint of the above effect, a mass ratio (liquid epoxy resin: solid epoxy resin) of liquid epoxy resin to solid epoxy resin is preferably set in the range of 1:0.3 to 1:3.5, 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.

[0050] (B) From the viewpoint of obtaining a magnetic layer exhibiting good mechanical strength, the content of epoxy resin is preferably 0.1% by mass or more, more preferably 0.3% by mass or more, more preferably 0.5% by mass or more, and 1% by mass or more when the non-volatile component in the resin composition is taken as 100% by mass. The upper limit of the epoxy resin content is not particularly limited as long as it achieves the effect of the present invention; 5% by mass or less is preferred, more preferably 3% by mass or less, and more preferably 2% by mass or less.

[0051] (B) The content (volume %) of epoxy resin is preferably 1% by mass or more, more preferably 3% by mass or more, and even more preferably 5% by mass or more, when the non-volatile component in the resin composition is taken as 100% by volume. The upper limit is not particularly limited as long as it achieves the effect of the present invention; preferably 25% by mass or less, more preferably 20% by mass or less, and even more preferably 15% by mass or less.

[0052] (B) The epoxy equivalent of the epoxy resin is preferably 50 g / eq. to 5000 g / eq., more preferably 50 g / eq. to 3000 g / eq., even more preferably 80 g / eq. to 2000 g / eq., and even more preferably 110 g / eq. to 1000 g / eq. By setting it within this range, a magnetic layer with sufficient crosslinking density and reduced surface roughness can be obtained. Furthermore, the epoxy equivalent can be determined according to JIS K7236, which is the mass of resin containing 1 equivalent of epoxy groups.

[0053] (B) The weight average molecular weight of the epoxy resin is preferably 100-5000, more preferably 250-3000, and even more preferably 400-1500. The weight average molecular weight of the epoxy resin is the weight average molecular weight converted from polystyrene by gel permeation chromatography (GPC).

[0054] -(C) Dispersant- The resin composition contains a dispersant that is a component (C) having a polyester skeleton as shown in the following general formula (1). (In general formula (1), each R independently represents a divalent hydrocarbon group with 2 to 10 carbon atoms, and n represents an integer from 2 to 1000.)

[0055] As mentioned above, increasing the content of (A) magnetic powder to improve relative permeability reduces the mechanical strength of the hardened resin composition layer. In this invention, since the resin composition contains (C) as a dispersant, compared with a resin composition that does not contain (C) (i.e., a resin composition having the same composition as the resin composition except for the absence of (C), it can improve both relative permeability and mechanical strength.

[0056] (C) The component has a polyester skeleton as shown in general formula (1). (In general formula (1), each R independently represents a divalent hydrocarbon group with 2 to 10 carbon atoms, and n represents an integer from 2 to 1000.)

[0057] In general formula (1), R represents a divalent hydrocarbon group with 2 to 10 carbon atoms. The hydrocarbon group has 2 or more carbon atoms, preferably 3 or more, and more preferably 4 or more. The upper limit of the number of carbon atoms is 10 or less, preferably 8 or less, and more preferably 6 or less. The hydrocarbon group can be any of linear, branched, or cyclic, with linear or branched hydrocarbon groups being preferred. Examples of hydrocarbon groups include aliphatic hydrocarbon groups and aromatic hydrocarbon groups, with aliphatic hydrocarbon groups being preferred. The hydrocarbon group can also be any of saturated or unsaturated hydrocarbon groups, with saturated hydrocarbon groups being preferred. Specific examples of hydrocarbon groups include alkyl, alkenyl, alkynyl, and aryl groups. Among these, from the viewpoint that the effects of the present invention can be significantly obtained, alkyl groups are particularly preferred.

[0058] Examples of alkyl groups include ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl, nonyl, and decyl. Examples of alkenyl groups include vinyl, propenyl, butenyl, pentenyl, hexenyl, heptenyl, octenyl, nonenyl, and decenyl. Examples of ynyl groups include ethynyl, propynyl, butynyl, pentynyl, hexynyl, heptynyl, octyynyl, nonynyl, and decynyl. Examples of aryl groups include phenyl and naphthyl. Butyl and pentyl are preferred as the radical (R).

[0059] The divalent hydrocarbon group represented by R in general formula (1) may have a substituent or may not have a substituent. The substituent is not particularly limited, and examples thereof include a halogen atom, -OH, -O-C1-6 alkyl, -N(C1-10 alkyl)2, C1-10 alkyl, C6-10 aryl, -NH2, -CN, -C(O)O-C1-10 alkyl, -COOH, -C(O)H, -NO2, etc. The term "Cp-q" (p and q are positive integers and satisfy p < q) means that the number of carbon atoms of the organic group described after this term is p to q. For example, the expression "C1-10 alkyl" means an alkyl group having 1 to 10 carbon atoms. These substituents may be bonded to each other to form a ring, and the ring structure also includes a spiro ring or a condensed ring.

[0060] The above substituents may further have a substituent (hereinafter sometimes referred to as a "secondary substituent"). As the secondary substituent, when not particularly described, the same ones as the above substituents can also be used.

[0061] In general formula (1), n represents an integer of 2 to 1000. n is 2 or more, preferably 5 or more, more preferably 10 or more. The upper limit is 1000 or less, preferably 500 or less, more preferably 100 or less, 50 or less.

[0062] Component (C) may contain an arbitrary skeleton in addition to the polyester skeleton represented by general formula (1) as long as the effects of the present invention are not hindered. Examples of the arbitrary skeleton include a polyester skeleton in which R in general formula (1) is a divalent hydrocarbon group having 1 or 11 or more carbon atoms (n is the same as in formula (1)), and a polyallylamine skeleton. For example, the terminal of the polyester skeleton is not particularly limited.

[0063] Examples of the terminal of component (C) include a residue of a carboxylic acid, a hydroxyl group, a hydrogen atom, etc., which will be described later.

[0064] Component (C) having a polyester skeleton represented by general formula (1) can be produced, for example, by reacting a lactone represented by general formula (2) and a carboxylic acid. <0000​​​​​​​

[0066] Carboxylic acids can function as initiators for the ring-opening polymerization of lactones represented by general formula (2). Examples of such carboxylic acids include ricinoleic acid, 9- and 10-hydroxystearic acid, castor oil fatty acids, hydrogenated castor oil fatty acids, lactic acid, 12-hydroxystearic acid, glycolic acid, and other hydroxycarboxylic acids; dodecanoic acid, stearic acid, etc. From the viewpoint that the effects of the present invention can be significantly obtained, hydroxycarboxylic acids are preferred.

[0067] The reaction temperature is preferably 120~220℃, and more preferably 160~210℃. The reaction time is 0.5~72 hours. When the reaction is carried out under a nitrogen flow, polyesters with a high degree of polymerization can be obtained.

[0068] Furthermore, from the perspective of controlling the reaction as necessary, the aforementioned reaction may also use a polymerization catalyst or polymerization initiator.

[0069] Examples of polymerization catalysts include quaternary ammonium salts such as tetramethylammonium chloride, tetrabutylammonium chloride, tetramethylammonium bromide, tetrabutylammonium bromide, tetramethylammonium iodide, tetrabutylammonium iodide, benzyltrimethylammonium chloride, benzyltrimethylammonium bromide, and benzyltrimethylammonium iodide; and tetramethylphosphonium chloride, tetrabutylphosphonium chloride, tetramethylphosphonium bromide, tetrabutylphosphonium bromide, tetramethylphosphonium iodide, tetrabutylphosphonium iodide, and benzyltrimethylphosphonium chloride. Quaternary phosphonium salts such as triphenylphosphonium bromide, triphenylphosphonium iodide, tetraphenylphosphonium chloride, tetraphenylphosphonium bromide, and tetraphenylphosphonium iodide; phosphorus compounds such as triphenylphosphine; organic carboxylic acids such as potassium acetate, sodium acetate, potassium benzoate, and sodium benzoate; alkali metal alkoxides such as sodium alkoxides and potassium alkoxides; tertiary amines; organotin compounds; organoaluminum compounds; organotitanate compounds such as tetrabutyl titanate; and zinc compounds such as zinc chloride.

[0070] Examples of aliphatic monocarboxylic acids that can be used as polymerization initiators include acetic acid, propionic acid, octanoic acid, nonanoic acid, decanoic acid, octyl acid, lauryl acid, myristic acid, palmitic acid, stearic acid, isononanoic acid, arachidic acid, etc.; and aromatic monocarboxylic acids such as benzoic acid and p-butylbenzoic acid, etc.

[0071] In the manufacture of component (C), in addition to the lactone and carboxylic acid shown in general formula (2), any monomer may be used without hindering the effects of the present invention. Examples of any monomer include polyallylamine. For example, when polyallylamine is used as any monomer, component (C) containing a polyallylamine backbone in addition to the polyester backbone shown in general formula (1) can be manufactured. The reaction temperature and reaction time are the same as those in the manufacture of component (C) having the polyester backbone shown in general formula (1).

[0072] Polyallylamine is obtained by polymerizing allylamine in the presence of a polymerization initiator and / or a chain transfer catalyst.

[0073] There are no particular limitations on the polymerization initiators, and examples include ketone peroxides such as methyl ethyl ketone, diacyl peroxides such as benzoyl peroxide, peroxydicarbonates such as diisopropyl peroxydicarbonate, peroxyketals such as 1,1-bis(t-butylperoxide)cyclohexane, hydroperoxides such as t-butyl hydroperoxide, peroxyesters such as t-butyl peroxyneopentate, other azobisisobutyronitrile, hydrogen peroxide, and first ferric salts. Polymerization initiators described in Japanese Patent Publication No. 2-14364 may also be used. One or more of these may be used alone.

[0074] There are no particular limitations on the catalysts used for chain transfer. Examples include alkyl thiols such as lauryl thiol, thiocarboxylic acids such as mercaptoacetic acid, 2-mercaptopropionic acid, and 3-mercaptopropionic acid, and thiocarboxylic acid esters such as butyl mercaptoacetate and 2-ethylhexyl mercaptoacetate. One or more of these can be used alone.

[0075] The weight average molecular weight of polyallylamine is preferably between 150 and 100,000, and more preferably between 600 and 20,000. When the weight average molecular weight is 150 or higher, the attraction force on particles such as component (A) can be increased, thereby improving particle dispersibility. When the weight average molecular weight is 100,000 or lower, particle aggregation can be suppressed, further improving particle dispersibility. Furthermore, polyallylamine with any weight average molecular weight can also be manufactured using the method described in Japanese Patent Publication No. 2-14364.

[0076] Polyallylamine can be sold as a commercial product. Examples of commercially available polyallylamine products include "PAA-01", "PAA-03", "PAA-05", "PAA-08", "PAA-15", "PAA-15C", and "PAA-25" manufactured by Nittobo Medical.

[0077] (C) The pH of the component is usually above 4 but below 7. The pH can be determined by an indicator method. Specifically, the test sample (at 22°C) with a dispersant concentration of 0.1 g / mL prepared by dissolving the dispersant in acetone is immersed in pH test paper for measurement. As pH test paper, pH test paper with a measurable pH range in the acidic region can be used (e.g., a measurement range of pH 0.0~14.0, pH 1.0~14.0, or pH 0.5~5.0, etc.), such as the pH test paper "pH Test Paper pH 1~14" (pH measurement range pH 1.0~14.0) manufactured by AS ONE Corporation.

[0078] From the viewpoint that the effects of this invention can be significantly obtained, the acid value of component (C) is preferably 1 mg KOH / g or higher, more preferably 3 mg KOH / g or higher, even more preferably 5 mg KOH / g, preferably 30 mg KOH / g or lower, more preferably 25 mg KOH / g or lower, and even more preferably 20 mg KOH / g or lower. The acid value can be determined by neutralization titration.

[0079] (C) When the component is a dispersant that reacts with polyallylamine, the amine value, from the viewpoint of achieving significant effects of the present invention, is preferably 1 mg KOH / g or higher, more preferably 5 mg KOH / g or higher, even more preferably 10 mg KOH / g or higher, preferably 45 mg KOH / g or lower, more preferably 40 mg KOH / g or lower, and even more preferably 35 mg KOH / g or lower. The amine value can be determined by neutralization titration.

[0080] From the viewpoint that the effects of the present invention can be significantly obtained, the weight-average molecular weight of component (C) is preferably 1000 or more, more preferably 1500 or more, more preferably 2000 or more, preferably 50000 or less, more preferably 40000 or less, and more preferably 30000 or less. The weight-average molecular weight is the weight molecular weight of polystyrene determined by gel permeation chromatography (GPC).

[0081] (C) The content of the components, from the viewpoint of significantly exerting the effect of the present invention, when the non-volatile components in the resin composition are taken as 100% by mass, it is preferably 0.1% by mass or more, more preferably 0.2% by mass or more, more preferably 0.3% by mass or more, and the upper limit is preferably 5% by mass or less, more preferably 3% by mass or less, and more preferably 1% by mass or less.

[0082] When the mass (mass%) of component (C) is taken as 100% by mass of the non-volatile component in the resin composition, and the mass (mass%) of magnetic powder (A) is taken as 100% by mass of the non-volatile component in the resin composition, (C1 / A1)×100 is preferably 0.1 or more, more preferably 0.2 or more, more preferably 0.3 or more, preferably 10 or less, more preferably 5 or less, and more preferably 1 or less. By adjusting the mass of component (A) and (C) to bring (C1 / A1)×100 into this range, the desired effects of the present invention can be obtained more significantly.

[0083] -(D) Hardener- The resin composition contains a (D) curing agent as component (D). The (D) curing agent is an epoxy resin curing agent that functions to cure the (B) epoxy resin, and a curing accelerator that functions to accelerate the curing speed of the (B) epoxy resin. The curing accelerator is usually used in conjunction with the epoxy resin curing agent. A resin composition containing only an epoxy resin curing agent as a (D) curing agent is preferred, and a composition containing both an epoxy resin curing agent as a (D) curing agent and a curing accelerator is even more preferred.

[0084] (Epoxy resin hardener) The epoxy resin curing agent is obtained by reacting it with epoxy resin (B) to cure the resin composition. Examples of epoxy resin curing agents include phenolic epoxy resin curing agents, naphthol-based epoxy resin curing agents, reactive ester-based epoxy resin curing agents, acid anhydride-based epoxy resin curing agents, benzoxazine-based epoxy resin curing agents, cyanate ester-based epoxy resin curing agents, and imidazole-based epoxy resin curing agents. From the viewpoint of achieving significant effects of the present invention, it is preferable to use one or more epoxy resin curing agents selected from phenolic epoxy resin curing agents and naphthol-based epoxy resin curing agents. One epoxy resin curing agent may be used alone, or two or more may be used in combination.

[0085] From the perspective of heat resistance and water resistance, phenolic epoxy resin curing agents with a phenolic varnish structure or naphthol-based epoxy resin curing agents with a phenolic varnish structure are preferred as curing agents for phenolic epoxy resins and naphthol-based epoxy resins, respectively. Among phenolic epoxy resin curing agents, nitrogen-containing phenolic epoxy resin curing agents are preferred, those with a triazine skeleton containing phenolic resin curing agents are more preferred, and those with a triazine skeleton containing phenolic varnish epoxy resin curing agents are even more preferred.

[0086] Specific examples of phenolic epoxy resin curing agents and naphthol-based epoxy resin curing agents include "MEH-7700", "MEH-7810", and "MEH-7851" manufactured by Meiwa Chemical Co., Ltd.; "NHN", "CBN", and "GPH" manufactured by Nippon Chemical Co., Ltd.; and "SN170", "SN180", "SN190", "SN475", "SN485", "SN495V", and "S" manufactured by Nippon Steel & Sumitomo Metal Chemical Co., Ltd. N375, SN395, DIC's TD-2090, LA-7052, LA-7054, LA-1356, LA-3018-50P, EXB-9500, HPC-9500, KA-1160, KA-1163, KA-1165, and Chung Yung Chemical's GDP-6115L and GDP-6115H, etc.

[0087] While there are no particular restrictions on the use of reactive ester-based epoxy resin curing agents, compounds with two or more highly reactive ester groups per molecule, such as phenolic esters, thiophenolic esters, N-hydroxyamine esters, and heterocyclic hydroxyl compounds, are generally preferred. These reactive ester-based epoxy resin curing agents are preferably obtained through the condensation reaction of carboxylic acid compounds and / or thiocarboxylic acid compounds with hydroxyl compounds and / or thiols. From the viewpoint of improving heat resistance, reactive ester-based epoxy resin curing agents obtained from carboxylic acid compounds and hydroxyl compounds are preferred, and those obtained from carboxylic acid compounds and phenolic compounds and / or naphthol compounds are even more preferred. Examples of carboxylic acid compounds include benzoic acid, acetic acid, succinic acid, maleic acid, itaconic acid, phthalic acid, isophthalic acid, terephthalic acid, and benzoic acid. Examples of phenolic or naphthol compounds include hydroquinone, resorcinol, bisphenol A, bisphenol F, bisphenol S, phenolphthalein, methylated bisphenol A, methylated bisphenol F, methylated bisphenol S, phenol, o-cresol, m-cresol, p-cresol, catechol, α-naphthol, β-naphthol, 1,5-dihydroxynaphthol, 1,6-dihydroxynaphthol, 2,6-dihydroxynaphthol, dihydroxybenzophenone, trihydroxybenzophenone, tetrahydroxybenzophenone, phloroglucinol, benzotriol, dicyclopentadiene-type diphenol compounds, and phenolic varnishes. The term "dicyclopentadiene-type diphenol compound" refers to a diphenol compound obtained by condensing one molecule of dicyclopentadiene with two molecules of phenol.

[0088] Specifically, reactive ester-based epoxy resin curing agents containing a dicyclopentadiene-type diphenol structure, reactive ester-based epoxy resin curing agents containing a naphthalene structure, reactive ester-based epoxy resin curing agents containing acetylated compounds of phenolic varnishes, and reactive ester-based epoxy resin curing agents containing benzoyl compounds of phenolic varnishes are preferred. The term "dicyclopentadiene-type diphenol structure" refers to a divalent structure formed by phenylene-dicyclopentadiene-phenylene.

[0089] As commercially available reactive ester-based epoxy resin curing agents, examples of reactive ester-based epoxy resin curing agents containing a dicyclopentadiene-type bisphenol structure include "EXB9451", "EXB9460", "EXB9460S", "HPC-8000-65T", "HPC-8000H-65TM", and "EXB-8000L-65TM" manufactured by DIC Corporation; and examples of reactive ester compounds containing a naphthalene structure include "EXB9416" manufactured by DIC Corporation. -70BK”; as an active ester epoxy resin curing agent containing phenolic varnish with acetylene, examples include “DC808” manufactured by Mitsubishi Chemical Corporation; as an active ester epoxy resin curing agent containing phenolic varnish with benzoylene, examples include “YLH1026”, “YLH1030”, and “YLH1048” manufactured by Mitsubishi Chemical Corporation; as an active ester epoxy resin curing agent containing phenolic varnish with acetylene, examples include “DC808” manufactured by Mitsubishi Chemical Corporation, etc.

[0090] Anhydride-based epoxy resin curing agents can be exemplified by epoxy resin curing agents having one or more anhydride groups within one molecule. Specific examples of anhydride-based epoxy resin curing agents include phthalic anhydride, tetrahydrophthalic anhydride, hexahydrophthalic anhydride, methyltetrahydrophthalic anhydride, methylhexahydrophthalic anhydride, methylnadic anhydride, hydrogenated methylnadic anhydride, trialkyltetrahydrophthalic anhydride, dodecenylsuccinic anhydride, 5-(2,5-dioxotetrahydro-3-furanyl)-3-methyl-3-cyclohexene-1,2-dicarboxylic anhydride, trimellitic anhydride, and phenyltetracarboxylic anhydride. Benzophenone tetracarboxylic anhydride, biphenyl tetracarboxylic anhydride, naphthalene tetracarboxylic anhydride, oxophthalic anhydride, 3,3'-4,4'-diphenyltetracarboxylic anhydride, 1,3,3a,4,5,9b-hexahydro-5-(tetrahydro-2,5-dioxo-3-furanyl)-naphtho[1,2-C]furan-1,3-dione, ethylene glycol bis(dehydrated trimellitate), styrene-maleic acid resin copolymerized with styrene and maleic acid, and other polymeric anhydrides.

[0091] Examples of commercially available anhydride-based epoxy resin hardeners include "HNA-100" and "MH-700" manufactured by Shin Nippon Rikka Co., Ltd.

[0092] Specific examples of benzoxazine-based epoxy resin hardeners include "HFB2006M" manufactured by Showa Polymer Co., Ltd., and "Pd" and "Fa" manufactured by Shikoku Chemical Co., Ltd.

[0093] 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-dimethylphenyl cyanate), 4,4'-ethylenediphenyl dicyanate, hexafluorobisphenol A dicyanate, 2,2-bis(4-cyanate)phenylpropane, 1,1-bis(4-cyanate phenylmethane), bis(4-cyanate-3,5-dimethylphenyl)methane, 1,3-bis(4-cyanate phenyl-1-(methylethylene))benzene, bis(4-cyanate phenyl)thioether, and bis(4-cyanate phenyl) ether, as well as multifunctional cyanate ester resins derived from phenolic varnishes and cresol varnishes, and some triazine-modified prepolymers of these cyanate ester resins. Specific examples of cyanate ester-based epoxy resin curing agents include Lonza Japan's "PT30" and "PT60" (both phenolic varnish-type multifunctional cyanate ester resins), "BA230", and "BA230S75" (a prepolymer of bisphenol A dicyanate that has been partially or completely triazinized into a trimer).

[0094] Examples of imidazole-based epoxy resin curing agents include 2-methylimidazolium, 2-undecylimidazolium, 2-heptadecylimidazolium, 1,2-dimethylimidazolium, 2-ethyl-4-methylimidazolium, 1,2-dimethylimidazolium, 2-ethyl-4-methylimidazolium, 2-phenylimidazolium, 2-phenyl-4-methylimidazolium, 1-benzyl-2-methylimidazolium, 1-benzyl-2-phenylimidazolium, 1-cyanoethyl-2-methylimidazolium, 1-cyanoethyl-2-undecylimidazolium, 1-cyanoethyl-2-ethyl-4-methylimidazolium, 1-cyanoethyl-2-phenylimidazolium, 1-cyanoethyl-2-undecylimidazolium trimellitate, 1-cyanoethyl-2-phenylimidazolium trimellitate, 2,4-diamino-6-[2'-methylimidazolyl-(1')]-ethyl-s-triazine, 2,4-di... Amino-6-[2'-undecylimidazolyl-(1')]-ethyl-s-triazine, 2,4-diamino-6-[2'-ethyl-4'-methylimidazolyl-(1')]-ethyl-s-triazine, 2,4-diamino-6-[2'-methylimidazolyl-(1')]-ethyl-s-triazine isocyanuric acid adduct, 2-phenylimidazolyl isocyanuric acid adduct, 2-phenyl-4,5-dihydroxy Imidazole compounds such as methylimidazole, 2-phenyl-4-methyl-5-hydroxymethylimidazole, 2,3-dihydro-1H-pyrrolo[1,2-a]benzimidazole, 1-dodecyl-2-methyl-3-benzylmethylimidazole onium chloride, 2-methylimidazoline, and 2-phenylimidazoline, as well as adducts of imidazole compounds with epoxy resins, are preferred, with 2-ethyl-4-methylimidazole and 1-benzyl-2-phenylimidazole being the most preferred.

[0095] As an imidazole-based epoxy resin curing agent, it can also be used in commercially available products, such as "2MZA-PW" and "2PHZ-PW" manufactured by Shikoku Chemical Industry Co., Ltd., and "P200-H50" manufactured by Mitsubishi Chemical Co., Ltd.

[0096] When the ratio of epoxy resin to epoxy resin curing agent is expressed as the ratio of [total number of epoxy groups in the epoxy resin] to [total number of reactive groups in the epoxy resin curing agent], a range of 1:0.2 to 1:2 is preferred, 1:0.3 to 1:1.5 is more preferred, and 1:0.4 to 1:1 is even more preferred. The reactive groups of the epoxy resin curing agent can be active hydroxyl groups, active ester groups, etc., and vary depending on the type of epoxy resin curing agent. Furthermore, the total number of epoxy groups in the epoxy resin is expressed as the sum of the mass of the non-volatile components of each epoxy resin divided by the epoxy equivalent, and the total number of reactive groups in the epoxy resin curing agent is expressed as the sum of the mass of the non-volatile components of each epoxy resin curing agent divided by the reactive group equivalent, and the sum of the reactive groups in the epoxy resin curing agent. By setting the ratio of epoxy resin to epoxy resin curing agent within this range, the heat resistance of the cured product can be further improved.

[0097] From the viewpoint that the effects of the present invention can be significantly obtained, the content of epoxy resin hardener is preferably 0.1% by mass or more when the resin component in the resin composition is 100% by mass, more preferably 0.5% by mass or more, more preferably 1% by mass or more, and the upper limit is preferably 5% by mass or less, more preferably 4% by mass or less, and more preferably 3% by mass or less.

[0098] (hardening accelerator) Curing accelerators typically act as catalysts in the curing reaction of (B) epoxy resins, promoting the curing process. Examples of curing accelerators include amine-based, imidazole-based, phosphorus-based, guanidine-based, and metal-based accelerators. From the viewpoint of reducing the viscosity of the resin composition, amine-based, imidazole-based, and guanidine-based curing accelerators are preferred; from the viewpoint of further improving the mechanical strength of the cured product, imidazole-based curing accelerators are preferred. Curing accelerators can be used alone or in combination of two or more. Curing accelerators are generally used in conjunction with epoxy resin curing agents.

[0099] Examples of amine-based hardening accelerators include trialkylamines such as triethylamine and tributylamine, 4-dimethylaminopyridine, benzyl dimethylamine, 2,4,6-tris(dimethylaminomethyl)phenol, and 1,8-diazabicyclo(5,4,0)-undecene, with 4-dimethylaminopyridine and 1,8-diazabicyclo(5,4,0)-undecene being preferred.

[0100] As an amine-based hardening accelerator, it can also be used in commercially available products, such as "PN-50", "PN-23", and "MY-25" manufactured by Ajinomoto Fine Techno Co., Ltd.

[0101] As an imidazole-based curing accelerator, it functions similarly to the aforementioned imidazole-based epoxy resin curing agents. When used in combination with other epoxy resin curing agents, the aforementioned imidazole-based epoxy resin curing agents may function as curing accelerators.

[0102] Examples of phosphorus-based hardening accelerators include triphenylphosphine, phosphonium borate compounds, tetraphenylphosphonium tetraphenyl borate, n-butylphosphonium tetraphenyl borate, tetrabutylphosphonium decanoate, (4-methylphenyl)triphenylphosphonium thiocyanate, tetraphenylphosphonium thiocyanate, and butyltriphenylphosphonium thiocyanate, with triphenylphosphine and tetrabutylphosphonium decanoate being preferred.

[0103] Examples of guanidine-based hardening promoters include dicyandiamide, 1-methylguanidine, 1-ethylguanidine, 1-cyclohexylguanidine, 1-phenylguanidine, 1-(o-tolyl)guanidine, dimethylguanidine, diphenylguanidine, trimethylguanidine, tetramethylguanidine, pentamethylguanidine, 1,5,7-triazabicyclo[4.4.0]dec-5-ene, 7-methyl-1,5,7-triazabicyclo[4.4.0]dec-5-ene, 1-methylbiguanidine, 1-ethylbiguanidine, 1-n-butylbiguanidine, 1-n-octadecylbiguanidine, 1,1-dimethylbiguanidine, 1,1-diethylbiguanidine, 1-cyclohexylbiguanidine, 1-allylbiguanidine, 1-phenylbiguanidine, and 1-(o-tolyl)biguanidine, with dicyandiamide and 1,5,7-triazabicyclo[4.4.0]dec-5-ene being preferred.

[0104] Examples of organometallic anneals or organometallic salts of metals such as cobalt, copper, zinc, iron, nickel, manganese, and tin can be cited as examples of organometallic anneals. Specific examples of organometallic anneals include organocobalt anneals such as cobalt(II) acetoacetone and cobalt(III) acetoacetone, organocopper anneals such as copper(II) acetoacetone, organozinc anneals such as zinc(II) acetoacetone, organoiron anneals such as iron(III) acetoacetone, organonickel anneals such as nickel(II) acetoacetone, and organomanganese anneals such as manganese(II) acetoacetone. Examples of organometallic salts include zinc octylate, tin octylate, zinc cycloalkanoate, cobalt cycloalkanoate, tin stearate, and zinc stearate.

[0105] From the viewpoint that the effects of the present invention can be significantly obtained, when the resin component in the resin composition is 100% by mass, it is preferably 0.001% by mass or more, more preferably 0.005% by mass or more, more preferably 0.01% by mass or more, and the upper limit is preferably 1% by mass or less, more preferably 0.1% by mass or less, and more preferably 0.05% by mass or less.

[0106] (D) From the viewpoint that the effects of the present invention can be significantly obtained, when the non-volatile component in the resin composition is taken as 100% by mass, the content of the hardener is preferably 0.1% by mass or more, more preferably 0.5% by mass or more, more preferably 1% by mass or more, and the upper limit is preferably 5% by mass or less, more preferably 4% by mass or less, and more preferably 3% by mass or less.

[0107] When the mass (mass%) of the curing agent (D) when the non-volatile component in the resin composition is 100% by mass is defined as D1, and the mass (mass%) of the dispersant (C) when the non-volatile component in the resin composition is 100% by mass is defined as C1, the C1 / D1 ratio is preferably 0.01 or higher, more preferably 0.05 or higher, even more preferably 0.1 or higher, preferably 5 or lower, more preferably 1.5 or lower, and even more preferably 1 or lower. Adjusting the mass of component (C) and component (D) to bring C1 / D1 into this range can more significantly achieve the desired effects of the present invention.

[0108] When the mass (mass %) of (A) magnetic powder, where the non-volatile component in the resin composition is 100% by mass, is defined as A1; when the mass (mass %) of (B) epoxy resin, where the non-volatile component in the resin composition is 100% by mass, is defined as B1; when the mass (mass %) of (C) dispersant, where the non-volatile component in the resin composition is 100% by mass, is defined as C1; and when the mass (mass %) of (D) curing agent, where the non-volatile component in the resin composition is 100% by mass, is defined as D1, the ratio (B1+C1+D1) / A1 is preferably 0.001 or more, more preferably 0.005 or more, more preferably 0.01 or more, preferably 1 or less, more preferably 0.5 or less, and more preferably 0.3 or less. Adjusting the mass of components (A) to (D) to bring (B1+C1+D1) / A1 into this range can more significantly achieve the desired effects of the present invention.

[0109] When the mass (mass%) of the magnetic powder (A) with the non-volatile component in the resin composition being 100% by mass is defined as A1, the mass (mass%) of the dispersant (C) with the non-volatile component in the resin composition being 100% by mass is defined as C1, and the mass (mass%) of the hardener (D) with the non-volatile component in the resin composition being 100% by mass is defined as D1, the ratio ((C1+D1) / A1)×100 is preferably 0.1 or more, more preferably 0.5 or more, more preferably 1 or more, preferably 10 or less, more preferably 5 or less, and more preferably 3 or less. By adjusting the mass of components (A), (C), and (D) to bring ((C1+D1) / A1)×100 into this range, the desired effects of the present invention can be obtained more significantly.

[0110] -(E) Thermoplastic resin- The resin composition contains thermoplastic resin (E) as component (E). By including component (E) in the resin composition, the stress of the hardened resin composition layer can be mitigated, thereby improving the mechanical strength of the hardened material.

[0111] Examples of (E) thermoplastic resins include phenoxy resins, polyvinyl acetal resins, polyolefin resins, polyimide resins, polybutadiene resins, polyamide-imide resins, polyether-imide resins, polyurethane resins, polyether-urethane resins, polyphenylene ether resins, polyether ether ketone resins, and polyester resins, with phenoxy resins being preferred. One type of (E) thermoplastic resin may be used alone, or in combination of two or more types.

[0112] Examples of phenoxy resins include those having one or more skeletons selected from the group consisting of bisphenol A, bisphenol F, bisphenol S, bisphenol acetophenone, phenolic varnish, biphenyl, fluorene, dicyclopentadiene, norbornene, naphthalene, anthracene, adamantane, terpene, and trimethylcyclohexane skeletons. The terminal group of a phenoxy resin may also be any functional group such as a phenolic hydroxyl group or an epoxy group. Specific examples of phenoxy resins include Mitsubishi Chemical's "1256" and "4250" (both phenoxy resins containing a bisphenol A backbone); Mitsubishi Chemical's "YX8100" (a phenoxy resin containing a bisphenol S backbone); Mitsubishi Chemical's "YX6954" (a phenoxy resin containing a bisphenol acetophenone backbone); Nippon Steel & Sumitomo Chemical's "FX280" and "FX293"; and Mitsubishi Chemical's "YL7500BH30", "YX6954BH30", "YX7553", "YX7553BH30", "YL7769BH30", "YL6794", "YL7213", "YL7290", "YL7482", and "YL7891BH30", etc.

[0113] Examples of polyethylene acetal resins include polyethylene formaldehyde resin and polyethylene butyral resin, with polyethylene butyral resin being preferred. Specific examples of polyethylene acetal resins include "Electrochemical Butyral 4000-2", "Electrochemical Butyral 5000-A", "Electrochemical Butyral 6000-C", and "Electrochemical Butyral 6000-EP" manufactured by Denki Kagaku Kogyo Co., Ltd.; and the S-LECBH series, BX series (e.g., BX-5Z), KS series (e.g., KS-1), BL series, and BM series manufactured by Sekisui Chemicals Co., Ltd.

[0114] Examples of polyolefin resins include low-density polyethylene, ultra-low-density polyethylene, high-density polyethylene, ethylene-vinyl acetate copolymer, ethylene-ethyl acrylate copolymer, ethylene-methyl acrylate copolymer, and other ethylene-based copolymers; as well as polyolefin polymers such as polypropylene and ethylene-propyl block copolymers.

[0115] Specific examples of polyimide resins include "SLK-6100" manufactured by Shin-Etsu Chemical Industry Co., Ltd., and "RIKACOATSN20" and "RIKACOATPN20" manufactured by Shin Nippon Rika Co., Ltd. Other specific examples of polyimide resins include linear polyimides (as described in Japanese Patent Application Publication No. 2006-37083) obtained by reacting difunctional hydroxyl-terminated polybutadiene, diisocyanate compounds, and tetracarboxylic anhydrides, and modified polyimides containing polyimides in a polysiloxane backbone (as described in Japanese Patent Application Publication Nos. 2002-12667 and 2000-319386, etc.).

[0116] Examples of polybutadiene resins include resins containing a hydrogenated polybutadiene backbone, polybutadiene resins containing hydroxyl groups, polybutadiene resins containing phenolic hydroxyl groups, polybutadiene resins containing carboxyl groups, polybutadiene resins containing acid anhydride groups, polybutadiene resins containing epoxy groups, polybutadiene resins containing isocyanate groups, polybutadiene resins containing urethane groups, and polyphenylene ether-polybutadiene resins.

[0117] Specific examples of polyamide-imide resins include "VylomaxHR11NN" and "VylomaxHR16NN" manufactured by Toyobo Co., Ltd. Other specific examples of polyamide-imide resins include modified polyamides such as "KS9100" and "KS9300" (a polysiloxane backbone containing polyamide-imide) manufactured by Hitachi Chemical Co., Ltd.

[0118] Specific examples of polyether resins include "PES5003P" manufactured by Sumitomo Chemical Co., Ltd.

[0119] Specific examples of polyurethane resins include Solvay Advanced Polymers' polyurethane "P1700" and "P3500".

[0120] Specific examples of polyphenylene ether resins include SABIC's "NORYL SA90". Specific examples of polyetherimide resins include GE's "Ultem".

[0121] Examples of polycarbonate resins include hydroxyl-containing polycarbonate resins, phenolic hydroxyl-containing polycarbonate resins, carboxyl-containing polycarbonate resins, anhydride-containing polycarbonate resins, isocyanate-containing polycarbonate resins, and aminocarbamate-containing polycarbonate resins. Specific examples of polycarbonate resins include "FPC0220" manufactured by Mitsubishi Gas Chemical Co., Ltd., "T6002" and "T6001" (polycarbonate diol) manufactured by Asahi Kasei Chemical Co., Ltd., and "C-1090," "C-2090," and "C-3090" (polycarbonate diol) manufactured by Kuraray Co., Ltd. Specific examples of polyetheretherketone (PEEK) resins include "Sumiploy K" manufactured by Sumitomo Chemical Co., Ltd.

[0122] Examples of polyester resins include polyethylene terephthalate resin, polyethylene naphthalate resin, polybutene terephthalate resin, polybutene naphthalate resin, polytrimethylene terephthalate resin, polytrimethylene naphthalate resin, and polycyclohexane dimethyl terephthalate resin.

[0123] (E) The weight-average molecular weight (Mw) of the thermoplastic resin is preferably greater than 5,000, more preferably 8,000 or higher, even more preferably 10,000 or higher, and especially preferably 20,000 or higher. There is no particular upper limit; for example, it can be less than 1 million, less than 500,000, or less than 100,000. (E) The weight-average molecular weight of the thermoplastic resin converted from polystyrene can be determined by gel permeation chromatography (GPC). Specifically, the weight-average molecular weight of the thermoplastic resin converted from polystyrene is determined using a Shimadzu LC-9A / RID-6A as the measuring apparatus, a Showa Denko Shodex K-800P / K-804L / K-804L as the column, and chloroform as the mobile phase. The column temperature is set at 40°C, and the measurement is performed using a standard curve of standard polystyrene.

[0124] (E) The content of thermoplastic resin relative to 100% by mass of the non-volatile components of the resin composition is preferably 0.1% by mass or more, more preferably 0.2% by mass or more, particularly preferably 0.3% by mass or more, preferably 5% by mass or less, more preferably 3% by mass or less, and particularly preferably 2% by mass or less. (E) When the amount of thermoplastic resin is within the aforementioned range, the magnetic properties of the cured resin composition become particularly good.

[0125] When the mass (mass %) of the thermoplastic resin (E) with the non-volatile component in the resin composition as 100% by mass is defined as E1, and the mass (mass %) of the epoxy resin (B) with the non-volatile component in the resin composition as 100% by mass is defined as B1, the B1 / E1 ratio is preferably 0.1 or more, more preferably 0.3 or more, more preferably 0.5 or more, preferably 5 or less, more preferably 1.5 or less, and more preferably 1 or less. By adjusting the mass of component (B) and component (E) to bring B1 / E1 into this range, the desired effects of the present invention can be obtained more significantly.

[0126] When the mass (mass %) of the thermoplastic resin (E) when the non-volatile component in the resin composition is 100% by mass is defined as E1, and the mass (mass %) of the dispersant (C) when the non-volatile component in the resin composition is 100% by mass is defined as C1, the C1 / E1 ratio is preferably 0.01 or higher, more preferably 0.05 or higher, more preferably 0.1 or higher, preferably 5 or lower, more preferably 1.5 or lower, and more preferably 1 or lower. By adjusting the mass of the (C) component and (E) to bring the C1 / E1 into this range, the desired effects of the present invention can be obtained more significantly.

[0127] When the non-volatile component in the resin composition is taken as 100% by mass, the mass (mass %) of (A) magnetic powder is taken as A1, the mass (mass %) of (B) epoxy resin is taken as B1, the mass (mass %) of (C) dispersant is taken as C1, the mass (mass %) of (D) curing agent is taken as D1, and the mass (mass %) of (E) thermoplastic resin is taken as E1, the ratio (B1+C1+D1+E1) / A1 is preferably 0.001 or more, more preferably 0.01 or more, more preferably 0.05 or more, preferably 1 or less, more preferably 0.5 or less, and more preferably 0.3 or less. By adjusting the quality of components (A) to (E) so that (B1+C1+D1) / A1 falls within this range, the desired effect of the present invention can be obtained more significantly.

[0128] When the mass (mass %) of the magnetic powder (A) with the non-volatile component in the resin composition being 100% by mass is defined as A1, the mass (mass %) of the dispersant (C) with the non-volatile component in the resin composition being 100% by mass is defined as C1, and the mass (mass %) of the thermoplastic resin (E) with the non-volatile component in the resin composition being 100% by mass is defined as E1, the value of ((C1+E1) / A1)×100 is preferably 0.1 or more, more preferably 0.5 or more, more preferably 1 or more, preferably 10 or less, more preferably 5 or less, and more preferably 3 or less. By adjusting the mass of components (A), (C), and (E) to bring ((C1+E1) / A1)×100 into this range, the desired effects of the present invention can be obtained more significantly.

[0129] -(F) Other Additives- The resin composition may further contain (F) other additives as necessary. Examples of such other additives include curing retarders such as triethyl borate; inorganic fillers (except those equivalent to magnetic powders); flame retardants; organic fillers; organometallic compounds such as organocopper compounds, organozinc compounds, and organocobalt compounds; as well as resin additives such as tackifiers; defoamers; leveling agents; adhesion promoters; and colorants.

[0130] -(G)solvent- The resin composition may further contain the solvent (G), which is a volatile component, among the non-volatile components (A) to (F) above.

[0131] Organic solvents are typically used as solvents for (G). Examples of organic solvents include ketone solvents such as acetone, methyl ethyl ketone, methyl isobutyl ketone, and cyclohexanone; ester solvents such as methyl acetate, ethyl acetate, butyl acetate, isobutyl acetate, isoamyl acetate, methyl propionate, ethyl propionate, and γ-butyrolactone; ether solvents such as tetrahydropyran, tetrahydrofuran, 1,4-dioxane, diethyl ether, diisopropyl ether, dibutyl ether, and diphenyl ether; alcohol solvents such as methanol, ethanol, propanol, butanol, and ethylene glycol; and 2-ethoxyethyl acetate, propylene glycol monomethyl ether acetate, diethylene glycol monoethyl ether acetate, ethyl diethylene glycol acetate, γ-butyrolactone, and methoxypropionic acid. Ether ester solvents such as methyl ester; ester alcohol solvents such as methyl lactate, ethyl lactate, and methyl 2-hydroxyisobutyrate; ether alcohol solvents such as 2-methoxypropanol, 2-methoxyethanol, 2-ethoxyethanol, propylene glycol monomethyl ether, and diethylene glycol monobutyl ether (butyl carbitol); acetamide solvents such as N,N-dimethylformamide, N,N-dimethylacetamide, and N-methyl-2-pyrrolidone; sulfoxide solvents such as dimethyl sulfoxide; nitrile solvents such as acetonitrile and propionitrile; aliphatic hydrocarbon solvents such as hexane, cyclopentane, cyclohexane, and methylcyclohexane; aromatic hydrocarbon solvents such as benzene, toluene, xylene, ethylbenzene, and trimethylbenzene. (G) Solvents may be used alone or in combination of two or more types.

[0132] The amount of solvent (G) is preferably set by adjusting the melt viscosity of the resin composition or the resin composition layer containing the resin composition to a suitable range. Alternatively, the resin composition may not contain solvent (G). For example, the amount of organic solvent contained in the above-mentioned resin composition relative to the total mass of the resin composition is preferably less than 1.0% by mass, more preferably less than 0.8% by mass, more preferably less than 0.5% by mass, and particularly preferably less than 0.1% by mass. While there is no particular limitation on the lower limit, it can be more than 0.001% by mass or not contained at all. By using a smaller amount of solvent in the resin composition, voids caused by solvent evaporation can be suppressed.

[0133] Although the thickness of the resin composition layer depends on the wiring thickness, core substrate thickness and through-hole size, it is preferred to be 5μm or more, preferably 10μm or more, especially 50μm or more, preferably 600μm or less, preferably 300μm or less, and especially preferably 200μm or less.

[0134] <Manufacturing Method of Resin Sheets> Resin sheets can be manufactured, for example, by a method comprising coating a resin composition onto a support. Alternatively, a resin composition layer can be manufactured, for example, by preparing a resin coating by dissolving or dispersing the resin composition in a solvent, applying the resin coating onto a support using a mold, and then drying it to form a resin composition layer. Furthermore, a resin composition layer can also be formed by directly coating a resin composition onto a support using a mold. The solvent described above (G) can be used as the solvent.

[0135] Drying can be carried out by known methods such as heating or blowing hot air. While there are no particular limitations on drying conditions, the content of organic solvents in the resin composition layer should be less than 10% by mass, preferably less than 5% by mass. Although this varies depending on the boiling point of the organic solvents in the resin coating, for example, when using a resin coating containing 30% to 60% by mass of organic solvents, a resin composition layer can be formed after drying at 50°C to 150°C for 3 to 10 minutes.

[0136] In resin sheets, a protective film, based on the support, can be further laminated onto the side not bonded to the resin composition layer (i.e., the reverse side of the support). The thickness of the protective film is not particularly limited, but can be, for example, 1 μm to 40 μm. By laminating the protective film, the adhesion of debris or scratches to the surface of the resin composition layer can be suppressed. Resin sheets can be stored in roll form. When a resin sheet has a protective film, the protective film can be peeled off to make it usable.

[0137] <Physical properties of the resin composition layer (resin composition), etc.> A hardened material obtained by heating the resin composition layer (resin composition) at 190°C for 90 minutes exhibits excellent mechanical strength (tensile strength). Therefore, the aforementioned hardened material can also achieve a magnetic layer with excellent tensile strength. As for tensile strength, 60 MPa or more is preferred, 70 MPa or more is more preferred, and 75 MPa or more is more preferred. While there is no particular upper limit, it can be 150 MPa or less, etc. Mechanical strength (tensile strength) can be measured using the method described in the examples below.

[0138] A cured material obtained by heating a resin composition layer (resin composition) at 190°C for 90 minutes exhibits a high relative permeability at a frequency of 50 MHz. Thus, the aforementioned cured material can realize a magnetic layer with high relative permeability. The relative permeability of this cured material at a frequency of 50 MHz is preferably 20 or higher, more preferably 20.5 or higher, and even more preferably 21 or higher. While there is no particular upper limit, it can be 100 or lower, etc. The relative permeability can be measured using the method described in the examples below.

[0139] A cured material obtained by heating a resin composition layer (resin composition) at 190°C for 90 minutes typically exhibits low magnetic loss at a frequency of 50 MHz. Thus, the aforementioned cured material can achieve a magnetic layer with low magnetic loss. The magnetic loss of this cured material 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. While there is no particular limitation on the lower limit, it can be 0.001 or more, etc. Magnetic loss can be measured using the method described in the examples below.

[0140] From the perspective of utilizing the advantages mentioned above, it is preferable to use a resin composition layer (resin composition) as a magnetic layer forming material on a circuit board. Furthermore, from the perspective of utilizing the advantages mentioned above, it is preferable to use a resin composition layer (resin composition) as a via filler for a core substrate. When laminating a core substrate and a resin sheet, inserting part or all of the resin composition layer into the via fills the via. Then, by curing the resin composition, a magnetic layer can be formed within the via.

[0141] [Resin Composition] The resin composition of the present invention contains (A) magnetic powder, (B) epoxy resin, (C) dispersant, (D) hardener and (E) thermoplastic resin. When the mass (mass %) of (E) thermoplastic resin is taken as 100% by mass of the non-volatile component in the resin composition, it is defined as E1. When the mass (mass %) of (B) epoxy resin is taken as 100% by mass of the non-volatile component in the resin composition, it is defined as B1. The ratio of B1 to E1 is 0.1 to 5 and (C) component has a polyester skeleton as shown in the following general formula (1). (In general formula (1), each R independently represents a hydrocarbon group with 2 to 10 carbon atoms, and n represents an integer from 2 to 1000.)

[0142] The resin composition may be in a state other than that of a resin composition layer formed on a sheet, or it may be the same composition as the aforementioned resin composition layer. The components contained in the resin composition are as described above.

[0143] [Hardened material] The cured product of the present invention is obtained by curing the resin composition layer of the present invention. Furthermore, the cured product of the present invention is obtained by curing the resin composition of the present invention. The curing conditions for the resin composition layer and the resin composition can use the conditions of step (2) described later. Also, preheating can be performed before heat curing the resin composition layer and the resin composition, and the preheating can be performed multiple times.

[0144] [Circuit substrate and its manufacturing method] The circuit board of one embodiment of the present invention includes a magnetic layer. This magnetic layer contains a cured resin composition layer of the aforementioned resin sheet, and preferably contains only the cured resin composition. The specific structure of the circuit board is not limited to having a magnetic layer containing the cured resin composition layer. The circuit board of the first embodiment is a circuit board having a core substrate as a substrate for forming through-holes and a magnetic layer filling the through-holes. Furthermore, the circuit board of the second embodiment is a circuit board containing a magnetic layer formed by the cured resin composition layer of the resin sheet. In these circuit boards, the magnetic layer may be a layer of cured resin composition, but it may also be a layer of cured resin composition. The manufacturing methods of the circuit board of the first and second embodiments will be described below. However, the manufacturing methods of the circuit board of the present invention are not limited to the first and second embodiments illustrated below.

[0145] <First Implementation Form> The circuit board of the first embodiment includes a core substrate with through-holes and a magnetic layer filling the through-holes. The circuit board includes, for example, the following sequence. (1) The step of laminating a core substrate and a resin sheet to form a through-hole, thereby filling the through-hole with a resin composition layer. (2) Step of hardening the resin composition layer to form a magnetic layer.

[0146] Furthermore, the method for manufacturing the circuit board in the first embodiment may include any combination of steps (1) to (2) described above. For example, the method for manufacturing the circuit board may include the following steps. (3) Steps for grinding the magnetic layer (4) The step of roughening the magnetic layer, and (5) The step of forming a conductor layer on the magnetic layer. The steps are usually performed in the order of (3), (4), and (5).

[0147] <Step (1)> Step (1) typically involves preparing a core substrate with through-holes. The core substrate can be prepared from commercially available materials. Alternatively, the core substrate can be prepared by manufacturing it using suitable materials. The following describes a method for manufacturing a core substrate for one example.

[0148] Figure 1 shows a schematic cross-sectional view of the core substrate 10 before forming vias in a method for manufacturing a circuit board according to a first embodiment of the present invention. The step of preparing the core substrate 10 may, as shown in the example in Figure 1, include preparing a core substrate 10 before forming vias that require a magnetic layer. This core substrate 10 is the substrate before forming the vias and may be a plate-like component.

[0149] The core substrate 10 typically includes a support substrate 11. Examples of the support substrate 11 include insulating substrates such as glass epoxy resin substrates, metal substrates, polyester substrates, polyimide substrates, BT resin substrates, and thermosetting polyphenylene ether substrates. Furthermore, a metal layer may also be provided on the support substrate 11. The metal layer may be provided on one side of the support substrate 11 or on both sides. An example is shown where metal layers 12 and 13 are provided on both surfaces of the support substrate 11. Examples of metal layers 12 and 13 include layers formed of metals such as copper. Metal layers 12 and 13 may be, for example, copper foil with a carrier, or metal layers formed of the material of the conductor layer described later.

[0150] Figure 2 shows a schematic cross-sectional view of the core substrate 10 in a method for manufacturing a circuit board according to a first embodiment of the present invention, in which a through-hole 14 is formed. The steps for preparing the core substrate 10 are illustrated in Figure 2, and may also include forming the through-hole 14 within the core substrate 10. The through-hole 14 is formed, for example, by drilling, laser irradiation, plasma irradiation, or other methods. Typically, the through-hole 14 is formed by forming a through-hole in the core substrate 10. As a specific example, the formation of the through-hole 14 can be performed using a commercially available drill bit apparatus. Examples of commercially available drill bit apparatus include, for example, the "ND-1S211" manufactured by Hitachi Via Mechanics.

[0151] Figure 3 shows a schematic cross-sectional view of a core substrate 10 in which a plating layer 20 is formed within a through-hole 14 in a method for manufacturing a circuit board according to a first embodiment of the present invention. The step of preparing the core substrate 10 may also include, as necessary, applying a roughening treatment to the core substrate 10 to form the plating layer 20 as shown in Figure 3. As the aforementioned roughening treatment, either a dry or wet roughening treatment may be performed. Examples of dry roughening treatment include plasma treatment. Examples of wet roughening treatment include a method that sequentially performs a swelling treatment using a swelling solution, a roughening treatment using an oxidizing agent, and a neutralization treatment using a neutralizing solution. The plating layer 20 can be formed by a plating method. The procedure for forming the plating layer 20 by the plating method can be the same as the formation of the conductor layer in step (5) described later. The figure shows an example where the plating layer 20 is formed within the through-hole 14, on the surface of the metal layer 12, and on the surface of the metal layer 13. Furthermore, in this example, the core substrate having the plating layer 20 is given the same symbol "10" as the core substrate 10 before the plating layer 20 is formed, and will be described accordingly.

[0152] Figure 4 shows a cross-sectional view, schematically representing the appearance of the laminated core substrate 10 and resin sheet 30 in a method for manufacturing a circuit board according to a first embodiment of the present invention. Step (1) includes, as shown in Figure 4, laminating the core substrate 10 and resin sheet 30 after preparing the core substrate 10 to form the through-hole 14. In this embodiment, an example of laminating a resin sheet 30 having a resin composition layer 31 and a support 32 onto one side 10U of the core substrate 10 will be described. In the following description, the side 10U of the core substrate 10 that is bonded to the resin sheet 30 will sometimes be referred to as the "first side 10U," and the opposite side will be referred to as the "second side 10D."

[0153] The lamination of the core substrate 10 and the resin sheet 30 is performed to fill part or all of the resin composition layer 31 into the through-hole 14. Thus, lamination is typically performed when joining the resin composition layer 31 and the core substrate 10. Specifically, the aforementioned lamination can be performed by heating and pressing the resin sheet 30 onto the core substrate 10, thereby attaching the resin composition layer 31 to the core substrate 10. As shown in Figure 4, when the resin sheet 30 has a support 32, the aforementioned lamination can be performed by pressing the resin sheet 30 towards the core substrate 10 from the support 32 side. Examples of components used for heat pressing (hereinafter sometimes referred to as "heat pressing components," not shown) include heated metal plates (SUS mirror plates, etc.) or metal rollers (SUS rollers, etc.). Although the heated pressing component can be directly pressed into the resin sheet 30, it is preferable to press it in through an elastic material such as heat-resistant rubber so that the resin sheet 30 can fully follow the uneven surface of the core substrate 10.

[0154] The lamination of the core substrate 10 and the resin sheet 30 can be performed, for example, by vacuum lamination. The lamination conditions can be as follows: The heat-pressing temperature is preferably 60°C to 160°C, more preferably in the range of 80°C to 140°C. The heat-pressing pressure is preferably 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 20 seconds to 400 seconds, more preferably in the range of 30 seconds to 300 seconds. Lamination is preferably performed under reduced pressure conditions below 13 hPa.

[0155] After lamination, the laminated resin sheet 30 can be smoothed under normal pressure (atmospheric pressure), for example, by pressing a heated pressing member into the support 32. The pressing conditions for smoothing can be the same as the heated pressing conditions for lamination described above. Furthermore, lamination and smoothing can be performed continuously using a vacuum laminate.

[0156] Figure 5 shows a cross-sectional view, schematically representing the appearance of the laminated core substrate 10 and resin sheet 30 in a method for manufacturing a circuit board according to a first embodiment of the present invention. As shown in Figure 5, by laminating the core substrate 10 and the resin sheet 30, the resin composition layer 31 of the resin sheet 30 enters the through-hole 14, thus filling the through-hole 14 with the resin composition layer 31. An example is illustrated where a portion of the resin composition layer 31 enters the through-hole 14, while another portion does not enter the through-hole 14 but adheres to the first surface 10U of the core substrate 10. In this way, a resin composition layer 31 can be formed on the first surface 10U of the core substrate 10. Another portion of the resin composition layer 31 that enters the through-hole 14 can further exit through the through-hole 14 from an opening on the second surface 10D side of the core substrate 10. In this way, a resin composition layer 31 can also be formed on the second surface 10D of the core substrate 10.

[0157] 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 illustrated where the support 32 is peeled off before step (2) after the core substrate 10 and the resin sheet 30 are laminated. However, the peeling off of the support 32 can also be performed after step (2).

[0158] <Step (2)> Figure 6 shows a schematic cross-sectional view illustrating step (2) of the method for manufacturing a circuit board according to the first embodiment of the present invention. After step (2) involves laminating the core substrate 10 and the resin sheet 30, as shown in Figure 6, the resin composition layer 31 is cured. By curing the resin composition layer 31, a magnetic layer 40 containing the cured resin composition can be formed. The magnetic layer 40 is formed within the through-hole 14 and can typically be further formed on the first surface 10U and the second surface 10D of the core substrate 10.

[0159] The resin composition layer 31 is typically cured by thermosetting. The thermosetting conditions for the resin composition layer 31 can be appropriately set within a range suitable for curing the resin composition layer 31. The curing temperature is preferably 60°C or higher, more preferably 70°C or higher, even more preferably 80°C or higher, preferably below 245°C, more preferably below 220°C, and even more preferably below 200°C. The curing time is preferably 5 minutes or more, more preferably 10 minutes or more, even more preferably 15 minutes or more, preferably below 120 minutes, more preferably below 110 minutes, and even more preferably below 100 minutes.

[0160] The curing degree of the magnetic layer 40 obtained in step (2) is preferably 80% or more, more preferably 85% or more, and even more preferably 90% or more. The curing degree can be measured, for example, using a differential scanning calorimeter.

[0161] The manufacturing method of the circuit board may also include a step of heating the core substrate 10 and the resin sheet 30 at a lower temperature than the temperature of the resin composition layer 31 before curing the resin composition layer 31 (preparatory heating step). For example, the resin composition layer 31 is first cured, and the resin composition layer 31 is usually preheated at a temperature of 50°C or higher but not exceeding 120°C (preferably 60°C or higher but not exceeding 110°C, and more preferably 70°C or higher but not exceeding 100°C) for a period of 5 minutes or more (preferably 5 minutes to 150 minutes, and more preferably 15 minutes to 120 minutes).

[0162] <Step (3)> Figure 7 shows a schematic cross-sectional view illustrating step (3) of the method for manufacturing a circuit board according to the first embodiment of the present invention. Step (3) may also include polishing the magnetic layer 40. Specifically, step (3) may also include a process of polishing the magnetic layer 40 on the outer portion of the through-hole 14. In the example shown in this embodiment, since the first surface 10U and the second surface 10D of the core substrate 10 have magnetic layers 40 formed thereon, the magnetic layers 40 on portions of the first surface 10U and the second surface 10D can be polished. The magnetic layer 40 on the outer portion of the through-hole 14 is generally an unwanted excess portion in the final product. By polishing as shown in Figure 7, this excess portion can be removed. Furthermore, by polishing, the polished surfaces 40U and 40D, which are the surfaces of the magnetic layer 40, can be planarized.

[0163] As a polishing method, a method can be used to remove unwanted portions of the magnetic layer 40. Examples of such polishing methods include polishing, belt polishing, and ceramic polishing. Examples of commercially available polishing devices include the "NT-700IM" manufactured by Ishii Optoelectronics Co., Ltd.

[0164] From the viewpoint that the arithmetic mean roughness (Ra) of the polished surfaces 40U and 40D of the magnetic layer 40 can improve the adhesion between them and the conductor layer (not shown in Figure 7), a surface roughness of 300 nm or more is preferred, 350 nm or more is preferable, and 400 nm or more is even more desirable. An upper limit of 1000 nm or less is preferred, 900 nm or less is preferable, and 800 nm or less is even more desirable. The surface roughness (Ra) can be measured, for example, using a non-contact surface roughness gauge.

[0165] After step (2) and before step (3), if the hardening degree of magnetic layer 40 is to be further improved, heat treatment can also be applied to magnetic layer 40. The temperature in the aforementioned heat treatment can be based on the aforementioned hardening temperature. Specifically, the heat treatment temperature is preferably above 120°C, more preferably above 130°C, more preferably above 150°C, preferably below 245°C, more preferably below 220°C, and more preferably below 200°C. The heat treatment time is preferably above 5 minutes, more preferably above 10 minutes, more preferably above 15 minutes, preferably below 150 minutes, more preferably below 120 minutes, and more preferably below 100 minutes.

[0166] By performing the above steps (1) to (2), and if necessary, by further performing step (3), a circuit board 100 having a core substrate 10 and a magnetic layer 40 filling the through-holes 14 of the core substrate 10 can be obtained. If necessary, steps (4) and (5) can be performed in the circuit board 100 thus obtained to form a conductor layer.

[0167] <Step (4)> Step (4) includes a process of roughening the magnetic layer. Typically, the polished surface of the magnetic layer is roughened. Furthermore, in step (4), not only the polished surface of the magnetic layer, but also the surfaces 10U and 10D of the core substrate 10 can be roughened.

[0168] While there are no particular limitations on the procedures and conditions for roughening treatment, the procedures and conditions used in the manufacturing of multilayer printed circuit boards can also be adopted. To give a specific example, roughening treatment can also be carried out by a method that includes swelling treatment with a swelling solution, roughening treatment with an oxidizing agent, and neutralization treatment with a neutralizing solution in sequence.

[0169] Examples of swelling solutions used in swelling processes include alkaline solutions and surfactant solutions, with alkaline solutions being preferred. Among alkaline solutions, sodium hydroxide solution and potassium hydroxide solution are preferred. Commercially available swelling solutions include, for example, "P" and "Swelling Dip Securigant SBU" manufactured by Atotech Japan.

[0170] The swelling treatment can be performed by immersing the magnetic layer in a swelling solution at 30°C to 90°C for 1 to 20 minutes. From the viewpoint of suppressing the swelling of the resin contained in the magnetic layer to an appropriate level, it is preferable to immerse the magnetic layer in a swelling solution at 40°C to 80°C for 5 to 15 minutes.

[0171] As an oxidant used in the roughening process, an alkaline permanganate solution, such as potassium permanganate or sodium permanganate dissolved in an aqueous solution of sodium hydroxide, can be cited as an example. The roughening process using an oxidant such as an alkaline permanganate solution is preferably carried out by immersing the magnetic layer in the oxidant solution heated to 60°C to 80°C for 10 to 30 minutes. Furthermore, the concentration of permanganate in the alkaline permanganate solution is preferably set at 5% to 10% by mass. Commercially available oxidants include, for example, alkaline permanganate solutions such as "Concentrate CompactP" and "Dosing Solution SecurityP" manufactured by Atotech Japan.

[0172] An acidic aqueous solution is preferred as the neutralizing liquid for neutralization treatment. Commercially available neutralizing liquids include, for example, "Reduction Solution SecurityP" manufactured by Atotech Japan. Neutralization can be performed by immersing the surface roughened by the oxidizing agent solution in a neutralizing liquid at 30°C to 80°C for 5 to 30 minutes. From a workability perspective, immersing the magnetic layer roughened by the oxidizing agent solution in a neutralizing liquid at 40°C to 70°C for 5 to 20 minutes is preferable.

[0173] From the viewpoint of improving adhesion between the magnetic layer surface and the conductor layer, the arithmetic mean roughness (Ra) of the roughened surface is preferably 300 nm or higher, more preferably 350 nm or higher, and even more preferably 400 nm or higher. The upper limit is preferably below 1500 nm, more preferably below 1200 nm, and even more preferably below 1000 nm. Surface roughness (Ra) can be measured, for example, using a non-contact surface roughness gauge.

[0174] <Step (5)> Figure 8 shows a schematic cross-sectional view of step (5) of the method for manufacturing a circuit board 100 according to the first embodiment of the present invention. Step (5) includes forming a conductor layer 50 on the polished surfaces 40U and 40D of the magnetic layer 40, as shown in Figure 8. This illustrates an example in which the conductor layer 50 is formed not only on the polished surfaces 40U and 40D of the magnetic layer 40, but also on the surrounding surfaces (e.g., the first surface 10U and the second surface 10D of the core substrate 10). Although Figure 8 shows an example of forming the conductor layer 50 on both sides of the core substrate 10, the conductor layer 50 may also be formed on only one side of the core substrate 10.

[0175] Figure 9 shows a schematic cross-sectional view of step (5) of the method for manufacturing a circuit board 100 according to the first embodiment of the present invention. As shown in Figure 9, step (5) may also 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 processes to form a patterned conductor layer 51.

[0176] Methods for forming the conductor layer 50 include, for example, plating, sputtering, and vapor deposition, with plating being preferred. In a preferred embodiment, a patterned conductor layer 51 with the desired wiring pattern can be formed by plating the surface of the magnetic layer 40 (and, if necessary, the core substrate 10) using a suitable method such as a semi-additive or fully additive method. Materials for the conductor layer 50 include, for example, single metals selected from gold, platinum, palladium, silver, copper, aluminum, cobalt, chromium, zinc, nickel, titanium, tungsten, iron, tin, and indium; and alloys of two or more metals grouped together with gold, platinum, palladium, silver, copper, aluminum, cobalt, chromium, zinc, nickel, titanium, tungsten, iron, tin, and indium. From the perspectives of versatility, cost, and ease of drafting, it is preferable to use chromium, nickel, titanium, aluminum, zinc, gold, palladium, silver, or copper, or nickel-chromium alloys, copper-nickel alloys, or copper-titanium alloys. Using chromium, nickel, titanium, aluminum, zinc, gold, palladium, silver, or copper, or nickel-chromium alloys, is even better, and using copper is the best.

[0177] The following is a detailed example of a method for forming the patterned conductor layer 51. A seed layer is formed on the polished surfaces 40U and 40D of the magnetic layer 40 using electroless plating. Next, a photomask pattern is formed on the seed layer as needed, followed by electroplating to form an electroplated layer. Subsequently, the photomask pattern is removed as needed, and the seed layer is further removed by etching or other processes to form the patterned conductor layer 51 with the desired wiring pattern. After the patterned conductor layer 51 is formed, annealing may be performed as needed to improve its adhesion strength. Annealing may be performed, for example, by heating at 150°C to 200°C for 20 to 90 minutes.

[0178] The thickness of the patterned conductor layer 51 is preferably 1 μm or more, more preferably 3 μm or more, even more preferably 5 μm or more, preferably 70 μm or less, more preferably 50 μm or less, even more preferably 40 μm or less, and especially preferably 10 μm or less.

[0179] By means of the above method, a circuit board 100 having a magnetic layer 40 is obtained. Since the magnetic layer 40 is obtained by curing a resin composition layer 31, it contains a cured resin composition. Therefore, since the magnetic layer 40 can contain a large amount of magnetic powder (not shown), it can have excellent magnetic properties.

[0180] <Second Implementation Form> The circuit board of the second embodiment includes a magnetic layer formed by curing a resin composition layer of a resin sheet. This circuit board, for example, includes the step of laminating (A) a resin sheet onto an inner substrate, thereby bonding the resin composition layer to the inner substrate to form the magnetic layer.

[0181] Furthermore, the manufacturing method of the circuit board in the second embodiment may include any step other than step (A). For example, the manufacturing method of the circuit board may include: (B) the step of creating openings in the magnetic layer; (C) The step of roughening the magnetic layer, and (D) The step of forming a conductor layer on the magnetic layer. The manufacturing method is preferably one that includes steps (A) to (D) in that order.

[0182] <Step (A)> Step (A) is a step of laminating a resin sheet onto an inner substrate to form a magnetic layer by bonding the resin composition layer to the inner substrate. In one embodiment of step (A), the resin sheet is laminated onto the inner substrate to bond the resin composition layer to the inner substrate, thereby thermosetting the resin composition layer and forming a magnetic layer.

[0183] Figure 10 is a schematic cross-sectional view illustrating step (A) of the method for manufacturing a circuit board according to the second embodiment of the present invention. Step (A) involves laminating a resin sheet 310 containing a support 330 and a resin composition layer 320a disposed on the support 330 onto an inner substrate 200, thereby bonding the resin composition layer 320a to the inner substrate 200.

[0184] The inner layer substrate 200 is an insulating substrate. Examples of materials for the inner layer substrate 200 include glass epoxy boards, metal substrates, polyester substrates, polyimide substrates, BT resin substrates, and thermosetting polyphenylene ether substrates. The inner layer substrate 200 can be an inner circuit board with wiring and the like precisely formed within this thickness.

[0185] As shown in Figure 10, the inner substrate 200 has a first conductor layer 420 disposed on a first main surface 200a and an external terminal 240 disposed on a second main surface 200b. The first conductor layer 420 may also contain a plurality of wirings. In the example shown, only the wiring of the coil-shaped conductive structure 400 constituting the sensor element is shown. The external terminal 240 is a terminal for electrically connecting an external device (not shown) to the sensor. The external terminal 240 may be configured as part of the conductor layer disposed on the second main surface 200b.

[0186] The conductor material that can form the first conductor layer 420 and the external terminal 240 is the same as the material of the conductor layer described in the "<Step (5)>" column of the first embodiment.

[0187] The first conductor layer 420 and the external terminal 240 can be a single-layer structure, or a single metal layer made of different types of metals or alloys, or a multiple-layer structure consisting of two or more alloy layers laminated together. Furthermore, 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.

[0188] While there are no particular limitations on the line (L) / space (S) ratio of the first conductor layer 420 and the external terminal 240, from the viewpoint that a magnetic layer with excellent smoothness can be obtained by reducing surface unevenness, it is generally 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. While there are no particular limitations on the lower limit of the line / space ratio, from the viewpoint of good embedding of the resin composition layer in the space, it is preferably 1 / 1 μm or more.

[0189] The inner layer substrate 200 is intended to have a plurality of through holes 220 extending from the first main surface 200a to the second main surface 200b. Through-hole wiring 220a can be provided in the through holes 220. The first conductor layer 420 in the through-hole wiring 220a is electrically connected to the external terminal 240.

[0190] The bonding between the resin composition layer 320a and the inner substrate 200 is the same as the lamination method of the core substrate and resin sheet described in the "<Step (1)>" column of the first embodiment.

[0191] After a resin sheet is laminated onto an inner substrate, the resin composition layer is thermocured to form a magnetic layer. As shown in Figure 11, the resin composition layer 320a bonded to the inner substrate 200 is thermocured to form a first magnetic layer 320.

[0192] The thermosetting conditions of the resin composition layer 320a are the same as those of the resin composition layer described in the "<Step (2)>" column of the first embodiment.

[0193] The support 330 can be removed between the thermosetting of step (A) and step (B), or it can be peeled off after step (B).

[0194] <Step (B)> Figure 12 shows a schematic cross-sectional view illustrating step (B) of the method for manufacturing a circuit board according to the second embodiment of the present invention. Step (B) involves forming a through hole 360 ​​by performing an opening process on the first magnetic layer 320.

[0195] The through-hole 360 ​​serves as the path for electrically connecting the first conductor layer 420 and the second conductor layer 440 (described later). The formation of the through-hole 360 ​​can correspond to the composition of the resin used in the formation of the magnetic layer, and can be implemented using tools such as drills, lasers, or plasma. The size or shape of the through-hole can be appropriately determined to suit the design of the circuit board.

[0196] <Step (C)> Step (C) includes applying a roughening treatment to the magnetic layer that forms the through hole. As a method for roughening treatment in step (C), it can be performed by the same method as described in the "<Step (4)>" column of the first embodiment.

[0197] The roughening process in step (C) can be a process of grinding the surface of the insulating layer. As a grinding method, it can be performed by the same grinding as described in the "<Step (3)>" column of the first embodiment.

[0198] From the viewpoint of improving plating adhesion, the arithmetic mean roughness (Ra) of the surface roughened as a magnetic layer is preferably 300 nm or more, more preferably 350 nm or more, and even more preferably 400 nm or more. The upper limit is preferably 1000 nm or less, more preferably 900 nm or less, and even more preferably 800 nm or less. Surface roughness (Ra) can be measured, for example, using a non-contact surface roughness gauge.

[0199] <Step (D)> Figure 13 shows a schematic cross-sectional view of step (D) of the method for manufacturing a circuit board according to the second embodiment of the present invention. Step (D) includes, as shown in Figure 13, forming a second conductor layer 440 on the first magnetic layer 320.

[0200] The conductor material that can form the second conductor layer 440 is the same as the material of the conductor layer described in the "<Step (5)>" column of the first embodiment.

[0201] From a thinning perspective, the thickness of the second conductor layer 440 is preferably below 70 μm, more preferably below 60 μm, even more preferably below 50 μm, and even more preferably below 40 μm. Ideally, it is below 30 μm, below 20 μm, below 15 μm, or below 10 μm. The lower limit is preferably above 1 μm, more preferably above 3 μm, and even more preferably above 5 μm.

[0202] 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 fully additive method, which includes an electroless plating step, a photomask pattern formation step, an electroplating step, and a flash etching step. By forming the second conductor layer 440 using a wet plating method, a second conductor layer 440 containing the desired wiring pattern can be formed. Furthermore, this step allows the wiring 360a within the through-hole to be incorporated into the through-hole 360.

[0203] The first conductor layer 420 and the second conductor layer 440, for example, as shown in Figures 14-16 below, can also be configured in a spiral shape. In one example, one end of the spiral-shaped wiring portion of the second conductor layer 440 is electrically connected to one end of the spiral-shaped wiring portion of the first conductor layer 420 via the through-hole wiring 360a. The other ends of the spiral-shaped wiring portion of the second conductor layer 440 are electrically connected to the landmass 420a of the first conductor layer 42 via the through-hole wiring 360a. In this way, the other ends of the spiral-shaped wiring portion of the second conductor layer 440 are electrically connected to the external terminal 240 via the through-hole wiring 360a, the landmass 420a, and the through-hole wiring 220a.

[0204] The coil-shaped conductive structure 400 is composed of a spiral wiring portion that is part of the first conductor layer 420, a spiral wiring portion that is part of the second conductor layer 440, and a through-hole wiring 360a that is electrically connected to the spiral wiring portion of the first conductor layer 420 and the spiral wiring portion of the second conductor layer 440.

[0205] Following step (D), a further step of forming a magnetic layer on the conductor layer can be performed. As shown in Figure 15, a second magnetic layer 340 is formed on the first magnetic layer 320 formed by the second conductor layer 440 and the wiring 360a within the through-hole. The second magnetic layer can also be formed by the same steps as those already described.

[0206] [Sensor components] The sensor component includes the circuit board of the present invention. When such a sensor component includes a circuit board obtained by the manufacturing method of the circuit board of the first embodiment, at least a portion of the hardened portion of the aforementioned resin composition layer has a sensor pattern formed by a conductor. Such a sensor component is applicable, for example, to the one described in Japanese Patent Application Publication No. 2016-197624.

[0207] Furthermore, when the circuit board is manufactured using the method of the second embodiment, the sensor substrate has a magnetic layer and a conductive structure embedded in at least a portion of the magnetic layer. A sensor element is formed by a portion of the magnetic layer containing the conductive structure and extending in the thickness direction of the magnetic layer, surrounded by the conductive structure. Figure 14 shows a schematic plan view of the sensor substrate containing the sensor element viewed from the thickness direction. Figure 15 is a schematic diagram of the cut edge of the sensor substrate shown in Figure 14, cut at the position indicated by the dotted line II-II. Figure 16 is a schematic plan view illustrating the structure of the first conductor layer in the sensor substrate.

[0208] As shown in Figures 14 and 15, one example of the circuit board 100 has 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), i.e., a stacked wiring board with stacked magnetic layers and stacked conductor layers. Furthermore, the sensor board 100 includes an inner layer board 200.

[0209] As shown in Figure 15, the magnetic portion 300 constituting the first magnetic layer 320 and the second magnetic layer 340 can be considered as an integral magnetic layer. Therefore, at least a portion of the coil-shaped conductive structure 400 is embedded in the magnetic portion 300. That is, in the sensor substrate 100 of this embodiment, the sensor element is composed of the coil-shaped conductive structure 400 and a core portion of the magnetic portion 300 extending in the thickness direction of the magnetic portion 300 and surrounded by the coil-shaped conductive structure 400.

[0210] As shown in Figure 16, in one example, the first conductor layer 420 includes a spiral-shaped wiring portion intended to form a coil-shaped conductive structure 400, and a rectangular landmass 420a electrically connected to the wiring 220a within the through-hole. In the example, the spiral-shaped wiring portion includes a straight portion, a curved portion bent at right angles, and a detour portion that causes the landmass 420a to meander. In the example, the spiral-shaped wiring portion of the first conductor layer 420 has a roughly rectangular overall outline and a shape that curls outwards in a counter-clockwise direction from the center.

[0211] Similarly, a second conductor layer 440 is provided on the first magnetic layer 320. The second conductor layer 440 contains a spiral-shaped wiring portion that is intended to form a coil-shaped conductive structure 400. In Figure 14 or Figure 15, the spiral-shaped wiring portion contains a straight portion and a bent portion that bends at right angles. In Figure 14 or Figure 15, the overall outline of the spiral-shaped wiring portion of the second conductor layer 440 is roughly rectangular, and it has a shape that curls outward from the center in a counterclockwise direction.

[0212] Such sensor components can be used as wiring boards for mounting electronic components such as semiconductor chips, or as (multilayer) printed wiring boards that use the wiring board as an inner layer substrate. Furthermore, they can be used as chip-mounted sensor components, or as surface-mounted printed wiring boards that use the chip sensor components.

[0213] Furthermore, various types of semiconductor devices can be manufactured using this wiring board. Semiconductor devices containing this wiring board are applicable to electrical products (such as computers, mobile phones, digital cameras, and televisions) and vehicles (such as motor vehicles, automobiles, trams, ships, and airplanes). [Example]

[0214] The present invention is described in detail below by way of embodiments, but the present invention is not limited to these embodiments. In the following description, unless otherwise specified, "parts" and "%" to indicate quantity represent "parts by mass" and "% by mass", respectively.

[0215] <Determination of pH of Dispersants (Indicator Method)> Dissolve the dispersant in acetone to prepare a test sample with a dispersant concentration of 0.1 g / mL (22℃). Stable immersion of pH test paper in the solution, followed by drying to remove excess moisture. Compare the color of the damp portion of the test paper with a color standard; the pH of the closest color is taken as the pH of each sample.

[0216] <Synthesis Example 1: Synthesis of Dispersant 1> In a reaction flask equipped with a thermometer, stirrer, nitrogen inlet, and reflux tube, 10.0 parts of 12-hydroxystearic acid (manufactured by Pure Chemical Industries, Inc.) and 190 parts of ε-caprolactone (manufactured by Pure Chemical Industries, Inc.) were added. The mixture was heated to 160°C over a nitrogen stream for 4 hours, and then heated at 160°C for 2 hours until the residual amount of ε-caprolactone was below 1%. The mixture was then cooled to room temperature. Hereinafter, this reaction solution is referred to as Dispersant 1. Dispersant 1 has a weight average molecular weight of 23,000 and an acid value of 9.0 mg KOH / g. The pH is 5 according to the indicator method.

[0217] <Synthesis Example 2: Synthesis of Dispersant 2> In a reaction flask equipped with a thermometer, stirrer, nitrogen inlet, and reflux tube, 10.0 parts of 12-hydroxystearic acid (manufactured by Pure Chemical Industries, Ltd.) and 180 parts of δ-valerolactone (manufactured by Tokyo Chemical Industry Co., Ltd.) were added. The mixture was heated to 160°C over a nitrogen stream for 4 hours, and then heated at 160°C for 2 hours until the residual amount of δ-valerolactone was less than 1%. The mixture was then cooled to room temperature. This reaction solution is referred to as Dispersant 2. Dispersant 2 has a weight average molecular weight of 22,000 and an acid value of 8.9 mg KOH / g. The pH is 5 according to the indicator method.

[0218] <Synthesis Example 3: Synthesis of Dispersant 3> In a reaction flask equipped with a thermometer, stirrer, nitrogen inlet, and reflux tube, a mixture of 25.0 parts xylene and 70 parts polyallylamine 10% aqueous solution ("PAA-1LV" manufactured by Nitto Spinning Co., Ltd., with a number average molecular weight of about 3,000) was stirred at 160°C. While distilling off the water using a separation device, xylene was refluxed into the reaction solution, and 114.21 parts of the dispersant obtained in Synthesis Example 1, heated to 160°C, were added. The reaction was carried out at 160°C for 2 hours. Further heating at 160°C for 4 hours, followed by distillation of xylene at 160°C, yielded dispersant 3. Dispersant 3 possesses an amine value of 31.0 mg KOH / g. After mixing, the amine value is 312.6 mg KOH / g. The pH, determined by the indicator method, is 6.

[0219] <Synthesis Example 4: Synthesis of Dispersant 4> In a reaction flask equipped with a thermometer, stirrer, nitrogen inlet, reflux tube, and water separator, 30.0 parts of xylene (manufactured by Pure Chemical Industries, Inc.), 300.0 parts of 12-hydroxystearic acid (manufactured by Pure Chemical Industries, Inc.), and 0.1 parts of tetrabutyl titanate (manufactured by Tokyo Chemical Industry Co., Ltd.) were added. The mixture was heated to 160°C over a nitrogen stream for 4 hours. Further heating at 160°C for 4 hours was then carried out, and the xylene was distilled off at 160°C to obtain dispersant 4. Dispersant 4 has a weight-average molecular weight of 6000 and an acid value of 23.0 mg KOH / g. The pH value in the indicator method is 5.

[0220] <Synthesis Example 5: Synthesis of Dispersant 5> In a reaction flask equipped with a thermometer, stirrer, nitrogen inlet, reflux tube, and water separator, 30.0 parts of xylene (manufactured by Pure Chemical Industries, Inc.), 300.0 parts of 12-hydroxystearic acid (manufactured by Pure Chemical Industries, Inc.), and 0.1 parts of tetrabutyl titanate (manufactured by Tokyo Chemical Industry Co., Ltd.) were added. The mixture was heated to 160°C over a nitrogen stream for 4 hours. It was then further heated at 160°C for 4 hours (at which point the acid value was approximately 20 mg KOH / g), and the xylene was distilled off at 160°C. Next, the mixture was cooled to room temperature, and the water produced during the heating reaction was separated from the xylene in the distillate. The xylene was then refluxed back into the reaction solution. This reaction solution was named polyester PE-1. In a reaction flask equipped with a thermometer, stirrer, nitrogen inlet, reflux tube, and water separator, a mixture of 25.0 parts xylene and 70 parts polyallylamine (a 10% aqueous solution manufactured by Nitto Spinning Co., Ltd., "PAA-1LV", with a number average molecular weight of approximately 3,000) was stirred at 160°C. While distilling off the water using a separator, xylene was backflowed into the reaction solution, and 2.5 parts polyester PE-1 were added. The reaction was carried out at 160°C for 2 hours. The mixture was then heated at 160°C for 4 hours to distill off the xylene. In dispersant 5, R in general formula (1) is a polyester backbone with 11 carbon atoms and has an amine value of 38.5 mg KOH / g and an acid value of 23.5 mg KOH / g. The amine value of the mixed dispersant 5 is 317 mg KOH / g. The pH of dispersant 5 obtained by indicator method is 6.

[0221] <Example 1: Manufacturing of Magnetic Coating 1> 2.41 parts by weight of mixed epoxy resin ("ZX-1059", a mixture of bisphenol A and bisphenol F epoxy resins, manufactured by Nippon Steel Chemical & Materials Co., Ltd.), 2.74 parts by weight of phenolic resin containing a triazine backbone ("LA-7054", manufactured by DIC Corporation, a 60% solid MEK solution with a hydroxyl equivalent of approximately 125), and phenoxy resin ("YL7553BH30", manufactured by Mitsubishi Chemical Co., Ltd., a 30% solid MEK and cyclohexylene resin). The following ingredients were used to prepare magnetic coating 1: 2.39 parts by weight of ketone 1:1 solution, 0.5 parts by weight of dispersant 1 (dispersant synthesized in Synthesis Example 1, a polyester dispersant with 5 carbon atoms), 3.0 parts by weight of solvent (cyclohexanone), 0.02 parts by weight of imidazole hardening accelerator ("2E4MZ", 2-ethyl-4-methylimidazolium, manufactured by Shikoku Chemical Industry Co., Ltd.), 27.91 parts by weight of magnetic powder ("MO3S", Fe-Mn ferrite, average particle size 0.4 μm, specific gravity 5.1 m² / g, manufactured by Powder Tech Co., Ltd.), and 93.19 parts by weight of magnetic powder ("MA-RCO-24", Fe-Ni alloy, manufactured by DOWA Electronics Co., Ltd., average particle size 3.0 μm).

[0222] <Example 2: Preparation of Magnetic Coating 2> In Example 1, the content of dispersant 1 (the dispersant synthesized in Synthesis Example 1, a polyester dispersant with 5 carbon atoms) was changed from 0.5 parts by mass to 1 part by mass. Magnetic coating 2 was prepared in the same manner as in Example 1, except for the above.

[0223] <Example 3: Preparation of Magnetic Coating 3> In Example 1, the content of dispersant 1 (the dispersant synthesized in Synthesis Example 1, a polyester dispersant with 5 carbon atoms) was changed from 0.5 parts by mass to 0.1 parts by mass. Magnetic coating 3 was prepared in the same manner as in Example 1, except for the above.

[0224] <Example 4: Modulation of Magnetic Coating 4> In Example 1, 0.5 parts by mass of dispersant 1 (the dispersant synthesized in Synthesis Example 1, a polyester dispersant with 5 carbon atoms) was changed to 0.5 parts by mass of dispersant 2 (the dispersant synthesized in Synthesis Example 2, a polyester dispersant with 4 carbon atoms). Magnetic coating 4 was prepared in the same manner as in Example 1, except for the above changes.

[0225] <Example 5: Preparation of Magnetic Coating 5> In Example 1, 0.5 parts by mass of dispersant 1 (the dispersant synthesized in Synthesis Example 1, a polyester dispersant with 5 carbon atoms) was changed to 0.5 parts by mass of dispersant 3 (the dispersant synthesized in Synthesis Example 3, a dispersant containing a polyester with 5 carbon atoms). Magnetic coating 5 was prepared in the same manner as in Example 1, except for the above changes.

[0226] <Example 6: Preparation of Magnetic Coating 6> In Example 1, 27.91 parts by weight of magnetic powder ("MO3S", Fe-Mn ferrite, average particle size 0.4 μm, specific gravity 5.1 m² / g, manufactured by Powder Tech) was changed to 27.91 parts by weight of magnetic powder ("MZO3S", Fe-Mn-Zn ferrite, average particle size 0.4 μm, specific gravity 5.1 m² / g, manufactured by Powder Tech). Except for the above, the magnetic coating 6 was prepared in the same manner as in Example 1.

[0227] <Comparative Example 1: Preparation of Magnetic Coating 7> In Example 1, 0.5 parts by mass of dispersant 1 (the dispersant synthesized in Synthesis Example 1, a polyester dispersant with 5 carbon atoms) was changed to 0.5 parts by mass of dispersant 4 (the dispersant synthesized in Synthesis Example 4, a polyester dispersant with 11 carbon atoms). Magnetic coating 7 was prepared in the same manner as in Example 1, except for the above changes.

[0228] <Comparative Example 2: Preparation of Magnetic Coating 8> In Example 1, 0.5 parts by mass of dispersant 1 (the dispersant synthesized in Synthesis Example 1, a polyester dispersant with 5 carbon atoms) was changed to 0.5 parts by mass of dispersant 5 (the dispersant synthesized in Synthesis Example 5, a dispersant containing polyester with 11 carbon atoms). Magnetic coating 8 was prepared in the same manner as in Example 1, except for the above changes.

[0229] <Comparative Example 3: Preparation of Magnetic Coating 9> In Example 1, 0.5 parts by mass of dispersant 1 (the dispersant synthesized in Synthesis Example 1, a polyester dispersant with 5 carbon atoms) was changed to 0.5 parts by mass of dispersant (ED-152, a dispersant without a polyester backbone, manufactured by Kusunoki Chemical Co., Ltd.). Magnetic coating 9 was prepared in the same manner as in Example 1, except for the above changes.

[0230] <Comparative Example 4: Preparation of Magnetic Coating 10> In Example 1, 0.5 parts by mass of dispersant 1 (the dispersant synthesized in Synthesis Example 1, a polyester dispersant with 5 carbon atoms) was changed to 0.5 parts by mass of dispersant (SC-1015F, a dispersant without a polyester backbone, manufactured by Nippon Oil Company). Magnetic coating 10 was prepared in the same manner as in Example 1, except for the above.

[0231] <Preparation of Resin Sheets> On a PET film (Toray's "Lumirror R80", 38 μm thick, softening point 130°C, hereinafter sometimes referred to as "release PET") prepared with magnetic coating in the examples and comparative examples, the thickness of the resin composition layer after drying was 100 μm. After drying at 65°C to 115°C (average 100°C) for 7 minutes, a resin sheet was obtained.

[0232] <Preparation of Thin-Layer Hardened Materials> Resin sheets were cut into squares with 200 mm sides. The cut resin sheets (200 mm sides) were then laminated onto a single side of a polyimide film (Ube Industries' Upilex 25S, 25 μm thick, 240 mm side) using a batch vacuum pressure laminator (Nikko Materials' two-stage accumulation laminator "CVP700"). The resin composition layer was brought into contact with the center of the smooth surface of the polyimide film. The lamination was performed by depressurizing the pressure for 30 seconds to below 13 hPa, followed by pressing at 100°C and 0.74 MPa for 30 seconds. This resulted in a multilayer film consisting of a support, a resin composition layer, and a polyimide film. After peeling off the support, the resin composition layer was thermosetting by heating at 190°C for 90 minutes. Subsequently, after peeling off the polyimide film, a sheet-like hardened material of the resin composition was obtained.

[0233] <Determination of Relative Permeability and Magnetic Loss> The obtained sheet-like hardened material was cut to obtain an evaluation sample 5 mm wide and 18 mm long. The relative permeability (μ') and magnetic loss (μ”) of this evaluation sample were measured using the Agilent Technologies HP8362B method at a measurement frequency of 50 MHz and a room temperature of 23°C via a 3-coil method. The magnetic loss was calculated using the formula tanδ = μ' / μ”. Furthermore, the relative permeability was evaluated according to the following criteria. 〇: Relative permeability is 20 or higher ×: Relative permeability not reaching 20

[0234] <Determination of Mechanical Strength (Tensive Strength)> The tensile strength of the obtained sheet-like hardened material was determined according to JIS K7127. The test results were evaluated based on the following criteria. 〇:60MPa or more ×: Not reaching 60MPa

[0235]

[0236] 10: Nuclear substrate 10U: First side 10D: Second Side 11:Support substrate 12: Metal layer 13: Metal layer 14: Through hole 20: Plating layer 30: Resin film 31: Resin composition layer 32: Support 40: Magnetic layer 40U: Grinding surface 40D: Grinding surface 50: Conductor layer 51: Patterned Conductor Layer 100: Circuit board 200: Inner layer substrate 200a: First primary surface 200b: Second Main Surface 220: Through hole 220a: Wiring inside through-hole 240:External terminal 300: Magnetic Section 310: Resin film 320a: Resin composition layer 320: First Insulation Layer 330: Support body 340: Second Insulation Layer 360: Through hole 360a: Wiring inside through hole 400: Coil-shaped conductive structure 420: First conductor layer 420a: Land 440: Second conductor layer

Claims

1. A resin sheet comprising a support and a resin composition layer formed of a resin composition disposed on the support, wherein, The resin composition contains (A) magnetic powder, (B) epoxy resin, (C) dispersant, (D) hardener and (E) thermoplastic resin, wherein component (C) has a polyester skeleton as shown in the following general formula (1), and (A) to (E) are non-volatile components; (in general formula (1), each R in the repeating structure can be the same or different, which represents a divalent hydrocarbon group with 2 to 10 carbon atoms, and n represents an integer from 2 to 1000).

2. The resin sheet of claim 1, wherein the content of component (C) is 0.1% to 5% by mass when the non-volatile components in the resin composition are taken as 100% by mass.

3. The resin sheet of claim 1, wherein component (A) contains magnetic powder with an average particle size of 1 μm to 10 μm (A-1) and magnetic powder with an average particle size of 0.005 μm to less than 1 μm (A-2).

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

5. The resin sheet of claim 1, wherein component (A) contains iron oxide powder, which contains at least one ferrite selected from Ni, Cu, Mn and Zn.

6. The resin sheet of claim 1, wherein the content of component (A) is 70% by mass or more and 98% by mass when the non-volatile components in the resin composition are taken as 100% by mass.

7. In the resin sheet of claim 1, when the mass of (E) thermoplastic resin is taken as E1 when the non-volatile component in the resin composition is taken as 100% by mass, and the mass of (B) epoxy resin is taken as B1 when the non-volatile component in the resin composition is taken as 100% by mass, the ratio of B1 / E1 is 0.1 or more and 5 or less.

8. The resin film as claimed in claim 1 is used for forming a magnetic layer on a circuit board.

9. The resin sheet as claimed in claim 1, which is used for filling through holes.

10. A circuit board comprising a magnetic layer, the magnetic layer being a cured resin composition layer of a resin sheet as claimed in any one of claims 1 to 9.

11. A circuit board comprising a substrate having through holes and a magnetic layer filling the through holes, the magnetic layer comprising a cured resin composition layer of a resin sheet as claimed in any one of claims 1 to 9.

12. A sensor component comprising a circuit board as claimed in claim 10.

13. A resin composition comprising (A) magnetic powder, (B) epoxy resin, (C) dispersant, (D) hardener and (E) thermoplastic resin, wherein when the non-volatile component in the resin composition is 100% by mass, the mass of (E) thermoplastic resin is E1, and when the non-volatile component in the resin composition is 100% by mass, the mass of (B) epoxy resin is B1, and B1 / E1 is 0.1 to 5, wherein component (C) has a polyester skeleton as shown in the following general formula (1), and (A) to (E) are non-volatile components; (in general formula (1), each R in the repeating structure may be the same or different, which represents a divalent hydrocarbon group with 2 to 10 carbon atoms, and n represents an integer from 2 to 1000).

14. A circuit board comprising a magnetic layer being a cured form of a resin composition as claimed in claim 13.

15. A circuit board comprising a substrate having through holes, and a cured resin composition of claim 13 filling the through holes.

16. A sensor component comprising a circuit board as claimed in claim 14 or 15.

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