JP7615892B2 - Resin Sheet - Google Patents

Description

The present invention relates to a resin sheet. It also relates to a printed wiring board, a semiconductor device, and a method for manufacturing a printed wiring board obtained by using the resin sheet.

In the manufacture of printed wiring boards, the insulating layer is formed by laminating and curing prepreg on a circuit board using a vacuum press process, as described in, for example, Patent Document 1.

JP 2017-57352 A

As printed wiring boards and the like become smaller in recent years, there is a demand to use a resin composition layer of a resin sheet instead of a prepreg in order to make the insulating layer thinner. When forming an insulating layer using a resin composition layer of a resin sheet, there is a method in which a resin composition layer is laminated and cured on a circuit board by a vacuum lamination method, and a method in which a resin composition layer is laminated and cured on a circuit board by a vacuum press treatment.

When forming an insulating layer by vacuum press processing using a resin composition layer of a resin sheet, the vacuum press processing applies a higher pressure to the resin composition layer of the resin sheet during lamination than the vacuum lamination method, and the uniformity of the thickness of the insulating layer may deteriorate due to resin flow (exudation of resin) in the resin composition layer, resulting in a deterioration of insulation reliability. On the other hand, if the viscosity of the resin is increased to suppress resin flow, the insulating layer may not be able to embed the wiring of the circuit board, resulting in poor embedding properties and poor insulation. In addition, if the support of the resin sheet has a metal foil with high roughness, the thickness of the insulating layer is likely to be thin in the rough areas, which may result in a significant deterioration in insulation reliability.

The object of the present invention is to provide a resin sheet capable of producing a cured product having excellent uniformity in the thickness of the insulating layer, embeddability, and insulation reliability; a printed wiring board and a semiconductor device formed using the resin sheet; and a method for manufacturing a printed wiring board.

As a result of intensive investigations into the above-mentioned problems, the present inventors have found that the above-mentioned problems can be solved by forming an insulating layer by vacuum press treatment using a resin sheet comprising a support including a metal foil having an arithmetic mean roughness (Ra) of more than 300 nm on the surface on the side bonded to the resin composition layer, and (A) a resin composition layer containing an inorganic filler having a specific surface area of 10 ^m2 /g or more provided on the support, wherein in dynamic viscoelasticity measurement of the resin composition layer at 60°C to 200°C, the maximum value of tan δ at 100°C or higher is 1.0 or more and 2.0 or less, and have thus completed the present invention.

That is, the present invention includes the following.
[1] A resin sheet for forming an insulating layer using a vacuum press treatment,
A support and a resin composition layer provided on the support,
the support has a metal foil having an arithmetic mean roughness (Ra) of more than 300 nm on the surface that is bonded to the resin composition layer;
The resin composition layer contains (A) an inorganic filler having a specific surface area of 10 m ² /g or more,
A resin sheet, wherein in dynamic viscoelasticity measurement of a resin composition layer from 60° C. to 200° C., the maximum value of tan δ at 100° C. or higher is 1.0 or higher and 2.0 or lower.
[2] The resin sheet according to [1], wherein the resin composition layer has a thickness of 30 μm or less.
[3] The resin sheet according to [1] or [2], wherein the resin composition layer contains any one of an active ester resin, a maleimide resin, and a vinyl resin.
[4] The resin sheet according to any one of [1] to [3], wherein the content of the component (A) is 73% by mass or less, when the content of the non-volatile components in the resin composition layer is 100% by mass.
[5] The resin sheet according to any one of [1] to [4], wherein the metal foil includes a copper foil.
[6] The resin sheet according to any one of [1] to [5], wherein the support has a thickness of 9 μm or more.
[7] A printed wiring board comprising an insulating layer made of a cured product of the resin composition layer of the resin sheet according to any one of [1] to [6].
[8] A semiconductor device comprising the printed wiring board according to [7].
[9] (I) a step of laminating the resin sheet according to any one of [1] to [6] on an inner layer substrate by vacuum pressing; and (II) a step of thermally curing the resin composition layer to form an insulating layer.
A method for manufacturing a printed wiring board, comprising:

The present invention provides a resin sheet capable of producing a cured product having excellent uniformity in the thickness of the insulating layer, embeddability, and insulation reliability; a printed wiring board and a semiconductor device formed using the resin sheet; and a method for manufacturing a printed wiring board.

The present invention will be described in detail below with reference to preferred embodiments. However, the present invention is not limited to the following embodiments and examples, and may be modified as desired without departing from the scope of the claims of the present invention and their equivalents.

[Resin sheet]
The resin sheet of the present invention is a resin sheet for forming an insulating layer using a vacuum press treatment. The resin sheet includes a support including a metal foil having an arithmetic mean roughness (Ra) of more than 300 nm on the surface bonded to a resin composition layer, and (A) a resin composition layer including an inorganic filler having a specific surface area of 10 ^m2 /g or more provided on the support, and is characterized in that the maximum value of tan δ at 100°C or higher is 1.0 or more and 2.0 or less in dynamic viscoelasticity measurement of the resin composition layer at 60°C to 200°C.

As mentioned above, when forming an insulating layer using a resin sheet (resin composition layer), the pressure applied to the resin sheet (resin composition layer) during lamination is higher in the vacuum press process than in the conventional vacuum lamination method, and the thickness of the insulating layer may not be uniform due to resin flow. On the other hand, if the viscosity of the resin composition layer is increased to suppress the exudation of the resin, the embeddability may be reduced and the insulation may be poor. The present inventor has found that the maximum value of tan δ (tan δ is the ratio E''/E'' of the storage modulus E' (GPa) and the loss modulus E'' (Pa)) in a specific temperature range in the dynamic viscoelasticity of the resin composition layer is related to the uniformity of the thickness of the insulating layer, embeddability, and insulation reliability. The present inventor has also found that the maximum value of tan δ can be adjusted by adjusting the amount of residual solvent in the resin composition layer in addition to the specific surface area of the inorganic filler in the resin composition layer, and as a result, it is possible to obtain a cured product with excellent uniformity of the thickness of the insulating layer, embeddability, and insulation reliability.

Each layer that makes up the resin sheet is described in detail below.

<Support>
In the resin sheet of the present invention, the support has a metal foil having an arithmetic mean roughness (Ra) of more than 300 nm on the support surface on which the resin composition layer is provided. Usually, the support surface having the arithmetic mean roughness (Ra) is the surface of the metal foil, and the surface of the metal foil is in contact with the resin composition layer. This allows the conductor layer described later to be formed from the support.

The arithmetic mean roughness (Ra) of the support surface on which the resin composition layer is provided is more than 300 nm, preferably 350 nm or more, more preferably 400 nm or more, and even more preferably 500 nm or more, from the viewpoint of improving adhesion with the resin composition layer. The upper limit is not particularly limited, but is preferably 1000 nm or less, more preferably 900 nm or less, and even more preferably 800 nm or less. The arithmetic mean roughness (Ra) is a value measured in accordance with ISO 25178, and can be measured using a non-contact surface roughness meter.

The ten-point average roughness (Rz) of the support surface on which the resin composition layer is provided is preferably more than 7000 nm, more preferably 8000 nm or more, and even more preferably 9000 nm or more, from the viewpoint of improving adhesion with the resin composition layer. There is no particular upper limit, but it is preferably 30000 nm or less, more preferably 20000 nm or less, and even more preferably 10000 nm or less. The ten-point average roughness (Rz) is a value measured in accordance with ISO 25178, and can be measured using a non-contact surface roughness meter.

The arithmetic mean roughness (Ra) and ten-point mean roughness (Rz) of the support surface can be adjusted to the above ranges, for example, by etching or polishing the support surface.

The support has a metal foil, and is preferably a metal foil. From the viewpoint of obtaining a significant effect of the present invention, the thickness of the support is preferably 9 μm or more, more preferably 10 μm or more, and even more preferably 11 μm or more. There is no particular upper limit, but it is preferably 30 μm or less, more preferably 20 μm or less, and even more preferably 15 μm or less. The metal foil may have a single layer structure or a multilayer structure. When the metal foil has a multilayer structure, it is preferable that the thickness of the entire metal foil is in this range, and the thickness of the ultra-thin metal foil may be, for example, in the range of 0.1 μm to 10 μm.

Examples of metal foils include copper foil and aluminum foil, with copper foil being preferred. As the copper foil, foil made of a single metal such as copper may be used, or foil made of an alloy of copper and another metal (e.g., tin, chromium, silver, magnesium, nickel, zirconium, silicon, titanium, etc.) may be used.

The metal foil may be a single-layer structure or a multi-layer structure in which two or more single metal layers or alloy layers made of different types of metals or alloys are laminated. Examples of multi-layer metal foils include metal foils containing a carrier metal foil and an ultra-thin metal foil bonded to the carrier metal foil. Such multi-layer metal foils may include a release layer between the carrier metal foil and the ultra-thin metal foil that enables the ultra-thin metal foil to be peeled off from the carrier metal foil. The release layer is not particularly limited as long as it can peel off the ultra-thin metal foil from the carrier metal foil, and examples of the release layer include an alloy layer of an element selected from the group consisting of Cr, Ni, Co, Fe, Mo, Ti, W, and P; an organic coating, and the like. When a multi-layer metal foil is used as the support, the resin composition layer is provided on the ultra-thin metal foil.

The method for producing the metal foil is not particularly limited, but it can be produced by known methods such as electrolysis and rolling.

The support may be provided with an optional layer other than the metal foil in combination with the metal foil. In this case, from the viewpoint of allowing the metal foil and the resin composition layer to be in direct contact with each other, it is preferable that the optional layer is provided on the side of the metal foil opposite the resin composition layer. Here, "direct" contact between the metal foil and the resin composition layer means that there is no other layer between the metal foil and the resin composition layer. In particular, it is preferable that there is no optional layer, and therefore it is preferable that the support is provided with only the metal foil.

The support may be a commercially available product. Examples of commercially available products include "HLP foil" and "JXUT-III foil" manufactured by JX Nippon Mining & Metals Corporation, "Microthin MT-Ex copper foil" and "TP-III foil" manufactured by Mitsui Mining & Smelting Co., Ltd., and "MW-G" manufactured by Mitsui Mining & Smelting Co., Ltd.

<Resin composition layer>
In the resin sheet of the present invention, the resin composition layer provided on the support contains (A) an inorganic filler having a specific surface area of 10 m ² /g or more.

The resin composition layer may further contain optional components in combination with component (A). Examples of optional components include (B) epoxy resin, (C) curing agent, (D) radical polymerizable compound, (E) thermoplastic resin, (F) curing accelerator, (G) polymerization initiator, and (H) other additives. Each component contained in the resin composition layer will be described in detail below.

--(A) Inorganic filler having a specific surface area of 10 m ² /g or more--
The resin composition layer contains, as component (A), an inorganic filler having a specific surface area of 10 ^m2 /g or more. By using a resin composition layer containing component (A), it is possible to improve embeddability and uniformity of the thickness of the insulating layer.

The specific surface area of the (A) component is ¹⁰ m 2 /g or more, preferably 15 m 2 /g or more, more preferably 20 m ² /g or more, and even more preferably 25 m ^{2 /g or more, from the viewpoint of improving embeddability and suppressing thickness variations caused by resin seepage to improve the uniformity of the insulating layer thickness. There is no particular upper limit, but it is preferably 60 m 2 / g} or less, 50 m ² /g or less, or 40 m ² /g or less. The specific surface area is obtained by adsorbing nitrogen gas to the sample surface using a BET fully automatic specific surface area measuring device (Macsorb HM-1210 manufactured by Mountech Co., Ltd.) according to the BET method, and calculating the specific surface area using the BET multipoint method.

The average particle size of component (A) is preferably 0.01 μm or more, more preferably 0.05 μm or more, and even more preferably 0.1 μm or more, from the viewpoint of improving embeddability and suppressing thickness variations caused by resin flow and improving the uniformity of the thickness of the insulating layer, and is preferably 5 μm or less, more preferably 4 μm or less, and even more preferably 3 μm or less.

The average particle size of component (A) can be measured by a laser diffraction/scattering method based on the Mie scattering theory. Specifically, a particle size distribution of the inorganic filler is created on a volume basis using a laser diffraction/scattering particle size distribution measuring device, and the median diameter is used as the average particle size. The measurement sample can be prepared by weighing 100 mg of inorganic filler and 10 g of methyl ethyl ketone into a vial and dispersing the mixture ultrasonically for 10 minutes. The measurement sample is measured using a laser diffraction particle size distribution measuring device with blue and red light wavelengths as the light source, and the volume-based particle size distribution of component (A) is measured using a flow cell method, and the average particle size can be calculated as the median diameter from the particle size distribution obtained. An example of a laser diffraction particle size distribution measuring device is the "LA-960" manufactured by Horiba, Ltd.

An inorganic compound is used as the material of component (A). Examples of materials for component (A) include silica, alumina, aluminosilicate, glass, cordierite, silicon oxide, barium sulfate, barium carbonate, talc, clay, mica powder, zinc oxide, hydrotalcite, boehmite, aluminum hydroxide, magnesium hydroxide, calcium carbonate, magnesium carbonate, magnesium oxide, boron nitride, aluminum nitride, manganese nitride, aluminum borate, strontium carbonate, strontium titanate, calcium titanate, magnesium titanate, bismuth titanate, titanium oxide, zirconium oxide, barium titanate, barium zirconate titanate, barium zirconate, calcium zirconate, zirconium phosphate, and zirconium tungstate phosphate. Among these, calcium carbonate and silica are preferred, and silica is particularly preferred. Examples of silica include amorphous silica, fused silica, crystalline silica, synthetic silica, and hollow silica. In addition, spherical silica is preferred as the silica. The component (A) may be used alone or in combination of two or more types.

Commercially available products of component (A) include, for example, "UFP-30" and "ASFP-20" manufactured by Denka; "SP60-05", "SP507-05", and "SPH516-05" manufactured by Nippon Steel Chemical & Material Co., Ltd.; "YC100C", "YA050C", "YA050C-MJE", and "YA010C" manufactured by Admatechs; "Silfil NSS-3N", "Silfil NSS-4N", and "Silfil NSS-5N" manufactured by Tokuyama Corporation; and "SC2500SQ", "SO-C4", "SO-C2", and "SO-C1" manufactured by Admatechs.

From the viewpoint of improving moisture resistance and dispersibility, it is preferable that the (A) component is treated with a surface treatment agent. Examples of the surface treatment agent include vinyl silane coupling agents, (meth)acrylic coupling agents, fluorine-containing silane coupling agents, amino silane coupling agents, epoxy silane coupling agents, mercapto silane coupling agents, silane coupling agents, alkoxy silanes, organo silazane compounds, and titanate coupling agents. Among them, amino silane coupling agents are preferable from the viewpoint of obtaining the effects of the present invention significantly. Moreover, the surface treatment agent may be used alone or in any combination of two or more types.

Commercially available surface treatment agents include, for example, Shin-Etsu Chemical Co., Ltd.'s "KBM1003" (vinyltriethoxysilane), Shin-Etsu Chemical Co., Ltd.'s "KBM503" (3-methacryloxypropyltriethoxysilane), Shin-Etsu Chemical Co., Ltd.'s "KBM403" (3-glycidoxypropyltrimethoxysilane), Shin-Etsu Chemical Co., Ltd.'s "KBM803" (3-mercaptopropyltrimethoxysilane), and Shin-Etsu Chemical Co., Ltd.'s "KBE903" (3-aminopropyltriethoxy silane), Shin-Etsu Chemical Co., Ltd.'s "KBM573" (N-phenyl-3-aminopropyltrimethoxysilane), Shin-Etsu Chemical Co., Ltd.'s "SZ-31" (hexamethyldisilazane), Shin-Etsu Chemical Co., Ltd.'s "KBM103" (phenyltrimethoxysilane), Shin-Etsu Chemical Co., Ltd.'s "KBM-4803" (long-chain epoxy-type silane coupling agent), Shin-Etsu Chemical Co., Ltd.'s "KBM-7103" (3,3,3-trifluoropropyltrimethoxysilane), etc.

From the viewpoint of improving the dispersibility of the inorganic filler, it is preferable that the degree of surface treatment with the surface treatment agent falls within a specified range. Specifically, 100 parts by mass of the inorganic filler is preferably surface-treated with 0.2 parts by mass to 5 parts by mass of the surface treatment agent, more preferably with 0.2 parts by mass to 3 parts by mass, and more preferably with 0.3 parts by mass to 2 parts by mass.

The degree of surface treatment by the surface treatment agent can be evaluated by the amount of carbon per unit surface area of the inorganic filler. From the viewpoint of improving the dispersibility of the inorganic filler, the amount of carbon per unit surface area of the inorganic filler is preferably 0.02 mg/m ² or more, more preferably 0.1 mg/m ² or more, and even more preferably 0.2 mg/m ² or more. On the other hand, from the viewpoint of suppressing the increase in the melt viscosity of the resin varnish and the melt viscosity in the sheet form, it is preferably 1 mg/m ² or less, more preferably 0.8 mg/m ² or less, and even more preferably 0.5 mg/m ² or less.

The amount of carbon per unit surface area of the inorganic filler can be measured after the surface-treated inorganic filler is washed with a solvent (e.g., methyl ethyl ketone (MEK)). Specifically, a sufficient amount of MEK as a solvent is added to the inorganic filler that has been surface-treated with a surface treatment agent, and ultrasonic cleaning is performed at 25°C for 5 minutes. After removing the supernatant and drying the solids, the amount of carbon per unit surface area of the inorganic filler can be measured using a carbon analyzer. An example of a carbon analyzer that can be used is the "EMIA-320V" manufactured by Horiba, Ltd.

From the viewpoint of adjusting the maximum value of tan δ within an appropriate range, the content of the (A) component is preferably 73% by mass or less, more preferably 72% by mass or less, even more preferably 71% by mass or less, 70% by mass or less, 69% by mass or less, or 68% by mass or less, and is preferably 30% by mass or more, more preferably 40% by mass or more, and even more preferably 50% by mass or more, when the non-volatile components in the resin composition layer are taken as 100% by mass, unless otherwise specified. In the present invention, the content of each component in the resin composition layer is the value when the non-volatile components in the resin composition layer are taken as 100% by mass.

-(B) Epoxy resin-
The resin composition layer may contain an epoxy resin (B) as the component (B). The epoxy resin (B) may be used alone or in combination of two or more kinds.

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

The resin composition layer preferably contains, as component (B), an epoxy resin having two or more epoxy groups in one molecule. From the viewpoint of obtaining the desired effect of the present invention significantly, the ratio of the epoxy resin having two or more epoxy groups in one molecule to 100% by mass of the non-volatile components of the thermosetting resin is preferably 50% by mass or more, more preferably 60% by mass or more, and particularly preferably 70% by mass or more.

Epoxy resins include epoxy resins that are liquid at a temperature of 20°C (hereinafter sometimes referred to as "liquid epoxy resins") and epoxy resins that are solid at a temperature of 20°C (hereinafter sometimes referred to as "solid epoxy resins"). The resin composition layer may contain only liquid epoxy resins or only solid epoxy resins as the thermosetting resin, but it is preferable to contain a combination of liquid epoxy resins and solid epoxy resins.

Preferably, the liquid epoxy resin has two or more epoxy groups in one molecule.

Preferred liquid epoxy resins are bisphenol A type epoxy resins, bisphenol F type epoxy resins, bisphenol AF type epoxy resins, naphthalene type epoxy resins, glycidyl ester type epoxy resins, glycidyl amine type epoxy resins, phenol novolac type epoxy resins, alicyclic epoxy resins having an ester skeleton, cyclohexane type epoxy resins, cyclohexane dimethanol type epoxy resins, glycidyl amine type epoxy resins, and epoxy resins having a butadiene structure, glycidyl cyclohexane type epoxy resins, and phenol phthalimidine type epoxy resins, with glycidyl cyclohexane type epoxy resins being more preferable.

Specific examples of liquid epoxy resins include DIC's "HP4032", "HP4032D", and "HP4032SS" (naphthalene type epoxy resins); Mitsubishi Chemical's "828US", "jER828EL", "825", and "Epicoat 828EL" (bisphenol A type epoxy resins); Mitsubishi Chemical's "jER807" and "1750" (bisphenol F type epoxy resins); Mitsubishi Chemical's "jER152" (phenol novolac type epoxy resin); and Mitsubishi Chemical's "630" and "630LSD" (glycidylamine type epoxy resins). ); "ZX1059" (a mixture of bisphenol A type epoxy resin and bisphenol F type epoxy resin) manufactured by Nippon Steel Chemical &Material; "EX-721" (glycidyl ester type epoxy resin) manufactured by Nagase ChemteX; "Celloxide 2021P" (alicyclic epoxy resin having an ester skeleton) manufactured by Daicel; "PB-3600" (epoxy resin having a butadiene structure) manufactured by Daicel; "ZX1658" and "ZX1658GS" (liquid 1,4-glycidylcyclohexane type epoxy resin) manufactured by Nippon Steel Chemical & Material. These may be used alone or in combination of two or more types.

As the solid epoxy resin, a solid epoxy resin having three or more epoxy groups in one molecule is preferable, and an aromatic solid epoxy resin having three or more epoxy groups in one molecule is more preferable.

As solid epoxy resins, bixylenol type epoxy resins, naphthalene type epoxy resins, naphthalene type tetrafunctional epoxy resins, cresol novolac type epoxy resins, dicyclopentadiene type epoxy resins, trisphenol 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, bisphenol AF type epoxy resins, and tetraphenylethane type epoxy resins are preferred, with bixylenol type epoxy resins and naphthalene type epoxy resins being more preferred.

Specific examples of solid epoxy resins include DIC's "HP4032H" (naphthalene type epoxy resin), "HP-4700", and "HP-4710" (naphthalene type tetrafunctional epoxy resin), "N-690" (cresol novolac type epoxy resin), "N-695" (cresol novolac type epoxy resin), "HP-7200", "HP-7200HH", and "HP-7200H" (dicyclopentadiene type epoxy resin). epoxy resins), "EXA-7311", "EXA-7311-G3", "EXA-7311-G4", "EXA-7311-G4S", "HP6000", "HP6000L" (naphthylene ether type epoxy resins); "EPPN-502H" (trisphenol type epoxy resin), "NC7000L" (naphthol novolac type epoxy resin), "NC3000H", "NC3000", "NC3000L" manufactured by Nippon Kayaku Co., Ltd.; Examples of epoxy resins include "NC3100" (biphenyl type epoxy resin); "ESN475V" (naphthalene type epoxy resin) and "ESN485" (naphthol novolac type epoxy resin) manufactured by Nippon Steel Chemical & Material Co., Ltd.; "YX4000H", "YL6121" (biphenyl type epoxy resin), "YX4000HK" (bixylenol type epoxy resin), and "YX8800" (anthracene type epoxy resin) manufactured by Mitsubishi Chemical Corporation; "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.; and "WHR-991S" (phenolphthalimidine type epoxy resin) manufactured by Nippon Kayaku Co., Ltd. These may be used alone or in combination of two or more.

When a liquid epoxy resin and a solid epoxy resin are used in combination as component (B), the ratio by mass of them (liquid epoxy resin:solid epoxy resin) is preferably 1:0.1 to 1:20, more preferably 1:0.3 to 1:10, and particularly preferably 1:0.5 to 1:5. By keeping the ratio of the liquid epoxy resin to the solid epoxy resin within this range, the desired effects of the present invention can be significantly obtained.

The epoxy equivalent of component (B) is preferably 50 g/eq. to 5000 g/eq., more preferably 50 g/eq. to 3000 g/eq., even more preferably 80 g/eq. to 2000 g/eq., and even more preferably 110 g/eq. to 1000 g/eq. Within this range, a cured product with sufficient crosslink density of the cured product of the resin composition layer can be obtained. The epoxy equivalent is the mass of an epoxy resin containing one equivalent of epoxy groups. This epoxy equivalent can be measured according to JIS K7236.

From the viewpoint of significantly achieving the desired effects of the present invention, the weight average molecular weight (Mw) of component (B) is preferably 100 to 5,000, more preferably 250 to 3,000, and even more preferably 400 to 1,500. The weight average molecular weight of the epoxy resin is the weight average molecular weight in terms of polystyrene measured by gel permeation chromatography (GPC).

The content of component (B) is preferably 5% by mass or more, more preferably 10% by mass or more, and even more preferably 15% by mass or more, based on 100% by mass of the non-volatile components in the resin composition layer, from the viewpoint of obtaining a cured product exhibiting good mechanical strength and insulation reliability. The upper limit of the epoxy resin content is preferably 35% by mass or less, more preferably 30% by mass or less, and particularly preferably 25% by mass or less, based on 100% by mass of the non-volatile components in the resin composition layer, from the viewpoint of obtaining a significant desired effect of the present invention.

--(C) Curing agent--
The resin composition layer may contain a curing agent (C) as the component (C). The curing agent (C) usually has a function of reacting with the component (B) to cure the resin composition. The curing agent (C) may be used alone or in combination of two or more kinds.

As the (C) curing agent, a curing agent with low polarity is preferable. Examples of the (C) curing agent include active ester resins, phenol resins, naphthol resins, benzoxazine resins, cyanate ester resins, carbodiimide resins, amine resins, and acid anhydride resins. Among them, from the viewpoint of obtaining the effects of the present invention more significantly, it is preferable to include an active ester resin.

As the active ester resin, a resin having one or more active ester groups in one molecule can be used. Among them, as the active ester resin, a resin having two or more highly reactive ester groups in one molecule, such as phenol esters, thiophenol esters, N-hydroxyamine esters, and esters of heterocyclic hydroxy compounds, is preferred. The active ester resin is preferably one obtained by a condensation reaction between a carboxylic acid compound and/or a thiocarboxylic acid compound and a hydroxy compound and/or a thiol compound. In particular, from the viewpoint of improving heat resistance, an active ester resin obtained from a carboxylic acid compound and a hydroxy compound is preferred, and an active ester resin obtained from a carboxylic acid compound and a phenol compound and/or a naphthol compound is more preferred.

Examples of carboxylic acid compounds include benzoic acid, acetic acid, succinic acid, maleic acid, itaconic acid, phthalic acid, isophthalic acid, terephthalic acid, and pyromellitic acid.

Examples of phenol compounds or naphthol compounds include hydroquinone, resorcin, bisphenol A, bisphenol F, bisphenol S, phenolphthaline, methylated bisphenol A, methylated bisphenol F, methylated bisphenol S, phenol, o-cresol, m-cresol, p-cresol, catechol, α-naphthol, β-naphthol, 1,5-dihydroxynaphthalene, 1,6-dihydroxynaphthalene, 2,6-dihydroxynaphthalene, dihydroxybenzophenone, trihydroxybenzophenone, tetrahydroxybenzophenone, phloroglucin, benzenetriol, dicyclopentadiene-type diphenol compounds, and phenol novolak. Here, "dicyclopentadiene-type diphenol compounds" refers to diphenol compounds obtained by condensing one molecule of dicyclopentadiene with two molecules of phenol.

Specific examples of preferred active ester resins include active ester resins containing a dicyclopentadiene-type diphenol structure, active ester resins containing a naphthalene structure, active ester resins containing an acetylated product of phenol novolac, and active ester resins containing a benzoylated product of phenol novolac. Among these, active ester resins containing a naphthalene structure and active ester resins containing a dicyclopentadiene-type diphenol structure are more preferred. The term "dicyclopentadiene-type diphenol structure" refers to a divalent structural unit consisting of phenylene-dicyclopentylene-phenylene.

Commercially available active ester resins include active ester resins containing a dicyclopentadiene-type diphenol structure such as "EXB9451", "EXB9460", "EXB9460S", "HPC-8000-65T", "HPC-8000H-65TM", and "EXB-8000L-65TM" (manufactured by DIC Corporation); active ester resins containing a naphthalene structure such as "EXB9416-70BK", "EXB-8150-65T", and "HP-B-8151-62T" (manufactured by DIC Corporation); and active ester resins containing an acetylated product of phenol novolac such as "EXB9416-70BK", "EXB-8150-65T", and "HP-B-8151-62T" (manufactured by DIC Corporation). Examples of active ester resins include "DC808" (manufactured by Mitsubishi Chemical Corporation); active ester resins containing benzoyl phenol novolac include "YLH1026" (manufactured by Mitsubishi Chemical Corporation); active ester resins that are acetylated phenol novolac include "DC808" (manufactured by Mitsubishi Chemical Corporation); active ester resins that are benzoyl phenol novolac include "YLH1026" (manufactured by Mitsubishi Chemical Corporation), "YLH1030" (manufactured by Mitsubishi Chemical Corporation), and "YLH1048" (manufactured by Mitsubishi Chemical Corporation); and the like.

From the viewpoint of heat resistance and water resistance, phenol-based resins and naphthol-based resins having a novolac structure are preferred. From the viewpoint of adhesion to the conductor layer, nitrogen-containing phenol-based curing agents are preferred, and triazine skeleton-containing phenol-based resins are more preferred.

Specific examples of phenol-based resins and naphthol-based resins include "MEH-7700", "MEH-7810", and "MEH-7851" manufactured by Meiwa Kasei Co., Ltd., "NHN", "CBN", and "GPH" manufactured by Nippon Kayaku Co., Ltd., "SN170", "SN180", "SN190", "SN475", "SN485", "SN495", "SN-495V", "SN375", and "SN395" manufactured by Nippon Steel Chemical & Material Co., Ltd., and "TD-2090", "LA-7052", "LA-7054", "LA-1356", "LA-3018-50P", and "EXB-9500" manufactured by DIC Corporation.

Specific examples of benzoxazine resins include "JBZ-OD100" (benzoxazine ring equivalent: 218), "JBZ-OP100D" (benzoxazine ring equivalent: 218), and "ODA-BOZ" (benzoxazine ring equivalent: 218) manufactured by JFE Chemical Corporation; "P-d" (benzoxazine ring equivalent: 217) and "F-a" (benzoxazine ring equivalent: 217) manufactured by Shikoku Kasei Corporation; and "HFB2006M" (benzoxazine ring equivalent: 432) manufactured by Showa Polymer Co., Ltd.

Examples of cyanate ester resins include bifunctional cyanate resins such as bisphenol A dicyanate, polyphenol cyanate, oligo(3-methylene-1,5-phenylene cyanate), 4,4'-methylenebis(2,6-dimethylphenyl cyanate), 4,4'-ethylidene diphenyl dicyanate, hexafluorobisphenol A dicyanate, 2,2-bis(4-cyanate)phenylpropane, 1,1-bis(4-cyanate phenylmethane), bis(4-cyanate-3,5-dimethylphenyl)methane, 1,3-bis(4-cyanate phenyl-1-(methylethylidene))benzene, bis(4-cyanate phenyl)thioether, and bis(4-cyanate phenyl)ether; polyfunctional cyanate resins derived from phenol novolac and cresol novolac; and prepolymers in which these cyanate resins have been partially converted to triazine. Specific examples of cyanate ester resins include Lonza Japan's "PT30", "PT30S" and "PT60" (phenol novolac type multifunctional cyanate ester resins), "ULL-950S" (multifunctional cyanate ester resin), "BA230", "BA230S75" (prepolymer in which part or all of bisphenol A dicyanate has been triazine-converted to form a trimer), and "BADCy" (bisphenol A dicyanate).

Specific examples of carbodiimide resins include Carbodilite (registered trademark) V-03 (carbodiimide group equivalent: 216, V-05 (carbodiimide group equivalent: 216), V-07 (carbodiimide group equivalent: 200), V-09 (carbodiimide group equivalent: 200), and Stavaxol (registered trademark) P (carbodiimide group equivalent: 302), all manufactured by Nisshinbo Chemical Co., Ltd.

Examples of amine-based resins include resins having one or more amino groups in one molecule, such as aliphatic amines, polyether amines, alicyclic amines, and aromatic amines. Among these, aromatic amines are preferred from the viewpoint of achieving the desired effects of the present invention. The amine-based resin is preferably a primary amine or secondary amine, and more preferably a primary amine. Specific examples of amine-based curing agents include 4,4'-methylenebis(2,6-dimethylaniline), diphenyldiaminosulfone, 4,4'-diaminodiphenylmethane, 4,4'-diaminodiphenylsulfone, 3,3'-diaminodiphenylsulfone, m-phenylenediamine, m-xylylenediamine, diethyltoluenediamine, 4,4'-diaminodiphenylether, 3,3'-dimethyl-4,4'-diaminobiphenyl, 2,2'-dimethyl-4,4'-diaminobiphenyl, 3,3'-dihydroxybenzidine, 2,2-bis(3-amino-4-hydroxyphenyl)-2,2'-diphenyl ... bis(4-aminophenyl)propane, 3,3-dimethyl-5,5-diethyl-4,4-diphenylmethanediamine, 2,2-bis(4-aminophenyl)propane, 2,2-bis(4-(4-aminophenoxy)phenyl)propane, 1,3-bis(3-aminophenoxy)benzene, 1,3-bis(4-aminophenoxy)benzene, 1,4-bis(4-aminophenoxy)benzene, 4,4'-bis(4-aminophenoxy)biphenyl, bis(4-(4-aminophenoxy)phenyl)sulfone, bis(4-(3-aminophenoxy)phenyl)sulfone, and the like. Commercially available amine-based resins may be used, such as "KAYABOND C-200S", "KAYABOND C-100", "KAYAHARD A-A", "KAYAHARD A-B", and "KAYAHARD A-S" manufactured by Nippon Kayaku Co., Ltd., and "Epicure W" manufactured by Mitsubishi Chemical Corporation.

Examples of acid anhydride resins include resins having one or more acid anhydride groups in one molecule. Specific examples of acid anhydride resins include phthalic anhydride, tetrahydrophthalic anhydride, hexahydrophthalic anhydride, methyltetrahydrophthalic anhydride, methylhexahydrophthalic anhydride, methylnadic anhydride, hydrogenated methylnadic anhydride, trialkyltetrahydrophthalic anhydride, dodecenyl succinic anhydride, 5-(2,5-dioxotetrahydro-3-furanyl)-3-methyl-3-cyclohexene-1,2-dicarboxylic anhydride, trimellitic anhydride, pyromellitic anhydride, and benzophenonetetracarboxylic dianhydride. Examples of such acid anhydrides include water, biphenyltetracarboxylic dianhydride, naphthalenetetracarboxylic dianhydride, oxydiphthalic dianhydride, 3,3'-4,4'-diphenylsulfonetetracarboxylic dianhydride, 1,3,3a,4,5,9b-hexahydro-5-(tetrahydro-2,5-dioxo-3-furanyl)-naphtho[1,2-C]furan-1,3-dione, ethylene glycol bis(anhydrotrimellitate), and polymeric acid anhydrides such as styrene-maleic acid resin, which is a copolymer of styrene and maleic acid.

When the resin composition layer contains an epoxy resin and a curing agent, the ratio of the amount of the epoxy resin to the amount of all the curing agents is preferably in the range of 1:0.01 to 1:5, more preferably 1:0.05 to 1:3, and even more preferably 1:0.1 to 1:2, in terms of the ratio of [total number of epoxy groups in the epoxy resin] to [total number of reactive groups in the curing agent]. Here, the "number of epoxy groups in the epoxy resin" refers to the total value obtained by dividing the mass of the non-volatile components of the epoxy resin present in the first resin composition by the epoxy equivalent. In addition, the "number of active groups in the curing agent" refers to the total value obtained by dividing the mass of the non-volatile components of the curing agent present in the first resin composition by the active group equivalent. By setting the ratio of the epoxy resin to the curing agent as a thermosetting resin within this range, a cured product with excellent flexibility can be obtained.

The content of the (C) curing agent is preferably 1% by mass or more, more preferably 3% by mass or more, and even more preferably 5% by mass or more, relative to 100% by mass of the non-volatile components in the resin composition layer, from the viewpoint of obtaining a significant effect of the present invention, and is preferably 15% by mass or less, more preferably 10% by mass or less, and even more preferably 8% by mass or less.

-(D) Radical polymerizable compound-
The resin composition layer may contain a radical polymerizable compound as the component (D). The component (D) may be used alone or in combination of two or more kinds.

In one embodiment, the radical polymerizable compound (D) is a radical polymerizable compound having an ethylenically unsaturated bond. The radical polymerizable compound (D) is not particularly limited, but may have a radical polymerizable group such as an unsaturated hydrocarbon group such as an allyl group, a 3-cyclohexenyl group, a 3-cyclopentenyl group, a p-vinylphenyl group, a m-vinylphenyl group, or an o-vinylphenyl group; or an α,β-unsaturated carbonyl group such as an acryloyl group, a methacryloyl group, or a maleimide group (2,5-dihydro-2,5-dioxo-1H-pyrrol-1-yl group). It is preferable that the radical polymerizable compound (D) has two or more radical polymerizable groups.

The radical polymerizable compound (D) may be, for example, a maleimide resin, a vinyl resin, a (meth)acrylic resin, an allyl resin, or the like. Among these, the component (D) preferably contains either a maleimide resin or a vinyl resin, and more preferably contains both a maleimide resin and a vinyl resin.

A maleimide resin (maleimide radical polymerizable compound) is, for example, a compound having one or more, preferably two or more, maleimide groups. The maleimide resin may be an aliphatic maleimide compound containing an aliphatic amine skeleton, or an aromatic maleimide compound containing an aromatic amine skeleton. Commercially available products include, for example, "SLK-2600" manufactured by Shin-Etsu Chemical Co., Ltd., "BMI-1500", "BMI-1700", "BMI-3000J", "BMI-689", and "BMI-2500" manufactured by Designer Molecules Inc. (dimer diamine structure-containing maleimide compounds), "BMI-6100" manufactured by Designer Molecules Inc. (aromatic maleimide compound), "MIR-5000-60T" and "MIR-3000-70MT" (biphenylaralkyl-type maleimide compounds) manufactured by Nippon Kayaku Co., Ltd., "BMI-70" and "BMI-80" manufactured by Kei-I Chemical Industry Co., Ltd., and "BMI-2300" and "BMI-TMH" manufactured by Daiwa Kasei Kogyo Co., Ltd. In addition, as the maleimide resin, the maleimide resin (maleimide compound containing an indane ring skeleton) disclosed in the Japan Institute of Invention and Innovation's Technical Journal No. 2020-500211 may be used.

Vinyl resins (vinyl radical polymerizable compounds (also called styrene radical polymerizable compounds)) are compounds having, for example, one or more, preferably two or more vinyl groups directly bonded to an aromatic carbon atom. Examples of vinyl resins include low molecular weight (molecular weight less than 1000) styrene compounds such as divinylbenzene, 2,4-divinyltoluene, 2,6-divinylnaphthalene, 1,4-divinylnaphthalene, 4,4'-divinylbiphenyl, 1,2-bis(4-vinylphenyl)ethane, 2,2-bis(4-vinylphenyl)propane, and bis(4-vinylphenyl)ether; high molecular weight (molecular weight 1000 or more) styrene compounds such as vinylbenzyl-modified polyphenylene ether resins and styrene-divinylbenzene copolymers. Commercially available styrene-based radical polymerizable compounds include, for example, "ODV-XET (X03)", "ODV-XET (X04)", and "ODV-XET (X05)" (styrene-divinylbenzene copolymers) manufactured by Nippon Steel Chemical & Material Co., Ltd., and "OPE-2St 1200" and "OPE-2St 2200" (vinylbenzyl-modified polyphenylene ether resins) manufactured by Mitsubishi Gas Chemical Co., Inc.

(Meth)acrylic resins ((meth)acrylic radically polymerizable compounds) are, for example, compounds having one or more, preferably two or more, acryloyl groups and/or methacryloyl groups. Examples of (meth)acrylic resins include cyclohexane-1,4-dimethanol di(meth)acrylate, cyclohexane-1,3-dimethanol di(meth)acrylate, tricyclodecane dimethanol di(meth)acrylate, neopentyl glycol di(meth)acrylate, 1,4-butanediol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, 1,8-octanediol di(meth)acrylate, and 1,9-nonanediol. aliphatic (meth)acrylic acid ester compounds having a low molecular weight (molecular weight less than 1000) such as di(meth)acrylate, 1,10-decanediol di(meth)acrylate, trimethylolpropane tri(meth)acrylate, trimethylolethane tri(meth)acrylate, glycerin tri(meth)acrylate, and pentaerythritol tetra(meth)acrylate; Examples of the ether-containing (meth)acrylic acid ester compound include low molecular weight (molecular weight less than 1000) ether-containing (meth)acrylic acid ester compounds such as acrylate, 3,6,9-trioxaundecane-1,11-diol di(meth)acrylate, polyethylene glycol di(meth)acrylate, polypropylene glycol di(meth)acrylate, 9,9-bis[4-(2-acryloyloxyethoxy)phenyl]fluorene, ethoxylated bisphenol A di(meth)acrylate, and propoxylated bisphenol A di(meth)acrylate; low molecular weight (molecular weight less than 1000) isocyanurate-containing (meth)acrylic acid ester compounds such as tris(3-hydroxypropyl)isocyanurate tri(meth)acrylate, tris(2-hydroxyethyl)isocyanurate tri(meth)acrylate, and ethoxylated isocyanuric acid tri(meth)acrylate; and high molecular weight (molecular weight 1000 or more) acrylic acid ester compounds such as (meth)acrylic-modified polyphenylene ether resins. Commercially available (meth)acrylic resins include, for example, "A-DOG" (dioxane glycol diacrylate) manufactured by Shin-Nakamura Chemical Co., Ltd., "DCP-A" (tricyclodecane dimethanol diacrylate) and "DCP" (tricyclodecane dimethanol dimethacrylate) manufactured by Kyoeisha Chemical Co., Ltd., "KAYARAD R-684" (tricyclodecane dimethanol diacrylate) and "KAYARAD R-604" (dioxane glycol diacrylate) manufactured by Nippon Kayaku Co., Ltd., and "SA9000" and "SA9000-111" (methacrylic modified polyphenylene ether) manufactured by SABIC Innovative Plastics.

An allyl-based resin (allyl-based radically polymerizable compound) is, for example, a compound having one or more, preferably two or more, allyl groups. Examples of allyl resins include aromatic carboxylic acid allyl ester compounds such as diallyl diphenate, triallyl trimellitate, diallyl phthalate, diallyl isophthalate, diallyl terephthalate, diallyl 2,6-naphthalenedicarboxylate, and diallyl 2,3-naphthalenecarboxylate; isocyanuric acid allyl ester compounds such as 1,3,5-triallyl isocyanurate and 1,3-diallyl-5-glycidyl isocyanurate; epoxy-containing aromatic allyl compounds such as 2,2-bis[3-allyl-4-(glycidyloxy)phenyl]propane; benzoxazine-containing aromatic allyl compounds such as bis[3-allyl-4-(3,4-dihydro-2H-1,3-benzoxazin-3-yl)phenyl]methane; ether-containing aromatic allyl compounds such as 1,3,5-triallyl ether benzene; and allyl silane compounds such as diallyl diphenyl silane. Commercially available allyl resins include "TAIC" (1,3,5-triallyl isocyanurate) manufactured by Nippon Kasei Chemical Industry Co., Ltd., "DAD" (diallyl diphenate) manufactured by Nisshoku Techno Fine Chemical Co., Ltd., "TRIAM-705" (triallyl trimellitate) manufactured by Wako Pure Chemical Industries, Ltd., "DAND" (2,3-diallyl naphthalene carboxylate) manufactured by Nippon Distillery Co., Ltd., "ALP-d" (bis[3-allyl-4-(3,4-dihydro-2H-1,3-benzoxazin-3-yl)phenyl]methane) manufactured by Shikoku Kasei Corporation, "RE-810NM" (2,2-bis[3-allyl-4-(glycidyloxy)phenyl]propane) manufactured by Nippon Kayaku Co., Ltd., and "DA-MGIC" (1,3-diallyl-5-glycidyl isocyanurate) manufactured by Shikoku Kasei Corporation.

The ethylenically unsaturated bond equivalent of component (D) is preferably 20 g/eq. to 3000 g/eq., more preferably 50 g/eq. to 2500 g/eq., even more preferably 70 g/eq. to 2000 g/eq., and particularly preferably 90 g/eq. to 1500 g/eq. The ethylenically unsaturated bond equivalent is the mass of the radical polymerizable compound per equivalent of the ethylenically unsaturated bond.

The weight average molecular weight (Mw) of component (D) is preferably 40,000 or less, more preferably 10,000 or less, even more preferably 5,000 or less, and particularly preferably 3,000 or less. The lower limit is not particularly limited, but may be, for example, 150 or more.

From the viewpoint of obtaining the effects of the present invention significantly, the content of the (D) component is preferably 10% by mass or more, more preferably 20% by mass or more, and even more preferably 25% by mass or more, when the non-volatile components in the resin composition layer are taken as 100% by mass. From the viewpoint of obtaining the effects of the present invention significantly, the upper limit of the content of the (D) component is preferably 40% by mass or less, more preferably 35% by mass or less, and particularly preferably 30% by mass or less.

As the components to be contained in the resin composition layer, it is preferable to use a material with low polarity from the viewpoint of improving the resin flow and insulation reliability. Examples of such low polarity materials include active ester resins, maleimide resins, vinyl resins, etc. Therefore, a preferred embodiment of the resin sheet is preferably one that contains at least one of (B) an epoxy resin, (C) a curing agent, and (D) a radical polymerizable compound in combination with component (A), and more preferably one that contains one of active ester resins, maleimide resins, and vinyl resins in combination with component (A).

-(E) Thermoplastic resin-
The resin composition layer may contain a thermoplastic resin (E) as the component (E). By including the component (E) in the resin composition layer, it is possible to obtain a cured product exhibiting good mechanical strength. The component (E) may be used alone or in combination of two or more kinds.

From the viewpoint of obtaining a significant effect of the present invention, the weight average molecular weight (Mn) of the (E) component is preferably 5,000 or more, more preferably 8,000 or more, particularly preferably 10,000 or more, and is preferably 100,000 or less, more preferably 80,000 or less, particularly preferably 50,000 or less. The weight average molecular weight of the (E) component is the weight average molecular weight in terms of polystyrene measured by gel permeation chromatography (GPC).

As the (E) component, a high molecular weight component having a weight average molecular weight within the above range can be used. Examples of such components include thermoplastic resins such as polyimide resins, phenoxy resins, polyvinyl acetal resins, polyolefin resins, polyamideimide resins, polyetherimide resins, polysulfone resins, polyethersulfone resins, polyetheretherketone resins, and polyester resins; and elastomers. Among these, from the viewpoint of obtaining the effects of the present invention significantly, it is preferable that the (E) component is at least one selected from polyimide resins, elastomers, and phenoxy resins.

The polyimide resin includes a structural unit represented by the following formula (e1) (hereinafter, also referred to as "structural unit (e1)") (hereinafter, sometimes referred to as "first polyimide resin"). In the first polyimide resin, the number of structural units (e1) is 1 or more, and is not particularly limited, but may be 100 or less, 50 or less, or 30 or less. When there are multiple structural units (e1), the structural units (e1) may be linked to each other as repeating units, or may not be linked to each other. When not linked to each other, it is preferable that the multiple structural units (e1) have other structural units (for example, a structural unit represented by formula (e2) described later) between them.

［式（ｅ１）中、
Ｒ_１は、下記式（ｅ１－１）で表される４価の基であり、
Ｒ_２は、下記式（ｅ１－２）で表される２価の基である。 The structural unit (e1) is represented by the following formula (e1).

[In formula (e1),
R ₁ is a tetravalent group represented by the following formula (e1-1):
_R2 is a divalent group represented by the following formula (e1-2).

（式（ｅ１－１）中、
Ａｒ_１１、Ａｒ_１２、Ａｒ_１３及びＡｒ_１４は、それぞれ独立に、置換基を有していてもよい芳香族環を表し、
Ｌ_１１、Ｌ_１２及びＬ_１３は、それぞれ独立に、２価の連結基を表し、
ｎｃ１は、０以上の整数を表す。）

(In formula (e1-1),
Ar ₁₁ , Ar ₁₂ , Ar ₁₃ and Ar ₁₄ each independently represent an aromatic ring which may have a substituent;
L ₁₁ , L ₁₂ and L ₁₃ each independently represent a divalent linking group;
nc1 represents an integer of 0 or more.

（式（ｅ１－２）中、
Ａｒ_２１、Ａｒ_２２、Ａｒ_２３及びＡｒ_２４は、それぞれ独立に、置換基を有していてもよい芳香族環を表し、
Ｌ_２１、Ｌ_２２及びＬ_２３は、それぞれ独立に、２価の連結基を表し、
ｎｃ２は、１以上の整数を表す。）］

(In formula (e1-2),
Ar ₂₁ , Ar ₂₂ , Ar ₂₃ and Ar ₂₄ each independently represent an aromatic ring which may have a substituent;
L ₂₁ , L ₂₂ and L ₂₃ each independently represent a divalent linking group;
nc2 represents an integer of 1 or more.

In formula (e1-1), the aromatic ring represented by Ar ₁₁ , Ar ₁₂ , Ar ₁₃ and Ar ₁₄ (hereinafter also referred to as "aromatic ring C") is preferably an aromatic ring having 6 to 100 carbon atoms, more preferably 6 to 50 carbon atoms, still more preferably 6 to 100 carbon atoms, and even more preferably 6 to 50 carbon atoms. Therefore, in a preferred embodiment, in formula (e1-1), Ar ₁₁ , Ar ₁₂ , Ar ₁₃ and Ar ₁₄ are each independently an aromatic carbocyclic ring having 6 to 14 carbon atoms which may have a substituent. Here, the term "aromatic ring" as used herein means a ring according to the Huckel rule in which the number of electrons contained in the π electron system on the ring is 4n+2 (n is a natural number), and includes a monocyclic aromatic ring and a fused aromatic ring in which two or more monocyclic aromatic rings are fused. The aromatic ring may be a carbocyclic ring or a heterocyclic ring. Examples of the aromatic ring include monocyclic aromatic rings such as a benzene ring, a furan ring, a thiophene ring, a pyrrole ring, a pyrazole ring, an oxazole ring, an isoxazole ring, a thiazole ring, an imidazole ring, a pyridine ring, a pyridazine ring, a pyrimidine ring, and a pyrazine ring; fused rings in which two or more monocyclic aromatic rings are fused, such as a naphthalene ring, an anthracene ring, a benzofuran ring, an isobenzofuran ring, an indole ring, an isoindole ring, a benzothiophene ring, a benzimidazole ring, an indazole ring, a benzoxazole ring, a benzisoxazole ring, a benzothiazole ring, a quinoline ring, an isoquinoline ring, a quinoxaline ring, an acridine ring, a quinazoline ring, a cinnoline ring, and a phthalazine ring; and fused rings in which one or more monocyclic aromatic rings are fused to one or more monocyclic non-aromatic rings, such as an indane ring, a fluorene ring, and a tetralin ring. Among these, aromatic carbon rings having 6 to 14 carbon atoms are preferred, with a benzene ring being more preferred.

In formula (e1-1), when Ar ₁₁ , Ar ₁₂ , Ar ₁₃ and Ar ₁₄ represent an aromatic ring having a substituent, the number of the substituents is not limited. Such substituents (hereinafter also referred to as "substituent S") include, independently of one another, a halogen atom, an alkyl group, a cycloalkyl group, an alkoxy group, a cycloalkyloxy group, an aryl group, an aryloxy group, an arylalkyl group, an arylalkoxy group, a monovalent heterocyclic group, an alkylidene group, an amino group, a silyl group, an acyl group, an acyloxy group, a carboxy group, a sulfo group, a cyano group, a nitro group, a hydroxy group, a mercapto group and an oxo group.

In formula (e1-1), the divalent linking group represented by L ₁₁ , L ₁₂ and L ₁₃ is preferably a divalent group containing one or more (e.g., 1 to 3000, 1 to 1000, 1 to 100, 1 to 50) skeletal atoms selected from carbon atoms, oxygen atoms, nitrogen atoms, sulfur atoms and silicon atoms. Examples of the divalent linking group include -SO ₂ -, -CO-, -COO-, -O-, -S-, -O-C ₆ H ₄ -O- (wherein -C ₆ H ₄ - represents a phenylene group), -O-C ₆ H ₄ -C(CH ₃ ) ₂ -C ₆ H ₄ -O-, -COO-(CH ₂ ) _q -OCO- (wherein q represents an integer of 1 to 20), -COO-H ₂ C-HC(-O-C(═O)-CH ₃ )-CH ₂ -OCO-, an alkylene group, an alkenylene group, an alkynylene group, an arylene group, a heteroarylene group, -C(═O)-, -C(═O)-O-, and -NR ⁰ - (wherein R ⁰ represents a hydrogen atom or an alkyl group having 1 to 3 carbon atoms. ) and -C(=O)-NR ⁰ - are included. As the alkylene group, an alkylene group having 1 to 10 carbon atoms is preferred, an alkylene group having 1 to 6 carbon atoms is more preferred, an alkylene group having 1 to 5 carbon atoms or an alkylene group having 1 to 4 carbon atoms is even more preferred. As the alkylene group, for example, a methylene group, an ethylene group, a propylene group, a butylene group, a pentylene group, a hexylene group, a dimethylmethylene group, etc. are mentioned, and a dimethylmethylene group is preferred. As the alkenylene group, an alkenylene group having 2 to 10 carbon atoms is preferred, an alkenylene group having 2 to 6 carbon atoms is more preferred, and an alkenylene group having 2 to 5 carbon atoms is even more preferred. The arylene group and heteroarylene group are preferably an arylene group or heteroarylene group having 6 to 20 carbon atoms, more preferably an arylene group or heteroarylene group having 6 to 10 carbon atoms. The above-mentioned alkyl group, alkylene group, alkenylene group, alkynylene group, arylene group, and heteroarylene group may further have a substituent. Examples of the substituent are the same as the examples of the substituent S. The divalent linking group represented by L ₁₁ , L ₁₂ , and L ₁₃ preferably does not contain an aromatic ring. In one embodiment, the divalent linking group represented by L ₁₁ and the divalent linking group represented by L ₁₃ are the same as each other, and the divalent linking group represented by L ₁₁ and the divalent linking group represented by L ₁₂ are different from each other. In a preferred embodiment, in formula (e1-1), L ₁₁ and L ₁₃ are -O-, and L ₁₂ is an alkylene group which may have a substituent, and in a more preferred embodiment, in formula (e1-1), Ar ₁₁ , Ar ₁₂ , Ar ₁₃ and Ar ₁₄ are each independently an aromatic carbocycle having 6 to 14 carbon atoms which may have a substituent, and in formula (e1-1), L ₁₁ and L ₁₃ are -O-, and L ₁₂ is an alkylene group which may have a substituent. In a further preferred embodiment, in formula (e1-1), L ₁₁ and L ₁₃ are -O-, and L ₁₂ is a dimethylmethylene group.

In formula (e1-2), examples of the aromatic rings represented by Ar ₂₁ , Ar ₂₂ , Ar ₂₃ and Ar ₂₄ and the substituents which the aromatic rings may have are the same as the examples of the aromatic ring C and the substituent S. Thus, in a preferred embodiment, in formula (e1-2), Ar ₂₁ , Ar ₂₂ , Ar ₂₃ and Ar ₂₄ are each independently an aromatic carbocyclic ring having 6 to 14 carbon atoms which may have a substituent. In a preferred embodiment, in formula (e1-2), L ₂₁ and L ₂₃ are -O-, and L ₂₂ is an alkylene group which may have a substituent, and in a more preferred embodiment, in formula (e1-2), Ar ₂₁ , Ar ₂₂ , Ar ₂₃ and Ar ₂₄ are each independently an aromatic carbocyclic ring having 6 to 14 carbon atoms which may have a substituent, and in formula (e1-2), L ₂₁ and L ₂₃ are -O-, and L ₂₂ is an alkylene group which may have a substituent. In a further preferred embodiment, in formula (e1-2), L ₂₁ and L ₂₃ are -O-, and L ₂₂ is a dimethylmethylene group. In a particularly preferred embodiment, in formula (e1-1), Ar ₁₁ , Ar ₁₂ , Ar ₁₃ and Ar ₁₄ are each independently an aromatic carbocyclic ring having 6 to 14 carbon atoms which may have a substituent, and in formula (e1-2), Ar ₂₁ , Ar ₂₂ , Ar ₂₃ and Ar ₂₄ are each independently an aromatic carbocyclic ring having 6 to 14 carbon atoms which may have a substituent. In another particularly preferred embodiment, in formula (e1-1), L ₁₁ and L ₁₃ are -O-, L ₁₂ is an alkylene group which may have a substituent, and in formula (e1-2), L ₂₁ and L ₂₃ are -O-, and L ₂₂ is an alkylene group which may have a substituent. In a more particularly preferred embodiment, in formula (e1-1), Ar ₁₁ , Ar ₁₂ , Ar ₁₃ and Ar ₁₄ are each independently an aromatic carbocycle having 6 to 14 carbon atoms which may have a substituent; in formula (e1-2), Ar ₂₁ , Ar ₂₂ , Ar ₂₃ and Ar ₂₄ are each independently an aromatic carbocycle having 6 to 14 carbon atoms which may have a substituent; in formula (e1-1), L ₁₁ and L ₁₃ are -O-, L ₁₂ is an alkylene group which may have a substituent; and in formula (e1-2), L ₂₁ and L ₂₃ are -O-, and L ₂₂ is an alkylene group which may have a substituent.

In formula (e1-1), nc1 preferably represents an integer of 1 or more. The upper limit of the integer represented by nc1 is not particularly limited, but may be, for example, 50, 40, 30, or 20.

In formula (e1-2), nc2 preferably represents an integer of 2 or more. The upper limit of the integer represented by nc2 is not particularly limited, but may be, for example, 60, 50, 40, or 30. In some embodiments, the integer represented by nc2 in formula (e1-1) is greater than the integer represented by nc1 and less than nc1+5. In certain embodiments, in formula (e1-1), nc1 is 1 and nc2 is 2.

The structural unit (e1) can be obtained, for example, by a known method for producing a polyimide resin, typically a method for imidizing a monomer composition containing a tetracarboxylic dianhydride and a diamine compound by polymerizing it, or a method for imidizing a monomer composition containing a tetracarboxylic dianhydride and a diisocyanate compound by polymerizing it. It is acceptable for the first polyimide resin to partially contain a polyamic acid structure that may be generated during the imidization process.

The structural unit (e1) in the above specific embodiment can be obtained, for example, by reacting 2,2-bis[4-(3,4-dicarboxyphenoxy)phenyl]propane dianhydride (a compound represented by the following formula (eI); hereinafter, also referred to as "BPADA") with 4,4'-[1,4-phenylenebis[(1-methylethylidene)-4,1-phenyleneoxy]]bisbenzeneamine (a compound represented by the following formula (eII); hereinafter, also referred to as "BPPAN"). That is, in the structural unit (e1), R ₁ is a skeleton derived from BPADA, and R ₂ is a skeleton derived from BPPAN.

The first polyimide resin may further include a structural unit represented by the following formula (e2) (hereinafter, also referred to as "structural unit (e2)"). Thus, in one embodiment, the first polyimide resin is a resin further including a structural unit represented by the following formula (e2). In the first polyimide resin, the number of structural units (e2) is 0 or more, and is not particularly limited, but may be 100 or less, 50 or less, or 30 or less. The structural unit (e2) may be linked to the group R ₂ of the structural unit (e1) through the nitrogen atom of the imide group, or may not be linked to the structural unit (e1). When there are a plurality of structural units (e2), the structural units (e2) may be linked to each other as a repeating unit, or may not be linked to each other. When not linked to each other, it is preferable that the plurality of structural units (e2) have another structural unit (e1, for example) between them.

（式（ｅ２）中、
Ｒ_３は、置換基を有していてもよい４価の脂肪族基又は置換基を有していてもよい４価の芳香族基を表し、
Ｒ_４は、置換基を有していてもよい２価の脂肪族基又は置換基を有していてもよい２価の芳香族基を表す。但し、Ｒ_３がＲ_１と同じ場合、Ｒ_４はＲ_２とは異なり、Ｒ_４がＲ_２と同じ場合、Ｒ_３はＲ_１とは異なる。） The structural unit (e2) is represented by the following formula (e2).

(In formula (e2),
_R3 represents a tetravalent aliphatic group which may have a substituent or a tetravalent aromatic group which may have a substituent;
_R4 represents a divalent aliphatic group which may have a substituent or a divalent aromatic group which may have a substituent. However, when _R3 is the same as _R1 , _R4 is different from _R2 , and when _R4 is the same as _R2 , _R3 is different from _R1 .

In formula (e2), the tetravalent aliphatic group represented by R ₃ contains at least a carbon atom, and is preferably a tetravalent group consisting of one or more (e.g., 1 to 3000, 1 to 1000, 1 to 100, 1 to 50) skeletal atoms selected from carbon atoms, oxygen atoms, nitrogen atoms, sulfur atoms, and silicon atoms. In formula (e2), the tetravalent aliphatic group represented by R ₃ is more preferably a tetravalent aliphatic group having 1 to 100 carbon atoms, and even more preferably 1 to 50 carbon atoms. In formula (e2), when R ₃ represents a tetravalent aliphatic group having a substituent, examples of the substituent are the same as the examples of the substituent S.

In formula (e2), the tetravalent aromatic group represented by R ₃ is preferably a tetravalent aromatic group having 6 to 100 carbon atoms, more preferably 6 to 50 carbon atoms, and even more preferably a tetravalent aromatic hydrocarbon group having 6 to 100 carbon atoms, still more preferably 6 to 50 carbon atoms. The aromatic group contains at least an aromatic ring. Examples of the aromatic ring contained in the aromatic group are the same as the examples of the aromatic ring represented by Ar ₁₁ , Ar ₁₂ , Ar ₁₃ and Ar ₁₄ in formula (e1-1). In formula (e2), when R ₃ represents a tetravalent aromatic group having a substituent, examples of the substituent are the same as the examples of the substituent S.

Examples of the tetravalent aromatic group represented by R ₃ include a group obtained by removing two acid anhydride groups from a tetracarboxylic dianhydride having an aromatic group which may have a substituent. The aromatic group includes at least an aromatic ring. Examples of the aromatic ring included in the aromatic group are the same as the examples of the aromatic ring C. When the aromatic group has a substituent, examples of the substituent are the same as the examples of the substituent S. Specific examples of tetracarboxylic dianhydrides having an aromatic group which may have a substituent include BPADA, pyromellitic dianhydride, 3,3',4,4'-biphenyltetracarboxylic dianhydride, 4,4'-oxydiphthalic anhydride, 3,3',4,4'-benzophenonetetracarboxylic dianhydride, and 3,3',4,4'-diphenylsulfonetetracarboxylic dianhydride.

In formula (e2), the divalent aliphatic group represented by R ₄ contains at least a carbon atom, and is preferably a divalent group consisting of one or more (e.g., 1 to 3000, 1 to 1000, 1 to 100, 1 to 50) skeletal atoms selected from carbon atoms, oxygen atoms, nitrogen atoms, sulfur atoms, and silicon atoms. In formula (e2), the divalent aliphatic group represented by R ₄ is more preferably a divalent aliphatic group having 1 to 100 carbon atoms, and even more preferably 1 to 50 carbon atoms. In formula (e2), when R ₄ represents a divalent aliphatic group having a substituent, examples of the substituent are the same as the examples of the substituent S, and are, for example, an alkyl group having 1 to 6 carbon atoms. Therefore, in an embodiment, R ₄ is a divalent aliphatic group which may have a substituent, and one of the substituents is an alkyl group having 1 to 6 carbon atoms. In a specific embodiment, R ₄ is a divalent aliphatic group which may have a substituent, and is a divalent group obtained by removing two amino groups from isophoronediamine.

When _R4 represents a divalent aliphatic group which may have a substituent, it may be a group obtained by removing two amino groups from a diamine compound having an aliphatic group which may have a substituent selected from 1,2-diaminoethane, 1,3-diaminopropane, 1,4-diaminobutane, 1,5-diaminopentane, 1,6-hexanediamine, 1,7-heptanediamine, 1,8-octanediamine, 1,9-nonanediamine, 1,10-decanediamine, 1,11-undecanediamine, and 1,12-dodecanediamine. These diamine compounds are characterized in that the aliphatic group is linear.

When _R4 represents a divalent aliphatic group which may have a substituent, it may be a group obtained by removing two amino groups from a diamine compound having an aliphatic group which may have a substituent selected from 1,2-diaminopropane, 1,2-diamino-2-methylpropane, 1,3-diamino-2-methylpropane, 1,3-diamino-2,2-dimethylpropane, 1,3-diaminopentane, and 1,5-diamino-2-methylpentane. These diamine compounds are characterized in that the aliphatic group is branched.

When R ₄ represents a divalent aliphatic group which may have a substituent, it may be a group obtained by removing two amino groups from a diamine compound having an aliphatic group which may have a substituent selected from 5-amino-1,3,3-trimethylcyclohexanemethylamine (isophoronediamine), 1,4-diaminocyclohexane, 1,3-diaminocyclohexane, 1,4-cyclohexanebis(methylamine), 1,3-cyclohexanebis(methylamine), 4,4'-diaminodicyclohexylmethane, bis(4-amino-3-methylcyclohexyl)methane, 3(4),8(9)-bis(aminomethyl)tricyclo[5.2.1.0 ^2,6 ]decane, 2,5(6)-bis(aminomethyl)bicyclo[2.2.1]heptane, 1,3-diaminoadamantane, 3,3'-diamino-1,1'-biadamantyl, and 1,6-diaminoadamantane. These diamine compounds are characterized in that the aliphatic groups contain alicyclic carbon rings.

In formula (e2), the divalent aromatic group represented by R ₄ is preferably a divalent aromatic group having 6 to 100 carbon atoms, more preferably 6 to 50 carbon atoms, and even more preferably a divalent aromatic hydrocarbon group having 6 to 100 carbon atoms, still more preferably 6 to 50 carbon atoms. The aromatic group contains at least an aromatic ring. Examples of the aromatic ring contained in the aromatic group are the same as the examples of the aromatic ring C. In formula (e2), when R ₄ represents a divalent aromatic group having a substituent, examples of the substituent are the same as the examples of the substituent S.

When _R4 represents a divalent aromatic group which may have a substituent, it may be a group obtained by removing two amino groups from a diamine compound having an aromatic group which may have a substituent selected from 4,4'-diaminodiphenyl ether, 1,4-phenylenediamine, and 2,2-bis[4-(4-aminophenoxy)phenyl]propane.

However, when _R3 is the same as _R1 , _R4 is different from _R2 , and when _R4 is the same as _R2 , _R3 is different from _R1 . In some embodiments, _R3 is the same as _R1 . That is, the structural unit (e2) is different from the structural unit (e1).

The structural unit (e2) can be obtained, for example, according to a known method for producing a polyimide resin. The structural unit (e2) in the specific embodiment can be obtained, for example, by reacting BPADA with isophorone diamine. That is, R ₃ in the structural unit (e2) is a skeleton derived from BPADA, and R ₄ is a skeleton derived from isophorone diamine. When R ₃ is the same as R ₁ , R ₃ and R ₁ are skeletons derived from BPADA. It is acceptable for the first polyimide resin to partially contain a polyamic acid structure that may be generated during the imidization process.

The terminal structure of the first polyimide resin is not particularly limited as long as it has the structural unit (e1). For example, the terminal structure of the polyimide resin may be an acid anhydride group derived from the raw material compound of the polyimide resin (e.g., an acid such as BPADA, or an amine compound such as BPPAN), or a carboxyl group or an amino group. When the raw material compound further contains maleic anhydride, the terminal structure of the polyimide resin may be a maleimide group.

The glass transition temperature Tg ^(c) (°C) of the polyimide resin is preferably 140°C or higher, more preferably 145°C or higher, even more preferably 150°C or higher, even more preferably 160°C or higher, and particularly preferably 170°C or higher. There is no particular upper limit, but it may be 300°C or lower, for example. The glass transition temperature Tg ^(c) (°C) can be measured using a Rigaku TMA device at a temperature rise rate of 5°C/min from 25°C to 250°C.

From the viewpoint of obtaining the effects of the present invention remarkably, the content (percentage) of the structural unit (e1) in the polyimide resin is preferably 5% by mass or more, more preferably 10% by mass or more, even more preferably 20% by mass or more, even more preferably 30% by mass or more, and particularly preferably 40% by mass or more. The content (percentage) of the structural unit (e1) in the polyimide resin may be, for example, 98% by mass or less, 95% by mass or less, 90% by mass or less, or 85% by mass or less. Here, the content (percentage) of the structural unit (e1) can be calculated from the ratio of the charged amount (parts by mass) of each material used to synthesize the polyimide resin, or alternatively, the molecular weight of the polyimide resin and the formula weight of the structural unit (e1) may be specified, and the content (percentage) of the structural unit (e1) may be calculated as the ratio of the formula weight of the structural unit (e1) to the molecular weight. When the polyimide resin is a polymer, it is preferable that the content (percentage) of the structural unit (e1) estimated from the degree of polymerization is within the above range.

When the polyimide resin further contains the structural unit (e2), the content (percentage) of the structural unit (e2) is allowed to be 0% by mass (i.e., no structural unit (e2) is contained), and the upper limit is not limited as long as the effect of the present invention is not excessively impaired. Therefore, the content (percentage) of the structural unit (e2) in the polyimide resin may be, for example, 1% by mass or more, 5% by mass or more, 10% by mass or more, 20% by mass or more, or 30% by mass or more, 95% by mass or less, 90% by mass or less, 80% by mass or less, 70% by mass or less, or 60% by mass or less. Here, the content (percentage) of the structural unit (e2) is calculated in the same manner as the content (percentage) of the structural unit (e1). When the polyimide resin is a polymer, it is preferable that the content (percentage) of the structural unit (e2) estimated from the degree of polymerization is within the above range.

The weight average molecular weight (Mw) of the polyimide resin is usually 1,000 or more, preferably 1.00 to 10,000, more preferably 1,000 to 5,000, and even more preferably 1,000 to 3,000. The weight average molecular weight of the resin can be measured as a polystyrene-equivalent value by gel permeation chromatography (GPC).

Another embodiment of the polyimide resin is a resin containing a first skeleton derived from BPADA and a second skeleton derived from BPPAN (hereinafter, sometimes referred to as the "second polyimide resin"). The material of the first skeleton is not limited to BPADA, so long as it is the same skeleton as the skeleton derived from BPADA. The material of the second skeleton is not limited to BPPAN, so long as it is the same skeleton as the skeleton derived from BPPAN. In the second polyimide resin, the number of first skeletons is 1 or more, and is not particularly limited, but may be 100 or less, 50 or less, or 30 or less. In the second polyimide resin, the number of second skeletons is 1 or more, and is not particularly limited, but may be 100 or less, 50 or less, or 30 or less.

The first and second skeletons described above can be derived from, for example, a known method for producing a polyimide resin, typically a method for imidizing a monomer composition containing a tetracarboxylic dianhydride and a diamine compound by polymerizing the monomer composition. The first and second skeletons can also be derived from a method for imidizing a monomer composition containing a tetracarboxylic dianhydride and a diisocyanate compound by polymerizing the monomer composition. Therefore, the second polyimide resin can contain the structural unit (e1) contained in the first polyimide resin. It is acceptable for the second polyimide resin to contain a portion of a polyamic acid structure that can be generated during the imidization process.

The second polyimide resin may further include a third skeleton different from the second skeleton. This third skeleton is derived from one or more diamine compounds selected from the group consisting of diamine compounds having an aliphatic group which may have a substituent and diamine compounds having an aromatic group which may have a substituent. Therefore, in one embodiment, the second polyimide resin is a resin further including a third skeleton different from the second skeleton, and the third skeleton is derived from one or more diamine compounds selected from the group consisting of diamine compounds having an aliphatic group which may have a substituent and diamine compounds having an aromatic group which may have a substituent. In the second specific polyimide resin, the number of third skeletons is 0 or more, and is not particularly limited, but may be 100 or less, 50 or less, or 30 or less.

When the diamine compound is a diamine compound having an aliphatic group, the aliphatic group contains at least a carbon atom, and is preferably a group consisting of one or more (e.g., 1 to 3000, 1 to 1000, 1 to 100, 1 to 50) skeletal atoms selected from carbon atoms, oxygen atoms, nitrogen atoms, sulfur atoms, and silicon atoms, more preferably an aliphatic group having 1 to 100 carbon atoms, and even more preferably 1 to 50 carbon atoms. When the aliphatic group has a substituent, examples of the substituent are the same as the examples of the substituent S.

When the diamine compound is a diamine compound having an aromatic group, the aromatic group is preferably a tetravalent aromatic group having 6 to 100 carbon atoms, more preferably 6 to 50 carbon atoms, and even more preferably a tetravalent aromatic hydrocarbon group having 6 to 100 carbon atoms, still more preferably 6 to 50 carbon atoms. The aromatic group contains at least an aromatic ring. Examples of the aromatic ring contained in the aromatic group are the same as the examples of the aromatic ring C. When the aromatic group has a substituent, examples of the substituent are the same as the examples of the substituent S.

The third skeleton may be a skeleton derived from a diamine compound having an aliphatic group having an alkyl group having 1 to 6 carbon atoms as a substituent. The third skeleton may also be a skeleton derived from isophorone diamine. Therefore, in one embodiment, the second polyimide resin is a resin that further includes a skeleton derived from a diamine compound having an aliphatic group having an alkyl group having 1 to 6 carbon atoms as a substituent. A specific example of such a skeleton is a skeleton derived from isophorone diamine. The skeleton derived from isophorone diamine (5-amino-1,3,3-trimethylcyclohexane methylamine) may be a skeleton derived from 5-isocyanato-1-(isocyanatomethyl)-1,3,3-trimethylcyclohexane.

The third skeleton may be derived from one or more diamine compounds having an aromatic group that may have a substituent, such as 4,4'-diaminodiphenyl ether, 1,4-phenylenediamine, and 2,2-bis[4-(4-aminophenoxy)phenyl]propane. Such a third skeleton is characterized by having an aromatic group.

The third skeleton may be derived from one or more diamine compounds having an aliphatic group which may have a substituent, such as 1,2-diaminoethane, 1,3-diaminopropane, 1,4-diaminobutane, 1,5-diaminopentane, 1,6-hexanediamine, 1,7-heptanediamine, 1,8-octanediamine, 1,9-nonanediamine, 1,10-decanediamine, 1,11-undecanediamine, and 1,12-dodecanediamine. Such a third skeleton is characterized in that the aliphatic group is linear.

The third skeleton may be derived from one or more diamine compounds having an aliphatic group that may have a substituent, such as 1,2-diaminopropane, 1,2-diamino-2-methylpropane, 1,3-diamino-2-methylpropane, 1,3-diamino-2,2-dimethylpropane, 1,3-diaminopentane, and 1,5-diamino-2-methylpentane. Such a third skeleton is characterized in that the aliphatic group is branched.

The third skeleton may be derived from one or more selected from diamine compounds having an aliphatic group which may have a substituent, such as 5-amino-1,3,3-trimethylcyclohexanemethylamine (isophoronediamine), 1,4-diaminocyclohexane, 1,3-diaminocyclohexane, 1,4-cyclohexanebis(methylamine), 1,3-cyclohexanebis(methylamine), 4,4'-diaminodicyclohexylmethane, bis(4-amino-3-methylcyclohexyl)methane, 3(4),8(9)-bis(aminomethyl)tricyclo[5.2.1.0 ^2,6 ]decane, 2,5(6)-bis(aminomethyl)bicyclo[2.2.1]heptane, 1,3-diaminoadamantane, 3,3'-diamino-1,1'-biadamantyl, and 1,6-diaminoadamantane. Such a third skeleton is characterized in that the aliphatic group contains an alicyclic carbon ring.

The above-mentioned third skeleton may be generated in the second polyimide resin by, for example, polymerizing a monomer composition containing a tetracarboxylic dianhydride that can be the material of the first skeleton and a diamine compound that can be the material of the second skeleton to form an imidization, by adding a diamine compound or a diisocyanate compound that can be the material of the third skeleton to the monomer composition or by sequentially mixing them during polymerization. Therefore, the second polyimide resin may contain the structural unit (e2) that the first polyimide resin may contain. It is acceptable for the second polyimide resin to contain a portion of a polyamic acid structure that can be generated during the imidization process.

The second polyimide resin may further include a fourth skeleton different from the first skeleton. This fourth skeleton is derived from one or more acids selected from the group consisting of acids other than BPADA. In the second polyimide resin, the number of the fourth skeletons is 0 or more, and is not particularly limited, but may be 100 or less, 50 or less, or 30 or less.

Examples of acids other than BPADA include tetracarboxylic dianhydrides having an aromatic group which may have a substituent. The aromatic group is preferably an aromatic group having 6 to 100 carbon atoms, more preferably 6 to 50 carbon atoms, and even more preferably an aromatic hydrocarbon group having 6 to 100 carbon atoms, even more preferably 6 to 50 carbon atoms. The aromatic group contains at least an aromatic ring. Examples of the aromatic ring contained in the aromatic group are the same as the examples of the aromatic ring C. When the aromatic group has a substituent, examples of the substituent are the same as the examples of the substituent S. Specific examples of tetracarboxylic dianhydrides having an aromatic group which may have a substituent include pyromellitic dianhydride, 3,3',4,4'-biphenyltetracarboxylic dianhydride, 4,4'-oxydiphthalic anhydride, 3,3',4,4'-benzophenonetetracarboxylic dianhydride, and 3,3',4,4'-diphenylsulfonetetracarboxylic dianhydride.

The glass transition temperature Tg ^(c') (°C) of the second polyimide resin is preferably 140°C or higher, more preferably 145°C or higher, even more preferably 150°C or higher, even more preferably 160°C or higher, and particularly preferably 170°C or higher. There is no particular upper limit, but it may be 300°C or lower, for example. The glass transition temperature Tg ^(c') (°C) can be measured according to the same method as that for the first polyimide resin.

From the viewpoint of enhancing the intended effect of the present invention, the total content ratio (percentage) of the first skeleton and the second skeleton in the second polyimide resin is preferably 4% by mass or more, more preferably 9% by mass or more, even more preferably 19% by mass or more, even more preferably 29% by mass or more, and particularly preferably 39% by mass or more. The total content ratio (percentage) of the first skeleton and the second skeleton may be, for example, 97% by mass or less, 94% by mass or less, 89% by mass or less, or 84% by mass or less. Here, the total content ratio (percentage) of the first skeleton and the second skeleton can be calculated from the ratio of the charged amount (parts by mass) contributing to the reaction of each material used to synthesize the second polyimide resin, and instead, the molecular weight of the second polyimide resin and the formula weight of the first skeleton and the second skeleton incorporated in the resin may be specified, and the total formula weight of the first skeleton and the second skeleton may be calculated as a ratio to the molecular weight. When the second polyimide resin is a polymer, it is preferable that the total content (percentage) of the first skeleton and the second skeleton estimated from the degree of polymerization be within the above range.

When the second polyimide resin further contains a third skeleton, the content ratio (percentage) of the third skeleton is allowed to be 0% by mass (i.e., no third skeleton), and the upper limit is not limited as long as the effect of the present invention is not excessively impaired. Therefore, the content ratio (percentage) of the third skeleton in the second polyimide resin may be, for example, more than 0% by mass, 4% by mass or more, 9% by mass or more, 19% by mass or more, or 29% by mass or more, 94% by mass or less, 89% by mass or less, 79% by mass or less, 69% by mass or less, or 59% by mass or less. Here, the content ratio (percentage) of the third skeleton is calculated in the same manner as the content ratio (percentage) of the first skeleton and the content ratio (percentage) of the second skeleton. When the second polyimide resin is a polymer, it is preferable that the content ratio (percentage) of the third skeleton estimated from the degree of polymerization is within the above-mentioned range. When the second polyimide resin further includes a fourth skeleton, the content (percentage) of the fourth skeleton is the same as the content (percentage) of the third skeleton.

The second polyimide resin is not particularly limited in its terminal structure, so long as it is a resin containing a first skeleton derived from BPADA and a second skeleton derived from BPPAN. For example, the terminal structure of the second polyimide resin may be an acid anhydride group, a carboxyl group, or an amino group derived from the raw material compound of the second polyimide resin (e.g., an acid such as BPADA, or an amine compound such as BPPAN). When the raw material compound further contains maleic anhydride, the terminal structure of the second polyimide resin may be a maleimide group.

The weight average molecular weight (Mw) of the second polyimide resin is usually 1,000 or more, preferably 1.00 to 10,000, more preferably 1,000 to 5,000, and even more preferably 1,000 to 3,000. The weight average molecular weight of the resin can be measured as a polystyrene-equivalent value by gel permeation chromatography (GPC).

Another embodiment of the polyimide resin is a resin obtained by polymerizing and imidizing a monomer composition containing at least BPADA and BPPAN (hereinafter, sometimes referred to as the "third polyimide resin"). Polymerization and imidization are not particularly limited, but are usually carried out in a solvent. In polymerization, the blending ratio of BPADA and BPPAN is preferably determined according to the total number of functional groups possessed by each component, and in one embodiment, the ratio of the total number of amino groups possessed by BPPAN in the monomer composition to the total number of acid anhydride groups possessed by BPADA is in the range of 0.1:1 to 10:1, preferably in the range of 0.5:1 to 10:1, more preferably in the range of 0.8:1 to 10:1, and even more preferably in the range of 0.9:1 to 10:1. Imidization is not particularly limited, but is usually carried out in a solvent by heating in the absence of a catalyst, by heating in the presence of a catalyst, or in the presence of a catalyst at room temperature. From the viewpoint of enhancing the intended effect of the present invention, it is preferable that the imidization is performed by heating in the absence of a catalyst. The third polyimide resin may be any of a random copolymer, an alternating copolymer, and a block copolymer. The third polyimide resin is not limited to such a polymerization and imidization method. It is acceptable for the third polyimide resin to contain a portion of a polyamic acid structure that may be generated during the imidization process. The third polyimide resin thus obtained contains the aforementioned structural unit (e1) contained in the first polyimide resin. The third polyimide resin thus obtained also contains the aforementioned first skeleton and second skeleton contained in the second polyimide resin.

The monomer composition may contain, as other monomers, an acid other than BPADA and/or a diamine compound other than BPPAN, or other monomers may be added during the reaction.

Examples of acids other than BPADA include tetracarboxylic dianhydrides having an aromatic group which may have a substituent. The aromatic group is preferably a tetravalent aromatic group having 6 to 100 carbon atoms, more preferably 6 to 50 carbon atoms, and even more preferably a tetravalent aromatic hydrocarbon group having 6 to 100 carbon atoms, even more preferably 6 to 50 carbon atoms. The aromatic group contains at least an aromatic ring. Examples of aromatic rings contained in the aromatic group are the same as the examples of aromatic ring C. When the aromatic group has a substituent, examples of the substituent are the same as the examples of substituent S. Specific examples of tetracarboxylic dianhydrides having an aromatic group which may have a substituent include pyromellitic dianhydride, 3,3',4,4'-biphenyltetracarboxylic dianhydride, 4,4'-oxydiphthalic anhydride, 3,3',4,4'-benzophenonetetracarboxylic dianhydride, and 3,3',4,4'-diphenylsulfonetetracarboxylic dianhydride. The molar ratio of the content of acids other than BPADA to the content of BPADA in the monomer composition is not particularly limited, but may be, for example, 0.5 or less, 0.4 or less, or 0.3 or less.

In one embodiment, the monomer composition further contains one or more diamine compounds selected from the group consisting of diamine compounds having an aliphatic group which may have a substituent and diamine compounds having an aromatic group which may have a substituent. The molar ratio of the content of diamine compounds other than BPPAN to the content of BPPAN in the monomer composition is not particularly limited, but may be, for example, 0.5 or less, 0.4 or less, or 0.3 or less.

When the diamine compound is a diamine compound having an aliphatic group, the aliphatic group contains at least a carbon atom, and is preferably a group consisting of one or more (e.g., 1 to 3000, 1 to 1000, 1 to 100, 1 to 50) skeletal atoms selected from carbon atoms, oxygen atoms, nitrogen atoms, sulfur atoms, and silicon atoms, more preferably an aliphatic group having 1 to 100 carbon atoms, and even more preferably 1 to 50 carbon atoms. When the aliphatic group has a substituent, examples of the substituent are the same as the examples of the substituent S.

When the diamine compound is a diamine compound having an aromatic group, the aromatic group is preferably a tetravalent aromatic group having 6 to 100 carbon atoms, more preferably 6 to 50 carbon atoms, and even more preferably a tetravalent aromatic hydrocarbon group having 6 to 100 carbon atoms, even more preferably 6 to 50 carbon atoms. The aromatic group contains at least an aromatic ring. Examples of the aromatic ring contained in the aromatic group are the same as the examples of the aromatic ring C. When the aromatic group has a substituent, examples of the substituent are the same as the examples of the substituent S. When the diamine compound is a diamine compound having an aromatic group that may have a substituent, examples thereof include one or more diamine compounds having an aromatic group such as 4,4'-diaminodiphenyl ether, 1,4-phenylenediamine, and 2,2-bis[4-(4-aminophenoxy)phenyl]propane.

When the diamine compound is a diamine compound having an aliphatic group which may have a substituent, a first example thereof may be a skeleton derived from one or more selected from diamine compounds having an aliphatic group which may have a substituent, such as 1,2-diaminoethane, 1,3-diaminopropane, 1,4-diaminobutane, 1,5-diaminopentane, 1,6-hexanediamine, 1,7-heptanediamine, 1,8-octanediamine, 1,9-nonanediamine, 1,10-decanediamine, 1,11-undecanediamine, and 1,12-dodecanediamine. The diamine compound according to this first example is characterized in that the aliphatic group is linear.

When the diamine compound is a diamine compound having an aliphatic group which may have a substituent, a second example thereof may be a skeleton derived from one or more selected from diamine compounds having an aliphatic group which may have a substituent, such as 1,2-diaminopropane, 1,2-diamino-2-methylpropane, 1,3-diamino-2-methylpropane, 1,3-diamino-2,2-dimethylpropane, 1,3-diaminopentane, and 1,5-diamino-2-methylpentane. The diamine compound according to this second example is characterized in that the aliphatic group is branched.

When the diamine compound is a diamine compound having an aliphatic group which may have a substituent, a third example thereof may be a skeleton derived from one or more selected from diamine compounds having an aliphatic group which may have a substituent, such as 5-amino-1,3,3-trimethylcyclohexanemethylamine (isophoronediamine), 1,4-diaminocyclohexane, 1,3-diaminocyclohexane, 1,4-cyclohexanebis(methylamine), 1,3-cyclohexanebis(methylamine), 4,4'-diaminodicyclohexylmethane, bis(4-amino-3-methylcyclohexyl)methane, 3(4),8(9)-bis(aminomethyl)tricyclo[5.2.1.0 ^2,6 ]decane, 2,5(6)-bis(aminomethyl)bicyclo[2.2.1]heptane, 1,3-diaminoadamantane, 3,3'-diamino-1,1'-biadamantyl, and 1,6-diaminoadamantane. The diamine compound according to the third example is characterized in that the aliphatic group contains an alicyclic carbon ring.

In accordance with the above, in one embodiment, the monomer composition further contains a diamine compound having an aliphatic group with an alkyl group having 1 to 6 carbon atoms as a substituent. In a specific embodiment, the monomer composition further contains isophorone diamine.

The third polyimide resin is not particularly limited in its terminal structure, so long as it is a resin obtained by polymerizing and imidizing the monomer composition. For example, the terminal structure of the third polyimide resin may be an acid anhydride group, a carboxyl group, or an amino group derived from a raw material compound (e.g., an acid such as BPADA, or an amine compound such as BPPAN) contained in the monomer composition of the third polyimide resin. When the raw material compound further contains maleic anhydride, the terminal structure of the third polyimide resin may be a maleimide group.

The weight average molecular weight (Mw) of the third polyimide resin is 1,000 or more, preferably 1.00 to 10,000, more preferably 1,000 to 5,000, and even more preferably 1,000 to 3,000. The weight average molecular weight of the resin can be measured as a polystyrene-equivalent value by gel permeation chromatography (GPC).

Examples of the phenoxy resin include phenoxy resins having one or more skeletons selected from the group consisting of bisphenol A skeleton, bisphenol F skeleton, bisphenol S skeleton, bisphenolacetophenone skeleton, novolac skeleton, biphenyl skeleton, fluorene skeleton, dicyclopentadiene skeleton, norbornene skeleton, naphthalene skeleton, anthracene skeleton, adamantane skeleton, terpene skeleton, and trimethylcyclohexane skeleton. The terminal of the phenoxy resin may be any functional group such as a phenolic hydroxyl group or an epoxy group. The phenoxy resin is preferably a phenoxy resin having a weight average molecular weight of 30,000 or more.

Specific examples of phenoxy resins include Mitsubishi Chemical's "1256" and "4250" (both phenoxy resins containing a bisphenol A skeleton); Mitsubishi Chemical's "YX8100" (phenoxy resin containing a bisphenol S skeleton); Mitsubishi Chemical's "YX6954" (phenoxy resin containing a bisphenol acetophenone skeleton); Nippon Steel Chemical & Material's "FX280" and "FX293"; Mitsubishi Chemical's "YL7500BH30", "YX6954BH30", "YX7553", "YX7553BH30", "YL7769BH30", "YL6794", "YL7213", "YL7290" and "YL7482"; and the like.

The polyamide-imide resin is a resin having an amide-imide structure. From the viewpoint of compatibility with other components in the resin composition layer, it is preferable to use polyamide-imide resins having an alicyclic structure in the molecular structure, polyamide-imide resins having a siloxane structure as described in JP-A-05-112760, polyamide-imide resins having a bulky branched chain structure, polyamide-imide resins made from asymmetric monomers, polyamide-imide resins having a multi-branched structure, etc.

Among them, from the viewpoint that the polyamide-imide resin has an isocyanuric ring structure, which improves compatibility and dispersibility of the resin varnish, (i) a polyamide-imide resin having an isocyanuric ring structure in the molecular structure (i.e., a polyamide-imide resin having an isocyanuric ring structure and an imide skeleton or an amide skeleton), (ii) a polyamide-imide resin having an isocyanuric ring structure and an alicyclic structure in the molecular structure (i.e., a polyamide-imide resin having an isocyanuric ring structure, an alicyclic structure, and an imide skeleton or an amide skeleton), and (iii) a polyamide-imide resin having a repeating unit containing an isocyanuric ring structure and an alicyclic structure (i.e., a polyamide-imide resin having a repeating unit containing an isocyanuric ring structure, an alicyclic structure, and an imide skeleton or an amide skeleton) are more preferable.

A preferred embodiment of the polyamide-imide resins (i) to (iii) includes (1) a carboxylic acid group-containing branched polyamide-imide obtained by reacting an isocyanuric ring-containing polyisocyanate compound derived from an alicyclic diisocyanate with an acid anhydride of a polycarboxylic acid having three or more carboxyl groups (hereinafter, the compound may be referred to as "(compound E-e1)"); (2) a carboxylic acid group-containing branched polymerizable polyamide-imide obtained by reacting compound (E-e1) with a compound having one epoxy group and one or more radically polymerizable unsaturated groups (hereinafter, the compound may be referred to as "compound (E-e2)"); or (3) a carboxylic acid group-containing branched polymerizable polyamide-imide obtained by reacting a compound having one hydroxyl group and one or more radically polymerizable unsaturated groups with the remaining isocyanate group in the synthesis process of compound (E-e1) (hereinafter, the compound may be referred to as "compound (E-e3)").

（式中、ｗは０～１５を表す。） Specific examples of the compound (E-e1) include compounds represented by the following general formula (I): The repeating unit in the compound represented by the general formula (I) is referred to as repeating unit (I-1).

(In the formula, w represents 0 to 15.)

（式中、Ｒ^４０は式（Ｉ）中の残基を表す。） An example of the compound (E-e2) is a compound (II) having a structure (I-2) in which GMA (glycidyl methacrylate) is added to any part of the carboxyl groups and/or terminal carboxyl groups of the repeating unit (I-1) in the general formula (I).

(In the formula, R ⁴⁰ represents a residue in formula (I).)

The ratio of GMA modification of carboxyl groups is preferably 0.3 mol% or more, more preferably 0.5 mol% or more, even more preferably 0.7 mol% or more, or 0.9 mol% or more, relative to the number of moles of carboxyl groups in compound (E-e1). The upper limit is preferably 50 mol% or less, more preferably 40 mol% or less, even more preferably 30 mol% or less, or 20 mol% or less.

（式中、Ｒ’は式（Ｉ）中の残基を表す。） Examples of the compound (E-e3) include compound (III) having a structure (I-3) in which any part of the repeating unit (I-1) and/or the terminal imide group in the above formula (I) is an isocyanate residue to which a hydroxyl group of pentaerythritol triacrylate is added.

(In the formula, R′ represents a residue in formula (I).)

The amount of pentaerythritol triacrylate added is preferably 40 mol% or less, more preferably 38 mol% or less, and even more preferably 35 mol% or less, based on the number of moles of isocyanate groups in the polyisocyanate at the time of charging. On the other hand, from the viewpoint of fully obtaining the effect of the addition, the amount of pentaerythritol triacrylate added is preferably 0.3 mol% or more, more preferably 3 mol% or more, and even more preferably 5 mol% or more, based on the number of moles of isocyanate groups in the polyisocyanate at the time of charging.

Polyamide-imide resins can be synthesized by various known methods. For a method of synthesizing polyamide-imide resins, see, for example, paragraphs 0020 to 0030 of International Publication No. 2010/074197, the contents of which are incorporated herein by reference.

Commercially available polyamide-imide resins can be used. Examples of commercially available products include modified polyamide-imides such as "Unidic V-8000" manufactured by DIC Corporation, "Viromax HR11NN" and "Viromax HR16NN" manufactured by Toyobo Co., Ltd., and "KS9100" and "KS9300" (polyamide-imide containing a polysiloxane skeleton) manufactured by Hitachi Chemical Co., Ltd.

From the viewpoint of compatibility with other components in the resin composition layer, the polyester resin preferably has a fluorene structure in its molecular structure, and preferably has a diol-derived structural unit and a dicarboxylic acid-derived structural unit in addition to the fluorene structure.

A specific example of a polyester resin is "OKP4HT" manufactured by Osaka Gas Chemicals Co., Ltd.

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

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

An example of a polyethersulfone resin is "PES5003P" manufactured by Sumitomo Chemical Co., Ltd.

The elastomer in component (E) is a resin with flexibility, preferably a resin with rubber elasticity or a resin that exhibits rubber elasticity by polymerizing with other components. Examples of rubber elasticity include resins that exhibit an elastic modulus of 1 GPa or less when a tensile test is performed in accordance with the Japanese Industrial Standards (JIS K7161) at a temperature of 25°C and a humidity of 40% RH. Elastomers are usually amorphous resin components that can be dissolved in organic solvents. One type of elastomer may be used alone, or two or more types may be used in any ratio.

In one embodiment, the elastomer is preferably a resin having one or more structures selected from a polybutadiene structure, a polysiloxane structure, a poly(meth)acrylate structure, a polyalkylene structure, a polyalkyleneoxy structure, a polyisoprene structure, a polyisobutylene structure, a polycarbonate structure, and a polystyrene structure in the molecule. "(Meth)acrylate" refers to methacrylate and acrylate.

In another embodiment, the elastomer is preferably one or more selected from resins having a glass transition temperature (Tg) of 25°C or less and resins that are liquid at 25°C or less. The glass transition temperature of a resin having a glass transition temperature (Tg) of 25°C or less is preferably 20°C or less, more preferably 15°C or less. The lower limit of the glass transition temperature is not particularly limited, but can usually be -15°C or more. Furthermore, a resin that is liquid at 25°C is preferably a resin that is liquid at 20°C or less, more preferably a resin that is liquid at 15°C or less. The glass transition temperature can be measured by DSC (differential scanning calorimetry).

An example of an elastomer is a resin containing a polybutadiene structure. The polybutadiene structure may be contained in the main chain or in a side chain. The polybutadiene structure may be partially or entirely hydrogenated. A resin containing a polybutadiene structure is sometimes called a "polybutadiene resin." Specific examples of polybutadiene resins include "Ricon 130MA8", "Ricon 130MA13", "Ricon 130MA20", "Ricon 131MA5", "Ricon 131MA10", "Ricon 131MA17", "Ricon 131MA20", and "Ricon 184MA6" (polybutadiene containing an acid anhydride group) manufactured by Cray Valley Corporation; "GQ-1000" (polybutadiene having hydroxyl and carboxyl groups introduced therein), "G-1000", "G-2000", and "G-3000" (polybutadiene having hydroxyl groups at both ends), "GI-1000", "GI-2000", and "GI-3000" (polybutadiene having hydrogenated hydroxyl groups at both ends) manufactured by Nippon Soda Co., Ltd.; and "FCA-061L" (hydrogenated polybutadiene skeleton epoxy resin) manufactured by Nagase ChemteX Corporation. Specific examples of polybutadiene resins include hydroxyl-terminated polybutadiene, linear polyimides made from diisocyanate compounds and tetrabasic acid anhydrides (polyimides described in JP 2006-37083 A and WO 2008/153208 A), and phenolic hydroxyl group-containing butadienes. The content of the butadiene structure in the polyimide resin is preferably 60% by mass to 95% by mass, more preferably 75% by mass to 85% by mass. For details of the polyimide resin, see JP 2006-37083 A and WO 2008/153208 A, the contents of which are incorporated herein by reference.

An example of an elastomer is a resin containing a poly(meth)acrylate structure. A resin containing a poly(meth)acrylate structure is sometimes called a "poly(meth)acrylic resin." Specific examples of poly(meth)acrylic resins include Teisan Resin manufactured by Nagase ChemteX Corporation, and ME-2000, W-116.3, W-197C, KG-25, and KG-3000 manufactured by Negami Chemical Industries, Ltd.

Examples of elastomers include resins containing a polycarbonate structure. Resins containing a polycarbonate structure are sometimes called "polycarbonate resins". Examples of such resins include carbonate resins that do not have a reactive group, hydroxyl group-containing carbonate resins, phenolic hydroxyl group-containing carbonate resins, carboxyl group-containing carbonate resins, acid anhydride group-containing carbonate resins, isocyanate group-containing carbonate resins, urethane group-containing carbonate resins, and epoxy group-containing carbonate resins. The reactive group here refers to a functional group that can react with other components, such as a hydroxyl group, a phenolic hydroxyl group, a carboxyl group, an acid anhydride group, an isocyanate group, a urethane group, and an epoxy group.
Specific examples of polycarbonate resins include "FPC0220" and "FPC2136" manufactured by Mitsubishi Gas Chemical Co., Ltd., "T6002" and "T6001" (polycarbonate diols) manufactured by Asahi Kasei Chemicals Corporation, and "C-1090", "C-2090", and "C-3090" (polycarbonate diols) manufactured by Kuraray Co., Ltd. In addition, linear polyimides made from hydroxyl-terminated polycarbonate, diisocyanate compounds, and tetrabasic acid anhydrides can also be used. The content of the carbonate structure in the polyimide resin is preferably 60% by mass to 95% by mass, more preferably 75% by mass to 85% by mass. For details of the polyimide resin, the description in International Publication No. WO 2016/129541 can be referred to, the contents of which are incorporated herein.

Examples of elastomers include resins containing a polysiloxane structure. Resins containing a polysiloxane structure are sometimes called "siloxane resins." Specific examples of siloxane resins include "SMP-2006," "SMP-2003PGMEA," and "SMP-5005PGMEA" manufactured by Shin-Etsu Silicones Co., Ltd., and linear polyimides made from amine-terminated polysiloxanes and tetrabasic acid anhydrides (see, for example, International Publication No. 2010/053185, JP 2002-12667 A, and JP 2000-319386 A).

Examples of elastomers include resins containing a polyalkylene structure or a polyalkyleneoxy structure. Resins containing a polyalkylene structure are sometimes called "alkylene resins". Resins containing a polyalkyleneoxy structure are sometimes called "alkyleneoxy resins". The polyalkyleneoxy structure is preferably a polyalkyleneoxy structure having 2 to 15 carbon atoms, more preferably a polyalkyleneoxy structure having 3 to 10 carbon atoms, and particularly preferably a polyalkyleneoxy structure having 5 to 6 carbon atoms. Specific examples of alkylene resins and alkyleneoxy resins include "PTXG-1000" and "PTXG-1800" manufactured by Asahi Kasei Fibers Corporation.

An example of an elastomer is a resin containing a polyisoprene structure. A resin containing a polyisoprene structure is sometimes called an "isoprene resin." Specific examples of isoprene resin include "KL-610" and "KL613" manufactured by Kuraray Co., Ltd.

An example of an elastomer is a resin containing a polyisobutylene structure. A resin containing a polyisobutylene structure is sometimes called an "isobutylene resin." Specific examples of isobutylene resins include Kaneka Corporation's "SIBSTAR-073T" (styrene-isobutylene-styrene triblock copolymer) and "SIBSTAR-042D" (styrene-isobutylene diblock copolymer).

An example of an elastomer is a resin containing a polystyrene structure. A resin containing a polystyrene structure is sometimes called a "styrene resin." The styrene resin may be a copolymer containing an arbitrary repeating unit other than the styrene unit in combination with the styrene unit, or may be a hydrogenated polystyrene resin.

The optional repeating unit may be, for example, a repeating unit having a structure obtained by polymerizing a conjugated diene (conjugated diene unit), or a repeating unit having a structure obtained by hydrogenating the conjugated diene (hydrogenated conjugated diene unit). The conjugated diene may be, for example, an aliphatic conjugated diene such as butadiene, isoprene, 2,3-dimethylbutadiene, 1,3-pentadiene, or 1,3-hexadiene; or a halogenated aliphatic conjugated diene such as chloroprene. The conjugated diene is preferably an aliphatic conjugated diene, and more preferably butadiene, from the viewpoint of obtaining the effects of the present invention significantly. The conjugated diene may be used alone or in combination of two or more types. The polystyrene resin may be a random copolymer or a block copolymer.

Examples of styrene resins include styrene-butadiene-styrene block copolymer (SBS), styrene-isoprene-styrene block copolymer (SIS), styrene-ethylene-butylene-styrene block copolymer (SEBS), styrene-ethylene-propylene-styrene block copolymer (SEPS), styrene-ethylene-ethylene-propylene-styrene block copolymer (SEEPS), styrene-butadiene-butylene-styrene block copolymer (SBBS), styrene-butadiene diblock copolymer, hydrogenated styrene-butadiene block copolymer, hydrogenated styrene-isoprene block copolymer, hydrogenated styrene-butadiene random copolymer, and styrene-maleic anhydride copolymer. Specific examples of styrene resins include hydrogenated styrene-based thermoplastic elastomers "H1041", "Tuftec H1043", "Tuftec P2000", and "Tuftec MP10" (manufactured by Asahi Kasei Corporation); epoxidized styrene-butadiene thermoplastic elastomers "Epofriend AT501" and "CT310" (manufactured by Daicel Corporation); modified styrene-based elastomers having hydroxyl groups "Septon HG252" (manufactured by Kuraray Co., Ltd.); modified styrene-based elastomers having carboxyl groups "Tuftec N503M", modified styrene-based elastomers having amino groups "Tuftec N501", modified styrene-based elastomers having acid anhydride groups "Tuftec M1913" (manufactured by Asahi Kasei Chemicals Corporation); unmodified styrene-based elastomers "Septon S8104" (manufactured by Kuraray Co., Ltd.); styrene-ethylene/butylene-styrene block copolymers "FG1924" (manufactured by Kraton Corporation), "EF-40" (CRAY (manufactured by VALLEY Co., Ltd.)

The number average molecular weight (Mn) of the elastomer is preferably 1,000 or more, more preferably 1,500 or more, even more preferably 3,000 or more, and particularly preferably 5,000 or more, and is preferably 1,000,000 or less, more preferably 900,000 or less. The number average molecular weight (Mn) can be measured in terms of polystyrene using GPC (gel permeation chromatography).

From the viewpoint of obtaining a significant effect of the present invention, the content of component (E) is preferably 1% by mass or more, more preferably 2% by mass or more, and even more preferably 3% by mass or more, and is preferably 20% by mass or less, more preferably 15% by mass or less, and even more preferably 10% by mass or less, assuming that the non-volatile components in the resin composition layer are 100% by mass.

-(F) Curing accelerator-
The resin composition may contain a curing accelerator (F) as the component (F). Examples of the curing accelerator (F) include phosphorus-based curing accelerators, amine-based curing accelerators, imidazole-based curing accelerators, guanidine-based curing accelerators, and metal-based curing accelerators. The amine-based curing accelerators and imidazole-based curing accelerators are preferred, and the amine-based curing accelerators are more preferred. The curing accelerator may be used alone or in combination of two or more.

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

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

Examples of imidazole-based curing accelerators include 2-methylimidazole, 2-undecylimidazole, 2-heptadecylimidazole, 1,2-dimethylimidazole, 2-ethyl-4-methylimidazole, 1,2-dimethylimidazole, 2-ethyl-4-methylimidazole, 2-phenylimidazole, 2-phenyl-4-methylimidazole, 1-benzyl-2-methylimidazole, 1-benzyl-2-phenylimidazole, 1-cyanoethyl-2-methylimidazole, 1-cyanoethyl-2-undecylimidazole, 1-cyanoethyl-2-ethyl-4-methylimidazole, 1-cyanoethyl-2-phenylimidazole, 1-cyanoethyl-2-undecylimidazolium trimellitate, 1-cyanoethyl-2-phenylimidazolium trimellitate, 2,4-diamino-6-[2'-methylimidazolyl-(1')]-ethyl-s-triazine, 2,4 -diamino-6-[2'-undecylimidazolyl-(1')]-ethyl-s-triazine, 2,4-diamino-6-[2'-ethyl-4'-methylimidazolyl-(1')]-ethyl-s-triazine, 2,4-diamino-6-[2'-methylimidazolyl-(1')]-ethyl-s-triazine isocyanuric acid adduct, 2-phenylimidazole isocyanuric acid adduct, 2-phenyl-4,5-dihydroxymethylimidazole, 2-phenyl Examples of the imidazole compounds include 1-dodecyl-4-methyl-5-hydroxymethylimidazole, 2,3-dihydro-1H-pyrrolo[1,2-a]benzimidazole, 1-dodecyl-2-methyl-3-benzylimidazolium chloride, 2-methylimidazoline, 2-phenylimidazoline, and adducts of imidazole compounds and epoxy resins, with 2-ethyl-4-methylimidazole and 1-benzyl-2-phenylimidazole being preferred.

Commercially available imidazole curing accelerators may be used, such as "P200-H50" manufactured by Mitsubishi Chemical Corporation.

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

Metal-based curing accelerators include, for example, organometallic complexes or organometallic salts of metals such as cobalt, copper, zinc, iron, nickel, manganese, and tin. Specific examples of organometallic complexes include organocobalt complexes such as cobalt (II) acetylacetonate and cobalt (III) acetylacetonate, organocopper complexes such as copper (II) acetylacetonate, organozinc complexes such as zinc (II) acetylacetonate, organoiron complexes such as iron (III) acetylacetonate, organonickel complexes such as nickel (II) acetylacetonate, and organomanganese complexes such as manganese (II) acetylacetonate. Organometallic salts include, for example, zinc octylate, tin octylate, zinc naphthenate, cobalt naphthenate, tin stearate, and zinc stearate.

From the viewpoint of obtaining a significant effect of the present invention, the content of the curing accelerator (F) is preferably 0.01% by mass or more, more preferably 0.02% by mass or more, and particularly preferably 0.03% by mass or more, when the non-volatile components in the resin composition layer are taken as 100% by mass, and is preferably 3% by mass or less, more preferably 2% by mass or less, and particularly preferably 1% by mass or less.

--(G) Polymerization initiator--
The resin composition layer may contain a polymerization initiator (G) as the component (G). By containing the polymerization initiator (G), it is possible to particularly cure the component (D).

The type of polymerization initiator is not particularly limited, but examples include radical generators such as cyclohexanone peroxide, tert-butyl peroxybenzoate, methyl ethyl ketone peroxide, dicumyl peroxide, tert-butylcumyl peroxide, di-tert-butyl peroxide, diisopropylbenzene hydroperoxide, cumene hydroperoxide, tert-butyl hydroperoxide, and 2,3-dimethyl-2,3-diphenylbutane. These may be used alone or in combination of two or more.

(G) The polymerization initiator may be a commercially available product. Examples of commercially available products include "Perhexine 25B" manufactured by NOF Corporation.

The content of the (G) polymerization initiator is preferably 0.01% by mass or more, more preferably 0.03% by mass or more, more preferably 0.05% by mass or more, and is preferably 3% by mass or less, more preferably 2% by mass or less, and even more preferably 1% by mass or less, based on 100% by mass of the non-volatile components in the resin composition layer, from the viewpoint of obtaining a significant effect of the present invention.

-(H) Other Additives-
The resin composition layer may further contain other additives as optional components in addition to the above-mentioned components. Examples of such additives include resin additives such as thickeners, defoamers, leveling agents, and adhesion-imparting agents. These additives may be used alone or in combination of two or more. The content of each additive can be appropriately set by a person skilled in the art.

The resin composition layer may further contain any solvent as a volatile component. The varnish viscosity can be adjusted by adding a solvent to the resin composition used to form the resin composition layer. Examples of the solvent include organic solvents. However, it is preferable that the resin composition layer does not contain toluene, and when the entire resin composition layer is taken as 100 mass, the toluene content is preferably 0.1 mass% or less, 0.01 mass% or less, 0.001 mass% or less, or 0.0001 mass% or less.

Examples of organic solvents include ketones such as methyl ethyl ketone (MEK) and cyclohexanone, aromatic hydrocarbons such as xylene and tetramethylbenzene, glycol ethers such as methyl cellosolve, butyl cellosolve, methyl carbitol, butyl carbitol, propylene glycol monomethyl ether, dipropylene glycol monoethyl ether, dipropylene glycol diethyl ether, and triethylene glycol monoethyl ether, esters such as ethyl acetate, butyl acetate, butyl cellosolve acetate, carbitol acetate, and ethyl diglycol acetate, aliphatic hydrocarbons such as octane and decane, and petroleum solvents such as petroleum ether, petroleum naphtha, hydrogenated petroleum naphtha, and solvent naphtha. These may be used alone or in combination of two or more.

In order to improve embeddability and uniformity of the thickness of the insulating layer, the melt viscosity of the resin composition layer is adjusted by adjusting the specific surface area of the inorganic filler and the amount of solvent in the resin composition layer, so that the maximum value of tan δ is 1.0 to 2.0. The amount of solvent (residual solvent amount) in the resin composition layer is preferably 3 mass% or less, more preferably 2.5 mass% or less, even more preferably 2 mass% or less, even more preferably 1.5 mass% or less, and particularly preferably 1 mass% or less. There is no particular lower limit, but it may be 0.0001 mass% or more.

In dynamic viscoelasticity measurement of the resin composition layer at 60°C to 200°C, the maximum value of tan δ at 100°C or higher is 1.0 or more, preferably 1.1 or more, and more preferably 1.3 or more, from the viewpoint of improving embeddability. In addition, the maximum value of tan δ is 2.0 or less, preferably 1.9 or less, and more preferably 1.8 or less, from the viewpoint of improving the uniformity of the thickness of the insulating layer. The maximum value of tan δ can be measured according to the method described in the examples below.

The thickness of the resin composition layer is preferably 30 μm or less, more preferably 25 μm or less, and even more preferably 20 μm or less, from the viewpoint of making the printed wiring board thinner and being able to provide a cured product with excellent insulation even if the cured product of the resin composition is a thin film. The lower limit of the thickness of the resin composition layer can usually be 5 μm or more, 10 μm or more, etc., from the viewpoint of increasing insulation reliability.

<Other demographics>
In one embodiment, the resin sheet may further include other layers as necessary. Examples of such other layers include a protective film provided on the surface of the resin composition layer that is not bonded to the support (i.e., the surface opposite to the support). The thickness of the protective film is not particularly limited, but is, for example, 1 μm to 40 μm. By laminating the protective film, adhesion of dirt and the like to the surface of the resin composition layer and scratches can be suppressed.

<Method of manufacturing resin sheet>
The resin sheet can be produced, for example, by preparing a resin varnish by dissolving the resin composition in an organic solvent, applying the resin varnish onto a support using a die coater or the like, and then drying the varnish to form a resin composition layer. The organic solvent may be any of those described above.

Drying may be performed by known methods such as heating or blowing hot air. There are no particular limitations on the drying conditions, but drying is performed so that the content of organic solvent in the resin composition layer is 10% by mass or less, preferably 5% by mass or less. Although it varies depending on the boiling point of the organic solvent in the resin varnish, for example, when using a resin varnish containing 30% by mass to 60% by mass of organic solvent, the resin composition layer can be formed by drying at 50°C to 150°C for 3 to 10 minutes.

The resin sheet can be stored in a roll. If the resin sheet has a protective film, it can be used by peeling off the protective film.

<Physical properties and uses of resin sheets>
The resin sheet of the present invention is a resin sheet for forming an insulating layer using a vacuum press treatment, and includes a support and a resin composition layer provided on the support, the support has a metal foil having an arithmetic mean roughness (Ra) of more than 300 nm on the surface on the side bonded to the resin composition layer, the resin composition layer contains (A) an inorganic filler having a specific surface area of 10 m ² /g or more, and in dynamic viscoelasticity measurement of the resin composition layer at 60° C. to 200° C., the maximum value of tan δ at 100° C. or more is 1.0 to 2.0. By forming an insulating layer by vacuum press treatment using such a resin sheet, an insulating layer having excellent embedding properties and uniformity in the thickness of the insulating layer as well as excellent insulation properties can be realized.

The resin composition layer of the resin sheet and the circuit board are laminated by vacuum pressing, and the resin composition layer is thermally cured at 100°C for 30 minutes and then at 200°C for 120 minutes. The cured resin composition layer exhibits excellent embeddability. Therefore, the cured resin provides an insulating layer with excellent embeddability. Specifically, the resin composition layer of the resin sheet is laminated to a glass cloth-based epoxy resin double-sided copper-clad laminate (hereinafter referred to as "copper-clad laminate") having circuit conductors (copper) formed on both sides in a 1 mm square lattice wiring pattern (residual copper rate of 59%). After laminating the resin composition layer to the copper-clad laminate, the resin composition layer is thermally cured by vacuum pressing under the above-mentioned thermal curing conditions to obtain an insulating layer. After etching the support, the embeddability of the resin composition layer in the 1 mm square lattice wiring pattern is observed using a FIB-SEM composite device, and the lattice pattern is embedded with the resin composition layer. The embeddability can be measured according to the method described in the examples below.

The resin composition layer of the resin sheet and the circuit board are laminated by vacuum pressing, and the resin composition layer is thermally cured at 100°C for 30 minutes and then at 200°C for 120 minutes, resulting in a cured resin composition layer that exhibits excellent insulation reliability. Thus, the cured product provides an insulating layer with excellent insulation reliability. Specifically, the resin composition layer of the resin sheet is laminated onto a glass cloth-based epoxy resin double-sided copper-clad laminate (hereinafter referred to as "copper-clad laminate") having circuit conductors (copper) formed on both sides in a 1 mm square lattice wiring pattern (residual copper rate of 59%). After laminating the resin composition layer onto the copper-clad laminate, the resin composition layer is thermally cured by vacuum pressing under the above-mentioned thermal curing conditions to obtain an insulating layer. After peeling off the support, electrolytic plating is performed to obtain a conductor layer on the insulating layer. The conductor layer side is the positive electrode and the copper-clad laminate side is the negative electrode, and the insulation resistance value after 100 hours under conditions of 110° C., 85% relative humidity, and 20 V DC voltage application is measured six times with an electrochemical migration tester using a highly accelerated life tester. At this time, the insulation resistance value of at least one test piece is preferably 1.00×10 ⁸ Ω or more, more preferably 1.00×10 ⁹ Ω or more. The average insulation resistance value of the six test pieces is preferably 1.00×10 ⁸ Ω or more, more preferably 1.00×10 ⁹ Ω or more. The insulation reliability can be evaluated according to the method described in the examples below.

By forming an insulating layer by vacuum press processing using the resin sheet of the present invention, an insulating layer exhibiting good embedding properties and insulation resistance can be obtained. Therefore, the resin sheet of the present invention can be suitably used as a resin sheet for forming an insulating layer by vacuum press processing (for forming an insulating layer by vacuum press processing). The resin sheet of the present invention has a support containing a metal foil, and the metal foil can be used to form a conductor layer. Therefore, the resin sheet of the present invention can be suitably used as a resin sheet for forming both an insulating layer and a conductor layer by vacuum press processing in the manufacture of a printed wiring board (for forming an insulating layer and a conductor layer by vacuum press processing). The resin sheet of the present invention can be suitably used to form an insulating layer (and a conductor layer) of a printed wiring board, preferably an interlayer insulating layer (and a conductor layer) of a printed wiring board. In the present invention, the term "printed wiring board" also includes a rewiring board of a semiconductor package.

[Printed Wiring Board and Method for Manufacturing Printed Wiring Board]
The printed wiring board of the present invention includes an insulating layer made of a cured product of the resin composition layer of the resin sheet of the present invention.

The printed wiring board can be produced, for example, by using the above-mentioned resin sheet by a method including the following steps (I) and (II).
(I) A step of laminating a resin sheet on an inner layer substrate by vacuum pressing; (II) A step of thermally curing the resin composition layer to form an insulating layer.

The "inner layer substrate" used in step (I) is a member that will be the substrate of the printed wiring board, and examples thereof include glass epoxy substrates, metal substrates, polyester substrates, polyimide substrates, BT resin substrates, and thermosetting polyphenylene ether substrates. The substrate may have a conductor layer on one or both sides, and the conductor layer may be patterned. An inner layer substrate having a conductor layer (circuit) formed on one or both sides of the substrate may be called an "inner layer circuit substrate." In addition, intermediate products on which an insulating layer and/or a conductor layer is to be formed during the manufacture of a printed wiring board are also included in the "inner layer substrate" of the present invention. When the printed wiring board is a circuit board with built-in components, an inner layer substrate with built-in components may be used.

The inner layer substrate and the resin sheet are laminated by vacuum pressing so that the resin composition layer of the resin sheet is bonded to the inner layer substrate. By laminating the inner layer substrate and the resin composition layer by vacuum pressing, it is possible to improve the dielectric properties, mechanical strength, and electrical properties.

First, the inner layer substrate and the resin sheet are set in a vacuum press device so that the resin composition layer of the resin sheet and the inner layer substrate are bonded. Next, a vacuum press process is performed to heat and press the inner layer substrate and the resin composition layer under reduced pressure conditions. The vacuum press process is preferably a vacuum heat press process (vacuum hot press process) in which heat is applied.

It is preferable to set the inner layer substrate and resin sheet in a vacuum press device via cushion paper, a metal plate such as a stainless steel plate (SUS plate), a release film, etc.

The vacuum press process can be carried out using a conventional vacuum press device that presses the inner layer substrate and the resin sheet from both sides with a heated metal plate such as a stainless steel plate. An example of a commercially available vacuum press device is the "VH1-1603" manufactured by Kitagawa Seiki Co., Ltd.

The vacuum pressing process may be performed only once, or may be repeated two or more times. When performing the process two or more times, the pressure, heating temperature, pressing time, etc. may be the same or different.

In the vacuum press process, the compression pressure (pressing force) is preferably 0.49 MPa or more, more preferably 0.98 MPa or more, and is preferably 7.9 MPa or less, more preferably 5.9 MPa or less.

In the vacuum press treatment, the atmospheric pressure, i.e., the pressure (degree of vacuum) during decompression in the chamber in which the laminate structure to be treated is stored, is preferably 3×10 ⁻² MPa or less, more preferably 1×10 ⁻² MPa or less. There is no particular lower limit, but it may be 1×10 ⁻¹⁰ MPa or more.

In the vacuum press treatment, the heating temperature varies depending on the composition of the resin composition layer, but is usually 150°C or higher, preferably 160°C or higher, more preferably 170°C or higher, or 180°C or higher. The upper limit of the heating temperature is not particularly limited, but it can usually be 240°C or lower. In addition, from the viewpoint of obtaining a remarkable effect of the present invention, the vacuum press treatment may be performed while increasing the temperature stepwise or continuously and/or decreasing the temperature stepwise or continuously. In addition, as described later, the resin composition layer may be thermally cured by heating in the vacuum press treatment to form an insulating layer.

In the vacuum press treatment, the pressing time is preferably 5 minutes or more, more preferably 10 minutes or more, and even more preferably 15 minutes or more. There is no particular upper limit, but it is preferably 300 minutes or less, more preferably 200 minutes or less, and even more preferably 150 minutes or less.

After laminating the resin sheet on the inner layer substrate by vacuum pressing, in step (II), the resin composition layer is thermally cured to form an insulating layer. For example, when performing pressing by vacuum hot pressing, a method of thermally curing the resin composition layer by using heat generated during pressing to form an insulating layer can be mentioned as a method of thermally curing the resin composition layer.

The thermal curing conditions for the resin composition layer are not particularly limited, and conditions normally used for forming an insulating layer for a printed wiring board may be used.

For example, the thermal curing conditions for the resin composition layer vary depending on the type of resin composition, but the curing temperature is preferably 120°C to 240°C, more preferably 150°C to 220°C, and even more preferably 170°C to 210°C. The curing time is preferably 5 minutes to 120 minutes, more preferably 10 minutes to 100 minutes, and even more preferably 15 minutes to 100 minutes.

Before the resin composition layer is thermally cured, the resin composition layer may be preheated at a temperature lower than the curing temperature. For example, prior to thermally curing the resin composition layer, the resin composition layer may be preheated for 5 minutes or more (preferably 5 minutes to 150 minutes, more preferably 15 minutes to 120 minutes, and even more preferably 15 minutes to 100 minutes) at a temperature of 50°C or more and less than 120°C (preferably 60°C or more and 115°C or less, and more preferably 70°C or more and 110°C or less).

The present inventors have confirmed that the uniformity of the thickness of the insulating layer may be worsened in the vacuum press process due to the resin flow during lamination of the resin sheet, compared to the vacuum lamination method. In this regard, the uniformity of the thickness of the insulating layer after the vacuum press process can be improved by adjusting the amount of residual solvent in addition to the specific surface area of the inorganic filler in the resin composition layer and setting the maximum value of tan δ to 1.0 or more and 2.0 or less. Specifically, the variation in the thickness of the insulating layer after the heat press process is preferably less than ±20%, more preferably less than ±15%, and even more preferably ±10% or less, relative to the standard thickness of the insulating layer. In other words, it is preferable that the insulating layer has a standard thickness that falls within the above range. The standard thickness can usually be the design thickness of the insulating layer. The lower limit can be 0%, ±0.1% or more, etc. The evaluation of the thickness of the insulating layer after the vacuum press process can be measured according to the method described in the examples below.

The resin sheet used in the present invention may include a process for forming a circuit by a subtractive process or a modified semi-additive process as step (III) since the support includes a metal foil.

In step (III), a circuit can be formed using a subtractive method or a modified semi-additive method, using a support (metal foil).

In the subtractive method, unnecessary parts of the metal foil (non-circuit forming parts) are selectively removed by etching or the like to form a circuit. The circuit formation by the subtractive method may be carried out according to a known procedure. For example, the circuit formation by the subtractive method can be carried out by a method including: i) providing an etching resist on the surface of the metal foil (i.e., the surface opposite to the surface bonded to the resin composition layer); ii) exposing and developing the etching resist to form a wiring pattern; iii) etching and removing the exposed metal foil parts; and iv) removing the etching resist.

In the modified semi-additive method, the non-circuit forming portion of the metal foil is protected by a plating resist, and a metal such as copper is thickly applied to the circuit forming portion by electrolytic plating, and then the plating resist is removed, and the metal foil other than the circuit forming portion is removed by etching to form a circuit. The circuit formation by the modified semi-additive method may be carried out according to a known procedure. For example, the circuit formation by the modified semi-additive method can be carried out by a method including: i) providing a plating resist on the surface of the metal foil (i.e., the surface opposite to the surface bonded to the resin composition layer), ii) exposing and developing the plating resist to form a wiring pattern, iii) electrolytic plating through the plating resist, iv) removing the plating resist, and v) etching and removing the metal foil other than the circuit forming portion. Note that, if the metal foil is thick, the entire surface of the metal foil may be thinned by etching or the like before the above i) so that the metal foil has a desired thickness (usually 5 μm or less, 4 μm or less, or 3 μm or less).

When manufacturing a printed wiring board, a step (IV) of drilling holes and a step (V) of roughening the insulating layer may be further carried out. These steps (IV) to (V) may be carried out according to various methods known to those skilled in the art and used in the manufacture of printed wiring boards. Furthermore, if necessary, the formation of the insulating layer and the conductor layer in steps (I) to (V) may be repeated to form a multilayer wiring board.

[Semiconductor device]
The semiconductor device of the present invention includes the printed wiring board of the present invention. The semiconductor device of the present invention can be manufactured by using the printed wiring board of the present invention.

Semiconductor devices include various semiconductor devices used in electrical appliances (e.g., computers, mobile phones, digital cameras, and televisions) and vehicles (e.g., motorcycles, automobiles, trains, ships, and aircraft).

The semiconductor device of the present invention can be manufactured by mounting a component (semiconductor chip) on a conductive portion of a printed wiring board. A "conductive portion" is a portion of a printed wiring board that transmits an electrical signal, and the portion may be either on the surface or embedded. In addition, there are no particular limitations on the semiconductor chip, so long as it is an electrical circuit element made of semiconductor material.

The method of mounting semiconductor chips when manufacturing semiconductor devices is not particularly limited as long as the semiconductor chip functions effectively, but specific examples include wire bonding mounting, flip chip mounting, bumpless buildup layer (BBUL) mounting, anisotropic conductive film (ACF) mounting, non-conductive film (NCF) mounting, etc. Here, "bumpless buildup layer (BBUL) mounting" refers to "a mounting method in which a semiconductor chip is directly embedded in a recess in a printed wiring board and the semiconductor chip is connected to the wiring on the printed wiring board."

The present invention will be described in more detail below using examples, but the present invention is not limited to these examples. In the following description, unless otherwise specified, "parts" and "%" mean "parts by mass" and "% by mass", respectively.

<Inorganic filler used>
Inorganic filler 1: 100 parts of spherical silica (Denki Kagaku Kogyo Co., Ltd. "UFP-30", average particle size 0.30 μm, specific surface area 30.7 m ² /g) surface-treated with 2 parts of N-phenyl-3-aminopropyltrimethoxysilane (Shin-Etsu Chemical Co., Ltd., KBM573).
Inorganic filler 2: 100 parts of spherical silica ("SO-C1" manufactured by Admatechs, average particle size 0.25 μm, specific surface area 11.2 m ² /g) surface-treated with 1 part of N-phenyl-3-aminopropyltrimethoxysilane (manufactured by Shin-Etsu Chemical Co., Ltd., KBM573).
Inorganic filler 3: 100 parts of spherical silica (Admatechs'"SO-C2", average particle size 0.50 μm, specific surface area 5.8 m ² /g) surface-treated with 1 part of N-phenyl-3-aminopropyltrimethoxysilane (Shin-Etsu Chemical Co., Ltd., KBM573).

<Synthesis Example 1: Synthesis of Polyimide Resin 1>
A monomer composition obtained by mixing 49.6 g of BPADA, 50.4 g of BPPAN, and 40 g of toluene as a solvent in 400 g of N,N-dimethylacetamide (hereinafter also referred to as "DMAc") as a solvent was stirred and reacted at room temperature and atmospheric pressure for 3 hours. As a result, a polyamic acid solution was obtained.

The polyamic acid solution was then heated and maintained at approximately 160°C while the condensed water was azeotropically removed with toluene under a nitrogen stream. It was confirmed that a specified amount of water had accumulated in the moisture content receiver and that no water was leaking out. After confirmation, the reaction solution was further heated and stirred at 200°C for 1 hour. It was then cooled. This resulted in a varnish containing 20% by mass of polyimide resin 1 as a non-volatile component.

From the above reaction pathway, it was estimated that polyimide resin 1 contains a structural unit represented by the following formula (e1a). In addition, from the above reaction pathway, it was estimated that polyimide resin 1 contains a first skeleton derived from BPADA and a second skeleton derived from BPPAN.

<Synthesis Example 2: Synthesis of Elastomer 1>
In a reaction vessel, 50 g of G-3000 (bifunctional hydroxyl group-terminated polybutadiene, number average molecular weight = 5047 (GPC method), hydroxyl group equivalent = 1798 g/eq., solid content 100 mass%: manufactured by Nippon Soda Co., Ltd.), 23.5 g of Ipsol 150 (aromatic hydrocarbon-based mixed solvent: manufactured by Idemitsu Petrochemical Co., Ltd.), and 0.005 g of dibutyltin laurate were mixed and dissolved uniformly. When the mixture became uniform, the temperature was raised to 50°C, and 4.8 g of toluene-2,4-diisocyanate (isocyanate group equivalent = 87.08 g/eq.) was added with further stirring, and the reaction was carried out for about 3 hours. Next, the reaction mixture was cooled to room temperature, and 8.96 g of benzophenonetetracarboxylic dianhydride (acid anhydride equivalent = 161.1 g/eq.), 0.07 g of triethylenediamine, and 40.4 g of ethyl diglycol acetate (manufactured by Daicel Corporation) were added thereto, and the mixture was heated to 130°C with stirring, and reacted for about 4 hours. The disappearance of the NCO peak at 2250 cm ^-1 was confirmed by FTIR. The disappearance of the NCO peak was regarded as the end point of the reaction, and the reaction mixture was cooled to room temperature and filtered with a 100 mesh filter cloth to obtain an elastomer 1 having an imide skeleton, a urethane skeleton, and a butadiene skeleton.
Viscosity: 7.5 Pa・s (25°C, E-type viscometer)
Acid value: 16.9 mg KOH / g
Solid content: 50% by mass
Number average molecular weight: 13723
Glass transition temperature: -10°C
Content of polybutadiene structure: 50/(50+4.8+8.96)×100=78.4% by mass

<Example 1: Preparation of resin composition 1>
5 parts of a bixylenol type epoxy resin ("YX4000HK" manufactured by Mitsubishi Chemical Corporation, epoxy equivalent: about 185), 5 parts of a naphthalene type epoxy resin ("ESN475V" manufactured by Nippon Steel & Sumikin Chemical Co., Ltd., epoxy equivalent: about 332), 2 parts of a cyclohexane type epoxy resin ("ZX1658GS" manufactured by Mitsubishi Chemical Corporation, epoxy equivalent: about 135), 10 parts of a phenoxy resin ("YX7553BH30" manufactured by Mitsubishi Chemical Corporation, a 1:1 solution of cyclohexanone:methyl ethyl ketone (MEK) with a solid content of 30 mass%, Mw=35,000), and 10 parts of cyclohexanone were heated and dissolved with stirring in a mixed solvent. After cooling to room temperature, 4.5 parts of an active ester curing agent (DIC Corporation's "HPC-8000L-65TM", active group equivalent of about 220, 1:1 solution of toluene:MEK with 65% by mass of non-volatile components), 35 parts of inorganic filler 1, and 0.1 part of an amine curing accelerator (4-dimethylaminopyridine (DMAP)) were mixed and uniformly dispersed in a high-speed rotating mixer, and then filtered with a cartridge filter (ROKITECHNO Corporation's "SHP020") to prepare resin composition 1.

<Example 2: Preparation of resin composition 2>
In Example 1, 4.5 parts of an active ester curing agent (DIC Corporation's "EXB-8000L-65TM", active group equivalent of about 220, toluene:MEK 1:1 solution with 65% by mass of non-volatile components) was changed to 4.7 parts of an active ester curing agent (DIC Corporation's "HP-B-8151-62T", active group equivalent of 238, toluene solution with 62% solids). Resin composition 2 was prepared in the same manner as in Example 1 except for the above.

<Example 3: Preparation of resin composition 3>
In Example 3, 35 parts of Inorganic Filler 1 was changed to 50 parts of Inorganic Filler 2. Resin composition 3 was prepared in the same manner as in Example 1 except for the above-mentioned points.

<Example 4: Preparation of resin composition 4>
In Example 1, 4.5 parts of an active ester curing agent (DIC Corporation's "EXB-8000L-65TM", active group equivalent of about 220, 1:1 solution of toluene:MEK with 65% by mass of non-volatile components) was replaced with 10 parts of a maleimide compound (Designer Molecules'"BMI-689");
The amount of the amine curing accelerator (4-dimethylaminopyridine (DMAP)) was changed from 0.1 parts to 0.05 parts.
Furthermore, 0.1 part of a polymerization initiator ("Perhexyne 25B" manufactured by NOF Corporation) was used.
Resin composition 4 was prepared in the same manner as in Example 1 except for the above.

Example 5: Preparation of resin composition 5
In Example 4, 10 parts of the maleimide compound ("BMI-689" manufactured by Designer Molecules) was replaced with 10 parts of a styrene-modified polyphenylene ether resin ("OPE-2St 1200" manufactured by Mitsubishi Gas Chemical Co., Ltd., Mn = 1200, toluene solution with a solid content of 65% by mass). Resin composition 5 was prepared in the same manner as in Example 4 except for the above.

<Example 6: Preparation of resin composition 6>
In Example 4, 4.5 parts of an active ester curing agent ("EXB-8000L-65TM" manufactured by DIC Corporation, active group equivalent of about 220, 1:1 solution of toluene:MEK with non-volatile components of 65% by mass) was further used. Resin composition 6 was prepared in the same manner as in Example 4 except for the above.

<Example 7: Preparation of resin composition 7>
In Example 6, 10 parts of a phenoxy resin ("YX7553BH30" manufactured by Mitsubishi Chemical Corporation, a 1:1 solution of cyclohexanone:methyl ethyl ketone (MEK) with a solid content of 30% by mass, Mw=35,000) and 15 parts of the polyimide resin 1 (non-volatile component 20% by mass) obtained in Synthesis Example 1 were used. Resin composition 7 was prepared in the same manner as in Example 6 except for the above points.

<Example 8: Preparation of resin composition 8>
In Example 6, 10 parts of a phenoxy resin ("YX7553BH30" manufactured by Mitsubishi Chemical Corporation, a 1:1 solution of cyclohexanone:methyl ethyl ketone (MEK) with a solid content of 30% by mass, Mw=35,000) and 6 parts of the elastomer obtained in Synthesis Example 2 (non-volatile components: 50% by mass) were used. Resin composition 8 was prepared in the same manner as in Example 6 except for the above.

<Example 9: Preparation of resin composition 9>
10 parts of a maleimide compound ("BMI-689" manufactured by Designer Molecules), 10 parts of a biphenyl skeleton-containing maleimide resin ("MIR-3000" manufactured by Nippon Kayaku Co., Ltd., a 1:1 solution of toluene:MEK with a non-volatile content of 70% by mass), 10 parts of a styrene-modified polyphenylene ether resin ("OPE-2St 1200" manufactured by Mitsubishi Gas Chemical Co., Ltd., Mn=1200, a toluene solution with a solid content of 65% by mass), and 6 parts of a hydrogenated styrene-based thermoplastic elastomer ("H1043" manufactured by Asahi Kasei Corporation, styrene/ethylene-butylene-butadiene ratio=67/33) were dissolved in a mixed solvent of 20 parts of solvent naphtha and 10 parts of cyclohexanone by heating with stirring. After cooling to room temperature, 50 parts of inorganic filler 1 and 0.1 parts of a polymerization initiator ("Perhexyne 25B" manufactured by NOF Corporation) were mixed thereto and uniformly dispersed in a high-speed rotating mixer, and then filtered through a cartridge filter ("SHP020" manufactured by ROKITECHNO CORPORATION) to prepare resin composition 9.

Example 10: Preparation of resin composition 10
In Example 9, 50 parts of Inorganic Filler 1 was changed to 65 parts of Inorganic Filler 2. Resin composition 10 was prepared in the same manner as in Example 9 except for the above-mentioned points.

<Example 11: Preparation of resin composition 11>
In the preparation of Example 9, 10 parts of a styrene-modified polyphenylene ether resin ("OPE-2St 1200" manufactured by Mitsubishi Gas Chemical Co., Ltd., Mn = 1200, toluene solution with a solid content of 65% by mass) was changed to 10 parts of a vinyl group-containing resin ("ODV-XET-X04" manufactured by Nippon Steel Chemical & Material Co., Ltd., weight average molecular weight 3110, 65% by mass solution). Resin composition 11 was prepared in the same manner as in Example 9 except for the above items.

<Example 12: Preparation of resin composition 12>
In Example 1, 4.5 parts of the active ester curing agent ("EXB-8000L-65TM" manufactured by DIC Corporation, active group equivalent of about 220, 1:1 solution of toluene:MEK with 65% by mass of non-volatile components) was changed to 5 parts of a triazine skeleton-containing phenolic resin ("LA7054" manufactured by DIC Corporation, MEK solution with 60% solids and hydroxyl group equivalent of about 125). Resin composition 12 was prepared in the same manner as in Example 1 except for the above.

<Comparative Example 1: Preparation of Resin Composition 13>
In Example 1, 35 parts of Inorganic Filler 1 was changed to 35 parts of Inorganic Filler 3. Resin composition 13 was prepared in the same manner as in Example 1 except for the above-mentioned points.

<Comparative Example 2: Preparation of Resin Composition 14>
In Example 1, the amount of the inorganic filler 1 was changed from 35 parts to 50 parts. Resin composition 14 was prepared in the same manner as in Example 1 except for the above-mentioned points.

Comparative Example 3: Preparation of Resin Composition 15
In Example 9, 50 parts of Inorganic Filler 1 was changed to 50 parts of Inorganic Filler 3. Resin composition 15 was prepared in the same manner as in Example 9 except for the above-mentioned points.

<Measurement of thickness of resin composition layer, etc.>
The thickness of the resin composition layer etc. was measured using a contact type film thickness meter (manufactured by Mitutoyo Corporation, MCD-25MJ).

<Preparation of resin sheet A>
As a support, an ultra-thin copper foil (MW-G manufactured by Mitsui Mining & Smelting Co., Ltd. (single-layer copper foil with a thickness of 12 μm, arithmetic mean roughness (Ra) 900 nm, ten-point average roughness (Rz) 8000 nm)) was prepared. Resin compositions 1 to 15 were uniformly applied to the ultra-thin copper foil of the support by a die coater so that the thickness of the resin composition layer after drying was 15 μm, and dried at 70 ° C. to 120 ° C. for 7 minutes to obtain a resin composition layer on the support. Next, a rough surface of a polypropylene film ("Alphan MA-411" manufactured by Oji F-Tex Co., Ltd., thickness 15 μm) was laminated as a protective film on the surface of the resin composition layer not bonded to the support so as to be bonded to the resin composition layer. This resulted in a resin sheet A consisting of the ultra-thin copper foil (support), the resin composition layer, and the protective film in that order. The arithmetic mean roughness (Ra) and ten-point average roughness (Rz) of the ultra-thin copper foil were measured using a non-contact surface roughness meter.

<Measurement of tan δ in dynamic viscoelasticity>
The dynamic viscoelasticity of the resin composition layer of the resin sheet A was measured using a dynamic viscoelasticity measuring device (UBM's "Rheosol-G3000"). 1 g of the sample resin composition taken from the resin composition layer was heated from the starting temperature of 60°C to 200°C at a heating rate of 5°C/min using a parallel plate with a diameter of 18 mm, and the dynamic viscoelasticity was measured under the measurement conditions of a measurement temperature interval of 2.5°C, a vibration frequency of 1 Hz, and a strain of 1 deg. The obtained values of E' and E'' were used to calculate tan δ using the following formula. The maximum value of tan δ at 100°C or higher was then determined.
tan δ=E″/E′

<Evaluation of Insulation Layer Thickness (Resin Flow), Insulation Reliability, and Embeddability after Vacuum Press Treatment>
1) Lamination of the laminate sheet to the copper-clad laminate using a vacuum press As the copper-clad laminate, a glass cloth-based epoxy resin double-sided copper-clad laminate (copper foil thickness 12 μm, substrate thickness 0.15 mm, Mitsubishi Gas Chemical Company's "HL832NSF LCA", 255 × 340 mm size) having a circuit conductor (copper) formed on both sides with a wiring pattern of 1 mm square lattice (residual copper rate 59%) was prepared. Both sides of the inner layer circuit board were subjected to a copper surface roughening treatment (copper etching amount 0.5 μm) using MEC's "CZ8201". The protective film was peeled off from the resin sheet A to expose the resin composition layer. Next, using a vacuum hot press machine (Kitagawa Seiki Co., Ltd., VH1-1603), the exposed resin composition layer was laminated on both sides of the copper-clad laminate so that it was in contact with the copper-clad laminate. The pressing conditions were a reduced pressure of 1×10 ^-3 MPa or less and a pressure condition of 20 kgf/cm ² , and the heating conditions were a first pressing temperature of 100° C. and a time of 30 minutes, and a second pressing temperature of 190° C. and a time of 120 minutes. After the resin composition layer was cured by heating with the press, the support was peeled off to obtain a cured substrate A.

2) Electroplating Using a chemical solution manufactured by Atotech Japan, an electrolytic copper plating process was performed under conditions in which copper was filled into the via holes. After that, a conductor layer having a land and conductor pattern with a thickness of 10 μm was formed on the surface of the insulating layer using a land pattern with a diameter of 1 mm that was conductive to the lower layer conductor and a circular conductor pattern with a diameter of 10 mm that was not connected to the lower layer conductor as a resist pattern for patterning by etching. Next, an annealing treatment was performed at 200° C. for 90 minutes. This substrate was designated as "Insulation Evaluation Substrate A."

3) Evaluation of the insulation reliability of the insulating layer The 10 mm diameter circular conductor side of the insulation evaluation board A was used as the positive electrode, and the lattice circuit conductor (copper) side of the inner layer circuit board connected to the land with a diameter of 1 mm was used as the negative electrode. Using a highly accelerated life tester ("PM422" manufactured by ETAC), the insulation resistance value after 100 hours under the conditions of 110°C, 85% relative humidity, and 20V DC voltage application was measured with an electrochemical migration tester ("ECM-100" manufactured by J-RAS). This measurement was performed six times, and the following evaluation criteria and insulation resistance values are shown in the table below. The insulation resistance values listed in the table below are the average values of the insulation resistance values of the six test pieces.
◯: The average insulation resistance value of the six test pieces was 1.00×10 ⁹ Ω or more.
Δ: The average insulation resistance value of the six test pieces was 1.00×10 ⁸ Ω or more and less than 1.00×10 ⁹ Ω.
×: The average insulation resistance value of the six test pieces is less than 1.00×10 ⁸ Ω.

4) Evaluation of Insulating Layer Thickness (Resin Flow) After Vacuum Press Treatment After etching the ultra-thin copper foil of the cured substrate A, a cross-section was observed using a FIB-SEM composite device ("SMI3050SE" manufactured by SII NanoTechnology Corporation), and the thickness of the insulating layer after vacuum press treatment was evaluated according to the following criteria.
◯: When the standard thickness of the insulating layer is 10 μm, the thickness of the insulating layer is less than 10 μm ±20%.
×: When the standard thickness of the insulating layer is 10 μm, the thickness of the insulating layer is 10 μm±20% or more.

5) Evaluation of embeddability of insulating layer after vacuum press treatment After the ultra-thin copper foil of the cured substrate A was etched, the embeddability of the resin composition layer in a wiring pattern of 1 mm square lattice was observed using a FIB-SEM composite device ("SMI3050SE" manufactured by SII Nano Technology Co., Ltd.) and evaluated according to the following criteria.
◯: The wiring pattern is buried in the insulating layer.
×: Voids are generated due to improper filling.

＊（Ａ）成分の含有量は、樹脂組成物中の不揮発成分を１００質量％とした場合の含有量を表す。

*The content of component (A) represents the content when the total amount of non-volatile components in the resin composition is taken as 100 mass %.

Claims (10)

A thermosetting resin sheet for forming an insulating layer using a vacuum press process,
A support and a resin composition layer provided on the support,
the support has a metal foil having an arithmetic mean roughness (Ra) of more than 300 nm on the surface that is bonded to the resin composition layer;
The resin composition layer contains (A) an inorganic filler having a specific surface area of 10 m ² /g or more,
(B) an epoxy resin and/or (D) a radical polymerizable compound,
A thermosetting resin sheet, in which a resin composition layer is heated from 60°C to 200°C at a heating rate of 5°C/min, and dynamic viscoelasticity is measured under measurement conditions of a frequency of 1 Hz and a strain of 1 deg , and the maximum value of tan δ at 100°C or higher is 1.0 or more and 2.0 or less. The thermosetting resin sheet according to claim 1 , wherein the resin composition layer has a thickness of 30 μm or less. The thermosetting resin sheet according to claim 1 or 2, wherein the resin composition layer contains any one of an active ester resin, a maleimide resin, and a vinyl resin. The thermosetting resin sheet according to any one of claims 1 to 3, wherein the content of the component (A) is 73% by mass or less when the content of the non-volatile components in the resin composition layer is 100% by mass. The thermosetting resin sheet according to any one of claims 1 to 4, wherein the content of the component (A) is 50% by mass or more when the content of the non-volatile components in the resin composition layer is 100% by mass. The thermosetting resin sheet according to claim 1 , wherein the metal foil comprises a copper foil. The thermosetting resin sheet according to any one of claims 1 to 6 , wherein the support has a thickness of 9 µm or more. A printed wiring board comprising an insulating layer made of a cured product of a resin composition layer of the thermosetting resin sheet according to any one of claims 1 to 7 . A semiconductor device comprising the printed wiring board according to claim 8 . (I) a step of laminating the thermosetting resin sheet according to any one of claims 1 to 7 on an inner layer substrate by vacuum pressing; and (II) a step of thermally curing the resin composition layer to form an insulating layer.
A method for manufacturing a printed wiring board, comprising: