Resin sheet with metal foil

Abstract

The present invention addresses the problem of providing, for example, a resin sheet with a metal foil capable of obtaining a cured product having a high glass transition temperature and excellent mechanical properties. The solution of the present invention is a metal foil-attached resin sheet provided with a metal foil, a resin composition layer, and a protective film in this order, in which the resin composition layer contains (A) a polyimide resin, (B) a phenoxy resin, and (C) an inorganic filler, when a1 is the content of the component (A) when the resin component in the resin composition layer is 100% by mass, and b1 is the content of the component (B) when the resin component in the resin composition layer is 100% by mass, a1 / b1 is 0.05-50.

Description

Technical Field

[0001] The present invention relates to a resin sheet with a metal foil. Further, the present invention relates to a circuit board manufactured using the resin sheet with a metal foil, a semiconductor device including the circuit board, and a method for manufacturing the circuit board. Background Art

[0002] Conventionally, polyimide resin having excellent heat resistance and insulation properties has been used in an insulating layer such as a circuit board (see, for example, Patent Documents 1 and 2).

[0003] Prior Art Documents Patent Documents Patent Document 1: Japanese Unexamined Patent Application Publication No. 2020-66694 Patent Document 2: Japanese Patent No. 6240798 Summary of the Invention

[0004] Technical Problem to be Solved by the Invention In recent years, as a method for forming a conductor layer on an insulating layer, a resin sheet with a metal foil is used. At this time, a resin sheet with a metal foil having a metal foil, a resin composition layer, and a protective film in this order is prepared, and the protective film is peeled off. Then, a vacuum pressing process (vacuum hot pressing process) of the inner layer substrate and the resin sheet with a metal foil is performed so that the resin composition layer is bonded to the inner layer substrate. Since the resin composition layer is thermally cured during the vacuum pressing process, an insulating layer including a cured product of the resin composition layer and a conductor layer equivalent to the metal foil can be formed on the inner layer substrate.

[0005] However, in the above method, the resin composition layer is in a state of being sandwiched between the inner layer substrate and the metal foil during the vacuum pressing process. Therefore, during the thermal curing of the resin composition layer, the intermolecular movement in the curing reaction of the resin component contained in the resin composition layer is suppressed. Therefore, the curing of the resin composition layer may not proceed sufficiently, the glass transition temperature of the insulating layer is low, and the mechanical properties of the cured product are poor.

[0006] Thus, the present inventors have found a new problem that the glass transition temperature of the cured product of the resin composition layer is low and the mechanical properties are poor when an insulating layer is formed by a vacuum pressing process using a resin sheet with a metal foil.

[0007] The present invention has been made in view of the above problems, and an object thereof is to provide: a resin sheet with a metal foil capable of obtaining a cured product having a high glass transition temperature and excellent mechanical properties; a circuit board manufactured using the resin sheet with a metal foil; a semiconductor device including the circuit board; and a method for manufacturing the circuit board.

[0008] Means for Solving the Technical Problem The inventors of the present invention have conducted in-depth research and found that: a resin sheet with a metal foil, which sequentially includes a metal foil, a resin composition layer, and a protective film, contains (A) a polyimide resin, (B) a phenoxy resin, and (C) an inorganic filler in the resin composition layer under the condition that each content is within a specified range, and thus a cured product with a high glass transition temperature and excellent mechanical strength can be obtained, thereby completing the present invention.

[0009] That is, the present invention includes the following content. [1] A resin sheet with a metal foil, which is a resin sheet with a metal foil that sequentially includes a metal foil, a resin composition layer, and a protective film, wherein the resin composition layer contains (A) a polyimide resin, (B) a phenoxy resin, and (C) an inorganic filler, when the content of component (A) when the resin components in the resin composition layer are 100% by mass is set as a1, and the content of component (B) when the resin components in the resin composition layer are 100% by mass is set as b1, a1 / b1 is 0.05 or more and 50 or less. [2] The resin sheet with a metal foil according to [1], wherein component (A) has an ester bond. [3] The resin sheet with a metal foil according to [1] or [2], which further contains (G) a flame retardant. [4] The resin sheet with a metal foil according to any one of [1] to [3], wherein when the weight-average molecular weight of component (A) is set as a2 and the weight-average molecular weight of component (B) is set as b2, a2 / b2 is 0.01 or more and 10 or less. [5] The resin sheet with a metal foil according to any one of [1] to [4], which further contains (D) a thermosetting resin. [6] The resin sheet with a metal foil according to any one of [1] to [5], which is used for forming an insulating layer and a conductor layer by vacuum pressing treatment. [7] The resin sheet with a metal foil according to any one of [1] to [6], wherein the metal foil is a copper foil. [8] A circuit board, which includes: an insulating layer formed by a cured product of the resin composition layer of the resin sheet with a metal foil according to any one of [1] to [7], and a conductor layer formed by the metal foil of the resin sheet with a metal foil according to any one of [1] to [7]. [9] A semiconductor device, which includes the circuit board described in [8].

[10] A method for manufacturing a circuit board, the manufacturing method includes: (I) A step of laminating the resin composition in the resin sheet with a metal foil according to any one of [1] to [7] on the inner layer substrate by vacuum pressing treatment, and (II) A step of thermally curing the resin composition layer to form an insulating layer. Effects of the Invention

[0010] According to the present invention, there can be provided: a resin sheet with a metal foil capable of obtaining a cured product having a high glass transition temperature and excellent mechanical properties; a circuit board manufactured using the resin sheet with a metal foil, a semiconductor device including the circuit board, and a method for manufacturing the circuit board. Detailed Embodiments

[0011] Hereinafter, embodiments and examples will be shown to describe the present invention in detail. However, the present invention is not limited to the embodiments and examples listed below, and can be arbitrarily modified and implemented without departing from the scope of the claims of the present invention and its equivalent scope.

[0012] [Resin Sheet with Metal Foil] The resin sheet with a metal foil of the present invention sequentially includes a metal foil, a resin composition layer, and a protective film. Usually, the metal foil is in direct contact with the resin composition layer, and no other layer is provided between the metal foil and the resin composition layer. In addition, usually, the resin composition layer is in direct contact with the protective film, and no other layer is provided between the resin composition layer and the protective film. The resin composition layer contains (A) a polyimide resin, (B) a phenoxy resin, and (C) an inorganic filler. When the content of the (A) component when the resin component excluding the (C) component in the resin composition layer is set to 100% by mass is a1, and the content of the (B) component when the resin component excluding the (C) component in the resin composition layer is set to 100% by mass is b1, a1 / b1 is 0.05 or more and 50 or less. Such a resin sheet with a metal foil can obtain a cured product having a high glass transition temperature and excellent mechanical properties. In addition, the resin sheet with a metal foil can usually also obtain a cured product having excellent thin-film flexibility, low dielectric constant and dielectric loss tangent, and excellent flame retardancy. Here, the thin-film flexibility refers to the property that the resin composition layer has high flexibility and can suppress cracks and notches in the resin composition layer.

[0013] <Metal Foil> The resin sheet with a metal foil of the present invention has a metal foil. The conductor layer of the circuit board can be formed of the metal foil. At this time, the conductor layer can be formed of the entire metal foil or a part of the metal foil.

[0014] Examples of the metal foil include, for example, copper foil, aluminum foil, etc., and copper foil is preferred. As the copper foil, a foil formed of single metal of copper or a foil formed of an alloy of copper and other metals (such as tin, chromium, silver, magnesium, nickel, zirconium, silicon, titanium, etc.) can be used.

[0015] The metal foil may have a single-layer structure or a multi-layer structure in which two or more single-metal layers or alloy layers formed of different metals or alloys are laminated. Examples of the metal foil having a multi-layer structure include a metal foil including a carrier metal foil and an extremely thin metal foil joined to the carrier metal foil. The metal foil having the multi-layer structure may also include a release layer between the carrier metal foil and the extremely thin metal foil that enables the extremely thin metal foil to be peeled off from the carrier metal foil. The release layer is not particularly limited as long as the extremely thin metal foil can be peeled off from the carrier metal foil, and examples thereof include an alloy layer of an element selected from Cr, Ni, Co, Fe, Mo, Ti, W, and P; an organic film, etc. It should be noted that when using a metal foil having a multi-layer structure, the resin composition layer is provided on the extremely thin metal foil.

[0016] From the viewpoint of significantly obtaining the effects of the present invention, the thickness of the metal foil is preferably 1 μm or more, more preferably 1.5 μm or more, and further preferably 2 μm or more. The upper limit is not particularly limited, and is preferably 35 μm or less, more preferably 25 μm or less, and further preferably 15 μm or less. In the case where the metal foil has a multi-layer structure, it is preferable that the thickness of the entire metal foil is within the above range, and the thickness of the extremely thin metal foil can be, for example, in the range of 0.1 μm or more and 10 μm or less.

[0017] The arithmetic mean roughness (Ra) of the surface of the metal foil that is joined to the resin composition layer is preferably 300 nm or more, preferably 350 nm or more, more preferably 400 nm or more, and further preferably 500 nm or more from the viewpoint of improving the adhesion to the resin composition layer. The upper limit is not particularly limited, and is preferably 1000 nm or less, more preferably 900 nm or less, and further preferably 800 nm or less. The arithmetic mean roughness (Ra) is a value measured based on ISO 25178, and can be measured using a non-contact surface roughness meter. Examples of the non-contact surface roughness meter include "WYKO NT3300" manufactured by VEECO INSTRUMENTS.

[0018] Commercially available products can be used as the metal foil. Examples of commercially available products of the metal foil include "Micro Thin MT18Ex", "Micro Thin MT18FL", "3EC-III", "3EC-M3-VLP", "3EC-M2S-VLP" manufactured by Mitsui Mining & Smelting Co., Ltd., "JDLC", "JTCSLC", "HA-V2", "HA", "HG" manufactured by JX Metals, "CF-TX4-SV", "V9", "HD", "FLEQ HD", "FUTF", "RCF-T4X", "RCF-T5B", etc. manufactured by Fukuda Metal Foil Powder Industry Co., Ltd.

[0019] As a method for manufacturing a metal foil, it can be manufactured by known methods such as electrolysis and rolling.

[0020] <Resin composition layer> The resin sheet with a metal foil has a resin composition layer. An insulating layer can be formed by thermally curing the resin composition layer. Generally, the insulating layer contains the cured product of the resin composition layer, and preferably contains only the cured product of the resin composition layer.

[0021] The resin composition layer contains (A) a polyimide resin, (B) a phenoxy resin, and (C) an inorganic filler. Additionally, as needed, the resin composition layer may contain (D) a thermosetting resin, (E) a thermoplastic resin (excluding substances belonging to component (A) and component (B)), (F) a flame retardant, (G) a curing accelerator, (H) other additives, and (I) a solvent.

[0022] In the present invention, unless otherwise specified, the content of each component in the resin composition layer is the value when the non-volatile components in the resin composition layer are set to 100% by mass. Additionally, in the present invention, the non-volatile components refer to the entire components in the resin composition layer after removing the solvent. Additionally, in the present invention, the resin components in the resin composition layer refer to the components in the non-volatile components of the resin composition layer after removing (C) the inorganic filler.

[0023] -(A) Polyimide resin- The resin composition layer contains a polyimide resin as component (A). By including component (A) in the resin composition layer, a cured product with a high glass transition temperature can be obtained. Component (A) can be used alone as one type or in combination of two or more types.

[0024] As the (A) polyimide resin, a resin having an imide bond in the repeating unit can be used. From the viewpoint of increasing the glass transition temperature of the cured product, it preferably has an ester bond. The (A) polyimide resin generally contains a resin obtained by the imidization reaction of a diamine compound and an acid anhydride.

[0025] The diamine compound used for preparing the (A) polyimide resin is not particularly limited, and examples thereof include aliphatic diamine compounds and aromatic diamine compounds. Among them, as the diamine compound, an aromatic diamine compound is preferred. From the viewpoint of increasing the glass transition temperature of the cured product, the diamine compound preferably has an ester bond, and more preferably an aromatic diamine compound having an ester bond.

[0026] As the aliphatic diamine compound, examples thereof include linear aliphatic diamine compounds such as 1,2-ethylenediamine, 1,2-diaminopropane, 1,3-diaminopropane, 1,4-diaminobutane, 1,6-hexanediamine, 1,5-diaminopentane, 1,10-diaminodecane; branched aliphatic diamine compounds such as 1,2-diamino-2-methylpropane, 2,3-diamino-2,3-butane, and 2-methyl-1,5-diaminopentane; alicyclic diamine compounds such as 1,3-bis(aminomethyl)cyclohexane, 1,4-bis(aminomethyl)cyclohexane, 1,4-diaminocyclohexane, 4,4'-methylenebis(cyclohexylamine); dimer acid type diamine (hereinafter also referred to as "dimer diamine"), etc., and dimer acid type diamine is preferred.

[0027] The so-called dimer acid type diamine refers to a diamine compound obtained by replacing two terminal carboxylic acid groups (-COOH) of dimer acid with aminomethyl (-CH 2 -NH 2 ) or amino group (-NH 2 ). Dimer acid is a known compound obtained by dimerizing unsaturated fatty acids (preferably unsaturated fatty acids having 11 to 22 carbon atoms, particularly preferably unsaturated fatty acids having 18 carbon atoms), and its industrial manufacturing process has been roughly standardized in the industry. For dimer acid, in particular, dimer acid mainly composed of dimer acid having 36 carbon atoms obtained by dimerizing inexpensive and easily available unsaturated fatty acids having 18 carbon atoms such as oleic acid and linoleic acid can be easily obtained. In addition, for dimer acid, depending on the manufacturing method, purification degree, etc., it sometimes contains an arbitrary amount of monomeric acid, trimeric acid, other polymeric fatty acids, etc. In addition, although double bonds remain after the polymerization reaction of unsaturated fatty acids, in this specification, hydrides having a reduced degree of unsaturation by further performing a hydrogenation reaction are also included in dimer acid. For dimer acid type diamine, commercially available products can be obtained, and examples thereof include "PRIAMINE 1073", "PRIAMINE 1074", "PRIAMINE 1075" manufactured by Croda Japan Co., Ltd., "VERSAMINE 551", "VERSAMINE 552" manufactured by Cognis Japan Co., Ltd., etc.

[0028] As the aromatic diamine compound, examples thereof include benzenediamine compounds, naphthalenediamine compounds, diphenylamine compounds, etc., and diphenylamine compounds are preferred.

[0029] The so-called phenylenediamine compound refers to a compound formed by a benzene ring having two amino groups. Further, the benzene ring here may optionally have 1 to 3 substituents. Specifically, as the phenylenediamine compound, 1,4-phenylenediamine, 1,2-phenylenediamine, 1,3-phenylenediamine, 2,4-diaminotoluene, 2,6-diaminotoluene, 3,5-diaminobiphenyl, 2,4,5,6-tetrafluoro-1,3-phenylenediamine, etc. can be cited.

[0030] As the substituent, there is no particular limitation, and examples thereof include a halogen atom, -OH, -O-C 1-6 alkyl, -N(C 1-10 alkyl) 2 、C 1-20 alkyl, C 2-30 alkenyl, C 2-30 alkynyl, C 6-10 aryl, -NH 2 、-CN, -C(O)O-C 1-10 alkyl, -COOH, -C(O)H, -NO 2 etc. Here, the term "C p-q "(where p and q are positive integers and satisfy p < q) means that the number of carbon atoms of the organic group described immediately after this term is p to q. For example, the expression "C 1-10 alkyl" means an alkyl group having 1 to 10 carbon atoms. These substituents may also combine with each other to form a ring, and the ring structure also includes a spiro ring or a fused ring.

[0031] The so-called naphthalenediamine compound refers to a compound formed by a naphthalene ring having two amino groups. Further, the naphthalene ring here may optionally have 1 to 3 substituents. As the substituent, it is the same as the substituent that the phenylenediamine compound may optionally have. Specifically, as the naphthalenediamine compound, 1,5-diaminonaphthalene, 1,8-diaminonaphthalene, 2,6-diaminonaphthalene, 2,3-diaminonaphthalene, etc. can be cited.

[0032] The so-called diphenylamine compound refers to a compound containing two aniline structures in the molecule. Further, the two benzene rings in the two aniline structures may each further optionally have 1 to 3 substituents. As the substituent, it is the same as the substituent that the phenylenediamine compound may optionally have. The two aniline structures in the diphenylamine compound may be directly bonded and / or bonded via one or two linking structures having 1 to 100 backbone atoms selected from carbon atoms, oxygen atoms, sulfur atoms, and nitrogen atoms. The diphenylamine compound also includes a compound in which the two aniline structures are bonded by two bonds.

[0033] As the "linking structure" in the diphenylamine compound, specifically, -NHCO-, -CONH-, -OCO-, -COO-, -CH 2 -, -CH 2CH 2 -、 -CH 2 CH 2 CH 2 -、 -CH 2 CH 2 CH 2 CH 2 -、 -CH 2 CH 2 CH 2 CH 2 CH 2 -、 -CH(CH 3 )-、 -C(CH 3 ) 2 -、 -C(CF 3 ) 2 -、 -CH=CH-、 -O-、 -S-、 -CO-、 -SO 2 -、 -NH-、 -Ph-、 -Ph-Ph-、 -C(CH 3 ) 2 -Ph-C(CH 3 ) 2 -、 -O-Ph-O-、 -O-Ph-Ph-O-、 -O-Ph-SO 2 -Ph-O-、 -O-Ph-C(CH 3 ) 2 -Ph-O-、 -Ph-CO-O-Ph-、 -C(CH 3 ) 2 -Ph-C(CH 3 ) 2 -、 -O-Ph-C(CH 3 ) 2 -Ph-C(CH 3 ) 2 -Ph-O-、 -Ph-O-Ph-C(CH 3 ) 2 -Ph-C(CH 3 ) 2 -Ph-O-Ph-、 the groups represented by the following formulas (I) and (II), and the groups formed by combining them, etc. In this specification, "Ph" represents 1,4-phenylene, 1,3-phenylene or 1,2-phenylene. Among them, as the linking structure, -COO-, -Ph-CO-O-Ph-, -C(CH 3 ) 2 -Ph-C(CH 3 ) 2 -、 -O-Ph-C(CH 3 ) 2 -Ph-C(CH 3 ) 2-Ph-O-, or -Ph-O-Ph-C(CH 3 ) 2 -Ph-C(CH 3 ) 2 -Ph-O-Ph-.

[0034] [Chemical Formula 1]

[0035] In one embodiment, as the diamine compound, the diamine compound represented by the following formula (A-1) is preferred. [Chemical Formula 2] (In formula (A-1), R 1 ~R 8 each independently represents a hydrogen atom, a halogen atom, a cyano group, a nitro group, -X 9 -R 9 or -X 10 -R 10 , at least one of R 1 ~R 8 is -X 10 -R 10 , X 9 each independently represents a single bond, -NR 9’ -, -O-, -S-, -CO-, -SO 2 -, -NR 9’ CO-, -CONR 9’ -, -OCO- or -COO-, R -9 each independently represents a substituted or unsubstituted alkyl group, or a substituted or unsubstituted alkenyl group, R 9’ each independently represents a hydrogen atom, a substituted or unsubstituted alkyl group, or a substituted or unsubstituted alkenyl group, X 10 each independently represents a single bond, -(substituted or unsubstituted alkylene)-, -NH-, -O-, -S-, -CO-, -SO 2 -, -NHCO-, -CONH-, -OCO- or -COO-, R 10 each independently represents a substituted or unsubstituted aryl group, or a substituted or unsubstituted heteroaryl group.)

[0036] R 9 and R 9The alkyl group represented by ' refers to a monovalent aliphatic saturated hydrocarbon group that is straight-chain, branched-chain or cyclic. As the alkyl group, an alkyl group having 1 to 6 carbon atoms is preferred, and an alkyl group having 1 to 3 carbon atoms is more preferred. Examples of such an alkyl group include methyl, ethyl, propyl, isopropyl, butyl, isobutyl, sec-butyl, tert-butyl, pentyl, isopentyl, neopentyl, cyclopentyl, cyclohexyl, and the like.

[0037] R in formula (A-1) 9 and R 9 The alkenyl group represented by ' refers to a monovalent unsaturated hydrocarbon group that is straight-chain, branched-chain or cyclic and has at least one carbon-carbon double bond. As the alkenyl group, an alkenyl group having 2 to 6 carbon atoms is preferred, and an alkenyl group having 2 or 3 carbon atoms is more preferred. Examples of such an alkenyl group include vinyl, 1-propenyl, 2-propenyl, 2-methyl-1-propenyl, 1-butenyl, 2-butenyl, 3-butenyl, 3-methyl-2-butenyl, 1-pentenyl, 2-pentenyl, 3-pentenyl, 4-pentenyl, 4-methyl-3-pentenyl, 1-hexenyl, 3-hexenyl, 5-hexenyl, 2-cyclohexenyl, and the like. As the substituent of the alkenyl group in the "substituted or unsubstituted alkenyl group", there is no particular limitation, and examples thereof include a halogen atom, a cyano group, an alkoxy group, an aryl group, a heteroaryl group, an amino group, a nitro group, a hydroxyl group, a carboxyl group, a sulfo group, and the like. As the number of substituents, 1 to 3 are preferred, and 1 is more preferred.

[0038] As the substituent of the alkyl group in the "substituted or unsubstituted alkyl group" and the substituent of the alkenyl group in the "substituted or unsubstituted alkenyl group", there is no particular limitation, and examples thereof include a halogen atom, a cyano group, an alkoxy group, an amino group, a nitro group, a hydroxyl group, a carboxyl group, a sulfo group, and the like. As the number of substituents, 1 to 3 are preferred, and 1 is more preferred.

[0039] The alkoxy group refers to a monovalent group (alkyl-O-) formed by bonding an alkyl group to an oxygen atom. As the alkoxy group, an alkoxy group having 1 to 6 carbon atoms is preferred, and an alkoxy group having 1 to 3 carbon atoms is more preferred. Examples of such an alkoxy group include methoxy, ethoxy, propoxy, isopropoxy, butoxy, isobutoxy, sec-butoxy, tert-butoxy, pentyloxy, and the like.

[0040] X in formula (A-1) 10 The alkylene group represented by refers to a divalent aliphatic saturated hydrocarbon group that is straight-chain, branched-chain or cyclic, preferably an alkylene group having 1 to 6 carbon atoms, more preferably an alkylene group having 1 to 3 carbon atoms. Examples of the alkylene group include -CH 2 -, -CH 2 -CH 2 -, -CH(CH 3 )-, -CH 2 -CH 2 -CH 2 -, -CH2 -CH(CH 3 )-,-CH(CH 3 )-CH 2 -,-CH(CH 3 ) 2 -,-CH 2 -CH 2 -CH 2 -CH 2 -,-CH 2 -CH 2 -CH(CH 3 )-,-CH 2 -CH(CH 3 )-CH 2 -,-CH(CH 3 )-CH 2 -CH 2 -,-CH 2 -C(CH 3 ) 2 -,-C(CH 3 ) 2 -CH 2 - etc. As the substituent of the alkylene group in the "substituted or unsubstituted alkylene group", there is no particular limitation, and examples thereof include a halogen atom, a cyano group, an alkoxy group, an aryl group, a heteroaryl group, an amino group, a nitro group, a hydroxyl group, a carboxyl group, a sulfo group, etc. As the number of substituents, 1 to 3 are preferred, and 1 is more preferred.

[0041] As the aryl group represented by R 10 in the formula (A-1), an aryl group having 6 to 14 carbon atoms is preferred, and an aryl group having 6 to 10 carbon atoms is more preferred. Examples of such an aryl group include a phenyl group, a 1-naphthyl group, a 2-naphthyl group, etc., and a phenyl group is preferred. As the substituent of the aryl group in the "substituted or unsubstituted aryl group", there is no particular limitation, and examples thereof include a halogen atom, a cyano group, an alkyl group, an alkoxy group, an aryl group, a heteroaryl group, an amino group, a nitro group, a hydroxyl group, a carboxyl group, a sulfo group, etc. As the number of substituents, 1 to 3 are preferred, and 1 is more preferred.

[0042] R 10The heteroaryl group represented refers to an aromatic heterocyclic group having 1 to 4 heteroatoms selected from an oxygen atom, a nitrogen atom, and a sulfur atom. The heteroaryl group is preferably a monocyclic, bicyclic, or tricyclic (preferably monocyclic) aromatic heterocyclic group having 5 to 12 members (preferably 5 or 6 members). Examples of such heteroaryl groups include a furyl group, a thienyl group, a pyrrolyl group, an oxazolyl group, an isoxazolyl group, a thiazolyl group, an isothiazolyl group, an imidazolyl group, a pyrazolyl group, a 1,2,3-oxadiazolyl group, a 1,2,4-oxadiazolyl group, a 1,3,4-oxadiazolyl group, a furazanyl group, a 1,2,3-thiadiazolyl group, a 1,2,4-thiadiazolyl group, a 1,3,4-thiadiazolyl group, a 1,2,3-triazolyl group, a 1,2,4-triazolyl group, a tetrazolyl group, a pyridyl group, a pyridazinyl group, a pyrimidinyl group, a pyrazinyl group, a triazinyl group, and the like. As the substituent of the heteroaryl group in the "substituted or unsubstituted heteroaryl group", it is the same as the substituent of the aryl group in the "substituted or unsubstituted aryl group".

[0043] R 1 ~R 8 each independently represents a hydrogen atom, a halogen atom, a cyano group, a nitro group, -X 9 -R 9 or -X 10 -R 10 。R 1 ~R 8 are preferably each independently a hydrogen atom or -X 10 -R 10 。

[0044] R 1 ~R 8 at least one of them is -X 10 -R 10 。Preferably, R 1 ~R 8 one or two of them are -X 10 -R 10 ,more preferably R 5 ~R 8 one or two of them are -X 10 -R 10 ,even more preferably R 5 and R 7 one or two of them are -X 10 -R 10 。

[0045] In one embodiment, preferably one or two of R 1 ~R 8 are -X 10 -R 10 ,and the others of R 1 ~R 8 are hydrogen atoms, more preferably R 5 ~R 8One or two of them are -X 10 -R 10 , and R 1 ~R 8 The others in are hydrogen atoms. More preferably, one or two of R 5 and R 7 are -X 10 -R 10 , and R 1 ~R 8 The others in are hydrogen atoms.

[0046] X 9 each independently represents a single bond, -NR 9’ -, -O-, -S-, -CO-, -SO 2 -, -NR 9’ CO-, -CONR 9’ -, -OCO- or -COO-. R 9 each independently represents a substituted or unsubstituted alkyl group, or a substituted or unsubstituted alkenyl group. X 9 is preferably a single bond.

[0047] R 9 ' each independently represents a hydrogen atom, a substituted or unsubstituted alkyl group, or a substituted or unsubstituted alkenyl group. R 9 is preferably a substituted or unsubstituted alkyl group.

[0048] X 10 each independently represents a single bond, -(substituted or unsubstituted alkylene)-, -NH-, -O-, -S-, -CO-, -SO 2 -, -NHCO-, -CONH-, -OCO- or -COO-. X 10 is preferably a single bond.

[0049] R 10 each independently represents a substituted or unsubstituted aryl group, or a substituted or unsubstituted heteroaryl group. R 10 is preferably a substituted or unsubstituted aryl group.

[0050] In one embodiment, the diamine compound represented by formula (A-1) is preferably the compound represented by the following formula (A-2), more preferably the compound represented by the following formula (A-3) (4-aminobenzoic acid 5-amino-1,1'-biphenyl-2-yl (alias: (5-amino-2-biphenyl)-4-aminobenzoate, PHBAAB). [Chemical formula 3] (In the formula, R 1 ~R 6 and R 8Each independently represents a hydrogen atom, a halogen atom, a cyano group, a nitro group, -X 9 -R 9 , and other symbols are the same as those in formula (A-1).) [Chemical formula 4]

[0051] In another embodiment, specific examples of the diamine compound include 4,4'-diamino-2,2'-bis(trifluoromethyl)-1,1'-biphenyl, 3,4'-diaminodiphenyl ether, 4,4'-diaminodiphenyl ether, 3,3'-diaminodiphenyl sulfone, 4,4'-diaminodiphenyl sulfone, 4,4'-diaminodiphenyl sulfide, 4-aminophenyl 4-aminobenzoate, 1,3-bis(3-aminophenoxy)benzene, 1,3-bis(4-aminophenoxy)benzene, 1,4-bis(4-aminophenoxy)benzene, 2,2-bis(4-aminophenyl)propane, 4,4'-(hexafluoroisopropylidene)dianiline, 2,2-bis[4-(4-aminophenoxy)phenyl]propane, 2,2-bis[4-(4-aminophenoxy)phenyl]hexafluoropropane, α,α-bis[4-(4-aminophenoxy)phenyl]-1,3-diisopropylbenzene, α,α-bis[4-(4-aminophenoxy)phenyl]-1,4-diisopropylbenzene, 4,4'-(9-fluorenylidene)dianiline, 2,2-bis(3-methyl-4-aminophenyl)propane, 2,2-bis(3-methyl-4-aminophenyl)benzene, 4,4'-diamino-3,3'-dimethyl-1,1'-biphenyl, 4,4'-diamino-2,2'-dimethyl-1,1'-biphenyl, 9,9'-bis(3-methyl-4-aminophenyl)fluorene, 5-(4-aminophenoxy)-3-[4-(4-aminophenoxy)phenyl]-1,1,3-trimethylindane, 4,4'-(m-phenylenediisopropylidene)dianiline (Bisaniline-M), 4,4'-[1,4-phenylenebis[(1-methylethylidene)-4,1-phenyleneoxy]]bis(aniline) (BPPAN), etc., and 4,4'-(m-phenylenediisopropylidene)dianiline and 4,4'-[1,4-phenylenebis[(1-methylethylidene)-4,1-phenyleneoxy]]bis(aniline) are preferred. It should be noted that 4,4'-(m-phenylenediisopropylidene)dianiline (Bisaniline-M) is a compound represented by the following formula (I), and 4,4'-[1,4-phenylenebis[(1-methylethylidene)-4,1-phenyleneoxy]]bis(aniline) (BPPAN) is a compound represented by the following formula (II). [Chemical formula 5]

[0052] In one embodiment, the diamine compound for preparing the polyimide resin preferably contains 4,4'-(m-phenylene diisopropylidene) diphenylamine (the compound shown in the above formula (I)), more preferably contains 4,4'-(m-phenylene diisopropylidene) diphenylamine and the diamine compound shown in formula (A-1) in combination, further preferably contains 4,4'-(m-phenylene diisopropylidene) diphenylamine and the diamine compound shown in formula (A-2) in combination, and even more preferably contains 4,4'-(m-phenylene diisopropylidene) diphenylamine and (5-amino-2-biphenyl)-4-aminobenzoate (the compound shown in the above formula (A-3)) in combination.

[0053] When the diamine compound for preparing the polyimide resin contains 4,4'-(m-phenylene diisopropylidene) diphenylamine, the content of the structure derived from 4,4'-(m-phenylene diisopropylidene) diphenylamine is preferably 10 mol% or more, more preferably 30 mol% or more, further preferably 50 mol% or more, and even more preferably 60 mol% or more based on 100 mol% of all the structures of the diamine compound constituting the polyimide resin.

[0054] The diamine compound can be a commercially available compound or a compound synthesized by a known method. For example, the diamine compound shown in formula (A-1) can be synthesized by the synthesis method described in Japanese Patent No. 6240798 or a method based on this method. The diamine compound can be used alone or in combination of two or more.

[0055] The acid anhydride for preparing the polyimide resin is not particularly limited, and in a preferred embodiment, it is an aromatic tetracarboxylic dianhydride. Examples of the aromatic tetracarboxylic dianhydride include pyromellitic dianhydride, naphthalenetetracarboxylic dianhydride, anthracenetetracarboxylic dianhydride, bis(phthalic anhydride), etc., and bis(phthalic anhydride) is preferred.

[0056] Pyromellitic dianhydride refers to the dianhydride of benzene having 4 carboxyl groups, and further, the benzene ring therein may optionally have 1 to 3 substituents. Here, as the substituent, it is preferably selected from a halogen atom, a cyano group, and -X 13 -R 13 (the same as the definition of the following formula (A-4)). Specific examples of pyromellitic dianhydride include pyromellitic dianhydride and 1,2,3,4-benzenetetracarboxylic dianhydride.

[0057] Naphthalenetetracarboxylic dianhydride refers to the dianhydride of naphthalene having 4 carboxyl groups, and further, the naphthalene ring therein may optionally have 1 to 3 substituents. Here, as the substituent, it is preferably selected from a halogen atom, a cyano group, and -X 13 -R 13(Same as the definition of the following formula (A-4)). As naphthalene tetracarboxylic dianhydride, specifically, 1,4,5,8-naphthalene tetracarboxylic dianhydride, 2,3,6,7-naphthalene tetracarboxylic dianhydride, etc. can be cited.

[0058] Anthracene tetracarboxylic dianhydride refers to the dianhydride of anthracene having 4 carboxyl groups. Further, the anthracene ring therein may optionally have 1 to 3 substituents. Here, as the substituent, it is preferably selected from a halogen atom, a cyano group, and -X 13 -R 13 (Same as the definition of the following formula (A-4)). As anthracene tetracarboxylic dianhydride, specifically, 2,3,6,7-anthracene tetracarboxylic dianhydride, etc. can be cited.

[0059] Bis(phthalic anhydride) refers to a compound containing 2 phthalic anhydrides in the molecule. Further, the 2 benzene rings in the 2 phthalic anhydrides may each optionally have 1 to 3 substituents. Here, as the substituent, it is preferably selected from a halogen atom, a cyano group, and -X 13 -R 13 (Same as the definition of the following formula (A-4)). The two phthalic anhydrides in bis(phthalic anhydride) may be directly bonded or bonded via a linking structure having 1 to 100 backbone atoms selected from carbon atoms, oxygen atoms, sulfur atoms, and nitrogen atoms.

[0060] As bis(phthalic anhydride), for example, the compound represented by formula (A-4) can be cited. [Chemical formula 6] (In the formula, R 11 and R 12 each independently represent a halogen atom, a cyano group, a nitro group, or -X 13 -R 13 , X 13 each independently represent a single bond, -NR 13’ -, -O-, -S-, -CO-, -SO 2 -, -NR 13’ CO-, -CONR 13’ -, -OCO- or -COO-, R 13 each independently represent a substituted or unsubstituted alkyl group, or a substituted or unsubstituted alkenyl group, R 13 ' each independently represent a hydrogen atom, a substituted or unsubstituted alkyl group, or a substituted or unsubstituted alkenyl group, Y represents a single bond, or a linking structure having 1 to 100 backbone atoms selected from carbon atoms, oxygen atoms, sulfur atoms, and nitrogen atoms, n1 and m1 each independently represent an integer of 0 to 3).

[0061] Y is preferably a linking structure having 1 to 100 backbone atoms selected from carbon atoms, oxygen atoms, sulfur atoms, and nitrogen atoms. n1 and m1 are preferably 0.

[0062] The "linking structure" in Y has 1 to 100 backbone atoms selected from carbon atoms, oxygen atoms, sulfur atoms, and nitrogen atoms. The "linking structure" is preferably -[A-Ph] a -A-[Ph-A] b -[wherein, A independently represents a single bond, -(substituted or unsubstituted alkylene)-, -O-, -S-, -CO-, -SO 2 -, -CONH-, -NHCO-, -COO-, or -OCO-, and a and b independently represent an integer of 0 to 2 (preferably 0 or 1)] shown divalent group.

[0063] The "linking structure" in Y, specifically, can be exemplified by -CH 2 -, -CH 2 CH 2 -, -CH 2 CH 2 CH 2 -, -CH 2 CH 2 CH 2 CH 2 -, -CH 2 CH 2 CH 2 CH 2 CH 2 -, -CH(CH 3 )-, -C(CH 3 ) 2 -, -O-, -CO-, -SO 2 -, -Ph-, -O-Ph-O-, -O-Ph-SO 2 -Ph-O-, -O-Ph-C(CH 3 ) 2 -Ph-O-, etc., preferably -O-Ph-C(CH 3 ) 2 -Ph-O-.

[0064] As the bisphthalic anhydride, specifically, 3,3',4,4'-benzophenonetetracarboxylic dianhydride, 3,3',4,4'-diphenylethertetracarboxylic dianhydride, 3,3',4,4'-diphenylsulfonetetracarboxylic dianhydride, 3,3',4,4'-biphenyltetracarboxylic dianhydride, 2,2',3,3'-biphenyltetracarboxylic dianhydride, 2,3,3',4'-biphenyltetracarboxylic dianhydride, 2,3,3',4'-benzophenonetetracarboxylic dianhydride, 2,3,3',4'-diphenylethertetracarboxylic dianhydride, 2,3,3',4'-diphenylsulfonetetracarboxylic dianhydride, 2,2'-bis(3,4-dicarboxyphenoxyphenyl)sulfone dianhydride, methylene-4,4'-bisphthalic dianhydride, 1,1-ethylidene-4,4'-bisphthalic dianhydride, 2,2-propylidene-4,4'-bisphthalic dianhydride, 1,2-ethylidene-4,4'-bisphthalic dianhydride, 1,3-propylidene-4,4'-bisphthalic dianhydride, 1,4-butylidene-4,4'-bisphthalic dianhydride, 1,5-pentylidene-4,4'-bisphthalic dianhydride, 1,3-bis(3,4-dicarboxyphenyl)benzene dianhydride, 1,4-bis(3,4-dicarboxyphenyl)benzene dianhydride, 1,3-bis(3,4-dicarboxyphenoxy)benzene dianhydride, 1,4-bis(3,4-dicarboxyphenoxy)benzene dianhydride, 2,2-bis(2,3-dicarboxyphenyl)propane dianhydride, 2,2-bis(3,4-dicarboxyphenyl)propane dianhydride, 4,4'-(4,4'-isopropylidenediphenoxy)bisphthalic dianhydride (BPADA), etc. can be cited.

[0065] In one embodiment, the phthalic acid compound represented by the formula (A-4) is preferably a compound represented by the following formula (A-5), and more preferably a compound represented by the following formula (A-6) (4,4'-(4,4'-isopropylidenediphenoxy)bisphthalic dianhydride: BPADA). [Chemical formula 7] (In the formula, R 11 and R 12 each independently represent a halogen atom, a cyano group, a nitro group or -X 13 -R 13 , n1 and m1 each independently represent an integer of 0 to 3, and other symbols are the same as those in the formula (A-4).) [Chemical formula 8]

[0066] The aromatic tetracarboxylic dianhydride can be a commercially available product or a substance synthesized by a known method or a method based thereon. The aromatic tetracarboxylic dianhydride can be used alone or in combination of two or more.

[0067] In one embodiment, the acid anhydride used for preparing the polyimide resin may contain other acid anhydrides in addition to the aromatic tetracarboxylic dianhydride.

[0068] As other acid anhydrides, specifically, 1,2,3,4-cyclobutanetetracarboxylic dianhydride, cyclopentanetetracarboxylic dianhydride, cyclohexane-1,2,3,4-tetracarboxylic dianhydride, cyclohexane-1,2,4,5-tetracarboxylic dianhydride, 3,3',4,4'-bicyclohexyltetracarboxylic dianhydride, carbonyl-4,4'-bis(cyclohexane-1,2-dicarboxylic acid) dianhydride, methylene-4,4'-bis(cyclohexane-1,2-dicarboxylic acid) dianhydride, 1,2-ethylene-4,4'-bis(cyclohexane-1,2-dicarboxylic acid) dianhydride, oxy-4,4'-bis(cyclohexane-1,2-dicarboxylic acid) dianhydride, thio-4,4'-bis(cyclohexane-1,2-dicarboxylic acid) dianhydride, sulfonyl-4,4'-bis(cyclohexane-1,2-dicarboxylic acid) dianhydride and other aliphatic tetracarboxylic dianhydrides can be cited.

[0069] The content of the structure derived from the aromatic tetracarboxylic dianhydride in all the structures of the acid anhydride constituting the polyimide resin is preferably 10 mol% or more, more preferably 30 mol% or more, still more preferably 50 mol% or more, still more preferably 70 mol% or more, still more preferably 90 mol% or more, and particularly preferably 100 mol%.

[0070] The polyimide resin preferably has a structural unit represented by the following general formula (A). [Chemical formula 9] (In general formula (A), R 51 each independently represents a single bond or a residue derived from bisphthalic anhydride, and R 52 each independently represents a single bond or a residue derived from a diamine compound.)

[0071] R 51 each independently represents a single bond or a residue derived from bisphthalic anhydride, and is preferably a residue derived from bisphthalic anhydride. The residue derived from bisphthalic anhydride represented by R 51 refers to a divalent group obtained by removing two phthalic anhydrides from bisphthalic anhydride. Regarding bisphthalic anhydride, as described above.

[0072] R 51 The examples of the residue derived from bisphthalic anhydride represented are the same as the examples of the "linking structure" represented by Y in formula (A-4). R 51The residue derived from the bisphthalic anhydride is preferably a divalent group obtained by removing two phthalic anhydrides from 4,4'-(4,4'-isopropylidenediphenoxy)bisphthalic anhydride (the compound represented by the above formula (A-6)).

[0073] R 52 Each independently represents a single bond or a residue derived from a diamine compound, preferably a residue derived from a diamine compound. R 52 The residue derived from the diamine compound is a divalent group obtained by removing two amino groups from the diamine compound. Regarding the diamine compound, as described above.

[0074] R 52 The residue derived from the diamine compound is preferably a divalent group obtained by removing two amino groups from 4,4'-(m-phenyleneisopropylidene)dianiline (the compound represented by the above formula (I)) or a divalent group obtained by removing two amino groups from the diamine compound represented by the formula (A-1), more preferably a divalent group obtained by removing two amino groups from 4,4'-(m-phenyleneisopropylidene)dianiline or the diamine compound represented by the formula (A-2), and further preferably a divalent group obtained by removing two amino groups from 4,4'-(m-phenyleneisopropylidene)dianiline or a divalent group obtained by removing two amino groups from (5-amino-2-biphenyl)-4-aminobenzoate (the compound represented by the above formula (A-3)).

[0075] In one embodiment, the polyimide resin may be a copolymer having a plurality of different structural units represented by the formula (A). In such an embodiment, the polyimide resin preferably has: R in the formula (A) 52 A structural unit that is a divalent group obtained by removing two amino groups from 4,4'-(m-phenyleneisopropylidene)dianiline (the compound represented by the above formula (I)), and R in the formula (A) 52 A structural unit that is a divalent group obtained by removing two amino groups from a diamine compound other than 4,4'-(m-phenyleneisopropylidene)dianiline. As the diamine compound other than 4,4'-(m-phenyleneisopropylidene)dianiline, the diamine compound represented by the formula (A-1) is preferred, the diamine compound represented by the formula (A-2) is more preferred, and (5-amino-2-biphenyl)-4-aminobenzoate (the compound represented by the above formula (A-3)) is further preferred. In a more preferred embodiment, the polyimide resin has: R in the formula (A) 52 A structural unit that is a divalent group obtained by removing two amino groups from 4,4'-(m-phenyleneisopropylidene)dianiline, and R in the formula (A) 52 A structural unit that is a divalent group obtained by removing two amino groups from (5-amino-2-biphenyl)-4-aminobenzoate.

[0076] In one embodiment, the polyimide resin preferably contains a structural unit (hereinafter sometimes referred to as "structural unit A1") obtained by reacting 4,4'-(m-phenylene diisopropylidene) diphenylamine (the compound represented by the above formula (I)) with 4,4'-(4,4'-isopropylidene diphenoxy) bisphthalic anhydride (BPADA: the compound represented by the above formula (A-6)). Further, in the above embodiment, it is more preferable that the polyimide resin, in addition to containing structural unit A1, further contains a structural unit obtained by reacting (5-amino-2-biphenyl)-4-aminobenzoate (the compound represented by the above formula (A-3)) with 4,4'-(4,4'-isopropylidene diphenoxy) bisphthalic anhydride.

[0077] (A) The polyimide resin can be prepared by a conventionally known method. As a known method, for example, a method of heating a mixture of a diamine compound, an acid anhydride and a solvent to react them can be cited. The mixing amount of the diamine compound is usually 0.5 to 1.5 molar equivalents, preferably 0.9 to 1.1 molar equivalents, relative to the acid anhydride.

[0078] As the solvent used in the preparation of (A) the polyimide resin, amide solvents such as N,N-dimethylacetamide, N,N-diethylacetamide, N,N-dimethylformamide, N-methyl-2-pyrrolidone can be cited; ketone solvents such as acetone, methyl ethyl ketone (MEK) and cyclohexanone; ester solvents such as γ-butyrolactone; hydrocarbon solvents such as cyclohexane and methylcyclohexane. In addition, in the preparation of the polyimide resin, an imidization catalyst, an azeotropic dehydration solvent, an acid catalyst, etc. can be used as needed. As the imidization catalyst, for example, tertiary amines such as triethylamine, triisopropylamine, triethylenediamine, N-methylpyrrolidone, N-ethylpyrrolidone, N,N-dimethyl-4-aminopyridine, pyridine can be cited. As the azeotropic dehydration solvent, for example, toluene, xylene, ethylcyclohexane, etc. can be cited. As the acid catalyst, for example, acetic anhydride can be cited. Those skilled in the art can appropriately set the usage amounts of the imidization catalyst, the azeotropic dehydration solvent, the acid catalyst, etc. The reaction temperature for preparing (A) the polyimide resin is usually 100 to 250 °C.

[0079] (A) The weight average molecular weight of the component is preferably 3000 or more, more preferably 5000 or more, further preferably 8000 or more, preferably 200000 or less, more preferably 100000 or less, further preferably 80000 or less. The Mw of component (A) can be measured by gel permeation chromatography (GPC) method as a value in terms of polystyrene.

[0080] The weight-average molecular weight of the component (A) is preferably 5000 or more, more preferably 8000 or more, still more preferably 10000 or more, preferably 100000 or less, more preferably 80000 or less, and still more preferably 50000 or less. The weight-average molecular weight means the weight-average molecular weight based on the content ratio of the amount of the component (A) present in the resin composition layer. Regarding the weight-average molecular weight, for example, when the resin composition layer contains a component (A) having a weight-average molecular weight of Mw1 and a content of w1 and a component (A) having a weight-average molecular weight of Mw2 and a content of w2, the weight-average molecular weight of the component (A) can be calculated as (Mw1×w1 + Mw2×w2) / (w1 + w2).

[0081] As the content of the component (A), when the non-volatile components in the resin composition layer are set to 100% by mass, it is preferably 0.1% by mass or more, more preferably 0.15% by mass or more, still more preferably 0.2% by mass or more, 0.3% by mass or more, 0.4% by mass or more, 0.5% by mass or more, preferably 30% by mass or less, more preferably 20% by mass or less, still more preferably 10% by mass or less, 8% by mass or less, 5% by mass or less, 4% by mass or less, 3% by mass or less, 2% by mass or less, 1% by mass or less.

[0082] The content of the component (A), when the resin components in the resin composition layer are set to 100% by mass, is preferably 0.5% by mass or more, more preferably 1% by mass or more, still more preferably 1.5% by mass or more, preferably 40% by mass or less, more preferably 30% by mass or less, still more preferably 20% by mass or less, 10% by mass or less, 5% by mass or less.

[0083] -(B) Phenoxy resin- The resin composition layer contains (B) phenoxy resin as the component (B). The (B) phenoxy resin as the component (B) does not contain substances belonging to the above-mentioned component (A). By making the resin composition layer contain (B) phenoxy resin, the stress during curing of the resin composition layer can be relaxed, the mechanical strength can be improved, and the film flexibility can also be improved. The component (B) can be used alone or in combination of two or more.

[0084] The weight-average molecular weight (Mw) of the (B) phenoxy resin is preferably 5000 or more, more preferably 8000 or more, still more preferably 10000 or more. The upper limit of this Mw is not particularly limited, preferably 100000 or less, more preferably 80000 or less, and still more preferably 50000 or less. The Mw of the component (B) can be measured by gel permeation chromatography (GPC) as a value in terms of polystyrene.

[0085] (B) The weight-average molecular weight of the phenoxy resin is preferably 5000 or more, more preferably 8000 or more, still more preferably 10000 or more, preferably 100000 or less, more preferably 80000 or less, and still more preferably 50000 or less. The weight-average molecular weight refers to the weight-average molecular weight based on the content ratio of the component (B) present in the resin composition layer. Regarding the weight-average molecular weight, for example, when the resin composition layer contains a component (B) having a weight-average molecular weight of Mw3 and a content of w3 and a component (B) having a weight-average molecular weight of Mw4 and a content of w4, the weight-average molecular weight of the component (B) can be calculated as (Mw3 × w3 + Mw4 × w4) / (w3 + w4).

[0086] When the weight-average molecular weight of the component (A) is a2 and the weight-average molecular weight of the component (B) is b2, a2 / b2 is preferably 0.01 or more, more preferably 0.05 or more, still more preferably 0.1 or more, 0.15 or more, 0.2 or more, 0.25 or more, preferably 10 or less, more preferably 8 or less, and still more preferably 5 or less, 4 or less, 3 or less, 2 or less. By containing the component (A) and the component (B) such that a2 / b2 is within the above range in the resin composition layer, the glass transition temperature is high, the flexibility of the film is excellent, and the mechanical strength of the cured product of the resin composition layer is excellent.

[0087] Examples of the (B) phenoxy resin include phenoxy resins having one or more skeletons selected from the bisphenol A skeleton, bisphenol F skeleton, bisphenol S skeleton, bisphenol acetophenone skeleton, phenol-formaldehyde skeleton, biphenyl skeleton, fluorene skeleton, dicyclopentadiene skeleton, norbornene skeleton, naphthalene skeleton, anthracene skeleton, adamantane skeleton, terpene skeleton, and trimethylcyclohexane skeleton. The terminal of the (E) phenoxy resin can be any functional group such as a phenolic hydroxyl group or an epoxy group.

[0088] Examples of commercially available products of the (B) phenoxy resin include "1256" and "4250" (both are phenoxy resins containing a bisphenol A skeleton) manufactured by Mitsubishi Chemical Corporation; "YX8100" (a phenoxy resin containing a bisphenol S skeleton) manufactured by Mitsubishi Chemical Corporation; "YX6954" (a phenoxy resin containing a bisphenol acetophenone skeleton) manufactured by Mitsubishi Chemical Corporation; "FX280" and "FX293" manufactured by Nippon Steel Chemical & Materials Co., Ltd.; "YL7500BH30", "YX6954BH30", "YX7553", "YX7553BH30", "YL7891BH30", "YX7200B35", "YL7769BH30", "YL6794", "YL7213", "YL7290", and "YL7482" manufactured by Mitsubishi Chemical Corporation, etc.

[0089] The content of the component (B) is preferably 0.1% by mass or more, more preferably 0.15% by mass or more, still more preferably 0.2% by mass or more, preferably 15% by mass or less, more preferably 10% by mass or less, still more preferably 8% by mass or less, 7% by mass or less, 5% by mass or less when the non-volatile components in the resin composition layer are set to 100% by mass.

[0090] The content of the component (B) is preferably 0.1% by mass or more, more preferably 0.5% by mass or more, still more preferably 1% by mass or more, 1.5% by mass or more, 2% by mass or more, preferably 25% by mass or less, more preferably 20% by mass or less, still more preferably 10% by mass or less, 8% by mass or less when the resin components in the resin composition layer are set to 100% by mass.

[0091] When the content of the component (A) when the resin components in the resin composition layer are set to 100% by mass is set as a1, and the content of the component (B) when the resin components in the resin composition layer are set to 100% by mass is set as b1, a1 / b1 is 0.05 or more, preferably 0.1 or more, more preferably 0.15 or more, still more preferably 0.2 or more. The upper limit is 50 or less, preferably 45 or less, more preferably 40 or less, still more preferably 35 or less, 30 or less, 25 or less, 20 or less, 15 or less, 10 or less, 5 or less or 4 or less. By adjusting the contents of the component (A) and the component (B) so that a1 / b1 is within the above range, a cured product having a high glass transition temperature, excellent film flexibility and mechanical strength can be obtained.

[0092] The total content of the component (A) and the component (B) is preferably 0.2% by mass or more, more preferably 0.3% by mass or more, still more preferably 0.4% by mass or more, preferably 45% by mass or less, more preferably 30% by mass or less, still more preferably 20% by mass or less when the non-volatile components in the resin composition layer are set to 100% by mass.

[0093] -(C) Inorganic filler- The resin composition layer contains an inorganic filler as the component (C). By using the resin composition layer containing the component (C), a cured product having a low dielectric constant and a low dielectric loss tangent can be obtained. The (C) inorganic filler can be used alone or two or more kinds can be used in any ratio in combination.

[0094] (C) The inorganic filler is contained in the resin composition layer in the form of particles. As the material of the (C) inorganic filler, an inorganic compound is used. Examples of the material of the (C) inorganic filler include silica, alumina, 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 phosphotungstate. Among them, 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 silica.

[0095] Examples of commercially available products of the (C) inorganic filler include "SP60-05" and "SP507-05" manufactured by Nippon Steel Chemical & Materials Co., Ltd.; "YC100C", "YA050C", "YA050C-MJE", "YA010C", "SC2500SQ", "SO-C4", "SO-C2", and "SO-C1" manufactured by Admatechs Co., Ltd.; "UFP-30", "DAW-03", and "FB-105FD" manufactured by Denka Co., Ltd.; "Silfil NSS-3N", "Silfil NSS-4N", and "Silfil NSS-5N" manufactured by Tokuyama Corporation; "CellSpheres" and "MGH-005" manufactured by Taiheiyo Cement Corporation, etc.

[0096] (C) The average particle diameter of the inorganic filler is not particularly limited, preferably 10 μm or less, more preferably 5 μm or less, further preferably 3 μm or less, still further preferably 2 μm or less, and particularly preferably 1.5 μm or less. The lower limit of the average particle diameter of the inorganic filler is not particularly limited, preferably 0.01 μm or more, more preferably 0.05 μm or more, further preferably 0.1 μm or more, and particularly preferably 0.2 μm or more. The average particle diameter of the inorganic filler can be measured by the laser diffraction / scattering method based on the Mie scattering theory. Specifically, a particle size distribution of the inorganic filler can be produced on a volume basis by a laser diffraction scattering type particle size distribution measuring device, and the median particle diameter thereof can be measured as the average particle diameter. As the measurement sample, a sample obtained by weighing 100 mg of the inorganic filler and 10 g of methyl ethyl ketone in a vial and dispersing them ultrasonically for 10 minutes can be used. For the measurement sample, using a laser diffraction type particle size distribution measuring device, the light source wavelength is set to blue and red, and the volume-based particle size distribution of the inorganic filler is measured by the flow cell method, and the average particle diameter is calculated as the median particle diameter from the obtained particle size distribution. Examples of the laser diffraction type particle size distribution measuring device include "LA-960" manufactured by Horiba, Ltd.

[0097] (C) The specific surface area of the inorganic filler is not particularly limited, preferably 0.1 m 2 / g or more, more preferably 0.5 m 2 / g or more, further preferably 1 m 2 / g or more, particularly preferably 3 m 2 / g or more. The upper limit of the specific surface area of the inorganic filler is not particularly limited, preferably 100 m 2 / g or less, more preferably 70 m 2 / g or less, further preferably 50 m 2 / g or less, still further preferably 30 m 2 / g or less, particularly preferably 10 m 2 / g or less. The specific surface area of the inorganic filler is obtained by adsorbing nitrogen on the surface of the sample using a 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.

[0098] From the viewpoints of improving moisture resistance and dispersibility, (C) the inorganic filler is preferably treated with a surface treatment agent. Examples of the surface treatment agent include fluorosilane coupling agents, aminosilane coupling agents, epoxysilane coupling agents, mercaptosilane coupling agents, silane coupling agents, alkoxysilanes, organosilazane compounds, titanate coupling agents, etc. In addition, the surface treatment agent can be used alone or two or more thereof can be used in any combination.

[0099] Examples of commercially available surface treatment agents include, for example, "KBM403" (3-glycidoxypropyltrimethoxysilane), "KBM803" (3-mercaptopropyltrimethoxysilane), "KBE903" (3-aminopropyltriethoxysilane), "KBM573" (N-phenyl-3-aminopropyltrimethoxysilane), "SZ-31" (hexamethyldisilazane), "KBM103" (phenyltrimethoxysilane), "KBM-4803" (long-chain epoxy type silane coupling agent), "KBM-7103" (3,3,3-trifluoropropyltrimethoxysilane), etc., all manufactured by Shin-Etsu Chemical Co., Ltd.

[0100] From the viewpoint of improving the dispersibility of the inorganic filler, the degree of surface treatment with the surface treatment agent is preferably within a specified range. Specifically, 100% by mass of the inorganic filler is preferably surface-treated with 0.2% to 5% by mass of the surface treatment agent, more preferably 0.2% to 3% by mass, and still more preferably 0.3% to 2% by mass.

[0101] The degree of surface treatment with 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 still more preferably 0.2 mg / m 2 or more. On the other hand, from the viewpoint of preventing an increase in the melt viscosity of the resin composition layer or the melt viscosity in the sheet form, the amount of carbon per unit surface area of the inorganic filler is preferably 1.0 mg / m 2 or less, more preferably 0.8 mg / m 2 or less, and still more preferably 0.5 mg / m 2 or less.

[0102] (C) The amount of carbon per unit surface area of the inorganic filler can be measured after cleaning the surface-treated inorganic filler with a solvent (e.g., methyl ethyl ketone (MEK)). Specifically, an adequate amount of MEK is added as a solvent to the surface-treated inorganic filler with a surface treatment agent, and ultrasonic cleaning is performed at 25 °C for 5 minutes. After removing the supernatant and drying the solid component, a carbon analyzer can be used to measure the amount of carbon per unit surface area of the inorganic filler. As the carbon analyzer, "EMIA-320V" manufactured by Horiba, Ltd. can be used, etc.

[0103] When the non-volatile components in the resin composition layer are set to 100% by mass, the content of (C) the inorganic filler is preferably 35% by mass or more, more preferably 40% by mass or more, and still more preferably 50% by mass or more. The upper limit is preferably 85% by mass or less, more preferably 80% by mass or less, and still more preferably 75% by mass or less.

[0104] -(D) Thermosetting resin- The resin composition layer may contain (D) a thermosetting resin as the (D) component. The (D) thermosetting resin as the (D) component does not include substances belonging to the (A) to (C) components. The type of the (D) thermosetting resin is not particularly limited as long as it can be cured by heat. The (D) thermosetting resin can be used alone or in combination of two or more.

[0105] Examples of the (D) thermosetting resin include epoxy resin, free radical polymerizable resin, phenol resin, cyanate ester resin, active ester resin, carbodiimide resin, acid anhydride resin, amine resin, benzoxazine resin, and thiol resin, etc. The thermosetting resin can be used alone or in combination of two or more.

[0106] From the viewpoint of significantly obtaining the effects of the present invention, the (D) thermosetting resin is preferably used in combination of an epoxy resin and a resin capable of reacting with the epoxy resin to cure the resin composition layer. The resin capable of reacting with the epoxy resin to cure the resin composition layer is sometimes hereinafter referred to as a "curing agent". Examples of the curing agent include, for example, phenol resin, cyanate ester resin, active ester resin, carbodiimide resin, acid anhydride resin, amine resin, benzoxazine resin, thiol resin, etc. Among them, as the curing agent, phenol resin and active ester resin are preferred. The curing agent can be used alone or in combination of two or more. In one embodiment, the thermosetting resin contains an epoxy resin and a phenol resin.

[0107] Epoxy resin is a thermosetting resin having epoxy groups. Examples of epoxy resins include tetramethylbisphenol type epoxy resin, biphenyl type epoxy resin, naphthalene type epoxy resin, bisphenol A type epoxy resin, bisphenol F type epoxy resin, bisphenol S type epoxy resin, bisphenol AF type epoxy resin, dicyclopentadiene type epoxy resin, triphenol type epoxy resin, naphthol novolak type epoxy resin, phenol novolak type epoxy resin, tert-butyl-catechol type epoxy resin, naphthol type epoxy resin, anthracene type epoxy resin, glycidylamine type epoxy resin, glycidyl ester type epoxy resin, cresol novolak type epoxy resin, phenol aralkyl type epoxy resin, linear aliphatic epoxy resin, epoxy resin having a butadiene structure, alicyclic epoxy resin, heterocyclic epoxy resin, epoxy resin containing a spiro ring, cyclohexane type epoxy resin, cyclohexanedimethanol type epoxy resin, naphthalene ether type epoxy resin, trimethylol type epoxy resin, tetraphenylethane type epoxy resin, isocyanurate type epoxy resin, phenolphthalimidine type epoxy resin, etc. The epoxy resin can be used alone or in combination of two or more.

[0108] (D) Among thermosetting resins, as the epoxy resin, it is preferably an epoxy resin having two or more epoxy groups in one molecule. With respect to 100% by mass of the epoxy resin, the proportion of the epoxy resin having two or more epoxy groups in one molecule is preferably 50% by mass or more, more preferably 60% by mass or more, particularly preferably 70% by mass or more, and usually 100% by mass or less.

[0109] Among epoxy resins, there are 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"). In the resin composition layer, as the epoxy resin, it may contain only the liquid epoxy resin, or may contain only the solid epoxy resin, or may also contain a combination of the liquid epoxy resin and the solid epoxy resin.

[0110] As the liquid epoxy resin, a liquid epoxy resin having two or more epoxy groups in one molecule is preferred.

[0111] As the liquid epoxy resin, bisphenol A type epoxy resin, bisphenol F type epoxy resin, bisphenol AF type epoxy resin, naphthalene type epoxy resin, glycidyl ester type epoxy resin, glycidylamine type epoxy resin, phenol novolak type epoxy resin, alicyclic epoxy resin having an ester skeleton, cyclohexane type epoxy resin, cyclohexanedimethanol type epoxy resin, and epoxy resin having a butadiene structure are preferred, and glycidylamine type epoxy resin, bisphenol A type epoxy resin, and bisphenol F type epoxy resin are more preferred, and bisphenol A type epoxy resin and bisphenol F type epoxy resin are further preferred.

[0112] As specific examples of the liquid epoxy resin, there can be mentioned "HP4032", "HP4032D", "HP4032SS" (naphthalene-type epoxy resin) manufactured by DIC Corporation; "828US", "828EL", "jER828EL", "825", "EPIKOTE 828EL" (bisphenol A-type epoxy resin) manufactured by Mitsubishi Chemical Corporation; "jER807", "1750" (bisphenol F-type epoxy resin) manufactured by Mitsubishi Chemical Corporation; "jER152" (phenol novolac-type epoxy resin) manufactured by Mitsubishi Chemical Corporation; "630", "630LSD", "604" (glycidylamine-type epoxy resin) manufactured by Mitsubishi Chemical Corporation; "ED-523T" (Glycirol-type epoxy resin) manufactured by ADEKA Corporation; "EP-3950L", "EP-3980S" (glycidylamine-type epoxy resin) manufactured by ADEKA Corporation; "EP-4088S" (dicyclopentadiene-type epoxy resin) manufactured by ADEKA Corporation; "ZX1059" (a mixture of bisphenol A-type epoxy resin and bisphenol F-type epoxy resin) manufactured by Nippon Steel Chemical & Material Co., Ltd.; "EX-721" (glycidyl ester-type epoxy resin) manufactured by Nagase ChemteX Corporation; "CELLOXIDE 2021P" (alicyclic epoxy resin having an ester skeleton) manufactured by Daicel Corporation; "PB-3600", "JP-100", "JP-200" (epoxy resin having a butadiene structure (epoxidized polybutadiene resin)) manufactured by Nippon Soda Co., Ltd.; "ZX1658", "ZX1658GS" (liquid 1,4-glycidylcyclohexane-type epoxy resin) manufactured by Nippon Steel Chemical & Material Co., Ltd., etc. They can be used alone or in combination of two or more kinds.

[0113] As the solid epoxy resin, a solid epoxy resin having 3 or more epoxy groups in one molecule is preferred, and an aromatic solid epoxy resin having 3 or more epoxy groups in one molecule is more preferred.

[0114] As the solid epoxy resin, tetramethylbisphenol-type epoxy resin (xylenol-type epoxy resin), naphthalene-type epoxy resin, naphthalene-type tetrafunctional epoxy resin, naphthol novolac-type epoxy resin, cresol novolac-type epoxy resin, dicyclopentadiene-type epoxy resin, triphenol-type epoxy resin, naphthol-type epoxy resin, biphenyl-type epoxy resin, naphthyl ether-type epoxy resin, anthracene-type epoxy resin, bisphenol A-type epoxy resin, bisphenol AF-type epoxy resin, phenol aralkyl-type epoxy resin, tetraphenylethane-type epoxy resin, phenol benzopyrrolidone-type epoxy resin are preferred, and xylenol-type epoxy resin and biphenyl-type epoxy resin are more preferred.

[0115] As specific examples of the solid epoxy resin, there can be mentioned "HP4032H" (naphthalene-type epoxy resin) manufactured by DIC Corporation; "HP-4700", "HP-4710" (naphthalene-type tetrafunctional epoxy resin) manufactured by DIC Corporation; "N-690" (cresol novolak-type epoxy resin) manufactured by DIC Corporation; "N-695" (cresol novolak-type epoxy resin) manufactured by DIC Corporation; "HP-7200", "HP-7200HH", "HP-7200H", "HP-7200L" (dicyclopentadiene-type epoxy resin) manufactured by DIC Corporation; "EXA-7311", "EXA-7311-G3", "EXA-7311-G4", "EXA-7311-G4S", "HP6000" (naphthyl ether-type epoxy resin) manufactured by DIC Corporation; "EPPN-502H" (triphenol-type epoxy resin) manufactured by Nippon Kayaku Co., Ltd.; "NC7000L" (naphthol novolak-type epoxy resin) manufactured by Nippon Kayaku Co., Ltd.; "NC3000H", "NC3000", "NC3000L", "NC3000FH", "NC3100" (biphenyl-type epoxy resin) manufactured by Nippon Kayaku Co., Ltd.; "ESN475V", "ESN4100V" (naphthalene-type epoxy resin) manufactured by Nippon Steel Chemical Co., Ltd.; "ESN485" (naphthol-type epoxy resin) manufactured by Nippon Steel Chemical Co., Ltd.; "ESN375" (dihydroxynaphthalene-type epoxy resin) manufactured by Nippon Steel Chemical Co., Ltd.; "YX4000H", "YX4000", "YX4000HK", "YL7890" (xylenol-type epoxy resin) manufactured by Mitsubishi Chemical Corporation; "YL6121" (biphenyl-type epoxy resin) manufactured by Mitsubishi Chemical Corporation; "YX8800" (anthracene-type epoxy resin) manufactured by Mitsubishi Chemical Corporation; "YX7700" (phenol aralkyl-type epoxy resin) manufactured by Mitsubishi Chemical Corporation; "PG-100", "CG-500" manufactured by Osaka Gas Chemical Co., Ltd.; "YX7760" (bisphenol AF-type epoxy resin) manufactured by Mitsubishi Chemical Corporation; "YL7800" (fluorene-type epoxy resin) manufactured by Mitsubishi Chemical Corporation; "jER1010" (bisphenol A-type epoxy resin) manufactured by Mitsubishi Chemical Corporation; "jER1031S" (tetraphenylethane-type epoxy resin) manufactured by Mitsubishi Chemical Corporation; "WHR991S" (phenol benzopyrrolidone-type epoxy resin) manufactured by Nippon Kayaku Co., Ltd. etc. They can be used alone or in combination of two or more.

[0116] When using a liquid epoxy resin and a solid epoxy resin in combination as the epoxy resin, the mass ratio thereof (liquid epoxy resin: solid epoxy resin) is preferably 1:0.01 to 1:20, more preferably 1:0.05 to 1:10, and particularly preferably 1:0.1 to 1:7.

[0117] The epoxy equivalent of the epoxy resin is preferably from 50 g / eq. to 5000 g / eq., more preferably from 60 g / eq. to 3000 g / eq., still more preferably from 80 g / eq. to 2000 g / eq., and particularly preferably from 110 g / eq. to 1000 g / eq. The epoxy equivalent represents the mass of the resin per 1 equivalent of epoxy groups. The epoxy equivalent can be measured according to JIS K7236.

[0118] The weight-average molecular weight (Mw) of the epoxy resin is preferably from 100 to 5000, more preferably from 250 to 3000, still more preferably from 400 to 1500. The weight-average molecular weight of the resin can be measured by gel permeation chromatography (GPC) as a value in terms of polystyrene.

[0119] When the non-volatile components in the resin composition layer are set to 100% by mass, the content of the epoxy resin as the (D) thermosetting resin is preferably 1% by mass or more, more preferably 5% by mass or more, particularly preferably 10% by mass or more, preferably 45% by mass or less, more preferably 40% by mass or less, and particularly preferably 30% by mass or less.

[0120] When the resin components in the resin composition layer are set to 100% by mass, the content of the epoxy resin as the (D) thermosetting resin is preferably 20% by mass or more, more preferably 25% by mass or more, particularly preferably 30% by mass or more, preferably 75% by mass or less, more preferably 70% by mass or less, and particularly preferably 65% by mass or less.

[0121] As the radically polymerizable resin as the (D) component, as long as it has 1 or more (preferably 2 or more) radically polymerizable unsaturated groups in 1 molecule, its type is not particularly limited. Examples of the radically polymerizable resin include resins having 1 or more selected from maleimide group, vinyl group, allyl group, styryl group, vinylphenyl group, acryloyl group, methacryloyl group, fumaroyl group, and maleoyl group as the radically polymerizable unsaturated groups. Among them, from the viewpoint of significantly obtaining the effects of the present invention, the radically polymerizable resin is preferably a maleimide resin.

[0122] As a maleimide resin, as long as it has one or more (preferably two or more) maleimide groups (2,5-dihydro-2,5-dioxo-1H-pyrrol-1-yl) in one molecule, its type is not particularly limited. Examples of the maleimide resin include: (1) maleimide resins containing an aliphatic skeleton (preferably an aliphatic skeleton having 36 carbon atoms derived from a dimer diamine) such as "BMI-3000J", "BMI-5000", "BMI-1400", "BMI-1500", "BMI-1700", "BMI-689" (all manufactured by Designer Molecules Inc.), "SLK6895-T90" (manufactured by Shin-Etsu Chemical Co., Ltd.); (2) maleimide resins containing an indane skeleton described in Japanese Invention Association Publication Technical Report Public Technology No. 2020-500211; (3) maleimide resins containing an aromatic ring skeleton directly bonded to the nitrogen atom of the maleimide group such as "MIR-3000-70MT" (manufactured by Nippon Kayaku Co., Ltd.), "BMI-4000" (manufactured by Daiwa Kasei Co., Ltd.), "BMI-80" (manufactured by KI Kasei Co., Ltd.).

[0123] As a (meth)acrylic resin, as long as it has one or more (preferably two or more) (meth)acryloyl groups in one molecule, its type is not particularly limited, and it may also be a monomer or an oligomer. Here, a term such as "(meth)acryloyl group" is a general term for an acryloyl group and a methacryloyl group. Examples of the (meth)acrylic resin include, in addition to (meth)acrylate monomers, (meth)acrylic resins such as "A-DOG" (manufactured by Shin-Nakamura Chemical Co., Ltd.), "DCP-A" (manufactured by Kyoeisha Chemical Co., Ltd.), "NPGDA", "FM-400", "R-687", "THE-330", "PET-30", "DPHA" (all manufactured by Nippon Kayaku Co., Ltd.).

[0124] Regarding the content of the free-radical polymerizable resin as the (D) thermosetting resin, when the non-volatile component in the resin composition layer is set to 100% by mass, it is preferably 1% by mass or more, more preferably 1.5% by mass or more, further preferably 2% by mass or more, preferably 10% by mass or less, more preferably 5% by mass or less, and further preferably 3% by mass or less.

[0125] Regarding the content of the free-radical polymerizable resin as the (D) thermosetting resin, when the resin component in the resin composition layer is set to 100% by mass, it is preferably 1% by mass or more, more preferably 2% by mass or more, further preferably 3% by mass or more, preferably 15% by mass or less, more preferably 10% by mass or less, and further preferably 8% by mass or less.

[0126] As the phenolic resin, a compound having one or more, preferably two or more hydroxyl groups bonded to an aromatic ring such as a benzene ring or a naphthalene ring in one molecule can be used. When the phenolic resin is combined with an epoxy resin, it can react with the epoxy resin to cure the resin composition layer, and thus is sometimes referred to as a "phenolic curing agent". From the viewpoint of significantly obtaining the effects of the present invention, the phenolic resin is preferably a phenolic resin having a novolak structure. In addition, from the viewpoint of adhesion, a nitrogen-containing phenolic resin is preferred, and a phenolic resin containing a triazine skeleton is more preferred. Among them, from the viewpoint of significantly obtaining the effects of the present invention, a linear novolak resin containing a triazine skeleton is preferred. Specific examples of the phenolic resin include, for example, "MEH-7700", "MEH-7810", "MEH-7851" manufactured by Meikwa Kasei Co., Ltd., "NHN", "CBN", "GPH" manufactured by Nippon Kayaku Co., Ltd., "SN-170", "SN-180", "SN-190", "SN-475", "SN-485", "SN-495", "SN-375", "SN-395" manufactured by Nippon Steel Chemical & Material Co., Ltd., "LA-7052", "LA-7054", "LA-3018", "LA-3018-50P", "LA-1356", "TD2090", "TD-2090-60M", "KA-1163" manufactured by DIC Corporation, etc.

[0127] As the active ester resin, it is generally preferable to use compounds having two or more highly reactive ester groups in one molecule, such as phenolic esters, thiophenolic esters, N-hydroxyamine esters, esters of heterocyclic hydroxy compounds, etc. When combined with an epoxy resin, the active ester resin can react with the epoxy resin to cure the resin composition layer, and thus is sometimes referred to as an "active ester-based curing agent". The active ester resin is preferably a resin obtained by a condensation reaction of a carboxylic acid compound and / or a thiocarboxylic acid compound with a hydroxy compound and / or a thiol compound. In particular, from the viewpoint of improving the swelling resistance to high-temperature reflow soldering, 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 the carboxylic acid compound include benzoic acid, acetic acid, succinic acid, maleic acid, itaconic acid, phthalic acid, isophthalic acid, terephthalic acid, pyromellitic acid, etc. Examples of the phenol compound or naphthol compound include hydroquinone, resorcinol, bisphenol A, bisphenol F, bisphenol S, phenolphthalin, 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, phloroglucinol, pyrogallol, dicyclopentadiene-type diphenol compound, novolak resin, etc. Here, the "dicyclopentadiene-type diphenol compound" refers to a diphenol compound obtained by condensing two molecules of phenol in one molecule of dicyclopentadiene.

[0128] Specifically, as the active ester resin, a dicyclopentadiene-type active ester resin, a naphthalene-type active ester resin containing a naphthalene structure, an active ester resin containing an acetylated product of a novolak resin, and an active ester resin containing a benzoylated product of a novolak resin are preferred, and at least one selected from the dicyclopentadiene-type active ester resin and the naphthalene-type active ester resin is more preferred. As the dicyclopentadiene-type active ester resin, an active ester resin containing a dicyclopentadiene-type diphenol structure is preferred.

[0129] Regarding commercially available products of active ester resins, for example, as active ester resins containing a dicyclopentadiene-type diphenol structure, examples include "EXB9451", "EXB9460", "EXB9460S", "EXB-8000L", "EXB-8000L-65M", "EXB-8000L-65TM", "HPC-8000L-65TM", "HPC-8000L-65T", "HPC-8000", "HPC-8000-65T", "EXB-8000H" (manufactured by DIC Corporation); as active ester resins containing a naphthalene structure, examples include "EXB-8100L-65T", "EXB-8150-60T", "EXB-8150-62T", "EXB-9416-70BK", "HPC-8150-62T", "EXB-8" (manufactured by DIC Corporation); as active ester resins containing phosphorus, an example is "EXB9401" (manufactured by DIC Corporation); as active ester resins that are acetylated products of linear phenolic resins, an example is "DC808" (manufactured by Mitsubishi Chemical Corporation); as active ester resins that are benzoylated products of linear phenolic resins, examples include "YLH1026", "YLH1030", "YLH1048" (manufactured by Mitsubishi Chemical Corporation); as active ester resins containing a styryl group and a naphthalene structure, an example is "PC1300-02-65MA" (manufactured by AIR WATER Corporation), etc.

[0130] As the cyanate ester resin, a compound having one or more, preferably two or more, cyanate ester groups in one molecule can be used. The cyanate ester resin can react with the epoxy resin in the case of being combined with the epoxy resin to cure the resin composition layer, and thus is sometimes referred to as a "cyanate ester-based curing agent". Examples of the cyanate ester resin include, for example, bisphenol A dicyanate ester, polyphenol cyanate ester (oligo(3-methylidene-1,5-phenylene cyanate ester)), 4,4'-methylenebis(2,6-dimethylphenyl cyanate ester), 4,4'-ethylenediphenyl dicyanate ester, hexafluorobisphenol A dicyanate ester, 2,2-bis(4-cyanate ester phenyl) propane, 1,1-bis(4-cyanate ester phenyl methane), bis(4-cyanate ester-3,5-dimethylphenyl) methane, 1,3-bis(4-cyanate ester phenyl-1-(methylethylidene)) benzene, bis(4-cyanate ester phenyl) sulfide, and bis(4-cyanate ester phenyl) ether, etc., bifunctional cyanate ester resins; polyfunctional cyanate ester resins derived from linear phenolic resins and cresol phenolic resins, etc., and prepolymers obtained by triazine-forming a part of these cyanate ester resins. Specific examples of the cyanate ester resin include "PT30" and "PT60" (both are linear phenolic resin-type polyfunctional cyanate ester resins), "BA230", "BA230S75" (prepolymers formed by triazine-forming a part or all of bisphenol A dicyanate ester to form a trimer), etc., manufactured by arxada Corporation.

[0131] As the carbodiimide resin, a compound having one or more, preferably two or more carbodiimide structures in one molecule can be used. When combined with an epoxy resin, the carbodiimide resin can react with the epoxy resin to cure the resin composition layer, and thus is sometimes referred to as a "carbodiimide-based curing agent". Specific examples of the carbodiimide resin include: aliphatic biscarbodiimides such as tetramethylene-bis(tert-butylcarbodiimide) and cyclohexane bis(methylene-tert-butylcarbodiimide); biscarbodiimides such as phenylenebis(xylenylcarbodiimide) and other aromatic biscarbodiimides; aliphatic polycarbodiimides such as polyhexamethylene carbodiimide, polytrimethylhexamethylene carbodiimide, polycyclohexylene carbodiimide, poly(methylenebiscyclohexylene carbodiimide), and poly(isophorone carbodiimide); aromatic polycarbodiimides such as poly(phenylene carbodiimide), poly(naphthylene carbodiimide), poly(tolylene carbodiimide), poly(methyldiisopropylphenylene carbodiimide), poly(triethylphenylene carbodiimide), poly(diethylphenylene carbodiimide), poly(triisopropylphenylene carbodiimide), poly(diisopropylphenylene carbodiimide), poly(xylenylene carbodiimide), poly(tetramethylxylenylene carbodiimide), poly(methylenediphenylene carbodiimide), and poly[methylenebis(methylphenylene) carbodiimide] and other polycarbodiimides. Commercially available products of the carbodiimide resin include, for example, "CARBODILITE V-02B", "CARBODILITE V-03", "CARBODILITE V-04K", "CARBODILITE V-07", and "CARBODILITE V-09" manufactured by Nisshinbo Chemical Inc.; "Stabaxol P", "Stabaxol P400", "Hycasyl 510", etc. manufactured by Lanxess Corporation.

[0132] As the acid anhydride resin, a compound having one or more, preferably two or more acid anhydride groups in one molecule can be used. When combined with an epoxy group, the acid anhydride resin can react with the epoxy resin to cure the resin composition layer, and thus is sometimes referred to as an "acid anhydride-based curing agent". Specific examples of the acid anhydride resin 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, benzophenone tetracarboxylic dianhydride, biphenyltetracarboxylic dianhydride, naphthalenetetracarboxylic dianhydride, oxydiphthalic dianhydride, 3,3'-4,4'-diphenylsulfone tetracarboxylic dianhydride, 1,3,3a,4,5,9b-hexahydro-5-(tetrahydro-2,5-dioxo-3-furanyl)-naphtho[1,2-c]furan-1,3-dione, ethylene glycol bis(trimellitate), polymer-type acid anhydrides such as styrene-maleic acid resin obtained by copolymerizing styrene and maleic acid, etc. Commercially available products of the acid anhydride resin include, for example, "HNA-100", "MH-700", "MTA-15", "DDSA", "OSA" manufactured by Shin Nippon Rika Co., Ltd., "YH-306", "YH-307" manufactured by Mitsubishi Chemical Corporation, "HN-2200", "HN-5500" manufactured by Resonac Corporation; "EF-30", "EF-40", "EF-60", "EF-80", etc. manufactured by Cray Valley Company.

[0133] As the amine resin, a compound having one or more, preferably two or more amino groups in one molecule can be used. When combined with an epoxy group, the amine resin can react with the epoxy resin to cure the resin composition layer, and thus is sometimes referred to as an "amine-based curing agent". Examples of the amine resin include aliphatic amines, polyether amines, alicyclic amines, aromatic amines, etc. Among them, aromatic amines are preferred. The amine resin is preferably a primary amine or a secondary amine, and more preferably a primary amine. Specific examples of the amine resin include 4,4'-methylenebis(2,6-dimethylaniline), 4,4'-diaminodiphenylmethane, 4,4'-diaminodiphenylsulfone, 3,3'-diaminodiphenylsulfone, m-phenylenediamine, m-xylenediamine, diethyltoluenediamine, 4,4'-diaminodiphenyl ether, 3,3'-dimethyl-4,4'-diaminobiphenyl, 2,2'-dimethyl-4,4'-diaminobiphenyl, 3,3'-dihydroxybenzidine, 2,2-bis(3-amino-4-hydroxyphenyl)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, etc. Commercially available products of the amine resin include, for example, "SEIKACURE-S" manufactured by SEIKA Corporation; "KAYABOND C-200S", "KAYABOND C-100", "KAYAHARD A-A", "KAYAHARD A-B", "KAYAHARD A-S" manufactured by Nippon Kayaku Co., Ltd.; "EpicureW" manufactured by Mitsubishi Chemical Corporation; "DTDA" manufactured by Sumitomo Seika Chemicals Co., Ltd., etc.

[0134] When combined with an epoxy resin, the benzoxazine resin can react with the epoxy resin to cure the resin composition layer, and thus is sometimes referred to as a "benzoxazine-based curing agent". Specific examples of the benzoxazine resin include "JBZ-OP100D", "ODA-BOZ" manufactured by JFE Chemical Corporation; "HFB2006M" manufactured by Showa Highpolymer Co., Ltd.; "P-d", "F-a" manufactured by Shikoku Kasei Kogyo Co., Ltd., etc.

[0135] When combined with an epoxy resin, the thiol resin can react with the epoxy resin to cure the resin composition layer, and thus is sometimes referred to as a "thiol-based curing agent". Examples of the thiol resin include trimethylolpropane tris(3-mercaptopropionate), pentaerythritol tetra(3-mercaptobutyrate), tris(3-mercaptopropyl)isocyanurate, etc.

[0136] The active group equivalent weight of the curing agent is preferably 50 g / eq. to 3000 g / eq., more preferably 100 g / eq. to 1000 g / eq., still more preferably 100 g / eq. to 500 g / eq., and particularly preferably 100 g / eq. to 300 g / eq. The active group equivalent weight is the mass of the curing agent per 1 equivalent of the active group.

[0137] The weight average molecular weight (Mw) of the curing agent is preferably 100 to 5000, more preferably 250 to 3000, still more preferably 400 to 1500. The weight average molecular weight of the resin can be measured by gel permeation chromatography (GPC) as a value in terms of polystyrene conversion.

[0138] When the number of epoxy groups in the epoxy resin is set to 1, the number of active groups in the curing agent is preferably 0.01 or more, more preferably 0.05 or more, still more preferably 0.1 or more, preferably 5 or less, more preferably 3 or less, and particularly preferably 2 or less. The "number of epoxy groups in the epoxy resin" represents the value obtained by summing up all the values obtained by dividing the mass of the epoxy resin present in the resin composition layer by the epoxy equivalent weight. In addition, the "number of active groups in the curing agent" represents the value obtained by summing up all the values obtained by dividing the mass of the curing agent present in the resin composition layer by the active group equivalent weight.

[0139] When the non-volatile components in the resin composition layer are set to 100% by mass, the content of the curing agent as the (D) thermosetting resin is preferably 1% by mass or more, more preferably 3% by mass or more, still more preferably 5% by mass or more, preferably 20% by mass or less, more preferably 15% by mass or less, and still more preferably 10% by mass or less.

[0140] When the resin components in the resin composition layer are set to 100% by mass, the content of the curing agent as the (D) thermosetting resin is preferably 10% by mass or more, more preferably 15% by mass or more, still more preferably 20% by mass or more, preferably 50% by mass or less, more preferably 45% by mass or less, and still more preferably 40% by mass or less.

[0141] When the non-volatile components in the resin composition layer are set to 100% by mass, the content of the (D) thermosetting resin is preferably 10% by mass or more, more preferably 15% by mass or more, still more preferably 20% by mass or more, preferably 65% by mass or less, more preferably 50% by mass or less, still more preferably 45% by mass or less, 40% by mass or less.

[0142] From the viewpoint of significantly obtaining the effects of the present invention, when the resin component in the resin composition layer is set to 100% by mass, the content of (D) thermosetting resin is preferably 40% by mass or more, more preferably 50% by mass or more, still more preferably 60% by mass or more, preferably 90% by mass or less, more preferably 88% by mass or less, still more preferably 85% by mass or less.

[0143] When the total content of components (A) to (D) is set to 100% by mass of the non-volatile components in the resin composition layer, it is preferably 15% by mass or more, more preferably 20% by mass or more, still more preferably 25% by mass or more, preferably 65% by mass or less, more preferably 60% by mass or less, still more preferably 60% by mass or less, 55% by mass or less, 50% by mass or less.

[0144] -(E) thermoplastic resin- The resin composition layer may contain (E) thermoplastic resin as component (E). The (E) thermoplastic resin as this component (E) does not include substances belonging to the above components (A) to (D). Component (E) may be used alone as one kind, or two or more kinds may be used in combination.

[0145] Examples of the (E) thermoplastic resin include polyvinyl acetal resin, polyolefin resin, polybutadiene resin, polyamideimide resin, polyetherimide resin, polysulfone resin, polyethersulfone resin, polyphenylene ether resin, polycarbonate resin, polyetheretherketone resin, polyester resin, etc. The (E) thermoplastic resin may be used alone as one kind, or two or more kinds may be used in combination.

[0146] Examples of the polyvinyl acetal resin include polyvinyl formal resin and polyvinyl butyral resin, and polyvinyl butyral resin is preferred. Specific examples of the polyvinyl acetal resin include S-LEC BH series, BX series (e.g., BX-5Z), KS series (e.g., KS-1), BL series, BM series, etc. manufactured by Sekisui Chemical Co., Ltd.

[0147] Examples of the polyolefin resin include ethylene-based copolymer resins such as low-density polyethylene, ultra-low-density polyethylene, high-density polyethylene, ethylene-vinyl acetate copolymer, ethylene-ethyl acrylate copolymer, and ethylene-methyl acrylate copolymer; polyolefin-based polymers such as polypropylene and ethylene-propylene block copolymer.

[0148] Examples of the polybutadiene resin include resins containing a hydrogenated polybutadiene skeleton, polybutadiene resins containing a hydroxyl group, polybutadiene resins containing a phenolic hydroxyl group, polybutadiene resins containing a carboxyl group, polybutadiene resins containing an acid anhydride group, polybutadiene resins containing an epoxy group, polybutadiene resins containing an isocyanate group, polybutadiene resins containing a urethane group, polyphenylene ether-polybutadiene resins, and the like.

[0149] Specific examples of the polyamideimide resin include "VYLOMAX HR11NN" and "VYLOMAX HR16NN" manufactured by Toyobo Co., Ltd. Specific examples of the polyamideimide resin also include modified polyamideimides such as "KS9100" and "KS9300" (polyamideimide containing a polysiloxane skeleton) manufactured by Resonac Co., Ltd.

[0150] Specific examples of the polyethersulfone resin include "PES5003P" manufactured by Sumitomo Chemical Co., Ltd.

[0151] Specific examples of the polysulfone resin include polysulfones "P1700" and "P3500" manufactured by Solvay Advanced Polymers.

[0152] Specific examples of the polyphenylene ether resin include "NORYL SA90" manufactured by SABIC. Specific examples of the polyetherimide resin include "Ultem" manufactured by GE. The polyphenylene ether resin may have one or more (preferably two or more) styryl groups or vinylphenyl groups in one molecule. Examples of such polyphenylene ether resins include, in addition to styrene monomers, "OPE-2St", "OPE-2St 1200", and "OPE-2St 2200" (all manufactured by Mitsubishi Gas Chemical Company).

[0153] Examples of the polycarbonate resin include carbonate resins containing a hydroxyl group, carbonate resins containing a phenolic hydroxyl group, carbonate resins containing a carboxyl group, carbonate resins containing an acid anhydride group, carbonate resins containing an isocyanate group, carbonate resins containing a urethane group, and the like. Specific examples of the polycarbonate resin include "FPC0220" manufactured by Mitsubishi Gas Chemical Company, "T6002" and "T6001" (polycarbonate diol) manufactured by Asahi Kasei Corporation, and "C-1090", "C-2090", and "C-3090" (polycarbonate diol) manufactured by Kuraray Co., Ltd. Specific examples of the polyetheretherketone resin include "Sumiploy K" manufactured by Sumitomo Chemical Co., Ltd.

[0154] Examples of the polyester resin include polyethylene terephthalate resin, polyethylene naphthalate resin, polybutylene terephthalate resin, polybutylene naphthalate resin, polypropylene terephthalate resin, polypropylene naphthalate resin, polycyclohexanedimethylene terephthalate resin, and the like.

[0155] (E) The thermoplastic resin may also be an organic filler that is insoluble in the solvent described below and exists in the resin composition layer in the form of particles. Examples of the organic filler include rubber particles, polyamide fine particles, silicone particles, core-shell type particles, etc., and rubber particles are preferred.

[0156] Examples of the rubber component contained in the rubber particles include olefin-based thermoplastic elastomers such as polybutadiene, polyisoprene, polychloroprene, ethylene-vinyl acetate copolymer, styrene-butadiene copolymer, styrene-isoprene copolymer, styrene-isobutene copolymer, acrylonitrile-butadiene copolymer, isoprene-isobutene copolymer, isobutene-butadiene copolymer, ethylene-propylene-diene terpolymer, ethylene-propylene-butene terpolymer, etc.; acrylic-based thermoplastic elastomers such as poly(propyl) (meth)acrylate, poly(butyl) (meth)acrylate, poly(cyclohexyl) (meth)acrylate, poly(octyl) (meth)acrylate, etc. Thermoplastic elastomers are preferred, and styrene-butadiene copolymers are more preferred. Furthermore, silicone-based rubbers such as polyorganosiloxane rubber may be mixed in the rubber component. The glass transition temperature of the rubber component contained in the rubber particles may be, for example, 0 °C or lower, preferably -10 °C or lower, more preferably -20 °C or lower, and further preferably -30 °C or lower.

[0157] As the rubber particles, commercially available products can be used, and examples include "EXL2655" manufactured by Dow Chemical Japan Co., Ltd., "AC3401N", "AC3816N", etc. manufactured by AICA Industries Co., Ltd.

[0158] The so-called core-shell type rubber particles are particulate organic fillers formed by core particles containing the rubber components listed above and one or more shell portions covering them. Furthermore, the core-shell type rubber particles are preferably core-shell type graft copolymer rubber particles formed by core particles containing the rubber components listed above and a shell portion formed by graft copolymerizing a monomer component copolymerizable with the rubber component contained in the core particles. Here, the so-called core-shell type does not necessarily refer only to the type in which the core particles and the shell portion can be clearly distinguished, but also includes the type in which the boundary between the core particles and the shell portion is not clear, and the core particles may not be completely covered by the shell portion.

[0159] The rubber component preferably contains 40% by mass or more, more preferably 50% by mass or more, and still more preferably 60% by mass or more in the core-shell graft copolymer particles. The upper limit of the content of the rubber component in the core-shell graft copolymer particles is not particularly limited, but from the viewpoint of sufficiently covering the core particles with the shell portion, it is preferably 95% by mass or less, 90% by mass or less, for example.

[0160] The monomer components forming the shell portion of the core-shell rubber particles include, for example, (meth)acrylic acid esters such as methyl (meth)acrylate, ethyl (meth)acrylate, butyl (meth)acrylate, cyclohexyl (meth)acrylate, octyl (meth)acrylate, glycidyl (meth)acrylate; (meth)acrylic acid; N-substituted maleimides such as N-methylmaleimide and N-phenylmaleimide; maleimide; α,β-unsaturated carboxylic acids such as maleic acid and itaconic acid; aromatic vinyl compounds such as styrene, 4-vinyltoluene, and α-methylstyrene; (meth)acrylonitrile, etc. Among them, (meth)acrylic acid esters are preferred, and methyl (meth)acrylate is more preferred.

[0161] Examples of commercially available products of the core-shell graft copolymer particles include "CHT" manufactured by Samsung SDI Co., Ltd.; "B602" manufactured by Techno UMG Co., Ltd.; "PARALOID EXL 2602", "PARALOID EXL 2603", "PARALOID EXL 2655", "PARALOID EXL 2311", "PARALOID EXL 2313", "PARALOID EXL 2315", "PARALOID KM 330", "PARALOID KM 336P", "PARALOID KCZ 201" manufactured by Dow Chemical Japan Co., Ltd.; "Metablen C-223A", "Metablen E-901", "Metablen S-2001", "Metablen W-450A", "Metablen SRK-200" manufactured by Mitsubishi Rayon Co., Ltd.; "Kaneace M-511", "Kaneace M-600", "Kaneace M-400", "Kaneace M-580", "Kaneace MR-01" manufactured by KANEKA Corporation, etc. They can be used alone or in combination of two or more.

[0162] The average particle diameter (average primary particle diameter) of the core-shell graft copolymer particles is not particularly limited, preferably 20 nm or more, more preferably 50 nm or more, still more preferably 80 nm or more, particularly preferably 100 nm or more, preferably 5000 nm or less, more preferably 2000 nm or less, still more preferably 1000 nm or less, particularly preferably 500 nm or less. The average particle diameter (average primary particle diameter) of the core-shell graft copolymer particles can be measured using a ζ-potential particle size distribution measuring device or the like.

[0163] (E) The weight average molecular weight (Mw) of the thermoplastic resin is preferably greater than 5000, more preferably 8000 or more, still more preferably 10000 or more, particularly preferably 20000 or more, preferably 100000 or less, more preferably 70000 or less, still more preferably 60000 or less, particularly preferably 50000 or less.

[0164] (E) When the non-volatile content of the resin composition layer is set to 100% by mass, the content of the (E) component is preferably 0.1% by mass or more, more preferably 0.5% by mass or more, still more preferably 1% by mass or more, preferably 5% by mass or less, more preferably 3% by mass or less, still more preferably 2% by mass or less.

[0165] (E) When the resin component of the resin composition layer is set to 100% by mass, the content of the (E) component is preferably 1% by mass or more, more preferably 1.5% by mass or more, still more preferably 2% by mass or more, preferably 5% by mass or less, more preferably 4% by mass or less, still more preferably 3% by mass or less.

[0166] When the content of the (E) component when the resin component in the resin composition layer is set to 100% by mass is set to e1, (a1 + b1) / (a1 + b1 + e1) is preferably 0.6 or more, more preferably 0.7 or more, still more preferably 0.8 or more, preferably 5 or less, more preferably 3 or less, still more preferably 1.5 or less. By adjusting the amounts of the (A) component, (B) component, and (E) component so that (a1 + b1) / (a1 + b1 + e1) is within the above range, the film flexibility can be further improved.

[0167] -(F) Flame retardant- The resin composition layer may contain a (F) flame retardant as the (F) component. The (F) flame retardant as the (F) component does not include substances belonging to the above (A) to (E) components. By containing the (F) flame retardant, the (F) flame retardant reacts with the epoxy resin in the (D) component, and the glass transition temperature and flame retardancy of the cured product can be further improved. The (F) component can be used alone or in combination of two or more.

[0168] Examples of the (F) flame retardant include, for example, phosphazene compounds, organophosphorus flame retardants, organonitrogen-containing phosphorus compounds, nitrogen compounds, organosilicon flame retardants, metal hydroxides, etc., and phosphazene compounds are preferred. The flame retardant can be used alone as one kind, or two or more kinds can be used in combination.

[0169] The phosphazene compound is not particularly limited as long as it is a cyclic compound composed of nitrogen and phosphorus, and the phosphazene compound is preferably a phosphazene compound having phenolic hydroxyl groups.

[0170] Specific examples of the phosphazene compound include, for example, "SPH-100", "SPS-100", "SPB-100", "SPE-100" manufactured by Otsuka Chemical Co., Ltd., "FP-100", "FP-110", "FP-300", "FP-400" manufactured by Fushimi Pharmaceutical Co., Ltd., etc., and "SPH-100" manufactured by Otsuka Chemical Co., Ltd. is preferred.

[0171] As the flame retardant other than the phosphazene compound, commercially available products can be used, and examples include "HCA-HQ" manufactured by Mitsuho Corporation, "PX-200" manufactured by Daihachi Chemical Industry Co., Ltd., etc. As the flame retardant, a flame retardant that is difficult to hydrolyze is preferred. For example, 10-(2,5-dihydroxyphenyl)-10H-9-oxa-10-phosphaphenanthrene-10-oxide, etc. are preferred.

[0172] When the non-volatile components in the resin composition layer are set to 100% by mass, the content of the (F) flame retardant is preferably 0.1% by mass or more, more preferably 0.5% by mass or more, further preferably 1% by mass or more, preferably 5% by mass or less, more preferably 3% by mass or less, and further preferably 2% by mass or less.

[0173] When the resin components in the resin composition layer are set to 100% by mass, the content of the (F) flame retardant is preferably 1% by mass or more, more preferably 1.5% by mass or more, further preferably 2% by mass or more, preferably 15% by mass or less, more preferably 10% by mass or less, and further preferably 8% by mass or less.

[0174] When the total content of the components (A) to (D) and the component (F) is set to 100% by mass of the non-volatile components in the resin composition layer, it is preferably 15% by mass or more, more preferably 20% by mass or more, further preferably 25% by mass or more, preferably 65% by mass or less, more preferably 60% by mass or less, and further preferably 60% by mass or less, 55% by mass or less, 50% by mass or less.

[0175] -(G) Curing accelerator- The resin composition layer may contain (G) a curing accelerator as the component (G). The (G) curing accelerator as the component (G) does not contain substances belonging to the above components (A) to (F). The (G) curing accelerator has a function as a curing catalyst that promotes the curing of the epoxy resin in the component (D).

[0176] As the (G) curing accelerator, a compound that promotes the curing of the epoxy resin can be used. As such a (G) curing accelerator, for example, a phosphorus-based curing accelerator, a urea-based curing accelerator, a guanidine-based curing accelerator, an imidazole-based curing accelerator, a metal-based curing accelerator, an amine-based curing accelerator, etc. can be cited. The (G) curing accelerator can be used alone as one kind, or two or more kinds can be used in combination.

[0177] Phosphorus curing accelerators include, for example, tetrabutylphosphonium bromide, tetrabutylphosphonium chloride, tetrabutylphosphonium acetate, tetrabutylphosphonium decanoate, tetrabutylphosphonium laurate, bis(tetrabutylphosphonium)pyromellitate, tetrabutylphosphonium hexahydrophthalate, tetrabutylphosphonium 2,6-bis[(2-hydroxy-5-methylphenyl)methyl]-4-methylphenolate, di-tert-butylmethylphosphonium tetraphenylborate and other aliphatic phosphonium salts; methyltriphenylphosphonium bromide, ethyltriphenylphosphonium bromide, propyltriphenylphosphonium bromide, butyltriphenylphosphonium bromide, benzyltriphenylphosphonium chloride, tetraphenylphosphonium bromide, p-tolyltriphenylphosphonium tetraphenylphosphonium; Aromatic phosphonium salts such as p-tolyl borate, tetraphenylphosphonium tetraphenyl borate, tetraphenylphosphonium tetra-p-tolyl borate, triphenylethylphosphonium tetraphenyl borate, tris(3-methylphenyl)ethylphosphonium tetraphenyl borate, tris(2-methoxyphenyl)ethylphosphonium tetraphenyl borate, (4-methylphenyl)triphenylphosphonium thiocyanate, tetraphenylphosphonium thiocyanate, butyltriphenylphosphonium thiocyanate; aromatic phosphine-borane complexes such as triphenylphosphine-triphenylborane; aromatic phosphine-quinone addition reactants such as triphenylphosphine-p-benzoquinone addition reactants; tributylphosphine, tri-tert-butylphosphine, trioctylphosphine, di-tert-butyl(2-butyl)phosphine aliphatic phosphines such as dibutylphenylphosphine, di-tert-butylphenylphosphine, methyldiphenylphosphine, ethyldiphenylphosphine, butyldiphenylphosphine, diphenylcyclohexylphosphine, triphenylphosphine, tri-o-tolylphosphine, tri-m-tolylphosphine, tri-p-tolylphosphine, tri(4-ethylphenyl)phosphine, tri(4-propylphenyl)phosphine, tri(4-isopropylphenyl)phosphine, tri(4-butylphenyl)phosphine, tri(4-tert-butylphenyl)phosphine, tri(2,4-dimethylphenyl)phosphine, tri(2,5-dimethylphenyl)phosphine, tri(2,6-dimethylphenyl)phosphine Aromatic phosphines such as tris(diphenyl)phosphine, tris(3,5-dimethylphenyl)phosphine, tris(2,4,6-trimethylphenyl)phosphine, tris(2,6-dimethyl-4-ethoxyphenyl)phosphine, tris(2-methoxyphenyl)phosphine, tris(4-methoxyphenyl)phosphine, tris(4-ethoxyphenyl)phosphine, tris(4-tert-butoxyphenyl)phosphine, diphenyl-2-pyridylphosphine, 1,2-bis(diphenylphosphino)ethane, 1,3-bis(diphenylphosphino)propane, 1,4-bis(diphenylphosphino)butane, 1,2-bis(diphenylphosphino)acetylene, and 2,2'-bis(diphenylphosphino)diphenyl ether.

[0178] Examples of the urea-based curing accelerators include, for example: 1,1-dimethylurea; aliphatic dimethylureas such as 1,1,3-trimethylurea, 3-ethyl-1,1-dimethylurea, 3-cyclohexyl-1,1-dimethylurea, 3-cyclooctyl-1,1-dimethylurea; aromatic dimethylureas such as 3-phenyl-1,1-dimethylurea, 3-(4-chlorophenyl)-1,1-dimethylurea, 3-(3,4-dichlorophenyl)-1,1-dimethylurea, 3-(3-chloro-4-methylphenyl)-1,1-dimethylurea, 3-(2-methylphenyl)-1,1-dimethylurea, 3-(4-methylphenyl)-1,1-dimethylurea, 3-(3,4-dimethylphenyl)-1,1-dimethylurea, 3-(4-isopropylphenyl)-1,1-dimethylurea, 3-(4-methoxyphenyl)-1,1-dimethylurea, 3-(4-nitrophenyl)-1,1-dimethylurea, 3-[4-(4-methoxyphenoxy)phenyl]-1,1-dimethylurea, 3-[4-(4-chlorophenoxy)phenyl]-1,1-dimethylurea, 3-[3-(trifluoromethyl)phenyl]-1,1-dimethylurea, N,N-(1,4-phenylene)bis(N’,N’-dimethylurea), N,N-(4-methyl-1,3-phenylene)bis(N’,N’-dimethylurea) [toluene bisdimethylurea], etc.

[0179] Examples of the guanidine-based curing accelerators include, for example: dicyandiamide, 1-methylguanidine, 1-ethylguanidine, 1-cyclohexylguanidine, 1-phenylguanidine, 1-(o-tolyl)guanidine, dimethylguanidine, diphenylguanidine, trimethylguanidine, tetramethylguanidine, pentamethylguanidine, 1,5,7-triazabicyclo[4.4.0]dec-5-ene, 7-methyl-1,5,7-triazabicyclo[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, 1-(o-tolyl)biguanide, etc.

[0180] As imidazole-based curing accelerators, examples 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-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 other imidazole compounds, as well as adducts of imidazole compounds and epoxy resins. As commercially available products of imidazole-based curing accelerators, examples include "1B2PZ", "2E4MZ", "2MZA-PW", "2MZ-OK", "2MA-OK", "2MA-OK-PW", "2PHZ", "2PHZ-PW", "Cl1Z", "Cl1Z-CN", "Cl1Z-CNS", "C11Z-A" manufactured by Shikoku Kasei Kogyo Co., Ltd.; "P200-H50" etc. manufactured by Mitsubishi Chemical Corporation.

[0181] As metal-based curing accelerators, examples include organometallic complexes or organometallic salts of metals such as cobalt, copper, zinc, iron, nickel, manganese, tin, etc. Specific examples of organometallic complexes include organocobalt complexes such as cobalt(II) acetylacetonate, 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; organomanganese complexes such as manganese(II) acetylacetonate, etc. As organometallic salts, examples include zinc octoate, tin octoate, zinc naphthenate, cobalt naphthenate, tin stearate, zinc stearate, etc.

[0182] Examples of the amine-based curing accelerator include trialkylamines such as triethylamine and tributylamine; 4-dimethylaminopyridine, benzyldimethylamine, 2,4,6-tris(dimethylaminomethyl)phenol, 1,8-diazabicyclo(5,4,0)-undecene, and the like. As the amine-based curing accelerator, commercially available products can be used, and examples include "MY-25" manufactured by Ajinomoto Fine-Techno Co., Ltd.

[0183] (G) When the non-volatile content in the resin composition layer is set to 100% by mass, the content of the curing accelerator is preferably 0.01% by mass or more, more preferably 0.05% by mass or more, still more preferably 0.1% by mass or more, preferably 1.5% by mass or less, more preferably 1% by mass or less, and still more preferably 0.5% by mass or less.

[0184] (G) When the resin component in the resin composition layer is set to 100% by mass, the content of the curing accelerator is preferably 0.1% by mass or more, more preferably 0.2% by mass or more, still more preferably 0.3% by mass or more, preferably 5% by mass or less, more preferably 3% by mass or less, and still more preferably 2% by mass or less.

[0185] -(H) Other additives- The resin composition layer may contain (H) other additives as optional non-volatile components. Examples of the (H) other additives include, for example, elastomers (excluding substances belonging to component (A), component (B), and component (E)); polymerization initiators; organometallic compounds such as organic copper compounds, organic zinc compounds, and organic cobalt compounds; colorants such as phthalocyanine blue, phthalocyanine green, iodine green, diazo yellow, crystal violet, titanium oxide, and carbon black; polymerization inhibitors such as hydroquinone, catechol, pyrogallol, and phenothiazine; leveling agents such as silicone-based leveling agents and acrylic polymer-based leveling agents; thickeners such as Benton (bentonite) and montmorillonite; defoaming agents such as silicone-based defoaming agents, acrylic-based defoaming agents, fluorine-based defoaming agents, and vinyl resin-based defoaming agents; ultraviolet absorbers such as benzotriazole-based ultraviolet absorbers; adhesion improvers such as urea silane; adhesion imparting agents such as triazole-based adhesion imparting agents, tetrazole-based adhesion imparting agents, and triazine-based adhesion imparting agents; antioxidants such as hindered phenol-based antioxidants; fluorescent brighteners such as stilbene derivatives; surfactants such as fluorine-based surfactants and silicone-based surfactants; dispersants such as phosphate ester-based dispersants, polyoxyalkylene-based dispersants, acetylene-based dispersants, silicone-based dispersants, anionic dispersants, and cationic dispersants; stabilizers such as borate ester-based stabilizers, titanate ester-based stabilizers, aluminate ester-based stabilizers, zirconate ester-based stabilizers, isocyanate-based stabilizers, carboxylic acid-based stabilizers, and carboxylic anhydride-based stabilizers; photo-polymerization initiator assistants such as tertiary amines; photosensitizers such as pyrazolines, anthracenes, coumarins, xanthones, and thioxanthones. The (H) other additives may be used alone or in combination of two or more.

[0186] <(I) Solvent> In the resin composition layer, (I) a solvent can be further included as an optional volatile component in combination with non-volatile components such as the above components (A) to (H). As the (I) solvent, an organic solvent is usually used. Examples of the organic solvent include: ketone solvents such as acetone, methyl ethyl ketone, methyl isobutyl ketone, and cyclohexanone; ester solvents such as methyl acetate, ethyl acetate, butyl acetate, isobutyl acetate, isopentyl acetate, methyl propionate, ethyl propionate, and γ-butyrolactone; ether solvents such as tetrahydropyran, tetrahydrofuran, 1,4-dioxane, diethyl ether, diisopropyl ether, dibutyl ether, diphenyl ether, and anisole; alcohol solvents such as methanol, ethanol, propanol, butanol, and ethylene glycol; ether ester solvents such as 2-ethoxyethyl acetate, propylene glycol monomethyl ether acetate, diethylene glycol monoethyl ether acetate, ethyl diglycol acetate, γ-butyrolactone, and methyl methoxypropionate; ester alcohol solvents such as methyl lactate, ethyl lactate, and methyl 2-hydroxyisobutyrate; ether alcohol solvents such as 2-methoxypropanol, 2-methoxyethanol, 2-ethoxyethanol, propylene glycol monomethyl ether, and diethylene glycol monobutyl ether (butyl carbitol); amide solvents such as N,N-dimethylformamide, N,N-dimethylacetamide, and N-methyl-2-pyrrolidone; sulfoxide solvents such as dimethyl sulfoxide; nitrile solvents such as acetonitrile and propionitrile; aliphatic hydrocarbon solvents such as hexane, cyclopentane, cyclohexane, and methylcyclohexane; aromatic hydrocarbon solvents such as benzene, toluene, xylene, ethylbenzene, and trimethylbenzene, etc. The (I) solvent can be used alone or in combination of two or more.

[0187] The amount of the (I) solvent is not particularly limited. For example, it can be 60% by mass or less, 40% by mass or less, 30% by mass or less, 20% by mass or less, 15% by mass or less, or 10% by mass or less, or can be 0% by mass, relative to 100% by mass of all the components of the resin composition layer.

[0188] From the viewpoints of thinning the circuit board and providing a cured product with excellent insulation even when the cured product of the resin composition layer is a thin film, the thickness of the resin composition layer is preferably 100 μm or less, more preferably 80 μm or less, and still more preferably 55 μm or less. The lower limit of the thickness of the resin composition layer is not particularly limited and can usually be 5 μm or more, 10 μm or more, etc.

[0189] <Protective film> The resin sheet with a metal foil includes a protective film. By laminating the protective film on the resin sheet with a metal foil, it is possible to suppress the adhesion of debris, etc. or the generation of damage on the surface of the resin composition layer.

[0190] Examples of the protective film include a film formed of a plastic material, a metal foil, and a release paper, and a film formed of a plastic material and a metal foil are preferred.

[0191] When using a film formed of a plastic material as the protective film, examples of the plastic material include polyesters such as polyethylene terephthalate (hereinafter sometimes simply referred to as "PET"), polyethylene naphthalate (hereinafter sometimes simply referred to as "PEN"), polycarbonate (hereinafter sometimes simply referred to as "PC"), acrylic polymers such as polymethyl methacrylate (PMMA), cyclic polyolefins, triacetyl cellulose (TAC), polyether sulfide (PES), polyether ketone, polyimide, etc. Among them, polyethylene terephthalate and polyethylene naphthalate are preferred, and inexpensive polyethylene terephthalate is particularly preferred.

[0192] When using a metal foil as the protective film, examples of the metal foil include copper foil, aluminum foil, etc., and copper foil is preferred. As the copper foil, a foil formed of single metal of copper can be used, or a foil formed of an alloy of copper and other metals (such as tin, chromium, silver, magnesium, nickel, zirconium, silicon, titanium, etc.) can be used.

[0193] For the protective film, the surface joined to the resin composition layer can be subjected to matting treatment, corona treatment, antistatic treatment.

[0194] In addition, as the protective film, a protective film with a release layer on the surface joined to the resin composition layer can be used. Examples of the release agent used in the release layer of the protective film with a release layer include one or more release agents selected from alkyd resins, polyolefin resins, polyurethane resins, and silicone resins. The protective film with a release layer can use commercially available products, such as PET films having a release layer mainly composed of an alkyd resin-based release agent, namely "SK-1", "AL-5", "AL-7" manufactured by Lintec Corporation, "Lumirror T60", "Lumirror R80", "Lumirror" manufactured by Toray Industries, Inc.; "Purex" manufactured by Teijin Limited; "Unipeel" manufactured by Unitika Ltd., etc.

[0195] The thickness of the protective film is not particularly limited, for example, it is 1 μm to 40 μm. In the case where the protective film is a multilayer structure such as a protective film with a release layer, it is preferred that the thickness of the entire protective film is within the above range.

[0196] <Manufacturing method of resin sheet with metal foil> Regarding the manufacturing method of the resin sheet with metal foil, for example, a resin varnish in which the components contained in the resin composition layer are dissolved in a solvent is prepared, and this resin varnish is coated on the protective film using a die coater or the like, and then dried to form a resin composition layer on the protective film. Then, by laminating a metal foil on the surface of the resin composition layer using a roll laminator or the like, a resin sheet with metal foil can be manufactured. Regarding the solvent, the above-mentioned solvents can be used.

[0197] Drying can be carried out by known methods such as heating and hot air blowing. The drying conditions are not particularly limited, and drying is carried out in such a manner that the content of the solvent in the resin composition layer is within the above range. Depending on the boiling point of the solvent in the resin varnish, for example, when using a resin varnish containing 30% to 60% by mass of the solvent, a resin composition layer can be formed by drying at 50°C to 150°C for 3 minutes to 10 minutes.

[0198] The resin sheet with a metal foil can be wound into a roll for storage. When using the resin sheet with a metal foil, it can be used by peeling off the protective film.

[0199] <Physical properties of the resin sheet with a metal foil, etc.> The resin sheet with a metal foil of the present invention has a resin composition layer containing component (A) and component (B) combined in a specified ratio, and thus exhibits the characteristic of a high glass transition temperature (Tg) of the cured product of the resin composition layer thermally cured by vacuum pressing treatment. The glass transition temperature of the cured product of the resin composition layer thermally cured by vacuum pressing treatment is preferably 150°C or higher, more preferably 155°C or higher, and further preferably 160°C or higher. The upper limit of the glass transition temperature of the cured product is not particularly limited and can be 300°C or lower, etc. The glass transition temperature can be measured by the method described in the examples below.

[0200] The resin sheet with a metal foil of the present invention exhibits excellent mechanical strength due to the high glass transition temperature (Tg) of the cured product of the resin composition layer. Therefore, an insulating layer with excellent mechanical strength is brought. In addition, as a result of the improvement in the mechanical strength of the cured product, a cured product with excellent bend resistance can be obtained. The resin sheet with a metal foil from which the protective film has been peeled is laminated in such a manner that the resin composition layer is in contact with the copper foil. After lamination, the resin composition layer is thermally cured by vacuum pressing treatment, and the copper foil is removed to obtain a cured product for evaluation. Then, the cured product for evaluation is cut into test pieces with a width of 2 mm and a length of 80 mm, and the tensile strength is measured using a tensile testing machine. At this time, the tensile strength is preferably 100 MPa or higher, more preferably 115 MPa or higher. The upper limit is not particularly limited and can be 1000 MPa or lower, etc. The measurement of the mechanical strength can be carried out by the method described in the examples below.

[0201] The resin composition layer in the resin sheet with a metal foil of the present invention generally exhibits excellent characteristics of thin film flexibility. Therefore, a resin sheet with a metal foil having excellent operability can be obtained. Specifically, the resin sheet with a metal foil is cut by a temporary assembly device, and the cracks and notches at the cut edge end are visually confirmed. As a result, there are no cracks or notches in the resin sheet with a metal foil. The evaluation of thin film flexibility can be measured by the method described in the examples below.

[0202] The resin sheet with a metal foil of the present invention generally shows excellent flame retardancy of the cured product of the resin composition layer. Therefore, the cured product provides an insulating layer with excellent flame retardancy. The flame retardancy is tested by the UL94 vertical burning test, preferably "V-1", more preferably "V-0", or more excellent than this. The evaluation of flame retardancy can be measured by the method described in the examples below.

[0203] The resin sheet with a metal foil of the present invention generally exhibits the characteristic of low tangent of dielectric loss angle of the cured product of the resin composition layer. Therefore, the cured product provides an insulating layer with a low tangent of dielectric loss angle. The tangent of dielectric loss angle is preferably 0.01 or less, more preferably 0.009 or less, further preferably 0.008 or less, or 0.005 or less. The lower limit is not particularly limited, but can be 0.0001 or more, etc. The measurement of the tangent of dielectric loss angle can be carried out according to the method described in the examples below.

[0204] The resin sheet with a metal foil of the present invention generally exhibits the characteristic of low dielectric constant of the cured product of the resin composition layer. Therefore, the cured product provides an insulating layer with a low dielectric constant. The dielectric constant is preferably 3.5 or less, more preferably 3.4 or less, further preferably 3.3 or less. The lower limit is not particularly limited, but can be 0.1 or more, etc. The measurement of the dielectric constant can be carried out according to the method described in the examples below.

[0205] The resin sheet with a metal foil of the present invention can provide a cured product having a high glass transition temperature, excellent film flexibility, and mechanical strength. Therefore, for the resin sheet with a metal foil of the present invention, in the manufacture of a circuit board, it can be suitably used as a resin sheet (for forming an insulating layer and a conductor layer) for forming these two layers; in the manufacture of a circuit board, it can be suitably used as a resin sheet (for forming an insulating layer and a conductor layer using a vacuum pressing process) for forming these two layers by a vacuum pressing process; in the manufacture of a printed wiring board, it can be suitably used as a resin sheet (for forming an insulating layer and a conductor layer) for forming these two layers; in the manufacture of a printed wiring board, it can be suitably used as a resin sheet (for forming an insulating layer and a conductor layer using a vacuum pressing process) for forming these two layers by a vacuum pressing process.

[0206] [Circuit Board and Method for Manufacturing the Same] The circuit board of the present invention can be manufactured using the resin sheet with a metal foil of the present invention. That is, a circuit board can be provided that includes an insulating layer formed of a cured product of a resin composition layer of the resin sheet with a metal foil of the present invention and a conductor layer formed of a metal foil.

[0207] Examples of the circuit board include a printed wiring board, a semiconductor chip package, and the like. The circuit board includes an insulating layer formed of a cured product of a resin composition layer of the resin sheet with a metal foil of the present invention and a conductor layer formed of a metal foil.

[0208] The circuit board can be manufactured, for example, using the above-mentioned resin sheet with a metal foil by a method including the following steps (I) and (II). (I) A step of laminating the resin composition layer in the resin sheet with a metal foil on an inner layer substrate by a vacuum pressing process; (II) A step of thermally curing the resin composition layer to form an insulating layer.

[0209] The "inner layer substrate" used in step (I) refers to a member that becomes the substrate of the circuit board, and examples thereof include a glass epoxy substrate, a metal substrate, a polyester substrate, a polyimide substrate, a BT resin substrate, a thermosetting polyphenylene ether substrate, and the like. In addition, the substrate may have a conductor layer on one or both sides thereof, and the conductor layer can be patterned. An inner layer substrate having a conductor layer (circuit) formed on one or both sides of the substrate is sometimes referred to as an "inner layer circuit board". In addition, in the manufacture of a circuit board, an intermediate product to which an insulating layer and / or a conductor layer is to be further formed is also included in the "inner layer substrate" as referred to in the present invention. When the circuit board is a component-embedded circuit board, an inner layer substrate having components embedded therein can be used.

[0210] Regarding the lamination of the inner substrate and the resin sheet with a metal foil, after peeling off the protective film, a vacuum pressing process is carried out to laminate the resin composition layer of the resin sheet with a metal foil to be joined to the inner substrate.

[0211] First, peel off the protective film of the resin sheet with a metal foil, and assemble the inner substrate and the resin sheet with a metal foil from which the protective film has been peeled off to a vacuum pressing device in such a way that the resin composition layer of the resin sheet with a metal foil is joined to the inner substrate. Then, a vacuum pressing process of thermocompression bonding the inner substrate and the resin composition layer is carried out under reduced pressure conditions.

[0212] The inner substrate and the resin sheet with a metal foil from which the protective film has been peeled off can also be assembled to the vacuum pressing device via a buffer paper, a metal plate such as a stainless steel plate (SUS plate), a release film, etc.

[0213] The vacuum pressing process can be carried out using a conventionally well-known vacuum pressing device, in which a metal plate such as a heated SUS plate is used to press the inner substrate and the resin sheet with a metal foil from which the protective film has been peeled off from both sides. As a commercially available vacuum pressing device, for example, "VH1-1603" manufactured by Kitakawa Seiki Co., Ltd. can be cited.

[0214] The vacuum pressing process can be carried out only once, or can be carried out repeatedly two or more times. In the case of carrying out repeatedly two or more times, the crimping pressure, heating temperature, pressing time, etc. can be the same or different.

[0215] In the vacuum pressing process, the crimping pressure (pressing force) is preferably 5 kgf / cm 2 or more, more preferably 10 kgf / cm 2 or more, further preferably 15 kgf / cm 2 or more, preferably 50 kgf / cm 2 or less, more preferably 35 kgf / cm 2 or less, further preferably 25 kgf / cm 2 or less.

[0216] In the vacuum pressing process, the pressure of the atmosphere, that is, the pressure (degree of decompression) during decompression in the chamber that houses the laminated structure of the object to be processed, is preferably 3×10 -2 MPa or less, more preferably 1×10 -2 MPa or less. There is no particular limitation on the lower limit, and it can be 1×10 -10 MPa or more, etc.

[0217] In the vacuum pressing process, the heating temperature also varies depending on the composition of the resin composition layer, preferably 80 °C or higher, more preferably 90 °C or higher, and further preferably 100 °C or higher. The upper limit of the heating temperature is not particularly limited and can generally be 300 °C or lower, etc. It should be noted that the resin composition layer can be thermally cured by heating in the vacuum pressing process to form an insulating layer.

[0218] In the vacuum pressing process, the pressing time is preferably 5 minutes or longer, more preferably 10 minutes or longer, and further preferably 15 minutes or longer. The upper limit is not particularly limited and is preferably 300 minutes or shorter, more preferably 200 minutes or shorter, and further preferably 150 minutes or shorter.

[0219] After laminating the resin sheet with a metal foil from which the protective film has been peeled off on the inner layer substrate by the vacuum pressing process, in step (II), the resin composition layer is thermally cured to form an insulating layer. As a method for thermally curing the resin composition layer, for example, in the case of performing a pressing process by the vacuum pressing process, a method of thermally curing the resin composition layer by using the heat during pressing to form an insulating layer can be cited.

[0220] The thermal curing conditions of the resin composition layer are not particularly limited, and conditions generally used when forming the insulating layer of a circuit board and a printed wiring board can be used.

[0221] For example, the thermal curing conditions of the resin composition layer vary depending on the type of the resin composition layer, etc. The curing temperature is preferably 120 °C to 240 °C, more preferably 150 °C to 220 °C, and further preferably 170 °C to 210 °C. The curing time is preferably 5 minutes to 120 minutes, more preferably 10 minutes to 100 minutes, and further preferably 15 minutes to 100 minutes.

[0222] Before thermally curing the resin composition layer, the resin composition layer can be preheated at a temperature lower than the curing temperature. For example, before thermally curing the resin composition layer, the resin composition layer can be preheated at a temperature of 50 °C or higher and less than 120 °C (preferably 60 °C or higher and 115 °C or lower, more preferably 70 °C or higher and 110 °C or lower) for 5 minutes or longer (preferably 5 minutes to 150 minutes, more preferably 15 minutes to 120 minutes, and further preferably 15 minutes to 100 minutes).

[0223] Since the resin sheet with a metal foil used in the present invention contains a metal foil, as step (III), it can include a step of forming a conductor layer (circuit) by a subtractive method or a modified semi-additive method.

[0224] In step (III), the metal foil in the resin sheet with a metal foil can be used to form a conductor layer by a subtractive method or a modified semi-additive method.

[0225] In the subtractive method, unnecessary portions (non-circuit forming portions) of the metal foil are selectively removed, such as by etching, to form a circuit. The circuit formation using the subtractive method can be carried out according to well-known steps. For example, the circuit formation using the subtractive method can be carried out by a method including the following steps: i) providing a resist layer on the surface of the metal foil (i.e., the surface opposite to the surface joined to the resin composition layer); ii) exposing and developing the resist layer to form a wiring pattern; iii) etching and removing the exposed metal foil portion; and iv) removing the resist layer.

[0226] In the modified semi-additive method, the non-circuit forming portions of the metal foil are protected by an anti-plating layer. After electrolytic plating to thicken a metal such as copper on the circuit forming portions, the anti-plating layer is removed, and the metal foil other than the circuit forming portions is removed by etching to form a circuit. The circuit formation using the modified semi-additive method can be carried out according to well-known steps. For example, the circuit formation using the modified semi-additive method can be carried out by a method including the following steps: i) providing an anti-plating layer on the surface of the metal foil (i.e., the surface opposite to the surface joined to the resin composition layer); ii) exposing and developing the anti-plating layer to form a wiring pattern; iii) performing electrolytic plating through the anti-plating layer; iv) removing the anti-plating layer; and v) etching and removing the metal foil other than the circuit forming portions. It should be noted that in the case where the metal foil is thick, before the above step i), the entire surface of the metal foil can be thinned by etching or the like so that the metal foil becomes a desired thickness (usually 5 μm or less, 4 μm or less, or 3 μm or less).

[0227] When manufacturing a circuit board, a step (IV) of opening holes and a step (V) of roughening the insulating layer can be further carried out. These steps (IV) to step (V) can be carried out according to various methods well-known to those skilled in the art used in the manufacture of circuit boards. In addition, if necessary, the formation of the insulating layer and the conductor layer in steps (I) to (V) can be repeatedly carried out to form a multilayer wiring board.

[0228] [Semiconductor device] The semiconductor device of the present invention includes the circuit board of the present invention. The semiconductor device of the present invention can be manufactured using the circuit board of the present invention.

[0229] Examples of the semiconductor device include various semiconductor devices for electrical products (e.g., computers, mobile phones, digital cameras, and televisions, etc.) and transportation means (e.g., motorcycles, automobiles, trams, ships, and airplanes, etc.).

[0230] The semiconductor device of the present invention can be manufactured by mounting components (semiconductor chips) on the conductive portions of the circuit board. The "conductive portion" refers to "the portion of the circuit board that transmits electrical signals", and its position can be on the surface or a buried portion. In addition, the semiconductor chip is not particularly limited as long as it is a circuit element made of semiconductor material.

[0231] The method of mounting the semiconductor chip when manufacturing the semiconductor device is not particularly limited as long as the semiconductor chip functions effectively. Specifically, examples include wire bonding mounting method, flip chip mounting method, mounting method based on built-in non-convex and non-concave layer (BBUL), mounting method based on anisotropic conductive film (ACF), mounting method based on non-conductive film (NCF), etc. Here, the "mounting method based on built-in non-convex and non-concave layer (BBUL)" refers to "a mounting method in which the semiconductor chip is directly buried in the recess of the circuit board and the semiconductor chip is connected to the wiring on the circuit board". Examples

[0232] Hereinafter, the present invention will be specifically described by way of examples. The present invention is not limited to these examples. It should be noted that in the following, "parts" and "%" respectively refer to "parts by mass" and "% by mass" unless otherwise specified.

[0233] <Synthesis Example 1: Synthesis of Polyimide Resin 1> In a 500 ml detachable flask equipped with a nitrogen inlet tube and a stirring device, 9.13 g (30 mmol) of 4-aminobenzoic acid 5-amino-1,1'-biphenyl-2-yl (compound of formula (A-3)), 15.61 g (30 mmol) of 4,4'-(4,4'-isopropylidenediphenoxy) bisphthalic anhydride, 94.64 g of N-methyl-2-pyrrolidone, 0.47 g (6 mmol) of pyridine, and 10 g of toluene were added. Under a nitrogen atmosphere, the reaction was carried out at 180 °C for 4 hours while removing toluene out of the system midway, thereby obtaining a polyimide solution containing polyimide resin (non-volatile component 20%). No precipitation of the synthesized polyimide resin 1 was found in the polyimide solution. The weight average molecular weight of polyimide resin 1 was 10,000.

[0234] <Synthesis Example 2: Synthesis of Polyimide Resin 2> In a 1000 ml detachable flask equipped with a nitrogen inlet tube and a stirring device, 62.46 g (120 mmol) of 4,4'-(4,4'-isopropylidenediphenoxy) bisphthalic anhydride (BPADA), 12.17 g (40 mmol) of (5-amino-2-biphenyl)-4-aminobenzoate (PHBAAB), 27.56 g (80 mmol) of 4,4'-(m-phenyleneisopropylidene) diphenylamine (Bisaniline-M), 303 g of N-methylpyrrolidone (NMP), 1.90 g (24 mmol) of pyridine, and 34 g of toluene were added. Under a nitrogen atmosphere, the reaction was carried out at 180 °C for 10 hours while removing toluene out of the system midway, thereby obtaining a 25 mass% polyimide solution. The weight-average molecular weight of the polyimide resin 2 was 50,000.

[0235] <Synthesis Example 3: Synthesis of Polyimide Resin 3> In a reaction vessel equipped with a stirrer, a water separator, a thermometer, and a nitrogen inlet tube, 65.0 g of a commercially available aromatic tetracarboxylic dianhydride (“BisDA-1000” manufactured by SABIC), 266.5 g of cyclohexanone, and 44.4 g of methylcyclohexane were added, and the solution was heated to 60 °C. Then, 43.7 g of a commercially available dimer diamine (“PRIAMINE 1075” manufactured by Croda Japan) and 5.4 g of 1,3-bis(aminomethyl)cyclohexane were added dropwise, and an imidization reaction was carried out at 140 °C for 1 hour. Thus, a polyimide solution (non-volatile content 30%) containing a dimer diamine polyimide resin was obtained. The weight-average molecular weight of the polyimide resin 3 was 25,000.

[0236] <Manufacture of Resin Varnish> Weigh each component in the mass parts described in the following table, and further mix 10 parts of methyl ethyl ketone (MEK) and 10 parts of cyclohexanone, and uniformly disperse them using a high-speed rotary mixer to obtain a resin varnish. [Table 1] (Table 1) *1: Represents the content when the resin component in the resin composition layer is set to 100 mass%. *2: Represents the content when the non-volatile component in the resin composition layer is set to 100 mass%.

[0237] The details of each component described in the table are as follows. (A) Polyimide Resin · Polyimide 1: The polyimide resin synthesized in Synthesis Example 1 · Polyimide 2: The polyimide resin synthesized in Synthesis Example 2 · Polyimide 3: The polyimide resin synthesized in Synthesis Example 3 (B) Phenoxy resin · YX7553BH30: A 1:1 solution of phenoxy resin, MEK and cyclohexanone with a non-volatile content of 30% by mass, weight average molecular weight 35,000, manufactured by Mitsubishi Chemical Corporation · YL7891BH30: A 1:1 solution of phenoxy resin, MEK and cyclohexanone with a non-volatile content of 30% by mass, weight average molecular weight 26,000, manufactured by Mitsubishi Chemical Corporation · YX7200B35: A MEK solution of phenoxy resin with a non-volatile content of 30% by mass, weight average molecular weight 10,000, manufactured by Mitsubishi Chemical Corporation (C) Inorganic filler · SO-C2: Spherical silica surface-treated with an amine-based alkoxysilane compound (“KBM573” manufactured by Shin-Etsu Chemical Co., Ltd.), average particle size 0.5 μm, specific surface area 5.8 m 2 / g, manufactured by Admatechs Co., Ltd. · UFP-30: Spherical silica surface-treated with an amine-based alkoxysilane compound (“KBM573” manufactured by Shin-Etsu Chemical Co., Ltd.), average particle size 0.3 μm, specific surface area 5.8 m 2 / g, manufactured by Denka Company Limited (D) Thermosetting resin · YX4000HK: Bixylenol-type epoxy resin, epoxy equivalent 194 g / eq., manufactured by Mitsubishi Chemical Corporation · NC-3000-L: Biphenyl-type epoxy resin, epoxy equivalent 269 g / eq., manufactured by Nippon Kayaku Co., Ltd. · ZX-1059: A 1:1 mixture of bisphenol A-type epoxy resin and bisphenol F-type epoxy resin, epoxy equivalent 169 g / eq., manufactured by Nippon Steel Chemical & Material Co., Ltd. · 630: Aminophenol-type epoxy compound, epoxy equivalent 98 g / eq., manufactured by Mitsubishi Chemical Corporation · HPC-8000-65T: An active ester resin containing a dicyclopentadiene-type diphenol structure, functional group equivalent 223 g / eq., a toluene solution with a non-volatile content of 65% by mass, manufactured by DIC Corporation · LA-7054: A phenolic curing agent having a triazine skeleton and a linear phenolic resin structure, functional group equivalent 125 g / eq., a MEK solution with a non-volatile content of 60% by mass, manufactured by DIC Corporation · SN-485: Naphthol-type phenolic curing agent, functional group equivalent 205 g / eq., manufactured by Nippon Steel Chemical & Material Co., Ltd. ·MIR-3000-70MT: A maleimide compound containing an aromatic ring skeleton, a 1:1 solution of MEK and toluene with a functional group equivalent of 275 g / eq. and a non-volatile content of 70% by mass, manufactured by Nippon Kayaku Co., Ltd. ·V03: A carbodiimide-based curing agent, a toluene solution with a functional group equivalent of 216 and a non-volatile content of 50% by mass, manufactured by Nisshinbo Chemical Inc. ·ODA-BOZ: A benzoxazine compound, a (E) thermoplastic resin manufactured by JFE Chemical Corporation with a functional group equivalent of 218 g / eq. ·FPC-0220: A polycarbonate resin with a viscosity-average molecular weight of 20,000, manufactured by Mitsubishi Gas Chemical Company, Inc. ·AC3816N: STAPHYLOID, a flame retardant manufactured by AICA Kogyo Co., Ltd. (F) ·FP-100: A phosphorus-based flame retardant, manufactured by Fushimi Pharmaceutical Co., Ltd. ·HCA-HQ-HST: A phosphorus-based flame retardant, a curing accelerator (G) manufactured by Sanko Co., Ltd. ·DMAP: Manufactured by Tokyo Chemical Industry Co., Ltd. ·1B2PZ: Manufactured by Shikoku Chemicals Corporation

[0238] <Manufacture of Resin Sheet with Metal Foil> Using a die coater, the resin varnishes obtained in the examples and comparative examples were coated on the release surface of a release-treated polyethylene terephthalate film (Toray Industries, Inc.'s "Lumirror R80, thickness 38 μm") serving as a support so that the thickness of the resin composition layer became 40 μm, and dried at 80 to 120 °C (average 100 °C) for 5 minutes. Then, using a roll laminator (manufactured by Daisheng Laminator Co., Ltd., "FIRST LAMINATOR VA-770H"), a copper foil with a carrier (manufactured by Mitsui Mining & Smelting Co., Ltd., "MicroThin MT18Ex", an ultra-thin copper foil with a thickness of 3 μm / a carrier copper foil with a thickness of 18 μm) having a carrier copper foil and an ultra-thin copper foil was laminated on the surface of the resin composition layer under the conditions of a roll pressing pressure of 0.25 MPa, a conveying speed of 0.3 m / min, and a roll temperature of 90 °C to obtain a resin sheet with a metal foil.

[0239] <Evaluation of Film Flexibility> The resin sheet with a metal foil was cut with a temporary assembly device, and the cracks and notches at the end of the cut edge were visually confirmed. Then, based on the following evaluation criteria, the resin notches were evaluated. 〇: There are no cracks or notches in the resin sheet with a metal foil. ×: There are cracks or notches in the resin sheet with a metal foil.

[0240] <Manufacture of Cured Product for Evaluation Based on Vacuum Pressing Curing> The support is peeled off from the resin sheet with a metal foil, and it is overlapped in such a way that another copper foil ("MicroThin MT18Ex" manufactured by Mitsui Mining & Smelting Co., Ltd.) is in contact with the resin composition layer. Using a vacuum press (VH1-1603 manufactured by Kitakawa Seiki Co., Ltd.), the vacuum degree during pressing is 1×10 -3 MPa or less, and the pressure condition is 20 kgf / cm 2 . As the heating condition, the first-stage pressing is at a temperature of 100 °C for 30 minutes, and the second-stage pressing is at a temperature of 190 °C for 120 minutes to thermally cure the resin composition layer. The thermally cured resin sheet with a metal foil is immersed in an aqueous solution of iron(II) chloride (manufactured by Tsurumi Soda Co., Ltd., Baumé 40). After removing the copper foil, it is dried at 130 °C for 15 minutes to obtain a sheet-shaped cured product. The obtained cured product is referred to as "the cured product for evaluation based on vacuum pressing curing".

[0241] <Measurement of Dielectric Constant and Dissipation Factor> The cured product for evaluation based on vacuum pressing curing is cut into test pieces with a width of 2 mm and a length of 80 mm. For this test piece, using "HP8362B" manufactured by Agilent Technologies, the dissipation factor is measured at a measurement frequency of 5.8 GHz and a measurement temperature of 23 °C by the resonant cavity perturbation method. Two test pieces are measured and the average value is calculated.

[0242] <Measurement of Glass Transition Temperature> The cured product for evaluation based on vacuum pressing curing is cut into test pieces with a width of about 5 mm and a length of about 15 mm. For this test piece, a dynamic viscoelasticity measuring device (EXSTAR6000, manufactured by SII Nano Technology Inc.) is used for thermomechanical analysis by the tensile load method. After installing the test piece on the above device, it is measured under the measurement conditions of a load of 200 mN and a heating rate of 2 °C / minute. The peak of the obtained tanδ is calculated as the glass transition temperature (°C) and evaluated according to the following criteria. 〇: 160 °C or higher △: 150 °C or higher and less than 160 °C ×: Less than 150 °C

[0243] <Measurement of Mechanical Strength> The cured product for evaluation based on vacuum pressing curing is used to measure the tensile strength with a tensile testing machine "RTC-1250A" manufactured by Orientec Co., Ltd., and the mechanical strength at 23 °C is measured. The measurement is carried out in accordance with JIS K7127. Five measurements are made, and the average value of the top 3 from top to bottom is calculated and evaluated according to the following criteria. 〇: 115 MPa or higher. △: 100 MPa or more and less than 115 MPa. ×: Less than 100 MPa.

[0244] <Evaluation of Flame Retardancy> In the same manner as the metal foil - attached resin sheet with a resin composition layer thickness of 40 μm, a metal foil - attached resin sheet with a resin composition layer thickness of 90 μm was produced. The support of the metal foil - attached resin sheet was peeled off and overlapped on both sides of the substrate after etching away the copper foil of a copper - clad laminate (Resonac Corporation's "MCL - E - 700G") with a substrate thickness of 0.2 mm. Using a vacuum press (manufactured by Kitakawa Seiki Co., Ltd., VH1 - 1603), the vacuum degree during pressing was 1×10 - 3 MPa or less, and the pressure condition was 20 kgf / cm 2 . As the heating condition, the first - stage pressing was at a temperature of 100 °C for 30 minutes, and the second - stage pressing was at a temperature of 190 °C for 120 minutes to thermally cure the resin composition layer. The thermally cured metal foil - attached resin sheet was immersed in an aqueous solution of iron(II) chloride (manufactured by Tsurumi Soda Co., Ltd., Baume degree 40), and after removing the copper foil, it was dried at 130 °C for 15 minutes to obtain a sample for the flame - retardancy test. Samples for the flame - retardancy test were cut to a width of 12.7 mm and a length of 127 mm, and the cut surfaces were polished with a polishing machine (Struers, RotoPol - 22). Taking the above 5 samples as a group, a flame - retardancy test was carried out according to the UL94 vertical flame - retardancy test and evaluated according to the following criteria. 〇: The evaluation result of the UL94 vertical flame - retardancy test is V - 0. △: The evaluation result of the UL94 vertical flame - retardancy test is V - 1. ×: The evaluation result of the UL94 vertical flame - retardancy test is other than V - 0 and V - 1.

[0245] [Table 2] (Table 2)

[0246] It can be seen that in Examples 1 to 9, the film has excellent flexibility, and even when the insulating layer is formed by vacuum pressing treatment, the glass transition temperature (Tg), film flexibility, mechanical strength, flame retardancy, dielectric loss tangent, and dielectric constant of the insulating layer are also excellent.

[0247] Relatively speaking, it can be seen that in Comparative Example 1, since there is no polyimide resin, the glass transition temperature after vacuum pressing treatment is low, and the mechanical strength and flame retardancy are inferior to those of Examples 1 to 9. It can be seen that in Comparative Examples 2 and 4, since there is no phenoxy resin, either the film flexibility or the mechanical strength is inferior to those of Examples 1 to 9. In addition, it can be seen that in Comparative Example 3, since there is no polyimide resin and phenoxy resin, even if it is desired to coat the resin varnish on the support, the resin varnish is repelled and it is impossible to form a thin film of the resin composition layer, and it is impossible to measure the glass transition temperature and the like. In addition, it can be seen that in Comparative Examples 5 and 6 outside the range where a1 / b1 is 0.05 or more and 50 or less, either the mechanical strength or the film flexibility is inferior to those of Examples 1 to 9.

Claims

1. A resin sheet with metal foil, comprising a metal foil, a resin composition layer and a protective film in this order, wherein: The resin composition layer comprises (A) a polyimide resin, (B) a phenoxy resin, and (C) an inorganic filler. When a1 is the content of the component (A) when the resin component in the resin composition layer is 100 mass %, and b1 is the content of the component (B) when the resin component in the resin composition layer is 100 mass %, a1 / b1 is 0.05 or more and 50 or less.

2. The resin sheet with metal foil according to claim 1, wherein (A) Component has an ester bond.

3. The resin sheet with metal foil according to claim 1, wherein The composition further comprises (G) a flame retardant.

4. The resin sheet with metal foil according to claim 1, wherein When the weighted average molecular weight of the component (A) is a2 and the weighted average molecular weight of the component (B) is b2, a2 / b2 is 0.01 or more and 10 or less.

5. The resin sheet with metal foil according to claim 1, wherein Further comprising (D) a thermosetting resin.

6. The resin sheet with metal foil according to claim 1, which is used to form an insulating layer and a conductor layer by vacuum pressing.

7. The resin sheet with metal foil according to claim 1, wherein The metal foil is copper foil.

8. A circuit substrate, comprising: An insulating layer formed by a cured product of a resin composition layer of a resin sheet with metal foil according to any one of claims 1 to 7, and A conductor layer formed using the metal foil of the resin sheet with metal foil according to any one of claims 1 to 7. 9 . A semiconductor device comprising the circuit substrate according to claim 8 .

10. A method for manufacturing a circuit substrate, the method comprising: (I) a step of laminating the resin composition layer in the resin sheet with metal foil 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.

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