Resin sheet and method for producing same, method for producing circuit board, and resin composition

Abstract

The present invention addresses the problem of providing a resin sheet capable of forming an insulating layer while suppressing unevenness. The solution of the present invention is a resin sheet which is provided with a resin composition layer. The resin composition layer contains (A) a curable resin containing a furan skeleton, (B) tetrahydrofuran, and (C) an inorganic filler; the amount of the curable resin (A) containing a furan skeleton is 2 mass% or more with respect to 100 mass% of the total amount of the resin composition layer; the amount of the tetrahydrofuran (B) is 0.1 mass% or more with respect to 100 mass% of the total amount of the resin composition layer; the amount of the (C) inorganic filler is 50% by mass or more with respect to 100% by mass of the non-volatile component of the resin composition layer.

Description

Technical Field

[0001] The present invention relates to a resin sheet and a method for producing the same, a method for producing a circuit board using the resin sheet, and a resin composition used for producing the resin sheet. Background Art

[0002] Circuit substrates such as printed wiring boards are widely used in various electronic devices. As a method for manufacturing a circuit substrate, a method for manufacturing a stacking method based on alternately stacking an insulating layer and a conductor layer on an inner substrate is known. The insulating layer is formed, for example, by a cured product of a resin composition. If a specific example is given, a resin composition layer comprising a resin composition is formed, and the resin composition layer is cured, thereby forming an insulating layer comprising a cured product of the resin composition.

[0003] In recent years, from the viewpoint of sustainability, the application of biomass resins as materials for insulating layers has been studied. As one of the biomass resins having excellent insulating properties, resins containing a furan skeleton are known (Patent Documents 1 and 2).

[0004] Prior art literature Patent Literature Patent Document 1: Japanese Patent No. 6631889 Patent Document 2: Japanese Patent Application Publication No. 2016-060766 Summary of the invention

[0005] Technical problem to be solved by the invention Biomass resins are generally resins with low heat resistance, but resins containing furan skeletons have high heat resistance. In addition, the linear thermal expansion coefficient of resins containing furan skeletons is relatively small. Therefore, the present inventors tried to form an insulating layer using a curable resin containing a furan skeleton.

[0006] Specifically, in order to improve dielectric loss tangent and linear thermal expansion coefficient, the inventors tried to prepare a resin composition comprising an inorganic filler and a curable resin containing a furan skeleton, and to form an insulating layer using a resin sheet having a resin composition layer comprising the resin composition. However, when the insulating layer was formed by this method, it was found that unevenness occurred in the insulating layer.

[0007] The unevenness of the insulating layer is specifically generated as follows. Generally, a method for forming an insulating layer using a resin sheet includes a step of laminating a resin sheet and an inner substrate in such a manner that the resin composition layer and the inner substrate are bonded, and a step of curing the resin composition layer to obtain the insulating layer. However, near the edge of the formed insulating layer, concave unevenness is observed along the edge.

[0008] The present invention has been made in view of the above problems, and its object is to provide: a resin sheet capable of forming an insulating layer while suppressing unevenness and a method for producing the same; a method for producing a circuit board using the resin sheet; and a resin composition capable of producing the resin sheet.

[0009] Means of solving technical problems The present inventors have conducted intensive research to solve the above-mentioned problems. As a result, the present inventors have found that the above-mentioned problems can be solved by combining a curable resin containing a furan skeleton in a specific range of amounts, tetrahydrofuran (THF) in a specific range of amounts, and an inorganic filler in a specific range of amounts, thereby completing the present invention. That is, the present invention includes the following contents.

[0010] <1> A resin sheet comprising a resin composition layer. The resin composition layer comprises (A) a curable resin containing a furan skeleton, (B) tetrahydrofuran, and (C) an inorganic filler, and the amount of the curable resin containing a furan skeleton (A) is 2% by mass or more relative to 100% by mass of the total amount of the resin composition layer. The amount of (B) tetrahydrofuran is 0.1% by mass or more relative to 100% by mass of the total amount of the resin composition layer. The amount of the (C) inorganic filler is 50% by mass or more based on 100% by mass of the nonvolatile components of the resin composition layer. <2> according to <1> The resin sheet, wherein the biomass ratio represented by the following formula (M2) of the non-volatile component in the resin composition layer is 0.1% by mass or more, and the biomass ratio (mass %) = (mass of biologically derived components in the non-volatile component / mass of the non-volatile component) × 100 (M2). <3> according to <1> or <2> The resin sheet is characterized in that the average linear thermal expansion coefficient of a cured product layer obtained by curing the resin composition layer is 50 ppm / °C or less. <4> according to <1> ~ <3> The resin sheet according to any one of the preceding claims, wherein a cured product layer obtained by curing the resin composition layer has a dielectric loss tangent of less than 0.015. <5> according to <1> ~ <4> The resin sheet according to any one of the preceding claims, wherein a cured product layer obtained by curing the resin composition layer has a glass transition temperature higher than 150°C. <6> A method for manufacturing a circuit substrate, wherein the method comprises: <1> ~ <5> The resin sheet described in any one of the above The manufacturing method comprises: A step of laminating the resin sheet and the inner layer substrate so that the resin composition layer is bonded to the inner layer substrate, and a step of curing the resin composition layer. <7> A resin composition comprising (A) a curable resin containing a furan skeleton, (B) tetrahydrofuran, and (C) an inorganic filler, wherein the amount of the curable resin containing the furan skeleton (A) is 2% by mass or more relative to 100% by mass of the total amount of the resin composition, and the amount of the tetrahydrofuran (B) is 1% by mass or more relative to 100% by mass of the total amount of the resin composition. The amount of the (C) inorganic filler is 50% by mass or more relative to 100% by mass of the nonvolatile components in the resin composition. <8> A method for manufacturing a resin sheet, wherein the resin sheet is manufactured using <7> The resin composition, the manufacturing method comprises: a step of coating the resin composition on a support, and a step of drying the applied resin composition to form a resin composition layer, The amount of (B) tetrahydrofuran in the resin composition layer is 0.1% by mass or more relative to 100% by mass of the total amount of the resin composition layer. Effects of the Invention

[0011] According to the present invention, there can be provided: a resin sheet capable of forming an insulating layer while suppressing unevenness and a method for producing the same; a method for producing a circuit board using the resin sheet; and a resin composition capable of producing the resin sheet. DETAILED DESCRIPTION

[0012] Hereinafter, the present invention will be described with reference to the embodiments and examples. However, the present invention is not limited to the embodiments and examples described below, and can be implemented with modifications within the scope of the claims and their equivalents.

[0013] In the present specification, the term "optionally having a substituent" with respect to a compound or a group means both the case where hydrogen atoms of the compound or group are not substituted with a substituent and the case where part or all of the hydrogen atoms of the compound or group are substituted with a substituent.

[0014] <Overview of Resin Sheet> A resin sheet according to one embodiment of the present invention comprises a resin composition layer. The resin composition layer comprises a specific range of amounts of (A) a curable resin containing a furan skeleton, a specific range of amounts of (B) tetrahydrofuran, and a specific range of amounts of (C) an inorganic filler. Hereinafter, "(A) a curable resin containing a furan skeleton" is sometimes referred to as "(A) a furan-type curable resin". By using the resin sheet according to this embodiment, an insulating layer can be formed while suppressing unevenness.

[0015] The present inventors have estimated a mechanism that can achieve the above-mentioned effects as follows. However, the technical scope of the present invention is not limited to the following mechanism.

[0016] When laminating the resin sheet and the inner substrate, heat and pressure are generally applied to the resin composition layer of the resin sheet. At this time, since the edge of the resin composition layer is generally open during lamination, the resin composition contained in the resin composition layer tends to flow easily near the edge of the resin composition layer.

[0017] In addition, in a conventional resin composition layer comprising (A) a furan curable resin and (C) an inorganic filler, the compatibility of the components contained in the resin composition layer is generally low. In particular, the compatibility of the (A) furan curable resin with components other than the (A) furan curable resin is low.

[0018] In the resin composition layer with low compatibility of each component, when heat and pressure are applied near the edge of the resin composition layer, some components are easy to flow, and other components are difficult to flow, and the fluidity of each component may produce differences like this. If the fluidity of each component produces differences like this, then the composition of the resin composition layer may produce deviations. Then, if the deviation of the composition is produced near the edge of the resin composition layer, then the large flow of a part of the components may be locally produced, and depressions are produced, forming unevenness. This depression is mostly formed into multiple depressions of strips.

[0019] In contrast, in the present embodiment, (B) tetrahydrofuran is further combined. Since the furan skeleton contained in (A) furan type curable resin is similar to the molecular skeleton of (B) tetrahydrofuran, (A) furan type curable resin has high compatibility with (B) tetrahydrofuran. In addition, (B) tetrahydrofuran can function as a good solvent with excellent compatibility with a variety of resins. Therefore, while including (A) furan type curable resin and (C) inorganic filler, the compatibility of the components contained in the resin composition layer can be improved as a whole, therefore, according to the resin sheet involved in the present embodiment, even when the resin sheet is laminated with the inner substrate, the uniformity of the high composition can be maintained. Therefore, it is possible to suppress the flow of a part of the components when laminating, so it is possible to suppress the unevenness during the formation of the insulating layer.

[0020] (A) Furan curable resin can be generally produced from biomass raw materials. Therefore, the resin sheet of the present embodiment using (A) furan curable resin can increase the biomass ratio, thereby reducing the dependence on fossil resources, and thus can contribute to environmental improvement from the perspective of sustainability.

[0021] Furthermore, the insulating layer formed using the resin sheet material of the present embodiment can generally reduce the average linear thermal expansion coefficient, thereby suppressing the warping of the circuit board. In addition, the insulating layer formed using the resin sheet material of the present embodiment can generally have a low dielectric loss tangent, thereby helping to reduce the signal loss of the circuit board. Furthermore, the insulating layer formed using the resin sheet material of the present embodiment can generally have a high glass transition temperature, thereby improving the heat resistance of the circuit board.

[0022] <(A) Furan type curable resin> The resin composition layer of the resin sheet contains (A) a furan curable resin as the (A) component. The (A) furan curable resin is a curable resin containing a furan skeleton. Therefore, the (A) furan curable resin can react under appropriate conditions to form a bond (bond) to cure the resin composition layer. The (A) furan curable resin can be a thermosetting resin or a photocurable resin, but is preferably a thermosetting resin.

[0023] (A) The furan type curable resin may be a resin having a furan skeleton that can react to form a bond. In addition, (A) the furan type curable resin may be a resin that contains an active group in addition to the furan skeleton, and the active group can react to form a bond. Examples of the active group include an epoxy group, a hydroxyl group (phenolic hydroxyl group) bonded to an aromatic ring, an active ester group, a cyanate group, a carbodiimide group, an acid anhydride group, an amino group, and a free radical reactive unsaturated group.

[0024] As the free radical reactive unsaturated group, for example, a group containing a non-aromatic carbon-carbon unsaturated bond can be cited. As specific examples of the free radical reactive unsaturated group, unsaturated hydrocarbon groups such as vinyl, allyl, 1-propenyl, 3-cyclohexenyl, 3-cyclopentenyl, 2-vinylphenyl, 3-vinylphenyl, and 4-vinylphenyl; α,β-unsaturated carbonyl groups such as acryloyl, methacryloyl, and maleimide (2,5-dihydro-2,5-dioxo-1H-pyrrol-1-yl) can be cited.

[0025] The number of active groups contained in one molecule of the (A) furan type curable resin may be 1 or 2 or more. When the (A) furan type curable resin contains 2 or more active groups, the 2 or more active groups may be the same or different. Furthermore, the (A) furan type curable resin may be a resin in which the furan skeleton can react to form a bond and the active group can react.

[0026] Among the above, furan type curable resins containing active ester groups are preferred. Therefore, (A) furan type curable resin preferably includes furan type curable resins containing active ester groups, or may only include furan type curable resins containing active ester groups. Furan type curable resins containing active ester groups generally do not generate polar groups such as hydroxyl groups due to reactions during curing. Therefore, since the polarity of the insulating layer can be reduced, the dielectric loss tangent of the insulating layer can be reduced.

[0027] As an example of a preferred furan type curable resin containing an active ester group, a resin represented by the following formula (A-1) can be mentioned.

[0028] [Chemical formula 1]

[0029] (In formula (A-1), R a1 and R a2 Each independently represents a monovalent aromatic group which may have a substituent; A a Each independently represents a group represented by the following formula (A-1-1) or formula (A-1-2); n a Represents the number of repetitions, satisfying 0≤n a ≤8. )

[0030] [Chemical formula 2]

[0031] (In formula (A-1-1), R a11 and R a12 Each independently represents a divalent aromatic group which may have a substituent; L a11 Each independently represents a single bond or a divalent linking group, R a11 and L a11 Can be joined together to form a ring. a Indicates a number in the range of 0 to 5.)

[0032] [Chemical formula 3]

[0033] (In formula (A-1-2), R a13 and R a14 Each independently represents a divalent aromatic group which may have a substituent; L a12 It represents a group represented by formula (A-1-3). a and c a Each independently represents a number in the range of 0 to 5. )

[0034] [Chemical formula 4]

[0035] (In formula (A-1-3), R a15 and R a16 Each independently represents a divalent aromatic group which may have a substituent; L a13 Each independently represents a single bond or a divalent linking group, R a15 and L a13 Can be joined together to form a ring. a Indicates a number in the range of 0 to 5.)

[0036] In formula (A-1), R a1 and R a2 Respectively independently represent a monovalent aromatic group optionally having a substituent. A monovalent aromatic group refers to a group after removing one hydrogen atom from the aromatic ring of an aromatic compound. In addition, an "aromatic ring" refers to a ring that follows the Huckel rule in which the number of electrons contained in the π electron system on the ring is 4n+2 (n is a natural number), and an "aromatic ring" includes a monocyclic aromatic ring and a condensed aromatic ring formed by condensing two or more monocyclic aromatic rings. The aromatic ring may be a carbocyclic ring or a heterocyclic ring. As a monovalent aromatic group optionally having a substituent, for example, an aryl group optionally having a substituent and a heteroaryl group optionally having a substituent can be cited. The number of carbon atoms in the monovalent aromatic group is preferably 3 or more, more preferably 4 or more, further preferably 5 or more, and further preferably 6 or more. The upper limit is preferably 24 or less, more preferably 18 or less, further preferably 14 or less, and further preferably 10 or less. The number of carbon atoms does not include the number of carbon atoms of the substituent.

[0037] From the viewpoint of obtaining an insulating layer having a high glass transition temperature, the monovalent aromatic group which may have a substituent is preferably an aryl group which may have a substituent. a1 and R a2 The number of carbon atoms of the aryl group in is preferably 6 to 20, more preferably 6 to 14, and further preferably 6 to 12. The number of carbon atoms does not include the number of carbon atoms of the substituent. a1 and R a2 The monovalent aromatic group optionally having a substituent represented by is preferably a phenyl group optionally having a substituent, a naphthyl group optionally having a substituent, or a biphenyl group optionally having a substituent; more preferably a phenyl group optionally having a substituent, or a naphthyl group optionally having a substituent; further preferably a naphthyl group optionally having a substituent.

[0038] As R a1 and R a2The substituent in the monovalent aromatic group which may optionally have a substituent includes, for example, a halogen atom, an alkyl group, a cycloalkyl group, an alkoxy group, an alkenyl group, a cycloalkyloxy group, an aryl group, an aryloxy group, an arylalkyl group, an arylalkoxy group, a monovalent heterocyclic group, an alkylidene group, an amino group, a silyl group, an acyl group, an acyloxy group, a carboxyl group, a sulfo group, a cyano group, a nitro group, a hydroxyl group, a hydroxyalkyl group, a mercapto group, and an oxo group. Among them, a monovalent hydrocarbon group such as an alkyl group, a cycloalkyl group, an alkenyl group, an aryl group, an arylalkyl group, a monovalent saturated hydrocarbon group such as an alkyl group and a cycloalkyl group is more preferred; and a bornyl group is further preferred.

[0039] In formula (A-1), A a Each independently represents a group represented by formula (A-1-1) or formula (A-1-2).

[0040] In formula (A-1-1), R a11 and R a12 Each independently represents a divalent aromatic group optionally having a substituent. A divalent aromatic group refers to a group obtained by removing two hydrogen atoms from an aromatic ring of an aromatic compound. Examples of divalent aromatic groups optionally having a substituent include an arylene group optionally having a substituent and a heteroarylene group optionally having a substituent. The number of carbon atoms in the divalent aromatic group is preferably 3 or more, more preferably 4 or more, further preferably 5 or more, further preferably 6 or more. The upper limit is preferably 30 or less, more preferably 24 or less, further preferably 18 or less, further preferably 14 or less, further preferably 10 or less. The number of carbon atoms does not include the number of carbon atoms in the substituent. In a preferred example, R a11 and R a12 The divalent aromatic group optionally having a substituent represented by is preferably a phenylene group optionally having a substituent, a naphthyl group optionally having a substituent, a phenylene-fluorenyl-phenylene group optionally having a substituent, or a biphenylene group optionally having a substituent; more preferably, it is a phenylene group optionally having a substituent, or a naphthyl group optionally having a substituent; more preferably, it is a phenylene group optionally having a substituent.

[0041] As R a11 and R a12 The substituent in the optionally substituted divalent aromatic group includes, for example, a1 and R a2 The substituents in the monovalent aromatic group which may have a substituent are the same as the examples. Among them, alkyl, alkenyl, aralkyl, and hydroxyl are preferred; aralkyl and hydroxyl are more preferred; and benzyl and hydroxyl are more preferred.

[0042] In formula (A-1-1), L a11Each independently represents a single bond or a divalent linking group. As a divalent linking group, there can be mentioned a divalent organic group formed by one or more (e.g., 1 to 3000, 1 to 1000, 1 to 100, 1 to 50) backbone atoms selected from carbon atoms, oxygen atoms, nitrogen atoms and sulfur atoms; preferably an oxygen atom, a carbonyl group, a sulfonyl group, a divalent aliphatic group optionally having a substituent, or a divalent aromatic group optionally having a substituent. In a preferred example, L a11 is a single bond, a divalent aliphatic group optionally having a substituent, an oxygen atom, a divalent aromatic group optionally having a substituent, a carbonyl group or a sulfonyl group; more preferably, a divalent aliphatic group optionally having a substituent. a11 The divalent aliphatic group in may be a divalent chain aliphatic group or a divalent cyclic aliphatic group.

[0043] L a11 The divalent chain aliphatic group in may be a saturated chain aliphatic group such as an alkylene group; or an unsaturated chain aliphatic group such as an alkenylene group or an alkapolyenylene group. The number of carbon atoms in the divalent chain aliphatic group is preferably 1 to 12, more preferably 1 to 6, and further preferably 1 to 4. The number of carbon atoms does not include the number of carbon atoms of the substituent. Examples of the divalent chain aliphatic group include alkylene groups such as methylene, ethylene, propylene, isopropylene, 1,1-dimethyl-3-methylpropylene, butylene, pentylene, and hexylene; alkenylene groups such as vinylene, propenylene, butenylene, pentenylene, and hexenylene; and the like.

[0044] L a11 The divalent cyclic aliphatic group in may be a monocyclic cyclic aliphatic group or a polycyclic cyclic aliphatic group containing multiple ring structures. The number of carbon atoms in the divalent cyclic aliphatic group is preferably 3 to 15, more preferably 3 to 12, and further preferably 3 to 10. The number of carbon atoms does not include the number of carbon atoms of the substituent. Examples of the divalent cyclic aliphatic group include cyclopropylene, cyclobutylene, cyclopentylene, cyclohexylene, decahydronaphthylene, norbornylene, dicyclopentylene, adamantylene, cyclopropenylene, cyclobutenylene, cyclopentenylene, cyclohexenylene, norbornylene, etc., preferably dicyclopentanylene.

[0045] As L a11The substituents in the divalent aliphatic group which may be substituted include, for example, a halogen atom, an alkoxy group, an alkenyl group, a cycloalkoxy group, an aryl group, an aryloxy group, an arylalkoxy group, a monovalent heterocyclic group, an amino group, a silyl group, an acyl group, an acyloxy group, a carboxyl group, a sulfo group, a cyano group, a nitro group, a hydroxyl group, a mercapto group, and an oxo group. a11 The substituent in the optionally substituted divalent aromatic group includes, for example, a1 and R a2 The substituents are the same as the substituents in the monovalent aromatic group which may have a substituent.

[0046] R a11 and L a11 can be combined to form a ring. a11 and L a11 When combined to form a ring, L a11 Preferably, it is a divalent aliphatic group which may have a substituent, and more preferably, it is an alkylene group which may have a substituent. a When R is 1, a11 and L a11 Combined together to form a ring. a11 and L a11 Preferably they are joined together to form an indane ring.

[0047] In formula (A-1-1), a a represents a number in the range of 0 to 5, preferably represents a number in the range of 0 to 4, more preferably represents a number in the range of 0 to 3, and further preferably represents a number in the range of 0 to 2. a When R is 1, a11 and L a11 Join together to form a ring.

[0048] In formula (A-1-2), R a13 and R a14 Each independently represents a divalent aromatic group which may have a substituent. a13 and R a14 The optionally substituted divalent aromatic group may be a11 The same is true for the divalent aromatic group optionally having a substituent represented by . When the divalent aromatic group has a substituent, the substituent is preferably an alkyl group, more preferably a methyl group.

[0049] In formula (A-1-2), L a 12 It represents a group represented by formula (A-1-3).

[0050] In formula (A-1-3), R a15 and Ra16 Each independently represents a divalent aromatic group which may have a substituent. a15 and R a16 The optionally substituted divalent aromatic group may be a11 The same is true for the divalent aromatic group optionally having a substituent represented by . When the divalent aromatic group has a substituent, the substituent is preferably an alkyl group, more preferably a methyl group.

[0051] In formula (A-1-3), L a13 Each independently represents a single bond or a divalent linking group. a13 With R a15 Can be combined together to form a ring. a13 The divalent linking group may be connected with L in formula (A-1-1) a11 In a preferred example, L a13 The divalent linking group represented by is an alkylene group having 1 to 12 carbon atoms which may have a substituent.

[0052] In formula (A-1-3), d a A number in the range of 0 to 5 may be expressed as a The numbers in the range of 0 to 5 are the same. a15 and L a13 can combine to form rings, especially when d a When it is 1, it preferably forms a ring.

[0053] In formula (A-1-2), b a and c a Each independently represents a number in the range of 0 to 5, preferably a number in the range of 0 to 4, more preferably a number in the range of 0 to 3, and even more preferably a number in the range of 0 to 2.

[0054] Among them, as A in formula (A-1) a , and examples thereof include groups represented by the following formulae (1a) to (13a). a 1 represents a number in the range of 0 to 4, b a 1 and c a 1 each independently represents a number in the range of 0 to 5, e a and f a Indicates that 1≤e a +f a Numbers greater than 0 and less than 4, and "*" represent binding sites. a 1 is a from formula (A-1-1) a The value after subtracting 1, b a 1 and c a1 and b in formula (A-1-2) a and c a same.

[0055] [Chemical formula 5]

[0056] In formula (A-1), n a Represents the number of repetitions, satisfying 0≤n a ≤8.n a It is preferably 2 or more, more preferably 3 or more, further preferably 4 or more, and is preferably 7 or less, more preferably 6 or less, further preferably 5 or less.

[0057] Specific examples of the resin represented by formula (A-1) include the following resins.

[0058] [Chemical formula 6]

[0059] [Chemical formula 7]

[0060] [Chemical formula 8]

[0061] [Chemical formula 9]

[0062] The resin represented by formula (A-1) can be produced, for example, by a production method comprising condensing a hydroxyl-containing aromatic compound having a phenolic hydroxyl group, a dicarboxylic acid halide having a furan skeleton, and a divalent phenol compound.

[0063] The hydroxyl-containing aromatic compound is a compound in which a hydroxyl group is bonded to a monovalent aromatic group. The aromatic group of the compound can constitute R in the formula (A-1). a1 and R a2 Examples of such compounds include 1-naphthol, phenol, and o-phenylphenol.

[0064] The diacyl halide having a furan skeleton is a compound in which two carbonyl halides are bonded to a furan skeleton. Examples of such compounds include 2,5-furandicarbonyl chloride and 2,5-thiophenedicarbonyl chloride. When a compound having a furan skeleton derived from biomass is used, the compound having a furan skeleton derived from biomass can be chlorinated and used as a raw material for the resin represented by formula (A-1).

[0065] The divalent phenol compound is a compound in which a diacyl halide having a furan skeleton can react with the phenol site of the phenol compound, and can constitute A in the formula (A-1). a Examples of such compounds include dicyclopentadiene-phenol addition polymer, 4,4'-(9-fluorenylidene)diphenol (bisphenol fluorene), 4,4'-dihydroxydiphenyl ether, 4,4'-dihydroxybenzophenone, bisphenol A, bisphenol F, 2,2'-diallylbisphenol A, bisphenol S, 4,4'-dihydroxybiphenyl, and 2,7-naphthalene diol.

[0066] In the condensation reaction, a catalyst such as a phase transfer catalyst such as tetra-n-butylammonium bromide can be used as needed. In addition, a base can also be used in the condensation reaction. Examples of the base include alkali metal hydroxides such as sodium hydroxide (caustic soda) and potassium hydroxide; tertiary amines such as triethylamine, pyridine, and N,N-diisopropylethylamine. The reaction temperature can be, for example, in the range of 0°C to 80°C. In addition, the reaction time can be, for example, in the range of 30 minutes to 8 hours.

[0067] Another example of a preferred furan-type curable resin containing an active ester group includes a resin represented by the following formula (A-2).

[0068] [Chemical formula 10]

[0069] (In formula (A-2), Ar b1 and Ar b2 Each independently represents a divalent aromatic group which may have a substituent; L b1 represents a single bond or a divalent linking group, Ar b1 and L b1 Can be combined to form a ring; X b1 and X b2 Each independently represents a substituent; a b and b b Each independently represents an integer from 0 to 3; n b Indicates 0 or 1. )

[0070] In formula (A-2), Ar b1 and Ar b2 Each independently represents a divalent aromatic group which may have a substituent. b1 and Ar b2 The optionally substituted divalent aromatic group may be combined with R in formula (A-1-1) a11The same is true for the divalent aromatic group which may have a substituent as represented by . When the divalent aromatic group has a substituent, the substituent is preferably an alkyl group, and more preferably a methyl group.

[0071] In formula (A-2), L b1 represents a single bond or a divalent linking group. b1 Can be used with Ar b1 Combined together to form a ring. b1 The divalent linking group may be connected with L in formula (A-1-1) a11 In a preferred example, L b1 The divalent linking group represented by is a divalent cyclic aliphatic group which may have a substituent, and more preferably a cyclohexylene group which may have a substituent. In addition, as the substituent, an alkyl group is preferred, and a methyl group is more preferred.

[0072] In formula (A-2), X b1 and X b2 Each independently represents a substituent. b1 and X b2 Can be combined with R in formula (A-1) a1 and R a2 The substituents in the monovalent aromatic group which may have a substituent are the same.

[0073] In formula (A-2), a b and b b Each independently represents an integer of 0 to 3, preferably 0 or 1, and more preferably 0.

[0074] In formula (A-2), n b Represents 0 or 1.

[0075] Specific examples of the resin represented by formula (A-2) include the following resins.

[0076] [Chemical formula 11]

[0077] The resin represented by formula (A-2) can be obtained from the market. Commercially available products of the resin represented by formula (A-2) include, for example, "BPTMC-FE" manufactured by Honshu Chemical Industry Co., Ltd. (resin of formula (b-1)), "BP-FE" manufactured by Honshu Chemical Industry Co., Ltd. (resin of formula (b-2)), and "TMPBP-FE" manufactured by Honshu Chemical Industry Co., Ltd. (resin of formula (b-3)).

[0078] In addition, in (A) furan type curable resin, it is preferred that the furan type curable resin contains a free radical reactive unsaturated group in addition to the furan skeleton. Therefore, (A) furan type curable resin preferably contains a furan type curable resin containing a free radical reactive unsaturated group in addition to the furan skeleton, or it may only contain a furan type curable resin containing the free radical reactive unsaturated group. The furan type curable resin containing the free radical reactive unsaturated group usually does not generate a polar group due to the reaction during curing. Therefore, since the polarity of the insulating layer can be reduced, the dielectric loss tangent of the insulating layer can be reduced.

[0079] As an example of the furan type curable resin containing a radically reactive unsaturated group in addition to the furan skeleton, a resin represented by the following formula (A-3) can be mentioned.

[0080] [Chemical formula 12]

[0081] (In formula (A-3), R c1 , R c2 and R c3 Each independently represents a hydrogen atom or an alkyl group having 1 to 6 carbon atoms; R c4 represents a divalent aliphatic group which may have a substituent; X c Each independently represents a substituent; a c Indicates an integer from 0 to 3. )

[0082] In formula (A-3), R c1 , R c2 and R c3 Each independently represents a hydrogen atom or an alkyl group having 1 to 6 carbon atoms. c1 and R c2 Preferably, a hydrogen atom, R c3 Preferred is a hydrogen atom or a methyl group.

[0083] In formula (A-3), R c4 represents a divalent aliphatic group which may have a substituent. c4 The divalent aliphatic group optionally having a substituent may be combined with the group L in formula (A-1-1) a11 The divalent aliphatic group optionally having a substituent is the same as that described in the examples of c4 It is preferably an alkylene group, and more preferably a methylene group.

[0084] In formula (A-3), X c Each independently represents a substituent. c Can be combined with R in formula (A-1) a1 and R a2The substituents in the monovalent aromatic group which may have a substituent are the same. c It is preferably an acyl group, and more preferably a formyl group.

[0085] In formula (A-3), a c It represents an integer of 0 to 3, and is preferably 0 or 1.

[0086] Specific examples of the resin represented by formula (A-3) include the following resins.

[0087] [Chemical formula 13]

[0088] The resin represented by the formula (A-3) can be produced by the method described in Japanese Patent No. 5776717, for example.

[0089] Furthermore, in (A) furan type curable resin, preferably the furan type curable resin that the furan skeleton can react to produce bonding. Therefore, (A) furan type curable resin preferably comprises the furan type curable resin that the furan skeleton can react to produce bonding, and may also only comprise the furan type curable resin that the furan skeleton can react to produce bonding. The furan skeleton can usually produce bonding through Diels-Alder reaction. In such Diels-Alder reaction, polar groups are usually not generated. Therefore, since the polarity of the insulating layer can be reduced, the dielectric loss tangent of the insulating layer can be reduced.

[0090] Examples of preferred furan-type curable resins in which a furan skeleton can react to form a bond include a resin represented by the following formula (A-4).

[0091] [Chemical formula 14]

[0092] (In formula (A-4), R d1 Each independently represents a optionally substituted d +1-valent aliphatic group; X d1 Each independently represents a hydrogen atom or a substituent; X d2 Each independently represents a substituent; a d Each independently represents 1 or 2; b d Each independently represents an integer from 0 to 3; c d Indicates an integer from 1 to 4. )

[0093] In formula (A-4), R d1 Each independently represents a optionally substituted d +1-valent aliphatic group. As described later, due to ad represents an integer of 1 or 2, so R d1 It may be a divalent or trivalent aliphatic group which may have a substituent.

[0094] R d1 The optionally substituted divalent aliphatic group may be combined with the L in formula (A-1-1) a11 The divalent aliphatic group optionally having a substituent is the same as that described in the examples. d1 When it is a divalent aliphatic group, the R d1 An alkylene group is preferred, and an alkylene group having 3 to 12 carbon atoms is more preferred.

[0095] R d1 The trivalent aliphatic group in the trivalent aliphatic group which may optionally have a substituent may be a chain aliphatic group or a cyclic aliphatic group. The trivalent chain aliphatic group preferably has 1 to 12 carbon atoms, more preferably 1 to 6, and further preferably 1 to 4. On the other hand, the trivalent cyclic aliphatic group preferably has 3 to 15 carbon atoms, more preferably 3 to 12, and further preferably 3 to 10 carbon atoms. The number of carbon atoms does not include the number of carbon atoms of the substituent. The trivalent chain aliphatic group may be a saturated chain aliphatic group or an unsaturated chain aliphatic group. In addition, the trivalent cyclic aliphatic group may be a monocyclic cyclic aliphatic group or a polycyclic cyclic aliphatic group. In addition, as R d1 The substituents in the optionally substituted trivalent aliphatic group include, for example, a11 The substituents in the optionally substituted divalent aliphatic group are the same as those in the examples. d1 When it is a trivalent aliphatic group, the R d1 An aliphatic group having 1 carbon atom (that is, a group obtained by removing three hydrogen atoms from methane) is preferred.

[0096] In formula (A-4), X d1 Each independently represents a hydrogen atom or a substituent. d1 When it is a substituent, the substituent may be a1 and R a2 The substituents in the monovalent aromatic group which may have a substituent are the same. d1 It is preferably a hydrogen atom or an alkyl group, and more preferably a hydrogen atom or a methyl group.

[0097] In formula (A-4), X d2 Each independently represents a substituent. d2 Can be combined with R in formula (A-1) a1 and R a2The substituents in the monovalent aromatic group which may have a substituent are the same. d2 Preferred are an alkyl group and a hydroxyalkyl group, and more preferred are a methyl group and a hydroxymethyl group.

[0098] In formula (A-4), a d Each independently represents 1 or 2.

[0099] In formula (A-4), b d Each independently represents an integer of 0 to 3, and preferably 0 to 2.

[0100] In formula (A-4), c d Indicates an integer from 1 to 4.

[0101] Specific examples of the resin represented by formula (A-4) include the following resins. d2 It represents an alkylene group having 1 or more carbon atoms.

[0102] [Chemical formula 15]

[0103] The resin represented by formula (A-4) is commercially available. Examples of commercially available products of the resin represented by formula (A-4) include "BioPrepolymer (registered trademark) 1552L" (resin of formula (d-1)) manufactured by Daiei Sangyo Kaisha, Ltd.

[0104] Another example of a preferred furan-type curable resin in which a furan skeleton can react to form a bond is a resin containing a structural unit represented by the following formula (A-5).

[0105] [Chemical formula 16]

[0106] (In formula (A-5), R e1 represents a hydrogen atom, an alkyl group optionally having an alkoxy group, a cycloalkyl group optionally having an alkoxy group, an acyl group optionally having an alkoxy group, an aralkyl group optionally having an alkoxy group, a silyl group, or a group derived from a monovalent polyethylene glycol or a derivative thereof.

[0107] In formula (A-5), R e1 represents a hydrogen atom, an alkyl group optionally having an alkoxy group, a cycloalkyl group optionally having an alkoxy group, an acyl group optionally having an alkoxy group, an aralkyl group optionally having an alkoxy group, a silyl group, or a group derived from a monovalent polyethylene glycol or a derivative thereof. The "group derived from a monovalent polyethylene glycol or a derivative thereof" means a group obtained by removing one hydrogen atom from a monovalent polyethylene glycol or a derivative thereof. e1It is preferably a hydrogen atom or an alkyl group which may have an alkoxy group, more preferably a hydrogen atom or an alkyl group which does not have an alkoxy group, further preferably an alkyl group having 1 to 5 carbon atoms, and particularly preferably a methyl group.

[0108] Specific examples of the resin represented by formula (A-5) include resins having the following structure. In the following formula, n e represents the number of repetitions of the structural unit and represents an integer of 1 or greater.

[0109] [Chemical formula 17]

[0110] The resin represented by formula (A-5) can be produced by the method described in, for example, JP-A-2010-43203.

[0111] As another example of a preferred furan type curable resin capable of reacting to form a bond with a furan skeleton, there is mentioned a resin containing a structural unit represented by the following formula (A-6).

[0112] [Chemical formula 18]

[0113] (In formula (A-6), R f1 and R f2 Each independently represents a hydrogen atom, a hydrocarbon group optionally having a substituent, or a hydrocarbonoxy group optionally having a substituent; when R f1 When it is a hydrocarbon group optionally having a substituent or a hydrocarbonoxy group optionally having a substituent, two R f1 They can be directly combined or combined with each other via a linking group to form a ring; R f3 Each independently represents a hydrocarbon group having 1 to 20 carbon atoms and optionally having a substituent, or a hydrocarbonoxy group having 1 to 20 carbon atoms and optionally having a substituent; Y f1 Each independently represents -CH2-, -CHR f4 -、-C(R f4 )2-、-PR f4 -、-S-、-O-、-Si(R f4 )2-、-NR f4 - or -CH=CH-; R f4 Each independently represents a hydrocarbon group having 1 to 8 carbon atoms; f represents an integer greater than 0 and less than 256; b f represents an integer greater than 0 and less than 128; where a f +2b f is an integer greater than or equal to 2 and less than or equal to 256. )

[0114] In formula (A-6), R f1 and R f2 R each independently represents a hydrogen atom, a hydrocarbon group which may have a substituent, or a hydrocarbonoxy group which may have a substituent. f1 and R f2 The hydrocarbon group (including the hydrocarbon group contained in the hydrocarbonoxy group) may be an aliphatic hydrocarbon group or an aromatic hydrocarbon group. The aliphatic hydrocarbon group is preferably a saturated aliphatic hydrocarbon group. f1 and R f2 The number of carbon atoms of the hydrocarbon group is usually 1 or more and 20 or less. f1 and R f2 When the hydrocarbon group is an aliphatic hydrocarbon group, the carbon number of the aliphatic hydrocarbon group is usually 1 or more, usually 20 or less, preferably 12 or less, more preferably 8 or less, and further preferably 4 or less. f1 and R f2 When the hydrocarbon group is an aromatic hydrocarbon group, the number of carbon atoms of the aromatic hydrocarbon group is usually 3 or more, preferably 6 or more, and usually 20 or less, preferably 16 or less, and more preferably 12 or less.

[0115] As R f1 and R f2 The substituents in the optionally substituted hydrocarbon group and the optionally substituted hydrocarbonoxy group include, for example, a1 and R a2 The substituents in the monovalent aromatic group which may have a substituent are the same as those in the examples.

[0116] When R f1 When it is a hydrocarbon group optionally having a substituent or a hydrocarbonoxy group optionally having a substituent, two R f1 The alkyl groups may be directly bonded or bonded to each other via a linking group to form a ring. Examples of the linking group include -S-, -O-, -CO-, -COO-, -OCO-, -COS-, -SCO-, -CONR f5 -、-NR f5 CO-、-OCONR f5 -, -SO2-, -CH=CH-, -CH=N-, -N=CH-, -N=N-, -Si(R f5 )2-etc.(R f5 each independently represents a hydrocarbon group having 1 to 8 carbon atoms).

[0117] In the above, R f1 and R f2 Preferred is a hydrogen atom.

[0118] In formula (A-6), R f3R each independently represents a hydrocarbon group which may have a substituent or a hydrocarbonoxy group which may have a substituent. f3 The optionally substituted hydrocarbon group and the optionally substituted hydrocarbonoxy group shown in f1 and R f2 The hydrocarbon group optionally having a substituent and the hydrocarbonoxy group optionally having a substituent are the same. f3 It is preferably a hydrocarbon group optionally having a substituent, more preferably a hydrocarbon group having no substituent, further preferably a saturated aliphatic hydrocarbon group, further preferably an alkyl group, and particularly preferably a methyl group. f3 They may be different, but are preferably the same groups.

[0119] In formula (A-6), Y f1 Each independently represents -CH2-, -CHR f4 -、-C(R f4 )2-、-PR f4 -、-S-、-O-、-Si(R f4 )2-、-NR f4 - or -CH=CH-. f4 Each independently represents a hydrocarbon group having 1 to 8 carbon atoms.

[0120] In formula (A-6), a f It represents an integer of 0 to 256, preferably an integer of 0 to 16, more preferably an integer of 2 to 8, and even more preferably 2, 4, or 8.

[0121] In formula (A-6), b f It represents an integer of 0 to 128, preferably an integer of 0 to 8, more preferably 0, 2 or 4, and even more preferably 0.

[0122] Among them, a f +2b f It is an integer of 2 to 256, preferably an integer of 2 to 16, more preferably an integer of 2 to 8, further preferably 2, 4 or 8, particularly preferably 4 or 8.

[0123] Furthermore, a contained in formula (A-6) f Unit and b f The arrangement of the units is not particularly limited, and the units may be arranged randomly, alternately, or continuously in the same structure.

[0124] In the resin containing the structural unit shown in formula (A-6), it is possible to combine with the structural unit shown in formula (A-6) to include any structural unit. As any structural unit, a structural unit from a diene compound and a structural unit from a diyne compound can be cited. The structural unit from a diene compound represents a structural unit having a structure obtained by polymerizing a diene compound. A diene compound is a compound having two carbon-carbon double bonds in one molecule, and for example, a hydrocarbon compound having two carbon-carbon double bonds and a compound having a structure in which an oxygen atom is between the carbon-carbon bonds of the hydrocarbon compound can be cited. In addition, a structural unit from a diyne compound represents a structural unit having a structure obtained by polymerizing a diyne compound. A diyne compound is a compound having two carbon-carbon triple bonds in one molecule, and for example, a hydrocarbon compound having two carbon-carbon triple bonds and a compound having an oxygen atom between the carbon-carbon bonds of the hydrocarbon compound can be cited. Therefore, the structural unit derived from the diene compound and the structural unit derived from the diyne compound may be, for example, a hydrocarbon group or a hydrocarbon group in which an oxygen atom is optionally present between carbon-carbon bonds (a hydrocarbon group in which an oxygen atom is present between carbon-carbon bonds). Specific examples of the arbitrary structural unit include: a divalent hydrocarbon group having 1 to 20 carbon atoms (e.g., an alkylene group), and a group in which an oxygen atom is present between carbon-carbon bonds of the divalent hydrocarbon group.

[0125] Specific examples of the resin represented by formula (A-6) include resins having the following structure. In the following formula, n f represents the number of repetitions of the structural unit and represents an integer of 1 or greater.

[0126] [Chemical formula 19]

[0127] The resin represented by formula (A-6) can be produced by the method described in International Publication No. 2023 / 100914, for example.

[0128] As still another example of a preferred furan type curable resin capable of reacting to form a bond with a furan skeleton, dimethyl 3,3′-dihexyl-5,5′-dimethoxy-2,2′-bifuran-4,4′-dicarboxylate and the like can be mentioned.

[0129] (A) The furan type curable resin may be used alone or in combination of two or more.

[0130] The number average molecular weight of the furan curable resin (A) is preferably 100 or more, more preferably 500 or more, and even more preferably 1000 or more, and is preferably 1000000 or less, more preferably 500000 or less, and even more preferably 100000 or less, and may be 10000 or less, 5000 or less, or 3000 or less. The number average molecular weight can be measured as a value in terms of polystyrene by gel permeation chromatography (GPC) method.

[0131] In the case where the (A) furan curable resin contains an active group other than a furan skeleton, the range of the active group equivalent of the (A) furan curable resin is preferably 100 g / eq. or more, more preferably 120 g / eq. or more, and further preferably 130 g / eq. or more, preferably 500000 g / eq. or less, more preferably 250000 g / eq. or less, and further preferably 50000 g / eq. or less, and may be 5000 or less, 2500 or less, or 1500 or less. For example, in the case where the (A) furan curable resin contains an active ester group as an active group, it is preferred that the (A) furan curable resin has an active group equivalent in the above range. The active group equivalent represents the mass of a resin containing 1 equivalent of active groups.

[0132] (A) furan type curable resin is preferably a resin manufactured using raw materials of plant origin. The resin containing the furan skeleton can be derived and synthesized from biomass such as plant-derived glucose, plant-derived cellulose, and plant-derived fructose. For example, raw material compounds having reactive groups at positions 2 and 5 of the furan skeleton such as 5-hydroxymethylfurfural and 2,5-furandicarboxylic acid can be derived and synthesized from biomass. Therefore, resins having groups other than hydrogen atoms bonded to positions 2 and 5 of the furan skeleton can be manufactured from these raw material compounds and used for (A) furan type curable resin. In this way, by using (A) furan type curable resin manufactured from biomass, it can help promote energy conservation, cost savings, and sustainability.

[0133] The extent of biomass usage can be represented by the biomass ratio. The biomass ratio of the (A) furan-type curable resin is preferably large, specifically, preferably 10% by mass or more, more preferably 15% by mass or more, and further preferably 20% by mass or more. The upper limit is preferably 100% by mass or less.

[0134] According to the definition of the Japan Organic Resources Association, "biomass" refers to renewable organic resources derived from living things excluding fossil resources (however, it includes inorganic resources such as shells directly produced by living things). Based on this definition, the biomass ratio of a material can be calculated as the ratio of the mass of the biological components in the material to the mass of the material. Therefore, the biomass ratio of a resin can be calculated using the following formula (M1). Biomass ratio (mass %) = (mass of biomass components in resin / mass of resin) × 100 (M1) However, even when a component certified based on the mass balance method is included, the mass balance method is not adopted, and the biomass ratio is calculated based on the above-mentioned formula (M1).

[0135] Relative to the total amount 100 mass % of the resin composition layer, the range of the amount of (A) furan type curable resin in the resin composition layer is usually 2 mass % or more, preferably 2.5 mass % or more, and more preferably 3 mass % or more. In the case where the resin composition layer includes the amount of (A) furan type curable resin in the above range, unevenness as a problem to be solved in the present embodiment will be formed in the past. In the present embodiment, the unevenness can be eliminated. In addition, in particular, in the case of using a resin with a large biomass ratio as (A) furan type curable resin, the biomass ratio of the resin composition layer can be increased by using more of the (A) furan type curable resin. From the viewpoint of using a sufficient amount of (C) inorganic filler to obtain an insulating layer with excellent properties such as a linear thermal expansion coefficient, the upper limit of the amount of (A) furan type curable resin is preferably 40 mass % or less, more preferably 30 mass % or less, and further preferably 20 mass % or less.

[0136] Relative to 100% by mass of the non-volatile components in the resin composition layer, the range of the amount of (A) furan type curable resin in the resin composition layer is preferably 2% by mass or more, more preferably 2.5% by mass or more, more preferably 3% by mass or more, preferably 50% by mass or less, more preferably 40% by mass or less, more preferably 30% by mass or less, and more preferably 20% by mass or less. The non-volatile components in the resin composition layer, unless otherwise specified, represent the components other than the solvent in the resin composition layer. When the amount of (A) furan type curable resin is within the above range, there is a tendency to easily form unevenness in the insulating layer in the past, but in this embodiment, the unevenness can be suppressed. In addition, when a resin with a large biomass ratio is used as (A) furan type curable resin, the biomass ratio of the resin composition layer can be increased. Furthermore, the linear thermal expansion coefficient, dielectric loss tangent and glass transition temperature of the insulating layer can usually be improved.

[0137] Relative to 100% by mass of the resin component in the resin composition layer, the range of the amount of (A) furan type curable resin in the resin composition layer is preferably 3% by mass or more, more preferably 5% by mass or more, particularly preferably 10% by mass or more, preferably 80% by mass or less, more preferably 70% by mass or less, further preferably 60% by mass or less, particularly preferably 40% by mass or less. Unless otherwise specified, the resin component in the resin composition layer refers to the component after removing (C) inorganic filler from the non-volatile component in the resin composition layer. When the amount of (A) furan type curable resin is within the above range, there is a tendency to easily form unevenness in the insulating layer in the past, but in this embodiment, the unevenness can be suppressed. In addition, when a resin with a large biomass ratio is used as (A) furan type curable resin, the biomass ratio of the resin composition layer can be increased. Furthermore, the linear thermal expansion coefficient, dielectric loss tangent and glass transition temperature of the insulating layer can usually be improved.

[0138] <(B)Tetrahydrofuran> The resin composition layer of the resin sheet contains (B) tetrahydrofuran as the (B) component. (B) Tetrahydrofuran is a component that can function as a solvent during the formation of the resin composition layer and is generally contained in the resin composition layer in a state compatible with the resin component such as the (A) furan type curable resin.

[0139] Relative to the total amount 100 mass % of the resin composition layer, the range of the amount of (B) tetrahydrofuran in the resin composition layer is usually 0.10 mass % or more, preferably 0.12 mass % or more, and more preferably 0.14 mass % or more. When the resin composition layer contains such an amount of (B) tetrahydrofuran, the unevenness of the insulating layer can be suppressed. The upper limit is preferably 5 mass % or less, more preferably 3 mass % or less, and further preferably 2 mass % or less.

[0140] The amount of (B) tetrahydrofuran in the resin composition layer can be analyzed and calculated by GC-MS (gas chromatography-mass spectrometry).

[0141] The amount of (B) tetrahydrofuran in the resin composition layer can be adjusted by, for example, adjusting the amount of (B) tetrahydrofuran blended in the resin varnish or adjusting the drying conditions of the resin varnish during the production process of the resin sheet.

[0142] The amount of (B) tetrahydrofuran in the resin composition layer is preferably in the range of 2 mass % or more, more preferably 5 mass % or more, further preferably 8 mass % or more, and is usually 100 mass % or less, preferably 80 mass % or less, and more preferably 60 mass % or less, relative to 100 mass % of the total solvent in the resin composition layer.

[0143] The amount of the solvent in the resin composition layer can be analyzed and calculated by the GC-MS method.

[0144] The amount of (B) tetrahydrofuran in the resin composition layer relative to 100% by mass of the (A) furan-type curable resin in the resin composition layer is preferably in the range of 0.5% by mass or more, more preferably 1% by mass or more, further preferably 1.5% by mass or more, and is preferably 50% by mass or less, more preferably 40% by mass or less, further preferably 30% by mass or less.

[0145] <(C) Inorganic filler> The resin composition layer of the resin sheet includes an inorganic filler (C) as a component (C). The inorganic filler (C) is a particle of an inorganic material. Therefore, the inorganic filler (C) is contained in the resin composition layer in the form of particles, and is usually contained in the insulating layer in a form that maintains the particle state. According to the inorganic filler (C), the linear thermal expansion coefficient of the insulating layer can be reduced, so the warping of the circuit board can be reduced.

[0146] Relative to the non-volatile component 100% by mass in the resin composition layer, the range of the amount of (C) inorganic filler in the resin composition layer is usually more than 50% by mass, preferably more than 55% by mass, more preferably more than 60% by mass, preferably less than 90% by mass, more preferably less than 85% by mass, and further preferably less than 80% by mass. In the case where the resin composition layer includes the amount of (C) inorganic filler in the above-mentioned range, the unevenness as the problem to be solved in the present embodiment can be formed in the past. In the present embodiment, the unevenness can be eliminated. In addition, the resin composition layer including the amount of (C) inorganic filler in the above-mentioned range can form an insulating layer with a small linear thermal expansion coefficient, and then the dielectric loss tangent and the glass transition temperature of the insulating layer can usually be improved.

[0147] As the inorganic material forming (C) inorganic filling material, inorganic compounds are generally used. As the material of (C) inorganic filling material, for example, silica, aluminum oxide, 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, calcium zirconate, zirconium phosphate and zirconium tungstate phosphate, etc., can be cited. Among them, silica and aluminum oxide are preferred, and silica is particularly preferred. Therefore, (C) inorganic filling material preferably includes silica, and it is also possible to include only silica. As silica, for example, amorphous silica, fused silica, crystalline silica, synthetic silica, hollow silica, etc. can be cited. As silica, spherical silica is preferred. (C) The inorganic filler may be used alone or in combination of two or more.

[0148] Commercially available products of (C) inorganic fillers include, for example, "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 Yaduma 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 Co., Ltd.; and "Cellspheres" and "MGH-005" manufactured by Pacific Cement Co., Ltd.

[0149] The average particle size of the inorganic filler (C) is preferably 0.01 μm or more, more preferably 0.05 μm or more, further preferably 0.1 μm or more, and is preferably 10 μm or less, more preferably 5 μm or less, further preferably 3 μm or less, further preferably 1 μm or less.

[0150] (C) The average particle size of the inorganic filler can be measured by a laser diffraction / scattering method based on Mie scattering theory. Specifically, the particle size distribution of the inorganic filler can be made on a volume basis by a laser diffraction scattering particle size distribution measuring device, and the median particle size can be measured as the average particle size. The sample can be measured using a sample obtained by weighing 100 mg of inorganic filler and 10 g of methyl ethyl ketone in a vial and dispersing it with ultrasound for 10 minutes. For the sample, a laser diffraction particle size distribution measuring device is used, and the light source wavelength is blue and red, and the particle size distribution of the volume basis of the inorganic filler is measured in a flow cell manner, and the average particle size is calculated as the median particle size according to the obtained particle size distribution. As a laser diffraction particle size distribution measuring device, for example, "LA-960" made by Horiba, Ltd. can be cited.

[0151] (C) The specific surface area of ​​the inorganic filler is preferably 0.1 m 2 / g or more, more preferably 0.5m 2 / g or more, more preferably 1m 2 / g or more, particularly preferably 3m 2 / g or more, preferably 100m 2 / g or less, more preferably 70m 2 / g or less, more preferably 50m 2 / g or less, more preferably 40m 2 The specific surface area of ​​the inorganic filler can be measured by the BET method, using a specific surface area measuring device (Macsorb HM-1210 manufactured by Mountech Co., Ltd.) to adsorb nitrogen on the surface of a sample and calculating the specific surface area using the BET multipoint method.

[0152] From the viewpoint of improving moisture resistance and dispersibility, (C) inorganic filler is preferably treated with a surface treatment agent. As the surface treatment agent, for example, fluorine-containing silane coupling agents, aminosilane coupling agents, epoxysilane coupling agents, mercaptosilane coupling agents, silane coupling agents, alkoxysilanes, organosilazane compounds, titanate coupling agents, etc. can be cited. The surface treatment agent can be used alone or in any combination of two or more.

[0153] Commercially available products of the surface treatment agent include, for example, “KBM403” (3-glycidoxypropyltrimethoxysilane) manufactured by Shin-Etsu Chemical Co., Ltd., “KBM803” (3-mercaptopropyltrimethoxysilane) manufactured by Shin-Etsu Chemical Co., Ltd., “KBE903” (3-aminopropyltriethoxysilane) manufactured by Shin-Etsu Chemical Co., Ltd., “KBM573” (N-phenyl-3-aminopropyltrimethoxysilane) manufactured by Shin-Etsu Chemical Co., Ltd., “SZ-31” (hexamethyldisilazane) manufactured by Shin-Etsu Chemical Co., Ltd., “KBM103” (phenyltrimethoxysilane) manufactured by Shin-Etsu Chemical Co., Ltd., “KBM-4803” (long-chain epoxy-type silane coupling agent) manufactured by Shin-Etsu Chemical Co., Ltd., and “KBM-7103” (3,3,3-trifluoropropyltrimethoxysilane) manufactured by Shin-Etsu Chemical Co., Ltd.

[0154] From the viewpoint of improving the dispersibility of the inorganic filler, the degree of surface treatment using the surface treatment agent is preferably controlled within a specific range. Specifically, 100% by mass of the inorganic filler is preferably surface treated with 0.2% by mass to 5% by mass of the surface treatment agent, more preferably with 0.2% by mass to 3% by mass of the surface treatment agent, and further preferably with 0.3% by mass to 2% by mass of the surface treatment agent.

[0155] The degree of surface treatment by the surface treatment agent can be evaluated by the amount of carbon per unit surface area of ​​the inorganic filler. From the viewpoint of improving the dispersibility of the inorganic filler, the amount of carbon per unit surface area of ​​the inorganic filler is preferably 0.02 mg / m 2 More preferably 0.1 mg / m 2 More preferably, 0.2 mg / m 2 On the other hand, from the viewpoint of preventing the melt viscosity of the resin composition layer from increasing, it is preferably 1.0 mg / m 2 Below, more preferably 0.8 mg / m 2 Below, more preferably 0.5 mg / m 2 the following.

[0156] (C) The amount of carbon per unit surface area of ​​the inorganic filler can be measured after the surface-treated inorganic filler is cleaned with a solvent (e.g., methyl ethyl ketone (MEK). Specifically, a sufficient amount of MEK is added as a solvent to the inorganic filler surface-treated with a surface treatment agent, and ultrasonic cleaning is performed at 25° C. for 5 minutes. After removing the supernatant and drying the solid component, the amount of carbon per unit surface area of ​​the inorganic filler can be measured using a carbon analyzer. As a carbon analyzer, "EMIA-320V" manufactured by Horiba, Ltd. can be used.

[0157] The total amount of the (A) furan-type curable resin and the (C) inorganic filler in the resin composition layer, relative to 100% by mass of the non-volatile component in the resin composition layer, is preferably in the range of 52% by mass or more, more preferably 53% by mass or more, further preferably 54% by mass or more, and is preferably 95% by mass or less, more preferably 90% by mass or less, and further preferably 86% by mass or less.

[0158] The total amount of the (A) furan-type curable resin, (B) tetrahydrofuran and (C) inorganic filler in the resin composition layer is preferably 53% by mass or more, more preferably 55% by mass or more, and further preferably 57% by mass or more, and is preferably 99% by mass or less, more preferably 95% by mass or less, and further preferably 90% by mass or less, relative to the total amount of the resin composition layer (100% by mass).

[0159] <(D) Any curable resin> The resin composition layer of the resin sheet may include any curable resin (D) other than the furan-type curable resin (A) as an arbitrary component. The curable resin (D) as the component (D) does not include substances belonging to the above-mentioned components (A) to (C). The curable resin (D) as the component (D) may be a thermosetting resin, a photocurable resin, or a combination thereof. Among them, the curable resin (D) preferably includes a thermosetting resin, or may include only a thermosetting resin. The curable resin (D) may be used alone or in combination of two or more.

[0160] Examples of any curable resin (D) include epoxy resins, phenol resins, active ester resins, carbodiimide resins, cyanate resins, anhydride resins, amine resins, benzoxazine resins, thiol resins, and radical polymerizable resins. Among them, epoxy resins are preferred. Hereinafter, epoxy resins classified as any curable resin (D) are sometimes referred to as "(D-1) epoxy resins".

[0161] (D-1) Epoxy resin is a curable resin having an epoxy group. When (A) furan curable resin contains an active group such as an active ester group that can react with an epoxy group, (D-1) epoxy resin can react with (A) furan curable resin to form a bond.

[0162] Examples of the epoxy resin (D-1) include biphenylol epoxy resins, bisphenol A epoxy resins, bisphenol F epoxy resins, bisphenol S epoxy resins, bisphenol AF epoxy resins, dicyclopentadiene epoxy resins, trisphenol epoxy resins, naphthol novolac epoxy resins, phenol novolac epoxy resins, tert-butyl-catechol epoxy resins, naphthalene epoxy resins, naphthol epoxy resins, anthracene epoxy resins, glycidylamine epoxy resins, glycidyl ester epoxy resins, cresol novolac epoxy resins, and bisphenol A epoxy resins. Lacquer type epoxy resin, phenol aralkyl type epoxy resin, biphenyl 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, naphthyl ether type epoxy resin, trimethylol type epoxy resin, tetraphenylethane type epoxy resin, isocyanurate type epoxy resin, phenolphthalimidine type epoxy resin, etc. (D-1) Epoxy resins may be used alone or in combination of two or more.

[0163] From the viewpoint of obtaining an insulating layer with excellent heat resistance, the (D-1) epoxy resin preferably includes an epoxy resin containing an aromatic structure. The aromatic structure is a chemical structure generally defined as an aromatic structure, and also includes polycyclic aromatics and aromatic heterocycles. Examples of the epoxy resin containing an aromatic structure include biphenylol type epoxy resins, bisphenol A type epoxy resins, bisphenol F type epoxy resins, bisphenol S type epoxy resins, bisphenol AF type epoxy resins, dicyclopentadiene type epoxy resins, trisphenol type epoxy resins, naphthol novolac type epoxy resins, phenol novolac type epoxy resins, tert-butyl-catechol type epoxy resins, naphthalene type epoxy resins, naphthol type epoxy resins, anthracene type epoxy resins, biphenylol type epoxy resins, glycidylamine type epoxy resins having an aromatic structure, and epoxy resins having an aromatic structure. The epoxy resins include glycidyl ester epoxy resins with aromatic structure, cresol novolac epoxy resins, biphenyl epoxy resins, linear aliphatic epoxy resins with aromatic structure, epoxy resins with butadiene structure with aromatic structure, alicyclic epoxy resins with aromatic structure, heterocyclic epoxy resins, epoxy resins containing spiro rings with aromatic structure, cyclohexanedimethanol epoxy resins with aromatic structure, naphthyl ether epoxy resins, trimethylol epoxy resins with aromatic structure, tetraphenylethane epoxy resins with aromatic structure, etc.

[0164] The (D-1) epoxy resin preferably contains an epoxy resin having two or more epoxy groups in one molecule. 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, and particularly preferably 70% by mass or more, relative to 100% by mass of the nonvolatile component of the epoxy resin.

[0165] Generally, epoxy resins include epoxy resins that are liquid at 20° C. (hereinafter sometimes referred to as “liquid epoxy resins”) and epoxy resins that are solid at 20° C. (hereinafter sometimes referred to as “solid epoxy resins”). (D-1) The epoxy resin may contain only a liquid epoxy resin, only a solid epoxy resin, or a combination of a liquid epoxy resin and a solid epoxy resin.

[0166] As the liquid epoxy resin, a liquid epoxy resin having two or more epoxy groups in one molecule is preferred.

[0167] As liquid epoxy resins, preferred are bisphenol A type epoxy resins, bisphenol F type epoxy resins, bisphenol AF type epoxy resins, naphthalene type epoxy resins, glycidyl ester type epoxy resins, glycidyl amine type epoxy resins, phenol novolac type epoxy resins, alicyclic epoxy resins having an ester skeleton, cyclohexane type epoxy resins, cyclohexanedimethanol type epoxy resins, and epoxy resins having a butadiene structure.

[0168] Specific examples of liquid epoxy resins include "HP4032", "HP4032D", and "HP4032SS" (naphthalene-type epoxy resins) manufactured by DIC Corporation; "828US", "828EL", "jER828EL", "825", and "EPIKOTE "828EL" (bisphenol A type epoxy resin); "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 Chemicals Co., Ltd.; "YD-8125G" (bisphenol A type epoxy resin) manufactured by Nippon Steel Chemicals Co., Ltd.; Nagase "EX-721" (glycidyl ester type epoxy resin) manufactured by ChemteX; "CELLOXIDE2021P" (alicyclic epoxy resin with ester skeleton) manufactured by Daicel Corporation; "PB-3600" manufactured by Daicel Corporation, "JP-100" and "JP-200" manufactured by Nippon Soda Co., Ltd. (epoxy resin with butadiene structure); "ZX1658" and "ZX1658GS" (liquid 1,4-glycidylcyclohexane type epoxy resin) manufactured by Nippon Steel Chemical Materials Co., Ltd., etc. These can be used alone or in combination of two or more.

[0169] As the solid epoxy resin, a solid epoxy resin having three or more epoxy groups in one molecule is preferred, and an aromatic solid epoxy resin having three or more epoxy groups in one molecule is more preferred.

[0170] As solid epoxy resins, preferred are biphenylol-type epoxy resins, naphthalene-type epoxy resins, naphthalene-type tetrafunctional epoxy resins, naphthol novolac-type epoxy resins, cresol novolac-type epoxy resins, dicyclopentadiene-type epoxy resins, trisphenol-type epoxy resins, naphthol-type epoxy resins, biphenyl-type epoxy resins, naphthyl ether-type epoxy resins, anthracene-type epoxy resins, bisphenol A-type epoxy resins, bisphenol AF-type epoxy resins, phenol aralkyl-type epoxy resins, tetraphenylethane-type epoxy resins, and phenol benzopyrrolidone-type epoxy resins.

[0171] Specific examples of solid epoxy resins include "HP4032H" (naphthalene-type epoxy resin) manufactured by DIC Corporation; "HP-4700" and "HP-4710" (naphthalene-type tetrafunctional epoxy resin) manufactured by DIC Corporation; "N-690" (cresol novolac-type epoxy resin) manufactured by DIC Corporation; "N-695" (cresol novolac-type epoxy resin) manufactured by DIC Corporation; "HP-7200", "HP-7200HH", "HP-7200H", and "HP-7200L" (dicyclopentadiene-type epoxy resin) manufactured by DIC Corporation; and "HP-7200HH" and "HP-7200H" and "HP-7200L" (dicyclopentadiene-type epoxy resin) manufactured by DIC Corporation. "EXA-7311", "EXA-7311-G3", "EXA-7311-G4", "EXA-7311-G4S", "HP6000", "HP6000L" (naphthyl ether type epoxy resin); "EPPN-502H" (trisphenol type epoxy resin) manufactured by Nippon Kayaku Co., Ltd., "NC7000L" (naphthol novolac 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 Chemicals; "ESN485" (naphthol type epoxy resin) manufactured by Nippon Steel Chemicals; "ESN375" (dihydroxynaphthalene type epoxy resin) manufactured by Nippon Steel Chemicals; "YX4000H", "YX4000", "YX4000HK", "YL7890" (biphenyl type epoxy resin) manufactured by Mitsubishi Chemical; "YL6121" (biphenyl type epoxy resin) manufactured by Mitsubishi Chemical; "YX8800" (anthracene type epoxy resin) manufactured by Mitsubishi Chemical "YX7700" (phenol aralkyl type epoxy resin) manufactured by Mitsubishi Chemical Corporation; "PG-100" and "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; "WHR-991S" (phenol benzopyrrolidone type epoxy resin) manufactured by Nippon Kayaku Co., Ltd., etc. These may be used alone or in combination of two or more.

[0172] When the epoxy resin combination (D-1) comprises a liquid epoxy resin and a solid epoxy resin, the mass ratio of these (liquid epoxy resin:solid epoxy resin) is preferably 20:1 to 1:20, more preferably 10:1 to 1:10, and particularly preferably 7:1 to 1:7.

[0173] The epoxy equivalent of the epoxy resin (D-1) is preferably in the range of 50 g / eq. to 5000 g / eq., more preferably 60 g / eq. to 3000 g / eq., further preferably 80 g / eq. to 2000 g / eq., and particularly preferably 110 g / eq. to 1000 g / eq. The epoxy equivalent represents the mass of the resin per 1 equivalent of epoxy group. The epoxy equivalent can be measured according to JIS K 7236.

[0174] The weight average molecular weight (Mw) of the epoxy resin (D-1) is preferably in the range of 100 to 5000, more preferably 250 to 3000, and even more preferably 400 to 1500. The weight average molecular weight of the resin can be measured as a value in terms of polystyrene by gel permeation chromatography (GPC).

[0175] The amount of the epoxy resin (D-1) in the resin composition layer relative to 100% by mass of the non-volatile component in the resin composition layer is preferably in the range of 1% by mass or more, more preferably 5% by mass or more, further preferably 10% by mass or more, and is preferably 45% by mass or less, more preferably 40% by mass or less, further preferably 35% by mass or less.

[0176] The amount of the epoxy resin (D-1) in the resin composition layer is preferably 10% by mass or more, more preferably 20% by mass or more, further preferably 40% by mass or more, and is preferably 90% by mass or less, more preferably 80% by mass or less, and further preferably 70% by mass or less, relative to 100% by mass of the resin component in the resin composition layer.

[0177] For (D-1) epoxy resin, it can be that (D-1) epoxy resins react with each other, and it can be that (D-1) epoxy resin and curing agent react. As curing agent, for example, resin containing active groups that can react with epoxy groups in (A) furan type curable resin and any curing agent (D-2) described later can be cited. In this way, when the curing agent that can react with (D-1) epoxy resin is included in the resin composition layer, the amount ratio of the number of epoxy groups of (D-1) epoxy resin to the number of active groups of curing agent is preferably within a specific range. Specifically, when the number of epoxy groups of (D-1) epoxy resin is set to 1, the range of the number of active groups of the active groups of the curing agent that can react with epoxy groups is preferably 0.1 or more, more preferably 0.2 or more, more preferably 0.3 or more, preferably 5.0 or less, more preferably 4.0 or less, and more preferably 3.0 or less. The “number of epoxy groups of (D-1) epoxy resin” refers to the value obtained by adding up all the values ​​obtained by dividing the mass of the nonvolatile components of the (D-1) epoxy resin present in the resin composition layer by the epoxy equivalent. In addition, the “number of active groups of the active groups of the curing agent capable of reacting with the epoxy group” refers to the value obtained by adding up all the values ​​obtained by dividing the mass of the nonvolatile components of the curing agent present in the resin composition layer by the active group equivalent of the active groups capable of reacting with the epoxy group.

[0178] (D) Any curable resin may also include any curing agent (D-2) that can react with an epoxy resin to cure the resin composition layer. In particular, (D) Any curable resin preferably includes (D-1) an epoxy resin and (D-2) Any curing agent. As (D-2) Any curing agent, for example, phenol resin, active ester resin, cyanate resin, carbodiimide resin, anhydride resin, amine resin, benzoxazine resin, thiol resin, etc. can be cited. Among them, phenol resin and active ester resin are preferred. In addition, (D-2) Any curing agent can be used alone or in combination of two or more.

[0179] As the phenol resin, a resin having one or more, preferably two or more hydroxyl groups (phenolic hydroxyl groups) bonded to aromatic rings such as a benzene ring and a naphthalene ring in one molecule can be used. From the viewpoint of heat resistance and water resistance, a phenol resin having a phenolic structure is preferred. In addition, from the viewpoint of adhesion, a nitrogen-containing phenol resin is preferred, and a phenol resin containing a triazine skeleton is more preferred. Among them, from the viewpoint of highly satisfying heat resistance, water resistance and adhesion, a linear phenolic resin containing a triazine skeleton is preferred. Specific examples of phenolic resins include "MEH-7700", "MEH-7810", and "MEH-7851" manufactured by Meiwa Chemicals Co., Ltd., "NHN", "CBN", and "GPH" manufactured by Nippon Kayaku Co., Ltd., "SN-170", "SN-180", "SN-190", "SN-475", "SN-485", "SN-495", "SN-375", and "SN-395" manufactured by Nippon Steel Chemicals Co., Ltd., and "LA-7052", "LA-7054", "LA-3018", "LA-3018-50P", "LA-1356", "TD2090", and "TD-2090-60M" manufactured by DIC Corporation.

[0180] As the active ester resin, a resin having one or more, preferably two or more, active ester groups in one molecule can be used. Among them, preferred active ester resins are phenolic esters, thiophenolic esters, N-hydroxylamine esters, esters of heterocyclic hydroxy compounds, and the like, which have two or more highly reactive ester groups in one molecule.

[0181] The active ester resin is preferably 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 heat resistance, an active ester resin obtained from a carboxylic acid compound and a hydroxy compound is preferred, and an active ester resin obtained from a carboxylic acid compound and a phenol compound and / or a naphthol compound is more preferred. Examples of the carboxylic acid compound include benzoic acid, acetic acid, succinic acid, maleic acid, itaconic acid, phthalic acid, isophthalic acid, terephthalic acid, pyromellitic acid, and the like. Examples of the phenol compound or naphthol compound include hydroquinone, resorcinol, bisphenol A, bisphenol F, bisphenol S, phenolphthalein, methylated bisphenol A, methylated bisphenol F, methylated bisphenol S, phenol, o-cresol, m-cresol, p-cresol, catechol, α-naphthol, β-naphthol, 1,5-dihydroxynaphthalene, 1,6-dihydroxynaphthalene, 2,6-dihydroxynaphthalene, dihydroxybenzophenone, trihydroxybenzophenone, tetrahydroxybenzophenone, phloroglucinol, pyrogallol, dicyclopentadiene-type diphenol compounds, and novolac resins. Here, the “dicyclopentadiene-type diphenol compound” refers to a diphenol compound obtained by condensing two molecules of phenol with one molecule of dicyclopentadiene.

[0182] Specifically, the active ester resin is preferably 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 novolac resin, and an active ester resin containing a benzoylated product of a novolac resin, and more preferably at least one selected from a dicyclopentadiene type active ester resin and a naphthalene type active ester resin. The dicyclopentadiene type active ester resin is preferably an active ester resin containing a dicyclopentadiene type diphenol structure.

[0183] Commercially available products of active ester resins include, for example, "EXB9451", "EXB9460", "EXB9460S", "EXB-8000L", "EXB-8000L-65M", "EXB-8000L-65TM", "HPC-8000L-65TM", "HPC-8000", "HPC-8000-65T", "HPC-8000H", and "HPC-8000H-65TM" (manufactured by DIC Corporation) as active ester resins containing a dicyclopentadiene-type diphenol structure; and "HP-B-8151-62T", "EXB-8100L-65T", "EXB-8150-60T", "EXB-8100L-65T", "EXB-8100-60 ... B-8150-62T", "EXB-9416-70BK", "HPC-8150-60T", "HPC-8150-62T", "EXB-8" (manufactured by DIC Corporation); as active ester resins containing phosphorus, "EXB9401" (manufactured by DIC Corporation) can be mentioned; as active ester resins of acetylated products of linear phenolic resins, "DC808" (manufactured by Mitsubishi Chemical Corporation) can be mentioned; as active ester resins of benzoylated products of linear phenolic resins, "YLH1026", "YLH1030", "YLH1048" (manufactured by Mitsubishi Chemical Corporation) can be mentioned; as active ester resins containing styrene and naphthalene structures, "PC1300-02-65MA" (manufactured by AIRWATER Corporation) and the like can be mentioned.

[0184] As the carbodiimide resin, a resin having one or more, preferably two or more, carbodiimide structures in one molecule can be used. Specific examples of the carbodiimide resin include: aliphatic biscarbodiimides such as tetramethylene-bis(tert-butylcarbodiimide) and cyclohexanebis(methylene-tert-butylcarbodiimide); biscarbodiimides such as aromatic biscarbodiimides such as phenylene-bis(xylylcarbodiimide); aliphatic polycarbodiimides such as polyhexamethylenecarbodiimide, polytrimethylhexamethylenecarbodiimide, polycyclohexylenecarbodiimide, poly(methylenebiscyclohexylenecarbodiimide), poly(isophoronecarbodiimide); poly(phenylenecarbodiimide), poly(

[0043] Polycarbodiimides include aromatic polycarbodiimides such as naphthylene carbodiimide), poly(tolylene carbodiimide), poly(methyl diisopropyl phenylene carbodiimide), poly(triethyl phenylene carbodiimide), poly(diethyl phenylene carbodiimide), poly(triisopropyl phenylene carbodiimide), poly(diisopropyl phenylene carbodiimide), poly(xylylene carbodiimide), poly(tetramethyl xylylene carbodiimide), poly(methylene diphenylene carbodiimide), and poly[methylene bis(methyl phenylene) carbodiimide]. Examples of commercially available carbodiimide resins include "CARBODILITE V-02B", "CARBODILITE V-03", "CARBODILITE V-04K", "CARBODILITE V-07" and "CARBODILITE V-09" manufactured by Nisshinbo Chemical Co., Ltd.; and "Stabaxol P", "Stabaxol P400" and "Hycasyl 510" manufactured by Lanxess Co., Ltd.

[0185] As the cyanate resin, a resin having one or more, preferably two or more, cyanate groups in one molecule can be used. Examples of the cyanate resin include difunctional cyanate resins such as bisphenol A dicyanate, polyphenol cyanate (oligo(3-methylene-1,5-phenylene cyanate)), 4,4′-methylenebis(2,6-dimethylphenylcyanate), 4,4′-ethylidene diphenyl dicyanate, hexafluorobisphenol A dicyanate, 2,2-bis(4-cyano)phenylpropane, 1,1-bis(4-cyanophenylmethane), bis(4-cyano-3,5-dimethylphenyl)methane, 1,3-bis(4-cyanophenyl-1-(methylethylidene))benzene, bis(4-cyanophenyl)sulfide and bis(4-cyanophenyl)ether; polyfunctional cyanate resins derived from phenol novolac resins and cresol novolac resins; and prepolymers obtained by triazinization of a portion of these cyanate resins. Specific examples of cyanate resins include "PT30" and "PT60" manufactured by Lonza (both are linear phenolic polyfunctional cyanate resins), "BA230" and "BA230S75" (prepolymers in which a part or all of bisphenol A dicyanate is triazine-formed to form a trimer), etc.

[0186] As the acid anhydride resin, a resin having one or more, preferably two or more acid anhydride groups in one molecule can be used. 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, dodecenylsuccinic anhydride, 5-(2,5-dioxotetrahydro-3-furyl)-3-methyl-3-cyclohexene-1,2-dicarboxylic anhydride, trimellitic anhydride, pyromellitic anhydride, benzophenonetetracarboxylic dianhydride, biphenyltetracarboxylic dianhydride, naphthalenetetracarboxylic dianhydride, oxydiphthalic dianhydride, 3,3'-4,4'-diphenylsulfonetetracarboxylic dianhydride, ethylene glycol bis(trimellitic anhydride ester), and polymer-type acid anhydrides such as styrene-maleic acid resin obtained by copolymerizing styrene and maleic acid. Commercially available products of the acid anhydride resin include, for example, "HNA-100", "MH-700", "MTA-15", "DDSA", and "OSA" manufactured by Shin Nippon Rika Co., Ltd., "YH-306" and "YH-307" manufactured by Mitsubishi Chemical Corporation, "HN-2200" manufactured by Resonac, and "EF-30", "EF-40", "EF-60", and "EF-80" manufactured by Cray Valley.

[0187] As the amine resin, a resin having one or more, preferably two or more, amino groups in one molecule can be used. Examples of the amine resin include aliphatic amines, polyether amines, alicyclic amines, aromatic amines, and the like, among which 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'-diaminodiphenyl sulfone, 3,3'-diaminodiphenyl sulfone, metaphenylenediamine, metaphenylenediamine, 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-hydroxybenzene bis(4-aminophenoxy)phenyl)sulfone, bis(4-(3-aminophenoxy)phenyl)sulfone, and the like. Examples of commercially available amine resins include “SEIKACURE-S” manufactured by SEIKA Corporation; “KAYABOND C-200S”, “KAYABOND C-100”, “KAYAHARD AA”, “KAYAHARD AB”, and “KAYAHARD AS” manufactured by Nippon Kayaku Co., Ltd.; “Epicure W” manufactured by Mitsubishi Chemical Corporation; and “DTDA” manufactured by Sumitomo Seika Chemicals Co., Ltd.

[0188] Specific examples of the benzoxazine resin include “JBZ-OP100D” and “ODA-BOZ” manufactured by JFE Chemical Co., Ltd.; “HFB2006M” manufactured by Showa High Molecular Co., Ltd.; and “Pd” and “Fa” manufactured by Shikoku Chemical Industry Co., Ltd.

[0189] Examples of the thiol resin include trimethylolpropane tris(3-mercaptopropionate), pentaerythritol tetrakis(3-mercaptobutyrate), and tris(3-mercaptopropyl)isocyanurate.

[0190] The range of the active group equivalent of the arbitrary curing agent (D-2) is preferably 50 g / eq. to 3000 g / eq., more preferably 100 g / eq. to 1000 g / eq., further preferably 100 g / eq. to 500 g / eq., particularly preferably 100 g / eq. to 300 g / eq.

[0191] The range of the weight average molecular weight of the arbitrary curing agent (D-2) may be the same as the range of the weight average molecular weight (Mw) of the epoxy resin (D-1).

[0192] The amount of any curing agent (D-2) in the resin composition layer is preferably in the range of 0.01% by mass or more, more preferably 0.1% by mass or more, further preferably 0.5% by mass or more, preferably 20% by mass or less, more preferably 15% by mass or less, and particularly preferably 10% by mass or less, relative to 100% by mass of the non-volatile component in the resin composition layer.

[0193] The amount of any curing agent (D-2) in the resin composition layer is preferably in the range of 0.1% by mass or more, more preferably 0.5% by mass or more, further preferably 1% by mass or more, and preferably 50% by mass or less, more preferably 40% by mass or less, further preferably 30% by mass or less, relative to 100% by mass of the resin component in the resin composition layer.

[0194] (D) Any curable resin may include (D-3) a radical polymerizable resin. (D-3) A radical polymerizable resin generally contains a non-aromatic carbon-carbon unsaturated bond. Therefore, as the (D-3) radical polymerizable resin, a resin containing a radically reactive unsaturated group may be used. The (D-3) radical polymerizable resin may be a resin in which the (D-3) radical polymerizable resins react with each other, or a resin in which the (D-3) radical polymerizable resin and the (A) furan-type curable resin react by a Diels-Alder reaction or the like. Such a (D-3) radical polymerizable resin preferably has two or more radically reactive unsaturated groups.

[0195] Examples of the radical polymerizable resin (D-3) include (meth)acrylic radical polymerizable resins, styrene radical polymerizable resins, allyl radical polymerizable resins, maleimide radical polymerizable resins, etc. The radical polymerizable resin (D-3) may be used alone or in combination of two or more.

[0196] As the (meth)acrylic radical polymerizable resin, a resin having one or more, preferably two or more, acryloyl groups and / or methacryloyl groups in one molecule can be used. Examples of the (meth)acrylic radical polymerizable resin include low molecular weight (molecular weight less than 1000) aliphatic (meth)acrylate compounds such as cyclohexane-1,4-dimethanol di(meth)acrylate, cyclohexane-1,3-dimethanol di(meth)acrylate, tricyclodecane dimethanol di(meth)acrylate, neopentyl glycol di(meth)acrylate, 1,4-butanediol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, 1,8-octanediol di(meth)acrylate, 1,9-nonanediol di(meth)acrylate, 1,10-decanediol di(meth)acrylate, trimethylolpropane tri(meth)acrylate, trimethylolethane tri(meth)acrylate, glycerol tri(meth)acrylate, and pentaerythritol tetra(meth)acrylate; and dioxanediol di(meth)acrylate, 3,6-dioxa-1,8-octanediol di(meth)acrylate, and 1,10-decanediol di(meth)acrylate. Ether-containing (meth)acrylate compounds having a low molecular weight (molecular weight less than 1000) such as glycol di(meth)acrylate, 3,6,9-trioxaundecane-1,11-diol di(meth)acrylate, polyethylene glycol di(meth)acrylate, polypropylene glycol di(meth)acrylate, 9,9-bis[4-(2-acryloyloxyethoxy)phenyl]fluorene, ethoxylated bisphenol A di(meth)acrylate, propoxylated bisphenol A di(meth)acrylate, etc.; isocyanurate-containing (meth)acrylate compounds having a low molecular weight (molecular weight less than 1000) such as tris(3-hydroxypropyl)isocyanurate tri(meth)acrylate, tris(2-hydroxyethyl)isocyanurate tri(meth)acrylate, ethoxylated isocyanuric acid tri(meth)acrylate, etc.; and high molecular weight (molecular weight 1000 or more) acrylate compounds such as (meth)acrylic acid-modified polyphenylene ether resin, etc. Here, the term "(meth)acrylic acid" includes acrylic acid, methacrylic acid and a combination thereof. In addition, the term "(meth)acrylate" includes acrylate, methacrylate and a combination thereof. As commercially available products of (meth)acrylic free radical polymerizable resins, for example, "A-DOG" (dioxanediol diacrylate) manufactured by Shin-Nakamura Chemical Industry Co., Ltd., "DCP-A" (tricyclodecane dimethanol diacrylate) manufactured by Kyoeisha Chemical Co., Ltd., "DCP" (tricyclodecane dimethanol dimethacrylate), "BPE-1300N" (ethoxylated bisphenol A dimethacrylate), "KAYARAD R-684" (tricyclodecane dimethanol diacrylate) manufactured by Nippon Kayaku Co., Ltd., "KAYARAD R-604" (dioxanediol diacrylate), "SA9000" and "SA9000-111" (methacrylic acid modified polyphenylene ether) manufactured by SABIC can be cited.

[0197] As the styrene-based free radical polymerizable resin, a resin having one or more, preferably two or more, vinyl groups directly bonded to aromatic carbon atoms in one molecule can be used. As the styrene-based free radical polymerizable resin, for example, low molecular weight (molecular weight less than 1000) styrene-based compounds such as divinylbenzene, 2,4-divinyltoluene, 2,6-divinylnaphthalene, 1,4-divinylnaphthalene, 4,4'-divinylbiphenyl, 1,2-bis(4-vinylphenyl)ethane, 2,2-bis(4-vinylphenyl)propane, bis(4-vinylphenyl)ether, and high molecular weight (molecular weight 1000 or more) styrene-based compounds such as vinylbenzyl-modified polyphenylene ether resin and styrene-divinylbenzene copolymer can be cited. Examples of commercially available styrene-based radical polymerizable resins include “ODV-XET (X03)”, “ODV-XET (X04)”, and “ODV-XET (X05)” (styrene-divinylbenzene copolymers) manufactured by Nippon Steel Chemical Materials Co., Ltd. and “OPE-2St 1200” and “OPE-2St 2200” (vinyl benzyl-modified polyphenylene ether resins) manufactured by Mitsubishi Gas Chemical Co., Ltd.

[0198] As the allyl radical polymerizable resin, a resin having one or more, preferably two or more, allyl groups in one molecule can be used. As the allyl radical polymerizable resin, for example, aromatic carboxylic acid allyl ester compounds such as diallyl diphenate, triallyl trimellitate, diallyl phthalate, diallyl isophthalate, diallyl terephthalate, 2,6-diallyl naphthalate, and 2,3-diallyl naphthoate; isocyanuric acid allyl ester compounds such as 1,3,5-triallyl isocyanurate and 1,3-diallyl-5-glycidyl isocyanurate; 2,2-bis[ Aromatic allyl compounds containing epoxy such as bis[3-allyl-4-(3,4-dihydro-2H-1,3-benzoxazin-3-yl)phenyl]methane; aromatic allyl compounds containing benzoxazine such as bis[3-allyl-4-(3,4-dihydro-2H-1,3-benzoxazin-3-yl)phenyl]methane; aromatic allyl compounds containing ether such as 1,3,5-triallyl ether benzene; allyl silane compounds such as diallyldiphenylsilane. Commercially available products of allyl radical polymerizable resins include, for example, "TAIC" (1,3,5-triallyl isocyanurate) manufactured by Nippon Chemical Industry Co., Ltd., Nisshoku Techno Fine Chemicals Co., Ltd., and Nisshoku Techno Fine Chemicals Co., Ltd. "DAD" (diallyl biphenyldicarboxylate) manufactured by Fujifilm Wako Pure Chemical Co., Ltd., "TRIAM-705" (triallyl trimellitate) manufactured by Fujifilm Wako Pure Chemical Co., Ltd., "DAND" (diallyl 2,3-naphthoate) manufactured by Nichikyu Techno Fine Chemicals Co., Ltd., "ALP-d" (bis[3-allyl-4-(3,4-dihydro-2H-1,3-benzoxazin-3-yl)phenyl]methane) manufactured by Shikoku Chemical Co., Ltd., "RE-810NM" (2,2-bis[3-allyl-4-(glycidyloxy)phenyl]propane) manufactured by Nippon Kayaku Co., Ltd., and "DA-MGIC" (1,3-diallyl-5-glycidyl isocyanurate) manufactured by Shikoku Chemical Co., Ltd.

[0199] As the maleimide-based free radical polymerizable resin, a resin having one or more, preferably two or more maleimide groups in one molecule can be used. The maleimide-based free radical polymerizable resin can be an aromatic maleimide resin having a maleimide group directly bonded to an aromatic ring, or an aliphatic maleimide resin having no maleimide group directly bonded to an aromatic ring. Commercially available products of maleimide-based radical polymerizable resins include, for example, "SLK-2600" manufactured by Shin-Etsu Chemical Co., Ltd., "BMI-1500", "BMI-1700", "BMI-3000J", "BMI-689", and "BMI-2500" (maleimide compounds containing a dimer diamine structure) manufactured by Designer Molecules Inc., "BMI-6100 (aromatic maleimide compound)" manufactured by Designer Molecules Inc., "MIR-5000-60T" and "MIR-3000-70MT" (biphenyl aralkyl type maleimide compounds) manufactured by Nippon Kayaku Co., Ltd., "BMI-70" and "BMI-80" manufactured by KI Chemicals Co., Ltd., and "BMI-2300" and "BMI-TMH" manufactured by Yamato Chemicals Co., Ltd. In addition, as the maleimide-based radical polymerizable resin, a maleimide resin (maleimide compound containing an indane ring skeleton) disclosed in Japan Invention Association Publication No. 2020-500211 can be used.

[0200] The radical polymerizable group equivalent of the radical polymerizable resin (D-3) is preferably 20 g / eq. to 3000 g / eq., more preferably 50 g / eq. to 2500 g / eq., further preferably 70 g / eq. to 2000 g / eq., and particularly preferably 90 g / eq. to 1500 g / eq. The radical polymerizable group equivalent represents the mass of the resin per 1 equivalent of the radical polymerizable group.

[0201] The weight average molecular weight (Mw) of the radical polymerizable resin (D-3) is preferably 40,000 or less, more preferably 10,000 or less, further preferably 5,000 or less, and particularly preferably 3,000 or less. The lower limit is not particularly limited, and may be, for example, 150 or more.

[0202] The amount of the (D-3) radical polymerizable resin in the resin composition layer relative to 100% by mass of the non-volatile component in the resin composition layer is preferably in the range of 0.1% by mass or more, more preferably 0.3% by mass or more, further preferably 0.5% by mass or more, preferably 10% by mass or less, more preferably 5% by mass or less, further preferably 3% by mass or less.

[0203] The amount of the (D-3) radical polymerizable resin in the resin composition layer is preferably in the range of 0.1% by mass or more, more preferably 1% by mass or more, further preferably 2% by mass or more, and preferably 30% by mass or less, more preferably 20% by mass or less, further preferably 10% by mass or less, relative to 100% by mass of the resin component in the resin composition layer.

[0204] The amount of any curable resin (D) in the resin composition layer relative to 100% by mass of the non-volatile component in the resin composition layer is preferably in the range of 1% by mass or more, more preferably 5% by mass or more, further 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.

[0205] The amount of any curable resin (D) in the resin composition layer is preferably in the range of 10% by mass or more, more preferably 20% by mass or more, further preferably 30% by mass or more, preferably 95% by mass or less, more preferably 90% by mass or less, and particularly preferably 80% by mass or less, relative to 100% by mass of the resin component in the resin composition layer.

[0206] <(E) Curing catalyst> The resin composition layer of the resin sheet may contain, as an optional component, a curing catalyst (E) that promotes the reaction of a curing resin such as (A) a furan-type curable resin and (D) an optional curable resin. The curing catalyst (E) as the component (E) does not contain any of the components (A) to (D) described above. The curing catalyst (E) as the component (E) may be used alone or in combination of two or more.

[0207] (E) curing catalysts include, for example, curing accelerators that are catalysts for accelerating the reaction of epoxy resins. Examples of curing accelerators include, for example, phosphorus curing accelerators, urea curing accelerators, guanidine curing accelerators, imidazole curing accelerators, metal curing accelerators, and amine curing accelerators. The curing accelerators may be used alone or in combination of two or more.

[0208] 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-butyldimethylphosphonium 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 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 are mentioned. Examples of commercially available phosphorus-based curing accelerators include "TBP-DA" manufactured by Hokko Chemical Industry Co., Ltd.

[0209] Examples of the urea curing accelerator include 1,1-dimethylurea; aliphatic dimethylureas such as 1,1,3-trimethylurea, 3-ethyl-1,1-dimethylurea, 3-cyclohexyl-1,1-dimethylurea, and 3-cyclooctyl-1,1-dimethylurea; 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) [toluenebisdimethylurea] and the like.

[0210] Examples of the guanidine-based curing accelerator include dicyandiamide, 1-methylguanidine, 1-ethylguanidine, 1-cyclohexylguanidine, 1-phenylguanidine, 1-(o-tolyl)guanidine, dimethylguanidine, diphenylguanidine, trimethylguanidine, tetramethylguanidine, pentamethylguanidine, 1,5,7-triazabicyclo[4.4.0]deca-5-ene, 7-methyl-1,5,7-triazabicyclo[4.4.0]deca-5-ene, 1-methyldiphenylamine, 1-ethyldiphenylamine, 1-n-butylbiguanidine, 1-n-octadecylbiguanidine, 1,1-dimethylbiguanidine, 1,1-diethylbiguanidine, 1-cyclohexylbiguanidine, 1-allylbiguanidine, 1-phenylbiguanidine, and 1-(o-tolyl)biguanidine.

[0211] Examples of the imidazole curing accelerator 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-undecylimidazole, 1-cyanoethyl-2-ethyl-4-methylimidazole, 1-cyanoethyl-2-phenylimidazole, 1-cyanoethyl-2-undecylimidazole trimellitate, 1-cyanoethyl-2-phenylimidazole trimellitate, 2,4-diamino-6-[2'-methylimidazolyl-(1') imidazole compounds such as 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, 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 adducts of imidazole compounds with epoxy resins. Commercially available products of imidazole-based curing accelerators include, for example, "1B2PZ", "2E4MZ", "2MZA-PW", "2MZ-OK", "2MA-OK", "2MA-OK-PW", "2PHZ", "2PHZ-PW", "Cl1Z", "Cl1Z-CN", "Cl1Z-CNS", and "C11Z-A" manufactured by Shikoku Chemical Industries, Ltd.; and "P200-H50" manufactured by Mitsubishi Chemical Corporation.

[0212] As metal curing accelerators, organic metal complexes or organic metal salts of metals such as cobalt, copper, zinc, iron, nickel, manganese, and tin can be cited. Specific examples of organic metal complexes include organic cobalt complexes such as cobalt acetylacetonate (II) and cobalt acetylacetonate (III); organic copper complexes such as copper acetylacetonate (II); organic zinc complexes such as zinc acetylacetonate (II); organic iron complexes such as iron acetylacetonate (III); organic nickel complexes such as nickel acetylacetonate (II); organic manganese complexes such as manganese acetylacetonate (II). As organic metal salts, for example, zinc octylate, tin octylate, zinc naphthenate, cobalt naphthenate, tin stearate, zinc stearate, etc. can be cited.

[0213] Examples of amine-based curing accelerators include trialkylamines such as triethylamine and tributylamine, 4-dimethylaminopyridine, benzyldimethylamine, 2,4,6-tris(dimethylaminomethyl)phenol, and 1,8-diazabicyclo(5,4,0)-undecene. Examples of commercially available amine-based curing accelerators include "MY-25" manufactured by Ajinomoto Fine-Techno Co., Ltd.

[0214] The amount of the curing accelerator in the resin composition layer relative to 100% by mass of the non-volatile component in the resin composition layer is preferably in the range of 0.01% by mass or more, more preferably 0.02% by mass or more, further preferably 0.05% by mass or more, preferably 2% by mass or less, more preferably 1% by mass or less, further preferably 0.5% by mass or less.

[0215] The amount of the curing accelerator in the resin composition layer relative to 100% by mass of the resin component in the resin composition layer is preferably in the range of 0.01% by mass or more, more preferably 0.1% by mass or more, further preferably 0.2% by mass or more, preferably 5% by mass or less, more preferably 2% by mass or less, further preferably 1% by mass or less.

[0216] (E) curing catalysts include, for example, free radical polymerization initiators that are catalysts for free radical reactions. The free radical polymerization initiators may be used alone or in any combination of two or more. The free radical polymerization initiators include, for example, peroxide-based free radical polymerization initiators, azo-based free radical polymerization initiators, and the like.

[0217] Examples of the peroxide-based radical polymerization initiator include hydroperoxide compounds such as 1,1,3,3-tetramethylbutyl hydroperoxide; dialkyl peroxide compounds such as tert-butyl isopropyl peroxide, di-tert-butyl peroxide, di-tert-hexyl peroxide, dicumyl peroxide, 1,4-bis(1-tert-butylperoxy-1-methylethyl)benzene, and 2,5-dimethyl-2,5-bis(tert-butylperoxy)hexane; dilauroyl peroxide, didecanoyl peroxide, dicyclohexyl peroxydicarbonate, bis(4-tert-butylcyclohexyl)peroxide; Peroxy diacyl compounds such as oxidized dicarbonates; peroxy ester compounds such as tert-butyl peroxyacetate, tert-butyl peroxybenzoate, tert-butyl peroxyisopropyl monocarbonate, tert-butyl peroxy-2-ethylhexanoate, tert-butyl peroxyneodecanoate, tert-hexyl peroxyisopropyl monocarbonate, tert-butyl peroxylaurate, 1,1-dimethylpropyl 2-ethylperoxyhexanoate, tert-butyl 2-ethylperoxyhexanoate, tert-butyl 3,5,5-trimethylperoxyhexanoate, tert-butyl peroxy-2-ethylhexyl monocarbonate, tert-butyl peroxymaleate, etc.; etc.

[0218] Examples of the azo radical polymerization initiator include azo nitrile compounds such as 2,2'-azobis(4-methoxy-2,4-dimethylvaleronitrile), 2,2'-azobis(2,4-dimethylvaleronitrile), 2,2'-azobisisobutyronitrile, 2,2'-azobis(2-methylbutyronitrile), 1,1'-azobis(cyclohexane-1-carbonitrile), 1-[(1-cyano-1-methylethyl)azo]formamide, and 2-phenylazo-4-methoxy-2,4-dimethylvaleronitrile; 2,2'-azobis[2-methyl-N-[1,1-bis(hydroxymethyl)-2-hydroxyethyl]propionamide], 2,2'-azobis[2-methyl-N-[1,1-bis( Azo amide compounds such as 2,2'-azobis[2-methyl-N-[2-(1-hydroxybutyl)]-propionamide], 2,2'-azobis[2-methyl-N-(2-hydroxyethyl)-propionamide], 2,2'-azobis(2-methylpropionamide) dihydrate, 2,2'-azobis[N-(2-propenyl)-2-methylpropionamide], 2,2'-azobis(N-butyl-2-methylpropionamide), 2,2'-azobis(N-cyclohexyl-2-methylpropionamide); alkylazo compounds such as 2,2'-azobis(2,4,4-trimethylpentane) and 2,2'-azobis(2-methylpropane); etc.

[0219] Examples of commercially available radical polymerization initiators include “PERBUTYL C”, “PERBUTYL A”, “PERBUTYL P”, “PERBUTYL L”, “PERBUTYL O”, “PERBUTYL ND”, “PERBUTYL Z”, “PERBUTYL I”, “PERCUMYL P”, “PERCUMYL D”, “PERHEXYL D”, “PERHEXYL A”, “PERHEXYL I”, “PERHEXYL Z”, “PERHEXYL ND”, “PERHEXYL O”, and “PERHEXYL PV” manufactured by NOF Corporation.

[0220] The amount of the free radical polymerization initiator in the resin composition layer relative to 100% by mass of the non-volatile component in the resin composition layer is preferably in the range of 0.01% by mass or more, more preferably 0.02% by mass or more, further preferably 0.05% by mass or more, preferably 2% by mass or less, more preferably 1% by mass or less, further preferably 0.5% by mass or less.

[0221] The amount of the free radical polymerization initiator in the resin composition layer relative to 100% by mass of the resin component in the resin composition layer is preferably in the range of 0.01% by mass or more, more preferably 0.1% by mass or more, further preferably 0.2% by mass or more, preferably 5% by mass or less, more preferably 2% by mass or less, further preferably 1% by mass or less.

[0222] The amount of the (E) curing catalyst in the resin composition layer relative to 100% by mass of the non-volatile component in the resin composition layer is preferably in the range of 0.01% by mass or more, more preferably 0.02% by mass or more, further preferably 0.05% by mass or more, and is preferably 2% by mass or less, more preferably 1% by mass or less, and further preferably 0.5% by mass or less.

[0223] The amount of the (E) curing catalyst in the resin composition layer is preferably in the range of 0.01% by mass or more, more preferably 0.1% by mass or more, further preferably 0.2% by mass or more, and is preferably 5% by mass or less, more preferably 2% by mass or less, further preferably 1% by mass or less, relative to 100% by mass of the resin component in the resin composition layer.

[0224] <(F) Polymer resin> The resin composition layer of the resin sheet may contain (F) a polymer resin as an arbitrary component. The (F) polymer resin as the (F) component does not contain any substance belonging to the above-mentioned (A) to (E) components. The (F) polymer resin is generally thermoplastic and is contained in the resin composition layer in a state compatible with resin components other than the (F) polymer resin. In addition, the (F) polymer resin may be used alone or in combination of two or more.

[0225] (F) The polymer resin includes, for example, phenoxy resin, acrylic resin, polyimide resin, polyvinyl acetal resin, polyolefin resin, polybutadiene resin, polyamide-imide resin, polyetherimide resin, polysulfone resin, polyethersulfone resin, polyphenylene ether resin, polycarbonate resin, polyetheretherketone resin, polyester resin and the like.

[0226] Examples of the phenoxy resin include phenoxy resins having one or more skeletons selected from the group consisting of bisphenol A skeleton, bisphenol F skeleton, bisphenol S skeleton, bisphenol acetophenone skeleton, phenolic skeleton, biphenyl skeleton, fluorene skeleton, dicyclopentadiene skeleton, norbornene skeleton, naphthalene skeleton, anthracene skeleton, adamantane skeleton, terpene skeleton, and trimethylcyclohexane skeleton. The terminal of the phenoxy resin may be any functional group such as a phenolic hydroxyl group or an epoxy group. Specific examples of phenoxy resins include "1256" and "4250" manufactured by Mitsubishi Chemical Corporation (both are phenoxy resins containing a bisphenol A skeleton); "YX8100" manufactured by Mitsubishi Chemical Corporation (a phenoxy resin containing a bisphenol S skeleton); "YX6954" manufactured by Mitsubishi Chemical Corporation (a phenoxy resin containing a bisphenol acetophenone skeleton); "FX280" and "FX293" manufactured by Nippon Steel Chemical Materials Co., Ltd.; "YL7500BH30", "YX6954BH30", "YX7553", "YX7553BH30", "YL7769BH30", "YL6794", "YL7213", "YL7290", "YL7482" and "YL7891BH30" manufactured by Mitsubishi Chemical Corporation; etc.

[0227] As acrylic resin, for example, a resin containing a (meth) acrylate structure can be cited. The acrylic resin can contain a (meth) acrylate structure in the main chain, and can also contain a (meth) acrylate structure in the side chain. Here, the term "(meth) acrylate structure" includes both acrylate structure and methacrylate structure. As a specific example of acrylic resin, Teisan resin "SG-70L", "SG-708-6", "WS-023", "SG-700AS", "SG-280TEA", "SG-80H", "SG-80H-3", "SG-P3", "SG-600TEA", "SG-790" made by Nagase ChemteX can be cited; "ME-2000", "W-116.3", "W-197C", "KG-25", "KG-3000" made by Negami Industries; "ARUFON UH-2000" made by Toagosei Co., Ltd., etc.

[0228] Specific examples of polyimide resins include "SLK-6100" manufactured by Shin-Etsu Chemical Co., Ltd., "RIKACOAT SN20" and "RIKACOAT PN20" manufactured by Shin-Nippon Chemical Co., Ltd., etc. Specific examples of polyimide resins include linear polyimides obtained by reacting bifunctional hydroxy-terminated polybutadiene, a diisocyanate compound and a tetrabasic acid anhydride (polyimides described in Japanese Unexamined Patent Publication No. 2006-37083), polyimides containing a polysiloxane skeleton (polyimides described in Japanese Unexamined Patent Publication No. 2002-12667 and Japanese Unexamined Patent Publication No. 2000-319386, etc.), and the like.

[0229] Examples of the polyvinyl acetal resin include polyvinyl formal resin and polyvinyl butyral resin, preferably polyvinyl butyral resin. 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, and BM series manufactured by Sekisui Chemical Co., Ltd.

[0230] Examples of the polyolefin resin include ethylene copolymer resins such as low-density polyethylene, ultra-low-density polyethylene, high-density polyethylene, ethylene-vinyl acetate copolymers, ethylene-ethyl acrylate copolymers, and ethylene-methyl acrylate copolymers; and polyolefin polymers such as polypropylene and ethylene-propylene block copolymers.

[0231] 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, etc. A part or all of the polybutadiene structure of the polybutadiene resin may be hydrogenated. Specific examples of the polybutadiene resin include "Ricon 130MA8", "Ricon 130MA13", "Ricon 130MA20", "Ricon 131MA5", "Ricon 131MA10", "Ricon 131MA17", "Ricon 131MA20", and "Ricon 184MA6" (polybutadiene containing anhydride groups) manufactured by Cray Valley, "GQ-1000" (polybutadiene into which hydroxyl groups and carboxyl groups are introduced), "G-1000", "G-2000", and "G-3000" (polybutadiene containing hydroxyl groups at both ends) manufactured by Nippon Soda Co., Ltd., "GI-1000", "GI-2000", and "GI-3000" (hydrogenated polybutadiene containing hydroxyl groups at both ends), and "FCA-061L" (hydrogenated polybutadiene skeleton epoxy resin) manufactured by Nagase ChemteX. In addition, as the specific example of polybutadiene resin, a polyimide resin having a polybutadiene structure, a polyurethane structure and an imide structure in the molecule can be enumerated. The polyimide resin can be manufactured as a linear polyimide resin (polyimide recorded in Japanese Unexamined Patent Publication No. 2006-37083 and International Publication No. 2008 / 153208) using hydroxyl-terminated polybutadiene, a diisocyanate compound and a tetrabasic acid anhydride as raw materials. The content of the butadiene structure of the polyimide resin is preferably 60% by mass to 95% by mass, more preferably 75% by mass to 85% by mass. The details of the polyimide resin can be referred to the records of Japanese Unexamined Patent Publication No. 2006-37083 and International Publication No. 2008 / 153208, and its content is incorporated into this specification.

[0232] Specific examples of the polyamideimide resin include "VYLOMAX HR11NN" and "VYLOMAX HR16NN" manufactured by Toyobo Co., Ltd. Specific examples of the polyamideimide resin include modified polyamideimides such as "KS9100" and "KS9300" (polyamideimide containing a polysiloxane skeleton) manufactured by Hitachi Chemical Co., Ltd.

[0233] Specific examples of the polyetherimide resin include "ULTEM" manufactured by GE.

[0234] Specific examples of the polysulfone resin include polysulfone "P1700" and "P3500" manufactured by Solvay Advanced Polymers.

[0235] Specific examples of the polyethersulfone resin include "PES5003P" manufactured by Sumitomo Chemical Co., Ltd. and the like.

[0236] Specific examples of the polyphenylene ether resin include "NORYL SA90" manufactured by SABIC.

[0237] As polycarbonate resin, for example, carbonate resin containing hydroxyl group, carbonate resin containing phenolic hydroxyl group, carbonate resin containing carboxyl group, carbonate resin containing acid anhydride group, carbonate resin containing isocyanate group, carbonate resin containing carbamate group, etc. can be cited. As a specific example of polycarbonate resin, "FPC0220" made by Mitsubishi Gas Chemical Co., Ltd., "T6002", "T6001" (polycarbonate diol) made by Asahi Chemical Co., Ltd., "C-1090", "C-2090", "C-3090" (polycarbonate diol) made by Kuraray Co., Ltd., etc. can be cited. In addition, as a specific example of polycarbonate resin, polyimide resin having imide structure, polyurethane structure and polycarbonate structure in the molecule can be cited. The polyimide resin can be manufactured as a linear polyimide resin using hydroxyl-terminated polycarbonate, diisocyanate compound and tetrabasic acid anhydride as raw materials. The content of the carbonate structure of the polyimide resin is preferably 60% to 95% by mass, and more preferably 75% to 85% by mass. The details of the polyimide resin can be found in International Publication No. 2016 / 129541, the contents of which are incorporated into this specification.

[0238] Specific examples of the polyetheretherketone resin include "Sumiploy K" manufactured by Sumitomo Chemical Co., Ltd. and the like.

[0239] Examples of the polyester resin include polyethylene terephthalate resin, polyethylene naphthalate resin, polybutylene terephthalate resin, polybutylene naphthalate resin, polytrimethylene terephthalate resin, polytrimethylene naphthalate resin, and polycyclohexane dimethyl terephthalate resin.

[0240] (F) The polymer resin generally has a large molecular weight. Specifically, the weight average molecular weight Mw of the polymer resin (F) is preferably greater than 5,000, more preferably 8,000 or more, more preferably 10,000 or more, more preferably 20,000 or more, preferably 100,000 or less, more preferably 70,000 or less, more preferably 60,000 or less, and more preferably 50,000 or less. The weight average molecular weight Mw can be measured by gel permeation chromatography (GPC) as a value converted to polystyrene.

[0241] The amount of the (F) polymer resin in the resin composition layer relative to 100% by mass of the non-volatile component in the resin composition layer is preferably in the range of 0.1% by mass or more, more preferably 0.2% by mass or more, further preferably 0.5% by mass or more, preferably 10% by mass or less, more preferably 8% by mass or less, further preferably 5% by mass or less.

[0242] The amount of the (F) polymer resin in the resin composition layer relative to 100% by mass of the resin component in the resin composition layer is preferably in the range of 0.1% by mass or more, more preferably 0.5% by mass or more, further preferably 1% by mass or more, and preferably 20% by mass or less, more preferably 10% by mass or less, further preferably 5% by mass or less.

[0243] <(G) Organic fillers> The resin composition layer of the resin sheet may also contain (G) an organic filler as an arbitrary component. The (G) organic filler as the (G) component does not contain substances belonging to the above-mentioned (A) to (F) components. The (G) organic filler is usually incompatible with resin components other than the (G) organic filler and is contained in the resin composition layer in the form of particles, and is contained in the insulating layer while maintaining the particles. In addition, the (G) organic filler as the (G) component may be used alone or in combination of two or more.

[0244] As (G) organic filler, particles of organic material can be used. As the organic material contained in the (G) organic filler, a rubber component is preferred. As the rubber component, silicone elastomers such as polydimethylsiloxane can be cited; olefin thermoplastic elastomers such as polybutadiene, polyisoprene, polychloroprene, ethylene-vinyl acetate copolymer, styrene-butadiene copolymer, styrene-isoprene copolymer, styrene-isobutylene copolymer, acrylonitrile-butadiene copolymer, isoprene-isobutylene copolymer, isobutylene-butadiene copolymer, ethylene-propylene-diene terpolymer, ethylene-propylene-butylene terpolymer; thermoplastic elastomers such as acrylic thermoplastic elastomers such as poly(meth)propyl acrylate, poly(meth)butyl acrylate, poly(meth)cyclohexyl acrylate, poly(meth)octyl acrylate, etc. The rubber component can also be further mixed with silicone rubbers such as polyorganosiloxane rubber. The rubber component contained in the rubber particles may have a glass transition temperature of, for example, 0°C or lower, preferably -10°C or lower, more preferably -20°C or lower, and further preferably -30°C or lower.

[0245] (G) The organic filler material may be a core-shell type rubber particle, wherein the core-shell type rubber particle is formed by graft copolymerization of a core particle containing the rubber component listed above and a monomer component copolymerizable with the rubber component contained in the core particle. Here, the core-shell type does not necessarily refer only to those in which the core particle and the shell portion can be clearly distinguished, but also includes those in which the boundary between the core particle and the shell portion is unclear, and the core particle may not be completely covered by the shell portion.

[0246] Specific examples of the (G) organic filler include "CHT" manufactured by Samsung SDI; "B602" manufactured by Techno-UMG; "PARALOID EXL-2602", "PARALOID EXL-2603", "PARALOID EXL-2655", "PARALOID EXL-2311", "PARALOID EXL2313", "PARALOID EXL-2315", "PARALOID KM-330", "PARALOID KM-336P", "PARALOID KCZ-201" manufactured by Dow; "Metablen C-223A", "Metablen E-901", "Metablen S-2001", "Metablen W-450A", "Metablen SRK-200" manufactured by Mitsubishi Rayon Co., Ltd.; and "Kane Ace M-511", "Kane Ace M-600", "Kane AceM-400", "Kane Ace M-580", "Kane Ace MR-01", "STAPHYLOID AC3355", "STAPHYLOID AC3816", "STAPHYLOID AC3816N", "STAPHYLOID AC3832", "STAPHYLOIDAC4030", "STAPHYLOID AC3364" and other products manufactured by AICA Industries.

[0247] The amount of the (G) organic filler in the resin composition layer is preferably 0.1% by mass or more, more preferably 0.2% by mass or more, further preferably 0.5% by mass or more, preferably 5% by mass or less, more preferably 2% by mass or less, further preferably 1% by mass or less, relative to 100% by mass of the non-volatile components in the resin composition layer.

[0248] The amount of the (G) organic filler in the resin composition layer is preferably in the range of 0.1% by mass or more, more preferably 0.5% by mass or more, further preferably 1% by mass or more, and is preferably 10% by mass or less, more preferably 5% by mass or less, further preferably 2% by mass or less, relative to 100% by mass of the resin component in the resin composition layer.

[0249] <(H) Optional Additives> The resin composition layer of the resin sheet may contain (H) any additive as an arbitrary component. The (H) arbitrary additive as the component does not contain substances belonging to the above-mentioned (A) to (G) components. Examples of the (H) arbitrary additive include organic metal 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; defoamers such as silicone-based defoamers, acrylic-based defoamers, fluorine-based defoamers, and vinyl resin-based defoamers; ultraviolet absorbers such as benzotriazole-based ultraviolet absorbers; adhesion enhancers such as urea silane; adhesion enhancers such as triazole-based adhesion enhancers, tetrazole-based adhesion enhancers, and triazine-based adhesion enhancers. agent; antioxidants such as hindered phenol antioxidants; fluorescent whitening agents such as stilbene derivatives; surfactants such as fluorine-based surfactants and silicone-based surfactants; flame retardants such as phosphorus-based flame retardants (such as phosphate compounds, phosphazene compounds, phosphinic acid compounds, red phosphorus), nitrogen-based flame retardants (such as melamine sulfate), halogen-based flame retardants, inorganic flame retardants (such as antimony trioxide); dispersants such as phosphate-based dispersants, polyoxyalkylene-based dispersants, acetylene-based dispersants, silicone-based dispersants, anionic dispersants, cationic dispersants; stabilizers such as borate-based stabilizers, titanate-based stabilizers, aluminate-based stabilizers, zirconate-based stabilizers, isocyanate-based stabilizers, carboxylic acid-based stabilizers, and carboxylic anhydride-based stabilizers.

[0250] <(I) Any solvent> The resin composition layer of the resin sheet may also contain (I) an arbitrary solvent as an arbitrary volatile component. (I) The arbitrary solvent does not contain the above-mentioned (B) tetrahydrofuran. As (I) the arbitrary solvent, an organic solvent is generally 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, isoamyl acetate, methyl propionate, ethyl propionate, and γ-butyrolactone; ether solvents such as tetrahydropyran, 1,4-dioxane, diethyl ether, diisopropyl ether, dibutyl ether, diphenyl ether, and anisole; alcohol solvents such as methanol, ethanol, propanol, butanol, and ethylene glycol; 2-ethoxyethyl acetate, propylene glycol monomethyl ether acetate, diethylene glycol monoethyl ether acetate, and carbitol acetate. Ether ester solvents such as acetate, γ-butyrolactone, and methyl methoxypropionate; ester alcohol solvents such as methyl lactate, ethyl lactate, and methyl 2-hydroxyisobutyrate; ether alcohol solvents such as 2-methoxypropanol, 2-methoxyethanol, 2-ethoxyethanol, propylene glycol monomethyl ether, and diethylene glycol monobutyl ether (butyl carbitol); amide solvents such as N,N-dimethylformamide, N,N-dimethylacetamide, and N-methyl-2-pyrrolidone; sulfoxide solvents such as dimethyl sulfoxide; nitrile solvents such as acetonitrile and propionitrile; aliphatic hydrocarbon solvents such as hexane, cyclopentane, cyclohexane, and methylcyclohexane; aromatic hydrocarbon solvents such as benzene, toluene, xylene, ethylbenzene, and trimethylbenzene, etc. (I) Any solvent can be used alone or in combination of two or more.

[0251] The amount of the (I) arbitrary solvent is preferably set so that the amount of all solvents in the resin composition layer (i.e., the total amount of (B) tetrahydrofuran and (I) arbitrary solvent) is controlled within a specific range. Specifically, the range of the amount of all solvents in the resin composition layer is preferably 0.1% by mass or more, more preferably 0.5% by mass or more, further preferably 1% by mass or more, preferably 20% by mass or less, more preferably 10% by mass or less, and further preferably 5% by mass or less, relative to the total amount of 100% by mass of the resin composition layer.

[0252] <Biomass Ratio of Resin Composition Layer> From the viewpoint of promoting energy saving, cost saving and sustainability, the biomass ratio of the non-volatile components in the resin composition layer is preferably higher. The range of the biomass ratio of the non-volatile components in the resin composition layer is preferably 0.1% by mass or more, more preferably 0.5% by mass or more, further preferably 1% by mass or more, and particularly preferably 2% by mass or more. The upper limit is preferably 100% by mass or less, and may also be 90% by mass or less or 80% by mass or less.

[0253] The biomass ratio of the nonvolatile components in the resin composition layer can be calculated using the following formula (M2). However, even if the nonvolatile components in the resin composition layer include components that are certified based on the mass balance method, the mass balance method is not used, and the biomass ratio is calculated based on the following formula (M2). Biomass ratio (mass %) = (mass of biomass-derived components in nonvolatile components / mass of nonvolatile components) × 100 (M2)

[0254] In addition, the biomass ratio of the resin component in the resin composition layer is preferably higher. The range of the biomass ratio of the resin component in the resin composition layer is preferably 0.1 mass % or more, more preferably 1 mass % or more, and particularly preferably 5 mass % or more. The upper limit is preferably 100 mass % or less, and may also be 90 mass % or less, 80 mass % or less, or 70 mass % or less.

[0255] The biomass ratio of the resin component in the resin composition layer can be calculated using the following formula (M3). However, even if the resin component in the resin composition layer includes a component certified based on the mass balance method, the mass balance method is not used, and the biomass ratio is calculated based on the following formula (M3). Biomass ratio (mass %) = (mass of biomass components in resin component / mass of resin component) × 100 (M3)

[0256] <Thickness of Resin Composition Layer> From the viewpoint of thinning, the thickness of the resin composition layer of the resin sheet is preferably 200 μm or less, more preferably 150 μm or less, and further preferably 100 μm or less. The lower limit of the thickness may be, for example, 1 μm or more, 3 μm or more, 5 μm or more.

[0257] <Characteristics of Cured Material Layer Obtained by Curing Resin Composition Layer> By curing the resin composition layer, a cured product layer can be obtained. Moreover, an insulating layer can be formed using the cured product layer. Usually, since heat is applied when the resin composition layer is cured, among the components contained in the resin composition layer, volatile components such as (B) tetrahydrofuran and (H) any solvent can volatilize due to the heat during curing. Therefore, the cured product layer obtained by curing the resin composition layer can contain non-volatile components such as (A) and (C) to (I) components or their reaction products.

[0258] The cured product layer obtained by curing the resin composition layer preferably has a small average linear thermal expansion coefficient. The average linear thermal expansion coefficient of the cured product layer is preferably in the range of 50 ppm / °C or less, more preferably 45 ppm / °C or less, and further preferably 40 ppm / °C or less. The lower limit may be, for example, 1 ppm / °C or more, 5 ppm / °C or more, 10 ppm / °C or more, etc.

[0259] The average linear thermal expansion coefficient of the cured layer can be measured by thermomechanical analysis using a tensile load method under the measurement conditions of a load of 1 g and a heating rate of 5°C / min in a temperature range of 25°C to 150°C. The measurement can be performed on a cured layer obtained by curing the resin composition layer under the curing conditions of 190°C and 90 minutes. The specific measurement method can be the method described in the <Measurement test of average linear thermal expansion coefficient (CTE) and glass transition temperature Tg> of the examples described later.

[0260] The cured product layer obtained by curing the resin composition layer preferably has a low dielectric loss tangent. The dielectric loss tangent of the cured product layer is preferably less than 0.015, more preferably less than 0.01, and further preferably less than 0.005. The lower limit may be, for example, 0.001 or more, 0.002 or more, etc.

[0261] The dielectric loss tangent of the cured layer can be measured by a resonant cavity perturbation method at a measurement frequency of 5.8 GHz and a measurement temperature of 23° C. The measurement can be performed on a cured layer obtained by curing the resin composition layer under the curing conditions of 190° C. and 90 minutes. The specific measurement method can be the method described in the <Measurement Test of Dielectric Loss Tangent> of the Examples described later.

[0262] The cured product layer obtained by curing the resin composition layer preferably has a high glass transition temperature. The glass transition temperature of the cured product layer is preferably higher than 150°C, more preferably higher than 152°C, and further preferably higher than 154°C. The upper limit may be, for example, 200°C or lower, 190°C or lower, 180°C or lower, etc.

[0263] The glass transition temperature of the cured layer can be measured by thermomechanical analysis using a tensile load method under the conditions of a load of 1 g and a heating rate of 5°C / min. The measurement can be performed on a cured layer obtained by curing the resin composition layer at 190°C for 90 minutes. The specific measurement method can be the method described in the <Measurement test of average linear thermal expansion coefficient (CTE) and glass transition temperature Tg> of the examples described later.

[0264] As mentioned above, the cured product layer obtained by curing the resin composition layer can include the non-volatile component of the resin composition layer or its reaction product.Therefore, the cured product layer can usually have the biomass ratio of the same scope as the biomass ratio of the non-volatile component in the resin composition layer.From the viewpoint of promoting sustainability, it is preferred that the cured product layer can have a high biomass ratio like this.

[0265] <Support body> The resin sheet may include a support. When the resin sheet includes a support, the resin composition layer is usually formed on the support. Examples of the support include a film of a plastic material, a metal foil, and a release paper, preferably a film of a plastic material and a metal foil.

[0266] When a film of a plastic material is used as a support, examples of the plastic material include polyesters such as polyethylene terephthalate (hereinafter sometimes referred to as "PET") and polyethylene naphthalate (hereinafter sometimes referred to as "PEN"), polycarbonate (hereinafter sometimes 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.

[0267] When a metal foil is used as a support, examples of the metal foil include copper foil and aluminum foil, preferably copper foil. The copper foil may be a foil made of a single metal of copper or an alloy of copper and other metals (e.g., tin, chromium, silver, magnesium, nickel, zirconium, silicon, titanium, etc.).

[0268] The support may be subjected to surface treatment such as matte treatment, corona treatment, antistatic treatment, etc. on the surface to be in contact with the resin composition layer.

[0269] As the support, a support with a release layer having a release layer on the surface bonded to the resin composition layer can be used. As a release agent used in the release layer of the support with a release layer, for example, one or more release agents selected from alkyd release agents, polyolefin release agents, polyurethane release agents and silicone release agents can be cited. The support with a release layer can use commercial products, for example, PET films having a release layer with a silicone release agent or an alkyd resin release agent as a main component, i.e., "PET501010", "SK-1", "AL-5", "AL-7" manufactured by Lintec, "Lumirror T60" manufactured by Toray Industries, "Purex" manufactured by Teijin, "Unipeel" manufactured by Unitika, etc.

[0270] The thickness of the support is not particularly limited, but is preferably 1 μm or more, more preferably 5 μm or more, further preferably 10 μm or more, and preferably 75 μm or less, more preferably 60 μm or less, further preferably 50 μm or less. When a support with a release layer is used, the overall thickness of the support with the release layer is preferably within the above range.

[0271] <Arbitrary component> As required, the resin sheet may have any member other than the resin composition layer and the support. For example, the resin sheet may have a protective film for protecting the resin composition layer. The protective film is usually provided on the surface of the resin composition layer that is not bonded to the support (i.e., the surface on the opposite side of the support). The thickness of the protective film is not particularly limited, for example, 1 μm to 40 μm. In the case of a protective film, it is possible to suppress the attachment of garbage or the like on the surface of the resin composition layer or the generation of damage. In the case where the resin sheet has a protective film, the resin sheet can usually be used by peeling off the protective film.

[0272] <Method for producing resin sheet> The above-mentioned resin sheet can be manufactured, for example, using a resin composition comprising (A) a furan-type curable resin, (B) tetrahydrofuran and (C) an inorganic filler. The resin composition is usually used in the state of a liquid composition in the manufacturing method of the resin sheet. Therefore, the above-mentioned resin composition is sometimes referred to as "resin varnish" below. The manufacturing method of the resin sheet using the resin varnish includes a step of applying the resin varnish on a support, and a step of drying the applied resin varnish to form a resin composition layer.

[0273] The resin varnish contains (A) furan type curable resin. The range of the amount of the (A) furan type curable resin in the resin varnish relative to the total amount of 100% by mass of the resin varnish can be the same as the range of the amount of the (A) furan type curable resin in the resin composition layer relative to the total amount of 100% by mass of the resin composition layer. Usually, the amount of solvents such as (B) tetrahydrofuran is reduced by drying, so the content of the (A) furan type curable resin is relatively increased by drying. Therefore, when the resin varnish containing the (A) furan type curable resin is used in the above-mentioned amount, the amount of the (A) furan type curable resin in the formed resin composition layer can be controlled within the above-mentioned specific range.

[0274] When the amount of non-volatile components or resin components is used as a reference, the content of (A) furan curable resin in the resin varnish is usually the same as the content of (A) furan curable resin in the resin composition layer. Therefore, the range of the amount of (A) furan curable resin in the resin varnish relative to 100% by mass of the non-volatile components in the resin varnish can be the same as the range of the amount of (A) furan curable resin in the resin composition layer relative to 100% by mass of the non-volatile components in the resin composition layer. In addition, the range of the amount of (A) furan curable resin in the resin varnish relative to 100% by mass of the resin component in the resin varnish can be the same as the range of the amount of (A) furan curable resin in the resin composition layer relative to 100% by mass of the resin component in the resin composition layer. The non-volatile components in the resin varnish, as long as they are not otherwise specified, represent the components in the resin varnish other than the solvent. In addition, the resin components in the resin varnish, as long as they are not otherwise specified, represent the components after removing the (C) inorganic filler in the non-volatile components in the resin varnish.

[0275] The resin varnish contains (B) tetrahydrofuran. The amount of (B) tetrahydrofuran in the resin varnish is usually 1% by mass or more, preferably 1.5% by mass or more, and more preferably 2% by mass or more, relative to the total amount of the resin varnish 100% by mass. When the resin composition layer contains such an amount of (B) tetrahydrofuran, the resin composition layer of the resin sheet can be smoothly formed. The upper limit is preferably 50% by mass or less, more preferably 40% by mass or less, and further preferably 30% by mass or less.

[0276] The amount of (B) tetrahydrofuran in the resin varnish is preferably in the range of 1% by mass or more, more preferably 5% by mass or more, further preferably 10% by mass or more, and is usually 100% by mass or less, preferably 80% by mass or less, and more preferably 60% by mass or less, relative to 100% by mass of the total solvent in the resin varnish.

[0277] The amount of (B) tetrahydrofuran in the resin varnish is preferably 5% by mass or more, more preferably 10% by mass or more, and further preferably 20% by mass or more relative to 100% by mass of the (A) furan-type curable resin in the resin varnish. The upper limit may be, for example, 1000% by mass or less, 700% by mass or less, 500% by mass or less, etc.

[0278] Resin varnish includes (C) inorganic filler. When the amount of non-volatile components is used as a benchmark, the content of (C) inorganic filler in resin varnish is usually the same as the content of (C) inorganic filler in resin composition layer. Therefore, the range of the amount of (C) inorganic filler in the resin varnish relative to 100% by mass of the non-volatile components in the resin varnish can be the same as the range of the amount of (C) inorganic filler in the resin composition layer relative to 100% by mass of the non-volatile components in the resin composition layer. In addition, the range of the total amount of (A) furan type curable resin and (C) inorganic filler in the resin varnish relative to 100% by mass of the non-volatile components in the resin varnish can be the same as the range of the total amount of (A) furan type curable resin and (C) inorganic filler in the resin composition layer relative to 100% by mass of the non-volatile components in the resin composition layer.

[0279] The resin varnish may contain (D) any curable resin as an optional component. When the amount of the non-volatile component or the resin component is used as a reference, the content of (D) any curable resin in the resin varnish is usually the same as the content of (D) any curable resin in the resin composition layer.

[0280] Therefore, the range of the amount of any curable resin (D) in the resin varnish relative to 100% by mass of the non-volatile components in the resin varnish can be the same as the range of the amount of any curable resin (D) in the resin composition layer relative to 100% by mass of the non-volatile components in the resin composition layer. In addition, the range of the amount of epoxy resin (D-1) in the resin varnish relative to 100% by mass of the non-volatile components in the resin varnish can be the same as the range of the amount of epoxy resin (D-1) in the resin composition layer relative to 100% by mass of the non-volatile components in the resin composition layer. Furthermore, the range of the amount of any curing agent (D-2) in the resin varnish relative to 100% by mass of the non-volatile components in the resin varnish can be the same as the range of the amount of any curing agent (D-2) in the resin composition layer relative to 100% by mass of the non-volatile components in the resin composition layer. The range of the amount of the radically polymerizable resin (D-3) in the resin varnish relative to 100% by mass of the nonvolatile components in the resin varnish may be the same as the range of the amount of the radically polymerizable resin (D-3) in the resin composition layer relative to 100% by mass of the nonvolatile components in the resin composition layer.

[0281] Furthermore, the range of the amount of any curable resin (D) in the resin varnish relative to 100% by mass of the resin component in the resin varnish may be the same as the range of the amount of any curable resin (D) in the resin composition layer relative to 100% by mass of the resin component in the resin composition layer. In addition, the range of the amount of the epoxy resin (D-1) in the resin varnish relative to 100% by mass of the resin component in the resin varnish may be the same as the range of the amount of the epoxy resin (D-1) in the resin composition layer relative to 100% by mass of the resin component in the resin composition layer. Furthermore, the range of the amount of any curing agent (D-2) in the resin varnish relative to 100% by mass of the resin component in the resin varnish may be the same as the range of the amount of any curing agent (D-2) in the resin composition layer relative to 100% by mass of the resin component in the resin composition layer. The range of the amount of the radically polymerizable resin (D-3) in the resin varnish relative to 100% by mass of the resin component in the resin varnish may be the same as the range of the amount of the radically polymerizable resin (D-3) in the resin composition layer relative to 100% by mass of the resin component in the resin composition layer.

[0282] The resin varnish may contain (E) a curing catalyst as an optional component. The content of the (E) curing catalyst in the resin varnish is usually the same as the content of the (E) curing catalyst in the resin composition layer, based on the amount of the nonvolatile component or the resin component.

[0283] Therefore, the range of the amount of (E) curing catalyst in the resin varnish relative to 100% by mass of the non-volatile components in the resin varnish can be the same as the range of the amount of (E) curing catalyst in the resin composition layer relative to 100% by mass of the non-volatile components in the resin composition layer. In addition, the range of the amount of curing accelerator in the resin varnish relative to 100% by mass of the non-volatile components in the resin varnish can be the same as the range of the amount of curing accelerator in the resin composition layer relative to 100% by mass of the non-volatile components in the resin composition layer. Furthermore, the range of the amount of free radical polymerization initiator in the resin varnish relative to 100% by mass of the non-volatile components in the resin varnish can be the same as the range of the amount of free radical polymerization initiator in the resin composition layer relative to 100% by mass of the non-volatile components in the resin composition layer.

[0284] In addition, the range of the amount of the (E) curing catalyst in the resin varnish relative to 100% by mass of the resin component in the resin varnish may be the same as the range of the amount of the (E) curing catalyst in the resin composition layer relative to 100% by mass of the resin component in the resin composition layer. In addition, the range of the amount of the curing accelerator in the resin varnish relative to 100% by mass of the resin component in the resin varnish may be the same as the range of the amount of the curing accelerator in the resin composition layer relative to 100% by mass of the resin component in the resin composition layer. Furthermore, the range of the amount of the free radical polymerization initiator in the resin varnish relative to 100% by mass of the resin component in the resin varnish may be the same as the range of the amount of the free radical polymerization initiator in the resin composition layer relative to 100% by mass of the resin component in the resin composition layer.

[0285] The resin varnish may contain (F) a polymer resin as an optional component. The content of the (F) polymer resin in the resin varnish is usually the same as the content of the (F) polymer resin in the resin composition layer, based on the amount of the nonvolatile component or the resin component.

[0286] Therefore, the range of the amount of the (F) polymer resin in the resin varnish relative to 100% by mass of the nonvolatile components in the resin varnish may be the same as the range of the amount of the (F) polymer resin in the resin composition layer relative to 100% by mass of the nonvolatile components in the resin composition layer. In addition, the range of the amount of the (F) polymer resin in the resin varnish relative to 100% by mass of the resin component in the resin varnish may be the same as the range of the amount of the (F) polymer resin in the resin composition layer relative to 100% by mass of the resin component in the resin composition layer.

[0287] The resin varnish may contain (G) an organic filler as an optional component. The content of the (G) organic filler in the resin varnish is usually the same as the content of the (G) organic filler in the resin composition layer, based on the amount of the nonvolatile component or the resin component.

[0288] Therefore, the range of the amount of the (G) organic filler in the resin varnish relative to 100% by mass of the nonvolatile components in the resin varnish may be the same as the range of the amount of the (G) organic filler in the resin composition layer relative to 100% by mass of the nonvolatile components in the resin composition layer. In addition, the range of the amount of the (G) organic filler in the resin varnish relative to 100% by mass of the resin component in the resin varnish may be the same as the range of the amount of the (G) organic filler in the resin composition layer relative to 100% by mass of the resin component in the resin composition layer.

[0289] The resin varnish may contain (H) any additive as an optional component. The content of (H) any additive in the resin varnish is usually the same as the content of (H) any additive in the resin composition layer, based on the amount of the nonvolatile component.

[0290] The resin varnish may contain (I) any solvent as an arbitrary volatile component. The amount of (I) any solvent is preferably set so that the amount of all solvents in the resin varnish (i.e., the total amount of (B) tetrahydrofuran and (I) any solvent) is controlled within a specific range. Specifically, the amount of all solvents in the resin varnish is preferably 5% by mass or more, more preferably 10% by mass or more, further preferably 20% by mass or more, preferably 60% by mass or less, more preferably 50% by mass or less, and further preferably 40% by mass or less, relative to the total amount of the resin varnish (100% by mass).

[0291] The range of the biomass ratio of the nonvolatile components in the resin varnish is usually the same as the range of the biomass ratio of the nonvolatile components in the resin composition layer. The biomass ratio of the nonvolatile components in the resin varnish can be calculated using formula (M2) in the same manner as the biomass ratio of the nonvolatile components in the resin composition layer.

[0292] The biomass ratio of the resin component in the resin varnish is usually in the same range as the biomass ratio of the resin component in the resin composition layer. The biomass ratio of the resin component in the resin varnish can be calculated using formula (M3) in the same manner as the biomass ratio of the resin component in the resin composition layer.

[0293] Resin varnish can be manufactured, for example, by mixing the components that can be contained in the resin varnish. Therefore, the resin varnish can be manufactured by a manufacturing method including the step of mixing (A) furan type curable resin, (B) tetrahydrofuran and (C) inorganic filler. The manufacturing method may also include the step of mixing any components such as (D) to (I). (A) to (I) components can be mixed partially or completely at the same time, or can be mixed sequentially. In addition, during the process of adding each component and mixing, the temperature can be appropriately adjusted. For example, it can be temporarily or always heated and / or cooled. In addition, during or after mixing, the resin varnish can be stirred or shaken using a stirring device such as a mixer or an oscillating device. Furthermore, as needed, degassing can be performed under low pressure conditions such as vacuum.

[0294] The method for manufacturing the resin sheet shown in this example includes the step of preparing a resin varnish and then coating the resin varnish on a support. The coating can be performed using an appropriate coating device such as a die coater. By coating the resin varnish, a film of the resin varnish is formed on the support.

[0295] The method for manufacturing the resin sheet shown in this example includes a step of drying the applied resin varnish to form a resin composition layer after applying the resin varnish. Drying can be carried out by heating, hot air blowing, etc. The drying conditions are set so that the resin composition layer involved in the above-mentioned embodiment can be obtained. The drying conditions may also be different depending on the composition and boiling point of the solvent of the resin varnish. For example, the drying conditions may be set within the range of a drying temperature of 50°C to 150°C and a drying time of 2 minutes to 10 minutes to form a resin composition layer containing (B) tetrahydrofuran in the above-mentioned range.

[0296] The method for manufacturing a resin sheet may further include any process in combination with the above process. For example, the method for manufacturing a resin sheet may include a process of laminating a protective film to the resin composition layer. In addition, for example, the method for manufacturing a resin sheet may include a process of winding the manufactured resin sheet into a roll shape for recycling.

[0297] <Circuit Board> The circuit board according to one embodiment of the present invention comprises a cured product layer obtained by curing the resin composition layer. The cured product layer can form an insulating layer of the circuit board. By using the resin sheet as the cured product layer to form the insulating layer, unevenness in the insulating layer can be suppressed.

[0298] The thickness range of the insulating layer is not particularly limited, and may be, for example, the same as the thickness range of the resin composition layer included in the resin sheet.

[0299] The insulating layer may preferably have a small average linear thermal expansion coefficient. The range of the average linear thermal expansion coefficient of the insulating layer may be the same as the range of the average linear thermal expansion coefficient of the cured product layer obtained by curing the resin composition layer. The average linear thermal expansion coefficient of the insulating layer may be measured by the same method as the method for measuring the average linear thermal expansion coefficient of the cured product layer.

[0300] The insulating layer may preferably have a low dielectric loss tangent. The dielectric loss tangent of the insulating layer may be in the same range as the dielectric loss tangent of the cured layer obtained by curing the resin composition layer. The dielectric loss tangent of the insulating layer may be measured by the same method as the method for measuring the dielectric loss tangent of the cured layer.

[0301] The insulating layer preferably has a high glass transition temperature. The range of the glass transition temperature of the insulating layer may be the same as the range of the glass transition temperature of the cured product layer obtained by curing the resin composition layer. The glass transition temperature of the insulating layer may be measured by the same method as the method for measuring the glass transition temperature of the cured product layer.

[0302] The insulating layer may preferably have a high biomass ratio. Specifically, the insulating layer may preferably have a biomass ratio in the same range as the biomass ratio of the non-volatile components in the resin composition layer. It is preferred that the insulating layer may have a high biomass ratio from the perspective of promoting sustainability.

[0303] Preferably, the circuit substrate has an inner substrate, and the insulating layer is provided on the inner substrate. In addition, the circuit substrate may have a conductor layer. For example, the conductor layer may be provided on the insulating layer. Such a circuit substrate may be manufactured, for example, by a manufacturing method including the following steps: Step (I) of laminating the resin sheet and the inner substrate so that the resin composition layer and the inner substrate are bonded to each other, and A step (II) of curing the resin composition layer.

[0304] "Inner layer substrate" is a member that becomes the base material of the circuit substrate, and examples thereof include glass epoxy substrate, metal substrate, polyester substrate, polyimide substrate, BT resin substrate, thermosetting polyphenylene ether substrate, etc. In addition, the inner layer substrate may have a conductor layer on one or both sides thereof. In addition, the conductor layer of the inner layer substrate may 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 substrate". In addition, when manufacturing a circuit substrate, an intermediate product on which an insulating layer and / or a conductor layer should be further formed is also included in the term "inner layer substrate". In addition, an inner layer substrate with built-in components may be used.

[0305] In process (I), by laminating resin sheet and inner substrate, a resin composition layer is formed on the inner substrate. The lamination of resin sheet and inner substrate is carried out in a manner that the resin composition layer of the resin sheet is joined to the inner substrate. The lamination can be carried out, for example, by heat-pressing the resin sheet to the inner substrate from the support body side. As a component for heat-pressing the resin sheet to the inner substrate (hereinafter also referred to as "heat-pressing component"), for example, a heated metal plate (SUS end plate, etc.) or a metal roller (SUS roller) etc. can be cited. It should be noted that it is preferred that the heat-pressing component is not directly pressed on the resin sheet, but is pressed via an elastic material such as heat-resistant rubber so that the resin sheet fully follows the surface unevenness of the inner substrate.

[0306] The lamination of the inner substrate and the resin sheet can be implemented by vacuum lamination. In the vacuum lamination method, the heating and pressing temperature is preferably 60°C to 160°C, more preferably in the range of 80°C to 140°C, the heating and pressing pressure is preferably 0.098MPa to 1.77MPa, more preferably in the range of 0.29MPa to 1.47MPa, and the heating and pressing time is preferably 20 seconds to 400 seconds, more preferably in the range of 30 seconds to 300 seconds. The lamination is preferably implemented under reduced pressure conditions of 26.7hPa or less.

[0307] Lamination can be performed using a commercially available vacuum laminator. Examples of commercially available vacuum laminators include a vacuum pressure laminator manufactured by Meiki Seisakusho Co., Ltd., a vacuum laminator manufactured by Nikko-Materials Co., Ltd., and a batch vacuum pressure laminator.

[0308] The method for manufacturing a circuit substrate may include smoothing the resin sheet after lamination at normal pressure (atmospheric pressure), for example, by pressing a heat-pressed component from the support side. The pressing conditions for the smoothing treatment may be the same as the conditions for the heat-pressed bonding of the above-mentioned lamination. The smoothing treatment may be performed using a commercially available laminator. The lamination and smoothing treatment may be performed continuously using the above-mentioned commercially available vacuum laminator.

[0309] The method for producing a circuit board according to this example includes a step (II) of curing the resin composition layer after the step (I). By curing the resin composition layer in the step (II), an insulating layer can be formed as a cured product layer of the resin composition layer.

[0310] The curing of the resin composition layer can be carried out by an appropriate method according to the type of curable resin such as (A) furan type curable resin and (D) any curable resin. For example, when the curable resin includes a thermosetting resin, the resin composition layer can be cured by heating. In addition, for example, when the curable resin includes a photocurable resin, the resin composition layer can be cured by light irradiation. In a preferred embodiment, since the curable resin includes a thermosetting resin, the step (II) cures the resin composition layer by heating.

[0311] The heat curing conditions of the resin composition layer may vary depending on the composition of the resin composition. For example, 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. In addition, 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.

[0312] The method for manufacturing a circuit substrate may include preheating the resin composition layer at a temperature lower than the curing temperature before the thermal curing of the resin composition layer. For example, before the resin composition layer is thermally cured, the resin composition layer may be preheated at a temperature of 50°C to 150°C, preferably 60°C to 140°C, and more preferably 70°C to 130°C for usually more than 5 minutes, preferably 5 minutes to 150 minutes, more preferably 15 minutes to 120 minutes, and further preferably 15 minutes to 100 minutes. Preheating is usually performed after step (I). In addition, in the case where a smoothing treatment is performed after lamination of the inner substrate and the resin sheet, preheating may be performed after the smoothing treatment.

[0313] When using a resin sheet having a support, the method for manufacturing a circuit substrate may include a step of peeling off the support after lamination of the inner substrate and the resin sheet. The peeling off of the support may be performed between step (I) and step (II), or after step (II). In addition, in the case where the method for manufacturing a circuit substrate includes a step (III) of forming holes in the insulating layer, a step (IV) of roughening the insulating layer, and a step (V) of forming a conductor layer as described later, the peeling off of the support may be performed between step (II) and step (III), between step (III) and step (IV), or between step (IV) and step (V).

[0314] The method for manufacturing a circuit substrate may include a step (III) of forming holes such as through holes and vias in the insulating layer after step (II). The method for forming the hole can be selected according to factors such as the composition of the resin composition layer used to form the insulating layer. For example, the hole can be formed by processing methods such as drilling, laser processing, and plasma processing, wherein laser processing is preferred. For example, the hole can be formed by irradiating a laser to the insulating layer after the peeling of the support, or the hole can be formed by irradiating a laser to the insulating layer via the support. The size and shape of the hole can be appropriately determined according to the design of the circuit substrate.

[0315] The method for manufacturing a circuit substrate may include a step (IV) of roughening the insulating layer. The surface of the insulating layer can be roughened by the roughening treatment. In addition, contamination (resin residue) can be removed from the insulating layer by the roughening treatment. Therefore, the roughening treatment is sometimes referred to as a "decontamination treatment". For example, if a hole is formed in step (III), contamination may be formed in the hole, so it is preferred to perform the roughening treatment of step (IV) after step (III) to remove the above-mentioned contamination.

[0316] The order and conditions of the roughening treatment are not particularly limited, and the known steps and conditions commonly used in forming the insulating layer of the circuit substrate can be adopted. For example, the insulating layer can be subjected to swelling treatment using a swelling solution, oxidation treatment using an oxidant, and neutralization treatment using a neutralizing solution in sequence to perform the roughening treatment.

[0317] As the swelling liquid used in the roughening treatment, for example, an alkaline solution, a surfactant solution, etc. can be cited, preferably an alkaline solution. As the alkaline solution, a sodium hydroxide solution and a potassium hydroxide solution are more preferred. As commercially available swelling liquids, for example, "Swelling Dip Securiganth P" and "Swelling Dip Securiganth SBU" manufactured by Atotech Japan Co., Ltd. can be cited. The swelling treatment using the swelling liquid can be carried out, for example, by immersing the insulating layer in a swelling liquid at 30°C to 90°C for 1 minute to 20 minutes. From the viewpoint of controlling the swelling of the resin of the insulating layer to an appropriate level, it is preferred to immerse the insulating layer in a swelling liquid at 40°C to 80°C for 5 minutes to 15 minutes.

[0318] As the oxidant used in the roughening treatment, an alkaline permanganate solution formed by dissolving potassium permanganate or sodium permanganate in an aqueous solution of sodium hydroxide can be cited. The roughening treatment using an oxidant such as an alkaline permanganate solution is preferably carried out by immersing the insulating layer in an oxidant solution heated to 60°C to 100°C for 10 minutes to 30 minutes. In addition, the concentration of permanganate in the alkaline permanganate solution is preferably 5% by mass to 10% by mass. As commercially available oxidants, alkaline permanganate solutions such as "Concentrate Compact CP" and "Dosing Solution Securiganth P" manufactured by Atotech Japan Co., Ltd. can be cited.

[0319] The neutralizing solution used in the roughening treatment is preferably an acidic aqueous solution, and commercially available products include, for example, "Reduction Solution Securiganth P" manufactured by Atotech Japan Co., Ltd. The neutralization treatment using the neutralizing solution can be performed by immersing the treated surface oxidized by the oxidizing agent in the neutralizing solution at 30°C to 80°C for 5 to 30 minutes. From the viewpoint of operability, a method in which the object oxidized by the oxidizing agent is immersed in the neutralizing solution at 40°C to 70°C for 5 to 20 minutes is preferred.

[0320] The method for producing a circuit board may include step (V) of forming a conductor layer on the insulating layer. When the method for producing a circuit board includes step (III) or (IV), step (V) of forming a conductor layer is usually preferably performed after steps (III) and (IV).

[0321] The conductor material used in the conductor layer is not particularly limited. In a preferred embodiment, the conductor layer comprises one or more metals selected from gold, platinum, palladium, silver, copper, aluminum, cobalt, chromium, zinc, nickel, titanium, tungsten, iron, tin and indium. The conductor layer may be a single metal layer or an alloy layer. As the alloy layer, for example, a layer formed by an alloy of two or more metals selected from the above metals (e.g., nickel-chromium alloy, copper-nickel alloy and copper-titanium alloy) may be cited. Among them, from the viewpoints of versatility, cost, ease of pattern formation, etc., of the formation of the conductor layer, a single metal layer of chromium, nickel, titanium, aluminum, zinc, gold, palladium, silver or copper, or an alloy layer of nickel-chromium alloy, copper-nickel alloy or copper-titanium alloy is preferred, a single metal layer of chromium, nickel, titanium, aluminum, zinc, gold, palladium, silver or copper, or an alloy layer of nickel-chromium alloy is more preferred, and a single metal layer of copper is more preferred.

[0322] The conductor layer may have a single-layer structure or a multi-layer structure including two or more single metal layers or alloy layers formed of different types of metals or alloys. When the conductor layer has a multi-layer structure, the layer in contact with the insulating layer is preferably a single metal layer of chromium, zinc or titanium or an alloy layer of a nickel-chromium alloy.

[0323] The thickness of the conductor layer varies depending on the design of the circuit board, but is preferably 3 μm to 35 μm, and more preferably 5 μm to 30 μm.

[0324] The conductor layer can be formed by plating. For example, the surface of the insulating layer can be plated by a conventionally known technique such as a semi-additive method or a full-additive method to form a conductor layer having a desired wiring pattern. From the viewpoint of simplicity of manufacture, a semi-additive method is preferred. An example of forming a conductor layer by a semi-additive method is shown below.

[0325] First, an electroless plating layer (plating seed layer) is formed on the surface of the insulating layer by electroless plating. Next, a mask pattern is formed on the formed electroless plating layer to expose a portion of the electroless plating layer corresponding to the desired wiring pattern. After an electrolytic plating layer is formed on the exposed electroless plating layer by electrolytic plating, the mask pattern is removed. Then, the unnecessary electroless plating layer is removed by etching, and a conductor layer having a desired wiring pattern can be formed.

[0326] As another example, the conductor layer can be formed using a metal foil. When a metal foil is used to form a conductor layer, it is preferred to implement step (V) between step (I) and step (II). For example, after step (I), the support is removed and a metal foil is laminated on the surface of the exposed resin composition layer. The lamination of the resin composition layer and the metal foil can be implemented by a vacuum lamination method. The lamination conditions can be the same as those described for step (I). Next, step (II) is implemented to form an insulating layer. Then, using the metal foil on the insulating layer, a conductor layer with a desired wiring pattern can be formed by known techniques such as a subtractive method and a modified semi-additive method. The metal foil can be manufactured, for example, by known methods such as an electrolytic method and a rolling method. As a commercially available product of a metal foil, for example, HLP foil, JXUT-III foil, 3EC-III foil, TP-III foil, etc. made by JX Metal Co., Ltd., and Mitsui Mining and Smelting Co., Ltd. can be cited.

[0327] When a conductor layer is formed on the insulating layer, the method for manufacturing the circuit board may include performing an annealing treatment after the formation of the conductor layer. The annealing treatment can improve the adhesion between the insulating layer and the conductor layer. The annealing treatment can be performed, for example, by heating at 150° C. to 210° C. for 20 minutes to 180 minutes.

[0328] In the method for manufacturing a circuit substrate, each of the above steps may be performed only once or may be repeated twice or more. For example, steps (I) to (V) may be repeated to form a circuit substrate having a multilayer structure such as a multilayer printed wiring board having a plurality of insulating layers and a conductor layer.

[0329] In the method for manufacturing a circuit substrate, any further process can be included in combination with the above-mentioned process. For example, the method for manufacturing a circuit substrate can include a process of setting a semiconductor chip in a manner of bonding with a conductor layer. If a specific example is given, in the case of manufacturing a circuit substrate for semiconductor chip packaging having a semiconductor chip, the method for manufacturing a circuit substrate can include a process of setting a semiconductor chip. For a semiconductor chip, appropriate conditions can be adopted that can connect the terminal electrodes of the semiconductor chip to the conductor layer formed on the insulating layer. For example, the conditions used in flip chip mounting can be adopted. In addition, the semiconductor chip can be bonded via an insulating adhesive or by reflow soldering. Furthermore, as needed, the semiconductor chip set can be filled with a molded bottom filling material. In addition, the method for manufacturing a circuit substrate can include, for example, a process of forming a sealing layer, a process of forming a solder resist layer, a process of cutting the manufactured circuit substrate and singulating, etc.

[0330] As the circuit substrate, for example, a printed wiring board and a semiconductor chip package can be cited. As the semiconductor chip package, for example, FC-CSP, MIS-BGA package, ETS-BGA package, fan-out (Fan-out) type WLP (Wafer Level Package, wafer level package), fan-in (Fan-in) type WLP, fan-out (Fan-out) type PLP (Panel Level Package, panel level package), fan-in (Fan-in) type PLP can be cited. In these semiconductor chip packages, it is preferred to use an insulating layer formed by curing the above-mentioned resin composition layer to form a rewiring formation layer. However, the circuit substrate is not limited to the circuit substrate exemplified here.

[0331] <Semiconductor Device> The above-mentioned circuit substrate can be used for manufacturing a semiconductor device. The semiconductor device has the above-mentioned circuit substrate. As the semiconductor device, various semiconductor devices for electrical products (for example, computers, mobile phones, smart phones, tablet devices, wearable devices, digital cameras, medical devices, and televisions, etc.) and transportation vehicles (for example, motorcycles, cars, trams, ships, and airplanes, etc.) can be cited. Example

[0332] The present invention is specifically described below with reference to the examples. However, the present invention is not limited to these examples. In the following description, "parts" and "%" indicating amounts refer to "parts by mass" and "% by mass" respectively unless otherwise expressly stated. In addition, the temperature conditions and pressure conditions are room temperature (23°C) and atmospheric pressure (1 atm) unless otherwise specified.

[0333] <Synthesis Example 1: Synthesis of polyester resin (1) containing furan skeleton> In a 0.3-liter four-necked round flask equipped with a stirring device, a thermometer, a dropping funnel, and a nitrogen blowing port, add 11.4 g of dicyclopentadiene-phenol polyaddition ("J-DPP85" manufactured by JFE Chemical Co., Ltd., hydroxyl equivalent 165 g / eq.), 4.98 g of 1-naphthol, 10.0 g of 2,5-furandicarbonyl chloride, 0.026 g of tetra-n-butylammonium bromide, and 50 g of toluene, stir while blowing nitrogen, and heat to 30°C to dissolve it. While paying attention to the heat, add 16.6 g of 25% sodium hydroxide (caustic soda) aqueous solution while finally raising the temperature to 60°C. The time required for the dropwise addition is 15 minutes. After stirring at 60°C for 1 hour, add 25 g of distilled water, stir, and discard the water layer. Wash the organic layer 3 times with the same operation. The organic layer was dried over sodium sulfate, and after filtering and drying the material, a portion of the solvent was distilled off from the resulting solution to obtain 24.7 g of the target furan skeleton-containing polyester resin (1) (active group equivalent of approximately 215 g / eq., biomass ratio of 28.4 mass%, toluene solution of 55% non-volatile component ratio) containing 45 mass% toluene.

[0334] [Chemical formula 20]

[0335] <Synthesis Example 2: Synthesis of polyester resin (2) containing furan skeleton> In a 0.3-liter four-necked round flask equipped with a stirring device, a thermometer, a dropping funnel, and a nitrogen blowing port, add 20.0 g of bisphenol A (hydroxyl equivalent 114 g / eq.), 8.1 g of phenol, 2,5-furandicarbonyl chloride 25.0 g, 0.053 g of tetra-n-butylammonium bromide, and 70 g of toluene, blow nitrogen while stirring, and heat to 30°C to dissolve. In a manner that the temperature is finally raised to 60°C, 48 g of 25% sodium hydroxide aqueous solution is added dropwise while paying attention to heat generation. The time required for the dropwise addition is 15 minutes. After stirring at 60°C for 1 hour, 25 g of distilled water is added, and after stirring, the water layer is discarded. The organic layer is then washed 3 times with the same operation. The organic layer was dried over sodium sulfate, and after filtering and drying the material, a portion of the solvent was distilled off from the resulting solution to obtain the target furan skeleton-containing polyester resin (2) having a solid content concentration of 45% by mass (active group equivalent of approximately 153 g / eq., biomass ratio >99% by mass, and non-volatile content of 45%).

[0336] [Chemical formula 21]

[0337] <Synthesis Example 3: Synthesis of polyester resin (3) containing furan skeleton> In Synthesis Example 1, 4.98 g of 1-naphthol was replaced with 8.0 g of camphene-modified phenol ("YS Resin CP" manufactured by Yasuhara Chemical Co., Ltd., hydroxyl equivalent 220 g / eq.). In addition, 11.4 g of dicyclopentadiene-phenol polyaddition ("J-DPP85" manufactured by JFE Chemical Co., Ltd., hydroxyl equivalent 165 g / eq.) was replaced with 7.9 g of bisphenol A (hydroxyl equivalent 114 g / eq.). Except for the above matters, the same operation as in Synthesis Example 1 was carried out to obtain the target polyester resin (3) containing a furan skeleton (active group equivalent of about 225 g / eq., biomass ratio of 88 mass%, non-volatile component ratio of 55%).

[0338] [Chemical formula 22]

[0339] <Synthesis Example 4: Synthesis of polyester resin (4) containing furan skeleton> In Synthesis Example 1, 4.98 g of 1-naphthol was replaced with 3.3 g of phenol. In addition, 11.4 g of dicyclopentadiene-phenol polyaddition product ("J-DPP85" manufactured by JFE Chemical Co., Ltd., hydroxyl equivalent 165 g / eq.) was replaced with 14 g of benzyl-modified bisphenol A (d and e are 1≤d+e≤4). Except for the above matters, the same operation as Synthesis Example 1 was carried out to obtain a polyester resin (4) containing a furan skeleton (active group equivalent of about 217 g / eq., biomass ratio of 71% by mass, toluene solution of non-volatile content of 46%) (wherein d and e represent numbers in the range of 1≤d+e≤4).

[0340] [Chemical formula 23]

[0341] <Synthesis Example 5: Synthesis of poly(5-methoxymethyl-2-vinylfuran) (PMMVF)> According to the method described in Example 1 of JP-A-2010-43203, poly(5-methoxymethyl-2-vinylfuran) (PMMVF) represented by the following formula (5) was obtained.

[0342] [Chemical formula 24]

[0343] <Synthesis Example 6: Synthesis of polycarbosilane> According to the method described in Example 2-3 of International Publication No. 2023 / 100914, a polycarbosilane represented by the following formula (6) was obtained.

[0344] [Chemical formula 25]

[0345] <Example 1> 50 parts of methyl ethyl ketone (MEK) and 10 parts of tetrahydrofuran (THF) were added as diluents to 15 parts of bisphenol A epoxy resin (Mitsubishi Chemical Corporation "828EL", epoxy equivalent of about 180 g / eq., biomass ratio 0 mass%), 20 parts of biphenyl epoxy resin (Nippon Kayaku Co., Ltd. "NC3000L", epoxy equivalent of about 269 g / eq., biomass ratio 0 mass%), and 20 parts of naphthalene epoxy resin (Nippon Steel Chemical Materials Co., Ltd. "ESN475V", epoxy equivalent of about 332 g / eq., biomass ratio 0 mass%), and heated and dissolved while stirring. The mixture was cooled to room temperature to prepare an epoxy resin dissolving composition.

[0346] The epoxy resin dissolved composition was mixed with 3 parts of a naphthol-type curing agent ("SN-485" manufactured by Nippon Steel Chemical Materials Co., Ltd., hydroxyl equivalent of about 205 g / eq., biomass ratio of 0 mass%), 40 parts of a furan skeleton-containing polyester resin (1) obtained in Synthesis Example 1 (active group equivalent of about 215 g / eq., biomass ratio of 28.4 mass%, toluene solution of 55% non-volatile content), and an amine-based curing accelerator (4-dimethylaminopyridine (DMAP), biomass ratio of 0 mass%, solid content of 5 mass%). A resin varnish was prepared by uniformly dispersing 4 parts of a MEK solution containing 0% by mass, 200 parts of spherical silica (SO-C2 manufactured by Yaduma Co., Ltd., with an average particle size of 0.5 μm and a biomass ratio of 0% by mass) surface-treated with a silane coupling agent (KBM-573 manufactured by Shin-Etsu Chemical Co., Ltd.), and 8 parts of a phenoxy resin (YX7553BH30 manufactured by Mitsubishi Chemical Corporation, a 1:1 solution of MEK and cyclohexanone containing 0% by mass and 30% by mass of non-volatile components) using a high-speed rotary mixer.

[0347] As a support, a polyethylene terephthalate film ("AL5" manufactured by Lintec Corporation, thickness 38 μm) having a release surface subjected to a release treatment was prepared. A resin varnish was evenly applied to the release surface of the support so that the thickness of the resin composition layer was 40 μm, and dried at 80° C. to 120° C. (average 100° C.) for 5 minutes to produce a resin sheet.

[0348] <Example 2> A resin varnish and a resin sheet were produced in the same manner as in Example 1 except that the drying time after application of the resin varnish was changed to 7 minutes.

[0349] <Example 3> 35 parts of methyl ethyl ketone (MEK) and 10 parts of tetrahydrofuran (THF) were added as diluents to 15 parts of bisphenol A epoxy resin (Mitsubishi Chemical Corporation "828EL", epoxy equivalent of about 180 g / eq., biomass ratio 0 mass%), 20 parts of biphenyl epoxy resin (Nippon Kayaku Co., Ltd. "NC3000L", epoxy equivalent of about 269 g / eq., biomass ratio 0 mass%), and 20 parts of naphthalene epoxy resin (Nippon Steel Chemical Materials Co., Ltd. "ESN475V", epoxy equivalent of about 332 g / eq., biomass ratio 0 mass%), and heated and dissolved while stirring. The mixture was cooled to room temperature to prepare an epoxy resin dissolving composition.

[0350] To the epoxy resin dissolved composition were mixed 5 parts of a phenolic curing agent containing a triazine skeleton ("LA-3018-50P" manufactured by DIC Corporation, an active group equivalent of about 151 g / eq., a biomass ratio of 0 mass%, and a non-volatile content of 50% in 2-methoxypropanol solution), 10 parts of the polyester resin (1) containing a furan skeleton obtained in Synthesis Example 1 (an active group equivalent of about 215 g / eq., a biomass ratio of 28.4 mass%, and a non-volatile content of 55% in toluene solution), 25 parts of an active ester compound ("HPC-8000-65T" manufactured by DIC Corporation, an active group equivalent of about 223 g / eq., a biomass ratio of 0 mass%, and a non-volatile content of 65% in toluene solution), and an amine curing accelerator (4-dimethylaminopyridine (DMAP), a biomass ratio of 0 mass%, and a non-volatile content of 65%). A resin varnish was prepared by uniformly dispersing 2 parts of a spherical silica (“UFP-30” manufactured by Denka, with an average particle size of 0.3 μm and a biomass ratio of 0% by mass and a biomass ratio of 0% by mass and a biomass ratio of 0% by mass and a solid content of 5% by mass) and 2 parts of a MEK solution having a biomass ratio of 0% by mass and a solid content of 5% by mass), 1 part of an imidazole curing accelerator (“1B2PZ” manufactured by Shikoku Chemical Industry Co., Ltd., 1-benzyl-2-phenylimidazole, a MEK solution having a biomass ratio of 0% by mass and a solid content of 10% by mass), 90 parts of spherical silica (“UFP-30” manufactured by Denka, with an average particle size of 0.3 μm and a biomass ratio of 0%), 12 parts of a phenoxy resin (“YX7553BH30” manufactured by Mitsubishi Chemical Corporation, a 1:1 solution of MEK and cyclohexanone having a biomass ratio of 0% by mass and a non-volatile content of 30% by mass), and 1 part of rubber particles (“STAPHYLOID AC3816N” manufactured by AICA Industries, with a biomass ratio of 0% by mass) using a high-speed rotary mixer to prepare a resin varnish.

[0351] The resin varnish was uniformly applied on the release surface of the support similar to Example 1 so that the thickness of the resin composition layer was 40 μm, and dried at 80° C. to 120° C. (average 100° C.) for 5 minutes to produce a resin sheet.

[0352] <Example 4> In Example 1, 1) The amount of the furan skeleton-containing polyester resin (1) obtained in Synthesis Example 1 (active group equivalent of about 215 g / eq., biomass ratio of 28.4 mass%, toluene solution of 55% non-volatile content) was changed from 40 parts to 20 parts, 2) 24 parts of the furan skeleton-containing polyester resin (2) obtained in Synthesis Example 2 (active group equivalent of about 153 g / eq., biomass ratio> 99 mass%, toluene solution of 45% non-volatile content) were added to the resin varnish, 3) 3 parts of naphthol-based curing agent ("SN-485" manufactured by Nippon Steel Chemical Materials Co., Ltd., hydroxyl equivalent of about 205 g / eq., biomass ratio of 0 mass%) were replaced with 5 parts of phenolic curing agent containing a triazine skeleton ("LA-3018-50P" manufactured by DIC Corporation, active group equivalent of about 151 g / eq., biomass ratio of 0 mass%, 2-methoxypropanol solution of 50% non-volatile content), 4) The amount of tetrahydrofuran (THF) used as the diluent was changed from 10 parts to 40 parts, 5) The dilution solvent of 50 parts of methyl ethyl ketone (MEK) was replaced with 20 parts of toluene. A resin varnish and a resin sheet were produced in the same manner as in Example 1 except for the above matters.

[0353] <Example 5> In Example 4, 1) 24 parts of the furan skeleton-containing polyester resin (2) obtained in Synthesis Example 2 (active group equivalent of about 153 g / eq., biomass ratio> 99 mass%, toluene solution of non-volatile content 45%) were replaced with 20 parts of the furan skeleton-containing polyester resin (3) obtained in Synthesis Example 3 (active group equivalent of about 225 g / eq., biomass ratio of 88 mass%, toluene solution of non-volatile content 55%), 2) Add 2 parts of a polyimide compound having a maleimide group at the end ("BMI-1500" manufactured by Designer Molecules Inc., biomass ratio 0 mass%) to the resin varnish, 3) The amount of tetrahydrofuran (THF) used as the diluent was changed from 40 parts to 20 parts 4) The amount of toluene used as the dilution solvent was changed from 20 parts to 40 parts. A resin varnish and a resin sheet were prepared in the same manner as in Example 4 except for the above matters.

[0354] <Example 6> 40 parts of toluene and 20 parts of tetrahydrofuran (THF) were added as diluent solvents to 5 parts of bisphenol A epoxy resin ("828EL" manufactured by Mitsubishi Chemical Corporation, epoxy equivalent of about 180 g / eq., biomass ratio of 0 mass%), 20 parts of biphenyl epoxy resin ("NC3000L" manufactured by Nippon Kayaku Co., Ltd., epoxy equivalent of about 269 g / eq., biomass ratio of 0 mass%), 10 parts of biphenyl epoxy resin ("YX4000HK" manufactured by Mitsubishi Chemical Corporation, epoxy equivalent of about 185 g / eq., biomass ratio of 0 mass%), and 20 parts of dicyclopentadiene epoxy resin ("HP7200HH" manufactured by DIC Corporation, epoxy equivalent of about 283 g / eq., biomass ratio of 0 mass%), and heated and dissolved while stirring. The mixture was cooled to room temperature to prepare an epoxy resin dissolving composition.

[0355] To the epoxy resin dissolved composition were mixed 5 parts of a phenolic curing agent containing a triazine skeleton ("LA-3018-50P" manufactured by DIC Corporation, an active group equivalent of about 151 g / eq., a biomass ratio of 0 mass%, and a non-volatile content of 50% in 2-methoxypropanol solution), 20 parts of the polyester resin (1) containing a furan skeleton obtained in Synthesis Example 1 (an active group equivalent of about 215 g / eq., a biomass ratio of 28.4 mass%, and a non-volatile content of 55% in toluene solution), 24 parts of the polyester resin (4) containing a furan skeleton obtained in Synthesis Example 4 (an active group equivalent of about 217 g / eq., a biomass ratio of 71 mass%, and a non-volatile content of 46% in toluene solution), and an amine curing accelerator (4-dimethylaminopyridine (DMAP)). ), 4 parts of a MEK solution having a biomass ratio of 0 mass% and a solid content of 5 mass%), 200 parts of spherical silica ("SO-C2" manufactured by Yaduma Co., Ltd., with an average particle size of 0.5 μm and a biomass ratio of 0 mass%) surface-treated with a silane coupling agent ("KBM-573" manufactured by Shin-Etsu Chemical Co., Ltd.), 8 parts of a phenoxy resin ("YX7553BH30" manufactured by Mitsubishi Chemical Corporation, a 1:1 solution of MEK and cyclohexanone having a biomass ratio of 0 mass% and a non-volatile content of 30 mass%), and 3 parts of a vinyl benzyl-modified polyphenylene ether ("OPE-2St2200" manufactured by Mitsubishi Gas Chemical Co., Ltd., a toluene solution having a biomass ratio of 0 mass% and a non-volatile content of 65%) are uniformly dispersed using a high-speed rotary mixer to produce a resin varnish.

[0356] The resin varnish was uniformly applied on the release surface of the support similar to Example 1 so that the thickness of the resin composition layer was 40 μm, and dried at 80° C. to 120° C. (average 100° C.) for 5 minutes to produce a resin sheet.

[0357] <Example 7> In Example 1, 1) The amount of the furan skeleton-containing polyester resin (1) obtained in Synthesis Example 1 (active group equivalent of about 215 g / eq., biomass ratio of 28.4 mass%, toluene solution of 55% non-volatile content) was changed from 40 parts to 30 parts, 2) 5 parts of an active ester compound containing a furan skeleton ("BPTMC-FE" manufactured by Honshu Chemical Industry Co., Ltd., active ester equivalent of about 249 g / eq., biomass ratio of 32% by mass) were added to the resin varnish, 3) The amount of tetrahydrofuran (THF) used as the diluent was changed from 10 parts to 40 parts, 4) The amount of methyl ethyl ketone (MEK) used as the dilution solvent was changed from 50 parts to 20 parts. A resin varnish and a resin sheet were produced in the same manner as in Example 1 except for the above matters.

[0358] <Example 8> In Example 1, 1) The amount of the furan skeleton-containing polyester resin (1) obtained in Synthesis Example 1 (active group equivalent of about 215 g / eq., biomass ratio of 28.4 mass%, toluene solution of 55% non-volatile content) was changed from 40 parts to 30 parts, 2) 5 parts of an active ester compound containing a furan skeleton ("BP-FE" manufactured by Honshu Chemical Industry Co., Ltd., active ester equivalent of about 187 g / eq., biomass ratio of 45% by mass) were added to the resin varnish, 3) The amount of tetrahydrofuran (THF) used as the diluent was changed from 10 parts to 40 parts, 4) The amount of methyl ethyl ketone (MEK) used as the dilution solvent was changed from 50 parts to 20 parts. A resin varnish and a resin sheet were produced in the same manner as in Example 1 except for the above matters.

[0359] <Example 9> In Example 1, 1) The amount of the furan skeleton-containing polyester resin (1) obtained in Synthesis Example 1 (active group equivalent of about 215 g / eq., biomass ratio of 28.4 mass%, toluene solution of 55% non-volatile content) was changed from 40 parts to 30 parts, 2) 5 parts of an active ester compound containing a furan skeleton ("TMPBP-FE" manufactured by Honshu Chemical Industry Co., Ltd., active ester equivalent of about 217 g / eq., biomass ratio of 36% by mass) were added to the resin varnish, 3) The amount of tetrahydrofuran (THF) used as the diluent was changed from 10 parts to 40 parts, 4) The amount of methyl ethyl ketone (MEK) used as the dilution solvent was changed from 50 parts to 20 parts. A resin varnish and a resin sheet were produced in the same manner as in Example 1 except for the above matters.

[0360] <Example 10> 50 parts of methyl ethyl ketone (MEK) and 10 parts of tetrahydrofuran (THF) were added as diluents to 5 parts of bisphenol A epoxy resin (Mitsubishi Chemical Corporation "828EL", epoxy equivalent of about 180 g / eq., biomass ratio 0 mass%), 10 parts of biphenyl epoxy resin (Nippon Kayaku Co., Ltd. "NC3000L", epoxy equivalent of about 269 g / eq., biomass ratio 0 mass%), and 20 parts of naphthalene epoxy resin (Nippon Steel Chemical Materials Co., Ltd. "ESN475V", epoxy equivalent of about 332 g / eq., biomass ratio 0 mass%), and heated and dissolved while stirring. The mixture was cooled to room temperature to prepare an epoxy resin dissolving composition.

[0361] Into this epoxy resin dissolving composition, 70 parts of the furan skeleton-containing polyester resin (1) obtained in Synthesis Example 1 (a toluene solution having an active group equivalent of about 215 g / eq., a biomass ratio of 28.4 mass%, and a nonvolatile content of 55%), 2 parts of an imidazole-based curing accelerator (“1B2PZ” manufactured by Shikoku Chemical Industry Co., Ltd., 1-benzyl-2-phenylimidazole, a MEK solution having a solid content of 10 mass%), 180 parts of spherical silica (“SO-C2” manufactured by Yaduma Co., Ltd., an average particle size of 0.5 μm, a biomass ratio of 0 mass%) surface-treated with a silane coupling agent (“KBM-573” manufactured by Shin-Etsu Chemical Co., Ltd.), and 5 parts of a phenoxy resin (“YX7553BH30” manufactured by Mitsubishi Chemical Corporation, a 1:1 solution of MEK and cyclohexanone having a biomass ratio of 0 mass% and a nonvolatile content of 30 mass%) were mixed and uniformly dispersed using a high-speed rotary mixer to prepare a resin varnish.

[0362] The resin varnish was uniformly applied on the release surface of the support similar to Example 1 so that the thickness of the resin composition layer was 40 μm, and dried at 80° C. to 120° C. (average 100° C.) for 5 minutes to produce a resin sheet.

[0363] <Example 11> 20 parts of tetrahydrofuran (THF) and 40 parts of methyl ethyl ketone (MEK) were added as diluents to 15 parts of bisphenol A epoxy resin (manufactured by Mitsui Chemicals, epoxy equivalent of about 170 g / eq., biomass ratio of 100 mass%), 10 parts of naphthyl ether epoxy resin ("HP-6000" manufactured by DIC Corporation, epoxy equivalent of about 250 g / eq., biomass ratio of 0 mass%), and 15 parts of furan resin ("BioPrepolymer (registered trademark) 1552L" manufactured by Daiei Sangyo Co., Ltd., biomass ratio of 100 mass%), and the mixture was heated and dissolved while stirring. The mixture was cooled to room temperature to prepare an epoxy resin dissolving composition.

[0364] The epoxy resin solution composition was mixed with 10 parts of a naphthol curing agent ("SN-485" manufactured by Nippon Steel Chemical Materials Co., Ltd., hydroxyl equivalent of about 205 g / eq., biomass ratio 0 mass%), 1 part of a phosphorus curing accelerator ("TBP-DA" manufactured by Hokko Chemical Industry Co., Ltd., biomass ratio 0 mass%, MEK solution of 20 mass% solid content), and a polymerization initiator ("PERHEXYL A resin varnish is prepared by uniformly dispersing 2 parts of spherical silica (“SO-C2” manufactured by Yaduma Co., Ltd., with an average particle size of 0.5 μm and a biomass ratio of 0 mass%) surface-treated with a silane coupling agent (“KBM-573” manufactured by Shin-Etsu Chemical Co., Ltd.), and 5 parts of biphenyl aralkylphenol formaldehyde varnish type maleimide (“MIR-3000-70MT” manufactured by Nippon Kayaku Co., Ltd., a MEK / toluene mixed solution with a biomass ratio of 0 mass% and a non-volatile content of 70%) using a high-speed rotary mixer to prepare a resin varnish.

[0365] The resin varnish was uniformly applied on the release surface of the support similar to Example 1 so that the thickness of the resin composition layer was 40 μm, and dried at 80° C. to 120° C. (average 100° C.) for 5 minutes to produce a resin sheet.

[0366] <Example 12> In Example 11, 1) 15 parts of furan resin ("BioPrepolymer (registered trademark) 1552L" manufactured by Daiei Sangyo Co., Ltd., biomass ratio 100 mass %) was replaced with 5 parts of PMMVF obtained in Synthesis Example 5, 2) The amount of methyl ethyl ketone (MEK) used as the dilution solvent was changed from 40 parts to 30 parts. A resin varnish and a resin sheet were produced in the same manner as in Example 11 except for the above matters.

[0367] <Example 13> In Example 11, a resin varnish and a resin sheet were produced in the same manner as in Example 11 except that 15 parts of the furan resin ("BioPrepolymer (registered trademark) 1552L" manufactured by Daiei Sangyo Co., Ltd., biomass ratio 100 mass %) was replaced with 15 parts of the polycarbosilane obtained in Synthesis Example 6.

[0368] <Example 14> In Example 13, a resin varnish and a resin sheet were produced in the same manner as in Example 13, except that 90 parts of spherical silica (“SO-C2” manufactured by Yaduma Co., Ltd., average particle size 0.5 μm, biomass ratio 0 mass%) surface-treated with a silane coupling agent (“KBM-573” manufactured by Shin-Etsu Chemical Co., Ltd.) was replaced with 90 parts of biomass silica (“Ethical Silica” manufactured by MIT Co., Ltd., average particle size 3.7 μm, biomass ratio 100 mass%) surface-treated with a silane coupling agent (“KBM-573” manufactured by Shin-Etsu Chemical Co., Ltd.).

[0369] <Comparative Example 1> In Example 1, 1) 10 parts of tetrahydrofuran (THF) as a diluent were not used, 2) The amount of methyl ethyl ketone (MEK) used as the dilution solvent was changed from 50 parts to 60 parts. A resin varnish and a resin sheet were produced in the same manner as in Example 1 except for the above matters.

[0370] <Comparative Example 2> In Comparative Example 1, 1) 40 parts of the furan skeleton-containing polyester resin (1) obtained in Synthesis Example 1 (active group equivalent of about 215 g / eq., biomass ratio of 28.4 mass%, toluene solution of 55% non-volatile content) were not used; 2) 34 parts of an active ester compound ("HPC-8000-65T" manufactured by DIC Corporation, active group equivalent of about 223 g / eq., biomass ratio of 0 mass%, non-volatile content of 65% toluene solution) was added to the resin varnish, 3) Three parts of a naphthol-type curing agent (“SN-485” manufactured by Nippon Steel Chemical Materials Co., Ltd., hydroxyl equivalent of approximately 205 g / eq., biomass ratio of 0 mass%) were replaced with five parts of a phenolic curing agent containing a triazine skeleton (“LA-3018-50P” manufactured by DIC Corporation, active group equivalent of approximately 151 g / eq., biomass ratio of 0 mass%, 2-methoxypropanol solution of 50% non-volatile content). A resin varnish and a resin sheet were produced in the same manner as in Comparative Example 1 except for the above matters.

[0371] <Comparative Example 3> In Comparative Example 2, 1) The amount of methyl ethyl ketone (MEK) used as the diluent was changed from 60 parts to 50 parts, 2) 10 parts of tetrahydrofuran (THF) was added as a diluent to the epoxy resin dissolved composition. A resin varnish and a resin sheet were produced in the same manner as in Comparative Example 2 except for the above matters.

[0372] <Comparative Example 4> In Example 11, 1) The amount of methyl ethyl ketone (MEK) used as the diluent was changed from 40 parts to 60 parts, 2) 20 parts of tetrahydrofuran (THF) were not used as a diluent solvent. A resin varnish and a resin sheet were produced in the same manner as in Example 11 except for the above matters.

[0373] <Test for measuring dielectric loss tangent> (1) Preparation of cured product for evaluation: A PET film ("501010" manufactured by Lintec, thickness 50 μm, 240 mm square) having a release-treated surface treated with a release agent and an untreated surface not treated with a release agent was prepared. A glass cloth-based epoxy resin double-sided copper-clad laminate ("R5715ES" manufactured by Panasonic, thickness 0.7 mm, 255 mm square) was stacked on the untreated surface of the PET film and fixed on the four sides with a polyimide adhesive tape (width 10 mm).

[0374] The resin varnish prepared in the examples and comparative examples was applied to the release agent treated surface of the fixed PET film by a die coater and dried at 80°C to 120°C (average 100°C) to form a resin composition layer with a thickness of 40 μm. The drying time was 5 minutes in Examples 1 and 3 to 14 and Comparative Examples 1 to 4, and 7 minutes in Example 2.

[0375] Then, the resin composition layer was thermally cured by heating in an oven at 190°C for 90 minutes. After thermal curing, the polyimide adhesive tape was peeled off, the glass cloth substrate epoxy resin double-sided copper-clad laminate was peeled off, and the PET film ("501010" manufactured by Lintec) was also peeled off to obtain a sheet-like cured product. The obtained cured product is sometimes referred to as a "cured product for evaluation".

[0376] (2) Determination of dielectric loss tangent: The evaluation sample was cut into pieces of 80 mm in length and 2 mm in width. The dielectric loss tangent of the evaluation sample was measured at a measurement frequency of 5.8 GHz and a measurement temperature of 23° C. by using a resonant cavity perturbation method using a measuring device (“HP8362B” manufactured by Agilent Technologies). The measurement was performed on two test pieces, and the average value was calculated.

[0377] <Testing of average linear thermal expansion coefficient (CTE) and glass transition temperature Tg> The cured product for evaluation was cut into a length of about 15 mm and a width of about 5 mm to obtain a test piece. A thermomechanical analysis device ("Thermo Plus TMA8310" manufactured by Rigaku Corporation) was used to perform thermomechanical analysis using a tensile load method. Specifically, after the test piece was installed in the above-mentioned device, it was measured twice continuously under the measurement conditions of a load of 1 g and a heating rate of 5°C / min. The temperature was raised to 200°C for the first time and to 260°C for the second time. In the second measurement, the glass transition temperature Tg and the average linear thermal expansion coefficient (CTE) from 25°C to 150°C were calculated.

[0378] <Evaluation Test of Unevenness after Lamination> (1) Preparation of inner substrate: Both sides of a glass cloth-based epoxy resin double-sided copper-clad laminate (copper foil thickness 18 μm, substrate thickness 0.4 mm, Panasonic "R1515A") having an inner layer circuit formed of copper foil on the surface were etched 1 μm with a microetchant (MEC "CZ8101"). The copper foil surface was roughened by etching to obtain an inner layer substrate.

[0379] (2) Lamination of resin sheets: The resin sheets obtained in the examples and comparative examples were laminated on both sides of the inner substrate in such a manner that the resin composition layer was in contact with the inner substrate using a batch vacuum pressurizing laminator (Nikko-materials, 2-stage stacking laminator "CVP700"). The lamination was performed by reducing the pressure for 30 seconds to adjust the air pressure to 13 hPa or less, and then pressing at 120°C and a pressure of 0.74 MPa for 30 seconds. Then, hot pressing was performed at 100°C and a pressure of 0.5 MPa for 60 seconds.

[0380] (3) Evaluation of unevenness after lamination: After lamination, an optical microscope was used to observe the edge of the resin composition layer around the inner substrate at a magnification of 50 times. The situation where a depression was observed near the edge of the resin composition layer was evaluated as "there is" unevenness. In addition, the situation where the above-mentioned depression was not observed was evaluated as "no" unevenness. Here, the observed depression is a plurality of strip-shaped depressions.

[0381] <Test for measuring the content of solvent and THF in resin composition layer> The amounts of the solvent and THF contained in the dried resin composition layer were analyzed and calculated by the GC-MS method.

[0382] <Results> The results of the above-mentioned Examples and Comparative Examples are shown in the following tables. In the following tables, the abbreviations have the following meanings. "Component A / total components (mass %)" in the column "Resin varnish" means the amount of the (A) furan type curable resin relative to 100 mass % of the total amount of the resin varnish. "Component C / non-volatile content (mass %)" in the column "Resin varnish" refers to the amount of the (C) inorganic filler relative to 100 mass % of the non-volatile content in the resin varnish. "Total solvent / total components (mass %)" in the column "Resin varnish" means the amount of the solvent relative to 100 mass % of the total amount of the resin varnish. "THF / total components (mass %)" in the "resin varnish" column: the amount of (B) tetrahydrofuran relative to 100 mass % of the total amount of the resin varnish. "THF / total components (mass %)" in the column "Resin composition layer" means the amount of (B) tetrahydrofuran relative to 100 mass % of the total amount of the resin composition layer. "Total solvent / total components (mass %)" in the column "Resin composition layer" refers to the amount of the solvent relative to 100 mass % of the total amount of the resin composition layer. "THF / total solvent (mass %)" in the "resin composition layer" column is the amount of (B) tetrahydrofuran relative to 100 mass % of the solvent in the resin composition layer. "Component A / total components (mass %)" in the column "Resin composition layer" means the amount of the (A) furan type curable resin relative to 100 mass % of the total amount of the resin composition layer. "Biomass ratio of non-volatile components (%)" in the column "Resin composition layer" refers to the biomass ratio of non-volatile components in the resin composition layer. "Biomass ratio of resin component (%)" in the column of "Resin composition layer" is the biomass ratio of the resin component in the resin composition layer. "Tg": glass transition temperature of the cured layer. "CTE": average coefficient of thermal expansion of the cured layer.

[0383] [Table 1]

[0384] <Discussion> Comparative Examples 1 to 4 are all experimental examples involving a resin composition layer containing (C) an inorganic filler. Among them, in Comparative Example 2, both (A) furan-type curable resin and (B) tetrahydrofuran were not used. In addition, in Comparative Example 3, (A) furan-type curable resin was not used, but (B) tetrahydrofuran was used. In these Comparative Examples 2 and 3, no unevenness was produced. Furthermore, in Comparative Examples 1 and 4, (A) furan-type curable resin was used, but (B) tetrahydrofuran was not used. In these Comparative Examples 1 and 4, unevenness was produced. Therefore, it can be understood from these results that the problem of unevenness is a unique problem produced in a resin composition layer containing (A) furan-type curable resin and (C) an inorganic filler.

[0385] In contrast, in Examples 1 to 14, the combination of (A) furan-type curable resin, (B) tetrahydrofuran, and (C) inorganic filler successfully suppressed the unevenness. Therefore, from the results of Examples 1 to 14, it can be understood that in order to increase the biomass ratio, even when (A) furan-type curable resin is used, the unevenness can be suppressed according to the configuration of the present invention.

Claims

1. A resin sheet comprising a resin composition layer, in, The resin composition layer comprises (A) a curable resin containing a furan skeleton, (B) tetrahydrofuran, and (C) an inorganic filler, wherein the amount of the curable resin containing a furan skeleton (A) is 2% by mass or more relative to 100% by mass of the total amount of the resin composition layer. The amount of (B) tetrahydrofuran is 0.1% by mass or more relative to 100% by mass of the total amount of the resin composition layer. The amount of the (C) inorganic filler is 50% by mass or more based on 100% by mass of the nonvolatile components of the resin composition layer.

2. The resin sheet according to claim 1, wherein The biomass ratio represented by the following formula (M2) in the nonvolatile component in the resin composition layer is 0.1% by mass or more, Biomass ratio (mass %)=(mass of biomass-derived components in nonvolatile components / mass of nonvolatile components)×100(M2).

3. The resin sheet according to claim 1, wherein The average linear thermal expansion coefficient of the cured product layer obtained by curing the resin composition layer is 50 ppm / °C or less.

4. The resin sheet according to claim 1, wherein The dielectric loss tangent of the cured product layer obtained by curing the resin composition layer is less than 0.

015.

5. The resin sheet according to claim 1, wherein The glass transition temperature of the cured product layer obtained by curing the resin composition layer is higher than 150°C.

6. A method for producing a circuit board, comprising using the resin sheet according to any one of claims 1 to 5, The manufacturing method comprises: A step of laminating the resin sheet and the inner layer substrate so that the resin composition layer is bonded to the inner layer substrate, and a step of curing the resin composition layer.

7. A resin composition comprising (A) a curable resin containing a furan skeleton, (B) tetrahydrofuran and (C) an inorganic filler, The amount of (A) the curable resin containing a furan skeleton is 2% by mass or more relative to 100% by mass of the total amount of the resin composition, and the amount of (B) tetrahydrofuran is 1% by mass or more relative to 100% by mass of the total amount of the resin composition, The amount of the (C) inorganic filler is 50% by mass or more relative to 100% by mass of the nonvolatile components in the resin composition.

8. A method for producing a resin sheet, comprising using the resin composition according to claim 7, The manufacturing method comprises: a step of coating the resin composition on a support, and a step of drying the applied resin composition to form a resin composition layer, The amount of (B) tetrahydrofuran in the resin composition layer is 0.1% by mass or more relative to 100% by mass of the total amount of the resin composition layer.

Images