JP7494715B2 - Resin composition - Google Patents

Description

The present invention relates to a resin composition containing an epoxy resin. It also relates to a cured product, a sheet-like laminate material, a resin sheet, a printed wiring board, and a semiconductor device obtained by using the resin composition.

A known manufacturing technique for printed wiring boards is the build-up method, in which insulating layers and conductor layers are stacked alternately. In build-up manufacturing methods, the insulating layers are generally formed by curing a resin composition.

Printed wiring boards are generally exposed to a wide range of temperature environments, from low-temperature environments such as room temperature to high-temperature environments such as reflow. If the dimensional stability is poor, the resin material of the insulating layer will repeatedly expand and contract, and the resulting distortion will cause cracks. In addition, in recent years, there has been a demand for further improvement in the dielectric properties of the insulating layer, such as the dielectric tangent.

Ester-modified epoxy resins have been known so far (Patent Document 1).

JP 2020-111735 A

The objective of the present invention is to provide a resin composition that can suppress the occurrence of cracks after desmearing and can produce a cured product with a low dielectric tangent (Df).

In order to achieve the object of the present invention, the inventors conducted extensive research and unexpectedly discovered that by using an ester-modified epoxy resin as a component of the resin composition and setting the content of inorganic filler to 50 mass% or more, it is possible to suppress the occurrence of cracks after desmearing and obtain a cured product with a low dielectric tangent (Df), which led to the completion of the present invention.

That is, the present invention includes the following.
[1] A resin composition comprising (A) an epoxy resin, (B) an active ester compound, and (C) an inorganic filler,
The component (A) is an epoxy resin (A-1) having two or more epoxy groups per molecule, and a compound represented by the formula (1):

[In the formula, R ¹ represents an alkyl group which may have a substituent or an aryl group which may have a substituent, and R ² represents an aryl group which may have a substituent.]
The modified epoxy resin is obtained by reacting an ester compound represented by the formula:
A resin composition, wherein the content of the component (C) is 50% by mass or more, relative to 100% by mass of non-volatile components in the resin composition.
[2] A resin composition comprising (A) an epoxy resin, (B) an active ester compound, and (C) an inorganic filler,
The component (A) is represented by formula (A-1) (2-1):

[In the formula, * indicates a binding site.]
and a group represented by formula (2-2):

[In the formula, R ¹ represents an alkyl group which may have a substituent or an aryl group which may have a substituent, R ² represents an aryl group which may have a substituent, and * represents a bonding site.]
The modified epoxy resin has a group represented by
A resin composition, wherein the content of the component (C) is 50% by mass or more, relative to 100% by mass of non-volatile components in the resin composition.

[3] The component (A-1) is represented by the formula (4-1):

[In the formula, R ⁴ each independently represents an alkyl group which may have a substituent or an aryl group which may have a substituent, and a represents 0, 1, 2, or 3.]
and a structural unit represented by formula (4-2):

[In the formula, R ¹ represents an alkyl group which may have a substituent, or an aryl group which may have a substituent, R ² represents an aryl group which may have a substituent, R ⁴ each independently represents an alkyl group which may have a substituent, or an aryl group which may have a substituent, and a represents 0, 1, 2, or 3.]
The resin composition according to the above [1] or [2], which is a modified epoxy resin having a structural unit represented by the following formula:
[4] The resin composition according to any one of [1] to [3] above, wherein the content of the component (A-1) is 1% by mass to 20% by mass, based on 100% by mass of the non-volatile components in the resin composition.
[5] The resin composition according to any one of [1] to [4] above, wherein the content of the component (B) is 5% by mass to 30% by mass, based on 100% by mass of non-volatile components in the resin composition.
[6] The resin composition according to any one of the above [1] to [5], wherein the component (A) further contains (A-2) an epoxy resin that is liquid at 20°C.
[7] The resin composition according to any one of the above [1] to [6], further comprising (D) a thermoplastic resin.
[8] The resin composition according to the above [7], wherein the component (D) comprises a thermoplastic resin selected from the group consisting of polyimide resins and phenoxy resins.
[9] The resin composition according to the above [7] or [8], wherein the weight average molecular weight (Mw) of the (D) component is 5,000 or more.
[10] The resin composition according to any one of the above [1] to [9], further comprising (E) a radically polymerizable compound.
[11] The resin composition according to the above [10], wherein the component (E) contains a (meth)acrylic radically polymerizable compound.
[12] The resin composition according to any one of the above [1] to [11], further comprising (F) an elastomer.
[13] The resin composition according to the above [12], wherein the component (F) contains core-shell type rubber particles.
[14] The resin composition according to any one of the above [1] to [13], further comprising (G) a curing accelerator.
[15] The resin composition according to any one of [1] to [14] above, wherein the dielectric loss tangent (Df) of a cured product of the resin composition is 0.0030 or less when measured at 5.8 GHz and 23° C.
[16] A cured product of the resin composition according to any one of [1] to [15] above.
[17] A sheet-like laminate material containing the resin composition according to any one of [1] to [15] above.
[18] A resin sheet comprising a support and a resin composition layer formed from the resin composition according to any one of [1] to [15] above, provided on the support.
[19] A printed wiring board comprising an insulating layer made of a cured product of the resin composition according to any one of [1] to [15] above.
[20] A semiconductor device comprising the printed wiring board according to [19] above.

The resin composition of the present invention can suppress the occurrence of cracks after desmearing and can obtain a cured product with a low dielectric tangent (Df).

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

<Resin Composition>
The resin composition of the present invention comprises (A) an epoxy resin, (B) an active ester compound, and (C) an inorganic filler, the epoxy resin (A) comprising an ester-modified epoxy resin (A-1) described below, and the content of the inorganic filler (C) is 50% by mass or more, assuming that the non-volatile components in the resin composition are 100% by mass. By using such a resin composition, it is possible to suppress the occurrence of cracks after a desmear treatment and to obtain a cured product having a low dielectric loss tangent (Df).

The resin composition of the present invention may further contain optional components in addition to (A) the epoxy resin, (B) the active ester compound, and (C) the inorganic filler. Examples of the optional components include (D) a thermoplastic resin, (E) a radically polymerizable compound, (F) an elastomer, (G) a curing accelerator, (H) other additives, and (I) an organic solvent. Each component contained in the resin composition will be described in detail below.

<(A) Epoxy Resin>
The resin composition of the present invention contains an epoxy resin (A). The epoxy resin (A) is a resin having one or more epoxy groups in one molecule. The epoxy resin (A) may be used alone or in any combination of two or more kinds in any ratio.

<(A-1) Ester-modified epoxy resin>
In the resin composition of the present invention, the (A) epoxy resin contains (A-1) an ester-modified epoxy resin.

In the first embodiment, the ester-modified epoxy resin (A-1) is an epoxy resin having two or more epoxy groups in one molecule, and the epoxy resin is modified with the formula (1):

[In the formula, R ¹ represents an alkyl group which may have a substituent or an aryl group which may have a substituent, and R ² represents an aryl group which may have a substituent.]
The modified epoxy resin is obtained by reacting an ester compound represented by the following formula:

R ¹ represents an alkyl group which may have a substituent, or an aryl group which may have a substituent.

In this specification, examples of the "substituent" in the "optionally substituted alkyl (group)" include monovalent substituents such as halogen atoms, aryl groups, alkyl-aryl groups (aryl groups which may be substituted with an alkyl group), alkyl-oxy groups, aryl-oxy groups, alkyl-carbonyl groups, and aryl-carbonyl groups. The number of substituents in the "optionally substituted alkyl (group)" is not particularly limited, but is preferably 0 to 5, and more preferably 0, 1, or 2.

In this specification, examples of the "substituent" in the "aryl (group) which may have a substituent" include monovalent substituents such as a halogen atom, an alkyl group, an aryl group, an alkyl-aryl group, an aryl-alkyl group (an alkyl group which may be substituted with an aryl group), an alkyl-oxy group, an aryl-oxy group, an alkyl-carbonyl group, and an aryl-carbonyl group. The number of substituents in the "aryl (group) which may have a substituent" is not particularly limited, but is preferably 0 to 5, and more preferably 0, 1, or 2.

Alkyl (group) means a linear, branched and/or cyclic monovalent aliphatic saturated hydrocarbon group. Unless otherwise specified, the alkyl (group) is preferably an alkyl (group) having 1 to 14 carbon atoms, more preferably an alkyl (group) having 1 to 10 carbon atoms, and particularly preferably an alkyl (group) having 1 to 6 carbon atoms. Examples of alkyl (group) include methyl, ethyl, propyl, isopropyl, butyl, isobutyl, sec-butyl, tert-butyl, pentyl, hexyl, heptyl, octyl, nonyl, decyl, cyclopentyl, cyclohexyl, methylcyclohexyl, dimethylcyclohexyl, trimethylcyclohexyl, cyclopentylmethyl, and cyclohexylmethyl. Aryl (group) means a monovalent aromatic hydrocarbon group obtained by removing one hydrogen atom from an aromatic carbon ring. Unless otherwise specified, the aryl (group) is preferably an aryl (group) having 6 to 14 carbon atoms, and particularly preferably an aryl (group) having 6 to 10 carbon atoms. Examples of the aryl (group) include a phenyl group, a 1-naphthyl group, and a 2-naphthyl group. The halogen atom is a fluorine atom, a chlorine atom, a bromine atom, or an iodine atom.

R ¹ is preferably an aryl group which may have a substituent, more preferably an aryl group which may be substituted with a group selected from a halogen atom, an alkyl group, an aryl group, an alkyl-aryl group, an aryl-alkyl group, an alkyl-oxy group, and an aryl-oxy group, even more preferably (1) a phenyl group which may be substituted with a group selected from a halogen atom, an alkyl group, an aryl group, an alkyl-aryl group, an aryl-alkyl group, an alkyl-oxy group, and an aryl-oxy group, (2) a 1-naphthyl group which may be substituted with a group selected from a halogen atom, an alkyl group, an aryl group, an alkyl-aryl group, an aryl-alkyl group, an alkyl-oxy group, and an aryl-oxy group, or (3) a 2-naphthyl group which may be substituted with a group selected from a halogen atom, an alkyl group, an aryl group, an alkyl-aryl group, an aryl-alkyl group, an alkyl-oxy group, and an aryl-oxy group, even more preferably a phenyl group which may be substituted with a group selected from a halogen atom, an alkyl group, an aryl group, an alkyl-aryl group, an aryl-alkyl group, an alkyl-oxy group, and an aryl-oxy group, and particularly preferably a phenyl group.

^R2 represents an aryl group which may have a substituent.

R ² is preferably an aryl group which may be substituted with a group selected from a halogen atom, an alkyl group, an aryl group, an alkyl-aryl group, an aryl-alkyl group, an alkyl-oxy group, and an aryl-oxy group, more preferably (1) a phenyl group which may be substituted with a group selected from a halogen atom, an alkyl group, an aryl group, an alkyl-aryl group, an aryl-alkyl group, an alkyl-oxy group, and an aryl-oxy group, (2) a 1-naphthyl group which may be substituted with a group selected from a halogen atom, an alkyl group, an aryl group, an alkyl-aryl group, an aryl-alkyl group, an alkyl-oxy group, and an aryl-oxy group, or (3) a 2-naphthyl group which may be substituted with a group selected from a halogen atom, an alkyl group, an aryl group, an alkyl-aryl group, an aryl-alkyl group, an alkyl-oxy group, and an aryl-oxy group, further preferably a 2-naphthyl group which may be substituted with a group selected from a halogen atom, an alkyl group, an aryl group, an alkyl-aryl group, an aryl-alkyl group, an alkyl-oxy group, and an aryl-oxy group, and particularly preferably a 2-naphthyl group.

(A-1) The "epoxy resin having two or more epoxy groups in one molecule" to be reacted with the ester compound represented by formula (1) to obtain an ester-modified epoxy resin can be a wide variety of known epoxy resins, and is not particularly limited thereto. Examples of such epoxy resins include bisphenol A type epoxy resins, bisphenol F type epoxy resins, bisphenol S type epoxy resins, bisphenol AF type epoxy resins, glycidyl ester type epoxy resins, glycidyl amine type epoxy resins, alicyclic epoxy resins having an ester skeleton, bisphenol Z type epoxy resins, anthracene type epoxy resins, naphthalene type epoxy resins, naphthalene tetrafunctional epoxy resins, naphthol type epoxy resins, phenol novolac type epoxy resins, bisphenol A type novolac epoxy resins, cresol novolac type epoxy resins, phenol aralkyl type epoxy resins, biphenyl type epoxy resins, bixylenol type epoxy resins, tetrafunctional ... Examples of the epoxy resin include triphenylmethane type epoxy resin, tetraphenylethane type epoxy resin, and dicyclopentadiene type epoxy resin; among them, naphthalene tetrafunctional epoxy resin, naphthol type epoxy resin, phenol novolac type epoxy resin, bisphenol A type novolac epoxy resin, cresol novolac type epoxy resin, phenol aralkyl type epoxy resin, biphenyl type epoxy resin, bixylenol type epoxy resin, triphenylmethane type epoxy resin, tetraphenylethane type epoxy resin, and dicyclopentadiene type epoxy resin are preferred; phenol novolac type epoxy resin, bisphenol A type novolac epoxy resin, cresol novolac type epoxy resin, phenol aralkyl type epoxy resin, biphenyl type epoxy resin, bixylenol type epoxy resin, triphenylmethane type epoxy resin, tetraphenylethane type epoxy resin, and dicyclopentadiene type epoxy resin are more preferred. (A-1) The "epoxy resin having two or more epoxy groups in one molecule" to be reacted with the ester compound represented by formula (1) to obtain the ester-modified epoxy resin may be one type alone or two or more types in combination.

The epoxy equivalent of the "epoxy resin having two or more epoxy groups in one molecule" to be reacted with the ester compound represented by formula (1) to obtain the (A-1) ester-modified epoxy resin is preferably 400 g/eq. or less, more preferably 350 g/eq. or less, and even more preferably 300 g/eq. or less, from the viewpoint of improving heat resistance, and is preferably 100 g/eq. or more, more preferably 120 g/eq. or more, and even more preferably 150 g/eq. or more, from the viewpoint of ensuring sufficient reactivity with the ester compound. The epoxy equivalent is the mass of the resin per equivalent of epoxy group. This epoxy equivalent can be measured according to JIS K7236.

The reaction equivalent ratio between the epoxy resin and the ester compound represented by formula (1) in the reaction to obtain the (A-1) ester-modified epoxy resin is the ratio of the number of moles of epoxy groups in the epoxy resin to the number of moles of ester groups (-CO-O-) in the ester compound (epoxy groups/ester groups), which is preferably 1.60 or more, more preferably 1.62 or more, even more preferably 1.63 or more, and particularly preferably 1.65 or more, and is preferably 6.0 or less, more preferably 5.5 or less, even more preferably 5.0 or less, and particularly preferably 4.5 or less.

(A-1) In the reaction to obtain the ester-modified epoxy resin, for example, a catalyst such as tertiary amines such as 4-(dimethylamino)pyridine and 1,4-diazabicyclo[2,2,2]octane, imidazoles such as 2-methylimidazole and 2-ethyl-4-methylimidazole, organic phosphorus compounds such as tris(p-tolyl)phosphine, and quaternary ammonium salts may be used. The amount of catalyst used is preferably 0.001 to 1% by weight based on the reaction solid content. In the reaction for obtaining the (A-1) ester-modified epoxy resin, for example, aromatic hydrocarbon solvents such as benzene, toluene, xylene, ethylbenzene, trimethylbenzene, etc.; ketone solvents such as acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, etc.; amide solvents such as N,N-dimethylformamide, N,N-dimethylacetamide, N-methyl-2-pyrrolidone, etc.; ether alcohol solvents such as 2-methoxypropanol, 2-methoxyethanol, 2-ethoxyethanol, propylene glycol monomethyl ether, diethylene glycol monobutyl ether (butyl carbitol), etc. may be used. When a solvent is used in the reaction for obtaining the (A-1) ester-modified epoxy resin, it is preferable to use the solvent so that the reaction solid concentration is 35 to 95 mass%. After the reaction is completed, the solvent may be removed or further added as necessary. The reaction temperature in the reaction for obtaining the (A-1) ester-modified epoxy resin is preferably 50 to 200°C, more preferably 100 or 180°C, and even more preferably 120°C to 160°C. (A-1) The reaction time for the reaction to obtain the ester-modified epoxy resin is usually 1 to 12 hours, preferably 3 to 10 hours.

In the second embodiment, the ester-modified epoxy resin (A-1) is represented by the formula (2-1):

[In the formula, * indicates a binding site.]
and a group represented by formula (2-2):

[In the formula, each symbol is as defined above.]
In this embodiment, the modified epoxy resin further has a group represented by the formula (2-3) in addition to the group represented by the formula (2-1) and the group represented by the formula (2-2):

[In the formula, each symbol is as defined above.]
The molar ratio of the group represented by formula (2-2) to the group represented by formula (2-1) in the modified epoxy resin (formula (2-2)/formula (2-1)) is preferably 1 or less. The number of groups represented by formula (2-1) in one molecule of the modified epoxy resin is preferably 2 or more.

In this embodiment, it is preferable that the group represented by formula (2-1), the group represented by formula (2-2), and the group represented by formula (2-3) are each directly bonded to an aromatic carbon atom in the aromatic ring.

The aromatic ring means a ring that follows the Huckel rule, in which the number of electrons contained in the π-electron system on the ring is 4p+2 (p is a natural number). The aromatic ring may be an aromatic carbocyclic ring having carbon atoms as ring-constituting atoms, or an aromatic heterocyclic ring having heteroatoms such as oxygen atoms, nitrogen atoms, and sulfur atoms in addition to carbon atoms as ring-constituting atoms, but in one embodiment, it is preferably an aromatic carbocyclic ring. In one embodiment, the aromatic ring is preferably a 5- to 14-membered aromatic ring, more preferably a 5- to 10-membered aromatic ring, and even more preferably a 5- or 6-membered aromatic ring. Specific examples of suitable aromatic rings include a benzene ring, a naphthalene ring, an anthracene ring, a phenanthrene ring, and the like, more preferably a benzene ring or a naphthalene ring, and particularly preferably a benzene ring.

The ester-modified epoxy resin (A-1) in this embodiment can be obtained, for example, by reacting an epoxy resin having two or more groups represented by formula (2-1) in one molecule with an ester compound represented by formula (1) described above. The reaction conditions can be the same as those for obtaining the ester-modified epoxy resin (A-1) in the first embodiment. Examples of the "epoxy resin having two or more groups represented by formula (2-1) in one molecule" include those having two or more groups represented by formula (2-1) in one molecule among the "epoxy resins having two or more epoxy groups in one molecule" described above.

In the second embodiment, the ester-modified epoxy resin (A-1) is preferably represented by formula (3-1):

[In the formula, ring Ar represents an aromatic ring which may have a substituent, and each ^R3 independently represents a hydrogen atom, an alkyl group which may have a substituent, or an aryl group which may have a substituent.]
and a structural unit represented by formula (3-2):

[In the formula, each symbol is as defined above.]
In this embodiment, the modified epoxy resin has a structural unit represented by the formula (3-3) in addition to the structural unit represented by the formula (3-1) and the structural unit represented by the formula (3-2):

[In the formula, each symbol is as defined above.]
The molar ratio of the structural unit represented by formula (3-2) to the structural unit represented by formula (3-1) in the modified epoxy resin (formula (3-2)/formula (3-1)) is preferably 1 or less. The number of the structural unit represented by formula (3-1) in one molecule of the modified epoxy resin is preferably 2 or more.

Ring Ar represents an aromatic ring which may have a substituent.

In this specification, examples of the "substituent" in the "optionally substituted aromatic ring" include monovalent substituents such as a halogen atom, an optionally substituted alkyl group, an optionally substituted aryl group, an optionally substituted alkyl-oxy group, an optionally substituted aryl-oxy group, an optionally substituted alkyl-carbonyl group, and an optionally substituted aryl-carbonyl group. The number of substituents in the "optionally substituted aromatic ring" is not particularly limited, but is preferably 0 to 5, and more preferably 0, 1, or 2.

The ring Ar is preferably (1) a benzene ring which may be substituted with a group selected from an alkyl group which may be substituted and an aryl group which may be substituted, or (2) a naphthalene ring which may be substituted with an alkyl group which may be substituted and an aryl group which may be substituted, more preferably a benzene ring which may be substituted with a group selected from an alkyl group which may be substituted and an aryl group which may be substituted, even more preferably a benzene ring which may be substituted with an alkyl group which may be substituted, and particularly preferably a benzene ring which may be substituted with an alkyl group which may be substituted.

Each ^R3 independently represents a hydrogen atom, an alkyl group which may have a substituent, or an aryl group which may have a substituent. ^R3 is preferably a hydrogen atom.

The ester-modified epoxy resin (A-1) in this embodiment can be obtained, for example, by reacting an epoxy resin having two or more structural units represented by formula (3-1) in one molecule with an ester compound represented by formula (1) described above. The reaction conditions can be the same as those for obtaining the ester-modified epoxy resin (A-1) in the first embodiment. Examples of the "epoxy resin having two or more groups represented by formula (3-1) in one molecule" include those having two or more structural units represented by formula (3-1) in one molecule among the "epoxy resins having two or more epoxy groups in one molecule" described above.

In the second embodiment, the ester-modified epoxy resin (A-1) is more preferably represented by formula (4-1):

[In the formula, R ⁴ each independently represents an alkyl group which may have a substituent or an aryl group which may have a substituent, and a represents 0, 1, 2, or 3.]
and a structural unit represented by formula (4-2):

[In the formula, each symbol is as defined above.]
In this embodiment, the modified epoxy resin has a structural unit represented by the formula (4-3) in addition to the structural unit represented by the formula (4-1) and the structural unit represented by the formula (4-2):

[In the formula, each symbol is as defined above.]
The molar ratio of the structural unit represented by formula (4-2) to the structural unit represented by formula (4-1) in the modified epoxy resin (formula (4-2)/formula (4-1)) is preferably 1 or less. The number of the structural unit represented by formula (4-1) in one molecule of the modified epoxy resin is preferably 2 or more.

Each ^R4 independently represents an alkyl group which may have a substituent, or an aryl group which may have a substituent.

R ⁴ is preferably, each independently, (1) an alkyl group which may be substituted with a group selected from a halogen atom, an aryl group, an alkyl-aryl group, an alkyl-oxy group, and an aryl-oxy group, or (2) an aryl group which may be substituted with a group selected from a halogen atom, an alkyl group, an aryl group, an alkyl-aryl group, an aryl-alkyl group, an alkyl-oxy group, and an aryl-oxy group, more preferably an alkyl group which may be substituted with a group selected from a halogen atom, an aryl group, an alkyl-aryl group, an alkyl-oxy group, and an aryl-oxy group, further preferably an alkyl group, and particularly preferably a methyl group.

a is 0, 1, 2 or 3, preferably 0 or 1.

The ester-modified epoxy resin (A-1) in this embodiment can be obtained, for example, by reacting an epoxy resin having two or more structural units represented by formula (4-1) in one molecule with an ester compound represented by formula (1) described above. The reaction conditions can be the same as those for obtaining the ester-modified epoxy resin (A-1) in the first embodiment. Examples of the "epoxy resin having two or more groups represented by formula (4-1) in one molecule" include those having two or more structural units represented by formula (4-1) in one molecule among the "epoxy resins having two or more epoxy groups in one molecule" described above.

The (A-1) ester-modified epoxy resin is preferably solid at 20°C. When the (A-1) ester-modified epoxy resin is solid at 20°C, its softening point is preferably 60°C or higher, more preferably 65°C or higher, even more preferably 70°C or higher, and particularly preferably 75°C or higher, from the viewpoint of improving the handleability of the resin, and is preferably 130°C or lower, more preferably 125°C or lower, even more preferably 120°C or lower, and particularly preferably 115°C or lower, from the viewpoint of ensuring sufficient solvent solubility. The softening point can be measured in accordance with JIS K7234.

The weight average molecular weight (Mw) of the ester-modified epoxy resin (A-1) is preferably 500 or more, more preferably 600 or more, even more preferably 700 or more, and particularly preferably 1,000 or more, from the viewpoint of further improving the dielectric properties, and is preferably 10,000 or less, more preferably 8,000 or less, even more preferably 7,000 or less, and particularly preferably 6,000 or less, from the viewpoint of improving the handleability. The weight average molecular weight of the resin can be measured as a polystyrene-equivalent value by gel permeation chromatography (GPC).

The epoxy equivalent of the ester-modified epoxy resin (A-1) is preferably 1,000 g/eq. or less, more preferably 900 g/eq. or less, and particularly preferably 800 g/eq. or less, from the viewpoint of improving heat resistance, and is preferably 300 g/eq. or more, more preferably 330 g/eq. or more, and even more preferably 360 g/eq. or more, from the viewpoint of further improving dielectric properties.

The content of the (A-1) ester-modified epoxy resin in the resin composition is not particularly limited, but is preferably 50% by mass or less, more preferably 30% by mass or less, even more preferably 20% by mass or less, even more preferably 15% by mass or less, and particularly preferably 12% by mass or less, when the non-volatile components in the resin composition are taken as 100% by mass. The lower limit of the content of the (A-1) ester-modified epoxy resin in the resin composition is not particularly limited, but is preferably 0.1% by mass or more, more preferably 0.5% by mass or more, even more preferably 1% by mass or more, even more preferably 3% by mass or more, and particularly preferably 5% by mass or more, when the non-volatile components in the resin composition are taken as 100% by mass.

<(A-2) Liquid epoxy resin>
In the resin composition of the present invention, the epoxy resin (A) may contain, in addition to the ester-modified epoxy resin (A-1), an optional component, an epoxy resin (A-2) that is liquid at 20° C. (sometimes abbreviated as "liquid epoxy resin" in this specification). The liquid epoxy resin (A-2) described here is an epoxy resin that does not fall under the category of the ester-modified epoxy resin (A-1).

(A-2) The liquid epoxy resin preferably contains a liquid epoxy resin having one or more epoxy groups in one molecule, and two or more epoxy groups in one molecule. The proportion of the liquid 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, based on 100% by mass of the liquid epoxy resin.

(A-2) Examples of liquid epoxy resins include bisphenol A type epoxy resins, bisphenol F type epoxy resins, bisphenol AF type epoxy resins, naphthalene type epoxy resins, glycidyl ester type epoxy resins, glycidyl amine type epoxy resins, phenol novolac type epoxy resins, alicyclic epoxy resins having an ester skeleton, cyclohexane type epoxy resins, cyclohexane dimethanol type epoxy resins, and epoxy resins having a butadiene structure.

(A-2) Specific examples of liquid epoxy resins include "HP4032", "HP4032D", and "HP4032SS" (naphthalene type epoxy resins) manufactured by DIC Corporation; "828US", "828EL", "jER828EL", "825", and "Epicoat 828EL" (bisphenol A type epoxy resins) manufactured by Mitsubishi Chemical Corporation; "jER807" and "1750" (bisphenol F type epoxy resins) manufactured by Mitsubishi Chemical Corporation; "jER152" (phenol novolac type epoxy resin) manufactured by Mitsubishi Chemical Corporation; "630", "630LSD", and "604" (glycidylamine type epoxy resins) manufactured by Mitsubishi Chemical Corporation; "ED-523T" (glycilol type epoxy resin) manufactured by ADEKA Corporation; "EP-3950L" and "EP-3980" manufactured by ADEKA Corporation. S" (glycidylamine type epoxy resin); "EP-4088S" (dicyclopentadiene type epoxy resin) manufactured by ADEKA; "ZX1059" (mixture of bisphenol A type epoxy resin and bisphenol F type epoxy resin) manufactured by Nippon Steel Chemical & Material Chemical Co., Ltd.; "EX-721" (glycidyl ester type epoxy resin) manufactured by Nagase ChemteX Corporation; "Celloxide 2021P" (alicyclic epoxy resin having an ester skeleton) manufactured by Daicel Corporation; "PB-3600" manufactured by Daicel Corporation, "JP-100" and "JP-200" (epoxy resin having a butadiene structure) manufactured by Nippon Soda Co., Ltd.; "ZX1658" and "ZX1658GS" (liquid 1,4-glycidylcyclohexane type epoxy resin) manufactured by Nippon Steel Chemical & Material Co., Ltd. These may be used alone or in combination of two or more types.

The epoxy equivalent of the liquid epoxy resin (A-2) is preferably 50 g/eq. to 5,000 g/eq., more preferably 60 g/eq. to 2,000 g/eq., even more preferably 70 g/eq. to 1,000 g/eq., and even more preferably 80 g/eq. to 500 g/eq. The epoxy equivalent is the mass of the resin per equivalent of epoxy groups. This epoxy equivalent can be measured according to JIS K7236.

The weight average molecular weight (Mw) of the liquid epoxy resin (A-2) is preferably 100 to 5,000, more preferably 150 to 3,000, and even more preferably 200 to 1,500. The weight average molecular weight of the resin can be measured by gel permeation chromatography (GPC) as a polystyrene-equivalent value.

The content of the liquid epoxy resin (A-2) in the resin composition is not particularly limited, but is preferably 40% by mass or less, more preferably 20% by mass or less, even more preferably 15% by mass or less, even more preferably 10% by mass or less, and particularly preferably 7% by mass or less, when the non-volatile components in the resin composition are taken as 100% by mass. The lower limit of the content of the liquid epoxy resin (A-2) in the resin composition is not particularly limited, but is preferably 0.01% by mass or more, more preferably 0.1% by mass or more, even more preferably 0.5% by mass or more, even more preferably 1% by mass or more, and particularly preferably 3% by mass or more, when the non-volatile components in the resin composition are taken as 100% by mass.

The mass ratio of the liquid epoxy resin (A-2) to the ester-modified epoxy resin (A-1) in the resin composition (component (A-2)/component (A-1)) is not particularly limited, but is preferably 0.05 or more, more preferably 0.1 or more, and particularly preferably 0.3 or more. The upper limit of the mass ratio of the liquid epoxy resin (A-2) to the ester-modified epoxy resin (A-1) in the resin composition (component (A-2)/component (A-1)) is not particularly limited, but is preferably 5 or less, more preferably 2 or less, and particularly preferably 1 or less.

<(A-3) Solid Epoxy Resin>
In the resin composition of the present invention, the epoxy resin (A) may contain, in addition to the ester-modified epoxy resin (A-1), an optional component, an epoxy resin (A-3) that is solid at 20° C. (sometimes abbreviated as "solid epoxy resin" in this specification). The solid epoxy resin (A-3) described here is an epoxy resin that does not fall under the category of the ester-modified epoxy resin (A-1).

(A-3) The solid epoxy resin preferably contains a solid epoxy resin having one or more epoxy groups in one molecule, and two or more epoxy groups in one molecule. The proportion of the solid 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, based on 100% by mass of the solid epoxy resin.

(A-3) As solid epoxy resins, preferred are bixylenol 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, naphthylene 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, phenolphthalimidine type epoxy resins, and phenolphthalein type epoxy resins.

(A-3) Specific examples of solid epoxy resins include DIC's "HP4032H" (naphthalene type epoxy resin); DIC's "HP-4700" and "HP-4710" (naphthalene type tetrafunctional epoxy resin); DIC's "N-690" (cresol novolac type epoxy resin); DIC's "N-695" (cresol novolac type epoxy resin); DIC's "HP-7200", "HP-7200HH", "HP-7200H", and "HP-7200L" (dicyclopentadiene type epoxy resin); DIC's "EXA-7 311", "EXA-7311-G3", "EXA-7311-G4", "EXA-7311-G4S", "HP6000" (naphthylene 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 Steel Chemical & Material Co., Ltd.; "ESN475V", "E "SN4100V" (naphthalene type epoxy resin); "ESN485" (naphthol type epoxy resin) manufactured by Nippon Steel Chemical & Material Co., Ltd.; "ESN375" (dihydroxynaphthalene type epoxy resin) manufactured by Nippon Steel Chemical & Material Co., Ltd.; "YX4000H", "YX4000", "YX4000HK", "YL7890" (bixylenol type epoxy resin) manufactured by Mitsubishi Chemical Co., Ltd.; "YL6121" (biphenyl type epoxy resin) manufactured by Mitsubishi Chemical Co., Ltd.; "YX8800" (anthracene type epoxy resin) manufactured by Mitsubishi Chemical Co., Ltd.; " Examples of such epoxy resins include "YX7700" (phenol aralkyl type epoxy resin); "PG-100" and "CG-500" manufactured by Osaka Gas Chemicals; "YL7760" (bisphenol AF type epoxy resin) manufactured by Mitsubishi Chemical; "YL7800" (fluorene type epoxy resin) manufactured by Mitsubishi Chemical; "jER1010" (bisphenol A type epoxy resin) manufactured by Mitsubishi Chemical; "jER1031S" (tetraphenylethane type epoxy resin) manufactured by Mitsubishi Chemical; and "WHR991S" (phenolphthalimidine type epoxy resin) manufactured by Nippon Kayaku Co., Ltd. These may be used alone or in combination of two or more types.

The epoxy equivalent of the solid epoxy resin (A-3) is preferably 50 g/eq. to 5,000 g/eq., more preferably 60 g/eq. to 2,000 g/eq., even more preferably 70 g/eq. to 1,000 g/eq., and even more preferably 80 g/eq. to 500 g/eq. The epoxy equivalent is the mass of the resin per equivalent of epoxy groups. This epoxy equivalent can be measured according to JIS K7236.

The weight average molecular weight (Mw) of the solid epoxy resin (A-3) is preferably 100 to 5,000, more preferably 250 to 3,000, and even more preferably 400 to 1,500. The weight average molecular weight of the resin can be measured as a polystyrene-equivalent value by gel permeation chromatography (GPC).

The content of the solid epoxy resin (A-3) in the resin composition is not particularly limited, but is preferably 40% by mass or less, more preferably 20% by mass or less, even more preferably 10% by mass or less, and even more preferably 5% by mass or less, assuming that the non-volatile components in the resin composition are 100% by mass.

The mass ratio of the solid epoxy resin (A-3) to the ester-modified epoxy resin (A-1) in the resin composition (component (A-3)/component (A-1)) is not particularly limited, but is preferably 3 or less, more preferably 2 or less, and particularly preferably 1 or less.

<(B) Active Ester Compound>
The resin composition of the present invention contains an active ester compound (B). The active ester compound (B) may be used alone or in combination of two or more at any ratio. The active ester compound (B) may function as an epoxy resin curing agent that reacts with the epoxy resin (A) to cure the epoxy resin.

(B) As the active ester compound, generally, compounds having two or more ester groups (highly reactive ester groups) in one molecule, such as phenol esters, thiophenol esters, N-hydroxyamine esters, and esters of heterocyclic hydroxy compounds, are preferably used. The active ester compound is preferably one obtained by a condensation reaction between a carboxylic acid compound and/or a thiocarboxylic acid compound and a hydroxy compound and/or a thiol compound. In particular, from the viewpoint of improving heat resistance, an active ester compound obtained from a carboxylic acid compound and a hydroxy compound is preferred, and an active ester compound 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, and pyromellitic acid. Examples of phenol compounds or naphthol compounds include hydroquinone, resorcin, bisphenol A, bisphenol F, bisphenol S, phenolphthaline, methylated bisphenol A, methylated bisphenol F, methylated bisphenol S, phenol, o-cresol, m-cresol, p-cresol, catechol, α-naphthol, β-naphthol, 1,5-dihydroxynaphthalene, 1,6-dihydroxynaphthalene, 2,6-dihydroxynaphthalene, dihydroxybenzophenone, trihydroxybenzophenone, tetrahydroxybenzophenone, phloroglucin, benzenetriol, dicyclopentadiene-type diphenol compounds, and phenol novolak. Here, "dicyclopentadiene-type diphenol compounds" refer to diphenol compounds obtained by condensing one molecule of dicyclopentadiene with two molecules of phenol.

Specifically, the active ester compound (B) is preferably a dicyclopentadiene-type active ester compound, a naphthalene-type active ester compound containing a naphthalene structure, an active ester compound containing an acetylated product of phenol novolac, or an active ester compound containing a benzoylated product of phenol novolac, and among these, at least one selected from a dicyclopentadiene-type active ester compound and a naphthalene-type active ester compound is more preferable, and a dicyclopentadiene-type active ester compound is even more preferable. As the dicyclopentadiene-type active ester compound, an active ester compound containing a dicyclopentadiene-type diphenol structure is preferable.

(B) Commercially available active ester compounds include, as active ester compounds containing a dicyclopentadiene-type diphenol structure, "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 compounds containing a naphthalene structure, "EXB-8100L-65T", "EXB-8150-60T", "EXB-8150-62T", "EXB-8100H-65TM" and "EXB-8150H-65TM" are available. XB-9416-70BK, HPC-8150-60T, HPC-8150-62T, and EXB-8 (manufactured by DIC Corporation); an active ester compound containing phosphorus is "EXB9401" (manufactured by DIC Corporation); an active ester compound which is an acetylated product of phenol novolac is "DC808" (manufactured by Mitsubishi Chemical Corporation); an active ester compound which is a benzoylated product of phenol novolac is "YLH1026", "YLH1030", and "YLH1048" (manufactured by Mitsubishi Chemical Corporation); an active ester compound containing a styryl group and a naphthalene structure is "PC1300-02-65MA" (manufactured by Air Water Inc.), and the like.

The active ester group equivalent of the (B) active ester compound is preferably 50 g/eq. to 500 g/eq., more preferably 50 g/eq. to 400 g/eq., and even more preferably 100 g/eq. to 300 g/eq. The active ester group equivalent is the mass of the active ester compound per equivalent of the active ester group.

The content of the (B) active ester compound in the resin composition is not particularly limited, but is preferably 50% by mass or less, more preferably 40% by mass or less, even more preferably 30% by mass or less, even more preferably 25% by mass or less, and particularly preferably 20% by mass or less, when the non-volatile components in the resin composition are taken as 100% by mass. The lower limit of the content of the (B) active ester compound in the resin composition is not particularly limited, but is preferably 0.1% by mass or more, more preferably 1% by mass or more, even more preferably 5% by mass or more, even more preferably 8% by mass or more, and particularly preferably 10% by mass or more, when the non-volatile components in the resin composition are taken as 100% by mass.

The mass ratio of the active ester compound (B) to the ester-modified epoxy resin (A-1) in the resin composition (component (B)/component (A-1)) is not particularly limited, but is preferably 0.5 or more, more preferably 1 or more, and particularly preferably 1.2 or more. The upper limit of the mass ratio of the active ester compound (B) to the ester-modified epoxy resin (A-1) in the resin composition (component (B)/component (A-1)) is not particularly limited, but is preferably 5 or less, more preferably 3 or less, and particularly preferably 2 or less.

<(B') Other Curing Agents>
The resin composition of the present invention may further contain a (B') curing agent other than the (B) component as an optional component. The (B') other curing agent may be used alone or in any combination of two or more. The (B') other curing agent may function as an epoxy resin curing agent that reacts with the (A) epoxy resin to cure it, similar to the (B) active ester compound.

(B') Other curing agents are not particularly limited, but examples thereof include phenol-based curing agents, carbodiimide-based curing agents, acid anhydride-based curing agents, amine-based curing agents, benzoxazine-based curing agents, cyanate ester-based curing agents, and thiol-based curing agents. (B') Other curing agents particularly preferably include phenol-based curing agents.

As the phenol-based hardener, a phenol-based hardener having a novolac structure is preferred from the viewpoint of heat resistance and water resistance. Also, from the viewpoint of adhesion to the adherend, a nitrogen-containing phenol-based hardener is preferred, and a triazine skeleton-containing phenol-based hardener is more preferred. Among them, a triazine skeleton-containing phenol novolac resin is preferred from the viewpoint of highly satisfying heat resistance, water resistance, and adhesion. Specific examples of phenol-based curing agents include "MEH-7700", "MEH-7810", and "MEH-7851" manufactured by Meiwa Kasei Co., Ltd., "NHN", "CBN", and "GPH" manufactured by Nippon Kayaku Co., Ltd., "SN-170", "SN-180", "SN-190", "SN-475", "SN-485", "SN-495", "SN-375", and "SN-395" manufactured by Nippon Steel Chemical & Material Co., Ltd., and "LA-7052", "LA-7054", "LA-3018", "LA-3018-50P", "LA-1356", "TD2090", and "TD-2090-60M" manufactured by DIC Corporation.

Carbodiimide-based curing agents include curing agents having one or more, preferably two or more, carbodiimide structures in one molecule, such as aliphatic biscarbodiimides such as tetramethylene-bis(t-butylcarbodiimide) and cyclohexane-bis(methylene-t-butylcarbodiimide); aromatic biscarbodiimides such as phenylene-bis(xylylcarbodiimide); and aliphatic polycarbodiimides such as polyhexamethylenecarbodiimide, polytrimethylhexamethylenecarbodiimide, polycyclohexylenecarbodiimide, poly(methylenebiscyclohexylenecarbodiimide), and poly(isophoronecarbodiimide). ; polycarbodiimides such as aromatic polycarbodiimides such as poly(phenylenecarbodiimide), poly(naphthylenecarbodiimide), poly(tolylenecarbodiimide), poly(methyldiisopropylphenylenecarbodiimide), poly(triethylphenylenecarbodiimide), poly(diethylphenylenecarbodiimide), poly(triisopropylphenylenecarbodiimide), poly(diisopropylphenylenecarbodiimide), poly(xylylenecarbodiimide), poly(tetramethylxylylenecarbodiimide), poly(methylenediphenylenecarbodiimide), and poly[methylenebis(methylphenylene)carbodiimide].

Commercially available carbodiimide curing agents include, for example, "Carbodilite V-02B," "Carbodilite V-03," "Carbodilite V-04K," "Carbodilite V-07," and "Carbodilite V-09" manufactured by Nisshinbo Chemical Co., Ltd.; and "Stavaxol P," "Stavaxol P400," and "Hi-Kasil 510" manufactured by Rhein Chemie.

Examples of acid anhydride curing agents include curing agents having one or more acid anhydride groups in one molecule, and curing agents having two or more acid anhydride groups in one molecule are preferred. Specific examples of acid anhydride curing agents include phthalic anhydride, tetrahydrophthalic anhydride, hexahydrophthalic anhydride, methyltetrahydrophthalic anhydride, methylhexahydrophthalic anhydride, methylnadic anhydride, hydrogenated methylnadic anhydride, trialkyltetrahydrophthalic anhydride, dodecenyl succinic anhydride, 5-(2,5-dioxotetrahydro-3-furanyl)-3-methyl-3-cyclohexene-1,2-dicarboxylic anhydride, trimellitic anhydride, pyromellitic anhydride, and benzophenonetetracarboxylic dianhydride. anhydride, biphenyltetracarboxylic dianhydride, naphthalenetetracarboxylic dianhydride, oxydiphthalic dianhydride, 3,3'-4,4'-diphenylsulfonetetracarboxylic dianhydride, 1,3,3a,4,5,9b-hexahydro-5-(tetrahydro-2,5-dioxo-3-furanyl)-naphtho[1,2-C]furan-1,3-dione, ethylene glycol bis(anhydrotrimellitate), and polymeric acid anhydrides such as styrene-maleic acid resin in which styrene and maleic acid are copolymerized. Commercially available acid anhydride curing agents include "HNA-100", "MH-700", "MTA-15", "DDSA", and "OSA" manufactured by New Japan Chemical Co., Ltd., "YH-306" and "YH-307" manufactured by Mitsubishi Chemical Corporation, "HN-2200" and "HN-5500" manufactured by Hitachi Chemical Co., Ltd., and "EF-30", "EF-40", "EF-60", and "EF-80" manufactured by Clay Valley.

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

Specific examples of benzoxazine-based curing agents include "JBZ-OP100D" and "ODA-BOZ" manufactured by JFE Chemical Corporation; "HFB2006M" manufactured by Showa Polymer Co., Ltd.; and "P-d" and "F-a" manufactured by Shikoku Chemical Industry Co., Ltd.

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

Examples of thiol-based curing agents include trimethylolpropane tris(3-mercaptopropionate), pentaerythritol tetrakis(3-mercaptobutyrate), and tris(3-mercaptopropyl)isocyanurate.

(B') The reactive group equivalent of the other curing agent is preferably 50 g/eq. to 3000 g/eq., more preferably 100 g/eq. to 1000 g/eq., even more preferably 100 g/eq. to 500 g/eq., and particularly preferably 100 g/eq. to 300 g/eq. The reactive group equivalent is the mass of the curing agent per equivalent of reactive group.

The content of the (B') other curing agent in the resin composition is not particularly limited, but is preferably 20% by mass or less, more preferably 10% by mass or less, even more preferably 5% by mass or less, and particularly preferably 3% by mass or less, when the non-volatile components in the resin composition are taken as 100% by mass. The lower limit of the content of the (B') other curing agent in the resin composition is not particularly limited, but may be, for example, 0% by mass or more, 0.01% by mass or more, 0.1% by mass or more, 0.5% by mass or more, etc., when the non-volatile components in the resin composition are taken as 100% by mass.

The mass ratio of the other curing agent (B') to the ester-modified epoxy resin (A-1) in the resin composition (component (B')/component (A-1)) is not particularly limited, but is preferably 1 or less, more preferably 0.5 or less, and particularly preferably 0.2 or less.

The content of the (B) active ester compound in the resin composition is preferably 10% by mass or more, more preferably 30% by mass or more, even more preferably 40% by mass or more, and particularly preferably 50% by mass or more, assuming that the total of the (B) active ester compound and (B') other curing agents in the resin composition is 100% by mass.

<(C) Inorganic filler>
The resin composition of the present invention contains an inorganic filler (C). The content of the inorganic filler (C) is 50% by mass or more, based on 100% by mass of the non-volatile components in the resin composition. The inorganic filler (C) is contained in the resin composition in the form of particles.

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

(C) Commercially available inorganic fillers include, for example, "UFP-30" manufactured by Denka Chemical Industry Co., Ltd.; "SP60-05" and "SP507-05" manufactured by Nippon Steel & Sumitomo Metal Materials Co., Ltd.; "YC100C", "YA050C", "YA050C-MJE", and "YA010C" manufactured by Admatechs Co., Ltd.; "UFP-30" manufactured by Denka Company; "Silfil NSS-3N", "Silfil NSS-4N", and "Silfil NSS-5N" manufactured by Tokuyama Corporation; "SC2500SQ", "SO-C4", "SO-C2", and "SO-C1" manufactured by Admatechs Co., Ltd.; and "DAW-03" and "FB-105FD" manufactured by Denka Company, Ltd.

(C) The average particle size of the inorganic filler is not particularly limited, but is preferably 10 μm or less, more preferably 5 μm or less, even more preferably 2 μm or less, even more preferably 1 μm or less, and particularly preferably 0.7 μm or less. (C) The lower limit of the average particle size of the inorganic filler is not particularly limited, but is preferably 0.01 μm or more, more preferably 0.05 μm or more, even more preferably 0.1 μm or more, and particularly preferably 0.2 μm or more. (C) The average particle size of the inorganic filler can be measured by a laser diffraction/scattering method based on the Mie scattering theory. Specifically, the particle size distribution of the inorganic filler is created on a volume basis using a laser diffraction/scattering particle size distribution measuring device, and the median diameter is used as the average particle size. The measurement sample can be prepared by weighing 100 mg of the inorganic filler and 10 g of methyl ethyl ketone into a vial and dispersing it by ultrasonic waves for 10 minutes. The measurement sample was measured using a laser diffraction type particle size distribution measuring device with blue and red light source wavelengths and a flow cell method to measure the volumetric particle size distribution of the inorganic filler, and the average particle size was calculated as the median diameter from the obtained particle size distribution. An example of a laser diffraction type particle size distribution measuring device is the "LA-960" manufactured by Horiba, Ltd.

The specific surface area of the inorganic filler (C) is not particularly limited, but is preferably 0.1 m ² /g or more, more preferably 0.5 m ² /g or more, even more preferably 1 m ² /g or more, and particularly preferably 3 m ² /g or more. The upper limit of the specific surface area of the inorganic filler (C) is not particularly limited, but is preferably 100 m ² /g or less, more preferably 70 m ² /g or less, even more preferably 50 m ² /g or less, and particularly preferably 40 m ² /g or less. The specific surface area of the inorganic filler is obtained by adsorbing nitrogen gas to the sample surface using a specific surface area measuring device (Macsorb HM-1210 manufactured by Mountec Co., Ltd.) according to the BET method, and calculating the specific surface area using the BET multipoint method.

It is preferable that the inorganic filler (C) is surface-treated with an appropriate surface treatment agent. By being surface-treated, the moisture resistance and dispersibility of the inorganic filler (C) can be improved. Examples of surface treatment agents include vinyl-based silane coupling agents such as vinyltrimethoxysilane and vinyltriethoxysilane; epoxy-based silane coupling agents such as 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, 3-glycidoxypropylmethyldimethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, and 3-glycidoxypropyltriethoxysilane; styryl-based silane coupling agents such as p-styryltrimethoxysilane; 3-methacryloxypropylmethyldimethoxysilane, 3-methacryloxypropyltrimethoxysilane, Methacrylic silane coupling agents such as 3-methacryloxypropylmethyldiethoxysilane and 3-methacryloxypropyltriethoxysilane; acrylic silane coupling agents such as 3-acryloxypropyltrimethoxysilane; N-2-(aminoethyl)-3-aminopropylmethyldimethoxysilane, N-2-(aminoethyl)-3-aminopropyltrimethoxysilane, 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, 3-triethoxysilyl-N-(1,3-dimethyl-butylidene)propylamine, N-phenyl-3-aminopropyltrimethoxysilane, N-phenyl Amino-based silane coupling agents such as N-(vinylbenzyl)-8-aminooctyltrimethoxysilane and N-(vinylbenzyl)-2-aminoethyl-3-aminopropyltrimethoxysilane; isocyanurate-based silane coupling agents such as tris-(trimethoxysilylpropyl)isocyanurate; ureido-based silane coupling agents such as 3-ureidopropyltrialkoxysilane; mercapto-based silane coupling agents such as 3-mercaptopropylmethyldimethoxysilane and 3-mercaptopropyltrimethoxysilane; isocyanate-based silane coupling agents such as 3-isocyanatepropyltriethoxysilane; 3-trimethoxypropyltrimethoxysilane; Examples of the surface treatment agent include an acid anhydride-based silane coupling agent such as silylpropylsuccinic anhydride; and alkylalkoxysilane compounds such as methyltrimethoxysilane, dimethyldimethoxysilane, phenyltrimethoxysilane, methyltriethoxysilane, dimethyldiethoxysilane, phenyltriethoxysilane, n-propyltrimethoxysilane, n-propyltriethoxysilane, hexyltrimethoxysilane, hexyltriethoxysilane, octyltriethoxysilane, decyltrimethoxysilane, 1,6-bis(trimethoxysilyl)hexane, and trifluoropropyltrimethoxysilane. The surface treatment agent may be used alone or in combination of two or more in any ratio.

Commercially available surface treatment agents include, for example, Shin-Etsu Chemical Co., Ltd.'s "KBM-1003" and "KBE-1003" (vinyl-based silane coupling agents); "KBM-303", "KBM-402", "KBM-403", "KBE-402", and "KBE-403" (epoxy-based silane coupling agents); "KBM-1403" (styryl-based silane coupling agents); "KBM-502", "KBM-503", "KBE-502", and "KBE-503" (methacrylic-based silane coupling agents); "KBM-5103" (acrylic-based silane coupling agents); "KBM-602", "KBM-603", "KBM-903", "KBE-903", "KBE-9103P", "KBM-573", and "KBM-575" (amino-based silane coupling agents). agent); "KBM-9659" (isocyanurate-based silane coupling agent); "KBE-585" (ureido-based silane coupling agent); "KBM-802", "KBM-803" (mercapto-based silane coupling agent); "KBE-9007N" (isocyanate-based silane coupling agent); "X-12-967C" (acid anhydride-based silane coupling agent); "KBM-13", "KBM-22", "KBM-103", "KBE-13", "KBE-22", "KBE-103", "KBM-3033", "KBE-3033", "KBM-3063", "KBE-3063", "KBE-3083", "KBM-3103C", "KBM-3066", "KBM-7103" (alkylalkoxysilane compound), etc.

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

The degree of surface treatment by the surface treatment agent can be evaluated by the amount of carbon per unit surface area of the inorganic filler. From the viewpoint of improving the dispersibility of the inorganic filler, the amount of carbon per unit surface area of the inorganic filler is preferably 0.02 mg/m ² or more, more preferably 0.1 mg/m ² or more, and even more preferably 0.2 mg/m ² or more. On the other hand, from the viewpoint of preventing an increase in the melt viscosity of the resin composition or the melt viscosity in the sheet form, it is preferably 1.0 mg/m ² or less, more preferably 0.8 mg/m ² or less, and even more preferably 0.5 mg/m ² or less.

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

The content of the inorganic filler (C) in the resin composition is 50% by mass or more, preferably 55% by mass or more, more preferably 60% by mass or more, even more preferably 62% by mass or more, and particularly preferably 64% by mass or more, when the non-volatile components in the resin composition are taken as 100% by mass. The upper limit of the content of the inorganic filler (C) in the resin composition is not particularly limited, but is preferably 90% by mass or less, more preferably 80% by mass or less, even more preferably 75% by mass or less, and particularly preferably 70% by mass or less, when the non-volatile components in the resin composition are taken as 100% by mass.

The mass ratio of the inorganic filler (C) to the ester-modified epoxy resin (A-1) in the resin composition (component (C)/component (A-1)) is not particularly limited, but is preferably 2 or more, more preferably 4 or more, and particularly preferably 5 or more. The upper limit of the mass ratio of the inorganic filler (C) to the ester-modified epoxy resin (A-1) in the resin composition (component (C)/component (A-1)) is not particularly limited, but is preferably 30 or less, more preferably 20 or less, and particularly preferably 10 or less.

<(D) Thermoplastic resin>
The resin composition of the present invention may further contain a thermoplastic resin (D) as an optional component. By including the thermoplastic resin (D) in the resin composition of the present invention, the adhesion to copper that can be used as a conductor layer can be further improved.

(D) Examples of the thermoplastic resin include polyimide resin, phenoxy resin, polyvinyl acetal resin, polyolefin resin, polybutadiene resin, polyamideimide resin, polyetherimide resin, polysulfone resin, polyethersulfone resin, polyphenylene ether resin, polycarbonate resin, polyetheretherketone resin, polyester resin, etc. In one embodiment, (D) thermoplastic resin preferably contains a thermoplastic resin selected from the group consisting of polyimide resin and phenoxy resin. In addition, the thermoplastic resin may be used alone or in combination of two or more types.

Specific examples of polyimide resins include "SLK-6100" manufactured by Shin-Etsu Chemical Co., Ltd., and "Rikacoat SN20" and "Rikacoat PN20" manufactured by New Japan Chemical Co., Ltd.

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

Specific examples of phenoxy resins include "1256" and "4250" manufactured by Mitsubishi Chemical Corporation (both phenoxy resins containing a bisphenol A skeleton); "YX8100" manufactured by Mitsubishi Chemical Corporation (phenoxy resin containing a bisphenol S skeleton); "YX6954" manufactured by Mitsubishi Chemical Corporation (phenoxy resin containing a bisphenol acetophenone skeleton); "FX280" and "FX293" manufactured by Nippon Steel & Sumikin Chemical Co., Ltd.; "YL7500BH30", "YX6954BH30", "YX7553", "YX7553BH30", "YL7769BH30", "YL6794", "YL7213", "YL7290", "YL7482", and "YL7891BH30" manufactured by Mitsubishi Chemical Corporation; and the like.

Examples of polyvinyl acetal resins include polyvinyl formal resins and polyvinyl butyral resins, with polyvinyl butyral resins being preferred. Specific examples of polyvinyl acetal resins include Denka Butyral 4000-2, Denka Butyral 5000-A, Denka Butyral 6000-C, and Denka Butyral 6000-EP manufactured by Denki Kagaku Kogyo Co., Ltd.; and 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.

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

Examples of polybutadiene resins include hydrogenated polybutadiene skeleton-containing resins, hydroxyl group-containing polybutadiene resins, phenolic hydroxyl group-containing polybutadiene resins, carboxyl group-containing polybutadiene resins, acid anhydride group-containing polybutadiene resins, epoxy group-containing polybutadiene resins, isocyanate group-containing polybutadiene resins, urethane group-containing polybutadiene resins, polyphenylene ether-polybutadiene resins, etc.

Specific examples of polyamide-imide resins include "Viromax HR11NN" and "Viromax HR16NN" manufactured by Toyobo Co., Ltd. Specific examples of polyamide-imide resins include modified polyamide-imides such as "KS9100" and "KS9300" (polyamide-imide containing a polysiloxane skeleton) manufactured by Hitachi Chemical Co., Ltd.

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

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

A specific example of a polyphenylene ether resin is NORYL SA90 manufactured by SABIC. A specific example of a polyetherimide resin is ULTEM manufactured by GE.

Examples of polycarbonate resins include hydroxyl group-containing carbonate resins, phenolic hydroxyl group-containing carbonate resins, carboxyl group-containing carbonate resins, acid anhydride group-containing carbonate resins, isocyanate group-containing carbonate resins, and urethane group-containing carbonate resins. Specific examples of polycarbonate resins include "FPC0220" manufactured by Mitsubishi Gas Chemical Co., Ltd., "T6002" and "T6001" (polycarbonate diols) manufactured by Asahi Kasei Chemicals Corporation, and "C-1090", "C-2090", and "C-3090" (polycarbonate diols) manufactured by Kuraray Co., Ltd. Specific examples of polyether ether ketone resins include "Sumiploy K" manufactured by Sumitomo Chemical Co., Ltd.

Examples of polyester resins include polyethylene terephthalate resin, polyethylene naphthalate resin, polybutylene terephthalate resin, polybutylene naphthalate resin, polytrimethylene terephthalate resin, polytrimethylene naphthalate resin, and polycyclohexane dimethyl terephthalate resin.

The weight average molecular weight (Mw) of the (D) thermoplastic resin is preferably 5,000 or more, more preferably 8,000 or more, even more preferably 10,000 or more, and particularly preferably 20,000 or more, from the viewpoint of obtaining a significant effect of the present invention, and is preferably 100,000 or less, more preferably 70,000 or less, even more preferably 60,000 or less, and particularly preferably 50,000 or less.

The content of the thermoplastic resin (D) in the resin composition is not particularly limited, but when the non-volatile components in the resin composition are taken as 100% by mass, it may be preferably 20% by mass or less, more preferably 10% by mass or less, even more preferably 5% by mass or less, and particularly preferably 2% by mass or less. The lower limit of the content of the thermoplastic resin (D) in the resin composition is not particularly limited, but when the non-volatile components in the resin composition are taken as 100% by mass, it may be, for example, 0% by mass or more, 0.001% by mass or more, preferably 0.01% by mass or more, more preferably 0.1% by mass or more, even more preferably 0.5% by mass or more, and particularly preferably 1% by mass or more.

<(E) Radically Polymerizable Compound>
The resin composition of the present invention may further contain a radical polymerizable compound (E) as an optional component. By containing the radical polymerizable compound (E) in the resin composition of the present invention, it is possible to further improve the smear removability by the desmear treatment. The radical polymerizable compound (E) may be used alone or in any combination of two or more kinds.

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

(E) The radical polymerizable compound may be, for example, a (meth)acrylic radical polymerizable compound, a styrene radical polymerizable compound, an allyl radical polymerizable compound, a maleimide radical polymerizable compound, etc.

The (meth)acrylic radically polymerizable compound is, for example, a compound having one or more, preferably two or more, acryloyl groups and/or methacryloyl groups. Examples of the (meth)acrylic radical polymerizable compound include aliphatic (meth)acrylic acid ester 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, glycerin tri(meth)acrylate, and pentaerythritol tetra(meth)acrylate; dioxane glycol Examples of the ether-containing (meth)acrylic acid ester compounds include di(meth)acrylate, 3,6-dioxa-1,8-octanediol 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, and propoxylated bisphenol A di(meth)acrylate; and isocyanurate-containing (meth)acrylic acid ester compounds such as tris(3-hydroxypropyl)isocyanurate tri(meth)acrylate, tris(2-hydroxyethyl)isocyanurate tri(meth)acrylate, and ethoxylated isocyanuric acid tri(meth)acrylate. Commercially available (meth)acrylic radical polymerizable compounds include, for example, "A-DOG" (dioxane glycol diacrylate) manufactured by Shin-Nakamura Chemical Co., Ltd., "DCP-A" (tricyclodecane dimethanol diacrylate) and "DCP" (tricyclodecane dimethanol dimethacrylate) manufactured by Kyoeisha Chemical Co., Ltd., and "KAYARAD R-684" (tricyclodecane dimethanol diacrylate) and "KAYARAD R-604" (dioxane glycol diacrylate) manufactured by Nippon Kayaku Co., Ltd.

The styrene-based radical polymerizable compound is, for example, a compound having one or more, preferably two or more, vinyl groups directly bonded to an aromatic carbon atom. Examples of the styrene-based radical polymerizable compound include divinylbenzene, 2,4-divinyltoluene, 2,6-divinylnaphthalene, 1,4-divinylnaphthalene, 4,4'-divinylbiphenyl, 1,2-bis(4-vinylphenyl)ethane, 2,2-bis(4-vinylphenyl)propane, and bis(4-vinylphenyl)ether.

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

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

The ethylenically unsaturated bond equivalent of the (E) radical polymerizable compound is preferably 20 g/eq. to 1000 g/eq., more preferably 50 g/eq. to 750 g/eq., even more preferably 70 g/eq. to 500 g/eq., and particularly preferably 90 g/eq. to 400 g/eq. The ethylenically unsaturated bond equivalent is the mass of the radical polymerizable compound per equivalent of the ethylenically unsaturated bond.

The molecular weight of the radically polymerizable compound (E) is preferably 10,000 or less, more preferably 5,000 or less, even more preferably 1,000 or less, and particularly preferably 500 or less. The lower limit is not particularly limited, but may be, for example, 150 or more.

The content of the radical polymerizable compound (E) in the resin composition is not particularly limited, but is preferably 30% by mass or less, more preferably 20% by mass or less, even more preferably 10% by mass or less, even more preferably 5% by mass or less, and particularly preferably 3% by mass or less, when the non-volatile components in the resin composition are taken as 100% by mass. The lower limit of the content of the radical polymerizable compound (E) in the resin composition is not particularly limited, but is, for example, 0% by mass or more, 0.001% by mass or more, preferably 0.01% by mass or more, more preferably 0.1% by mass or more, even more preferably 0.5% by mass or more, and particularly preferably 1% by mass or more, when the non-volatile components in the resin composition are taken as 100% by mass.

<(F) Elastomer>
The resin composition of the present invention may contain an elastomer (F) as an optional component. By including the elastomer (F) in the resin composition of the present invention, the crack resistance after desmearing can be further improved. The elastomer (F) means a resin having flexibility, and is preferably a resin exhibiting rubber elasticity or a resin exhibiting rubber elasticity by reacting with another component. Examples of resins exhibiting rubber elasticity include resins exhibiting an elastic modulus of 1 GPa or less when a tensile test is performed in accordance with the Japanese Industrial Standards (JIS K7161) at a temperature of 25° C. and a humidity of 40% RH.

The (F) elastomer may be a particulate elastomer component (particulate elastomer) that maintains a particulate form in the resin composition, or an amorphous non-particulate elastomer component (non-particulate elastomer) that tends to be mixed or dissolved in the resin composition. The (F) elastomer preferably includes a particulate elastomer. The particulate elastomer is preferably spherical.

The particulate elastomer is preferably a rubber particle containing, as a rubber component, a silicone-based elastomer such as polydimethylsiloxane; an olefin-based thermoplastic elastomer such as polybutadiene, polyisoprene, polychlorobutadiene, 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, or ethylene-propylene-butene terpolymer; or an acrylic-based thermoplastic elastomer such as polypropyl(meth)acrylate, polybutyl(meth)acrylate, polycyclohexyl(meth)acrylate, or polyoctyl(meth)acrylate. Furthermore, the rubber component may be mixed with a silicone-based rubber such as polyorganosiloxane rubber. The rubber component contained in the rubber particles has a glass transition temperature of, for example, 0°C or lower, preferably -10°C or lower, more preferably -20°C or lower, and even more preferably -30°C or lower.

From the viewpoint of obtaining the desired effect of the present invention significantly, the particulate elastomer preferably contains core-shell type rubber particles. The core-shell type rubber particles are particulate elastomers consisting of core particles containing a rubber component as described above and one or more shell layers covering the core particles. Furthermore, the core-shell type rubber particles are preferably core-shell type graft copolymer rubber particles consisting of core particles containing a rubber component as described above and a shell portion obtained by graft copolymerization of a monomer component copolymerizable with the rubber component contained in the core particles. The core-shell type here does not necessarily refer only to those in which the core particle and the shell portion are clearly distinguishable, but also includes those in which the boundary between the core particle and the shell portion is unclear, and the core particle does not necessarily have to be completely covered by the shell portion.

The rubber component is preferably contained in the core-shell rubber particles in an amount of 40% by mass or more, more preferably 50% by mass or more, and even more preferably 60% by mass or more. The upper limit of the rubber component content in the core-shell rubber particles is not particularly limited, but from the viewpoint of sufficiently covering the core particles with the shell portion, it is preferably, for example, 95% by mass or less, and more preferably 90% by mass.

The monomer components forming the shell portion of the core-shell type rubber particles include, for example, (meth)acrylic acid esters such as methyl (meth)acrylate, ethyl (meth)acrylate, butyl (meth)acrylate, cyclohexyl (meth)acrylate, octyl (meth)acrylate, and glycidyl (meth)acrylate; (meth)acrylic acid; N-substituted maleimides such as N-methylmaleimide and N-phenylmaleimide; maleimide; α,β-unsaturated carboxylic acids such as maleic acid and itaconic acid; aromatic vinyl compounds such as styrene, 4-vinyltoluene, and α-methylstyrene; (meth)acrylonitrile; and among these, it is preferable to include (meth)acrylic acid esters, and more preferably to include methyl (meth)acrylate. Note that "(meth)acrylic acid" means methacrylic acid or acrylic acid.

Commercially available core-shell type rubber particles include, for example, "CHT" manufactured by Cheil Industries, Inc.; "B602" manufactured by UMGABS, Inc.; "Paraloid EXL-2602", "Paraloid EXL-2603", "Paraloid EXL-2655", "Paraloid EXL-2311", "Paraloid-EXL2313", "Paraloid EXL-2315", "Paraloid KM-330", and "Paraloid KM-330" manufactured by Dow Chemical Japan. Examples include Pararoid KM-336P, Pararoid KCZ-201, Mitsubishi Rayon's Metablen C-223A, Metablen E-901, Metablen S-2001, Metablen W-450A, and Metablen SRK-200, and Kaneka's Kane Ace M-511, Kane Ace M-600, Kane Ace M-400, Kane Ace M-580, and Kane Ace MR-01.

The average particle size (average primary particle size) of the particulate elastomer is not particularly limited, but is preferably 20 nm or more, more preferably 30 nm or more, and even more preferably 50 nm or more. The upper limit of the average particle size (average primary particle size) of the particulate elastomer is not particularly limited, but is preferably 5,000 nm or less, more preferably 2,000 nm or less, and even more preferably 1,000 nm or less. The average particle size (average primary particle size) of the particulate elastomer can be measured using a zeta potential particle size distribution measuring device or the like.

The content of the (F) elastomer in the resin composition is not particularly limited, but is preferably 30% by mass or less, more preferably 20% by mass or less, even more preferably 10% by mass or less, even more preferably 5% by mass or less, and particularly preferably 3% by mass or less, when the non-volatile components in the resin composition are taken as 100% by mass. The lower limit of the content of the (F) elastomer in the resin composition is not particularly limited, but is, for example, 0% by mass or more, 0.001% by mass or more, preferably 0.01% by mass or more, more preferably 0.05% by mass or more, even more preferably 0.1% by mass or more, and particularly preferably 0.5% by mass or more, when the non-volatile components in the resin composition are taken as 100% by mass.

<(G) Curing Accelerator>
The resin composition of the present invention may contain, as an optional component, a curing accelerator (G). The curing accelerator (G) has the function of accelerating the curing of the epoxy resin (A).

Examples of the curing accelerator include phosphorus-based curing accelerators, urea-based curing accelerators, guanidine-based curing accelerators, imidazole-based curing accelerators, metal-based curing accelerators, and amine-based curing accelerators. (G) The curing accelerator may be used alone or in combination of two or more types.

Examples of phosphorus-based curing accelerators include aliphatic phosphonium salts such as tetrabutylphosphonium bromide, tetrabutylphosphonium chloride, tetrabutylphosphonium acetate, tetrabutylphosphonium decanoate, tetrabutylphosphonium laurate, bis(tetrabutylphosphonium)pyromellitate, tetrabutylphosphonium hydrogenhexahydrophthalate, tetrabutylphosphonium 2,6-bis[(2-hydroxy-5-methylphenyl)methyl]-4-methylphenolate, and di-tert-butyldimethylphosphonium tetraphenylborate; methyltriphenylphosphonium bromide, ethyltriphenylphosphonium bromide, propyltriphenylphosphonium bromide, butyltriphenylphosphonium bromide, benzyltriphenylphosphonium chloride, tetraphenylphosphine aromatic phosphonium salts such as sulfonium bromide, p-tolyltriphenylphosphonium tetra-p-tolylborate, tetraphenylphosphonium tetraphenylborate, tetraphenylphosphonium tetra-p-tolylborate, triphenylethylphosphonium tetraphenylborate, tris(3-methylphenyl)ethylphosphonium tetraphenylborate, tris(2-methoxyphenyl)ethylphosphonium tetraphenylborate, (4-methylphenyl)triphenylphosphonium thiocyanate, tetraphenylphosphonium thiocyanate, and butyltriphenylphosphonium thiocyanate; aromatic phosphine-borane complexes such as triphenylphosphine-triphenylborane; aromatic phosphine-quinone addition products such as triphenylphosphine-p-benzoquinone addition products; tributylphosphine, tri-t Aliphatic phosphines such as tert-butylphosphine, trioctylphosphine, di-tert-butyl(2-butenyl)phosphine, di-tert-butyl(3-methyl-2-butenyl)phosphine, and tricyclohexylphosphine; dibutylphenylphosphine, di-tert-butylphenylphosphine, methyldiphenylphosphine, ethyldiphenylphosphine, butyldiphenylphosphine, diphenylcyclohexylphosphine, triphenylphosphine, tri-o-tolylphosphine, tri-m-tolylphosphine, tri-p-tolylphosphine, tris(4-ethylphenyl)phosphine, tris(4-propylphenyl)phosphine, tris(4-isopropylphenyl)phosphine, tris(4-butylphenyl)phosphine, tris(4-tert-butylphenyl)phosphine, tris(2,4-dimethylphenyl)phosphine, ) phosphine, tris(2,5-dimethylphenyl)phosphine, tris(2,6-dimethylphenyl)phosphine, tris(3,5-dimethylphenyl)phosphine, tris(2,4,6-trimethylphenyl)phosphine, tris(2,6-dimethyl-4-ethoxyphenyl)phosphine, tris(2-methoxyphenyl)phosphine, tris(4-methoxyphenyl)phosphine, tris(4-ethoxyphenyl)phosphine, tris(4-tert-butoxyphenyl)phosphine, diphenyl-2-pyridylphosphine, 1,2-bis(diphenylphosphino)ethane, 1,3-bis(diphenylphosphino)propane, 1,4-bis(diphenylphosphino)butane, 1,2-bis(diphenylphosphino)acetylene, 2,2'-bis(diphenylphosphino)diphenyl ether and other aromatic phosphines.

Examples of urea-based hardening accelerators include aliphatic dimethylureas such as 1,1-dimethylurea, 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, and 3-(3,4-dimethylphenyl)-1,1-dimethylurea. aromatic dimethylurea such as 3-(4-isopropylphenyl)-1,1-dimethylurea, 3-(4-methoxyphenyl)-1,1-dimethylurea, 3-(4-nitrophenyl)-1,1-dimethylurea, 3-[4-(4-methoxyphenoxy)phenyl]-1,1-dimethylurea, 3-[4-(4-chlorophenoxy)phenyl]-1,1-dimethylurea, 3-[3-(trifluoromethyl)phenyl]-1,1-dimethylurea, N,N-(1,4-phenylene)bis(N',N'-dimethylurea), N,N-(4-methyl-1,3-phenylene)bis(N',N'-dimethylurea) [toluene bisdimethylurea], etc.

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

Examples of imidazole-based curing accelerators include 2-methylimidazole, 2-undecylimidazole, 2-heptadecylimidazole, 1,2-dimethylimidazole, 2-ethyl-4-methylimidazole, 1,2-dimethylimidazole, 2-ethyl-4-methylimidazole, 2-phenylimidazole, 2-phenyl-4-methylimidazole, 1-benzyl-2-methylimidazole, and 1-benzyl-2-furan. 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-undecylimidazolium trimellitate, 1-cyanoethyl-2-phenylimidazolium trimellitate, 2,4-diamino-6-[2'-methylimidazolyl- (1')]-ethyl-s-triazine, 2,4-diamino-6-[2'-undecylimidazolyl-(1')]-ethyl-s-triazine, 2,4-diamino-6-[2'-ethyl-4'-methylimidazolyl-(1')]-ethyl-s-triazine, 2,4-diamino-6-[2'-methylimidazolyl-(1')]-ethyl-s-triazine isocyanuric acid adduct, 2-phenylimidazole isocyanuric acid adduct, Examples include imidazole compounds such as 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, and 2-phenylimidazoline, as well as adducts of imidazole compounds and epoxy resins.

Commercially available imidazole curing accelerators may be used, such as "1B2PZ", "2MZA-PW", and "2PHZ-PW" manufactured by Shikoku Chemical Industry Co., Ltd., and "P200-H50" manufactured by Mitsubishi Chemical Corporation.

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

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.

Commercially available amine-based curing accelerators may be used, such as "MY-25" manufactured by Ajinomoto Fine-Techno Co., Ltd.

The content of the (G) curing accelerator in the resin composition is not particularly limited, but is preferably 15% by mass or less, more preferably 10% by mass or less, even more preferably 5% by mass or less, and particularly preferably 2% by mass or less, when the non-volatile components in the resin composition are taken as 100% by mass. The lower limit of the content of the (G) curing accelerator in the resin composition is not particularly limited, but may be, for example, 0% by mass or more, 0.001% by mass or more, 0.01% by mass or more, 0.1% by mass or more, 0.5% by mass or more, when the non-volatile components in the resin composition are taken as 100% by mass.

<(H) Other Additives>
The resin composition of the present invention may further contain any additive as a non-volatile component. Examples of such additives include radical polymerization initiators such as peroxide radical polymerization initiators and azo radical polymerization initiators; thermosetting resins other than epoxy resins such as epoxy acrylate resins, urethane acrylate resins, urethane resins, cyanate resins, thermosetting polyimide resins, benzoxazine resins, unsaturated polyester resins, phenolic resins, melamine resins, and silicone resins; 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 leveling agents and acrylic polymer leveling agents; thickeners such as bentone and montmorillonite; defoamers such as silicone defoamers, acrylic defoamers, fluorine defoamers, and vinyl resin defoamers. surfactants such as fluorine-based surfactants and silicone-based surfactants; flame retardants such as phosphorus-based flame retardants (e.g., phosphate ester compounds, phosphazene compounds, phosphinic acid compounds, red phosphorus), nitrogen-based flame retardants (e.g., melamine sulfate), halogen-based flame retardants, inorganic flame retardants (e.g., antimony trioxide); dispersants such as phosphate ester-based dispersants, polyoxyalkylene-based dispersants, acetylene-based dispersants, silicone-based dispersants, anionic dispersants, and cationic dispersants; stabilizers such as borate-based stabilizers, titanate-based stabilizers, aluminate-based stabilizers, zirconate-based stabilizers, isocyanate-based stabilizers, carboxylic acid-based stabilizers, and carboxylic acid anhydride-based stabilizers. The other additives (H) may be used alone or in any combination of two or more kinds at any ratio. The content of the other additives (H) can be appropriately determined by a person skilled in the art.

<(I) Organic Solvent>
The resin composition of the present invention may further contain an arbitrary organic solvent as a volatile component in addition to the non-volatile components described above. (I) As the organic solvent, any known organic solvent may be appropriately used, and the type is not particularly limited. (I) As the organic solvent, for example, ketone-based solvents such as acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, etc.; ester-based solvents such as methyl acetate, ethyl acetate, butyl acetate, isobutyl acetate, isoamyl acetate, methyl propionate, ethyl propionate, γ-butyrolactone, etc.; ether-based solvents such as tetrahydropyran, tetrahydrofuran, 1,4-dioxane, diethyl ether, diisopropyl ether, dibutyl ether, diphenyl ether, anisole, etc.; alcohol-based solvents such as methanol, ethanol, propanol, butanol, ethylene glycol, etc.; 2-ethoxyethyl acetate, propylene glycol monomethyl ether acetate, diethylene glycol monoethyl ether acetate, ethyl diglycol acetate, γ-butyrolactone, methoxypropionic acid, etc. Examples of the organic solvent include ether ester solvents such as methyl lactate, ethyl lactate, methyl 2-hydroxyisobutyrate, and the like; ester alcohol solvents such as 2-methoxypropanol, 2-methoxyethanol, 2-ethoxyethanol, propylene glycol monomethyl ether, diethylene glycol monobutyl ether (butyl carbitol), and the like; amide solvents such as N,N-dimethylformamide, N,N-dimethylacetamide, N-methyl-2-pyrrolidone, and the like; sulfoxide solvents such as dimethyl sulfoxide, and the like; nitrile solvents such as acetonitrile, propionitrile, and the like; aliphatic hydrocarbon solvents such as hexane, cyclopentane, cyclohexane, and methylcyclohexane, and the like; aromatic hydrocarbon solvents such as benzene, toluene, xylene, ethylbenzene, and trimethylbenzene, and the like. (I) The organic solvent may be used alone or in combination of two or more kinds at any ratio.

In one embodiment, the content of (I) the organic solvent is not particularly limited, but when the total amount of all components in the resin composition is taken as 100% by mass, it may be, for example, 60% by mass or less, 40% by mass or less, 30% by mass or less, 20% by mass or less, 15% by mass or less, 10% by mass or less, etc.

<Method of producing resin composition>
The resin composition of the present invention can be produced, for example, by adding (A) epoxy resin, (B) active ester compound, (C) inorganic filler, if necessary (D) thermoplastic resin, if necessary (E) radical polymerizable compound, if necessary (F) elastomer, if necessary (G) curing accelerator, if necessary (H) other additives, if necessary, and if necessary (I) organic solvent to an arbitrary preparation vessel in any order and/or partially or entirely at the same time and mixing. In addition, the temperature can be appropriately set in the process of adding and mixing each component, and heating and/or cooling may be performed temporarily or throughout. In addition, during or after the process of adding and mixing, the resin composition may be stirred or shaken using a stirring device or shaking device such as a mixer to disperse uniformly. In addition, degassing may be performed under low pressure conditions such as under vacuum at the same time as stirring or shaking.

<Characteristics of Resin Composition>
The resin composition of the present invention comprises (A) an epoxy resin, (B) an active ester compound, and (C) an inorganic filler, the epoxy resin (A) comprises (A-1) an ester-modified epoxy resin, and the content of the inorganic filler (C) is 50 mass% or more, assuming that the non-volatile components in the resin composition are 100 mass%. By using such a resin composition, it is possible to suppress the occurrence of cracks after a desmear treatment and to obtain a cured product having a low dielectric loss tangent (Df).

The cured product of the resin composition of the present invention can suppress the occurrence of cracks after desmearing. Therefore, in one embodiment, after producing a circuit board and performing a desmearing process as in the following Test Example 2, when 100 copper pads of the circuit board are observed, the number of cracks can be preferably 10 or less.

The cured product of the resin composition of the present invention may be characterized by a low dielectric loss tangent (Df). Thus, in one embodiment, the dielectric loss tangent (Df) of the cured product of the resin composition when measured at 5.8 GHz and 23°C as in Test Example 1 below may be preferably 0.0200 or less, 0.0100 or less, more preferably 0.0090 or less, 0.0080 or less, 0.0070 or less, even more preferably 0.0060 or less, 0.0050 or less, 0.0040 or less, and particularly preferably 0.0035 or less, 0.0030 or less, 0.0027 or less.

<Applications of the resin composition>
The resin composition of the present invention can be suitably used as a resin composition for insulating purposes, particularly as a resin composition for forming an insulating layer. Specifically, it can be suitably used as a resin composition for forming an insulating layer (resin composition for forming an insulating layer for forming a conductor layer) for forming a conductor layer (including a rewiring layer) formed on an insulating layer. In addition, in a printed wiring board described later, it can be suitably used as a resin composition for forming an insulating layer of a printed wiring board (resin composition for forming an insulating layer of a printed wiring board). The resin composition of the present invention can also be used in a wide range of applications requiring a resin composition, such as a resin sheet, a sheet-like laminate material such as a prepreg, a solder resist, an underfill material, a die bonding material, a semiconductor encapsulant, a hole filling resin, and a component embedding resin.

Furthermore, for example, when a semiconductor chip package is manufactured through the following steps (1) to (6), the resin composition of the present invention can be suitably used as a resin composition for a rewiring formation layer serving as an insulating layer for forming a rewiring layer (resin composition for forming a rewiring formation layer) and as a resin composition for sealing a semiconductor chip (resin composition for sealing a semiconductor chip). When a semiconductor chip package is manufactured, a rewiring layer may be further formed on the sealing layer.
(1) A step of laminating a temporary fixing film on a substrate;
(2) A step of temporarily fixing a semiconductor chip on a temporary fixing film;
(3) forming an encapsulation layer on the semiconductor chip;
(4) peeling the substrate and the temporary fixing film from the semiconductor chip;
(5) forming a rewiring formation layer as an insulating layer on the surface of the semiconductor chip from which the base material and the temporary fixing film have been peeled off; and (6) forming a rewiring layer as a conductor layer on the rewiring formation layer.

In addition, the resin composition of the present invention provides an insulating layer with good component embedding properties, so it can also be used suitably when the printed wiring board is a circuit board with built-in components.

<Sheet-like laminate material>
The resin composition of the present invention can be used by coating in the form of a varnish, but from an industrial perspective, it is generally preferred to use the resin composition in the form of a sheet-like laminate material containing the resin composition.

The following resin sheets and prepregs are preferred as sheet-like laminate materials.

In one embodiment, the resin sheet comprises a support and a resin composition layer provided on the support, and the resin composition layer is formed from the resin composition of the present invention.

The thickness of the resin composition layer is preferably 50 μm or less, more preferably 40 μm or less, from the viewpoint of making the printed wiring board thinner and being able to provide a cured product with excellent insulating properties even if the cured product of the resin composition is a thin film. The lower limit of the thickness of the resin composition layer is not particularly limited, but can usually be 5 μm or more, 10 μm or more, etc.

Examples of the support include films made of plastic materials, metal foils, and release paper, with films made of plastic materials and metal foils being preferred.

When a film made of a plastic material is used as the support, examples of the plastic material include polyesters such as polyethylene terephthalate (hereinafter sometimes abbreviated as "PET") and polyethylene naphthalate (hereinafter sometimes abbreviated as "PEN"), polycarbonate (hereinafter sometimes abbreviated as "PC"), acrylics such as polymethyl methacrylate (PMMA), cyclic polyolefins, triacetyl cellulose (TAC), polyether sulfide (PES), polyether ketone, polyimide, etc. Among these, polyethylene terephthalate and polyethylene naphthalate are preferred, and inexpensive polyethylene terephthalate is particularly preferred.

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

The support may be subjected to a matte treatment, corona treatment, or antistatic treatment on the surface that is to be bonded to the resin composition layer.

As the support, a support with a release layer having a release layer on the surface to be bonded to the resin composition layer may be used. Examples of the release agent used in the release layer of the support with a release layer include one or more release agents selected from the group consisting of alkyd resins, polyolefin resins, urethane resins, and silicone resins. The support with a release layer may be a commercially available product, such as "SK-1", "AL-5", and "AL-7" manufactured by Lintec Corporation, "Lumirror T60" manufactured by Toray Industries, "Purex" manufactured by Teijin Limited, and "Unipeel" manufactured by Unitika Limited, which are PET films having a release layer mainly composed of an alkyd resin-based release agent.

The thickness of the support is not particularly limited, but is preferably in the range of 5 μm to 75 μm, and more preferably in the range of 10 μm to 60 μm. When using a support with a release layer, it is preferable that the thickness of the entire support with the release layer is in the above range.

In one embodiment, the resin sheet may further include an optional layer as necessary. For example, such an optional layer may be a protective film similar to the support provided on the surface of the resin composition layer that is not bonded to the support (i.e., the surface opposite the support). The thickness of the protective film is not particularly limited, but is, for example, 1 μm to 40 μm. By laminating the protective film, it is possible to suppress adhesion of dirt and the like and scratches on the surface of the resin composition layer.

The resin sheet can be produced, for example, by preparing a resin varnish by dissolving the liquid resin composition in an organic solvent or by applying the resin varnish to a support using a die coater or the like, and then drying the varnish to form a resin composition layer.

The organic solvent may be the same as the organic solvent described as a component of the resin composition. The organic solvent may be used alone or in combination of two or more kinds.

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

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

In one embodiment, the prepreg is formed by impregnating a sheet-like fiber substrate with the resin composition of the present invention.

The sheet-like fiber substrate used for the prepreg is not particularly limited, and may be any commonly used substrate for prepregs, such as glass cloth, aramid nonwoven fabric, or liquid crystal polymer nonwoven fabric. From the viewpoint of making the printed wiring board thinner, the thickness of the sheet-like fiber substrate is preferably 50 μm or less, more preferably 40 μm or less, even more preferably 30 μm or less, and particularly preferably 20 μm or less. There is no particular lower limit to the thickness of the sheet-like fiber substrate. It is usually 10 μm or more.

Prepregs can be manufactured by known methods such as the hot melt method and the solvent method.

The thickness of the prepreg can be in the same range as the resin composition layer in the resin sheet described above.

The sheet-like laminate material of the present invention can be suitably used to form an insulating layer of a printed wiring board (for an insulating layer of a printed wiring board), and can be even more suitably used to form an interlayer insulating layer of a printed wiring board (for an interlayer insulating layer of a printed wiring board).

<Printed Wiring Board>
The printed wiring board of the present invention includes an insulating layer made of a cured product obtained by curing the resin composition of the present invention.

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

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

The lamination of the inner layer substrate and the resin sheet can be carried out, for example, by heat-pressing the resin sheet to the inner layer substrate from the support side. Examples of the member for heat-pressing the resin sheet to the inner layer substrate (hereinafter also referred to as the "heat-pressing member") include a heated metal plate (such as a SUS panel) or a metal roll (SUS roll). Note that rather than pressing the heat-pressing member directly onto the resin sheet, it is preferable to press it via an elastic material such as heat-resistant rubber so that the resin sheet can sufficiently follow the surface irregularities of the inner layer substrate.

The lamination of the inner layer substrate and the resin sheet may be performed by a vacuum lamination method. In the vacuum lamination method, the heat-pressure bonding temperature is preferably in the range of 60°C to 160°C, more preferably in the range of 80°C to 140°C, the heat-pressure bonding pressure is preferably in the range of 0.098MPa to 1.77MPa, more preferably in the range of 0.29MPa to 1.47MPa, and the heat-pressure bonding time is preferably in the range of 20 seconds to 400 seconds, more preferably in the range of 30 seconds to 300 seconds. The lamination may be performed under reduced pressure conditions, preferably at a pressure of 26.7hPa or less.

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 applicator manufactured by Nikko Materials Co., Ltd., and a batch-type vacuum pressure laminator.

After lamination, the laminated resin sheets may be smoothed under normal pressure (atmospheric pressure), for example by pressing a heat-pressure bonding member from the support side. The pressing conditions for the smoothing treatment may be the same as the heat-pressure bonding conditions for the lamination. The smoothing treatment may be performed using a commercially available laminator. Note that lamination and smoothing treatment may be performed consecutively using the commercially available vacuum laminator.

The support may be removed between steps (I) and (II), or after step (II).

In step (II), the resin composition layer is cured (e.g., thermally cured) to form an insulating layer made of a cured product of the resin composition. The curing conditions for the resin composition layer are not particularly limited, and conditions that are typically used when forming an insulating layer for a printed wiring board may be used.

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

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

When manufacturing a printed wiring board, the steps of (III) drilling holes in the insulating layer, (IV) roughening the insulating layer, and (V) forming a conductor layer may be further carried out. These steps (III) to (V) may be carried out according to various methods known to those skilled in the art that are used in the manufacture of printed wiring boards. When the support is removed after step (II), the removal of the support may be carried out between steps (II) and (III), between steps (III) and (IV), or between steps (IV) and (V). Furthermore, the formation of the insulating layer and the conductor layer in steps (II) to (V) may be repeated as necessary to form a multilayer wiring board.

In another embodiment, the printed wiring board of the present invention can be manufactured using the above-mentioned prepreg. The manufacturing method is basically the same as when a resin sheet is used.

Step (III) is a step of drilling holes in the insulating layer, which allows holes such as via holes and through holes to be formed in the insulating layer. Step (III) may be performed using, for example, a drill, a laser, plasma, etc., depending on the composition of the resin composition used to form the insulating layer. The dimensions and shape of the holes may be appropriately determined depending on the design of the printed wiring board.

Step (IV) is a step of roughening the insulating layer. Usually, smears are also removed in this step (IV). The procedure and conditions of the roughening treatment are not particularly limited, and known procedures and conditions that are usually used when forming an insulating layer for a printed wiring board can be adopted. For example, the insulating layer can be roughened by carrying out a swelling treatment with a swelling liquid, a roughening treatment with an oxidizing agent, and a neutralization treatment with a neutralizing liquid in this order.

The swelling liquid used in the roughening treatment is not particularly limited, but includes an alkaline solution, a surfactant solution, etc., and is preferably an alkaline solution, and more preferably a sodium hydroxide solution or a potassium hydroxide solution. Examples of commercially available swelling liquids include "Swelling Dip Securigans P" and "Swelling Dip Securigans SBU" manufactured by Atotech Japan. The swelling treatment using the swelling liquid is not particularly limited, but can be performed by immersing the insulating layer in a swelling liquid at 30°C to 90°C for 1 to 20 minutes, for example. From the viewpoint of suppressing the swelling of the resin of the insulating layer to an appropriate level, it is preferable to immerse the insulating layer in a swelling liquid at 40°C to 80°C for 5 to 15 minutes.

The oxidizing agent used in the roughening treatment is not particularly limited, but examples thereof include an alkaline permanganate solution in which potassium permanganate or sodium permanganate is dissolved in an aqueous solution of sodium hydroxide. The roughening treatment using an oxidizing agent such as an alkaline permanganate solution is preferably performed by immersing the insulating layer in an oxidizing agent solution heated to 60°C to 100°C for 10 to 30 minutes. The concentration of permanganate in the alkaline permanganate solution is preferably 5% by mass to 10% by mass. Examples of commercially available oxidizing agents include alkaline permanganate solutions such as "Concentrate Compact CP" and "Dosing Solution Securigans P" manufactured by Atotech Japan.

The neutralizing solution used in the roughening treatment is preferably an acidic aqueous solution, and a commercially available product such as "Reduction Solution Securigant P" manufactured by Atotech Japan is an example.

Treatment with a neutralizing solution can be carried out by immersing the surface that has been roughened with an oxidizing agent in a neutralizing solution at 30°C to 80°C for 5 to 30 minutes. From the standpoint of workability, etc., it is preferable to immerse the object that has been roughened with an oxidizing agent in a neutralizing solution at 40°C to 70°C for 5 to 20 minutes.

In one embodiment, the arithmetic mean roughness Ra of the insulating layer surface after the roughening treatment is preferably 500 nm or less, more preferably 400 nm or less, and even more preferably 300 nm or less. The lower limit is not particularly limited, and may be, for example, 1 nm or more, 2 nm or more, etc. The root mean square roughness (Rq) of the insulating layer surface after the roughening treatment is preferably 500 nm or less, more preferably 400 nm or less, and even more preferably 300 nm or less. The lower limit is not particularly limited, and may be, for example, 1 nm or more, 2 nm or more, etc. The arithmetic mean roughness (Ra) and root mean square roughness (Rq) of the insulating layer surface can be measured using a non-contact surface roughness meter.

Step (V) is a step of forming a conductor layer, and the conductor layer is formed on the insulating layer. The conductor material used for the conductor layer is not particularly limited. In a preferred embodiment, the conductor layer contains one or more metals selected from the group consisting of 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, and examples of the alloy layer include layers formed from alloys of two or more metals selected from the above group (e.g., nickel-chromium alloy, copper-nickel alloy and copper-titanium alloy). Among them, from the viewpoints of versatility, cost, ease of patterning, etc. of the conductor layer formation, a single metal layer of chromium, nickel, titanium, aluminum, zinc, gold, palladium, silver or copper, or an alloy layer of a nickel-chromium alloy, a copper-nickel alloy, or a 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 a nickel-chromium alloy is more preferred, and a single metal layer of copper is even more preferred.

The conductor layer may be a single-layer structure, or a multi-layer structure in which two or more single metal layers or alloy layers made of different types of metals or alloys are laminated. 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.

The thickness of the conductor layer depends on the desired printed wiring board design, but is generally between 3 μm and 35 μm, preferably between 5 μm and 30 μm.

In one embodiment, the conductor layer may be formed by plating. For example, a conductor layer having a desired wiring pattern can be formed by plating the surface of the insulating layer using a conventionally known technique such as a semi-additive method or a full-additive method, and from the viewpoint of ease of production, it is preferable to form the conductor layer by a semi-additive method. Below, an example of forming the conductor layer by a semi-additive method is shown.

First, a plating seed layer is formed on the surface of the insulating layer by electroless plating. Next, a mask pattern is formed on the formed plating seed layer to expose a portion of the plating seed layer corresponding to the desired wiring pattern. A metal layer is formed on the exposed plating seed layer by electrolytic plating, and the mask pattern is then removed. Thereafter, unnecessary plating seed layer is removed by etching or the like, and a conductor layer having the desired wiring pattern can be formed.

In another embodiment, the conductor layer may be formed using a metal foil. When the conductor layer is formed using a metal foil, it is preferable to perform step (V) between steps (I) and (II). For example, after step (I), the support is removed, and a metal foil is laminated on the exposed surface of the resin composition layer. The lamination of the resin composition layer and the metal foil may be performed by a vacuum lamination method. The lamination conditions may be the same as those described for step (I). Next, step (II) is performed to form an insulating layer. Thereafter, a conductor layer having a desired wiring pattern can be formed by a conventionally known technique such as a subtractive method or a modified semi-additive method using the metal foil on the insulating layer.

Metal foils can be manufactured by known methods such as electrolysis and rolling. Commercially available metal foils include HLP foil and JXUT-III foil manufactured by JX Nippon Mining & Metals Corporation, and 3EC-III foil and TP-III foil manufactured by Mitsui Mining & Smelting Co., Ltd.

<Semiconductor Device>
The semiconductor device of the present invention includes the printed wiring board of the present invention. The semiconductor device of the present invention can be manufactured using the printed wiring board of the present invention.

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

The present invention will be specifically explained below with reference to examples. The present invention is not limited to these examples. In the following, "parts" and "%" representing amounts mean "parts by mass" and "% by mass", respectively, unless otherwise specified. Unless otherwise specified, the temperature and pressure conditions are room temperature (23°C) and atmospheric pressure (1 atm).

Example 1
Ten parts of epoxy resin A (a modified epoxy resin having a structure represented by the following formula (A) synthesized by the method described in Example 1 of JP2020-111735A (1≦x≦5, 0≦y≦1, 0≦z≦1, maximum peak m/z=588.3 (x=z=1, y=0) according to the FD/MS measurement results), epoxy equivalent of about 455 g/eq.) and 5 parts of a naphthalene skeleton-containing epoxy resin ("HP-4032-D" manufactured by DIC Corporation, epoxy equivalent of about 140 g/eq.) were dissolved in 15 parts of MEK. Thereto, 65 parts of spherical silica (average particle size 0.5 μm, Admatechs' SO-C2) surface-treated with an amino-based silane coupling agent (Shin-Etsu Chemical's KBM-573), 1 part of core-shell rubber particles (Dow's EXL-2655), 24 parts of active ester curing agent (DIC's HPC-8000-65T, active ester equivalent 223, toluene solution with solid content of 65% by mass), 2 parts of acrylate compound (Shin-Nakamura Chemical's A-DOG), 5 parts of phenoxy resin (Mitsubishi Chemical's YX7553BH30, MEK/cyclohexanone mixed solution with solid content of 30% by mass), and 0.1 parts of curing accelerator (Wako Pure Chemical Industries' 4-dimethylaminopyridine) were added and uniformly dispersed with a high-speed rotating mixer to prepare a resin composition.

Example 2
A resin composition was prepared in the same manner as in Example 1, except that 25 parts of an active ester curing agent ("HPC-8150-62T" manufactured by DIC Corporation, active ester equivalent 234, toluene solution with a solid content of 62%) was used instead of 24 parts of an active ester curing agent ("HPC-8000-65T" manufactured by DIC Corporation, a toluene solution with a solid content of 65% by mass).

Example 3
Instead of 24 parts of an active ester curing agent (DIC Corporation "HPC-8000-65T", a toluene solution with a solid content of 65% by mass), 25 parts of an active ester curing agent (DIC Corporation "HPC-8150-62T", active ester equivalent 234, toluene solution with a solid content of 62%) was used, and instead of 5 parts of a phenoxy resin (Mitsubishi Chemical Corporation "YX7553BH30", a MEK / cyclohexanone mixed solution with a solid content of 30% by mass), a polyimide resin (Shin-Etsu Chemical Co., Ltd. "SLK-6100", an anisole solution with a solid content of 25%) was used. A resin composition was prepared in the same manner as in Example 1.

Example 4
A resin composition was prepared in the same manner as in Example 1 except that 24 parts of an active ester curing agent (DIC Corporation's "HPC-8150-62T", active ester equivalent 234, toluene solution with a solid content of 62%) was used instead of 24 parts of an active ester curing agent (DIC Corporation's "HPC-8000-65T", a toluene solution with a solid content of 65% by mass) and 2 parts of a triazine-containing cresol novolak resin (DIC Corporation's "LA-3018-50P", a propylene glycol monomethyl ether solution with a nitrogen content of 18% and a solid content of 50% by mass) was further added.

Example 5
Instead of 24 parts of an active ester curing agent (DIC Corporation "HPC-8000-65T", a toluene solution with a solid content of 65% by mass), 24 parts of an active ester curing agent (DIC Corporation "HPC-8150-62T", active ester equivalent 234, toluene solution with a solid content of 62%) was used, the amount of spherical silica (average particle size 0.5 μm, Admatechs Co., Ltd. "SO-C2") surface-treated with an amino-based silane coupling agent (Shin-Etsu Chemical Co., Ltd. "KBM-573") was changed from 65 parts to 82 parts, and a resin composition was prepared in the same manner as in Example 1, except that 2 parts of a triazine-containing cresol novolak resin (DIC Corporation "LA-3018-50P", a propylene glycol monomethyl ether solution with a nitrogen content of 18% and a solid content of 50% by mass) were further added.

<Comparative Example 1>
A resin composition was prepared in the same manner as in Example 1, except that 9 parts of a naphthalene-type epoxy resin ("ESN-475V" manufactured by Nippon Steel Chemical & Material Co., Ltd., epoxy equivalent 330) was used instead of the epoxy resin A, 26 parts of an active ester curing agent ("HPC-8150-62T" manufactured by DIC Corporation, active ester equivalent 234, toluene solution with a solid content of 62%) was used instead of 24 parts of an active ester curing agent ("HPC-8000-65T" manufactured by DIC Corporation, toluene solution with a solid content of 65% by mass), and 2 parts of a triazine-containing cresol novolak resin ("LA-3018-50P" manufactured by DIC Corporation, propylene glycol monomethyl ether solution with a nitrogen content of 18% and a solid content of 50% by mass) were further added.

<Comparative Example 2>
Instead of 24 parts of an active ester curing agent (DIC Corporation "HPC-8000-65T", a toluene solution with a solid content of 65% by mass), 25 parts of an active ester curing agent (DIC Corporation "HPC-8150-62T", active ester equivalent 234, toluene solution with a solid content of 62%) was used, the amount of spherical silica (average particle size 0.5 μm, Admatechs Co., Ltd. "SO-C2") surface-treated with an amino-based silane coupling agent (Shin-Etsu Chemical Co., Ltd. "KBM-573") was changed from 65 parts to 35 parts, and a resin composition was prepared in the same manner as in Example 1 except that 2 parts of a triazine-containing cresol novolak resin (DIC Corporation "LA-3018-50P", a propylene glycol monomethyl ether solution with a nitrogen content of 18% and a solid content of 50% by mass) were further added.

<Production Example 1: Resin sheet with resin composition layer thickness of 40 μm>
A polyethylene terephthalate film with a release layer ("AL5" manufactured by Lintec Corporation, thickness 38 μm) was prepared as a support. The resin compositions obtained in the examples and comparative examples were uniformly applied onto the release layer of this support so that the thickness of the resin composition layer after drying was 40 μm. Thereafter, the resin composition was dried at 80° C. to 100° C. (average 90° C.) for 4 minutes to obtain a resin sheet including a support and a resin composition layer.

<Production Example 2: Resin sheet with resin composition layer thickness of 25 μm>
Similarly to Preparation Example 1, the resin compositions obtained in the Examples and Comparative Examples were uniformly applied so that the thickness of the resin composition layer after drying would be 25 μm, and dried at 70° C. to 80° C. (average 75° C.) for 2.5 minutes to obtain a resin sheet including a support and a resin composition layer.

<Test Example 1: Measurement of dielectric tangent>
The resin sheet produced in Production Example 1 was heated at 190°C for 90 minutes to thermally cure the resin composition layer. The support was then peeled off to obtain a cured product of the resin composition. This cured product was cut into a test piece having a width of 2 mm and a length of 80 mm. The dielectric loss tangent (Df) of the test piece was measured at a measurement frequency of 5.8 GHz and a measurement temperature of 23°C by a cavity resonance perturbation method using an Agilent Technologies "HP8362B". Measurements were performed on three test pieces, and the average values are shown in Table 1 below.

<Test Example 2: Evaluation of crack resistance after desmear treatment>
The 25 μm thick resin sheet obtained in Production Example 2 was laminated on both sides of a core material (Hitachi Chemical Co., Ltd. "E705GR", thickness 400 μm) in which circular copper pads (copper thickness 35 μm) with a diameter of 350 μm were formed in a grid shape at intervals of 400 μm so that the residual copper rate was 60%. Using a batch type vacuum pressure laminator (Nikko Materials Co., Ltd. two-stage build-up laminator "CVP700"), the resin composition layer was bonded to the inner layer substrate. This lamination was performed by decompressing for 30 seconds to an atmospheric pressure of 13 hPa or less, and then pressing for 30 seconds at a temperature of 100 ° C and a pressure of 0.74 MPa. This was placed in a 130 ° C oven and heated for 30 minutes, and then transferred to a 170 ° C oven and heated for 30 minutes. The support layer was then peeled off, and the resulting circuit board was immersed in a swelling liquid, Swelling Dip Securigant P, manufactured by Atotech Japan Co., Ltd., at 60° C. for 10 minutes. Next, the circuit board was immersed in a roughening liquid, Concentrate Compact P, manufactured by Atotech Japan Co., Ltd. (aqueous solution of KMnO ₄ : 60 g/L, NaOH: 40 g/L), at 80° C. for 30 minutes. Finally, the circuit board was immersed in a neutralizing liquid, Reduction Solution Securigant P, manufactured by Atotech Japan Co., Ltd., at 40° C. for 5 minutes. 100 copper pads of the circuit board after the roughening treatment were observed to confirm the presence or absence of cracks in the resin composition layer. If there were 10 or less cracks, the result was marked as “◯”, and if there were more than 10 cracks, the result was marked as “×”.

The amounts of raw materials used and non-volatile component contents of the resin compositions of the examples and comparative examples, as well as the measurement results and evaluation results of the test examples, are shown in Table 1 below.

Referring to Table 1, Comparative Example 1, which does not use ester-modified epoxy resin, has a poor evaluation of crack resistance, and Comparative Example 2, which uses less than 50% by mass of inorganic filler, has a poor evaluation of crack resistance and a high dielectric tangent value. In contrast, it can be seen that these problems can be overcome when using a resin composition containing (A) epoxy resin, (B) active ester compound, and (C) inorganic filler, in which (A) epoxy resin contains ester-modified epoxy resin and the content of (C) inorganic filler is 50% by mass or more.

Claims (19)

A resin composition comprising (A) an epoxy resin, (B) an active ester compound, and (C) an inorganic filler,
The component (A) is an epoxy resin (A-1) having two or more epoxy groups per molecule, and a compound represented by the formula (1):

[In the formula, R ¹ represents an alkyl group which may have a substituent or an aryl group which may have a substituent, and R ² represents an aryl group which may have a substituent.]
The modified epoxy resin is obtained by reacting an ester compound represented by the formula:
The component (A) further comprises (A-2) an epoxy resin that is liquid at 20°C (excluding those that fall under the category of component (A-1));
The weight average molecular weight (Mw) of the component (A-2) is 100 to 5,000,
the mass ratio of the content of the component (A-2) to the content of the component (A-1) (component (A-2)/component (A-1)) is 0.3 or more and 2 or less;
the mass ratio of the content of the component (B) to the content of the component (A-1) (component (B)/component (A-1)) is 1 or more and 5 or less;
A resin composition, wherein the content of the component (C) is 60 % by mass or more and 75% by mass or less , when the total amount of non-volatile components in the resin composition is 100% by mass. A resin composition comprising (A) an epoxy resin, (B) an active ester compound, and (C) an inorganic filler,
The component (A) is represented by formula (A-1) (2-1):

[In the formula, * indicates a binding site.]
and a group represented by formula (2-2):

[In the formula, R ¹ represents an alkyl group which may have a substituent or an aryl group which may have a substituent, R ² represents an aryl group which may have a substituent, and * represents a bonding site.]
The modified epoxy resin has a group represented by
The component (A) further comprises (A-2) an epoxy resin that is liquid at 20°C (excluding those that fall under the category of component (A-1));
The weight average molecular weight (Mw) of the component (A-2) is 100 to 5,000,
the mass ratio of the content of the component (A-2) to the content of the component (A-1) (component (A-2)/component (A-1)) is 0.3 or more and 2 or less;
the mass ratio of the content of the component (B) to the content of the component (A-1) (component (B)/component (A-1)) is 1 or more and 5 or less;
A resin composition, wherein the content of the component (C) is 60 % by mass or more and 75% by mass or less , when the total amount of non-volatile components in the resin composition is 100% by mass. The component (A-1) is represented by the formula (4-1):

[In the formula, R ⁴ each independently represents an alkyl group which may have a substituent or an aryl group which may have a substituent, and a represents 0, 1, 2, or 3.]
and a structural unit represented by formula (4-2):

[In the formula, R ¹ represents an alkyl group which may have a substituent, or an aryl group which may have a substituent, R ² represents an aryl group which may have a substituent, R ⁴ each independently represents an alkyl group which may have a substituent, or an aryl group which may have a substituent, and a represents 0, 1, 2, or 3.]
The resin composition according to claim 1 or 2, which is a modified epoxy resin having a structural unit represented by the following formula: The resin composition according to any one of claims 1 to 3, wherein the content of component (A-1) is 1% by mass to 20% by mass, assuming that the non-volatile components in the resin composition are 100% by mass. The resin composition according to any one of claims 1 to 4, wherein the content of component (B) is 5% by mass to 30% by mass, assuming that the non-volatile components in the resin composition are 100% by mass. The resin composition according to any one of claims 1 to 5, further comprising (D) a thermoplastic resin. The resin composition according to claim 6, wherein component (D) contains a thermoplastic resin selected from the group consisting of polyimide resins and phenoxy resins. The resin composition according to claim 6 or 7, wherein the weight average molecular weight (Mw) of component (D) is 5,000 or more. The resin composition according to any one of claims 1 to 8, further comprising (E) a radically polymerizable compound. The resin composition according to claim 9, wherein component (E) contains a (meth)acrylic radical polymerizable compound. The resin composition according to any one of claims 1 to 10, further comprising (F) an elastomer. The resin composition according to claim 11, wherein component (F) contains core-shell type rubber particles. The resin composition according to any one of claims 1 to 12, further comprising (G) a curing accelerator. The resin composition according to any one of claims 1 to 13, wherein the dielectric loss tangent (Df) of the cured product of the resin composition is 0.0030 or less when measured at 5.8 GHz and 23°C. A cured product of the resin composition according to any one of claims 1 to 14. A sheet-like laminate material containing the resin composition according to any one of claims 1 to 14. A resin sheet having a support and a resin composition layer formed from the resin composition according to any one of claims 1 to 14 provided on the support. A printed wiring board having an insulating layer made of a cured product of the resin composition according to any one of claims 1 to 14. A semiconductor device including the printed wiring board according to claim 18.