JP7600579B2 - Resin composition - Google Patents

Description

The present invention relates to a resin composition. It also relates to a resin sheet, a reflective sheet, and a printed wiring board obtained using the resin composition.

In printed wiring boards, there is an increasing use of low-power light-emitting diodes (LEDs) that are directly mounted on the board, such as for backlighting liquid crystal displays in mobile terminals, computers, televisions, etc., and as light sources for lighting fixtures.

A reflector is formed on the outermost layer of such a printed wiring board to reflect light emitted from the light source and increase the efficiency of extracting the light.

As a material for such a reflector, for example, a diffusion curable resin composition containing a photosensitive carboxyl group-containing resin, a predetermined photopolymerization initiator, a photopolymerizable monomer, titanium oxide surface-treated with silica and alumina, an organic solvent, and a predetermined amount of at least one of barium sulfate and talc has been disclosed (see Patent Document 1).

JP 2015-212841 A

However, the reflector made of the curable resin composition for diffusion described in Patent Document 1 has low reflectivity, and there is still room for improvement before the reflector can be used for mini-LEDs and micro-LEDs. In addition, the reflector must be flexible to accommodate the various shapes of light sources.

The present invention was devised in view of the above problems, and aims to provide a resin composition with a low minimum melt viscosity that can give a cured product with excellent reflectance before and after a heat resistance test; a resin sheet containing the resin composition; a reflective sheet; and a printed wiring board.

The inventors conducted extensive research to solve the above problems and discovered that titanium oxide surface-treated with silica and alumina, as in the diffusion curable resin composition described in Patent Document 1, is oxidized by light, resulting in a decrease in reflectance. As a result of extensive research, the inventors discovered that by incorporating (A) a white inorganic pigment surface-treated with a silane coupling agent not containing a nitrogen atom into the resin composition, a cured product can be obtained that has excellent reflectance and reflectance after a heat resistance test, and furthermore, the minimum melt viscosity can be reduced, thereby completing the present invention.

That is, the present invention includes the following.
[1] (A) A resin composition comprising a white inorganic pigment that has been surface-treated with a silane coupling agent that does not contain nitrogen atoms.
[2] The resin composition according to [1], wherein the content of the component (A) is 10% by mass or more and 60% by mass or less, when the total amount of non-volatile components in the resin composition is 100% by mass.
[3] The resin composition according to [1] or [2], further comprising an epoxy resin (B).
[4] The resin composition according to [3], wherein the content of the (B) component is 1 mass % or more and 50 mass % or less, when the non-volatile components in the resin composition are 100 mass %.
[5] The resin composition according to any one of [1] to [4], wherein the component (A) is one or more selected from aluminum oxide, titanium oxide, zirconium oxide, magnesium oxide, barium titanate, zinc oxide, cerium oxide, and calcium carbonate.
[6] The resin composition according to any one of [1] to [5], wherein the silane coupling agent not containing a nitrogen atom is at least one selected from a phenylsilane coupling agent, an alkylsilane coupling agent, an epoxysilane coupling agent, a vinylsilane coupling agent, a (meth)acrylic silane coupling agent, and a styrylsilane coupling agent.
[7] The resin composition according to any one of [1] to [6], further comprising (C) silica.
[8] The resin composition according to any one of [1] to [7], which is for light reflection.
[9] A resin sheet comprising a support and a resin composition layer provided on the support, the resin composition layer comprising the resin composition according to any one of [1] to [8].
[10] The resin sheet according to [9], wherein the minimum melt viscosity of the resin composition layer is 5000 poise or less.
[11] A reflective sheet comprising a cured product of the resin composition according to any one of [1] to [8].
[12] A printed wiring board comprising the reflective sheet according to [11].
[13] A printed wiring board comprising the cured reflective sheet according to [11] as an interlayer insulating layer or a solder resist layer.

The present invention provides a resin composition with a low minimum melt viscosity that can produce a cured product with excellent reflectance before and after a heat resistance test; a resin sheet containing the resin composition; a reflective sheet; and a printed wiring board.

FIG. 1 is a schematic cross-sectional view showing an example of a printed wiring board.

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

[Resin composition]
The resin composition of the present invention contains, as component (A), a white inorganic pigment that has been surface-treated with a silane coupling agent that does not contain a nitrogen atom. In the present invention, by including component (A), a cured product having excellent reflectance before and after a heat resistance test can be obtained, and a resin composition having a low minimum melt viscosity can be obtained.

The resin composition may further contain optional components in addition to component (A). Examples of optional components include (B) epoxy resin, (C) silica, (D) curing agent, (E) curing accelerator, (F) thermoplastic resin, (G) other additives, and (H) organic solvent. Each component contained in the resin composition will be described in detail below.

<(A) White Inorganic Pigment Surface-Treated with a Silane Coupling Agent Containing No Nitrogen Atoms>
The resin composition contains, as component (A), a white inorganic pigment that has been surface-treated with a silane coupling agent that does not contain a nitrogen atom. By including component (A) in the resin composition, it is possible to obtain a cured product having improved reflectance and reflectance after a heat resistance test.

In one embodiment, the white inorganic pigment refers to an inorganic compound having a reflectance of 90% or more for light with a wavelength of 500 nm, and the white inorganic pigment does not include (C) silica, which will be described later. The white inorganic pigment has a function of improving reflectance. One type of white inorganic pigment may be used alone, or two or more types may be used in combination.

Examples of white inorganic pigment materials include white metal oxides such as aluminum oxide (alumina), titanium oxide, zirconium oxide, magnesium oxide, zinc oxide, cerium oxide, antimony oxide, tin oxide, barium titanate, strontium titanate, calcium titanate, magnesium titanate, bismuth titanate, barium titanate zirconate, barium zirconate, and calcium zirconate; white metal sulfides such as zinc sulfide and strontium sulfide; white metal hydroxides such as aluminum hydroxide, magnesium hydroxide, and calcium hydroxide; white metal nitrides such as boron nitride, aluminum nitride, and manganese nitride; calcium carbonate, barium carbonate, carbon dioxide, and carbon dioxide. Examples of the white metal carbonates include magnesium carbonate, strontium carbonate, and lead carbonate; white metal sulfates include barium sulfate, calcium sulfate, and lead sulfate; white metal phosphates include zinc phosphate, titanium phosphate, zirconium phosphate, and zirconium tungstate phosphate; white metal borates include aluminum borate; and white minerals such as cordierite, talc, clay, mica, hydrotalcite, and boehmite. Among these, it is preferable to use one or more selected from aluminum oxide, titanium oxide, zirconium oxide, magnesium oxide, barium titanate, zinc oxide, cerium oxide, and calcium carbonate, and titanium oxide is particularly suitable. As the titanium oxide, any of rutile type, anatase type, and brookite type may be used, and among them, rutile type is preferable from the viewpoint of further improving the reflectance and the reflectance after the heat resistance test. Titanium oxide obtained by a method such as a sulfuric acid method or a chlorine method can be used. The material of the white inorganic pigment may be one type alone or a mixture of two or more types. The shape of the white inorganic pigment may be, for example, irregular, crushed, scaly, or spherical.

Examples of commercially available white inorganic pigments include "PX3788" manufactured by Sakai Chemical Industry Co., Ltd.; Typec "CR-50", "CR-57", "CR-80", "CR-90", "CR-93", "CR-95", "CR-97", "CR-60", "CR-63", "CR-67", "CR-58", "CR-85", and "UT771" manufactured by Ishihara Sangyo Co., Ltd.; Typepure "R-100", "R-101", "R-102", "R-103", "R-104", "R-105", "R-108", "R-900", "R-902", "R-960", "R-706", and "R-931" manufactured by DuPont; "AHP300" manufactured by Nippon Light Metal Co., Ltd.; and Alnabeads "CB-P05" and "CB-A30S" manufactured by Showa Denko KK.

From the viewpoint of obtaining the effects of the present invention prominently, the specific surface area of the white inorganic pigment is preferably 0.5 m ² /g or more, more preferably 1 m ² /g or more, and particularly preferably 2 m ² /g or more. There is no particular upper limit, but it is preferably 80 m ² /g or less, 70 m ² /g or less, or 60 m ² /g or less. The specific surface area is obtained according to the BET method by adsorbing nitrogen gas onto the surface of a sample using a specific surface area measuring device (Macsorb HM-1210 manufactured by Mountech Co., Ltd.) and calculating the specific surface area using the BET multipoint method.

From the viewpoint of significantly obtaining the desired effect of the present invention, the average particle size of the white inorganic pigment is preferably 0.01 μm or more, more preferably 0.05 μm or more, even more preferably 0.1 μm or more, and is preferably 10 μm or less, more preferably 7 μm or less, even more preferably 5 μm or less.

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

The white inorganic pigment is surface-treated with a silane coupling agent that does not contain nitrogen atoms. By surface-treating the white inorganic pigment with a silane coupling agent that does not contain nitrogen atoms, it is possible to obtain a cured product that has excellent reflectance before and after heat resistance testing. In addition, surface-treating the white inorganic pigment with a silane coupling agent that does not contain nitrogen atoms reduces the minimum melt viscosity of the resin composition, making it possible to improve flexibility.

When a white inorganic pigment is surface-treated with a silane coupling agent containing nitrogen atoms, such as an aminosilane coupling agent, the nitrogen atoms contained in the silane coupling agent themselves are oxidized by light, causing the white inorganic pigment to yellow. In addition, the nitrogen atoms contained in the silane coupling agent act as a catalyst for photooxidation, promoting oxidation and deterioration of the cured product of the resin composition, resulting in a decrease in reflectance. In the present invention, the white inorganic pigment is surface-treated with a silane coupling agent that does not contain nitrogen atoms, so the yellowing of the white inorganic pigment caused by the silane coupling agent is suppressed. In addition, since the silane coupling agent that does not contain nitrogen atoms does not itself act as a catalyst, it is possible to suppress a decrease in the reflectance of the cured product of the resin composition.

As the silane coupling agent that does not contain a nitrogen atom, a compound that does not contain a nitrogen atom and has two different functional groups in the molecule can be used. Examples of such silane coupling agents include phenylsilane coupling agents, alkylsilane coupling agents, epoxysilane coupling agents, vinylsilane coupling agents, (meth)acrylic silane coupling agents, and styrylsilane coupling agents. The silane coupling agent that does not contain a nitrogen atom may be used alone or in any combination of two or more types. Here, the (meth)acrylic silane coupling agent is a concept that includes both acrylic silane coupling agents and methacrylic silane coupling agents.

Examples of phenylsilane coupling agents include phenyltrimethoxysilane and phenyltriethoxysilane.

Examples of alkylsilane coupling agents include methyltrimethoxysilane, dimethyldimethoxysilane, methyltriethoxysilane, dimethyldiethoxysilane, n-propyltrimethoxysilane, n-propyltriethoxysilane, hexyltrimethoxysilane, hexyltriethoxysilane, octyltriethoxysilane, decyltrimethoxysilane, and 1,6-bis(trimethoxysilyl)hexane.

Examples of epoxy silane coupling agents include 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, 3-glycidoxypropylmethyldimethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, and 3-glycidoxypropyltriethoxysilane.

Examples of vinylsilane coupling agents include vinyltrimethoxysilane and vinyltriethoxysilane.

Examples of (meth)acrylic silane coupling agents include 3-methacryloxypropylmethyldimethoxysilane, 3-methacryloxypropyltrimethoxysilane, 3-methacryloxypropylmethyldiethoxysilane, 3-methacryloxypropyltriethoxysilane, and 3-acryloxypropyltrimethoxysilane.

An example of a styrylsilane coupling agent is p-styryltrimethoxysilane.

Among them, the silane coupling agent not containing a nitrogen atom is preferably at least one selected from a phenylsilane coupling agent, an alkylsilane coupling agent, an epoxysilane coupling agent, a vinylsilane coupling agent, a (meth)acrylicsilane coupling agent, and a styrylsilane coupling agent, more preferably at least one selected from a phenylsilane coupling agent, an epoxysilane coupling agent, and a (meth)acrylicsilane coupling agent, and even more preferably a phenylsilane coupling agent.

Commercially available silane coupling agents that do not contain nitrogen atoms can be used. Commercially available silane coupling agents that do not contain nitrogen atoms include, for example, "KBM-103" and "KBE-103" (phenylsilane coupling agents) manufactured by Shin-Etsu Chemical Co., Ltd.; "KBM-13", "KBM-22", "KBE-13", "KBE-22", "KBM-3033", "KBE-3033", "KBM-3063", "KBE-3063", "KBE-3083", "KBM-3103C", "KBM-3066", and "KBM-7103" (alkylsilane coupling agents). coupling agent); "KBM-1003", "KBE-1003" (vinyl silane coupling agent); "KBM-303", "KBM-402", "KBM-403", "KBE-402", "KBE-403" (epoxy silane coupling agent); "KBM-1403" (styryl silane coupling agent); "KBM-502", "KBM-503", "KBE-502", "KBE-503", "KBM-5103" ((meth)acrylic silane coupling agent), etc.

The degree of surface treatment with a silane coupling agent that does not contain nitrogen atoms is, from the viewpoint of obtaining a significant effect of the present invention, preferably 0.2 parts by mass or more, more preferably 0.5 parts by mass or more, and even more preferably 0.8 parts by mass or more, relative to 100 parts by mass of the white inorganic pigment, and is preferably 10 parts by mass or less, more preferably 8 parts by mass or less, and even more preferably 5 parts by mass or less.

Silane coupling agents that do not contain nitrogen atoms can be evaluated by the amount of carbon per unit surface area of the white inorganic pigment. From the viewpoint of improving the dispersibility of the white inorganic pigment, the amount of carbon per unit surface area of the white inorganic pigment is preferably 0.02 mg/m ² or more, more preferably 0.1 mg/m ² or more, and even more preferably 0.2 mg/m ² or more. On the other hand, from the viewpoint of suppressing the increase in the minimum melt viscosity of the resin composition and the minimum melt viscosity in the sheet form, it is preferably 1 mg/m ² or less, more preferably 0.8 mg/m ² or less, and even more preferably 0.5 mg/m ² or less.

The amount of carbon per unit surface area of the white inorganic pigment can be measured after the surface-treated white inorganic pigment is washed with a solvent (e.g., methyl ethyl ketone (MEK)). Specifically, a sufficient amount of MEK as a solvent is added to the white inorganic pigment that has been surface-treated with a silane coupling agent that does not contain nitrogen atoms, 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 white inorganic pigment can be measured using a carbon analyzer. An example of a carbon analyzer that can be used is the "EMIA-320V" manufactured by Horiba, Ltd.

From the viewpoint of obtaining the effects of the present invention prominently, the content of the (A) component, relative to 100 mass% of the non-volatile components in the resin composition, is preferably 10 mass% or more, more preferably 15 mass% or more, even more preferably 20 mass% or more, and is preferably 60 mass% or less, more preferably 50 mass% or less, even more preferably 40 mass% or less, and particularly preferably 30 mass% or less.
In the present invention, the content of each component in the resin composition is a value when the non-volatile components in the resin composition are taken as 100 mass %, unless otherwise specified.

In addition, from the viewpoint of obtaining a significant effect of the present invention, the content of the silane coupling agent not containing a nitrogen atom in component (A) is preferably 0.05% by mass or more, more preferably 0.1% by mass or more, and even more preferably 0.15% by mass or more, and is preferably 1% by mass or less, more preferably 0.8% by mass or less, and even more preferably 0.5% by mass or less, when the non-volatile components in the resin composition are taken as 100% by mass.

The content of the white inorganic pigment excluding the silane coupling agent in component (A) is preferably 10% by mass or more, more preferably 15% by mass or more, and even more preferably 20% by mass or more, and is preferably 60% by mass or less, more preferably 50% by mass or less, even more preferably 40% by mass or less, and particularly preferably 30% by mass or less, based on 100% by mass of the non-volatile components in the resin composition, in order to obtain a significant effect of the present invention.

<(B) Epoxy Resin>
In addition to the above-mentioned components, the resin composition may further contain an epoxy resin as component (B) as an optional component. The epoxy resin means a curable resin having an epoxy group. The epoxy resin (B) may be used alone or in combination of two or more kinds.

(B) Examples of epoxy resins include bixylenol type epoxy resins, bisphenol A type epoxy resins, bisphenol F type epoxy resins, bisphenol S type epoxy resins, bisphenol AF type epoxy resins, hydrogenated bisphenol A type epoxy resins, dicyclopentadiene type epoxy resins, trisphenol type epoxy resins, naphthol novolac type epoxy resins, phenol novolac type epoxy resins, tert-butyl-catechol type epoxy resins, naphthalene type epoxy resins, naphthol type epoxy resins, anthracene type epoxy resins, glycidylamine type epoxy resins, and glycidyl estherin type epoxy resins. terephthalate type epoxy resins, cresol novolac type epoxy resins, phenol aralkyl type epoxy resins, biphenyl type epoxy resins, linear aliphatic epoxy resins, epoxy resins having a butadiene structure, alicyclic epoxy resins, heterocyclic epoxy resins, spiro ring-containing epoxy resins, cyclohexane type epoxy resins, cyclohexane dimethanol type epoxy resins, naphthylene ether type epoxy resins, trimethylol type epoxy resins, tetraphenylethane type epoxy resins, isocyanurate type epoxy resins, phenolphthalimidine type epoxy resins, phenolphthalein type epoxy resins, etc.

The resin composition preferably contains, as the epoxy resin (B), an epoxy resin having two or more epoxy groups in one molecule. The proportion of the epoxy resin having two or more epoxy groups in one molecule relative to 100% by mass of the non-volatile components of the epoxy resin (B) is preferably 50% by mass or more, more preferably 60% by mass or more, and particularly preferably 70% by mass or more.

Epoxy resins include epoxy resins that are solid at a temperature of 25°C (hereinafter sometimes referred to as "solid epoxy resins") and epoxy resins that are liquid at a temperature of 25°C (hereinafter sometimes referred to as "liquid epoxy resins"). The resin composition of the present invention may contain only solid epoxy resins as the epoxy resin (B), or may contain only liquid epoxy resins, or may contain a combination of solid and liquid epoxy resins.

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

As solid epoxy resins, bixylenol type epoxy resins, naphthalene type epoxy resins, naphthalene type tetrafunctional epoxy resins, 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 are preferred, with bisphenol AF type epoxy resins being more preferred.

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-73 11", "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" manufactured by Nippon Steel Chemical & Material Co., Ltd. (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.; "YX77" manufactured by Mitsubishi Chemical Co., Ltd. 00" (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; "WHR991S" (phenolphthalimidine type epoxy resin) manufactured by Nippon Kayaku Co., Ltd. These may be used alone or in combination of two or more types.

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

Preferred liquid epoxy resins are bisphenol A type epoxy resins, bisphenol F type epoxy resins, bisphenol AF type epoxy resins, hydrogenated bisphenol A 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, with bisphenol A type epoxy resins being more preferable.

Specific examples of liquid epoxy resins include DIC's "HP4032", "HP4032D", and "HP4032SS" (naphthalene type epoxy resins); Mitsubishi Chemical's "828US", "828EL", "825", and "Epicoat 828EL" (bisphenol A type epoxy resins); Mitsubishi Chemical's "jER807" and "1750" (bisphenol F type epoxy resins); Mitsubishi Chemical's "jER152" (phenol novolac type epoxy resin); Mitsubishi Chemical's "630", "630LSD", and "604" (glycidylamine type epoxy resins); ADEKA's "ED-523T" (glycirol type epoxy resin); ADEKA's "EP-3950L" and "EP-3980S" (glycidylamine type epoxy resins); ADEKA's Examples of epoxy resins include "EP-4088S" (dicyclopentadiene type epoxy resin) manufactured by Nippon Steel Chemical & Material Co., Ltd.; "ZX1059" (mixture of bisphenol A type epoxy resin and bisphenol F type epoxy resin) manufactured by Nippon Steel Chemical & Material Co., Ltd.; "EX-721" (glycidyl ester type epoxy resin) manufactured by Nagase Chemtex Corporation; "Celloxide 2021P" (alicyclic epoxy resin having an ester skeleton) manufactured by Daicel Corporation; "PB-3600" manufactured by Daicel Corporation, "JP-100" and "JP-200" (epoxy resin having a butadiene structure) manufactured by Nippon Soda Co., Ltd.; "ZX1658" and "ZX1658GS" (1,4-glycidylcyclohexane type epoxy resin) manufactured by Nippon Steel Chemical & Material Co., Ltd., and "YX8000" (hydrogenated bisphenol A type epoxy resin) manufactured by Mitsubishi Chemical Corporation. These may be used alone or in combination of two or more types.

The (B) epoxy resin may be a solid epoxy resin, a liquid epoxy resin, or a combination thereof, but it is preferable that it contains a solid epoxy resin, and it is particularly preferable that it is a combination of a solid epoxy resin and a liquid epoxy resin.

When a combination of a solid epoxy resin and a liquid epoxy resin is used as the (B) epoxy resin, the mass ratio thereof (solid epoxy resin:liquid epoxy resin) is preferably 20:1 to 1:20, more preferably 10:1 to 1:10, and particularly preferably 3:1 to 1:3.

The epoxy equivalent of the (B) epoxy resin is preferably 50 g/eq. to 5,000 g/eq., more preferably 60 g/eq. to 1,000 g/eq., even more preferably 80 g/eq. to 500 g/eq., and even more preferably 100 g/eq. to 300 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 (B) epoxy resin 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 by gel permeation chromatography (GPC) as a polystyrene-equivalent value.

From the viewpoint of obtaining a significant effect of the present invention, the content of (B) epoxy resin is preferably 1% by mass or more, more preferably 5% by mass or more, even more preferably 10% by mass or more, and particularly preferably 15% by mass or more, and is preferably 50% by mass or less, more preferably 40% by mass or less, even more preferably 35% by mass or less, and particularly preferably 30% by mass or less, when the non-volatile components in the resin composition are taken as 100% by mass.

<(C) Silica>
The resin composition of the present invention may further contain silica as component (C) as an optional component in addition to the above-mentioned components.

Examples of (C) silica include amorphous silica, fused silica, crystalline silica, synthetic silica, and hollow silica. In addition, spherical silica is preferred as (C) silica. The specific surface area and average particle size of (C) silica may be the same as those of (C) white inorganic pigment. (C) silica may be used alone or in combination of two or more types.

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

(C) From the viewpoint of improving moisture resistance and dispersibility, it is preferable that the silica is treated with a surface treatment agent. Examples of the surface treatment agent include fluorine-containing silane coupling agents such as 3,3,3-trifluoropropyltrimethoxysilane; aminosilane-based coupling agents such as 3-aminopropyltriethoxysilane, N-phenyl-8-aminooctyl-trimethoxysilane, and N-phenyl-3-aminopropyltrimethoxysilane; epoxysilane-based coupling agents such as 3-glycidoxypropyltrimethoxysilane; mercaptosilane-based coupling agents such as 3-mercaptopropyltrimethoxysilane; silane-based coupling agents; alkoxysilanes such as phenyltrimethoxysilane; organosilazane compounds such as hexamethyldisilazane; and titanate-based coupling agents. Among them, the surface treatment agent is preferably an aminosilane-based coupling agent. Moreover, the surface treatment agent may be used alone or in any combination of two or more types.

Examples of commercially available surface treatment agents include Shin-Etsu Chemical's "KBM403" (3-glycidoxypropyltrimethoxysilane), Shin-Etsu Chemical's "KBM803" (3-mercaptopropyltrimethoxysilane), Shin-Etsu Chemical's "KBE903" (3-aminopropyltriethoxysilane), Shin-Etsu Chemical's "KBM573" (N-phenyl-3-aminopropyltrimethoxysilane), Shin-Etsu Chemical's "SZ-31" (hexamethyldisilazane), Shin-Etsu Chemical's "KBM103" (phenyltrimethoxysilane), Shin-Etsu Chemical's "KBM-4803" (long-chain epoxy-type silane coupling agent), and Shin-Etsu Chemical's "KBM-7103" (3,3,3-trifluoropropyltrimethoxysilane).

From the viewpoint of improving the dispersibility of (C) silica, 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 parts by mass of (C) silica is surface-treated with 0.2 parts by mass to 5 parts by mass of the surface treatment agent, it is preferable that it is surface-treated with 0.2 parts by mass to 3 parts by mass, and it is preferable that it is surface-treated with 0.3 parts by mass to 2 parts by mass.

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

From the viewpoint of obtaining a significant effect of the present invention, the content of (C) silica is preferably 5% by mass or more, more preferably 10% by mass or more, even more preferably 20% by mass or more, 25% by mass or more, and is preferably 50% by mass or less, more preferably 45% by mass or less, even more preferably 40% by mass or less, when the non-volatile components in the resin composition are taken as 100% by mass.

In order to obtain a significant effect of the present invention, the total content of the white inorganic pigment excluding the silane coupling agent in component (A) and component (C) is preferably 20% 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, and 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.

When the non-volatile components in the resin composition are taken as 100% by mass, the content (mass%) of component (A) is taken as A1, and the content (mass%) of component (C) is taken as C1. From the viewpoint of obtaining a significant effect of the present invention, C1/A1 is preferably 0.1 or more, more preferably 0.3 or more, and even more preferably 0.5 or more, and is preferably 10 or less, more preferably 5 or less, and even more preferably 3 or less.

<(D) Curing Agent>
In addition to the above-mentioned components, the resin composition may further contain a curing agent as an optional component (D). The curing agent (D) has a function of reacting with the epoxy resin (B) to cure the resin composition. The curing agent (D) may be used alone or in combination of two or more kinds.

(D) The curing agent is 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, thiol-based curing agents, and active ester-based curing agents. (D) The curing agent preferably includes a phenol-based curing agent.

The phenol-based hardener is a hardener having two or more phenolic hydroxyl groups in one molecule, and examples thereof include bisphenol-based hardeners, biphenyl-type phenol-based hardeners, naphthalene-type phenol-based hardeners, phenol novolac-type phenol-based hardeners, naphthylene ether-type phenol-based hardeners, triazine skeleton-containing phenol-based hardeners, polyphenylene ether-type phenol-based hardeners, phenol aralkyl-type phenol-based hardeners, cresol novolac-type phenol-based hardeners, and bisphenol-type phenol-based hardeners. Among these, bisphenol-based hardeners are preferred, and more preferred are bisphenol-based hardeners selected from bisphenol compounds having fluorine atoms, bisphenol compounds having an alicyclic structure, and bisphenol compounds having a fluorene skeleton, and even more preferred are bisphenol compounds having fluorine atoms, and particularly preferred is bisphenol AF.

Specific examples of commercially available phenol-based hardeners include "BiS-AF," "BiSOFP-A," "BiS-Z," and "BiSOC-FL" manufactured by Central Glass Co., Ltd.

Carbodiimide-based curing agents are curing agents that have two or more carbodiimide structures in one molecule, and examples of such curing agents include aliphatic biscarbodiimides such as tetramethylene-bis(t-butylcarbodiimide) and cyclohexane-bis(methylene-t-butylcarbodiimide); aromatic biscarbodiimides such as phenylene-bis(xylylcarbodiimide); aliphatic polycarbodiimides such as polyhexamethylenecarbodiimide, polytrimethylhexamethylenecarbodiimide, polycyclohexylenecarbodiimide, poly(methylenebiscyclohexylenecarbodiimide), and poly(isophoronecarbodiimide); Examples of polycarbodiimides include aromatic polycarbodiimides such as 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.

An acid anhydride curing agent is a curing agent having one or more carboxylic acid anhydride groups (-CO-O-CO-) in one molecule, and examples thereof include phthalic anhydride, pyromellitic dianhydride, 1,4,5,8-naphthalene tetracarboxylic dianhydride, 2,3,6,7-naphthalene tetracarboxylic dianhydride, 3,3',4,4'-benzophenone tetracarboxylic dianhydride, oxydiphthalic dianhydride, 3,3',4,4'-diphenylsulfone tetracarboxylic dianhydride, 3,3',4,4'-diphenyl ether tetracarboxylic dianhydride, 3,3',4,4'-biphenyl tetracarboxylic dianhydride, methylene-4,4' aromatic acid anhydride-based curing agents such as diphthalic dianhydride; aliphatic acid anhydride-based curing agents such as tetrahydrophthalic anhydride, hexahydrophthalic anhydride, methyltetrahydrophthalic anhydride, methylhexahydrophthalic anhydride, methylnadic anhydride, hydrogenated methylnadic anhydride, trialkyltetrahydrophthalic anhydride, dodecenylsuccinic anhydride, cyclopentanetetracarboxylic dianhydride, and cyclohexane-1,2,4,5-tetracarboxylic dianhydride; and polymer anhydride-based curing agents such as styrene/maleic anhydride copolymer and alkyl (meth)acrylate/styrene/maleic anhydride copolymer. 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, and "HN-2200" and "HN-5500" manufactured by Hitachi Chemical Co., Ltd.

The amine-based curing agent is a curing agent having two or more amino groups, and examples thereof include aliphatic amines, polyether amines, alicyclic amines, aromatic amines, etc., among which 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, and the like. 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).

Thiol-based curing agents are curing agents that have two or more mercapto groups, and examples of such curing agents include trimethylolpropane tris(3-mercaptopropionate), pentaerythritol tetrakis(3-mercaptobutyrate), and tris(3-mercaptopropyl)isocyanurate.

As the active ester curing agent, a compound having one or more active ester groups in one molecule can be used. Among them, as the active ester curing agent, a compound having two or more highly reactive ester groups in one molecule, such as phenol esters, thiophenol esters, N-hydroxyamine esters, and esters of heterocyclic hydroxy compounds, is preferred. The active ester curing agent 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 curing agent obtained from a carboxylic acid compound and a hydroxy compound is preferred, and an active ester curing agent obtained from a carboxylic acid compound and a phenol compound and/or a naphthol compound is more preferred.

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

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

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

Commercially available active ester curing agents include "EXB9451", "EXB9460", "EXB9460S", "HPC-8000-65T", "HPC-8000H-65TM", and "EXB-8000L-65TM" (manufactured by DIC Corporation) as active ester curing agents containing a dicyclopentadiene-type diphenol structure; "EXB9416-70BK" and "EXB-8150-65T" (manufactured by DIC Corporation) as active ester curing agents containing a naphthalene structure; and "EXB9416-70BK" and "EXB-8150-65T" (manufactured by DIC Corporation) as active ester curing agents containing an acetylated product of phenol novolac. Examples of such a hardener include "DC808" (manufactured by Mitsubishi Chemical Corporation); "YLH1026" (manufactured by Mitsubishi Chemical Corporation) as an active ester-based hardener containing a benzoyl derivative of phenol novolac; "DC808" (manufactured by Mitsubishi Chemical Corporation) as an active ester-based hardener which is an acetylated derivative of phenol novolac; "YLH1026" (manufactured by Mitsubishi Chemical Corporation), "YLH1030" (manufactured by Mitsubishi Chemical Corporation), and "YLH1048" (manufactured by Mitsubishi Chemical Corporation) as active ester-based hardeners which are benzoyl derivatives of phenol novolac; etc.

The reactive group equivalent of the (D) 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. For example, in the case of a phenol-based curing agent, the reactive group is a phenolic hydroxyl group. In the case of an acid anhydride-based curing agent, one equivalent of a carboxylic anhydride group (-CO-O-CO-) corresponds to two equivalents of reactive groups.

The content of (D) the curing agent is preferably 1% by mass or more, more preferably 2% by mass or more, and even more preferably 3% by mass or more, based on 100% by mass of the non-volatile components in the resin composition, from the viewpoint of obtaining a significant effect of the present invention, and is preferably 50% by mass or less, more preferably 30% by mass or less, and even more preferably 10% by mass or less.

<(E) Curing Accelerator>
The resin composition may contain a curing accelerator (E) as an optional component. The curing accelerator (E) has a function of accelerating the curing reaction of the epoxy resin (A). The curing accelerator (E) may be used alone or in combination of two or more kinds.

(E) Curing accelerators include, for example, phosphorus-based curing accelerators, imidazole-based curing accelerators, amine-based curing accelerators, guanidine-based curing accelerators, metal-based curing accelerators, etc. Among them, as (E) curing accelerators, from the viewpoint of obtaining the effects of the present invention significantly, phosphorus-based curing accelerators and imidazole-based curing accelerators are preferred, and phosphorus-based curing accelerators are more preferred.

From the viewpoint of obtaining the effects of the present invention more prominently, it is preferable that the phosphorus-based curing accelerator contains one or more selected from the group consisting of phosphonium salts and phosphines.

Examples of phosphonium salts 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-butylmethylphosphonium tetraphenylborate; methyltriphenylphosphonium bromide, ethyltriphenylphosphonium bromide, propyltriphenylphosphonium bromide, butyltriphenylphosphonium bromide, and the like. Examples of aromatic phosphonium salts include phenylphosphonium bromide, benzyltriphenylphosphonium chloride, tetraphenylphosphonium 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.

Examples of phosphines include aliphatic phosphines such as tributylphosphine, tri-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, and 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-biphenylphosphine, Examples of such aromatic phosphines include bis(diphenylphosphino)ethane, 1,3-bis(diphenylphosphino)propane, 1,4-bis(diphenylphosphino)butane, 1,2-bis(diphenylphosphino)acetylene, and 2,2'-bis(diphenylphosphino)diphenylether; aromatic phosphine-borane complexes such as triphenylphosphine-triphenylborane; and aromatic phosphine-quinone adducts such as triphenylphosphine-p-benzoquinone adducts.

Commercially available phosphorus-based curing accelerators may be used, such as "TBP-DA" manufactured by Hokko Chemical Industry Co., Ltd.

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

Commercially available imidazole curing accelerators may be used, such as "P200-H50" manufactured by Mitsubishi Chemical Corporation and "1B2PZ-10M" manufactured by Shikoku Kasei Co., Ltd.

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

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

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

From the viewpoint of obtaining a significant effect of the present invention, the content of (E) the curing accelerator is preferably 0.1% by mass or more, more preferably 0.2% by mass or more, and even more preferably 0.3% by mass or more, and is preferably 10% by mass or less, more preferably 7% by mass or less, and even more preferably 5% by mass or less, when the non-volatile components in the resin composition are taken as 100% by mass.

<(F) Thermoplastic resin>
The resin composition of the present invention may contain a thermoplastic resin (F) as an optional component. The thermoplastic resin (F) may be used alone or in combination of two or more kinds. It may also be used.

(F) Examples of thermoplastic resins include phenoxy resins, polyvinyl acetal resins, acrylic resins, polyolefin resins, polybutadiene resins, polyimide resins, polyamideimide resins, polysulfone resins, polyethersulfone resins, polyphenylene ether resins, polyetherimide resins, polycarbonate resins, polyetheretherketone resins, and polyester resins. Among these, resins selected from phenoxy resins, acrylic resins, and polyphenylene ether resins are preferred, and phenoxy resins are more preferred.

Examples of the phenoxy resin include phenoxy resins having one or more skeletons selected from the group consisting of bisphenol A skeleton, bisphenol F skeleton, bisphenol S skeleton, bisphenolacetophenone skeleton, novolac skeleton, biphenyl skeleton, fluorene skeleton, dicyclopentadiene skeleton, norbornene skeleton, naphthalene skeleton, anthracene skeleton, adamantane skeleton, terpene skeleton, and trimethylcyclohexane skeleton. The terminal of the phenoxy resin may be any functional group such as a phenolic hydroxyl group or an epoxy group. The phenoxy resin may be used alone or in combination of two or more kinds.
Specific examples of the phenoxy resin include "1256" and "4250" manufactured by Mitsubishi Chemical Corporation (both of which are phenoxy resins containing a bisphenol A skeleton); "YX8100" (phenoxy resin containing a bisphenol S skeleton) manufactured by Mitsubishi Chemical Corporation; "YX6954" (phenoxy resin containing a bisphenol acetophenone skeleton) manufactured by Mitsubishi Chemical Corporation, "FX280" and "FX293" manufactured by Nippon Steel Chemical & Material Co., Ltd.; "YX7200B35", "YL7500BH30", "YX6954BH30", "YX7553", "YX7553BH30", "YL7769BH30", "YL6794", "YL7213", "YL7290", and "YL7482" manufactured by Mitsubishi Chemical Corporation.

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 the 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.

Acrylic resin refers to a polymer obtained by polymerizing monomer components including (meth)acrylic acid ester monomers. The monomer components constituting the acrylic resin may contain, in addition to (meth)acrylic acid ester monomers, (meth)acrylamide monomers, styrene monomers, functional group-containing monomers, etc. as copolymerization components. Specific examples of acrylic resins include "ARUFON UP-1000", "ARUFON UP-1010", "ARUFON UP-1020", "ARUFON UP-1021", "ARUFON UP-1061", "ARUFON UP-1080", "ARUFON UP-1110", "ARUFON UP-1170", "ARUFON UP-1190", "ARUFON UP-1500", "ARUFON UH-2000", "ARUFON UH-2041", "ARUFON UH-2190", "ARUFON UHE-2012", "ARUFON UC-3510", and "ARUFON UP-1021", all manufactured by Toagosei Co., Ltd. UG-4010, ARUFON US-6100, ARUFON US-6170, etc. These may be used alone or in combination of two or more.

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; and polyolefin-based elastomers 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 polyimide resins include "Rikacoat SN20" and "Rikacoat PN20" manufactured by New Japan Chemical Co., Ltd. Specific examples of polyimide resins also include modified polyimides such as linear polyimides obtained by reacting bifunctional hydroxyl-terminated polybutadiene, a diisocyanate compound, and a tetrabasic acid anhydride (polyimides described in JP-A-2006-37083), and polysiloxane skeleton-containing polyimides (polyimides described in JP-A-2002-12667 and JP-A-2000-319386, 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.

Specific examples of polyphenylene ether resins include the oligophenylene ether-styrene resins "OPE-2St1200" and "OPE-2St2200" manufactured by Mitsubishi Gas Chemical Company, Inc., and "NORYL SA90" manufactured by SABIC. Specific examples of polyetherimide resins include "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 resins, etc.

The weight average molecular weight (Mw) of the (E) thermoplastic resin is preferably 8,000 or more, more preferably 10,000 or more, and particularly preferably 20,000 or more, from the viewpoint of significantly obtaining the desired effects of the present invention, and is preferably 70,000 or less, more preferably 60,000 or less, and particularly preferably 50,000 or less.

(F) The thermoplastic resin is preferably a thermoplastic resin that, when formed into a film of 20 μm, has a transmittance of 80% or more for light with a wavelength of 450 nm incident perpendicularly to the film surface.

The content of (E) thermoplastic resin is preferably 1% by mass or more, more preferably 5% by mass or more, and even more preferably 10% by mass or more, and is preferably 30% by mass or less, more preferably 25% by mass or less, and even more preferably 20% by mass or less, based on 100% by mass of non-volatile components in the resin composition, from the viewpoint of significantly obtaining the desired effect of the present invention.

<(G) Other Additives>
The resin composition may further contain any additive as a non-volatile component. Examples of such additives include organic fillers such as rubber particles; leveling agents such as silicone-based leveling agents and acrylic polymer-based leveling agents; thickeners such as bentone and montmorillonite; defoamers such as silicone-based defoamers, acrylic defoamers, fluorine-based defoamers, and vinyl resin-based defoamers; ultraviolet absorbers such as benzophenone-based ultraviolet absorbers, benzotriazole-based ultraviolet absorbers, and salicylic acid-based ultraviolet absorbers; adhesion improvers such as urea silane; adhesion imparters such as triazole-based adhesion imparters, tetrazole-based adhesion imparters, and triazine-based adhesion imparters; hindered phenol-based antioxidants; fluorescent brighteners such as stilbene derivatives; fluorine-based Examples of the additives include surfactants such as surfactants and silicone 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, and inorganic flame retardants (e.g., antimony trioxide); dispersants such as phosphate ester dispersants, polyoxyalkylene dispersants, acetylene dispersants, silicone dispersants, anionic dispersants, and cationic dispersants; stabilizers such as borate stabilizers, titanate stabilizers, aluminate stabilizers, zirconate stabilizers, isocyanate stabilizers, carboxylic acid stabilizers, and carboxylic anhydride stabilizers. (G) Other additives may be used alone or in combination of two or more at any ratio. (G) The content of other additives can be appropriately set by a person skilled in the art.

<(H) Organic Solvent>
The resin composition may further contain an arbitrary organic solvent as a volatile component in addition to the non-volatile components described above. As the (H) organic solvent, a known one can be appropriately used, and the type is not particularly limited. As the (H) organic solvent, for example, ketone-based solvents such as acetone, methyl ethyl ketone (MEK), 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, 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 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 (butylcarbitol), 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, methylcyclohexane, and the like; aromatic hydrocarbon solvents such as benzene, toluene, xylene, ethylbenzene, trimethylbenzene, and the like. The organic solvent (H) may be used alone or in any combination of two or more kinds at any ratio.

The content of (H) organic solvent is not particularly limited, but when all components in the resin composition are taken as 100% by mass, it can be, for example, 80% by mass or less, 70% by mass or less, 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, 5% by mass or less, etc.

<Physical properties and applications of resin composition>
Since the resin composition of the present invention contains the component (A), a cured product having excellent reflectance and reflectance after a heat resistance test can be obtained. Furthermore, a resin composition having a low minimum melt viscosity can be obtained. Therefore, the resin composition of the present invention can be suitably used as a resin composition (light reflecting resin composition) for obtaining a cured product for light reflection applications for reflecting light from a light source. Specifically, it can be suitably used as a resin composition for a reflective sheet formed on the outermost layer of a printed wiring board. Examples of light sources include light emitting diodes (LEDs), mini LEDs, and micro LEDs. In addition, the resin composition of the present invention can be suitably used as a resin composition for insulating the solder resist layer of a printed wiring board. Therefore, the resin composition of the present invention can be suitably used as a resin composition for forming a layer that serves both as a solder resist layer and a reflective sheet. Furthermore, the resin composition of the present invention can be suitably used as a resin composition for interlayer insulation of a printed wiring board. Therefore, the resin composition of the present invention can be suitably used as a resin composition for forming an interlayer insulating layer.

The resin composition of the present invention contains component (A), and therefore exhibits the characteristic of a low minimum melt viscosity. The minimum melt viscosity of the resin composition is preferably 5000 poise or less, more preferably 4500 poise or less, and even more preferably 4000 poise or less. The lower limit of the minimum melt viscosity is 100 poise or more, more preferably 500 poise or more, and even more preferably 1000 poise or more. Here, the term "minimum melt viscosity" refers to the minimum melt viscosity at 60°C to 200°C. The minimum melt viscosity can be measured using a dynamic viscoelasticity measuring device. The minimum melt viscosity can be measured according to the method described in the examples below. When the minimum melt viscosity of the resin composition is within this range, the resin composition has excellent flexibility.

The cured product obtained by curing the resin composition at 180°C for 60 minutes exhibits excellent reflectance of light having a wavelength of 460 nm. Therefore, the cured product can reflect light with high reflectance, and provides a reflective sheet with improved reflectance of light having a wavelength of 460 nm, for example. The reflectance is preferably 90% or more, more preferably 91% or more, and even more preferably 92% or more. The upper limit of the reflectance can be 100% or less. The reflectance can be measured according to the method described in the examples below.

The resin composition is cured at 180°C for 60 minutes, and then subjected to a heat resistance test at 125°C for 100 hours. The cured product can reflect light with a high reflectance, and exhibits excellent reflectance for light with a wavelength of 460 nm, for example. Thus, the cured product provides a reflective sheet with improved reflectance for light with a wavelength of 460 nm after the heat resistance test. The reflectance after the heat resistance test is preferably 85% or more, more preferably 88% or more, and even more preferably 90% or more. The upper limit of the reflectance after the heat resistance test can be 100% or less. The reflectance after the heat resistance test can be measured according to the method described in the examples below.

It is preferable that the amount of decrease in reflectance of the cured product of the resin composition due to the heat resistance test treatment is small. For example, the reflectance of the cured product obtained by curing the resin composition at 180°C for 60 minutes is represented as ρ0 for light having a wavelength of 460 nm. Furthermore, the reflectance of the cured product at 460 nm for light after the heat resistance test treatment at 125°C for 100 hours is represented as ρ1. In this case, the amount of decrease in reflectance due to the heat resistance test treatment, Δρ=ρ0-ρ1, is preferably 10% or less, more preferably 8% or less, and even more preferably 6% or less.

[Resin sheet]
The resin sheet of the present invention includes a support and a resin composition layer formed from the resin composition of the present invention provided on the support.

The thickness of the resin composition layer is preferably 200 μm or less, more preferably 100 μm or less, and even more preferably 80 μm or less, from the viewpoint of making the printed wiring board thinner and being able to provide a cured product with excellent insulation even if the cured product of the resin composition is a thin film. The lower limit of the thickness of the resin composition layer 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, with inexpensive polyethylene terephthalate being 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, and examples thereof include "PET501010", "SK-1", "AL-5", and "AL-7" manufactured by Lintec Corporation, which are PET films having a release layer mainly composed of an alkyd resin-based release agent; "Lumirror T60" manufactured by Toray Industries, Inc.; "Purex" manufactured by Teijin Limited; and "Unipeel" manufactured by Unitika Limited.

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 other layers as necessary. Examples of such other layers include 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 directly applying the liquid resin composition or dissolving the resin composition in an organic solvent, applying this to a support using a die coater or the like, and then drying to form a resin composition layer.

The organic solvent may be the same as the organic solvent (H) described above. The organic solvent may be used alone or in combination of two or more.

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 (resin varnish), for example, when using a resin composition (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.

[Cured product]
The cured product of the present invention is obtained by curing the resin composition of the present invention. The curing conditions of the resin composition may be the conditions of step (II) described below. In addition, the resin composition may be preheated before curing, and heating may be performed multiple times including preheating.

[Reflective sheets, printed wiring boards]
The reflective sheet of the present invention includes a cured product of the resin composition of the present invention. The printed wiring board of the present invention includes the reflective sheet of the present invention. As shown in FIG. 1, the printed wiring board 1 includes a reflective sheet 3 formed on a substrate 2, and a light source 4 is disposed on a surface 31 of the reflective sheet 3. Examples of the light source 4 include a light-emitting diode (LED), a mini LED, and a micro LED.

The reflective sheet contains a cured product of the resin composition of the present invention, and therefore can reflect light with a high reflectance. For example, the reflectance of light having a wavelength of 460 nm is preferably 90% or more, more preferably 94% or more, and even more preferably 95% or more. The upper limit of the reflectance can be 100% or less. In addition, the reflective sheet contains a cured product of the resin composition of the present invention, and therefore can reflect light with a high reflectance even after the heat resistance test treatment. For example, the reflectance of light having a wavelength of 460 nm after the heat resistance test treatment is preferably 85% or more, more preferably 88% or more, and even more preferably 90% or more. The upper limit of the reflectance after the heat resistance test treatment can be 100% or less. The reflectance and the reflectance after the heat resistance test treatment can be measured, for example, using a multichannel spectrometer (MCPD-7700, manufactured by Otsuka Electronics Co., Ltd.).

The reflective sheet contains a cured product of the resin composition of the present invention, and therefore can also be included as an interlayer insulating layer or a solder resist layer. Therefore, it is preferable that the printed wiring board of the present invention contains the reflective sheet as an interlayer insulating layer or a solder resist layer.

The printed wiring board and the reflective sheet of the present invention can be produced, for example, by a method including the following steps (I), (II) and (III) using the above-mentioned resin sheet.
(I) a step of laminating the resin composition layer of the resin sheet on a substrate so that the resin composition layer is bonded to the substrate; (II) a step of thermally curing the resin composition layer to form a reflective sheet; and (III) a step of arranging a light source on the reflective sheet.

There are no limitations on the substrate used in step (I), and for example, a circuit board having an insulating layer, a conductor layer formed on the insulating layer, and a solder resist layer formed on the conductor layer may be used. The insulating layer and solder resist layer included in this circuit board may be formed using the reflective sheet of the present invention.

The substrate and the resin sheet can be laminated, for example, by heat-pressing the resin sheet to the substrate from the support side. Examples of the member for heat-pressing the resin sheet to the 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 adequately follow the surface irregularities of the substrate.

The lamination of the 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 is preferably performed under reduced pressure conditions of 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 thermally cured to form a reflective sheet. For example, the thermal curing conditions for the resin composition layer vary depending on the type of resin composition, but the curing temperature is preferably 120°C to 240°C, more preferably 130°C to 220°C, and even more preferably 150°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 curing the resin composition, the resin composition may be preheated at a temperature lower than the curing temperature. For example, prior to thermally curing the resin composition, the resin composition may be preheated for 5 minutes or more (preferably 5 minutes to 150 minutes, more preferably 15 minutes to 120 minutes, and even more preferably 15 minutes to 100 minutes) at a temperature of 50°C or higher and lower than 120°C (preferably 60°C or higher and 115°C or lower, and more preferably 70°C or higher and 110°C or lower).

In order to increase the efficiency of extracting light emitted from the light source, the surface of the reflective sheet facing the light source may have a recess in addition to being flat as shown in Figure 1.

In step (III), a light source is placed on the reflective sheet. For example, if the reflective sheet has a recess on its surface, the light source is placed in the recess.

If necessary, the light source may be electrically connected and then sealed to fix it in place.

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

<White inorganic pigment used>
White inorganic pigment 1: 100 parts of titanium oxide (average particle size 0.26 μm, Sakai Chemical Industry Co., Ltd.'s "PX3788") was surface-treated with 1 part of phenyltrimethoxysilane (Shin-Etsu Chemical Co., Ltd.'s "KBM-103", molecular weight 198.1) represented by the following structural formula (wherein Me represents a methyl group).

White inorganic pigment 2: 100 parts of titanium oxide (average particle size 0.26 μm, Sakai Chemical Industry Co., Ltd.'s "PX3788") was surface-treated with 3 parts of 3-glycidoxypropyltrimethoxysilane (Shin-Etsu Chemical Co., Ltd.'s "KBM-403", molecular weight 236.1) represented by the following structural formula (wherein Me represents a methyl group).

White inorganic pigment 3: 100 parts of titanium oxide (average particle size 0.26 μm, Sakai Chemical Industry Co., Ltd.'s "PX3788") was surface-treated with 3 parts of 3-methacryloxypropyltrimethoxysilane (Shin-Etsu Chemical Co., Ltd.'s "KBM-503", molecular weight 248.1) represented by the following structural formula (wherein Me represents a methyl group).

White inorganic pigment 4: 100 parts of titanium oxide (average particle size 0.26 μm, Sakai Chemical Industry Co., Ltd.'s "PX3788") surface-treated with 3 parts of phenyltrimethoxysilane (Shin-Etsu Chemical Co., Ltd., molecular weight 198.1, "KBM-103") shown in the above structural formula.

White inorganic pigment 5: 100 parts of titanium oxide (average particle size 0.26 μm, Sakai Chemical Industry Co., Ltd.'s "PX3788") was surface-treated with 0.6 parts of N-phenyl-3-aminopropyltrimethoxysilane (Shin-Etsu Chemical Co., Ltd.'s "KBM-573", molecular weight 255.1) represented by the following structural formula (wherein Me represents a methyl group).

White inorganic pigment 6: 100 parts of titanium oxide (average particle size 0.26 μm, "PX3788" manufactured by Sakai Chemical Industry Co., Ltd.) was surface-treated with 0.6 parts of 3-aminopropyltrimethoxysilane (manufactured by Shin-Etsu Chemical Co., Ltd., molecular weight 179.1) represented by the following structural formula (wherein Me represents a methyl group).

Example 1
Four parts of a liquid bisphenol A type epoxy resin (epoxy equivalent 180, Mitsubishi Chemical Corporation's "Epikote 828EL"), four parts of a solid fluorine atom-containing epoxy resin (epoxy equivalent 245 g/eq., Mitsubishi Chemical Corporation's "YL7760"), and 20 parts of a phenoxy resin containing a biphenyl skeleton and a cyclohexane skeleton (Mitsubishi Chemical Corporation's "YX7200B35", weight average molecular weight 30,000, MEK solution with solids content of 35 mass %) were heated and dissolved in 8 parts of MEK with stirring. To this was added 10.1 parts of white inorganic pigment 1 (10 parts of titanium oxide, 0.1 part of silane coupling agent), 10 parts of spherical silica (average particle size 0.5 μm, Admattex Co., Ltd. "SO-C2", aminosilane treated), 4 parts of bisphenol AF (a solution of Central Glass Co., Ltd. "BiS-AF" adjusted with MEK to a non-volatile content of 50%), and 0.2 parts of a phosphorus-based curing accelerator ((TBP-DA), Hokko Chemical Industry Co., Ltd.), and the mixture was uniformly dispersed using a high-speed rotary mixer to prepare resin composition 1.

A PET film with a release layer ("PET501010" manufactured by Lintec Corporation, thickness 38 μm) was prepared as a support. Resin composition 1 was uniformly applied onto the release layer of this support so that the thickness of the resin composition layer after drying would be 50 μm. Resin composition 1 was then heated at 80°C for 4 minutes to obtain resin sheet 1 including a resin composition layer with a thickness of 50 μm.

Example 2
In Example 1, 10.1 parts of the white inorganic pigment 1 was changed to 10.3 parts of the white inorganic pigment 2 (10 parts of titanium oxide, 0.3 parts of silane coupling agent).
Resin composition 2 and resin sheet 2 were prepared in the same manner as in Example 1 except for the above.

Example 3
In Example 1, 10.1 parts of White Inorganic Pigment 1 was changed to 10.3 parts of White Inorganic Pigment 3 (10 parts of titanium oxide, 0.3 parts of silane coupling agent).
Resin composition 3 and resin sheet 3 were prepared in the same manner as in Example 1 except for the above points.

Example 4
In Example 1, 10.1 parts of White Inorganic Pigment 1 was changed to 10.3 parts of White Inorganic Pigment 4 (10 parts of titanium oxide, 0.3 parts of silane coupling agent).
Resin composition 4 and resin sheet 4 were prepared in the same manner as in Example 1 except for the above.

Example 5
In Example 1, the amount of white inorganic pigment 1 was changed from 10.1 parts to 15.15 parts (titanium oxide 15 parts, silane coupling agent 0.15 parts), and the amount of spherical silica (average particle size 0.5 μm, Admattex Co., Ltd. "SO-C2", aminosilane treated) was changed from 10 parts to 15 parts.
Resin composition 5 and resin sheet 5 were prepared in the same manner as in Example 1 except for the above.

Example 6
In Example 1, the amount of white inorganic pigment 1 was changed from 10.1 parts to 20.2 parts, and spherical silica (average particle size 0.5 μm, Admatechs'"SO-C2", aminosilane-treated) was not used.
Resin composition 6 and resin sheet 6 were prepared in the same manner as in Example 1 except for the above points.

Example 7
In Example 1, 4 parts of the liquid bisphenol A type epoxy resin (epoxy equivalent 180, Mitsubishi Chemical Corporation's "Epicoat 828EL") was changed to 4 parts of a hydrogenated liquid epoxy resin (epoxy equivalent 205 g/eq., Mitsubishi Chemical Corporation's "YX8000").
Resin composition 7 and resin sheet 7 were prepared in the same manner as in Example 1 except for the above points.

<Comparative Example 1>
In Example 1, 10.1 parts of the white inorganic pigment 1 was changed to 10 parts of titanium oxide not treated with a silane coupling agent (average particle size 0.26 μm, "PX3788" manufactured by Sakai Chemical Industry Co., Ltd.).
Resin composition 8 and resin sheet 8 were prepared in the same manner as in Example 1 except for the above points.

<Comparative Example 2>
In Example 1, 10.1 parts of White Inorganic Pigment 1 was changed to 10.06 parts of White Inorganic Pigment 5 (15 parts of titanium oxide, 0.06 part of silane coupling agent).
Resin composition 9 and resin sheet 9 were prepared in the same manner as in Example 1 except for the above points.

<Comparative Example 3>
In Example 1, 10.1 parts of White Inorganic Pigment 1 was changed to 10.06 parts of White Inorganic Pigment 6 (15 parts of titanium oxide, 0.06 part of silane coupling agent).
A resin composition 10 and a resin sheet 10 were prepared in the same manner as in Example 1 except for the above points.

<Fabrication of Evaluation Substrate A>
(1) Undercoat treatment of inner layer circuit board A circuit pattern was formed by etching on both sides of a glass cloth-based epoxy resin double-sided copper-clad laminate (copper foil thickness 18 μm, substrate thickness 0.8 mm, Matsushita Electric Works "R5715ES") to produce an inner layer circuit board with an in-plane copper area of 30%. The copper circuit of the obtained inner layer circuit board was roughened with a microetching agent (Mec Co., Ltd. "CZ8100"). Then, it was dried at 190° C. for 30 minutes.

(2) Lamination of Resin Sheets The resin sheets 1 to 10 prepared in each of the Examples and Comparative Examples were laminated on both sides of the inner layer circuit board prepared in (1) above using a batch type vacuum pressure laminator (MVLP-500, manufactured by Meiki Co., Ltd.) The resin sheets were laminated by reducing the pressure for 30 seconds to 13 hPa or less, and then pressing at 120°C for 30 seconds at a pressure of 0.74 MPa.

(3) Smoothing of Resin Sheet Next, the laminated resin sheet was smoothed by heat pressing at atmospheric pressure, 100° C., and a pressure of 0.5 MPa for 60 seconds. Thereafter, the support was peeled off to obtain a substrate including a resin composition layer, an inner layer circuit board, and a resin composition layer in this order.

(4) Curing of Resin Sheet This substrate was cured at 180° C. for 60 minutes to obtain an evaluation substrate A.

<Measurement of reflectance after curing>
Evaluation substrate A was cut to a width of 50 mm and a length of 50 mm, and the cross section was polished. The reflectance of light with a wavelength of 460 nm was measured using a multichannel spectrometer (Otsuka Electronics Co., Ltd., MCPD-7700) and evaluated according to the following criteria.
Evaluation criteria: ⊚: Reflectance is 95% or more; ◯: Reflectance is 90% or more but less than 95%; △: Reflectance is 85% or more but less than 90%; ×: Reflectance is less than 85%

<Measurement of reflectance after heat resistance test treatment>
The evaluation substrate A was heated at 125° C. for 100 hours, cut into a piece 50 mm wide and 50 mm long, and the cross section was polished. The reflectance of light with a wavelength of 460 nm was measured using a multichannel spectrometer (MCPD-7700, manufactured by Otsuka Electronics Co., Ltd.) and evaluated according to the following criteria.
Evaluation criteria: ⊚: Reflectance is 90% or more; ◯: Reflectance is 85% or more and less than 90%; △: Reflectance is 80% or more and less than 85%; ×: Reflectance is less than 80%

<Measurement of minimum melt viscosity>
The dynamic viscoelasticity of the resin composition layers of the resin sheets 1 to 10 produced in the examples and comparative examples was measured using a dynamic viscoelasticity measuring device (Rheosol-G3000 manufactured by U.B.M. Co., Ltd.). The measurement was performed from a starting temperature of 60° C. to 200° C., with a temperature rise rate of 5° C./min, an interval temperature of 2.5° C., and a vibration frequency of 1 Hz/deg, and was evaluated according to the following criteria.
〇: 5000 poise or less.
×: More than 5000 poise.

＊（Ａ）成分の量及び（Ｃ）成分の合計量とは、樹脂組成物中の不揮発成分を１００質量％とした場合の、（Ａ）成分のうち、窒素原子を含まないシランカップリング剤の白色無機顔料、及び（Ｃ）成分の合計含有量を表す。

*The amount of component (A) and the total amount of component (C) refer to the total content of the white inorganic pigment of the silane coupling agent not containing a nitrogen atom in component (A) and component (C) when the non-volatile components in the resin composition are taken as 100 mass%.

1 Printed wiring board 2 Substrate 3 Reflective sheet 31 Reflective sheet surface 4 Light source

Claims (10)

A resin composition comprising: (A) a white inorganic pigment surface-treated with a silane coupling agent not containing a nitrogen atom ; ( B) an epoxy resin ; and (C) silica ,
The content of the component (A) is 10% by mass or more and 60% by mass or less, when the total amount of non-volatile components in the resin composition is 100% by mass,
(B) A resin composition, in which the epoxy resin comprises a combination of a solid epoxy resin and a liquid epoxy resin. The resin composition according to claim 1 , wherein the content of the component (B) is 1% by mass or more and 50% by mass or less, when the total amount of non-volatile components in the resin composition is 100% by mass. 3. The resin composition according to claim 1, wherein the component (A) is at least one selected from the group consisting of aluminum oxide, titanium oxide, zirconium oxide, magnesium oxide, barium titanate, zinc oxide, cerium oxide, and calcium carbonate. The resin composition according to any one of claims 1 to 3, wherein the silane coupling agent not containing a nitrogen atom is at least one selected from the group consisting of a phenylsilane coupling agent, an alkylsilane coupling agent, an epoxysilane coupling agent, a vinylsilane coupling agent, a (meth ) acrylic silane coupling agent, and a styrylsilane coupling agent. The resin composition according to any one of claims 1 to 4 , which is for light reflection. A resin sheet comprising a support and a resin composition layer provided on the support, the resin composition layer comprising the resin composition according to any one of claims 1 to 5 . The resin sheet according to claim 6 , wherein the resin composition layer has a minimum melt viscosity of 5,000 poise or less. A reflecting sheet comprising a cured product of the resin composition according to any one of claims 1 to 5 . A printed wiring board comprising the reflective sheet according to claim 8 . A printed wiring board comprising the cured reflective sheet according to claim 8 as an interlayer insulating layer or a solder resist layer.

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