JP7556241B2 - Thermosetting white resin composition, white cured product, resin sheet, reflective sheet, printed wiring board, and semiconductor device - Google Patents

Description

The present invention relates to a thermosetting white resin composition. It also relates to a white cured product, a resin sheet, a reflective sheet, a printed wiring board, and a semiconductor device obtained using the thermosetting white resin composition.

In the field of printed wiring boards, there has been an increase in the use of light-emitting diodes (LEDs) that emit light with low power, which are directly mounted on the board, for backlighting of liquid crystal displays in mobile terminals, computers, televisions, etc., and as light sources for lighting fixtures. LEDs have become increasingly miniaturized in recent years, and there are LEDs known as mini-LEDs and micro-LEDs.

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

This reflective sheet is required to have a high light reflectance, and as a material for the reflective sheet, for example, Patent Document 1 discloses a resin composition that contains rutile-type titanium oxide produced by the chlorine method and a curable resin, in which the blending ratio of the rutile-type titanium oxide is 30 to 600 parts by mass per 100 parts by mass of the curable resin, and does not contain an active energy ray-curable resin.

Patent Document 2 discloses a resin composition for a white insulating film that contains a binder polymer, crosslinked polymer particles containing a white pigment, a thermosetting resin, a compound having a radical polymerizable group in the molecule, a photopolymerization initiator, and a phosphorus-based flame retardant (paragraph [0212]). Patent Document 3 relates to an active energy ray-curable resin composition (paragraph [0001]).

JP 2017-220681 A Patent No. 5797279 Patent No. 6095310

However, the inventors' investigations revealed that, depending on the composition of the thermosetting white resin composition containing a white pigment, it may not be possible to obtain a cured product that has high light reflectance and excellent resistance to deterioration.

The object of the present invention, which has been devised in view of the above problems, is to provide a thermosetting white resin composition that produces a cured product having high light reflectance and excellent resistance to deterioration; and to provide a white cured product, a resin sheet, a reflective sheet, a printed wiring board, and a semiconductor device obtained using the thermosetting white resin composition.

As a result of intensive research to solve the above problems, the inventors have discovered that a thermosetting white resin composition containing (A) an epoxy resin and (C) a white inorganic pigment, containing (B) a phenolic curing agent as a curing agent, and having a boiling water absorption rate of the cured product of the composition of the present invention of 1.0 mass % or less, can solve the above problems and provide a cured product having high light reflectance and excellent resistance to deterioration, thereby completing the present invention.

That is, the present invention includes the following.
[1] A thermosetting white resin composition comprising (A) an epoxy resin, (B) a phenol-based curing agent, and (C) a white inorganic pigment, wherein the thermosetting white resin composition is heat-cured at 180°C for 90 minutes to obtain a cured product having a thickness of 50 µm, and when the cured product after molding is boiled for 1 hour, the boiling water absorption of the cured product after molding is 1.0 mass% or less.
[2] The thermosetting white resin composition according to [1], wherein the content of the component (B) is 20% by mass or less, based on 100% by mass of non-volatile components in the resin composition.
[3] The thermosetting white resin composition according to [1] or [2], wherein the component (C) is at least one selected from aluminum oxide, titanium oxide, zirconium oxide, magnesium oxide, barium titanate, zinc oxide, cerium oxide, and calcium carbonate.
[4] The thermosetting white resin composition according to any one of [1] to [3], wherein the content of the component (C) is 20% by mass or more, based on 100% by mass of non-volatile components in the resin composition.
[5] The thermosetting white resin composition according to any one of [1] to [4], wherein the content of component (A) is 1 to 50 mass%, the content of component (B) is 1 to 20 mass%, and the content of component (C) is 20 to 60 mass%, relative to 100 mass% of non-volatile components in the resin composition.
[6] The thermosetting white resin composition according to any one of [1] to [5], further comprising (D) an inorganic filler.
[7] The thermosetting white resin composition according to [6], wherein the content of the component (D) is 70% by mass or less, based on 100% by mass of non-volatile components in the resin composition.
[8] The thermosetting white resin composition according to [6] or [7], wherein the total content of the (C) component and the (D) component is 20 mass% or more, relative to 100 mass% of the non-volatile components in the resin composition.
[9] (E-1) The thermosetting white resin composition according to any one of [1] to [8], further comprising a thermoplastic resin having a weight average molecular weight (Mw) of 10,000 or more, which has a transmittance of 80% or more at a wavelength of 450 nm when formed into a film having a thickness of 20 μm.
[10] The thermosetting white resin composition according to any one of [1] to [9], wherein the degree of cure of the cured product obtained by thermal curing at 180°C for 30 minutes is 80% or more when measured by differential scanning calorimetry.
[11] The thermosetting white resin composition according to any one of [1] to [10], wherein a film-like cured product obtained by thermal curing at 180° C. for 90 minutes has a cure shrinkage rate of 0.5% or less in an in-plane direction.
[12] The thermosetting white resin composition according to any one of [1] to [11], having a reflectance of 90% or more for light with a wavelength of 460 nm.
[13] The thermosetting white resin composition according to any one of [1] to [12], which is for forming an insulating layer or a solder resist layer of a printed wiring board.
[14] The thermosetting white resin composition according to any one of [1] to [13], which is for light reflection.
[15] A white cured product of the thermosetting white resin composition according to any one of [1] to [14].
[16] A resin sheet comprising a support and a resin composition layer provided on the support, the resin composition layer comprising the thermosetting white resin composition according to any one of [1] to [14].
[17] The resin sheet according to [16], wherein the minimum melt viscosity of the resin composition layer is 5,000 poise or less.
[18] A reflecting sheet comprising a cured product of the thermosetting white resin composition according to any one of [1] to [14].
[19] A printed wiring board comprising the reflective sheet according to [18] as an interlayer insulating layer or a solder resist.
[20] A printed wiring board comprising an insulating layer containing a cured product of the thermosetting white resin composition according to any one of [1] to [14].
[21] A semiconductor device comprising the printed wiring board according to [19] or [20].

The present invention provides a thermosetting white resin composition that can produce a cured product having high light reflectance and excellent resistance to deterioration; and a white cured product, a resin sheet, a reflective sheet, a printed wiring board, and a semiconductor device obtained using the thermosetting white resin composition.

FIG. 1 is a schematic cross-sectional view showing an example of a printed wiring board. FIG. 2 is a top view diagrammatically showing a sheet-like cured product when calculating the degree of cure shrinkage and the cure shrinkage rate.

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

[Thermosetting white resin composition]
The thermosetting white resin composition of the present invention is a thermosetting white resin composition containing (A) an epoxy resin, (B) a phenol-based curing agent, and (C) a white inorganic pigment, and is hard to cure at 180° C. When the cured product obtained by heat curing for 90 minutes at 40 mm square is molded into a 40 mm square shape, the boiling water absorption of the molded cured product is 1.0% by mass or less when boiled for 1 hour. It is characterized by:

The thermosetting white resin composition of the present invention (hereinafter, simply referred to as the "resin composition of the present invention" or "resin composition") has the above-mentioned characteristics, and thus can produce a cured product having high light reflectance and excellent resistance to deterioration. Here, the deterioration resistance can be confirmed, for example, from the degree of decrease in light reflectance after exposure to a harsh environmental test and the degree of decrease in adhesion to a conductor (hereinafter, also referred to as "conductor adhesion"). In addition, the white cured product of the resin composition of the present invention has a low boiling water absorption value, and therefore tends to have excellent moisture resistance. Furthermore, the white cured product of the resin composition of the present invention also tends to have excellent properties such as insulation (especially insulation at a narrow pitch where L/S is less than 100 μm/100 μm, for example, insulation at a narrow pitch of 50 μm/50 μm or less, especially insulation at a narrow pitch of less than 15 μm/15 μm), low curing shrinkage, and low warpage. Therefore, the resin composition of the present invention provides a white cured product (insulating layer) with excellent properties, and contributes significantly to meeting the demand for white materials or light-reflecting materials used in modern printed wiring boards and semiconductor devices.

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

-(A) Epoxy resin-
The resin composition of the present invention contains an epoxy resin (A). The epoxy resin (A) means a curable resin having an epoxy group. The epoxy resin (A) may be used alone or in combination of two or more kinds.

(A) 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 (A), 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 (A) 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 (A), 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.

Preferred solid epoxy resins are bixylenol type epoxy resins, naphthalene type epoxy resins, naphthalene type tetrafunctional epoxy resins, naphthol novolac type epoxy resins, cresol novolac type epoxy resins, dicyclopentadiene type epoxy resins, trisphenol type epoxy resins, naphthol type epoxy resins, biphenyl type epoxy resins, naphthylene ether type epoxy resins, anthracene type epoxy resins, bisphenol A type epoxy resins, bisphenol AF type epoxy resins, phenol aralkyl type epoxy resins, tetraphenylethane type epoxy resins, phenolphthalimidine type epoxy resins, and phenolphthalein type epoxy resins.

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; "YX7760" (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.

Specific examples of liquid epoxy resins include "HP4032", "HP4032D", and "HP4032SS" (naphthalene type epoxy resins) manufactured by DIC Corporation; "828US", "828EL", "jER828EL", and "825" (bisphenol A type epoxy resins) manufactured by Mitsubishi Chemical Corporation; "jER807" and "1750" (bisphenol F type epoxy resins) manufactured by Mitsubishi Chemical Corporation; "jER152" (phenol novolac type epoxy resin) manufactured by Mitsubishi Chemical Corporation; "630", "630LSD", and "604" (glycidylamine type epoxy resins) manufactured by Mitsubishi Chemical Corporation; "ED-523T" (glycilol type epoxy resin) manufactured by ADEKA Corporation; "EP-3950L" and "EP-3980S" (glycidylamine type epoxy resins) manufactured by ADEKA Corporation; and "EP-4088S" (glycidylamine type epoxy resin) manufactured by ADEKA Corporation. Examples of such epoxy resins include "ZX1059" (a mixture of bisphenol A and bisphenol F epoxy resins) manufactured by Nippon Steel Chemical & Material Co., Ltd.; "EX-721" (glycidyl ester 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 Steel Chemical & Material Co., Ltd.; "ZX1658" and "ZX1658GS" (1,4-glycidylcyclohexane epoxy resin) manufactured by Nippon Steel Chemical & Material Co., Ltd.; "YX8000" (hydrogenated bisphenol A epoxy resin) manufactured by Mitsubishi Chemical Corporation; and "KF-101" (epoxy modified silicone resin) manufactured by Shin-Etsu Chemical Co., Ltd. These may be used alone or in combination of two or more types.

The (A) 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 solid epoxy resin and liquid epoxy resin is used as the (A) 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.

As the epoxy resin (A), one or more epoxy resins selected from (A-1) silicone-free epoxy resins and (A-2) silicone-containing epoxy resins can be used. A typical example of a silicone-containing epoxy resin is an epoxy-modified silicone resin, and a commercially available product thereof is "KF-101" manufactured by Shin-Etsu Chemical Co., Ltd. From the viewpoint of producing a cured product having excellent moisture resistance or preventing swelling of the cured product during reflow treatment, the epoxy resin (A) contains at least the component (A-1), and preferably the mass of the component (A-1) is greater than the mass of the component (A-2), more preferably the content of the component (A-2) is 10 mass% or less when the content of the non-volatile components of the resin composition is 100 mass%, and even more preferably the epoxy resin is composed of one or more selected from the component (A-1) (i.e., does not contain the component (A-2)).

The epoxy equivalent of the (A) 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 resin per equivalent of epoxy groups. This epoxy equivalent can be measured according to JIS K7236.

The weight average molecular weight (Mw) of the (A) 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 as a polystyrene-equivalent value by gel permeation chromatography (GPC).

In order to obtain the effects of the present invention more significantly, the content of the epoxy resin (A) is preferably 1% by mass or more, more preferably 5% by mass or more, even more preferably 10% by mass or more, 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, particularly preferably 30% by mass or less, when the non-volatile components in the resin composition are taken as 100% by mass. In order to obtain a cured product with excellent low cure shrinkage properties, the content of the epoxy resin (A) is preferably 40% by mass or less, more preferably 35% by mass or less, when the non-volatile components in the resin composition are taken as 100% by mass. Therefore, in a preferred embodiment, the content of the component (A) is 1 to 50% by mass, when the non-volatile components in the resin composition are taken as 100% by mass.

-(B) Phenol-based hardener-
The resin composition of the present invention contains a phenol-based curing agent (B). The curing agent has a function of reacting with the thermosetting resin to cure the resin composition. The phenol-based curing agent (B) may be used alone or in combination of two or more kinds.

(B) The phenol-based hardener is preferably 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.

More preferably, the (B) phenol-based curing agent is a bisphenol-based curing agent selected from a bisphenol compound having a fluorine atom, a bisphenol compound having an alicyclic structure, and a bisphenol compound having a fluorene skeleton. Even more preferably, the (B) phenol-based curing agent is a bisphenol-based curing agent selected from a bisphenol compound having a fluorine atom and a bisphenol compound having an alicyclic structure. Particularly preferably, the (B) phenol-based curing agent is bisphenol AF or bisphenol Z.

(B-1) Commercially available phenolic hardeners include, specifically, "BIS-AF" and "BIS-Z" manufactured by Central Glass Co., Ltd., "BisE" and "BisP-TMC" manufactured by Honshu Chemical Industry Co., Ltd., "BisA", "BisF", and "BisP-M" manufactured by Mitsui Fine Chemicals Co., Ltd., "BisP-AP", "BisP-MIBK", "BisP-B", "Bis-Z", "BisP-CP", "o,o'-BPF", "BisP-IOTD", "BisP-IBTD", "BisP-DED", and "BisP-BA" manufactured by Honshu Chemical Industry Co., Ltd. Examples of such products include "Bis-C", "Bis26X-A", "BisOPP-A", "BisOTBP-A", "BisOCHP-A", "BisOFP-A", "BisOC-Z", "BisOC-FL", "BisOFP-A", "BisOC-CP", "BisOCHP-Z", "Methylene Bis P-CR", "TM-BPF", "BisOC-F", "Bis3M6B-IBTD", "BisOC-IST", "BisP-IST", "BisP-PRM", "BisP-LV", and "BisP-CDE".

The reactive group equivalent of the (B) phenolic 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 compound per equivalent of reactive group. The reactive group is, for example, a phenolic hydroxyl group.

From the viewpoint of obtaining the effects of the present invention significantly, the content of the (B) phenol-based 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, and preferably 20% by mass or less, more preferably 15% by mass or less, and even more preferably 10% by mass or less, when the non-volatile components in the resin composition are taken as 100% by mass. From the viewpoint of producing a cured product having excellent resistance to deterioration of light reflectance, the content of the (B) phenol-based curing agent is preferably less than the content of the (A) component, and when the non-volatile components in the resin composition are taken as 100% by mass, it is more preferable that it is 15% by mass or less, and even more preferable that it is 10% by mass or less. Therefore, in a preferred embodiment, the content of the (B) component is 20% by mass or less, when the non-volatile components in the resin composition are taken as 100% by mass. In a more preferred embodiment, the content of the (B) component is 1 to 20% by mass, when the non-volatile components in the resin composition are taken as 100% by mass. Furthermore, in a more preferred embodiment, when the non-volatile components in the resin composition are taken as 100% by mass, the content of component (A) is 1 to 50% by mass, and the content of component (B) is 1 to 20% by mass.

-(C) White inorganic pigment-
The resin composition of the present invention contains a white inorganic pigment (C). In one embodiment, the white inorganic pigment (C) refers to an inorganic compound having a reflectance of 90% or more for light having a wavelength of 500 nm. The white inorganic pigment (C) does not contain the component (D) described below. The white inorganic pigment (C) has a function of improving light reflectance. The white inorganic pigment (C) may be used alone or in combination of two or more kinds.

(C) Examples of white inorganic pigments 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; white metal carbonates such as calcium carbonate, barium carbonate, magnesium carbonate, strontium carbonate, and lead carbonate; white metal sulfates such as barium sulfate, calcium sulfate, and lead sulfate; white metal phosphates such as zinc phosphate, titanium phosphate, zirconium phosphate, and zirconium tungstate phosphate; white metal borates such as aluminum borate; and white minerals such as cordierite, talc, clay, mica, hydrotalcite, and boehmite.

Among these, it is preferable that the white inorganic pigment (C) is one or more selected from aluminum oxide, titanium oxide, zirconium oxide, magnesium oxide, barium titanate, zinc oxide, cerium oxide, and calcium carbonate. Therefore, in a preferred embodiment, the component (C) is one or more selected from aluminum oxide, titanium oxide, zirconium oxide, magnesium oxide, barium titanate, zinc oxide, cerium oxide, and calcium carbonate.

The (C) white inorganic pigment preferably contains titanium oxide, and is also preferably made of titanium oxide. The titanium oxide may be any of rutile, anatase, and brookite types, but the rutile type is preferred from the viewpoint of further improving the light reflectance and suppressing the decrease in light reflectance after exposure to harsh environments. Titanium oxide obtained by a method such as a sulfuric acid method or a chlorine method can be used. The (C) white inorganic pigment material may be one type alone or a mixture of two or more types. The shape of the (C) white inorganic pigment may be, for example, irregular, crushed, scaly, or spherical, but is preferably spherical.

(C) 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 Kaisha; 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.

The specific surface area of the (C) 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.

The average particle size of the (C) white inorganic pigment is preferably 0.01 μm or more, more preferably 0.05 μm or more, and even more preferably 0.1 μm or more, from the viewpoint of significantly obtaining the desired effects of the present invention, and is preferably 10 μm or less, more preferably 5 μm or less, and even more preferably 2 μm or less.

The average particle size of the (C) 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 (C) white inorganic pigment is created on a volume basis using a laser diffraction/scattering particle size distribution measuring device, and the median diameter is used as the average particle size. The measurement sample can be prepared by weighing 100 mg of the (C) 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 (C) 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.

(C) The white inorganic pigment is preferably treated with a surface treatment agent from the viewpoint of improving moisture resistance and dispersibility. The surface treatment agent may be used alone or in any combination of two or more types. Examples of the surface treatment agent include silane coupling agents such as vinyl silane coupling agents, epoxy silane coupling agents, styryl silane coupling agents, (meth)acrylic silane coupling agents, amino silane coupling agents, isocyanurate silane coupling agents, ureido silane coupling agents, mercapto silane coupling agents, isocyanate silane coupling agents, acid anhydride silane coupling agents, alkyl silane coupling agents, and phenyl silane coupling agents. From the viewpoint of improving the deterioration resistance of the light reflectance, the surface treatment agent is preferably a surface treatment agent that does not contain nitrogen atoms (containing no nitrogen atoms), and more preferably a silane coupling agent that does not contain nitrogen atoms (containing no nitrogen atoms). Examples of silane coupling agents that do not contain nitrogen atoms include silane coupling agents selected from phenyl silane coupling agents, alkyl silane coupling agents, epoxy silane coupling agents, vinyl silane coupling agents, (meth)acrylic silane coupling agents, and styryl silane coupling agents.

Examples of phenyl silane coupling agents include phenyl trimethoxy silane and phenyl triethoxy silane. Examples of alkyl silane coupling agents include methyl trimethoxy silane, dimethyl dimethoxy silane, methyl triethoxy silane, dimethyl diethoxy silane, n-propyl trimethoxy silane, n-propyl triethoxy silane, hexyl trimethoxy silane, hexyl triethoxy silane, octyl triethoxy silane, decyl trimethoxy silane, and 1,6-bis (trimethoxy silyl) hexane. Examples of epoxy silane coupling agents include 2- (3,4-epoxy cyclohexyl) ethyl trimethoxy silane, 3-glycidoxy propyl methyl dimethoxy silane, 3-glycidoxy propyl trimethoxy silane, 3-glycidoxy propyl methyl diethoxy silane, and 3-glycidoxy propyl triethoxy silane.

Examples of vinyl-based silane coupling agents include vinyltrimethoxysilane and vinyltriethoxysilane. Examples of (meth)acrylic-based silane coupling agents include 3-methacryloxypropylmethyldimethoxysilane, 3-methacryloxypropyltrimethoxysilane, 3-methacryloxypropylmethyldiethoxysilane, 3-methacryloxypropyltriethoxysilane, and 3-acryloxypropyltrimethoxysilane. Examples of styryl-based silane coupling agents include p-styryltrimethoxysilane.

Commercially available surface treatment agents include, for example, Shin-Etsu Chemical Co., Ltd.'s "KBM-103" and "KBE-103" (phenyl silane coupling agents); "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" (alkyl silane coupling agents); and "KBM-1003" and "KBE-1003" (vinyl silane coupling agents). ); "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); octenyltrimethoxysilane "KBM-1083" manufactured by Shin-Etsu Chemical Co., Ltd.; coupling agent "Plenact" manufactured by Ajinomoto Fine-Techno Co., Ltd., etc.

From the viewpoint of improving the dispersibility of the (C) white inorganic pigment, 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 the (C) white inorganic pigment 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 amount of carbon per unit surface area of the white inorganic pigment (C). From the viewpoint of improving the dispersibility of the white inorganic pigment (C), the amount of carbon per unit surface area of the white inorganic pigment (C) 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 an increase in the melt viscosity of the resin varnish and the melt viscosity in the sheet form, it is preferably 1 mg/m ² or less, more preferably 0.8 mg/m ² or less, and even more preferably 0.5 mg/m ² or less.

The amount of carbon per unit surface area of the (C) white inorganic pigment can be measured after the surface-treated (C) 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 (C) white inorganic pigment that has been surface-treated with a surface treatment agent, and ultrasonic cleaning is performed at 25°C for 5 minutes. After removing the supernatant and drying the solids, the amount of carbon per unit surface area of the (C) 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.

In order to obtain the effects of the present invention more significantly, the content of the white inorganic pigment (C) is preferably 20% by mass or more, more preferably 21% by mass or more, and even more preferably 25% by mass or more, and is preferably 60% by mass or less, more preferably 58% by mass or less, and even more preferably 55% by mass or less, when the non-volatile components in the resin composition are taken as 100% by mass. Therefore, in a preferred embodiment, the content of the (C) component is 20 to 60% by mass, when the non-volatile components in the resin composition are taken as 100% by mass. In a more preferred embodiment, when the non-volatile components in the resin composition are taken as 100% by mass, the content of the (A) component is 1 to 50% by mass, the content of the (B) component is 1 to 20% by mass, and the content of the (C) component is 20 to 60% by mass.

-(D) Inorganic filler-
The resin composition of the present invention may contain an inorganic filler (D) as an optional component. Therefore, in a preferred embodiment, the resin composition of the present invention contains an inorganic filler (D). The inorganic filler (D) may be used alone or in combination of two or more kinds.

(D) An example of the inorganic filler is silica. Examples of silica include amorphous silica, fused silica, crystalline silica, synthetic silica, and hollow silica. In addition, spherical silica is preferred as the (D) inorganic filler. The specific surface area and average particle size of the (D) inorganic filler are the same as those of the (C) white inorganic pigment.

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; "Silfil NSS-3N", "Silfil NSS-4N", and "Silfil NSS-5N" manufactured by Tokuyama Corporation; and "SC2500SQ", "SO-C4", "SO-C2", and "SO-C1" manufactured by Admatechs.

From the viewpoint of improving moisture resistance and dispersibility, it is preferable that the (D) inorganic filler is treated with a surface treatment agent. Examples of the surface treatment agent include the same as the surface treatment agent for the (C) white inorganic pigment. The degree of surface treatment of the (D) inorganic filler with the surface treatment agent is the same as that of the (C) white inorganic pigment.

The content of the inorganic filler (D) is 0% by mass or more, and from the viewpoint of obtaining the effects of the present invention more significantly, when the non-volatile components in the resin composition are taken as 100% by mass, it is preferably 70% by mass or less, more preferably 50% by mass or less, even more preferably 40% by mass or less, and particularly preferably 35% by mass or less, and may be, for example, 1% by mass or more, 5% by mass or more, 10% by mass or more, 15% by mass or more, 20% by mass or more, etc. Therefore, in a preferred embodiment, the content of the (D) component is 70% by mass or less, when the non-volatile components in the resin composition are taken as 100% by mass.

From the viewpoint of suppressing cracks while maintaining high light reflectance, the total content of the (C) white inorganic pigment and the (D) inorganic filler is preferably 20% by mass or more, more preferably 30% by mass or more, even more preferably 40% by mass or more, 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, particularly preferably 70% by mass or less, when the non-volatile components in the resin composition are taken as 100% by mass. Therefore, in a preferred embodiment, the total content of the (C) component and the (D) component is 20% by mass or more, when the non-volatile components in the resin composition are taken as 100% by mass.

The mass ratio of (D) silica to (C) white inorganic pigment (mass of (D) component/mass of (C) component) is 0 or more, and from the viewpoint of suppressing cracks while maintaining high light reflectance, is preferably 0.1 or more, more preferably 0.2 or more, and particularly preferably 0.5 or more, and is preferably 20.0 or less, more preferably 10.0 or less, even more preferably 5.0 or less, and particularly preferably 2.0 or less or 1.5 or less. Therefore, in a preferred embodiment, the mass ratio of (D) component to (C) component is 20.0 or less.

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

(E) 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. Of these, resins selected from phenoxy resins, acrylic resins, and polyphenylene ether resins are preferred.

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

(E) The weight average molecular weight of the thermoplastic resin is preferably 8,000 or more, more preferably 10,000 or more, even more preferably 20,000 or more, and is preferably 100,000 or less, more preferably 70,000 or less, even more preferably 60,000 or less. The weight average molecular weight of the resin can be measured as a polystyrene-equivalent value by gel permeation chromatography (GPC).

The (E) thermoplastic resin is at least one selected from (E-1) a high molecular weight thermoplastic resin and (E-2) a low molecular weight thermoplastic resin. Here, the high molecular weight thermoplastic resin is a thermoplastic resin having a weight average molecular weight (Mw) of 10,000 or more. From the viewpoint of producing a cured product having high light reflectance, excellent conductor adhesion, and excellent insulation properties, it is preferable that the (E) thermoplastic resin contains at least one selected from (E-1) a high molecular weight thermoplastic resin, for example, "YX7200B35" manufactured by Mitsubishi Chemical Corporation. From the viewpoint of producing a cured product having excellent low cure shrinkage properties, it is preferable that the (E) thermoplastic resin contains at least one selected from (E-2) a low molecular weight thermoplastic resin, for example, "Noryl (registered trademark) SA90" manufactured by SABIC Corporation. From the viewpoint of producing a cured product with high light reflectance, excellent conductor adhesion, insulating properties, and low cure shrinkage, the (E) thermoplastic resin may contain (E-1) one or more types selected from high molecular weight thermoplastic resins and (E-2) one or more types selected from low molecular weight thermoplastic resins.

The (E) thermoplastic resin preferably has a transmittance of 80% or more at a wavelength of 450 nm when formed into a film having a thickness of 20 μm. Therefore, in a preferred embodiment, the resin composition of the present invention further contains (E-1) a thermoplastic resin having a weight average molecular weight (Mw) of 10,000 or more, which has a transmittance of 80% or more at a wavelength of 450 nm when formed into a film having a thickness of 20 μm.

The content of (E) thermoplastic resin is 0% by mass or more, and from the viewpoint of obtaining a significant effect of the present invention, when the non-volatile components in the resin composition are taken as 100% by mass, the content is preferably 50% by mass or less, more preferably 40% by mass or less, even more preferably 30% by mass or less, and particularly preferably 25% by mass or less, and is preferably 0.1% by mass or more, more preferably 1% by mass or more, even more preferably 5% by mass or more, and particularly preferably 10% by mass or more.

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

(F) Examples of the curing accelerator include phosphorus-based curing accelerators, imidazole-based curing accelerators, amine-based curing accelerators, guanidine-based curing accelerators, and metal-based curing accelerators. Among them, from the viewpoint of achieving a higher light reflectance, phosphorus-based curing accelerators and imidazole-based curing accelerators are preferred as (F) curing accelerators, with phosphorus-based curing accelerators being more preferred.

The phosphorus-based curing accelerator preferably contains one or more selected from the group consisting of phosphonium salts and phosphines, in order to achieve a higher light reflectance.

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-biphenyl 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)diphenyl ether; 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 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 octoate, tin octoate, zinc naphthenate, cobalt naphthenate, tin stearate, and zinc stearate.

The content of the (F) curing accelerator is 0% by mass or more, and from the viewpoint of obtaining the effects of the present invention significantly or from the viewpoint of controlling the curing time, when the non-volatile components in the resin composition are taken as 100% by mass, the content is preferably 5% by mass or less, more preferably 3% by mass or less, even more preferably 1% by mass or less, and particularly preferably 0.8% by mass or less, for example, preferably 0.001% by mass or more, more preferably 0.01% by mass or more, even more preferably 0.05% by mass or more, and particularly preferably 0.1% by mass or more.

- (G) Other additives -
The resin composition of the present invention may further contain any additive as a non-volatile component. Examples of such additives include curing agents other than the (B) component, such as carbodiimide-based curing agents, acid anhydride-based curing agents, amine-based curing agents, benzoxazine-based curing agents, cyanate ester-based curing agents, and thiol-based curing agents. Among these, from the viewpoint of providing a cured product with excellent insulating properties, curing agents other than acid anhydride-based curing agents (for example, "Rikacid TH" manufactured by New Japan Chemical Co., Ltd.); photocurable components such as (meth)acrylic resins and radical polymerizable compounds, as well as diluents and photopolymerization initiators as assistants therefor; 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; urea silanes, etc. Examples of the suitable additives include adhesion improvers; adhesion imparting agents such as triazole-based adhesion imparting agents, tetrazole-based adhesion imparting agents, and triazine-based adhesion imparting agents; antioxidants such as hindered phenol-based antioxidants; fluorescent brightening agents such as stilbene derivatives; surfactants such as fluorine-based surfactants and silicone-based surfactants; flame retardants such as phosphorus-based flame retardants (e.g., phosphate ester compounds, phosphazene compounds, phosphinic acid compounds, and 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-based dispersants, polyoxyalkylene-based dispersants, acetylene-based dispersants, silicone-based dispersants, anionic dispersants, and cationic dispersants; and stabilizers such as borate-based stabilizers, titanate-based stabilizers, aluminate-based stabilizers, zirconate-based stabilizers, isocyanate-based stabilizers, carboxylic acid-based stabilizers, and carboxylic acid anhydride-based stabilizers. (G) Other additives may be used alone or in any combination of two or more kinds in any ratio. The content of (G) other additives can be appropriately set by a person skilled in the art. For example, the photocurable component and its auxiliary are usually contained in an amount that does not impair the thermosetting property of the resin composition of the present invention.

-(H) Organic solvent-
The resin composition of the present invention may further contain an arbitrary organic solvent as a volatile component in addition to the non-volatile components described above. As the (H) organic solvent, a known one may 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, 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, methyl methoxypropionate, etc. Examples of the organic solvent include ether ester solvents such as methyl lactate, ethyl lactate, and methyl 2-hydroxyisobutyrate; ether alcohol solvents such as 2-methoxypropanol, 2-methoxyethanol, 2-ethoxyethanol, propylene glycol monomethyl ether, and diethylene glycol monobutyl ether (butyl carbitol); amide solvents such as N,N-dimethylformamide, N,N-dimethylacetamide, and N-methyl-2-pyrrolidone; sulfoxide solvents such as dimethyl sulfoxide; nitrile solvents such as acetonitrile and propionitrile; aliphatic hydrocarbon solvents such as hexane, cyclopentane, cyclohexane, and methylcyclohexane; and aromatic hydrocarbon solvents such as benzene, toluene, xylene, ethylbenzene, and trimethylbenzene. The organic solvent (H) may be used alone or in combination of two or more in 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, 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.

In the present invention, the resin composition can be produced, for example, by adding and mixing components (A), (B), and (C), and, if necessary, components (D), (E), (F), (G), and (H) other additives, and organic solvent, in any order and/or all at once, to any preparation vessel. In addition, the temperature can be appropriately set during the process of adding and mixing each component, and heating and/or cooling can be performed temporarily or throughout. In addition, during or after the process of adding and mixing, the resin composition can be stirred or shaken using a stirring or shaking device such as a mixer to disperse it uniformly. In addition, degassing can be performed under low pressure conditions such as under vacuum at the same time as stirring or shaking.

As described above, the thermosetting white resin composition of the present invention containing (A) epoxy resin and (C) white inorganic pigment contains (B) phenolic curing agent as a curing agent, and the boiling water absorption of the cured product is 1.0 mass% or less, resulting in a cured product with high light reflectance and excellent deterioration resistance. In addition, the white cured product of the resin composition of the present invention also tends to have excellent moisture resistance. Furthermore, the white cured product of the resin composition of the present invention also tends to have excellent properties such as insulation, low cure shrinkage, and low warpage. Therefore, the resin composition of the present invention realizes the provision of a white cured product (insulating layer) with excellent properties, and significantly contributes to the demand for white materials or light reflecting materials used in recent printed wiring boards and semiconductor devices.

In one embodiment, the white cured product of the resin composition of the present invention is characterized by having a high light reflectance. For example, the cured product obtained by thermal curing at 180 ° C for 90 minutes has a reflectance Ref0 of 90% or more, preferably more than 95% for light with a wavelength of 460 nm. In one embodiment, the high light reflectance of the white cured product of the resin composition of the present invention is characterized by excellent resistance to deterioration. For example, the cured product obtained by thermal curing at 180 ° C for 90 minutes does not blister after a reflow test, and has a reflectance Ref1 of 90% or more for light with a wavelength of 460 nm. For example, the cured product obtained by thermal curing at 180 ° C for 90 minutes has a reflectance Ref2 of 90% or more for light with a wavelength of 460 nm after a heat resistance test. Here, reflectances Ref0, Ref1, and Ref2 respectively indicate the reflectance before the reflow test and heat resistance test, the reflectance after the reflow test, and the reflectance after the heat resistance test, and can be measured by the method described in the section <Evaluation of reflectance deterioration resistance - Measurement of reflectances Ref0, Ref1, and Ref2 and overall evaluation> below. In this way, the white cured product of the resin composition of the present invention has a high light reflectance in common before the reflow test, before the heat resistance test, after the reflow test, and after the heat resistance test, and the reflectance for light with a wavelength of 460 nm is 90% or more.

In one embodiment, the white cured product of the resin composition of the present invention is characterized by excellent conductor adhesion. For example, the cured product obtained by thermal curing at 180°C for 90 minutes has an adhesion strength S0 of 0.5 kgf/cm or more, preferably 0.8 kgf/cm or more. In one embodiment, the excellent conductor adhesion of the white cured product of the resin composition of the present invention is characterized by excellent deterioration resistance. For example, the cured product obtained by thermal curing at 180°C for 90 minutes has an adhesion strength S1 of 0.3 kgf/cm or more, preferably 0.7 kgf/cm or more after a high-temperature, high-humidity test. Here, the adhesion strengths S0 and S1 respectively indicate the adhesion strength before the high-temperature, high-humidity test and the adhesion strength after the high-temperature, high-humidity test, and can be measured by the method described in the section <Evaluation of Deterioration Resistance of Conductor Adhesion - Measurement and Evaluation of Adhesion Strengths S0 and S1> below. Thus, the white cured product of the resin composition of the present invention has excellent conductor adhesion both before and after the high-temperature, high-humidity test, and is 0.3 kgf/cm or more.

In one embodiment, the white cured product of the resin composition of the present invention tends to exhibit the characteristic of excellent insulation. For example, the cured product obtained by thermal curing at 180 ° C. for 90 minutes has a resistance value Res0 between lines with a very narrow pitch (L / S: 10 μm / 10 μm) of 1 × 10 ⁶ Ω or more, preferably 1 × 10 ⁷ Ω or more. In one embodiment, the excellent insulation of the white cured product of the resin composition of the present invention exhibits the characteristic of excellent deterioration resistance. For example, the cured product obtained by thermal curing at 180 ° C. for 30 minutes has a resistance value Res1 after a high temperature and high humidity test of 1 × 10 ⁷ Ω or more, preferably 1 × 10 ⁸ Ω or more. Here, the resistance values Res0 and Res1 respectively indicate the adhesion strength before the high temperature and high humidity test and the insulation resistance value after the high temperature and high humidity test, and can be measured by the method described in the section <Evaluation of insulation - Measurement and evaluation of resistance values Res0 and Res1 -> described later. Thus, the white cured product of the resin composition of the present invention has excellent insulation properties, which are 1 x ¹⁰ Ω or more, both before and after the high-temperature, high-humidity test. The above-mentioned excellent insulation properties can be achieved even with a wide pitch of L/S: 100 μm/100 μm, but the present invention has the advantage that it can be achieved even with a pitch of less than L/S: 50 μm/50 μm or even with an even narrower pitch.

In addition, when the resin composition of the present invention is thermally cured at 180°C for 90 minutes to obtain a 50 μm thick cured product, which is then molded into a 40 mm square, the boiled water absorption rate when the molded cured product is boiled for 1 hour is 1.0 mass% or less, which is clear from the fact that the white cured product of the resin composition of the present invention also has excellent moisture resistance. The boiled water absorption rate is preferably 0.9 mass% or less, more preferably 0.8 mass% or less, and even more preferably 0.7 mass% or less, 0.6 mass% or less, 0.5 mass% or less, or 0.4 mass% or less. The boiled water absorption rate can be measured by the method described in the section <Evaluation of moisture resistance - Measurement of boiled water absorption rate> below. The boiled water absorption rate can be controlled, for example, by the content of the (C) component and the (D) component.

In one embodiment, the resin composition of the present invention tends to produce a white cured product with excellent low cure shrinkage. For example, the cure shrinkage rate s' in the in-plane direction of a film-shaped cured product obtained by heat-curing the resin composition of the present invention at 180°C for 90 minutes is 0.5% or less, preferably 0.4% or less. The cure shrinkage rate s' in the in-plane direction can be measured by the method described in the section <Evaluation of low cure shrinkage - Measurement of cure shrinkage rate> below. Therefore, in a preferred embodiment, a thermosetting white resin composition is provided in which the cure shrinkage rate in the in-plane direction of a film-shaped cured product heat-cured at 180°C for 90 minutes is 0.5% or less. The cure shrinkage rate can be controlled, for example, by the content of the (A), (C), and (D) components or the content of the (meth)acrylic resin.

In one embodiment, the resin composition of the present invention tends to produce a white cured product with excellent low warpage. For example, when the resin composition of the present invention is thermally cured at 180°C for 90 minutes, the absolute value of the amount of warpage of the resulting white cured product is less than 20 mm, preferably less than 10 mm. The amount of warpage can be measured by the method described in the section <Evaluation of low warpage - Measurement and evaluation of amount of warpage> below.

The resin composition of the present invention is preferably adjusted so that the degree of cure of the cured product obtained by thermal curing at 180°C for 30 minutes is 80% or more when the cured product is measured by differential scanning calorimetry. Therefore, in a preferred embodiment, a thermosetting white resin composition is provided in which the degree of cure of the cured product obtained by thermal curing at 180°C for 30 minutes is 80% or more when the cured product is measured by differential scanning calorimetry. The degree of cure can be controlled, for example, by selecting the (F) component and its content.

The thermosetting white resin composition of the present invention can provide a white cured product having a high light reflectance. Furthermore, a white cured product having excellent resistance to deterioration 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 (resin composition for forming a solder resist layer). 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 insulating layers of printed wiring boards, particularly for interlayer insulation. Therefore, the resin composition of the present invention can be suitably used as a resin composition for forming an interlayer insulation layer.

[Resin sheet]
The resin sheet of the present invention comprises a support and a resin composition layer provided on the support, the resin composition layer including the thermosetting white resin composition of the present invention.

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.

The resin composition layer preferably has a minimum melt viscosity of 5000 poise or less, more preferably 2000 poise or less, even more preferably 1000 poise or less, and particularly preferably 500 poise or less. Therefore, in a preferred embodiment, a resin sheet is provided in which the resin composition layer has a minimum melt viscosity of 5000 poise or less.

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 dissolving the liquid resin composition in an organic solvent or by applying the resin varnish to a support using a die coater or the like, and then drying the varnish to form a resin composition layer.

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

Drying may be performed by known methods such as heating or blowing hot air. There are no particular limitations on the drying conditions, but drying is performed so that the content of organic solvent in the resin composition layer is 10% by mass or less, preferably 5% by mass or less. Although it varies depending on the boiling point of the organic solvent in the resin composition (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.

The resin composition of the present invention used in the resin composition layer has a low melt viscosity and therefore has excellent flexibility. Therefore, the resin sheet exhibits the property of having excellent flexibility. Specifically, when the resin sheet is folded 180° along an axis having a diameter of 1 mm so that the support is on the inside, cracking of the resin sheet is suppressed.

[White cured product]
The white cured product of the present invention is a cured product of the thermosetting white resin composition of the present invention, and is usually 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 white thermosetting 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 such as a light emitting diode (LED) is disposed on a surface 31 of the reflective sheet 3.

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 for light having a wavelength of 460 nm is preferably 90% or more, and more preferably 92% 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 a heat resistance test treatment. For example, the reflectance for light having a wavelength of 460 nm after a heat resistance test treatment is preferably 90% or more, more preferably 91% or more, and even more preferably 92% or more. The upper limit of the reflectance after a heat resistance test treatment can be 100% or less. The reflectance and the reflectance after a heat resistance test treatment can be measured, for example, using a multichannel spectrometer ("MCPD-7700" manufactured by Otsuka Electronics Co., Ltd.).

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); 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 substrate and the resin sheet can be laminated, for example, by heat-pressing the resin sheet onto the substrate from the support side. Examples of the member for heat-pressing the resin sheet onto 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 conform to the surface irregularities of the substrate.

The substrate and the resin sheet may be laminated 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 resin composition of the present invention can also be used to form an insulating layer contained in a printed wiring board. In this case, the resin composition of the present invention is used to form an insulating layer formed in the above-mentioned method for producing a printed wiring board. The resin composition of the present invention can also be used to form a solder resist layer of a printed wiring board. In this case, the resin composition of the present invention is used to form a solder resist layer formed in the above-mentioned method for producing a printed wiring board. The above-mentioned reflective sheet may form a part or all of an interlayer insulating layer or a solder resist. Therefore, in a preferred embodiment, a printed wiring board is provided that includes a reflective sheet as an interlayer insulating layer or a solder resist. The techniques for forming an insulating layer and the techniques for forming a solder resist layer are widely known in the art, and the resin composition of the present invention can be applied to any of these methods and techniques.

[Semiconductor device]
The semiconductor device of the present invention includes the printed wiring board of the present invention. The semiconductor device of the present invention may include an insulating layer containing a cured product of the resin composition layer of the present invention. Examples of such semiconductor devices include a printed wiring board itself, a semiconductor chip package, a multi-chip package, a package-on-package, a wafer-level package, a panel-level package, and a system-in-package.

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

The present invention will be specifically explained below with reference to examples. The present invention is not limited to these examples. In the following, "parts" and "%" representing amounts mean "parts by mass" and "% by mass", respectively, unless otherwise specified. Unless otherwise specified, the temperature and pressure conditions are room temperature (25°C) and atmospheric pressure (1 atm).

--Examples 1 to 6 and Comparative Examples 1 to 4--
Examples and comparative examples of the resin composition containing a component selected from the group consisting of component (A), component (B), and component (C) are illustrated below.

[Example 1]
(1) Preparation of Resin Varnish 4 parts of silicone-free epoxy resin a1a as component (A-1) (liquid bisphenol A type epoxy resin "jER828EL" manufactured by Mitsubishi Chemical Corporation, epoxy equivalent: 180 g/eq.), 4 parts of silicone-free epoxy resin a1b as component (A-1) (solid fluorine atom-containing epoxy resin "YX7760" manufactured by Mitsubishi Chemical Corporation, epoxy equivalent: 245 g/eq.), and 20 parts of thermoplastic resin e1 as component (E-1) (biphenyl skeleton- and cyclohexane skeleton-containing phenoxy resin "YX7200B35" manufactured by Mitsubishi Chemical Corporation, weight average molecular weight (Mw): 30,000, methyl ethyl ketone (MEK) solution with non-volatile components of 35% by mass) were dissolved in 8 parts of MEK by heating with stirring. The thermoplastic resin e1 was formed into a film having a thickness of 20 μm, and the transmittance of light having a wavelength of 450 nm was measured, which was 88%. A commercially available bar coater was used for the film formation, and a commercially available spectrophotometer (multichannel spectrometer "MCPD-7700" manufactured by Otsuka Electronics Co., Ltd.) was used for the transmittance measurement.

To this was added a white inorganic pigment c as component (C) (rutile-type titanium oxide "PX3788" manufactured by Sakai Chemical Industry Co., Ltd., treated with phenylsilane "KBM-103" manufactured by Shin-Etsu Chemical Co., Ltd., average particle size: 0.26 μm, specific surface area: 13.2 m2 ⁾ . /g, reflectance to light with a wavelength of 460 nm: 99%, reflectance to light with a wavelength of 500 nm: 99%), 10 parts of an inorganic filler d as a component (D) (spherical silica "SO-C2" manufactured by Admatechs Co., Ltd., treated with methacrylic silane "KBM-503" manufactured by Shin-Etsu Chemical Co., Ltd., average particle size 0.5 μm, reflectance to light with a wavelength of 500 nm: about 80%), 4 parts of a solution of a phenolic curing agent ba as a component (B) (a solution in which bisphenol AF "BIS-AF" manufactured by Central Glass Co., Ltd. was adjusted to 50% by mass of non-volatile components with MEK), and 0.2 parts of a curing accelerator as a component (phosphorus-based catalyst "TBP-DA" manufactured by Hokko Chemical Industry Co., Ltd.) were mixed and uniformly dispersed in a high-speed rotating mixer. In this way, a resin varnish (non-volatile content: 61.8% by mass) of a resin composition containing the components (A), (B) and (C) was prepared. The resin varnish prepared in this way is also referred to as "resin varnish A".

(2) Preparation of resin sheet A PET film with a release layer ("PET501010" manufactured by Lintec Corporation, thickness: 38 μm) was prepared as a support. The above-mentioned resin varnish A was uniformly applied onto the release layer of this support so that the thickness of the resin composition layer after drying was 50 μm. Then, it was heated at 80 ° C. for 4 minutes. As a result, a resin sheet having a support and a resin composition layer having a thickness of 50 μm was obtained. The resin sheet prepared in this manner is also called "thermosetting resin sheet B1".

In addition, when the resin composition layer of the thermosetting resin sheet B1 obtained in Example 1 was thermally cured at 180°C for 30 minutes to obtain a cured product, the degree of cure of the cured product was confirmed to be 88% when measured by differential scanning calorimetry using a differential scanning calorimeter (Hitachi High-Tech Science Corporation, "DSC7020"). Similarly, in Examples 2 to 6 and Comparative Example 3, the degree of cure of the cured product of the resin composition layer was confirmed to be 80% or more, while in Comparative Examples 1 and 2, the degree of cure was confirmed to be less than 80%.

(3) Evaluation Using the thermosetting resin sheet B1, various measurements and evaluations described later in the section "Measurement method and evaluation method" were carried out.

[Example 2]
Instead of 4 parts of the solution of the phenolic curing agent ba as the component (B), 4 parts of a solution of the phenolic curing agent bb (a solution of bisphenol Z "BIS-Z" manufactured by Central Glass Co., Ltd. adjusted to 50% by mass of non-volatile components with MEK) was used. Except for the above, a resin varnish A was prepared in the same manner as in Example 1, a thermosetting resin sheet B1 was produced, and an evaluation was performed using the thermosetting resin sheet B1.

[Example 3]
Instead of 4 parts of silicone-free epoxy resin a1a and 4 parts of silicone-free epoxy resin a1b as the component (A-1), 4 parts of silicone-free epoxy resin a1c (hydrogenated liquid epoxy resin "YX8000" manufactured by Mitsubishi Chemical Corporation, epoxy equivalent: 205 g/eq.) and 4 parts of silicone-free epoxy resin a1d (biphenyl-type epoxy resin "YX4000H" manufactured by Mitsubishi Chemical Corporation, epoxy equivalent: 195 g/eq.) were used. Except for the above, resin varnish A was prepared in the same manner as in Example 1, and a thermosetting resin sheet B1 was produced, and evaluation was performed using the thermosetting resin sheet B1.

[Example 4]
Instead of 20 parts of the thermoplastic resin e1 (non-volatile component 35% by mass) as the (E-1) component, 7 parts of the thermoplastic resin e2 (SABIC's low molecular weight polyphenylene ether "Noryl (registered trademark) SA90", molecular weight: 1700, non-volatile component 100% by mass) as the (E-2) component was used. Except for the above, the resin varnish A was prepared in the same manner as in Example 1, and the thermosetting resin sheet B1 was produced and evaluated using the thermosetting resin sheet B1. The thermoplastic resin e2 was formed into a film with a thickness of 20 μm, and the transmittance of light with a wavelength of 450 nm was measured, which was 85%.

[Example 5]
The amount of the white inorganic pigment c as the component (C) was changed from 10 parts to 16 parts, and the amount of the inorganic filler d as the component (D) was changed from 10 parts to 16 parts. Except for the above, the resin varnish A was prepared in the same manner as in Example 1, and the thermosetting resin sheet B1 was produced and evaluated using the thermosetting resin sheet B1.

[Example 6]
Instead of 10 parts of white inorganic pigment c as component (C) and 10 parts of inorganic filler d as component (D), 20 parts of white inorganic pigment c was used. That is, the amount of component (C) was increased, and component (D) was not used. Except for the above, resin varnish A was prepared in the same manner as in Example 1, a thermosetting resin sheet B1 was produced, and evaluation was performed using the thermosetting resin sheet B1.

[Comparative Example 1]
Instead of 4 parts of the solution of the phenol-based curing agent ba as the component (B), 4 parts of a solution of an acid anhydride-based curing agent as the component (B') (a solution of "Rikacid TH" (1,2,3,6-tetrahydrophthalic anhydride) manufactured by New Japan Chemical Co., Ltd., adjusted to 50% by mass of non-volatile components with MEK) was used. Except for the above, resin varnish A was prepared in the same manner as in Example 1, a thermosetting resin sheet B1 was produced, and evaluation was performed using the thermosetting resin sheet B1.

[Comparative Example 2]
Instead of 4 parts of the silicone-free epoxy resin a1a and 4 parts of the silicone-free epoxy resin a1b as the component (A-1), 4 parts of the silicone-free epoxy resin a1a as the component (A-1) and 4 parts of a silicone-containing epoxy resin (liquid epoxy-modified silicone resin "KF-101" manufactured by Shin-Etsu Chemical Co., Ltd., epoxy equivalent: 350 g/eq.) as the component (A-2) were used. That is, instead of 4 parts of the silicone-free epoxy resin a1b as a part of the epoxy resin (A), a silicone-containing epoxy resin was used. Except for the above, a resin varnish A was prepared in the same manner as in Example 1, a thermosetting resin sheet B1 was produced, and an evaluation was performed using the thermosetting resin sheet B1.

[Comparative Example 3]
Instead of 10 parts of white inorganic pigment c as component (C) and 10 parts of inorganic filler d as component (D), 20 parts of inorganic filler d were used. That is, the amount of component (D) was increased, and component (C) was not used. Except for the above, resin varnish A was prepared in the same manner as in Example 1, a thermosetting resin sheet B1 was produced, and evaluation was performed using the thermosetting resin sheet B1.

[Comparative Example 4]
(1) Preparation of resin varnish 3 parts of silicone-free epoxy resin a1e (biphenyl-type epoxy resin "NC3000H" manufactured by Nippon Kayaku Co., Ltd., epoxy equivalent: 272 g/eq.) as component (A-1), 2 parts of silicone-free epoxy resin a1f (tetrakishydroxyphenylethane-type epoxy resin "jER1031S" manufactured by Mitsubishi Chemical Corporation, epoxy equivalent: 200 g/eq.) as component (A-1), 10 parts of acrylate (bisphenol A-type epoxy acrylate "ZAR-2000" manufactured by Nippon Kayaku Co., Ltd., acid value: 99 mg KOH/g, non-volatile content 70% by mass) as component (G-1), and 1 part of diluent (dipentaerythritol hexaacrylate "DPHA" manufactured by Nippon Kayaku Co., Ltd., acrylic group equivalent: 96 g/eq.) as component (G-2) were dissolved by heating with stirring in 6 parts of MEK and 10 parts of ethyl diglycol acetate.

4 parts of white inorganic pigment c as component (C), 4 parts of inorganic filler d as component (D), and 0.04 parts of a photopolymerization initiator (BASF's "Irgacure 819" (bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide)) as component (G-3) were mixed thereto and uniformly dispersed in a high-speed rotating mixer. This produced the resin varnish of Comparative Example 4.

(2) Preparation of resin sheet A PET film with a release layer ("PET501010" manufactured by Lintec Corporation, thickness: 38 μm) was prepared as a support. The resin varnish of Comparative Example 4 was uniformly applied onto the release layer of this support so that the thickness of the photosensitive resin composition layer after drying was 50 μm. Then, it was heated at 80 ° C. for 4 minutes. As a result, a resin sheet having a support and a photosensitive resin composition layer having a thickness of 50 μm was obtained. The resin sheet prepared in this manner is also called "photocurable resin sheet B2".

(3) Evaluation Photocurable resin sheet B2 was used to carry out various measurements and evaluations described in the "Measurement and Evaluation Methods" section below.

- Measurement and evaluation methods -
Next, various measurement and evaluation methods will be described.
<Evaluation of flexibility - Measurement of minimum melt viscosity>
To evaluate flexibility, the minimum melt viscosity was measured as follows.
The support was peeled off from the thermosetting resin sheet B1 or photocurable resin sheet B2 (hereinafter, these are also collectively referred to simply as "resin sheet B") obtained in the examples and comparative examples, and 25 sheets of the same resin composition layer were stacked to obtain a resin composition layer laminate having a thickness of 1.25 mm. Subsequently, the resin composition layer laminate was punched out with a diameter of 20 mm in the stacking direction to prepare a measurement sample. For the measurement sample prepared, the minimum melt viscosity (poise) was identified from the melt viscosity curve obtained by measuring the dynamic viscoelastic modulus using a dynamic viscoelasticity measuring device (manufactured by UBM, "Rheogel-G3000") from a starting temperature of 60 ° C. to 200 ° C. under the measurement conditions of a heating rate of 5 ° C./min, a measurement temperature interval of 2.5 ° C., a vibration frequency of 1 Hz, and a strain of 5 deg.

<Evaluation of Deterioration Resistance of Reflectance-Measurement of Reflectances Ref0, Ref1, and Ref2 and Overall Evaluation->
1. Measurement of reflectance Ref0 (reflectance after curing) (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, "R5715ES" manufactured by Matsushita Electric Works, Ltd.), to prepare 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 micro-etching agent ("CZ8100" manufactured by MEC Co., Ltd.). In this way, a plurality of inner layer circuit boards S subjected to undercoat treatment were prepared.

(2) Lamination of Resin Sheet The resin sheet B was laminated to both sides of the inner layer circuit board S using a batch type vacuum pressure laminator ("MVLP-500" manufactured by Meiki Seisakusho Co., Ltd. (now Japan Steel Works, Ltd.)) so that the resin composition layer was bonded. The lamination was performed according to the lamination conditions of 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) Curing of Resin Sheet B (3-1) Thermal Curing of Thermosetting Resin Sheet B1 The thermosetting resin sheets B2 laminated on both sides of the inner layer circuit board were cured in the following manner.
The support was peeled off from the thermosetting resin sheet B1 laminated on both sides of the inner layer circuit board, and the sheet was thermally cured at 180° C. for 90 minutes. As a result, the resin composition layer was almost completely cured. In this way, an evaluation sample C1 was obtained.

(3-2) Photocuring of Photocurable Resin Sheet B2 The photocurable resin sheet B2 laminated on both sides of the inner layer circuit board was cured in the following manner.
The support was peeled off from the photocurable resin sheet B2 laminated on both sides of the inner layer circuit board, and the exposed photosensitive resin composition layer was exposed to ultraviolet light at 100 mJ/ ^cm2 to be photocured. Then, a 1% by mass aqueous solution of sodium carbonate at 30°C as a developer was spray-developed on the entire surface of the photosensitive resin composition layer at a spray pressure of 0.2 MPa for 2 minutes. After the spray development, ultraviolet light was irradiated at 1 J/ ^cm2 , and a heat treatment was further performed at 190°C for 90 minutes. As a result, the photosensitive resin composition layer was almost completely cured. In this way, an evaluation sample C2 was obtained.

(4) Measurement Evaluation samples C1 and C2 were cut into a width of 50 mm and a length of 50 mm. Then, the reflectance Ref0 (%) of the obtained evaluation samples C1 and C2 with respect to light having a wavelength of 460 nm was measured using a multichannel spectrometer ("MCPD-7700" manufactured by Otsuka Electronics Co., Ltd.). This reflectance Ref0 indicates the reflectance of the evaluation sample after the resin composition layer is cured and before the evaluation sample is subjected to the reflow test and HAST test described below.

2. Measurement of reflectance Ref1 (reflectance after reflow test) (1) Reflow test Evaluation samples C1 and C2 were cut to obtain small pieces of 100 mm x 50 mm. These small pieces were passed twice through a reflow device ("HAS-6116" manufactured by Nippon Antom Co., Ltd.) that reproduces a solder reflow temperature of a peak temperature of 260°C, to obtain sample D (the reflow temperature profile conforms to IPC/JEDEC J-STD-020C).

(2) Measurement Thereafter, the reflectance Ref1 (%) of Sample D with respect to light having a wavelength of 460 nm was measured using a multichannel spectrometer ("MCPD-7700" manufactured by Otsuka Electronics Co., Ltd.). This reflectance Ref1 indicates the reflectance of the sample subjected to the reflow test. However, for Comparative Example 2, since swelling was observed in Sample D, the measurement of the reflectance was omitted. An example of the evaluation criteria for reflectance Ref1 is shown below.

Evaluation criteria for reflectance Ref1:
◎: Reflectance exceeds 90%. ○: Reflectance is 85% or more and less than 90%. △: Reflectance is 80% or more and less than 85%. ×: Reflectance is less than 80%. ×: Blistering occurs.

3. Measurement of reflectance Ref2 (reflectance after HAST test) (1) First HAST test (high temperature and high humidity test)
The evaluation samples C1 and C2 were cut to obtain small pieces of 100 mm×50 mm, which were then heated under high-temperature and high-humidity conditions of 125° C. and 85% relative humidity for 100 hours (first HAST test) to obtain sample E.

(2) Measurement After that, the reflectance Ref2 (%) of sample E with respect to light having a wavelength of 460 nm was measured using a multichannel spectrometer ("MCPD-7700" manufactured by Otsuka Electronics Co., Ltd.). This reflectance Ref2 indicates the reflectance of the sample subjected to the HAST test. An example of the evaluation criteria for the reflectance Ref2 is shown below.

Evaluation criteria for reflectance Ref2:
◎: Reflectance exceeds 90%. ○: Reflectance is 85% or more and less than 90%. △: Reflectance is 80% or more and less than 85%. ×: Reflectance is less than 80%.

4. Overall evaluation of reflectance The reflectance of the cured product of the resin composition obtained in the examples and comparative examples was evaluated overall based on the reflectances Ref0, Ref1, and Ref2 measured in the above 1 to 3. The evaluation criteria for the deterioration resistance of the reflectance of the cured product of the resin composition adopted this time are shown below.

Overall evaluation criteria for reflectance deterioration resistance:
⊚: All three excellent conditions of reflectance Ref0 exceeding 95%, Ref1 exceeding 90%, and Ref2 exceeding 90% are met, and no blistering occurs in the reflow test. ◯: Although at least one of the above three excellent conditions is not met, the three good conditions of reflectance Ref0 exceeding 90% and one or both of reflectances Ref1 and Ref2 being 85% or more and less than 90% are met, and no blistering occurs in the reflow test. △: At least one of the above three good conditions is not met, and none of the following three poor conditions are met, and no blistering occurs in the reflow test. ×: At least one of the three poor conditions of reflectance Ref0 less than 85%, Ref1 less than 80%, and Ref2 less than 80% are met, or the poor condition of blistering occurs in the reflow test is met.

As a result of the above evaluation, the reflectance of the cured resin compositions of the examples rated as "◎" and "◯" in the visible light region (wavelength range: 380 nm to 750 nm) was measured, and it was confirmed that the reflectance was 85% or higher for all of the evaluation samples C1, C2, sample D, and sample E.

<Evaluation of Deterioration Resistance of Conductor Adhesion - Measurement and Evaluation of Adhesion Strength S0, S1 ->
1. Obtaining adhesion strength S0 (adhesion strength before HAST test) (1) Copper foil preparation The shiny side of copper foil "3EC-III" (electrolytic copper foil, 35 μm) manufactured by Mitsui Mining & Smelting Co., Ltd. was immersed in MEC Etch Bond "CZ-8101" manufactured by MEC Corporation to roughen the copper surface (Ra value = 1 μm) and apply anti-rust treatment (CL8300). This copper foil is called CZ copper foil. It was then heated in an oven at 130°C for 30 minutes.

(2) Lamination of resin sheets The thermosetting resin sheet B1 and the photocurable resin sheet B2 were each laminated to the glossy surface of the CZ copper foil prepared in (1) above using a batch-type vacuum pressure laminator ("MVLP-500" manufactured by Meiki Seisakusho Co., Ltd.) so that the resin composition layer was bonded. The lamination was performed 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. As a result, a thermosetting resin sheet F1 with copper foil and a photocurable resin sheet F2 with copper foil were obtained.

(3) Curing of Resin Sheet F with Copper Foil (3-1) Thermal Curing of Thermosetting Resin Sheet F1 with Copper Foil The thermosetting resin sheet F1 with copper foil was cured by the following procedure.
The support was peeled off from the thermosetting resin sheet F1 with the copper foil, and the sheet was thermally cured at 180° C. for 90 minutes. As a result, the resin composition layer was almost completely cured. In this way, a cured product G1 with the copper foil was obtained.

(3-2) Photocuring of Photocurable Resin Sheet F2 with Copper Foil The photocurable resin sheet F2 with copper foil was cured by the following method.
The support was peeled off from the photocurable resin sheet F2 with copper foil, and the exposed photosensitive resin composition layer was exposed to ultraviolet light at 100 mJ/ ^cm2 to be photocured. Thereafter, a 1% by mass aqueous solution of sodium carbonate at 30°C as a developer was spray-developed on the entire surface of the photosensitive resin composition layer at a spray pressure of 0.2 MPa for 2 minutes. After the spray development, ultraviolet light was irradiated at 1 J/ ^cm2 , and then heat treatment was performed at 190°C for 90 minutes. As a result, the photosensitive resin composition layer was almost completely cured. In this way, a cured product G2 with copper foil was obtained.

(4) Adhesion to an internal circuit board Each of the cured products G1 and G2 with copper foil was adhered to both sides of an internal circuit board S using Aron Alpha Ex so that the cured product of the resin composition layer was bonded. Next, this adhesive was placed in a batch-type vacuum pressure laminator ("MVLP-500" manufactured by Meiki Seisakusho Co., Ltd.) and subjected to the same lamination conditions as described above. This resulted in flattening. In this way, an evaluation sample H containing, in this order, CZ copper foil, the cured product of the resin composition layer, the internal circuit board S, the cured product of the resin composition layer, and CZ copper foil was obtained.

(5) Measurement The evaluation sample H was cut into small pieces of 150 mm x 30 mm. A cutter was used to make a 10 mm wide and 100 mm long cut in the copper foil portion of the small piece, and one end of the copper foil was peeled off and gripped with a gripper (Autocom type testing machine "AC-50C-SL" manufactured by TSE Corporation). Using an Instron universal testing machine, the load when 35 mm was peeled off in the vertical direction at a speed of 50 mm/min at room temperature was measured in accordance with JIS C6481 to obtain an adhesion strength S0 (kgf/cm (=N/cm)). This adhesion strength S0 is the adhesion strength before the second HAST test described below.

2. Obtaining adhesion strength S1 (adhesion strength after HAST test) (1) Second HAST test (high temperature and high humidity test)
Evaluation Sample H was heated under high temperature and high humidity conditions of 130° C. and 85% relative humidity for 100 hours (second HAST test) to obtain Evaluation Sample I.

(2) Measurement Thereafter, the evaluation sample I was cut into small pieces of 150 mm × 30 mm, and the load was measured for each small piece in the same manner as in the measurement of the adhesion strength S0 described above to obtain an adhesion strength S1. This adhesion strength S1 is the adhesion strength after the second HAST test.

3. Overall evaluation of conductor adhesion deterioration resistance Based on the adhesion strengths S0 and S1 obtained in 1. to 2. above, the conductor adhesion deterioration resistance of the cured products of the resin compositions obtained in the Examples and Comparative Examples was evaluated overall. The evaluation criteria for conductor adhesion of the cured products of the resin compositions used this time are shown below.

Overall evaluation criteria for conductor adhesion deterioration resistance:
⊚: Meets two excellent conditions, that is, adhesion strength S0 is 0.8 kgf/cm or more and adhesion strength S1 is 0.7 kgf/cm or more. ◯: Does not meet at least one of the above two excellent conditions, but meets two good conditions, that is, adhesion strength S0 is 0.5 kgf/cm or more and adhesion strength S1 is 0.3 kgf/cm or more. Δ: Does not meet at least one of the above three good conditions, and does not meet all of the following three poor conditions. ×: Meets at least one of the two poor conditions, that is, adhesion strength S0 is less than 0.3 kgf/cm and adhesion strength S1 is less than 0.2 kgf/cm.

<Evaluation of insulation properties-measurement and evaluation of resistance values Res0 and Res1->
1. Measurement of Resistance Res0 (Insulation Resistance before HAST Test) (1) Roughening Treatment The evaluation samples C1 and C2 were first immersed in a swelling solution (Atotech Japan's "Swelling Dip Securigant P", an aqueous solution of sodium hydroxide containing diethylene glycol monobutyl ether) at 60° C. for 10 minutes, then in a roughening solution (Atotech Japan's "Concentrate Compact P", an aqueous solution of KMnO ₄ : 60 g/L, NaOH: 40 g/L) at 80° C. for 20 minutes, and finally in a neutralizing solution (Atotech Japan's "Reduction Solution Securigant P", an aqueous solution of sulfuric acid) at 40° C. for 5 minutes. Then, the samples were dried at 80° C. for 30 minutes. In this way, a substrate subjected to roughening treatment was obtained.

(2) Formation of electroless plating layer A conductor layer was formed on the roughened substrate by a semi-additive method. Specifically, the roughened substrate was first immersed in an electroless plating solution containing _PdCl2 at 40°C for 5 minutes, and then immersed in an electroless copper plating solution at 25°C for 20 minutes. After that, the substrate was heated at 150°C for 30 minutes to perform an annealing treatment. In this way, a substrate provided with a conductor layer was obtained.

(3) Lamination of dry film A dry film ("RY-5107" manufactured by Hitachi Chemical Co., Ltd.) was laminated on one side (the conductor layer side) of a substrate provided with a conductor layer using a batch type vacuum pressure laminator ("MVLP-500" manufactured by Meiki Seisakusho Co., Ltd.). The lamination was performed by reducing the pressure for 30 seconds to 13 hPa or less, and then pressing at 100°C and a pressure of 0.74 MPa for 30 seconds.

(4) Exposure Using an exposure machine (Ushio Inc.'s projection exposure machine "UX-2240SM"), the dry film was exposed (200 mJ) to form a comb-tooth pattern wiring (line/space (L/S) ratio: 10 μm/10 μm), and then developed using a 1% by mass aqueous solution of sodium carbonate.

(5) Formation of electroplated layer The substrate prepared in (4) was subjected to copper sulfate electroplating to form a conductor layer with a thickness of 5 μm, followed by annealing at 190° C. for 60 minutes.

(6) Formation of Wiring in a Comb-tooth Pattern The surface of the substrate obtained in (5) was washed to remove the dry film, and then etching was performed to form wiring in a comb-tooth pattern.

(7) Lamination of adhesive film The resin sheet B was laminated using a batch type vacuum pressure laminator ("MVLP-500" manufactured by Meiki Seisakusho Co., Ltd.) so that the resin composition layer was bonded to the comb-tooth pattern wiring of the substrate obtained in (6). The lamination was performed by reducing the pressure for 30 seconds to 13 hPa or less, and then pressing at 100°C and a pressure of 0.74 MPa for 30 seconds. In this way, a substrate J provided with the resin sheet B was obtained.

(8) Curing of Resin Sheet B (8-1) Thermal Curing of Thermosetting Resin Sheet B1 The thermosetting resin sheet B1 provided on the substrate J was cured in the following manner.
The support was peeled off from the thermosetting resin sheet B1 provided on the substrate J to expose the resin composition layer. Then, the resin composition layer was thermally cured at 190° C. for 90 minutes. As a result, the resin composition layer was almost completely cured to form an insulating layer. In this way, the substrate K1 on which the insulating layer was formed was obtained.

(8-2) Photocuring of Photocurable Resin Sheet B2 The photocurable resin sheet B2 provided on the substrate J was cured by the following method.
The support was peeled off from the photocurable resin sheet B2 provided on the substrate J to expose the resin composition layer. Then, the exposed photosensitive resin composition layer was exposed to ultraviolet light at 100 mJ/ ^cm2 to be photocured. Then, a 1% by mass aqueous solution of sodium carbonate at 30°C as a developer was spray-developed on the entire surface of the photosensitive resin composition layer at a spray pressure of 0.2 MPa for 2 minutes. After the spray development, ultraviolet light was irradiated at 1 J/ ^cm2 , and a heat treatment was further performed at 190°C for 90 minutes. As a result, the photosensitive resin composition layer was almost completely cured. In this way, a substrate K2 on which an insulating layer was formed was obtained.

(9) Preparation of test pieces for measuring resistance value The resin on both ends of the comb-tooth pattern of the substrates K1 and K2 obtained in (8) was scraped off to expose the copper, and copper wires were soldered to 10 locations as electrodes. The substrates were then washed with dichloromethane and methanol in that order, and then dried in an oven at 130° C. for 30 minutes. In this manner, test piece L0 was obtained.

(10) Measurement The resistance value Res0 between each line of the test piece L0 was measured using a resistance measuring device (insulation resistance measuring device "ECM-100" manufactured by J-RAS). This resistance value Res0 is the insulation resistance value before the third HAST test described below. The average value of the resistance value Res0 is shown in Tables 1 and 2.

2. Measurement and evaluation of resistance value Res1 (resistance value after HAST test) (1) Third HAST test The test piece L0 was subjected to a high temperature and high humidity environment at a temperature of 130° C. and a relative humidity of 85% using a HAST tester ("PM422" manufactured by Kusumoto Chemical Industries, Ltd.), and a voltage of 3.3 V was applied to both ends of the electrodes. After 200 hours, the test piece (hereinafter also referred to as "test piece L1") after the HAST test (third HAST test) was taken out.
(2) Measurement The resistance value Res1 of the test piece L1 was measured in the same manner as the resistance value Res0 of the test piece L0. This resistance value Res1 is the insulation resistance value after the above-mentioned third HAST test. The average value of the resistance value Res1 is shown in Tables 1 and 2.
(3) Evaluation The resistance value Res1 was evaluated according to the following evaluation criteria.
Evaluation criteria for resistance value Res1:
◯: Less than three wirings have a resistance value Res1 of less than 1×10 ⁷ Ω. ×: Three or more wirings have a resistance value Res1 of less than 1×10 ⁷ Ω.

(4) Confirmation of Inter-Line Insulation Film Thickness After measuring the resistance value Res1, the cross section of the test piece L1 was observed with an optical microscope, and it was confirmed that the inter-line insulation film thickness was 4 to 6 μm.

<Evaluation of moisture resistance - Measurement of boiling water absorption rate>
(1) Preparation of Cured Product for Evaluation Resin sheet B, cut to a size of 240 mm square, was placed on a glass cloth-based epoxy resin double-sided copper-clad laminate ("R5715ES" manufactured by Matsushita Electric Works, Ltd., thickness: 0.7 mm, 255 mm square) so that the untreated surface of the support faced the glass cloth-based epoxy resin double-sided copper-clad laminate, and the four sides of the resin sheet B were fixed with polyimide adhesive tape (width 10 mm). In this way, a substrate M with resin sheet B fixed thereto was obtained.

(3) Hardening of Resin Sheet B (2-1) Thermal Hardening of Thermosetting Resin Sheet B1 The thermosetting resin sheet B1 fixed to the substrate M was hardened in the following manner.
The substrate M with the resin sheet B fixed thereto was placed in an environment at 190° C. for 90 minutes, and the resin composition layer was almost completely thermally cured. After removing the substrate M, the polyimide adhesive tape was peeled off in a room temperature atmosphere, and then the cured product of the resin composition layer was removed from the substrate together with the support. Then, the support was peeled off from the cured product. In this way, a sheet-shaped cured product N1 having a thickness of 50 μm was obtained.

(2-2) Photocuring of the Photocurable Resin Sheet B2 The photocurable resin sheet B2 fixed to the substrate M was cured by the following method.
The polyimide adhesive tape and the support were peeled off from the photocurable resin sheet F2 fixed to the substrate M, and the exposed photosensitive resin composition layer was exposed to ultraviolet light at 100 mJ/ ^cm2 to be photocured. Then, the entire surface of the photosensitive resin composition layer was spray-developed with a 1% by mass aqueous sodium carbonate solution at 30°C as a developer at a spray pressure of 0.2 MPa for 2 minutes. After the spray development, the layer was irradiated with ultraviolet light at 1 J/ ^cm2 , and then heated at 190°C for 90 minutes. As a result, the photosensitive resin composition layer was almost completely cured. Then, the sheet-shaped cured product placed on the substrate M was taken out. In this way, a sheet-shaped cured product N2 having a thickness of 50 μm was obtained.

(3) Measurement of boiling water absorption Each of the sheet-like cured materials N1 and N2 was cut into a 40 mm square test piece. The test piece was dried at 130° C. for 30 minutes and then weighed (the weighed mass was designated as A (g)).
Next, the test piece was immersed in boiled ion-exchanged water for 1 hour. Then, the test piece was immersed in ion-exchanged water at room temperature (25°C) for 1 minute. After that, the test piece was taken out, and water droplets on the surface were wiped off using a clean wiper (manufactured by Kuraray Kuraflex Co., Ltd.), and then weighed (the weighed mass was designated as B (g)). The boiled water absorption (mass%) of each of the five test pieces was calculated from the following formula. The boiled water absorption means the percentage of the mass increase after the test piece was immersed in boiling water for 1 hour relative to the mass of the test piece before immersion (JIS K6911-1995). The boiled water absorption is shown in Tables 1 and 2.
Boiling water absorption rate = ((B-A)/A) x 100

<Evaluation of low cure shrinkage - Measurement of cure shrinkage rate ->
(1) Preparation of polyimide film with resin sheet Resin sheet B was laminated on one side of a polyimide film (Ube Industries, Ltd., "Upilex (registered trademark) 25S", 25 μm thick, 240 mm square) using a batch-type vacuum pressure laminator (two-stage build-up laminator "CVP700" manufactured by Nikko Materials Co., Ltd.) so that the resin composition layer was bonded to the center of the smooth surface of the polyimide film. The lamination was performed by reducing the pressure for 30 seconds to 13 hPa or less, and then pressing at 100 ° C. and a pressure of 0.74 MPa for 30 seconds. As a result, a polyimide film with a resin sheet was obtained.

(2) Measurement of initial length L For the polyimide film with resin sheet, four through holes (diameter about 6 mm) were formed by punching from the support side of the resin sheet B at positions about 20 mm away from the four corners of the resin composition layer. These through holes are tentatively designated A, B, C, and D in a clockwise direction (see FIG. 2). Next, after peeling the support from the polyimide film with resin sheet, the distance L between the centers of the two through holes (L _AB , L _BC , L _CD , L _DA , L _AC , and L _BD shown in FIG. 2) was measured with a non-contact image measuring device (manufactured by Mitutoyo Corporation, Quick Vision, "QVH1X606-PRO III_BHU2G").

(3) Curing of Resin Sheet B (3-1) Curing of Thermosetting Resin Sheet B1 The thermosetting resin sheet B1 on the polyimide film was cured by the following procedure.
The polyimide film with resin sheet was placed so that the polyimide film surface faced a glass cloth-based epoxy resin double-sided copper-clad laminate (Matsushita Electric Works, Ltd. "R5715ES", 0.7 mm thick) of 255 mm size, and the four sides were fixed with polyimide adhesive tape (width 10 mm). Then, it was heated at 180 ° C for 90 minutes. As a result, the resin composition layer was almost completely thermally cured to become a cured layer. Thereafter, the laminate with the polyimide film with resin sheet fixed was taken out, the polyimide adhesive tape was peeled off, and then the polyimide film with the cured layer was removed from the laminate, and the cured layer was further peeled off from the polyimide film. This resulted in a sheet-like cured product O1.

(3-2) Photocuring of Photocurable Resin Sheet B2 The photocurable resin sheet B2 on the polyimide film was cured by the following method.
The support was peeled off from the polyimide film with the resin sheet, and the exposed photosensitive resin composition layer was exposed to ultraviolet light at 100 mJ/ ^cm2 to be photocured. Thereafter, a 1% by mass aqueous solution of sodium carbonate at 30°C as a developer was spray-developed on the entire surface of the photosensitive resin composition layer at a spray pressure of 0.2 MPa for 2 minutes. After the spray development, ultraviolet light was irradiated at 1 J/ ^cm2 , and then a heat treatment was performed at 190°C for 90 minutes. As a result, the photosensitive resin composition layer was almost completely cured to become a cured layer. Then, the cured layer was taken out together with the polyimide film, and the polyimide film was then peeled off. In this way, a sheet-shaped cured product O2 was obtained.

(4) Calculation of thermal curing shrinkage For each of the sheet-shaped cured materials O1 and O2, the distance L'(L' _AB , L' _BC , L' _CD , L' _DA , L' _AC , L' _BD ) between the centers of the two through holes formed in (2) above was measured using a non-contact image measuring device, in the same manner as the distance L.

The heat curing shrinkage s _AB of the distance L _AB between through holes A-B was calculated by the following formula: Here, as is clear from the formula, the heat curing shrinkage means the shrinkage after curing in the in-plane direction of the film-like cured product (the in-plane direction including the x-axis and y-axis shown in FIG. 2 ).
s _AB = (L _AB - L' _AB )/L _AB
Similarly, _the heat curing shrinkage rates _sBC , _sCD , _sDA , sAC and _sBD of the distances _LBC , _LCD , _LDA , _LAC and _LBD were determined.

Next, the heat curing shrinkage s' (%) of the cured material layer was calculated by the following formula: Here, the heat curing shrinkage means the shrinkage (percentage) after curing in the in-plane direction (the in-plane direction including the x-axis and y-axis shown in FIG. 2 ) of the film-like cured material, calculated by the following formula:
Heat curing shrinkage rate s'={(s _AB + s _BC + s _CD + s _DA + s _AC + s _BD )/6}×100

<Evaluation of low warpage --Measurement and evaluation of warpage amount-->
(1) Lamination of resin sheet The resin sheet B was laminated onto a SUS304 plate (hereinafter, simply referred to as "SUS plate") having a thickness of 0.2 mm and a thickness of 15 cm x 30 cm using a batch-type vacuum pressure laminator ("MVLP-500" manufactured by Meiki Seisakusho Co., Ltd.) so that the resin composition layer was bonded. The lamination was performed by reducing the pressure for 30 seconds to a pressure of 13 hPa or less, and then pressing for 30 seconds at 100 ° C. and a pressure of 0.74 MPa. This resulted in a SUS plate on which the resin sheet B was laminated. Here, the size of the resin sheet B on this SUS plate was 15 cm x 30 cm, the same as the SUS plate.

(2) Curing of Resin Sheet B (2-1) Curing of Thermosetting Resin Sheet B1 The thermosetting resin sheet B1 on the SUS plate was cured in the following manner.
The support was peeled off from the SUS plate on which the resin sheet B was laminated, and the plate was heated at 180° C. for 90 minutes. As a result, the resin composition layer was almost completely cured. The cured resin composition layer was then peeled off from the SUS plate. In this way, a sample P1 for warpage evaluation was obtained.

(2-2) Photocuring of Photocurable Resin Sheet B2 The photocurable resin sheet B2 on the SUS plate was cured according to the following procedure.
The support was peeled off from the SUS plate on which the resin sheet B was laminated, and the exposed photosensitive resin composition layer was exposed to ultraviolet light at 100 mJ/ ^cm2 to be photocured. Then, a 1% by mass aqueous solution of sodium carbonate at 30°C as a developer was spray-developed on the entire surface of the photosensitive resin composition layer at a spray pressure of 0.2 MPa for 2 minutes. After the spray development, ultraviolet light was irradiated at 1 J/ ^cm2 , and then heat treatment was performed at 190°C for 90 minutes. As a result, the photosensitive resin composition layer was almost completely cured. Then, the cured photosensitive resin composition layer was peeled off from the SUS plate. In this way, a sample P2 for warpage evaluation was obtained.

(3) Measurement of the amount of warpage The samples P1 and P2 for evaluating warpage were placed on a smooth table with the surface on the side where the central part was the convex part facing downward, and three of the four corners were fixed to the table. This resulted in the remaining corner being separated from the table. Next, the longest distance from the top surface of the table to the bottom surface of the remaining corner of the samples P1 and P2 for evaluating warpage was measured and used as the amount of warpage. The absolute value of the amount of warpage was evaluated according to the following evaluation criteria.

Warpage evaluation criteria:
◯: Absolute value of the amount of warping is less than 10 mm △: Absolute value of the amount of warping is 10 mm or more and less than 20 mm ×: Absolute value of the amount of warping is 20 mm or more

The results of Examples 1 to 6 and Comparative Examples 1 to 4 are shown in Tables 1 and 2. Table 2 follows Table 1.

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

Claims (18)

A thermosetting white resin composition comprising (A) an epoxy resin, (B) a phenol-based curing agent , and ( C) a white inorganic pigment , and further comprising or not comprising (D) an inorganic filler,
The component (B) is a bisphenol-based curing agent selected from a bisphenol compound having a fluorine atom, a bisphenol compound having an alicyclic structure, and a bisphenol compound having a fluorene skeleton,
The content of the component (A) is 10 to 35% by mass, relative to 100% by mass of the non-volatile components in the resin composition;
The content of the (C) component is 20 to 60 mass% relative to 100 mass% of the non-volatile components in the resin composition,
In the case where the component (D) is contained, the content of the component (D) is 20 to 40 mass% relative to 100 mass% of the non-volatile components in the resin composition,
A thermosetting white resin composition, in which a cured product having a thickness of 50 μm obtained by thermal curing at 180° C. for 90 minutes is molded into a 40 mm square, and the molded cured product has a boiling water absorption of 1.0 mass% or less when boiled for 1 hour. The thermosetting white resin composition according to claim 1, wherein the content of component (B) is 20% by mass or less, assuming that the non-volatile components in the resin composition are 100% by mass. The thermosetting white resin composition according to claim 1 or 2, wherein component (C) is at least one selected from aluminum oxide, titanium oxide, zirconium oxide, magnesium oxide, barium titanate, zinc oxide, cerium oxide, and calcium carbonate. The thermosetting white resin composition according to any one of claims 1 to 3 , wherein the content of component ( B) is 1 to 20 mass% based on 100 mass% of non-volatile components in the resin composition. 2. The thermosetting white resin composition according to claim 1 , wherein the total content of the component (C) and the content of the component (D) is 20% by mass or more, relative to 100% by mass of non-volatile components in the resin composition. The thermosetting white resin composition according to any one of claims 1 to 5, further comprising (E-1) a thermoplastic resin having a weight average molecular weight (Mw) of 10,000 or more, which has a transmittance of 80% or more at a wavelength of 450 nm when formed into a film having a thickness of 20 μm. The thermosetting white resin composition according to any one of claims 1 to 6 , wherein a degree of cure of a cured product obtained by thermal curing at 180°C for 30 minutes is 80% or more when measured by differential scanning calorimetry. 8. The thermosetting white resin composition according to claim 1, wherein a film-like cured product obtained by thermal curing at 180° C. for 90 minutes has a cure shrinkage rate of 0.5% or less in an in-plane direction. The thermosetting white resin composition according to any one of claims 1 to 8 , which has a reflectance of 90% or more for light with a wavelength of 460 nm. The thermosetting white resin composition according to any one of claims 1 to 9 , which is used for forming an insulating layer or a solder resist layer of a printed wiring board. The thermosetting white resin composition according to any one of claims 1 to 10 , which is for light reflection. A white cured product of the thermosetting white resin composition according to any one of claims 1 to 11 . A resin sheet comprising: a support; and a resin composition layer provided on the support, the resin composition layer comprising the thermosetting white resin composition according to any one of claims 1 to 11 . The resin sheet according to claim 13 , 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 thermosetting white resin composition according to any one of claims 1 to 11 . A printed wiring board comprising the reflective sheet according to claim 15 as an interlayer insulating layer or a solder resist. A printed wiring board comprising an insulating layer comprising a cured product of the thermosetting white resin composition according to any one of claims 1 to 11 . A semiconductor device comprising the printed wiring board according to claim 16 or 17 .

Images