Epoxy resin curing agents, epoxy resin formulations, bonding materials, conductive materials, thermally conductive materials, adhesives for camera modules, structural adhesives, matrix resins for fiber-reinforced plastics, impregnated and fixed materials, intermediate layer insulating films, film-type anti-welding materials, sealing sheets, conductive films, anisotropic conductive films, thermally conductive films, and methods for producing colored cured products.

Abstract

The invention relates to an epoxy resin curing agent containing: a core (A) containing a nitrogen-containing compound; and a layer (B) covering the core (A), in which, when the epoxy resin curing agent is stained with ruthenium tetroxide and osmium tetroxide and then observed by transmission electron microscopy to obtain a luminescence plot by image processing, the inner part of layer (B) has a luminescence region α, and the luminescence α is higher than the luminescence β at the outermost part of layer (B) and the luminescence γ at the boundary between layer (B) and core (A).

Description

Epoxy resin curing agents, epoxy resin compositions, sealing materials, conductive materials, thermally conductive materials, adhesives for camera modules, structural adhesives, matrix resins for fiber-reinforced plastics, impregnating adhesives, interlayer insulating films, film-type solder resists, sealing sheets, conductive films, anisotropically conductive films, thermally conductive films, and methods for producing dyed cured products

[0001] The present invention relates to an epoxy resin curing agent, an epoxy resin composition, an encapsulating material, an electrically conductive material, a thermally conductive material, an adhesive for camera modules, a structural adhesive, a matrix resin for fiber-reinforced plastics, an impregnating fixing material, an interlayer insulating film, a film-type solder resist, an encapsulating sheet, an electrically conductive film, an anisotropically conductive film, a thermally conductive film, and a method for producing a dyed cured product.

[0002] Epoxy resins, in the form of epoxy resin compositions containing an epoxy resin curing agent, are used in a wide range of applications, including insulating materials for electrical and electronic components such as semiconductor packages and camera modules, sealing materials, adhesives, conductive materials, matrix resins for fiber-reinforced plastics, impregnating adhesives for motor coils, and adhesives for automotive structures.

[0003] In recent years, semiconductor packages have used film materials such as underfill materials that protect bump connections and the circuit surface of chips, die attach films for chip adhesion, films for forming interlayer insulating layers, and films for forming solder resist layers, and the epoxy resin compositions are used as the underfill materials and various film materials.

[0004] As an epoxy resin composition applicable to underfill materials, for example, an epoxy resin composition containing a microcapsule-type curing agent has been disclosed (see, for example, Patent Document 1). Also, as an epoxy resin composition applicable to film materials, for example, an epoxy resin composition containing a microcapsule-type curing agent has been disclosed (see, for example, Patent Document 2).

[0005] JP 2020-31227 A JP 2017-95570 A

[0006] As mentioned above, epoxy resin compositions are used in a variety of applications, and the components in the composition are selected appropriately for each application. Typical possible composition systems include, for example, epoxy resin compositions containing a low-molecular-weight epoxy compound as a reactive diluent for underfill applications. For film applications, examples include epoxy resin compositions containing solvents such as methyl ethyl ketone (MEK) or cyclohexanone when preparing the varnish. For dual-cure adhesive applications that are cured by both light and heat, examples include epoxy resin compositions containing a low-molecular-weight acrylic compound. Epoxy resin curing agents that can impart storage stability and reactivity to these various composition systems are required.

[0007] Furthermore, when an epoxy resin composition contains a filler, the cured product obtained by curing the epoxy resin composition is required to have an excellent appearance, i.e., an appearance in which the filler is uniformly dispersed in the cured product. In recent years, with the increasing functionality of electronic materials, there has been a demand for an excellent appearance in a smaller area than before. In other words, even aggregates of filler or curing agent that would be considered relatively small by conventional standards have recently been viewed as problematic in terms of appearance.

[0008] From the above viewpoints, there is still room for improvement in the microcapsule-type curing agents and epoxy resin compositions containing the same disclosed in Patent Documents 1 and 2.

[0009] An object of the present invention is to provide an epoxy resin curing agent and the like which imparts excellent stability and reactivity to an epoxy resin composition mixed with a low molecular weight epoxy compound, a solvent, or a low molecular weight acrylic compound, and which can impart an excellent appearance even in a microscopic area when an epoxy resin composition containing a filler is cured.

[0010] As a result of extensive research, the present inventors have found that the above-mentioned problems can be solved by an epoxy resin curing agent having a specific configuration, and have thus completed the present invention. That is, the present invention encompasses the following aspects. [1] An epoxy resin curing agent comprising: a core (A) containing a nitrogen-containing compound; and a layer (B) covering the core (A), wherein, when the epoxy resin curing agent is stained with ruthenium tetroxide and osmium tetroxide and then observed under a transmission electron microscope and a brightness graph is obtained by image processing, the interior of the layer (B) has a region having a brightness α, and the brightness α is higher than the brightness β of the outermost portion of the layer (B) and the brightness γ of the boundary between the layer (B) and the core (A). [2] The epoxy resin curing agent according to [1], wherein the core (A) contains 0.001 to 20 mass % of an amine compound (a) having a molecular weight of 50 to 300. [3] The epoxy resin curing agent according to [1] or [2], wherein the core (A) comprises at least one selected from the group consisting of imidazoles, aliphatic amine compounds, and cyclic amine compounds including tertiary amines. [4] The epoxy resin curing agent according to any one of [1] to [3], wherein the core (A) comprises an imidazole amine adduct compound. [5] The particle size D of the core (A) at an undersize cumulative fraction of 50% ５０ [6] The epoxy resin curing agent according to any one of [1] to [4], wherein the particle size D of the core (A) at an undersize cumulative fraction of 99% is more than 0.3 μm and not more than 12 μm. ９９ and the above D ５０ The ratio of ９９ / D ５０ [7] The epoxy resin curing agent according to [5], wherein the specific surface area Y (m ２ / g) to the D ５０ [8] The epoxy resin curing agent according to [5] or [6], wherein the specific surface area Y (m ２ / g) to the D ５０The epoxy resin curing agent according to any one of [5] to [7], wherein the value obtained by multiplying the pore size distribution by the surface roughness (μm) is more than 9.0 and not more than 18.0. [9] An epoxy resin composition comprising the epoxy resin curing agent according to any one of [1] to [8] and an epoxy resin (C).

[10] The epoxy resin composition according to [9], wherein the mass ratio of the epoxy resin curing agent to the epoxy resin (C), in terms of epoxy resin curing agent:epoxy resin (C), is 0.1:100 to 1000:100.

[11] The epoxy resin composition according to [9] or

[10] , further comprising an alcohol compound (D) represented by the following formula (1): (In formula (1), X １ represents an alkylene group having 2 to 5 carbon atoms which may have a substituent R, and the substituents R and R １ ~R ５ each independently represents a hydrogen atom, an alkyl group, an unsaturated aliphatic group, an aromatic group, a substituent containing a heteroatom, or a halogen atom, １ ~R ５

[12] The epoxy resin composition according to

[11] , wherein the content of the alcohol compound (D) is 0.0001% by mass or more and 5% by mass or less, based on the total amount of the epoxy resin composition.

[13] The epoxy resin composition according to

[11] or

[12] , wherein the alcohol compound (D) comprises at least one selected from the group consisting of 3-phenoxy-1-propanol, 3-phenoxy-1,2-propanediol, 3-phenoxy-1,3-propanediol, 3-(ortho-toluoxy-1,2-propanediol, 3-(2-methoxyphenoxy)propane-1,2-diol, bisphenol A (3-hydroxypropyl)glycidyl ether, and bisphenol A (2,3-dihydroxypropyl)glycidyl ether.

[14] The epoxy resin composition according to any one of [9] to

[13] , wherein the core (A) comprises 0.001 to 20 mass% of an amine compound (a) having a molecular weight of 50 to 300, and the amine compound (a) comprises at least one selected from the group consisting of imidazoles, aliphatic amine compounds, and cyclic amine compounds including tertiary amines.

[15] An encapsulating material comprising the epoxy resin curing agent according to any one of [1] to [8] or the epoxy resin composition according to any one of [9] to

[14] .

[16] A conductive material comprising the epoxy resin curing agent according to any one of [1] to [8] or the epoxy resin composition according to any one of [9] to

[14] .

[17] A thermally conductive material comprising the epoxy resin curing agent according to any one of [1] to [8] or the epoxy resin composition according to any one of [9] to

[14] .

[18] An insulating material comprising the epoxy resin curing agent according to any one of [1] to [8] or the epoxy resin composition according to any one of [9] to

[14] .

[19] An adhesive for a camera module comprising the epoxy resin curing agent according to any one of [1] to [8] or the epoxy resin composition according to any one of [9] to

[14] .

[20] A structural adhesive comprising the epoxy resin curing agent according to any one of [1] to [8] or the epoxy resin composition according to any one of [9] to

[14] .

[21] A matrix resin for fiber-reinforced plastics, comprising the epoxy resin curing agent according to any one of [1] to [8] or the epoxy resin composition according to any one of [9] to

[14] .

[22] An impregnating adhesive material, comprising the epoxy resin curing agent according to any one of [1] to [8] or the epoxy resin composition according to any one of [9] to

[14] .

[23] An interlayer insulating film, comprising the epoxy resin curing agent according to any one of [1] to [8] or the epoxy resin composition according to any one of [9] to

[14] .

[24] A film-type solder resist, comprising the epoxy resin curing agent according to any one of [1] to [8] or the epoxy resin composition according to any one of [9] to

[14] .

[25] An encapsulating sheet, comprising the epoxy resin curing agent according to any one of [1] to [8] or the epoxy resin composition according to any one of [9] to

[14] .

[26] A conductive film, comprising the epoxy resin curing agent according to any one of [1] to [8] or the epoxy resin composition according to any one of [9] to

[14] .

[27] An anisotropic conductive film comprising the epoxy resin curing agent according to any one of [1] to [8] or the epoxy resin composition according to any one of [9] to

[14] .

[28] A thermally conductive film comprising the epoxy resin curing agent according to any one of [1] to [8] or the epoxy resin composition according to any one of [9] to

[14] .

[29] A method for producing a dyed cured product, comprising: a step (S1) of electronically staining, with ruthenium tetroxide, an epoxy resin curing agent having a core (A) and a layer (B) covering the core (A),

[0011] According to the present invention, it is possible to provide an epoxy resin curing agent or the like which imparts excellent stability and reactivity to an epoxy resin composition mixed with a low molecular weight epoxy compound, a solvent, or a low molecular weight acrylic compound, and which can impart an excellent appearance even in a microscopic area when an epoxy resin composition containing a filler is cured.

[0012] 7 is an edited image obtained by image analysis of a TEM image of epoxy resin curing agent 1 in Example 1, where lines are drawn at predetermined positions to confirm dyeability. It is a graph plotting the brightness at each position along the line segments in the image of FIG. 1 . It is an edited image obtained by image analysis of a TEM image of epoxy resin curing agent 3 in Example 3, where lines are drawn at predetermined positions to confirm dyeability. It is a graph plotting the brightness at each position along the line segments in the image of FIG. 3 . It is an edited image obtained by image analysis of a TEM image of epoxy resin curing agent 4 in Example 4, where lines are drawn at predetermined positions to confirm dyeability. It is a graph plotting the brightness at each position along the line segments in the image of FIG. 5 . It is an edited image obtained by image analysis of a TEM image of epoxy resin curing agent R-1 in Comparative Example 1, where lines are drawn at predetermined positions to confirm dyeability. It is a graph plotting the brightness at each position along the line segments in the image of FIG. 7 . It is an image showing the results of appearance evaluation of a microregion in Example 1. It is an image showing the results of appearance evaluation of a microregion in Comparative Example 1.

[0013] Hereinafter, a mode for carrying out the present invention (hereinafter also referred to as "the present embodiment") will be described in detail. The following present embodiment is an example for explaining the present invention, and is not intended to limit the present invention to the following content. The present invention can be carried out by appropriately modifying it within the scope of its gist.

[0014] [Epoxy Resin Curing Agent] The epoxy resin curing agent of the present embodiment comprises a core (A) containing a nitrogen-containing compound, a layer (B) coating the core (A), and the epoxy resin curing agent, which are stained with ruthenium tetroxide and osmium tetroxide and then observed under a transmission electron microscope (hereinafter also referred to as "TEM") to obtain a brightness graph by image processing. The interior of the layer (B) has a region having a brightness α, and the brightness α is higher than the brightness β of the outermost portion of the layer (B) and the brightness γ of the boundary between the layer (B) and the core (A) (hereinafter, the layer (B) having the above region is also referred to as "having the desired dyeability"). Because the epoxy resin curing agent of the present embodiment is configured as described above, it can impart excellent stability and reactivity even when mixed with a low-molecular-weight epoxy compound, a solvent, or a low-molecular-weight acrylic compound to form an epoxy resin composition, and can also impart excellent appearance even in a microscopic region when formed into an epoxy resin composition containing a filler and cured. In this embodiment, it is sufficient that at least a portion of the epoxy resin curing agent has the desired dyeability, and the larger the region having the desired dyeability, the more preferable. It is particularly preferable that the entire region of the epoxy resin curing agent has the desired dyeability.

[0015] (Staining Method and TEM Observation) The staining method and the observation method after staining of the epoxy resin curing agent of this embodiment are described below. First, 10.6 mL of the main agent (Quetol 812, manufactured by Nissin EM Co., Ltd.), 9.4 mL of the curing agent (Methyl nadic anhydride: MNA, manufactured by Nissin EM Co., Ltd.), and 0.34 mL of a reaction accelerator (2,4,6-Tris(dimethyl amino methyl)phenol, manufactured by Nissin EM Co., Ltd.: DMP-30) were mixed and stirred with a stirrer for 15 minutes, and then air bubbles were removed by vacuum degassing to obtain an epoxy resin composition for dyeing. Next, the epoxy resin curing agent of this embodiment was electron-stained by coexisting it with ruthenium tetroxide in a sealed, light-shielded container at room temperature and atmospheric pressure for 10 minutes, and then mixed with the above-mentioned epoxy resin composition for dyeing and cured at 40°C for 42 hours to obtain a cured product in which the epoxy resin curing agent was embedded. 80 nm sections were then prepared using an ultramicrotome, and the sections were then coexisted with osmium tetroxide in a sealed, light-shielded container at room temperature and atmospheric pressure for 2 hours to obtain observation samples electron-stained with osmium tetroxide vapor. The observation samples were then irradiated with an electron beam using a TEM, adjusted so that the focus was on the sample, and observed at an accelerating voltage of 120 kV and a magnification of 30,000 times to obtain TEM observation images. These operations can be performed in more detail based on the methods described in the Examples below. (Obtaining a brightness graph of layer (B) by image processing) The obtained TEM observation image is read into the image analysis software ImageJ, and a median filter (Radius 2.0 pixels) is applied. Then, a line segment is drawn from the outermost part of layer (B) to include the boundary between core (A) and layer (B), and the brightness along the line segment is graphed. These operations can be performed in more detail based on the method described in the Examples below.

[0016] [Core (A) Containing Nitrogen-Containing Compound] The core (A) containing a nitrogen-containing compound is a particle or particle group containing a nitrogen-containing compound (hereinafter, these are also collectively referred to as "core (A) particles"). The nitrogen-containing compound is not particularly limited, but examples thereof include low-molecular-weight amine compounds, amine adduct compounds, modified polyamine compounds, aliphatic polyamine compounds, heterocyclic polyamine compounds, alicyclic polyamine compounds, aromatic amine compounds, polyamidoamine compounds, ketimine compounds, urethane amine compounds, amide compounds, etc. These may be used alone or in combination of two or more.

[0017] Examples of low molecular weight amine compounds include, but are not limited to, compounds not containing a tertiary amine, such as methylamine, ethylamine, propylamine, butylamine, ethylenediamine, propylenediamine, hexamethylenediamine, diethylenetriamine, triethylenetetramine, ethanolamine, propanolamine, cyclohexylamine, isophoronediamine, aniline, toluidine, diaminodiphenylmethane, diaminodiphenylsulfone, dimethylamine, diethylamine, dipropylamine, dibutylamine, dipentylamine, dihexylamine, dimethanolamine, diethanolamine, dipropanolamine, dicyclohexylamine, piperidine, piperidone, diphenylamine, phenylmethylamine, and phenylethylamine; 2-dimethylaminoethanol, 1-methyl-2-dimethylaminoethanol, 1-phenoxymethyl-2-dimethylaminoethanol, and 2-diethylaminoethanol. aminoalcohols such as ethanol, 1-butoxymethyl-2-dimethylaminoethanol, methyldiethanolamine, triethanolamine, and N-β-hydroxyethylmorpholine; aminophenols such as 2-(dimethylaminomethyl)phenol and 2,4,6-tris(dimethylaminomethyl)phenol; imidazole, 2-methylimidazole, 4-methylimidazole, 2-ethyl-4-methylimidazole, 2-undecylimidazole, 2-heptylimidazole, Imidazoles such as tadecyl imidazole, 2-phenyl imidazole, 1-aminoethyl-2-methyl imidazole, 1-(2-hydroxy-3-phenoxypropyl)-2-methyl imidazole, 1-(2-hydroxy-3-phenoxypropyl)-2-ethyl-4-methyl imidazole, 1-(2-hydroxy-3-butoxypropyl)-2-methyl imidazole, and 1-(2-hydroxy-3-butoxypropyl)-2-ethyl-4-methyl imidazole;1-(2-hydroxy-3-phenoxypropyl)-2-phenylimidazoline, 1-(2-hydroxy-3-butoxypropyl)-2-methylimidazoline, 2-methylimidazoline, 2,4-dimethylimidazoline, 2-ethylimidazoline, 2-ethyl-4-methylimidazoline, 2-benzylimidazoline, 2-phenylimidazoline, 2-(o-tolyl)-imidazoline, tetramethylene-bis-imidazoline, 1,1,3-trimethyl-1,4-tetramethylene-bis-imidazoline, 1,3,3-trimethyl-1,4-tetramethylene imidazolines such as 1,1,3-trimethyl-1,4-tetramethylene-bis-4-methylimidazoline, 1,3,3-trimethyl-1,4-tetramethylene-bis-4-methylimidazoline, 1,2-phenylene-bis-imidazoline, 1,3-phenylene-bis-imidazoline, 1,4-phenylene-bis-imidazoline, and 1,4-phenylene-bis-4-methylimidazoline; trimethylamine, triethylamine, benzyldimethylamine, N,N-dimethyl-ethylamine, N,N-dimethyl-butylamine, N,N -dimethyldecylamine, N,N-dimethyl-m-toluidine, N,N-dimethyl-p-toluidine, 2,6,10-trimethyl-2,6,10-triazaundecane, N,N'-dimethylpiperazine, 1,4-diazabicyclo[2.2.2]octane (DABCO), 1-azabicyclo[2.2.2]octan-3-one, 1,8-diazabicyclo(5,4,0)-undecene-7, 1,5-diazabicyclo(4,3,0)-nonene-5, hexamethylenetetramine, dimethylaminopropylamine, diethylaminopropylamine, dipropylamine tertiary aminoamines such as aminopropylamine, dibutylaminopropylamine, dimethylaminoethylamine, diethylaminoethylamine, dipropylaminoethylamine, dibutylaminoethylamine, N-methylpiperazine, N-aminoethylpiperazine, diethylaminoethylpiperazine, 2-dimethylaminopyridine, and 4-dimethylaminopyridine; aminomercaptans such as 2-dimethylaminoethanethiol, 2-mercaptobenzimidazole, 2-mercaptobenzothiazole, 2-mercaptopyridine, and 4-mercaptopyridine;Examples include aminocarboxylic acids such as N,N-dimethylaminobenzoic acid, N,N-dimethylglycine, nicotinic acid, isonicotinic acid, and picolinic acid; and aminohydrazides such as N,N-dimethylglycine hydrazide, nicotinic acid hydrazide, and isonicotinic acid hydrazide. These may be used alone or in combination of two or more.

[0018] Examples of the amine adduct compound include, but are not limited to, compounds obtained by reacting one or more of a carboxylic acid compound, a sulfonic acid compound, a urea compound, an isocyanate compound, and an epoxy resin with the low-molecular-weight amine compound described above. In this embodiment, the amine adduct compound preferably includes an imidazole amine adduct compound. The imidazole amine adduct may be a reaction product of an imidazole with, for example, one or more of a carboxylic acid compound, a sulfonic acid compound, a urea compound, an isocyanate compound, and an epoxy resin. From the viewpoint of formability of layer (B), the imidazole amine adduct compound preferably includes a reaction product of an imidazole and an epoxy resin. From the viewpoint of mechanical strength, the imidazole amine adduct compound preferably includes a reaction product of an imidazole and an epoxy resin.

[0019] Examples of the carboxylic acid compound include, but are not limited to, succinic acid, adipic acid, sebacic acid, phthalic acid, and dimer acid.

[0020] The sulfonic acid compound is not limited to the following, but examples thereof include ethanesulfonic acid and p-toluenesulfonic acid.

[0021] Examples of the urea compound include, but are not limited to, urea, methyl urea, dimethyl urea, ethyl urea, and t-butyl urea.

[0022] Examples of isocyanate compounds include, but are not limited to, aliphatic diisocyanates, alicyclic diisocyanates, aromatic diisocyanates, aliphatic triisocyanates, polyisocyanates, etc. Examples of aliphatic diisocyanates include, but are not limited to, ethylene diisocyanate, propylene diisocyanate, butylene diisocyanate, hexamethylene diisocyanate, trimethylhexamethylene diisocyanate, etc. Examples of alicyclic diisocyanates include, but are not limited to, isophorone diisocyanate, 4,4'-dicyclohexylmethane diisocyanate, norbornane diisocyanate, 1,4-isocyanatocyclohexane, 1,3-bis(isocyanatomethyl)-cyclohexane, 1,3-bis(2-isocyanatopropyl-2-yl)-cyclohexane, etc. Examples of aromatic diisocyanates include, but are not limited to, tolylene diisocyanate, 4,4'-diphenylmethane diisocyanate, xylene diisocyanate, and 1,5-naphthalene diisocyanate. Examples of aliphatic triisocyanates include, but are not limited to, 1,6,11-undecane triisocyanate, 1,8-diisocyanate-4-isocyanatomethyloctane, and 1,3,6-triisocyanatomethylhexane. Examples of polyisocyanates include, but are not limited to, polymethylene polyphenyl polyisocyanate and polyisocyanates derived from the diisocyanate compounds. Examples of polyisocyanates derived from the diisocyanate compounds include isocyanurate polyisocyanates, biuret polyisocyanates, urethane polyisocyanates, allophanate polyisocyanates, and carbodiimide polyisocyanates.

[0023] The epoxy resin is not limited to the following, but examples thereof include bifunctional epoxy resins such as bisphenol A type epoxy resin, bisphenol F type epoxy resin, bisphenol AD ​​type epoxy resin, bisphenol M type epoxy resin, bisphenol P type epoxy resin, tetrabromobisphenol A type epoxy resin, hydrogenated bisphenol A type epoxy resin, biphenyl type epoxy resin, tetramethylbiphenyl type epoxy resin, tetrabromobiphenyl type epoxy resin, diphenyl ether type epoxy resin, benzophenone type epoxy resin, phenyl benzoate type epoxy resin, diphenyl sulfide type epoxy resin, diphenyl sulfoxide type epoxy resin, diphenyl sulfone type epoxy resin, diphenyl disulfide type epoxy resin, naphthalene type epoxy resin, anthracene type epoxy resin, hydroquinone type epoxy resin, methylhydroquinone type epoxy resin, dibutylhydroquinone type epoxy resin, resorcinol type epoxy resin, methylresorcinol type epoxy resin, and catechol type epoxy resin. Examples of epoxy resins include trifunctional epoxy resins such as N,N-diglycidylaminobenzene epoxy resins and triazine epoxy resins; tetrafunctional epoxy resins such as tetraglycidyldiaminodiphenylmethane epoxy resins and diaminobenzene epoxy resins; polyfunctional epoxy resins such as phenol novolac epoxy resins, cresol novolac epoxy resins, triphenylmethane epoxy resins, tetraphenylethane epoxy resins, dicyclopentadiene epoxy resins, naphthol aralkyl epoxy resins, and brominated phenol novolac epoxy resins; monoepoxy compounds such as butyl glycidyl ether, hexyl glycidyl ether, phenyl glycidyl ether, allyl glycidyl ether, para-tert-butylphenyl glycidyl ether, ethylene oxide, propylene oxide, paraxylyl glycidyl ether, glycidyl acetate, glycidyl butyrate, glycidyl hexoate, and glycidyl benzoate, and alicyclic epoxy resins. These may be used alone or in combination of two or more.

[0024] Examples of amide compounds include, but are not limited to, dicyandiamide and its derivatives, such as guanidine compounds, compounds obtained by adding an acid anhydride to an amine compound, and hydrazide compounds. Examples of hydrazide compounds include, but are not limited to, succinic acid dihydrazide, adipic acid dihydrazide, phthalic acid dihydrazide, isophthalic acid dihydrazide, terephthalic acid dihydrazide, p-oxybenzoic acid hydrazide, salicylic acid hydrazide, phenylaminopropionic acid hydrazide, and maleic acid dihydrazide. Examples of guanidine compounds include, but are not limited to, dicyandiamide, methylguanidine, ethylguanidine, propylguanidine, butylguanidine, dimethylguanidine, trimethylguanidine, phenylguanidine, diphenylguanidine, and toluylguanidine. These compounds may be used alone or in combination.

[0025] Among these compounds having a nitrogen atom, from the viewpoint of achieving both reactivity during heat curing and stability during storage when formed into an epoxy resin composition, low molecular weight amine compounds, amine adduct compounds and amide compounds are preferred, low molecular weight amine compounds and amine adduct compounds are more preferred, and compounds containing both low molecular weight amines and amine adduct compounds are particularly preferred.

[0026] The low-molecular-weight amine compound preferably contains an amine compound (a) having a molecular weight of 50 to 300. That is, from the viewpoint of suppressing thickening due to the amine passing from the core (A) through the layer (B) and reacting with the epoxy resin when an epoxy resin composition is prepared, the molecular weight is preferably 50 or more, more preferably 60 or more, and even more preferably 70 or more. Furthermore, from the viewpoint of achieving high reactivity due to excellent diffusing ability, the molecular weight is preferably 300 or less, more preferably 270 or less, and even more preferably 240 or less.

[0027] As the amine compound (a), from the viewpoint of excellent reactivity with epoxy resins, imidazoles, aliphatic amine compounds, and cyclic amine compounds containing tertiary amines are preferred. As the imidazole compounds, imidazole, 2-methylimidazole, 4-methylimidazole, 2-ethyl-4-methylimidazole, 2-undecylimidazole, and 2-phenylimidazole are more preferred. As the aliphatic amine compounds, ethylenediamine, propylenediamine, hexamethylenediamine, diethylenetriamine, triamine, and methylimidazole are more preferred. Ethylenetetramine, ethanolamine, propanolamine, cyclohexylamine, isophoronediamine, dimethylamine, diethylamine, dipropylamine, dibutylamine, dipentylamine, and piperidine are more preferred, and as the cyclic amine compound containing a tertiary amine, 1,4-diazabicyclo[2.2.2]octane, 1-azabicyclo[2.2.2]octan-3-one, and 1,8-diazabicyclo(5,4,0)-undecene-7, 1,5-diazabicyclo(4,3,0)-nonene-5 are more preferred.

[0028] From the viewpoint of achieving both reactivity during heat curing and storage stability when formed into an epoxy resin composition, the content of the low molecular weight amine compound in the core (A) is preferably from 0.001 to 20% by mass, more preferably from 0.003 to 18% by mass, even more preferably from 0.005 to 16% by mass, even more preferably from 0.008 to 14% by mass, and particularly preferably from 0.01 to 12% by mass. From the same viewpoint as above, the content of the amine compound (a) in the core (A) is preferably from 0.001 to 20% by mass, more preferably from 0.003 to 18% by mass, even more preferably from 0.005 to 16% by mass, even more preferably from 0.008 to 14% by mass, and particularly preferably from 0.01 to 12% by mass.

[0029] From the viewpoint of mechanical strength, the amine adduct compound is preferably a compound obtained by reacting an epoxy resin with a low molecular weight amine compound. As the epoxy resin, from the viewpoint of toughness, bisphenol A type epoxy resin and bisphenol F type epoxy resin are preferred. As the low molecular weight amine compound, from the viewpoint of imparting excellent reactivity with epoxy resin to the obtained amine adduct compound, imidazole compounds, compounds having at least one primary amino group and / or secondary amino group but no tertiary amino group, and compounds having at least one tertiary amino group and at least one active hydrogen group are more preferred among the above-mentioned low molecular weight amine compounds.

[0030] The low-molecular-weight amine compound contained in the core (A) may be an unreacted low-molecular-weight amine compound that is reused when an amine adduct compound is obtained by reacting any one or more of a carboxylic acid compound, a sulfonic acid compound, a urea compound, an isocyanate compound, and an epoxy resin with the low-molecular-weight amine compound.

[0031] The core (A) may contain components other than the nitrogen-containing compound, and examples thereof include, but are not limited to, phenol-based curing agents, acid anhydride-based curing agents, and catalyst-type curing agents.

[0032] Examples of phenol-based curing agents include, but are not limited to, phenol novolac resin, cresol novolac resin, phenol aralkyl resin, cresol aralkyl resin, naphthol aralkyl resin, biphenyl-modified phenol resin, biphenyl-modified phenol aralkyl resin, dicyclopentadiene-modified phenol resin, aminotriazine-modified phenol resin, naphthol novolac resin, naphthol-phenol co-condensed novolac resin, naphthol-cresol co-condensed novolac resin, and allyl acrylic phenol resin.

[0033] Examples of acid anhydride curing agents include, but are not limited to, phthalic anhydride, trimellitic anhydride, pyromellitic anhydride, maleic anhydride, tetrahydrophthalic anhydride, methyltetrahydrophthalic anhydride, methylnadic anhydride, hexahydrophthalic anhydride, and methylhexahydrophthalic anhydride.

[0034] Examples of catalyst-type curing agents include, but are not limited to, cationic thermosetting catalysts, BF3-amine complexes, and the like.

[0035] From the viewpoint of storage stability, it is preferable that the core (A) is solid at 25°C and 1013 hPa. This tends to prevent the components of the core (A) from eluting out of the layer (B) even if scratches are generated in the layer (B) when the core (A) is mixed with other components to obtain an epoxy resin composition, and to maintain storage stability.

[0036] Particle size D of core (A) at 50% cumulative undersize fraction ５０ It is preferable that the D of the core (A) is more than 0.3 μm and not more than 12 μm. ５０ When the D of the core (A) is larger than 0.3 μm, aggregation of the cores can be further prevented, the formation of the layer (B) becomes easier, and the storage stability of the epoxy resin composition tends to be further improved. ５０ By making the diameter of the core (A) 12 μm or less, when a desired epoxy resin composition is obtained by blending diluents, fillers, pigments, dyes, flow control agents, thickeners, reinforcing agents, mold release agents, wetting agents, stabilizers, flame retardants, surfactants, organic solvents, conductive fine particles, crystalline alcohol, other resins, etc., it is possible to prevent the formation of large particle aggregates, and the cured product tends to have sufficient long-term reliability. ５０ The lower limit of is preferably more than 0.3 μm, more preferably 0.4 μm or more, and even more preferably 0.5 μm or more. The upper limit is preferably 12 μm or less, more preferably 10 μm or less, and even more preferably 9 μm or less.

[0037] Core (A) D ５０ "mean particle diameter" refers to the average particle diameter defined by the median diameter. More specifically, it refers to the Stokes diameter measured by a laser diffraction / light scattering method using a particle size distribution analyzer ("HORIBA LA-920" manufactured by Horiba, Ltd.).

[0038] Core (A) D ５０The method for controlling the value of D to the above-mentioned range is not limited to the following, but for example, a method for precisely controlling the grinding process of the lump core material, a method for performing a coarse grinding process and a fine grinding process as the grinding process of the lump core material, and further using a precise classification device to obtain the desired D ５０ and a method of spray-drying a solution in which a lump of core material is dissolved in a solvent. As the apparatus used for pulverization, for example, a ball mill, an attritor, a bead mill, a jet mill, etc. can be used as needed, but it is preferable to use an impact pulverizer. As the impact pulverizer, for example, jet mills such as a swirling flow powder collision type jet mill and a powder collision type counter jet mill can be mentioned. A jet mill is a device that uses a high-speed jet stream using air or the like as a medium to collide solid materials with each other to form fine particles. Methods for precise control in the pulverization process include a method of controlling the temperature, humidity, pulverization amount per unit time, etc. during pulverization. After the pulverization process, a precise classification device can be used to obtain the desired D. ５０ As a method for obtaining the above-mentioned powder by classification, for example, after pulverization, the powder is classified to obtain a powder of a predetermined D ５０ To obtain the powder or granular material, methods include classification using a sieve (e.g., a standard sieve such as 325 mesh or 250 mesh) or a classifier, and classification by air force depending on the specific gravity of the particles. Examples of classifiers used include wet classifiers and dry classifiers, with dry classifiers generally being preferred. Examples of such classifiers include the "Elbow Jet" manufactured by Nittetsu Mining Co., Ltd., the "Fine Sharp Separator" manufactured by Hosokawa Micron Corporation, the "Variable Impactor" manufactured by Sankyo Dengyo Co., Ltd., the "Spedic Classifier" manufactured by Seishin Enterprise Co., Ltd., the "Donaserec" manufactured by Nippon Donaldson Co., Ltd., the "YM Microcassette" manufactured by Yaskawa Corporation, the "Turbo Classifier" manufactured by Nisshin Engineering, and various other dry classification devices such as air separators, micron separators, Microbrex, and AccuCut, but are not limited to these.

[0039] As a method for directly granulating the particles constituting the core without pulverization, there is mentioned a method of spray-drying a solution in which a lump of core material is dissolved in a solvent. Specifically, there is mentioned a method in which the core material is uniformly dissolved in an appropriate organic solvent, and then the solution is sprayed as fine droplets, and then dried by hot air or the like. In this case, there is mentioned a conventional spray dryer. As a method for granulating the core particles, there is mentioned a method in which the core material is uniformly dissolved in an appropriate organic solvent, and then, while vigorously stirring the homogeneous solution, a poor solvent for the nitrogen-containing compound constituting the core (A) is added, thereby precipitating the core (A) in the form of fine particles. Next, there is mentioned a method in which the precipitated particles are separated by filtration, and then the solvent is dried and removed at a low temperature below the melting point of the core (A). D of the core (A) in a particulate state is mentioned. ５０ As a method for adjusting the amount of the powder by a method other than classification, for example, ５０ By mixing multiple particles with different D ５０ For example, in the case of a large particle size core (A) that is difficult to crush or classify, a separate small particle size core (A) can be added and mixed to adjust the D ５０ can also be used as a curing agent that falls within the above range. The curing agent obtained in this manner may be further classified, if necessary. Examples of mixers used for the purpose of mixing such powders include a container rotation type mixer that rotates the container body containing the powder to be mixed, a fixed container type mixer that mixes by mechanical stirring or air current stirring without rotating the container body containing the powder, and a combined type mixer that rotates the container containing the powder and also uses other external forces to mix.

[0040] Core (A) is D ５０ Particle size D at 99% cumulative undersize fraction ９９ The ratio (hereinafter simply referred to as "D ９９ / D ５０ From the viewpoint of preventing aggregation of particles, the particle size distribution represented by (D) is preferably 8.0 or less, more preferably 7.0 or less, even more preferably 6.0 or less, and particularly preferably 5.5 or less. ９９ / D ５０By making the D be 8.0 or less, the number of coarse particles in the powder particles of the core (A) is small, the formation of aggregates is suppressed, and when the epoxy resin composition is prepared, the physical properties of the cured product obtained by curing the epoxy resin composition tend to be prevented from being impaired. ９９ / D ５０ The smaller the value of D, the sharper the particle size distribution of the core (A), and when the epoxy resin composition is prepared, it tends to be easier to obtain a homogeneous cured product and good curing performance. ９９ / D ５０ is preferably 1.0 or more. ９９ / D ５０ When the ratio is 1.0 or more, the formation of many gaps between the core (A) particles tends to be suppressed. ９９ / D ５０ is more preferably 1.2 or more, more preferably 1.5 or more, still more preferably 1.7 or more, and particularly preferably 2.0 or more. ９９ "D" means the average particle diameter defined by the median diameter. More specifically, it refers to the Stokes diameter measured by a laser diffraction / light scattering method using a particle size distribution analyzer ("HORIBA LA-920" manufactured by Horiba, Ltd.). ９９ / D ５０ As a method for controlling the value within the above-mentioned range, ５０ The conditions for the method of controlling the desired D ９９ / D ５０ One example is to adjust it so that

[0041] In one embodiment, the core (A) has a specific surface area value Y (m ２ / g) to the particle size D ５０ The value obtained by multiplying the specific surface area Y (m) of the core (A) by the specific surface area Y (m) of the core (A) may be 3.0 or more and 9.0 or less. When the value is 3.0 or more, aggregation of the core (A) particles tends to be suppressed, and when the value is 9.0 or less, the formation of the layer (B) tends to be facilitated. From the viewpoint of suppressing aggregation of the core (A) particles, the value may be 3.5 or more, or may be 4.0 or more. From the viewpoint of facilitating the formation of the layer (B), the value may be 8.6 or less, or may be 8.3 or less. The specific surface area Y (m２ / g) can be measured based on the method described in the Examples.

[0042] In one embodiment, the core (A) has a specific surface area value Y (m ２ / g) to particle size D ５０ The value obtained by multiplying the thickness by the thickness (μm) may be greater than 9.0 and equal to or less than 18.0. When the value is greater than 9.0, the reactivity tends to be improved, and when the value is equal to or less than 18.0, a layer (B) having sufficient stability tends to be formed. From this viewpoint, the value may be equal to or less than 17.0, or may be equal to or less than 16.5.

[0043] Specific surface area value Y (m ２ / g) to particle size D ５０ As a method for adjusting the value multiplied by (μm) in the range of 3.0 to 18.0, for example, ５０ Examples of methods for modifying the surface of the core (A) include adjusting the conditions for controlling the particle diameter and modifying the surface of the core (A). Examples of methods for modifying the surface include mechanically rounding the particles and hot air treatment, which tend to reduce the above value. On the other hand, the above value can be increased by appropriately setting the above-mentioned pulverizer and pulverization conditions, the classification device and classification conditions, etc.

[0044] [Layer (B)] The layer (B) is not particularly limited as long as it has the desired dyeability, and examples thereof include layers containing synthetic resins and inorganic oxides. Among these, it is preferable that the layer (B) contains a synthetic resin from the viewpoints of stability during storage and ease of destruction when heated.

[0045] The synthetic resin used in layer (B) is not limited to the following, but examples thereof include epoxy resins, phenol resins, polyester resins, polyethylene resins, nylon resins, polystyrene resins, urethane resins, etc. Among these, epoxy resins, phenol resins, and urethane resins are preferred from the viewpoint of the balance between the stability of layer (B) and its destructibility upon heating.

[0046] The epoxy resin used in layer (B) is not limited to the following, but examples include epoxy resins having two or more epoxy groups, resins produced by reacting an epoxy resin having two or more epoxy groups with a compound having two or more active hydrogen atoms, and reaction products of a compound having two or more epoxy groups with a compound having one active hydrogen atom and a carbon-carbon double bond. Among these, from the viewpoint of stability, resins produced by reacting a compound having two or more epoxy groups with a compound having two or more active hydrogen atoms are preferred, and reaction products of an amine-based curing agent with an epoxy resin having two or more epoxy groups are particularly preferred. Examples of epoxy resins include the epoxy resins described above, and examples of amine-based curing agents include the nitrogen-containing compounds used in core (A).

[0047] Examples of phenolic resins include, but are not limited to, phenol-formaldehyde polycondensates, cresol-formaldehyde polycondensates, resorcinol-formaldehyde polycondensates, bisphenol A-formaldehyde polycondensates, and polyethylene polyamine-modified phenol-formaldehyde polycondensates.

[0048] Examples of polyester resins include, but are not limited to, ethylene glycol-terephthalic acid-polypropylene glycol polycondensates, ethylene glycol-butylene glycol-terephthalic acid polycondensates, and terephthalic acid-ethylene glycol-polyethylene glycol polycondensates.

[0049] Examples of polyethylene resins include, but are not limited to, ethylene-propylene-vinyl alcohol copolymers, ethylene-vinyl acetate copolymers, and ethylene-vinyl acetate-acrylic acid copolymers.

[0050] Examples of nylon resins include, but are not limited to, adipic acid-hexamethylenediamine polycondensate, sebacic acid-hexamethylenediamine polycondensate, and p-phenylenediamine-terephthalic acid polycondensate.

[0051] Examples of polystyrene resins include, but are not limited to, styrene-butadiene copolymers, styrene-butadiene-acrylonitrile copolymers, acrylonitrile-styrene-divinylbenzene copolymers, and styrene-propenyl alcohol copolymers.

[0052] Examples of urethane resins include, but are not limited to, isocyanate monomers such as butyl isocyanate, cyclohexyl isocyanate, octadecyl isocyanate, phenyl isocyanate, tolylene diisocyanate, diphenylmethane diisocyanate, xylylene diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, tolidine diisocyanate, naphthalene diisocyanate, and triphenylmethane triisocyanate, or condensates thereof, or polycondensates of polymers thereof with monoalcohols or polyhydric alcohols. Among these, urethane resins which are addition polymers of monoalcohols or polyhydric alcohols and monoisocyanates or polyhydric isocyanates are preferred.

[0053] Examples of inorganic oxides include, but are not limited to, boron oxide, boron compounds such as boric acid esters, silicon dioxide, calcium oxide, etc. Among these, boron oxide is preferred from the viewpoints of the stability of the film constituting the shell and the ease of destruction when heated.

[0054] From the viewpoint of the balance between storage stability and curability when the epoxy resin composition of the present embodiment is prepared, the layer (B) preferably contains two or more reaction products selected from the group consisting of an isocyanate compound, an active hydrogen compound, a nitrogen-containing compound, and an epoxy resin.

[0055] As the isocyanate compound, nitrogen-containing compound, and epoxy resin, the compounds described above for the core (A) can be used.

[0056] Examples of active hydrogen compounds include, but are not limited to, water, compounds having at least one primary amino group and / or secondary amino group, compounds having at least one hydroxyl group, etc. These active hydrogen compounds may be used alone or in combination of two or more.

[0057] Examples of compounds having at least one primary amino group and / or secondary amino group include, but are not limited to, aliphatic amines, alicyclic amines, aromatic amines, etc. Examples of aliphatic amines include, but are not limited to, alkylamines such as methylamine, ethylamine, propylamine, butylamine, and dibutylamine; alkylenediamines such as ethylenediamine, propylenediamine, butylenediamine, and hexamethylenediamine; polyalkylenepolyamines such as diethylenetriamine, triethylenetetramine, and tetraethylenepentamine; and polyoxyalkylenepolyamines such as polyoxypropylenediamine and polyoxyethylenediamine. Examples of alicyclic amines include, but are not limited to, cyclopropylamine, cyclobutylamine, cyclopentylamine, cyclohexylamine, and isophoronediamine. Examples of aromatic amines include, but are not limited to, aniline, toluidine, benzylamine, naphthylamine, diaminodiphenylmethane, and diaminodiphenylsulfone.

[0058] Examples of compounds having at least one hydroxyl group include alcohol compounds, phenol compounds, etc. Examples of alcohol compounds include, but are not limited to, methyl alcohol, propyl alcohol, butyl alcohol, amyl alcohol, hexyl alcohol, heptyl alcohol, octyl alcohol, nonyl alcohol, decyl alcohol, undecyl alcohol, lauryl alcohol, dodecyl alcohol, stearyl alcohol, eicosyl alcohol, allyl alcohol, crotyl alcohol, propargyl alcohol, cyclopentanol, cyclohexanol, benzyl alcohol, cinnamyl alcohol, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, diglyceryl ether, methyl ... Examples of the alcohol compound include monoalcohols such as ethylene glycol monobutyl; polyhydric alcohols such as ethylene glycol, polyethylene glycol, propylene glycol, polypropylene glycol, 1,3-butanediol, 1,4-butanediol, hydrogenated bisphenol A, neopentyl glycol, glycerin, trimethylolpropane, and pentaerythritol; and polyhydric alcohols such as compounds having two or more secondary hydroxyl groups per molecule, obtained by reacting a compound having at least one epoxy group with a compound having at least one hydroxyl group, carboxyl group, primary amino group, secondary amino group, or thiol group. These alcohol compounds may be primary, secondary, or tertiary alcohols. Examples of phenolic compounds include, but are not limited to, monophenols such as carbolic acid, cresol, xylenol, carvacrol, motil, and naphthol, and polyhydric phenols such as catechol, resorcinol, hydroquinone, bisphenol A, bisphenol F, pyrogallol, phloroglucin, 2-(dimethylaminomethyl)phenol, and 2,4,6-tris(dimethylaminomethyl)phenol. From the viewpoints of latency and solvent resistance, these compounds having at least one hydroxyl group are preferably polyhydric alcohols or polyhydric phenols, and more preferably polyhydric alcohols.

[0059] The reaction conditions for preparing the reaction product of two or more compounds selected from the group consisting of isocyanate compounds, active hydrogen compounds, nitrogen-containing compounds, and epoxy resins contained in layer (B) as described above are not particularly limited, but are typically a temperature range of −10° C. to 150° C. and a reaction time of 10 minutes to 12 hours.

[0060] When an isocyanate compound and an active hydrogen compound are used to prepare the reaction product contained in layer (B), the compounding ratio, expressed as an equivalent ratio of isocyanate groups in the isocyanate compound to active hydrogens in the active hydrogen compound, is preferably in the range of 1:0.1 to 1:1000.

[0061] The reaction can be carried out in a predetermined dispersion medium, if necessary. Examples of the dispersion medium include solvents, plasticizers, resins, etc. Examples of the solvent include, but are not limited to, hydrocarbons such as benzene, toluene, xylene, cyclohexane, mineral spirits, and naphtha; ketones such as acetone, methyl ethyl ketone (MEK), methyl isobutyl ketone (MIBK), and cyclohexanone; esters such as ethyl acetate, n-butyl acetate, and propylene glycol monomethyl ethyl ether acetate; alcohols such as methanol, isopropanol, n-butanol, butyl cellosolve, and butyl carbitol; and water. Examples of the plasticizer include, but are not limited to, phthalate diester plasticizers such as dibutyl phthalate and di(2-ethylhexyl) phthalate; aliphatic dibasic acid ester plasticizers such as di(2-ethylhexyl) adipate; phosphate triester plasticizers such as tricresyl phosphate; and glycol ester plasticizers such as polyethylene glycol ester. Examples of resins include, but are not limited to, silicone resins, epoxy resins, phenolic resins, etc. These may be used alone or in combination of two or more.

[0062] Among the above, the reaction between the epoxy resin and the nitrogen-containing compound is usually carried out at a temperature ranging from −10° C. to 150° C., preferably from 0° C. to 100° C., for a reaction time of 1 hour to 168 hours, preferably from 2 hours to 72 hours. The dispersion medium is preferably a solvent or a plasticizer.

[0063] The mass % of the reaction product in layer (B) is usually 1 mass % or more, preferably 50 mass % or more, and may be 100 mass %.

[0064] Examples of methods for forming the layer (B) include the following methods (1) to (3). (1): A method in which core (A) particles and a material for forming the layer (B) (layer (B)-forming material) are dissolved and dispersed in a solvent that is a dispersion medium, and then the solubility of the layer (B)-forming material in the dispersion medium is reduced to precipitate it on the surface of the core (A) particles. (2): A method in which core (A) particles are dispersed in a dispersion medium, and the layer (B)-forming material is added to the dispersion medium to precipitate it on the core (A) particles. (3): A method in which the layer (B)-forming material is added to the dispersion medium, and the surface of the core (A) particles is used as a reaction site to generate the layer (B). Here, the methods (2) and (3) are preferred because they allow reaction and coating to occur simultaneously.

[0065] In the methods (1) to (3), examples of the dispersion medium include a solvent, a plasticizer, a resin, etc. The solvent, the plasticizer, and the resin may be the same as those used in the reaction to prepare the reaction product of two or more compounds selected from the group consisting of an isocyanate compound, an active hydrogen compound, a nitrogen-containing compound, and an epoxy resin contained in the layer (B).

[0066] After forming layer (B) by methods (2) and (3), the method for separating the epoxy resin curing agent from the dispersion medium is not particularly limited, but examples include a method of removing the dispersion medium and unreacted raw materials for forming layer (B) by filtration. After removing the dispersion medium, it is preferable to wash the epoxy resin curing agent. The washing method is not particularly limited, but after separation by filtration, the residue can be washed with a solvent that does not dissolve it. By drying after filtration or washing, the epoxy resin curing agent can be obtained in powder form. The drying method is not particularly limited, but drying at a temperature below the melting point or softening point of core (A) and layer (B) is preferred, and examples include vacuum drying. By forming the epoxy resin curing agent in powder form, the blending process of the epoxy resin and the epoxy resin can be easily performed. Furthermore, using an epoxy resin as the dispersion medium is preferable because it allows for the formation of layer (B) and an epoxy resin composition integrated with the epoxy resin to be obtained simultaneously.

[0067] The reaction for forming the layer (B) is carried out in a temperature range of -10°C to 150°C, preferably 0°C to 100°C, for a reaction time of 10 minutes to 72 hours, preferably 30 minutes to 24 hours. After the reaction for forming the layer (B) is completed, it is preferable to leave the epoxy resin curing agent at rest in an environment of 5 to 12°C or less for 8 hours or more (to undergo a resting step). When the resting step is performed, the layer (B) tends to have the desired dyeability. In the resting step in this embodiment, it is preferable that the difference between the set temperature and the actually measured temperature is small; for example, at the start time t １ to the end time t ２ Minimum temperature T Ｌ and maximum temperature T ＨIt is preferable that the difference between the temperature and the temperature is 4°C or less. In this case, it becomes easier to obtain a layer (B) having the desired dyeability. As mentioned above, the formation reaction can be carried out using a dispersion medium, and an operation to remove the dispersion medium may be carried out between the formation reaction and the standing step. Furthermore, the set temperature in the standing step may be lower than the temperature conditions of the formation reaction. For example, the set temperature in the standing step may be set to be 40°C or more lower, or 45°C or more lower than the reaction temperature in the formation reaction. Furthermore, the formation reaction and the standing step may be carried out in the same system or in different systems.

[0068] The presence of layer (B) can be confirmed by TEM observation, which will be described later. The thickness of layer (B) is preferably 1 nm to 1000 nm, more preferably 2 nm to 800 nm, even more preferably 3 nm to 600 nm, and even more preferably 4 nm to 400 nm. A thickness of layer (B) of 1 nm or more tends to impart sufficient stability. Furthermore, a thickness of layer (B) of 1000 nm or less tends to impart sufficient reactivity. Here, the thickness of layer (B) refers to the distance between any point on the boundary between layer (B) and core (A) that corresponds to the luminance γ of the boundary and the point on the outermost surface of layer (B) that corresponds to the luminance β, at the shortest point. Furthermore, the thickness of layer (B) may vary depending on the location. In such a case, the thickness range is preferably within the range of 1 nm to 1000 nm, more preferably within the range of 2 nm to 800 nm, more preferably within the range of 3 nm to 600 nm, and more preferably within the range of 4 nm to 400 nm.

[0069] [Dyeability of Layer (B)] When the epoxy resin curing agent of this embodiment is stained with ruthenium tetroxide and osmium tetroxide, and then observed under a TEM to obtain a brightness graph through image processing, the interior of the layer (B) has a region with brightness α, and the brightness α is higher than the brightness β of the outermost portion of the layer (B) and the brightness γ of the boundary between the layer (B) and the core (A). The presence of the above-mentioned region within the layer (B) can be confirmed based on the method described in the Examples below. When the epoxy resin curing agent is a masterbatch-type epoxy resin curing agent composition described below, a dispersion medium can be added as needed, and the epoxy resin and curing agent components can be separated using a centrifuge. The curing agent component can then be collected and dried to obtain a single epoxy resin curing agent. Examples of dispersion mediums include solvents, plasticizers, resins, etc., and can be selected from commercially available dispersion mediums depending on the solubility of the layer (B).

[0070] In this specification, when a layer having different dyeability from the region of the epoxy resin composition for dyeing and the core (A) is found between them in the above-mentioned TEM observation, this layer is referred to as layer (B). The difference in dyeability can be confirmed by visually inspecting the TEM image. Furthermore, the difference in dyeability can be confirmed by the fact that the brightness from the region of the epoxy resin composition for dyeing to the core (A) is not monotonous in the above-mentioned brightness graph.

[0071] The layer (B) may be a single layer or a multilayer.

[0072] In this specification, the outermost portion of the layer (B) is defined as the area with the lowest luminance near the boundary between the layer (B) and the epoxy resin composition region for dyeing, and the boundary between the core (A) and the layer (B) is defined as the area with the lowest luminance near the boundary between the core (A) and the layer (B). When the layer (B) is multi-layered, it is sufficient that at least one layer (B) has the desired dyeability, and it is preferable that all layers (B) have the desired dyeability. The epoxy resin curing agent of this embodiment may have a circularity of 0.90 or more, 0.93 or more, 0.95 or more, or 0.98 or more. The circularity represents the degree of proximity to a perfect sphere, and the circularity of a perfect sphere is 1. Furthermore, the surface of the epoxy resin curing agent (the surface of the layer (B)) may be smooth or may have irregularities. When the surface of the layer (B) is smooth, an image in which the boundary between the layer (B) and the epoxy resin composition region for dyeing appears linear or curved can be observed as a result of TEM image analysis (see Figures 1 and 3 described later). On the other hand, when the surface of the layer (B) is uneven, an image in which the boundary between the layer (B) and the epoxy resin composition region for dyeing appears wavy or wrinkled can be observed as a result of TEM image analysis (see Figure 5 described later). In addition, this embodiment may include a case in which the brightness of the highest brightness point in the layer (B) is higher than the maximum brightness of the core (A), as shown in Figure 2 described later, and a case in which the brightness of the highest brightness point in the layer (B) is lower than the maximum brightness of the core (A), as shown in Figure 4 described later. Either aspect can be preferably used as long as a brightness α higher than the brightness β and brightness γ is observed.

[0073] As a result of extensive research, the inventors have found that by subjecting the epoxy resin curing agent to the above-mentioned standing step after the completion of the reaction for forming layer (B), an epoxy resin curing agent of this embodiment (hereinafter also referred to as a low-staining epoxy resin curing agent) can be obtained, which has a region within layer (B) where the stainability with ruthenium tetroxide or osmium tetroxide is significantly reduced by the above-mentioned dyeing method. Compared to epoxy resin curing agents (hereinafter also referred to as high-staining epoxy resin curing agents) having a coating layer whose entire layer is easily stained with ruthenium tetroxide or osmium tetroxide, this low-staining epoxy resin curing agent maintains its reactivity while improving resistance to low-molecular-weight epoxy resin compounds, solvents, and low-molecular-weight acrylic resins. It can also impart excellent storage stability when applied to epoxy resin compositions containing these. Furthermore, an epoxy resin composition containing a filler was prepared using the low-staining epoxy resin curing agent, and after curing, the appearance of the cured product in a small area was observed. Compared to high-staining epoxy resin curing agents, this cured product has a more uniformly dispersed filler and an excellent appearance.

[0074] The mechanism by which the low-dyeing epoxy resin curing agent of this embodiment improves resistance to low-molecular-weight epoxy compounds, solvents, and low-molecular-weight acrylic compounds while maintaining reactivity is presumed to be as follows, although it is not intended to be limiting. The low-dyeing epoxy resin layer (B) exhibits low dyeability because its high crosslinking density makes it difficult for ruthenium tetroxide or osmium tetroxide to penetrate into the layer during dyeing. That is, the presence of crosslinking points and molecular chains in a high-density state suppresses the penetration of low-molecular-weight epoxy compounds, solvents, and low-molecular-weight acrylic compounds into layer (B), preventing dissolution of the core (A) by these low-molecular-weight compounds, thereby exhibiting excellent storage stability. On the other hand, at high temperatures during the reaction, the effect of improving strength is very small, so reactivity is maintained.

[0075] When an epoxy resin composition containing a filler is prepared using the low-staining epoxy resin curing agent of this embodiment and then cured, and the appearance of the cured product in a small area is observed, the cured product has an excellent appearance in which the filler is more uniformly dispersed. The mechanism by which this cured product has an excellent appearance in which the filler is more uniformly dispersed is presumed to be as follows, although this is not intended to be limiting. The layer (B) of the low-staining epoxy resin curing agent has high surface hardness because crosslinks and molecular chains are present at a high density. This reduces the contact area when the curing agent collides with the filler during blending, thereby reducing the probability of aggregation between the curing agent and the filler, and the filler can remain uniformly dispersed even after curing.

[0076] As described above, when evaluating the dyeability of the epoxy resin curing agent of this embodiment, a dyed cured product is obtained. That is, the method for producing a dyed cured product of this embodiment includes the steps of: (S1) electron-staining an epoxy resin curing agent having a core (A) and a layer (B) covering the core (A) with ruthenium tetroxide; (S2) obtaining a cured product of a composition containing the epoxy resin curing agent that has undergone the step (S1); and (S3) electron-staining a slice of the cured product with osmium tetroxide. The epoxy resin curing agent used in step (S1) corresponds to the epoxy resin curing agent of this embodiment. Steps (S2) and (S3) can be performed in the same manner as the method for evaluating the dyeability of layer (B) described above. By subjecting the dyed cured product to the TEM observation and image processing described above, it is typically confirmed that the interior of layer (B) has a region with a higher brightness than the brightness of the outermost portion and the boundary.

[0077] [Epoxy Resin Composition] The epoxy resin curing agent of this embodiment can be an epoxy resin composition containing an epoxy resin (C). The above-mentioned epoxy resin composition can also be used as a masterbatch-type epoxy resin curing agent composition. In other words, this embodiment also includes a masterbatch-type epoxy resin curing agent composition containing the epoxy resin curing agent of this embodiment.

[0078] [Epoxy Resin (C)] The above-mentioned epoxy resins can be used as the epoxy resin (C). The epoxy resin (C) may be used alone or in combination of two or more.

[0079] In the present embodiment, the mass ratio of the epoxy resin curing agent to the epoxy resin (C) (epoxy resin curing agent:epoxy resin) is preferably 0.1:100 to 1000:100, more preferably 0.5:100 to 500:100, and particularly preferably 1:100 to 200:100, from the viewpoints of imparting sufficient reactivity, suppressing aggregation between epoxy resin curing agents, and imparting sufficient mechanical strength to a cured product. Furthermore, when the above-described epoxy resin composition is used as a masterbatch-type curing agent, from the viewpoint of imparting sufficient reactivity as a curing agent and suppressing aggregation of the curing agents themselves, the mass ratio of the epoxy resin curing agent of the present embodiment to the epoxy resin (C) (epoxy resin curing agent:epoxy resin) is preferably 0.1:100 to 1000:100, more preferably 1:100 to 500:100, even more preferably 5:100 to 300:100, still more preferably 10:100 to 200:100, and particularly preferably 20:100 to 150:100.

[0080] The epoxy resin composition of the present embodiment preferably contains a bisphenol-type epoxy resin as the epoxy resin (C) from the viewpoints of handleability and heat resistance, and more preferably contains one or more of a bisphenol A-type epoxy resin and a bisphenol F-type epoxy resin from the viewpoint of imparting sufficient mechanical properties.

[0081] From the viewpoint of obtaining an epoxy resin composition having excellent electrical properties and an excellent balance between curability and storage stability, the total chlorine content in the epoxy resin (C) is preferably 2500 ppm or less, more preferably 2000 ppm or less, even more preferably 1500 ppm or less, and particularly preferably 900 ppm or less. From the viewpoint of achieving a predetermined technical significance, the total chlorine content in the epoxy resin (A) is preferably 0.01 ppm or more, more preferably 0.05 ppm or more, even more preferably 0.1 ppm or more, and particularly preferably 0.5 ppm or more.

[0082] Here, the total chlorine content in the epoxy resin (C) refers to the total amount of organic chlorine and inorganic chlorine contained in the epoxy resin (C), and is a value based on the mass of the epoxy resin (C). The total chlorine content in the epoxy resin (C) is measured by the following method. The epoxy resin (C) is washed with xylene, and washing and filtration are repeated until no epoxy resin remains in the xylene washing solution. The filtrate is then distilled under reduced pressure at 100°C or less to obtain the epoxy resin. A 1-10 g sample of the obtained epoxy resin is precisely weighed to a titer of 3-7 mL, dissolved in 25 mL of ethylene glycol monobutyl ether, and 25 mL of 1 N KOH propylene glycol solution is added to the sample, followed by boiling for 20 minutes. The total chlorine content can be calculated from the titer obtained by titration with an aqueous silver nitrate solution.

[0083] Here, of the total chlorine, the chlorine contained in 1,2-chlorohydrin groups is generally referred to as hydrolyzable chlorine. The amount of hydrolyzable chlorine in the epoxy resin (C) is preferably 100 ppm or less, more preferably 50 ppm or less, even more preferably 0.01 to 20 ppm, and even more preferably 0.05 to 10 ppm. When the amount of hydrolyzable chlorine in the epoxy resin (C) is 100 ppm or less, this is advantageous from the viewpoint of achieving both high curability and storage stability in the epoxy resin composition of this embodiment, and a cured product of the epoxy resin composition of this embodiment tends to exhibit excellent electrical properties.

[0084] The hydrolyzable chlorine content in the epoxy resin (C) can be measured by the following method: 3 g of a sample is dissolved in 50 mL of toluene, 20 mL of a 0.1 N KOH methanol solution is added to the solution, and the mixture is boiled for 15 minutes. The content of hydrolyzable chlorine can be calculated from the amount of titration obtained by titration with an aqueous silver nitrate solution.

[0085] [Alcohol compound (D) represented by formula (1)] The epoxy resin composition of the present embodiment may further contain an alcohol compound (D) (hereinafter also referred to as "component (D)") represented by the following formula (1): By containing component (D), the epoxy resin composition of the present embodiment tends to have improved low-temperature curing properties while maintaining storage stability.

[0086]

[0087] In formula (1), X １ represents an alkylene group having 2 to 5 carbon atoms which may have a substituent R, and the substituents R and R １ ~R ５ each independently represents a hydrogen atom, an alkyl group, an unsaturated aliphatic group, an aromatic group, a substituent containing a heteroatom, or a halogen atom, １ ~R ５ The substituent containing a hetero atom may be, for example, a substituent containing a halogen atom.

[0088] Examples of the alcohol compound represented by formula (1) include, but are not limited to, 3-phenoxy-1-propanol, 3-phenoxy-1,2-propanediol, 3-phenoxy-1,3-propanediol, 3-(ortho-toluoxy-1,2-propanediol, 3-(2-methoxyphenoxy)propane-1,2-diol, bisphenol A (3-hydroxypropyl) glycidyl ether, and bisphenol A (2,3-dihydroxypropyl) glycidyl ether, with bisphenol A (2,3-dihydroxypropyl) glycidyl ether being particularly preferred. These may be used alone or in combination of two or more.

[0089] The amount of component (D) added is preferably 0.0001% by mass or more, more preferably 0.001% by mass or more, even more preferably 0.005% by mass or more, and particularly preferably 0.01% by mass or more, based on the total amount of the epoxy resin composition, from the viewpoint of fully exhibiting the effect of improving reactivity when added to the epoxy resin composition of this embodiment. Furthermore, from the viewpoint of preventing deterioration of storage stability due to excessive addition, the amount is preferably 5% by mass or less, more preferably 3% by mass or less, even more preferably 2.5% by mass or less, and even more preferably 2% by mass or less.

[0090] Component (D) may be added when mixing with other components, or may be generated in the system after mixing, or may be generated in the system when producing the core (A), layer (B), and epoxy resin (C).

[0091] [Other Additives] In addition to the components described above, the epoxy resin composition of the present embodiment may further contain, as needed, epoxy resin curing agents other than the epoxy resin curing agent of the present embodiment, low molecular weight epoxy compounds, solvents, low molecular weight acrylic compounds, organic fillers, inorganic fillers, pigments, dyes, flow control agents, thickeners, release agents, wetting agents, flame retardants, surfactants, resins other than epoxy resins, and the like.

[0092] Examples of epoxy resin curing agents other than the epoxy resin curing agent of the present embodiment include the nitrogen-containing compounds, phenol-based curing agents, acid anhydride-based curing agents, and catalyst-based curing agents listed as components of the core (A) described above, as well as active ester-based curing agents, cyanate ester-based curing agents, and thiol-based curing agents.

[0093] An active ester curing agent functions as a curing agent for epoxy resins and has an active ester in its molecule. By including an active ester curing agent in the epoxy resin composition of this embodiment, the dielectric loss tangent tends to be lowered because the reaction between the active ester and the epoxy group does not produce hydroxyl groups, which are a factor in increasing the dielectric loss tangent in the epoxy resin composition. The active ester curing agent is not particularly limited, but from the viewpoint of ensuring crosslink density, a compound having two or more active ester groups in one molecule is preferred. Furthermore, from the viewpoint of the heat resistance of the epoxy resin composition of this embodiment, an active ester compound obtained by reacting a carboxylic acid compound and / or a thiocarboxylic acid compound with a hydroxy compound and / or a thiol compound is more preferred, and an active ester compound obtained by reacting a carboxylic acid compound with one or more compounds selected from a phenol compound, a naphthol compound, and a thiol compound is even more preferred. Furthermore, an aromatic compound having two or more active ester groups in one molecule obtained by reacting a carboxylic acid compound with an aromatic compound having a phenolic hydroxyl group is even more preferred. Furthermore, an aromatic compound obtained by reacting a compound having at least two or more carboxylic acids in one molecule with an aromatic compound having a phenolic hydroxyl group, and having two or more active ester groups in one molecule of the aromatic compound, is even more preferred. The active ester curing agent may be linear or multi-branched. Furthermore, if the compound having at least two or more carboxylic acids in one molecule contains an aliphatic chain, it tends to be able to improve compatibility with epoxy resins, and if it contains an aromatic ring, it tends to be able to improve heat resistance.

[0094] Examples of the carboxylic acid compound include benzoic acid, acetic acid, succinic acid, maleic acid, itaconic acid, phthalic acid, isophthalic acid, terephthalic acid, and pyromellitic acid. In particular, from the viewpoint of the heat resistance of the epoxy resin composition of this embodiment, succinic acid, maleic acid, itaconic acid, phthalic acid, isophthalic acid, and terephthalic acid are preferred, and isophthalic acid and terephthalic acid are more preferred. Examples of the thiocarboxylic acid compound include, but are not limited to, thioacetic acid and thiobenzoic acid. Examples of the phenol compound or naphthol compound include, but are not limited to, hydroquinone, resorcinol, bisphenol A, bisphenol F, bisphenol S, phenolphthalene, methylated bisphenol A, methylated bisphenol F, methylated bisphenol S, phenol, o-cresol, m-cresol, p-cresol, catechol, α-naphthol, β-naphthol, 1,5-dihydroxynaphthalene, 1,6-dihydroxynaphthalene, 2,6-dihydroxynaphthalene, dihydroxybenzophenone, trihydroxybenzophenone, tetrahydroxybenzophenone, phloroglucinol, benzenetriol, dicyclopentadienyldiphenol, and phenol novolak.Among these, from the viewpoints of the heat resistance of the epoxy resin composition of the present embodiment and solubility in epoxy resins and solvents, bisphenol A, bisphenol F, bisphenol S, methylated bisphenol A, methylated bisphenol F, methylated bisphenol S, catechol, α-naphthol, β-naphthol, 1,5-dihydroxynaphthalene, 1,6-dihydroxynaphthalene, 2,6-dihydroxynaphthalene, dihydroxybenzophenone, trihydroxybenzophenone, tetrahydroxybenzophenone, phloroglucin, benzenetriol, dicyclopentadienyldiphenol, and phenol novolak are preferred, and catechol, 1,5-dihydroxynaphthalene, 1,6-dihydroxynaphthalene, 2,6-dihydroxynaphthalene, dihydroxybenzophenone, trihydroxybenzophenone, tetrahydroxybenzophenone, phloroglucin, benzenetriol, dicyclopentadienyldiphenol, and phenol novolak are preferred.

[0033] Examples of the thiol compound include, but are not limited to, benzenedithiol, triazinyldiphenol, and benzophenone.

[0034] Examples of the thiol compound include, but are not limited to, benzenedithiol, triazinyldiphenol, and benzophenone.

[0035] Examples of the thiol compound include, but are not limited to, benzenedithiol, triazinyldiphenol, and benzophenone.

[0036] Examples of the thiol compound include, but are not limited to, benzenedithiol, triazinyldiphenol, and benzophenone.

[0037] Examples of the thiol compound include, but are not limited to, benzenedithiol, triazinyldiphenol, and benzophenone.

[0038] Examples of the thiol compound include, but are not limited to, benzenedithiol, triazinyldiphenol, and benzophenone. [0039 ...

[0095] As the active ester compound serving as the active ester curing agent, the active ester compounds disclosed in JP-A-2004-277460 and JP-A-2013-40270 may be used, or commercially available active ester compounds may also be used. Examples of commercially available active ester compounds include those manufactured by DIC Corporation under the trade names EXB9451, EXB9460, EXB9460S, and HPC-8000-65T (active ester compounds containing a dicyclopentadiene-type diphenol structure), EXB9416-70BK (active ester compound containing a naphthalene structure), and EXB9050L-62M (phosphorus atom-containing active ester compound), and those manufactured by Mitsubishi Chemical Corporation under the trade names DC808 (active ester compound containing an acetylated product of phenol novolac), and YLH1026 (active ester compound containing a benzoylated product of phenol novolac). These may be used alone or in combination of two or more.

[0096] A cyanate ester curing agent functions as a curing agent for epoxy resins and has a cyanato group in its molecule. The inclusion of a cyanate ester curing agent as an additive in the epoxy resin composition of this embodiment produces an oxazoline ring or an oxazolidinone ring upon reaction with the epoxy group, imparting flexibility to the epoxy resin composition. Furthermore, trimerization of the cyanato group results in the formation of a triazine skeleton, which tends to reduce warpage and improve heat resistance in particular. Furthermore, since hydroxyl groups are less likely to be generated during the reaction, the dielectric loss tangent tends to be kept low.

[0097] Examples of cyanate ester curing agents include, but are not limited to, novolac-type (phenol novolac type, alkylphenol novolac type, etc.) cyanate ester resins, dicyclopentadiene-type cyanate ester resins, bisphenol-type (bisphenol A type, bisphenol F type, bisphenol S type, etc.) cyanate ester resins, and prepolymers of these partially triazine-modified resins. Specific examples of cyanate ester resins include bisphenol A dicyanate, polyphenol cyanate (oligo(3-methylene-1,5-phenylene cyanate), 4,4'-methylenebis(2,6-dimethylphenyl cyanate), 4,4'-ethylidene diphenyl dicyanate, hexafluorobisphenol A dicyanate, 2,2-bis(4-cyanato)phenylpropane, 1,1-bis(4-cyanatophenylmethane), bis(4-cyanato-3,5-dimethylphenyl) cyanate ( ... Examples of suitable cyanate resins include bifunctional cyanate resins such as 1,3-bis(4-cyanatophenyl-1-(methylethylidene))methane, 1,3-bis(4-cyanatophenyl)thioether, and bis(4-cyanatophenyl)ether; polyfunctional cyanate resins derived from phenol novolak, cresol novolak, and phenolic resins containing a dicyclopentadiene structure; and prepolymers in which these cyanate resins are partially triazine-modified. These may be used alone or in combination of two or more.

[0098] The thiol curing agent may be any agent containing two or more thiol groups in one molecule, and is not limited to the following, for example, 3,3'-dithiodipropionic acid, trimethylolpropane tris(thioglycolate), pentaerythritol tetrakis(thioglycolate), ethylene glycol dithioglycolate, 1,4-bis(3-mercaptobutyryloxy)butane, tris[(3-mercaptopropionyloxy)-ethyl]-isocyanurate, 1,3,5-tris(3-mercaptobutyloxyethyl)- Examples of the alkyl acrylate include 1,3,5-triazine-2,4,6(1H,3H,5H)-trione, trimethylolpropane tris(3-mercaptopropionate), pentaerythritol tetrakis(3-mercaptopropionate), pentaerythritol tetrakis(3-mercaptobutyrate), dipentaerythritol hexakis(3-mercaptopropionate), 1,3,4,6-tetrakis(2-mercaptoethyl)glycoluril, 4-butanedithiol, 1,6-hexaneedithiol, and 1,10-decanedithiol. From the viewpoint of impact resistance, 1,4-bis(3-mercaptobutyryloxy)butane, 1,3,5-tris(3-mercaptobutyloxyethyl)-1,3,5-triazine-2,4,6(1H,3H,5H)-trione, pentaerythritol tetrakis(3-mercaptopropionate), and pentaerythritol tetrakis(3-mercaptobutyrate) are preferred, and from the viewpoint of low-temperature curing ability, pentaerythritol tetrakis(3-mercaptopropionate) and pentaerythritol tetrakis(3-mercaptobutyrate) are more preferred. These may be used alone or in combination of two or more.

[0099] In this specification, the low molecular weight epoxy compound excludes the compounds exemplified above as the epoxy resin (C) and refers to a compound having a viscosity of 1 mPa s or more and less than 3 Pa s at 25° C. Low molecular weight epoxy compounds are also sometimes called reactive diluents.

[0100] Examples of low molecular weight epoxy compounds include, but are not limited to, the following epoxy compounds having no aromatic ring and epoxy compounds having an aromatic ring. Examples of monofunctional epoxy compounds having no aromatic ring include compounds such as n-butyl glycidyl ether, t-butyl glycidyl ether, allyl glycidyl ether, and 2-ethylhexyl glycidyl ether. Examples of monofunctional epoxy compounds having one or more aromatic rings include styrene oxide, phenyl glycidyl ether, cresyl glycidyl ether, p-sec-butylphenyl glycidyl ether, t-butylphenyl glycidyl ether, and compounds such as SY-OPG (trade name, manufactured by Sakamoto Yakuhin Kogyo Co., Ltd.). Examples of bifunctional epoxy compounds having no aromatic ring include 1,4-cyclohexanedimethanol diglycidyl ether, 1,3-cyclohexanedimethanol diglycidyl ether, (3,4-epoxycyclohexyl)methyl-3,4-epoxycyclohexylcarboxylate, ethylene glycol diglycidyl ether, diethylene glycol diglycidyl ether, propylene glycol diglycidyl ether, 1,6-hexanediol diglycidyl ether, neopentyl glycol diglycidyl ether, dicyclopentadiene dimethanol diglycidyl ether, vinylcyclohexene dioxide, and compounds such as Mitsubishi Chemical Corporation (trade name: YX-8000) and Sakamoto Yakuhin Kogyo Co., Ltd. (trade name: SR-8EGS). Examples of difunctional epoxy compounds having one or more aromatic rings include hexahydrophthalic acid diglycidyl ether, resorcinol diglycidyl ether, tert-butylhydroquinone diglycidyl ether, diglycidyl ether of polyoxyalkylene bisphenol A, N,N-diglycidylaniline, N,N-diglycidyl-o-toluidine, etc. Examples of trifunctional epoxy compounds include trimethylolpropane triglycidyl ether, glycerin triglycidyl ether, N,N-bis(2,3-epoxypropyl)-4-(2,3-epoxypropoxy)aniline, etc.

[0101] Examples of the solvent include, but are not limited to, hydrocarbons such as toluene, xylene, cyclohexane, mineral spirits, and solvent naphtha; ketones such as acetone, methyl ethyl ketone (MEK), methyl isobutyl ketone (MIBK), and cyclohexanone; esters such as ethyl acetate, n-butyl acetate, and propylene glycol monomethyl ethyl ether acetate; alcohols such as isopropanol, n-butanol, butyl cellosolve, butyl carbitol, and 1-methoxy-2-propanol; and amide solvents such as dimethylformamide, dimethylacetamide, and N-methylpyrrolidone.

[0102] The low molecular weight acrylic compound refers to an acrylic compound having a molecular weight of 700 or less, and includes, but is not limited to, a compound having (meth)acryloyl groups at both ends of a polyalkylene oxide, polyethylene glycol di(meth)acrylate, polypropylene glycol di(meth)acrylate, polybutylene glycol di(meth)acrylate, trimethylolpropane-type polyfunctional (meth)acrylate, pentaerythritol-type polyfunctional (meth)acrylate, dipentaerythritol-type polyfunctional (meth)acrylate, epoxy (meth)acrylate, and the like.

[0103] The organic filler functions as an impact buffer, capable of mitigating stress generated by impact. By including an organic filler, the epoxy resin composition of this embodiment can further improve adhesion to various connecting members. It also tends to suppress the occurrence and progression of fillet cracks. Examples of organic fillers include, but are not limited to, organic fine particles of acrylic resin, silicone resin, butadiene rubber, polyester, polyurethane, polyvinyl butyral, polyarylate, polymethyl methacrylate, acrylic rubber, polystyrene, NBR, SBR, silicone-modified resin, and copolymers containing these as components. From the perspective of improving adhesion, examples of organic fine particles include alkyl (meth)acrylate-butadiene-styrene copolymer, alkyl (meth)acrylate-silicone copolymer, silicone-(meth)acrylic copolymer, composites of silicone and (meth)acrylic acid, composites of alkyl (meth)acrylate-butadiene-styrene and silicone, and composites of alkyl (meth)acrylate and silicone. Furthermore, organic fine particles having a core-shell structure, in which the core layer and shell layer have different compositions, can also be used. Examples of core-shell type organic fine particles include particles having a silicone-acrylic rubber core to which an acrylic resin is grafted, particles having an acrylic copolymer to which an acrylic resin is grafted, etc. These organic fillers may be used alone or in combination of two or more.

[0104] The inorganic filler can adjust the thermal expansion coefficient of the epoxy resin composition of this embodiment, and therefore the inclusion of the inorganic filler tends to contribute to improving the heat resistance and moisture resistance when the epoxy resin composition of this embodiment is used as an underfill material. Examples of inorganic fillers include, but are not limited to, silicates such as talc, calcined clay, uncalcined clay, mica, and glass; oxides such as titanium oxide, aluminum oxide (alumina), fused silica (e.g., fused spherical silica and fused crushed silica), synthetic silica, and crystalline silica; carbonates such as calcium carbonate, magnesium carbonate, and hydrotalcite; hydroxides such as aluminum hydroxide, magnesium hydroxide, and calcium hydroxide; sulfates such as barium sulfate and calcium sulfate; sulfites such as calcium sulfite; borates such as zinc borate, barium metaborate, aluminum borate, calcium borate, and sodium borate; and nitrides such as aluminum nitride, boron nitride, and silicon nitride. Among these, fused silica, crystalline silica, and synthetic silica powder are preferred from the viewpoint of improving heat resistance, moisture resistance, and strength, and aluminum oxide and boron nitride are also preferred. The use of these materials can suppress the coefficient of linear thermal expansion, which is expected to improve thermal cycle tests. The shape of the inorganic filler is not particularly limited, and may be, for example, amorphous, spherical, or flaky. These inorganic fillers may be used alone or in combination of two or more.

[0105] Examples of pigments include, but are not limited to, kaolin, aluminum oxide trihydrate, aluminum hydroxide, chalk powder, gypsum, calcium carbonate, antimony trioxide, pentone, silica, aerosol, lithopone, baryte, and titanium dioxide.

[0106] Examples of dyes include, but are not limited to, natural dyes such as plant-derived dyes such as madder and indigo, and mineral-derived dyes such as yellow ochre and red clay, synthetic dyes such as alizarin and indigo, and fluorescent dyes.

[0107] Examples of flow control agents include, but are not limited to, organic silane compounds such as silane coupling agents; organic titanium compounds such as titanium tetraisopropoxide and titanium diisopropoxybis(acetylacetonate); and organic zirconium compounds such as zirconium tetra-normal-butoxide and zirconium tetraacetylacetonate.

[0108] Examples of thickeners include, but are not limited to, animal-based thickeners such as gelatin; plant-based thickeners such as polysaccharides and cellulose; and chemically synthesized thickeners such as polyacrylic thickeners, modified polyacrylic thickeners, polyether thickeners, urethane-modified polyether thickeners, and carboxymethyl cellulose.

[0109] Examples of the release agent include, but are not limited to, fluorine-based release agents, silicone-based release agents, and acrylic release agents made of a copolymer of glycidyl (meth)acrylate and a linear alkyl (meth)acrylate having 16 to 22 carbon atoms.

[0110] Examples of wetting agents include, but are not limited to, unsaturated polyester copolymer wetting agents having an acidic group, such as acrylic polyphosphate ester.

[0111] Examples of flame retardants include, but are not limited to, metal hydroxides such as aluminum hydroxide and magnesium hydroxide, halogen-based flame retardants such as chlorine compounds and bromine compounds, phosphorus-based flame retardants such as condensed phosphate esters, antimony-based flame retardants such as antimony trioxide and antimony pentoxide, and inorganic oxides such as silica.

[0112] Examples of surfactants include, but are not limited to, anionic surfactants such as alkylbenzene sulfonates and alkyl polyoxyethylene sulfates, cationic surfactants such as alkyl dimethyl ammonium salts, amphoteric surfactants such as alkyl dimethyl amine oxides and alkyl carboxy betaines, and nonionic surfactants such as linear alcohols and fatty acid esters having 25 or more carbon atoms.

[0113] Resins other than epoxy resins include, but are not limited to, silicone resins, phenolic resins, phenoxy resins, polyvinyl butyral resins, polyvinyl acetal resins, polyacrylic resins, polyimide resins, and elastomers having functional groups such as carboxyl groups, hydroxyl groups, vinyl groups, and amino groups.

[0114] [Method for Producing Epoxy Resin Composition] The method for producing an epoxy resin composition of this embodiment includes a step of obtaining a mixture of the epoxy resin curing agent having the core (A) and layer (B) of this embodiment, and an epoxy resin (C). Examples of steps for obtaining the mixture include, but are not limited to, (1) a step of adding the epoxy resin (C) to the epoxy resin curing agent of this embodiment, (2) a step of adding the epoxy resin curing agent of this embodiment to the epoxy resin (C), and (3) a step of adding the epoxy resin (C) to a masterbatch in which the epoxy resin curing agent of this embodiment and a dispersion medium are combined. The mixing method included in the method for producing an epoxy resin composition of this embodiment is also not particularly limited, and can be appropriately selected from, for example, a method using a planetary mixer or a method using a three-roll mill. The method for producing an epoxy resin curing agent of this embodiment is as described above.

[0115] Furthermore, the present embodiment also includes an epoxy resin composition obtained by treating the epoxy resin composition of the present embodiment as a masterbatch-type epoxy resin curing agent composition, and adding and mixing the epoxy resin (C) and other additive components to the masterbatch-type epoxy resin curing agent composition. Examples of the mixing method include thoroughly mixing until homogeneous using a mixing roll such as a three-roll mill, a dissolver, a planetary mixer, a kneader, an extruder, or the like.

[0116] The epoxy resin curing agent, epoxy resin composition, and epoxy resin composition preparation for film of this embodiment, which will be described later, can also be subjected to a heat treatment at a temperature of 30°C to 80°C for 1 to 168 hours. The heating method is not particularly limited, and examples thereof include heating in an oven, incubator, water bath, oil bath, etc. The temperature history is also not particularly limited, and for example, the temperature may be increased stepwise or all at once. When heating the epoxy resin curing agent, after the reaction for forming layer (B) is completed, the epoxy resin curing agent is allowed to stand in an environment of 5 to 12°C for 8 hours or more before heating.

[0117] [Specific Aspects of Epoxy Resin Composition] The epoxy resin composition of the present embodiment is suitable for, but is not limited to, sealing materials for electrical and electronic components such as underfill materials and relay sealing materials, conductive materials such as conductive pastes, thermally conductive materials, insulating materials, adhesives for camera modules, structural adhesives, matrix resins for fiber-reinforced plastics, impregnation and fixing materials for motor coils, and the like. In addition to the above, the epoxy resin composition of the present embodiment is also suitable for, but is not limited to, interlayer insulating films, film-type solder resists, sealing sheets, conductive films, anisotropically conductive films, thermally conductive films, and the like. For each of the above applications, a single epoxy resin composition of the present embodiment may serve multiple applications. Examples of such applications include, but are not limited to, when the epoxy resin composition of the present embodiment contains silver particles as a filler, the conductive material obtainable from the epoxy resin composition can also serve as a thermally conductive material. As described above, the epoxy resin composition of the present embodiment can be preferably used as a sealing material, an electrically conductive material, a thermally conductive material, an insulating material, an adhesive for a camera module, a structural adhesive, a matrix resin for fiber-reinforced plastics, an impregnating fixing material, an interlayer insulating film, a film-type solder resist, an encapsulating sheet, an electrically conductive film, an anisotropically conductive film, and / or a thermally conductive film. In other words, the sealing material, the electrically conductive material, the thermally conductive material, the insulating material, the adhesive for a camera module, a structural adhesive, a matrix resin for fiber-reinforced plastics, an impregnating fixing material, an interlayer insulating film, a film-type solder resist, an encapsulating sheet, an electrically conductive film, an anisotropically conductive film, and a thermally conductive film of the present embodiment all contain the epoxy resin composition of the present embodiment (the epoxy resin curing agent of the present embodiment).

[0118] For example, when the epoxy resin composition of this embodiment is used as an underfill material, it requires heat stability for rapid penetration between the semiconductor chip and the substrate, as well as excellent curing properties at temperatures between 120°C and 150°C. The epoxy resin composition of this embodiment, containing an epoxy resin curing agent, can combine all of these properties. Conductive materials may contain conductive particles such as solder particles, nickel particles, nano-sized metal crystals, particles with metal surfaces coated with other metals, and gradient copper and silver particles, as well as solvents. However, the epoxy resin curing agent of this embodiment has a strong layer (B) that provides resistance to metal particles and also solvents. Therefore, an epoxy resin composition containing the epoxy resin curing agent of this embodiment can provide a conductive material with excellent stability. Thermally conductive materials incorporate a curing agent and a metal with high thermal conductivity, such as silver, a metal oxide such as zinc oxide, a ceramic such as boron nitride, aluminum nitride, or alumina, or an inorganic filler such as silica. Thermoelectric conductive materials require stability during storage, but it is difficult to achieve excellent stability if the curing agent is not isolated from the liquid component. Even if a coating layer is present to isolate the curing agent component from the liquid component, if its strength is insufficient, it will be destroyed upon impact with the filler. The epoxy resin composition containing the epoxy resin curing agent of this embodiment has excellent properties and can provide a stable thermally conductive material. Structural adhesives, such as those typically used in automotive structural applications, are often placed in high-temperature, high-humidity environments after application, requiring excellent stability against both heat and moisture. The epoxy resin composition containing the epoxy resin curing agent of this embodiment can provide a structural adhesive with excellent stability against both heat and moisture. For example, dual-cure adhesives are used in camera module adhesives, which are cured by both light and heat during active alignment between a lens holder and an electronic component equipped with an image sensor such as a CMOS sensor. Dual-cure adhesives contain both an epoxy resin and an acrylic resin. Even when the epoxy resin curing agent of this embodiment contains both, it can provide a camera module adhesive that combines sufficient stability and reactivity.Matrix resins for fiber-reinforced plastics and impregnating and fixing materials for motor coils are required to have performance throughout the process from impregnation to curing, i.e., the ability to penetrate into gaps in fine fibers or coils, stability during penetration, and curing ability. The epoxy resin composition containing the epoxy resin curing agent of this embodiment is suitable because it can combine all of these properties.

[0119] [Film Comprising the Epoxy Resin Composition of the Present Embodiment] This embodiment also includes a film having a resin composition layer containing the epoxy resin curing agent and / or epoxy resin composition of the present embodiment. In this case, the epoxy resin composition can also function as an epoxy resin curing agent or curing accelerator. The epoxy resin composition of this embodiment has excellent solvent resistance and is suitable for films. The film of this embodiment has, for example, a predetermined support and a resin composition layer formed on the support from an epoxy resin composition preparation liquid described below, and may optionally have a protective layer on the surface of the resin composition layer opposite the support.

[0120] The support is preferably a material that can withstand the temperature during drying of the organic solvent. Examples of such a support include, but are not limited to, polyethylene terephthalate film, polyvinyl alcohol film, polyvinyl chloride film, vinyl chloride copolymer film, polyvinylidene chloride film, vinylidene chloride copolymer film, polymethyl methacrylate copolymer film, polystyrene film, polyacrylonitrile film, styrene copolymer film, polyamide film, cellulose derivative film, etc. These films can also be stretched as needed.

[0121] The protective layer is preferably made of a material capable of sufficiently maintaining the surface smoothness of the resin composition layer, and examples of such a protective layer include, but are not limited to, polyethylene film, polypropylene film, polyethylene terephthalate film treated for easy peeling, and oriented polypropylene film.

[0122] [Method for Preparing Epoxy Resin Composition Preparation for Film] An example of a method for preparing an epoxy resin composition preparation for forming a resin composition layer of a film is to mix the epoxy resin curing agent and / or epoxy resin composition of this embodiment with other additives, a film-forming polymer, etc., add an organic solvent, and mix the mixture using a planetary mixer or the like. As the film-forming polymer, any polymer can be used that has the effect of suppressing cracking, cissing, and excessive flow and maintaining the film shape when the epoxy resin composition preparation is applied and then dried to remove the organic solvent. Examples of such film-forming polymers include, but are not limited to, phenoxy resin, polyvinyl butyral resin, polyvinyl acetal resin, polyacrylic resin, polyimide resin, and elastomers having functional groups such as carboxyl, hydroxyl, vinyl, and amino groups. Film-forming polymers are sometimes called binder polymers. There are no particular limitations on the organic solvent, and known organic solvents can be used. Examples of solvents include, but are not limited to, hydrocarbons such as toluene, xylene, cyclohexane, mineral spirits, and solvent naphtha; ketones such as acetone, methyl ethyl ketone (MEK), methyl isobutyl ketone (MIBK), and cyclohexanone; esters such as ethyl acetate, n-butyl acetate, and propylene glycol monomethyl ethyl ether acetate; alcohols such as methanol, isopropanol, n-butanol, butyl cellosolve, and butyl carbitol; and amide solvents such as dimethylformamide, dimethylacetamide, and N-methylpyrrolidone.

[0123] [Film Manufacturing Method] The film of this embodiment can be produced by sequentially laminating a support, a resin composition layer, and, if necessary, a protective layer. Known methods can be used to laminate the support, resin composition layer, and protective layer. For example, a mixed solution containing the epoxy resin composition of this embodiment and an organic solvent is prepared, and then coated onto a support using a known method such as an applicator or bar coater. The coated solution is then dried to form a resin composition layer on the support. The drying method is not particularly limited, but examples include oven drying and hot air blowing. The drying temperature and time are also not particularly limited. However, from the viewpoint of thoroughly removing the solvent and suppressing deformation of the support due to excessive heating and excessive reaction of the resin composition layer during drying, drying at a temperature range of 50°C to 160°C for a drying time of 1 minute to 30 minutes is preferred, and drying at 80°C to 150°C for 3 minutes to 25 minutes is more preferred. The drying temperature may be constant or may be applied with a temperature gradient. Next, if necessary, a protective layer is laminated on the formed resin composition layer to produce a film.

[0124] [Specific Aspects of Films Comprising the Epoxy Resin Composition of the Present Embodiment] Films comprising the epoxy resin composition of the present embodiment can be used, for example, as interlayer insulating films, film-type solder resists, encapsulating sheets, conductive films, anisotropically conductive films, and thermally conductive films, without being limited thereto. The epoxy resin composition of the present embodiment has excellent solvent resistance and storage stability, making it possible to extend the coatable time of an epoxy resin composition preparation for film containing the composition, and also to extend the shelf life of the resulting film. Furthermore, since the epoxy resin composition of the present embodiment has excellent curability at temperatures of 150°C or less, the film of the present embodiment also has excellent curability. The above-mentioned properties are commonly required for interlayer insulating films, film-type solder resists, encapsulating sheets, conductive films, anisotropically conductive films, and thermally conductive films, and therefore the film of the present embodiment is suitable for these applications.

[0125] Hereinafter, the present embodiment will be described with reference to specific examples and comparative examples, but the present embodiment is not limited to the following examples and comparative examples. In the following, "parts" and "%" are by mass unless otherwise specified.

[0126] [Production of Core (A) Containing Nitrogen-Containing Compound] (Production Example 1) One equivalent (based on epoxy groups) of bisphenol A-type epoxy resin E-1 (epoxy equivalent: 186 g / eq, total chlorine content: 600 ppm, hydrolyzable chlorine content: 50 ppm) and one equivalent (based on active hydrogen) of 2-methylimidazole were reacted at 80°C in a 1:1 mixed solvent of n-butanol and toluene. Thereafter, unreacted 2-methylimidazole was distilled off together with the solvent under reduced pressure to obtain a solid substance 1 at 25°C. Next, the substance 1 was pulverized using a jet mill and further classified using a classifier to obtain a solid substance having a specific surface area of ​​3.71 m. ２ / g, average particle size under sieve D ５０ is 2.63 μm, D ９９ / D ５０ Core component 1 having a particle size distribution of 5.5 and containing 0.005% by mass of 2-methylimidazole (abbreviated as "2MI" in the table) was obtained. ５０ and D ９９ is determined by measuring the particle size distribution of the core (A) at an undersize cumulative fraction of 50% based on the Stokes diameter measured by a laser diffraction / light scattering method using a particle size distribution analyzer (HORIBA LA-920 manufactured by HORIBA Ltd.). ５０ The particle size of the core (A) at an undersize cumulative fraction of 99% is defined as D ９９ The specific surface area was measured using a fully automatic BET specific surface area measuring device HM model-1201 manufactured by Mountech Co., Ltd., using a mixed gas of N2 / He = 30 / 70 (volume ratio) as the adsorption gas (the same applies to the following production examples).

[0127] (Production Example 2) Using the core component 1, a Kryptron Orb manufactured by EarthTechnica Corporation was used, and the temperature was 10°C, the humidity was 30%, the rotation speed was 13,500 rpm, the supply rate was 10 kg / hr, and the air volume was 3 m ３A cyclone collector and a bag filter were attached to the classifier, and classification was performed to obtain a specific surface area of ​​2.51 m. ２ / g, D ５０ is 2.80 μm, D ９９ / D ５０ Core component 2 having a particle size distribution of 3.8 and containing 0.005% by mass of 2-methylimidazole was obtained.

[0128] (Production Example 3) One equivalent (based on epoxy groups) of bisphenol A epoxy resin E-1 (epoxy equivalent: 186 g / eq, total chlorine content: 600 ppm, hydrolyzable chlorine content: 50 ppm) and 1.2 equivalents (based on active hydrogen) of 2-methylimidazole were reacted at 80°C in a 1:1 mixed solvent of n-butanol and toluene. Then, excess 2-methylimidazole was distilled off together with the solvent under reduced pressure to obtain solid substance 2 at 25°C. Substance 2 was then pulverized in a turbo mill and further classified using a classifier to obtain a solid having a specific surface area of ​​3.61 m. ２ / g, average particle size under sieve D ５０ is 2.41 μm, D ９９ / D ５０ Core component 3 having a particle size distribution of 5.1 and containing 0.2% by mass of 2-methylimidazole was obtained.

[0129] (Production Example 4) One equivalent (based on epoxy groups) of bisphenol F epoxy resin E-2 (BisF resin, epoxy equivalent: 172 g / eq, total chlorine content: 500 ppm, hydrolyzable chlorine content: 100 ppm) and one equivalent (based on active hydrogen) of 2-methylimidazole were reacted at 80°C in a 1:1 mixed solvent of n-butanol and toluene. Thereafter, excess 2-methylimidazole and the solvent were distilled off under reduced pressure, yielding solid substance 3 at 25°C. The resulting substance 3 was pulverized in a turbo mill to obtain a solid having a specific surface area of ​​3.91 m. ２ / g, average particle size under sieve D ５０ is 2.55 μm, D ９９ / D ５０ Core component 4 having a particle size distribution of 4.0 and containing 0.01% by mass of 2-methylimidazole was obtained.

[0130] (Production Example 5) One equivalent (based on epoxy groups) of bisphenol A epoxy resin E-1 (epoxy equivalent weight 186 g / eq, total chlorine content 600 ppm, hydrolyzable chlorine content 50 ppm) and one equivalent of diethylenetriamine (abbreviated as "DETA" in the table) were reacted at 80°C in a 1:1 mixed solvent of xylene and isopropyl alcohol. The excess diethylenetriamine and the solvent were then distilled off under reduced pressure to obtain solid substance 4 at 25°C. 45 g of substance 4, 45 g of substance 1, and 11 g of 1,4-diazabicyclo[2.2.2]octane (abbreviated as "DABCO" in the table) were melt-mixed at 150°C to obtain solid substance 5 at 25°C. Substance 5 was then pulverized in a turbo mill and further classified using a classifier to obtain a specific surface area of ​​2.69 m. ２ / g, average particle size under sieve D ５０ is 2.88 μm, D ９９ / D ５０ Core component 5 was obtained, which had a particle size distribution of 4.7, contained 10 mass % of 1,4-diazabicyclo[2.2.2]octane, and further contained 0.1 mass % of diethylenetriamine and 2-methylimidazole in total.

[0131] (Production Example 6) The substance 1 was pulverized by a jet mill and further classified by a classifier to obtain a powder with a specific surface area of ​​4.32 m ２ / g, average particle size under sieve D ５０ is 2.27 μm, D ９９ / D ５０ Core component 6 having a particle size distribution of 3.4 and containing 0.005% by mass of 2-methylimidazole was obtained.

[0132] Example 1 100 parts by mass of bisphenol A epoxy resin E-1 (epoxy equivalent 186 g / eq, total chlorine content 600 ppm, hydrolyzable chlorine content 50 ppm), 100 parts by mass of bisphenol F epoxy resin E-2 (epoxy equivalent 172 g / eq, total chlorine content 500 ppm, hydrolyzable chlorine content 100 ppm), 100 parts by mass of core component 1, and 10 parts by mass of core surface coating material C-1 (MR-400 manufactured by Nippon Polyurethane Co., Ltd.) were dispersed and mixed, and then reacted at 55°C for 5 hours. The mixture was then allowed to stand for 12 hours under conditions set at 9°C (standing step), to obtain a masterbatch-type epoxy resin curing agent composition 1. During the standing step, the temperature was monitored, and the temperature was measured at the start point t １ to the end time t ２ Minimum temperature T Ｌ and maximum temperature T Ｈ It was confirmed that the difference between the temperature of the sample and the temperature of the container was 4°C or less. That is, it was confirmed that the temperature change when the container was left standing for 12 hours under conditions set at 9°C was within the range of 9°C ± 2°C (the temperature change during the standing step was confirmed in the same manner hereafter).

[0133] (Evaluation of dyeability of layer (B)) First, 10.6 mL of a base agent (Quetol 812, manufactured by Nissin EM Co., Ltd.), 9.4 mL of a curing agent (methyl nadic anhydride: MNA, manufactured by Nissin EM Co., Ltd.), and 0.34 mL of a reaction accelerator (2,4,6-Tris(dimethyl amino methyl)phenol, manufactured by Nissin EM Co., Ltd.: DMP-30) were mixed and stirred with a stirrer for 15 minutes, and then air bubbles were removed by vacuum degassing to obtain an epoxy resin composition for dyeing. Next, toluene was added to the masterbatch-type epoxy resin curing agent composition 1, and the epoxy resin and curing agent components were separated using a centrifuge. The curing agent component was then collected and dried to obtain epoxy resin curing agent 1. The obtained epoxy resin curing agent 1 was allowed to coexist with ruthenium tetroxide in a sealed and light-shielded container at room temperature and atmospheric pressure for 10 minutes to be electron-stained, and then mixed with the above-mentioned epoxy resin composition for dyeing and cured at 40°C for 42 hours to obtain a cured product in which epoxy resin curing agent 1 was embedded. 80 nm slices were prepared using an ultramicrotome, and the slices were allowed to coexist with osmium tetroxide in a sealed and light-shielded container at room temperature and atmospheric pressure for 2 hours to obtain observation samples that were electron-stained with osmium tetroxide vapor. The observation sample was irradiated with an electron beam using a TEM, and the focus was adjusted to be on the sample. Observation was performed at an accelerating voltage of 120 kV and a magnification of 30,000 times to obtain images 1 of the core (A) and layer (B). The obtained image 1 was read using image analysis software ImageJ (ImageJ 1.53t Java 1.8.0_345 (64-bit)) and subjected to a median filter (Radius 2.0 pixels). A line segment was then drawn from the outermost part of layer (B) to include the boundary between core (A) and layer (B), yielding image 1' (Figure 1). Graph 1, which plots the brightness along this line segment, was obtained (Figure 2). In graph 1, the vertical axis represents brightness, and the horizontal axis represents the distance from the outermost end of layer (B) on the line segment (the same applies to subsequent graphs).

[0134] From the obtained image 1′ and graph 1, it was confirmed that, when a brightness graph was obtained from the outermost part of the layer (B) to the boundary between the layer (B) and the core (A), the inside of the layer (B) of the epoxy resin curing agent 1 had a region having a brightness higher than the brightness of the outermost part and the brightness of the boundary.

[0135] Example 2 100 parts by mass of bisphenol A epoxy resin E-1 (epoxy equivalent 186 g / eq, total chlorine content 600 ppm, hydrolyzable chlorine content 50 ppm), 100 parts by mass of bisphenol F epoxy resin E-2 (epoxy equivalent 172 g / eq, total chlorine content 500 ppm, hydrolyzable chlorine content 100 ppm), 200 parts by mass of core component 2, and 10 parts by mass of core surface coating material C-1 (MR-400 manufactured by Nippon Polyurethane Co., Ltd.) were dispersed and mixed, reacted at 55°C for 5 hours, and then allowed to stand at 9°C for 12 hours to obtain masterbatch-type epoxy resin curing agent composition 2. It was confirmed that the temperature change during the 12-hour stand at 9°C was within the range of 9°C ± 2°C.

[0136] The dyeability of the contained epoxy resin curing agent 2 was confirmed by treating the masterbatch-type epoxy resin curing agent composition 2 in the same manner as in the masterbatch-type epoxy resin curing agent composition 1. As a result, when a luminance graph was obtained from the outermost part of the layer (B) to the boundary between the layer (B) and the core (A), it was confirmed that the inside of the layer (B) had a region having a luminance higher than that of the outermost part and that of the boundary.

[0137] [Example 3] 100 parts by mass of bisphenol A type epoxy resin E-1 (epoxy equivalent 186 g / eq, total chlorine content 600 ppm, hydrolyzable chlorine content 50 ppm), 100 parts by mass of bisphenol F type epoxy resin E-2 (epoxy equivalent 172 g / eq, total chlorine content 500 ppm, hydrolyzable chlorine content 100 ppm), 100 parts by mass of core component 3, and 10 parts by mass of core surface coating material C-2 (Tosoh Corporation Coronate T100), and then, after reacting for 5 hours at 55 ° C., the mixture was allowed to stand for 12 hours under conditions set at 9 ° C., to obtain a masterbatch type epoxy resin curing agent composition 3. It was confirmed that the temperature change when left to stand for 12 hours under conditions set at 9 ° C. was in the range of 9 ° C. ± 2 ° C.

[0138] The dyeability of the masterbatch-type epoxy resin curing agent composition 3 was confirmed in the same manner as in the masterbatch-type epoxy resin curing agent composition 1. That is, in image 2 obtained by image analysis of a TEM observation image of the epoxy resin curing agent 3, a line was drawn at a predetermined position to confirm the dyeability, to obtain image 2' (FIG. 3). Graph 2 was obtained by plotting the brightness along this line (FIG. 4). From image 2' and graph 2, it was confirmed that, when a brightness graph was obtained from the outermost portion of the layer (B) to the boundary between the layer (B) and the core (A), the interior of the layer (B) of the epoxy resin curing agent 3 had a region having a brightness higher than that of the outermost portion and that of the boundary.

[0139] Example 4 100 parts by mass of bisphenol A epoxy resin E-1 (epoxy equivalent 186 g / eq, total chlorine content 600 ppm, hydrolyzable chlorine content 50 ppm), 100 parts by mass of bisphenol F epoxy resin E-2 (epoxy equivalent 172 g / eq, total chlorine content 500 ppm, hydrolyzable chlorine content 100 ppm), 100 parts by mass of core component 4, 4 parts by mass of core surface coating material C-1 (MR-400 manufactured by Nippon Polyurethane Co., Ltd.), and 3 parts by mass of core surface coating material C-3 (Duranate TPA-100 manufactured by Asahi Kasei Corporation) were dispersed and mixed, reacted at 55°C for 5 hours, and then allowed to stand at 9°C for 12 hours to obtain masterbatch-type epoxy resin curing agent composition 4. It was confirmed that the temperature change after standing at 9°C for 12 hours was within the range of 9°C ± 2°C.

[0140] The dyeability of the epoxy resin curing agent 4 containing the masterbatch-type epoxy resin curing agent composition 4 was confirmed in the same manner as in the masterbatch-type epoxy resin curing agent composition 1. That is, in image I obtained by image analysis of a TEM observation image of the epoxy resin curing agent 4, a line was drawn at a predetermined position to obtain image I' to confirm the dyeability ( FIG. 5 ). Graph G, which plots the brightness along this line, was obtained ( FIG. 6 ). From image I' and graph G, it was confirmed that, when a brightness graph was obtained from the outermost portion of layer (B) to the boundary between layer (B) and core (A), the interior of layer (B) had a region with a brightness higher than that of the outermost portion and that of the boundary. Furthermore, in FIG. 5 , the boundary between layer (B) and the region of the epoxy resin composition for dyeing appears wavy or wrinkled, suggesting that the surface of layer (B) was rough. In addition, when comparing Fig. 5 (epoxy resin curing agent 4) with Fig. 1 (epoxy resin curing agent 1) and Fig. 3 (epoxy resin curing agent 3), the boundary between the layer (B) and the epoxy resin composition for dyeing region in Figs. 1 and 3 appears to be linear, suggesting that the surface of the layer (B) in epoxy resin curing agents 1 and 3 is a smooth surface compared to epoxy resin curing agent 4 described later.

[0141] Example 5 100 parts by mass of bisphenol A epoxy resin E-1 (epoxy equivalent 186 g / eq, total chlorine content 600 ppm, hydrolyzable chlorine content 50 ppm), 100 parts by mass of bisphenol F epoxy resin E-2 (epoxy equivalent 172 g / eq, total chlorine content 500 ppm, hydrolyzable chlorine content 100 ppm), 120 parts by mass of core component 5, and 10 parts by mass of core surface coating material C-1 (MR-400 manufactured by Nippon Polyurethane Co., Ltd.) were dispersed and mixed, and the mixture was reacted at 55°C for 5 hours and then allowed to stand at 9°C for 12 hours to obtain masterbatch-type epoxy resin curing agent composition 5. It was confirmed that the temperature change after standing at 9°C for 12 hours was within the range of 9°C ± 2°C.

[0142] The dyeability of the contained epoxy resin curing agent 5 was confirmed by treating the masterbatch-type epoxy resin curing agent composition 5 in the same manner as in the masterbatch-type epoxy resin curing agent composition 1. As a result, when a luminance graph was obtained from the outermost part of the layer (B) to the boundary between the layer (B) and the core (A), it was confirmed that the inside of the layer (B) had a region having a luminance higher than that of the outermost part and that of the boundary.

[0143] Example 6 90 parts by mass of bisphenol A epoxy resin E-1 (epoxy equivalent 186 g / eq, total chlorine content 600 ppm, hydrolyzable chlorine content 50 ppm), 90 parts by mass of bisphenol F epoxy resin E-2 (epoxy equivalent 172 g / eq, total chlorine content 500 ppm, hydrolyzable chlorine content 100 ppm), 20 parts by mass of naphthalene epoxy resin E-3 (epoxy equivalent 142 g / eq, total chlorine content 700 ppm, "HP4032D" manufactured by DIC Corporation), 100 parts by mass of core component 1, and 10 parts by mass of core surface coating material C-1 (MR-400 manufactured by Nippon Polyurethane Co., Ltd.) were dispersed and mixed, and the mixture was reacted at 55°C for 5 hours and then allowed to stand at 9°C for 12 hours, thereby obtaining masterbatch-type epoxy resin curing agent composition 6. It was confirmed that the temperature change when the container was left standing for 12 hours under conditions set at 9°C was within the range of 9°C ± 2°C.

[0144] The dyeability of the contained epoxy resin curing agent 6 was confirmed by treating the masterbatch-type epoxy resin curing agent composition 6 in the same manner as in the masterbatch-type epoxy resin curing agent composition 1. As a result, when a luminance graph was obtained from the outermost part of the layer (B) to the boundary between the layer (B) and the core (A), it was confirmed that the inside of the layer (B) had a region having a luminance higher than that of the outermost part and that of the boundary.

[0145] Example 7 100 parts by mass of bisphenol A epoxy resin E-1 (epoxy equivalent 186 g / eq, total chlorine content 600 ppm, hydrolyzable chlorine content 50 ppm), 100 parts by mass of bisphenol F epoxy resin E-2 (epoxy equivalent 172 g / eq, total chlorine content 500 ppm, hydrolyzable chlorine content 100 ppm), 100 parts by mass of core component 1, and 10 parts by mass of core surface coating material C-1 (MR-400 manufactured by Nippon Polyurethane Co., Ltd.) were dispersed and mixed, reacted at 55°C for 5 hours, and then allowed to stand at 6°C for 8 hours to obtain masterbatch-type epoxy resin curing agent composition 7. It was confirmed that the temperature change after standing at 6°C for 8 hours was within the range of 6°C ± 2°C.

[0146] The dyeability of the contained epoxy resin curing agent 7 was confirmed by treating the masterbatch type epoxy resin curing agent composition 7 in the same manner as in the masterbatch type epoxy resin curing agent composition 1. As a result, when a luminance graph was obtained from the outermost part of the layer (B) to the boundary between the layer (B) and the core (A), it was confirmed that the inside of the layer (B) had a region having a luminance higher than that of the outermost part and that of the boundary.

[0147] Example 8 100 parts by mass of bisphenol A epoxy resin E-1 (epoxy equivalent 186 g / eq, total chlorine content 600 ppm, hydrolyzable chlorine content 50 ppm), 100 parts by mass of bisphenol F epoxy resin E-2 (epoxy equivalent 172 g / eq, total chlorine content 500 ppm, hydrolyzable chlorine content 100 ppm), 100 parts by mass of core component 1, and 10 parts by mass of core surface coating material C-1 (MR-400 manufactured by Nippon Polyurethane Co., Ltd.) were dispersed and mixed, reacted at 55°C for 5 hours, and then allowed to stand at 12°C for 24 hours to obtain masterbatch-type epoxy resin curing agent composition 8. It was confirmed that the temperature change after standing at 12°C for 24 hours was within the range of 12°C ± 2°C.

[0148] The masterbatch-type epoxy resin curing agent composition 8 was treated in the same manner as in the masterbatch-type epoxy resin curing agent composition 1 to confirm the dyeability of the contained epoxy resin curing agent 8. As a result, when a luminance graph was obtained from the outermost part of the layer (B) to the boundary between the layer (B) and the core (A), it was confirmed that the inside of the layer (B) had a region having a luminance higher than that of the outermost part and that of the boundary.

[0149] Example 9 100 parts by mass of bisphenol A epoxy resin E-1 (epoxy equivalent 186 g / eq, total chlorine content 600 ppm, hydrolyzable chlorine content 50 ppm), 100 parts by mass of bisphenol F epoxy resin E-2 (epoxy equivalent 172 g / eq, total chlorine content 500 ppm, hydrolyzable chlorine content 100 ppm), 100 parts by mass of core component 6, and 10 parts by mass of core surface coating material C-1 (MR-400 manufactured by Nippon Polyurethane Co., Ltd.) were dispersed and mixed, reacted at 55°C for 5 hours, and then allowed to stand at 9°C for 12 hours to obtain masterbatch-type epoxy resin curing agent composition 9. It was confirmed that the temperature change after standing at 9°C for 12 hours was within the range of 9°C ± 2°C.

[0150] The masterbatch-type epoxy resin curing agent composition 9 was treated in the same manner as in the masterbatch-type epoxy resin curing agent composition 1 to confirm the dyeability of the contained epoxy resin curing agent 9. As a result, when a luminance graph was obtained from the outermost part of the layer (B) to the boundary between the layer (B) and the core (A), it was confirmed that the inside of the layer (B) had a region having a luminance higher than that of the outermost part and that of the boundary.

[0151] Comparative Example 1: 100 parts by mass of bisphenol A epoxy resin E-1 (epoxy equivalent 186 g / eq, total chlorine content 600 ppm, hydrolyzable chlorine content 50 ppm), 100 parts by mass of bisphenol F epoxy resin E-2 (epoxy equivalent 172 g / eq, total chlorine content 500 ppm, hydrolyzable chlorine content 100 ppm), 100 parts by mass of core component 1, and 10 parts by mass of core surface coating material C-1 (MR-400 manufactured by Nippon Polyurethane Co., Ltd.) were dispersed and mixed, reacted at 55°C for 5 hours, and then allowed to stand at 25°C for 12 hours to obtain masterbatch-type epoxy resin curing agent R-1. It was confirmed that the temperature change after standing at 25°C for 12 hours was within the range of 25°C ± 2°C.

[0152] The dyeability of the epoxy resin curing agent R-1 was confirmed using the masterbatch-type epoxy resin curing agent composition R-1 in the same manner as in the masterbatch-type epoxy resin curing agent composition 1. That is, in image 3 obtained by image analysis of a TEM observation image of epoxy resin curing agent 3, a line was drawn at a predetermined position to confirm the dyeability, to obtain image 3' (FIG. 7). Graph 3 was obtained by plotting the brightness along this line (FIG. 8). From image 3' and graph 3, it was confirmed that, when a brightness graph was obtained from the outermost portion of layer (B) to the boundary between layer (B) and core (A), the interior of layer (B) of epoxy resin curing agent R-1 did not have a region having a brightness higher than that of the outermost portion and that of the boundary.

[0153] Comparative Example 2 100 parts by mass of bisphenol A epoxy resin E-1 (epoxy equivalent 186 g / eq, total chlorine content 600 ppm, hydrolyzable chlorine content 50 ppm), 100 parts by mass of bisphenol F epoxy resin E-2 (epoxy equivalent 172 g / eq, total chlorine content 500 ppm, hydrolyzable chlorine content 100 ppm), 100 parts by mass of core component 1, and 10 parts by mass of core surface coating material C-1 (MR-400 manufactured by Nippon Polyurethane Co., Ltd.) were dispersed and mixed, reacted at 55°C for 5 hours, and then allowed to stand at 50°C for 24 hours to obtain epoxy resin curing agent R-2 of Comparative Example 2. It was confirmed that the temperature change after standing at 50°C for 24 hours was within the range of 50°C ± 2°C.

[0154] The masterbatch-type epoxy resin curing agent composition R-2 was treated in the same manner as in the masterbatch-type epoxy resin curing agent composition 1 to confirm the dyeability of the contained epoxy resin curing agent R-2. As a result, when a luminance graph was obtained from the outermost part of the layer (B) to the boundary between the layer (B) and the core (A), it was confirmed that the inside of the layer (B) did not have a region having a luminance higher than that of the outermost part and that of the boundary.

[0155] Comparative Example 3: 100 parts by mass of bisphenol A epoxy resin E-1 (epoxy equivalent 186 g / eq, total chlorine content 600 ppm, hydrolyzable chlorine content 50 ppm), 100 parts by mass of bisphenol F epoxy resin E-2 (epoxy equivalent 172 g / eq, total chlorine content 500 ppm, hydrolyzable chlorine content 100 ppm), 100 parts by mass of core component 1, and 20 parts by mass of core surface coating material C-1 (MR-400 manufactured by Nippon Polyurethane Co., Ltd.) were dispersed and mixed, reacted at 55°C for 5 hours, and then allowed to stand at 25°C for 12 hours to obtain epoxy resin curing agent R-3 of Comparative Example 3. It was confirmed that the temperature change after standing at 25°C for 12 hours was within the range of 25°C ± 2°C.

[0156] The dyeability of the contained epoxy resin curing agent R-3 was confirmed by treating the masterbatch type epoxy resin curing agent composition R-3 in the same manner as in the masterbatch type epoxy resin curing agent composition 1. As a result, when a luminance graph was obtained from the outermost part of the layer (B) to the boundary between the layer (B) and the core (A), it was confirmed that the inside of the layer (B) did not have a region having a luminance higher than that of the outermost part and that of the boundary.

[0157] [Method for Evaluating Properties] (Evaluation of Stability to Low Molecular Weight Epoxy Compounds) (Method for Preparing Epoxy Resin Composition for Evaluating Stability to Low Molecular Weight Epoxy Compounds) 30 parts of the masterbatch-type epoxy resin curing agent composition described in Examples 1 to 9 and Comparative Examples 1 to 3, 100 parts of jER828 (manufactured by Mitsubishi Chemical Corporation), and 30 parts of a low molecular weight epoxy compound o-CGE (ortho-cresyl glycidyl ether; viscosity at 25°C: 7 mPa s; manufactured by Sigma-Aldrich) were weighed, and then these components were mixed in a non-bubbling kneader while stirring for 2 minutes and degassing for 3 minutes, to prepare an epoxy resin composition for evaluating stability to low molecular weight epoxy compounds. (Stability to Low-Molecular-Weight Epoxy Compounds) The initial viscosity immediately after preparation of an epoxy resin composition for evaluating stability to low-molecular-weight epoxy compounds and the viscosity after storage of the epoxy resin composition for stability evaluation after leaving it at 40°C for 21 days were measured using an E-type viscometer at room temperature (25°C), and the viscosity after storage was calculated using the following formula (2): Viscosity after storage = Viscosity after storage / Initial viscosity Formula (2) Evaluation was made according to the viscosity after storage according to the following criteria: Good: 1.0 times ≦ viscosity after storage < 1.3 times Fair: 1.3 times ≦ viscosity after storage < 2.0 times Bad: 2.0 times ≦ viscosity after storage

[0158] (Reactivity of Epoxy Resin Composition Containing Low-Molecular-Weight Epoxy Compound) Approximately 10 mg of an epoxy resin composition (uncured state) for evaluating stability to low-molecular-weight epoxy compounds was weighed out, and the temperature was raised from 25°C to 250°C at a rate of 20°C / min using a DSC EXSTER7020 (manufactured by Hitachi High-Tech Science Corporation). A DSC curve was obtained, and the temperature at the point where the heat flow was maximum was taken as the DSC exothermic peak temperature. The exothermic peak temperature was evaluated according to the following criteria: ◎◎: exothermic peak temperature≦120°C ◎: 120°C<exothermic peak temperature≦130°C ○: 130°C<exothermic peak temperature≦140°C △: 140°C<exothermic peak temperature≦150°C ×: 150°C<exothermic peak temperature

[0159] (Evaluation of Stability to MEK) (Method of Preparing Epoxy Resin Composition for Evaluating Stability to MEK) 50 parts by mass of jER828 (manufactured by Mitsubishi Chemical Corporation), 50 parts by mass of PKHB (manufactured by Gabriel Phenoxies), and 100 parts by mass of MEK were mixed and dissolved to obtain a solution, to which 15 parts by mass of the masterbatch-type epoxy resin curing agent composition described in Examples 1 to 9 and Comparative Examples 1 to 3 was added to obtain an epoxy resin composition for evaluating stability to MEK. (Stability to MEK) The initial viscosity of the epoxy resin composition for evaluating stability to MEK immediately after its preparation and the post-storage viscosity of the epoxy resin composition for stability evaluation after leaving it at 25°C for 24 hours were measured using an E-type viscometer at room temperature (25°C), and the post-storage viscosity ratio was calculated using the following formula (3): Post-storage viscosity ratio = Post-storage viscosity / Initial viscosity ... Formula (3) Evaluation was performed according to the following criteria depending on the post-storage viscosity ratio. 〇: 1.0 times ≦ viscosity magnification after storage < 2.0 times △: 2.0 times ≦ viscosity magnification after storage < 3.0 times ×: 3.0 times ≦ viscosity magnification after storage

[0160] (Evaluation of Stability to Low Molecular Weight Acrylic Compounds) (Method of Preparing Epoxy Resin Composition for Evaluating Stability to Low Molecular Weight Acrylic Compounds) 50 parts by mass of the masterbatch-type epoxy resin curing agent composition described in Examples 1 to 9 and Comparative Examples 1 to 3, 100 parts by mass of jER828 (manufactured by Mitsubishi Chemical Corporation), and 50 parts by mass of epoxy acrylate (Epoxy Ester 3000A manufactured by Kyoeisha Chemical Co., Ltd.) were weighed and mixed in a non-bubbling kneader, followed by stirring for 2 minutes and degassing for 3 minutes, to prepare an epoxy resin composition for evaluating stability to low molecular weight acrylic compounds. (Stability to Low Molecular Weight Acrylic Compounds) The initial viscosity of the epoxy resin composition for evaluating stability to low molecular weight acrylic compounds immediately after preparation and the post-storage viscosity of the epoxy resin composition for stability evaluation after leaving it at 40°C for 7 days were measured at room temperature (25°C) using an E-type viscometer, and the post-storage viscosity multiplier was calculated using the following mathematical formula (4): Viscosity multiplier after storage=viscosity after storage / initial viscosity Formula (4) Evaluation was performed according to the viscosity multiplier after storage according to the following criteria: ◯: 1.0 times≦viscosity multiplier after storage<1.5 times Δ: 1.5 times≦viscosity multiplier after storage<2.0 times ×: 2.0 times≦viscosity multiplier after storage

[0161] (Reactivity of Epoxy Resin Composition Containing Low-Molecular-Weight Acrylic Compound) Approximately 10 mg of an epoxy resin composition (uncured) for evaluating stability to low-molecular-weight acrylic compounds was weighed out, and the temperature was raised from 25°C to 250°C at a rate of 20°C / min using an EXSTER7020 (Hitachi High-Tech Science Corporation). A DSC curve was obtained, and the temperature at the point where the heat flow was maximum was taken as the DSC exothermic peak temperature. The exothermic peak temperature was evaluated according to the following criteria: ◎◎: Exothermic peak temperature≦120°C ◎: 120°C<exothermic peak temperature≦130°C ○: 130°C<exothermic peak temperature≦140°C △: 140°C<exothermic peak temperature≦150°C ×: 150°C<exothermic peak temperature

[0162] (Appearance Evaluation of Microregions) (Method for Preparing Epoxy Resin Composition for Evaluating Appearance of Microregions) 15 parts by mass of the masterbatch-type epoxy resin curing agent composition described in Examples 1 to 9 and Comparative Examples 1 to 3, 30 parts by mass of jER828 (manufactured by Mitsubishi Chemical Corporation), 5 parts by mass of a low molecular weight epoxy compound o-CGE (ortho-cresyl glycidyl ether; viscosity at 25°C 7 mPa·s; manufactured by Sigma-Aldrich), and SO-E2 (spherical silica manufactured by Admatechs Co., Ltd.; D) as a filler were mixed. ５０ = 0.8 μm), and 50 parts by mass of filler-free regions were weighed out, and then these components were mixed in a non-bubbling kneader, stirring for 2 minutes and degassing for 3 minutes, to prepare an epoxy resin composition for evaluating the appearance of microregions. (Evaluation of Appearance of Microregions) The epoxy resin composition for evaluating the appearance of microregions was kept in an oven at 180°C for 1 hour to obtain a cured product. The obtained cured product was cut with a diamond cutter, polished with sandpaper, and the surface was gold-deposited, and the polished surface was observed with an SEM at 1000x magnification. The obtained SEM image was binarized, and the area ratio of filler-free regions with a circle equivalent diameter of 3 μm or more was calculated. Evaluation was made according to the area ratio of filler-free regions according to the following criteria: ◯: Less than 5% ×: 5% or more

[0163] Table 1 shows the weight percentage of the low-molecular-weight amine having a molecular weight of 50 to 300 contained in the core (A) of Examples 1 to 9 and Comparative Examples 1 to 3, the dyeability of the layer (B), and the properties of the epoxy resin composition adjusted for each evaluation item. The dyeability of the layer (B) was evaluated according to the following criteria: ◯: When a luminance graph is obtained from the outermost part of the layer (B) to the boundary between the layer (B) and the core (A), the interior of the layer (B) has a region having a luminance higher than that of the outermost part and the luminance of the boundary. ×: When a luminance graph is obtained from the outermost part of the layer (B) to the boundary between the layer (B) and the core (A), the interior of the layer (B) does not have a region having a luminance higher than that of the outermost part and the luminance of the boundary.

[0164]

[0165] Comparing the Examples and Comparative Examples, when a brightness graph was obtained from the outermost portion of the layer (B) to the boundary between the layer (B) and the core (A), it was found that epoxy resin curing agents 1 to 9, which had a portion inside the layer (B) with higher brightness than the outermost portion and the boundary between the layer (B) and the core (A), had both excellent stability and reactivity with low molecular weight epoxy compounds, MEK, and low molecular weight acrylic resins.

[0166] Furthermore, in terms of the appearance of a minute region, when a brightness graph was obtained from the outermost portion of the layer (B) to the boundary between the layer (B) and the core (A), it was found that it was superior to have a portion inside the layer (B) that was brighter than the outermost portion and the boundary between the layer (B) and the core (A). The appearance of Example 1 is shown in Figure 9, and the appearance of Comparative Example 1 is shown in Figure 10.

[0167] Here, from the results of Comparative Examples 1 to 3, it was found that when a masterbatch-type epoxy resin curing agent composition is heat-treated, the amount of core surface coating material is increased, and the temperature is not controlled, when a brightness graph is obtained from the outermost part of layer (B) to the boundary between layer (B) and core (A), it is not possible to obtain an epoxy resin curing agent having a portion inside layer (B) that is brighter than the outermost part and the boundary between layer (B) and core (A).

[0168] (Effect of Addition of Component (D)) 3 parts by mass of bisphenol A (2,3-dihydroxypropyl) glycidyl ether (manufactured by Merck) was further added as component (D) to the epoxy resin composition for evaluating stability to low molecular weight epoxy compounds, which used the masterbatch type epoxy resin curing agent composition of Example 1, and evaluation of stability to low molecular weight epoxy compounds and reactivity was carried out. As a result, the stability to low molecular weight epoxy compounds was ◯, and the reactivity of the epoxy resin composition containing low molecular weight epoxy compounds was ◎◎, demonstrating that reactivity was improved while stability was maintained.

[0169] Although the present embodiment has been described above, the present invention is not limited to this embodiment, and can be modified as appropriate within the scope of the invention.

[0170] The epoxy resin curing agent and epoxy resin composition of this embodiment impart excellent reactivity and stability even when coexisting with low-molecular-weight epoxy compounds, solvents, and low-molecular-weight acrylic compounds, and furthermore, exhibit excellent appearance in microareas, and therefore have industrial applicability in sealing materials for electric and electronic components such as underfill materials and relay sealing materials, conductive materials such as conductive pastes, thermally conductive materials, insulating materials, adhesives for camera modules, structural adhesives, matrix resins for fiber-reinforced plastics, impregnation fixing materials for motor coils, etc. Furthermore, because the epoxy resin curing agent and epoxy resin composition of this embodiment have excellent solvent resistance, they also have industrial applicability in film applications such as interlayer insulating films, film-type solder resists, sealing sheets, conductive films, anisotropically conductive films, and thermally conductive films.

Claims

1. An epoxy resin curing agent having a core (A) containing a nitrogen-containing compound and a layer (B) coating the core (A), wherein when the epoxy resin curing agent is stained with ruthenium tetroxide and osmium tetroxide, and then observed under a transmission electron microscope to obtain a brightness graph by image processing, the inside of the layer (B) has a region having a brightness α, and the brightness α is higher than the brightness β of the outermost part of the layer (B) and the brightness γ of the boundary between the layer (B) and the core (A).

2. The epoxy resin curing agent according to claim 1, wherein the core (A) contains 0.001 to 20 mass % of an amine compound (a) having a molecular weight of 50 to 300.

3. The epoxy resin curing agent according to claim 1, wherein the core (A) comprises at least one member selected from the group consisting of imidazoles, aliphatic amine compounds, and cyclic amine compounds including tertiary amines.

4. The epoxy resin hardener according to claim 1, wherein the core (A) comprises an imidazole-based amine adduct compound.

5. Particle size D of the core (A) at 50% cumulative undersize fraction ５０ The epoxy resin curing agent according to claim 1, wherein the average particle diameter is more than 0.3 μm and not more than 12 μm.

6. Particle size D of the core (A) at an undersize cumulative fraction of 99% ９９ and the above D ５０ The ratio of ９９ / D ５０ The epoxy resin curing agent according to claim 5, wherein the molecular weight is 8 or less.

7. The specific surface area Y (m ２ / g) to the D ５０ The epoxy resin curing agent according to claim 5, wherein the value multiplied by (μm) is 3.0 or more and 9.0 or less.

8. The specific surface area Y (m ２ / g) to the D ５０ The epoxy resin curing agent according to claim 5, wherein the value multiplied by (μm) is more than 9.0 and not more than 18.

0.

9. An epoxy resin composition comprising the epoxy resin curing agent according to claim 1 and an epoxy resin (C).

10. The epoxy resin composition according to claim 9, wherein the mass ratio of the epoxy resin curing agent to the epoxy resin (C), in terms of epoxy resin curing agent:epoxy resin (C), is 0.1:100 to 1000:

100.

11. The epoxy resin composition according to claim 9, further comprising an alcohol compound (D) represented by the following formula (1): (In formula (1), X １ represents an alkylene group having 2 to 5 carbon atoms which may have a substituent R, and the substituents R and R １ ~R ５ each independently represents a hydrogen atom, an alkyl group, an unsaturated aliphatic group, an aromatic group, a substituent containing a heteroatom, or a halogen atom, １ ~R ５ may be a fused ring compound in which any one selected from the following constitutes the same ring.) 12. The epoxy resin composition according to claim 11, wherein the content of the alcohol compound (D) is 0.0001 mass % or more and 5 mass % or less based on the total amount of the epoxy resin composition.

13. The epoxy resin composition according to claim 11, wherein the alcohol compound (D) comprises at least one selected from the group consisting of 3-phenoxy-1-propanol, 3-phenoxy-1,2-propanediol, 3-phenoxy-1,3-propanediol, 3-(ortho-toluoxy-1,2-propanediol, 3-(2-methoxyphenoxy)propane-1,2-diol, bisphenol A (3-hydroxypropyl)glycidyl ether, and bisphenol A (2,3-dihydroxypropyl)glycidyl ether.

14. The epoxy resin composition according to claim 13, wherein the core (A) contains 0.001 to 20 mass % of an amine compound (a) having a molecular weight of 50 to 300, and the amine compound (a) contains at least one type selected from the group consisting of imidazoles, aliphatic amine compounds, and cyclic amine compounds including tertiary amines.

15. An encapsulating material comprising the epoxy resin curing agent according to any one of claims 1 to 8, or the epoxy resin composition according to any one of claims 9, 11, 13 and 14.

16. A conductive material comprising the epoxy resin curing agent according to any one of claims 1 to 3, or the epoxy resin composition according to any one of claims 9, 11, 13 and 14.

17. A thermally conductive material comprising the epoxy resin curing agent according to any one of claims 1 to 3, or the epoxy resin composition according to any one of claims 9, 11, 13 and 14.

18. An insulating material comprising the epoxy resin curing agent according to any one of claims 1 to 3, or the epoxy resin composition according to any one of claims 9, 11, 13 and 14.

19. An adhesive for a camera module, comprising the epoxy resin curing agent according to any one of claims 1 to 3, or the epoxy resin composition according to any one of claims 9, 11, 13 and 14.

20. A structural adhesive comprising the epoxy resin curing agent according to any one of claims 1 to 3, or the epoxy resin composition according to any one of claims 9, 11, 13 and 14.

21. A matrix resin for fiber-reinforced plastics, comprising the epoxy resin curing agent according to any one of claims 1 to 3, or the epoxy resin composition according to any one of claims 9, 11, 13 and 14.

22. An impregnating adhesive comprising the epoxy resin hardener according to any one of claims 1 to 3, or the epoxy resin composition according to any one of claims 9, 11, 13 and 14.

23. An interlayer insulating film comprising the epoxy resin curing agent according to any one of claims 1 to 3, or the epoxy resin composition according to any one of claims 9, 11, 13 and 14.

24. A film-type solder resist comprising the epoxy resin curing agent according to any one of claims 1 to 3, or the epoxy resin composition according to any one of claims 9, 11, 13 and 14.

25. An encapsulating sheet comprising the epoxy resin curing agent according to any one of claims 1 to 3, or the epoxy resin composition according to any one of claims 9, 11, 13 and 14.

26. A conductive film comprising the epoxy resin curing agent according to any one of claims 1 to 3, or the epoxy resin composition according to any one of claims 9, 11, 13 and 14.

27. An anisotropic conductive film comprising the epoxy resin curing agent according to any one of claims 1 to 3, or the epoxy resin composition according to any one of claims 9, 11, 13 and 14.

28. A thermally conductive film comprising the epoxy resin curing agent according to any one of claims 1 to 3, or the epoxy resin composition according to any one of claims 9, 11, 13 and 14.

29. A method for producing a dyed cured product, comprising: a step (S1) of electronically staining, with ruthenium tetroxide, an epoxy resin curing agent having a core (A) and a layer (B) covering the core (A); a step (S2) of obtaining a cured product of a composition containing the epoxy resin curing agent that has been subjected to the step (S1); and a step (S3) of electronically staining a slice of the cured product with osmium tetroxide.

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