Epoxy resin curing agent, epoxy resin composition containing same and cured product thereof

Abstract

Provided is an epoxy resin curing agent containing the following component (X) and component (Y). (X) A reaction product of the following component (A) and component (B): (A) a reaction product of (a1) an alicyclic polyvalent carboxylic acid or an acid anhydride thereof and (a2) a polyhydric alcohol; and (B) one or more compounds selected from a bifunctional alicyclic epoxy compound and a bisphenol-type epoxy compound (Y) An alicyclic polyvalent carboxylic acid anhydride

Description

Curing agent for epoxy resin, epoxy resin composition containing the same, and cured product thereof

[0001] The present invention relates to a curing agent for epoxy resins, an epoxy resin composition containing the same, and a cured product thereof.

[0002] In recent years, most of the optical semiconductor devices, such as light-emitting elements (e.g., light-emitting diodes (LEDs)) and light-receiving elements, which have been put to practical use in various display boards, light sources for image reading, traffic signals, large display units, etc., are manufactured using encapsulating resins. Epoxy resin compositions are generally used as such encapsulating resins because of their excellent heat resistance, adhesive properties, moisture resistance, mechanical strength, electrical properties, etc.

[0003] Conventionally, for example, an epoxy resin composition comprising an epoxy resin, a curing agent, and a polyester having a specific structure (Patent Document 1), and an epoxy resin composition containing an epoxy resin curing agent in which a specific dendritic polymer is added as a modifier to a polycarboxylic acid anhydride (Patent Document 2) have been proposed.

[0004] JP 2004-131553 A JP 2007-314740 A

[0005] However, as improvements in light-emitting devices have led to smaller sizes and higher currents, the heat generated by LEDs when they are turned on for long periods of time and the short-wavelength light they emit can cause deterioration of encapsulating resins, making them more susceptible to discoloration. To address this issue, the use of cured products of alicyclic epoxy resins and acid anhydrides has been proposed. However, acid anhydrides have a high vapor pressure and tend to evaporate partially during curing, leading to poor curing and the cured product's surface becoming recessed, resulting in poor appearance and making it difficult to ensure stable quality. Furthermore, increasing the amount of catalyst to improve curing or using highly active amine catalysts has led to a loss of transparency and discoloration. Therefore, conventional epoxy resin compositions have had difficulty providing high reliability to optical semiconductor devices.

[0006] An object of the present invention is to provide an epoxy resin curing agent that can ensure stable quality and impart high reliability to optical semiconductor devices by suppressing poor appearance due to insufficient curing or the occurrence of dents on the surface of the cured product without impairing transparency. Another object of the present invention is to provide an epoxy resin composition containing the epoxy resin curing agent and a cured product of the epoxy resin composition.

[0007] The present inventors have found that by incorporating a reaction product obtained by further reacting one or more selected from a bifunctional alicyclic epoxy compound and a bisphenol-type epoxy compound with a reaction product of an alicyclic polycarboxylic acid or an acid anhydride thereof with a polyhydric alcohol, together with an alicyclic polycarboxylic acid anhydride, it is possible to obtain a curing agent for epoxy resins that can impart high reliability to optical semiconductor devices, since poor appearance due to insufficient curing or the occurrence of dents on the surface of the cured product can be suppressed without impairing transparency, and stable quality can be ensured.

[0008] That is, the present invention provides the following [1] to [8]. [1] An epoxy resin curing agent comprising the following component (X) and component (Y): (X) a reaction product of the following component (A) and component (B): (A) (a1) a reaction product of an alicyclic polycarboxylic acid or an anhydride thereof with (a2) a polyhydric alcohol (B) one or more selected from a difunctional alicyclic epoxy compound and a bisphenol-type epoxy compound (Y) an alicyclic polycarboxylic acid anhydride [2] The epoxy resin curing agent according to the above [1], wherein component (A) is a compound represented by the following formula (i), and component (B) is a compound represented by the following formula (ii): [3] The epoxy resin curing agent according to [1] or [2], wherein the ratio of component (X) to component (Y) in the epoxy resin curing agent is such that, in a chromatogram obtained by analyzing the epoxy resin curing agent by high performance liquid chromatography, the ratio of the peak area attributable to component (X) to the peak area attributable to component (Y) is 0.1 to 0.7. [4] The epoxy resin curing agent according to any one of [1] to [3], wherein component (X) contains one or more structural units selected from a structural unit represented by the following formula (1), a structural unit represented by the following formula (2), a structural unit represented by the following formula (3), and a structural unit represented by the following formula (4). [5] An epoxy resin composition comprising the epoxy resin curing agent according to any one of [1] to [4] and an epoxy resin. [6] A cured product obtained by curing the epoxy resin composition according to [5]. [7] An optical semiconductor device in which an optical semiconductor element is encapsulated with the cured product according to [6].

[0009]

[0010]

[0011] [In the formula, R 1 and R 3 each independently represents an alkanediyl group which may have a characteristic group containing an oxygen atom, and R 2represents a hydrogen atom or an alkyl group.] [8] A method for producing an epoxy resin curing agent according to any one of [1] to [4] above, comprising the following steps (1) and (2): Step (1) reacting the following component (Y) with the following component (a2) in an amount of 0.1 to 5 mass % relative to the component (Y); and Step (2) mixing the reaction liquid obtained from Step (1) with the following component (B) in an amount of 0.3 to 7 times by mass relative to the component (a2), wherein: (Y) is an alicyclic polycarboxylic acid anhydride; (a2) is a polyhydric alcohol; and (B) is one or more selected from a difunctional alicyclic epoxy compound and a bisphenol-type epoxy compound.

[0012] According to the present invention, it is possible to provide an epoxy resin curing agent that can ensure stable quality by suppressing poor appearance due to insufficient curing or the occurrence of dents on the surface of the cured product without impairing transparency, and can impart high reliability to optical semiconductor devices. The present invention can also provide an epoxy resin composition containing the epoxy resin curing agent, and a cured product of the epoxy resin composition.

[0013] [Epoxy Resin Curing Agent] The epoxy resin curing agent of the present invention contains the following component (X) and component (Y) as active ingredients.

[0014] <Component (X)> The epoxy resin curing agent of the present invention contains, as component (X), a reaction product of component (A) and component (B). -Component (A)- Component (A) is a reaction product of (a1) an alicyclic polycarboxylic acid or its acid anhydride with (a2) a polyhydric alcohol. Component (A) can contain one or more types. Examples of component (a1) include polycarboxylic acids selected from cycloalkane polycarboxylic acids and cycloalkene polycarboxylic acids, which have one or more pairs of carboxy groups bonded to adjacent carbon atoms on an alicyclic ring, or acid anhydrides formed by dehydration condensation of the one or more pairs of carboxy groups. Component (a1) can be used alone or in combination of two or more types.

[0015] Examples of alicyclic polycarboxylic acids include alicyclic dicarboxylic acids such as 1,2-cyclohexanedicarboxylic acid, 4-cyclohexene-1,2-dicarboxylic acid, 1-cyclohexene-1,2-dicarboxylic acid, 3-methyl-1,2-cyclohexanedicarboxylic acid, 4-methyl-1,2-cyclohexanedicarboxylic acid, 3-methyl-4-cyclohexene-1,2-dicarboxylic acid, and 4-methyl-4-cyclohexene-1,2-dicarboxylic acid; alicyclic tricarboxylic acids such as 1,2,4-cyclohexanetricarboxylic acid; and alicyclic tetracarboxylic acids such as 1,2,3,4-cyclopentanetetracarboxylic acid and 1,2,4,5-cyclohexanetetracarboxylic acid. Among these, alicyclic dicarboxylic acids are preferred.

[0016] Examples of the alicyclic polycarboxylic acid anhydride include alicyclic dicarboxylic acid anhydrides such as 3,4,5,6-tetrahydrophthalic anhydride, 1,2,3,6-tetrahydrophthalic anhydride, dimethyltetrahydrophthalic anhydride, hexahydrophthalic anhydride, 4-methylhexahydrophthalic anhydride, norbornene dicarboxylic acid anhydride, methylbicyclo[2.2.1]heptane-2,3-dicarboxylic acid anhydride, bicyclo[2.2.1]heptane-2,3-dicarboxylic acid anhydride, bicyclo[2.2.1]hept-5-ene-2,3-dicarboxylic acid anhydride, and methylbicyclo[2.2.1]hept-5-ene-2,3-dicarboxylic acid anhydride; and alicyclic tetracarboxylic acid dianhydrides such as 1,2,4,5-cyclopentanetetracarboxylic acid dianhydride and 1,2,4,5-cyclohexanetetracarboxylic acid dianhydride.

[0017] Among these, as component (a1), from the viewpoint of easily enjoying the effects of the present invention, an alicyclic polycarboxylic acid anhydride is preferred, an alicyclic dicarboxylic acid anhydride is more preferred, one or more selected from tetrahydrophthalic anhydride, methyltetrahydrophthalic anhydride, methyl-endomethylenetetrahydrophthalic anhydride, hexahydrophthalic anhydride, and 4-methylhexahydrophthalic anhydride is even more preferred, and one or more selected from hexahydrophthalic anhydride and 4-methylhexahydrophthalic anhydride is even more preferred.

[0018] Component (a2) is not particularly limited as long as it is an alcohol having two or more hydroxyl groups in the molecule. Furthermore, the hydrocarbon group constituting the polyhydric alcohol may have a characteristic group containing an oxygen atom. Examples of such characteristic groups include an oxyalkanediyl group, a carbonyl group, a carbonate group, and a (meth)acryloyloxy group, and one or more of these groups may be present. Examples of oxyalkanediyl groups include an oxyethylene group, an oxypropylene group, and an oxybutylene group, and two or more groups may be present. Furthermore, the term "(meth)acryloyloxy group" encompasses both an "acryloyloxy group" and a "methacryloyloxy group."

[0019] Specific examples of component (a2) include dihydric alcohols such as ethylene glycol, diethylene glycol, triethylene glycol, polyethylene glycol, 1,2-propanediol, polypropylene glycol, polyoxyethyleneoxypropylene glycol, 1,3-propanediol, 1,4-butanediol, polybutylene glycol, 1,5-pentanediol, 1,6-hexanediol, 1,7-heptanediol, 1,8-octanediol, 1,9-nonanediol, 1,10-decanediol, 1,12-dodecanediol, neopentyl glycol, 1,4-butenediol, and polycarbonate; trihydric alcohols such as glycerin and trimethylolpropane; tetrahydric alcohols such as pentaerythritol, diglycerin, sorbitan, and mannitan; and pentahydric or higher alcohols such as sorbitol and polyglycerin. Component (a2) can be used singly or in combination of two or more.

[0020] Among these, as component (a2), a dihydric alcohol is preferred from the viewpoint of making it easier to enjoy the effects of the present invention, and one or more selected from ethylene glycol, diethylene glycol, triethylene glycol, polyethylene glycol, 1,2-propanediol, polypropylene glycol, polyoxyethyleneoxypropylene glycol, and 1,3-propanediol are more preferred, and one or more selected from ethylene glycol, diethylene glycol, triethylene glycol, polyethylene glycol, 1,2-propanediol, and polypropylene glycol are even more preferred.

[0021] Furthermore, if the molecular weight of component (a2) is too large, it may behave as a thermoplastic resin, resulting in a large thermal expansion coefficient, which may cause a decrease in the reliability of the encapsulated optical semiconductor device. From this perspective, the molecular weight of component (a2) is preferably 2000 or less, more preferably 1500 or less, even more preferably 800 or less, and even more preferably 400 or less. The lower limit of the molecular weight of component (a2) is not particularly limited, and it may be 60 or more.

[0022] A preferred embodiment of the reaction product of component (a1) and component (a2) is, for example, a compound represented by the following formula (i).

[0023]

[0024] [In the formula, R 1 represents an alkanediyl group which may have a characteristic group containing an oxygen atom, and R 2 represents a hydrogen atom or an alkyl group.

[0025] R 1The alkanediyl group in the above formula (1) may be linear or branched. The number of carbon atoms in the alkanediyl group is preferably 1 to 20, more preferably 2 to 12, and even more preferably 2 to 6. Specific examples include a methylene group, an ethane-1,1-diyl group, an ethane-1,2-diyl group, a propane-1,1-diyl group, a propane-1,2-diyl group, a propane-1,3-diyl group, a propane-2,2-diyl group, a butane-1,2-diyl group, a butane-1,3-diyl group, a butane-1,4-diyl group, a pentane-1,4-diyl group, a pentane-1,5-diyl group, a hexane-1,5-diyl group, a hexane-1,6-diyl group, a 2-methylpropane-1,2-diyl group, and a 2,2-dimethylpropane-1,3-diyl group.

[0026] R 1 The alkanediyl group in the above formula (1) may have a characteristic group containing an oxygen atom. Such a characteristic group may be present between the carbon-carbon bonds of the alkanediyl group or at the terminal. Examples of such a characteristic group include an oxyalkanediyl group, a carbonyl group, a carbonate group, and a (meth)acryloyloxy group. One or more types of characteristic groups may be present. The oxyalkanediyl group and the (meth)acryloyloxy group are as explained above.

[0027] R 2 The alkyl group in the above formula (1) may be linear or branched. The number of carbon atoms in the alkyl group is preferably 1 to 20, more preferably 1 to 12, and even more preferably 1 to 6. Specific examples include a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, a sec-butyl group, a t-butyl group, a pentyl group, and a hexyl group.

[0028] -Component (B)- Component (B) is one or more selected from difunctional alicyclic epoxy compounds and bisphenol-type epoxy compounds.

[0029] The difunctional alicyclic epoxy compound is not particularly limited as long as it is a compound that dissolves in component (a1), but a compound that is liquid at room temperature (25°C ± 10°C) and has a molecular weight of 500 or less is preferred. The epoxy equivalent is preferably 210 g / eq or less, more preferably 100 to 150 g / eq. In this specification, the "epoxy equivalent of the epoxy compound" refers to the mass of an epoxy resin containing one equivalent of epoxy groups, and can be measured in accordance with JIS K-7236.

[0030] The bifunctional alicyclic epoxy compound is not particularly limited as long as it has an alicyclic skeleton and two epoxy groups in one molecule, but examples thereof include 3',4'-epoxycyclohexylmethyl-3,4-epoxycyclohexanecarboxylate, ε-caprolactone-modified 3,4-epoxycyclohexylmethyl 3',4'-epoxycyclohexanecarboxylate, bis(3,4-epoxycyclohexylmethyl)adipate, vinylcyclohexene dioxide, hydrogenated bisphenol A diglycidyl ether, and tetrahydroindene diepoxide. Among these, the compound represented by the following formula (ii) is preferred in that it is easier to enjoy the effects of the present invention.

[0031]

[0032] [In the formula, R 3 represents an alkanediyl group which may have a characteristic group containing an oxygen atom.

[0033] R 3 The alkanediyl group in the above formula (1) may be linear or branched, and may have a characteristic group containing an oxygen atom. The number of carbon atoms in the alkanediyl group is preferably 1 to 20, more preferably 1 to 12, and even more preferably 1 to 6. Specific examples of the alkanediyl group and the characteristic group include R 1 The same can be mentioned.

[0034] Commercially available bifunctional alicyclic epoxy compounds include, for example, CELLOXIDE 2021P and CELLOXIDE 2081 (both manufactured by Daicel Chemical Industries, Ltd.), CYRACURE UVR-6110 (manufactured by The Dow Chemical Company), ERL4221 (manufactured by Polysciences), TTA20 and TTA21 (both manufactured by Tetra Chemical), and Syna-Epoxy 21 (manufactured by Synergia).

[0035] The bisphenol-type epoxy resin is not particularly limited as long as it is a compound that dissolves in component (a1), but is preferably a compound that is liquid at room temperature (25°C ± 10°C) and has two or more epoxy groups in the molecule, and more preferably such a compound has a molecular weight of 500 or less. The epoxy equivalent is also preferably 200 g / eq or less, more preferably 150 to 200 g / eq.

[0036] Examples of bisphenol-type epoxy resins include bisphenol A-type epoxy resins, bisphenol E-type epoxy compounds, bisphenol F-type epoxy resins, bisphenol S-type epoxy compounds, and bisphenol AF-type epoxy resins. Among these, bisphenol A-type epoxy resins and bisphenol F-type epoxy resins are preferred, and bisphenol AF-type epoxy resins are more preferred, as they allow the effects of the present invention to be more easily achieved.

[0037] Commercially available bisphenol A epoxy resins include jER827 and jER828 (manufactured by Mitsubishi Chemical Corporation), YD-127 and YD-128 (manufactured by Nippon Steel Chemical & Material Co., Ltd.), EPICLON 840, EPICLON 850 and EPICLON 850-S (manufactured by DIC Corporation), D.E. R331 and D.E. R332 (manufactured by The Dow Chemical Company). Commercially available bisphenol F epoxy resins include jER806 and jER807 (manufactured by Mitsubishi Chemical Corporation), YDF-170 (manufactured by Nippon Steel Chemical & Material Co., Ltd.), EPICLON 830 and EPICLON 835 (manufactured by DIC Corporation), D.E. R354 (manufactured by The Dow Chemical Company) can be mentioned.

[0038] Among these, component (X) is preferably a reaction product of a compound represented by formula (i) above and a compound represented by formula (ii) above. The chemical structure of the reaction product preferably contains one or more structural units selected from a structural unit represented by formula (1) below, a structural unit represented by formula (2) below, a structural unit represented by formula (3) below, and a structural unit represented by formula (4) below, more preferably contains one or more structural units selected from a structural unit represented by formula (1) below and a structural unit represented by formula (2) below, and even more preferably contains a structural unit represented by formula (1) below. Note that isomers exist in the structural unit, but they may be a single isomer or a mixture of isomers.

[0039]

[0040] [In the formula, R 1 and R 3 each independently represents an alkanediyl group which may have a characteristic group containing an oxygen atom, and R 2 represents a hydrogen atom or an alkyl group.

[0041] R 1 , R 2 and R 3 is as explained above.

[0042] Component (X) preferably has a number average molecular weight (Mn) measured by gel permeation chromatography (GPC) of 1,000 to 5,000, more preferably 1,250 to 4,000, and even more preferably 1,500 to 3,500. Mn is measured by the method described in the Examples below.

[0043] <Component (Y)> The epoxy resin curing agent of the present invention contains an alicyclic polycarboxylic acid anhydride as component (Y). Examples of component (Y) include the alicyclic polycarboxylic acid anhydrides described in connection with component (a1). Among these, alicyclic dicarboxylic acid anhydrides are preferred, with one or more selected from tetrahydrophthalic anhydride, methyltetrahydrophthalic anhydride, methyl-endomethylenetetrahydrophthalic anhydride, hexahydrophthalic anhydride, and 4-methylhexahydrophthalic anhydride being more preferred, and one or more selected from hexahydrophthalic anhydride and 4-methylhexahydrophthalic anhydride being even more preferred.

[0044] The ratio of component (X) to component (Y) in an epoxy resin curing agent is such that, in a chromatogram obtained by analyzing the epoxy resin curing agent by high-performance liquid chromatography (HPLC), the ratio of the peak area attributable to component (X) to the peak area attributable to component (Y) is preferably 0.1 to 0.7, more preferably 0.15 to 0.6, even more preferably 0.2 to 0.5, and even more preferably 0.2 to 0.4. Within these ranges, sufficient workability is ensured while sufficient curing is achieved, and depressions on the surface of the cured product are suppressed, making it easier to ensure stable quality. The analysis conditions are as follows, and the ratio of the peak area attributable to component (X) to the peak area attributable to component (Y) is calculated based on the obtained chromatogram.

[0045] Apparatus: Tosoh Corporation "HLC-8320GPC" Column: Two Tosoh Corporation "TSKgel GMHHR-H" columns connected together Mobile phase: Tetrahydrofuran Column temperature: 40°C Flow rate: 1.0 mL / min Sample concentration: 2 mg / mL Sample injection volume: 100 μL Detector: Differential refractometer Standard material: Standard PMMA

[0046] [Method for producing an epoxy resin curing agent] Examples of methods for producing an epoxy resin curing agent of the present invention include the following (α) or (β): (α) A method of mixing component (X) and component (Y). (β) A method including the following steps (1) and (2): Step (1) A step of reacting component (Y) with 0.1 to 5% by mass of component (a2) relative to component (Y). Step (2) A step of mixing the reaction liquid obtained from step (1) with component (B) in an amount of 0.3 to 7 times by mass relative to component (a2).

[0047] In the above (α), the mixing ratio of the component (X) and the component (Y) is as explained above.

[0048] In the above (β), the amount of component (a2) used in step (1) is preferably 0.5 to 4 mass %, and more preferably 1 to 3 mass %, relative to component (Y) from the viewpoint of ensuring stable quality. Also, the amount of component (B) used in step (2) is preferably 0.5 to 6 times by mass, more preferably 1 to 5 times by mass, even more preferably 1 to 4 times by mass, and still more preferably 1.5 to 3.5 times by mass, relative to component (a2), from the viewpoint of improving workability by increasing viscosity and ensuring stable quality.

[0049] Known methods can be applied to step (1), for example, by stirring and mixing component (Y) with component (Y). Reaction conditions can be appropriately set. For example, the reaction temperature is preferably 40 to 120°C, more preferably 50 to 100°C, and even more preferably 60 to 90°C. The total reaction time is preferably 0.5 to 5 hours, more preferably 1 to 3 hours, and even more preferably 1 to 2 hours. The reaction may be carried out in two or more stages; for example, a reaction at 60 to 90°C for 1 to 2 hours may be followed by a reaction at a lower temperature for 1 to 2 hours. A catalyst may also be added in the second or subsequent reaction stages. The catalyst is not particularly limited as long as it is one commonly used in the relevant technical field. The amount of catalyst used can be appropriately set within a range that does not impair the effects of the present invention.

[0050] In step (2), the mixing method and mixing order are not particularly limited as long as the reaction liquid after step (1) and component (B) can be mixed. For example, component (B) may be added to the reaction liquid after step (1), and the mixture may be stirred and mixed to cause the reaction. The reaction may be carried out in two or more stages. The reaction conditions can be appropriately set, and for example, the reaction temperature is preferably 40 to 150°C, more preferably 50 to 120°C, and even more preferably 60 to 100°C. The total reaction time is preferably 2 to 15 hours, more preferably 4 to 12 hours, and even more preferably 6 to 10 hours.

[0051] In step (2), a catalyst may be added. The catalyst is not particularly limited as long as it is one commonly used in the technical field, and examples thereof include acidic compounds such as hydrochloric acid, sulfuric acid, methanesulfonic acid, trifluoromethanesulfonic acid, paratoluenesulfonic acid, nitric acid, trifluoroacetic acid, and trichloroacetic acid; metal hydroxides such as sodium hydroxide, potassium hydroxide, calcium hydroxide, and magnesium hydroxide; amine compounds such as triethylamine, tripropylamine, and tributylamine; heterocyclic compounds such as pyridine, dimethylaminopyridine, 1,8-diazabicyclo[5.4.0]undec-7-ene, imidazole, triazole, and tetrazole; and tetramethylammonium hydroxide. Examples of suitable catalysts include quaternary ammonium salts such as tetraethylammonium hydroxide, tetrapropylammonium hydroxide, tetrabutylammonium hydroxide, trimethylethylammonium hydroxide, trimethylpropylammonium hydroxide, trimethylbutylammonium hydroxide, trimethylcetylammonium hydroxide, trioctylmethylammonium hydroxide, tetramethylammonium chloride, tetramethylammonium bromide, tetramethylammonium iodide, tetramethylammonium acetate, and trioctylmethylammonium acetate; phosphonium salts such as tetra-n-butylphosphonium o,o-diethylphosphorodithionate and tetrabutylphosphonium benzotriazolate; orthotitanic acids such as tetraethyl orthotitanate and tetramethyl orthotitanate; metal salts such as tin octylate, cobalt octylate, zinc octylate, manganese octylate, calcium octylate, sodium octylate, potassium octylate, and zinc stearate; and metal complexes such as zinc acetylacetonate and zinc benzoylacetonate. These catalysts can be used singly or in combination of two or more.

[0052] The amount of catalyst used can be appropriately set, but is preferably 0.01 to 5 mass %, and more preferably 0.1 to 3 mass %, based on the total amount of component (Y), component (a2), and component (B). Within this range, coloration of the cured product can be prevented while suppressing a decrease in heat resistance.

[0053] After the reaction is completed, if a catalyst is used, the catalyst may be removed or inactivated by carrying out adsorption filtration, neutralization, or the like, as necessary.

[0054] In this manner, the epoxy resin curing agent of the present invention can be produced efficiently.

[0055] [Epoxy Resin Composition] The epoxy resin composition of the present invention contains the epoxy resin curing agent of the present invention described above and an epoxy resin. Any epoxy resin commonly used in the art can be used without any particular limitation. For example, the above-mentioned epoxy compounds (e.g., bifunctional alicyclic epoxy resins, bisphenol-type epoxy resins) can be used as the epoxy resin. Other examples include phenol novolac-type epoxy resins obtained by reacting phenol novolac with epichlorohydrin, and glycidyl ester-type epoxy resins obtained by reacting polycarboxylic acids with epichlorohydrin. The epoxy resin may contain one or more types. Among these, one or more selected from bifunctional alicyclic epoxy resins and bisphenol-type epoxy resins are preferred, with bifunctional alicyclic epoxy resins being more preferred, and epoxy resins represented by the above formula (ii) being even more preferred.

[0056] The epoxy resin composition of the present invention may contain other components. Examples include light dispersants, antireflection agents, flexibilizers, heat stabilizers, ultraviolet absorbers, flame retardants, antistatic agents, antifoaming agents, thixotropy-imparting agents, mold release agents, antioxidants, chain transfer agents, plasticizers, stress-reducing agents, coupling agents, and light scattering agents. The content of these other components can be appropriately set within a range that does not impair the effects of the present invention.

[0057] The epoxy resin composition of the present invention can be produced by mixing the epoxy resin curing agent of the present invention, an epoxy resin, and, if necessary, other components.

[0058] The ratio of epoxy resin curing agent to epoxy resin can be determined based on functional group equivalent weight, but from the perspective of work efficiency, it may also be determined based on mass. For example, the ratio of epoxy resin curing agent to 100 parts by mass of epoxy resin is preferably 100 to 150 parts by mass, more preferably 105 to 140 parts by mass, and even more preferably 110 to 130 parts by mass. When the ratio is within this range, heat curing under these conditions can suppress poor appearance due to insufficient curing or the occurrence of dents on the surface of the cured product without impairing transparency, thereby producing a cured product of stable quality. Furthermore, sufficient curing is achieved, suppressing volatilization during curing and eliminating the risk of a significant decrease in the mechanical properties of the cured product.

[0059] [Cured Product] The cured product of the present invention is obtained by curing the epoxy resin composition of the present invention. The cured product of the present invention can be produced by known methods, and the temperature and time of heat curing are not particularly limited. For example, the temperature is preferably 90 to 180°C, and the total reaction time is preferably 1 to 12 hours. Heat curing may be carried out in two or more stages, for example, by heating at 90 to 140°C for 0.5 to 2 hours, followed by heating at a higher temperature for 0.5 to 2 hours. Heat curing under these conditions can prevent poor curing or poor appearance due to the occurrence of dents on the surface of the cured product without impairing transparency, thereby producing a cured product of consistent quality.

[0060] [Optical semiconductor device] The optical semiconductor device of the present invention is one in which an optical semiconductor element is encapsulated with the cured product of the present invention. As explained above, the cured product of the present invention suppresses poor appearance due to insufficient curing or depressions on the surface of the cured product without impairing transparency, so the optical semiconductor device of the present invention can have high reliability. Examples of optical semiconductor elements include LED light-emitting elements and photodiode elements. For example, the epoxy resin composition can be provided on the surface of the LED light-emitting element or the like by a method such as coating, potting, or impregnation, and then heated and cured to encapsulate the LED light-emitting element or the like.

[0061] The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples.

[0062] 1. Raw Materials In the Examples and Comparative Examples, the raw materials used in the production of the epoxy resin curing agent and the epoxy resin composition are shown below. (Y) alicyclic polycarboxylic acid anhydride: a mixture of 4-methylhexahydrophthalic anhydride and hexahydrophthalic anhydride [RIKACID MH-700 (manufactured by New Japan Chemical Co., Ltd.), acid anhydride equivalent 166 (g / eq)] (a2) polyhydric alcohol ethylene glycol (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., >99%, first-class reagent, Mw 62.07) catalyst (c1) DBU salt: 2-ethylhexanoate of DBU (U-CAT SA102, manufactured by San-Apro Co., Ltd.) (c2) phosphonium salt: tetrabutylphosphonium o,o-diethylphosphorodithioate (Hishicolin PX-4ET, manufactured by Nippon Chemical Industry Co., Ltd.) (c3) zinc octoate: Nikka Octix Zinc (manufactured by Nippon Chemical Industry Co., Ltd.), Zn 18% Bifunctional epoxy compound (B1) bifunctional alicyclic epoxy compound 3',4'-epoxycyclohexylmethyl-3,4-epoxycyclohexanecarboxylate [Celloxide 2021P (manufactured by Daicel Corporation), epoxy equivalent 137 (g / eq)] (B2) Bisphenol A type epoxy compound EPICLON 850-S (manufactured by DIC Corporation), epoxy equivalent 180 to 190 (g / eq)

[0063] 2. Number average molecular weight (Mn) of component (X) Mn was measured by gel permeation chromatography (GPC) under the following conditions: Apparatus: "HLC-8320GPC" manufactured by Tosoh Corporation Column: Two connected "TSKgel Super HM-M" columns manufactured by Tosoh Corporation Mobile phase: Tetrahydrofuran Column temperature: 40°C Flow rate: 0.6 mL / min Sample concentration: 2 mg / mL Sample injection amount: 60 μL Detector: Differential refractometer Standard material: Standard polystyrene

[0064] 3. Ratio of component (X) and component (Y) in epoxy resin curing agent High performance liquid chromatography (HPLC) analysis was performed under the following conditions: Apparatus: Tosoh Corporation "HLC-8320GPC" Column: Two Tosoh Corporation "TSKgel GMHHR-H" columns connected together Mobile phase: Tetrahydrofuran Column temperature: 40°C Flow rate: 1.0 mL / min Sample concentration: 2 mg / mL Sample injection volume: 100 μL Detector: Differential refractometer Standard material: Standard PMMA

[0065] Based on the chromatogram obtained by HPLC analysis, the ratio of the peak area derived from component (X) to the peak area derived from component (Y) was calculated. The retention times of the peaks derived from component (Y) and component (X) used in this example are as follows: (1) Examples 1 to 3 and Comparative Examples 1 to 3 Retention time of the peak derived from component (Y): 18.4 to 20.0 minutes Retention time of the peak derived from component (X): 13.5 to 18.0 minutes (2) Example 4 Retention time of the peak derived from component (Y): 18.4 to 20.0 minutes Retention time of the peak derived from component (X): 12.8 to 17.8 minutes

[0066] 4. Evaluation Methods (1) Workability (Viscosity) In the Examples and Comparative Examples, 0.25 mL of the obtained epoxy resin curing agent was measured using a syringe, and viscosity was measured under the following conditions using a rheometer (HAAKE MARS40, manufactured by Thermo Fisher Scientific).

[0067] Measurement conditions: Parallel plates with a diameter of 20 mm, a gap of 0.5 mm, shear rate: 24 s-1, measurement temperature: 25°C

[0068] (2) Transparency (i) Transmittance: 5 g of epoxy resin composition was weighed into a 5 cm diameter Teflon dish and step-cured in a hot air dryer at 135°C for 1 hour and 150°C for 4 hours to obtain a cured product. The obtained cured product was cut into 15 x 30 x 2 mm pieces and measured for transmittance at wavelengths of 400 nm and 600 nm using a UV-Visible-Infrared Spectrophotometer (JASCO Corporation, V770). (ii) Retention Rate after Heat Curing: The test pieces were heat-treated in a hot air dryer at 150°C for 168 hours, and the transmittance at a wavelength of 400 nm was measured again. The degree of deterioration in transmittance from the initial value was calculated as a percentage, which was taken as the retention rate. (iii) YI Value (Color Tone: Yellow Index) Using a color meter (SM-T, manufactured by Suga Test Instruments Co., Ltd.), the test optoelectronic components obtained by potting the epoxy resin composition were arranged so that the cured surface of the components covered the measurement area, and the chromaticity coordinates (X, Y, Z) were measured using a reflection method including specular reflection with a field of view of 2 degrees, and the YI value was calculated using the following formula.

[0069] YI = (1.2769 x coordinate X - 1.0592 x coordinate Z) / coordinate Y

[0070] (3) Measurement of Appearance Volatilization Amount The masses of 144 test optoelectronic components obtained by potting the epoxy resin composition were measured before and after the epoxy resin composition was poured into them, and after curing, and the volatilization amount was calculated as a percentage from the change in mass.

[0071] (4) Reliability (i) Tg (glass transition temperature) A probe of a thermomechanical analyzer (TMA7100, manufactured by Hitachi High-Tech Science Corporation) was brought into contact with the surface of a cured epoxy resin material of a test optoelectronic component obtained by potting the epoxy resin composition, and measurement was performed under the following conditions.

[0072] Measurement conditions: Atmosphere: Nitrogen; Measurement temperature range: 20 to 260°C; Heating rate: 10°C / min

[0073] (ii) Flexural strength: The epoxy resin composition was cured in a mold (100 × 120 × 4 mm) by step curing at 135°C / 1 hour and 150°C / 4 hours. The obtained cured product was cut into a flat plate (100 × 10 × 4 mm) conforming to JIS K-6911 5.17.1, and the flexural strength was measured using a universal testing machine (TENSILON universal testing machine RTF1310, manufactured by A&D Co., Ltd.) under the standard conditions.

[0074] 5. Evaluation Criteria (1) Workability: Taking into consideration ease of handling and the possibility of adding a third component, viscosity was used as an index to evaluate the composition according to the criteria shown in Table 1. (2) Transparency: Transmittance, retention rate after heat curing, and YI value were used as indexes to evaluate the composition according to the criteria shown in Table 1. (3) Appearance: Since a large amount of volatilization causes depressions on the light extraction surface (open surface), resulting in poor appearance and poor visibility due to reflection of external light, the composition was evaluated according to the criteria shown in Table 1 using the amount of volatilization as an index. (4) Reliability: Using the first Tg measurement value and flexural strength as indexes, the composition was evaluated according to the criteria shown in Table 1. Note that, in terms of flexural strength, if the maximum stress of the cured product is 90 MPa or more, it can be determined that the epoxy resin composition is sufficiently cured.

[0075]

[0076] 6. Examples and Comparative Examples (1) Epoxy Resin Curing Agent Example 1: (Y) alicyclic polycarboxylic acid anhydride was weighed into a beaker and heated and stirred under a nitrogen stream. Next, after the liquid temperature reached 80°C, (a2) polyhydric alcohol was added, and stirring was continued for 90 minutes while maintaining the temperature at approximately 80°C. Heating was then temporarily stopped, the temperature was lowered to 50-60°C, (c3) zinc octoate was added, and stirring was continued for another 30 minutes. After the catalyst was fully dispersed, the temperature was again raised to 80-90°C, and (B1) difunctional alicyclic epoxy compound was added. Stirring was continued for 7 hours while maintaining the temperature. After cooling, an epoxy resin curing agent was obtained. The stirring speed was adjusted to 200-400 rpm while monitoring the liquid state. It was confirmed that component (X) in the epoxy resin curing agent had an Mn of 1500 and contained the structural unit represented by formula (1) above. The ratio of component (X) to component (Y) in the epoxy resin curing agent (peak area ratio by HPLC) was 0.2.

[0077] Example 2 An epoxy resin curing agent was obtained in the same manner as in Example 1, except that the amount of component (a2) used was changed. It was confirmed that component (X) in the epoxy resin curing agent had an Mn of 1500 and contained the structural unit represented by formula (1) above. The ratio of component (X) to component (Y) in the epoxy resin curing agent (HPLC peak area ratio) was 0.1.

[0078] Example 3 An epoxy resin curing agent was obtained in the same manner as in Example 1, except that the amount of component (B1) used was changed. It was confirmed that component (X) in the epoxy resin curing agent had an Mn of 1700 and contained the structural unit represented by formula (1) above. The ratio of component (X) to component (Y) in the epoxy resin curing agent (HPLC peak area ratio) was 0.4.

[0079] Example 4 An epoxy resin curing agent was obtained in the same manner as in Example 1, except that component (B) was changed to (B2) a bisphenol A-type epoxy compound. The Mn of component (X) in the epoxy resin curing agent was 1600. The ratio of component (X) to component (Y) in the epoxy resin curing agent (HPLC peak area ratio) was 0.4.

[0080] Comparative Example 1 An epoxy resin curing agent was obtained in the same manner as in Example 1, except that the catalyst was changed to (c1) DBU salt and component (B) was not added.

[0081] Comparative Example 2 An epoxy resin curing agent was obtained in the same manner as in Example 1, except that the catalyst was changed to (c2) a phosphonium salt and component (B) was not added.

[0082] Comparative Example 3 An epoxy resin curing agent was obtained in the same manner as in Example 1, except that component (B) was not added.

[0083] (2) Epoxy resin compositions The epoxy resin curing agents obtained in the respective Examples and Comparative Examples and an epoxy resin [(B1) bifunctional alicyclic epoxy compound] were weighed out in the amounts shown in Table 1, and mixed in a planetary mixer (ARV310, manufactured by Thinky Corporation) at 2000 rpm for 2 minutes to obtain epoxy resin compositions.

[0084] (3) Using a cured product / optical semiconductor product dispenser (AD2000, manufactured by Iwashita Engineering Co., Ltd.), the epoxy resin compositions obtained in each example and comparative example were potted into LED device packages (cases) with a depth of 0.9 mm and a size of 3.5 x 2.8 mm, and then cured in a hot air dryer using step cures at 135°C / 1 hour and 150°C / 4 hours to obtain test optoelectronic components containing the cured product. The dispensed amount was adjusted to 3.5 micrograms per shot.

[0085]

[0086] As shown in Table 1, the epoxy resin compositions containing the epoxy resin curing agents of the Examples have good transparency and suppress poor appearance due to insufficient curing or the occurrence of dents on the surface of the cured product, ensuring stable quality and imparting high reliability to optical semiconductor devices. In particular, it can be seen that the performance of the epoxy resin curing agent of Example 1 is remarkably superior.

Claims

1. A curing agent for epoxy resins, comprising the following components (X) and (Y): (X) a reaction product of the following components (A) and (B): (A) (a1) a reaction product of an alicyclic polycarboxylic acid or its anhydride with (a2) a polyhydric alcohol; (B) one or more selected from a difunctional alicyclic epoxy compound and a bisphenol-type epoxy compound; and (Y) an alicyclic polycarboxylic acid anhydride.

2. The epoxy resin curing agent according to claim 1, wherein component (A) is a compound represented by the following formula (i), and component (B) is a compound represented by the following formula (ii). [In the formula, R 1 and R 3 each independently represents an alkanediyl group which may have a characteristic group containing an oxygen atom, and R 2 represents a hydrogen atom or an alkyl group.

3. The epoxy resin curing agent according to claim 1, wherein the ratio of component (X) to component (Y) in the epoxy resin curing agent is such that, in a chromatogram obtained by analyzing the epoxy resin curing agent by high performance liquid chromatography, the ratio of the peak area attributable to component (X) to the peak area attributable to component (Y) is 0.1 to 0.

7.

4. The epoxy resin curing agent according to claim 1, wherein component (X) contains one or more structural units selected from the structural unit represented by the following formula (1), the structural unit represented by the following formula (2), the structural unit represented by the following formula (3), and the structural unit represented by the following formula (4). [In the formula, R 1 and R 3 each independently represents an alkanediyl group which may have a characteristic group containing an oxygen atom, and R 2 represents a hydrogen atom or an alkyl group.

5. An epoxy resin composition comprising the epoxy resin curing agent according to any one of claims 1 to 4 and an epoxy resin.

6. A cured product obtained by curing the epoxy resin composition according to claim 5.

7. An optical semiconductor device in which an optical semiconductor element is encapsulated with the cured product according to claim 6.

8. A method for producing an epoxy resin curing agent according to any one of claims 1 to 4, comprising the following steps (1) and (2): Step (1) reacting the following component (Y) with the following component (a2) in an amount of 0.1 to 5% by mass relative to component (Y); and Step (2) mixing the reaction liquid obtained from step (1) with the following component (B) in an amount of 0.3 to 7 times by mass relative to component (a2): (Y) an alicyclic polycarboxylic acid anhydride, (a2) a polyhydric alcohol, and (B) one or more selected from a difunctional alicyclic epoxy compound and a bisphenol-type epoxy compound.

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