Photocurable resin composition

Abstract

The present invention provides a photocurable resin composition which has favorable thick film curability and of which the cured product after curing is excellent in flexibility and heat resistance. The photocurable resin composition according to the present invention includes component (A): a polyorganosiloxane having one or more vinyl groups in one molecule, component (B): a compound having one or more mercapto groups in one molecule, component (C): a photoinitiator, and component (D): hollow resin particles.

Description

Photocurable resin composition

[0001] The present invention relates to a photocurable resin composition.

[0002] Packings, adhesives, and sealants used in automotive and electronic components have traditionally been required to have flexible properties from the viewpoint of shock and vibration resistance. Furthermore, when used as packing or sealants, they are required to have the strength (reaction force) to resist high compressive stresses applied to components and heat resistance (see, for example, Patent Document 1). Furthermore, photocurability, which allows for rapid curing, is required for the purpose of shortening line takt time. Photocurable sealants are required to have thick-film curing properties because the curing process occurs when the sealant is cured by light irradiation, which can result in the surface curing while the interior remains uncured.

[0003] Japanese Patent Publication No. 2004-331764

[0004] Conventional photocuring sealants have been able to achieve a certain degree of thick film curing and flexibility, but if they are too flexible, the sealant will collapse, and there are no products that are satisfactory in terms of repulsion force or heat resistance. When trying to create a more flexible photocuring adhesive or sealant, there is a risk that the sealing properties and heat resistance will be lost, and there have been no products that combine thick film curing, flexibility, repulsion force, and heat resistance.

[0005] As a result of extensive research to achieve the above object, the present inventors have discovered a photocurable resin composition that has good thick-film curability, flexibility (low hardness and elongation), and excellent repulsion and heat resistance.

[0006] The gist of the present invention will now be described.

[0007] [1] A photocurable resin composition comprising components (A) to (D): component (A): a polyorganosiloxane having one or more vinyl groups per molecule; component (B): a compound having one or more mercapto groups per molecule (excluding component (A)); component (C): a photoinitiator; and component (D): hollow resin particles.

[0008] [2] The photocurable resin composition according to [1], wherein the component (B) is a mercapto group-containing polyorganosiloxane.

[0009] [3] The photocurable resin composition according to [1] or [2], wherein the content of the component (D) is 0.1 to 50 parts by mass per 100 parts by mass of the component (A).

[0010] [4] The photocurable resin composition according to [2], wherein the component (B) is a mercapto group-containing polyorganosiloxane having mercapto groups only on the side chains.

[0011] [5] The photocurable resin composition according to [1] or [2], further comprising a non-reactive silicone oil as component (E).

[0012] [6] The photocurable resin composition according to [1] or [2], further comprising an inorganic filler as component (F).

[0013] [7] The photocurable resin composition according to [1] or [2], wherein the component (C) is an acetophenone-based photoinitiator.

[0014] [8] The photocurable resin composition according to [1] or [2], wherein the average particle size of the component (D) is 10 to 200 μm.

[0015] [9] The photocurable resin composition according to [1] or [2], wherein the true specific gravity of the component (D) is 0.001 to 0.3.

[0016]

[10] A cured product obtained by curing the photocurable resin composition according to [1] or [2].

[0017] The present invention provides a photocurable resin composition that has good thick-film curing properties, and the cured product has excellent flexibility (hardness, elongation), and excellent heat resistance and sealing properties (reaction force, compression set).

[0018] The present invention will be described in detail below. However, the present invention is not limited to the following embodiments. In this specification, "X to Y" means a range including the numerical values ​​(X and Y) written before and after it as the lower and upper limits, respectively, and means "X or more and Y or less." Furthermore, in this specification, "mass" is synonymous with "weight."

[0019] The component (A) of the present invention is a polyorganosiloxane having one or more vinyl groups per molecule. Component (A) is the main component for obtaining a cured product with excellent flexibility and heat resistance. The molecular structure of component (A) is substantially linear, but may contain a branched structure in part. Examples of component (A) include polydimethylsiloxanes capped at both molecular chain terminals with vinyl groups; dimethylsiloxane-diphenylsiloxane copolymers capped at both molecular chain terminals with vinyl groups; dimethylsiloxane-methylvinylsiloxane-diphenylsiloxane copolymers capped at both molecular chain terminals with vinyl groups; polydimethylsiloxanes capped at one molecular chain terminal with vinyl groups and the other with trimethoxy groups; polydimethylsiloxanes capped at one molecular chain terminal with vinyl groups and the other with trimethylsiloxy groups; and dimethylsiloxane-methylvinylsiloxane-diphenylsiloxane copolymers capped at both molecular chain terminals with trimethylsiloxy groups. Among these, polydimethylsiloxanes having both molecular chain terminals capped with vinyl groups are preferred due to their excellent flexibility. The component (A) may contain one type alone, or two or more types in combination.

[0020] The kinematic viscosity (25°C) of the component (A) is 5,000 to 70,000 mm ２ / s is preferred, and 10,000 to 50,000 mm ２ / s is more preferable, and 20,000 to 40,000 mm ２ / s is most preferred. ２ In the present invention, the kinematic viscosity (25°C) is a value measured in accordance with JIS Z 8803:2011.

[0021] Component (B) of the present invention is a compound having one or more mercapto groups in one molecule, excluding component (A). Component (B) is a major component that, when used in combination with component (A), can provide a thick-film curing property and a cured product with excellent flexibility. Component (B) is not particularly limited as long as it is a compound having one or more mercapto groups in one molecule. Specific examples of component (B) include primary thiol compounds such as trimethylolpropane tris(3-mercaptopropionate), tris-[(3-mercaptopropionyloxy)-ethyl]-isocyanurate, pentaerythritol tetrakis(3-mercaptopropionate), tetraethylene glycol bis(3-mercaptopropionate), and dipentaerythritol hexakis(3-mercaptopropionate); pentaerythritol tetrakis(3-mercaptobutyrate), 1,4-bis(3-mercaptopropionate); Examples of the component (B) include secondary thiol compounds such as 1,3,5-tris(3-mercaptobutyryloxy)butane, 1,3,5-tris(3-mercaptobutyryloxyethyl)-1,3,5-triazine-2,4,6(1H,3H,5H)-trione, trimethylolpropane tris(3-mercaptobutyrate), trimethylolethane tris(3-mercaptobutyrate), trimethylolpropane tris(3-mercaptobutyrate), and trimethylolethane tris(3-mercaptobutyrate); and mercapto group-containing polyorganosiloxanes. Component (B) may contain one type alone or two or more types in combination. From the viewpoint of obtaining excellent elongation and repulsion when combined with component (A), component (B) is preferably a mercapto group-containing polyorganosiloxane, and more preferably a mercapto group-containing polyorganosiloxane having mercapto groups only on the side chain.

[0022] The mercapto group-containing polyorganosiloxane having mercapto groups only on the side chains has a structure represented by the following general formula (1).

[0023]

[0024] (In formula (1), R is a divalent organic group, and m and n are each an integer of 1 or more.)

[0025] The kinematic viscosity (25°C) of the component (B) is 1 to 1,000 mm２ / s is preferred, and 10 to 500 mm ２ / s is more preferable, and 100 to 300 mm ２ / s is most preferred. ２ By satisfying this condition, separation after mixing with component (A) is unlikely, and a cured product having excellent elongation can be obtained.

[0026] The functional group equivalent of the mercapto group in component (B) is preferably 100 to 5,000 g / mol, more preferably 500 to 4,000 g / mol, and most preferably 1,000 to 3,000 g / mol. By ensuring that the functional group equivalent of the mercapto group is 100 to 5,000 g / mol, a cured product with excellent thick-film curability and elongation can be obtained.

[0027] The content of the component (B) is preferably 0.01 to 100 parts by mass, more preferably 1 to 70 parts by mass, and most preferably 5 to 30 parts by mass, per 100 parts by mass of the component (A). By having the content of the component (B) be 0.01 to 100 parts by mass per 100 parts by mass of the component (A), a cured product having excellent thick-film curability and elongation can be obtained.

[0028] The component (C) of the present invention is a photoinitiator. A photoinitiator is a compound that decomposes to generate radical species when irradiated with active energy rays such as ultraviolet light or visible light. Examples of the component (C) include acetophenone-based photoinitiators, benzoin-based photoinitiators, benzophenone-based photoinitiators, thioxanthone-based photoinitiators, and acylphosphine oxide-based photoinitiators. The component (C) may be used alone or in combination of two or more types.

[0029] Examples of the acetophenone-based photoinitiator include, but are not limited to, diethoxyacetophenone, 2-hydroxy-2-methylpropiophenone, benzyl dimethyl ketal, 4-(2-hydroxyethoxy)phenyl-(2-hydroxy-2-propyl)ketone, 1-hydroxycyclohexylphenyl ketone, 2-methyl-2-morpholino(4-thiomethylphenyl)propan-1-one, 2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)butanone, and 2-hydroxy-2-methyl-1-[4-(1-methylvinyl)phenyl]propanone oligomer.

[0030] Examples of the benzoin-based photoinitiator include, but are not limited to, benzoin, benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, and benzoin isobutyl ether.

[0031] Examples of the benzophenone-based photoinitiator include, but are not limited to, benzophenone, methyl o-benzoylbenzoate, 4-phenylbenzophenone, 4-benzoyl-4'-methyl-diphenyl sulfide, 3,3',4,4'-tetra(t-butylperoxycarbonyl)benzophenone, 2,4,6-trimethylbenzophenone, 4-benzoyl-N,N-dimethyl-N-[2-(1-oxo-2-propenyloxy)ethyl]benzenemethanaminium bromide, and (4-benzoylbenzyl)trimethylammonium chloride.

[0032] Examples of the thioxanthone-based photoinitiator include, but are not limited to, 2-isopropylthioxanthone, 4-isopropylthioxanthone, 2,4-diethylthioxanthone, 2,4-dichlorothioxanthone, 1-chloro-4-propoxythioxanthone, and 2-(3-dimethylamino-2-hydroxy)-3,4-dimethyl-9H-thioxanthone-9-one mesochloride.

[0033] Examples of the acylphosphine oxide photoinitiator include, but are not limited to, bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide, 2,4,6-trimethylbenzoyl-diphenylphosphine oxide, and 2,4,6-trimethylbenzoylphenylethoxyphosphine oxide.

[0034] From the viewpoint of thick-film curability when mixed with the components (A) and (B), the component (C) is preferably an acetophenone-based photoinitiator, more preferably 2-hydroxy-2-methylpropiophenone and / or 1-hydroxycyclohexyl phenyl ketone, and most preferably 2-hydroxy-2-methylpropiophenone.

[0035] The molecular weight of the component (C) is preferably 50 to 500, more preferably 70 to 400, and most preferably 100 to 300. When the molecular weight is 50 to 500, a photocurable resin composition having excellent thick-film curing properties can be obtained.

[0036] The content of the component (C) is preferably 0.1 to 20 parts by mass, more preferably 0.3 to 10 parts by mass, and most preferably 0.5 to 1.5 parts by mass, per 100 parts by mass of the component (A). Furthermore, the content of the component (C) is preferably 0.5 to 20 parts by mass, more preferably 1 to 10 parts by mass, and most preferably 3 to 8 parts by mass, per 100 parts by mass of the component (B). By ensuring that the content is within the above range, a photocurable resin composition with excellent thick-film curing properties can be obtained.

[0037] The component (D) of the present invention is hollow resin particles. Hollow resin particles are hollow bodies having a hollow portion and are formed from a resin. By including the component (D), a cured product can be obtained that does not collapse even when compressed under high compression and has good repulsion force, thereby achieving high sealing properties.

[0038] The shape of component (D) is not particularly limited and may be any shape, such as spherical, needle-like, fibrous, or plate-like. However, a spherical shape is preferred from the viewpoints of dispersibility in components (A) and (B) and sealability at high compression. In the present invention, spherical means an aspect ratio of 1.0 to 2.0, preferably 1.0 to 1.5, but does not necessarily mean a perfect sphere. In the case of a spherical shape, the aspect ratio is determined by the ratio of the major axis to the minor axis.

[0039] The average particle size of component (D) is not particularly limited, but is preferably 10 to 200 μm, more preferably 40 to 170 μm, and most preferably 100 to 150 μm. An average particle size of 10 to 200 μm allows the cured product to have low repulsion and high sealing properties even under high compression conditions. Here, the average particle size of component (D) is the particle size at a cumulative volume ratio of 50% (D50) in the particle size distribution determined by laser diffraction scattering.

[0040] The resin constituting the component (D) is not particularly limited, but is preferably a thermoplastic resin, more preferably a polymer (homopolymer) of one or more monomers selected from the group consisting of vinylidene chloride, acrylonitrile, methacrylonitrile, acrylic acid esters, and methacrylic acid esters, or a copolymer of two or more monomers. From the viewpoint of sealability at high compression, a copolymer is preferred, more preferably a copolymer containing acrylonitrile as a structural unit, and most preferably an acrylonitrile-methacrylonitrile-methyl methacrylate copolymer. From the viewpoint of dispersibility in the components (A) and (B) and sealability at high compression, a component (D) having an inorganic filler attached to its surface is preferred, and a component (D) having calcium carbonate attached is more preferred.

[0041] The component (D) may contain one type alone, or may contain a combination of two or more types having different resins or shapes.

[0042] From the viewpoint of dispersibility in components (A) and (B), the true specific gravity of component (D) is preferably 0.001 to 0.3, more preferably 0.01 to 0.2, and most preferably 0.01 to 0.15. The true specific gravity of component (D) can be determined by a method in accordance with JIS Z8807:2012.

[0043] The content of the component (D) is preferably 0.1 to 50 parts by mass, more preferably 0.5 to 30 parts by mass, and most preferably 3 to 15 parts by mass, per 100 parts by mass of the component (A). When the content of the component (D) is 0.1 to 50 parts by mass per 100 parts by mass of the component (A), the cured product has low repulsion and can achieve high sealability even under high compression conditions.

[0044] In the present invention, it is preferable to further include a non-reactive silicone oil as component (E). The non-reactive silicone oil referred to here is a polyorganosiloxane that does not have reactive groups such as vinyl groups, (meth)acryloyl groups, mercapto groups, alkoxysilyl groups, or epoxy groups, and refers to a polyorganosiloxane in which the terminals and side chains are blocked with alkyl groups. By including component (E), the elongation can be further improved. From the viewpoint of improving the elongation, the alkyl groups of component (E) are preferably methyl groups and / or ethyl groups, more preferably methyl groups, and most preferably consisting of only methyl groups.

[0045] The kinematic viscosity (25°C) of the component (E) is 0.01 to 100 mm ２ / s is preferred, and 0.1 to 80 mm ２ / s is more preferable, and 1 to 30 mm ２ / s is most preferable. ２ By setting the elongation ratio at 1 / s, a cured product having an even more excellent elongation percentage can be obtained.

[0046] The volatile content of component (E) after 24 hours at 150°C is preferably 0 to 10%, more preferably 0 to 7%, and most preferably 0 to 5%. A volatile content of 0 to 10% does not reduce the heat resistance of the cured product.

[0047] The content of the component (E) is preferably 5 to 50% by mass, more preferably 10 to 30% by mass, and most preferably 15 to 25% by mass, relative to 100 parts by mass of the entire photocurable resin composition. Furthermore, the content of the component (E) is preferably 5 to 100 parts by mass, more preferably 10 to 70 parts by mass, and most preferably 20 to 50 parts by mass, relative to 100 parts by mass of the component (A). By keeping the content within the above range, a cured product with even better elongation can be obtained, and there is no risk of a decrease in heat resistance.

[0048] The photocurable resin composition of the present invention may further contain an inorganic filler as component (F). Examples of component (F) include, but are not limited to, alumina powder, calcium carbonate powder, talc powder, silica powder, fumed silica powder, silver powder, nickel powder, palladium powder, carbon powder, tungsten powder, and plating powder. These may be used alone or in combination of two or more. Among these, from the viewpoint of not reducing elongation, inorganic fillers selected from the group consisting of calcium carbonate powder, talc powder, fumed silica powder, and silica powder are preferred, fumed silica powder is more preferred, and fumed silica powder surface-treated with dimethylpolysiloxane is most preferred.

[0049] The BET specific surface area of ​​the component (F) is 10 to 700 m ２ / g is preferred, and 80 to 500m ２ / g is more preferable, and 100 to 300m ２ / g is most preferable. ２ / g, there is no risk of the elongation rate decreasing.

[0050] The content of the component (F) is preferably 0.5 to 30 parts by mass, more preferably 1 to 20 parts by mass, and most preferably 3 to 10 parts by mass, per 100 parts by mass of the component (A). By having the content of the component (F) be 0.5 to 30 parts by mass per 100 parts by mass of the component (A), there is no risk of a decrease in elongation.

[0051] The present invention may contain an appropriate amount of a light stabilizer, an antioxidant, and an anti-rust agent within the range that does not impair the properties of the present invention. The addition of these can improve storage stability and heat resistance.

[0052] Examples of the light stabilizer include ultraviolet absorbers and radical scavengers, such as bis(2,2,6,6-tetramethyl-4-piperidyl)sebacate, bis(1,2,2,6,6-pentamethyl-4-piperidyl)sebacate, 4-benzoyloxy-2,2,6,6-tetramethylpiperidine, 1-[2-[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionyloxy]ethyl]-4-[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionyloxy]-2,2,6,6-tetramethylpiperidine, 1,2, 2,6,6-Pentamethyl-4-piperidinyl-methacrylate, bis(1,2,2,6,6-pentamethyl-4-piperidinyl)[[3,5-bis(1,1-dimethylethyl)-4-hydroxyphenyl]methyl]butylmalonate, decanedioic acid bis(2,2,6,6-tetramethyl-1(octyloxy)-4-piperidinyl)ester, reaction products of 1,1-dimethylethyl hydroperoxide with octane, N,N',N'',N'''-tetrakis-(4,6-bis-(butyl-(N-methyl-2,2,6,6-tetramethylpiperidin-4-yl)-isopropyl)propionate (2,2,6,6-tetramethyl-4-piperidyl)amino)-triazin-2-yl)-4,7-diazadecane-1,10-diamine, polycondensate of dibutylamine, 1,3,5-triazine, N,N'-bis(2,2,6,6-tetramethyl-4-piperidyl-1,6-hexamethylenediamine and N-(2,2,6,6-tetramethyl-4-piperidyl)butylamine, poly[[6-(1,1,3,3-tetramethylbutyl)amino-1,3,5-triazine-2,4-diyl][(2,2,6,6-tetramethyl-4-piperidyl)imino]hexamethylene[(2,2,6,6-tetramethyl-4-piperidyl)imino]hexamethylene[[6-(1,1,3,3-tetramethylbutyl)amino-1,3,5-triazine-2,4-diyl][ ... peridylinyl)imino]], polymer of dimethyl succinate and 4-hydroxy-2,2,6,6-tetramethyl-1-piperidineethanol, 2,2,4,4-tetramethyl-20-(β-lauryloxycarbonyl)ethyl-7-oxa-3,20-diazadispiro[5.1.11.2]henicosan-21-one, β-alanine, N-(2,2,6,6-tetramethyl-4-piperidinyl)-dodecyl ester / tetradecyl ester, N-acetyl-3-dodecyl-1-(2,2,6,6-tetramethyl-4-piperidinyl)pyrrolidine-2,5-dione, 2,2,4,4-Tetramethyl-7-oxa-3,20-diazadispiro[5.1.11.2]henicosan-21-one, 2,2,4,4-tetramethyl-21-oxa-3,20-diazadispiro[5.1.11.2]-henicosan-20-propanoic acid dodecyl ester / tetradecyl ester, propanediol, [(4-methoxyphenyl)-methylene]-bis(1,2,2,6,6-pentamethyl-4-piperidinyl)ester hindered amine compounds such as esters of 2,2,6,6-tetramethyl-4-piperidinol, higher fatty acid esters of 1,3-benzenedicarboxamide, N,N'-bis(2,2,6,6-tetramethyl-4-piperidinyl), and bis(1,2,2,6,6-pentamethyl-4-piperidyl) sebacate; benzophenone compounds such as octabenzone; and 2-(2H-benzotriazol-2-yl)-4-(1,1,3,3-tetramethylbutyl) Benzotriazole compounds such as phenol, 2-(2-hydroxy-5-methylphenyl)benzotriazole, 2-[2-hydroxy-3-(3,4,5,6-tetrahydrophthalimido-methyl)-5-methylphenyl]benzotriazole, 2-(3-tert-butyl-2-hydroxy-5-methylphenyl)-5-chlorobenzotriazole, 2-(2-hydroxy-3,5-di-tert-pentylphenyl)benzotriazole, reaction products of methyl 3-(3-(2H-benzotriazol-2-yl)-5-tert-butyl-4-hydroxyphenyl)propionate with polyethylene glycol, and 2-(2H-benzotriazol-2-yl)-6-dodecyl-4-methylphenol; benzoate compounds such as 2,4-di-tert-butylphenyl-3,5-di-tert-butyl-4-hydroxybenzoate;Examples of such a light stabilizer include triazine-based compounds such as 5-triazin-2-yl)-5-[(hexyl)oxy]phenol. These may be used alone or in combination of two or more. Among these, hindered amine-based light stabilizers are preferred from the viewpoint of improving storage stability. The content of the light stabilizer is preferably 0.001 to 1 mass%, more preferably 0.005 to 0.1 mass%, and most preferably 0.01 to 0.05 mass%, relative to 100 mass% of the total photocurable resin composition. By having the light stabilizer content be 0.001 to 1 mass%, there is no risk of a decrease in elongation or sealability.

[0053] Examples of the antioxidant include quinone compounds such as β-naphthoquinone, 2-methoxy-1,4-naphthoquinone, methylhydroquinone, hydroquinone, hydroquinone monomethyl ether, mono-tert-butylhydroquinone, 2,5-di-tert-butylhydroquinone, p-benzoquinone, 2,5-diphenyl-p-benzoquinone, and 2,5-di-tert-butyl-p-benzoquinone; phenothiazine, 2,2-methylene-bis(4-methyl-6-tert-butylphenol), catechol, tert-butylcatechol, and 2-butyl-4-hydroxybenzoquinone. Hydroxyanisole, 2,6-di-tert-butyl-p-cresol, 2-tert-butyl-6-(3-tert-butyl-2-hydroxy-5-methylbenzyl)-4-methylphenyl acrylate, 2-[1-(2-hydroxy-3,5-di-tert-pentylphenyl)ethyl]-4,6-di-tert-pentylphenyl acrylate, 4,4'-butylidenebis(6-tert-butyl-3-methylphenol), 4,4'-thiobis(6-tert-butyl-3-methylphenol), 3,9-bis[2-[3-(3-tert-butyl N,N'-hexane-1,6-diylbis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionyloxy]-1,1-dimethylethyl]-2,4,8,10-tetraoxaspiro[5,5]undecane, pentaerythritol tetrakis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], thiodiethylene bis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], octadecyl-3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, N,N'-hexane-1,6-diylbis[3-(3,5-di -tert-butyl-4-hydroxyphenyl)propionamide], benzenepropanoic acid, 3,5-bis(1,1-dimethylethyl)-4-hydroxy, C7-C9 side chain alkyl ester, 2,4-dimethyl-6-(1-methylpentadecyl)phenol, diethyl [[3,5-bis(1,1-dimethylethyl)-4-hydroxyphenyl]methyl]phosphonate, 3,3',3'',5,5',5''-hexa-tert-butyl-a,a',a''-(mesitylene-2,4,6-tolyl)tri-p-cresol, calcium diethylbis[[3,5-bis(1,1-dimethylethyl)-4-hydroxyphenyl]methyl]phosphonate, 4,6-bis(octylthiomethyl)-o-cresol, ethylene bis(oxyethylene)bis[3-(5-tert-butyl-4-hydroxy-m-tolyl)propionate], hexamethylene bis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], 1,3,5-tris(3,5-di-tert-butyl-4-hydroxybenzyl)-1,3,5-tris(trimethylsilyl) 1,3,5-triazine-2,4,6(1H,3H,5H)-trione, 1,3,5-tris[(4-tert-butyl-3-hydroxy-2,6-xylyl)methyl]-1,3,5-triazine-2,4,6(1H,3H,5H)-trione, reaction products of N-phenylbenzenamine with 2,4,6-trimethylpentene, 2,6-di-tert-butyl-4-(4,6-bis(octylthio)-1,3,5-triazin-2-ylamino)phenol, picric acid, citric acid, 3-(4-hydroxy-3 phenolic antioxidants such as tris(2,4-di-tert-butylphenyl)phosphite, tris[2-[[2,4,8,10-tetra-tert-butyldibenzo[d,f][1,3,2]dioxaphosphen-6-yl]oxy]ethyl]amine, bis(2,4-di-tert-butylphenyl)pentaerythritol diphosphite, bis[2,4-bis(1,1-dimethylethyl)-6-methylphenyl] Phosphorus-based antioxidants such as ethyl ester phosphorous acid, tetrakis(2,4-di-tert-butylphenyl)[1,1-bisphenyl]-4,4'-diylbisphosphonite, and 6-[3-(3-tert-butyl-4-hydroxy-5-methylphenyl)propoxy]-2,4,8,10-tetra-tert-butyldibenz[d,f][1,3,2]dioxaphosphene; dilauryl 3,3'-thiodipropionate, dimyristyl 3,3'-thiodipropionate, distearyl 3,Examples of suitable antioxidants include sulfur-based antioxidants such as 3'-thiodipropionate, pentaerythrityl tetrakis(3-laurylthiopropionate), and 2-mercaptobenzimidazole; amine-based compounds such as phenothiazine; lactone-based compounds; and vitamin E-based compounds. From the viewpoint of improving heat resistance, phenol-based antioxidants are preferred, and hindered phenol-based antioxidants are more preferred. The content of the antioxidant is preferably 0.001 to 1 mass%, more preferably 0.005 to 0.1 mass%, and most preferably 0.01 to 0.05 mass%, relative to 100 mass% of the total photocurable resin composition. By limiting the content of the antioxidant to 0.001 to 1 mass%, there is no risk of a decrease in elongation or sealing properties.

[0054] The rust inhibitor is not particularly limited, and examples thereof include sodium benzoate, benzotriazole, chromates (e.g., zinc chromate, calcium chromate, strontium chromate, barium chromate, zinc potassium chromate, and tetrabasic zinc chromate), phosphates (e.g., zinc phosphate, zinc phosphosilicate, aluminum zinc phosphate, calcium zinc phosphate, calcium phosphate, aluminum pyrophosphate, calcium pyrophosphate, aluminum dihydrogen tripolyphosphate, aluminum metaphosphate, calcium metaphosphate, zinc phosphomolybdate, and aluminum phosphomolybdate), nitrites (e.g., sodium nitrite, calcium nitrite, strontium nitrite, barium nitrite, and ammonium nitrite), and phytates (e.g., zinc phytate, sodium phytate, potassium phytate, and calcium phytate). sodium, etc.), tannates (e.g., sodium tannate, potassium tannate, etc.), polyamine compounds (e.g., N-(2-hydroxyethyl)ethylenediaminetriacetic acid (HEDTA), ethylenediaminetetraacetic acid (EDTA), diethylenetriaminepentaacetic acid (DTPA), propylenediaminetetraacetic acid (PDTA), iminodiacetic acid, nitrilotriacetic acid (NTA), diethylenetriaminepentamethylenephosphonic acid (DTPMP), and alkali metal salts thereof); intercalation compounds obtained by intercalating monoalkylamines, polyamines, quaternary ammonium ions, etc. into layered phosphates such as aluminum dihydrogen tripolyphosphate; MIO, lead cyanamide, ammonium metavanadate, ammonium dizircofluoride, zinc molybdate, aluminum molybdate, barium metaborate, and zinc salts of organic nitro compounds. Among these, 1,2,3-benzotriazole is preferred from the viewpoint of not reducing heat resistance. The content of the rust inhibitor is preferably 0.001 to 1 mass%, more preferably 0.005 to 0.1 mass%, and most preferably 0.01 to 0.05 mass%, relative to 100 mass% of the total photocurable resin composition. By having the content of the rust inhibitor be 0.001 to 1 mass%, there is no risk of a decrease in elongation or sealing property.

[0055] <Applications> The photocurable resin composition of the present invention can be used as an adhesive, a sealant, etc., but is preferably used as a sealant due to its excellent repulsion force and compression set. The sealant is not particularly limited, and can be used for substrates such as various metals, glasses, ceramics, and resins. Specific applications include, in the automotive and transportation fields, sealing of automotive switches, vehicle bodies, headlamps, engine interior components, electrical components, structural adhesives, drive engines, brake oil tanks, etc. In flat panel displays, the composition can be used to seal liquid crystal displays, organic electroluminescence displays, light-emitting diode displays, and field emission displays. The composition can also be used to seal electronic mobile devices such as mobile phones and multi-function mobile phones, and camera modules. In the recording field, the composition can be used to seal CDs (Compact Discs), DVDs (Digital Versatile Discs), MDs (Mini Discs), pickup lenses, hard disk peripherals (spindle motor components, magnetic head actuator components, etc.), Blu-ray discs, etc. In the battery field, it can be used for sealing and buffering purposes for Li batteries, manganese batteries, alkaline batteries, nickel-based batteries, fuel cells, silicon-based solar cells, dye-sensitized solar cells, organic solar cells, etc. In the optical component field, it can be used for sealing the periphery of optical switches in optical communication systems, optical fiber materials around optical connectors, optical passive components, optical circuit components, and the periphery of optoelectronic integrated circuits, etc. In the optical equipment field, it can be used for sealing still camera lens materials, finder prisms, target prisms, finder covers, light-receiving sensor parts, photographic lenses, etc.

[0056] <Coating Method> The photocurable resin composition of the present invention can be applied to an adherend by known methods for applying sealants or adhesives. For example, methods such as dispensing using an automatic coater, spraying, inkjet printing, screen printing, gravure printing, dipping, and spin coating can be used. Note that the photocurable resin composition of the present invention is liquid at 25°C from the viewpoint of coatability.

[0057] <Curing Conditions> When the photocurable resin composition of the present invention is cured by irradiating it with ultraviolet light, visible light, or other light, the light source is not particularly limited, and examples thereof include a low-pressure mercury lamp, a medium-pressure mercury lamp, a high-pressure mercury lamp, an ultra-high-pressure mercury lamp, a black light lamp, a microwave-excited mercury lamp, a metal halide lamp, a sodium lamp, a halogen lamp, a xenon lamp, an LED, a fluorescent lamp, sunlight, and an electron beam irradiation device. The wavelength is not particularly limited, and light of 200 to 500 nm, for example, is used. The exposure dose of light irradiation is 3 to 70 kJ / m2 from the viewpoint of the properties of the cured product. ２ or more, more preferably 5 to 60 kJ / m ２ The present invention also includes a cured product obtained by curing the photocurable resin composition.

[0058] The present invention will now be described in more detail with reference to examples, but the present invention is not limited to these examples. (Hereinafter, the photocurable resin composition will also be referred to simply as the composition.)

[0059] [Example 1, Comparative Examples 1 to 4] The following components were prepared to prepare the compositions: Component (A): Polyorganosiloxane having vinyl groups at both ends (kinematic viscosity (25°C) 30,000 mm ２ / s) Component (A'-1): urethane acrylate containing acryloyl groups at both ends (trade name: UF-8001G (manufactured by Kyoeisha Chemical Co., Ltd.)) Component (A'-2): acrylic polymer containing acryloyl groups at both ends (trade name: XMAP RC100C (manufactured by Kaneka Corporation)) Component (A'-3): isobornyl acrylate (trade name: IBXA (manufactured by Osaka Organic Chemical Industry Ltd.)) Component (A'-4): n-octyl acrylate (trade name: NOAA (manufactured by Osaka Organic Chemical Industry Ltd.)) Component (B): polyorganosiloxane having a structure of general formula (1) and no vinyl group but having mercapto groups only on the side chain (trade name: KF-2001 (manufactured by Shin-Etsu Chemical Co., Ltd.), kinematic viscosity (25 ° C) 200 mm ２ / s, functional group equivalent 1,900 g / mol) (C) component: 2-hydroxy-2-methylpropiophenone (trade name: Doublecure 173 (manufactured by Doublebond Chemical Co., Ltd.), molecular weight 164.20 g / mol) (D) component: spherical resin hollow filler with calcium carbonate attached to the surface (trade name: EMC-120R (manufactured by Nippon Fillite Co., Ltd.), average particle size 120 μm, true specific gravity 0.1 g / cm ３ ) (D') component: glass hollow filler (trade name: Glass Bubbles K1 (manufactured by 3M Japan Ltd.)) (E) component: dimethyl silicone oil (trade name: KF-96-20cs (manufactured by Shin-Etsu Chemical Co., Ltd.), kinematic viscosity (25°C) 20 mm ２ / s, volatile content (150°C / 24 hours) 4.0% or less) Component (F): fumed silica powder surface-treated with dimethylpolysiloxane (trade name: Aerosil RY200 (manufactured by Nippon Aerosil Co., Ltd.), BET specific surface area 200 m ２ / g) Component (G-1): bis(1,2,2,6,6-pentamethyl-4-piperidyl) sebacate (hindered amine-based light stabilizer, trade name: TINUVIN 765 (manufactured by BASF Japan Ltd.)) Component (G-2): octyl 3-(4-hydroxy-3,5-diisopropylphenyl)propionate (hindered phenol-based antioxidant, trade name: IRGANOX 1135 (manufactured by BASF Japan Ltd.)) Component (G-3): 1,2,3-benzotriazole (reagent)

[0060] Resin compositions of Example 1 and Comparative Examples 1 to 4 were prepared. All components except for component (C) were weighed and mixed at room temperature for 30 minutes in a planetary mixer. Component (C) was added in the dark, and the components were mixed for 30 minutes in a planetary mixer. Detailed amounts of the components were as shown in Table 1.

[0061] The thick film curability, hardness, elongation, resilience, and compression set (100°C, 150 hours) were measured for each of the resin compositions of Example 1 and Comparative Examples 1 to 4. The results are summarized in Table 1.

[0062] [Thick Film Curability] A composition was placed in a glass container having a diameter of 2 cm to a depth of 10 mm, and ultraviolet light (wavelength: 365 nm) was irradiated to the container using a high-pressure mercury lamp with a belt conveyor type irradiator at an integrated light intensity of 30 kJ / m ２ The uncured material was wiped off, and the thickness of the cured material was measured with a vernier caliper, and the measured value was recorded as "thick film curability (mm)." A thickness of 3.0 mm or more was considered to be acceptable.

[0063] [Hardness] Each photocurable resin composition was poured into a frame of 200 mm x 200 mm x 1.0 mm (the thickness of the photocurable resin composition was set to 1 mm). ２ The test piece was cured by irradiating it with ultraviolet light of 1000 kJ / min to produce a sheet-like cured product. This process was repeated to obtain six sheets of cured product, which were then stacked to a thickness of 6 mm to form a test piece. The pressure surface of an E-type durometer (hardness tester) was pressed with a force of 10 N while being kept parallel to the test piece, so that the pressure surface and the test piece were closely attached to each other. The maximum value was read during measurement, and this was taken as the "hardness." Details were in accordance with JIS K 6253 (2012). Test pieces with a maximum hardness of less than E50 were considered to pass.

[0064] [Elongation] The thickness of each photocurable resin composition was set to 1 mm, and the cumulative light amount was 30 kJ / m ２ The test piece was cured by irradiating ultraviolet light of 1000 nm to produce a sheet-like cured product. Test pieces were punched out with a No. 3 dumbbell, and benchmark lines were written on the test pieces at 20 mm intervals. The test pieces were fixed to the chuck of a tensile tester and pulled at a pulling speed of 500 mm / min until the test piece broke. Since the test piece stretched during measurement and the spacing between the benchmark lines widened, the spacing between the benchmark lines was measured with a vernier caliper until the test piece broke. The percentage of elongation was calculated based on the initial spacing between the benchmark lines. An elongation of 130% or more was considered acceptable, and an elongation of 150% or more was considered more preferable.

[0065] [Reaction Force (Stress at 70% Compression)] Each photocurable resin composition was applied in a sheet form using a spacer with a thickness of 2 mm, and the cumulative light dose was 30 kJ / m ２The cured product was cured by irradiating it with ultraviolet light of 1000 kPa to produce a sheet-like cured product. A 2 mm thick, 20 mm square piece was cut from the cured product and used as a sample. Next, using a compression device (Instron: Model No. 8874) in an atmosphere of 25°C, the reaction force (unit: kPa) applied to the sensor was measured when the sample was compressed by 70% of its 2 mm thickness (i.e., when the sample was compressed to a thickness of 1.4 mm) at a test compression rate of 0.1 mm / sec. A reaction force of 300 to 1000 kPa was considered acceptable, and a reaction force within this range was considered to be an excellent sealant.

[0066] [Compression Set] Each photocurable resin composition was applied in a sheet form using a spacer with a thickness of 2 mm, and the cumulative light dose was 30 kJ / m ２ The cured product was cured by irradiating it with ultraviolet light at 100°C for 150 hours, and the sheet-like cured product was produced. A 2 mm thick, 20 mm square specimen was cut from the cured product to serve as a test piece for evaluating compression set. The test piece was compressed at a compression rate of 70% using a jig and spacer as specified in JIS-K-6262:2013, and then placed in a constant temperature bath at 100°C for 150 hours. The test piece was then removed from the constant temperature bath, returned to room temperature, and the jig was removed. After a further 24 hours, the thickness of each test piece was measured, and the correlation between this and the thickness measured for the test piece before heat compression was applied to the following equation to evaluate compression set. A compression set of 60% or less was deemed acceptable, and a compression set within the above range indicates excellent heat sealing properties and therefore heat resistance. Compression set [%] = (measured film thickness before test - measured film thickness after 24 hours) / (measured film thickness before test - spacer thickness) x 100 (%)

[0067]

[0068] As shown in Table 1, Example 1, which contained components (A) to (D), showed good results in hardness, elongation, thick-film curability, reaction force, and compression set after heating at 100°C for 150 hours. On the other hand, Comparative Example 1, which did not contain component (D), could not be measured because the reaction force was too low. Comparative Example 2, which used urethane acrylate instead of component (A), failed in all categories except thick-film curability due to the lack of flexibility of the cured product. Comparative Example 3, which used an acryloyl group-containing acrylic polymer instead of component (A), showed good results in hardness, sealing ability, and heat resistance, but was unsatisfactory in elongation and thick-film curability. Comparative Example 4, which used hollow glass particles instead of component (D), failed to measure the reaction force because the cured product collapsed during the reaction force measurement. From the above, it can be seen that the inclusion of components (A) to (D) allows for the production of cured products with good thick-film curability, flexibility, sealing ability, and heat resistance.

[0069] Although the present invention has been described in detail and with reference to specific embodiments, it will be apparent to those skilled in the art that various changes and modifications can be made thereto without departing from the spirit and scope of the present invention. This application is based on a Japanese patent application (Patent Application No. 2024-058443) filed on April 1, 2024, the contents of which are incorporated herein by reference.

[0070] The photocurable resin composition of the present invention has good thick-film curing properties and is flexible, so that it can buffer external stress on application members. Furthermore, despite its flexibility, it has excellent sealing properties and heat resistance, so that it can be used as a sealant for various parts such as automobile parts and electronic parts, and is therefore very useful.

Claims

1. A photocurable resin composition containing components (A) to (D). Component (A): polyorganosiloxane having one or more vinyl groups per molecule. Component (B): compound having one or more mercapto groups per molecule (excluding component (A)). Component (C): photoinitiator. Component (D): hollow resin particles.

2. The photocurable resin composition according to claim 1, wherein component (B) is a mercapto group-containing polyorganosiloxane.

3. The photocurable resin composition according to claim 1 or 2, wherein the content of the component (D) is 0.1 to 50 parts by mass per 100 parts by mass of the component (A).

4. The photocurable resin composition according to claim 2, wherein component (B) is a mercapto-containing polyorganosiloxane having mercapto groups only on the side chains.

5. The photocurable resin composition according to claim 1 or 2, further comprising a non-reactive silicone oil as component (E).

6. The photocurable resin composition according to claim 1 or 2, further comprising an inorganic filler as component (F).

7. The photocurable resin composition according to claim 1 or 2, wherein component (C) is an acetophenone-based photoinitiator.

8. The photocurable resin composition according to claim 1 or 2, wherein the average particle size of component (D) is 10 to 200 μm.

9. The photocurable resin composition according to claim 1 or 2, wherein the true specific gravity of component (D) is 0.001 to 0.

3.

10. A cured product obtained by curing the photocurable resin composition according to claim 1 or 2.

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