Photocurable resin composition and method for producing seal member

Abstract

Provided is a photocurable resin composition comprising components (A) to (D), wherein the content of each of the components is within a specific range.　Component (A) is a polymer which has a number-average molecular weight of 1,000-100,000 and which has a polyisobutylene skeleton and two or more (meth)acryloyl groups. Component (B) is a monofunctional (meth)acrylate compound which has a C4-18 linear or branched hydrocarbon group and which has one (meth)acryloyl group per molecule. Component (C) is inorganic particles which have an average particle size of 0.1-200 μm and the surfaces of which are modified by an organic group. Component (D) is a photoradical polymerization initiator.

Description

Photocurable resin composition and method for producing sealing material

[0001] The present disclosure relates to a photocurable resin composition and a method for producing a sealing material.

[0002] A fuel cell is a battery that generates electricity by reacting a chemical fuel (usually hydrogen) and an oxidant (usually oxygen) supplied from an external source. Four common types of fuel cells are available: polymer electrolyte fuel cells, phosphoric acid fuel cells, molten carbonate fuel cells, and solid oxide fuel cells. Among these, polymer electrolyte fuel cells have the following advantages: (1) a low operating temperature and (2) lightweight and compact design, making them increasingly popular for automotive and residential applications. A cell, the building block of a polymer electrolyte fuel cell, is constructed with a membrane electrode assembly (MEA) sandwiched between separators. The MEA has a polymer electrolyte membrane sandwiched between a fuel electrode (anode) catalyst layer and an air electrode (cathode) catalyst layer. Each electrode catalyst layer has a porous gas diffusion layer on the side opposite the polymer electrolyte membrane. By stacking these cells into a cell stack, high voltage and power can be generated. The separators are formed with flow paths for gases (fuel gas on the anode side, oxidizing gas on the cathode side) that pass between the cells and through the cells to be supplied to each electrode, as well as flow paths for a coolant (e.g., a mixed solution of water and ethylene glycol) that passes between the cells for cooling during power generation. In this case, if the sealing properties of each flow path are insufficient, problems such as mixing of the gases supplied to the electrodes and a decrease in power generation efficiency may occur. Therefore, to prevent leakage of the gases and coolant, sealing materials are used inside the cells (e.g., around the MEA) and between adjacent separators.

[0003] As the sealing material, a heat-curable resin composition utilizing a hydrosilylation reaction (Patent Document 1) and ethylene-propylene-diene rubber (EPDM) (Patent Document 2) have been proposed, but a heating process is required for curing, which has the drawback of requiring a long process time. Therefore, in recent years, sealing materials using photocurable resin compositions that can shorten the time of the curing process have been studied, and a photocurable resin composition containing an acrylic polymer having a (meth)acryloyl group (Patent Document 3) and a photocurable resin composition containing a polyisobutylene resin having a (meth)acryloyl group (Patent Document 4) have been proposed.

[0004] International Publication No. 2017 / 154777 Japanese Patent Application Laid-Open No. 2017-188417 Japanese Patent Application Laid-Open No. 2022-057075 International Publication No. 2023 / 090088

[0005] In order for a fuel cell sealing material to maintain its sealing performance over the long term, it must have excellent sag resistance (i.e., not lose its elasticity over the long term). Compression set testing is a known method for evaluating sag resistance. The smaller the compression set, the better the sag resistance. As described above, fuel cell sealing materials are exposed to fuel gas, oxidizing gas, and coolant (e.g., a mixed solution of water and ethylene glycol) at high temperatures. Furthermore, when hydrogen is used as the fuel gas and oxygen as the oxidizing gas, they are exposed to water generated during power generation. Therefore, fuel cell sealing materials must have excellent heat resistance, water resistance, and coolant resistance. Furthermore, fuel cell sealing materials must maintain sufficient repulsive force to ensure sealing performance over a wide range of temperatures and compression ratios. Regarding temperature, the sealing material must maintain its rubber elasticity and have sufficient repulsive force not only during operation (around 100°C) but also at low temperatures (e.g., -30°C) when considering the use of fuel cells in cold regions. Regarding the compression ratio, fuel cells are used in a cell stack in which cells are stacked, so the sealing material used between separators varies in compression ratio due to the influence of variations in the thickness of the components. Therefore, it is necessary for the sealing material to have sufficient repulsive force even at a low compression ratio (e.g., 20%). It is also required that the sealing material not crack even at a high compression ratio (e.g., 50%). From the above, in order to be used as a sealing material for fuel cells, it is necessary for the material to have small compression set and excellent long-term durability, as well as sufficient repulsive force at low temperatures and low compression ratios (good sealing properties), and not crack even at a high compression ratio. However, a photocurable resin composition that can produce a cured product that simultaneously satisfies all of these requirements has not been identified.

[0006] Patent Document 3 reports a photocurable resin composition that has a small compression set at -30°C and produces a cured product that does not crack even when compressed to 50%, but no sealing test at low compression ratios has been conducted, so its performance is unknown. Furthermore, fuel cell sealing materials require water resistance at high temperatures and resistance to coolants (e.g., mixed solutions of water and ethylene glycol), but the acrylic polymer claimed has poor hydrolysis resistance, so the durability of the resulting sealing material may be insufficient.

[0007] Patent Document 4 reports a photocurable resin composition that has good sealing properties at a compression ratio of 20% (the temperature is unknown, but it is assumed to be above room temperature since the composition was submerged in water) and that produces a cured product that does not crack even when compressed to 50% at 95°C, but does not evaluate sealing properties at low temperatures (e.g., evaluation of reaction force at low temperatures).The acrylate monomer having an alicyclic hydrocarbon group with 5 to 25 carbon atoms, as claimed, has a high Tg, so the rubber elasticity of the resulting sealant at low temperatures may be insufficient.

[0008] The present disclosure has been made in consideration of the above circumstances. An object of the present disclosure is to provide a photocurable resin composition that produces a cured product with small compression set at high temperatures, sufficient compression reaction force at low temperatures, excellent pressure-resistant sealing properties at low compression ratios, and excellent crack suppression properties at high compression ratios. Another object of the present disclosure is to provide a method for producing a sealing material using the photocurable resin composition.

[0009] Specific means for solving the above problems include the following aspects. <1> The composition comprises the following components (A) to (D): component (A): a polymer having a number average molecular weight of 1,000 to 100,000 and having a polyisobutylene skeleton and two or more (meth)acryloyl groups; component (B): a monofunctional (meth)acrylate compound having a linear or branched hydrocarbon group with 4 to 18 carbon atoms and having one (meth)acryloyl group per molecule; component (C): inorganic particles having an average particle size of 0.1 μm or more and 200 μm or less and having a surface modified with an organic group; component (D): a photoradical polymerization initiator; and optionally comprising the following components (E) and (F): component (E): a photoradical polymerizable polymer other than component (A); component (F): a photoradical polymerizable monomer other than component (B). A photocurable resin composition, in which the total content of the component (A) and the component (E) is 30 parts by mass to 90 parts by mass, the content of the component (B) is 10 parts by mass to 70 parts by mass, the content of the component (C) is 5 parts by mass to 120 parts by mass, the content of the component (D) is 0.1 parts by mass to 6 parts by mass, and the content of the component (F) is 0 parts by mass to 13 parts by mass. <2> The photocurable resin composition according to <1>, in which the content of the component (A) is 20 parts by mass to 90 parts by mass and the content of the component (E) is 0 parts by mass to 30 parts by mass, relative to 100 parts by mass of the total content of the component (A), component (B), component (E), and component (F), which are the photoradical polymerizable components. <3> The photocurable resin composition according to <1> or <2>, wherein the component (A) contains a polyisobutylene resin having a number average molecular weight of 1,000 to 100,000 and having (meth)acryloyl groups at both ends. <4> The photocurable resin composition according to any one of <1> to <3>, wherein the component (B) contains a monofunctional (meth)acrylate compound having a linear or branched hydrocarbon group with 4 to 10 carbon atoms and having one (meth)acryloyl group per molecule.<5> The component (D) comprises the following components (D-1) and (D-2): component (D-1): a photoradical polymerization initiator having a molar absorption coefficient of 10 L / (mol cm) or more at at least one wavelength (I) of 395 nm to 435 nm; and component (D-2): a photoradical polymerization initiator having a molar absorption coefficient of less than 10 L / (mol cm) at any wavelength of 395 nm to 435 nm and a molar absorption coefficient of 10 L / (mol cm) or more at at least one wavelength (II) of 280 nm to 385 nm. The photocurable resin composition according to any one of <1> to <4>, wherein the content of the component (D-1) is 0.01 parts by mass to 0.9 parts by mass and the content of the component (D-2) is 0.1 parts by mass to 5 parts by mass, relative to 100 parts by mass of the total content of the photoradical polymerizable components (A), (B), (E), and (F). <6> The photocurable resin composition according to <5>, wherein the component (D-1) includes at least one compound selected from the group consisting of an acylphosphine oxide compound, an α-aminoalkylphenone compound having a 4-morpholinophenyl group, an oxime ester compound having a 4-phenylthiophenyl group, and a thioxanthone compound. <7> The photocurable resin composition according to <5> or <6>, wherein the component (D-2) includes at least one compound selected from the group consisting of α-hydroxyalkylphenone compounds, α-aminoalkylphenone compounds (excluding those having a 4-morpholinophenyl group), benzil ketal compounds, oxime ester compounds (excluding those having a 4-phenylthiophenyl group), and benzophenone compounds. <8> The photocurable resin composition according to <1>, which is a photocurable resin composition for use in a sealing material. <9> The photocurable resin composition according to <1>, which is a photocurable resin composition for use in a sealing material for fuel cells. <10> A method for producing a sealing material, comprising the steps of irradiating the photocurable resin composition according to any one of <5> to <7> with light (a) including the wavelength (I) and irradiating with light (b) including the wavelength (II), in this order, wherein the irradiation energy of the light (a) in the wavelength range of 200 nm to 385 nm is 0.2 times or less the irradiation energy of the light (a) in the wavelength range of 395 nm to 435 nm.<11> The illuminance of the light (a) is 10 mW / cm. ２ ~5,000mW / cm ２ , irradiation dose 50 mJ / cm ２ ~5,000mJ / cm ２ and the illuminance of the light (b) is 10 mW / cm ２ ~5,000mW / cm ２ , irradiation dose 50 mJ / cm ２ ~10,000mJ / cm ２ <12> The method for producing a sealing material according to <10> or <11>, wherein the produced sealing material is for a fuel cell.

[0010] According to the present disclosure, there is provided a photocurable resin composition which produces a cured product having small compression set at high temperatures, sufficient compression reaction force at low temperatures, excellent pressure-resistant sealing properties at low compression ratios, and excellent crack suppression properties at high compression ratios. The present disclosure also provides a method for producing a sealing material using the photocurable resin composition.

[0011] 1 is a schematic diagram of an evaluation sample of a photocurable resin composition. FIG. 2 is a schematic cross-sectional view of a pressure-resistant seal test device.

[0012] In the present disclosure, a numerical range expressed using "to" means a range that includes the numerical values ​​written before and after "to" as the lower and upper limits. In the present disclosure, when multiple substances corresponding to each component are present in the composition, the amount of each component in the composition means the total amount of the multiple substances present in the composition, unless otherwise specified. In the numerical ranges described in stages in the present disclosure, the upper or lower limit described in one numerical range may be replaced with the upper or lower limit of another numerical range described in stages. In the numerical ranges described in the present disclosure, the upper or lower limit of that numerical range may be replaced with a value shown in the examples. In the present disclosure, combinations of preferred embodiments are more preferred embodiments. In the description of groups (atomic groups) in the present disclosure, a description that does not specify whether they are substituted or unsubstituted includes both unsubstituted and substituted groups. In the present disclosure, "(meth)acrylate" means at least one of acrylate and methacrylate. In the present disclosure, "urethane (meth)acrylate" means a (meth)acrylate polymer having a urethane skeleton.

[0013] The terms "number average molecular weight" and "weight average molecular weight" refer to the polystyrene equivalent values ​​of the molecular weight measured by gel permeation chromatography (hereinafter also referred to as "GPC"). Gel permeation chromatography (GPC) measurement is performed under the measurement conditions described below, and the polystyrene equivalent number average molecular weight (Mn) and weight average molecular weight (Mw) can be obtained. <Measurement conditions> Apparatus: HLC-8320 manufactured by Tosoh Corporation Column: TSKgel-SuperMultipore HZ-M (4.6 mm ID x 15 cm) x 3 (for low molecular weight, exclusion limit molecular weight 2 million) manufactured by Tosoh Corporation Column temperature: 40°C Eluent: tetrahydrofuran (0.35 ml / min) Detector: differential refractometer (RI) Sample concentration: 0.1%

[0014] The "molar absorption coefficient" refers to the value of ε shown in the following formula (A). ε is determined by the Lambert-Beer equation for an acetonitrile solution containing a photoradical polymerization initiator. In formula (A), I represents the intensity of transmitted light, Io represents the intensity of transmitted light through pure acetonitrile, c represents the molar concentration (M), d represents the thickness of the solution layer (cm), and log(Io / I) represents the absorbance. Formula (A): ε = log(Io / I) / (c x d) The molar absorption coefficient of a photoradical polymerization initiator can be measured, for example, according to the following method. Using acetonitrile as the solvent, the photoradical polymerization agent is dissolved to a concentration of 1 g / L, and the absorbance is measured at room temperature using a quartz cell with a UV-visible spectrophotometer, and calculated using the Lambert-Beer law. For wavelengths where the absorbance exceeds 2.0, the photoradical polymerization initiator is dissolved at a concentration where the absorbance falls within the range of 0.1 to 2.0, and the absorbance is measured at room temperature using a quartz cell with an ultraviolet-visible spectrophotometer, and the absorbance is calculated using the Beer-Lambert law.

[0015] Hereinafter, "irradiating with light (a) containing at least one wavelength (I) in the range of 395 nm to 435 nm" will also be referred to as "light irradiation (a)." Hereinafter, "irradiating with light (b) containing at least one wavelength (II) in the range of 200 nm to 385 nm" will also be referred to as "light irradiation (b)."

[0016] (Photocurable Resin Composition) The photocurable resin composition according to the present disclosure comprises the following components (A) to (D): component (A): a polymer having a number average molecular weight of 1,000 to 100,000 and having a polyisobutylene skeleton and two or more (meth)acryloyl groups; component (B): a monofunctional (meth)acrylate compound having a linear or branched hydrocarbon group with 4 to 18 carbon atoms and having one (meth)acryloyl group per molecule; component (C): inorganic particles having an average particle size of 0.1 μm or more and 200 μm or less and having a surface modified with an organic group; component (D): a photoradical polymerization initiator; and optional components (E) and (F): the following components (E): a photoradical polymerizable polymer other than component (A); and component (F): a photoradical polymerizable monomer other than component (B). With respect to 100 parts by mass of the total content of the photoradical polymerizable components (A), (B), (E), and (F), the total content of the components (A) and (E) is 30 to 90 parts by mass, the content of the component (B) is 10 to 70 parts by mass, the content of the component (C) is 5 to 120 parts by mass, the content of the component (D) is 0.1 to 6 parts by mass, and the content of the component (F) is 0 to 13 parts by mass.

[0017] As mentioned above, conventional photocurable resin compositions have the problem that the resulting cured product is poor in at least one of compression set at high temperatures, compression reaction force at low temperatures, pressure-resistant sealing properties at low compression ratios, and crack suppression properties at high compression ratios. The present inventors have discovered that by including components (A) to (D) as a photocurable resin composition and adjusting the contents of components (A) to (F) within the above-mentioned specific ranges, the resulting cured product has small compression set at high temperatures, sufficient compression reaction force at low temperatures, excellent pressure-resistant sealing properties at low compression ratios, and excellent crack suppression properties at high compression ratios. The estimated mechanism is shown below.

[0018] By including the above amount of component (A), a crosslinked structure is formed, improving the reaction force at low compression, improving sealing performance, and improving sag resistance and reducing compression set. If the blending amount is too small, the blending effect becomes insufficient, while if the blending amount is too large, compression crack resistance deteriorates, resulting in cracks occurring at high compression. Furthermore, if the molecular weight of component (A) exceeds 100,000, the crosslinked structure becomes less, resulting in insufficient reaction force at low compression. Furthermore, component (A) has a polyisobutylene skeleton, which provides excellent heat resistance and hydrolysis resistance, and its low glass transition temperature allows the cured product to exhibit rubber elasticity even at low temperatures and sufficient reaction force. By including the above amount of component (B), the glass transition temperature of the sealing material can be lowered without impairing the glass transition temperature of component (A), allowing the sealing material to exhibit rubber elasticity even at low temperatures and sufficient reaction force. Furthermore, the presence of an alkyl group having 4 or more carbon atoms allows miscibility with component (A), and the resulting cured product has excellent hydrolysis resistance. By including the above amount of component (C), the reaction force at low compression ratios is improved, improving sealing performance. If the content is too low, the compounding effect will be insufficient, while if the content is too high, the settling resistance will deteriorate, the compression set will increase, and the compression cracking resistance will deteriorate, causing cracks to occur under high compression. Furthermore, if the average particle size is less than 0.1 μm, the thixotropy of the photocurable resin composition will increase, the fluidity will deteriorate, and handling will become difficult. Furthermore, since the surface is modified with an organic group, the dispersibility in the (A) and (B) components will be improved. The (D) component is necessary for curing the photocurable resin composition by light irradiation.

[0019] The photocurable resin composition according to the present disclosure will be described in detail below. The photocurable resin composition according to the present disclosure can be suitably used as a photocurable resin composition for a sealant, and more suitably used as a photocurable resin composition for a sealant of a fuel cell.

[0020] <Component (A): Polymer Having a Number Average Molecular Weight of 1,000 to 100,000 and Having a Polyisobutylene Skeleton and Two or More (Meth)acryloyl Groups> The photocurable resin composition according to the present disclosure includes component (A), in which the total content of component (A) and component (E) is 30 parts by mass to 90 parts by mass per 100 parts by mass of the total content of component (A), component (B), component (E), and component (F), which are photoradical polymerizable components.

[0021] The polyisobutylene skeleton refers to the following structure: Here, n is 2 or greater. Furthermore, the component (A) may have only one of the following structures, or two or more of them.

[0022]

[0023] Although isobutylene is primarily used as the monomer constituting component (A), other monomers may be copolymerized within a range that does not impair the effects of the present disclosure. Examples of other monomers include olefins having 4 to 12 carbon atoms, vinyl ethers, aromatic vinyl compounds, vinyl silanes, and allyl silanes. Specific examples include isoprene, amylene, 1,3-butadiene, 1-butene, 2-butene, 2-methyl-1-butene, 3-methyl-1-butene, pentene, 4-methyl-1-pentene, hexene, vinylcyclohexene, α-pinene, β-pinene, limonene, styrene, indene, α-methylstyrene, methoxystyrene, methylstyrene (either o-, m-, or p-isomer), trimethylstyrene, chlorostyrene, dichlorostyrene, methyl vinyl ether, ethyl vinyl ether, isobutyl vinyl ether, vinyltrichlorosilane, and vinylmethyl Examples of the silane include dichlorosilane, vinyldimethylchlorosilane, vinyldimethylmethoxysilane, vinyltrimethylsilane, divinyldichlorosilane, divinyldimethoxysilane, divinyldimethylsilane, 1,3-divinyl-1,1,3,3-tetramethyldisiloxane, trivinylmethylsilane, tetravinylsilane, allyltrichlorosilane, allylmethyldichlorosilane, allyldimethylchlorosilane, allyldimethylmethoxysilane, allyltrimethylsilane, diallyldichlorosilane, diallyldimethoxysilane, and diallyldimethylsilane.

[0024] Among these, isoprene, amylene, 1,3-butadiene, 1-butene, α-pinene, β-pinene, limonene, styrene, indene, α-methylstyrene, methylstyrene (including o-, m- and p-isomers), methyl vinyl ether, ethyl vinyl ether and isobutyl vinyl ether are preferred from the viewpoint of copolymerizability.

[0025] When using other monomers copolymerizable with isobutylene, from the viewpoint of maintaining the effects of the present disclosure, the content of the other monomers in component (A) may be preferably 50% by mass or less, more preferably 30% by mass or less, and even more preferably 10% by mass or less.

[0026] The number average molecular weight of component (A) is 1,000 to 100,000, and from the viewpoints of compression set at high temperatures, compression reaction force at low temperatures, pressure-resistant sealing properties at low compression ratios, crack suppression properties at high compression ratios, and ease of handling, it is preferably 2,000 to 100,000, more preferably 3,000 to 80,000, and even more preferably 5,000 to 50,000.

[0027] There are no particular restrictions on the molecular weight distribution of component (A), but from the viewpoints of compression set at high temperatures and ease of handling, the value expressed as (weight average molecular weight Mw) / (number average molecular weight Mn) is preferably in the range of 1.0 to 1.8, more preferably in the range of 1.0 to 1.5, and even more preferably in the range of 1.0 to 1.3.

[0028] The number of (meth)acryloyl groups in component (A) is 2 or more, and from the viewpoints of compression set at high temperatures, compression reaction force at low temperatures, pressure-resistant sealing properties at low compression ratios, and crack suppression properties at high compression ratios, the number is preferably 2 to 10, more preferably 2 to 5, and particularly preferably 2. Furthermore, from the viewpoint of reactivity during photocuring, the (meth)acryloyl group is preferably an acryloyl group.

[0029] The manner in which the (meth)acryloyl group in component (A) is bonded to the main chain of the polymer is not particularly limited, and examples thereof include an ester bond, an ether bond, an amide bond, a urethane bond, a thioether bond, a carbonate bond, a urea bond, a bond consisting of a divalent or higher hydrocarbon group that does not contain a hetero atom, etc. Among these, from the viewpoints of ease of synthesis and availability, an ester bond, an ether bond, an amide bond, or a urethane bond is preferred.

[0030] There are no particular restrictions on the bonding position of the (meth)acryloyl group in component (A), and the (meth)acryloyl group may be bonded to any position in the main chain. However, from the viewpoints of compression set at high temperatures, compression reaction force at low temperatures, pressure-resistant sealing properties at low compression ratios, and crack suppression properties at high compression ratios, it is preferable for the (meth)acryloyl group to be bonded to at least one or more terminals of the main chain, and it is more preferable for the (meth)acryloyl group to be bonded to both terminals of the main chain.

[0031] There are no particular restrictions on the structure of the (meth)acryloyl group in component (A), but from the standpoints of availability of raw materials and ease of production, a structure represented by the following formula (A) is preferred.

[0032]

[0033] In formula (A), R １Ａ represents a hydrogen atom or a methyl group, R ２Ａ represents an alkylene group having 2 to 6 carbon atoms, and R ３Ａ each independently represents a monovalent hydrocarbon group or alkoxy group having 1 to 20 carbon atoms, nA represents an integer of 0 to 4, and * represents the bonding position to another structure.

[0034] R in formula (A) ２Ａ Specific examples of the group include, for example, —CH ２ CH ２ -, -CH ２ CH ２ CH ２ -, -CH ２ CH ２ CH ２ CH ２ -, -CH ２ CH ２ CH ２ CH ２ CH ２ -, -CH ２ CH ２ CH ２ CH ２ CH ２ CH ２ Among these, -CH ２ CH ２ -, -CH ２ CH ２ CH ２ -, -CH ２ CH ２ CH ２ CH ２ - is preferred from the viewpoint of availability and reactivity of raw materials.

[0035] R in formula (A) ３ＡSpecific examples of the monovalent hydrocarbon group and alkoxy group having 1 to 20 carbon atoms in the formula (I) include a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, a sec-butyl group, a tert-butyl group, a pentyl group, a hexyl group, a 2-ethylhexyl group, a nonyl group, a decanyl group, a methoxy group, an ethoxy group, a propoxy group, an isopropoxy group, and a butoxy group.

[0036] Among these, from the viewpoint of reactivity, nA is 0, or nA is 1 or 2 and R ３Ａ is preferably a methyl group, and from the viewpoint of availability of raw materials, nA is more preferably 0.

[0037] The method for producing component (A) is not particularly limited, but reference can be made to production methods described in International Publication No. 2013 / 047314, JP-A No. 2013-216782, International Publication No. 2017 / 099043, etc. Specifically, the method comprises reacting TiCl 3 in the presence of a monofunctional and / or polyfunctional polymerization initiator. ４ and an electron donor component such as a nitrogen-containing compound, to produce a polyisobutylene polymer skeleton by living cationic polymerization of isobutylene, and then functionalizing the polymer terminals with a phenoxyalkyl (meth)acrylate compound or the like. These reactions are carried out at low temperatures, such as −70° C. These methods are preferred because the raw materials are easily available, productivity is high, and they can be used industrially.

[0038] Component (A) may also be a commercially available product, such as "KANEKA EPION EP400V" manufactured by Kaneka Corporation, but is not limited thereto.

[0039] The component (A) may be used alone or in any combination of two or more. From the viewpoints of compression set at high temperatures, compression reaction force at low temperatures, pressure-resistant sealing properties at low compression ratios, and crack suppression properties at high compression ratios, the content of the component (A) is preferably 20 parts by mass to 90 parts by mass, more preferably 40 parts by mass to 85 parts by mass, and particularly preferably 50 parts by mass to 80 parts by mass, relative to 100 parts by mass of the total content of the photoradical polymerizable components (A), (B), (E), and (F). Furthermore, the total content of the (A) component and the (E) component is 30 parts by mass to 90 parts by mass relative to 100 parts by mass of the total content of the (A), (B), (E) component, and (F) components, which are photoradical polymerizable components. From the viewpoints of compression set at high temperatures, compression reaction force at low temperatures, pressure-resistant sealing properties at low compression ratios, and crack suppression properties at high compression ratios, the total content of the (A) component and the (E) component is preferably 35 parts by mass to 90 parts by mass, more preferably 40 parts by mass to 85 parts by mass, and particularly preferably 50 parts by mass to 80 parts by mass.

[0040] <Component (B): Monofunctional (meth)acrylate Compound Having a Linear or Branched Hydrocarbon Group with 4 to 18 Carbon Atoms and One (meth)acryloyl Group per Molecule> The photocurable resin composition according to the present disclosure includes component (B), and the content of component (B) is 10 parts by mass to 70 parts by mass relative to 100 parts by mass of the total content of components (A), (B), (E), and (F), which are photoradical polymerizable components.

[0041] From the viewpoint of reactivity during photocuring, component (B) is preferably an acrylate compound. Also, from the viewpoints of compression set at high temperatures and hydrolysis resistance, component (B) is preferably an alkyl(meth)acrylate compound. Also, the molecular weight of component (B) is preferably less than 1,000.

[0042] The number of carbon atoms (also referred to as the "number of carbon atoms") in the hydrocarbon group in component (B) is 4 to 18, and from the viewpoint of compression reaction force at low temperatures, it is preferably 4 to 12, more preferably 4 to 10, and particularly preferably 6 to 9. Furthermore, from the viewpoint of compression set at high temperatures, the hydrocarbon group in component (B) is preferably an alkyl group.

[0043] Examples of the linear or branched alkyl group having 4 to 18 carbon atoms include a butyl group, an isobutyl group, an s-butyl group, a t-butyl group, a pentyl group, an isopentyl group, a t-pentyl group, a neopentyl group, a hexyl group, an isohexyl group, a heptyl group, an octyl group, an isooctyl group, a 2-ethylhexyl group, a nonyl group, an isononyl group, a decyl group, an isodecyl group, an undecyl group, a dodecyl group (a lauryl group), a stearyl group, and an isostearyl group.

[0044] Examples of the component (B) include alkyl(meth)acrylates represented by the following formula (B-1) and (meth)acrylates of ethylene oxide adducts of alkyl alcohols represented by the following formula (B-2).

[0045]

[0046] In formulas (B-1) and (B-2), R １Ｂ represents a hydrogen atom or a methyl group, R ２Ｂ represents a linear or branched alkyl group having 4 to 18 carbon atoms; nB represents an integer of 1 to 4;

[0047] The content of the component (B) is 10 to 70 parts by mass relative to 100 parts by mass of the total content of the photoradical polymerizable components (A), (B), (E), and (F), and from the viewpoints of compression set at high temperatures, compression reaction force at low temperatures, pressure-resistant sealability at low compression ratios, and crack suppression at high compression ratios, the content of the component (B) is preferably 15 to 65 parts by mass, and more preferably 20 to 60 parts by mass.

[0048] <Component (C): Inorganic Particles Having an Average Particle Diameter of 0.1 μm or More and 200 μm or Less and Surface-Modified with an Organic Group> The photocurable resin composition according to the present disclosure includes component (C), and the content of component (C) is 5 parts by mass to 120 parts by mass per 100 parts by mass of the total content of components (A), (B), (E), and (F), which are photoradical polymerizable components.

[0049] Examples of inorganic particles in component (C) include silica, alumina, titania, zirconia, germania, cerium oxide, zinc oxide, boron nitride, silicon carbide, talc, smectite, mica, bentonite, sepiolite, and kaolin. Among these, silica, alumina, and titania are preferred, and silica is more preferred, from the viewpoints of compression set at high temperatures, compression reaction force at low temperatures, pressure-resistant sealing properties at low compression ratios, and crack suppression properties at high compression ratios. The shape of the inorganic particles is not particularly limited, and examples include spherical, plate-like, needle-like, fibrous, and irregular shapes. Among these, spherical shapes are preferred from the viewpoint of ease of handling of the resulting photocurable resin composition.

[0050] The average particle size of the inorganic particles in component (C) is 0.1 μm or more and 200 μm or less, and from the viewpoints of compression set at high temperatures, compression reaction force at low temperatures, pressure-resistant sealing properties at low compression ratios, and crack suppression properties at high compression ratios, it is preferably 0.1 μm or more and 100 μm or less, more preferably 0.1 μm or more and 10 μm or less, even more preferably 0.3 μm or more and 5 μm or less, and particularly preferably 0.5 μm or more and 2 μm or less. Note that the average particle size of the inorganic particles in component (C) in the present disclosure means the volume average particle size measured by a laser diffraction particle size distribution measurement method.

[0051] The inorganic particles in component (C) are inorganic particles whose surfaces are modified with an organic group, and from the viewpoint of dispersibility in components (A) and (B), the organic group is preferably a hydrophobic group such as an alkyl group, or a group having a radical polymerizable group.Furthermore, from the viewpoint of compression reaction force at low temperatures and pressure-resistant sealing property at low compression ratios, the organic group is more preferably a group having a radical polymerizable group, and particularly preferably a group having a (meth)acryloyl group.The surface treatment method of the inorganic particles is not particularly limited, but examples thereof include a method of contacting inorganic particles with a coupling agent such as a silane coupling agent, a method of contacting inorganic particles with an organosilicon compound such as dimethyldichlorosilane, hexamethyldisilazane, or silicone oil, and reacting the hydroxyl groups remaining on the surface of the inorganic particles with the organosilicon compound, and the like.

[0052] The component (C) may be used alone or in any combination of two or more. The content of the component (C) is 5 to 120 parts by mass relative to 100 parts by mass of the total content of the photoradical polymerizable components (A), (B), (E), and (F). From the viewpoints of compression set at high temperatures, compression reaction force at low temperatures, pressure-resistant sealability at low compression ratios, and crack suppression at high compression ratios, the content is preferably 5 to 100 parts by mass, more preferably 5 to 70 parts by mass, and particularly preferably 10 to 60 parts by mass.

[0053] <Component (D): Photoradical Polymerization Initiator> The photocurable resin composition according to the present disclosure includes component (D), and the content of component (D) is 0.1 parts by mass to 6 parts by mass relative to 100 parts by mass of the total content of components (A), (B), (E), and (F), which are photoradical polymerizable components. Component (D) is a compound that generates radicals upon irradiation with light and initiates polymerization of components (A) and (B), which are compounds having radical polymerizable groups, component (C), which has a radical polymerizable group on its surface, and components (E) and (F), which will be described later.

[0054] Specific examples of component (D) include benzyl dimethyl ketal, benzil, benzoin, benzoin ethyl ether, benzoin isopropyl ether, benzoin isobutyl ether, 1-hydroxycyclohexyl phenyl ketone, 2-hydroxy-2-methyl-1-phenylpropan-1-one, 2,2-dimethoxy-1,2-diphenylethan-1-one, 1-[4-(2-hydroxyethoxy)phenyl]-2-hydroxy-2-methyl-1-propan-1-one, oligo[2-hydroxy-2-methyl-1-[4-1-(methylvinyl)phenyl]propanone, 2-hydroxy-1-[4-[4- aromatic ketone compounds such as (2-hydroxy-2-methylpropionyl)benzyl]phenyl]-2-methylpropan-1-one, 2-methyl-1-[4-(methylthio)]phenyl]-2-morpholinopropan-1-one, 2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)butan-1-one, 2-dimethylamino-2-(4-methylbenzyl)-1-(4-morpholin-4-yl-phenyl)-butan-1-one, ADEKA OPTOMER N-1414 (manufactured by ADEKA Corporation), phenylglyoxylic acid methyl ester, ethyl anthraquinone, and phenanthrenequinone; Benzophenone compounds such as benzophenone, 2-methylbenzophenone, 3-methylbenzophenone, 4-methylbenzophenone, 2,4,6-trimethylbenzophenone, 4-phenylbenzophenone, 4-(methylphenylthio)phenylphenylmethane, methyl-2-benzophenone, 1-[4-(4-benzoylphenylsulfanyl)phenyl]-2-methyl-2-(4-methylphenylsulfonyl)propan-1-one, 4,4'-bis(dimethylamino)benzophenone, 4,4'-bis(diethylamino)benzophenone, N,N'-tetramethyl-4,4'-diaminobenzophenone, N,N'-tetraethyl-4,4'-diaminobenzophenone and 4-methoxy-4'-dimethylaminobenzophenone;Acylphosphine oxide compounds such as bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide, 2,4,6-trimethylbenzoyldiphenylphosphine oxide, ethyl(2,4,6-trimethylbenzoyl)phenylphosphonate, and bis(2,6-dimethoxybenzoyl)-2,4,4-trimethylpentylphosphine oxide; thioxanthone compounds such as thioxanthone, 2-chlorothioxanthone, 2,4-diethylthioxanthone, isopropylthioxanthone, 1-chloro-4-propylthioxanthone, 3-[3,4-dimethyl-9-oxo-9H-thioxanthone-2-yl]oxy]-2-hydroxypropyl-N,N,N-trimethylammonium chloride, and fluorothioxanthone; acridone compounds such as acridone and 10-butyl-2-chloroacridone; Oxime ester compounds such as 1,2-octanedione 1-[4-(phenylthio)-2-(O-benzoyloxime)] and ethanone 1-[9-ethyl-6-(2-methylbenzoyl)-9H-carbazol-3-yl]-1-(O-acetyloxime); 2,4,5-triarylimidazole dimers such as 2-(o-chlorophenyl)-4,5-diphenylimidazole dimer, 2-(o-chlorophenyl)-4,5-di(m-methoxyphenyl)imidazole dimer, 2-(o-fluorophenyl)-4,5-phenylimidazole dimer, 2-(o-methoxyphenyl)-4,5-diphenylimidazole dimer, 2-(p-methoxyphenyl)-4,5-diphenylimidazole dimer, 2,4-di(p-methoxyphenyl)-5-phenylimidazole dimer and 2-(2,4-dimethoxyphenyl)-4,5-diphenylimidazole dimer; and acridine derivatives such as 9-phenylacridine and 1,7-bis(9,9'-acridinyl)heptane.

[0055] From the viewpoints of compression set at high temperatures, compression reaction force at low temperatures, and reactivity during photocuring, the component (D) preferably contains the following components (D-1) and (D-2): Component (D-1): a photoradical polymerization initiator having a molar absorption coefficient of 10 L / (mol cm) or more at at least one wavelength (I) of 395 nm to 435 nm; Component (D-2): a photoradical polymerization initiator having a molar absorption coefficient of less than 10 L / (mol cm) at any wavelength of 395 nm to 435 nm, and a molar absorption coefficient of 10 L / (mol cm) or more at at least one wavelength (II) of 280 nm to 385 nm, particularly 280 nm to 380 nm.

[0056] From the viewpoints of compression set at high temperatures and compression reaction force at low temperatures, the component (D) preferably contains a component (D-1). Examples of the component (D-1) include acylphosphine oxide compounds, α-aminoalkylphenone compounds that satisfy the requirements for the component (D-1), oxime ester compounds that satisfy the requirements for the component (D-1), and thioxanthone compounds.

[0057] "Acylphosphine oxide compounds" refer to compounds having an acylphosphine oxide structure. "α-aminoalkylphenone compounds" refer to compounds having an α-aminoalkylphenone structure. "Oxime ester compounds" refer to compounds having an oxime ester structure. "Thioxanthone compounds" refer to compounds having a thioxanthone structure.

[0058] Examples of acylphosphine oxide compounds include 2,4,6-trimethylbenzoyl-diphenyl-phosphine oxide (Omnirad TPO H, manufactured by IGM Resins) and bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide (Omnirad 380 (819), manufactured by IGM Resins). Examples of α-aminoalkylphenone compounds that satisfy the conditions for component (D-1) include 2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)butan-1-one (Omnirad 369, manufactured by IGM Resins) and 2-dimethylamino-2-(4-methylbenzyl)-1-(4-morpholin-4-yl-phenyl)butan-1-one (IRGACURE 379 and 379EG, manufactured by BASF). Examples of oxime ester compounds that satisfy the conditions of component (D-1) include 1-[4-(phenylthio)phenyl]-1,2-octanedione-2-(O-benzoyloxime) (IRGACURE OXE01, manufactured by BASF), etc. Examples of thioxanthone compounds include thioxanthone, 2-chlorothioxanthone, 2,4-diethylthioxanthone, isopropylthioxanthone, 1-chloro-4-propylthioxanthone, 3-[3,4-dimethyl-9-oxo-9H-thioxanthone-2-yl]oxy]-2-hydroxypropyl-N,N,N-trimethylammonium chloride, and fluorothioxanthone.

[0059] Among these, from the viewpoint of reactivity during photocuring, it is preferable that component (D-1) contains at least one compound selected from the group consisting of an acylphosphine oxide compound, an α-aminoalkylphenone compound having a 4-morpholinophenyl group, an oxime ester compound having a 4-phenylthiophenyl group, and a thioxanthone compound. This allows for efficient partial curing of the photocurable resin composition in the irradiation step (a) using light irradiation, which will be described later. Component (D-1) may be at least one compound selected from the group consisting of an acylphosphine oxide compound, an α-aminoalkylphenone compound that satisfies the requirements for component (D-1), an oxime ester compound, and a thioxanthone compound that satisfies the requirements for component (D-1). From the viewpoint of further reducing the compression set at high temperatures of the resulting photocurable resin composition, it is more preferable that component (D-1) contains an acylphosphine oxide compound, and even more preferably an acylphosphine oxide compound.

[0060] The component (D-1) may be used alone or in any combination of two or more. From the viewpoints of compression set at high temperatures, compression reaction force at low temperatures, and reactivity during photocuring, the content of the component (D-1) is preferably 0.01 to 0.9 parts by mass, more preferably 0.05 to 0.7 parts by mass, even more preferably 0.08 to 0.5 parts by mass, and particularly preferably 0.1 to 0.4 parts by mass, relative to 100 parts by mass of the total content of the photoradical polymerizable components (A), (B), (E), and (F).

[0061] From the viewpoint of reactivity during photocuring, the component (D) preferably contains the component (D-2). Examples of the component (D-2) include an α-hydroxyalkylphenone compound, an α-aminoalkylphenone compound that satisfies the requirements for the component (D-2), an oxime ester compound that satisfies the requirements for the component (D-2), a benzyl ketal compound, and a benzophenone compound.

[0062] "α-Hydroxyalkylphenone compounds" refer to compounds having an α-hydroxyalkylphenone structure. "Benzil ketal compounds" refer to compounds having a benzil ketal structure. "Benzophenone compounds" refer to compounds having a benzophenone structure.

[0063] Examples of α-hydroxyalkylphenone compounds include 2-hydroxy-1-[4-[4-(2-hydroxy-2-methylpropionyl)benzyl]phenyl]-2-methylpropan-1-one (Omnirad 127D, manufactured by IGM Resins), 1-hydroxycyclohexyl phenyl ketone (Omnirad 184, manufactured by IGM Resins), 2-hydroxy-2-methyl-1-phenylpropan-1-one (Omnirad 1173, manufactured by IGM Resins), 1-[4-(2-hydroxyethoxy)phenyl]-2-hydroxy-2-methyl-1-propan-1-one (Omnirad 2959, manufactured by IGM Resins), and oligo[2-hydroxy-2-methyl-1-[4-1-(methylvinyl)phenyl]propanone (ESACURE Examples of α-aminoalkylphenone compounds that satisfy the conditions for component (D-2) include 2-methyl-1[4-(methylthio)phenyl]-2-morpholinopropan-1-one (IRGACURE 907, manufactured by BASF). Examples of benzyl ketal compounds include 2,2-dimethoxy-1,2-diphenylethan-1-one (Omnirad 651, manufactured by IGM Resins). Examples of oxime ester compounds that satisfy the conditions for component (D-2) include 1-[9-ethyl-6-(2-methylbenzoyl)-9H-carbazol-3-yl]ethanone-1-(O-acetyloxime) (IRGACURE OXE02, manufactured by BASF). Examples of benzophenone compounds include benzophenone, 2-methylbenzophenone, 3-methylbenzophenone, 4-methylbenzophenone, 2,4,6-trimethylbenzophenone, 4-phenylbenzophenone, 4-(4-methylphenylthio)benzophenone, 1-[4-(4-benzoylphenylsulfanyl)phenyl]-2-methyl-2-(4-methylphenylsulfonyl)propan-1-one, 4,4'-bis(dimethylamino)benzophenone, 4,4'-bis(diethylamino)benzophenone, and 4-methoxy-4'-dimethylaminobenzophenone.

[0064] The component (D-2) is preferably at least one selected from the group consisting of α-hydroxyalkylphenone compounds, α-aminoalkylphenone compounds (excluding those having a 4-morpholinophenyl group), benzyl ketal compounds, oxime ester compounds (excluding those having a 4-phenylthiophenyl group), and benzophenone compounds. This allows the curing of the photocurable resin composition to proceed efficiently and sufficiently in the irradiation step (b) using light irradiation, which will be described later. The component (D-2) may be at least one selected from the group consisting of α-hydroxyalkylphenone compounds, benzyl ketal compounds, and benzophenone compounds.

[0065] The component (D-2) may be used alone or in any combination of two or more. From the viewpoints of compression set at high temperatures and reactivity during photocuring, the content of the component (D-2) is preferably 0.1 to 5 parts by mass, more preferably 0.2 to 4 parts by mass, and even more preferably 0.5 to 2 parts by mass, relative to 100 parts by mass of the total content of the photoradical polymerizable components (A), (B), (E), and (F).

[0066] <Component (E): Other Photoradically Polymerizable Polymer Except for Component (A)> The photocurable resin composition according to the present disclosure includes component (E) as an optional component, and the total content of component (A) and component (E) is 30 parts by mass to 90 parts by mass per 100 parts by mass of the total content of component (A), component (B), component (E), and component (F), which are photoradically polymerizable components.

[0067] As component (E), a (meth)acrylate polymer having a (meth)acryloyl group in part of the polymer backbone (particularly at the end of the polymer backbone) is particularly preferred. The backbone of the (meth)acrylate polymer is not particularly limited, and examples thereof include a urethane backbone (i.e., urethane (meth)acrylate), a hydrocarbon backbone without a double bond (e.g., hydrogenated polybutadiene, hydrogenated polyisoprene, etc.), a polyacrylic acid ester backbone, a polyether backbone, a hydrocarbon backbone with a double bond, a polyester backbone, and a polycarbonate backbone.

[0068] Among these, from the viewpoints of availability and ease of production, urethane (meth)acrylate is preferred as component (E). The urethane (meth)acrylate may have a skeleton such as a hydrocarbon skeleton without a double bond (e.g., hydrogenated polybutadiene, hydrogenated polyisoprene, etc.), a polyether skeleton, a hydrocarbon skeleton with a double bond, a polyester skeleton, or a polycarbonate skeleton.

[0069] Among these, from the viewpoints of compression set at high temperatures, compression reaction force at low temperatures, and hydrolysis resistance, it is preferable that the urethane (meth)acrylate contains a hydrocarbon skeleton having no double bonds or a polyether skeleton, and it is more preferable that the hydrocarbon skeleton having no double bonds contains a skeleton consisting of at least one of hydrogenated polybutadiene and hydrogenated polyisoprene (hereinafter also referred to as a "polydiene skeleton").

[0070] The component (E) may be a commercially available product. Examples of bifunctional urethane (meth)acrylates having a polyether skeleton include the Art Resin series (UN-6200, UN-6207, UN-6306, UN-6304, UN-6305, UN-6060S, etc.) manufactured by Negami Chemical Industrial Co., Ltd. Examples of bifunctional urethane (meth)acrylates having a hydrogenated polybutadiene skeleton include TEAI-1000 manufactured by Nippon Soda Co., Ltd. The component (E) may contain one type alone or two or more types.

[0071] Hereinafter, the case where the urethane (meth)acrylate contains a polydiene skeleton will be described.

[0072] Suitable examples of the urethane (meth)acrylate include a urethane reaction product of a polydiene alcohol, a polyisocyanate, and a (meth)acrylate having a hydroxyl group, and an addition reaction product of a polydiene alcohol with a compound having an isocyanate group and a (meth)acryloyl group.

[0073] The following describes preferred raw material compounds for the urethane (meth)acrylate, namely, polydiene alcohol, polyisocyanate, and compound containing a hydroxyl group and a (meth)acryloyl group.

[0074] Examples of polydiene alcohols include polydiene diols and hydrogenated polydiene diols. Examples of polydiene diols include polybutadiene diols, polyisoprene diols, and butadiene-styrene copolymer diols. Examples of hydrogenated polydiene diols include hydrogenated polybutadiene diols, hydrogenated polyisoprene diols, and hydrogenated products of butadiene-styrene copolymer diols. Of these, those in which the double bonds are hydrogenated are preferred because they provide good compression set at high temperatures. Particularly preferred are hydrogenated polybutadiene diols and hydrogenated polyisoprene diols, and these two may be used in combination. The number average molecular weight of the polydiene alcohol is preferably 500 to 5,000, more preferably 1,000 to 4,000.

[0075] The polyisocyanate is preferably a compound having two isocyanate groups per molecule (hereinafter also referred to as "diisocyanate"). If a compound having three or more isocyanate groups per molecule is used, gelation may occur during synthesis, or even if synthesis is possible without gelation, the resulting urethane (meth)acrylate may be prone to cracking at high compression ratios due to the presence of three or more (meth)acryloyl groups. From the viewpoint of suppressing gelation and cracking at high compression ratios, a compound having two isocyanate groups per molecule is preferred. Examples of diisocyanates include aliphatic diisocyanates (e.g., hexamethylene diisocyanate, etc.), alicyclic diisocyanates (e.g., isophorone diisocyanate, hydrogenated tolylene diisocyanate, hydrogenated diphenylmethane diisocyanate, and hydrogenated xylylene diisocyanate, etc.), and aromatic diisocyanates (e.g., tolylene diisocyanate, diphenylmethane diisocyanate, tolidine diisocyanate, naphthalene diisocyanate, and xylylene diisocyanate, etc.).

[0076] Examples of compounds containing a hydroxyl group and a (meth)acryloyl group include 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, caprolactone-modified 2-hydroxyethyl (meth)acrylate, and glycidol di(meth)acrylate. Among these compounds, preferred compounds containing a hydroxyl group and a (meth)acryloyl group are hydroxyalkyl (meth)acrylates (2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, etc.).

[0077] The component (E) may be used alone or in any combination of two or more. From the viewpoints of compression set at high temperatures, compression reaction force at low temperatures, pressure-resistant sealing properties at low compression ratios, crack suppression properties at high compression ratios, and water resistance, the content of the component (E) is preferably 0 parts by mass to 30 parts by mass, more preferably 0 parts by mass to 20 parts by mass, even more preferably 0 parts by mass to 10 parts by mass, and particularly preferably 0 parts by mass, relative to 100 parts by mass of the total content of the photoradical polymerizable components (A), (B), (E), and (F). That is, it is particularly preferable that the photocurable resin composition according to the present disclosure does not contain the component (E).

[0078] <Component (F): Other Photoradically Polymerizable Monomer Except for Component (B)> The photocurable resin composition according to the present disclosure includes component (F) as an optional component, and the content of component (F) is 0 parts by mass to 13 parts by mass relative to 100 parts by mass of the total content of components (A), (B), (E), and (F), which are photoradically polymerizable components.

[0079] Examples of the component (F) include monofunctional (meth)acrylate compounds having only linear or branched hydrocarbon groups with 1 to 3 carbon atoms as the hydrocarbon group, monofunctional (meth)acrylate compounds having only linear or branched hydrocarbon groups with 19 or more carbon atoms as the hydrocarbon group, monofunctional (meth)acrylate compounds having an alicyclic hydrocarbon group, monofunctional (meth)acrylate compounds having an aromatic ring, monofunctional (meth)acrylate compounds having a heterocycle, polyfunctional (meth)acrylate compounds, (meth)acrylic acid, (meth)acrylamide compounds, olefin compounds, and styrene compounds.Specific examples include methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, isopropyl (meth)acrylate, icosyl (meth)acrylate, docosyl (meth)acrylate, cyclohexyl (meth)acrylate, isobornyl (meth)acrylate, dicyclopentenyl (meth)acrylate, dicyclopentanyl (meth)acrylate, 1-adamantyl (meth)acrylate, benzyl (meth)acrylate, phenoxyethyl (meth)acrylate, 2-hydroxy-3-phenoxypropyl (meth)acrylate, (1-naphthyl)methyl (meth)acrylate, tetrahydrofurfuryl (meth)acrylate, 1,6-hexanediol di(meth)acrylate, 1,8-octanediol di(meth)acrylate, 1,9-nonanediol di(meth)acrylate, 1,10-decanediol di(meth)acrylate, 1,12-dodecanediol di( ... Examples of the diol di(meth)acrylate include hexanediol di(meth)acrylate, 3-methyl-1,5-pentanediol di(meth)acrylate, 2,4-diethyl-1,5-pentanediol di(meth)acrylate, butylethylpropanediol di(meth)acrylate, 3-methyl-1,7-octanediol di(meth)acrylate, 2-methyl-1,8-octanediol di(meth)acrylate, neopentyl glycol di(meth)acrylate, diethylene glycol di(meth)acrylate, tetraethylene glycol di(meth)acrylate, trispropylene glycol di(meth)acrylate, trimethylolpropane tri(meth)acrylate, tris(2-acryloxyethyl)isocyanurate, pentaerythritol tetra(meth)acrylate, dipentaerythritol hexa(meth)acrylate, and dipentaerythritol penta(meth)acrylate.

[0080] The (F) component may be used alone or in any combination of two or more. The content of the (F) component is 0 to 13 parts by mass relative to 100 parts by mass of the total content of the photoradical polymerizable components (A), (B), (E), and (F). From the viewpoints of compression set at high temperatures, compression reaction force at low temperatures, pressure-resistant sealability at low compression ratios, crack suppression at high compression ratios, and water resistance, the content is preferably 0 to 10 parts by mass, more preferably 0 to 5 parts by mass, and particularly preferably 0 part by mass. That is, it is particularly preferable that the photocurable resin composition according to the present disclosure does not contain the (F) component.

[0081] <Other Components> The photocurable resin composition according to the present disclosure may contain other components as long as the effects of the present disclosure are not impaired. Examples of other components include a thermal polymerization initiator, an ultraviolet absorber, a light stabilizer, an antioxidant, a polymerization inhibitor, a silane coupling agent, a non-reactive polymer, a filler (excluding component (C)), metal particles, metal oxide particles, an ion trapping agent, an antifoaming agent, a leveling agent, a dye, and a pigment.

[0082] The sealing material according to the present disclosure is obtained by curing the photocurable resin composition according to the present disclosure. The shape of the sealing material is appropriately selected depending on the application of the sealing material, and examples thereof include a ring, a packing, a gasket, a diaphragm, an oil seal, a bearing seal, a lip seal, a plunger seal, a door seal, a lip, a face seal, a gas delivery plate seal, a wafer support seal, and a barrel seal.

[0083] The sealing material has a small compression set at high temperatures, a sufficient compression reaction force at low temperatures, excellent pressure-resistant sealing properties at low compression ratios, excellent crack suppression properties at high compression ratios, and excellent water resistance. Therefore, the sealing material is preferably used for fuel cells. Examples of fuel cells include solid polymer fuel cells.

[0084] Hereinafter, the sealing material for fuel cells will also be referred to as "sealing material for fuel cells."

[0085] Examples of shapes of the fuel cell sealing material include an O-ring shape, a V-ring shape, a rod shape, a sheet shape, and a block shape.

[0086] In fuel cells, it is important to seal the components of a single cell or to seal between the components of a single cell. A fuel cell sealing material can provide good sealing between the components and between the components. Examples of the components of a single cell include an electrolyte membrane, electrodes, separators, and a frame.

[0087] (Method for manufacturing sealing material) There are no particular limitations on the method for manufacturing the sealing material according to the present disclosure, but it is preferable that the method includes, in this order, a step of irradiating the photocurable resin composition according to the present disclosure with light (a) including the wavelength (I) and a step of irradiating with light (b) including the wavelength (II) (hereinafter also referred to as the "irradiation step"), and that the irradiation energy of the light (a) in the wavelength range of 200 nm to 385 nm is 0.2 times or less the irradiation energy of the light (a) in the wavelength range of 395 nm to 435 nm. Furthermore, in the photocurable resin composition according to the present disclosure used in the method for producing a sealing material according to the present disclosure, the component (D) comprises the following components (D-1) and (D-2): component (D-1): a photoradical polymerization initiator having a molar absorption coefficient of 10 L / (mol cm) or more at at least one wavelength (I) of 395 nm to 435 nm; and component (D-2): a photoradical polymerization initiator having a molar absorption coefficient of less than 10 L / (mol cm) at any wavelength of 395 nm to 435 nm, and having a molar absorption coefficient of 10 L / (mol cm) or more at at least one wavelength (II) of 280 nm to 380 nm. It is preferable that the content of the (D-1) component is 0.01 parts by mass to 0.9 parts by mass and the content of the (D-2) component is 0.1 parts by mass to 5 parts by mass relative to 100 parts by mass of the total content of the (A), (B), (E), and (F) components, which are the photoradical polymerizable components.

[0088] In addition to the irradiation step, the method for producing a sealing material according to the present disclosure may further include a step of preparing a photocurable resin composition (hereinafter also referred to as a "preparation step") and a step of molding the photocurable resin composition into the shape of a sealing material (hereinafter also referred to as a "molding step"). The preparation step, molding step, and irradiation step are performed in this order. Below, a description will be given of a case where the method for producing a sealing material according to the present disclosure includes the preparation step, molding step, and irradiation step.

[0089] <Preparation Step> In the preparation step, a photocurable resin composition is prepared.

[0090] The method for preparing the photocurable resin composition is not particularly limited and may be any known method. The photocurable resin composition may be kneaded using a kneader. Examples of kneaders include a kneader, a Banbury mixer, a roll mill, and a single-screw extruder.

[0091] <Molding Step> In the molding step, the photocurable resin composition is molded into the shape of the sealing material.

[0092] The method for molding the photocurable resin composition is appropriately selected depending on the shape of the sealing material, and any known method may be used.

[0093] When the sealing material is in the form of a bead, the photocurable resin composition can be molded, for example, using a coating device having a needle-shaped coating unit, which ejects the photocurable resin composition from the needle-shaped coating unit to mold the photocurable resin composition into a bead shape.

[0094] When the shape of the sealing material is not bead-shaped, examples of the molding method of the photocurable resin composition include a method of injecting the composition into a molding die. The cavity of the molding die (i.e., the molding space) corresponds to the shape of the sealing material. The configuration of the molding die is not particularly limited, and any known configuration may be used. The material of the molding die is not particularly limited as long as it can cure the photocurable resin composition in the irradiation step, and examples include glass, resin, and metal. The molding die may also be equipped with a heating means, a cooling means, a decompression means, a pressurization means, etc. The method of injecting the photocurable resin composition into the molding die is not particularly limited, and any known method may be used.

[0095] In the irradiation step, the photocurable resin composition is irradiated with light (a) containing at least one wavelength (I) of 395 nm to 435 nm, and then with light (b) containing at least one wavelength (II) of 200 nm to 385 nm, thereby curing the photocurable resin composition and obtaining a sealing material.

[0096] -Light Irradiation (a)- The wavelength of the light (a) may include at least one wavelength (I) between 395 nm and 435 nm, and is appropriately selected depending on the type of component (D-1), etc. The wavelength (I) may include at least one between 395 nm and 420 nm, or at least one between 400 nm and 410 nm, or may include 405 nm. The illuminance of the light (a) is appropriately selected depending on the type of component (D-1), etc. The illuminance of the light (a) is 100 mW / cm ２ ~5,000mW / cm ２ or 200 mW / cm ２ ~2,000mW / cm ２ or 500 mW / cm ２ ~1,500mW / cm ２ The irradiation dose of the light (a) is appropriately selected depending on the type of the component (D-1), etc. The irradiation dose of the light (a) is 100 mJ / cm ２ ~5,000mJ / cm ２ or 200 mJ / cm ２ ~4,000mJ / cm ２ or 1,000 mJ / cm ２ ~4,000mJ / cm ２ may be.

[0097] In the light irradiation (a), the wavelength was 405 nm and the illuminance was 500 mW / cm ２ ~1,500mW / cm ２ , the irradiation dose was 1,000 mJ / cm ２ ~4,000mJ / cm ２ This allows partial curing of the photocurable resin composition to proceed efficiently in a short period of time.

[0098] The light source for the light irradiation (a) is preferably an LED (light emitting diode), but multi-wavelength light sources such as low-pressure mercury lamps, medium-pressure mercury lamps, high-pressure mercury lamps, ultra-high-pressure mercury lamps, and metal halide lamps equipped with a wavelength cut filter can also be used.

[0099] The light irradiation (a) may be carried out while heating the photocurable resin composition. After the light irradiation (a) is carried out, the photocurable resin composition may be heated as necessary.

[0100] -Light Irradiation (b)- The wavelength of light (b) may include at least one wavelength (II) between 200 nm and 385 nm, and is appropriately selected depending on the types of component (D-1) and component (D-2), etc. The wavelength (II) may include at least one wavelength between 300 nm and 385 nm, or at least one wavelength between 350 nm and 380 nm, or may include 365 nm. The illuminance of light (b) is appropriately selected depending on the types of component (D-1) and component (D-2), etc. The illuminance of light (b) is 100 mW / cm ２ ~5,000mW / cm ２ or 200 mW / cm ２ ~3,000mW / cm ２ or 500 mW / cm ２ ~2,000mW / cm ２ The irradiation dose of light (b) is appropriately selected depending on the type of component (D-1) and the type of component (D-2), etc. The irradiation dose of light (b) is 200 mJ / cm ２ ~10,000mJ / cm ２ or 500 mJ / cm ２ ~10,000mJ / cm ２ or 2,000 mJ / cm ２ ~7,000mJ / cm ２ may be.

[0101] In the case of light irradiation (b), the wavelength was 365 nm and the illuminance was 500 mW / cm ２ ~2,000mW / cm ２ , the irradiation dose is 2,000 mJ / cm ２ ~7,000mJ / cm ２This allows the curing of the photocurable resin composition to proceed efficiently and sufficiently in a short time.

[0102] The light source for light irradiation (b) is not particularly limited, and examples thereof include LED, low-pressure mercury lamp, medium-pressure mercury lamp, high-pressure mercury lamp, ultra-high-pressure mercury lamp, metal halide lamp, and UV (ultraviolet) electrodeless lamp.

[0103] The light irradiation (b) may be carried out continuously after the light irradiation (a). The light irradiation (b) may be carried out while heating the photocurable resin composition. After the light irradiation (b), the photocurable resin composition may be heated as needed.

[0104] Among these, the illuminance of the light (a) is 100 mW / cm ２ ~5,000mW / cm ２ , irradiation dose 100 mJ / cm ２ ~5,000mJ / cm ２ and the illuminance of the light (b) is 100 mW / cm ２ ~5,000mW / cm ２ , irradiation dose 200 mJ / cm ２ ~10,000mJ / cm ２ When the content is within the above range, the sealing material can be obtained by curing in a short time without impairing the effects of the present disclosure.

[0105] Hereinafter, the present disclosure will be described more specifically with reference to examples, but the present disclosure is not limited to the following examples as long as it does not deviate from the gist of the disclosure.

[0106] 1. Preparation of Photocurable Resin Composition Abbreviations of materials used in the examples and comparative examples are listed below.

[0107] Component (A) EP400V: acryloyl-terminated polyisobutylene ("KANEKA EPION EP400V" manufactured by Kaneka Corporation, Mn = 15,000, Mw = 17,000, viscosity 3,500,000 mPa·s @ 23°C)

[0108] Component (B) NOAA: n-octyl acrylate (NOAA manufactured by Osaka Organic Chemical Industry Ltd.) IDAA: isodecyl acrylate (IDAA manufactured by Osaka Organic Chemical Industry Ltd.) M-120: acrylate of 2-ethylhexyl alcohol with 2 moles of ethylene oxide (Aronix M-120 manufactured by Toagosei Co., Ltd.)

[0109] Component (C) SC2500-SMJ: surface methacrylic-modified silica (manufactured by ADMAFINE Co., Ltd., SC2500-SMJ, average particle size 0.5 μm); 15SM-C1: surface methacrylic-modified silica (manufactured by ADMAFINE Co., Ltd., 15SM-C1, average particle size 1.5 μm); SC2500-SQ: surface hydrophobized silica (manufactured by ADMAFINE Co., Ltd., SC2500-SQ, average particle size 0.5 μm);

[0110] Comparative components for component (C) (component (C')): RX200: surface-hydrophobized silica (RX200 manufactured by Nippon Aerosil Co., Ltd., average particle size 12 nm); SE-1: surface-untreated silica (Excellica SE-1 manufactured by Tokuyama Corporation, average particle size 1 μm); MX-500L: crosslinked polymethyl methacrylate (MX-500L manufactured by Soken Chemical & Engineering Co., Ltd., average particle size 5 μm).

[0111] Component (D-1) O-380: bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide (Omnirad 380, manufactured by IGM Resins)

[0112] Component (D-2) O-907: 2-methyl-1[4-(methylthio)phenyl]-2-morpholinopropan-1-one (Omnirad 907D, manufactured by IGM Resins)

[0113] Component (E) (comparison component to component (A)) PUA-1: urethane acrylate having a hydrogenated polybutadiene skeleton. This is the urethane acrylate component contained in the product of Synthesis Example 1.

[0114] Component (F) (comparison component for component (B)) IBXA: isobornyl acrylate (IBXA manufactured by Osaka Organic Chemical Industry Ltd.)

[0115] Synthesis Example 1: Synthesis of urethane acrylate (PUA-1) having a hydrogenated polybutadiene skeleton. A 3 L four-neck separable flask was charged with 1,100 g (0.66 mol of hydroxyl groups) of KRASOL HLBHP3000 (hydroxyl value 33.7 mg KOH / g, Mn approximately 3,000) manufactured by Cray Valley as a hydrogenated polybutadiene having hydroxyl groups, 0.88 g of 2,6-di-t-butyl-p-cresol, and 504 g of isodecyl acrylate (hereinafter referred to as "IDAA"), and the contents were dissolved by stirring using a stirrer. A thermometer, gas inlet tube, and reflux condenser were attached to the flask, and the contents were stirred while a mixed gas of oxygen and nitrogen (5% oxygen) was passed through the upper part of the liquid. 97.7 g of isophorone diisocyanate (0.88 mol of isocyanate groups) was added and mixed. To this solution, 12 g of IDAA in which 0.012 g of ferric acetylacetonate had been dissolved was added and mixed, and then the temperature was raised. After stirring and mixing for 1.5 hours at 80°C, 34.8 g of 4-hydroxybutyl acrylate (0.24 mol as hydroxyl groups) and 12 g of IDAA in which 0.012 g of ferric acetylacetonate had been dissolved were added and reacted for 3 hours. The disappearance of the isocyanate groups was confirmed by infrared absorption (IR) spectroscopy, and the synthesis was terminated. The resulting product was a mixture containing 70% urethane acrylate having a hydrogenated polybutadiene skeleton (hereinafter referred to as "PUA-1") and 30% IDAA as a diluent monomer. GPC analysis of the resulting product confirmed that the peak of the PUA-1 component was distinct from the monomer components. The polystyrene-equivalent molecular weight of the PUA-1 component was 16,000 in Mn and 29,000 in Mw.

[0116] (Examples 1 to 10 and Comparative Examples 1 to 8: Preparation of Photocurable Resin Compositions) First, the components except for component (C) and component (C') were blended in the proportions shown in Table 1 and stirred and mixed according to a conventional method. At this time, the mixture was heated to approximately 80°C as necessary. Subsequently, component (C) and component (C') were blended with the above blend in the proportions shown in Table 1 and mixed for 10 minutes using a planetary stirring and degassing device to obtain a photocurable resin composition. Photocurable resin compositions in which precipitation of component (C) and component (C') was confirmed were deemed to have poor dispersibility and were not evaluated in the following steps 2. Furthermore, photocurable resin compositions that did not flow even when the container containing the prepared photocurable resin composition was tilted were deemed to have insufficient fluidity and were not evaluated in the following steps 2. The number of parts of PUA-1 in Table 1 indicates the number of parts of only the urethane acrylate component contained in the product of Synthesis Example 1. The number of parts of component (B) includes the number of parts of component (B) contained in the product of Synthesis Example 1, and indicates the total number of parts of component (B) contained in the product of Synthesis Example 1 and the number of parts of component (B) added later.

[0117] 2. Preparation of Evaluation Samples of Photocurable Resin Composition The photocurable resin composition prepared in 1. above was applied to a 0.1 mm thick SUS304 plate (stainless steel plate) using an automatic coater to form a square-shaped coating with an inner diameter of 30 mm, as shown in Figure 1. The photocurable resin composition was applied to a width of 2 mm and a height of 1 mm. Next, the coating was irradiated under nitrogen using a 405 nm LED (surface-type LED irradiator manufactured by CCS Corporation) under the conditions shown in Table 1 (Example 1 ended here). Finally, the coating was irradiated under nitrogen using a 365 nm LED (surface-type LED irradiator manufactured by CCS Corporation) under the conditions shown in the table. In this way, an evaluation sample was obtained in which the cured product (1) was adhered in a square shape to a 0.1 mm thick SUS304 plate (2) as shown in Figure 1. A C12684 illuminance meter manufactured by Hamamatsu Photonics K.K. was used to measure the illuminance.

[0118] 3. Evaluation of High-Temperature Compression Cracking Resistance of Photocurable Resin Compositions A straight section was cut from the evaluation sample obtained in 2. above while still attached to the SUS304 plate so that the length of the cured product was 7 mm, and used for evaluation. A rheometer, Discovery HR-20, manufactured by TA Instruments, was used for the measurement. The cured sample was compressed to a predetermined compression ratio at a rate of 1 μm / s at 95°C, and then released at a rate of 1 μm / s until the compression ratio reached 0%. This cycle was repeated five times, and then the sample was visually inspected for damage. Tests were conducted at compression ratios of 50% and 55%. High-temperature compression cracking resistance was evaluated as follows. If the sample broke at a compression ratio of 50%, the evaluation in 4. below was not performed. A: No damage at a compression ratio of 55% B: No damage at a compression ratio of 50%, and damage at a compression ratio of 55% C: Damage at a compression ratio of 50%

[0119] 4. Evaluation of High-Temperature Compression Set of Photocurable Resin Composition A straight section was cut from the evaluation sample obtained in 2. above while still attached to the SUS304 plate so that the length of the cured product was 7 mm, and used for evaluation. A compression set test was performed using a jig and conditions in accordance with JIS K6262:2013. The sample was compressed using a jig so that the compression ratio of the cured product was 50%, and then placed in a thermostatic chamber at 140°C for 72 hours. The jig was then removed from the thermostatic chamber, the compression was released, and the sample was removed from the jig and left at 25°C for 30 minutes or more. Finally, the thickness of each sample was measured, and the compression set was calculated. The high-temperature compression set was evaluated as follows: A: Compression set less than 10% B: Compression set 10% or more but less than 30% C: Compression set 30% or more

[0120] 5. Evaluation of Pressure-Resistant Sealing of Photocurable Resin Compositions The pressure-resistant sealing test apparatus is shown in Figure 2. A 0.3 mm thick SUS304 plate (3) with a 10 mm diameter circular hole was placed on top of the evaluation sample obtained in 2. above, with the hole positioned inside the square-shaped cured product (1), to prepare a test piece. A spacer (4) was inserted between the SUS304 plates (2) and (3) of the test piece so that the compression ratio of the cured product after compression was 10%, and the test piece was compressed by clamping it with a jig (5). Air set to a predetermined pressure was sent through a pipe (6) attached to the jig (5) to increase the internal pressure of the test piece (a rubber packing (7) was attached to the jig (5) to seal between the jig (5) and the SUS304 plate (3) with the hole). The internal pressure was increased stepwise to 200 kPaA, 300 kPaA, and 400 kPaA, and each internal pressure was maintained for 5 minutes. If there was no change, it was determined that there was no leakage. The pressure-resistant sealing property was judged as follows: A: No leakage at 400 kPaA B: No leakage at 300 kPaA or less, leakage at 400 kPaA C: Leakage at 300 kPaA or less

[0121] 6. Evaluation of Low-Temperature Compression Reaction Force Retention of Photocurable Resin Composition A straight section was cut from the evaluation sample obtained in 2. above while still adhered to the SUS304 plate so that the length of the cured product was 7 mm, and used for evaluation. A TA Instruments Discovery HR-20 rheometer was used for the measurement. First, the cured sample was compressed at 25°C to a compression ratio of 50% at a rate of 1 μm / s, and then held for 4 hours while maintaining the compression ratio at 50%. Next, while maintaining the compression ratio at 50%, the temperature was lowered to -30°C and held for 3 minutes. Finally, the compression reaction force was measured while releasing at a rate of 0.05 μm / s until the compression ratio reached 0%, and the compression ratio when the compression reaction force became 0 N or less was calculated. The smaller the compression ratio at this time, the better the sealing material's low-temperature rubber elasticity, as it maintains a reaction force over a wide range of compression ratios in a low-temperature environment. Therefore, the low-temperature compression reaction force retention was evaluated as follows. A: The compression ratio at which the compression reaction force becomes 0N or less is less than 30%. B: The compression ratio at which the compression reaction force becomes 0N or less is 30% or more but less than 45%. C: The compression ratio at which the compression reaction force becomes 0N or less is 45% or more.

[0122] The evaluation results are summarized in Table 1.

[0123]

[0124] 7. Evaluation of Coolant Resistance (Water / Ethylene Glycol Mixed Solution) of Photocurable Resin Composition (Only Example 3) A 1 mm-thick silicone rubber cutout in the shape of a No. 6 dumbbell as described in JIS K6251:2023 was placed on a polyethylene terephthalate (PET) film, and the photocurable resin composition of Example 3 prepared in section 1 above was poured into it, followed by lamination with a PET film. Irradiation was performed using a 405 nm LED (surface-type LED irradiator manufactured by CCS Corporation) under the conditions listed in Table 1, followed by irradiation using a 365 nm LED (surface-type LED irradiator manufactured by CCS Corporation) under the conditions listed in Table 1. The PET films on both sides were peeled off, and the silicone rubber was removed to obtain a No. 6 dumbbell-shaped cured product. The thus-obtained No. 6 dumbbell-shaped cured product was immersed in a container filled with a water / ethylene glycol mixed solution (50 / 50 by mass), sealed, and placed in a thermostatic chamber at 95°C for 1,000 hours. The cured product was removed and allowed to cool and air-dry sufficiently in an environment of 23°C, after which a tensile test was performed at 23°C (initial grip distance: 30 mm, tensile speed: 50 mm / min). A tensile test was also performed on the cured product that had not been immersed, and the modulus of elasticity, elongation at break, and stress at break were compared before and after immersion. The elongation at a given point in time was calculated by "{(grip distance at a given point in time) - (initial grip distance)} ÷ (initial grip distance) × 100". The modulus of elasticity was calculated by "{(stress at 10% elongation) - (stress at 5% elongation)} ÷ 0.05". As a result, as shown in Table 2, no decrease in the values ​​was observed in any of the items, and no deterioration of the cured product was confirmed.

[0125]

[0126] The disclosure of Japanese Patent Application No. 2024-060977, filed on April 4, 2024, is incorporated herein by reference in its entirety. All documents, patent applications, and technical standards mentioned herein are incorporated herein by reference to the same extent as if each individual document, patent application, and technical standard was specifically and individually indicated to be incorporated by reference.

[0127] 1: cured product, 2, 3: SUS304 plate, 4: spacer, 5: jig, 6: pipe, 7: rubber packing

Claims

1. Comprising the following components (A) to (D): Component (A): a polymer having a number average molecular weight of 1,000 to 100,000 and having a polyisobutylene skeleton and two or more (meth)acryloyl groups; Component (B): a monofunctional (meth)acrylate compound having a linear or branched hydrocarbon group with 4 to 18 carbon atoms and having one (meth)acryloyl group per molecule; Component (C): inorganic particles having an average particle size of 0.1 μm to 200 μm and having a surface modified with an organic group; Component (D): a photoradical polymerization initiator; and optionally comprising the following components (E) and (F): Component (E): a photoradical polymerizable polymer other than component (A); Component (F): a photoradical polymerizable monomer other than component (B). For a total of 100 parts by mass of the photoradical polymerizable components (A), (B), (E), and (F), A photocurable resin composition, comprising: a total content of the (A) component and the (E) component of 30 to 90 parts by mass; a content of the (B) component of 10 to 70 parts by mass; a content of the (C) component of 5 to 120 parts by mass; a content of the (D) component of 0.1 to 6 parts by mass; and a content of the (F) component of 0 to 13 parts by mass.

2. The photocurable resin composition according to claim 1, wherein the content of component (A) is 20 to 90 parts by mass and the content of component (E) is 0 to 30 parts by mass, relative to 100 parts by mass of the total content of the photoradical polymerizable components (A), (B), (E), and (F).

3. The photocurable resin composition according to claim 1, wherein component (A) comprises a polyisobutylene resin having a number average molecular weight of 1,000 to 100,000 and having (meth)acryloyl groups at both ends.

4. The photocurable resin composition according to claim 1, wherein component (B) contains a monofunctional (meth)acrylate compound having a linear or branched hydrocarbon group with 4 to 10 carbon atoms and one (meth)acryloyl group per molecule.

5. The photocurable resin composition according to claim 1, wherein the component (D) comprises the following components (D-1) and (D-2): Component (D-1): a photoradical polymerization initiator having a molar absorption coefficient of 10 L / (mol cm) or more at at least one wavelength (I) of 395 nm to 435 nm; Component (D-2): a photoradical polymerization initiator having a molar absorption coefficient of less than 10 L / (mol cm) at all wavelengths of 395 nm to 435 nm, and a molar absorption coefficient of 10 L / (mol cm) or more at at least one wavelength (II) of 280 nm to 385 nm. The photocurable resin composition according to claim 1, wherein the content of the component (D-1) is 0.01 to 0.9 parts by mass and the content of the component (D-2) is 0.1 to 5 parts by mass, relative to 100 parts by mass of the total content of the photoradical polymerizable components (A), (B), (E), and (F).

6. The photocurable resin composition according to claim 5, wherein the component (D-1) comprises at least one compound selected from the group consisting of acylphosphine oxide compounds, α-aminoalkylphenone compounds having a 4-morpholinophenyl group, oxime ester compounds having a 4-phenylthiophenyl group, and thioxanthone compounds.

7. The photocurable resin composition according to claim 5, wherein the component (D-2) comprises at least one compound selected from the group consisting of α-hydroxyalkylphenone compounds, α-aminoalkylphenone compounds (excluding those having a 4-morpholinophenyl group), benzil ketal compounds, oxime ester compounds (excluding those having a 4-phenylthiophenyl group), and benzophenone compounds.

8. The photocurable resin composition according to claim 1, which is a photocurable resin composition for use as a sealing material.

9. The photocurable resin composition according to claim 1, which is a photocurable resin composition for use as a sealing material for fuel cells.

10. A method for producing a sealing material, comprising the steps of irradiating the photocurable resin composition according to any one of claims 5 to 7 with light (a) containing wavelength (I) and light (b) containing wavelength (II), in this order, wherein the irradiation energy of the light (a) in the wavelength range of 200 nm to 385 nm is 0.2 times or less the irradiation energy of the light (a) in the wavelength range of 395 nm to 435 nm.

11. The illuminance of the light (a) is 10 mW / cm ２ ~5,000mW / cm ２ , irradiation dose 50 mJ / cm ２ ~5,000mJ / cm ２ and the illuminance of the light (b) is 10 mW / cm ２ ~5,000mW / cm ２ , irradiation dose 50 mJ / cm ２ ~10,000mJ / cm ２ The method for producing a sealing material according to claim 10, 12. The method for producing a sealing material according to claim 10, wherein the produced sealing material is for a fuel cell.

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