Ultraviolet-curable silicone composition

Abstract

To provide an ultraviolet-curable silicone composition capable of forming a silicone cured product of high hardness and high strength, in which the components are mutually compatible, thereby preventing turbidity and separation.SOLUTION: The ultraviolet-curable silicone composition contains: (A) an organopolysiloxane having in its molecular structure a (meth)acrylic group, (B) a lactam compound or a cyclic urethane compound having a vinyl group attached to a nitrogen atom, which is represented by formula (1) or (2) (R1 and R2 each denote H, an alkyl group, an aryl group, or an aralkyl group), and (C) a photopolymerization initiator in an effective amount.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to an ultraviolet-curable silicone composition, specifically to an ultraviolet-curable transparent silicone composition that contains an acrylic-modified silicone and an N-vinyl group-containing lactam or cyclic urethane compound and undergoes radical polymerization and cures when exposed to ultraviolet light. [Background technology]

[0002] UV-curable silicone materials are widely used in adhesives, coatings, sealants, lens materials, etc. UV-curable silicone materials require less energy to harden than heat-curable silicone materials, making them environmentally friendly, and the short UV exposure time makes them suitable for mass production, which has led to them attracting increasing attention in recent years.

[0003] Although adding inorganic fillers is a known method for improving the hardness and strength of cured silicone products, there are limitations to applying this method to UV-curable silicones due to their need to transmit UV light. For this reason, a method is sometimes used in which a (meth)acrylate compound is added to the (meth)acrylic-modified silicone base polymer and used as a reinforcing agent. As an example, Patent Document 1 describes the addition of an acrylic monomer to a UV-curable and condensation-curable siloxane polymer to improve the physical properties of the cured product.

[0004] Meanwhile, N-vinylamide compounds are known to be useful as radically polymerizable monomers. Patent Document 2 reports that, with regard to photocurable compositions for 3D printing, a compound having an N-vinyloxazolidinone skeleton is mixed with an acrylic oligomer such as polyester acrylate to provide a strong dilution effect to the composition while imparting high rigidity and toughness to the cured product. This effect is thought to be due to the fact that acrylic groups and N-vinyl are known to be easily copolymerized for electronic reasons. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Special Publication No. 2023-521261 [Patent Document 2] Special Publication No. 2022-502557 Summary of the Invention [Problem to be solved by the invention]

[0006] However, since silicones tend to separate from polar solvents, including amides, N-vinylamide compounds cannot always be used in silicone compositions, and there has been little knowledge regarding their use. Therefore, an object of the present invention is to provide an ultraviolet-curable silicone composition that produces a silicone cured product with high hardness and strength, in which the components are compatible with each other and do not become cloudy or separate. [Means for solving the problem]

[0007] As a result of extensive research aimed at solving the above problems, the present inventors have found that the following composition can achieve the above object, and have thus completed the present invention. That is, the present invention provides the following ultraviolet-curable silicone composition. [1] (A) an organopolysiloxane having a (meth)acrylic group in the molecule; (B) a lactam compound or a cyclic urethane compound having a vinyl group bonded to a nitrogen atom, represented by the following formula (1) or (2): [ka] (In formulas (1) and (2), R 1 and R 2 each independently represents a hydrogen atom, a substituted or unsubstituted alkyl group having 1 to 20 carbon atoms, an aryl group, or an aralkyl group, or R1 and R 2 Two or more of these may be bonded to form a ring, and n is an integer of 2 to 10.) and (C) Photopolymerization initiator: effective amount An ultraviolet-curable silicone composition comprising: [2] The ultraviolet-curable silicone composition according to [1], further comprising a (meth)acrylate compound having no siloxane skeleton as component (D). [3] The ultraviolet-curable silicone composition according to [1] or [2], wherein a 500 μm-thick cured product obtained by irradiating the ultraviolet-curable silicone composition according to [1] or [2] with ultraviolet light has a light transmittance of 95% or more for light at 800 nm. [Effects of the Invention]

[0008] The silicone composition of the present invention undergoes a radical reaction between a (meth)acrylic-modified siloxane polymer and an N-vinylamide compound to produce a silicone cured product with relatively high hardness and strength, and the components are compatible with each other, are transparent, and do not become cloudy or separate. Therefore, the silicone composition of the present invention is thought to be applicable to ultraviolet-curable silicone adhesives, coating agents, sealants, lens materials, mold materials, nanoimprint materials, etc. DETAILED DESCRIPTION OF THE INVENTION

[0009] The present invention will be described in detail below.

[0010] Component (A) Component (A) is an organopolysiloxane having (meth)acrylic groups in the molecule. Component (A) is an organopolysiloxane having radical reactive groups that undergoes radical polymerization of the (meth)acrylic groups upon mixing with at least the photopolymerization initiator (component (C) described below) and exposure to ultraviolet light, rapidly forming a cured silicone product. Preferred examples of component (A) include the organopolysiloxanes (i) to (iii) below. Furthermore, the amount of (meth)acrylic groups in 100 g of component (A) is preferably 0.001 to 0.7 mol.

[0011] (i) An organopolysiloxane represented by the following formula (3): [ka] (In formula (3), R 3 each independently represents a substituted or unsubstituted alkyl group, aryl group, or aralkyl group having 1 to 20 carbon atoms; R 4 each independently represents an oxygen atom or an alkylene group having 1 to 20 carbon atoms, and R 5 each independently represents a group having a (meth)acrylic group, l represents a number satisfying 30 to 1,000, m represents a number satisfying 0 to 20, a and b each independently represent an integer of 0 to 3, and a+b+m is a number of 2 or more.

[0012] R in equation (3) 3 Specific examples of R include alkyl groups having 1 to 20 carbon atoms, such as methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, tert-butyl, n-hexyl, cyclohexyl, n-octyl, 2-ethylhexyl, and n-decyl; aryl groups having 6 to 20 carbon atoms, such as phenyl, tolyl, xylyl, and naphthyl; and aralkyl groups having 7 to 20 carbon atoms, such as benzyl and phenylethyl. Some or all of the hydrogen atoms bonded to the carbon atoms of these alkyl, aryl, or aralkyl groups may be substituted with other substituents, specific examples of which include halogen- or cyano-substituted alkyl groups, such as chloromethyl, bromoethyl, trifluoropropyl, and cyanoethyl. Among these, R3 As the alkyl group, an alkyl group having 1 to 5 carbon atoms and a phenyl group are preferred, and a methyl group, an ethyl group and a phenyl group are more preferred.

[0013] Furthermore, R in equation (3) 4 The alkylene group having 1 to 20 carbon atoms may be linear, branched, or cyclic, and specific examples thereof include methylene, ethylene, propylene, trimethylene, tetramethylene, isobutylene, pentamethylene, hexamethylene, heptamethylene, octamethylene, nonamethylene, and decylene groups. Among these, R 4 As the alkyl group, an oxygen atom, a methylene group, an ethylene group, or a trimethylene group is preferred, and an oxygen atom or an ethylene group is particularly preferred.

[0014] R in equation (3) 5 represents a group having a (meth)acrylic group, and is preferably any one of an acryloyloxyalkyl group, a methacryloyloxyalkyl group, an acryloyloxyalkyloxy group, a methacryloyloxyalkyloxy group, an acryloyloxyalkylsiloxy group, and a methacryloyloxyalkylsiloxy group. Specific examples thereof include, but are not limited to, those represented by the following formulas:

[0015] [ka] (In the formula, f represents a number satisfying 1≦f≦4.)

[0016] In formula (3), a and b represent integers of 0 to 3, and the sum together with m, a+b+m, is a number of 2 or greater. Preferably, a and b are each 1 or 2, and more preferably both are 2. Furthermore, when a and b are both 2, it is more preferable that m is 0, that is, a+b+m is 4. If a+b+m is less than 2, radical reactions are less likely to occur, which can lead to problems such as oil bleeding from the surface of the silicone cured product.

[0017] In formula (3), m represents a number satisfying the range of 0 to 20, preferably 0 to 10, and particularly preferably 0 to 5. If m exceeds 20, the silicone cured product will be hard and brittle, which may cause cracks.

[0018] In formula (3), l represents a number satisfying the range of 30 to 1,000, preferably 30 to 500, and particularly preferably 50 to 400. If l is less than 30, the compound is likely to volatilize in air, while if it exceeds 1,000, the photopolymerization reaction is difficult to occur, and curing may not proceed or may not proceed sufficiently, which may result in problems such as oil bleeding from the surface of the cured silicone product. The bonding order of the siloxane units in parentheses in formula (3) is not limited to the above, and the siloxane units may form block units or be bonded randomly.

[0019] The viscosity of component (i) at 23°C is preferably 50 to 10,000,000 mPa·s, and more preferably 1,000 to 100,000 mPa·s. If the viscosity is less than 50 mPa·s, the component will be prone to volatilization under atmospheric pressure or when reduced pressure is applied for degassing. If the viscosity exceeds 10,000,000 mPa·s, component (i) will have a high viscosity, which will deteriorate workability and make it difficult to mix uniformly with components (B) and (C), which are undesirable. Here, the viscosity is measured using a rotational viscometer.

[0020] Specific examples of component A-(i) include the following: [ka]

[0021] (ii) A urea group-containing organopolysiloxane represented by the following formula (4): [ka] (In the formula, R 3 and R 4 is the same as that shown in formula (3). o is a number between 10 and 1,000, and R6 are each independently an acrylic group-containing organic group represented by the following formula:

[0022] [ka] In the above formula, the dashed lines represent bonds.

[0023] In formula (4), o represents a number satisfying the range of 10 to 1,000, preferably 10 to 700, and particularly preferably 30 to 500. If o is less than 10, the urea group will form hydrogen bonds, making the copolymer more likely to become solid. If o exceeds 1,000, the viscosity will be too high, making it difficult to mix with components (B) to (D), which will be described later. Furthermore, the number-average molecular weight (Mn) of component (ii), as determined by GPC measurement (standard polystyrene equivalent) using a THF solvent, is preferably 3,000 to 100,000.

[0024] (iii) Organopolysiloxane represented by the following average formula (5): [ka] (In the formula, R 3 is the same as above, A is a siloxane unit satisfying the following formula (6) or (7), and p, q, and r are numbers that satisfy p>0, q>0, and r>0, respectively, and that satisfy (p+q+r)=1.

[0025] [ka] (In formulas (6) and (7), R 3 , R 4 and R 5 is the same as above, c represents an integer of 1 to 3, and s represents a number of 0 to 10.

[0026] Specific examples of component A-(iii) include the following: B 0.06 (ViMe2SiO 1 / 2 ) 0.01 (MeSiO 1 / 2 )0.39 (SiO 4 / 2 ) 0.54 (wherein B is a methacryloyloxy group-containing siloxane represented by the following formula): [ka]

[0027] In formula (6), c represents an integer of 1 to 3, preferably 1 or 2, and particularly preferably 1.

[0028] In formula (5), p, q, and r are numbers that satisfy p>0, q>0, and r>0, respectively, and that satisfy (p+q+r)=1.

[0029] The ratio (p+q) / r of M units to Q units in the component (iii) is preferably 0.3 to 2.0, and more preferably 0.5 to 1.0.

[0030] The number average molecular weight of component (iii), as determined by GPC measurement (standard polystyrene equivalent) using a THF solvent, is preferably 3,000 to 100,000, and more preferably 2,000 to 10,000.

[0031] Since component (iii) may be solid at 25°C, it may be dissolved in an organopolysiloxane such as component (i) above before use.

[0032] Component (A) may be used alone or in combination with two or more. Component (iii) may be solid at 25°C. Therefore, it may be dissolved in an organopolysiloxane such as component (i) or (ii), or a liquid organic compound containing a (meth)acrylic group. The weight ratio of component (iii) to component (i), component (ii), or the liquid organic compound containing a (meth)acrylic group when dissolved is preferably 1:0.1 to 1:10, more preferably 1:0.2 to 1:2. The viscosity of the solution at 25°C is preferably 100,000 mPa·s or less (typically 1 to 100,000 mPa·s), more preferably 10,000 mPa·s or less (e.g., 5 to 10,000 mPa·s). Viscosities exceeding 100,000 mPa·s at 25°C may result in poor fluidity and difficult handling.

[0033] In the composition of the present invention, the content of component (A) is preferably 40 to 97 mass %, more preferably 60 to 95 mass %.

[0034] (B) Component Component (B) is a lactam compound or a cyclic urethane compound having a vinyl group bonded to a nitrogen atom, and is a compound represented by the following formula (1) or (2). When the (meth)acrylic group contained in component (A) or the (meth)acrylate compound of component (D), which will be described later, is used, the (meth)acrylic group undergoes a radical polymerization reaction with component (B) to form a three-dimensional crosslink, yielding a cured silicone product.

[0035] The lactam compound represented by the following formula (1) or the cyclic urethane compound represented by the following formula (2) is easily and uniformly mixed with component (A), and the composition becomes transparent and does not exhibit problems such as separation even after being left to stand for a long period of time.

[0036] [ka] (In formulas (1) and (2), R 1 and R 2each independently represents a hydrogen atom, a substituted or unsubstituted alkyl group having 1 to 20 carbon atoms, an aryl group, or an aralkyl group, or R 1 and R 2 Two or more of these may be bonded to form a ring, and n is an integer of 2 to 10.)

[0037] R 1 and R 2 The alkyl group represented by the formula (I) is preferably an alkyl group having 1 to 20 carbon atoms, and examples thereof include methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, tert-butyl, n-hexyl, cyclohexyl, n-octyl, 2-ethylhexyl, and n-decyl groups. R 1 and R 2 The aryl group represented by the formula (I) is preferably an aryl group having 6 to 20 carbon atoms, and examples thereof include phenyl, tolyl, xylyl, and naphthyl groups. R 1 and R 2 The aralkyl group represented by the formula (I) is preferably an aralkyl group having 7 to 20 carbon atoms, and examples thereof include a benzyl group and a phenylethyl group. In addition, some or all of the hydrogen atoms bonded to carbon atoms of these alkyl groups, aryl groups, or aralkyl groups may be substituted with other substituents, specific examples of which include halogen-substituted or cyano-substituted alkyl groups such as chloromethyl, bromoethyl, trifluoropropyl, and cyanoethyl groups. Among these, R 1 and R 2 As the alkyl group, an alkyl group having 1 to 5 carbon atoms and a phenyl group are preferred, and a methyl group, an ethyl group and a phenyl group are more preferred. R 1 and R 2 When two or more of these are bonded to form a ring, R on the same carbon atom 1 and R 2 and may be bonded to form a spiro ring, and R on different carbon atoms may 1 and R 1 or R 2 and may be bonded to form a fused ring or a bridged ring.1 and R 2 The ring formed by combining two or more of the above may be a monocyclic or polycyclic ring, and there is no particular limitation on the number of atoms constituting the ring, but it is preferably a 5- or 6-membered ring. Also, R 1 and R 2 Some or all of the hydrogen atoms bonded to carbon atoms constituting the ring formed by bonding two or more of the above may also be substituted with the above-mentioned halogen atoms, cyano groups, etc.

[0038] Specific examples of component (B) include N-vinylpyrrolidone, N-vinylpiperidone, N-vinylcaprolactam, N-vinyloxazolidin-2-one, N-vinyl-[1,3]-oxazinan-2-one, and N-vinyl-[1,3]-oxazepan-2-one. N-vinylamide compounds such as those shown below can also be used. Among these, N-vinylpyrrolidone, N-vinylcaprolactam, and 5-methyl-3-vinyloxazolidin-2-one are preferred from the viewpoint of compatibility with component (A). [ka]

[0039] The present invention may use one or more types of component (B). When component (B) is solid, it may be dissolved in a solvent such as acetone or toluene, or in the (meth)acrylate compound of component (D), which will be described later, before being added to the silicone composition.

[0040] In the composition of the present invention, the blend amount of component (B) is preferably 3 to 40 mass %, more preferably 5 to 30 mass %. If the amount of component (B) in the composition is less than 3% by mass, it may not be effective in increasing the hardness or strength of the silicone cured product, while if it exceeds 40% by mass, it may not be miscible with the silicone, causing it to become cloudy or separate.

[0041] (C) Component Component (C) is a photopolymerization initiator that generates organic radical species by absorbing ultraviolet light, which act as the starting point for radical polymerization reactions. Specific examples of the photopolymerization initiator that can be used in the present invention include 2,2-diethoxyacetophenone, 2,2-dimethoxy-1,2-diphenylethan-1-one (Omnirad 651, manufactured by IGM Resins BV), 1-hydroxy-cyclohexyl-phenyl-ketone (Omnirad 184, manufactured by IGM Resins BV), ethyl phenyl(2,4,6-trimethylbenzoyl)phosphinate (Omnirad TPO-L, manufactured by IGM Resins BV), 2-hydroxy-2-methyl-1-phenyl-propan-1-one (Omnirad 1173, manufactured by IGM Resins BV), 2-hydroxy-1-{4-[4-(2-hydroxy-2-methyl-propionyl)-benzyl]-phenyl}-2-methyl-propan-1-one (Omnirad 127), 2-(dimethylamino)-2-(4-methylbenzyl)-1-(4-morpholinophenyl)butan-1-one (Omnirad 379, manufactured by IGM Resins BV), and phenylglyoxylic acid methyl ester (Omnirad MBF, manufactured by IGM Resins BV). Among these, from the viewpoint of compatibility with components (A), (B), and (C), 2,2-diethoxyacetophenone, 2-hydroxy-2-methyl-1-phenyl-propan-1-one (Omnirad 1173, manufactured by IGM Resins BV), and ethyl phenyl(2,4,6-trimethylbenzoyl)phosphinate (Omnirad TPO-L, manufactured by IGM Resins BV) are preferred. Component (C) may be used alone or in combination of two or more.

[0042] The amount of photopolymerization initiator added is an effective amount as a photopolymerization initiator, and is preferably in the range of 0.01 to 20 parts by mass, more preferably 0.5 to 5 parts by mass, relative to 100 parts by mass of the total mass of components (A) and (B), or, when a (meth)acrylic monomer of component (D) described below is used, the total mass plus the weight of that monomer. If the amount added is less than 0.01 part by mass, curability may be insufficient, and if added in an amount exceeding 20 parts by mass, deep curability may be impaired.

[0043] (D) Component Component (D) is a (meth)acrylate compound that does not have a siloxane skeleton and is optionally added to components (A), (B), and (C). It is used as a dissolving agent or viscosity modifier when component (B) is solid, and also contributes to further increasing the hardness and strength of the silicone cured product by radical polymerization with components (A) and (B). Component (D) differs from component (A) in that it does not have a siloxane skeleton.

[0044] Specific examples of component (D) include monofunctional acrylate compounds such as isoamyl acrylate, lauryl acrylate, stearyl acrylate, ethoxydiethylene glycol acrylate, methoxytriethylene glycol acrylate, 2-ethylhexyldiglycol acrylate, phenoxyethyl acrylate, phenoxydiethylene glycol acrylate, tetrahydrofurfuryl acrylate, 4-tert-butylcyclohexyl acrylate, and isobornyl acrylate; polyfunctional acrylate compounds such as triethylene glycol diacrylate, polytetramethylene glycol diacrylate, neopentyl glycol diacrylate, 1,6-hexanediol diacrylate, dimethyloltricyclodecane diacrylate, trimethylolpropane triacrylate, and pentaerythritol tetraacrylate; and mixtures thereof. Monofunctional acrylate compounds are particularly preferred as component (D), with 4-tert-butylcyclohexyl acrylate and isobornyl acrylate being particularly preferred.

[0045] The (meth)acrylate compound of component (D) may be used alone or in combination with other compounds, and the total amount added is preferably 0 to 50 parts by mass, more preferably 1 to 50 parts by mass, and even more preferably 1 to 30 parts by mass, per 100 parts by mass of components (A), (B), and (C). If the total amount added of component (D) exceeds 50 parts by mass per 100 parts by mass of components (A), (B), and (C), the silicone cured product may become brittle and prone to cracking, and cure shrinkage may also be significant.

[0046] Other ingredients In addition to the components (A) to (D), the UV-curable silicone composition of the present invention may also contain other components, such as those exemplified below, as long as the object of the present invention is not impaired. Examples of suitable adhesives include organic compounds having an adhesion-imparting group such as a carbonyl group, an epoxy group, or an alkoxysilyl group in one molecule to impart adhesion to the substrate; organopolysiloxanes having a condensation-curable group such as a silanol group or an alkoxysilyl group; metal catalysts such as organotitanium, organozirconium, or organobismuth that activate the adhesion-imparting group or catalyze the condensation-curing reaction; thixotropy control agents such as fumed silica; reinforcing agents such as crystalline silica; antioxidants; light stabilizers; heat resistance improvers such as metal oxides and metal hydroxides; flame retardants such as platinum group metal catalysts; thermal conductivity fillers such as alumina and crystalline silica; viscosity modifiers such as non-reactive silicone oils that do not have reactive functional groups; and conductivity imparting agents such as metal powders of silver, gold, etc.

[0047] Method for producing the composition The UV-curable silicone composition of the present invention can be produced by mixing the above-described components. The order in which the components are added is not particularly limited, and any known mixing device can be used for mixing. The UV-curable silicone composition of the present invention is transparent because the components are compatible with each other, and not only does it not become cloudy or separate immediately after production, but also does not exhibit problems such as cloudiness or separation even after being left to stand for a long period of time in a dark place. Specifically, after production of the UV-curable silicone composition of the present invention, even after being left to stand for one week in a sealed, light-shielded place at 23°C, no cloudiness or separation was observed by visual inspection. Furthermore, the ultraviolet-curable silicone composition of the present invention becomes a cured silicone product by the subsequent ultraviolet irradiation step.

[0048] UV irradiation process The ultraviolet irradiation step is carried out by irradiating the liquid silicone composition with ultraviolet light. A 365 nm UV-LED lamp, a metal halide lamp, a high-pressure mercury lamp, or the like can be used as a source of ultraviolet light. The ultraviolet irradiation method includes irradiating the composition with an appropriate amount of ultraviolet light. However, when performing the irradiation on a transparent substrate such as glass or a resin film, ultraviolet light may be irradiated through the glass or film. The ultraviolet irradiation may be carried out in air, or in a nitrogen or argon atmosphere to suppress the influence of oxygen, which inhibits curing. For ultraviolet irradiation, light having a wavelength of preferably 200 to 500 nm, more preferably 200 to 450 nm is used. From the viewpoint of preventing discoloration, the irradiation temperature is preferably 20 to 40°C, and the irradiation intensity is preferably 30 to 2,000 mW / cm. 2 The irradiation dose is preferably 150 to 100,000 mJ / cm 2 is preferred. [Example]

[0049] [Examples 1 to 9, Table 1; Comparative Examples 1 to 10, Table 2] The following components were mixed in the amounts (parts by mass) shown in Table 1 or Table 2 to prepare ultraviolet-curable silicone compositions. After mixing the components and thoroughly degassing, the silicone composition was irradiated with a UV-LED lamp with a wavelength of 365 nm at an irradiation intensity of 100 mW / cm under a nitrogen atmosphere. 2 and a dose of 3,000 mJ / cm 2 The resin was cured by irradiating it with ultraviolet light so that the cured resin was cured. The hardness of the cured product at 23°C was measured using a durometer A hardness tester in accordance with JIS-K6249. Furthermore, No. 2 dumbbell specimens were prepared from the cured product, and a tensile test was conducted in accordance with JIS-K6249 at 23°C and a speed of 500 mm / min to measure the tensile strength. Furthermore, a cured product having a thickness of 500 μm was prepared using the above procedure, and the transmittance at 800 nm was measured using a spectrophotometer. The appearance of the composition was visually inspected immediately after preparation, and then left to stand for one week in a sealed, light-shielded environment at 23°C, after which visual inspection was performed to determine whether any changes such as turbidity or separation occurred. In Comparative Examples 8 and 9, where the composition was visually inspected immediately after preparation and showed precipitation of component (B) and cloudiness, curing by the ultraviolet irradiation step and evaluation of the cured product were not performed.

[0050] Component (A) (A)-1 A chain-like dimethylpolysiloxane represented by the following formula ((meth)acrylic group content: 0.032 mol / 100 g, viscosity at 23°C: 23 Pa s) [ka]

[0051] (A)-2 An acryloyloxy-blocked organopolysiloxane represented by the following formula ((meth)acrylic group content: 0.014 mol / 100 g, viscosity at 23°C: 3,000 mPa·s) [ka] (In the formula, the arrangement of each siloxane unit in parentheses is random.)

[0052] (A)-3 A methacryloyloxy-blocked organopolysiloxane represented by the following formula ((meth)acrylic group content: 0.017 mol / 100 g, viscosity at 23°C: 3,800 mPa·s) [ka]

[0053] (A)-4 Siloxane units represented by the following formula / (ViMe2SiO 1 / 2 Unit) / (Me3SiO 1 / 2 Organopolysiloxane ((meth)acrylic group amount 0.070 mol / 100 g, number average molecular weight 5,700) with a molar ratio of (SiO2 unit) / (SiO2 unit) of 0.06 / 0.01 / 0.390 / 0.540 [ka]

[0054] (B) Component (B)-1 N-vinylcaprolactam (BASF, NVC) (B)-2 N-vinylpyrrolidone (purchased from Tokyo Chemical Industry Co., Ltd.) (B)-3 5-methyl-3-vinyloxazolidin-2-one (BASF, VMOX) (B)-4 N-vinylacetamide (for comparison, purchased from Tokyo Chemical Industry Co., Ltd.)

[0055] (C) Component (C)-1 Ethyl phenyl(2,4,6-trimethylbenzoyl)phosphinate (Omnirad TPO-L, manufactured by IGM Resins BV)

[0056] (D) Component (D)-1 4-tert-Butylcyclohexyl acrylate (TBCHA, manufactured by KJ Chemicals Co., Ltd.) (D)-2 Isobornyl acrylate (IB-XA, manufactured by Kyoeisha Chemical Co., Ltd.)

[0057] [Table 1]

[0058]

Table 2

Claims

1. (A) an organopolysiloxane having a (meth)acrylic group in the molecule; (B) a lactam compound or a cyclic urethane compound having a vinyl group bonded to a nitrogen atom, represented by the following formula (1) or (2): 【Chemical 1】 (In formulas (1) and (2), R 1 and R 2 each independently represents a hydrogen atom, a substituted or unsubstituted alkyl group having 1 to 20 carbon atoms, an aryl group, or an aralkyl group, or R 1 and R 2 Two or more of these may be bonded to form a ring, and n is an integer of 2 to 10. and (C) Photopolymerization initiator: effective amount An ultraviolet-curable silicone composition comprising:

2. 2. The ultraviolet-curable silicone composition according to claim 1, further comprising a (meth)acrylate compound having no siloxane skeleton as component (D).

3. 3. The ultraviolet-curable silicone composition according to claim 1, wherein a cured product having a thickness of 500 μm obtained by irradiating the ultraviolet-curable silicone composition according to claim 1 with ultraviolet light has a light transmittance of 95% or more for light at 800 nm.

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