Photoreactive organopolysiloxane, its production method, and photocurable composition

Abstract

To provide a photoreactive organopolysiloxane that has excellent compatibility to polymerizable organic compounds such as an acrylate compound, and has a photopolymerization initiation site capable of providing photocurability even in atmospheric air.SOLUTION: This photoreactive organopolysiloxane has a structural unit ratio represented by formula (1), and contains 1-90 mass% of a group having a photopolymerization initiation site. (1): (R13SiO1 / 2)a(R12SiO2 / 2)b(R1SiO3 / 2)c(SiO4 / 2)d. (In the formula, each R1 independently represents an alkyl group or an aryl group optionally having a substituent group and respectively including 1-20 carbon atoms or 6-20 carbon atoms, or a group having a photopolymerization initiation site, a represents a number of 0.1-0.8, b represents a number of 0-0.5, c represents a number of 0-0.5, and d represents a number of 0.2-0.9, and a+b+c+d=1 is satisfied).SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a photoreactive organopolysiloxane, a method for producing the same, and a photocurable composition. [Background technology]

[0002] Photocurable coating compositions are widely used to coat transparent plastic materials because they have a short curing time and can be cured at low temperatures. The plastic material used as the substrate has a lower surface hardness than glass and is easily scratched, so the photocurable coating film used must be scratch-resistant and abrasion-resistant. In this regard, Patent Document 1 reports that a photocurable coating composition containing a photopolymerization initiator and a polymerizable compound having a siloxane skeleton can give a photocurable coating film that combines excellent curability, weather resistance, and transparency.

[0003] Furthermore, when a photocurable coating composition is cured in the atmosphere, oxygen inhibits the curing of the coating film, and therefore a large amount of photopolymerization initiator must be used. On the other hand, since the crosslinking density of the film decreases as the amount of photopolymerization initiator added increases, the addition of an excessive amount of photopolymerization initiator causes deterioration of scratch resistance and abrasion resistance. Moreover, if the amount of photopolymerization initiator added is large, problems such as bleeding out of unreacted photopolymerization initiator and resulting deterioration of transparency and yellowing of the coating film may occur. Therefore, there is a demand for a photopolymerization initiator that can photocure a coating film even in the atmosphere and that does not cause a decrease in transparency or yellowing.

[0004] In this regard, Patent Documents 2 and 3 propose photocurable coating compositions using surfactant photoinitiators in which a photopolymerization initiation site is bonded to a silicone backbone. It has been reported that these cured coating films can increase the water contact angle on the surface, but the film hardness does not tend to improve. Furthermore, the introduction of a silicone backbone generally reduces compatibility with acrylic paints and acrylic urethane paints. Furthermore, photoinitiators that function as surfactants can cause deterioration in the appearance of the coating film due to surface segregation, making it difficult to increase the amount of photoinitiator added. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2016-132713 [Patent Document 2] Patent No. 5068413 [Patent Document 3] Patent No. 4675461 Summary of the Invention [Problem to be solved by the invention]

[0006] The present invention has been made in view of the above circumstances, and has as its object to provide a photoreactive organopolysiloxane that has excellent compatibility with polymerizable organic compounds such as acrylate compounds and has a photopolymerization initiation site that can impart photocurability even in the atmosphere, and a photocurable composition that gives a cured product that has excellent transparency and scratch resistance and is less prone to yellowing. [Means for solving the problem]

[0007] As a result of extensive research conducted by the present inventors to achieve the above-mentioned object, they discovered that specific photoreactive organopolysiloxanes in which a photopolymerization initiation site has been introduced by chemical bonding exhibit excellent compatibility with polymerizable organic compounds such as acrylate compounds and serve as photopolymerization initiators that can impart photocurability even in the atmosphere, and that photocurable compositions containing the photoreactive organopolysiloxanes of the present invention give cured products that have excellent transparency and scratch resistance and little yellowing, and thus completed the present invention.

[0008] That is, the present invention is 1. A photoreactive organopolysiloxane having a structural unit ratio represented by the following formula (1) and containing 1 to 90 mass % of a group having a photopolymerization initiation site: (R 1 3SiO 1 / 2 ) a (R 1 2SiO 2 / 2 ) b (R 1 SiO 3 / 2 ) c (SiO 4 / 2 ) d (1) (In the formula, R 1 are each independently an alkyl group having 1 to 20 carbon atoms or an aryl group having 6 to 20 carbon atoms, each of which may have a substituent, or a group having a photopolymerization initiation site, a is a number from 0.1 to 0.8, b is a number from 0 to 0.5, c is a number from 0 to 0.5, and d is a number from 0.2 to 0.9, and a+b+c+d=1 is satisfied. 2. The photoreactive organopolysiloxane of 1, wherein the group having a photopolymerization initiation site is any of groups represented by the following formulas (2) to (7): [ka] [In the formula, R 4 represents an aryl group having 6 to 20 carbon atoms which may have a substituent, and R 5 represents a hydrogen atom, or an optionally substituted alkyl group having 1 to 20 carbon atoms or an optionally substituted aryl group having 6 to 20 carbon atoms; R 6represents an arylene group having 6 to 20 carbon atoms which may have a substituent, and R 7 represents a halogen atom, or an alkyl group having 1 to 20 carbon atoms, an alkenyl group having 2 to 20 carbon atoms, or an aryl group having 6 to 20 carbon atoms, each of which may have a substituent; R 8 represents an aryl group having 6 to 20 carbon atoms which may have a substituent, or -R 6 -SiR 2 (3-n) R 3 n A group represented by (R 2 each independently represents a hydrogen atom, or an alkyl group having 1 to 20 carbon atoms, an alkenyl group having 2 to 20 carbon atoms, or an aryl group having 6 to 20 carbon atoms, each of which may have a substituent; R 3 each independently represents a hydroxyl group, an alkoxy group having 1 to 6 carbon atoms, or a halogen atom; R 6 has the same meaning as above, and n represents an integer of 1 to 3. X represents a single bond or an alkylene group having 1 to 20 carbon atoms which may have a substituent and which may contain an ether structure, ester structure, amide structure, urethane structure, urea structure, sulfide structure or sulfoxide structure in the chain, and the dashed line represents a bond to the silicon atom. 3. The photoreactive organopolysiloxane of 1 or 2, which contains 15 to 80 mass % of the group having the photopolymerization initiation site. 4. A photoreactive organopolysiloxane in which a is a number from 0.3 to 0.7, b is a number from 0 to 0.2, c is a number from 0 to 0.2, and d is a number from 0.3 to 0.7. 5. A photoreactive organopolysiloxane in which b and c are 0. 6. A method for producing a photoreactive organopolysiloxane, comprising the step of reacting an organohydrogenpolysiloxane having a constitutional unit ratio represented by the following formula (8) with one or more compounds having a photopolymerization initiation site represented by the following formulas (9) to (14), A method for producing a photoreactive organopolysiloxane, in which the proportion of the compound having a photopolymerization initiation moiety represented by the following formulas (9) to (14) is 1 to 90 mass% based on the total of the organohydrogenpolysiloxane having a constitutional unit ratio represented by the following formula (8) and the compound having a photopolymerization initiation moiety represented by the following formulas (9) to (14): (R 9 3SiO 1 / 2 ) a (R 9 2SiO 2 / 2 ) b (R 9 SiO 3 / 2 ) c (SiO 4 / 2 ) d (8) (In the formula, R 9 each independently represents an alkyl group having 1 to 20 carbon atoms or an aryl group having 6 to 20 carbon atoms, each of which may have a substituent, or a hydrogen atom; a is a number from 0.1 to 0.8, b is a number from 0 to 0.5, c is a number from 0 to 0.5, and d is a number from 0.2 to 0.9, and a+b+c+d=1 is satisfied. [ka] [In the formula, R 4 represents an aryl group having 6 to 20 carbon atoms which may have a substituent, and R 5 represents a hydrogen atom, or an optionally substituted alkyl group having 1 to 20 carbon atoms or an optionally substituted aryl group having 6 to 20 carbon atoms; R 6 represents an arylene group having 6 to 20 carbon atoms which may have a substituent, and R 7 represents a halogen atom, or an alkyl group having 1 to 20 carbon atoms, an alkenyl group having 2 to 20 carbon atoms, or an aryl group having 6 to 20 carbon atoms, each of which may have a substituent; R 8 represents an aryl group having 6 to 20 carbon atoms which may have a substituent, or -R 6 -SiR 2 (3-n) R 3 n A group represented by (R 2each independently represents a hydrogen atom, or an alkyl group having 1 to 20 carbon atoms, an alkenyl group having 2 to 20 carbon atoms, or an aryl group having 6 to 20 carbon atoms, each of which may have a substituent; R 3 each independently represents a hydroxyl group, an alkoxy group having 1 to 6 carbon atoms, or a halogen atom; R 6 has the same meaning as above, and n represents an integer of 1 to 3.) and Y represents an alkenyl group having 2 to 20 carbon atoms or a hydroxyalkyl group having 1 to 20 carbon atoms, which may have a substituent and which may contain an ether structure, ester structure, amide structure, urethane structure, urea structure, sulfide structure or sulfoxide structure in the chain.] 7. The method for producing a photoreactive organopolysiloxane according to 6, wherein the proportion of the compound having a photopolymerization initiation moiety represented by the formulas (9) to (14) is 15 to 80 mass% based on the total of the organohydrogenpolysiloxane having the structural unit ratio represented by the formula (8) and the compound having a photopolymerization initiation moiety represented by the formulas (9) to (14). 8. The method for producing a photoreactive organopolysiloxane according to 6, wherein a is a number from 0.3 to 0.7, b is a number from 0 to 0.2, c is a number from 0 to 0.2, and d is a number from 0.3 to 0.7. 9. The method for producing the photoreactive organopolysiloxane of 6, wherein b and c are 0. 10. A method comprising the step of subjecting an organohydrogenpolysiloxane having the constitutional unit ratio represented by the formula (8) to a hydrosilylation reaction with one or more compounds having a photopolymerization initiation site represented by the formulas (9) to (14), a method for producing a photoreactive organopolysiloxane according to claim 6, wherein Y is an alkenyl group having 2 to 20 carbon atoms which may have a substituent and which may contain an ether structure, an ester structure, an amide structure, a urethane structure, a urea structure, a sulfide structure, or a sulfoxide structure in the chain; 11. A method for producing a polymerizable composition comprising the steps of: subjecting an organohydrogenpolysiloxane having a constitutional unit ratio represented by the formula (8) to a dehydrogenation condensation reaction with one or more compounds having a photopolymerization initiation site represented by the formulas (9) to (14), 6. A method for producing a photoreactive organopolysiloxane according to claim 6, wherein Y is a hydroxyalkyl group having 1 to 20 carbon atoms, which may have a substituent and which may contain an ether structure, an ester structure, an amide structure, a urethane structure, a urea structure, a sulfide structure, or a sulfoxide structure in the chain; 12. A method for producing a photoreactive organopolysiloxane according to 6, comprising a step of subjecting a compound having an aliphatic unsaturated bond and no photopolymerization initiation site to a hydrosilylation reaction with an organohydrogenpolysiloxane having the structural unit ratio represented by formula (8) above, or a reaction product of an organohydrogenpolysiloxane having the structural unit ratio represented by formula (8) above with one or more compounds having a photopolymerization initiation site represented by formulas (9) to (14) above; 13. A method for producing a photoreactive organopolysiloxane according to 6, comprising a step of subjecting a compound having a hydroxyl group but not having a photopolymerization initiation site to a dehydrogenative condensation reaction with an organohydrogenpolysiloxane having the structural unit ratio represented by formula (8) above, or a reaction product of an organohydrogenpolysiloxane having the structural unit ratio represented by formula (8) above with one or more compounds having a photopolymerization initiation site represented by formulas (9) to (14) above; 14. A photocurable composition comprising the photoreactive organopolysiloxane of 1 and a compound having a radically polymerizable unsaturated bond. 15. A cured product obtained by curing the photocurable composition of 14. to provide. [Effects of the Invention]

[0009] The photoreactive organopolysiloxane of the present invention has a photopolymerization initiation site introduced into the polysiloxane skeleton via a chemical bond, which makes it possible to prevent bleed-out of the photopolymerization initiator when used in a photocurable composition, and thus to prevent the accompanying deterioration in transparency and yellowing of the coating film. Furthermore, the photoreactive organopolysiloxane of the present invention has excellent compatibility with polymerizable organic compounds such as acrylate compounds, allowing for increased amounts to be added to curable compositions. In addition, the polymerization of the polymerizable monomer begins at the photopolymerization initiation site bonded to the polysiloxane skeleton, and the polysiloxane becomes a crosslinking point that is incorporated into the coating film, preventing a decrease in coating film hardness due to the photopolymerization initiator and imparting excellent atmospheric photocurability. As described above, by adding the photoreactive organopolysiloxane of the present invention to a photocurable composition, a coating film can be effectively cured in the atmosphere, and a cured product having excellent scratch resistance, transparency, and low yellowing can be obtained. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 2 is a graph showing the relationship between the scratch resistance and the effective photoinitiator content of the cured films produced in Examples 2-1 to 2-3 and Comparative Examples 2-1 to 2-3. [Figure 2] FIG. 2 is a graph showing the relationship between the initial Hz and the effective photoinitiator content of the cured films produced in Examples 2-1 to 2-3 and Comparative Examples 2-1 to 2-3. [Figure 3] FIG. 2 is a graph showing the relationship between the yellow index (YI) and the effective photoinitiator content of the cured films prepared in Examples 2-1 to 2-3 and Comparative Examples 2-1 to 2-3. DETAILED DESCRIPTION OF THE INVENTION

[0011] The present invention will be specifically described below. (1) Photoreactive organopolysiloxane The photoreactive organopolysiloxane of the present invention has a structural unit ratio represented by the following formula (1) and contains 1 to 90 mass % of a group having a photopolymerization initiation site. 1 / 2 ) is the siloxane unit represented by M unit, (RSiO 2 / 2 ) is a siloxane unit represented by D unit, (RSiO 3 / 2 ) is a siloxane unit represented by T unit, (SiO 4 / 2 ) is sometimes called a Q unit. (R 1 3SiO 1 / 2 )a (R 1 2SiO 2 / 2 ) b (R 1 SiO 3 / 2 ) c (SiO 4 / 2 ) d (1)

[0012] In the above formula (1), R 1 The alkyl group having 1 to 20 carbon atoms, preferably 1 to 5 carbon atoms, may be linear, cyclic, or branched, and specific examples thereof include linear or branched alkyl groups such as methyl, ethyl, n-propyl, i-propyl, n-butyl, s-butyl, t-butyl, n-pentyl, n-hexyl, n-heptyl, n-octyl, n-nonyl, n-decyl, n-undecyl, n-dodecyl, n-tridecyl, n-tetradecyl, n-pentadecyl, n-hexadecyl, n-heptadecyl, n-octadecyl, n-nonadecyl, and n-icosyl groups, and cycloalkyl groups such as cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl, and cyclooctyl groups. Of these, linear alkyl groups having 1 to 3 carbon atoms are preferred, and a methyl group is more preferred. R 1 Examples of the aryl group having 6 to 20 carbon atoms, preferably 6 to 12 carbon atoms, include phenyl, biphenyl, and naphthyl groups, with the phenyl group being preferred. These alkyl and aryl groups may have a substituent, and examples of such a substituent include alkoxy groups such as methoxy and ethoxy groups; halogen atoms such as fluorine atoms, chlorine atoms, and bromine atoms; hydroxyl groups; cyano groups; and isocyanate groups.

[0013] R 1The photopolymerization initiation moiety contained in the group having a photopolymerization initiation moiety is not particularly limited as long as it has a structure that is excited by exposure to light and provides excitation energy to a compound containing a radical polymerizable group to initiate a curing reaction. Specific examples thereof include a benzyl ketal structure, an α-hydroxyalkylphenone structure, an α-aminoalkylphenone structure, an acylphosphine oxide structure, a benzoylformic acid structure, a benzoyl formate ester structure, a benzophenone structure, an oxime ester structure, a titanocene structure, an o-benzoylbenzoic acid ester structure, a benzoin structure, a benzoin ether structure, a xanthone structure, a thioxanthone structure, a disulfide structure, a quinone structure, a halogenated hydrocarbon, an amine, and an organic peroxide, and combinations of these structures are also possible.

[0014] In the present invention, the group having a photopolymerization initiation site is preferably a group represented by the following formulas (2) to (7).

[0015] [ka]

[0016] In each of the above formulas, R 4 represents an aryl group having 6 to 20 carbon atoms which may have a substituent, and R 5 represents a hydrogen atom, or an optionally substituted alkyl group having 1 to 20 carbon atoms or an optionally substituted aryl group having 6 to 20 carbon atoms; R 6 represents an arylene group having 6 to 20 carbon atoms which may have a substituent, and R 7 represents a halogen atom, or an alkyl group having 1 to 20 carbon atoms, an alkenyl group having 2 to 20 carbon atoms, or an aryl group having 6 to 20 carbon atoms, each of which may have a substituent; R 8 represents an aryl group having 6 to 20 carbon atoms which may have a substituent, or -R 6 -SiR 2 (3-n) R 3 n A group represented by (R 2each independently represents a hydrogen atom, or an alkyl group having 1 to 20 carbon atoms, an alkenyl group having 2 to 20 carbon atoms, or an aryl group having 6 to 20 carbon atoms, each of which may have a substituent; R 3 each independently represents a hydroxyl group, an alkoxy group having 1 to 6 carbon atoms, or a halogen atom; R 6 has the same meaning as above, and n represents an integer of 1 to 3.) and Y represents an alkenyl group having 2 to 20 carbon atoms or a hydroxyalkyl group having 1 to 20 carbon atoms, which may have a substituent and which may contain an ether structure, ester structure, amide structure, urethane structure, urea structure, sulfide structure or sulfoxide structure in the chain.

[0017] R 4 Specific examples of the aryl group having 6 to 20 carbon atoms, preferably 6 to 12 carbon atoms, which may have a substituent, include phenyl, 4-methoxyphenyl, 4-hydroxyphenyl, 4-(2-hydroxyethoxy)phenyl, biphenyl, and naphthyl groups, and from the viewpoints of storage stability and photopolymerizability, phenyl and 4-(2-hydroxyethoxy)phenyl groups are preferred.

[0018] R 5 The alkyl group having 1 to 20 carbon atoms, preferably 1 to 5 carbon atoms, which may have a substituent, is 1 Examples of the alkyl group include the same alkyl groups as those exemplified above, and the substituents thereof include the same groups as those mentioned above. R 5 The aryl group having 6 to 20 carbon atoms, preferably 6 to 12 carbon atoms, which may have a substituent, is exemplified by the above-mentioned R 1 Examples of the aryl groups include the same aryl groups as those exemplified above, and the substituents thereof include the same groups as those mentioned above. Among these, R 5 is preferably a hydrogen atom or a phenyl group.

[0019] R 6Specific examples of the arylene group having 6 to 20 carbon atoms, preferably 6 to 12 carbon atoms, which may have a substituent include phenylene, methylphenylene, dimethylphenylene, biphenylene, and naphthylene groups, with phenylene and dimethylphenylene groups being preferred.

[0020] R 7 Examples of the halogen atom include fluorine, chlorine, bromine and iodine atoms. R 7 The alkyl group having 1 to 20 carbon atoms, preferably 1 to 5 carbon atoms, may be linear, branched, or cyclic, and specific examples thereof include methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, n-pentyl, n-hexyl, cyclohexyl, n-heptyl, and n-octyl groups. R 7 The alkenyl group having 2 to 20 carbon atoms, preferably 2 to 10 carbon atoms, may be linear, branched, or cyclic, and specific examples thereof include vinyl, allyl, butenyl, hexenyl, and octenyl groups. R 7 Examples of the aryl group having 6 to 20 carbon atoms, preferably 6 to 12 carbon atoms, include phenyl, biphenyl, and naphthyl groups. These alkyl groups, alkenyl groups, and alkenyl groups may have a substituent, and examples of such a substituent include alkoxy groups such as methoxy and ethoxy groups; halogen atoms such as fluorine atoms, chlorine atoms, and bromine atoms; hydroxyl groups; and cyano groups. The aryl group may also have a substituent, and examples of such a substituent include alkyl groups such as methyl and ethyl groups; alkoxy groups such as methoxy and ethoxy groups; halogen atoms such as fluorine atoms, chlorine atoms, and bromine atoms; hydroxyl groups; and cyano groups. Among these, R 7 As the alkyl group, a phenyl group is preferred.

[0021] R 8 The aryl group having 6 to 20 carbon atoms, which may have a substituent, is 4Examples of the aryl group include the same groups as those exemplified above, but a phenyl group is preferred. Also, R 8 -R 6 -SiR 2 (3-n) R 3 n A group represented by (R 2 each independently represents a hydrogen atom, or an alkyl group having 1 to 20 carbon atoms, an alkenyl group having 2 to 20 carbon atoms, or an aryl group having 6 to 20 carbon atoms, each of which may have a substituent; R 3 each independently represents a hydroxyl group, an alkoxy group having 1 to 6 carbon atoms, or a halogen atom; R 6 has the same meaning as above, and n represents an integer of 1 to 3.

[0022] R 2 The alkyl group having 1 to 20 carbon atoms, the alkenyl group having 2 to 20 carbon atoms, and the aryl group having 6 to 20 carbon atoms include the above-mentioned R 7 Among them, alkyl groups having 1 to 3 carbon atoms with little steric hindrance are preferred, and methyl groups are more preferred. R 3 The halogen atoms in the above R 7 The atoms are the same as those exemplified above. R 3 The alkyl group in the alkoxy group having 1 to 6 carbon atoms may be straight-chain, branched-chain, or cyclic, and specific examples thereof include methoxy, ethoxy, and n-propoxy groups. Among these, R 3 is preferably a methoxy group.

[0023] n is an integer of 1 to 3, but in consideration of reactivity, 2 or 3 is preferred, and 3 is more preferred.

[0024] X represents a single bond or an alkylene group having 1 to 20 carbon atoms which may have a substituent and which may contain an ether bond, an ester structure, an amide structure, a urethane structure, a urea structure, a sulfide structure, or a sulfoxide structure in the chain. The alkylene group having 1 to 20 carbon atoms may be linear, branched, or cyclic, and specific examples thereof include methylene, ethylene, trimethylene, propylene, tetramethylene, pentamethylene, hexamethylene, heptamethylene, octamethylene, nonamethylene, and cyclohexylene groups. These alkylene groups have particularly good compatibility with organic materials when they have a large number of carbon atoms (8 or more carbon atoms), and are particularly effective in improving scratch resistance when introduced into a cured film when they have a small number of carbon atoms (3 or less carbon atoms). The alkylene group may have a substituent, and examples of such a substituent include an alkoxy group such as a methoxy or ethoxy group; a halogen atom such as a fluorine atom, a chlorine atom, or a bromine atom; a hydroxyl group; and a cyano group. Furthermore, an ether structure, an ester structure, an amide structure, a urethane structure, a urea structure, a sulfide structure, a sulfoxide structure, or the like may be present as part of the structure.

[0025] The photoreactive organopolysiloxane of the present invention contains 1 to 90 mass %, preferably 10 to 85 mass %, and more preferably 15 to 80 mass % of groups having a photopolymerization initiation site. If the content of groups having a photopolymerization initiation site is less than 1 mass %, the photocurability may be insufficient, whereas if it exceeds 90 mass %, the transparency of the obtained cured product may decrease or yellowing may occur.

[0026] a, b, c, and d are numbers that satisfy a+b+c+d=1. Here, a (i.e., the content ratio of M units) is a number from 0.1 to 0.8, preferably from 0.3 to 0.7, and more preferably from 0.5 to 0.7. If a is less than 0.1, the storage stability of the photoreactive organopolysiloxane and its compatibility with polymerizable organic compounds such as acrylate compounds may be insufficient. On the other hand, if a exceeds 0.8, the hardness of the resulting cured product may decrease. b (i.e., the content ratio of D units) is a number from 0 to 0.5, preferably a number from 0 to 0.2, and more preferably 0. If b exceeds 0.5, the hardness of the resulting cured product may decrease. c (i.e., the content ratio of T units) is a number from 0 to 0.5, preferably a number from 0 to 0.2, and more preferably 0. If c exceeds 0.5, the compatibility between the photoreactive organopolysiloxane and the polymerizable organic compound such as an acrylate compound may be insufficient. d (i.e., the content ratio of Q units) is a number from 0.2 to 0.9, preferably from 0.3 to 0.7, and more preferably from 0.3 to 0.5. If d is less than 0.2, the hardness of the resulting cured product may decrease. On the other hand, if d exceeds 0.9, the storage stability of the photoreactive organopolysiloxane and its compatibility with polymerizable organic compounds such as acrylate compounds may be insufficient. The ratio of each constituent unit of the photoreactive organopolysiloxane is, for example, 29 This can be confirmed by a known method using Si-NMR (nuclear magnetic resonance) spectroscopy.

[0027] The number-average molecular weight of the photoreactive organopolysiloxane of the present invention is not particularly limited, but is preferably 1,000 to 30,000, more preferably 2,000 to 20,000, and even more preferably 3,000 to 15,000. A number-average molecular weight of 20,000 or less prevents high viscosity, improves workability, and provides excellent storage stability. Furthermore, a number-average molecular weight of 1,000 or more improves curability and the hardness of the resulting cured product. The number average molecular weight in the present invention is a polystyrene-equivalent value measured by gel permeation chromatography (GPC) (the same applies hereinafter).

[0028] (2) Method for producing photoreactive organopolysiloxane Next, an example of the method for producing the photoreactive organopolysiloxane of the present invention will be described in detail. The photoreactive organopolysiloxane of the present invention can be obtained by a production method including a step of introducing, into an organohydrogenpolysiloxane having a constitutional unit ratio represented by the following formula (8), one or more compounds having a photopolymerization initiation site represented by the following formulas (9) to (14), via a hydrosilylation reaction or a dehydrogenation reaction. (R 9 3SiO 1 / 2 ) a (R 9 2SiO 2 / 2 ) b (R 9 SiO 3 / 2 ) c (SiO 4 / 2 ) d (8)

[0029] [ka] (In the formula, R 4 , R 5 , R 6 , R 7 and R 8 represents the same meaning as in the above formulas (2) to (7), and Y represents an alkenyl group having 2 to 20 carbon atoms or a hydroxyalkyl group having 1 to 20 carbon atoms, which may have a substituent and may contain an ether structure, ester structure, amide structure, urethane structure, urea structure, sulfide structure or sulfoxide structure in the chain.

[0030] In the above formula (8), R 9 are each independently an alkyl group having 1 to 20 carbon atoms or an aryl group having 6 to 20 carbon atoms, each of which may have a substituent, or a hydrogen atom, and at least one in one molecule is a hydrogen atom. a is a number from 0.1 to 0.8, b is a number from 0 to 0.5, c is a number from 0 to 0.5, and d is a number from 0.2 to 0.9, and a+b+c+d=1 is satisfied.

[0031] R 9The alkyl group having 1 to 20 carbon atoms, preferably 1 to 5 carbon atoms, may be linear, cyclic, or branched, and specific examples thereof include linear or branched alkyl groups such as methyl, ethyl, n-propyl, i-propyl, n-butyl, s-butyl, t-butyl, n-pentyl, n-hexyl, n-heptyl, n-octyl, n-nonyl, n-decyl, n-undecyl, n-dodecyl, n-tridecyl, n-tetradecyl, n-pentadecyl, n-hexadecyl, n-heptadecyl, n-octadecyl, n-nonadecyl, and n-icosyl groups, and cycloalkyl groups such as cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl, and cyclooctyl groups, and of these, a methyl group is preferred. Examples of the aryl group having 6 to 20 carbon atoms, preferably 6 to 12 carbon atoms, include phenyl, biphenyl, and naphthyl groups, with the phenyl group being preferred. These alkyl and aryl groups may have a substituent, and examples of such a substituent include alkoxy groups such as methoxy and ethoxy groups; halogen atoms such as fluorine atoms, chlorine atoms, and bromine atoms; hydroxyl groups; cyano groups; and isocyanate groups.

[0032] The hydrogen atoms bonded to silicon atoms (Si-H groups) in organohydrogenpolysiloxanes serve as reaction sites when functional groups having photopolymerization initiation sites are introduced using hydrosilylation or dehydrocondensation reactions. R contained in one molecule of organohydrogenpolysiloxane 9 The number of hydrogen atoms relative to the total number of units is a number sufficient to ensure that the proportion of compounds having a photopolymerization initiation moiety represented by the following formulas (9) to (14), which are subjected to a hydrosilylation reaction or dehydrocondensation reaction described below, is 1 to 90 mass %, preferably 10 to 85 mass %, and more preferably 15 to 80 mass %, of the total of the organohydrogenpolysiloxane having the structural unit ratio represented by the following formula (8) and the compounds having a photopolymerization initiation moiety represented by the following formulas (9) to (14).

[0033] a, b, c, and d are numbers that satisfy a+b+c+d=1. Here, a (i.e., the content ratio of M units) is a number from 0.1 to 0.8, preferably from 0.3 to 0.7, and more preferably from 0.5 to 0.7. If a is less than 0.1, the storage stability of the photoreactive organopolysiloxane and its compatibility with polymerizable organic compounds such as acrylate compounds may be insufficient. On the other hand, if a exceeds 0.8, the hardness of the cured product obtained using the photoreactive organopolysiloxane may be reduced. b (i.e., the content ratio of D units) is a number from 0 to 0.5, preferably a number from 0 to 0.2, and more preferably 0. If b exceeds 0.5, the hardness of the cured product obtained using the photoreactive organopolysiloxane may decrease. c (i.e., the content ratio of T units) is a number from 0 to 0.5, preferably a number from 0 to 0.2, and more preferably 0. If c exceeds 0.5, the compatibility between the photoreactive organopolysiloxane and the polymerizable organic compound such as an acrylate compound may be insufficient. d (i.e., the content ratio of Q units) is a number from 0.2 to 0.9, preferably from 0.3 to 0.7, and more preferably from 0.3 to 0.5. If d is less than 0.2, the hardness of the resulting cured product may decrease. On the other hand, if d exceeds 0.9, the storage stability of the photoreactive organopolysiloxane and its compatibility with polymerizable organic compounds such as acrylate compounds may be insufficient.

[0034] The number-average molecular weight of the organohydrogenpolysiloxane is not particularly limited, but is preferably 500 to 10,000, more preferably 800 to 7,000, and even more preferably 1,000 to 5,000. A number-average molecular weight of 10,000 or less prevents high viscosity, improves workability, and provides excellent storage stability. Furthermore, a number-average molecular weight of 500 or more improves the curability of the photoreactive organopolysiloxane and the hardness of the resulting cured product.

[0035] The organohydrogenpolysiloxane, which is a raw material used in the method for producing a photoreactive organopolysiloxane of the present invention, can be produced by a known method, for example, as described in JP-A-2017-75283.

[0036] In the above formulas (9) to (14), Y is an alkenyl group having 2 to 20 carbon atoms or a hydroxyalkyl group having 1 to 20 carbon atoms, which may have a substituent and may contain an ether structure, ester structure, amide structure, urethane structure, urea structure, sulfide structure, or sulfoxide structure in the chain, and is a group that undergoes a hydrosilylation reaction (in the case of an alkenyl group) or a dehydrocondensation reaction (in the case of a hydroxyalkyl group) with Si-H groups in the organohydrogenpolysiloxane.

[0037] Examples of the alkenyl group having 2 to 20 carbon atoms, preferably 2 to 10 carbon atoms, include vinyl, allyl, 3-butenyl, 5-hexenyl, 7-octenyl, 9-decenyl, and 11-dodecenyl groups. Examples of the hydroxyalkyl group having 1 to 20 carbon atoms, preferably 1 to 10 carbon atoms, include hydroxymethyl, 2-hydroxyethyl, 3-hydroxypropyl, 4-hydroxybutyl, 5-hydroxypentyl, 6-hydroxyhexyl, and 8-hydroxyoctyl groups. These alkenyl groups or hydroxyalkyl groups have particularly good compatibility with organic materials when they have a large number of carbon atoms (8 or more carbon atoms), and are particularly effective in improving scratch resistance when introduced into a cured film when they have a small number of carbon atoms (3 or less carbon atoms). The alkenyl group or hydroxyalkyl group may have an unsaturated bond or a substituent other than a hydroxyl group in the structure. Examples of such a substituent include alkoxy groups such as methoxy and ethoxy groups; halogen atoms such as fluorine atoms, chlorine atoms, and bromine atoms; hydroxyl groups; and cyano groups. Furthermore, these structures may include an ether structure, ester structure, amide structure, urethane structure, urea structure, sulfide structure, sulfoxide structure, etc.

[0038] In the hydrosilylation reaction in the method for producing a photoreactive organopolysiloxane of the present invention, it is preferable to add a catalyst to promote the reaction between the alkenyl group in the compound having a photopolymerization initiation site represented by any of the above formulas (9) to (14) and the Si-H group in the organohydrogenpolysiloxane represented by the above formula (8). Examples of hydrosilylation reaction catalysts include platinum black, chloroplatinic acid, alcohol-modified chloroplatinic acid, and complexes of chloroplatinic acid with olefin, vinylsiloxane, acetylene alcohol, etc. The amount added may be appropriately selected depending on the desired curing rate, but is usually 0.1 to 500 ppm, and preferably 1 to 200 ppm, calculated as the mass of platinum group metal relative to the mass of the compound having a photopolymerization initiation site used in the reaction.

[0039] The conditions for the hydrosilylation reaction are not particularly limited, but a reaction temperature of 20 to 120°C and a reaction time of 1 to 8 hours are preferred, and a reaction temperature of 20 to 100°C and a reaction time of 1 to 6 hours are more preferred.

[0040] In the dehydrogenation condensation reaction in the method for producing a photoreactive organopolysiloxane of the present invention, it is preferable to add a catalyst to promote the reaction between the hydroxy group in the compound having a photopolymerization initiation site represented by any of the above formulas (9) to (14) and the Si-H group in the organohydrogenpolysiloxane represented by the above formula (8). Examples of dehydrocondensation reaction catalysts include metal compounds such as palladium complexes, platinum complexes, and palladium on carbon, basic compounds such as diethylhydroxyamine, and Lewis acid compounds such as tris(pentafluorophenyl)borane. The amount of catalyst added may be appropriately selected depending on the desired curing rate, but is usually 0.05 to 2.0 mol %, and preferably 0.1 to 1.0 mol %, based on the compound having a photopolymerization initiation site to be subjected to the reaction.

[0041] The catalyst used in the dehydrogenation condensation reaction may be removed after the reaction by a known method using an adsorbent, etc. Specifically, basic compounds such as diethylhydroxyamine can be adsorbed and removed using an anion exchange resin such as Kyoward 700 (manufactured by Kyowa Chemical Industry Co., Ltd.), and solid catalysts such as palladium on carbon can be removed by filtration.

[0042] The conditions for the dehydrogenation condensation reaction are not particularly limited, but a reaction temperature of 20 to 150°C and a reaction time of 1 to 8 hours are preferred, and a reaction temperature of 20 to 120°C and a reaction time of 1 to 6 hours are more preferred.

[0043] The proportion of the compound having a photopolymerization initiation site represented by the above formulas (9) to (14) to be subjected to a hydrosilylation reaction or a dehydrocondensation reaction is 1 to 90 mass %, preferably 10 to 85 mass %, and more preferably 15 to 80 mass %, of the total of the organohydrogenpolysiloxane having the structural unit ratio represented by the above formula (8) and the compound having a photopolymerization initiation site represented by the above formulas (9) to (14). If the proportion of the compound having a photopolymerization initiation site is less than 1 mass %, the photocurability of the resulting photoreactive organopolysiloxane may be insufficient, while if it exceeds 90 mass %, the transparency of the resulting cured product may decrease or yellowing may occur.

[0044] Furthermore, the method may include a step of subjecting a compound having an aliphatic unsaturated bond or a hydroxyl group but no photopolymerization initiation site to a hydrosilylation reaction (when the compound has an aliphatic unsaturated bond) or a dehydrogenation condensation reaction (when the compound has a hydroxyl group) with an organohydrogenpolysiloxane having the structural unit ratio represented by formula (8) above or a reaction product of an organohydrogenpolysiloxane having the structural unit ratio represented by formula (8) above and a compound having a photopolymerization initiation site represented by any of formulas (9) to (14) above.

[0045] Examples of compounds having an aliphatic unsaturated bond or a hydroxyl group but no photopolymerization initiation site include compounds having an aliphatic unsaturated bond such as pentene, hexene, heptene, octene, nonene, decene, dodecene, styrene, and allylbenzene; and compounds having a hydroxyl group such as methanol, ethanol, propanol, butanol, pentanol, hexanol, heptanol, octanol, ethylene glycol monomethyl ether, propylene glycol monomethyl ether, ethylene glycol monoethyl ether, propylene glycol monoethyl ether, diethylene glycol monomethyl ether, dipropylene glycol monomethyl ether, diethylene glycol monoethyl ether, dipropylene glycol monoethyl ether, and benzyl alcohol. These compounds are reacted with an organohydrogenpolysiloxane having the structural unit ratio represented by the above formula (8) or with a reaction product of an organohydrogenpolysiloxane having the structural unit ratio represented by the above formula (8) and a compound having a photopolymerization initiation site represented by the above formulas (9) to (14), and an alkyl group or an oxyalkyl group is introduced, thereby making it possible to adjust the storage stability, viscosity, or compatibility with acrylate compounds, etc., of the photoreactive organopolysiloxane.

[0046] In the method for producing a photoreactive organopolysiloxane of the present invention, an organic solvent may be used. The organic solvent is preferably an aprotic organic solvent to prevent side reactions and catalyst deactivation. Specific examples include ethers such as dioxane and tetrahydrofuran, and aromatic hydrocarbons such as toluene, o-xylene, m-xylene, and p-xylene. These may be used alone or in combination.

[0047] (3) Photocurable composition The above-described photoreactive organopolysiloxane of the present invention can be used as a photocurable composition by mixing it with a compound having a radically polymerizable unsaturated bond. The compound having a radically polymerizable unsaturated bond is not particularly limited as long as it is a curable monomer or oligomer having one or more radically polymerizable unsaturated bonds. Specific examples thereof include (meth)acrylate compounds, styrene compounds, maleimide compounds, fumaric acid ester compounds, and mixtures of thiol compounds and compounds having unsaturated bonds, and these may be used alone or in combination of two or more.

[0048] The (meth)acrylate compound may be either monofunctional or polyfunctional. In the present invention, the term "(meth)acrylate" means "acrylate" or "methacrylate." Specific examples of monofunctional (meth)acrylates include ethyl acrylate, butyl acrylate, ethylhexyl acrylate, 2-hydroxyethyl acrylate, isobornyl acrylate, and tetrahydrofurfuryl acrylate.

[0049] Specific examples of polyfunctional (meth)acrylates include 1,4-butanediol diacrylate, 1,6-hexanediol diacrylate (HDDA), tetraethylene glycol diacrylate, neopentyl glycol diacrylate, ethylene glycol diacrylate, polyethylene glycol (n=2 to 15) diacrylate, polypropylene glycol (n=2 to 15) diacrylate, polybutylene glycol (n=2 to 15) diacrylate, 2,2-bis(4-acryloxyethoxyphenyl)propane, 2,2-bis(4-acryloxydiethoxyphenyl)propane, trimethylolpropane diacrylate, bis(2-acryloxyethyl)-hydroxyethyl-isocyanurate, and trimethylolpropane. triacrylate (TMPTA), tris(2-acryloxyethyl) isocyanurate, pentaerythritol triacrylate, pentaerythritol tetraacrylate, dipentaerythritol tetraacrylate, dipentaerythritol pentaacrylate, dipentaerythritol hexaacrylate (DPHA), caprolactone-modified dipentaerythritol hexaacrylate (acrylate product of an adduct of dipentaerythritol and ε-caprolactone), caprolactone-modified dipentaerythritol hydroxypentaacrylate, ditrimethylolpropane tetraacrylate, N-vinylpyrrolidone, aliphatic urethane acrylate oligomer, aliphatic polyester acrylate oligomer, etc.

[0050] Furthermore, the photocurable composition of the present invention may contain, as necessary, a photoinitiator other than the above-described photoreactive organopolysiloxane, a polymerization inhibitor, an antioxidant, an ultraviolet absorber, a light stabilizer, a solvent, and the like, within limits that do not impair the effects of the present invention. Photoreaction initiators other than the above photoreactive organopolysiloxanes are excited by exposure to light and provide excitation energy to a compound containing a radically polymerizable group, thereby initiating a curing reaction due to ultraviolet irradiation. In the photocurable composition of the present invention, the photoreactive organopolysiloxane functions as a photoinitiator, and therefore it is not necessarily necessary to add other photoinitiators. However, by using other photoinitiators in combination as needed, it is possible to control properties such as surface curability, deep curability, and visible light curability. Examples of photoreaction initiators other than the above-mentioned photoreactive organopolysiloxanes include acetophenone and its derivatives, benzophenone and its derivatives, o-benzoylbenzoic acid esters, benzoin and its derivatives, benzoin ethers and its derivatives, xanthone and its derivatives, disulfide compounds, quinone compounds, halogenated hydrocarbons, amines, organic peroxides, etc. Among these, from the viewpoints of compatibility and stability, compounds containing a substituted or unsubstituted benzoyl group, such as acetophenone and its derivatives, benzophenone and its derivatives, o-benzoylbenzoic acid esters, benzoin and its derivatives, benzoin ethers and its derivatives, and xanthone and its derivatives; and organic peroxides are more preferred.

[0051] Specific examples of photoinitiators include acetophenone, propiophenone, 2-hydroxy-2-methylpropiophenone, 2,2-dimethoxy-1,2-diphenylethan-1-one, 2-hydroxy-2-methyl-1-phenyl-propan-1-one, 1-hydroxy-cyclohexyl-phenyl-ketone, 1-[4-(2-hydroxyethoxy)-phenyl]-2-hydroxy-2-methyl-1-propan-1-one, 2-hydroxy-1-{4-[4 -(2-hydroxy-2-methyl-propionyl)-benzyl]phenyl}-2-methyl-propan-1-one, 2-methyl-1-(4-methylthiophenyl)-2-morpholinopropan-1-one, 2-benzyl-2-dimethylamino-(4-morpholinophenyl)-butanone-1, 2-(dimethylamino)-2-[(4-methylphenyl)methyl]-1-[4-(4-morpholinyl)phenyl]-1-butanone, 2,4,6-trimethylbenzoyl -diphenyl-phosphine oxide, bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide, 1,2-octanedione, 1-[4-(phenylthio)-, 2-(O-benzoyloxime)], ethanone, 1-[9-ethyl-6-(2-methylbenzoyl)-9H-carbazol-3-yl]-, 1-(O-acetyloxime), a mixture of oxyphenylacetic acid, 2-[2-oxo-2-phenylacetoxyethoxy]ethyl ester and oxyphenylacetic acid, 2-(2-hydroxyethoxy)ethyl ester, phenylglyoxylic acid methyl ester, ethyl-4-dimethylaminobenzoate, 2-ethylhexyl-4-dimethylaminobenzoate, bis(2,6-dimethoxybenzoyl)-2,4,4-trimethyl-pentylphosphine oxide, benzoyl peroxide, cumene peroxide, and the like. These may be used alone or in combination of two or more.

[0052] Among these photoinitiators, acetophenone, propiophenone, 2-hydroxy-2-methylpropiophenone, 2,2-dimethoxy-1,2-diphenylethan-1-one, 2-hydroxy-2-methyl-1-phenyl-propan-1-one, 1-hydroxy-cyclohexyl-phenyl-ketone, 1-[4-(2-hydroxyethoxy)-phenyl]-2-hydroxy-2-methyl-1-propan-1-one, 2-hydroxy-1-{4-[4-(2-hydroxy-2-methyl-propionyl)-benzyl]phenyl}-2-methyl-propan-1-one, 2-methyl-1-(4-methylthiophenyl)-2-morpholinopropan-1-one, 2-benzyl-2-dimethylamino-(4-morpholino)-2-methyl ... Preferred are 2,4,6-trimethylbenzoyl-diphenyl-phosphine oxide, bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide; 1,2-octanedione, 1-[4-(phenylthio)-, 2-(O-benzoyloxime)], ethanone, 1-[9-ethyl-6-(2-methylbenzoyl)-9H-carbazol-3-yl]-, 1-(O-acetyloxime); and a mixture of oxyphenylacetic acid, 2-[2-oxo-2-phenylacetoxyethoxy]ethyl ester and oxyphenylacetic acid, 2-(2-hydroxyethoxy)ethyl ester. When a photoreaction initiator is used, the amount thereof is preferably 0.1 to 10 parts by mass per 100 parts by mass of the solid content in the photocurable composition.

[0053] Specific examples of the polymerization inhibitor include hydroquinone, p-methoxyphenol, t-butylcatechol, phenothiazine, benzofuroxan, nitrosobenzene, 2-methyl-2-nitrosopropane dimer, and Nt-butyl-α-phenylnitrone. When a polymerization inhibitor is used, the amount added is about 100 to 10,000 ppm based on the mass of the organosilicon compound having a (meth)acrylic group used in the composition.

[0054] The antioxidant can be used to prevent oxidation of the cured product of the composition and improve weather resistance, and examples thereof include hindered amine-based and hindered phenol-based antioxidants. Specific examples of the hindered amine antioxidant include N,N',N'',N'''-tetrakis-(4,6-bis(butyl-(N-methyl-2,2,6,6-tetramethylpiperidin-4-yl)amino)-triazin-2-yl)-4,7-diazadecane-1,10-diamine, dibutylamine·1,3,5-triazine·N,N'-bis-(2,2,6,6-tetramethyl-4-piperidyl-1,6-hexamethylenediamine)·N-(2,2,6,6-tetramethyl-4-piperidyl)butylamine, and the like. Polycondensation polymer of ethylamine, poly[{6-(1,1,3,3-tetramethylbutyl)amino-1,3,5-triazine-2,4-diyl}{(2,2,6,6-tetramethyl-4-piperidyl)imino}hexamethylene{(2,2,6,6-tetramethyl-4-piperidyl)imino}], polymer of dimethyl succinate and 4-hydroxy-2,2,6,6-tetramethyl-1-piperidineethanol, [bis(2,2,6,6-tetramethyl-1(octyloxy)-4-piperidyl)decanediate]ester methyl 1,2,2,6,6-pentamethyl-4-piperidyl sebacate, bis(2,2,6,6-tetramethyl-4-piperidyl) sebacate, bis(1,2,2,6,6-penta ... lysyl) sebacate, 1-[2-[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionyloxy]ethyl]-4-[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionyloxy]-2,2,6,6-tetramethylpiperidine, 4-benzoyloxy-2,2,6,6-tetramethylpiperidine, 8-acetyl-3-dodecyl-7,7,9,9-tetramethyl-1,3,8-triazaspiro[4.5]decane-2,4-dione, and the like.

[0055] Specific examples of hindered phenol antioxidants include pentaerythritol-tetrakis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], thiodiethylene-bis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], octadecyl-3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, N,N'-hexane-1,6-diylbis[3-(3, 5-di-tert-butyl-4-hydroxyphenylpropioamide)], benzenepropanoic acid 3,5-bis(1,1-dimethylethyl)-4-hydroxy C7-C9 side chain alkyl ester, 2,4-dimethyl-6-(1-methylpentadecyl)phenol, diethyl [[3,5-bis(1,1-dimethylethyl)-4-hydroxyphenyl]methyl]phosphonate, 3,3',3'',5,5',5''-hexane-tert-butyl-4-a ,a',a''-(Mesitylene-2,4,6-tolyl)tri-p-cresol, calcium diethyl bis[[[3,5-bis-(1,1-dimethylethyl)-4-hydroxyphenyl]methyl]phosphonate], 4,6-bis(octylthiomethyl)-o-cresol, ethylene bis(oxyethylene) bis[3-(5-tert-butyl-4-hydroxy-m-tolyl)propionate], hexamethylene bis[3-(3,5-di-tert- butyl-4-hydroxyphenyl)propionate], 1,3,5-tris(3,5-di-tert-butyl-4-hydroxybenzyl)-1,3,5-triazine-2,4,6-(1H,3H,5H)-trione, reaction products of N-phenylbenzenamine and 2,4,4-trimethylpentene, 2,6-di-tert-butyl-4-(4,6-bis(octylthio)-1,3,5-triazin-2-ylamino)phenol, and the like. The antioxidants may be used alone or in combination of two or more.

[0056] The ultraviolet absorber is a light resistance stabilizer, and is a component used to prevent photodegradation and improve weather resistance, and examples thereof include benzotriazole-based, triazine-based, benzophenone-based, and benzoate-based absorbers. Specific examples of the ultraviolet absorber include 2,4-di-tert-butyl-6-(5-chlorobenzotriazol-2-yl)phenol, 2-(2H-benzotriazol-2-yl)-4,6-di-tert-pentylphenol, 2-(2H-benzotriazol-2-yl)-4-(1,1,3,3-tetramethylbutyl)phenol, reaction products of methyl 3-(3-(2H-benzotriazol-2-yl)-5-tert-butyl-4-hydroxyphenyl)propionate / polyethylene glycol 300, and 2-(2H-benzotriazol-2-yl)-4-hydroxyphenyl)propionate. benzotriazole-based ultraviolet absorbers such as 2-(4,6-diphenyl-1,3,5-triazin-2-yl)-6-(straight-chain and branched-chain dodecyl)-4-methylphenol; triazine-based ultraviolet absorbers such as 2-(4,6-diphenyl-1,3,5-triazin-2-yl)-5-[(hexyl)oxy]phenol; benzophenone-based ultraviolet absorbers such as octabenzone; benzoate-based ultraviolet absorbers such as 2,4-di-tert-butylphenyl-3,5-di-tert-butyl-4-hydroxybenzoate; and organic compounds in which the above components are modified with silyl groups and / or acrylic groups. The above ultraviolet absorbents may be used alone or in combination of two or more.

[0057] Light stabilizers are components used to prevent photo-oxidative degradation of the cured product. Examples include benzotriazole-based, hindered amine-based, and benzoate-based compounds. Hindered amine-based compounds are preferred, and tertiary amine-containing hindered amine-based light stabilizers are more preferred in terms of improving the storage stability of the composition. Specific examples of tertiary amine-containing hindered amine light stabilizers include TINUVIN 622LD, TINUVIN 144, TINUVIN 123, and CHIMASSORB119FL (all manufactured by Asahi Denka Co., Ltd.); MARK LA-57, LA-62, LA-67, and LA-63 (all manufactured by Asahi Denka Co., Ltd.); and SANOL LS-765, LS-292, LS-2626, LS-1114, and LS-744 (all manufactured by Sankyo Co., Ltd.). These may be used alone or in combination of two or more.

[0058] The solvent is not particularly limited as long as it can dissolve or disperse the above components, but it is preferable that the main solvent is an organic solvent with high polarity. Specific examples of organic solvents include alcohols such as methanol, ethanol, isopropyl alcohol, n-butanol, isobutanol, t-butanol, and diacetone alcohol; ketones such as methyl propyl ketone, diethyl ketone, methyl isobutyl ketone, cyclohexanone, and diacetone alcohol; ethers such as dipropyl ether, dibutyl ether, anisole, dioxane, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, propylene glycol monomethyl ether, and propylene glycol monomethyl ether acetate; and esters such as ethyl acetate, propyl acetate, butyl acetate, and cyclohexyl acetate. These may be used alone or in combination of two or more.

[0059] The amount of solvent used is preferably an amount that results in a solids concentration of the photocurable composition of the present invention of 1 to 80% by mass, particularly 10 to 60% by mass. Outside this range, defects may occur in the coating film obtained by applying and curing the composition. Specifically, at a concentration below the above range, the coating film is prone to sagging, twisting, and mottling, and the desired hardness and scratch resistance may not be achieved. Furthermore, at a concentration above the above range, the coating film may be prone to blushing, whitening, and cracking.

[0060] In addition to the above-mentioned additives, the photocurable composition of the present invention may contain other additives, such as silicone resins, leveling agents, thickeners, pigments, dyes, metal powders, heat ray reflecting / absorbing agents, flexibility imparting agents, antistatic agents, antifouling agents, and water repellency imparting agents, as needed, within limits that do not adversely affect the objects and effects of the present invention. For example, as the leveling agent, "KP-341" manufactured by Shin-Etsu Chemical Co., Ltd., "BYK-180" and "BYK-190" manufactured by BYKChemie, "LE-604" manufactured by Kyoeisha Chemical Co., Ltd., and the like can be used.

[0061] (4) Cured product The photocurable composition of the present invention can be cured by irradiating it with ultraviolet light in an atmosphere such as air or nitrogen. Examples of lamps with a wavelength range within the reactivity range include a high-pressure mercury lamp (UV-7000) and metal halide lamps (MHL-250, MHL-450, MHL-150, MHL-70) manufactured by Ushio Inc., a metal halide lamp (JM-MTL2KW) manufactured by JMtech, an ultraviolet irradiation lamp (OSBL360) manufactured by Mitsubishi Electric Corporation, an ultraviolet irradiation device (UD-20-2) manufactured by Japan Storage Battery Co., Ltd., a fluorescent lamp (FL-20BLB) manufactured by Toshiba Corporation, and H bulb, H plus bulb, D bulb, Q bulb, and M bulb manufactured by Fusion. The irradiation dose is 100 to 12,000 mJ / cm 2 is preferred, and 300 to 8,000 mJ / cm 2 is more preferable, and 500 to 6,000 mJ / cm 2 is even more preferred.

[0062] (5) Coated articles A coated article can be obtained by applying the photocurable composition of the present invention directly or via at least one other layer to at least one surface of a substrate and curing it by the above-mentioned light irradiation to form a coating.

[0063] The substrate is not particularly limited, but examples thereof include plastic molded bodies, wood products, ceramics, glass, metals, and composites thereof. In addition, substrates whose surfaces have been treated, specifically substrates that have been treated with chemical conversion treatment, corona discharge treatment, plasma treatment, acid or alkaline solution, etc., and decorative plywood in which the substrate body and the surface are coated with different types of paint can also be used. In particular, when a cured film made of the photocurable composition of the present invention is formed on a polycarbonate substrate, it may be possible to improve the scratch resistance and weather resistance of the polycarbonate.

[0064] Alternatively, the surface of a substrate on which other functional layers have been formed in advance may be coated with the photocurable composition of the present invention. Examples of other functional layers include a primer layer, an anti-rust layer, a gas barrier layer, a waterproof layer, and a heat ray shielding layer, and one or more of these layers may be formed in advance on the substrate. The coated article may be further coated on the surface on which the cured film made of the composition is formed with one or more layers such as a vapor deposition layer formed by a chemical vapor deposition (CVD) method, a hard coat layer, an anti-rust layer, a gas barrier layer, a waterproof layer, a heat-shielding layer, an anti-fouling layer, a photocatalytic layer, an anti-static layer, or the like. Furthermore, the surface of the coated article opposite to the surface on which the cured film made of the composition is formed may be coated with one or more layers such as a hard coat layer, an anti-rust layer, a gas barrier layer, a waterproof layer, a heat ray shielding layer, an antifouling layer, a photocatalyst layer, or an antistatic layer.

[0065] The method for applying the photocurable composition may be appropriately selected from known techniques, and various application methods such as brush coating, spraying, dipping, flow coating, roll coating, curtain coating, spin coating, and knife coating can be used.

[0066] The thickness of the cured film in the coated article of the present invention is not particularly limited and may be appropriately selected depending on the intended use, but is preferably 0.1 to 50 μm, and more preferably 1 to 20 μm in order to satisfy the hardness, scratch resistance, long-term stable adhesion, and absence of cracks of the cured film. The film thickness can be appropriately adjusted by devising the coating method.

[0067] One of the features of the coated article of the present invention is the visible light transmittance of the cured film. Visible light transmittance is generally evaluated by the haze of the cured film, and the smaller the haze, the better the visible light transmittance. The haze can be measured using a turbidity meter NDH2000 (manufactured by Nippon Denshoku Industries Co., Ltd.). The haze of a cured film generally increases as the film thickness increases. In the coated article of the present invention, when the thickness of the cured film is 20 μm or less, the haze is preferably 2.0 or less, more preferably 1.0 or less, and even more preferably 0.7 or less. [Example]

[0068] The present invention will be explained in more detail below with reference to Synthesis Examples, Examples and Comparative Examples, but the present invention is not limited to these Examples.

[0069] [1] Preparation of compounds having photopolymerization initiation sites [Synthesis Example 1] Synthesis of compound (i) having a photopolymerization initiation site In a 500 mL glass reactor equipped with a stirrer and thermometer, 150 g of methyl benzoylformate, 85 g of 3-butenol, and 6 g of paratoluenesulfonic acid monohydrate were mixed and refluxed at 120°C for 8 hours. The by-product methanol was then distilled off at 100°C. After cooling the solution, 200 g of toluene was added and the mixture was washed with 200 g of water. After repeating the same washing procedure three times, the toluene layer was concentrated under reduced pressure to obtain compound (i) having a photopolymerization initiation site.

[0070] [ka]

[0071] [Synthesis Example 2] Synthesis of compound (ii) having a photopolymerization initiation site In a 500 mL glass reactor equipped with a stirrer and a thermometer, 50 g of 2,4,6-trimethylbenzoyl-diphenyl-phosphine oxide (Omnirad TPO H, manufactured by IGM Resins BV), 37 g of N-bromosuccinimide (NBS), 0.6 g of azobisisobutyronitrile (AIBN), and 500 mL of carbon tetrachloride were mixed, and then the mixture was heated and stirred at 80°C under nitrogen for 3 hours. The reaction solution was filtered, and the filtrate was evaporated under reduced pressure to obtain the following product (ii-1). Next, 40 g of the product (ii-1) obtained above, 20 g of silver acetate, and 300 g of acetic acid were mixed in a 500 mL glass reactor equipped with a stirrer and a thermometer, and the mixture was heated and stirred at 100°C for 3 hours. After filtering the reaction solution, 500 mL of ion-exchanged water and 500 mL of toluene were added, and the organic layer was recovered by separation. This was followed by two washing procedures with 500 mL of ion-exchanged water. The toluene was then removed by distillation under reduced pressure, and product (ii-2) was obtained by column chromatography using a mixture of hexane:ethyl acetate (3:2) as the developing solvent. Furthermore, in a 300 mL glass reactor equipped with a stirrer and thermometer, 10 g of the product (ii-2) obtained above, 80 mL of tetrahydrofuran, and 80 mL of ion-exchanged water were stirred, and 20 mL of concentrated hydrochloric acid was added dropwise. After heating and stirring the reaction solution at 80 °C for 12 hours, the reaction solution was filtered, and 300 mL of ion-exchanged water and 300 mL of toluene were added. The organic layer was recovered by separation. This was followed by washing twice with 300 mL of ion-exchanged water. The solvent was then removed by distillation under reduced pressure, yielding compound (ii) having a photopolymerization initiation site.

[0072] [ka]

[0073] [2] Preparation of photoreactive organopolysiloxane [Example 1-1] (1) Organohydrogenpolysiloxane synthesis process In a 500 mL glass reactor equipped with a stirrer and thermometer, 84 g of 1,1,2,2-tetramethyldisiloxane, 56 g of isopropyl alcohol, 56 g of ion-exchanged water, and 122 g of concentrated hydrochloric acid were mixed. The mixture was cooled to -5°C, and then 114 g of ethyl silicate 40 (Colcoat Co., Ltd.) was added dropwise with stirring. The mixture was stirred for 16 hours, after which 122 g of toluene was added to the reaction solution. The mixture was stirred for 30 minutes and then allowed to stand for 60 minutes. The separated aqueous layer was then recovered, and 122 g of ion-exchanged water was added to the reaction solution. The mixture was stirred for 30 minutes and then allowed to stand for 60 minutes. The separated aqueous layer was then recovered. The same water washing procedure was repeated three times to remove acidic components. Volatile components in the resulting solution were removed by vacuum distillation to obtain organohydrogenpolysiloxane (HMQ-1, M units / Q units = 1.6).

[0074] (2) Introduction of photopolymerization initiation sites by hydrosilylation 9.0 g of the compound (i) having a photopolymerization initiation site obtained in Synthesis Example 1 and 0.1 g of a platinum catalyst (CAT-PL-50T, manufactured by Shin-Etsu Chemical Co., Ltd.) were added to a 100 ml glass reaction vessel and stirred. Under a nitrogen atmosphere, a mixed solution of 5.0 g of the organohydrogenpolysiloxane (HMQ-1) obtained above and 5.0 g of toluene was added, and stirring was continued at 60°C for 3 hours. Volatile components contained in the resulting solution were removed by distillation under reduced pressure to obtain a liquid photoreactive organopolysiloxane (I).

[0075] [Example 1-2] (1) Organohydrogenpolysiloxane synthesis process In a 500 mL glass reactor equipped with a stirrer and thermometer, 8 g of 1,1,2,2-tetramethyldisiloxane, 91 g of 1,1,1,2,2,2-hexamethyldisiloxane, 56 g of isopropyl alcohol, 56 g of ion-exchanged water, and 122 g of concentrated hydrochloric acid were mixed. The mixture was cooled to -5°C, and then 114 g of ethyl silicate 40 (Colcoat Co., Ltd.) was added dropwise with stirring. The mixture was stirred for 16 hours, after which 122 g of toluene was added to the reaction solution. The mixture was stirred for 30 minutes and then allowed to stand for 60 minutes. The separated aqueous layer was then recovered, and 122 g of ion-exchanged water was added to the reaction solution. The mixture was stirred for 30 minutes and then allowed to stand for 60 minutes. The separated aqueous layer was then recovered. The acidic components were removed by repeating the same water washing procedure three times. The volatile components in the resulting solution were removed by distillation under reduced pressure to obtain organohydrogenpolysiloxane (HMQ-2, M units / Q units=1.6).

[0076] (2) Introduction of photopolymerization initiation sites by hydrosilylation 0.9 g of the compound (i) having a photopolymerization initiation site obtained in Synthesis Example 1 and 0.1 g of a platinum catalyst (CAT-PL-50T, manufactured by Shin-Etsu Chemical Co., Ltd.) were added to a 100 ml glass reaction vessel and stirred. Under a nitrogen atmosphere, a mixed solution of 5.0 g of the organohydrogenpolysiloxane (HMQ-2) obtained above and 5.0 g of toluene was added, and stirring was continued at 60°C for 3 hours. Volatile components contained in the resulting solution were removed by distillation under reduced pressure to obtain a liquid photoreactive organopolysiloxane (II).

[0077] [Examples 1-3] A liquid photoreactive organopolysiloxane (III) was obtained in the same manner as in Example 1-1, except that in the step of introducing a photopolymerization initiation moiety by hydrosilylation in Example 1-1, the amount of compound (i) having a photopolymerization initiation moiety added was changed to 6 g and 1.2 g of 1-hexene was further added.

[0078] [Examples 1-4] 16.1 g of the compound (ii) having a photopolymerization initiation site obtained in Synthesis Example 2, 0.02 g of diethylhydroxyamine (DEHA), and 10 g of toluene were added to a 100 ml glass reaction vessel and stirred. Under a nitrogen atmosphere, a mixed solution of 5.0 g of the organohydrogenpolysiloxane (HMQ-1) obtained above and 5.0 g of toluene was added, and the mixture was heated under reflux for 10 hours to carry out a dehydrogenation condensation reaction. The resulting solution was cooled to room temperature, and 0.2 g of Kyoward 700 (Kyowa Chemical Industry Co., Ltd.) was added and stirred for 1 hour. After removing solids by filtration, the volatile components contained in the solution were removed by distillation under reduced pressure to obtain a liquid photoreactive organopolysiloxane (IV).

[0079] [Examples 1-5] A liquid photoreactive organopolysiloxane (V) was obtained in the same manner as in Example 1-4, except that the compound (ii) having a photopolymerization initiation site in Example 1-4 was changed to 9.9 g of 1-[4-(2-hydroxyethoxy)-phenyl]-2-hydroxy-2-methyl-1-propan-1-one (formula (iii) below, manufactured by IGM Resins BV, OMNIRAD 2959).

[0080] [ka]

[0081] [Comparative Example 1-1] In a 500 mL glass reactor equipped with a stirrer and thermometer, 101 g of 1,1,1,2,2,2-hexamethyldisiloxane, 56 g of isopropyl alcohol, 56 g of ion-exchanged water, and 122 g of concentrated hydrochloric acid were mixed and cooled to -5°C. Then, 114 g of ethyl silicate 40 (Colcoat Co., Ltd.) was added dropwise. After stirring the mixture for 16 hours, 122 g of toluene was added to the reaction solution, which was stirred for 30 minutes and then allowed to stand for 60 minutes. The separated aqueous layer was then recovered, and 122 g of ion-exchanged water was added to the reaction solution. The mixture was stirred for 30 minutes and then allowed to stand for 60 minutes. The separated aqueous layer was then recovered. The same water washing procedure was repeated three times to remove acidic components. Volatile components in the resulting solution were removed by distillation under reduced pressure, yielding liquid organopolysiloxane (VI) (M / Q = 1.6).

[0082] The physical properties of the polysiloxanes obtained in the above Examples and Comparative Examples are shown in Table 1. The content of the photopolymerization initiation site in Table 1 was calculated as [amount of compound having a photopolymerization initiation site added] / [amount of organohydrogenpolysiloxane added + amount of compound having a photopolymerization initiation site added] × 100 (mass %). The number average molecular weight in the present invention is a polystyrene-equivalent value measured by gel permeation chromatography (GPC) using tetrahydrofuran (THF) as a developing solvent. The sample used was a solution diluted with THF to a polysiloxane concentration of 0.5% by mass.

[0083] [Table 1]

[0084] [3] Preparation of photocurable composition [Examples 2-1 to 2-7, Comparative Examples 2-1 to 2-5] A solution of 80 parts by mass of dipentaerythritol hexaacrylate (DPHA) and 20 parts by mass of 1,6-hexanediol diacrylate (HDDA) as acrylate compounds, and 70 parts by mass of propylene glycol monomethyl ether (PGM) as a solvent was mixed with the organopolysiloxanes (I to VI) obtained in Examples 1-1 to 1-5 and Comparative Example 1-1, methyl benzoylformate, or 2-hydroxy-2-methyl-1-phenyl-propan-1-one (Omnirad 1173, manufactured by IGM Resins BV) in the amounts (parts by mass) shown in Table 2 to prepare a photocurable composition. The content of the photopolymerization initiation moiety was calculated by multiplying the amount of polysiloxane by the content of the photopolymerization initiation moiety / 100. The polysiloxane content is the amount obtained by subtracting the content of the photopolymerization initiation site from the amount of polysiloxane blended.

[0085] [Table 2]

[0086] The photocurable compositions obtained in Examples 2-1 to 2-7 and Comparative Examples 2-1 to 2-5 were flow coated onto a polycarbonate plate (5 mm thick, product name: Takiron PC Clear-1600 type, manufactured by Takiron C.I. Co., Ltd.), dried at 25°C for 5 minutes, heated at 80°C for 5 minutes, and then irradiated with 600 mJ / cm 2 in the air using a high-pressure mercury lamp. 2 A cured film with a thickness of approximately 15 μm was prepared by irradiating ultraviolet light (ultraviolet integrated energy of wavelength 300 to 390 nm, measured with an Iwasaki Electric Co., Ltd. UVPF-A1 (PD-365) ultraviolet integrated illuminance meter), and curability was evaluated. The physical properties of the cured film (haze, yellow index, scratch resistance) were evaluated at 1800 mJ / cm. 2 The results are shown in Tables 3 to 5.

[0087] [Curability] When the coating film was irradiated with ultraviolet light of a predetermined energy, it was evaluated as "good" if it cured, and as "bad" if it did not cure. Initial Haze (Hz) Measurement was performed using a haze meter (NDH5000SP, manufactured by Nippon Denshoku Industries Co., Ltd.) The higher the haze value, the poorer the transparency, and generally, at 1% or more, slight cloudiness is visible to the naked eye. [Yellow Index (YI)] The measurement was carried out by measuring transmitted light using a colorimeter Z-300A (manufactured by Nippon Denshoku Industries Co., Ltd.) The higher the YI value, the stronger the yellow color, and generally, a value of 1 or higher allows the naked eye to distinguish the yellow color. [Scratch resistance (ΔHz)] In accordance with ASTM 1044, an SC-10F abrasion wheel was attached in a Taber abrasion test, and the haze after 500 rotations at a load of 500 gf was measured using a haze meter (NDH5000SP, manufactured by Nippon Denshoku Industries Co., Ltd.), and the difference (% points) from the value before the abrasion test was calculated.

[0088] [Table 3]

[0089] [Table 4]

[0090] [Table 5]

[0091] As shown in Tables 3 to 5, in terms of the physical properties of the cured film of the photocurable composition, Examples 2-1 to 2-7, which satisfy the requirements of the present invention, are able to produce coating films with superior transparency and low yellowing compared to Comparative Examples 2-1 to 2-5, when the effective photoinitiator content is the same. In particular, even systems with low effective photoinitiator content, such as Examples 2-1 and 2-4, exhibit good curability with low light irradiation energy. The system of Comparative Example 2-1, in which an equal amount of a typical photoinitiator was added, did not cure with low light irradiation energy, and similarly, the system containing no photopolymerization initiation moiety, such as Comparative Example 2-5, did not exhibit any curing behavior upon light irradiation, suggesting that the compounds obtained by the present invention exhibit excellent atmospheric curability. 1, which shows the relationship between scratch resistance and effective photoinitiator content, it can be seen that the photoreactive organopolysiloxane of the present invention effectively improves abrasion resistance as the amount added increases, whereas the improvement effect is small in the comparative example systems to which a general photoinitiator is added. This suggests that the photoreactive organopolysiloxane of the present invention has multiple photopolymerization initiation sites bonded to the polysiloxane, and therefore the polysiloxane is incorporated into the coating film structure as crosslinking points, thereby increasing the crosslink density of the coating film and effectively improving scratch resistance.

[0092] Furthermore, Figure 2, which shows the relationship between initial Hz and effective photoinitiator content, shows that the transparency of the coating film does not change significantly even when the photoreactive organopolysiloxane of the present invention is added in increasing amounts, whereas in the comparative example, systems containing a general photoinitiator, transparency deteriorates significantly as the amount added increases. This is thought to be due to the presence of many unreacted components when a large amount of a general photoinitiator is added, which causes phase separation of these components as the coating film cures. The photoreactive organopolysiloxane of the present invention has a structure in which multiple photopolymerization initiation sites are bonded to the polysiloxane, which is thought to suppress phase separation of unreacted components, thereby exhibiting good transparency.

[0093] Furthermore, Figure 3, which shows the relationship between the yellow index (YI) and the effective photoinitiator content, shows that the photoreactive organopolysiloxane of the present invention does not significantly yellow the coating film even when the amount added is increased, whereas in the comparative example, systems containing a general photoinitiator, yellowing progresses significantly as the amount added is increased. This phenomenon is thought to be due to the fact that when a large amount of a general photoinitiator is added, reactions occur between the unreacted and reacted components, generating a large amount of by-products that cause yellowing. The compound of the present invention has a structure in which multiple photopolymerization initiation sites are bonded to the polysiloxane, which suggests that the mobility and diffusion of the unreacted and reacted components is reduced, thereby suppressing the generation of by-products that cause yellowing. From the above, it has been demonstrated that a compound satisfying the requirements of the present invention can effectively cure a coating film in the atmosphere even with a small amount of effective photoinitiator content, and can also impart excellent transparency and low yellowing.

Claims

1. A photoreactive organopolysiloxane having a structural unit ratio represented by the following formula (1) and containing 1 to 90 mass % of a group having a photopolymerization initiation site: (R 1 3 SiO 1 / 2 ) a (R 1 2 SiO 2 / 2 ) b (R 1 SiO 3 / 2 ) c (SiO 4 / 2 ) d (1) (In the formula, R 1 are each independently an alkyl group having 1 to 20 carbon atoms or an aryl group having 6 to 20 carbon atoms, each of which may have a substituent, or a group having a photopolymerization initiation site, a is a number of 0.1 to 0.8, b is 0, c is a number of 0 to 0.5, and d is a number of 0.2 to 0.9, and a+b+c+d=1 is satisfied.

2. 2. The photoreactive organopolysiloxane according to claim 1, wherein the group having a photopolymerization initiation site is any of groups represented by the following formulas (2) to (7): 【Chemical 1】 [In the formula, R 4 represents an aryl group having 6 to 20 carbon atoms which may have a substituent, R 5 represents a hydrogen atom, or an optionally substituted alkyl group having 1 to 20 carbon atoms or an optionally substituted aryl group having 6 to 20 carbon atoms; R 6 represents an arylene group having 6 to 20 carbon atoms which may have a substituent, R 7 represents a halogen atom, or an alkyl group having 1 to 20 carbon atoms, an alkenyl group having 2 to 20 carbon atoms, or an aryl group having 6 to 20 carbon atoms, each of which may have a substituent; R 8 represents an aryl group having 6 to 20 carbon atoms which may have a substituent, or -R 6 -SiR 2 (3-n) R 3 n A group represented by R 2 each independently represents a hydrogen atom, or an alkyl group having 1 to 20 carbon atoms, an alkenyl group having 2 to 20 carbon atoms, or an aryl group having 6 to 20 carbon atoms, each of which may have a substituent; R 3 each independently represents a hydroxyl group, an alkoxy group having 1 to 6 carbon atoms, or a halogen atom; R 6 has the same meaning as above, and n represents an integer of 1 to 3. X represents a single bond or an alkylene group having 1 to 20 carbon atoms which may have a substituent and which may contain an ether structure, ester structure, amide structure, urethane structure, urea structure, sulfide structure or sulfoxide structure in the chain, and the dashed line represents a bond to the silicon atom.

3. 3. The photoreactive organopolysiloxane according to claim 1, which contains 15 to 80% by mass of the group having the photopolymerization initiation site.

4. 2. The photoreactive organopolysiloxane according to claim 1, wherein a is a number from 0.3 to 0.7, c is a number from 0 to 0.2, and d is a number from 0.3 to 0.

7.

5. 2. The photoreactive organopolysiloxane according to claim 1, wherein c is 0.

6. A method for producing a photoreactive organopolysiloxane, comprising the step of reacting an organohydrogenpolysiloxane having a constitutional unit ratio represented by the following formula (8) with one or more compounds having a photopolymerization initiation site represented by the following formulas (9) to (14): A method for producing a photoreactive organopolysiloxane, wherein the proportion of the compound having a photopolymerization initiation moiety represented by any of the following formulas (9) to (14) is 1 to 90 mass% based on the total of the organohydrogenpolysiloxane having a structural unit ratio represented by the following formula (8) and the compound having a photopolymerization initiation moiety represented by the following formulas (9) to (14): (R 9 3 SiO 1 / 2 ) a (R 9 2 SiO 2 / 2 ) b (R 9 SiO 3 / 2 ) c (SiO 4 / 2 ) d (8) (In the formula, R 9 each independently represents an alkyl group having 1 to 20 carbon atoms or an aryl group having 6 to 20 carbon atoms, each of which may have a substituent, or a hydrogen atom; a is a number of 0.1 to 0.8, b is 0, c is a number of 0 to 0.5, and d is a number of 0.2 to 0.9, and the relationship a+b+c+d=1 is satisfied. 【Chemistry 2】 [In the formula, R 4 represents an aryl group having 6 to 20 carbon atoms which may have a substituent, R 5 represents a hydrogen atom, or an optionally substituted alkyl group having 1 to 20 carbon atoms or an optionally substituted aryl group having 6 to 20 carbon atoms; R 6 represents an arylene group having 6 to 20 carbon atoms which may have a substituent, R 7 represents a halogen atom, or an alkyl group having 1 to 20 carbon atoms, an alkenyl group having 2 to 20 carbon atoms, or an aryl group having 6 to 20 carbon atoms, each of which may have a substituent; R 8 represents an aryl group having 6 to 20 carbon atoms which may have a substituent, or -R 6 -SiR 2 (3-n) R 3 n A group represented by R 2 each independently represents a hydrogen atom, or an alkyl group having 1 to 20 carbon atoms, an alkenyl group having 2 to 20 carbon atoms, or an aryl group having 6 to 20 carbon atoms, each of which may have a substituent; R 3 each independently represents a hydroxyl group, an alkoxy group having 1 to 6 carbon atoms, or a halogen atom; R 6 has the same meaning as above, and n represents an integer of 1 to 3. Y represents an alkenyl group having 2 to 20 carbon atoms or a hydroxyalkyl group having 1 to 20 carbon atoms, which may have a substituent and may contain an ether structure, ester structure, amide structure, urethane structure, urea structure, sulfide structure or sulfoxide structure in the chain.

7. The method for producing a photoreactive organopolysiloxane according to claim 6, wherein the proportion of the compound having a photopolymerization initiation moiety represented by any of the formulas (9) to (14) is 15 to 80 mass% based on the total of the organohydrogenpolysiloxane having the structural unit ratio represented by formula (8) and the compound having a photopolymerization initiation moiety represented by any of the formulas (9) to (14).

8. 7. The method for producing a photoreactive organopolysiloxane according to claim 6, wherein a is a number from 0.3 to 0.7, c is a number from 0 to 0.2, and d is a number from 0.3 to 0.

7.

9. 7. The method for producing a photoreactive organopolysiloxane according to claim 6, wherein c is 0.

10. The method includes a step of subjecting an organohydrogenpolysiloxane having a constitutional unit ratio represented by formula (8) to a hydrosilylation reaction with one or more compounds having a photopolymerization initiation site represented by formulas (9) to (14), 7. The method for producing a photoreactive organopolysiloxane according to claim 6, wherein Y is an alkenyl group having 2 to 20 carbon atoms which may have a substituent and which may contain an ether structure, ester structure, amide structure, urethane structure, urea structure, sulfide structure, or sulfoxide structure in the chain.

11. The method includes a step of subjecting an organohydrogenpolysiloxane having a constitutional unit ratio represented by formula (8) to a dehydrogenation condensation reaction with one or more compounds having a photopolymerization initiation site represented by formulas (9) to (14), 7. The method for producing a photoreactive organopolysiloxane according to claim 6, wherein Y is a hydroxyalkyl group having 1 to 20 carbon atoms, which may have a substituent and which may contain an ether structure, ester structure, amide structure, urethane structure, urea structure, sulfide structure, or sulfoxide structure in the chain.

12. 7. The method for producing a photoreactive organopolysiloxane according to claim 6, comprising a step of subjecting a compound having an aliphatic unsaturated bond and no photopolymerization initiation site to a hydrosilylation reaction with an organohydrogenpolysiloxane having the structural unit ratio represented by formula (8) or a reaction product of an organohydrogenpolysiloxane having the structural unit ratio represented by formula (8) with one or more compounds having a photopolymerization initiation site represented by formulas (9) to (14).

13. 7. The method for producing a photoreactive organopolysiloxane according to claim 6, comprising a step of subjecting a compound having a hydroxyl group but no photopolymerization initiation site to a dehydrogenation condensation reaction with an organohydrogenpolysiloxane having the structural unit ratio represented by formula (8) or a reaction product of an organohydrogenpolysiloxane having the structural unit ratio represented by formula (8) with one or more compounds having a photopolymerization initiation site represented by formulas (9) to (14).

14. A photocurable composition comprising the photoreactive organopolysiloxane of claim 1 and a compound having a radically polymerizable unsaturated bond.

15. A cured product obtained by curing the photocurable composition according to claim 14.

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