Organopolysiloxane having photodegradable group

Abstract

To provide an organopolysiloxane which has a photodegradable group and generates an ethylenically unsaturated group upon light irradiation.SOLUTION: Provided is an organopolysiloxane having one or more groups selected from a photodegradable group represented by formula (2) and a group having a different position of the bond to the photodegradable group. (In the formula, R1 represents an alkyl group, a cycloalkyl group, an aralkyl group or an aryl group, and R2 independently represents a hydrogen atom, an alkyl group, or an aryl group. The line bearing a wiggly line indicates a bond).SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to an organopolysiloxane having a photodecomposable group. [Background technology]

[0002] Silicone compositions made of organopolysiloxanes are used in a wide range of fields as potting materials, adhesives, etc., due to their excellent heat resistance, weather resistance, and other properties. Known methods for curing silicone compositions include heating, reacting with moisture in the air, and irradiating light, but photocurable compositions that cure quickly without heating have been attracting attention due to demands for energy saving and decarbonization. As photocuring methods, a method using photoradical polymerization (Patent Document 1), a method using photocationic polymerization (Patent Document 2), and a method using a photoactive platinum complex (Patent Document 3) have been proposed, and they are used according to their respective properties. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 3894873 [Patent Document 2] Patent No. 5000538 [Patent Document 3] Patent No. 5342830 [Non-patent literature]

[0004] [Non-Patent Document 1] PSMariano, et al., J.Org.Chem. 1996, 61, 3304-3314 [Non-Patent Document 2] Oh, Sun Wha, Journal of Photoscience (2005), 12(1), 47-50 Summary of the Invention [Problem to be solved by the invention]

[0005] The method using a photoactive platinum complex utilizes the addition reaction (hydrosilylation reaction) of an alkenyl group and a Si-H group, and the addition reaction is initiated by activating the platinum complex by light irradiation, resulting in curing. Although many methods for activating a catalyst by light irradiation have been reported, no examples have been known in which an addition reaction is initiated by generating a reactive substituent such as an alkenyl group or a Si-H group by light irradiation. Non-Patent Documents 1 and 2 report the generation of vinylsilane by light irradiation in a specific compound having a trimethylsilyl group, but do not provide any suggestion regarding the application to organopolysiloxane and its curing. Since photoactive platinum complexes are generally expensive, if reactive groups can be generated by light irradiation, effects such as cost reduction can be expected in photocurable silicone compositions.

[0006] The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an organopolysiloxane which has photodecomposable groups and generates ethylenically unsaturated groups upon irradiation with light. [Means for solving the problem]

[0007] In order to solve the above problems, the present invention provides an organopolysiloxane having one or more photodecomposable groups represented by the following general formulas (1) and (2). [ka] [ka] (In the formula, R 1 is a substituted or unsubstituted alkyl, cycloalkyl, aralkyl or aryl group; R 2 are independently a hydrogen atom, a substituted or unsubstituted alkyl group, or a substituted or unsubstituted aryl group. A wavy line represents a bond.

[0008] In such organopolysiloxanes, the photodegradable groups absorb ultraviolet light and undergo a Norrish type II reaction to decompose, generating groups containing ethylenically unsaturated bonds, and therefore the organopolysiloxanes can be used as substrates in hydrosilylation reactions with Si-H groups.

[0009] In the organopolysiloxane of the present invention, R 1 is preferably a substituted or unsubstituted aryl group.

[0010] Such a photodecomposable group improves light absorption and allows the photodecomposition reaction to proceed more efficiently.

[0011] In the organopolysiloxane of the present invention, the R 2 is preferably a hydrogen atom.

[0012] Such a photodecomposable group has excellent reactivity in the photodecomposition reaction, and after decomposition, can generate a vinyl group that has excellent reactivity in the hydrosilylation reaction.

[0013] The organopolysiloxane of the present invention preferably has a content of the above-mentioned photodecomposable group of 0.2 mol or less per 100 g.

[0014] With such an organopolysiloxane, there is no risk of a decrease in the transmittance of irradiated light due to light absorption by the photodecomposable group, and the photodecomposition reaction can proceed deep into the layer.

[0015] Furthermore, the organopolysiloxane of the present invention preferably has an average of two or more of the above photodecomposable groups per molecule.

[0016] Such organopolysiloxanes are capable of forming crosslinks in a hydrosilylation reaction with compounds having Si-H groups, and therefore photocurable silicone compositions using such organopolysiloxanes exhibit excellent curability and the mechanical properties of the cured products.

[0017] The organopolysiloxane of the present invention having an average of two or more photodegradable groups per molecule preferably further has two or more hydrogen atoms bonded to silicon atoms per molecule.

[0018] Such organopolysiloxanes can be mixed with a platinum group metal catalyst to provide photocurable silicone compositions.

[0019] The present invention provides a photocurable silicone composition containing an organopolysiloxane having an average of two or more photodecomposable groups per molecule as described above, an organohydrogenpolysiloxane having two or more hydrogen atoms bonded to silicon atoms per molecule, and a platinum group metal catalyst.

[0020] The present invention also provides a photocurable silicone composition containing an organopolysiloxane having an average of two or more of the above-mentioned photodecomposable groups per molecule and two or more hydrogen atoms bonded to silicon atoms per molecule, and a platinum group metal catalyst.

[0021] These photocurable silicone compositions have excellent thermal stability and can be cured by irradiation with light without the use of a photoactive platinum complex. In addition, they have good surface curing properties at the air interface compared to radical reactions that are inhibited by oxygen.

[0022] The present invention further provides a silicone cured product obtained by curing the above-mentioned photocurable silicone composition.

[0023] Such a silicone cured product can be suitably used for applications such as adhesives, protective coatings, and sealants. Effect of the Invention

[0024] As explained above, the organopolysiloxane of the present invention can generate ethylenically unsaturated bond-containing groups capable of undergoing hydrosilylation reactions with Si-H groups upon irradiation with light. Therefore, the hydrosilylation reaction can be induced with light irradiation as the starting point without using a photoactive platinum complex, which is extremely advantageous in terms of reducing the cost of photocurable silicone compositions. [Brief description of the drawings]

[0025] [Figure 1] 1 shows 1H-NMR spectra of the organohydrogenpolysiloxane obtained in Example 1-2 before and after UV irradiation. The upper part shows the 1H-NMR spectrum before UV irradiation, and the lower part shows the 1H-NMR spectrum after UV irradiation. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0026] As described above, there has been a need for the development of organopolysiloxanes that are capable of generating hydrosilylation reactive groups upon irradiation with light.

[0027] Means for Solving the Problems The present inventors have conducted intensive research into the above-mentioned problems and have discovered that by introducing a photodecomposable group having a specific structure into an organopolysiloxane, it is possible to convert the group into an ethylenically unsaturated bond-containing group by irradiation with light, thereby completing the present invention.

[0028] That is, the present invention is an organopolysiloxane having one or more photodecomposable groups represented by the following general formulas (1) and (2). [ka] [ka] (In the formula, R 1 is a substituted or unsubstituted alkyl, cycloalkyl, aralkyl or aryl group; R 2 are independently a hydrogen atom, a substituted or unsubstituted alkyl group, or a substituted or unsubstituted aryl group. A wavy line represents a bond.

[0029] The present invention will be described in detail below, but the present invention is not limited thereto.

[0030] In the present invention, the term "ethylenically unsaturated bond" refers to a multiple bond between carbon atoms that is active in a hydrosilylation reaction.

[0031] [Organopolysiloxane] The present invention relates to an organopolysiloxane having one or more photodecomposable groups represented by the following general formulas (1) and (2). [ka] [ka] (In the formula, R 1 is a substituted or unsubstituted alkyl, cycloalkyl, aralkyl or aryl group; R 2 are independently a hydrogen atom, a substituted or unsubstituted alkyl group, or a substituted or unsubstituted aryl group. A wavy line represents a bond.

[0032] The photodegradable group is decomposed by absorbing irradiated light in a reaction known as the Norrish type II reaction, as shown in the following scheme, to generate an ethylenically unsaturated bond. For this reaction to proceed, it is necessary for the photodegradable group to have an abstractable hydrogen atom at the γ-position of the carbonyl group. [ka] (In the formula, R 1 and R 2 is the same as above. The wavy lines represent bonds.)

[0033] Above R 1Examples of the alkyl group include a methyl group, an ethyl group, a propyl group, a butyl group, a pentyl group, a hexyl group, etc., examples of the cycloalkyl group include a cyclopentyl group, a cyclohexyl group, etc., examples of the aryl group include a phenyl group, a toluyl group, a mesityl group, a naphthyl group, a biphenyl group, an anthranyl group, etc., and examples of the aralkyl group include a benzyl group, etc.

[0034] Some or all of the hydrogen atoms bonded to the carbon atoms of these groups may be substituted with functional groups such as a hydroxy group, a hydroxyalkyl group, an amino group, an aminoalkyl group, an amido group, an alkylamide group, an alkoxy group, an alkoxyalkyl group, an alkoxycarbonyl group, and an alkoxycarbonylalkyl group, or with halogen atoms such as chlorine and fluorine.

[0035] Above R 1 is preferably a substituted or unsubstituted aryl group from the viewpoint of light absorption necessary for causing a photodecomposition reaction. When it is a substituted aryl group, it is preferably a para-substituted aryl group from the viewpoint of efficiency of the photodecomposition reaction.

[0036] Above R 2 The alkyl group and aryl group of R 1 From the viewpoint of photodecomposition reactivity and the fact that the ethylenically unsaturated bond-containing group obtained after decomposition becomes a vinyl group having excellent hydrosilylation reactivity, the above R 2 is preferably a hydrogen atom.

[0037] The photodecomposable group may be directly bonded to silicon atom, or may be bonded to silicon atom via divalent linking group.The divalent linking group can be substituted or unsubstituted alkylene group, arylene group, etc., and can contain one or more bonds such as ether bond, ester bond, amide bond, urethane bond, urea bond, etc., and some or all of the hydrogen atoms bonded to the carbon atom of these substituents can be substituted with functional groups such as hydroxyl group, hydroxyalkyl group, amino group, aminoalkyl group, amide group, alkylamide group, alkoxy group, alkoxyalkyl group, alkoxycarbonyl group, and alkoxycarbonylalkyl group, or halogen atoms such as chlorine and fluorine.

[0038] Specific examples of the photodegradable group include those represented by the following formulas (3) and (4), but are not limited thereto. [ka] [ka] (In the formula, the wavy line represents a bond.)

[0039] The content of the photodecomposable groups represented by the general formulae (1) and (2) in the organopolysiloxane of the present invention is preferably 0.2 mol or less per 100 g of organopolysiloxane, and more preferably 0.05 mol or less per 100 g. Within this range, there is no risk of a decrease in the transmittance of irradiated light due to light absorption by the photodecomposable groups, and the photodecomposition reaction proceeds deep into the organopolysiloxane.

[0040] The molecular structure of the organopolysiloxane of the present invention is not particularly limited, and examples thereof include linear, branched, partially branched linear, cyclic, and three-dimensional network structures.

[0041] The organopolysiloxane of the present invention preferably has an average structure represented by the following formula (5). (R 3 R 4 2SiO 0.5) a (R 4 3SiO 0.5 ) b (R 3 R 4 SiO) c (R 4 2SiO) d (R 3 SiO 1.5 ) e (R 4 SiO 1.5 ) f (SiO2) g (5)

[0042] In formula (5), R 3 are independently a photodecomposable group represented by the above formula (1) or (2), and in formula (5), R 4 are independently a hydrogen atom, a substituted or unsubstituted alkyl group, or a substituted or unsubstituted aryl group. Examples of the alkyl group include a methyl group, an ethyl group, a propyl group, a butyl group, a pentyl group, and a hexyl group. Examples of the aryl group include a phenyl group, a toluyl group, a mesityl group, a naphthyl group, a biphenyl group, and an anthranyl group. Some or all of the hydrogen atoms bonded to carbon atoms of these groups may be substituted with a functional group such as a hydroxy group, a hydroxyalkyl group, an amino group, an aminoalkyl group, an amido group, an alkylamide group, an alkoxy group, an alkoxyalkyl group, an alkoxycarbonyl group, and an alkoxycarbonylalkyl group, or with a halogen atom such as chlorine or fluorine. In formula (5), R 4 is preferably a hydrogen atom, a methyl group or a phenyl group.

[0043] In the above formula (5), a, b, c, d, e, and f represent the number of each structural unit, and a+c+e≧1. From the viewpoint of curability when made into a photocurable composition, it is preferable that a+c+e≧2.

[0044] In the organopolysiloxane of the present invention, the photodecomposable groups are decomposed by light irradiation to generate ethylenically unsaturated bond-containing groups. From the viewpoint of absorption by carbonyl groups, the irradiated light preferably has a wavelength of 200 to 500 nm, more preferably 300 to 400 nm. The illuminance of the irradiated light is 30 to 2,000 mW / cm. 2 is preferable, and the irradiation amount (accumulated light amount) is 100 to 100,000 mJ / cm 2 However, from the viewpoint of suppressing side reactions and saving energy, a maximum of 20,000 mJ / cm is recommended. 2 The light source used may be any device that generates light including a wavelength range capable of decomposing the photodecomposable substituent, and various light sources such as a low pressure mercury lamp, a medium pressure mercury lamp, a high pressure mercury lamp, a metal halide lamp, a xenon lamp, and an ultraviolet LED can be used. Since the photodecomposition reaction of the organopolysiloxane of the present invention is an intramolecular reaction and is not easily inhibited by oxygen as in general radical reactions, the light irradiation can be carried out in normal air, but may also be carried out in an inert gas atmosphere such as nitrogen or argon.

[0045] [Photocurable silicone composition] When the organopolysiloxane of the present invention has two or more photodecomposable groups on average per molecule, it can be mixed with a platinum group metal catalyst and, if necessary, an organohydrogenpolysiloxane having two or more hydrogen atoms bonded to silicon atoms (Si-H groups) per molecule to give a photocurable silicone composition.When the organopolysiloxane of the present invention has two or more photodecomposable groups on average per molecule and further has two or more Si-H groups per molecule, it can be mixed with a platinum group metal catalyst to give a photocurable silicone composition.That is, in this case, it is not necessary to add an organohydrogenpolysiloxane separately.

[0046] The platinum group metal catalyst may be any catalyst capable of promoting the addition reaction between a substituent having an ethylenically unsaturated bond and a Si-H group, and any conventionally known platinum group metal catalyst may be used.

[0047] Specific examples of the platinum group metal catalyst include platinum group metals such as platinum (including platinum black), rhodium, and palladium; H2PtCl4·nH2O, H2PtCl6·nH2O, NaHPtCl6·nH2O, KHPtCl6·nH2O, Na2PtCl6·nH2O, K2PtCl4·nH2O, PtCl4·nH2O, PtCl2, and Na2HPtCl4·nH2O (wherein, n is an integer of 0 to 6, and preferably 0 or 6); Examples of platinum group metal catalysts include platinum chloride, chloroplatinic acid and chloroplatinate salts; alcohol-modified chloroplatinic acid; complexes of chloroplatinic acid and olefins; platinum black, platinum group metals such as palladium supported on supports such as alumina, silica and carbon; rhodium-olefin complexes; chlorotris(triphenylphosphine)rhodium (Wilkinson's catalyst); and complexes of platinum chloride, chloroplatinic acid or chloroplatinate salts with vinyl group-containing siloxanes.

[0048] The amount of platinum group metal catalyst is not limited as long as it is an amount that promotes the hydrosilylation reaction, but typically it is preferably 0.1 to 500 ppm, and more preferably 0.5 to 200 ppm, calculated as the mass of platinum group metal relative to the total mass of organopolysiloxane.

[0049] The organohydrogenpolysiloxane having at least two, and preferably three or more, hydrogen atoms bonded to silicon atoms (i.e., Si-H groups) in one molecule may be any of resinous substances having a linear, branched, cyclic, or three-dimensional network structure.

[0050] Examples of organohydrogenpolysiloxanes include cyclic methylhydrogenpolysiloxanes such as 1,1,3,3-tetramethyldisiloxane, 1,3,5,7-tetramethyltetracyclosiloxane, and 1,3,5,7,8-pentamethylpentacyclosiloxane; methylhydrogenpolysiloxanes capped with trimethylsiloxy groups at both ends of the molecular chain; dimethylsiloxane-methylhydrogensiloxane copolymers capped with trimethylsiloxy groups at both ends of the molecular chain; Methylhydrogenpolysiloxane capped with silanol groups at both molecular chain ends, dimethylsiloxane-methylhydrogensiloxane copolymer capped with silanol groups at both molecular chain ends, dimethylpolysiloxane capped with dimethylhydrogensiloxy groups at both molecular chain ends, methylhydrogenpolysiloxane capped with dimethylhydrogensiloxy groups at both molecular chain ends, dimethylsiloxane-methylhydrogensiloxane copolymer capped with dimethylhydrogensiloxy groups at both molecular chain ends, etc.; R2(H)SiO 1 / 2 Units and SiO 4 / 2 units, and optionally RSiO 1 / 2 Units, R2SiO 2 / 2 Units: R(H)SiO 2 / 2 Units: (H)SiO 3 / 2 Units or RSiO 3 / 2 A silicone resin that may contain units (wherein R is an unsubstituted or substituted monovalent hydrocarbon group that does not have an ethylenically unsaturated bond, 1 (Similar examples include those mentioned above.)

[0051] In the photocurable silicone composition of the present invention, the ratio of the number of hydrogen atoms bonded to silicon atoms (ie, Si-H groups) to each of the above photodecomposable groups is preferably in the range of 0.1 to 5, and more preferably in the range of 0.5 to 2.0.

[0052] In addition to the components described above, the photocurable silicone composition of the present invention may contain, as optional components, additives such as adhesion promoters, fillers, antistatic agents, flame retardants, antifoaming agents, flow control agents, light stabilizers, solvents, non-reactive resins, and radically polymerizable compounds. EXAMPLES

[0053] The present invention will be specifically described below using examples and comparative examples, but the present invention is not limited to these.

[0054] In addition, R in the following formulas (6) and (7) 5 is a group represented by the following structural formula (3), and R in the following formulas (6) and (7) 6 is a group represented by the following structural formula (4). 1 H-NMR analysis was performed using a Bruker Biospin NMR instrument (AVANCE III 400). [ka] [ka] (In the formula, the wavy line represents a bond.)

[0055] [Synthesis Example 1] Synthesis of 1-phenyl-3-buten-1-one 29.2g of anhydrous aluminum chloride and 300mL of dichloromethane were added to a 500mL three-neck flask purged with nitrogen and stirred under a nitrogen atmosphere. 28.0g of benzoyl chloride was gradually added dropwise while stirring under ice cooling, and after returning to room temperature, stirring was continued for 20 minutes. 27.4g of allyltrimethylsilane dissolved in 80mL of dichloromethane was gradually added dropwise under ice cooling, and after returning to room temperature, stirring was continued for 4 hours. The solution, which became a deep reddish brown, was gradually added to ice water, and after stirring for about 1 hour, the dichloromethane layer was separated. After dehydration with sodium sulfate, dichloromethane was distilled off under reduced pressure and the target product, 1-phenyl-3-buten-1-one (13.3g), was obtained by vacuum distillation.

[0056] [Example 1-1] In a 200 mL three-neck flask, add 100 mL of 1,0 ... 0.5 ]2[(CH3)2SiO] 2020 g of an organohydrogenpolysiloxane represented by the formula (I), 10 g of toluene, and 0.02 g of a 0.5% toluene solution of platinum(0)-1,3-divinyl-1,1,3,3-tetramethyldisiloxane complex were added, and 4.2 g of 1-phenyl-3-buten-1-one obtained in Synthesis Example 1 was added dropwise while stirring at 85°C under a nitrogen atmosphere. After reacting at 85°C for 4 hours, the toluene was distilled off under reduced pressure to obtain the target product (16.1 g). 1 As a result of H-NMR analysis, it was confirmed that the polymer was an organopolysiloxane having an average number of constituent units represented by the following formula (6). [R 5 (CH3)2SiO 0.5 ] 1.2 [R 6 (CH3)2SiO 0.5 ] 0.8 [(CH3)2SiO] 20 (6)

[0057] [Example 1-2] In a 200 mL three-neck flask, add 100 mL of 1,0 ... 0.5 ]2[(CH3)HSiO] 20 [(CH3)2SiO] 63 20 g of an organohydrogenpolysiloxane represented by the formula: was added to the reaction mixture, 10 g of toluene, and 0.02 g of a 0.5% toluene solution of platinum(0)-1,3-divinyl-1,1,3,3-tetramethyldisiloxane complex. 3.6 g of 1-phenyl-3-buten-1-one obtained in Synthesis Example 1 was added dropwise to the reaction mixture while stirring at 85°C under a nitrogen atmosphere. After reacting for 4 hours at 85°C, the toluene was distilled off under reduced pressure to obtain the target product (23.1 g). 1 As a result of H-NMR analysis, it was confirmed that the compound was an organohydrogenpolysiloxane having an average number of constituent units represented by the following formula (7). [(CH3)3SiO 0.5 ]2[R 5 (CH3)SiO] 4.6 [R 6 (CH3)SiO] 2.7 [(CH3)HSiO] 12.7 [(CH3)2SiO] 63 (7)

[0058] [Examples 1-3] In a 200 mL three-neck flask, add 100 mL of 1,0 ... 0.5 ]2[(CH3)HSiO] 23.7 [(CH3)2SiO] 255 50 g of an organohydrogenpolysiloxane represented by the formula: 70 g of toluene, and 0.05 g of a 0.5% toluene solution of platinum(0)-1,3-divinyl-1,1,3,3-tetramethyldisiloxane complex were added, and 3.5 g of 1-phenyl-3-buten-1-one obtained in Synthesis Example 1 was added dropwise while stirring at 85°C under a nitrogen atmosphere. After reacting for 4 hours at 85°C, the toluene was distilled off under reduced pressure to obtain the target product (47.0 g). 1 As a result of H-NMR analysis, it was confirmed that the compound was an organohydrogenpolysiloxane having an average number of constituent units represented by the following formula (8). [(CH3)3SiO 0.5 ]2[R 5 (CH3)SiO] 5.5 [R 6 (CH3)SiO] 1.7 (CH3)HSiO] 16.5 [(CH3)2SiO] 255 (8)

[0059] [Example 2-1] The deuterated chloroform solution of the organohydrogenpolysiloxane obtained in Example 1-2 was placed in a glass NMR measurement container, 1 H-NMR spectrum measurement was performed. A 365 nm UV LED irradiation device manufactured by CCS Inc. was used, and the NMR measurement container containing the above solution was irradiated with 10,000 mJ / cm 2 After exposure to UV light 1 H-NMR was measured.

[0060] Chemical shifts in the range of 5-9 ppm 1 The H-NMR spectrum is shown in Figure 1. The upper panel shows the spectrum before UV light irradiation, and the lower panel shows the spectrum after UV light irradiation.

[0061] Upon irradiation with UV light, three new peaks [δ6.05 (1H, dd, J = 20.0 Hz, 14.8 Hz), 5.86 (1H, dd, J = 14.8 Hz, 4.0 Hz), and 5.66 (1H, dd, J = 20.0 Hz, 4.0 Hz)] were generated in the chemical shift region of 5.6 to 6.1 ppm, confirming the generation of vinyl groups by decomposition of the photodegradable groups.

[0062] [Examples 3-1 to 3-5, Comparative Examples 3-1 and 3-2] The components below were mixed in the amounts (parts by mass) shown in Table 1 to prepare a photocurable silicone composition. Sx(7): Organohydrogenpolysiloxane obtained in Example 1-2 Sx(8): Organohydrogenpolysiloxane obtained in Example 1-3 Cat: Platinum(0)-1,3-divinyl-1,1,3,3-tetramethyldisiloxane complex, 0.5% solution in toluene

[0063] The obtained compositions of Examples 3-1 to 3-5 were placed in aluminum petri dishes and irradiated with UV light using the light source described below at the irradiation intensity and irradiation time shown in Table 1. After 12 hours in the dark, the presence or absence of curing and the cured thickness from the surface irradiated with UV light were confirmed. The results are shown in Table 1. <Light source> MHL: Metal halide lamp irradiation device manufactured by iGraphics Co., Ltd. (iUV electronic control device UBX0601-01) LED: 365nm UV LED irradiation device manufactured by CCS Corporation

[0064] The compositions of Comparative Examples 3-1 and 3-2 obtained were checked for hardening after 12 hours in the dark without irradiation with UV light. The results are shown in Table 1.

[0065] [Table 1]

[0066] As shown in Table 1, the photocurable silicone compositions of Examples 3-1 to 3-5 were cured by irradiation with UV light. In particular, Examples 3-3, 3-4, and 3-5, which used the organohydrogenpolysiloxane obtained in Example 1-3, showed a high curing thickness and were found to have excellent deep curing properties. On the other hand, the compositions of Comparative Examples 3-1 and 3-2, which were not irradiated with UV light, did not show any curing.

[0067] The results in Table 1 show that the organopolysiloxane of the present invention is capable of inducing a hydrosilylation reaction initiated by irradiation with light, thereby curing the composition, without the use of a photoactive platinum complex.

[0068] In this way, the organopolysiloxane of the present invention is capable of generating ethylenically unsaturated bond-containing groups capable of undergoing hydrosilylation reactions with Si-H groups upon irradiation with light, and therefore is capable of inducing hydrosilylation reactions initiated by light irradiation without the need for a photoactive platinum complex, which is extremely advantageous in terms of reducing the cost of photocurable silicone compositions.

[0069] The present invention is not limited to the above-described embodiment. The above-described embodiment is merely an example, and anything that has substantially the same configuration as the technical idea described in the claims of the present invention and exhibits similar effects is included in the technical scope of the present invention.

Claims

1. An organopolysiloxane characterized by having at least one photodecomposable group represented by the following general formulas (1) and (2): 【Chemistry 1】 【Chemistry 2】 (In the formula, R １ is a substituted or unsubstituted alkyl group, cycloalkyl group, aralkyl group, or aryl group; R 2 are independently a hydrogen atom, a substituted or unsubstituted alkyl group, or a substituted or unsubstituted aryl group. A wavy line represents a bond.

2. R １ 2. The organopolysiloxane according to claim 1, wherein is a substituted or unsubstituted aryl group.

3. R ２ 2. The organopolysiloxane according to claim 1, wherein: is a hydrogen atom.

4. 2. The organopolysiloxane according to claim 1, wherein the content of said photodecomposable group is 0.2 mol or less per 100 g.

5. 2. The organopolysiloxane according to claim 1, which has an average of two or more photodecomposable groups per molecule.

6. 6. The organopolysiloxane according to claim 5, further comprising two or more hydrogen atoms bonded to silicon atoms in each molecule.

7. 6. A photocurable silicone composition comprising the organopolysiloxane according to claim 5, an organohydrogenpolysiloxane having two or more silicon-bonded hydrogen atoms per molecule, and a platinum group metal catalyst.

8. A photocurable silicone composition comprising the organopolysiloxane according to claim 6 and a platinum group metal catalyst.

9. A cured silicone product obtained by curing the photocurable silicone composition according to claim 7 or 8.

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