Light curable silicone resin compositions

Abstract

The objective of this invention is to provide a photocurable polysiloxane composition that can form a cured material with a wide designable range of complex elastic moduli, high attenuation, and excellent shear elongation. The photocurable polysiloxane composition of the present invention comprises: an organopolysiloxane (A) containing mercaptoalkyl groups; a linear organopolysiloxane (B) containing aliphatic unsaturated groups at at least two ends; and a photopolymerization initiator (C); component (A) is composed of: an organopolysiloxane (A1) containing mercaptoalkyl groups at both ends, and an organopolysiloxane (A2) containing two or more mercaptoalkyl groups per molecule that can bond with silicon atoms; the ratio of the number of mercaptoalkyl groups in component (A) to the number of aliphatic unsaturated groups in component (B) is 0.70 or more and less than 1.00, and the ratio of the number of mercaptoalkyl groups in component (A1) to the number of aliphatic unsaturated groups in component (B) is 0.06 or more.

Description

Technical Field

[0001] This invention relates to a photocurable polysiloxane composition, and more specifically to a photocurable polysiloxane composition capable of forming a cured product (polysiloxane gel) with a wide range of designable elastic moduli, high attenuation, and excellent shear elongation. Prior Technology

[0002] Background Technology Polysiloxane gels possess excellent heat resistance, electrical insulation, and flexibility, making them suitable for use as sealants, coatings, potting compounds, and vibration damping materials for electrical and electronic components. With the increasing automation of production in recent years, thiol-olefin reaction-based photocurable polysiloxane resin compositions are primarily used in electronic machinery. These compositions possess photopolymerizable functional groups and can be cured by light such as ultraviolet light to form polysiloxane gels.

[0003] In recent years, with the diversification of applications, there has been an increasing demand for photocurable polysiloxane (PS) resin compositions capable of forming a cured product (polysiloxane gel) in applications such as sealing materials, coating materials, potting materials, vibration damping materials, vibration control materials, and optical adhesives (OCR, OCA). This cured product (polysiloxane gel) possesses excellent basic properties such as hardness, damping performance, and viscosity, as well as excellent tensile strength. This is because improving the damping performance of polysiloxane gel tends to increase its flexibility, making it prone to deformation under impact or vibration. If tensile strength is lacking, the polysiloxane gel is easily damaged. Therefore, maintaining high damping performance and excellent tensile strength is crucial for such applications. Especially when used as a vibration control material, shear elongation is important; a material that does not break even when the shear strain rate (elongation) exceeds 100% is required. The basic physical properties of such polysiloxane gels are generally designed by adjusting the composition of photocurable polysiloxanes by including solid fillers such as silicon oxide or resin. However, this method is difficult to balance attenuation performance and tensile strength, which has become a problem. Therefore, in Patent Document 1, in order to improve the tensile strength of photocurable polysiloxane compositions, an ultraviolet-curable polysiloxane composition is proposed, which includes: a specific linear organic polysiloxane (B) containing aliphatic unsaturated groups; an organic polysiloxane (A2) containing more than two mercaptoalkyl groups that can bond with silicon atoms; and a specific organic polysiloxane (A1) containing dithiols at both ends; and the ratio of the number of thiol groups in component (A1+A2) to the number of aliphatic unsaturated groups in component (B) is 1 to 3. Prior technology documents Patent documents

[0004] [Patent Document 1] Japanese Patent No. 6426023 Summary of the Invention

[0005] Invention Summary The problem the invention aims to solve However, in the photocurable polysiloxane composition of Patent Document 1, although the tensile properties of the cured material are improved, the complex modulus of elasticity becomes too high, resulting in poor attenuation. Furthermore, in applications such as coating materials, potting materials, and vibration damping materials, when solid fillers such as silica or resin are included in the photocurable polysiloxane composition to adjust the viscosity in the uncured state, the complex modulus of elasticity of the cured material further increases. Therefore, there is still room for improvement in terms of narrowing the designable range of the elastic modulus of the cured material (polysiloxane) of the photocurable polysiloxane composition.

[0006] Therefore, the present invention is intended to solve the aforementioned problems of the prior art and aims to provide a photocurable polysiloxane composition that can form a cured material with a wide designable range of complex elastic moduli, high attenuation and excellent shear elongation. The means to solve the problem

[0007] The photocurable polysiloxane composition of the present invention is characterized by containing: an organopolysiloxane (A) containing mercaptoalkyl groups; a linear organopolysiloxane (B) containing aliphatic unsaturated groups at at least two ends; and a photopolymerization initiator (C); the organopolysiloxane (A) is composed of: an organopolysiloxane (A1) containing mercaptoalkyl groups at both ends, and an organopolysiloxane (A2) containing two or more mercaptoalkyl groups per molecule that can bond with silicon atoms; the ratio of the number of mercaptoalkyl groups in the organopolysiloxane (A) to the number of aliphatic unsaturated groups in the organopolysiloxane (B) is 0.70 or more and less than 1.00, and the ratio of the number of mercaptoalkyl groups in the organopolysiloxane (A1) to the number of aliphatic unsaturated groups in the organopolysiloxane (B) is 0.06 or more. Furthermore, in this specification, the organopolysiloxane containing mercaptoalkyl groups (A) is also referred to as organopolysiloxane (A) or component (A); the organopolysiloxane containing mercaptoalkyl groups at both ends (A1) is also referred to as organopolysiloxane (A1) or component (A1); the organopolysiloxane containing two or more mercaptoalkyl groups that bond with silicon atoms per molecule (A2) is also referred to as organopolysiloxane (A2) or component (A2); the linear organopolysiloxane containing at least two aliphatic unsaturated groups at both ends (B) is also referred to as organopolysiloxane (B) or component (B); and the photopolymerization initiator (C) is also referred to as component (C).

[0008] The photocurable polysiloxane composition of the present invention is composed of: an organopolysiloxane (A1) and a linear organopolysiloxane (B) crosslinking to extend the chain length of the organopolysiloxane (B), wherein the organopolysiloxane (A1) contains mercaptoalkyl groups at both ends, and the linear organopolysiloxane (B) contains aliphatic unsaturated groups at both ends. Furthermore, the silicone chain between the crosslinking points is lengthened by crosslinking the organopolysiloxane (A2) with the aliphatic unsaturated groups remaining in the above-mentioned extended chain length organopolysiloxane molecules. The organopolysiloxane (A2) contains two or more mercaptoalkyl groups that can bond with silicon atoms in one molecule. At this point, the ratio of the number of mercaptoalkyl groups in the organopolysiloxane (A) to the number of aliphatic unsaturated groups in the organopolysiloxane (B) is set to 0.70 or more and less than 1.00, and the ratio of the number of mercaptoalkyl groups in the organopolysiloxane (A1) to the number of aliphatic unsaturated groups in the organopolysiloxane (B) is set to 0.06 or more. In this way, the viscoelastic properties of the cured product (polysiloxane gel) of the photocurable polysiloxane composition are controlled, and thus a photocurable polysiloxane composition with a wide range of designable complex moduli, high attenuation, and excellent shear elongation can be obtained.

[0009] Furthermore, in the photocurable polysiloxane composition of the present invention, the content of photopolymerization initiator (C) is preferably 0.05 to 50 parts by weight relative to 100 parts by weight of organopolysiloxane (B). This allows for the acquisition of a photocurable polysiloxane composition with excellent performance based on the aforementioned effects. Also, in the photocurable polysiloxane composition of the present invention, the aliphatic unsaturated group in the organopolysiloxane (B) is preferably vinyl. This allows for the acquisition of a photocurable polysiloxane composition with excellent performance based on the aforementioned effects.

[0010] Furthermore, the photocurable polysiloxane composition of the present invention may further include a filler (D). In this way, a photocurable polysiloxane composition can be obtained, which, in addition to having the aforementioned effects, can also form a cured product endowed with desired viscoelastic properties and functionality.

[0011] Furthermore, in the photocurable polysiloxane composition of the present invention, the filler (D) is preferably selected from at least one substance chosen from the group consisting of silicon oxide, polysiloxane, solid resin, fibrous compound, and metal oxide. This allows for the selection of suitable components of the photocurable polysiloxane composition, thereby enabling the formation of cured products endowed with various viscoelastic properties and functionalities. Invention Effects

[0012] The photocurable polysiloxane composition of the present invention comprises: an organopolysiloxane (A), a linear organopolysiloxane (B) having aliphatic unsaturated groups at both ends, and a photopolymerization initiator (C), wherein the organopolysiloxane (A) is composed of: an organopolysiloxane (A1) having mercaptoalkyl groups at both ends, and an organopolysiloxane (A2) having mercaptoalkyl groups that can bond with silicon atoms; and the photocurable polysiloxane composition of the present invention is configured such that the organopolysiloxane (B) has its chain length extended by the organopolysiloxane (A1). This material crosslinks with organopolysiloxane (A2); and by setting the ratio of the number of mercaptoalkyl groups in organopolysiloxane (A1) to the number of aliphatic unsaturated groups in organopolysiloxane (B), and the ratio of the number of mercaptoalkyl groups in organopolysiloxane (A) to the number of aliphatic unsaturated groups in organopolysiloxane (B) within a specific range, a photocurable polysiloxane composition can be provided, which can form a cured material with a wide designable range of complex elastic moduli, high attenuation, and excellent shear elongation. This allows for the provision of sealants, coatings, potting compounds, vibration damping materials, and optical adhesives (OCR, OCA) that do not break even when shear elongation exceeds 100% and exhibit high attenuation. Implementation

[0013] Forms used to implement inventions The photocurable polysiloxane composition of the present invention comprises: an organopolysiloxane (A) containing mercaptoalkyl groups; a linear organopolysiloxane (B) containing aliphatic unsaturated groups at at least two ends; and a photopolymerization initiator (C); the organopolysiloxane (A) is composed of: an organopolysiloxane (A1) containing mercaptoalkyl groups at both ends, and an organopolysiloxane (A2) containing two or more mercaptoalkyl groups per molecule that can bond with silicon atoms; the ratio of the number of mercaptoalkyl groups in the organopolysiloxane (A) to the number of aliphatic unsaturated groups in the organopolysiloxane (B) is 0.70 or more and less than 1.00, and the ratio of the number of mercaptoalkyl groups in the organopolysiloxane (A1) to the number of aliphatic unsaturated groups in the organopolysiloxane (B) is 0.06 or more. The following is a detailed description.

[0014] (Organopolysiloxane (A)) The organosiloxane (A) containing mercaptoalkyl groups that constitutes the photocurable polysiloxane composition of the present invention is composed of: an organosiloxane (A1) containing mercaptoalkyl groups at both ends, and an organosiloxane (A2) containing two or more mercaptoalkyl groups that can bond with silicon atoms per molecule.

[0015] (Organopolysiloxane (A1)) The organopolysiloxane (A1) constituting organopolysiloxane (A) is a linear organopolysiloxane with mercaptoalkyl groups at both ends, and is a component that functions as a chain length extender. It extends the chain length of organopolysiloxane (B) by reacting the mercaptoalkyl groups at both ends with the aliphatic unsaturated groups of organopolysiloxane (B) through a thiol-ene reaction. As a specific preferred example, it is an organopolysiloxane with the structure shown in Formula 1: (where Ra is independently a C1-C6 alkyl, C6-C12 aryl, or -Si(OX)3 (where X is independently a C1-C6 alkyl), Rb is independently a C1-C6 alkyl or C6-C12 aryl, and Rc is independently a C1-C6 alkyl). p should preferably be an integer greater than or equal to 3, representing a number that ensures the viscosity of the organopolysiloxane (Al) at 23°C is 1 to 200 cP. Furthermore, in this specification, the viscosity of the composition or constituent material of the present invention refers to the value measured using a rotational viscometer with rotors No. 2 to 4 at 30 to 60 rpm and 23°C. There are no particular limitations on the specific organopolysiloxane (Al), for example, the model "X-22-167C" (mercaptoequivalent: 0.4348 mmol / g) from Shin-Etsu Chemical Industry Co., Ltd. can be used.

[0016] [Chemical Formula 1]

[0017] Furthermore, regarding other embodiments of photocurable polysiloxane compositions, when the polysiloxane gel is used in applications where high heat resistance is not required, the organopolysiloxane (A1) can also be a structure in which a portion of the silicate chain is replaced by a hydrocarbon chain. Additionally, a portion or all of the formulation of the organopolysiloxane (A1) can be replaced by a chain length extender composed of a straight-chain hydrocarbon structure with thiol groups at both ends.

[0018] (Organopolysiloxane (A2)) The organopolysiloxane (A2) constituting organopolysiloxane (A) is an organopolysiloxane containing two or more mercaptoalkyl groups that bond with silicon atoms per molecule. It is also a crosslinking agent, which crosslinks organopolysiloxane (B) by reacting the aliphatic unsaturated groups of organopolysiloxane (B) with the mercaptoalkyl groups that bond with silicon atoms through a thiol-ene reaction, thereby curing the photocurable polysiloxane resin composition. The main chain structure of organopolysiloxane (A2) can be linear, branched, or cyclic. From the viewpoint of enabling three-dimensional crosslinking, organopolysiloxanes in which the side chains of the main chain are replaced with mercaptoalkyl groups are preferable. There are no particular limitations on the specific organopolysiloxane (A2). For example, products such as Shin-Etsu Chemical Co., Ltd.'s "KF-2001" (mercaptoequivalent: 0.5263 mmol / g) or Gelest's "SMS-022" (mercaptoequivalent: 0.3286 mmol / g) can be used.

[0019] (Organopolysiloxane (B)) The organopolysiloxane (B) constituting the photocurable polysiloxane composition of the present invention is a linear organopolysiloxane containing aliphatic unsaturated groups at at least two ends. For example, a linear organopolysiloxane with the structure of the following formula 2 can be selected: (where R is an aliphatic unsaturated group, and R1 to R4 are the same or different types of non-substituted or substituted monovalent hydrocarbon groups. Also, q is an integer of 10 or more, preferably a number that sets the viscosity of the organopolysiloxane (B) at 23°C to 100 to 25000 cP). Regarding the aliphatic unsaturated group, examples include vinyl, propenyl, butenyl, hexenyl, etc., and from the viewpoint of ease of synthesis, vinyl is preferred. Specific examples of R1 to R4 include C1 to C6 alkyl groups (e.g., methyl, ethyl, propyl, etc.) or C6 to C12 aryl groups (e.g., phenyl, tolyl, xylyl, etc.). From the viewpoint of ease of synthesis, methyl is preferred for C1 to C6 alkyl groups, and phenyl is preferred for C6 to C12 aryl groups. There are no particular limitations on the specific organopolysiloxane (B), and for example, Gelest's product "DMS-V33" (vinyl equivalent: 0.0465 mmol / g) and Gelest's product "DMS-V22" (vinyl equivalent: 0.2222 mmol / g) can be used.

[0020] [Chemical Formula 2]

[0021] Regarding the mixing ratio of organopolysiloxane (A) and organopolysiloxane (B) composed of organopolysiloxane (A1) and organopolysiloxane (A2), from the viewpoint of obtaining a hardened material with a wide range of designable and adjustable complex elastic moduli, high attenuation, and excellent shear elongation, the ratio of the number of mercaptoalkyl groups in organopolysiloxane (A) to the number of aliphatic unsaturated groups in organopolysiloxane (B) is 0.70 or more and less than 1.00, and the ratio of the number of mercaptoalkyl groups in organopolysiloxane (A1) to the number of aliphatic unsaturated groups in organopolysiloxane (B) is 0.06 or more. When the ratio of the number of mercaptoalkyl groups in organopolysiloxane (A) to the number of aliphatic unsaturated groups in organopolysiloxane (B) is less than 0.70, insufficient crosslinking due to the thiol-ene reaction results in the photocurable polysiloxane composition not curing. When the ratio is 1.00 or higher, the elastic modulus of the cured material becomes too high, and good attenuation properties cannot be obtained. Therefore, the ratio of the number of mercaptoalkyl groups in organopolysiloxane (A) to the number of aliphatic unsaturated groups in organopolysiloxane (B) is preferably 0.70 or higher and less than 1.00, more preferably 0.70 or higher and less than 0.95, and even more preferably 0.70 or higher and less than 0.90. Furthermore, when the ratio of the number of mercaptoalkyl groups in organopolysiloxane (A1) to the number of aliphatic unsaturated groups in organopolysiloxane (B) is less than 0.06, good shear elongation of the cured material cannot be obtained. Therefore, the ratio of the number of mercaptoalkyl groups in the organopolysiloxane (A1) to the number of aliphatic unsaturated groups in the organopolysiloxane (B) is preferably 0.06 or more, more preferably 0.06 or more and 0.5 or less, and even more preferably 0.1 or more and 0.5 or less.

[0022] (Photopolymerization initiator (C)) The photopolymerization initiator (C) constituting the photocurable polysiloxane composition of the present invention is a component that can promote the following crosslinking reaction, and can use known agents acting on thiol-ene reactions, wherein the aforementioned crosslinking reaction is: a crosslinking reaction between the mercaptoalkyl group in the organic polysiloxane (A) and the aliphatic unsaturated group in the organic polysiloxane (B) under ultraviolet irradiation. Specifically, examples include: 1-hydroxy-cyclohexyl-phenyl-one, 2,2-dimethoxy-2-phenylacetophenone, oxycarbinone, fluorenone, benzaldehyde, fluorene, anthraquinone, triphenylamine, carbazole, 3-methylacetophenone, 4-chlorodiphenyl ketone, 4,4'-dimethoxydiphenyl ketone, 4,4'-diaminodiphenyl ketone, milchnerone, benzoyl ether, benzoyl ethyl ether, benzyl dimethyl ketal, 1-(4-isopropylphenyl)-2-hydroxy-2-methylpropane-1-one, 2-hydroxy 2-Methyl-1-phenylpropane-1-one, thioxanthone, diethylthioxanthone, 2-isopropylthioxanthone, 2-chlorothioxanthone, 2-methyl-1-[4-(methylthio)phenyl]-2-morpholinyl-propane-1-one, 2,4,6-trimethylbenzyldiphenylphosphine oxide, bis-(2,6-dimethoxybenzyl)-2,4,4-trimethylpentylphosphine oxide; Omnirad 184, 369, 651, 500, 907, 1173, TPO H (all manufactured by BASF), etc., from the viewpoint of promoting crosslinking reactions, acetophenone-based agents are preferred. Photopolymerization initiators (C) can be used alone or in combination of two or more. Furthermore, the amount of photopolymerization initiator (C) should be sufficient to effectively initiate the thiol-ene reaction by ultraviolet light, preferably 0.05 to 50 parts by mass relative to 100 parts by mass of organopolysiloxane (B), and more preferably 0.1 to 5 parts by mass.

[0023] (filler (D)) The photocurable polysiloxane composition of the present invention may further include a filler (D) to impart viscoelastic properties or other functionalities to the cured material. As the filler (D), it is not particularly limited as long as it can impart a moderating effect on the viscoelastic properties or functionalities of the cured material and is in powder form without hindering the thiol-ene reaction. For example, the following can be appropriately selected according to the purpose: AEROSIL (registered trademark) from Aerosil Corporation of Japan or REOLOSIL (registered trademark) from Tokuyama Corporation; fumed silica represented by WACKER HDK (registered trademark) manufactured by Asahi Kasei Wacker Corporation; silica or polysiloxane resins such as alumina; metal oxides such as TOKUSIL (registered trademark) from Tokuyama Corporation; fibrous compounds such as cellulose nanofibers; etc.

[0024] Furthermore, any additives may be added to the photocurable polysiloxane composition of the present invention within a range that does not impede the effect of the present invention. For example, as needed, pigments or conductive agents, flame retardants, dispersants, adhesiveness and bonding agents, polymerization inhibitors, antioxidants as additives to improve weather resistance, ultraviolet absorbers, light stabilizers, and other well-known additives may be used.

[0025] Regarding adhesiveness and bonding agents, for example, it is preferable to be one or more polysiloxane-based bonding enhancers selected from the group consisting of MQ resin, MDQ resin, MT resin, MDT resin, MDTQ resin, DQ resin, DTQ resin, and TQ resin (excluding aliphatic unsaturated groups and thiol groups). From the viewpoint of fluidity or dispersibility in light-curing polysiloxane compositions, it is more preferably to be one or more polysiloxane-based bonding enhancers selected from the group consisting of MQ resin, MDQ resin, MDT resin, and MDTQ resin. From the viewpoint of adhesiveness-imparting effect and ease of structure control, MQ resin is more preferred. Furthermore, silane coupling agents may also be added to improve adhesion to the substrate. Examples of silane coupling agents include: triethoxysilane, 3-mercaptopropyltrimethoxysilane, 3-epoxypropoxypropyltrimethoxysilane, 3-epoxypropoxypropyltriethoxysilane, 1,3-bis(3-methacryloxypropyl)tetramethyldisiloxane, trimethoxysilylpropyldiallyl isocyanate, bis(trimethoxysilylpropyl)allyl isocyanate, tri(trimethoxysilylpropyl)isocyanate, triethoxysilylpropyldiallyl isocyanate, bis(triethoxysilylpropyl)allyl isocyanate, tri(triethoxysilylpropyl)isocyanate, etc. Furthermore, other examples of silane coupling agents include disiloxane compounds containing functional groups such as (meth)acryloxy, alkoxy (e.g., methoxy, ethoxy, propoxy), and amino groups, such as 1,3-bis(3-methacryloxypropyl)tetramethyldisiloxane. From the viewpoint of improving adhesion and bonding properties, compounds containing aliphatic unsaturated groups are preferred, particularly 3-methacryloxypropyltriethoxysilane, 3-methacryloxypropyltrimethoxysilane, and 1,3-bis(3-methacryloxypropyl)tetramethyldisiloxane. One or more adhesion-improving agents may be used.

[0026] Regarding antioxidants, those capable of adding the following functions—preventing oxidation of the hardened components of the present invention and improving weather resistance—can be used, such as hindered amine antioxidants or hindered phenolic antioxidants. As hindered amine antioxidants, those known to the public can be appropriately selected, for example: N,N′,N″,N″′-tetra-(4,6-bis(butyl-(N-methyl-2,2,6,6-tetramethylpiperidin-4-yl)amino)-triazine-2-yl)-4,7-diazadecane-1,10-diamine, dibutylamine, 1,3,5-triazine, N,N′-bis(2,2,6,6-tetramethyl-4-piperidinyl-1,6-hexamethylenediamine, N-(2,2,6,6-tetramethyl) Polycondensates of 4-piperidinyl)butylamine, poly[{6-(1,1,3,3-tetramethylbutyl)amino-1,3,5-triazine-2,4-diyl}{(2,2,6,6-tetramethyl-4-piperidinyl)imino}hexamethylene{(2,2,6,6-tetramethyl-4-piperidinyl)imino}], polymers of dimethyl succinate and 4-hydroxy-2,2,6,6-tetramethyl-1-piperidinol, [bis(2,2,6,6-tetramethyl-1-octyloxy)succinate] 4-piperidinyl) ester, product of reaction of 1,1-dimethylethyl hydroperoxide with octane (70%), polypropylene (30%), bis(1,2,2,6,6-pentamethyl-4-piperidinyl)[[3,5-bis(1,1-dimethylethyl)-4-hydroxyphenyl]methyl]butyl malonate, methyl 1,2,2,6,6-pentamethyl-4-piperidinyl sebacate, bis(2,2,6,6-tetramethyl-4-piperidinyl) sebacate, bis(1,2,2,6,6) -Pentamethyl-4-piperidinyl) sebacate, 1-[2-[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propoxy]ethyl]-4-[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propoxy]-2,2,6,6-tetramethylpiperidine, 4-benzopyroxy-2,2,6,6-tetramethylpiperidine, 8-acetylated-3-dodecyl-7,7,9,9-tetramethyl-1,3,8-triazaspiro[4.5]decane-2,4-dione, etc.

[0027] On the other hand, as hindered phenolic antioxidants, well-known ones can be appropriately selected, such as: neopentyl tetroxide [3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], dithioethylene bis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], octadecyl-3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, N,N′-hexane-1,6-diylbis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] ... -Di-tert-butyl-4-hydroxyphenylpropionamide), 3,5-bis(1,1-dimethylethyl)-4-hydroxyC7-C9 alkyl ester of phenylpropionate, 2,4-dimethyl-6-(1-methylpentadecanyl)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″-(meta-trimethyl) Toluene-2,4,6-tolyl)tri-p-cresol, diethylbis[[[3,5-bis-(1,1-dimethylethyl)-4-hydroxyphenyl]methyl]phosphonate calcium], 4,6-bis(octylthiomethyl)-o-cresol, ethylbis(ethylene oxide)bis[3-(5-tert-butyl-4-hydroxy-m-tolyl)propionate], hexamethylenebis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], 1,3,5 -Ref. (3,5-Di-tripropylbutyl-4-hydroxybenzyl)-1,3,5-triazine-2,4,6-(1H,3H,5H)-trione, the reaction product of N-phenylaniline and 2,4,4-trimethylpentene, 2,6-di-tripropylbutyl-4-(4,6-bis(octylthio)-1,3,5-triazine-2-ylamino)phenol, etc., but not limited to these. The above antioxidants may be one or more.

[0028] Regarding light stabilizers, those capable of providing the function of preventing photo-oxidative degradation of the composition or its hardened form of the present invention can be used. Examples include benzotriazole compounds, hindered amine compounds, and benzoate compounds. Among these, hindered amine light stabilizers are preferred. Furthermore, to improve the storage stability of the composition, hindered amine light stabilizers containing tertiary amines are preferred. Examples of hindered amine light stabilizers containing tertiary amines include: Tinuvin 622LD, Tinuvin 144, and Chimassor C119FL (all manufactured by BASF); Mark LA-57, LA-62, LA-67, and LA-63 (all manufactured by Asahi Denka Kogyo Co., Ltd.); and Sanol LS-765, LS-292, LS-2626, LS-1114, and LS-744 (all manufactured by Sankyo Co., Ltd.). Furthermore, regarding ultraviolet absorbers that function as lightfastness stabilizers, examples include benzotriazole, triazine, diphenyl ketone, and benzoate compounds. Well-known absorbers can be appropriately selected, such as 2,4-di-tributyl-6-(5-chlorobenzotriazole-2-yl)phenol, 2-(2H-benzotriazole-2-yl)-4,6-di-tripentylphenol, 2-(2H-benzotriazole-2-yl)-4-(1,1,3,3-tetramethylbutyl)phenol, the reaction product of methyl 3-(3-(2H-benzotriazole-2-yl)-5-tributyl-4-hydroxyphenyl)propionate / polyethylene glycol 300, 2- Benzotriazole-based UV absorbers such as (2H-benzotriazole-2-yl)-6-(linear and side-chain dodecyl)-4-methylphenol; triazine-based UV absorbers such as 2-(4,6-diphenyl-1,3,5-triazin-2-yl)-5-[(hexyl)oxy]-phenol; diphenyl ketone-based UV absorbers such as octabenzone; and benzoate-based UV absorbers such as 2,4-di-tertiary butylphenyl-3,5-di-tertiary butyl-4-hydroxybenzoate. The above-mentioned light stabilizers and UV absorbers may be one or more types.

[0029] (Properties of light-curable polysiloxane composition) In the physical properties of the photocurable polysiloxane composition of the present invention, the viscosity of the composition can be appropriately set according to the application, but from the viewpoint of coating properties or spraying properties by means of a dispensing device, the viscosity at 23°C is preferably 50~10000 cP, more preferably 70~9000 cP, and even more preferably 100~7000 cP.

[0030] (Properties of cured products of light-curing polysiloxane compositions) The photocurable polysiloxane composition of the present invention, by having the above-described structure, crosslinks with organic polysiloxane (A2) in a state where organic polysiloxane (B) is linked to organic polysiloxane (A1) and the chain length of organic polysiloxane (B) is extended. In this way, the siloxane chain between the crosslinking points becomes longer, which helps to improve the shear elongation of the cured material. Then, the ratio of the number of mercaptoalkyl groups in the organopolysiloxane (A1) to the number of aliphatic unsaturated groups in the organopolysiloxane (B) is set to 0.06 or more, and the ratio of the number of mercaptoalkyl groups in the organopolysiloxane (A) to the number of aliphatic unsaturated groups in the organopolysiloxane (B) is set to 0.70 or more and less than 1.00. This allows the linkage reaction between component (A1) and component (B), and the crosslinking reaction between component (B) and component (A2) with extended chain lengths, to proceed in a manner that achieves the desired cured material properties. This results in a polysiloxane gel with a wide designable range of complex elastic moduli, high attenuation, and excellent shear elongation. Specifically, regarding the attenuation of the cured material, the tanδ (10Hz) of the viscoelastic properties is preferably 0.5 or more, and when used as a vibration damping material for precision machinery, it is preferably in the range of 0.5 to 2.0. Furthermore, the shear elongation of the hardened material is preferably 110% or more, more preferably 200% or more, and even more preferably 300% or more, relative to the shear elongation of the hardened material described below. The aforementioned hardened material is composed of a composition excluding component (A1), namely, an organopolysiloxane (A2) and an organopolysiloxane (B), wherein the ratio of the number of mercaptoalkyl groups in the organopolysiloxane (A) to the number of aliphatic unsaturated groups in the organopolysiloxane (B) is equal. Especially when used as a vibration damping material for precision machinery, tanδ and shear elongation are preferably within the above-mentioned ranges.

[0031] (Applications of light-curing polysiloxane compositions) The photocurable polysiloxane composition of this invention exhibits high attenuation and shear elongation after photocuring. Therefore, it can be used as a sealant, coating material, potting compound, vibration damping material, and optical adhesive (OCR, OCA) that does not break even when the shear elongation exceeds 100% and maintains high attenuation. Furthermore, it maintains high attenuation and is not easily broken even for vibrations in the high-frequency range above 10Hz in optical devices such as optical pickup modules, making it suitable as a vibration damping component with excellent vibration damping properties.

[0032] The photocurable polysiloxane composition of the present invention can be obtained by mixing the above-mentioned components (A) to (C) or (A) to (D), and fillers or other various components added as needed, in a predetermined mixing ratio. The order in which the above-mentioned components (A) to (C) or (A) to (D) are mixed is not particularly limited. Furthermore, regarding component (A), components (A1) and (A2) can be partially or completely pre-reacted in the presence of a photopolymerization initiator (C) to extend the chain length before mixing components (B) or (D). The mixing mechanism is not particularly limited; known methods such as manual mixers or chemical mixers can be used. The photocurable polysiloxane composition of the present invention is cured by irradiation with an active energy beam. Examples of active energy beams include ultraviolet light, electron beams, X-rays, or radiation; however, from the viewpoint of ease of operation, ultraviolet light is preferred. There are no particular limitations on the light source or wavelength range of the ultraviolet light used for irradiation. For example, the following can be used: low-pressure mercury lamps, medium-pressure mercury lamps, high-pressure mercury lamps, ultra-high-pressure mercury lamps, black light lamps, microwave-excited mercury lamps, metal halide lamps, sodium lamps, halogen lamps, xenon lamps, LEDs, fluorescent lamps, sunlight, electron beam irradiation devices, and all other known sources. [Example]

[0033] The present invention will now be described in more detail through examples and comparative examples. However, the present invention is not limited to these examples.

[0034] [Measurement and Evaluation Methods] For each component of the Examples and Comparative Examples, the photocurable polysiloxane component was formed into a sheet on a transparent PP film with a hardened thickness of 2 mm. It was then irradiated with 3000 mJ / cm2 of ultraviolet light with a wavelength of 365 nm from both the top and bottom surfaces to harden it, thus becoming the test sample. The above sheet was stamped into a φ25 mm shape, and the following measurements (1) to (3) were performed using a rheometer (ARES-G2, manufactured by TA Instruments).

[0035] (1) Shear elongation Strain sweep tests were conducted on each sample at 25°C, 1.0 Hz, and a strain rate of 100–1500%. The strain value at which tanδ reaches its minimum was taken as the shear elongation. Regarding the elongation improvement rate (%), the following composition was prepared as the composition of each comparative example: a composition consisting only of organopolysiloxane (A2) and organopolysiloxane (B) without component (A1), and where the ratio of the number of mercaptoalkyl groups (SH) in organopolysiloxane (A) to the number of aliphatic unsaturated groups (Vi) in organopolysiloxane (B) (hereinafter referred to as the SH / Vi ratio) was equal. The ratio of the shear elongation of the sample in each example to the shear elongation of the sample in each comparative example was calculated as the elongation improvement rate (%). An elongation improvement rate of 110% or higher was considered acceptable (○), and less than 110% was considered unacceptable (×). Furthermore, when calculating the elongation improvement rate, only the following comparative examples are used, which do not contain the aforementioned organopolysiloxane (Al) corresponding to the examples described below and have an equal SH / Vi ratio. Examples 1, 4 and Comparative Example 7 are Comparative Example 1, Example 2 is Comparative Example 2, Example 3 is Comparative Example 3, Example 5 is Comparative Example 4, Examples 6, 9 and Comparative Example 14 are Comparative Example 8, Example 7 is Comparative Example 9, Example 8 is Comparative Example 10, and Example 10 is Comparative Example 11.

[0036] (2) Attenuation (tanδ) The dynamic viscoelasticity of each sample was measured according to JIS K7244-10, and the tanδ at 25℃ and 10Hz was obtained. A tanδ of 0.5 or higher was considered acceptable (○), and a tanδ of less than 0.5 was considered unacceptable (×).

[0037] (3) Modulus of elasticity (complex modulus of elasticity G*) The dynamic viscoelasticity of each sample was measured according to JIS K7244-10, and the complex elastic modulus G* at 25℃ and 10Hz was obtained.

[0038] [Example 1] 0.60g of Shin-Etsu Chemical Co., Ltd. product X-22-167C (mercaptoequivalent: 0.4348mmol / g) as organopolysiloxane (A1), 0.93g of Shin-Etsu Chemical Co., Ltd. product KF-2001 (mercaptoequivalent: 0.5263mmol / g, referred to as component A2-1 in the table below) as organopolysiloxane (A2), 18.07g of Gelest Co., Ltd. product DMS-V33 (vinyl equivalent: 0.0465mmol / g, referred to as component B-1 in the table below) as organopolysiloxane (B), and 0.40g of IGM Resins BV Co., Ltd. product Omnirad1173 as photopolymerization initiator (C) are placed into a capped plastic container. The mixture was formulated with an SH / Vi ratio of 0.89 and a ratio of the number of mercaptoalkyl groups (SH(A1)) in the organopolysiloxane (A1) to the number of aliphatic unsaturated groups (Vi) in the organopolysiloxane (B) (hereinafter referred to as the SH(A1) / Vi ratio) of 0.31. The mixture was kneaded at 2000 rpm for 3 minutes using a rotation-revolution mixer (product name: Awa Tori (registered trademark) ARE-350, Thinky Co., Ltd.), followed by centrifugation at 2200 rpm for 1 minute to remove bubbles, yielding the photocurable polysiloxane composition of Example 1. The photocurable polysiloxane composition was then measured and evaluated according to the above-described determination and evaluation methods, including (1) shear elongation, (2) attenuation, and (3) modulus of elasticity.

[0039] [Example 2] Except that components (A1), (A2), (B), and (C) (hereinafter also referred to as constituent components) in Example 1 were replaced with the formulations shown in Table 1, the SH / Vi ratio was 0.70, and the SH(A1) / Vi ratio was 0.31, the photocurable polysiloxane composition of Example 2 was obtained by the same method as in Example 1. The photocurable polysiloxane composition was then subjected to the above-described determination and evaluation methods for (1) shear elongation, (2) attenuation, and (3) elastic modulus.

[0040] [Example 3] Except that the components in Example 1 were replaced with the formulations shown in Table 1, the SH / Vi ratio was 0.99, and the SH(Al) / Vi ratio was 0.31, the photocurable polysiloxane composition of Example 3 was obtained by the same method as in Example 1. The photocurable polysiloxane composition was then subjected to the above-described determination and evaluation methods for (1) shear elongation, (2) attenuation, and (3) elastic modulus.

[0041] [Example 4] Except that the components in Example 1 were replaced with the formulations shown in Table 1, the SH / Vi ratio was 0.89, and the SH(Al) / Vi ratio was 0.06, the photocurable polysiloxane composition of Example 4 was obtained by the same method as in Example 1. The photocurable polysiloxane composition was then subjected to the above-described determination and evaluation methods for (1) shear elongation, (2) attenuation, and (3) elastic modulus.

[0042] [Example 5] Except for further adjusting 0.40 g of fumed silica (AEROSIL product, model: R972) as filler (D) in Example 1 (equivalent to 2.00 wt% relative to the total weight of components (A1), (A2), (B), and (C)), the photocurable polysiloxane composition of Example 5 was obtained by the same method as in Example 1. The photocurable polysiloxane composition was then subjected to determination and evaluation of (1) shear elongation, (2) attenuation, and (3) modulus of elasticity according to the above-described determination and evaluation methods.

[0043] [Example 6] The organopolysiloxane (A2) in Example 1 was replaced with a product from Gelest, model: SMS-022 (thiol equivalent: 0.3286 mmol / g, referred to as component A2-2 in the table below), and the organopolysiloxane (B) was replaced with a product from Gelest, model: DMS-V22 (vinyl equivalent: 0.2222 mmol / g, referred to as component B-2 in the table below), resulting in the formulation shown in Table 2. The formulation was prepared with an SH / Vi ratio of 0.89 and an SH(A1) / Vi ratio of 0.10. The photocurable polysiloxane composition of Example 6 was obtained using the same method as in Example 1. The photocurable polysiloxane composition was then subjected to the above-described determination and evaluation methods for (1) shear elongation, (2) attenuation, and (3) elastic modulus.

[0044] [Example 7] Except that the components of Example 6 were replaced with those shown in Table 2, the SH / Vi ratio was 0.80, and the SH(Al) / Vi ratio was 0.09, the photocurable polysiloxane composition of Example 7 was obtained by the same method as in Example 6. The photocurable polysiloxane composition was then subjected to the above-described determination and evaluation methods for (1) shear elongation, (2) attenuation, and (3) elastic modulus.

[0045] [Example 8] Except that the components of Example 6 were replaced with those shown in Table 2, the SH / Vi ratio was 0.99, and the SH(Al) / Vi ratio was 0.10, the photocurable polysiloxane composition of Example 8 was obtained by the same method as in Example 6. The photocurable polysiloxane composition was then subjected to the above-described determination and evaluation methods for (1) shear elongation, (2) attenuation, and (3) elastic modulus.

[0046] [Example 9] Except that the components of Example 6 were replaced with those shown in Table 2, the SH / Vi ratio was 0.89, and the SH(Al) / Vi ratio was 0.06, the photocurable polysiloxane composition of Example 9 was obtained by the same method as in Example 6. The photocurable polysiloxane composition was then subjected to the above-described determination and evaluation methods for (1) shear elongation, (2) attenuation, and (3) elastic modulus.

[0047] [Example 10] Except for further adjusting 0.40 g of fumed silica (AEROSIL product, model: R972) as filler (D) in Example 6 (equivalent to 2.04 wt% relative to the total weight of components (A1), (A2), (B), and (C)), the photocurable polysiloxane composition of Example 10 was obtained by the same method as in Example 6. The photocurable polysiloxane composition was then subjected to determination and evaluation of (1) shear elongation, (2) attenuation, and (3) elastic modulus according to the above-described determination and evaluation methods.

[0048] [Comparative Example 1] Except that the components in Example 1 were replaced with those shown in Table 3, the component (A1) was not present, the SH / Vi ratio was 0.89, and the SH(A1) / Vi ratio was 0.00, the photocurable polysiloxane composition of Comparative Example 1 was obtained by the same method as in Example 1. The photocurable polysiloxane composition was then subjected to the above-described determination and evaluation methods for (1) shear elongation, (2) attenuation, and (3) elastic modulus.

[0049] [Comparative Example 2] Except that the components in Comparative Example 1 were replaced with those shown in Table 3 and the SH / Vi ratio was 0.70, the photocurable polysiloxane composition of Comparative Example 2 was obtained by the same method as that of Comparative Example 1. The photocurable polysiloxane composition was then measured and evaluated according to the above-described measurement and evaluation methods, including (1) shear elongation, (2) attenuation and (3) elastic modulus.

[0050] [Comparative Example 3] Except that the components in Comparative Example 1 were replaced with those shown in Table 3 and the SH / Vi ratio was 0.99, the photocurable polysiloxane composition of Comparative Example 3 was obtained by the same method as that of Comparative Example 1. The photocurable polysiloxane composition was then measured and evaluated according to the above-described determination and evaluation methods for (1) shear elongation, (2) attenuation and (3) elastic modulus.

[0051] [Comparative Example 4] Except for further blending fumed silica (AEROSIL product, model: R972) as filler (D) in Comparative Example 1, replacing each component with the formulation shown in Table 3, and setting the SH / Vi ratio to 0.89, the photocurable polysiloxane composition of Comparative Example 4 was obtained by the same method as in Comparative Example 1. The photocurable polysiloxane composition was then tested and evaluated according to the above-described determination and evaluation methods for (1) shear elongation, (2) attenuation, and (3) elastic modulus.

[0052] [Comparative Example 5] Except that the components in Example 1 were replaced with those shown in Table 3, the SH / Vi ratio was 0.67, and the SH(Al) / Vi ratio was 0.30, the photocurable polysiloxane composition of Comparative Example 5 was obtained by the same method as in Example 1. The photocurable polysiloxane composition was then subjected to the above-described determination and evaluation methods for (1) shear elongation, (2) attenuation, and (3) elastic modulus.

[0053] [Comparative Example 6] Except that the components in Example 1 were replaced with those shown in Table 3, the SH / Vi ratio was 1.05, and the SH(Al) / Vi ratio was 0.31, the photocurable polysiloxane composition of Comparative Example 6 was obtained by the same method as in Example 1. The photocurable polysiloxane composition was then subjected to the above-described determination and evaluation methods for (1) shear elongation, (2) attenuation, and (3) elastic modulus.

[0054] [Comparative Example 7] Except that the components in Example 1 were replaced with those shown in Table 3, the SH / Vi ratio was 0.89, and the SH(Al) / Vi ratio was 0.05, the photocurable polysiloxane composition of Comparative Example 7 was obtained by the same method as in Example 1. The photocurable polysiloxane composition was then subjected to the above-described determination and evaluation methods for (1) shear elongation, (2) attenuation, and (3) elastic modulus.

[0055] [Comparative Example 8] Except that the components in Example 6 were replaced with those shown in Table 4, the component without (A1), the SH / Vi ratio was 0.89, and the SH(A1) / Vi ratio was 0.00, the photocurable polysiloxane composition of Comparative Example 8 was obtained by the same method as in Example 6. The photocurable polysiloxane composition was then subjected to the above-described determination and evaluation methods for (1) shear elongation, (2) attenuation, and (3) elastic modulus.

[0056] [Comparative Example 9] Except that the components in Comparative Example 8 were replaced with those shown in Table 4 and the SH / Vi ratio was 0.80, the photocurable polysiloxane composition of Comparative Example 9 was obtained by the same method as that of Comparative Example 8. The photocurable polysiloxane composition was subjected to the above-described determination and evaluation methods for (1) shear elongation, (2) attenuation and (3) elastic modulus.

[0057] [Comparative Example 10] Except that the components in Comparative Example 8 were replaced with those shown in Table 4 and the SH / Vi ratio was 0.99, the photocurable polysiloxane composition of Comparative Example 10 was obtained by the same method as that of Comparative Example 8. The photocurable polysiloxane composition was subjected to the above-described determination and evaluation methods for (1) shear elongation, (2) attenuation and (3) elastic modulus.

[0058] [Comparative Example 11] Except for further blending fumed silica (AEROSIL product, model: R972) as filler (D) in Comparative Example 8, replacing each component with the blending shown in Table 4, and having an SH / Vi ratio of 0.89, the photocurable polysiloxane composition of Comparative Example 11 was obtained by the same method as in Comparative Example 8. The photocurable polysiloxane composition was then tested and evaluated according to the above-described determination and evaluation methods for (1) shear elongation, (2) attenuation, and (3) elastic modulus.

[0059] [Comparative Example 12] Except that the components in Example 6 were replaced with those shown in Table 4, the SH / Vi ratio was 0.69, and the SH(Al) / Vi ratio was 0.09, the photocurable polysiloxane composition of Comparative Example 12 was obtained by the same method as in Example 6. The photocurable polysiloxane composition was then subjected to the above-described determination and evaluation methods for (1) shear elongation, (2) attenuation, and (3) elastic modulus.

[0060] [Comparative Example 13] Except that the components in Example 6 were replaced with those shown in Table 4, the SH / Vi ratio was 1.05, and the SH(Al) / Vi ratio was 0.10, the photocurable polysiloxane composition of Comparative Example 13 was obtained by the same method as in Example 6. The photocurable polysiloxane composition was then subjected to the above-described determination and evaluation methods for (1) shear elongation, (2) attenuation, and (3) elastic modulus.

[0061] [Comparative Example 14] Except that the components in Example 6 were replaced with those shown in Table 4, the SH / Vi ratio was 0.89, and the SH(Al) / Vi ratio was 0.05, the photocurable polysiloxane composition of Comparative Example 14 was obtained by the same method as in Example 6. The photocurable polysiloxane composition was then subjected to the above-described determination and evaluation methods for (1) shear elongation, (2) attenuation, and (3) elastic modulus.

[0062] The evaluation results of Examples 1-5 are shown in Table 1, and the evaluation results of Examples 6-10 are shown in Table 2. Furthermore, the evaluation results of Comparative Examples 1-7 are shown in Table 3, and the evaluation results of Comparative Examples 8-14 are shown in Table 4.

[0063] [Table 1]

[0064] [Table 2]

[0065] [Table 3]

[0066] [Table 4]

[0067] As can be seen from the results of Examples 1 to 10, the photocurable polysiloxane composition of the present invention can obtain a photocurable polysiloxane composition with high attenuation and excellent shear elongation by having the following configuration: the aforementioned configuration contains: a linear organopolysiloxane (B) having at least two aliphatic unsaturated groups at both ends; an organopolysiloxane (A1) having two mercaptoalkyl groups at both ends and functioning as a chain length extender of the organopolysiloxane (B); an organopolysiloxane (A2) having mercaptoalkyl groups that bond with silicon atoms and functioning as a curing agent for crosslinked organopolysiloxane (B); and a photopolymerization initiator (C); and an SH / Vi ratio of 0.70 or more and less than 1.00, and an SH(A1) / Vi ratio of 0.06 or more. Furthermore, the results of the complex modulus G* in Examples 1-5 and Examples 6-10 show that even with only the composition of organic polysiloxane polymers, a wide range of complex moduli of hardened materials can be designed.

[0068] Furthermore, the results of Examples 5 and 10 show that even with the inclusion of filler (D), the shear elongation is excellent, exhibiting a high elongation improvement rate. Also, a comparison of the results of Examples 1-5 and Examples 6-10 shows that the effects of the present invention can be obtained even by changing the types of organopolysiloxane (A2) and organopolysiloxane (B).

[0069] On the other hand, a comparison of the results of Examples 1-4 with those of Comparative Examples 1-4, and a comparison of the results of Examples 6-9 with those of Comparative Examples 8-11, shows that even under the same conditions of each component and SH / Vi ratio, when the organic polysiloxane (A1), which functions as a chain length extender for the organic polysiloxane (B) and has mercaptoalkyl groups at both ends, is not included, the measured values ​​of shear elongation and attenuation (tanδ) are poor, and it is impossible to achieve both shear elongation and attenuation. Furthermore, according to the results of the comparative examples, the measured value of the elastic modulus (G*) also increases, limiting the designable range of the complex elastic modulus of the cured material. Moreover, the results of Comparative Examples 5 and 12 show that when the SH / Vi ratio is less than 0.70, the crosslinking caused by the thiol-ene reaction becomes insufficient, and curing is impossible. The results of Comparative Examples 6 and 13 show that when the SH / Vi ratio is 1.00 or higher, good attenuation cannot be obtained. Furthermore, the results of Comparative Examples 7 and 14 show that if the SH(Al) / Vi ratio is less than 0.06, the shear elongation cannot be improved. From these results, it is important that the formulation of each component is set such that the SH(Al) / Vi ratio is 0.06 or higher, and the SH / Vi ratio is 0.70 or higher and less than 1.00. Industrial availability

[0070] The photocurable polysiloxane composition of the present invention can form a cured material with a wide designable range of complex elastic moduli, high attenuation and excellent shear elongation. Therefore, it can be used as a sealing material for electrical and electronic parts, a coating material, potting material, vibration damping material for sensors, and an optical adhesive (OCR, OCA) for image display devices. It is particularly suitable for use in narrow spaces in small electrical and electronic products.

Claims

1. A photocurable polysiloxane composition, characterized in that it comprises: an organopolysiloxane (A) containing mercaptoalkyl groups; a linear organopolysiloxane (B) containing aliphatic unsaturated groups at at least two ends; and a photopolymerization initiator (C); wherein the organopolysiloxane (A) is composed of: an organopolysiloxane (A1) containing mercaptoalkyl groups at both ends, and an organopolysiloxane (A2) containing two or more mercaptoalkyl groups per molecule that can bond with silicon atoms; wherein the ratio of the number of mercaptoalkyl groups in the organopolysiloxane (A) to the number of aliphatic unsaturated groups in the organopolysiloxane (B) is 0.70 or more and less than 1.00; and the ratio of the number of mercaptoalkyl groups in the organopolysiloxane (A1) to the number of aliphatic unsaturated groups in the organopolysiloxane (B) is 0.06 or more.

2. The photocurable polysiloxane composition as claimed in claim 1, wherein the content of the aforementioned photopolymerization initiator (C) is 0.05 to 50 parts by weight relative to 100 parts by weight of the aforementioned organopolysiloxane (B).

3. The light-curing polysiloxane composition of claim 1 or 2 further comprises a filler (D).

4. The light-curing polysiloxane composition of claim 3, wherein the aforementioned filler (D) is selected from at least one substance in the group consisting of silicon oxide, polysiloxane, solid resin, fibrous compound and metal oxide.

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