Method for curing photocurable silicone composition

Abstract

To provide a method for curing a photocurable silicone composition that does not cause inhibition of surface hardening even when cured in air.SOLUTION: A method for curing a photocurable silicone composition comprising (A) 100 pts.mass of an organopolysiloxane represented by the following general formula (1), and (B) 0.1 to 10 pts.mass of a polymerization initiator that generates radicals upon exposure to light having a wavelength of 200 to 300 nm, includes a step of applying light using an LED having an emission peak wavelength in a range of 200 to 300 nm.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a method for curing a photocurable silicone composition.

Background Art

[0002] For curing silicone compositions, crosslinking reactions using hydrosilylation reactions, heat curing reactions using peroxides as initiators, and condensation crosslinking reactions using moisture in the air have been used for a long time. In recent years, as energy conservation and process shortening are increasingly required, an ultraviolet curing reaction that can be cured in a short time at room temperature has attracted attention. Among ultraviolet curing reactions, radical curable compositions using a photo radical polymerization initiator in particular are excellent in storage stability under light shielding and can also be liquefied (Patent Documents 1 and 2).

[0003] However, in recent years, when attempting to cure an existing ultraviolet curable silicone composition in the air using an LED having an emission wavelength of 350 to 400 nm, which is becoming the mainstream of ultraviolet light sources, there have been problems such as curing inhibition caused by oxygen, where the surface does not cure or tack remains. Further, when performing ultraviolet irradiation with the composition sandwiched between transparent members to prevent curing inhibition by oxygen, it has been necessary to wipe the composition in the portions not covered by the transparent members before ultraviolet irradiation and to wash uncured materials after irradiation.

[0004] As a method for improving the surface curability of a radical curable composition in air, an ultraviolet curable silicone composition that combines a hydrosilylation reaction using a platinum group metal catalyst activated by light irradiation and a radical reaction using a photo radical polymerization initiator has been proposed (Patent Document 3). However, photoactive platinum group metal catalysts are generally costly, and it has been necessary to use organohydridopolysiloxane having a hydrogen atom bonded to a silicon atom in combination.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

Problems to be Solved by the Invention

[0006] The present invention has been made in view of the above circumstances, and an object thereof is to provide a method for curing a photocurable silicone composition that does not cause surface curing inhibition even when cured in the air.

Means for Solving the Problems

[0007] In order to solve the above problems, in the present invention, (A) Organopolysiloxane represented by the following general formula (1): 100 parts by mass,

Chemical formula

Chemical formula

[0008] In the case of such a method for curing a photocurable silicone composition of the present invention, due to the presence of phenyl groups in the component (A), a cured product of the photocurable silicone composition can be obtained simply and at low cost without causing surface curing inhibition even in the air.

[0009] In the method for curing a photocurable silicone composition of the present invention, 3 to 50% of the total number of R 1 and R 5 in the component (A) is preferably a phenyl group.

[0010] In the case of such a method for curing a photocurable silicone composition of the present invention in which the component (A) satisfies such a range, both surface curability and deep curability can be achieved.

[0011] Further, in the method for curing a photocurable silicone composition of the present invention, the number of (meth)acrylic groups in the component (A) is preferably 3 or more per molecule.

[0012] In the case of the curing method of the photocurable silicone composition of the present invention containing the component (A) as described above, the curability can be improved.

[0013] Moreover, in the curing method of the photocurable silicone composition of the present invention, it is preferable that the component (B) is a polymerization initiator that generates radicals even by light of more than 300 nm and 450 nm or less.

[0014] In the case of the curing method of the photocurable silicone composition of the present invention in which the component (B) is such a polymerization initiator, not only the surface curability but also the deep curability can be improved.

[0015] Furthermore, the curing method of the photocurable silicone composition of the present invention preferably includes a step of irradiating light using an LED having an emission peak wavelength in the range of more than 300 nm and 450 nm or less.

[0016] In the case of the curing method of the photocurable silicone composition of the present invention including such a step, the deep curability can be further improved.

Effect of the Invention

[0017] As described above, in the case of the curing method of the photocurable silicone composition of the present invention, a cured product of the photocurable silicone composition can be obtained simply and at low cost without causing surface curing inhibition even in the air.

Modes for Carrying Out the Invention

[0018] As described above, there has been a demand for the development of a curing method for a photocurable silicone composition excellent in surface curability and deep curability.

[0019] As a result of intensive studies on the above problems, the present inventors have found that a curing method of irradiating a photocurable silicone composition containing an organopolysiloxane having a (meth)acrylic group at the molecular chain terminal and a phenyl group in the side chain with LED light in a specific wavelength region is excellent in surface curability even in the air, and have completed the present invention.

[0020] That is, the present invention relates to (A) 100 parts by mass of an organopolysiloxane represented by the following general formula (1): [Chemical formula] (In the formula, n is an integer of 5 or more, p and q are integers of 0 to 3, p + q is an integer of 1 to 6, and Z 1 may be the same or different and is an oxygen atom or a substituted or unsubstituted divalent hydrocarbon group having 1 to 10 carbon atoms, and R 1 may be the same or different and is a substituted or unsubstituted monovalent hydrocarbon group having 1 to 12 carbon atoms, provided that one or more of R 1 are phenyl groups, and R 2 may be the same or different and is a group represented by the following general formula (2).) [Chemical formula] (In the formula, m is any one of 0, 1, and 2, R 3 may be the same or different and is a hydrogen atom, a phenyl group, or a halogenated phenyl group, R 4 may be the same or different and is a hydrogen atom or a methyl group, R 5 may be the same or different and is a substituted or unsubstituted monovalent hydrocarbon group having 1 to 12 carbon atoms, Z 2 may be the same or different and is -R 6 - or -R 6 -O-(R 6 is a substituted or unsubstituted divalent hydrocarbon group having 1 to 10 carbon atoms.) and Z 3is an oxygen atom or a divalent hydrocarbon group having 1 to 10 carbon atoms which may be substituted or unsubstituted, and the broken line represents a bond.) and (B) A polymerization initiator that generates radicals by light having a wavelength of 200 to 300 nm: 0.1 to 10 parts by mass A method for curing a photocurable silicone composition containing characterized by including a step of irradiating light using an LED having an emission peak wavelength in the range of 200 to 300 nm.

[0021] Hereinafter, the present invention will be described in detail, but the present invention is not limited thereto. <Component (A)> Component (A) is an organopolysiloxane represented by the following formula (1). [Chemical formula]

[0022] In the above formula (1), n is an integer of 5 or more, preferably 10 to 5000, more preferably 100 to 1000. When n is an integer less than 5, the workability before curing is poor, and a photocurable silicone composition lacking flexibility after curing is obtained.

[0023] p and q are integers of 0 to 3, and p + q is an integer of 1 to 6. From the viewpoint of curability, it is preferable that p + q is in the range of 2 to 6.

[0024] Z 1 are each independently an oxygen atom or a divalent hydrocarbon group having 1 to 10 carbon atoms which may be the same or different, and from the viewpoint of the durability of the cured product, an alkylene group having 1 to 6 carbon atoms is preferable, and an alkylene group having 1 to 3 carbon atoms is particularly preferable. Examples of such an alkylene group include a methylene group, an ethylene group, and a trimethylene group, and part or all of the hydrogen atoms of these hydrocarbon groups may be substituted with a halogen atom such as fluorine, bromine, or chlorine, or a cyano group.

[0025] R1 is a monovalent hydrocarbon group having 1 to 12 carbon atoms, which may be the same or different and may be substituted or unsubstituted, preferably having 1 to 8 carbon atoms. Specifically, alkyl groups such as methyl group, ethyl group, propyl group, isopropyl group, butyl group, isobutyl group, tert-butyl group, pentyl group, neopentyl group, hexyl group, octyl group, nonyl group, decyl group, cycloalkyl groups such as cyclohexyl group, aryl groups such as phenyl group, tolyl group, xylyl group, naphthyl group, aralkyl groups such as benzyl group, phenylethyl group, phenylpropyl group, alkenyl groups such as vinyl group, allyl group, propenyl group, isopropenyl group, butenyl group, hexenyl group, octenyl group, and those in which some or all of the hydrogen atoms of these groups are substituted with halogen atoms such as fluorine, bromine, chlorine, cyano group, etc., for example, halogen-substituted alkyl groups such as chloromethyl group, chloropropyl group, bromoethyl group, trifluoropropyl group, and cyanoethyl group, etc. are mentioned, and methyl group and phenyl group are preferred.

[0026] However, R 1 One or more of them are phenyl groups, preferably 3 to 50%, more preferably 5 to 30% of R 1 are phenyl groups. Although the detailed mechanism of action is unknown, by including a phenyl group in the side chain of the organopolysiloxane of component (A), the curability of the surface of the photocurable silicone composition by light irradiation with a wavelength of 200 to 300 nm becomes good.

[0027] In the above formula (1), R 2 is a group represented by the following formula (2), which may be the same or different.

Chemical formula

[0028] In the above formula (2), m is any one of 0, 1, 2, preferably 1 or 2.

[0029] R 3is a hydrogen atom, a phenyl group, or a halogenated phenyl group, which may be the same or different from each other. Among them, a hydrogen atom is preferred from the viewpoints of radical reactivity, reactivity with Si-H, and synthesis.

[0030] R 4 is a hydrogen atom or a methyl group, which may be the same or different from each other.

[0031] R 5 is a substituted or unsubstituted monovalent hydrocarbon group having 1 to 12 carbon atoms, and hydrocarbon groups similar to those of the above R 1 can be exemplified. Among them, a methyl group and a phenyl group are preferred.

[0032] Among the total number of R 1 in the above formula (1) and R 2 in the above formula (2), it is preferable that 3 to 50% is a phenyl group. When the phenyl group is in the range of 3 to 50%, particularly, both surface curability and deep curability can be achieved, which is preferable.

[0033] Z 2 is -R 6 - or -R 6 -O-(R 6 is a substituted or unsubstituted divalent hydrocarbon group having 1 to 10 carbon atoms. ). R 6 As the divalent hydrocarbon group of, hydrocarbon groups similar to those of the above Z 1 can be exemplified. Among them, an ethylene group and a trimethylene group are preferred.

[0034] Z 3 is an oxygen atom or a substituted or unsubstituted divalent hydrocarbon group having 1 to 10 carbon atoms. As the divalent hydrocarbon group, hydrocarbon groups similar to those of the above Z 1 can be exemplified. As Z 3 an oxygen atom, an ethylene group, and a trimethylene group are preferred.

[0035] The number of (meth)acrylic groups in component (A) is preferably 3 or more, more preferably 4 to 6 per molecule. Having 3 or more is preferable because the curability is improved.

[0036] The viscosity of component (A) at 25°C is preferably in the liquid state of 0.01 to 1,000 Pa·s. The viscosity can be, for example, a value measured by a rotational viscometer.

[0037] Component (A) is preferably the following M 3MA unit, D unit and D 2Φ unit, or an organopolysiloxane composed of M 2A unit, D unit and D 2Φ unit.

Chemical formula

[0038] Specific examples of component (A) are shown below. The arrangement order of the diorganosiloxane units may be arbitrary.

Chemical formula

[0039] Such organopolysiloxanes can be produced by known methods. For example, the organopolysiloxanes represented by the above formulas (A-1) and (A-2) can be obtained as a hydrosilylation reaction product of a dimethylsiloxane·diphenylsiloxane copolymer blocked with trivinylsiloxy groups at both ends and 3-(1,1,3,3-tetramethyldisiloxanyl)propyl methacrylate (CAS No. 96474-12-3).

[0040] The organopolysiloxanes represented by the above formulas (A-3) and (A-4) can be obtained by reacting a dimethylvinylsiloxy group-blocked dimethylsiloxane·diphenylsiloxane copolymer with dichloromethylsilane and then reacting the resulting product with 2-hydroxyethyl acrylate.

[0041] These component (A) may be used alone or in combination of two or more.

[0042] <Component (B)> Component (B) is a polymerization initiator that generates radicals by light with a wavelength of 200 to 300 nm. For example, any photo radical polymerization initiator known in the art for curing acrylic functional groups such as benzoin and substituted benzoin, dialkoxyacetophenone such as diethoxyacetophenone, benzophenone and substituted benzophenone, acetophenone and substituted acetophenone, and xanthone and substituted xanthone can be used.

[0043] From the viewpoint of improving surface curability and deep curability, component (B) is preferably a polymerization initiator that generates radicals not only by light with a wavelength of 200 to 300 nm but also by light with a wavelength exceeding 300 nm and 450 nm or less.

[0044] Specific examples of such photo radical polymerization initiators include 2,2 - diethoxyacetophenone, 2,2 - dimethoxy - 1,2 - diphenylethane - 1 - one (Omnirad 651 manufactured by IGM Resins B.V., absorption wavelength peaks: 252 nm, 325 nm), 1 - hydroxy - cyclohexyl - phenyl - ketone (Omnirad 184 manufactured by IGM Resins B.V., absorption wavelength peaks: 243 nm, 331 nm), 2 - hydroxy - 2 - methyl - 1 - phenyl - propan - 1 - one (Omnirad 1173 manufactured by IGM Resins B.V., absorption wavelength peaks: 244 nm, 330 nm), 2 - hydroxy - 1 - {4 - [4 - (2 - hydroxy - 2 - methyl - propionyl) - benzyl] - phenyl} - 2 - methyl - propan - 1 - one (Omnirad 127 manufactured by BASF, IGM Resins B.V., absorption wavelength peaks: 243 nm, 332 nm), 2 - methyl - 1 - [4 - (methylthio)phenyl] - 2 - morpholinopropan - 1 - one (Omnirad 907 manufactured by IGM Resins B.V., absorption wavelength peaks: 230 nm, 303 nm), 2 - benzyl - 2 - dimethylamino - 1 - (4 - morpholinophenyl) - 1 - butanone (Omnirad 369 manufactured by IGM Resins B.V., absorption wavelength peaks: 232 nm, 323 nm), 2 - dimethylamino - 2 - (4 - methylbenzyl) - 1 - (4 - morpholin - 4 - yl - phenyl) - butan - 1 - one (Omnirad 379EG manufactured by IGM Resins B.V., absorption wavelength peaks: 233 nm, 320 nm), bis(2,4,6 - trimethylbenzoyl) - phenylphosphine oxide (Omnirad 819 manufactured by IGM Resins B.V., absorption wavelength peaks: 237 nm, 380 nm), 2,4,6 - trimethylbenzoyl - diphenyl - phosphine oxide (Omnirad TPO H manufactured by IGM Resins B.V., absorption wavelength peaks: 275 nm, 379 nm), methyl benzoylformate (Omnirad MBF manufactured by IGM Resins B.V., absorption wavelength peaks: 255 nm, 325 nm) and mixtures thereof, etc.

[0045] Among the above (B) components, from the perspective of compatibility with the (A) component, preferred are 2,2 - diethoxyacetophenone, 2 - hydroxy - 2 - methyl - 1 - phenyl - propan - 1 - one (Omnirad 1173 manufactured by IGM Resins B.V.), and 2 - dimethylamino - 2 - (4 - methylbenzyl) - 1 - (4 - morpholin - 4 - yl - phenyl) - butan - 1 - one (Omnirad 379EG manufactured by IGM Resins B.V.).

[0046] The content of the (B) component is 0.1 to 10 parts by mass, preferably 0.2 to 8 parts by mass, more preferably 0.5 to 6 parts by mass with respect to 100 parts by mass of the (A) component. If the content of the (B) component is less than 0.1 part by mass, the effect of promoting curing may not be obtained, and if it exceeds 10 parts by mass, the mechanical properties of the cured product may deteriorate.

[0047] <Other components> In the photocurable silicone composition used in the curing method of the photocurable silicone composition of the present invention, components such as an adhesion improver, a radical reaction controller, a reactive diluent, a non - reactive diluent, and an inorganic filler may be added according to the purpose.

[0048] As the adhesion improver, organosilicon compounds such as silanes and siloxanes containing a functional group that imparts adhesiveness, and non - silicone - based organic compounds are used. More specifically, those that do not simultaneously contain a radical - reactive group and an alkoxysilyl group in one molecule are preferred. For example, (meth)acryloxypropyltrimethoxysilane, trialkyl - or triallyl - isocyanurate, glycidoxypropyltrimethoxysilane, and vinyltrimethoxysilane can be mentioned.

[0049] Examples of the radical reaction inhibitor include phenolic radical reaction inhibitors such as dibutylhydroxytoluene (BHT), and amine - based radical reaction inhibitors such as diphenylamine derivatives.

[0050] The reactive diluent or non-reactive diluent is used for the purpose of adjusting the viscosity of the photocurable silicone composition or adjusting the hardness of the cured product, and examples thereof include compounds having a (meth)acrylic group other than the component (A), and non-(meth)acrylic polysiloxanes.

[0051] Examples of the compound having a (meth)acrylic group other than the component (A) include polyethylene glycol di(meth)acrylate and isobornyl methacrylate.

[0052] Examples of the non-(meth)acrylic polysiloxane include dimethylpolysiloxane blocked at both ends with trimethylsiloxy groups, dimethylpolysiloxane-diphenylsiloxane copolymer blocked at both ends with trimethylsiloxy groups, dimethylpolysiloxane blocked at both ends with trivinylsiloxy groups, dimethylpolysiloxane-diphenylsiloxane copolymer blocked at both ends with trivinylsiloxy groups, dimethylpolysiloxane blocked at both ends with dimethylvinylsiloxy groups, dimethylsiloxane-diphenylsiloxane copolymer blocked at both ends with dimethylvinylsiloxy groups, and silicone rubber.

[0053] Examples of the inorganic filler can include reinforcing silicas such as fumed silica and crystalline silica, and silica surface-treated with an organosilicon compound having a (meth)acryloyl group can also be used.

[0054] <Method for preparing the photocurable silicone composition> In the present invention, the method for preparing the photocurable silicone composition is not particularly limited and can be carried out by mixing, stirring, and dispersing the above-mentioned respective components. The devices for mixing, stirring, dispersing, etc. are not particularly limited, but a Lyca machine equipped with a stirring and heating device, a three-roll mill, a ball mill, a planetary mixer, a bead mill, etc. can be used. Also, these devices may be used in appropriate combination.

[0055] <Curing method> The curing method of the photocurable silicone composition of the present invention includes a step I of irradiating light using an LED having an emission peak wavelength in the range of 200 to 300 nm.

[0056] The irradiation intensity of light in step I is preferably 20 to 2,000 mW / cm 2 and the irradiation dose is preferably 100 to 10,000 mJ / cm 2 The temperature during irradiation is preferably 10 to 60 °C, more preferably 20 to 40 °C.

[0057] The curing method of the photocurable silicone composition of the present invention preferably further includes a step II of irradiating light using an LED having an emission peak wavelength in the range of more than 300 nm and 450 nm or less. By performing step II, the curing of the deep part of the composition, which is difficult to reach with short-wavelength light, can be efficiently promoted, so that a thicker cured product can be obtained.

[0058] The irradiation intensity of light in step II is preferably 100 to 3,000 mW / cm 2 and the irradiation dose is preferably 100 to 20,000 mJ / cm 2 The temperature during irradiation is preferably 10 to 60 °C, more preferably 20 to 40 °C.

[0059] The above step I and step II may be performed simultaneously, or step II may be performed after step I, or step I may be performed after step II.

Example

[0060] Hereinafter, the present invention will be specifically described using examples and comparative examples, but the present invention is not limited thereto.

[0061] The abbreviations representing each siloxane unit are as follows.

Chemical formula

[0062] [Preparation Examples 1 to 8] The following components were mixed in the compositions (parts by mass) shown in Table 1 to prepare photocurable silicone compositions i to viii.

[0063] [Component (A)] (A-1) M 3MA 2D 390 D 2Φ 43 An organopolysiloxane represented by (viscosity at 25°C: 10 Pa·s) (A-2) M 3MA 2D 94 D 2Φ 41 An organopolysiloxane represented by (viscosity at 25°C: 2.8 Pa·s) (A-3) M 2A 2D 216 D 2Φ 7 An organopolysiloxane represented by (viscosity at 25°C: 1.0 Pa·s) (A-4) M 2A 2D 243 D 2Φ 27 An organopolysiloxane represented by (viscosity at 25°C: 3.4 Pa·s) (A’-5) M 3MA 2D 510 An organopolysiloxane represented by (viscosity at 25°C: 10 Pa·s) (A’-6) M 2A 2D 180 An organopolysiloxane represented by (viscosity at 25°C: 1.0 Pa·s) (A’-7) M 3V 2D 390 D 2Φ 43 An organopolysiloxane represented by (viscosity at 25°C: 10 Pa·s)

[0064] [Component (B)] (B-1) 2-Hydroxy-2-methyl-1-phenyl-propan-1-one (Omnirad 1173 manufactured by IGM Resins B.V.) (B-2) 2-Dimethylamino-2-(4-methylbenzyl)-1-(4-morpholin-4-yl-phenyl)-butan-1-one (Omnirad 379EG manufactured by IGM Resins B.V.)

[0065]

Table 1

[0066] [Examples 1 to 7 and Comparative Examples 1 to 4] Regarding the photocurable silicone compositions obtained in Preparation Examples 1 to 8, they were poured into a silicone rubber mold having a depression of 10 mm × 10 mm × 10 mm, and after performing light irradiation by the following light irradiation methods I to IV, the following evaluations were conducted. The evaluation results are shown in Table 2.

[0067] <Light Irradiation Methods I to IV> Light Irradiation Method I: (Step I) Using a UV-LED irradiator (MS-A0202EF) manufactured by Matsuo Sangyo Co., Ltd., in the air at room temperature (25°C), ultraviolet light with a wavelength peak of 275 nm was irradiated at an intensity of 50 mW / cm 2 for 100 seconds. Light Irradiation Method II: (Step II) Using a UV-LED irradiator (MS-B2101AF) manufactured by Matsuo Sangyo Co., Ltd., in the air at room temperature (25°C), ultraviolet light with a wavelength peak of 365 nm was irradiated at an intensity of 1400 mW / cm 2 for 7 seconds. Light Irradiation Method III: After performing Step I, Step II was performed. Light Irradiation Method IV: After performing Step II, Step I was performed.

[0068] <Thickness of the Cured Product> The cured part was taken out from the photocurable silicone composition immediately after performing light irradiation by Light Irradiation Methods I to IV, and the thickness was measured with a micrometer (M820-25VA) manufactured by Mitutoyo Corporation. <Surface Curing Property> After irradiating the photocurable silicone composition with light, those that had hardened up to the surface and were tack-free when touched with a finger were evaluated as "tack-free", those that had hardened up to the surface but still had tack were evaluated as "tacky", and those that had not hardened on the surface and were in a liquid state were evaluated as "liquid".

[0069]

Table 2

[0070] As shown in Table 2, in the curing methods according to Examples 1 to 5 in which the light irradiation method I (Step I) corresponding to the light irradiation step of the present invention was performed, cured products without surface tack were obtained. In Examples 6 and 7 in which Step I and Step II were used in combination, in addition to surface curability, they had particularly excellent deep curability. On the other hand, in Comparative Examples 1 and 2 in which the (A) component was changed to an organopolysiloxane having no phenyl group, and in Comparative Example 3 in which the radical reactive group of the (A) component was changed to a vinyl group, the surface curability deteriorated. Also, in Comparative Example 4 in which only the light irradiation method II of Step II was performed, the surface of the photocurable silicone composition did not cure.

[0071] As described above, it was found that with the curing method of the photocurable silicone composition of the present invention that irradiates LED light in a specific wavelength region, a cured product of a photocurable silicone composition excellent in surface curability can be obtained without causing surface curing inhibition even in the air.

[0072] This specification includes the following aspects. [1]: (A) Organopolysiloxane represented by the following general formula (1): 100 parts by mass,

Chemical formula

Chemical formula

[0073] Note that the present invention is not limited to the above-described embodiments. The above-described embodiments are examples, and any configuration that has substantially the same configuration as the technical idea described in the claims of the present invention and exhibits the same operational effects is included in the technical scope of the present invention.

Claims

1. (A) 100 parts by mass of an organopolysiloxane represented by the following general formula (1): 【Chemical Formula 1】 (In the formula, n is an integer of 5 or more, p and q are integers of 0 to 3, p + q is an integer of 1 to 6, and Z １ may be the same or different and is an oxygen atom or a divalent hydrocarbon group having 1 to 10 carbon atoms which may be substituted or unsubstituted, and R １ may be the same or different and is a monovalent hydrocarbon group having 1 to 12 carbon atoms which may be substituted or unsubstituted, provided that one or more of R １ are phenyl groups, and R ２ are groups represented by the following general formula (2) which may be the same or different. ) 【Chemical Formula 2】 (In the formula, m is any one of 0, 1, 2, and R ３ may be the same or different and is a hydrogen atom, a phenyl group or a halogenated phenyl group, and R ４ may be the same or different and is a hydrogen atom or a methyl group, and R ５ may be the same or different and is a monovalent hydrocarbon group having 1 to 12 carbon atoms which may be substituted or unsubstituted, and Z ２ may be the same or different and is -R ６ - or -R ６ -O-(R ６ is a divalent hydrocarbon group having 1 to 10 carbon atoms which may be substituted or unsubstituted. ), and Z ３ is an oxygen atom or a divalent hydrocarbon group having 1 to 10 carbon atoms which may be substituted or unsubstituted, and the broken line represents a bond. ) And, (B) 0.1 to 10 parts by mass of a polymerization initiator that generates radicals by light having a wavelength of 200 to 300 nm A method for curing a photocurable silicone composition containing characterized by including a step of irradiating light using an LED having an emission peak wavelength in the range of 200 to 300 nm.

2. said R １ and R ５ A method for curing the photocurable silicone composition according to claim 1, characterized in that 3 to 50% of the total number of said R and R is a phenyl group.

3. A method for curing the photocurable silicone composition according to claim 1, characterized in that the number of (meth)acrylic groups in component (A) is 3 or more per molecule.

4. A method for curing the photocurable silicone composition according to claim 1, characterized in that component (B) contains a polymerization initiator that generates radicals even by light with a wavelength exceeding 300 nm and not exceeding 450 nm.

5. A method for curing the photocurable silicone composition according to claim 1, further comprising a step of irradiating light using an LED having an emission peak wavelength in the range exceeding 300 nm and not exceeding 450 nm.

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