Alkenyl group-containing cyclic siloxane derivative, method for producing same, curable composition, and cured product of same

Abstract

The present invention is an alkenyl group-containing cyclic siloxane derivative, which is characterized by being an addition reaction product of (i) an organic silicon compound represented by general formula (1) and (ii) an alkenyl group-containing cyclic siloxane represented by general formula (2). Due to this configuration, provided is an organic modified silicone that excels in safety and simple production steps, has low viscosity, and, when used in a curable composition, provides a cured product that has excellent hardness and permeability of light in a short-wavelength range.

Description

Alkenyl group-containing cyclic siloxane derivatives, methods for producing the same, curable compositions, and cured products thereof.

[0001] This invention relates to alkenyl group-containing cyclic siloxane derivatives, methods for producing the same, curable compositions, and cured products thereof.

[0002] It has been known that organic modified silicone resin compositions having a bis(dimethylsilyl)benzene skeleton in their main chain are hybrid resins that possess the high heat resistance and high transparency of silicone resins (dimethylsilicone resins) as well as the high hardness, high toughness, and high gas barrier properties of organic resins such as polyolefin resins and polyethylene terephthalate resins.

[0003] Patent Document 1 proposes an addition-curing type organic modified silicone composition that provides a cured product with high hardness and toughness and excellent light transmittance in the short wavelength region by using an addition reaction product having two or more Si-H groups in one molecule, obtained by adding bis(dimethylsilyl)benzene, which has an excess amount of Si-H groups, to an alkenyl group contained in an organosilicon compound having an alkenyl group as a crosslinking agent.

[0004] However, bis(dimethylsilyl)benzene used in the above addition reaction is bioaccumulative and has a high boiling point, so a step to remove excess bis(dimethylsilyl)benzene, such as by heating and distilling under reduced pressure, was necessary.

[0005] Japanese Patent Publication No. 2021-59682

[0006] In conventional technology, in the production of addition-curing organic modified silicone compositions that yield cured products with high hardness and toughness and excellent light transmittance in the short-wavelength region, bis(dimethylsilyl)benzene remains as an unreacted substance, requiring a step to remove it.

[0007] The present invention has been made to solve the above problems and aims to provide an alkenyl group-containing cyclic siloxane derivative that is excellent in safety and ease of manufacturing, has low viscosity, and when used as a curable composition, gives a cured product with excellent hardness and light transmittance in the short wavelength region.

[0008] To achieve the above objectives, the present invention provides an alkenyl group-containing cyclic siloxane derivative characterized by being an addition product of (i) an organosilicon compound represented by the following general formula (1) and (ii) an alkenyl group-containing cyclic siloxane represented by the following general formula (2). (In the formula, R １ (This refers to a substituted or unsubstituted divalent hydrocarbon group having 1 to 12 carbon atoms.) (In the formula, R ２ These are independently alkenyl groups having 2 to 12 carbon atoms, and R ３ (where a is independently a methyl group or a phenyl group, a is an integer from 2 to 5, b is an integer from 0 to 5, a+b is an integer from 3 to 5, and the arrangement of siloxane units may be arbitrary.)

[0009] The present invention provides a curable composition that, due to its low viscosity, offers good workability and handling, and yields a cured product with excellent hardness and light transmittance in the short wavelength region upon curing.

[0010] Furthermore, the alkenyl group-containing cyclic siloxane derivative is the R in the general formula (1) above. １ However, a phenylene group is preferred.

[0011] In the above general formula (1), R １ It is preferable that it be like this.

[0012] Furthermore, the alkenyl group-containing cyclic siloxane derivative of the present invention is R in the general formula (1) above. ２ However, it is a vinyl group, and the R ３ Preferably, the group is a methyl group, a is 3 or 4, and b is 0.

[0013] In the above general formula (1), R ２ It is preferable that it be like this.

[0014] Further, the present invention provides a curable composition comprising: (A) the alkenyl group-containing cyclic siloxane derivative described above; (B) an organosilicon compound having two or more hydrogen atoms bonded to silicon atoms in one molecule; and (C) a hydrosilylation reaction catalyst.

[0015] The curable composition of the present invention is a curable composition that provides a cured product excellent in hardness and light transmittance in the short wavelength region.

[0016] Further, the present invention provides a cured product obtained by curing the curable composition.

[0017] The cured product of the present invention can provide a cured product excellent in hardness and light transmittance in the short wavelength region.

[0018] The present invention provides a method for producing the alkenyl group-containing cyclic siloxane derivative described above, which includes a step of mixing the component (ii) in an amount of more than 1.0 mol and not more than 6.0 mol with respect to 1.0 mol of the component (i) and performing a hydrosilylation reaction in the presence of both.

[0019] By setting the molar ratio of the component (ii) to the component (i) within such a range, it is possible to prevent the residual of the unreacted component (i). Therefore, the removal step of the component (i) is not required, and the production can be carried out more safely and simply.

[0020] As described above, in the case of the alkenyl group-containing cyclic siloxane of the present invention, it has a low viscosity and can provide a cured product that is excellent in hardness and light transmittance in the short wavelength region when used in a curable composition. Further, in the case of the method for producing the alkenyl group-containing cyclic siloxane of the present invention, the step of removing the component (i) is not required, and the production can be carried out more safely and simply. Furthermore, the cured product obtained from the curable composition of the present invention can be suitably used for applications such as protection, sealing or adhesion of light emitting diode elements, wavelength change or adjustment, or lenses. It is also useful as a material for various optical parts such as lens materials, encapsulating materials for optical devices or optical parts, display materials, insulating materials for electronic devices or electronic parts, and further as a coating material. Moreover, the semiconductor device of the present invention using such a curable composition has excellent reliability.

[0021] As described above, there has been a demand for the development of a curable composition that is excellent in safety, simplicity of the manufacturing process, has a low viscosity, and can provide a cured product that is excellent in hardness and light transmittance in the short wavelength region.

[0022] As a result of intensive studies on the above problems, the present inventors have found that a curable composition containing a specific alkenyl group-containing cyclic siloxane derivative can solve the above problems, and have completed the present invention.

[0023] That is, the present invention is an alkenyl group-containing cyclic siloxane derivative, which is an addition reaction product of (i) an organosilicon compound represented by the following general formula (1) and (ii) an alkenyl group-containing cyclic siloxane represented by the following general formula (2). (In the formula, R １ is a divalent hydrocarbon group having 1 to 12 carbon atoms, which may be substituted or unsubstituted.) (In the formula, R ２ is independently an alkenyl group having 2 to 12 carbon atoms, R ３ is independently a methyl group or a phenyl group, a is an integer of 2 to 5, b is an integer of 0 to 5, a + b is an integer of 3 to 5, and the arrangement of the siloxane units may be arbitrary.)

[0024] The present invention will be described in detail below, but the present invention is not limited to these descriptions.

[0025] [(A) Alkenyl group-containing cyclic siloxane derivatives] Components (i) and (ii) of the alkenyl group-containing cyclic siloxane derivatives of the present invention will be described below.

[0026] [Component (i)] Component (i) in the alkenyl group-containing cyclic siloxane derivative of the present invention is an organosilicon compound represented by the following formula (1). (In the formula, R １ (This refers to a substituted or unsubstituted divalent hydrocarbon group having 1 to 12 carbon atoms.)

[0027] In the above general formula (1), R １ Examples of divalent hydrocarbon groups having 1 to 12 carbon atoms represented by include alkylene groups such as methylene group, ethylene group, n-propylene group, n-butylene group, n-pentylene group, n-hexylene group, cyclohexylene group, n-octylene group, etc., and arylene groups such as phenylene group, naphthylene group, etc., and the above R １ A phenylene group is particularly preferred.

[0028] The organosilicon compounds represented by the above general formula (1) can be used individually or in combination of two or more.

[0029] [Component (ii)] Component (ii) in the alkenyl group-containing cyclic siloxane derivative of the present invention is an alkenyl group-containing cyclic siloxane represented by the following formula (2). (In the formula, R ２ These are independently alkenyl groups having 2 to 12 carbon atoms, and R ３ (where a is independently a methyl group or a phenyl group, a is an integer from 2 to 5, b is an integer from 0 to 5, a+b is an integer from 3 to 5, and the arrangement of siloxane units may be arbitrary.)

[0030] The above R ２Examples of alkenyl groups having 2 to 12 carbon atoms, represented by , include linear alkenyl groups such as vinyl, allyl, propenyl, butenyl, pentenyl, hexenyl, heptenyl, and octenyl groups, and cyclic alkenyl groups such as cyclohexenyl and norborneyl groups. Vinyl and allyl groups are preferred, and vinyl groups are more preferred.

[0031] The above R ３ This group is independently either a methyl group or a phenyl group, but a methyl group is more preferred.

[0032] The above a is an integer between 2 and 5, preferably 3 or 4; the above b is an integer between 0 and 5, preferably 0; and the above a + b is an integer between 3 and 5, preferably 3 or 4.

[0033] The following are some preferred examples of alkenyl group-containing cyclic siloxanes represented by the above general formula (2), but are not limited to these. Furthermore, the alkenyl group-containing cyclic siloxanes represented by the above general formula (2) can be used individually or in combination of two or more types. (The arrangement of siloxane units in the formula may be arbitrary.)

[0034] The alkenyl group-containing cyclic siloxane derivative of the present invention may contain hydrogen atoms (Si-H groups) bonded to unreacted silicon atoms derived from component (i) above, but it is preferable that all Si-H groups undergo hydrosilylation. That is, an addition reaction product of (i) n molecules of an organosilicon compound represented by the above general formula (1) and (ii) n+1 molecules of an alkenyl group-containing cyclic siloxane represented by the above general formula (2) is preferred, for example, one represented by the following formula. (In the equation, n is an integer between 1 and 10, p and q are integers satisfying p + q + (p + 2) = n + 1, and r, s, and t are integers satisfying r + s + t + (2r + s + 2) = n + 1. Dashed lines represent combinations.)

[0035] [Method for Producing Alkenyl Group-Containing Cyclic Siloxane Derivatives] The present invention provides a method for producing alkenyl group-containing cyclic siloxane derivatives, comprising the steps of (i) mixing 1.0 mole of an organosilicon compound represented by the general formula (1) with (ii) an alkenyl group-containing cyclic siloxane represented by the general formula (2) in an amount greater than 1.0 mole and less than or equal to 6.0 moles, preferably greater than 1.5 moles and less than or equal to 3.0 moles, and carrying out a hydrosilylation reaction in the presence of both. By using such a range, it is possible to prevent the residue of unreacted component (i), thus eliminating the need for a step to remove component (i), and enabling safer and simpler production.

[0036] As catalysts used in the hydrosilylation reaction, known catalysts can be used. Examples include platinum-based catalysts such as platinum-supported carbon powder, platinum black, platinum-dic chloride, chloroplatinic acid, reaction products of chloroplatinic acid and monohydric alcohols, complexes of chloroplatinic acid and olefins, and platinum bisacetate; and platinum group metal catalysts such as palladium-based catalysts and rhodium-based catalysts. Furthermore, there are no particular limitations on the addition reaction conditions, purification conditions, and solvent use, and known methods may be used.

[0037] The alkenyl group content of the alkenyl group-containing cyclic siloxane derivative of the present invention is preferably 0.1 to 0.7 moles per 100 g, and more preferably 0.2 to 0.6 moles.

[0038] The weight-average molecular weight (Mw) of the alkenyl group-containing cyclic siloxane derivative of the present invention, measured by gel permeation chromatography on a standard polystyrene basis, is preferably 500 to 20,000, and more preferably 1,000 to 10,000.

[0039] The viscosity of the alkenyl group-containing cyclic siloxane derivative of the present invention, as measured by a rotational viscometer at 23°C, is preferably 10 to 10,000 mPa·s, and more preferably 100 to 5,000 mPa·s. Within this range, the resulting curable composition tends to have good workability and handling properties, and is less prone to the entrapment of bubbles and air during molding and curing.

[0040] The alkenyl group-containing cyclic siloxane derivative of the present invention may consist of one compound or a combination (mixture) of two or more compounds.

[0041] [Curable Composition] The curable composition of the present invention is a curable composition comprising (A) the above-mentioned alkenyl group-containing cyclic siloxane derivative, (B) an organosilicon compound having two or more hydrogen atoms bonded to silicon atoms in one molecule, and (C) a hydrosilylation reaction catalyst.

[0042] [Component (A)] Component (A) in the curable composition of the present invention is an alkenyl group-containing cyclic siloxane derivative which is the addition product of (i) an organosilicon compound represented by the above general formula (1) and (ii) an alkenyl group-containing cyclic siloxane represented by the above general formula (2).

[0043] [Component (B)] Component (B) in the curable composition of the present invention is an organosilicon compound having two or more hydrogen atoms bonded to silicon atoms in one molecule, and functions as a crosslinking agent that crosslinks with aliphatic unsaturated bonds contained in component (A) through a hydrosilylation reaction. There is no particular upper limit to the number of hydrogen atoms bonded to silicon atoms contained in one molecule of component (B), but it can be, for example, 50 or less.

[0044] The above component (B) is preferably one or more selected from the group consisting of an organohydrogenpolysiloxane represented by the following general formula (3), an organohydrogenpolysiloxane represented by the following formula (4), and an organosilicon compound represented by the following general formula (5).

[0045] (R ４ Each of these is independently either a methyl group or a phenyl group, where c is an integer from 1 to 3, and d is an integer from 1 to 3. The order of the siloxane units in parentheses is arbitrary.

[0046] [(C ６ H ５ ) SiO ３／２ ] ｅ [H(C ６ H ５ ) (CH ３) SiO １／２ ] ｅ＋２ (4) (In the formula, e is an integer between 1 and 3.)

[0047] (In the formula, m is an integer between 1 and 3. Dashed lines represent connections.)

[0048] The above component (B) may consist of one compound or a combination (mixture) of two or more compounds.

[0049] The amount of component (B) described above should be sufficient to cure the curable composition of the present invention in the presence of the hydrosilylation catalyst of component (C) described later, but preferably it is an amount such that the molar ratio of Si-H groups in component (B) to the number of aliphatic unsaturated bonds in component (A) is 0.2 to 5, and more preferably it is an amount such that it is 0.8 to 2.

[0050] [Component (C)] As the hydrosilylation reaction catalyst for component (C) in the curable composition of the present invention, known catalysts can be used. Examples include platinum-based catalysts such as platinum metal-supported carbon powder, platinum black, platinum-dic chloride, chloroplatinic acid, reaction products of chloroplatinic acid and monohydric alcohols, complexes of chloroplatinic acid and olefins, and platinum bisacetate; and platinum group metal catalysts such as palladium-based catalysts and rhodium-based catalysts. Furthermore, there are no particular limitations on the addition reaction conditions, purification conditions, and the use of solvents, and known methods may be used.

[0051] The amount of component (C) incorporated into the curable composition of the present invention may be any amount that is effective as a catalyst, but preferably it is 1 to 500 ppm, more preferably 1 to 100 ppm, of platinum group metal atoms relative to the total mass of the curable composition.

[0052] [Other Components] In addition to the components (A) to (C) above, the curable composition of the present invention may contain, as needed, components such as antioxidants and inorganic fillers. The following describes optional components.

[0053] [Antioxidant] In the cured product of the curable composition of the present invention, there may be unreacted aliphatic unsaturated bonds in component (A) above, which can be oxidized by oxygen in the atmosphere, causing the cured product to become discolored. Therefore, such discoloration can be prevented by incorporating an antioxidant into the curable composition of the present invention as needed.

[0054] Known antioxidants can be used, such as 2,6-di-t-butyl-4-methylphenol, 2,5-di-t-amylhydroquinone, 2,5-di-t-butylhydroquinone, 4,4'-butylidenebis(3-methyl-6-t-butylphenol), 2,2'-methylenebis(4-methyl-6-t-butylphenol), and 2,2'-methylenebis(4-ethyl-6-t-butylphenol). One of these compounds may be used alone as an antioxidant, or two or more may be used in combination.

[0055] When using the above-mentioned antioxidant, the amount to be blended is not particularly limited, but it is preferably 1 to 10,000 ppm, and more preferably 10 to 1,000 ppm, relative to the total mass of components (A) and (B). By blending within the above range, the antioxidant capacity is fully exhibited, and a cured product with excellent optical properties is obtained without discoloration, clouding, oxidative degradation, etc.

[0056] [Inorganic Fillers] In order to adjust the viscosity of the curable composition of the present invention, the hardness of the cured product obtained from the curable composition of the present invention, etc., or to improve the strength, inorganic fillers such as nanosilica, fused silica, crystalline silica, titanium oxide, nanoalumina, and alumina may be added.

[0057] When using the inorganic filler described above, the amount blended is preferably 0.1 to 20 parts by mass, and more preferably 1 to 10 parts by mass, based on 100 parts by mass of the total of components (A) and (B).

[0058] [Adhesion Enhancer] The curable composition of the present invention may contain an adhesion enhancer. Examples of adhesion enhancers include silane coupling agents and their oligomers, and polysiloxanes having reactive groups similar to those of silane coupling agents.

[0059] Adhesion improvers are optional components added to the curable composition of the present invention to improve the adhesion of the curable composition and its cured product to a substrate. Here, the substrate refers to metallic materials such as gold, silver, copper, and nickel; ceramic materials such as aluminum oxide, aluminum nitride, and titanium oxide; and polymer materials such as silicone resins and epoxy resins. One of these adhesion improvers may be used alone, or two or more may be used in combination.

[0060] When using an adhesion improver, the amount to be added is preferably 1 to 30 parts by mass, and more preferably 1 to 10 parts by mass, relative to 100 parts by mass of the total of components (A) and (B). With such an amount, the curable composition of the present invention and its cured product effectively improve adhesion to the substrate and are less prone to discoloration.

[0061] Suitable specific examples of adhesion improvers include, but are not limited to, those represented by the following formula.

[0062]

[0063]

[0064] [Other] In addition, to ensure pot life, addition reaction control agents such as 1-ethynylcyclohexanol and 3,5-dimethyl-1-hexyne-3-ol can be added.

[0065] Furthermore, light stabilizers can be used to provide resistance to photodegradation caused by light energy such as sunlight and fluorescent lamps. Hindered amine-based stabilizers that capture radicals generated by photooxidative degradation are suitable as light stabilizers, and the antioxidant effect is further improved when used in combination with antioxidants. Specific examples of light stabilizers include bis(2,2,6,6-tetramethyl-4-piperidyl) sebacate and 4-benzoyl-2,2,6,6-tetramethylpiperidine.

[0066] The viscosity of the curable composition of the present invention, as measured by a rotational viscometer at 23°C, is preferably 10 to 5000 mPa·s, and more preferably 20 to 1000 mPa·s. Within this range, the resulting composition tends to have good workability and handling properties, and is less prone to the entrapment of bubbles and air during molding and curing.

[0067] [Cured product] The curable composition of the present invention can be cured to obtain a cured product of the present invention. That is, the present invention provides a cured product obtained by curing the curable composition of the present invention.

[0068] The cured product exhibits high hardness, mechanical strength, and crack resistance, as well as excellent light transmittance and gas barrier properties in the short-wavelength region. While there are no particular limitations on the curing conditions for the curable composition of the present invention, it is preferable to use a temperature of 60 to 180°C and a curing time of 5 to 300 minutes.

[0069] The cured product obtained from the curable composition of the present invention preferably has a light transmittance of 70% or more at a wavelength of 450 nm at 25°C with a thickness of 1 mm.

[0070] Furthermore, from the viewpoint of making it less susceptible to external stress and minimizing the adhesion of dirt and other debris, it is preferable that the above-mentioned curable composition, upon curing, forms a cured product with a hardness of 70 or higher on ShoreD, as specified in ASTM D 2240.

[0071] A cured product of the present invention having such optical properties can be suitably used for applications such as protecting, sealing, or bonding light-emitting diode elements, changing or adjusting wavelengths, or for use in lenses, and is also a useful material for various optical components such as lens materials, sealing materials for optical devices or optical components, and display materials.

[0072] The present invention will be specifically described below using examples, but the present invention is not limited to these examples.

[0073] Furthermore, in the examples, １ ¹H-NMR measurements were performed using a Bruker BioSpin AVANCE III. GPC (gel permeation chromatography) measurements were performed using a Tosoh HLC-8320GPC, with tetrahydrofuran (THF) as the mobile phase, and the results were measured in polystyrene equivalent.

[0074] [Example 1-1] 517 g (2.2 mol) of 1,3,5-trimethyl-1,3,5-trivinylcyclotrisiloxane and 0.2 g of a toluene solution of platinum 1,3-divinyl-1,1,3,3-tetramethyldisiloxane complex (platinum content 0.5% by mass) were placed in a 2 L four-necked flask equipped with a stirrer, condenser, dropping funnel, and thermometer, and the mixture was heated to an internal temperature of 105°C. 194 g (1.0 mol) of 1,4-bis(dimethylsilyl)benzene was added dropwise. After the addition was complete, the mixture was stirred at 90-100°C for 3 hours. After stirring, the mixture was returned to 25°C. １ The disappearance of the Si-H group peak was confirmed by 1H-NMR spectroscopy. After adding 3.4 g of activated carbon and stirring for 1 hour, the mixture was filtered, and excess 1,3,5-trimethyl-1,3,5-trivinylcyclotrisiloxane was removed by vacuum concentration to obtain 482 g of alkenyl group-containing cyclic siloxane derivative (A-1).

[0075] The obtained alkenyl group-containing cyclic siloxane derivative (A-1) is presumed to be a mixture of addition reaction products obtained by the reaction of n+1 molecules of 1,3,5-trimethyl-1,3,5-trivinylcyclotrisiloxane with n molecules of 1,4-bis(dimethylsilyl)benzene represented by the following formula. Its viscosity at 23°C was 4000 mPa·s, its weight-average molecular weight by GPC was 2857, and its vinyl group content was 0.40 mol / 100g.

[0076] (In the equation, n is an integer between 1 and 10, and p and q are integers that satisfy p + q + (p + 2) = n + 1. Dashed lines represent combinations.)

[0077] [Example 1-2] 190 g (0.55 mol) of 1,3,5,7-tetramethyl-1,3,5,7-tetravinylcyclotetrasiloxane and 0.1 g of a toluene solution of platinum 1,3-divinyl-1,1,3,3-tetramethyldisiloxane complex (platinum content 0.5% by mass) were placed in a 500 mL four-necked flask equipped with a stirrer, condenser, dropping funnel, and thermometer, and the mixture was heated to an internal temperature of 105°C. 49 g (0.25 mol) of 1,4-bis(dimethylsilyl)benzene was added dropwise. After the addition was complete, the mixture was stirred at 90-100°C for 3 hours. After stirring, the mixture was returned to 25°C. １ The disappearance of the Si-H group peak was confirmed by 1H-NMR spectroscopy. After adding 2.4 g of activated carbon and stirring for 1 hour, the mixture was filtered, and excess 1,3,5,7-tetramethyl-1,3,5,7-tetravinylcyclotetrasiloxane was removed by vacuum concentration to obtain 482 g of alkenyl group-containing cyclic siloxane derivative (A-2).

[0078] The obtained alkenyl group-containing cyclic siloxane derivative (A-2) is presumed to be a mixture of addition reaction products obtained by the reaction of n+1 molecules of 1,3,5,7-tetramethyl-1,3,5,7-tetravinylcyclotetrasiloxane with n molecules of 1,4-bis(dimethylsilyl)benzene represented by the following formula. Its viscosity at 23°C was 3000 mPa·s, its weight-average molecular weight determined by GPC was 5344, and its vinyl group content was 0.50 mol / 100g.

[0079] (In the equation, n is an integer between 1 and 10, and r, s, and t are integers that satisfy r + s + t + (2r + s + 2) = n + 1. Dashed lines represent combinations.)

[0080] [Examples 2-1 and 2-2] The following components were mixed in the composition ratios shown in Table 1 below (values ​​represent parts by mass) to prepare a curable composition such that the molar ratio of Si-H groups to alkenyl groups in the composition ([Si-H groups] / [alkenyl groups]) was 1.1. In the following examples, the symbols representing the constituent units of organopolysiloxane are as follows: M Ｈ : H(CH ３ ) ２ SiO １／２ D ２Φ : (C ６ H ５ ) ２ SiO ２／２ D Ｈ : H(CH ３ ) SiO ２／２

[0081] (A) Component (A-1) Addition product obtained in Example 1-1 (A-2) Addition product obtained in Example 1-2

[0082] (B) Component M Ｈ ２ D ２Φ ２ D Ｈ ２ Linear organohydrogenpolysiloxane represented by

[0083] (C) Toluene solution of the platinum-1,3-divinyl-1,1,3,3-tetramethyldisiloxane complex (platinum content: 0.5% by mass)

[0084]

[0085] [Performance Evaluation Method] The curable compositions obtained in the above examples were evaluated for their cured product performance according to the following method.

[0086] (1) A curable composition was poured into a mold made of hardened glass plates and cured at 150°C for 4 hours to obtain a cured product with a thickness of 2 mm. The hardness (Shore D) of each cured product was measured at 23°C according to ASTM D 2240 and the results are shown in Table 2.

[0087] (2) Light transmittance The 400 nm light transmittance of each 2 mm thick cured material, prepared in the same manner as the hardness measurement described above, was measured using a spectrophotometer. The measurement results are shown in Table 2 below.

[0088] As shown in Tables 1 and 2 above, the curable compositions of Examples 2-1 and 2-2 have low viscosity, excellent hardness of 70 or higher, and provide cured products with excellent light transmittance of 70% or higher.

[0089] The present invention encompasses the following aspects: [1]: An alkenyl group-containing cyclic siloxane derivative, characterized in that it is an addition product of (i) an organosilicon compound represented by the following general formula (1) and (ii) an alkenyl group-containing cyclic siloxane represented by the following general formula (2). (In the formula, R １ (This refers to a substituted or unsubstituted divalent hydrocarbon group having 1 to 12 carbon atoms.) (In the formula, R ２ These are independently alkenyl groups having 2 to 12 carbon atoms, and R ３ (1) is independently a methyl group or a phenyl group, a is an integer from 2 to 5, b is an integer from 0 to 5, a + b is an integer from 3 to 5, and the arrangement of siloxane units may be arbitrary.) [2]: The above R １ The alkenyl group-containing cyclic siloxane derivative according to [1], characterized in that it is a phenylene group. [3]: The R ２ However, it is a vinyl group, and the R ３The alkenyl group-containing cyclic siloxane derivative according to [1] or [2], characterized in that the above is a methyl group, a is 3 or 4, and b is 0. [4]: ​​A curable composition characterized by comprising (A) an alkenyl group-containing cyclic siloxane derivative according to any one of [1] to [3], (B) an organosilicon compound having two or more hydrogen atoms bonded to a silicon atom in one molecule, and (C) a hydrosilylation reaction catalyst. [5]: A cured product characterized by being obtained by curing the curable composition according to [4]. [6]: A method for producing an alkenyl group-containing cyclic siloxane derivative according to any one of [1] to [3], comprising the step of mixing component (ii) with 1.0 mole of component (i) in an amount greater than 1.0 mole and less than or equal to 6.0 moles, and carrying out a hydrosilylation reaction in the presence of both.

[0090] It should be noted that the present invention is not limited to the embodiments described above. The embodiments described above are illustrative, and any configuration that is substantially identical to the technical idea described in the claims of the present invention and achieves similar effects is included within the technical scope of the present invention.

Claims

1. An alkenyl group-containing cyclic siloxane derivative characterized by being an addition product of (i) an organosilicon compound represented by the following general formula (1) and (ii) an alkenyl group-containing cyclic siloxane represented by the following general formula (2). (In the formula, R １ (This refers to a substituted or unsubstituted divalent hydrocarbon group having 1 to 12 carbon atoms.) (In the formula, R ２ These are independently alkenyl groups having 2 to 12 carbon atoms, and R ３ (where a is independently a methyl group or a phenyl group, a is an integer from 2 to 5, b is an integer from 0 to 5, a+b is an integer from 3 to 5, and the arrangement of siloxane units may be arbitrary.) 2. The aforementioned R １ The alkenyl group-containing cyclic siloxane derivative according to claim 1, characterized in that it is a phenylene group.

3. The aforementioned R ２ However, it is a vinyl group, and the R ３ The alkenyl group-containing cyclic siloxane derivative according to claim 1, characterized in that a is a methyl group, a is 3 or 4, and b is 0.

4. A curable composition characterized by comprising: (A) an alkenyl group-containing cyclic siloxane derivative according to any one of claims 1 to 3; (B) an organosilicon compound having two or more hydrogen atoms bonded to a silicon atom in one molecule; and (C) a hydrosilylation reaction catalyst.

5. A cured product characterized by being obtained by curing the curable composition described in claim 4.

6. A method for producing an alkenyl group-containing cyclic siloxane derivative according to any one of claims 1 to 3, comprising the step of mixing component (ii) with 1.0 mole of component (i) in an amount greater than 1.0 mole and less than or equal to 6.0 moles, and carrying out a hydrosilylation reaction in the presence of both.

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