Curable silicone composition and cured product thereof

Abstract

The present invention relates to a curable silicone composition comprising (A) a diorganopolysiloxane having two silicon-bonded alkenyl groups at both ends of a molecular chain, (B) an organopolysiloxane having a silicon-bonded alkenyl group, (C) an organopolysiloxane having a silicon-bonded hydrogen atom, and (D) a hydrosilylation reaction catalyst, but does not contain an organosilicon compound having two or more silicon-bonded alkoxy groups in the molecule. The composition is curable to form a cured product exhibiting excellent optical properties even when subjected to high temperature and high humidity conditions.

Description

Technical Field

[0001] The invention relates to a curable organic silicon composition and a cured product thereof. Background Art

[0002] The curable silicone compositions can be cured to form cured products having high transparency and high elongation, so that they are used as adhesives or pressure-sensitive adhesives to improve the visibility of optical displays.

[0003] For example, Patent Document 1 discloses a curable silicone composition comprising: at least one organopolysiloxane having at least two alkenyl groups in the molecule, at least one organohydrogenpolysiloxane having at least two silicon-bonded hydrogen atoms in the molecule, a hydrosilylation reaction catalyst, and an adhesion promoter such as 3-glycidoxypropyltrimethoxysilane, 3-methacryloxypropyltrimethoxysilane, and the like.

[0004] Meanwhile, Patent Document 2 discloses a curable silicone composition comprising: a linear or partially branched organopolysiloxane having an alkenyl group in a molecule, a resinous organopolysiloxane having an alkenyl group in a molecule, a linear or partially branched organohydrogenpolysiloxane having a silicon-bonded hydrogen atom at a molecular chain end, a resinous organohydrogenpolysiloxane having a silicon-bonded hydrogen atom in a molecule, a hydrosilylation reaction catalyst, and an organosilicon compound having two or more silicon-bonded alkoxy groups in a molecule, such as 1,6-bis(trimethoxysilyl)hexane.

[0005] However, these curable silicone compositions have problems in forming cured products that exhibit poor optical properties when subjected to high temperature and high humidity conditions. That is, the cured products under severe conditions exhibit haze and low transparency.

[0006] Prior art literature

[0007] Patent Literature

[0008] Patent Document 1: U.S. Patent Application Publication No. 2014 / 0150972A1

[0009] Patent Document 2: U.S. Patent Application Publication No. 2022 / 0002493A1 Summary of the invention

[0010] Technical issues

[0011] An object of the present invention is to provide a curable silicone composition capable of forming a cured product exhibiting excellent optical characteristics even when subjected to high temperature and high humidity conditions, and further to provide a cured product exhibiting excellent optical characteristics.

[0012] Solution to the problem

[0013] The curable silicone composition of the present invention comprises:

[0014] (A) a diorganopolysiloxane represented by the following general formula:

[0015] R 1 2R 2 SiO(R 1 2SiO) m S i 1 2R 2

[0016] Each R 1 is independently an alkyl group having 1 to 12 carbon atoms, each R 2 is independently an alkenyl group having 2 to 12 carbon atoms, and "m" is an integer from 100 to 1000;

[0017] (B) an organopolysiloxane resin represented by the following average unit formula:

[0018] (R 1 3SiO 1 / 2 ) a (R 2 R 1 2SiO 1 / 2 ) b (SiO 4 / 2 ) c (HO 1 / 2 ) d

[0019] Where R 1 and R 2 As described above, and "a", "b", "c" and "d" are numbers satisfying the following conditions: a ≥ 0, b > 0, 0.3 ≤ c ≤ 0.7, 0 ≤ d ≤ 0.05, and a + b + c = 1, and the amount relative to 100 parts by mass of component (A) is 1.0 to 5.0 parts by mass;

[0020] (C) an organopolysiloxane having silicon-bonded hydrogen atoms, the amount of the organopolysiloxane being such that the molar ratio of silicon-bonded hydrogen atoms provided by component (C) to 1 mol of alkenyl groups provided by components (A) and (B) is in the range of 0.5 to 2; and

[0021] (D) an effective amount of a hydrosilylation reaction catalyst,

[0022] However, the curable silicone composition does not include an organosilicon compound having two or more silicon-bonded alkoxy groups in the molecule.

[0023] In various embodiments, component (C) is typically an organopolysiloxane comprising the following components (c1) and (c2):

[0024] (c1) a diorganopolysiloxane having silicon-bonded hydrogen atoms at both molecular chain ends, and

[0025] (c2) an organopolysiloxane resin represented by the following average unit formula:

[0026] (R 1 3SiO 1 / 2 ) e (HR 1 2SiO 1 / 2 ) f (SiO 4 / 2 ) g (HO 1 / 2 ) h

[0027] Each R 1 is independently an alkyl group having 1 to 12 carbon atoms, and "e", "f", "g" and "h" are numbers satisfying the following conditions: e≥0, f>0, 0.3≤g≤0.7, 0≤h≤0.05, and e+f+g=1.

[0028] In various embodiments, the molar ratio of silicon-bonded hydrogen atoms provided by component (c1) to silicon-bonded hydrogen atoms provided by component (c2) is generally in the range of 5 to 60.

[0029] In various embodiments, the curable silicone composition may further include: (E) a hydrosilylation reaction inhibitor in an amount of about 0.00001 to about 0.5 parts by mass relative to 100 parts by mass of the total mass of components (A) to (C).

[0030] The cured product of the present invention is obtained by curing the above-mentioned curable silicone composition.

[0031] Effects of the Invention

[0032] The curable silicone composition of the present invention can be cured to form a cured product that exhibits excellent optical properties even when subjected to high temperature and high humidity conditions. The cured product of the present invention exhibits excellent optical properties.

[0033] definition

[0034] The term "comprising" or "containing" is used in its broadest sense herein to mean and encompass the concepts of "including", "comprising", "consisting essentially of", and "consisting of". The use of "for example", "for example", "such as", and "comprising" to list illustrative examples is not meant to be limited to the listed examples. Therefore, "for example" or "such as" means "for example, but not limited to" or "such as, but not limited to" and encompasses other similar or equivalent examples. As used herein, the term "about" is used to reasonably encompass or describe minor variations of numerical values ​​measured by instrumental analysis or as a result of sample processing. Such minor variations can be approximately ±0-25, ±0-10, ±0-5, or ±0-2.5% of a numerical value. In addition, the term "about" is applicable to two numerical values ​​when associated with a range of values. In addition, the term "about" is applicable to numerical values ​​even when not explicitly stated.

[0035] In general, as used herein, a hyphen "-" or dash "-" within a range of values ​​means "to" or "up to"; ">" means "higher than" or "greater than"; "≥" means "at least" or "greater than or equal to"; "<" means "lower than" or "less than"; and "≤" means "at most" or "less than or equal to". Each of the foregoing patent applications, patents, and / or patent application publications is each expressly incorporated by reference in its entirety in one or more non-limiting embodiments. DETAILED DESCRIPTION

[0036] <Curable Silicone Composition>

[0037] First, the curable silicone composition of the present invention will be described in detail.

[0038] <Component (A)>

[0039] Component (A) is a diorganopolysiloxane represented by the following general formula:

[0040] R 1 2R 2 SiO(R 1 2SiO) m S i 1 2R 2 .

[0041] In the above formula, each R 1 is independently an alkyl group having 1 to 12 carbon atoms. Examples of the alkyl group include a methyl group, an ethyl group, a propyl group, a butyl group and an octyl group, among which a methyl group is preferred.

[0042] In the above formula, each R 2is independently an alkenyl group having 2 to 12 carbon atoms. Examples of the alkenyl group include a vinyl group, an allyl group, a butenyl group, a pentenyl group, a hexenyl group, a heptenyl group, an octenyl group, a nonenyl group, a decenyl group, an undecenyl group and a dodecenyl group, wherein a vinyl group is preferred.

[0043] In the above formula, "m" is an integer of 100 to 1000, alternatively an integer of 100 to 800. This is because when "m" is greater than or equal to the lower limit of the above range, the mechanical properties of the obtained cured product are sufficient, and when it is less than or equal to the upper limit of the above range, the obtained composition has a suitable viscosity in processing and handling.

[0044] The viscosity of component (A) at 25° C. is not limited, but it is generally in the range of about 100 mPa·s to about 100,000 mPa·s, alternatively in the range of about 200 mPa·s to about 50,000 mPa·s, alternatively in the range of about 300 mPa·s to about 50,000 mPa·s. Note that in this specification, the viscosity is a value measured at 23° C.±2° C. using a B-type viscometer according to ASTM D 1084.

[0045] Component (B) is an organopolysiloxane resin represented by the following average unit formula:

[0046] (R 1 3SiO 1 / 2 ) a (R 2 R 1 2SiO 1 / 2 ) b (SiO 4 / 2 ) c (HO 1 / 2 ) d .

[0047] In the above formula, R 1 and R 2 As described above. Examples thereof include the same groups as those described above.

[0048] In the above formula, "a", "b", "c" and "d" are numbers satisfying the following conditions: a≥0, b>0, 0.3≤c≤0.7, 0≤d≤0.05, and a+b+c=1, optionally 0.1≤a≤0.5, 0.01≤b≤0.2, 0.4≤c≤0.7, 0≤d≤0.05, and a+b+c=1, or optionally 0.2≤a≤0.5, 0.01≤b≤0.2, 0.4≤c≤0.7, 0≤d≤0.05, and a+b+c=1. This is because, if "a", "b", "c" and "d" are numbers within the above range, the cured product obtained by curing the composition of the present invention will have appropriate hardness and mechanical strength.

[0049] The amount of component (B) is in the range of 1.0 to 5.0 parts by mass, alternatively in the range of 1.0 to 3.0 parts by mass, relative to 100 parts by mass of component (A). This is because when the amount is greater than or equal to the lower limit of the above range, the mechanical properties of the obtained cured product are sufficient, and when it is less than or equal to the upper limit of the above range, the obtained composition has a suitable viscosity in processing and handling.

[0050] <Component (C)>

[0051] Component (C) is a crosslinking agent for component (A) and component (B) in the composition of the present invention, and is an organopolysiloxane having silicon-bonded hydrogen atoms. In addition to the hydrogen atoms in component (C), examples of groups bonded to silicon atoms include: alkyl groups having 1 to 12 carbon atoms, such as methyl groups, ethyl groups, propyl groups, butyl groups, pentyl groups, hexyl groups, heptyl groups, octyl groups, nonyl groups, decyl groups, undecyl groups, dodecyl groups, etc.; aryl groups having 6 to 20 carbon atoms, such as phenyl groups, tolyl groups, xylyl groups, etc.; aralkyl groups having 7 to 20 carbon atoms, such as benzyl groups, phenethyl groups, etc.; and halogen-substituted alkyl groups having 1 to 12 carbon atoms, such as 3-chloropropyl groups, 3,3,3-trifluoropropyl groups, etc. From the viewpoint of economic efficiency and heat resistance, methyl groups are preferred.

[0052] Examples of the molecular structure of component (C) include linear, partially branched linear, branched, cyclic, and three-dimensional network structures, and the molecular structure is preferably linear, partially branched linear, branched, or three-dimensional network structure.

[0053] Component (C) is generally an organopolysiloxane comprising the following components (c1) and (c2):

[0054] (c1) a diorganopolysiloxane having silicon-bonded hydrogen atoms at both molecular chain ends; and

[0055] (c2) an organopolysiloxane resin represented by the following average unit formula:

[0056] (R 1 3SiO 1 / 2 ) e (HR 1 2SiO 1 / 2 ) f (SiO 4 / 2 ) g (HO 1 / 2 ) h .

[0057] Component (c1) acts as a chain extender in the hydrosilylation reaction with component (A) and component (B) and improves the flexibility of the cured product. Examples of groups other than hydrogen atoms that are bonded to silicon atoms in component (c1) include alkyl groups, aryl groups, aralkyl groups, and halogen-substituted alkyl groups as described above, among which methyl groups and phenyl groups are preferred from the viewpoints of economic efficiency and heat resistance.

[0058] Examples of such component (c1) include dimethylpolysiloxanes terminated at both molecular chain ends by dimethylhydrogensiloxy groups, copolymers of dimethylsiloxanes terminated at both molecular chain ends by dimethylhydrogensiloxy groups and methylphenylsiloxane, and mixtures of two or more types thereof.

[0059] Component (c2) functions as a crosslinking agent in the hydrosilylation reaction with component (A) and component (B), and improves the mechanical properties of the cured product.

[0060] In the formula of component (c2), each R 1 is independently an alkyl group having 1 to 12 carbon atoms. Examples of the alkyl group are as described above. Among them, a methyl group is preferred from the viewpoint of economic efficiency and heat resistance.

[0061] In the formula of component (c2), "e", "f", "g" and "h" are numbers satisfying the following conditions: e≥0, f>0, 0.3≤g≤0.7, 0≤h≤0.05 and e+f+g=1, optionally 0≤e≤0.3, 0.1≤f≤0.7, 0.3≤g≤0.6, 0≤h≤0.05 and e+f+g=1, or optionally 0≤e≤0.1, 0.3≤f≤0.7, 0.3≤g≤0.6, 0≤h≤0.01 and e+f+g=1. This is because, if "e", "f", "g" and "h" are numbers within the above ranges, the cured product obtained by curing the composition of the present invention will have appropriate hardness and mechanical strength.

[0062] The molar ratio of silicon-bonded hydrogen atoms provided by component (c1) to silicon-bonded hydrogen atoms provided by component (c2) is not limited, but it is usually in the range of 5 to 60, alternatively in the range of 10 to 60, or alternatively in the range of 10 to 30. This is because when the molar ratio is greater than or equal to the lower limit of the above range, the adhesive properties of the resulting cured product are sufficient, and when the molar ratio is less than or equal to the upper limit of the above range, the mechanical properties of the resulting cured product are sufficient.

[0063] The amount of component (C) is such an amount that the molar ratio of the silicon-bonded hydrogen atoms provided by component (C) to 1 mol of alkenyl groups provided by component (A) and component (B) is in the range of 0.5 to 2, alternatively in the range of 0.8 to 2, or alternatively in the range of 0.5 to 1.5. This is because if the amount is greater than or equal to the lower limit of the above range, the obtained composition will be fully cured. However, on the other hand, if the amount is less than or equal to the upper limit of the above range, the mechanical properties of the cured product obtained will be enhanced.

[0064] <Component (D)>

[0065] Component (D) is a hydrosilylation reaction catalyst for promoting the curing of the composition of the present invention. The example of the hydrosilylation reaction catalyst includes a platinum-based catalyst, a rhodium-based catalyst and a palladium-based catalyst, and a platinum-based catalyst is preferred. The example of a platinum-based catalyst includes a platinum fine powder, platinum black, a platinum-loaded silica fine powder, a platinum-loaded activated carbon, chloroplatinic acid, an alcohol solution of chloroplatinic acid, an olefin complex of platinum and an alkenylsiloxane complex of platinum.

[0066] The amount of component (D) is an effective amount for promoting the curing of the composition of the present invention, and specifically is an amount in which the platinum atoms in the catalyst are in the range of about 0.1 ppm to about 1,000 ppm, alternatively in the range of about 1 ppm to about 500 ppm in terms of mass unit relative to the composition of the present invention. This is because when the content of component (D) is greater than or equal to the lower limit of the above range, the curing of the resulting composition proceeds, while when the content is less than or equal to the upper limit of the above range, the resulting cured product becomes less prone to discoloration.

[0067] <Component (E)>

[0068] The composition of the present invention may further contain (E) a hydrosilylation reaction inhibitor in order to control its crosslinking reaction. Examples of component (E) include acetylenic alcohols such as 1-ethynylcyclohexan-1-ol, 2-methyl-3-butyn-2-ol, 3,5-dimethyl-1-hexyn-3-ol and 2-phenyl-3-butyn-2-ol; enyne compounds such as 3-methyl-3-pentene-1-yne and 3,5-dimethyl-3-hexene-1-yne; methylalkenylsiloxane oligomers such as 1,3,5,7-tetramethyl-1,3,5,7-tetravinylcyclotetrasiloxane and 1,3,5,7-tetramethyl-1,3,5,7-tetrahexenylcyclotetrasiloxane; alkoxysilanes such as dimethylbis(3-methyl-1-butyn-3-oxy)silane and methylvinyl Bis(3-methyl-1-butyn-3-oxy)silane; alkynyloxysilane compounds, such as methyltris(1-methyl-1-phenyl-propynyloxy)silane, dimethylbis(1-methyl-1-phenyl-propynyloxy)silane, methyltris(1,1-dimethyl-propynyloxy)silane, dimethylbis(1,1-dimethyl-propynyloxy)silane; triazoles, phosphines, thiols, hydrazines, sulfoxides, phosphates, nitriles, hydroperoxides, amines, ethylenically unsaturated isocyanates, fumarates (e.g., dialkyl fumarates, dienyl fumarates and / or dialkoxyalkyl fumarates), maleates (e.g., diallyl maleate), olefins, and combinations thereof.

[0069] The amount of component (E) is not limited, and from the perspective of giving the composition of the present invention sufficient usable life, relative to 100 parts by mass of the total mass of components (A) to (C), the amount is generally in the range of about 0.00001 parts by mass to about 0.5 parts by mass, alternatively in the range of about 0.0001 parts by mass to about 0.5 parts by mass, or alternatively in the range of about 0.0001 parts by mass to about 0.1 parts by mass. This is because when the amount of component (E) is greater than or equal to the lower limit of the above range, the usable life of the composition of the present invention is sufficient for use, and when the content is less than or equal to the upper limit of the above range, the curability of the composition of the present invention is good for use.

[0070] <Other components>

[0071] The composition of the present invention may contain antioxidants, reactive diluents, leveling agents, fillers, antistatic agents, defoamers, pigments, etc. within the scope of not impairing the purpose of the present invention. However, the composition of the present invention does not contain an organosilicon compound having two or more silicon-bonded alkoxy groups in the molecule. The organosilicon component is generally used as an adhesion promoter to improve the bonding strength of the resulting cured product. Examples of the organosilicon compound include 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropylmethyldimethoxysilane, 3-methcryloxypropyltormethoxysilane and other alkoxysilane compounds; and 1,6-bis(trimethoxysilyl)hexane, 1,6-bis(triethoxysilyl)hexane, 1,6-bis(methyldimethoxysilyl)hexane, 1,7-bis(trimethoxysilyl)heptane, 1,8-bis(trimethoxysilyl)octane, 1,9-bis(trimethoxysilyl)nonane, 2,7-bis(trimethoxysilyl)nonane and other organosilicon compounds having one or more alkoxysilyl groups.

[0072] <Cured Product>

[0073] Next, the cured product of the present invention will be described in detail.

[0074] The cured product can be obtained by curing the above-mentioned curable silicone composition. The hardness of the cured product is not limited, but it generally has a 1 / 4 cone penetration of 20 to 90, as measured using a penetrometer specified in ASTM D1403. This is because when its penetration value is greater than or equal to the lower limit of the above range, the cured product can have good peel strength, and when the penetration value is less than or equal to the upper limit of the above range, the cured product can have good mechanical properties.

[0075] Although the shape of the cured product is not limited, examples thereof include sheets, films, tapes, and agglomerates. In addition, integration with various types of substrates is also possible.

[0076] Example

[0077] The curable silicone composition and the cured product of the present invention will be described in further detail below using practical examples and comparative examples. However, the present invention is not limited to the following examples. It should be noted that in the formula, Me and Vi represent a methyl group and a vinyl group, respectively. The viscosity of the organopolysiloxane is measured as follows.

[0078] <Viscosity>

[0079] The viscosity at 23±2° C. was measured by using a B-type viscometer (Brookfield HADVIII Type Rotational Viscometer, using RV-03, 10 rpm, 2 min) according to ASTM D 1084 “Standard Test Methods for Viscosity of Adhesive”.

[0080] <Penetration value>

[0081] The curable silicone composition having a thickness of 10 mm or more was left to cure at 120° C. for 40 minutes in an aluminum pan, and the 1 / 4 cone penetration at 25° C. was measured using Anton Paar Penetrometer PNR 12 manufactured by Anton Paar GmbH.

[0082] <180° Peel Strength>

[0083] The curable silicone composition having a thickness of 1 mm and a width of 25 mm was left to cure between a glass plate and a PET film at 60° C. for 30 minutes and then post-cured for 3 days at 25° C. The 180° peel strength was measured at a peel speed of 305 mm / min.

[0084] <Cohesive failure>

[0085] After measuring the 180° peel strength, the percentage of cohesive failure of the cured product to the glass plate and the PET film was measured.

[0086] <Initial Haze and Transmittance>

[0087] The curable silicone composition having a thickness of 1 mm was left to cure on a glass plate at 70° C. for 40 minutes and then post-cured for 3 days at 25° C. The haze and transmittance at 25° C. of the cured product were measured using a spectrophotometer CM-5 manufactured by Konica Minoluta.

[0088] <Haze and transmittance after high temperature / high humidity test>

[0089] The cured product on the glass plate was subjected to 85°C / 85%RH conditions for 3 days and then cooled.The haze and transmittance at 25°C of the cured product after the high temperature / high humidity test were measured by a spectrophotometer CM-5 manufactured by Konica Minoluta.

[0090] <Practical Examples 1-3 and Comparative Examples 1-2>

[0091] The curable silicone composition shown in Table 1 was prepared using the components mentioned below. First, component (A), component (B) and component (D) were uniformly mixed. Next, component (C) and component (E) were added to produce a curable silicone composition. The resulting cured product was evaluated as described above. These results are given in Table 1. The "SiH / Vi ratio" in Table 1 represents the molar ratio of silicon-bonded hydrogen atoms provided by component (C) to vinyl groups provided by component (A) and component (B). And the "SiH ratio" in Table 1 represents the molar ratio of silicon-bonded hydrogen atoms provided by component (c1) to silicon-bonded hydrogen atoms provided by component (c2).

[0092] The following components were used as component (A).

[0093] Component (a-1): dimethylpolysiloxane having a vinyl group content of 0.21% by mass and a viscosity of 2400 mPa·s, and represented by the following formula:

[0094] ViMe2SiO(Me2SiO) 290 SiMe2Vi

[0095] Component (a-2): dimethylpolysiloxane having a vinyl group content of 0.14% by mass and a viscosity of 9600 mPa·s, and represented by the following formula:

[0096] ViMe2SiO(Me2SiO) 522 SiMe2Vi

[0097] The following components were used as component (B).

[0098] Component (b-1): an organopolysiloxane resin having a vinyl group content of 1.8% by mass and represented by the following average unit formula:

[0099] (Me3SiO 1 / 2 ) 0.39 (ViMe2SiO 1 / 2 ) 0.05 (SiO 4 / 2 ) 0.56

[0100] The following components were used as component (C).

[0101] Component (c-1): dimethylpolysiloxane having a silicon-bonded hydrogen atom content of 0.14 mass% and represented by the following formula:

[0102] HMe2SiO(Me2SiO) 20 SiMe2H

[0103] Component (c-2): a resinous organopolysiloxane having a silicon-bonded hydrogen atom content of 1.0 mass% and represented by the following average unit formula:

[0104] (HMe2SiO 1 / 2 ) 0.63 (SiO 4 / 2 ) 0.37

[0105] The following components were used as component (D).

[0106] Component (e-1): a solution of a Pt-1,3-divinyl-1,1,3,3-tetramethyldisiloxane complex in 1,3-divinyl-1,1,3,3-tetramethyldisiloxane (the Pt content in the solution is 0.9 mass %)

[0107] The following components were used as component (E).

[0108] Component (e-1): a mixture containing 3% by mass of 1-ethynyl-cyclohexane-1-ol and 97% by mass of dimethylpolysiloxane, having a vinyl group content of 0.21% by mass and a viscosity of 2400 mPa·s and represented by the following formula:

[0109] ViMe2SiO(Me2SiO) 290 SiMe2Vi

[0110] The following components are used as the organic compound having two or more alkoxysilyl groups in the molecule.

[0111] Component (f-1): 1,6-bis(trimethoxysilyl)hexane

[0112]

[0113]

[0114] Industrial Applicability

[0115] The curable silicone composition of the present invention has excellent curability and is cured to form a cured product that exhibits excellent optical properties even under high temperature and high humidity conditions. Therefore, the curable silicone composition can be used as an adhesive and a pressure-sensitive adhesive for display devices such as optical displays (including touch panels) and optical semiconductor devices (including micro LEDs).

Claims

1. A curable silicone composition, comprising: (A) a diorganopolysiloxane represented by the following general formula: R 1 2R 2 SiO(R 1 2SiO) m SiR 1 2R 2 Each R 1 is independently an alkyl group having 1 to 12 carbon atoms, each R 2 is independently an alkenyl group having 2 to 12 carbon atoms, and "m" is an integer from 100 to 1000; (B) an organopolysiloxane resin represented by the following average unit formula: (R 1 3SiO 1 / 2 ) a (R 2 R 1 2SiO 1 / 2 ) b (SiO 4 / 2 ) c (HO 1 / 2 ) d Where R 1 and R 2 As described above, and "a", "b", "c" and "d" are numbers satisfying the following conditions: a ≥ 0, b > 0, 0.3 ≤ c ≤ 0.7, 0 ≤ d ≤ 0.05, and a + b + c = 1, and the amount relative to 100 parts by mass of component (A) is 1.0 to 5.0 parts by mass; (C) an organopolysiloxane having silicon-bonded hydrogen atoms, the amount of the organopolysiloxane being such that the molar ratio of silicon-bonded hydrogen atoms provided by component (C) to 1 mol of alkenyl groups provided by components (A) and (B) is in the range of 0.5 to 2; and (D) an effective amount of a hydrosilylation reaction catalyst, However, the curable silicone composition does not include an organosilicon compound having two or more silicon-bonded alkoxy groups in the molecule.

2. The curable silicone composition according to claim 1, wherein component (C) is an organopolysiloxane comprising the following components (c1) and (c2): (c1) a diorganopolysiloxane having silicon-bonded hydrogen atoms at both molecular chain ends, and (c2) an organopolysiloxane resin represented by the following average unit formula: (R 1 3SiO 1 / 2 ) e (HR 1 2SiO 1 / 2 ) f (SiO 4 / 2 ) g (HO 1 / 2 ) h Each R 1 is independently an alkyl group having 1 to 12 carbon atoms, and "e", "f", "g" and "h" are numbers satisfying the following conditions: e≥0, f>0, 0.3≤g≤0.7, 0≤h≤0.05, and e+f+g=1.

3. The curable silicone composition according to claim 2, wherein the molar ratio of silicon-bonded hydrogen atoms provided by component (c1) to silicon-bonded hydrogen atoms provided by component (c2) is in the range of 5 to 60.

4. The curable silicone composition according to claim 1, further comprising: (E) a hydrosilylation reaction inhibitor, wherein the amount of the hydrosilylation reaction inhibitor is from about 0.00001 parts by mass to about 0.5 parts by mass relative to 100 parts by mass of the total mass of components (A) to (C). 5 . A cured product obtained by curing the curable silicone composition according to claim 1 .

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