Hardening silicone composition and hardened material thereof

Abstract

The present invention relates to a curable silicone composition containing (A) a diorganopolysiloxane having two alkenyl groups bonded to silicon atoms at both ends of the molecular chain, (B) an organopolysiloxane resin having an alkenyl group bonded to a silicon atom, (C) an organopolysiloxane having a hydrogen atom bonded to a silicon atom, and (D) a hydrosilylation reaction catalyst, provided that it does not contain an organosilicon compound having two or more alkoxy groups bonded to silicon atoms in one molecule. By curing this composition, a cured product having excellent optical properties can be formed even when exposed to high temperature and high humidity conditions.

Description

Technical Field

[0001] The present invention relates to a curable silicone composition and a cured product thereof.

Background Art

[0002] Since a curable silicone composition can be cured to form a cured product having high transparency and high elongation, it is used as an adhesive or a pressure-sensitive adhesive for improving the visibility of an optical display.

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

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

[0005] However, these curable silicone compositions have a problem that when exposed to high temperature and high humidity conditions, a cured product having poor optical properties is formed. That is, the cured product under severe conditions shows haze and has low transparency.

[0006] Prior Art Documents Patent Documents Patent Document 1: US Patent Application Publication No. 2014 / 0150972 (A1) Patent Document 2: US Patent Application Publication No. 2022 / 0002493 (A1) Summary of the Invention

[0007] Technical Problem An object of the present invention is to provide a curable silicone composition capable of forming a cured product exhibiting excellent optical properties even when exposed to high temperature and high humidity conditions, and further to provide a cured product exhibiting excellent optical properties. Means for Solving the Problems

[0008] The curable silicone composition of the present invention comprises (A) The following general formula: R 1 2R 2 SiO(R 1 2SiO) m SiR 1 2R 2 a diorganopolysiloxane represented by (wherein 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 of 100 to 1000), and (B) 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 an organopolysiloxane resin represented by (wherein R 1 and R 2is as described above, where "a", "b", "c", and "d" are numbers satisfying a≧0, b>0, 0.3≦c≦0.7, 0≦d≦0.05, and a + b + c = 1, and is in an amount of 1.0 to 5.0 parts by mass based on 100 parts by mass of component (A), (C) An organopolysiloxane having a silicon atom-bonded hydrogen atom, in an amount such that the molar ratio of the silicon atom-bonded hydrogen atom provided by component (C) to the alkenyl group provided by components (A) and (B) is in the range of 0.5 to 2. (D) An effective amount of a hydrosilylation reaction catalyst, and provided that the curable silicone composition does not contain an organosilicon compound having two or more silicon atom-bonded alkoxy groups in one molecule.

[0009] In various embodiments, component (C) typically comprises the following component (c1) and component (c2): (c1) A diorganopolysiloxane having silicon atom-bonded hydrogen atoms at both ends of the molecular chain, and (c2) 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 An organopolysiloxane resin represented by (wherein each R 1 is independently an alkyl group having 1 to 12 carbon atoms, and "e", "f", "g", and "h" are numbers satisfying e≧0, f>0, 0.3≦g≦0.7, 0≦h≦0.05, and e + f + g = 1).

[0010] In various embodiments, the molar ratio of the silicon-bonded hydrogen atom provided by component (c1) to the silicon-bonded hydrogen atom provided by component (c2) is typically in the range of 5 to 60.

[0011] In various embodiments, the curable silicone composition may further contain an (E) hydrosilylation reaction inhibitor in an amount of about 0.00001 to about 0.5 parts by mass based on 100 parts by mass of the total mass of components (A) to (C).

[0012] The cured product of the present invention is obtained by curing the above curable silicone composition.

[0013] Advantages of the Invention By curing the curable silicone composition of the present invention, a cured product can be formed which exhibits excellent optical properties even when placed under high temperature and high humidity conditions. The cured product of the present invention exhibits excellent optical properties.

[0014] Definitions The term "comprising" or "comprise" is used herein in the broadest sense and means "including", "include", "consist(ing) essentially of", and "consist(ing) of", encompassing those concepts. The use of "for example", "e.g.", "such as", and "including" for listing examples is not limited to the examples listed. Thus, "for example" or "such as" means "for example, but not limited to" or "such as, but not limited to", including other similar or equivalent examples. The term "about" as used herein serves to reasonably encompass or describe slight variations in numerical values measured by instrumental analysis or as a result of handling samples. Such slight variations can be on the order of ±0 to 25, ±0 to 10, ±0 to 5, or ±0 to 2.5% of the numerical value. Further, the term "about" applies to both values of a range of values when related to such a range. Further, the term "about" may apply to a numerical value even if not explicitly stated.

[0015] Generally, as used herein, a hyphen "-" or a tilde "~" in a range of values means "to" or "through", ">" means "above" or "greater-than", "≧" means "at least" or "greater-than or equal to", "<" means "below" or "less-than", and "≦" means "at most" or "less-than or equal to". Each of the aforementioned patent applications, patents, and / or patent publications is hereby incorporated by reference in its entirety into this specification, individually and by reference in one or more non-limiting embodiments.

DETAILED DESCRIPTION OF THE INVENTION

[0016] <Curable silicone composition> First, the curable silicone composition of the present invention will be described in detail.

[0017] <Component (A)> Component (A) is a diorganopolysiloxane represented by the following general formula: R 1 2R 2 SiO(R 1 2SiO) m SiR 1 2R 2 In the above formula, each R

[0018] 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.

[0019] 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, among which the vinyl group is preferred.

[0020] In the above formula, "m" is an integer of 100 to 1000, or an integer of 100 to 800. This is because when "m" is equal to or greater than the lower limit of the above range, the mechanical properties of the obtained cured product are sufficient, while when "m" is equal to or less than the upper limit of the above range, the obtained composition has a viscosity suitable for processing and handling.

[0021] The viscosity of component (A) at 25 °C is not limited, but typically it is in the range of about 100 mPa·s to about 100,000 mPa·s, or in the range of about 200 mPa·s to about 50,000 mPa·s, or in the range of about 300 mPa·s to about 50,000 mPa·s. It should be noted that in this specification, the viscosity is the value measured at 23 ± 2 °C using a B-type viscometer in accordance with ASTM D1084.

[0022] Component (B) is 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 and is an organopolysiloxane resin represented by.

[0023] In the above formula, R 1 and R 2 are as described above. Examples thereof include the same groups as those described above.

[0024] In the above formula, "a", "b", "c", and "d" satisfy the 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 ranges, the cured product obtained by curing this composition has appropriate hardness and mechanical strength.

[0025] The amount of component (B) is in the range of 1.0 to 5.0 parts by mass, or in the range of 1.0 to 3.0 parts by mass, based on 100 parts by mass of component (A). This is because when the amount is not less than the lower limit of the above range, the mechanical properties of the obtained cured product are sufficient, while when the amount is not more than the upper limit of the above range, the obtained composition has a viscosity suitable for processing and handling.

[0026] <Component (C)> Component (C) is a cross-linking agent for components (A) and (B) in this composition and is an organopolysiloxane having a silicon atom-bonded hydrogen atom. Examples of the groups bonded to the silicon atoms other than the hydrogen atoms in component (C) include alkyl groups having 1 to 12 carbon atoms such as methyl group, ethyl group, propyl group, butyl group, pentyl group, hexyl group, heptyl group, octyl group, nonyl group, decyl group, undecyl group, dodecyl group; aryl groups having 6 to 20 carbon atoms such as phenyl group, tolyl group, xylyl group; aralkyl groups having 7 to 20 carbon atoms such as benzyl group, phenethyl group; and halogen-substituted alkyl groups having 1 to 12 carbon atoms such as 3-chloropropyl group, 3,3,3-trifluoropropyl group. From the viewpoints of economy and heat resistance, the methyl group is preferred.

[0027] Examples of the molecular structure of component (C) include linear, linearly branched with a single branch, branched chain, cyclic, and three-dimensional network structures. Preferably, the molecular structure is linearly branched with a single branch, branched chain, or three-dimensional network structure.

[0028] Component (C) typically comprises the following components (c1) and (c2): (c1) A diorganopolysiloxane having silicon atom-bonded hydrogen atoms at both ends of the molecular chain, and (c2) 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 an organopolysiloxane containing an organopolysiloxane resin represented by the formula.

[0029] Component (c1) functions as a chain extender in the hydrosilylation reaction with components (A) and (B), improving the flexibility of the cured product. Examples of the groups bonded to silicon atoms other than hydrogen atoms in component (c1) include the above-mentioned alkyl groups, aryl groups, aralkyl groups, and halogen-substituted alkyl groups. Among them, from the viewpoints of economy and heat resistance, methyl groups and phenyl groups are preferred.

[0030] Examples of such component (c1) include dimethylpolysiloxane with dimethylhydrogensiloxy groups protecting both ends of the molecular chain, a copolymer of dimethylsiloxane and methylphenylsiloxane with dimethylhydrogensiloxy groups protecting both ends of the molecular chain, and mixtures of two or more of these types.

[0031] Component (c2) functions as a crosslinking agent in the hydrosilylation reaction with components (A) and (B), improving the mechanical properties of the cured product.

[0032] 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, from the viewpoints of economy and heat resistance, a methyl group is preferable.

[0033] In the formula of component (c2), "e", "f", "g", and "h" satisfy the conditions of 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 this composition has appropriate hardness and mechanical strength.

[0034] The molar ratio of the silicon-bonded hydrogen atoms provided by component (c1) to the silicon-bonded hydrogen atoms provided by component (c2) is not limited, but is typically in the range of 5 to 60, or in the range of 10 to 60, or in the range of 10 to 30. This is because when the molar ratio is not less than the lower limit of the above range, the adhesion properties of the obtained cured product are sufficient, while when the molar ratio is not more than the upper limit of the above range, the mechanical properties of the obtained cured product are sufficient.

[0035] The amount of component (C) is such that the molar ratio of the silicon-bonded hydrogen atoms provided by component (C) to 1 mole of the alkenyl group provided by components (A) and (B) is in the range of 0.5 to 2, or in the range of 0.8 to 2, or in the range of 0.5 to 1.5. This is to sufficiently cure the obtained composition when the amount is not less than the lower limit of the above range. However, on the other hand, when it is not more than the upper limit of the above range, the mechanical properties of the obtained cured product are improved.

[0036] <Component (D)> Component (D) is a hydrosilylation reaction catalyst for promoting the curing of the present composition. Examples thereof include platinum-based catalysts, rhodium-based catalysts, and palladium-based catalysts, with platinum-based catalysts being preferred. Examples of platinum-based catalysts include platinum fine powder, platinum black, platinum-supported silica fine powder, platinum-supported activated carbon, chloroplatinic acid, an alcohol solution of chloroplatinic acid, an olefin complex of platinum, and an alkenylsiloxane complex of platinum.

[0037] The amount of component (D) is an effective amount for promoting the curing of the present composition. Specifically, with respect to the present composition, the amount is such that the platinum atoms in the catalyst are in the range of about 0.1 to about 1000 ppm, or about 1 to about 500 ppm, by mass. This is because when the content of component (D) is not less than the lower limit of the above range, the curing of the resulting composition proceeds, while when the content is not more than the upper limit of the above range, the resulting cured product is less likely to discolor.

[0038] <Component (E)> The composition may also contain an (E) hydrosilylation reaction inhibitor to control its crosslinking reaction. Examples of component (E) include alkynyl 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-penten-1-yne and 3,5-dimethyl-3-hexen-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, alkynyloxysilanes such as dimethylbis(3-methyl-1-butyn-3-oxy)silane and methylvinylbis(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, and dimethylbis(1,1-dimethyl-propynyloxy)silane; triazole, phosphine, mercaptan, hydrazine, sulfoxide, phosphate, nitrile, hydroperoxide, amine, ethylenically unsaturated isocyanate, fumarate (e.g., dialkyl fumarate, dialkenyl fumarate, and / or dialkoxyalkyl fumarate), maleate (e.g., diallyl maleate), alkene, and combinations thereof.

[0039] The amount of component (E) is not limited, but from the viewpoint of imparting sufficient pot life to the composition, it is typically in the range of about 0.00001 to about 0.5 parts by mass, or about 0.0001 to about 0.5 parts by mass, or alternatively about 0.0001 to about 0.1 parts by mass, based on 100 parts by mass of the total mass of components (A) to (C). This is because when the amount of component (E) is above the lower limit of the above range, the pot life of the composition becomes sufficient for use, and when it is below the upper limit of the above range, the curability of the composition becomes good for use.

[0040] <Other components> The composition may contain an antioxidant, a reactive diluent, a leveling agent, a filler, an antistatic agent, an antifoaming agent, a pigment, etc., as long as the object of the present invention is not impaired. However, the composition does not contain an organosilicon compound having two or more silicon atom-bonded alkoxy groups in one molecule. Organosilicon components are generally used as adhesion promoters to improve the adhesion strength of the resulting cured product. Examples of organosilicon compounds include 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropylmethyldimethoxysilane, 3-methacryloxypropyltormethoxysilane, 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.

[0041] <Cured product> Next, the cured product of the present invention will be described in detail.

[0042] The cured product can be obtained by curing the above-described curable silicone composition. The hardness of the cured product is not limited, but typically has a 1 / 4 cone penetration of 20 to 90 when measured using a penetrometer defined in ASTM D1403. This is because when the penetration is above the lower limit of the above range, the cured product can have good peel strength, while when the penetration is below the upper limit of the above range, the cured product can have good mechanical properties.

[0043] The shape of the cured product is not limited, and examples thereof include a sheet, a film, a tape, and a mass. Furthermore, integration with various types of substrates is also possible.

Examples

[0044] The curable silicone composition and cured product of the present invention will be described in more detail below using Examples and Comparative Examples. The present invention is not limited to the following Examples. In the formulas, Me and Vi represent a methyl group and a vinyl group, respectively. The viscosity of the organopolysiloxane was measured as follows.

[0045] <Viscosity> The viscosity at 23 ± 2°C was measured using a B-type viscometer (Brookfield HADVIII Type rotational viscometer, using RV-03 at 60 rpm for 2 minutes) in accordance with ASTM D 1084, "Standard Test Methods for Viscosity of Adhesive".

[0046] <Penetration> A curable silicone composition with a thickness of 10 mm or more was left to cure in an aluminum dish at 120°C for 40 minutes, and the 1 / 4 cone penetration at 25°C was measured using an Anton Paar penetrometer PNR 12 manufactured by Anton Paar GmbH.

[0047] <180° Peel Strength> A curable silicone composition with 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 at 25°C for 3 days. The 180° peel strength was measured at a peel rate of 305 mm / min.

[0048] <Cohesive Failure> After measuring the 180° peel strength, the cohesive failure rate of the cured product with respect to the glass plate and the PET film was measured.

[0049] <Initial Haze and Transmittance> A curable silicone composition with a thickness of 1 mm was left to cure on a glass plate at 70°C for 40 minutes, and then post-cured at 25°C for 3 days. The haze and transmittance of the cured product at 25°C were measured using a spectrophotometer CM-5 manufactured by Konica Minoluta.

[0050] <Haze and transmittance after high temperature and high humidity test> 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 and high humidity test were measured using a spectrophotometer CM-5 manufactured by Konica Minoluta.

[0051] <Examples 1 to 3 and Comparative Examples 1 to 2> Using the components described below, curable silicone compositions shown in Table 1 were prepared. First, components (A), (B), and (D) were uniformly mixed. Next, components (C) and (E) were added to produce a curable silicone composition. The obtained cured products were evaluated as described above. These results are shown in Table 1. "SiH / Vi ratio" in Table 1 indicates the molar ratio of silicon atom-bonded hydrogen atoms provided by component (C) to vinyl groups provided by components (A) and (B). "SiH ratio" in Table 1 indicates the molar ratio of silicon atom-bonded hydrogen atoms provided by component (c1) to silicon atom-bonded hydrogen atoms provided by component (c2).

[0052] The following components were used as component (A). Component (a-1): having a vinyl group content of 0.21% by mass and a viscosity of 2400 mPa·s, and having the following formula: ViMe2SiO(Me2SiO) 290 SiMe2Vi Dimethylpolysiloxane represented by. Component (a-2): having a vinyl group content of 0.14% by mass and a viscosity of 9600 mPa·s, and having the following formula: ViMe2SiO(Me2SiO) 522 SiMe2Vi Dimethylpolysiloxane represented by.

[0053] The following components were used as component (B). Component (b-1): having a vinyl group content of 1.8% by mass and having the following average unit formula: (Me3SiO 1 / 2 ) 0.39 (ViMe2SiO1 / 2 ) 0.05 (SiO 4 / 2 ) 0.56 An organopolysiloxane resin represented by

[0054] The following components were used as component (C). Component (c-1): The content of silicon atom-bonded hydrogen atoms is 0.14% by mass, and the following formula: HMe2SiO(Me2SiO) 20 SiMe2H Dimethylpolysiloxane represented by Component (c-2): The content of silicon atom-bonded hydrogen atoms is 1.0% by mass, and the following average unit formula: (HMe2SiO 1 / 2 ) 0.63 (SiO 4 / 2 ) 0.37 Resinous organopolysiloxane represented by

[0055] The following components were used as component (D). Component (e-1): A solution of Pt-1,3-divinyl-1,1,3,3-tetramethyldisiloxane complex in 1,3-divinyl-1,1,3,3-tetramethyldisiloxane (Pt content in the solution is 0.9% by mass)

[0056] The following components were used as component (E). Component (e-1): 3% by mass of 1-ethynyl-cyclohexan-1-ol, a vinyl group content of 0.21% by mass, a viscosity of 2400 mPa·s, and the following formula: ViMe2SiO(Me2SiO) 290 SiMe2Vi A mixture containing 97% by mass of dimethylpolysiloxane represented by

[0057] As an organic compound having two or more alkoxysilyl groups in one molecule, the following components were used. Component (f-1): 1,6-bis(trimethoxysilyl)hexane

[0058]

Table 1

[0059] Industrial Applicability The curable silicone composition of the present invention has excellent curability and cures to form a cured product that exhibits excellent optical properties even when exposed to high temperature and high humidity conditions. Therefore, the curable silicone composition is useful as an adhesive and a pressure-sensitive adhesive for use in display devices (including touch panels) such as optical displays and opto-semiconductor devices (including micro LEDs).

Claims

Claim 1 A curable silicone composition comprising: (A) A diorganopolysiloxane represented by the following general formula: R １ ２ R ２ SiO(R １ ２ SiO) ｍ SiR １ ２ R ２ (B) An organopolysiloxane resin represented by the following average unit formula: (wherein each R １ is independently an alkyl group having 1 to 12 carbon atoms, and each R ２ is independently an alkenyl group having 2 to 12 carbon atoms, and "m" is an integer from 100 to 1000), and (C) An organopolysiloxane having silicon-bonded hydrogen atoms in an amount such that the molar ratio of the silicon-bonded hydrogen atoms provided by component (C) to 1 mole of the alkenyl groups provided by components (A) and (B) is in the range of 0.5 to 2; and (R １ ３ SiO １／２ ) ａ (R ２ R １ ２ SiO １／２ ) ｂ (SiO ４／２ ) ｃ (HO １／２ ) ｄ (D) An effective amount of a hydrosilylation reaction catalyst, provided that the curable silicone composition does not contain an organosilicon compound having two or more silicon-bonded alkoxy groups in one molecule. (wherein R １ and R ２ are as described above, and "a", "b", "c", and "d" are numbers satisfying a ≧ 0, b > 0, 0.3 ≦ c ≦ 0.7, 0 ≦ d ≦ 0.05, and a + b + c = 1, and are in an amount of 1.0 to 5.0 parts by mass with respect to 100 parts by mass of component (A)), and A curable silicone composition. Claim 2 Component (C) comprises the following components (c1) and (c2): (c1) A diorganopolysiloxane having silicon-bonded hydrogen atoms at both ends of the molecular chain; and (c2) An organopolysiloxane resin represented by the following average unit formula: Claim 3 The curable silicone composition according to claim 2, wherein the molar ratio of the silicon-bonded hydrogen atoms provided by component (c1) to the silicon-bonded hydrogen atoms provided by component (c2) is in the range of 5 to 60. (R １ ３ SiO １／２ ) ｅ (HR １ ２ SiO １／２ ) ｆ (SiO ４／２ ) ｇ (HO １／２ ) ｈ Claim 4 (In the formula, each R １ is independently an alkyl group having 1 to 12 carbon atoms, and "e", "f", "g", and "h" are numbers satisfying e ≧ 0, f > 0, 0.3 ≦ g ≦ 0.7, 0 ≦ h ≦ 0.05, and e + f + g = 1), and the curable silicone composition according to claim 1, which is an organopolysiloxane containing the same. The curable silicone composition according to claim 1, further comprising (E) a hydrosilylation reaction inhibitor in an amount of about 0.00001 to about 0.5 parts by mass based on 100 parts by mass of the total mass of components (A) to (C). Claim 5 A cured product obtained by curing the curable silicone composition according to any one of claims 1 to 4. ​ ​ ​

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