Curable silicone composition that provides a highly transparent cured silicone material

1. A curable silicone composition comprising

(A) 100 mass parts of an alkenyl-containing organopolysiloxane comprising

(A-1) a dialkylpolysiloxane that has an average of at least two alkenyl groups in each molecule and a viscosity at 25° C. of at least 1,000 mPa·s to not more than 50,000 mPa·s, at from 50 mass % to not more than 80 mass % of component (A), and

(A-2) an alkenyl-containing, resin-form organopolysiloxane that comprises the SiO 4/2 unit, R 1 2 R 2 SiO 1/2 unit, and R 1 3 SiO 1/2 unit wherein R 1 is C 1-10 alkyl and R 2 is alkenyl, and that contains the alkenyl group in the range from at least 1 mass % to less than 3.5 mass %, at from 20 mass % to not more than 50 mass % of component (A);

(B) an organopolysiloxane that has an average of at least three silicon-bonded hydrogen atoms in each molecule wherein the silicon-bonded groups other than the silicon-bonded hydrogen are C 1-10 alkyl, in an amount that provides 0.8 to 2 moles silicon-bonded hydrogen in this component per 1 mole of the total alkenyl in component (A),

wherein component (B) is an organopolysiloxane comprising

(B-1) an organopolysiloxane that contains at least 0.7 mass % silicon-bonded hydrogen and that comprises SiO 4/2 units and HR 3 2 SiO 1/2 units in a ratio ranging from 1.50 to 2.50 moles of HR 3 2 SiO 1/2 units per 1 mole of SiO 4/2 units wherein R 3 is C 1-10 alkyl, at 50 to 100 mass % of component (B), and

(B-2) a straight-chain organopolysiloxane that contains at least 0.3 mass % silicon-bonded hydrogen wherein the silicon-bonded groups other than the silicon-bonded hydrogen are C 1-10 alkyl, at 0 to 50 mass % of component (B); and

(C) a hydrosilylation reaction catalyst in a catalytic quantity, and provides a highly transparent cured silicone material that has a hardness measured using the type A durometer specified in JIS K 6253 is in the range from at least 30 to not more than 80, the elongation as specified in JIS K 6251 is at least 50%, the parallel light transmittance at 25° C. measured in accordance with JIS K 7105 on a 6 mm optical path length is at least 90%, and the parallel light transmittance at 200° C. is a value that is at least 99% of the parallel light transmittance at 25° C.

2. A highly transparent cured silicone material provided by the thermosetting of a curable silicone composition comprising

(A) 100 mass parts of an alkenyl-containing organopolysiloxane comprising

(A-1) a dialkylpolysiloxane that has an average of at least two alkenyl groups in each molecule and a viscosity at 25° C. of at least 1,000 mPa·s to not more than 50,000 mPa·s, at from 50 mass % to not more than 80 mass % of component (A), and

(A-2) an alkenyl-containing, resin-form organopolysiloxane that comprises the SiO 4/2 unit, R 1 2 R 2 SiO 1/2 unit, and R 1 3 SiO 1/2 unit wherein R 1 is C 1-10 alkyl and R 2 is alkenyl and that contains the alkenyl group in the range from at least 1 mass % to less than 3.5 mass %, at from 20 to not more than 50 mass % of component (A);

(B) an organopolysiloxane that has an average of at least three silicon-bonded hydrogen atoms in each molecule wherein the silicon-bonded groups other than the silicon-bonded hydrogen are C 1-10 alkyl, in an amount that provides 0.8 to 2 moles silicon-bonded hydrogen in this component per 1 mole of the total alkenyl in component (A),

wherein component (B) is an organopolysiloxane comprising

(B-1) an organopolysiloxane that contains at least 0.7 mass % silicon-bonded hydrogen and that comprises SiO 4/2 units and HR 3 2 SiO 1/2 units in a ratio ranging from 1.50 to 2.50 moles of HR 3 2 SiO 1/2 units per 1 mole of SiO 4/2 units wherein R 3 is C 1-10 alkyl, at 50 to 100 mass % of component (B), and

(B-2) a straight-chain organopolysiloxane that contains at least 0.3 mass % silicon-bonded hydrogen wherein the silicon-bonded groups other than the silicon-bonded hydrogen are C 1-10 alkyl, at 0 to 50 mass % of component (B); and

(C) a hydrosilylation reaction catalyst in a catalytic quantity, and having a hardness measured using the type A durometer specified in JIS K 6253 in the range from at least 30 to not more than 80, an elongation as specified in JIS K 6251 of at least 50%, a parallel light transmittance at 25° C. measured in accordance with JIS K 7105 on a 6 mm optical path length of at least 90%, and a value for the parallel light transmittance at 200° C. that is at least 99% of the parallel light transmittance at 25° C.

3. The highly transparent cured silicone material according to claim 2 , which has a hardness measured using the type A durometer specified in JIS K 6253 in the range from at least 65 to not more than 75.

4. A cured silicone composite comprising a substrate that forms a single article with a cured silicone layer that is provided by the thermosetting of a curable silicone composition according to claim 1 .

5. A cured silicone composite obtained by coating the curable silicone composition according to claim 1 on a substrate and then thermosetting the curable silicone composition.

6. The highly transparent cured silicone material according to claim 2 , which has a hardness measured using the type A durometer specified in JIS K 6253 in the range from at least 65 to not more than 75.

7. The curable silicone composition according to claim 1 , wherein component (A-1) is included in an amount ranging from 55 mass % to not more than 70 mass % of component (A).

8. The highly transparent cured silicone material according to claim 2 , wherein component (A-1) is included in an amount ranging from 55 mass % to not more than 70 mass % of component (A).

9. The curable silicone composition according to claim 1 , wherein component (A-2) is included in an amount ranging from 30 mass % to not more than 45 mass % of component (A).

10. The highly transparent cured silicone material according to claim 2 , wherein component (A-2) is included in an amount ranging from 30 mass % to not more than 45 mass % of component (A).