Patent ID: 8859693

Claim:
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.