Patent ID: 8735525

Claim:
A curable composition that comprises: (A) a linear organosiloxane compound, which is represented by an average composition formula of Formula 1, of which a viscosity at 25° C. is from 1,000 mPa·s to 100,000 mPa·s, and of which a molar ratio of an alkenyl group having 2 to 12 carbon atoms and bound to a silicon atom with respect to the total silicon atoms ranges from 0.02 to 0.2; (B) a crosslinking type organosiloxane compound, which is represented by an average composition formula of Formula 2, of which a viscosity at 25° C. is 5,000 mPa·s or more, and of which a molar ratio of an alkenyl group having 2 to 12 carbon atoms and bound to a silicon atom with respect to the total silicon atoms ranges from 0.15 to 0.35; and (C) a hydrogen siloxane compound, which is represented by Formula 3, of which a viscosity at 25° C. is 300 mPa·s or less, of which a molar ratio of a hydrogen atom bound to a silicon atom with respect to the total silicon atoms ranges from 0.2 to 0.8 and of which a molar ratio of an aryl group with respect to the total silicon atoms is from 0.4 to 0.8, the organosiloxane compound (B) being comprised in a weight ratio of 50 parts by weight to 700 parts by weight relative to 100 parts by weight of the organosiloxane compound (A), and a molar ratio of a hydrogen atom bound to a silicon atom in the siloxane compound (C) with respect to an alkenyl group bound to a silicon atom in the organosiloxane compounds (A) and (B) ranging from 0.8 to 1.2: (R 1 R 2 R 3 SiO 1/2 ) a (R 4 R 5 SiO 2/2 ) b (R 6 SiO 3/2 ) c (SiO 4/2 ) d [Formula 1] (R 7 R 8 R 9 SiO 1/2 ) e (R 10 R 11 SiO) f (R 12 SiO 3/2 ) g (SiO 4/2 ) h [Formula 2] wherein R 1 to R 12 independently represent an alkoxy group having 1 to 12 carbon atom(s), a hydroxy group, an epoxy group, an alkyl group having 1 to 12 carbon atom(s), a halogenated alkyl group having 1 to 12 carbon atom(s), an alkenyl group having 2 to 12 carbon atoms, an aryl group having 6 to 18 carbon atoms or an arylalkyl group having 6 to 19 carbon atoms, with the provision that at least one of R 1 to R 6 is an alkenyl group having 2 to 12 carbon atoms and at least one of R 7 to R 12 is an alkenyl group having 2 to 12 carbon atoms; R's independently represent hydrogen, an epoxy group, an alkyl group having 1 to 12 carbon atom(s), a halogenated alkyl group having 1 to 12 carbon atom(s), an alkenyl group having 2 to 12 carbon atoms, an aryl group having 6 to 18 carbon atoms or an arylalkyl group having 6 to 19 carbon atoms; a is in a range of 0 to 0.5, b is in a range of 0.5 to 0.98, c is in a range of 0 to 0.2, d is in a range of 0 to 0.1, e is in a range of 0 to 0.5, f is in a range of 0 to 0.3, g is in a range of 0.3 to 0.85, h is in a range of 0 to 0.2, n is in a range of 1 to 2, with the provision that a+b+c+d is 1 and e+f+g+h is 1.