Patent ID: 8846828

Claim:
A curable organopolysiloxane composition comprising: (A) a branched-chain organopolysiloxane that contains in one molecule at least three alkenyl groups and at least 30 mole % of all silicon-bonded organic groups in the form of aryl groups; (B) a linear-chain organopolysiloxane that contains aryl groups and has both molecular terminals capped with diorganohydrogensiloxy groups, wherein component (B) is used in such an amount that the content of silicon-bonded hydrogen atoms contained in component (B) to one mole of alkenyl groups contained in component (A) is in the range of 0.5 to 2 moles; (C) a branched-chain organopolysiloxane that contains in one molecule at least three diorganohydrogensiloxy groups and at least 15 mole % of all silicon-bonded organic groups are in the form of aryl groups, wherein the content of the diorganohydrogensiloxy groups contained in this component is in the range of 1 to 20 mole % per total amount of the diorganohydrogensiloxy groups contained in component (B) and in the present component; (D) a hydrosilylation catalyst in an amount required to accelerate curing of the composition; and (E) a linear-chain organopolysiloxane that contains in one molecule at least two alkenyl groups and at least 30 mole % of all silicon-bonded organic groups in the form of aryl groups, said component (E) being used in an amount of greater than 0 and equal to or less than 25 parts by mass per 100 parts by mass of component (A).