Patent ID: 7625986

Claim:
An addition-curable organopolysiloxane resin composition having, in a state of a cured body, a hardness of 60 to 100 at 25° C. and of 40 to 100 at 150° C. as measured in accordance with the provisions of ASTM D2240-86, said composition comprising: (A) 100 parts by weight of an organopolysiloxane resin represented by the following average compositional formula: R 1 a R 2 b SiO (4−a−b)/2 (1) where R 1 designates alkenyl groups with 2 to 10 carbon atoms, R 2 designates substituted or non-substituted univalent hydrocarbon groups (except for alkenyl groups), at least 50 mole % of R 2 is comprised of phenyl groups; “a” is within the range of 0.09 to 0.16, and “b” is within the range of 1.00 to 1.20, said organopolysiloxane resin being comprised of at least alkenyl groups and phenyl groups and having a weight-average molecular weight, with polystyrene as reference and determined by gel chromatography, equal to or exceeding 3000; (B) 10 to 50 parts by weight of an organooligosiloxane represented by the following average compositional formula: R 3 c R 4 d SiO (4−c−d)/2 (2) where R 3 designates alkenyl groups with 2 to 10 carbon atoms, R 4 designates substituted or non-substituted univalent hydrocarbon groups (except for alkenyl groups), at least 10 mole % of R 4 is comprised of phenyl groups; “c” is within the range of 0.60 to 0.80, and “d” is within the range of 1.50 to 2.10, said organooligosiloxane being comprised of at least alkenyl groups and phenyl groups; (C) 20 to 100 parts by weight of an organohydrogenoligosiloxane or organohydrogenpolysiloxane represented by the following average compositional formula: H e R 5 f SiO (4−e−f)/2 (3) where R 5 designates substituted or non-substituted univalent hydrocarbon groups (except for alkenyl groups), at least 20 mole % of R 5 is comprised of phenyl groups; “e” is within the range of 0.35 to 0.65, and “f” is within the range of 0.90 to 1.70; and (D) an addition-reaction catalyst in a catalytic quantity.