A curable organopolysiloxane composition comprising: (A) an organopolysiloxane having a form of anywhere from a liquid having a
viscosity of 20 mPa.s or greater to a gum that exhibits
plasticity,containing the following components a1) and a2) at a
mass ratio of 100:0 to 50:50: a1) organopolysiloxane comprising an alkenyl group having 4 to 12 carbon atoms, the alkenyl group having a vinyl
moiety content of 0.5 to 3.0
mass%, and a2) organopolysiloxane with an alkenyl group having 2 to 3 carbon atoms, the alkenyl group having a vinyl
moiety content of 0.5 to 3.0
mass%; (B) an organopolysiloxane having a form from a liquid having a
viscosity of 1,000,000 mPas or greater to a gum that exhibits
plasticity, the organopolysiloxane optionally comprising an alkenyl group having 2 to 12 carbon atoms, the alkenyl group having a vinyl
moiety content of less than 0.100 mass%; (C) an organohydrogen polysiloxane comprising at least two
silicon-bonded
hydrogen atoms within its molecule; (D) a
hydrosilylation catalyst; and (E) as desired, an
organic solvent; the
mass ratio of components (A) and (B) being in a range from 90:10 to 99:1.