0% by weight of the entire trialkoxysilanes, and (C) a hydrolysis condensate (component c) of a tetraalkoxysilane of the following formula (II-2), Si(OR4)4???(II-2) wherein R4 is an alkyl group having 1 to 4 carbon atoms, the organosiloxane resin containing 5 to 45% by weight of the component a, 50 to 80% by weight, as R2SiO3/2, of the component b and 2 to 30% by weight, as SiO2, of the component