"Specific and preferable examples of the organosilane compound are those compounds of the formula in which both R2 and R3 are a methyl group or one or both of R2 and R3 are a phenyl group provided that if one of R2 and R3 is a phenyl group, the other is a methyl group, R1 is a hydrogen atom or a methyl group, and n is 1 or 3." . . . . .