To unnecessitate a developing process after an imagewise exposing process and to obtain a printing plate using no dampening water at the time of printing by using a solid organopolysiloxane compd. and a photothermic conversion material dispersed in the compd.

This compsn. is composed of an organopolysiloxane compd. and a photothermic conversion material dispersed in the compd. The compd. is, e.g. dimethylpolysiloxane, methylhydrogenpolysiloxane, methylpolysiloxane having hydrogen atoms at both terminals, methylphenylpolysiloxane, alkyl modified polysiloxane, amino modified polysiloxane or carboxyl modified polysiloxane. A coloring material effectively absorbing light in a wavelength region from UV to near IR and capable of efficiently converting the light into heat energy is preferably used as the photothermic conversion material.