PLANOGRAPHIC PRINTING PLATE AND PREPARATION THEREOF

PURPOSE:To obtain a planographic printing plate wherein waterless printing is possible, and which can impart a high image density and high printing durability by providing an ink repellent thermal recording layer based on a thermoplastic resin having specific glass transition temp. and silicone rubber and a protective sheet on a support. CONSTITUTION:A mixture of thermoplastic resin having glass transition temp. of 50-110 deg.C, silicone rubber and a proper solvent such as toluene is dispersed and mixed by a dispersing machine such as a ball mill, a paint shaker, an ultrasonic homogenizer or a sand mill to obtain a dispersion which is, in turn, applied to a support and subsequently heated and dried to be subjected to crosslinking reaction to provide a thermal recording layer 2 and, thereafter, a protective sheet 3 is laminated to the layer 2 to prepare a printing base plate. As the silicone rubber, various thermosetting silicone rubbers based on dimethylpolysiloxane are used. The ratio of the thermoplastic resin and the silicone rubber is 1.8:1-4.8:1, pref., 2.5:1-4.3:1 on a solid wt. basis.