US Patent 8491993 Polymeric dyes, overcoat compositions and thermal lithographic printing plates

A thermal lithographic printing plate overcoat composition comprising (a) a water-soluble polymeric dye having an absorption band between about 300 and about 600 nm; and (b) micro-particles or nano-particles is provided. A negative-working thermal lithographic printing plate comprising (a) a hydrophilic substrate; (b) a near infrared imaging layer disposed on the hydrophilic substrate; and (c) an overcoat layer disposed on the imaging layer, said overcoat layer comprising a water-soluble polymeric dye having an absorption band between about 300 and about 600 nm; and micro-particles or nano-particles is also provided. Finally, a water-soluble polymeric dye having an absorption band between about 300 and about 600 nm is provided.