Preparation of Polymerizable Infrared Absorbing Dye and Lithographic Printing Plate Precursor

(3-(5-Mercapto-1,3,4-thiadiazol-2-yl)ureido)ethyl methacrylate (MTUEMA) was synthesized by the reaction of 2-amino-5-mercapto-1,3,4-thiadiazole and 2-isocyanatoethyl methacrylate. A polymerizable infrared absorbing dye (R-IR830) was synthesized by the modification reaction of a cyanine dye (IR830, maximum absorbance at 830 nm) with MTUEMA. The heat-sensitive polymer particle containing the R-IR830 unit was prepared by the mini-emulsion copolymerization of styrene, acrylonitrile and R-IR830. A negative-working lithographic printing plate precursor based on the heat-sensitive polymer particle was prepared and studied. The prepared printing plate precursor could afford a high-quality image after the laser exposure step and developing process with rinse water.