Details:
Summary:
Digital imaging of lithographic printing plates by near IR exposure (ca 800 - 1200 nm) is attractive from both economic and ecological standpoints, including ambient light stability as well as the prospect for minimal processing requirements. As with other computer-to-plate (CTP) approaches, the utilization of contact masks is also obviated. Exposure with semiconductor diode and YAG lasers has been reported whereby the incident IR photons are absorbed by pigments and/or dyes to produce electronically- and/or vibrationally-excited states, which subsequently cause chemical and/or physical changes in the exposed regions of the coating compositions. We have developed positive- and negative-working digital plates, which can be utilized for conventional printing with fountain solution, as well as for printing waterless. The imaging processes include (1) ablative in-situ mask generation, thereby converting any analog printing plate into a digital plate, (2) ablation of single-layer coatings and (3) thermal crosslinking. Highlights of our work will be presented with emphasis on high performance compositions. Current studies are directed to minimizing processing requirements.