Lithographic printing plates having a photopolymerizable imaging layer overcoated with an oxygen barrier layer

摘要

Improved lithographic printing plates adapted to be imagewise-exposed with ultraviolet- or visible-light-emitting lasers such as argon-ion lasers and frequency doubled Nd:YAG lasers, are comprised of a radiation-sensitive layer and an oxygen barrier layer. The radiation-sensitive layer includes one or more addition-polymerizable ethylenically-unsaturated compounds and a photopolymerization initiator system comprised of a spectral sensitizer that sensitizes in the ultraviolet or visible regions of the spectrum and an N-aryl, O-aryl or S-aryl polycarboxylic acid co-initiator; the oxygen barrier layer comprises fully hydrolyzed polyvinyl alcohol; and a basic compound is incorporated in the oxygen barrier layer or the radiation-sensitive layer or both in an amount sufficient to control thermal fog susceptibility of the lithographic printing plate. Such plates are able to effectively meet the requirements of very high photospeed, freedom from thermal fog and very good shelf-life required in computer-to-plate systems.