Abstract: A high speed photopolymerization negative-acting printing plate containing a layer comprising a photo-sensitized polymerization initiator and polymerizable ethylenically unsaturated compound, exhibits higher speed and good shelf life when at least 20% by weight of the total initiator is situated in an oxygen barrier top coat. Addition of p-substituted-N-disubstituted-anilines to the polymerizable layer gives further improvement in stability.

Abstract: A high speed visible light sensitive photopolymerizable composition useful for printing plates comprising(a) at least one free radically polymerizable monomer having at least one ethylenically unsaturated group,(b) an ethylenically unsaturated free radically polymerizable oligomer having carboxyl groups substituted thereon,(c) a visible light sensitizing initiator system for free radical polymerization comprising an initiator selected from diaryl iodonium salts, halogenated triazines, and triaryl iodonium salts which are photoinitiating electron acceptor compounds having a reduction potential in the range 0.0 to -1.5 eV, spectrally sensititzed with at least one merocyanine sensitizer containing a constrained alkylamino group, preferably a julolidinyl group.

Abstract: A visible light sensitive free radical polymerization photoinitiator composition comprising (a) an initiator selected from diaryl iodonium salts, halogenated triazines, and triaryl sulfonium salts having a reduction potential in the range 0.0 to -1.5 eV, and (b) at least one merocyanine sensitizer containing a constrained alkylamino group.These initiator compositions give high speed polymerization reactions with ethylenically unsaturated monomers and oligomers.