Process of using positive and negative working imaging systems from photoactive plastisols

Claim 1

A positive image forming process which comprises (a) exposing imagewise a photoactive element comprising a substrate bearing a layer of a photoactive, thermally coalescible polyvinyl chloride resin plastisol dispersion consisting essentially of (a) particles having a mean diameter in the range of 0.1 to 20 μm of a solid polyvinyl chloride polymer having attached to the backbone thereof photopolymerizable or photocrosslinkable groups taken from the group consisting of anhydrides, carbonyl, carboxyl, isocyanate, methylol and ethylenically unsaturated substituents in amounts of 0.1 to 16% by weight based on the total weight of polymer, the polymer having an inherent viscosity in the range of 0.1 to 1.2 and being dispersed in (b) a liquid medium compatible with the particles that comprises a plasticizer for the polymer and is nonvolatile at room temperature and has no substantial solvent activity for the polymer at room temperature and (c) a photoinitiator or photoinitiator system present either as a separate component or as a photoactive substituent on the polymer backbone, the photoinitiator or photoinitiator system being capable, upon exposure to actinic radiation, of causing polymerization or crosslinking of the photopolymerizable or photocrosslinkable polymer, respectively, the weight ratio of solid polymer (a) to weight ratio of plasticizer (b) being 70/30 to 30/70 (b) heating the exposed element to coalesce the plastisol layer solely in the unexposed image areas, and (c) removing the plastisol layer in the exposed image areas by washing the areas with a solvent for the plasticizer component of the plastisol.