Photosensitive negative-working toning process

Claim 1

A process for preparing negative tonable images which comprises exposing imagewise a photosensitive element comprising a support bearing a layer of a negative-working tonable photoimaging composition which comprises (a) at least one organic polymeric binder taken from the group consisting of polyvinylformal, polyvinylpyrrollidone, polyacrylate, cellulose acetate, polymethacrylate, and polyvinyl acetate; (b) a photosensitizer which upon absorption of actinic radiation is capable of generating an acid; and at least one acetal compound taken from the group of ##STR4## wherein R is hydrogen, alkyl of 1 to 18 carbon atoms, phenyl and substituted phenyl, and R 1 is taken from the group of alkylene of 2 to 12 carbon atoms and heteroalkylene of 2 to 12 carbon atoms, and ##STR5## wherein R 2 is alkyl of 1 to 18 carbon atoms, furyl, substituted furyl, phenyl, substituted phenyl, naphthyl, and substituted naphthyl, R 3 is alkyl of 1 to 18 carbon atoms, and OR 3 when taken together form a 5, 6 or 7 membered ring, the polymeric binder (a) being plasticized by the decomposition product of one of compound (c) (1), compound (c) (2) or the combination of compounds (c) (1) and (2), and toning the exposed image areas of said element.