Acutance agents for use in thermally-developable photosensitive compositions

Claim 1

In a photosensitive, heat-developable, dry silver sheet material containing an image forming system including in one layer a photosensitive silver halide catalyst-forming means and, as heat image-forming means, an organic silver compound, said image-forming system further including toner and a reducing agent the oxidation-reduction reaction of which latter with said organic silver compound being catalyzed by silver halide catalyst; the improvement characterized by the inclusion in said layer with said organic silver compound of an acutance agent represented by the formula ##STR10## wherein: Z represents the atoms necessary to complete a mono-or polycyclic dihydroheterocyclic nucleus having 5 to 6 atoms in the ring including the N of the formula; R 1 is an alkyl, substituted alkyl, alkenyl or aryl group; m = 0 or 1; k = 0, 1 or 2; T is an aprotic electron-withdrawing group having a σ para value of 0.45 to 0.63 selected from CF 3 or CN and R 2 and R 3 are hydrogen or together constitute a condensed carbocyclic aromatic ring.