Diffusion transfer material and process

A photographic silver halide material comprising a support carrying at least one unexposed alkali-permeable silver halide hydrophilic colloid emulsion layer and containing a compound, which is immobile in an alkali-permeable colloid medium when contacted with an alkaline liquid and which is capable of being reduced by a silver halide developing agent at a rate slower than that of image-wise developable silver halide in the photographic material and in reduced state is capable of releasing a photographically useful group, characterized in that said compound corresponds to the following general formula:

• ##STR31## wherein:
• R.sup.10 and R.sup.20 (same or different)
• (1) represent an alkyl group, a cycloalkyl group, an alkenyl group, a cycloalkenyl group or an aralkyl group,
• (2) represent an aryl group, or
• (3) represent a heterocyclic ring residue, or
• R.sup.10 and R.sup.20 are ringclosed, either R.sup.10 or R.sup.20 containing a ballasting group conferring diffusion resistance to the compound in hydrophilic colloid media when penetrated by an aqueous alkaline liquid;
• L.sup.1 and L.sup.2 (same or different) represent a ##STR32## --SO.sub.2 --;
• --NHCO--;
• --NHSO.sub.2 --;
• ##STR33## --O--SO.sub.2 -- or ##STR34## group;
• p and q (same or different) represent an integer 0 or 1;
• Z represents an atom or an atom group which is electronegative with respect to carbon, and
• PUG represents together with Z a releasable photographically useful group.