Process for forming direct-positive image

Claim 1

A process for forming a direct-positive image comprising the step of developing an imagewise exposed photosensitive material comprising a support and at least one photographic emulsion layer thereon containing nonprefogged silver halide grains capable of forming an internal latent image, said developing step being carried out in the presence of a combination of a nucleating agent and at least one compound having at least one mercapto group selected from a mercapto-tetrazaindene, a mercapto-triazaindene and a mercapto-pentazaindene, futher provided that the hydrogen atom of said mercapto group may be replaced by an alkali metal atom or an ammonium group wherein said nucleating agent is represented by the following general formula (N-I) or (N-II): ##STR38## wherein Z represents a non-metallic atomic group necessary to complete an unsubstituted or substituted, 5-membered or 6-membered hetero ring; R 1 represents an unsubstituted or substituted aliphatic group; and R 2 represents a hydrogen atom, or an unsubstituted or substituted aliphatic or aromatic group; provided that at least one group selected from R 1 , R 2 , and Z may be substituted with an alkynyl group, an acyl group, a hydrazino group or a hydrazono group; and R 1 and R 2 may combine to form a 6-membered ring or a dihydropyridinium skeleton; ##STR39## wherein R 21 represents an aliphatic group, an aromatic group, or a heterocyclic group; R 22 represents a hydrogen atom, an alkyl group, an aralkyl group, an aryl group, an alkoxy group, an aryloxy group, or an amino group; G represents a carbonyl group, a sulfonyl group, a sulfoxy group, a phosphoryl group, or an iminomethylene group represented by ##STR40## R 23 and R 24 each represents a hydrogen atom or one of R 23 and R 24 represents a hydrogen atom and the other represents an alkysulfonyl group, an arylsulfonyl group or an acyl group, said nucleating agent being incorporated in said photosensitive material in an amount of from about 10 -8 to 10 -2 per mole of silver halide therein and said compound having at least one mercapto group being incorporated in said photosensitive material in an amount of from about 10 -6 to 10 -2 mole per mole of silver halide therein, the developing step being carried out at a pH of from about 10 to 11.5.