Direct positive photographic silver halide emulsion and color photographic light-sensitive material comprising same

A color diffusion transfer photographic light-sensitive material comprising at least one photosensitive silver halide emulsion layer combined with a dye image-forming substance provided on a support, said dye image-forming substance comprising a nondiffusive compound represented by the following formula (I) which releases a diffusive dye or precursor thereof or changes in its diffusivity in connection with silver development,

• wherein said at least one silver halide emulsion layer comprises at least one internal latent image type direct positive photographic silver halide emulsion comprising tabular silver halide grains having a core/shell structure with a core and an external shell, composed of silver bromide, and having an average grain diameter of not less than 0.3 μm and an aspect ratio of from not less than 2 to not more than 100 in an amount of not less than 50% of all silver halide grains as calculated in terms of area, with the average grain thickness a along the main plane of the external shell thereof being from not less than 0.2 μm to not more than 1.5 μm and the average grain thickness b perpendicular to the main plane of the external shell thereof being from not less than 0.04 μm to not more than 0.30 μm;
• wherein grains are subjected to chemical sensitization in the presence of at least one compound selected from the group consisting of compounds represented by the following formula (A), (B) and (C):
• R—SO2—S—M (A)
• R—SO2—S—R1 (B)
• R—SO2S—(L)m—SSO2—R2 (C)
• wherein R, R1 and R2 may be the same or different and each represents an aliphatic group, aromatic group or heterocyclic group;
• M represents a cation;
• L represents a divalent linking group;
• m represents 0 or an integer of 1;
• the compounds of the formula (A), (B) and (C) may be each in the form of polymer containing as a repeating unit a divalent group derived from the structure represented by the formulae (A), (B) and (C), respectively;
• and R, R1, R2 and L may be optionally connected to each other to form a ring;
• and
• wherein formula (I) is as follows:
• (DYE−Y)n−Z (I)
• wherein DYE represents a dye group or a dye group precursor group whose absorption wavelength has been shifted to short wavelength;
• Y represents a mere bond or bridging group;
• Z represents a group which makes a difference in the diffusivity of the compound represented by (DYE−Y)n−Z or releases DYE to make a difference in diffusivity between the released DYE and (DYE−Y)n−Z in correspondence or counter correspondence to a photosensitive silver salt having an imagewise latent image;
• and n represents an integer of 1 or 2, with the proviso that when n is 2, the plurality of (DYE−Y)'s may be the same or different.