Silver halide photographic element

摘要

This invention provides a photographic element comprising at least one silver halide emulsion layer in which the silver halide is sensitized with a compound of the formula (a): DELTA -(t)m-XY' XY'-(t)m - DELTA DELTA -(t)m-XY'-(t)m- DELTA wherein DELTA is protective group that is eliminated during development of the photographic element, t is a timing group, m is an integer from 0 to 3, and XY' is a fragmentable electron donor moiety in which X is an electron donor group and Y' is a leaving proton H or a leaving group Y, with the proviso that if Y' is a proton, a base, beta <->, is present in the emulsion or is covalently linked directly or indirectly to X, and wherein: 1) X-Y' has an oxidation potential between 0 and about 1.4 V; 2) the oxidized form of X-Y' undergoes a bond cleavage reaction to give the radical X<•> and the leaving fragment Y'; and 3) the radical X<•> has an oxidation potential <-0.7V.