Patent ID: 7358038
Filing Date: 2008-04-15
Classification: G03C

Abstract:
1. A black and white photothermographic material comprising, on at least one side of a support, an image forming layer comprising at least a photosensitive silver halide, a non-photosensitive organic silver salt, a reducing agent for silver ions, and a binder, wherein 50% or more of a total projected area of the photosensitive silver halide is occupied by tabular grains having a (111) face as a major face, the tabular grains have at least 2 parallel twin crystal planes in a grain, and a variation coefficient of a distribution of distances between closest twin crystal planes is 20% or less, wherein the grains are prepared by a nucleation step and a ripening step comprising a combination of plural means among following a) to d); a) in the presence of a gelatin having an average molecular weight of 50,000 or less, b) in the presence of a gelatin having a methionine content of 30 μmol or less per 1 g of the gelatin, c) at a temperature 0° C. to 30° C. during the nucleation step, and d) at a concentration of a silver nitrate solution and an alkali halide solution 0.01 mol/L to 0.8 mol/L during the nucleation step; and the image forming layer further comprises a nucleator represented by the following formulae (H), (G), (P), (A), (B) or (C); wherein in the formula (H). A