| 摘要 |
PURPOSE:To establish the method for preparing the prefogged direct positive type silver halide emulsion high in sensitivity and maximum density and contrast and good in storage stability by specifying the preparing method. CONSTITUTION:The prefogged direct positive silver halide emulsion is prepared by forming silver halide grains, and then, fogging the surfaces of the silver halide grains to form silver nuclei, and bleaching some of the silver nuclei while controlling pH to <=4.5 and/or pAg to >=8.0, adding a reducing agent at <=50 deg.C after fogging the grains and forming the silver nuclei and before refrigerating them, thus permitting the sensitivity, Dmax, and contrast to be enhanced at the same time by partially oxidizing the fogged nuclei on the surfaces of the grains, especially, the unnecessary silver nuclei not contributing to enhancement of Dmax and development speed.
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