| 摘要 |
PURPOSE: To enhance color developing speed by mixing an aqueous solution of a silver salt with an aqueous solution of an alkali metal or ammonium bromide or chloride in a dispersion medium containing silver halide crystals having a hexagonal system lattice structure and forming silver halide twin crystals containing an iodide and the other halide. CONSTITUTION: The flat silver halide crystals has a hexagonal lattice structure and an average thickness smaller than 0.6μm and an average aspect ratio of 2:1 in at least 90mol% and contain at least 90mol% iodide and they are formed in a colloidal dispersion medium. An aqueous solution of a silver salt and that of an alkali metal or ammonium bromide or chloride or an aqueous solution of its mixture are mixed in a dispersion medium containing these silver halide crystals to form the silver halide twin crystals containing the iodide and the other halides, and the twin crystals are optionally grown and their sizes are increased and the emulsion is chemically sensitized, thus permitting color developing speed to be enhanced.
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