Silver halide precipitation and methine dye spectral sensitization process and products thereof

In a method of preparing a spectrally sensitized radiation-sensitive silver halide emulsion comprising introducing into a reaction vessel an aqueous solution of a silver salt, an aqueous solution of a halide salt, a peptizer and a methine spectral sensitizing dye, the dye being added to the reaction vessel during the course of introducing at least one of the aqueous salt solutions, the improvement comprising

• delaying addition of the spectral sensitizing dye until silver halide grain nuclei are present in the reaction vessel having a mean diameter which is at least 0.01 of the mean diameter of the silver halide grains of the radiation-sensitive silver halide emulsion to be prepared, a spectral sensitizing amount of the dye being added to the reaction vessel before 85 percent by weight of the silver salt solution has been introduced.

In a method of preparing a spectrally sensitized radiation-sensitive gelatino-silver chloride emulsion comprising introducing into a reaction vessel an aqueous solution of a silver salt, an aqueous solution of a chloride salt, a gelatin peptizer and a cyanine or merocyanine spectral sensitizing dye, the dye being added to the reaction vessel during the course of introducing at least the silver salt solution,

• the improvement comprising
• delaying introduction of the spectral sensitizing dye into the reaction vessel until at least 1 percent by weight of the silver salt solution has been introduced.

In a method of preparing a spectrally sensitized radiation-sensitive gelatino-silver bromoiodide emulsion comprising introducing into a reaction vessel an aqueous solution of a silver salt, an iodide salt and a bromide salt contained in one or more aqueous solutions, a gelatin peptizer and a cyanine spectral sensitizing dye, the dye being added to the reaction vessel during the course of introducing at least the silver salt solution,

• the improvement comprising
• delaying introduction of the spectral sensitizing dye into the reaction vessel until at least 2 percent by weight of the silver salt solution has been introduced and completing introduction of the spectral sensitizing dye before 80 percent by weight of the silver salt solution has been introduced.

In a method of preparing a spectrally sensitized radiation-sensitive gelatino-silver iodide emulsion comprising introducing into a reaction vessel an aqueous solution of a silver salt, an aqueous solution of an iodide salt, a gelatin peptizer and a cyanine spectral sensitizing dye, the dye being added to the reaction vessel during the course of introducing at least the silver salt solution,

• the improvement comprising
• delaying introduction of the spectral sensitizing dye into the reaction vessel until at least 2 percent by weight of the silver salt solution has been introduced and completing introduction of the spectral sensitizing dye before 80 percent by weight of the silver salt solution has been introduced.