Silver halide emulsion
AssigneeKonica Corporation
InventorsHiroshi Takada, Katsuhiko Heki
Life of this patent
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Abstract
A silver halide emulsion is disclosed, comprising tabular silver halide grains having an average iodide content of 3 to 15 mol % and comprising silver halide phases differing in halide composition, at least 50% of the total projected area of the tabular silver halide grains being accounted for by grains having an aspect ratio of not less than 12, wherein the first silver halide phase (A) has an average iodide content of not more than 3 mol % and accounting for 50 to 85% of total silver, the second phase (B) locating outside the phase (A), having an average iodide content of 8 to 25 mol % and accounting for 10 to 35% of total silver, and the third outermost phase having an average iodide content of not more than 4 mol % 0.5 to 15% of total silver.
Claims17
A silver halide emulsion comprising a dispersing medium and tabular silver halide grains having an average iodide content of 3 to 15 mol % and comprising silver halide phases, at least 50% of the total projected area of the tabular silver halide grains being accounted for by grains having an aspect ratio of not less than 12, wherein
- a first of the silver halide phases is a phase (A) having an average iodide content of not more than 3 mol % and accounting for 50 to 85% of total silver,
- a second of the silver halide phases is a phase (B) locating outside the phase (A), having an average iodide content of 8 to 25 mol % and accounting for 10 to 35% of total silver, and
- a third of the silver phases is an outermost phase having an average iodide content of not more than 4 mol % and accounting for 0.5 to 15% of total silver.
The silver halide emulsion of claim if wherein the tabular grains exhibit a coefficient of variation of grain size of not more than 25%.
A method of preparing a silver halide emulsion wherein the silver halide emulsion comprises tabular silver halide grains having an average overall iodide content of 3 to 15 mol % and at least 50% of total projected area of the tabular grains is accounted for grains having an aspect ratio of not less than 12, the tabular silver halide grains each comprising a phase (A), a phase (B) and an outermost phase, wherein the phase (A) has an average iodide content of not more than 3 mol %, accounting for 50 to 85% of total silver, the phase (B) is located outside the phase (A), having an average iodide content of 8 to 25 mol % and accounting for 10 to 35% of total silver, and an outermost phase has an average iodide content of not more than 4 mol %, accounting for 0.5 to 15% of total silver;
- the method comprising:
- a nucleation step of forming nucleus grains by mixing a silver salt and a halide salt in a dispersing medium,
- a ripening step of ripening the nucleus grains, then,
- a grain growth step of growing the nucleus grains by mixing a silver salt and a halide salt or adding silver halide grains,
- wherein the nucleation step is performed at a temperature of 5 to 20° C. in the presence of gelatin having an average molecular weight of not more than 30,000.
Dependencies are inferred from the claim text.