Claims
- 1. A method of forming forming silver halide grains comprising
- forming a precipitation dispersion for silver halide grains,
- precipitating silver halide grains by introducing silver and halide salts into the precipitation,
- after about 65 to about 90 percent of the silver salt that will form the silver mass to be precipitated has been added, adding to said precipitation dispersion selenium salt dopant in an amount to about 1.4.times.10.sup.-6 mole per mole of silver, based on the total mass of silver to be precipitated,
- continuing precipitation until all the silver mass has been added and said silver halide grains reach a desired size, ending the precipitation process, and recovering said grains, said grains comprising silver, iodide and bromide, and said grains having of an aspect ratio of at least 8 to 1.
- 2. The method of claim 1 wherein said silver halide grains are precipitated utilizing an accelerated double jet technique.
- 3. The method of claim 1 wherein said ending precipitation is performed by coagulation washing to remove bromide ion.
- 4. The method of claim 1 wherein about 67 percent of said silver salt has been added when said selenium salt is added to said precipitation dispersion.
- 5. The method of claim 1 wherein after precipitation is ended said grains are sensitized, couplers and other addenda added, and the emulsion is coated as a layer of photographic film.
- 6. The method of claim 1 wherein said selenium salt comprises potassium selenocyanate.
- 7. The method of claim 1 wherein said salt comprises a metallic selenium salt.
- 8. The method of claim 1 wherein said selenium salt comprises an organo metallic salt.
- 9. The method of claim 8 wherein said organo metallic salt comprises a seleno thiourea salt.
- 10. The method of claim 1 wherein said silver halide grains comprise between 1 and 44 mole percent of silver iodide.
- 11. The method of claim 9 wherein said silver halide grains comprise between about 1 and 12 mole percent of silver iodide.
- 12. The method of claim 11 wherein said aspect ratio is at least 20 to 1.
- 13. Photo sensitive silver halide grains comprising silver halide grains comprising silver, bromide, iodide, and about 1.4.times.10.sup.-6 mole selenium per mole of silver, said grains having an aspect ratio of at least 8 to 1 and about the outer third of said grains comprise selenium.
- 14. The grains of claim 13 wherein the sub-surfaces of said grains comprise selenium.
Parent Case Info
This is a continuation of application Ser. No. 367,904, filed Jun. 19, 1989, now abandoned.
US Referenced Citations (12)
Continuations (1)
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Number |
Date |
Country |
Parent |
367904 |
Jun 1989 |
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