Method for making tabular grain silver halide emulsion
US6673529B1 · kind B1 · utility
Assignee
Inventors
Key dates
| Filing date | Jul 11, 2002 |
| Grant date | Jan 6, 2004 |
| Priority date | — |
| Expiry date | Jul 11, 2022 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG03C2200/03
- WIPO fieldOptics
- WIPO sectorInstruments
Abstract
A process of preparing a high bromide tabular grain emulsion comprising a dispersion medium and silver halide grains including tabular grains having {111} major faces and an aspect ratio of at least 2, which contain greater than 50 mole percent bromide, based on silver, and which account for greater than 50 percent of total grain projected area, where such tabular grains have an average aspect ratio of at least 5, the process comprising (i) in a grain nucleation step creating in a dispersing medium tabular silver halide grain nuclei containing parallel twin planes and (ii) in a grain growth step subsequently growing the tabular grain nuclei into tabular grains in a silver halide reaction vessel by adding a silver ion source and a halide ion source to the reaction vessel and precipitating silver halide onto the tabular grain nuclei, wherein thiocyanate ion is introduced into the silver halide reaction vessel prior to the addition of at least the final 10 mole percent of the total silver added to the reaction vessel, and further wherein the introduced thiocyanate ion concentration is at most 0.4 mole %, based on the total silver added to the reaction vessel. Use of thiocyanate during…
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.