Preparation of silver halide tabular emulsions in the presence of polar aprotic solvents and/or alcohols
US5541051A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Jan 18, 1995 |
| Grant date | Jul 30, 1996 |
| Priority date | — |
| Expiry date | Jan 18, 2015 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG03C1/015
- WIPO fieldOptics
- WIPO sectorInstruments
Abstract
This invention offers a new method to produce tabular silver halide grains, more preferably silver bromide or silver bromoiodide grains, having a tabularity, defined as the ratio between the aspect ratio and the thickness of the emulsion crystals, of at least 25 and a homogeniety of the distribution of said silver halide emulsion crystals, defined as a hundred times the ratio between the standard deviation and the average projective crystal diameter of said crystals of less than 30, characterized by the steps of adding to a reaction vessel containing at least one polar aprotic solvent a silver salt in an amount to get a concentration from 0.01 to 1M of said silver salt and a halide salt in an amount to get a concentration 1 to 10.sub.4 times the molar concentration of said silver salt; dissolving the said silver salt and the said halide salt; adding a protic solvent to the said reaction vessel in order to form twinned tabular nuclei; colloidally stabilizing said twinned tabular nuclei by the addition of a protective colloid apart or together with at least one protic solvent or with a mixture of at least one protic and at least one aprotic solvent, in order to obtain a ratio by weig…
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.