Preparation of silver halide tabular emulsions in the presence of non-aqueous polar aprotic solvents and/or protic solvents having a dissociation constant smaller than that of water
US5478718A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Jan 18, 1995 |
| Grant date | Dec 26, 1995 |
| Priority date | — |
| Expiry date | Jan 18, 2015 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG03C1/0051
- WIPO fieldOptics
- WIPO sectorInstruments
Abstract
A method has been found for the preparation of tabular silver halide emulsions 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 forming silver halide grain nuclei by introduction of an aqueous silver salt solution and an aqueous halide salt solution, both solutions optionally comprising at least one non-aqueous solvent, in a reaction vessel containing water, a protective colloid and at least one non-aqueous aprotic solvent or a protic solvent having a dissociation constant smaller than that of water in a ratio by weight of solvent versus water from 5 to 60%; adding an aqueous silver salt solution and an aqueous halide salt solution to the said reaction vessel containing the said silver halide grain nuclei at a pBr value higher than 2.0; flocculating the grown silver halide emulsion grains; washing and redispersing them.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.