Silver halide emulsions comprising tabular crystals, emulsions and the processing thereof
US6312882A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | Feb 28, 1996 |
| Grant date | Nov 6, 2001 |
| Priority date | — |
| Expiry date | Feb 28, 2016 |
Classification
- Technology area (CPC Y)Emerging Cross-Sectional Technologies
- CPC primaryY10S430/167
- WIPO fieldOptics
- WIPO sectorInstruments
Abstract
A method is disclosed for preparing a light-sensitive silver halide emulsion comprising tabular grains containing colloidal silica sol as a protective colloid, said tabular grains having an average grain thickness of not more than 0.3 .mu.m, an average aspect ratio of more than 12:1, a total projective area of said tabular grains of at least 50% and a coverage degree by silica sol particles within the range from 50 to 2000%, comprising following steps: PA1 precipitating in a reaction medium silver halide by means of a double-jet or triple-jet technique applied to aqueous solutions of silver nitrate and halide salts in colloidal silica having an average particle size in the range from 0.003 .mu.m to 0.30 .mu.m as a protective colloid, in the presence of at least one onium compound, selected from the group consisting of a phosphonium compound, a iodonium compound and an ammonium compound, except for an ammonium compound containing NH.sub.4.sup.+ -ions; but in the absence of gelatin, wherein a ratio by weight of said colloidal silica to said onium compound(s) is obtained between 3 and 400; PA1 controlling nucleation and growth steps by means of variable flow rate(s) of aqueous solutio…
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