Method for preparing tabular grains rich in silver chloride with reduced thickness growth and improved homogeneity
US6010840A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Jan 19, 1999 |
| Grant date | Jan 4, 2000 |
| Priority date | — |
| Expiry date | Jan 19, 2019 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG03C2200/47
- WIPO fieldOptics
- WIPO sectorInstruments
Abstract
A method has been described for preparing a gelatinous emulsion having grains rich in silver choride, wherein at least 70%, and more preferred 90%, of the total projected area of all grains is provided by {111} tabular grains having an average aspect ratio of more than 2:1, an average equivalent circular diameter of at least 0.3 .mu.m and an average thickness of from 0.05 to 0.25 .mu.m , wherein a percent variation on average equivalent circular diameter of said tabular grains is 30% or less and wherein a percent variation on average thickness of said tabular grains is 20% or less and wherein said tabular grains are present in percent numerical amounts of at least 90%, said method comprising following steps: PA1 preparing in a reaction vessel a dispersion medium comprising an initial amount of a crystal habit modifying agent; PA1 precipitating therein silver halide crystal nuclei by double-jet precipitation of an aqueous silver nitrate and an aqueous solution comprising halide ions, wherein less than 10% by weight of a total amount of silver nitrate used is consumed; PA1 growing said silver halide crystal nuclei by further precipitation of silver halide by means of double-jet preci…
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.