Preparation of silver halide tabular emulsions in the presence o

Details Preparation of silver halide tabular emulsions in the presence o Preparation of silver halide tabular emulsions in the presence o

1995-01-18

1996-07-30

Bowers, Jr., Charles L.

Radiation imagery chemistry: process, composition, or product th

Radiation sensitive product

Silver compound sensitizer containing

430567, G03C 1015

Patent

active

055410510

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 weight of water to (a)protic solvent of not more than 40:60 in the reaction vessel; optionally growing said twinned tabular nuclei to tabular silver halide emulsion crystals in the same or in another reaction vessel by the addition of an aqueous soluble silver salt solution and a aqueous soluble halide salt solution; flocculating and decanting the said emulsion crystals obtained, followed by washing and redispersing or applying dialysis or ultrafiltration techniques.

REFERENCES:
patent: 3871887 (1975-03-01), Jones
patent: 4419442 (1983-12-01), Falxa et al.
patent: 4725534 (1988-02-01), Kagami et al.
patent: 4751176 (1988-06-01), Pham

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