Preparation of tabular emulsion grains rich in chloride

Abstract

A method for the preparation of silver halide tabular emulsion grains, containing at least 75 % chloride, wherein at least 50 % of the total projected area of all the grains is provided by the tabular grains, and wherein the tabular grains exhibit an average aspect ratio of at least 5:1, an average thickness not greater than 0.5 micron and an average diameter of at least 0.6 micron. The method comprises preparing a dispersion medium containing a gelatino-peptizer, and a compound ##STR1## wherein Z represents the atoms necessary to form a fused on aromatic carbocyclic or heterocyclic, unsubstituted or substituted ring, e.g., substituted with alkyl, alkenyl, aryl, alkoxy, hydroxy, mercapto, carboxy, amino or halogen, R is hydrogen or a substituent as defined for ring Z; n is 1 or 0, and Q represents carbon in which case n=1, or Q represents nitrogen, in which latter case n =0; in a concentration ranging from 10.sup.-4 to 10.sup.-2 molar. The pH of the medium is adjusted to between 5.0 and 9.0 and to a pCl between 1.0 and 2.0 by means of a chloride ions providing salt; performing a silver halide precipitation comprising at least one double jet step by introducing in the dispersion medium at least one solution containing chloride ions and at least one solution containing silver ions in such a way that pCl is maintained between 1.0 and 2.0, pH is maintained between 5.0 and 9.0 and the concentration of compound (Ia) or (Ib) is maintained between 10.sup.-4 molar and 10.sup.-2 molar; and removing excess of soluble salts by a wash technique performed at a pH value comprised between 4.0 and 9.0.

Dependencies are inferred from the claim text.