Process for the preparation of photographic silver halide emulsions having tabular grains.

摘要

A process for the preparation of a photographic emulsion containing tabular silver halide grains having an aspect ratio in the range from 12:1 to 3:1 and a monomodal narrow size distribution comprising: (i) preparing a dispersing medium/bromide mixture having a pBr in the range 0.7 to 1.0, (ii) adding to the mixture silver nitrate and further halide as necessary to maintain an excess of bromide whereby tabular seed grains are formed, (iii) adding ammoniacal base solution to the mixture to achieve at least 0.02N of the base after at least 20% by weight of the total silver nitrate has been added, (iv) adding further silver nitrate and halide by balanced double jet procedure whilst maintaining a concentration of ammoniacal base of at least 0.02N, whereby tabular grains are formed. c