A process of conducting epitaxial deposition as a continuation of emulsion precipitation

摘要

A process is disclosed of conducting in a single reaction vessel selective site high chloride epitaxy deposition as a continuation of host high bromide {1111} tabular grain emulsion precipitation. A host tabular grain emulsion is precipitated accounting for 0.05 to 1.5 moles of silver per liter of dispersing medium. Any iodide at the major faces of the tabular grains is uniformly distributed and any iodide in a surface region of the grains amounts to less than 7 mole, based on silver in the surface region. Until epitaxy is formed, pH is held in the range of 3 to 8. Gelatino-peptizer in an amount of 1 to 40 grams per Ag mole is added to the emulsion. Chloride ion in a range of from 0.03 to 0.15 mole per liter is dispersed in the emulsion. pBr is held in the range of from 3.0 to 3.8 until epitaxy is formed. Iodide ion in a concentration of from 5 X 10<Sup>-6</Sup> to 1 X 10<Sup>-4</Sup> mole per square meter of grain surface area is uniformly adsorbed to the major surfaces of the tabular grains.