Inherently Stable High-Aspect-Ratio Silver Chloride Tabular Emulsions

Abstract

A wide variety of silver bromide crystal morphologies can be produced in a straightforward manner by changing the excess bromide level during emulsion precipitation. A number of these conditions produce morphologies bounded by {111} faces, most notably the twinned tabular form. Silver chloride does not inherently lend itself to such a variety in part because the {111} crystal face is not stable without strongly adsorbed growth modifiers. A new type of inherently stable high-aspect-ratio tabular silver chloride has been precipitated by adding small amounts of iodide (less than 0.1 mole% overall) early in the process to induce anisotropic grain growth under low supersaturation conditions. Unlike the traditional twinned tabular morphology, these new crystals possess stable {100} major faces, contain no twin planes, and do not require organic growth modifiers for formation or stability. Photographic performance consistent with the high surface-to-volume ratio, such as high light absorption and covering power, is obtained using conventional methods of spectrochemical sensitization.