Composite silver halide grains with improved reciprocity and process for their preparation

Abstract

A process for the preparation of a radiation-sensitive silver halide emulsion comprised of high chloride cubical host grains containing from 0.05 to 3 mole percent iodide, based on total silver, and epitaxially deposited silver bromide, where the iodide is incorporated in the host grains in a controlled, non-uniform distribution forming a core containing at least 50 percent of total silver, an iodide free surface shell having a thickness of greater than 50 Å, and a sub-surface shell that contains a maximum iodide concentration is disclosed, the process comprising: (a) providing in a stirred reaction vessel a dispersing medium and high chloride silver halide cubical grains which form the high chloride host grain cores, (b) adding fine silver iodide grains to the reaction vessel and ripening out the fine silver iodide grains to form the sub-surface shells that contain a maximum iodide concentration, (c) precipitating silver chloride onto the sub-surface shells to form an iodide free surface shell, and (d) depositing silver bromide in an amount of from 0.05 to 5 mole percent, based on total silver, on the host grain surfaces in the presence of an iridium dopant. Also disclosed are photographic recording elements comprising a support and at least one light sensitive silver halide emulsion layer comprising silver halide grains prepared as described above, and an electronic printing method which comprises subjecting a radiation sensitive silver halide emulsion layer of a recording element to actinic radiation of at least 10,ergs/cm,for up to 100&mgr; seconds duration in a pixel-by-pixel mode, wherein the silver halide emulsion layer is comprised of silver halide grains prepared as described above.