High bromide tabular grain emulsions with dislocations in peripheral regions

Abstract

A photographic emulsion is disclosed comprised of a radiation-sensitive high bromide tabular grain emulsion. At least 50 percent of total grain projected area is accounted for by tabular grains each comprised of (a) less than 12 mole percent iodide and greater than 50 mole percent bromide, based on silver, (b) a central region accounting for at least 50 percent of grain projected area, and (c) a peripheral region containing crystal lattice dislocations and a higher iodide concentration than the overall average iodide concentration of the tabular grains. The emulsion contains a hydrophilic colloid peptizer derived from a water dispersible cationic starch. The iodide and dislocations in the peripheral regions contribute to increased photographic speeds. The water dispersing cationic starch facilitates emulsion precipitation and chemical sensitization.

Dependencies are inferred from the claim text.