GB1521730A - Sensitization of a silver halide photographic emulsion - Google Patents

Abstract

1521730 Silver halide emulsion sensitization FUJI PHOTO FILM CO Ltd 25 Nov 1975 [26 Nov 1974] 48461/75 Heading G2C A process of raising the sensitivity of a silver halide photographic emulsion comprises incorporating in a sulphur-sensitized silver halide emulsion which contains grains having a crystal form selected from octahedral, tetradecahedral spherical, plate, irregular spherical, irregular polyhydral and oblate forms whose average grain size does not exceed 0À5Ám, and wherein the silver halide contains 98À6 to 100 mole % of silver bromide, any remainder being silver iodide, at least one hydroxy-tetrazaindene compound of the Formulae (I) or (II) wherein R' and R<SP>2</SP> each represents a hydrogen atom, an alkyl group or an alkyl group substituted with one or two aryl groups, or an alkoxy, hydroxy, carbonyl or alkoxy carbonyl group; an aryl group or an aryl group substituted with one or more alkyl groups, one or more halogen atoms, one or more halogen atoms, one or more hydroxy groups, one or more alkoxy groups, one or more carboxy groups or one or more alkoxy carbonyl groups; and n represents 1 or 2. An average grain size not above 0À35Ám is preferred. Sensitization processes using noble metals, and selenium sensitization can be used in a combination with the sulphur sensitization. Hydroxytetrazaindenes are listed. The amount is suitably 0À001 to 0À5, preferably 0À01 to 0À2 mol per mol of silver halide.