Eastman-kodak Company

Philip J Zola

Seshadri Jagannathan

Terrence Robert O'Toole

Thomas B Brust

Roger L Klaus

John W Boettcher

Michael W Orem

Roger H Piggin

Julia S Tan

Philip J Dale

Ming Jye Lin

David Lawrence Benzing

Jane H Chronis

A radiation-sensitive emulsion comprised of an aqueous dispersing medium and a coprecipitated grain population including tabular grains containing greater than 50 mole percent bromide, based on silver, having &lcub;111&rcub; major faces, and accounting for greater than 90 percent of total grain projected area, wherein said dispersing medium is comprised of (a) a gelatin which has been modified to convert at least one carboxylic acid group thereof to a group that does not exhibit pH-dependent ionization within the pH range from 4.0 to 7.0, and (b) a polyalkylene oxide block copolymer surfactant.

High bromide tabular grain emulsions precipitated in a novel dispersing medium

A process of preparing a radiation-sensitive silver halide emulsion is disclosed in which a polyalkylene oxide block copolymer surfactant is employed. Dispersion of the polyalkylene oxide block copolymer surfactant in the aqueous dispersing medium is increased by the inclusion of an auxiliary surfactant. The auxiliary surfactants are selected from among those that, in the form of an aqueous solution containing 10 percent by weight of the auxiliary surfactant based on total weight of the aqueous solution, is miscible in all proportions with at least one of water and the polyalkylene oxide block copolymer surfactant.

Processes of preparing radiation-sensitive silver halide emulsions

A process is disclosed of preparing a photographic emulsion comprised of high bromide silver halide tabular grains accounting for greater than 90 percent of total grain projected area. The grains exhibit a low level of size dispersity by reason of forming in the presence of a dispersing medium containing a polyalkylene oxide block copolymer surfactant a population of silver halide grain nuclei containing twin planes, the halide content of the grain nuclei consisting essentially of silver bromide, and growing the silver halide grain nuclei containing twin planes to form the tabular silver halide grains. Inadvertent variation in tabular grain sizes and thicknesses from one precipitation to the next are minimized by growing the silver halide grain nuclei at a pH in the range of from 3.0 to 8.0 and in the presence of at least a 0.01M concentration of a partially dissociated acid having a pKa that is within 2.5 units of the pH and that forms a silver salt more soluble than the silver halide incorporated in the grains.

Robust process for preparing high Br low COV tabular grain emulsions

The invention is generally accomplished by providing nucleation of silver halide crystals or grain without backmixing or exposure to previously nucleated grains. Generally this is accomplished by injecting a solution of silver nitrate into a solution of sodium bromide and peptizer as it is moving in pipe in a type of flow which does not provide back mixing and moves in generally plug flow. The plug flow is carried out until nucleation is complete and then the nucleated grains are transferred to a mixing container where they are ripened, grown, and subjected to the normal treatments, such as sensitization, applied to the silver halide to be used photgraphically.

Plug-flow process for the nucleation of silver halide crystals

A process is disclosed for the preparation of a tabular grain silver bromoiodide emulsion in which silver bromoiodide laminae are formed on the major faces of the tabular grains. The sensitivity of the emulsion as a function of pressure applied is rendered more nearly constant by forming the silver bromoiodide laminae on the major faces of the tabular grains within a pAg and temperature range defined by Curve A in FIG. 1. The laminae are formed by first precipitating iodide as a silver salt at peripheral sites on the tabular grains and then precipitating silver bromoiodide onto the major faces of the host tabular grains with the primary source of iodide being the previously deposited iodide. The emulsions produced exhibit high sensitivity to exposing radiation and reduced sensitivity to localized pressure.

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Webster, NY, United States of America

Philip J Zola