Eastman-kodak Company

Mark A Whitson

Pranab Bagchi

Tienteh M Chen

Thomas Joseph Dannhauser

John D Lewis

Anthony Adin

Sang H Kim

Jerzy A Budz

Richard E Beal

Wai K Lam

The invention describes silver halide packet emulsion grains or crystals that are conventionally precipitated using gelatin of a given isoelectric pH, surrounded by a layer of gelatin-grafted-polymer particles wherein the grafted gelatin has a different isoelectric pH and the said gelatin-grafted-polymer particles are optionally chemically bonded to the gelatin surrounding the silver halide microcrystals. Such packet emulsions can form the basis for a mixed-packet color photographic system.

Attachment of gelatin-grafted polymer particles to pre-precipitated

This invention describes the composition and method of preparation of heteroflocculated packet emulsion clusters containing a light sensitive and selectively photosensitized silver halide emulsion particles and particles of photographic agents such as dye-forming coupler particles. The silver halide emulsion particles are associated with a layer of adsorbed peptizing gelatin with an isoelectric pH of P.sub.1 and the grafted gelatin of the gelatin-grafted-polymer particles comprising the photographic agent has an isoelectric pH of P.sub.2 such that P.sub.1 is different than P.sub.2. At least one of the peptizing and grafted gelatins is an isoing gelatin which is sufficiently derivatized to remove ionic groups thereof such that approaching the isoelectric pH in an aqueous solution of the isoing gelatin causes massive heteroflocculation. Formation of packet emulsion clusters is achieved by heteroflocculation between oppositely charged silver halide particles and gelatin-grafted-latex polymer particles comprising the photographic agents by shift of the pH to within 0.5 pH units of the isoelectric pH of the isoing gelatin and at a value between the two isoelectric pH values of two different types of gelatins used. The heteroflocculated packet emulsions can be further stabilized via hardening of the gelatins surrounding the particles in the packet clusters using a concentrated gelatin hardener. Such packet emulsion clusters are suitable for use in mixed packet color photography.

Mixed packet color photographic system

Attachment of gelatin-grafted plymer particles to pre-precipitated

This invention describes the use of gelatin-grafted-polymer particles as peptizers for the preparation of silver halide photographic emulsions, whereby the gelatin-grafted-polymer particles remain attached to the AgX crystals after preparation of the emulsions. In an embodiment of this invention, the core polymer particles are loaded with photographically useful agents. When the photographic agent is a dye-forming coupler, multicolor mixed-packet systems can be constructed using the packet emulsions prepared in the manner of this invention.

Gelatin-grafted-polymer particles as peptizer for silver halide emulsions

This invention provides a method of preparing a silver halide photographic emulsion which comprises adding to the silver halide emulsion before or during precipitation a non-labile chalcogen compound represented by Formula I:

Silver halide photographic emulsions precipitated in the presence of

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Webster, NY, United States of America

Mark A Whitson