Eastman-kodak Company

Steven J Sargeant

Pranab Bagchi

Brian Thomas

Gary J Mcsweeney

James T Beck

This invention describes a process of coprecipitating a photographic material such as a dye-forming coupler inside a base ionizable polymeric particle. Preparation of such a dispersion is performed by providing a first flow comprising a solution of a surfactant in water containing a polymer ionizable by base, providing a second flow comprising a water miscible solvent, base, water, and the photographic material, then mixing the said first and said second flow and immediately neutralizing the mixed flow to precipitate the photographic material inside the polymer particles forming a fine particle colloidal dispersion of the photographic material. The polymer dispersions of the invention are characterized by high photographic activity and high dye-stability in some cases.

Polymer co-precipitated coupler dispersion

Base and auxiliary solvent solubilized precipitated dispersions of couplers and other photographic materials usually produce very small particle dispersions, and usually such dispersions are extremely highly reactive because of the smallness of the particle size. However, some relatively more hydrophobic couplers, even through they produce small particles when a dispersion if formed by the precipitation technique, lead to extremely unreactive dispersions. The method of this invention constitutes a single step coprecipitation technique where a base deprotonation compound, preferably a liquid carboxylic acid, is incorporated into the precipitated particles to produce photographically highly active coupler dispersions. The invention is performed by providing a first flow of an aqueous surfactant solution and a second flow comprising a basic solution of the coupler and the base deprotonable compound in a water miscible volatile auxiliary solvent and mixing the said first and second streams either simultaneously or immediately following thereof, neutralizing said streams with an acid solution. Such immediate neutralization protects any hydrolizable surfactants that may be utilized in the crude emulsion stream. In a preferred method, the first and the second stream may be brought together immediately prior to neutralization or directly into a mixer with addition of acid directly into the mixer to neutralize the dispersion to form a dispersion of fine particles.

Increased photographic activity precipitated coupler dispersions

The invention is generally accomplished by utilization of a surfactant for very small particle photographic dispersions. Three types of such surfactants that have been identified are as follows:

Preparation of low viscosity small particle photographic dispersions in

Base and auxiliary solvent solubilized precipitated dispersions of couplers and other photographic materials usually produce very small particle dispersions, and usually such dispersions are extremely highly reactive because of the smallness of the particle size. However, some relatively more hydrophobic couplers, even though they produce small particles when a dispersion is formed by the precipitation technique, lead to extremely unreactive dispersions. The method of this invention constitutes a single step coprecipitation technique where a base deprotonation compound, preferably a liquid carboxylic acid, is incorporated into the precipitated particles to produce photographically highly active coupler dispersions. The invention is performed by providing a first flow of an aqueous surfactant solution and a second flow comprising a basic solution of the coupler and the base deprotonable compound in a water miscible volatile auxiliary solvent and mixing the said first and second streams either simultaneously or immediately following thereof, neutralizing said streams with an acid solution. Such immediate neutralization protects any hydrolizable surfactants that may be utilized in the crude emulsion stream. In a preferred method, the first and the second stream may be brought together immediately prior to neutralization or directly into a mixer with addition of acid directly into the mixer to neutralize the dispersion to form a dispersion of fine particles.

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Honeoye Falls, NY, United States of America

Steven J Sargeant