Method of dispersing water insoluble photographically useful compounds

#The present invention relates to a method of dispersing oil-soluble photographically useful compounds into a hydrophilic colloid composition or into water and to such dispersions formed, and to photographic elements containing such dispersions in a hydrophilic colloid layer.

#In the manufacture of a photographic silver halide emulsion layer or other hydrophilic colloid coatings, one must often blend water-insoluble or sparingly soluble photographically useful compounds (hereinafter referred to as oil-soluble photographically useful compounds) in such coatings. It may further be required that such compounds which are insoluble in the hydrophilic colloid vehicle be uniformly dispersed in the form of extremely fine particles. Such oil-soluble photographically useful compounds include oil-soluble couplers, UV absorbing agents, oxidized developer scavengers, light stabilizers, fade preventing agents, antioxidants, dye precursors for color diffusion transfer, dye developers, etc.

#Various methods are known for emulsifying and dispersing such oil-soluble photographically useful compounds including methods disclosed in U.S. Pat. Nos. 2,739,888, 3,352,681, etc. for dispersing UV absorbing agents; the methods disclosed in U.S. Pat. Nos. 2,360,290, 2,728,659, 3,700,453, etc. for dispersing diffusion-resistant alkylhydroquinones used for preventing color fogging, color stain and color mixing.

#The following examples demonstrate the use of water soluble maleic anhydride based copolymers in accordance with the invention, as well as comparison examples employing monomeric surfactants, sulfonated polymeric or non-maleic anhydride based carboxylic group containing polymeric surfactants. The weight-average molecular weights reported for the polymeric surfactants were determined by size exclusion chromatography with a low-angle light-scattering attachment, using DMF or THF as the solvent for the anhydride parent copolymers. The structures of photographically useful compound C-1, M-1, Y-1 and A-1 dispersed in the examples are as follows:

#C-1 M-1 Y-1 A-1

#The dispersions of the present invention were all prepared by neutralizing the parent maleic anhydride copolymers with sodium hydroxide to form a base hydrolyzed water-soluble polymeric surfactant. The water-soluble polymeric surfactant was added to the aqueous gelatin phase to provide emulsification for the oil soluble phase containing the photographically useful compound.