Radiation imagery chemistry: process – composition – or product th – Radiation sensitive product – Identified radiation sensitive composition with color...
Reexamination Certificate
2001-09-05
2002-10-29
Letscher, Geraldine (Department: 1752)
Radiation imagery chemistry: process, composition, or product th
Radiation sensitive product
Identified radiation sensitive composition with color...
C430S546000, C430S631000, C430S634000, C430S931000, C430S935000, C430S551000, C430S527000, C430S531000, C430S543000, C430S529000, C430S536000, C430S449000
Reexamination Certificate
active
06472136
ABSTRACT:
FIELD OF THE INVENTION
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.
BACKGROUND OF THE INVENTION
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.
Oil soluble compounds are usually dissolved in substantially water-insoluble, high boiling organic solvents (for example, high boiling point organic solvents) and then dispersed into a hydrophilic colloid aqueous solution with the aid of a surface active agent as an emulsifier. Usually, anionic surfactants are used to disperse oil-soluble photographically useful compounds. For example, the method set forth in U.S. Pat. No. 2,332,027 employs Gardinol WA (a sulfonated coconut fatty alcohol, Du Pont de Nemours & Co.) and triisopropylnaphthalenesulfonates. U.S. Pat. No. 3,676,141 describes a method relying upon a combination of an anionic surfactant containing a sulfonyl group and a nonionic surfactant containing an anhydrohexyl ester unit. U.S. Pat. Nos. 4,198,478, 4,291,113, and 4,569,905 describe the use of ionic polymeric surfactants.
In designing and fabricating a color photographic product, the light-sensitive coatings have finite thicknesses and the presence of incorporated compounds in the form of coarse particles in the coatings can cause light scattering and deteriorate the transparency of the finished product. Furthermore, the image sharpness as well as the graininess of the photograph can be remarkably deteriorated. In contrast, when a coupler is dispersed in fine particles, the surface area per unit of weight of the coupler increases which in turn increases the rate and the efficiency of dye development, thus bringing about an improvement in the covering power of the resulting color image. Accordingly, it is important that crystallization of components in the dispersed oil phase and growth of coarse particles during storage of an emulsified product be prevented. While the use of some polymeric surfactants such as sulfonated polymeric surfactants as described in U.S. Pat. No. 4,291,113 has been found to prevent crystallization and growth of some photographically useful compound dispersed particles, the results have been found to be dependent upon the molecular weight of the sulfonated polymeric surfactants for many photographically useful compounds. Where high molecular weights are required for effective performance with respect to preventing crystallization and particle growth, other dispersion features, such as initial dispersion particle size, may be negatively impacted by the higher viscosities associated with use of higher molecular weight surfactants.
U.S. Pat. No. 4,201,589 discloses the use of polymeric oil soluble dispersants to stabilize dispersion droplets of photographically useful substances. These dispersants are incorporated into the organic phase and often require the use of volatile organic solvents which is undesirable from an environmental standpoint.
It would be desirable to provide a method for dispersing oil-soluble photographically useful compounds in water or a hydrophilic colloid composition to obtain excellent stability such that crystallization and particle growth of the dispersed compounds is minimized, wherein polymeric compounds which provide good protection against crystallization and particle growth are used which are not strongly dependent upon molecular weight for providing such feature for a variety of photographically useful compounds. It would further be desirable to provide such a method which employs a water-soluble polymeric surfactant which has excellent emulsification and stabilizing properties for dispersions of photographically useful compounds.
Maleic anhydride copolymers are commercially well known and have been used extensively as dispersing agents and emulsifiers for stabilizing pigments and solid particle suspensions, hydraulic drill fluid additives, floor wax, and scale inhibitors for water, but have not been taught for use as emulsifiers for use in preparing dispersions of oil-soluble photographically useful compounds. Representative patent disclosures relating to maleic anhydride copolymers include U.S. Pat. Nos. 3,488,311, 4,358,573, 4,522,992, 4,859,752, 4,871,823, 6,020,061.
SUMMARY OF THE INVENTION
In accordance with one embodiment of the invention, a method for forming a dispersion of an oil-soluble photographically useful compound in water or a hydrophilic colloid composition is disclosed, comprising dispersing the compound in the presence of a base hydrolyzed maleic anhydride derived water soluble anionic group containing polymeric surfactant, wherein the polymeric surfactant comprises a copolymer obtained from the copolymerization of a maleic anhydride monomer and a copolymerizable ethylenically unsaturated hydrophobic monomer and the anionic groups of the polymeric surfactant comprise primarily carboxy groups that have been obtained upon base hydrolysis of the anhydride groups of the copolymer.
The use of base hydrolyzed maleic anhydride derived copolymers in place of conventional small-molecule surfactants as a dispersing agent to stabilize photographically active water-insoluble dye couplers or other organic oil-soluble photographically useful compounds enables a dramatic reduction of crystallization of such organic molecules on long-term keeping. In comparison to primarily sulfonic acid group containing water soluble polymeric surfactants, the stabilizing effect of the primarily carboxy group containing hydrolyzed maleic anhydride based polymeric surfactants generally exhibit less molecular weight dependence. The use of water soluble maleic anhydride derived dispersants eliminates any need for use of volatile organic solvents to incorporate the dispersant, which is advantageous from an environmental standpoint.
DETAILED DESCRIPTION OF THE INVENTION
Dispersions prepared in accordance with the invention are prepared by melting or dissolving one or more photographically useful compound in an organic solvent to form an organic phase which is then dispersed in an aqueous medium. Where a high boiling (e.g., boiling point greater than 150° C.), substantially water immiscible solvent is used (i.e., a permanent solvent), it remains in the resulting photographic dispersion. The use of permanent solvents to disperse water insoluble photographically useful compounds in an aqueous medium is well known. Such high-boiling organic solvents are described, for example, in U.S. Pat. Nos. 2,322,027, 2,533,514 and 2,835,579, Japanese Patent Publication No. 23233/71, U.S. Pat. No. 3,287,134, British Pat. No. 958,441, Japanese Patent Application (OPI) No. 1031/72, British Pat. No. 1,222,753, U.S. Pat. No. 3,936,303, Japanese Patent Application (OPI) Nos. 26037/76 and 82078/75, U.S. Pat. Nos. 2,353,262, 2,852,383, 3,554,755, 3,676,137, 3,676,142, 3,700,454, 3,748,141, 3,837,863, German Patent Application
Amos Delaina A.
Schroeder Kurt M.
Tan Julia S.
Anderson Andrew J.
Eastman Kodak Company
Letscher Geraldine
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