The processing of silver halide color film generally involves the steps of color evolution, bleaching, fixing, stabilizing and drying. The stabilizing bath is used as the final step in the processing of color films in order to reduce stain and/or to enhance dye stability. The stability of the dye image is believed to be affected by the presence of unreacted coupler in the emulsion layers, because the coupler and the dye can react slowly with one another to degrade a color image. Dye stability is also believed to be influenced by temperature, humidity, air quality, and exposure to light. In particular the image from magenta dye tends to fade much more rapidly than either the cyan or the yellow dye image. The addition of a compound that releases a methylene group to a stabilizing formulation can prevent the redox degradation of the magenta coupler that would otherwise cause magenta dye fade. Stabilizing solutions are aqueous formulations that contain a compound that produces a methylene group as the key component for dye stabilization.
Typical stabilizing solutions often contain an aldehyde, in particular formaldehyde, as the methylene-releasing agent. Formaldehyde possesses the added benefit of high volatility, so that any residual formaldehyde on the base side of the film is readily removed in a drying step. However in recent years concerns over the hazardous effects of formaldehyde have stimulated the development of stabilizing solutions that do not contain hazardous components, and alternative stabilizing compositions have been formulated.
Hexamethylenetetramine (HMTA) is an acceptable substitute for some or all of the formaldehyde in the stabilizing bath. HMTA is a water-soluble, nonvolatile crystalline compound with superior methylene-releasing properties. HMTA does not release significant levels of formaldehyde into solution or as vapor at the pH of the stabilizer solution (.about.pH 7 to 9). However, color negative films processed in machines that provide minimal or no squeegeeing of the film after stabilization in a HMTA-containing stabilizing bath will exhibit an objectionable residue on the base side of the film upon drying. This residue contains significant amounts of HMTA.
A laid open Japanese patent application from Konica Corporation (63/244,036) has described the use of a stabilizing solution consisting of a sulfite-ion releasing compound, and at least one of the following surfactants: anionic surfactant of the alkyl polyalklyeneoxides or alkyl arylpolyalkyleneoxides containing sulfate or phosphate groups, nonionic hydrocarbon polyalklyeneoxide surfactants, or a water-soluble organic siloxane type compound. The application suggests that such a formulation can be useful in preventing the adherence of crystals which form on the surface of the stabilizing bath.
A second laid open Japanese application from Konica (40/25,835) has disclosed the use of an HMTA-containing stabilizing solution containing at least one of the following surfactants: anionic polyalkyleneoxide sulfates or phosphates, nonionic polyalkyleneoxide alcohols or water soluble organic siloxane compounds.
It is the object of the present invention to provide a stabilizer solution containing HMTA that significantly reduces or completely eliminates observable residue on the base side of the color negative film, and which can be dried without forming drying marks or spots.
USPTO Backgrounds
USPTO Backgrounds