Radiation imagery chemistry: process – composition – or product th – Nonradiation sensitive image processing compositions or... – Developer
Reexamination Certificate
2003-02-26
2004-02-03
Le, Hoa Van (Department: 1752)
Radiation imagery chemistry: process, composition, or product th
Nonradiation sensitive image processing compositions or...
Developer
Reexamination Certificate
active
06686135
ABSTRACT:
FIELD OF THE INVENTION
This invention relates in general to photography and in particular to improved black-and-white developing compositions that can be provided in a single-part format. More particularly, it relates to improved and stabilized ascorbic acid black-and-white developing compositions and to methods for their use in processing photographic silver halide materials.
BACKGROUND OF THE INVENTION
Photographic black-and-white developing compositions containing a silver halide black-and-white developing agent are well known in the photographic art for reducing silver halide grains containing a latent image to yield a developed photographic image. Many useful developing agents are known in the art Hydroquinone and similar dihydroxybenzene compounds and ascorbic acid (and derivatives) are the most common. Such compositions generally contain other components such as sulfites, buffers, antifoggants, halides and hardeners.
Dihydroxybenzenes (such as hydroquinone) are the most common black-and-white developing agents and are quite active to provide development in various black-and-white photographic elements with or without booster and nucleating compounds. However, they are disadvantageous from several technical and environmental considerations. For example, hydroquinone compositions are not completely stable in air, being prone to aerial oxidation. The by-products from instability are often insoluble, black and tarry materials that contaminate the processing solutions and equipment.
The oxidation of hydroquinones also leads to higher pH that in turn leads to increased developer activity. Images can be produced faster so the processing time must be reduced. The net effect is less control of the process, and less desirable sensitometric properties in the processed materials.
In addition, bydroquinones have become an increasing concern from the point of view of potential toxicity and environmental pollution.
Another class of black-and-white developing agents are known in many publications as ascorbic acid and its various derivatives, for example as described in U.S. Pat. No. 5,236,816 (Purol et al.). While these types of developing agents are considerably more suitable to the environment, a major concern with ascorbic acid type developing agents is their stability to aerial oxidation.
U.S. Pat. No. 5,702,875 (Opitz et al.) describes weakly alkaline (pH 7 to 9) ascorbic acid developing compositions for processing black-and-white photographic materials. The developing composition is highly successful in the industry in two-part dry or liquid form. The two-part dry form is particularly preferred but there are opportunities to improve its stability and powdered consistency.
There is a need however for more stable ascorbic acid developing compositions for processing photographic silver halide materials that require a black-and-white developing step. It would be highly desirable to have such developing compositions in a single-part so mixing of multiple solutions or powders is avoided.
SUMMARY OF THE INVENTION
The invention provides an aqueous black-and-white photographic developing composition that is essentially free of dihydroxybenzene compounds and comprises:
a) an ascorbic acid developing agent, and
b) a water-miscible hydroxy-containing organic solvent having a molecular weight of from about 50 to about 200, the weight ratio of the organic solvent to water being from about 0.1:1 to about 8:1.
In a preferred embodiment, the present invention provides a single-part, aqueous, black-and-white photographic developing composition having a pH of from about 8 to about 11 and that is essentially free of dihydroxybenzene compounds and comprises:
a) from about 0.1 to about 0.5 mol/l of an ascorbic acid developing agent,
b) a water-miscible hydroxy-containing organic solvent having a molecular weight of from about 50 to about 200, the weight ratio of the organic solvent to water being from about 0.1:1 to about 1:1,
c) from about 0.001 to about 0.2 mol/l of sulfite ions,
d) from about 0.0005 to about 0.01 mol/l of a 3-pyrazolidone co-developing agent, and
e) either or both of an organic antifoggant and metal ion sequestering agent.
In addition, the present invention provides a two-part aqueous black-and-white developing composition kit comprising:
a) an aqueous first solution having a pH of from about 3 to about 6 that is essentially free of dihydroxybenzene compounds and comprises:
at least 0.05 mol/l of an ascorbic acid developing agent,
a water-miscible hydroxy-containing organic solvent having a molecular weight of from about 50 to about 200, the weight ratio of the organic solvent to water being from about 0.05:1 to about 8:1, and
at least 0.0005 mol/l of a 3-pyrazolidone co-developing agent, and
b) a second aqueous solution having a pH of from about 8 to about 12 and comprising a borate buffer and at least 0.05 mol/l of sulfite ions.
Further, the present invention provides a method of providing an image comprising contacting an imagewise exposed silver halide photographic material with the black-and-white photographic developing composition described above for at least 10 seconds.
In addition, a method of this invention provides an image comprising contacting an imagewise exposed silver halide photographic material with a black-and-white photographic developing composition formed by mixing the first and second solutions of the black-and-white developing composition kit described above for at least 10 seconds.
The present invention provides a stabilized black-and-white developing composition (single-part of two-part) by the use of a specific water-miscible hydroxy-containing organic solvents in the aqueous composition containing the ascorbic acid. This composition is substantially free of dihydroxybenzene compounds such as hydroquinone and its derivatives.
The improved stability (that is, reduced aerial oxidation) would generally reduce composition color change, loss in developing agent concentrations, and the formation of precipitates. Thus, shelf-life stability of the compositions is improved. Additionally there is improved pH stability of these compositions and we have noted less evaporation in compositions containing the water-miscible hydroxy-containing organic solvents.
DETAILED DESCRIPTION OF THE INVENTION
The present invention is useful for black-and-white development in any photographic silver halide material requiring at least one black-and-white development step. Such types of silver halide materials include, but are not limited to, particularly, radiographic films, aerial films, black-and-white motion picture films, duplicating and copy films, graphic arts films, positive- and negative-working microfilms, and amateur and professional continuous tone black-and-white films. The general constructions of such materials are well known in the art but specific features that render them particularly adaptable to the present invention are described below in more detail.
In addition, the black-and-white developing composition of this invention can be used in the “first” (black-and-white) development step(s) to obtain color images in color reversal photographic silver halide materials (details described below).
The black-and-white photographic developing compositions of this invention contain one or more ascorbic acid developing agents as a first essential component. An “ascorbic acid” developing agent means ascorbic acid and derivatives thereof. Ascorbic acid developing agents are described in a considerable number of publications regarding photographic processing. Useful ascorbic acid developing agents include ascorbic acid and the analogues, isomers and derivatives thereof Such compounds include, but are not limited to, D-, L-, or D,L-ascorbic acid, sugar-type derivatives thereof (such as sorboascorbic acid, &ggr;-lactoascorbic acid, 6-desoxy-L-ascorbic acid, L-rhamnoascorbic acid, imino-6-desoxy-L-ascorbic acid, glucoascorbic acid, fucoascorbic acid, glucoheptoascorbic acid, maltoascorbic acid, L-arabosascorbic acid), sodium ascorbate, potassium ascorbate, isoascorbic acid (or L-
Flavin Susan M.
Schwartz Paul A.
Le Hoa Van
Tucker J. Lanny
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