Radiation imagery chemistry: process – composition – or product th – Nonradiation sensitive image processing compositions or... – Bleach or intensification
Reexamination Certificate
1994-10-04
2001-10-16
Le, Hoa Van (Department: 1752)
Radiation imagery chemistry: process, composition, or product th
Nonradiation sensitive image processing compositions or...
Bleach or intensification
C430S373000, C430S414000, C430S943000
Reexamination Certificate
active
06303279
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to photographic developer/amplifier solutions useful in redox amplification processes.
BACKGROUND OF THE INVENTION
Redox amplification processes have been described, for example in British Specification Nos. 1,268,126, 1,399,481, 1,403,418 and 1,560,572. In such processes colour materials are developed to produce a silver image (which may contain only small amounts of silver) and then treated with a redox amplifying solution (or a combined developer-amplifier) to form a dye image.
The developer-amplifier solution contains a colour developing agent and an oxidising agent which will oxidise the colour developing agent in the presence of the silver image which acts as a catalyst.
Oxidised colour developer reacts with a colour coupler to form the image dye. The amount of dye formed depends on the time of treatment or the availability of colour coupler and is less dependent on the amount of silver in the image as is the case in conventional colour development processes.
Examples of suitable oxidising agents include peroxy compounds including hydrogen peroxide and compounds which provide hydrogen peroxide, eg addition compounds of hydrogen peroxide; cobalt (III) complexes including cobalt hexammine complexes; and periodates. Mixtures of such compounds can also be used.
A serious problem with developer/amplifier solutions is their stability because they contain both an oxidising agent (eg the peroxide) and a reducing agent (the colour developing agent) which react together spontaneously thus leading to loss of activity in a matter of an hour or two.
In comparison, conventional photographic colour developer solutions suffer loss of activity by aerial oxidation of the colour developing agent. A typical commercial colour developer solution, however, will be stable for a week or two. Both diethylhydroxylamine and hydroxylamine sulphate have been proposed as anti-oxidants for colour developer solutions.
Colour developer solutions for silver chloride colour papers do not contain hydroxylamine sulphate because it can act as a black and white developing agent and this severely inhibits dye yield. Instead, diethylhydroxylamine is used because it does not inhibit dye yield.
When using low silver colour papers closely related to currently used silver chloride colour papers to be processed in a redox developer/amplifier it has been found that diethylhydroxylamine works as an effective antioxidant at first but its oxidation products cause a severe loss of hydrogen peroxide after a few hours.
Adding hydroxylamine sulphate to a developer/amplifier, as with conventional colour developers, causes dye yield to be seriously inhibited. However, the inventor has found that, unlike the case with conventional colour developers, the inhibiting effect of hydroxylamine sulphate can be overcome by increasing the level of peroxide.
Russian specification A-1075227 describes a method for producing a monochrome image by a lengthy process which includes a redox amplification step as step 9 of a 12 step process. The amplifier solution contains both resorcin and hydroxylamine and is shown to be an improvement over using resorcin alone. The solutions contain no alkaline material and it is therefore assumed that their pH values are low. The combination of resorcin and hydroxylamine is said to be essential and thus there is no disclosure that hydroxylamine alone has any utility. The present solutions have a pH of 10.5-12 and contain no resorcin.
SUMMARY OF THE INVENTION
According the the present invention there is provided an aqueous redox amplifier composition comprising a colour developing agent, hydrogen peroxide or a compound which provides hydrogen peroxide and hydroxylamine or a salt thereof wherein the concentration ranges are:
hydrogen peroxide from 0.5 to 15 ml/l (as 30% w/w solution),
hydroxylamine or a salt thereof from 0.25 to 8 g/l (as hydroxylamine sulphate), and wherein the pH is in the range from 10.5 to 12.
The concentration range of the hydrogen peroxide is preferably from 0.5 to 7 ml/l and especially from 0.5 to 2 (as 30% w/w solution).
The concentration range of the hydroxylamine component is from 0.5 to 4 and especially from 0.5 to 2 g/l (as hydroxylamine sulphate).
The pH is buffered by a phosphate. The pH is preferably in the range 11 to 11.7 and especially from 11 to 11.4.
The ratio of hydrogen peroxide to hydroxylamine compound is from 1.5 to 2.5 (ml/l 30% w/w hydrogen peroxide solution:g/l hydroxylamine compound as hydroxylamine sulphate) and more preferably the ratio of hydrogen peroxide to hydroxylamine compound is from 1.75 to 2.0 (ml/l 30% w/w hydrogen peroxide solution:g/l hydroxylamine compound as hydroxylamine sulphate).
The composition is preferably free of any compound that forms a dye on reaction with oxidised colour developer.
ADVANTAGEOUS EFFECT OF THE INVENTION
The developer/amplifier solution is stabilised against loss of dye yield and as the solution ages peroxide is slowly lost. However, the effect of this loss is compensated for by the concomitant oxidation of hydroxylamine sulphate which, in turn, diminishes its inhibiting effect on peroxide. This effect was entirely unexpected as a similar effect is not observed in conventional colour developers. The stabilised developer/amplifier remains a pale straw colour without forming any deposits.
In addition hydroxylamine sulphate is more acceptable to operators who dislike the smell of diethylhydroxylamine.
DETAILED DESCRIPTION OF THE INVENTION
The hydroxylamine compound may be hydroxylamine chloride, phosphate or, preferably, sulphate. The phosphate buffer may be potassium hydrogen phosphate (K
2
HPO
4
) or other phosphates, carbonates, silicates and mixtures thereof.
The relative proportions of hydrogen peroxide (as ml/l of a 30% w/w solution) and hydroxylamine compound (as g/l hydroxylamine sulphate) need to be balanced to give the required result. It has been found that the hydrogen peroxide concentration needs to be about twice the hydroxylamine sulphate concentration.
The colour photographic material to be processed may be of any type but will preferably contain low amounts of silver halide. Preferred total silver halide coverages are in the range 6 to 300, preferably 10 to 200 mg/m
2
and particularly 10 to 100 mg/m
2
(as silver). The material may comprise the emulsions, sensitisers, couplers, supports, layers, additives, etc. described in Research Disclosure, December 1978, Item 17643, published by Kenneth Mason Publications Ltd, Dudley Annex, 12a North Street, Emsworth, Hants P010 7DQ, U.K.
In a preferred embodiment the photographic material to be processed comprises a resin-coated paper support and the emulsion layers comprise more than 80%, preferably more than 90% silver chloride and are more preferably composed of substantially pure silver chloride.
The photographic materials can be single colour materials or multicolour materials. Multicolour materials contain dye image-forming units sensitive to each of the three primary regions of the spectrum. Each unit can be comprised of a single emulsion layer or of multiple emulsion layers sensitive to a given region of the spectrum. The layers of the materials, including the layers of the image-forming units, can be arranged in various orders as known in the art.
A typical multicolour photographic material comprises a support bearing a yellow dye image-forming unit comprised of at least one blue-sensitive silver halide emulsion layer having associated therewith at least one yellow dye-forming coupler, and magenta and cyan dye image-forming units comprising at least one green- or red-sensitive silver halide emulsion layer having associated therewith at least one magenta or cyan dye-forming coupler respectively. The material can contain additional layers, such as filter layers.
The color developing compositions may be utilized in the various processing systems known in the art. They may be particularly useful with Low Volume Thin Tank processing systems. A Low Volume Thin Tank processor provides a small volume for holding processing
Eastman Kodak Company
Le Hoa Van
Tucker J. Lanny
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