Radiation imagery chemistry: process – composition – or product th – Regenerating image processing composition – Developer
Patent
1993-03-11
1994-06-28
Bowers, Jr., Charles L.
Radiation imagery chemistry: process, composition, or product th
Regenerating image processing composition
Developer
430367, 430373, 430414, 430421, 430442, 430936, 430943, G03C 518, G03C 526, G03C 522, G03C 700
Patent
active
053246241
DESCRIPTION:
BRIEF SUMMARY
This invention relates to a method of forming a photographic colour image and specifically to such a method employing image amplification techniques.
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 reducing agent, for example 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. The photographic material used in such a process may be a conventional coupler-containing silver halide material or an image transfer material containing redox dye releasers. Oxidised colour developer reacts with a colour coupler (usually contained in the photographic material photographic material) to form image dye. The amount of dye formed depends on the time of treatment or the availability of colour coupler rather than 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, e.g. addition compounds of hydrogen peroxide; cobalt (III) complexes including cobalt hexaammine complexes; and periodates. Mixtures of such compounds can also be used. A particular application of this technology is in the processing of silver chloride colour paper, especially such paper with low silver levels.
In order to avoid having to use a solution which contains both colour developing agent and an oxidant (which solution is inherently unstable), it is well known that, in addition to treating the photographic material with a single developer/amplifier it is possible first to develop the silver image and later, in a separate bath, to treat with an amplifying bath to form the dye image using the previously formed silver image as a catalyst. The amount of dye in such a system is limited by the amount of colour developing agent carried over into the second bath from the first. In order to provide sufficient colour developer it would be necessary to have a level of colour developing agent in the developer bath which would be too high for continuous running.
One way of operating such a known amplification process has been proposed in Japanese Kokai 61/088259 in which, before the developer/amplification step the photogaphic material is treated in a "pre-processing liquid" which contains colour developing agent but not oxidant. In the commercial world, however, thought needs to be given to keeping the processing running in stable condition over long periods of time.
The present invention provides a process which can be operated under commercial conditions of use in, say, a minilab showing considerable advantages in a number of areas.
According to the present invention there is provided a method of forming a photographic colour image comprising processing an imagewise exposed photographic silver halide colour material in a first processing bath containing a colour developing agent (developer), a second processing bath containing an amplifying oxidant and an optional colour developer developing agent (developer/amplifier), and optionally further processing baths, said baths being replenished characterised in that the overflow from the developer bath is fed to the developer/amplifier bath.
A number of advantages accrue from the present invention: developer/amplifier could be because about 20% of the image has already been formed. This also means that the developer/amplifier solution is more stable thus leading to less time-dependant replenishment when the processing system is idle. developing agent added to the amplifier bath composition) as compared to combined developer/amplifier systems, is avoided. are noticeable in small
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Bowers Jr. Charles L.
Eastman Kodak Company
Pasterczyk J.
Roberts Sarah Meeks
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