Radiation imagery chemistry: process – composition – or product th – Regenerating image processing composition
Patent
1992-04-07
1993-11-09
Van Le, Hoa
Radiation imagery chemistry: process, composition, or product th
Regenerating image processing composition
430361, 430399, 430414, 430477, G03C 731
Patent
active
052601846
DESCRIPTION:
BRIEF SUMMARY
This invention relates to a method of forming a photographic colour image and in particular, to a method of forming such an image by a redox amplification process.
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 to form a dye image. The redox amplifying solution contains a reducing agent, for example a colour developing agent, and an oxidising agent which is more powerful than silver halide and 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 (usually contained in the 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, cobalt (III) complexes including cobalt hexammine complexes, and periodates. Mixtures of such compounds can also be used.
Since the amplifying solution contains both an oxidising agent and a reducing agent it is inherently unstable. The best reproducibility for such a process is obtained by using a "one shot" system, where the oxidant is added to the developer and the solution mixed and used immediately (or after a short built in delay) and then discarded. This leads to the maximum solution usage possible with maximum effluent, and a processor has to be designed which uses small volumes of solution (a major difficulty) in order to minimize the effluent. As a result chemical costs are a maximum and the whole system is unattractive especially for a minilab environment where minimum effluent is required. It is believed that it is this that has inhibited commercial use of this process.
The present invention provides a method by which amplification may be achieved while overcoming the disadvantages of unstable processing solutions.
According to the present invention there is provided a method of forming a dye image in a photographic silver halide element containing a dye-providing compound and having in a layer thereof an imagewise distribution of catalytic silver which comprises the step of treating the material with a redox amplifying solution comprising a reducing agent and a redox amplification oxidant characterised in that the redox amplification oxidant is removed from the solution after use and the so-treated solution is re-used after the addition of fresh redox amplification oxidant.
FIG. 1 is a plot of the sensitometries of each of strips (1), (2), and (3), which are described in detail in Example 1, below.
FIG. 2 is a plot of the sensitometries of strips (4) and (5), also described in detail in Example 1, below.
FIG. 3 is a plot comparing the sensitometries of strips (2), (3), and (5), which are described in detail in Example 1, below.
FIG. 4 is a plot of the sensitometries of strips (6), (7), and (8), which are described in detail in Example b 2, below.
FIG. 5 is a plot of the sensitometries of strips (9) and (10), which are described in detail in Example 2, below.
FIG. 6 is a plot comparing the sensitometries of strips (6), (8), and (8), which are described in detail in Example 2, below.
FIG. 7 is a schematic of a redox amplification system in accordance with the invention. The system is described in detail in several later paragraphs.
FIG. 8 is a schematic of an electrolytic cell for removal of hydrogen peroxide from the developer-amplifier solution, as described below in Example 3.
FIG. 9 is a plot of hydrogen peroxide concentration against time for several metal and metal oxide catalysts examined for peroxide removal, as described below in Example 5.
FIG. 10 is a plot of sulphate, sulphite, and CD3 versus ion exchange column bed
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patent: 4040834 (1977-08-01), Iwano et al.
patent: 4529687 (1985-07-01), Hirai et al.
patent: 4859575 (1989-08-01), Kurematsu et al.
Marsden Peter D.
Twist Peter J.
Eastman Kodak Company
Le Hoa Van
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