Radiation imagery chemistry: process – composition – or product th – Nonradiation sensitive image processing compositions or... – Developer
Reexamination Certificate
2003-07-11
2004-05-25
Le, Hoa Van (Department: 1752)
Radiation imagery chemistry: process, composition, or product th
Nonradiation sensitive image processing compositions or...
Developer
Reexamination Certificate
active
06740479
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a solution for sludge formation and “pi-line” artefact, while processing silver halide photographic materials.
BACKGROUND OF THE INVENTION
From an ecological point of view, there is a continuous pressure on waste reduction in photographic processing.
Combined with customer demands for a more convenient processing, this results in ever decreasing replenishing rates for both developer and fixer. Sludge formation is one of the major problems when attempting to further reduce the replenishing rates and to avoid waste. Otherwise for industrial radiography wherein in a normal processing cycle in an automatic processing machine use is made of film transport over racks, wherein each of said racks is provided with a lot of rollers immersed in the different processing baths, pollution by e.g. dust being carried into the processor by the film to be processed and generation of very small metallic silver particles in the developer, due to the development process, together with the evitable manipulations like arrest in development, start of the circulation of processing and regeneration liquids make the generated solid particles become deposited onto the rollers of the racks. So when a film is introduced into the processor as a first film of a whole series of films, its first contact with the first stained roller releases the deposit from the said roller or disturbs the deposited layer and as a consequence thereof, after one rotation of the said roller the unevenly distributed dirt or stain comes into contact again with the transported film surface so that it may be deposited onto said surface. The artefact described hereinbefore, recurrently repeated, not only at the first roller, but also at the further rollers that are mounted onto the racks is called “pi-line” as it is recurrently depicted at a distance corresponding with the circumference of the rollers.
A lot of compounds suitable for use as sludge preventing additives are known for developer compositions as has extensively been illustrated in the patent literature, e.g. in GB-A 2 029 037, U.S. Pat. Nos. 3,628,955; 4,169,733; 4,310,622; 4,371,610; 4,391,900; 4,546,070; 5,240,823; 5,356,761; 5,385,811; 5,518,868 ; 5,641,620; 5,707,793 and 5,840,472 as well as in EP-A's 0 136 582, 0 223 883, 0 785 467, 0 789 272, 0 851 282, 1 061 413 and 1 061 414. None of the proposed solutions can however be considered as an ultimate solution in order to avoid sludge formation in all applied conditions and even U.S. Pat. No. 5,518,868 although moreover offering a solution for the “pi-line” artefact from the side of the silver halide photographic material as well as from the side of processing solutions leaves still room for further improvements.
Same can be concluded from GB-A 1,225,406 wherein sulphonated tannin polymers act as generally known dispersing agents, suggesting to have a stabilizing effect on colloidal silver present in the developer while processing, not acting therein as a silver complexing compound due to the absence of a silver adsorbing group in its polymeric structure.
Hence, there remains a continuous need for additives for processing solutions, thereby preventing formation of sludge and “pi-line”. Almost all of the additives known from the patent literature have a low molecular weight as a common property. A lot of these compounds are the result of a combination of a strong silver ion complexing group as e.g. a heteroaromatic thiol and a solubilizing group such as a sulphonate or carboxylate. These compounds are known to prevent, or at least inhibit, the reduction of silver ions in solution, to prevent the deposition of silver nanoclusters in the developer and to inactivate the catalytic activity of those potentially formed silver nanoclusters for further reduction of dissolved silver ions.
Disadvantageous however is their ability to dissolve quite a lot of silver ions from the emulsion during processing, which results in a significant increase in silver ion concentration in the developer. However above a critical concentration of silver ions in the developer those compounds, known from the state-of-the-art as “sludge preventing additives”, loose their activity. In order to solve this well-known problem, components known as “dissolution regulators (inhibitors)” have been added to the developer as has clearly been illustrated in JP-A's 59-079244, 59-079250, 59-079251, 60-080839, 04-277739 and 04-333046, in EP-A 0 272 217 and in U.S. Pat. Nos. 5,300,410; 5,364,746; 5,457,011; 5,821,040; 6,238,853 and 6,238,854. Typical examples of those dissolution inhibitors are the small heterocyclic thiols without solubilizing groups. They are very effective in preventing or inhibiting dissolution of silver ions in a developer, but they are negativating the desired sensitometry as their influence on speed and developability of the processed silver halide materials is questionable. As depending on the conditions of the developer during processing both speed and developability of the developed materials is decreased to an unexpectable and almost inadmissable extent, it is extremely difficult to balance the ratio of both the sludge preventing compound and the dissolution inhibitor.
SUMMARY OF THE INVENTION
As becomes clear from the problems posed hereinbefore, it remains a stringent object to provide chemical compounds as additives avoiding formation of sludge and “pi-line” in developer compositions to a better extent than known until now.
The above-mentioned advantageous effects have been realized by providing an aqueous silver halide photographic processing solution having the specific features set out in claim
1
.
Specific features for preferred embodiments of the invention are set forth in the dependent claims, while further advantages and embodiments of the present invention will become apparent from the following description.
DETAILED DESCRIPTION OF THE INVENTION
It has now unexpectedly been found that selected polymeric compounds are very effective in preventing sludge, without negatively influencing (increasing) the dissolution rate of the silver halide and/or (decreasing) developability or speed of photographic materials, when making use therefrom in their processing cycle.
The selected polymeric compounds preventing sludge formation, particularly suitable for use in processing solutions according to the present invention therefore comprise at least one monomer unit having a silver ion completing moiety and at least one monomer unit having a solubilizing group. The group complexing silver ions and the solubilizing group are, in a particular embodiment, comprised in the same monomer unit. In a preferred embodiment according to the present invention the processing solution comprises as an additive a polymeric compound having a thiol or a salt thereof as a group complexing silver ions, a group capable of generating a thiol by hydrolysis or a disulfide. By providing such polymeric compounds having a specific silver affinity reduction of silver ions becomes suppressed or inhibited, and, if colloidal silver would be generated, to stabilize the said silver in dispersed form, further thereby passivating the silver nuclei in order to avoid growth thereof and deposit of mud.
In a further preferred embodiment, the solubilizing group is selected from the group consisting of a carboxylic acid or salt thereof, a sulfonic acid or salt thereof, a phosphonic acid or salt thereof, a phosphate and a sulfate. Moreover it has been shown that non-ionic groups like in (meth)acrylamides and hydrofunctional polymers are very useful additives.
Polymeric compounds suitable for use as “anti-sludging” additives in the processing solution according to the present invention can be prepared according to any known polymerisation technique, such as radical polymerisation of ethylenically unsatured monomers, polycondensates for the preparations of e.g. polyesters, polyurethanes and polycarbonates and polymers obtained by anionic or cationic ringopening polymerisations.
Also modifications (polymer analogue re
Loccufier Johan
Louwet Frank
Roefs Andre
Agfa-Gevaert
Guy Joseph T.
Le Hoa Van
Nexsen Pruet , LLC
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