Radiation imagery chemistry: process – composition – or product th – Color imaging process – Using identified radiation sensitive composition in the...
Reexamination Certificate
2000-11-03
2002-12-03
Le, Hoa Van (Department: 1752)
Radiation imagery chemistry: process, composition, or product th
Color imaging process
Using identified radiation sensitive composition in the...
Reexamination Certificate
active
06489089
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to the processing of color silver halide photographic materials. It more specifically relates to a method of bleach/fixing color silver bromoiodide photographic materials.
BACKGROUND OF THE INVENTION
During processing of silver halide color photographic elements, the developed silver is oxidized to silver(I) by a bleaching agent, and the silver(I) is concurrently or subsequently dissolved by a fixing agent and removed from the element. If the silver is bleached and fixed concurrently, the process is referred to as a bleach/fixing process. Bleach/fixing of silver halide photographic elements containing silver chloride or silver bromochloride emulsions is well known and relatively rapid and complete silver oxidation in the presence of those kinds of emulsions can be accomplished. Bleaching agents that are commonly used in these bleach/fixers are complexes of high valent metal ions such as iron(III) with aminopolycarboxylic acid ligands, for example the ammonium salts of complexes of Fe(III) with ethylenediaminetetraacetic acid (EDTA), N-methyliminodiacetic acid (MIDA), diethylenetriaminepentaacetic acid (DTPA), and ethylenediaminedisuccinic acid (EDDS). Fixing agents that are commonly employed are ammonium or sodium thiosulfate salts, sometimes in combination with thiocyanate salts such as ammonium or sodium thiocyanate.
There continues to be interest in rapid photographic processing of photographic elements, including rapid bleaching or bleach/fixing. However, when silver halide color negative photographic elements containing predominantly silver bromide or silver iodobromide emulsions (such as color negative camera films) are bleached and fixed, bleaching and fixing can be slow and is often incomplete, particularly in a bleach/fixing process. In particular, iodide in the silver halide emulsions can retard bleaching and fixing. The residual silver can lead to variability in the photographic response and in the quality of the photographic image due to density variations from the residual silver. To help overcome this bleaching difficulty several alternative approaches have been tried. Silver halide emulsions with low iodide content (less than 2 mol %, preferably less than 1 mol %, more preferably less than 0.5 mol %) may be used, as described in EP 0 271 061 B1 (Ikenoue et al). Unfortunately such emulsions can lack the desired sensitivity to light that is necessary for a practical camera film element. Bleaching accelerators such as organic thiols or amines, silver salts of organic thiols, or compounds which release organic thiols, have been incorporated into the film elements, the bleaching solutions, or processing solutions used before the bleaching solution, as described in U.S. Pat. No. 3,893,858 (Wabnitz); U.S. Pat. No. 4,552,834 (Lau et al); U.S. Pat. Nos. 4,865,956; 4,923,784 (Harder et al); GB 1,138,842; Swiss Pat. 336,257; and EP 0 329 052 A2 (Kuse et al). However, these compounds often cause instability of the bleaching solution, or lose their effectiveness over time, and often bleaching is still incomplete despite the use of these accelerators. Coupler compounds that release bleach-accelerating compounds during image development (so-called bleach accelerator-releasing couplers, or BARCs) have been dispersed and incorporated into color negative film elements as described in U.S. Pat. No. 5,135,839 (Szajewski); U.S. Pat. No. 5,300,406 (Begley et al); U.S. Pat. No. 5,318,879 (Begley et al); U.S. Pat. No. 5,358,828 (Begley et al); U.S. Pat. No. 5,840,470 (Bohan et al); and EP 0 193 389 B2 (Hall et al)).
These compounds can improve bleaching by bleaching agents such as the ammonium, potassium, or sodium salts of Fe(III)EDTA, Fe(III)EDDS, Fe(III)(MIDA)2, Fe(III)(DTPA), or relatively dilute Fe(III)PDTA (a complex of Fe(III) with 1,3-propanediaminetetraacetic acid) that have relatively weak bleaching power, especially bleaching solutions of these bleaching agents that have been weakened during continued processing by the carrying-in of preceding color developer solution. Despite the use of these BARCs, which significantly improve bleaching rates, bleaching is still often too slow or incomplete for a rapid bleaching process. Stronger bleaching agents can be used, such as FeCl
3
, potassium ferricyanide, relatively concentrated Fe(III)PDTA, hydrogen peroxide, periodate, or various catalyzed persulfate bleaches. But these bleaching agents, while effective, often require additional processing solutions (e.g. stop baths, accelerator baths) that are inconvenient for rapid, efficient processing. Furthermore, these bleaching agents are not compatible with thiosulfate fixing solutions and it has not been possible to prepare stable bleach/fixing solutions using these bleaching agents with the commonly used thiosulfate fixing agent.
There remains a need for a rapid, complete, non-staining silver removal process for silver halide color negative elements that have silver iodobromide emulsions with average iodide content of more than 1 mol % and good light sensitivity. There also remains a need for rapid processes that result in less densitometry variability, and that provide the rapid attainment of a stable density image.
SUMMARY OF THE INVENTION
This invention provides a method of bleaching and fixing a developed silver halide color negative element comprising
mixing a bleaching solution containing an oxidizing agent with a fixing solution containing a silver ion solubilizing agent to form a bleach/fixing solution;
shortly after or simultaneously with said mixing, bleach/fixing the silver halide element by contacting it with the bleach/fixing solution; and
discarding the bleach/fixing solution after one use;
wherein the bleach/fixing step is performed at an elevated temperature; and
wherein the silver halide color negative element comprises a silver bromoiodide emulsion with an average iodide content of more than 1 mol % iodide.
This method allows the separate bleaching and fixing processing steps for silver bromoiodide color negative elements to be combined into one bleach/fixing step. With this invention strong oxidizing agents such as high concentrations of Fe(III)PDTA or Fe(III)(MIDA)
2
can be used in combination with silver ion solubilizing agents, (particularly thiosulfate), a combination which is not stable when stored in a single solution with bleach/fixing properties. This method makes it possible to remove silver from silver bromoiodide emulsions without the need for accelerators added to either the silver halide photographic element or to the bleach/fixing solution, although they may be added if desired. With this method high speed silver halide color negative elements can be bleached and fixed in 30 to 90 seconds in a single solution with complete removal of the incorporated silver components.
Additionally the process is efficient and cost effective. No seasoning of the process solution occurs from one silver halide color negative element to degrade the silver removal rate of subsequent elements. Additionally only the minimum amount of solution required to process the film element is used in the process. Since small volumes are used, the temperature of the process can be raised rapidly with a minimum amount of energy required and need only be maintained at the high temperature for the short time of the process. The waste solutions may be easily collected for treatment to remove the silver ion by conventional means such as electrolysis.
DETAILED DESCRIPTION OF THE INVENTION
In this invention a bleaching solution containing an oxidizing agent and a fixing solution containing a silver ion solubilizing agent are mixed to form a bleach/fixing solution. Shortly after or simultaneously with said mixing, the developed silver halide element is bleach/fixed by contacting it with the bleach/fixing solution. The bleaching solution and the fixing solution may be mixed by any means which will accomplish the goal of combining the two solutions and then making them available for contact with the silver halide element. It is anticipated that the
Brown Eric R.
Fyson John R.
Eastman Kodak Company
Le Hoa Van
Meeks Roberts Sarah
LandOfFree
Bleach/fix solution for single-use silver removal in color... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Bleach/fix solution for single-use silver removal in color..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Bleach/fix solution for single-use silver removal in color... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2973514