Radiation imagery chemistry: process – composition – or product th – Color imaging process – Using identified radiation sensitive composition in the...
Reexamination Certificate
1996-08-27
2002-06-25
Le, Hoa Van (Department: 1752)
Radiation imagery chemistry: process, composition, or product th
Color imaging process
Using identified radiation sensitive composition in the...
C430S490000, C430S492000
Reexamination Certificate
active
06410215
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to stabilizing color developer solutions, and to the processing of silver bromoiodide color negative films. In particular, it relates to stabilizing color developer solutions having a pH of less than 10, where such solutions are held at high temperatures for extended periods of time.
BACKGROUND OF THE INVENTION
Production of photographic color images from light sensitive materials basically consists of two processes. First, color negative images are generated by light exposure of camera speed light sensitive films, which are sometimes called “originating” elements because the images are originated therein by the film user (that is, “picture taker”). These negative images are then used to generate positive images in light sensitive materials having a reflective base using a “printer”. These latter materials are sometimes known as “display” elements and the resulting images may be known as “prints” or motion picture projection films.
The light sensitive materials are processed in several steps and processing solutions to provide the necessary images in automatic processing machines. Traditionally, this service has required one or two days for providing the customer with the desired prints. In recent years, customers have wanted faster service, and in some locations known as “mini-labs”, it is desired to provide the customer with the desired prints within an hour. This requires the photoprocessing methods to be even faster, and reducing the processing time to within a few minutes is the ultimate desire in the industry.
Reduction in processing time of the “display” elements or color photographic papers has been facilitated by a number of recent innovations, including the use of predominantly silver chloride emulsions in the display elements.
Color negative films generally comprise little or no silver chloride in their emulsions, and generally have silver bromide as the predominant silver halide. More typically, the emulsions are silver bromoiodide emulsions with silver iodide levels up to several mol percent. Such films require these types of emulsions because emulsions containing high silver chloride have not demonstrated sufficient light sensitivity to be used as camera speed materials although they have the advantage of being rapidly processed without major changes to the color developer solution.
However, to shorten the processing time, specifically the color development time, of films containing silver bromoiodide emulsions, more active color developer solutions are needed. Various attempts have been made to increase color developer activity by increasing the pH, color developing agent concentration or temperature. However, when these changes are made, the stability of the solution often diminishes. For example, when the development temperature is increased from the conventional 37.8° C., and the color developer solution is held (or used) in the processing tanks for extended periods of times, silver bromoiodide elements processed with such solutions often exhibit unacceptably high density in the unexposed areas of the elements, that is unacceptably high Dmin.
Various methods have been proposed for stabilizing color developer solutions during use, but these methods are primarily used in processing high silver chloride emulsions. For example, color developers in U.S. Pat. No. 4,876,174 are stabilized for processing high silver chloride by containing dialkylhydroxylamine antioxidants or preservatives. Other preservatives are also described in the art, such as hydrazines, hydroxamic acid and alpha-hydroxyketones, as described for example in U.S. Pat. Nos. 4,897,339 and 4,906,554. Another method for stabilization is to use an anionic surface active agent in combination with a substituted alkylhydroxylamine to process high silver chloride elements having a dry thickness of less than 15 &mgr;m, as described in U.S. Pat. No. 5,091,292. Still another method involves using a processor having a small surface ratio of the color developer so it has less contact with air.
All of the foregoing methods have been designed for processing high silver chloride photographic papers, and have not been shown to be effective in processing color negative silver bromoiodide films.
Attempts have also been made to stabilize color developing solutions prior to their use, by storing them in sealed containers having low permeability to oxygen, as described in U.S. Pat. No. 4,814,260. Components that produce gases in the solutions are removed or replaced by non-gas producing components. Other storage containers have been designed from multilayers of various polymeric materials to reduce oxygen transmittance. However, these attempts fail to provide stability when the color developer solutions are being held for long periods of time at high temperature in the processing machine, especially when development is carried out at high temperature.
Copending and commonly assigned U.S. Ser. No. 08/590,241 filed Jan. 23, 1996, by Cole describes a method for high temperature color development of silver bromoiodide films wherein the color developing solution includes a certain hydroxylamine antioxidant. These antioxidants provide remarkable color developing solution stability, but there is a need for additional means for stabilizing the solution against an increase in Dmin during high temperature processing.
Thus, there remains a need for a process for rapid color development of silver bromoiodide films using color developer solutions stabilized for high temperature keeping.
SUMMARY OF THE INVENTION
The problems described above have been overcome with a method of photoprocessing comprising:
contacting an imagewise exposed color negative photographic film element containing at least one silver bromoiodide emulsion, with a color developer solution having a pH greater than about 9 but less than 10, and comprising:
a color developing agent present at from about 0.01 to about 0.1 mol/l, and
an organic antioxidant present at from about 0.001 to about 0.5 mol/l, the antioxidant having the formula:
R—N(OH)—R′
wherein R and R′ are independently hydrogen, substituted or unsubstitued alkyl of 1 to 10 carbon atoms or substituted or unsubstituted aryl,
the contacting being carried out at from about 50 to about 65° C. for from about 20 to about 150 seconds.
This invention also provides a method of stabilizing a color developer solution comprising:
a color developing agent present at from about 0.01 to about 0.1 mol/l, and
an organic antioxidant present at from about 0.001 to about 0.5 mol/l, the antioxidant having the formula described above, the method comprising adjusting or maintaining the color developer solution pH at greater than about 9 but less than 10.
Moreover, this invention comprises a stabilized color developer solution having a pH greater than about 9 but less than 10, and comprising:
a color developing agent present at from about 0.01 to about 0.1 mol/l, and
an organic antioxidant as described above that is present at from about 0.001 to about 0.5 mol/l.
The methods and color developer solution of this invention allow for rapid color development of camera ready film elements containing a silver bromoiodide emulsion. The color developer solutions are remarkably stable even when kept and used at relatively high temperatures, that is, above 50° C. for extended periods of time, for example, up to 144 hours at a temperature of 60° C. The color developer solutions have a pH greater than about 9 and less than 10 to provide the desired solution stability at high temperatures. Thus, solution stabilization can be provided for high temperature processing by adjusting and/or maintaining solution pH within this narrow range.
It has been unexpectedly found that the combination of photographic elements having silver bromoiodide emulsions and color developer solutions having these features minimizes the unacceptable increase in Dmin when the color developer solutions are kept and/or used at high processing temperatures for extended periods of time. For example, the &Dgr;
Eastman Kodak Company
Le Hoa Van
Tucker J. Lanny
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