Radiation imagery chemistry: process – composition – or product th – Thermographic process – Heat applied after imaging
Reexamination Certificate
2000-12-21
2002-08-27
Le, Hoa Van (Department: 1752)
Radiation imagery chemistry: process, composition, or product th
Thermographic process
Heat applied after imaging
C430S351000
Reexamination Certificate
active
06440648
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to a silver halide film that, after imagewise exposure, is capable of being color developed either (1) in a wet-chemical multi-tank process at a temperature of 60° C. or less by immersion in a phenylenediamine-containing developer solution or its equivalent, followed by desilvering in one or more subsequent solutions, or alternatively, (2) by thermal treatment of the film. This invention further relates to a silver halide film containing a blocked inhibitor which is an amido compound, said amido compound improving contrast when the film is thermally processed.
BACKGROUND OF THE INVENTION
With the remarkable advances in the fields of solid-state imaging devices and various hard-copy printing technologies made in recent years, both electronic imaging systems and silver-halide photographic systems have become available to the consumer. At the present time, silver halide photographic systems tend to be superior with respect to high sensitivity and high image quality. One particular shortcoming of the silver-halide system, however, in comparison to electronic imaging systems is that the photographic element requires a so-called wet-development process that typically requires substantial volumes of processing solutions. Thus, the development of a “dry” process for a silver-halide color photographic system has been a goal of the photographic industry for many years.
A dry development process can be accomplished by the use of photothermographic elements such as described in Research Disclosure 17029 (Research Disclosure PT). Generally, in these kinds of systems, development occurs by reduction of silver ions in the photosensitive silver halide to metallic silver as in conventional non-thermal systems, but the developing agent is contained within the element, so that it is unnecessary to immerse the photographic element in an aqueous solution containing a developing agent. Research Disclosure PT discloses a type B photothermographic system, wherein the type B elements contain in reactive association a binder, a photosensitive silver halide (prepared in situ or ex situ) and an oxidation-reduction image forming combination comprising (1) a metallic salt or complex of an organic compound as an oxidizing agent, and (2) an organic reducing agent or developing agent. “Dry processing” can also be accomplished by the use of diffusion transfer elements, see, for example EP 0762 201 (Matsumoto). One problem with such “dry” systems has been to achieve a commercially viable system that produces a quality of image comparable, in the eyes of the average film consumer, to traditional silver-halide film.
A practical color photothermographic system for general use with respect to consumer cameras would have significant advantages. Such film would be amenable to development at kiosks using dry equipment. A consumer could bring an imagewise exposed photothermographic film to a kiosk located at any one of a number of diverse locations, optionally independent from a wet-development lab, where the film could be developed and printed without any manipulation by third-party technicians. A consumer might also be more prone to owning and operating film development equipment at home if it was a dry system. Thus, the development of a successful photothermographic system could open up new opportunities for greater convenience and speed of film processing for a wider cross-section of consumers.
At this time thermal processors are not as available as are conventional aqueous processors, such as Kodak C-41 processors, which are widely available as a mature industry standard. The unavailability of thermal processors and associated equipment can hinder the adoption of dry photothermographic films by the consumer. Photothermographic films that could also be processed by Kodak C-41 chemistry or the like would overcome this disadvantage. Photothermographic films with such backwards compatibility would permit the consumer to enjoy the benefits unique to thermal processing (kiosk processing, low environmental impact, etc.) when thermal processing is accessible, and would also allow the consumer to take advantage of the current ubiquity of C-41 processing when thermal processing may not be accessible. However, differences in the requirements of films which are thermally processed vs. films which are wet processed make it difficult to provide one film which may be processed in two different ways.
In order to be acceptable for commercial application, it is necessary that a photothermographic system be stable before exposure, while avoiding desensitizing of the silver halide during storage. If these factors are not present the system may have increased fog and/or decreased Dmax after development. At the same time, the system must have sufficiently fast kinetics (including unblocking of the developing agent) when the exposed film is being developed by thermal activation. For a backwards compatible film, the requirement might be that the components in the photothermographic film, designed exclusively for the dry photothermographic development (for example the blocked developing agent and anti-fogging agents) do not adversely affect or interfere with the sensitometry of the film when it is developed by traditional wet-processing.
In photothermographic film systems used to capture full color images, once the film has been developed the scanning of the scene luminance content is only possible over a limited density range, determined by the scanner design. If the film densities are too high, scanning is either not possible or becomes subject to signal to noise problems and scene information is lost. It is essential to design color photothermographic films to have sufficient latitude , that is, to be capable of recording all required scene luminance information in a density range that can be scanned. Therefore, such film designs must have a lower gamma and so reach a lower maximum density in each color record than is normal for conventional films.
It is well known that certain heterocyclic molecules with relatively acidic hydrogen atoms bonded to a ring nitrogen or an adjacent sulfur atom act as development restrainers or inhibitors in photographic film and paper systems. Development inhibitors are utilized to either slow or stop development of silver halide grains. They can be used to correct unwanted dye absorption, improve sharpness and reduce granularity of films. Various methods have been described for chemically blocking these inhibitors so that they are stable to storage in the film but can be released in a timely fashion upon development. Release of inhibitor typically is achieved under aqueous alkaline conditions by reaction with base or other nucleophile in the processing solution. In particular, blocked inhibitors have found use in image transfer systems. Research Disclosure article 13118, March 1975 and U.S. Pat. Nos. 4,255,510 and 4,256,881 describe materials that use alkali-hydrolyzable groups to block the inhibitors, specifically N-mono substituted and N, N-disubstituted amido groups. Other methods of non-imagewise release involve reaction of a suitably blocked inhibitor with base or other nucleophile in the processing solution, such as described in U.S. Pat. No. 5,354,650, are known but have not been found useful in photothermography.
In conventional photographic systems, such as color negative films, the addition of free inhibitors, even in small quantities, leads to loss of sensitivity. It is therefore useful to release inhibitors imagewise by chromogenic development using, for example, Development Inhibitor Releasing (DIR) couplers. DIR couplers are used to control film response to light by reducing photographic gamma in an imagewise fashion. However, in many cases DIR couplers are not effective gamma reducers in photothermographic systems. Therefore it is necessary that the photothermograhic system include other types of inhibitors which are effective gamma reducers.
What is needed is a backwards compatible film which has a low enough gamma to satisfy the wide latitude
Hoag Benjamin P.
Southby David T.
Yang Xiqiang
Le Hoa Van
Meeks Roberts Sarah
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