Radiation imagery chemistry: process – composition – or product th – Retrieving image made using radiation imagery
Reexamination Certificate
2000-11-09
2003-03-25
Chea, Thorl (Department: 1752)
Radiation imagery chemistry: process, composition, or product th
Retrieving image made using radiation imagery
C430S351000, C430S353000, C430S404000, C430S566000, C430S531000, C430S618000, C430S619000, C430S959000
Reexamination Certificate
active
06537712
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to color photothermographic elements containing blocked developing agents and to methods of developing such elements.
BACKGROUND OF THE INVENTION
In conventional color photography, films containing light-sensitive silver halide are employed in hand-held cameras. Upon exposure, the film carries a latent image that is only revealed after suitable processing. These elements have historically been processed by treating the camera-exposed film with at least a developing solution having a developing agent that acts to form an image in cooperation with components in the film. Developing agents commonly used are reducing agents, for example, p-aminophenols or p-phenylenediamines.
Typically, developing agents (also herein referred to as developers) present in developer solutions are brought into reactive association with exposed photographic film elements at the time of processing. Segregation of the developer and the film element has been necessary because the incorporation of developers directly into sensitized photographic elements can lead to desensitization of the silver halide emulsion and undesirable fog. Considerable effort, however, has been directed to producing effective blocked developing agents (also referred to herein as blocked developers) that might be introduced into silver halide emulsion elements without deleterious desensitization or fog effects. Accordingly, blocked developing agents have been sought that would unblock under preselected conditions of development after which such developing agents would be free to participate in image-forming (dye or silver metal forming) reactions.
U.S. Pat. No. 3,342,599 to Reeves discloses the use of Schiff-base developer precursors. Schleigh and Faul, in a
Research Disclosure
(129(1975) pp. 27-30), describes the quaternary blocking of color developers and the acetamido blocking of p-phenylenediamines. (All Research Disclosures referenced herein are published by Kenneth Mason Publications, Ltd., Dudley Annex, 12a North Street, Emsworth, Hampshire P010 7DQ, ENGLAND.) Subsequently, U.S. Pat. No. 4,157,915 to Hamaoka et al. and U.S. Pat. No. 4,060,418 to Waxman and Mourning describe the preparation and use of blocked p-phenylenediamines in an image-receiving sheet for color diffusion transfer.
All of these approaches have failed in practical product applications because of one or more of the following problems: desensitization of sensitized silver halide; unacceptably slow unblocking kinetics; instability of blocked developer yielding increased fog and/or decreased Dmax after storage, lack of simple methods for releasing the blocked developer, inadequate or poor image formation, and other problems. Especially in the area of photothermographic color films, other potential problems include poor discrimination and poor dye-forming activity. In addition to the aforementioned U.S. Pat. No. 4,157,915, blocked developing agents involving &bgr;-elimination reactions during unblocking have been disclosed in European Patent Application 393523 and kokais 57076453; 2131253; and 63123046, the latter specifically in the context of photothermographic elements.
Recent developments in blocking and switching chemistry have led to blocked developing agents, including p-phenylenediamines, that perform relatively well. In particular, compounds having “&bgr;-ketoester” type blocking groups (strictly, &bgr;-ketoacyl blocking groups) are described in U.S. Pat. No. 5,019,492. With the advent of the &bgr;-ketoester blocking chemistry, it has become possible to incorporate p-phenylenediamine developers in film systems in a form from which they only become active when required for development. The &bgr;-ketoacyl blocked developers are released from the film layers in which they are incorporated by an alkaline developing solution containing a dinucleophile, for example hydroxylamine.
There remains a need for blocked developers, useful in photothermographic elements, exhibiting good discrimination and low fog, which at the same time, exhibit good unblocking kinetics. Good discrimination and low fog are especially challenging when heating an element containing silver halide and blocked developers. It is an object to obtain a phototothermographic element or film incorporating blocked developing agents that provide good dye-forming activity and which, at the same time, yield good discrimination and little or no increased fog during development. There is especially a need for blocked developers which are useful in dry color photothermographic systems which do no require the application of processing solutions. These are usually developed at higher temperatures than systems in which some, albeit limited amounts of, aqueous solutions are employed during development, usually in the presence of a base.
With respect to developing agents for photothermogrpaphic color elements, there is a continuing need for photothermographic imaging elements that contain a developing agent in a form that is stable until development yet can be rapidly and easily developed once processing has been initiated by heating the element and/or by applying a processing solution, such as a solution of a base or acid or pure water, to the element. A completely dry or apparently dry process is most desirable. The existence of such a process would allow for very rapidly processed films that can be processed simply and efficiently in photoprocessing kiosks. Such kiosks, with increased numbers and accessibility, could ultimately allow for, relatively speaking, anytime and anywhere silver-halide film development.
SUMMARY OF THE INVENTION
This invention relates to a color photothermographic element comprising a blocked developer that decomposes (i.e., unblocks) on thermal activation to release a developing agent. By thermal activation is meant heating at a temperature of at least 60° C., preferably at least 80° C., more preferably at least 100° C., for 0.5 to 60 sec, preferably 1 to 60 sec, more preferably 2 to 30 sec. In dry processing embodiments, thermal activation preferably occurs at temperatures between about 80 to 180° C., preferably 100 to 160° C. In not completely dry development systems, thermal activation preferably occurs at temperatures between about 60 and 140° C. in the presence of added acid, base and/or water. In one preferred embodiment of the invention, the photothermographic element comprises an effective amount of a thermal solvent. In another preferred embodiment of the invention, the photothermographic element comprises a mixture of organic silver salts (inclusive of complexes) at least one of which is a silver donor.
The invention additionally relates to a method of image formation having the steps of: thermally developing an imagewise exposed photographic element having a blocked developer that decomposes on thermal activation to release a developing agent to form a developed image. In one embodiment of the invention, a positive image can be formed by scanning the developed image to form a first electronic image representation (or “electronic record”) from said developed image, digitizing said first electronic record to form a digital image, modifying said digital image to form a second electronic image representation, and storing, transmitting, printing or displaying said second electronic image representation.
The invention further relates to a one-time use camera having a light sensitive photographic element comprising a support and a blocked developer that decomposes to release a photographically useful group on thermal activation. The invention further relates to a method of image formation having the steps of imagewise exposing such a light sensitive photographic element in a one-time-use camera having a heater and thermally processing the exposed element in the camera.
In particular, the present invention is directed to photothermographic elements comprising blocked developers having a half-life (t
½
)≦20 min (as determined below). In has further been found that the specified half-life can be obtained by the use of a
Irving Lyn M.
Irving Mark E.
Levy David H.
Mooberry Jared B.
Owczarczyk Zbyslaw R.
Chea Thorl
Eastman Kodak Company
Konkol Chris P.
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