Radiation imagery chemistry: process – composition – or product th – Radiation sensitive product – Two or more radiation-sensitive layers containing other than...
Reexamination Certificate
2001-11-21
2003-06-10
Chea, Thorl (Department: 1752)
Radiation imagery chemistry: process, composition, or product th
Radiation sensitive product
Two or more radiation-sensitive layers containing other than...
C430S502000, C430S512000, C430S517000, C430S543000, C430S559000, C430S566000, C430S570000, C430S607000, C430S613000, C430S620000, C430S944000, C430S964000
Reexamination Certificate
active
06576411
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to photothermographic capture films. In particular, this invention relates to the use of a dye as a passivating agent that absorbs onto the surface of organic silver salts to improve raw stock speed and, hence, the performance of photothermographic systems.
BACKGROUND OF THE INVENTION
Imaging elements that can be processed, after imagewise exposure, simply by heating the element are referred to as photothermographic elements. Preferably, photothermographic films do not require any processing solutions and instead contain within them all the chemistry required for development of a photographic image. These film chemistries are designed so that at room temperature they are inactive, but at elevated temperatures (greater than 120° C.) the film chemistries become functionally active.
A problem in designing such photothermographic films is that it has been found that certain properties may degrade over time, including speed. It is desirable that photothermographic elements be capable of maintaining its imaging properties, including speed, during storage periods. This is referred to as Raw Stock Keeping (“RSK”). Ideally, film should be storage stable, under normal conditions, preferably for at least 12 months, more preferably for at least 24 months. If a film speed loses are too much during storage, poor or unacceptable image formation can occur.
Raw stock keeping is especially a problem for color photothermographic films (color “PTG films”), compared to conventional films or even black & white PTG films. This is because at least three color records are required, and all the components needed for development and image formation must be incorporated into the imaging element, in intimate proximity, in potentially reactive association, prior to development. Thus, there are a greater number of potentially reactive components that can prematurely react during storage. Furthermore, color photothermographic film involves new and unfamiliar chemistries and systems, in which the performance of new and complex combinations of components is unpredictable and subject to undesirable interactions, incompatibilities, or side reactions. The imaging chemistry must be designed to provide fast, high quality latent image formation during image capture, but must not interact prematurely. Similarly, the film must be capable of fast development and high quality image formation during thermal processing, but the same components must not prematurely interact before the processing step.
There remains a need for a photothermographic film that does not exhibit any significant loss of speed during raw stock keeping.
PROBLEM SOLVED BY THE INVENTION
In photothermographic (PTG) film, silver-halide emulsions are spectrally sensitized to make them sensitive to various wavelengths of light in the visible spectrum. This spectral sensitization is accomplished by adsorbing sensitizing dye to the emulsions. However, it has been observed that the organic silver salts in the system also have a large propensity to adsorb sensitizing dye, such that when the organic silver salts are in contact with a dyed silver halide emulsion, they can remove dye from the silver halide emulsion, resulting in a loss of photographic speed. The ability of the organic silver salts to adsorb dye is related not only to the adsorption strength of the materials for sensitizing dye, but also to the high surface area for adsorption of the particles, related to their small grain size. There are several opportunities for the organic silver salts to contact the silver halide emulsions and transfer sensitizing dye within pre-coating melts, during coating (when dual melted), or in the film during raw stock keeping.
SUMMARY OF THE INVENTION
It has been found that speed loss on raw stock keeping in color photothermographic film can be prevented or minimized by the use of a dye as a passivating agent to make organic silver salts or ligands less detrimental or “friendlier” toward silver halide emulsions. In particular, the present invention involves passivating the organic silver salts with a dye adsorbate that blocks the surface of the organic silver salt or ligand, resulting in a significant reduction in sensitizing dye loss from the silver halide emulsion and concomitant reduction of speed loss in the ultimate coated layer, including both “fresh speed loss” (speed loss present prior to storage) and speed loss after storage (the latter characterized as “raw stock keeping”).
The invention is also directed to a method of making a photothermographic element to prevent speed loss and to improve raw stock keeping.
Definitions of terms, as used herein, include the following:
In the descriptions of the photothermographic materials of the present invention, “a” or “an” component refers to “at least one” of that component. For example, the silver salts described herein can be used individually or in mixtures.
Heating in a substantially water-free condition as used herein, means heating at a temperature of from about 50° to about 250° C. with little more than ambient water vapor present. The term “substantially water-free condition” means that the reaction system is approximately in equilibrium with water in the air, and water for inducing or promoting the reaction is not particularly or positively supplied from the exterior to the material. Such a condition is described in T. H. James,
The Theory of the Photographic Process
, Fourth Edition, Macmillan 1977, p 374.
“Color photothermographic material(s)” means a construction comprising at least three photothermographic emulsion layers a photothermographic set of layers of different “hue” and any supports, topcoat layers, blocking layers, antihalation layers, subbing or priming layers, and the like. The term “hue” includes non-visible “colors” capable of providing image formation analogous to visible colors. These materials also include multilayer constructions in which one or more imaging components are in different layers, but are in “reactive association” so that they readily come into contact with each other during imaging and/or development. For example, one layer can include the non-photosensitive source of reducible silver ions and another layer can include the reducing composition, but the two reactive components are in reactive association with each other.
“Emulsion layer,” “imaging layer,” or “photothermographic emulsion layer,” means a layer of a photothermographic material that contains the photosensitive silver halide (when used) and non-photosensitive source of reducible silver ions.
“Non-photosensitive” means not intentionally light sensitive.
The term “organic silver salt” is herein meant to include salts as well as ligands comprising two ionized species. The silver salts used to make the core-shell particles are preferably comprised of silver salts of organic coordinating ligands. Many examples of such organic coordinating ligands are described below.
The terms “blocked developer” and “developer precursor” are the same and are meant to include developer precursors, blocked developer, hindered developers, developers with blocking and/or timing groups, wherein the term “developer” is used to indicate a reducing substance for silver ion.
Research Disclosure
is a publication of Kenneth Mason Publications Ltd., Dudley House, 12 North Street, Emsworth, Hampshire PO10 7DQ England (also available from Emsworth Design Inc., 147 West 24th Street, New York, N.Y. 10011).
DETAILED DESCRIPTION OF THE INVENTION
The present invention is directed to a photothermographic element comprising at least three imaging layers comprising a developer or developer precursor, a coupler in the case of color or monochrome imaging elements, silver halide, and at least one organic silver compound. At least one of the organic silver compounds is a silver donor, which typically is present at levels in the range of 5 to 3,000 g/mol of imaging silver. The dividing line of whether an organic silver compound functions as a silver donor (exclusively or partly) is sometimes unclear, and for pre
Bryant Gregg P.
Hanna JoAnn D.
Irving Mark E.
Liebert Nancy B.
Mis Mark R.
Chea Thorl
Konkol Chris P.
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