Radiation imagery chemistry: process – composition – or product th – Post imaging processing – Physical developing
Reexamination Certificate
2001-12-28
2003-11-18
Schilling, Richard L. (Department: 1752)
Radiation imagery chemistry: process, composition, or product th
Post imaging processing
Physical developing
C430S415000, C430S416000, C430S447000, C430S550000, C430S605000, C430S617000, C430S955000
Reexamination Certificate
active
06649330
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a method of incorporating sequestered silver ions into a hydrophilic colloid layer of a photographic element, and to photographic elements containing sequestered silver ions which may be released upon exposure to photographic processing solutions.
BACKGROUND OF THE INVENTION
The photographic system, in its most basic form, is comprised of silver halide (capable of detecting light and storing it as latent image) and developer molecules (capable of converting the latent image to a visible image). These two chemistries, however, are incompatible, as unexposed silver halide is thermodynamically unstable with respect to reduction in the presence of developer molecules. The consequence of this is that modern photography typically requires multiple steps: exposure and processing.
The effect of Ag ion upon the photographic system has long been a topic of study (see, e.g., “The Theory of the Photographic Process”, T. H. James, ed.; 4
th
ed., Chapter 13, 1977). Control of the Ag ion concentration is known to be important in the manufacture of silver halide emulsions, and in the production and processing of silver halide imaging elements. Most notably, the introduction of Ag ion into a silver halide imaging element may induce a phenomenon known as “solution physical development”, in which silver ion in solution is adsorbed onto developing silver halide grains. The silver ion is then reduced by the developer, forming silver metal, and thereby can advantageously add to the overall density of the image. This process, however, is most often indiscriminate and leads to the build-up of fog in the system with no net gain in imaging efficiency. As a result of this, solution physical development process is generally avoided in most photographic systems, with the exception of some reversal processes. It would be desirable to provide photographic materials in which silver ions are effectively sequestered prior to photographic processing, so as to minimize build up of fog density, and which are released upon introduction of common photographic processing solutions and made available for enhancement of the photographic image.
Incorporation of active chemistry directly into film formulations, to either simplify or improve processing after exposure, has long been a goal in the photographic industry. Some photographically useful compounds are difficult to incorporate in a stable fashion into a light-sensitive material, however, or cause serious deterioration in the photographic capability if incorporated. These compounds, if incorporated directly into the photographic elements, typically need to be stabilized or rendered harmless by chemical modification prior to photographic processing. Methods of incorporating development and other active chemistries into photographic element formulations have been described in a number of patents and publications. Schleigh and Faul, in Research Disclosure 129 (1975) describe methods of appending color developers with “blocking” chemistry to prevent premature reaction. U.S. Pat. No. 6,261,757 to Irving et al. describes photographic articles in which developers and other photographic chemistries are ionically bound to the surface of ion-exchange resins.
U.S. Pat. No. 4,942,119 discloses materials comprising radiation sensitive silver compositions entrapped or encapsulated in the cages of a microporous sodalite lattice, prepared from synthetic sodium sodalites by a silver ion exchange process. There is no disclosure, however, of the use of such materials as a source of silver ions during processing of a photographic element comprising a silver halide emulsion.
EP 0 909 981 discloses silver halide photographic materials comprising zeolites loaded with a photographically useful group. Use of zeolites loaded with aqueous soluble silver salts and halide salts for the in situ preparation of ultramicrocrystalline silver halides for ripening onto coarser silver halide grains in a reaction vessel is also disclosed, but there is no disclosure of the use of such materials to incorporate sequestered silver ions which are to be released during processing of a photographic element.
Clearfield and Cheng (
J. Inorg. Nucl. Chem
., 42, 1341 (1980)) have reported compositions and methods of preparing the following materials: Zr(AgPO
4
)
2
.H
2
O, ZrAg
0.22
H
1.78
(PO
4
)
2
and ZrAg
0.75
H
1.25
(PO
4
)
2
. There is no disclosure, however, of the use of such materials as a source of silver ions during processing of a photographic element comprising a silver halide emulsion.
SUMMARY OF THE INVENTION
In accordance with one embodiment of the invention, a photographic element is described comprising a support bearing one or more hydrophilic colloid layers including at least one photographic silver halide emulsion layer, wherein sequestered silver ions are incorporated into at least one hydrophilic colloid layer in the form of a silver ion containing material which sequesters silver ions prior to photographic processing and releases silver ions upon exposure to photographic processing solutions.
In accordance with another embodiment of the invention, a method for preparing a photographic element is described comprising forming a silver ion containing material which sequesters silver ions, adding the silver ion containing material to a hydrophilic colloid layer coating composition, and coating the hydrophilic colloid layer coating composition to form a layer of the photographic element, wherein the silver ion containing material which sequesters silver ions releases silver ions upon exposure of the photographic element to photographic processing solutions.
In accordance with a further embodiment of the invention, a method of processing a photographic material after exposure is described comprising contacting a photographic material according to the invention with a photographic processing solution having a greater concentration of cations other than silver ions relative to the silver ion containing material such that a cation concentration gradient is established, and releasing silver ions from the silver ion containing material by ion exchange with the silver ion containing material.
In accordance with particular embodiments of the invention, the silver ion containing material comprises a silver ion-exchanged zeolite material or an intercalation composition comprising a layered host material having silver ions inserted as guest ions between the layers of the host material. The invention provides novel photographic materials and a method of incorporating silver ions directly into a photographic imaging element with improved stability and keeping response. The incorporation of silver ion containing materials into a photographic element in accordance with the invention enables increased upper scale density without excessive build-up of fog in the system.
DETAILED DESCRIPTION OF THE INVENTION
In accordance with the invention, sequestered silver ions are incorporated into at least one hydrophilic colloid layer in the form of a silver ion containing material which sequesters silver ions prior to photographic processing and releases silver ions upon exposure to photographic processing solutions. In accordance with particular embodiments, the silver ion containing material comprises a silver ion-exchanged zeolite material or an intercalation composition comprising a layered host material having silver ions inserted as guest ions between the layers of the host material.
Intercalation is a process in which a layered material, referred to as the host, swells or opens to accommodate other molecules or ions, referred to as the guest:
Host+guest→Host(guest)
x
Layered compounds capable of sequestering ions and molecules by intercalation have been described in a number of publications. The choice of host material is dependent upon the particular molecule to be intercalated, and a layered host material for use in accordance with the present invention, e.g., may be chosen which intercalates only cations. The choice of layered host materials for
Bringley Joseph F.
Honan James S.
Lushington Kenneth J.
Qiao Tiecheng A.
Anderson Andrew J.
Eastman Kodak Company
Schilling Richard L.
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