Radiation imagery chemistry: process – composition – or product th – Radiation sensitive product – Silver compound sensitizer containing
Reexamination Certificate
2000-06-13
2001-07-17
Le, Hoa Van (Department: 1752)
Radiation imagery chemistry: process, composition, or product th
Radiation sensitive product
Silver compound sensitizer containing
C430S362000, C430S448000
Reexamination Certificate
active
06261757
ABSTRACT:
FIELD OF THE INVENTION
This invention pertains to photographic elements, and in particular to photographic elements incorporating reducing agents stabilized using ion exchange polymers, a method of activating the reducing agent, and a method of processing said photographic element.
BACKGROUND OF THE INVENTION
It is well known in the art that the introduction of photographically useful compounds, such as photographic developers, couplers, development inhibitors, electron transfer agents, base precursors, fixing agents, i.e., ligand capable of binding silver, silver stabilizing agents and the like, into photographic elements can lead to premature reaction of the photographically useful compound with the other components of the photographic element. For example, placing conventional color developers, such as p-phenylenediamines and p-aminophenols, into sensitized photographic elements leads to desensitization of the silver halide emulsion and unsuitable fog. Much effort has therefore been directed at trying to produce effective blocked developers, which can be introduced in silver halide emulsion elements without deleterious desensitization or fog effects and which unblock chemically under conditions of development so that developer is free to participate in color forming (dye forming) reactions.
U.S. Pat. No. 3,342,599, to Reeves, discloses the use of Schiff base developer precursors. 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 carbamate blocked p-phenylenediamines. Color developing agents having &agr;-ketoacyl blocking groups are described in U.S. Pat. No 5,019,492.
All of these approaches and inventions 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; and the requirement of a dinucleophile, such as hydroxylamine, to initiate developer release.
The addition of a blocking group to a color developing agent results in an increase in molecular weight and generally results in a decrease in water solubility of the resulting blocked version of the parent color developing agent. As a result, the incorporation of these blocked developers in photographic elements is carried out using colloidal gelatin dispersions of the blocked developers. These dispersions are prepared using means well known in the art, wherein the developer precursor is dissolved in a high vapor pressure organic solvent (for example, ethyl acetate), along with, in some cases, a low vapor pressure organic solvent (such as dibutylphthalate), and then emulsified with an aqueous surfactant and gelatin solution. After emulsification, usually done with a colloid mill, the high vapor pressure organic solvent is removed by evaporation or by washing, as is well known in the art.
PROBLEM TO BE SOLVED BY THE INVENTION
There has been a need for a photographic element incorporating a reducing agent, such as a developing agent, which is stable until development. Then, the element can be developed rapidly and easily. There has also been a need to simplify the preparation of the developer dispersion method and to eliminate the need for organic solvents in coating formulations. There has also been a need for a process for developing an image in a photographic element which employs a developing solution having a simplified composition.
SUMMARY OF THE INVENTION
These and other needs have been satisfied by providing photographic elements comprising polymers with ion exchangeable groups (ionomers, polyesterionomers, and ion-containing latices) which limit diffusion of reducing agents under coating conditions. The immobilization of the reducing agent prevents interaction with the silver halide emulsion under film storage conditions. The active reducing agent can be released from the ion exchange polymer by contacting the film with a high ionic strength solution and/or a solution of appropriate pH to release the active compound from the ion exchange polymer, and/or raising the temperature to release the active reducing agent. In the case of developer release, for example, the high pH environment initiates developer release by deprotonating the developer molecule. This breaks the ionic interaction between the previously protonated developer and the ion exchange polymer, allowing the developer molecules to diffuse away from the ion exchange polymer. A second driving force for developer diffusion can be provided by immersion in a high ionic strength solution. In this case, the high concentration of ions in the activating solution compete with the developer for the exchange sites of the ion exchange polymer, which tends to displace the developer from the exchange sites.
One aspect of the invention comprises a photographic element comprising at least one light-sensitive silver halide layer on a support, wherein the photographic element also comprises at least one reducing agent ionically bound to a particulate ion exchange matrix having an average particle size of about 0.01 to about 10 &mgr;m.
The ion exchanged reducing agent can be incorporated in a photographic element within a light-sensitive layer or within a light-insensitive layer adjacent a light sensitive layer.
Another aspect of this invention comprises a method of activating a reducing agent incorporated in a photographic element which comprises a support and at least one light-sensitive layer and at least one reducing agent ionically bound to a particulate ion exchange matrix having an average particle size of about 0.01 to about 10 &mgr;m, said method comprising contacting the element with a solution or solution contained within a coated binder having an ionic strength of greater than 0.001 M.
Yet another aspect of this invention comprises a method of activating a reducing agent incorporated in a photographic element which comprises a support, at least one light sensitive layer and at least one reducing agent ionically bound to a particulate ion exchange matrix having an average particle size of about 0.01 to about 10 &mgr;m, said method comprising heating the element to a temperature above about 50° C.
Still another aspect of this invention comprises a method of processing the photographic element comprising a support, at least one light-sensitive layer and at least one reducing agent ionically bound to a particulate ion exchange matrix having an average particle size of about 0.01 to about 10 &mgr;m, said method comprising contacting the element with a processing solution having a pH greater than 8.
A further aspect of this invention is a method of imaging comprising the steps of:
forming an image in an imagewise exposed light-sensitive silver halide element comprising a support, a light-sensitive silver halide emulsion layer, and a reducing agent ionically bound to a particulate ion exchange material having an average particle size of about 0.01 and about 10 &mgr;m;
scanning said formed image to form a first electronic image representation from said formed image;
digitizing said first electronic image to form a digital image;
modifying said digital image to form a second electronic image representation; and
transforming, storing, transmitting, printing or displaying said second electronic image representation.
An additional aspect of this invention is a method of forming an image comprising the steps of:
forming an image in an imagewise exposed light-sensitive silver halide element comprising a support, a light-sensitive silver halide emulsion layer, and a reducing agent ionically bound to a particulate ion exchange material having an average particle size of about 0.01 and about 10 &mgr;m;
scanning said formed image to form an electronic image representation from said formed image; and
transforming, storing, transmitting, printing or displaying said electronic image representation.
REFERENCES:
patent: 3342599 (1967-09-01), Reeves
patent: 4060418 (1977-11-01), Waxman et
Irving Lyn M.
Irving Mark E.
Noonan John M.
Eastman Kodak Company
Le Hoa Van
Meeks Roberts Sarah
Rice Edith A.
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