Radiation imagery chemistry: process – composition – or product th – Radiation sensitive product – Silver compound sensitizer containing
Reexamination Certificate
2001-02-28
2002-12-03
Chea, Thorl (Department: 1752)
Radiation imagery chemistry: process, composition, or product th
Radiation sensitive product
Silver compound sensitizer containing
C430S603000, C430S604000, C430S605000, C430S611000, C430S613000, C430S620000
Reexamination Certificate
active
06489091
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to photothermographic materials exhibiting enhanced sensitivity and superior storage stability and in particular to black-and-white photothermographic materials exhibiting enhanced sensitivity and superior storage stability of silver images after thermal development.
BACKGROUND OF THE INVENTION
In the field of medical treatment and graphic arts, there have been problems in working property with respect to effluents produced from wet-processing of image forming materials, and recently, reduction of the processing effluent is strongly demanded in terms of environmental protection and space saving.
Accordingly, there are needed techniques regarding photothermographic materials for photographic use which are capable of forming black images exhibiting high sharpness, enabling efficient exposure by means of a laser imager or laser image setter. As one such a technique is known a thermally developable photosensitive material, which comprises a support having thereon an organic silver salt, light-sensitive silver halide grains and a reducing agent, as described in U.S. Pat. Nos. 3,152,904 and 3,487,075; and D. H. Klosterboer, “Thermally Processed Silver Systems” (Imaging Processes and Materials, Neblette, 8th Edition, edited by J. M. Sturge, V. Walworth, and A. Shepp, page 279, 1989), etc.
One feature of the photothermographic material, which comprises a light sensitive layer containing silver halide grains as a photo-sensor and an organic silver salt as a silver ion source and an incorporated reducing agent is that images are formed through thermal development at a temperature of 80 to 140° C., without further fixing. To achieve not only a consistent supply of silver ions to the silver halide but also prevention of deterioration in transparency caused by light scattering, it has been attempted to improve the shape of organic silver salt particles so that the particles are optimally arranged in the light sensitive layer without disadvantageously affecting light scattering.
However, in the photothermographic materials, image problems have still tended to occur because normal image formation is locally hindered due to the presence of silver halide and organic silver coagula.
On the other hand, when silver halides or organic silver salts are forcibly disperse-pulverized by employing a homogenizer, problems occur in which fog increases, sensitivity decreases, leading to deteriorated image quality. Therefore, techniques have been demanded which are capable of yielding greater light sensitivity as well as higher density without an increase in the silver amount, while decreasing fogging.
SUMMARY OF THE INVENTION
Accordingly, it is an object of the present invention to provide a thermally developable photothermographic material exhibiting enhanced sensitivity and reduced fogging caused after storage over a long period of time and also exhibiting superior stability silver images after thermal development, and an image forming process by the use thereof.
The object of the invention can be accomplished by the following constitution:
1) A photothermographic material comprising on a support a light sensitive layer containing an organic silver salt, light sensitive silver halide grains and a solvent, wherein the organic silver salt comprises tabular organic silver salt grains exhibiting an average needle ratio of not less than 1.1 and less than 10.0, the silver halide grains having been subjected to chemical sensitization
2) a photothermographic material comprising a light sensitive layer containing an organic silver salt, a light sensitive silver halide and a solvent, wherein the organic silver salt comprises tabular grains exhibiting an aspect ratio of not less than 3 and an average needle ratio measured from the major face direction of not less than 1.1 and less than 10.0; the silver halide being chemically sensitized;
3) a photothermographic material comprising a support having thereon a light sensitive layer containing an organic silver salt, a light sensitive silver halide, a reducing agent and a binder , wherein when a cross section vertical to the surface of the support is electron-microscopically observed, not less than 70% of the total projected area of the organic silver salt particles is accounted for by organic silver salt particles having a particle projected area of less than 0.025 &mgr;m
2
and not more than 10% of the total projected area of the organic silver salt particles is accounted for by organic silver salt particles having a particle projected area of not less than 0.2 &mgr;m
2
; the silver halide being chemically sensitized;
4) The photothermographic material described in 1), 2) or 3), wherein the light sensitive silver halide is subjected to chemical sensitization which is performed using an organic sensitizer containing a chalcogen atom in the absence of an oxidizing agent during the process of manufacturing the photothermographic material, the silver halide being mixed with the organic silver salt, dispersed, dewatered and dried.
DETAILED DESCRIPTION OF THE INVENTION
One of the preferred embodiments of the invention is that the light sensitive silver halide relating to this invention is subjected to chemical sensitization, which is achieved using an organic sensitizer containing a chalcogen atom in the absence of an oxidizing agent in the manufacturing process of the photothermographic material.
The organic sensitizers containing a chalcogen atom include, for example, organic sensitizers having various structures, described in JP-A No 60-150046, 4-109240 and 11-218874 (hereinafter, the term, JP-A refers to an unexamined, published Japanese Patent Application).
Examples of atomic groups containing a group for promoting adsorption onto silver halide include an atomic group containing a mercapto group (e.g., mercaptooxadiazole, mercaptotetrazole, mercaptotriazole, mercaptodiazole, mercaptothiazole, mercaptothiadiazole, mercaptooxazole, mercaptoimidazole, mercaptobenzothiazole, mercaptobenzoxazole, mercaptobenzimidazole, mercaptotetrazaindene, mercaptopyridyl, mercaptoquinolyl, 2-mercaptopyridyl, mercaptophenyl, mercaptonaphthyl, etc.), an atomic group containing a thione group (e.g., thiazoline-2-thione, oxazoline-2-thione, imidazoline-2-thione, benzothiazoline-2-thione, benzimidazoline-2-thione, thiazolidine-2-thion, etc.), an atomic group capable of forming an imino silver (e.g., triazole, tetrazole, benzotriazole, hydroxyazaindene, benzimidazole, indazole, etc.), and an atomic group containing an ethenyl group (e.g., 2-[N-(2-propynyl)amino]benzothiazole, N-(propynyl)carbazole, etc.}.
In this invention, the group for promoting adsorption onto silver halide is distinct from a labile chalcogen atom site. Thus, it is not a group capable of releasing a chalcogen atom to form a silver chalcogenide.
In this invention, the compound containing a labile chalcogen atom site refers to a compound capable of forming a silver chalcogenide in the presence of silver nitrate. Further, the chalcogen atom means a sulfur atom, selenium atom or tellurium atom.
Examples of the atomic group containing a labile sulfur atom site include a thiourea group containing atominc group [e.g., N,N′-diethylthiourea, N-ethyl-N′-(2-thiazolyl)thiourea, N,N-dimethylthiourea, N-phenylthiourea, etc.], a thioamido group containing atomic group (e.g., thiobenzamide, thioacetoamide, etc.), an atomic group containing a polysulfide or phosphine sulfide group [e.g., bis(pentafluorophenyl)phenylphoshine sulfide, diethylphosphine sulfide, dimethylphenylphosphine sulfide, etc.], and a thioxoazolidinone group containing atomic group (e.g., ethylrhodanine, 5-benzylidene-3-ethylrhodanine, 1,3-diphenyl-2-thiohydantoin, 3-ethyl-4-oxooxazolidine-2-thione, etc.).
Examples of the atomic group containing a labile selenium atom site include a selenourea group containing atomic group [e.g., N,N-dimethylselenourea, selenourea, N-acetyl-N,N′-diethylselenourea, N-trifluoroacetyl-N′,N′-dimethylselenourea, N-ethyl
Bierman, Muserlian and Lucas
Chea Thorl
Konica Corporation
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