Radiation imagery chemistry: process – composition – or product th – Radiation sensitive product – Silver compound sensitizer containing
Reexamination Certificate
2000-08-03
2003-01-28
Chea, Thorl (Department: 1752)
Radiation imagery chemistry: process, composition, or product th
Radiation sensitive product
Silver compound sensitizer containing
C430S567000, C430S604000, C430S607000, C430S613000, C430S614000, C430S615000
Reexamination Certificate
active
06511797
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a photothermographic material.
BACKGROUND OF THE INVENTION
In the field of medical diagnosis, these days it is highly desired to reduce the waste from processing solutions from the perspective of environmental protection and space saving. Also, it is required to have photothermographic materials for medical diagnosis and ordinary photography which is capable of being efficiently exposed with laser image setters or laser imagers to form sharp and clear monochromatic images of high resolution. Such photothermographic materials meeting these requirements could provide users with simple photothermographic systems that do not require solution-type processing chemicals and therefore do not pollute the environment.
The same applies to the field of ordinary image-forming materials, which, however, shall differ from those in the field of medical diagnosis. Specifically, photo-images for medical diagnosis must clarify the details of body parts and therefore must have sharp and good image quality with fine graininess. In addition, for easy diagnosis thereon, preferred are cold monochromatic images in the field of medical diagnosis. At present, various types of hard copy systems with pigment and dye, for example, ink jet printers and electrophotographic systems are available for ordinary imaging systems. However, No satisfactory systems for forming photo-images enough for medical diagnosis are available.
On the other hand, photothermographic systems with silver salts of an organic acid used therein are described, for example, in U.S. Pat. Nos. 3,152,904 and 3,457,075, and in D. Klosterboer, Imaging Processes and Materials, “Thermally Processed Silver Systems”, Neblette, 8th ed., compiled by J.Sturge, V. Walworth and A. Shepp, Chapter 9, p.279, (1989). In general, photothermographic materials have a photosensitive layer which contains a catalytically active amount of a photocatalyst (e.g., silver halide), a reducing agent, a reducible silver salt (e.g., silver salt of an organic acid), and optionally a color tone adjustor for controlling silver tones, all of which are dispersed in a binder matrix in the layer. Photothermographic materials of that type are, after having been imagewise exposed, heated at a high temperature (for example, at 80° C. or higher) to form monochromatic silver images through oxidation-reduction reaction between the silver halide or the reducible silver salt (which serves as an oxidizing agent) and the reducing agent therein. The oxidation-reduction reaction is accelerated by the catalytic action of the latent image of the exposed silver halide. Therefore, the monochromatic silver images are formed in the exposed area of the materials. This technique is disclosed in many references such as typically U.S. Pat. No. 2,910,377 and Japanese Patent Publication (hereinafter referred to as JP-B) 4924/1968. The photothermographic systems with a silver salt of an organic acid could realize good image quality and tones enough for photo-images for medical diagnosis applications.
Silver halide grains are used for the photosensitive elements in the photothermographic materials. Silver halide grains having a grain size of 0.01 &mgr;m or larger can be produced according to a specifically controlled method for producing them in photographic gelatin. However, fine silver halide grains having a grain size of from 0.005 &mgr;m to 0.1 &mgr;m have a problem that, after a while, smaller grains often dissolve and aggregate to be large grains through physical ripening. To that effect, such fine silver halide grains are unstable.
One method for preventing silver halide grains from growing large is known, in which is used a stabilizer for stabilizing photographic performances of the grains. The stabilizer includes, for example, tetrazaines and mercaptothiazoles. However, in case where such a stabilizer is added to silver halide grains to such a degree that it can fix the size of the grains, the grains could hardly receive a spectral sensitizing dye to be adsorbed onto their surfaces. As a result, photographic materials containing the thus-stabilized silver halide grains could not ensure desired sensitivity. In the method, therefore, it is difficult to well control the size of silver halide grains without interfering with the photographic performance. If the size of silver halide grains can be controlled, some advantages can be obtained. For example, emulsions of the grains could be stored more stably, and the number of the grains produced from a predetermined amount of silver could be increased.
The photothermographic materials of the type mentioned above have a problem that that, after image formation, they are often fogged and their minimum density often increases while in storage.
One technique known in the art for preventing the photothermographic materials from fogging is the use of a mercury compound that serves as an antifoggant. The use of a mercury compound as an antifoggant is disclosed in, for example, U.S. Pat. No. 3,589,903. However, use of such a mercury compound is unfavorable from the viewpoint of environmental protection, and development of non-mercury antifoggants is desired. Some non-mercury antifoggants are known, including, for example, thiosulfonic acids, sulfinic acids, N-halogeno compounds, lithium salts, peroxides, rhodium salts, cobalt salts, palladium compounds, cerium compounds, disulfide compounds, polymer acids, organic polyhalogen compounds, etc. These compounds are disclosed in Japanese Patent Laid-Open (hereinafter referred to as JP-A) Nos. 78227/1976, 123331/1975, U.S. Pat. No. 3,589,903, JP-A 10724/1974, 97613/1974, 90118/1974, 22431/1976, U.S. Pat. No. 3,885,968, JP-A 101019/1975, 116024/1975, 134421/1975, 47419/1976, 42529/1976, 51323/1976, 119624/1975, 120328/1975, 121332/1976, 58022/1979, 70543/1981, 99335/1981, 90842/1984, 129642/1986, 129845/1987, 208191/1994, 5621/1995, 2781/1995, 15809/1996, U.S. Pat. Nos. 5,340,712, 5,369,000, 5,464,737, etc. Among these non-mercury antifoggants, it is reported that polyhalogen compounds such as those described in U.S. Pat. Nos. 3,874,946, 4,756,999, 5,340,712, European Patents Laid-open 605981A1, 622666A1, 631176A1, JP-B165/1979, JP-A2781/1995, etc., have good antifogging effects.
Given that situation, it is desired is to provide photothermographic materials which have little fogging, and have good photographic properties and of which the images formed thereon have little deteriorated while in storage.
SUMMARY OF THE INVENTION
The object of the present invention is to solve the problems in the related art mentioned above. Specifically, the object of the present invention is to provide a photothermographic material capable of giving fogless images and having good storage stability to the effect that the images formed thereon are have little deteriorated while in storage while being exposed to light.
Having assiduously studied so as to solve the problems mentioned above, the present inventors have found that, when an organic polyhalogen compound is added to a photothermographic material having, on one surface of its support, at least one type of photosensitive silver halide grains, a non-photosensitive silver salt of an organic acid, a reducing agent for silver ions, and a binder, and when silver halide grains having a hexacyano-metal complex in their outermost surfaces are used in the photothermographic material, then excellent photothermographic material shaving desired advantage scan be obtained. On the basis of this finding, the present inventors have completed the present invention.
According to the invention, there is provided a photothermographic material having, on one surface of its support, at least one type of photosensitive silver halide grains, a non-photosensitive silver salt of an organic acid, a reducing agent for silver ions, and a binder; which contains an organic polyhalogen compound of the following general formula (I) and in which the silver halide grains have a hexacyano-metal complex of the following general formula (II) in their outermost
Birch & Stewart Kolasch & Birch, LLP
Chea Thorl
Fuji Photo Film Co. , Ltd.
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