Radiation imagery chemistry: process – composition – or product th – Radiation sensitive product – Silver compound sensitizer containing
Reexamination Certificate
1999-11-22
2001-07-31
Chea, Thorl (Department: 1752)
Radiation imagery chemistry: process, composition, or product th
Radiation sensitive product
Silver compound sensitizer containing
C430S620000
Reexamination Certificate
active
06268118
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a photosensitive emulsion, thermally developable material containing the emulsion as well as to an image recording method an image forming method employing said thermally developable material.
BACKGROUND OF THE INVENTION
Conventionally, in printing plate making and medical fields, effluent generated by wet processing of image forming materials has been concerned from the ease of work. Recently, a decrease in the processing effluent has been strongly demanded from the viewpoint of environmental protection as well as saving of floor space. Accordingly, needed has been the development of techniques regarding light/heat sensitive photographic materials which can be subjected to efficient exposure employing a laser image setter as well as a laser imager and can form sharp and clear black-and-white images of high resolution.
As techniques to meet those requirements, thermally developable materials for preparing photographic images employing thermal development methods are disclosed in, for example, U.S. Pat. Nos. 3,152,904 and 3,457,075, and D. Morgan and B. Shely, “Thermally Processed Silver Systems” in “Imaging Processes and Materials”, Neblette, 8th edition, edited by Sturge, V. Walworth, A Shepp, page 2, 1969.
The feature of these thermally developable materials is that images are formed by thermal development, generally at 80 to 140° C. employing reducing agents incorporated into the photosensitive layer, and the fixing step is eliminated. However, in the above-cited thermally developable materials, image problems have 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, and image quality deteriorated. 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 fog.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a thermally developable material, and in detail to provide a thermally developable material and an image forming method which exhibit high sensitivity, reduced image deffects as well as low fog.
The present invention and the embodiment thereof are described below.
A thermally developable photosensitive material having a photosensitive layer comprising a photosensitive silver halide, an organic silver salt, a reducing agent and a binder, wherein the organic silver salt comprises tabular organic silver salt grains having an aspect ratio of at least 3, and average of needle ratio of the tabular organic silver salt grains measured from principal plane direction is not less than 1.1 and less than 10.
In the thermally developable photosensitive material described above, the organic silver salt comprises at least 80% by number of tabular organic silver salt grains having an aspect ratio of at least 3, and average of needle ratio of the tabular organic silver salt grains measured from principal plane direction is not less than 1.1 and less than 5.0.
The aspect ratio of the tabular organic silver salt grains is preferably 3 to 20, more preferably 3 to 10.
The ratio of organic silver salt grains which have a projection area of no more than 0.025 &mgr;m
2
is preferably at least 70 percent of the total projection area. The ratio of grains which have a projection area of at least 0.2 &mgr;m
2
is preferably not more than 10 percent of the total projection area appeared in a perpendicular cross section of the support surface of said photosensitive material observed by an electron microscope.
The photosensitive layer preferably comprises zirconium in an amount of 0.01 to 0.5 mg per g of silver, more preferably 0.01 to 0.3 mg per g of silver.
The silver salt has preferably monodisperse grain size distribution.
The monodisperse degree of the silver salt grains is preferably 1 to 30%.
The whole amount of silver is preferably 2.4 g/m
2
or lower, more preferably 0.5 to 2.4 g/m
2
as converted silver.
The average grain diameter of the organic silver salt is preferably 0.01 to 0.8 &mgr;m, more preferably 0.05 to 0.5 &mgr;m.
The average grain size of silver halide is preferably 0.01 to 0.1 &mgr;m.
The preferable reducing agent is a hindered phenol compound.
The content of the total solvents contained in the thermally developable photosensitive material is 5 to 1000 mg/m
2
, more preferably 10 to 300 mg/m
2
.
The photosensitive emulsion comprising a photosensitive silver halide and an organic silver salt in which the organic silver salt comprises tabular organic silver salt grains having an aspect ratio of at least 3, and average of needle ratio of the tabular organic silver salt grains measured from principal plane direction is not less than 1.1 and less than 10.
In the photosensitive emulsion the organic silver salt preferably comprises at least 80% by number of tabular organic silver salt grains having an aspect ratio of at least 3, and average of needle ratio of the tabular organic silver salt grains measured from principal plane direction is not less than 1.1 and less than 5.0.
A photosensitive emulsion preferably comprises zirconium in an amount of 0.01 to 0.5 mg per g of silver.
DETAILED DESCRIPTION OF THE INVENTION
The present invention will be detailed below.
A photosensitive emulsion comprises an organic silver salt, photosensitive silver halide and a solvent, and the photosensitive layer comprises zirconium in an amount of 0.01 to 0.5 mg per g of silver. A particularly preferred case is one in which said photosensitive layer comprises zirconium in an amount of 0.01 to 0.3 mg.
An organic silver salt employed in the present invention is described.
In the present invention the organic silver salt has preferably monodisperse grain size distribution. The monodispersed grains as described herein are the same as the case for silver halides, and said monodisperse degree is preferably 1 to 30%.
The average grain diameter of the organic silver salt is preferably 0.01 to 0.8 &mgr;m, and is more preferably 0.05 to 0.5 &mgr;m.
The average grain size is average of the diameter of circle having same area of respective grains observed by microscope.
The organic silver salt comprises tabular grains preferably have an aspect ratio of at least 3, and the number average of the needle ratio of said grains measured from the principal plane direction is not less than 1.1 and less than 10, more preferably not less than 1.1 and less than 5. The grains having an aspect ratio of at least 3 is denoted that number of grains satisfying aspect ratio of at least 3 occupies not less than 50% by number.
The organic silver salts employed in the present invention preferably comprise tabular organic silver salt grains of at least 60 percent (in number) of the entire organic silver salts, more preferably at least 70 percent (in number), and most preferably at least 80 percent (in number).
The aspect ratio of the above-mentioned tabular organic silver salt grains is obtained employing procedures described below.
AR=grain diameter (in &mgr;m)/Thickness (in &mgr;m)
The aspect ratio (AR) of the tabular organic silver salt grains employed in the present invention is preferably 3 to 20, and more preferably 3 to 10. The above-mentioned range is considered to be the preferred one, based on the following criteria. When the aspect ratio is too small, organic silver salt grains are likely close packed. When it is too large, organic silver salt grains likely overlap each other, and are likely dispersed while adhering to each other. As a result, light scattering etc. tend to occur and the visual transparency of photosensitive materials tends to decrease.
In the present invention, the above-mentioned tabular organic silver salt grains preferably have small anisotropy in the shape of two planes i.e., principal planes, having a maximum area, which are arranged near
Iwasaki Keiko
Shima Tetsuo
Bierman Jordan B.
Bierman, Muserlian and Lucas
Chea Thorl
Konica Corporation
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