Radiation imagery chemistry: process – composition – or product th – Radiation sensitive product – Silver compound sensitizer containing
Reexamination Certificate
2003-05-15
2004-04-13
Le, Hoa Van (Department: 1752)
Radiation imagery chemistry: process, composition, or product th
Radiation sensitive product
Silver compound sensitizer containing
Reexamination Certificate
active
06720135
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a silver halide photographic emulsion (hereinafter, also denoted as a silver halide emulsion or simply as an emulsion) and a silver halide photographic light sensitive material (hereinafter, also denoted as a photographic material), and in particular to a silver halide photographic emulsion exhibiting enhanced sensitivity and superior graininess, and improved lowering of sensitivity and deterioration of image quality caused by radiation rays, and a silver halide photographic material by use thereof.
BACKGROUND OF THE INVENTION
Recently, popularization of photographing instruments such as cameras have greatly advanced and brought about increased opportunities for picture-taking by use of silver halide photographic materials. Further enhanced sensitivity and image quality are still more strongly desired.
One of the essential factors for enhancement of sensitivity and image quality is silver halide grains and development of silver halide grains aimed at enhancing sensitivity and image quality of photographic material has been promoted in the photographic art.
As is generally conducted, decreasing a silver halide grain size to enhance image quality tends to reduce sensitivity and there were limits to allow enhanced sensitivity to be compatible with enhanced image quality.
There have been studied techniques for enhancing the ratio of sensitivity to grain size to achieve further enhancements of sensitivity and image quality. For example, techniques of using tabular silver halide grains were disclosed in JP-A Nos. 58-111935, 58-111936, 58-111937, 58-113927 and 59-99433 (hereinafter, the term, JP-A refers to an unexamined Japanese Patent Application Publication). Compared to so-called regular crystal silver halide grains such as octahedral, tetradecahedral or cubic grains, tabular silver halide grains have a larger surface area, whereby a larger amount of a sensitizing dye is adsorbed onto the grain surface, advantageously achieving further the enhanced sensitivity. The use of tabular silver halide grains having a still higher aspect ratio (i.e., the ratio of grain diameter to grain thickness) was also disclosed in JP-A Nos. 6-230491, 6-235988, 6-258745 and 6-289516.
JP-A No. 63-92942 disclosed a technique of providing a core having a relatively high iodide content in the interior of tabular silver halide grains and JP-A No. 63-163541 disclosed a technique of using tabular silver halide grains having at least 5 of a ratio of grain thickness to the longest spacing between twin planes, both of which contributed to enhancement of sensitivity and graininess.
JP-A No. 63-106746 disclosed a technique of using tabular silver halide grains substantially having a layer structure parallel to two opposed major faces, and JP-A No. 1-279237 disclosed a technique of using tabular silver halide grains having a layer structure divided by a face substantially parallel to the two opposed major faces and an average surface iodide content higher by at least 1 mol % than an average overall iodide content.
JP-A No. 3-121445 disclosed silver halide grains having parallel twin planes and an interfacial layer having regions differing in iodide content, while JP-A No. 63-305343 disclosed tabular silver halide grains having development initiation points in the vicinity of corners of the grain, and JP-A No. 2-34 disclosed silver halide grains comprising a (100) face and a (111) face.
JP-A No. 1-183644 disclosed tabular silver halide grains having a uniform distribution of iodide content among grains.
There was also disclosed a technique for achieving carrier control by metal-doping, in which a polyvalent metal oxide is occluded within silver halide grains, thereby improving photographic characteristics.
JP-A Nos. 3-196135 and 3-189641 disclosed a silver halide emulsion which was prepared in the presence of an oxidizing agent for silver and associated effects with respect to sensitivity and fogging when using a silver halide photographic material by use of the emulsion. Further, JP-A No. 63-220238 disclosed a silver halide emulsion comprising tabular grains in which the position of dislocation lines is specified; JP-A No. 3-175440 disclosed a silver halide emulsion tabular grains, in which dislocation lines are concentrated near corners of the grain; JP-B No. 3-18695 (hereinafter, the term, JP-B refers to a Japanese Patent Publication) disclosed a technique of using silver halide grains having a definite core/shell structure; and JP-A No. 3-31245 disclosed a technique concerning silver halide grains having core/shell three-layer structure. These techniques were studied to enhance sensitivity.
JP-A Nos. 6-11781, 6-11782, 6-27564, 6-250309, 6-250310, 6-250311, 6-250313 and 6-242527 disclosed the use of iodide ion releasing compounds, achieving improvements in sensitivity, fogging and pressure resistance.
However, in the foregoing prior art, there is a limit to allow enhancing sensitivity to be compatible with enhancing image quality. Recently, effects of natural radiation rays on silver halide color photographic materials using a high-sensitive silver halide emulsion were high-lighted, for example, in “Shashin Kogyo” page 92, No. 11,1986 reported details of the influence of natural radiation rays on high-speed photographic film. Influence of natural radiation rays on silver halide photographic materials is well known to be due to &ggr;-ray and exposure thereto results in an increased fog density, accompanied by deteriorated graininess.
As described above, present techniques for silver halide grains are insufficient for satisfying recent requirements in photographic material and development of superior techniques is still desired. Specifically, development of a technique enabling precise control of sensitivity speck sites and halide composition on the surface of silver halide grains is needed to accomplish still more effective chemical sensitization and spectral sensitization to achieve enhanced photographic performance and the foregoing techniques do not sufficiently meet such requirements.
SUMMARY OF THE INVENTION
The present invention has come into being in view of the foregoing situation. Thus, it is an object of the invention to provide a silver halide photographic emulsion exhibiting enhanced sensitivity and superior graininess, improved in lowering of sensitivity and deterioration of image quality caused by radiation rays, and a silver halide photographic material by use the same.
The object of the invention was accomplished by the following constitution:
1. A silver halide photographic emulsion comprising silver halide grains, wherein 70% to 100% of total grain projected area is accounted for by tabular grains, the tabular grains having an average aspect ratio of 20 to 500 and an average spacing between twin planes of 10 to 160 A, and at least 80% by number of the tabular grains being accounted for by hexagonal tabular grains having an adjacent edge ratio of not less than 1.0 and less than 1.2;
2. A silver halide photographic emulsion comprising silver halide grains, wherein the silver halide grains have an average aspect ratio of 20 to 500 and a spacing between twin planes of 10 to 160 A, and at least 80% by number of the silver halide grains is accounted for by hexagonal tabular grains having a adjacent edge ratio of not less than 1.0 and less than 1.2;
3. A silver halide photographic material comprising on a support at least one silver halide emulsion layer, wherein the silver halide emulsion layer comprises a silver emulsion, as described above.
DETAILED DESCRIPTION OF THE INVENTION
One aspect of this invention concerns a silver halide photographic emulsion, in which 70 to 100% of the total grain projected area is accounted for by tabular grains, the tabular grains have an average aspect ratio of 20 to 500, 80 to 100% by number of the tabular grains is accounted for by hexagonal tabular grains having an adjacent edge ratio of not less than 1.0 and less than 1.2, and the tabular grains have an average spacing between twin planes of 10 to 160 A.
In t
Kondo Toshiya
Sekiya Tadanobu
Konica Corporation
Le Hoa Van
Muserlian Lucas and Mercanti
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