Radiation imagery chemistry: process – composition – or product th – Radiation sensitive product – Silver compound sensitizer containing
Reexamination Certificate
2002-01-14
2004-04-13
Letscher, Geraldine (Department: 1752)
Radiation imagery chemistry: process, composition, or product th
Radiation sensitive product
Silver compound sensitizer containing
C430S607000, C430S611000, C430S551000, C430S627000, C430S630000, C430S631000, C430S634000, C430S570000, C430S581000, C430S582000, C430S583000, C430S584000, C430S585000
Reexamination Certificate
active
06720134
ABSTRACT:
CROSS-REFERENCE TO RELATED APPLICATIONS
This application is based upon and claims the benefit of priority from the prior Japanese Patent Applications No. 2001-006756, filed Jan. 15, 2001; No. 2001-130131, filed Apr. 26, 2001; and 2001-378886, filed Dec. 12, 2001, the entire contents of three of which are incorporated herein by reference.
BACKGROUND OF THE INVENTION
The present invention relates to a silver halide photographic emulsion having a high sensitivity, excellent storability, and excellent reciprocity law property at low illumination. More specifically, the present invention relates to a silver halide photographic emulsion having excellent stability, which change little in its performance during the time from dissolution to coating of the emulsion, and further having excellent pressure resistance.
The use of tabular silver halide grains (to be referred to as “tabular grains” hereinafter) to obtain a high-speed silver halide photographic lightsensitive material is well known to those skilled in the art. As methods of sensitizing these tabular grains, methods of sensitizing by using epitaxial junction are disclosed in Jpn. Pat. Appln. KOKAI Publication No. (hereinafter referred to as JP-A-) 59-133540. Also, applications to thinner tabular grains or to tabular grains having larger equivalent-circle diameters are disclosed in JP-A's-8-69069, 8-101472, 8-101474, 8-101475, 8-171162, 8-171163, 8-101473, 8-101476, 9-211762, and 9-211763, and U.S. Pat. Nos. 5,612,176, 5,614,359, 5,629,144, 5,631,126, 5,691,127, and 5,726,007. An epitaxial sensitization method disclosed mainly in these patent applications and patents refers to a method of depositing silver halide having a relatively high silver chloride content on a host tabular grain having a relatively high silver bromide content by epitaxial junction.
However, an epitaxial emulsion prepared in such a manner is basically unstable, and thus unsuitable to obtain a stable performance of a photographic lightsensitive material. The reason is that the solubility product of silver chloride is larger than the solubility product of silver bromide, so silver chloride readily undergoes halogen conversion. Therefore, a sensitive material using the epitaxial emulsion lowers its sensitivity and increases fog during storage.
On the other hand, a technique of depositing silver halide having a relatively high silver bromide content to a host tabular grain having a relatively high silver bromide content by epitaxial junction is disclosed in JP-A-58-108526 and JP-A-5-232610.However, the research of the present invention reveals that these emulsions are insufficient in sensitivity and have a problem of considerable reduction in sensitivity in the case of performing long-exposure at low illumination (low intensity reciprocity law failure is large). In order to provide a photographic material having a sufficient sensitivity even at a photographic scene of such relatively dark conditions that the shutter speed cannot be made fast, a silver halide emulsion having a small reciprocity law failure at low illumination is strongly desired.
Meanwhile, the silver halide emulsion is generally used being coated on a support. In order to provide a lightsensitive material having a stable performance, a silver halide emulsion which changes little in its performance during the time from dissolution to coating of the emulsion, is strongly desired. However, with respect to the stability in a dissolved state, the conventional epitaxial emulsion was unstable and was required to be improved.
In general, various pressures are applied to a photographic lightsensitive material coated with a silver halide emulsion. For example, a 35-mm color negative film or a color reversal film is caught in a film cartridge, folded when it is loaded in a camera, and stretched during a frame advance. A silver halide emulsion which provides a lightsensitive material having excellent resistance to such external pressures is strongly needed. However, it becomes clear that the level of the pressure resistance of the conventional epitaxial emulsion is highly unsatisfactory.
Further, in order to obtain a silver halide photographic lightsensitive material having a high sensitivity, it is suitable to use a silver halide emulsion comprising tabular silver halide grains with a large ratio of surface area to volume. This increases the adsorption of the sensitizing dyes on the surfaces of the grains, and as a result, a higher spectral sensitization can be obtained.
However, the problem of a rise in residual color after processing occurs, due to this increased adsorption of sensitizing dyes. It was found that, in this invention, by using sensitizing dyes having a high sensitivity and less residual color, described in JP-A-2001-75224, for an epitaxial emulsion, residual color after processing can be improved, while maintaining high spectral sensitization.
BRIEF SUMMARY OF THE INVENTION
It is an object of the present invention to provide a silver halide photographic emulsion having a high sensitivity, high storage stability, and excellent reciprocity law property at low illumination. Furthermore, it is another object of the present invention to provide the silver halide photographic emulsion which is also excellent in both stability in the dissolved state and pressure resistance.
The above objects are achieved by means (1) to (21) below.
(1) A silver halide photographic emulsion comprising grains, wherein 70% or more of the total projected area of the grains is occupied by silver halide grains each meeting requirements (a) to (d) below:
(a) the grain is composed of a tabular silver halide host grain having two mutually parallel main planes and aspect ratio of 2 or more, and a silver halide protrusion portion epitaxially joined on the surface of the host grain;
(b) the silver bromide contents of both the host grain and the protrusion portion are 70 mol % or more;
(c) the percentage of the silver amount in the protrusion is 12% or less of the silver amount in the host grain; and
(d) the grain has a shallow electron-trapping zone.
(2) The silver halide photographic emulsion described in item (1) above, wherein 70% or more of the total projected area of the grains is occupied by silver halide grains each further meeting the following requirement (e) in addition to the above requirements (a) to (d):
(e) at least one main plane of the host grain has at least one apex, and the protrusion portion is present on each apex of the main plane.
(3) The silver halide photographic emulsion described in item (1) above, wherein 70% or more of the total projected area of the grains is occupied by silver halide grains each further meeting the following requirement (f) in addition to the above requirements (a) to (d):
(f) the silver iodide content of each silver halide grain is in a range of 0.6I to 1.4I mol %, wherein I (mol %) is the average silver iodide content of all the grains.
(4) The silver halide photographic emulsion described in item (2) above, wherein 70% or more of the total projected area of the grains is occupied by silver halide grains each further meeting the following requirement (f) in addition to the above requirements (a) to (e):
(f) the silver iodide content of each silver halide grain is in a range of 0.6I to 1.4I mol %, wherein I (mol %) is the average silver iodide content of all the grains.
(5) The silver halide photographic emulsion described in item (1) above, wherein 70% or more of the total projected area of the grains is occupied by silver halide grains each further meeting the following requirement (g) in addition to the above requirements (a) to (d) &bgr;(g) the grain has a hole-trapping zone.
(6) The silver halide photographic emulsion described in item (2) above, wherein 70% or more of the total projected area of the grains is occupied by silver halide grains each further meeting the following requirement (g) in addition to the above requirements (a) to (e):
(g) the grain has a hole-trapping zone.
(7) The silver halide photographic emulsion described in item (3) above, wherein 70% o
Haraguchi Nobuyuki
Ikeda Hideo
Miyamoto Yasushi
Mori Takayoshi
Nishikawa Toshihiro
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