Radiation imagery chemistry: process – composition – or product th – Radiation sensitive product – Silver compound sensitizer containing
Reexamination Certificate
2001-03-01
2004-02-10
Ashton, Rosemary (Department: 1752)
Radiation imagery chemistry: process, composition, or product th
Radiation sensitive product
Silver compound sensitizer containing
C430S569000, C430S546000, C430S551000, C430S607000, C430S608000, C430S628000
Reexamination Certificate
active
06689553
ABSTRACT:
CROSS-REFERENCE TO RELATED APPLICATIONS
This application is based upon and claims the benefit of priority from the prior Japanese Patent Application No. 2000-065104, filed Mar. 9, 2000, the entire contents of which are incorporated herein by reference.
BACKGROUND OF THE INVENTION
The present invention relates to a silver halide photographic emulsion and, more particularly, to a silver halide photographic emulsion containing silver halide grains by which deterioration by oxygen is improved, and a silver halide photographic light-sensitive material containing the emulsion.
In silver halide photographic emulsions, improving the sensitivity/graininess ratio is the most important object.
As a method of improving the sensitivity/graininess ratio of a silver halide photographic emulsion, the use of tabular grains which increase the efficiency of light absorption is known in, e.g., U.S. Pat. No. 4,956,269. The sensitivity can be improved by increasing the aspect ratio of such tabular grains and increasing the amount of a spectral sensitizing dye. Reduction sensitization is also known as a method of increasing the grain sensitivity.
Improving the sensitivity, however, often lowers the resistance against deterioration of a light-sensitive material during storage. In particular, oxygen participates in an increase in fog during storage, so it is strongly desired to improve this fog increase.
As a method of improving the fog increase caused by oxygen, it is possible to use a radical scavenger which deactivates oxygen or organic radicals generated in a light-sensitive material by oxygen. Examples are phenol-based compounds described in, e.g., Jpn. Pat. Appln. KOKAI PUBLICATION No. (hereinafter referred to as JP-A-)7-72599 and hydroxyamine-based compounds represented by, e.g., formulas (A-I) to (A-III) described in JP-A-8-76311 and U.S. Pat. No. 5,719,007, formula (S2) described in JP-A-10-10668, formula (S1) described in JP-A-11-15102, and formula (S1) described in JP-A-10-90819.
JP-A's-9-96883 and 11-153840 have disclosed methods of preparing tabular grains in the presence of an oxidizer for silver, but do not predict a reduction of fog by a halogen oxoacid salt of the present invention. Also, Jpn. Pat. Appln. KOKOKU PUBLICATION No. (hereinafter referred to as JP-B-)52-14625 has disclosed a method of intensifying dye images in the presence of a chlorite. However, unlike the present invention JP-B-52-14625 does not describe any method of using the chlorite during the preparation of emulsions.
BRIEF SUMMARY OF THE INVENTION
It is an object of the present invention to provide a silver halide emulsion in which changes in fog caused by oxygen during storage are significantly improved without lowering the sensitivity, and a silver halide photographic light-sensitive material containing the emulsion.
Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out hereinafter.
DETAILED DESCRIPTION OF THE INVENTION
The present inventors made extensive studies and have found a means for maintaining improved sensitivity and suppressing an increase in fog by oxygen. Specifically, the present inventors have found a means to previously remove fine silver nuclei, which exist on the surface or in the interior of an emulsion grain and presumably cause oxygen fog, by the use of an oxidizer.
That is, the object of the present invention is achieved by silver halide photographic emulsions described below and a silver halide photographic light-sensitive material using the emulsions.
(1) A silver halide photographic emulsion comprising silver halide grains, wherein the emulsion was prepared in the presence of at least one halogen oxoacid salt represented by formula (I) below:
M(XO
n
)
m
Formula (I)
wherein M represents an alkali metal ion or alkaline-earth metal ion, x represents a halogen atom, n represents 2 or 3, and m represents 1 or 2.
(2) The silver halide photographic emulsion described in item (1) above, wherein the halogen oxoacid salt is chlorite.
(3) The silver halide photographic emulsion described in item (1) or (2) above, wherein 50% or more of the total projected area of all the silver halide grains contained in the emulsion is occupied by tabular silver halide grains, each having (111) faces as parallel main planes and an aspect ration of 5 or more.
(4) The silver halide photographic emulsion described in any one of items (1) to (3) above, wherein the emulsion was reduction sensitized by at least one reduction sensitizer selected from a group consisting of (a) thiourea dioxide, (b) hydroxyamines and their derivatives, and (c) dihydroxybenzenes and their derivatives.
(5) A silver halide photographic light-sensitive material having at least one silver halide emulsion layer on a support, wherein the silver halide photographic emulsion described in any one of items (1) to (4) above is contained in the at least one silver halide emulsion layer.
The present invention will be described in detail below.
First, details of a halogen oxoacid salt represented by formula (I) will be described.
The halogen atom represented by X is preferably chlorine, bromine, or iodine, and more preferably, chlorine. The halogen oxoacid salt is preferably chlorite, bromate, or iodate, and most preferably, chlorite.
The alkali metal ion or alkaline-earth metal ion represented by M is preferably a potassium ion, sodium ion, magnesium ion, or calcium ion, and more preferably, a sodium ion.
Practical examples of a halogen oxoacid salt defined in the present invention are sodium chlorite, potassium chlorite, potassium iodate, and sodium bromate. However, the present invention is not limited to these examples.
The halogen oxoacid salt can be used in any one of silver halide grain emulsion preparing steps. The halogen oxoacid salt can be added once or can be added two or more times separately during the emulsion preparing steps. The halogen oxoacid salt preferably be added once or more times during the preparing process that is selected from during silver halide grain formation, after silver halide grain formation and before the start of a desilvering step, during the desilvering step, before the start of chemical ripening, and during the chemical ripening step. The halogen oxoacid salt is more preferably added at least once during the emulsion preparing process that is selected from during grain formation and before the start of chemical ripening, during the chemical ripening step, and after the completion of the chemical ripening. When a silver halide emulsion is to be reduction-sensitized by using a reducing agent as will be described later, the halogen oxoacid salt is preferably added. It is unpreferable to add the halogen oxoacid salt when a coating solution is prepared using a silver halide emulsion already chemically ripened after grain formation, because the effect of the present invention is impaired.
The concentration of the halogen oxoacid salt in a step in which it is used is preferably 1×10
−6
to 1×10
−3
mol, and more preferably, 5×10
−6
to 2×10
−4
mol per mol of silver halide.
Two or more types of the halogen oxoacid salts can be used together.
The halogen oxoacid salt is preferably added in the form of an aqueous solution or aqueous gelatin solution. When the halogen oxoacid salt is used as an aqueous solution, the pH is preferably adjusted by a known buffering agent. The pH is preferably 6 to 10, and more preferably, 7 to 9.5.
Silver halide emulsion of the present invention will be described in detail below.
Silver halide grains contained in the emulsion of the present invention have regular crystals such as cubic, octahedral, or tetradecahedral crystals, irregular crystals such as spherical or tabular crystals, crystals having crystal defects such as twin planes, or
Funakubo Takeshi
Morimoto Kiyoshi
Sakurazawa Mamoru
Sasaki Hirotomo
Ashton Rosemary
Walke Amanda C.
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