Radiation imagery chemistry: process – composition – or product th – Radiation sensitive product – Silver compound sensitizer containing
Reexamination Certificate
2003-03-27
2004-03-30
Le, Hoa Van (Department: 1752)
Radiation imagery chemistry: process, composition, or product th
Radiation sensitive product
Silver compound sensitizer containing
Reexamination Certificate
active
06713244
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a silver halide emulsion comprising high silver iodide and a photographic light-sensitive material using the emulsion.
BACKGROUND OF THE INVENTION
Silver iodide is a directive transition type and as compared with silver chloride and silver bromide which are an indirect transition type, this silver halide crystal has a large light absorption coefficient in the blue exposure region but also has a high recombination probability and therefore, high sensitization thereof is difficult. Because of this reason, a grain having a high silver iodide content of 90 mol % or more or a silver halide emulsion containing a region having a high silver iodide content is scarcely used in a photographic light-sensitive material, despite large light absorption in the blue region.
SUMMARY OF THE INVENTION
An object of the present invention is to attain high sensitization of a high silver iodide-containing silver halide emulsion which has large light absorption but is difficult of high sensitization.
(1) A silver halide emulsion comprising a silver halide grain having a high silver iodide-containing phase, the surface of the silver halide grain being adsorbed with a substance capable of reducing by 50% or more the light emission intensity at 460 nm attributable to the high silver iodide-containing phase at 77° K.
(2) The silver halide emulsion as described in (1), wherein the grain surface is adsorbed with an adsorbing substance capable of reducing by 70% or more the light emission intensity at 460 nm.
(3) The silver halide emulsion as described in (1) or (2), wherein a silver iodide content of the high silver iodide-containing phase is 93 mol % or more.
(4) The silver halide emulsion as described in any one of (1) to (3), wherein the silver halide grain comprises a hexacyano metal complex.
(5) A silver halide photographic light-sensitive material comprising the silver halide emulsion described in any one of (1) to (4).
(6) A heat-developable photographic light-sensitive material comprising the silver halide emulsion described in any one of (1) to (4).
DETAILED DESCRIPTION OF THE INVENTION
The present invention is described in detail below.
The high iodide silver halide emulsion of the present invention is described below.
The light-sensitive silver halide for use in the present invention may have a halogen composition of silver iodobromide, silver iodochlorobromide or silver iodide. Among these, silver iodide and silver iodobromide are preferred. However, if a region having a silver iodide content of 90 mol % or more (high silver iodide-containing phase, hereinafter also called a high silver iodide phase) is not present in the grain, the effect of the present invention cannot be satisfactorily obtained. The high silver iodide phase preferably occupies at least 10 mol % or more, more preferably 60 mol % or more, based on the silver halide in the grain as a whole. The silver iodide content of the high silver iodide phase is preferably from 93 to 100 mol %. The halogen composition distribution in the grain may be uniform (namely, the grain as a whole is a high silver iodide phase and this is called a high silver iodide grain), or the halogen composition may be changed stepwise or continuously. Also, a silver halide grain having a core/shell structure is preferably used. The structure of the core/shell grain is preferably a 2- to 5-ply structure, more preferably a 2- to 3-ply structure.
The size of the high silver iodide grain or high silver iodide phase is preferably small or thin so as to bring out the effect of the present invention and specifically, the size is preferably 0.20 &mgr;m or less, more preferably from 0.01 to 0.15 &mgr;m, still more preferably from 0.01 to 0.05 &mgr;m. The size of the grain as used herein means a diameter of a circular image having the same area as the projected area of a silver halide grain (in the case of a tabular grin, the projected area of the main plane). The size of the high silver iodide phase means a thickness of the platy phase when the high silver iodide phase is formed on a tabular grin, or a thickness of the shell when the high silver iodide phase is formed on a cubic grain, an octahedral grain, a tetradecahedral grain or the like.
The light emission at 460 nm of the high silver iodide phase at 77° K of the present invention is described below.
The 77° K can be specifically realized by dipping the emulsion in liquid nitrogen. The light emission may be measured using a direct transition absorption band of high silver iodide at 300 to 400 nm by a fluorescent measuring apparatus, however, in the present invention, this is defined as the light emission when light is excited as monochromatic light of 355 nm. More specifically, a light emission intensity at 460 nm with excited light of 355 nm is detected using a spectral fluorescence photometer Model 850 manufactured by Hitachi, Ltd., where only a monochromatizing filter peculiar to the apparatus is equipped in the excited light side, a band pass filter of transmitting light at 400 nm or more is equipped in the fluorescence detection side, and the light emission intensity in the wavelength range from 400 to 600 nm is measured at a sweeping rate of 60 nm/min. The decrease of the light emission quantity sometimes depends on the quantity of excited light absorbed. Accordingly, the light emission quantity used in the present invention is defined as a light emission quantity in the case of exciting a high silver iodide emulsion corresponding to 1.5 g/m
2
in terms of silver under the above-described conditions with a decrease percentage occurred when fluorescence intensity is measured in the range from 400 to 600 nm at a sweeping rate of 60 nm/sec using the above-described apparatus.
The sample must be carefully prevented from being irradiated with light until the measurement of fluorescence is started.
The compound capable of decreasing the light emission intensity for use in the present invention is described below.
Specific examples of the compound capable of decreasing the light emission intensity for use in the present invention include those described below, however, the present invention is not limited thereto. The important matter is that the compound can reduce the light emission intensity to 50% or less. Depending on the high iodide silver halide emulsion selected, the light emission intensity may not decrease to 50% or less. For example, unless the amount of the compound adsorbed to a grain is sufficiently large, the light emission intensity cannot be decreased, however, as is well known, the amount adsorbed is affected by the combination use with other photographically useful compounds and by the shape and composition of grain and therefore, even if the compound is decided, this does not always lead to the effect of the present invention. Furthermore, as described above with respect to the preferred grain size, if the grain size is large, the emulsion of the present invention is difficult to prepare. In order to sensitize the grain to a sufficiently high level of photographic light sensitivity, it is important to decrease the light emission intensity at 77° K to 50% or less and for more enhancing the preferred effect, to 70% or less. As the light emission intensity more decreases, a higher effect is obtained.
[Specific Examples of Preferred Compounds]
1) An FED sensitizer (fragmentable electron donating sensitizer) which generates two electrons with one photon is preferably contained. Preferred examples of the FED sensitizer include the compounds described in U.S. Pat. Nos. 5,747,235, 5,747,236, 6,054,260 and 5,994,051 and JP-A-2002-287293. As for the step of adding the FED sensitizer, any step in the process of producing a light-sensitive emulsion from the crystal growth until the preparation step immediately before coating is preferably used. The amount added varies depending on various conditions but is, as a guide, from 10
−5
to 10
−1
mol, preferably from 10
−4
to 5×10
−2
mol, per mol of silver halide.
2
Fuji Photo Film Co. , Ltd.
Le Hoa Van
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