Photographic silver halide emulsion

Details Photographic silver halide emulsion Photographic silver halide emulsion

2003-01-27

2004-01-13

Le, Hoa Van (Department: 1752)

Radiation imagery chemistry: process, composition, or product th

Nonradiation sensitive image processing compositions or...

Developer

Reexamination Certificate

active

06677109

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to a silver halide photographic material, a photographic material containing thin tabular grains, and a method for producing the same.
BACKGROUND OF THE INVENTION
Silver halide grains are generally produced by the reaction of a silver salt aqueous solution and a halide salt aqueous solution in a colloidal aqueous solution in a reaction solution. That is, a single jet method of pouring a protective colloid represented by gelatin and a halide salt aqueous solution into a reaction vessel and adding a silver salt aqueous solution thereto with stirring the above aqueous solution, and a double jet method of pouring a gelatin aqueous solution into a reaction vessel, and adding a halide salt aqueous solution and a silver salt aqueous solution thereto are known. Comparing both methods, silver halide grains having narrow grain size distribution can be obtained by a double jet method, and the halide composition can be changed freely with the growth of the grains.
Further, it is known that the growing speed of silver halide-grains is largely influenced by the concentration of silver ions (halide ions) in a reaction vessel, the concentration of a silver halide solvent, the distance between grains and the grain size. In particular, the uniformity in concentration of silver ions or halide ions produced of a silver salt aqueous solution and a halide salt aqueous solution added to a reaction vessel differs in growing speed by each concentration, which results in the formation of a heterogeneous silver halide emulsion. For preventing this ununiformity, it is necessary to make the reaction of a silver salt aqueous solution and a halide salt aqueous solution supplied into a colloidal aqueous solution by rapid and uniform mixture so as to make the concentration of silver ions or halide ions in a reaction vessel uniform. However, it has been difficult to produce homogeneous silver halide grains by prior art techniques of the addition of a halide salt aqueous solution or a silver salt aqueous solution, since an area where the concentration of halide ions or silver ions is high is brought about in the vicinity of the place of addition of each reaction solution.
For resolving the uniform distributions of concentrations of silver ions and halide ions as above, a trial for growing silver halide grains has been made by providing a reaction vessel with a mixer separately, and supplying a silver salt aqueous solution and a halide salt aqueous solution to the mixer, and mixing the aqueous solutions rapidly. For example, there are disclosed in JP-A-53-37414 (the term “JP-A” as used herein means an “unexamined published Japanese patent application”) and JP-B-48-21045 (the term “JP-B” as used herein means an “examined Japanese patent publication”) a method of circulating a protective colloid aqueous solution (containing silver halide grains) in a reaction vessel from the bottom of the reaction vessel by a pump, providing the reaction vessel with a mixer midway in the circulating system, supplying a silver salt aqueous solution and a halide salt aqueous solution to the mixer, and mixing the aqueous solutions rapidly in the mixer, to thereby grow silver halide grains, and an apparatus used for that purpose. A method of circulating a protective colloid aqueous solution (containing silver halide grains) in a reaction vessel from the bottom of the reaction vessel by a pump, and pouring a halide salt aqueous solution and a silver salt aqueous solution by a pump midway in the circulating system is disclosed in U.S. Pat. No. 3,897,935. A method of circulating a protective colloid aqueous solution in a reaction vessel (containing silver halide grains) by a pump from the reaction vessel, pouring a halogenated alkali metal salt aqueous solution, diffusing the aqueous solution until it becomes homogeneous, and thereafter pouring a silver salt aqueous solution to the system and mixing them, to thereby form silver halide grains, and an apparatus used for that purpose are disclosed in JP-A-53-47397. It is certainly possible to independently change the flow of an aqueous solution in a reaction vessel and the stirring efficiency of a mixer in a circulating system according to these methods, therefore, grains can be grown on more uniform condition of concentration distribution. However, silver halide crystal fed from a reaction vessel with a protective colloid aqueous solution is eventually subjected to uniform and rapid growth at the inlets of a halide salt aqueous solution and a silver salt aqueous solution. Therefore, it is theoretically impossible to get rid of the concentration distribution in the vicinity of a mixing zone or the inlets of aqueous solutions, thus the object of growing silver halide grains uniformly cannot be achieved.
As one means for solving this problem fundamentally, a method of growing silver halide grains in a reaction vessel by adding fine grains which have been formed in advance in an external mixer to the reaction vessel is disclosed in U.S. Pat. Nos. 5,035,991, 5,270,159, 5,250,403, EP 274852, EP 523842 and Japanese Patent 2684397. According to this method,a silver and a halogen seed are fed as silver halide fine grains. Since the silver halide fine grains are spread all over the reaction vessel, and then dissolved and silver ions and halide ions are supplied at the same time, the distributions of concentrations of silver ions and halide ions are largely improved (become uniform).
However, when fine grains supplied from an external mixer are large in size, time is taken to dissolve the fine grains, which causes inefficiency such that grain formation is prolonged. It is disclosed in Japanese Patent Nos. 2,008,051 and 2,060,301 that low temperature formation is effective to form small size silver halide grains. However, gelatin which is the most ordinary dispersion medium coagulates at low temperature, and it is very difficult to form grains at 30° C. or lower. In particular, continuous nucleation is difficult in a closed type external mixer due to the generation of clogging. For the solution of this problem, JP-B-7-111550 discloses that silver halide grains can be formed even at temperature as low as 15° C. or lower without being accompanied by coagulation of a reaction solution by using gelatin or synthetic protective colloid having a lowered molecular weight.
As described above, in the techniques of growing silver halide grains by feeding fine grains, the miniaturization of the fine grains for supply has been contrived, but the size distribution of the fine grains to be supplied is far from satisfaction, and the size of the fine grains disclosed in JP-B-7-111550 is 20 nm or greater. Therefore, finer grains have been earnestly desired.
On the other hand, tabular silver halide grains are ordinarily used in photographic materials, in particular, photographic materials for photographing. The reason is mainly because tabular silver halide grains have a great surface area/volume ratio and this is advantageous to spectral sensitization. That is, silver halide having light absorption sensitivity only in a blue region is generally spectrally sensitized by adsorbing a sensitizing dye onto the surface of a grain, and tabular grains having a great surface area/volume ratio have a large dye adsorption amount per a grain, thus light absorption amount increases and high sensitivity can be achieved. Therefore, studies of making a surface area/volume ratio greater have been advanced. In particular, as an effective means to form a thin tabular grain, a method of restricting the growth of a tabular grain in the thickness direction by making use of a crystal phase-controlling agent is known. The examples of these methods are disclosed in U.S. Pat. Nos. 5,411,853, 5,418,125 and JP-A-10-104769, but a crystal phase-controlling agent is not preferred, since it is competitive with the adsorption of a sensitizing dye. The techniques of forming a thin tabular grain without using a crystal phase-controlling agent is disclosed in U.S. Pat. No. 4,713,320 and JP-A-11-108536

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