Radiation imagery chemistry: process – composition – or product th – Radiation sensitive product – Silver compound sensitizer containing
Reexamination Certificate
2000-03-24
2002-04-16
Baxter, Janet (Department: 1752)
Radiation imagery chemistry: process, composition, or product th
Radiation sensitive product
Silver compound sensitizer containing
C430S567000
Reexamination Certificate
active
06372420
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a method for producing a silver halide photographic emulsion.
BACKGROUND OF THE INVENTION
The production of silver halide photographic emulsions is usually carried out by adding silver ions and halide ions into reaction vessels equipped with stirrers. Nucleation occurs by initial addition, and crystal growth is performed by subsequent addition. Stirring methods include various methods, for example, as described in JP-A-7-219092 (the term “JP-A”, as used herein means an “unexamined published Japanese patent application”), JP-A-8-171156, JP-A-4-283741, JP-B-8-22739 (the term “JP-B” as used herein means an “examined Japanese patent publication”) and U.S. Pat. No. 3,782,954. However, when nucleation is conducted by such methods, nucleation and nuclear growth occur in parallel even by any of these stirring methods, because solutions circulate in reaction vessels. It is therefore difficult to form monodisperse nuclei.
In the field of silver halide photography, tabular silver halide grains having large light-receiving areas have been widely used as light-sensitive elements. For increasing the light-receiving efficiency, thin tabular silver halide grains are preferred. However, according to the methods as described above, the tabular silver halide grains in the course of growth pass through a high supersaturation region in the vicinity of an opening for adding silver ions or halide ions to cause the harmful effect that the tabular grains are increased in thickness.
For solving these problems, there is a method of providing an external mixer in addition to the reaction vessel, forming fine silver halide grains with the external mixer, and using them in the nucleation stage or the growth stage. According to this method, an aqueous solution of a silver salt, an aqueous solution of a halide and an aqueous solution of a dispersing medium are added to the external mixer to continuously form fine grains. The fine grains can be used for nucleation and/or growth. In such a method, it is desired that the mixer can completely mix the added solutions for as short a time as possible. It is unfavorable that a long time is taken for mixing, or that the added solutions circulate in the external mixer.
As the reaction vessels, various type ones can be used. For example, in U.S. Pat. No. 5,250,403 and JP-A-10-43570, mixing is performed with an agitating blade in a small-volume mixer. However, in such a method, the added solutions circulate in the mixer.
In JP-A-4-139440 and PCT International Publication JP-A-6-507255, mixing is performed without mechanical stirring, so that there is no circulation of the added solutions. In this method, however, the mixing power is insufficient because of absence of stirring.
For maintaining the sufficient mixing power without mechanical stirring, there is a method of turning the added solutions into jet streams, and conducting mixing by their kinetic energy. JP-A-8-334848 discloses a method for producing a silver halide photographic emulsion utilizing kinetic energy of such jet streams. However, the patent is directed to a method for producing a silver halide photographic emulsion by the single jet process, and utterly different from a method using the external mixer. Further, the kinetic energy used herein is insufficient for mixing the whole contents of the reaction vessel, so that mechanical stirring is used in combination.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide a method for producing a silver halide photographic emulsion, which can continuously form small-sized and monodisperse silver halide grains. Another object of the present invention is to obtain monodisperse silver halide grains by using the above silver halide photographic emulsion as nuclei. A further object of the present invention is to make it possible to form thin tabular silver halide grains by using the above silver halide photographic emulsion for crystal growth.
The objects of the present invention are attained by the following:
(1) A method for producing a silver halide photographic emulsion comprising turning at least one of an aqueous solution of a silver salt and an aqueous solution of a halide into a linear jet stream having a high flow rate, and mixing the two kinds of solutions with each other for a short time, thereby continuously forming silver halide grains;
(2) A method for producing a silver halide photographic emulsion comprising turning at least one of an aqueous solution of a silver salt and an aqueous solution of a halide into a linear jet stream having a high flow rate, and mixing the two kinds of solutions with each other without their circulation, thereby continuously forming silver halide grains;
(3) A method for producing a silver halide photographic emulsion comprising turning at least one of an aqueous solution of a silver salt and an aqueous solution of a halide into a linear jet stream having a high flow rate, and mixing the two kinds of solutions with each other without mechanical stirring, thereby continuously forming silver halide grains;
(4) A method for producing a silver halide photographic emulsion comprising turning at least one of an aqueous solution of a silver salt and an aqueous solution of a halide into a linear jet stream having a high flow rate, and passing the two kinds of solutions through a capillary parallel to the jet stream and having recesses on the inside thereof to mix them with each other for a short time, thereby continuously forming silver halide grains;
(5) A method for producing a silver halide photographic emulsion comprising turning at least one of an aqueous solution of a silver salt and an aqueous solution of a halide into a linear jet stream having a high flow rate, and passing the two kinds of solutions through a capillary parallel to the jet stream and having recesses on the inside thereof to mix them with each other without their circulation, thereby continuously forming silver halide grains; and
(6) A method for producing a silver halide photographic emulsion comprising turning at least one of an aqueous solution of a silver salt and an aqueous solution of a halide into a linear jet stream having a high flow rate, and passing the two kinds of solutions through a capillary parallel to the jet stream and having recesses on the inside thereof to mix them with each other without mechanical stirring, thereby continuously forming silver halide grains.
DETAILED DESCRIPTION OF THE INVENTION
In the invention, an aqueous solution of silver nitrate is usually used as the aqueous solution of the silver salt. When the silver halide grains obtained in the method of the present invention are used as nuclei, the concentration of the aqueous solution is preferably 4 mol/liter or less, more preferably 1 mol/liter or less, and most preferably 0.2 mol/liter or less. When the grains are used for crystal growth, the use of an aqueous solution having a high concentration is preferred from the viewpoint of productivity. The concentration thereof is preferably from 0.5 mol/liter to 4 mol/liter, and more preferably 1.0 mol/liter or more. The temperature of the aqueous solution is preferably from 5° C. to 75° C.
The aqueous solutions of the halides usually used in the present invention include aqueous solutions of potassium bromide, sodium bromide, potassium chloride, sodium chloride, potassium iodide, sodium iodide and mixtures thereof. When the silver halide grains obtained in the method of the present invention are used as nuclei, the concentration of the aqueous solution is preferably 4 mol/liter or less, more preferably 1 mol/liter or less, and most preferably 0.2 mol/liter or less. When the grains are used for the crystal growth, the use of an aqueous solution having a high concentration is preferred from the view point of productivity. The concentration thereof is preferably from 0.5 mol/liter to 4 mol/liter, and more preferably 1.0 mol/liter or more. The temperature of the aqueous solution is preferably from 5° C. to 75° C.
It is preferred that at leas
Miki Masaaki
Saito Hirokazu
Baxter Janet
Birch & Stewart Kolasch & Birch, LLP
Walke Amanda C.
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