Radiation imagery chemistry: process – composition – or product th – Radiation sensitive product – Silver compound sensitizer containing
Reexamination Certificate
2001-04-05
2003-11-11
Baxter, Janet (Department: 1752)
Radiation imagery chemistry: process, composition, or product th
Radiation sensitive product
Silver compound sensitizer containing
C430S567000
Reexamination Certificate
active
06645713
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to method of manufacturing silver halide emulsions and apparatus thereof for producing photographic silver halide emulsions comprising silver halide particles.
2. Description of Related Art
There have been various types of method to form silver halide particles used as photographic photosensitive material.
Those particles are commonly formed by the reaction of silver ions and halide ions in a sufficiently great reactor equipped with a stirrer having a stirring blade or blades. In such a case, efficiency of stirring in the reactor is important, and therefore various types of stirring are proposed as described, for example, in Japanese Patent Application Laid-Open Nos. 7-219092, 8-171156 and 4-283741, Japanese Patent Publication Nos. 8-22739 and 55-10545, and U.S. Pat. No. 3,782,954.
In order to form silver halide particles (for example, particles with a high monodispersity, particles with a high ratio of plates in case of planar particles etc.) preferable as photographic silver halide emulsions, one of the functions required on these stirrers is to mix homogeneously and instantaneously in a microscopic scale. To achieve homogeneous mixing, a method is often adopted of diluting aqueous silver salt solution and aqueous halide salt solution to be added with a liquid already present in the reactor before both salts react with each other. However, the emulsion of silver halide particles thus obtained is commonly not preferable as photographic photosensitive material, unless they are well diluted. For example, in the case where the solutions are added in the phase of nuclear formation to prepare planar particles, a higher ratio of nonparallel cubic twin and a higher polydispersity of planar particles are observed in growing particles, if stirring is not sufficient and/or the solutions have not been diluted well. This phenomenon can be verified by decreasing revolving speed using the stirrer which is described in Japanese Patent Publication No. 55-10545.
Furthermore, in the case where poor dilution occurs in the growing phase, new nuclei form near the inlet for addition and remain as solid without complete dissolution, so that particles formed in the growing phase are incorporated into the emulsion of silver halide particles obtained. Such a phenomenon is observed markedly in the particular case of growth at a high supersaturation.
The above discussion suggests that stirring is important and active use of the bulk solution for dilution may be preferred. However, since the bulk solution usually contains particles already formed, the problem of recirculation then arises wherein particles once formed circulates again near the entering solutions. If recirculation occurs in the phase of nuclear formation, recirculating nuclei prevents formation of new nuclei. Accordingly, in the case where an emulsion of smaller particles is to be prepared, for example, increased addition of the solutions for nuclear formation will not bring about corresponding increase in nuclear formation, indicating that recirculation exerts an adverse effect on formation of smaller particles. In addition, since a difference in particle size arises between nuclei grown by recirculation and those not grown, nuclear polydispersity due to recirculation makes it difficult to prepare an emulsion of monodispersed particles, indicating again that recirculation exerts an adverse effect.
A method of applying microparticles prepared preliminarily to the nuclear formation process or the nuclear growth process is available in order to solve these problems. In this method, aqueous silver salt solution, aqueous halide salt solution, and in many cases, aqueous solution of a dipersing agent as well are introduced into a reaction vessel of small volume, while microparticles are removed through the outlet in parallel and continuously. The microparticles obtained can be used for nuclear formation and/or nuclear growth.
This method has the advantage of achieving more easily increased formation of nuclei due to much less recirculation. It is desirable to minimize the size of produced nuclei in order to maximize the number of nuclei. However, more powerful stirring is required to attain satisfactory mixing because the stirrer used in this method cannot take advantage of the above-mentioned dilution effect caused by the bulk solution. In case of unsatisfactory stirring, for example, for preparing an emulsion of planar particles, increased production of undesirable non-planar particles is one of the problems. In the mixer, as described in Japanese Patent Application Laid-Open No. 6-507255, the ratio of non-planar particles increases, compared to a mixer used in the presence of circulating bulk solution. In addition, in the mixer, as described in Japanese Patent Application Laid-Open No. 8-332364, high speed stirring has difficulty in keeping the perimeter of the rotational axis sealed.
Silver halide microparticles may be also introduced into another reaction vessel containing silver halide seed particles to grow the seed particles. Silver halide microparticles can be formed using the stirrer described in Japanese Patent Application Laid-Open No. 10-43570, or Japanese Patent Application Laid-Open No. 1-183417, and they can be used for growing seed particles.
The stirrer, for example, described in Japanese Patent Application Laid-Open No. 10-43570, as shown in
FIG. 3
, comprises a stirring container
5
where a given number of inlets
1
,
2
and
3
are provided to introduce liquids to be mixed and an outlet
4
is also provided to remove the liquid produced after they are stirred, a pair of stirring blades
6
,
6
which are arranged at facing positions spaced apart in the stirring container
5
and driven to rotate in directions opposite to each other so as to control the stirred state of the liquid in the stirring container, and driving means
8
,
8
which arrange outer magnets
7
,
7
out of the stirring container, the magnets
7
,
7
being composed of magnetic couplings which are aligned close to the respective stirring blades
6
,
6
out of the walls of the stirring container and without a through axis, and drives the outer magnets
7
,
7
rotationally so as to revolve the stirring blades
6
,
6
.
Use of this method enables uniform mixed crystals or very thin planar particles to be prepared because a highly concentrated area of silver ions or halide ions is unlikely to exist, compared with the method of adding aqueous silver salt solution and aqueous halide salt solution. In this method, silver halide microparticles as source of seed particles are preferably dissolved rapidly, and for the purpose preferably have small diameters and no crystal defects such as twin.
In case of using silver halide microparticles for growing seed particles, aqueous silver salt solution and aqueous halide salt solution preferably have higher concentrations when they are added on formation of silver halide microparticles. However, as the concentrations of the solutions to be added increase, produced microparticles tends to have polydispersity due to no available dilution by the bulk solution, and when the microparticles are transferred into the vessel for growing seed crystals, larger particles or particles containing twin become undissolved to remain. These remaining microparticles interfere with spectral and chemical sensitizations of the emulsion of silver halide particles, and also cause unfavorable light scattering, indicating that such an emulsion of silver halide particles containing remaining microparticles of silver halide is not preferable as photographic photosensitive material.
Accordingly, obtaining an emulsion of silver halide microparticles with small mean size or an emulsion of silver Halide microparticles with monodispersity is important to obtain an emulsion of silver halide particles favorable as photographic photosensitive material.
As another method of forming silver halide particles which is different from the mixing means described above using stir
Fuji Photo Film Co. , Ltd.
Sughrue & Mion, PLLC
Walke Amanda C.
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