Loading patent…
AssigneeFuji Photo Film Co., Ltd.
InventorsShinji Ikari, Mikio Ihama, Haruyasu Nakatsugawa, Tetsuro Mitsui, Kazutaka Takahashi
Estimating the term…
A process for producing a photosensitive silver halide emulsion is disclosed, comprising silver halide grains and a dispersion medium, said process comprising steps of adding a water-soluble silver solution, an aqueous alkali halide solution and an aqueous solution of gelatin having a molecular weight of 5,000 to 30,000 or less to a mixing vessel different from a reactor for the production of emulsion to prepare silver halide fine grains, adding the silver halide fine grains to the reactor for the production of emulsion to grow silver halide grains, and ultrafiltering the silver halide grains during the addition of silver halide fine grains, wherein 50% or more of the entire projected area of said emulsion grains is occupied by silver halide tabular grains having an aspect ratio of 10 or more and a thickness of 0.15 μm or less.
A process for producing a photosensitive silver halide emulsion comprising silver halide grains and a dispersion medium, said process comprising steps of adding a water-soluble silver solution, an aqueous alkali halide solution and an aqueous solution of gelatin having a molecular weight of 5,000 to 30,000 or less to a mixing vessel different from a reactor for the production of emulsion to prepare silver halide fine grains, adding the silver halide fine grains to the reactor for the production of emulsion to grow silver halide grains, and ultrafiltering the silver halide grains during the addition of silver halide fine grains, wherein 50% or more of the entire projected area of said emulsion grains is occupied by silver halide tabular grains having an aspect ratio of 10 or more and a thickness of 0.15 μm or less.
A process for producing a silver halide emulsion through nucleation, ripening and growth steps, said silver halide emulsion being a photosensitive silver halide emulsion comprising silver halide grains and a dispersion medium, wherein 50% or more of the entire projected area of grains is occupied by silver halide tabular grains having an aspect retio of 10 or more, the total silver concentration in the silver halide emulsion at the start of ripening step is from 0.0015 to 0.15 mass %, and ultrafiltration is used in a part of the emulsion preparation steps.
Dependencies are inferred from the claim text.
Drawings are temporarily unavailable. Open the PDF at USPTO
From the US filing history. Foreign family members aren’t listed.
Backward citations are indexed for grants only.
Silver halide emulsions; Preparation thereof; Physical treatment thereof; Incorporation of additives therein: tabular grain emulsions
Products made by additive manufacturing
With macromolecular additives; with layer-forming substances: proteins, e.g. gelatine derivatives; Hydrolysis or extraction products of proteins
Tabular grain emulsions: aspect ratio of tabular grains in general; High aspect ratio; Intermediate aspect ratio; Low aspect ratio
Term end not estimated
The present invention relates to a production process of a silver halide emulsion, more specifically, the present invention relates to a production process of a thinner tabular grain emulsion.
Tabular silver halide grains having a large light-receiving area are widely used as a photosensitive element. For increasing the light-receiving efficiency of the tabular silver halide grain, the smaller grain thickness is more preferred. The preparation of silver halide grains comprises two main steps of nucleation for forming grains working out to nuclei for growth, and grain growth. For the nucleation, a method of directly adding a water-soluble silver solution and an aqueous alkali halide solution to a reactor having a stirring unit of various types is used. However, the grains as nuclei in the course of growth pass through a high supersaturation region in the vicinity of a port for adding silver ion or halide ion and this causes a harmful effect that the tabular grains are increased in thickness. To overcome this problem, JP-A-10-43570 (the term “JP-A” as used herein means an “unexamined published Japanese patent application”) and JP-A-2000-338620 disclose a method of adding a water-soluble silver solution, an aqueous alkali halide solution and an aqueous dispersion medium solution to an outside mixing vessel different from the reactor of undertaking the growth, thereby continuously forming silver halide fine grains, adding the silver halide fine grains to the reactor, and growing the grains as nuclei while dissolving the silver halide fine grains. However, the methods disclosed cannot produce silver halide fine grains having a narrow distribution and are not satisfied for obtaining thinner tabular grains.
On the other hand, in the production of silver halide grains of a silver halide emulsion, the total of the amount of water containing a dispersion medium necessary for stirring, the amount of water-soluble silver solution, the amount of aqueous alkali halide solution and the amount of additives is designed to be lower than the maximum liquid amount of a reactor. In the case of increasing the production amount and elevating the productivity, the production amount per once operation can be increased by increasing the concentrations of water-soluble silver salt and aqueous alkali halide solution occupying the majority of the liquid amount. However, the concentrations of water-soluble silver solution and halide ion are appropriately determined to obtain intended silver halide grains and if these concentrations are increased, not only the grain size, grain shape and grain size distribution are changed but also the photographic properties such as fog, sensitivity and gradation are adversely affected. In order to eliminate these adverse effects, it is necessary to remove the added aqueous solutions together with unnecessary salts while not changing the concentrations of water-soluble silver solution and aqueous alkali halide solution added. For this purpose, a method of using dehydrating and desalting apparatuses during the growth is disclosed in U.S. Pat. Nos. 4,334,012 and 5,242,597, European Patents 795,455 and 843,206, JP-A-11-231449, JP-A-11-237703, JP-A-11-352618, JP-A-2000-56420, JP-A-2000-56421, JP-A-2000-66320, JP-A-2001-56518, JP-A-2001-59994 and JP-A-2001-100348. However, according to these methods, a water-soluble silver solution and an aqueous alkali halide solution are directly added to a reactor and thick tabular grains are disadvantageously produced.
FIG. 1 is a cross-sectional view schematically showing the apparatus according to the practical embodiment of the present invention.
FIG. 2 is a cross-sectional view schematically showing the production process in the mixing vessel according to the practical embodiment of the present invention.
FIG. 3 is a perspective view schematically showing the structure of magnetic coupling used in the stirring unit of the mixing vessel according to the practical embodiment of the present invention.
In the present invention, the silver halide tabular grain means a gain where one or more twin plane is crystallographically present. This twin plane is present in parallel to the face (main plane) having a maximum area of the grain. In the present invention, the tabular grain is preferably a grain having one or two sheet of this twin plane.
The diameter and thickness of the grain of the present invention can be determined by an electron microphotograph of grains according to the method described in U.S. Pat. No. 4,434,226. More specifically, the thickness of the grain can be easily determined by depositing a metal from the oblique direction of a grain together with a latex for reference, measuring the length of the shadow thereof on an electron microphotograph, and calculating the thickness with reference to the length of the shadow of latex. The silver halide grain of the present invention satisfies the condition that in the entire projected area of grains observed through an electron microscope, from 50 to 100% have an average aspect (a ratio of the diameter of the main plane of a grain to the thickness of the grain) of 10 or more, preferably from 20 to 200. The thickness of the silver halide grain is preferably from 0.01 to 0.15 μm, more preferably 0.1 μm or less. The average aspect ratio can be determined by averaging the aspect ratios of all tabular grains but in a simple method, the average aspect ratio can also be determined as a ratio of the average diameter to the average thickness of all tabular grains. The diameter of the main plane is preferably from 1 to 10 μm, more preferably from 3.0 to 10 μm.
The emulsion of the present invention is preferably monodisperse. The coefficient of variation in the equivalent-circle diameter of the projected area of all silver halide grains is preferably 25% or less, more preferably 20% or less. The coefficient of variation in the equivalent-circle diameter as used herein means a value obtained by dividing the standard deviation of the distribution of equivalent circle diameters of individual silver halide grains by the average equivalent-circle diameter.