JPH06214329A - Manufacture of silver halide particles - Google Patents

Abstract

PURPOSE: To improve a method for forming a small-grain emulsion having a uniform grain size distribution. CONSTITUTION: An aq. soln. contg. a water-soluble halide, a water-soluble silver salt and a protective colloid is prepared in a reactor, silver halide grains are formed by the reaction between the halide and the silver salt in the reactor, and both the nucleation and crystal growth occur in the reactor in this production method. Most of the protective colloid is the modified mammal gelatins having 5,000-30,000 average mol.wt. range.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a method for producing silver halide grains and a method for preparing a photographic emulsion.

[0002]

BACKGROUND OF THE INVENTION The formation of silver halide grains has two main steps. That is, (a) nucleation step and (b) crystal growth step. The nucleation step (a) is a step in which new crystals are formed and the number of crystals rapidly increases. The crystal growth step is a step in which a new layer is added to an existing crystal. Nucleation is rapid and generally occurs within 1 minute.
Crystal growth is relatively slow, typically taking 20-60 minutes.

In the formation of photographic emulsions silver halide grains are precipitated in the presence of a protective colloid, gelatin. Since conventional gelatin solutions exhibit sol-gel properties,
Generally, precipitation of silver halide emulsions using gelatin as a peptizer is limited to temperatures above 35 ° C.

Research Disclosure
No. According to 28453 (December 1987), a solution of fish gelatin remains liquid even at temperatures up to 10 ° C, and it is possible to precipitate silver halide at a temperature lower than usual. However, fish gelatin may contain high concentrations of sulfur-containing impurities and is generally not recommended for precipitation of silver halide emulsions.

EP-A-374853 discloses that a nucleation step (a) is carried out by carrying out the nucleation step (a) in a separate mixer outside the reactor in which the crystal growth step (b) is carried out. It describes a method for producing silver halide grains in which the crystal growth step (b) is separately performed. The purpose of this described method is to produce silver halide crystal grains which exhibit a homogeneous halide composition in each crystal and no halide distribution between grains. The nucleation step in this method is carried out at a lowered temperature in the presence of low molecular weight gelatin obtained from ordinary gelatin. However, the use of low molecular weight gelatin in this method is limited to step (a) in the mixer and not to step (b) in the main reactor.

[0006]

There is a need to improve the method of forming small grain emulsions having a uniform grain size distribution.

[0007]

According to the present invention, an aqueous solution containing a water-soluble halide, a water-soluble silver salt and a protective colloid is prepared in a reactor, and the halide and the solution are prepared in the reactor. A method for producing silver halide grains in which silver halide grains are formed by reaction with a silver salt, and both nucleation and crystal growth occur in the reactor, and most of the protective colloid has an average molecular weight of Range is 5,000 to 30,
There is provided a method of manufacture characterized in that it is a modified mammalian gelatin of 000 Daltons.

Furthermore, according to the present invention, an aqueous solution containing a water-soluble halide, a water-soluble silver salt and a protective colloid is prepared in a reactor, and the halide and the silver salt are prepared in the reactor. A method of making a photographic emulsion in which the reaction results in the formation of silver halide grains, both nucleation and crystal growth occurring in the reactor, most of the protective colloid comprising:
A process for the preparation is provided which is a modified mammalian gelatin having an average molecular weight range of 5,000 to 30,000 daltons.

Silver halide grains are produced by reacting an aqueous silver salt solution with an aqueous halide solution in an aqueous colloid solution in a reactor. This can be done in any suitable way. Possible modes of operation include:
The single jet method and the double jet method are included. In the single jet method, an aqueous solution containing a colloid and a halide is placed in a reactor, and an aqueous silver salt solution is added with stirring for an appropriate time. In the double jet method (which is the preferred method), an aqueous colloid solution is placed in a reactor, and an aqueous halide solution and an aqueous silver salt solution are added to the solution in the reactor.

Denatured mammalian gelatin is about 5,
In the range of 000 to 30,000, preferably about 10,000
The average molecular weight in the range of 0 to 20,000 is shown. Such modified gelatin can be obtained by various methods and can be obtained by treating an aqueous solution of ordinary gelatin having an average molecular weight of generally about 100,000 with a gelatinolytic enzyme such as trypsin. Alternatively, acid is used to heat in a low pH, eg in the range pH = 1 to 3, or base is used to increase the pH, eg pH = 1.
Gelatin may be hydrolyzed by heating in the range of 0 to 12.

Suitably the process is carried out at temperatures below 35 ° C., preferably in the temperature range 5 to 35 ° C. Above all, ambient temperature, ie a temperature range of about 18 to about 20 ° C., is very suitable for carrying out the process. It is preferred to avoid heating the reactor. The treatment temperature is within a narrow range, i.e. within 0.5 [deg.] C., especially between 0.25 and
It is preferable to control within the range of 0.3 ° C. The halides and silver salts are preferably those which can be used to deposit silver chloride, silver bromide, silver bromoiodide or silver chlorobromide.
Particularly preferred as the halide is sodium chloride, and particularly preferred as the silver salt is silver nitrate. When the halide and silver salt are fed to the reactor by the double jet method, it is customary to feed them at the same or close rates, the appropriate rate depending to some extent on the scale of the processing operation. During the treatment, it is preferable to control the vAg of the solution so that it does not fluctuate significantly. By changing the processing conditions, silver halide grains and emulsions having various characteristics can be obtained. Among the emulsions that can be obtained are cubic emulsion chloride emulsions with edge lengths of about 0.05 to about 0.2 microns.

[0012]

The present invention is further described in the following examples.

Example 1 2,000 ml of an 8% solution of acid-hydrolyzed gelatin (molecular weight 20,000 dalton) was placed in a reaction kettle (reactor),
Then, the whole volume was adjusted to 4.25 liters using deionized water. The temperature was lowered to 20 ° C. and the vAg was adjusted to +120 mV with sodium chloride solution. Then, a cooled 3.0 molar solution of silver nitrate and sodium chloride was added over 20 minutes. During this time, vAg is +1 from beginning to end
While controlling to 20 mV, injection speed is 20 ml
/ Min to a final rate of 180 ml / min increasing linearly. At this point, a sample was taken and observed with an electron microscope. A cubic morphology emulsion with an edge length of 0.12 microns was obtained.

Example 2 2,000 ml of an 8% solution of acid-hydrolyzed gelatin (molecular weight 20,000 dalton) was placed in a reaction kettle (reactor),
Then, the whole volume was adjusted to 4.0 liters using deionized water. The temperature was lowered to 20 ° C. and the vAg was adjusted to +120 mV with sodium chloride solution. Then, a cooled 3.0 molar solution of silver nitrate and sodium chloride was added to the kettle at 200 ml / min over 5 minutes while controlling the vAg at +120 mV all the time. After completion of the pouring, the emulsion sample was sampled and observed with an electron microscope. A cubic morphology emulsion with an edge length of 0.055 micron was obtained.

Other embodiments of the present invention are described below.

The average molecular weight of mammalian gelatin is 10,0.
A method characterized in that it is in the range of 00 to 20,000 Daltons.

Mammalian gelatin is treated with normal gelatin by trypsin, a gelatin-degrading enzyme, or p
A process characterized in that it was obtained by heating ordinary gelatin at a low pH of H = 1-3 or a high pH of pH = 10-12.

An aqueous solution containing a water-soluble halide, a water-soluble silver salt and a protective colloid is prepared in a reactor, and the reaction of the halide and the silver salt in the reactor produces silver halide grains. A method of making a photographic emulsion that is formed, where both nucleation and crystal growth occur in the reactor,
Most of the protective colloids have an average molecular weight range of 5,000.
The above-mentioned production method, which is a modified mammalian gelatin of 0 to 30,000 daltons.

The molecular weight of mammalian gelatin is 10,000.
A method in the range of ˜20,000 Daltons.

A process characterized in that mammalian gelatin is obtained by treating ordinary gelatin with a gelatinolytic enzyme.

The method wherein the gelatinolytic enzyme is trypsin.

Mammalian gelatin was added at a low p of pH = 1 to 3.
H or a method obtained by heating ordinary gelatin at a high pH of pH = 10-12.

A process characterized in that it is carried out in the temperature range 5 to 35 ° C.

A method characterized in that the treatment temperature is controlled within the range of 0.25 to 0.3 ° C.

[0025]

The advantages of the present invention include, for example, the precipitation of emulsion having a small grain size and the small dispersion of grain size distribution.
Mostly comes from the reduced solubility of silver halides found at low temperatures. Nucleation at low temperatures by the method of the present invention can result in emulsions exhibiting morphology and / or size not otherwise obtainable. It is also possible to obtain a core shell or banded structure with more discrete separation between layers of different composition.

Claims (1)

[Claims] 1. A water-soluble halide and a water-soluble silver salt,
An aqueous solution containing a protective colloid is prepared in a reactor, and silver halide grains are formed in the reactor by the reaction of the halide and the silver salt, and both nucleation and crystal growth are performed in the reactor. In the method for producing silver halide grains therein, most of said protective colloid is modified mammalian gelatin having an average molecular weight range of 5,000 to 30,000 daltons. .