JPH0452451B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to a method for producing a silver halide photographic emulsion;
In particular, it relates to improvements in desalination methods and equipment. More specifically, in the flocculation method, it is possible to shorten the static settling time, significantly shortening the emulsion preparation time, and it is easy to redisperse the emulsion obtained after decantation. By stirring and mixing for a short time without causing any problems in the subsequent process, an emulsion with excellent photographic properties such as less fogging can be obtained, and furthermore, the emulsion to be prepared can be improved. The present invention relates to a method for producing a photographic emulsion and an apparatus therefor, which can greatly improve the yield. [Prior Art] The method for producing silver halide photographic emulsions is usually carried out by subjecting a water-soluble silver salt and a water-soluble halide to a metathesis reaction in a hydrophilic colloid such as an aqueous gelatin solution, thereby producing silver halide in the hydrophilic colloid. The practice is to form crystals in a dispersed manner, lower the temperature to complete physical ripening, and then remove excess salts, which are by-products of the metathesis reaction. One method for removing excess salts is the flocculation method, in which silver halide grains are coagulated and precipitated together with hydrophilic colloids by adding a flocculant to the emulsion that has undergone physical ripening, and separated from the mother liquor containing salts. It has been known. The flocculation method is now widely used because it has advantages such as better efficiency than the noodle method and continuous thin film method, which are known as other methods for removing salts. has been done. That is, the noodle method is a method in which unnecessary salts are removed using the principle of osmotic pressure in cold water under conditions that do not dissolve the noodles obtained by cooling, setting, and cutting a photosensitive emulsion. A method is known in which a thin film of gelled emulsion is continuously immersed in water and desalted to form a thin film of the emulsion on a rotating support, desalted in a water washing tank, and then peeled off and recovered. For example, the method described in Japanese Patent Publication No. 49-46255 can be mentioned. However, the former noodle method has drawbacks such as long desalination time, large installation space, large processing losses, and large amounts of washing water.On the other hand, the latter continuous thin film This method requires a large amount of washing water, has large scraping losses, large variations in salt removal rate, and has drawbacks such as a large gelatin/Agx value. In this respect, the flocculation method described above is a technology that does not have the drawbacks of the other two methods described above, and is, for example, US Pat. No. 2,614,928, US Pat.
British Patent No. 1005784, British Patent No. 1033189, British Patent No. 945334
No. 981251, Specifications, Special Publication No. 40-21020,
Publications No. 46-43429, JP-A No. 55-45066 and the same
Examples include the methods described in Publications No. 49-94319. However, these conventional flocculation methods still have the drawback of requiring a long static precipitation time and a long preparation time. Furthermore, when preparing emulsions continuously, it is necessary to add flocculants in precisely proportionate amounts, and if the basis weight of this precipitant is too large, the formation and size of emulsion flocs may become uneven. In some cases, the redispersibility of the resulting emulsion deteriorates, which may impede subsequent steps. Furthermore, silver halide was suspended in the supernatant of the mother liquor containing salts, reducing the yield, or depending on the type of flocculant used, had an adverse effect on photographic performance. As a technique for solving these drawbacks, methods described in, for example, Japanese Patent Publications No. 48-13057 and Japanese Patent Publication No. 50-10157 have been proposed. The former method is an invention in which a flocculant is added to a gelatin-containing solution before the end of physical ripening, and has some effect on improving the redispersibility and yield of the resulting emulsion and simplifying the basis weight of the precipitant. is demonstrated. On the other hand, the latter method is an invention that employs a centrifugal separation method, and is effective in saving washing water and shortening the process. However, even with these inventions, stability, photographic performance, etc. are not necessarily sufficient, and it cannot be said that all of the above-mentioned problems have been solved. [Object of the Invention] The present invention has been made to solve the above-mentioned problems, and it is possible to stably and reliably obtain an emulsion with excellent photographic performance, and to maintain excellent photographic performance for a long time. A first object of the present invention is to provide a method and apparatus for producing a silver halide photographic emulsion that can be stably maintained over a long period of time. The second object of the present invention is to provide a method for producing a silver halide photographic emulsion in which the time required to complete the desalting step is significantly shorter than in the conventional method, and the emulsion preparation time can be significantly shortened. The purpose is to provide equipment. A third object of the present invention is that the emulsion obtained after decantation can be easily redispersed, there is no risk of interfering with subsequent steps, and the emulsion can be stabilized by sufficient stirring and mixing in a short period of time. It is an object of the present invention to provide a method for producing a silver halide photographic emulsion and an apparatus therefor, which can produce a high-quality emulsion. The fourth object of the present invention is that the photographic performance is not adversely affected by the basis weight accuracy of the flocculant used, and even if a large amount of precipitant is used, the halogen-free emulsion to be prepared is not adversely affected. An object of the present invention is to provide a method for producing a silver oxide photographic emulsion and an apparatus therefor. A fifth object of the present invention is to provide a method and apparatus for producing a silver halide photographic emulsion, which can greatly improve the yield of the prepared emulsion compared to conventional methods. [Summary of the Invention] The method of the present invention that achieves the above objects involves mixing a water-soluble silver salt and a water-soluble halide in the presence of a hydrophilic colloid to form silver halide crystals dispersed in the hydrophilic colloid. Then, physical ripening is completed by a known method (lowering the temperature and/or using a physical ripening inhibitor, etc.), and at or after the completion of the physical ripening, silver halide crystals are prepared in the presence of an agglomerating agent. In the method of coagulating and precipitating and removing the by-product salt produced by the double decomposition reaction between the water-soluble silver salt and the water-soluble halide, the flocculant is removed when the pressure inside the container is initially maintained below atmospheric pressure. It is characterized by adding and mixing, leaving to stand, and then increasing the pressure in the container to atmospheric pressure or higher, and repeating the depressurization and pressurization several times. Furthermore, the apparatus according to the present invention includes a tank whose interior can be depressurized to below atmospheric pressure and pressurized to above atmospheric pressure, in the apparatus used to carry out the above method;
equipment that can adjust the flow rate of the flocculant and add and supply it while maintaining the pressure when the inside of the tank is depressurized; equipment that stirs and mixes the internal liquid when the inside of the tank is depressurized or pressurized; It is characterized by having equipment for discharging a specified amount of liquid to the outside of the tank when the inside of the tank is pressurized. As a result of extensive research into the cause of the long sedimentation time, which is a drawback of the flocculation method (precipitation method), the present inventors have discovered that, among the flocs formed, the presence of minute flocs It was found that the micro flocs were not aggregated and were floating due to the failure of the flocculant to react uniformly. Furthermore, it was found that when stirring was performed strongly to ensure uniform reaction, foaming occurred and it took a long time for the foam to break. The present invention has been made based on these findings. [Structure of the Invention] An embodiment of the present invention will be described below with reference to the accompanying drawings. FIG. 1 is a schematic explanatory diagram showing an embodiment of a manufacturing apparatus according to the present invention. In the figure, 1 is a tank whose interior can be reduced to atmospheric pressure or pressurized to above atmospheric pressure.A jacket 2 for temperature control is provided on the outer surface of the tank 1, and a drain valve 3 is provided at the bottom. There is. 4 is a vacuum pump for reducing the pressure inside the tank 1, and 5 is a compressor for pressurizing the inside of the tank 1. 6 is a three-way valve provided to prevent pressurization and depressurization from occurring at the same time. 7 is a supply port for silver halide photographic emulsion; 8
is a water supply port, and 9 is a three-way valve. 10 is tank 1
This is a stirrer for stirring the internal liquid when the internal pressure is reduced or increased. Reference numeral 11 denotes equipment that can adjust the flow rate of the flocculant while maintaining the pressure when the pressure inside the tank 1 is reduced, and can also add and supply the flocculant. 12 is a pump that discharges a specified amount of liquid to the outside of the tank 1 when the inside of the tank 1 is pressurized. Next, the operation of the device having the above configuration will be explained. The pressure inside the tank 1 is reduced by a vacuum pump 4, and while maintaining a specified degree of vacuum, a silver halide photographic emulsion dispersed with a hydrophilic colloid such as gelatin is supplied. This emulsion is a so-called liquid (desalted emulsion) containing unnecessary salts immediately after mixing. The degree of reduced pressure mentioned above varies depending on the temperature, composition and surface tension of the emulsion to be desalted, but is usually -500 mmHg to -750 mmHg.
A range of mmHg is desirable. However, depending on the composition of the emulsion to be desalted, there are many that boil at temperatures above -760 mmHg, and in this case it is desirable to reduce the pressure below the degree that reaches the boiling point. Next, while maintaining the specified degree of vacuum inside the tank 1, the agitator 10 is started to achieve the specified mixing degree.
Next, a specified amount of flocculant for flocculation and precipitation (several types may be used) is added from the addition equipment 11 and mixed.
After the addition and mixing of the flocculant is completed, stirring is stopped. Immediately after the stirring is stopped, the pressure inside the tank is rapidly returned to atmospheric pressure by the compressor 5, or the pressure is increased to a specified pressure higher than atmospheric pressure. The above-mentioned degree of pressurization differs depending on the emulsion to be desalted. During pressurized operation, the degree of depressurization may be -500 due to boiling, etc.
This is done when mmHg cannot be maintained, and pressurization conditions do not need to be used, as this usually complicates the equipment. The range of pressurization degree is 500% pressure difference with depressurization degree.
It is desirable to set it between mmHg and 700mmHg. For example, if the degree of decompression is -400mmHg,
Pressure range is set to +100mmHg to +300mmHg. If the inside of the tank is pressurized after the silver halide grains have settled, after returning the pressurized state to atmospheric pressure, the supernatant liquid containing unnecessary salts and not containing silver halide grains is pumped to the pump 12. Only the specified amount is discharged. After the discharge is completed, the pressure inside the tank 1 is reduced to the specified degree again if necessary. When the pressure inside the tank 1 is reduced, pure water for dilution is supplied into the tank 1 from the water supply port 8 while maintaining the degree of pressure reduction. Next, the stirrer 10 is started and the second flocculant addition is performed. After the addition and mixing of the flocculant is completed, the agitator 10 is stopped, and the pressure inside the tank 1 is immediately returned to atmospheric pressure or is pressurized to a specified pressure higher than atmospheric pressure. After the silver halide particles have settled, if the inside of the tank 1 is pressurized, return the internal pressure to atmospheric pressure, and then drain the specified amount of supernatant liquid that contains unnecessary salts and does not contain silver halide particles. . If necessary, the above operation may be repeated, and when the bubbles are broken, the above depressurization operation, return to atmospheric pressure, or pressurization operation may be repeated several times.
Enables complete bubble breakage. The silver halide in the present invention may be any of silver chloride, silver chlorobromide, silver chloroiodide, silver bromide, silver iodobromide, and silver chloroiodobromide, and there are also restrictions on the grain size of this crystal. There isn't. In addition, there are no restrictions on the manufacturing method for producing these silver halide salts, such as the single-jet method,
Any of the double jet method, ammonia method, or controlled double jet method in which silver potential is controlled may be used. Any flocculant can be used in the present invention. For example, organic solvents described in British Patent No. 819039, US Patent No.
3007796 specification, French Patent No. 1333773, etc., inorganic substances described in US Patent No. 2618556, casein compounds described in US Patent No. 3144355, US Patent No.
2481650, 2719146, 2728662, 2768079, and French Patent No. 1311549, which have binding properties with amino groups, and also with gelatin. Anionic soaps that form complexes, such as those described in US Pat. No. 2,489,341 and US Pat. No. 2,527,261,
Specification No. 2772165, Japanese Patent Publication No. 48-13057, No. 40
Copolymers described in -21020 publication, US Patent No. 861984, etc., nitrogen-containing heterocycles described in Japanese Patent Publication No. 40-27470, Belgian Patent No. 637343, etc. Naphthalene compounds described in British Patent No. 945334, Japanese Patent Publication No. 35-16086, etc., or West German Patent No.
Polyethylene sulfonic acids described in Japanese Patent Publication No. 1146117, etc., phenol derivatives described in Japanese Patent Publication No. 43-27562, etc., phosphoric acid esters described in Belgian Patent No. 642112, etc., Japanese Patent Application Laid-Open No. 52-35624 Ethylene-based copolymers described in et al. can be preferably used. The present invention is applicable to any emulsion manufacturing method, such as an ammonia method, a neutral method, or an acid method. Further, in the present invention, the water-soluble silver salt and the water-soluble halide may be mixed in the hydrophilic colloid by any of forward mixing, back mixing, and simultaneous mixing, and the conversion method or coating emulsion ( Converged grain method etc. may be adopted. Conventional conditions can be applied to the physical ripening conditions of the present invention. i.e. temperature,
Physical ripening conditions such as pH, silver ion concentration, time, stirring conditions, and type and concentration of hydrophilic colloid can be optimally selected depending on the type of silver halide photographic emulsion of interest. Furthermore, metal atoms such as iridium, rhodium, ruthenium, osmium, cobalt, bismuth, and cadmium may be contained in these silver halide crystal grains. Furthermore, it may be a surface latent image type or an internal latent image type. The silver halide photographic emulsion according to the present invention thus prepared is chemically ripened by any known method. That is, this silver halide photographic emulsion contains active gelatin, a sulfur sensitizer such as allylthiocarbamide, thiourea, cystine, a selenium sensitizer, a noble metal sensitizer such as a gold sensitizer, ruthenium, rhodium, iridium, etc. Chemical sensitization can be carried out by using sensitizers such as these alone or in combination as appropriate. Furthermore, this silver halide photographic emulsion can be optically sensitized, for example, with cyanine dyes or merocyanine dyes. The silver halide photographic emulsion may be stabilized with triazoles, tetrazoles, imidazoles, azaindenes, quaternary benzothiazolium compounds, zinc or cadmium compounds, and may also be stabilized with quaternary ammonium salts, polyethylene glycol, etc. sensitizing compounds may also be included.
Various photographic additives such as suitable gelatin plasticizers, gelatin hardeners, spreading agents such as saponins, and coating aids such as sulfosuccinates may also be included. Furthermore, various additives commonly used in photography, such as antifoggants and ultraviolet absorbers, can also be included, if necessary. In the present invention, gelatin is preferably used as the hydrophilic colloid as a dispersant for silver halide, but in addition to gelatin, various natural or synthetic colloidal substances such as gelatin derivatives and polyvinyl alcohol may be used alone or in combination. It can also be used in combination with gelatin. [Effects of the Invention] The silver halide photographic emulsion obtained by the method of the present invention has good redispersibility and good coating properties, so it can be coated on a suitable support such as a film to produce various silver halide photographic light-sensitive materials. suitable for obtaining. According to the method of the present invention, since the settling time is significantly shorter than that required in the conventional method, the emulsion preparation time can be greatly shortened, and the photographic performance is improved due to the accuracy of the basis weight of the flocculant used. Since there is no adverse effect of this, there is no need to accurately measure the flocculant in proportion to the amount of hydrophilic colloid such as gelatin after physical ripening, especially during continuous emulsion preparation, and redispersion of the resulting emulsion is easy. An emulsion that has excellent photographic performance with less fog, which has stable quality and excellent stability over time due to sufficient stirring and mixing in a short period of time, and which does not pose any risk of interfering with subsequent processes. can be obtained. Also,
The separation of the coagulated and settled emulsion from the mother liquor is stable and reliable, so the yield of the emulsion can be greatly improved compared to conventional methods, and it is also possible to obtain an emulsion with extremely good coating properties, which makes it possible to improve film production. It is suitable for obtaining various silver halide photographic materials by coating on supports such as. Furthermore, fog can be significantly reduced by increasing the rate at which the temperature is lowered during cooling to complete physical ripening. The silver halide photographic emulsion obtained by the present invention has the above-mentioned characteristics and can be used in various applications such as graphic films, micro films, color negative films, color reversal films, X-ray films, direct positive films, and motion picture positive films. It can be used as an emulsion for silver halide photographic materials. [Examples] Hereinafter, the present invention will be explained in more detail with reference to Examples, but the embodiments of the present invention are not limited thereto. Example 1 Prepare the solutions listed in Table 1 below,
Physical ripening was performed by a double jet method to obtain a light-sensitive silver halide photographic emulsion. The liquid was used as a mother liquid, and the liquid was added and mixed using the double jet method. The reaction temperature at that time was 60°C, and the addition time was 40 minutes.

[Table] 70 c.c. of each of the following flocculants [A] and [B] were added and mixed per 1 liter of the silver halide emulsion obtained above, and the emulsion was allowed to settle. Stirring for mixing was performed vigorously. [A]; A flocculant made by dissolving a condensation product of naphthalene sulfonic acid and formaldehyde in pure water at a concentration of 5 wt/V% [B]; A flocculant prepared by dissolving magnesium sulfate in pure water at a concentration of 15 wt/V% This flocculant [ When adding and mixing A] and [B], the pressure in the tank is reduced, and after the addition is completed, the pressure is returned to atmospheric pressure and allowed to settle. At this time, [] the amount of foaming (volume per 1 liter of emulsion) before returning the pressure in the tank to atmospheric pressure after the addition of the coagulant, and [] the amount of foam remaining after returning the pressure in the tank to atmospheric pressure. The degree of pressure reduction in the tank (varying up to ~) was measured as a parameter, and the results plotted are shown in Figure 2. The results are clear from Figure 2. When the pressure inside the tank was reduced and stirring was performed, the foaming amount was -300 mm.
400c.c. to 500c.c. with decompression degree below Hg, 600c.c. without decompression
cc, and the amount of bubbles after returning the tank to atmospheric pressure was smaller as the pressure inside the tank was reduced. When the straight line shown in FIG. 2 is expressed as an equation, it is expressed by the following equation. Vf=A×H+B Here, Vf=Amount of foam remaining per 1 liter of emulsion after the operation from reduced pressure to atmospheric pressure [cc/l] H=Degree of reduced pressure when bubbles are generated in the tank [-mmHg] A, B= Constants specific to emulsions Therefore, in order to keep the amount of bubbles that exist at atmospheric pressure to a low level, the pressure in the tank when bubbles are generated should be at least -500
It turns out that it is best to keep it below mmHg. Example 2 In each experiment of Example 1, the pressure was returned to atmospheric pressure, and then settling was performed, and the settling time was measured from the silver concentration in the supernatant. The measurement conditions and method are as follows. [1] Sampling: As shown in FIG. 3, the emulsion was sampled with a pipette 13 at a point 5 cm from the bottom of the tank 1 (R=5 cm). The frequency of sampling was once every 30 seconds. [2] Analysis method: Analysis was performed using an atomic absorption spectrophotometer. As a result of the above measurements, Table 2 shows the time at which the silver concentration became 5 ppm or less.

[Table] From Table 2, it can be seen that by reducing the pressure inside the tank and destroying the bubbles, the time required for static settling can be significantly shortened.

[Brief explanation of the drawing]

FIG. 1 is a schematic explanatory diagram showing one embodiment of the manufacturing apparatus according to the present invention, FIG. 2 is a graph showing the relationship between the amount of foaming and the degree of pressure reduction in the tank, and FIG. 3 is a schematic diagram showing the sampling position. In the figure, 1 is a tank, 10 is a stirrer, and 11 is a flocculant addition and supply facility.

Claims (1)

[Claims] 1. A water-soluble silver salt and a water-soluble halide are mixed in the presence of a hydrophilic colloid to form silver halide crystals dispersed in the hydrophilic colloid, and physical ripening is completed. At or after the end of physical ripening,
In the method of coagulating and precipitating silver halide crystals in the presence of a flocculant and removing the by-product salt produced by the metathesis reaction between the water-soluble silver salt and the water-soluble halide, the pressure inside the container is When the pressure is maintained below atmospheric pressure, a flocculant is added and mixed, and the mixture is allowed to stand still.
A method for producing a silver halide photographic emulsion, characterized in that the pressure inside the container is then increased to atmospheric pressure or higher, and further the depressurization and pressurization are repeated a plurality of times. 2 Mixing a water-soluble silver salt and a water-soluble halide in the presence of a hydrophilic colloid to form silver halide crystals dispersed in the hydrophilic colloid, completing physical ripening, and at the end of the physical ripening or After finishing,
In an apparatus used to coagulate and precipitate silver halide crystals in the presence of a flocculant and to remove by-product salts produced by the metathesis reaction between the water-soluble silver salt and the water-soluble halide, the interior is A tank that can be depressurized below atmospheric pressure and pressurized above atmospheric pressure;
equipment that can adjust the flow rate of the flocculant and add and supply it while maintaining the pressure when the inside of the tank is depressurized; equipment that stirs and mixes the internal liquid when the inside of the tank is depressurized or pressurized; 1. An apparatus for producing a silver halide photographic emulsion, comprising equipment for discharging a specified amount of liquid to the outside of the tank when the inside of the tank is pressurized.