JPH0254534B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a negative-working silver halide photographic emulsion with high sensitivity and excellent production stability, and more specifically, a negative-working silver halide photographic emulsion containing silver halide grains formed in an environment with a low pH and an excess of silver ions. Regarding photographic emulsions. In recent years, there has been a demand for silver halide photographic materials with high sensitivity. For amateur films, for example, color and black-and-white photographic paper requires high-speed shutter and quick processing to eliminate shutter shake caused by the miniaturization of screen sizes, and high sensitivity is required due to the electronicization and simplification of the printing process. These include photographic materials for printing, and medical X-ray photographic materials for which there is a strong demand to reduce the amount of radiation exposure. Furthermore, recently, due to the sharp rise in silver prices, there has been a call for lower silver quantities, and high sensitivity technology is essential for this purpose. Various techniques for increasing sensitivity have been studied in the past, but there is still room for research. For example, silver halide grains form surface latent images and/or internal latent images upon exposure. The surface latent image is developed with a normal developer to give optical density,
Internal latent images are not developed. For this reason, in negative-working silver halide emulsions, silver halide grains that tend to form internal latent images have a greater sensitivity loss than silver halide grains that form surface latent images, resulting in lower sensitivity. . Conventional silver halide grains usually have higher internal sensitivity than surface sensitivity when unsensitized. Therefore, it is desired to find a method for preparing negative-working silver halide emulsions with high surface sensitivity and low internal sensitivity. On the other hand, most conventional silver halide emulsions have a wide grain size distribution and irregular crystal habits, so it is difficult to know whether each grain is being chemically sensitized optimally. It's hard to say. For this reason, at present, the inherent sensitivity of each particle is not fully brought out. Therefore, in recent years, monodisperse emulsions (ie, silver halide emulsions with a narrow grain size distribution and uniform crystal habit) have been attracting attention. Although its preparation methods are already known in various literature, most of them are preparation methods in the halide ion excess region. On the halide ion excess side, the region in which a monodisperse emulsion can be obtained is limited to a narrow and controllably unstable region where silver ions and halide ions are approximately equimolar. In other words, a slight increase in excess halide ion concentration changes the crystal habit from cubic to 14
The emulsion changes to a hedron, then to an octahedron, and then to a twinned polydisperse emulsion. Many documents have clarified that photographic properties differ greatly between these crystal habits. Therefore, although it is possible to prepare a monodisperse emulsion with an excess of halide ions in the laboratory, it is not suitable for continuing stable industrial production. Therefore, it is strongly desired to find a method for industrially stably preparing monodispersed emulsions. A first object of the present invention is to provide a method for producing a negative-working silver halide photographic emulsion that has high surface sensitivity and low internal sensitivity. A second object of the present invention is to provide a method for producing a negative silver halide photographic emulsion having a narrow grain size distribution and uniform crystal habit. A third object of the present invention is to provide a method for industrially stably producing a negative-working silver halide photographic emulsion that achieves the above two objects. A fourth object of the present invention is to provide a method that can achieve the above three objects in a short preparation time. Other objects of the invention will become apparent from the description below. The above object of the present invention is to provide a method for producing a negative-working silver halide photographic emulsion by the double jet method (excluding the case where an ammoniacal silver nitrate solution is used), in which the pAg value is This is achieved by a method for producing a negative-working silver halide photographic emulsion, which is characterized by maintaining a pH value of 2 to 5 and a PH value of 1 to 4. The present invention is characterized in that a silver halide monodisperse emulsion is prepared in a silver-excessive region. Its silver ion concentration is approximately 1×10 ^-5 ~1×10 ^-2 mol/(pAg5 ~
2) is preferable, which is 10 to 1 million times higher concentration than the conventional one. If the concentration is too low than the above, there will be a problem in production stability, whereas if it is too high, fog will occur inside the silver halide grains and the surface sensitivity will decrease. Overall, about pAg4.5 to pAg2.5 is more preferred. The silver ion concentration should be kept high until at least one-fifteenth of the total silver amount is added. If this value is too small than the above, twins are likely to occur, resulting in a wide particle size distribution, making it difficult to stably obtain a monodispersed emulsion. After adding one-fifteenth of the total silver amount, the silver ion concentration may be lowered to 1×10 ⁻⁵ mol/or less. Further, it is desirable that the amount is 1×10 ^-7 mol/or less (pAg 7 or more) at the end of the addition. It is generally known that silver halide grains can be formed in any of basic, neutral and acidic conditions. The method according to the invention is carried out in an acidic region at least while maintaining a high silver ion concentration. As the pH increases, internal sensitivity and internal fog increase,
Surface sensitivity decreases. The lower the PH value, the more effective it is, but there are problems such as a decrease in the protective colloid properties due to hydrolysis of the protective colloid or corrosion of the mixing tank due to acid, so a pH of up to about 1 is practical. this
The pH value only needs to be a period during which the silver ion concentration is kept high during the process of silver halide grain formation, and even if the silver ion concentration is lowered and then raised to about 8, the effect of the present invention will not be affected. However, it is preferable not to exceed PH7.5 in terms of keeping internal sensitivity and internal fog low. There are no particular restrictions on the acid used to obtain a low pH, but nitric acid, sulfuric acid, acetic acid, etc. are preferred. In the present invention, after the nucleation period of silver halide grains has ended, it is desirable to increase the rate of addition of water-soluble silver salt and water-soluble halide as the silver halide grains grow. By increasing the addition rate, a more uniform monodisperse emulsion is obtained and mixing time is reduced. Therefore, it is advantageous for industrial production and is preferable in that the chances of formation of structural defects inside the silver halide grains are reduced. As a way to speed up this addition rate,
No. 48-36890, No. 52-16364, JP-A-55-142329
As described in each publication of the above-mentioned publication, the rate of addition of the aqueous silver salt solution and the aqueous halide solution may be increased continuously or stepwise. The upper limit of the above addition rate may be the flow rate just before new core particles are generated, and the value is determined by temperature, pH, pAg, degree of stirring, composition of silver halide grains, solubility, grain size, interparticle distance, crystal habit. ,
Alternatively, it varies depending on the type and concentration of the protective colloid. Silver halides used in the present invention include silver bromide, silver iodobromide, silver chlorobromide, silver chlorobromoiodide, silver chloride,
Although silver chloroiodide is included, the most preferred silver halide composition is silver iodobromide containing 10 mol % or less of silver iodide. Furthermore, the silver halide grains used in the present invention are
Preferably, the average particle size is from about 0.05 to about 2 microns. It is also desirable that at least 80% by weight of the silver halide grains have a diameter that is within ±40% of the average grain diameter. Further, these silver halide grains or silver halide emulsions may contain an iridium salt and/or a rhodium salt in order to improve flash exposure characteristics. The negative-working silver halide photographic emulsion prepared by the method of the present invention is chemically sensitized after water-soluble salts are removed by a conventional method. Chemical sensitization methods include, for example, sulfur sensitization using sodium thiosulfate and thiourea compounds, gold sensitization using chloroauric acid salts, gold trichloride, etc., thiourea dioxide, stannous chloride, and silver ripening. reduction sensitization method using etc., other palladium sensitization method,
There are selenium sensitization methods, etc., and these methods can be used alone or in combination of two or more. A stabilizer can be added to the negative-working silver halide emulsion prepared by the method of the present invention after chemical sensitization is completed. For example, 4-hydroxy-6-methyl-1,3,3a,7-tetrazaindene, 5-
Any stabilizer known in the art including mercapto-1-phenyltetrazole, 2-mercaptobenzothiazole, etc. can be used. Further, if necessary, optical sensitizers such as cyanine dyes and merocyanine dyes may be used alone or in combination to optically sensitize to a desired wavelength range. For example, US Patent No. 2493784, US Patent No. 2519001,
Same No. 2977229, Same No. 3480343, Same No. 3672897,
Same No. 3703377, Same No. 2688545, Same No. 2912329,
Same No. 3397060, Same No. 3511664, Same No. 3522052,
Same No. 3527641, Same No. 3615613, Same No. 3615632,
Same No. 3615635, Same No. 3615641, Same No. 3617295,
Same No. 3617293, Same No. 3628964, Same No. 3635721,
Same No. 3656959, Same No. 3694217, Same No. 3743510,
Dyes described in Patent No. 3769301, Patent No. 3793020, etc. can be used. The negative silver halide photographic emulsion produced by the method of the present invention can use gelatin, a gelatin derivative, or a synthetic hydrophilic polymer as a vehicle.
Additionally, various photographic additives can be included. As the hardening agent, aldehyde compounds, ketone compounds, halogen-substituted acids such as mucochloric acid, ethyleneimine compounds, vinyl sulfon compounds, etc. can be used. As the spreading agent, saponin, lauryl or oleyl monoether of polyethylene glycol, etc. are used. There are no particular limitations on the development accelerator, but compounds such as benzimidazole compounds (for example, those described in JP-A-49-24427), quaternary ammonium salts, and polyethylene glycol can be used. As physical property improvers, alkyl acrylate,
A polymer latex made of a homo- or copolymer of alkyl methacrylate, acrylic acid, etc. can be contained. The negative-working silver halide photographic emulsion according to the method of the present invention includes a compound obtained by addition copolymerizing glycidol and ethylene oxide to a phenolaldehyde condensate (for example, the one described in JP-A-51-56220), lanolin, etc. ethylene oxide adducts and alkali metal and/or alkaline earth metal salts (for example, JP-A-55-70837), water-soluble inorganic chlorides and matting agents (JP-A-55-161230),
Addition condensate of glycidol and ethylene oxide to phenol aldehyde condensate and fluorine-containing succinic acid compound
Antistatic agents such as No. 1) can be added. Furthermore, PH adjusters, thickeners, granularity improvers,
A matting agent or the like can be included. Supports for light-sensitive materials made using the emulsion of the present invention prepared as described above include, for example, rosette paper, polyethylene-coated paper, polypropylene synthetic paper, glass, cellulose acetate, cellulose nitrate, polyvinyl acetal, polypropylene. , polyester films such as polyethylene terephthalate, polystyrene, etc.
These supports are appropriately selected depending on the intended use of each silver halide photographic material. Further, it is desirable that these supports undergo surface hydrophilic treatment and subbing treatment. When the photographic emulsion according to the present invention is applied to a silver halide color photographic light-sensitive material, in addition to the above-mentioned various additives, various constituent elements of the light-sensitive material well known to those skilled in the art may be coexisting. There are no drawbacks. For example, as belonging to these,
There are compounds that react with oxidized developing agents to form dyes, ie, so-called diffusion-resistant couplers. More specifically, there are yellow couplers represented by diketomethine type, magenta couplers represented by 5-pyrazolone type, and cyan couplers represented by phenol type and naphthol type.
In addition to these couplers, there are also so-called DIR couplers that release a development inhibitor during a color reaction, and so-called colored couplers that adjust masking density. These couplers are
Illustrated in Research Disclosure (RD) 9232. Types of silver halide photographic materials to which the photographic emulsion according to the present invention can be applied include color photographic paper, color negative film, color positive film,
Any of black and white films (for example, X-ray photosensitive materials, printing photosensitive materials, etc.), diffusion transfer type photographic photosensitive materials, etc. may be used. Exposure of the photographic emulsion according to the method of the present invention varies depending on the state of optical sensitization, purpose of use, etc., but includes tungsten, fluorescent light, arc light, xenon, sunlight, xenon flash, cathode ray tube flying spot, laser light, Various types of light sources such as electron beams, X-rays, and fluorescent screens for X-ray photography can be used as appropriate, and in addition to normal exposure with an exposure time of 1/10 ³ to 100 seconds, xenon flash, cathode ray tube, and laser light can also be used. In this case, a short time to flash exposure of 1/10 ⁴ to 1/10 ⁹ seconds can be applied. Next, 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 While controlling pAg to the value shown in Table 1 below,
Using the double jet method at PH value 2.0 and 60℃,
Eight types (A to H) of silver iodobromide emulsions containing 2.0 mol % of silver iodide were prepared. The addition rate of the double diet was 1.0 ml/min at the beginning of 2.0 mol/min of silver nitrate and 2.0 mol/min of the mixed solution of potassium bromide and potassium iodide, and gradually increased each to 50 ml/min at the end. It was a minute.
To obtain the desired pAg value, the addition rate of the potassium bromide and potassium iodide mixture was varied slightly from that of the silver nitrate solution. In addition, the pH value was adjusted with sulfuric acid and potassium hydroxide. The time required for addition was 80 minutes. However, without increasing the addition rate, approximately 20 hours of addition was required. After mixing, remove pAg with an aqueous solution of potassium bromide.
Adjust the pH to 10.0 with an aqueous solution of potassium hydroxide.
6.5, and water-soluble salts were removed by a conventional flocculation method at 40°C. After gold sensitization and sulfur sensitization were applied to each of these eight emulsions A to H, 4-hydroxy-6-
Polyethylene that has been stabilized by adding methyl-1,3,3a,7-tetradesigndene, and further added with common photographic additives such as spreading agents, thickeners, hardeners, etc., and then subbed-treated. Samples Nos. 1 to 8 were prepared by coating and drying on a terephthalate film base in a conventional manner so that the amount of Ag was 50 mg/100 cm ² . Sensitometry of each of these samples was performed as follows. For exposure, a light source with a color temperature of 5400 was used, and exposure was performed for 1/50 second through an optical wedge. The exposure amount is
It was 3.2CMS. For development, surface development and internal development were performed according to the following formulation. [Surface developer] p-monomethylaminophenol sulfate
2.0g d-isoascorbic acid 10.0g Potassium bromide 1.0g Sodium metaborate/4H ₂ O 40.0g Finish with water. Process 1000ml at 20℃ for 10 minutes. [Surface latent image bleaching solution] Red blood salt 30g Phenosafranin 12.5mg Finish with water 1000ml Treat at 20℃ for 10 minutes. [Internal developer] Sodium thiosulfate/5H ₂ O is added to the above surface developer.
Add 10g of. After treating the surface with the above latent image bleaching solution, wash it with running water for 10 minutes.
Rinse with water for 1 minute and perform internal development at 20°C for 10 minutes. The properties of the obtained emulsion grains are shown in Table 2, and the development results are shown in Table 3. Note that the sensitivity is based on the sample
It is expressed as a relative sensitivity with the surface sensitivity of No. 2 as 100. In the table, S represents sensitivity, Fog represents fog density, and γ represents contrast.

【table】

[Table] Expressed by average particle size. Therefore, the smaller this value is, the better the monodispersity is.

【table】

[Table] As is clear from Tables 2 and 3, silver halide grains formed in an environment with high silver ion concentration and low pH have a It can be seen that not only the surface sensitivity relative to the internal sensitivity is high and the contrast is high, but also the stability when the excess ion concentration changes in the same way, that is, the stability of production, is particularly excellent. Example 2 In the preparation of emulsion B in Example 1, pAg was 3.5.
Emulsions I and J were prepared by changing the PH as shown in Table 4 below.
Samples Nos. 9 to 11 were obtained by coating and drying in the same manner as above.
Further, after exposure and development as in Example 1, photographic properties were measured. The results are shown in Table-4.

[Table] As is clear from Table 4, it can be seen that the lower the PH, the higher the sensitivity can be obtained. Example 3 In the forward mixing method, the pH was set to 2.0 and three types of conventional twinned polydisperse emulsions were obtained by varying the mixing time. It was a silver iodobromide emulsion containing 2.0 mol% of silver iodide. These emulsions K, L, M and emulsion B for comparison were chemically sensitized in the same manner as in Example 1, coated and dried to obtain samples Nos. 12 to 15.
Further, exposure and development were carried out as in Example 1. The properties of the obtained emulsion grains are shown in Table 5, and the development results are shown in Table 6.

[Table] * Same as Table-2.

[Emulsion N]

Set pAg = 3.0 during mixing and pAg = 8.0 after mixing. [Emulsion O] While adding 1/10 of the total amount of silver, add at pAg=3.0, and for the rest add at pAg=8.0. [Emulsion P] The pAg at the beginning of mixing is set to 3.0, and as the mixing progresses, the pAg is gradually increased to 4.5 when 1/10 of the total silver amount is added, and the pAg is set to 8.0 at the end of mixing.
Make it so that [Emulsion Q] Add 1/20 of the total silver amount at pAg=3.0, and add the rest at pAg=8.0. These emulsions were chemically sensitized, coated, dried, exposed and developed in the same manner as in Example 1. Table of results obtained.
7 and Table 8.

[Table] * Same as Table-2.

[Table] As is clear from Table 8, the silver halide grains formed in the silver-excess region had high surface sensitivity until at least 1/15 of the total silver amount was added.
It can be seen that the contrast is also high.

Claims (1)

[Claims] 1. In a method for producing a negative-working silver halide photographic emulsion by the double jet method (excluding the case where an ammoniacal silver nitrate solution is used), the pAg value is maintained until at least one-fifteenth of the total amount of silver is added. 2 to 5,
and a method for producing a negative silver halide photographic emulsion, which is characterized by maintaining a pH value of 1 to 4. 2. The negative-working halogen according to claim 1, wherein the rate of addition of the water-soluble silver salt and the water-soluble halide is increased continuously or stepwise as the silver halide grains grow. A method for producing a silver oxide photographic emulsion. 3. A negative-working silver halide photographic emulsion according to claim 1 or 2, wherein at least 80% by weight of the silver halide grains have a diameter within ±40% of the average grain diameter. Production method. 4. The negative-working halogen according to any one of claims 1 to 3, wherein the silver halide photographic emulsion is reduction sensitized, sulfur sensitized and/or gold sensitized. A method for producing a silver oxide photographic emulsion.