JPH0433019B2 - - Google Patents

Description

BACKGROUND OF THE INVENTION Technical Field The present invention relates to silver halide photographic emulsions. Prior Art and its Problems In recent years, with the development of photographic technology, there has been a strong desire for higher sensitivity of silver halide photographic materials.
For example, high-speed shutters in cameras, rapid processing of color and black and white photographic paper, electronics and simplification in the printing industry, X-ray technology in the medical field, etc.
The sensitivity has been increased in response to demands such as reducing the radiation dose of radiation exposure. However, most conventional silver halide photographic emulsions consist of grains with a wide grain size distribution, and for this reason, it cannot be said that optimal chemical sensitization is performed on all grains during chemical sensitization. Currently, the inherent sensitivity of each particle is not fully brought out. Generally, when chemical ripening is performed for a long time, various mechanical pressures are applied to the unexposed film, resulting in frequent blackening, that is, pressure blackening, which is observed after development. Conversely, if the chemical ripening time is shortened, pressure blackening becomes less likely to occur, but desensitization observed after exposure and development, ie, pressure desensitization, occurs frequently due to the mechanical pressure applied before exposure. For this reason, it is extremely difficult to determine the optimum chemical sensitization time that minimizes the occurrence of pressure blackening and pressure desensitization. For example, in the case of medical X-ray film, since the film size is large, pressure blackening and pressure desensitization are likely to occur during handling due to bending of the film, such as so-called nail folding. In addition, automatic exposure and developing devices using mechanical transport are now widely used as medical X-ray photography systems, but mechanical forces are applied to the film in these devices, especially in dry areas such as winter. , the aforementioned pressure blackening and pressure desensitization are likely to occur. Such a phenomenon may cause serious trouble in medical diagnosis. Various methods have been proposed to reduce such pressure darkening and pressure desensitization. For example, US Patent No. 3655390, British Patent No.
No. 1307373, U.S. Patent No. 3772032, etc.
Method of Adding Gelatin Plasticizer, U.S. Patent No.
There are methods of adding pressure antifogging agents, such as in No. 3655390, No. 3445235, and No. 2628167. Examples of the former gelatin plasticizer include polymer dispersions such as latex and hygroscopic substances, but these are not preferred because they change sensitivity, fogging, etc., and adversely affect the physical properties of photosensitive materials such as adhesion. Further, as the latter pressure fog preventive agent, amine borane compounds, iridium rhodium salts, and water-soluble bismuth salts are mentioned, but these lead to a decrease in sensitivity. Purpose of the Invention The present invention was made in view of the above-mentioned circumstances, and its main purpose is to provide high-sensitivity, high-contrast contrast with less pressure blackening and pressure desensitization, without adversely affecting the photographic performance or physical properties of the photosensitive material. An object of the present invention is to provide a surface latent image type silver halide monodispersed emulsion. These objects are achieved by the invention described below. That is, in the present invention, the average silver iodide content in the grains is 0.5 to 10 mol%.
It is a single silver halide grain that has a localized portion of silver iodide at a concentration of 20 mol% or more inside the grain and has a rounded octahedral, hexahedral, or dodecahedral shape. This is a silver halide photographic emulsion consisting of a dispersed emulsion and characterized by being chemically sensitized. Specific Configuration of the Invention The specific configuration of the present invention will be described in detail below. The silver halide grains in the emulsion of the present invention are silver halide containing silver iodide, and may be any of silver iodochloride, silver iodobromide, and silver chloroiodobromide. In that you can get
Silver iodobromide is preferred. The average silver iodide content in such silver halide grains is 0.5 to 10 mol%, preferably 1 to 8 mol%. With such an average silver iodide content, an emulsion with high sensitivity, low fog, and good development progress and fixing properties can be obtained. Inside such silver halide grains, there are localized portions in which silver iodide is localized at a high concentration of at least 20 mol % or more. In this case, it is preferable that the inside of the particle be located as far inward as possible from the outer surface of the particle, and it is particularly preferable that the localized portion exists in a portion that is 0.01 μm or more away from the outer surface. Furthermore, the localized portion may exist in a layered manner inside the particle, or the entire core may serve as the localized portion. That is, it is preferable that part or all of the grain core, excluding the shell portion having a thickness of 0.01 μm or more from the outer surface, is a localized portion with a silver iodide concentration of 20 mol % or more. In addition, more preferable results can be obtained when the silver iodide concentration in the localized portion is 30 to 40 mol%. The outside of such localized areas is usually coated with silver halide without silver iodide.
That is, in a preferred embodiment, from the outer surface
The shell portion having a thickness of 0.01 μm or more, particularly 0.01 to 1.5 μm, is formed of silver halide (usually silver bromide) that does not contain silver iodide. The emulsion of the present invention is a monodispersed emulsion of such silver halide grains. In other words, the size distribution of the silver halide grains dispersed in the protective colloid is narrow. Specifically, the average grain size is taken as the average grain size, and the standard deviation is σ.
The coefficient of variation (σ/) is 20% or less. Note that and σ may be determined by measuring one side or the diameter of 500 or more particles using a photomicrograph or the like. By forming such a monodispersed emulsion, sensitization treatment such as chemical sensitization can be sufficiently performed, extremely high sensitivity can be obtained, and there is little softening of tone due to sensitization treatment, resulting in high contrast. Before chemical sensitization, the silver halide grains of the present invention are
The crystal is surface-treated by aging at a pAg of 10.5 or more, and the number of (111) planes on the surface is increased by 5% or more to give it roundness. That is, in preparing a monodisperse emulsion, first, grain growth of crystals is performed. In grain growth, silver ions and halide solutions may be added alternately in time series, but it is preferable to use the so-called double jet method. The supply of silver ions and halide ions is necessary and sufficient for the growth of only existing grains, without dissolving the existing crystal grains as the crystal grains grow, and conversely not allowing the generation and growth of new grains. The supply rate is increased continuously or stepwise at the critical supply rate for supplying silver halide or within its permissible range. As for this increasing method,
No. 48-36890, No. 52-16364, JP-A-55-142329
It is stated in the No. This critical feed rate is determined by temperature, pH, pAg, degree of stirring, composition of silver halide grains, solubility, grain size,
Although it varies depending on the grain sensitivity distance, crystal habit, or type and concentration of protective colloid, it can be easily determined experimentally by methods such as microscopic observation of emulsion grains suspended in the solution phase and turbidity measurement. You can ask for it. By gradually increasing the addition rate within this critical supply rate or its allowable range, a monodisperse emulsion, that is, one with a coefficient of variation of 20% or less, can be obtained. In order to obtain the monodisperse emulsion of the present invention, it is particularly preferable to use seed crystals and grow grains by supplying silver ions and halide ions using the seed crystals as growth nuclei. Note that the seed crystal may be previously subjected to reduction sensitization. The wider the particle size distribution of this seed crystal, the wider the particle size distribution after particle growth. Therefore, in order to obtain a monodisperse emulsion, it is preferable to use seed crystals with a narrow particle size distribution at the seed crystal stage. Additionally, to obtain normal crystal grains, normal crystal seeds are used, and to obtain twin crystal particles, twin seeds are used; It is easy to obtain a narrow one. Therefore, in an embodiment of the present invention, it is preferable to use normal crystal seeds to obtain normal crystal particles. In the present invention, inside the particle (from the outer wall of the particle)
As for the method of forming localized areas of high concentration silver iodide of at least 20 mol % on the inside of the grains (separated by 0.01 μm or more), it is preferable to use seed crystals, but methods that do not use seed crystals are preferable. It may be. When seed crystals are not used, there is no silver halide that can serve as growth nuclei in the reaction liquid phase (hereinafter referred to as mother liquor) containing protected gelatin before the start of ripening, so silver ions and at least 20 mol% or more are first added. Halide ions containing a high concentration of iodine ions are supplied to form growth nuclei. Then, additional supply is continued to grow particles from the growth nuclei. lastly,
A shell layer having a thickness of 0.01 μm or more is formed on silver halide containing no silver iodide. If using seed crystals, at least 20
Silver iodide of mol % or more may be formed and then covered with a shell layer. Alternatively, the amount of silver iodide in the seed crystal is set to 0 or within the range of 10 mol % or less, and at least 20 mol % of silver iodide is formed inside the grain in the step of growing the seed crystal, and then the shell layer is formed. It may be coated with. In this case, in the present invention, the ratio of silver iodide to total silver halide in the entire grain is 0.5 to 10.
Since the former method has a larger crystal grain size than the latter, and the grain size distribution is wider, it is easier to obtain a monodisperse emulsion with a multilayer structure like the latter. Therefore, the effects of the present invention become more significant. In the present invention, during particle growth before chemical sensitization, the pAg of the mother liquor containing protective colloid is at least
It is necessary to increase the (111) planes by more than 5% and to round the particles by passing through an atmosphere with a strong bromine ion excess of 10.5 or more, preferably 11.5 or more. This achieves the desired effects of the present invention. In this case, the increase rate of the (111) plane is relative to that before passing through the above pAg atmosphere of 10.5 or more, and especially if the increase rate of the (111) plane is 10% or more,
More preferably, it is 10 to 20%. By the way, as outlined in many books on photographic engineering or photochemistry (for example, see Fundamentals of Photographic Engineering, published by Corona Publishing, 1978, pages 159-161), silver halide grains are usually mirror-like. It has a face with index (111) or (100). When it has 100% (111) faces, it is a regular octahedron, and when it has 100% (100) faces, it is a regular hexahedron. Furthermore, when it has both a (111) plane and a (100) plane, it has a tetradecahedron shape. Regarding whether the outer surface of silver halide grains is covered with (111) or (100) planes, and how to measure the ratio, see the report by Akira Hirata, “Bulletin of the Society of Science. Photography of Japan” No. 13, pages 5-15 (1963). In the present invention, during grain growth before chemical sensitization,
Mother liquor containing protective colloid has a pAg of at least 10.5
By passing the above atmosphere once,
Using Hirata's measurement method, it can be easily confirmed whether the (111) plane has increased by 5% or more. In this case, the time to set the above pAg is before chemical sensitization, but preferably from the time when silver ions are added for the growth of silver halide grains to before the desalting process, especially after the addition of silver ions is completed. In particular, it is preferable to carry out the so-called desalting step which is usually carried out before chemical sensitization. This is because it is easy to obtain a monodispersed emulsion with a narrow particle size distribution. Note that aging in an atmosphere where pAg is 10.5 or more is preferably performed for 2 minutes or more. Such pAg control increases the number of (111) planes by 5% or more, resulting in a rounded shape. In addition, in the present invention, after increasing the (111) plane of the particle, chemical sensitization is performed on the grown crystal that has already grown, and the seed crystal is chemically sensitized separately from this. It's okay. On the other hand, JP-A-57-115539 describes a method of passing through an atmosphere with a pAg of 11.5 or more during silver halide growth, but the method described in the publication is the opposite of the procedure in the present invention. In this case, the desired effect of the present invention is not achieved. In addition, JP-A-57-182730 describes a method for producing a spherical monodispersed emulsion, but the emulsion grains do not have localized portions, and the effect of the present invention is not found in such emulsions. It won't happen. In the present invention, chemical sensitization methods applied to grown particles include, for example, sulfur sensitization methods using sodium thionitrate, thiourea compounds, etc., gold sensitization methods using chlorauric acid salts, gold trichloride, etc., and thiourea dioxide , a reduction sensitization method using stannous chloride, silver ripening, etc., a palladium sensitization method, a selenium sensitization method, etc., and these methods can be used alone or in combination of two or more. In the present invention, the effects of increasing sensitivity and improving pressure blackening and pressure desensitization resistance are as follows:
It becomes noticeable when this chemical sensitization is applied. In this case, it is particularly preferable to use gold sensitization and sulfur sensitization together. Such silver halide grains typically have a grain size of 0.3 to
It has an average particle size of 3 μm. A stabilizer can be added to the silver halide emulsion of the present invention prepared in this manner after chemical sensitization is completed. For example, 4-hydroxy-6-
Methyl-1,3,3a,7-tetrazaindene,
5-Mercapto-1-phenyltetrazole, 2
- Any stabilizer known in the art can be used, including mercaptobenzothiazole and the like. Further, by using an optical sensitizer such as a cyanine dye or a merocyanine dye alone or in combination as necessary, it is possible to optically sensitize to a desired wavelength range. For example, US Patent No. 2493784, US Patent No. 2519001,
Same No. 2977229, No. 3480343, No. 3672897, Same No.
No. 3703377, No. 2688545, No. 2912329, No.
No. 3397060, No. 3511664, No. 3522052, No. 3522052, No. 3511664, No. 3522052, No.
No. 3527641, No. 3615613, No. 3615632, No. 3615632, No. 3615613, No. 3615632, No.
No. 3615635, No. 3615641, No. 3617295, No. 3615635, No. 3615641, No. 3617295, No.
No. 3617293, No. 3628964, No. 3635721, No.
No. 3656959, No. 3694217, No. 3743510, No.
Dyes described in No. 3769301, No. 3793020, etc. can be used. In the silver halide photographic emulsion of the present invention, gelatin, gelatin derivatives, synthetic hydrophilic polymers, etc. can be used as the protective colloid of the vehicle.
Additionally, various photographic additives may be included. As the hardening agent, an aldohyde compound, a ketone compound, a halogen-substituted acid such as mucochloric acid, an ethyleneimine compound, a vinyl sulfonate compound, etc. can be used. As the spreading agent, saponin, lauryl or oleyl monoether of polyethylene glycol, etc. are used. The development accelerator is not particularly limited, but compounds such as thioether compounds, benzimidazole compounds (for example, those described in JP-A-49-24427), quaternary ammonium salts, polyethylene glycol, etc. 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 silver halide photographic emulsion 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), a lanolin-based ethylene oxide addition bodies, alkali metal salts and/or alkaline earth metal salts (for example, those described in JP-A-53-14022), water-soluble inorganic chlorides and matting agents (Japanese Patent Application No. 1983-14022),
69242), an addition condensate obtained by addition-condensing glycidol and ethylene oxide to a phenolaldehyde condensate, and a fluorine-containing succinic acid compound (patent application
An antistatic agent such as No. 52-104940) can be added. In addition, PH adjusters, thickeners, granularity improvers,
It may contain a matting agent for improving the film surface. When the photographic emulsion of the present invention is applied to a silver halide color photographic light-sensitive material, no drawbacks will arise even if various known constituent elements for light-sensitive materials are present in addition to the above-mentioned various additives. For example, these include compounds that react with oxidized developing agents to form dyes, ie, so-called diffusion-resistant couplers. More specifically, there are yellow couplers represented by diketomethyl type, magenta couplers represented by 5-pyrazolone type, and cyan couplers represented by phenol type and naphthol type. Examples include so-called DIR couplers, which release inhibitors, and so-called colored couplers, which adjust the masking concentration. These couplers are illustrated in Research Disclosure (RD) 9232. The types of silver halide photographic light-sensitive materials to which the photographic emulsion of the present invention can be applied include color photographic paper, color negative film, color positive film, black and white film (for example, X-ray light-sensitive materials, light-sensitive materials for printing, etc.), and diffusion transfer type films. Any photographic material may be used. Exposure for the photographic emulsion of the present invention varies depending on the state of optical sensitization, purpose of use, etc., but may be performed using tungsten, fluorescent lamps, mercury lamps, arc lamps, xenon, sunlight, xenon flash, cathode ray tube flying spots, laser beams, etc. , electron beams, X-rays, fluorescent screens for X-ray photography, and the like can be used as appropriate. In addition to the normal exposure time of 1/1000 to 100 seconds,
For xenon flash, cathode ray tube, and laser light, short exposure times of 1/10 ⁴ to 1/40 ⁹ seconds can be applied. Specific Effects of the Invention The light-sensitive material using the emulsion of the present invention can be produced without impairing the effects of the various physical property improvers as described above.
It is characterized by high sensitivity and good pressure blackening and pressure desensitization resistance. Further, the present invention has no adverse effects on photographic performance such as sensitivity and fog. In the present invention, the effect of improving sensitivity and resistance to pressure blackening and pressure desensitization is due to the localization of silver iodide inside the grains and the fact that silver iodide is ripened in a high pAg atmosphere during crystal growth before chemical ripening. This is a synergistic effect of the two, and is not an independent effect of each. Furthermore, there is also the effect that red safelight fog and thermal fog are reduced. Specific Examples of the Invention 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 A monodisperse cubic crystal emulsion of silver iodobromide containing 2.0 mol % of silver iodide with an average grain size of 0.3 μm was obtained by a double jet method while controlling the temperature at 60° C., pAg=8, and PH=2.0. From the electron micrograph of this emulsion,
The incidence of twin grains was 1% or less in number. After desalting the particles, add silver nitrate solution to
Silver ripening was performed for 70 minutes at °C, pAg = 3, and pH = 6. Of this emulsion, an amount corresponding to 2 mol % of the total silver halide used for growth was used as a seed crystal to grow in the following manner. That is, the seed crystals were dissolved in a solution 8.5 containing protected gelatin and ammonia kept at 40°C, and the pH was further adjusted with glacial acetic acid. Using this solution as a mother liquid, a 3.2N ammonia special silver ion aqueous solution and a halide aqueous solution were added by a double jet method in a flow pattern as shown in FIG. 1, followed by stirring and mixing. In this case, as shown in Table 1, by changing the ammonia concentration and PHpAg of this mother liquor and changing the iodine ion content in the additive solution, iodine is added to the interior at various concentrations as shown in Table 1. Localized silver oxide. Next, while keeping the pAg constant at 9.0, the pH was changed from 9 to 8 in proportion to the amount of ammoniacal silver ion added to form a shell of pure silver bromide. In this way, seven types of monodispersed emulsions shown in Table 1 were prepared (Nos.-1 to -6). Emulsion No.
Emulsions other than No.-1 and No.-6 were ripened at pAg of 11.5 for 3 minutes at the end of grain growth to round the grains. In each emulsion, the total ratio of silver iodide to the total silver halide was 2 mol %. In addition, the AgI mol% of the localized part of silver iodide is
As shown in Table 1, the shell thickness of silver bromide is 0.5 to 0.8 μm, and the average particle diameter is 1.21 to 1.23 μm.
It was set as m. Excess water-soluble salts were removed from each emulsion obtained by a coagulation precipitation method, and ammonium thiocyanate, chloroauric acid, and hypo were added to perform gold-sulfur sensitization. and 4-hydroxy-6-methyl-1,
After adding 3,3a,7-tetrazaindene and common photographic additives such as spreading agents, thickeners, and hardeners, the amount of silver was is 60mg/
A sample for sensitometry was obtained by coating and drying in a conventional manner to a thickness of 100 cm ² . In addition, each sample was published in "Butylene of the Society of Science Photography of Japan" No. 13, 5 by Akira Hirata.
Based on ~15 pages (1963), manufactured by Memoto Denshisha
JDX-10RA was used to determine the increase in (111) planes before and after aging at pAg11.5. The results are shown in Table 1.
Shown below.

[Table] Wedge exposure was performed on each sample at 3.2 CMS, and development processing was performed for 90 seconds with XD-90 processing solution using a QX-1200 automatic processor manufactured by Konishi Roku Photo Industry Co., Ltd. to determine the sensitivity of each sample. I asked for it. Sensitivity is expressed as the reciprocal of the amount of light required to increase the blackening density by 1.0 due to exposure, and is expressed as a relative value with -1 being 100. Two pieces of each sample were heated for about 12 hours and 25 minutes.
It was maintained at a constant temperature and humidity of 50% relative humidity and 50% relative humidity, and was bent approximately 280 degrees with a radius of curvature of 2 cm. One of each of the two sheets was developed without exposure 3 minutes after it was folded. The difference between the density of the darkened portion caused by the bending and the fog density was defined as ΔD ₁ and was used as a measure of pressure darkening. In other words, the smaller this value is, the better the pressure blackening resistance is. Fold the other one of each two pieces and then
After a few minutes, it was exposed to light using an optical wedge and developed. The darkening density of each wedge of this sample was measured, and the difference in density between the desensitized area caused by bending and the area that was not bent was defined as △D ₂ , and each density
△D ₂ was divided by D ₂ to calculate the average value △D ₂ /D ₂ , and this value was used as a guideline for pressure desensitization. In other words, the smaller this value is, the better the pressure desensitization resistance is. The results of this pressure blackening and pressure desensitization are shown in Table 2. In addition, Table 2 shows the sensitivity of comparative sample-1.
The sensitivity, which is expressed as a relative sensitivity when set to 100, and the fog density excluding the base density are listed together.

[Table] From the results shown in Tables 1 and 2, it can be seen that according to the present invention, both pressure blackening and pressure desensitization are improved without any influence on fog sensitivity. To add more, sample No.-1 and -2
By comparing the results with No.
By comparing -6 and -6, it can be seen that this is not due only to localization of high concentration of silver iodide inside the grains. That is, it can be seen that the extremely excellent effects of the present invention are due to the mutual effect of both. Comparative Example Emulsion-1, -4,- exemplified in Example 1
Got 5. Furthermore, by the method shown in Example 1 of JP-A No. 57-64226, 2 mol% Ag and an average particle size of 1.20 μm were obtained by the so-called single-jet method.
A polydisperse iodobromide emulsion-8 with m and σ/0.28 was obtained. Each of these emulsions was subjected to gold-sulfur sensitization in the same manner as in Example 1.
Take aged samples up to 1 minute, add additives,
Various samples were obtained by coating and drying. Each sample was bent in the same manner as in Example 1, and the resulting pressure blackening and pressure desensitization were measured. Sensitometric sensitivity was also measured. The results are shown in Table 3.

【table】

[Table] From the results shown in Table 3, it can be seen that the silver halide emulsion of the present invention has high sensitivity and extremely excellent resistance to pressure blackening and pressure desensitization.

[Brief explanation of drawings]

FIG. 1 is a graph showing the supply flow rate profile of silver ions and halide ions during silver halide grain growth of each sample in Examples.

Claims (1)

[Claims] 1 The average silver iodide content in the grain is 0.5 to 10 mol%, the grain has a localized portion of silver iodide at a concentration of 20 mol% or more, and the shape is a rounded hexahedron. Alternatively, a silver halide photographic emulsion comprising a monodisperse emulsion of dodecahedral silver halide grains and being chemically sensitized.