JPH0617988B2 - Silver halide photographic emulsion and method for producing the same - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Technical Field The present invention relates to a silver halide emulsion, and more particularly to an emulsion comprising silver halide grains having a novel structure and a method for producing the same.

Prior art and its problems Tabular silver halide grains containing parallel twin planes (hereinafter referred to as tabular grains) have the following merits as photographic characteristics, and therefore, commercially available light-sensitive materials which have been conventionally highly sensitive. Has been used for.

That is, 1) its specific surface area is large, and a large amount of sensitizing dye can be adsorbed on the surface, -blue (blue) / blue (blue)
High sensitivity, 2) When an emulsion containing tabular grains is coated and dried, the grains are arranged parallel to the base surface, so the thickness of the coating layer can be made thin and the sharpness is good, 3) X-ray photography In the system, when a sensitizing dye is added to the tabular grains, the extinction coefficient of the dye is larger than the extinction coefficient of indirect transition of silver halide (AgX), and crossover light can be remarkably reduced, resulting in deterioration of image quality. 4) When tabular grains with a high aspect ratio are developed, the covering power is high, and the silver concentration and dye concentration are leveled to improve RMS grain characteristics. 5) Parallel multiple twinning The tabular grains have a latent image easily formed in the edge trough portion of the tabular grain, prevent latent image dispersion and have high sensitivity, 6) have little light scattering, and can obtain an image with high resolution,
Etc.

On the other hand, the core portion of non-tabular grains, for example, regular type silver halide (AgX) grains such as cubes and octahedra is made into an AgBrI layer having a high iodine content, and a reduction sensitized silver nucleus is contained in the core portion, A double-structured particle in which the shell portion of the particle is an AgBrI layer or an AgBrClI layer having a low iodine content is disclosed in JP-A-60-143331 and JP-A-60-143332, Journal of Image Science, 29 , 193 (19).
85) and the like, and based on the researches of the present inventors, it is known that the following merits are provided in the exposure process and the development process.

First of all, for the photosensitization process, 1) the high light absorption coefficient of the layer with high iodine content (core part) makes the blue light absorption efficiency high and the blue sensitivity high, 2) blue ( When exposed to blue), holes are transferred to a layer (core part) having a high iodine content due to its band structure characteristics, electrons are trapped in the chemically sensitized nuclei on the surface, charge separation occurs, and recombination probability increases. Decrease, and the blue sensitivity increases. 3) Since the core part is made of a layer with a high iodine content, it is possible to reduce the number of dye holes to silver halide compared to when the surface is of a high iodine type. High sensitivity of color sensitization because injection does not occur easily.

On the other hand, with respect to the development process, 1) the core portion is a layer having a high iodine content, and therefore the initial development activity is higher than that in the case where the surface is of a high iodine type, and therefore there is less variation in development and exposure is performed. Latent image is used effectively, 2) Late development progress is moderately slowed down.Therefore, in case of color negative development, not all particles are developed and development is stopped midway to suppress the spread of each dye cloud. Therefore, it is considered that there are merits such that the graininess is improved, and the DIR effect, which is effective in the later development process in the parallel development process such as color negative development, can be increased.

From the above, a tabular grain ratio having a large specific surface area is high, a core is a double structure grain having a high iodine content AgBrI layer, and a photographic emulsion comprising tabular AgX has excellent photographic characteristics. Is expected to show.

In producing such grains, the first major problem is that when a high iodine content AgBrI layer is incorporated in the core portion of tabular grains as described in JP-A-58-113928. Thick non-tabular grains are produced.

For example, CRBerry and SJMarino, Journal of Physic
al chemistry, 62 , 881 (1958), APHTrivelli and WFSmith, The Photographic Jour
nal, 80 volumes, 285 (1949), EBGutoff, Photographic Science and Engineering,
14 , 248-257 (1970), Cugnac and Chate
au, Science & Industry Photography, 33 , 121 (1962), etc., all of the methods for producing tabular grains comprising a core portion having a high iodine content have a thick non-tabular grain ratio. It gives high grains and cannot be said to have the characteristics of the tabular grains described above.

The second problem is that a conventional grain forming method (especially a method of adding I ⁻ in a reaction vessel before introducing a silver salt and a halide salt, US Pat. No. 4,150,944,
No. 4,184,877 and No. 4,184,878, in which AgI is used as a seed crystal), the iodine content of the core portion of the tabular grains can be set to a desired constant composition. It is not possible to form an AgBrI layer having a uniform composition. And such particles are disclosed in JP-A-59-9943.
As described in No. 3, photographic properties such as pressure characteristics are not preferable.

Various studies have been made on these problems.

For example, as to the first problem, Japanese Patent Laid-Open No. 58-113
No. 928, the reaction vessel before introducing the silver salt and the bromide salt was set to a state in which I ⁻ was substantially absent (iodine ion content was less than 0.5 mol%), and its pBr value was 0.6. ~ 1.
6 to adjust the central region to substantially AgBr (AgBrI
The iodide ion content of (4) is preferably less than 5 mol%, more preferably less than 3 mol%) to form tabular core grains in a region where the proportion of non-tabular grains mixed is small, and then high tabular core grains are formed thereon. An AgX grain having a triple structure in which an iodine content layer (almost a solid solution limit, more preferably an intermediate layer of 6 to 20 mol%) is laminated, and an AgBrI layer having a low iodine content is laminated thereon as a shell portion. Disclosure.

However, the particles formed by this method have the following drawbacks.

a) Since the high iodine content layer is formed only in the intermediate layer, the volume fraction of the entire high iodine content layer cannot be made large (for example, in the case of tabular grains, the thickness is 0 at the nucleation stage). .03
The projected particle size is, for example, 1 μm.
And tabular grains with an aspect ratio of 10 have a thickness of 0.1μ
m, and in the double-structured particles, the thickness of the shell layer needs to be 0.01 to 0.03 μm or more,
Tabular grains with a high aspect ratio are not preferable because the thickness of this intermediate layer cannot be sufficiently set and the volume fraction of the high iodine layer in the total volume cannot be made large), b) core layer When there is a large difference in the iodine content between the intermediate layer and the intermediate layer and between the intermediate layer and the shell layer, and there is a layer with a large difference in the iodine content in the grains as described above, when pressure is applied to the grains, The stress concentrates there, which may cause electron trap centers and cause so-called pressure desensitization. C) When a high iodine AgBrI layer is laminated on the AgBr grain, a uniform thickness is formed on the host grain. It is not necessarily simple, because it does not stack with and grows epitaxially, or it causes conversion accompanied by dissolution of host particles.

In Japanese Patent Application No. 60-294553, the iodine ion concentration in the reaction vessel before introducing the silver salt and the bromide salt is determined. However, the iodide content of the core grains in the examples is 5 to 6 mol% AgBrI. In addition, the halogen composition is not uniform in the method of adding iodine ions to such a reaction vessel in advance.

According to the method described in JP-A-55-142329 by the present inventor, the addition rate of silver salt and halide salt in the crystal growth stage of tabular grains is set to 30 to 100% of the crystal critical growth rate.
The pBr value at that time is kept at pBr 2.0 to 4.8 during the first 1/3 or more of the crystal growth period and pBr 1.5 to 4.8 during the remaining first 1/3 or more.

In this method, the average particle size is 0.96 μm and the coefficient of variation is 1
The content was 1.6%, and an extremely uniform size distribution of grains was obtained as an emulsion composed of multiple twin grains (double structure grains of AgBrI layer having a high iodine content in the core portion). Since the nucleation conditions of the grains are inappropriate, the proportion of non-parallel twin grains is large.

Further, the double-structured twin grains shown in the example of JP-A-60-143331 have a large proportion of potato-like grains because the nucleation is performed by the rush addition single jet method. Has become.

In addition, JP-A 61-14630 and 58-2111
Nos. 43 and 59-99433 also describe tabular silver iodobromide grains, but they do not solve the above problems.

Therefore, a double-structure tabular grain having a core portion of a high iodine content AgBrI layer and a shell portion of a low iodine content AgBrI layer or AgBrClI layer having a high developing activity, and a thick non-tabular grain It is desired to develop an emulsion containing less grains.

II Object of the Invention The object of the present invention is to have high sensitivity, good sharpness,
It is an object of the present invention to provide a silver halide photographic emulsion capable of preventing deterioration of image quality, having high covering power, good RMS grain characteristics, and high resolution, and a method for producing the same.

III. DISCLOSURE OF THE INVENTION Such an object is achieved by the present invention described below.

That is, in the present invention, at least 60% or more of the total projected area of silver halide grains has a multilayer structure having a core and one or more shells, and has a tabular AgBrI or X-ray profile based on the (220) plane. AgBrI
Cl particles, which account for 60% or more, have a core AgI content of 7 mol% to the solid solution limit, and an outermost shell shell AgI content of 0 or 6 mol% or less. A silver halide photographic emulsion characterized by being a hexagonal grain having an aspect ratio of 2 to 40 and a coefficient of variation between the side lengths of six sides of a hexagon being within 25%. The method of producing a silver halide emulsion which undergoes nucleation of silver halide grains, Ostwald ripening and grain growth, wherein the gelatin concentration in the reaction solution at the time of nucleation is 0.8 to 20% by weight, and silver salt is used. And the addition rate of the halide salt is 6 × 10 ^{−4 to} 2.9 × 10 per reaction solution.
Nucleation is performed at ^-1 mol / min, and the pBr value in the reaction solution at the time of nucleation is 1.0 to 2.5, and at least 60% or more of the total projected area of the silver halide grains is more than the core and one or more. Tabular AgBrI or AgBrICl particles having a X-ray profile based on the (220) plane, the core AgI content of the particles accounting for 60% or more is 7 mol% to solid solution It is the limit, the AgI content of the shell is 0 or 6 mol% or less, the average aspect ratio is 2 to 40, and the variation coefficient between the side lengths of the six sides of the hexagon is within 25%. A method for producing a silver halide emulsion, characterized in that a silver halide emulsion containing silver halide grains which are hexagonal grains is obtained.

IV Specific Configuration of the Invention Hereinafter, the specific configuration of the present invention will be described in detail.

The silver halide photographic emulsion of the present invention contains at least 60% or more, preferably 70% or more of the total projected area of silver halide grains.
As described above, more preferably 90% or more is a flat plate-like AgBrI or Ag having a core and one or more shells.
BrICl grains, more preferably substantially regular hexagonal tabular grains composed of parallel twin planes, having a core AgI
The content is 7 mol% to solid solution limit, preferably 10 to 40 mol%, more preferably 15 to 40 mol%, and the AgI content of the outermost shell is 6 mol% or less, preferably 3 mol% or less (0 (Including mol%). And, the AgCl content of the shell is preferably 0 to 40 mol%.

Furthermore, the shell is preferably two layers, but two or more layers (for example, two layers)
Layers, 3 layers, etc.), the AgI content of the shell need not be uniform throughout the shell, and the average AgI content of each shell may be different. For example, it may be gradually decreased as it goes to the outermost layer, and conversely it may be gradually increased.

Multi-layered tabular AgBrI or AgBrICl grains with at least 60% of total projected area of silver halide grains
The reason therefor is that if it is less than 60%, excellent photographic characteristics as tabular silver halide grains cannot be obtained.

In the present invention, the tabular grains preferably have a substantially regular hexagonal shape.

Here, a substantially regular hexagonal tabular grain means hexagonal 6
A particle whose coefficient of variation between the lengths of two sides is within 25%.
The hexagonal angle is exactly 120 ° according to the law of constant crystal plane angle. However, the corners may be slightly rounded when viewed microscopically. The coefficient of variation between the side lengths is (maximum side length-minimum side length) / (average side length) × 100.

The AgI content of the core is set to 7 mol% to the solid solution limit of 7
This is because if it is less than mol%, excellent photographic characteristics of AgX particles having a high iodine content core portion cannot be obtained in both the light-sensitive process and the developing process. If the solid solution limit is exceeded, pure AgI particles are separately formed. However, pure AgI causes defective fixing. Here, the solid solution limit refers to the maximum amount of mixture that can exist as a solid solution while maintaining the NaCl type crystal structure. The solid solubility limit is, for example, Gmelins Handbuch deranorga
nischen Chemie P402-P403, for example, AgBrI is 38.6 mol%.

The core may contain AgCl, but it is usually not contained. This is because if the core contains AgCl, the band gap becomes smaller in the band structure described later, which is not desirable.

Also, the AgI content of shell is 6 mol% or less,
This is because if it exceeds 6 mol%, it is disadvantageous in terms of charge separation efficiency of electrons and holes, color sensitization efficiency, and initial development speed.

Tabular AgBrI to AgBrICl particles of AgCl
The content of 40 mol% or less is disadvantageous in terms of blue light absorption efficiency, particle stability, and fogging when it exceeds 40 mol%, and its chemical sensitization property, particularly gold sensitization property is poor. This is because the difference in lattice constant from the core layer becomes large and the pressure characteristics and the like deteriorate.

In the present invention, it is more preferable for the purpose of the present invention that the core portion having a high AgI concentration has a reduction sensitized silver nucleus. Whether or not it has this reduction-sensitized silver nucleus,
It can be easily judged from the fact that an inversion image of internal fog existing when exposed and internally developed by an ordinary method to write an HD curve is observed.

It is more preferable that the core layer of the particles of the present invention does not contain Cl. The reason is that the more Cl ⁻ contained in the core layer, the lower the energy level of the valence band of the core layer, and the thinner the particles of the effect of the present invention. Cl ^- is 1
0 mol% or less is preferable, 5 mol% or less is more preferable,
It is particularly preferably 1 mol% or less.

As the halogen composition of the shell layer, Cl is 40 mol% or less, preferably 30 mol% or less, more preferably 2 mol% or less.
The inclusion of -30 mol% has the following advantages.

Development activity on the surface of silver halide grains is enhanced, and initial development is accelerated.

The band structure is as shown in FIG. 1. By containing Cl, the valence band of the shell layer is further lowered, and hole injection from the sensitizing dye is more difficult to occur.

As shown in FIG. 1 as a band structure, the band gap difference in the valence band between the core and the shell becomes larger,
To promote the separation of electrons and holes.

Further, the structure of the silver halide grain in the invention will be described.

The ratio of the number Nt of tabular grains to the number Nn of non-parallel twin grains is preferably Nn / Nt <0.25, more preferably Nn / Nt <0.15, that is, the total number of grains. When N is set, Nt / N = 0.7 to 1.0, and more preferably Nt / N = 0.81 to 1.0 (these correspond to the above in terms of projected area).

The distribution of the iodide ion content in the core portion of the tabular grains is usually uniform, but may have a distribution. For example, even if the concentration becomes higher toward the inside or the outside, it has a maximum or minimum concentration in the intermediate region. What you may have.

The volume ratio of the core portion of the tabular grains is preferably 0.1
It should be 5 to 0.95.

The thickness of the outermost shell is preferably 0.01 to 0.
Must be 2 μm.

The average particle size of the tabular grains is preferably 0.2 to 5 μm,
The average thickness is more preferably 0.3 to 2 μm, and the average thickness is preferably 0.05 to 0.6 μm, more preferably 0.0.
6 to 0.3 μm.

The tabular grains have an average aspect ratio of preferably 2 to 40, more preferably 4 to 30, and particularly preferably 5 to 20.

Next, a method for producing the silver halide photographic emulsion of the present invention will be described.

In the present invention, the silver halide grains undergo nucleation, Ostwald ripening and grain growth.

In the nucleation stage in this case, the concentration of gelatin in the reaction solution is 0.8 to 20% by weight, preferably 1.0 to 6.0% by weight, and the addition of a silver salt and a halide salt to an aqueous gelatin solution. The rate is 6 × 10 ^{−4 to} 2.9 × 10 ⁻¹ mol /
Min, preferably 3 × 10 ^{−3 to} 1.5 × 10 ⁻¹ mol / min,
And the pBr value in the reaction solution is 1.1 to 2.5, preferably 1.3 to 2.1.

Furthermore, the temperature in the reaction solution during nucleation is preferably 15 to 50 ° C, and more preferably 20 to 45 ° C.

Then, through such a process, a silver halide emulsion containing tabular silver halide grains having parallel twin planes as described above is produced.

In this case, substantially no iodide salt is contained in the reaction vessel before the introduction of the silver salt and the halide salt for nucleation, and the degree of supersaturation at that time is substantially non-parallel twin grains. In the non-existing region, that is, from the electron micrograph of the finally generated grains, the number Nn of non-parallel twin grains and the number Nt of tabular grains are measured, and Nn / Nt <0.25, more preferably Nn / Nt < The area is controlled to be 0.15. Such a ratio of Nn / Nt is as described above when it corresponds to the total projected area of the silver halide grains.

Here, "substantially containing no iodide salt" means that the amount of iodide salt added in advance is 3 mol% or less of the amount of silver added in the first minute.

It has been conventionally known that when a high iodine content layer is introduced into the central portion of a tabular grain, the mixing ratio of non-parallel twin grains increases, and the cause is that the degree of supersaturation during nucleation depends on the iodine content. It has been found that this is due to an increase in the increase, and the present invention introduces a high iodine content layer in the center of the tabular grain without the inclusion of non-parallel twin grains by controlling other supersaturation regulators. Makes it possible.

The results of studies on the nucleation conditions for this are shown below.

Conventionally, when the Br ⁻ concentration of the solution at the time of nucleation is increased, twin planes are formed.
R. Berry and DC Skillman, Journal of Applied Physic
s, 33 , 1900 (1962), it is considered to be generated due to the deposition of AgBr ₃ ²⁻ , and J. Rodgers, Symp.
osium paper on Growth of Photosensitive Crystals, C
ambridge, England P.M. 12-14 (SePt.1978)
State that twin formation starts when the relative concentration of AgBr ₃ ²⁻ reaches 50%.

That is, twin plane formation has been considered in relation to the presence of AgBr ₃ ²⁻ .

However, in the present invention, if the Br ⁻ concentration in the reaction solution is decreased, the twin plane generation probability can be decreased. Furthermore, even if the pBr value of the solution is the same, the present inventor
It has been found that it is preferable to use at least one or more of the following means.

The higher the gelatin concentration, the lower the twin plane formation probability. The higher the stirring speed and the better the stirring condition, the lower the twin plane formation probability. Addition of aqueous solution of silver salt and halide salt. Decreasing the speed decreases the probability of twin plane formation.

Further, even if the gelatin aqueous solution having the same concentration as the gelatin aqueous solution in the reaction vessel is used for the AgNO ₃ aqueous solution and the KBr aqueous solution, the same result is obtained, and therefore the gelatin concentration diluting effect is not obtained by increasing the addition rate.

Furthermore, increasing the nucleation temperature decreases the probability of twin plane formation.

Add a silver halide solvent such as NH ₃ or thioether,
The higher the solubility, the lower the probability of twin plane formation.

Gelatin obtained from the skin of a fish living in the cold sea as a gelatin seed (a gelatin that has a low content of proline and hydroxyproline and is unlikely to form hydrogen bonds between chains, such as Norl
Using Hipure gelatin from and (Canada) reduces the probability of twin plane formation.

In connection with the above, if gelatin is added to one or both of the silver salt and halide salt aqueous solutions to be added, the dilution effect of the gelatin concentration near the addition port of these aqueous solutions will disappear and the twin plane generation probability will decrease. (In this case, as the gelatin to be added, particularly alkali-treated gelatin or its low molecular weight gelatin (molecular weight 2000 to 100,000)
Is preferred).

When the temperature of the reaction solution is lower than 35 ° C, the lower the pH of the reaction solution, the lower the probability of twin plane formation.
The dependence is small above ℃.

Irrelevant salts in reaction mixture (eg NaNO ₃ and KNO ₃ )
The higher the concentration, the lower the probability of twin plane formation.

Then, in any of the above cases, if the generation rate of twin planes can be moved in a direction of increasing, the frequency of tabular grain formation will increase, and if it further increases, the proportion of non-parallel twin grains will eventually increase. .

In the conventional method, the effect of iodide ions is remarkable. For example, if the iodine content is increased from 0 mol% to 5 mol%, the probability of tabular grain formation is increased by about 8 times. In addition, there was a problem that the generation ratio of non-parallel twin crystal nuclei was significantly increased.

As a cause of this, in addition to the supersaturation factor, a stacking fault surface stabilization factor due to an increase in the lattice constant is considered.
Therefore, if an attempt is made to introduce a high iodine content layer of 7 mol% or more into the core portion of the tabular grains, the production rate of the non-parallel twin grains becomes very high in the conventional method. Until now, it was not possible to elucidate the method of removing it, but the present inventor has discovered a method of removing it.

That is, the effects of the above-mentioned supersaturation factors are additive to each other, and the reason why the generation ratio of the non-parallel twin grains increases due to the mixing of iodine ions is that the generation probability of stacking faults increases. One or two or more factors,
The non-parallel twin grains can be removed by acting to reduce the twin plane generation frequency. Preferably pB
In addition to the method of controlling the r-value, it is used as a method of controlling the addition rate of the gelatin concentration, the silver halide solvent, the temperature at the time of nucleation of the. The higher the iodide ion content, the more frequently twin planes are generated, and the degree of action depends on the iodoion content. The preferable region is Nn / Nt <from the electron micrograph of the replica method of the finally generated particles.
It is to adjust the above-mentioned factors 1 to 0.25, more preferably Nn / Nt <0.15. Practically, from FIG. 6, the increase in the number of tabular grains generated with an increase in the iodine content is read, and the increase is shown in FIG.
The amount to be canceled may be read using the relationship of the graph in FIG. 11 and an action may be taken.

In the present invention, in order to form AgBrI nuclei having a particularly high iodine content, desirable nucleation conditions are (a) increasing the gelatin concentration in the reaction solution, (b) improving the stirring condition, and (c) adding a silver salt. Slowing down the addition rate of halide salt, g) increasing the temperature during nucleation within a range where the monodispersity of the resulting grains is acceptable, h) adding silver halide solvent, d) adding Addition of gelatin to the aqueous silver salt or halide salt solution, e) decreasing the Br ^- concentration in the reaction solution, and f) increasing the irrelevant salt concentration in the reaction solution, and other appropriate actions described above. You should take

In the present invention, the iodide salt is not substantially contained in the reaction vessel before introducing the silver salt and the halide salt,
The reason is as follows.

If iodide salt is added to the reaction vessel in advance, when the silver salt aqueous solution and the halide salt are added, the amount of A is higher than that of AgBr.
Since the solubility of gI is about 1/1000 to 1/9000 in the range of 20 ° to 80 ° C, first, AgI is produced and then AgBrI.
Is considered to be generated. This is CR Berry and SJMa
rino, Journal of Phys. Chem., 62 , 881 (195
8) and the particle formation method described in U.S. Pat. No. 4,150,994 which uses AgI nuclei as seed crystals, and has a drawback that the iodine content distribution is broadened. Not preferable. However, it has been found that if the amount of iodide salt added to the reaction vessel in advance is 3 mol% or less of the amount of silver added in the first minute, the adverse effect thereof is small.

In addition, the following conditions may be mentioned as conditions for nucleation of the present invention.

a) The gelatin concentration is 0.8 to 20 wt%, preferably 1.0 to 15 wt%, and more preferably 1.
0 to 6 wt% is effective, and the photographic gelatin used is ordinary photographic gelatin, but at 35 ° C.
It is difficult to use a high-concentration (1.6 to 20 wt%) gelatin solution at the following temperatures, and especially low molecular weight gelatin (molecular weight 2000 to 10
10,000), modified gelatin such as phthalated gelatin, gelatin taken from the skin of fish living in the cold sea, etc. are particularly difficult to set, and b) as an additive mixing device for improving agitation, US Patent No. No. 3,785,777 (1974) and German Paten
t Application (OLS) No. 2,556,888, it is preferable to use an in-liquid addition mixing device for the reaction solution, c) The addition rate of silver salt and halide salt is 6 × 10 per 1 aqueous gelatin solution. ^-4 mol / min to 2.9x
10 ^-1 mol / min, d) Ordinary photographic gelatin is used as the gelatin to be added to the aqueous silver salt or halide salt solution, but the concentration should be such that the aqueous solutions do not set. However, if a heating device for these liquids is attached, it is possible to add even higher concentrations (about 20 wt%). As the low molecular weight gelatin (molecular weight 2000 to 100,000) or modified gelatin, it is difficult to set, and therefore, it is particularly preferable.

When gelatin is added to the aqueous silver salt or halide salt solution to be added, the gelatin species, concentration and temperature should be the same as the gelatin species, concentration and temperature in the reaction vessel. Is maintained, and more uniform nucleation can be performed, so that it is more preferable.

e) As the Br ⁻ concentration in the reaction solution, pBr 1.0 to
2.5 can be used, and f) the irrelevant salt concentration in the reaction solution is 1.0 × 10 ^-2 ~
1 mol /, more preferably 1 × 10 ^{-1 to 1} mol / region can be used, and g) the pH of the reaction solution can be usually pH 2 to 10 for introducing reduction-sensitized silver nuclei. The pH is preferably in the range of 8.0 to 9.5, and preferably 2.0 to 8.0 when not introduced. H) The temperature of the reaction solution is 15 to The temperature range of 50 ° C. can be used, but the temperature range of 20 to 45 ° C. is more preferable in order to improve the operability and the monodispersity of the produced particles. I) The AgX solvent added to the reaction solution is usually 0 to 1 ．
5 × 10 ^-1 mol / preferably 1 × 10 ^{-4 to} 1.5 × 10
^-1 mol / region can be used, and the following can be used as the AgX solvent.

More preferably, during the nucleation period of the present invention, all of the above-mentioned supersaturation factors or the total supersaturation factor of all the supersaturation factors are kept constant. This is because if the supersaturation factor rises too much during the nucleation period, non-parallel twin grains are mixed, and if it is lowered too much, the probability of tabular grain formation decreases.

The upper limit of the degree of supersaturation is given by Nn / Nt <0.2, and the lower limit is the ratio of tabular grain formation (the number of tabular grains produced during nucleation Nt / the total number of grains produced during nucleation No)> 0.2.
%, More preferably Nn / Nt> 0.5%.

Such a ratio is obtained by observing the average volume of one tabular grain with an electron microscope, determining the number Nt of tabular grains produced from the amount of added silver added, and using the direct method of grains sampled immediately after the nucleation period. It is obtained by observing the particle shape and assuming that the particle shape is spherical from the observation by an electron microscope and the amount of added silver.

From the above examination results, the manufacturing conditions as described above are set.

The particles thus nucleated are subsequently described in JP-A-60-29.
Ostwald ripening as described in 4553 to reduce non-tabular grains (non-twinned grains, single twinned grains, etc.) and increase tabular grain proportions. It keeps all supersaturation factors during nucleation uniform, and the flattening rate (Nt / N
This is because if the action of increasing the stacking fault formation probability is performed in an attempt to raise the value of (o) to 15% or more, the inclusion of non-parallel twin grains increases.

Therefore, even if all of the supersaturation factors are made uniform in the nucleation stage, the flattening rate does not exceed 20%.
However, at least 60% of the total projected area of the grains of the invention
As described above, preferably 70% or more, and more preferably 90% or more are tabular grains. Therefore, it is necessary to perform Ostwald ripening for increasing the tabularization rate after nucleation.

Therefore, the grain of the present invention undergoes a process of nucleation → Ostwald ripening → crystal growth, but during the crystal growth of the tabular grain, 1
Parts, non-tabular grains (untwinned grains or single twinned grains)
The crystal growth may be carried out while the aging disappears.

Further, the particles of the present invention have nucleation → first Ostwald ripening →
A process of crystal growth → second Ostwald ripening can also be taken.

The conditions for this first Ostwald ripening are pBr1.3-
It is desirable that the temperature is 2.6 and the temperature is 40 to 80 ° C.

In order to carry out this ripening more efficiently, a silver halide solvent described below may be used.

As another aging method, pBr1.
After ripening in the 3 to 2.2 region to increase the flattening rate, a silver salt may be added next and ripening in the pBr 1.7 to 3.3 region may be carried out to perform two-stage ripening.

After aging as described above, grains are grown.

The conditions for grain growth follow those described in JP-A-55-142329. That is, the Br ⁻ concentration in the reaction solution during grain growth is
pBr 1.5-3.3, temperature 45-80 ° C, AgNO
Substantially perform grain growth with the addition of the double jet method ₃ solution and a halide salt aqueous solution, but the addition rate is faster rate than Ostwald ripening rate is and tabular grain new nuclei is not generated occurs, The rate of addition increases with grain growth. The term "substantially" refers to a period of 1/2 or more of the crystal growth period. Specifically, the addition rate is set to a growth rate of about 30 to 100% of the critical growth rate of crystal grains.

The method of increasing the addition rate of silver ions and halogen ions can be according to the description in JP-A-55-142329.

The core portion of the particles of the present invention may be one obtained by nucleation → Ostwald ripening as the core portion, or one obtained by nucleation → Ostwald ripening → crystal growth may be used as the core portion.

In the latter case, Ag having a high iodine content even during the crystal growth period
It is necessary to form a BrI layer. In that case, the iodide salt that is usually added can be contained in the aqueous solution of the halide salt to which the double jet is added.

In addition, after this crystal growth, non-planar fine particles (0.1 μm)
In the case where a mixture of (m diameter or less) is found, fine particles can be eliminated by adding Ostwald ripening as necessary. The aging conditions are preferably pBr 1.7 to 3.3 and temperature 40 to 80 ° C.

Further, the iodide salt aqueous solution may be added as a triple jet, and may be added independently from another addition port.

By the above operation, the core layer of the double structure particle of the present invention is formed.

The core layer of the tabular grains of the present invention contains reduction sensitized silver nuclei. However, by keeping the pH of the solution during formation of the core layer at 8.0 to 9.5, reduction sensitized silver is formed in the core layer. A nucleus can be introduced.

When the halogen composition of the next shell layer is AgBrI, crystal growth is continued under the same conditions as above. However, the halide salt aqueous solution added I ^- adding from another addition port as content or triple jet I ^- addition rate decreases in accordance with the iodide content of the shell layer.

On the other hand, when the halogen composition of the shell layer is set to AgBrClI, excess Br ⁻ in the reaction solution may be removed by washing with water or ultrafiltration at the time when the formation of particles in the core layer is completed, or the double layer for forming the core layer may be used. After the jet addition is completed, the addition of Br ⁻ is stopped, and the silver salt and iodide salt aqueous solution is continuously added to remove excess Br ⁻ in the reaction solution.

The Br ^- concentration was brought to pBr> 2.2 by the above operation, and then a chloride salt such as KCl was added, and a double jet of an aqueous solution of silver salt and halide salt under Cl ^- excess concentration of pCl 0.8 to 2.2 was added. Add shells by adding. The aqueous solution of halide salt contains chloride salt, bromide salt and iodide salt, and the composition ratio thereof can be appropriately selected according to the halogen composition ratio of the shell layer.

Also in this case, in order to prevent a steep gradient of Cl ⁻ or I ⁻ content from being formed between the core layer and the shell layer, the halogen composition ratio in the halide salt aqueous solution to be added, or another addition port It is sufficient to gradually change the addition rate of Cl ⁻ or I ⁻ added from the above without abrupt change.

The pH at the time of forming the shell layer is preferably 7.5 to 9.3.

The aspect ratio of the double-structured grain of the present invention is the diameter / thickness ratio, the diameter refers to the diameter of a circle having an area equal to the projected area of the grain, and the thickness refers to the distance between two parallel planes.
The average aspect ratio is 2 to 40, and the definition of the average aspect ratio follows Japanese Patent Laid-Open No. 58-113928.

In the ripening process of the present invention, a silver halide solvent may be used to accelerate ripening.

A silver halide solvent may be used to promote crystal growth during the crystal growth period after ripening.

Examples of the silver halide solvent often used include thiocyanate, ammonia, thioether, thioureas and the like.

For example, thiocyanate (US Pat. No. 2,222,264
No. 2, ibid. 2,448,534, ibid. 3,320,06
9, etc.), ammonia, thioether compounds (for example, US Pat. Nos. 3,271,157 and 3,574,6).
No. 28, No. 3,704,130, No. 4,297,
439, No. 4,276,347, etc.) and thione compounds (for example, JP-A Nos. 53-144319 and 53-8).
2408, 55-77737, etc.), amine compounds (for example, JP-A-54-100717, etc.) and the like can be used.

In the process of silver halide grain formation or physical ripening,
Cadmium salt, zinc salt, lead salt, thallium salt, iridium salt or its complex salt, rhodium salt or its complex salt, iron salt or iron complex salt may coexist.

As the dispersion medium (binder or protective colloid) of the photographic emulsion of the present invention, the above-mentioned gelatin is advantageously used, but other hydrophilic colloids can also be used.

For example, gelatin derivatives, graft polymers of gelatin with other polymers, proteins such as albumin and casein; cellulose derivatives such as hydroxyethyl cellulose, carboxymethyl cellulose, cellulosic sulfates, sugar derivatives such as sodium alginate and starch derivatives;
Various synthetic hydrophilic polymer substances such as polyvinyl alcohol, polyvinyl alcohol partial acetal, poly-N-vinylpyrrolidone, polyacrylic acid, polymethacrylic acid, polyacrylamide, polyvinylimidazole, polyvinylpyrazole, and other single or copolymers. Can be used.

As gelatin, in addition to the above, lime-processed gelatin, acid-processed gelatin, and Britain Society of the
Scientific Photography of Japan (Bull.Soc.Sci.Phot.Japan.) No. 16, 30 (19)
The oxygen-treated gelatin as described in 66) may be used, or a hydrolyzed product or an enzymatically decomposed product of gelatin can also be used. Examples of gelatin derivatives include gelatin such as acid halides, acid anhydrides, isocyanates, bromoacetic acid, alkane sultones, vinyl sulfonamides,
Maleinimide compounds, polyalkylene oxides,
Those obtained by reacting various compounds such as epoxy compounds are used.

The photographic emulsion of the present invention includes an antifoggant, a stabilizer, a sensitizing dye, and a photographic property improving agent (for example, development acceleration, hardening, sensitization).
And other compounds can be included. Here, the antifoggant, stabilizer, and sensitizing dye can be used by being present in any step of the production process of the photographic emulsion, and after production,
It can be present at any stage until just before coating. Examples of the former include a silver halide grain forming step, a physical ripening step and a chemical ripening step.

The silver halide emulsion of the present invention, together with other emulsions if necessary, may be provided on the support in one or more layers (for example, two layers or three layers).
Can be provided. Further, it is not limited to one side of the support, and may be provided on both sides. It is also possible to superimpose emulsions having different color sensitivities.

The silver halide emulsion of the present invention is a black-and-white silver halide photographic light-sensitive material (for example, X-ray sensitive material, lith-type light-sensitive material, black-and-white photographic negative film, etc.) and color photographic light-sensitive material (for example, color negative film, color reversal film). , Color paper, etc.). Further, it can be used as a light-sensitive material for diffusion transfer (for example, color diffusion transfer element, silver salt diffusion transfer element), a photothermographic material (black and white, color).

In addition, emulsion washing method, chemical sensitization method, antifoggant, dispersion medium, stabilizer, curing agent, dimensional stability improving agent, antistatic agent, coating aid, dye, color coupler, etc. of the emulsion of the present invention, Regarding the prevention of adhesion, improvement of photographic characteristics (for example, development acceleration, hardening, sensitization) and the use thereof, for example, Research Disclosure, 176, 1978.
December issue (item 17643), JP-A-58-1
No. 13926, No. 58-113927, No. 58-11
Reference can be made to the descriptions of 3928 and 59-90842.

V. Specific Actions and Effects of the Invention According to the present invention, tabular AgBrI or AgBrICl grains having a multilayer structure in which at least 60% or more of the total projected area of silver halide grains is composed of a core and one or more shells, Since the AgI content is 7 mol% to the solid solution limit and the AgI content of the outermost shell is 0 or 6 mol% or less, the sensitivity is high, the sharpness is good, the deterioration of the image quality can be prevented, and It is possible to obtain a silver halide photographic emulsion having a high covering power, good RMS grain characteristics, and an image having high resolution.

Especially in terms of sensitivity, blue sensitivity and minus blue sensitivity are high,
Moreover, the light scattering property is small.

In the black and white system, the covering power is high, in the X-ray system, the crossover light is reduced, the initial development speed is high, in the color system, the DIR effect is high, and the controllability when stopping the development in the middle is good. It has good properties and can give excellent black and white photographs and color photographic images.

Next, the effect of the silver halide grains in the present invention on the photosensitizing process and the developing process will be described.

First, in the photosensitization process, the holes transferred to the core react with the reduction-sensitized silver nuclei in the core, and emit interstitial silver ions and electrons (Ag ₂ + holes → A
g ⁺ + Ag → 2Ag ⁺ + e), and the emitted electrons are trapped in the chemically sensitized nuclei on the surface, increasing the surface sensitivity, that is, both electrons and holes generated by light absorption are latent images on the surface. Since it is applied to the formation, it is considered to have high sensitivity.

On the other hand, with respect to the development process, grains having a high iodide content and a slow progress of development have a small spread of the silver filament after development, and the spread of the dye cloud formed around the silver filament is also suppressed to be small, resulting in graininess. Is good, and when a layer with high iodine content (core portion) is developed, it releases iodine ions, which diffuse to the surroundings and are captured by nearby AgX grains in the form of halogen conversion. It is conceivable that a so-called short-distance DIR effect of controlling the development of surrounding particles is exerted, and an image having a good sharpness with an edge effect is obtained.

In addition to the effects peculiar to silver halide in the present invention, those of the present invention also have the effects on the photosensitive process and the development process of the above regular type silver halide grains.

Such a photographic emulsion has a gelatin concentration in the reaction solution of 0.8 to 20% by weight, a silver salt and a silver salt in a method for producing a silver halide emulsion through nucleation of silver halide grains, Ostwald ripening and grain growth. It can be obtained by nucleation at a halide salt addition rate of 6 × 10 ^{−4 to} 2.9 × 10 ⁻¹ mol / min and a pBr value of 1.1 to 2.5 in the reaction solution.

VI Specific Examples of the Invention Hereinafter, the present invention will be described in more detail by showing specific examples, comparative examples and reference examples of the present invention.

Reference Example 14 Gelatin, water and KBr were placed in a reaction vessel having a volume of 4.
Was added, and the pH was adjusted to 6 with HNO ₃ and KOH, and an aqueous solution of a halide salt (100 ml) and an aqueous solution of silver nitrate (100 ml, 32.6 g of AgNO ₃ ) were mixed with stirring by a simultaneous mixing method. Add and after stirring for 2 minutes,
The precipitation agent and the acid were added and the mixture was washed with water to a yield of 700 ml, 350 ml of which was used as a seed crystal emulsion, and these gelatin aqueous solutions (water 1000 ml, KBr 2 g, deionized alkali-treated gelatin 25 g) were added to adjust the pH to 6.4. After that, the temperature was raised to 60 ° C. and the mixture was aged for 18 minutes, and then 250 ml of AgNO ₃ aqueous solution (containing 26 g of AgNO ₃ ) and 250 ml of KBr aqueous solution (containing 18.94 g of KBr) were simultaneously added over 25 minutes (pBr1.9). . After leaving for 5 minutes,
Again, 250 ml of AgNO ₃ aqueous solution (containing 39 g of AgNO ₃ ) and 250 ml of KBr aqueous solution (containing 28.0 g of KBr) were simultaneously added over 25 minutes (pBr 1.9).
Furthermore, only 12.2 ml of AgNO ₃ aqueous solution (AgNO ₃
1.9 g) was continuously added.

After the addition was completed, after stirring for 5 minutes, the temperature was raised to 75 ° C,
It was aged until the spherical fine particles almost disappeared.

After that, the temperature was returned to 35 ° C. and washed with water to disperse.

A transmission electron microscope (TE
M), and the average volume of the particles was determined from the projected particle size and the thickness. The number of tabular grains was determined from this value and the amount of silver added.

In the above production method, only the conditions during the nucleation period (up to the stage before raising the temperature to 60 ° C.) are changed, and after that, all the grains are treated under the same conditions (conditions in which new tabular grains are not formed). Aged and grains were grown.

By this method, the nucleation conditions were variously changed, and the relationship between the nucleation conditions and the number of tabular grains produced was investigated (Nos. 2 to 11).
Figure).

Fig. 2 shows the concentration of gelatin, Fig. 3 shows the stirring speed, Fig. 4 shows the addition time, Fig. 5 shows the temperature, Figs. 6 and 7 show the silver halide solvent, and Fig. 8 shows. Is the excess KBr during nucleation
FIG. 9 shows the relationship between the amount of irrelevant salts (NaNO ₃ and KNO ₃ ), FIG. 10 shows the iodine content of halogen balls, and FIG. 11 shows the relationship between pH and the number of tabular grains produced. It is a graph.

From these results, the probability of occurrence of stacking faults was determined by the concentration of gelatin in the reaction solution, the number of revolutions of stirring, the time of addition, the temperature, the amount of silver halide solvent, the Br ^- concentration, the irrelevant salt concentration, the pH, the iodine content of the halide salt aqueous solution to be added. It can be seen that it depends on the content of the chloride salt.

The standard experimental conditions in FIGS. 2 to 11 are:
The stirring speed was 750 rpm, the addition time was 4 minutes, the pH was 6.0, and the gelatin concentration was 12.5 g / (1.25 wt%).

Example 14 In a reaction vessel having a volume of 4, an aqueous gelatin solution (water 1000 ml, deionized alkali treated gelatin 12.5) was used.
g, KBr 2 g, 1N KOH solution 6.2 ml, pH 9.0
Was adjusted to pBr 1.77), and the solution temperature was maintained at 30 ° C., while 100 mL of AgNO ₃ aqueous solution (AgNO ₃ 3
2.6g) and 100ml of halide salt solution (K
Br 18.6 g and KI 6.37 g were added simultaneously over 4 minutes (flow rate: 25 ml / min), and after stirring for 2 minutes, a precipitating agent and a 1N nitric acid solution were added to precipitate the emulsion at pH 4.0. Washed with water.

The yield was 700 ml, and 350 ml of this was used as a seed crystal emulsion, and an aqueous gelatin solution (1000 ml of water, KBr2
g, deionized alkali-treated gelatin 25 g),
After adjusting to pH 9.0, the temperature was raised to 65 ° C. 65 ° C
After aging for 18 minutes (silver potential-18 mV), AgNO ₃
250 ml of an aqueous solution (containing 26 g of AgNO ₃ ) and 250 ml of an aqueous KBr solution (containing 18.94 g of KBr) were simultaneously added to 1
Added over 5 minutes. After stirring for 5 minutes, Ag of the same concentration
Adjust to pBr 2.3 with NO ₃ solution and add NH ₃ (25 wt
%) Solution 2.0 ml, NH ₄ NO ₃ (50 wt%) solution 3.
0 ml was added, the temperature was raised to 75 ° C., ripening was carried out for 60 minutes, the temperature was lowered to 30 ° C., the emulsion was washed with water and dispersed.

In this case, the gelatin concentration during nucleation was 1.25 wt%, the addition rate of silver salt was 4.8 × 10 ^-2 mol / min, the addition rate of halide salt was 4.87 × 10 ^-2 mol / min, And pB
The r value was 1.77.

Regarding the obtained emulsion grains, the number of tabular grains (Nt), the number of non-parallel twin grains (Nn) and the total number of grains (N) in the replica image were examined.

Further, the average particle diameter and the average thickness of the tabular grains were examined to determine the aspect ratio (average particle diameter / average thickness).

Furthermore, the ratio of the projected area of tabular grains to the total projected area of grains was investigated. The coefficient of variation of tabular grains was determined.

Average particle size 0.52 μm Average thickness 0.055 μm Average aspect ratio 9.5 Ratio of tabular grains (projected area) 99.0% Ratio of tabular grains (Nt / N) 0.986 Nn / Nt 0 On the other hand, when the X-ray diffraction of the emulsion grains sampled after nucleation and after ripening was measured, the X-ray diffraction profile based on the (220) plane showed a uniform composition of about 20 mol% AgBrI.

Molar fraction of core 0.39 AgI content of core 20 mol% Comparative Example 1 In Example 1, the amount of KBr in the reaction vessel at the time of nucleation was 4
g, the temperature is 25 ° C., and the aqueous solution of halogenated salt is 10
Particle formation was carried out by the same formulation as in Example 1 except that the amount was 0 ml (containing 19.0 g of KBr and 6.7 g of KI).

In this case, the gelatin concentration during nucleation is 1.25 wt%,
The silver salt addition rate was 4.8 × 10 ⁻² mol / min, the halide salt addition rate was 4.95 × 10 ⁻² mol / min, and the pBr value was 1.47.

The characteristic values similar to those in Example 1 are shown below.

Average particle size 0.36 μm Average thickness 0.3 μm Average aspect ratio 1.2 Ratio of tabular grains (projected area) 28% Ratio of tabular grains (Nt / N) 0.22 Nn / Nt 3.5 Coefficient of variation 41% Molar fraction of core 0.39 AgI content of core 20 mol% In a reaction vessel having the volume of Example 24, an aqueous gelatin solution (1000 ml of water, 20 g of deionized alkali-treated gelatin,
₃ g of KBr, adjusted to pH 9.0 with 10 ml of 1N KOH solution, pBr1.6) was added, and 100 ml of AgNO ₃ aqueous solution (32.6 g of AgNO ₃ was added while keeping the solution temperature at 30 ° C).
And 100 ml of halide salt aqueous solution (KBr1
8.8 g and KI 6.37 g) were added simultaneously over 4 minutes (flow rate: 25 ml / min), and after stirring for 2 minutes, a precipitating agent and a 1N nitric acid solution were added to precipitate the emulsion at pH 4.0. Washed with water.

The yield was 700 ml, and 350 ml of this was used as a seed crystal emulsion, and an aqueous gelatin solution (1000 ml of water, KBr2
g, deionized alkali-treated gelatin 25 g),
After adjusting to pH 9.0, the temperature was raised to 65 ° C. 65 ° C
After aging for 18 minutes (silver potential-18 mV), AgNO ₃
250 ml of an aqueous solution (containing 26 g of AgNO ₃ ) and 250 ml of an aqueous KBr solution (containing 18.94 g of KBr) are simultaneously added to 2
Added over 5 minutes. After the addition was completed, the mixture was stirred for 5 minutes, adjusted to pBr 2.3 with an AgNO ₃ solution having the same concentration, and adjusted to NH 3.
2.0 ml of ₃ (25 wt%) solution, NH ₄ NO ₃ (50 wt
%) Solution was added, the temperature was raised to 75 ° C., ripening was carried out for 60 minutes, the temperature was lowered to 30 ° C., the emulsion was washed with water and dispersed.

In this case, the gelatin concentration during nucleation was 2.0 wt%, the addition rate of silver salt was 4.8 × 10 ^-2 mol / min, the addition rate of halide salt was 4.94 × 10 ^-2 mol / min, And pBr
The value was 1.6. Further, the same characteristic values as in Example 1 are shown below.

Average particle size 0.56 μm Average thickness 0.055 μm Average aspect ratio 10.2 Ratio of tabular grains (projected area) 98.2% Ratio of tabular grains (Nt / N) 0.97 Nn / Nt 0 On the other hand, when the X-ray diffraction of the emulsion grains sampled after nucleation and after ripening was measured, the X-ray diffraction profile based on the (220) plane showed a uniform composition of about 20 mol% AgBrI. .

Core size 0.39 AgI content of core 20 mol% In a reaction vessel having the volume of Example 34, an aqueous gelatin solution (1000 ml of water, 20 g of deionized alkali-treated gelatin,
2 g of KBr, adjusted to pH 9.0 with 10 ml of 1N KOH solution, pBr 1.77) was added, and 100 ml of AgNO ₃ aqueous solution (AgNO ₃ 32.6) was added while keeping the solution temperature at 30 ° C.
g) and 100 ml of an aqueous halide salt solution (KBr1
6.4 g and KI 9.55 g) were added simultaneously over 4 minutes (flow rate: 25 ml / min), and after stirring for 2 minutes, a precipitating agent and a 1N nitric acid solution were added to precipitate the emulsion at pH 4.0. Washed with water.

The yield was 400 ml, and 200 ml of this was used as a seed crystal emulsion, and an aqueous gelatin solution (water 1150 ml, KBr2
g, deionized alkali-treated gelatin 25 g),
After adjusting to pH 9.0, the temperature was raised to 65 ° C. 65 ° C
After aging for 18 minutes (silver potential-18 mV), AgNO ₃
250 ml of an aqueous solution (containing 26 g of AgNO ₃ ) and 250 ml of an aqueous KBr solution (containing 18.94 g of KBr) are simultaneously added to 2
Added over 5 minutes. After the addition was completed, the mixture was stirred for 5 minutes, adjusted to pBr 2.3 with an AgNO ₃ solution having the same concentration, and adjusted to NH 3.
2.0 ml of ₃ (25 wt%) solution, NH ₄ NO ₃ (50 wt
%) Solution was added, the temperature was raised to 75 ° C., the mixture was aged for 60 minutes, the temperature was lowered to 30 ° C., the emulsion was washed with water and dispersed.

In this case, the gelatin concentration during nucleation was 2.0 wt%, the addition rate of silver salt was 4.8 × 10 ^-2 mol / min, the addition rate of halide salt was 4.88 × 10 ^-2 mol / min, And pBr
The value was 1.77.

Further, the same characteristic values as in Example 1 are shown below.

Average particle size 0.57 μm Average thickness 0.056 μm Average aspect ratio 10.2 Ratio of tabular grains (projected area) 97.5% Ratio of tabular grains (Nt / N) 0.96 Nn / Nt 0 On the other hand, when the X-ray diffraction of the emulsion grains sampled after nucleation and after ripening was measured, the X-ray diffraction profile based on the (220) plane showed a uniform composition of about 30 mol% AgBrI. .

Molar fraction of core 0.39 AgI content of core 30 mol% Example 4 Compared with Example 1, the nucleation to aging conditions were the same, and the growth condition was 250 ml of AgNO ₃ aqueous solution (AgNO ₃ 2
6g) and 250ml halide salt solution (KBr
14.5 g and KI 4.8 g) were added simultaneously over 30 minutes. After the addition is complete, pour the same concentration of AgNO ₃ solution.
After adjusting to Br2.3, 9 ml of NH ₄ NO ₃ (50 wt%) solution and 5 ml of NH ₃ (25 wt%) water were added, and the temperature was 75 ° C.
After aging for 50 minutes, the temperature was lowered to 30 ° C. and the emulsion was washed with water and dispersed.

The characteristic values similar to those in Example 1 are shown below.

Average particle size 0.56 μm Average thickness 0.08 μm Average aspect ratio 7.0 Ratio of tabular grains (projected area) 98% Ratio of tabular grains (Nt / N) 0.97 Nn / Nt 0.03 Coefficient of variation 34% The X-ray diffraction of this emulsion grain was measured and found to be (220).
The face-based X-ray diffraction profile gave a diffraction peak based on the core layer of AgBrI of uniform composition of about 20 mol%.

To 700 ml of this emulsion, a gelatin aqueous solution (NaCl 6 g,
Gelatin (15 g, H ₂ O 300 ml) was added to adjust the pH to 6.0, and at 60 ° C., 70 ml of AgNO ₃ aqueous solution (AgNO).
₃ including 10g) and 70ml of halide salt aqueous solution (KB
(including 5.6 g of r and 1.5 g of NaCl) was added over 10 minutes to form a shell layer of AgBr ₈₀ Cl ₂₀ composition.

The X-ray diffraction of this emulsion grain was measured and found to be (220)
The X-ray diffraction profile based on the plane is about 20 mol% of A
A profile was given indicating the presence of the gBrI core layer and the AgBr ₇₀ Cl ₃₀ shell layer.

Molar fraction of core 0.81 AgI content of core 20 mol% Shell thickness 0.01 μm AgI content of shell 0% Example 54 In a reaction vessel having a volume of 4, gelatin aqueous solution (water 1000 ml, deionized alkaline treatment) was used. 20g gelatin,
The pH was adjusted to pH 9.0 with 1.4 g of KBr and 10 ml of 1N KOH, pBr1.93 was added, and 100 ml of an aqueous AgNO ₃ solution (AgNO ₃ 32.6) was added while keeping the solution temperature at 30 ° C.
g), 100 ml of halide salt aqueous solution (KBr1
8.6 g and KI 6.37 g) were added simultaneously over 4 minutes (flow rate 25 ml / min) and then stirred for 2 minutes,
The emulsion was precipitated at pH 4.0 by adding a precipitant and a 1N nitric acid solution, and washed with water. Yield 700ml, 350 of which
ml as seed crystal emulsion, and add gelatin aqueous solution (water 1000
ml, KBr 0.6 g, deionized alkali-treated gelatin 25 g) were added, and NH ₃ (25 wt%) water 2.0 ml, NH
Add 3.0 ml of ₄ NO ₃ (50 wt%) water and add 60 at 75 ° C.
Aged for minutes. The characteristic values obtained from the TEM photograph of the emulsion grains at this point are shown below.

Average particle size 1.1 μm Average thickness 0.1 μm Average aspect ratio 11.0 Ratio of tabular grains (projected area) 96% Ratio of tabular grains (Nt / N) 0.93 Nn / Nt = 0. 078 coefficient of variation 40% On the other hand, when X-ray diffraction of emulsion grains was measured,
X-ray diffraction profile based on 0) plane is about 20 mol%
It showed a uniform composition of AgBrI.

After this, the temperature is raised to 55 ° C. and pH is adjusted to 8 with 1N HNO ₃ solution.
After adjusting to 8, 125 ml of AgNO ₃ aqueous solution (AgNO _3
3 including 13 g) and an aqueous KBr solution 125ml (KBr12
controlled double jet addition over 25 minutes at -15 mV. After the addition was completed, the mixture was stirred for 5 minutes, then the temperature was lowered to 30 ° C., the emulsion was washed with water and dispersed.

The X-ray diffraction of this emulsion grain was measured and found to be (220)
The X-ray diffraction profile based on the plane is about 20 mol% of A
A profile was given indicating the presence of the gBrI core layer and the AgBr shell layer.

Molar fraction of core 0.556 AgI content of core 20 mol% Shell thickness 0.022 μm AgI content of shell 0% In this case, the gelatin concentration during nucleation is 2 wt% and the addition rate of silver salt is 4.8. × 10 ^-2 mol / min, halide salt addition rate is 4.85 × 10 ^-2 mol / min, and pBr
The value was 1.9.

The particles of Examples 1 to 3 were substantially regular hexagons, and the coefficient of variation between the lengths of the six sides was within 25%.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing changes in band structure depending on the halogen composition of the shell layer of silver halide grains. Fig. 2 shows the gelatin concentration, Fig. 3 shows the stirring speed, and 4th.
Figure is the addition time, Figure 5 is the temperature, Figures 6 and 7 are
The silver halide solvent and FIG. 8 show the excess KB during nucleation.
Fig. 9 shows the irrelevant salt concentration (NaNO ₃ and KN
O ₃ ), FIG. 10 is a graph showing the iodine content of halogen balls, and FIG. 11 is a graph showing the relationship between pH and the number of tabular grains produced.

Claims (5)

[Claims] 1. A tabular AgBrI having a multilayer structure in which at least 60% or more of the total projected area of silver halide grains has a core and one or more shells, and which has an X-ray profile based on the (220) plane, or AgBrICl particles, the Ag of the core of which is 60% or more
The I content is 7 mol% to the solid solution limit, and the AgI content of the outermost shell is 0 or 6 mol% or less,
A silver halide photographic emulsion comprising hexagonal grains having an average aspect ratio of 2 to 40 and a coefficient of variation between the side lengths of six sides of the hexagon being within 25%. 2. A silver halide photographic emulsion according to claim 1, wherein the AgCl content of the shell is 0 or 40 mol% or less. 3. A method for producing a silver halide emulsion which undergoes nucleation of silver halide grains, Ostwald ripening and grain growth, wherein the gelatin concentration in the reaction solution at the time of nucleation is 0.8 to 20% by weight, and silver is The addition rate of the salt and halide salt is 6 × 10 ^{−4 to} 2.9 × 10 ⁻¹ mol / min per reaction solution, and the pBr value in the reaction solution at the time of nucleation is 1.0.
A flat plate having a multi-layer structure in which at least 60% or more of the total projected area of silver halide grains is composed of a core and one or more shells, and has an X-ray profile based on the (220) plane. AgBrI or AgBrICl particles in the form of particles, wherein the AgI content of the core of the particles occupying 60% or more is from 7 mol% to the solid solution limit,
Hexagonal particles having a shell AgI content of 0 or 6 mol% or less, an average aspect ratio of 2 to 40, and a coefficient of variation between side lengths of six sides of a hexagon of 25% or less. A method for producing a silver halide emulsion, characterized in that a silver halide emulsion containing silver halide grains is obtained. 4. The method for producing a silver halide photographic emulsion according to claim 3, wherein the AgCl content of the shell is 0 or 40 mol% or less. 5. The temperature in the reaction solution during nucleation is 15 to 50 ° C.
The method for producing a silver halide emulsion according to claim 3 or 4, wherein