JPH0485530A - Silver halide photographic sensitive material having high sensitivity and improved image quality - Google Patents

Abstract

PURPOSE:To improve various characteristics by using core-shell type silver iodobromide particles having a specified ratio of diameter to thickness and a specified silver iodide content so that the particles account for half or more of the total projection area of all of silver halide particles. CONSTITUTION:When an emulsion is produced, 7.2l aq. soln. A1 contg. 150g ossein gelatin, 53.1g potassium bromide and 24g potassium iodide, 6l aq. soln. B1 contg. 1.5kg silver nitrate, 3l aq. soln. C1 contg. 1,327g potassium bromide and 1.2g 1-phenyl-5-mercapto-tetrazole dissolved in methanol and 705ml aq. ammonia soln. D1 having 28% concn. are prepd. The soln. A1 is stirred at 40 deg.C, the solns. B1,C1 are added to the soln. A1 in 30 sec and nuclei are formed. After the lapse of 1 min and 30 sec, the soln. C1 is added in 20 sec and aging is carried out for 5 min. The resulting product having 0.071mol/l concn. of KBr and 0.63 mol/l concn. of ammonia is adjusted to pH6.0, immediately desalted and washed to obtain an emulsion contg. single dispersed spherical particles having 0.26 mum average particle size and 18% distribution range. High sensitivity is ensured and various characteristics can be improved.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a silver halide photographic light-sensitive material, which has particularly high sensitivity and excellent image quality! (sharpness, pressure characteristics, graininess)
This invention relates to an improved silver halide photographic material.

[Background of the invention]

In recent years, with the development of photographic technology, there has been a strong desire for higher sensitivity and higher image quality of silver halide photographic materials. One way to achieve high sensitivity and high sharpness is to use silver halide grains having a tabular shape. However, tabular grains
Although it is highly sensitive, it has the disadvantage of deteriorating pressure characteristics (particularly pressure fog). Improvements in the problem of pressure characteristics are desired in view of the need for faster processing. That is, there is a strong demand for speedy processing of photosensitive materials, and particularly in recent years, with the increase in consumption of photosensitive materials, there has been a strong demand for speedy processing in a short time. This can be said in any field of photosensitive materials, but for example, medical X
In the field of radiation-sensitive materials, the number of X-ray photographs taken is increasing due to a rapid increase in the number of diagnoses and an increase in the number of test items.At the same time, it is necessary to inform patients of the diagnosis results as quickly as possible, and for this reason, rapid processing is desirable. It is rare. Especially angiography,
During intraoperative photography, it is essentially necessary to view the photos as quickly as possible.

Against this background, various types of rapid processing technologies have been developed. For example, in image forming processing, high pH and high temperature (30 to 40°C)
) Attempts have been made to accelerate processing by developing with
Particularly when processing is carried out using an automatic processor, the pressure resistance of the photosensitive material deteriorates and so-called roller marks are generated due to the pressure of the conveying roller, which may lead to deterioration of image quality.

As described above, along with the trend towards higher sensitivity and higher image quality as mentioned above, in conjunction with the above-mentioned demand for faster processing, the demand for improved pressure characteristics in silver halide photographic materials is increasing more than ever.

For this reason, various methods have been considered for improving the pressure characteristics. Regarding the pressure characteristics, some improvement can be made by using an emulsion consisting of a core/shell type silver halide having a silver iodobromide phase with a high silver iodide content, but this is not sufficient. On the contrary, the average silver iodide content of the grains as a whole is relatively low, the developability is too fast, and the graininess deteriorates, which is not necessarily satisfactory.

Deterioration of graininess is an important problem in terms of photographic performance.For example, x49! Photographs can also lead to misdiagnosis. Therefore, emulsions containing grains having the above-mentioned problems are not preferred as emulsions for light-sensitive materials in which graininess is a serious problem, such as X-ray light-sensitive materials.

[Object of the Invention] The present invention solves the problems of the prior art described above, and provides a photosensitive material that is highly sensitive and has improved sharpness, pressure characteristics, and graininess, and therefore provides good images even when processed quickly, for example. The object of the present invention is to provide a silver halide photographic material from which the following can be obtained.

[Structure of the invention]

The object of the present invention was achieved by a silver halide photographic material containing the following silver halide grains. That is, the silver halide photographic material of the present invention has a tabular shape with a grain diameter/grain thickness ratio of 2 or more, and a silver iodide content of 10.
At least a grain internal phase consisting of silver iodobromide of mol % or more and a grain outer shell consisting of silver iodobromide having a silver iodide content of 7 mol % or less, and an average silver iodide content of 1 .5 mol% or more of silver halide grains, the halogen obtained by forming 80% or more of the silver iodide in the grain internal phase by a halogen substitution method by 50% of the internal phase growth of the grain. The silver halide grains contain a silver halide emulsion that occupies 50% or more of the projected area. The present inventor has developed a silver halide emulsion (hereinafter, as appropriate) in which the silver halide grains as described above (hereinafter also referred to as "silver halide grains j according to the present invention") occupying 50% or more of the projected area. The present invention was completed based on the discovery that a light-sensitive material containing the "emulsion of the invention" (sometimes referred to as "the emulsion of the invention") satisfies the object of the invention.

The present invention will be explained in more detail below. First, the silver halide grains contained in the light-sensitive material of the present invention will be explained.

Silver halide grains are generally produced and used in the form of silver halide emulsions containing the grains.

The silver halide grains according to the present invention are tabular grains having a grain diameter/grain thickness ratio of 2 or more.

In the present invention, the particle diameter is the diameter when a projected image of the particle is converted into a circular image with the same area. Grain thickness refers to the distance between two mutually opposing principal planes of a tabular grain.

The silver halide grains according to the present invention have a grain diameter/grain thickness ratio of 2 or more, preferably 3 or more, more preferably 5 or more.

In the emulsion of the present invention, the silver halide grains according to the present invention occupy 50% or more of the projected area of all silver halide grains,
It preferably accounts for 70% or more, more preferably 90% or more.

The projected area of a particle can be determined from the sum of the particle areas. Both the total projected area and the projected area for determining the grain diameter can be obtained by observing with an electron microscope silver halide crystal samples distributed on a sample stage to such an extent that grains do not overlap. The thickness of the particles can be obtained by obliquely observing the sample using an electron microscope.

The silver halide grains according to the present invention have a silver iodide content of 10
The grain has an internal phase consisting of silver iodobromide in a mole % or more. The term "internal phase of the grain" as used herein refers to such an internal region having a high iodine content. The silver iodide content of the internal phase is preferably 10
-45 mol%, particularly preferably 15-40 mol%
It is.

Further, the silver halide grains according to the present invention have grain outer shells made of silver iodobromide with a silver iodide content of 7 mol % or less. A particle outer shell is a layer existing on the surface side of a particle. The silver iodide content of the grain outer shell is more preferably 5 mol % or less.

The silver iodobromide constituting the inner phase and outer shell is essentially silver iodobromide, and may include other substances (such as other silver halides) to the extent that they do not inhibit the properties of silver iodobromide. It does not prevent the mixture of

The average silver iodide content of the silver halide grains according to the present invention is 1
．． It is 5 mol% or more. Preferably 1.5-30 mol%
It is.

The silver halide grains according to the present invention preferably consist essentially of silver iodobromide as a whole.

However, silver halide of other compositions, such as silver chloride, may be contained within a range that does not impair the effects of the present invention.

Further, the emulsion of the present invention containing silver halide grains of 50% or more of the projected area of the grains is also preferably substantially a silver iodobromide emulsion. However, grains other than the silver halide grains according to the present invention may be contained, or an emulsion containing the silver halide grains according to the present invention and other emulsions may be mixed and used.

In order to obtain an emulsion containing silver halide grains according to the present invention, a means for growing a core/shell type silver halide emulsion starting from seed grains is used, as in the method described in JP-A-60-138538. In this case, the center of the grain may have a silver halide composition region (composition region of the seed grain) different from the core forming the internal phase of the grain. In such a case, the silver halide composition of the seed grains may be any composition such as silver bromide, silver iodobromide, silver chloroiodide, silver chlorobromide, silver chloride, etc. The content rate of
Silver iodobromide or silver bromide of 0 mol % or less is preferred. In this case, the proportion of the seed grains in all silver halide grains is preferably 50% or less, particularly preferably 10% or less.

The silver halide grains according to the present invention necessarily have the above grain inner layer and grain outer shell layer, but may have one or more intermediate layers between them.

Further, it is possible to have an extremely thin outermost layer on the outside of the outer shell layer.

The distribution state of silver iodide in the silver halide grains according to the present invention can be detected by various physical measurement methods. This can be investigated by measuring luminescence at low temperatures or by X-ray diffraction.

The standard measurement method for X-ray diffraction uses Cu as a target, uses α rays as a radiation source, and uses a tube voltage of 40K.
V, tube current 100+++^ of silver halide (4,
20) This is a method of determining the diffraction curve of a surface using a powder method. Generally the width of the slit to increase the resolution of the measuring instrument,
It is necessary to appropriately select the scanning recording speed, set the step angle of the goniometer to 0.02 degrees, and correct the diffraction temperature by inserting a standard sample such as silicon. Furthermore, silver halide emulsion samples are usually used after gelatin is removed using enzymes and dried.

For example, the fact that the core has a silver iodide content of 5 mol% or more means that in the X-ray diffraction curve of the silver halide emulsion, the diffraction intensity region corresponds to the α line for Cu of 5 mol% or more of silver iodobromide. At any one point, the diffraction angle is 1 with respect to the peak intensity.
This can be confirmed by the presence of 0% or more.

In the silver halide grains according to the present invention, 80% or more of the silver iodide in the internal phase is formed by the halogen substitution method by 50% of the growth of the internal phase of the grain. The halogen substitution method in the present invention mainly involves adding iodide to
This refers to a method of causing rogane substitution, and the compounds to be added include, for example, potassium iodide, sodium iodide,
Iodide steel (II) (Culz), their aqueous solutions, silver iodide (silver iodide may be added by forming silver iodide,
Examples include addition of silver ions and iodide ions (for example, silver nitrate solution and iodide solution may be added while simultaneously mixing), silver iodide emulsions (including emulsions consisting of fine grain silver iodide), etc. . The iodide addition position (point of time of addition) may be any position as long as it is up to 50% of the internal phase growth, and the iodide may be added at two or more positions within this period. It's okay. The iodide addition time may be rush addition in which all iodide is added in a short time, or may be added over several minutes or more.

pAg during internal phase growth of silver halide grains according to the present invention
The value is preferably 8.4 or less, more preferably 7 or more and 8.4 or less. In addition, the pH during internal phase growth
(If is preferably 9.8 or more, more preferably 10 or more and 11 or less.

In the production of the emulsion of the present invention, or in the production of an emulsion containing silver halide grains other than the present invention to be used together (the same applies to the description of the emulsions below), JP-A-60-1385
As mentioned above, it is possible to use a method of growing a core/shell type silver halide emulsion starting from seed grains, as in the method described in No. 38.

Further, in preparing the emulsion, known silver halide solvents such as ammonia, thioether, thiourea, etc. can be present during grain growth.

Furthermore, silver halide grains are treated with cadmium salts, zinc salts, lead salts,
At least one metal ion selected from thallium salts, iridium salts (including complex salts), rhodium salts (including complex salts), and iron salts (including complex salts) is added to the inside of the particles and/or
Alternatively, these metal elements can be contained in the particle surface layer, and reduction sensitizing nuclei can be provided inside and/or on the particle surface by placing the particle in an appropriate reducing atmosphere.

Unnecessary soluble salts may be removed from the silver halide emulsion after the growth of silver halide grains is completed, or they may be left contained. When removing the salts, Research Disclosure (Research Disclosure) is required.
Closure (hereinafter abbreviated as RD) can be carried out based on the method described in Section H of No. 17643.

The silver halide grains may be grains in which latent images are mainly formed on the surface or grains in which latent images are mainly formed inside the grains, and the size of the silver halide grains is preferably 0.05 to 30 um, preferably 0.1-20μm1
More preferably, the thickness is 0.2 to 10 μm.

As the silver halide photographic emulsion used in the light-sensitive material of the present invention, any one can be used, such as a polydisperse emulsion with a wide grain size distribution or a monodisperse emulsion with a narrow grain size distribution.
Each may be used alone, or a mixture of several types may be used. In carrying out the present invention, monodispersed emulsions are preferred.

The monodisperse silver halide emulsion is preferably one in which the weight of silver halide contained within a 20% range of grain sizes centered on the average grain size Y is 60% or more of the weight of all silver halide grains, and more preferably Preferably 70% or more, more preferably 8
It is 0% or more.

Here, the average particle diameter t is defined as the particle diameter ri when the product n1Xri3 of the frequency ni of particles having the particle diameter ri and ri3 is the maximum (3 significant figures, the smallest digit is 5 to 40
people).

The particle size ri is the diameter when the projected image is converted into a circular image with the same area.

The particle size can be obtained, for example, by photographing the particle with an electron microscope at a magnification of 10,000 to 50,000 times and measuring the particle diameter or projected area on the print (
The number of particles to be measured is assumed to be 1,000 or more at random).

Particularly preferred highly monodisperse emulsions are those with a distribution width of 20% or less, more preferably 15% or less.

Here, the average particle diameter and standard deviation are determined from ri defined above.

A method for obtaining a monodispersed emulsion is to add a water-soluble silver salt solution and a water-soluble halide solution to a gelatin solution containing seed particles.
There is a method of adding by double jet method under the control of g and pH, and such means can be used.

In determining the addition rate, refer to JP-A-54-48521.
No. 58-49938 can be referred to.

As a method for obtaining a more advanced monodispersed emulsion, JP-A-60-1
The growth method in the presence of tetrazaindene disclosed in No. 22935 can be applied.

The silver halide emulsion used in carrying out the present invention is as follows:
After the growth of silver halide grains is completed, a PAg ion concentration suitable for chemical sensitization can be achieved by a suitable method. For example, research disclosure No. 17643 (Research D) such as flocculation method and noodle washing method
isclosure No. 17643).

In the case of chemical sensitization, ordinary sulfur sensitization, reduction sensitization, noble metal sensitization, and combinations thereof are used. More specific chemical sensitizers include allylthiocarbamide (
Allyl thiocarbamide), thioureas, thiosulfates, sulfur sensitizers such as thioethers and cystine:
Noble metal sensitizers such as assim chloro palladate; reduction sensitizers such as tin chloride, phenylhydrazine and retactone; and the like.

Photographic emulsions used in the practice of this invention may be spectrally sensitized with cyanine dyes and others. Sensitizing dyes may be used alone or in combinations thereof (combinations of sensitizing dyes are often used, especially for the purpose of supersensitization.

Various hydrophilic colloids can be used as binders in the photographic emulsion used in the present invention.

Colloids used for this purpose include, for example, gelatin, colloidal albumin, polysancharides, cellulose derivatives, synthetic resins, polyvinyl compounds including polyvinyl alcohol derivatives, acrylamide polymers, etc. Colloids can be mentioned.

The silver halide photosensitive material of the present invention can be prepared by using a commonly used photographic hardening agent in its coating solution, such as an aldehyde hardener or an aziridine hardener (for example, PB Report 19921, US Pat.
, No. 950,197, No. 2,964,404, No. 2,983,611, No. 3,271,175, Japanese Patent Publication No. 46-40898, Japanese Unexamined Patent Publication No. 51-91
No. 315), isoxazole systems (e.g., those described in U.S. Pat. No. 33L609), and epoxy systems (e.g., U.S. Pat. No. 3,047,394).
No. 1, West German Patent No. 1,085,663, British Patent No. 1,
Specifications of No. 033,518, Japanese Patent Publication No. 48-35495
(mentioned in the publication), vinyl sulfone type (e.g. P
B Report 19,920, West German Patent No. 1. ．． 100,9
No. 42, British Patent No. L251,091, Patent Application No. 1973-
No. 54236, No. 48-110996, U.S. Patent No. 3
No. 53,964 and No. 3,490,911), acryloyl type (for example, Japanese Patent Application No. 1973-
No. 27949, U.S. Pat. No. 3,640,720), carbodiimides (e.g., U.S. Pat. No. 2,938.892, Japanese Patent Publication No. 1986-387)
15 and Japanese Patent Application No. 49-15095), maleimide-based, acetylene-based, methanesulfonic acid ester-based, triazine-based, and polymer-based hardening agents can be used. In addition, as a thickening agent, for example, U.S. Pat.
, No. 167.410, Belgian Patent No. 558.143
Polyols as gelatin plasticizers (for example, U.S. Pat.
No. 766.979 and French Patent No. L395,5 as latex.
44, those described in Japanese Patent Publication No. 48-43125, British Patent No. 1,221 as a matting agent,
Those described in the specification of No. 980 can be used.

Furthermore, desired coating aids can be used in the component layers of the silver halide photographic material of the present invention, such as saponin or sulfosuccinic acid surfactants, such as those described in British Patent No. Gansho 47-89630
or as anionic surfactants such as those described in Japanese Patent Publication No. 43-18166,
US Patent Box 3.514,293, French Patent Box 2.
Specifications of No. 025,688, Japanese Patent Publication No. 43-10247
Those described in the No. 1 publication can be used.

Various compounds can be added to the above-mentioned photographic emulsion in order to prevent a decrease in sensitivity and the occurrence of fog during the manufacturing process, storage or processing of the light-sensitive material. These compounds include 4-hydroxy-6-methyl-1°3.3a, 7-chitrazaindene, 3-methyl-benzothiazole, 1-phenyl-3-mercaptotetrazole, many heterocyclic compounds, mercury-containing compounds, Many compounds have been known for a long time, including mercapto compounds and metal salts.

An example of a compound that can be used is K. Miesl.

The Theory of the Photographic Process
Photographic Process) (3rd edition, 1966) lists the original documents, as well as JP-A Nos. 49-81024, 50-6306, and 50
Any of the antifogging agents well known in the art, such as those described in No. 19429 and US Pat. No. 3,850,639, can be used.

In addition, various techniques used in photography can be applied when implementing the present invention.

〔Example〕

Examples of the present invention will be described below. Note that, as a matter of course, the present invention is not limited to the examples described below.

Example 1 (Preparation of spherical seed emulsion used in Examples and Comparative Examples) A monodisperse spherical seed emulsion was prepared by the method disclosed in JP-A-61-6643.

Thereafter, the pH was adjusted to 6.0, and the solution was immediately desalted and washed with water. When this seed emulsion was observed under an electron microscope, it was found to be a monodisperse spherical emulsion with an average grain size of 0.26 μm and a distribution width of 18%.

Comparative Example-1 (Preparation of monodispersed cubic emulsion) D. 705 m of ammonia water (28%) To the AI solution vigorously stirred at 140°C, B1 solution and 01 solution were added in 30 seconds by double jet method to generate nuclei. I did it. The pBr at this time was 1.09 to 1.15.

After 1 minute and 30 seconds, C3 solution was added for 20 seconds and aged for 5 minutes. The KBr concentration during ripening was 0.071 mol/2,
Ammonia concentration was 0.63 mol/l.

480 ml of water [991.6 g of silver nitrate] To the A2 solution which was vigorously stirred at 60°C, the B2 solution and the D2 solution were added over 10 minutes by the double jet method. Then, liquid C2 and liquid B2 were added over 140 minutes using a double jet method. At this time, the initial addition flow rate was 1/8 of the final addition flow rate, and was increased linearly with time. While adding these solutions, pH=2, pAg=8
was adjusted to a constant value. After the addition is complete, adjust the pH with sodium carbonate.
6, and after adding 150 g of potassium bromide, immediately desalted and washed with water to obtain a monodisperse cubic emulsion of silver iodobromide containing 2 mol% of silver iodide with an average grain size of 0.3 μm. Ta. According to electron microscopic observation, the incidence of twins was 1% or less in number.

Comparative Example-2 (Preparation of cubic comparison hole IJEm-A) Comparative Example-
Using the seed emulsion No. 1, a cubic comparative emulsion Em-A having an average silver iodide content of 2 mol % was obtained.

The liquid was maintained at 40°C, and the seed emulsion (seed crystals) of Comparative Example 1 was dissolved therein, and acetic acid was added to adjust the pH to 9.5. After adding B3 solution and adjusting the pAg to 7.3, add B3 solution and 0.
The three liquids were added by a double jet method to form a silver iodobromide layer containing 30 mol % of silver iodide (Step-1).

Next, after adjusting the pH to 9 and pAg-9, liquid D3 and liquid E were added at the same time, and after growth, the particles were further grown to 90% of the particle size. At this time, the pH was gradually lowered to 9.0 to 8.20 (Step-2).

After adding Fff liquid to make P A g = 11, further D
Solution 3, E, and Solution were added to grow the emulsion while gradually lowering the pH to 8 to obtain a silver iodobromide emulsion having an average grain size of 0.7 μm and containing 12 mol % of iodide (Step-3).

Next, as shown below, a desalting step was performed to remove excess salt.

The silver halide emulsion solution was kept at 40°C, and the following compound (a
) (exemplary compound n-1 shown in JP-A-58-140322) to precipitate silver halide grains,
After draining the supernatant, add pure water at 40°C. Then, magnesium sulfate (MgSO4) is added to precipitate the silver halide grains again, and the supernatant liquid is removed. Repeat this process again, add 15g of gelatin/AgX1 mole, and
An emulsion with H=6.0 and p A g =8.5 was obtained (Step-4). (AgX indicates silver halide. The same applies hereinafter). This is designated as emulsion Em-A.

Compound (a) Comparative Example-3 (Preparation of cubic comparative emulsion Em-B-H) Using the seed emulsion of Comparative Example-1, a cubic comparative emulsion Em- having an average silver iodide content of 2 mol% was prepared. B-H was obtained.

In step-1 in the preparation of the emulsion Em-A of Em-B-H, after adjusting the pH and PAg as shown in Table-1, the pH and pA
Table 1 was added while adding ammoniacal silver ion solution and potassium bromide solution by double jet method while keeping g constant.
An aqueous solution of potassium iodide was added at different addition speeds using the method shown in Figure 1, and iodide l! was added using the halogen substitution method. A silver iodobromide layer containing 30 mol % was formed. Then the above emulsion E,
Steps 2 to 4 were carried out in the same manner as in m-A to obtain emulsions Em-B to Em-H as shown in Table 1.

At this time, the volume ratio of core and shell was unchanged from that of emulsion Em-A, and the average grain size was adjusted to 0.7 μm.

Comparative Example 4 (Preparation of cubic comparative emulsion Em-1zO) Using the seed emulsion of Comparative Example 1, a cubic comparative emulsion Em-1-0 having an average silver iodide content of 2 mol % was obtained.

il of Em-1 to O In Comparative Example-3 above, silver iodide was added as shown in Table-2 instead of the potassium iodide aqueous solution added, and 30 mol% of silver iodide was added by the halogen substitution method. A silver iodobromide layer was formed. After that, step 2 is carried out similarly to emulsion Em-A.
4 to obtain emulsions Em-I to 0 as shown in Table 2. In this case as well, the volume ratio of core and shell is emulsion Em-
It was prepared without changing A, but with an average particle size of 0.7 μm.

Comparative Example 5 (Preparation of tabular comparative emulsion Em-P) The seed emulsion of Example 1 was used, the average grain volume was the same as Em-A, and the average silver iodide content was 2.25 mol. A comparative emulsion Em-P was obtained consisting of tabular silver halide grains of %.

Keep the 1082 A4 liquid at 75°C with water and add the seed emulsion of Example-1 (
Seed crystals) were dissolved, and Liquid 84 and Liquid 04 were added using a double jet method. At this time, the pH was adjusted to 2.0 with nitric acid and the PAg was adjusted to 8.0.
I kept it. The addition time was 16 minutes, and the addition rate was linearly increased to 1.27 times between the initial and final times.The D4 solution and the E4 solution were added to the same solution using a double jet method. At this time, the pH was maintained at 2.0 and the PAg at 8.0. The addition time was 38 minutes, and the addition rate was increased linearly by a factor of 1.80 between the initial and final times. After the addition was completed, desalination was carried out in the same manner as in Comparative Example-2, and p and Ag were 8.5 and pF (
An emulsion of 5.85 was obtained.

When the obtained emulsion was observed under an electron microscope, it was found to be 100%
It is a silver halide emulsion consisting of twin grains, with an average grain size of 0.95 μm and a distribution width of 14%, and a projected area of 80 μm.
% particle diameter/particle thickness ratio was between 2.5 and 3.0.

Example-2 (Preparation of tabular comparative emulsion Em-Q-S and emulsions Em-1 to Em-9 according to the present invention) The seed emulsion of Example-1 was used, and the average grain volume was the same as that of Em-A. A tabular comparative emulsion Em-Q-3 and emulsions Em-1 to Em-9 according to the present invention having an average silver iodide content of 2.25 mol % were obtained.

In the emulsion preparation in Comparative Example 5 of Em-~S and Em-~9, an ammoniacal silver ion solution and a potassium bromide solution were added by a double jet method during core formation, and the following Table 3 was added. A silver iodobromide layer containing 30 mol % of silver iodide was formed by the halogen substitution method by adding an aqueous potassium iodide solution at different addition rates using the method shown below. Thereafter, a shell portion was formed in the same manner as in Comparative Example 5 above, and an emulsion E m -Q as shown in Table 3 was prepared.
-S and Em-1 to Em-9 were obtained.

At this time, the volume ratio of core and shell was unchanged from that of emulsion Em-P, and when the obtained emulsion was observed with an electron microscope, the average grain size, width of distribution, and grain diameter were as shown in Table 3. /grain thickness ratio.

Example 3 (Preparation of tabular comparative emulsions Em, -T to ■ and emulsions Em-10 to Em-18 according to the present invention) Using the seed emulsion of Example 1, the average grain volume was Em,
Comparative tabular emulsions Em-T to Em-1 and Em-10 to Em-18 according to the present invention having the same volume as that of -A and having an average silver iodide content of 2.25 mol % were obtained.

In the above Example-2 of Em-T to V and Em-10 to Em-18, Table 4 shows an AgI (silver iodide) fine grain emulsion prepared as below instead of the potassium iodide aqueous solution added. A silver iodobromide layer containing 30 mol % of silver iodide was formed by a halogen substitution method.

(Creation of Agl fine particles) Add an aqueous solution containing 5% by weight of ossein gelatin to a reaction vessel, and add 1 mol each of 3.5N silver nitrate aqueous solution and 3.5N hydrium iodide aqueous solution for 30 minutes while stirring at 40°C. It was added at a constant rate. OPAg during addition is pAgf of the conventional method.
It was maintained at 13.5 using #I# means. The produced silver iodide was a mixture of β-Agl and γ-AgI with an average grain size of 0.06 μm. This emulsion is used as an Agl fine grain emulsion to form a silver iodobromide layer as described above.

Thereafter, a shell portion was formed in the same manner as in Comparative Example 5 above, and the front
Emulsions E m -T~■ and Em-10~ as shown in 4.
Got a day.

At this time, the volume ratio of the core and shell was unchanged from that of emulsion EmP, and when the obtained emulsion was observed with an electron microscope,
The silver halide grains had the average grain size, breadth of distribution, and grain diameter/grain thickness ratio as shown in Table 4.

Example 4 Next, appropriate gold-sulfur enrichment was applied to the silver halide emulsions Em-A to ■ and Em-1 to Em-18 obtained in Comparative Examples 2, 3, and 4 and Examples 2 and 3, respectively. I gave it a feeling. Immediately before the end of this chemical sensitization, add the following sensitizing dye to dye A: dye B = 20:1.
Add 1000 1 mol Ag in the ratio of 4-hydroxy-
6-methyl-1,3゜3a,7-chitrazaindene 2
．． 5g 1 mole Ag was added.

t-Butylucate D-L 400 tag.

Polyvinylpyrrolidone (molecular weight 10,000) 1.0
g.

Styrene-maleic anhydride copolymer 2.5g.

Trimethylolpropane 10g.

Diethylene glycol 5 g.

Nitrophenyl-triphenylphosphonium chloride 50B.

1. Ammonium 3-dihydroxybenzene-4-sulfonate 4 g + Sodium 2-mercaptobenzimidazole-5-sulfonate
15 mg of 2-mercaptobenzothiazole, 10 μg of H 1,1-dimethylol-1-bromo-1-nitromethane per mole of silver halide as an opalescent layer additive in each emulsion.

In addition, as a protective layer additive, the compound of Gelatin 1
The following amount was added per g.

CsF+ySOJ 3mg P19C9or CH2C)IzO-)rvcHzG
Matting agent consisting of polymethyl methanol alcohol with 2 mg of HzOH and an average particle size of 5 μm.
70 mg of colloidal resin IJ force having an average particle size of 0.013 μm was added.

Further, as a hardening agent, the following compound was added in an amount of 7 μm per gram of gelatin.

Ctb=C)IsO□ocuzsozco=ctiz
It was coated uniformly on both sides of a polyethylene terephthalate film base that had been subjected to subbing treatment to obtain a double-sided emulsion sheet-like light-sensitive material. At this time, the amount of silver per side was t, 9g/
The gelatin for the emulsion was coated at 2 g/rr, and the gelatin for the protective film was coated at 1 g/rr.

Each sample thus obtained was evaluated four times as described below.

(Sensitometric evaluation) The obtained sample was sandwiched between X-ray photographic intensifying screens K O-250 (manufactured by Konica Corporation), and after xl irradiation via a Venetrometer B type (manufactured by Konica Medical Corporation), Using a 5RX-501 automatic processor, processing was performed for 45 seconds using an XD-3R developing solution.

The sensitivity of each sample developed as described above was evaluated. The sensitivity was expressed as a relative value, with the reciprocal of the amount of irradiation energy required for Sample 1 to give a density of fog+1.0 as 100.

The results obtained are shown in Table-5.

(Evaluation of Graininess) Graininess is determined by exposing the entire surface to light, and determining the blackening density from 0.6 to 0.8.
Visual evaluation was performed on a 20 cm x 20 cm developed sample in the area of . Based on a five-point evaluation, 5: Very good 4: Good 3: Practical 2: Roughness within a practical range: Roughness was too severe to be practical.

(Evaluation of sharpness) In order to examine sharpness, a square wave chart was photographed for each sample, and the MTF was measured using a contrast method. In addition, MTF showed the value of 2.0 spatial frequencies/kaku.

(Pressure fog evaluation) For each sample of 13 × 35, heated at 23°C for about 1 hour.
The film was kept at a constant temperature with a relative humidity of 42%, and under these conditions, it was bent at a radius of curvature of 4 cm and developed without being exposed to light. The difference between the density of the blackened portion caused by the bending and the fog density was defined as ΔD, and was used as a measure of pressure fog. In other words, the smaller this value is, the better the resistance to pressure wrinkling.

Margins below - Table Table Table (Continued) Evaluation of Examples and Comparative Examples As is clear from the data in each table above, the samples according to the present invention are highly sensitive and have low graininess, sharpness, and pressure fog. It shows excellent performance and high image quality.

〔Effect of the invention〕

As described above, the silver halide photographic material of the present invention has the effects of being highly sensitive and having improved sharpness, pressure characteristics, and graininess.

Claims (1)

[Claims] 1. A grain internal phase consisting of silver iodobromide with a grain diameter/grain thickness ratio of 2 or more and a silver iodide content of 10 mol % or more, and a silver iodide content of 7 mol %. % or less, and has an average silver iodide content of 1.5 mol % or more, which accounts for 50% of the internal phase growth of the grains. Silver halide grains obtained by forming 80% or more of the silver iodide in the internal phase of the grains by a halogen substitution method contain a silver halide emulsion that occupies 50% or more of the projected area. A silver halide photographic light-sensitive material.