JPH04234034A - Stabilization of plate-shaped particle with pyrimidine derivative - Google Patents

Abstract

PURPOSE: To stabilize a highly photosensitive platy silver halide particle emulsion in an autoradiographic material. CONSTITUTION: When a photographic material contg. a silver halide emulsion contg. platy particles having an average aspect ratio of at least 4 is produced, the platy particles are stabilized with a mercapto substd. pyrimidine deriv. represented by formula I, wherein R is H, a satd. or olefinic unsatd. aliphatic group or aryl, Z is a group of ring forming members required to complete a heterocyclic ring selected from among condensed benzene, condensed cyclohexene, condensed cyclopentene, pyridine, tetrahydropyridine, pyrimidine, pyrrole, furan, thiophene, oxazol, isoxazol, imidazole or pyrazole and R or Z contains at least one carboxy or sulfo group.

Description

Description: This invention relates to photographic silver halide emulsion technology, and in particular to the stabilization of tabular silver halide emulsion grains. Platy-shaped particles have been known in photographic technology for some time. As long ago as 1961, Berry et al.
photographic science and en
The production and growth of plate-shaped silver bromide iodide grains has been published in Gineering, Vol. 5, No. 6. A discussion of plate-like particles is given by Foca.
r Press Published in 1966, Photograp
hic Emusion Chemistry No. 66~
Duffin describes it on page 67. The first patent documents include Bogg U.S. Pat. No. 4,063,951, Le
U.S. Pat. No. 4,067,739 and Mater
nagan U.S. Pat. No. 4,150,994, No. 41
No. 84877 and No. 4184878. However, the platelet particles described herein cannot be considered to exhibit a high diameter-to-thickness ratio, commonly referred to as aspect ratio. A number of US patent applications filed on September 30, 1982 and issued in 1984 describe platelet grains with high aspect ratios and their advantages in photographic applications. Wilgus U.S. Patent No. 4,434,226
Silver bromide iodide grains having a thickness of less than 0.3 microns, a diameter of at least 0.6 microns and an average aspect ratio greater than 8:1 and accounting for at least 50% of the total projected area of the entire emulsion Are listed. Similar spectrally sensitized particles are described in US Pat. No. 4,439,520 to Koffron. Affot U.S. Patent No. 4425
No. 425 describes radiographic materials containing plate-like grains having an aspect ratio of at least 8:1. No. 4,425,426 to Affot has a 5:1
Similar particles have been described with aspect ratios of ~8:1. Solberg U.S. Patent No. 4,433,048
No. 6, which describes plate-shaped silver bromide iodide grains having a heterogeneous distribution of silver iodide. Research Disclo for research on high aspect ratio silver halide emulsions
Sure Volume 225 (January 1983) Section 22534. [0003] High aspect ratio platelet grains exhibit several significant photographic advantages. Their special morphology allows them to adsorb larger amounts of certain spectral sensitizers per mole of silver halide compared to classical spherical particles. As a result, such spectrally sensitized platelet grains exhibit a wide separation between their blue speed and minus blue speed. The sharpness of photographic images can also be improved using platelet grains due to their lower light scattering properties compared to conventional spherical emulsion grains. The usual order of photosensitive layers in color negative materials can be changed and the yellow filter layer can be omitted. In the developed black-and-white image, high covering power or reduced silver halide coverage can be achieved even at high cure levels, and improved sharpness can also be achieved if desired. In the field of radiographic materials, where highly light-sensitive radiographic emulsions are coated on both sides of a transparent support for particularly important applications, the high light absorption of platelet grains in the spectrally sensitized band is important in screen-film pairs. This effectively reduces crossover, which is a major factor in sharpness. Crossover is a measure of the photographic response of each emulsion layer to exposure from a screen placed on the opposite side of a double coated film. This emission passes through the second emulsion layer and the support and reduces the sharpness of the final radiographic image. Like conventional emulsions, platelet grain emulsions provide anti-fog properties that minimize fog build-up during processing of newly coated photographic materials and/or minimize fog build-up during long-term storage of said materials. It is necessary to stabilize it by means of agents or stabilizers. Many groups of compounds can be added to conventional silver halide emulsions as antifoggants or stabilizers. Suitable examples include, for example, heterocyclic nitrogen-containing compounds such as benzothiazolium salts, nitroimidazole, nitrobenzimidazole, chlorobenzimidazole, bromobenzimidazole, mercaptothiazole, mercaptobenzothiazole, mercaptobenzimidazole, mercaptothiadiazole, amino triazole,
These include benzotriazole (preferably 5-methyl-benzotriazole), nitrobenzotriazole, mercaptopyrimidine, mercaptotriazine, benzothiazoline-2-thione and oxazoline-thione. A particularly useful group of compounds is the azaindenes, such as trizaindenes, tetrazaindenes and pentazylindenes, especially Z.
Wiss. Photo. Volume 47 (1952) 2-5
Birr on page 8, and U.S. Pat.
No. 225 and No. 2,450,397 by Heimbach. The most commonly known and most widely used azaindene is 4-hydroxy-6-methyl-1, hereinafter abbreviated as TAI.
, 3,3a,7-tetrazaindene. Other groups include triazolopyrimidines such as those described in GB 1203757, GB 1209146, JP 50-39537, and other compounds such as benzenethiosulfonic acid. A widely used group of stabilizers is the group of mercaptotetrazoles, especially the group of 1-phenyl-5-mercaptotetrazoles. Specially substituted 1-phenyl-
The group of mercaptotetrazoles is disclosed in U.S. Patent No. 488,827.
No. 3, it is described as a stabilizer for plate-like grain emulsions. A general survey of stabilizers and antifoggants can be found in Research Disclosure No. 1
7643 (1978) Chapter VI. Special problems arise when attempting to stabilize highly photosensitive silver bromide iodide or silver bromide tabular grains. Some groups of stabilizers, such as mercapto compounds, tend to desensitize platelet particles too strongly in the concentration range in which they are effective as stabilizers. Tetrazaindene is also insufficient in stabilizing high aspect ratio platelet particles, as described in the aforementioned US Pat. No. 4,888,273. Experimental results show that tetrazaindenes, e.g. TAI, partially desorb the spectral sensitizer from the particle surface and in this way degrade the measurement in the corresponding spectral band and, in the case of double-coated radiographic materials, remove the gelatin phase. The hypsochromic spectral shift of the desorbed green spectral sensitizer in the chromatography is shown to increase crossover. Decreasing the tetrazaindene concentration abolishes stabilization. This problem of using tetrazaindene stabilization is even more severe with low silver iodide contents of the silver bromide iodide grains, and is most severe with silver bromide emulsions containing no silver iodide. However, for applications in double-sided coated radiographic materials, platelet grains with low or no silver iodide content are preferred, since they This is because of its fast development and fixing speed. Desorption of the spectral sensitizer can be partially overcome by adding a certain amount of soluble iodide salt at the final stage of emulsion preparation, but in this case the grain surface is partially converted to AgBrI, which is inferior. It provides increased sensitivity. It is an object of the present invention to provide an effective stabilization system for platelet particles. Another object of the invention is to produce highly light-sensitive silver bromide iodide and silver bromide tabular grain emulsions without deteriorating the crossover percentage when the emulsions are coated on both sides in radiographic materials. The purpose is to stabilize effectively. Platy grains having a minimum average aspect ratio of 4:1 and accounting for at least 50% of the total projected area of all emulsion grains are effectively stabilized with mercapto-substituted pyrimidine derivatives represented by the general formula: : [0011] In the formula, R represents hydrogen, a saturated or olefinic unsaturated aliphatic group, or an aryl group, and Z represents a condensed benzene, cyclopentene or cyclohexene ring, or pyridine, tetrahydropyridine, pyrimidine, represents the ring members necessary to complete the heterocyclic ring selected from pyrrole, furan, thiophene, oxazole, isoxazole, imidazole or pyrazole rings;
However, R or Z contains at least one carboxy group or sulfo group. In a preferred embodiment, the stabilizer used according to the invention is another stabilizer of the tetrazaindene type, for example 4-hydroxy-6-methyl-1,3,3a,7-
Combine with Tetrainden (TAI). The compounds of the present invention are disclosed in the aforementioned US Pat. No. 3,692.
Although already known to those skilled in the art from No. 527, their specific and surprising effectiveness for stabilizing platelet particles over the more familiar class of stabilizers was recognized for the first time. It has not been announced yet. It is further very surprising to find that substituting part or all of the tetrazaindene with a compound according to the invention overcomes the desorption of the spectral sensitizer caused by said tetrazaindene. . Representative examples by general formula of stabilizers for use in accordance with the present invention include the following compounds. ##STR4## The most effective stabilizers of these particular examples are: is compound 1. The stabilizer used according to the invention can be used in processing solutions,
For example, they can be added to the developing bath, but preferably they are added to the photographic material itself. Although they can be added to any of the hydrophilic colloid layers of the photographic material, e.g. to the non-light-sensitive interlayer, preferably they are most closely attached to the tabular silver halide grains in order to adequately perform their stabilizing function. It is included in the photosensitive emulsion layer where it is easily adsorbed. They can be added in the form of an aqueous solution or a solution in an organic solvent, such as a methanol solution. Alternatively, it can be added in the form of a dispersion, for example a gelatin-containing dispersion, preferably containing a high boiling oil former. They are preferably present in concentrations ranging from 10@-7 to 10@-3 moles per mole of silver halide. The compound according to the invention can be used as a sole stabilizer, or it can be combined with other representatives of other known stabilizer groups. Preferably it is combined with a tetrazaindene stabilizer, such as 4-hydroxy-6-methyl-1,3,3a,7-tetrazaindene (TAI). Preferably, the tetrazaindene stabilizer is present in a concentration ranging from 10@-6 to 10@-3 moles per mole of silver halide. The photographic plate-like silver halide emulsions can be used in various photographic materials, such as photographic materials for graphic arts, so-called amateur or professional still black-and-white and color photographic materials, diffusion transfer reversal photographic materials, slow-speed reproduction materials or high-speed camera photosensitivity. Can be used for material and film recording. In a preferred embodiment of the invention, the emulsion is incorporated into a high-speed radiographic material. The photographic material can contain a single emulsion layer, or it can be formed of two or more emulsion layers. For color photography, the material contains blue, green and red sensitive layers, each of which can be single or multiple. Besides the light-sensitive emulsion layer, the photographic material can contain several light-insensitive layers, such as a protective layer, one or more backing layers, one or more subbing layers, and one or more intermediate layers. In a preferred embodiment of the radiographic material, emulsion layers are provided on both sides of a transparent support coated on each side with a protective layer. The silver halide composition of the tabular silver halide emulsion used in the present invention is not particularly limited, and includes, for example, silver chloride, silver bromide, silver iodide, silver chlorobromide, silver bromoiodide, and silver chloride. It can be any composition selected from silver bromide iodide. However, in a preferred embodiment of the high-speed radiographic material, platelet silver bromide iodide emulsions are used, most preferably with low silver iodide contents of less than 1% or without any silver iodide. do. The platelet emulsion grains can be prepared by any method known to those skilled in the art, such as by Research Disclos.
ure, Vol. 225 (January 1983), Section 22534, or any other or similar method. Their minimum aspect ratio is 4:1. Preferably their minimum average diameter is 0.6μ and their maximum average thickness is 0.3μ. The emulsions can be desalted in the usual manner, for example by dialysis, by flocculation and redispersion, or by ultrafiltration. To form the photographic emulsions used in accordance with the present invention, two or more separately prepared tabular silver halide emulsions can be mixed. The grain size distribution of the tabular silver halide grains of the photographic emulsion to be used according to the invention can be monodisperse or heterodisperse. Tabular silver halide emulsions in the context of the present invention are, for example, P.I. Chimi by Glafkids
e et Physique Photography
que; G. F. Duffin's Photog
rapic emulsion chemistry
;V. L. Making of Zelikman
and Coating Photographic
Emulsion; and Akademische
Verlagsgesellschaft published 1968, H. Edited by Frieser, Die Grund
Lagen der Photogaphischen
Prozesse mit Silberhalog
It can be chemically sensitized as described in Eniden. As described in the above literature, chemical sensitization is carried out using sulfur-containing compounds such as thiosulfates, thiocyanates, thioureas, sulfites, mercapto compounds,
and by ripening in the presence of small amounts of rhodamine. The emulsions can also be sensitized with gold-sulfur ripeners or with reductants such as tin compounds, amines, hydrazine derivatives, formamidine-sulfinic acid, and silane compounds as described in British Patent No. 789,823. [0032] Tabular silver halide emulsions are manufactured by John Wi
ley and Sons, published in 1964, by F. M
．． Hammer's The Cyanine Dyes
Spectral sensitization can be achieved with methine dyes such as those described in and Related Compounds. Dyes that can be used for spectral sensitization include cyanine dyes, merocyanine dyes, complex cyanine dyes, complex merocyanine dyes, hemicyanine dyes, styryl dyes and hemioxonol dyes. Particularly valuable dyes are those belonging to the cyanine dyes, merocyanine dyes and complex merocyanine dyes. A survey of useful chemical groups of spectral sensitizing dyes and particularly useful examples in combination with platelet particles can be found in the Research Disclosure cited above.
It is shown in Section 22534. In conventional emulsion manufacturing, spectral sensitization traditionally follows completion of chemical sensitization. However, in the context of platelet grains, spectral sensitization can occur simultaneously with the chemical sensitization step or even before its completion. In a preferred embodiment of the radiographic material, in relation to the practical tendency in medical X-ray practice to use screens containing green light-emitting phosphors:
Green sensitization is preferred. Preferred green sensitizing compounds in this case include anhydro-5,5'-dichloro-9-ethyl-3,3
'-di-(3-sulfobutyl)-oxacarbocyanine and sulfopropyl-containing homologs. It is particularly possible to bring about epitaxial deposition at the surface of the platelet grains at any stage of the emulsion preparation, for example by the addition of very fine silver halide grains capable of Ostwald ripening or by the addition of soluble silver salts. Conceivable. Epitaxial deposition at selected green or corner positions is preferred. In this case, the presence of so-called position-directing agents, such as iodide ions, can be advantageous. Besides silver halide, another essential component of the light-sensitive emulsion layer is a binder. The binder is a hydrophilic colloid, preferably gelatin. However, gelatin can be replaced in part or in whole by synthetic, semi-synthetic or natural polymers. Synthetic substitutes for gelatin include, for example, polyvinyl alcohol, poly-N-vinylpyrrolidone, polyvinylimidazole, polyvinylpyrazole, polyacrylamide, polyacrylic acid and derivatives thereof, especially copolymers thereof. Natural substitutes for gelatin include, for example, other proteins such as zein, albumin, and casein, cellulose, saccharides, starch, and alginates. Semi-synthetic alternatives to gelatin are generally gelatin derivatives obtained by altering gelatin with modified natural products, such as alkylating or acylating agents, or by grafting polymerizable monomers onto gelatin. , and cellulose derivatives such as hydroxyalkylcellulose, carboxymethylcellulose, phthaloylcellulose, and cellulose sulfate. The gelatin can be lime-treated or acid-treated gelatin. The preparation of such gelatin species is described, for example, in Academic Press, 1977, A.
G. Ward and A. Edited by Courts, The
Science and Technology
f Gelation, pages 295-296. Zeralin is also Bull. Soc. Sci.
Photo. Japan, No. 16, 30 pages (
It can also be enzyme-treated gelatin, as described in (1966). The binder of the photographic material, especially when the binder used is gelatin, may be a suitable hardener, such as those based on epoxides, those based on ethyleneimine, those based on vinylsulfones, such as 1,3-vinylsulfonyl. -2-propanol, chromium salts such as chromium acetate and chromium alum, aldehydes such as formaldehyde, glyoxal and glutaraldehyde, N-methylol compounds such as dimethylol urea and methylol dimethylhydantoin, dioxane derivatives such as 2,3-dihydroxy-dioxane, activated vinyl compounds. e.g. 1,3,5-triacryloyl-hexahydro-s-tothiazine, active halogen compounds e.g. 2,4-dichloro-6-hydroxy-s
- Can be cured with triazines and mucohalogen acids such as mucochloric acid and mucophenoxychloroic acid. These curing agents can be used alone or in combination. The binder can also be cured with fast-reacting curing agents such as carbamoylpyridinium salts as described in U.S. Pat. No. 4,063,952. The photographic materials of the invention may further contain various surfactants in the photographic emulsion layer or in at least one other hydrophilic colloid layer. Suitable surfactants include nonionic surfactants such as saponins, alkylene oxides such as polyethylene glycol, polyethylene glycol/polypropylene glycol condensation products, polyethylene glycol alkyl ethers or polyethylene glycol alkyl aryl ethers, polyethylene glycol esters, polyethylene glycol sorbitan. esters, polyalkylene glycol alkylamines or alkylamides, silicone-polyethylene oxide adducts, glycidol derivatives, fatty acid esters of polyhydric alcohols and alkyl esters of saccharides; containing acid groups such as carboxy, sulfo, phospho, sulfate or phosphate groups. anionic surfactants such as amino acids, aminoalkylsulfonic acids, aminoalkyl sulfates or phosphates, amphoteric surfactants such as alkyl betaines and amine-N-oxides; and alkylamine salts, aliphatic, aromatic or heterocyclic quaternary Included are cationic surfactants such as ammonium salts, aliphatic or heterocyclic containing phosphonium or sulfonium salts. Such surfactants are used for various purposes, such as as coating aids, as antistatic compounds, as compounds that improve lubricity, as compounds that facilitate dispersion and emulsification, as compounds that prevent or reduce adhesion, and for photographic properties. and can be used as compounds to improve, for example, high contrast, sensitization and development acceleration. Preferred surface active coatings are compounds containing perfluorinated alkyl groups. Development acceleration can be achieved with the aid of various compounds, preferably polyalkylene derivatives having a molecular weight of at least 400, such as those described in US Pat. The photographic materials of the invention may further contain various other additives, such as compounds which improve the dimensional stability of the photographic materials, UV absorbers, spacing agents and plasticizers. Additives suitable for improving the dimensional stability of photographic materials include, for example, water-soluble or nearly insoluble synthetic polymers such as alkyl (meth)acrylates, alkoxy(
Meth)acrylate, glycidyl (meth)acrylate, (meth)acrylamide, vinyl ester, acrylonitrile, olefin and styrene polymers, acrylic acid, methacrylic acid, α,β-unsaturated dicarboxylic acid, hydroxyalkyl (meth)acrylate There are dispersions of copolymers with , sulfoalkyl (meth)acrylate, and styrene sulfonic acid. Generally, the average particle size of the spacing agent is 0.
It is included between 2 and 10 μm. Spacing agents can be alkali soluble or insoluble. Alkali-insoluble spacing agents usually remain permanently in the photographic material,
Alkali-soluble spacing agents, on the other hand, are usually removed therefrom in an alkaline processing bath. Suitable spacing agents can be made from polymethyl methacrylate, copolymers of acrylic acid and methyl methacrylate, and hydroxypropyl methyl cellulose hexahydrophthalate. Other suitable spacing agents are U.S. Pat.
It is stated in No. 8. The support of the photographic material can be opaque or transparent, for example a paper support or a resin support. When a paper support is used, preference is given to one coated on one or both sides with an alpha-olefin polymer, such as a polyethylene layer optionally containing an antihalation dye or pigment. Organic resin supports, such as cellulose nitrate film, cellulose acetate film, poly(
vinyl acetal) film, polystyrene film,
Poly(ethylene terephthalate) film, polycarbonate film, polyvinyl chloride film or poly-α
- It is also possible to use olefin films, such as polyethylene or polypropylene films. The thickness of such an organic resin film is preferably 0.07 to 0.35 mm. These organic resin supports are preferably coated with a subbing layer which can contain water-insoluble particles such as silica or titanium dioxide. In a preferred embodiment of the medical radiographic material, a transparent blue-colored poly(ethylene terephthalate) film is preferably coated on both sides with two emulsion layers. The photographic material containing the platelet grains stabilized according to the invention is imagewise exposed by any convenient radiation source according to its particular application. For the preferred embodiment of the green sensitized x-ray material, suitable commercially available green light emitting screens include KODAK LANEX and AGF.
There is A CURIX ORTHO. Photographic materials in the context of the present invention are preferably processed in automatically operated equipment. For radiography,
X-ray material processing machines available on the market include AGFA-GE
VAERT N. V. CUR marketed by
IX U 242 and EASTMAN KODAK C
o. KODAK RP-X- marketed by
There is OMAT M 6A-N. The following examples illustrate, but do not limit, the invention. Example 1.1 Preparation of emulsion sample: 3180 ml deionized water, 18.54 g
of KBr and 12.5 g of inert gelatin at pH 5.8 and 70 °C.
25 ml of NO3 solution and 25 ml of 2.94 molar KBr solution were added in 28 seconds by double jet precipitation. Next, solution 47 containing 47.5 g of phthaloyl gelatin
5 ml was added followed by physical aging for 10 minutes. pB
2.9 of AgNO3 to adjust r to 2.03.
The 4 molar solution was added at a rate of 5 ml/sec over 564 seconds. Then 928 ml of a 2.94 molar AgNO3 solution and a 2.94 molar KBr solution were added simultaneously at a rate of 5 ml/sec initially and increasing linearly to 49 ml/sec. During this precipitation step pBr was kept at a fixed value of 2.03. Finally, the pH was adjusted to 3.5 with sulfuric acid solution and the temperature was lowered to 40°C. After washing, 160 g of inert gelatin was added and the pH and pAg were adjusted to 5.5 and 7.64, respectively. The platelet particles thus obtained have an average thickness of 0.20μ and are described in British Patent No. 2110402 by Abot
It had an average aspect ratio of 6.6 as measured by the method described by t. 80% of the total projected area was covered by platelet particles. In the next manufacturing step, the emulsion was divided into several parts. Each portion contains 935 mg of anhydro-5,5'-
Spectrally sensitized to the green spectral band with dichloro-9-ethyl-3,3'-di-(3-sulfobutyl)-oxacarbocyanine, then
5.1 μmol of sodium thiosulfate, 1.73 μmol of chloroplatinic acid and AgNO3 per mole of AgNO3
Chemically sensitized with 1.32 mmol potassium thiocyanate per mole. The time of chemical sensitization was adjusted for each sample to obtain the best fog/density ratio after coating and processing. After cooling each emulsion sample, the desired amount of stabilizer was added to each sample (see Table 1). Each emulsion sample was then coated on both sides of a polyethylene terephthalate film with AgNO3/
A silver coverage of 2 x 3.0 g expressed as m2 was coated. A protective layer containing 1.1 g/m2 of gelatin was applied on both sides and formaldehyde was used as a hardening agent. 1.2 Evaluation of photographic properties: The coated samples were exposed to green light with an emission maximum at 545 nm through a continuous tone wedge. Some of the samples were stored at 57° C. and 34% relative humidity to simulate long-term storage. The processing was carried out using the following processing solution: a developer solution adjusted to pH 10.1 containing as average components hydroquinone, 1-phenyl-5-pyrazolidinone, potassium sulfite, 5-nitroindazole and glutardialdehyde;
It was run in an X-ray film processor (90 second cycle) using a conventional fixing solution containing ammonium thiosulfate adjusted to 4.3. The crossover percentage was determined as follows. A film-screen material consisting of a double coated emulsion sample in close contact with a single green emitting screen on the x-ray attenuation side and a white paper replacing a second screen on the other side was exposed to varying x-ray doses. After processing these materials, sensitivity measurement curves (concentration as a function of X-ray dose) were determined. From the difference in sensitivity, log E, between these two layers,
The % crossover was calculated according to the following formula: % crossover=100/log E
Tetrazaindene (TAI) and the stabilizer of the present invention, 2
-Sensitivity measurement results of stabilization of the above-mentioned plate-like particles by mercapto-4-hydroxy-6-carboxy-quinazoline (Compound 1) are shown. Sensitivity is expressed as a relative arithmetic value,
Sample 1 has a reference value of 100. Table 2 represents the % crossover values. [0055]
Table 1 Sample TAI concentration
Compound 1 concentration Fog Sensitivity Fog 57°C/34% No. mmol/
Mol Ag mmol/mol Ag
Fresh Fresh After 3 days
1 1.20 0
0.030 100 0.33
7 2 2.40 0
0.023 75 0.
122 3 1.20 0.225
0.009 100 0.014
4 2.40 0.225
0.008 91 0.015
[0056]
Table 2
Sample No. crossover%
Note
1 39
Comparison 2
57
comparison
3
41 The present invention
4
52 Present invention 0057
] The results in Tables 1 and 2 show that the use of TAI as the sole stabilizer was effective at 57°C and 34°C without significant cross-over degradation.
% relative humidity shows that the fog increase cannot be limited after conditioning the material for 3 days. In contrast, the quinazoline derivatives according to the invention in combination with TAI significantly reduced the post-adjustment fog increase without significant changes in the crossover percentage.

Claims (10)

[Claims] 1. A support and at least one light-sensitive emulsion layer containing tabular silver halide grains having an average aspect ratio of at least 4:1 and accounting for at least 50% of the total projected area of all grains. In the photographic material containing the emulsion, the emulsion has the general formula: represents a ring member necessary to complete a heterocyclic ring selected from tetrahydropyridine, pyrimidine, pyrrole, furan, thiophene, oxazole, isoxazole, imidazole or pyrazole ring, and R or Z is at least one carboxy group or Photographic material characterized in that it is stabilized with a mercapto-substituted pyrimidine derivative represented by (containing a sulfo group). 2. The photographic material according to claim 1, wherein the stabilizer is a quinazoline derivative shown below. 3. Photographic material according to claim 1, characterized in that the stabilizer is added to the emulsion at a concentration of 10@-7 mol to 10@-3 mol per mole of silver halide. 4. The photographic material according to claim 1, wherein the stabilizer is combined with a tetraazaindene stabilizer. 5. The tetraazaindene stabilizer is 4-
5. Photographic material according to claim 4, characterized in that it is hydroxy-6-methyl-1,3,3a,7-tetraazaindene. 6. Photographic material according to claim 1, characterized in that the grains of the platelet emulsion exhibit a minimum average diameter of 0.6μ and a maximum average thickness of 0.3μ. 7. Photographic material according to claim 1, characterized in that said photographic material is a radiographic X-ray recording material. 8. Photographic material according to claim 7, characterized in that said radiographic material contains a high speed tabular silver bromide iodide emulsion coated on both sides of a transparent support. 9. Photographic material according to claim 8, characterized in that said radiographic material is green sensitized. 10. The plate-like particles are epitaxially deposited on their surfaces.
Photographic materials according to any one of item 9.