Photographic silver halide emulsion, photographic light-sensitive material using same emulsion, and method of processing same light-sensitive material

A photographic silver halide emulsion is disclosed, comprising tabular grains: the tabular grains having a silver chloride content of at least 95 mole %, an aspect ratio of at least 2 and a distance between the main planes of 0.13 .mu.m or less; wherein the tabular grains occupy at least 90%, based on total projected area, of the total silver halide grains in the emulsion and have a variation coefficient of 20% or less in the distance between the main planes; and a silver halide photographic material comprising a support having thereon the silver halide emulsion and a method of development-processing the silver halide photographic material are disclosed.

FIELD OF THE INVENTION
 The present invention relates to a photographic silver halide emulsion, a
 photographic light-sensitive material using such an emulsion and a method
 of development-processing such a light-sensitive material. In particular,
 this invention is concerned with a photographic tabular silver halide
 grain emulsion comprising silver chloride grains or silver chlorobromide,
 chloroiodide or chloroiodobromide grains having a high chloride content.
 BACKGROUND OF THE INVENTION
 Hitherto, various techniques for utilizing silver halide grains with a high
 silver chloride content (specifically, the silver halide grains having a
 chloride content of at least 95 mole %, which are referred to as the
 high-silver chloride grains hereinafter) have been proposed with the
 intention of making the photographic processing simple and rapid.
 Utilizing high-silver chloride grains has advantages of enhancing the
 reusability of processing solutions as well as increasing the development
 speed. Therefore, the photosensitive materials comprising high-silver
 chloride grains occupy the mainstream of photosensitive materials for
 printing, such as color photographic printing paper. In the present
 invention, processing time means the time from the initiation of
 processing (contact of a photographic material with a developing solution)
 to drying (Dry to Dry).
 The high-silver chloride grains formed under ordinary conditions are grains
 having (100) faces as their external surfaces (referred to as {100} grains
 hereinafter). The grains put into practical use were also cubic grains. In
 recent years, tabular {100} grains have been developed since they have
 advantages of enabling effective spectral sensitization and ensuring a
 great covering power after development due to their large specific surface
 area (high ratio of the surface areas to the volume of each grain).
 Examples of such tabular grains are disclosed in U.S. Pat. Nos. 5,320,938,
 5,264,337 and 5,292,632. Having high spectral sensitization efficiency is
 important particularly for high-silver chloride grains in which absorption
 of light in the blue-sensitive region is slight as compared with silver
 from iodide grains.
 However, the high-silver chloride {100} grains have a problem of being
 easily fogged, as compared with commonly used silver bromide grains. In
 order to overcome this problem, high-silver chloride grains having (111)
 faces as their external surfaces (referred to as {111} grains) are
 utilized. Examples of these grains are disclosed in JP-A-6-138619 (the
 term "JP-A" as used herein means an "unexamined published Japanese patent
 application").
 The formation of high-silver chloride {111} grains requires special
 contrivances. For instance, the method of forming high-silver chloride
 tabular grains in the presence of ammonia is disclosed by Wey in U.S. Pat.
 No. 4,399,215. The use of ammonia makes it difficult to form practically
 useful fine grains because silver chloride grains originally having high
 solubility is produced with a higher solubility condition. In addition,
 the pH at the time of manufacturing grain is raised to 8-10 by the use of
 ammonia; as a result, the grains are easily fogged. On the other hand, the
 high-silver chloride {111} grains formed in the presence of thiocyanates
 are disclosed by Maskasky in U.S. Pat. No. 5,061,617. Similarly to
 ammonia, the thiocyanates increase the solubility of silver chloride.
 Further, there are known the methods of using the following additives
 [crystal phase controlling agents (which is sometimes called crystal habit
 control agents)] at the time of grain formation for the purpose of forming
 high-chloride grains the surfaces of which are constituted of (111) faces:

Crystal habit
 Document control agent Inventor
 U.S. Pat. No. 4,400,463 Azaindenes + Maskasky
 Thioether peptizer
 U.S. Pat. No. 4,783,398 2,4-Dithiazolidinone Mifune et al.
 U.S. Pat. No. 4,713,323 Aminopyrazolopyrimi- Maskasky
 dine
 U.S. Pat. No. 4,983,508 Bispyrimidinium salts Ishiguro
 et al.
 U.S. Pat. No. 5,185,239 Triaminopyridine Maskasky
 U.S. Pat. No. 5,178,997 7-Azaindole compounds Maskasky
 U.S. Pat. No. 5,178,998 Xanthine Maskasky
 JP-A-64-70741 Dyes Nishikawa
 et al.
 JP-A-3-212639 Aminothioether Ishiguro
 JP-A-4-283742 Thiourea derivatives Ishiguro
 JP-A-4-335632 Triazolium salts Ishiguro
 JP-A-2-32 Bispyridinium salts Ishiguro
 et al.
 JP-A-8-227117 Monopyridinium salts Ozeki et al.
 The grains obtained using those methods have comparatively large sizes,
 specifically an average equivalent circle diameter of about 1 .mu.m (the
 term "average equivalent circle diameter" used herein means the average
 value of diameters of circles having the same areas as the projected areas
 of grains). From a practical point of view, however, it has so far been
 desired to form silver halide grains having a thin tabular shape, a high
 silver chloride content and grain sizes smaller than those achievable by
 the methods described above. In particular, thin tabular grains have been
 desired because they have a large specific surface area. Examples of thin
 high-silver chloride {111} tabular grains are disclosed in U.S. Pat. Nos.
 5,217,858 and 5,183,732. However, a decrease in thickness of tabular
 grains causes a problem that the grains are easily dissolved during the
 photographic processing. In the practical color development-processing,
 the photosensitive materials are passed through a developer, a
 bleach-fixing solution and a washing solution in this order. Therefore,
 there is great danger of contaminating a developer with a fix-bleaching
 solution. As a result of the contamination, dissolution physical
 development impairs the photographic properties (sensitizing and
 increasing contrast). These phenomena are also promoted by decrease in
 grain size.
 When the grain thickness distribution or/and the grain size distribution
 are broad (polydispersed), the grains in a thin grain section or a small
 size section of the distribution are especially subject to dissolution,
 and so they have low stability in processing solutions. In the documents
 described above, the tabular grains having an average equivalent circle
 diameter of 0.8 .mu.m or less are disclosed, but the proportion of such
 tabular grains to the total grains is 85%, on a projected area basis. In
 the case of containing iodide in tabular grains, the proportion of the
 tabular grains to the total grains is 70%. When the grains having
 different grain shapes are intermingled, they lack the uniformity in
 adsorption of sensitizing dyes thereto and the chemical sensitization
 thereof to result in deterioration of photographic characteristics.
 SUMMARY OF THE INVENTION
 Therefore, an object of the present invention is to provide a photographic
 silver halide emulsion comprising tabular high-silver chloride grains
 which has a high sensitivity, hardly causes fog and ensures high
 development-processing stability; a photographic light-sensitive material
 comprising such an emulsion, and a method of development-processing such a
 light-sensitive material.
 The object is attained with the following embodiments according to the
 present invention:
 1. A photographic silver halide emulsion comprising tabular grains: the
 tabular grains having a silver chloride content of at least 95 mole %, an
 aspect ratio of at least 2 and a distance between main planes of 0.13
 .mu.m or less; wherein the tabular grains occupy at least 90%, based on
 the total projected area, of the total silver halide grains in the
 emulsion and have a variation coefficient of 20% or less in the distance
 between the main planes.
 Further, preferred embodiments are shown below.
 2. The silver halide emulsion as described in the above item 1, wherein the
 tabular grains have an average equivalent circle diameter of 0.8 .mu.m or
 less.
 3. The silver halide emulsion as described in the above item 1, wherein the
 tabular grains have a variation coefficient of 22% or less in the
 equivalent circle diameter.
 4. The silver halide emulsion as described in the above item 1, wherein the
 tabular grains comprise tabular grains having (111) faces as the main
 plane.
 5. The silver halide emulsion as described in the above item 1, wherein the
 tabular grains have a silver iodide content of from 0.2 to 0.6 mole %
 based on the silver.
 6. The silver halide emulsion as described in the above item 1, wherein
 said tabular grains have a silver bromide content of from 0.1 to 4 mole %
 based on the silver.
 7. The silver halide emulsion as described in the above item 1, wherein the
 tabular grains each comprise a core and a shell as the outermost layer and
 the silver iodide content in the shell is at least 2 mole %.
 8. The silver halide emulsion as described in the above item 1, wherein the
 tabular grains each contain a bromide-localized phase in which the
 difference between the bromide-localized phase and other phases in bromide
 concentration is at least 6 mole %.
 9. The silver halide emulsion as described in the above item 8, wherein the
 bromide-localized phase contains an iridium compound in a proportion of
 from 1.times.10.sup.-8 to 1.times.10.sup.-5 mole % based on the total
 silver in each grain.
 10. A silver halide photographic material comprising a support having
 thereon at least two light-sensitive layers, wherein the light-sensitive
 layer arranged farthest from the support comprises a silver halide
 emulsion comprising tabular grains:
 the tabular grains having a silver chloride content of at least 95 mole %,
 an aspect ratio of at least 2 and a distance between main planes of 0.13
 .mu.m or less; wherein the tabular grains occupy at least 90%, based on
 the total projected area, of the total silver halide grains in the
 emulsion and have a variation coefficient of 20% or less in the distance
 between the main planes.
 11. A silver halide photographic material comprising a support having
 thereon at least one silver halide emulsion layer, wherein at least one of
 the emulsion layers comprises a silver halide emulsion comprising tabular
 grains:
 the tabular grains having a silver chloride content of at least 95 mole %,
 an aspect ratio of at least 2 and a distance between main planes of 0.13
 .mu.m or less; wherein the tabular grains occupy at least 90%, based on
 the total projected area, of the total silver halide grains in the
 emulsion and have a variation coefficient of 20% or less in the distance
 between the main planes.
 12. A method of development-processing a silver halide photographic
 material, wherein the photographic material processed is a silver halide
 photographic material comprising a support having thereon at least two
 light-sensitive layers, wherein the light-sensitive layer arranged
 farthest from the support comprises a silver halide emulsion comprising
 tabular grains:
 the tabular grains having a silver chloride content of at least 95 mole %,
 an aspect ratio of at least 2 and a distance between main planes of 0.13
 .mu.m or less; wherein the tabular grains occupy at least 90%, based on
 the total projected area, of the total silver halide grains in the
 emulsion and have a variation coefficient of 20% or less in the distance
 between the main planes, and the dry-to-dry processing time is 60 sec or
 less.
 13. A method of development-processing a silver halide photographic
 material, wherein the photographic material processed is a silver halide
 photographic material comprising a support having thereon at least one
 silver halide emulsion layer, wherein at least one of the emulsion layers
 comprises a silver halide emulsion comprising tabular grains:
 the tabular grains having a silver chloride content of at least 95 mole %,
 an aspect ratio of at least 2 and a distance between main planes of 0.13
 .mu.m or less; wherein the tabular grains occupy at least 90%, based on
 the total projected area, of the total silver halide grains in the
 emulsion and have a variation coefficient of 20% or less in the distance
 between the main planes, and the dry-to-dry processing time is 60 sec. or
 less.

DETAILED DESCRIPTION OF THE INVENTION
 The methods for forming tabular grains are described below. First, the
 method of forming {111} tabular grains is illustrated. The {111} tabular
 grains of the present invention are basically formed by three steps of
 nucleation, ripening and growth. In a case of forming superfine grains,
 the growth process may be omitted.
 &lt;Nucleation&gt;
 The tabular grains are obtained by forming two parallel twin planes. The
 formation of twin planes depends chiefly on the temperature, the
 dispersing medium (gelatin) concentration and the halide concentration.
 Therefore, it is necessary to impose appropriate conditions on those
 factors. When the nucleation is carried out in the presence of a crystal
 habit control agent, the suitable gelatin concentration is from 0.1 to
 10%.
 On the other hand, JP-A-8-184931 discloses that the nucleation in the
 absence of a crystal habit control agent is desirable for the formation of
 monodisperse grains. When the nucleation is carried out using no crystal
 habit control agent, the suitable gelatin concentration is from 0.03 to
 10%, preferably from 0.05 to 1.0%. The chloride concentration is from
 0.001 to 1 mole/l, preferably from 0.003 to 0.1 mole/l. The nucleation
 temperature, though can be chosen arbitrarily from the range of 2 to
 60.degree. C., is desirably from 5.degree. C. to 45.degree. C.,
 particularly preferably from 5.degree. C. to 35.degree. C.
 The gelatin suitable for nucleation is gelatin having a high molecular
 weight of at least 1.0.times.10.sup.5.
 For the formation of tabular nuclei, it is desirable that the pCl be from
 1.2 to 2.3. In particular, the pCl range of 1.2 to 1.8 is adequate to make
 the thickness monodisperse.
 &lt;Ripening&gt;
 Although the nuclei of tabular grains are formed in the first nucleation
 step, many nuclei other than the nuclei of tabular grains are also present
 in the reaction vessel just after nucleation. This situation requires the
 techniques of retaining tabular grains alone and making other grains
 disappear by ripening after nucleation. When usual Ostwald ripening is
 carried out, the tabular grain nuclei also dissolve and disappear, and
 thereby the number of the tabular grain nuclei is decreased; as a result,
 the tabular grains obtained increase in size. In order to prevent the
 increase in grain size, crystal habit control agents are added. In
 particular, the use of a crystal habit control agent in combination with
 phthalated, succinated, or trimellited gelatin is effective in making the
 grain thickness monodisperse as well as enhancing the effect of the
 crystal habit control agent and preventing the tabular grain nuclei from
 dissolving. In the combined use, the proportion of the crystal habit
 control agent to the phthalated, succinated or trimellited gelatin is an
 important factor. Specifically, it is desirable that the crystal habit
 control agent be used in an amount of 3.times.10.sup.-6 to
 6.times.10.sup.-6 mole per gram of phthalated, succinated or trimellited
 gelatin. Therein, the crystal habit control agent and the gelatin solution
 may be added simultaneously or successively. Preferably, they are added as
 a previously mixed solution.
 In the ripening, the pAg is particularly important, and it is preferable
 that the silver potential is from 60 to 130 mV against the saturated
 calomel electrode (SCE).
 Efficient ripening can be achieved by carrying out the ripening at a
 temperature higher than the nucleation temperature. In particular, it is
 desirable that the ripening temperature be higher than the nucleation
 temperature by at least 15.degree. C.
 &lt;Growth&gt;
 Cases are illustrated below where the nuclei formed are physically ripened
 and further made to grow in the presence of a crystal habit control agent
 by the addition of a silver salt and halides. Herein, the chloride
 concentration is controlled to 5 mole/l or less, preferably 0.05 to 1
 mole/l. The temperature during the grain growth can be chosen from the
 range of 10 to 95.degree. C., preferably 30 to 75.degree. C.
 It is desirable that the total amount of crystal habit control agent used
 be at least 6.times.10.sup.-5 mole, especially from 3.times.10.sup.-4 to
 6.times.10.sup.-2 mole, per mole of silver halide in the finished
 emulsion. The crystal habit control agent may be added at any time, from
 the nucleation to the physical ripening and during the grain growth of the
 silver halide grains. For instance, the crystal habit control agent may be
 previously added to a reaction vessel. In the case of forming small-size
 tabular grains, it is desirable to keep on adding the crystal habit
 control agent and increasing the concentration thereof with the progress
 of grain growth.
 When the amount of dispersing medium used at the time of nucleation or
 grain growth is insufficient for the grain growth, it is required to make
 up for the shortage by further adding the dispersing medium. For the
 growth, it is desirable that the gelatin be present in an amount of 10 g/l
 to 100 g/l. The gelatin preferable for supplementation is phthalated
 gelatin or trimellited gelatin.
 The pH during the grain formation, though it has no particular limitation,
 is desirably neutral or in an acidic region.
 As mentioned above, many compounds are disclosed with respect to the
 crystal habit control agents used for forming {111} tabular silver
 chloride grains. For forming the {111} tabular grains of the present
 invention, the compounds represented by the following formulae (I), (II)
 and (III), especially formula (III), are preferred as crystal habit
 control agent:
 ##STR1##
 In Formula (I), R.sub.1 is desirably a straight-chain, branched or cyclic
 alkyl group having 1 to 20 carbon atoms (e.g., methyl, ethyl, isopropyl,
 t-butyl, n-octyl, n-decyl, n-hexadecyl, cyclopropyl, cyclopentyl,
 cyclohexyl), an alkenyl group having 2 to 20 carbon atoms (e.g., allyl,
 2-butenyl, 3-pentenyl), or an aralkyl group having 7 to 20 carbon atoms
 (e.g., benzyl, phenetyl). Each of these groups reposented by R.sub.1 may
 have a substituent. Examples of such a substituent include the following
 substitutable groups represented by R.sub.2 to R.sub.6.
 R.sub.2, R.sub.3, R.sub.4, R.sub.5 and R.sub.6 may be the same as or
 different from one another. Each of them is a hydrogen atom or a
 substitutable group. Examples of such a substitutable group include a
 halogen atom, an alkyl group, an alkenyl group, an alkynyl group, an
 aralkyl group, an aryl group, a heterocyclic group (e.g., pyridyl, furyl,
 imidazolyl, piperidyl, morpholino), an alkoxy group, an aryloxy group, an
 amino group, an acylamino group, an ureido group, an urethane group, a
 sulfonylamino group, a sulfamoyl group, a carbamoyl group, a sulfonyl
 group, a sulfinyl group, an alkyloxycarbonyl group, an acyl group, an
 acyloxy group, a phosphoric acid amide group, an alkylthio group, an
 arylthio group, a cyano group, a sulfo group, a carboxyl group, a hydroxyl
 group, a phosphono group, a nitro group, a sulfino group, an ammonio group
 (e.g., trimethylammonio group), a phosphonio group and a hydradino group.
 Each of these groups may be further substituted.
 R.sub.2 and R.sub.3, R.sub.3 and R.sub.4, R.sub.4 and R.sub.5, and R.sub.5
 and R.sub.6, may be condensed to form a quinoline, isoquinoline or
 acridine ring.
 X.sup.- represents a counter anion, with examples including a halogen ion
 (e.g., chlride ion, bromide ion), nitrate ion, sulfate ion,
 p-toluenesulfonate ion or trifluoromethane-sulfonate ion.
 In Formula (I), it is desirable that R.sub.1 be an aralkyl group and at
 least one of the other substituents R.sub.2 to R.sub.6 be an aryl group.
 Therein, it is more preferable that R.sub.1 be an aralkyl group, R.sub.4 be
 an aryl group and X.sup.- be a halogen ion. Examples of such compounds are
 disclosed as the Crystal Habit Control Agents 1 to 29 in EP-A-0723187.
 However, the invention should not be construed as being limited to these
 exemplified ones.
 The compounds represented by Formulae (II) and (III) respectively are
 illustrated below.
 A.sub.1, A.sub.2, A.sub.3 and A.sub.4 each represent a nonmetallic element
 necessary for completing a nitrogen-containing hetero ring, which may
 further contain an oxygen, nitrogen or sulfur atom in the ring or/and form
 a condensed ring by condensing together with a benzene ring. The hetero
 rings formed by A.sub.1, A.sub.2, A.sub.3 and A.sub.4 respectively may
 have substituent groups, which may be the same as or different from one
 another. Examples of substituent groups include an alkyl group, an aryl
 group, an aralkyl group, an alkenyl group, a halogen atom, an acyl group,
 an alkoxycarbonyl group, an aryloxycarbonyl group, a sulfo group, a
 carboxyl group, a hydroxyl group, an alkoxy group, an aryloxy group, an
 amido group, a sulfoamoyl group, a carbamoyl group, an ureido group, an
 amino group, a sulfonyl group, a cyano group, a nitro group, a mercapto
 group, an alkylthio group and an arylthio group. Suitable examples of
 A.sub.1, A.sub.2, A.sub.3 and A.sub.4 each include 5- and 6-membered rings
 (such as a pyridine ring, an imidazole ring, a thiazole ring, an oxazole
 ring, a pyrazine ring and a pyrimidine ring). Preferably, each ring is a
 pyridine ring.
 B represents a divalent linking group. Herein, the divalent linking group
 is a linking group consisting of an alkylene group, an arylene group, an
 alkenylene group, --SO.sub.2 --, --SO--, --O--, --S--, --CO--,
 --N(R'.sub.2)-- (wherein R'.sub.2 is an alkyl group, an aryl group or a
 hydrogen atom) and alone or in combination. Preferably, B is an alkylene
 or alkenylene group.
 m represent 0 or 1.
 R.sub.1 and R.sub.2 each represent an alkyl group having 1 to 20 carbon
 atoms. R.sub.1 and R.sub.2 may be the same or different from each other.
 Herein, the alkyl group means a substituted or unsubstituted alkyl group.
 The substituent groups for the alkyl group are the same as those
 exemplified as the substituent groups of A.sub.1, A.sub.2, A.sub.3 or
 A.sub.4.
 Suitable examples of R.sub.1 and R.sub.2 each include an alkyl groups
 having 4 to 10 carbon atoms. Preferably, R.sub.1 and R.sub.2 are each an
 alkyl group substituted by a substituted or unsubstituted aryl group.
 X represents an anion. Examples of such an anion include chloride ion,
 bromide ion, iodide ion, nitrate ion, sulfate ion, p-toluenesulfonate ion
 and oxalate ion. n represents 0 or 1, and it is 0 when the inner salt is
 formed.
 Examples of the compounds represented by formulae (II) and (III)
 respectively include the Compounds (1) to (42) disclosed in U.S. Pat. No.
 4,983,508 and the Compounds (1) to (32) disclosed in U.S. Pat. No.
 5,432,052. However, the present invention should not be construed as being
 limited to those compounds.
 In the next place, the {100} tabular grains are illustrated.
 The {100} tabular grains are tabular grains having (100) faces as their
 main planes. As to the shape of the main planes, each main plane may be a
 right-angled parallelogram, a triangle or pentagon formed by lacking one
 corner of the right-angled parallelogram (the part lacked from the
 parallelogram has a shape of right triangle formed by the apex of the
 corner and the sides diverging from the apex), or a quadrangle to an
 octagon formed by lacking two to four corners of the right-angled
 parallelogram.
 The lacked part is supplemented to form a right-angled parallelogram.
 Herein, this parallelogram is referred to as a supplemented quadrilateral.
 As to the lengths of adjacent sides in both right-angled parallelogram and
 supplemented quadrilateral, it is desirable that the ratio between them
 (the ratio between the long side length to the short side length) be from
 1 to 6, preferably 1 to 4, more preferably 1 to 2.
 The silver halide tabular emulsion grains having (100) main planes can be
 formed, e.g., as follows: The addition of aqueous solutions of silver salt
 and halide to a dispersing medium, such as an aqueous solution of gelatin,
 and the mixing thereof with stirring are carried out in the presence of
 silver iodide or iodide ion, or silver bromide or bromide ion, as
 disclosed in JP-A-6-301129, JP-A-6-347929, JP-A-9-34045 and JP-A-9-96881.
 Since the bromide and the iodide are different from the chloride in
 crystal lattice size, they give rise to distortions in nuclei and thereby
 crystal defects to cause anisotropic crystal growth, such as screw
 dislocations, are introduced to the nuclei. Once the screw dislocation has
 been introduced, the formation of two-dimensional nuclei on the plane
 having a screw dislocation is no longer a rate-limiting step in the grain
 growth under conditions of low supersaturation; as a result,
 crystallization proceeds on this plane. Therefore, the introduction of
 screw dislocations can lead to the formation of tabular grains. The term
 "conditions of low supersaturation" as used herein means 35% or less,
 preferably 2 to 20%, of critical supersaturation upon addition. Although
 it is not definitely established that the crystal defects are screw
 dislocations, the crystal defects are thought to be screw dislocations in
 a high probability, judging from the direction in which the dislocations
 are introduced and the fact that the anisotropic growth is induced.
 JP-A-8-122954 and JP-A-9-189977 disclose that the retention of such
 dislocations introduced is favorable for making the tabular grains
 thinner.
 The mixing upon nucleation is important for forming tabular grains
 monodisperse in thickness, so that it is required to mix the aqueous
 solutions of silver nitrate and halides in a short time with stirring at a
 high efficiency. When the mixing apparatus disclosed in JP-A-51-83097 is
 used, it is desirable that the stirring be performed at 800 to 2,000
 r.p.m., particularly 1,000 to 2,000 r.p.m.
 In another method for forming the {100} tabular grains, (100) face forming
 accelerators are added. As such accelerators, JP-A-6-347928 discloses
 imidazoles and 3,5-diaminotriazolesl, while JP-A-8-339044 discloses
 polyvinyl alcohols. However, the invention should not be construed as
 being limited to those methods.
 In the silver halide emulsion of the present invention, the tabular grains
 having a distance between the main planes of 0.13 .mu.m or less and an
 aspect ratio of at least 2 occupy at least 90% of the total grains based
 on the total projected area of the total silver halide grains in the
 emulsion. With respect to the shape of tabular grains, each grain
 generally has two parallel planes. These parallel planes are referred to
 as the main planes, and a distance between the main planes is defined as a
 thickness. The thickness is desirably 0.1 .mu.m or less, particularly
 desirably from 0.02 to 0.08 .mu.m. Uniformity is essential for grain
 thickness, and so it is required that the silver halide tabular grains of
 the present invention have a variation coefficient (a value obtained by
 dividing a standard deviation by a mean value) of 20% or less, preferably
 16% or less, with respect to the grain thickness. The grain thickness can
 be determined by the shadow length from electron microscope photography
 utilizing a carbon replica process in combination with metal deposition.
 The average equivalent circle diameter of the total tabular grains can be
 arbitrarily chosen from the range of 0.3 to 10 .mu.m. The term "equivalent
 circle diameter" as used herein means the diameter of a circle having the
 same area as the projected area of a grain in an electron microscope
 photography. Further, the diameter/thickness ratio is referred to as the
 aspect ratio. When the grains are used in a photosensitive material for
 rapid processing, it is desirable for them to have their individual
 equivalent circle diameters in the small-size range of 0.3 to 0.8 .mu.m.
 In this small-size range, the processing stability decreases due to
 dissolution physical development, so that the present invention can fully
 achieve its effects. Therefore, this range is especially important for the
 the present invention. Moreover, it is desirable that the distribution of
 equivalent circle diameters of grains be monodisperse, and the present
 invention can have the greatest effects when the variation coefficient of
 equivalent circle diameter is not higher than 22%.
 The average aspect ratio is desirably at least 5, preferably from 8 to 20.
 The tabular grains of the present invention are grains having silver
 chloride content of at least 95 mole %, particularly preferably at least
 98 mole %.
 The tabular grains of the present invention, though may be uniform in
 structure, preferably have the so-called core/shell structure, that is,
 the structure constituted of a core part and a shell part surrounding the
 core part. In the core part, it is desirable that at least 95% of the
 silver halide be silver chloride. The core part may be made up of two or
 more sections differing in halide composition. For the shell part, it is
 desirable to occupy 50% or less, particularly 20% or less, of the total
 volume of each grain.
 It is desirable for the tabular grains of the present invention to contain
 silver iodide in a proportion of 0.1 mole % to 0.8 mole % based on the
 total silver. In particular, the iodide content of 0.2 mole % to 0.6 mole
 % is desirable. The silver iodide is preferably contained in the shell
 part (outermost layer). The iodide content in the shell part is desirably
 from 1.0 mole % to 13 mole %, especially from 2 mole % to 10 mole %. By
 containing silver iodide, the effect of a monodispersed thickness
 distribution upon processing stability is enhanced.
 By containing silver bromide also, it is possible to enhance the effect of
 a monodispersed thickness distribution upon processing stability.
 The suitable bromide content is from 0.1 mole % to 4 mole %. It is
 desirable that the bromide content be higher in the shell part than in the
 core part. Further, it is desirable that the phase differing in a bromide
 content by at least 6 mole % (bromide-localized phase) from the other
 phases be present inside the grains. Preferably, the bromide-localized
 phase at least 6 mole % higher in bromide content than the other phases is
 present in the shell part. The bromide-localized phase desirably contains
 an iridium compound in a proportion of 1.times.10.sup.-8 mole % to
 1.times.10.sup.-6 mole % based on the total silver in each grain, and
 thereby the shape of tabular grains is stabilized and photographic
 properties under high intensity exposure are improved.
 The crystal habit control agent existing on the grain surfaces after grain
 formation influences the adsorption of sensitizing dyes and the
 development. Therefore, it is desirable that the crystal habit control
 agent be removed after grain formation. When the crystal habit control
 agent is removed, however, it becomes difficult for high-silver chloride
 grains to maintain (111) faces under usual conditions. Therefore, it is
 desirable to replace the crystal habit control agent with a
 photographically useful compound, such as a sensitizing dye, and thereby
 to retain the grain shape. The methods for grain shape retention are
 disclosed in, e.g., JP-A-9-80656, JP-A-9-106026, and U.S. Pat. Nos.
 5,221,602, 5,286,452, 5,298,387, 5,298,388 and 5,176,992.
 The crystal habit control agent desorbed from the grains in accordance with
 such a method as mentioned above is desirably removed from the emulsion by
 washing with water. The washing can be carried out at a temperature not
 causing the coagulation of gelatin generally used as protective colloid.
 As to the washing method, known techniques, such as flocculation and
 ultrafiltration, can be adopted. Specifically, when the crystal habit
 control agent used in the present invention is a pyridinium salt, the
 suitable washing temperature is preferably 40.degree. C. or above,
 particularly preferably 50.degree. C. or above.
 The desorption of a crystal habit control agent from grains is promoted
 under low pH. In the processing step, therefore, the lower pH is
 preferable as far as it does not cause too much aggragation among grains.
 The silver halide grains of the present invention can contain ions or
 complex ions of metals belonging to group VIII of the Periodic Table, such
 as osmium, iridium, rhodium, platinum, ruthenium, palladium, cobalt,
 nickel or iron, alone or in combination. Therein, two or more of these
 metals may be used.
 The compounds donating the foregoing metal ions may be added to an aqueous
 gelatin solution functioning as dispersing medium, an aqueous halide
 solution, an aqueous silver salt solution or another aqueous solution
 during silver halide grains formation, or the fine silver halide grains
 previously containing metal ions may be added to the silver halide
 emulsion and dissolved therein to result in incorporation of the metal
 ions in the silver halide emulsion grains. The treatment for incorporating
 metal ions into the grains can be carried out before, during or just after
 the grain formation. In other words, it can be made at any stage of grain
 formation, but the stage is chosen depending on the location intended for
 the metal ions inside the grains and the amount of metal ions to be
 incorporated.
 In the silver halide grains of the present invention, it is desirable that
 at least 50 mole %, preferably at least 80 mole %, more preferably 100
 mole %, of the metal-ion donating compounds used be localized in the
 surface layer the volume of which corresponds to 50% or less, preferably
 30% or less, of the total grain volume. The localization of metal ions in
 the surface layer can inhibit an increase in internal sensitivity, so that
 it is advantageous for achievement of high sensitivity. Such concentrative
 incorporation of metal ion-donating compounds in the surface layer can be
 effected, e.g., by first forming silver halide grains to constitute the
 core part (the part other than the surface layer), and then adding aqueous
 solutions of water-soluble silver salt and halides while supplying the
 metal ion-providing compounds thereto, thereby forming the surface layer
 of the grains.
 In addition to the group VIII metals, various polyvalent metal ion
 impurities can be introduced into the silver halide emulsion of the
 present invention in the process of forming or physically ripening the
 emulsion grains. The amount of these impurities added can cover a wide
 range depending on the purpose of their introduction. Specifically, the
 suitable addition amount is from 10.sup.-9 to 10.sup.-2 mole per mole of
 the silver halide.
 The silver halide emulsions used in the present invention are generally
 chemically sensitized. Examples of a method for chemical sensitization
 include the so-called gold sensitization methods using gold compounds
 (disclosed, e.g., in U.S. Pat. Nos. 2,448,060 and 3,320,069),
 sensitization methods using metals, such as iridium, platinum, rhodium and
 palladium (disclosed, e.g., in U.S. Pat. Nos. 2,448,060, 2,566,245 and
 2,556,263), sulfur sensitization methods using sulfur-containing compounds
 (disclosed, e.g., in U.S. Pat. No. 2,222,264), selenium sensitization
 methods using selenium compounds, tellurium sensitization methods using
 tellurium compounds, and reduction sensitization methods using tin salts,
 thiourea dioxide or polyamines (disclosed, e.g., in U.S. Pat. Nos.
 2,487,850, 2,518,698 and 2,521,925). These sensitization methods can be
 used alone or in combination.
 The silver halide emulsions used in the present invention are preferably
 emulsions subjected to gold sensitization known in this industry. This is
 because the gold sensitization can further reduce the variations caused in
 photographic properties by exposure to scanning laser beams or the like.
 For gold sensitization, chloroauric acid or salts thereof, gold
 thiocyanates and gold thiosulfates can be used. The amounts of these
 compounds added, though can be changed depending on the situation, range
 from 5.times.10.sup.-7 to 5.times.10.sup.-2 mole, preferably from
 1.times.10.sup.-6 to 1.times.10.sup.-3 mole, per mole of silver halide.
 The addition of those compounds is carried out before the completion of
 all the chemical sensitization treatments adopted for the present
 invention.
 It is also desirable in the present invention that any of sensitization
 methods other than gold sensitization, e.g., sulfur sensitization,
 selenium sensitization, tellurium sensitization, reduction sensitization
 and noble sensitization using noble metals other than gold compound, be
 used in combination with gold sensitization.
 To the silver halide emulsions used in the present invention, various
 compounds or precursors thereof can be added for the purpose of preventing
 the generation of fog during the production, storage or photographic
 processing, or stabilizing the photographic properties. Suitable examples
 of those compounds are the compounds disclosed in JP-A-62-215272, pages 39
 to 72. The emulsions used in the present invention are preferably a
 so-called surface latent image type emulsion in which the latent image is
 mainly formed on the surface of the grains.
 It is desirable that the silver halide emulsion layer comprising the
 tabular grains of the present invention be arranged farther from the
 support than other light-sensitive layers, or at the location near the
 surface of the photosensitive material so as to be at a short distance
 from processing solutions.
 This is because the dissolution physical development by a fix-bleaching
 solution is more serious for the silver halide grains in a layer near the
 processing solution. In the case of rapid development-processing, it is
 required to perform the processing with a highly active fix-bleaching
 solution at a high temperature; as a result, the dissolution of silver
 halide grains is promoted. Therefore, the effects of the present invention
 are important in the case of rapid processing.
 There are no particular restrictions as to additives used for the present
 photographic emulsions, the layer structure as a photographic
 light-sensitive material using the photographic emulsion of the present
 invention, and the compositions of processing solutions including a
 developer. For those elements, the descriptions in the following documents
 can be referred to.

Photographic
 constitutional element JP-A-7-104448 JP-A-7-310895
 Support column 7, line column 5, line
 12, to column 12, 40, to column
 line 19 9, line 26
 Stabilizer, column 75, lines column 18, line
 Antifoggant 9-18 11, to column
 31, line 37
 Chemical sensitizer column 74, line column 81,
 45, to column 75, lines 9-17
 6 line
 Spectral sensitizer column 75, line column 81, line
 19, to column 76, 21, to column
 line 45 82, line 48
 Cyan coupler column 12, line column 88, line
 20, to column 39, 49, to column
 line 49 89, line 19
 Yellow coupler column 87, line column 89,
 40, to column 88, lines 19-30
 line 3
 Magenta coupler column 88, line column 32, line
 4, to column 89, 34, to column
 line 19 77, line 44
 Method for emulsified column 71, line column 87,
 dispersion 3, to column 72, lines 35-48
 line 11
 Color image stabilizer column 39, line column 87, line
 50, to column 70, 49, to column
 line 9 88, line 48
 Discoloration column 70, line
 inhibitor 10, to column 71,
 line 2
 Dyes column 77, line column 9, line
 42, to column 78, 27, to column
 line 41 18, line 10
 Layer structure column 39, lines column 31, line
 11-26 38, to column
 32, line 33
 Scanning exposure column 76, line column 82, line
 6, to column 77, 49, to column
 line 41 83, line 12
 Developer column 88, line
 19, to column 89,
 line 22
 Now, the invention will be illustrated in greater detail by reference to
 the following examples.
 EXAMPLE 1
 &lt;Preparation of Tabular Grains&gt;
 Experiment 1 (Comparison): Superfine high-silver chloride {111} tabular
 grains (A)
 A solution containing 2.0 g of sodium chloride and 2.4 g of inert gelatin
 in 1.2 liter of water was placed in a reaction vessel and kept at
 33.degree. C. Thereto, 60 ml of an aqueous solution containing 9 g of
 silver nitrate and 60 ml of an aqueous solution containing 3.22 g of
 sodium chloride were added over a 1-minute period with stirring by a
 double jet method. After a 1-minute lapse from the completion of the
 addition, 40 ml of an aqueous solution containing 0.8 millimole of a
 crystal habit control Agent 1 (illustrated below) was added. After
 additional one minute, 2.0 g of sodium chloride was added. Then, 25
 minutes were spent for raising the temperature of the reaction vessel to
 60.degree. C., and the temperature of 60.degree. C. was kept for 16
 minutes to achieve the ripening. At least 90%, based on the projected
 area, of the thus formed grains (A) were tabular grains having an aspect
 ratio of at least 2, an average equivalent circle diameter of 0.28 .mu.m
 and an average thickness of 0.08 .mu.m. The variation coefficient of
 thickness was 35.1%.
 ##STR2##
 Experiment 2 (Invention): Superfine high-silver chloride {111} tabular
 grains (B)
 The grain formation was carried out in the same manner as in Experiment 1,
 except that 290 ml of a 10% phthalated gelatin solution was added
 simultaneously with the addition of the crystal habit control Agent 1. At
 least 95%, based on the total projected area, of the thus obtained grains
 (B) were tabular grains having an aspect ratio of at least 2, an average
 equivalent circle diameter of 0.32 .mu.m and an average thickness of 0.074
 .mu.m. The variation coefficient of thickness was 19.8%.
 Experiment 3 (Invention): Superfine high-silver chloride {111} tabular
 grains (C)
 The grain formation was carried out in the same manner as in Experiment 1,
 except that 490 ml of a 10% phthalated gelatin solution was added
 simultaneously with the addition of the crystal habit control Agent 1. At
 least 95%, based on the total projected area, of the thus obtained grains
 (C) were tabular grains having an aspect ratio of at least 2, an average
 equivalent circle diameter of 0.34 .mu.m and an average thickness of 0.070
 .mu.m. The variation coefficient of thickness was 14.6%.
 Experiment 4 (Comparison): Grains (D) having grown from grains (A)
 After the ripening in Experiment 1, 290 ml of a 10% phthalated gelatin
 solution, 0.8 millimole of the crystal habit control Agent 1 and 3.0 g of
 NaCl were added. After the completion of the addition, an aqueous solution
 containing 113.1 g of silver nitrate and an aqueous solution containing
 41.3 g of NaCl were added at respectively accelerated flow rates over a
 40-minute period. For 10 minutes before the completion of the addition,
 1.times.10.sup.-5 mole of potassium ferrocyanide was also added at a
 constant flow rate. After the completion of the addition, 2.8 millimoles
 of KSCN and 0.8 millimole of a sensitizing Dye A as illustrated below were
 added, and then stirred for 20 minutes at a temperature of 75.degree. C.
 ##STR3##
 After the temperature was lowered to 40.degree. C., the washing was carried
 out using an ordinary flocculation method. After washing, 67 g of gelatin,
 80 ml of phenol (5%) and 150 ml of distilled water were added. The thus
 obtained emulsion was adjusted to pH 6.2 and pAg 7.5 by the addition of
 sodium hydroxide and a silver nitrate solution. At least 95%, based on the
 total projected area, of the thus formed grains (D) were tabular grains
 having an average equivalent circle diameter of 1.32 .mu.m and an average
 thickness of 0.127 .mu.m. The variation coefficient of thickness was
 30.6%, and the variation coefficient of equivalent circle diameter was
 24.0%.
 Experiment 5 (Invention): Grains (E) having grown from grains (B)
 After the ripening in Experiment 2, an aqueous solution containing 113.1 g
 of silver nitrate and an aqueous solution containing 41.3 g of NaCl were
 added at respectively accelerated flow rates over a 40-minute period.
 Simultaneously with the addition of these solutions, 0.8 millimole of the
 crystal habit control Agent 1 was added at an accelerated flow rate
 (proportional to the amount of silver nitrate added). For 10 minutes
 before the completion of the addition, 1.times.10.sup.-5 mole of potassium
 ferrocyanide was further added at a constant flow rate. After the
 completion of the addition, 2.8 millimoles of KSCN and 0.8 millimole of
 the sensitizing Dye A were added, and then allowed to stand for 15 minutes
 at 75.degree. C.
 After the temperature was lowered to 40.degree. C., the washing was carried
 out using an ordinary flocculation method. After washing, 67 g of gelatin,
 80 ml of phenol (5%) and 150 ml of distilled water were added. The thus
 obtained emulsion was adjusted to pH 6.2 and pAg 7.5 by the addition of
 sodium hydroxide and a silver nitrate solution. At least 95%, based on the
 total projected area, of the thus formed grains (E) were tabular grains
 having an average equivalent circle diameter of 1.41 .mu.m and an average
 thickness of 0.116 .mu.m. The variation coefficient of thickness was
 18.9%, and the variation coefficient of equivalent circle diameter was
 22.0%.
 Experiment 6 (Invention): Grains (F) having grown from grains (C)
 After the ripening in Experiment 3, the grain formation and the preparation
 of the emulsion were carried out in the same manner as in Experiment 5. At
 least 95%, based on the total projected area, of the thus formed grains
 (F) were tabular grains having an average equivalent circle diameter of
 1.46 .mu.m and an average thickness of 0.113 .mu.m. The variation
 coefficient of thickness was 14.9%, and the variation coefficient of
 equivalent circle diameter was 20.1%.
 Experiment 7 (Comparison): Small-size {111} tabular grains
 A solution containing 2.0 g of sodium chloride and 2.4 g of inert gelatin
 in 1.2 liter of water was placed in a reaction vessel and kept at
 33.degree. C. Thereto, 45 ml of an aqueous solution containing 18 g of
 silver nitrate and 45 ml of an aqueous solution containing 6.2 g of sodium
 chloride were added over a 1-minute period with stirring by a double jet
 method. After a 1-minute lapse from the completion of the addition, 0.8
 millimole of the crystal habit control Agent 1 was added. After additional
 one-minute lapse, 1.0 g of sodium chloride was added. Then, the
 temperature of the reaction vessel was raised up to 60.degree. C. over a
 period of 25 minutes, and kept at 60.degree. C. for 16 minutes to achieve
 ripening. Thereafter, 560 g of a 10% aqueous solution of phthalated
 gelatin was added. Then, 0.8 millimole of the crystal habit control Agent
 1 was further added. Subsequently thereto, the pCl in the reaction vessel
 was adjusted to 1.24. Then, 255 ml of an aqueous solution containing 102 g
 of silver nitrate and 255 ml of an aqueous solution containing 35.3 g of
 sodium chloride were added at respectively accelerated flow rates over a
 period of 11 minutes. From 9 minutes on to 11 minutes after the addition
 of those solutions began, an aqueous solution containing 3 mg of potassium
 ferrocyanate was added.
 Thereafter, 27 ml of a 1% potassium thiocyanate, 4.8.times.10.sup.-4
 mole/mole Ag of a sensitizing Dye B and 3.2.times.10.sup.-4 mole/mole Ag
 of a sensitizing Dye C were further added. Then, the reaction system was
 heated to 75.degree. C. and stirred for 20 minutes as the temperature was
 kept at 75.degree. C.
 ##STR4##
 After the temperature was lowered to 40.degree. C., the washing was carried
 out using an ordinary flocculation method. After washing, 67 g of gelatin,
 80 ml of phenol (5%) and 150 ml of distilled water were added. The thus
 obtained emulsion was adjusted to pH 6.2 and pAg 7.5 by the addition of
 sodium hydroxide and a silver nitrate solution. The thus obtained emulsion
 comprised pure silver chloride tabular grains (G), at least 95%, based on
 the total projected area, of which were tabular grains having an aspect
 ratio of at least 2. The tabular grains (G) had an average equivalent
 circle diameter of 0.54 .mu.m and an average thickness of 0.111 .mu.m, and
 their variation coefficients of thickness and equivalent circle diameter
 were 21.5% and 24.3% respectively.
 Experiment 8 (Invention): Small-size {111} tabular grains (H)
 The grain formation was carried out in the same manner as in Experiment 7,
 except that after 1 minute from the completion of the nucleation 560 ml of
 a 10% aqueous solution of phthalated gelatin was added simultaneously with
 the addition of the crystal habit control agent. At the time the ripening
 was carried out for 16 minutes, silver halide grains were sampled and
 electron micrographs thereof were taken (See FIG. 1). According to FIG. 1,
 the average equivalent circle diameter of these tabular grains is 0.29
 .mu.m and the average thickness thereof is 0.07 .mu.m. The finally
 obtained emulsion comprised tabular grains (H), at least 95%, based on the
 total projected area, of which were tabular grains having an aspect ratio
 of at least 2. These tabular grains (H) had an average equivalent circle
 diameter of 0.58 .mu.m and an average thickness of 0.102 .mu.m, and their
 variation coefficients of thickness and equivalent circle diameter were
 16.6% and 19.5% respectively.
 Experiment 9 (Invention): Small-size iodide-containing {111} tabular grains
 (I)
 The grain formation was carried out in the same manner as in Experiment 8,
 except that at the last stage of grain formation, from 9 minutes on to 11
 minutes, an aqueous solution containing 0.24 g of KI was added together
 with 3 mg of potassium ferrocyanide. The thus obtained emulsion comprised
 tabular grains (I), at least 95%, based on total projected area, of which
 were tabular grains having an aspect ratio of at least 2. These tabular
 grains (I) had an average equivalent circle diameter of 0.58 .mu.m and an
 average thickness of 0.104 .mu.m. The electron micrograph of the tabular
 grains (I) is shown in FIG. 2. These tabular grains had variation
 coefficients of 18.6% and 21.5% with respect to the thickness and the
 equivalent circle diameter respectively.
 Experiment 10 (Invention): Iodide- and bromide-containing {111} tabular
 grains (J)
 After forming grains in the same manner as in Experiment 9, an aqueous
 solution containing 1.2 g of silver nitrate and an aqueous solution
 containing 0.84 g of KBr and 8.times.10-8 mole of iridium hexachloride
 were further added over a 5-minute period at constant flow rates.
 Thereafter, the washing was carried out using the same method as in
 Experiment 9. The thus obtained emulsion comprised tabular grains (J), at
 least 95%, based on the projected area, of which were tabular grains
 having an aspect ratio of at least 2. These tabular grains (J) had an
 average equivalent circle diameter of 0.60 .mu.m and an average thickness
 of 0.102 .mu.m, and their variation coefficients of thickness and
 equivalent circle diameter were 17.3% and 20.8% respectively.
 Experiment 11 (Comparison): {100} Tabular grains (K)
 In the reaction vessel disclosed in JP-A-51-83097, a mixture of 1,200 ml of
 water, 25 g of gelatin (demineralized alkali-processed ossein gelatin
 having a methionine content of about 40 .mu. mole/g), 1 g of NaCl and 4.5
 ml of 1N HNO.sub.3 solution was placed and thermostated at 40.degree. C.
 The pH of this mixture was 4.5. To the mixture with stirring at 250 r.p.m,
 a solution containing AgNO.sub.3 in a concentration of 0.2 g/ml (Solution
 Ag-1) and a solution containing NaCl in a concentration of 0.069 g/ml
 (Solution X-1) were added simultaneously for 15 seconds at the flow rate
 of 48 ml/min. After a 3-minute lapse, a solution containing KBr in a
 concentration of 0.012 g/ml (Solution X-2) was further added for 20
 seconds at the flow rate of 60 ml/min. After additional 3-minute lapse,
 the Solutions Ag-1 and X-1 were furthermore added simultaneously for 45
 seconds at the flow rate of 48 ml/min. Then, the number of revolutions for
 stirring was increased to 750 r.p.m. After the resulting reaction mixture
 was stirred for 1 minute, thereto was added an aqeuous gelatin solution
 (containing 10 g of gelatin, 7 ml of 1N NaOH and 1.7 g of NaCl in 120 ml
 of water). After a 4-minute lapse, the temperature was raised to
 75.degree. C. over a 12-munite period, and the ripening was carried out
 for 25 minutes. Further, 7.5 ml of a solution containing 0.01 g/ml of KI
 was added, and the ripening was further continued for 5 minutes.
 Thereafter, the sensitizing Dyes B and C were added in the amounts of
 4.8.times.10.sup.-4 mole/mole Ag and 3.2.times.10.sup.-4 mole/mole Ag
 respectively, and the stirring was continued for additional 20 minutes.
 The temperature was lowered to 40.degree. C., and then the washing was
 carried out using an ordinary flocculation method. After washing, gelatin
 and distilled water were added so that the gelatin content was made 0.1 g
 per gram of emulsion. Further, the emulsion obtained was adjusted to pH
 6.2 and pAg 7.5 by the addition of sodium hydroxide and sodium chloride.
 Therefrom, emulsion grains was sampled, and the electron micrographic
 images (TEM images) as the replicas of these grains were observed. As a
 result of the observation, it was found that 96%, based on the total
 projected area, of the total AgX grains were tabular grains having (100)
 faces as the main planes, and these tabular grains had the average
 equivalent circle diameter of 0.68 .mu.m, the variation coefficient of
 20.4% with respect to the equivalent circle diameter, the average distance
 between the main planes of 0.12 .mu.m, and the variation coefficient of
 33.4% with respect to the distance between the main planes, and the
 average aspect ratio of 6.6.
 Experiment 12 (Invention): {100} Tabular grains (L)
 In the reaction vessel disclosed in JP-A-51-83097, a mixture of 1,200 ml of
 water, 25 g of gelatin (demineralized alkali-processed ossein gelatin
 having a methionine content of about 40 .mu. mole/g), 1 g of NaCl and 4.5
 ml of 1N HNO.sub.3 solution was placed and thermostated at 40.degree. C.
 (the pH of this mixture was 4.5). To the mixture with stirring at 1,200
 r.p.m, the solution Ag-1 (containing 0.2 g/ml of AgNO.sub.3) and the
 solution X-1 (containing 0.069 g/ml of NaCl) were added simultaneously for
 15 seconds at the flow rate of 48 ml/min. After a 3-minute lapse, the
 solution X-2 (containing 0.012 g/ml of KBr) was further added for 20
 seconds at the flow rate of 60 ml/min. After additional 3-minute lapse,
 the solutions Ag-1 and X-1 were furthermore added simultaneously for 45
 seconds at the flow rate of 48 ml/min. Then, the number of revolutions for
 stirring was decreased to 750 r.p.m. After the resulting reaction mixture
 was stirred for 1 minute, thereto was added an aqueous gelatin solution
 (containing 10 g of gelatin, 7 ml of 1N NaOH and 1.7 g of NaCl in 120 ml
 of water). After a 4-minute lapse, the temperature was raised to
 75.degree. C. over a 12-munite period, and the ripening was carried out
 for 25 minutes. Further, 7.5 ml of a solution containing 0.01 g/ml of KI
 was added, and the ripening was further continued for 5 minutes.
 Thereafter, the sensitizing Dyes B and C were added in the amounts of
 4.8.times.10.sup.-4 mole/mole Ag and 3.2.times.10.sup.-4 mole/mole Ag
 respectively, and the stirring was continued for additional 20 minutes.
 The temperature was lowered to 40.degree. C., and then the washing was
 carried out using an ordinary flocculation method. After washing, gelatin
 and distilled water were added so that the gelatin content was made 0.1 g
 per gram of emulsion. Further, the emulsion obtained was adjusted to pH
 6.2 and pAg 7.5 by the addition of sodium hydroxide and sodium chloride.
 Therefrom, emulsion grains was sampled, and the electron micrographic
 images (TEM images) as the replicas of these grains were observed. As a
 result of the observation, it was found that 98%, based on the total
 projected area, of the total AgX grains were tabular grains having (100)
 faces as the main planes, and these tabular grains had the average
 equivalent circle diameter of 0.66 .mu.m, the variation coefficient of
 16.7% with respect to the equivalent circle diameter, the average distance
 between the main planes of 0.11 .mu.m, and the variation coefficient of
 14.9% with respect to the distance between the main planes, and the
 average aspect ratio of 7.3.
 Experiment 13: Chemically sensitized emulsions
 Each of the emulsions prepared in Experiments 4 to 12 was chemically
 sensitized at 60.degree. C. to the optimum extent by the use of sodium
 thiosulfonate, 1-(5-methylureido-phenyl)-5-mercaptotetrazole, sodium
 thiosulfate and chloroauric acid. Thus, chemically sensitized Emulsions D
 to L were prepared.
 Experiment 14: Preparation of coated samples and evaluation of photographic
 properties and stability
 The surface of a paper support coated with polyethylene resin on both sides
 was subjected to corona discharge treatment, and then provided with a
 gelatin subbing layer to which sodium dodecylbenzenesulfonate was added.
 On the subbing layer, the first to the seventh photographic constituent
 layers were coated one after another to prepare a silver halide color
 photographic material as a coated sample, which had the compositions as
 illustrated below in the constituent layers respectively.
 The coating solutions for photographic constituent layers were prepared in
 the following manners respectively.
 &lt;Preparation of Coating Solutions&gt;
 Couplers, image stabilizers and ultraviolet absorbents were dissolved in
 certain solvents and ethyl acetate, and the solution obtained was
 emulsified and dispersed in a 10 weight % aqueous gelatin solution
 containing a surfactant by means of a high speed-agitation emulsifying
 machine (dissolver) to prepare an emulsified dispersion.
 The emulsified dispersion was mixed with an emulsion having a high chloride
 content so as to have the composition as described below, thereby
 preparing a coating solution.
 To a coating solution for each constituent layer, sodium
 1-oxy-3,5-dichloro-s-triazine as a gelatin-hardening agent and
 preservatives (antiseptics) Ab-1, Ab-2 and Ab-3 were added so that their
 respective total contents in each coated sample were 15.0 mg/m.sup.2, 5.0
 mg/m.sup.2 and 10.0 mg/m.sup.2.
 ##STR5##
 The high chloride content emulsion used for each light-sensitive emulsion
 layer is as follows:
 Blue-sensitive emulsion layer
 Each of the emulsions shown in Table 1.
 Green-sensitive emulsion layer
 A 1:3 (silver mol ratio) mixture of large-sized and small-sized silver
 chlorobromide emulsions. Both of these emulsions had a cubic crystal form,
 one of which had an average grain size of 0.45 .mu.m and a variation
 coefficient of 10% with respect to the grain size distribution
 (large-sized Emulsion G1), and the other of which had an average grain
 size of 0.35 .mu.m and a variation coefficient of 8% with respect to the
 grain size distribution (small-sized Emulsion G2), and both of them
 contained 0.4 mole % of silver bromide wherein the bromide was localized
 in part of the surface of the-grain mainly comprising silver chloride.
 Further, sensitizing Dyes D and E illustrated below were added to the
 Emulsion G1 in the amounts of 3.0.times.10.sup.-4 mole and
 4.0.times.10.sup.-5 mole, respectively, per mole of silver halide, while
 they were added to the Emulsion G2 in the amounts of 3.6.times.10.sup.-4
 mole and 2.8.times.10.sup.-4 mole/mole, respectively, per mole of silver
 halide.
 ##STR6##
 Red-sensitive emulsion layer
 A 1:1 (silver mol ratio) mixture of large-sized and small-sized silver
 chlorobromide emulsions. Both of these emulsions had a cubic crystal form,
 one of which had an average grain size of 0.40 .mu.m and a variation
 coefficient of 9% with respect to the grain size distribution (large-sized
 Emulsion R1), and the other of which had an average grain size of 0.30
 .mu.m and a variation coefficient of 11% with respect to the grain size
 distribution (small-sized Emulsion R.sub.2), and both of them contained
 0.5 mole % of silver bromide wherein the bromide was localized in part of
 the surface of the grain mainly comprising silver chloride. Further,
 sensitizing Dyes G and H illustrated below were added to the Emulsion R1
 in the same amount of 9.0.times.10.sup.-5 mole/mole-silver halide, while
 they were added the Emulsion R.sub.2 in the amount of 1.2.times.10.sup.-4
 mole/mole-silver halide. Furthermore, Compound I illustrated below was
 added in the amount of 3.0.times.10.sup.-3 mole/mole silver halide.
 ##STR7##
 In addition, 1-(3-methylureidophenyl)-5-mercapto-teterazole was added to
 the blue-sensitive, green-sensitive and red-sensitive emulsion layers in
 the amounts of 3.3.times.10.sup.-4 mole, 1.0.times.10.sup.-3 mole and
 5.9.times.10.sup.-4 mole, respectively, per mole of silver halide.
 Further, 1-(3-methylureidophenyl)-5-mercaptotetrazole was also added to the
 second layer, the fourth layer, the sixth layer and the seventh layer so
 as to have the coverage (i.e., the coating amount) of 0.2 mg/m.sup.2, 0.2
 mg/m.sup.2, 0.6 mg/m.sup.2 and 0.1 mg/m.sup.2 respectively.
 Furthermore, 4-hydroxy-6-methyl-1,3,3a,7-tetra-azaindene was added to the
 blue-sensitive emulsion layer and the green-sensitive emulsion layer in
 the amounts of 1.times.10.sup.-4 mole and 2.times.10.sup.-4 mole,
 respectively, per mole of silver halide.
 To the red-sensitive emulsion layer, methacrylic acid/butyl acrylate (1/1
 by weight) copolymer having average molecular weight of 200,000 to 400,000
 was further added so as to have the coverage of 0.05 g/m.sup.2.
 In addition, disodium catechol-3,5-disulfonate was added to the second
 layer, the fourth layer and the sixth layer so as to have the coverage of
 6 mg/m.sup.2, 6 mg/m.sup.2 and 18 mg/m.sup.2 respectively.
 Further, the dyes illustrated below (their respective coverage rates are
 designated in parentheses) were added in order to inhibit an irradiation
 phenomenon from occurring.
 ##STR8##
 &lt;Layer Constitution&gt;
 The composition of each constituent layer is described below. Each figure
 on the right side designates the coverage (g/m.sup.2) of the ingredient
 corresponding thereto. As to the silver halide emulsion, the figure
 represents the coverage based on silver.
 Support:
 Polyethylene resin-laminated paper containing as white pigments TiO.sub.2
 in the proportion of 16 weight % and ZnO in the proportion of 4 weight %,
 as a brightening agent 4,4'-bis(5-methylbenzoxazolyl)stilbene at the
 coverage of 13 mg/m.sup.2 and as a bluish dye (ultramarine) at the
 coverage of 96 mg/m.sup.2 in the polyethylene resin laminate on the side
 of the first layer.

First Layer (red-sensitive emulsion layer):
 The foregoing red-sensitive emulsion 0.12
 Gelatin 0.59
 Cyan coupler (EXC-1) 0.13
 Cyan coupler (EXC-2) 0.03
 Color stain inhibitor (Cpd-7) 0.01
 Color image stabilizer (Cpd-9) 0.04
 Color image stabilizer (Cpd-15) 0.19
 Color image stabilizer (Cpd-18) 0.04
 Solvent (Solv-5) 0.09
 Second Layer (color stain inhibiting layer)
 Gelatin 0.60
 Color stain inhibitor (Cpd-19) 0.09
 Color stain inhibiting aid (Cpd-5) 0.007
 Color stain inhibitor (Cpd-7) 0.007
 Ultraviolet absorbent (UV-C) 0.05
 Solvent (Solv-5) 0.11
 Third Layer (green-sensitive emulsion layer)
 The foregoing green-sensitive emulsion 0.14
 Gelatin 0.73
 Magenta coupler (EXM) 0.15
 Ultraviolet absorbent (UV-A) 0.05
 Color image stabilizer (Cpd-2) 0.02
 Color stain inhibitor (Cpd-7) 0.008
 Color image stabilizer (Cpd-8) 0.07
 Color image stabilizer (Cpd-9) 0.03
 Color image stabilizer (Cpd-10) 0.009
 Dye (Cpd-11) 0.0001
 Solvent (Solv-3) 0.06
 Solvent (Solv-4) 0.11
 Solvent (Solv-5) 0.06
 Fourth Layer (color stain inhibiting layer):
 Gelatin 0.48
 Color stain inhibitor (Cpd-4) 0.07
 Color stain inhibiting aid (Cpd-5) 0.006
 Color stain inhibitor (Cpd-7) 0.006
 Ultraviolet absorbent (UV-C) 0.04
 Solvent (Solv-5) 0.99
 Fifth Layer (Blue-sensitive emulsion layer):
 Emulsion shown in Table 1 0.24
 Gelatin 1.25
 Yellow coupler (ExY) 0.57
 Color image stabilizer (Cpd-1) 0.07
 Color image stabilizer (Cpd-2) 0.04
 Color image stabilizer (Cpd-3) 0.07
 Color image stabilizer (Cpd-8) 0.02
 Solvent (Solv-1) 0.21
 Sixth Layer (ultraviolet absorbing layer):
 Gelatin 0.32
 Ultraviolet absorbent (UV-C) 0.42
 Solvent (Solv-7) 0.08
 Seventh Layer (protective layer):
 Gelatin 0.70
 Acryl-modified copolymer of polyvinyl 0.04
 alcohol (modification degree: 17%)
 Liquid paraffin 0.01
 Surfactant (Cpd-13) 0.01
 Polydimethylsiloxane 0.01
 Silicon dioxide 0.003
 The structural formulae of the ingredients used herein are illustrated
 below:
 ##STR9##
 ##STR10##
 ##STR11##
 ##STR12##
 Coated Samples D to L were prepared using the emulsions shown in Table 1,
 respectively, in the blue-sensitive layer of the photosensitive material,
 the constituent layers of which have the foregoing compositions.
 &lt;Exposure&gt;
 Exposure of gradation of three color separation was performed with blue
 (B), green (G) and red (R) laser beams. At that time, laser output was
 corrected so as to obtain optimum improvements in each sample.
 Exposure Apparatus
 The three kinds of light sources used were as follows: the YAG solid laser
 device (oscillation wavelength; 946 nm) utilizing semiconductor laser
 GaAlAs (oscillaltion wavelength; 808.5 nm) as excitation light source,
 wherein the beams generated were subjected to the wavelength conversion
 using SHG crystal of LiNbO.sub.3 having an inverted domain structure and
 therefrom the beam of 473 nm was picked out; the YVO.sub.4 solid laser
 device (oscillation wavelength; 1064 nm) utilizing semiconductor laser
 GaAlAs (oscillaltion wavelength; 808.5 nm) as excitation light source,
 wherein the beams generated were subjected to the wavelength conversion
 using SHG crystal of LiNbO.sub.3 having an inverted domain structure and
 therefrom the beam of 532 nm was picked out; and an AlGaInP laser device
 (oscillation wavelength; 680 nm; Type No. LN9R20, produced by Matsushita
 Electric Industrial Co., Ltd.). Blue, green and red laser beams each
 underwent intensity modulation by means of AOM, made to travel in the
 direction perpendicular to the scanning direction by means of a polygon
 mirror, and sequentially scanned a color photographic paper to perform the
 exposure. Therein, the semiconductor laser temperature-related
 fluctuations in the quantity of light was controlled by using a Peltier
 element to keep the temperature constant. The scanning exposure thus
 performed was 600 dpi, and the B, G and R laser beams had the same beam
 diameter of 65 .mu.m, measured with a light beam diameter measurement
 apparatus 1180GP (a product of Beam Scan Inc. (USA)). Additionally, all
 the laser beams used were circular beams, because the difference between
 the beam diameters in the main scan and the sub-scan directions was found
 to be within 1%.
 &lt;Photographic Processing; dry-to-dry time of 180 seconds&gt;
 The thus exposed Samples were each subjected to the processing using a
 CP45X system made by Fuji Photo Film Co., Ltd.
 The reflection densities of the Samples colored by the processing were
 measured with a TCD-type densitometer made by Fuji Photo Film Co., Ltd.
 The sensitivity was represented by the exposure amount required for
 providing the colored density 1.0 higher than the fog density. With
 respect to the blue-sensitive layer, the sensitivities shown in Table 1
 are relative values, with the Coated Sample D being taken as 100.
 &lt;Processing Stability Test&gt;
 In order to examine the stability of Samples, the processing was carried
 out using the same CP45X system as mentioned above, except that the
 bleach-fixing solution P2 was mixed in the developer P1 in the amount of
 0.5 ml per liter of P1. The processing stability is defined as the
 relative value of the sensitivity in the case of development with the
 P2-mixed developer to the sensitivity in the case of development with the
 P2-free developer, and the values determined are shown in Table 1. The
 sensitivities therein are those measured as the exposure amounts required
 for providing the density of fog +1.5.
 As is apparent from the results of Table 1, every sample containing the
 emulsion according to the invention had high sensitivity, low fog and high
 processing stability. Although the processing stability was generally
 especially low in the emulsions comprising small-size grains, the present
 invention markedly achieved its effect upon the processing stability in
 the cases of small-size emulsion grains; as a result, the processing
 stability was greatly improved. Further, the effect of the present
 invention was promoted by the use of iodide and bromide in combination
 with chloride.
 Although the present effects were remarkable even in the case of {100}
 tabular grains, the present invention achieved more remarkable effects in
 the case of {111} tabular grains.
 TABLE 1
 Equivalent
 Circle
 Diameter Thickness Process-
 Coated Variation Variation Composition Blue Exposure ing
 Sample Grains Coefficient Coefficient Main Planes Fog Sensitivity
 Stability
 D D 1.32 .mu.m 0.127 .mu.m AgCl 0.03 100 0.08
 Comparison
 24.0% 30.6% (111)
 E E 1.41 .mu.m 0.116 .mu.m AgCl 0.02 115 0.05
 invention
 22.0% 18.9% (111)
 F F 1.46 .mu.m 0.113 .mu.m AgCl 0.02 131 0.03
 invention
 20.1% 14.9% (111)
 G G 0.54 .mu.m 0.111 .mu.m AgCl 0.03 28 0.14
 comparison
 24.3% 21.5% (111)
 H H 0.58 .mu.m 0.102 .mu.m AgCl 0.02 35 0.06
 invention
 19.5% 15.6% (111)
 I I 0.58 .mu.m 0.102 .mu.m AgClI 0.02 88 0.05
 invention
 21.5% 15.6% (111)
 J J 0.60 .mu.m 0.102 .mu.m AgClIBr 0.02 85 0.04
 invention
 20.8% 16.3 % (111)
 K K 0.68 .mu.m 0.120 .mu.m AgCl 0.04 78 0.14
 comparison
 20.4% 33.4 % (100)
 L L 0.66 .mu.m 0.11 .mu.m AgCl 0.03 80 0.07
 invention
 16.7% 14.9 % (100)
 EXAMPLE 2
 Experiment 15: Use of monodisperse grains in the lowest layer
 Samples were prepared in the same manner as in Experiment 14, except that
 the first layer and the fifth layer in each of the coated Samples G to J
 were replaced with each other, and referred to as Samples RG to RJ
 respectively. These samples underwent the same tests as in Experiment 14.
 The results obtained are shown in Table 2.
 TABLE 2
 Equivalent
 Circle
 Diameter Thickness Process-
 Coated Variation Variation Composition Blue Exposure ing
 Sample Grains Coefficient Coefficient Main Planes Fog Sensitivity
 Stability
 RG G 0.54 .mu.m 0.111 .mu.m AgCl 0.03 100 0.09
 Comparison
 24.3% 21.5% (111)
 RH H 0.58 .mu.m 0.102 .mu.m AgCl 0.02 121 0.06
 Invention
 19.5% 15.6% (111)
 RI I 0.58 .mu.m 0.104 .mu.m AgClI 0.02 305 0.04
 Invention
 21.5% 18.6% (111)
 RJ J 0.60 .mu.m 0.102 .mu.m AgClIBr 0.02 295 0.03
 Invention
 20.8% 16.3% (111)
 As is apparent from the results of Table 2, the processing stability was
 improved by the present invention, but the improved effect was small, as
 compared with the cases where the layer containing monodisperse grains was
 arranged as the uppermost layer.
 EXAMPLE 3
 Experiment 16: Photographic processing performed in dry-to-dry time of 60
 seconds
 The same coated Samples G to J as prepared in Experiment 14 were each
 subjected to the following processing that was performed in the dry-to-dry
 time of 60 seconds. Additionally, the exposure of each Sample was carried
 out in the same manner as in Experiment 14.

Amount.sub.-- Tank
 Processing step Temperature Time replenished* volume
 Color development 45.degree. C. 15 sec. 35 ml 2 liter
 Bleach-fix 40.degree. C. 15 sec. 38 ml 1 liter
 Rinsing (1) 40.degree. C. 10 sec. -- 1 liter
 Rinsing (2) 40.degree. C. 10 sec. -- 1 liter
 Rinsing (3) 40.degree. C. 10 sec. 90 ml 1 liter
 Drying 80.degree. C. 10 sec. -- --
 [The rinsing was conducted in 3-tank counter-current system from the
 rinsing tank (3) to the rinsing tank (1)]
 *: per m.sup.2 of photographic material
 In the above process, water of rinsing (3) tank was force fed to a reverse
 osmosis membrane, the penetrated water was charged to rinsing (3), tank,
 and concentrated water not passed the reverse osmosis membrane was fed
 back to rinsing (2) tank and used. For saving the crossover time, blades
 were installed connecting each rinsing tank and samples were passed
 therebetween. A spraying apparatus as disclosed in JP-A-8-314088 was
 installed in each step and a circulating processing solution was sprayed
 to samples at spraying rate per one tank of from 4 to 6 liters/minute.
 The composition of each processing solution is described below.

Tank Amount
 Bleach-fixing solution solution replenished*
 First replenisher 260 ml 18 ml
 Second replenisher 290 ml 20 ml
 Water to make 1,000 ml
 pH (25.degree. C.) adjusted to 5.0
 The compositions of the first and second replenishers are as follows.

First Replenisher:
 Water 150 ml
 Ethylenebisquanidine nitrate 30 g
 Ammonium sulfite monohydrate 226 g
 Ethylenediaminetetraacetic acid 7.5 g
 Brightening agent (*1) 1.0 g
 Ammonium bromide 30 g
 Ammonium thiosulfate (700 g/l) 340 ml
 Water to make 1,000 ml
 pH (25.degree. C.) adjusted to 5.82
 Second Replenisher:
 Water 140 ml
 Ethylenediaminetetraacetic acid 11.0 g
 Ammonium ethylenediaminetetra 384 g
 acetatoferrate(III)
 Acetaic acid (50%) 230 ml
 Water to make 1,000 ml
 pH (25.degree. C.) adjusted to 3.35
 *1: Brightening agent of triazinylaminostilbene type, Hakkol FWA-SF (trade
 name, a product of Showa Kagaku k.k.)
 Rinsing Solution:
 Ion exchange water (in which calcium and magnesium ion concentrations were
 each 3 ppm or less).
 The test results are shown in Table 3. The sensitivities shown in Table 3
 are relative values, with the coated Sample G being taken as 100. In the
 rapid processing also, the present invention achieved remarkable effects.
 TABLE 3
 Equivalent
 Circle
 Diameter Thickness Process-
 Coated Variation Variation Composition Blue Exposure ing
 Sample Grains Coefficient Coefficient Main Planes Fog Sensitivity
 Stability
 RG G 0.54 .mu.m 0.111 .mu.m AgCl 0.03 100 0.15
 Comparison
 24.3% 21.5% (111)
 RH H 0.58 .mu.m 0.102 .mu.m AgCl 0.02 128 0.07
 Invention
 19.5% 15.6% (111)
 RI I 0.58 .mu.m 0.104 .mu.m AgClI 0.02 320 0.05
 Invention
 21.5% 18.6% (111)
 RJ J 0.60 .mu.m 0.102 .mu.m AgClIBr 0.02 313 0.04
 Invention
 20.8% 16.3% (111)
 EFFECT OF THE INVENTION
 The photographic silver halide emulsions, the photographic materials
 comprising the emulsion and the processing method according to the
 invention enable the achievement of high sensitivity, low fog and
 excellent processing stability.
 While the invention has been described in detail and with reference to
 specific embodiments thereof, it will be apparent to one skilled in the
 art that various changes and modifications can be made therein without
 departing from the spirit and scope thereof.