EP0613042B1

EP0613042B1 - Process for preparation of seed crystal emulsion

Info

Publication number: EP0613042B1
Application number: EP94102737A
Authority: EP
Inventors: Yasuo C/O Fuji Photo Film Co. Ltd. Kashi
Original assignee: Fuji Photo Film Co Ltd
Current assignee: Fujifilm Holdings Corp
Priority date: 1993-02-25
Filing date: 1994-02-23
Publication date: 2005-08-17
Anticipated expiration: 2014-02-23
Also published as: DE69434455D1; EP0613042A3; EP0613042A2; DE69434455T2

Description

The present invention relates to a silver halide photographic material having excellent pressure properties which comprises an emulsion of tabular silver halide grains which can be prepared at an improved producibility.
The recent technical trend of silver halide color photographic materials is toward the pursuit of high sensitivity as represented by ISO1600 photographic light-sensitive materials for picture taking and of graininess, sharpness and color reproducibility satisfactory for photographic light-sensitive materials for use with small-format cameras such as 110 size system and disk size system and photographic light-sensitive materials for use with films equipped with lens as represented by "Utsurundesu Hi" and "Utsurundesu Panoramic". A further improvement is required of each of the various properties.
In respect to these requirements, the use of tabular grains intended for the enhancement of sensitivity, e.g., by the enhancement of the efficiency of color sensitization by a sensitizing dye, the improvement of the relationship between sensitivity and graininess and the enhancement of sharpness and covering power is disclosed in U.S. Patents 4,434,226, 4,414,310, 4,433,048, 4,414,306 and 4,459,353, JP-A-58-113927 (The term "JP-A" as used herein means an "unexamined published Japanese patent application") and JP-A-59-119350 (corresponding to U.S. Patent 4,490,458).
In order to make the use of the properties of the foregoing tabular grains, attempts have been made to adapt tabular grains in various size ranges. In particular, tabular grains in a large size range are important for the purpose of improving the relationship between sensitivity and graininess and thus have been studied.
For the prior art methods for the preparation of tabular grains, reference can be made to JP-A-58-113927 (corresponding to U.S. Patent 4,433,048), JP-A-58-113928 (corresponding to U.S. Patent 4,434,226), JP-A-58-127921, and JP-A-1-158426. However, these preparation methods are disadvantageous in that they have a prolonged process time required for large size tabular grains to form and thus exhibit a poor producibility. Further, large size tabular grains thus prepared are not necessarily satisfactory in respect to the pressure properties of photographic light-sensitive materials comprising these tabular grains.
As a method for the preparation of silver halide grains there can be used a so-called seed crystal method, i.e., method which comprises the growth of seed grains which have been separately prepared. By employing the seed crystal method, the reduction of grain formation procedures and of variation in production conditions can be accomplished. Further, the use of monodisperse seed crystal grains enables the preparation of tabular grains having an improved monodispersibility.
As a seed crystal method for the preparation of tabular grains there is disclosed a grain formation method using a spherical seed crystal (aspect ratio: 1) in JP-B-3-46811 (The term "JP-B" as used herein means an "examined Japanese patent publication") (corresponding to U.S. Patent 4,798,775). However, grains thus obtained exhibit an aspect ratio of not more than 3.0. Thus, this seed crystal method cannot provide final grains having a high aspect ratio.
Moreover, JP-A-61-112142, JP-A-62-58237, and JP-A-55-142329 (corresponding to U.S. Patent 4,301,241) disclose a grain formation method using a multi-twin grain. This method is suitable for the preparation of tabular grains having a high aspect ratio. However, this method is disadvantageous in that if a seed crystal which has been desilvered and redispersed is not immediately allowed to grow, it causes fluctuations in properties and thus gives a poor stability in production conditions.
As mentioned above, the prior art seed crystal methods cannot realize the stable production of tabular grains having a high aspect ratio and thus need further improvements.
EP-A-359506 discloses silver halide emulsions prepared by forming silver halide crystals in a colloid dispersing medium, mixing said medium with aqueous solutions of silver salt and halides, adding a silver halide solvent to the medium, causing the produced twinned crystals to increase in size and removing the formed water-soluble salts and chemically and spectrally sensitising the emulsion.
JP-A-63-231334 discloses highly sensitive silver halide photosensitive materials containing silver halide including silver iodide used as seed crystal.
EP-A-610597, a document according to Art. 54(3) EPC discloses a method of preparing a tabular grain silver halide emulsion involving growing a silver halide seed emulsion.
Further, JP-A-3-196136 and JP-A-3-196137 (corresponding to EP-A-438791) disclose an approach which comprises the grain formation in the presence of a silver oxidizing agent. However, no examples have been known in which this approach is applied to the preparation of seed crystal emulsion.
It is therefore the object of the present invention to provide a method for the preparation of a seed emulsion enabling high producibility, improved pressure properties, and the stable preparation of tabular grains having a high aspect ratio.
The object of the present invention will become more apparent from the following detailed description and examples. This object is solved with the process and uses as defined in the appendent claims.
Preferred embodiments are defined in the subclaims.
The present invention will be further described hereinafter.
The process for the preparation of a silver halide emulsion consists of two main procedures, i.e., preparation of seed crystal grains and growth of seed crystal grains.
The procedure for the preparation of seed crystal grains consists of grain formation procedure involving nucleation, ripening and growth, and the subsequent desalting/washing procedure. If desire, refrigeration procedures or the subsequent refrigeration procedure may be employed. The seed crystal emulsion produced can be used for the preparation of a tabular silver halide emulsion.
The foregoing procedure involving the growth of seed crystal grains comprises a procedure for further growth of grains in the presence of the foregoing seed crystal grains, a desalting/washing procedure, a chemical sensitization procedure, etc.
The seed crystal grains produced according to the present invention will be further described hereinafter.
The silver oxidizing agent for use in the preparation of the seed crystal emulsion according to the present invention is a compound which acts on a metallic silver to convert it to silver ions. Particularly effective is a compound which converts a small particle size of silver atoms by-produced during the formation of silver halide grains to silver ions. The silver ions thus formed may form a difficultly water-soluble silver salt such as silver halide, silver sulfide and silver selenide or a water-soluble silver salt such as silver nitrate.
The thiosulfonate is selected from the compounds represented by the formulae (I) to (III).
In the process for the preparation of a seed crystal emulsion according to the present invention, at least one of the foregoing silver oxidizing agents is added to the system during preparation. The terminology "during preparation" as used herein is basically meant to allow the addition of the oxidizing agent during any procedure. In particular, the addition is preferably effected during the formation of grains. The addition is also preferably effected during desalting/washing procedure.
The silver oxidizing agent may be previously incorporated in the reaction vessel. Preferably, the silver oxidizing agent is added to the system during any proper period in the grain formation procedure. Alternatively, the silver oxidizing agent may be previously added to an aqueous solution of a water-soluble silver salt or water-soluble alkali halide which is then used to form grains. A still further preferred method is to add the silver oxidizing agent to the system in several batches with the progress of grain formation or in a continuous manner for a prolonged period of time.
The amount of the silver oxidizing agent to be added is preferably in the range of 10^-7 to 10^-1 mol, more preferably 10^-6 to 10^-2 mol, most preferably 10^-5 to 10^-3 mol per mol of silver halide.
The incorporation of the silver oxidizing agent in the system during the preparation of a seed crystal emulsion can be accomplished by any method commonly used for the addition of additives to a photographic emulsion. In some detail, if the silver oxidizing agent is a water-soluble compound, it may be added to the system in the form of an aqueous solution having a proper concentration. If the silver oxidizing agent is a water-insoluble or difficultly water-soluble compound, it may be added to the system in the form of a solution in a solvent which has no adverse effects on photographic properties among suitable organic solvents miscible with water, such as alcohol, glycol, ketone, ester and amide.
Referring further to the thiosulfonic compounds represented by the foregoing formulae (I) to (III), if R, R¹ and R² each represents an aliphatic group, it is a saturated or unsaturated straight-chain, branched or cyclic aliphatic hydrocarbon group, preferably a C_1-22 alkyl group or a C_2-22 alkenyl or alkinyl group, which may be further substituted by substituents.
Examples of the foregoing alkyl group include methyl, ethyl, propyl, butyl, pentyl, hexyl, octyl, 2-ethylhexyl, decyl, dodecyl, hexadecyl, octadecyl, cyclohexyl, isopropyl, and t-butyl.
Examples of the foregoing alkenyl group include allyl, and butenyl. Examples of the foregoing alkinyl group include propargyl, and butynyl.
If R, R¹ and R² each represents an aromatic group, it may be a monocyclic or condensed aromatic group, preferably a C_6-20 aromatic group such as phenyl and naphthyl, which may be further substituted by substituents.
If R, R¹ and R² each represents a heterocyclic group, it may be a 3- to 15-membered ring group containing at least one element selected from the group consisting of nitrogen, oxygen, sulfur, selenium and tellurium and at least one carbon atom, preferably a 3- to 6-membered heterocyclic group such as pyrrolidine, piperidine, pyridine, tetrahydrofuran, thiophene, oxazole, thiazole, imidazole, benzothiazole, benzoxazole, benzimidazole, selenazole, benzoselenazole, terrazole, triazole, benzotriazole, tetrazole, oxadiazole and thiadiazole.
Examples of substituents on R, R¹ and R² include an alkyl group (e.g., methyl, ethyl, hexyl), an alkoxy group (e.g., methoxy, ethoxy, octyl), an aryl group (e.g., phenyl, naphthyl, tolyl), a hydroxyl group, a halogen atom (e.g., fluorine, chlorine, bromine, iodine), an aryloxy group (e.g., phenoxy), an alkylthio group (e.g., methylthio, butylthio), an arylthio group (e.g., phenylthio), an acyl group (e.g., acetyl, propionyl, butyryl, valeryl), a sulfonyl group (e.g., methylsulfonyl, phenylsulfonyl), an acylamino group (e.g., acetylamino, benzoylamino), a sulfonylamino group (methanesulfonylamino, benzenesulfonylamino), an acyloxy group (e.g., acetoxy, benzoxy), a carboxyl group, a cyano group, a sulfo group, an amino group, a -SO₂SM group (in which M represents a monovalent cation), and a -SO₂R¹ group (in which R¹ is as defined above).
The divalent linking group represented by L may be an atom or atomic group containing at least one of C, N, S and O. In some detail, an alkylene group, an alkenylene group, an alkinylene group, an arylene group, -O-, -S-, -NH-, -CO-, -SO₂-, etc. may be used singly or in combination.
L is preferably a divalent aliphatic group or a divalent aromatic group. If L is a divalent aliphatic group, its specific examples include a xylylene group, and the following groups:
-CH₂-CH=CH-CH₂-, -CH₂C≡CCH₂-,
If L is a divalent aromatic group, its specific examples include a phenylene group and a naphthylene group.
These substituents may be further substituted by the foregoing substituents.
M is preferably a metallic ion or organic cation. Examples of such a metallic ion include a lithium ion, a sodium ion, and a potassium ion. Examples of the organic cation include an ammonium ion (e.g., ammonium, tetramethylammonium, tetrabutylammonium), a phosphonium ion (e.g., tetraphenylphosphonium) and a guanidyl group.
If the compound represented by the formula (I), (II) or (III) is a polymer, it may contain as its recurring unit the following compounds (in which M and R each is as defined above):
These polymers may be homopolymers or copolymers with other copolymerizable monomers.
Specific examples of the compound represented by the formula (I), (II) or (III) will be tabulated in Table A hereinafter, but the present invention should not be construed as being limited thereto.
The synthesis of the compound represented by the formula (I), (II) or (III) can be easily accomplished by any proper method as described or cited in JP-A-54-1019, British Patent 972,211, Journal of Organic Chemistry, vol. 53, page 396, (1988), and Chemical Abstracts, vol. 59, 9776e.
Most preferred among these compounds represented by the formula (I), (II) or (III) is one represented by the formula (I).
The seed crystal grains produced according to the present invention are tabular grains having twinning planes.
The terminology "tabular grains" as used herein is a general term for grains having one twinning plane or two or more parallel twinning planes. The terminology "twinning plane" as used herein means a (111) plane on both sides of which ions on all lattice points are mirror images of each other.
The frequency of formation of twinning planes during nucleation depends on various supersaturation factors. For details, reference can be made to JP-A-63-92942.
In general, as these supersaturation factors are increased, the sequential change of crystal form of grains formed are a) octahedral regular grains, b) grains having a single twinning plane, c) grains having two parallel twinning planes (object), d) grains having nonparallel twinning planes, and e) grains having three or more twinning planes in this order. These various supersaturation factors are adjusted such that the proportion of occurrence of grains c) in finally obtained grains falls within the range defined by the effects of the present invention.
Other preferred conditions under which nucleation is effected will be described hereinafter. An aqueous solution of a water-soluble silver salt or both an aqueous solution of a water-soluble silver salt and an aqueous solution of a halide to be added during nucleation each preferably contain a dispersant in an amount of 0.05 to 2.0% by weight. The dispersant may be a commonly used photographic gelatin, preferably a low molecular weight gelatin. The temperature at which nucleation is effected is from 5°C to 60°C, preferably 15°C to 50°C. The rate at which silver nitrate is added is preferably from 0.5 g/min. to 30 g/min. per ℓ of aqueous reaction solution.
The composition of the aqueous solution of a halide to be added is defined by the proportion of I^- to Br^- ranging from not less than 4.5 mol% to not more than the intrinsic critical value, preferably from not less than 4.5 mol% to not more than 10 mol%.
The concentration of salts foreign to the reaction in the reaction solution is preferably from 0 to 1 mol/ℓ. The pH value of the reaction solution may be from 2 to 10. The concentration of a silver halide solvent in the reaction solution is preferably from 0 to 3.0 x 10^-1 mol/ℓ.
The tabular seed crystal emulsion produced according to the present invention comprises grains having an aspect ratio (diameter in terms of circle/thickness of silver halide grains) of not less than 2.0, preferably from not less than 2.0 to not more than 10.0, particularly from not less than 3.0 to not more than 8.0, in a proportion of not less than 50%, preferably not less than 70%, particularly not less than 85%, of all silver halide grains in the emulsion as calculated in terms of projected area. The average diameter of tabular seed crystal grains produced according to the present invention is preferably not more than 0.5 µm, particularly from not less than 0.2 µm to not more than 0.4 µm, as calculated in terms of sphere. The average thickness of tabular seed crystal grains produced according to the present invention is preferably not more than 0.2 µm, particularly not more than 0.15 µm.
The tabular seed crystal grains produced according to the present invention may comprise any of silver bromide, silver bromoiodide, silver chloride, silver bromochloride, silver bromochloroiodide and silver chloroiodide.
The tabular seed crystal grains produced according to the present invention may have either a structure made of at least two layers having substantially different halogen compositions or a uniform halogen composition structure.
The emulsion having a structure differing in halogen composition from layer to layer may comprise a high iodine content layer as core and a low iodine content layer as an outermost layer or vice versa.
The grain size distribution preferably is monodisperse and has a fluctuation coefficient of not more than 20%.
The process for the preparation of tabular seed crystal grains according to the present invention will be described hereinafter.
In the present invention, the process for the preparation of tabular seed crystal grains comprises steps of simultaneously adding an aqueous solution of a water-soluble silver salt and an aqueous solution of a halide to an aqueous solution of gelatin contained in a reaction vessel, and then ripening the mixture to form tabular nuclear grains.
Preferred conditions under which tabular nuclear grains are formed are as follows:
1) The effective gelatin concentration is required to range from 0.8 wt.% to 20 wt.%, preferably 1.0 wt.% to 15 wt.%, more preferably 1.0 wt.% to 6 wt.%. As gelatin there may be used a commonly used photographic gelatin. However, a gelatin solution which exhibits a high concentration (1.6 to 20 wt.%) at a temperature of not higher than 35°C can be set and thus can hardly be used. At a temperature as low as not higher than 35°C, low molecular weight gelatin (molecular weight: 2,000 to 100,000), modified gelatin such as phthalated gelatin, gelatin obtained from the skin of fishes living in cold sea can hardly be set and are particularly desirable.
2) As an addition/mixing apparatus for stressing agitation there is preferably used an apparatus for submerged addition as disclosed in U.S. Patent 3,785,777 (1974), and German Patent Application (OLS) No. 2,556,888.
3) The rate at which a silver salt and a halide are added to the system is from 6 x 10^-4 mol/min. to 2.9 x 10^-1 mol/min. per ℓ of aqueous solution of gelatin.
4) As gelatin to be added to the aqueous solution of a silver salt or a halide there may be used a commonly used photographic gelatin. The concentration of gelatin to be added needs to be such that the aqueous solution cannot be set, normally from 0.05 wt.% to 1.6 wt.%. If an apparatus for heating the aqueous solution is additionally provided, gelatin can be added in a higher concentration (about 20 wt.%). In this case, low molecular weight gelatin (molecular weight: 2,000 to 100,000), modified gelatin, etc. can hardly be set and thus are particularly desirable.More preferably, the type, concentration and temperature of gelatin to be added to the aqueous solution of a silver salt or a halide are the same as those of gelatin contained in the reaction vessel to keep these supersaturation factors uniform in the vicinity of the inlet, enabling more uniform nucleation.
5) The concentration of Br^- in the reaction solution is kept to pBr 1.0 to 2.5.
6) The concentration of salts foreign to the reaction in the reaction solution is from 1.0 x 10^-2 to 1 mol/ℓ, preferably 1 x 10^-1 to 1 mol/ℓ.
For the acceleration of ripening of silver halide grains, a silver halide solvent is useful. For example, it is known to allow excess halogen ions to exist in the reaction vessel to accelerate ripening. Thus, it is obvious that ripening can be accelerated only by introducing an aqueous solution of a halide into the reaction vessel. Other ripening agents may be used. These ripening agents may be entirely blended in a dispersing medium in the reaction vessel before the addition of the silver salt and halide. Alternatively, these ripening agents may be introduced into the reaction vessel with the addition of one or more halides, silver salts or deflocculating agents. These ripening agents may be independently introduced into the reaction vessel during the addition of the halide and silver salt.
As ripening agents other than the foregoing halogen ions there may be used ammonia, amine compound, and thiocyanate such as thiocyanate of alkaline metal, particularly sodium thiocyanate, potassium thiocyanate and ammonium thiocyanate. The use of such a thiocyanate ripening agent is taught in U.S. Patents 2,222,264, 2,448,534 and 3,320,069. Further, known thioether ripening agents as described in U.S. Patents 3,271,157, 3,574,628 and 3,737,313 may be used. Moreover, thione compounds as disclosed in JP-A-53-82408 and JP-A-53-144319 may be used.
In the present invention, a step for the growth of tabular nuclear grains thus obtained is involved.
In the step for the growth of grains, it is desirable to add a silver salt solution and a halide solution to the system in such a manner that the production of new crystal nuclei is inhibited. The size of emulsion grains can be adjusted by properly selecting the amount of seed crystal grain and the kind and amount of solvent.
Alternatively, a method may be used which comprises supplying part or all of silver to be added during the growth of grains in the form of finely divided grains of silver halide as described in JP-A-62-99751.
Though subject to the method for the use of silver salt as defined herein, the tabular seed crystal grains produced according to the present invention can be prepared in accordance with a known process for the preparation of tabular silver halide emulsion. For the process for the preparation of tabular silver halide emulsions, reference can be made to Duffin, "Photographic Emulsion Chemistry", Focal Press, New York, (1966), pp. 66 - 72, and A.P.H. Tribelli, W.F. Smith, "Phot. Journal", 80, (1940), page 285. Better reference can be made to JP-A-58-113927, JP-A-58-113928, and JP-A-58-127921.
Further reference can be made to Cleve, "Photography Theory and Practice", (1930), page 131, Gutoff, "Photographic Science and Engineering", vol. 14, pp. 248-257, (1970), U.S. Patents 4,434,226, 4,414,310, 4,433,048 and 4,439,520, British Patent 2,112,157 and Japanese Patent Application Nos. 3-280961, 3-112259 and 3-119081 (corresponding to JP-A-4-330429, JP-A-318839 and JP-A-4-324440, respectively).
In the present invention, it is essential that the tabular seed crystal grains be washed for desalting to form a newly prepared protective colloid dispersion. The washing temperature can be selected depending on the purpose and is preferably from 5°C to 50°C. The pH value during washing can be selected depending on the purpose and is preferably from 2 to 10, more preferably 3 to 8. The pAg value during washing can be selected depending on the purpose and is preferably from 5 to 10. As the washing process there can be selected from noodle washing, dialysis process using a diaphragm, centrifugal separation process, coagulation sedimentation process and ion exchanging process. As coagulation sedimentation process there can be selected from sulfate process, organic solvent process, water-soluble polymer process and gelatin derivative process.
The seed crystal emulsion thus prepared is then refrigerated or frozen, if necessary. The storage temperature is preferably not higher than 5°C.
The procedure involving the growth of tabular seed crystal grains produced according to the present invention will be described hereinafter.
The procedure involving the growth of seed crystal grains consists of a procedure for further growth of grains in the presence of the foregoing seed crystal grains, procedures for desalting/washing, chemical sensitization, etc. The amount of seed crystals to be used in the foregoing procedures is arbitrary and is preferably not more than 1/10, more preferably not more than 1/20, particularly not more than 1/25 of the molar amount of the silver salt supplied for growth as calculated in terms of molar amount of silver. Although the seed crystal at any time between after the preparation of seed crystal and before the growth of seed crystal can be arbitrarily selected to be used in the procedure, the seed crystal thus prepared is preferably refrigerated for not less than 1 day before subjected to growth.
The growth of grains in the presence of seed crystal grains can be effected in the same manner as in the foregoing preparation of seed crystal.
The tabular silver halide grains prepared will be further described hereinafter.
The terminology "tabular grains" as used herein is a general term for grains having one twinning plane or two or more parallel twinning planes. The terminology "twinning plane" as used herein means a (111) plane on both sides of which ions on all lattice points are mirror images of each other.
In the tabular silver halide emulsion, the terminology "aspect ratio" means the ratio of diameter of silver halide grain to thickness of silver halide grain, i.e., division of the diameter of individual silver halide grain by its thickness. The terminology "grain diameter" as used herein indicates the diameter of the circle having the same area as the projected area of silver halide grain observed under a microscope or electron microscope. Therefore, the aspect ratio of not less than 3 means that the diameter of the circle is not less than 3 times the thickness of the grain.
By way of example, the aspect ratio can be determined by obtaining a transmission electromicrograph of a replica of an emulsion specimen on which the diameter of individual grains as calculated in terms of circle and the thickness of the grains are then measured. The thickness of the grains is calculated from the length of the shadow of the replica.
The tabular silver halide emulsion comprises silver halide grains having an aspect ratio of not less than 3.0, preferably from not less than 3.0 to not more than 10.0, particularly from not less than 4.0 to not more than 8.0, in a proportion of not less than 50%, preferably not less than 70%, particularly not less than 85%, of all silver halide grains in the emulsion as calculated in terms of projected area. The average diameter of tabular silver halide grains is preferably not less than 0.8 µm, particularly from not less than 0.8 µm to not more than 5 µm, particularly from not less than 1.0 µm to not more than 3.0 µm as calculated in terms of sphere. The average thickness of tabular silver halide grains is preferably from not less than 0.05 µm to not more than 0.5 µm.
The tabular silver halide grains may comprise any of silver bromide, silver bromoiodide, silver chloride, silver bromochloride, silver bromochloroiodide and silver chloroiodide.
The tabular silver halide grains may have either a structure made of at least two layers having substantially different halogen compositions or a uniform halogen composition structure.
The emulsion having a structure differing in halogen composition from layer to layer may comprise a high iodine content layer as core and a low iodine content layer as an outermost layer or vice versa. The layer structure may comprise three or more layers. The iodine content preferably falls towards the outermost layer.
The properties of silver halide grains in the tabular silver halide emulsion can be properly controlled by allowing various compounds to exist in the system during the precipitation of silver halide grains. These compounds may be previously allowed to exist in the reaction vessel. Alternatively, these compounds may be added to the system with the addition of one or more salts in accordance with a commonly used process. By allowing a compound of copper, iridium, lead, bismuth, cadmium, zinc, chalcogen such as sulfur, selenium and tellurium, gold and the group VIII noble metal to exist in the system during the precipitation of silver halide grains as described in U.S. Patents 2,448,060, 2,628,167, 3,737,313 and 3,772,031 and Research Disclosure (hereinafter referred to as "R.D."), No. 13452, vol. 134, (June 1975), the properties of silver halide grains can be properly controlled.
The silver halide emulsion is preferably subjected to reduction sensitization during grain formation, between after grain formation and before chemical sensitization other than reduction sensitization, during chemical sensitization or after chemical sensitization.
As reduction sensitization there can be selected from a process which comprises the addition of a reduction sensitizer to a silver halide emulsion, a process called silver ripening which comprises allowing silver halide grains to grow or ripen silver halide grains in an atmosphere of pAg as low as 1 to 7, and a process called high pH ripening which comprises allowing silver halide grains to grow or ripen silver halide grains in an atmosphere of pH as high as 8 to 11. Two or more of these processes may be used in combination.
The foregoing process involving the addition of a reduction sensitizer is advantageous in that the level of reduction sensitization can be closely controlled.
As reduction sensitizers there have been known stannous salts, ascorbic acid and derivatives thereof, amines, polyamines, hydrazine derivative, formamidinesulfinic acid, silane compounds, and borane compounds. As the reduction sensitizer employable in the present invention there can be selectively used any of these known reduction sensitizers. Two or more of these compounds may be used in combination. Preferred examples of reduction sensitizers employable in the present invention include stannous chloride, thiourea dioxide, dimethylamineborane, and ascorbic acid and derivatives thereof. The amount of the reduction sensitizer to be added in the present invention needs to be selected depending on the production conditions of emulsion and is preferably from 10^-7 mol to 10^-3 mol per mol of silver halide.
The reduction sensitizer may be added to the system in the form of solution in a solvent such as water, alcohols, glycols, ketones, esters and amides during the growth of grains. The reduction sensitizer may be previously added to the system in the reaction vessel. Preferably, it is added to the system at any proper time during the growth of silver halide grains. Alternatively, the reduction sensitizer may be previously added to an aqueous solution of a water-soluble silver salt or water-soluble alkali halide which is then subjected to precipitation of silver halide grains. In another preferred example, the reduction sensitizer solution may be added to the system in several batches or in a continuous manner for a prolonged period of time with the progress of growth of silver halide grains.
The silver halide emulsion to be used in the present invention may be subjected to a treatment for rounding grains as disclosed in European Patents 96,727B1 and 64,412B1, or surface modification as disclosed in West German Patent 2,306,447C2 and JP-A-60-221320.
The silver halide emulsion normally has a flat grain surface but may preferably have an intentionally roughened grain surface as necessary. Examples of such roughened grains include grains having a hole on part of crystal such as vertex and center of plane as described in JP-A-58-106532 and JP-A-60-221320, and raffle grains as described in U.S. Patent 4,643,966.
The tabular grains in the emulsion to be used in the present invention preferably have a dislocation line. This dislocation can be selected from dislocation linearly introduced with respect to a specific direction in the crystal orientation of grain, curved dislocation, and dislocation introduced into the entire part or a specific part of grain, such as dislocation definitely introduced into the fringe of grain.
The emulsion to be used in the present invention may be either a so-called polydisperse emulsion having a wide distribution of size of silver halide grains or a monodisperse emulsion having a narrow distribution of size of silver halide grains depending on the purpose. As a measure of the size distribution of silver halide grains there may be used the coefficient of fluctuation of the diameter of circles having the same area as the projected area of grains or the diameter of spheres having the same volume as that of grains. The monodisperse emulsion to be used in the present invention is preferably one having a grain size variation coefficient of not more than 25%, more preferably not more than 20%, particularly not more than 15%.
The tabular silver halide emulsion may be subjected to chemical sensitization such as sulfur sensitization and gold sensitization. The site on the emulsion grain which is subjected to chemical sensitization depends on the composition, structure and shape of the emulsion grain as well as the purpose of the emulsion. A chemical sensitizing nucleus may be embedded inside the grain, may be embedded shallow in the surface of the grain or may be formed on the surface of the grain. The effects of the present invention can be exerted in any of these configurations, particularly in the case where a chemical sensitizing nucleus is formed in the vicinity of the surface of the grain. In other words, the effects of the present invention can be better exerted with a surface latent image type emulsion than an internal latent image type emulsion.
The chemical sensitization can be effected with an active gelatin as described in T. H. James, "The Theory of the Photographic Process", 4th ed., Macmillan, (1977), pp. 67 - 76. The chemical sensitization can also be effected with sensitizers such as sulfur, selenium, tellurium, gold, platinum, palladium and iridium, singly or in combination, at a pAg value of 5 to 10, a pH value of 5 to 8 and a temperature of 30°C to 80°C as described in R.D. Nos. 12008, vol. 120, (April 1974), and 13452, vol. 134, (June 1975), U.S. Patents 2,642,361, 3,297,446, 3,772,031, 3,857,711, 3,901,714, 4,266,018 and 3,904,415 and British Patent 1,315,755.
As a gold sensitizer employable in the present invention there may be preferably used a gold complex (see U.S. Patent 2,399,083).
Particularly preferred among these gold sensitizers are potassium chloroaurate, potassium aurithiocyanate, auric trichloride, sodium aurithiosulfate, and 2-aurosulfo-benzothiazole methochloride.
The content of such a gold sensitizer in the silver halide grain phase is preferably in the range of 10^-9 to 10^-3 mol, particularly 10^-8 to 10^-4 mol per mol of silver halide.
Examples of a sulfur sensitizer employable in the present invention include thiosulfates, thioureas, thiazoles, rhodanines, and other compounds (as described in U.S. Patents 1,574,944, 2,410,689, 2,278,947, 2,728,668, 3,656,955, 4,030,928 and 4,067,740). Particularly preferred among these sulfur sensitizers are thiosulfates, thioureas and rhodanines.
The optimum amount of the sulfur sensitizer can be selected depending on the grain size, chemical sensitization temperature, pAg, pH, etc. and is normally in the range of 10^-7 to 10^-3 mol, preferably 5 x 10^-7 to 10^-4 mol, more preferably 5 x 10^-7 to 10^-5 mol per mol of silver halide.
The chemical sensitization temperature can be properly determined in the range of 30°C to 90°C. The pAg value can be properly determined in the range of not less than 5 to not more than 10. The pH value can be properly determined in the range of not less than 4.
In the present invention, the foregoing chemical sensitization can be accompanied by sensitization with a metal such as iridium, platinum, rhodium and palladium (as described in U.S. Patents 2,448,060, 2,566,245 and 2,566,263), selenium sensitization with a selenium compound or tellurium sensitization with a tellurium compound.
The chemical sensitization may be effected in the presence of a chemical sensitization aid. As such a chemical sensitization aid employable in the present invention there may be used a compound which is known to inhibit fog and increase sensitivity during chemical sensitization, such as azaindene, azapyridazine and azapyrimidine. Examples of chemical sensitization aids are described in U.S. Patents 2,131,038, 3,411,914 and 3,554,757, JP-A-58-126526 and Duffin, "Photographic Emulsion Chemistry", pp. 138 - 143.
The silver halide emulsion may be subjected to spectral sensitization with a methine dye or other dyes. Examples of a spectral sensitizing dye to be used in the present invention include a cyanine dye, a melocyanine dye, a complex cyanine dye, a complex melocyanine dye, a holopolar cyanine dye, a hemicyanine dye, a styryl dye and a hemioxonol dye. Particularly useful among these dyes are a cyanine dye, a melocyanine dye and a complex melocyanine dye. Any of nuclei which are commonly used as basic heterocyclic nuclei for cyanine dyes can be applied to these dyes. Examples of suitable nuclei which can be applied to these dyes include a pyrroline nucleus, an oxazoline nucleus, a thiazoline nucleus, a pyrrole nucleus, an oxazole nucleus, a thiazole nucleus, a selenzazole nucleus, an imidazole nucleus, a tetrazole nucleus, a pyrridine nucleus and a nucleus obtained by fusion of alicyclic hydrocarbon ring(s) to the nucleus or a nucleus obtained by fusion of aromatic hydrocarbon ring(s) to the nucleus, e.g., an indolenine nucleus, a benzindolenine nucleus, an indole nucleus, a benzoxazole nucleus, a naphthooxazole nucleus, a benzothiazole nucleus, a naphthothiazole nucleus, a benzoselenazole nucleus, a benzimidazole nucleus and a quinoline nucleus. These nuclei may contain substituents on carbon atoms.
Examples of suitable nuclei which can be applied to the melocyanine dye or the complex melocyanine dye include those having a ketomethylene structure such as a 5- or 6-membered heterocyclic nucleus, e.g., a pyrazoline-5-one nucleus, a thiohydantoin nucleus, a 2-thiooxazolidine-2,4-dione nucleus, a rhodanine nucleus and a thiobarbituric acid nucleus.
These sensitizing dyes can be used singly or in combination. In particular, a combination of sensitizing dyes is often used for the purpose of supersensitization. Typical examples of such a combination are described in U.S. Patents 2,688,545, 2,977,229, 3,397,060, 3,522,052, 3,527,641, 3,617,293, 3,628,964, 3,666,480, 3,672,898, 3,679,428, 3,703,377, 3,769,301, 3,814,609, 3,837,862 and 4,026,707, British Patents 1,344,281 and 1,507,803, JP-B-43-4936, JP-B-53-12375, JP-A-52-110618 and JP-A-52-109925.
In combination with these sensitizing dyes, a dye which does not exhibit a spectral sensitizing effect itself or a substance which does not substantially absorb visible light but exhibits a supersensitizing effect can be incorporated in the emulsion.
These dyes may be added to the emulsion at any stage in the preparation of the emulsion which has heretofore been known useful. In general, it may be added between the completion of chemical sensitization and the coating. As described in U.S. Patents 3,628,969 and 4,225,666, it may be added at the same time with the chemical sensitizer to effect spectral sensitization and chemical sensitization at the same time. Alternatively, as described in JP-A-58-113928, it may be added before the chemical sensitization or it may be added before the completion of the precipitation of silver halide grains to initiate the spectral sensitization. Further, as taught in U.S. Patent 4,225,666, the above mentioned compound may be added batchwise, that is, part of the compound may be added before the chemical sensitization and the rest of the compound may be added after the chemical sensitization. As taught in U.S. Patent 4,183,756, it may be added at any stage during the formation of silver halide grains.
These dyes can be used in an amount of 4 x 10^-6 to 8 x 10^-3 mole per mol of silver halide.
As a protective colloid for use in the preparation of a silver halide emulsion and a binder for other hydrophilic colloidal layers there may be advantageously used gelatin. Other hydrophilic colloids can be used.
Examples of the foregoing hydrophilic colloids employable in the present invention include a protein such as a gelatin derivative, a graft polymer of gelatin with other high molecular weight compounds, albumin and casein, a cellulose derivative such as hydroxyethyl cellulose, carboxymethyl cellulose and a sulfuric ester of cellulose, a sugar derivative such as sodium alginate and starch derivative, and various synthetic hydrophilic high molecular weight compounds such as homopolymer and copolymer, e.g., a polyvinyl alcohol, a polyvinyl alcohol partial acetal, a poly-N-vinylpyrrolidone, a polyacrylic acid, a polymethacrylic acid, a polyacrylamide, a polyvinylimidazole, a polyvinylpyrazole.
As the foregoing gelatin there may be used lime-processed gelatin as well as acid-processed gelatin or enzyme-processed gelatin as described in Bull. Soc. Sci. Photo. Japan. No. 16, page 30, (1966). Further, a hydrolyzate of gelatin or product of enzymatic decomposition of gelatin may be used.
The use of a low molecular weight gelatin having a molecular weight of not more than 70,000 during nucleation is particularly desirable in the present invention.
On the other hand, the photographic light-sensitive material can comprise a support having provided thereon at least one blue-sensitive layer, at least one green-sensitive layer and at least one red-sensitive layer which can optionally comprise a light-insensitive layer, wherein the light-sensitive layer comprises the silver halide emulsion prepared in the aforementioned manner. The number of silver halide emulsion layers and light-insensitive layers and the order of arrangement of these layers are not specifically limited. In a typical embodiment, the silver halide photographic material comprises a support having provided thereon at least one light-sensitive layer consisting of a plurality of silver halide emulsion layers having substantially the same color sensitivity and different light sensitivities. The light-sensitive layer is a unit light-sensitive layer having a color sensitivity to any of blue light, green light and red light. In the multi-layer silver halide color photographic material, these unit light-sensitive layers are normally arranged in the order of red-sensitive layer, green-sensitive layer and blue-sensitive layer as viewed from the support. However, the order of arrangement can be optionally reversed depending on the purpose of application. Alternatively, two light-sensitive layers having the same color sensitivity can be arranged with at least one light-sensitive layer(s) having a different color sensitivity interposed therebetween.
Light-insensitive layer(s) such as various interlayers can be provided between these silver halide light-sensitive layers and on the uppermost layer and lowermost layer.
These interlayers can comprise couplers, DIR compounds or the like as described in JP-A-61-43748, JP-A-59-113438, JP-A-59-113440, JP-A-61-20037 and JP-A-61-20038. These interlayers can further comprise a color stain preventing agent as commonly used.
The plurality of silver halide emulsion layers constituting each unit light-sensitive layer can be preferably in a two-layer structure, i.e., high sensitivity emulsion layer and low sensitivity emulsion layer, as described in West German Patent 1,121,470 and British Patent 923,045. In general, these layers are preferably arranged in such an order that the light sensitivity becomes lower towards the support. Furthermore, a light-insensitive layer can be provided between these silver halide emulsion layers. As described in JP-A-57-112751, JP-A-62-200350, JP-A-62-206541 and JP-A-62-206543, a low sensitivity emulsion layer can be provided remote from the support while a high sensitivity emulsion layer can be provided nearer to the support.
In an embodiment of such an arrangement, a low sensitivity blue-sensitive layer (BL), a high sensitivity blue-sensitive layer (BH), a high sensitivity green-sensitive layer (GH), a low sensitivity green-sensitive layer (GL), a high sensitivity red-sensitive layer (RH) and a low sensitivity red-sensitive layer (RL) can be arranged in this order from the side remotest from the support. In another embodiment, BH, BL, GL, GH, RH and RL can be arranged in this order from the side remotest from the support. In a further embodiment, BH, BL, GH, GL, RL and RH can be arranged in this order from the side remotest from the support.
As described in JP-B-55-34932, a blue-sensitive layer, GH, RH, GL and RL can be arranged in this order from the side remotest from the support. Alternatively, as described in JP-A-56-25738 and JP-A-62-63936, a blue-sensitive layer, GL, RL, GH and RH can be arranged in this order from the side remotest from the support.
As described in JP-B-49-15495, a layer arrangement can be used such that the uppermost layer is a silver halide emulsion layer having the highest sensitivity, the middle layer is a silver halide emulsion layer having a sensitivity lower than that of the uppermost layer, and the lowermost layer is a silver halide emulsion layer having a sensitivity lower than that of the middle layer. In such a layer arrangement, the light sensitivity becomes lower towards the support. Even if the layer structure comprises three layers having different light sensitivities, a middle sensitivity emulsion layer, a high sensitivity emulsion layer and a low sensitivity emulsion layer can be arranged in this order from the side remote from the support in a color-sensitive layer as described in JP-A-59-202464.
Alternatively, in the foregoing three-layer structure, a high sensitivity emulsion layer, a low sensitivity emulsion layer and a middle sensitivity emulsion layer or a low sensitivity emulsion layer, a middle sensitivity emulsion layer and a high sensitivity emulsion layer may be arranged in this order from the side remote from the support. In the case of four or more layer structure, too, the arrangement of layers may be similarly altered.
In order to improve color reproducibility, a donor layer (CL) for an interimage effect having a different spectral sensitivity distribution from the main light-sensitive layers such as BL, GL and RL is preferably provided adjacent or close to these main layers as described in U.S. Patents 4,663,271, 4,705,744 and 4,707,436, and JP-A-62-160448 and JP-A-63-89850.
As described above, various layer structures and arrangements can be selected depending on the purpose of light-sensitive material.
Silver halide grains other than the foregoing tabular grains to be used in the present invention will be described hereinafter. A suitable silver halide to be incorporated in the photographic emulsion layer in the photographic light-sensitive material to be used in the present invention is silver bromoiodide, silver chloroiodide or silver bromochloroiodide containing silver iodide in an amount of about 30 mol% or less. Particularly suitable is silver bromoiodide or silver chloroiodide each containing silver iodide in an amount of about 2 mole% to about 10 mol%.
Silver halide grains in the emulsions for use in the present invention may be grains having a regular crystal form, such as cube, octahedron and tetradecahedron, or those having an irregular crystal form such as sphere and plate, those having a crystal defect such as twinning plane, or those having a composite of these crystal forms.
The silver halide grains may be either fine grains of about 0.2 µm or smaller in diameter or larger grains having a projected area diameter of up to about 10 µm. The emulsion may be either a monodisperse emulsion or a polydisperse emulsion.
The preparation of the silver halide photographic emulsion other than the emulsion comprising the foregoing tabular grains which can be used in the present invention can be accomplished by any suitable method as described in Research Disclosure No. 17643 (December 1978), pp. 22 - 23, "I." Emulsion Preparation and Types", No. 18716 (November 1979), page 648, and No. 307105 (November 1989), pp. 863 - 865, P. Glafkides, "Chimie et Physique Photographique", Paul Montel (1967), G. F. Duffin, "Photographic Emulsion Chemistry", Focal Press, (1966), and V. L. Zelikman et al., "Making and Coating Photographic Emulsion", Focal Press, (1964).
In the present invention, monodisperse emulsions as described in U.S. Patents 3,574,628 and 3,655,394, and British Patent 1,413,748 can be preferably used in the present invention.
Tabular grains having an aspect ratio of about 3 or more which have been prepared in accordance with a method other than the preparation method according to the present invention can be used in the present invention. The preparation of such tabular grains can be easily accomplished by any suitable method as described in Gutoff, "Photographic Science and Engineering", vol. 14, pp. 248 - 257, (1970), U.S. Patents 4,434,226, 4,414,310, 4,433,048 and 4,439,520 and British Patent 2,112,157.
The individual silver halide crystals to be used in the present invention may have either a homogeneous structure or a heterogeneous structure composed of a core and an outer shell differing in halogen composition, or may have a layered structure. Furthermore, the grains may have fused thereto a silver halide having a different halogen composition or a compound other than silver halide, e.g., silver thiocyanate, lead oxide, etc. by an epitaxial junction. Mixtures of grains having various crystal forms may also be used.
The silver halide emulsion employable in the present invention may be of the surface latent image type in which latent images are mainly formed on the surface of grains, the internal latent image type in which latent images are mainly formed inside grains or the type in which latent images are formed both on the surface and inside grains. The emulsion needs to be a negative type emulsion. If the emulsion is of the internal latent image type, it may be a core/shell type internal latent image emulsion as disclosed in JP-A-63-264740. A process for the preparation of such a core/shell type internal latent image emulsion is described in JP-A-59-133542. In this emulsion, the thickness of the shell depends on development process, etc. and is preferably in the range of 3 to 40 nm, particularly 5 to 20 nm.
The silver halide emulsion to be used in the present invention is normally subjected to physical ripening, chemical ripening and spectral sensitization. Additives to be used in these steps are described in Research Disclosure Nos. 17643, 18716 and 307105 as tabulated below.
In the light-sensitive material, two or more kinds of light-sensitive silver halide emulsions which are different in at least one of grain size, grain size distribution, halogen composition, grain shape and sensitivity may be incorporated in the same layer in admixture as mentioned above.
Surface-fogged silver halide grains as described in U.S. Patent 4,082,553, internally-fogged silver halide grains as described in U.S. Patent 4,626,498 and JP-A-59-214852, or colloidal silver may be preferably incorporated in a light-sensitive silver halide emulsion layer and/or substantially light-insensitive hydrophilic colloidal layer. The term "internally- or surface-fogged silver halide grains" as used herein means "silver halide grains (emulsion) which can be uniformly (nonimagewise) developed regardless of whether they were present in the exposed portion or unexposed portion on the light-sensitive material". Processes for the preparation of internally- or surface-fogged silver halide grains are described in U.S. Patent 4,626,498, and JP-A-59-214852.
Silver halides forming the core of internally-fogged core/shell type silver halide grains may have the same or different halogen compositions. Internally- or surface-fogged silver halide grains may comprise any of silver chloride, silver bromochloride, silver bromoiodide and silver bromochloroiodide. The size of these fogged silver halide grains is not specifically limited, and its average grain size is preferably in the range of 0.01 to 0.75 µm, particularly 0.05 to 0.6 µm. The crystal form of these grains is not specifically limited and may be regular. These emulsions may be polydisperse but is preferably monodisperse (silver halide grains at least 80% by weight or number of which are those having grain diameters falling within ±30% from the average grain size).
In the present invention, light-insensitive finely divided silver halide grains are preferably used. Light-insensitive finely divided silver halide grains are silver halide grains which are not exposed to light upon imagewise exposure for taking of dye images so that they are not substantially developed at development process. Preferably, these silver halide grains are not previously fogged.
These light-insensitive finely divided silver halide grains have a silver bromide content of 0 to 100 mole% and may optionally contain silver chloride and/or silver iodide, preferably 0.5 to 10 mole% of silver iodide.
These light-insensitive finely divided silver halide grains preferably have an average diameter of 0.01 to 0.5 µm, more preferably 0.02 to 0.2 µm as calculated in terms of diameter of circle having the same area as the projected area of grain.
These light-insensitive finely divided silver halide grains can be prepared in the same manner as ordinary light-sensitive silver halide. In this case, the surface of the light-insensitive finely divided silver halide grains needs neither chemically nor spectrally be sensitized. However, prior to the addition of the emulsion to a coating solution, a known stabilizer such as triazole, azaindene, benzothiazolium or mercapto compound and zinc compound is preferably added to the emulsion. Colloidal silver can be preferably incorporated in the layer containing these finely divided silver halide grains.
The coated amount of silver in the light-sensitive material of the present invention is preferably in the range of 6.0 g/m² or less, most preferably 4.5 g/m² or less.

Known photographic additives which can be used in the present invention are also described in the above cited three R.D.'s as tabulated below.

	Kind of additive	RD17643	RD18716	RD307105
1.	Chemical sensitizer	p. 23	p. 648 right column (RC)	p. 866
2.	Sensitivity increasing agent		do.
3.	Spectral sensitizer and supersensitizer	pp. 23-24	p. 648 RC -p. 649 RC	pp. 866-868
4.	Brightening agent	p. 24	p. 647 RC	p. 868
5.	Antifoggant and stabilizer	pp. 24-25	p. 649 RC	pp. 868-870
6.	Light absorbent, filter dye, and ultraviolet absorbent	pp. 25-26	p. 649 RC -p. 650 left column (LC)	p. 873
7.	Stain inhibitor	p. 25 RC	p. 650 LC-RC	p.872
8.	Dye image stabilizer	p. 25	p. 650 LC	do.
9.	Hardening agent	p. 26	p. 651 LC	pp. 874-875
10.	Binder	p. 26	do.	pp. 873-874
11.	Plasticizer and lubricant	p. 27	p. 650 RC	p. 876
12.	Coating aid and surface active agent	pp. 26-27	do.	pp. 875-876
13.	Antistatic agent	p. 27	do.	pp. 876-877
14.	Matting agent			pp. 878-879

In order to inhibit deterioration in photographic properties due to formaldehyde gas, a compound capable of reacting with and solidifying formaldehyde as disclosed in U.S. Patents 4,411,987 and 4,435,503 can be incorporated in the light-sensitive material.
The light-sensitive material preferably comprises a mercapto compound as disclosed in U.S. Patents 4,740,454 and 4,788,132, JP-A-62-18539 and JP-A-1-283551.
The light-sensitive material preferably comprises a fogging agent, a development accelerator, a silver halide solvent or a compound for releasing precursors thereof as disclosed in JP-A-1-106052 regardless of the amount of developed silver produced by development.
The light-sensitive material preferably comprises a dye which has been dispersed by a method as disclosed in Published unexamined International Application No. WO88/04794 and Published unexamined International Application No. 1-502912 or a dye as disclosed in EP317,308A, U.S. Patent 4,420,555 and JP-A-1-259358.
The light-sensitive material can comprise various color couplers. Specific examples of the color couplers are described in the patents described in the above cited R.D. No. 17643, VII-C to G and No. 307105, VII-C to G.
Preferred yellow couplers include those described in U.S. Patents 3,933,501, 4,022,620, 4,326,024, 4,401,752, 4,248,961, 3,973,968, 4,314,023 and 4,511,649, JP-B-58-10739, British Patents 1,425,020 and 1,476,760 and European Patent 249,473A.
Preferred magenta couplers include 5-pyrazolone compounds and pyrazoloazole compounds. Particularly preferred are those described in U.S. Patents 4,310,619, 4,351,897, 3,061,432, 3,725,064, 4,500,630, 4,540,654 and 4,556,630, European Patent 73,636, JP-A-60-33552, JP-A-60-43659, JP-A-61-72238, JP-A-60-35730, JP-A-55-118034, JP-A-60-185951, R.D. Nos. 24220 (June 1984) and 24230 (June 1984), and Published unexamined International Application No. WO88/04795.
Cyan couplers include naphthol and phenol couplers. Preferred are those described in U.S. Patents 4,052,212, 4,146,396, 4,228,233, 4,296,200, 2,369,929, 2,801,171, 2,772,162, 2,895,826, 3,772,002, 3,758,308, 4,334,011, 4,327,173, 3,446,622, 4,333,999, 4,775,616, 4,451,559, 4,427,767, 4,690,889, 4,254,212 and 4,296,199, West German Patent Publication (OLS) No. 3,329,729, European Patents 121,365A and 249,453A and JP-A-61-42658. Further, pyrazoloazole couplers as disclosed in JP-A-64-553, JP-A-64-554, JP-A-64-555 and JP-A-64-556 and imidazole couplers as disclosed in U.S. Patent 4,818,672 can be used.
Typical examples of polymerized dye-forming couplers are described in U.S. Patents 3,451,820, 4,080,211, 4,367,282, 4,409,320 and 4,576,910, British Patent 2,102,137, and European Patent 341,188A.
Couplers which form a dye having moderate diffusibility preferably include those described in U.S. Patent 4,366,237, British Patent 2,125,570, European Patent 96,570 and West German Patent Publication (OLS) No. 3,234,533.
Colored couplers for correction of unnecessary absorptions of the developed dye preferably include those described in R.D. No. 17643, VII-G, R.D. No. 307105, VII-G, U.S. Patents 4,163,670, 4,004,929 and 4,138,258, JP-B-57-39413 and British Patent 1,146,368. Furthermore, couplers for correction of unnecessary absorption of the developed dye by a fluorescent dye released upon coupling as described in U.S. Patent 4,774,181 and couplers containing as a release group a dye precursor group capable of reacting with a developing agent to form a dye as described in U.S. Patent 4,777,120 can be preferably used.
The photographic light-sensitive material may preferably comprise compounds capable of releasing a photographically useful residue upon coupling. Preferred examples of DIR couplers which release a development inhibitor are described in the patents cited in R.D. 17643, VII-F, R.D. 307105, VII-F, JP-A-57-151944, JP-A-57-154234, JP-A-60-184248, JP-A-63-37346, JP-A-63-37350 and U.S. Patents 4,248,962 and 4,782,012.
Bleach accelerator-releasing couplers as disclosed in R.D. Nos. 11449 and 24241 and JP-A-61-201247 are effective for the reduction of time required for processing step having bleaching capacity. In particular, when incorporated in a light-sensitive material comprising the above mentioned tabular silver halide grains, these couplers remarkably exhibit its effect. Couplers capable of imagewise releasing a nucleating agent or a developing accelerator at the time of development preferably include those described in British Patents 2,097,140 and 2,131,188, JP-A-59-157638 and JP-A-59-170840. Further, compounds which undergo redox reaction with the oxidation product of a developing agent to release a fogging agent, a development accelerator, a silver halide solvent or the like as disclosed in JP-A-60-107029, JP-A-60-252340, JP-A-1-44940 and JP-A-1-45687 are preferred.
In addition to the foregoing couplers, the photographic material can further comprise competing couplers as described in U.S. Patent 4,130,427, polyequivalent couplers as described in U.S. Patents 4,283,472, 4,338,393, and 4,310,618, DIR redox compound-releasing couplers, DIR coupler-releasing couplers, DIR coupler-releasing redox compounds or DIR redox-releasing redox compounds as described in JP-A-60-185950 and JP-A-62-24252, couplers capable of releasing a dye which returns to its original color after release as described in European Patents 173,302A and 313,308A, couplers capable of releasing a ligand as described in U.S. Patent 4,553,477, couplers capable of releasing a leuco dye as described in JP-A-63-75747, and couplers capable of releasing a fluorescent dye as described in U.S. Patent 4,774,181.
The incorporation of the couplers for use in the present invention in the light-sensitive material can be accomplished by any suitable known dispersion method such as oil-in-water dispersion method and latex dispersion method.
Examples of high boiling solvents to be used in the foregoing oil-in-water dispersion process are described in U.S. Patent 2,322,027. Specific examples of high boiling organic solvents having a boiling point of 175°C or higher at normal pressure which can be used in the oil-in-water dispersion process include phthalic esters (e.g., dibutyl phthalate, dicyclohexyl phthalate, di-2-ethylhexyl phthalate, decyl phthalate, bis(2,4-di-t-amylphenyl)phthalate, bis(2,4-di-t-amylphenyl)isophthalate, bis(1,1-diethylpropyl)-phthalate), phosphoric or phosphonic esters (e.g., triphenyl phosphate, tricresyl phosphate, 2-ethylhexyl diphenyl phosphate, tricyclohexyl phosphate, tri-2-ethylhexyl phosphate, tridodecyl phosphate, tributoxy ethyl phosphate, trichloropropyl phosphate, di-2-ethylhexyl phenyl phosphonate), benzoic esters (e.g., 2-ethylhexyl benzoate, dodecyl benzoate, 2-ethylhexyl-p-hydroxy benzoate), amides (e.g., N,N-diethyldodecanamide, N,N-diethyllaurylamide, N-tetradecylpyrrolidone), alcohols or phenols (e.g., isostearyl alcohol, 2,4-di-tert-amylphenol), aliphatic carboxylic esters (e.g., bis(2-ethylhexyl)sebacate, dioctyl azerate, glycerol tributylate, isostearyl lactate, trioctyl citrate), aniline derivatives (e.g., N,N-dibutyl-2-butoxy-5-tert-octylaniline), and hydrocarbons (e.g., paraffin, dodecylbenzene, diisopropylnaphthalene). As an auxiliary solvent there can be used an organic solvent having a boiling point of about 30°C or higher, preferably 50°C to about 160°C. Typical examples of such an organic solvent include ethyl acetate, butyl acetate, ethyl propionate, methyl ethyl ketone, cyclohexanone, 2-ethoxyethyl acetate, and dimethylformamide.
The process and effects of the foregoing latex dispersion method and specific examples of latexes to be used in dipping are described in U.S. Patent 4,199,363, West German Patent Application (OLS) Nos. 2,541,274 and 2,541,230.
The color photographic light-sensitive material preferably comprises various antiseptics or anti-fungal agents such as phenetyl alcohol and 1,2-benzisothiazoline-3-one, n-butyl-p-hydroxybenzoate, phenol, 4-chloro-3,5-dimethylphenol, 2-phenoxyethanol and 2-(4-thiazolyl)benzimidazole as described in JP-A-63-257747, JP-A-62-272248 and JP-A-1-80941.
The present invention can be applied to various color photographic materials. Typical examples include color negative films for general purposes or for cinematographic purposes, color reversal films for slides or television purposes, color papers, color positive films and color reversal papers.
Suitable supports which can be used in the present invention are described in the above cited R.D. 17643 (page 28), R.D. 18716 (right column on page 647 to left column on page 648), and R.D. 307105 (page 897).
In the photographic light-sensitive material, the total thickness of all hydrophilic colloidal layers on the emulsion side is preferably in the range of 28 µm or less, more preferably 23 µm or less, further preferably 18 µm or less, particularly 16 µm or less. The film swelling T_1/2 is preferably in the range of 30 seconds or less, more preferably 20 seconds or less. The film thickness is determined after being stored at a temperature of 25°C and a relative humidity of 55% for 2 days. The film swelling T_1/2 can be determined by a method known in the art, e.g., by means of a swellometer of the type as described in A. Green et al., "Photographic Science and Engineering", vol. 19, No. 2, pp. 124-129. T_1/2 is defined as the time taken until half the saturated film thickness is reached wherein the saturated film thickness is 90% of the maximum swollen film thickness reached when the light-sensitive material is processed with a color developer at a temperature of 30°C over 195 seconds.
The film swelling T_1/2 can be adjusted by adding a film hardener to gelatin as binder or altering the ageing condition after coating. The percentage swelling of the light-sensitive material is preferably in the range of 150 to 400%. The percentage swelling can be calculated from the maximum swollen film thickness determined as described above in accordance with the equation: (maximum swollen film thickness - film thickness)/film thickness.
The photographic light-sensitive material preferably comprises a hydrophilic colloidal layer (hereinafter referred to as "backing layer") having a total dried thickness of 2 µm to 20 µm on the side other than the emulsion layer side. The back layer preferably contains the above mentioned light absorbent, filter dye, ultraviolet absorbent, antistatic agent, hardener, binder, plasticizer, lubricant, coating aid, surface active agent, etc. The backing layer preferably exhibits a percentage swelling of 150 to 500%.
The photographic light-sensitive material can be subjected to development in accordance with an ordinary method as described in R.D. 17643 (pp. 28 - 29), R.D. 18716 (left column to right column on page 651) and R.D. 307105 (pp. 880 - 881).
The color developer to be used in the development of the photographic light-sensitive material is preferably an alkaline aqueous solution containing as a main component an aromatic primary amine color developing agent. As such a color developing agent there can be effectively used an aminophenolic compound. In particular, p-phenylenediamine compounds are preferably used. Typical examples of such p-phenylenediamine compounds include 3-methyl-4-amino-N,N-diethylaniline, 3-methyl-4-amino-N-ethyl-N-β-hydroxyethylaniline, 3-methyl-4-amino-N-ethyl-N-β-methanesulfonamidoethylaniline, 3-methyl-4-amino-N-ethyl-N-β-methoxyethylaniline, and sulfates, hydrochlorides and p-toluenesulfonates thereof. Particularly preferred among these compounds is 3-methyl-4-amino-N-ethyl-N-β-hydroxyethylaniline sulfate. These compounds can be used in combination of two or more thereof depending on the purpose of application.
The foregoing color developer normally contains a pH buffer such as carbonate, borate and phosphate of an alkali metal or a development inhibitor or fog inhibitor such as chlorides, bromides, iodides, benzimidazoles, benzothiazoles and mercapto compounds. If desired, the foregoing color developer may further contain various preservatives such as hydroxylamine, diethylhydroxylamine, sulfites, hydrazines (e.g., N,N-biscarboxymethylhydrazine), phenylsemicarbazides, triethanolamine and catecholsulfonic acids, organic solvents such as ethylene glycol and diethylene glycol, development accelerators such as benzyl alcohol, polyethylene glycol, quaternary ammonium salts, and amines, color-forming couplers, competing couplers, auxiliary developing agents such as 1-phenyl-3-pyrazolidone, viscosity-imparting agents, various chelating agents exemplified by aminopolycarboxylic acids, aminopolyphosphonic acids, alkylphosphonic acids, and phosphonocarboxylic acids (e.g., ethylenediaminetetraacetic acid, nitrilotriacetic acid, diethylenetriaminepentaacetic acid, cyclohexanediaminetetraacetic acid, hydroxyethyl-iminodiacetic acid, 1-hydroxyethylidene-1,1-diphosphonic acid, nitrilo-N,N,N-trimethylenephosphonic acid, ethylenediamine-N,N,N,N-tetramethylenephosphonic acid, and ethylenediamine-di(o-hydroxyphenylacetic acid), and salts thereof).
If the photographic light-sensitive material is subjected to reversal process, it is normally subjected to black-and-white development before color development. The black-and-white developer may comprise known black-and-white developing agents such as dihydroxybenzenes (e.g., hydroquinone), 3-pyrazolidones (e.g., 1-phenyl-3-pyrazolidone) and aminophenols (e.g., N-methyl-p-aminophenol) singly or in combination.
The color developer or black-and-white developer usually has a pH of from 9 to 12. The replenishment rate of the developer is usually 3 ℓ or less per m² of the light-sensitive material, though depending on the type of the color photographic material to be processed. The replenishment rate may be reduced to 500 mℓ/m² or less by decreasing the bromide ion concentration in the replenisher. If the replenishment rate is reduced, the area of the processing tank in contact with air is preferably reduced to inhibit the evaporation and air oxidation of the processing solution.
The area of the photographic processing solution in contact with air in the processing tank can be represented by an opening rate as defined by the following equation: Opening rate = [area of processing solution in contact with air (cm2)/[volume of processing solution (cm3)]
The opening rate as defined above is preferably in the range of 0.1 or less, more preferably 0.001 to 0.05. Examples of methods for reducing the opening rate include a method which comprises putting a cover such as floating lid on the surface of the processing solution in the processing tank, a method as disclosed in JP-A-1-82033 utilizing a mobile lid, and a slit development method as disclosed in JP-A-63-216050. The reduction of the opening rate is preferably effected in both color development and black-and-white development steps as well as all the subsequent steps such as bleach, blix, fixing, washing and stabilization. The replenishment rate can also be reduced by a means for suppressing accumulation of the bromide ion in the developing solution.
The color development time is normally predetermined between 2 minutes and 5 minutes. By carrying out color development at a high temperature and a high pH value with a highly concentrated color developing agent, the processing time can be further reduced.
The photographic emulsion layer which has been color-developed is normally subjected to bleach. Bleach may be effected simultaneously with fixation (i.e., blix), or these two steps may be carried out separately. For speeding up of processing, bleach may be followed by blix. Further, any of an embodiment wherein two blix baths connected in series are used, an embodiment wherein blix is preceded by fixation, and an embodiment wherein blix is followed by bleach may be selected arbitrarily according to the purpose. Bleaching agents to be used include compounds of polyvalent metals, e.g., iron (III), peroxides, quinones, and nitro compounds. Typical examples of these bleaching agents are organic complex salts of iron (III) with, e.g., aminopolycarboxylic acids such as ethylenediaminetetraacetic acid, diethylenetriaminepentaacetic acid, cyclohexanediaminetetraacetic acid, methyliminodiacetic acid, 1,3-diaminopropanetetraacetic acid and glycol ether diaminetetraacetic acid, or citric acid, tartaric acid, malic acid, etc. Of these, aminopolycarboxylic acid-iron (III) complex salts such as ethylene-diaminetetraacetato iron (III) complex salts and 1,3-diaminopropanetetraacetato iron (III) complex salts are preferred in view of speeding up of processing and conservation of the environment. In particular, aminopolycarboxylic acid-iron (III) complex salts are useful in both of a bleaching solution and a blix solution. The pH value of a bleaching solution or blix solution comprising such an aminopolycarboxylic acid-iron (III) complex salts is normally in the range of 4.0 to 8. For speeding up of processing, the processing can be effected at an even lower pH value.
The bleaching bath, blix bath or a prebath thereof can contain, if desired, a bleaching accelerator. Examples of useful bleaching accelerators include compounds containing a mercapto group or a disulfide group as described in U.S. Patent 3,893,858, West German Patents 1,290,812 and 2,059,988, JP-A-53-32736, JP-A-53-57831, JP-A-53-37418, JP-A-53-72623, JP-A-53-95630, JP-A-53-95631, JP-A-53-104232, JP-A-53-124424, JP-A-53-141623, JP-A-53-28426 and Research Disclosure No. 17129 (July 1978), thiazolidine derivatives as described in JP-A-50-140129, thiourea derivatives as described in JP-B-45-8506, JP-A-52-20832, JP-A-53-32735 and U.S. Patent 3,706,561, iodides as described in West German Patent 1,127,715 and JP-A-58-16235, polyoxyethylene compounds as described in West German Patents 966,410 and 2,748,430, polyamine compounds as described in JP-B-45-8836, compounds as described in JP-A-49-40943, JP-A-49-59644, JP-A-53-94927, JP-A-54-35727, JP-A-55-26506, and JP-A-58-163940, and bromine ions. Preferred among these compounds are compounds containing a mercapto group or disulfide group because of their great acceleratory effects. In particular, the compounds disclosed in U.S. Patent 3,893,858, West German Patent 1,290,812, and JP-A-53-95630 are preferred. The compounds disclosed in U.S. Patent 4,552,834 are also preferred. These bleaching accelerators may be incorporated into the light-sensitive material. These bleaching accelerators are particularly effective for blix of color light-sensitive materials for picture taking.
The bleaching solution or blix solution preferably contains an organic acid besides the above mentioned compounds for the purpose of inhibiting bleach stain. A particularly preferred organic acid is a compound with an acid dissociation constant (pKa) of 2 to 5. In particular, acetic acid, propionic acid, hydroxyacetic acid, etc. are preferred.
Examples of fixing agents to be contained in the fixing solution or blix solution include thiosulfates, thiocyanates, thioethers, thioureas, and a large amount of iodides. The thiosulfates are normally used. In particular, ammonium thiosulfate can be most widely used. Further, thiosulfates are preferably used in combination with thiocyanates, thioether compounds, thioureas, etc. As preservatives of the fixing or blix bath there can be preferably used sulfites, bisulfites, carbonyl bisulfite adducts or sulfinic acid compounds as described in European Patent 294769A. The fixing solution or blix solution preferably contains aminopolycarboxylic acids or organic phosphonic acids for the purpose of stabilizing the solution.
In the present invention, a compound having a pKa value of from 6.0 to 9.0, preferably an imidazole such as imidazole, 1-methylimidazole, 1-ethylimidazole and 2-methylimidazole, is preferably added to the fixing solution or blix solution in an amount of 0.1 to 10 mol/ℓ to adjust the pH value thereof.
The total time required for desilvering step in the development process is preferably as short as possible so long as no maldesilvering occurs. The desilvering time is preferably in the range of 1 to 3 minutes, more preferably 1 to 2 minutes. The processing temperature is in the range of 25°C to 50°C, preferably 35°C to 45°C. In the preferred temperature range, the desilvering rate can be improved and stain after processing can be effectively inhibited.
In the desilvering step, the agitation is preferably intensified as much as possible. Specific examples of such an agitation intensifying method include a method as described in JP-A-62-183460 which comprises jetting the processing solution to the surface of the emulsion layer in the light-sensitive material, a method as described in JP-A-62-183461 which comprises improving the agitating effect by a rotary means, a method which comprises improving the agitating effect by moving the light-sensitive material with the emulsion surface in contact with a wiper blade provided in the bath so that a turbulence occurs on the emulsion surface, and a method which comprises increasing the total circulated amount of processing solution. Such an agitation improving method can be effectively applied to the bleaching bath, blix bath or fixing bath. The improvement in agitation effect can be considered to expedite the supply of a bleaching agent, fixing agent or the like into emulsion film, resulting in an improvement in desilvering rate. The above mentioned agitation improving means can work more effectively when a bleach accelerator is used, remarkably increasing the bleach acceleration effect and eliminating the inhibition of fixing by the bleach accelerator.
The automatic developing machine to be used in the processing of the light-sensitive material is preferably equipped with a light-sensitive material conveying means as disclosed in JP-A-60-191257, JP-A-60-191258 and JP-A-60-191259. Such a conveying means can remarkably reduce the amount of the processing solution carried from a bath to its subsequent bath, providing a high effect of inhibiting deterioration of the properties of the processing solution. This effect is remarkably effective for the reduction of the processing time or the amount of replenisher required at each step.
It is usual that the thus desilvered silver halide color photographic material are subjected to washing and/or stabilization. The quantity of water to be used in the washing can be selected from a broad range depending on the characteristics of the light-sensitive material (for example, the kind of materials such as couplers, etc.), the end use of the light-sensitive material, the temperature of washing water, the number of washing tanks (number of stages), the replenishment system (e.g., counter-current system or concurrent system), and other various factors. Of these factors, the relationship between the number of washing tanks and the quantity of water in a multistage counter-current system can be obtained according to the method described in "Journal of the Society of Motion Picture and Television Engineers", vol. 64, pp. 248 - 253 (May 1955). According to the multi-stage counter-current system described in the above reference, although the requisite amount of water can be greatly reduced, bacteria would grow due to an increase of the retention time of water in the tank, and floating masses of bacteria stick to the light-sensitive material. In the processing for the color light-sensitive material, in order to cope with this problem, the method of reducing calcium and magnesium ion concentrations described in JP-A-62-288838 can be used very effectively. Further, it is also effective to use isothiazolone compounds or thiabenzazoles as described in JP-A-57-8542, chlorine type bactericides, e.g., chlorinated sodium isocyanurate, benzotriazole, and bactericides described in Hiroshi Horiguchi, "Bokinbobaizai no kagaku", published by Sankyo Shuppan, (1986), Eisei Gijutsu Gakkai (ed.), "Biseibutsu no mekkin, sakkin, bobigijutsu", Kogyogijutsukai, (1982), and Nippon Bokin Bobi Gakkai (ed.), "Bokin bobizai jiten" (1986).
The washing water has a pH value of from 4 to 9, preferably from 5 to 8 in the processing for the light-sensitive material. The temperature of the water and the washing time can be selected from broad ranges depending on the characteristics and end use of the light-sensitive material, but usually ranges from 15 to 45°C in temperature and from 20 seconds to 10 minutes in time, preferably from 25 to 45°C in temperature and from 30 seconds to 5 minutes in time. The light-sensitive material may be directly processed with a stabilizer in place of the washing step. For the stabilization, any of the known techniques as described in JP-A-57-8543, JP-A-58-14834 and JP-A-60-220345 can be used.
The aforesaid washing step may be followed by stabilization in some cases. For example, a stabilizing bath containing a dye stabilizer and a surface active agent as is used as a final bath for color light-sensitive materials for picture taking can be used. Examples of such a dye stabilizer include aldehydes such as formalin and glutaraldehyde, N-methylol compounds, hexamethylenetetramine and aldehyde-bisulfite adducts. This stabilizing bath may also contain various chelating agents or antifungal agents.
The overflow accompanying replenishment of the washing bath and/or stabilizing bath can be reused in other steps such as desilvering.
In a processing using an automatic developing machine, if the above mentioned various processing solutions are subject to concentration due to evaporation, the concentration is preferably corrected for by the addition of water.
The photographic light-sensitive material may contain a color developing agent for the purpose of simplifying and expediting processing. Such a color developing agent is preferably used in the form of various precursors, when it is contained in the light-sensitive material. Examples of such precursors include indoaniline compounds as described in U.S. Patent 3,342,597, Schiff's base type compounds as described in U.S. Patent 3,342,599, R.D. 14,850 and R.D. 15,159, and aldol compounds as described in R.D. 13,924, metal complexes as described in U.S. Patent 3,719,492, and urethane compounds as described in JP-A-53-135628.
The photographic light-sensitive material may optionally comprise various 1-phenyl-3-pyrazolidones for the purpose of accelerating color development. Typical examples of such compounds are described in JP-A-56-64339, JP-A-57-144547 and JP-A-58-115438.
With respect to the photographic light-sensitive material, the various processing solutions are used at a temperature of 10°C to 50°C. The standard temperature range is normally from 33°C to 38°C. However, a higher temperature range can be used to accelerate processing, reducing the processing time. On the contrary, a lower temperature range can be used to improve the picture quality or the stability of the processing solutions.
Techniques and inorganic and organic materials employable in the preparation of the color photographic light-sensitive material are described in the following parts of JP-A-3-161745:
1. Layer structure: line 1, lower left column, page 28 - line 7, upper right column, page 29
2. Silver halide emulsion: line 8, upper right column, page 29 - line 12, upper right column, page 30
3. Yellow coupler: line 5 - line 11, lower right column, page 30
4. Magenta coupler: line 12, lower right column, page 30 - line 3, page 31
5. Cyan coupler: line 4 - line 16, upper left column, page 31
6. Polymer coupler: line 17, upper left column - line 1, upper right column, page 31
7. Functional coupler: line 2, upper right column - line 5, lower right column, page 31
8. Antiseptic/mildewproofing agent: line 10 - line 17, upper right column, page 32
9. Formalin scavenger: line 16 - line 20, lower left column, page 30
10. Other additives: line 19, lower right column, page 35 - line 14, upper right column, page 36, and line 13, upper right column - line 15, lower left column, page 30
11. Dispersion method: line 8, lower right column, page 31 - line 9, upper right column, page 32
12. Support: line 4 - line 6, lower left column, page 32
13. Thickness/physical properties of film: line 7, lower left column - line 10, lower right column, page 32
14. Color development process: line 15, lower right column, page 32 - line 16, lower right column, page 33
15. Desilvering process: line 17, lower right column, page 32 - line 16, upper left column, page 35
16. Automatic developing machine: line 17, lower left column - line 5, upper right column, page 35
17. Washing/stabilization process: line 6, upper right column - line 15, lower right column, page 35
The silver halide photographic material may also be applied to heat-developable photographic light-sensitive materials as described in U.S. Patent 4,500,626, JP-A-60-133449, JP-A-59-218443, JP-A-61-238056 and European Patent 210,660A2.
When applied to a film unit with lens as described in JP-B-2-32615 and JP-B-U-3-39784 (The term "JP-B-U" as used herein means an "examined Japanese utility model publication"), the silver halide photographic material can more easily exert its effects.
The present invention will be further described in the following examples, but the present invention should not be construed as being limited thereto.

EXAMPLE 1

(Preparation of seed crystal emulsion Em-1)

A 1 M aqueous solution of silver nitrate and a 1 M aqueous solution of potassium bromide and potassium iodide (92/8 by molar ratio) were added to a solution of 6 g of an inert low molecular weight gelatin (average molecular weight: 50,000) and 2.5 g of potassium bromide in 1 ℓ of distilled water at a flow rate of 50 cc/min., respectively, for 40 seconds while the latter was stirred at a temperature of 30°C. Subsequently, the pAg value of the emulsion thus obtained was adjusted to 8.5. To the emulsion was then added 20 g of an inert gelatin. The emulsion was then heated to a temperature of 65°C. The emulsion was then ripened with 50 g of ammonium nitrate and 100 cc of a 1 M aqueous solution of sodium hydroxide for 30 minutes to form tabular nuclei. To the emulsion was then added 8 g of glacial acetic acid. A hundred cc of a 1 M aqueous solution of silver nitrate and a 1 M aqueous solution of potassium bromide were added to the emulsion by an equimolecular amount at a rate close to the critical growth rate to effect shell formation. Thus, tabular silver bromide grains were allowed to grow to obtain Emulsion Em-1. In this process, the silver potential was kept to +10 mV with respect to saturated calomel electrode. The amount of silver nitrate used for the growth of grains totalled 135 g.
Emulsion Em-1 thus obtained was then subjected to desalting by an ordinary flocculation process. To the emulsion was then added gelatin. The pH and pAg values of the emulsion were then adjusted to 6.0 and 8.5, respectively. The emulsion was then refrigerated.
Em-1 was an emulsion of tabular silver halide grains with a diameter of 0.18 µm as calculated in terms of sphere and a variation coefficient of 27% comprising grains of an aspect ratio of not less than 3.0 in a proportion of 92% of all silver halide grains as calculated in terms of projected area.

(Preparation of seed crystal emulsions Em-2 to Em-10)

Seed crystal emulsions Em-2 to Em-7 were prepared in the same manner as Em-1 except that Compound I-2 or Compound I-16 was added to the system shortly before the formation of shell in an amount as set forth in Table 1 below to effect grain formation.
Seed crystal emulsion Em-8 was prepared in the same manner as Em-1 except that Compound I-16 was added to the system shortly before the initiation of formation of grains in an amount as set forth in Table 1 to effect grain formation.
Seed crystal emulsion Em-9 was prepared in the same manner as Em-1 except that Compound I-16 was added to the system during the addition of gelatin after desalting in an amount as set forth in Table 1 to effect grain formation.
Seed crystal emulsion Em-10 was prepared in the same manner as Em-1 except that Compound I-16 was added to the system shortly before the initiation of formation of shell and during the addition of gelatin after desalting in an amount as set forth in Table 1 to effect grain formation.

(Preparation of seed crystal emulsions Em-11 and Em-12)

Seed crystal emulsion Em-11 was prepared as an emulsion of tabular silver halide grains with a diameter of 0.18 µm as calculated in terms of sphere and a variation coefficient of 19% comprising grains of an aspect ratio of not less than 2.0 in a proportion of 5% of all silver halide grains as calculated in terms of projected area in the same manner as Em-1 except that the silver potential during shell formation was altered to +40 mV.
Seed crystal emulsion Em-12 was prepared in the same manner as Em-11 except that Compound I-16 was added to the system shortly before the initiation of formation of shell in an amount as set forth in Table 1.

(Preparation of Em-1-1)

An aqueous solution (1350 mℓ) containing 20 g of deionized gelatin and Em-1 which had been refrigerated for 1 day after preparation as a seed crystal emulsion in an amount of 0.03 mol as calculated in terms of silver was kept at a temperature of 75°C and the pH value thereof was adjusted to 5.5. Subsequently, an aqueous solution of silver nitrate (AgNO₃: 115 g) and an aqueous solution of halide (KI content: 2.0 mol% per KBr content) were added to the emulsion at an accelerated flow rate by a double jet process for 32 minutes so that seed crystal grains were allowed to grow at a rate close to the critical growth rate. In this process, the silver potential was kept to -25 mV with respect to saturated calomel electrode. Subsequently, an aqueous solution containing 8.0 g of potassium iodide was added to the emulsion. An aqueous solution of silver nitrate (AgNO₃: 53 g) and an aqueous solution of potassium bromide (KBr: 37 g) were then added to the emulsion by a double jet process. The resulting emulsion was then desalted by an ordinary flocculation process. To the emulsion was then added gelatin. The emulsion was then adjusted to pH 5.5 and pAg 8.8 to obtain an emulsion Em-1-1. Em-1-1 was an emulsion of tabular silver halide grains with a diameter of 0.78 µm as calculated in terms of sphere and a variation coefficient of 22% comprising grains of an aspect ratio of not less than 4.0 in a proportion of 86% of all silver halide grains contained therein as calculated in terms of projected area.

(Preparation of Em-1-2 and Em-1-3)

An emulsion Em-1-2 was prepared in the same manner as Em-1-1 except that Em-1 which had been refrigerated for 90 days after preparation was used as a seed crystal emulsion.
An emulsion Em-1-3 was prepared in the same manner as Em-1-1 except that Em-1 which had been refrigerated for 1 day after preparation and then dissolved at a temperature of 75°C for 8 hours was used as a seed crystal emulsion.
The grains in these emulsions exhibited the same properties as that in Em-1-1.

(Preparation of Em-2-1 to Em-10-1, Em-2-2 to Em-10-2, Em-2-3 to Em-10-3)

Emulsions Em-2-1 to Em-10-1 were prepared in the same manner as Em-1-1 except that Em-2 to Em-10 were used as seed crystal emulsions, respectively.
Emulsions Em-2-2 to Em-10-2 were prepared in the same manner as Em-1-2 except that Em-2 to Em-10 were used as seed crystal emulsions, respectively.
Emulsions Em-2-3 to Em-10-3 were prepared in the same manner as Em-1-3 except that Em-2 to Em-10 were used as seed crystal emulsions, respectively.
The grains in these emulsions exhibited the same properties as that in Em-1-1.

(Preparation of Em-11-1 and Em-12-1)

Emulsions Em-11-1 to Em-12-1 were prepared in the same manner as Em-1-1 except that Em-11 to Em-12 were used as seed crystal emulsions, respectively. In this process, the silver potential during the formation of grains was kept to -40 mV. Em-11-1 and Em-12-1 each was an emulsion of tabular silver halide grains with a diameter of 0.78 µm as calculated in terms of sphere and a variation coefficient of 32% comprising grains of an aspect ratio of not less than 4.0 in a proportion of 71% of all silver halide grains contained therein as calculated in terms of projected area.

(Preparation of Em-11-2, Em-11-3, Em-12-2 and Em-12-3)

Emulsions Em-11-2 and Em-12-2 were prepared in the same manner as Em-1-2 except that Em-11 to Em-12 were used as seed crystal emulsions, respectively. In this process, the silver potential during the formation of grains was kept to -40 mV.
Emulsions Em-11-3 and Em-12-3 were prepared in the same manner as Em-1-3 except that Em-11 to Em-12 were used as seed crystal emulsions, respectively. In this process, the silver potential during the formation of grains was kept to -40 mV.
The grains in these emulsions exhibited the same properties as that in Em-11-1.
The emulsions thus prepared were each subjected to gold and sulfur sensitization as follows. These emulsions were each heated to a temperature of 60°C. To these emulsions each were sequentially added a sensitizing dye A having the formula shown hereinafter, a fog inhibitor A, sodium thiosulfate, chloroauric acid, potassium thiocyanate and N,N-dimethylselenourea in amounts of 6.8 x 10^-4 mol/mol Ag, 1.2 x 10^-4 mol/mol Ag, 8.5 x 10^-6 mol/mol Ag, 1.7 x 10^-5 mol/mol Ag, 1.2 x 10^-3 mol/mol Ag and 0.5 x 10^-5 mol/mol Ag, respectively, so that they were each subjected to optimum chemical sensitization. The terminology "subjected to optimum chemical sensitization" as used herein is meant to say that the emulsion is subjected to chemical sensitization such that the sensitivity reaches the highest value when the emulsion thus chemically sensitized is exposed to light for 1/100 seconds.
On a triacetylcellulose support were coated various layers having the following formulations sequentially from the support side. Thus, Specimens 101 to 136 were prepared by using the foregoing chemically sensitized emulsions as emulsion layers.

(1) Emulsion layer

Emulsion : Various emulsions	(2.4 x 12^-2 mol/m² as calculated in terms of silver)
Coupler set fort hereinafter	(1.2 x 10^-3 mol/m²)
Tricresyl phosphate	(1.10 g/m²)
Gelatin	(2.30 g/m²)

(2) Protective layer

Sodium salt of 2,4 dichloro-6-hydroxy-S-triazine	(0.08 g/m²)
Gelatin	(1.80 g/m²)

Specimens 101 to 136 thus obtained were each then allowed to stand at a temperature of 40°C and a relative humidity of 70% for 14 hours. A part of each of these specimens was immediately subjected to the subsequent exposure and development processes. The other part of each of these specimens was stored at a temperature of 40°C and a relative humidity of 40% for 30 days and then each of the resulting specimens was subjected to the subsequent exposure and development processes. The exposure was carried out through a gelatin filter SC50 available from Fuji Photo Film Co., Ltd. and a continuous wedge for 1/100 seconds, and the color development process was carried out in the following manner.

These specimens thus processed were each measured for density by means of a green filter.

Step	Processing time	Processing temp.
Color development	2 min. 00 sec.	40°C
Blix	3 min. 00 sec.	40°C
Washing (1)	20 sec.	35°C
Washing (2)	20 sec.	35°C
Stabilization	20 sec.	35°C
Drying	50 sec.	65°C

Color developer	(unit: g)
Diethylenetriaminepentaacetic acid	2.0
1-Hydroxyethylidene-1,1-diphosphonic acid	3.0
Sodium sulfite	4.0
Potassium carbonate	30.0
Potassium bromide	1.4
Potassium iodide	1.5 mg
Hydroxylamine sulfate	2.4
4-[N-ethyl-N-β-hydroxyethylamino]-2-methylaniline sulfate	4.5
Water to make	1.0 ℓ
pH	10.05

Washing solution

Tap water was passed through a mixed bed column filled with an H type strongly acidic cation exchange resin (Amberlite IR-120B produced by Rohm & Haas) and an OH type anion exchange resin (Amberlite IR-400 produced by Rohm & Haas) so that the calcium and magnesium ion concentrations were each reduced to 3 mg/ℓ or less. To the solution were then added 20 mg/ℓ of dichlorinated sodium isocyanurate and 1.5 g/ℓ of sodium sulfate to obtain a washing solution.

The pH range of the solution was from 6.5 to 7.5.

Stabilizing solution	(unit: g)
37% Formalin	2.0 mℓ
Polyoxyethylene-p-monononyl phenyl ether (average polymerization degree: 10)	0.3
Disodium ethylenediaminetetraacetate	0.05
Water to make	1.0 ℓ
pH	5.0 - 8.5

The sensitivities of these specimens each was determined as the reciprocal of the exposure represented by lux•second giving a density of fog plus 0.2 relative to that of Specimen 101 as 100 as well as that of the specimen comprising a fresh seed crystal emulsion (i.e., the specimen represented by the Em number the numeral at the end of which was 1) as 100.
The results of evaluation of Specimens 101 to 136 are set forth in Tables 2 and 3 below.
The results set forth in Table 2 show that the emulsion preparation process according to the present invention can provide an emulsion of tabular grains having an extremely small variation of properties with different storage conditions of seed crystal emulsion, a high sensitivity and an improved preservability.

EXAMPLE 2

In the preparation of Em-1-1 of Example 1, the process was scaled up by a factor of 70 or 490. The resulting emulsions were referred to as "Em-101-1" and "Em-201-1", respectively. In these processes, apparatus of a scale enlarged by a factor of 70 and 490 (factor of 4.12 and 7.88 in length, respectively) that had been built geometrically similar with the preparation apparatus used in Example 1 were used.
For Em-10-1 of Example 1, similar scaling up was effected to obtain Em-110-1 and Em-210-1.
These emulsions were then subjected to gold and sulfur sensitization in the same manner as in Example 1. Specimens 201 to 204 were prepared from these emulsions.

These specimens were then evaluated in the same manner as in Example 1. The results are set forth in Table 3.

Specimen No.	Emulsion Used	Sensitivity	Fog	Remarks
101	Em-1-1	100	0.09	Comparative
201	Em-101-1	91	0.14	Comparative
202	Em-201-1	85	0.16	Comparative
106	Em-10-1	100	0.05	Present Invention
203	Em-110-1	103	0.04	Present Invention
204	Em-210-1	100	0.05	Present invention

The results set forth in Table 3 show that the emulsion preparation process according to the present invention can provide an emulsion of tabular grains having a small dependence on scaling up.

EXAMPLE 3

A multi-layer color light-sensitive material was prepared as Specimen 301 by coating on an undercoated cellulose triacetate film support various layers having the following compositions:

(Composition of light-sensitive layer)

Materials to be incorporated in the various layers are classified into the following categories:
ExC: cyan coupler; ExM: magenta coupler; ExY: yellow coupler; ExS: sensitizing dye; UV: ultraviolet absorbent; HBS: high boiling organic solvent; H: gelatin hardener
The coated amount of silver halide and colloidal silver is represented in g/m² as calculated in terms of silver. The coated amount of coupler, additive and gelatin is represented in g/m². The coated amount of sensitizing dye is represented in the number of moles per mole of silver halide in the same layer.

(Specimen 301)

1st layer: antihalation layer
Black colloidal silver	0.18 in terms of silver
Gelatin	1.40
ExM-1	0.18
ExF-1	2.0 x 10^-3
HBS-1	0.20

2nd layer: interlayer
Silver bromoiodide emulsion G	0.065 in terms of silver
2,5-Di-t-pentadecylhydroquinone	0.18
ExC-2	0.020
UV-1	0.060
UV-2	0.080
UV-3	0.10
HBS-1	0.10
HBS-2	0.020
Gelatin	1.04

3rd layer: low sensitivity red-sensitive emulsion layer
Silver bromoiodide emulsion A	0.30 in terms of silver
Silver bromoiodide emulsion B	0.30 in terms of silver
ExS-1	7.2 x 10^-5
ExS-2	2.2 x 10^-5
ExS-3	3.5 x 10^-4
ExC-1	0.17
ExC-3	0.030
ExC-4	0.10
ExC-5	0.020
ExC-7	0.0050
ExC-8	0.010
Cpd-2	0.025
HBS-1	0.10
Gelatin	0.87

4th layer: middle sensitivity red-sensitive emulsion layer
Silver bromoiodide emulsion D	0.68 in terms of silver
ExS-1	3.5 x 10 ^-4
ExS-2	2.0 x 10 ^-5
ExS-3	5.1 x 10 ^-4
ExC-1	0.13
ExC-2	0.060
ExC-3	0.0070
ExC-4	0.090
ExC-5	0.025
ExC-7	0.0010
ExC-8	0.0070
Cpd-2	0.023
HBS-1	0.10
Gelatin	0.75

5th layer: high sensitivity red-sensitive emulsion layer
Silver bromoiodide emulsion Em-301	1.75 in terms of silver
ExS-1	2.2 x 10^-4
ExS-2	1.3 x 10^-4
ExS-3	2.8 x 10^-4
ExC-1	0.18
ExC-3	0.045
ExC-6	0.020
ExC-8	0.025
Cpd-2	0.050
HBS-1	0.20
HBS-2	0.10
Gelatin	1.15

6th layer: interlayer
Cpd-1	0.10
HBS-1	0.50
Gelatin	1.10

7th layer: low sensitivity green-sensitive emulsion layer
Silver bromoiodide emulsion C	0.35 in terms of silver
ExS-4	3.0 x 10 ^-5
ExS-5	2.1 x 10 ^-4
ExS-6	8.0 x 10 ^-4
ExM-1	0.010
ExM-2	0.33
ExM-3	0.086
ExY-1	0.015
HBS-1	0.30
HBS-3	0.010
Gelatin	0.73

8th layer: middle sensitivity green-sensitive emulsion layer
Silver bromoiodide emulsion D	0.80 in terms of silver
ExS-4	3.2 x 10^-5
ExS-5	2.2 x 10^-4
ExS-6	8.4 x 10^-4
ExM-2	0.13
ExM-3	0.030
ExY-1	0.018
HBS-1	0.16
HBS-3	8.0 x 10^-3
Gelatin	0.90

9th layer: high sensitivity green-sensitive emulsion layer
Silver bromoiodide emulsion E	1.45 in terms of silver
ExS-4	3.7 x 10 ^-5
ExS-5	8.1 x 10 ^-5
ExS-6	3.2 x 10 ^-4
ExC-1	0.010
ExM-1	0.030
ExM-4	0.040
ExM-5	0.019
Cpd-3	0.040
HBS-1	0.25
HBS-2	0.10
Gelatin	1.44

10th layer: yellow filter layer
Yellow colloidal silver	0.030 in terms of silver
Cpd-1	0.16
HBS-1	0.60
Gelatin	0.60

11th layer: low sensitivity blue-sensitive emulsion layer
Silver bromoiodide emulsion C	0.18 in terms of silver
ExS-7	8.6 x 10^-4
ExY-1	0.020
ExY-2	0.22
ExY-3	0.50
ExY-4	0.020
HBS-1	0.28
Gelatin	1.10

12th layer: middle sensitivity blue-sensitive emulsion layer
Silver bromoiodide emulsion D	0.40 in terms of silver
ExS-7	7.4 x 10^-4
ExC-7	7.0 x 10^-3
ExY-2	0.050
ExY-3	0.10
HBS-1	0.050
Gelatin	0.78

13th layer: high sensitivity blue-sensitive emulsion layer
Silver bromoiodide emulsion F	1.00 in terms of silver
ExS-7	4.0 x 10^-4
ExY-2	0.10
ExY-3	0.10
HBS-1	0.070
Gelatin	0.86

14th layer: 1st protective layer
Silver bromoiodide emulsion G	0.20 in terms of silver
UV-4	0.11
UV-5	0.17
HBS-1	5.0 x 10^-2
Gelatin	1.00

15th layer: 2nd protective layer
H-1	0.40
B-1 (diameter: 1.7 µm)	5.0 x 10 ^-2
B-2 (diameter: 1.7 µm)	0.10
B-3	0.10
S-1	0.20
Gelatin	1.20

In order to improve the preservability, processability, pressure resistance, mildew resistance, bacteria resistance, antistatic properties, and coating properties of the material, W-1 to W-3, B-4 to B-6, F-1 to F-17, iron salt, lead salt, gold salt, platinum salt, iridium salt and rhodium salt were incorporated in the various layers.
The formulations of the silver bromoiodide emulsions A to G are set forth in Table 4 below.
In Table 4,
(1) Emulsions A to F were subjected to reduction sensitization with thiourea dioxide and thiosulfonic acid during the preparation of grains in accordance with an example in JP-A-2-191938 (corresponding to U.S. Patent 5,061,614);
(2) Emulsions A to F were subjected to gold sensitization, sulfur sensitization and selenium sensitization in the presence of the spectral sensitizing dye as set forth with reference to the various light-sensitive layers and sodium thiocyanate in accordance with an example in JP-A-3-237450 (corresponding to EP-A-443453);
(3) The preparation of tabular grains was conducted with the use of a low molecular weight gelatin in accordance with an example in JP-A-1-158426; and
(4) The tabular grains and regular crystal grains having a grain structure were observed under a high voltage electron microscope to exhibit a transition line as described in JP-A-3-237450 (corresponding to EP-A-443453).
Em-301 used in the 5th layer was an emulsion prepared in the same manner as Em-1-1 of Example 1 except that the sensitizing dye A to be used was replaced by ExS-1 in an amount of 2.2 x 10^-4 mol/mol Ag, ExS-2 in an amount of 1.3 x 10^-5 mol/mol Ag and ExS-3 in an amount of 2.8 x 10^-4 mol/mol Ag.
Specimens 302 to 309 each was prepared in the same manner as Specimen 301 except that Em-301 to be incorporated in the 5th layer was replaced by an emulsion prepared by replacing the sensitizing dye in the same manner as for Em-301 above on the basis of the emulsions for Example 1 set forth in Table 5.
The color photographic light-sensitive material specimens 301 to 309 thus prepared were exposed to light in the same manner as in Example 1, and then processed by means of an automatic developing machine in the manner shown below until the accumulated amount of replenisher of the bleaching solution reached three times the tank capacity.

(Processing method)

Step	Processing time	Processing temperature	Replenishment rate	Tank Capacity
Color development	3 min. 15 sec.	37.8°C	25 mℓ	10 ℓ
Bleach	45 sec.	38°C	5 mℓ	4 ℓ
Blix (1)	45 sec.	38°C	--	4 ℓ
Blix (2)	45 sec.	38°C	30 mℓ	4 ℓ
Washing (1)	20 sec.	38°C	--	2 ℓ
Washing (2)	20 sec.	38°C	30 mℓ	2 ℓ
Stabilization	20 sec.	38°C	20 mℓ	2 ℓ
Drying	1 min.	55°C

The blix and washing steps were effected in a countercurrent process by which the washing water flows backward from the bath (2) to the bath (1). The overflow solution from the bleaching bath was entirely introduced into the blix bath (2).
The amount of carry-over from the blix bath to the washing bath was 2 mℓ per 1 m of 35-mm wide photographic light-sensitive material specimen.
The various processing solution had the following compositions:

Color developer

	Running Solution (g)	Replenisher (g)
Diethylenetriaminepentaacetic acid	5.0	6.0
Sodium sulfite	4.0	5.0
Potassium carbonate	30.0	37.0
Potassium bromide	1.3	0.5
Potassium iodide	1.2 mg	--
Hydroxylamine sulfate	2.0	3.6
4-[N-ethyl-N-β-hydroxyethylamino]-2-methylaniline sulfate	4.7	6.2
Water to make	1.0 ℓ	1.0 ℓ
pH	10.00	10.15

Bleaching solution

	Running solution (g)	Replenisher (g)
Ammonium 1,3-diaminopropanetetraacetato ferrate monohydrate	144.0	206.0
1,3-Diaminopropanetetraacetic acid	2.8	4.0
Ammonium bromide	84.0	120.0
Ammonium nitrate	17.5	25.0
27% Aqueous ammonia	10.0	1.8
98% Acetic acid	51.1	73.0
Water to make	1.0 ℓ	1.0 ℓ
pH	4.3	3.4

Blix solution

	Running solution (g)	Replenisher (g)
Ammonium ethylenediaminetetraacetato ferrate dihydrate	50.0	---
Disodium ethylenediaminetetraacetate	5.0	25.0
Ammonium sulfite	12.0	20.0
Aqueous solution of ammonium thiosulfate (700 g/ℓ)	290.0 mℓ	320.0 mℓ
27% Aqueous ammonia	6.0 mℓ	15.0 mℓ
Water to make	1.0 ℓ	1.0 ℓ
pH	6.7	8.0

Washing solution (Common to both running solution and replenisher)

Tap water was passed through a mixed bed column filled with an H type strongly acidic cation exchange resin (Amberlite IR-120B produced by Rohm & Haas) and an OH type strongly basic anion exchange resin (Amberlite IRA-400) so that the calcium and magnesium ion concentrations were each reduced to 3 mg/ℓ or less. To the solution were then added 20 mg/ℓ of dichlorinated sodium isocyanurate and 150 mg/ℓ of sodium sulfate to obtain a washing solution. The pH range of the solution was from 6.5 to 7.5.

Stabilizing solution	(Common to both running solution and replenisher)
	(unit: g)
37% Formalin	1.2 mℓ
Surface active agent [C₁₀H₂₁-O-(CH₂CH₂O)₁₀-H]	0.4
Ethylene glycol	1.0
Water to make	1.0 ℓ
pH	5.0 - 7.0

The sensitivities of the various specimens are represented by the reciprocal of the exposure giving fog density and fog density plus 0.1 on the characteristic curve of cyan dye image relative to that of Specimens 301, 304 and 307 as 100.
These specimens were stored at a temperature of 40°C and a relative humidity of 40% for 30 days, and then evaluated in the same manner as described above. The results are set forth in Table 5.
The results set forth in Table 5 show that the photographic light-sensitive materials comprise an emulsion of tabular grains having a small variation of properties with different storage conditions of seed crystal emulsion, a high sensitivity and an improved preservability.
HBS-1: Tricresyl phosphate
HBS-2: Di-n-butyl phthalate

As mentioned above, the process for the preparation of the silver halide seed emulsion according to the present invention provides an improved producibility and exerts a remarkable effect of providing a silver halide photographic material having an excellent sensitivity/graininess ratio and improved pressure properties.
The present invention further provides that a tabular silver halide emulsion that can be prepared with a drastically improved stability at the production process. Moreover, in accordance with the present invention, a photographic light-sensitive material having a high sensitivity and an excellent preservability can be provided using such an emulsion.

Claims

A process for the preparation of a seed crystal emulsion comprising nucleation, ripening, growth and desalting/washing, said process comprising the use of at least one silver oxidizing agent selected among the compounds represented by the following Formula (I), (II) or (III): R-SO₂S-M R-SO₂S-R¹ R-SO₂S-L_m-SSO₂-R² wherein R, R¹ and R², which may be the same or different, each represents an aliphatic group, an aromatic group or a heterocyclic group; M represents a cation; L represents a divalent linking group; m represents 0 or 1; the compounds represented by the Formulae (I), (II) and (III) each may be a polymer comprising as a recurring unit a divalent group derived from the structures represented by the Formulae (I), (II) and (III), respectively; and R, R¹, R² and L may be optionally connected to each other to form a ring.
The process as claimed in claim 1, which comprises simultaneously adding an aqueous solution of a water-soluble silver salt and an aqueous solution of a halide to an aqueous solution of a low molecular weight gelatin contained in a reaction vessel, and then ripening the mixture to form tabular nuclear grains.
The process as claimed in claim 2, wherein the composition of said aqueous solution of a halide is defined by the proportion of I^- to Br^- ranging from not less than 4.5 mol% to not more than the intrinsic critical value.
The process as claimed in claim 1, which comprises simultaneously adding an aqueous solution of a water-soluble silver salt and an aqueous solution of a halide to an aqueous solution of a low molecular weight gelatin contained in a reaction vessel, and then ripening the mixture to form tabular nuclear grains.
The process as claimed in claim 4, wherein the composition of said aqueous solution of a halide is defined by the proportion of I^- to Br^- ranging from not less than 4.5 mol% to not more than the intrinsic critical value.
Use of the seed crystal emulsion prepared according to any of claims 1 to 5 for the preparation of a tabular silver halide emulsion.
Use of a compound represented by the following formulae (I), (II) or (III): R-SO₂S-M R-SO₂S-R¹ R-SO₂S-L_m-SSO₂-R² for stabilizing a seed crystal emulsion.
The process as claimed in claim 1, wherein the compound of Formula (I), (II) or (III) is added during the preparation of the seed crystal emulsion.