Abstract:
A silver halide emulsion comprises silver halide grains having a silver chloride content of not less than 10 mol % and a silver bromide content of not less than 0.1 mol % the silver halide grains being formed in the presence of at least one of compounds represented by the following Formula I: 
     Formula I 
     
       Y.sub.n1 MBr.sub.n2 X.sub.n3 
     
     wherein M represents an ion selected from the group consisting of rhenium, ruthenium, osmium, platinum, palladium, and iridium ion; Y represents a cation; X represents a ligand coordinating M; n 1  represents an integer of 0 to 3; and n 2  and n 3  each represent an integer, provided that n 2  ≧n 3  and n 2  +n 3  =4 or 6.

Description:
FIELD OF THE INVENTION 
     The present invention relates to a silver halide emulsion and a silver halide photographic light-sensitive material, and more particularly to a silver halide emulsion and a silver halide photographic light-sensitive material excellent in properties of high contrast gradation and reciprocity law failure and also excellent in latent image stability. 
     BACKGROUND OF THE INVENTION 
     Recently, rapid processing has been demanded for a light-sensitive material for a color paper in order to finish a large amount of prints in a short delivery time. As one method, there is known a method to enhance the speed of color developing by the use of a silver chloride emulsion or a silver bromochloride emulsion having a high silver chloride content as a silver halide emulsion. For example, the above-mentioned technology is disclosed in U.S. Pat. Nos. 4,183,756 and 4,225,666 and Japanese Patent Publication Open to Public Inspection (hereinafter referred to as Japanese Patent O.P.I. Publication) Nos. 26589/1980, 91444/1983, 95339/1983, 94340/1983, 95736/1983, 106538/1983, 107531/1983, 107532/1983, 107533/1983, 108533/1983 and 125612/1983. 
     However, silver chloride emulsions or silver bromochloride emulsions having a high silver chloride content have problems in that fogging is noticeable, sensitivity is low and fluctuation in sensitivity and gradation due to reciprocity law failure, namely due to exposure intensity, is great. In order to solve the above-mentioned problems, various studies have been conducted. In Japanese Patent O.P.I. Publication Nos. 139323/1976 and 171947/1984, technologies to improve processing stability and reciprocity law failure by adding compounds containing a metal in the 8th group of the periodic table are disclosed. 
     However, the above-mentioned technologies are not sufficient to solve the above-mentioned problems on silver chloride or silver halide having a high silver chloride content. In addition, in Japanese Patent O.P.I. Publication No. 183647, a technology to enhance sensitivity, to improve reciprocity law failure and also to improve fluctuation of sensitivity and gradation caused by a change of temperature in exposure is disclosed. 
     It is commonly known that doping of iridium compounds is effective for improvement in reciprocity law failure of silver halide emulsions. In Japanese Patent O.P.I. Publication No. 4935/1968, a technology to obtain small fluctuation in terms of gradation in a wide range of exposure time by adding an iridium compound when preparing silver halide grains is disclosed. In addition, there is disclosed a technology to improve sensitivity law failure by removing iridium from the surface of silver halide grains in U.S. Pat. No. 4,997,751. 
     While most of the above-mentioned problems were solved by the above-mentioned technologies, there still remains a problem that change in sensitivity is great (latent image stability is poor) depending upon intervals of time between exposure and processing. Especially, it is disclosed by Twickey in Journal of Photographic Science Volume 33, p 201 that a technology to dope an iridium compound known as a compound for improving reciprocity law failure noticeably deteriorates latent image stability at an initial stage after exposure, though the problem of reciprocity law failure is surely solved. Therefore, it is not desirable practically. In Japanese Patent O.P.I. Publication No. 135832/1980, it is disclosed that high sensitivity and improvement in reciprocity law failure can be achieved by doping cadmium, lead, copper and zinc. However, according to the study of the present inventors, it has been found that enhancement in high sensitivity and improvement in reciprocity law failure cannot be achieved concurrently and that initial latent image stability is deteriorated. 
     In Japanese Patent O.P.I. Publication No. 188437/1991, a technology to improve reciprocity law failure and to reduce fluctuation in developing density caused by the period of time from exposure to processing by adding an iridium compound and an iron compound on the surface layer side by 50% or more of grain volume. However, according to the study of the present inventors, it is found that problems still remain practically in that gradation fluctuates due to the period of time from exposure to processing while reciprocity law failure is improved when employing the above-mentioned technologies and that contrast is lowered due to inactive processing. 
     In Japanese Patent O.P.I. Publication No. 105940/1991, a technology to improve initial latent image stability by doping iridium in a specific region is disclosed. However, further improvement is necessary thereto. In the above-mentioned technology, there is no description about an iridium compound having a bromide ligand. The compound employed is K 3  IrCl 6 . In Japanese Patent O.P.I. Publication No. 9034/1992, K 3  IrCl 6  is employed in a pure silver chloride emulsion not containing bromide ion in a comparative example of the Examples. It is very undesirable, being poor in latent image stability and having low contrast compared with K 3  IrCl 6  employed in a comparative example in the same manner. 
     According to our study, it was found that emulsions containing bromide ion by the use of K 3  IrBr 6  have especially excellent latent image stability. In addition, though Japanese Patent O.P.I. Publication discloses an iridium compound having a chloride ligand, no description about a bromide ligand is observed at all. 
     In addition, when iridium compounds having a chloride ligand are employed, it was found that silver chloride, especially having a high silver chloride content ratio, and silver bromochloride are not desirable because they cause tailing phenomenon (a phenomenon wherein density is enhanced slightly on the amount of exposure at an extremely low exposure region) producing blurred photography. 
     Studies for employing polyvalent metal compounds in a silver halide emulsion have long been tried. In Basis for Photography edited by Japan Photographic Society, published by CORONA PUBLISHING CO., LTD, 1978 on page 545, a technology is given to dope Cd 2+ , Pd 2+ , Cu 2+  or trivalent metal in order to produce electron trap. In Research Disclosure Journal Volume 176 (December of 1978) RD-17643, a technology is given to prepare a direct print emulsion in the presence of tin, lead, copper, cadmium, bismuth, magnesium, rhodium and iridium. U.S. Pat. No. 3,923,513 describes that 4-valent ions such as lead, antimony, bismuth, arsenic, gold, iridium, rhodium, platinum, osmium and iridium are useful for internal-image emulsions described therein. Japanese Patent O.P.I. Publication No. 285941/1989 describes preventing fluctuation in sensitivity and gradation caused by a period of time by the aquation of noble metals of the 8th group. Japanese Patent O.P.I. Publication No. 56238/1990 describes composition distribution of AgCl and metals of the 8th group. Japanese Patent O.P.I. Publication No. 20852/1990 describes silver halide emulsions containing a complex of transition metals having a nitrosyl or thionitrosyl ligand. Japanese Patent O.P.I. Publication No. 20853/1990 describes enhancement of sensitivity achieved by the use of osmium, iridium, rhenium and ruthenium complexes having a cyano ligand. Japanese Patent O.P.I. Publication No. 20855/1990 describes a technology to change the properties of emulsion by adding face-centered cubic grains and Re compound into a silver halide emulsion, wherein the problem of reciprocity law failure at low intensity is reduced by adding rhenium pentabromide complex into a silver bromide emulsion or a silver bromoiodide emulsion. 
     However, despite the above-mentioned technologies, a satisfactory emulsion in terms of high-contrast gradation property, reciprocity law failure and initial latent image stability has not been obtained. 
     SUMMARY OF THE INVENTION 
     An object of the present invention is to provide a silver halide emulsion and a silver halide photographic light-sensitive material excellent in high-contrasted gradation property and reciprocity law failure and also excellent in latent image stability. 
     The above-mentioned objects of the present invention are attained by a silver halide emulsion or a silver halide photographic light-sensitive material of the following items (1) to (3). 
     (1) A silver halide emulsion comprising silver halide grains having a silver chloride content of not less than 10 mol % and a silver bromide content of not less than 0.1 mol %, wherein the silver halide grains contain at least one kind of compound represented by the following Formula I inside of or on the surface of the grains, or the silver halide grains are formed in the presence of the compound. 
     Formula I 
     
         Yn.sub.1 MBrn.sub.2 Xn.sub.3 
    
     wherein M represents an ion selected from the group consisting of a rhenium, ruthenium, osmium, platinum, palladium, and iridium ion; Y represents a cation; X represents a ligand coordinating M; n 1  represents an integer of 0 to 3; and n 2  and n 3  each represent an integer, provided that n 2  ≧n 3  and n 2  +n 3  =4 or 6. 
     (2) The silver halide emulsion described in item (1) subjected to gold sensitization or gold sulfur sensitization. 
     (3) A silver halide photographic light-sensitive material containing a silver halide emulsion described in items (1) or (2). 
     Hereunder, we will explain the present invention in detail. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     In the present invention, in order to produce silver halide grains in the presence of a compound represented by Formula I (hereinafter referred to as &#34;compound I&#34;), there is means to add compound I to a kettle before the grains are produced or means to add compound I consecutively or at one time while the grains are being produced. It is preferable that compound I is contained in the silver halide grains. 
     The silver halide grains of the present invention are preferably silver bromochloride grains substantially not containing iodide. In addition, the silver chloride content of the silver halide grains is preferably not less than 95 mol % and not more than 99.9 mol %, and more preferably 98-99.9 mol % and most preferably 99.3% to 99.9 mol %. The silver bromide content is preferably 0.1-2.0 mol %, and more preferably, 0.1-0.7 mol %. 
     Silver halide grains of the present invention may have a uniform composition or localized phase of silver bromide on the surface or inside thereof. Silver halide emulsions of the present invention may contain silver halide grains other than silver halide grains of the present invention. 
     In addition, in a silver halide emulsion layer containing silver halide grains having a silver chloride content of not less than 90 mol %, the ratio of silver halide grains having a silver chloride content of not less than 90 mol % to the total silver halide grains contained in aforesaid emulsion layer is preferably not less than 60 mol % and more preferably not less than 80 mol %. 
     There is no limitation to the grain diameter of a silver halide grain. However, considering rapid processing property, sensitivity and other photographic properties, it is preferably 0.2-1.6 μm and more preferably 0.25-1.2 μm. The grain diameter of the above-mentioned grains can be measured by various methods employed ordinarily in the art. Typical ones are described in Analysis Methods for Grain Diameter (A.S.T.M. Symposium on Light Microscopy, 1955, pp. 94-122) or 2nd chapter in Theory of Photographic Process (Written by Mees and James, 3rd edition, published by MacMillan Publishing Co., Inc. (1966). 
     The grain diameter of silver halide grains can be calculated by the use of the projected area of grains or the approximate value thereof. 
     When the shape of grains is substantially uniform, grain distribution can be represented almost exactly by the use of a diameter or a projected area. Grain distribution of silver halide grains is poly-dispersed or mono-dispersed. Preferable is a mono-dispersed silver halide having variation coefficient of not more than 0.22 in grain distribution of silver halide grains and more preferable is one having a variation coefficient of not more than 0.15. Here, variation coefficient represents a coefficient indicating a width of the distribution of the grain diameter, and it is defined by the following. 
     Variation coefficient=S/R 
     (S represents the standard deviation of grain diameter distribution and R represents an average grain diameter.) 
     wherein grain diameter is referred to as a diameter in the case of spherical silver halide grains, and a diameter when the projection of grains is converted to a sphere having the same area when the form of grains is cubic or other than spherical. 
     For an apparatus and a method for preparing silver halide emulsions, various kinds of conventional methods can be employed. 
     Silver halide emulsions of the present invention may be prepared by either of an acid method, a neutrality method or an ammonium method. Aforesaid grains may be grown at one time or may be grown after preparing seed grains. A method of preparing seed grains and a method of growing them may be the same or different. 
     As a method to react soluble silver halide and soluble chalogenized salt, any of a normal precipitation method, a reverse precipitation method, a simultaneous precipitation method and combinations thereof may be employed. Of them, a simultaneous precipitation method is preferable. In addition, as a style of a simultaneous precipitation method, the pAg controlled double jet method described in Japanese Patent O.P.I. Publication No. 48521/1979 can be employed. 
     In addition, an apparatus to feed aqueous solutions containing hydrophilic silver salt and hydrophilic chalogenized substance salt from an apparatus placed in a reacting initial liquid described in Japanese Patent O.P.I. Publication Nos. 92523/1982 and 92524/1982, an apparatus described in German Patent No. 2921164 wherein the density of hydrophilic silver salts and hydrophilic halogenized substance salt aqueous solutions are consecutively changed for addition and an apparatus described in Japanese Patent Publication No. 501776/1981 for forming grains while keeping distance between silver halide grains constant by taking out the reacting initial liquid from the reactor and condensing it by the use of an ultra-filtration method. 
     In addition, if necessary, silver halide solvents such as thioether may be employed. In addition, compounds having a mercapto group, nitrogen-containing heterocyclic compounds or sensitizing dyes may be added to silver halide grains when they are formed or after formation of grains is finished. 
     An arbitrary form of silver halide grains of the present invention may be employed. One preferable example is a cube having {100} plane as a crystal surface. In addition, grains having octahedral, tetradecahedral or dodecahedral forms can be prepared by the use of methods described in U.S. Pat. Nos. 4,183,756 and 4,225,666 and Japanese Patent O.P.I. Publication No. 26589/1980, Japanese Patent Publication No. 42737/1980 and The Journal of Photographic Science (J. Photogr. Sci) 21,39 (1973). In addition, grains having a twinned crystal may be employed. 
     For silver halide grains of the present invention, a uniform shape of grains may be employed, or grains wherein various shapes are mixed may also be employed. 
     In the present invention, metal ions can be added inside silver halide grains and/or on the surface thereof by the use of cadmium salt, zinc salt, lead salt or their complex salts, rhodium salt or its complex salts or iridium salts or its complex salt not in the present invention in the course of forming silver halide grains and/or in the course of growing them. In addition, by inserting silver halide grains in an appropriate reductive solution, reductive sensitization nuclei can be provided thereto inside of or on the surface of grains. 
     Unnecessary soluble salts can be removed from an emulsion containing silver halide grains after the growth of silver halides has finished, or the above-mentioned emulsion is allowed to keep containing them. When removing aforesaid salts, they can be removed by a method described in Research Disclosure No. 17643. 
     Silver halide grains employed in an emulsion of the invention may be grains wherein latent images are formed on the surface thereof or may be grains wherein they are formed inside the grains. Of them, the most preferable are surface-latent-image-forming type silver halide grains wherein latent images are mainly formed on the surface thereof. 
     In addition, an emulsion can be sensitized optically to a desired wavelength region by employing a sensitizing dye. As sensitizing dyes, cyanine dyes, merocyanine dyes, complex cyanine dyes, complex merocyanine dyes, horocyanine dyes, hemicyanine dyes, styryl dyes and hemioxanol dyes can be employed. 
     Silver halide emulsions employed in the present invention can be sensitized by the use of a sensitization method employing a reductive substance, a sensitization method employing chalcogen sensitizer and a sensitization method employing noble metal compounds. The above-mentioned sensitization methods can be employed in combination. Of them, sulfur sensitization, gold sensitization and gold-sulfur sensitization which is a combination thereof are especially preferable for the present invention. 
     Chalcogen sensitizers applicable to silver halide emulsions employed in the present invention include sulfur sensitizers, selenium sensitizers and tellurium sensitizers. Of them, sulfur sensitizers are preferable. As a sulfur sensitizer, thiosulfate salt, arylthiocarbamydo thiourea, arylisothiacyanate, cystine, p-toluenethiosulfonic acid salt and rhodanine are cited. 
     Compounds represented by Formula I of the present invention are those called ordinarily complex salts or complex. Among metals represented by M in Formula I, preferable are iridium, palladium and platinum. The more preferable is iridium. Ligand represented by X is halogen, H 2  O, amine or OH. 
     Hereunder, we will illustrate examples of compounds represented by Formula I. However, the present invention is not limited thereto. 
     (1) K 3  RuBr 6 , (2) K 2  RuBr 6 , (3) Na 3  RuBr 6 , (4) Na 2  RuBr 6 , (5) K 3  RuBr 4  Cl 2 , (6) K 2  RuBr 4  Cl 2 , (7) K 2  RuBr 3  Cl 3 , (8) K 3  RuBr 3  Cl 3 , (9) K 3  RuBr 5  Cl, (10) K 2  RuBr 5  Cl 1 , (11) K 3  RuBr 5  (H 2  O), (12) K 3  RuBr 5  (H 2  O) 2 , (13) K 3  RuBr 5  I, (14) K 2  RuBr 5  I, (15) K 3  IrBr 6 , (16) K 2  IrBr 6 , (17) Na 3  IrBr 6 , (18) Na 2  IrBr 6 , (19) K 3  IrBr 4  Cl 2 , (20) K 2  IrBr 4  Cl 2 , (21) K 2  IrBr 3  Cl 3 , (22) K 3  IrBr 3  Cl 3  , (23) K 3  IrBr 5  Cl, (24) K 2  IrBr 5  Cl 1  (25) K 3  IrBr 5  (H 2  O), (26) K 3  IrBr 5  (H 2  O) 2 , (27) K 3  IrBr 5  I, (28) K 2  IrBr 5  I, (29) K 3  OsBr 6 , (30) K 2  OsBr 6 , (31) Na 3  OsBr 6 , (32) Na 2  OsBr 6 , (33) K 3  OsBr 4  Cl 2 , (34) K 2  OsBr 4  Cl 2 , (35) K 2  OsBr 3  Cl 3 , (36) K 3  OsBr 3  Cl 3 , (37) K 3  OsBr 5  Cl, (38) K 2  OsBr 5  Cl 1 , (39) K 3  OsBr 5  (H 2  O), (40) K 3  OsBr 5  (H 2  O) 2 , (41) K 3  OsBr 5  I, (42) K 2  OsBr 5  I, (43) K 3  ReBr 6 , (44) K 2  ReBr 6 , (45) Na 3  ReBr 6 , (46) Na 2  ReBr 6 , (47) K 3  ReBr 4  Cl 2 , (48) K 2  ReBr 4  Cl 2 , (49) K 2  ReBr 3  Cl 3 , (50) K 3  ReBr 3  Cl 3 , (51) K 3  ReBr 5  Cl, (52) K 2  ReBr 5  Cl 1 , (53) K 3  ReBr 5  (H 2  O), (54) K 3  ReBr 5  (H 2  O) 2 , (55) K 3  ReBr 5  I, (56) K 2  ReBr 5  I, (57) K 2  PdBr 4 , (58) K 2  PdBr 6 , (59) Na 2  PdBr 4 , (60) K 2  PtBr 4 , (61) K 2  PtBr 6   
     As a noble metal sensitizer applicable to silver halide emulsions employed in the present invention, gold sensitization is preferable. In a gold sensitizer, the number of oxidation of gold is allowed to be mono-valent or tri-valent. Chloroaurate and potassium chloroaurate are allowed to be employed. 
     It is common that dye-forming couplers employed for silver halide photographic light-sensitive materials of the present invention are selected in the manner that, in each emulsion layer, dyes which absorb light-sensitive spectral light and sensitize aforesaid emulsion are formed. To blue sensitive emulsion layers, yellow dye forming couplers are employed. To green sensitive emulsion layers, magenta dye forming couplers are formed. To red sensitive emulsion layer, cyan dye forming couplers are employed. However, depending upon the purpose, silver halide color photographic light-sensitive materials may be prepared through a combination different from the combination described above. 
     To light-sensitive materials of the present invention, anti-color fogging agents, image stabilizers, hardeners, plasticizers, anti-irradiation dyes, polymer latex, UV absorbers, formalin scavengers, development accelerators, fluorescent brightening agents, matting agents, lubricants, anti-static agents and surfactants can arbitrarily be added. The above-mentioned compounds are described in Japanese Patent O.P.I. Publication Nos. 215272 and 46436. The light-sensitive materials of the present invention can form images by being subjected to conventional color developing. 
     EXAMPLES 
     Hereunder, we will show examples of the present invention. However, the present invention is not limited thereto. 
     Example 1 
     To 1000 ml of 2% aqueous gelatin solution kept at 40° C., Solution A and Solution B mentioned below were added simultaneously in 30 minutes while controlling pAg to 6.5 and pH to 3.0. Next, Solution C and Solution D were added simultaneously in 120 minutes while controlling pAg to 7.3 and pH to 5.5. In this case, pAg was controlled by the use of a method described in Japanese Patent O.P.I. Publication No. 45437/1984, and pH was controlled employing sulfuric acid and an aqueous sodium hydroxide solution. 
     
         ______________________________________(Solution A)Sodium chloride           3.42 gPotassium bromide         0.03 gWater was added to make 200 ml.(Solution B)Silver nitrate            10 gWater was added to make 200 ml.(Solution C)Sodium chloride           78.7 gPotassium bromide         0.157 gWater was added to make 446 ml.(Solution D)Silver nitrate            190 gWater was added to make 380 ml.______________________________________ 
    
     The resulting solution was subjected to desalting employing a 10% aqueous solution of Demol N produced by Kao Atlas and a 30% aqueous solution of magnesium sulfate. Next, the mixed solution was mixed with a gelatin aqueous solution. Thus, a mono-dispersed cubic silver halide emulsion EMP-1 having an average grain diameter of 0.40 μm, variation coefficient (standard deviation/average grain diameter) of 0.07 and a silver chloride content of 99.9 mol % was prepared. 
     EMP-1 was subjected to the most suitable sensitization employing the following compounds at 65° C. so that a green sensitive silver halide emulsion Em-1 was prepared. 
     Sodium thiosulfate 1.5 mg/mol of AgX 
     Stabilizer SB-1 6×10 -4  mol/AgX 
     Sensitizing dye GS-1 3×10 -4  mol/AgX ##STR1## 
     Next, silver halide emulsion Em-2 was prepared in the same way as in Em-1 except that a compound I-(16) in quantity of 1×10 -8  mol per mol of silver was added to Solution C. 
     Emulsions shown in Table 2 were prepared employing exemplified compounds shown in Table 2 in place of Compound I-(16) which was added to Em-2. In addition, emulsions shown in Table 2 were prepared as comparative samples employing the following compounds IR-1 to IR-6 in place of Compound I-(16) of Em-2. 
     IR-1 : K 2  IrCl 6   
     IR-2 : K 2  ReCl 6   
     IR-3 : K 3  [RuCl 5  NO] 
     IR-4 : K 2  PtCl 4   
     IR-5 : K 2  PdCl 4   
     IR-6 : K 2  OsCl 6   
     Each of the following layer was coated on a support wherein polyethylene is contained on one side of a support and titanium oxide was coated on the other side (a side on which photographic structural layers were coated) of a support so that Sample No. 101 was prepared. 
     
                       TABLE 1______________________________________                      Amount of addingLayer    Additive          (g/m.sup.2)______________________________________Second layer    Gelatin           1.0First layer    Em-1              0.36 in conversion(Green                         to silver amountsensitive)    Magenta coupler (MM-1)                      0.35    Dye image stabilizer (ST-3)                      0.15    Dye image stabilizer (ST-4)                      0.15    Dye image stabilizer (ST-5)                      0.15    TOP               0.2Support  Polyethylene laminated    paper______________________________________ 
    
     Incidentally, H-1 was added to the second layer as a hardener. 
     H-1 
     
         C(CH.sub.2 SO.sub.2 CH═CH.sub.2).sub.4 
    
     Samples Nos. 102 to 114 were prepared in the same manner as in Sample No. 101 except that Em-2 to Em-14 were employed respectively in place of Em-1 of Sample No. 101. 
     Properties of samples obtained in the above-mentioned manner were evaluated under the following method. Table 2 shows the results thereof. 
     (1) Sensitometry 
     Samples were subjected to wedge exposure to green light for 0.05 seconds, and then subjected to color developing under the following processing steps. Then, their densities were measured employing an optical densitometer (Model PDA-65,  produced by Konica), and the sensitivity thereof was represented by a logarithm of an inverse of the exposure amount necessary for obtaining a density higher than fog density by 0.8. Incidentally, gradation γ 2  is represented by an inverse of the difference of exposure amount between a density higher than fog density by 0.2 and a density higher than fog density by 0.7. 
     (2) Reciprocity Law Failure 
     Samples were subjected to wedge exposure to green light for 10 seconds so that the exposure amount was the same as above, and then, subjected to the sensitometry in the same manner as above. Sensitivity of each sample was represented by relative sensitivity when the sensitivity obtained under the 0.05 second exposure was defined to be 100. 
     (3) Fog Density 
     Unexposed samples were subjected to color developing. The density thereof was measured employing an optical densitometer (Model PDA-65, produced by Konica). 
     (4) Latent Image Stability 
     The densities of a sample subjected to developing 10 seconds after exposure with green light and a sample subjected to developing 5 minutes after exposure with green light respectively were measured employing a densitometer Model PDA-65 produced by Konica. Then, the difference Δγ 2  between gradation obtained when a sample was developed 5 minutes after exposure and that obtained when a sample was developed 10 seconds after exposure was calculated. 
     Δγ 2  =γ 2  (developed 5 minutes after exposure)-γ 2  (developed 10 seconds after exposure) 
     γ 2  : Inverse of the difference of exposure amount between the density higher than fog density by 0.2 and the density higher than fog density by 0.7. 
     Processing conditions employed for evaluation were as follows. 
     
         ______________________________________Processing step Temperature                      Time______________________________________Color developing           35 ± 0.3° C.                      45 secondsBleach-fixing   35 ± 0.5° C.                      45 secondsStabilizing      30 - 34° C.                      90 secondsDrying           60 - 80° C.                      60 seconds______________________________________Color developerPure water                  800    mlTriethanol amine            10     gN,N-diethylhydroxylamine    5      gPotassium bromide           0.02   gPotassium chloride          2      gPotassium sulfite           0.3    g1-hydroxyethylidene-1,1-diphosphate                       1.0    gEthylenediaminetetraacetate 1.0    gDisodium catecol-3,5-diphosphate                       1.0    gN-ethyl-N-β-methanesulfonamidoethyl-3-methyl-4-                       4.5    gaminoaniline sulfateFluorescent brightening agent (4,4&#39;-                       1.0    gdiaminostylbenzsulfonic acid derivative)Potassium carbonate         27     gWater is added to make 1 l in total,and pH is regulated to 10.10.Bleach-fixerAmmonium ferric ethylenediamine tetraacetic                       60     gacid bihydrateEthylenediamine tetraacetic acid                       3      gAmmonium thiosulfate (70% aqueous solution)                       100    mlAmmonium sulfite (40% aqueous solution)                       27.5   mlWater was added to make 1 l in total, and pH wasregulated with potassium carbonate or glacial acetate.Stabilizer5-chloro-2-methyl-4-isothiazoline-3-on                       1.0    gEthyleneglycol              1.0    g1-hydroxyethylidene-1,1-diphosphate                       2.0    gEthylenediaminetetraacetate 1.0    gAmmonium hydroxide (20% aqueous solution)                       3.0    gFluorescent brightening agent (4,4&#39;-                       1.5    gdiaminostylbenzsulfonic acid derivative)Water was added to make 1 l in total, and pH wasregulated to 7.0 with sulfuric acid or potassiumhydroxide.______________________________________ 
    
     
                                           TABLE 2__________________________________________________________________________                       Reciprocity                             Latent imageSample    Emulsion    Compound I           Sensitivity                 Gradation                       law failure                             stability                                    Note__________________________________________________________________________101 Em-1 --     100   1.4   66    +0.02  Comp.102 Em-2 I-(16) 78    2.4   78    +0.02  INV.103 Em-3 I-(6)  75    2.0   72    +0.03  INV.104 Em-4 I-(44) 79    1.9   75    +0.04  INV.105 Em-5 I-(1)  80    2.0   71    +0.04  INV.106 Em-6 I-(30) 82    1.8   75    +0.04  INV.107 Em-7 I-(60) 78    2.1   76    +0.03  INV.108 Em-8 I-(59) 82    2.2   78    +0.03  INV.109 Em-9 IR-1   78    1.8   78    +0.08  Comp.110  Em-10    IR-2   76    1.9   73    +0.05  Comp.111  Em-11    IR-3   80    1.7   74    +0.07  Comp.112  Em-12    IR-4   78    1.9   73    +0.05  Comp.113  Em-13    IR-5   82    1.8   74    +0.04  Comp.114  Em-14    IR-6   84    1.8   76    +0.05  Comp.__________________________________________________________________________ Comp.: Comparative Inv.: Invention 
    
     As is apparent from Table 2, samples employing a bromide ligand could obtain extremely high-contrasted emulsions. In addition, it was found that their reciprocity law failure and latent image stability were excellent. Samples containing an iridium compound had defects in that sensitivity and latent image stability were deteriorated, though the reciprocity law failure was improved. On the contrary, it was found that, in the case of Sample 102 of the present invention, the reciprocity law failure was improved and latent image stability was rarely deteriorated compared with Sample 108. 
     Example 2 
     Emulsions were prepared in the same manner as in Em-2 and Em-9 of Example 1 except that sodium thiosulfate, sodium chloroaurate and SB-1 was employed in chemical sensitization, and were defined to be Em-15 and Em-16, respectively. 
     Samples wherein Em-15 and Em-16 were coated in the same manner as in Em-1 respectively were defined to be Sample 115 and Sample 116. These samples were subjected to evaluation in the same manner as in Example 1. Table 3 shows the results thereof. 
     
                                           TABLE 3__________________________________________________________________________    Sodium         Sensi- Reciprocity                                Latent imageSample    Emulsion    chloroauric acid            Compound I                   tivity law failure                                stability                                       Note__________________________________________________________________________102 Em-2 no      I-(16)  78    78    +0.02  INV.115 Em-15    yes     I-(16) 189    80    +0.03  INV.109 Em-9 no      --      78    78    +0.08  Comp.116 Em-16    yes     --     190    81    +0.43  Comp.__________________________________________________________________________ Inv.: Invention Comp.: Comparative 
    
     Sample 116 subjected especially to sodium chloroaurate sensitization was so excellent in high sensitivity as to be superior to Sample 119. However, it was found that it has problems that reciprocity law failure and latent image stability are deteriorated. However, with regard to Sample 115 in the present invention, it was found that it has high sensitivity and extremely improved latent image stability though the reciprocity law failure is slightly deteriorated. 
     Example 3 
     In preparing EMP-1 of Example 1, time of addition for Solution A and Solution B and time of addition for Solution C and Solution D were modified so that a mono-dispersed cubic emulsion having an average grain diameter of 0.71 μm (length of one side of cubic), variation coefficient of 0.07 and a silver halide content ratio of 99.9 mol % was prepared. This emulsion was sensitized most appropriately at 65° employing sodium thiosulfate of 0.8 mg/molAgX, SB-1 of 6×10 -4  mol/mol AgX and sensitizing dye BS-1 of 4×10 -4  mol/mol AgX. The resulting emulsion was defined to be EMP-2. ##STR2## 
     Emulsions the same as EMP-2 except that I-16 or IR-1 were added respectively to 1×10 -8  mol/mol AgX of Solution C. The resulting emulsion were defined to be Em-17 and Em-18, respectively. 
     Emulsions the same as Em-17 and Em-18 except that 1.5 mg/mol AgX of sodium chloroaurate was added for sensitization were prepared. The resulting emulsions were defined to be Em-19 and Em-20. 
     A mono-dispersed cubic emulsion having an average grain diameter of 0.52 μm (in terms of a length of one side of cubic), variation coefficient of 0.07 and silver chloride content ratio of 99.9 mol % was prepared in the same manner as in EMP-1 of Example 1 except that the time of addition for Solution A and Solution B and the time of addition for Solution C and Solution D were changed. This emulsion was subjected to the most suitable sensitization at 67° C. by the use of 2.0 mg/mol AgX of sodium thiosulfate, 7×10 -4  mol/mol AgX of SB-1 and 7×10 -5  mol/mol AgX of sensitization dye RS-1. The resulting emulsion was defined to be EMP-3. ##STR3## 
     Emulsions the same as EMP-3 except that 1×10 -8  mol/mol AgX of I-16 and IR-1 were respectively added to Solution C were prepared. The resulting emulsions were defined to be Em-21 and Em-22. 
     Emulsions the same as Em-21 and Em-22 except that 0.3 mg/mol AgX of sodium chloroaurate was added were prepared. The resulting emulsions were defined to be Em-23 and Em-24. 
     On a paper support wherein polyethylene was laminated on one side thereof and polyethylene containing titanium oxide was laminated on the other side (on which photographic structural layers were coated), there were coated layers having the following constitution so that multi-layer silver halide color photographic light-sensitive material 201 was prepared. 
     The coating solution was prepared as follows. 
     First Layer Coating Solution 
     To 26.7 g of Yellow coupler Y-1, 10.0 g of Dye image stabilizer ST-1, 6.67 g of ST-2, 0.67 g of Additive HQ-1 and 6.67 g of high boiling organic solvent DNP, 60 ml of ethyl acetate was added to obtain a solution. The solution was emulsified and dispersed into 220 ml of 10% aqueous gelatin solution containing 7 ml of 20% surfactant SU-1. Thus, Yellow coupler dispersion solution was prepared. To this dispersion solution, anti-mildew agent F-1 was added. This dispersion solution was mixed with a blue sensitive silver halide emulsion (containing 8.67 g of silver) prepared under the following conditions so that Coating solution for the first layer was prepared. 
     Coating solutions for 2nd layer to 7th layer were prepared in the same manner as in the above-mentioned Coating solution for the 1st layer. In addition, H-2 was added to 2nd layer and 4th layer and H-1 was added to 7th layer as hardeners. As coating aids, Surfactants $U-2 and SU-3 were added for regulating surface tension. Tables 4 and 5 show the constitution of the above-mentioned each layer. 
     
                       TABLE 4______________________________________                         Amount ofLayer     Constitution        adding (g/m.sup.2)______________________________________Seventh layer     Gelatin             1.00(Protective)Sixth layer     Gelatin             0.40(UV absorbing)     UV absorber (UV-1)  0.10     UV absorber (UV-2)  0.04     UV absorber (UV-3)  0.16     Anti stain agent (HQ-1)                         0.01     DNP                 0.20     PVP                 0.03     Anti irradiation dye (AIC-1)                         0.02Fifth layer     Gelatin             1.30(Red sensitive)     Red sensitive silver                         0.21     bromochloride emulsion (Em-R)     Cyan coupler (EC-1) 0.24     Cyan coupler (EC-2) 0.08     Dye image stabilizer (ST-1)                         0.20     Anti stain agent (HQ-1)                         0.01     HBS-1               0.20     DOP                 0.20Fourth layer     Gelatin             0.94(UV absorbing)     UV absorber (UV-1)  0.28     UV absorber (UV-2)  0.09     UV absorber (UV-3)  0.88     Anti stain agent (HQ-1)                         0.03     DNP                 0.40______________________________________ 
    
     
                       TABLE 5______________________________________                         Amount ofLayer     Constitution        adding (g/m.sup.2)______________________________________Third layer     Gelatin             1.40(Green    Green sensitive silver                         0.17sensitive)     bromochloride emulsion (Em-G)     Magenta coupler (MM-1)                         0.35     Dye image stabilizer (ST-3)                         0.15     Dye image stabilizer (ST-4)                         0.15     Dye image stabilizer (ST-5)                         0.15     DNP                 0.20     Anti-irradiation dye (AIM-1)                         0.01Second layer     Gelatin             1.20(Intermediate)     Anti-stain agent (HQ-2)                         0.03     Anti-stain agent (HQ-3)                         0.03     Anti-stain agent (HQ-4)                         0.05     Anti-stain agent (HQ-5)                         0.23     DIDP                0.06     Anti-mildew agent (F-1)                         0.002First layer     Gelatin             1.2(Blue sensitive)     Blue sensitive silver     bromochloride emulsion (Em-B)                         0.26     Yellow coupler (YY-1)                         0.80     Dye image stabilizer (ST-1)                         0.30     Dye image stabilizer (ST-2)                         0.20     Anti-stain agent (HQ-l)                         0.02     Anti-irradiation dye (AIY-1)                         0.01     DNP                 0.20Support   Polyethylene laminated paper______________________________________ *Added amounts of silver halide emulsion were represented in terms of silver. ##STR4## 
    
     Samples 202 to 204 were prepared in the same manner as in Sample 201 except that emulsions used for each light-sensitive silver halide layers were replaced as shown in Table 6. 
     
                                           TABLE 6__________________________________________________________________________Emulsion layer     Compound of the present    Blue Green         Red  invention I or                            SensitizationSample    sensitive    sensitive         sensitive              comparative compound (IR)                            chloroauric acid__________________________________________________________________________201 Em-17    Em-2 Em-21              I-(16)        no202 Em-18    Em-1 Em-22              IR-1          no203 Em-19    Em-15         Em-23              I-(16)        yes204 Em-20    Em-16         Em-24              IR-1          yes__________________________________________________________________________ 
    
     The resulting samples were subjected to exposure and processing in the same manner as in Example 1 except that the color of filter used in exposure was changed to blue, green and red. They were subjected to evaluation in the same manner as in Example 1. Incidentally, sensitivity was represented by a relative sensitivity when the sensitivity of Sample 201 was defined to be 100. Table 7 shows the results thereof. 
     
                                           TABLE 7__________________________________________________________________________             Reciprocity                    Latent imageSample        Speed             law failure                    stability                           Gradation                                 Note__________________________________________________________________________201   Blue sensitive layer         100 81     +0.02  2.25  Inv.   Green sensitive layer         100 78     +0.02  2.30   Red sensitive layer         100 79     +0.03  2.22202   Blue sensitive layer          98 82     +0.04  1.45  Comp.   Green sensitive layer          98 80     +0.04  1.50   Red sensitive layer         100 81     +0.05  1.34203   Blue sensitive layer         220 79     +0.03  2.11  Inv.   Green sensitive layer         224 80     +0.03  2.2   Red sensitive layer         218 80     +0.02  2.32204   Blue sensitive layer         217 82     +0.42  1.85  Comp.   Green sensitive layer         226 82     +0.44  1.8   Red sensitive layer         224 86     +0.40  1.75__________________________________________________________________________ Inv.: Invention Comp.: Comparative 
    
     From Table 7, it is found that multi-layer silver halide color light-sensitive material of the present invention can offer noticeable effects. It is especially found that Sample 203 subjected to chemical sensitization by the use of sodium chloroaurate is remarkably excellent in terms of latent image stability compared with Sample 204 subjected to sensitization in the same manner. 
     Namely, it was found that the present invention can offer samples having high sensitivity and satisfactory reciprocity law failure and latent image stability when samples are chemically sensitized by the use of sodium chloroaurate. 
     Example 4 
     In reference to Japanese Patent O.P.I. Publication No. 183647/1989, an emulsion having a localized phase of silver bromide on the surface of grains was prepared. 
     To a 3% aqueous gelatin solution kept at 50° C., 6 g of sodium chloride was added. To the solution, a solution containing 10 g of silver nitrate and a solution containing 3.44 g of sodium chloride were added while stirring vigorously, followed by adding a solution containing 232 g of silver nitrate and 79.8 g of sodium chloride under rigorous stirring. Next, to the solution, 290 mg of sensitizing dye GS-1 was added. The mixture was stirred for 15 minutes. Then, to the mixture, an aqueous solution containing 8 g of silver nitrate and a solution containing 0.55 g of sodium chloride 0.5 g of potassium bromide were added and mixed at 40° C. while stirring vigorously. The solution was subjected to desalt, washing and re-dispersion in the same manner as in EMP-1. Thus, an emulsion having an average grain diameter of 0.40 μm and a variation coefficient of 0.07 was prepared. When the above-mentioned emulsion was subjected to X-ray diffraction measurement, the main peak of 100% of silver by chloride and the sub-peak of 60-90 mol % of silver chloride were obserbed. Therefore, it was found that grains wherein a silver bromide phase was localized was prepared. Next, the above-mentioned emulsion was subjected to the most suitable chemical sensitization employing sodium thiosulfate, sodium chloroaurate and the above-mentioned compound SB-1. The resulting emulsion was defined to be Em-25. To an aqueous solution containing 79.8 g of sodium chloride used in preparing Em-25, Compound I-16 was added in the same amount as Em-2 for preparation. By changing content amount of potassium bromide in preparing grains of Em-25 as shown in Table 7, emulsion Em-27 which was subjected to chemical sensitization in the same manner as in Em-25 was prepared. Next, emulsions Em-26 and Em-28 were prepared in the same manner as in Em-2 except that Br content ratio was changed. An emulsion subjected to chemical sensitization in the same manner as Em-25 was prepared. Employing the above-mentioned emulsions, coating samples Nos. 205 to 208 were prepared. They were subjected to evaluation in the same manner as Example 1. 
     From comparison between Sample 205 and Sample 208, it was found that the emulsion having localized phase of Br can offer a favorable sample in terms of reciprocity law failure and latent image stability having high sensitivity. In addition, from Samples 206 and 208, it was found that emulsions having Br content of 0.3% mol are more favorable.