The present invention relates to a silver halide light-sensitive material (hereinafter also referred to as a light-sensitive material), particularly to a light-sensitive material using an emulsion comprising silver halide grains doped with a polyvalent metal and subjected to reduction sensitization.

There is an eager demand for higher sensitivities and lower fogging in present light-sensitive materials. Further, improvement in preservability is also increasingly demanded to maintain these photographic properties over a much longer period.

There have so far been studied in the art various sensitizing techniques such as use of an internally high iodide containing core/shell emulsion for preventing recombination of electrons and positive holes, selective growth of chemically sensitized specks for raising latent image forming efficiency, and use of supersensitizers for raising efficiency of electron transfer from sensitizing dyes to silver halide crystal grains. But, a more systematic and overall combination of plural techniques is required to meet the growing demand for higher sensitivities.

The most typical technique for higher sensitivities is the use of an internally high iodide containing core/shell silver halide emulsion, in which the core is shelled with silver iodobromide having a silver iodide content lower than that in the core, or with silver bromide. But this emulsion type involves a contradiction between the prevention of electron-positive hole recombination, which is attributable to the presence of high iodide containing cores, and the deterioration in developability, which is becomes worse by the increase in total iodide content that depends primarily upon the iodide content of such cores; therefore, solution of this contradiction has been demanded.

Among the many techniques disclosed so far to attain the intended high sensitivity, reduction sensitization is the most typical.

For example, B.H. Carroll used tin compounds in U.S. Pat. No.2,487,850, S.C. Rowe used polyamine compounds in U.S. Pat. No.2,512,925, P.A. Faelens employed dioxythiourea in British Pat. No.789,823, and S.S. Collier tried various approaches to reduction sensitization by use of dimethylamine borane, stannous chloride and hydrazine as materials as well as high pH ripening and low pAg ripening as sensitizing conditions, as seen in Photographic Science and Engineering, Vol.23, p.113 (1979).

Further, use of ascorbic acid as a reducing agent is disclosed in Japanese Pat. O.P.I. Pub. Nos.136852/1990 and 196232/1990.

These reduction sensitization methods, though capable of performing sensitization, have a serious problem that their effects are lowered with aging, and solution to this has been desired. In addition, each of these methods involves a large rise in fog and is not satisfactorily sufficient judging from the recent requirements of lower fogging and higher sensitivity.

The first object of the present invention is to provide a silver halide photographic light-sensitive material containing a silver halide emulsion high in sensitivity and less in fog. The second object of the present invention is to provide a silver halide photographic light-sensitive material containing a silver halide emulsion free from change in fog and sensitivity caused by aging.

The above objects of the invention are attained by a silver halide photographic light-sensitive material having, on a support, at least one silver halide emulsion layer, wherein the silver halide emulsion is subjected to reduction sensitization, and silver halide grains in the emulsion contain a polyvalent metal in an amount not less than 10⁻⁶ mol per mol of silver halide.

The constituents of the invention are hereunder described in detail.

The reduction sensization of the invention may be carried out in the course of silver halide grain formation, after the formation of grains, or after chemical ripening. However, it is preferable to carry out the reduction sensitization during grain formation in view of higher sensitivities.

Preferred reducing agents are thiourea dioxide and ascorbic acid and derivatives thereof. Other preferred reducing agents include polyamines such as hydrazine and diethylenetriamine; dimethylamine boranes; and sulfites.

Examples of the ascorbic acid derivative include L-ascorbic acid, sodium L-ascorbate, potassium L-ascorbate, DL-ascorbic acid, sodium D-ascorbate, L-ascorbic acid-6-acetate and L-ascorbic acid-6-palmitate.

Preferably, the addition amount of the reducing agent is varied according to types of reducing agents; sizes, compositions and crystal habits of silver halide grains; and environmental conditions such as temperature, pH and pAg of a reaction system. However, in the case of thiourea dioxide, favorable results can be added in an amount of about 0.01 to 2 mg per mol of silver halide. In the case of ascorbic acid, the addition amount is preferably within the range of 50 mg to 2 g per mol of silver halide.

Preferred conditions for the reduction sensitization are a temperature range of 40 to 70°C, a time range of 19 to 200 minutes, a pH range of 5 to 11, and a pAg range of 1 to 10 (here, the pAg value is given by (logarithm of Ag⁺ ion concentration) × -1).

Silver nitrate is preferably used as a water soluble silver salt. By the addition of a water soluble silver salt, the so-called silver ripening, one of the reduction sensitizing techniques, is carried out. The pAg during silver ripening is 1 to 6, preferably 2 to 4. Other conditions such as temperature, pH and time are preferably the same as those in the above reduction sensitization.

As stabilizers for a silver halide emulsion containing silver halide grains subjeted to the reduction sensitization of the invention, conventional stabilizers described later can be used. Favorable results can often be produced by simultaneous use of the antioxidants disclosed in Japanese Pat. O.P.I. Pub. No.82831/1982 and/or the thiosulfonic acids disclosed in V.S. Gahler's article, Zeitshrift für Wissenschaftliche Photographie Bd.63, 133 (1969) and Japanese Pat. O.P.I. Pub. No.1019/1979. Addition of these compounds may be made in any of the emulsion preparation processes from the growth of crystals to the preparation of coating emulsion before coating.

The objects of the invention cannot be attained only by these reduction sensitizing techniques, and it is necessary that a polyvalent metal be contained in silver halide grains in conjunction as described hereinafter.

The polyvalent metal used in the invention is a metal capable of forming a polyvalention, and usable polyvalent metals are Mg, Ca, Sr, Ba, Al, Sc, Y, La, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ga, Mo, Ru, Rh, Pd, Os, Ir, Pt, Cd, Hg, Re, Tl, In, Sn, Pb and Bi. These metals may be added in the form of salts, such as ammonium salts, acetates, nitrates, sulfates, phosphates and hydroxylates, which can be dissolved at the time of grain formation.

Such salts include, for example, CdBr₂, CdCl₂, Cd(NO₃)₂, Pb(NO₃)₂, Pb(CH₃COO)₂, K₃[Fe(CN)₆], (NH₄)₄[Fe(CN)₆], K₃IrCl₆, (NH₄)₃RhCl₆.

Among them, Fe, Ir, Cd, Pb, In, Os and Re are particularly preferred as polyvalent metals; preferred ligands are CN, CO and O₂.

Typical examples thereof include [Re(CN)₆]⁻⁴, [Ru(CN)₆]⁻⁴, [Os(CN)₆]⁻⁴, [ReF(CN)₅]⁻⁴, [RuF(CN)₅]⁻⁴, [OsF(CN)₅]⁻⁴, [ReCl(CN)₅]⁻⁴, [RuCl(CN)₅]⁻⁴, [OsCl(CN)₅]⁻⁴, [ReBr(CN)₅]⁻⁴, [RuBr(CN)₅]⁻⁴, [Fe(O)₂Cl₄]⁻³, [Fe(O)₂Br₄]⁻³, [Fe(O)₂I₄]⁻³, [Re(O)₂(N₃)₄]⁻³, [Re(O)₂(OCN)₄]⁻³, [Re(O)₂(SCN)₄]⁻³, [Re(O)₂(SeCN)₄]⁻³, [Re(O)₂(TeCN)₄]⁻³, [Re(O)₂(CN)₄]⁻³, [Os(O)₂Cl₄]⁻², [Os(O)₂Br₄]⁻², [Os(O)₂I₄]⁻², [Os(O)₂(N₃)₄]⁻², [Os(O)₂(OCN)₄]⁻², [Os(O)₂(SCN)₄]⁻², [Os(O)₂(SeCN)₄]⁻², [Ru(CO)Cl₄(N₃)]⁻³, [Ru(CO)Br₄(N₃)]⁻³, [Ru(CO)I₄(N₃)]⁻³, [Fe(CO)(CN)₅]⁻³, [Fe(CO)Cl(CN)₄]⁻³, [Fe(CO)Br(CN)₄]⁻³, [Fe(CO)I(CN)₄]⁻³, [Fe(CO)Cl₄(CN)]⁻³, [Fe(CO)Br₄(CN)]⁻³, [Fe(CO)I₄(CN)]⁻³, [Co(CO)(CN)₅]⁻², [Co(CO)(SCN)₅]⁻², [Co(CO)(N₃)₅]⁻², [Co(CO)(CN)₄Cl]⁻², [Co(CO)(CN)₄Br]⁻², [Co(CO)(CN)₄I]⁻², [V(NO)(CN)₅]⁻³, [Cr(NO)(CN)₅]⁻³, [Mn(NO)(CN)₅]⁻³, [Fe(NO)(CN)₅]⁻², [Ru(NO)Cl₅]⁻², [Ru(NO)Br₅]⁻², [Ru(NO)I₅]⁻², [Ru(NO)F₅]⁻², [Ru(NO)Cl₃(H₂O)₂]⁰, [Ru(NO)Cl₃(H₂O)]⁻¹ and [Ru(NO)Cl₄(OCN)]⁻².

The addition amount of the polyvalent metal is not less than 10⁻⁶ mol, preferably 10⁻⁶ to 10⁻⁴ per mol of silver halide. An addition amount less than 10⁻⁶ mol does not bring out the favorable effect of the invention.

The objects of the invention can be attained more effectively as the addition amount increases.

Preferably, the polyvalent metal compound is added in the form of solution of a suitable solvent, such as water, methanol or acetone.

In order to stabilize the solution, an aqueous solution of hydrogen halide (e.g., HCl, HBr) or an alkali halide (e.g., KCl, KBr, NaBr) may be added thereto. If necessary, there may be incorporated an acid or an alkali. The polyvalent metal compound may be added in a reaction vessel before grain formation or in the course of grain formation.

The polyvalent metal compound may also be dissolved in an aqueous solution of a water soluble silver salt (e.g., AgNO₃), or in that of an alkali halide (e.g., NaCl, KBr, KI), and then added continuously during the formation of silver halide grains. Further, there may also be prepared a solution of the polyvalent metal compound independently of the water soluble silver salt or alkali halide, to add continuously at a suitable time during the formation of grains. Combination of various addition methods is also carried out.

The amount of polyvalent cations doped in silver halide grains can be quantitatively determined by atomic absorption spectroscopy or inductively coupled plasma (ICP) emission spectroscopy. For cations having a high atomization temperature such as Ir, ICP emission spectral analysis is used, and to analyze Pb, Cd or Fe, atomic absorption spectroscopy can be employed.

A sample for the analysis is usually prepared as follows: Firstly, an emulsion is diluted with water and centrifuged to separate silver halide grains from gelatin. In this procedure, if polyvalent cations are considered to be present in the emulsion as a sparingly soluble salt, a solvent which can dissolve it, such as an acid, is added in conjunction with water to remove them. The silver halide grains so separated from the emulsion are then converted into a sample for the analysis by dissolving them in an ammonium thiosulfate solution.

The wording "silver halide grains contain a polyvalent metal" means a case where the polyvalent metal being present in the inner portion of grains, a case where it being present in the vicinity of the outermost layer of grains, a case where it being present in the outermost layer, and combinations thereof.

The preferable location where the polyvalent metal is doped depends upon preparation methods, compositions and crystal forms of emulsion grains. Thus, though not limititive, doping at the inner portion of grains is preferred to that near the outermost layer.

It has not yet been made clear as to why the effect of the invention is exhibited as super-additivity when reduction sensitization and doping with the polyvalent metal are combined. But it is conceivable that the reason lies in prevention of electron-positive hole recombination attributable to reduction sensitization (which is positive hole trapping) and polyvalent metal doping (which is electron trapping); or prevention of electron-positive hole recombination attributable to reduction sensitization (which is positive hole trapping) and polyvalent metal doping (which is different in state of positive hole trapping caused by reduction sensitization). Anyway, there isn't much doubt that combination of the techniques different in functions brings out the effects with super-additivity.

The term "super-additivity" used here means the phenomenon that the effect of the invention is revealed beyond the sum of the effect of reduction sensitization and the effect of polyvalent metal doping.

Photographic emulsion layers in the light-sensitive material of the invention may use any type of silver halide grains among silver bromide, silve iodobromide, silver iodochlorobromide, silver chlorobromide and silver chloride. Silver bromide or silver chlorobromide is preferable, and silver iodobromide containing not more than 30 mol% silver iodide is more preferable.

The effect of the invention by polyvalent metal doping is equally revealed in core/shell grains of internally high AgI containing type, grains having the same AgI content along their diameters, and AgBr grains. When core/shell grains of internally high AgI containing type or multilayered grains of internally high AgI containing type are used, it is preferable that the polyvalent metal be doped in the core or intermediate layer.

Silver halide grains in the photographic emulsion may be the so-called regular grains having a symmetrical crystal form such as cubic, octahedral or tetradecahedral form; or they may have an irregular crystal form such as a spherical crystal form, have a crystal defect such as twin planes or have the above crystal forms in combination.

These silver halide grains may be small-sized grains not larger than 0.1 micron in diameter or large-sized grains having a projected area diameter up to 10 microns. These may also be monodispersed ones having a narrow grain size distribution or polydispersed ones having a wide grain size distribution.

In making the light-sensitive material of the invention, the emulsion of the invention and other silver halide emulsions independent of the invention used when necessary are preferably subjected to physical ripening, chemical ripening and spectral sensitization appropriate for respective spectrally sensitive layers. Additives usable in such processes are illustrated in Research Disclosure Nos. 17643, 18716, 308119 (hereinafter abbreviated as RD17643, RD18716 and RD308119, respectively).

Locations of the relevant descriptions are as follows: Item Page, Section of RD308119 Page of RD17643 Page of RD18716 Chemical sensitizer 996 III-A 23 648 Spectral sensitizer 996 IV-A-A,B C,D,H,I,J 23-24 648-9 Supersensitizer 996 IV-A-E,J 23-24 648-9 Antifoggant 998 VI 24-25 649 Stabilizer 998 VI 24-25 649

Conventional photographic additives usable in the invention are also illustrated in the above Research Disclosures. Locations of the relevant descriptions are as follows: Item Page, Section of RD308119 Page of RD17643 Page of RD18716 Anticolor-mixing agent 1002 VII-I 25 650 Dye image stabilizer 1002 VII-J 25 Whitening agent 998 V 24 UV absorbent 1003 VIII-C 25-26 XIII-C Light absorbent 1003 VIII 25-26 Light scattering agent 1003 VIII Filter dye 1003 VIII 25-26 Binder 1003 IX 26 651 Antistatic agent 1006 XIII 27 650 Hardener 1004 X 26 651 Plasticizer 1006 XII 27 650 Lubricant 1006 XII 27 650 Surfactant & coating aid 1005 XI 26-27 650 Matting agent 1007 XVI Developing agent (contained in light-sensitive material) 1011 XX-B

The light-sensitive material of the invention may use various couplers according to colors to be formed in respective layers. Typical examples thereof are illustrated in the above Research Disclosures as shown below. Item Page, Section of RD308119 Section of RD17643 Yellow coupler 1001 VII-D VII C-G Magenta coupler 1001 VII-D VII C-G Cyan coupler 1001 VII-D VII C-G Colored coupler 1002 VII-G VII G BAR coupler 1001 VII-F DIR coupler 1002 VII-F VII F Other useful-residue releasing coupler 1001 VII-F Alkali soluble coupler 1001 VII-E

When these additives are used in the light-sensitive material of the invention, these can be incorporated by the dispersion method described in Section IV of RD308119.

In the invention, there may be used the supports described on page 28 of RD17643, on pages 647-8 of RD 18716 and in Section XVII of RD308119.

In the light-sensitive material of the invention, there may be provided auxiliary layers such as the filter layer and intermediate layer described in Section VII-K of RD308119.

The light-sensitive material of the invention may have various layer configurations such as conventional layer order, inverted layer order and unit layer structure.

The invention can be applied to a variety of color light-sensitive materials represented by color negative films for general purpose or for cinema, color reversal films for slide or for TV, color paper, color positive films and color reversal paper.

The light-sensitive material of the invention can be processed by the usual methods described on pages 28-29 of RD17643, on 615 page of RD18716 and in Section XIX of RD308119.

The present invention is described in detail with the following examples, but the embodiment of the invention is not limited to them.

First, the method for preparing an emulsion used in this example, EmA-1, is described.

In the preparation, the following aqueous solutions (a-1) to (a-4) were used. Aqueous solution (a-1) Gelatin 51.93 g 28% Aqueous ammonia 1056 ml 56% Acetic acid 10590 ml Water was added to 11827 ml Aqueous solution (a-2) Silver nitrate 1587 g 28% Aqueous ammonia 1294 ml Water was added to 2669 ml Aqueous solution (a-3) Gelatin 34.93 g Potassium bromide 1454.7 g Water was added to 3493 ml Emulsion solution (a-4) containing fine silver iodide grains (average grain size: 0.06 µm) Fine silver iodide grain stock solution (containing 45.6 g/mol AgI of gelatin, made up to 1467 ml) 1239 ml 4-hydroxy-6-methyl-1,3,3a,7-tetrazaindene 5.22 g Water was added to 2294 ml

While vigorously stirring aqueous solution (a-1) at 60°C, 0.407 mole equivalent of a monodispersed silver iodide emulsion, comprising grains containing 2 mol% silver iodide and having an average size of 0.27 µm, was added as seed emulsion. Then, the pH and pAg were adjusted with acetic acid and an aqueous solution of potassium bromide.

Subsequently, while controlling the pH and pAg as shown in Table 1, aqueous solutions (a-2), (a-3) and (a-4) were added by the double-jet method at flow rates shown in Tables 2 and 3. Table 1 shows the grain growth conditions of EmA-1. Ag(%) 0 29 29* 56 100 pH 7.0 → 7.0 6.0 → → → 6.0 pAg 7.5 → 7.5 9.7 ↘ 10.1 → 10.1 * The environments of pH and pAg were quickly changed when the Ag content reached 29%.

Table 2 shows the addition rates of aqueous solutions (a-2) and (a-3); Table 3 gives the addition rate of aqueous solution (a-4). Time (min) Addition Rate (ml/min) (a-2) (a-3) 0 11.56 10.98 8.61 10.21 9.70 19.4 9.30 8.83 28.8 5.72 5.44 70.3 9.13 8.68 76.5 13.65 12.91 78.2 18.25 12.91 90.6 32.81 54.47 102.7 77.01 86.56 113.4 103.66 111.75 114.4 103.66 111.75 Time (min) Addition Rate (ml/min) 0 0 28.8 0 28.8 83.69 34.5 90.16 35.1 31.80 59.8 42.13 60.3 12.09 76.5 14.42 82.2 22.53 82.4 16.78 96.3 0 112.7 0 112.7 0 114.4 0

To the resulting solution was added a solution of phenylcarbamyl gelatin, and then the pH was adjusted in order to deposit grains, followed by desalting and washing. The resulting emulsion EmA-1 comprised monodispersed grains having an average particle size of 0.8 µm and an average silver iodide content of 8.0 mol%.

Subsequently, emulsions EmA-2 to EmA-4 of the invention were prepared.

Emulsion EmA-2 was prepared in exactly the same manner as in EmA-1, except that an aqueous solution containing 1 × 10⁻⁵ mol/mol AgX of K₄[Fe(CN)₆] was continuously added from 28.8 to 34.5 minutes after starting addition of the above aqueous solutions (a-2), (a-3) and (a-4), with grains kept growing. This EmA-2 was an emulsion in which only high silver iodide containing cores were doped with iron ions.

Emulsion EmA-3 was prepared in exactly the same manner as in EmA-1, except that an aqueous solution containing 1 × 10⁻⁵ mol/mol AgX of K₄[Fe(CN)₆] was continuously added from 35.1 to 96.3 minutes after starting the addition of the above aqueous solutions, while grains were growing. This EmA-3 was an emulsion in which only intermediate layers were doped with iron ions.

Emulsion EmA-4 was prepared in exactly the same manner as in EmA-3, except that when the growth of intermediate layers doped with iron ions was complete, unnecessary iron ions were removed by washing and then the outermost shell was formed. This EmA-4 was an emulsion in which doping with iron ions was strictly limited to intermediate layers.

Emulsion EmA-5 was prepared in exactly the same manner as in EmA-1, except that addition of the above aqueous solutions was discontinued 34.5 minutes after the start of the addition and then silver ripening was carried out for 30 minutes at pAg=3 and pH=6 by adding 3.5 N silver nitrate solution. This EmA-5 was an emulsion subjected to reduction sensitization by silver ripening at the interface between the high silver iodide containing core and the intermediate layer.

Emulsion EmA-6 was prepared in exactly the same manner as in EmA-1, except that 1 × 10⁻⁶ mol/mol AgX of thiourea dioxide was added 34.5 minutes after starting addition of the above aqueous solutions. This EmA-6 was an emulsion subjected to reduction sensitization with thiourea dioxide at the interface between the high silver iodide containing core and the intermediate layer.

Emulsion EmA-7 was prepared in exactly the same manner as in EmA-1, except that 1 × 10⁻³ mol/mol AgX of ascorbic acid was added 35.5 minutes after starting addition of the above aqueous solutions. This EmA-7 was an emulsion subjected to reduction sensitization with ascorbic acid at the interface between the high silver iodide containing core and the intermediate layer.

Emulsion EmA-8 was prepared in exactly the same manner as in EmA-7, except that 5 × 10⁻⁵ mol/mol AgX of C₂H₅SO₂SNa was added 33.5 minutes after starting addition of the above aqueous solutions. This EmA-8 was an emulsion subjected to addition of C₂H₅SO₂SNa and reduction sensitization with ascorbic acid near the interface between the high silver iodide containing core and the intermediate layer.

Emulsion EmA-9 was prepared in exactly the same manner as in EmA-1, except that only high silver iodide containing cores were doped with iron ions and reduction sensitization was carried out at the interface between the high silver iodide containing core and the intermediate layer, by referring to the procedures of EmA-2 and EmA-8.

Emulsion EmA-10 was prepared in exactly the same manner as in EmA-1, except that only intermediate layers were doped with iron ions and reduction sensitization by silver ripening was carried out at the interface between the high silver iodide containing core and the intermediate layer, by referring to the procedures of EmA-3 and EmA-5.

Emulsion EmA-11 was prepared in exactly the same manner as in EmA-1, except that only intermediate layers were doped with iron ions and reduction sensitization was carried out using thiourea dioxide at the interface between the high silver iodide containing core and the intermediate layer, by referring to the procedures of EmA-3 and EmA-6.

Emulsion EmA-12 was prepared in exactly the same manner as in EmA-1, except that only intermediate layers were doped with iron ions and reduction sensitization was carried out using ascorbic acid at the interface between the high silver iodide containing core and the intermediate layer, by referring to the procedures of EmA-3 and EmA-7.

Emulsion EmA-13 was prepared in exactly the same manner as in EmA-1, except that only intermediate layers were doped with iron ions and reduction sensitization was carried out using ascorbic acid and C₂H₅SO₂SNa at the interface between the high silver iodide containing core and the intermediate layer, by referring to the procedures of EmA-3 and EmA-8.

Emulsion EmA-14 was prepared in exactly the same manner as in EmA-1, except that doping with iron ions was perfectly limited to intermediate layers alone and reduction sensitization was carried out using ascorbic acid and C₂H₅SO₂SNa at the interface between the high silver iodide containing core and the intermediate layer, by referring to the procedures of EmA-4 and EmA-8.

Each of the resulting emulsions EmA-1 to EmA-14 was adjusted to pAg 8.0 and ripened for 60 minutes under conditions of 55°C and pH 5.8 by adding 2.0 × 10⁻⁶ mol/mol AgX of sodium thiosulfate. After adding a mixed solution of 4.4 × 10⁻⁷ mol/mol AgX of chloroauric acid and ammonium thiocyanate, each emulsion was further ripened for 60 minutes.

Then, each emulsion was spectrally sensitized by allowing it to adsorb the combination of the following sensitizing dyes SD-A, SD-B and SD-C. Further, magenta couplers M-A, M-B and M-C were added thereto.

After adding a proper amount of sodium 2-hydroxy-4,6-dichlorotriazine evenly, each emulsion was applied to a subbed cellulose triacetate support so as to give a silver coating weight of 2.0 g/m², followed by coating to give light-sensitive material samples 1 to 14.

Each sample was wedgewise exposed to green light by the usual method, color-developed in the following color developing processes and then evaluated for photographic properties. The evaluation results are shown in Table 14, where the sensitivity is given by a value relative to the sensitivity of sample 1 (comparison) which is set at 100. Process (at 38°C) Processing Time Color developing 3 min 15 sec Bleaching 6 min 30 sec Washing 3 min 15 sec Fixing 6 min 30 sec Washing 3 min 15 sec Stabilizing 1 min 30 sec Drying

Compositions of processing solutions used in the respective processes were as follows: Color Developer 4-Amino-3-methyl-N-ethyl-N-β-hydroxyethylaniline sulfate 4.75 g Anhydrous sodium sulfite 4.25 g Hydroxylamine 1/2sulfate 2.0 g Anhydrous potassium carbonate 37.5 g Sodium bromide 1.3 g Trisodium nitrilotriacetate (monohydrate) 2.5 g Potassium hydroxide 1.0 g Water was added to 1000 ml, and the pH was adjusted to 10.6 with sodium hydroxide. Bleach Ammonium ferric ethylenediaminetetraacetate 100.0 g Diammonium ethylenediaminetetraacetate 10.0 g Ammonium bromide 150.0 g Glacial acetic acid 10.0 g Water was added to 1000 ml, and the pH was adjusted to 6.0 with aqueous ammonia. Fixer Ammonium thiosulfate 175.0 g Anhydrous sodium sulfite 8.6 g Sodium metasulfite 2.3 g Water was added to make 1000 ml, and the pH was adjusted to 6.0 with acetic acid. Stabilizer Formalin (37% aqueous solution) 1.5 ml Koniducks (made by Konica Corp.) 7.5 ml Water was added to 1000 ml. Sample No. Emulsion Fogging Green Sensitivity Sensitivity after 1-week Standing 1 A-1 0.20 100 80 2 A-2 0.22 120 100 3 A-3 0.18 180 150 4 A-4 0.15 220 180 5 A-5 0.22 170 140 6 A-6 0.25 175 150 7 A-7 0.25 180 150 8 A-8 0.15 200 170 9 (Invention) A-9 0.22 250 200 10 (Invention) A-10 0.25 270 270 11 (Invention) A-11 0.22 280 280 12 (Invention) A-12 0.20 275 270 13 (Invention) A-13 0.15 300 290 14 (Invention) A-14 0.15 310 310

It can be seen from Table 4 that samples 9 to 14 using chemically sensitized emulsions of the invention have original sensitivities higher than those of comparative samples and virtually retain their high sensitivities even after standing for one week.

The following emulsions were prepared and used to prepare a multilayer light-sensitive material, sample 101.

Em-1:

surface low silver iodide containing, monodispersed emulsion; average grain size: 0.8 µm; average silver iodide content: 8.0 mol%

Em-2:

surface low silver iodide containing, monodispersed emulsion; average grain size: 0.38 µm; average silver iodide content: 8 mol%

Em-3:

surface low silver iodide containing, monodispersed emulsion; average grain size: 0.65 µm; average silver iodide content: 8 mol%

Em-4:

surface low silver iodide containing, monodispersed emulsion; average grain size: 0.85 µm; average silver iodide content: 8 mol%

Em-5:

surface low silver iodide containing, monodispersed emulsion; average grain size: 1.20 µm; average silver iodide content: 6 mol%

Em-6:

surface low silver iodide containing, monodispersed emulsion; average grain size: 0.70 µm; average silver iodide content: 8 mol%

Em-7:

surface low silver iodide containing, monodispersed emulsion; average grain size: 1.40 µm; average silver iodide content: 8 mol%

Em-8:

surface low silver iodide containing, monodispersed emulsion; average grain size: 0.08 µm; average silver iodide content: 4 mol%

Emulsion EmB-1 was the same emulsion as Em-2 described in Japanese Pat. O.P.I. Pub. No.241336/1991 and prepared as follows:

While stirring at 40°C 5-wt% aqueous ossein gelatin solution was placed in a reaction vessel and 1 mol each of 3.5 N aqueous silver nitrate solution and 3.5 N potassium iodide aqueous solution were added thereto at a constant addition rate over a period of 30 minutes.

During the addition, the pAg was kept at 13.5 by a usual controlling means. The resulting silver iodide was a mixture of β-AgI and γ-AgI each having an average grain size of 0.06 µm. This emulsion is hereinafter referred to as the fine silver iodide grain emulsion.

A monodispersed, spherical seed emulsion was prepared in the following manner: Solution A₃ Ossein gelatin 150 g Potassium bromide 53.1 g Potassium iodide 24 g Water was added to 7200 ml Solution B₃ Silver nitrate 1800 g Water was added to 6000 ml Solution C₃ Potassium bromide 1327 g 1-Phenyl-5-mercaptotetrazole (dissolved in methanol) 0.3 g Water is added to make 3000 ml Solution D₃ Aqueous ammonia (28%) 705 ml

Solutions B₃ and C₃ were added by the double jet method in 30 seconds to solution C₃ being vigorously stirred at 49°C to form nuclei, with the pBr controlled between 1.09 and 1.15.

After 1 minute and 30 seconds, solution D₃ was added thereto in 20 seconds, followed by a 5-minute ripening at a KBr concentration of 0.071 mol/l and an ammonia concentration of 0.63 mol/l.

The pH was then adjusted to 6.0, and desalted and washed. An electron microscopic observation of the resulting emulsion proved that it comprised monodispersed spherical grains having an average size of 0.36 µm and a grain size distribution extent of 18%. This emulsion is hereinafter referred to as the seed emulsion.

Using the following three aqueous solutions and emulsion solution containg the silver iodide fine grain emulsion, and the seed emulsion, there was prepared an emulsion of the invention comprising grains having an average size of 1.25 µm. Aqueous solution A₂ Gelatin 231.9 g 10% Methanol solution of HO(CH₂CH₂O)_m[CH(CH₃)CH₂O]₁₇(CH₂CH₂O)_nH (average molecular weight: about 1300) 30.0 ml 28% Aqueous ammonia 1056 ml Water was added to 11827 ml Aqueous solution B₂ Silver nitrate 1587 g 28% Aqueous ammonia 1295 ml Water was added to 2669 ml Aqueous solution C₂ Potassium bromide 1572 g Water was added to 3774 ml Emulsion solution D₂ containing the fine silver iodide grain emulsion The silver iodide fine grain emulsion 1499.3 g 4-Hydroxy-6-methyl-1,3,3a,7-tetrazaindene 5.2 g 10% Aqueous potassium hydroxide solution 14.75 ml Water was added to 1373 ml

While stirring aqueous solution A₂ vigorously at 60°C, 0.407 mole equivalent of the seed emulsion was added, and the pH and pAg were adjusted with acetic acid and an aqueous potassium bromide solution.

Then, aqueous solutions B₂ and C₂ as well as emulsion solution D₂ containing fine silver iodide grains were added thereto by the triple-jet method at addition rates shown in Tables 6, 7 and 8, with the pH and pAg controlled as shown in Table 5.

After completion of the addition, an aqueous phenylcarbamyl gelatin solution was added to deposit grains by adjusting the pH of the mixed solution. Grains deposited were subjected to desalting and washing, followed by adjustment of the resulting emulsion at 40°C to pH 5.80 and pAg 8.06. Obtained was a monodispersed silver iodobromide emulsion comprising grains having an average size of 1.25 µm, an average silver iodide content of 8.0 mol% and a grain size distribution extent of 13.2%. This emulsion is hereunder referred to as Em-2. In Table 9, Em-2's recipe-based grain structure and the volume ratio of respective phases are summarized. Table 5 shows the grain growth conditions of Em-2. Ag(%) 0 29 29 56 100 pH 7.0 → 7.0 ↓ 6.0 → 6.0 → 6.0 pAg 7.8 → 7.8 ↓ 9.7 ↘ 10.1 → 10.1 In the table 5, → indicates to keep pH or pAg constant, ↘ continuous drop, and ↓ sharp drop.

Table 6 shows the addition pattern of aqueous solution B₂, Table 7 that of aqueous solution C₂, and Table 8 that of aqueous solution D₂. Time (min) Addition Rate (ml/min) 0 12.2 25.6 13.0 42.6 12.9 43.9 8.4 67.5 11.0 97.3 14.8 97.7 20.6 105.0 22.3 105.4 25.4 112.3 32.1 112.6 35.1 129.4 90.3 145.7 194.2 145.7 200.5 147.4 203.9 Time (min) Addition Rate (ml/min) 0 10.9 25.6 11.7 42.6 11.6 43.9 7.6 97.5 13.3 97.7 18.6 105.0 20.0 105.0 36.5 112.0 56.2 112.3 60.6 121.2 106.0 121.4 91.4 132.4 263.3 132.7 141.8 147.4 230.0 Time (min) Addition Rate (ml/min) 0 0 43.9 0 43.9 73.6 51.7 80.6 52.5 28.5 84.3 40.4 84.9 11.6 97.7 13.0 105.0 14.1 105.4 16.3 112.3 20.6 112.6 6.2 130.4 17.5 132.7 22.1 145.7 34.4 1st Phase 2nd Phase 3rd Phase 4th Phase 5th Phase 6th Phase Recipe-based Silver Iodide Content (mol%) 2 0 35 10 3 0 Ratio of D₂/B₂ Molar Addition Rate (%) 0 0 100 35 10 10 3 0 Volume Ratio (%) 3.8 9.2 15.8 6.7 58.7 5.8 1.8 9.2 4.8

This Em-2 had the following properties: Average grain size: 1.25 µm Monodispersity (extent of distribution): 14.0% Average silver iodide content: 8.0 mol% Deviation in silver iodide content at grain periphery: 0.0 mol% Relative standard deviation of silver iodide content: 9.0% Surface silver iodide content: 0.0 mol% Average aspect ratio: 3.3

EmB-2 was prepared as an emulsion of the invention in exactly the same manner as in EmB-1, except that when formation of the 2nd phase was complete, silver sensitization was carried out for 30 minutes at pAg 3 and pH 6 by adding a silver nitrate solution. EmB-2 was an emulsion subjected only to reduction sensitization.

EmB-3 was prepared in the same manner as in EmB-1, except that Pb was used for doping by adding 1 × 10⁻⁴ mol/mol AgX of aqueous Pb(NO₃)₂ solution to the 3rd phase of EmB-1. This emulsion was one doped using Pb alone as polyvalent metal.

EmB-4 was prepared in the same manner as in EmB-3, except that Os was used for doping by adding 1 × 10⁻⁴ mol/mol AgX of aqueous K₄Os(CN)₆ solution instead of Pb(NO₃)₂. This was an emulsion doped using Os alone as polyvalent metal.

EmB-5 was prepared in the same manner as in EmB-2, except that Pb was used for doping by adding 1 × 10⁻⁴ mol/mol AgX of Pb(NO₃)₂ to the 3rd phase of EmB-2. This was an emulsion subjected to reduction sensitization and further doped using Pb alone as polyvalent metal.

EmB-6 was prepared in the same manner as in EmB-2, except that 1 × 10⁻⁴ mol/mol AgX of K₄O₅(CN)₆ was doped to the 3rd phase of EmB-2.

The difference among EmB-1 to EmB-6 was only whether or not these were subjected to reduction sensitization and doping with a polyvalent metal; their grain size and core/shell structure were the same.

The component of the multilayer sample 101 is described below.

In the following descriptions of the composition, addition amounts of compounds are in grams per square meter unless otherwise indicated. Amounts of silver halides and colloidal silvers are shown in amounts of silver present, and addition amounts of sensitizing dyes are given in moles per mol of AgX.

1st layer: antihalation layer Black colloidal silver 0.18 g Gelatin 1.57 g UV absorbent (UV-1) 0.17 g High boiling solvent (Oil-1) 0.14 g 2nd layer: 1st intermediate layer Gelatin 1.00 g 3rd layer: 1st red-sensitive emulsion layer Silver iodobromide emulsion (EmB-2) 0.66 g Silver iodobromide emulsion (EmB-3) 0.29 g Gelatin 1.29 g Sensitizing dye (S-1) 3.21 × 10⁻⁴mol Sensitizing dye (S-2) 2.71 × 10⁻⁴ mol Sensitizing dye (S-3) 3.45 × 10⁻⁵ mol Coupler (C-1) 0.96 g Colored coupler (CC-1) 0.07 g High boiling solvent (Oil-1) 0.52 g 4th layer: 2nd intermediate layer Gelatin 0.75 g 5th layer: 1st green-sensitive emulsion layer Silver iodobromide emulsion (EmB-2) 0.66 g Silver iodobromide emulsion (EmB-3) 0.29 g Gelatin 1.08 g Sensitizing dye (S-7) 2.67 × 10⁻⁴ mol Sensitizing dye (S-6) 2.23 × 10⁻⁴ mol Sensitizing dye (S-5) 4.48 × 10⁻⁵ mol Sensitizing dye (S-8) 7.04 × 10⁻⁶ mol Coupler (M-4) 0.13 g Coupler (M-2) 0.29 g Colored coupler (CM-1) 0.082 g High boiling solvent (Oil-3) 0.51 g 6th layer: 2nd green-sensitive emulsion layer Silver iodobromide emulsion (EmB-4) 0.76 g Gelatin 0.80 g Sensitizing dye (S-7) 1.45 × 10⁻⁴ mol Sensitizing dye (S-6) 1.21 × 10⁻⁴ mol Sensitizing dye (S-5) 2.43 × 10⁻⁵ mol Sensitizing dye (S-8) 3.82 × 10⁻⁶ mol Coupler (M-4) 0.036 g Coupler (M-2) 0.077 g Colored coupler (CM-2) 0.035 g High boiling solvent (Oil-3) 0.15 g 7th layer: 3rd intermediate layer Gelatin 0.55 g SC-1 0.032 g 8th layer: 1st blue-sensitive emulsion layer Silver iodobromide emulsion (EmB-3) 0.76 g Gelatin 1.16 g Sensitizing dye (S-11) 2.88 × 10⁻⁴ mol Sensitizing dye (S-9) 7.19 × 10⁻⁵ mol Coupler (Y-1) 0.40 g High boiling solvent (Oil-3) 0.16 g 9th layer: 4th intermediate layer Gelatin 0.75 g SC-1 0.044 g 10th layer: 2nd red-sensitive emulsion layer Silver iodobromide emulsion (EmB-1) 0.95 g Gelatin 0.93 g Sensitizing dye (S-1) 1.74 × 10⁻⁴ mol Sensitizing dye (S-2) 1.47 × 10⁻⁵ mol Sensitizing dye (S-3) 1.87 × 10⁻⁵ mol Coupler (C-1) 0.33 g High boiling solvent (Oil-1) 0.33 g 11th layer: 3rd red-sensitive emulsion layer Silver iodobromide emulsion (EmB-5) 2.30 g Gelatin 1.49 g Sensitizing dye (S-1) 1.16 × 10⁻⁴ mol Sensitizing dye (S-2) 9.80 × 10⁻⁵ mol Sensitizing dye (S-3) 1.25 × 10⁻⁵ mol Coupler (C-2) 0.19 g SC-1 0.027 g High boiling solvent (Oil-1) 0.43 g 12th layer :5th intermediate layer Gelatin 0.75 g SC-1 0.044 g 13th layer: 3rd green-sensitive emulsion layer Silver iodobromide emulsion (EmB-1) 1.82 g Gelatin 0.62 g Sensitizing dye (S-7) 9.62 × 10⁻⁵ mol Sensitizing dye (S-6) 8.00 × 10⁻⁵ mol Sensitizing dye (S-5) 1.61 × 10⁻⁵ mol Sensitizing dye (S-8) 2.53 × 10⁻⁶ mol Coupler (M-3) 0.06 g Coupler (M-2) 0.13 g Colored coupler (CM-2) 0.01 g High boiling solvent (Oil-1) 0.35 g 14th layer: 6th intermediate layer Gelatin 0.75 g SC-1 0.044 g 15th layer: 2nd blue-sensitive emulsion layer Silver iodobromide emulsion (EmB-6) 1.06 g Gelatin 0.925 g Sensitizing dye (S-11) 2.17 × 10⁻⁴ mol Sensitizing dye (S-9) 1.12 × 10⁻⁵ mol Coupler (Y-1) 0.31 g High boiling solvent (Oil-3) 0.13 g 16th layer: 3rd blue-sensitive emulsion layer Silver iodobromide emulsion (EmB-7) 1.84 g Gelatin 1.10 g Sensitizing dye (S-11) 1.44 × 10⁻⁴ mol Sensitizing dye (S-9) 5.65 × 10⁻⁵ mol Coupler (Y-1) 0.52 g High boiling solvent (Oil-3) 0.21 g 17th layer: 1st protective layer Silver iodobromide emulsion (EmB-8) 0.10 g Gelatin 1.52 g UV absorbent (UV-1) 0.006 g UV absorbent (UV-2) 0.099 g High boiling solvent (Oil-1) 0.0065 g High boiling solvent (Oil-4) 0.0065 g 18th layer: 2nd protective layer Gelatin 0.55 g Alkali soluble matting agent (silica; average particle size: 2 µm) 0.12 g Polymethylmethacrylate (average particle size: 2 µm) 0.02 g Lubricant (WAX-1) 0.04 g

Besides the above compositions, there were added in each layer coating aid (Su-1), dispersants (Su-2, Su-3), gelatin hardeners (H-1, H-2), stabilizer (Stab-1) antifoggants (AF-1, AF-2) and antiseptic agent (DI-1).

Multilayer samples 102 to 106 were prepared in exactly the same way as in sample 101, except that EmB-2 to EmB-6 were used in place of EmB-1 used in the 3rd green-sensitive emulsion layer, the 13th layer, of sample 101.

Samples 101 to 106 were subjected to wedgewise exposure through a yellow filter and processed in the following procedure. Process (38°C) Processing Time Color developing standard 2 min 45 sec Bleaching 6 min 30 sec Washing 3 min 15 sec Fixing 6 min 30 sec Washing 3 min 15 sec Stabilizing 1 min 30 sec Drying

Composition of the precessing solutions used in the respective processes were the same as that used in Example 1.

The relative sensitivity was determined for each sample using green light. The results are shown in Table 10, where the sensitivity has the same meaning as that in Example 1 and is expressed by values relative to the sensitivity of sample 101 after one-day standing which is set at 100. Sample No. Emulsion Fogging Green Sensitivity 101 EmB-1 0.30 100 102 EmB-2 0.35 120 103 EmB-3 0.32 130 104 EmB-4 0.32 130 105 (Invention) EmB-5 0.28 180 106 (Invention) EmB-6 0.29 175

It can be understood that samples 105 and 106, using emulsions subjected to both reduction sensitization and polyvalent metal doping, are low in fog and high in sensitivity as compared with the other samples.

A multilayer, color light-sensitive material, sample 201, was prepared by forming layers of the following compositions on a subbed triacetylcellulose film support. In the following descriptions of the composition, figures for respective components show coating amounts in g/m², those for silver halides indicate coating amounts in silver equivalent, and those for sensitizing dyes show coating amounts in moles per mole of silver halide contained in the same layer.

1st layer: antihalation layer Black colloidal silver (silver) 0.18 Gelatin 0.40 2nd layer: intermediate layer 2,5-di-t-pentadecylhydroquinone 0.18 EX-1 0.07 EX-3 0.02 EX-11 0.002 U-1 0.06 U-2 0.08 U-3 0.10 HBS-1 0.10 HBS-2 0.02 Gelatin 1.04 3rd layer: 1st red-sensitive emulsion layer EmC-1 (silver) 0.50 Sensitizing dye I 6.9 × 10⁻⁵ Sensitizing dye II 1.8 × 10⁻⁵ Sensitizing dye III 3.1 × 10⁻⁴ EX-2 0.335 EX-10 0.020 Gelatin 0.87 4th layer : 2nd red-sensitive emulsion layer EmC-2 (silver) 1.0 Sensitizing dye I 5.1 × 10⁻⁵ Sensitizing dye II 1.4 × 10⁻⁵ Sensitizing dye III 2.3 × 10⁻⁴ EX-2 0.400 EX-3 0.050 EX-10 0.015 Gelatin 1.30 5th layer: 3rd red-sensitive emulsion layer EmC-3 (silver) 1.60 EX-3 0.010 EX-4 0.080 EX-2 0.097 HBS-1 0.22 HBS-2 0.10 Gelatin 1.63 6th layer: intermediate layer EX-5 0.040 HBS-1 0.20 Gelatin 0.80 7th layer: 1st green-sensitive emulsion layer EmC-1 (silver) 0.30 Sensitizing dye V 3.0 × 10⁻⁵ Sensitizing dye VI 1.0 × 10⁻⁵ Sensitizing dye VII 3.8 × 10⁻⁴ EX-6 0.260 EX-1 0.021 EX-7 0.030 EX-8 0.025 HBS-1 0.100 HBS-3 0.010 Gelatin 0.63 8th layer: 2nd green-sensitive emulsion layer EmC-2 (silver) 0.45 Sensitizing dye V 2.1 × 10⁻⁵ Sensitizing dye VI 7.0 × 10⁻⁵ Sensitizing dye VII 2.6 × 10⁻⁴ EX-6 0.094 EX-8 0.018 EX-7 0.026 HBS-1 0.160 HBS-3 0.008 Gelatin 0.50 9th layer: 3rd green-sensitive emulsion layer EmC-3 (silver) 1.2 EX-12 0.040 EX-1 0.025 HBS-1 0.25 HBS-2 0.10 Gelatin 1.54 10th layer: yellow filter layer Yellow colloidal silver (silver) 0.05 EX-5 0.08 HBS-1 0.03 Gelatin 0.95 11th layer: 1st blue-sensitive emulsion layer EmC-1 (silver) 0.22 Sensitizing dye VIII 3.5 × 10⁻⁴ EX-9 0.721 EX-8 0.042 HBS-1 0.28 Gelatin 1.10 12th layer: 2nd blue-sensitive emulsion layer EmC-2 (silver) 0.45 Sensitizing dye VIII 2.1 × 10⁻⁴ EX-9 0.154 EX-10 0.007 HBS-1 0.05 Gelatin 0.78 13th layer: 3rd blue-sensitive emulsion layer EmC-3 (silver) 0.77 Sensitizing dye VIII 2.2 × 10⁻⁴ EX-9 0.20 HBS-1 0.07 Gelatin 1.69 14th layer: 1st protective layer Emulsion 1 (silver) 0.5 U-4 0.11 U-5 0.17 HBS-1 0.05 Gelatin 1.00 15th layer: 2nd protective layer Polymethylmethacrylate particles (diameter; about 1.5 µm) 0.54 S-1 0.20 Gelatin 1.20

In addition to the above components, gelatin hardener (H-1), surfactants, and thickener (B-1) were added to each layer; the coating amount of thickener (B-1) was 0.165 g/m².

Emulsions used were as follows:

EmC-1:

a monodispersed, internally high silver iodide containing, dual structure core/shell emulsion; average grain size: 0.46 µm; average silver iodide content; 8.0 mol%.

EmC-2:

a monodispersed, internally high silver iodide containing, dual structure core/shell emulsion; average grain size: 0.78 µm; average silver iodide content; 8.0 mol%.

EmC-3:

an emulsion same as Em-B-2 described in Japanese Pat. O.P.I. Pub. No.241336/1991.

EmC-4:

an emulsion prepared as an emulsion of the invention in the same manner as EmC-3, except that 5 × 10⁻⁵ mol/mol AgX of C₂H₅SO₂SNa was added 1 minute before the completion of core formation of EmC-3, and that 1 × 10⁻ ³ mol/mol AgX of ascorbic acid was added 1 minute after the start of shell formation.

EmC-5:

an emulsion prepared in the same manner as in EmC-3, except that 1 × 10⁻⁵ mol/mol AgX of aqueous K₄[Fe(CN)₆] solution was added to solution C₄₋₂ of EmC-3.

EmC-6:

an emulsion prepared in the same manner as in EmC-4, except that 1 × 10⁻⁵ mol/mol AgX of aqueous K₄[Fe(CN)₆] solution was added to solution C₄₋₂ of EmC-4.

Multilayer samples 202 to 204 were prepared in the same manner as in multilayer sample 201, except that EmC-4 to EmC-6 were used in place of EmC-3. Each sample was exposed and processed as in Example 2 to obtain the results shown in Table 11. Sample No. Emulsion Fogging Green Sensitivity 201 EmC-3 0.32 100 202 EmC-4 0.35 120 203 EmC-5 0.25 115 204 (Invention) EmC-6 0.25 175

As is seen in Table 11, sample 204, which was subjected to both reduction sensitization and polyvalent metal doping, was remarkably low in fogging and high in sensitivity.