EP0619515B1

EP0619515B1 - Surface latent image type silver halide photographic emulsion

Info

Publication number: EP0619515B1
Application number: EP19940104787
Authority: EP
Inventors: Hiroyuki C/O Fuji Photo Film Co. Ltd. Mifune; Hirotomo C/O Fuji Photo Film Co. Ltd. Sasaki
Original assignee: Fuji Photo Film Co Ltd
Current assignee: Fujifilm Holdings Corp
Priority date: 1993-04-07
Filing date: 1994-03-25
Publication date: 2000-12-20
Anticipated expiration: 2014-03-25
Also published as: DE69426431T2; EP0619515A1; DE69426431D1

Description

The present invention relates to a silver halide photographic emulsion, and more particularly to a surface latent image type silver halide photographic emulsion containing silver halide grains which have been formed by using a labile tellurium compound suitable for forming silver telluride, whereby tellurium ions are doped into the silver halide grains, and which exhibits sensitivity improved particularly when exposed to the illumination of low intensity for a long time or when subjected to spectral sensitization.
In recent years, it has been increasingly demanded that silver halide photographic light-sensitive materials have higher sensitivity, better graininess, higher gradation and higher sharpness, and also greater process-readiness such as development processing readiness.
Generally, a silver halide photographic emulsion is spectrally sensitized with a sensitizing dye to be photographically sensitive to light beams in a wavelength region, such as green light, red light and infrared rays, which the silver halide cannot absorb. To acquire desired sensitivity, desired gradation, and the like, the emulsion is subjected to so-called chemical sensitization, such as chalcogen sensitization (e.g., sulfur sensitization, selenium sensitization, or tellurium sensitization), noble metal sensitization (e.g., gold sensitization), or reduction sensitization, or a combination of these.
Apart from this, efforts have been made to improve the photographic sensitivity of the surface of silver halide grains by doping ions different from silver ions and halogen ions into the silver halide grains.
In particular, some techniques are known which consists in doping the anions of different kinds, more specifically ions of Sulfur Group (known also as VIB Group, or chalcogen) atom, such as sulfur, selenium, or tellurium, into the silver halide grains. U.S. Patent 3,772,031, for example, discloses the technique of uniformly doping the ions of Sulfur Group atom used in concentration of 2 to 10 ppm into the silver halide grains, thereby to increase the surface sensitivity of the grains.
JP-C-4-506267 (corresponding to WO 90-16014 and also to U.S. Patent 5,166,045) discloses the technique of doping the ions of Sulfur Group atom, particularly selenium ions (selenocyanate) into the 65 to 90% of all silver used in forming silver halide grains. ("JP-C" means Published Unexamined PCT Domestic Patent Application.)
Further, JP-A-4-33541 discloses the technique of doping the ions of Sulfur Group atom and an ion compound into the grains in an emulsion having a high content of silver chloride. (JP-A means "Published Unexamined Japanese Patent Application.) In the examples disclosed in these patent publications, however, the grains are doped with sulfur or selenium only, and not doped with tellurium. U.S. Patent 5,164,292 discloses the technique of doping selenium or iridium into the surface area existing in the silver halide grains.
As described above, several techniques are known, wherein the ions of Sulfur Group atom are doped into the silver halide grains, thereby to improve the surface sensitivity of the silver halide grains. The specific examples of these techniques involve use of sulfur and selenium only. U.S. Patent 3,772,031, JP-C-4-506267, and JP-A-4-33541, all mentioned above, disclose four specific examples of tellurium compounds. Of these examples, allyltellurourea, allyisotellurocyanate, and tellurocarabamide (tellurourea) are compounds which are not reported to have been synthesized hitherto. Further, potassium tellurocyanate (KTeCN) is an extremely labile compound not reported to have been isolated, as is described in Gmelin Handbuch der anorganischen Chemie, 8. Auflage, Kolenstoff Teil D-6 Verfinduingen (Sections 3-6 and 3-4).
As indicated above, tellurium is considerably different from sulfur and selenium, though they are same elements of Sulfur Group atom. The aforementioned three patent publications disclose no particular examples involving tellurium. Hence it can be said that any actual doping of tellurium ions has not been known.
U.S. Patent 4,923,794 and JP-A-53-57817 disclose the technique of adding specific tellurium compounds during the forming of silver halide grains. The tellurium compounds actually used (i.e., telluroethers and tellurides) do not form silver telluride by decomposing in a silver halide emulsion. Rather, they function as silver halide solvents for forming a complex obtained by reaction with silver ions; they are used for an object totally different from the object of the present invention.
As is known generally, the tellurium compounds are far more difficult to synthesize and stably isolate, than the sulfur and selenium compounds. As well expected from its nature of element, tellurium bonds to silver ions much more firmly than sulfur and selenium bond to silver ions. Thus it is necessary to prepare tellurium compounds which may be used to dope tellurium ions into the silver halide grains with high efficiency and high reproducibility.
Therefore, it has been greatly desired that a technique be developed which can dope the tellurium ions into the silver halide grains with high reproducibility.
The first object of the present invention is to provide a silver halide photographic emulsion having high sensitivity.
The second object of the present invention is to provide a silver halide photographic emulsion which exhibits an excellent sensitivity when subjected to spectral sensitization and/or when exposed to low illumination intensity for a long time.
The third object of the present invention is to provide a silver halide emulsion having improved photographic properties, by employing a technique of doping tellurium ions into the silver halide grains, with high reproducibility and with excellent production suitability.
The above-mentioned objects of the present invention are achieved by the emulsion specified below:
A surface latent image type silver halide photographic emulsion characterized by containing silver halide grains which are made of a silver bromide-based compound having a silver bromide content of 60 mol% or more and selected from the group consisting of silver bromide, silver iodobromide, silver chlorobromide or silver chloroiodobromide, which have been formed in the presence of a tellurium compound which forms silver telluride in silver bromide emulsion at a pseudo-first-order reaction rate constant k of 1 × 10^-7 min^-1 to 1 × 10^-1 min^-1, and in which tellurium ions have been thereby doped.
The present invention will be described in detail.
The rate at which to form silver telluride in a silver halide emulsion can be determined by one of the tests (a) and (b) described below.
(a) When a tellurium compound is added in a great amount, the silver telluride formed absorbs light in the visible region. Hence, the method for sulfur sensitizers disclosed in E. Mosar, "Journal of Photographic Science," Vol. 14, p. 181 (1966) and ibid, Vol. 16, p. 102 (1968) can be applied. More specifically, an emulsion which contains octahedral silver bromide grains having an average size of 0.5 µm (containing 0.75 mol of AgBr and 80g of gelatin per kilogram) is maintained at 50°C, while holding pH and pAg at 6.3 and 8.3, respectively. A tellurium compound dissolved in an organic solvent (e.g., methanol) is added to the emulsion, in an amount of 1 × 10^-3 mol/mol Ag. The resultant emulsion is filled in a cell having a thickness of 1 cm. Then, the reflectivity (R) which the emulsion exhibits to light having a wavelength of 520 nm is detected at times by means of a spectrophotometer having an integrating sphere, by using the reflectivity of a blank emulsion as reference. Every reflectivity, thus detected, is substituted in the Kubelka-Munk Formula, (1-R)²/2R. From changes in the reflectivity (R), a pseudo-first-order reaction rate constant K min^-1 is determined.
(b) A tellurium compound may be added in so small an amount that the absorption of light in the visible region can hardly be detected. In this case, a tellurium sensitizer is added to the same silver bromide emulsion (50 °C, pAg 8.3, pH = 6.3) as used in the test (a), the emulsion is immersed in an aqueous solution of a halogen salt or an aqueous solution of a water-soluble mercapto compound, thereby isolating the tellurium sensitizer unreacted. Then, Te of the silver telluride formed in silver bromide is quantitatively analyzed continuously by means of atomic adsorption spectrometry, thereby obtaining a pseudo-first-order reaction rate constant K min^-1.
The pseudo-first-order reaction rate constants k of the tellurium compounds used in the present invention, which have been obtained by performing the test described above, are as follows:
Compound (4): 7 × 10^-5 min^-1
Compound (10): 2 × 10^-3 min^-1
Compound (18): 2 × 10^-4 min^-1
Compound (23): 1 × 10^-2 min^-1
Compound (39): 8 × 10^-4 min^-1
Compound (62): 6 × 10^-4 min^-1
Compound (63): 2 × 10^-2 min^-1
In the case of 3-telluro-pentane-1,5-diol (the compound disclosed in U.S. Patent 4,923,794) and bis-(p-ethoxyphenyl)telluride (the compound disclosed in JP-A-53-57817), no silver telluride is formed, k is 0, and k of K₂Te is 10 min^-1 or more. These compounds are not suitable for tellurium ion doping.
Namely, tellurium compounds which have k ranging from 1 × 10^-7 to 1 × 10^-1 min^-1, preferably 1 × 10^-6 to 1 × 10^-1 min^-1 are suitable for the tellurium ion doping according to the present invention, which has high reproducibility.
If k exceeds 1 × 10^-1 min^-1, the reaction rate will be so high that the silver halide grains may be doped not uniformly between them. On the other hand, if k is less than 1 × 10^-7, the reaction rate will be so low that tellurium ions will hardly be doped into the grains, and k less than 1 × 10^-7 is not practical and not preferable.
More specifically, tellurium ions are doped into grains by using a tellurium compound represented by any of the following formulas (I), (II) and (III).
In the formula (I), R₁₁ and R₁₂ and R₁₃ represent aliphatic groups, aromatic groups, heterocyclic groups, -OR₁₄, -NR₁₅(R₁₆), -SR₁₇, -OSiR₁₈(R₁₉)(R₂₀), X or hydrogen atoms, R₁₄ and R₁₇ represent aliphatic groups, aromatic groups, heterocyclic groups or hydrogen atoms or cations, R₁₅ and R₁₆ represent aliphatic groups, aromatic groups, heterocyclic groups or hydrogen atoms, R₁₈, R₁₉ and R₂₀ represent aliphatic groups, and X represents halogen atoms.
In the formula (II), R₂₁ represents aliphatic group, aromatic group, heterocyclic group or -NR₂₃(R₂₄), R₂₂ represents -NR₂₅(R₂₆), -N(R₂₇)N(R₂₈)R₂₉ or -OR₃₀, R₂₃, R₂₄, R₂₅, R₂₆, R₂₇, R₂₈, R₂₉ and R₃₀ represent aliphatic groups, aromatic groups, heterocyclic groups or acyl groups, R₂₁ and R₂₅, R₂₁ and R₂₇, R₂₁ and R₂₈, R₂₁ and R₃₀, R₂₃ and R₂₅, R₂₃ and R₂₇, R₂₃ and R₂₈, and R₂₃ and R₃₀ may be bonded to each other to form a ring. R₃₁(Te)_n-R₃₂ In the formula (III), R₃₁ and R₃₂ may be same or different and each represent -(C=Y')-R₃₃, R₃₃ represents a hydrogen atom, aliphatic group, aromatic group, heterocyclic group, -NR₃₄(R₃₅), -OR₃₆ or -SR₃₇, Y' represents an oxygen atom, a sulfur atom, or NR₃₈, R₃₄, R₃₅, R₃₆, R₃₇ and R₃₈ represent hydrogen atoms, aliphatic groups, aromatic groups, or heterocyclic groups, and n is 1 or 2.
Tellurium compounds represented by the formulas (I), (II) and (III) will be explained in detail.
First, compounds of the formula (I) will be described in detail.
The aliphatic groups represented by R₁₁, R₁₂, R₁₃, R₁₄, R₁₅, R₁₆, R₁₇, R₁₈, R₁₉, and R₂₀ in the formula (I) are preferably those having 1 to 30 carbon atoms. Particularly preferable are alkyl group, alkenyl group, alkynyl group, and aralkyl group, each having 1 to 20 carbon atoms and present in the form of a straight chain, a branch, or a ring. Examples of alkyl group, alkenyl group, alkynyl group and aralkyl group are: methyl, ethyl, n-propyl, isopropyl, t-butyl, n-octyl, n-decyl, n-hexadecyl, cyclopentyl, cyclohexyl, allyl, 2-butenyl, 3-pentenyl, propargyl, 3-pentynyl, benzyl, and phenetyl.
The aromatic groups represented by R₁₁, R₁₂, R₁₃, R₁₄, R₁₅, R₁₆, and R₁₇ in the formula (I) are preferably those having 6 to 30 carbon atoms. Particularly preferred is aryl group having 6 to 20 carbon atoms and present in the form of a single ring or a condensed ring, such as phenyl group or naphthyl group.
The heterocyclic groups identified by R₁₁, R₁₂, R₁₃, R₁₄, R₁₅, R₁₆, and R₁₇ in the formula (I) are saturated or unsaturated 3- to 10-membered heterocyclic groups, each having at least one atom selected from the group consisting of a nitrogen atom, an oxygen atom and a sulfur atom. They can form a single ring, or can form a condensed ring together with an aromatic ring or a heterocyclic ring. The heterocyclic groups are preferably 5- to 6-membered aromatic heterocyclic groups, such as pyridyl, furyl, thienyl, thiazolyl, imidazolyl, and benzimidazolyl.
The cations represented by R₁₄ and R₁₇ in the formula (I) are of, for example, alkali metal or ammonium.
The halogen atom identified by X in the formula (I) is, for example, a fluorine atom, a chlorine atom, a bromine atom, or a iodine atom.
The aliphatic groups, the aromatic groups, and the heterocyclic groups, all specified above, can be substituted. The substituent groups are represented below.
Typical examples of the substituent groups are: alkyl group, aralkyl group, alkenyl group, alkynyl group, aryl group, alkoxy group, aryloxy group, amino group, acylamino group, ureido group, urethane group, sufonylamino group, sulfamoyl group, carbamoyl group, sufonyl group, sufinyl group, alkyloxycarbonyl group, aryloxycarbonyl group, acyl group, acyloxy group, phosphoric amido group, diacylamino group, imido group, alkylthio group, arylthio group, a halogen atom, cyano group, sulfo group, carboxyl group, hydroxyl group, phosphono group, nitro group, and heterocyclic group. These groups may be further substituted.
In the case where two or more substituent groups are used, they can be either same or different.
R₁₁, R₁₂, and R₁₃ may be bonded to each other with phosphorus atoms to form a ring. Further, R₁₅ and R₁₆ may be bonded to each other, to form a nitrogen-containing heterocyclic ring.
In the formula (I), R₁₁, R₁₂, and R₁₃ are preferably aliphatic groups or aromatic groups. More preferably, they are alkyl groups or aromatic groups.
Compounds of the formula (II) will be described in detail.
The aliphatic groups, the aromatic groups and the heterocyclic groups, which are represented by R₂₁, R₂₃, R₂₄, R₂₅, R₂₆, R₂₇, R₂₈, R₂₉, and R₃₀ in the formula (II), are of the same meaning as in the formula (I).
The acyl groups represented by R₂₃, R₂₄, R₂₅, R₂₆, R₂₇, R₂₈, R₂₉, and R₃₀ are preferably those having 1 to 30 carbon atoms. More preferably, they are acyl groups having 1 to 20 carbon atoms and present in the form of a straight chain or a branch. Examples of these acyl groups are acetyl, benzoyl, formyl, pivaloyl, and decanoyl.
In the case where R₂₁ and R₂₅, R₂₁ and R₂₇, R₂₁ and R₂₈, R₂₁ and R₃₀, R₂₃ and R₂₅, R₂₃ and R₂₇, R₂₃ and R₂₈, and R₂₃ and R₃₀ are bonded to each other to form a ring, the ring is, for example, alkylene groups, arylene groups, aralkylene groups or alkenylene groups.
The aliphatic groups, the aromatic groups, and the heterocyclic groups can be substituted by the substituent groups specified in the formula (I).
In the formula (II), R₂₁ is preferably aliphatic group, aromatic group, or -NR₂₃(R₂₄), where R₂₂ is -NR₂₅(R₂₆). R₂₃, R₂₄, R₂₅, and R₂₆ are aliphatic groups or aromatic groups.
More preferably, in the formula (II), R₂₁ is aromatic group or -NR₂₃(R₂₄), and R₂₂ is -NR₂₅(R₂₆). R₂₃, R₂₄, R₂₅, and R₂₆ are alkyl groups or aromatic groups. Preferably, R₂₁ and R₂₅, and R₂₃ and R₂₅ are attached to each other through alkylene group, arylene group, aralkylene group or alkenylene group, forming a ring.
Compounds of the formula (III) will be described in detail.
The aliphatic groups, the aromatic groups or the heterocyclic groups, which are represented by R₃₃, R₃₄, R₃₅, R₃₆, R₃₇, and R₃₈ in the formula (III), are of the same meaning as in the formula (I).
The aliphatic groups, the aromatic groups, and the heterocyclic groups represented by R₃₃, R₃₄, R₃₅, R₃₆, R₃₇, and R₃₈ can be substituted by the substituent groups specified in the formula (I).
R₃₁ and R₃₂, R₃₄ and R₃₅ may be bonded to each other to form a ring.
In the formula (III), R₃₁ and R₃₂ is preferably -(C=Y')-R₃₃, R₃₃ is -NR₃₄(R₃₅) or -OR₃₆, and Y' is an oxygen atom. R₃₄, R₃₅, and R₃₆ represent aliphatic groups, aromatic groups or heterocyclic groups.
Specific examples of the compounds represented by the formulas (I), (II) and (III) are as follows. Nonetheless, the compounds used in the present invention are not limited to these specified below.
The compounds of the formulas (I), (II) and (III), which are used in the present invention, can be synthesized by the methods disclosed in, for example, Journal of Chemical Society (A), 2927, (1969); Journal of Organometallic Chemistry 4, 320 (1965); ibid., 1, 200 (1963); ibid., 113, C35, C35 (1976); Phosphorus Sulfur, 15, 155 (1983); Chemische Berichte, 109, 2996 (1976); Journal of Chemical Society Chemical Communication, 635 (1980); ibid., 1102 (1979); ibid., 645 (1979); ibid., 820 (1987); Journal of Chemical Society Perkin Transaction, 1, 2191 (1980); S Patai, ed., the Chemistry of Organo Selenium and Tellurium Compounds, Vol. 2, pp. 216-267 (1987); Tetrahedron Letters, 31, 3587 (1990); Journal of Chemical Research Synopses, 2, 56 (1990); Bulletin of the Chemical Society of Japan, 62, 2117 (1989); ibid., 60, 771 (1987); Journal of organometallic Chemistry, 338, 9 (1988); ibid., 306, C36 (1986); Journal of the Chemical Society of Japan, Vol. 7, 1475 (1987); Zeitschrift Chemie, 26, 179 (1986); Chemistry Letters, 3, 475 (1987); Indian Journal of Chemistry, Section A, 25A, 57 (1986); Angewandte Chemie, 97, 1051 (1985); Spectrochemica Acta, Part A, 38A, 185 (1982); Organic Preparations and Procedures International, 10, 289 (1978); and Organometallics, 1, 470 (1982).
The amount in which any tellurium compound is used in the present invention depends upon various doping conditions, such as the composition of the silver halide used, time of adding, temperature, pH, and pAg. The tellurium compound can be used in as large an amount as possible, provided that it would not induce excessive internal fog or excessive internal sensitivity. Generally, the tellurium compound in an amount of 1 × 10^-7 to 3 × 10^-4 mol/mol Ag, preferably about 5 × 10^-7 to 1 × 10^-4 mol/mol Ag.
If the amount of the tellurium compound used exceeds 3 × 10^-4 mol/mol Ag, the reaction proceeds so fast that the silver halide grains may be doped not uniformly between them. If the amount of the tellurium compound used is less than 1 × 10^-7 mol/mol Ag, the reaction proceeds so slowly that the grains will hardly be doped. The amount outside the range is unpractical and undesirable.
In the present invention, the tellurium compound can be added at any time, so long as tellurium ions are doped into the silver halide grains. To be specific, tellurium ions can be doped into the grains at any timing of step, from a time before the forming of the grains to a time immediately before the completion of the grain forming. The tellurium ions may be doped uniformly, at a specific position within each grain, for example, into the surface area of the grains. The doping concentration can be varied, the doping can be performed either continuously or intermittently, further, the tellurium ions are doped into the particular portions of the grains, like epitaxial grains.
One part of the addition of the tellurium compound, which has started during the forming of grains, may continue even after the completion of the grain forming.
In the present invention, the tellurium compound can be added by introducing a solution into a reaction vessel wherein silver halide grains are being formed, in the form of an another addition system or a mixture with a halogen salt solution, or the like, said solution having been prepared by dissolving the tellurium compound in water, a water-soluble organic solvent (e.g., methanol, propanol, trifluoroethanol, acetone, methylcellosolve, or N,N-dimethylformamide) or by dispersing the tellurium compound in hydrophilic colloidal solution such as gelatin.
The compounds used in the present invention, represented by the formulas (I), (II), and (III), are similar to the tellurium sensitizers disclosed in, for example, JP-A-4-333043, JP-A-4-204640, JP-A-4-2713441, and JP-A-4-129787. However, any of the sensitizers disclosed in the publications chemically sensitizes, mainly, the surface of a silver halide grain, and is not intended for use in doping tellurium ions into the silver halide grains as in the present invention.
The forming of silver halide grains in the present invention is a step in which an aqueous solution of a silver salt (e.g., silver nitrate) and an aqueous solution of a halogen salt (e.g., potassium bromide, potassium iodide or sodium chloride), or a water dispersion of soluble, already prepared, fine-grain silver halide emulsion is added to an aqueous solution containing hydrophilic protective colloid such as gelatin at a constant speed or a varying speed, either simultaneously or at different times, thereby precipitating and forming silver halide grains at a single stage or a plurality of stages.
Silver halide grains can be prepared at a temperature ranging from 5°C to 95°C, at any desired pH and any desired pAg, for a desired period of time. The "completion of the forming of silver halide grains," in the present invention, means a moment after which the silver halide no longer change in term of size, shape or crystal habit. In effect, it means a point after silver salt, halogen salt or the like has been added and the physical ripening has been performed.
The silver halide emulsion used in the present invention contains a silver bromide-based compound having a silver bromide content of 60 mol% or more and selected from the group consisting of silver bromide, silver iodobromide silver chlorobromide and silver chloroiodobromide preferably from the group consisting of silver bromide and silver iodobromide. The silver bromide content is preferably 75 mol% to 100 mol%. The silver iodide content is preferably 0 to 20 mol%, and the silver chloride content is preferably 0 to 30 mol%.
The silver halide grains used in the present invention are regular crystals such as cubic ones or octahedral ones, irregular crystals such as spherical ones or tabular ones, or crystals of composite shapes. A mixture of grains having different crystal shapes may be used, but it is desirable to use grains having a regular crystal shape.
The silver halide grains used in the present invention may have different phases in the core or the surface, or may have a uniform phase. Multi-layered structure grains which have different iodide compositions in the core and the surface (particularly, the core has a higher iodide content) are preferred, too. The silver halide grains used in the present invention are those in which a latent image is formed mainly on the surface.
In the process of forming silver halide grains or in physical ripening, it is possible to use, e.g., cadmium salt, zinc salt, thallium salt, iridium salt or its complex salt, rhodium salt or its complex salt, or iron salt or its complex salt.
The silver halide emulsion used in the present invention is preferably a tabular grain emulsion, in which grains having a thickness of 0.5 µm or less, preferably 0.3 µm or less, a diameter of preferably 0.6 µm or more, and an average aspect ratio of 3 or more, occupy 50% or more of the total projected area of all grains.
Particularly preferable as a silver halide emulsion for use in the present invention is a monodisperse emulsion which has a statistical variation coefficient of 30% or less, preferably 20% or less. The variation coefficient is a value S/d obtained by dividing the standard deviation S of the equivalent-circuit diameters of individual silver halide grains by an average diameter d, in the distribution represented by the equivalent-circle diameter calculated from the projected area of all grains. Two or more emulsions may be used in the form of a mixture.
The photographic emulsion which is used in the present invention can be prepared by methods described in, for example, P. Glafkides, "Chemie et Phisique 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 order to control the growth of the grains during the forming of silver halide grains, a solvent for silver halide may be used, such as ammonia, potassium rhodanide, ammonium rhodanide, thioether compound (e.g., any of those disclosed in U.S. Patents 3,271,157, 3,574,628, 3,704,130, 4,297,439, and 4,276,374), thione compound (e.g., any of those disclosed in JP-A-53-144319, JP-A-53-82408, and JP-A-55-77737), or amine compound (e.g., any of those disclosed in JP-A-54-100717.
In the present invention, the surface of each grain can be chemically sensitized after silver halide grains have been formed. Chalcogen sensitization such as sulfur sensitization selenium sensitization or tellurium sensitization noble metal sensitization, and reduction sensitization are applied, either singly or in combination.
In sulfur sensitization, a labile sulfur compound can be used. Examples of the unstable sulfur compound are those disclosed in P. Glafkides, "Chemie et Phisique Photographique" Paul Montel, 1987, 5th edition, Research Disclosure, Vol. 307, No. 307105, and the like. Specific examples of the unstable sulfur compound are: thiosulfates (e.g., hypo), thioureas (e.g., diphenyl thiourea, triethyl thiourea, N-ethyl-N'-(4-methyl-2-thiazolyl)thiourea and carboxymethyltrimethyl thiourea), thioamides (e.g., thioacetoamide), rhodanines (e.g., diehtyl rhodanine and 5-benzylidene-N-ethyl-rhodanine), phosphine sulfides (e.g., trimethylphosphine sulfide), thiohydantoins, 4-oxo-oxazoline-2-thiones, disulfides or polysulfides (e.g., dimorpholine disulfide, cystine and hexathiokanethione), mercapto compounds (e.g., cysteine), polythionate, a sulfur compound such as elemental sulfur, and active gelatin.
In selenium sensitization, a labile selenium compound can be used. Examples of the unstable selenium compound are those disclosed in, for example, JP-A-43-13489, JP-A-44-15748, JP-A-4-25832, JP-A-4-109240, JP-4-271341, and JP-5-40324.
Specific examples of labile selenium sensitizers are: colloidal selenium, selenoureas (e.g., N,N-dimethyl selenourea, trifluoromethycarbonyl-trimethyl selenourea, and acetyl-trimethyl selenourea), selenoamides (e.g., selenoacetoamide and N,N-dimethylphenyl selenoamide), phosphineselenides (e.g., triphenyl phosphineselenide, and pentafluorophenyl-triphenyl phosphineselenide), selenophosphates (e.g., tri-p-tolylselenophosphate, and tri-n-butylselenophosphate), selenoketones (e.g., slenobenzophenone), isoselenocyanates, selenocarboxylic acids, selenoesters, and diacylselenides.
In tellurium sensitization, the tellurium compounds used in the present invention and the known labile tellurium compounds can be used. Specific examples of these are: telluroureas (e.g., tetramethyl tellurourea, N,N'-dimethylethylene tellurorea, and N,N'-diphenylethylene tellurourea), phosphinetellurides (e.g., butyl-diisopropyl phosphinetelluride, tributyl phosphinetelluride, tributoxy phosphinetelluride, and ethoxy-diphenyl phosphinetelluride), and diacyl(di) tellurides (e.g., bis(diphenylcarbamoyl)ditelluride, bis(N-phenyl-N-methylcarbamoyl)ditelluride, bis(N-phenyl-N-methylcarbamoyl)telluride, and bis(ethoxycarbonyl)telluride).
In noble metal sensitization, there can be used salts of noble metals such as gold, platinum, palladium and iridium, which are disclosed in P. Glafkides, "Chemie et Phisique Photographique," Paul Montel, 1987, 5th edition, Research Disclosure, Vol. 307, No. 307105, and the like. Of these noble metal sensitizations, gold sensitization is preferred. More specifically, any one of the gold compounds described in, for example, U.S. Patents 2,642,361, 5,049,484, and 5,049,485 may be used in addition to chloroauric acid, potassium chloroaurate, potassium auricthiocyanate, gold sulfide or gold selenide.
In reduction sensitization, used can be made of the known reducing compounds described in P. Glafkides, "Chemie et Phisique Photographique," Paul Montel, 1987, 5th edition, Research Disclosure, Vol. 307, No. 307105, and the like. To be more specific, there may be used aminoiminomethanesulfinic acid (also known as thiourea dioxide), borane compound (e.g., dimethylaminobarane), hydrazine compound (e.g., hydrazine and p-tolylhydrazine), polyamine compound (e.g., diethyltriamine and triethylenetetramine), stannous chloride, silane compound, reductons (e.g., ascorbic acid), sulfite, aldehyde compound, and hydrogen gas. The reduction sensitization may be conducted in a high pH atmosphere or a silver ion-rich (or, silver ripening) atmosphere.
These chemical sensitizations may be performed singly or in combination. When two or more of them are employed together, a combination of chalcogen sensitization and gold sensitization is particularly desirable. Reduction sensitization is conducted, Preferably during the forming of silver halide grains.
The amount in which a chalcogen sensitizer is used in the present invention depends on the type of the silver halide grains used, the conditions of the chemical sensitization and the like. Nonetheless, it is used in an amount of 1 × 10^-8 to 1 × 10^-2 mol per mol of silver halide, preferably about 1 × 10^-7 to 5 × 10^-3 mol per mol of silver halide.
The amount in which a noble metal sensitizer is used in the present invention is about 1 × 10^-7 to 1 × 10^-2 mol per mol of silver halide.
The conditions under which to perform chemical sensitization in the present invention are not limited particularly. Nonetheless, pAg is from 6 to 11, preferably 7 to 10; pH is 4 to 10, preferably 5 to 8; and the temperature is 40 to 95°C, preferably 45 to 85°C.
Photographic emulsions used in the present invention are preferably subjected to spectral sensitization by methine dyes and the like in order to achieve the effects of the present invention. Usable dyes involve a cyanine dye, a merocyanine dye, a composite cyanine dye, a composite merocyanine dye, a holopolar cyanine dye, a hemicyanine dye, a styryl dye, and a hemioxonole dye. Most useful dyes are those belonging to a cyanine dye, a merocyanine dye, and a composite merocyanine dye. Any nucleus commonly used as a basic heterocyclic nucleus in cyanine dyes can be contained in these dyes. Examples of a necleus are a pyrroline nucleus, an oxazoline nucleus, a thiozoline nucleus, a pyrrole nucleus, an oxazole nucleus, a thiazole nucleus, a selenazole necleus, an imidazole nucleus, a tetrazole nucleus, and a pyridine nucleus; a nucleus in which an aliphatic hydrocarbon ring is fused to any of the above nuclei; and a nucleus in which an aromatic hydrocarbon ring is fused to any of the above nuclei, e.g., an indolenine nucleus, a benzindolenine nucleus, an indole nucleus, a benzoxadole nucleus, a naphthoxazole nucleus, a benzthiazole nucleus, a naphthothiazole nucleus, a benzoselenazole nucleus, a benzimidazole nucleus, and a quinoline nucleus. These nuclei may have a substituent on a carbon atom.
It is possible for a merocyanine dye or a composite merocyanine dye to have a 5- or 6-membered heterocyclic nucleus as a nucleus having a ketomethylene structure. Examples are a pyrazoline-5-one nucleus, a thiohydantoin nucleus, a 2-thiooxazolidine-2,4-dione nucleus, a thiazolidine-2,4-dione nucleus, a rhodanine nucleus, and a thiobarbituric acid nucleus.
Although these sensitizing dyes may be used singly, they can also be used together. The combination of sensitizing dyes is often used for a supersensitization purpose. Representative examples of the 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.
Emulsions may contain, in addition to the sensitizing dyes, dyes having no spectral sensitizing effect or substances not essentially absorbing visible light and presenting sueprsensitization.
The sensitizing dyes can be added to an emulsion at any point in preparation of an emulsion, which is conventionally known to be useful. Most ordinarily, the addition is performed after completion of chemical sensitization and before coating. However, it is possible to perform the addition at the same timing as addition of chemical sensitizing dyes to perform spectral sensitization and chemical sensitization simultaneously, as described in U.S. Patents 3,628,969 and 4,225,666. It is also possible to perform the addition prior to chemical sensitization, as described in JP-A-58-113928, or before completion of formation of a silver halide grain precipitation to start spectral sensitization. Alternatively, as disclosed in U.S. Patent 4,225,666, these compounds can be added separately; a portion of the compounds may be added prior to chemical sensitization, while the remaining portion is added after that. That is, the compounds can be added at any timing during formation of silver halide grains, including the method disclosed in U.S. Patent 4,183,756.
The addition amount may be 4 × 10^-6 to 8 × 10^-3 mole per mole of silver halide. However, for a more preferable silver halide grain size of 0.2 to 1.2 µm, an addition amount of about 5 × 10^-5 to 2 × 10^-3 mole per mole of silver halide is effective.
The silver halide photographic emulsion according to the present invention can be applied to various color light-sensitive materials and various black-and-white light-sensitive materials. Representative examples of the material are a color negative film for a general purpose or a movie, a color reversal film for a slide or a television, color paper, a color positive film, color reversal paper, light-sensitive material of diffusion transfer color type, and color light-sensitive material of heat development type. The present invention can also be applied to black-and-white light-sensitive materials for used in X-ray photography, by using the three-color coupler mixing described in Research Disclosure No. 17123 (July 1978) and the like and the black coloring coupler described in U.S. Patent 4,126,461, British Patent 2,102,136 and the like. Furthermore, the present invention can be applied to print-making film such as lithograph film or scanner film, X-ray photographic film for direct and indirect medical use or industrial use, black-and-white negative photographic film, black-and-white printing paper, COM or ordinary microfilm, light-sensitive material of diffusion transfer silver-salt type, and light-sensitive material of printout type.
Various techniques and various organic and inorganic materials, which can be utilized with the silver halide photographic emulsion of the present invention and also with silver halide photographic light-sensitive material using the emulsion, are generally those described in Research Disclosure No. 308119 (1989).

In addition, there are other techniques and organic and inorganic materials, which can be utilized with color photographic light-sensitive materials to which the silver halide photographic emulsion of the present invention can be applied. These techniques and organic and inorganic materials are described in European Patent 436,983A2, at the parts specified below, and also in some other European patents identified below:

Item	Related Part
1)	Layer structure	Page 146, line 34 to page 147, line 25
2)	Silver halide emulsion	Page 147, line 26 to page 148, line 12
3)	Yellow couplers	Page 137, line 35 to page 146, line 33; page 149, lines 21-23
4)	Magenta couplers	Page 149, lines 24-28; European Pat. 421,453A1, page 3, Line 5 to page 25, line 55
5)	Cyan couplers	Page 149, line 29-33; European Pat. 432,80A2, page 3, line 28 to page 40, line 2
6)	Polymer couplers	Page 149, lines 34-38; European Pat. 435,334A2, page 113, line 39 to page 123, line 37
7)	Colored couplers	Page 53, line 42 to page 137, line 34; page 149, lines 39-45
8)	Other functional couplers	Page 7, line 1 to page 53, line 41; page 149, line 46 to page 150, line 3; European Pat. 435,334A2, page 3, line 1 to page 29, line 50
9)	Antiseptic and antifungal agents	Page 150, lines 25-28
10)	Formalin scavenger	Page 149, lines 15-17
11)	Other additives	Page 153, lines 38-47; European Pat. 421,453A1, page 75, line 21 to page 84, line 56, and page 27, line 40 to page 37, line 40
12)	Dispersing method	Page 150, lines 4-24
13)	Supports	Page 150, lines 32-34
14)	Thickness and physical properties of film	Page 150, lines 35-49
15)	Color developing	Page 150, line 50 to page 151, line 47
16)	Desilvering	Page 151, line 48 to page 152, line 53
17)	Automatic Development machine	Page 152, line 54 to page 153, line 2
18)	Washing, Stabilizing	Page 153, lines 3-37

There is no particular limitation to additives and the like, which may be used in X-ray purpose photographic light-sensitive materials made by applying the silver halide photographic emulsion of the present invention. For example, those specified in the following publications can be used.

Item	Related Part
1)	Silver halide emulsions and methods of manufacturing them	JP-A-2-68539, page 8, lower-right col., line 6 from the bottom, to page 10, upper-right col., line 12; JP-A-3-24537, page 2, lower-right col., line 10 to page 6, upper-right col., line 1, and page 10, upper-left col., line 16 to page 11, lower-left col., line 19; JP-A-4-107442
2)	Methods of chemical sensitization	JP-A-2-68539, page 10, upper-right col., line 13 to upper-left col., line 16; JP-A-5-313282
3)	Antifoggants and stabilizers	JP-A-2-68539, page 10, lower-left col., line 17 to page 11, upper-left col., line 7, and page 3, lower-left col., line 2 to page 4, lower-left col.
4)	Color tone modifier	JP-A-62-276539, page 2, lower-left col., line 7 to page 10, lower-left col., line 20; JP-A-3-94249, page 6, lower-left col., line 15 to page 11, upper-right col., line 19
5)	Spectral sensitizing dyes	JP-A-2-68539, page 4, lower-right col, line 4 to page 8, lower-right col.
6)	Surfactants, and antistatic agents	JP-A-2-68539, page 11, lower-right col., line 14 to page 12, upper-left col., line 9
7)	Matting agents, lubricants, and plasticizers	JP-A-2-68539, page 12, upper-left col., line 10 to upper-right col., line 10, and page 14, lower-left col., line 10 to lower-right col., line 1
8)	Hydrophilic colloids	JP-A-2-68539, page 12, upper-right col., line 11 to lower-left col., line 16
9)	Hardening agents	JP-A-2-68539, page 12, lower-left col., line 17 to page 13, lower-left col., line 6
10)	Supports	JP-A-2-68539, page 13, upper-right col., lines 7-20
11)	Cross-over cut method	JP-A-2-264944, page 4, upper-right col., line 20 to page 14, upper-right col.
12)	Dyes, mordants	JP-A-2-68539, page 13, lower-left col., line 1 to page 14, lower-left col., line 9; JP-A-3-24537, page 14, lower-left col. to page 16, lower-right col.
13)	Polyhydroxy benzenes	JP-A-3-39948, page 11, upper-left col. to page 12, lower-left col.; European Pat. 452772A
14)	Layer structure	JP-A-3-198041
15)	Developing methods	JP-A-2-103037, page 16, upper-right col., line 7 to page 19, lower-left col., line 15; JP-A-2-115837, page 3, lower-right col., line 5 to page 6, upper-right col., line 10

There is no particular limitation to additives, developing methods, and the like, which may be used with printing-purpose light-sensitive materials made by applying the silver halide photographic emulsion of the present invention. For example, those specified in the following publications can be used.

Item	Related Part
1)	Hydrazine nucleatting agents	JP-A-2-12236, page 2, upper-right col., line 19 to page 7, upper-right col., line 3; Formula (II) and compounds II-1 to II-54 disclosed in JP-A-3-174143, page 20, lower-right col., line 1 to page 27, upper-right col., line 20
2)	Nucleation accelerators	Formulas (II-m) to (II-p) and compounds II-1 to II-22 in JP-A-2-103536, page 9, upper-right col., line 13 to page 16, upper-left col., line 10; compounds described in JP-A-1-179939
3)	Silver halide emulsions, and methods of manufacturing them	Selenium sensitization described in JP-A-2-97937, page 20, lower-right col., line 12 to page 21, lower-left col., line 14, JP-A-2-12236, page 7, upper-right col., line 19 to page 8, lower-left col., line 12, and JP-A-5-11389
4)	Spectral sensitizing dyes	Spectral sensitizing dyes described in JP-A-2-12236, page 8, lower-left col., line 13 to lower-right col., line 4, JP-A-2-103536, page 16, lower-right col., line 3 to page 17, lower-left col., line 20, JP-A-1-112235, JP-A-2-124560, JP-A-3-7928, JP-A-5-11389
5)	Surfactants	JP-A-2-12236, page 9, upper-right col., line 7 to lower-right col., line 7; JP-A-2-18542, page 2, lower-left col., line 13 to page 4, lower-right col., line 18
6)	Antifoggants	Thiosulfinic acid compounds described in JP-A-2-103536, page 17, lower-right col., line 19 to page 18, upper-right col., line 4 and page 18, lower-right col., lines 1-5; JP-A-1-237538
7)	Polymer latexes	JP-A-2-103536, page 18, lower-left col., lines 12-20
8)	Compounds having acid radicals	JP-A-2-103536, page 18, lower-right col., line 6 to page 19, upper-left col., line 1
9)	Matting agents lubricants, and plasticizers	JP-A-2-103536, page 19, upper-left col., line 15 to page 19, upper-right col., line 15
10)	Hardening agents	JP-A-2-103536, page 18, upper-left col., lines 5-17
11)	Dyes	Dyes described in JP-A-2-103536, page 17, lower-right col., lines 1-18, and solid dyes described in JP-A-2-294638 and JP-A-5-11382
12)	Binders	JP-A-2-18542, page 3, lower-right col., lines 1-20
13)	Black-spot preventing agents	Compounds described in U.S. Patent 4,956,257 and JP-A-1-18832
14)	Redox compounds	Compounds represented by the formula (I) in JP-A-2-301743 (particularly, Examples compounds 1 to 50); compounds of the formulas (R-1), (R-2) and (R-3) on page 3 to 20 and Examples compounds 1 to 75; and compounds described in JP-A-5-257239 and Japanese Patent Application 3-15648
15)	Monomethine compounds	Compounds represented by the formula (II) in JP-A-2-287532 (particularly, Examples compounds II-1 to II-26)
16)	Dihydroxy benzenes	Compounds described in JP-A-3-39948, page 11, upper-left col. to page 12, lower-left col., and compounds described European Pat. 452772A
17)	Development, and developing solutions	JP-A-2-103536, page 19, upper-right col., line 16 to page 21, upper-left col., line 8

Examples

Specific examples of the present invention will now be described. Nonetheless, the present invention is not limited to these examples. Various changes may be made without departing the scope of the present invention.

Example 1

First, 75 mℓ, of a silver nitrate aqueous solution IA (1 mol) and a potassium bromide aqueous solution IB (1 mol) were simultaneously added, over 8 minutes, to 1 litter of a pH 5.3 aqueous solution containing 0.5g of potassium bromide and 30g of gelatin, while stirring the solution and maintaining the solution at 75°C and while holding silver potential at 0 mV with respect to a saturated calomel electrode. Next, 1.2g of potassium bromide was added to the resultant solution. Furthermore, 677 mℓ, of a silver nitrate aqueous solution IIA (1 mol) and a potassium bromide aqueous solution IIB (1 mol) were simultaneously added to solution over 54 minutes, while holding the silver potential at -30 mV.
Along with the addition of the solution IIA, 75 mℓ of a methanol solution of any one of the compounds shown in Table 1 (presented later), that was to be used for doping, was added to the solution over 50 minutes. As a result, Emulsions 1 to 16 were prepared.
Each of the silver bromide emulsions, thus prepared, was a monodisperse octahedral emulsion having an average grain diameter of 0.34 µm and a variation coefficient of 10% in terms of average grain diameter, whether the emulsion contained a compound used for doping or whichever type that compound is.
After grains had been formed, each emulsion was desalted by means of ordinary flocculation and then washed with water. Then, gelatin and water were added to the emulsion, thereby adjusting pH and pAg to 6.4 and 8.6, respectively.
To a portion of each emulsion (each grain having its surface not chemically sensitized), there were added gelatin, 4-hydroxy-6-methyl-1,3,3a,7-tetraazinedene, potassium polystyrenesulfonate, and sodium dodecylbenzenesulfonate. The emulsion was then coated on a triacetyl cellulose film support having an undercoating layer, by means of co-extrusion method, together with a protective layer which contained gelatin, polymethylmethacrylate grains and 2,4-dichloro-6-hydroxy-s-triazine sodium salt. As a result, Samples 1 to 16 were formed.
Samples 1 to 16 were subjected to sensitometry exposure (10 seconds) in which light was applied through an optical wedge. Thereafter, the samples were developed for 20°C for 10 minutes with MAA-1 developing solution specified below. After the development, the samples were stopped, fixed, washed, dried, and tested for their densities, by ordinary methods.

MAA-1 developing solution

Metol 2.5g

Ascorbic acid 10g

Nabox (NaBO₂ · 4H₂O) 35g

Potassium bromide 1g

Water to make 1 liter

The relative sensitivity of each sample was represented by a relative value of a reciprocal of the exposure amount required to impart an optical density of fog +1.0. The relative sensitivity was represented by a relative value, assuming that the sensitivity of the Sample 3 is 100. The results of the test were as is shown in the following Table 1:

Emulsion	Sample	Compound used for doping	Addition amount (mol/mol Ag)	Sensitivity	Remarks
1	1	--	--	4	Comparative example
2	2	Thioacetoamide	(S)	7 × 10^-6	70	"
3	3	"		2.1 × 10^-5	100	"
4	4	Selenourea	(Se)	2.1 × 10^-5	145	"
5	5	(4)	(Te)	7 × 10^-6	331	Present invention
6	6	(10)	(Te)	7 × 10^-6	339	"
7	7	(10)	(Te)	2.1 × 10^-5	316	"
8	8	(18)	(Te)	7 × 10^-6	340	"
9	9	(23)	(Te)	7 × 10^-6	282	Present invention
10	10	(26)	(Te)	7 × 10^-6	321	"
11	11	(39)	(Te)	2 × 10^-6	186	"
12	12	(39)	(Te)	7 × 10^-6	380	"
13	13	(39)	(Te)	2.1 × 10^-5	372	"
14	14	(43)	(Te)	7 × 10^-6	355	"
15	15	(62)	(Te)	7 × 10^-6	363	"
16	16	K₂Te	(Te)	7 × 10^-6	51	Comparative example

As is evident from Table 1, the samples which had the tellurium ions doped into the grains by using the compound used in the present invention exhibited, in using a smaller amount of the compound, such a high sensitivity as could not be expected from the samples which had sulfur or selenium ions doped into the grains, when all these samples were subjected to low illumination intensity and long-time exposure.
On the other hand, the sample which had a compound (K₂Te) which fast generates silver telluride doped into the grains, had a low sensitivity and achieved but a considerably soft gradation, and could not acquire the advantage of using the tellurium ions doping.

Example 2

A portion of each of Emulsions 1, 3, 4, 6, 8, 9, 12, 14, 15 and 16 of Example 1 was heated to 60°C. Then, 1.2 × 10^-5 mol/mol AgX of bis(N-phenyl-N-methyl)carbamoyl telluride was added to the portion (but, 1.6 × 10^-5 mol/mol AgX to the portion of Emulsion 1), thereby optimally tellurium-sensitizing the surface of each silver halide grain. As a result of this, Samples 20 to 29 were formed.

Thereafter, Samples 20 to 29 were subjected to exposure in the same way as in Example 1, except that each was exposed to light twice, for 10 seconds and for 10^-3 second. The results of the exposure were as is shown in the following Table 2. It should be noted that the sensitivity each sample exhibited after exposed for 10 seconds and the sensitivity it exhibited after exposed for 10^-3 second were represented in a relative sensitivity. The relative sensitivity was represented by a relative value, assuming that the sensitivity of the Sample 21 is 100. (Sample 3 had a relative sensitivity of 68 after exposed for 10 seconds.)

Emulsion	Sample	Compound used for doping	Sensitivity 10 sec	Sensitivity 10^-3 sec	Fog	Remarks
1	20	--	58	91	0.03	Comparative example
3	21	Thioacetoamide	(S)	100	100	0.04	"
4	22	Selenourea	(Se)	121	110	0.06	"
6	23	(10)	(Te)	191	118	0.05	Present invention
8	24	(18)	(Te)	186	123	0.05	"
9	25	(23)	(Te)	170	120	0.04	"
12	26	(39)	(Te)	219	120	0.05	"
14	27	(43)	(Te)	195	116	0.05	"
15	28	(62)	(Te)	204	118	0.04	"
16	29	K₂Te	(Te)	81	94	0.08	Comparative example

As is clear from Table 2, the samples which had the tellurium ions doped into the grains by using the compound used in the present invention, in the case of having silver halide grains chemically sensitized at its surface, had a higher sensitivity than the emulsions which had sulfur or selenium ions doped into the grains, and had not a high sensitization degree after short-time exposure of 10^-3 second, when all these samples were subjected to low illumination intensity and long-time exposure, though they had a sensitivity not so higher than those whose silver halide grains had not been chemically sensitized at its surface.

Example 3

First, a silver nitrate aqueous solution IA (containing 32g of AgNO₃, 0.7g of gelatin having an average molecular weight of 200,000 and 0.14 mℓ of 1N HNO₃O in 100 mℓ) and a KBr aqueous solution IB (containing 23.2g of KBr and 0.7g of gelatin having an average molecular weight of 200,000 in 100 mℓ) were added to 1 liter of an aqueous solution heated to 30°C and containing 4.5g of KBr and 7g of gelatin having an average molecular weight of 200,000, each in an amount of 27.5 cc, over at the rate of 25 cc/min, by means of double-jet method while stirring the aqueous solution. An emulsion was thereby prepared.
To 350 mℓ of this emulsion, used as seed crystal, 650 mℓ of a gelatin aqueous solution (containing 20g of gelatin and 1.2g of KBr) was added. The resultant solution was heated to 75°C and ripened for 40 minutes. Thereafter, an silver nitrate aqueous solution IIA (containing 1.7g of AnNO₃) was added to the solution over 1 minute and 30 seconds. Next, 6.2 mℓ of an NH₄NO₃ aqueous solution (50 wt%) and 6.2 mℓ of an NH₃ aqueous solution (25 wt%) were added, and the resultant solution was ripened for 40 minutes. Then, the emulsion was adjusted to pH 7.0, with an HNO₃(3N) solution, and 1g of KBr was added to the emulsion. Thereafter, a silver nitrate aqueous solution IIIA (containing 10g of AgNO₃ in 100 mℓ) and a mixture aqueous solution IIIB of KBr and KI (containing 8.4g of KBr and 0.6g of KI in 100 mℓ) were added by CDJ (Controlled Double-Jet) at the rate of 8 mℓ/min for the first 10 minutes, and at the rate of 15 mℓ/min for the next 20 minutes at silver potential of -20 mV. Then, 500 mℓ of a methanol solution of each compound shown in Table 3, was simultaneously and continuously added, for the last 10 minutes of the addition of the solution IIIA, thereby obtaining Emulsions 20 to 27. Also, 500 mℓ of a methanol solution of the compound last-mentioned in Table 3 was added, at a time, 10 minutes before the completion of addition of the solution IIIA, thereby obtaining Emulsion 28. Emulsions 20 to 28, thus obtained, had monodisperse hexagonal tabular silver iodobromide grains having an average diameter of 1.1 µm, an average thickness of 0.16 µm, an aspect ratio of 6.9, and an average variation coefficient of 12.5% in terms of average diameter.
After the addition process of compound solution, each emulsion was cooled to 35°C, desalted by ordinary flocculation and then washed with water. Then, gelatin and water were added to the emulsion, thereby adjusting pH and pAg to 6.8 and 8.4, respectively.
Each emulsion was heated to 56°C. Anhydro-5-chloro-5'-phenyl-9-ethyl-3,3'-di(3-sulfopropyl)oxacarbocyanine hydroxide sodium salt was added as a sensitizing dye to the emulsion. Thereafter, chloroauric acid (1.2 × 10^-5 mol/mol Ag), sodium thiosulfate (3.6 × 10^-5 mol/mol Ag), triphenylphosphine selenide (9 × 10^-6 mol/mol Ag), and potassium thiocyanate (1 × 10^-3 mol/mol Ag) were added to each emulsion, thereby optimally gold-sulfur-selenium sensitizing the surface of each silver halide grain.
Thereafter, a magenta coupler, i.e., 3-{3-[2,4-di-tert-amylphenoxy)butylylamino]benzoylamino}-1-(2,4,6-trichlorophenyl)pyrazoline-5-on oil, i.e., tricresylphosphate, a stabilizer, i.e., 4-hydroxy-6-methyl-1,3,3a,7-tetraazinedene, antifoggants, i.e., monosodium 1-(m-sulfophenyl)-5-mercaptotetrazole and 1-(p-carboxyphenyl)-5-mercaptotetrazole, a coating aid, i.e., sodium dodecylbenzenesulfonate, a hardening agent, i.e., 1,2-bis(vinylsulfonylacetylamino)ethane, and an antiseptic, i.e., phenoxyethanol were added to each emulsion. Each emulsion was coated on a triacetyl cellulose film support having an undercoating layer, by means of co-extrusion method, together with a protective gelatin layer which contained polymethylmethacrylate grains. As a result, Samples 41 to 49 were formed.

Samples 41 to 49 were subjected to sensitometry exposure (10 seconds) in which light was applied through a yellow filter, and were then developed under the conditions which will be specified below.

(Processing Method)
Process	Time	Temp.
Color development	2 min. 15 sec.	38°C
Bleaching	6 min. 30 sec.	38°C
Washing	2 min. 10 sec.	24°C
Fixing	4 min. 20 sec.	38°C
Washing (1)	1 min. 05 sec.	24°C
Washing (2)	1 min. 00 sec.	24°C
Stabilization	1 min. 05 sec.	38°C
Drying	4 min. 20 sec.	55°C

The compositions of the solutions used in the color-developing process are as follows:

(Color Developing Solution)	(g)
Diethylenetriaminepentaacetate	1.0
1-hydroxyethylidine-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-hydroxyl-ethylamino)-2-methylaniline sulfate	4.5
Water to make	1.0 liter
pH	10.05

(Bleaching Solution)	(g)
Ferric sodium ethylenediamine tetraacetate trihydrate	100.0
Disodium ethylenediamine tetraacetate	10.0
Ammonium bromide	140.0
Ammonium nitrate	30.0
Ammonia water (27%)	6.5 mℓ
Water to make	1.0 liter
pH	6.0

(Fixing Solution)	(g)
Disodium ethylenediamine tetraacetate	0.5
Sodium sulfite	7.0
Sodium bisulfite	5.0
Ammonium thiosulfate aqueous solution (70%)	170.0 mℓ
Water to make	1.0 liter
pH	6.7

(Stabilizing Solution)	(g)
Formalin (37%)	2.0 mℓ
Polyethylene-p-monononylphenylether (polymerization degree: 10)	0.3
Disodium ethylenediamine tetraacetate	0.05
Water to make	1.0 liter
pH	5.0-8.0

Processed samples 41 to 49 were tested for their densities, using a green filter. The obtained results of the photographic properties which the samples presented were as is shown in Table 3. The relative sensitivity of each sample is represented by a relative value of a reciprocal of the exposure amount required to impart an optical density (fog + max. density/2). The relative sensitivity of each sample was represented by a relative value, assuming that the sensitivity of the sample 41 is 100.

Emulsion	Sample	Compound used for doping	Addition amount (mol/mol Ag)	Fog	Relative spectral sensitivity	Remarks
20	41	Thioacetoamide	(S)	8 × 10^-6	0.22	100	Comparative example
21	42	Selenourea	(Se)	8 × 10^-6	0.35	108	"
22	43	(15)	(Te)	4 × 10^-6	0.26	145	Present invention
23	44	(39)	(Te)	4 × 10^-6	0.24	166	"
24	45	(63)	(Te)	4 × 10^-6	0.24	152	"
25	46	(70)	(Te)	4 × 10^-6	0.25	148	"
26	47	K₂Te	(Te)	4 × 10^-6	0.45	85	Comparative example
27	48	--		--	0.20	78	"
28	49	(39)	(Te)	4 × 10^-6	0.24	158	Present invention

As evident from Table 3, the samples which had the tellurium ions into the grains by using the compound used in the present invention exhibited such a high spectral sensitivity as could not be expected from the samples which had sulfur or selenium ions doped into the grains, accompanied by no increase in fog, when all these samples were subjected to low illumination intensity and long-time exposure.

Claims

A surface latent image type silver halide photographic emulsion containing silver halide grains which are made of a silver bromide-based compound having a silver bromide content of 60 mol% or more and being selected from the group consisting of silver bromide, silver iodobromide, silver chlorobromide and silver chloroiodobromide, which have been formed in the presence of a tellurium compound, characterized in that

said tellurium compound forms a silver telluride in silver bromide emulsion at a pseudo-first-order reaction rate constant of 1 x 10^-7 min^-1 to 1 x 10^-1 min^-1,

said tellurium ions have been thereby doped into said silver halide grains, and

said tellurium compound is one represented by the following formula (I) or (III):
where R₁₁, R₁₂ and R₁₃ represent aliphatic groups, aromatic groups, heterocyclic groups, -OR₁₄, -NR₁₅(R₁₆), -SR₁₇, -OSiR₁₈(R₁₉)(R₂₀), X or hydrogen atoms, R₁₄ and R₁₇ represent aliphatic groups, aromatic groups, heterocyclic groups or hydrogen atoms or cations, R₁₅ and R₁₆ represent aliphatic groups, aromatic groups, heterocyclic groups or hydrogen atoms, R₁₈, R₁₉ and R₂₀ represent aliphatic groups, and X represents halogen atoms, R₃₁-(Te)_n-R₃₂ where R₃₁ and R₃₂ may be the same or different and each represent -(C=Y')-R₃₃, R₃₃ represents a hydrogen atom, aliphatic group, aromatic group, heterocyclic group, -NR₃₄(R₃₅), -OR₃₆ or -SR₃₇, Y' represents an oxygen atom, a sulfur atom, or NR₃₈, R₃₄, R₃₅, R₃₆, R₃₇ and R₃₈ represent hydrogen atoms, aliphatic groups, aromatic groups, or heterocyclic groups, and n is 1 or 2.
The surface latent image type silver halide photographic emulsion according to claim 1, characterized in that said tellurium compound is one represented by the following formula (III): R₃₁-(Te)_n-R₃₂ where R₃₁ and R₃₂ may be the same or different and each represent -(C=Y')-R₃₃, R₃₃ represents a hydrogen atom, aliphatic group, aromatic group, heterocyclic group, -NR₃₄(R₃₅), -OR₃₆ or -SR₃₇, Y' represents an oxygen atom, a sulfur atom, or NR₃₈, R₃₄, R₃₅, R₃₆, R₃₇ and R₃₈ represent hydrogen atoms, aliphatic groups, aromatic groups, or heterocyclic groups, and n is 1 or 2.
The surface latent image type silver halide photographic emulsion according to claim 1, characterized in that said tellurium compound is added in an amount of 1 x 10^-7 to 3 x 10^-4 mol per mol of silver.
The surface latent image type silver halide photographic emulsion according to claim 2, characterized in that said tellurium compound is added in an amount of 1 x 10^-7 to 3 x 10^-4 mol per mol of silver.
The surface latent image type silver halide photographic emulsion according to claim 1, characterized in that the surface of each grain has been subjected to chemical sensitization after tellurium ions had been doped into the silver halide grains.
The surface latent image type silver halide photographic emulsion according to claim 1, characterized in that the surface of each grain has been subjected to chalcogen sensitization after tellurium ions had been doped into the silver halide grains.
The surface latent image type silver halide photographic emulsion according to claim 1, characterized in that the surface of each grain has been subjected to gold-chalcogen sensitization after tellurium ions had been doped into the silver halide grains.
The surface latent image type silver halide photographic emulsion according to claim 1, characterized in that said forming of the silver halide grains is performed in the presence of iridium salt, iron salt or complex salts thereof.
The surface latent image type silver halide photographic emulsion according to claim 1, characterized in that said silver halide grains are tabular grains which have an average aspect ratio of 3 or more and which occupy 50% or more of the total projected area of all grains.
The surface latent image type silver halide photographic emulsion according to claim 1, characterized in that said silver halide grains are monodisperse grains which have a variation coefficient of 30% or less in terms of diameters of projected area of all grains.
The surface latent image type silver halide photographic emulsion according to claim 1, characterized in that said silver halide grains contain spectral sensitizing dyes.