Direct Positive Photographic Material

The present invention relates to a direct positive photographic material having at least one photographic emulsion layer containing previously non-fogged internal latent image-type silver halide grains, which provides a positive image having a lowered minimum image density (Dmin) without lowering the maximum image density (Dmax).

A method of forming a direct positive image is well known, where a direct positive photographic material having a previously non-fogged internal latent image-type silver halide emulsion is imagewise exposed and then subjected to surface-development after or during fogging.

The above-mentioned latent image-type silver halide photographic emulsion means a silver halide photographic emulsion of such a type that the silver halide grains therein have light-sensitive nuclei essentially in the inside thereof and a latent image is formed essentially in the inside of the grains by exposure.

Various techniques have been known in this technical field. For instance, U.S. Pat. Nos. 2,592,250, 2,466,957, 2,497,875, 2,588,982, 3,317,322, 3,761,266, 3,761,276 and 3,796,577 and British Patents 1,151,363, 1,150,553 and 1,011,062 illustrate the essential techniques of the field.

Using the known methods, direct positive photographic materials having a relatively high sensitivity can be obtained.

The details of the mechanism of forming direct positive images are set forth, for example, in T. H. James, The Theory of the Photographic Process, Ed. 4, Chap. 7, pages 182 to 193 and U.S. Pat. No. 3,761,276. JP-A-1-52146 (the term "JP-A" as used herein means an "unexamined published Japanese patent application") illustrates a technique of incorporating a metal into silver halide grains so as to elevate the contrast of the photographic material containing the grains. JP-A-1-254946 illustrates a method of obtaining a hard (high-contrast) direct positive photographic material, which contains a thiosulfonic acid in the emulsion and which forms an image having a lowered Dmin.

In order to put a direct positive photographic material into practical use, the material must provide a hard image having a high Dmax and a low Dmin. However, where additives are added to conventional direct positive photographic materials so as to lower the value of Dmin of the image to be formed, the value of Dmax is often lowered because of the addition. For instance, in the method of the above-mentioned JP-A-1 52146, Dmax of the image formed is often lowered when the material contains a large amount of a metal.

In accordance with the method of JP-A-1-254946, a direct positive photographic material providing a hard image having a lowered Dmin can be obtained. However, the material to be produced by the method has drawbacks in that (1) the fresh sensitivity is low and (2) the time-dependent variation of sensitivity during storage (or increase of sensitivity) is great.

Accordingly, the object of the present invention is to provide a direct positive photographic material, which has a high time-dependent stability and which may form a hard image having a high Dmax and a low Dmin.

The subject matter of the present invention has been attained by a direct positive photographic material comprising a support having thereon at least one photographic emulsion layer containing previously non-fogged internal latent image-type silver halide grains, wherein the photographic emulsion layer contains at least one compound of general formula (I), (II) or (III):

wherein M represents a hydrogen atom or a cation, and wherein the internal latent image-type silver halide grains are silver bromide, silver chloride, silver iodobromide, silver chlorobromide or silver chloroiodobromide grains and contain at least one metal selected from the group comprising manganese, copper, zinc, cadmium, rhenium, lead, bismuth, indium, thallium, zirconium, lanthanum, chromium, mercury and metals of Group VIII of the Periodic Table.

As one preferred embodiment of the direct positive photographic material of the present invention, the photographic emulsion layer may further contain at least one compound of formulae (IV), (V) and (VI):

wherein R, R.sup.1 and R.sup.2, which may be the same or different, each represents an aliphatic group, an aromatic group or a heterocyclic group, M.sup.1 represents a cation, L represents a divalent linking group, and m represents 0 or 1.

Compounds of formulae (I), (II) and (III) will be explained in detail hereunder.

wherein M represents a hydrogen atom or a cation.

As the cation of M, preferred are metal ions and organic cations. As the metal ion, preferred are alkali metals, alkaline earth metals, titanium, aluminium and silicon. More preferably, the metal ion is selected from lithium ions, sodium ions and potassium ions. Examples of usable organic cations include ammonium ions, phosphonium ions and sulfonium ions.

Specific examples of compounds of formulae (I), and (III) are mentioned below, which, however, are not limitative.

These compounds may easily be produced, for example, by a known method of introducing sulfur dioxide into an aqueous solution or suspension containing a metal hydroxide or carbonate, or they are easily available as commercial products.

The above-mentioned compounds of formulae (I), (II) and (III) are incorporated into the internal latent image-type silver halide grains-containing photographic emulsion layer of the present invention.

For incorporating them into the emulsion, they may be added to a coating composition containing the emulsion grains just before coating, but preferably, they are previously added to the emulsion of the invention. More preferably, they are added to the internal latent image-type silver halide grains of the invention during formation of the grains. Most preferably, they are added to the grains during formation of the core grains, or during chemical sensitization or conversion of the core grains.

The amount of the compounds present in the emulsion is generally from 10.sup.-7 to 10.sup.-3 mol, preferably from 10.sup.-6 to 10.sup.-3 mol, per mol of the internal latent image-type silver halide of the invention.

Compounds of formulae (I), (II) and (III) of the invention may be used alone or in combination with two or more of them.

Next, compounds of formulae (IV), (V) and (VI) will be explained in detail hereunder.

wherein R, R.sup.1 and R.sup.2, which may be the same or different, each represents an aliphatic group, an aromatic group or a heterocyclic group, M.sup.1 represents a cation, L represents a divalent linking group, and m represents 0 or 1.

Where R, R.sup.1 and R.sup.2 each are an aliphatic group, it is preferably an alkyl group having from 1 to 22 carbon atoms, or an alkenyl or alkynyl group having from 2 to 22 carbon atoms, and the group may optionally be substituted. As the alkyl group, examples include a methyl group, an ethyl group, a propyl group, a butyl group, a pentyl group, a hexyl group, an octyl group, a 2-ethylhexyl group, a decyl group, a dodecyl group, a hexadecyl group, an octadecyl group, a cyclohexyl group, an isopropyl group, and a t-butyl group.

As the alkenyl group, examples include an allyl group, and a butenyl group.

As the alkynyl group, examples include a propargyl group, and a butynyl group.

The aromatic group of R, R.sup.1 or R.sup.2 has preferably from 6 to 20 carbon atoms and includes, for example, a phenyl group and a naphthyl group. The group may cptionally be substituted.

The heterocyclic group of R, R.sup.1 or R.sup.2 is a 3-membered to 15-membered ring having at least one element selected from nitrogen, oxygen, sulfur, selenium and tellurium and includes, for example, a pyrrolidine ring, a piperidine ring, a pyridine ring, a tetrahydrofuran ring, a thiophene ring, an oxazole ring, a thiazole ring, an imidazole ring, a benzothiazole ring, a benzoxazole ring, a bendimidazole ring, a selenazole ring, a benzoselenazole ring, a tellurazole ring, a triazole ring, a benzotriazole ring, a tetrazole ring, an oxadiazole ring, and a thiadiazole ring.

Where the groups of R, R.sup.1 and R.sup.2 are substituted ones, examples of the possible substituents include an alkyl group (e.g., methyl, ethyl, hexyl), an alkoxy group (e.g., methoxy, ethoxy, octyloxy), an aryl group (e.g., phenyl, naphthyl, tolyl), a hydroxyl group, a halogen atom (e.g., fluorine, chlorine, bromine, iodine), an aryloxy group (e.g., phenoxy), an alkylthio group (e.g., methylthio, butylthio), an arylthio group (e.g., phenylthio), an acyl group (e.g., acetyl, propionyl, butyryl, valeryl), a sulfonyl group (e.g., methylsulfonyl, phenylsulfonyl), an acylamino group (e.g., acetylamino, benzoylamino), a sulfonylamino group (e.g., methanesulfonylamino, benzenesulfonylamino), an acyloxy group (e.g., acetoxy, benzoxy), a carboxyl group, a cyano group, a sulfo group and an amino group. The carbon range of the alkyl, alkoxy, aryl, aryloxy, alkylthio, arylthio, acyl, acylamino and acyloxy groups is up to 30, preferably up to 16.

These substituents may further be substituted by any of the above-mentioned substituents.

L is preferably a divalent C.sub.1-20 aliphatic group or a divalent C.sub.6-20 aromatic group. Examples of the divalent aliphatic group of L include --(CH.sub.2).sub.n -- (n=1.about.12), --CH.sub.2 --CH.dbd.CH--CH.sub.2 --, --CH.sub.2 C.tbd.CCH.sub.2 --, ##STR1## and a xylylene group. Examples of the divalent aromatic group of L include a phenylene group and a naphthylene group.

These groups may optionally be substituted by the above-mentioned substituents. Two or more of the linking groups may further be linked to each other.

M.sup.1 is preferably a metal ion or an organic cation. As the metal ion, examples include lithium ions, sodium ions and potassium ions. As the organic ion, examples include ammonium ions (e.g., ammonium, tetramethylammonium, tetrabutylammonium), phosphonium ions (e.g., tetraphenylphosphonium) and guanidyl groups.

Specific examples of compounds of formulae (IV), (V) and (VI) are mentioned below, which, however, are not limitative. ##STR2##

Compounds of formulae (IV), (V) and (VI) for use in the present invention can easily be produced by the methods described in JP-A-54-1019 and British Patent 72,211.

Of the compounds of formulae (IV), (V) and (VI), preferred are those of formula (IV).

The above-mentioned compounds of formulae (IV), (V) and (VI) of the present invention are incorporated into the internal latent image-type silver halide grains-containing photographic emulsion layer of the invention.

For incorporating them into the emulsion layer, they may be added to a coating composition containing the emulsion grains just before coating, but preferably, they are previously added to the emulsion of the invention. More preferably, the compounds of formulae (IV), (V) and (VI) of the present invention are added to the internal latent image-type silver halide grains of the invention during formation of the grains. Most preferably, the compounds of formulae (IV), (V) and (VI) of the invention are added to core/shell grains during formation of the core grains, or during chemical sensitization or conversion of the core grains.

The amount of the compounds present in the emulsion is generally from 10.sup.-6 to 10.sup.-2 mol, preferably from 10.sup.-5 to 10.sup.-2 mol, per mol of the internal latent image-type silver halide of the invention.

Compounds of formulae (IV), (V) and (VI) of the invention may be used alone or in combination with two or more of them.

At least one compound of the above-mentioned formulae (I), (II) and (III) of the invention and at least one compound of the above-mentioned formulae (IV), (V) and (VI) of the invention may be added to the coating composition or emulsion containing the internal latent image-type silver halide grains of the invention individually at different times, but they are preferably added thereto simultaneously at the same time.

As the case may be, at least one of the compounds of formulae (I), (II) and (III) of the invention and at least one of the compounds of formulae (IV), (V) and (VI) of the invention may previously be blended in water or in an organic solvent and the resulting blend may be added to the coating composition or emulsion containing the internal latent image-type silver halide grains of the invention.

The previously non-fogged internal latent image-type silver halide emulsion for use in the present invention is an emulsion containing silver halide grains, the surfaces of which are not previously fogged, and which form a latent image essentially in the inside of the grains. More concretely, the emulsion may be identified as follows. A silver halide emulsion is coated on a transparent support in a determined amount (0.5 to 3 g/m.sup.2) which is exposed for a determined period of from 0.01 second to 10 seconds and then developed with the following developer (A) (internal developer) at 18.degree. C. for 5 minutes, and the maximum density of the image formed is determined by conventional photographic densitometry. In addition, the same silver halide emulsion was coated on the same support in the same manner as above and then exposed also in the same manner as above. The thus exposed material is then developed with the following developer (B) (surface developer) at 20.degree. C. for 6 minutes and the maximum density of the image formed is determined also in the same manner as above. When the value of the maximum density obtained in the former (developed with the internal developer (A)) is at least 5 times, more preferably at least 10 times, of that obtained in the latter (developed with the surface developer (B)), the emulsion tested is an internal latent image-type emulsion.

Examples of internal latent image-type emulsions include conversion-type silver halide emulsions as described in U.S. Pat. No. 2,592,250, as well as core/shell type silver halide emulsions as described in U.S. Pat. Nos. 3,761,276, 3,850,637, 3,923,513, 4,035,185, 4,395,478 and 4,504,570, JP-A-52-156614, 55-127549, 53-60222, 56-22681, 59-208540, 60-107641, 61-3137 and 62-215272 and patent publications as mentioned in Research Disclosure No. 23510 (issued in November, 1983), page 236.

The internal latent image-type silver halide grains for use in the present invention may be either in the form of a conversion-type emulsion or in the form of a core/shell type emulsion, but preferably they have a core/shell laminate structure in view of the easy controllability of the photographic sensitivity and gradation of the emulsion. Regarding the structure of the core/shell silver halide grain, the core and shell are preferably composed of silver iodobromide, silver chlorobromide, silver chloride or silver chloroiodobromide, which contains silver bromide and 10 mol % or less, preferably 3 mol % or less, silver iodide. The core may be either a so-called conversion type one or a general one. The halogen composition of the core and that of the shell may be the same as or different from each other. As core/shell type structure-having silver halide emulsions, for example, those as described in JP-A-55-127549, U.S. Pat. No. 4,395,478 and West German Patent 2,332,802C2 may be employed.

The internal latent image-type silver halide grains of the present invention contain at least one selected from the group comprising manganese, copper, zinc, cadmium, lead, bismuth, indium, thallium, zirconium, lanthanum, chromium, rhenium, mercury and metals of Group VIII of the Periodic Table, and the amount of the metal(s) present in the grains is preferably from 10.sup.-9 to 10.sup.-2 mol, more preferably from 10.sup.-8 to 10.sup.-3 mol, per mol of silver halide.

Of the metals, especially preferred are lead, iridium, rhodium, rhenium, iron and bismuth. Most preferred are lead, iridium and rhodium.

The position of the previously non-fogged internal latent image-type emulsion of the invention, into which the above mentioned metal(s) is introduced, is not specifically limited.

For incorporating the metal into the silver halide grains, a metal ion in the form of an aqueous solution thereof or an organic solvent solution thereof may be added to the step of forming silver halide grains by blending a silver ion solution and an aqueous halogen solution. Alternatively, a metal ion in the form of an aqueous solution thereof or an organic solvent solution thereof may be added to the grains as already formed and thereafter the resulting grains may be coated further with a silver halide.

The method of incorporating the metal into silver halide grains is described in detail, for example, in U.S. Pat. Nos. 3,761,276 and 4,395,478 and JP-A-59-216136.

The silver halide grains for use in the present invention preferably have a mean grain size of from 0.1 micron to 1.5 microns, especially from 0.2 micron to 1.2 microns. (The grain size indicates a diameter of the grain when the grain is spherical or nearly spherical or indicates a length of the edge of the grain when it is a cubic grain; and the mean grain size indicates a mean value based on the projected area of the grains.) The grain size distribution in the emulsion for use in the present invention may be either narrow or broad, but a so-called "monodispersed" silver halide emulsion which has such a narrow grain size distribution that 90% by weight or by number or more, especially 95% by weight or by number or more, of the total grains has a grain size falling within the range of the mean grain size plus/minus 40%, more preferably plus/minus 30%, most preferably plus/minus 20%, is preferably employed in the present invention for the purpose of improving the graininess and sharpness of the photographic material. Additionally, in order to satisfy the intended gradation of the photographic material, two or more monodispersed silver halide emulsions each having a different grain size distribution or plural grains each having the same size but having a different sensitivity may be blended into one and the same layer or may be coated as different layers, in forming an emulsion layer having a substantially same color sensitivity. Additionally, a combination of two or more polydispersed silver halide emulsions or a combination of a monodispersed emulsion and a polydispersed emulsion may be blended into one and the same layer or may be coated as different layers.

The silver halide emulsion for use in the present invention may be chemically sensitized in the inside of the grains or on the surface thereof, by sulfur or selenium sensitization, reduction sensitization and/or noble metal sensitization.

Examples of chemical sensitization are described in detail, for example, in the patent publications as mentioned in Research Disclosure, No. 17643-III (issued in December, 1978), page 23.

The photographic emulsion for use in the present invention is color-sensitized with photographic sensitizing dyes by a conventional method. Especially useful dyes for this purpose are cyanine dyes, merocyanine dyes and complex merocyanine dyes, and these dyes may be used alone or in combination with two or more of them. The dyes may be combined with super-color sensitizing agents. Examples of color sensitizing dyes and super-color sensitizing agents which may be employed in the present invention are described in detail, for example, in the patent publications as mentioned in Research Disclosure, No. 17643-IV (issued in December, 1978), pages 23 to 24.

The photographic emulsion for use in the present invention can contain an antifoggant or a stabilizer for the purpose of preventing the emulsion from fogging or for stabilizing the photographic property of the emulsion, during manufacture, storage or photographic processing of the photographic material. Examples of compounds as antifoggants or stabilizers are described in detail, for example, in Research Disclosure, No. 17643-VI (issued in December, 1978) and E. J. Birr, Stabilization of Photographic Silver Halide Emulsion (published by Focal Press in 1974).

In forming direct positive color images in accordance with the present invention, various color couplers are used. Color couplers are compounds which react with the oxidation product of an aromatic primary amine-type color developing agent by coupling reaction to form or release a substantially non-diffusive dye. Preferably, they are substantially non-diffusive compounds by themselves. Specific examples of useful color couplers include naphthol or phenol compounds, pyrazolone or pyrazoloazole compounds, and open-chain or heterocyclic ketomethylene compounds. Examples of these cyan, magenta and yellow couplers which may be employed in the present invention are described in Research Disclosure, No. 17643 (issued in December, 1978, Page 25, Item VII-D; ibid., No. 18717 (issued in November, 1979); and JP-A-62-215272; as well as in patent publications as referred to in them.

Additionally, colored couplers which have a function of correcting an unnecessary absorption in the short wavelength range of dyes formed in the photographic material, couplers capable of forming coloring dyes having a pertinent diffusibility, colorless couplers, DIR couplers capable of releasing a development inhibitor with coupling reaction, and polymerized couplers may also be used in the present invention.

As a binder or protective colloid to be in the emulsion layers or interlayers of the photographic material of the present invention, gelatin is advantageously used, but any other hydrophilic colloid may also be used.

The photographic material of the present invention can contain a color-fogging inhibitor or a color-mixing inhibitor.

Specific examples of these inhibitors are described in JP-A-62-215272, pages 185 to 193.

A coloring enhancer may be used in the present invention for the purpose of improving the coloring capacity of the couplers in the photographic material. Specific examples of compounds of the enhancer are described in JP-A-62-215272, pages 121 to 125.

The photographic material of the present invention may contain an anti-irradiation dye, an antihalation dye, an ultraviolet absorbent, a plasticizer, a brightening agent, a mat agent, an aerial fogging inhibitor, a coating aid, a hardening agent, an antistatic agent and a slide property-improving agent. Specific examples of the additives are described in Research Disclosure, No. 17643, VIII to XIII (issued in December, 1978), pages 25 to 27, and ibid, No. 18716 (issued in November, 1979), pages 647 to 651.

The present invention may apply to a multi-layer multi-color photographic material having at least two layers each having a different color sensitivity on a support. For instance, a multi-layer natural color photographic material, which generally has at least one red-sensitive emulsion layer, at least one green-sensitive emulsion layer and at least one blue-sensitive emulsion layer on a support can be used. The order of forming the layers on a support may freely be selected. As preferred examples of the order of the layers, red-sensitive, green-sensitive and blue-sensitive layers are formed on a support in this order, or green-sensitive, red-sensitive and blue-sensitive layers are on a support in this order. The respective layers mentioned above may be composed of two or more sub-emulsion layers each having a different sensitivity degree; or a non-light-sensitive layer may be present between two or more emulsion layers each having the same color-sensitivity. In general, a cyan-forming coupler is incorporated into a red-sensitive emulsion layer, a magenta-forming coupler into a green-sensitive emulsion layer, and an yellow-forming coupler into a blue-sensitive emulsion layer. As the case may be, however, different combinations may also be employed.

The photographic material of the present invention preferably has other various auxiliary layers, such as a protective layer, an interlayer, a filter layer, an anti-halation layer, a backing layer and a white reflecting layer, in addition to the above-mentioned silver halide emulsion layers.

In preparing the photographic material of the present invention, the photographic emulsion layers and other layers are coated on a support, for example, one as described in Research Disclosure, No. 17643, VVII (issued in December, 1978), page 28 or in European Patent 0,102,253 and JP-A-61-97655. The coating method described in Research Disclosure, No. 17643, XV, pages 28 to 29 can be utilized.

The present invention may be applied to various color photographic:materials.

For instance, it may be applied to color reversal films for slides or televisions, color reversal papers and instant color films, as typical examples. Additionally, it may also be applied to color hard copies for storing images to be formed in full-color duplicators or CRT.

The present invention may also be applied to black-and-white photographic materials of utilizing three coupler mixing photography, as described in Research Disclosure, No. 17123 (issued in July, 1978).

Further, the present invention may also be applied to black-and-white photographic materials.

Examples of black-and-white (B/W) photographic materials to which the present invention may be applied include B/W direct positive photographic materials (for example, X-ray photographic materials, duplicating photographic materials, micro photographic materials, picture-taking photographic materials, printing photographic materials) as described in JP-A-59-208540 and 60-260039.

Fogging of the photographic materials of the present invention may be effected by "light-fogging" and/or "chemical-fogging", which will be explained hereunder.

Precisely, in accordance with "light-fogging" for exposure of the complete surface of the photographic material by fogging exposure, the photographic material is imagewise exposed and then light-fogged after and/or during development of the material. That is, the imagewise exposed photographic material is light-fogged by exposure while the material is dipped in a developer or in a previous bath of development, or after the material has been taken out from the developer or pre-bath but it has not dried up. Most preferably, the light-fogging by exposure is effected in a developer.

As a light source for the fogging exposure, one having a wavelength falling within the wavelength range to which the photographic material is sensitive may be used. In general, a fluorescent lamp, tungsten lamp, xenon lamp or sun light may be used. Concrete methods of such fogging exposure are described in for example, British Patent 1,151,363, JP-B-45-12710, 45-12709, 58-6936 (the term "JP-B" as used herein means an "examined Japanese patent publication"), JP-A-48-9727, JP-A-56-137350, JP-A-57-129438, JP-A-58-62652, JP-A-58-60739, JP-A-58-70223 (corresponding to U.S. Patent 4,440,851), JP-A-58-120248 (corresponding to European Patent 89101A2). For photographic materials having a light-sensitivity to lights of all wavelength ranges, for example, color photographic materials, a light source having a high color rendition (preferably, one which is almost nearly white) is desired. The illuminance of the light to be applied to the photographic material is from 0.01 to 2000 lux, preferably from 0.05 to 30 lux, more preferably from 0.05 to 5 lux. Where the photographic material has an emulsion of a higher sensitivity, the illuminance of the light to be applied thereto is preferably lower. Adjustment of the illuminance may be effected by controlling the luminous intensity of the Iight source used. If desired, exposure may be effected by the use of various filters, or the distance between the photographic material and the light source and the angle of the light source to the photographic material may appropriately be varied. The illuminance of the fogging light may continuously be varied from a low illuminance to a high illuminance, or it may be stepwise increased.

Preferably, light-irradiation to the photographic material for light-fogging is effected after the material has been dipped in a developer or a pre-bath thereof and the developer or the pre-bath liquid has been sufficiently infiltrated into the material. The time between infiltration of the developer or liquid into the material and light-fogging of the material is generally from 2 seconds to 2 minutes, preferably from 5 seconds to 1 minute, more preferably from 10 seconds to 30 seconds.

The exposure time for fogging is generally from 0.01 second to 2 minutes, preferably from 0.1 second to 1 minute, more preferably from 1 second to 40 seconds.

Where the photographic material of the invention is fogged by "chemical-fogging", a nucleating agent may be incorporated into the photographic material or into the processing solution to be used for processing the material. Preferably, it is incorporated into the photographic material.

The "nucleating agent" as referred to herein is a substance which acts on the previously non-fogged internal latent image-type silver halide emulsion during surface development of the emulsion to thereby form a direct positive image. In accordance with the present invention, the photographic material is preferably fogged in the presence of a nucleating agent.

Where the nucleating agent is incorporated into the photographic material, it is preferably added to the internal latent image-type silver halide emulsion layer constituting the material. However, it may be added to any other layer, such as an interlayer, a subbing layer or a backing layer, so far as the nucleating agent may diffuse and adsorb to the silver halide grains in the emulsion layer during coating or during processing.

Where the nucleating agent is added to the processing solution, it may be incorporated into the developer or into the pre-bath thereof having a lower pH value, as so described in JP-A-58-178350.

Two or more different kinds of nucleating agents may be used in combination, as the case may be.

As the nucleating agent for use in the present invention, compounds of the following formulae (N-I) and (N-II) are preferred. Especially preferred are compounds of formula (N-I). ##STR3##

In formula (N-I), Z.sub.1 represents a non-metallic atomic group necessary for forming a 5 membered or 6-membered heterocyclic group; R.sup.1N represents an aliphatic group; and R.sup.2N represents a hydrogen atom, an aliphatic group or an aromatic group. Z.sub.1, R.sup.1N and R.sup.2N may optionally be substituted; and R.sup.2N may be bonded to the hetero ring formed by Z.sub.1 to from a ring. However, at least one of R.sup.1N, R.sup.2N and Z.sub.1 must contain an alkynyl group, an acyl group, a hydrazine group or a hydrazone group; or R.sup.1N and R.sup.2N form a 6-membered ring comprising dihydropyridinium skeleton. Y represents a pair ion for charge balance of the molecule; and n represents 0 or 1.

More precisely, the hetero ring completed by Z.sub.1 includes, for example, quinoxalinium, benzothiazolium, benzimidazolium, pyridinium, thiazolinium, thiazolium, naphthothiazolium, selenazolium, benzoselenazolium imidazolium, tetrazolium, indolenium, pyrrolinium, acridinium, phenanthridinium, isoquinolinium, oxazolium, naphthoxazolium and benzoxazolium nuclei. Examples of substituents which may be in the group Z.sub.1, are a C.sub.1-8 alkyl group, a C.sub.2-10 alkenyl group, a C.sub.7-16 aralkyl group, a C.sub.6-15 aryl group, a C.sub.2-10 alkynyl group, a hydroxyl group, a C.sub.1-8 alkoxy group, a C.sub.6-15 aryloxy group, a halogen atom, a C.sub.0-16 amino group, a C.sub.1-8 alkylthio group, a C.sub.6-15 arylthio group, a C.sub.1-9 acyloxy group, an C.sub.1-9 acylamino group, a C.sub.1-8 sulfonyl group, a C.sub.1-8 sulfonyloxy group, a C.sub.0-8 sulfonylamino group, a carboxyl group, a C.sub.1-9 acyl group, a C.sub.1-8 carbamoyl group, a C.sub.0-8 sulfamoyl group, a sulfo group, a cyano group, a C.sub.1-10 ureido group, a C.sub.1-10 urethane group, a C.sub.1-10 carbonate group, a C.sub.0-10 hydrazine group, a C.sub.0-10 hydrazone group and a C.sub.0-10 imino group. Suitable substituent(s) present in the group Z include at least one selected from the above-mentioned substituents. Where the group Z has two or more substituents, the substituents may be the same or different. Additionally, the above-mentioned substituents may further be substituted by any of the above substituents.

Further, another example of the substituent present in the group Z.sub.1 include a heterocyclic quaternay ammonia group completed by Z.sub.1 via a appropraite linking group L. In this case, the compound is said to have a so-called dimer structure.

Examples of heterocyclic groups completed by the group Z.sub.1 are preferably quinolinium, benzothiazolium, benzimidazolium, pyridinium, acridinium, phenanthridinium and isoquinolinium nuclei. More preferred are quinolinium and benzothiazolium nuclei; and most preferred is a quinolinium nucleus.

The aliphatic group represented by R.sup.1N or R.sup.2N is preferably an unsubstituted alkyl group having from 1 to 18 carbon atoms, or a substituted alkyl group in which the alkyl moiety has from 1 to 18 carbon atoms. Examples of substituents present in the substituted alkyl group include the same substituents as described above for Z.sub.1. Additionally, R.sup.2N may be bonded to the hetero ring completed by Z.sub.1 to form a ring.

The aromatic group represented by R.sup.2N is preferably one having from 6 to 20 carbon atoms, which includes, for example, a phenyl group and a naphthyl group. Examples of substituents in the aromatic group include the substituents for the group Z.sub.1 described above. Preferably, R.sup.2N is an aliphatic group; and most preferably, it is a methyl group, a substituted methyl group, or a group bonded to the hetero ring completed by the group Z.sub.1 to form a ring.

At least one of the groups R.sup.1N, R.sup.2N and Z has an alkynyl group, an acyl group, a hydrazine group or a hydrazone group; or R.sup.1N and R.sup.2N form a 6-membered ring to complete a dihydropyridinium skeleton. These may optionally be substituted by substituents, for example, those as described above as substituents of the group Z.sub.1.

In accordance with the present invention, preferred is the case where at least one of R.sup.1N, R.sup.2N and Z.sub.1 or at least one of the substituents on the 6-membered ring formed by R.sup.1N and R.sup.2N is an alkynyl group or an acyl group, or the case where R.sup.1N and R.sup.2N are bonded to form a dihydropyridinium skeleton. More preferably, the compound contains at least one alkynyl group, most preferably at least one propargyl group.

A group of the formula X.sup.1 --(L.sup.1).sub.m -- is preferred, in which X.sup.1 represents a silver halide adsorption-accelerating group, L.sup.1 represents a divalent linking group, and m represents 0 or 1 as the silver halide adsorption-accelerating group which may be in the substituents of R.sup.1N, R.sup.2N and Z.sub.1.

Preferred examples of silver halide adsorption-accelerating groups represented by X.sup.1 include a thioamido group, a mercapto group and a 5-membered or 6-membered heterocyclic group.

These groups may optionally be substituted by substituents, for example, those as described with respect to the substituents of the group Z.sub.1. The thioamido group is preferably a non-cyclic thioamido group (for example, a thiourethane group or a thioureido group).

A heterocyclic mercapto group is especially preferred as the mercapto group represented by X.sup.1 with examples, including 5-mercaptotetrazole, 3-mercapto-1,2,4-triazol, 2-mercapto-1,3,4-thiadiazole, and 2-mercapto-1,3,4-oxadizole.

The 5-membered or 6-membered nitrogen-containing heterocyclic group as represented by X.sup.1 is composed of nitrogen, oxygen, sulfur and carbon atoms. Preferably, it is to form an imino silver, for example, including a benzotriazole and an aminothiatriazole.

The divalent linking group as represented by L.sup.1 is an atom or an atomic group containing at least one of C, N, S and O atoms. Specifically, examples include a C.sub.1-10 alkylene group, a C.sub.1-10 alkenylene group, a C.sub.2-10 alkynylene group, a C.sub.6-15 arylene group, --O--, --S--, --NH--, --N.dbd., --CO-- and --SO.sub.2 --, as well as a combination of two or more of these groups. The groups may optionally be substituted. Examples of preferred combinations of these groups are ##STR4##

Examples of the pair ion Y for charge balance are, for example, bromide ion, chloride ion, iodide ion, p-toluenesulfonate ion, ethylsulfonate ion, perchlorate ion, trifluoromethanesulfonate ion, thiocyan ion, boron tetrafluoride ion and phosphorus hexafluoride ion.

These compounds and methods of their prepariation are described, for example, in patent publications referred to in Research Disclosure, No. 2543 (issued on January, 1983, pages 50 to 54) and No. 3213 (issued on August, 1983, pages 267 to 270), as well as in JP-B-49-38164, JP-B-52-19452 and JP-B-52-47326, JP-A-52-69613, JP-A-52-3426, JP-A-55-138742 and JP-A-60-11827, and U.S. Pat. Nos. 4,306,016 and 4,471,044. ##STR5##

In formula (N-II), R.sup.3N represents an aliphatic group, an aromatic group, or a heterocyclic group; R.sup.4N represents a hydrogen atom, an alkyl group, an aralkyl group, an aryl group, an alkoxy group, an aryloxy group or an amino group; G represents a carbonyl group, a sulfonyl group, a sulfoxy group, a phosphoryl group or an iminomethylene group (HN.dbd.C.dbd.); and both R.sup.5N and R.sup.6N are hydrogen atoms, or one of them represents a hydrogen atom and the other represents an alkylsulfonyl group, an arylsulfonyl group or an acyl group. G, R.sup.4N and R.sup.6N may form, together with the hydrazine nitrogen atoms, a hydrazone structure (.dbd.N--N.dbd.C.dbd.). The above-mentioned groups may optionally be substituted by substituent(s), if possible.

More particularly, R.sup.3N may be substituted by a substituent, which in turn may be further substituted, such as an alkyl group, an aralkyl group, an alkoxy group, an amino group substituted by an alkyl or aryl group, an acylamino group, a sulfonylamino group, a ureido group, a urethane group, an aryloxy group, a sulfamoyl group, a carbamoyl group, an aryl group, an alkylthio group, an arylthio group, a sulfonyl group, a sulfinyl group, a hydroxy group, a halogen atom, a cyano group, a sulfo group and a carboxyl group, with a ureido group or sulfonamido group preferred, which groups may link together to form a ring, if possible.

Preferably, R.sup.3N represents an aromatic group, an aromatic heterocyclic ring group or an aryl-substituted methyl group, with an aryl group (e.g., a phenyl group and a naphthyl group) more preferred.

Preferably, R.sup.4N represents a hydrogen atom, an alkyl group (e.g., a methyl group) or an aralkyl group (e.g., an o-hydroxybenzyl group), with a hydrogen atom particularly preferred.

The substituents for R.sup.4N include those for R.sup.3N as well as an acyl group, an acyloxy group, an alkyloxycarbonyl group, an aryloxycarbonyl group, an alkenyl group, an alkynyl group and a nitro group, which may be further substituted any of those substituents. and, if possible, may link together to form a ring.

R.sup.3N or R.sup.4N, in particular R.sup.3N, may contain a diffusion-resistant group such as a coupler, ballast group (preferably linked through a ureido group) and may contain a group X.sup.2 --L.sup.2 --m.sup.2 capable of accelerating adsorption onto the surface of silver halide grains, where X.sup.2 has the same meaning as XI in general formula (N-I) and preferably represents a thioamide group (excluding a thiosemicarbazide and its substitution product), a mercapto group or a 5- or 6- membered nitrogen-containing heterocyclic ring group, L.sup.2 represents a divalent liking group and has the same meaning as L.sup.1 in general formula (N-I), and m.sup.2 is 0 or 1.

Preferably, X2 represents a non-cyclic thioamido group (e.g., a thioureido group and a thiourethane group), a cyclic thioamido group (i.e., a mercapto-substituted nitrogen-containing heterocyclic ring, e.g., a 2-mercaptothiadiazole group, a 3-mercapto-1,2,4-triazole group, a 5-mercaptotetrazole group, a 2-mercapto-1,3,4-oxadiazole group and a 2-mercaptobenzoxazole group)or a nitrogen-containing heterocyclic ring group (e.g., a benzotriazole group, benzimidazole group and an indazole group).

Most preferably, X.sup.2 is determined based on the photosensitive material. For example, in the case of a color photosensitive material that uses a coloring material (a so-called coupler) that forms a dye when coupled with the oxidation product of a p-phenylenediamine type developing agent, X.sup.2 preferably represents a mercapto-substituted nitrogen-containing heterocyclic ring or a nitrogen-containing heterocyclic ring that will form an imino silver. In the case of a color photosensitive material that uses a coloring material (a so-called DRR compound) that forms a diffudion-resistant dye by cross-oxidizing the oxidation product of a developing agent, X.sup.2 preferably represents a non-cyclic thiamido group or a mercapto-substituted nitorgen-containing heterocyclic ring. In the case of a black-and-white plhotosensitive material, X.sup.2 preferably represents a mercapto-substituted nitrogen-containing heterocyclic ring or a nitrogen-containing heterocyclic ring that will form an imino silver.

Most preferably, R.sup.5N and R.sup.6N represent a hydrogen atom.

Most preferably, G in general formula (N-II) represents a carbonyl group.

Preferably, the compound represents by general formula (N-II) contains a group capable of being absorbed onto a silver halide or a group having a ureido group.

Particularly, examples of hydrazine type nucleating agents having a group capable of being absorbed onto a silver halide, and synthetic methods therefor and described, for example, in U.S. Pat. Nos. 4,030,925, 4,080,207, 4,031,127, 3,718,470, 4,269,929, 4,276,364, 4,278,748, 4,385,108, 4,459,928, and 4,560,638, British Patent 2,011,391B and JP-A-54-74729, JP-A-55-163533, JP-A-55-74536, and JP-A-60-179734.

Examples of other hydrazine type nucleating agents and synthetic methods therfor are described, for example, in JP-A-57-86829, U.S. Pat. Nos. 4,560,638, 4,478,528, 2,563,785 and 2,588,982.

Specific examples of compounds of the formulae (N-I) and (N-II) are described below, which, however, do not whatsoever restrict the scope of the present invention. ##STR6##

The nucleating agent may be incorporated into the photographic material or into the processing solution to be used for processing the material. Preferably, it is incorporated into the photographic material.

Where the nucleating agent is incorporated into the photographic material, it is preferably added to the internal latent image-type silver halide emulsion layer constituting the material. However, it may also be added to any other layer, such as an interlayer, a subbing layer or a backing layer, so long as the nucleating agent may diffuse and adsorb to the silver halide grains in the emulsion layer during coating or during processing. Where the nucleating agent is added to the processing solution, it may be incorporated into the developer or into the pre-bath thereof having a lower pH value, as so described in JP-A-58-178350.

Where the nucleating agent is incorporated into the photographic material, the amount of the agent is preferably from 10.sup.-8 to 10.sup.-2 mol, more preferably from 10.sup.-7 to 10.sup.-3 mol, per mol of silver halide.

Where the nucleating agent is added to the processing solution, the amount of the agent is preferably from 10.sup.-5 to 10.sup.-1 mol/liter, more preferably from 10.sup.-4 to 10.sup.-2 mol/liter.

In the present invention, a nucleation accelerator, such as those mentioned below, may be used for the purpose of accelerating the effect of the above-described nucleating agent.

As the nucleation accelerator to be used for this purpose, examples include tetrazaindenes, triazaindenes and pentazaindenes having at least one mercapto group which may optionally be substituted by an alkali metal atom or an ammonium group, as well as compounds described in JP-A-63-106656, pages 6 to 16.

Specific examples of nucleation accelerators are set forth below, which, however, are not limitative.

(A-1): 3-Mercapto-1,2,4-triazolo[4,5-a]pyridine

(A-2): 3-Mercapto-1,2,4-triazolo[4,5-a]pyrimidine

(A-3): 5-Mercapto-1,2,4-triazolo[1,5-a]pyrimidine

(A-4): 7-(2-Dimethylaminoethyl)-5-mercapto-1,2,4-triazolo-[1,5-a]pyrimidine

(A-5): 3-Mercapto-7-methyl-1,2,4-triazolo[4,5-a]pyrimidine

(A-6): 3,6-Dimercapto-1,2,4-triazolo[4,5-b]pyridazine

(A-7): 2 Mercapto-5-methylthio-1,3,4-thiadiazole

(A-8): 3-Mercapto-4-methyl-1,2,4-triazole

(A-9): 2-(3-Dimethylaminopropylthio) 5-mercapto-1,3,4-thiadiazole hydrochloride

(A-10): 2-(2-Morpholinoethylthio)-5-mercapto-1,3,4-thiadizole hydrochloride

The nucleation accelerator may be incorporated into the photographic material or into the processing solution to be used for processing the material. Preferably, it is incorporated into the photographic material, especially into the internal latent image-type silver halide emulsion layer and other hydrophilic colloid layers (e.g., interlayer, protective layer) constituting the material. Most preferably, the nucleation accelerator is incorporated into the silver halide emulsion layer or the adjacent layers thereof.

For development of the photographic material of the present invention, a color developer is used, which is preferably an alkaline aqueous solution containing an aromatic primary amine color developing agent. As the color developing agent, p-phenylenediamine compounds are preferably used, though aminophenol compounds may also be used. Specific examples of the preferred compounds include 3-methyl-4-amino-N,N-diethylaniline, 3-methyl-4-amino-N-ethyl-N-.beta.-hydroxyethylaniline, 3-methyl-4-amino-N-.beta.-methanesulfonamidoethylaniline, 3-methyl-4-amino-N-ethyl-N-.beta.-methoxyethylaniline, and sulfates, hydrochlorides and p-toluenesulfonates thereof. Two or more of these compounds may be used in combination.

The color developer to be used for processing the photographic material of the present invention has a pH value of from 9 to 12, preferably from 9.5 to 11.5.

After color-developed, the photographic material of the invention is generally bleached. Bleaching of the material may be effected simultaneously with fixation thereof (as bleach-fixation) or may be effected separately therefrom. Further, in order to accelerate the processing, bleaching may be followed by bleach-fixation. As the case may be, continuous bleach-fixation may be effected by the use of a two-bath bleach-fixation system; or fixation may be effected prior to bleach-fixation; or bleach-fixation may be followed by bleaching. The processes may freely be selected in accordance with the objectives of the present invention.

The silver halide color photographic material of the present invention is generally rinsed and/or stabilized, after it has been desilvered. The amount of the rinsing water to be used in the rinsing step may be broadly defined in accordance with the characteristics of the photographic material to be processed (for example, coupler and other raw materials constituting the photographic material), the use of the material, the temperature of the rinsing water, the number of the rinsing tanks (the number of the rinsing stages), the replenishment system of normal current or countercurrent, and other various conditions. Among them, the relation between the number of the rinsing tanks and the amount of the rinsing water in a multi-stage countercurrent system may be obtained on the basis of the method described in Journal of the Society of Motion Picture and Television Engineers, Vol 64, pages 248 to 253 (May 1955 issue).

The silver halide color photographic material of the present invention can contain a color developing agent for the purpose of simplifying and promoting the processing of the material. In this case, various precursors of color developing agents are preferably used for incorporating the agent to the material.

On the other hand, where the photographic material of the invention is a black-and-white photographic material, various known developing agents may be used for developing the material. For instance, usable agents include polyhydroxybenzenes such as hydroquinone, 2-chlorohydroquirone, 2-methylhydroquinone, catechol or pyrogallol; aminophenol such as p-aminophenol, N-methyl-p-aminophenol or 2,4-diaminophenol; 3-pyrazolidones such as 1-phenyl-3-pyrazolidones, 1-phenyl-4,4'-dimethyl-3-pyrazolidone, 1 phenyl-4-methyl-4-hydroxymethyl-3-pyrazolidone or 5,5-dimethyl-1-phenyl-3-pyrazolidone; and ascorbic acids. These compounds may be used alone or in combination with two or more of them. Additionally, developers described in JP-A-58-55928 may also be used.

The present invention will be explained in more detail by way of the following examples, which, however, are not intended to restrict the scope of the present invention.

An aqueous solution of potassium bromide and an aqueous solution of silver nitrate were simultaneously added to an aqueous solution of gelatin while vigorously stirring at 50.degree. C., over a period of 15 minutes, to obtain octahedral silver bromide grains having a mean grain size of 0.20 micron, whereupon 3,4-dimethyl-1,3-thiazoline-2-thione was added thereto in an amount of 0.1 g per mol of silver. Then, the resulting emulsion was chemically sensitized by adding 5 mg per mol of silver of sodium thiosulfate and 7 mg per mol of silver of chloroauric acid (tetrahydrate) thereto in order followed by heating at 75.degree. C. for 80 minutes. The thus formed core grains were grown further under the same precipitation conditions as that for the first time. Accordingly, a monodispersed octahedral core/shell silver bromide emulsion having a mean grain size of 0.30 micron was finally obtained. The fluctuation coefficient of the grain size was about 10%. 1.5 mg per mol of silver of sodium thiosulfate and 1.5 mg per mol of silver of chloroauric acid (tetrahydrate) were added to the emulsion and heated at 60.degree. C. for 60 minutes, whereby the emulsion was chemically sensitized to give an internal latent image-type silver halide emulsion.

Other internal latent image-type silver halide emulsions (A-1) to (A-9) and (B-1) to (B-9) were prepared in the same manner as above, except that a metal compound and a compound of formulae (I) to (III) as indicated in Table 1 and Table 2 below were added to the grains.

Both surfaces of a paper support (thickness: 100 microns) were laminated with polyethylene. The following first to fourteenth layers were formed on the surface of the support and the following fifteenth and sixteenth layers were on the back surface thereof to prepare a photographic material sample. The laminated polyethylene below the first layer contained 4 g/m.sup.2 of titanium oxide as a white pigment and 0.003 g/m.sup.2 of ultramarine as a blueish dye. The chromaticity of the surface of the support was 88.0, -0.20, -0.75 as L*, a*, b* system.

The components coated and the amounts thereof are mentioned below, as a unit of g/m.sup.2. The amount of silver halide coated is represented by the amount of silver therein. Emulsions in the photographic layers were prepared in accordance with the method of preparing Emulsion (Em-1). However, the emulsion in the fourteenth layer was a Lippmann emulsion, the surface of which was not chemically sensitized.

The light-sensitive layers contained 10.sup.-3 % by weight to silver halide of ExZK-1 as a nucleating agent and 10.sup.-2 % by weight to silver halide of Cpd-22 as a nucleation accelerator. Further, the layers contained Alkanol XC (by E. I. Du Pont De Numours & Co.) and sodium alkylbenzenesulfonate as an emulsion-dispersion aid and succinate and Magefac F-120 (by Dainippon Ink and Chemicals, Inc.) as a coating aid. The silver halide-containing layers and the colloidal silver-containing layers contained a mixture of Cpd-23, Cpd-24 and Cpd-25 as a stabilizer. Compounds used for preparing the sample are mentioned below. ##STR7##

In the 3rd, 4th, 6th, 7th, 11th and 12th layers, emulsions as prepared by the same method as Em-1 were used. Accordingly, Sample (A) was prepared.

Other samples Nos. 1 to 18 were prepared in the same manner as Sample (A), except that the emulsion as indicated in Table 3 below was used in the third layer in place of Emulsion (Em-1). The thus prepared samples were incubated under the conditions of 60.degree. C. and 55% RH and under the conditions of 45.degree. C. and 75% RH for 3 days. The non-incubated samples and incubated samples were wedgewise exposed in an ordinary manner (color temperature 3200.degree. K., 0.1 second, 100 CMS) and then processed in accordance with the following processing procedure (A). The properties of the cyan image formed in each sample were shown in Table 3 below.

In procedure (A), rinsing was effected by a so-called countercurrent replenishment system where the replenisher was added to the rinsing bath (2) and the overflown liquid from the rinsing bath (2) was introduced into the rinsing bath (1), whereupon the amount of the carryover of the bleach-fixing solution from the bleach-fixing bath to the rinsing bath (1) along with the photographic material being processed was 35 ml/m.sup.2, and the magnification of the rinsing replenisher to the carryover of the bleach-fixing solution was 9.1 times.

The processing solutions used above had the following compositions.

City water was passed through a mixed bed column filled with H-type strong acidic cation-exchange resin (Amberlite IR120B, by Rhom & Haas) and OH-type anion-exchange resin (Amberlite IR-400, by Rhom & Haas) whereby the calcium ion concentration and magnesium ion concentration were reduced to 3 mg/liter or less, respectively. Subsequently, 20 mg/liter of sodium dichloroisocyanurate and 0.15 g/liter of sodium sulfate were added to the water. The resulting solution had a pH value falling within the range of from 6.5 to 7.5.

As shown in Table 3, samples Nos. 1 to 9 each containing an emulsion of the present invention were all superior to the Comparative samples Nos. 10 to 18 and comparative sample (A), which did not contain an emulsion of the present invention in that both the decrease of Dmax and the increase of Dmin after incubation in the former were smaller than those in the latter.

The same process as in Example 1 was repeated, except that the following nucleating agent ExZK-2 was further added to the light-sensitive layers in an amount of 1.5.times.10.sup.-5 mol per mol of silver halide, in addition to the nucleating agent ExZK-1. The same results were obtained.

ExZK-2: 1-Formyl-2-{4-[3-{3-[3-(5-mercaptotetrazol-1-yl)phenyl]ureido}benzenesulfo namido]phenyl}-hydrazine

The same process as in Example 1 was repeated, except that Emulsion (Em-1) was used in the third layer and one of Emulsion (B-1) to (B-9) and (Em-1) was used in the sixth layer. The magenta image density of the positive image formed was measured, and the same results as those in Example 1 were obtained.

Emulsion (Em-2) was prepared in the same manner as in preparation of Emulsion (Em-1), except that the temperature in formation of cores was changed to 72.degree. C. A metal ion compound and a compound of formulae (I) to (III) were added to the emulsion, in the same manner as in preparation of (B-1) to (B-9). Then, the same process as in Example 1 was repeated, except that the emulsions thus prepared were used in the eleventh layer. The yellow image density of the positive image formed was measured, and the same results as those in Example 1 were obtained.

Emulsions (C-1) to (C-6) were prepared, as shown in Table 4 below. Photographic material samples were prepared in the same manner as above, using one of the thus prepared emulsions in the third layer.

Photographic material samples were prepared in the same manner as in Example 1, except that one of Emulsions (C-1) to (C-6) was used in the third layer. These samples were incubated under the conditions of 50.degree. C. and 55% RH for 7 days and then wedgewise exposed in an ordinary manner (color temperature 4800.degree. K., 0.1 second, 100 CMS). These were then processed in accordance with the processing procedure (A) in the same manner as in Example 1, except that the color development time was 120 seconds or 135 seconds.

The results obtained are shown in Table 5 below.

From the results in Table 5 above, it is noted that Samples Nos. 1 to 6 which further contained a compound of formulae (IV) to (VI) were more excellent as the Dmax value was higher even when the development time was short.

The same process as in Example 1 was repeated, except that the following yellow coupler was used and the developing agent in the developer was changed to N-ethyl-N-hydroxyethyl- 4-aminoaniline sulfate. The same results were obtained. ##STR8##

While the invention has been described in detail and with reference to specific embodiments thereof, it will be apparent to one skilled in the art that various changes and modifications can be made therein without departing from the spirit and scope thereof.