GB1600573A

GB1600573A - Process for forming high-contrast silver images

Info

Publication number: GB1600573A
Application number: GB233278A
Authority: GB
Original assignee: Konica Minolta Inc
Current assignee: Konica Minolta Inc
Priority date: 1977-02-01
Filing date: 1978-01-20
Publication date: 1981-10-21
Also published as: DE2803177A1; JPS5395628A; JPS5950975B2

Description

(54) PROCESS FOR FORMING HIGH-CONTRAST SILVER IMAGES (71) We, KONISHIROKU PHOTO INDUSTRY CO. LTD., a Corporation organized and existing under the laws of Japan, of 1-10, 3-chome, Nihonbashi-Muro-machi, Chuo-ku, Tokyo, Japan, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: The invention relates to a process for forming a high contrast silver image by processing a light-sensitive silver halide photographic material. Particularly, it relates to a process for forming a high contrast silver image, capable of forming a silver image consisting of dots with high contrast and high quality, and of improving the developing stability.

More particularly, it relates to a process for forming a high contrast silver image which is advantageously applied to novel high contrast light-sensitive silver halide photographic material such as lith type (printing) light-sensitive silver halide material or photocopy type light-sensitive silver halide photographic material fit for forming dot - or line image; which shows a superior preservability of the developing solution; and which employs a superior developing fatigue-resistant developing solution capable of maintaining the prescribed developing period and of saving the supply solution even when large amounts of light-sensitive silver halide photographic material are processed.

It has been known to form a photographic image with an extremely high contrast by using some kind of a light-sensitive silver halide photographic material.

It has been known, for example, to obtain a high contrast image, e.g. a line- or dot-image, by processing, with an alkaline hydroquinone developing solution containing sulfite ions in a very low concentration, a light-sensitive material which comprises a silver chlorobromide emulsion containing silver chloride in a high content (at least more than 50 mole So), the grains of which emulsion being minute (average grain size; ca. 0.2 Il), uniform in shape, and the grain size distribution thereof being narrow. The above mentioned kind of light-sensitive silver halide material is known as the 12th type light-sensitive material.

In printing business, there is usually required such a process as to convert a continuous gradation original image to a dot image, i.e. a process to convert the densitites of the continuous gradation to a predetermined numbered assembly of dots respectively having area of the same densities but proportional in size to the densities of the coninuous gradation. In order to carry out this, the lith type light-sensitive material is subjected to development, after photographing the original image through a cross- or contact-screen, to form the dot image on the light-sensitive material.

For this purpose, there has been employed a light-sensitive silver halide photographic material containing a silver halide emulsion, the grains of which being minute and being uniform in size and shape. Even when this kind of a light-sensitive silver halide photographic material is employed, the intermediate density region is reproduced, beside the maximum density region and the minimum one (fog), when the material is processed with a standard black and white developing solution. The intermediate density region or the so-called fringe is undesirable for producing printing plates and makes the dot quality worse.

There has heretofore been employed the lith type light-sensitive material also for the reproduction of a line image. For the same reason, however, there have been obtained images having at best the y-value of 5 - 6 of the characteristic curve, which value is lower than 7 - 9 required for forming the desirable line image, if the standard black and white developing solution is employed. In order to avoid this, there has been employed, as mentioned above, a specific developing solution called "infectious developing solution".

Here, the term infectious developing solution, or lith type developing solution means a developing solution in which hydroquinone is substantially and solely the developing agent and sulfite ions are contained in low concentration, as specifically described in J. A. C.

Yule, Journal of The Franklin Institute, vol. 239, p.221 (1945).

As can be expected from the composition, it is inevitable that the control system for obtaining a negative or positive dot with high quality constantly becomes complicated because the lith type developing solution is liable to be auto-oxidized and has a poor preservability.

Although much efforts have been made to improve the preservability of lith type developing solution, there have been found no developing solutions, with which a high dot quality is obtained, having a preservability comparable to a continuous gradation developing solution, e.g. Metol/hydroquinone developing solution or phenidone/hydroquinone developing solution.

The above-mentioned and under-mentioned other objects of the invention may be attained by a process for forming a high contrast silver image from an imagewise-exposed light-sensitive silver halide photographic material comprising a support coated with at least one hydrophilic colloidal layer, said hydrophilic colloidal layer, or at least one of said hydrophilic colloidal layers, comprising a silver halide emulsion layer, and said photographic material containing a tetrazolium compound, which process comprises treating said imagewise-exposed material with a developer and/or a processing solution and then with a developer, both of which developer and/or processing solution contain a heterocyclic compound with a nitrogen-containing ring, and substituted with at least one methyl, hydroxymethyl or nitro group on a ring thereof.

The inventors have found previously that a high contrast silver image may be formed by processing a light-sensitive silver halide photographic material containing a tetrazolium compound within at least one hydrophilic colloidal layer, after imagewise exposure, with a developing solution containing a hydroquinone series or a non-hydroquinone series developing agent.

The inventors have found, after further studies of the developing process, that not only a silver image with an extremely superior dot quality may be obtained but also the stability of developing solution, i.e. preservability of the developing solution, oxidation resistance and developing fatigue resistance may be improved remarkably, by incorporating at least one specific compound, i.e. a nitrogen-containing heterocyclic compound substituted with at least one methyl, hydroxymethyl or nitro group on a ring thereof (hereinafter referred to as a nitrogen-containing heterocyclic compound of the invention) into the devloping solution and/or the processing solution prior to the developing.

The inventors have found further that the photographic performance may not be influenced by a mixing of the fixing solution into the developing solution, when the developing solution and/or the processing solution prior to the developing, containing a nitrogen-containing heterocyclic compound of the invention is employed.

Namely, so-called reverse mixing takes place and, particularly in case of lith developing, the optimum developing point moves and thus influences remarkably the photographic performance, when a light-sensitive silver halide photographic material is conveyed continuously with an automatic developer.

Whereas, according to the invention, the optimum developing point is kept stable and no movement thereof is observed.

Furthermore, it has turned out, according to the invention that no oxidation product of the developing agent is accumulated due to improved preservability of the developing solution and thus the color pollution of the processed light-sensitive silver halide photographic material may be prevented; that no insoluble substances like a sludge precipitate in the developing solution comes out even when light-sensitive silver halide photographic material is processed in large amounts; and that a broad developing latitude fit for the practical dot quality may be obtained.

There is no specific limitation as to the nature of the nitrogen-containing heterocyclic compound of the invention to be contained in the developing solution and/or the processing solution prior to the developing, as far as it is a nitrogen-containing heterocyclic ring compound substituted with at least one methyl, hydroxymethyl or nitro group on a ring thereof (not necessarily the heterocyclic ring).

Preferably, the ring of the nitrogen-containing heterocyclic compound of the invention is selected from imidazoline-, imidazole-, imidazolone-, imidazolidine-, imidazolidone-, pyrazoline-, pyrazol-, pyrazolone-, pyrazolidine-, pyrazolidone-, oxazoline-, oxazole-, oxazolone-, oxazolidine-, oxazolidone-, thiazoline-, thiazole-, thiazolone-, thiazolidine-, thiazolidone-, selenazoline-, selenazole-, selenazolone-, oxadiazole-, thiadiazol-, triazole-, tetrazole-, pyrazine-, pyrimidine-, pyridazine-, triazine-, oxazine-, thiazine-, tetrazine-, benzimidazole-, indazole-, benzoxazole-, benzothiazole-, benzoselenazole-, naphthoimidazole-, benzotriazole-, napththoxazole-, naphthothiazole- and polyazaindene rings (e.g.

triazaindene, tetraazaindene or pentaazaindene). In the invention, particularly preferred are, among compounds having the above-mentioned rings, those in which the substitutent is a nitro group.

The following are concrete, but non-limiting examples of the nitrogen-containing heterocyclic compound of the invention preferably employed in the invention:

Although the nitrogen-containing heterocyclic compound of the invention is not limited to those illustrated above, preferably employed among the above-illustrated compounds are 5-nitrobenzimidazole, 5-nitroindazole, 6-nitroindazole and 5-nitrobenzotriazole.

At least one nitrogen-containing heterocyclic compound of the invention is used in the developing solution or the processing solution prior to the developing. Eventually, two or more compounds may be used in combination, depending on the varieties of light-sensitive silver halide photographic material to be processed and on the developing conditions.

The nitrogen-containing heterocyclic compound of the invention may readily be synthetized according to the methods described in e.g. U.S. Patent 3,615,501; 2,324,123; 2,384,593; 2,496,940; 3,137,578; 2,496,940; 3,082,088; 3,473,924; 3,575,699; 3,687,660; 2,271,229 and 2,496,940; and British Patent 1,141,773 and 1,376,600.

Alternatively, it may readily be synthesized by the methods described in literatures such as "Daiyuki-kagaku" edited by Munio Kotake (Published by Asakura Shoten; 1971) or A. Weissberger, "The Chemistry of heterocyclic compounds" (N.Y. Interscience, 1950 1964).

The amount of addition of the nitrogen-containing heterocyclic compound of the invention is not critical, but is 0.1 mg - 5g per litre, preferably 0.5 mg - 2 g per litre when contained in the developing solution, and is 0.1 mg - 5 g per litre, preferably 0.5 mg - 2 g per litre, more preferably 1 mg - 1.5 g per litre when contained in the processing solution prior to the developing.

The nitrogen-containing heterocyclic compound of the invention is used contained in the developing solution or the processing solution prior to the developing (hereinafter referred to as pre-bath) and may readily be added thereto, e.g. by following methods because it has a superior solubility and a little foaming property. Namely, it may be added to the developing solution or pre-bath, by dissolving it in an aqueous acidic or alkaline solution (e.g. acetic acid or aqueous sodium hydroxide solution) or in an organic solvent such as ethyleneglycols, ethanolamines or alcohols. Alternatively, it may be added to the developing solution or the pre-bath, by dissolving it in an anionic, nonionic, cationic or amphoteric surfactant or by micelle dispersing it in the above-mentioned surfactant.

Representative and non-limiting examples of the developing solution and pre-bath preferably used in the invention and containing a nitrogen-containing heterocyclic compound of the invention are given below: 1. Examples of the developing solution [developing solution 1] Metol 3.5 g anhydrous sodium sulfite 40 g hydroquinone 9g sodium carbonate monohydrate 50 g potassium bromide 2.5 g triethyleneglycol 20 g water to make 1 litre (pH = 10.20) [developing solution 2] Metol 8g anhydrous sodium sulfite 60 g sodium carbonate monohydrate 54 g potassium bromide 2.5 g 1-phenyl-5-mercaptotetrazole 10 mg water to make 1 litre (pH = 10.20) [developing solution 3] 1-phenyl-3-pyrazolidone 0.3 g hydroquinone 10 g anhydrous sodium sulfite 40 g sodium carbonate monohydrate 20 g potassium bromide 3g disodium ethylenediaminetetraacetate 1 g triethanolamine 30 g water to make 1 litre (pH = 10.25) 2. Examples of pre-bath [pre-bath 1] disodium ethylenediaminetetraacetate 1 g anhydrous sodium sulfite 10 g triethanolamine 20 g water to make 1 litre (pH = 10.0) [pre-bath 2] disodium ethylenediaminetetraacetate 1 g sodium carbonate monohydrate 10 g potassium bromide 3g sodium sulfite 10 g triethyleneglycol 30 g water to make 1 litre (pH = 10.5) There may be employed various kinds of developing agents, solely or jointly, in the developing solution of the invention.

As the developing agents to be used, are included, e.g. organic or inorganic developing agents or auxiliary developing agents, solely or jointly, described in e.g. E.K. Mees and T.H. James, "The Theory of The Photographic Process" 3rd ed., pp278 - 381 (1966).

Preferred are ferrous oxalate, hydroxylamine, N-hydroxymorpholine, hydroquinones such as hydroquinone, hydroquinone monosulfonate, chlorohydroquinone or tbutylhydroquinone, catechol, resorcinol, pyrogallol, amidole, pyrazolidones such as 1-phenyl-3-pyrazolidone, p-aminophenols such as p-aminophenol, glycine or Metol, p-phenylenediamines such as p-phenylenediamine or 4-amino-N-ethyl-N-ethoxyaniline, ascorbic acid or the like. More preferred are Metol, combinations of 1-phenyl-3pyrazolidone and Metol, 1-phenyl-3-pyrazolidone and hydroquinone, Metol and hydroquinone, 1-phenyl-3-pyrazolidone, Metol and t-butylhydroquinone, 1-phenyl-3pyrazolidone and ascorbic acid, or 1-phenyl-3-pyrazolidone and p-aminophenol.

It is possible that similar good results may be obtained by using more diverse combinations.

The developing agent contained in the developing solution of the invention is used in an ordinary amount, i.e. 10-5 - 1 mole per litre of the developing solution.

A preserver like sulfites such as sodium sulfite, potassium sulfite or ammonium sulfite may jointly be employed in the developing solution used in the invention without impairing the effects of the invention; and this is another characteristic of the invention. The sulfite is contained preferably in an amount of 10-5 - 10-l mole per litre. Similarly, hydroxylamine or hydrazides may also be employed as the preservers.

There may optionally be added in the developing solution an alkali hydroxide, alkali borate, alkali carbonate or amine to adjust pH and to give buffer function; an inorganic or organic developing retarder such as potassium bromide; a heavy metal sequestering agent (water softener) such as ethylenediaminetetraacetic acid; a hardner such as formalin, glyoxal or glutaraldehyde; a surfactant such as sodium dodecylbenzenesulfonate; a developing accelerator such as polyethyleneglycol oleate; or a coloring coupler such as 2,4-dibromo-a-naphthol.

Furthermore, a contrast agent or a toe-part cutting agent often used for the conventional high contrast developing solution may be added without giving undesirable influence on the photographic quality.

As mentioned above, the developing solution of the invention contains a developing agent selected from known silver halide developing agents with no structural, physical or chemical limitation, and may further contain various kinds of photographic additives.

It is desirable that the developing solution of the invention has a pH value of 8.5 - 12.

The process of the invention comprises processing a light-sensitive silver halide photographic material containing a tetrazolium compound (hereinafter referred to as the light-sensitive silver halide photographic material of the invention), after imagewise exposure, with a developing solution and/or pre-bath containing at least a nitrogencontaining heterocyclic compound of the invention.

For example, the temperature at which the developing or pre-bathing is carried out is preferably not more than 50"C, more preferably around 30"C, and the time required for developing is within 5 minutes, in general, particularly preferably within 2 minutes, by which good results are often obtained. After the developing, the subsequent processes such as washing, stopping, stabilizing and fixing, and if necessary, prehardening and neutralization are performed, using conventional processing solutions employed for the processes.

The processes may be carried out either by the so-called manual processing like a bath-or tray-development, or by the automatic processing like a roller- or hanger-development.

According to a preferred embodiment of the invention, the processing solution in the bath development was more than 30 times stabler over long period than the conventional lith type developing solution. Especially, when the known particular developing solution containing sulfite ion in an extremely low concentration is employed in order to improve the dot quality of the lith type light-sensitive material, it became of no use for several hours.

Whereas, according to a preferred method of the invention, the processing solution could be stably employed after three months have passed, and the dot quality using the solution was then comparable to that using a newly prepared solution. When the pre-bath containing a nitrogen-containing heterocyclic compound of the invention is used, it is desirable that the process with the pre-bath be performed immediately before the process with the developing solution, though other processes may be performed inbetween.

As can be understood by the above description, the invention relates to a process of novel light-sensitive silver halide photographic material, affording a superior line-or dot-quality, by processing a light-sensitive silver halide photographic material containing a tetrazolium compound, with a developing solution and/or pre-bath containing a nitrogen-containing heterocyclic compound of the invention.

In accordance with the process of the invention, a superior high contrast silver image may be obtained when a diffusible tetrazolium compound is used. When a non-diffusible tetrazolium compound is used, a dot image which is more superior than that obtained in accordance with the method disclosed in Japanese Patent Application No. 50-94295 may be obtained.

The light-sensitive silver halide photographic material used for forming a high contrast silver image according to the invention will be explained as follows.

The tetrazolium compound of the invention is preferably contained within the silver halide emulsion layer. More generally, it is contained within the silver halide emulsion layer and/or a directly or indirectly adjacent layer thereto. Alternatively, the tetrazolium compound of the invention may be coated direct on the outermost layer of the light-sensitive photographic material, or on the outermost layer of the material upon preparation, by means of overcoat method or the like, by dissolving the tetrazolium compound in an appropriate organic solvent.

It is desirable that the silver halide contained in the silver halide emulsion layer has a mean grain size of 0.05 - 0.8i.

In this invention, the term "non-diffusible tetrazolium compound" means a compound which does not dissolve from the light-sensitive material to the developing solution during the development. In other words, the compound does not dissolve in a concentration of several %, preferably not more than 2 %, when a gelatin layer containing the compound is dipped for 10 minutes in an aqueous solution at 20 - 400C having the same ion strength and pH-value as those of the developing solution.

The representative tetrazolium compounds employed in the invention include the following compounds represented by the general formulae:

In the above formulae, R1, R3, R4, R5, R8, R9, Rlo and Rl1 individually represent groups selected from an alkyl group (e.g. methyl, ethyl, propyl or dodecyl), an allyl group, a phenyl group (e.g. phenyl, tolyl, hydroxyphenyl, carboxyphenyl, aminophenyl or mercaptophenyl), a naphthyl group (e.g. a-naphthyl, (3-naphthyl, hydroxynaphthyl, carboxynaphthyl or aminonaphthyl,) and a heterocyclic group (e.g. thiazolyl), benzothiazolyl, oxazolyl, pyrimidinyl, pyridyl,).

The group can advantageously contain an electron sharing group capable of forming a metal chelate or a complex and; R2, R6 and R7 each represent a group selected from an allyl group, a phenyl group, a naphthyl group, a heterocyclic group, an alkyl group (e.g. methyl, ethyl, propyl, butyl, mercaptomethyl or mercaptoethyl), hydroxyl, carboxyl or the salt thereof, a carboxyalkyl group (e.g. a methoxycarbonyl or ethoxycarbonyl), an amino group (e.g. amino, ethylamino or anilino), mercapto, nitro and hydrogen; D represents a divalent aromatic group; E represents a group selected from an alkylene group, an arylene group and an aralkylene group; X? is an anion; and n is 1 or 2, provided that the compound forms an intramolecular salt when n is 1.

The following are typical examples of the tetrazolium compounds used in the invention but not intended to limit the salt of tetrazolium compound thereof.

(1) 2-(Benzothiazol-2-yl)-3-phenyl-5-dodecyl-2H-tetrazolium bromide (2) 2 ,3-Diphenyl-5-(4-t-octyloxyphenyl)-2H-tetrazolium chloride (3) 2,3,5-Triphenyl-2H-tetrazolium chloride (4) 2,3 ,5-Tri(p-carboxyethylphenyl)-2H-tetrazolium chloride (5) 2-(Benzothiazol-2-yl)-3-phenyl-5-(o-chlorophenyl)-2H-tetrazolium bromide (6) 2,3-Diphenyl-2H-tetrazolium chloride (7) 2,3-Diphenyl-5-methyl-2H-tetrazolium chloride (8) 3-(p-Hydroxyphenyl)-5-methyl-2-phenyl-2H-tetrazolium bromide (9) 2,3-Diphenyl-5-ethyl-2H-tetrazolium bromide 10) 2,3-Diphenyl-5-n-hexyl-2H-tetrazolium bromide 11) 5-Cyano-2,3-diphenyl-2H-tetrazolium bromide 12) 2-(Benzothiazol-2-yl)-5-phenyl-3-(4-tolyl)-2H-tetrazolium bromide (13) 2-(Benzothiazol-2-yl)-5-(4-chlorophenyl)-3-(4-nitrophenyl)-2H-tetrazolium chloride 14) 5-Ethoxycarbonyl-2,3-di(3-nitrophenyl)-2H-tetrazolium chloride 15) 5-Acetyl-2 ,3-di(p-ethoxyphenyl)-2H-tetrazolium bromide 16) 2,5-Diphenyl-3-(p-tolyl)-2H-tetrazolium chloride (17) 2,5-Diphenyl-3-(p-iodophenyl)-2H-tetrazolium chloride (18) 2,3-Diphenyl-5-(p-diphenyl)-2H-tetrazolium chloride 19 5-(p-Bromophenyl)-2-phenyl-3-(2,4,6-trinitrophenyl)-2H-tetrazolium chloride 20 3-(p-Hydroxyphenyl)-5-(p-nitrophenyl)-2-phenyl-2H-tetrazolium chloride (21) 5-(3,4-Dimethoxyphenyl)-3-(2-ethoxyphenyl)-2-(4-methoxyphenyl)-2H- tetrazolium chloride (22) 5-(4-Cyanophenyl)-2,3-diphenyl-2H-tetrazolium chloride (23) 3-(p-Acetamidophenyl)-2,5-diphenyl-2H-tetrazolium bromide (24) 5-Acetyl-2 ,3-diphenyl-2H-tetrazolium bromide (25) 5-(Fur-2-yl)-2,3-diphenyl-2H-tetrazolium chloride (26) 5-(Thien-2-yl)-2,3-diphenyl-2H-tetrazolium chloride (27) 2,3-Diphenyl-5-(pyrid-4-yl)-2H-tetrazolium chloride 28) 2,3-Diphenyl-5-(quinol-2-yl)-2H-tetrazolium bromide (lug) 2,3-Diphenyl-5- benzoxazol-2-yl)-2H-tetrazolium bromide (30) 2 3-Diphenyl-5-nitro-2H-tetrazolium bromide (31) 2,2' 3,3 '-Tetraphenyl-5 5 '-1 ,4-butylene-di-(2H-tetrazolium) bromide (32) 2,2' ,3,3 '-Tetraphenyl-5,5 '-p-phenylene-di-(2H-tetrazolium) bromide (33) 2-(4,5-Dimethylthiazol-2-yl)-3,5-diphenyl-2H-tetrazolium bromide (34) 3 ,5-Diphenyl-2-(triazin-2-yl)-2H-tetrazolium chloride (35) 2-(Benzothiazol-2-yl)-3-(4-methoxyphenyl)-5-phenyl-2H-tetrazolium bromide (36) 2-p-Iodophenyl-3-p-nitrophenyl-5-phenyl-2H-tetrazolium chloride (37) 2-(Benzothiazol-2-yl)-3-phenyl-5-dodecyl-2H-tetrazolium stearate (38) 2,3-Diphenyl-5-(4-t-octyloxyphenyl)-2H-tetrazolium laurate (39) 2,3,5-Triphenyl-2H-tetrazolium di-2-ethylhexylsulfosuccinate (40) 2,3 ,5-Tri(p-carboxyethylphenyl)-2H-tetrazolium stearate (41) 2-(Benzothiazol-2-yl)-3-phenyl-5-(o-chlorophenyl) 2H-tetrazolium p-dodecyl benzenesulfonate (42 2,3-Diphenyl-2H-tetrazolium di-2-ethylhexylsulfosuccinate (43 2,3-Diphenyl-5-methyl-2H-tetrazolium p-octylbenzenesulfonate (44) 3-(p-Hydroxyphenyl)-5-methyl-2-phenyl-2H-tetrazolium stearate (45) 2,3-Diphenyl-5-ethyl-2H-tetrazlium di-3-methylnonylsulfonate (46) 2,3-Diphenyl-5-n-hexyl-2H-tetrazolium p-octadecylbenzenesulfonate (47) 5-Cyano-2,3-diphenyl-2H-tetrazolium di-2-ethylhexylsulfosuccinate (48) 2-(Benzothiazol-2-yl)-5-phenyl-3-(4-tolyl)-2H-tetrazolium p-dodecylbenzen sulfonate (49) 2-(Benzothiazol-2-yl)-5-(4-chlorophenyl)-3-(4-nitrophenyl)-2H-tetrazolium di-iso propylnaphtalensulfonate (50) 5-Ethoxycarbonyl-2,3-di(3-nitrophenyl)-2H-tetrazolium stearate (51) 5-Acetyl-2,3-di (p-ethoxyphenyl)-2H-tetrazolium laurate (52) 2,5-Diphenyl-3-(p-tolyl)-2H-tetrazolium stearate 53) 2,5-Diphenyl-3-(p-iodophenyl)-2H-tetrazolium laurate (54) 2,3-Diphenyl-5- p-diphenyl)-2H-tetrazolium di-isopropylnaphthalenesulfonate (55) 5-(p-Bromophenyl) -2-phenyl-3-(2 ,4,6-trichlorophenyl)-2H-tetrazolium di-isopropylnaphthalene-di-sulfonate (56) 3-(p-Hydroxyphenyl)-5-(p-nitrophenyl)-2-phenyl-2H-tetrazolium p-dodecyl benzenesulfonate (57) 5 -(3 ,4- im 5-(3,4-Dimethoxyphenyl)-3-(2-ethoxyphenyl)-2-(4-methoxyphenyl)-2H-tetra- zolium di-2-ethylhexylsulfosuccinate (58) 5-(4-Cyanophenyl)-2,3-diphenyl-2H-tetrazolium laurate (59) 3-(p-Acetamidophenyl)-2,5-diphenyl-2H-tetrazolium stearate (60) 5-Acetyl-2,3-diphenyl-2H-tetrazolium p-octadecylbenzenesulfonate (61) 5-(Fur-2-yl)-2,3-diphenyl-2H-tetrazolium di-2-ethylhexylsulfonate (62) 5-(Thien-2-yl)-2,3-diphenyl-2H-tetrazolium stearate (63) 2,3-Diphenyl-5- pyrid-4-yl)-2H-tetrazolium laurate (64) 2,3-Diphenyl-5-(quinol-2-yl)-2H-tetrazolium stearate (65) 2,3-Diphenyl-5-(benzoxazol-2-yl)-2H-tetrazolium laurate (66) 2,3-Diphenyl-5-nitro-2H-tetrazolium di-isopropylnaphthalenesulfonate (67) 2,2' ,3 ,3 ' -Tetraphenyl-5 ,5 '-1 ,4-butylene-di-(2H-tetrazolium) di-3-propyl-nonyl sulfonate (68) 2,2' 3,3 '-Tetraphenyl-5 5 '-p-phenylene-di-(2H-tetrazolium)p-dodecylbenzene- sulfonate (69) 2-(4,5-Dimethylthiazol-2-yl)-3 ,5-diphenyl-2H-tetrazolium stearate (70) 3 ,5-Diphenyl-2-(triazin-2-yl)-2H-tetrazolium laurate (71) 2-(Benzothiazol-2-yl)-3-(4-methoxyphenyl)-5-phenyl-2H-tetrazolium p-tolyl sulfonate.

(72) 2-p-iodophenyl-3-p-nitrophenyl-5-phenyl-2H-tetrazolium di-isopropyl naphthalene-disulfonate (73) 2,3 ,5-triphenyl-2H-tetrazolium di-isopropylnaphthalene-di-sulfonate Among the diffusible and non-diffusible tetrazolium compounds, 2,3,5-triphenyl-2Htetrazolium series compounds are preferably used in the invention.

Joint use of plural tetrazolium compounds may bring about more preferable characteristics.

For instance, particularly preferable combination in the invention is a combination of a compound obtained from 2,3,5-triphenyl-2H-tetrazolium chloride and 2,5-diphenyl-3-(piodophenyl)-2H-tetrazolium or 23 ,5-triphenyl-2H-tetrazolium and diisopropylnaphthalenedisulfonic acid; and a compound obtained from 2-p-iodophenyl-3-p-nitrophenyl-5phenyl-2H-tetrazolium and diethylhexylsuccinate sulfonic acid, which brings about merits, e.g. broad developing latitude.

When the tetrazolium compound of the invention is used as the non-diffusible type, the non-diffusible compound obtained by reacting the a the dispersion is not sufficiently homogeneous, good results may be obtained by exposing the emulsion dispersion to an ultrasonic wave or by use of a suitable homogenizer such as Manton-Gaulin homogenizer.

Among the non-diffusible tetrazolium compounds used in the invention, those obtained from 2,3,5-triphenyl-2H-tetrazolium and diisopropylnaphthalenedisulfonate, 2,3,5triphenyl-2H-tetrazolium and diethylhexylsuccinate disulfonic acid, and, 2-p-iodophenyl-3p-nitrophenyl-5-phenyl-2H-tetrazolium and diethylhexylsuccinate disulfonic acid are preferably employed.

As mentioned above, the tetrazolium compounds of this invention may be used both in diffusible and non-diffusible tetrazolium compounds. However, the higher contrast omage may be obtained by employing the non-diffusible tetrazolium compounds. Accordingly, it is advantageous to employ the non-diffusible tetrazolium compound when an especially superior dot quality is required.

On the other hand, the use of too much high contrast light-sensitive material sometimes brings about insufficient reproduction of the line image, particularly those of fine letters and lines. In this case an image with more superior quality may be obtained by the use of the diffusible tetrazolium compound.

According to a preferred embodiment of the invention, the tetrazolium compound of the invention is incorporated into a silver halide emulsion layer.

According to another preferred embodiment of the invention, the compound is incorporated in a layer adjacent (or a layer adjacent to said adjacent layer) to the layer containing the silver halide emulsion.

The above-mentioned tetrazolium compounds of the invention may preferably be employed in an amount of 0.0001 - 10 mole, more preferably 0.001 - 1 mole, per mole of the silver halide contained in the light-sensitive silver halide photographic material of the invention. As the silver halide employed for the light-sensitive silver halide photographic material of the invention includes any silver halide used for the conventional silver halide photographic materials, e.g. silver bromide, silver chlorobromide, silver iodobromide, silver chloroiodobromide or silver chloride and the like.

The average grain size of the silver halide in the invention is 0.05 - 1.5 Il, preferably 0.1 0.8 11, more preferably 0.25 - 0.25 11 and at least 75 %, preferably more than 80 % of the total grains are within a range of 0.6 - 1.4, preferably 0,7 - 1.3 times larger than the average grain size. Furthermore, the silver halide comprises silver chlorobromide or chloroiodobromide containing at least 50 mole % silver chloride and satisfies the above-mentioned grain size and the distribution thereof. The silver halide of the invention having the above-mentioned average grain size and the distribution thereof may be prepared by any known method described, e.g. in U.S. Patents 2,592,250, 3,276,877, 3,317,322, 2,222,264, 3,320,069 and 3,206,313 and in Journal of Photographic Science 12(5), 242-251 (1964).

Silver halides prepared by other methods may also be employed in mixture.

According to the most preferred concrete embodiment of the invention, the silver halide of the invention is silver chloroiodobromide or chlorobromide having an average grain size of 0.1 - 0.8 , preferably 0.25 - 0.5 Ce and at least 80 % of the total grains being within a range of 0.7 - 1.3 times larger than the average grain size.

The silver halide emulsion of the invention may be sensitized with various kinds of chemical sensitizers. As the sensitizer, are mentioned, for example; activated gelatin, sulfur sensitizers (e.g. sodium thiosulfate, aryl thiocarbamide, thiourea or aryl isocyanate, etc.), selenium sensitizers (e.g. N,N-dimethylserenourea or selenourea, etc.), reducing sensitizers (e.g. triethylenetetramine or stannic chloride, etc.) and various noble metal sensitizers represented by potassium chloroaurite, potassium auriothiocyanate, potassium chloroaurate, 2-auro-sulfobenzothiazole methylchloride, ammonium chloropalladate, potassium chloroplatinate and sodium chloropalladite. The sensitizer may be employed alone, or mixed together. Ammonium thiocyanate may be auxiliarily employed when a gold sensitizer is employed.

Furthermore, the silver halide emulsion used in the invention may be sensitized optically with one or more sensitizing dyes to give a light sensitivity within the desired light-sensitive wave length.

Various kinds of sensitizing dyes may be employed for the purpose. As the optical sensitizers employed advantageously in the invention are mentioned, e.g. a cyanine, merocyanine, tri- or tetranuclei merocyanine, tri- or tetranuclei cyanine, styryl, holopolar cyanine, hemicyanine, oxonole, hemioxonole, and the like.

The optical sensitizers preferably contain with the chemical structure thereof a nitrogen-containing heterocyclic nucleus, e.g. a basic group such as thiazoline or thiazole, or rhodanine, thiohydantoin, oxazolidine-dione, barbituric acid, thiobarbituric acid or pyrazolone. The nucleus may be substituted with an alkyl, hydroxyalkyl, halogen, phenyl, cyano or alkoxy group or may be fused with a hydrocarbon or hetero-cyclic ring.

When the optical sensitizers mentioned above, particularly merocyanine dye is employed, not only optical sensitization but also broadening of developing latitude may be achieved.

The silver halide emulsion of the invention may preferably be stabilized with 5 ,6-trimethylene-7-hydroxy-s4riazole(1 ,5-a)-pyrimidine, 5 ,6-tetramethylene-7-hydroxy-s- triazolo(1,5-a)-pyrimidine, 5-methyl-7-hydroxy-s-triazolo(1 ,5-a)pyrimidine, 7-hydroxy-s triazolo(l ,5-a)pyrimidine, 5-methyl-6-bromo-7-hydroxy-s-triazolo(1 ,5-a)pyrimidine, esters or salts of gallic acid (e.g. isoamyl gallate, dodecyl gallate, propyl gallate or sodium gallate), mercaptans (e.g. 1-phenyl-5-mercaptotetrazole or 2-mercaptobenzothiazole), benzotriazoles (e.g. 5-bromobenzotriazole or 4-methylbenzotriazole) and benzimidazoles (e.g.

6-nitrobenzimidazole). Such stabilizers are described in, e.g. U.S. Patents 2,444,607, 2,716,062, 3,512,982 and 3,342,596, German Patent Publication 1,189,380, 2,058,626, 2,118,411 and 2,149,789, Japanese Patent Publication 39-2825, 43-4133, 47-4417 and 49-13566. Furthermore, the silver halide emulsion of the invention may contain a latent image stabilizer such as a sulfur-containing amino acid, or a gradation-adjusting agent such as a cadmium or rhodium salt, described in, e.g. German Patent Publication 2,217,153 and 2,217,895.

It has been known in, e.g. British Patent 775,197 and U.S. Patent 3,488,709, to employ a rhodium or cadmium salt to increase the contrast of silver halide emulsion. However, problems still remain when the rhodium salt is empoyed. For example, the use of rhodium salt tends to cause an unevenness of the product due to the minute amount of addition and the narrow allowable range thereof of the salt, and thus makes it difficult to produce stable photographic materials. In case of the cadmium salt, it has to be added as little as possible from an ecological viewpoint, for it is washed out by film-processing and comes finally into the environment. The cadmium salts are known to prevent the metabolism and to be harmful to living tissues. Cadmium may be detected not only in air but also in the body of sea animals. As a result of interest in public health and in the maintenance of normal ecological balance in view of the toxicity of rare metals, including cadmium mentioned above, the inventors have reached the invention relating to a novel method to obtain a light-sensitive material with sufficiently high contrast, even in no use of such harmful metals. When the above-mentioned silver halide and tetrazolium compound of the invention are incorporated into the hydrophilic colloidal layer, the hydrophilic colloid advantageously employed in the invention is gelatin. As other hydrophilic colloids than gelatin are mentioned, e.g. colloidal albumin, agar, gum arabic, arginic acid, hydrolyzed cellulose acetate, acrylamide, imidated polyamide, polyvinyl alcohol, hydrolyzed, polyvinyl acetate, water-soluble polymer described in, e.g. British Patent 523,661, U.S. Patents 3,341,332, German Patent Publication 2,255,711 and 2,046,682, gelatin derivatives such as phenylcarbamyl gelatin acylated- or phthalated-gelatin described in, e.g. U.S. Patents 2,614,928 and 2,525,753, or graft-polymerized monomers on gelatin having the ethylene group and being capable of polymerization, such as acrylic acid and the ester thereof, styrene, a methacrylic acid and the ester thereof, described in e.g. U.S. Patents 2,548,520 and 2,831,767. Such hydrophilic colloids may also be applied to a layer containing no silver halide, e.g. an antihalation layer, a protective layer or an intermediate layer.

The light-sensitive silver halide material of the invention may be prepared by coating the above-mentioned layer containing the silver halide and the tetrazolium compound of the invention on a suitable photographic base. As the representative supports employed in the invention are mentioned, e.g. a baryta paper, a polyethylene-coated paper, a synthetic polypropylene paper, a glass plate, a cellulose acetate or cellulose nitrate film, a polyester film such as a polyethylene terephthalate film, a polyamide film, a polypropylene film, a polycarbonate film, a polystyrene film and the like. The supports are optionally selected depending on the purpose for which the light-sensitive photographic material is used.

Representative light-sensitive silver halide photographic material of the invention comprises at least one hydrophilic colloidal layer, coated on the support, containing a silver halide of this invention and the tetrazolium compound of the invention.

It is preferable in the light-sensitive silver halide photographic material of the invention that a protective layer having a suitable thickness is coated. The protective layer is advantageously a gelatin layer, the thickness of which is preferably 0.1 - 10 ,u, more preferably 0.8 - 2.0 U The hitherto known lith type light-sensitive silver halide photographic materials usually have a protective layer. In this invention, however, the protective layer plays an important role different from known ones.

The protective layer is, in general, coated for the purpose to protect the silver halide emulsion layer from an incidental mechanical damage during production processes, e.g.

cutting, winding or wrapping process, or during photographing and/or processing caused by contact of the light-sensitive material with other substance.

It has turned out that the protective layer of the invention not only protects the above-mentioned silver halide emulsion but also plays an important role for processing stability. That is, while the lith type light-sensitive material has to be able to form a very high contrast line- and dot-image, if a compound oxidizable of a developing agent i.e. the tetrazolium compound is added in the light-sensitive silver halide photographic material to obtain the above-mentioned high contrast silver image, the above-mentioned tetrazolium compound as the oxidizing agent gives a large influence on the development during the progress thereof and consequently, the quality of the line- or dot-image obtained is largely influenced by the difference of e.g. a developing time, a temperature and an amount of the exposure.

It is not necessarily elucidated in the process of the invention why the presence of the protective layer may act effectively on the stability of the image quality and of the developing process. Presumably, the protective layer may have a function to control, adequately the infiltration rate of Metol or t-phenyl-3-pyrazolidone from the processing solution into the light-sensitive material, or the diffusion rate of the tetrazolium compound within the light-sensitive material or therefrom to the processing solution.

This effect is remarkable when the tetrazolium compound of the invention is employed.

The effect is not so remarkable when other oxidizing agent than the tetrazolium compound, described in, e.g. Japanese Laid Open Patent Application No. 18317/1977 are employed.

Various kinds of photographic additives may optionally be added to the abovementioned hydrophilic colloidal layer of the invention, as far as they do not impair the effect of the invention. As the additives, are mentioned, e.g. a gelatin plasticizer, a hardening agent, a surface active agent, an image stabilizer, an ultraviolet absorber, an antistaining agent, a pH adjuster, an antioxidant, an antistatic agent, a viscosity-increasing agent, a granularity improving agent, a dye, a mordant, a brightening agent, a development regulator, a matting agent, and the like.

Among the additives mentioned above, the following may particularly and preferably be employed: viscosity-increasing agents and plasticizers, described in U.S. Patents 2,960,404 and 3,767,410, German Patent Publication 1,904,604, Belgian Patent 558,143 and 762,833, Japanese Patent Publication 43-4939 and 45-15462 and Japanese Patent Provisional Publication 48-63715, e.g. a styrene/sodium maleate copolymer and dextran sulfate, etc; hardning agents of an aldehyde, epoxy, ethyleneimine, active halogen, vinylsulfone, isocyanate, sulfonic acid ester, carbodiimide, a mucochloric acid, or acyloyls, etc.; image stabllizers, e.g. 6,6' -butylidene-bis(2-t-butyl-4-methylphenol) and 4,4'-methylene-bis(2, 6- di-t-butylphenol), etc.; ultraviolet absorbers, described in, e.g. U.S. Patent 3,253,921, British Patent 1,309,349, Japanese Patent Publication 48-736, 48-5496, 48-41572, 48-30492 and 48-31255, particularly 2-(2' -hydroxy-5 '-t-butylphenyl)-benzotriazole, 2-(2'-hydroxy 3,5 '-di-t-butylphenyl)-benzotriazole, 2-(2' -hydroxy-3 '-t-butyl-5 '-butylphenyl)-5- chlorobenzotriazole and 2-(2 ' -hydrozy-3' ,5 ' -di-t-butylphenol)-5-chlorobenzotriazole; surface active agents for coating aids, emulsifiers, infiltration-improving agents for a processing solution, defoamers, or for controlling various physical properties of the light-sensitive material, described in, e.g. U.S. Patents 3,026,202 and 3,514,293, British Patents 548,532 and 1,216,389, French Patent 202,588, Belgian Patent 773,459, Japanese Patent Publication 44-26580, 43-17922, 43-17926, 43-13166 and 48-20785 and Japanese Patent Provisional Publication 48-101118, including anionic, cationic nonionic and amphoteric compounds; mordants described in, e.g. U.S. Patents 2,113,381 and 2,548,564; antistaining agents described in, e.g. U.S. Patents 2,360,210, 2,728,659, 2,732,300 and 3,700,453, particularly 2-methyl-5-hexadecyl-hydroquinone, 2-methyl-5-sec-octadecylhydroquinone and 2,5-di-t-octylhydroquinone, etc.; antistatic agents described in, e.g. U.S.

Patents 2,882,157 and 2,972,535, Japanese Patent Publication 46-24159, 46-39312, 48-43809, 49-4853, 49-64 and 47-8742 and Japanese Patent Provisional Publication 48-89979, 48-20785, 48-43130, 48-90391 and 47-33627; matting agents described in, e.g.

U.S. Patents 2,992,101 and 2,956,884, British Patent 1,221,980, French Patent 1,395,544 and Japanese Patent Publication 48-43125, particularly silica gel having a grain size of 0.5 20 U and polymethylmethacrylate having a grain size of 0.5 - 20 ; developing promoters, e.g. benzyl alcohol, a polyoxyethylene series compound and an addition polymer of polyoxyethylene with glycidol.

In accordance with the process of the invention, there is obtained a high contrast silver image. The invention is therefore applicable to various fields wherein a high contrast black and white recording is required. The light-sensitive material of the invention is, for example, applied preferably to a printing- or micro-sensitive material.

The process of the invention for forming a lith type photographic image has superior characteristics which no conventional processes have yet reached.

The invention is further concretely explained by the following Examples, which by no means restrict the scope of the invention: Comparison I A silver chloroiodobromide-gelatin emulsion comprising silver halide of 85 mole % chloride, 14 mole % bromide and 1 mole % iodide, having an average grain size of 0.3 y was sensitized chemically with sulfur- and gold-sensitizers. To the emulsion was added polyethyleneglycol (m.w. = 1540) oleic acid ether in an amount of 200 mg per mole of silver. The emulsion was coated on a polyethylene terephthalate support in such amounts that those of the silver and the gelatin were 50 mg and 35 mg per 100 cm2, respectively.

Further, on the silver halide emulsion layer, was coated gelatin in an amount of 15 mg per 100 cm2 as a protective layer. The above-mentioned elements were wedge-exposed with a tungsten lamp through a gray contact screen and then processed according to the following processes: Developing : 2 min. (30"C) Fixing : 2 min.

Washing : 2 min.

Drying The following compositions were employed in the processing bath: [Developing solution] Hydroquinone 15 g Formaldehyde sodium bisulfite 50 g Sodium sulfite 2g Boric acid 8g Sodium carbonate monohydrate 85 g Potassium bromide 2.5 g Disodium ethylenediaminetetraacetate 1 g Water to make 1 litre (pH = 10.0) [Fixing solution Ammonium thiosulfate decahydrate 150 g Anhydrous sodium bisulfite 10 g Sodium acetate trihydrate 15 g Glacial acetic acid 17 g Water to make 1 litre (pH = 4.20) Comparison 2 A material was prepared in the similar manner as in Comparison 1, except that hexaammine cobalt chloride was added to the emulsion prior to coating in an amount of 3 g per mole of silver. The material was exposed in the similar manner as in Comparison 1 and processed according to the following processes and processing solutions: Developing 1 min. (30"C) Fixing 1 min.

Washing 1 min.

Drying [Developing solution] Metol 3.5 g Anhydrous sodium sulfite 40 g Hydroquinone 9g Sodium carbonate monohydrate 50 g Potassium bromide 2.5 g Triethyleneglycol 20 g water to make 1 litre (pH = 10.20) As the fixing solution, the same composition as in Comparison 1 was used.

Comparison 3 A material was prepared in the similar manner as in Comparison lj except that 2,3,5-triphenyltetrazolium chloride was added to the emulsion, instead of the hexaamine cobalt chloride in Comparison 2, in an amount of 4 g per mole of silver.

The material was exposed in the similar manner as in Comparison 1 and processed in the similar manner as in Comparison 2.

Comparison 4 A material was prepared in the similar manner as in Comparison 1, except that a non-diffusible tetrazolium compound synthesized from 2,3 ,5-triphenyl-2H-tetrazolium chloride and sodium diisopropylnaphthalenedisulfonate was added to the emulsion, instead of the hexaamine cobalt chloride in Comparison 2, in an amount of 2 g per mole of silver.

Example 1 A material was prepared in the similar manner as in Comparison 3. In this example, the developing solution was obtained by adding nitrogen-containing heterocyclic compounds [A]-D], in the amounts given below, solubilized in triethanolamine to the developing solution 1 used in Comparison 2. The fixing solution had the same composition as in Comparison 1.

nitrogen-containing heterocyclic compounds] A] above-illustrated compound (6) 100 mg [B] above-illustrated compound (1) 50 mg [C] above-illustrated compound (15) 200 mg [D] above-illustrated compound (11) 200 mg Example 2 A material was prepared in the similar manner as in Comparison 4. In this example, developing solutions containing the same nitrogen-containing heterocyclic compounds as in Example 1 were used.

The photographic qualities of materials obtained by the processes of Comparisons 1 - 4 and Examples 1 and 2 were measured. The processes were performed in two ways, i.e. a process with the developing solution freshly prepared, and a process with the developing solution which was allowed to stand for 24 hours after processing therewith the above-mentioned materials of 1 m2 per litre developing solution. The results are shown in Table 1.

TABLE 1 24 Hours after Immediately after processing material preparation of ion of 1m2 per litre developing solution developing solution Process dot * dot * y fog quality y fog quality Comparison 1 15.8 0.04 4.0 3.2 0.04 1.0 Comparison 2 7.7 0.05 3.0 6.0 0.06 2.5 Comparison 3 9.8 0.04 3.0 8.3 0.04 3.0 Comparison 4 10.2 0.04 3.2 9.6 0.04 3.2 Example 1 cont .) [A] 12.8 0.04 3.5 12.3 0.04 3.5 ditto (contg.l B 15.7 0.04 4.0 14.9 0.04 4.0 ditto (contg.) C 10.8 0.04 3.5 9.7 0.04 3.5 ditto (contg.) D 11.9 0.04 3.5 10.6 0.04 3.5 Example 2 (contg.) [A] 15.2 0.04 4.0 14.8 0.04 4.0 ditto (contg.) B 18.6 0.04 4.5 17.4 0.04 4.5 ditto (contg.) g. C 13.1 0.04 4.0 12.8 0.04 4.0 ditto (contg.) D 14.7 0.04 4.0 12.9 0.04 4.0 * The dot quality means an evaluation value of a microscopic quality of an image obtained through a contact screen. The dot image produces usually a part called "shadow dot" and a part called "highlight dot", and dots having various sizes are drawn up regularly in the intermediate part between the two parts. The "dot quality" in Table 1 means an evaluation value of a part called "50% dot", i.e. the concentration at which 50 % is clear and 50 % is developed, and is expressed by a progresive scale. Namely, "5" means to be highly excellent and "1" means to be extremely bad. Generally, the value not less than "3" suffices practical use.

As is evident from the results shown in Table 1, the process of light-sensitive silver halide photographic material containing a tetrazolium compound with the developing solution containing a nitrogen-containing heterocyclic compound of the invention affords superior photographic qualities, particularly a good dot quality, as well as remarkable improvement of oxidation resistance and developing fatigue resistance.

Example 3 A material was prepared in the similar manner as in Example 1 and processed according to the following processes: Pre-bath : 1 min. (30"C) Developing :1 min. (30"C) Fixing : 1 min.

Washing : 1 min.

Drying.

Among the processing baths employed, the pre-bath consisted of the pre-bath 1 mentioned above, and a nitrogen-containing heterocyclic compound of the invention [E] [H dissolved in triethanolamine.

nitrogen-containing heterocyclic compounds] E] above-illustrated compound (19) 150 mg [F] above-illustrated compound (16) 200 mg [G] above-illustrated compound (26) 500 mg [H] above-illustrated compound ( 4) 80 mg The developing solution having the same composition as in Comparison 2, and the fixing solution having the same composition as in Comparison 1 were employed.

Example 4 A material was prepared in the similar manner as in Example 2. In this Example, the pre-bath incorporated with the nitrogen-containing hetrocyclic compound [E]-H] was used, as was the case in Example 3.

The photographic qualities of materials obtained by the processes of Example 3 and 4 were measured, and the results are shown in Table 2.

TABLE 2 Process y fog dot quality Example 3 (contg.) [E] 11.3 0.04 3.5 ditto (contg.) F 14.3 0.04 3.5 ditto (contg.) G 15.0 0.04 4.0 ditto (contg.) [H] 17.6 0.04 4.5 Example 4 (contg.) [E] 12.9 0.04 3.5 ditto (contg [E] 17.6 0.04 4.5 ditto (contg. 4 14.8 0.04 4.0 ditto (contg. Fd 15.1 0.04 4.0 ditto (contg. H 18.1 0.04 4.5 As is evident from the results shown in Table 2, the process of the invention affords preferable photographic qualities, also when the nitrogen-containing heterocyclic compound of the invention is contained in the pre-bath.

Comparison 5 A silver iodobromide-gelatin emulsion comprising silver halide of 98.5 mole % bromide and 1.5 mole % iodide, having an average grain size of 0.55 U was sensitized chemically with sulfur- and gold-sensitizers. The emulsion was coated on a polyethylene terephthalate support in such amounts that these of the silver and the gelatin were 55 mg and 40 mg per 100 cm2, respectively. Further, gelatin was coated on the emulsion in an amount of 15 mg per 100 cm as a protective layer. The above-mentioned material was exposed and processed in the similar manner as in Comparison 1.

Comparison 6 Comparison 5 was repeated, except that sodium bichromate was added, prior to the coating, to the emulsion in an amount of 3 g per mole of silver. The above-mentioned material was exposed in the similar manner as in Comparison 1 and processed according to the following processes: Developing : 1.5 min. (30"C) Fixing : 1 min.

Washing : 1 min.

Drying : 45 sec.

The developing solution having the same composition as the above-mentioned developing solution 3, and the fixing solution having the same composition as in Comparison 1 were employed, respectively.

Comparison 7 A material was prepared in the similar manner as in Comparison 5, except that 2-p-iodophenyl-3-p-nitriphenyl-5-phenyl-2H-tetrazolium chloride was added to the emulsion, instead of sodium bichromate in Comparison 6, in an amount of 6 g per mole of silver.

The material was exposed in the similar manner as in Comparison 1 and processed in the similar manner as in Comparison 6.

Comparison 8 A material was prepared in the similar manner as in Comparison 5, except that a non-diffusible tetrazolium compound synthesized from 2-p-iodophenyl-3-p-nitrophenyl-5phenyl-2H-tetrazolium chloride and sodium diethylhexylsuccinate sulfonate was added to the emulsion, instead of sodium bichromate in Comparison 6, in an amount of 3 g per mole of silver. The material was exposed in the similar manner as in Comparison 1 and processed in the similar manner as in Comparison 6.

Example 5 A material was prepared in the similar manner as in Comparison 7. In this Example, the developing solution was obtained by adding nitrogen-containing heterocyclic compounds [I] - [L], in the amounts given below, to the developing solution 3 used in Comparison 6.

nitrogen-containing heterocyclic compounds] I] above-illustrated compound ( 5) 60 mg [J] above-illustrated compound ( 8) 200 mg [K] above-illustrated compound (17) 300 mg [L] above-illustrated compound (10) 200 mg Example 6 A material was prepared in the similar manner as in Comparison 8. In this Example, the developing solution containing the above-mentioned nitrogen-containing heterocyclic compounds [I] - [L] used in Example 5 was employed.

The photographic qualities of materials obtained by the processes of Comparisons 5 - 8 and Examples 5 and 6 were measured. The processes were performed in two ways, i.e. a process with the developing solution freshly prepared, and a process with the developing solution which was allowed to stand for 24 hours after processing therewith the above-mentioned materials of 1 m2 per litre developing solution. The results are shown in Table 3.

TABLE 3 24 Hours after Immediately after processing material preparation of of 1 m2 per litre developing solution developing solution Process dot dot y fog quality y fog quality Comparison 5 2.0 0.30 1.0 1.1 0.35 1.0 Comparison 6 7.2 0.05 2.5 6.3 0.05 2.0 Comparison 7 8.9 0.04 3.0 8.1 0.04 3.0 Comparison 8 10.5 0.04 3.2 9.5 0.04 3.2 Example 5 (contg.) [I] 16.8 0.04 4.0 15.5 0.04 4.0 ditto (contg.) [J] 15.0 0.04 4.0 14.8 0.04 4.0 ditto (contg.) (K] 12.3 0.04 3.5 11.4 0.04 3.5 ditto (contg.) [L 13.0 0.04 3.5 12.1 0.04 3.5 Example 6 (contg.) [I] 17.2

Among the processing baths employed, the pre-bath consisted of the pre-bath 2 mentioned above and nitrogen-containing heterocyclic comounds of the invention [M] - [0] dissolved in triethanolamine.

nitrogen-containing heterocyclic compounds] M above-illustrated compound (21) 150 mg No above-illustrated compound ( 7) 100 mg a above-illustrated compound (28) 100 mg The developing solution used was the Developing solution 2 mentioned above and the fixing solution used had the same composition as in Comparison 1, respectively.

Example 8 A material was prepared in the similar manner as in Example 6. In this Example, the material was processed in the similar manner as in Example 7 with the pre-bath incorporated with the nitrogen-containing heterocyclic compound of the invention [M] [O], as was the case in Example 7.

The photographic qualities of materials obtained by the processes of Examples 7 and 8 were measured, and the results are shown in Table 4.

TABLE 4 dot Y fog quality Process Example 7 (contg.) [M] 14.7 0.04 3.5 ditto (contg.) N1 16.5 0.04 4.0 ditto (contg.) 0 13.4 0.04 3.5 Example 8 (cony .) [M] 15.0 0.04 4.0 ditto (contg.) N 17.4 0.04 4.5 ditto (contg.) low 13.6 0.04 3.5 As is evident from the results shown in Table 4, the process of the invention affords preferable photographic qualities also when the nitrogen-containing heterocyclic compound of the invention is contained in the pre-bath.

WHAT IS CLAIMED IS: 1. A process for forming a high contrast silver image from an imagewise-exposed light-sensitive silver halide photographic material comprising a support coated with at least one hydrophilic colloidal layer, said hydrophilic colloidal layer, or at least one of said hydrophilic colloidal layers, comprising a silver halide emulsion layer, and said photographic material containing a tetrazolium compound, which process comprises treating said imagewise-exposed material, with a developer and/or a processing solution and then with a developer, both of which developer and/or processing solution contain a heterocyclic compound with a nitrogen-containing ring, and substituted with at least one methyl, hydroxymethyl or nitro group on a ring thereof.

2. A process for forming a high contrast silver image as claimed in Claim 1 wherein the heterocyclic ring of said nitrogen-containing heterocyclic compound is selected from the group consisting of imidazoline-, imidazole-, imidazolone-, imidazolidine-, imidazolidone-, pyrazoline-, pyrazole-, pyrazolone-, pyrazolidine-, pyrazolidone-, oxazoline-, oxazole-, oxazolone-, oxazolidine-, oxazolidone-, thiazoline-, thiazole-, thiazolone-, thiazolidine-, thiazolidone-, selenazoline-. selenazole-, selenazolone-, oxadiazole-, thiadiazol-, triazole-, tetrazole-, pyrazine-, pyrimidine-, pyridazine-, triazine-, oxazine-, thiazine-, tetrazine-, benzimidazole-, indazole-, benzoxazole-, benzothiazole-, benzoselenazole-, naphthoimidazole-, benzotriazole-, naphthoxazole-, naphthothiazole-, and polyazaindene rings.

3. A process for forming a high contrast silver image as claimed in Claim 2 said nitrogen-containing heterocyclic compound is substituted with a nitro group.

4. A process for forming a high contrast silver image as claimed in Claim 2 wherein said nitrogen-containing heterocyclic compound is substituted with a methyl group.

5. A process for forming a high contrast silver image as claimed in Claim 2 wherein said nitrogen-containing heterocyclic compound is 5-methylbenztriazole.

6. A process for forming a high contrast silver image as claimed in Claim 3 wherein said nitrogen-containing heterocyclic compound substituted with a nitro group is selected from the group consisting of 5-nitrobenzimidazole, 5-nitroindazole, 6-nitroindazole and 5 nitrobenzotriazole.

7. A process for forming a high contrast silver image as claimed in Claim 3 wherein said

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. Among the processing baths employed, the pre-bath consisted of the pre-bath 2 mentioned above and nitrogen-containing heterocyclic comounds of the invention [M] - [0] dissolved in triethanolamine. nitrogen-containing heterocyclic compounds] M above-illustrated compound (21) 150 mg No above-illustrated compound ( 7) 100 mg a above-illustrated compound (28) 100 mg The developing solution used was the Developing solution 2 mentioned above and the fixing solution used had the same composition as in Comparison 1, respectively. Example 8 A material was prepared in the similar manner as in Example 6. In this Example, the material was processed in the similar manner as in Example 7 with the pre-bath incorporated with the nitrogen-containing heterocyclic compound of the invention [M] [O], as was the case in Example 7. The photographic qualities of materials obtained by the processes of Examples 7 and 8 were measured, and the results are shown in Table 4. TABLE 4 dot Y fog quality Process Example 7 (contg.) [M] 14.7 0.04 3.5 ditto (contg.) N1 16.5 0.04 4.0 ditto (contg.) 0 13.4 0.04 3.5 Example 8 (cony .) [M] 15.0 0.04 4.0 ditto (contg.) N 17.4 0.04 4.5 ditto (contg.) low 13.6 0.04 3.5 As is evident from the results shown in Table 4, the process of the invention affords preferable photographic qualities also when the nitrogen-containing heterocyclic compound of the invention is contained in the pre-bath. WHAT IS CLAIMED IS:

1. A process for forming a high contrast silver image from an imagewise-exposed light-sensitive silver halide photographic material comprising a support coated with at least one hydrophilic colloidal layer, said hydrophilic colloidal layer, or at least one of said hydrophilic colloidal layers, comprising a silver halide emulsion layer, and said photographic material containing a tetrazolium compound, which process comprises treating said imagewise-exposed material, with a developer and/or a processing solution and then with a developer, both of which developer and/or processing solution contain a heterocyclic compound with a nitrogen-containing ring, and substituted with at least one methyl, hydroxymethyl or nitro group on a ring thereof.

nitrogen-containing heterocyclic compound is 5-nitroindazole.

8. A process for forming a high contrast silver image as claimed in Claim 3 wherein said nitrogen-containing heterocyclic compound is 5-nitrobenzotriazole.

9. A process for forming a high contrast silver image as claimed in Claim 1 wherein the content of the nitrogen-containing heterocyclic compound substituted with a methyl, hydroxymethyl or nitro group, contained in the developing solution and/or the processing solution prior to the developing, is at a range of from 0.5 mg - 2 g per litre.

10. A process for forming a high contrast silver image as claimed in Claim 1 wherein the silver halide contained in the silver halide emulsion layer is of an average grain size of from 0.05 - 0.8 ,u.

11. A process for forming a high contrast silver image as claimed in Claim 1 wherein the tetrazolium compound is a compound represented by the general formulae [I], [II] or [III], or a compound comprising said compound and an anionic surfactant: general formula [I]

general formula [II]

general formula [III]

[in the above formulae, R1, R3, R4, R5, R8, Rg, R10 and R1l each represent groups selected from alkyl, allyl, phenyl, naphthyl and heterocyclic groups which groups optionally being groups capable of forming a metal chelate or complex; R2, R6 and R7 each represent groups selected from allyl, phenyl, naphthyl, heterocyclic, alkyl, hydroxyl, carboxyl or a salt thereof, carboxyalkyl, amino, mercapto and nitro groups and hydrogen atom; D is a arylene group; E is a group selected from alkylene, arylene and aralkylene groups; XE' is an anion; and n is 1 or 2, provided that when the compound forms an intromolecular salt, n is 1.

12. A process for forming a high contrast silver image as claimed in Claim 11 wherein the anion is selected from the group of a higher alkylbenzenesulfonate anion, a higher alkylsulfate ester anion, a dialkylsulfosuccinate anion, a polyetheralcoholsulfate ester anion, a higher fatty acid anion, a polymeric anion or an alkylnaphthalenesulfonate anion, said higher alkyl groups or higher fatty and anions having at least 5 carbon atoms.

13. A process for forming a high contrast silver image as claimed in Claim 11 wherein R1, R2 and R3 individually represent a phenyl group.

14. A process for forming a high contrast silver image as claimed in Claim 11 wherein the tetrazolium compound is a 2,3,5-triphenyl-2H-tetrazolium diisopropylnaphthalenedisulfonate, 2,3,5-triphenyl-2H-tetrazolium di-2-ethylhexylsuccinate disulfonate, or 2-piodophenyl-3-p-nitrophenyl-5-phenyl-2H-tetrazolium diethylhexyl succinate sulfonate.

15. A process for forming a high contrast silver image as claimed in Claim 1 wherein the developing solution contains Metol, hydroquinone or 1-phenyl-3-pyrazolidone as a developing agent.

16. A process for forming a high contrast silver image as claimed in Claim 15 wherein the developing solution contains a sulfite ion in an amount of from 1 x 10-2 to 1 x 10-1 mole per litre.

17. A process for forming a high contrast silver image as claimed in Claim 15 wherein the developing solution has a pH value of from 8.5 to 12.

18. A process as claimed in Claim 1 and substantially as hereinbefore described with reference to any of Examples 1 to 8.