Process for forming direct positive color image

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FIELD OF THE INVENTION

This invention relates to a process for direct positive color image which comprises subjecting direct positive silver halide photosensitive material to color development processing in the presence of a nucleating agent and/or carrying out fogging exposure, after an imagewise exposure to light.

BACKGROUND OF THE INVENTION

There is well known a photographic process which can obtain a direct positive image without the need of reversal processing step or a negative film.

The conventionally known processes which form positive images by the use of direct positive silver halide photosentitive materials, when considering their usefulness in practice, excluding very special ones, may be divided into the following two main types.

In one of these types, use is made of a silver halide emulsion which has been preliminarily fogged, and by destroying the fogged nuclei (latent image) in the exposed area by taking advantage of solarization or Hershel effect one can obtain a direct positive image after the development.

In another type, one can obtain a direct positive image by subjecting a silver halide emulsion of internal latent image type which has not been fogged, to surface development processing after the fogging treatment or during the fogging treatment after the imagewise exposure.

The term "silver halide emulsion of internal latent image type" as used herein means a silver halide emulsion of such a type that photosensitive nuclei are contained mainly in the interior of the silver halide grains, and so latent image is mainly formed in the interior of the grains by exposure.

As compared with the process of the former type, the process of the latter type is in general high in the photographic sensitivity, so that it is adapted for the use requiring a high photographic speed, and this invention relates to the latter type.

In this technical field, hitherto, various techniques have been known, and the chief of them are described in the specifications of 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, 3,796,577, and British Pat. Nos. 1,151,363, 1,150,553, 1,011,062, etc.

In accordance with these prior-known processes there are obtainable photosensitive materials which have comparatively high photographic speed as the direct positive type.

Also, further particulars concerning the mechanism of the formation of a direct positive image are described, for instance, in T. H. James: "The Theory of the Photographic Process" 4th Ed., Chapter 7, pp. 182 to 193, U.S. Pat. No. 3,761,276, etc. According to these descriptions it is believed that by the action of the surface desensitization due to the so-called internal latent image which was formed in the interior of the silver halide by the first exposure through a pattern, only the surfaces of the silver halide grains in the unexposed area are allowed to form selectively fogged nuclei, and then by carrying out the ordinary, so-called surface development processing a photographic image (direct positive image) is formed in the unexposed area.

As the means for forming selectively fogged nuclei as above described, there are known a process, called generally "a light fogging method", in which the second exposure is given all over the surface of the photosensitive layer (for instance, British Pat. No. 1,151,363) and process, called "a chemical fogging method", using a nucleating agent. With regard to the latter method there is a description for instance in Research Disclosure vol. 151, No. 15162 (November, 1976), pp. 76 to 78.

Formation of a direct positive color image may be achieved by subjecting a silver halide photosensitive material of internal latent image type to surface color development processing either after the fogging treatment or during the fogging treatment, and thereafter, by bleaching and fixing (or blix) treatments, followed by ordinary water wash and/or stabilization treatment.

The light fogging method has disadvantages such that the performance of the finished products of the photosensitive material is liable to vary depending on the variations of the exposure, time of development, composition of developing solution, processing temperature, etc. and moreover, the method requires a long time of development, and is difficult to obtain high maximum density.

On the other hand, the chemical fogging method has disadvantages in that since the speed of development is low when the pH of the developing solution is low, the pH should be made high, but as the developing agent is readily deteriorated by aerial oxidation when pH is high, the fogging effect is reduced.

As above-described the conventional fogging methods were both difficult to obtain stabilized and satisfactory direct positive images. As the means for solving such a problem there were proposed compounds which can exhibit nucleating action even at a pH of 12 or less in Japanese Patent Application (OPI) No. 69613/77 (the term "OPI" as used herein means an "Unexamined Published Application"), U.S. Pat. Nos. 3,615,615 and 3,850,638. These nucleating agents however have the defects such that they either act upon the silver halide or decompose themselves during the storage of the photosensitive materials prior to the processing, and eventually the maximum density after the processing is lowered.

In U.S. Pat. No. 3,227,552 it is described that the speed of development at a moderate density can be raised by the use of hydroquinone derivatives. But, even by their use the speed of development was not sufficient, and especially at a pH of 12 or less no sufficient speed could be obtained.

Also, in Japanese Patent Application (OPI) No. 170843/85 it is described that by the addition of mercapto compounds having a carboxylic group or a sulfonic acid group the maximum density can be attained. But, even by the addition of these compounds the maximum density cannot be fully improved. Moreover, the pH of the developing solution is 12.0 indicating insufficient stability of the developing solution.

Japanese Patent Application (OPI) No. 134848/80 described that by treating with a processing solution (pH 12.0) containing a tetraazaindene series compound in the presence of a nucleating agent the minimum density is lowered so as to prevent the formation of the second reversal negative image. But, in this process, the maximum density cannot be high, and the speed of development also cannot be fast.

Further, Japanese Patent Publication No. 12709/70 describes that a triazoline-thion or tetraazoline-thione series compound is added as an antifoggant to the photosensitive material forming a direct positive image by the light fogging method. But, even by these methods high maximum density and fast speed of development could not be attained.

Thus, none of the techniques have hitherto been able to obtain a direct positive color image which has a high maximum density and a low minimum density in a stabilized state by a short time of processing using a developing solution having a low pH (pH 12 or less).

On the other hand, in order to accelerate the speed of development and color development of a color developing solution, there have hitherto been proposed various methods. In these methods, in order that the developing agent may form a dye by coupling with a coupler, it is essential that the color developing agent itself is held in the dispersed oil drops of the coupler, and as the additives for increasing the rate of its penetration and promoting the color development various kinds of additives are known. Especially, benzyl alcohol is best known as an additive having a large effect upon such promotion of color development, and so it has hitherto been used in various color photographic materials, and it is still at present widely in use.

Benzyl alcohol is in some degree soluble in water, but not easily soluble, so that in order to enhance the solubility diethylene glycol, triethylene glycol or alkanolamine is usually added to benzyl alcohol.

However, in the above-described compounds and the benzyl alcohol itself also, the environmental pollution load is large in the disposal of waste water since the BOD or COD value becomes high, and therefore, as tobenzyl alcohol, its reduction or removal has been expected from the standpoint of the waste water disposal in spite of its mertis in the improvement in color development, solubility, etc.

Furthermore, even when in use of solvents such as the above-described diethylene glycol or the like the solubility of benzyl alcohol was not sufficient to such an extent that it caused to take much labor and time for the preparation of the developing solution.

Still further, when benzyl alcohol is brought into the subsequent bath, which may be a bleaching bath or a bleach-fix bath together with the developing solution, and as the result it accumulates therein, a leuco body is formed depending on the kind of cyan dyes, causing a decrease in the color developing density. In addition to the above, as the accumulation of benzyl alcohol further makes insufficient the washing out of the components of the developing solution, especially of color developing solution, it was found that the components thus remaining cause the deterioration of the storage stability of images.

From these viewpoints, the reduction or removal of benzyl alcohol from developing solution is being keenly desired.

In the present color labo industry these problems are not as yet solved on the one hand, and because of the strong request for the shortened delivery time of finished print, the time of processing is under the necessity of being shortened on the other hand.

It is, however, very obvious that if the time of development is shortened using a color developing solution from which benzyl alcohol has been removed the color developing density remarkably lowers, so that the prior art can never fulfil all the requirements simultaneously.

The direct positive color photosensitive material is also liable to be affected by the variation of the pH of color developing agent as compared with the ordinary negative color photosensitive material. Especially when a color developing solution containing no benzyl alcohol is used in the processing, the lowering of the maximum density due to lowering of pH is marked.

It was also found that when the direct positive color photosensitive material is stored under the condition of high temperature and high humidity prior to the development, the maximum density is liable to lower.

Also, the direct positive color photosensitive material produces the second reversal (re-reversal) negative image by high intensity exposure. Especially when a color developing solution containing no benzyl alcohol is used in the processing, such a tendency is more pronounced, and also, when a color developing solution deteriorated by running is used in the processing, a marked lowering occurs.

In addition, the direct positive color photosensitive material shows a defect in that the grains of the color image are liable to become coarse as compared with the photosensitive material using the ordinary emulsion of negative type. Especially such a defect is more pronounced when a color developing solution containing nobenzyl alcohol is used in the processing, when the photosensitive material has been stored for a long period of time, or when a color developing solution has been fatigued by running.

SUMMARY OF THE INVENTION

Thus, the object of this invention is to provide a process for direct formation of positive color image, of which color developing density lowers in a lesser degree even when a short time of processing is carried out using a color developing solution containing no benzyl alcohol, and in particular to provide a color photosensitive material which can achieve an efficient color development even under the above-described conditions, as well as to provide a process for direct formation of positive color image by the use of such a photosensitive material.

Another object of this invention is to provide a process for direct formation of positive color image, of which the maximum density is hardly variable even when the pH of the color developing solution containing no benzyl alcohol varies.

Still another object of this invention is to provide a process for direct formation of positive color image, which is of high image quality such that the grains do not become coarse even when a color developing solution containing no benzyl alcohol is used in the processing, when the photosensitive material which has been stored for a long period of time is used, or when the color developing solution which is fatigued by running is used in the processing.

Further the object of this invention is to provide a process for direct formation of positive color image by the use of a photosensitive material having good storage stability.

It is also the object of this invention to provide a process for direct formation of positive color image, in which the second reversal (re-reversal) negative image is rarely produced when a color developing solution containing no benzyl alcohol is used in running treatment.

DETAILED DESCRIPTION OF THE INVENTION

It was found that the above-described objects of this invention could be effectively achieved by the following process: that is,

"A process for forming direct positive color image comprising imagewise exposing a photosensitive material containing at least one emulsion layer of silver halide of internal latent image type, which has not been preliminarily fogged, and a color image-forming coupler, developing said exposed material using a surface developing solution containing an aromatic primary amine color developing agent, in the presence of a nucleating agent and/or in the condition that fogging exposure in carried out prior to the developing step or during the developing step; bleaching and fixing said developed material, wherein said color coupler is a compound which is in itself substantially nondiffusible, and moreover, capable of forming or releasing a substantially nondiffusible dye upon oxidative coupling with said aromatic primary amine color developing agent, and said development processing is carried out at a pH of 11.5 or less using a developing solution containing substantially no benzyl alcohol in the presence of at least one compound (i.e., nucleation promoter) selected from the group consisting of the compounds represented by the later described general formula I."

Herein the expression "substantially no benzyl alcohol" means that benzyl alcohol is contained in an amount of 2 ml or less, or preferably 0.5 ml or less per liter of the developing solution, or more preferably, it is not contained entirely.

The expression "substantially nondiffusible dye" means that dye is nondiffusible or diffusible in a degree not to effect on photographic performances.

Further, the term "a nucleating agent" means a substance which functions to form a direct positive image when an emulsion of silver halide of internal latent image type which has not been preliminarily fogged, is subjected to surface development processing.

Also, the term "a nucleation promoter" means a substance, which is in itself substantially incapable of functioning as the above-described nucleating agent, but can act as a promoter of the action of a nucleating agent by hightening the maximum density of a positive image and/or by quickening the time of development required for a direct positive image to each a definite density. These nucleation promoters can be used in combination of two or more thereof.

The nucleation promoters useful in this invention are represented by the following general formula (I).

General formula (I-a)

A[(Y.sup.1).sub.n R].sub.m

wherein A represents a group being adsorbed on silver halide.

Examples of compounds having a group A being adsorbed on silver halide include compounds having a mercapto group attached to a heterocyclic ring, heterocyclic compounds capable of forming iminosilver, and hydrocarbons having a mercapto group.

Examples of compounds having a mercapto group attached to a heterocyclic ring include substituted or unsubstituted mercaptoazoles such as a mercaptotetrazole, a mercaptotriazole, a mercaptoimidozole, a mercaptothiadiazole, a mercaptooxadiazole, a mercaptoselenadiazole, a mercaptooxazole, a mercaptothiazole, a mercaptobenzoxazole, a mercaptobenzimidazole, a mercaptobenzthiazole, etc., (e.g., 5-mercaptotetrazoles, 3-mercapto-1,2,4-triazoles, 2-mercaptoimidazoles, 2-mercapto-1,3,4-thiadiazoles, 5-mercapto-1,2,4-thiadiazoles, 2-mercapto-1,3,4-oxadiazoles, 2-mercapto-1,3,4-selenadiazoles, 2-mercaptooxazoles, 2-mercaptothiazoles, 2-mercaptobenzoxazoles, 2-mercaptobenzimidazoles, 2-mercaptobenzthiazoles, etc.), substituted or unsubstituted mercaptopyrimidines (e.g., 2-mercaptopyrimidines, etc.), etc.

Examples of heterocyclic compounds capable of forming iminosilver include respectively substituted or unsubstituted indazoles, benzimidazoles, benzotriazoles, benzoxazoles, benzthiazoles, imidazoles, thiazoles, oxazoles, triazoles, tetrazoles, azaindenes, pyrazoles, indoles, etc.

Substituents substituted on a mercapto group attached to a heterocyclic ring and on a heterocyclic compound capable of forming iminosilver include the same as those substituted on a heterocyclic ring composing a compound represented by the general formula (II).

Examples of hydrocarbons having a mercapto group include alkylmercaptanes, arylmercaptanes, alkenylmercaptanes, aralkylmercaptanes, etc., wherein the alkyl moiety has 1 to 12 carbon atoms, the aryl moiety has 6 to 12 carbon atoms and the alkenyl moiety has 2 to 12 carbon atoms.

Y.sup.1 represents a divalent group consisting of an atom or atomic group selected from the group consisting of nitrogen atom, carbon atom, nitrogen atom, oxygen atom, and sulfur atom. The examples of the divalent connecting group include ##STR1##

R.sub.1, R.sub.2, R.sub.3, R.sub.4, R.sub.5, R.sub.6, R.sub.7, R.sub.8, R.sub.9, and R.sub.10 represent a hydrogen atom, respectively substituted or unsubstituted alkyl groups preferably having 1 to 12 carbon atoms (e.g., methyl, ethyl, propyl, n-butyl, etc.), substituted or unsubstituted aryl groups preferably having 6 to 12 carbon atoms (e.g., phenyl, 2-methyl-phenyl, etc.), substituted or unsubstituted alkenyl groups preferably having 3 to 12 carbon atoms (e.g. propenyl, 1-methylvinyl, etc.), or substituted or unsubstituted aralkyl groups preferably having 7 to 12 carbon atoms (e.g., benzyl, phenetyl, etc.).

R represents a polar substituent group or an organic group containing at least one of a thioether group preferably having 2 to 12 carbon atoms, an amino group preferably having 1 to 12 carbons atoms (including salts thereof), an ammonium group, an ether group preferably having 2 to 12 carbon atoms, and heterocyclic group (including salts thereof). As these organic groups there may be mentioned those which are obtained by combining a group selected from respectively substitued or unsubstituted alkyl group preferably 1 or 12 carbon atoms, alkenyl group preferably 2 or 12 carbon atoms, aralkyl group preferably 7 or 12 carbon atoms, aryl groups having 6 to 12 carbon atoms with the above-described groups, or further combinations of these organic groups. Specific examples of such groups include a dimethylaminoethyl group, an aminoethyl group, a diethylaminoethyl group, a dibutylaminoethyl group, a dimethylaminopropyl hydrochloride, a dimethylaminoethylthioethyl group, a 4-dimethylaminophenyl group, a 4-dimethylaminobenzyl group, a methylthioethyl group, an ethylthiopropyl group, a 4-methylthio-3-cyanophenyl group, a methylthiomethyl group, a trimethylammonioethyl group, a methoxyethyl group, a methoxyethoxyethoxyethyl group, a methoxyethylthioethyl group, a 3,4-dimethoxyphenyl group, a 3-chloro-4-methoxyphenyl group, a morpholinoethyl group, a 1-imidazolylethyl group, a morpholinoethylthioethyl group, a pyrrolidinoethyl group, a piperidinopropyl group, a 2-pyridylmethyl group, 2-(1-imidazolyl)ethylthioethyl group, a pyrazolylethyl group, a triazolylethyl group, a methoxyethoxyethoxyethoxycarbonyl-aminoethyl group, etc.

The polar substituent group preferably includes a hydrogen atom, a halogen atom (e.g., chlorine atom, bromine atom, etc.), a hydroxy group, a nitro group, a cyano group, respectively substituted or unsubstituted sulfonyl groups (e.g., methanesulfonyl, ethanesulfonyl, p-toluenesulfonyl, etc.), carbamoyl groups (e.g., unsubstituted carbamoyl, methylcarbamoyl, etc.), sulfamoyl groups (e.g., unsubstituted sulfamoyl, methylsulfamoyl group, etc.), carbonamido (carboxylic acid amido) groups (e.g., acetamido, benzamido, etc.), sulfonamido groups (e.g., methanesulfonamido, benzenesulfonamido, etc.), acyloxy group (e.g., acetyloxy, benzoyloxy, etc.), ureido groups (e.g., unsubstituted ureido, methylureido, ethylureido, etc.), acyl groups (e.g., acetyl, benzoyl, etc.), thioureido groups (e.g., unsubstituted ureido, methylureido, etc.), sulfonyloxy groups (e.g., methanesulfonyloxy, p-toluenesulfonyloxy, etc.), oxycarbonyl groups (e.g., methoxycarbonyl, phenoxycarbonyl, etc.), oxysulfonyl groups (e.g., methoxysulfonyl, phenoxysulfonyl, ethoxysulfonyl, etc.), oxycarbonylamino groups (e.g., ethoxycarbonylamino, phenoxycarbonylamino, etc.), or a mercapto group.

n represents 0 or 1, and m represents 1 or 2.

Substituents substituted on the alkyl group, the aryl group, the alkenyl group and the aralkyl described above include the same as substituents on a heterocyclic ring composing a compound represented by the general formula (II).

Of the compounds represented by the general formula (I), the following compounds represented by the general formulas (II) and (III) are preferable. ##STR2##

In the general formula (II), Q represents preferably an atomic group required for the formation of a 5- or 6-membered heterocyclic ring containing at least one atom selected from the group consisting of carbon atom, nitrogen atom, oxygen atom, sulfur atom, and selenium atom. This heterocyclic ring may be such a one condensed with a aromatic or heterocyclic ring.

Examples of heterocyclic rings include tetrazoles, triazoles, imidazoles, thiadiazoles, oxadiazoles, selenadiazoles, oxazoles, thiazoles, benzoxazoles, benzthiazoles, benzimidazoles, pyrimidines, etc.

M represents a hydrogen atom, an alkali metal atom (e.g., sodium atom, potassium atom, etc.), an ammonium group, such as an alkylammonium group, an alkaryl ammonium group, an aryl ammonium group, etc., wherein each alkyl group has 0 to 12 carbon atoms and each aryl group has 0 or 6 to 12 carbon atoms, (e.g., trimethylammonium, dimethylbenzalammonium, etc.), and a group which can be replaced by H or an alkali metal atom under an alkaline condition such as an acyl group preferably having 2 to 12 carbon atoms, a sulfonylalkyl group preferably having 3 to 12 carbon atoms, a cyanoalkyl group preferably having 3 to 12 carbon atoms, etc., (e.g., acetyl, cyanoethyl, methane sulfonylethyl, etc.)

These heterocyclic rings may also be substituted by a nitro group, a halogen atom, (e.g., chlorine atom, bromine atom, etc.), a mercapto group, a cyano group, respectively substituted or unsubstituted alkyl groups preferably having 1 to 12 carbon atoms (e.g., methyl, ethyl, propyl, t-butyl, cyanoethyl, etc.), wherein the preferable substituent for the alkyl group includes an acyloxy group, a sulfonyl group, a sulfonyloxy group, a carbamoyl group, an ureido group, a sulfamoyl group, a thioureido group, a carbonamido group, an oxycabonyl group, a sulfonamido group, a cyano group and a halogen atom, aryl groups preferably having 6 to 12 carbon atoms (e.g., phenyl, 4-methanesulfonamidophenyl, 4-methylphenyl, 3,4-dichlorophenyl, naphthyl, etc.), alkenyl group preferably having 2 to 12 carbon atoms (e.g., allyl, etc.), aralkyl groups preferably having 7 to 12 carbon atoms (e.g., benzyl, 4-methylbenzyl, phenetyl, etc.), sulfonyl groups preferably having 0 to 12 carbon atoms (e.g., methanesulfonyl, ethanesulfonyl, p-toluenesulfonyl, etc.), carbamoyl groups preferably having 1 to 12 carbon atoms (e.g., unsubstituted carbamoyl, methylcarbamoyl, phenylcarbamoyl, etc.), sulfamoyl groups preferably having 0 to 12 carbon atoms (e.g., unsubstituted sulfamoyl, methylsulfamoyl, phenylsulfamoyl, etc.), carboxylic acid amido groups preferably having 2 to 12 carbon atoms (e.g., acetamido, benzamido, etc.), sulfonamido groups preferably having 1 to 12 carbon atoms (e.g., methane