EP0262930A2

EP0262930A2 - Process for forming a colour positive image

Info

Publication number: EP0262930A2
Application number: EP19870308628
Authority: EP
Inventors: Atushi Kamitakahara; Keiji Ogi
Original assignee: Konica Minolta Inc
Current assignee: Konica Minolta Inc
Priority date: 1986-09-29
Filing date: 1987-09-29
Publication date: 1988-04-06
Anticipated expiration: 2007-09-29
Also published as: EP0262930A3; JPS63184739A; CA1317502C; DE3786974D1; EP0262930B1; DE3786974T2

Abstract

Disclosed is an internal latent image type light-sensitive silver halide photographic material capable of forming a color positive image by effecting surface development processing after fogging was carried out, and/or while fogging is carried out, with use of a color developing solution containing 1 g/liter or less of a solvent having a log P of 0.4 or more, having a sulfite ion concentration of 2 × 10⁻² mole or less per liter of the color developing solution and having a bromide ion concentration of 5 × 10⁻³ mole or less per liter of the color developing solution, wherein a silver halide grain contained in at least one layer of photographic constituent layers of the light-sensitive material comprises a core and at least one layer of a shell covering the core, and the shell contains at least silver chloride as its surface composition, and also disclosed is an internal latent image type light-sensitive silver halide photographic material which further comprises containing a heterocyclic mercapto compound.

Description

BACKGROUND OF THE INVENTION

This invention relates to an internal latent image type light-sensitive silver halide photographic material, and, particularly, to an internal latent image type light-sensitive silver halide photographic material that can afford a color positive image stable to the fogging treatment at the time of the color developing treatment or the like.
In these years, it has become possible to take a photograph from an original such as a manuscript or typescript for printing or a reversal film on an internal latent image type light-sensitive silver halide photographic material by utilizing a copying apparatus, followed by fogging in a color developing solution and thereafter developing, to obtain a positive image directly on a sheet of color photographic paper or on a color film. For this reason, there has become available such a copying apparatus installed in photograph shops, copy shops and so forth.
However, in order to obtain a stable image with good quality by the developing in the above photographic system, it is required for the processing performances of processing solutions to be always kept in a constant state. Accordingly, since the respective processing solutions are consumed and deteriorated when a large quantity of light-sensitive materials are processed for color development and so forth, it is necessary to make ready for replenishing solutions for appropriately replenishing the respective processing solutions to cover a shortage, or recover the deteriorated activity of processing solutions by use of replenishing solutions to maintain the initial activity, thus carrying out stable processing. Particularly when the deteriorated processing solutions are replenished, it follows as a matter of course that the processing solutions are overflowed and collected as waste liquor. The waste liquor thus collected may sometimes contain harmful components or components undesirable for preventing environmental pollution, and therefore it is necessary to beforehand make them harmless before the waste liquor is thrown away. Thus, it requires much cost and labor to make harmless the harmful components in the processing solutions. In particular, an organic solvent having a log P of 0.4 or more, such as benzyl alcohol acting as a color development accelerator has so high values for BOD and COD that such a solvent is desired to be used in an amount as small as possible or not to be used at all.
However, if the color developing is carried out by using the organic solvent such as benzyl alcohol in an amount as small as possible or without using it, there can be a problem that the oxidized product of a color developing agent produced by the color development reaction may preferentially react with sulfite ions used as an anti-oxidant of the color developing agent in the developing solution, rather than undergo the coupling reaction to react with a coupler in a light-sensitive material, thereby causing a lowering of the image density.
As a means for solving this problem, it is effective to lower the concentration of the sulfite ions to enhance the above coupling reaction. If, however, the processing is carried out with use of a color developing solution having a lowered sulfite ion concentration, there can be a problem that the image may suffer great variation depending on the variation of processing conditions. For example, in the light-sensitive material containing an internal latent image type silver halide grains comprising a silver bromide shell as described in U.S. Patent No. 3,206,313, there can be a problem that a positive image may readily vary depending on the variation factors at the time of fogging.
Namely, this variation, when fogged by light, may occur because the illuminance of light may be decreased owing to the deterioration of a light source, or the exposure amount at a light-sensitive face may be decreased owing to the filter action caused by coloring due to oxidation of the color developing solution. When fogged by a fogging agent, there may occur a lowering of the concentration of the fogging agent because of the air oxidation or the like. In particular, it may sometimes occur that the maximum density of the image to be obtained is extremely lowered because of the above variation, to raise another problem.
Now, as a technique for restraining the lowering of the image density, reported is to apply chemical ripening to a certain degree on the surface of a silver halide grain (see U.S. Patent No. 3,761,276). This, however, can not necessarily be satisfactory.

SUMMARY OF THE INVENTION

An object of this invention is provide an internal latent image type light-sensitive silver halide photographic material that can afford a positive image in a stable state, and a second object thereof is to provide a internal latent image type light-sensitive silver halide photographic material that can be processed by a processing solution having less environmental load of waste liquor.
In this invention, the above objects can be achieved by an internal latent image type light-sensitive silver halide photographic material capable of forming a color positive image by effecting surface development processing after fogging was carried out, and/or while fogging is carried out, with use of a color developing solution containing 1 g/lit or less of a solvent having a log P of 0.4 or more, and having a low sulfite ion concentration, wherein a silver halide grain contained in at least one layer of photographic constituent layers of said light-sensitive material comprises a core and at least one layer of a shell covering said core, and said shell contains at least silver chloride as its surface composition.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

In the light-sensitive material of this invention, the silver halide grain contained in at least one photographic constituent layer thereof comprises a core and at least one layer of a shell covering said core, and said shell contains at least silver chloride as its surface composition. Accordingly, there can be used silver halides having any halogen composition as the surface compostion so long as the silver chloride is substantially contained as the surface composition of the shell. For example, they may include silver chloride, silver chlorobromide, silver chloroiodobromide and silver chloroiodide.
The shell layer of the above silver halide grain in this invention may entirely cover the surface of the silver halide grain, or may selectively cover part of the surface. In this invention, the shell surface layer containing silver chloride may preferably occupies 10 % or more of the grain surface.
The shell in the above silver halide grain may comprise a single layer having a compositionally single silver halide, or may be a composite shell comprising two or more layers. In the preferred embodiment, an amount of the silver chloride in the silver halide grain is 50 mole % or more.
In the case the composite layer shell is used, this comprises at least an outermost layer and a layer contiguous thereto, but may have the structure such that layers having different silver halide composition from each other are laminated.
The shell layer of said composite layer may also have the structure such that the silver halide composition continuously changes in the diametrical direction of the silver halide grain.
In the case the above composite layer shell is used, the whole of the grain or the inside thereof may have any silver halide composition so long as the silver chloride is contained in the outermost layer, or at least the surface thereof, of the composite layer shell, or the surface portion of the shell corresponding to the layer contiguous to the outermost layer. There may be included, for example, silver iodobromide, silver bromide, silver chlorobromide, silver chloroiodide, silver chloroiodobromide, etc. It is preferred that an amount of the silver chloride in the surface composition of the shell layer is 50 mole % or more.
The shell may preferably cover 50 % or more of the surface area of the core, and may particularly preferably cover the core entirely.
The core may preferably chiefly comprise silver bromide, or may further contain silver chloride and/or silver iodobromide. The shape of the silver halide grain which forms the core may be of any shape, for example, a cube, a regular octahedron, a dodecahedron, a tetradecahedron, or a mixed form of these; or a sphere, a flat plate, a free-shaped grain, or an appropriately mixed form of these. In practicing this invention, the average grain size and grain size distribution of the silver halide grain constituting the core can be varied in a wide range depending on the photographic performances desired, but the grain size distribution of a narrower width is more preferred. In other words, the silver halide grain constituting the core may preferably be substantially monodisperse.
Here, the "core is comprised of a monodisperse silver halide grain" means that in the silver halide grain constituting the core, the weight of silver halide grains included in a grain size range of ± 20 % with an average grain size
as the central value comprises 60 % or more, preferably 70 % or more, particularly preferably 80 % or more, of the total silver halide weight.
Here, the average grain size
refers to the grain size r_i at which the product of the frequency n_i of the grain having the grain size r_i, and r_i³, i.e., n_i × r_i³, makes a maximum (effective numeral: three figures; smallest figure number is rounded).
The grain size herein mentioned refers to the diameter in the case of a spherical silver halide grain, and, in the case of the grains other than the spherical grain, it refers to the diameter assumed by calculating its projected image into a round image having the same area.
The grain size can be determined, for example, by projecting the grain with enlargement to 10,000 to 50,000 magnification with use of an electron microscope, and actually measure on a print obtained the grain diameter or area at the time of projection (assuming that the number of grains to be measured is 1,000 or more indiscriminately).
As methods for producing the above monodisperse core emulsion, there can be used, for example, the double jet method as disclosed in Japanese Patent Publication No. 36890/1973, Japanese Unexamined Patent Publications No. 48520/1979 and No. 65521/1979, etc. In addition, there can be also used the pre-mixing method as disclosed in Japanese Unexamined Patent Publication No. 158220/1979.
In the working of this invention, the core of the silver halide grain may be subjected to chemical sensitization or doped with a metallic ion, or both of these may be applied or none of both of these may be applied at all.
As the chemical sensitization, there can be employed any of sensitizing methods according to sulfur sensitization, gold sensitization, reduction sensitization, noble metal sensitization and a combination of any of these sensitizing methods. Thiosulfate, thioureas, thiazoles, rhodanines and other compounds can be used as a sulfur sensitizer. Such methods are described, for example, in U.S. Patents No. 1,574,944, No. 1,623,499, No. 2,410,689, No. 3,656,955, etc.
The core of the silver halide grain used in the working of this invention can be also sensitized by a water soluble gold compound as described, for example, in U.S. Patent No. 2,399,083, No. 2,597,856, No. 2,642,361, etc., or can be also sensitized with use of a reduction sensitizer. Reference to such methods can be made in the disclosures, for example, in U.S. Patents No. 2,487,850, No. 2,518,698, No. 2,983,610, etc.
Still also, noble metal sensitization can be carried out with use of noble metal compounds such as platinum, iridium, palladium, etc. Reference to such a method can be made in the disclosures, for example, in U.S. Patent No. 2,488,060 and British Patent No. 618,061.
The core of the silver halide grain can be also doped with a metallic ion. To dope the core with the metallic ion, for example, the latter may be added in the form of a water soluble salt of the metallic ion at any time in the course of the formation of core grains. Preferable examples for the metallic ion includes metallic ions such as lead, antimony, bismuth, gold, osmium and rhodium. These metallic ions may be used in concentration of 1 × 10⁻³ to 1 × 10⁻⁴ mol per mol of silver.
However, cores used as the core of the silver halide grain may not be subjected to the above chemical sensitization or doping with metallic ions. In such a case, a sensitivity center is considered to be produced by, e.g., the formation of crystal distortion at the interface between the core and shell in the course the core particle is covered with the shell. Reference to this can be made in the disclosures in U.S. Patents No. 3,935,014 and No. 3,957,488.
In the above method for forming the shell on the core, the double jet method or the pre-mixing method can be used. Alternatively, the shell can be also formed by mixing finely particulate silver halide into a core emulsion, followed by Ostwald ripening.
As mentioned above, the silver halide grain is formed into a core/shell type, and also the surface composition is controlled to contain silver chloride, so that the fogging can be effectively carried out to increase the maximum density of the resulting image and obtain a good and stable image.
Further, an amount of the silver chloride in the silver halide grain is not particularly limited and may be often used silver halide grains containing a larger amount of silver chloride depending upon the demand of shortage in processing time. In the preferred embodiment, the amount of the silver chloride is at least 50 mole %, more preferably 80 mole % or more based on the total amount of the silver halide. In the other preferred embodiment, if a light-sensitive material containing silver halide having much amount of silver chloride is combinedly used with a heterocyclic compound having a mercapto group, more excellent positive image can be obtained.
As the heterocyclic compound having a mercapto group, the following compound represented by the formula (I) is preferred.
wherein M represents a hydrogen atom, an alkali metal atom, an ammonium group or a protective group for a mercapto group; Z represents a group of non-metallic atoms necessary for forming a heterocyclic group, said heterocyclic group may have one or more substituents or may be fused.
As the protective group for the mercapto group represented by M is a group forming a mercapto group by clea vage in the presence of an alkali, and more specifically, may include an acyl group, an alkoxycarbonyl group, an alkylsulfonyl group, etc.
As the heterocyclic group represented by
it may have atoms as constituting rings such as a carbon atom, a nitrogen atom, an oxygen atom, a sulfur atom, a selenium atom, etc., and may be preferred a 5- to 6-membered ring.
Specific examples of the heterocyclic ring may include imidazole, benzoimidazole, naphthoimidazole, thiazole, thiazoline, benzothiazole, naphthothiazole, oxazole, benzoxazole, naphthoxazole, selenazole, benzoselenazole, naphthoselenazole, triazole, benzotriazole, tetrazole, oxadiazole, thiadiazole, pyridine, pyrimidine, triazine, purine, azaindene, etc.
As the substituent which may have been bonded to such heterocyclic groups, there may be mentioned, for example, a halogen atom, hydroxy, amino, nitro, mercapto, carboxy and its salt, sulfo and its salts, alkyl, alkoxy, aryl, aryloxy, alkylthio, arylthio, acylamino, sulfonamide, carbamoyl, sulfamoyl, etc.
Of these compounds represented by the formula (I), particularly preferably employable compound can be shown by the following formulae (II), (III) and (IV):
In the formulae (II) to (IV), M has the same meaning as in M of the formula (I).
In the formula (II), Ar represents a phenyl group, a naphthyl group or a cycloalkyl group; and R¹ represents a hydrogen atom or a substituent of Ar.
In the formula (III), Z¹ represents an oxygen atom, a sulfur atom, a selenium atom or a group -NH-; R² represents a hydrogen atom or a substituent.
In the formula (IV), Z² represents an oxygen atom, a sulfur atom, a selenium atom or a group
where R⁴ represents a hydrogen atom, an alkyl group, an alkenyl group, a cycloalkyl group, an aryl group, an aralkyl group, -COR⁵, -SO₂R⁵, -NHCOR⁶ or -NHSO₂R⁶; R⁵ represents an alkyl group, an aryl group or amino group; R⁶ represents an alkyl group, a cycloalkyl group, an aryl gropu or an aralkyl group); R³ represents a hydrogen atom, an alkyl group, an alkenyl group, a cycloalkyl group, an aryl group, an aralkyl group, a heterocyclic group or an amino group.
In the following, representative examples of the compounds represented by the formula (I) to be used in the present invention (hereinafter referred to as the compound of the present invention) are shown but the present invention is not limited by these.
The above compounds can be easily synthesized by the already known method. For example, they can be obtained in accordance with the method disclosed in U.S. Patent No. 2,403,927 and No. 3,376,310, Japanese Unexamined Patent Publication No. 59463/1980, or Journal of the Chemical Society, p. 4237 (1977), etc. Also, a part of the compounds can be obtained as commercial products.
The above compounds can be added in the light-sensitive material elements by dissolving in water or an organic solvent having miscibility with water such as methanol, acetone, etc. or by dissolving in a weak alkali or a weak acid. An amount thereof may vary depending upon a kind of the compounds to be used or a layer to be added, and when it is added to a silver halide emulsion layer, the amount is in the range of 10⁻⁶ to 10⁻³ mole, more preferably 10⁻⁵ to 10⁻³ mole per mole of silver halide.
The compound of the present invention may be added, in addition to the silver halide emulsion layer of the light-sensitive material, to any layers of the constituent layers provided in the conventional light-sensitive material such as a protective layer, an intermediate layer, a filter layer, a halation preventive layer, a subbing layer, etc., but the silver halide emulsion layer is particularly preferred.
The internal latent image type silver halide emulsion used in this invention will be described below.
The internal latent image type silver halide emulsion used in this invention can be used by overlapping emulsions having different sensitivities as emulsion layers or mixing them in order to widen its exposure latitude. In this instance, the proportion of the coated silver amount in the respective emulsion layers can be arbitrarily determined depending on the photographic performances required.
In the present invention, an internal latent image type silver halide grain that has not preliminarily been fogged can be used as the internal latent image type silver halide grain. In this instance, what is meant by the grain surface having not preliminarily been fogged is that the density is not more than 0.6, preferably not more than 0.4, obtained when a test piece produced by coating the emulsion to be used on a transparent film support so as to have 35 mgAg/cm² is, without exposure to light, developed for 10 minutes at 20°C with use of surface developing solution A shown below.
Surface developing solution A:
Metol 2.5 g
ℓ-Ascorbic acid 10 g
NaBO₂·4H₂O 35 g
KBr 1 g
Made up to 1 liter by adding water.
As the silver halide emulsion used in the silver halide emulsion layer for the formation of the color positive image in the light-sensitive material of this invention, there can be preferably used an emulsion that can give sufficient density when the test piece of the light-sensitive material of this invention, containing the internal latent image type silver halide grain that has not preliminarily been fogged and has been prepared in the above manner, is exposed to light followed by developing with use of internal developing solution B having the formulation shown below.
Internal developing solution B:
Metol 2 g
Sodium sulfite (anhydrous) 90 g
Hydroquinone 8 g
Sodium carbonate (monohydrate) 52.5 g
KBr 5 g
KI 0.5 g
Made up to 1 liter by adding water.
To describe more specifically, it is an emulsion that can show, when a part of the above test piece is exposed to light through a luminous intensity scale over a certain given period not longer than 1 second followed by developing for 10 minutes at 20°C with use of Internal development solution B, the density of at least 5 times, preferably at least 10 times, greater than that obtained when another part of the test piece exposed to light under the same conditions is developed for 10 minutes at 20°C with use of Surface developing solution A.
The silver halide emulsion usable in working this invention can be chemically sensitized by use of a sensitizing dye usually used. It is useful also for the silver halide emulsion used in working this invention to use in combination a sensitizing dye used in the supersensitization of internal latent image type silver halide emulsions, negative silver halide emulsions, etc. Reference to the sensitizing dye can be made in Research Disclo sures No. 15162 and No. 17643.
To obtain a direct positive image with use of the light-sensitive material according to this invention, the positive image can be readily obtained by carrying out image exposure (or photographing) followed by surface developing. Specifically, the principal steps for producing the positive image comprise subjecting to image exposure a light-sensitive photographic material having an internal latent image type silver halide emulsion layer that has not preliminarily been fogged, used in this invention, and thereafter carrying out surface developing after the processing for producing a fog nucleus by chemical action or optical action, namely the fogging, is carried out and/or in the course the fogging is carried out. Here, the fogging can be carried out by applying whole surface exposure or by using a compound capable of producing a fog nucleus, i.e., a fogging agent.
The whole surface exposure carried out in respect of the light-sensitive photographic material of this invention is carried out by dipping in, or wetting by, a developing solution or other aqueous solution a light-sensitive material subjected to image exposure, followed by wholly and uniformly exposing it to light. As a light source used here may be any light that is in the wavelength region in which the above light-sensitive photographic material can be sensitive to light. Alternatively, a highly luminous light such as flash light can also be irradiated, or a weak light may be irradiated for a long time. The time for the whole surface exposure can be varied in a wide range so as to finally obtain an optimum positive image, depending on the above light-sensitive photographic material, developing condition, and type of the light source to be used. As for the amount of exposure in the whole surface exposure, most preferred is to apply an exposure amount of a certain given range in the combination thereof with the light-sensitive material. Usually, an excessive exposure amount may cause increase in minimum density or desensitization to lower the image quality. However, employment of the light-sensitive material of this invention makes it possible to lessen the degree of image deterioration and obtain a stable image.
A fogging agent that can be used in the processing in which the light-sensitive photographic material of this invention is chemically fogged will be described below. As the fogging agent used in working this invention, there can be used compounds of the types covering a wide range. This fogging agent may be present at the time the developing is carried out, and thus, for example, it may be contained in a constituent layer, other than a support, of the light-sensitive photographic material (in particular, preferably in a silver halide emulsion layer), or in the developing solution or a processing solution precedent to the developing. It can be also used in an amount varying in a wide range depending on the purpose, and, when used by adding it in the silver halide emulsion layer, in an amount of 1 to 1,500 mg, preferably 10 to 1,000 mg, per mol of silver halide. Also, when used by adding it in the processing solution such as the developing solution, it can be added preferably in an amount of 0.01 to 5 g/liter, particularly preferably 0.05 to 1 g/liter.
The fogging agent used in this invention may include, for example, the hydrazines described in U.S. Patents No. 2,563,785 and No. 2,588,982 or the hydrozide or hydrazine compounds described in U.S. Patent No. 3,227,522; the heterocyclic quaternary nitrogen chloride compounds described in U.S. Patents No. 3,615,615, No. 3,718,479, No. 3,719,494, No. 3,734,738 and No. 3,759,901; and also a compounds having a group adsorptive to the surface of silver halide, such as the acylhydrazinophenylthioureas described in U.S. Patent No. 4,030,925. These fogging agents can also be used in combination. For example, Research Disclosure No. 15162 discloses a combined use of a non-adsorptive fogging agent with an adsorptive fogging agent. This technique for the combined use may be effective also in this invention. The fogging agent used in this invention may be any of the adsorptive type or non-adsorptive type, which also may be used in combination.
The developing agent that can be used in the surface developing solution used in the developing of the light-sensitive photographic material of this invention may include usual silver halide developing agents, for example, polyhydroxybenzenes such as hydroquinone, aminophenols, 3-pyrazolidones, ascorbic acid and derivatives thereof, reductones and phenylenediamines, or a mixture of these. Specifically, it may include hydroquinone, aminophenol, N-methylaminophenol, 1-phenyl-3-pyrazolidone, 1-phenyl-4,4-dimethyl-3-pyrazolidone, 1-phenyl-4-methyl-4-hydroxymethyl-3-pyrazolidone, ascorbic acid, N,N-diethyl-p-phenylenediamine, diethylamino-o-toluidine, 4-amino-3-methyl-N-ethyl-N-(β-methanesulfonamidoethyl)anil ine, 4-amino-3-methyl-N-ethyl-N-(β-hydroxyethyl)aniline, etc. These developing agents may also be previously contained in an emulsion so that it can be acted on silver halide in the course the light-sensitive photographic material is dipped in an aqueous solution having a high pH.
The developing solution used in this invention may further contain a particular antifoggant and a developing restrainer. It is also possible to incorporate these additives for the developing solution in a constituent layer of the light-sensitive photographic material in an arbitrary fashion.
In the case the light-sensitive photographic material of this invention is actually used for full color photography, at least one of each of a red-sensitive silver halide emulsion layer, a green-sensitive silver halide emulsion layer and a blue-sensitive silver halide emulsion layer is coated on a support as a photographic constituent layer. Here, at least one layer of the light-sensitive silver halide emulsion layers contains the core/shell type grain comprising a core and a shell covering said core, and also contain silver chloride as the surface composition of the shell. Of course, all of the light-sensitive silver halide emulsion layers may preferably contain the internal latent image type silver halide grain according to this invention. Also, each of the light-sensitive silver halide emulsion layers may be a same light-sensitive layer or may be separated into two or more layers each having different sensitivity. In such an instance, at least one of the same light-sensitive layers each having different sensitivity may contain the internal latent image type silver halide grain according to this invention, but all of the emulsion layers may preferably contain the internal latent image type silver halide grain of this invention.
The color developing solution used in the light-sensitive material of this invention will be described. The color developing solution contains 1 g/lit or less of a solvent having a log P of 0.4 or more and having a low sulfite ion concentration.
The above log P refers to a value determined from partition coefficient P of n-octanol/water. Value P can be determined from the formula shown below.
A logarithm of the value P thus determined refers to the value log P, which value has been hitherto widely used in the fields of agricultural chemicals and pharmaceuticals as a measure for oil solubility. The value log P can be known also from log P_oct in the table disclosed in Chemical Review, Vol. 71, No. 6, pp. 555-613, 1971. It also can be theoretically determined according to the calculation method disclosed in Ecological Chemistry, Vol. 6, pp. 3-11, but a found value may more preferably be used, and a value observed by using n-octanol may particularly more preferably be used.
The solvent having a log P of 0.4 or more, that is not desired to be added in the developing solution used in the light-sensitive material of this invention, includes aliphatic alcohols, aliphatic glycol ethers, alicyclic alcohols or aromatic alcohols, and, among these, particularly those having 5 to 20 carbon atoms.
Specific examples thereof may include;
Benzyl alcohol log P 1.0
o-Hydroxybenzyl alcohol log P 0.73
Cyclohexanol log P 1.23
2-Benzyloxyethanol log P 0.41
Anisyl alcohol log P 0.70
1-Pentanol log P 0.4 or more
Phenylethyl alcohol log P 1.36
p-Tolylcarbinol log P 1.36
Phenol log P 0.4 or more
p-Hydroxybenzyl alcohol log P 0.4 or more
Benzylamine log P 0.4 or more
Diethylene glycol monobutyl ether log P 0.41.
The above solvents are, as mentioned above, compounds that may accelerate the coupling reaction of an oxidized product of a color developing agent with a coupler in the light-sensitive material, and the content thereof is controlled to 1 g/lit or less. By controlling it to such a low concentration, BOD or COD values can be suppressed to low values even when the above color developing solution having been deteriorated is thrown away, and there can be provided an effective countermeasure for environmental pollution. Moreover, by controlling the concentration of the sulfite ions serving as a preservative to a lower concentration, it is intended to restrain the reaction with the above solvent to enhance the coupling reaction in the color development processing. What is meant by "having a low sulfite ion concentration" in this invention is that the sulfite ions is in such a concentration that they can serve as a preservative and at the same time can suppress the reaction with the above solvent having a log P of 0.4 or more, so as not to inhibit the coupling reaction in the color developing solution. Thus, the concentration may preferably be 2.0 × 10⁻² mole or less, more preferably about 1.0 × 10⁻² mole, per liter of the color developing solution.
Since the coupling reaction can be effectively carried out by controlling the sulfite ion concentration to a lower concentration as mentioned above, it is possible to make higher the maximum density of the color image colordeveloped by the above color developing solution, and to obtain a good image.
In addition, conjointly with the employment of the core/shell grain containing silver chloride in the surface composition of the internal latent image type silver halide grain, it is possible to obtain a light-sensitive material that can be stable in the processing and can have a good image quality.
This invention will be described below specifically by giving Examples. However, as a matter of course, the embodiments of this invention are by no means limited to Examples shown below.

Example 1

An aqueous solution of silver nitrate and an aqueous solution of potassium bromide in equimolar amounts were simultaneously added over a period of about 40 minutes at 50°C according to the controlled double jet method, to obtain a tetradecahedral silver bromide emulsion having an average grain size of 0.4 µm. However, 5 minutes after the addition of the aqueous solution of silver nitrate and the aqueous solution of potassium bromide was started, potassium hexachloroiridate was added in an amount of 0.02 mg per mol of silver. To the emulsion thus obtained, sodium thiosulfate was added in an amount of 2.0 mg per mol of silver, followed by chemical sensitization for 60 minutes at 60°C to obtain emulsion A.
Using this emulsion A for the formation of core grains, core/shell emulsions B to E shown below were obtained.

Emulsion B:

Using emulsion A for the formation of core grains, an aqueous solution of silver nitrate and an aqueous solution of potassium bromide were further simultaneously added to obtain a tetradecahedral core/shell emulsion having an average grain size of 0.6 µm.

Emulsion C:

Using emulsion A for the formation of core grains, an aqueous solution of silver nitrate and an aqueous solution of potassium bromide were further simultaneously added to be grown up to grains of 0.5 µm, and successively an aqueous solution of silver nitrate and an aqueous solution of sodium chloride were further simultaneously added to obtain a cubic core/shell emulsion having an average grain size of 0.6 µm.

Emulsion D:

Core/shell emulsion D was obtained in substantially the same manner as for the above emulsion C. This emulsion D, however, was prepared by adding an aqueous solution containing potassium bromide and sodium chloride (KBr : NaCl = 1 : 3 in molar ratio) in place of the aqueous solution of sodium chloride.

Emulsion E:

Core/shell emulsion E was obtained in substantially the same manner as for the above emulsion C. This emulsion E, however, was prepared by adding an aqueous solution containing potassium bromide and sodium chloride (KBr : NaCl = 1 : 1 in molar ratio) in place of the aqueous solution of sodium chloride.

Emulsion F:

Core/shell emulsion F was obtained in substantially the same manner as for the above emulsion C. This emulsion F, however, was prepared by adding an aqueous solution containing potassium bromide and sodium chloride (KBr : NaCl = 3 : 1 in molar ratio) in place of sodium chloride.
To each of emulsions B to F obtained in the above, added was a dispersion obtained by dissolving a sensitizing dye sodium 5,5′-diphenyl-9-ethyl-3,3′-disulfopropyloxycarbocyanate and a magenta coupler 1-(2,4,6-trichlorophenyl)-3-(2-chloro-5-octadecylsuccinimidoanilino)-5-pyrazolone in a solvent, followed by emulsification dispersion in an aqueous gelatin solution, to which a hardening agent was further added. The resulting emulsion was coated on a resin-coated paper support to have a coated silver amount of 4 mg/100 cm², followed by drying to obtain samples No. 1 to No. 5.
Each of these samples was subjected to wedge exposure through a yellow filter, followed by developing for 3 minutes at 38°C with use of the developing solution formulated as follows.
4-Amino-3-methyl-N-ethyl-N-(β-methanesulfonamidoethyl)aniline sulfate 5 g
Sodium sulfite (anhydrous) 1 × 10⁻² M/lit
Sodium carbonate (monohydrate) 15 g
Potassium bromide 0.6 g
Made up to 1 liter by adding water
(Adjusted to pH 10.2 with use of potassium hydroxide.)
For 20 seconds after 20 seconds from the starting of the developing, however, the whole surface was uniformly exposed to light by use of white light and with the exposure amount as shown in Table 1 below, followed by bleach-fixing and washing according to a conventional manner, and drying. Thereafter, samples No. 1 to No. 5 were developed under the same conditions as those described above except that the concentration of sodium sulfite in the color developing solution was controlled to 0.03 M/lit.
As will be clear from the results shown in Table 1, it is understood that silver chloride may be contained in the surface composition of the outermost layer of the core/shell grain according to this invention, so that the maximum density can be remarkably improved and there can be obtained a good positive image stable also to the change in the fogging exposure amount.
It is also understood that the maximum density of the resulting image is abruptly lowered when the sulfite ion concentration in the color developing solution is made to vary from 1 × 10⁻² which is the low concentration as mentioned in this invention to 3 × 10⁻² which is not the low concentration.
It is therefore understood that in the light-sensitive material of this invention, an image having a high maximum density can be obtained when the sulfite ion concentration is controlled to the range of the low concentration.

Example 2

An aqueous solution of silver nitrate and an aqueous solution of potassium bromide in equimolar amounts were simultaneously added at 50°C and mixed to obtain a tetradecahedral silver bromide emulsion G having an average grain size of 0.4 µm.
Using this emulsion G for the formation of core grains, there were obtained core/shell emulsions H to L as shown below.

Emulsion H:

Using emulsion G for the formation of core grains, an aqueous solution of silver nitrate and an aqueous solution of potassium bromide were further simultaneously added to obtain a tetradecahedral core/shell emulsion having an average grain size of 0.6 µm.

Emulsion I:

Using emulsion G for the formation of core grains, an aqueous solution of silver nitrate and an aqueous solution of sodium chloride were simultaneously added to obtain a cubic core/shell emulsion having an average grain size of 0.6 µm.

Emulsion J:

Core/shell emulsion J was obtained in substantially the same manner as for the above emulsion I. This emulsion J, however, was prepared by adding an aqueous solution containing potassium bromide and sodium chloride (KBr : NaCl = 1 : 4 in molar ratio) in place of the aqueous solution of sodium chloride.

Emulsion K:

Core/shell emulsion K was obtained in substantially the same manner as for the above emulsion I. This emul sion K, however, was prepared by adding an aqueous solution containing potassium bromide and sodium chloride (KBr : NaCl = 1 : 1 in molar ratio) in place of the aqueous solution of sodium chloride.

Emulsion L:

Core/shell emulsion L was obtained in substantially the same manner as for the above emulsion I. This emulsion L, however, was prepared by adding an aqueous solution containing potassium bromide and sodium chloride (KBr : NaCl = 4 : 1 in molar ratio) in place of sodium chloride.
To each of the above emulsions H to L, the sensitizing dye represented by the formula shown below was added.
Also prepared was an emulsified solution obtained by dispersing 2,4-dichloro-3-methyl-6-[α-(2,4-di-tert-amylphenoxy)butylamido)phenol as a cyan coupler in dibutyl phthalate and ethyl acetate and dispersed in an aqueous gelatin solution.
Next, this emulsified dispersion was added and mixed in each emulsion to which the above sensitizing dye was added, to which a hardening agent was added. The resulting emulsion was coated on a resin-coated paper support to have a coated silver amount of 5.0 mg/100 cm², followed by drying to obtain samples No. 6 to No. 10.
Each of these samples was subjected to wedge exposure through a yellow filter, followed by developing for 3 minutes at 38°C with use of the developing solution formulated as follows.
4-Amino-3-methyl-N-ethyl-N-(β-methanesulfonamidoethyl)aniline sulfate 5.0 g
Sodium sulfite (anhydrous) 6 × 10⁻³ M/lit
Potassium carbonate 20 g
Potassium bromide 0.5 g
Benzyl alcohol 0.6 g
B-Acetyl-phenylhydrozine (fogging agent)
in the amount as shown in Table 2
Made up to 1 liter by adding water
(Adjusted to pH 12.0 with use of potassium hydroxide.)
Subsequently, bleach-fixing and washing was carried out according to a conventional manner, followed by drying. On each sample thus obtained, the maximum density and minimum density of a cyan positive image were measured to obtain the results as shown in Table 2 below.
As will be clear from the results shown in Table 2, it is understood that silver chloride may be contained in the surface composition of the outermost layer of the core/shell grain according to this invention, so that the maximum density can be remarkably improved and a good positive image showing a high maximum density can be stably obtained even with varied concentration of fogging agent.

Example 3

An aqueous solution of silver nitrate and an aqueous solution of potassium bromide in equimolar amounts were simultaneously added at 50°C and mixed to obtain a cubic silver bromide emulsion M having an average grain size of 0.2 µm.
Using this emulsion M for the formation of core grains, an aqueous solution of silver nitrate and an aqueous solution of potassium bromide were further simultaneously added to obtain a cubic core/shell emulsion N having an average grain size of 0.7 µm (silver chloride content: 98 mole %).
To the above emulsion N, an emulsified solution prepared by dissolving α-[4-(1-benzyl-2-phenyl-3,5-dioxo-1,2,4-triazolidinyl)]-α-pyvalyl-2-chloro-5-[δ-(2,4-di-tert-amylphenoxy)butyramido]acetanilide as a yellow coupler in a solvent and dispersing in an aqueous gelatin solution was added. Then, a hardening agent was added to the emulsion to which the above sensitizing dye was added. The resulting emulsion was coated on a resin-coated paper support to have a coated silver amount of 6 mg/100 cm², followed by drying to obtain sample No. 11.
Also, samples No. 12 and No. 13 were prepared in the same manner as in sample No. 11 except for adding a heterocyclic mercapto compound (3) described hereinbefore.
Each of these samples was subjected to wedge exposure, followed by developing for 1 minute at 38°C with use of the developing solution formulated as follows.
4-Amino-3-methyl-N-ethyl-N-(β-methanesulfonamidoethyl)aniline sulfate 5 g
Triethanolamine 8 ml
N,N-Diethylhydroxylamine 4 ml
Sodium sulfite (anhydrous) 0.15 g
Sodium chloride 2 g
Sodium carbonate 15 g
Made up to 1 liter by adding water
(Adjusted to pH 10.2 with use of sodium hydroxide.)
For 5 seconds after 10 seconds from the starting of the developing, however, the whole surface was uniformly exposed to light by use of white light and with the exposure amount as shown in Table 3 below, followed by bleach-fixing and washing according to a conventional manner, and drying.
As will be clear from the results shown in Table 3, it is understood that by processing the light-sensitive material containing the emulsion N of the core/shell grain according to the present invention with the above color developing solution containing no benzyl alcohol and having low sulfite ion concentration, a good positive image can be stably obtained even with varied concentration of fogging agent (sample No. 11). Also, by using the heterocyclic mercapto compound, a positive image can further be improved since the minimum density is restrained (sample No. 12). However, as disclosed in Japanese Patent Publication No. 12709/1970 (which corresponds to U.S. Patent No. 3,733,198), when the heterocyclic compound is used with a large amount (sample No. 13), the maximum density is lowered while the effect of the present invention can be obtained.
As described in the above, it is possible according to this invention to afford an internal latent image type light-sensitive silver halide photographic material that can show a higher maximum density of the positive image formed by the color developing, and can be stable also to the variation in the fogging conditions.
It is also possible to obtain an internal latent image type light-sensitive silver halide photographic material that can obtain an image of good quality as mentioned above even when processed by use of processing solutions having a small environmental load such as BOD and COD.

Claims

1. An internal latent image type light-sensitive silver halide photographic material capable of forming a color positive image by effecting surface development processing after fogging was carried out, and/or while fogging is carried out, with use of a color developing solution, characterized in that said color developing solution contains 1 g/liter or less of a solvent having a log P of 0.4 or more and has a sulfite ion concentration of 2 × 10⁻² mole or less per liter of the color developing solution and that a silver halide grain contained in at least one layer of photographic constituent layers of said light-sensitive material comprises a core and at least one layer of a shell covering said core, and said shell contains at least silver chloride as its surface composition.

2. An internal latent image type light-sensitive silver halide photographic material capable of forming a color positive image by effecting surface development processing after fogging was carried out, and/or while fogging is carried out, with use of a color developing solution, characterized in that said color developing solution contains 1 g/liter or less of a solvent having a log P of 0.4 or more and has a sulfite ion concentration of 2 × 10⁻² mole or less per liter of the color developing solution and that a silver halide grain contained in at least one layer of photographic constituent layers of said light-sensitive material comprises a core and at least one layer of a shell covering said core, said shell contains at least silver chloride as its surface composition, and said light-sensitive material contains a heterocyclic mercapto compound.

3. The internal latent image type light-sensitive silver halide photographic material according to Claim 1 or 2, wherein an amount of silver chloride in said shell is at least 50 mole %.

4. The internal latent image type light-sensitive silver halide photographic material according to Claim 1 or 2, wherein said solvent having a log P of 0.4 or more is at least one selected from the group consisting of aliphatic alcohols, aliphatic glycol ethers, alicyclic alcohols and aromatic alcohols.

5. The internal latent image type light-sensitive silver halide photographic material according to Claim 1 or 4, wherein said solvent has 5 to 20 carbon atoms.

6. The internal latent image type light-sensitive silver halide photographic material according to Claim 3 or 5, wherein said solvent is at least one selected from the group consisting of benzyl alcohol, o-hydroxybenzyl alcohol, cyclohexanol, 2-benzyloxyethanol, anisyl alcohol, 1-pentanol, phenylethyl alcohol, p-tolylcarbinol, phenol, p-hydroxybenzyl alcohol, benzylamine and diethylene glycol monobutyl ether.

7. The internal latent image type light-sensitive silver halide photographic material according to Claim 1 or 2, wherein said sulfite ion concentration is 1 × 10⁻² mole or less per liter of the color developing solution.

8. The internal latent image type light-sensitive silver halide photographic material according to Claim 2, wherein said heterocyclic mercapto compound is a compound represented by the formula:

wherein M represents a hydrogen atom, an alkali metal atom, an ammonium group or a protective group for a mercapto group; Z represents a group of non-metallic atoms necessary for forming a heterocyclic group, said heterocyclic group may have one or more substituents or may be fused.

9. The internal latent image type light-sensitive silver halide photographic material according to Claim 8, wherein said heterocyclic mercapto compound is selected from the compounds represented by formula (II), (III), or (IV)

wherein M represents a hydrogen atom, an alkali metal atom, an ammonium group or a protective group for a mercapto group; Ar represents a phenyl group, a naphthyl group or a cycloalkyl group; R¹ represents a hydrogen atom or a substituent of Ar; R² represents a hydrogen atom or a substituent; R³ represents a hydrogen atom, an alkyl group, an alkenyl group, a cycloalkyl group, an aryl group, an aralkyl group, a heterocyclic group or an amino group; Z¹ represents an oxygen atom, a sulfur atom, a selenium atom or a group -NH-; Z² represents an oxygen atom, a sulfur atom, a selenium atom or a group

where R⁴ represents a hydrogen atom, an alkyl group, an alkenyl group, a cycloalkyl group, an aryl group, an aralkyl group, -COR⁵, -SO₂R⁵, -NHCOR⁶ or -NHSO₂R⁶; R⁵ represents an alkyl group, an aryl group or amino group; R⁶ represents an alkyl group, a cycloalkyl group, an aryl group or an aralkyl group.

10. The internal latent image type light-sensitive silver halide photographic material according to Claim 2, wherein an amount of said heterocyclic mercapto compound is 10⁻⁵ or more and less than 10⁻³ mole per mole of Ag.

11. The internal latent image type light-sensitive silver halide photographic material according to Claim 2, wherein a content of said silver chloride in said silver halide grain is 50 mole % or more.

12. The internal latent image type light-sensitive silver halide photographic material according to Claim 2, wherein a concentration of a bromide ion contained in said developing solution is 5 × 10⁻³ mole or less per liter of said developing solution.

13. The internal latent image type light-sensitive silver halide photographic material according to Claim 8, wherein an amount of said heterocyclic mercapto compound is 10⁻⁵ or more and less than 10⁻³ mole per mole of Ag.

14. The internal latent image type light-sensitive silver halide photographic material according to Claim 6, wherein an amount of silver chloride in said shell is at least 50 mole %.

15. The internal latent image type light-sensitive silver halide photographic material according to Claim 6, wherein an amount of said heterocyclic mercapto compound is 10⁻⁵ or more and less than 10⁻³ mole per mole of Ag.

16. The internal latent image type light-sensitive silver halide photographic material according to Claim 13, wherein said solvent is at least one selected from the group consisting of benzyl alcohol, o-hydroxybenzyl alcohol, cyclohexanol, 2-benzyloxyethanol, anisyl alcohol, 1-pentanol, phenylethyl alcohol, p-tolylcarbinol, phenol, p-hydroxybenzyl alcohol, benzylamine and diethylene glycol monobutyl ether.

17. A process for forming a color positive image which comprises subjecting an internal latent image type light-sensitive silver halide photographic material in which a silver halide grain contained in at least one layer of photographic constituent layers of said light-sensitive material comprises a core and at least one layer of a shell covering said core, and said shell contains at least silver chloride as its surface composition, to surface development processing after fogging was carried out and/or while fogging is carried out, with use of a color developing solution containing 1 g/liter or less of a solvent having a log P of 0.4 or more and having a sulfite ion concentration of 2 × 10⁻² mole or less per liter of the color developing solution.