Classifications

• • G—PHYSICS
  • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
  • G03C—PHOTOSENSITIVE MATERIALS FOR PHOTOGRAPHIC PURPOSES; PHOTOGRAPHIC PROCESSES, e.g. CINE, X-RAY, COLOUR, STEREO-PHOTOGRAPHIC PROCESSES; AUXILIARY PROCESSES IN PHOTOGRAPHY
  • G03C1/00—Photosensitive materials
  • G03C1/005—Silver halide emulsions; Preparation thereof; Physical treatment thereof; Incorporation of additives therein
  • G03C1/485—Direct positive emulsions
  • G03C1/48538—Direct positive emulsions non-prefogged, i.e. fogged after imagewise exposure
• • G—PHYSICS
  • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
  • G03C—PHOTOSENSITIVE MATERIALS FOR PHOTOGRAPHIC PURPOSES; PHOTOGRAPHIC PROCESSES, e.g. CINE, X-RAY, COLOUR, STEREO-PHOTOGRAPHIC PROCESSES; AUXILIARY PROCESSES IN PHOTOGRAPHY
  • G03C1/00—Photosensitive materials
  • G03C1/005—Silver halide emulsions; Preparation thereof; Physical treatment thereof; Incorporation of additives therein
  • G03C1/035—Silver halide emulsions; Preparation thereof; Physical treatment thereof; Incorporation of additives therein characterised by the crystal form or composition, e.g. mixed grain
• • G—PHYSICS
  • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
  • G03C—PHOTOSENSITIVE MATERIALS FOR PHOTOGRAPHIC PURPOSES; PHOTOGRAPHIC PROCESSES, e.g. CINE, X-RAY, COLOUR, STEREO-PHOTOGRAPHIC PROCESSES; AUXILIARY PROCESSES IN PHOTOGRAPHY
  • G03C7/00—Multicolour photographic processes or agents therefor; Regeneration of such processing agents; Photosensitive materials for multicolour processes
  • G03C7/30—Colour processes using colour-coupling substances; Materials therefor; Preparing or processing such materials
  • G03C7/407—Development processes or agents therefor
  • G03C7/413—Developers

Definitions

• 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.
• 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.
• 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.
• 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.
• the organic solvent such as benzyl alcohol
• 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.
• 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.
• 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.
• 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.
• 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.
• 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.
• 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.
• 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.
• an amount of the silver chloride in the silver halide grain is 50 mole % or more.
• 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.
• 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.
• 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.
• 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.
• the silver halide grain constituting the core may preferably be substantially monodisperse.
• 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.
• 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 i 3, i.e., n i ⁇ r i 3, 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).
• 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.
• 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.
• noble metal sensitization can be carried out with use of noble metal compounds such as platinum, iridium, palladium, etc.
• 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.
• a 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.
• 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.
• cores used as the core of the silver halide grain may not be subjected to the above chemical sensi­tization or doping with metallic ions.
• 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.
• the double jet method or the pre-mixing method can be used.
• the shell can be also formed by mixing finely particulate silver halide into a core emulsion, followed by Ostwald ripening.
• 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.
• 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.
• 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.
• 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.
• the heterocyclic compound having a mercapto group the following compound represented by the formula (I) is preferred.
• 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.
• 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.
• 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.
• 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.
• substituents 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.
• M has the same meaning as in M of the formula (I).
• Ar represents a phenyl group, a naphthyl group or a cycloalkyl group; and R1 represents a hydrogen atom or a substituent of Ar.
• Z1 represents an oxygen atom, a sulfur atom, a selenium atom or a group -NH-;
• R2 represents a hydrogen atom or a substituent.
• Z2 represents an oxygen atom, a sulfur atom, a selenium atom or a group
• 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.
• 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 preferively 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 can be used by overlapping emul­sions having different sensitivities as emulsion layers or mixing them in order to widen its exposure latitude.
• the proportion of the coated silver amount in the respective emulsion layers can be arbitra­rily determined depending on the photographic perfor­mances required.
• 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.
• 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.
• 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.
• 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.
• the positive image can be readily obtained by carrying out image exposure (or photographing) followed by surface developing.
• 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.
• 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.
• 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.
• 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.
• 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.
• an excessive exposure amount may cause increase in minimum density or desensitization to lower the image quality.
• 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.
• 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 preferively 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.
• fogging agents can also be used in combination.
• 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.
• 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-( ⁇ -methanesulfonamidoethyl)anil ine, 4-amino-3-methyl-N-ethyl-N-( ⁇ -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.
• 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.
• 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.
• all of the light-sensitive silver halide emulsion layers may preferably contain the internal latent image type silver halide grain according to this invention.
• 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.
• 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.
• 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.
• 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.
• 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.
• 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.
• 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.
• 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 ⁇ m.
• potassium hexachloroiridate was added in an amount of 0.02 mg per mol of silver.
• 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.
• Emulsion B
• 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 ⁇ m.
• Emulsion C is a diagrammatic representation of Emulsion C:
• 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 ⁇ m, 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 ⁇ m.
• Emulsion D is a first Emulsion D:
• Core/shell emulsion D was obtained in substantially the same manner as for the above emulsion C.
• Emulsion E is a diagrammatic representation of Emulsion E:
• Core/shell emulsion E was obtained in substantially the same manner as for the above emulsion C.
• Emulsion F is a first Emulsion F:
• Core/shell emulsion F was obtained in substantially the same manner as for the above emulsion C.
• 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.
• 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.
• 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.
• 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 ⁇ m.
• Emulsion H is a diagrammatic representation of Emulsion H:
• 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 ⁇ m.
• Emulsion I is a diagrammatic representation of Emulsion I:
• 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 ⁇ m.
• Core/shell emulsion J was obtained in substantially the same manner as for the above emulsion I.
• Emulsion K
• Core/shell emulsion K was obtained in substantially the same manner as for the above emulsion I.
• Emulsion L is a first Emulsion L:
• Core/shell emulsion L was obtained in substantially the same manner as for the above emulsion I.
• the sensitizing dye represented by the formula shown below was added.
• 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.
• 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.
• 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 ⁇ m.
• 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 ⁇ m (silver chloride content: 98 mole %).
• 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.

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• 1987
  • 1987-09-29 CA CA000548152A patent/CA1317502C/en not_active Expired - Fee Related
  • 1987-09-29 JP JP24281087A patent/JPS63184739A/ja active Pending
  • 1987-09-29 DE DE19873786974 patent/DE3786974T2/de not_active Expired - Fee Related
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