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
  • G03C1/06—Silver halide emulsions; Preparation thereof; Physical treatment thereof; Incorporation of additives therein with non-macromolecular additives
  • G03C1/08—Sensitivity-increasing substances
• • 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
  • G03C1/0051—Tabular grain emulsions
  • G03C1/0053—Tabular grain emulsions with high content of silver chloride
• • 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
  • G03C1/06—Silver halide emulsions; Preparation thereof; Physical treatment thereof; Incorporation of additives therein with non-macromolecular additives
  • G03C1/07—Substances influencing grain growth during silver salt formation
• • 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
  • G03C1/06—Silver halide emulsions; Preparation thereof; Physical treatment thereof; Incorporation of additives therein with non-macromolecular additives
  • G03C1/08—Sensitivity-increasing substances
  • G03C2001/0845—Iron compounds

Definitions

• the present invention relates to the preparation of a silver halide tabular grain emulsion rich in chloride with improved sensitometric characteristics and to photographic materials containing such an emulsion.
• High aspect ratio tabular grains exhibit several pronounced photographic advantages. Thanks to their particular morphology greater amounts of spectral sensitizers can be adsorbed per mole silver halide compared to classical globular grains. As a consequence such spectrally sensitized tabular grains show an improved speed-granularity relationship and a wide separation between their blue speed and minus blue speed. Sharpness of photographic images can be improved using tabular grains thanks to their lower light scattering properties again compared to conventional globular emulsion grains. In color negative materials the conventional sequence of the light sensitive layers can be altered and the yellow filter layer can be omitted.
• growth modifiers can be used to precipitate octahedral and rhombic dodecahedral silver chloride crystals and they attributed the crystal habit modification to variations in surface hydratation caused by those additives; typical examples of these modifiers included adenine, thiourea, hypoxanthine, benzimidazole and benzothiazole derivatives.
• the mechanism of the growth modifying action of adenine was studied in detail by Szucs in J. Signal AM Vol. 6 (1978) No 5 p. 381-405.
• tabular chloride rich emulsion grains are contemplated.
• So Wey US 4,399,215 discloses tabular silver chloride with an aspect ratio of at least 8:1 and parallel (111) major crystal faces. Precipitation conditions include the use of ammonia. Rather thick tabular grains are obtained.
• Wey US 4,414,306 discloses tabular silver chlorobromide grains with at least an annular region where the molar ratio of chloride to bromide ranges up to 2:3.
• Tufano US 4,804,621 describes a process for preparing chloride rich tabular grains in the presence of aminoazapyridine growth modifiers represented by a general formula of which adenine and derivatives are excluded.
• EP 0 481 133 describes the presence of adenine-like compounds in the preparation of chloride rich tabular grains using conventional gelatin, and Maskasky US 5,183,732 discloses similar compounds.
• Maskasky further describes triaminopyrimidines in US 5,185,239, xanthine derivatives in US 5,178,998, and other heterocyclic compounds in US 5,178,997, all as growth modifiers in the preparation of chloride rich tabular emulsions.
• JP-A-05-113619 tabular silver halide grains are disclosed containing an iron dopant and having been subjected to intense reduction.
• the preferred embodiment and the examples are restraint to sensitive AgBr(I) emulsions.
• the present invention deals with a further extension and improvement on the cited teachings on the preparation of chloride rich tabular grains.
• the objects of the present invention are realized by providing a tabular grain emulsion and a method for its preparation, said emulsion containing at least 95 % chloride, wherein at least 50 % of the total projected area of all the grains is provided by said tabular grains, and wherein said tabular grains exhibit an average aspect ratio of at least 3:1, an average thickness not greater than 0,5 micron and an average sphere equivalent diameter of at least 0,3 micron, characterized in that said emulsion is doped during grain formation with a compound providing complex iron(II) ions.
• a crystal growth modifier is also present during grain formation.
• the sphere equivalent diameter is defined as the diameter of a hypothetical spherical grain with the same volume as the corresponding tabular grain.
• the equivalent circular diameter is defined as the diameter of the circle having an area equal to the projected area of the tabular grain as viewed in a photomicrograph.
• Preferred dopants are the potassium or sodium salts of hexacyanoferrate(II).
• the rest of the halide is preferably bromide the iodide content being limited to at most 2 mole %.
• the chloride content is at least 99 mole %, and in a most preferred embodiment the emulsion is pure silver chloride.
• the precipitation for the formation of the tabular grains of present invention can be principally performed by one double jet step it is preferred to perform a sequence of a nucleation step and at least one growth step.
• a nucleation step preferably 0.5 % to 5.0 % is added during said nucleation step which consists preferably of an approximately equimolecular addition of silver and halide salts.
• the rest of the silver and halide salts is added during one or more consecutive double jet growth steps under precipitation conditions favouring the formation of tabular chloride rich grains as defined above.
• the different steps of the precipitation can be alternated by physical ripening steps.
• an increasing flow rate of silver and halide solutions is preferably established, e.g.
• the flow rate at the end is about 3 to 5 times greater then at the start of the growth step.
• These flow rates can be monitored by e.g. magnetic valves.
• the pCl is maintained between 1.0 and 2.0, preferably between 1.0 and 1.5 during the different stages of the precipitation, and the pH is maintained between 4.0 and 9.0, preferably between 5.5 and 7.0.
• the iron complex dopant can be added at several stages of the emulsion grain formation, e.g. before the start of the precipitation in the reaction vessel, during one of the precipitation stages or during physical ripening. Apart from being present in the reaction vessel it can be present in one or more halide solutions or in one or more separate solutions.
• Useful ligands giving rise to complex iron(II) ions include :
• the complex iron ions are preferably added as their potassium salt or sodium salt.
• EP 0 541 067 discloses heat-developable silver halide emulsions containing hexacyanoferrate(II) or (III).
• iron(III) complex salts particularly potassium hexacyanoferrate(III) is since long known, e.g. from US 3,741,767, for its oxidizing properties resulting in a reduction of internal sensitivity centres during grain formation.
• complex iron(II) ions is recognized to solve problems associated with chloride rich tabular grains.
• the most preferred compound for use in the practice of the present invention is hexacyanoferrate(II) in its potassium or sodium salt form, preferably potassium.
• the substance is preferably added in a total concentration between 10 ⁇ 6 mole and 10 ⁇ 4 mole, most preferably between 0.5x10 ⁇ 6 and 2.0x10 ⁇ 5 mole per mole of total silver halide.
• a crystal growth modifier is also present during one or more of the stages of grain formation.
• useful growth modifiers present during precipitation include following compounds :
• the most preferred crystal growth modifier is adenine (G-1).
• the modifier can be present in the reaction vessel before the start of the precipitation or can be added during one of the precipitation stages or physical ripening period(s). It can be added as a separate solution or it can be dissolved in a halide solution.
• the emulsion is washed in order to remove soluble inorganic salts. This can be performed by well-known techniques such as repeated flocculation and washing followed by redispersion, or, more preferably, by ultrafiltration.
• the tabular silver halide emulsions in connection with the present invention can be chemically sensitized after washing as described e.g. in "Chimie et Physique Photographique” by P. Glafkides, in “Photographic Emulsion Chemistry” by G.F. Duffin, in “Making and Coating Photographic Emulsion” by V.L. Zelikman et al, and in "Die Grundlagen der Photographischen mit Silberhalogeniden” edited by H. Frieser and published by Akademische Verlagsgesellschaft (1968).
• chemical sensitization can be carried out by effecting the ripening in the presence of small amounts of compounds containing sulphur e.g.
• emulsions can be sensitized also by means of gold-sulphur ripeners or by means of reductors e.g. tin compounds as described in GB 789,823, amines, hydrazine derivatives, formamidine-sulphinic acids, and silane compounds.
• reductors e.g. tin compounds as described in GB 789,823, amines, hydrazine derivatives, formamidine-sulphinic acids, and silane compounds.
• the tabular silver halide emulsions can be spectrally sensitized with methine dyes such as those described by F.M. Hamer in "The Cyanine Dyes and Related Compounds", 1964, John Wiley & Sons.
• Dyes that can be used for the purpose of spectral sensitization include cyanine dyes, merocyanine dyes, complex cyanine dyes, complex merocyanine dyes, hemicyanine dyes, styryl dyes and hemioxonol dyes.
• Particularly valuable dyes are those belonging to the cyanine dyes, merocyanine dyes and complex merocyanine dyes.
• spectral sensitization In classical emulsion preparation spectral sensitization traditionally follows the completion of chemical sensitization. However, in connection with tabular grains, it is specifically considered that spectral sensitization can occur simultaneously with or even precede completely the chemical sensitization step.
• spectral sensitization can occur simultaneously with or even precede completely the chemical sensitization step.
• Maskasky US Ser. No 431,855, titled CONTROLLED SITE EPITAXIAL SENSITIZATION discloses the chemical sensitization after spectral sensitization at one or more ordered discrete edge sites of tabular grains. This can be done with the tabular chloride rich emulsions prepared according to the method of the present invention.
• the photographic tabular grains in connection with the present invention can be used in various types of photographic elements. Because of their chloride rich character they are preferably used for those applications which do not require extreme high sensitivity. Preferred embodiments include graphic arts e.g. recording materials for the ouput of scanners, phototypesetters and imagesetters, duplicating materials, radiographic hard-copy materials, diffusion transfer materials and black-and-white or colour print materials which produce prints starting from negatives in amateur or professional still photography or prints for cinematographic exhibition.
• graphic arts e.g. recording materials for the ouput of scanners, phototypesetters and imagesetters, duplicating materials, radiographic hard-copy materials, diffusion transfer materials and black-and-white or colour print materials which produce prints starting from negatives in amateur or professional still photography or prints for cinematographic exhibition.
• the photographic element can contain one single emulsion layer, as it is the case for many applications, or it can be built up by two or even more emulsion layers.
• the material contains blue, green and red sensitive layers each of which can be single or multiple.
• the photographic material can contain several non-light sensitive layers, e.g. a protective layer, one or more backing layers, one or more subbing layers, and one or more intermediate layers, e.g. filter layers.
• the silver halide emulsion layer(s) in accordance with the present invention or the non-light-sensitive layers may comprise compounds preventing the formation of fog or stabilizing the photographic characteristics during the production or storage of the photographic elements or during the photographic treatment thereof.
• Many known compounds can be added as fog-inhibiting agent or stabilizer to the silver halide emulsion. Suitable examples are e.g.
• heterocyclic nitrogen-containing compounds such as benzothiazolium salts, nitroimidazoles, nitrobenzimidazoles, chlorobenzimidazoles, bromobenzimidazoles, mercaptothiazoles, mercaptobenzothiazoles, mercaptobenzimidazoles, mercaptothiadiazoles, aminotriazoles, benzotriazoles (preferably 5-methyl-benzotriazole), nitrobenzotriazoles, mercaptotetrazoles, in particular 1-phenyl-5-mercapto-tetrazole, mercaptopyrimidines, mercaptotriazines, benzothiazoline-2-thione, oxazoline-thione, triazaindenes, tetrazaindenes and pentazaindenes, especially those described by Birr in Z.
• benzothiazolium salts such as benzothiazolium salts, nitroimidazoles, nitrobenzimidazoles, chlor
• colour couplers e.g. colour couplers, couplers bearing a releasable photographic useful group and scavengers for oxidized developer
• typical ingredients for colour materials can be soluble or added in dispersed form, e.g. with the aid of so-called oilformers or they can be added in polymeric latex form.
• the gelatin binder of the photographic elements can be hardened with appropriate hardening agents such as those of the epoxide type, those of the ethylenimine type, those of the vinylsulfone type e.g. 1,3-vinylsulphonyl-2-propanol, chromium salts e.g. chromium acetate and chromium alum, aldehydes e.g. formaldehyde, glyoxal, and glutaraldehyde, N-methylol compounds e.g. dimethylolurea and methyloldimethylhydantoin, dioxan derivatives e.g.
• appropriate hardening agents such as those of the epoxide type, those of the ethylenimine type, those of the vinylsulfone type e.g. 1,3-vinylsulphonyl-2-propanol, chromium salts e.g. chromium acetate and
• the photographic element of the present invention may further comprise various kinds of surface-active agents in the photographic emulsion layer or in at least one other hydrophilic colloid layer.
• Suitable surface-active agents include non-ionic agents such as saponins, alkylene oxides e.g.
• polyethylene glycol polyethylene glycol/polypropylene glycol condensation products, polyethylene glycol alkyl ethers or polyethylene glycol alkylaryl ethers, polyethylene glycol esters, polyethylene glycol sorbitan esters, polyalkylene glycol alkylamines or alkylamides, silicone-polyethylene oxide adducts, glycidol derivatives, fatty acid esters of polyhydric alcohols and alkyl esters of saccharides; anionic agents comprising an acid group such as a carboxy, sulpho, phospho, sulphuric or phosphoric aster group; ampholytic agents such as aminoacids, aminoalkyl sulphonic acids, aminoalkyl sulphates or phosphates, alkyl betaines, and amine-N-oxides; and cationic agents such as alkylamine salts, aliphatic, aromatic, or heterocyclic quaternary ammonium salts, aliphatic or heterocyclic ring
• Such surface-active agents can be used for various purposes e.g. as coating aids, as compounds preventing electric charges, as compounds improving slidability, as compounds facilitating dispersive emulsification, as compounds preventing or reducing adhesion, and as compounds improving the photographic characteristics e.g higher contrast, sensitization, and development acceleration.
• Development acceleration can be accomplished with the aid of various compounds, preferably polyalkylene derivatives having a molecular weight of at least 400 such as those described in e.g. US 3,038,805 - 4,038,075 - 4,292,400.
• the photographic element of the present invention may further comprise various other additives such as e.g. compounds improving the dimensional stability of the photographic element, UV-absorbers, spacing agents and plasticizers.
• Suitable additives for improving the dimensional stability of the photographic element are e.g. dispersions of a water-soluble or hardly soluble synthetic polymer e.g. polymers of alkyl(meth)acrylates, alkoxy(meth)acrylates, glycidyl (meth)acrylates, (meth)acrylamides, vinyl esters, acrylonitriles, olefins, and styrenes, or copolymers of the above with acrylic acids, methacrylic acids, Alpha-Beta-unsaturated dicarboxylic acids, hydroxyalkyl (meth)acrylates, sulphoalkyl (meth)acrylates, and styrene sulphonic acids.
• a water-soluble or hardly soluble synthetic polymer e.g. polymers of alkyl(meth)acrylates, alkoxy(meth)acrylates, glycidyl (meth)acrylates, (meth)acrylamides, vinyl esters,
• UV-absorbers are e.g. aryl-substituted benzotriazole compounds as described in US 3,533,794, 4-thiazolidone compounds as described in US 3,314,794 and 3,352,681, benzophenone compounds as described in JP-A 2784/71, cinnamic ester compounds as described in US 3,705,805 and 3,707,375, butadiene compounds as described in US 4,045,229, and benzoxazole compounds as described in US 3,700,455.
• UV-absorbers are especially useful in colour print materials where they prevent the fading by light of the colour images formed after processing.
• Spacing agents can be present of which, in general, the average particle size is comprised between 0.2 and 10 micron. Spacing agents can be soluble or insoluble in alkali. Alkali-insoluble spacing agents usually remain permanently in the photographic element, whereas alkali-soluble spacing agents usually are removed therefrom in an alkaline processing bath. Suitable spacing agents can be made e.g. of polymethyl methacrylate, of copolymers of acrylic acid and methyl methacrylate, and of hydroxypropylmethyl cellulose hexahydrophthalate. Other suitable spacing agents have been described in US 4,614,708.
• the photographic material can contain several non light sensitive layers, e.g. an anti-stress top layer, one or more backing layers, and one or more intermediate layers eventually containing filter- or antihalation dyes that absorb scattering light and thus promote the image sharpness.
• Suitable light-absorbing dyes are described in e.g. US 4,092,168, US 4,311,787, DE 2,453,217, and GB 7,907,440.
• One or more backing layers can be provided at the non-light sensitive side of the support.
• These layers which can serve as anti-curl layer can contain e.g. matting agents like silica particles, lubricants, antistatic agents, light absorbing dyes, opacifying agents, e.g. titanium oxide and the usual ingredients like hardeners and wetting agents.
• the support of the photographic material may be opaque or transparent, e.g. a paper support or resin support.
• a paper support preference is given to one coated at one or both sides with an Alpha-olefin polymer, e.g. a polyethylene layer which optionally contains an anti-halation dye or pigment.
• an organic resin support e.g. cellulose nitrate film, cellulose acetate film, poly (vinyl acetal) film, polystyrene film, poly(ethylene terephthalate) film, polycarbonate film, polyvinylchloride film or poly-Alpha-olefin films such as polyethylene or polypropylene film.
• the thickness of such organic resin film is preferably comprised between 0.07 and 0.35 mm.
• These organic resin supports are preferably coated with a subbing layer which can contain water insoluble particles such as silica or titanium dioxide.
• the photographic material containing tabular grains prepared according to the present invention can be image-wise exposed by any convenient radiation source in accordance with its specific application.
• Processing conditions and composition of processing solutions are dependent from the type of photographic material in which the tabular grains prepared according to the present invention are applied.
• rapid access developers can be used; alternatively so-called lith developers or the more recent "hard dot rapid access” developers can be used depending on the specific composition and use of the photographic element.
• lith developers or the more recent "hard dot rapid access” developers can be used depending on the specific composition and use of the photographic element.
• an automatically operating processing apparatus is used provided with a system for automatic replenishment of the processing solutions.
• Example 1 control emulsion
• a reaction vessel contained 2 l of a solution that was 0.5 % in bone gelatine, 0.15 M in NaCl and 0.003 M in adenine. The pH was adjusted to 5.5. Two further solutions were prepared: solution A that was 3 M in AgNO3 and solution B that was 3 M in NaCl and 0.015 M in KI. To the stirred reaction vessel content at 45 °C simultaneously were added 10 ml of solution A and 10 ml of solution B during a period of 30 sec. Then the temperature was rised to 70 °C and held for 15 min. 1 l of a solution that was 6.5 % in bone gelatin was added.
• Solution A was added with accelerated flow rate from 5 ml/min to 25 ml/min over a period of 66 min.
• the pCl was held constant at 1.3 by adding solution B.
• the pH was lowered to 3.0 and the coagulated emulsion washed 3 times with 4 l of a solution that was 0.015 M in NaCl.
• the resulting solid phase was resuspended at 45 °C to a total weight of 2.8 kg with a solution that was 7.5 % in gelatine and 0.015 M in NaCl.
• the pH was adjusted to 5.0 and the pAg to 7.3.
• the resulting emulsion contained a tabular grain population of 90 % of the total projected area of the grains with an average sphere equivalent diameter of 0.52 micron, an average equivalent circular diameter of the major parallel planes of 0.85 micron, an average thickness of 0.13 micron and an average aspect ratio of 6.5.
• Example 2 emulsion of the invention
• a reaction vessel contained 2 l of a solution that was 0.5 % in bone gelatine, 0.15 M in NaCl and 0.003 M in adenine. The pH was adjusted to 5.5. Three further solutions were prepared: solution A that was 3 M in AgNO3, solution B that was 3 M in NaCl and 0.015 M in KI and solution C that was 3 M in NaCl, 0.015 M in KI and 1.7x10 ⁇ 4 M in K4Fe(CN)6.3H2O. To the stirred reaction vessel content at 45 °C simultaneously were added 10 ml of solution A and 10 ml of solution B during a period of 30 sec. Then the temperature was rised to 70 °C and held for 15 min.
• Solution A was added with accelerated flow rate from 5 ml/min to 22.6 ml/min during a period of 58 min.
• the pCl was held constant at 1.3 by adding solution B.
• Solution A was added with accelerated flow rate from 22.6 ml/min to 25 ml/min during a period of 8 min.
• the pCl was held constant at 1.3 by adding solution C.
• the pH was lowered to 3.0 and the coagulated emulsion washed 3 times with 4 l of a solution that was 0.015 M in NaCl.
• the resulting solid phase was resuspended at 45 °C to a total weight of 2.8 kg with a solution that was 7.5 % in gelatine and 0.015 M in NaCl.
• the pH was adjusted to 5.0 and the pAg to 7.3.
• the resulting emulsion contained a tabular grain population of 90 % of the total projected area of the grains with an average sphere equivalent diameter of 0.52 micron, an average equivalent circular diameter of 0.85 micron, an average thickness of 0.13 micron and an average aspect ratio of 6.5.
• Example 3 emulsion of the invention
• the emulsion was prepared similarly as the emulsion of example 2, except that solution C was 3.0x10 ⁇ 4 M in K4Fe(CN)6.3H2O.
• Example 4 emulsion of the invention
• the emulsion was prepared similarly as the emulsion of example 2, except that solution C was 5.3x10 ⁇ 4 M in K4Fe(CN)6.3H2O.

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• 1993
  • 1993-10-07 EP EP93202846A patent/EP0647877A1/fr not_active Withdrawn

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