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
  • G03C1/09—Noble metals or mercury; Salts or compounds thereof; Sulfur, selenium or tellurium, or compounds thereof, e.g. for chemical sensitising
• • 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
• • 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
  • G03C1/04—Silver halide emulsions; Preparation thereof; Physical treatment thereof; Incorporation of additives therein with macromolecular additives; with layer-forming 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
  • G03C1/06—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
  • G03C1/46—Silver halide emulsions; Preparation thereof; Physical treatment thereof; Incorporation of additives therein having more than one photosensitive layer
• • 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
  • G03C2001/0357—Monodisperse emulsion
• • 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
  • G03C1/09—Noble metals or mercury; Salts or compounds thereof; Sulfur, selenium or tellurium, or compounds thereof, e.g. for chemical sensitising
  • G03C2001/096—Sulphur sensitiser
• • 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
  • G03C1/09—Noble metals or mercury; Salts or compounds thereof; Sulfur, selenium or tellurium, or compounds thereof, e.g. for chemical sensitising
  • G03C2001/098—Tellurium
• • 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
  • G03C2200/00—Details
  • G03C2200/03—111 crystal face

Definitions

• the present invention relates to a method of preparing a highly photosensitive image-forming element and more particularly to a highly sensitive photographic silver halide emulsion having an improved speed in the presence of an organo-tellurium compound.
• selenium compounds which were suggested for use in order to get an increased sensitivity were substituted selenourea (as described e.g. in EP-A 0 280 031, EP-A 0 458 278), selenoethers (e.g. in JP-A 2-132434, JP-A 4-271341, JP-A 6-175258, US-A 5,532,120), diselenides (e.g. in EP-A 0 703 492), selenoesters (e.g. in US-A 5,306,613), selenoketones (e.g. in EP-A 0 476 345), fosfineselenides (e.g.
• inorganic and organic tellurium complexes as chemically sensitizing compounds have been described as in CA 800,985 (elemental tellurium), sodium telluride and hydrogen telluride (GB 1,295,462) and sodium thiosulfatotelluride (GB 1,396,696).
• Specific complexes like stable palladium-tellurium complexes have been described in GB 2,316,184.
• Organo-tellurium compounds have been described in EP-A ⁇ s 0 350 903, 0 572 662, 0 572 663, 0 573 649, 0 573 650, 0 619 515, 0 542 306, 0 661 589 and in US-A's 3,284,206; 4,076,537; 4,148,659; 4,188,218; 4,251,623; 5,215,880; 5,273,872; 5,273,874; 5,296,345, 5,340,695; 5,393,655; 5,395,745; 5,459,027; 5,561,033; 5,654,134; 5,677,120 and 5,759,760 and in DE-A's 1 96 16498, 1 96 19443, 1 96 48013 and 1 98 43081.
• a method of chemically sensitizing a silver halide emulsion has thus been disclosed, wherein said emulsion has silver halide grains and a binder, said method comprising the steps of adding thereto, besides a chemically sensitizing agent providing sulphur, an organo-tellurium sensitizing compound providing tellurium in a molar ratio amount versus sulphur of less than 0.30.
• a light-sensitive silver halide photographic element has also been provided which has been made highly sensitive by chemically sensitizing a silver halide emulsion by the method as described hereinbefore.
• organo-tellurium compounds used in order to chemically sensitize silver halide emulsions crystals by the method of the present invention.
• Said organo-tellurium compounds are satisfying formula (I):
• Another preferred group of compounds which are useful in the method of the present invention in order to get chemically sensitized silver halide emulsions having showing high speed is represented by formula (II): wherein each of R' and R" independently represents a subtituted or unsubstituted alkyl, alkenyl, alkynyl, aryl or heteroaryl group.
• the compound according to the formula (III) is a preferred organo-tellurium compound for use in the method of the present invention:
• the amount of the organo-tellurium chalcogenic compound according to the formulae (I)-(III) given hereinbefore for use in the method of the present invention is varying depending on the type of said compound used, the type of silver halide grain, the conditions of chemical sensitization, etc..
• the molar ratio of the organic compound(s) providing tellurium and of the compound(s) providing sulphur should be less than 0.30, preferably in the range from 0.05 up to 0.25, and still more preferable in the range from 0.08 up to 0.24, in order to provide highly sensitive light-sensitive emulsions for use in light-sensitive materials with an optimized speed-fog relationship.
• a higher speed is attained with an acceptable fog level than in conditions departing from those as described in the method of the present invention and, more particularly, wherein the same speed-fog relationship cannot be attained in the absence of the organo-tellurium compounds as described.
• an amount of sulphur should be provided in the range from 1 x 10 -7 mole up to 1 x 10 -3 mole per mole of silver, and more preferably in the range from 5 x 10 -6 mole up to 5 x 10 -5 mole per mole of silver, depending on the specific grain surface and grain volume.
• Organo-tellurium chemical sensitizers which are more or less soluble in water can be added to the dispersion of silver halide crystals as an aqueous solution and, if desired, can be mixed up with a water soluble organic solvent.
• Organo-tellurium sensitizers which are not water soluble can be introduced after solving the compound in a water soluble organic solvent which is normally used for the introduction of water insoluble products in a photographic silver halide emulsion.
• An alternative way in order to introduce an insoluble chemical chalcogenic sensitizer is making use of an "oil-in-water" dispersion or, if desired, a dispersion as disclosed in EP-A 0 703 492.
• the said compound is therefore added to the silver halide emulsion before chemical sensitization in the form of a solid partical dispersion in water.
• addition of tellurium(II) complexes as sensitizers having low solubility in water and/or in an organic solvent to a silver halide emulsion as those described in US-A 5,677,120 is advantageously performed in form of an aqueous solid particle dispersion as has been described in US-A 5,759,760.
• the tellurium compound used in the method according to the present invention is added as a zeolite loaded PUG as has been described in EP-A 0 909 981, wherein the said PUG or photographically useful group is corresponding with the said tellurium compound.
• Measures in order to provide suitable addition methods of the organo-tellurium sensitizing complexes or compounds are especially in favour of stability under ambient keeping conditions.
• the chemical sensitization with compounds satisfying formula (I) or (II), added in the method of the present invention, which includes the preferred compound according to formula (III), is preferably carried out in the presence of a silver halide solvent like e.g. a thiocyanate salt.
• a silver halide solvent like e.g. a thiocyanate salt.
• This can be added as a sodium, a potassium or preferably as an ammonium salt without however being limited thereto.
• Thiocyanate salt can be added before, during or after the addition of said compound of the present invention and before, during or after the addition of any other chemical sensitizer which can be used together with the said organo-tellurium sensitizer.
• the amount of the thiocyanate which is present together with the said chemical sensitizer is limited between 10 -6 and 10 -1 mole per mole of silver halide and preferably situated between 10 -5 and 10 -2 mole per mole of silver halide.
• the organo-tellurium compounds of the present invention can be used in combination with other known chemical sensitizers, wherein besides other organic or inorganic tellurium compounds providing tellurium to the silver halide grain, compounds providing sulphur, selenium and noble metals (like gold as the most well-known) are not excluded.
• the tellurium sensitization itself can be carried out in the presence of a sulphur compound and if desired in the presence of a noble metal (e.g. gold).
• the tellurium sensitization can be used in combination with a reduction sensitization too.
• a salt of a noble metal e.g., gold, iridium, palladium, platinum
• gold salts are preferably used in the method of the present invention as noble metal sensitizers.
• gold sensitizers include chloroauric acid, goldsulfide, chloroaurate salts, aurithiocyanate, gold selenide and gold telluride.
• the amount of the noble metal sensitizer may vary between 10 -8 and 10 -2 mole per mole of silver halide.
• Sulphur sensitization can be carried out with sulphur compounds like thiosulphates, thioureas, rhodamines, etc..
• the sulphur sensitizer can be used in an amount of about 10 -8 to 10 -2 mole per mole of silver halide provided that, according to the method of the present invention, besides said chemically sensitizing agent providing sulphur, an organo-tellurium sensitizing compound providing tellurium is added in a molar ratio amount versus sulphur of less than 0.30
• Reduction sensitization is characterized by treatment of the silver halide emulsion with a reducing compound like thioureum dioxide, hydrazine derivatives, sulphinic acid, polyamine compounds, stannous chloride, borane compounds, reductones like ascorbic acid, etc..
• Reduction sensitization can also be carried out at a low pAg or a high pH or at both and if desired at elevated temperature. This kind of sensitization is referred to as "silver ripening". More information about it can be found in Research Disclosure, Vol. 307, item 307105, p. 863-885, published November 1989, and in P.Glafkides "Chimie et Physique Photographic", P.Montel - Paris, 5 th Ed.,1987.
• the method of preparing a photosensitive element according to the present invention thus comprises as an essential feature the step of chemically sensitizing at least one silver halide emulsion in the presence of the organo-tellurium compound preferably represented by formula (I) or (II), besides a chemically sensitizing agent providing sulphur, in a molar ratio amount of tellurium versus sulphur of less than 0.30.
• the chemical sensitization described in the method of the present invention is further preferably carried out under conditions of pAg in the range of 6 to 11, but preferably between 7 and 10, in conditions of pH in the range of 3 to 10, preferably 4 to 8.5, while the temperature is situated in the range between 40 to 95 degrees C, preferably between 45 to 85 °C.
• the silver halide emulsion which should be treated with chemically sensitizing agents in order to become highly light-sensitive as disclosed in the method of the present invention can be prepared in various ways by conventional methods. After a nucleation step, optionally followed by a physical ripening step, one or more grain growth step(s) make(s) the formed nuclei further grow.
• reactants are added to the reaction vessel in form of solutions of silver and halide salts or in the form of preformed silver halide nuclei or fine grains which easily dissolve in the precipitation medium due to their size (up to at most about 0.050 ⁇ m) and/or composition (e.g.high solubility of preformed grains rich in silver chloride is much higher than for preformed grains rich in silver bromide, which has in turn a much higher solubility product than silver iodide).
• the individual reactants can be added through surface or subsurface delivery tubes by hydrostatic pressure or by an automatic delivery system for maintaining control of pH and/or pAg in the reaction vessel and of the rate of the reactant solutions introduced in it.
• the reactant solutions or dispersions can be added at a constant rate or a constantly increasing, decreasing or fluctuating rate, if desired in combination with stepwise delivery procedures.
• Dopants which are introduced in emulsions of the present invention are those which can act as a permanent or as a non-permanent electron trap as has e.g. been illustrated in EP-A 0 862 084, in EP-A 0 922 994 or in EP-Application 98201009, filed March 25, 1998.
• the doping procedure itself can normally be executed at any stage during the grain growth phase of the emulsion preparation.
• dopants can also be added in an indirect way by the addition of a dispersion containing very fine soluble silver halide grains or nuclei comprising the dopant. More additional information about the introduction and the use of dopants in the emulsion crystals of this invention can be found in Research Disclosure, 38957 (September 1996), section I-D.
• the photographic emulsions prepared in this way contain silver halide crystals comprising chloride, bromide or iodide alone or in combination thereof.
• Other silver salts which can be incorporated in a limited amount in the silver halide lattice are silver phosphate, silver thiocyanate, silver citrate and some other silver salts like silver formate.
• the chloride and bromide halide can be combined in all ratios in order to form a silver chlorobromide salt.
• Iodide ions however can be coprecipitated with chloride and/or bromide ions in order to form a iodohalide with an iodide amount which depends on the saturation limit of iodide in the crystal lattice with the given halide composition.
• the composition of the halide can change in the crystal in a continuous or discontinuous way.
• Emulsions containing crystals composed of various sections with different halide compositions are used for several photographic applications. So a structure with a difference in halide composition between the center and the rest of the crystal (what is called “core-shell"-emulsion) or with more than two crystal parts differing in halide composition (called a "band”-emulsion) may occur.
• Changes in halide composition can be realized by direct precipitation or in an indirect way by a so-called “conversion step", wherein fine silver halide grains of a certain halide composition are dissolved in the presence of the so-called host grains forming a "shell” or "band” on the given grain.
• Crystals formed by the emulsion preparation methods described above have a morphology which can be tabular or non-tabular.
• a light-sensitive silver halide photographic emulsion has been provided, wherein emulsion grains have been doped with a compound (called "dopant") providing shallow electron traps (SET's).
• dopant a compound providing shallow electron traps (SET's).
• SET's shallow electron traps
• said third-jet is adding the dopant solution in the vicinity of the stirrer, where also new rapidly dissolving fine grain nuclei are formed which are precipitated further onto growing tabular crystals.
• an organic hole trapping dopant as e.g. those chosen from carboxylic acid salts - as formates described in EP-A 0 922 994- or alpha hydroxy sulphenic acid salts as described in EP-Application No. 98204078, filed November 30, 1998) is not excluded, and even preferred in order to further improve the fog-speed relationship of the emulsions prepared according to the method of the present invention.
• Dopants used in the preparation method of tabular silver halide crystals which can also be added to the tabular grains of the present invention are e.g. Ir (see US-A's 5,164,292; 5,399,476; 5,807,667) or group VIII metal ions as has e.g. been described in EP-A's 0 503 736 and 0 515 894. Most frequently occurring dopants in literature are ruthenium, rhodium and iridium. Combinations of one or more dopant(s) may be added, in the same or different preparation steps of tabular silver halide crystals.
• tabular grains hole trapping dopants may be advised as those chosen from carboxylic acid salts - as formates - or alpha hydroxy sulphenic acid salts as described in EP-Application No. 98204079, filed November 30, 1998.
• Further addition of small amounts of e.g. iridium compounds (as potassium hexachloroiridate (III)) added during and/or at the end of the precipitation step and/or in the chemical ripening step is highly preferred and may lead to a positive effect on processing latitude, in that e.g. less differences in sensitivity and gradation are observed after fluctuations in developing time within a range of about 5 seconds and in processing temperature within a range of about 10°C.
• Said emulsion having shallow electron traps preferably comprises a binder and core-shell tabular grains doped with a dopant, characterized in that said grains contain as a dopant a compound providing shallow electron traps (more preferably a hexacyano complex of ruthenium), said complex being present in the core of said core-shell tabular grains and wherein said core represents an amount of precipitated silver halide extending up to at most 95 % of all precipitated silver halide (more preferably extending up to at most 80 % of all precipitated silver halide) as disclosed in EP-Application No. 99201625, filed May 25, 1999.
• the aspect ratio (ratio of equivalent circular diameter to thickness) can vary from “low” ( ⁇ 2) over “medium” (from 2 to 8) to "high” (more than 8) where especially in the case of the ultra thin tabular crystals high aspect ratios can be realized.
• the major faces of the formed tabular grains can have a ⁇ 111 ⁇ or a ⁇ 100 ⁇ -habit.
• the structure which is considered to be more stable for ⁇ 100 ⁇ tabular grains in analogy with stable cubic grains having (100) faces) has, opposite thereto, to be stabilized for thermodynamically unstable ⁇ 111 ⁇ tabular grains (by a "habit modifying agent" like adenine as an example of the preferred aminoazaindenes).
• iodide releasing agent as described in EP-A 0 561 415 and in EP-A 0 563 708 and applied on emulsions before, during or after chemically sensitization in addition to the method and the conditions of the present invention as described hereinbefore.
• the emulsions chemically sensitized as described hereinbefore, whether or not doped with one or more compounds providing shallow electron traps have grains composed of silver bromide, silver chloride, silver iodide or a combination thereof.
• a hydrophilic colloid is used as a binder or a protective colloid for the emulsion or any other layer of the photographic material of the invention.
• Gelatin is the most well-known and advantageously used hydrophilic colloid.
• the preparation of conventional lime-treated or acid-treated gelatin which is suitable for use in the emulsions and materials of the present invention has been descibed in e.g. "The Science and Technology of Gelatin", edited by A.G.Ward and A.Courts, Academic Press 1977, page 295 and further.
• the gelatin can also be enzyme-treated as described in Bull.Soc.Sci.Phot.Japan, Nr 16, page 30 (1966).
• Gelatin may, however, be replaced in part or integrally by synthetic, semi-synthetic, or natural polymers.
• Synthetic substitutes for gelatin are e.g. polyvinyl alcohol, poly-N-vinyl pyrrolidone, polyvinyl imidazole, polyvinyl pyrazole, polyacrylamide, polyacrylic acid, and derivatives thereof, in particular copolymers thereof.
• Natural substitutes for gelatin are e.g. other proteins such as zein, albumin and casein, cellulose, saccharides, starch, and alginates.
• the semi-synthetic substitutes for gelatin are modified natural products e.g.
• gelatin derivatives obtained by conversion of gelatin with alkylating or acylating agents, by grafting of polymerisable monomers on gelatin or prehardened gelatins with blocked functional groups as a consequence of this prehardening treatment, cellulose derivatives such as hydroxyalkyl cellulose, carboxymethyl cellulose, phthaloyl cellulose, and cellulose sulphates and even potato starch.
• Part of gelatin may further be replaced with a synthetic or natural high-molecular material.
• An interesting substitute for gelatin may be silica as has been described in the published EP-A's 0 392 092, 0 517 961, 0 528 476, 0 649 051 and 0 704 749.
• EP-A 0 528 476 a method of preparing a silver halide light-sensitive photographic material incorporating layers of silver halide precipitated in colloidal silica serving as a protective colloid is given.
• the silver halides are prepared in colloidal silica, leading to emulsion crystals that are stable at the end of the precipitation, without however having a predictable mean crystal diameter and crystal size distribution.
• Emulsions prepared according to the method of the present invention have as a binder gelatin, colloidal silica sol or cationic oxidized starch, without however excluding combinations thereof.
• the emulsions can be coagulated and washed after precipitation in order to remove the excess soluble salts.
• These procedures well-known in-the-art are used apart or together with alternative methods like dia- or ultrafiltration and ion-exchange as described e.g. in Research Disclosure, No. 38957 (September 1996), section III.
• Additional gelatin or another hydrophilic colloid, suitable for use as a binder material can be added at a later stage of emulsion preparation, e.g. after washing, in order to establish optimal coating conditions and/or in order to establish the required thickness of the coated emulsion layer.
• gelatin to silver halide ratio silver halide being expressed as the equivalent amount of silver nitrate, ranging from 0.3 to 1.0 is then obtained.
• Another binder may also be added instead of or in addition to gelatin.
• Useful vehicles, vehicle extenders, vehicle-like addenda and vehicle related addenda have been described e.g. in Research Disclosure N° 38957 (1996), Chapter II.
• the silver halide emulsion crystals chemically sensitized in the method of the present invention which are prepared in one of the ways described hereinbefore preferably contain crystals which have a spherical equivalent diameter (SED) of not more than 1.5 ⁇ m but preferable less than 1.0 ⁇ m.
• SED spherical equivalent diameter
• the spherical equivalent diameter (SED) of the crystal represents the diameter of the sphere which has the same volume as the average volume of the silver halide crystals of the said emulsion.
• emulsions the grains of which have been chemically sensitized according to the method of the present invention are those wherein said grains have a ⁇ 111 ⁇ crystal habit with an aspect ratio of more than 2, more preferably from 5 up to 25; an average equivalent crystal diameter of at least 0.5 ⁇ m, more preferably from 0.6 ⁇ m up to 2.0 ⁇ m; an average thickness of from 0.06 to 0.30 ⁇ m, more preferably from 0.06 up to 0.20 ⁇ m and wherein said grains are accounting for a total projected area of at least 90 % with respect to all grains.
• said emulsion has tabular grains which have a hexagonal ⁇ 111 ⁇ crystal habit with amitual variation coefficient on average crystal diameter of 25 % or less.
• the emulsions can be surface-sensitive emulsions which form latent images primarily on the surface of the silver halide grains or they can be emulsions forming their latent-image primarily in the interior of the silver halide grain.
• the emulsions can further be negative-working emulsions such as surface sensitive emulsions or unfogged internal latent image-forming emulsions.
• direct-positive emulsions of the unfogged, latent image-forming type which are positive-working by development in the presence of a nucleating agent, and even pre-fogged direct-positive emulsions can be used in the present invention.
• Silver halide emulsions chemically sensitized by the method of the present invention may be further spectrally sensitized with dyes from different classes which include polymethine dyes comprising cyanines, merocyanines, tri-, tetra- and polynuclear cyanines and merocyanines, oxanols, hemioxanols, styryls, merostyryls and so on, depending on the application (light or energy source for which the material comprising said emulsions should be sensitive). Sometimes more than one spectral sensitizer may be used in the case that a larger part of the spectrum has to be covered.
• spectral sensitization is performed prior to chemical sensitization.
• the photographic elements comprising the silver halide emulsions prepared according to the method of the present invention may include various compounds which should be provided as they play a role in the material itself or afterwards in the processing, finishing or warehousing the photographic material. These products can be stabilizers and anti-foggants. Antifoggants prevent occurrence of a fog while a stabilizer has a function of stabilizing photographic properties. Antifoggant and stabilizer are used in preparation, storage or processing step of the photographic material. Antifoging agents and stabilizers may be azoles, mercaptopyrimidines, mercaptotriazines, azaindenes, etc.. Further suitable examples are e.g. those described in Research Disclosure, 38957(September 1996), section VII.
• Hydrophilic colloidal layer (silver halide emulsion layer, backing layer, antihalation layer, etc.) of the photographic material comprising emulsions prepared according to the method of the present invention may contain an inorganic or an organic hardening agent (see Research Disclosure, 38957(September 1996) section IIB), brighteners (see Research Disclosure, 38957(September 1996) section VI), light absorbers and scattering materials (see Research Disclosure, 38957 (September 1996) section VIII), coating aids (see Research Disclosure, 38957(September 1996) section IXA), antistatic agents (see Research Disclosure, 38957(September 1996) section IXC), matting agents (see Research Disclosure, 38957(September 1996) section IXD) and development modifiers (see Research Disclosure, 38957(September 1996) section XVIII).
• an inorganic or an organic hardening agent see Research Disclosure, 38957(September 1996) section IIB
• brighteners see Research Disclosure, 38957(September 1996) section VI
• Said photographic elements may further comprise various other additives such as e.g. compounds improving the dimensional stability of the photographic element, ultraviolet absorbers and spacing agents.
• 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.
• UV-absorbers are e.g.
• aryl-substituted benzotriazole compounds as described in US-A 3,533,794, 4-thiazolidone compounds as described in US-A 3,314,794 and 3,352,681, benzophenone compounds as described in JP-A 56-2784, cinnamic ester compounds as described in US-A's 3,705,805 and 3,707,375, butadiene compounds as described in US-A 4,045,229, and benzoxazole compounds as described in US-A 3,700,455 and those described in Research Disclosure, 38957 (September 1996) Section VI, wherein also suitable optical brighteners are mentioned. Spacing agents may be present of which, in general, the average particle size is comprised between 0.2 and 10 ⁇ m.
• 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-A 4,614,708.
• any thickening agent may be used in order to regulate the viscosity of the coating solution, provided that they do not particularly affect the photographic characteristics of the silver halide emulsion in the coated photographic material.
• Preferred thickening agents include aqueous polymers such as polystyrene sulphonic acid, dextran, sulphuric acid esters, polysaccharides, polymers having a sulphonic acid group, a carboxylic acid group or a phosphoric acid group as well as colloidal silica.
• Polymeric thickeners well-known from the literature resulting in thickening of the coating solution may even be used in combination with colloidal silica. Patents concerning thickening agents are e.g.
• the layer binder should of course dispose of an acceptably high number of functional groups, which by reaction with an appropriate hardening agent can provide a sufficiently resistant layer.
• functional groups are especially the amino groups, but also carboxylic groups, hydroxy groups, and active methylene groups.
• Hardeners may be added to the antistress layer, covering one or more light-sensitive silver halide emulsion layers before or during the coating procedure, or to one or more of the said emulsion layers.
• the binders of the photographic element especially when the binder used is gelatin, 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 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. 2,3-dihydroxy-dioxan, active vinyl compounds e.g. 1,3,5-triacryloyl-hexa-hydro-s-triazine, active halogen compounds e.g.
• chromium salts e.g. chromium acetate and chromium alum
• aldehydes e.g. formaldehyde, glyoxal, and glutaraldehyde
• 2,4-dichloro-6-hydroxy-s-triazine and mucohalogenic acids e.g. mucochloric acid and mucophenoxy-chloric acid.
• These hardeners can be used alone or in combination.
• the binders can also be hardened with fast-reacting hardeners such as carbamoylpyridinium salts.
• Formaldehyde and phloroglucinol can e.g. be added respectively to the protective layer(s) and to the emulsion layer(s). Further suitable possibilities for hardening can be found in Research Disclosure, 38957(September 1996), section IIB.
• the photographic elements can be coated on a variety of supports which can be flexible or rigid.
• the flexible materials include plastic films and papers while the rigid materials include glass, metals, etc..
• the surface of the support is generally subjected to undercoating treatment (like corona discharge, irradiation with ultraviolet rays, etc.) in order to enhance the adhesion with the silver halide emulsion layer (see Research Disclosure, 38957(September 1996), section XV and the references cited therein).
• the photographic elements can be exposed to actinic radiation, especially in the visible, near-ultraviolet and near-infrared region of the spectrum, to form a latent image (see Research Disclosure, 38957(September 1996) section XVI).
• any optional light source releasing a radiation corresponding to the sensitivity wavelength of the photographic material can be employed.
• the light sources generally used include natural light, incandescent lamp, halogen lamp, mercury lamp, fluorescent lamp and all types of flash light sources.
• Light sources that emit light in the ultraviolet to infrared region can be also used as recording light sources.
• Photographic materials can for example also be exposed to gas lasers, semiconductor lasers, light emitting diodes or plasma light sources. In the same way the material can be exposed to a LCD-'light source' or to a fluorescent surface given by a phosphor stimulated with electron rays.
• the latent-image formed in the silver halide crystals of emulsions prepared according to the method of the present invention can, after exposure, be processed in order to form a visible image. Therefore various methods are known and many developing, fixing and stabilizing agents are described for the formation of photographic silver image.
• the know-how for processing photographic silver halide materials which can principally be used in relation with the present invention is described in Research Disclosure, No. 176043, December1978; sections XIX to XXIV and in Research Disclosure, 38957(September 1996) section XIX).
• Presence of specified stabilizing agents like e.g. thiazoles, mercaptanes or polysulfide compounds is in favour of reaching low fogging levels and, to a certain extent, as illustrated in US-A 5,654,134, in favour of reciprocity law characteristics.
• Ascorbic acid should be interpreted in a broad sense and includes ascorbic acid isomers, derivatives, salts and analogous compounds (including some reductones and reductic acid derivatives). The most preferred compounds are ascorbic acid, iso-ascorbic acid and their salts. Useful combinations of developers containing an ascorbic acid developing agent which should be preferably used in the scope of the present invention is described for many applications (in graphic materials, radiography, non-destructive testing materials, micrography, laser materials, etc.) in Research Disclosure No. 37152(March 1995), pages 185-224.
• the photographic emulsions prepared according to the method of the present invention can be used in various applications as described e.g. EP-A's 0 794 456 and 0 862 088 for laser imaging (hard-copy materials) and radiological imaging respectively (silver halide photographic emulsion suitable for use in single-side and double-side coated radiographic materials respectively, combined with intensifying screens provided with luminescent phosphors emitting light for which the silver halide photographic materials are light-sensitive and thus made suitable for use in medical diagnosis), but also in multi-layered multicolour materials.
• These multicolour materials comprise a support and two or more silver halide emulsion layers that have different spectral sensitivities.
• the multi-layered colour photographic material generally comprises at least one red-sensitive emulsion layer, at least one green-sensitive emulsion layer and at least one blue-sensitive emulsion layer on a support.
• a non-light sensitive layer may be provided between two or more emulsion layers having the same colour sensitivity. Otherwise, another emulsion layer having a different colour sensitivity can be provided between two or more emulsion layers having the same color sensitivity.
• a light-reflecting layer such as a layer of silver halide grains can be provided under a high sensitive layer, particularly under a high blue-sensitive layer in order to enhance the sensitivity.
• the silver halide material can also contain different types of couplers which can be incorporated in colour photographic materials.
• the red-sensitive emulsion layer contains generally a cyan coupler
• the green-sensitive layer generally contains a magenta coupler
• the blue-sensitive emulsion layer generally contains a yellow coupler. All the information which can be important for the application of the present invention in these type of materials is extensively described in Research Disclosure, 38957(September 1996) section X. More information with respect to the various colour applications which belong also to the scope of the present invention, can be found in US-A 5,532,120.
• Processing in order to form a visible dye image for colour materials means contacting the element with a colour developing agent in order to reduce developable silver halide and to oxidize the colour developing agent, which in turn normally reacts with a coupler to form a dye (see Research Disclosure, 38957(September 1996) section XX).
• single-side or double-side coated silver halide photographic materials comprising a support and coated thereon on one or both sides respectively one or more hydrophilic light-sensitive layers, wherein at least one of said layers comprises a light-sensitive silver halide emulsion prepared according to the method as extensively described and disclosed hereinbefore.
• Film materials comprising tabular ⁇ 111 ⁇ grains rich in silver bromide were the following.
• a nucleation step was performed by introducing solution A and solution B simultaneously in dispersion medium C both at a flow rate of 24 ml/min during 30 seconds. After a physical ripening time of 7 minutes, the temperature was raised to 70 °C in 25 minutes and after another 7 minutes pH was adjusted to a value of 5.0, making use from a solution of 2 molar of sodium hydroxide.
• a second neutralization step was performed by addition of solution A at a rate of 5 ml/minute during 300 seconds and of solution B at a rate in order to get a UAg value of 10 mV (mV versus sat. Ag/AgCl reference electrode).
• Grain growth was performed by addition at a linearly increasing velocity from 5 ml/min. up to 10 ml/min. of 478 ml of solution A in 3824 seconds, while adding solution B at a rate in order to get a constant UAg value of 10 mV.
• a third neutralization step was performed by addition of solution A at a constant rate of 5 ml per minute during 395 seconds.
• a fourth neutralization step was performed by addition of solution A at a rate of 5 ml/minute during 120 seconds and of solution B at a rate in order to get a UAg value of 60 mV.
• Grain growth was performed in a second growth step by addition at a linearly increasing velocity from 5 ml/min. up to 25 ml/min. of 932 ml of solution A in 3728 seconds, while adding solution B at a rate in order to get a constant UAg value of 60 mV.
• the pH value of the said dispersing medium was adjusted to a value of 3.5 with sulphuric acid and after cooling to 20°C the obtained flocculate was decanted and washed twice with an amount of 3 1 of demineralized water (11°C) in order to remove the soluble salts present. After decanting to a volume of 1.351 1 the washing procedure was repeated twice and after the last washing step, followed by sedimentation, decantation was performed in order to have an emulsion volume as low as possible. An emulsion having ⁇ 111 ⁇ silver bromoiodide tabular grains having iodide present in an amount of 0.1 mole % was thus obtained. Peptization was further performed by addition of gelatin in order to get a gesi of 0.5 for an emulsion the concentration of which, expressed as an equivalent amount of silver nitrate, of 236 g/kg.
• the said silver bromoiodide tabular emulsion showed the following grain characteristics:
• the diameter of the grain was defined as the diameter of the circle having an area equal to the projected area of the grain as viewed in the said photographs.
• Data for E.V.D. were obtained after computing signals obtained from reduction of individual grains and representative for the volume of each grain before reduction.
• the UAg-value of the emulsion was adjusted at +100 mV (against a silver/silver chloride reference electrode) and the pH-value at 6.0 with sodium hydroxide.
• Chemical ripening agents were adapted to the crystal size of the emulsions: amounts are given in the Table 1 hereinafter.
• Chemical ripening agents were gold thiocyanate, sodium thiosulphate as a source of sulphur, the tellurium compound according to the formula (III) as a source of tellurium and toluene thiosulphonic acid (see formula IV) was used as predigestion agent.
• the amounts of each chemical ripening agent (given in ml per mole of silver) are represented in Table 1.
• the chemical ripening was optimized in order to obtain an optimal fog-sensitivity relationship after 2 hours at 54°C.
• Stabilizing compound (V) was added as last solution in an amount of 1.28 x 10 -4 mole per mole of silver.
• the molar ratio of tellurium and sulphur has been given in the Table 1. Apart from the Emulsion No. 1 wherein no tellurium compound has been added, the said molar ratio ranges from 1:12 up to 4:3. Comp./EM 1 2 3 4 5 6 7 8 9 Na 2 S 2 O 3 .5aq 1 1 1 1 1 1 0.5 0.75 0.75 Te-comp.III 0 0.25 0.5 1 2 4 0.5 0.25 0.5 HAuCl 4 .4H 2 O 1 1 1 1 1 1 1 1 1 1 1 Te/S - 0.08 0.16 0.32 0.64 1.28 0.32 0.11 0.22
• the resulting photographic material contained per side an amount of silver halide corresponding to 3.5 grams of AgNO 3 per m 2 and an amount of gelatin corresponding to 2.8 g/m 2 .
• the processing was run in the developer G138®, followed by fixing in fixer G335® and rinsing at the indicated temperature of 35°C for a total processing time of 45 seconds.
• the said developer and fixer are trademark products from Agfa-Gevaert N.V..

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  • 1999-07-23 EP EP99202439A patent/EP1070986A1/de not_active Withdrawn
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