EP0866362A1 - Verfahren zur Herstellung von tafelförmigen (111)-Silberchloro(bromo)jodikristallen - Google Patents

Verfahren zur Herstellung von tafelförmigen (111)-Silberchloro(bromo)jodikristallen Download PDF

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EP0866362A1
EP0866362A1 EP98200706A EP98200706A EP0866362A1 EP 0866362 A1 EP0866362 A1 EP 0866362A1 EP 98200706 A EP98200706 A EP 98200706A EP 98200706 A EP98200706 A EP 98200706A EP 0866362 A1 EP0866362 A1 EP 0866362A1
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Prior art keywords
silver
grains
iodide
crystal
emulsion
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French (fr)
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Peter Verrept
Ann Verbeek
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Agfa Gevaert NV
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Agfa Gevaert NV
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    • 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
    • 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
    • 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
    • G03C2200/43—Process
    • 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
    • G03C2200/44—Details pH value

Definitions

  • the present invention relates to the preparation of tabular silver halide emulsion grains rich in silver chloride showing enhanced monodispersity in grain size and to a method of controlling thickness of said grains.
  • Tabular silver halide grains are well-known for practical use since the early eighties as crystals possessing two parallel faces with a ratio between the diameter of a circle having the same area as these faces, and the thickness, being the distance between the two major faces, equal to two or more.
  • tabular grains with high aspect ratio and their advantages in photographic applications are described as in US-A's 4,434,226 (high aspect ratios of more than 8:1); 4,439,520 (specifically about spectral sensitization); 4,425,425 (radiographic materials containing tabular grains with an aspect ratio of at least 8:1) and 4,425,426 (similar grains having an aspect ratio between 5:1 and 8:1).
  • a survey on high aspect ratio silver halide emulsions appeared in Research Disclosure, Volume 225, Jan 1983, Item 22534.
  • the main photographic advantages of tabular grains compared to normal globular grains are a high covering power at high forehardening levels as described in US-A 4,414,304, a high developability and higher sharpness especially in double side coated spectrally sensitized materials thereby lowering of cross-over as specifically described in US-A's 4,425,425 and 4,425,426.
  • a common variability coefficient (defined as a ratio between average standard deviation on equivalent circular diameter and the said average equivalent circular diameter) of 0.30 to 0.45 is calculated, due to the presence of quite a large number of non-tabular grains having a sphere equivalent diameter of less than 0.3 ⁇ .
  • Radiographic materials comprising emulsions having monodisperse tabular silver brom(oiod)ide crystals have e.g. been described in US-A's 5,252,442 and 5,508,158.
  • the same preparation methods as for the forementioned tabular grains rich in silver bromide can however not be applied as such in preparing tabular grains rich in silver chloride, especially due to the presence of crystal habit modifiers, usually adenine, as this leads to the disadvantages set forth hereinbefore.
  • a method has been found of preparing a silver halide emulsion comprising silver chlorobromoiodide or silver chloroiodide tabular grains with at least 75 mole % of chloride and from 0.1 up to 3 mole % of iodide, based on silver, further having ⁇ 111 ⁇ crystal faces, an average aspect ratio of at least 2:1, with at least 50 %, more preferable at least 75 % and still more preferable more than 90 % of the total projected area of all grains being provided by said tabular grains and with a variation coefficient on sphere equivalent diameter (SED) of said grains being lower than 0.30, more preferably lower than 0.25 and most preferable from 0.05 up to at most 0.15, said method comprising the steps of
  • a method has unexpectedly been found in order to make thickness of the tabular ⁇ 111 ⁇ silver chloroiodide or silver chlorobromoiodide grains perfectly predictable, wherein an essential step is the lowering of the initial pH value after nucleation by setting it to a value of lower than 6.0, more preferred to a value of not more than 4.0 for at least 30 seconds, followed by resetting pH to the said initial pH.
  • This setting of the pH value " completely differs from pH correction or pH adjustment due to spontaneous pH lowering which may take place during running an aqueous acidic solution of silver nitrate in a double jet precipitation step, thereby causing pH decrease in the reaction vessel to a value lower than the said initial pH value has e.g. been described in Example 15B from US-A 5,183,732.
  • a pH adjustment was performed in order to maintain the initial pH value in the reaction vessel by addition of an alkaline solution of sodium hydroxide.
  • the said lowering in the sense of intended setting of pH to a lower value immediately occurs after ending nucleation, during a physical ripening step following the said nucleation, during a physical ripening step inbetween one or more growth steps, during growth or at the end of growth, but before flocculation or ultrafiltration, wherein said ultrafiltration may be performed off-line or on-line.
  • spectral sensitizing dye(s) may be added. It may further be useful to perform said essential step wherein pH is lowered more than once within the period after nucleation but before flocculation or ultrafiltration.
  • Compounds that are useful as crystal habit modifier of crystals rich in silver chloride include substances disclosed in EP-A's 0 481 133 and 0 532 801 and in US-A's 5,176,991; 5,176,992; 5,178,997; 5,178,998; 5,183,732; 5,185,239; 5,217,858; 5,221,602; 5,252,452; 5,264,337; 5,272,052; 5,298,385; 5,298,387; 5,298,388; 5,399,478; 5,405,738; 5,411,852 and 5,418,125.
  • the crystal habit growth modifier used has a chemical structure according to the formula Ia or Ib, wherein:
  • adenine is the most preferred, said modifier being representative as an example of the presented 2-hydro-aminoazines.
  • the said tabular grains even account for at least 90 % of the total projected area of all grains.
  • Said grains preferably have an average crystal diameter of from 0.3 to 3.0 ⁇ m, more preferred from 0.5 to 2.5 ⁇ m and still more preferred from 0.5 to 1.5 ⁇ m, for an average thickness of the tabular grain from at least 0.05 ⁇ m up to at most 0.50 ⁇ m, more preferred from 0.05 to 0.35 ⁇ m and still more preferred from 0.05 to 0.20 ⁇ m
  • Average aspect ratios of the tabular grains obtained after calculation from the ratio of diameter to thickness measured for each grain are in the range 2:1 to 100:1, more preferred from 5:1 to 50:1 and still more preferred from 5:1 to 20:1 or even from 8:1 to 20:1.
  • Crystal distributions wherein the said variation coefficient on sphere equivalent diameter (SED) of all grains is less than 0.25 and more preferably from 0.05 up to 0.15 are attained for the ⁇ 111 ⁇ tabular silver chlorobromoiodide or silver chloroiodide emulsions prepared according to the method of the present invention.
  • the determining step in the method of the present invention after the precipitation of silver chlor(oiod)ide or silver chlorobrom(oiod)ide nuclei in a dispersion medium having an initial pH value maintained between 6.0 and 9.0 during nucleation is the setting after the said nucleation step of pH to a value of lower than 6.0 for at least 30 seconds, and more preferably to a value of not more than 4.0, followed by resetting pH to the said initial pH.
  • lowering of pH is performed during physical ripening steps in between the growth steps.
  • said pH adjustment is performed during the first physical ripening step (after nucleation) before any growth step has been carried out.
  • said pH adjustment is carried out during precipitation or growth, thus while silver and halide salt solutions are running.
  • Preparation methods of tabular grains having a ⁇ 111 ⁇ crystal habit are normally characterized by the presence of a nucleation step, wherein preferably up to at most 10 % of the total amount of silver salt in a diluted medium having a concentration of at most 0.03 molar is consumed at a constant temperature between 35°C and 55°C, other temperature intervals however not being excluded. If iodide is present a concentration of not more than 0.5 % is preferred in the nucleation step in order to prevent formation of nuclei in an excessive amount. Although bromide may be present in the nucleation step if silver chlorobromoiodide crystals are prepared, its absence is preferred and chloride present therein in an amount of at least 99.5 % is commonly occurring.
  • One or more growth steps, with at least one physical ripening step inbetween, are normally following said nucleation step.
  • the growing volume in the reaction vessel leading to an increased dilution of emulsion crystals in the reaction vessel, may be held constant by removing excessive amounts of soluble alkaline nitrates and of water by means of dialysis and/or ultrafiltration.
  • growing the said nuclei is performed by double jet precipitation, wherein iodide salt solutions are optionally present in the said halide salt solutions essentially consisting of chloride salts and optionally of bromide salts characterized further by maintaining the said chloride salts in the reaction vessel at a constant concentration of less than 0.15 M.
  • nuclei are thus further grown by double jet precipitation, wherein the rest of the total amount of silver is consumed and wherein iodide salts are optionally present in halide salt solutions (normally as alkali iodide solution in an alkali chloride solution, wherein chloride salts are present in excessive amounts versus iodide salts) essentially consisting of chloride salts and optionally of bromide salts (if silver chlorobromoiodide crystals are prepared) and wherein a chloride ion concentration of less than 0.15 M is maintained.
  • halide salt solutions normally as alkali iodide solution in an alkali chloride solution, wherein chloride salts are present in excessive amounts versus iodide salts
  • bromide salts if silver chlorobromoiodide crystals are prepared
  • a ratio of gelatin, if used as protective hydrophilic colloid binder, to silver, expressed as an equivalent amount of silver nitrate, of about 5 is calculated, which is rather high. Said ratio, also called “gesi” decreases during the following growth steps to a value of about 0.3.
  • an increase of the temperature of the reaction vessel to about 70°C is normally performed during a time of about 20 minutes in order to hold said temperature at the same value during growth of the tabular grains.
  • pH remains at the same value of about 6.0 (wherein said expression about " takes into account that during running aqueous acidic silver nitrate solutions, pH will spontaneously decrease slightly up to e.g.
  • pAg further commonly decreases to a value between 6.5 and 7.0 or a corresponding value of about 135 mV versus a silver/silver chloride reference electrode.
  • the halide distribution in the tabular grains is homogeneous or heterogeneous over the whole crystal volume.
  • phases differing in silver halide composition are present over the crystal volume said crystal is said to have a core-shell structure. More than one shell can be present and between different phases it can be recommended to have a phase enriched in silver iodide by applying the so-called conversion technique during preparation.
  • At least one conversion step is performed, wherein converting the said emulsion grains is performed by adding inorganic iodide salts and/or organic iodide releasing compounds to the reaction vessel.
  • At least one conversion step is performed, wherein converting the said emulsion grains is performed by adding silver iodide microcrystals having an average crystal size of at most 0.05 ⁇ m
  • silver chlorobromoiodide or silver chloroiodide emulsions are thus prepared by converting the said emulsion grains so that the said emulsion comprises tabular grains having a variable iodide profile, in that the grains have been enriched in iodide at the crystal surface, said profile being characterized by the presence of iodide ions in the crystal volume in lower amounts than at the crystal surface of the said tabular grains and in that an amount of 50 to 100 mole % of the total amount of iodide ions is located at the surface of said tabular grains.
  • Iodide ions are therefore provided by using aqueous solutions of inorganic salts thereof as e.g. potassium iodide, sodium iodide or ammonium iodide as described in RD No. 39433, published January 1997, but as an alternative iodide ions provided by organic compounds releasing iodide ions are very useful as has e.g. been described in EP-A's 0 561 415, 0 563 701, 0 563 708, 0 649 052 and 0 651 284, in WO 96/13759 and in RD No. 39423, published January 1997.
  • iodide ions provided by organic agents releasing iodide ions are preferred, such as mono iodide acetic acid, mono iodide propionic acid, mono iodide ethanol and even hydrogels containing iodide ions, capable to generate iodide ions.
  • Generation of iodide ions is triggered in the preparation method by changing the pH value in the reaction vessel during or, preferably, after addition of the said organic agent releasing iodide ions, wherein this pH change is performed therein in such a way as required by the method of the present invention.
  • said tabular grains are enriched in iodide by adding silver iodide microcrystals having an average crystal size of up to at most 0.05 ⁇ m.
  • Generation of iodide ions is triggered therein by differences in solubility between large ⁇ 111 ⁇ tabular silver chlor(oiod)ide or silver chlorobrom(oiodid)ide crystals and such fine silver iodide microcrystals, a phenomenon that is well-known as "Ostwald ripening".
  • Combinations of inorganic and organic agents providing iodide ions may also be useful.
  • the presence of iodide ions thereby stabilizes the (111)-crystal faces: it has e.g. been established that the concentration of crystal habit modifier present at the surface of the tabular grains rich in silver chloride can be decreased to a considerable extent when iodide ions are present, as iodide ions, provided to the surface of the said grains, lead to preservation of a stable crystal habit.
  • Iodide ions can thus replace conventional crystal habit modifiers such as adenine, etc..
  • Other compounds as spectral sensitizers or stabilizers can also be used as suitable compounds replacing said crystal habit modifiers due to their crystal habit stabilizing action.
  • the tabular silver chlorobromoiodide emulsion crystals used according to the method of the present invention preferably have an amount of silver bromide of not more than 10 mole %, based on silver.
  • Bromide ions may be provided from at least one inorganic and/or organic agent providing bromide ions.
  • Emulsions comprising silver chlorobromoiodide or chloroiodide ⁇ 111 ⁇ tabular crystals may be built up so that an amount of 20 to 100 mole %, and even an amount of 50 to 100 mole % of the total amount of iodide ions is located at the surface of the said emulsion crystals as e.g. in EP-A 0 678 772 cited hereinbefore.
  • Iodide ions can be present in one or more shell regions, in form of zones wherein iodide ions are concentrated locally.
  • distributions of ⁇ 111 ⁇ silver halide crystals rich in chloride over the whole population of a silver halide emulsion are made homogeneous up to a variation coefficient on sphere equivalent diameter (SED) of all grains being lower than 0.30.
  • SED sphere equivalent diameter
  • photographic advantages of ⁇ 111 ⁇ tabular grains compared to normal globular grains are a high covering power at high forehardening levels, a high developability and higher sharpness thanks to a reduced degree of cross-over, especially in double side coated spectrally sensitized materials.
  • tabular grains those rich in silver chloride (as well as those rich in silver bromide), especially in early days of their development, had two important disadvantages which should be encountered being their high susceptibility to mechanical stress and their an unacceptable reddish-brown colour of developed silver if compared with the desired cold-black colour shown by more globular grains.
  • Tabular grains rich in silver chloride even show a worse image tone than those rich in bromide having comparable dimensions (thickness and aspect ratio) after processing in classical processing solutions used in the processing of classical radiological materials.
  • Reddish-brown colour of developed thinner ⁇ 111 ⁇ tabular grains prepared according to the method of the present invention can further be corrected by increasing the optical density in the red region of the visible spectrum by adding suitable dyes to the undercoat layer, to the emulsion layer and/or to the protective layer.
  • This non-image wise colour correction method has been disclosed in references as e.g. JP-A's 03 100 645; 01 029 838; 01 312 536; 03 103 846; 03 094 249; 03 255 435; 61 285 445; and the issued EP-A 271 309 and US-A 4,861,702. This however inevitably leads to an undesirable higher gross-fog of the photographic material.
  • a more suitable way consists in an image-wise colour correction.
  • multilayer silver halide photographic negative image type materials comprising on at least one side of a support a multilayer composition of at least two layers of negative image type silver halide emulsions adjacent to each other, wherein the emulsion layer closest to the said support comprises ⁇ 111 ⁇ silver chloroiodide or silver chlorobromoiodide tabular emulsion crystals prepared by the method of the present invention and wherein the adjacent layer(s) farther from the said support comprise(s) essentially cubic emulsion crystals selected from the group consisting of silver chloride, silver chlorobromide and silver bromide.
  • the halide composition of the said cubic emulsion crystals or of the said tabular emulsion crystals or both includes chloride. Coating of two or more layers however is not advantageous, neither economically, nor ecologically as coating of higher amounts of silver halide can be expected.
  • Tabular ⁇ 111 ⁇ grain emulsion grains prepared according to the method of the present invention may further be doped with whatever a dope as e.g. with group VIII metal ions like Rh 3+ , Ir 4+ , Ru 2+ and Co 2+ or with Cd 2+ , Zn 2+ or Pb 2+ or even with a mixture thereof.
  • group VIII metal ions like Rh 3+ , Ir 4+ , Ru 2+ and Co 2+ or with Cd 2+ , Zn 2+ or Pb 2+ or even with a mixture thereof.
  • Other suitable dopants used during precipitation or chemical ripening of said emulsion crystals may be e.g. Fe, Ni, Ru, Rh, Pd, Os, Pt, Hg, Tl and Au.
  • ruthenium, rhodium and iridium are preferred.
  • Combinations of one or more dopant(s) may be added, in the same or different preparation steps of the said ⁇ 111 ⁇ tabular silver chloroiodide or silver chlorobromoiodide crystals.
  • the said dopants can be divided homogeneously or heterogeneously over the total crystal volume. So in the core or in the shell or even at the crystal surface, as is e.g. the case when conversion techniques are applied, the said halide ions and/or the said dopants may be concentrated.
  • potassium hexachloroiridate(III) added during chemical ripening, are from 0.5 to 20 ⁇ mole per mole of silver and more preferred from 1 to 5 ⁇ mole per mole as has been described in EP-A 0 794 456 and US-A 5,712,081.
  • the most well-known and practically used hydrophilic colloidal binder is gelatin.
  • Gelatin as a dispersing medium 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 polymerizable 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.
  • modified natural products e.g. gelatin derivatives obtained by conversion of gelatin with alkylating or acylating agents, by grafting of polymerizable 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.
  • gelatin having a lower methionine content is often used in the preparation of tabular ⁇ 111 ⁇ silver halide crystals rich in chloride.
  • the most preferred gelatin used has a methionine content of from 1 to 60 ⁇ mole/g depending on each specific case. More preferably gelatin having a methionine content of from 1 to 50 ⁇ mole/g, and still more preferably amounts from 1 to 30 ⁇ mole/g (4400 p.p.m.) may be preferably used: according to US-A 4,713,323, oxidized gelatin is defined as a gelatin having a methionine content of less than 30 ⁇ mole/g.
  • a preparation method of tabular grain emulsions wherein in the grain growth process use is made of gelatin derivatives with chemically modified NH 2 -groups and wherein said gelatin has a specific methionine content has been described in e.g. EP-A 0 697 618. Oxidation of methionine reduces the complexing ablity of gelatin.
  • a preparation method of gelatin having a controlled methionine content is disclosed in US-A 5,412,075.
  • Another factor which may be important in the nucleation and/or grain growth mechanism of ⁇ 111 ⁇ tabular grains rich in chloride is the calcium content of gelatin used as a colloidal binder.
  • the calcium content is about 0.4 %, which corresponds with about 100 mmole/kg, measured at the end of the preparation process of inert gelatin.
  • Complex-bound calcium ions strongly decrease the electric potential carried by gelatin.
  • Substantially "calcium free gelatin” is thus defined as gelatin with a calcium content at a level below 40 ppm which corresponds with the analytical detection limit.
  • EP-A 0 809 135 a process has been disclosed for the preparation of a photographic silver halide emulsion comprising one or more precipitation steps in a reaction vessel, said emulsion comprising ⁇ 111 ⁇ tabular grains, containing at least 50 mole % of chloride, wherein at least 50 % of the total projected area of all grains is provided by said tabular grains, and wherein said tabular grains exhibit an average aspect ratio of at least 5, an average thickness of at most 0.5 ⁇ m, and an average diameter of at least 0.6 ⁇ m, characterized in that during said one or more precipitation steps a gelatin binder is present in said reaction vessel which is substantially free of calcium ions.
  • 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 and 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.
  • silica sols are required as colloidal binder commercially available such as the "Syton” silica sols (a trademarked product of Monsanto Inorganic Chemicals Div.), the "Ludex” silica sols (a trademarked product of du Pont de Nemours & Co., Inc.), the "Nalco” and “Nalcoag” silica sols (trademarked products of Nalco Chemical Co), the "Snowtex” silica sols of Nissan Kagaku K.K. and the "Kieselsol, Types 100, 200, 300, 500 and 600" (trademarked products of Bayer AG).
  • Particle sizes of the silica sol particles are in the range from 3 nm to 30 ⁇ m.
  • the smaller particles in the range from 3 nm to 0.3 ⁇ m, and still more preferable from 3 nm up to 7 nm are preferred as the covering degree that can be achieved will be higher and as the protective action of the colloidal silica will be more effective.
  • the precipitation reaction of the ⁇ 111 ⁇ tabular silver chloroiodide or silver chlorobromoiodide emulsion crystals proceeds in a dispersing medium wherein the ratio by weight of gelatin to an equivalent amount of silver nitrate is up to 0.35, unless colloidal silica is used in order to replace gelatin partially or totally. It is clear that this condition will be not fullfilled either when use is made in the reaction vessel, in part or integrally of a non-aqueous medium, of a non-aqueous solvent instead of water, as has been disclosed e.g. in US-A's 5,478,718 and 5,541,051.
  • the emulsion mixture is normally cooled to about 40°C, before or after adding a flocculate being a polymeric compound as e.g. polystyrene sulphonic acid, providing as a anionic polymer a behaviour depending on pH.
  • a flocculate being a polymeric compound as e.g. polystyrene sulphonic acid, providing as a anionic polymer a behaviour depending on pH.
  • a flocculate being a polymeric compound as e.g. polystyrene sulphonic acid, providing as a anionic polymer a behaviour depending on pH.
  • a flocculate being a polymeric compound as e.g. polystyrene sulphonic acid, providing as a anionic polymer a behaviour depending on pH.
  • the pH of the said dispersing medium is adjusted with an acid to a value in order to get a qualitatively good flocculate.
  • Said flocculate may become decanted and
  • adenine to an allowable residual amount preferably at most 0.3 mg/g of gelatin
  • an ultrafiltration washing procedure as disclosed e.g. in Research Disclosure, Vol. 102, Oct. 1972, Item 10208, Research Disclosure Vol. 131, March, Item 13122 and Mignot US-A 4,334,012.
  • Said ultrafiltration technique may be applied on-line during the whole precipitation, in order to reduce the increasing amount of water, thus avoiding dilution of the reaction vessel and increasing amounts of soluble salts like the mainly occurring potassium nitrate. Examples thereof have been described e.g. in EP-A 0 577 886.
  • ultrafiltration may be proceeded in order to get the desired pH and pAg values, required when performing further treatment steps as e.g. addition to coating solutions.
  • Any washing step may further be performed by means of halide containing water, preferably water containing chloride ions.
  • Redispersion may further be performed by addition of extra hydrophilic colloid.
  • values of gesi and/or sisi may be enhanced up to values desired in order to prepare stable coating solutions as will be clear from the description following hereinafter.
  • a suitable mixture of spectral sensitizers that is applied is the anhydro-5,5'-dichloro-3,3'-bis(n-sulphobutyl)-9-ethyl oxacarbocyanine or anhydro-5,5'-dichloro-3,3'-bis(n-sulpho-propyl)-9-ethyloxacarbocyanine compound spectrally sensitizing ⁇ 111 ⁇ tabular grains prepared according to the method of the present invention apart or together with the anhydro-5,5'-dicyano-1,1'-diethyl-3,3'-di(2-acetoxyethyl)-ethyl-imidacarbocyanine compound.
  • spectral sensitization traditionally follows the completion of chemical sensitization. However in connection with tabular grains, it is highly contemplated that spectral sensitization occurs simultaneously with or even precedes completely the chemical sensitization step.
  • spectral sensitizing dye it can be advantageous to add an amount of a spectral sensitizing dye to the emulsion crystals just before cooling of the dispersion at the end of the growth stage, but in principle the addition of said dye may be performed at any stage of the precipitation, during or after redispersing or before, during or after chemical ripening. The addition can further be performed in one or more portions. So in US-A 5,286,621 it has been shown that spectral sensitizer is added in amounts ranging from 10 -5 to 5 x 10 -3 moles per mole of silver halide as a whole after completion of the precipitation or in several fractions during and after precipitation.
  • dyes absorbing radiation in the red or infrared wavelength region of the wavelength spectrum may be added, said dyes being selected from the group consisting of di-, tri-, tetra-, penta- and heptamethine cyanines and merocyanines, rhodacyanines and polynuclear merocyanines as e.g. the dyes absorbing in the infrared region, are described e.g. in JP-A 02 071 257 and in Research Disclosure 00 289 052, May 1988, p. 301-303 and the red-light absorbing heptamethines as in EP-A 0 757 285, and rhodacyanines as in EP-A 0 473 209.
  • Dyes absorbing in the blue wavelength region of the visible spectrum for use as spectral sensitizers for tabular silver halide grains rich in chloride have been described in JP-A 01-196031 and in US-A's 4,494,212; 4,952,491 and 5,376,523.
  • spectral sensitizers may be used as well as mixtures of emulsions being the same or different, wherein each part may be spectrally sensitized with another spectral sensitizer or with another combination of spectral sensitizers.
  • Spectral sensitizers having asymmetrical heterocycles may be useful with respect to improvements in residual colouration after processing.
  • Suitable supersensitizers are e.g. heterocyclic mercapto compounds containing at least one electronegative substituent as described e.g. in US-A 3,457,078, nitrogen-containing heterocyclic ring-substituted aminostilbene compounds as described e.g. in US-A 2,933,390 and US-A 3,635,721, aromatic organic acid/formaldehyde condensation products as described e.g. in US-A 3,743,510, cadmium salts, and azaindene compounds.
  • heterocyclic mercapto compounds containing at least one electronegative substituent as described e.g. in US-A 3,457,078, nitrogen-containing heterocyclic ring-substituted aminostilbene compounds as described e.g. in US-A 2,933,390 and US-A 3,635,721, aromatic organic acid/formaldehyde condensation products as described e.g. in US-A 3,743,510, cadmium salts, and azainden
  • Spectral sensitizers may be added partially before, partially after or integrally after chemical sensitization with a total amount needed to reach the optimal coverage degree which especially as a consequence of the presence of the large specific surface of ⁇ 111 ⁇ tabular grains may differ from amounts added to cubic grains with a factor of about 2 or 3.
  • the said spectral sensitizers are chosen as a function of the radiation source used e.g. as a function of the light emitted by luminescent phosphors coated in phosphor layers of intensifying screens brought into contact with single-side or double-side coated film materials during X-ray exposure, wherein emulsions comprising silver chlorobromoiodide or silver chloroiodide tabular grains with at least 75 mole % of chloride and from 0.1 up to 3 mole % of iodide, based on silver, further having ⁇ 111 ⁇ crystal faces, an average aspect ratio of at least 2:1, with at least 50 % of the total projected area of all grains being provided by said tabular grains and with a variation coefficient on sphere equivalent diameter (SED) of all grains being lower than 0.30, prepared according to the method of the present invention are coated.
  • SED variation coefficient on sphere equivalent diameter
  • Silver halide emulsion grains after precipitation and redispersion are called “primitive” or “unripened” as long as no chemical sensitizer(s) is (are) added. It is a common method to add chemical sensitizers after redispersion and in the case of tabular grains during and/or after spectral sensitization as already suggested hereinbefore.
  • the surface of the silver halide grains rich in chloride may be treated with slightly oxidizing compounds as e.g. toluene thiosulphonic acid and/or corresponding salts thereof in order to reduce small silver specks to grow to fog centers in an uncontrolled manner.
  • thiosulphate, thiocyanate, thioureas selenium e.g. selenosulphate, selenocyanate, selenoureas; tellurium e.g. tellurosulphate, tellurocyanate, telluroureas; sulphites, mercapto compounds, rhodamines etc..
  • the emulsions can be sensitized also by means of gold-sulphur ripeners, gold-selenium ripeners, gold-sulphur-selenium ripeners, or by means of reductors e.g.
  • tin compounds as described in GB-A 789,823, amines, hydrazine derivatives, formamidine-sulphinic acids, and silane compounds although care should be taken in order to prevent the emulsion from fog formation in an uncontrollable way.
  • the unstable selenium sensitizers there are isoselenocyanates (e.g., aliphatic isoselencyanates such as allylisoselenosyanate), selenoureas, selenoketones, selenoamides, selenocarboxylic acids (e.g.
  • 2-selenopropionic acid, and 2-selenobutyric acid selenoesters diacylselenides (e.g. bis(3-chloro-2,6-dimethoxybenzoyl)selenide), selenophosphates, phosphineselenides, preferably triphenylphosphorselenide and colloidal elemental selenium.
  • diacylselenides e.g. bis(3-chloro-2,6-dimethoxybenzoyl)selenide
  • selenophosphates e.g. bis(3-chloro-2,6-dimethoxybenzoyl)selenide
  • phosphineselenides preferably triphenylphosphorselenide and colloidal elemental selenium.
  • unstable type selenium compounds shown above are however not limited thereto in any way.
  • unstable type selenium compounds are sensitizers for silver halide emulsions rich in silver chloride, the structure of the compounds is not so important if selenium is unstable and it is generally understood that the organic moiety of a selenium sensitizer molecule has no role except that it carries selenium and makes the selenium exist in a silver halide emulsion in an unstable form.
  • Preferred chemical sensitizers are those generating silver selenide in an emulsion comprising the ⁇ 111 ⁇ tabular grains prepared according to the present invention at a temperature of from 45°C up to 70°C and at a potential difference between a silver electrode and a saturated silver /silver chloride electrode of from 100 up to 200 mV only as set forth in EP-Application No. 97200590, filed March 1, 1997.
  • Patent literature with respect to the use of selenium sensitizers for chemical ripening of silver halide grains rich in silver chloride can be found in EP-A's 0 443 453, 0 454 278; 0 458 278; 0 513 748; 0 590 593; 0 661 589 and 0 718 674 and in US-A's 4,810,626; 5,306,613 and 5,348,850, wherein said selenium sensitizers are normally used together with other sensitizers as at least gold and optionally sulphur.
  • Especially useful labile compounds providing sulphur are e.g. tetramethyl-thiodithioacetic acid diamide and dimethylamino-dithiomercaptane.
  • suitable as a binder material can be added at a later stage of the emulsion preparation e.g. after washing, to establish optimal coating conditions and/or to establish the required thickness of the coated emulsion layer.
  • a 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.
  • any thickening agent Prior to coating 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 characteris-tics of the silver halide light-sensitive 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. US-A 3,167,410; Belgian Patent No. 558.143 and JP-A's 53-18687 and 58-36768. Negative effects on physical stability possibly resulting from the addition of polymeric compounds can be avoided by exclusion of those compounds and by restricting extra additions of colloidal silica.
  • hydrophilic colloidal layer compositions on a support by slide-hopper or curtain-coating techniques, wherein said compositions have gelatin in low amounts in order to provide a ratio by weight of gelatin to silver halide expressed as an equivalent amount of silver nitrate in the range from 0.05 to 0.4
  • thickening agents composed of synthetic clay and anionic macromolecular polyelectrolytes wherein said synthetic clay is present in an amount of at least 85 % by weight versus the total amount of thickening agents are recommended as has been disclosed in EP-A 0 813 105.
  • a light-sensitive silver halide photographic material is disclosed in EP-Application No. 96202601, filed September 18, 1996, wherein said material comprises a support and one or more hydrophilic colloidal silver halide emulsion layers having silver halide crystals with colloidal silica as a protective colloid the said layer(s) having a gesi, defined as ratio by weight of gelatin to silver, in the range from 0 to less than 0.05 and a sisi, defined as ratio by weight of silica to silver, in the range from 0.01 to less than 0.10, wherein said weight of silver in the calculation of gesi and sisi is expressed as an equivalent amount of silver nitrate.
  • Photographic material having thin emulsion layers e.g. layers with a layer thickness of less than 5 ⁇ m, containing less than 5 g of gelatin, preferably about 3 and more preferably about 2 g/m 2 offer the advantage that besides rapid processing applicability and the rapid drying of the wet processed material an improvement in sharpness is observed.
  • drying characteristics in the processor are mainly determined by the water absorption of the hydrophilic layers of the photographic material, and since the water absorption is directly proportional to the gelatin content of the layers and inversely proportional to the amount of hardener, added to the layer, its composition is optimised with a low gelatin content and a high hardening degree in order to allow hardener free processing within a total processing time cycle from 30 to at most 50 seconds dry-to-dry.
  • a total amount of gelatin of less than 3 g/m 2 per side is, if possible, present for the desired application.
  • 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 rich in chloride 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, chromium salts e.g. chromium acetate and chromium alum, aldehydes e.g.
  • N-methylol compounds e.g. dimethylolurea and methyloldimethylhydantoin
  • dioxan derivatives e.g. 2,3-dihydroxydioxan
  • active vinyl compounds e.g. 1,3,5-triacryloylhexahydro-s-triazine
  • active halogen compounds e.g. 2,4-dichloro-6-hydroxy-s-triazine
  • mucohalogenic acids e.g. mucochloric acid and mucophenoxy-chloric acid.
  • the binders can also be hardened with fast-reacting hardeners such as carbamoylpyridinium salts.
  • 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).
  • Other preferred hardening agents may specifically be bis-vinyl-sulphonyl-methyl-ether (BVSME) or ethylene-bis-vinylsulphone.
  • Materials used in image-forming processes commonly have a hardening degree corresponding with a water absorption of the unexposed material of less than 4 g/m 2 /g gelatin, and more preferably of less than 3 g/m 2 /g gelatin after immersion in demineralized water at 25°C during 3 minutes.
  • Another method to express the same may consist in determination of the swelling degree of the layers of the material: said swelling degree is preferably not exceeding 200% and even more preferably not more than 150 % as can be measured from thickness ratios of the layers of the material before and after immersion in demineralized water as described hereinbefore.
  • sensitometric properties as e.g. sensitivity (also called speed), gradation (also called contrast and specified in the the toe, the linear part and/or the shoulder of the characteristic curve), fog and maximum density in preferred rapid processing conditions that are expected to be particularly advantageous for emulsions rich in silver chloride having gelatin, derivatives and/or substitutes thereof as e.g. colloidal silica etc., discussed hereinbefore.
  • sensitivity also called speed
  • gradation also called contrast and specified in the the toe, the linear part and/or the shoulder of the characteristic curve
  • fog and maximum density in preferred rapid processing conditions that are expected to be particularly advantageous for emulsions rich in silver chloride having gelatin, derivatives and/or substitutes thereof as e.g. colloidal silica etc., discussed hereinbefore.
  • 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-mercaptotetrazole, 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, chloro
  • the photographic element may further comprise various kinds of coating physical property modifying addenda as described in RD N° 36544 (1994), Chapter IX and RD N° 38957 (1996), Chapter IX, wherein coating aids, plasticizers and lubricants, antistats and matting agents have been described.
  • Development acceleration can be accomplished by incorporating in emulsion layer(s) or adjacent layers various compounds, preferably polyalkylene derivatives having a molecular weight of at least 400 such as those described in e.g. US-A's 3,038,805; 4,038,075 and 4,292,400 as well as in EP-A's 0 634 688 and 0 674 215.
  • the photographic element 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. 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, ⁇ - ⁇ -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,
  • Suitable 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 in US-A 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 RD N° 38957, Chapter 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.
  • a material with a single or a duplitized emulsion layer coated on one (single-side coated) or both sides (double-side coated) of the support preferably contains at least one silver chloroiodide or silver chlorobromoiodide emulsion prepared according to the method of the present invention disclosed hereinbefore.
  • a mixture of two or more emulsions from crystals rich in chloride having the same or different crystal sizes, the same or a different crystal habit, a different or the same chemical ripening treatment and/or a different or the same coverage degree with one or more spectral sensitisers being different from each other or the same, as those described hereinbefore may be added to at least one light-sensitive emulsion layer.
  • Single-side coated materials have e.g. been described in US-A 5,449,599, in EP-A's 0 610 608 and 0 712 036 and in EP-A 0 794 456 and the corresponding US-A 5,712,081.
  • Double-side coated materials have e.g. been described in US-A 5,397,687 and in EP-A's 0 678 772, 0 754 971 and 0 754 972.
  • the photographic material may contain several light-insensitive layers at the side of the support carrying said light-sensitive emulsion layer(s), e.g. a protective antistress layer which can be split up into two layers, one of them being an underlying interlayer or an outermost afterlayer coated or sprayed on top of the "basic" protective antistress layer, one or more subbing layers, one or more intermediate layers e.g. filter layers and even an afterlayer containing e.g. hardening agent(s), antistatic agent(s), filter dyes for safety-light purposes etc.
  • a protective antistress layer which can be split up into two layers, one of them being an underlying interlayer or an outermost afterlayer coated or sprayed on top of the "basic" protective antistress layer
  • subbing layers one or more intermediate layers e.g. filter layers and even an afterlayer containing e.g. hardening agent(s), antistatic agent(s), filter dyes for safety-light purposes etc.
  • Protective antistress layers preferably contain coating aids and coating physical property modifying addenda mentioned in RD's Nos. 36544 and 38957, published September 1994 and 1996 respectively, Chapter IX. Antistatic properties are especially preferred in order to prevent blackening after processing in form of sparks etc. due to abrupt decharging of electrostatic charges during production and/or handling before exposure and/or processing. It is highly preferred to add antistatic agents to the protective antistress layer or to an afterlayer coated thereupon as has been described e.g. in EP-A's 0 534 006, 0 644 454 and 0 644 456 and US-A's 4,670,374 and 4,670,376. Particularly preferred antistatic agents showing permanent antistatic character, retention i.a.
  • Backing layers applied to a material having at least one emulsion layer at one side of a light-sensitive silver halide material having emulsion crystals rich in chloride used in the image-forming systems essentially contain as ingredients hydrophilic colloids, one or more antihalation dye(s), matting agent(s), surfactant(s), antistatic agent(s), lubricant(s) and hardening agent(s), said ingredients being same as discussed hereinbefore.
  • Amounts of hydrophilic colloids may be chosen in order to prevent curl of the single side emulsion coated material, such as in US-A 5,155,013.
  • non-swelling hydrophobic polymers can be used in the backing layer as has e.g. been described in US-A 5,326,686. Further measures to prevent curling have been disclosed e.g. in JP-A's 02-24645; 02-85847 and 02-87138.
  • the support of the photographic materials comprising silver halide emulsion having crystals rich in chloride, used for X-ray imaging may be a transparent resin, preferably a blue coloured polyester support like polyethylene terephthalate.
  • the thickness of such organic resin film is preferably about 175 ⁇ m.
  • Other hydrophobic resin supports are well known to those skilled in the art and are made e.g. of polystyrene, polyvinyl chloride, polycarbonate and polyethylene naphthalate.
  • the support is further provided with a substrate layer at both sides to have good adhesion properties between the adjacent layers and said support: one or more subbing layers known to those skilled in the art for adhering thereto a hydrophilic colloid layer may be present.
  • Suitable subbing layers for polyethylene terephthalate supports are described e.g. in US-A's 3,397,988, 3,649,336, 4,123,278 and 4,478,907.
  • a preferred layer arrangement wherein a subbing layer composition comprising as a latex copolymer vinylidene chloride, methylacrylate and itaconic acid has been covered with hydrophilic layers being at least one gelatinous dye containing layer comprising one or more dyes, at least one silver halide emulsion layer, at least one protective antistress layer, and optionally an afterlayer has been described in EP-A 0 752 617.
  • said hydrophilic layers have a swelling ratio of not more than 200 % and in said hydrophilic layers are coated simultaneously by the slide-hopper coating or by the slide-hopper curtain coating technique. Further information on suitable supports can be found in RD's Nos. 36544 and 38957, Chapter XV, published September 1994 and 1996 respectively.
  • penetrating radiation which is high energy radiation belonging to the class of X-rays, ⁇ -rays and high energy elementary particle radiation, e.g. ⁇ -rays, electron beam or neutron radiation.
  • phosphors For the conversion of penetrating radiation into visible light and/or ultraviolet radiation luminescent substances are used called phosphors.
  • the energy, expressed in kVp depends on the specific application, as e.g. for the detection of bone, wherein radiation energy of about 80 kVp is used or for soft tissue as in breast imaging wherein no more than 35 kVp is permitted.
  • a metal filter usually a lead filter, can be used in combination with the photographic film.
  • much higher energies are used of e.g. 235 kVp.
  • Light emitted imagewise by intensifying screens as in medical diagnosis irradiates a contacting photographic silver halide emulsion layer film which after exposure is developed to form therein a silver image in conformity with the X-ray image.
  • the X-ray film comprises a transparent film support double-side coated with a silver halide emulsion layer. During the X-ray irradiation said film is arranged in a cassette between two X-ray conversion screens each of them making contact with their corresponding silver halide emulsion layer.
  • An autoradiograph is a photographic record formed through the intermediary of penetrating radiation emitted by radioactive material contained in an object, e.g. microtome cut for biochemical research.
  • Phosphors suitable for use in the conventional radiographic system must have a high prompt emission on X-ray irradiation and low after-glow in favour of image-sharpness.
  • the increased thickness itself can give rise to increased unsharpness of the emitted light when the refractive indices of phosphor binder and binder of the protective coating differ but also the presence of the particles themselves having different refractive index compared with that of the binder of the protective coating.
  • the luminescent article disclosed therein comprises a self-supporting or supported layer of phosphor particles dispersed in a resin binder having applied thereto a protective coating having an embossed structure, more particularly a protective coating having a layer thickness d comprised between 1 and 50 ⁇ m and having an embossed surface roughness R z so that the ratio between roughness R z and thickness d is at least 0.35.
  • the embossed protective layer can be provided on the phosphor layer in order to protect it against mechanical and chemical damage by the steps of (1) coating onto said phosphor containing layer a liquid radiation-curable composition having at the coating temperature a viscosity of at least 450 mPa.s, measured with a Hoeppler viscometer,that does not penetrate for a substantial degree into the phosphor containing layer, (2) providing an embossed structure to the coating, and (3) curing said coating by radiation.
  • the type of binder and the high volume ratio of phosphor to binder it is possible to obtain thin phosphor coatings offering not only high resolution but also high sensitivity without the need for increasing the packing density by compressing in order to reduce the voids as defined in EP-A 0 393 662 to a value of not less than 70%. Moreover the phosphor layer retains high protection against mechanical damage and thus high ease of manipulation.
  • a practically useful binder medium for the phosphor particles has further been disclosed in WO94000530.
  • the binding medium substantially consists of one or more hydrogenated styrene-diene block copolymers, having a saturated rubber block, as rubbery and/or elastomeric polymers.
  • the polymer can be represented by the formula A-B-A (tri-block) or by the formula A-B (di-block), wherein A represents styrene and B represents the hydrogenated diene block e.g. ethylene-butylene or ethylene-propylene.
  • an X-ray phosphor screen comprising a support and a layer which comprises a mixture of phosphors essentially consisting of (1) a monoclinic M' structure yttrium tantalate, niobate or tantalate-niobate phosphor, and (2) a rare earth activated alkaline earth fluorohalide phosphor and which may comprise one or more dyes characterized in that the dyes (if any) have a maximum absorption in the wavelength region between 410 and 500 nm and an extinction at said wavelength of maximum absorption of at least twice that at any wavelength below 410 nm and that the amount of said dye(s), the ratio by weight of said phosphors characterizing the phosphor mixture, the phosphor coverage, and the reflectance of the support are selected in such a way that a synergystic effect is obtained between screen speed and sharpness for each
  • Screen/film combinations may be symmetric or asymmetric: this means that screens differing in speed and/or radiation emitted therefrom are differing and/or that there is a difference in speed and/or contrast and/or spectral sensitivity at both sides of the film support.
  • a symmetric combination for chest imaging is disclosed in EP-A 0 661 592 and in US-A 5,380,636 wherein speed differences of duplitized layers are at least 0.3 and 0.5 log E, and wherein said layers are spectrally sensitized to the same and to different regions of the electromagnetic spectrum respectively.
  • Asymmetric combinations can be found in US-A 5,238,795 and in EP-A 0 449 101.
  • Green light-emitting screen-film systems having cross-over exposure of at most 15 %, absorbing X-rays of 80 kVp for at least 25 % and offering a CFT of 0.79 and 0.36 at 1 and 3 cycles/mm have been described in US-A's 5,460,916 and 5,462,832.
  • duplitized emulsions differing in photographic speed by at least 0.15 log E a reduction in cross-over exposure in double side coated materials can be obtained.
  • Cross-over reductions of less than 5 % or at most 15 %, depending on the optical density, have been described in US-A 5,354,648 and USH 0001105 for asymmetric duplitized film materials.
  • Pentamethine oxonol dyes may be helpful in order to reduce cross-over to less than 10 % in such film-screen combination as has been described in US-A 5,252,443.
  • UV-absorbing methine compounds may be even admixed in the polyester support or in an intermediate layer between the subbing layer and the emulsion layer closest to the support as has been disclosed in WO's 93005443 and 93005444.
  • a coated silver amount expressed as an equivalent amount of silver nitrate is preferably from 2 to 6 g/m 2 , and more preferably from 3 to 5 g/m 2 as in EP-A 0 794 456 and the correspon,ding US-A 5,712,081.
  • These low amounts of silver coated permit remarkably shorter total processing cycles as the well-known 90 seconds cycle: even processing times from 30 up to 50 seconds become available.
  • a more favourable situation is attained from the viewpoint of ecology as less waste is produced in the processing of films having been coated from low amounts of silver: less developing and fixing solutions are used and lower replenishment amounts will be required.
  • an automatically operating apparatus is used provided with a system for automatic replenishment of the processing solutions.
  • the processing dry-to-dry within a short processing time of from 30 to less than 50 seconds of materials coated from low amounts of silver is made possible by the steps of
  • a normally used configuration in the processing apparatus shows the following consecutive tank units corresponding with, as consecutive solutions: developer-fixer-rinse water.
  • developer-fixer-rinse water As consecutive solutions the sequence developer-fixer-fixer-rinse water-rinse water is preferred.
  • One washing step between developing and fixation and one at the end before drying may also be present. More details can be found in EP-Application No. 96203728, filed December 30, 1996.
  • Emulsion A (comparative example) (AgCl 98.9 I 1.1 silver chloroiodide tabular grain emulsion) :
  • a nucleation step was performed by introducing solution A1 and solution B1 simultaneously in dispersion medium C, at a flow rate of 45 ml/min for both of them during 40 seconds. During a physical ripening time of 20 minutes, the temperature was increased to 70 °C.
  • a growth step was performed during a time of 28 minutes and 50 seconds by introducing a double jet solution A1 at an initial flow rate of 5 ml/min, said flow rate being immediately linearly increased to a flow rate of 13.7 ml/min, together with a solution B1 at a flow rate in order to maintain a constant potential of + 115 mV measured by a silver electrode versus a Ag/AgCl sat Ingold reference electrode.
  • solution A1 was introduced in a time interval of 16 minutes at a constant flow rate of 5 ml/min in order to get a potential value of + 135 mV.
  • Fig. 2 the silver chloriodide distribution is given of the emulsion as obtained from reduction of silver halide grains, thus representing the abundance of equivalent volume diameters (EVD) calculated from spheres representing the same volume of the reduced silver halide (tabular or non-tabular) grain. From this EVD distribution a variation coefficient of 0.38 was calculated.
  • EVD equivalent volume diameters
  • an amount of inert gelatin was added in order to adjust the ratio by weight of gelatin to silver halide (expressed as silver nitrate) to a value of 0.4.
  • the emulsion was containing an amount of silver chloroiodide of 215 g per kg, expressed as an equivalent amount of silver nitrate.
  • Emulsions B, C and D were prepared in the same way as emulsion A. During this particular step the pH was adjusted to a lower value being
  • Emulsion Time at pH 4.0 during step of pAg adjustment
  • Flow Rate of A1 during step of pAg adjustment mean thickness ( ⁇ m) variation coefficient on EVD A(comp.) - 5 ml/min. 0.13 0.38
  • Emulsion G shows the possibility to carry out the pH adjustment during the first physical ripening step before any growth step has been carried out.
EP98200706A 1997-03-19 1998-03-06 Verfahren zur Herstellung von tafelförmigen (111)-Silberchloro(bromo)jodikristallen Withdrawn EP0866362A1 (de)

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EP98200706A Withdrawn EP0866362A1 (de) 1997-03-19 1998-03-06 Verfahren zur Herstellung von tafelförmigen (111)-Silberchloro(bromo)jodikristallen

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Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5176991A (en) * 1992-01-27 1993-01-05 Eastman Kodak Company Process of preparing for photographic use high chloride tabular grain emulsion
US5183732A (en) * 1991-09-20 1993-02-02 Eastman Kodak Company Process for the preparation of high chloride tabular grain emulsions (V)

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5183732A (en) * 1991-09-20 1993-02-02 Eastman Kodak Company Process for the preparation of high chloride tabular grain emulsions (V)
US5176991A (en) * 1992-01-27 1993-01-05 Eastman Kodak Company Process of preparing for photographic use high chloride tabular grain emulsion

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