EP0964300B1 - Thermographisches Schwarz-Weiss-Aufzeichnungsmaterial mit verbessertem Bildton - Google Patents

Thermographisches Schwarz-Weiss-Aufzeichnungsmaterial mit verbessertem Bildton Download PDF

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Publication number
EP0964300B1
EP0964300B1 EP19990201624 EP99201624A EP0964300B1 EP 0964300 B1 EP0964300 B1 EP 0964300B1 EP 19990201624 EP19990201624 EP 19990201624 EP 99201624 A EP99201624 A EP 99201624A EP 0964300 B1 EP0964300 B1 EP 0964300B1
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EP
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Prior art keywords
silver
recording material
thermographic recording
organic
silver salt
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EP19990201624
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English (en)
French (fr)
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EP0964300A1 (de
Inventor
Geert Defieuw
Johan Loccufier
Yvan Hoogmartens
Ingrid Geuens
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Agfa Gevaert NV
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Agfa Gevaert NV
Agfa Gevaert AG
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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
    • G03C1/494—Silver salt compositions other than silver halide emulsions; Photothermographic systems ; Thermographic systems using noble metal compounds
    • G03C1/498—Photothermographic systems, e.g. dry silver
    • G03C1/4989—Photothermographic systems, e.g. dry silver characterised by a thermal imaging step, with or without exposure to light, e.g. with a thermal head, using a laser
    • 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
    • G03C1/494—Silver salt compositions other than silver halide emulsions; Photothermographic systems ; Thermographic systems using noble metal compounds
    • G03C1/498—Photothermographic systems, e.g. dry silver
    • G03C1/49809—Organic silver compounds
    • 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
    • G03C2200/42—Mixtures in general

Definitions

  • the present invention relates to thermographic recording materials whose prints have improved image tone.
  • Thermal imaging or thermography is a recording process wherein images are generated by the use of thermal energy.
  • direct thermal thermography a visible image pattern is formed by image-wise heating of a recording material containing matter that by chemical or physical process changes colour or optical density.
  • Such recording materials become photothermographic upon incorporating a photosensitive agent which after exposure to UV, visible or IR light is capable of catalyzing or participating in a thermographic process bringing about changes in colour or optical density.
  • DE-OS 27 21 828 discloses a thermally developable light-sensitive material, consisting of a support, which contains thereon or in one or more layers at least (a) an organic silver salt, (b) a photocatalyst and (c) a reducing agent, wherein the organic silver salt (a) contains at least a silver salt with an uneven number of 21 or more carbon atoms; and examples with mixtures of two and three organic silver salts of monocarboxylic acids precipitated together, but all with 20 are more carbon atoms.
  • US-P 5,677,121 discloses a heat-developablesilver halide infrared ray-sensitive material comprising a support having on one side of the support an emulsion layer containing a binder, a nonsensitive silver salt, a reducing agent for silver ion and silver halide grains spectrally sensitized at a wavelength within the region of from 750 to 1400nm, wherein the nonsensitive silver salt comprises a mixture of silver salts of at least three organic carboxylic acids, one of the acids is behenic acid, and the content of the behenic acid in the acids is from not less than 35 to less than 90 mol %.
  • thermographic recording materials are subjected to image-wise heating whereas photothermographic materials are subjected to image-wise exposure and overall heating and much stronger reducing agents are used in thermographic recording materials than in photothermographic recording materials.
  • thermographic recording materials are heated for much shorter times, typically 10 to 20 ms, during thermal development in thermographic printing than photothermographic recording materials, for which 10s is an average heating time. Such shorter heating times make it difficult to obtain neutral image tones.
  • EP-A 730 196 discloses a heat-sensitive recording material suited for use in direct thermal imaging and having image-stabilization properties which material contains in a binder on a support (i) a substantially light-insensitive organic silver salt capable of thermally activated reduction to silver in thermal working relationship with (ii) at least one reducing agent capable of reducing the substantially light-insensitive organic silver salt when thermally activated, characterized in that the recording material contains in admixture with the reducing agent(s) at least one colourless photo-oxidizing substance that on exposure to ultraviolet radiation yields free radicals capable of inactivating the reducing agent(s) by oxidation, thereby rendering the reducing agent(s) incapable of reducing the organic silver salt to silver.
  • the organic silver salt is silver palmitate, silver stearate or silver behenate or mixtures thereof.
  • the efficacy of such physical mixtures is not exemplified. Physical mixtures in which each component forms a separate phase cannot be equated with mixed crystals in which the components together form a single phase.
  • thermographic recording materials exhibit an insufficiently neutral image colour. This is particularly important for thermographic recording materials for medical diagnostic applications for which image tone requirements are particularly severe, particularly at low optical densities.
  • Prior art thermographic recording materials coated from solvent exhibit image tone closer to these requirements than those coated from aqueous media, although the latter are producible using much more environmentally friendly coating processes.
  • thermographic recording materials coated from solvent or aqueous media and comprising mixed crystals of substantially light insensitive organic silver salts exhibit a more neutral image tone than physical mixtures thereof.
  • thermosensitive black and white thermographic recording material having a support and a thermosensitive element containing a substantially light-insensitive organic silver salt, an organic reducing agent therefor in thermal working relationship therewith and a binder, wherein the thermosensitive element contains substantially light-insensitive mixed crystals of two or more silver salts of organic carboxylic acids with one or more carboxylic acid groups.
  • a recording process is further provided according to the present invention comprising the steps of: (i) bringing an outermost layer of the above-mentioned thermographic recording material in proximity with a heat source; and (ii) applying heat from the heat source imagewise to the recording material while maintaining proximity to the heat source to produce an image; and (iii) removing the recording material from the heat source.
  • the heat source is a thermal head with a thin film thermal head being particularly preferred.
  • substantially light-insensitive is meant not intentionally light sensitive.
  • substantially solvent-free aqueous medium is meant that solvent, if present, is present in amounts below 10% by volume of the aqueous medium.
  • the substantially light-insensitive mixed crystals of two or more silver salts of organic carboxylic acids with one or more carboxylic acid groups of the present invention are produced by slow addition, preferably metered, of a soluble silver salt to a solution or dispersion of a mixture of acids, or their salts, whose silver salts are capable of forming mixed crystals.
  • Mixed crystals of the present invention have the X-ray diffraction pattern of the organic silver salt which is present in the greatest quantity, although the peaks may be slightly shifted compared with the X-ray diffraction spectrum of pure crystals of the organic silver salt present in the greatest quantity.
  • the silver salts of organic carboxylic acids with one or more carboxylic acid groups are present in the mixed crystals of the mixed crystals used in the thermographic recording material of the present invention in molar concentrations of at least 5 mole% and particularly preferably with molar concentrations of at least 8 mole%.
  • At least one of the two or more organic silver salts in the mixed crystals used in the thermographic recording material of the present invention is a silver salt of an aliphatic monocarboxylic acid with at least 12 carbon atoms, e.g. silver laurate, silver palmitate, silver stearate, silver hydroxystearate, silver behenate, silver arichidate and silver salts of modified aliphatic carboxylic acids with thioether group as described e.g. in GB-P 1,111,492.
  • Particularly preferred silver salts of aliphatic carboxylic acids are selected from the group consisting silver stearate, silver arichidate and silver behenate.
  • the total molar concentration of silver salts of aliphatic monocarboxylic acids in the mixed crystals used in the thermographic recording materials of the present invention is at least 40 per cent and particularly preferably at least 51% per cent.
  • the mixed crystals consist of two or more silver salts of aliphatic monocarboxylic acids with at least 12 carbon atoms, with three or more silver salts of aliphatic monocarboxylic acids with at least 12 carbon atoms being preferred and mixed crystals consisting of a mixture of silver stearate, silver behenate and silver arichidate being particularly preferred.
  • the mixed crystals consisting of two or more silver salts of aliphatic monocarboxylic acids with at least 12 carbon atoms may be used on their own or in admixture with one or more organic silver salt in the thermosensitive element.
  • one of the two or more organic silver salts is a silver salt of an aliphatic dicarboxylic acid.
  • Preferred aliphatic dicarboxylic acids are selected from the group consisting of silver adipate, silver pimelate, silver suberate, silver azealate, silver sebacate, silver nonane-dicarboxylate, silver decane-dicarboxylate and silver undecane-dicarboxylate. It is preferred that the molar concentration of the silver salt of an aliphatic dicarboxylic acid in the mixed crystals of two or more organic silver salts is at least 15 per cent.
  • the molar concentration of silver salt of an aliphatic dicarboxylic acid in the mixed crystals of two or more organic silver salts is less than 50 per cent.
  • the mixed crystals of two or more organic carboxylic acid may be used on their own or in admixture with one or more organic silver salt in the thermosensitive element.
  • organic silver salt may be used in admixture with the mixed crystals of the present invention.
  • Preferred organic silver salts are silver salts of aliphatic monocarboxylic acids, known as fatty acids, wherein the aliphatic carbon chain has preferably at least 12 C-atoms.
  • Mixed crystals of two or more organic silver salts may be dispersed by standard dispersion techniques e.g. using ball mills, bead mills, microfluidizers, ultrasonic apparatuses, rotor stator mixers etc. have been found to be useful in this regard.
  • thermosensitive element comprises substantially light-insensitive mixed crystals of two or more organic silver salts, an organic reducing agent therefor in thermal working relationship therewith and a binder.
  • the element may comprise a layer system in which the ingredients may be dispersed in different layers, with the proviso that the two ingredients are in reactive association with one another i.e. during the thermal development process the reducing agent must be present in such a way that it is able to diffuse to the mixed crystal of two or more organic silver salts and any organic silver salt present so that reduction to silver can occur.
  • Suitable organic reducing agents for the reduction of mixed crystals of two or more organic silver salts are organic compounds containing at least one active hydrogen atom linked to O, N or C.
  • Catechol-type reducing agents i.e. reducing agents containing at least one benzene nucleus with two hydroxy groups (-OH) in ortho-position, such as catechol, 3-(3,4-dihydroxyphenyl) propionic acid, 1,2-dihydroxybenzoic acid, gallic acid and esters e.g. methyl gallate, ethyl gallate, propyl gallate, tannic acid, and 3,4-dihydroxy-benzoic acid esters are preferred, with those described in EP-B 692 733 and EP-A 903 625.
  • Combinations of reducing agents may also be used that on heating become reactive partners in the reduction of the substantially light-insensitive organic silver salt containing mixed crystals of two or more organic silver salts.
  • combinations of sterically hindered phenols with sulfonyl hydrazide reducing agents such as disclosed in US-P 5,464,738; trityl hydrazides and formyl-phenyl-hydrazides such as disclosed in US-P 5,496,695; trityl hydrazides and formyl-phenyl-hydrazides with diverse auxiliary reducing agents such as disclosed in US-P 5,545,505, US-P 5.545.507 and US-P 5,558,983; acrylonitrile compounds as disclosed in US-P 5,545,515 and US-P 5,635,339; and 2-substituted malonodialdehyde compounds as disclosed in US-P 5,654,130.
  • thermosensitive element Film-forming binders of the thermosensitive element
  • the film-forming binder of the thermosensitive element containing mixed crystals of two or more organic silver salts may be all kinds of natural, modified natural or synthetic resins or mixtures of such resins, in which the mixed crystals of two or more organic silver salts can be dispersed homogeneously either in aqueous or solvent media: e.g. cellulose derivatives such as ethylcellulose, cellulose esters, e.g.
  • cellulose nitrate carboxymethylcellulose, starch ethers, galactomannan
  • polymers derived from ⁇ , ⁇ -ethylenically unsaturated compounds such as polyvinyl chloride, after-chlorinated polyvinyl chloride, copolymers of vinyl chloride and vinylidene chloride, copolymers of vinyl chloride and vinyl acetate, polyvinyl acetate and partially hydrolyzed polyvinyl acetate, polyvinyl alcohol, polyvinyl acetals that are made from polyvinyl alcohol as starting material in which only a part of the repeating vinyl alcohol units may have reacted with an aldehyde, preferably polyvinyl butyral, copolymers of acrylonitrile and acrylamide, polyacrylic acid esters, polymethacrylic acid esters, polystyrene and polyethylene or mixtures thereof.
  • Suitable water-soluble film-forming binders for use in thermographic recording materials according to the present invention are: polyvinyl alcohol, polyacrylamide, polymethacrylamide, polyacrylic acid, polymethacrylic acid, polyvinylpyrrolidone, polyethyleneglycol, proteinaceous binders such as gelatin, modified gelatines such as phthaloyl gelatin, polysaccharides, such as starch, gum arabic and dextran and water-soluble cellulose derivatives.
  • a preferred water-soluble binder for use in the thermographic recording materials of the present invention is gelatin.
  • Preferred water-dispersible binders for use according to the present invention are water-dispersible film-forming polymers with covalently bonded ionic groups selected from the group consisting of sulfonate, sulfinate, carboxylate, phosphate, quaternary ammonium, tertiary sulfonium and quaternary phosphonium groups.
  • Further preferred water-dispersible binders for use according to the present invention are water-dispersible film-forming polymers with covalently bonded moieties with one or more acid groups.
  • Water-dispersible binders with crosslinkable groups, e.g. epoxy groups, aceto-acetoxy groups and crosslinkable double bonds are also preferred.
  • Particularly preferred water-dispersible binders for use in the thermographic recording materials of the present invention are polymer latexes.
  • thermosensitive element preferably further contains a so-called toning agent known from thermography or photothermography.
  • Suitable toning agents are the phthalimides and phthalazinones within the scope of the general formulae described in US-P 4,082,901. Further reference is made to the toning agents described in US-P 3,074,809, 3,446,648 and 3,844,797.
  • Other particularly useful toning agents are the heterocyclic toner compounds of the benzoxazine dione or naphthoxazine dione type as disclosed in GB-P 1,439,478, US-P 3,951,660 and US-P 5,599,647.
  • thermographic recording materials of the present invention In order to obtain improved shelf-life and reduced fogging, stabilizers and antifoggants may be incorporated into the thermographic recording materials of the present invention.
  • the thermosensitive element preferably further contains at least one polycarboxylic acid and/or anhydride thereof in a molar percentage of at least 10 with respect to all the organic silver salt(s) present and in thermal working relationship therewith, with a molar percentage of at least 15 with respect to all the organic silver salt(s) being particularly preferred.
  • the polycarboxylic acid may be aliphatic (saturated as well as unsaturated aliphatic and also cycloaliphatic) or an aromatic polycarboxylic acid. These acids may be substituted e.g. with alkyl, hydroxyl, nitro or halogen. They may be used in anhydride form or partially esterified on the condition that at least two free carboxylic acids remain or are available in the heat recording step.
  • thermographic recording materials of the present invention may contain one or more surfactants, which may be anionic, non-ionic or cationic surfactants and/or one or more dispersants.
  • the recording material may contain in addition to the ingredients mentioned above other additives such as antistatic agents, e.g. non-ionic antistatic agents including a fluorocarbon group as e.g. in F 3 C(CF 2 ) 6 CONH(CH 2 CH 2 O)-H, silicone oil, e.g. BAYSILONETM ⁇ l MA (from BAYER AG, GERMANY), ultraviolet light absorbing compounds, white light reflecting and/or ultraviolet radiation reflecting pigments and/or optical brightening agents.
  • antistatic agents e.g. non-ionic antistatic agents including a fluorocarbon group as e.g. in F 3 C(CF 2 ) 6 CONH(CH 2 CH 2 O)-H
  • silicone oil e.g. BAYSILONETM ⁇ l MA (from BAYER AG, GERMANY)
  • ultraviolet light absorbing compounds e.g. BAYSILONETM ⁇ l MA (from BAYER AG, GERMANY)
  • the support for the thermosensitive element according to the present invention may be transparent, translucent or opaque, e.g. having a white light reflecting aspect and is preferably a thin flexible carrier made e.g. from polypropylene, polycarbonate or polyester, e.g. polyethylene terephthalate.
  • the support may be in sheet, ribbon or web form and subbed if need be to improve the adherence to the thereon coated thermosensitive element.
  • the support may be made of an opacified resin composition. Should a transparent base be used, the base may be colourless or coloured, e.g. having a blue colour.
  • One or more backing layers may be provided to control physical properties such as curl and static.
  • the outermost layer of the recording material may in different embodiments of the present invention be the outermost layer of the thermosensitive element, a protective layer applied to the thermosensitive element or a layer on the opposite side of the support to the thermosensitive element.
  • the thermosensitive element is provided with a protective layer to avoid local deformation of the thermosensitive element and to improve resistance against abrasion.
  • the protective layer preferably comprises a binder, which may be solvent-soluble, solvent-dispersible, water-soluble or water-dispersible.
  • a binder which may be solvent-soluble, solvent-dispersible, water-soluble or water-dispersible.
  • solvent-soluble binders polycarbonates as described in EP-A 614 769 are particularly preferred.
  • water-soluble or water-dispersible binders are preferred for the protective layer, as coating can be performed from an aqueous composition and mixing of the protective layer with the immediate underlayer can be avoided by using a solvent-soluble or solvent-dispersible binder in the immediate underlayer.
  • a protective layer according to the present invention may comprise in addition a thermomeltable particle optionally with a lubricant present on top of the protective layer as described in WO 94/11199.
  • a thermomeltable particle optionally with a lubricant present on top of the protective layer as described in WO 94/11199.
  • at least one solid lubricant having a melting point below 150°C and at least one liquid lubricant in a binder is present, wherein at least one of the lubricants is a phosphoric acid derivative.
  • the outermost layer according to the present invention may be crosslinked.
  • Crosslinking can be achieved by using crosslinking agents such as described in WO 95/12495 for protective layers, e.g. tetra-alkoxysilanes, polyisocyanates, zirconates, titanates, melamine resins etc., with tetraalkoxysilanes such as tetramethylorthosilicate and tetraethylorthosilicate being preferred.
  • the outermost layer of the recording material according to the present invention may comprise a matting agent.
  • Suitable matting agents are described in WO 94/11198 and include e.g. talc particles and optionally protrude from the outermost layer.
  • Solid or liquid lubricants or combinations thereof are suitable for improving the slip characteristics of the thermographic recording materials according to the present invention.
  • Preferred solid lubricants are thermomeltable particles such as those described in WO 94/11199.
  • thermographic recording materials used in the present invention may also contain antihalation or acutance dyes which absorb infra-red light, for absorption by a dye which converts the absorbed infra-red light into heat, which has passed through the thermosensitive element thereby preventing its reflection.
  • antihalation or acutance dyes which absorb infra-red light, for absorption by a dye which converts the absorbed infra-red light into heat, which has passed through the thermosensitive element thereby preventing its reflection.
  • Such dyes may be incorporated into the thermosensitive element or in any other layer of the recording material of the present invention.
  • any layer of the recording material of the present invention may proceed by any coating technique e.g. such as described in Modern Coating and Drying Technology, edited by Edward D. Cohen and Edgar B. Gutoff, (1992) VCH Publishers Inc. 220 East 23rd Street, Suite 909 New York, NY 10010, U.S.A.
  • Thermographic imaging is carried out by the image-wise application of heat either in analogue fashion by direct exposure through an image of by reflection from an image, or in digital fashion pixel by pixel either by using an infra-red heat source, for example with a Nd-YAG laser or other infra-red laser, with a thermographic material preferably containing an infra-red absorbing compound, or by direct thermal imaging with a thermal head.
  • an infra-red heat source for example with a Nd-YAG laser or other infra-red laser
  • a thermographic material preferably containing an infra-red absorbing compound
  • thermal printing image signals are converted into electric pulses and then through a driver circuit selectively transferred to a thermal printhead.
  • the thermal printhead consists of microscopic heat resistor elements, which convert the electrical energy into heat via Joule effect.
  • Such thermal printing heads may be used in contact or close proximity with the recording material.
  • the operating temperature of common thermal printheads is in the range of 300 to 400°C and the heating time per picture element (pixel) may be less than 1.0ms, the pressure contact of the thermal printhead with the recording material being e.g. 200-500g/cm 2 to ensure a good transfer of heat.
  • the image-wise heating of the recording material with the thermal printing heads may proceed through a contacting but removable resin sheet or web wherefrom during the heating no transfer of recording material can take place.
  • Activation of the heating elements can be power-modulated or pulse-length modulated at constant power.
  • the image-wise heating can be carried out such that heating elements not required to produce an image pixel generate an amount of heat (H e ) in accordance with the following formula: 0.5 H D ⁇ H e ⁇ H D wherein H D represents the minimum amount of heat required to cause visible image formation in the recording material.
  • EP-A 654 355 discloses a method for making an image by image-wise heating by means of a thermal head having energizable heating elements, wherein the activation of the heating elements is executed duty cycled pulsewise.
  • EP-A 622 217 discloses a method for making an image using a direct thermal imaging element producing improvements in continuous tone reproduction.
  • Image-wise heating of the recording material can also be carried out using an electrically resistive ribbon incorporated into the material.
  • Image- or pattern-wise heating of the recording material may also proceed by means of pixel-wise modulated ultra-sound.
  • Thermographic imaging can be used for the production of transparencies and reflection type prints.
  • Application of the present invention is envisaged in the fields of both graphics images requiring high contrast images with a very steep dependence of print density upon applied dot energy and continuous tone images requiring a weaker dependence of print density upon applied dot energy, such as required in the medical diagnostic field.
  • thermographic recording materials on a white opaque base are used, whereas in the medical diagnostic field black-imaged transparencies are widely used in inspection techniques operating with a light box.
  • a UAg defined as the potential difference between a silver electrode of ⁇ 99.99% purity in the aqueous liquid and a reference electrode consisting of a Ag/AgCl-electrode in 3M KCl solution at room temperature connected with the aqueous liquid via a salt bridge consisting of a 10% KNO 3 salt solution
  • 315mV a ca. 12% dispersion of organic silver salt.
  • the organic silver salt was then filtered off and washed four times with deionized water with 2% of 2-propanol, after which it was dried for 72 hours at 45°C.
  • X-ray diffraction spectra were then run on the dried organic silver salts of types I to VII and X to XII with an X-ray diffractometer using a CuK ⁇ X-ray source at a current of 30mA and an energy of 40kV in the Bragg angle 2 ⁇ range 1.5 to 55° with a step-size of 0.05° and a step-time of ls.
  • the XRD-spectra obtained all corresponded to the reference spectrum of the Joint Committee on Powder Diffraction Standards (JCPDS) Powder Diffraction File for AgB: 4-48, published by the International Centre for Diffraction Data, 12 Campus Boulevard, Newtown Square, Pennsylvania 19073-3273 U.S.A.
  • 40g of the organic silver salt dispersion was mixed with 29.86g of a 30% solution of B79, 0.90g of a 2-butanone dispersion containing 4.13% of B79, 14.01% of T01 and 25.86%, 0.40g of BAYSILONTM MA and 0.323g of adipic acid and 15g of 2-butanone to a homogeneous dispersion.
  • thermosensitive elements of the thermographic recording materials of INVENTION EXAMPLES 1 to 10 and COMPARATIVE EXAMPLE 1 produced with type I to VII and IX to XI mixed crystals of organic silver salts and the silver behenate reference, organic silver salt type XII, respectively.
  • thermographic recording materials of INVENTION EXAMPLES 1 to 7 and COMPARATIVE EXAMPLE 1 were subjected to 7 days conditioning at 45°C and 70% relative humidity to produce "fresh materials" for printing.
  • thermographic printing of the thermographic recording materials of INVENTION EXAMPLES 1 to 10 and COMPARATIVE EXAMPLE 1 the print head was separated from the imaging layer by a thin intermediate material contacted with a slipping layer of a separable 5 ⁇ m thick polyethylene terephthalate ribbon coated successively with a subbing layer, heat-resistant layer and the slipping layer (antifriction layerygiving a ribbon with a total thickness of 6 ⁇ m.
  • the printer was equipped with a thin film thermal head with a resolution of 300 dpi and was operated with a line time of 19ms (the line time being the time needed for printing one line). During this line time the print head received constant power.
  • the average printing power being the total amount of electrical input energy during one line time divided by the line time and by the surface area of the heat-generating resistors was 1.6 mJ/dot being sufficient to obtain maximum optical density in each of the thermographic recording materials of INVENTION EXAMPLES 1 to 10 and COMPARATIVE EXAMPLE 1.
  • the maximum density, D max , of the prints given in table 3 were measured through a visible filter with a MACBETHTM TR924 densitometer in the grey scale step corresponding to data levels of 64 and 0 respectively and the D max -values are given in table 3 for INVENTION EXAMPLE 1 to 10 and COMPARATIVE EXAMPLE 1 together with the change in D max -values upon printing a fresh material subjected to 7 days conditioning at 45°C and 70% relative humidity (RH) compared with printing a fresh material also measured through a visible filer.
  • RH relative humidity
  • the image tone of fresh prints made with the thermographic recording materials of INVENTION EXAMPLES 1 to 10 and COMPARATIVE EXAMPLE 1 were assessed on the basis of the L*, a* and b* CIELAB-values.
  • the L*, a* and b* CIELAB-values were determined by spectrophotometric measurements according to ASTM Norm E179-90 in a R(45/0) geometry with evaluation according to ASTM Norm E308-90.
  • the a* and b* CIELAB-values of fresh prints of the thermographic recording materials of INVENTION EXAMPLES 1 to 10 and COMPARATIVE EXAMPLE 1 at optical densities, D, of 0.5 and 1.0 are summarized in table 3.
  • Colour neutrality on the basis of CIELAB-values corresponds to a* and b* values of zero, with a negative a*-value indicating a greenish image-tone becoming greener as a* becomes more negative, a positive a*-value indicating a reddish image-tone becoming redder as a* becomes more positive, a negative b*-value indicating a bluish image-tone becoming bluer as b* becomes more negative and a positive b*-value indicating a yellowish image-tone becoming more yellow as b* becomes more positive.
  • thermographic recording materials of INVENTION EXAMPLES 1 to 10 are lower than the corresponding value for the reference thermographic recording material of COMPARATIVE EXAMPLE 1.
  • Prints with the thermographic recording materials of INVENTION EXAMPLES 1 and 2 with mixed crystals of organic silver salts prepared with HYSTRENETM 9022 from WITCO exhibit good tone neutrality as did the prints made with mixed crystals of organic silver salts of types IV and VI consisting of 67mol% of silver behenate and 33mol% of silver adipate and silver sebacate of INVENTION EXAMPLES 4 and 6 respectively.
  • 100g of the respective organic silver salt was added to a mixture of 100g of 10% solution of Surfactant Nr. 1 and 300g of deionized water and the mixture stirred for 30 minutes with an ULTRA TURRAX stirrer.
  • the resulting dispersions were then passed through a Type M110F high pressure homogenizer from MICROFLUIDICSTM Corporation at a pressure of 350 bar to obtain a finely divided aqueous dispersion of the organic silver salt.
  • the final concentration of the different organic silver salts in the resulting dispersions is given in table 4.
  • 0.310g of boric acid was mixed with 12.287g of deionized water and 3.450g of K17881 and the K17881 was allowed to swell for 30 minutes before heating the swollen gelatin up to 36°C.
  • the following ingredients were then added with stirring: 4.865g of an aqueous dispersion of 6.44% of K7598 and 18.88% of phthalazinone followed by 10 minutes stirring, then 2g of the organic silver salt dispersion (for type see table 4) and deionized water (for quantity see table 4) followed by 10 minutes stirring, then the rest of the organic silver salt dispersion (for total quantity, type and concentration of the organic silver salt see table 4), then 1g of deionized water at a temperature of 50°C and 1g of R01 dissolved in 2g of ethanol, then 1g of an aqueous solution containing 19.2% of formaldehyde and 6.75% of methanol and finally 2g of deionized water.
  • thermographic recording materials of INVENTION EXAMPLES 11 to 14 and COMPARATIVE EXAMPLE 2 were carried out as described for the thermographic recording materials of INVENTION EXAMPLES 1 to 10 and COMPARATIVE EXAMPLE 1.
  • the maximum densities, D max , and minimum densities, D min , of the prints produced with the thermographic recording materials of INVENTION EXAMPLES 11 to 14 and COMPARATIVE EXAMPLE 2 measured through a blue filter with a MACBETHTM TR924 densitometer in the grey scale step corresponding to data levels of 64 and 0 respectively are given in table 5.
  • thermosensitive elements of the thermographic recording materials of INVENTION EXAMPLES 15 to 17 and COMPARATIVE EXAMPLES 3 to 5 produced with type VIII to X mixed crystals and mixtures of type XII and type XIII, respectively.
  • the coating weights of silver are given in table 6. After drying all thermographic recording materials were subjected to 7 days conditioning at 45°C and 70% relative humidity before printing.
  • thermographic recording materials of INVENTION EXAMPLES 15 to 17 and COMPARATIVE EXAMPLE were carried out as described for the thermographic recording materials of INVENTION EXAMPLES 1 to 10 and COMPARATIVE EXAMPLE 1.
  • the maximum densities, D max , and minimum densities, D min , of the prints produced with the thermographic recording materials of INVENTION EXAMPLES 15 to 17 and COMPARATIVE EXAMPLE 3 to 5 measured through a blue filter with a MACBETHTM TR924 densitometer in the grey scale step corresponding to data levels of 64 and 0 respectively are given in table 5.
  • Colour neutrality of images on blue base on the basis of CIELAB-values therefore corresponds to an a* value of -8.34 and a b* value of -15.71, with a more negative a*-value than -8.34 indicating a greenish image-tone becoming greener as a* becomes more negative, a value of a* more positive (i.e. less negative) than -8.34 indicating a reddish image-tone becoming redder as a* becomes more positive (i.e. less negative), a more negative b*-value than -15.71 indicating a bluish image-tone becoming bluer as b* becomes more negative and a more positive (i.e.
  • thermographic recording materials of INVENTION EXAMPLE 15 16 and 17 with mixed crystals of silver behenate and silver stearate with 90, 70 and 50 mole% silver behenate respectively are compared with the thermographic recording materials of COMPARATIVE EXAMPLES 3, 4 and 5 with physical mixtures of silver behenate and silver stearate with 90, 70 and 50 mole% silver behenate respectively, the a*- and b*-values for the thermographic recording materials of INVENTION EXAMPLES 3, 4 and 5 are more neutral (i.e.
  • thermographic recording materials with mixed crystals of silver salts of organic carboxylic acids is surprisingly improved over that with thermographic recording materials with physical mixtures of the same silver salts of organic carboxylic acids in the same molar concentrations and therefore that the performance of mixed crystals of silver salts of organic carboxylic acids cannot be equated with that of physical mixtures thereof.

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  • Optics & Photonics (AREA)
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Claims (10)

  1. Ein wesentlich lichtunempfindliches thermografisches Schwarzweiß-Aufzeichnungsmaterial mit einem Träger und einem wärmeempfindlichen Element, das ein wesentlich lichtunempfindliches organisches Silbersalz, ein organisches Reduktionsmittel dafür in thermischer wirksamer Beziehung dazu und ein Bindemittel enthält, dadurch gekennzeichnet, daß das wärmeempfindliche Element wesentlich lichtunempfindliche Mischkristalle von zwei oder mehr Silbersalzen von organischen Carbonsäuren mit einer oder mehr Carbonsäuregruppen enthält.
  2. Ein thermografisches Aufzeichnungsmaterial nach Anspruch 1, dadurch gekennzeichnet, daß zumindest eins der zwei oder mehr organischen Silbersalze ein Silbersalz von alifatischen Monocarbonsäuren mit zumindest 12 Kohlenstoffatomen ist.
  3. Ein thermografisches Aufzeichnungsmaterial nach Anspruch 2, dadurch gekennzeichnet, daß die Mischkristalle aus zwei oder mehr Silbersalzen von alifatischen Monocarbonsäuren mit zumindest 12 Kohlenstoffatomen bestehen.
  4. Ein thermografisches Aufzeichnungsmaterial nach Anspruch 3, dadurch gekennzeichnet, daß die Mischkristalle aus einem Gemisch aus Silberstearat, Silberbehenat und Silberarachidat bestehen.
  5. Ein thermografisches Aufzeichnungsmaterial nach Anspruch 2, dadurch gekennzeichnet, daß die alifatische Monocarbonsäure aus der Gruppe bestehend aus Silberstearat, Silberarachidat und Silberbehenat gewählt wird.
  6. Ein thermografisches Aufzeichnungsmaterial nach Anspruch 1, dadurch gekennzeichnet, daß eins der zwei oder mehr organischen Silbersalze ein Silbersalz einer alifatischen Dicarbonsäure ist.
  7. Ein thermografisches Aufzeichnungsmaterial nach Anspruch 6, dadurch gekennzeichnet, daß die alifatische Dicarbonsäure aus der Gruppe bestehend aus Silberadipat, Silberpimelat, Silbersuberat, Silberazelat, Silbersebacat, Silbernonandicarboxylat, Silberdecandicarboxylat und Silberundecandicarboxylat gewählt wird.
  8. Ein thermografisches Aufzeichnungsmaterial nach Anspruch 1, dadurch gekennzeichnet, daß das wärmeempfindliche Element weiterhin zumindest eine Polycarbonsäure und/oder ein Polycarbonsäureanhydrid in einem Molverhältnis von zumindest 10, bezogen auf die Gesamtmenge des (der) organischen Silbersalze(s), enthält.
  9. Ein thermografisches Aufzeichnungsmaterial nach Anspruch 1, dadurch gekennzeichnet, daß das wärmeempfindliche Element weiterhin ein organisches Silbersalz einer alifatischen Monocarbonsäure mit zumindest 12 Kohlenstoffatomen enthält.
  10. Ein durch die nachstehenden Schritte gekennzeichnetes Aufzeichnungsverfahren : (i) Anordnen einer Außenschicht eines wesentlich lichtunempfindlichen thermografischen Schwarzweiß-Aufzeichnungsmaterials mit einem Träger und einem wärmeempfindlichen Element, das ein wesentlich lichtunempfindliches organisches Silbersalz, ein organisches Reduktionsmittel dafür in thermischer wirksamer Beziehung dazu und ein Bindemittel enthält, in der Nähe einer Heizquelle, (ii) bildmäßige Beaufschlagung des thermografischen Aufzeichnungsmaterials mit von der Heizquelle gelieferter Wärme zur Herstellung eines Bildes, wobei das Aufzeichnungsmaterial in der Nähe der Heizquelle gehalten wird, und (iii) Entfernen des thermografischen Aufzeichnungsmaterials von der Heizquelle, wobei das wärmeempfindliche Element wesentlich lichtunempfindliche Mischkristalle von zwei oder mehr Silbersalzen von organischen Carbonsäuren mit einer oder mehr Carbonsäuregruppen enthält.
EP19990201624 1998-06-08 1999-05-25 Thermographisches Schwarz-Weiss-Aufzeichnungsmaterial mit verbessertem Bildton Expired - Lifetime EP0964300B1 (de)

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US6472131B1 (en) 2000-05-04 2002-10-29 Eastman Kodak Company Asymmetric silver salt dimers and imaging compositions, materials and methods using same
US6355408B1 (en) 2000-05-04 2002-03-12 Eastman Kodak Company Core-shell silver salts and imaging compositions, materials and methods using same
US6558895B2 (en) 2000-09-11 2003-05-06 Agfa-Gevaert Photothermographic recording materials with improved stability
EP1186947A1 (de) * 2000-09-11 2002-03-13 Agfa-Gevaert Photothermographische Aufzeichnungsmaterialien mit verbesserter Stabilität
EP1258775A3 (de) * 2001-03-29 2006-07-26 Agfa-Gevaert N.V. Photothermographische Materialien und Aufzeichnungsverfahren dafür
EP1246001A1 (de) * 2001-03-29 2002-10-02 Agfa-Gevaert Thermographische Materialien und Aufzeichnungsverfahren dafür
US6686133B2 (en) 2001-03-29 2004-02-03 Agfa-Gevaert Photothermographic materials processable at lower temperatures and recording processes therefor
US6548236B1 (en) * 2001-11-21 2003-04-15 Eastman Kodak Company Core/shell silver donors for photothermographic systems comprising an oxidatively less reactive shell
US6576414B1 (en) * 2001-11-21 2003-06-10 Eastman Kodak Company Core/shell silver donors for photothermographic systems comprising an oxidatively more reactive shell
US6803177B2 (en) 2002-07-30 2004-10-12 Eastman Kodak Company Silver compounds and compositions, thermally developable materials containing same, and methods of preparation
US7175977B2 (en) 2003-12-18 2007-02-13 Agfa-Gevaert Stabilizers for use in thermographic recording materials
US7097961B2 (en) 2004-05-17 2006-08-29 Agfa Gevaert Stabilizers for use in substantially light-insensitive thermographic recording materials
EP1637338B1 (de) 2004-09-17 2007-04-04 Agfa-Gevaert Im wesentlichen lichtunempfindliches thermographisches Aufzeichnungsmaterial
US7179768B2 (en) 2004-11-05 2007-02-20 Agfa-Gevaert Toning agents for use in thermographic recording materials
EP2199100A1 (de) 2008-12-22 2010-06-23 Agfa-Gevaert N.V. Sicherheitslaminate für Sicherheitsdokumente

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