EP0687572B1 - Wärmeempfindliches Aufzeichnungsverfahren - Google Patents

Wärmeempfindliches Aufzeichnungsverfahren Download PDF

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Publication number
EP0687572B1
EP0687572B1 EP95201340A EP95201340A EP0687572B1 EP 0687572 B1 EP0687572 B1 EP 0687572B1 EP 95201340 A EP95201340 A EP 95201340A EP 95201340 A EP95201340 A EP 95201340A EP 0687572 B1 EP0687572 B1 EP 0687572B1
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EP
European Patent Office
Prior art keywords
acid
process according
recording process
silver
silver salt
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English (en)
French (fr)
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EP0687572A1 (de
Inventor
Carlo C/O Agfa-Gevaert N.V. Uyttendaele
Herman C/O Agfa-Gevaert N.V. Uytterhoeven
Guy C/O Agfa-Gevaert N.V. Jansen
Bartholomeus C/O Agfa-Gevaert N.V. Horsten
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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
    • G03C1/494—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
    • G03C1/49827—Reducing agents
    • 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
    • G03C1/49836—Additives
    • G03C1/49845—Active additives, e.g. toners, stabilisers, sensitisers
    • 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
    • G03C2200/26—Gamma

Definitions

  • the present invention relates to a direct thermal imaging process for continuous tone reproduction.
  • Thermal imaging or thermography is a recording process wherein images are generated by the use of imagewise modulated thermal energy.
  • thermography two approaches are known :
  • Thermal dye transfer printing is a recording method wherein a dye-donor element is used that is provided with a dye layer wherefrom dyed portions or incorporated dyes are transferred onto a contacting receiver element by the application of heat in a pattern normally controlled by electronic information signals.
  • Thermography is concerned with materials which are substantially not photosensitive, but are sensitive to heat or thermosensitive. Imagewise applied heat is sufficient to bring about a visible change in a thermosensitive imaging material.
  • thermographic recording materials are of the chemical type. On heating to a certain conversion temperature, an irreversible chemical reaction takes place and a coloured image is produced.
  • 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.
  • the electric pulses thus converted into thermal signals manifest themselves as heat transferred to the surface of the thermal paper wherein the chemical reaction resulting in colour development takes place.
  • a heat-sensitive recording material is used in the form of an electrically resistive ribbon having a multilayered structure in which a carbon-loaded polycarbonate is coated with a thin aluminium film (ref. Progress in Basic Principles of Imaging Systems - Proceedings of the International Congress of Photographic Science GmbH (Cologne), 1986 ed. by Friedrich Granzer and Erik Moisar - Friedr. Vieweg & Sohn - Braunschweig/Wiesbaden Figure 6. p. 622).
  • Current is injected into the resistive ribbon by electrically addressing a printhead electrode contacting the carbon-loaded substrate, thus resulting in highly localized heating of the ribbon beneath the energized electrode.
  • the recording material is image-wise or pattern-wise heated by means of a modulated laser beam.
  • image-wise modulated infra-red laser light is absorbed in the recording layer in infra-red light absorbing substances converting infra-red radiation into the necessary heat for the imaging reaction.
  • the imagewise applied laser light has not necessarily to be infrared light since the power of a laser in the visible light range and even in the ultraviolet region can be thus high that sufficient heat is generated on absorption of the laser light in the recording material.
  • laser which may be a gas laser, gas ion laser, e.g. argon ion laser, solid state laser, e.g. Nd:YAG laser, dye laser or semi-conductor laser.
  • the image signals for modulating the laser beam or current in the micro-resistors of a thermal printhead are obtained directly e.g. from opto-electronic scanning devices or from an intermediary storage means, e.g. magnetic disc or tape or optical disc storage medium, optionally linked to a digital image work station wherein the image information can be processed to satisfy particular needs.
  • an intermediary storage means e.g. magnetic disc or tape or optical disc storage medium
  • thermographic recording material contains a polymeric binder, di- or triarylmethane thiolactone dye precursor in combination with silver behenate and 3,5-dihydroxybenzoic acid as an organic acidic reagent.
  • Said reagent acts as a weak reducing agent and provides a stable one-pot coating composition.
  • Other organic acidic reagents such as phthalic acid are described in column 6 of said US-P.
  • Banding is a phenomenon characterized by the presence in the thermographic image of parallel stripes of different optical density in the print direction and is typical for the use of thermal printheads containing an array of geometrically juxtaposed heating resistors that may show a spread in resistance value and/or contact-pressure with the recording material.
  • a direct thermal imaging process operating with a thermal printhead in conjunction with a heat-sensitive recording material capable of yielding images with maximum density higher than 2.5 and gradation sufficiently low for continuous tone reproduction as is needed e.g. in portrait reproduction for identification documents and in the medical diagnostic field based on images produced by e.g. radiography ultrasound or nuclear magnetic resonance (NMR) signals.
  • NMR nuclear magnetic resonance
  • a direct thermal imaging process wherein a non-photosensitive direct thermal recording material is heated dot-wise, and said direct thermal recording material comprises an imaging layer containing uniformly distributed in a film-forming polymeric binder (i) one or more substantially light-insensitive organic silver salts, said silver salt(s) being uniformly in thermal working relationship with (ii) one or more organic reducing agents therefor, however neither including 3,5-dihydroxybenzoic acid as acidic reagent nor di-tert-butyl-p-cresol as a sole reducing agent, characterized in that said imaging layer contains at least one polycarboxylic acid and/or anhydride thereof in a molar percentage of at least 20 with respect to said silver salt(s).
  • Said mole percentage is preferably in the range of 20 to 30.
  • thermo working relationship is meant here that said substantially light-insensitive silver salt and said organic reducing agent can react by means of heat to form metallic silver.
  • said ingredients (i) and (ii) may be present in the same binder-containing layer or in different layers wherefrom by heat they can come into reactive contact with each other, e.g. by diffusion or sublimation.
  • NSV numerical gradation value
  • E 2.5 is the minimal energy in Joule applied in a dot area of 87 ⁇ m x 87 ⁇ m of the recording material that obtains by said energy an optical density value of 2.5
  • E 0.1 is the maximal energy in Joule applied in a dot area of the recording material that obtains by said energy an optical density value of 0.1.
  • Said optical density values are values above the inherent optical density of the "unheated" recording material having always already some optical density by the inherent optical density of the imaging layer and its support.
  • thermo head printer developed for thermosensitometric measurement purposes and having distinct groups of micro-resistors being arranged in succession along the width of the printhead array. From group to group said resistors receive a linearly increasing amount of electrical energy within the line time of the printer. The input of electrical energy per group of resistors is controlled by linearly increasing the period of time from group to group wherein a constant current at constant voltage is applied, said current and voltage being kept constant over the whole printing period.
  • the line time is the time needed for printing one single line with the thermal head.
  • the line time is a period of time of 32 ms wherein the imaging material with respect to the print array travels a distance of one pixel length, viz. 87 ⁇ m.
  • the continuous tone reproduction capability of a heat-sensitive imaging material used according to the present invention is favoured by a relatively high binder to silver salt weight ratio in the imaging layer.
  • a relatively high binder to silver salt weight ratio in the imaging layer Preferably said ratio is in the range of 1/2 to 6/1, and more preferably from 1/1 to 4/1.
  • Substantially light-insensitive organic silver salts particularly suited for use in a direct thermal recording material according to the present invention are silver salts of aliphatic carboxylic acids known as fatty acids, wherein the aliphatic carbon chain has preferably at least 12 C-atoms, e.g. silver laurate, silver palmitate, silver stearate, silver hydroxystearate, silver oleate and silver behenate, which silver salts are also called "silver soaps”.
  • Modified aliphatic carboxylic acids with thioether group as described e.g. in GB-P 1,111,492 and other organic silver salts as described in GB-P 1,439,478, e.g.
  • silver benzoate and silver phthalazinone may be used likewise to produce a thermally developable silver image.
  • Organic reducing agents suitable for use according to the present invention are aromatic di- and tri-hydroxy compounds having at least two hydroxy groups in ortho- or para-position on the same aromatic nucleus, e.g. benzene nucleus, more particularly e.g. hydroquinone and substituted hydroquinones, catechol, pyrogallol, gallic acid and gallic acid esters.
  • aromatic di- and tri-hydroxy compounds having at least two hydroxy groups in ortho- or para-position on the same aromatic nucleus, e.g. benzene nucleus, more particularly e.g. hydroquinone and substituted hydroquinones, catechol, pyrogallol, gallic acid and gallic acid esters.
  • Particularly useful are polyhydroxy spiro-bis-indane compounds, especially these corresponding to the following general formula: wherein :
  • polyhydroxy-spiro-bis-indane compounds described in US-P 3,440,049 as photographic tanning agent, more especially 3,3,3',3'-tetramethyl-5,6,5',6'-tetrahydroxy-1,1'-spiro-bis-indane (called indane I) and 3,3,3',3'-tetramethyl-4,6,7,4',6',7'-hexahydroxy-1,1'-spiro-bis-indane (called indane II).
  • Indane is also known under the name hydrindene.
  • catechol-type reducing agents by which is meant reducing agents containing at least one benzene nucleus with two hydroxy groups (-OH) in ortho-position e.g. 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.
  • auxiliary reducing agents are e.g. sterically hindered phenols, that on heating become reactive partners in the reduction of the substantially light-insensitive silver salt such as silver behenate, or are bisphenols, e.g. of the type described in US-P 3,547,648.
  • the auxiliary reducing agents may be present in the imaging layer or in a polymeric binder layer adjacent thereto.
  • polycarboxylic acid(s) and/or anhydrides thereof in thermal working relationship with the substantially light-insensitive silver salt has an image gradation-lowering effect as can be learned from the Examples.
  • the polycarboxylic acid may be aliphatic (saturated as well as unsaturated aliphatic and likewise cycloaliphatic) as well as 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.
  • saturated aliphatic dicarboxylic acids containing at least 4 carbon atoms e.g. : succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, nonane-dicarboxylic acid, decane-dicarboxylic acid, undecane-dicarboxylic acid.
  • Suitable unsaturated dicarboxylic acids are : maleic acid, citraconic acid, itaconic acid and aconitic acid.
  • a particularly effectively gradation lowering substituted polycarboxylic acid is citric acid, and derivative thereof acetonedicarboxylic acid and further iso-citric acid and ⁇ -ketoglutaric acid.
  • Preferred aromatic polycarboxylic acids are ortho-phthalic acid and 3-nitro-phthalic acid, tetrachlorophthalic acid, mellitic acid, pyromellitic acid and trimellitic acid and the anhydrides thereof.
  • the silver image density depends on the coverage of said substantially light-insensitive silver salts in combination with said polycarboxylic acids and reducing agent(s) and has to be preferably such that, on heating above 120 °C, an optical density of at least 2.5 can be obtained.
  • the thickness of the imaging layer is preferably in the range of 5 to 50 ⁇ m.
  • said substantially light-insensitive organic silver salt and said organic reducing agent are present in different layers wherefrom by heat they can come into reactive contact with each other.
  • the film-forming water-insoluble polymeric binder of the imaging layer of the present direct thermal recording material is preferably a thermoplastic resin or mixture of such resins, wherein the silver salt can be dispersed homogeneously.
  • a thermoplastic resin or mixture of such resins wherein the silver salt can be dispersed homogeneously.
  • all kinds of natural, modified natural or synthetic water-insoluble resins may be used, e.g. cellulose derivatives such as ethylcellulose. cellulose esters, e.g.
  • cellulose nitrate 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 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 and polyethylene or mixtures thereof.
  • aldehyde preferably polyvinyl butyral
  • copolymers of acrylonitrile and acrylamide polyacrylic acid esters, polymethacrylic acid esters and polyethylene or mixtures thereof.
  • a particularly suitable polyvinyl butyral containing a minor amount of vinyl alcohol units is marketed under the tradename BUTVAR B79 of Monsanto USA and provides a good adherence to paper and properly subbed polyester supports.
  • the layer containing the organic silver salt is commonly coated from an organic solvent containing the binder in dissolved form.
  • the binder of the imaging layer may be combined with waxes or "heat solvents” also called “thermal solvents” or “thermosolvents” improving the reaction speed of the redox-reaction at elevated temperature.
  • heat solvent in this invention is meant a non-hydrolyzable organic material which is in solid state in the recording layer at temperatures below 50 °C but becomes a plasticizer for the recording layer in the heated region and/or liquid solvent for at least one of the redox-reactants, e.g. the reducing agent for the organic silver salt, at a temperature above 60 °C.
  • redox-reactants e.g. the reducing agent for the organic silver salt
  • the recording layer contains in admixture with said organic silver salt and reducing agents a so-called toning agent known from thermography or photo-thermography.
  • 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 within the scope of following general formula : in which :
  • a toner compound particularly suited for use in combination with polyhydroxy benzene reducing agents is 3,4-dihydro-2,4-dioxo-1,3,2H-benzoxazine described in US-P 3,951,660.
  • the imaging layer may contain other additives such as free fatty acids, 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, 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
  • ultraviolet light absorbing compounds e.g. in F 3 C(CF 2 ) 6 CONH(CH 2 CH 2 O)-H
  • white light reflecting and/or ultraviolet radiation reflecting pigments e.g. in UV light absorbing compounds
  • optical brightening agents e.g., a fluorocarbon group as e.g. in F 3 C(CF 2 ) 6 CONH(CH 2 CH 2 O)-H
  • the support for the heat-sensitive recording material according to the present invention is preferably a thin flexible carrier made e.g. from paper, polyethylene coated paper or transparent resin film, e.g. made of a cellulose ester, e.g. cellulose triacetate, 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 heat-sensitive imaging layer.
  • the coating of the imaging layer may proceed by any coating technique e.g. 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.
  • Direct thermal imaging can be used for both the production of transparencies and reflection type prints.
  • the support may be transparent or opaque, e.g. the support has a white light reflecting aspect.
  • a paper base is used which may contain white light reflecting pigments, optionally also applied in an interlayer between the recording layer and said base.
  • said base may be colourless or coloured, e.g. has a blue colour.
  • the recording materials of the present invention are particularly suited for use in thermographic recording techniques operating with thermal print-heads.
  • Suitable thermal printing heads are e.g. a Fujitsu Thermal Head (FTP-040 MCS001), a TDK Thermal Head F415 HH7-1089, and a Rohm Thermal Head KE 2008-F3.
  • the imagewise heating of the recording material with said printheads proceeds through a contacting but removable resin sheet or web wherefrom during said heating no transfer of imaging material can take place.
  • the imaging layer when being the outermost layer may contain hydrophilic finely divided (colloidal) optically transparent inert inorganic pigments such as transparent colloidal silica not masking the lateron formed silver image.
  • the imaging layer is coated with a protective coating and/or contains substances having anti-sticking properties e.g. (a) lubricating agent(s).
  • the outermost layer of the heat-sensitive recording material according to the present invention may comprise a dissolved lubricating material and/or a dispersed particulate lubricating material, e.g. talc particles, optionally protruding from the outermost layer.
  • suitable lubricating materials are a surface active agent, a liquid lubricant, a solid lubricant or mixtures thereof.
  • the surface active agents may be any agents known in the art such as carboxylates, sulfonates, phosphates, aliphatic amine salts, aliphatic quaternary ammonium salts, polyoxyethylene alkyl ethers. polyethylene glycol fatty acid esters, fluoroalkyl C 2 -C 20 aliphatic acids.
  • liquid lubricants include silicone oils, synthetic oils, saturated hydrocarbons and glycols.
  • solid organic lubricants include various higher alcohols such as stearyl alcohol, fatty acids and fatty acid esters.
  • outermost slipping layers are mentioned layers made from a styrene-acrylonitrile copolymer or a styrene-acrylonitrile-butadiene copolymer or binder mixture hereof containing as lubricant in an amount of 0.1 to 10 % by weight with respect to said binder(s) a polysiloxane-polyether copolymer or polytetrafluoroethylene or a mixture hereof.
  • Another suitable outermost slipping layer may be obtained by coating a solution of at least one silicon compound and a substance capable of forming during the coating procedure a polymer having an inorganic backbone which is an oxide of a group IVa or IVb element as described in published European patent application 0554576.
  • a subbed polyethylene terephthalate support having a thickness of 100 ⁇ m was doctor blade-coated from a coating composition containing methyl ethyl ketone as a solvent and the following ingredients so as to obtain thereon after drying for 1 h at 50 °C an imaging layer containing : silver behenate 5.30 g/m 2 polyvinyl butyral (BUTVAR B79-tradename) 5.30 g/m 2 ethyl gallate 1.18 g/m 2 3,4-dihydro-2,4-dioxo-1,3,2H-benzoxazine 0.39 g/m 2 3-nitro-phthalic acid ((NPA) in g/m 2 (see Table 1)
  • thermo head printer developed for thermosensitometric measurement purposes and having distinct groups of micro-resistors being arranged in succession along the width of the printhead array. From group to group said resistors receive a linearly increasing amount of electrical energy within the line time of the printer.
  • the input of electrical energy per group of resistors is controlled by linearly increasing the period of time from group to group wherein a constant current at constant voltage is applied, said current and voltage being kept constant over the whole printing period.
  • the line time is a period of time of 32 ms wherein the imaging material with respect to the print array travels a distance of a pixel length of 87 ⁇ m.
  • the print head was separated from the imaging layer by a thin intermediate material and made contact with the slipping layer of a separatable intermediate 5 ⁇ m thick polyethylene terephthalate ribbon being coated in consecutive order with a subbing layer, heat-resistant layer and said slipping layer (anti-friction layer) giving the ribbon a total thickness of 6 ⁇ m.
  • Said subbing layer also called primer layer, is a layer of a copolyester being a polycondensation product of ethylene glycol, adipic acid, neopentyl glycol, terephthalic acid, isophthalic acid and glycerol.
  • TEGOGLIDE 410 polyether modified polydimethylsiloxane
  • the numerical gradation value (NGV) corresponding with the quotient of the fraction (2.5 - 0.1)/(E 2.5 - E 0.1 ) was determined; herein E 2.5 is the energy in Joule applied in a dot area of 87 ⁇ m x 87 ⁇ m of the imaging layer that obtains by said energy an optical density value of 2.5, and E 0.1 is the energy in Joule applied in a dot area of the imaging layer material that obtains by said energy an optical density value of 0.1.
  • the applied energy in Joule is actually the electrical input energy measured for each resistor of the thermal head.
  • the recording materials A5 and A6 are invention materials, the other ones are comparative test materials.
  • a subbed polyethylene terephthalate support having a thickness of 100 ⁇ m was doctor blade-coated from a coating composition containing methyl ethyl ketone as a solvent and the following ingredients so as to obtain thereon after drying for 1 h at 50 °C an imaging layer containing : silver behenate 5.00 g/m 2 polyvinyl butyral (BUTVAR B79-tradename) 8.00 g/m 2 ethyl gallate 3.20 g/m 2 3,4-dihydro-2,4-dioxo-1,3,2H-benzoxazine 0.36 g/m 2 ortho-phthalic acid ((OPA) in g/m 2 (see Table 2)
  • the recording materials B4 and B5 are invention materials whereas the recording materials B1 to B3 are "non-invention" comparative test materials.
  • a subbed polyethylene terephthalate support having a thickness of 100 ⁇ m was doctor blade-coated from a coating composition containing methyl ethyl ketone as a solvent and the following ingredients so as to obtain thereon after drying for 1 h at 50 °C an imaging layer containing : silver behenate 4.50 g/m 2 polyvinyl butyral (BUTVAR B79-tradename) 17.60 g/m 2 n-butyl ester of 3,4-dihydroxy-benzoic acid 1.06 g/m 2 3,4-dihydro-2,4-dioxo-1,3,2H-benzoxazine 0.33 g/m 2 pimelic acid (PIA) in g/m 2 (see Table 3) BAYSILON ⁇ l A (tradename of BAYER AG) 20 mg/m 2
  • Material C0 is the "blanco" material free from polyacid. TABLE 3 Material PIA g/m 2 mole % of acid to silver behenate NGV C0 none - 3.10 C1 0.140 9 3.50 C2 0.280 18 3.10 C3 0.440 27.5 2.00
  • the recording material C3 is an invention material whereas the recording materials C1 and C2 are "non-invention" comparative test materials.
  • a subbed polyethylene terephthalate support having a thickness of 100 ⁇ m was doctor blade-coated from a coating composition containing methyl ethyl ketone as a solvent and the following ingredients so as to obtain thereon after drying for 1 h at 50 °C an imaging layer containing : silver behenate 4.50 g/m 2 polyvinyl butyral (BUTVAR B79-tradename) 17.60 g/m 2 n-butyl ester of 3,4-dihydroxy-benzoic acid 1.06 g/m 2 3,4-dihydro-2,4-dioxo-1,3,2H-benzoxazine 0.33 g/m 2 ortho-phthalic acid (OPA) in g/m 2 (see Table 4) BAYSILON ⁇ l A (tradename of BAYER AG) 20 mg/m 2
  • Material D0 is the "blanco" material free from polyacid.
  • TABLE 4 Material OPA g/m 2 mole % of acid to silver behenate NGV D0 none - 3.10 D1 0.150 9 3.40 D2 0.300 18 3.00 D3 0.460 27.5 1.80
  • the recording material D3 is an invention material whereas the recording materials D1 and D2 are "non-invention" comparative test materials.
  • a subbed polyethylene terephthalate support having a thickness of 100 ⁇ m was doctor blade-coated from a coating composition containing methyl ethyl ketone as a solvent and the following ingredients so as to obtain thereon after drying for 1 h at 50 °C an imaging layer containing : silver behenate 5.30 g/m 2 polyvinyl butyral (BUTVAR B79-tradename) 5.30 g/m 2 ethyl gallate 1.18 g/m 2 3,4-dihydro-2,4-dioxo-1,3,2H-benzoxazine 0.39 g/m 2 ortho-phthalic acid ((OPA) or benzoic acid (BA) in g/m 2 (see Table 5)
  • the recording material E4 is an invention materials, the other ones are “non-invention" comparative test materials.
  • a subbed polyethylene terephthalate support having a thickness of 100 ⁇ m was doctor blade-coated from a coating composition containing methyl ethyl ketone as a solvent and the following ingredients so as to obtain thereon after drying for 1 h at 50 °C an imaging layer containing : silver behenate 4.50 g/m 2 polyvinyl butyral (BUTVAR B79-tradename) 17.60 g/m 2 n-butyl ester of 3,4-dihydroxy-benzoic acid 1.06 g/m 2 3,4-dihydro-2,4-dioxo-1,3,2H-benzoxazine 0.33 g/m 2 pimelic acid (PIA) and o-phthalic acid (OPA) in g/m 2 (see Table 6) BAYSILON ⁇ l A (tradename of BAYER AG) 20 mg/m 2
  • Material F0 is a blanco material free from polyacid.
  • TABLE 6 Material PIA g/m 2 OPA g/m 2 mole % of acid to silver behenate NGV F0 none none - 3.1 F1 0.44 none 27.5 2.0 F2 0.23 0.24 (14 + 14) 2.3
  • the recording material E1 and E2 are invention materials.
  • a subbed polyethylene terephthalate support having a thickness of 100 ⁇ m was doctor blade-coated from a coating composition containing methyl ethyl ketone as a solvent and the following ingredients so as to obtain thereon after drying for 1 h at 50 °C an imaging layer containing : silver behenate 5.30 g/m 2 polyvinyl butyral (BUTVAR B79-tradename) 5.30 g/m 2 ethyl gallate 1.18 g/m 2 3,4-dihydro-2,4-dioxo-1,3,2H-benzoxazine 0.39 g/m 2 pimelic acid (PIA) or adipic acid (ADI) or sebacic acid (SEBA) in g/m 2 (see Table 7)
  • the recording materials G1 to G3 are invention materials.
  • a subbed polyethylene terephthalate support having a thickness of 100 ⁇ m was doctor blade-coated from a coating composition containing methyl ethyl ketone as a solvent and the following ingredients so as to obtain thereon after drying for 1 h at 50 °C an imaging layer containing per m 2 : silver behenate 4.50 g polyvinyl butyral (BUTVAR B79-tradename) see Table X adipic acid (AA) see Table X 3,4-dihydro-2,4-dioxo-1,3,2H-benzoxazine 0.33 g/m 2 tetrachlorophthalic anhydride (TCFA) see Table X reducing agent see Table X BAYSILON ⁇ l A (tradename of BAYER AG) 20 mg
  • the maximum optical density (Dmax) obtainable with di-tert-butyl-p-cresol or 3,5-dihydroxy benzoic acid as sole reducing agents is too low for defining the numerical gradation value NGV (see non-invention recording materials X2, X3, X5 and X6).
  • the optical background density, also called minimum density (Dmin) is practically the same for all of the recording materials X1-X6.

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  • Physics & Mathematics (AREA)
  • Optics & Photonics (AREA)
  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Materials Engineering (AREA)
  • General Physics & Mathematics (AREA)
  • Heat Sensitive Colour Forming Recording (AREA)
  • Non-Silver Salt Photosensitive Materials And Non-Silver Salt Photography (AREA)

Claims (12)

  1. Ein thermisches Direktbilderzeugungsverfahren, in dem ein lichtunempfindliches thermisches Direktaufzeichnungsmaterial punktweise erhitzt wird und das thermische Direktaufzeichnungsmaterial eine ein oder mehrere gleichmäßig in einem filmbildenden polymeren Bindemittel (i) verteilte, wesentlich lichtunempfindliche, organische Silbersalze enthaltende Bilderzeugungsschicht enthält, wobei das (die) Silbersalz(e) gleichmäßig in thermisch aktiver Beziehung zu (ii) einem oder mehreren damit benutzten Reduktionsmitteln steht (stehen), wobei aber 3,5-Dihydroxybenzoesäure als saures Reagens und Di-tert-butyl-p-kresol als einziges Reduktionsmittel ausgeschlossen sind, dadurch gekennzeichnet, daß die Bilderzeugungsschicht wenigstens eine Polycarbonsäure und/oder wenigstens ein Polycarbonsäureanhydrid in einem Molverhältnis von wenigstens 20 bezogen auf das (die) Silbersalz(e) enthält.
  2. Aufzeichnungsverfahren nach Anspruch 1, dadurch gekennzeichnet, daß der Molprozentsatz zwischen 20 und 30 liegt.
  3. Aufzeichnungsverfahren nach Anspruch 1 oder 2, dadurch gekennzeichnet, daß das wesentlich lichtunempfindliche organische Silbersalz ein Silbersalz einer alifatischen Carbonsäure mit wenigstens 12 Kohlenstoffatomen ist.
  4. Aufzeichnungsverfahren nach Anspruch 3, dadurch gekennzeichnet, daß das organische Silbersalz Silberpalmitat, Silberstearat oder Silberbehenat oder eine Mischung derselben ist.
  5. Aufzeichnungsverfahren nach irgendeinem der vorstehenden Ansprüche, dadurch gekennzeichnet, daß das Reduktionsmittel ein Reduktionsmittel des Polyhydroxybenzoltyps ist.
  6. Aufzeichnungsverfahren nach irgendeinem der vorstehenden Ansprüche, dadurch gekennzeichnet, daß das Reduktionsmittel Pyrocatechin, 3-(3,4-Dihydroxyphenyl)propionsäure, 1,2-Dihydroxybenzoesäure, Gallussäure oder ein Gallussäureester, Gerbsäure, ein 3,4-Dihydroxybenzoesäureester oder eine Polyhydroxyspiro-bis-indanverbindung ist.
  7. Aufzeichnungsverfahren nach irgendeinem der vorstehenden Ansprüche, dadurch gekennzeichnet, daß die Polycarbonsäure oder das Polycarbonsäureanhydrid eine gegebenenfalls mit einer Alkyl-, Hydroxyl-, Nitro- oder Halogengruppe substituierte, alifatische oder aromatische Polycarbonsäure ist.
  8. Aufzeichnungsverfahren nach irgendeinem der vorstehenden Ansprüche, dadurch gekennzeichnet, daß die Polycarbonsäure Bernsteinsäure, Glutarsäure, Adipinsäure, Pimelinsäure, Korksäure, Azelainsäure, Sebacinsäure, Nonandicarbonsäure, Decandicarbonsäure, Undecandicarbonsäure, Maleinsäure, Zitrakonsäure, Itakonsäure, Aconitsäure, Zitronensäure, Acetondicarbonsäure, Isozitronensäure, α-Ketoglutarsäure, ortho-Phthalsäure, 3-Nitrophthalsäure, Tetrachlorphthalsäure, Mellitsäure, Pyromellitsäure, Trimellitsäure oder ein Anhydrid derselben ist.
  9. Aufzeichnungsverfahren nach irgendeinem der vorstehenden Ansprüche, dadurch gekennzeichnet, daß die Aufzeichnungsschicht in Zumischung mit dem Silbersalz wenigstens ein Tönungsmittel enthält, das ein Phthalimid, ein Phthalazinon oder eine heterocyclische Verbindung entsprechend der folgenden allgemeinen Formel ist:
    Figure imgb0006
     in der bedeuten :
    X O oder eine N-Alkylgruppe,
    R1, R2, R3 und R4 (gleich oder verschieden) Wasserstoff, eine Alkylgruppe, eine Cycloalkylgruppe, eine Alkoxygruppe, eine Alkylthiogruppe, eine Hydroxylgruppe, eine Dialkylaminogruppe oder eine Halogengruppe, oder in der R1 und R2 oder R2 und R3 zusammen die zum Vervollständigen eines anellierten aromatischen Ringes benötigten Ringglieder, oder R3 und R4 zusammen die zum Vervollständigen eines anellierten aromatischen Ringes oder Cyclonhexanringes benötigten Ringglieder bedeuten.
  10. Aufzeichnungsverfahren nach Anspruch 1, dadurch gekennzeichnet, daß das Bindemittel-Silbersalz-Gewichtsverhältnis in der Bilderzeugungsschicht zwischen 1/2 und 6/1 liegt.
  11. Aufzeichnungsverfahren nach irgendeinem der vorstehenden Ansprüche, dadurch gekennzeichnet, daß das Bindemittel ein Polyvinylbutyral ist.
  12. Aufzeichnungsverfahren nach irgendeinem der Ansprüche 1 bis 11, dadurch gekennzeichnet, daß das wesentlich lichtunempfindliche organische Silbersalz und das organische Reduktionsmittel in verschiedenen Schichten enthalten sind, von denen sie unter Einwirkung von Wärme in reaktionsfähigem Kontakt miteinander kommen können.
EP95201340A 1994-06-15 1995-05-23 Wärmeempfindliches Aufzeichnungsverfahren Expired - Lifetime EP0687572B1 (de)

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