EP0901040B1 - Matériau d'enregistrement thermographique pratiquement insensible à la lumière ayant une meilleure stabilité et un ton de l'image amélioré - Google Patents

Matériau d'enregistrement thermographique pratiquement insensible à la lumière ayant une meilleure stabilité et un ton de l'image amélioré Download PDF

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Publication number
EP0901040B1
EP0901040B1 EP98202542A EP98202542A EP0901040B1 EP 0901040 B1 EP0901040 B1 EP 0901040B1 EP 98202542 A EP98202542 A EP 98202542A EP 98202542 A EP98202542 A EP 98202542A EP 0901040 B1 EP0901040 B1 EP 0901040B1
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EP
European Patent Office
Prior art keywords
recording material
thermosensitive element
image
insensitive
substantially light
Prior art date
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EP98202542A
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German (de)
English (en)
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EP0901040A1 (fr
Inventor
Johan Loccufier
David Terrell
Carlo Uyttendaele
Bart Horsten
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Agfa Gevaert NV
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Agfa Gevaert NV
Agfa Gevaert AG
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Classifications

    • G—PHYSICS
    • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
    • G03C—PHOTOSENSITIVE MATERIALS FOR PHOTOGRAPHIC PURPOSES; PHOTOGRAPHIC PROCESSES, e.g. CINE, X-RAY, COLOUR, STEREO-PHOTOGRAPHIC PROCESSES; AUXILIARY PROCESSES IN PHOTOGRAPHY
    • G03C1/00—Photosensitive materials
    • G03C1/494—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
    • 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
    • G03C1/005—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
    • G03C1/34—Fog-inhibitors; Stabilisers; Agents inhibiting latent image regression
    • 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
    • G03C1/34—Fog-inhibitors; Stabilisers; Agents inhibiting latent image regression
    • G03C1/346—Organic derivatives of bivalent sulfur, selenium or tellurium
    • G—PHYSICS
    • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
    • G03C—PHOTOSENSITIVE MATERIALS FOR PHOTOGRAPHIC PURPOSES; PHOTOGRAPHIC PROCESSES, e.g. CINE, X-RAY, COLOUR, STEREO-PHOTOGRAPHIC PROCESSES; AUXILIARY PROCESSES IN PHOTOGRAPHY
    • 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
    • G03C1/49872—Aspects relating to non-photosensitive layers, e.g. intermediate protective layers
    • 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
    • G03C1/76—Photosensitive materials characterised by the base or auxiliary layers
    • G03C1/7614—Cover layers; Backing layers; Base or auxiliary layers characterised by means for lubricating, for rendering anti-abrasive or for preventing adhesion
    • 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
    • G03C1/76—Photosensitive materials characterised by the base or auxiliary layers
    • G03C1/7614—Cover layers; Backing layers; Base or auxiliary layers characterised by means for lubricating, for rendering anti-abrasive or for preventing adhesion
    • G03C2001/7635—Protective layer
    • G—PHYSICS
    • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
    • G03C—PHOTOSENSITIVE MATERIALS FOR PHOTOGRAPHIC PURPOSES; PHOTOGRAPHIC PROCESSES, e.g. CINE, X-RAY, COLOUR, STEREO-PHOTOGRAPHIC PROCESSES; AUXILIARY PROCESSES IN PHOTOGRAPHY
    • G03C2200/00—Details
    • G03C2200/33—Heterocyclic
    • 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
    • G03C2200/40—Mercapto compound

Definitions

  • the present invention relates to a substantially light-insensitive thermographic recording material suitable for thermal development. In particular, it concerns improvements in stabilization thereof.
  • Thermal imaging or thermography is a recording process wherein images are generated by the use of imagewise modulated thermal energy.
  • a survey of "direct thermal” imaging methods is given e.g. in the book “Imaging Systems” by Kurt I. Jacobson-Ralph E. Jacobson, The Focal Press - London and New York (1976), Chapter VII under the heading "7.1 Thermography”.
  • Direct thermal 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.
  • WO 94/16361 discloses a multilayer heat-sensitive material for direct thermal recording for which no intermediate drying of organic noble metal salts is necessary and which is coatable from aqueous dispersions.
  • This material comprises: a colour-forming amount of finely divided, solid colourless noble metal or iron salt of an organic acid distributed in a carrier composition; a color-developing amount of a cyclic or aromatic organic reducing agent, which at thermal copy and printing temperatures is capable of a colour-forming reaction with the noble metal or iron salt; and an image toning agent; characterized in that (a) the carrier composition comprises a substantially water-soluble polymeric carrier and a dispersing agent for the noble metal or iron salt and (b) the material comprises a protective overcoating layer for the colour-forming layer.
  • suitable antifoggants for use in the invention are well-known photographic antifoggants such as 2-mercaptobenzo-triazole, chromate, oxalate, carbonate, benzotriazole (BZT), 5-methylbenzotriazole, 5,6-dimethylbenzotriazole, 5-bromobenzotriazole, 5-chlorobenzo-triazole, 5-nitrobenzotriazole, 4-nitro-6-chlorobenzotriazole, 5-nitro-6-chlorobenzotriazole, 4-hydroxy-6-methyl-1,3,3a,7-tetraazaindene, benzimidazole, 2-methylbenzimidazole, 5-nitrobenzimidazole, 1-phenyl-5-mercaptotetrazole (PMT), 2-mercaptobenzimidazole, 2-mercaptobenzothiazole, 2-mercaptobenzoxazole, 2-mercaptothiazoline, 2-mercapto-4-methyl-6,6'-dimethylpyr
  • EP-A 809 143 which falls under Article 54(3) EPC, discloses a substantially non-photosensitive recording material comprising a thermosensitive element comprising a substantially light-insensitive organic silver salt, an organic reducing agent therefor in thermal working relationship therewith and a binder, on a support, characterized in that the thermosensitive element further comprises in reactive association with the substantially light-insensitive organic silver salt and the organic reducing agent a substituted or unsubstituted compound with an unsaturated 5-membered heterocyclic ring consisting of nitrogen and carbon atoms with at least one of the nitrogen atoms having a hydrogen atom and none of the carbon atoms being part of a thione-group, the ring not being annulated with an aromatic ring system and the compound being exclusive of 1,2,4-triazole and substituted 1,2,4-triazole compounds.
  • EP-A 809 144 which falls under Article 54(3) EPC, discloses a substantially non-photosensitive recording material comprising a thermosensitive element comprising a substantially light-insensitive organic silver salt, an organic reducing agent therefor in thermal working relationship therewith and a binder, on a support, characterized in that the thermosensitive element further comprises in reactive association with the substantially light-insensitive organic silver salt and the organic reducing agent a substituted or unsubstituted 1,2,4-triazole compound with at least one of the nitrogen atoms having a hydrogen atom and none of the carbon atoms being part of a thione-group, the compound not being annulated with an aromatic ring system.
  • EP-A 809 142 which falls under Article 54(3) EPC, discloses a recording material comprising a support, a thermosensitive element and a protective layer therefor, the thermosensitive element comprising a substantially light-insensitive organic silver salt, an organic reducing agent therefor in thermal working relationship therewith and a binder, wherein the thermosensitive element further comprises in reactive association with the substantially light-insensitive organic silver salt and the organic reducing agent a substituted, exclusive of groups having an exclusively electron withdrawing character, or unsubstituted compound with an unsaturated 5-membered heterocyclic ring annulated with an aromatic ring system, the ring consisting of nitrogen and carbon atoms with at least one of the nitrogen atoms having a hydrogen atom and none of the carbon atoms being directly linked to a sulfur atom or being part of a carbonyl-group.
  • thermographic recording materials it is therefore an object of the invention to provide a means of stabilizing the image of thermographic recording materials during storage.
  • EP-A 809 142, EP-A 809 143 and EP-A 809 144 address the problem of background colour resulting from exposure to light, which is a particular problem in thermographic materials used for producing continuous tone transparencies for medical and other applications having numerical gradation values less than or equal to 2.3.
  • the present invention addresses the problem of stabilization of the background density during storage prior to use of the intrinsically more thermosensitive thermographic materials based on substantially light-insensitive organic silver salts and reducing agents used for producing steep gradation, so-called graphics images, with numerical gradation values greater than 2.3 as transparencies or on a white support, for which the prior art stabilizers are unsuitable.
  • thermosensitive element containing a substantially light-insensitive organic silver salt, an organic reducing agent therefor in thermal working relationship therewith and a binder
  • thermosensitive element further contains a unsaturated heterocyclic stabilizer compound, which stabilizes said thermosensitive element against the influence of light, represented by formula (I) : where Q are the necessary atoms to form a 5- or 6-membered aromatic heterocyclic ring, which may also be substituted, A is selected from hydrogen, a counterion to compensate the negative charge of the thiolate group or a group forming a symmetrical or an asymmetrical disulfide and the recording material is capable of producing prints with a numerical gradation value defined as the quotient of the fraction (2.5 - 0.1)/(E 2.5 - E 0.1 ) greater than 2.3, where E 2.5 is the energy in Joule applied in a dot area of 87 ⁇ m x
  • a thermal image recording process comprising the steps of: (i) providing a substantially light-insensitive recording material, as described above; (ii) bringing an outermost layer of the recording material into proximity with a heat source; (iii) applying heat from a heat source image-wise to the recording material while maintaining proximity to the heat source to produce an image; and (iv) separating the recording material from the heat source.
  • a thermal image forming process is realized, wherein the heat source is a thermal head.
  • substantially light-insensitive is meant not intentionally light sensitive.
  • the stabilizer compound for use in the present invention may be further substituted, which substitution also includes the atoms necessary to form an annulated unsaturated carbocyclic or heterocyclic ring system.
  • Preferred substituents include acylamido, aryl-SO 2 NH-, alkyl-SO 2 NH-, aryl-NHSO 2 -, alkyl-NHSO 2 -, arylamino, alkyl, aryl, nitro and cyano groups and halogen atoms.
  • Preferred stablizer compounds used in the present invention have an unsaturated 5- or 6-membered ring.
  • Particularly preferred stabilizer compounds used in the present invention are represented by the formulae:
  • Suitable stabilizer compounds for use in the present invention are given below:
  • thermosensitive element comprises a substantially light-insensitive organic silver salt and an organic reducing agent therefor in thermal working relationship therewith in reactive association with a compound represented by formula (I).
  • the element may comprise a layer system in which the ingredients may be dispersed in different layers, with the proviso that all three ingredients are in reactive association with one another i.e. during the thermal development process the reducing agent and the stabilizer compound must be present in such a way that they are able to diffuse to the substantially light-insensitive organic silver salt particles so that reduction of the organic silver salt to silver giving the desired image-tone can take place.
  • the stabilizer compound must be present in such a way that the thermosensitive element can be stabilized against the influence of light.
  • Preferred organic silver salts 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, with silver behenate being particularly preferred.
  • Such silver salts are also called "silver soaps”.
  • Suitable organic reducing agents for the reduction of the substantially light-insensitive organic silver salts are organic compounds containing at least one active hydrogen atom linked to O, N or C, such as is the case with, aromatic di- and tri-hydroxy compounds; aminophenols; METOLTM; p-phenylenediamines; alkoxynaphthols, e.g. 4-methoxy-1-naphthol described in US-P 3,094,41; pyrazolidin-3-one type reducing agents, e.g.
  • PHENIDONETM pyrazolin-5-ones; indan-1,3-dione derivatives; hydroxytetrone acids; hydroxytetronimides; hydroxylamine derivatives such as for example described in US-P 4,082,901; hydrazine derivatives; and reductones e.g. ascorbic acid; see also US-P 3,074,809, 3,080,254, 3,094,417 and 3,887,378.
  • Preferred catechol-type reducing agents are benzene compounds in which the benzene nucleus is substituted by no more than two hydroxy groups which are present in 3,4-position on the nucleus and have in the 1-position of the nucleus a substituent linked to the nucleus by means of a carbonyl group disclosed in EP-A 692 733.
  • the silver image density depends on the coverage of the above defined reducing agent(s) and organic silver salt(s) and has to be such that, on heating above 100 °C, an optical density of at least 2.5 can be obtained.
  • an optical density of at least 2.5 can be obtained.
  • at least 0.10 moles of reducing agent per mole of organic silver salt is used.
  • auxiliary reducing agents are e.g. sterically hindered phenols, such as described in US-P 4,001,026; bisphenols, e.g. of the type described in US-P 3,547,648; or sulfonamidophenols as described in Research Disclosure 17842 published in February 1979, US-P 4,360,581, US-P 4,782,004 and in EP-A 423 891.
  • the auxiliary reducing agents may be present in the imaging layer or in a-polymeric binder layer in thermal working relationship thereto.
  • auxiliary reducing agents that may be used in conjunction with the above mentioned primary reducing agents are hydrazides such as disclosed in EP-A 762 196, 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 organic reducing metal salts, e.g. stannous stearate described in US-P 3,460,946 and 3,547,648.
  • hydrazides such as disclosed in EP-A 762 196, sulfonyl hydrazi
  • the thermosensitive element may comprise in addition at least one polycarboxylic acid and/or anhydride thereof in a molar percentage of at least 15 with respect to all the organic silver salt(s) present and in thermal working relationship therewith.
  • the polycarboxylic acid may be aliphatic (saturated as well as unsaturated aliphatic and also cycloaliphatic) or an aromatic polycarboxylic acid, may be substituted and 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.
  • the film-forming binder of the thermosensitive element containing the substantially light-insensitive organic silver salt may be all kinds of natural, modified natural or synthetic resins or mixtures of such resins, wherein the organic silver salts can be dispersed homogeneously: e.g. cellulose derivatives such as ethylcellulose, cellulose esters, e.g.
  • cellulose nitrate carboxymethylcellulose, starch ethers, galactomannan, polyesters, polyurethanes, polycarbonates, polymers derived from ⁇ , ⁇ -ethylenically unsaturated compounds such as after-chlorinated polyvinyl chloride, partially hydrolyzed polyvinyl acetate, polyvinyl alcohol, polyvinyl acetals, preferably polyvinyl butyral, and homopolymers and copolymers produced using monomers selected from the group consisting of: vinyl chloride, vinylidene chloride, acrylonitrile, acrylamides, methacrylamides; methacrylates, acrylates, methacrylic acid, acrylic acid, vinyl esters, styrenes, dienes and alkenes; or mixtures thereof.
  • vinyl chloride vinylidene chloride
  • acrylonitrile acrylamides, methacrylamides
  • methacrylates methacrylic acid
  • acrylic acid acrylic acid
  • vinyl esters st
  • the layer containing the organic silver salt is commonly coated onto a support in sheet- or web-form from an organic solvent containing the binder dissolved therein, but may be applied from an aqueous medium as a latex, i.e. as an aqueous polymer dispersion.
  • a latex i.e. as an aqueous polymer dispersion.
  • the dispersible polymer has preferably some hydrophilic functionality.
  • the ratio of the total weight of any binders in the thermosensitive element to the total weight of organic silver salts in the thermosensitive element is preferably less than 2.0 and the thickness of the recording layer is preferably in the range of 5 to 50 ⁇ m.
  • binders or mixtures thereof may be used in conjunction 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 heavy metal salt, at a temperature above 60°C.
  • the recording layer contains preferably in admixture with the organic silver salts and reducing agents 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.
  • Other particularly useful toning agents are the heterocyclic toner compounds of the benzoxazine dione or naphthoxazine dione type are described in GB-P 1,439,478, US-P 3,951,660 and US-P 5,599,647.
  • the recording layer may contain in addition to the ingredients mentioned above other additives such as free fatty acids, surface-active 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, ultraviolet light absorbing compounds, white light reflecting and/or ultraviolet radiation reflecting pigments and/or optical brightening agents.
  • additives such as free fatty acids, surface-active 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, ultraviolet light absorbing compounds, white light reflecting and/or ultraviolet radiation reflecting pigments and/or optical brightening agents.
  • the support for the thermal imaging material 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 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.
  • 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 thermosensitive recording layer.
  • the support may be made of an opacified resin composition as described in EP's 194 106 and 234 563 and US-P's 3,944,699, 4,187,113, 4,780,402 and 5,059,579. 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.
  • the outermost layer of the substantially light-insensitive 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 coated 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 hydrophobic (solvent soluble) of hydrophilic (water soluble).
  • a binder which may be hydrophobic (solvent soluble) of hydrophilic (water soluble).
  • hydrophobic binders polycarbonates as described in EP-A 614 769 are particularly preferred.
  • hydrophilic binders are preferred for the protective layer, as coating can be performed from an aqueous composition and mixing of the hydrophilic protective layer with the immediate underlayer can be avoided by using a hydrophobic binder in the immediate underlayer.
  • a protective layer according to the present invention may further comprise a thermomeltable particle optionally with a lubricant present on top of the protective layer as described in WO 94/11199.
  • the lubricant which may be a surface active agent, a solid lubricant or a liquid lubricant, may be applied with or without a polymeric binder.
  • Other additives can also be incorporated in the protective layer e.g. colloidal particles such as colloidal silica.
  • the outermost layer of the substantially light-insensitive recording material may comprise a hydrophilic binder.
  • Suitable hydrophilic binders for the outermost layer are, for example, gelatin, polyvinylalcohol, cellulose derivatives or other polysaccharides, hydroxyethylcellulose, hydroxypropylcellulose, with hardenable binders being preferred and polyvinylalcohol being particularly preferred.
  • 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, with tetraalkoxysilanes such as tetramethylorthosilicate and tetraethylorthosilicate being preferred.
  • crosslinking agents such as described in WO 95/12495 for protective layers, e.g. tetra-alkoxysilanes, polyisocyanates, zirconates, titanates, melamine resins, with tetraalkoxysilanes such as tetramethylorthosilicate and tetraethylorthosilicate being preferred.
  • the outermost layer of the substantially light-insensitive 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 such as described above for use in protective layers are also suitable for incorporation in the outermost layer to improve the slip characteristics of the substantially light-insensitive recording materials according to the present invention.
  • an antistatic layer is the outermost layer on the other side of the support to the thermosensitive element.
  • any layer of the substantially light-insensitive 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, or by direct thermal imaging with a thermal head.
  • 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 via the Joule effect into heat, which is transferred to the surface of the thermographic material, wherein the chemical reaction resulting in the development of a black and white image takes place.
  • Such thermal printing heads may be used in contact or close proximity with the recording layer.
  • 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 1.0 ms, 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 layer 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.
  • EP-A 654 355 describes 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 pulse-wise.
  • the thermographic materials are not suitable for reproducing images with fairly large number of grey levels as is required for continuous tone reproduction.
  • 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 thermographic material can also be carried out using an electrically resistive ribbon incorporated into the material.
  • Image- or pattern-wise heating of the thermographic material may also proceed by means of pixel-wise modulated ultra-sound, using e.g. an ultrasonic pixel printer as described e.g. in US-P 4,908,631.
  • Direct thermal imaging can be used for both the production of transparencies and reflection type prints.
  • Application of the present invention is envisaged in the fields of graphics images requiring high contrast images with a very steep print density applied dot energy dependence.
  • substantially light-insensitive recording materials on a white opaque base are used as well as transparencies used in inspection techniques operating with a light box.
  • thermosensitive element thermosensitive element
  • a 100 ⁇ m thick support coated with the following subbing-layer composition # terpolymer latex of vinylidene chloride/methyl acrylate/itaconic acid (88/10/2) 162mg/m 2 # colloidal silica (KIESELSOLTM 100F from BAYER) 38mg/m 2 # alkyl sulfonate surfactant (Surfactant Nr. 1) 0.6mg/m 2 # aryl sulfonate surfactant (Surfactant Nr. 2) 4mg/m 2 was doctor blade-coated with a coating composition containing butanone as a solvent and the following ingredients so as to obtain thereon.
  • 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 (anti-friction layer) giving 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 32ms (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 1.86 mJ/dot being sufficient to obtain maximum optical density in each of the thermographic materials of COMPARATIVE EXAMPLE 1 and INVENTION EXAMPLES 1 to 5.
  • the maximum densities, D max , and minimum densities D min , of the prints were measured through a blue filter with a MacBethTM TR904 densitometer in the grey scale step corresponding to data levels of 255 and 0 respectively and are given in table 2.
  • thermographic materials of COMPARATIVE EXAMPLE 1 and INVENTION EXAMPLES 1 to 5 were evaluated on the basis of the observed changes in minimum density, ⁇ D min , and maximum density, ⁇ D max , printing the thermographic recording materials before and after heating the materials at 57°C in a relative humidity (RH) of 34% for 3 days in the dark. The results are given in table 2.

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Claims (7)

  1. Matériau d'enregistrement monofeuille essentiellement non photosensible comprenant un support et un élément thermosensible contenant un sel d'argent organique essentiellement non photosensible, un agent de réduction organique pour ce dernier en relation de travail thermique avec lui et un liant, caractérisé en ce que ledit élément thermosensible contient en outre un composé de stabilisation hétérocyclique insaturé qui stabilise ledit élément thermosensible contre l'influence de la lumière, représenté par la formule (I) :
    Figure 00250001
    dans laquelle Q représente les atomes nécessaires pour former un noyau hétérocyclique aromatique pentagonal ou hexagonal qui peut également être substitué, A est choisi parmi le groupe comprenant un atome d'hydrogène, un ion antagoniste pour compenser la charge négative du groupe thiolate et un groupe formant un disulfure symétrique ou asymétrique, ledit matériau d'enregistrement étant capable de produire des copies qui possèdent une valeur de gradation numérique, définie comme étant le quotient de la fraction (2,5 - 0,1)/(E2,5 - E0,1), supérieure à 2,3, E2,5 représentant l'énergie en Joule appliquée dans une aire de points de trame de 87 µm x 87 µm de la couche de formation d'image qui produit une valeur densité optique de 2,5, et E0,1 représentant l'énergie en Joule appliquée dans une aire de points de trame de la couche de formation d'image qui produit une valeur densité optique de 0,1.
  2. Matériau d'enregistrement selon la revendication 1, dans lequel ledit composé de stabilisation répond à la formule indiquée ci-après:
    Figure 00260001
  3. Matériau d'enregistrement selon la revendication 1, dans lequel ledit composé de stabilisation répond à la formule indiquée ci-après:
    Figure 00260002
  4. Matériau d'enregistrement selon l'une quelconque des revendications précédentes, dans lequel le rapport du poids total de n'importe quel liant dans ledit élément thermosensible au poids total des sels d'argent organiques dans ledit élément thermosensible est inférieur à 2,0.
  5. Matériau d'enregistrement selon l'une quelconque des revendications précédentes, dans lequel ledit élément thermosensible est recouvert d'une couche de protection.
  6. Procédé d'enregistrement d'images thermiques comprenant les étapes consistant à : (i) procurer un matériau d'enregistrement essentiellement non photosensible selon l'une quelconque des revendications 1 à 5 ; (ii) amener à proximité d'une source de chaleur une couche dudit matériau d'enregistrement située le plus à l'extérieur; (iii) appliquer de la chaleur à partir d'une source de chaleur en forme d'image sur ledit matériau d'enregistrement tandis que l'on maintient ce dernier à proximité de ladite source de chaleur dans le but de produire une image ; et (iv) mettre ledit matériau d'enregistrement à l'écart de ladite source de chaleur.
  7. Procédé de formation d'image thermique selon la revendication 6, dans lequel ladite source de chaleur est une tête thermique.
EP98202542A 1997-09-03 1998-07-29 Matériau d'enregistrement thermographique pratiquement insensible à la lumière ayant une meilleure stabilité et un ton de l'image amélioré Expired - Lifetime EP0901040B1 (fr)

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US6902880B2 (en) 2002-11-14 2005-06-07 Agfa-Gevaert Stabilizers for use in substantially light-insensitive thermographic recording materials
US7060655B2 (en) 2002-11-14 2006-06-13 Agfa Gevaert Stabilizers for use in substantially light-insensitive thermographic recording materials
US6908731B2 (en) 2002-11-14 2005-06-21 Agfa-Gevaert Stabilizers for use in substantially light-insensitive thermographic recording materials
US7175977B2 (en) 2003-12-18 2007-02-13 Agfa-Gevaert Stabilizers for use in thermographic recording materials
US7294605B2 (en) 2003-12-18 2007-11-13 Agfa-Healthcare Thermographic recording materials containing a mesionic, 1,2,4-triazolium-3-thiolate compound
US7097961B2 (en) 2004-05-17 2006-08-29 Agfa Gevaert Stabilizers for use in substantially light-insensitive thermographic recording materials
EP1598207B1 (fr) * 2004-05-17 2008-01-16 Agfa HealthCare NV Stabilisateurs à utiliser dans des matériaux d' enregistrement thermographiques essentiellement non photosensibles

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US5424182A (en) * 1993-01-15 1995-06-13 Labelon Corporation Aqueous coating composition for thermal imaging film
EP0687572B1 (fr) * 1994-06-15 1997-08-20 Agfa-Gevaert N.V. Méthode pour l'enregistrement par la chaleur

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