EP0677775B1 - Thermotransferaufzeichnungsverfahren - Google Patents

Thermotransferaufzeichnungsverfahren Download PDF

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Publication number
EP0677775B1
EP0677775B1 EP19950200411 EP95200411A EP0677775B1 EP 0677775 B1 EP0677775 B1 EP 0677775B1 EP 19950200411 EP19950200411 EP 19950200411 EP 95200411 A EP95200411 A EP 95200411A EP 0677775 B1 EP0677775 B1 EP 0677775B1
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EP
European Patent Office
Prior art keywords
layer
imaging process
donor
thermal imaging
dye
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EP19950200411
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English (en)
French (fr)
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EP0677775A1 (de
Inventor
Geert C/O Agfa-Gevaert N.V. Defieuw
Wilhelmus C/O Agfa-Gevaert N.V. Janssens
Luc C/O Agfa-Gevaert N.V. Vanmaele
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Agfa Gevaert NV
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Agfa Gevaert NV
Agfa Gevaert AG
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Priority to EP19950200411 priority Critical patent/EP0677775B1/de
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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
    • G03C1/4989—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
    • G03C2200/00—Details
    • G03C2200/22—Dye or dye precursor

Definitions

  • the present invention relates to a thermal imaging process, more in particular to a method wherein a thermotransferable reducing agent of a donor element is transferred image-wise to a receiving layer comprising a thermoreducible silver source, by means of e.g. a thermal head or a laser.
  • Thermal imaging or thermography is a recording process wherein images are generated by the use of image-wise modulated thermal energy.
  • thermography two approaches are known :
  • Thermography is converned with materials which are not photosensitive, but are heat sensitive. Imagewise applied heat is sufficient to bring about a visible change in a thermosensitive imaging material.
  • a recording material which contains a coloured support or support coated with a coloured layer which itself is overcoated with an opaque white light reflecting layer that can fuse to a clear, transparent state whereby the coloured support is no longer masked.
  • Physical thermographic systems operating with such kind of recording material are described on pages 136 and 137 of the above mentioned book of Kurt I. Jacobson et al.
  • 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.
  • thermoreducible silver source in combination with a reducing agent in a direct thermal film in order to increase the optical density in transmission of a printed image
  • a thermoreducible silver source in combination with a reducing agent in a direct thermal film in order to increase the optical density in transmission of a printed image
  • continuous tones can be obtained by the printing method
  • the gradation produced by the printing method is too high. Fluctuations in the heat transfer from the heat source to the printing material result in a density difference of the final image.
  • a direct thermal printing method moreover has the disadvantage that in the non-image places the coreactants always remains unchanged, impairing the shelf-life and preservability.
  • US-A-3 094 417 discloses a heat-sensitive copy-sheet product capable of becoming locally visibly altered and highly infra-red absorptive on localized brief heating at a conversion temperature between about 90°C and about 150°C, comprising a paper-like backing, a visibly heat-sensitive layer, and a surface layer comprising a heat-transferable image-forming component; the heat-sensitive layer comprising chemically inter-reactant components in physically distinct and chemically inter-reactive relationship for interreaction to form a visibly distinct and infra-red absorptive reaction product upon heating the layer to the conversion temperature, one of the inter-reactant components being readily desensitizable against the inter-reaction by exposure, in solution in an inert solvent at a concentration just sufficient to permit distinctly visible reaction with the other of the components in the solvent, to radiation in the near-ultraviolet range of approximately 3000 to 4200 angstroms (300 to 420 nm) wavelength as obtained from a BH
  • JP-A-61 259 253 discloses a heat developing colour-photographic material containing at least photosensitive silver halide, binder, electron donor, anti-diffusion dye donor which releases movable dye by being reduced with an electron donor, on a support, wherein the electron donor is an alkyl or aryl (sulphon)amido naphthol derivative.
  • Research Disclosure no. 17706 discloses a photothermographic material which comprises a support coated with a layer which contains, or with layers which together contain, (a) a photographic silver halide, (b) an oxidation-reduction image-forming combination (i) a reducible silver salt and (ii) at least one reducing agent which comprises an azomethine or azo dye (c) a development modifier and (d) a synthetic polymeric binder, wherein the azo dye reducing agent is a compound of the formula (I).
  • US-A-3 767 414 discloses a method of imaging comprising a stratum containing a polymeric heavy metal azolate to heat at least at image areas and in the presence of a photosensitive reducing agent to provide on the sheet material a visible image, wherein the reducing agent is supplied from a second sheet held in face-to-face contact with the first sheet material.
  • 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 dye is transferred onto a contacting receiving element by the application of heat in a pattern normally controlled by electronic information signals.
  • thermosublimation printing dyes are transferred to a receiving element. It is possible to obtain an image with an excellent grey tone, however, with limited optical densities (2.0 - 2.5).
  • a thermal imaging process is provided using (i) a donor element comprising on a support a donor layer containing a binder and a thermotransferably reducing agent capable of reducing a silver source to metallic silver upon heating and (ii) a receiving element comprising on a support a receiving layer comprising a silver source capable of being reduced by means of heat in the presence of a reducing agent, the thermal imaging process comprising the steps of
  • This printing method is further referred to as 'reducing agent transfer printing' or 'RTP' and provides images having a high optical density.
  • a thermal imaging process is provided using (i) a donor element including on a support a donor layer containing a binder, a thermotransferable reducing agent capable of reducing a silver source to metallic silver upon heating and a thermotransferable dye and (b) a heat-resistant layer provided on the side of the support opposite to the side having the donor layer and (ii) a receiving element including on a support a receiving layer containing a silver source capable of being reduced by means of heat in the presence of a reducing agent, the thermal imaging process comprising the steps of
  • the donor element for use according to present invention comprises on one side of the donor element a donor layer, comprising a thermotransferable reducing agent capable of reducing a silver source to metallic silver, a thermotransferable dye and a binder.
  • the reducing agent for the silver source may comprise any of the conventional photographic developers known in the art, such as phenidone, hydroquinones and catechol provided that the reducing agent is thermotransferable.
  • Suitable reducing agents are aminohydroxycycloalkenone compounds, esters of amino reductones, N-hydroxyurea derivatives, hydrazones of aldehydes and ketones, phosphoramidophenols, phosphoramidoanilines, polyhydroxybenzenes, e.g.
  • ethyl gallate, propyl gallate and the like gallic acid amides, sulfhydroxamic acids. sulfonamidoanilines, 2-tetrazolylthiohydroquinones, e.g., 2-methyl-5-(1-phenyl-5-tetrazolylthio)hydroquinone, , tetrahydroquinoxalines, e.g.
  • 1,2,3,4-tetrahydroquinoxaline amidoximes, azines, hydroxamic acids, 5-pyrazolones, sulfonamidophenol reducing agents, 2-phenylindan-1,3-dione and the like, 1,4-dihydropyridines, such as 2,6-dimethoxy-3,5-dicarbethoxy-1,4-dihydropyridine, bisphenols, e.g., bis(2-hydroxy-3-t-butyl-5-methylphenyl) methane, bis(6-hydroxy-m-toly)mesitol, 2,2-bis (4-hydroxy-3-methylphenyl)propane, 4,4-ethylidene-bis(2-t-butyl-6-methylphenol) and 2,2-bis(3,5-dimethyl-4-hydroxyphenyl) propane, ascorbic acid derivatives and 3-pyrazolidones.
  • 1,4-dihydropyridines such as 2,6-dimethoxy-3,5-dicarbeth
  • Reducing agents being coloured in an oxidized form or capable of forming colour in an oxidized form (further referred to as color forming reducing agents) can also be used.
  • Specific examples are 4-methoxynaphthol and leucoazomethines in particular leucoindoanilines such as for example: Reducing agents derived from dihydroxy or trihydroxyphenyl compounds are especially preferred. Highly preferred are 4-phenyl pyrocatechol and propyl gallate.
  • thermotransferable dyes for use in connection with the present invention are dyes having a hue that is complementary to the hue of the metallic silver image that forms in the image receiving layer of the image receiving element.
  • dyes that can be used in connection with the present invention are azomethine dyes as disclosed in EP 400,704 and US 5.134.115, indoaniline dyes as disclosed in US 4.987.119, US 4.695.287, US 4.829.047 and US 4.983.493, azo dyes as disclosed in EP 344.592, EP 218.397, EP 302.628, EP 352.006 and EP 546.700, anthraquinone dyes as disclosed in US 4.940.692 and EP 209.911, azino dyes as disclosed in EP-A 611 663, heterocyclic dyes as disclosed in US 5.175.069 or mixtures of these dyes such disclosed in e.g.
  • the use of a dye having an absorption maximum in the range above 500nm is preferred and in particular the use of a cyan or a blue dye is especially preferred, while images obtained with reducing agent transfer printing are usually coloured yellow to brown.
  • the extinction coefficient of the dye at the absorption maximum is preferably at least 8000 1/(mol*cm) and more preferably at least 20000 1/(mol*cm).
  • the amount of dye or dye mixture is preferably lower than the amount of reducing agent or reducing agent mixture in the donor layer.
  • a dye can have a positive influence on the stability of the donor element during storage at elevated temperature (40-60°C). More particularly, the crystallization of the reducing agent(s) can be avoided as already mentioned above.
  • hydrophilic or hydrophobic binders can be used, although the use of hydrophobic binders is preferred.
  • Hydrophilic binders which can be used are polyvinylalcohol, gelatine, polyacrylamide and hydrophilic cellulosic binders such as hydroxyethyl cellulose, hydroxypropyl cellulose and the like.
  • the hydrophobic binders may be used as a dispersion in e.g. water or as a solution in an organic solvent.
  • Suitable binders for the donor layer are cellulose derivatives, such as ethyl cellulose, methyl cellulose, cellulose nitrate, cellulose acetate formate, cellulose acetate hydrogen phthalate, cellulose acetate, cellulose acetate propionate, cellulose acetate butyrate, cellulose acetate pentanoate, cellulose acetate benzoate, cellulose triacetate; vinyl-type resins and derivatives, such as polyvinyl acetate, polyvinyl butyral, copolyvinyl butyral-vinyl acetal-vinyl alcohol, polyvinyl pyrrolidone, polyvinyl acetoacetal, polyacrylamide; polymers and copolymers derivated from acrylates and acrylate derivatives, such as polymethyl metahcrylate and styreneacrylate copolymers: polyester resins; polycarbonates; copoly(styrene-co-acrylonitrile); polysulfones
  • the binder for the donor layer in accordance with the present invention comprises poly(styrene-co-acrylonitrile) or a mixture of poly(styrene-coacrylonitrile) and a toluenesulphonamide condensation product.
  • the binder for the donor layer preferably comprises a copolymer comprising styrene units and acrylonitrile units, preferentially at least 60% by weight of styrene units and at least 25% by weight of acrylonitrile units binder.
  • the binder copolymer may, of course, comprise other comonomers than styrene units and acrylonitrile units. Suitable other comonomers are e.g. butadiene, butyl acrylate, and methyl methacrylate.
  • the binder copolymer preferably has a glass transition temperature of at least 50°C.
  • the donor layer génerally has a thickness of about 0.2 to 5.0 ⁇ m, preferably 0.4 to 2.0 ⁇ m, and the amount ratio of reducing agent and dye to binder generally ranges from 9:1 to 1:3 by weight, preferably from 3:1 to 1:2 by weight.
  • the donor layer may also contain other additives such as i.a. thermal solvents, stabilizers, curing agents, preservatives, dispersing agents, antistatic agents, defoaming agents, and viscosity-controlling agents.
  • additives such as i.a. thermal solvents, stabilizers, curing agents, preservatives, dispersing agents, antistatic agents, defoaming agents, and viscosity-controlling agents.
  • the donor layer in accordance with the present invention may consist of multiple layers. In the latter case the thermotransferable dye and thermotransferable reducing agent may be provided in different layers.
  • any material can be used as the support for the donor element provided it is dimensionally stable and capable of withstanding the temperatures involved, up to 400°C over a period of up to 20 msec, and is yet thin enough to transmit heat applied on one side through to the reducing agent on the other side to effect transfer to the receiver sheet within such short periods, typically from 1 to 10 msec.
  • Such materials include polyesters such as polyethylene terephthalate, polyamides, polyacrylates, polycarbonates, cellulose esters, fluorinated polymers, polyethers, polyacetals, polyolefins, polyimides, glassine paper and condenser paper. Preference is given to a support comprising polyethylene terephthalate.
  • the support preferably has a thickness of 3 to 10 ⁇ m in order to allow for a good heat transfer across the support, so that a good transfer of dye(s) and reducing agent(s) is obtained.
  • the support may also be coated with an adhesive of subbing layer, if desired.
  • Subbing layers comprising aromatic copolyesters, vinylidene chloride copolymers, organic titanate, zirconates and silanes, polyester urethanes and the like can be used.
  • the donor layer of the donor element can be coated on the support or printed thereon by a printing technique such as a gravure process.
  • a barrier layer for the reducing agent and the dye comprising a hydrophilic polymer may also be employed between the support and the donor layer of the donor element to enhance the transfer of reducing agent and dye by preventing wrong-way transfer thereof backwards to the support.
  • the barrier layer may contain any hydrophilic material that is useful for the intended purpose.
  • gelatin polyacrylamide, polyisopropyl acrylamide, butyl methacrylate-grafted gelatin, ethyl methacrylate-grafted gelatin, ethyl acrylate-grafted gelatin, cellulose monoacetate, methylcellulose, polyvinyl alcohol, polyethyleneimine, polyacrylic acid, a mixture of polyvinyl alcohol and polyvinyl acetate, a mixture of polyvinyl alcohol and polyacrylic acid, or a mixture of cellulose monoacetate and polyacrylic acid.
  • hydrophilic polymers e.g. those described in EP 227,091 also have an adequate adhesion to the support and the donor layer, so that the need for a separate adhesive or subbing layer is avoided.
  • the particular hydrophilic polymers used in a single layer in the donor element thus perform a dual function, hence are referred to as barrier/subbing layers.
  • the back of the support (the side opposite to that carrrying the dye layer) is typically provided with a heat-resistant layer to facilitate passage of the donor element past the thermal printing head.
  • An adhesive layer may be provided between the support and the heat-resistant layer.
  • Any heat-resistant layer known in the field of thermal sublimation printing or wax printing can be used in the present invention.
  • the heat-resistant layer generally comprises a lubricant and a binder.
  • the binder is either a cured binder as described in e.g. EP 153,880, EP 194,106.
  • Well known lubricants are polysiloxanes such as those mentioned in EP 267,469, US 4,738,950, US 4,866,028, US 4,753,920 and US 4,782,041.
  • Especially useful slipping agents are polysiloxanepolyether block or graft polymers.
  • lubricants for the heat-resistant slipping layer of the donor element are phosphoric acid derivatives such as those mentioned in EP 153,880 and EP 194,106.
  • metal salts of long fatty acids such as mentioned in EP 458,538, EP 458,522, EP 314,348, JP 01/241,491 and JN 01/222,993
  • wax compounds such as polyolefin waxes such as e.g. polyethylene or polypropylene wax, carnauba wax, bees wax, glycerine monostearate, amid wax such as ethylene bisstearamide and the like.
  • a heat-resistant layer such as mentioned in EP 634 291 is especially preferred.
  • Inorganic particles such as salts derived from silica such as e.g. talc, clay, china clay, mica, chlorite, silica, or carbonates such as calcium carbonate, magnesium carbonate or calcium magnesium carboante (dolomite) can be further added to the heat-resistant layer.
  • silica such as e.g. talc, clay, china clay, mica, chlorite, silica
  • carbonates such as calcium carbonate, magnesium carbonate or calcium magnesium carboante (dolomite) can be further added to the heat-resistant layer.
  • a mixture of talc and dolomite particles is highly preferred.
  • a particular heat-resistant layer for the present invention comprises as a binder a polycarbonate derived from a bis-(hydroxyphenyl)-cycloalkane, corresponding to general formula (I) : wherein :
  • Lubricants and binder can be coated in a single layer, or can be casted in a separate layer. It is highly preferred to cast the salt of a fatty acid in the heat resistant layer (e.g. as a dispersion) and the polysiloxane based lubricant in a separate topcoat. This separate topcoat is preferably casted from a non-solvent for the heat-resistant layer.
  • the heat-resistant layer of the donor element may be coated on the support or printed thereon by a printing technique such as a gravure printing.
  • the heat-resistant layer thus formed has a thickness of about 0.1 to 3 ⁇ m, preferably 0.3 to 1.5 ⁇ m.
  • a subbing layer is provided between the support and the heat-resistant layer to promote the adhesion between the support and the heat-resistant layer.
  • subbing layer any of the subbing layers known in the art for dye-donor elements can be used.
  • Suitable binders that can be used for the subbing layer can be chosen from the classes of polyester resins, polyurethane resins, polyester urethane resins, modified dextrans, modified cellulose, and copolymers comprising recurring units such as i.a. vinyl chloride, vinylidene chloride, vinyl acetate, acrylonitrile, methacrylate, acrylate. butadiene, and styrene (e.g. poly(vinylidene chloride-co-acrylonitrile).
  • Suitable subbing layers have. been described in e.g. EP 138,483, EP 227,090, EP 564010, US 4,567,113, US 4,572,860, US 4,717,711, US 4,559,273, US 4,695,288, US 4,727,057, US 4,737,486, US 4,965,239, US 4,753,921, US 4,895,830, US 4,929,592, US 4,748,150, US 4,965,238, and US 4,965,241.
  • the receiving element for use according to the printing method of the present invention comprises a receiving layer provided on a support, said receiving layer comprising a silver source capable of being reduced by means of heat in the presence of a reducing agent.
  • the reducible silver source may comprise any material that contains a reducible source of silver ions.
  • Silver salts of organic and hetero-organic acids particularly long chain fatty carboxylic acids (comprising from 10 to 30, preferably 15 to 25 carbon atoms) are preferred.
  • Complexes of organic or inorganic silver salts in which the ligand has a gross stability constant for silver ion of between 4.0 and 10.0 are also useful. Examples of suitable silver salts are disclosed in Research Disclosure Nos.
  • 17029 and 29963 include : salts of organic acids, e.g., gallic acid, oxalic acid, behenic acid, stearic acid, palmitic acid, lauric acid and the like; silver carboxyalkylthiourea salts, e.g., 1-(3-carboxypropyl)thiourea, 1-(3-carboxypropyl)-3,3-dimethylthiourea and the like; complexes of silver with the polymeric reaction product of an aldehyde with a hydroxy-substituted aromatic carboxylic acid, e.g., aldehydes, such as formaldehyde, acetaldehyde and butyraldehyde, and hydroxy-substituted acids, such as salicyclic acid, benzilic acid, 3,5-dihdyroxybenzilic acid and 5,5-thiodisalicylic acid; silver salts or complexes of thiones,
  • the silver source is preferably added as a dispersion to the coating liquid of the receiving layer.
  • thermoplastic water insoluble resins are used wherein the ingredients can be dispersed homogeneously or form therewith a solid-state solution.
  • thermoplastic water insoluble resins are used wherein the ingredients can be dispersed homogeneously or form therewith a solid-state solution.
  • natural, modified natural or synthetic resins may be used, e.g.
  • cellulose derivatives such as ethylcellulose, cellulose esters, carboxymethylcellulose, starch ethers, polymers derived from ⁇ , ⁇ -ethlenically unsatured 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, e.g. polyvinyl butyral, copolymers of acrylonitrile and acrylamide, polyacrylic acid esters, polymethacrylic acid esters and polyethylene or mixtures thereof.
  • a particularly suitable ecologically interesting (halogen-free) binder is polyvinyl butyral.
  • a polyvinyl butyral containing some vinyl alcohol units is marketed under ButvarTM B79 of Monsanto USA.
  • the binder to organic silver salt weight ratio is preferably in the range of 0.2 to 6, and the thickness of the image forming layer is preferably in the range of 5 to 16 ⁇ m.
  • toning agent in the receiving layer or in a layer adjacent to said receiving layer.
  • This toning agent serves to change the tone of the silver image from brown to black or grey.
  • Suitable toning agents are e.g. phthalazinone, phthalazine, phthalimide, succinimide, phthalic acid, benzimidazole or a compound according to formula (II) :
  • phthalazinone or compound (II) is highly preferred.
  • release agent in the receiving element on the side of the receiving layer.
  • This release agent may be added to the coating solution of the receiving layer or may be applied, optionally in a mixture with other ingredients, as a separate layer called the release layer on top of said receiving layer.
  • the use of a release layer is preferred, since the release agent is in that case on top of the receiving element.
  • the release agent is preferred in the printing method of the present invention since the reducing agents useful in the present invention can give rise to a sticky contact between donor element and receiving element.
  • release agents inorganic and organic release agents can be used. Among them, the organic release agent, are preferred.
  • Solid waxes, fluorine- or phosphate-containing surfactants and silicone oils can be used as releasing agent.
  • Suitable releasing agents have been described in e.g. EP 133012, JP 85/19138, and EP 227092.
  • a separate release layer incorporating the release agent
  • other ingredients such as binders, plasticizers, or particulate fillers such as talc, silica or collodial particles can be added to said release layer, provided that the transfer of the reducing agent to the receiving layer comprising the reducible silver source can take place.
  • binders for the release layer are polyvinylbutyral, ethylcellulose, cellulose acetate propionate, cellulose acetate butyrate, polyvinylchloride, copolymers of vinylchloride, vinylacetate and vinylalcohol, aromatic or aliphatic copolyesters, polymethylmethacrylate, polycarbonates derived from bisphenol A, polycarbonates comprising bisphenols according to formula (I) and the like.
  • the release layer can also act as a protective layer for the images.
  • An adhesive layer is usually provided between the support and the receiving layer, such as those mentioned in e.g. US 4,748,150, US 4,954,241, US 4,965,239 and US 4,965,238 and EP-A 574 055.
  • the subbing layer can further comprise other polymers, particles, or low molecular weight additives.
  • Addition of inorganic particles such as silica, colloidal silica, water soluble polymers suchas gelatin, polymeric latices, polystyrene sulfonic acid and polystyrene sulfonic acid sodium salt, surfactants such as cationic, anionic, amphoteric and non-ionic surfactants, and polymeric dispersants is preferred.
  • colloidal silica the above mentioned surfactants, butadiene containing latices suchas poly(butadiene-co-methylmethacrylate-co-itaconic acid), polystyrene sulfonic acid and polystyrene sulfonic acid sodium salt.
  • butadiene containing latices suchas poly(butadiene-co-methylmethacrylate-co-itaconic acid), polystyrene sulfonic acid and polystyrene sulfonic acid sodium salt.
  • the subbing layer of the present invention is applied directly to the support of the receiving element.
  • the subbing layer can be applied by coextrusion or can be coated on the support. Coating from aqueous solution is preferred due to its simplicity and the possibility of adding other ingredients.
  • the receiving layer is usually hydrophobic in order to enhance the absorption of reducing agent into the receiving element.
  • the polyester recycling procedure uses a cleaning step whereby the film waste is immersed in an alkaline or acid soap solution in water. It is an object of this cleaning process to remove all layers casted on the polymeric substrate.
  • hydrophilic polymers which can be used in such intermediate layers are polyvinyl alcohol, polyacrylamide, hydroxyethylcellulose, gelatin, polystyrene sulfonic acid, polyethylene glycol, poly(meth)acrylic acid, poly(meth)acrylic acid, alkali metal salts of polyacrylic acid, crosslinked copolymers containing (meth)acrylic acid or alkali metal salts of (meth)acrylic acid, alkali metal salts of polystyrene sulfonic acid, dextran, carrageenan and the like.
  • Alkali metal salts of polystyrene sulfonic acid such as the sodium salt of polystyrene sulfonic acid is highly preferred, since the use of this polymer in the intermediate layer results in better anti-static properties of the dye-receiving elment.
  • Anti-static coatings such as those described in EP 440,957 can be incorporated in the intermediate layer. This results both in a higher hydrophilicity and in better anti-static properties.
  • the intermediate layer may further comprise polymeric dispersions or latices, surfactants, inorganic particles suchas silica and colloidal silica and the like. Addition of surfactants, colloidal silica and/or latices is preferred. Addition of silica to the intermediate layer decreases sticking to the coating roll after coating. Addition of latices to the intermediate layer improves the addition and improves the removing step in the recycling process in case of acrylic acid or methacrylic acid type latices.
  • the intermediate layer may also have a cushioning property, such as mentioned in US 4,734,397.
  • the support for the receiver sheet or element may be a transparant film of e.g. polyethylene terephthalate, a polyether sulfone, a polyimide, a cellulose ester, or a polyvinyl alcohol-coacetal.
  • the support may also be a reflective one such as barytacoated paper, polyethylene-coated paper, or white polyester i.e. white-pigmented polyester. Blue-coloured polyethylene terephthalate film can also be used as a support.
  • subbing layer is useful for application on polyethylene-coated paper, substrates based on polyester, transparent or reflective, are preferred. In this case, the subbing layer can be applied before, during or after the biaxial stretching procedure.
  • a backcoat can be provided, optionally in combination, with an appropriate subbing layer to improve the adhesion between the backcoat and the support.
  • Hydrophilic as well as hydrophobic backcoats can be used. Hydrophilic backcoats can be applied easily from water, while hydrophobic backcoats have the advantage that the backcoat performs well at all humidity levels (no curl).
  • hydrophilic backcoat layers are layers comprising polyvinylalcohol, polyethylene glycol, polyacrylamide, hydroxyethylcellulose, dextran and gelatin.
  • gelatin is highly preferred.
  • hydrophilic backcoat layers may further comprise dispersions or latices of hydrophobic polymers, inorganic particles, surfactant and the like.
  • the addition of these particles can be used in order to obtain a specific surface gloss, such as mentioned in EP-A-543441.
  • Especially preferred particles are silica and polymethylmethacrylate beads of 0.5 to 10 ⁇ m.
  • Antistatic treatment can also be provided to said backcoat layer.
  • hydrophobic backcoat layers are backcoat layers comprising addition polymers suchas polymethylmethacrylate, polyvinylchloride and polycondensates such as polyesters, polycarbonates in combination with the above mentioned particles for the hydrophilic backcoat layers.
  • hydrophobic backcoat layers it can be useful to provide an intermediate hydrophilic layer between the subbing layer and the backcoat layer, such as those mentioned for use at the receiving side of the dye-receiving element, in order to improve the removal of the backcoat layer in the recycling procedure.
  • the printing method of the present invention preferably uses a thermal head to selectively heat specific portions of the donor element in contact with a receiving element.
  • the thermal head can be a thick or thin film thermal head although the use of a thin film thermal head is preferred, since this offers more opportunities to obtain appropriate gradation.
  • the pressure applied to the thermal head is preferably between 120 and 400 g/cm heater line. A spatial resolution of 150 dpi or higher is preferred.
  • the average printing power is calculated as the total amount of energy applied during one line time divided by the line time and by the surface area of the heat-generating elements.
  • the time needed for printing one single line with the thermal head also called the line time, is preferably below 45 ms. Longer line times result in longer printing times and more deformation of the receiving sheet and/or receiving layer.
  • an overall heat treatment of the receiving element may be performed.
  • This heat treatment can be e.g. done with an infrared source, a heated air stream or a hot plate but is preferably done by means of a heated roller.
  • the transferred reducing agent can further react with the reducible silver source and the dye further migrates into the receiving layer.
  • the heat treatment time for the overall heating can be adjusted.
  • the heated rollers can be used to uncurl the receiving sheet after printing.
  • a subbed polyethylene terephthalate support having a thickness of 100 ⁇ m was coated in order to obtain the following receiving layer : silver behenate 4.5 g/m 2 compound II mentioned above 0.34 g/m 2 polyvinylbutyral (ButvarTM B79, Monsanto) 4.5 g/m 2
  • a release layer was coated from hexane comprising 0.03 g/m 2 TegoglideTM 410 (polyether-polysiloxane blockcopolymer from Goldschmidt). This receiving element was used in the following printing examples.
  • Both sides of a 5.7 ⁇ m thick polyethylene terephthalate support were coated with a subbing layer of a copolyester comprising ethylene glycol, adipic acid, neopentyl glycol, terephthalatic acid, isophthalic acid, and glycerol.
  • a copolyester comprising ethylene glycol, adipic acid, neopentyl glycol, terephthalatic acid, isophthalic acid, and glycerol.
  • the resulting subbing layer was covered with a solution in methyl ethyl ketone of 13% of a polycarbonate having the following structural formula (III) : wherein n represents the number of units to obtain a polycarbonate having a relative viscosity of 1.30 as measured in a 0.5% solution in dichloromethane, 0.5% of talc (Nippon Talc P3, Interorgana) and 0.5% of zinc stearate.
  • structural formula (III) wherein n represents the number of units to obtain a polycarbonate having a relative viscosity of 1.30 as measured in a 0.5% solution in dichloromethane, 0.5% of talc (Nippon Talc P3, Interorgana) and 0.5% of zinc stearate.
  • the other side of the donor element was provided with a donor layer.
  • the nature of the ingredients is mentioned in table 1.
  • the amount of reducing agent(s) and dye(s) are given in weight % in the coating solution.
  • the binder (10 weight %) was casted together with the reducing agent(s) and the dye(s) from a solution in butanone. These coating solutions were applied at a wet thickness of 10 ⁇ m by means of a wire bar. The resulting layer was dried by evaporation of the solvent.
  • Printing was performed by contacting the donor layer of the donor element with the receiving layer of the receiving element, followed by heating by means of a thermal head.
  • the thermal head was a thin film thermal head heated at an average printing power of 5 Watt/mm 2 and a line time of 18 ms with a resolution of 300 dpi.
  • the pressure applied between the thermal head and the rotating drum carrying the receiving and donor element was 160 g/cm heater line. After printing, the receiving element was separated from the donor element.
  • the printed image was a 16-step grey scale between data level 0 and 255 (8 bit).
  • the data levels of the different steps were choosen equidistant with respect to the input data level in order to obtain the native sensitometry.
  • All receiving elements were subsequent to the image-wise heating overall heated on a hot plate of 118°C for 10 seconds.
  • the optical maximal densities of the overall heated prints were measured after a visual filter in a MacbethTM TR924 densitometer in the grey scale part corresponding to data level 255.
  • the evaluation of the grey tone of the printed images after heat treatment was determined by visual inspection of the print on a negatoscope (light box).

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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)
  • Thermal Transfer Or Thermal Recording In General (AREA)

Claims (9)

  1. Ein thermisches Bilderzeugungsverfahren, in dem folgende Elemente benutzt werden : (i) ein Donorelement, das auf einem Träger (a) eine Donorschicht, die ein Bindemittel, ein wärmeübertragbares Reduktionsmittel, das eine Silberquelle bei Erhitzung zu Metallsilber zu reduzieren vermag, und einen wärmeübertragbaren Farbstoff enthält, und (b) eine wärmebeständige Schicht enthält, die auf die der die Donorschicht tragenden Seite des Trägers gegenüberliegende Trägerseite aufgetragen ist, und (ii) ein Empfangselement, das auf einem Träger eine Empfangsschicht mit einer Silberquelle enthält, die in Gegenwart eines Reduktionsmittels durch Erhitzung reduziert werden kann, wobei das thermische Bilderzeugungsverfahren durch folgende Schritte gekennzeichnet ist :
    Anordnen der Donorschicht des Donorelements in schichtseitiger Beziehung zur Empfangsschicht des Empfangselements,
    bildmäßige Erhitzung einer so erhaltenen Anordnung, wodurch eine Menge der wärmeübertragbaren Reduktionsmittel entsprechend der zugelieferten Wärmemenge bildmäßig auf das Empfangselement übertragen wird,
    Abtrennung des Donorelements vom Empfangselement, und
    anschließende vollflächige Erhitzung des Empfangselements.
  2. Thermisches Bilderzeugungsverfahren nach Anspruch 1, dadurch gekennzeichnet, daß das in Gewicht ausgedrückte Mengenverhältnis des wärmeübertragbaren Reduktionsmittels und des wärmeübertragbaren Farbstoffes zum Bindemittel zwischen 3:1 und 1:2 liegt.
  3. Thermisches Bilderzeugungsverfahren nach Anspruch 1 oder 2, dadurch gekennzeichnet, daß der Farbstoff einen Absorptionshöchstwert von über 500 nm aufweist.
  4. Thermisches Bilderzeugungsverfahren nach Anspruch 1 oder 3, dadurch gekennzeichnet, daß der molare Extinktionskoeffizient des Farbstoffes zumindest 8000 1/(Mol*cm) beträgt.
  5. Thermisches Bilderzeugungsverfahren nach einem der Ansprüche 1 bis 4, dadurch gekennzeichnet, daß der Farbstoff aus der Gruppe bestehend aus Azomethinfarbstoffen, Anthrachinonfarbstoffen, Azofarbstoffen, Indoanilinfarbstoffen und Azinofarbstoffen gewählt wird.
  6. Thermisches Bilderzeugungsverfahren nach einem der vorstehenden Ansprüche, dadurch gekennzeichnet, daß die Stärke des Trägers zwischen 3 und 10 µm liegt.
  7. Thermisches Bilderzeugungsverfahren nach einem der vorstehenden Ansprüche, dadurch gekennzeichnet, daß die vollflächige Erhitzung mittels einer beheizten Walze vorgenommen wird.
  8. Thermisches Bilderzeugungsverfahren nach einem der vorstehenden Ansprüche, dadurch gekennzeichnet, daß das Empfangselement fernerhin ein Tönungsmittel enthält.
  9. Thermisches Bilderzeugungsverfahren nach einem der vorstehenden Ansprüche, dadurch gekennzeichnet, daß die bildmäßige Erhitzung mittels eines Thermokopfes durchgeführt wird.
EP19950200411 1994-03-25 1995-02-21 Thermotransferaufzeichnungsverfahren Expired - Lifetime EP0677775B1 (de)

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EP19950200411 EP0677775B1 (de) 1994-03-25 1995-02-21 Thermotransferaufzeichnungsverfahren

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EP94200796 1994-03-25
EP19950200411 EP0677775B1 (de) 1994-03-25 1995-02-21 Thermotransferaufzeichnungsverfahren

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EP0677775B1 true EP0677775B1 (de) 2002-06-12

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US6066445A (en) * 1996-12-19 2000-05-23 Eastman Kodak Company Thermographic imaging composition and element comprising said composition
US5928855A (en) * 1998-03-20 1999-07-27 Eastman Kodak Company Thermographic imaging element
US5922528A (en) * 1998-03-20 1999-07-13 Eastman Kodak Company Thermographic imaging element
US5994052A (en) * 1998-03-20 1999-11-30 Eastman Kodak Company Thermographic imaging element
US5928856A (en) * 1998-03-20 1999-07-27 Eastman Kodak Company Thermographic imaging element

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Publication number Priority date Publication date Assignee Title
BE612241A (de) * 1961-01-03 1900-01-01
US3767414A (en) * 1972-05-22 1973-10-23 Minnesota Mining & Mfg Thermosensitive copy sheets comprising heavy metal azolates and methods for their use
JPS61259253A (ja) * 1985-05-14 1986-11-17 Fuji Photo Film Co Ltd 熱現像カラ−感光材料
CA2016687A1 (en) * 1989-05-31 1990-11-30 Agfa-Gevaert Naamloze Vennootschap Dyes and dye-donor elements for use in thermal dye sublimation transfer
DE69310045T2 (de) * 1992-08-03 1997-12-11 Minnesota Mining & Mfg Laseradressierbares wärmeempfindliches Aufzeichnungsmaterial

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