EP0860288B1 - Beschichtung für Thermodruckkopf - Google Patents

Beschichtung für Thermodruckkopf Download PDF

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Publication number
EP0860288B1
EP0860288B1 EP19970200518 EP97200518A EP0860288B1 EP 0860288 B1 EP0860288 B1 EP 0860288B1 EP 19970200518 EP19970200518 EP 19970200518 EP 97200518 A EP97200518 A EP 97200518A EP 0860288 B1 EP0860288 B1 EP 0860288B1
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EP
European Patent Office
Prior art keywords
printing head
thermal printing
coating
alkoxy group
thermal
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Lifetime
Application number
EP19970200518
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English (en)
French (fr)
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EP0860288A1 (de
Inventor
Agfa-Gevaert N.V. Defieuw Geert
Afga-Gevaert N.V. Samijn Raf
Afga-Gevaert N.V. Loccufier Johan
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Agfa Gevaert NV
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Agfa Gevaert NV
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Filing date
Publication date
Application filed by Agfa Gevaert NV filed Critical Agfa Gevaert NV
Priority to DE1997604844 priority Critical patent/DE69704844T2/de
Priority to EP19970200518 priority patent/EP0860288B1/de
Priority to US09/018,740 priority patent/US6028618A/en
Priority to JP5000598A priority patent/JPH10235915A/ja
Publication of EP0860288A1 publication Critical patent/EP0860288A1/de
Application granted granted Critical
Publication of EP0860288B1 publication Critical patent/EP0860288B1/de
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

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Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
    • B41J—TYPEWRITERS; SELECTIVE PRINTING MECHANISMS, i.e. MECHANISMS PRINTING OTHERWISE THAN FROM A FORME; CORRECTION OF TYPOGRAPHICAL ERRORS
    • B41J2/00—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed
    • B41J2/315—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed characterised by selective application of heat to a heat sensitive printing or impression-transfer material
    • B41J2/32—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed characterised by selective application of heat to a heat sensitive printing or impression-transfer material using thermal heads
    • B41J2/335—Structure of thermal heads
    • B41J2/33505—Constructional details
    • B41J2/3353—Protective layers
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
    • B41J—TYPEWRITERS; SELECTIVE PRINTING MECHANISMS, i.e. MECHANISMS PRINTING OTHERWISE THAN FROM A FORME; CORRECTION OF TYPOGRAPHICAL ERRORS
    • B41J2/00—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed
    • B41J2/005—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed characterised by bringing liquid or particles selectively into contact with a printing material
    • B41J2/01—Ink jet
    • B41J2/135—Nozzles
    • B41J2/16—Production of nozzles
    • B41J2/1606—Coating the nozzle area or the ink chamber
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
    • B41J—TYPEWRITERS; SELECTIVE PRINTING MECHANISMS, i.e. MECHANISMS PRINTING OTHERWISE THAN FROM A FORME; CORRECTION OF TYPOGRAPHICAL ERRORS
    • B41J2/00—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed
    • B41J2/315—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed characterised by selective application of heat to a heat sensitive printing or impression-transfer material
    • B41J2/32—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed characterised by selective application of heat to a heat sensitive printing or impression-transfer material using thermal heads
    • B41J2/335—Structure of thermal heads
    • B41J2/3355—Structure of thermal heads characterised by materials
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
    • B41J—TYPEWRITERS; SELECTIVE PRINTING MECHANISMS, i.e. MECHANISMS PRINTING OTHERWISE THAN FROM A FORME; CORRECTION OF TYPOGRAPHICAL ERRORS
    • B41J2/00—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed
    • B41J2/315—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed characterised by selective application of heat to a heat sensitive printing or impression-transfer material
    • B41J2/32—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed characterised by selective application of heat to a heat sensitive printing or impression-transfer material using thermal heads
    • B41J2/335—Structure of thermal heads
    • B41J2/33555—Structure of thermal heads characterised by type
    • B41J2/3356—Corner type resistors
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
    • B41J—TYPEWRITERS; SELECTIVE PRINTING MECHANISMS, i.e. MECHANISMS PRINTING OTHERWISE THAN FROM A FORME; CORRECTION OF TYPOGRAPHICAL ERRORS
    • B41J2/00—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed
    • B41J2/315—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed characterised by selective application of heat to a heat sensitive printing or impression-transfer material
    • B41J2/32—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed characterised by selective application of heat to a heat sensitive printing or impression-transfer material using thermal heads
    • B41J2/335—Structure of thermal heads
    • B41J2/33555—Structure of thermal heads characterised by type
    • B41J2/33565—Edge type resistors
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
    • B41J—TYPEWRITERS; SELECTIVE PRINTING MECHANISMS, i.e. MECHANISMS PRINTING OTHERWISE THAN FROM A FORME; CORRECTION OF TYPOGRAPHICAL ERRORS
    • B41J2/00—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed
    • B41J2/315—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed characterised by selective application of heat to a heat sensitive printing or impression-transfer material
    • B41J2/32—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed characterised by selective application of heat to a heat sensitive printing or impression-transfer material using thermal heads
    • B41J2/335—Structure of thermal heads
    • B41J2/33555—Structure of thermal heads characterised by type
    • B41J2/3357—Surface type resistors
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
    • B41J—TYPEWRITERS; SELECTIVE PRINTING MECHANISMS, i.e. MECHANISMS PRINTING OTHERWISE THAN FROM A FORME; CORRECTION OF TYPOGRAPHICAL ERRORS
    • B41J2/00—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed
    • B41J2/315—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed characterised by selective application of heat to a heat sensitive printing or impression-transfer material
    • B41J2/32—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed characterised by selective application of heat to a heat sensitive printing or impression-transfer material using thermal heads
    • B41J2/335—Structure of thermal heads
    • B41J2/3359—Manufacturing processes

Definitions

  • the present invention relates to a coating for thermal printing heads used for the image-wise heating of thermographic materials.
  • thermography is a recording process wherein images are generated by the use of image-wise modulated thermal energy.
  • thermography three basic approaches are known:
  • thermographic processes A survey of thermographic processes is given in "Unconventional Imaging Processes" by E. Brinckman, G. Delzenne, A. Poot and J. Willems, The Focal Press - London and New York (1978), Chapter 4 under the heading "4.10 Thermography”.
  • 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.
  • Thermal dye transfer printing materials are described, for example, in EP-B 133 012 and EP-A 133 011.
  • EP-A 671 283 Processes in which image formation is obtained by the image-wise transfer of an ingredient necessary for the chemical or physical process bringing about changes in colour or optical density to a receptor element are, for example, described in EP-A 671 283.
  • Materials for such processes are, for example, described in EP-A's 671 283, 671 284, 674 216, 677 775, 677 776, 678 775, 682 438, 683 428 and 706 080.
  • Direct thermal thermography is concerned with materials which are substantially not photosensitive, but are sensitive to heat or thermosensitive. Image-wise applied heat is sufficient to bring about a visible change in a thermosensitive imaging material. Most of the "direct" 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. This irreversible reaction can be, for example, the reaction of a leucobase with an acid to produce the corresponding dye or the reduction of an organic or inorganic metal compound (e.g. silver, gold, copper or iron compounds) to its corresponding metal thereby producing a visible image.
  • an organic or inorganic metal compound e.g. silver, gold, copper or iron compounds
  • imaging materials are described, for example, in US-P 3,080,254, EP-B 614 770, EP-B 614 769, EP-A 685 760, US-P 5,527,757, EP-A 680 833, US-P 5,536,696, EP-B 669 876, EP-A 692 391, US-P 5,527,758, EP-A 692 733, US-P 5,547,914, EP-A 730 196 and EP-A 704 318.
  • thermal printing head failure can be due to physical abrasion and/or chemical erosion and chemical interaction between the protective layer of the thermal printing head and the ingredients of the imaging materials at the elevated temperatures at which image formation takes place.
  • Physical abrasion of thermal printing heads can be reduced by incorporating lubricants into the imaging materials which come into contact with the thermal printing head as disclosed for example in EP-A 669 876.
  • thermographic materials in direct contact with the thermal printing head during image-wise printing has an adverse effect on the operating lifetime of thermal printing heads which becomes more severe as the temperature at which printing is carried out is increased. For high printing temperatures a means of limiting or preventing the diffusion of these ions to the thermal printing head is therefore required. Furthermore, it is desirable for ecological reasons to coat thermographic materials from aqueous solutions or dispersions and it is extremely difficult to exclude these ions from water, hydrophilic dispersion agents and hydrophilic ingredients in general to attain a concentration of sodium and potassium ions below the 601ppm stipulated in US 4 396 684.
  • pinholes or spots are typically 3 to 10 ⁇ m deep and 5 to 50 ⁇ m in diameter.
  • the failure of individual heating elements in thermal printing heads in the absence of substantial abrasion of the protective layer of the thermal printing head may be due to chemical interaction between the heating elements of the thermal printing head and ions or molecules from the imaging materials which have diffused through the thinner protective coating to or have reacted directly with the heating elements exposed at the bottom of pinholes.
  • thermographic recording materials In order to extend the operating lifetime of thermal printing heads used for the image-wise heating of thermographic recording materials, it is therefore necessary to prevent diffusion of ions and molecules from the thermographic recording materials to the heating elements in general and through the pinholes in the protective layer in particular.
  • a thermal printing head comprising an outermost protective layer and a coating on the outermost surface of the outermost protective layer, characterized in that the coating comprises a hydrolyzed silane, the silane having the general formula: SiR 1 R 2 R 3 R 4 wherein R 1 , R 2 and R 3 are independently a C1 to C4 alkoxy group, a substituted C1 to C4 alkoxy group, bromine or chlorine; and R 4 is a C1 to C4 alkyl group; a substituted C1 to C4 alkyl group, a C1 to C4 alkoxy group or a substituted C1 to C4 alkoxy group.
  • a process for coating a thermal printing head comprising a linear array of resistor elements with a heat-resistant support on one side of the resistor elements and at least one protective layer on the other side thereof, comprising the steps of: (i) applying a coating to the outermost surface of the outermost protective layer of the thermal printing head; (ii) heating the coating; and (iii) removing poorly adhering parts of the coating from the outermost surface of the thermal printing head by cleaning or printing, characterized in that the coating is applied as a solution or dispersion comprising water and a silane having the above-mentioned general formula.
  • thermographic printing process comprising the steps of: (i) bringing a substantially non-photosensitive thermographic recording material into thermal contact with a thermal printing head having the coating described above; (ii) image-wise heating the thermographic recording material with the thermal printing head; and (iii) separating the thermographic recording material from the thermal printing head.
  • the outermost surface of the outermost protective layer, preferably silicon nitride, of a thermal printing head is coated with a coating comprising water and a silane having the general formula: SiR 1 R 2 R 3 R 4 wherein R 1 , R 2 and R 3 are independently a C1 to C4 alkoxy group, bromine or chlorine; and R 4 is a C1 to C4 alkyl group, a substituted C1 to C4 alkyl group, a C1 to C4 alkoxy group, bromine or chlorine.
  • the substituted C1 to C4 alkyl groups may be substituted with any substituents including, for example, the following groups: acryloyloxy, methacryloyloxy, amino, substituted amino, carboxyl, carboxyester, acyl, epoxy, glycidyloxy, epoxyoxy, oxoamine, nitrile, vinyl, substituted vinyl, hydroxy, thiol, thiooxoalkyl, thiooxoaryl, fluoroalkyl etc.
  • substituents including, for example, the following groups: acryloyloxy, methacryloyloxy, amino, substituted amino, carboxyl, carboxyester, acyl, epoxy, glycidyloxy, epoxyoxy, oxoamine, nitrile, vinyl, substituted vinyl, hydroxy, thiol, thiooxoalkyl, thiooxoaryl, fluoroalkyl etc.
  • silanes according to the present invention are selected from the group consisting of ⁇ -glycidyloxypropyltrimethoxysilane, methacryloyloxypropyltrimethoxy-silane, tetramethylorthosilicate and tetraethylorthosilicate.
  • the silanes of the present invention may be on their own or in admixture with one of more other silanes.
  • the use of a mixure of ⁇ -glycidyl-oxypropyltrimethoxysilane and tetraethylorthosilicate or a mixture of methacryloyloxypropyltrimethoxysilane and tetraethylorthosilicate in the coating composition is particularly preferred.
  • the coating may further comprise curable silicone compounds, which when used on their own to coat the protective layers of thermal printing heads produce coatings which are too soft to withstand the abrasive effect of printing thermographic recording materials; a catalyst to promote the hydrolysis of the silanes of the present invention such as an acid, e.g. hydrochloric acid, methanesulfonic acid or formic acid, a basic catalyst, e.g.
  • an alcoholate of titanium, zirconium or aluminium, imidazole etc. colloidal inorganic particles, such as oxides, hydrated oxides, nitrides and carbides of silicon, boron, aluminium and transition metals such as zinc, titanium and zirconium with a specific surface area of preferably at least 100m 2 /g, for example, silica, aluminium oxide, zinc oxide, bentonite, boehmite and the like; an aromatic polyol with a molecular weight less than or equal to 1000, such as bisphenol A, bisphenol F, bisphenol S and 1,5-dihydroxynaphthalene, vinyl or substituted vinyl monomers such as methyl methacrylate, binders, such as polyvinyl alcohol which react with the hydrolysed silane, inorganic compounds, such as metal nitrates, metal chlorides etc., organometallic compounds, such as metal acetates, metal formates, metal alkoxides etc., metal chelates, such as metal acety
  • the dispersion medium or solvent can be deionized water, one or more organic solvents or a mixture of water and one or more organic solvents.
  • suitable organic solvents are methanol, ethanol, n-propanol, isopropanol, butanol, sec-butanol, tert-butanol, methanone, 2-butanone etc.
  • Curing of the coating is usually performed thermally, but radiation curing may also be carried out with appropriate ingredients, for example silanes comprising substituted vinyl groups.
  • the silanes Upon contact with water the silanes hydrolyze and the viscosity of the solution or dispersion begins to increase. Coating may be carried out before significant viscosity increase has taken place or when the viscosity of the solution or dispersion has increased by prepolymerization to the required coating viscosity.
  • the coating may at the end of the coating process, i.e. after any cleaning step, cover the outermost surface of the outermost protective layers of the thermal printing head or only a part thereof, but must at least fill any pinholes present in the outermost surface.
  • the process for coating a thermal printing head of the present invention may be carried out as many times as is necessary to achieve the objects of the present invention, the coating thickness resulting from each process cycle preferably not exceeding 1 ⁇ m.
  • thermographic recording material substantially non-photosensitive thermographic recording material
  • a substantially non-photosensitive thermographic recording material comprises a material or set of materials necessary for image formation.
  • the substantially non-photosensitive thermographic recording material comprises a donor ribbon comprising a sublimable dye layer and a receiving layer for the sublimable dye.
  • thermosensitive element which under the influence of imagewise heating forms an image either in the element itself or after peeling off a material delaminated during the image-wise heating.
  • the element may comprise a layer system and any active ingredients may be present in different layers although in thermal working relationship with one another during the thermal development process.
  • thermosensitive elements may, for example, comprise leuco dyes with acid-releasing ingredients, substantially light-insensitive reducible silver sources and reducing agents therefor in thermal working relationship therewith or delaminatable pigment layers.
  • the element comprises a substantially light-insensitive reducible silver source, a reducing agent therefor in thermal working relationship therewith and a binder.
  • Suitable organic reducing agents for the reduction of the substantially light-insensitive organic heavy metal 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; METOL (tradename); p-phenylene-diamines; alkoxynaphthols, e.g. 4-methoxy-1-naphthol described in US-P 3,094,41; pyrazolidin-3-one type reducing agents, e.g.
  • PHENIDONE (tradename); 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.
  • 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, hydroquinone and substituted hydroquinones
  • catechol, pyrogallol, gallic acid and gallic acid esters are preferred.
  • catechol-type reducing agents are disclosed in EP-A 692 733, e.g. 3,4-dihydroxybenzoic acid esters such as ethyl and butyl 3,4-dihydroxybenzoate.
  • auxiliary reducing agents are e.g. sterically hindered phenols, that on heating become reactive partners in the reduction of the substantially light-insensitive organic heavy metal salt such as silver behenate, such as described in US-P 4,001,026; are bisphenols, e.g. of the type described in US-P 3,547,648; or are sulfonamidophenols.
  • the auxiliary reducing agents may be present in the imaging layer or in a polymeric binder layer in thermal working relationship thereto.
  • thermosensitive element Film-forming binders of the thermosensitive element
  • the film-forming binder of the thermosensitive element containing the substantially light-insensitive reducible silver source may be all kinds of natural, modified natural or synthetic resins or mixtures of such resins, wherein the organic heavy metal salt can be dispersed homogeneously: e.g. cellulose derivatives such as ethylcellulose, cellulose esters, e.g.
  • cellulose nitrate carboxymethylcellulose, starch ethers, galactomannan
  • polymers derived from ⁇ , ⁇ -ethylenically unsaturated compounds such as polyvinyl chloride, after-chlorinated polyvinyl chloride, copolymers of vinyl chloride and vinylidene chloride, copolymers of vinyl chloride and vinyl acetate, polyvinyl acetate and partially hydrolyzed polyvinyl acetate, polyvinyl alcohol, polyvinyl acetals that are made from polyvinyl alcohol as starting material in which only a part of the repeating vinyl alcohol units may have reacted with an aldehyde, preferably polyvinyl butyral, copolymers of acrylonitrile and acrylamide, polyacrylic acid esters, polymethacrylic acid esters, polystyrene and polyethylene or mixtures thereof.
  • 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. 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 described in GB-P 1,439,478 and US-P 3,951,660.
  • 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 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, e.g. BAYSILONE ⁇ l A (tradename of BAYER AG - GERMANY), ultraviolet light absorbing compounds, white light reflecting and/or ultraviolet radiation reflecting pigments, silica, and/or optical brightening agents.
  • antistatic agents e.g. non-ionic antistatic agents including a fluorocarbon group as e.g. in F 3 C(CF 2 ) 6 CONH(CH 2 CH 2 O)-H
  • silicone oil e.g. BAYSILONE ⁇ l A (tradename of BAYER AG - GERMANY)
  • ultraviolet light absorbing compounds e.g. BAYSILONE ⁇ l A (tradename of BAYER AG
  • 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 transparent resin film, 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. Should a transparent base be used, the base may be colourless or coloured, e.g. have a blue colour.
  • the outermost layer of the substantially non-photosensitive thermographic recording material on the same side of the support as the thermosensitive element, according to the present invention, may be a protective layer applied to the thermosensitive element to avoid local deformation of the thermosensitive element and to improve resistance against abrasion or the outermost layer of the thermosensitive element.
  • Such protective layers may also comprise particulate material, e.g. talc particles, optionally protruding from the protective outermost layer as described in WO 94/11198.
  • Other additives can also be incorporated in the protective layer e.g. colloidal particles such as colloidal silica.
  • a maximum dynamic frictional coefficient between the thermal printing head assembly and the outermost layer in contact with the thermal printing head assembly of less than 0.3 can be attained by one skilled in the art by a combination of one or more matting agents, as described in WO 94/11198 with one or more thermomeltable particles optionally with one or more lubricants, as described in WO 94/11199, or with at least one solid lubricant having a melting point below 150°C and at least one liquid lubricant in a binder, wherein at least one of the lubricants is a phosphoric acid derivative.
  • the outermost layer of the recording material on the same side of the support as the thermosensitive element comprises a water-dispersible, a water-soluble or a water-soluble and a water-dispersible binder.
  • Suitable water-soluble binders for the outermost layer in contact with the thermal printing head assembly are, for example, gelatin, polyvinylalcohol, cellulose derivatives or other polysaccharides, hydroxyethylcellulose, hydroxypropylcellulose etc., with hardenable binders being preferred and polyvinylalcohol being particularly preferred.
  • Suitable water-dispersible binders are, for example, polymer lattexes.
  • the outermost layer of the recording material in contact with the thermal printing head assembly may be crosslinked.
  • Crosslinking can be achieved by using crosslinking agents such as described in WO 95/12495 for protective layers, e.g. tetra-alkoxysilanes, polyisocyanates, zirconates, titanates, melamine resins etc., with tetraalkoxysilanes such as tetramethylorthosilicate and tetraethylorthosilicate being preferred.
  • the outermost layer of the recording material in contact with the thermal printing head assembly 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.
  • the outermost layer of the recording material according to the present invention may comprise at least one lubricant.
  • suitable lubricating materials are surface active agents, liquid lubricants, solid lubricants which do not melt during thermal development of the recording material, solid lubricants which melt (thermomeltable) during thermal development of the recording material or mixtures thereof.
  • the lubricant is preferably selected from a group consisting of silicon derivatives, polyolefins, fatty acid derivatives, fatty alcohol derivatives and phosphoric acid derivatives.
  • thermographic recording material comprising a support and a thermosensitive element, of the present invention, may further comprise an outermost antistatic layer on the opposite side of the support to the thermosensitive element. Suitable antistatic layers therefor are described, for example, in US 5,354,613.
  • 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.
  • thermographic printing process a pressure of at least 100g per cm of linear array of resistor elements is applied between the substantially non-photosensitive thermographic recording material and the thermal printing head assembly.
  • thermographic image-wise heating of the recording material proceeds by Joule effect heating in that selectively energized electrical resistors of a thermal printing head array are used in contact or close proximity with the recording layer.
  • the image signals for modulating the current in the microresistors of a thermal printhead are obtained directly or from an intermediary storage means, optionally linked to a digital image work station wherein the image information can be processed to satisfy particular needs.
  • Activation of the heating elements can be power-modulated or pulse-length modulated at constant power.
  • Thermographic imaging can be used for both the production of transparencies and reflection type prints.
  • hard copy field recording materials on a white opaque base are used.
  • Black-imaged transparencies with transparent bases are used in both the graphics and medical diagnostic fields.
  • graphics field dots and lines are printed using thermographic recording materials with a hard gradation and the transparencies are used as masks in the exposure of photosensitive compositions on printing plate bases in the process of printing plate preparation.
  • black-imaged transparencies are widely used in inspection techniques operating with a light box.
  • a subbed polyethylene terephthalate support having a thickness of 175 ⁇ m was doctor blade-coated with a coating composition containing 2-butanone as a solvent and the following ingredients so as to obtain thereon, after drying for 1 hour at 50°C, a layer containing:
  • thermographic recording material A printing run was carried out with sheets of the above-described substantially non-photosensitive thermographic recording material in an experimental printer equipped with a thin film thermal printing head with a pinhole in its outermost protective layer.
  • Printing was carried out with a printer in which the above-mentioned thin film thermal printing head had been installed in which the sheets of substantially non-photosensitive thermographic material were fed at a speed of 4mm/s onto a drum past the thermal printing head mounted in such a way as to contact the substantially non-photosensitive thermographic material.
  • the thermal printing head was operated at a line time of 19ms (the line time being the time needed for printing one line), during which it received constant power, and at an average printing power, being the total amount of electrical energy used for printing one line divided by the line time and the surface area of the heat-generating resistors, of 1.25mJ/dot, being sufficient to obtain maximum density in said recording material.
  • a defective heating element, corresponding in position to the pinhole in the outermost protective layer of the thermal printing head was detected in the prints as a white line after 50 prints.
  • GPTS glycidyloxypropyltrimethoxysilane
  • a printing run of 1000 prints was carried out with a thermal printing head with a pinhole using sheets of the above-described substantially non-photosensitive thermographic material as described for COMPARATIVE EXAMPLE 1. Evaluation of the thermal printing head with a microscope afterwards showed that the pinholes in the protective layer had remained filled with the coating and that no discolouration of the heating elements in the thermal printing head had taken place. Furthermore none of the heating elements of the thermal printing head was defective after this printing run of 1000 prints, which shows that application of a coating, according to the present invention, to the protective layer of a thermal printing head with a pinhole has prevented the premature failure of the heating elements observed with a thermal printing head with a pinhole which had not been subjected to the above-described treatment, see COMPARATIVE EXAMPLE 1.
  • Dispersion B was then applied from a pipette via an injection needle to the outermost protective layer of the same type of thin film thermal printing head as used in COMPARATIVE EXAMPLE 1 to fill the pinholes therein.
  • the excess of dispersion B was removed from the thermal printing head either by applying a current to the heating elements thereof for about 7 minutes, removing the excess dispersion with a cloth moistened with 2-butanone and then heating the thermal printing head for 40 minutes at 130°C.
  • Dispersions C, D and E were then each applied from a pipette via an injection needle to the outermost protective layer of different thin film thermal printing heads each with a pinhole in its outermost protective layer to fill the pinholes therein.
  • the thermal printing heads were then heated for 15 minutes at 65°C and the excess of the dispersions removed by applying a cloth moistened with a mixture of 2-butanone and isooctane.

Landscapes

  • Engineering & Computer Science (AREA)
  • Manufacturing & Machinery (AREA)
  • Heat Sensitive Colour Forming Recording (AREA)
  • Electronic Switches (AREA)
  • Application Of Or Painting With Fluid Materials (AREA)
  • Paints Or Removers (AREA)

Claims (10)

  1. Ein Thermodruckkopf mit einer Außenschutzschicht und einer Schicht auf der äußersten Oberfläche der Außenschutzschicht, dadurch gekennzeichnet, daß die Schicht ein hydrolysiertes Silan der allgemeinen Formel SiR1R2R3R4 enthält, in der R1, R2 und R3 je unabhängig voneinander eine C1-C4-Alkoxygruppe, eine substituierte Cl-C4-Alkoxygruppe, ein Bromatom oder ein Chloratom bedeuten und R4 eine C1-C4-Alkylgruppe, eine substituierte C1-C4-Alkylgruppe, eine C1-C4-Alkoxygruppe oder eine substituierte C1-C4-Alkoxygruppe bedeutet.
  2. Thermodruckkopf nach Anspruch 1, dadurch gekennzeichnet, daß als Silan γ-Glycidyloxypropyltrimethoxysilan, Methacryloyloxypropyltrimethoxysilan, Tetramethylorthosilikat oder Tetraethylorthosilikat benutzt wird.
  3. Thermodruckkopf nach Anspruch 1 oder 2, dadurch gekennzeichnet, daß die Schicht ferner kolloidale anorganische Teilchen mit einer spezifischen Oberfläche von wenigstens 100 m2/g enthält.
  4. Thermodruckkopf nach irgendeinem der vorstehenden Ansprüche, dadurch gekennzeichnet, daß die Außenschutzschicht als Hauptbestandteil Siliciumnitrid enthält.
  5. Ein durch die nachstehenden Schritte definiertes Verfahren zur Beschichtung eines Thermodruckkopfes, der eine lineare Matrix von Widerstandselementen mit einem hitzebeständigen Träger an einer Seite der Widerstandselemente und wenigstens einer Schutzschicht an der anderen Seite der Widerstandselemente umfaßt :
    (i) Auftrag einer Schicht auf die äußerste Oberfläche der Außenschutzschicht des Thermodruckkopfes,
    (ii) Erhitzung dieser Schicht, und
    (iii) Entfernung schwach haftender Teile der Schicht von der äußersten Oberfläche des Thermodruckkopfes durch Reinigung oder Drucken, dadurch gekennzeichnet, daß die Schicht in Form einer wäßrigen Lösung oder Dispersion mit Silan der allgemeinen Formel SiR1R2R3R4 aufgetragen wird, in der R1, R2 und R3 je unabhängig voneinander eine C1-C4-Alkoxygruppe, eine substituierte C1-C4-Alkoxygruppe, ein Bromatom oder ein Chloratom bedeuten und R4 eine C1-C4-Alkylgruppe, eine substituierte C1-C4-Alkylgruppe, eine C1-C4-Alkoxygruppe oder eine substituierte C1-C4-Alkoxygruppe bedeutet.
  6. Verfahren zur Beschichtung eines Thermodruckkopfes nach Anspruch 5, dadurch gekennzeichnet, daß die Lösung oder Dispersion Methacryloyloxypropyltrimethoxysilan oder Tetraethylorthosilikat enthält.
  7. Verfahren zur Beschichtung eines Thermodruckkopfes nach Anspruch 5 oder 6, dadurch gekennzeichnet, daß die Schicht ferner kolloidale anorganische Teilchen mit einer spezifischen Oberfläche von wenigstens 100 m2/g enthält.
  8. Ein durch die folgenden Schritte definiertes thermografisches Druckverfahren :
    (i) thermisches Inkontaktbringen eines wesentlich lichtunempfindlichen thermografischen Aufzeichnungsmaterials mit einem Thermodruckkopf,
    (ii) bildmäßige Erhitzung des thermografischen Aufzeichnungsmaterials mit dem Thermodruckkopf, und
    (iii) Abtrennung des thermografischen Aufzeichnungsmaterials vom Thermodruckkopf, dadurch gekennzeichnet, daß der Thermodruckkopf mit einer hydrolysiertes Silan enthaltenden Schicht überzogen ist, wobei das Silan der allgemeinen Formel SiR1R2R3R4 entspricht, in der R1, R2 und R3 je unabhängig voneinander eine C1-C4-Alkoxygruppe, eine substituierte C1-C4-Alkoxygruppe, ein Bromatom oder ein Chloratom bedeuten und R4 eine C1-C4-Alkylgruppe, eine substituierte C1-C4-Alkylgruppe, eine C1-C4-Alkoxygruppe oder eine substituierte C1-C4-Alkoxygruppe bedeutet.
  9. Thermografisches Druckverfahren nach Anspruch 8, dadurch gekennzeichnet, daß das wesentlich lichtunempfindliche thermografische Aufzeichnungsmaterial einen Träger und ein wärmeempfindliches Element enthält, das ein wesentlich lichtunempfindliches organisches Silbersalz, ein zugehöriges Reduktionsmittel in thermischer wirksamer Beziehung dazu und ein Bindemittel enthält.
  10. Thermografisches Druckverfahren nach Anspruch 9, dadurch gekennzeichnet, daß die Außenschicht des Aufzeichnungsmaterials an derselben Seite des Trägers wie das wärmeempfindliche Element ein wasserdispergierbares Bindemittel, ein wasserlösliches Bindemittel oder ein wasserlösliches und ein wasserdispergierbares Bindemittel enthält.
EP19970200518 1997-02-22 1997-02-22 Beschichtung für Thermodruckkopf Expired - Lifetime EP0860288B1 (de)

Priority Applications (4)

Application Number Priority Date Filing Date Title
DE1997604844 DE69704844T2 (de) 1997-02-22 1997-02-22 Beschichtung für Thermodruckkopf
EP19970200518 EP0860288B1 (de) 1997-02-22 1997-02-22 Beschichtung für Thermodruckkopf
US09/018,740 US6028618A (en) 1997-02-22 1998-02-04 Thermal printing head coating
JP5000598A JPH10235915A (ja) 1997-02-22 1998-02-17 感熱印刷ヘツドコーテイング

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
EP19970200518 EP0860288B1 (de) 1997-02-22 1997-02-22 Beschichtung für Thermodruckkopf

Publications (2)

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EP0860288A1 EP0860288A1 (de) 1998-08-26
EP0860288B1 true EP0860288B1 (de) 2001-05-16

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US6281921B1 (en) * 1999-02-15 2001-08-28 Riso Kagaku Corporation Method for treating the surface of thermal printing heads
US6451420B1 (en) * 2000-03-17 2002-09-17 Nanofilm, Ltd. Organic-inorganic hybrid polymer and method of making same
CN101213077B (zh) 2005-06-29 2010-11-24 东洋纺织株式会社 聚乙烯系树脂层叠薄膜

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KR930004777B1 (ko) * 1987-01-31 1993-06-08 가부시키가이샤 도시바 내열성 절연피복재 및 이것을 이용한 써말 헤드
DE3918472A1 (de) * 1989-06-06 1990-12-13 Siemens Ag Hydrophobierungsmittel und anwendungsverfahren, insbesondere bei tintenstrahldruckkoepfen
US5218381A (en) * 1992-04-28 1993-06-08 Xerox Corporation Hydrophobic coating for a front face of a printhead in an ink jet printer

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DE69704844T2 (de) 2001-11-08
DE69704844D1 (de) 2001-06-21
JPH10235915A (ja) 1998-09-08
EP0860288A1 (de) 1998-08-26

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