EP1104700A1 - Thermokopf - Google Patents

Thermokopf Download PDF

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Publication number
EP1104700A1
EP1104700A1 EP99204069A EP99204069A EP1104700A1 EP 1104700 A1 EP1104700 A1 EP 1104700A1 EP 99204069 A EP99204069 A EP 99204069A EP 99204069 A EP99204069 A EP 99204069A EP 1104700 A1 EP1104700 A1 EP 1104700A1
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EP
European Patent Office
Prior art keywords
thermal head
heating
thermal
head according
heating elements
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.)
Granted
Application number
EP99204069A
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English (en)
French (fr)
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EP1104700B1 (de
Inventor
Hans c/o Agfa-Gevaert N.V. Strijckers
Karsten Dierksen
Robert c/o Agfa-Gevaert N.V. Overmeer
Eric C/O Agfa-Gevaert N.V. Kaerts
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Agfa Gevaert NV
Original Assignee
Agfa Gevaert NV
Agfa Gevaert AG
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Priority to EP19990204069 priority Critical patent/EP1104700B1/de
Priority to DE1999627693 priority patent/DE69927693T2/de
Priority to JP2000360936A priority patent/JP2001162848A/ja
Publication of EP1104700A1 publication Critical patent/EP1104700A1/de
Application granted granted Critical
Publication of EP1104700B1 publication Critical patent/EP1104700B1/de
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    • 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
    • B41J2/33515—Heater 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
    • B41J2/315—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
    • B41J2/3357—Surface type resistors

Definitions

  • the present invention relates to a device operable for applying thermal energy to a recording medium, the device comprising a thermal head having energisable heating elements which are individually addressable.
  • the recording medium is a thermographic material
  • the head relates to thermal imaging, generally called thermography.
  • Thermal imaging or thermography is a recording process wherein images are generated by the use of imagewise modulated thermal energy.
  • Thermography is concerned with materials which are not photosensitive, but are sensitive to heat or thermosensitive and wherein imagewise applied heat is sufficient to bring about a visible change in a thermosensitive imaging material, by a chemical or a physical process which changes the optical density.
  • thermographic recording material m comprises on a support a thermosensitive layer comprising an organic silver salt, which generally is in the form of a sheet.
  • the imaging element 3 is mounted on a rotatable drum 15, driven by a drive mechanism (not shown) which continuously advances (see arrow Y representing a so-called slow-scan direction) the drum 15 and the imaging element 3 past a stationary thermal print head 16.
  • This head 16 presses the imaging element 3 against the drum 15 and receives the output of the driver circuits (not shown for the sake of greater clarity).
  • the thermal print head 16 normally includes a plurality of heating elements equal in number to the number of pixels in the image data present in a line memory. The imagewise heating of the heating element is performed on a line by line basis, the "line” may be horizontal or vertical depending on the configuration of the printer, with the heating resistors geometrically juxtaposed each along another and with gradual construction of the output density.
  • Each of these resistors is capable of being energised by heating pulses, the energy of which is controlled in accordance with the required density of the corresponding picture element.
  • the output energy increases and so the optical density of the hardcopy image 17 on the imaging element 3.
  • lower density image data cause the heating energy to be decreased, giving a lighter picture 17.
  • a digital signal representation is obtained; then, the image signal is applied via a digital interface to a storing means (not shown) of the thermal printer 10.
  • the digital image signal is processed.
  • the recording head 16 is controlled so as to produce in each pixel the density value corresponding with the processed digital image signal value.
  • electrical current may flow through the associated heating elements. In this way a thermal hardcopy 17 of the electrical image data is recorded.
  • a variable density image pixel is formed.
  • Figure 3 (known from e.g. EP 0 627 319, in the name of Agfa-Gevaert) is a detailed cross-section of a flat thermal head TH, indicated as part 16 in the present drawings.
  • This head comprises at least an insulating substrate 34 (e.g. a ceramic such as glass filled e.g. with alumina Al 2 O 3 , with a relatively high thermal conductivity of e.g. 40.10 -3 cal/cm,sec °C; thickness between 1 and 60 ⁇ m), a protrusion 35 (e.g. a layer,' composed of glass or the like, with a positioning bulb having a circular or sectional configuration; with a low thermal conductivity of e.g. 2.10 -3 cal/cm.sec.°C), a heating element 36 of electrically resistive material(e.g.
  • an insulating substrate 34 e.g. a ceramic such as glass filled e.g. with alumina Al 2 O 3 , with a relatively high thermal conductivity of e.g. 40.10 -3 cal/cm,sec °C; thickness between 1 and 60 ⁇ m
  • a protrusion 35 e.g. a layer,' composed of glass or the
  • tungsten W chromium oxide CrO2, tantalum nitride Ta2N, tantalum silicate TaSi or TaSiO, ruthenium oxide RuO 2 , CrSiO, or the like
  • a protective layer 37 e.g. of glass or siliciumnitride having 5 to 10 ⁇ m thickness
  • electrodes 48, 49 e.g. 0,7 um thickness, composed of a metal as Al or Cu .
  • the protective layer 37 itself may be composed of an oxidant-resistant layer of about 2 ⁇ m SiO 2 and a wear-resistant layer of about 8 ⁇ m of Ta 2 O 5 or the like.
  • the head further comprises also a heatsink 31 (at least 1 mm thickness), a temperature sensor 32, and a bonding layer 33.
  • FIG 4 is a detailed cross-section of another type of a thermal head 16 known from prior art (e.g. US 5,635,974 of Kyocera).
  • reference number 34 denotes an electrically insulating substrate comprising a ceramic substrate 34a and a glaze layer 34b; a heating element 36, electrodes 48 and 49 (made of Al, Au, Cu or the like), and a protective layer 37 (e.g. filler-containing-glass).
  • the description given hereinafter mainly comprises six sections, namely (i) terms and definitions used in the present application, (ii) preferred embodiments of a transparent thermal head, (iii) heating materials suitable for use according to the present invention, (iv) use of a thermal head according to the present invention, (v) use of a thermal head according to the present invention combined with a laser, and (vi) further use of a thermal head according to the present invention.
  • thermographic material (being a thermographic recording material, hereinafter indicated by symbol m) comprises both a thermosensitive imaging material and a photothermographic imaging material (being a photosensitive thermally developable photographic material).
  • thermographic imaging element Ie is a part of a thermographic material m (both being indicated by ref. nr. 3). Hence, symbolically: m ⁇ Ie.
  • thermographic imaging element Ie comprises both a (direct or indirect) thermal imaging element and a photothermographic imaging element.
  • thermographic imaging element Ie will mostly be shortened to the term imaging element.
  • heating material (hereinafter indicated by symbol hm) is meant a layer of material which is electrically conductive so that heat is generated when it is activated by an electrical power supply.
  • a heating element Hi is a part of the heating material hm .
  • hm ⁇ Hi symbolically:
  • a heating element Hi (as e.g. H1, H2, H3 ...) being a part of the heating material hm is conventionally a rectangular or square portion defined by the geometry of suitable electrodes.
  • a heating element is also part of a heating system, which system further comprises a power supply, a data capture unit, a processor, a switching matrix, leads, etc.
  • An “original” is any hardcopy or softcopy containing information as an image in the form of variations in optical density, transmission, or opacity.
  • Each original is composed of a number of picture elements, so-called “pixels”. Further, in the present application, the terms pixel and dot are regarded as equivalent.
  • the terms pixel and dot may relate to an input image (known as original) as well as to an output image (in softcopy or in hardcopy, e.g. known as print).
  • thermal printing head a heat-sensitive receiving material (in case of so-called one-sheet thermal printing) or a combination of a heat-sensitive donor material and a receiving (or acceptor) material (in case of so-called two-sheet thermal printing), and a transport device which moves the receiving material or the donor-acceptor combination relative to the thermal printing head.
  • the thermal head usually consists of a one-dimensional array of heating elements arranged on a ceramic substrate which is itself mounted on a heat-dissipating base element or heatsink hs.
  • a thermal head TH is optically transparent.
  • the description which follows in the instant section, comprises three subsections: (ii-a) a description of global characteristics common to different embodiments of the invention, (ii-b) a description of some preferred embodiments of the invention and focused on cross-sectional views, and (ii-c) a description of the electrodes and of the heating elements, being focused on planviews of a thermal head.
  • the heating material hm is e.g. indium-tin-oxide ITO.
  • ITO indium-tin-oxide
  • a process for producing a transparent thermal head now will be described, although other processes could also be used.
  • a conducting layer as heating material hm is applied by sputtering, by chemical vapor deposition, spraying followed by pyrolysis, metal evaporation followed by oxidation, etc, to a transparent substrate which is preferentially glass (e.g. Baltron 255, Balzers). Thereafter, the completely coated substrate can be structured by removing the conduction layer spatially selectively. This can be done e.g. by using a tape as mask and later removing the ITO on untaped locations by means of lithographic techniques.
  • the area of ITO that is not covered with adhesive tape is then removed from the glass substrate e.g. by etching.
  • etching For example, a pinch of zinc powder is applied to and spread over the area to be etched away by using a spatula.
  • a few drops of semiconcentrated hydrochloric acid are pipetted on the zinc powder by using a disposable pipette.
  • the hydrochloric acid is poured off the substrate and any residual zinc removed by rinsing with a few drops of hydrochloric acid.
  • the substrates are immersed in a beaker containing water, rinsed with water and rubbed dry with paper.
  • the adhesive tape is peeled off and the substrate is cleaned first with acetone, then with ethanol and finally with distilled water. This cleaning operation is repeated until all traces of adhesive have been removed from the surface.
  • the heating material hm is connected with a conducting layer, such as silver (R ⁇ 1 ⁇ / ), to produce electrodes.
  • a conducting layer such as silver (R ⁇ 1 ⁇ / )
  • the electrodes are electrically connected with wires and a voltage can be applied.
  • the resistance of this system is e.g. between 5 and 25 ⁇ / ⁇ , e.g about 8 to 10 ⁇ / ⁇ .
  • the size of the thermal head was 50 mm x 50 mm. Although there is no limitation in the number and size (cf. spatial resolution expressed in dpi) of the structure, in one experiment a 3 mm x 50 mm wide ITO structure in the centre of a substrate was used.
  • a flat-type thermal head according to the present invention comprises at least a heatsink 31, heating elements 39, electrodes 48, 49, and optionally additional layers, wherein at least the heating elements are optically transparent. More specifically, the heating elements 39 are part of a heating material 36, especially a transparent heating material.
  • Figs. 6.1 and 6.2 represent two exemplary embodiments according to the present invention.
  • Figs. 6.1 illustrates a heatsink 31 which is thermally conductive and optically transparent (e.g. made from glass, a flexible glass, polycarbonate, or polyacrylonitrile, optionally comprising a filler), a transparent conducting layer as heating material hm (e.g. made from an ITO-layer) comprising transparent heating elements 39 (e.g. 39a, 39b, 39c...), electrodes 48-49 and preferably a transparent protective layer 37.
  • thermally conductive and optically transparent e.g. made from glass, a flexible glass, polycarbonate, or polyacrylonitrile, optionally comprising a filler
  • a transparent conducting layer as heating material hm e.g. made from an ITO-layer
  • transparent heating elements 39 e.g. 39a, 39b, 39c
  • electrodes 48-49 e.g. 39a, 39b, 39c
  • Figs. 6.2 illustrates a heatsink 31 which is thermally conductive but not necessarily optically transparent (e.g. made from aluminium) and which has locally a sufficiently open zone (see ref. nr. 29), a transparent conducting layer as heating material hm (e.g. made from an ITO-layer) comprising transparent heating elements 39 (e.g. 39a, 39b, 39c ...), electrodes 48-49, preferably a transparent protective layer 37, and optionally an insulating substrate 34.
  • a transparent conducting layer as heating material hm e.g. made from an ITO-layer
  • transparent heating elements 39 e.g. 39a, 39b, 39c
  • heating material hm having surface conductance or (ii) heating material hm having a bulk conductance .
  • the non-conducting side of the heating material hm may be in direct contact with the heatsink hs, even if the heatsink is made of an electrically conducting material (such as aluminium).
  • the heating material hm only may be in direct contact with the heatsink hs, if the heatsink is made of an electrically non-conducting material (e.g.
  • the heating material hm may not be in direct contact with the heatsink hs, if the heatsink is made of an electrically conducting material (such as aluminium), and here an additional insulating layer is needed between heating elements 39 and the heatsink 31 (see e.g. insulating substrate 34 in Fig. 6.2).
  • an additional insulating layer is needed between heating elements 39 and the heatsink 31 (see e.g. insulating substrate 34 in Fig. 6.2).
  • insulating layer m may be given by providing a oxide-layer, generally a thin oxide-layer, being both electrically insulating and thermally sufficient conductive.
  • heatsink 31 different embodiments can be differentiated. So, if the heatsink hs has electrically insulating characteristics, no additional insulating layer is needed between heating elements 39 and heatsink 31 (which case is illustrated e.g. in Fig. 6.1.). Alternatively, if the heatsink hs has no electrically insulating characteristics (such as e.g. aluminium) an additional insulating layer is needed between heating elements 39 and heatsink 31 (which case is illustrated e.g. in Fig. 6.2).
  • electrically insulating characteristics such as e.g. aluminium
  • Other materials suitable for providing such an insulating substrate 34 may comprise siliciumnitride (optionally being doped), AlN, or diamond-like thin film coating such as Dylyn TM , etc.
  • Dylyn TM is a trademark of Advanced Refractory Technologies Inc., USA; the product is available in Europe from Bekaert Dymonics, Belgium. A few technical characteristics comprise e.g.
  • thickness between 0,01 and 10 ⁇ m; thermal stability up to 400°C (or 673 K); dielectric breakdown strength > 10 6 V/cm; electrical resistivity being controllable between 10 14 and 10 -2 ⁇ cm, thermal conductivity about 70 W/m.K .
  • an additional layer may be introduced between the heating element 39 and the heatsink 31 in order to reduce possible transition resistance of heat.
  • Fisher Elektronik commercialises e.g. (i) silicon thermal transfer compounds comprising silicon oil and inorganic fillingmaterial (e.g. metal oxides), and (ii) siliconfree thermal transfer compounds comprising a synthetic liquid without silicon and inorganic fillingmaterial (e.g. metal oxides). These materials have interesting characteristics such as thermal conductivities up to 1 W/mK, a dielectric strength up to 40 kV/mm, a specific resistance greater than 10 12 ⁇ .cm, an operating temperature range up to + 250 °C (or 523 K), etc. (cf. Data sheets from Fischer Elektronik & Dau).
  • the temperature of the insulating substrate 34 rarely exceeds + 100 °C (or 373 K), generally even not + 70 °C (or 343 K).
  • the temperature of the heatsink 31 rarely exceeds + 60 °C (or 333 K).
  • the abovementioned optionally additional layers comprise a protective layer 37 and optionally at least one bonding layer.
  • the protective layer 37 comprises glass or siliciumnitride or is composed of an oxidant-resistant layer of SiO 2 and a wear-resistant layer of Ta 2 O 5
  • a thermal head further also comprises a temperature sensor.
  • the heats'ink 31, the bonding layer 33, the insulating substrate 34 and the additional layers (e.g. 37) are optically transparent, at least at zones corresponding to the heating elements.
  • the illustrated embodiment has discontinuous areas of heating material hm (see e.g. ref. nrs.. 39a, 39b, etc.).
  • the thermal print head 16 typically comprises an array of individually addressable, electrically resistive heating elements. These individually energisable juxtaposed heating elements 39 for image-wise heating the thermosensitive layer are energised by the application of voltage to produce heat as current flows therethrough. The heat produced by a heating element is applied to a localised pixel area on the imaging element in contact with the energised element to activate the dye and produce a visible pixel therein.
  • Figs. 6.1 and 6.2 illustrate a heatsink hs (ref 31) which is transparent by being made of optical transparent material (see Fig. 6.1), or by having locally a sufficient open zone (see ref 29 in Fig. 6.2). Further, Figs. 6.1 and 6.2 show a transparent conducting layer as heating material 39 (e.g. made from ITO-layer), with discontinue heating elements 39a, 39b, 39c; leads or lead wires with signal electrodes 48a, 48b, 48c ...and counter electrodes 49a, 49b, 49c ...
  • heating material 39 e.g. made from ITO-layer
  • any individual heating element H in the linear array may be energised simply by applying voltage between its corresponding electrodes. Indeed, when an energising voltage, typically in the range of 12 to 18 volts, is applied between electrodes 48a and 49a, it causes a current to flow through the rectangular portion 39a of heating material in between, designated element H1. The current through the resistive material hm of heating element H1 generates thermal energy which heats up the pixel area of the imaging element in contact with heating element H1 causing the image-forming thermographic system to change colour once a threshold temperature is exceeded.
  • the next element H2 in the array may be energised by applying voltage between its corresponding electrodes 48b and '49b.
  • a thermal print head 16 comprises a continuous strip of heating material hm and is diagrammatically shown in dual Figs. 7 and 8.
  • Fig. 8 also illustrates some components of the signal processing system (e.g. power supply and signal processor 44 and switching matrix 46).
  • the thermal head comprises an elongated rectangular substrate 34 made of ceramic, glass or the like, a continuous elongated strip of heating material 36, extending along the length of substrate 34, formed of a film of electrically conductive-resistive heating material hm, and a plurality of equally spaced, interdigitated electrodes 48-49 which make electrical contact to heating material 36 (the technical term interdigitated here is nearly equivalent to interlocked or interpenetrated).
  • the signal electrodes 48 and the counter electrodes 49 serve to divide the continuous strip of heating material 36 into a serial array of individually addressable thermal heating elements Hi.
  • an energising voltage typically in the range of 12 to 18 volts
  • it causes a current to flow through that portion, e.g. a rectangular portion, of heating material 36 therebetween, designated as heating element H1.
  • the current through the resistive material of element H1 generates thermal energy or heat which impinges upon the pixel area of the imaging element in contact with element H1 causing the dye therein to react and change colour once the threshold temperature is exceeded.
  • the next element H2 in the array may be energised by applying voltage between its corresponding electrodes 48b and 49x.
  • the next successive element H3 may be energised by impressing voltage between 48c and 49y, etc.
  • Any individual element Hi in the linear array may be energised simply by applying voltage between its corresponding electrodes.
  • Leads or lead wires generally are connected to a matrix switching system which facilitates the application of energising voltage to selected electrodes. Through the switching system, any or all of the heating elements Hi may be energised simultaneously on response to appropriate data input signals.
  • the print head 16 is of the line printing type and includes a laterally extending support member or substrate 34 made of electrically insulating material.
  • Substrate 34 has an elongated laterally extending window 47, which is coextensive with the length of a line of the image to be recorded, into which the free ends of a plurality of signal electrodes 48a, 48b, 48c ... extend in interdigitated relationship with a plurality of corresponding spaced counter electrodes 49x, 49y, 49z ...
  • the electrodes 48 and 49 are mounted on substrate 34 and each comprises a separate electrical contact having its end opposite the free end connected to a matrix switching device 46 which is operated by a print head signal processor and power supply 44.
  • Electrodes 48 and 49 are in engagement with a corresponding segment of heating heating element hm.
  • the recording signal Vs is applied to the first signal electrode 48a which is paired with the first counter-electrode 49x i.e..
  • the print head signal processor 44 operates the matrix switching device 46 so that voltage Vs is applied to electrode 48a and the counter-electrode 39x is lowered to a ground potential relative to Vs so that a current flow path I is established therebetween to generate heat in the corresponding pixel area section of the imaging element.
  • signal voltage Vs is applied to the second signal electrode 48b with this paired with the first counter-electrode 49x.
  • a pixel is printed in the next adjacent area C by pairing the second signal electrode 48b with the next counter-electrode 39y ...etc. Additional electrode pairs are provided along the entire length of window 47.
  • the electrodes 38 comprise "strictly" individual electrodes 48, 49 energising each of the heating elements 39 (as e.g. illustrated in Figs. 6.3, 7 and 8).
  • the electrodes 38 comprise a common electrode (not shown) and an individual electrode (not shown) energising each of the heating elements.
  • the heating elements have a width smaller than 80 or even smaller than 70 ⁇ m. So, a spatial resolution of 320 dpi or even 360 dpi is attainable.
  • the transparent heating material hm is e.g. indium-tin-oxide ITO.
  • metal oxides may also be used in conductive layers, for example non-stoichiometric and doped oxides of tin, indium, cadmium, zinc and their alloys.
  • Well known examples of the latter category include tin oxide (TO) doped with antimony (ATO) or fluorine (FTO), indium oxide (IO) doped with tin (ITO), and zinc oxide doped with indium (IZO).
  • TO tin oxide
  • ATO antimony
  • FTO fluorine
  • ITO indium oxide
  • IZO zinc oxide doped with indium
  • These metal oxides exhibit high transmittance in the visible spectral region, and nearly metallic conductivity. The electrical as well as the optical properties of these materials can be tailored by controlling the deposition conditions and other process steps.
  • usable transparent heating materials comprise: In 2 O 3 optionally doped with O 2 , Sn, Ti, Pb, F; snO/O 2 optionally doped with O 2 , Sb, F, Cl, Br, I, P, As, In, Th, Te, W; ZnO optionally doped with O 2 , In, Al; Cd 2 SnO 4 or CdSnO 3 or mixtures thereof (as e.g. Cadmium stannate); Bi 2 O 3 MoO 3; TiO 2 ; WO 2 ; RhO 2 ; ReO 2 ; Na X WO 3 ; Zn 2 SnO 4
  • Fig. 9 is a diagram showing the optical transmission of an ITO as a function of the wavelength which is suitable for use according to the present invention.
  • I.e ref. nr. 81 gives the transmittance curve of a heating material hm ITO.
  • the heating material hm applied in the thermal head is optically transparent by having, in the wavelength range from 350 to 1200 nm, a transparency higher than 70 %. More preferably, the heating material hm is optically transparent by having in the wavelength range from 700 to 1100 nm a transparency higher than 80%.
  • a preferred thermal head TH has heating material hm selected from In 2 O 3 optionally doped with oxygen, Sn, Ti, Pb, F; SnO/O 2 optionally doped with oxygen, Sb, F, Cl, Br, I, P, As, In, Th, Te, W; ZnO optionally doped with oxygen, In, Al; Cd 2 SnO 4 , or CdSnO 3 , or mixtures thereof (as cadmium stannate); Bi 2 O 3 ; MoO 3 ; TiO 2 ; WO 2 ; RhO 2 ; ReO 2 ; Na X WO 2 ; Zn 2 SnO 4 ; V205.
  • the transparent (e.g. ITO being Indium-Tinoxide) layer is replaced by transparent conductive organic polymers e.g. polyacetylene, polypyrrole, polyaniline (PANI), polythiophene e.g. polydioxylthiophene (PEDT), etc.
  • transparent conductive organic polymers e.g. polyacetylene, polypyrrole, polyaniline (PANI), polythiophene e.g. polydioxylthiophene (PEDT), etc.
  • the transparent conductive layer is prepared by applying a mixture containing (a) a polythiophene with the formula wherein each of R1 and R2 independently represents hydrogen or a C1-4 alkyl group or together represent an optionally substituted C1-4 alkylene group or a cycloalkylene group, preferably an ethylene group, an optionally alkyl-substituted methylene group, an optionally C1-12 alkyl- or phenyl-substituted 1,2-ethylene group, a 1,3-propylene group or a 1,2-cyclohexylene group, (b) a polyanion compound and (c) an organic compound containing 2 or more OH and/or COOH groups or amide or lactam groups.
  • a polythiophene with the formula wherein each of R1 and R2 independently represents hydrogen or a C1-4 alkyl group or together represent an optionally substituted C1-4 alkylene group or a cycloalkylene group, preferably an ethylene group, an optionally alkyl
  • a commercial conductive and transparent foil comprising a heat-stabilised polyester film carrying a water based transparent conductive coating polymer is known as ORGACON (registered tradename of Agfa-Gevaert), e.g. type ORGACON-EL.
  • Fig 10 is a diagram showing the optical transmission of ORGACON-EL with respect to the wavelength, suitable for use according to the present invention.
  • Ref. nr. 82a is the transmittance curve of the heating material.
  • Fig 11 is a diagram showing the optical transmission, the absorption and the reflectance of ORGACON-EL with respect to the wavelength, suitable for use according to the present invention.
  • Ref. nr. 82b is the transmittance curve of a heating material ORGACON-EL
  • ref. nr. 83 the absorption curve
  • ref. nr. 84 the reflection curve of the same heating material ORGACON-EL . It has to be noticed that, especially in the range above 350 nm, both the absorption and the reflection of the heating material hm are very low.
  • resistivity presented in this document are measured according to the following method.
  • a sample of the heating material hm is cut to obtain a strip having e.g. a length of 275 mm and a width of 35 mm. Electrodes are applied over the width of the strip at a distance of 100 mm from each other.
  • the electrodes are made e.g. of a conductive polymer, ECCOCOAT CC-2 available from Emerson & Cumming Speciality polymers, or of another material assuring good electrical contacts (e.g. Ag).
  • a constant potential is then applied over the electrodes and the current flowing through the circuit is measured e.g. on a Pico-amperemeter KEITHLEY 485.
  • the heating material hm has a surface resistivity (SR) between 5 and 3000 ⁇ / ⁇ .
  • the heating material hm has a specific resistivity pbetween 10 -5 ⁇ .cm and 1 ⁇ . cm or a specific conductivity ⁇ between 1 and 105 s/cm, or between 1 and 10 4 S/cm, or even between 1 and 10 3 S/cm.
  • Such specific conductivity a thus ranges from semi-metallic to near-metallic conductivity.
  • thermal heads according to the present invention may be connected to one another in a longitudinal direction (so-called butting or staggering) in order to achieve a larger thermal head.
  • a thermal head TH scans in X-direction (the so-called fast-scan direction) over the heating material m from one side of a printing line to the other side (so-called shuttling), in order to attain pagewide-heating.
  • line-type print heads having a one dimensional array have been referred to, the present invention can also make use of two dimensionally arranged print head arrays.
  • a thermal head TH can be realised by a so-called thick-film technique (such as lithography, screen-printing; with heating elements of e.g. 20 ⁇ m thickness) or by a so-called thin-film technique (such as vapour deposition or sputtering; with heating elements of e.g. 0,1 ⁇ m thickness).
  • thick-film technique such as lithography, screen-printing; with heating elements of e.g. 20 ⁇ m thickness
  • thin-film technique such as vapour deposition or sputtering; with heating elements of e.g. 0,1 ⁇ m thickness
  • thermography e.g. in thermography and in photothermography.
  • the head is applicable in various machines such as printers, plotters, facsimiles, copiers, output terminals such as CAD systems, etc.
  • thermographic material m suitable for application within the present invention comprises on a support a thermosensitive layer incorporating an organic silver salt and a reducing agent contained in said thermosensitive layer and/or in (an) other optional layer(s).
  • a cross-section of such a thermographic material m is disclosed in co-pending application entitled "IMPROVED METHOD FOR THERMAL RECORDING", filed on a same date and incorporated herein by reference. Further details about the composition of such a thermographic material m may be read in EP 0 692 733 (in the name of Agfa-Gevaert).
  • thermal print head can be used for uniform heating, e.g. in thermography.
  • a non-transparent thermal head can be used for uniform heating, e.g. in cases of so-called preheating or in cases of so-called postheating.
  • uniform heating by means of a thermal head TH may be used advantageously in an imaging or recording apparatus.
  • sheets fed through a recording apparatus may be subjected to a drying operation prior to imaging, in order to reduce the moisture content, e.g. below 60 %. Indeed, a lower moisture content may be favourable for jamfree transport of the sheet and/or for the quality of imaging.
  • Such paper conditioning or dehumidifying means can incorporate a thermal head according to the present invention.
  • uniform heating by means of a thermal head can be used in other applications, such as elecrophotography (e.g. for fixing a powder image), in drying wet-processed photographic materials (such as microfilms, medical prints, printing plates ...), in heating ink-jet images, etc.
  • FIG. 5 shows a recording method using a transparent thermal head according to the present invention combined with a laser.
  • Such method for recording an image on a thermal imaging element Ie comprises the steps of providing (e.g. by means of a rotatable drum 15) a thermographic material m (ref. 3) having a thermal imaging element Ie, a transparent thermal head TH (ref. 16) having energisable heating elements (Hi), and a radiation beam L (ref. 41), capturing input data (see input data block 22), processing (in processing unit 24) the digital image signals, activating heating elements of said thermal head and imagewise and scanwise exposing said imaging element by means of said radiation beam, wherein said imagewise and scanwise exposing is carried out by passing said radiation beam through transparent parts of said thermal head.
  • an important advantage of a transparent thermal head comprises the possibility of e.g. directing a density control through the thermal head, e.g. for controlling a density while it is formed on a the thermographic material. Because pixel formation is not obscured by the head 16, it can be easily monitored with a photocell detector.
  • FIG. 2 schematically shows the basic functions of a thermal printer which uses a reductor (donor) ribbon.
  • a thermal printer which uses a reductor (donor) ribbon.
  • Reduction ribbon printing uses a thermal print head 16, which can be a thick or a thin film thermal print head, to selectively heat specific portions of the donor element 2 in contact with a receiving element 1.
  • Supply roller 13 and take-up roller 14 are driven by variable speed motor 18 with a predetermined tension in the web or ribbon of the donor element 2.
  • a thermal head TH also may be used in a method for recording an image on a thermal imaging element (m) comprising the steps of providing a thermographic material having a thermal imaging element, and providing at least two thermal heads (TH 1 and TH 2 ) each having energisable heating elements (Hi), activating heating elements of the first thermal head such that a preheat temperature (T o ) in the imaging element is reached which is below the conversion temperature (Tc) of the imaging element, imagewise exposing the imaging element by means of the second thermal head having a level of energy corresponding to a gradation (optionally also standing for e.g. density, colour, etc.) of the image to be recorded on the imaging element, wherein at least one of the thermal heads is transparent.
  • the energy is supplied in two steps: first providing a uniform situation, and secondly a fine-adjusted tuning to the precise end-situation, wherein the second step is as small, and hence as accurate, as possible.
  • a preheating from ambient temperature up to 80°C (or 353 K) would be less favourable than a preheating from ambient temperature up to 110 °C (or 383 K).
  • Thermal imaging can be used for both the production of transparencies and reflection type prints.
  • hard copy field recording materials on white opaque base are used, whereas in the medical diagnostic field black imaged transparencies find wide application in inspection techniques operating with a light box.
  • the present invention clearly can also be applied in the case of coloured images, in the case of which the electrical image signals corresponding to different colour selections are sequentially subjected to typical corresponding transformation lookup tables such that the diagnostic visual perception of the coloured hardcopy reaches an optimum.
EP19990204069 1999-12-01 1999-12-01 Thermodruckkopf Expired - Lifetime EP1104700B1 (de)

Priority Applications (3)

Application Number Priority Date Filing Date Title
EP19990204069 EP1104700B1 (de) 1999-12-01 1999-12-01 Thermodruckkopf
DE1999627693 DE69927693T2 (de) 1999-12-01 1999-12-01 Thermodruckkopf
JP2000360936A JP2001162848A (ja) 1999-12-01 2000-11-28 サーマルヘッド

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
EP19990204069 EP1104700B1 (de) 1999-12-01 1999-12-01 Thermodruckkopf

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EP1104700A1 true EP1104700A1 (de) 2001-06-06
EP1104700B1 EP1104700B1 (de) 2005-10-12

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EP (1) EP1104700B1 (de)
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Cited By (3)

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Publication number Priority date Publication date Assignee Title
CN100441419C (zh) * 2004-06-24 2008-12-10 阿尔卑斯电气株式会社 热敏打印机
CN101767488B (zh) * 2008-12-27 2012-07-18 鸿富锦精密工业（深圳）有限公司 热打印头与热打印系统
CN107221835A (zh) * 2017-06-09 2017-09-29 昆山瑞顶萤智能光电科技有限公司 一种激光光源的高效散热装置

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Publication number Priority date Publication date Assignee Title
EP1453879B2 (de) * 2001-12-04 2011-09-21 Agfa-Gevaert Verfahren zur herstellung einer zusammensetzung enthaltend ein polymer oder copolymer von 3,4-dialkoxythiopen und ein nicht-wässriges lösungsmittel
CA2982419C (en) * 2015-04-13 2021-03-30 Jan Franck Device and method for manufacturing printed circuit boards for electrical and/or electronic circuits
JP2018176549A (ja) * 2017-04-13 2018-11-15 ローム株式会社 サーマルプリントヘッド、および、サーマルプリントヘッドの製造方法

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WO1998010333A1 (de) 1996-09-06 1998-03-12 Agfa-Gevaert Aktiengesellschaft Verfahren und vorrichtung zum aufzeichnen von informationen auf thermisch entwickelbarem fotografischem material
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Publication number Priority date Publication date Assignee Title
CN100441419C (zh) * 2004-06-24 2008-12-10 阿尔卑斯电气株式会社 热敏打印机
CN101767488B (zh) * 2008-12-27 2012-07-18 鸿富锦精密工业（深圳）有限公司 热打印头与热打印系统
CN107221835A (zh) * 2017-06-09 2017-09-29 昆山瑞顶萤智能光电科技有限公司 一种激光光源的高效散热装置

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EP1104700B1 (de) 2005-10-12
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DE69927693D1 (de) 2005-11-17

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