EP1104699A1 - Verbessertes Thermoaufzeichnungsverfahren - Google Patents

Verbessertes Thermoaufzeichnungsverfahren Download PDF

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Publication number
EP1104699A1
EP1104699A1 EP99204070A EP99204070A EP1104699A1 EP 1104699 A1 EP1104699 A1 EP 1104699A1 EP 99204070 A EP99204070 A EP 99204070A EP 99204070 A EP99204070 A EP 99204070A EP 1104699 A1 EP1104699 A1 EP 1104699A1
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EP
European Patent Office
Prior art keywords
imaging element
thermal
thermal head
imagewise
heating
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EP99204070A
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English (en)
French (fr)
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EP1104699B1 (de
Inventor
Hans c/o Agfa-Gevaert N.V. Strijckers
Karsten Dierksen
Robert c/o Agfa-Gevaert N.V. Overmeer
Patrick C/O Agfa-Gevaert N.V. Van Den Bergen
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Agfa Gevaert NV
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Agfa Gevaert NV
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Priority to EP99204070A priority Critical patent/EP1104699B1/de
Priority to DE69926131T priority patent/DE69926131D1/de
Priority to JP2000362609A priority patent/JP2001162845A/ja
Priority to US09/728,467 priority patent/US6475709B2/en
Publication of EP1104699A1 publication Critical patent/EP1104699A1/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
    • 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
    • B41J2/435—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed characterised by selective application of radiation to a printing material or impression-transfer material
    • B41J2/475—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed characterised by selective application of radiation to a printing material or impression-transfer material for heating selectively by radiation or ultrasonic waves
    • B41J2/4753—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed characterised by selective application of radiation to a printing material or impression-transfer material for heating selectively by radiation or ultrasonic waves using thermosensitive substrates, e.g. paper

Definitions

  • the present invention relates to a method and a device for thermal recording by means of a thermal head having energisable heating elements. Even, more in particular, the invention is related to thermal recording by means of such a thermal head and a radiation beam, even more preferably a transparent thermal head and a laserbeam.
  • 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 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.
  • the heating of the thermographic recording material may be originating from image signals which are converted to electric pulses and then through a driver circuit selectively transferred to a thermal print head.
  • the thermal print head consists of microscopic heat resistor elements, which convert the electrical energy into heat via the Joule effect.
  • the electric pulses thus converted into thermal signals manifest themselves as heat transferred to the surface of the thermographic material, e.g. paper, wherein the chemical reaction resulting in colour development takes place.
  • This principle is described in "Handbook of Imaging Materials” (edited by Arthur S. Diamond - Diamond Research Corporation - Ventura, California, printed by Marcel Dekker, Inc. 270 Madison Avenue, New York, ed. 1991, p. 498-499).
  • a particular interesting direct thermal imaging element uses an organic silver salt in combination with a reducing agent. An image can be obtained with such a material because under influence of heat the silver salt is developed to metallic silver.
  • thermographic imaging element 3 shows a cross-section of a composition of a thermographic material m suitable for application within the present invention.
  • the material of the thermographic imaging element 3 comprises a polyethylene terephthalate (PET) support 65 of about 60 to 180 ⁇ m (e.g. 175 ⁇ m), carrying a subbing layer or substrate 66 of about 0,1 to 1 um (e.g. 0.2 ⁇ m) thickness, an emulsion layer 67 of about 7 to 25 ⁇ m (e.g. 20 ⁇ m) thickness, and a protective layer 68 of about 2 to 6 ⁇ m (e.g.
  • PET polyethylene terephthalate
  • thermographic material m may be read in EP 0 692 733 (in the name of Agfa-Gevaert).
  • the thermographic material can also contain one or more light-to-heat converting agents, preferably in layer 66, 67 or 68. This light-to-heat converting agent is often an infrared absorbing component and maybe added to the thermographic material in any form, e.g. as a solid particle dispersion or a solution of an infrared absorbing dye.
  • thermographic recording material m comprises on a support a thermosensitive layer, 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.
  • 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) preferred embodiments of methods using a transparent thermal head combined with a laser beam, (iv) photothermographic applicability of the present invention, (v) laserthermographic applicability of the present invention (vi) further applicability of the present invention.
  • thermographic material being a thermographic recording material, hereinafter indicated by symbol m
  • thermosensitive imaging material 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.
  • thermal head according to the present invention and a working method will be explained in depth.
  • laserthermography is meant an art of direct thermography comprising a uniform preheating step not by any laser and an imagewise exposing step by means of a laser.
  • thermal printing head a heat-sensitive receiving material or a combination of a heat-sensitive donor material and a receiving (or acceptor) material, 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.
  • thermal printing methods and devices for thermal printing are known since many years, e.g. for direct thermal printing EP-0 622 217(in the name of Agfa-Gevaert N.V.), etc.
  • imagewise exposing of an imaging element is carried out by means of a thermal head having energisable heating elements.
  • a thermal head having energisable heating elements is optically transparent materials.
  • a transparent thermal head reference is made to the co-pending patent application entitled “THERMAL HEAD”, filed by the same patent assignee and on the same date; which is explicitly comprised within the instant application.
  • 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.
  • Fig. 9 is a diagram showing the optical transmission of ITO with respect to the wavelength of measurement, suitable for use according to the present invention.
  • Reference number 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%.
  • the heating material hm has a transparency higher than 80% at least at the wavelength of the laserbeam (e.g. at 830, 870, 1054 or 1064 nm).
  • Fig. 13 is an equipment 160 for measuring the optical transmission of a heating material hm (such as ITO) related to the wavelength of exposure.
  • a heating material hm such as ITO
  • a heating material 36 e.g. made from ITO
  • a thermographic imaging element 3 are kept in place by two transparent-but-isolating means (e.g. glass plates) 163-164.
  • a light source e.g. a halogen lamp
  • a power supply 168 brings a single square wave pulse 169 onto heating material 36, thus generating heat, in consequence of which the thermographic imaging element 3 develops an optical density to be measured.
  • the amplitude of the pulse is chosen such as to generate an amount of heat sufficient to trigger the thermographic process and is related to the conductivity of the transparent heating material.
  • the measuring equipment 160 comprises a spectrophotometer 166 having a certain wave-range (e.g. between 200 and 2500 nm) and registering a sufficient number of spectra in a given time-span (e.g. 18 spectra in 36 msec).
  • a computer 167 is convenient for programming the experimental parameters and for carrying out the relevant calculations.
  • the single square wave pulse 169 has a constant amplitude (of e.g. 46 Volt) but an increasing pulse width (of e.g. 6 ms, 8 ms, 10 ms ).
  • the single square wave pulse 169 has an increasing amplitude (of e.g.
  • thermographic imaging element 3 increases as the power (e.g. between 5 and 10 W/mm 2 ) of the square wave pulse 169 increases.
  • the same can be verified for different thicknesses of the heating material 36, e.g. between 0,1 and 30 ⁇ m, or between 0,2 um and 5 um.
  • Fig. 10 is a diagram showing the optical transmission (see ref. nr. 85) of a laserthermographic material (indicated as "Med. 1"), suitable for use according to the present invention.
  • Fig. 11 is a diagram showing the optical transmittance (see ref. nr. 86), the absorption (see ref. nr. 87) and the reflection (see ref. nr. 88) curves with respect to the wavelength of measurement of another laserthermographic material (indicated as "Med. 2"), suitable for use according to the present invention.
  • a laser with a wavelength between 830 and 870 nm can be applied advantageously. Indeed, such laserbeam is efficiently transmitted through a heating material hm (e.g. ITO illustrated in Fig. 9) and is efficiently absorbed by a thermographic material (e.g. Med. 1 illustrated in Fig. 10).
  • a heating material hm e.g. ITO illustrated in Fig. 9
  • thermographic material e.g. Med. 1 illustrated in Fig. 10
  • a laser with a wavelength of e.g. 1054 or 1064 nm can be applied advantageously. Indeed, such laserbeam is efficiently transmitted through a heating material hm (e.g. ITO illustrated in Fig. 9) and is efficiently absorbed by a thermographic material (e.g. Med. 2 illustrated in Fig. 11). ,
  • a heating material hm e.g. ITO illustrated in Fig. 9
  • thermographic material e.g. Med. 2 illustrated in Fig. 11
  • a laser emitting in the infrared and/or near-infrared i.e. emitting in the wavelength range 700-1500 nm.
  • Suitable lasers include a Nd-YAG-laser (neodymium-yttrium-aluminium-garnet; 1064 nm) or a Nd-YLF laser (neodymium-yttrium-lanthanum-fluoride; 1053 nm).
  • Typical suitable semiconductor laser diodes emit e.g. at 830 nm or at 860-870 nm.
  • the required laser power depends on the pixel dwell time of the laser beam, which is dependent on the scan speed (e.g. between 0.1 and 20 m/s, preferably between 0.5 and 5 m/s) and the spot diameter of the laser beam (defined at 1/e 2 of maximum intensity e.g. between 1 and 100 ⁇ m, preferably between 10 and 25 ⁇ m).
  • the heating material hm may be selected from a group consisting of In 2 O 3 , optionally doped; SnO/O 2 , optionally doped; ZnO, optionally doped; Cd 2 SnO 4, or CdSnO 3 ; Bi 2 O 3 ; MoO 3 ; TiO 2 ; WO 2 ; RhO 2 ; ReO 2 ; Na X WO 3 ; Zn 2 SnO 4 and V205.
  • Another example comprises a commercial conductive and transparent polymer known as (registered tradename of Agfa-Gevaert), e.g. type ORGACON-EL.
  • thermography for recording an image of varied density utilise some type of sensor to detect a variable parameter (e.g. actual density or dot size) of the print.
  • a variable parameter e.g. actual density or dot size
  • An electronic closed-loop system makes the necessary adjustments in the printing process.
  • Fig. 3 shows a preferred embodiment of a method according to the present invention, using a transparent thermal head 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. nr. 3) having a thermal imaging element Ie, a transparent thermal head TH (ref. nr. 16) having energisable heating elements (Hi, ref. nr. 39), and a radiation beam L (ref. nr. 41), capturing input data (see input data block 22), processing (in processing unit 24) the digital image signals, activating heating elements of the thermal head and imagewise and scanwise exposing the imaging element by means of the radiation beam, wherein the imagewise and scanwise exposing is carried out by passing the radiation beam through transparent parts of the thermal head.
  • thermographic material m comprises the steps of
  • thermographic material m comprises the steps of
  • the heating means comprises a thermal head.
  • thermographic material m comprises the steps of
  • the method comprises before the imagewise and scanwise exposing, an additional step of activating heating elements such that a preheat temperature To in the imaging element is reached which is below the conversion temperature Tc (ref. nr. 55) of the imaging element (see ref. nr. 136).
  • the heating step and the exposing step are carried out at least partly simultaneously.
  • the activating of heating elements (ref. nr. 39) of a thermal head is carried out imagewise.
  • the imagewise and scanwise exposing by means of a radiation beam is modified in that the imagewise and scanwise exposing is carried out by means of a laserdiodearray (see ref. nr. 137).
  • thermographic material is on one and the same holding or guiding means (e.g. drum 15) during both the imagewise exposing step and the heating step.
  • the method according to the present invention may also comprise an additional step of controlling the activating heating elements of a transparent thermal head by monitoring the gradation (or density, or colour) while developing the thermal imaging element by passing a monitoring beam through the transparent thermal head (see ref. nr. 138).
  • Fig. 12 gives a survey flow-chart of several method-steps according to the present invention. As, after having disclosed a lot of preferred embodiments according to the present invention, a separate disclosure in full depth of Fig. 12 seems to be redundant. Yet, some remarks may be relevant: (i) dash lines indicate that no explicit duration of time is stated, (2) arrowed dash lines indicate that no restrictive order of sequence is stated, (3) preheating may be applied in many embodiments, (4) a monitoring of the image (say gradation, or density or colour) also may be applied in many embodiments, (5) in some embodiments more than one thermal head (e.g. TH1, TH2) may be applied, (6) in some embodiments a laserdiodearray LDA may be applied.
  • dash lines indicate that no explicit duration of time is stated
  • arrowed dash lines indicate that no restrictive order of sequence is stated
  • preheating may be applied in many embodiments
  • (4) a monitoring of the image also may be applied in many embodiments
  • Fig. 6 shows several preferred hardware-embodiments of a method according to the present invention.
  • transparent thermal heads are indicated 6 by a single capital H; whereas non-transparent thermal heads are indicated in Fig. 6 by a single capital H with an "upperscore”.
  • indicated are a non-transparent thermal head H (at the left side) known from prior art and a transparent head H (at the right side) according to the above-mentioned co-pending application.
  • Fig. it is illustrated that the use of a transparent head offers more options for designing the thermal recording unit (w.r.t. the later Fig. 7, also referred to as imaging and processing unit 125) than a nontransparent head.
  • the illustrations are made in a schematical form , wherein symbol m indicates a thermal imaging material and wherein symbol Y (see also Figs. 1, 3, 7 and 8) indicates the slowscan direction.
  • symbol m indicates a thermal imaging material
  • symbol Y indicates the slowscan direction.
  • At the left side several embodiments are grouped which comprise at least two devices comprising at least one nontransparent thermal head; these devices may be situated at a same side of the thermographic material m, or on opposite sides of m.
  • thermographic material m At the right side several embodiments are grouped which comprise at least two devices, more in particular comprising at least one transparent thermal head; these devices may be situated at a same side of the thermographic material m, or on opposite sides of m, or even integrated within one single compact device.
  • Reference number 71 illustrates schematically a thermal comprising two non-transparent thermal heads ( H 1 and H 2 ) situated at a same side of m and operating in sequential order (along direction Y).
  • H 1 may uniform preheat the thermographic material m
  • H 2 imagewise heats the thermographic material m.
  • Ref. nr. 72 illustrates schematically a thermal recording unit comprising a non-transparent thermal head ( H 1 ) and a laser (L1) situated at a same side of m and operating in sequential order (along direction Y).
  • H 1 may uniform preheat the thermographic material m
  • L1 imagewise exposes the thermographic material m.
  • Ref. nr. 73 relates to a thermal recording unit comprising a laser (L1) and a non-transparent thermal head ( H 1 ) and situated at a same side of m and operating in sequential order (along direction Y).
  • L1 may uniform preheat the thermographic material m
  • H 1 imagewise activates the thermographic material m.
  • Ref. nr. 74 relates to a thermal recording unit comprising at least two non-transparent thermal heads ( H 1 , H 2 ) and situated at opposite sides of m and operating in sequential or in non-sequential order (along direction Y).
  • H 1 may uniform preheat the thermographic material m
  • Ref. nr. 75 relates to a thermal recording unit comprising at least one non-transparent thermal head ( H 1 ) and at least one laser (L1) situated at opposite sides of m and operating in sequential or in non-sequential order (along direction Y).
  • H 1 non-transparent thermal head
  • L1 laser
  • H 1 may uniform preheat the thermographic material m
  • L1 imagewise exposes the thermographic material m.
  • Ref. nr. 91 illustrates schematically a thermal recording unit comprising two transparent thermal heads ( H 1 and H 2 ) situated at a same side of m and operating in sequential order (along direction Y).
  • H 1 may uniform preheat the thermographic material m
  • H2 imagewise heats the thermographic material m.
  • Ref. nr. 96 illustrates schematically a thermal recording unit comprising two thermal heads ( H 1 and H2), in particularly one non-transparent head ( H 1 ) and one transparent head (H2), situated at a same side of m and operating in sequential order (along direction Y).
  • H 1 may uniform preheat the thermographic material m
  • Ref. nr. 92 illustrates schematically a thermal recording unit comprising a transparent thermal head ( H 1 ) and a laser (L1), both situated at a same side of m and operating in sequential order (along direction Y).
  • H1 may uniform preheat the thermographic material m
  • Ref. nr. 93 illustrates an analogue system, but with inverted positions of L1 and H1, and corresponding functions; e.g. L1 imagewise exposes the thermographic material m and H 1 heats (uniform or imagewise) the thermographic material m as in case of photothermography.
  • Ref. nr. 97 illustrates schematically a thermal recording unit comprising a transparent thermal head ( H 1 ) and a laser (L1), both situated at a same side of m and at a same locality along direction Y.
  • H1 may uniform preheat the thermographic material m
  • Ref. nr. 94 is somewhat similar to ref. nr. 74, but comprises at least two transparent thermal heads (H1, H2) and corresponding functions.
  • Ref. nr. 95 is somewhat similar to ref. nr. 75, but comprises at least one transparent thermal head (H1) and corresponding functions.
  • Ref. nr. 98 is somewhat similar to ref. nr. 92, but now both devices (H1, L1) are at the same side and at a same position along Y.
  • Ref. nr. 99 is somewhat similar to ref. nrs. 97 and 98, but now both devices (H1, L1) are at the same side and at a same position along Y and integrated within one single and compact device, e.g. a transparent thermal head as disclosed in the above-mentioned co-pending patent application.
  • a second important advantage of a transparent thermal head comprises the possibility of e.g. directing a recording radiation beam through the thermal head.
  • a combination of a transparent thermal head and a radiation beam, the combination being suitable for thermally operated printing devices is e.g. illustrated in Fig. 8 (to be explained in a later paragraph).
  • laser recording can be applied (i) from the same side and (ii) at the same location relative to the thermographic material as the heating with the thermal head.
  • thermographic material as the heating with the thermal head
  • a first heating e.g. by a heated drum 15, or platen, or roll
  • a second heating e.g. by means of heating elements Hi
  • This prior art comprises a disadvantage in heating the imaging element 3 from the backside.
  • support layer 65 being formed of a plastic (such as PET), is not a particularly good thermal conductor. Therefore it takes slightly longer for the temperature in the emulsion layer 67 to build up to the threshold value than if the thermal energy is applied directly to the emulsion layer 67. This, of course, slows down the recording process.
  • thermographic material m An embodiment which uses a thermal head, being non-transparent or being transparent, and a radiation beam at a same side of thermographic material m, resolves the just mentioned problem. But, in case of a non-transparent thermal head, some distance is needed between the thermal head and the radiation beam (because of constructional dimensions), which introduces another disadvantage.
  • thermographic material m After having received a first energy of the heating elements, the temperature on thermographic material m will decrease before entering the impact region of the laser beam.
  • thermographic material m If a transparent thermal head and a laser beam are combined at the same side and at the same place of the thermographic material m, both mentioned disadvantages are solved.
  • a laser diode emits light which is converted to heat upon impact with emulsion layer 67, it does not have to make contact with emulsion layer 67 as does a resistive heating element 39. Therefore, the laser 118 and the thermal head 16 may be located on the same side and on the same location (see also ref. 99 in Fig. 6). This is possible because thermal print head TH does not block nor obscure the field of view of the laser beam L. Thus, in this configuration of a thermal recording system, there is no need to apply heat to emulsion layer 67 from the backside through support 65.
  • the present invention it is also possible by the present invention to attain a greater sharpness, because there is only a very small distance between the heat source and the heat sensitive thermographic material. (The laser does not have to travel through support 65(see Fig. 2) and hence no unsharpness is created by light diffraction caused by differences in the refractive index of the different layers of the thermal imaging material located between the thermosensitive layer and the light source.
  • the fog can be lowered, thus upgrading the quality of discriminance in information (cf. ratio of Dmax to Dmin).
  • Another advantage of this invention is that the dimensional stability is improved due to the very local and short heating by the combination transparent thermal head.
  • the use of a thermal head for an increased dimensional stability is described in the patent EP 0 933 672 of Konica. In the cited patent it is explained that a good size repetition accuracy is necessary in graphic arts imaging materials used for colour printing. However another requirement for high quality colour printing is a resolution of at least 1200 dpi, more preferably 2400 dpi.
  • a high resolution image can be obtained by applying a laserbeam through the thermal head, wherein the laserspot is smaller in dimensions than a heating element of the thermal head.
  • the laser and thermal head can be installed into the thermal recording unit as a single compact device. This allows the thermal recording unit itself to be a compact device rendering high resolution images.
  • Fig. 4.1 to 4.3 respectively show the activation (see VHi) of a heating element Hi (ref. nr. 39), the activation (see VLi)of a radiation beam L and the resulting temperature (see Tm) in the thermographic material m.
  • VHi a predefined voltage
  • VHi commonly between 12 and 18 V, e.g. 15 V
  • This pulse is indicated by ref. nr. 51 and has an amplitude symbolised by logical level 0 for the off-state and logical level 1 for the on-state.
  • thermographic material m first increases along a first heating curve 53 from time tO to tl, then increases along a second heating curve 54, optionally to a stable level corresponding with a desired density level, and thereafter e.g. decreases along a third heating (or cooling) curve 56.
  • Tc (ref. nr. 55) indicates the threshold temperature of the thermographic material m.
  • Fig. 5.1 shows the evolution of the density (see Dm) on the thermographic material m related to the scanning time.
  • a density evolution along curve 57 starts from an initial density D1 (generally being as low as possible, but restricted by the optical density of the untreated thermal imaging material if no decolourizing components or layers are present in the thermal imaging material, and also influenced by a possible fog Df).
  • D1 initial density
  • Tc conversion temperature
  • Fig. 5.2 shows the resultant density on the thermographic material m after completion of the scanning time and is related to the scanning distance.
  • the endresult renders a pixel 58 at a desired level of density D2.
  • thermographically imaging elements for producing images by means of imagewise exposing followed by uniform heating are generally known.
  • a typical composition of such thermographically imaging elements includes photosensitive silver halide in combination with an oxidation-reduction combination of, for example, an organic silver salt and a reducing agent therefor.
  • thermographic systems An overview of thermographic systems is given in the book “Imaging Systems” by Kurt I. Jacobson and Ralph E. Jacobson, The Focal Press, London and New York, 1976, in chapter V under the title “Systems based on unconventional processing” and in chapter VII, entitled “thermographic systems", in particular "7.1 Thermography” and "7.2 Photothermography”.
  • Photothermographic imaging elements are typically processed by imagewise exposure, for example in contact with an original or after electronic image processing with the aid of a laser, as a result of which a latent image is formed on the silver halide.
  • the latent image formed exerts a catalytic effect on the oxidation-reduction reaction between the reducing agent and the non-photosensitive organic silver salt, usually silver behenate, as a result of which a visible density is formed at the exposed locations.
  • the processing conditions are defined by the choice of the non-photosensitive organic silver salt and a reducing agent therefor.
  • the processing temperature is around 120°C (or 393 K), for five seconds. Further information on the thermographic materials and on such imagewise exposures can be found, for example, in Patent Application EP A 96.201.530.1. of Agfa-Gevaert.
  • the imagewise exposing is carried out by means of a radiation beam, while the uniform heating afterwards is carried out by means of a thermal head.
  • thermographic imaging element 16 is a thermal print head
  • 41 is a laser beam
  • 102 a supply magazine
  • 104 a belt
  • 105 a tension roller
  • 107 a sheet of thermographic material
  • 108 a roller 109 a roller
  • 110 a controller
  • 113 a ventilator
  • 116 imaged and processed sheets
  • 117 a keyboard 118 a laser source ,119 a modulator
  • 120 a first objective
  • 121 a polygon mirror 122 a second objective
  • 123 blank sheets to be imaged 124 a sheet feeder, 125 an imaging and processing unit, 126 a pressure roller.
  • Fig. 8 shows a preferred embodiment of a laserthermographic apparatus with an array of laser diodes and a thermal head according to the present invention.
  • Additional reference numbers 40 represent a laserdiodearray, 101 an impact line of the exposure through a transparent thermal head 16, and 18 a motor for rotating the drum 15.
  • Thermal imaging can be used for production of both transparencies and reflection-type prints.
  • thermographic recording materials based on an opaque, usually white, base are used, whereas in the medical diagnostic field monochrome, usually black, images on a transparent base find wide application, since such prints can conveniently be viewed by means of a light box.
  • thermo recording unit comprising a transparent thermal head and laser located in one point (the embodiments 98 and 99 of Fig. 6).
  • the preferred situation of having the nontransparent head on the same side of the thermosensitive layer is only possible if the opaque base has a high transparency at the wavelength of the laser light source.
  • the nontransparent thermal head has to be located at the backside of the thermal imaging material (i.e. opposite side of the thermosensitive layer) a slow down of the recording process occurs as described above.
  • Direct thermal printing may be directed towards a method of representing an image of the human body obtained during medical imaging and most particularly to a printer intended for printing medical image picture data received from a medical imaging device.
  • the image data may be medical image picture data received from a medical image camera.
  • the image data may be graphical image picture data received from a computerised publishing system.
  • image data may be in the form of screens representing graphical images for use in printing art. These screens can be obtained by computer Desk-Top Publishing systems, such as e.g. Ventura Publisher TM . These systems combine both text and pictures, retrieved from e.g. manual input in word processors, OCR, picture scanners and software used for image manipulation (e.g. Adobe Photoshop TM ). Such systems output alphanumeric data in different file formats, that can be defined by the user, such as e.g. Postscript TM . These output files can be transformed to a format that can be "understood" by the thermal printer. If necessary, additional data can be attached to the file to control the settings of the printer.
  • Computer Desk-Top Publishing systems such as e.g. Ventura Publisher TM .
  • These systems combine both text and pictures, retrieved from e.g. manual input in word processors, OCR, picture scanners and software used for image manipulation (e.g. Adobe Photoshop TM ).
  • Such systems output alphanumeric data in different file formats
  • direct thermal printing mainly comprises so-called monosheet imaging elements (indicated by ref. nr. 3 in Fig. 1).
  • direct thermal printing also comprises a so-called “donor ribbon or donor element” -which may be “a protective ribbon” or which may be “a reduction ribbon”- and a so-called “receiving element”. More information hereabout can be found in the above-mentioned co-pending application entitled "THERMAL HEAD”.
  • Direct thermal monosheet imaging elements are described in e.g. EPA-94.201.717.9 and EPA-94.201.954.8 (both in the name of Agfa-Gevaert) and in WO 94/16361 (in the name of Labelon Corp. USA).
  • Direct thermal printing with a so called protective ribbon is described e.g. in EPA-92.204.008.4 (in the name of Agfa-Gevaert).
  • Direct thermal printing with a so called reduction ribbon is described e.g. in EPA-92.200.612.3 (in the name of Agfa-Gevaert).
  • thermographic material (m) Apparatus for recording an image on a thermographic material (m) incorporating anyone of the preceding methods is also included within the present invention.
EP99204070A 1999-12-01 1999-12-01 Thermoaufzeichnungsverfahren-und-Vorrichtung Expired - Lifetime EP1104699B1 (de)

Priority Applications (4)

Application Number Priority Date Filing Date Title
EP99204070A EP1104699B1 (de) 1999-12-01 1999-12-01 Thermoaufzeichnungsverfahren-und-Vorrichtung
DE69926131T DE69926131D1 (de) 1999-12-01 1999-12-01 Thermoaufzeichnungsverfahren-und-Vorrichtung
JP2000362609A JP2001162845A (ja) 1999-12-01 2000-11-29 改良型感熱式記録法
US09/728,467 US6475709B2 (en) 1999-12-01 2000-11-30 Method for thermal recording

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EP99204070A EP1104699B1 (de) 1999-12-01 1999-12-01 Thermoaufzeichnungsverfahren-und-Vorrichtung

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Cited By (5)

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Publication number Priority date Publication date Assignee Title
US6475709B2 (en) 1999-12-01 2002-11-05 Agfa-Gevaert Method for thermal recording
EP1300251A1 (de) 2001-10-02 2003-04-09 Agfa-Gevaert Thermische Aufzeichnung mittels Lichtpunktabtastung
US6798439B2 (en) 2001-10-02 2004-09-28 Agfa-Gevaert Thermal recording by means of a flying spot
DE102008007228B4 (de) * 2008-02-01 2012-02-02 OCé PRINTING SYSTEMS GMBH Verfahren und Vorrichtung zum Erzeugen mindestens eines Druckbildes auf einem Bildträger
EP2945019A1 (de) * 2008-01-24 2015-11-18 Quad/Graphics, Inc. Drucken mit farbveränderlichem material

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP7363444B2 (ja) 2019-12-16 2023-10-18 株式会社リコー 画像形成装置

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US3457075A (en) 1964-04-27 1969-07-22 Minnesota Mining & Mfg Sensitized sheet containing an organic silver salt,a reducing agent and a catalytic proportion of silver halide
JPS60208787A (ja) * 1984-04-03 1985-10-21 沖電気工業株式会社 面サ−マルデイスプレイ
US4763136A (en) * 1986-04-08 1988-08-09 Oki Electric Industry Co., Ltd. Planar thermal head and display device incorporating the same
JPS63274562A (ja) * 1987-05-07 1988-11-11 Fujitsu Ltd 多色サ−マルプリンタ
JPH0281644A (ja) * 1988-09-20 1990-03-22 Nec Corp 熱転写プリンタ
WO1994016361A1 (en) 1993-01-15 1994-07-21 Labelon Corporation Thermal imaging material and preparation
JPH07314744A (ja) * 1994-05-30 1995-12-05 Fuji Xerox Co Ltd 熱印字記録装置
EP0792750A2 (de) * 1996-02-29 1997-09-03 Mitsubishi Denki Kabushiki Kaisha Vorrichtung und Verfahren zur Aufzeichnung

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JPH0281644A (ja) * 1988-09-20 1990-03-22 Nec Corp 熱転写プリンタ
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JPH07314744A (ja) * 1994-05-30 1995-12-05 Fuji Xerox Co Ltd 熱印字記録装置
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Cited By (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US6475709B2 (en) 1999-12-01 2002-11-05 Agfa-Gevaert Method for thermal recording
EP1300251A1 (de) 2001-10-02 2003-04-09 Agfa-Gevaert Thermische Aufzeichnung mittels Lichtpunktabtastung
US6798439B2 (en) 2001-10-02 2004-09-28 Agfa-Gevaert Thermal recording by means of a flying spot
EP2945019A1 (de) * 2008-01-24 2015-11-18 Quad/Graphics, Inc. Drucken mit farbveränderlichem material
US9460373B2 (en) 2008-01-24 2016-10-04 Quad/Graphics, Inc. Printing using color changeable material
US10286682B2 (en) 2008-01-24 2019-05-14 Quad/Graphics, Inc. Printing using color changeable material
US11833840B2 (en) 2008-01-24 2023-12-05 Quad/Graphics, Inc. Printing using color changeable material
DE102008007228B4 (de) * 2008-02-01 2012-02-02 OCé PRINTING SYSTEMS GMBH Verfahren und Vorrichtung zum Erzeugen mindestens eines Druckbildes auf einem Bildträger

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EP1104699B1 (de) 2005-07-13
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