EP1300251B1 - Enregistrement thermique au moyen d'un spot mobile - Google Patents

Enregistrement thermique au moyen d'un spot mobile Download PDF

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Publication number
EP1300251B1
EP1300251B1 EP20020102332 EP02102332A EP1300251B1 EP 1300251 B1 EP1300251 B1 EP 1300251B1 EP 20020102332 EP20020102332 EP 20020102332 EP 02102332 A EP02102332 A EP 02102332A EP 1300251 B1 EP1300251 B1 EP 1300251B1
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Prior art keywords
thermographic material
substantially light
temperature
light
insensitive
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German (de)
English (en)
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EP1300251A1 (fr
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Rudi c/o AGFA-GEVAERT Vanhooydonck
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Agfa Gevaert NV
Agfa Gevaert AG
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Agfa Gevaert NV
Agfa Gevaert AG
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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
    • B41J2/435—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
    • G—PHYSICS
    • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
    • G03C—PHOTOSENSITIVE MATERIALS FOR PHOTOGRAPHIC PURPOSES; PHOTOGRAPHIC PROCESSES, e.g. CINE, X-RAY, COLOUR, STEREO-PHOTOGRAPHIC PROCESSES; AUXILIARY PROCESSES IN PHOTOGRAPHY
    • G03C1/00—Photosensitive materials
    • G03C1/494—Silver salt compositions other than silver halide emulsions; Photothermographic systems ; Thermographic systems using noble metal compounds
    • G03C1/498—Photothermographic systems, e.g. dry silver
    • G03C1/4989—Photothermographic systems, e.g. dry silver characterised by a thermal imaging step, with or without exposure to light, e.g. with a thermal head, using a laser
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
    • B41M—PRINTING, DUPLICATING, MARKING, OR COPYING PROCESSES; COLOUR PRINTING
    • B41M5/00—Duplicating or marking methods; Sheet materials for use therein
    • B41M5/26—Thermography ; Marking by high energetic means, e.g. laser otherwise than by burning, and characterised by the material used

Definitions

  • the present invention relates to a method and an apparatus for thermal recording.
  • Thermal imaging or thermography is a recording process wherein images are generated by the use of imagewise modulated thermal energy.
  • 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.
  • a particular interesting direct thermal imaging element uses an organic silver salt in combination with a reducing agent. Such combination may be imaged by a suitable heat source such as e.g. a thermal head, a laser etc.
  • a black and white image can be obtained with such a material because under the influence of heat the silver ions are developed to metallic silver.
  • thermographic material by means of so-called “flying spot scanning” is well-known from the prior art.
  • the thermal recording can be carried out with the aid of different types of recording devices, e.g. a flat bed type recording (see Fig. 1), a capstan type recording device (see Fig. 2), an internal drum type ITD recording device (see Fig. 3) or an external drum type XTD recording device (see Figs. 4, 5 and 6).
  • a flat bed type recording see Fig. 1
  • a capstan type recording device see Fig. 2
  • an internal drum type ITD recording device see Fig. 3
  • an external drum type XTD recording device see Figs. 4, 5 and 6
  • An extensive description of such recording devices can be found e.g. in EP 0 734 148 and in US 5,932,394 (both in the name of Agfa-Gevaert), so that in the present description any explicit and extensive replication is superfluous.
  • US 5,278,578 shows a method for avoiding banding in thermal transfer drum recording using an array of thermal lasers.
  • EP-A 0 485 148 discloses an image recording apparatus for recording an image by application of light beam to a photosensitive member, comprising: a photosensitive member; light source means for emitting first and second beams, one of the first and second beams bearing image information; and scanning means for scanning said photosensitive member with the first and second beams with a time interval so that they are overlapped on said photosensitive material.
  • EP-A 0 842 782 discloses a method of thermally recording a gradation image on a thermosensitive recording material (S) having a photothermal converting agent for converting light energy into thermal energy to develop a color at a density depending on the thermal energy, comprising the steps of: applying a laser beam (L) having a level of light energy depending on a gradation of an image to be recorded on the thermosensitive recording medium (S); and scanning the thermosensitive recording medium (S) with the laser beam (L) at a speed of at least 5 m/s.
  • EP-A 1 104 699 discloses a method for recording an image on a thermographic material (m) comprising the steps of: providing a thermographic material having a thermal imaging element (le), a transparent thermal head (TH) having energisable heating elements (Hi), and a radiation beam (L), activating heating elements of said thermal head and imagewise and scanwise exposing said imaging element by means of said radiation beam, such that the total energy resulting from said thermal head and from said radiation beam has a level corresponding to a gradation of the image to be recorded on said imaging element, wherein said imagewise and scanwise exposing is carried out by passing said radiation beam through transparent parts of said thermal head
  • US 5,990,917 discloses a mechanical scanning laser system having preheating for recording on a thermal recording medium
  • thermosensitive imaging element includes an image forming layer on a hydrophilic surface of a lithographic base, said image
  • Thermal recording according to the prior art by means of a flying spot laser on a thermographic material generally only gives a sufficient density if the energy radiated by the laser beam is so high that unwanted side-effects occur (e.g. burning, shrinkage and irregular expansion). If one diminishes the energy in order to eliminate such side effects, the output density is unacceptably low.
  • the present invention provides a method of recording information according to claim 1, and an apparatus for thermal recording an image according to claim 10.
  • Embodiments of the present invention are also realized by the use of the above-mentioned method in laser thermography.
  • laser thermography 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 (see e.g. EP-A 1 104 699).
  • thermography for the purposes of the present application is concerned with materials which are not directly photosensitive, but are sensitive to heat or thermosensitive and wherein a visible change in a thermosensitive imaging material is brought about by the application of sufficient imagewise applied heat to bring about a change in optical density.
  • This image-wise applied heat can be applied by a heat source in the direct vicinity of the thermosensitive material or it can be realized in the thermosensitive material as a result of the absorption of image-wise applied light by the presence in the thermosensitive material of at least one light-to-heat conversion agent.
  • thermosensitive material (or more completely worded as a 'thermographic recording material', hereinafter indicated by symbol m) comprises a thermosensitive element or direct thermal imaging element being substantially light-insensitive, and a support.
  • light-insensitive means that light is not directly involved in the image-forming process, but does not exclude light being indirectly involved such as in the case of light absorption by at least one light-to-heat conversion agent.
  • substantially light-insensitive means not intentionally light sensitive.
  • main-scan-speed v x or "processing speed” are used interchangeably, as well as the terms “slow-scan speed v y " or "transportation speed”.
  • processing direction X and the transportation direction Y are indicated in many drawings (see Figs. 1, 3, 4, 5 and 8.1).
  • the "sweep-time" t s (in s) of a flying spot laser system is the time between the beginning of the scanning of one line 40 of pixels (BOL j ) and the beginning of the scanning of the same line of pixels (BOL j+1 ).
  • Fig. 8.1 showing three consecutive scanning lines on a thermographic material passing through an internal (stationary) drum ITD, or mounted on e.g. an external (rotating) drum XTD.
  • n f the number of faces and n p the number of revolutions of the polygon mirror (per second)
  • t s 1 n f ⁇ n p expressed in s
  • the "total line-time t l " of a flying spot laser system is the time between the beginning of the printing of one line of pixels and the beginning of the printing of the next line of pixels in the printer transport direction Y (often called “slow-scan or sub-scan direction”; and clearly differentiated from a so-called “fast-scan or main-scan direction X").
  • n p (rpm) t s (ms) n s corresponding to a t 1 of 225 ms t 1 of 630 ms t 1 of 1260 ms 30.00 7.5 21 42 250 15.00 15.0 42 84 500 10.00 22.5 63 126 750 7.50 30.0 84 168 1000 6.00 37.5 105 210 1250 5.00 45.0 126 252 1500 4.29 52.5 147 294 1750 3.75 60.0 168 336 2000 3.33 67.5 189 378 2250 3.00 75.0 210 420
  • the term "line-width b l " may be self-speaking and is shown (having ref. nr. 44) in Fig. 8.2.
  • the "spatial resolution” means the precision (or separation) with which a picture is reproduced, measured in number of lines that can be distinguished in a picture e.g. expressed in lines/mm, or in dots per inch (dpi).
  • the highest resolution which can be attained by a thermographic system is here symbolised by dpi upp .
  • pixel-writing time t p (expressed in s) means the time needed for writing one pixel.
  • spatial resolution (expressed in dots per inch DPI)
  • efficiency ⁇ of radiation beam is defined in relation to a geometrical spread of the available intensity (or power) of the radiation beam (e.g. a Gaussian laser beam as shown in Fig.
  • An "original” is any hard-copy or soft-copy 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. Furthermore, according to the present invention, the terms pixel and dot may relate to an input image (known as original) as well as to an output image (in soft-copy or in hard-copy, e.g. known as print).
  • a "pixel output D o " or shortly an “output D o " comprises a quantification of a pixel printed on a thermographic material, the quantification possibly relating to characteristics as density (symbolised by D), size, etc.
  • the substantially light-insensitive thermographic material m having a burning temperature T b used in the present invention, comprises a thermosensitive element having a conversion temperature T c , a support and at least one light-to-heat conversion agent.
  • the substantially light-insensitive thermographic material m may be opaque or transparent.
  • the thickness of the thermosensitive element is generally in the range of about 7 to 25 ⁇ m (e.g. 20 ⁇ m) and the thickness of the support is generally in the range of about 60 to 180 ⁇ m (e.g. 175 ⁇ m).
  • Suitable support materials include poly(ethylene terephthalate).
  • the substantially light-insensitive thermographic material m may further comprise a subbing or substrate layer 66 with a typical thickness of about 0,1 to 1 ⁇ m (e.g. 0.2 ⁇ m) and/or a protective layer 68 with a typical thickness of about 2 to 6 ⁇ m (e.g. 4 ⁇ m) on the same side of the support as the thermosensitive element (for numbering see Fig. 17).
  • a backing layer 69 may be provided containing an antistatic and/or a matting agent (or roughening agent, or spacing agent, terms that often are used as synonyms) to prevent sticking and/or to aid transport of the substantially light-insensitive thermographic material m. Further details about the configuration of such substantially light-insensitive thermographic material m are disclosed in EP 0 692 733.
  • the light-to-heat conversion agents are preferably transparent to visible light and are to be found in the thermosensitive element and/or in an adjacent layer thereto as a solid particle dispersion, a solution or part as solid particles and part as a solution therein.
  • Suitable light-to-heat conversion agents include infrared absorbing dye and absorbers.
  • the light-to-heat conversion agents are preferably homogeneously distributed together or separately in the thermosensitive element, a constituent layer of the thermosensitive element and/or an adjacent layer to the thermosensitive element.
  • the thermosensitive element contains the ingredients necessary for bringing about the image-forming reaction.
  • the element may comprise a layer system in which the ingredients necessary for bringing about the image-forming reaction may be dispersed in different layers, with the proviso that the ingredients active in the image-forming reaction are in reactive association with one another i.e. during the thermal development process one type of active ingredient must be present in such a way that it can diffuse to the other types of active ingredients so that the image-forming reaction can occur.
  • thermosensitive material with different image-forming reactions can be used in the present invention.
  • a preferred thermographic material for use in the present invention is the so-called "laser induced dye transfer LIDT", which is described in US 5,804,355.
  • a preferred image-forming reaction is the reaction of one or more substantially light-insensitive organic silver salts with one or more reducing agents, the reducing agents being present in such a way that they are able to diffuse to the particles of substantially light-insensitive organic silver salt so that reduction to silver can occur.
  • substantially light-insensitive organic silver salts for use in the substantially light-insensitive thermographic material used in the present invention are substantially light-insensitive silver salts of an organic carboxylic acid, with substantially light-insensitive silver salts of a fatty acid, such as silver behenate, being particularly preferred.
  • conversion temperature or threshold T c is defined as being the minimum temperature of the substantially light-insensitive thermographic material m necessary during a certain time range to bring about an image-forming reaction, so as to form visually perceptible image.
  • a substantially light-insensitive thermographic material used according to the present invention generally has a T c between 75 and 120°C, more specifically between 80 and 110°C.
  • the "burning temperature T b" of a substantially light-insensitive thermographic material m is the lowest temperature at which any burning might occur, irrespectively in which layer it might happen (e.g. in a support 65, in a substrate layer 66, in a thermosensitive element 67, in a protective layer 68, or/and in a backing layer 69, see Fig. 17 for the numbering).
  • an apparatus for thermal recording an image in a substantially light-insensitive thermographic material m having a burning temperature T b , the substantially light-insensitive thermographic material m comprising a thermosensitive element having a conversion temperature T c , a support, and at least one light-to-heat conversion agent comprises a means for generating a radiation beam 20 including wavelengths ⁇ absorbed by the light-to-heat conversion agent and an optical means of scanning a line 40 of the substantially light-insensitive thermographic material m with the radiation beam 20 at different positions thereon along a scanning direction at each point of time in a scanning cycle.
  • the radiation beam 20 is capable of being modulated in accordance with the information to be recorded.
  • the optical scanning means is capable of heating the line of the substantially light-insensitive thermographic recording material m to a first predetermined temperature T 1 being above the conversion temperature T c and below the burning temperature T b of the substantially light-insensitive thermographic material m.
  • the apparatus further comprises a means of cooling the line 40 of the substantially light-insensitive thermographic material m to a second predetermined temperature T 2 being below the conversion temperature T c .
  • the apparatus further comprises a means of re-scanning the line of the substantially light-insensitive thermographic material m a plurality of times n s with the radiation beam being identically modulated in accordance with the information to be recorded.
  • Fig. 6 is a pictorial view of an apparatus for thermal recording according to the present invention.
  • thermographic material is mountable on a holding means 14 (which might be a flat bed), e.g. on an external drum 15.
  • thermographic material is mountable on a holding means 14, for example a drum, capable of heating the substantially light-insensitive thermographic material to a preheating temperature T p below a conversion temperature T c of the substantially light-insensitive thermographic material.
  • the means of generating a radiation beam 20 is a laser beam.
  • the means of generating a radiation beam 20 is a coherent light source (11) comprising a semiconductor- or diode-laser (optionally fibre coupled), a diode-pumped laser (as a neodymium-laser), or an ytterbium fibre laser.
  • 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 laser diodes emit e.g. at 830 nm or at 860-870 nm.
  • thermosensitive element e.g. reduction of a substantially light-insensitive silver salt of the thermographic material, and a perceptible image appears.
  • a motor (not shown in drawing Fig. 6) transports the drum one step.
  • the means of generating a radiation beam 20 is a laser beam (e.g. A YAG-doped ytterbium-laser Yb-YAG emitting a beam of 1030 nm with 20 W power in continuous wave; e.g. type 'DisKlaser' available from the company NANOLASE) which is modulated by a modulator 28, e.g. an acoustic modulator, which can be activated or deactivated.
  • a laser beam e.g. A YAG-doped ytterbium-laser Yb-YAG emitting a beam of 1030 nm with 20 W power in continuous wave; e.g. type 'DisKlaser' available from the company NANOLASE
  • a modulator 28 e.g. an acoustic modulator, which can be activated or deactivated.
  • Fig. 6 shows the laser beam 20 being deflected by a first mirror 26, passing through a modulator 28, e.g. an acoustic modulator, which can be activated or deactivated.
  • a modulator 28 e.g. an acoustic modulator, which can be activated or deactivated.
  • the laser beam goes to a second mirror 27 and may pass through two lenses to adjust the (vertical) beam-diameter an then comes to moving mirror 10, e.g. a polygon with eight faces.
  • This polygon turns the beam via a f ⁇ objective 29 to a torroidal lens (not explicitly shown) which focuses the beam on the substantially light-insensitive thermographic material.
  • the optical scanning means comprises a light deflecting means for deflecting the laser beam to scan the substantially light-insensitive thermographic material m with the deflected laser beam, such as a polygon mirror.
  • the radiation beam scans faster or slower over the substantially light-insensitive thermographic material m, depending upon the speed of the movable components in the optical scanning means, such as a polygon mirror.
  • the apparatus further includes a further heating means.
  • the apparatus further includes a further heating means comprising an external drum, such as shown in Fig. 4 and Fig. 8.1 and disclosed in US 5,932,394.
  • Fig. 4 schematically shows an external drum type recording device having a so called “imaging array” (e.g. a laser-array).
  • a carriage carrying an array 19 of e.g. laser-diodes has to move (or to sweep) at least two times from one side (e.g. BOL) of the drum 15 to the other side (e.g. EOL) of the drum.
  • BOL the side of the drum 15
  • EOL e.g. EOL
  • such an array preferably scans the substantially light-insensitive thermographic material m (5) with at least two laser beams at a same time (sometimes called "comb-wise"), thus gaining (because of the electro-optical simultaneity) in line-time.
  • the apparatus further includes a further heating means comprising a transparent thermal head (which is not separately shown in Fig. 5), as disclosed in EP-A 1 104 699.
  • Fig. 5 shows a preferred embodiment of a laser thermographic apparatus suitable for use in a method according to the present invention.
  • ref. 5 is the thermal imaging element
  • 20 is a laser beam
  • 102 a supply magazine 104 a belt
  • 105 a tension roller 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.
  • a full description of a laser thermographic printer can be found in DE-A 196 36 253.
  • the apparatus includes controllable parameters comprising 1) specifications of the substantially light-insensitive thermographic material m and the light-to-heat conversion agent, 2) temperature T p of the drum, 3) position of the thermosensitive element with respect to the drum, 4) power of a laser, 5) input of a modulator 6) transportation speed vy of the substantially light-insensitive thermographic material m, 7) speed n p of a rotating optical means, 8) number n s of sweeps during one line-time t 1 .
  • the apparatus excludes a transparent thermal head.
  • a method for recording information comprising the steps of: providing an apparatus for thermal recording 1, a substantially light-insensitive thermographic material m (5), the thermographic material having a burning temperature T b (e.g. about 300°C), and comprising a thermosensitive element having a conversion temperature T c (e.g. ranging between 80°C and 110°C, according to the specific type of thermographic material), a support, and at least one light-to-heat conversion agent; generating a radiation beam 20 including wavelengths ⁇ absorbed by the light-to-heat conversion agent and being modulated in accordance with the information to be recorded (i.e.
  • Fig. 7 shows the evolution over time of the temperature attained in a thermographic material while applying a plurality of scannings according to the present invention).
  • the method further comprises cooling the line 40 of the substantially light-insensitive thermographic material m to a second predetermined temperature T 2 being below the conversion temperature T c , with non-forced cooling, i.e. natural, physical decay of the temperature over time, being preferred.
  • non-forced cooling i.e. natural, physical decay of the temperature over time. Examples of forced cooling is cooling with a blower.
  • the second predetermined temperature T 2 is between the conversion temperature T c and the ambient temperature T a .
  • the second predetermined temperature T 2 is nearly at ambient temperature T a .
  • the method further comprises the removal of the substantially light-insensitive thermographic material m from the apparatus for thermal recording 1, thereby delivering a hard-copy print (indicated by ref. nr. 17 in Fig. 5) of the information.
  • an upper limit of spatial resolution (dpi upp ) is controlled by determining a main-scan-speed v y in relation to the first predetermined temperature T 1 .
  • the main-scan-speed v x might be increased.
  • the speed of the radiation beam over the substantially light-insensitive thermographic material increases with increasing speed of the rotating polygon.
  • the normally non-square distribution of the intensity of the laser beam see Fig. 13
  • only a part of the thermographic material irradiated attains a temperature higher than the conversion temperature T c (see Figs. 14.1 and 14.2).
  • T c conversion temperature
  • the method further comprises a step of controlling a spatial resolution (dpi) of the hardcopy print 17 by choosing the first temperature T 1 substantially higher than T c .
  • the first temperature T 1 is relatively close to the T c (as shown in Fig. 14.1 for a thermographic material scanned at a rather high main-scan-speed v x ), which results in thinner lines be obtained.
  • the first temperature T 1 is relatively far away from the T c (as shown in Fig. 14.2 for a same thermographic material scanned at a rather low main-scan-speed v x ), which results in thicker lines being obtained.
  • the first temperature T 1 should be decreased.
  • Figs. 14.1 and 14.2 also illustrate another embodiment of the present invention.
  • the spatial resolution (dpi) of the hardcopy print 17 can be controlled by selecting the type of thermographic material, especially with respect to the conversion temperature T c e.g. if an apparatus were to comprise two or more film cassettes comprising at least two kinds of thermographic materials, say m 1 and m 2 having respective conversion temperatures T c1 and T c2 .
  • Fig. 14.1 shows the geometrical spread 62 of the temperature T m reached in a thermographic material when scanned according to a preferred embodiment
  • Fig. 14.2 shows the geometrical spread 63 of the temperature T m reached in a thermographic material when scanned according to a second preferred embodiment.
  • Fig. 14.1 shows the geometrical spread of the temperature T m reached in a thermographic material when scanned with a high speed laser beam
  • Fig. 14.2 shows the geometrical spread of the temperature T m reached in a thermographic material when scanned with a low speed laser beam.
  • Fig. 14.1 shows the geometrical spread of the temperature T m reached in a first substantially light-insensitive thermographic material m 1 when scanned with a laser beam
  • Fig. 14.2 shows the geometrical spread of the temperature T m reached in a second substantially light-insensitive thermographic material m 2 when scanned with a same laser beam.
  • Fig. 11 shows the actual evolution over time of the temperature T m in the thermosensitive element if an information is recorded in one single sweep
  • Fig. 12 shows the actual evolution over time of the temperature T m attained in the thermosensitive element if an information is recorded by applying a plurality of scannings according to the method of the present invention. Applying a plurality of scannings eliminates unwanted side-effects such as deformation, colouring and burning.
  • the plurality of times n s comprises at least two times (n s ⁇ 2; see also Figs. 7, 10 and 12).
  • the plurality of times n s is defined such that a desired pixel output (D o ) is achieved.
  • the first temperature T 1 is relatively close to T c (as shown in Fig. 14.1), which results in thinner lines being attained such that more sweeps have to be performed in order to attain a sufficient density in the output print 17 (especially in the mid of the line width 44, see Figs. 8.2, 10, 14.1 and 14.2).
  • the first temperature T 1 is relatively distant to the T c (as shown in Fig. 14.2), thereby obtaining thicker lines and generally requiring less sweeps.
  • an upper limit of spatial resolution (dpi upp ) is controlled by determining an energy radiated by the radiation beam in relation to a main-scan-speed v x .
  • the laser output is required to produce a sufficient energy to enable a desired density to be obtained with the substantially light-insensitive thermographic material m.
  • a laser scans over the thermographic material, the temperature on the recorded pixels rises, the imaging-forming reaction occurs and a perceptible image appears.
  • a motor (not shown in drawing Fig. 6) transports the drum one step.
  • the method further comprises a step of defining a position (wherein the scanning of the substantially light-insensitive thermographic material m is carried out) of the thermosensitive element with respect to a holding means 14 or a drum 15.
  • a position wherein the scanning of the substantially light-insensitive thermographic material m is carried out
  • Fig. 18.1 and 18.2 respectively showing a thermographic system incorporating a first and a second position (REPL versus RPEL) of the thermosensitive element with respect to a holding means 14, or a drum 15.
  • the method further comprises a step of further heating (also called “background heating or preheating") the substantially light-insensitive thermographic material m to a preheating temperature T p before and/or during scanning thereof with the radiation beam (see Figs. 5 and 7).
  • Fig. 17 shows a cross-section of a configuration of a substantially light-insensitive thermographic material m suitable for application within the present invention.
  • the substantially light-insensitive thermographic material m comprises a thermosensitive element consisting of at least one layer, the thermosensitive element comprising a substantially light-insensitive organic silver salt and a reducing agent therefor in thermal relationship therewith, the reducing agent being in a layer of said thermosensitive element containing said substantially light-insensitive organic silver salt and/or in an adjacent layer of the thermosensitive element such that the reducing agent is present such that it is in thermal working relationship with said substantially light-insensitive organic silver salt.
  • the method further comprises a step of further heating the substantially light-insensitive thermographic material m with a transparent thermal head.
  • DOE diffractive optical elements
  • the substantially light-insensitive thermographic material excludes an image-forming layer on a hydrophilic surface.
  • the apparatus for thermal recording an image is used for recording information in substantially light-insensitive thermographic materials for medical and graphics applications.
  • the line-time t l can be derived from the sweep-time t s (cf. n p and equation 4)and from the number n s of sweeps.
  • Fig. 10 records the results of the first set of experiments and shows an output density (e.g. ranging up to 4.5 D) for a substantially light-insensitive thermographic material m, as a function of:
  • Figs. 15 and 16 record the results of the second set of experiments, which confirmed: (i) that a higher speed of revolution of the polygon normally resulted in a smaller line-width and hence in a higher spatial resolution, but also (ii) that a higher speed of rotation of the polygon resulted in a lower efficiency ⁇ of the thermographic system.
  • our tests concerning spatial resolution resulted in Fig. 15 showing the efficiency ⁇ of the laser system when different line-thicknesses were applied, and in Fig. 16 showing the efficiency ⁇ of the laser system when different spatial resolutions were applied.
  • Fig. 14.1 is referred to in which the geometrical spread of the temperature attained in a first substantially light-insensitive thermographic material m 1 when scanned with a Gaussian laser beam, and to Fig. 14.2 showing the geometrical spread of the temperature reached in a second substantially light-insensitive thermographic material m 2 when scanned with a same Gaussian laser beam. It may be noted that according to the present invention, high spatial resolutions e.g. higher than 600 or even 1200 dpi or small line-widths e.g. smaller than 40 or even 20 ⁇ m are attained.

Claims (12)

  1. Procédé d'enregistrement d'informations, comprenant les étapes de :
    - fourniture d'un appareil d'enregistrement thermique (1), une matière thermographique essentiellement insensible à la lumière m (5), ladite matière thermographique ayant une température de combustion Tb, et comprenant un élément thermosensible ayant une température de conversion Tc, un support et au moins un agent de conversion de lumière en chaleur ;
    - génération d'un faisceau de rayonnement (20) comportant des longueurs d'ondes λ absorbées par ledit agent de conversion de lumière en chaleur et modulé conformément audites informations à enregistrer,
    - balayage d'une ligne (40) de ladite matière thermographique essentiellement insensible à la lumière m une première fois avec ledit faisceau de rayonnement, chauffant ainsi ladite ligne de ladite matière thermographique essentiellement insensible à la lumière m à une première température prédéterminée T1 supérieure à ladite température de conversion Tc et inférieure à ladite température de combustion Tb de ladite matière thermographique essentiellement insensible à la lumière m ; et
    caractérisé par l'étape de :
    - re-balayage de ladite même ligne de ladite matière thermographique essentiellement insensible à la lumière m une pluralité de fois ns avec ledit faisceau de rayonnement modulé de façon identique conformément auxdites informations à enregistrer.
  2. Procédé selon la revendication 1, dans lequel le procédé comprend en outre l'étape de refroidissement de ladite ligne de ladite matière thermographique essentiellement insensible à la lumière m à une deuxième température prédéterminée T2 inférieure à ladite température de conversion Tc.
  3. Procédé selon la revendication 1, dans lequel une limite supérieure de résolution spatiale (dpiupp) est commandée en déterminant une vitesse de balayage principale vx relativement à ladite première température prédéterminée T1.
  4. Procédé selon l'une quelconque des revendications 1 à 3, dans lequel ladite pluralité de fois ns comprend au moins deux fois (ns ≥ 2).
  5. Procédé selon la revendication 4, dans lequel ladite pluralité de fois ns est définie de façon à obtenir une sortie de pixel désirée (Do).
  6. Procédé selon la revendication 1, dans lequel une limite supérieure de résolution spatiale est commandée en déterminant une énergie rayonnée par ledit faisceau de rayonnement relativement à une vitesse de balayage principale vx.
  7. Procédé selon la revendication 1, comprenant une étape de chauffage supplémentaire de la matière thermographique essentiellement insensible à la lumière m à une température de préchauffage Tp avant et/ou durant le balayage de celle-ci avec le faisceau de rayonnement.
  8. Procédé selon la revendication 1, comprenant une étape de définition d'une position de l'élément thermosensible par rapport à un moyen de support (14) ou un tambour (15).
  9. Procédé selon l'une quelconque des revendications précédentes, dans lequel ladite matière thermographique essentiellement insensible à la lumière m comprend un élément thermosensible consistant en au moins une couche, ledit élément thermosensible comprenant un sel d'argent organique essentiellement insensible à la lumière et un agent réducteur de celui-ci en relation thermique avec lui, ledit agent réducteur se trouvant dans une couche dudit élément thermosensible contenant ledit sel d'argent organique essentiellement insensible à la lumière et/ou dans une couche adjacente dudit élément thermosensible de telle sorte que ledit agent réducteur soit présent de façon à avoir une relation de travail thermique avec ledit sel d'argent organique essentiellement insensible à la lumière.
  10. Appareil (1) d'enregistrement thermique d'une image dans une matière thermographique essentiellement insensible à la lumière m ayant une température de combustion Tb, ladite matière thermographique essentiellement insensible à la lumière m comprenant un élément thermosensible ayant une température de conversion Tc, un support et au moins un agent de conversion de lumière en chaleur, comprenant
    - des moyens pour générer un faisceau de rayonnement (20) comportant des longueurs d'ondes λ absorbées par ledit agent de conversion de lumière en chaleur ; et
    - des moyens optiques pour balayer une ligne (40) de ladite matière thermographique essentiellement insensible à la lumière m avec ledit faisceau de rayonnement (20) à différentes positions sur celle-ci le long d'un sens de balayage à chaque point de temps dans un cycle de balayage
    caractérisé en ce que l'appareil comprend en outre un moyen de re-balayage de la ligne de la matière thermographique essentiellement insensible à la lumière m une pluralité de fois ns avec le faisceau de rayonnement modulé de façon identique conformément aux informations à enregistrer.
  11. Appareil selon la revendication 10, comprenant en outre un moyen de chauffage supplémentaire.
  12. Utilisation d'un procédé selon la revendication 1 en thermographie laser.
EP20020102332 2001-10-02 2002-09-09 Enregistrement thermique au moyen d'un spot mobile Expired - Lifetime EP1300251B1 (fr)

Priority Applications (1)

Application Number Priority Date Filing Date Title
EP20020102332 EP1300251B1 (fr) 2001-10-02 2002-09-09 Enregistrement thermique au moyen d'un spot mobile

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Application Number Priority Date Filing Date Title
EP01000515 2001-10-02
EP10005155 2001-10-02
EP20020102332 EP1300251B1 (fr) 2001-10-02 2002-09-09 Enregistrement thermique au moyen d'un spot mobile

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EP1300251B1 true EP1300251B1 (fr) 2006-12-27

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Family Cites Families (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS6277983A (ja) * 1985-10-02 1987-04-10 Copal Electron Co Ltd 熱記録装置
US5278578A (en) * 1989-12-18 1994-01-11 Eastman Kodak Company Thermal printer capable of using dummy lines to prevent banding
US5066962A (en) * 1989-12-27 1991-11-19 Eastman Kodak Company Laser thermal printer having a light source produced from combined beams
US5398052A (en) 1990-11-07 1995-03-14 Canon Kabushiki Kaisha Image forming apparatus using overlapping light beams
EP0692733B1 (fr) 1994-07-07 1998-02-04 Agfa-Gevaert N.V. Procédé directe pour l'enregistrement thermique
DE69517504T2 (de) 1995-03-22 2001-02-08 Agfa Gevaert Nv Zeitmodulierte stochastische Halbtonrasterung
US5804355A (en) 1996-03-14 1998-09-08 Agfa-Gevaert N.V. Producing a contone image by sequentially exposing a thermo-sensitive imaging material by means of a set of radiation beams
JP3596574B2 (ja) 1996-11-18 2004-12-02 富士写真フイルム株式会社 熱記録方法
DE19654018A1 (de) * 1996-12-21 1998-06-25 Roland Man Druckmasch Verfahren und Vorrichtung zum Erzeugen einer Durckbildverteilung
DE69926131D1 (de) 1999-12-01 2005-08-18 Agfa Gevaert Nv Thermoaufzeichnungsverfahren-und-Vorrichtung

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