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WO1995007513A1 - Procede d'impression de colorant par transfert thermique faisant appel a une source laser - Google Patents

Procede d'impression de colorant par transfert thermique faisant appel a une source laser Download PDF

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Publication number
WO1995007513A1
WO1995007513A1 PCT/GB1994/001985 GB9401985W WO9507513A1 WO 1995007513 A1 WO1995007513 A1 WO 1995007513A1 GB 9401985 W GB9401985 W GB 9401985W WO 9507513 A1 WO9507513 A1 WO 9507513A1
Authority
WO
WIPO (PCT)
Prior art keywords
laser
dye
donor element
donor
receiver
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.)
Ceased
Application number
PCT/GB1994/001985
Other languages
English (en)
Inventor
Kenneth West Hutt
Richard Anthony Hann
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.)
Imperial Chemical Industries Ltd
Original Assignee
Imperial Chemical Industries Ltd
Priority date (The priority date 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 date listed.)
Filing date
Publication date
Application filed by Imperial Chemical Industries Ltd filed Critical Imperial Chemical Industries Ltd
Publication of WO1995007513A1 publication Critical patent/WO1995007513A1/fr
Anticipated expiration legal-status Critical
Ceased legal-status Critical Current

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Classifications

    • 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
    • B41M5/382—Contact thermal transfer or sublimation processes
    • B41M5/38207—Contact thermal transfer or sublimation processes characterised by aspects not provided for in groups B41M5/385 - B41M5/395
    • G—PHYSICS
    • G06—COMPUTING OR CALCULATING; COUNTING
    • G06K—GRAPHICAL DATA READING; PRESENTATION OF DATA; RECORD CARRIERS; HANDLING RECORD CARRIERS
    • G06K15/00—Arrangements for producing a permanent visual presentation of the output data, e.g. computer output printers
    • G06K15/02—Arrangements for producing a permanent visual presentation of the output data, e.g. computer output printers using printers
    • G06K15/028—Arrangements for producing a permanent visual presentation of the output data, e.g. computer output printers using printers by thermal printers
    • G06K15/029—Arrangements for producing a permanent visual presentation of the output data, e.g. computer output printers using printers by thermal printers using optical beams

Definitions

  • the present invention relates to a method of operating a laser source to effect dye thermal transfer printing.
  • thermal transfer printing methods in which dye is transferred by melting, diffusion or sublimation respectively.
  • a dye donor ribbon comprising a dye layer on a supporting substrate
  • a dye receiver ribbon comprising a dye receiving layer on a supporting substrate
  • a localised source of energy is used to heat up selected pixel regions of the dye layer to cause the dye in those regions to become thermally mobile and diffuse into the receiver layer to produce printed pixels.
  • a desired print image may thus be produced in the receiver ribbon by heating an appropriate selection of pixel regions in the dye layer.
  • Laser sources are often chosen as the energy source, because they can provide a relatively intense, localised and controllable output.
  • a laser light absorbing material is then provided in the donor ribbon to produce the heating effect, and is either dispersed in the dye layer or is formed as a separate layer.
  • the invention relates to the efficient use of a laser source in dye thermal transfer printing.
  • the present invention provides a method of laser dye thermal transfer printing in which a laser source is operated to heat selected pixel regions of a dye donor element to effect transfer of dye from the dye donor element to a dye receiver element, wherein the laser source heats each selected pixel region for less than about 15 microseconds, preferably for less than 10 microseconds.
  • a laser source is operated to heat selected pixel regions of a dye donor element to effect transfer of dye from the dye donor element to a dye receiver element, wherein the laser source heats each selected pixel region for less than about 15 microseconds, preferably for less than 10 microseconds.
  • the present invention is based on the recognition that, although a donor element such as a ribbon may be 10 to 20 microns thick, dye need only travel a distance of between 1 to 2 microns from near the surface of the ribbon's dye layer into the surface region of the receiver layer in order to effect transfer and produce a print image in the receiver element. Therefore, the heated region produced by the laser beam in the donor element and across into the receiver element need only be of this approximate extent in the dye transfer direction (i.e. in a direction from the donor to the receiver element) , and any further extension of the heated region is not utilised in the transfer process, and would waste energy and reduce efficiency.
  • the present invention therefore increases energy efficiency of laser dye thermal transfer printing by using short laser pulses to provide a degree of thermal diffusion which does not result in a significant amount of heat being wasted, but which does ensure that dye transfer still takes place.
  • the spread of heat through the donor/receiver elements is not sharp but may be characterised by a thermal diffusion coefficient D which is dependent on the particular materials from which the two elements are made.
  • D thermal diffusion coefficient
  • the invention may be defined as providing a method of laser dye thermal transfer printing in which a laser source is operated to heat selected pixel regions of a dye donor element to effect transfer of dye from the donor element to a dye receiver element, wherein the heated region produced by the source in the donor element and across into the receiver element does not extend substantially further than about 2 microns in the dye transfer direction.
  • the dye In order for the dye to transfer properly to the receiver, it should be capable of diffusing at least 1 micron into the surface. For this to occur, this region of the media must attain a sufficient temperature. If the pulse time is greater than 1 microsecond, then this temperature is reached during the pulse. If the pulse time is shorter, then the temperature is reached in the time taken for the heat to dissipate. In either case, the energy is used most efficiently by being delivered in less than 15 or preferably 10 microseconds.
  • Preferred power density levels delivered at the donor element are greater than 1 x 10 9 Wm ⁇ 2 .
  • the pulse width would be very short, in the order of 10 ns, and the power density at the donor element very high, e.g. 1 x 10 12 Wm ⁇ 2 .
  • a high powered laser diode might be pulsed at 10 ⁇ s intervals at a power density of 1 x 10 9 Wm "2 at the donor element.
  • the application of heat at a higher power density can be further advantageous in that the diffusion coefficient of a dye will typically increase with increasing temperature, so that at about 250 D C, the dye diffusion coefficient is typically about 10" 9 m 2 /s, whilst at about 350-400 ⁇ C, the dye diffusion coefficient approaches the thermal diffusion coefficient D of the donor/receiver materials, i.e. the dye diffuses as quickly as the heat.
  • This is an optimised condition, as there is little advantage to be gained from a dye diffusion coefficient which is significantly higher than the thermal diffusion coefficient D, and higher temperatures may, in any case, lead to a breakdown of ribbon polymers or dye molecules.
  • the heating time of a pixel region of the donor element may be set by applying a laser pulse of appropriate duration to the region, or by continuously scanning a laser beam across the region so that the beam moves across the region in the desired heating time (the width of the region may be defined to be equal to the full width of the laser beam taken at the 1/e intensity point of the beam's Gaussian cross-section profile).
  • the laser source itself may be of any suitable type, such as a laser diode, and the pulse lengths envisaged by the invention may be delivered by the rapid modulation of many types of laser source. Modulation may be internal of the laser, e.g. Q-switching, or external, e.g. by an acousto-optic modulator or mechanical beam chopper.
  • the dye ribbon may be supplied with a laser light absorber supercoat, i.e. a layer of laser light absorbing material which is provided over the dye layer, or with an absorber layer or a high concentration of absorber particles within but near the surface of the dye layer.
  • a laser light absorber supercoat i.e. a layer of laser light absorbing material which is provided over the dye layer, or with an absorber layer or a high concentration of absorber particles within but near the surface of the dye layer.
  • the laser light could also or alternatively be supplied to the donor element through the receiver layer, so that the light first contacts the regions of the donor element nearest the receiver element and does not need to pass through the body of the donor element.
  • the receiver ribbon needs to be transparent to the laser light, but this will not usually be a problem.
  • either pulse- width modulation or a reduction in laser power may be used to vary the amount of energy applied to each pixel region.
  • a plurality of short pulses may be applied successively, rather than using a single prolonged pulse, provided that the total elapsed time is less than 15, preferably 10, ⁇ s.
  • Figure 1 is a schematic diagram of a laser dye thermal transfer printing apparatus which may be operated in accordance with embodiments of the invention
  • Figure 2 is a schematic horizontal cross-section through the donor/receiver interface at II-II in Fig. 1 showing the temperature gradient produced by the laser heating;
  • Figure 3 is a graph of print energy against optical density when printing using a short pulsed YAG laser and a relatively long pulsed laser diode
  • Figure 4 is a graph of laser pulse time against optical density when printing with a laser diode ⁇ supplying the same energy for each pulse time.
  • a dye thermal transfer printing apparatus 1 in which a receiver ribbon 2 and a dye donor ribbon 3 are fed between the nip of a pressure roller 4 and a support plate 5.
  • the receiver ribbon 2 comprises a dye receiver layer 2a on a supporting substrate 2b
  • donor ribbon 3 comprises a dye layer 3a (of dye and laser light absorbing material dispersed in a binder) on a supporting substrate 3b.
  • the support plate 5 and receiver ribbon 2 are transparent to laser light 6 from a laser source 7, such as a laser diode.
  • the laser light 6 is scanned across the dye donor ribbon 3 by a rotating polygon mirror 8, and a flat field lens 9 is provided between the polygon 8 and support plate 5 to ensure that the laser light 6 is scanned across the dye donor ribbon in a flat focal plane rather than a curved one.
  • the laser source 7 is pulsed as the polygon 8 scans the light 6 across the donor ribbon 3, and the laser pulses are synchronised with the rotation of the polygon 8, so that each pulse heats a selected pixel region of the dye layer 3a lying along the scan line.
  • a printed image is produced pixel-line-by- pixel-line in the receiver layer 2a of the receiver ribbon 2.
  • the laser source 7 is activated to produce a series of laser pulses whose power density is greater than 1 x 10 9 Wm" 2 , and which are each less than 10 microseconds in duration. This ensures that the heat effect produced by each laser pulse is limited to a 2 micron region of the donor/receiver contact region.
  • the temperature gradient produced is as shown in Fig. 2, with the -temperature at the point of laser absorption being about 1,000°C, and with the heat diffusing outwardly to produce temperatures to about 400°C at the heated region's outer periphery which lies in the receiver layer 2a.
  • the dye diffuses through the heated region to transfer from the dye layer 3a to the receiver layer 2a.
  • either the power of each of the pulses may be modulated to accord with the amount of dye desired to be transferred from each pixel region, or the length of each pulse may be varied within the 10 microsecond limit.
  • the light beam 6 may be continuously on, and the scanning rate of the polygon 8 may be set such that the laser beam 6 crosses each pixel region of the dye layer 2a in less than 10 microseconds, a pixel region being defined by the width of the laser beam taken at the 1/e of maximum intensity points of the beam's Gaussian cross-sectional profile.
  • Continuous tone printing may then be produced by modulating the power of the beam 6, or by rapidly pulsing the laser source 7 on and off in a duty cycle as it passes across a pixel element so that the pixel element only receives light energy for a desired fraction of the time taken for the beam to cross the pixel region.
  • Example 1 In order to illustrate the invention, two dyesheets of similar properties were prepared, one sensitive to a YAG laser source (1060nm) and the second sensitive to a diode laser source (820nm) . Formulations for each dyecoat are summarised below. In addition, each dyecoat was formulated so that the OD of IRA dyes at the wavelength of each laser source were the same to within experimental error, to ensure the same proportion of incident radiation was absorbed in each case. In both cases, a two layer structure was used, the top dye layer common to both, and the subcoat beneath identical in terms of resin but containing absorbers matched to the wavelength of the laser being used. Differences in the solvent systems used to coat the absorber layers are due to solubility differences of the two absorbers. Absorber layers:
  • the coatings were laid down using a meyer bar onto 23 ⁇ m S grade Melinex (ICI) PET film, the absorber coatings in each case were cured at 100°C for 5 minutes before the dye layer was coated over the top.
  • the resulting absorption properties of the dyesheets so produced were as follows:
  • a receiver sheet comprising a dye compatible coating on transparent 0 grade Melinix (ICI) , and the YAG sensitive dyesheet were held against an arc to retain laser focus by the application of 1 atm pressure.
  • optical efficiency of the apparatus measured as 61% by measurement of power of incident radiation at the media surface and proportion of light reflected away from media.
  • the duty cycle of the laser was set to 1.3kHz.
  • the laser was then pulsed at varying powers and simultaneously scanned across the media via a galvanometer scanner to print blocks of magenta on the receiver.
  • the diode sensitive dyesheet was used in the same way and imaged with an SDL l50mW diode laser operating at 820nm whose output was collimated using a 160mm achromat lens and projected onto the media.
  • the incident laser power was lOOmW and the full spot size 20 x 30 ⁇ m (full width at half power maximum) .
  • the laser was pulsed for various pulse lengths at between 25 and 300 ⁇ S and the laser scanned across the media using a galvanometer scanner as before.
  • Figure 3 shows the comparison of print energy (expressed in Jem" 2 ) with optical density for the two dyesheet systems.
  • the more rapid build up of optical density in the YAG experiment reflects the more rapid pulse time used in operating the YAG laser.
  • This example again sets out to illustrate the advantage of applying laser power more rapidly, thereby improving the efficiency of the dye transfer system.
  • a diode laser source capable of delivering up to 200mW was used to image a dyesheet comprising a dye coat made by coating the following solution onto 23 ⁇ m S grade melinex film with a meyer bar to give a coating with an OD 560nm of 4.1 and on OD 820nm of 0.7.
  • the dyesheet was then held against a sample of receiver film identical to that used in example 1 and irradiated in a similar fashion, the laser being pulsed at times between 10 and 30 ⁇ s and scanned with a galvanometer scanner. In each case however the laser power was altered so that the print energy delivered to the media was the same in each print, this energy being 1.1 Jem" 2 . The extent of dye transfer was determined by measuring the optical density as before.
  • the laser powers and OD realised at the different pulse time are summarised in the table and in figure 4.
  • Figure 4 shows that reducing the time period over which the laser energy is delivered to the media increases the efficiency of the dye transfer process.

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  • Engineering & Computer Science (AREA)
  • Physics & Mathematics (AREA)
  • General Engineering & Computer Science (AREA)
  • General Physics & Mathematics (AREA)
  • Theoretical Computer Science (AREA)
  • Optics & Photonics (AREA)
  • Thermal Transfer Or Thermal Recording In General (AREA)
  • Electronic Switches (AREA)

Abstract

Un faisceau laser à balayage (7) chauffe des régions sélectionnées d'éléments d'images d'un ruban (3) donneur de colorant afin de faire transférer le colorant vers un ruban récepteur (2) pour y créer une image. Le faisceau (7) chauffe chaque région sélectionnée d'éléments d'images pendant moins de 15 microsecondes environ. Ceci accroît l'efficacité d'impression, tandis qu'on obtient, grâce à de brèves durées de chauffe, des régions chauffées d'environ 2 microns dans le sens du transfert du colorant, ce qui est tout ce que l'on demande pour transférer le colorant de la couche donneuse (3a) vers la couche réceptrice (2a).
PCT/GB1994/001985 1993-09-10 1994-09-12 Procede d'impression de colorant par transfert thermique faisant appel a une source laser Ceased WO1995007513A1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
GB9318803.5 1993-09-10
GB939318803A GB9318803D0 (en) 1993-09-10 1993-09-10 Laser dye thermal transfer printing

Publications (1)

Publication Number Publication Date
WO1995007513A1 true WO1995007513A1 (fr) 1995-03-16

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PCT/GB1994/001985 Ceased WO1995007513A1 (fr) 1993-09-10 1994-09-12 Procede d'impression de colorant par transfert thermique faisant appel a une source laser

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GB (1) GB9318803D0 (fr)
WO (1) WO1995007513A1 (fr)

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0343443A2 (fr) * 1988-05-25 1989-11-29 Agfa-Gevaert AG Méthode et dispositif pour faire une copie thermique
EP0464588A1 (fr) * 1990-06-26 1992-01-08 Eastman Kodak Company Utilisation du vide pour améliorer la densité dans le transfert thermique de colorants induit par laser
US5143893A (en) * 1990-11-27 1992-09-01 Ricoh Company, Ltd. Sublimation-type thermal image transfer recording medium
WO1993003928A1 (fr) * 1991-08-16 1993-03-04 E.I. Du Pont De Nemours And Company Moyens de formation d'images en ecriture directe par infrarouges
EP0533592A2 (fr) * 1991-09-20 1993-03-24 Eastman Kodak Company Méthode et dispositif d'impression thermique d'images firement détaillées de qualité photographique

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0343443A2 (fr) * 1988-05-25 1989-11-29 Agfa-Gevaert AG Méthode et dispositif pour faire une copie thermique
EP0464588A1 (fr) * 1990-06-26 1992-01-08 Eastman Kodak Company Utilisation du vide pour améliorer la densité dans le transfert thermique de colorants induit par laser
US5143893A (en) * 1990-11-27 1992-09-01 Ricoh Company, Ltd. Sublimation-type thermal image transfer recording medium
WO1993003928A1 (fr) * 1991-08-16 1993-03-04 E.I. Du Pont De Nemours And Company Moyens de formation d'images en ecriture directe par infrarouges
EP0533592A2 (fr) * 1991-09-20 1993-03-24 Eastman Kodak Company Méthode et dispositif d'impression thermique d'images firement détaillées de qualité photographique

Also Published As

Publication number Publication date
GB9318803D0 (en) 1993-10-27

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