WO1998032594A1 - Feuilles thermiques pour l'application numerique de decorations - Google Patents

Feuilles thermiques pour l'application numerique de decorations Download PDF

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Publication number
WO1998032594A1
WO1998032594A1 PCT/US1998/001416 US9801416W WO9832594A1 WO 1998032594 A1 WO1998032594 A1 WO 1998032594A1 US 9801416 W US9801416 W US 9801416W WO 9832594 A1 WO9832594 A1 WO 9832594A1
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WO
WIPO (PCT)
Prior art keywords
thermal transfer
thermal
transfer foil
layer
foil
Prior art date
Application number
PCT/US1998/001416
Other languages
English (en)
Inventor
Stephen L. Aroneo
Original Assignee
General Scanning, Inc.
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 General Scanning, Inc. filed Critical General Scanning, Inc.
Priority to AU60411/98A priority Critical patent/AU6041198A/en
Publication of WO1998032594A1 publication Critical patent/WO1998032594A1/fr

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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
    • B41M5/40—Thermography ; Marking by high energetic means, e.g. laser otherwise than by burning, and characterised by the material used characterised by the base backcoat, intermediate, or covering layers, e.g. for thermal transfer dye-donor or dye-receiver sheets; Heat, radiation filtering or absorbing means or layers; combined with other image registration layers or compositions; Special originals for reproduction by thermography
    • B41M5/42—Intermediate, backcoat, or covering layers
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B44—DECORATIVE ARTS
    • B44C—PRODUCING DECORATIVE EFFECTS; MOSAICS; TARSIA WORK; PAPERHANGING
    • B44C1/00—Processes, not specifically provided for elsewhere, for producing decorative surface effects
    • B44C1/16—Processes, not specifically provided for elsewhere, for producing decorative surface effects for applying transfer pictures or the like
    • B44C1/165—Processes, not specifically provided for elsewhere, for producing decorative surface effects for applying transfer pictures or the like for decalcomanias; sheet material therefor
    • B44C1/17—Dry transfer
    • B44C1/1712—Decalcomanias applied under heat and pressure, e.g. provided with a heat activable adhesive
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B44—DECORATIVE ARTS
    • B44C—PRODUCING DECORATIVE EFFECTS; MOSAICS; TARSIA WORK; PAPERHANGING
    • B44C1/00—Processes, not specifically provided for elsewhere, for producing decorative surface effects
    • B44C1/16—Processes, not specifically provided for elsewhere, for producing decorative surface effects for applying transfer pictures or the like
    • B44C1/165—Processes, not specifically provided for elsewhere, for producing decorative surface effects for applying transfer pictures or the like for decalcomanias; sheet material therefor
    • B44C1/17—Dry transfer
    • B44C1/1712—Decalcomanias applied under heat and pressure, e.g. provided with a heat activable adhesive
    • B44C1/1729—Hot stamping techniques
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
    • B41M—PRINTING, DUPLICATING, MARKING, OR COPYING PROCESSES; COLOUR PRINTING
    • B41M2205/00—Printing methods or features related to printing methods; Location or type of the layers
    • B41M2205/06—Printing methods or features related to printing methods; Location or type of the layers relating to melt (thermal) mass transfer
    • 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
    • B41M5/38214—Structural details, e.g. multilayer systems
    • 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
    • B41M5/40—Thermography ; Marking by high energetic means, e.g. laser otherwise than by burning, and characterised by the material used characterised by the base backcoat, intermediate, or covering layers, e.g. for thermal transfer dye-donor or dye-receiver sheets; Heat, radiation filtering or absorbing means or layers; combined with other image registration layers or compositions; Special originals for reproduction by thermography
    • B41M5/42—Intermediate, backcoat, or covering layers
    • B41M5/426—Intermediate, backcoat, or covering layers characterised by inorganic compounds, e.g. metals, metal salts, metal complexes
    • 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
    • B41M5/40—Thermography ; Marking by high energetic means, e.g. laser otherwise than by burning, and characterised by the material used characterised by the base backcoat, intermediate, or covering layers, e.g. for thermal transfer dye-donor or dye-receiver sheets; Heat, radiation filtering or absorbing means or layers; combined with other image registration layers or compositions; Special originals for reproduction by thermography
    • B41M5/42—Intermediate, backcoat, or covering layers
    • B41M5/44—Intermediate, backcoat, or covering layers characterised by the macromolecular compounds

Definitions

  • This invention relates to thermal foils for decorative transfer of images to various types of coarse surfaces .
  • Hot stamping of metallic foils has been widely used for decorating, with graphics and text, such items as book covers wallets, attache cases, handbags, or suitcases. These articles are made of leathers, vinyls or textiles, which have surfaces with deep grains or fibers having valleys, for example, 0.001 inches or even 0.003 inches in depth.
  • the metallic foil transferred by heat and high pressure, typically has a mirror-like surface for shiny appearance.
  • the transferred material includes a tinted or clear lacquer top layer covering the metal surface to provide protection and a rich gold or other appearance.
  • to transfer the metallic material one has to first fabricate a custom-made metal die with raised and recessed areas corresponding to the particular design.
  • the raised areas press the foil against the receiving substrate to transfer the material having the desired pattern while heat is applied.
  • the stamping press applies pressures of hundreds of pounds or more to the die. While this type of transfer has been widely used, it also has drawbacks. For example, it takes a relatively long time to fabricate the die and the fabrication process is relatively expensive. There are other widely used techniques for decorative printing, but they also require fabrication of special tools for different designs. For example, silk screen printing requires fabrication of a print screen and pad printing requires fabrication of a pad.
  • Computer controlled thermal printing is a different thermal process. It uses a thermal printhead controlled by a computer to print an image, typically, on paper. The thermal printhead generates heat localized over dots of a computer generated pattern to be printed.
  • a thermal printing ribbon disposed between the printhead and the paper or other web, releases ink that is thermally transferred in tiny amounts to the paper.
  • the ink layer consists of a particulate or liquid-like material.
  • the thermal printing ribbon also includes constituents that facilitate good adherence of the ink dots to the paper surface.
  • the entire process is relatively fast and economical. However, this process has not been equated with hot stamping because of limitations of the process and the materials on which a precise image could be formed.
  • Thermal printing has been used for decorative printing on papers of varying surface qualities. To improve the quality of the transferred image, printheads have been used to transfer several layers of ink on the same dot or puffing particles have been included in the transfer composition to fill irregularities on the printed surface. In either case, the thermal printing process and its effects have differed significantly from the hot stamping process that transfers relatively larger chunks of metallic material to the surface to achieve a specular effect.
  • the invention relates to a variety of thermal transfer foils that are used to transfer sharp images with specular metallic surfaces to articles having very rough surfaces. These foils can be used in both hot stamping and digital decorating techniques.
  • the thermal transfer foils include several layers having their composition optimized for different transfer temperatures or pressures, different types of images, or different types of surfaces.
  • a thermal transfer foil in another important aspect, includes a carrier film and several layers including at least one thermally activatable release coating, at least one lacquer layer adhered to the release coating, a specular metal layer adhered to lacquer layer, and at least one thermally activatable adhesive layer.
  • the adhesive layer expands under heat and pressure to fill voids in a substrate during thermal transfer of the lacquer, metal and adhesive layers thereby enabling the metal layer to retain substantially its specular property after the transfer.
  • the layers are selected for use in a digital decorating system.
  • the adhesive layer includes an adhesive substance and a microsphere-like puffing agent.
  • the adhesive substance includes two components, a first component providing brittleness to the adhesive layer and a second component providing ductility to the adhesive layer after thermal activation. The two components are provided in relative amounts according to a ratio optimized for different types of images.
  • the metal layer includes aluminum.
  • the microsphere-like puffing agent comprises particles of a selected size.
  • the microsphere- like puffing agent is selected to. expand at a selected temperature.
  • the microsphere-like puffing agent is selected to expand at a selected temperature and a selected pressure.
  • the substrate is one of the following materials: leather, vinyl and textile.
  • the lacquer layer is selected to protect the metal layer after thermal transfer.
  • the lacquer layer includes a pigment that alters light reflected from the metal layer to have an appearance of a metallic color.
  • the lacquer layer includes a pigment that alters light reflected from the metal layer to have an appearance of a selected color.
  • the carrier film has, on its side opposite to the release layer, a heat-resistive lubricating property.
  • the above-described thermal transfer foil is used to transfer an image to a rough substrate by delivering a selected amount of heat and pressure to a pattern of pixels that form the image.
  • This heat and pressure delivered to the foil thermally activates the release coating and the adhesive layer and causes expansion of the adhesive layer.
  • the expansion fills voids in the substrate while the metal layer substantially retains its specular property after the thermal transfer of the image.
  • the process of delivering the heat and pressure to the foil includes delivering heat to a thermal line of pixels by a thermal printhead, exerting a selected amount of pressure between the thermal line of pixels and the thermal transfer foil positioned on the surface, and producing relative movement between the thermal line of pixels and the transfer foil and the surface while controlling energy delivered to the pixels according to successive lines of the image.
  • FIG. 1 is a perspective view of a digital decorating system.
  • Fig. 2 is a diagrammatic side view of a thermal transfer system.
  • Fig. 3 is a perspective view of a printhead of the thermal transfer system.
  • Fig. 4 is a view of the bottom of the printhead taken on line 4-4 of Fig. 3.
  • Fig. 4A is a magnified view of a portion of Fig. Fig. 5 is a highly magnified, cross-sectional view of a thermal foil according to the present invention.
  • Fig. 5A is a highly magnified schematic view of a thermal transfer process.
  • Fig. 5B is a highly magnified view of a substrate and the thermal foil after thermal transfer.
  • Fig. 6 is a diagrammatic side view of the thermal transfer system including a bulk heater for heating the substrate or the thermal foil.
  • Figs. 6A and 6B are diagrammatic side views of the thermal transfer system, including a second printhead for preheating the substrate, and the thermal foil, respectively.
  • Figs. 7 and 7A are simplified perspective views of the thermal transfer system designed for preheating the substrate .
  • Fig. 8 is a magnified view of irregularities of an edge produced by a standard thermal transfer
  • Fig. 8A is a magnified view of a smoother edge produced by an "edge enhancement" algorithm according to the present invention.
  • Fig. 9 is a diagrammatic view of a circular image to be thermally transferred to a substrate.
  • Fig. 9A is a diagrammatic plan view of a uniform energy distribution for the thermal image transfer of the image of Fig. 9, and Fig. 9B is a. highly magnified view of a portion of Fig. 9A.
  • Figs. 9C and 9D are highly magnified views of the transferred image employing the uniform energy distribution of Fig. 9A and a "line enhancement" algorithm according to the present invention, respectively.
  • Fig. 10 is a diagrammatic view of pixels considered in an enhancement algorithm and a chart with different thermal transfer combinations considered by the algorithm.
  • Fig. 11 is a block diagram of the thermal transfer algorithm.
  • Fig. 12 is a block diagram of the overall organization of the digital decorating system.
  • a digital decorating system 10 includes a personal computer 12 interfaced with a thermal transfer system 14.
  • Computer 12 performs overall control over the digital decorating process and generates a selected image.
  • Thermal transfer system 14 is a compact, table top system for transferring the provided image to a selected surface of an article (for example, vinyl, leather, plastic, textile or paper) .
  • thermal transfer system 14 includes a microcontroller 16, a drive assembly 22, a thermal foil assembly 30, and a thermal printhead assembly 40.
  • Drive assembly 22 i.e., advancing mechanism
  • stage 24 constructed to move an article 26 before and during the image transfer process.
  • Drive assembly 22 receives signals 38 from microcontroller 16.
  • Thermal foil assembly 30 includes thermal foil 32 spooled on a supply roll 34 and a set of rollers 36 constructed to advance, foil 32 (together with article 26 being advanced by stage 24) at a selected rate determined by control signals 38.
  • Thermal printhead assembly 40 includes at least one printhead 42 pressed against article 26 by a force member 41 and responsive to control signals 44 from microcontroller 16.
  • Force member 41 is constructed to vary the pressure exerted by the printhead. The pressure is in the range of about 1 to 10 pounds per inch, and more preferably in the range of about 2 to 8 pounds per inch.
  • a preferred printhead assembly 40 currently uses about 5 pounds per inch of print line for most substrates 25.
  • printhead 42 is an edge type printhead that includes a set of electrical connectors 46, a heat sink 48, and a ceramic member 50. While the thermal printhead assembly is stationary during the thermal transfer process, it can be repositioned to a different location prior to the transfer process. The repositioning achieves easy access to different locations of the decorated items.
  • Electrical connectors 46 are connected to a plurality of energizable heater elements constructed and arranged to selectively heat each of a line of pixels on the surface of ceramic member 50.
  • the heater elements 52 are made of strip 53 of a resistive material deposited on the bottom surface of ceramic member 50, and connected to a plurality of leads 54 and a common ground terminal 56.
  • Microcontroller 16 provides control signals 44 to a current source (not shown) that applies energizing current, for instance to lead 54A. The current flows from 54A to ground terminal 56 through a portion of resistive strip 53, which forms one heating element 52A.
  • Ceramic member 50 also includes a relatively thin but hard layer of glass that covers strip 53 and the leads.
  • the heating elements heat the corresponding pixels (i.e., dots) on the surface of the glass layer, and the surface is in contact with thermal foil 32.
  • the temperature of a pixel depends on the amount of energy delivered to the corresponding heater element and the thermal history and instant printing condition of the printhead.
  • Thermal printhead assembly 40 may use different printheads having resolution of 200, 300, or 400 dots per inch.
  • Microcontroller 16 receives a selected image from computer 12 and generates a data matrix corresponding to the image area.
  • the data matrix includes an enhancement of the image by electronic means to improve its visual appearance and physical character after the thermal transfer to surface 25 of article 26.
  • the enhancement algorithm generates selected levels of energy delivered to each pixel at each position of stage 24, as opposed to application of the same energy condition to all pixels, as is frequently done, for example, in direct thermal printing.
  • the data matrix can be visualized as a three-dimensional matrix with two- dimensional spatial information, and the energy level data, generated by the enhancement algorithm, represented as the third dimension.
  • the enhancement algorithm is interactive, that is, capable of adjusting the individual levels of energy relative to the local shape of the image, the thermal history of the pixel, levels of energy applied to the neighboring pixels, the overall temperature of ceramic member 50 and heat sink 48, the morphology of surface 25, and the. type of material to be thermally transferred. Furthermore, in certain embodiments, the enhancement algorithm uses a set of sensors distributed on printhead 42 that provide further input data for a dynamic analysis of the energy conditions for determining energy levels to be applied to the pixels.
  • the enhancement capabilities of the system enable high quality images to be printed that can be compared to those produced by various hot stamping techniques that use pressure dies.
  • Digital decorating system 10 can operate in different modes to produce different types of images on surface 25.
  • the first mode is achieved by direct application of heat and pressure from the surface of ceramic member 50 to surface 25 of article 26.
  • printhead 42 applies to surface 25 pressure induced by force member 41 and heat selectively generated by the heater elements to thermally alter the material surface and thereby transfer the image.
  • This mode does not use thermal foil assembly 30.
  • the second image transfer mode employs thermal foil assembly 30 to thermally transfer material to surface 25 and thereby create the image.
  • Other modes employ multiple print heads without foils, or with one or multiple foils or ribbons .
  • An enhancement algorithm employed in a particular system is selected in accordance with the mode of transfer, the desired image quality and the general operating parameters such as type of foil and type of substrate involved.
  • stationary printhead 42 applies heat and pressure to foil 32 and surface 25, both of which move underneath printhead 42.
  • the enhancement algorithm controls the energy sequence delivered to each pixel of the image (and the pressure delivered by force member 41) .
  • Each pixel receives the energy from a current source or a voltage source.
  • each pixel receives constant current over three time intervals (called sub-stripes) while thermal foil 32 and substrate 25 move continuously at a low speed (2 mm/sec. to 25 mm/sec.)
  • foil 32 and substrate 25 can remain stationary while each pixel receives constant current or zero current over the three sub-stripes.
  • Each sub-stripe lasts about one millisecond and the current is either on or off during the interval.
  • foils 32 may include different thicknesses of the continuous metal layer that is thermally transferred to substrate 25 together with the lacquer and adhesive layers of the laminate.
  • the metal laminate tends to separate from (or peel off of) the thermally resistive carrier film in flakes or small sheets of material, whereas continuity of the deposited material is desired to achieve a specular effect. This significantly differs from the thermal transfer of particulate or liquid like material, such as the thermal ink.
  • the digital decorating system monitors and controls the overall temperature of printhead 42, which may include one or more temperature sensors .
  • a current source delivers current pulses to the tiny heater elements 52, which in turn convey heat to thermal foil 32 and ceramic member 50.
  • the decorating system may include a heat exchange unit that controls the overall temperature of printhead 42.
  • thermal foil 32 includes a thermally resistive carrier film 71, a lacquer layer 75, a thin metal layer 77, and a thermally activated adhesive layer 79, which includes resins and fillers mixed together with a puffing agent (layers are shown not scaled in size relative to each other) .
  • a release coating 73 made of, for example, synthetic wax.
  • Carrier film 71 itself may have lubricating properties or may be back- coated with a heat-resistive lubricant. The lubricant inhibits sticking and promotes the movement of printhead 42 pressing on thermal foil 32 (and article 26) at a relatively high pressure.
  • Fig. 5A shows a highly magnified schematic view of the thermal transfer process.
  • Thermal foil 32 and article 26 move together in direction 94 relative to stationary printhead 42.
  • the thermal line of printhead 42 delivers heat to thermal foil 32 and the heat, in turn, activates thermally sensitive release layer 73 and adhesive layer 79.
  • the applied heat melts (or at least softens) release layer 73A, which in turn releases layers 75, 77 and 79 from carrier film 71.
  • the heat and pressure activated the puffing agent present in adhesive layer 79.
  • a modified adhesive layer 79A fills voids and valleys located on surface 25 and bonds metal layer 77 to surface 25.
  • Adhesive layer 79 includes a puffing agent made of expandable microspheres and an adhesive compound.
  • microsphere is equivalent to "particle” since the microspheres can have different shapes including a somewhat disk-like shape.
  • the expandable microspheres and the adhesive components are selected to be brittle at the deposition temperature to provide relatively sharp breaks and clean edges of the deposited material.
  • the sharp breaks are important for achieving sharp images during the thermal transfer.
  • the edges depend also on the particle size of the microspheres.
  • the particle size is in the range of 10 to 100 microns and preferably 50 to 90 microns.
  • a substantially larger particle size tends to produce visual graininess in the transferred foil and thus degrade the image, although larger particles fill effectively the irregularities on surface 25, which can exceed 0.003 inch in depth.
  • the adhesive cannot be too brittle because the deposited metal layer will have many cracks and will look like a "shattered mirror" .
  • the deposited adhesive cannot be too ductile because the transferred layers will not break off easily.
  • thermal foils 32 with different adhesives and different puffing agents (i.e., microspheres) .
  • puffing agents i.e., microspheres
  • the first type are microspheres made of thermal foaming agents (e.g., SaranTM, ExpansolTM) that have a volatile hydrocarbon trapped in the polymer matrix.
  • the second type microspheres include a shell that encapsulates a thermal expansion substance (i.e., volatile organic liquids available over a range of boiling points below 150°C)
  • Adhesive layer 79 also may include resins, gums, such as shellac, and synthetics, such as acrylics, polyesters, epoxys, alkyds, and various copolymers.
  • microspheres expand at a range of temperatures which is lower than the usual plastic molding temperatures, for example, as low as about 70 °C.
  • Thermal foils 32 are also designed with the expansion temperature in mind. High expansion temperatures limit the speed of thermal transfer or require significant preheating.
  • the main criteria for the adhesive layer are a smooth, continuous surface of the transferred layers across areas of high roughness and high contrast of the deposited image .
  • Carrier film 71 is preferably polyethylene terephthalate polyester (mylar) .
  • carrier film 71 is polyimide, polyester, polycarbonate, triacetyl cellulose, nylon, cellophane and other plastic films. Depending upon the application the thickness of the film varies from as thin as 1/4 mil (0.00025 inch) to one mil (0.001) .
  • Carrier film 71 may be back-coated with a heat- resistive lubricant, such as sili.con, epoxy resin, fluorine resin, polyimide resin, phenol resin, polyester or vinyl ester resins or nitro cellulose.
  • Release layer 73 is usually a very thin layer sometimes approaching a mono-molecular layer of a release agent.
  • the release agents include natural waxes such as carnauba wax, oricurry wax, candle wax, or montan wax, synthetics, such as Fischer-Tropsch waxes, pertoleum waxes, such as paraffin wax microcrystalline wax, and other materials such as stearic acid.
  • Lacquer layer 75 includes colorants, such as dyes or transparent pigment dispersions. The particle size of these should be small enough that they do not scatter visible light. (The scattering would produce milkiness or whiteness in the film that is ordinarily not desired for decorating purposes.) To protect metal layer 77, lacquer layer 75 is relatively hard and durable.
  • Lacquer layer 75 is made of a thermoplastic, such as Acryloid A-10 (made by Rhom and Haas) mixed with cellulose nitrate.
  • lacquer layer 75 may be a relatively soft chlorinated rubber (Parlon by Hercules) .
  • the lacquer layer may also be one of a number of cross-linked coating materials, ranging from cellulose esters cured with melamine to UV cured urethane or epoxy acrylates.
  • lacquer layer 75 may include several layers to achieve intercoat adhesion and durability.
  • Metal layer 77 includes a thin layer of vacuum deposited metal, which only few nanometers thick.
  • Thermal foils 32 are prepared by depositing a very thin layer of a release agent on carrier film 71 and then depositing lacquer layer 75. Then a thin layer of aluminum is sputtered in vacuum (10 6 Torr) onto lacquer layer 75. Adhesive layer 79 is deposited onto metal layer 77 using a Gravure applicator (available from John Dusenbury) . Adhesive layer 79 is in the range of 0.3 mil to 1 mil about and preferably 0.75 mil. A "tie coat" may be used to bond the adhesive layer onto the aluminum layer. Since adhesive layer 79 is thicker than layers 73, 75 and 77 (carrier film 71 being the thickest), it must not have tensile strength in the plane of the carrier film.
  • adhesive layer 79 includes 5% to 30% (and more preferably 10% to 20%) of a puffing agent, 30% to 55% (and more preferably 40% to 50%) of an adhesive mixture, 30% to 40% of water to get optimal viscosity during application, 0.1% to 4% (and more preferably 1% to 4%) of a surfactant, and less than 1% of a defomer.
  • the defomer reduces or completely prevents foaming at the head of the applicator.
  • the surfactant such as SurafinalTM 104 (available from Air Products) or IgepalTM (available from Rhone Polenc) , wets the adhesive film being applied to the mylar film and prevents dry spots or beading.
  • the adhesive mixture includes a liquid emulsion polymer that provides brittleness to the adhesive layer and a PVC acrylic copolymer (or an ethylene vinyl chlorid emulsion) that provides ductility to the adhesive layer.
  • the relative ratio of these two adhesives can vary depending on the desired properties of the thermal foil, which can be customized for different types of images, different substrates and different decorating systems.
  • the preferred composition of the adhesive layer includes 15% of Expancel 820D, (available from Akzo-Nobel) , 15% Neocryl BT-44 (a liquid emulsion available from Zeneca) ; 30% Airflex 4530 (an ethylene vinyl chlorid emulsion available from Air Products) ;
  • thermal transfer system 10 employs a bulk heater 80 for preheating substrate surface 25 or thermal foil 32. Both surface 25 and thermal foil 32 have a relatively low heat capacity and thus, to preheat effectively, bulk heater 80 is located relatively close to the heater elements of printhead 42.
  • Microcontroller 16 sends control signals (84) to bulk heater 80 and, in preferred embodiments, receives back temperature signals from thermal sensors located on the heating surfaces.
  • bulk heater 80 heats its surface 81, which provides heat to surface 25.
  • One or more temperature sensors, embedded on surface 81 detect the temperature of surface 25 and provide a signal to microcontroller 16.
  • Microcontroller 16 receives the temperature signal and adjusts the power provided to bulk heater 80 in a feedback arrangement.
  • the temperature of surface 25 is selected to soften material 26 and make it more receptive to printing (for example, in the case of vinyl), or it is selected to preheat material 26 to reduce the time needed for thermal transfer at each dot.
  • the softening of heat-sensitive materials i.e., vinyl
  • bulk heater 80 heats its surface 82, which provides heat to thermal foil 32.
  • thermal transfer system 10 employs a second printhead 43, located in close proximity to printhead 42, for selectively preheating surface 25.
  • second printhead 43 preheats surface 25 only at the locations where printhead 42 subsequently transfers the metal foil to surface 25. The preheating improves adhesion of thermal foil 32.
  • the preheating also enables "differential" heating of thermal foil 32 by delivering additional heat from preheated surface 25 to the bottom layer of the foil.
  • the preheating temperature in certain preferred instances, is selected to be higher than the softening temperature and can even be selected to be so high as to alter the surface composition of surface 25 since any potential discoloration will be covered by the transferred foil. For example, heating the surface of vinyl above about 200°F renders the selectively heated areas more receptive to the thermal deposition. These areas do not appear different to the naked eye, but common foil adhesives are found to selectively adhere to such a latent heat image relative to areas untouched by the heat.
  • thermal transfer system 10 employs a second printhead 43A for selectively preheating thermal foil 32.
  • Printhead 43A can not only preheat thermal foil 32 but also thermally transfer an initial layer of material to surface 25.
  • the initial layer pretreats surface 25 and can include a puffing material that fills valleys in the surface.
  • printhead 42 thermally transfers the metal and lacquer layers with an additional adhesive layer to surface 25.
  • printheads 42 and 43A are arranged to transfer material from two separate thermal foils. The transferred images of the foils do not need to be identical, but, in certain advantageous arrangements, can be arranged and controlled to complement each other.
  • a substrate heater 84 includes a heat lamp 86 (for example, an infrared lamp) coupled to a planar light guide 87 (e.g., of quartz) constructed to deliver a line of the generated heat to surface 25.
  • Microcontroller 16 sends control signals 88 to a heater controller 90, which regulates power delivered to heat lamp 86.
  • a temperature sensor 92, or an array of them, located in thermal communication with substrate 25, measures the temperature of the substrate just before the substrate reaches the line of pixels at printhead 42. Temperature sensor 92 also provide feedback data (93) to controller 90.
  • This embodiment can use different temperature sensors., including infrared sensors.
  • a substrate heater 94 uniformly heats substrate 25 with hot air of a selected temperature.
  • Substrate heater 94 includes an air pump or fan 95 and a heater 96 connected to a nozzle device 97, which delivers jets of hot air to substrate 25.
  • the enhancement algorithm includes specific advantageous thermal transfer techniques, referred to as “line enhancement,” “edge enhancement,” “lacquer protection” and “trailing edge.”
  • the “edge enhancement” technique enables the generation of clearly defined edges in the thermally transferred pattern, while enabling the fill area to provide a uniform, desirable appearance.
  • microcontroller 16 "looks" for initial transfer pixels and generates higher energy levels for pixels that form an edge, especially the leading edge of the image.
  • the leading, peripheral pixels i.e., edge pixels
  • the temperature gradient enables the transferred material to separate from the material remaining on the foil in a well-defined manner relative to the heated pattern. This is particularly applicable to leading edges and side edges in a patterned area being progressively transferred.
  • microcontroller 16 also takes into account the temperature of ceramic member 50 and heat sink 48 and the temperature of surface 25. These temperatures may also be adjusted to create the optimal temperature gradient.
  • the temperature gradient enables a clean break and transfer of the lacquer, metal and adhesive layers.
  • Figs. 8 and 8A sketch the difference in the transferred image of line L, wherein the shaded areas 99 represent the layers laid down to form the image while the white areas 98 represent surface 25. As shown in Fig. 8, without the edge enhancement algorithm, the edge L tends to be irregular.
  • microcontroller 16 directs a much lower energy to the pixels (i.e., interior "fill” pixels), where the image is. also transferred.
  • the lower energy heats the pixel to a temperature wherein the thermal transfer still occurs due to the selected properties of the metal foil, because a lower energy level is sufficient to continue the peeling and transfer process.
  • the lower energy level decreases the generated heat, which prevents damage to the lacquer layer that can produce a tarnished appearance to the reflective decoration. This is the "lacquer protection" technique.
  • thermal printing i.e., thermal transfer of ink.
  • This enhancement algorithm is specific to thermal foils transferring metal.
  • the "line smoothing" routine in a novel way eliminates a stair-step appearance of lines or edges that lie diagonally to the direction of the thermal transfer motion. For example, if the image is a circular pattern, as shown in Fig. 9 (or any pattern with a line that lies at an acute angle to the direction of motion) , a uniform distribution of energy over the matrix at the transfer points of the edge will generate a stair-step pattern of thermally transferred material (see Fig. 9A) . This uniform application of energy and the thermally transferred material are shown in Figs. 9B and 9C, respectively.
  • a low level of energy is applied to a pixel lying outwardly of the edge pixel (i.e., a pixel not assigned as part of the computer generated image) so that a partial material transfer occurs in a corner region of that pixel and a smoother appearance, as suggested in Fig. 9D, is achieved.
  • the most effective angles for this techniques lie at about 45 degrees to the thermal transfer axis, while a beneficial range is generally between about 30 degrees and 60 degrees for fine art work.
  • Fig. 10 illustrates in a simple way a matrix employed for implementing the enhancement techniques with respect to assigning different energy levels to the individual pixels of an image. (As mentioned above, the algorithm also takes into account the substrate and foil temperatures, the overall temperature of the printhead, the pressure, and the type of the substrate, but theses will be discussed separately.) On the top, Fig. 10 shows the rows and columns of pixels being printed by printhead 42 in print direction 94.
  • the row “n” indicates the line of dots about to be transferred (or not transferred depending on the image)
  • the row “n-1” is a line that has been transferred in the preceding print stripe
  • "n-2" is a line that has been transferred in the stripe preceding "n-1.”
  • the algorithm has to assign an energy level to a pixel E.
  • the algorithm "looks” at the pattern around pixel E of the image to be transferred.
  • the chart in Fig. 10 indicates possible combinations of the transfer states for pixels A, B, C, and D, wherein "0” denotes no transfer, according to the computer- generated image, and "1" denotes material transfer.
  • microcontroller 16 executes the "lacquer protection" routine, which prevents thermal damage to the lacquer layer. Additionally, if there was material transfer at pixel B, but not at its neighboring pixels in rows "n-1,” (or there was material transfer at pixels A and B, but not at their neighboring pixels in rows “n-2" and "n-1") the algorithm "looks" for lines at an angle to the transfer direction. For example, if there is material transfer at pixels B and C, pixel E receives energy E 5 , which is about three-quarters of the energy of pixels B and C.
  • microcontroller 16 executes the "line smoothing" routine.
  • the "line smoothing" routine directs a small amount of energy to the corner pixel next to heated pixels B and C for partial transfer of material that removes the stairstep pattern, as described above.
  • microcontroller 16 directs a small amount of energy to pixel E for partial transfer.
  • the algorithm can also "look at” the next succeeding stripe. If there is material transfer at pixels E, but no transfer at pixel F (or pixels of the "n+1" stripe) , microcontroller 16 executes a "trailing edge" routine and pixel F receives no energy.
  • the "trailing edge" routine does not assign increased values of energy to the last transferred stripe, that is, there is no increased heating of the leading edge as executed by the "edge enhancement” routine.
  • the thermal gradient may be needed for some types of thermal foils. This is again due to the unique properties of the metal layer that tends to break off clean at the trailing edge.
  • a simplified version of the enhancement algorithm in general, achieves very good results by only "looking at" a partial image and considering just a few transfer stripes .
  • Fig. 11 shows diagrammatically the thermal transfer algorithm.
  • the computer provides image data (100) to a stripe generator 102, which analyzes each thermal line to be transferred and provides this to a sub-stripe generator 104.
  • sub- stripe generator 104 generates sub-stripe data (112) and the corresponding power (energy) control signals for a power controller 110.
  • Power controller 110 also receives print speed data 108 and foil & substrate data and delivers current signals for each sub-stripe to the heater elements of the printhead.
  • the printhead includes a temperature sensor that sends temperature data (116) to power controller 110.
  • Fig. 12 shows a block diagram of the overall organization of digital decorating system 10.
  • Microcontroller 16 runs the enhancement algorithms (126) and the system control algorithms (128) .
  • Microcontroller 16 receives image data 100, user parameters 120, system parameters 122 and thermal foil parameters 124.
  • User parameters 120 include information about the object and surface being decorated.
  • System parameters 122 includes manufacturer information the printhead rating, the heater ratings and other.
  • Thermal foil parameters 124 are parameters unique to the foil currently used.
  • Microcontroller 16 controls print speed 130, printhead force 134, printhead power 138, s.ubstrate heat 142 and foil heat 146 and can receive their actual values, measured by sensors 132, 136, 140, 144, and 148 in a feedback loop 150. //
  • BYTE AnalogFromHeadTemp (int temp): void ClearPrintHead (BOOL latch): void Co puteStrobeEnergy (void); int GetHeadHeatMax (void):
  • BYTE GetHeadNu ber void
  • int GetHeadOverTemp void
  • double GetMaxWatts void
  • int GetNPixels void
  • int GetResolution void
  • int Get ordsPerLine void
  • double HeadResistancePromAnalog BYTE data
  • int HeadTe pFromAnalog BYTE data
  • BOOL IsPrintDone void: void HIPrlnt (void): void SendStripe (void): void SetCo pensation (int comp); void SetOutyCycle (int n); double SetForce (int n);
  • BOOL SetupPrinting (int * pBM int * pLen. int xLoc. int yLoc): void StartPrinting (void):
  • head_info_t 1 head_info_t; static const head_info_t near neadlnfo [N_HEADTYPES+1] - ⁇ ( ,”N0 PRINTHEAD INSTALLED". -0. 0. 0. 0x0000.
  • stat-ic void near buildEdgeStripe void
  • stat-ic void near getNextStripe void
  • static void near setStrobeEnergy int ss
  • static void near shiftStripe WORD near * ⁇ Stripe
  • static void near startPCycleTimer double speed
  • temp is a printhead temperature value in degrees F
  • ARGUMENTS latch: TRUE- shift and latch data. FALSE" shift data only
  • PURPOSE Builds print energy rolloff table "rol loffTable” for upcoming print cycle.
  • look-up values are generated for the timer and mode words / / necessary to produce the desired micpostrobe duty cycle for
  • pulseCount (WORD) (PERI0D_C0UNT * ssMicroDuty): mode - 4; )
  • AFFECTS Shuts off microstrobes. kill stripe interrupts
  • outportb HEAD_STROBE_CTRL. 0; // disable strobes outportb (DDS_ICR. (DDSIcr &- -ENABLE_STRIPE_IRQ)) // disable stripe irq printing - FALSE: //reset "printing" flag
  • DDSIcr &- ⁇ ENABLE_STRIPE_IRQ // reset stripe irq enable bit outportb(DDS_ICR.
  • BOOL errStat - FALSE //error flag: none yet int oldBM - * pBM; //raster file numbers: original, shifted int newBM:
  • DDSIcr ENABLE_STRIPE_IRQ: //Enable stripe timer IRQ: "or” in irq enable bit outportb (DDS_ICR. DDSIcr): // set enable bit in port
  • /Vtrlg logic analyzer start computing edge stripe data outportb (LPT1, inportb (LPT1)
  • next_rshift //(data is inverted) next_rshift: asm lodsw //get a word from notCurrentStripe asm rcr ax. 1 //shift 1 bit right asm stosw //store shifted version in notLeftSt ⁇ pe asm loop next_rshift //loop till done
  • word ptr notRlghtStripe [bx] asm lodsw //get word from notCurrentStripe asm not ax //flip it to normal polarity asm and ax.
  • dx //AND it with mask bits in DX asm xor ax.
  • clearData //XOR it with "dots off" bits in clearData asm stosw //store it in edgestripe asm add bx. 2 //Increment offset to next mask asm loop next_edge //loop till done asm pop es //restore original contents of ES
  • PURPOSE Fetches a stripe of raster data from the print buffer Builds array normalSt ⁇ pe[] for shifting to head Builds arrays notPrevSt ⁇ peC] and notCurrentStr ⁇ pe[] for later use in computing edge enhancement stripe
  • AFFECTS updates print buffer pointer bufPtr updates arrays normalStripe[] , notPrevStripeU and notCurrentStripe[]
  • ⁇ WORD pulseCount //timer counter value for microstrobe on-t1me BYTE mode: //timer mode for microstrobe on-t1me WORD tHeadAverage; //average of recent head thermistor A/D readings 1nt i; //general -purpose counter
  • DIGITAL_IN //Set port address for reading waitShiftDone: asm in ax.
  • dx //read (slow, since it waits for ISA bus) asm and ax.
  • HEAD_SHIFT_DONE //is shift done signal hi yet asm jz waitShiftDone //loop if it ain't //endi f
  • Stripe timer (does not enable stripe IRQs)
  • duty cycle is rolled off by a constant amount per degree F, unaffected by the Print Energy setting
  • PROTOTYPE IN local ARGUMENTS: For SetConstantRolloff: new value for constantRolloff flag

Landscapes

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

Abstract

L'invention concerne une feuille (32) de transfert thermique comprenant un film support (71) et plusieurs couches comportant un enduit antiadhérent (73) à activation thermique, une couche de laque (75) collée à l'enduit antiadhérent (73), une couche métallique spéculaire (77) collée à la couche de laque (75), et une couche adhésive (79) à activation thermique. La couche adhésive (79) se dilate sous l'effet de la chaleur et de la pression pour combler les vides d'un substrat (26), au cours du transfert thermique de la couche de laque (75), de la couche métallique (77) et de la couche adhésive (79), la couche métallique (77) pouvant ainsi garder sensiblement sa propriété spéculaire après le transfert. On utilise la feuille de transfert thermique (32) pour transférer une image sur un substrat rugueux (26) par application de chaleur et de pression, en quantités déterminées, sur une configuration de pixels formant l'image. Cette chaleur et cette pression appliquées sur la feuille (32) activent thermiquement l'enduit antiadhérent (73) et la couche adhésive (79), et entraînent la dilatation de la couche adhésive (79), laquelle, à son tour, comble les vides du substrat (26), la couche métallique (77) gardant sensiblement sa propriété spéculaire après le transfert thermique de l'image.
PCT/US1998/001416 1997-01-28 1998-01-27 Feuilles thermiques pour l'application numerique de decorations WO1998032594A1 (fr)

Priority Applications (1)

Application Number Priority Date Filing Date Title
AU60411/98A AU6041198A (en) 1997-01-28 1998-01-27 Thermal foils for digital decorating

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US78957897A 1997-01-28 1997-01-28
US08/789,578 1997-01-28

Publications (1)

Publication Number Publication Date
WO1998032594A1 true WO1998032594A1 (fr) 1998-07-30

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PCT/US1998/001416 WO1998032594A1 (fr) 1997-01-28 1998-01-27 Feuilles thermiques pour l'application numerique de decorations

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AU (1) AU6041198A (fr)
WO (1) WO1998032594A1 (fr)

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US6493014B2 (en) * 2000-12-22 2002-12-10 Impress Systems Optical security device printing system
WO2004045868A1 (fr) * 2002-11-19 2004-06-03 Newhill Technologies, Llc Procede d'impression thermique numerique
WO2007049070A1 (fr) * 2005-10-24 2007-05-03 Peter John Hoggard Procédé et appareil pour une impression par sublimation
EP1970202A1 (fr) 2007-03-12 2008-09-17 Brother Kogyo Kabushiki Kaisha Bande à lettre, cassette de bande magnétique, traducteur imprimeur sur bande
CN108864978A (zh) * 2018-06-14 2018-11-23 浙江驰怀烫印科技有限公司 一种无苯类溶剂残留的大输液袋烫印色带及其制备方法

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4215170A (en) * 1978-02-28 1980-07-29 Eurographics Holding, N. V. Metallization process
US4902364A (en) * 1988-08-02 1990-02-20 Dennison Manufacturing Company Heat transfer decorations with patterned metallization

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4215170A (en) * 1978-02-28 1980-07-29 Eurographics Holding, N. V. Metallization process
US4902364A (en) * 1988-08-02 1990-02-20 Dennison Manufacturing Company Heat transfer decorations with patterned metallization

Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US6493014B2 (en) * 2000-12-22 2002-12-10 Impress Systems Optical security device printing system
WO2004045868A1 (fr) * 2002-11-19 2004-06-03 Newhill Technologies, Llc Procede d'impression thermique numerique
WO2007049070A1 (fr) * 2005-10-24 2007-05-03 Peter John Hoggard Procédé et appareil pour une impression par sublimation
EP1970202A1 (fr) 2007-03-12 2008-09-17 Brother Kogyo Kabushiki Kaisha Bande à lettre, cassette de bande magnétique, traducteur imprimeur sur bande
CN108864978A (zh) * 2018-06-14 2018-11-23 浙江驰怀烫印科技有限公司 一种无苯类溶剂残留的大输液袋烫印色带及其制备方法
CN108864978B (zh) * 2018-06-14 2021-02-02 浙江驰怀烫印科技股份有限公司 一种无苯类溶剂残留的大输液袋烫印色带及其制备方法

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