EP0153693B1 - Printing device - Google Patents

Abstract

A printing device for the production of tamper-proof printing on print receiving material comprises a printing head which carries individually controllable heating elements and a color transmitting embossing foil.

Description

The invention relates to the use of an embossing film for printing on plastic surfaces, in particular plastic cards.

For counterfeit-proof personalization of identity cards, authorization cards, such as check cards and the like, made of plastic, it is known to use printing devices with positive embossing types, with which the corresponding personal alphanumeric data are embossed on the cards, so that they protrude from the front of the card during embossing or as embossing when embossing into the front of the card.

In the former case, after the embossing, the raised data above is generally colored with an embossing film. The structure and function of such an embossing film are explained in more detail below. In the latter case, an ink ribbon for coloring the data can be fed to the printing device during embossing.

In the known type of personalization described, only the letter and number types available in the printing device can be printed. As is well known, the speed when printing with embossing types is limited. The machines required for this are mechanically very complex, prone to repair and expensive.

Furthermore, it is not possible to provide a magnetic tape provided with magnetically readable data in the area of the card intended for embossing, which tape is frequently present today with identity and authorization cards. Such a magnetic tape would namely be destroyed when the data was embossed. The same applies to cards with integrated microcircuits (IC's), since these generally extend at least over a large part of the card area. Cards provided with ICs can therefore not be printed at all using the known printing processes described.

It is also known to use identity and authorization cards with a paper layer between the plastic carrier layer and a protective film and to discolor the paper layer with a program-controlled laser beam. Not only can predefined letters and numbers be generated with this, it is also possible to vary the size of the letters and numbers or to record Chinese or Arabic characters or images. However, the devices using a laser beam are extremely expensive. In addition, they should also not be suitable for the production of cards provided with an IC.

So-called thermal printers have been developed to enable the data to be reproduced quickly in modern data processing and data transmission. These have a printhead which is brought into contact with a paper coated with thermosensitive ink. Thermal printers have the advantage that they can not only be used to print predetermined letters and numbers, but also, for example, images, letters and numbers of different sizes and fonts as well as Chinese and Arabic characters.

The known thermal printers usually work according to the principle of a dot printer, in which a plurality of dots put together result in the characters to be printed. For this purpose, the print head has a large number of heating elements which are arranged in a row and print these points. The thermosensitive printing paper migrates at right angles to the row of heating elements. The heating elements are controlled individually, so that the color of the thermosensitive paper changes only on the controlled heating elements. In this way, the desired pattern is printed on the paper. Such a thermal print head is described, for example, in the brochure “Introduction to Thermal Print Head Technology from Rohm.

However, these thermal printers are not suitable for personalizing identity and authorization cards. The thermosensitive paper is neither UV nor chemical resistant, so that it changes color over time. Pressing on a protective layer is also not possible because of the elevated temperature required for this. Furthermore, the thermosensitive layer with visible color can scarcely be printed, which, however, means that it cannot be changed, e.g. B. Non-personal data is often requested.

Thermal printers with an ink ribbon are known from DE-A-2 315 226 and EP-A-0 098 033. Such an ink ribbon consists of a carrier film and a layer of a meltable mass with a dye and is intended for printing on paper. In order to print plastic surfaces with a thermal print head using such ink ribbons, it is known to provide the ink layer with a sublimable dye, the detached color point on the plastic surface being irradiated with an infrared source in order to allow it to penetrate into the plastic surface (brochure «A new method of non-impact printing •, page 10, from Armor SA, Nantes, France). The arrangement is relatively complex due to the special ink ribbon and the infrared source and, moreover, only allows a relatively slow printing.

So-called stamping foils are also known. These are composite films made from a carrier film, e.g. B. a polyester film with a generally wax-containing separating layer, a color layer adjoining the separating layer and a thermoreactive adhesive layer adjoining the colored layer, wherein between separating layer and Color layer usually a protective coating layer is also provided.

The stamping foils are pressed on with hot stamping presses (so-called hot stamping) with a pressure of several 100 kp or even several tons, as for example in the brochure «Stamping Foil Program •, last page, from the company Leonhard Kurz, Fürth, from May 1978. The adhesive layer is activated so that the composite film is separated from the separating layer, the carrier film being removed and the color layer optionally provided with a protective coating layer adhering to the material in question. A hot stamping press for stamping foils with an electromagnetically actuatable stamp is known from CH-A-458 411. Such stamping foils are used for a wide variety of purposes. Thanks to their excellent adhesion, they are used e.g. B. used for coating motor vehicle bumpers or bathtubs. They are also used for printing on a wide variety of materials, such as paper, leather, wood, etc. The printing is carried out using an elevated pressure stamp that can be heated to the activation temperature of the adhesive as a printing cliché.

From DE-A-1 449 637 it is known to arrange a plurality of printing stamps corresponding to such printing blocks, which can be moved selectively in order to obtain the high pressure required when using an embossing film, in order to apply letters to any carrier. However, the known stamp arrangement has essentially the same disadvantages as the embossing devices described at the outset, i. H. the printing speed is low, the printing device required for this is mechanically complex, prone to repair and expensive, and the number of characters is limited by the number of printing stamps.

The invention has for its object to print plastic surfaces quickly and with largely variable characters by a simply constructed printing arrangement. This object is inventively achieved in that an embossing foil as color transmitting material for a device for printing Kunststoffo- about ^f lächen-type thermal printing head is used with an individually controllable heating elements, which is pressed with a usual for such printing heads, relatively low pressure to the stamping film.

According to the invention, a commercially available thermal print head can be used. The costs of the printing device used according to the invention are thereby many times lower than in the known devices described above for tamper-proof printing on plastic surfaces, in particular plastic identity or authorization cards. According to the invention, the high printing speed of the thermal print head is also used, i. H. for example, check cards can be personalized in a few seconds.

Commercially available stamping foils can also be successfully used as stamping foils, for example the stamping foils from Leonhard Kurz, Fürth. It can be metal foils, in which z. B. serves a polyester film and is used as metal evaporated high-purity aluminum. Other suitable metal foils are e.g. B. real gold foils, chrome foils or bronze foils. Color foils, imitation gold foils etc. are also suitable.

The fact that in view of the high pressures required when pressing embossing foils with embossing presses, it is possible to obtain a satisfactory impression on a plastic surface with an embossing foil with a thermal printhead which only allows a relatively moderate amount of pressure to be regarded as surprising.

The reason for this unforeseeable circumstance is likely to be that, despite the short activation time, the heating elements are heated to a relatively high temperature, which causes an explosive expansion of the carrier film at the relevant points. As a result, an additional pressure component is exerted on the detaching color point and an intimate connection of the same is brought about with the plastic surface.

In order to ensure good temperature transfer from the heating elements of the thermal print head to the embossing film or the adhesive layer, a flat support for the material to be printed is required.

For the same reason, it is necessary for the material to be printed to have the same thickness, at least transversely to the transport direction. The surface roughness of the material to be printed should also be less than 10 f.lm. Otherwise, the exposure time and / or pressure of the printhead must be increased.

Since the heating elements of the thermal print head can be individually controlled by EDP, any printing units can be produced with the device according to the invention, that is, in addition to alphanumeric data such. B. also pictures or barcodes. The color of the embossing foil and thus the printing unit can also be chosen as desired.

As mentioned, the stamping foils on the market have such a high degree of adhesion that they are used today even for highly stressed components such as motor vehicle bumpers. This high level of liability also comes into its own according to the invention and has a correspondingly high level of security against forgery of the printing units produced according to the invention.

Furthermore, according to the invention, identity or authorization cards provided with a magnetic tape or an IC can also be printed in a forgery-proof manner over the full area of the card.

• Figur 1 einen Schnitt durch eine handelsübliche Prägefolie in stark vergrößerter Wiedergabe;
• Figur 2 schematisch eine Ausführungsform einer erfindungsgemäß verwendbaren Druckvorrichtung ;
• Figur 3 eine Ansicht des Thermodruckkopfes der Vorrichtung von unten in stark vergrößerter, schematischer Wiedergabe ; und
• Figur 4 eine nach der Erfindung mit alphanumerischen Daten bedruckte Karte.

The invention is explained in more detail below with reference to the accompanying drawings. In it show:

• Figure 1 shows a section through a standard embossing foil in greatly enlarged reproduction;
• FIG. 2 schematically shows an embodiment of a printing device that can be used according to the invention;
• Figure 3 is a bottom view of the thermal print head of the device in a greatly enlarged, schematic representation; and
• Figure 4 is a card printed with alphanumeric data according to the invention.

According to Figure 1, a commercially available stamping film is formed by a composite film, which consists of a carrier layer 1, for. B. made of polyethylene, a separating layer 2, z. B. of wax or a wax-like material, a lacquer layer 3, a color layer 4 and an adhesive layer 5 which can be thermally activated, for example at a temperature of approximately 110 ° C.

Instead of polyethylene, the carrier layer can also consist of polyester. It usually has a thickness of 5 to 50 microns, preferably 12 to 25 microns. The separating layer 2 is made very thin as a release layer. The lacquer layer 3 has a thickness of 0.5 to 3 µm, preferably 1.25-1.50 µm. The color layer 4 can, for. B. by a metallization with a thickness of 0.01 to 0.10 J.Lm, preferably 0.02 to 0.05 microns. The adhesive layer 5 is usually applied in several layers and has a thickness of 0.5 to 5 μm, preferably 1.5 to 3 μm.

The lacquer layer 3 imparts the desired color. In the case of a colorless lacquer layer 3 and a subsequent metallization or color layer 4 of pure aluminum, a silver color is produced. Is the paint layer 3 z. B. colored yellow transparent, a golden color is generated. If the color layer 4 is formed by a pigment dye, it has a thickness of a few μm. The structure of the stamping foil is e.g. B. also described in the brochure “Embossing on plastics from Leonhard Kurz, Fürth.

If a z. B. pressed to 120 ° C pressing tool on the carrier layer 1, the adhesive layer 5 is activated, whereby it connects the color layer 4 including the protective lacquer layer 3 with the base, while the carrier film 1 detaches while softening the wax layer 2.

According to Figure 2, the printing device has, for example, a conveyor belt 8 rotating around rollers 6 and 7, on which the material to be printed 9, for. B. credit cards, the thermal print head 10 is supplied. If they have a magnetizable carrier (e.g. a magnetic tape), the desired data can be magnetically recorded on the credit cards beforehand.

Furthermore, two pressure rollers 11 and 12 are provided, which press the material 9 to be printed firmly against the conveyor belt 8, as well as a counter-pressure roller 13, which is arranged directly under the print head 10 and the material 9 to be printed on the conveyor belt 8 when printing against the bottom of the thermal print head 10 holds.

The embossing film 14 is unwound from an unwinding roller 15 and fed to the material 9 to be printed and the print head 10 via a deflection roller 16. The roller 6, which drives the conveyor belt 8, is in turn driven by a stepper motor 17.

The stepper motor 17 is designed so that it z. B. each one millimeter transport path of the material to be printed 9 carries out three steps.

According to FIG. 3, the print head 10 has on its underside a row of heating elements 18 which extends across the entire printing width and runs transversely to the transport direction of the material 9. The heating elements 18 can be resistors which are arranged on a ceramic substrate 19. The distance between adjacent heating elements is, for example, 0.3 mm, measured from the center of the heating element 18 to the center of the heating element 18.

The heating elements 18 are connected to microchips 22 via conductor tracks 21 vapor-deposited on the ceramic substrate 19. The microchips 22 have a thickness that is greater than the board of the heating elements 18 via the ceramic substrate 19, which is approximately 0.3 to 0.4 mm. I.e. a flat, rigid or difficult to bend material, in particular a plastic card, cannot be brought into contact with the heating elements 18 if the microchips 22 and the heating elements 18 are applied in one plane of the ceramic substrate 19.

In order to make contact between the heating elements 18 and a card which is not flexible or difficult to bend, the thermal printhead 10 is preferably designed such that the heating elements 18 form the most protruding areas on the underside of the thermal printhead 10, i. H. project further from the ceramic substrate 19 than the microchips 22. This can be achieved, for example, by arranging the microchips 22 in a recess in the ceramic substrate 19 or by arranging the microchips on a surface of the ceramic substrate 19 which is in line with the plane of the Underside of the thermal print head, on which the heating elements 18 are located, encloses an angle of preferably less than 90 ° in order to prevent sharp edges for the conductor tracks 21.

The heating elements 18 reach the temperature required for activating the adhesive layer 5, e.g. B. 120 ° C at a current in the range of 1 mA in a few ms.

The heating elements 18 can be controlled with an EDP system. The printhead 10 is about an axis running transversely to the transport direction or parallel to the row of heating elements 18, as indicated by the arrow 20 in FIG too pivotable. In this way, the print head is pressed against the material 9 to be printed between two transport steps and is relieved during the transport of the material 9. The print head can then be relieved leads if the heating elements 18 are not controlled. The control of the device with which the print head 10 is pressed against the material 9 to be printed is also carried out by means of the computer system.

The printing device shown in Figures 2 and 3 can write in two coordinates. The x coordinate extends in the transport direction of the material to be printed, the y coordinate at right angles to it. The data for the x coordinate, i.e. the time grid, consist of one bit. The data for the y coordinate, on the basis of which the EDP system controls the heating elements 18 to be activated, consist of several bits. The control and clocking of the transport of the material to be printed takes place with the x-bit in such a way that after setting the x-bit the motor 17 transports the material to be printed 9 past the print head, for example by 0.3 mm. As mentioned, the device which presses the print head against the material 9 is actuated in the interval between two successive transport steps. At the same time, the heating elements 18 to be activated are activated and thereby heated due to the y-bit. Each controlled heating element 18 leads to a point-like activation of the adhesive layer 5 and thus to a fixed point of the ink layer 4. The size of the distance between adjacent heating elements 18 and the size of the transport steps in the x direction determine the screen density of the printing unit produced with the device according to the invention .

Since the print head 10 presses the stamping film 14 against the material 9 to be printed, no separate transport device for the stamping film 14 needs to be provided in the device.

The printhead 10 is preheated by means of an electrical resistance heater to a constant temperature of 110 ° C., that is to 10 ° C. below the activation temperature of the adhesive layer 5 of the film 14. This reduces the heating-up time of the heating element 18 and enables faster and more uniform printing.

FIG. 4 shows a plastic card that has been provided with alphanumeric data using the device.

Furthermore, instead of the stationary print head 10 shown in FIG. 2, the device can also be designed such that the print head 10 is moved step by step over the material to be printed, which is useful, for example, when printing large objects. For example, this embodiment of the device is applicable to the printing of skis, e.g. B. depending on variable data, such as the manufacturing number, to apply a bar code.

Claims (1)

1. Use of an embossing foil as colour transmitting material for a device for printing on plastic surfaces with a thermal printing head having heating elements which are selectively controllable, the thermal printing head being pressed onto the embossing foil with a relatively low pressure usual for such printing heads.

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