EP0628431A1 - Multilayer record carrier and process for marking a multilayer record carrier - Google Patents

Abstract

For the multi-coloured marking of identification cards and the like, the multilayer identification card receives an outer coloured layer (3) of a first colour and an inner coloured layer (2) of a second colour. While the outer coloured layer absorbs practically no laser-beam light used for marking, the second inner coloured layer absorbs the laser light. By this means, in the marking process, the material of the second coloured layer is degraded thermally, that is to say evaporated, sublimated or subjected to a chemical or physical reaction, with the consequence that the first layer is blasted away in particles by means of the formation of pressure. By this means, the second coloured layer becomes visible. Instead of the second coloured layer, provision can also be made of a transparent lacquer layer having corresponding properties, in order, as an example, to expose a multi-coloured security printed image under this transparent lacquer layer. <IMAGE>

Description

The invention relates to a record carrier, in particular an identification card, and a method for producing such a record carrier.

In a special case, the record carriers in question here are identity cards, e.g. B. credit cards, credit cards, authorization cards or business cards and the like. Identity cards of this type have a format prescribed by standards and generally have a multilayer structure. On one side of the card are e.g. B. by printing or general photographic information, e.g. B. the name of a credit institution, an organization or the like, and optionally a security print image (guilloche pattern), which is placed on the card surface or inside the card. In addition, the user-related information such as the name of the card holder, customer number, account number, card number or the like is introduced.

For the color inscription of multi-layer ID cards, it has already been proposed (DE-PS 30 48 733) to provide differently colored layer areas one above the other, the absorption behavior and the evaporation points of the individual color layers being selected such that selective control of the ink layer is achieved by appropriate control of the laser beam intensity. The outermost layer of paint is therefore removed at lower laser beam intensities than the deeper layers of paint.

The problem with these record carriers is that due to tolerances of the layer thicknesses and short distances between the evaporation / sublimation points, several irradiation runs are often necessary in order to achieve the complete removal of the individual layers, which is absolutely necessary for a high-contrast display. With this labeling method, several removal processes are therefore required per removed layer, which represents a certain obstacle to the mass production of such recording media. The selection of the color layers also has a restrictive effect on the laser beam intensity with regard to the absorption behavior of the color concerned and the evaporation points of the different color layers.

The invention has for its object to provide a recording medium according to the preamble of claim 1, in which the removal of a layer of color by laser beam can be carried out easily and quickly. In addition, the invention is intended to provide a method for labeling a multilayer recording medium.

The solution to these problems is specified in the independent patent claims, with preferred developments of the invention being specified in the subclaims.

While in the prior art the upper first layer reacts to the impinging laser beam and is removed in order to expose the underlying second layer and to make its color visible, in the recording medium according to the invention the first layer is penetrated by the laser beam without having any significant effect . It is only in the second layer below that the material is thermally broken down by the penetrating laser beam. In the present context, the term "thermally degraded" means evaporation, ie a transition from the solid to the liquid and then into the gaseous phase, sublimation, ie a transition from the solid to the gaseous phase, chemical decomposition with gas formation or chemical reaction as z. B. arises when igniting thermite particles.

The thermal degradation of the material of the second layer at the point hit by the laser beam causes an abrupt increase in the internal pressure of the card material at the point in question, with the result that the relatively thin layer area above it is unable to resist the high pressure and, as it were, is blown off becomes. In a labeling process, in the course of which a laser beam is guided over the card surface in accordance with the information to be recorded, small areas of the second layer are thermally degraded continuously or pixel by pixel, and accordingly small areas of the outer first color layer are blasted away. In these areas, the second color layer is then freed from the overlying color layer and the information recorded in this way is visible in the color contrast of these two color layers.

The thickness and degradation behavior of the second color layer, which contrasts with the outer color layer, should be matched to the intensity of the laser beam in such a way that it is only partially removed. After the labeling process, the second color layer is thus exposed in the areas hit by the laser beam, and its color is clearly recognizable.

For the second layer of paint in particular, which is to be thermally degraded, there is a relatively large range of colors available which are admixed with pigments to impart the desired properties. The second color layer is sensitized by such pigments. It can e.g. B. soot or aluminum bronze particles, depending on whether it is a dark or a light color. The pigments are chosen with regard to their body color and / or concentration in such a way that they leave the intrinsic color of the color layer practically unaffected, ie the pigments used for sensitization themselves should not have any influence on the Have coloring of this layer. Almost any color type (acrylic, PVC colors, etc.) can thus be modified in any color for the lettering according to the invention and used in the modified form.

The pigments in the color layer act as absorption centers, which absorb the incident laser light and thereby release thermal energy, through which, for example, color is evaporated, with the result that, for. B. by this vapor pressure the material of the first layer is blasted off at the point hit by the laser beam.

In a further embodiment which is advantageous for many areas of application, the second layer, i. H. the thermally degradable layer, made of a transparent lacquer layer, which is embedded between two contrasting color layers. Like the aforementioned layer of paint, this lacquer layer is also sensitized by admixing pigments that absorb the laser light. Suitable pigments for this purpose are pigments with a light body color (e.g. aluminum bronze particles) or those which, even at low concentrations (e.g. in the per mille range), show sufficient effects under the influence of laser beams, but only have an insignificant effect on the transparency of the lacquer layer. If the record carrier is then labeled, the underlying layer of color can be seen through the at least partially removed transparent lacquer layer. The underlying color layer can e.g. B. a multicolor print or be formed as a single-color layer.

The color layers are preferably printing ink layers applied using the screen printing process or correspondingly colored, superimposed, thin plastic films.

The effect of the inscription on the recording media according to the invention is particularly interesting when the first, i.e. H. the outer color layer is a halftone print (or is a first color layer provided with halftone print), in particular a black gradient grid that changes in intensity from place to place and is applied to a differently colored second layer. Due to the thermally degradable second layer, the raster print is removed locally, so that the labeled characters z. B. differ only in color from the background. Such gradient grids are known per se. He comes with an ID card e.g. B. as a shadow that darkens from the lower edge of the ID card to the upper edge.

In particular when using a transparent lacquer layer as a thermally degradable layer, there is the possibility of providing a multicolored print under the lacquer layer, because the lacquer layer leaves the print in the lower layer completely intact. This makes it possible to achieve particularly effective patterns which also provide effective protection against counterfeiting, particularly when the multicolored print is a guilloche pattern.

Interesting visual effects can be achieved if a relief structure z. B. arises from gravure printing or a relief structure is embossed, which continues over the layers above. These relief-like surfaces can be labeled in the same way as smooth surfaces according to the inventive method. The security against forgery of laser engraving (lettering) is particularly important here, since such structures cannot be labeled in this simple form using mechanical engraving, which is known per se.

If the laser beam is aimed at this relief-shaped surface at an acute angle, the recorded information changes its appearance depending on the viewing angle and, in extreme cases, is only visible from the side from which the recording was made.

A guilloche print, which is applied to the carrier material and thereby extends into the second, thermally degradable layer to such an extent that it is exposed after laser irradiation, increases the security against forgery or security against forgery. After the removal of the first color layer, the guilloche print in the second color layer, which has a contrast to this color layer, is clearly visible. Here too, counterfeiting or counterfeiting by means of a stylus are made more difficult and the special security of laser engraving becomes clear.

The marking of a record carrier with a laser beam, which forms an acute angle to the record carrier, is particularly effective if the record carrier is provided with an embossed structure in the form of, for example, a corrugated iron structure, half cylinders, hemispheres, lens elements or the like. This is because the laser beam can first be guided over the embossed structure in a certain direction at a certain angle with respect to the plane of the recording medium. Only the "slopes" of this embossed structure facing the laser beam are labeled. If you then rotate the recording medium in its plane and then guide the laser beam over the embossed structure at the same or a different acute angle, the "slopes" of the embossed structure are labeled with the laser beam once from one side and once from the other side, correspondingly the label direction is a different picture when viewed from the corresponding direction if the different sides of the embossing structure are designed accordingly. It is therefore possible to generate different images for different directions of view on opaque surfaces, these images also being able to be viewed separately from one another depending on the viewing angle, or complementing one another with a vertical viewing angle.

Fig. 1

eine Skizze, die den Stand der Technik veranschaulicht,

Fig. 2

eine teilweise Querschnittsansicht eines Aufzeichnungsträgers, in welchem mittels Laserstrahl eine Beschriftung eingebracht wird,

Fig. 3 - 6

weitere Ausführungsformen eines Aufzeichnungsträgers im Querschnitt,

Fig. 7

einen unter einem spitzen Winkel beschrifteten Aufzeichnungsträger,

Fig. 8

eine Skizze, die das Abtasten eines mit einer Prägestruktur versehenen Aufzeichnungsträgers mit einem Laserstrahl unter einem spitzen Winkel veranschaulicht und

Fig. 9

eine Draufsicht auf eine Ausweiskarte mit verschiedenen Reliefstrukturen.

Exemplary embodiments of the invention are explained in more detail below with reference to the drawing. Show it:

Fig. 1

a sketch illustrating the state of the art,

Fig. 2

FIG. 2 shows a partial cross-sectional view of a recording medium in which a label is introduced by means of a laser beam,

3 - 6

further embodiments of a record carrier in cross section,

Fig. 7

a record carrier labeled at an acute angle,

Fig. 8

a sketch illustrating the scanning of a recording medium provided with an embossed structure with a laser beam at an acute angle and

Fig. 9

a plan view of an identification card with different relief structures.

Fig. 1 shows in cross section part of a known ID card (DE-OS 30 48 735), which is here z. B. can be a check card. Two color layers B and C are applied to a base layer A. For the sake of clarity, the map layers are shown in this and in the following figures in a form that is not to scale. These two layers of paint differ in their color and in their absorption properties and evaporation points. Since the layer thicknesses are not always exactly uniform at different points, but fluctuate within certain limits and the evaporation points are usually relatively close together, the dosage of the laser beam intensity is a problem for the exposure of the desired color layer. The layers are therefore preferably removed step by step in a plurality of irradiation processes with a correspondingly low intensity in order to expose one layer in a targeted manner and not to cause an incomplete or complete removal together with further layers in an undesired manner. For example, several, e.g. B. two, labeling steps (D, E) to remove an area in the layer C performed. Then, if necessary, further labeling steps (F, G) for removing a location of layer B are carried out. In this way, multi-colored representations are generated in several process steps.

FIG. 2 shows a view similar to FIG. 1, but of an identification card constructed according to the invention. On the outside of a base layer 1 there are a first color layer 3 which is essentially transparent to laser light and a second color layer 2 which absorbs laser light and is provided with pigments. The colors of the color layers 2 and 3 are different.

Color layers that do not or hardly absorb laser light are known. Dyes which absorb the laser light in the manner mentioned are obtained according to the invention by adding practically any dyes to pigments which, depending on the brightness of the dye, have dark or light body colors. Soot particles are used for dark colors, for example aluminum bronze particles for light colors. This ensures that the color retains its color regardless of the added pigments.

In FIG. 2, laser beam recording is carried out at a point 4 at a right angle with respect to the plane of the identity card. The laser beam L penetrates the first color layer 3 in a region 5. In this region 5, the energy of the laser beam is practically not absorbed by the material of the first color layer 3.

In the second color layer 2, however, part of the laser beam energy is absorbed by the pigments contained in this color layer 2. There is a degradation (evaporation, sublimation, etc.) of the material of the second ink layer 2 in the area 6. The pressure that arises during this degradation blows away the overlying first ink layer 3, but this blasting away is relatively narrowly limited to the point 4 which is hit by the laser beam L. The color layer 2, in particular its thickness, degradation properties etc. and the recording parameters such as laser beam intensity etc. are matched to one another in such a way that this color layer is only partially removed and is thus visible in contrast with the first color layer.

This second color layer 2 can - as shown in Fig. 3 - on a z. B. Guilloche print image 7 can be applied. The guilloche lines are then, depending on how pronounced the craters 8 generated by the laser beam are more or less exposed and are therefore visible.

Fig. 4 shows a further embodiment of an identification card in a sectional view. On the outside of a base layer 11 there is a first color layer 13, under which there is a transparent lacquer layer 14 and a further color layer 12. The color layers 13 and 12 have different colors. In the transparent lacquer layer, which consists for example of a transparent synthetic resin, there are pigments in low concentration that absorb the laser light. As shown in Fig. 3, a laser beam penetrates the upper color layer 13 and degrades the affected area in the transparent lacquer layer 14 with the result that the upper color layer 13 is blown away in this area and thus through the hole created and through the exposed transparent lacquer layer 14 through which the underlying color layer 12 is visible. In addition to this base layer 11, there may be further layers of the identity card which are not of interest here, e.g. B. a layer on the back of the card. The same applies to the card shown in FIG. 2.

FIG. 5 shows an exemplary embodiment which is similar to the exemplary embodiment according to FIG. 2, with the exception that the first color layer 23 is formed here by a so-called halftone print which only gives the second color layer 22 a preferably continuously changing tint. The raster print 23 consists of a fine black print, which lays a kind of shadow on the color layer 22, which z. B. continuously darkened from the lower edge of the ID card to the upper edge. The removal of individual areas 24 of the raster print 23 and parts of the color layer 22, which has been sensitized to the laser beam inscription by adding pigment, exposes the latter completely. The labeled Areas differ from the unlabeled areas only in the different color tones.

In the embodiment according to FIG. 6, there are embossments 34 running into a base layer 31 into the plane of the drawing, on the outside there is a continuous first color layer 33 which hardly absorbs laser light, and below the first color layer 33 there is a second color layer 32 (this can also be transparent) that the laser light absorbs. Individual areas of the color layers 32 and 33 are removed by scanning with a laser beam. The second color layer 32 can also only be removed to a certain depth so that its color is visible or replaced by a transparent lacquer layer sensitized in the form described above by admixing pigments. In the latter case, the top of the base layer 31 or the embossments 34 is then visible in the labeled areas.

In Fig. 6, the laser beam strikes the plane of the identity card at approximately a right angle. However, the laser beam can also be directed at the identification card at an acute angle, as is shown by the arrows P in FIG. 6. The structure of the card according to FIG. 6 is in principle similar to the structure according to FIG. 5. However, due to the oblique irradiation with laser light, only the inclined surfaces 35 of the embossments 34 facing the light source are "labeled", while the inclined surfaces 36 facing away from the light source are hardly or at all not be affected by laser light.

The acute angle between the incident laser beam and the identity card plane means that the outer color layer 33 is visible from one side (from the left in FIG. 7), while the other is visible Side (right in Fig. 7) mainly the areas exposed by the inscription with laser light are visible.

8 shows another illustration of a layer 41 provided with an embossed structure 42 (alternating field shape). B. a transparent, thermally degradable lacquer layer 45 and then an outer color layer 46. Now the recording medium is scanned in accordance with the direction of the arrow at an acute angle by a laser beam, so that, for. B. line-shaped the base 41 is exposed on the inclined surfaces 35 of the embossed structure 42 shown in FIG. 7 and facing the laser. With a z. B. line-shaped recording process, only sections 44 a b, c are exposed in a scanning line 44 due to shadowing by the embossed structures. The result is a direction-dependent image that cannot be reproduced in this form in terms of copying technology or photography.

If the recording medium is subsequently rotated through 180 ° or the laser beam is deflected accordingly, a further labeling process can follow, in which another image, possibly in a different color, is introduced onto the opposite inclined surfaces 36 of the embossed structure by exposing deeper layers (not shown).

As shown in FIG. 9, such optically varying images can be applied over a large area to an identification card 50 by providing the entire card with, for example, individual embossing lines 51 which run through the card and essentially follow a predetermined direction. However, only a partial area of the card can be provided with an embossed structure 52, the embossed structures, as shown in FIG. 8, directly against one another adjacent in continuous form. This area can e.g. B. can be labeled from different directions with different image motifs, which in turn can only be seen separately from the respective recording direction and can complement one another when viewed vertically.

The exemplary embodiments described last significantly increase the security against forgery of the identity card. Engraving of this type, which due to the inventive measure of removing partial areas of an upper color layer as extremely sharp-edged labeling areas on an uneven surface, cannot be achieved with simple means by mechanical engraving means.

In principle, the creation of such "images with directional effect" by labeling relief structures at an acute angle of incidence even with conventional card structures, such as. As shown in Fig. 1, possible, but the cards can also have only a simple opaque, structured surface or surface labeling, which discolors under the action of a laser beam. The information is not generated by removing layers and exposing deeper, color-contrasting layers, but by directly changing the color of an outer plastic or color layer.

Claims (2)

Record carrier, in particular identification card, with an outer layer or coating that changes its color or its contrast to the environment visibly under the action of a laser beam, characterized in that at least this layer has a relief structure, preferably in the form of half-cylinder elements, hemispherical elements, structures similar to corrugated iron or The like, and that information is recorded by means of a laser beam at an acute angle to the plane of the recording medium in the area of this relief structure, the inclined surfaces of the relief structure facing the recording direction being labeled differently from the inclined surfaces facing away from it, so that the information recorded in this way depends on the respective viewing angle - show different manifestations. Method for labeling a record carrier, in particular an identification card, with an outer layer or coating which changes its color or its contrast to the environment visibly under the action of a laser beam, characterized in that at least in this layer a relief structure, preferably in the form of half-cylinder elements , Hemispherical elements, structures similar to corrugated iron and the like, and that information is recorded by means of a laser beam at an acute angle to the recording medium plane in the region of this relief structure, the inclined surfaces of the relief structure facing the recording direction being labeled differently from the inclined surfaces facing away from them, so that the information recorded in this way - depending on the respective viewing angle - show different manifestations.

Images