DE102022000012A1 - Method for producing a security feature, security feature for a card-shaped data carrier and card-shaped data carrier - Google Patents

Abstract

The invention relates to a method for producing a security feature (20) for a card-shaped data carrier (10), which has the following steps: - providing (100) at least one first material (30) in a main extruder of an extrusion device (40); (101) of at least one second material (32) in an auxiliary extruder of the extrusion device (40), the first material (30) and the second material (32) having different thermoplastic behavior;- heating (102) the first material (30 ) to form a first melt (31) and the second material (32) to form a second melt (33);- co-extrusion (103) of the first melt (31) and the second melt (33) to form a multilayer film (34), in the area of a die outlet gap (41a) of the extrusion device (40), in particular after the first and second melts (31, 33) emerge from the die outlet gap (41a), a pressure (P) is applied to the extruded multilayer film (34) is applied (104), whereby a stress distribution pattern (21) is formed as a security feature (20) on the multilayer film (34). The invention also relates to a security feature (20) and a card-shaped data carrier (10).

Description

The invention relates to a method for producing a security feature for a card-shaped data carrier, a security feature for a card-shaped data carrier and a card-shaped data carrier with a security feature.

A large number of card-shaped data carriers, for example smart cards, chip cards, in particular with RFID technology (Radio Frequency Identification), integrated circuit cards, dual interface cards or identification cards, are known from the prior art. In particular, the use of smart cards, such as credit cards or payment cards, has become established for carrying out financial transactions. Card-shaped data carriers such as documents of value, for example passport and ID documents, ID cards and the like are being used to an increasing extent in public areas, but also in the internal area.

Optical security elements on the card-shaped data carriers are known and should generally increase security against forgery. In view of the decreasing price and the consequent increasing availability of advanced reproduction equipment, there is a fear that counterfeit reproductions of card-shaped data carriers will be produced. Depending on the criminals' level of expertise, some reproductions could fool not only the general public who use the card-shaped data carriers, but also validation machines and readers used to authenticate users and authenticate transactions.

The object of the present invention is to improve the production of security features for card-shaped data carriers in order to prevent illegal reproduction.

This object is achieved by a method for producing a security feature, a security feature for a card-shaped data carrier and a card-shaped data carrier according to the independent patent claims. Configurations and developments of the invention are specified in the dependent claims. Features and details that are described in connection with the method according to the invention for producing a security feature for a card-shaped data carrier also apply in connection with the security feature according to the invention for a card-shaped data carrier and the card-shaped data carrier with a security feature and vice versa, so that with regard to the disclosure can always be mutually referred to the individual aspects of the invention.

Within the scope of the application, the invention can preferably be used for smart cards, in particular for credit cards and payment cards. However, it can also be used for other RFID devices, such as key cards, access cards, tokens, wearables or security IDs.

• - Bereitstellen von wenigstens einem ersten Material in einem Hauptextruder einer Extrusionsvorrichtung;
• - Bereitstellen von wenigstens einem zweiten Material in einem Nebenextruder der Extrusionsvorrichtung, wobei das erste Material und das zweite Material ein unterschiedliches thermoplastisches Verhalten aufweisen;
• - Erhitzen des ersten Materials zur Ausbildung einer ersten Schmelze und des zweiten Materials zur Ausbildung einer zweiten Schmelze;
• - Ko-Extrusion der ersten Schmelze und der zweiten Schmelze zur Ausbildung einer mehrschichtigen Folie, wobei im Bereich eines Düsenaustrittsspaltes der Extrusionsvorrichtung, insbesondere nach dem Austreten der ersten und der zweiten Schmelze aus dem Düsenaustrittsspalt, ein Druck auf die extrudierte mehrschichtige Folie ausgeübt wird, wodurch ein Spannungsverteilungsmuster als Sicherheitsmerkmal an der mehrschichtigen Folie ausgebildet wird.

According to one aspect of the invention, a method for producing a security feature for a card-shaped data carrier is provided, which has the following steps:

• - Providing at least one first material in a main extruder of an extrusion device;
• - Providing at least one second material in a secondary extruder of the extrusion device, wherein the first material and the second material have different thermoplastic behavior;
• - heating the first material to form a first melt and the second material to form a second melt;
• - Co-extrusion of the first melt and the second melt to form a multi-layer film, pressure being exerted on the extruded multi-layer film in the area of a die outlet gap of the extrusion device, in particular after the first and second melt emerges from the die outlet gap, as a result a stress distribution pattern is formed as a security feature on the multilayer film.

Within the scope of the application, an extrusion device is used for co-extrusion, which has a main extruder and a secondary extruder. For example, it can be provided that the first material and the second material are provided as granules for the main extruder and the secondary extruder. In general, any number of materials can be provided for the extrusion device, in particular three or four or more materials. Furthermore, it is conceivable that, in general, several materials are provided for the main extruder and several materials for the secondary extruder. With co-extrusion, different materials can generally be conveyed through the same extrusion device. In the extrusion device, for example, the first material in the main extruder and the second material in the secondary extruder can be heated or melted to form a respective melt. The first melt and the second Melts are then pressed out of a die outlet gap of a die of the extrusion device to form the multilayer film. In this case, the die outlet gap represents a shaping opening, with the melts being combined and formed as layers of the multi-layer film. The melts usually harden or solidify after exiting the die outlet gap due to cooling in the layers of the multilayer film. A thickness profile of the multi-layer film can be defined or variably adjusted by means of the nozzle outlet gap. In the context of the application, it is generally conceivable that the multi-layer film is made up of at least two or else three or four or more layers. In this case, for example, a layer of the first melt can be provided as an intermediate layer between two adjacent layers of the second melt as external layers.

The application provides for the first material and the second material to have different thermoplastic behavior. In the context of the application, the thermoplastic behavior refers to the plastic deformability of a material under the application of heat or by heating. For example, the materials can differ in terms of their melt viscosity and, in particular, in terms of their glass transition temperatures.

Compared to lamination, the use of co-extrusion has the advantage that the entire material is completely melted and is available for the layered composite of the multi-layer film, with lamination under pressure and heat only material at the interfaces of the layers for the composite is available. Consequently, the durability of the laminate of the multi-layer film can be enhanced by the co-extrusion. Subsequent to the production of the multi-layer film, the card-shaped data carrier can also be produced by lamination of the multi-layer film, for example as an overlay film with additional core films.

Furthermore, the application provides that in the area of a die outlet gap of the extrusion device, in particular after the first and the second melt emerges from the die outlet gap, pressure is exerted on the extruded multilayer film, as a result of which a stress distribution pattern is formed as a security feature on the multilayer film becomes. In other words, an external pressure is applied to the multilayer film, creating tension on or in at least one layer or all layers of the multilayer film. Depending on the pressure applied, the stress in the layers of the film can vary and form a stress distribution pattern. This stress distribution pattern can be visualized using stress optics. With stress optics, the stress distribution in transparent layers or foils can be examined by using polarized light. The basis for this is the property of many optically isotropic materials to become birefringent under mechanical stress. As a result, the plane of polarization of the incident light is rotated or elliptically or circularly polarized light is produced. This can be made visible with a polarization filter, which allows conclusions to be drawn about the distribution and size of the mechanical stress at all points in the layers.

The invention thus has the advantage that the stress distribution pattern on or in the multi-layer film represents an additional security feature which significantly increases the counterfeit security of a card-shaped data carrier with such a security feature. In particular, the stress distribution pattern cannot be seen with the naked eye without using a polarizing filter. However, the voltage distribution pattern can be visualized or detected with the polarization filter. This has the advantage that the stress distribution pattern as a security feature cannot be reproduced by making a photocopy of the card-shaped data carrier or by scanning and printing, even if the copy or print is of the highest quality. Furthermore, as a security feature, the voltage distribution pattern enables the card-shaped data carrier to be authenticated simply by applying a polarization filter. Consequently, an illegal reproduction of the card-shaped data carrier can be prevented and the authenticity of the card-shaped data carrier can be guaranteed by means of the security feature.

In a particularly preferred embodiment, it can be provided that due to the different thermoplastic behavior after the first and second melts emerge from the die outlet gap, the first melt solidifies before the second melt and the stress distribution pattern is formed in the first melt. In particular, the pressure is exerted on the extruded multilayer film immediately after the melts emerge from the die outlet gap. Since, for example, the first melt solidifies earlier than the second melt, a stress can be generated in the first melt by exerting or introducing pressure. In particular, this allows the stress distribution pattern to be formed in the first melt.

It can preferably be provided that the first melt has a higher glass transition temperature than the second melt, in particular 140°C, and the second melt has a lower glass transition temperature, in particular 70°C, in relation to the first melt. The glass transition temperature or, to put it another way, the softening temperature, generally describes the temperature at which a plastic exhibits the greatest change in deformability without reaching the melt temperature. This so-called glass transition consequently separates the brittle, energy-elastic area below from the soft, entropy-elastic area above Area or rubber-elastic area. In other words, a material whose glass transition temperature is 70°C may have a rubbery state at a higher temperature, such as 80°C, and a solid or solidified state at a lower temperature, such as 60°C. It is preferably provided within the scope of the application that the first melt or the first material has a significantly different glass transition temperature than the second melt or the second material. In other words, the difference in the glass transition temperatures of the first melt and the second melt is very large. In the example given, the difference in the glass transition temperatures is the difference between 140°C and 70°C and is therefore 70°C. In other words, the glass transition temperatures of the first melt and the second melt are very far apart. This means, for example, that the first melt and the second melt or, to put it another way, the first material and the second material exhibit significantly different thermoplastic behavior. Thus, for example, the first melt can solidify earlier than the second melt when it exits the nozzle exit gap, since the second melt can be in the rubber-elastic or meltable state for a longer time due to the lower glass transition temperature when it exits the nozzle exit gap.

It can advantageously be provided that a ratio of the glass transition temperature of the second melt and the glass transition temperature of the first melt is at least 20% and at most 70%, in particular 50%. In the given example of a glass transition temperature of 140°C for the first melt and a glass transition temperature of 70°C for the second melt, the ratio would be 50%. It can thus preferably be ensured that the first melt and the second melt or the first material and the second material exhibit significantly different thermoplastic behavior. This different thermoplastic behavior in turn guarantees the efficient formation of the stress distribution pattern as a security feature for the card-shaped data carrier.

Provision can particularly preferably be made for the first material to be formed by at least one first polymer and the second material to be formed by at least one second polymer. By way of example, it can be provided that the first material is formed by polycarbonate, it being possible for polycarbonate to have a glass transition temperature of approximately 140°C. Furthermore, it can be provided, for example, that the second material is formed by polyethylene terephthalate (PETG), where PETG can have a glass transition temperature of approximately 70°C.

It can preferably be provided that the pressure on the extruded multilayer film is realized by structuring a roll surface of at least one calender roll adjacent to the die outlet gap. In particular, it is provided that the multilayer film exiting or extruded from the die outlet gap can be conveyed further via at least one adjacent calender roll. In other words, the calender roll serves to convey the extruded multi-layer film. More preferably, several calender rolls or a calender roll arrangement can be provided. The calender roller can in particular be set into a rotational movement and is designed to be electrically driven, for example. For example, the structuring of the roll surface of the calender roll can be formed by at least one structural element. In particular, a large number of structural elements are provided on the roller surface. The structural elements can vary, for example, in their length and/or height and/or width, or they can all be of the same design. The structural element or structural elements can be formed, for example, by at least one projection and/or at least one recess. For example, a large number of projections and/or recesses can be formed on the roller surface. Any geometric shape can be provided for the projection or the recess. The projections and/or the recesses form the structuring of the roller surface or represent a variation in the height of the roller surface. Depressions, indentations, edges, teeth, gaps, millings or the like can generally also be provided. In particular, pressure can be exerted on the conveyed multi-layer film by means of the structural elements or generally the structuring of the roller surface. In other words, by means of the structuring of the roll surface, a tension in the multilayer term film can be formed and a stress distribution pattern can be generated.

As an alternative or in addition, it can be provided that the pressure on the extruded multi-layer film is realized by an uneven setting of a thickness profile of the extruded multi-layer film. The thickness profile of the multilayer film can preferably be adjusted by adjusting or varying the size or, to put it another way, the height of the die outlet gap. For example, the size or height of the nozzle outlet gap can be regulated or controlled automatically. It can also be provided that the size of the nozzle outlet gap is varied along a width of the nozzle outlet gap. It is preferably provided that the die outlet gap is arranged between a first die lip and a second die lip of the die of the extrusion device. To set the size or height of the nozzle outlet gap, a large number of adjusting elements, in particular adjusting bolts, can be arranged on the first nozzle lip, for example, which can each be controlled electrically by a controller, for example. These adjusting elements can, for example, be mechanically coupled to the nozzle lip in such a way that the respective adjusting element can exert mechanical pressure or mechanical traction on a position of the nozzle lip, as a result of which the nozzle lip is deformed at the corresponding position, in particular enlarged or reduced. Consequently, the size of the die outlet gap at the corresponding position can also be increased or decreased and the thickness profile of the multilayer film can thus be varied. In particular, this can produce an uneven setting of the thickness profile. In other words, a stress can thereby be formed in the multi-layer film and a stress distribution pattern can be generated.

Provision can preferably be made for the size of the nozzle outlet gap to be set variably.

In a particularly preferred embodiment, it can be provided that the stress distribution pattern is designed as a logo or as a window. A rectangular window can preferably be formed as a stress distribution pattern on the multilayer film by appropriate structuring of the roller surface. For this purpose, a corresponding rectangular structural element can be provided on the roller surface, for example. In general, flat stress distribution patterns can be realized by structuring the roll surface. Certain logos or even words or letters or numbers can also be displayed in this way, for example. In other words, any geometric design can be formed as a stress distribution pattern. Provision can also be made for an area with increased stress and an area with reduced stress to be formed at least partially on the multi-layer film. For example, such film areas with different voltages can display colors from light to dark or in a specific color range and can be visualized using the polarization filter. In particular, different colors can also be generated by means of a specific setting of the voltage distribution.

Overall, it can be said that by combining materials with different thermoplastic behavior for the co-extrusion and applying pressure to the extruded multilayer film, a stress distribution pattern can be generated as a security feature on or in the multilayer film, which can also be used after a subsequent Lamination to a card-shaped data carrier can be visualized in a simple manner using a polarization filter. It should be emphasized in particular that the stress distribution pattern is present in the card-shaped data carrier despite the subsequent lamination. In other words, the stresses generated according to the invention and thus the security feature are retained even during and after a subsequent lamination. This is possible because the second material has, for example, a lower glass transition temperature than the first material and consequently can also be laminated below the glass transition range of the first material.

According to a second aspect of the invention, a security feature for a card-shaped data carrier is provided, which is produced by the method according to one of the preceding embodiments. The same advantages and modifications as previously described apply. This includes in particular the multi-layer film with the stress distribution pattern, which can be used for a card-shaped data carrier, for example as an overlay film.

According to a third aspect of the invention, a card-shaped data carrier, in particular a smart card, is provided, having a card body on or in which a security feature according to one of the preceding embodiments is arranged. The same advantages and modifications as previously described apply. For example, the security feature can be arranged on the card body in the form of a multilayer overlay film with a stress distribution pattern.

• 1: eine schematische Ansicht für ein Verfahren zum Herstellen eines Sicherheitsmerkmals für einen kartenförmigen Datenträger;
• 2: eine prinzipielle Darstellung einer Herstellung einer mehrschichtigen Folie mit einem Spannungsverteilungsmuster als Sicherheitsmerkmal;
• 3: eine schematische Ansicht eines kartenförmigen Datenträgers mit einem Sicherheitsmerkmal;
• 4: eine schematische Ansicht des kartenförmigen Datenträgers nach 3 mit dem durch einen Polarisationsfilter visualisierten Sicherheitsmerkmal; und
• 5 eine schematische Ansicht einer mehrschichtigen Folie für einen kartenförmigen Datenträger mit einer Polarisationsfilteranordnung.

The present invention is described below by way of example within the scope of embodiments with reference to the attached figures. It goes without saying that individual features of the embodiments can be freely combined with one another, insofar as this makes technical sense, without departing from the scope of the present invention. Elements with the same function and mode of operation are provided with the same reference symbols in the figures. The figures below show schematically:

• 1 1: a schematic view of a method for producing a security feature for a card-shaped data carrier;
• 2 : a basic representation of a production of a multi-layer film with a stress distribution pattern as a security feature;
• 3 1: a schematic view of a card-shaped data carrier with a security feature;
• 4 : a schematic view of the card-shaped data carrier 3 with the security feature visualized through a polarization filter; and
• 5 a schematic view of a multilayer film for a card-shaped data carrier with a polarization filter arrangement.

1 shows a schematic view of a method for producing a security feature for a card-shaped data carrier, not shown. The card-shaped data carrier is designed, for example, as a smart card, in particular as a credit card or payment card. Further details on the procedure are available with regard to 2 described.

The method has the following steps as an example: In a first method step 100, a first material is provided in a main extruder of an extrusion device. In a second method step 101, a second material is provided in an auxiliary extruder of the extrusion device. The first material and the second material exhibit different thermoplastic behavior. For example, the materials can differ in terms of their melt viscosity and, in particular, in terms of their glass transition temperatures.

In a third method step 102, the first material is heated to form a first melt and the second material is heated to form a second melt. In other words, the first material and the second material are converted into a meltable state.

In a fourth method step 103, the first melt and the second melt are co-extruded to form a multi-layer film. In a fifth method step 104, in particular, pressure is exerted on the extruded multilayer film in the area of a die outlet gap of the extrusion device, in particular after the first and the second melt emerges from the die outlet gap. Due to the different thermoplastic behavior and the application of pressure, a stress distribution pattern can be formed as a security feature on the multilayer film, for example.

This has the advantage that the stress distribution pattern on or in the multi-layer film represents an additional security feature, which significantly increases the counterfeit security of a card-shaped data carrier with such a security feature. In particular, the stress distribution pattern cannot be seen with the naked eye without using a polarizing filter. However, the stress distribution pattern can be visualized or detected with a polarization filter. Consequently, an illegal reproduction of the card-shaped data carrier can be prevented and the authenticity of the card-shaped data carrier can be guaranteed by means of the security feature.

The order of the steps of the method according to the invention is not necessarily limited to the order described.

2 shows a basic representation of a production of a multi-layer film 34 with a stress distribution pattern as a security feature. The multilayer film 34 can be used, for example, as an overlay film for a card-shaped data carrier, such as a smart card, preferably a credit card. The multilayer film 34 is exemplified by co-extrusion using a method according to FIG 1 manufactured.

Here, an extrusion device 40 is provided, which has a main extruder, not shown, and an auxiliary extruder, not shown. For example, it can be provided that the first material 30 and the second material 32 are provided as granules for the main extruder and the secondary extruder. In general, different materials can be conveyed through the same extrusion device 40 in the case of co-extrusion. In the extrusion device 40, for example, the first material 30 in the main extruder and the second material 32 in the secondary extruder can be heated or melted to form a respective melt 31, 33. The The first melt 31 and the second melt 33 are then pressed out of a nozzle outlet gap 41a of a nozzle 41 of the extrusion device 40 . The nozzle outlet gap 41a here represents a shaping opening, with the melts 31, 33 being combined and formed as layers of the multilayer film 34. For example, the first melt 31 forms a central layer which is arranged between two layers of the second melt 33 .

The melts 31, 33 usually harden or solidify after exiting the nozzle exit gap 41a due to cooling in the layers of the multilayer film 34. Because of the different thermoplastic behavior after the first and second melts 31, 33 emerge from the nozzle outlet gap 41a, the first melt 31 can, for example, solidify before the second melt 33 in terms of time. By way of example, provision can be made for the first material 30 to be formed by polycarbonate, with polycarbonate being able to have a glass transition temperature of approximately 140°C. Furthermore, provision can be made, for example, for the second material 32 to be formed by PETG, with PETG being able to have a glass transition temperature of approximately 70°C. Due to the large difference in the glass transition temperatures, the melts 31, 33 therefore have significantly different thermoplastic behavior.

By means of the nozzle outlet gap 41a, a thickness profile of the multilayer film 34 can be defined or variably adjusted, for example. The size of the nozzle outlet gap 41a can be regulated or set, for example, by means of adjusting elements, as a result of which the thickness profile of the multilayer film 34 can be varied.

In particular, after the first and second melts 31, 33 emerge from the die outlet gap 41a, a pressure P is exerted on the extruded multilayer film 34, as a result of which a stress distribution pattern is formed on the multilayer film 34 as a security feature. The pressure P is preferably exerted immediately after the melts 31, 33 emerge from the nozzle outlet gap 41a, so that the melts 31, 33 have not yet completely solidified and the stress distribution pattern can be formed. This stress distribution pattern can be made visible by means of the stress optics through a polarization filter. For example, the pressure P on the extruded multi-layer film 34 is realized by structuring a respective roll surface 51 of two calender rolls 50 adjacent to the die outlet gap 41a. In particular, the multi-layer film 34 is conveyed between the two calender rolls 50 and transported further. The direction in which the pressure is exerted by the calender rolls 50 on the multilayer film 34 is illustrated by means of the arrow. For example, the structuring of the roll surfaces 51 of the two calender rolls 50 can have a number of structural elements, such as projections or recesses.

As an alternative or in addition, it can be provided that the pressure on the extruded multi-layer film 34 is realized by an uneven adjustment of a thickness profile of the extruded multi-layer film 34 .

3 shows a card-shaped data carrier 10, which is designed, for example, as a smart card, in particular as a dual-interface card. The card-shaped data carrier 10 has a rectangular card body 11 with a surface 11a. The surface 11a is formed by a multi-layer film 34. FIG. This multilayer film 34 is according to a method according to 1 and 2 educated. The card body 11 also has an arrangement area 12 for accommodating a chip module, the chip module being arranged in the arrangement area 12 of the card body 11 . The arrangement area 12 is formed, for example, by a cutout or a cavity in the card body 11, in which the chip module can be stored in a protected manner, in particular glued in place.

The chip module has a chip, not shown, a contact structure 13 for contact-based data communication with an external reading device, and an antenna, not shown, for contactless data communication with the external reading device. In particular, the chip module is thus designed as an RFID module, for example.

A security feature 20 according to the invention is arranged on the card body 11 . In particular, the security feature 20 is formed on the multi-layer film 34 which forms the surface 11a of the card body 11 . By way of example, the security feature 20 is produced according to a method which is described in 1 and 2 is described. The security feature 20 is formed by a planar window 22 having a stress distribution pattern 21 . The stress distribution pattern 21 is generated in particular due to the different thermoplastic behavior of the first and second melts 31, 33 and the pressure exerted on the multilayer film 34.

In 3 is the stress distribution pattern 21 not visible to the naked eye and appears only as a planar window 22. However, the stress distribution pattern 21 can by means of the Span optics or made visible with a polarization filter. The visualized stress distribution pattern 21 is shown in FIG 4 shown.

4 thus shows a schematic view of the card-shaped data carrier 10 3 with the security feature 20 visualized by a polarization filter as a stress distribution pattern 21. With the polarization filter, it is possible to draw conclusions about the distribution and magnitude of the mechanical stress within the window 22. For example, on the left side within the window 22 is an area of high mechanical stress which is represented by the dark gray shading. Furthermore, an area of low stress is formed on the right side within the window 22, which is represented by the light gray shading.

Certain logos or else words or letters or numbers can also generally be represented as a voltage distribution pattern 21 . In other words, any geometric design can be formed as a stress distribution pattern 21 .

Consequently, the stress distribution pattern 21 on the multi-layer film 34 represents an additional security feature 20 which increases the counterfeit security of the card-shaped data carrier 10 . In particular, the stress distribution pattern 21 cannot be seen with the naked eye without using a polarizing filter. However, the stress distribution pattern 21 can be visualized or detected with the polarization filter. This has the advantage that the stress distribution pattern 21 as a security feature 20 cannot be reproduced by making a photocopy of the card-shaped data carrier 10 or by scanning and printing, even if the copy or the print is of the highest quality.

5 shows a schematic view of a multi-layer film 34 for a card-shaped data carrier 10 with a polarization filter arrangement 60. The multi-layer film 34 is according to FIG 3 formed and has the stress distribution pattern 21, not shown for clarity. As in terms of 1 and 2 described, the solidified first melt 31 is arranged as an intermediate layer between a layer of the solidified second melt 33 arranged above and below. The multilayer film 34 is placed between the polarizing filter arrangement 60 to visualize the stress distribution pattern. In particular, the multi-layer film 34 is arranged between a first polarization filter 61 and a second polarization filter 62 .

By way of example, it is provided that light falls in the direction of the arrow from below via the second polarization filter 62 onto the multi-layer film 34 . A user who looks at the multilayer film 34 from above through the first polarization filter 61 by means of the schematically indicated eye A, for example, can recognize the stress distribution pattern, as shown in FIG 4 was illustrated. Consequently, the authenticity of the multi-layer film 34 or of the card-shaped data carrier 10 with the multi-layer film 34 can be verified by means of the polarization filter arrangement 60 through the visualized stress distribution pattern.

Reference List

10

card-shaped data carrier

11

card body

11a

surface

12

layout area

13

contact structure

20

security feature

21

stress distribution pattern

22

Window

30

first material

31

first melt

32

second material

33

second melt

34

multilayer foil

40

extrusion device

41

jet

41a

nozzle exit gap

50

calender roll

51

roller surface

60

polarization filter arrangement

61

first polarizing filter

62

second polarizing filter

A

Eye

P

Print

100

first step in the process

101

second process step

102

third step

103

fourth step

104

fifth step

Claims (11)

Method for producing a security feature (20) for a card-shaped data carrier (10), which has the following steps: - Providing (100) of at least one first material (30) in a main extruder of an extrusion device (40); - Providing (101) at least one second material (32) in a secondary extruder of the extrusion device (40), wherein the first material (30) and the second material (32) have a different thermoplastic behavior; - heating (102) the first material (30) to form a first melt (31) and the second material (32) to form a second melt (33); - Co-extrusion (103) of the first melt (31) and the second melt (§3) to form a multilayer film (34), wherein in the area of a nozzle exit gap (41a) of the extrusion device (40), in particular after the exit of the first and the second melt (31, 33) from the die exit gap (41a), a pressure (P) is exerted (104) on the extruded multilayer film (34), whereby a stress distribution pattern (21) as a security feature (20) on the multilayer film (34) is formed. procedure after claim 1 , characterized in that due to the different thermoplastic behavior after the emergence of the first and the second melt (31, 33) from the nozzle outlet gap (41a), the first melt (31) solidifies before the second melt (33) in terms of time and the stress distribution pattern ( 21) is formed in the first melt (31). Method according to one of the preceding claims, characterized in that the first melt (31) has a higher glass transition temperature than the second melt (33), in particular 140°C, and the second melt (33) has a higher glass transition temperature than the first melt ( 31) has a lower glass transition temperature, in particular 70°C. Method according to one of the preceding claims, characterized in that a ratio of the glass transition temperature of the second melt (33) and the glass transition temperature of the first melt (31) is at least 20% and at most 70%, in particular 50%. Method according to one of the preceding claims, characterized in that the first material (30) is formed by at least one first polymer and the second material (32) by at least one second polymer. Method according to one of the preceding claims, characterized in that the pressure (P) on the extruded multi-layer film (34) is realized by structuring a roll surface (51) of at least one calender roll (50) adjacent to the die outlet gap (41a). Method according to one of the preceding claims, characterized in that the pressure (P) on the extruded multi-layer film (34) is realized by non-uniform adjustment of a thickness profile of the extruded multi-layer film (34). Method according to one of the preceding claims, characterized in that a variable setting of a size of the nozzle outlet gap (41a) takes place. Method according to one of the preceding claims, characterized in that the stress distribution pattern (21) is designed as a logo or as a window (22). Security feature (20) for a card-shaped data carrier (10), which by the method according to one of Claims 1 until 9 is made. Card-shaped data carrier (10), in particular a smart card, having a card body (11) on or in which a security feature (20). claim 10 is arranged.

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