SECURITY ELEMENT, SECURITY DOCUMENT AND METHOD FOR PRODUCING A SECURITY DOCUMENT

Description

[0001] The present invention relates to a security element for use in a security document. The invention also relates to a security document and a method for producing a security document.

[0002] To increase the counterfeit protection of security documents, especially valuable documents, various features and methods are used to make forgery or alteration difficult or impossible. A security document typically consists of several layers, preferably bonded together by lamination. The data to be incorporated for personalizing the document is embedded within the material under a preferably transparent top layer to protect it from manipulation. This can be achieved by laser personalization of the otherwise finished data carrier. Another method involves applying a preferably transparent top layer to the data carrier after personalization.

[0003] A valuable or security document can be defaced by removing the top layer and, after manipulating the underlying data, applying a new top layer. Holograms can be used to protect the document from tampering, as described, among others, in publications WO 2017 109 119 A1, DE 10 2007 042 386 A1, and EP 2 738 624 B1. For this purpose, a special holographic film is exposed accordingly and applied to the data carrier. Furthermore, the surface of a security document can be microstructured, which makes any manipulation of the top layer detectable. Another possibility is disclosed in publication EP 1 970 211 A1. In this case, the document is marked with a laser on its narrow side edges to create an optical connection between the layers. This is also described in publications WO 98 / 19869 and...DE 697 23 283 T2 introduces a security feature in which information is introduced into multiple layers of the document by perforating the data carrier.

[0004] EP 3 552 837 A1 describes a security document with a security element that has a structure comprising structural elements with dimensions of less than 200 µm. These structural elements can be introduced using ultrashort laser pulses in the microsecond and femtosecond range, resulting in micro- or nano-holes. EP 3 552 837 A1 discloses a security element for use in a security document, comprising a metal foil in whose surface a structural element is introduced, consisting of a laser-induced periodic microstructure. EP 3 552 837 A1 does not disclose a metal mesh, nor does it disclose that a metal foil with holes is first provided and then the metal foil is structured.

[0005] Most known methods treat one layer or the surface of the document at a time, generating a feature with a specific appearance. By separating the layers or treating the surface, it is possible to alter or replace this appearance. Perforation, which affects multiple layers of the document, is also a feature with a specific appearance, for example, in the form of holes, which also weakens the document's stability.

[0006] The following definitions are taken from European Patent EP 2 738 624 B1. As defined therein, in the context of the present invention, a security element is understood to be a structural unit comprising at least one security feature. Security elements serve to protect security documents, which may also include valuable documents, against forgery or copying. A security feature can be an independent structural unit that can be attached, for example, by gluing, to a security document, which may also be a valuable document. It can also be an integral part of a security document. A security feature is a structure that can only be produced or reproduced with increased effort compared to simple copying, or not at all, without authorization. Security documents typically have a substrate, a printing layer, and optionally a transparent cover layer.A substrate is a support structure onto which the printed layer containing information, images, patterns, and the like is applied. Suitable materials for a substrate include all standard paper- and / or plastic-based materials. Examples of security documents include identity cards, passports, driver's licenses, ID cards, access control badges, visas, tax stamps, tickets, vehicle registration documents, banknotes, checks, postage stamps, credit cards, various chip cards, and adhesive labels.

[0007] Against the background described above, the object of the present invention is to further improve the counterfeit protection of security elements and security documents.

[0008] This problem is solved by a security element for use in a security document according to claim 1, by a security document according to claim 3, and by a method for producing a security document according to claim 5. The dependent claims contain further advantageous embodiments of the invention.

[0009] The security element according to the invention is designed for use in a security document, for example as a component or as a layer arrangement within a security document.

[0010] The security element comprises a preferably calendered metal mesh with a structural element embedded in its surface, consisting of a laser-induced periodic microstructure. Such laser-induced periodic surface structures form optical gratings, which, among other things, allow the creation of structural colors, making them particularly suitable as elements for the counterfeit protection of security documents. The laser-induced periodic microstructure thus forms the optical grating, resulting in a unique color pattern that varies depending on the illumination and viewing angle. When the microstructured metal mesh is laminated, it is typically encased by the card material, preventing the security element with the laser-induced periodic microstructure from being removed from the laminated card without damage.

[0011] The at least one structural element with its periodic microstructure can be arranged on the surface and / or within the surface and / or inside a layer. Preferably, at least one structural element comprises a number of individual structural components, which can be configured, for example, as depressions, such as holes, and / or protrusions and / or cavities and / or pixels, such as colored pixels. The at least one structural element in any case has a periodic structure formed by a number of structural components. The use of periodic structures facilitates the detection of tampering and thus enables rapid verification of the authenticity of a security document.

[0012] A "microstructure" is defined as an arrangement of structural components with dimensions of less than 100 micrometers (100 µm), in particular less than 10 micrometers (10 µm), and preferably less than 1 micrometer (1 µm). The smaller the dimensions, the more difficult it is to counterfeit or manipulate the security element. The spacing between the structural components is also preferably less than 100 micrometers (100 µm), in particular less than 10 micrometers (10 µm), and preferably less than 1 micrometer (1 µm).

[0013] The structural elements and / or components are generated using ultrashort laser pulses, for example, with a pulse duration of less than 10 picoseconds (10 ps), particularly less than 1 picosecond (1 ps) or less than 500 femtoseconds (500 fs). Laser structures in the micro- or nanometer range, in particular, can be fabricated relatively easily with ultrashort laser pulses. The application of ultrashort laser pulses enables precise manufacturing and efficient production of the structural elements. In particular, ultrashort laser pulses minimize or prevent thermal or mechanical damage to the structural elements during processing. With a suitable selection of processing parameters, virtually melt-free processing with high precision is possible. Due to the short interaction time of the ultrashort laser pulses with the material, material removal does not cause any color change in the material.On the other hand, a specific appearance, such as a change in the color of the structural elements, can also be created by a targeted selection of the processing parameters.

[0014] Preferably, the laser-induced periodic microstructure is introduced using ultrashort laser pulses, with a periodicity of between half the wavelength and the full wavelength of the laser beam being present or utilized. This allows a characteristic periodic structure to be formed on the metal surface. This structure is abbreviated LSFL (low spatial frequency laser-induced periodic surface structure).

[0015] However, it is also possible to implement a different structuring, which occurs, for example, when the laser-induced periodic microstructure is introduced using ultrashort laser pulses, where a periodicity of less than half the wavelength of the laser beam is present or utilized. This creates a characteristic periodic surface structure. This structure is abbreviated HSFL (high spatial frequency laser-induced periodic surface structure).

[0016] In a particularly advantageous variant, the security element is designed for a specific security document or for a specific type of security document containing specific security information, and the structure of the structural elements contains security information and / or personalized data, i.e., information that can be attributed to the holder of the security document for that specific security document. This increases the counterfeit protection.

[0017] The security document according to the invention is composed of a number of layers, preferably two or more layers. It comprises a security element according to the invention as described above. The security document according to the invention has the features and advantages mentioned above in connection with the security element according to the invention. In particular, it can comprise laminated layers. The security document can be, for example, an identity card, a passport, a driver's license, a company ID card, or another security document.

[0018] The microstructured metal mesh is preferably integrated into the layered structure of the security document, with the security element being covered on both sides by at least one of the layers. This ensures that the security element cannot be removed or detached from the layered structure or the layered composite without damage. Damage to the layered composite or the security element would indicate an unauthorized tampering attempt.

[0019] To further secure the security document, it has proven advantageous to include person-specific and / or document-specific reference information on one of its layers, and to have a structural element with a shape that corresponds to or reproduces the reference information. This allows for the detection of forgery of the layers or the structural element with the microstructured metal mesh without significant effort.

[0020] The advantages, advantageous designs and effects described in connection with the safety element and the safety document according to the invention are achieved in this way by the method according to the invention.

[0021] The process for producing a security document, which has a layered structure consisting of a number of layers and includes a security element that has a metal mesh and / or a metal foil with individualizing holes, in the surface of which a structural element is introduced which consists of a laser-induced periodic microstructure, comprises the following steps: Providing a preferably calendered metal mesh, in particular in the form of a film and / or a metal foil provided with individualizing holes; structuring the surface of the metal mesh and / or the metal foil provided with individualizing holes with a periodic microstructure by means of ultrashort laser pulses, thereby forming a structural element; inserting the microstructured metal mesh and / or the microstructured metal foil provided with individualizing holes between at least two layers; and pressing the layers with the microstructured metal mesh and / or with the microstructured metal foil provided with individualizing holes together to form a layer structure, thereby forming the security document.

[0022] Preferably, the microstructured metal fabric and / or the microstructured metal foil provided with individualizing holes is laminated under high pressure and at high temperature into a card body consisting of individual layers under a transparent cover film.

[0023] In order to create a characteristic structural element and thus a specifically defined safety element, it has proven advantageous to adjust, regulate or change the pulse energy of the laser beam during or after the structuring of the surface.

[0024] Alternatively or additionally, it is possible to adjust, regulate or change the pulse duration of the laser beam during or after the structuring of the surface.

[0025] Alternatively or additionally, it is possible to adjust, regulate or change the polarization of the laser beam during or after the structuring of the surface.

[0026] To further individualize the safety element and the microstructure in the surface of the metal mesh and / or the microstructured metal foil provided with individualizing holes, it is alternatively or additionally provided that the laser wavelength of the laser beam is set, regulated or changed during or after the structuring of the surface.

[0027] Alternatively or additionally, the laser fluence of the laser beam is adjusted, regulated or changed during or after the structuring of the surface.

[0028] Preferably, the laser-induced periodic microstructure is introduced using ultrashort laser pulses, wherein the periodicity of this microstructure is between half the wavelength of the laser beam and the whole wavelength of the laser beam; thus, it is introduced into the metal surface in the form of LSFL (= LSFL for "low spatial frequency laser-induced periodic surface structure").

[0029] Alternatively, the laser-induced periodic microstructure can be introduced using ultrashort laser pulses, where the periodicity of this microstructure is less than half the wavelength of the laser beam; thus, it is introduced into the metal surface in the form of HSFL (= HSFL for "high spatial frequency laser-induced periodic surface structure").

[0030] When generating the structural elements, the metal surface can be moved relative to a focused laser beam and / or scanned by a focused laser beam. The movement of the metal surface relative to a focused laser beam preferably occurs in an xy-plane. Scanning can be performed using movable mirrors. It is advantageously possible to change the angle of incidence of the laser beam with respect to the surface normal of the metal surface during or after the surface structuring process.

[0031] Further features, properties, and advantages of the present invention are described in more detail below with reference to exemplary embodiments and the accompanying figures. All features described so far and below are advantageous both individually and in any combination. The exemplary embodiments described below are merely examples and do not limit the scope of the invention.

[0032] The figures are not necessarily detailed or to scale and may be enlarged or reduced to provide a better overview. Therefore, the functional details disclosed here are not to be understood as limiting, but merely as an illustrative basis that provides guidance to those skilled in this field of technology for using the present invention in a variety of ways.

[0033] The expression "and / or" used here, when used in a series of two or more elements, means that each of the listed elements can be used alone, or any combination of two or more of the listed elements can be used. For example, if a composition is described as containing the components A, B, and / or C, the composition can contain A alone; B alone; C alone; A and B in combination; A and C in combination; B and C in combination; or A, B, and C in combination. Fig. 1 schematically shows the production of a security element by laser structuring of a metal mesh in the form of a metal foil and / or a metal foil with individualized holes, wherein the ultrashort pulsed laser beam is aligned coaxially with the surface normal of the metal surface. Fig. 2 schematically shows the production of a security element by laser structuring of a metal mesh in the form of a metal foil and / or a metal foil with individualized holes, wherein the ultrashort pulsed laser beam is aligned at a non-zero angle with respect to the surface normal of the metal surface. Fig. 3 shows, by way of example, the laser-induced periodic surface structure after laser treatment in accordance with the Figures 1 or 2Fig. 4 schematically shows the production of a security document with a security element formed with a laser-induced periodic surface structure, and Fig. 5 shows a finished security document formed with a security element provided with a laser-induced periodic surface structure.

[0034] In the Figures 1 and 2 The production of a security element 11 for use with a security document 10 is shown, by way of example and not to scale. The security element 11 comprises a metal mesh, preferably calendered, and / or a metal foil 5 provided with individualizing holes, into the surface 3 of which a structural element 21 is introduced, which consists of a laser-induced periodic microstructure introduced with a laser beam 100 of ultrashort laser pulses.

[0035] The periodicity of the microstructure introduced by ultrashort laser pulses is, for example, between half the wavelength of the laser beam 100 and the full wavelength of the laser beam 100, resulting in a laser-induced periodic microstructure in the metal surface 3 (LSFL). Alternatively, the periodicity of the microstructure introduced by ultrashort laser pulses is less than half the wavelength of the laser beam 100 (HSFL). In either case, the periodicity of the microstructure is in the submicrometer range, and the microstructure forms an optical grating.

[0036] The laser beam 100 is operated with predefined parameters. During laser processing, the pulse energy, pulse duration, polarization, wavelength of the laser radiation, and the number of pulses per area ("laser fluence") can be controlled and regulated.

[0037] Figure 2This refers to the possibility that the angle of incidence of the laser beam 100 can also be specified, changed, and controlled. It is indicated that the surface normal 4 of the metal surface 3 is displaced so that the laser beam 100 travels at a specified angle with respect to the surface normal 4 and is tilted relative to the surface normal 4.

[0038] In Figure 3 A high-resolution representation of the laser-induced periodic microstructure, and thus the surface 3 in the area of ​​the structural element 21, can be seen.

[0039] In Figure 4 Figure 1 illustrates a procedure for producing security document 10 with a security element 11. It comprises the following steps: Providing the preferably calendered metal mesh and / or a metal foil 5 provided with individualizing holes, structuring the surface 3 of the metal mesh and / or a metal foil 5 provided with individualizing holes with a periodic microstructure by means of ultrashort laser pulses, thereby forming the structural element 21 ( Figure 1, Figure 2 ), Inserting the microstructured metal fabric and / or the microstructured metal foil 5 provided with individualizing holes between at least two layers 1, 2, and pressing the layers 1, 2 with the microstructured metal fabric and / or the microstructured metal foil 5 provided with individualizing holes to form a layer structure, thereby forming the security document 10.

[0040] The pressing of the structured metal fabric and / or the microstructured metal foil 5 provided with individualizing holes with the further layers 1, 2 of the security document 10 preferably takes place under high pressure and under high temperature, so that an inseparable laminate, i.e. an inseparable card body, is created in the interior of which the security element of the microstructure is embedded.

[0041] In Figure 5The security document is recognizable, in which the security element 11 with the microstructured metal mesh and / or the microstructured metal foil 5 with individualizing holes is embedded. Depending on the viewing angle and illumination angle, a viewer sees a colored image created by the structural element 11 with its periodic microstructure. It is possible that one of the layers 1, 2 is provided with person-specific and / or document-specific reference information, and that the structural element 21 has a shape that corresponds to or reproduces the reference information. This increases the counterfeit protection of the security document 10 thus formed.

[0042] The color perceived by the viewer depends not only on the viewing and illumination angle but also on the parameters used in creating the microstructure. This allows for the targeted and locally defined generation of different color areas side by side, which together form a color image. The perceived color of the image changes depending on the viewing and illumination angle. Unlike the spectral color separation of a grating, the colors here are locally differentiated because a multitude of gratings are generated depending on the processing parameters of the metal surface.

[0043] The security element 11 and the security document 10 according to the invention are therefore characterized by improved protection against counterfeiting, wherein the security element 11 can no longer be detached from the composite of the card body of the security document 10 without destruction, so that manipulations can be verified quickly and easily. REFERENCE MARK LIST

[0044] 1 Layer 2 Top layer 3 Surface 4 Surface normal 5 Metal fabric, metal foil with individualizing holes 10 Security document 11 Security element 21 Structural element 100 Laser beam

Claims

1. A security element (11) for use in a security document (10), comprising a metal mesh in whose surface (3) a structural element (21) is incorporated, which consists of a laser-induced periodic microstructure.

2. The security element (10) according to claim 1, characterized in that the metal mesh is calandrated.

3. A security document (10) having a layered structure composed of a number of layers (1, 2), characterized in that it comprises a security element (11) according to claim 1 or 2.

4. The security document (10) according to claim 3, characterized in that the security element (11) is integrated into the layered structure and that the security element (11) is covered on both sides by at least one of the layers (1, 2).

5. A method for producing a security document (10) which has a layered structure composed of a number of layers (1, 2) and which comprises a security element (11) having a metal mesh and / or a metal foil (5) provided with individualizing holes, in whose surface (3) a structural element (21) is introduced, which consists of a laser-induced periodic microstructure, comprising the steps of: - providing a metal mesh and / or a metal foil (5) provided with individualizing holes, - structuring the surface (3) of the metal mesh and / or the metal foil (5) provided with the individualizing holes with a periodic microstructure using ultrashort laser pulses, thereby forming a structural element (21), - inserting the structured metal mesh and / or the microstructured metal foil (5) provided with individualizing holes between at least two layers (1, 2), and - pressing the layers (1, 2) with the structured metal mesh and / or the structured metal foil (5) provided with individualizing holes into a layer structure, thereby forming the security document (10).

6. The method according to claim 5, characterized in that the pulse energy of the laser beam (100) is set, controlled, or changed during the structuring of the surface (3).

7. The method according to claim 5 or 6, characterized in that the pulse duration of the laser beam (100) is set, controlled, or changed during or while structuring the surface (3).

8. The method according to any one of claims 5 to 7, characterized in that the polarization of the laser beam (100) is set, controlled, or changed during the structuring of the surface (3).

9. The method according to any one of claims 5 to 8, characterized in that the laser wavelength of the laser beam (100) is set, controlled, or changed during the structuring of the surface (3).

10. The method according to any one of claims 5 to 9, characterized in that the laser fluence of the laser beam (100) is set, controlled or changed during or while structuring the surface (3).

11. The method according to any one of claims 5 to 10, characterized in that the angle of incidence of the laser beam (100) relative to the surface normal (4) of the metal mesh and / or relative to the metal foil (5) provided with individualized holes is changed during or while structuring the surface (3),.

12. The method according to any one of claims 5 to 11, characterized in that the laser-induced periodic microstructure is introduced by means of ultrashort laser pulses, wherein the periodicity of the microstructure lies between half the wavelength of the laser beam (100) and the full wavelength of the laser beam (100).

13. The method according to any one of claims 5 to 12, characterized in that the laser-induced periodic microstructure is introduced by means of ultrashort laser pulses, wherein the periodicity of the microstructure is smaller than half the wavelength of the laser beam (100).