WO2004037560A2

WO2004037560A2 - Security element for identity documents and valuable documents

Info

Publication number: WO2004037560A2
Application number: PCT/EP2003/011548
Authority: WO
Inventors: Lars Hoffmann; Norbert Holl; Jürgen Schützmann; Bernd Wunderer; Manfred Heim; Marius Dichtl
Original assignee: Giesecke & Devrient Gmbh
Priority date: 2002-10-21
Filing date: 2003-10-17
Publication date: 2004-05-06
Also published as: AU2003298090A1; WO2004037560A3; DE10248954A1; AU2003298090A8

Abstract

The invention relates to a security element (2), particularly for banknotes (1), comprising one or more electrically conductive components, and to a corresponding device for verifying security elements. The inventive security element (2) is characterized in that a coding is given to one or more of the components by the spatial structure, particularly by the spatial extension and/or position and/or shape.

Description

Security element for ID and value documents

The invention relates to a security element, in particular for identification and value documents, and a device for testing such a security element according to the preamble of claims 1 and 24, respectively.

A security paper with a multilayer security element is known from WO 02/02350 AI, which has a visually testable effect and is provided with an integrated circuit. Depending on the use of the security element, various information can be stored in the integrated circuit, which can be read out again if necessary.

Such security elements allow documents to be reliably secured against unauthorized copying, duplication or manipulation and can be checked both visually and by machine. However, the use of integrated circuits involves additional costs, which can be too high for certain applications. Corresponding devices for mechanically checking such security elements, in particular for reading out the information stored in the integrated circuits, are also relatively expensive.

It is an object of the invention to provide a security element which is as simple and inexpensive to manufacture as possible with a high level of security against tampering and manipulation, and to provide a device which allows security elements to be tested as reliably as possible with a simple structure.

This object is achieved by the security element or the device according to claim 1 or 26 and 34. Advantageous further developments are the subject of the dependent claims. The security element according to the invention is characterized in that the spatial structure, in particular the spatial extent and / or position and / or shape, of one or more of the electrically conductive components of the security element provides a coding.

In a first embodiment, the device according to the invention is characterized in that an induction current is induced by a first magnetic field generated by first means in the electrically conductive components of the security element, the spatial structure of which is coded. The induction current causes a second magnetic field, which is detected by second means. The coding is determined in a value device on the basis of the detected second magnetic field.

In a second embodiment, the device according to the invention is characterized in that means for generating an electric field for testing the security element are present, the electric field being changed by the electrically conductive components, the spatial structure of which provides a coding, and a Evaluation device determines the coding on the basis of the changed electrical field.

The invention is based on the idea of providing a closed electrical circuit as a security element, the electrically conductive components of which are designed and / or coupled to one another such that an electrical circuit current can flow through the components. Depending on the respective spatial structure of the individual components, their electrical and / or magnetic properties vary, so that the security element due to the respective spatial structure of the Components an electrically and / or magnetically coded information can be impressed.

This coding is detected in the device according to the invention in that one or more induction currents are induced in the closed circuit by means of a magnetic field which varies in time and / or in space. The induced circulating currents flow through the individual, generally components with different spatial structures and accordingly cause different second magnetic fields. These are recorded using suitable sensory means and evaluated to determine the coded information impressed on the circuit.

The security elements according to the invention can be produced simply and inexpensively, in particular in comparison to integrated circuits, and ensure a high level of security against attempts at counterfeiting and manipulation. The device according to the invention and the corresponding method allow reliable testing of such security elements with a simple construction or simple implementation.

In a preferred embodiment of the security elements according to the invention, the components are designed as electrically conductive layers. The coded information is given here by the thickness and / or size and / or shape and / or the type of material of the flat conductive layers. The layers are produced, for example, by means of printing processes or other techniques for applying thin layers. The layers are either created directly on the object to be provided with the security element, for example a security paper or a document, or on a carrier layer. testifies which, together with the security element, is applied, for example glued, to the object.

Preferably, at least some of the components of the electrical circuit can be obtained by a method in which first a negative representation of a positive representation to be generated, i.e. of the electrical circuit or at least one component thereof, is printed on a base, for example a plastic film as a carrier layer. Rotogravure processes, such as Intaglio or web intaglio printing. A thin cover layer of electrically conductive or semiconductive material is then applied to the printed negative representation, for example by vapor deposition, printing or other coating techniques. In a subsequent washing process in a suitable solvent, the structure of the applied negative image is removed together with the material of the cover layer located on this structure, so that essentially only the areas of the cover layer outside the structures of the negative image remain on the base, a Positive representation with a high contour sharpness is obtained. With this method, electrical circuits of any complex structure can be generated in a simple and inexpensive manner.

Alternatively, components of the electrical circuit can also be produced by other methods. For example, etching processes are particularly suitable, in which the desired recesses are produced from a thin, electrically conductive layer applied to a base by etching away the layer material at the appropriate locations. In a preferred embodiment of the security element, individual sections of the electrically conductive layer have different conductivities by which the coding is given. The differently high electrical conductivities are preferably realized by different layer thicknesses and / or rasterization and / or different materials in the individual sections of the layer.

In a further preferred embodiment of the security element it is provided that one or more of the components form a closed conductor loop, due to their spatial structure, in particular layer thickness and / or width of individual conductor tracks and / or their distance from one another and / or their material, the coding is given. In order to increase the information density impressed into the conductor loop, it is provided in particular that individual sections of the conductor loop components have different spatial structures by which the coding is given.

A further embodiment of the invention provides that the electrical circuit is designed as a transformer circuit, which is composed of at least two interconnected electrical coils, the transformation behavior of which represents the coding.

In another preferred embodiment, the electrical circuit is designed as an oscillating circuit, which is composed of at least one electrical coil and at least one capacitor. In this case, the coding is given by the resonance behavior, in particular the resonance frequency, of the resonant circuit. The invention is explained in more detail below with reference to figures. Show it:

Fig. La - e examples of security elements with different coding structures;

2a-e further examples of security elements;

3 shows a banknote with a security element according to the invention;

FIG. 4 shows a cross section through the banknote shown in FIG. 3;

5a shows a printed coil in negative representation;

Fig. 5b the coil shown in Fig. 5a in a positive representation;

5c a capacitor plate in a positive representation;

Fig. 6 shows a cross section through an oscillating circuit

Safety element;

7 shows a safety element designed as a transformer circuit with a device for testing it;

8 shows an embodiment of the device according to the invention for testing a coded security element; 9 shows a further embodiment of the device according to the invention for testing a coded security element;

10a-b show a perspective illustration of the principle of testing a security element with the associated signal curve;

11a-b show a perspective illustration of the principle of the detection of periodically arranged security elements with an associated signal curve; and

12a-d further embodiments of security elements.

Figures la to le show examples of security elements with different coding structures.

The security element 2 shown in Figure la is formed by a thin, electrically conductive layer in the form of an elongated rectangle. The typical thickness of the layer is in the range between approximately 25 and 500 nm, preferably above 250 nm, in order to ensure a sufficiently high electrical conductivity for the detection of electrical induction currents. Typical widths of the security element are between 1 and 20 mm, typical lengths between 30 and 90 mm. Metals, such as aluminum, nickel, copper or conductive silver, or semiconducting materials, in particular based on organic polymers, are preferably used as the electrically conductive material. The material can also be applied using electrically conductive inks, in particular electrically conductive printing inks. Compared to the example shown in FIG. 1 a, the security element 2 shown in FIG. 1 b has a recess 4 in the form of a narrow, elongated rectangle in the inner region of the layer. The closed electrically conductive structure 3 in the outer region of the layer thus forms a closed conductor loop. Depending on the manufacturing process, recesses 4 with very small widths of up to approximately 0.2 mm can be produced.

FIG. 1c shows a development of the closed conductor loop shown in FIG. 1b, the recesses 6a and 6b each having different spatial structures in individual sections of the conductor loop. In the example shown, there are individual square recesses 6b which are connected to one another by mutual overlap or narrow recesses 6a. The arrangement of the individual recesses 6a and 6b which merge into one another is here symmetrical to the longitudinal axis of the closed, electrically conductive structure 5.

In contrast, the security element 2 in FIG. 1d shows an arrangement of the respective recesses 6a and 6b which is asymmetrical with respect to the longitudinal axis of the closed electrically conductive structure 5, a tooth-like profile of the recesses 6a and 6b being obtained.

In the example shown in FIG. 1e, square recesses 8a and 8b of different sizes are provided, which are separated from one another by electrically conductive webs of the electrically conductive structure 7.

The spatial structure of the respective security element 2, in particular the layer thickness and / or dimensions and / or shape and / or material of the electrically conductive structure 3, 5 and 7 or of the recesses 4, 6a, 6b, 8a and 8b, can be selected the security element 2 a Memorize coded information. The security elements 2 of FIGS. 1c to 1e, which are structured differently in individual sections, represent a bit coding of information with up to nine bits, which can be read by checking the individual differently structured sections of the respective security element 2 separately.

FIGS. 2a to 2e show further examples of security elements according to the invention with bit coding.

The security element 2 shown in FIG. 2a has a closed, electrically conductive structure 21 in the outer region and step-shaped recesses 20a and 20b which merge into one another in the inner region of the layer.

The security element 2 shown in FIG. 2b further develops the one shown in FIG. 2a in that the closed electrically conductive structure 21 also has a step-shaped course in the outer region of the layer.

The security element 2 shown in FIG. 2c shows a further possibility of coding in the form of comb-shaped recesses 22a and 22b. The content of coded information essentially corresponds to the information contained in the security elements 2 of FIGS. 2a and 2b with step-shaped coding, a tooth-like recess 22b being arranged at the location of the flanks 20a / 20b and 20b / 20a of the step-shaped recesses , This coding principle is further illustrated in the examples in FIGS. 2d and 2e. FIG. 3 shows a document in the form of a banknote 1 with a security element 2 according to the invention. A carrier layer 10 is applied to the banknote 1, which is provided with the security element 2 described in more detail in connection with FIG. 2a. The carrier layer 10 is preferably a plastic film, for example made of PET, PVC or PE, with typical thicknesses between 2 and 20 μm.

FIG. 4 shows an enlarged cross section through the bank note 1 shown in FIG. 3 with the security element 2 perpendicular to the plane of the bank note 1 along the line BB ′. The individual differently structured sections with the electrically conductive structures 21 and the recesses 20a of the electrically conductive layer can be seen on the carrier layer 10.

In the example shown here, the carrier layer 10 is glued to an intermediate layer 14 with the electrically conductive structures 21 located on its upper side by means of an adhesive layer 12, in particular a layer of laminating adhesive. This layer system is applied to the bank note 1, for example by means of a further adhesive layer (not shown). Alternatively, the carrier layer 10 can also be glued directly onto the bank note 1 with the adhesive layer 12 without an intermediate layer 14. A security element 2 introduced in this way into such a layer system or applied to the bank note 1 is difficult to access from the outside and is therefore well protected against attempts at manipulation. In general, however, the carrier film 10 can also be applied to the bank note 1 with the underside opposite the security element 2. In the described variants of the example shown, the carrier layer 10 with the electrically conductive structures 21 located thereon is preferably designed as a self-supporting label.

In a further preferred embodiment, the security element 2 is applied to the security paper or the banknote 1 with the aid of a so-called transfer film. Here, a thin carrier layer is releasably applied to a transfer film. The security element 2 is then produced on the carrier layer, preferably using one of the methods described above. An adhesive layer is applied to the carrier layer provided with the security element 2 and is activated by heat and pressure during the transfer of this layer structure to the security paper or the bank note 1, so that the carrier layer together with the security element 2 on the security paper or the bank note 1 is attached. In a last step, the transfer film is removed.

The carrier layer 10 and / or the intermediate layer 14 can be designed such that it has an optical effect which is characteristic of the security element. In particular, this can show an optically variable effect, in which the security element generates different visual impressions from different viewing angles. This can preferably be achieved by at least one additional layer with optically variable pigments, in particular interference layer or liquid crystal pigments, and / or with diffraction structures in the form of a relief structure, such as a hologram. This additional authenticity feature makes it even more difficult to imitate or manipulate the security element according to the invention. The structure of a security element designed as an oscillating circuit is explained in more detail below with reference to FIGS. 5a to 5c and 6.

FIG. 5a shows a negative representation 50 of a spiral coil 51, the ends of which have contact surfaces 52. The negative representation 50 is printed on a carrier layer 10, preferably by means of gravure printing processes, in particular intaglio printing processes or rotary gravure printing processes using engraved and / or etched cylinders. Printing inks with a high pigment content, which is typically more than 10 percent by weight in the dry printing ink, are particularly suitable for this.

After the printing ink has dried, a thin cover layer of conductive material, such as e.g. Aluminum, or nickel, applied. Typical thicknesses of this cover layer are between approximately 30 nm and 500 nm. The cover layer is preferably applied by vapor deposition, printing or other coating techniques.

The structure of the negative image 50 is then removed in a washing process together with the parts of the cover layer lying on the structure. When using water-soluble printing inks, in which starch, alcohol or cellulose is preferably used as the binder, only water is required in this washing process.

At the end of the washing process, a positive representation of the spiral coil 51 including contact surfaces 52, consisting of the electrically conductive material, is retained.

With the described method, particularly fine structures with typical structure sizes of up to 0.1 mm and at the same time very high contours Create sharpness. This method is particularly suitable for producing structured security elements 2, as shown in FIGS. 1 a to 1 a, 2 a to 2 e and 7.

FIG. 5c shows an electrically conductive surface region 53 produced in an analogous manner on a further carrier layer 15 using the method described above. If the surface region 53 is brought together with an electrically insulating layer over the contact surfaces 52 shown in FIG. 5b, a surface region 53 is formed and the contact surfaces 52 as existing capacitor plates 52/53. The capacitor 52/53 forms an oscillating circuit 51 to 53 together with the coil 51.

Due to the spatial structure of coil 51 and capacitor 52/53, i.e. Size and shape, as well as the number of turns or spacing from one another, the resonant circuit 51 to 53 receives a characteristic resonance, by means of which certain information can be impressed on the resonant circuit.

The resonance behavior, in particular the resonance frequency, of the resonant circuit 51 to 53 is determined, for example, by detecting the resonance absorption of the resonant circuit in a high-frequency alternating electromagnetic field, in particular by measuring the detuning of a high-frequency transmitter caused by the resonant circuit 51 to 53. A signal increase which can be detected at the resonant frequency of the resonant circuit 51 to 53 generally only occurs when the quality of the resonant circuit, which is calculated from the ohmic resistance of the circuit, the inductance of the coil 51 and the capacitance of the capacitor 52/53, is greater than 1. Typical frequencies are between approximately 1 MHz and 1 GHz. Typical widths and / or spacings of the coil turns 51 are between approximately 0.1 mm and 2 mm, preferably 0.2 mm, typical layer thicknesses between 30 nm and 1000 nm, preferably approximately 500 nm. The typical number of turns the coil 51 is between 5 and 100, in particular around 40.

Alternatively, the properties of the resonant circuit 51 to 53 can also be determined using an impedance analyzer. The frequency profile of the impedance, ie the AC resistance, of a transmitting coil is measured, the magnitude and phase of the impedance preferably being detected. The transmitter coil consists of copper wire with a typical diameter of approximately 0.7 mm and a typical length of approximately 85 mm. The inductance of the transmitter coil is in the range between 50 and 100 nH, its resonance frequency between approximately 50 and 500 MHz. If the resonant circuit 51 to 53 to be examined is brought into the near field generated by the transmitter coil, the impedance of the transmitter coil changes due to the magnetic coupling of the two coils. This change is maximal in the frequency range of the resonance frequency of the resonant circuit 51 to 53. With this method, not only can the detuning of the transmitter caused by the oscillating circuit 51 to 53 be measured, but also its individual characteristics can be recognized. With the help of the impedance analysis, a particularly precise detection and evaluation of the properties of the resonant circuit 51 to 53 and the coding contained therein is possible. A suitable, simply constructed detection device comprises a tunable transmitter (VCO) or a transmitter with, preferably three to four, permanently adjustable transmission frequencies and a detection circuit for measuring the impedance at, preferably three to four, permanently adjustable frequencies. FIG. 6 shows a cross section through an oscillating circuit 51 to 53, which comprises the components shown in FIGS. 5b and 5c. The coil 51 is applied together with the contact surfaces 52 on a first carrier layer 10, the capacitor plate 53 on a second carrier layer 15. An electrically insulating layer 16, preferably made of plastic, is provided between the two carrier layers 10 and 15 and forms the dielectric between the contact surfaces 52 and the capacitor plate 53 of the capacitor.

The layer system 10/16/15 is applied to a bank note 1 in this example, for example by gluing. However, it can also be partially or completely introduced into a bank note 1 in order to achieve particularly high security against tampering and manipulation.

Analogously to the embodiment described in more detail in FIG. 4, in the example of FIG. 6 the first and / or second carrier layer 10 or 15 can also be designed such that it has an optical effect which is characteristic of the security element.

A particularly simple alternative to the example shown here is to apply the coil 51 with the contact surfaces 52 on the one hand and the capacitor plate 53 on the other to one of the two sides of a carrier layer (not shown). In this case, the dielectric is formed by the carrier layer itself.

In an even simpler variant, the resonant circuit is formed only by a short-circuited coil (not shown) applied to a carrier layer, a separate capacitor being dispensed with. The capacities required for such a resonant circuit come from So-called parasitic capacitances, which form among other things between the individual conductor tracks of the coil.

FIG. 7 shows a security element 2 designed as a transformer circuit with a device 48 for testing it.

The security element 2 is applied to the bank note 1 by means of a carrier layer 10, analogously to the exemplary embodiment described in FIGS. 3 and 4. In this example, the electrically conductive layer of the security element 2 has two wide, rectangular recesses which are connected to one another by a narrow recess. In this way, a closed electrical circuit is obtained, which can be thought of as composed of two electrical coils 30 and 31, the ends of which are connected to one another via two electrically conductive connections 32. The electrical circuit thus represents a simple transformer circuit 30 to 32 with a turns ratio of the two coils 30 and 31 of 1: 1.

If, for example, an alternating magnetic field is applied to the coil 30, electric currents are induced in it, which can flow via the connections 32 into the other coil 31 and in turn generate an alternating magnetic field there, which is detected by a detector arranged in the region of the coil 31 can be. From the type and strength of the alternating field detected, the type and / or the structure of the transformer circuit 30 to 32 and thus the encoded information contained in it can be inferred. In this example, the coding is given in particular by the size ratio of the coils 30 and 31 or the recesses in the area of the coils 30 and 31 and / or the number of turns ratio of the two coils 30 and 31 to one another. The latter can for example be changed in that a coil 30 or 31 is coupled to one or more further coils, optionally in additional layers of the security element 2.

In the right part of FIG. 7, a suitable device 48 for testing the safety element 2 designed as a transformer circuit is shown. An excitation coil 40 with a ferrite core 42 is operated with electrical alternating voltage from the voltage source 44. Typical frequencies of the alternating voltages are between approximately 1 and 30 MHz, in particular approximately 13.56 MHz. By means of a transport device (not shown), the bank note 1 is brought in the transport direction T into the area of the device 48, where the coil 30 of the security element 2 comes to rest in the area of the excitation coil 40. The alternating magnetic field emanating from the excitation coil 40 then induces electrical currents in the coil 30, which flow through the electrical connections 32 to the coil 31 and generate an alternating magnetic field there, which is detected by the detection coil 41 with a ferrite core 43. The electrical currents and / or voltages induced in the detection coil 41 are measured by a measuring device 45 and, if necessary, subjected to a further evaluation.

In the function of the ferrite core 42 or 43, other materials with a comparably high magnetic permeability can also be used instead of ferrite. The cross section of the ferrite core 42 or 43 is preferably less than or equal to the inner cross section, ie the recess, of the respective coil 30 or 31, so that the ferrite core 42 or 43 is virtually enclosed by the respective coil 30 or 31 during the measurement becomes. Typical distances between the transformer circuit 30 to 32 and the ferrite cores 40 and 41 with the coil 42 and 43 are in the range between 0.1 and 2 mm, preferably between 0.7 and 1 mm, in order to ensure good magnetic coupling with a low susceptibility to interference, in particular as a result of banknote jams in the area of the device 48. The time periods within which the transformer circuit of a bank note 1 is checked are preferably in the range of milliseconds, so that bank notes 1 passing the device 48 can also be checked quickly with a high degree of reliability. This is particularly important for use in banknote processing machines with a high transport and processing rate.

In the example shown in FIG. 7, the two coils 30 and 31 have the same rectangular cross section with only one turn each. As already explained, the respective cross sections and / or number of turns of the coils can be selected differently, for example by coupling a further coil (not shown) to the coil 31. In this case, the currents induced on the detection coil 41 are increased so that a particularly sensitive testing of the transformer circuit 30 to 32 is made possible. An increase in the efficiency of the transformer circuit 30 to 32 is also possible by means of an additional coil (not shown) coupled to the coil 30, by means of which the total inductance in the region of the coil 30 and thus the respective induced currents increase accordingly. In certain applications in which the transformer circuit 30 to 32 for the bank notes 1 to be checked is not continuously placed exactly at the same location, means 48 can be provided in the device 48 which detect the position of the transformer circuit 30 to 32 in advance and the Adjust the position of the ferrite cores 40 and 41 including the coils 42 and 43 accordingly. The means mentioned can be, for example, optical sensors. 8 shows an embodiment of the device according to the invention for testing a coded security element. As already explained in more detail in connection with the examples in FIGS. 2a, 2b and 2d, the security element 2 applied to the banknote 1 by means of a carrier layer 10 has a step-shaped recess 20a. The test device consists of two first means 60, which generate a time-varying magnetic field. For this purpose, an excitation coil 40 with coil core 42 and a voltage source (not shown for reasons of clarity) are provided for supplying voltage to the excitation coil 40. The variable magnetic field generated is preferably a periodically variable magnetic field. An AC voltage source is used as the voltage source. If the bank note 1 with the security element 2 is transported in the transport direction T into the area of the first means 60, then the alternating magnetic fields generated by the first means 60 induce induction currents in the security element 2, which can form 2 circular currents due to the electrically closed structure of the security element , These circular currents in turn cause magnetic fields, which can be detected by second means 61a and 61b and 62a to 62d. The second means each comprise a detection coil 41 with a second coil core 43 and a measuring device (not shown) for detecting the currents and / or voltages induced in the detection coil 41.

With the step-shaped course of the recess 20a in the inner region of the layer, the induced circular current varies accordingly in the individual sections of the outer region of the layer. The resulting different magnetic fields are detected by the second means 61a and 61b and 62a to 62d. The respectively induced voltages or Currents are forwarded to an evaluation device (not shown) to determine the coding.

In the example shown, the second means have two position sensors 61a and 61b and four code sensors 62a to 62d. The position sensors 62a to 62d detect the respective position of individual coding units, in the present case bit coding, units 1 and 0. The signals of the code sensors 62a to 62d are then compared with the signals of the position sensors 61a and 61b during the evaluation, so that for each code sensor 62a to 62d a coding unit, ie 1 or 0, can be determined. In the present example, the code sensors 62a to 62d detect the bit sequence "0110".

The encoding contained in security element 2 can also be correctly recognized by position sensors 61a and 61b even if it is inserted into the test device in the wrong direction. Depending on the application, e.g. when checking documents that have been correctly inserted and aligned, it is also possible to dispense with one or both position sensors 61a and 61b. In these cases, the position sensors 61a and 61b can also serve as code sensors.

As an alternative to the example shown, the first means 60 can have only one excitation coil 42 with coil core 42, which generates an alternating magnetic field at only one end or at another area of the security element 2. Of course, however, several first means 60 can also be provided, which are arranged, for example, at regular intervals along the security element 2. FIG. 9 shows a further embodiment of the device according to the invention for testing a coded security element. The statements relating to FIG. 8 apply correspondingly to bank note 1 and security element 2 located thereon. In contrast to the exemplary embodiment described there, the first magnetic field, which induces 2 induction currents in the security element, is generated by means of a permanent magnet 73. The permanent magnet 73 is coupled by an iron yoke 74 to a second coil core 43, which is surrounded by a detection coil 41. A spatially inhomogeneous second magnetic field is formed between the permanent magnet 73 and the second coil core 43. If the banknote 1 together with the security element 2 is transported past the second means 71a and 71b and 72a to 72d in the transport direction T, induction currents are induced in the security element 2 due to its movement in the inhomogeneous second magnetic fields, which currents depend on the structure of the respective section of the security element 2 in the area of the individual sensors 71a and 71b and 72a to 72d. Analogous to the exemplary embodiment described in FIG. 8, an evaluation device (not shown) is also provided here, which determines the coding contained in the security element 2 from the currents or voltages induced in the detection coils 41. As in the exemplary embodiment described in FIG. 8, position sensors 71a and 71b can also be provided here, which detect the position of the respective coding units.

The mode of operation of the device according to the invention was explained in more detail in FIGS. 8 and 9 as an example for the testing of security elements 2 with a step-like coding. In principle, however, the devices described are suitable for a large number of different structured closed electrical circuits, in particular for the security elements shown in Figures la to le and 2a to 2e.

Figure 10a shows a perspective view of the device described in Figure 9 for testing a security element using a static magnetic field. 10b shows the associated signal curve. In the example shown, a bank note 1 is transported past a sensor 71 in the transport direction T. For reasons of clarity, only one sensor 71 has been drawn in this illustration; depending on the application, several such sensors 71 can of course be arranged side by side in accordance with the example described in FIG. 9.

In this case, the security element 2 is formed by a closed conductor loop, in which a circulating current is induced when the inhomogeneous first magnetic field of the permanent magnet 73 passes through.

This circular current causes a second magnetic field which is opposite to the change in the first magnetic field. As a result, the magnetic flux density changes in the second coil core 43, as a result of which a voltage is induced in the detection coil 41.

A typical course of the induced voltage is shown in Fig. 10b. Depending on the position X of the bank note 1, the voltage signal S shows a positive and a negative voltage pulse, which can be explained by the different direction of the circular current Ik induced in the two parts of the conductor loop 2 and the magnetic fields correspondingly differently oriented therefrom. Depending on the layer thickness and / or width of the individual conductor tracks of the conductor loop and / or their distance from one another, the detected voltage signal S varies, from which the coding can be deduced in a suitable evaluation method. In the exemplary embodiment shown, in addition to the sensor 71, a further detection coil 47 is provided with a coil core 46 which is not coupled to the permanent magnet 73 of the sensor 71. In the detection coil 47, which is arranged opposite the transport direction T by the sensor 71, voltages are essentially only induced when the conductor loop 2 is sufficiently wide or the material in the conductor loop layer has a sufficiently high magnetic remanence, since only in these cases Change in the magnetic flux density in the coil core 46 is given.

FIG. 11a shows a perspective illustration of a further application of the device according to the invention in the detection of periodically arranged security elements. Figure 11b shows the associated waveform. A document 1 provided with a plurality of security elements 2 is transported in the transport direction T past the sensor 71, which has already been described in connection with FIG. 10a. The individual security elements 2 preferably correspond to the example of a continuous electrically conductive layer described in FIG. In this case, coding is provided by the structure of the individual security elements 2 and their arrangement relative to one another. In the example shown, all security elements 2 have an identical shape and are arranged periodically, that is to say at equal intervals from one another.

If the document 1 is now transported past the permanent magnet 73 of the sensor 71 at a constant transport speed T in the transport direction T, eddy currents are induced in the security elements 2, which in turn each cause a magnetic field that induces the voltage signal curve S shown in FIG. 11b in the detection coil 41. In the event that analogous to the example shown in Figure 9 If a plurality of sensors 71a, 71b, 72a to 72d are arranged next to one another, eddy currents are generated at a plurality of points on the security elements 2, which are superimposed on a circulating current flowing through the entire security element 2, similar to that described in connection with FIG. 10a.

The voltage signal S in FIG. 11b shows an essentially periodic voltage curve in the area of the security elements 2. The coding on document 1 can be derived from the number of periods and their signal level. Document 1 is preferably a so-called separating card, which is used to separate different packets of banknotes when they are processed in an automatic banknote processing machine. The device according to the invention for checking security elements can therefore be used both for checking documents themselves, in particular banknotes, and for checking or recognizing separating cards used in banknote processing.

Another form of coding banknotes or separating cards consists in the arrangement of a plurality of security elements 2 with different widths and / or at different distances relative to one another, as a result of which a type of bar code is obtained which can be read in a simple manner with the device described above.

The recesses 4, 6a, 6b, 8a, 8b, 20a, 20b, 22a and 22b of the security elements described above are each formed as openings through the electrically conductive structures 3, 5, 7, 21, 23, 30 to 32 and 51 to 53 , ie there is no electrically conductive material in the region of a recess. In a preferred alternative embodiment, but in the area of a recess 4, 6a, 6b, 8a, 8b, 20a, 20b, 22a and 22b there is electrically conductive material, the electrical conductivity of which is relative to the respective electrically conductive structure 3, 5, 7, 21, 23, 30 to 32 and 51 to 53 is reduced. A reduced conductivity is preferably achieved by a smaller layer thickness of the material in the area of the recess. As has already been explained in connection with FIG. 1 a, typical layer thicknesses of structures with a sufficiently high electrical conductivity for the detection of induction currents lie above approximately 250 nm. A significant reduction in the electrical conductivity in the region of the recess is accordingly achieved by layer thicknesses, which are significantly smaller than 250 nm and which empirical values are accordingly below approximately 150 nm, in particular in the range between 20 nm and 50 nm.

The typical layer thicknesses given above preferably apply to aluminum layers. When using other electrically conductive materials, e.g. other metals or electrically conductive printing inks, with a different specific electrical conductivity, the thicknesses of the corresponding layers are correspondingly larger or smaller.

This embodiment has the particular advantage that the recesses are opaque and consequently cannot be seen with the naked eye in transmitted light. Due to the small absolute differences in thickness between the electrically conductive structure and the recess of the order of magnitude of approximately 200 nm, neither manual palpation nor visual recognition of the coding structures in reflection geometry is possible. Such security elements are therefore particularly suitable as carriers of information that is to be kept secret and is only machine-readable. Figures 12a and 12b show further embodiments of security elements.

The security element 2 shown in FIG. 12 a essentially has the structure of the security element shown in FIG. 1 a, recesses in the form of interruptions 24 being additionally made in different sections of the electrically conductive layer, by means of which the electrically conductive sections 23 are separated from one another , As a result of the sequence of electrically insulating interruptions 24 and conductive sections 23 along the security element 2, the latter receives a bit coding, which can preferably be checked or read using the device shown in FIG. 9. Analogous to the example shown in FIG. 9, nine measuring heads each of the same distance are to be provided in this case with the construction described in connection with the sensors 72a to 72d. If, during the test, the security element 2 is moved past the device according to the invention, induction currents, in particular eddy currents, are induced in the conductive sections 23, analogously to the explanations in connection with FIGS. 8 and 9, which generate a magnetic field which is generated by the sensors can be detected. In the area of the interruptions 24, on the other hand, no induction currents are induced, so that the sensors at these points do not deliver a signal, or at least a signal that differs from the sensors via the conductive sections. In this way, the coding "010010110" contained in the security element 2 is read.

FIG. 12b shows a development of the security element shown in FIG. 12a, in which instead of interruptions, sections 26 are provided which have a smaller thickness in comparison to the electrically conductive sections 25 and thus a reduced electrical one Show conductivity. The device shown in FIG. 9 is also particularly suitable for such security elements. The statements relating to the example shown in FIG. 12a apply correspondingly to reading or checking the coding, stronger induction currents being induced in the electrically conductive sections 25 than in sections 26 with lower electrical conductivity. Accordingly, the signals generated by the individual measuring heads above the sections 25 and 26 differ, so that the coding "010010110" contained in the security element 2 is also measured here.

Alternatively, the device shown in FIG. 8 can also be used to test such security elements, it being necessary to ensure, in particular by the selection of a sufficient thickness of the sections 26, that closed induction currents can flow through the security element 2.

A special variant of this embodiment is characterized in that the thickness of the sections 26 and thus their electrical conductivity is chosen so that no sufficiently high electrical currents can flow to be detected with the device described in FIGS. 8 and 9 to be able to. In the test in the corresponding device, the sections 26 then behave in principle like the interruptions 24 of the security element 2 shown in FIG. 12a. Typical thicknesses of the sections 26 are between 20 nm and 50 nm, typical thicknesses of the electrically conductive sections 25 above 150 nm, in particular above 250 nm. As already explained in more detail above, security elements 2 designed in this way have the particular advantage that the coding contained cannot be recognized by the naked eye or by palpation. This variant of the security element is preferably produced as follows:

Applying, in particular vapor deposition, a first layer of metal or printing a first layer of electrically conductive printing ink onto a base;

Printing a negative representation of the coding on the first layer, the portions of the first layer remaining unprinted on which a second layer is to be applied; Applying, in particular vapor deposition, a second layer of metal or printing a second layer of electrically conductive printing ink onto the negative image;

Removing the printed negative representation together with the regions of the second layer located on the printed regions of the negative representation in a washing process, so that only regions of the second layer remain on the first layer which correspond to a positive representation of the coding.

The first layer has a much lower electrical conductivity than the second layer. This is preferably due to a much smaller thickness of the first layer compared to the thickness of the second

Layer reached. The thickness of the first layer is preferably less than 50 nm and the thickness of the second layer is greater than 150 nm.

In a further process variant, the differently thick sections of the layer are produced as follows:

Printing a negative representation of the coding on a base; Applying, in particular vapor deposition, a first layer of metal or printing a first layer of electrically conductive printing ink onto the negative image; Removing the printed negative image together with the areas of the first layer located on the printed areas of the negative image in a washing process, so that only areas of the first layer remain on the base which correspond to a positive image of the coding;

Applying, in particular vapor deposition, a second layer of metal or printing a second layer of electrically conductive printing ink onto the positive representation of the coding.

In this variant, the thickness of the first layer is chosen so that it is substantially greater than the thickness of the second layer, so that the electrically conductive sections of the first layer have a significantly higher electrical conductivity than the sections of the second layer.

Starting from FIG. 12b, it is also possible to provide an optical diffraction structure, in particular a hologram, in the thin sections 26. In principle, it is also possible to combine the electrically conductive sections 25 in a first layer level with a diffraction-optical structure extending over the entire length of the security element 2 in a second layer level. The diffraction-optical structure in the second layer plane, which is introduced into a thin metal layer with typical thicknesses between 20 nm and 50 nm, has a negligibly low electrical conductivity compared to the electrically conductive sections 25, so that the coding given by the arrangement of the sections 25 with the The device shown in FIG. 9, as described in connection with FIGS. 12a and 12b, can be read or checked.

In addition, it is possible to design security elements such that the thickness of the layer and thus the electrical conductivity of the layer varies continuously along one dimension of the layer, in particular along the longitudinal extent. Alternatively, the layer can have more than two different thicknesses in different sections, so that in the cross-section of the layer a kind of stair structure is obtained with stair steps of different heights over one dimension of the layer. The coding of such security elements can also be detected or read out using the devices according to FIGS. 8 and 9 described in more detail above. The individual measuring heads 61, 62 and 71, 72 in this case deliver signals which are dependent on the layer thickness of the respective section of the layer and are evaluated accordingly for further decoding.

FIGS. 12c and 12d show further embodiments of the coding principles shown in FIGS. 12a and 12b.

Instead of interruptions 24 or thin layers 28, sections 28 with a grid are provided in the security element 2 of FIG. 12c. The thickness of the layer in the sections 28 of the grid is preferably equal to the thickness of the layer in the electrically conductive sections 27. In the illustrated example of a so-called line grid, the electrically conductive layer in the grid sections 28 is interrupted by a large number of small, elongated cutouts. As a result, the electrical conductivity of the sections 28 is reduced to such an extent that circuit currents can no longer be detected there with the devices shown in FIGS. 8 and 9. The rastered sections 28 thus behave like the interruptions 24 or the very thin layers 26 of the security elements 2 shown in FIGS. 12a and 12b. The detection of the coding "010010110" is carried out in detail in accordance with the statements in connection with FIGS. 8, 9 and 12a and 12b. Instead of line grids, for example, dot grids or cross grids can also be provided, it being possible for the electrical conductivity of the grid sections 28 to be predetermined in a targeted manner via the structure of the respective grid and the size of individual grid elements.

In the security element 2 shown in FIG. 12d, different grids are provided in different sections 29 and 34 of the layer. The grid of the sections 34 corresponds to the grid shown in the sections 28 of FIG. 12c, as a result of which they have a very low electrical conductivity. The rasterization of the sections 29 is designed as a dot raster in which the individual, conductive raster dots (drawn in black) touch. The electrical conductivity of these sections 29 is thereby lower than in the corresponding sections 27 of the security element shown in FIG. 12c, but this is sufficiently high for inductive detection. The detection of the encoding "010010110" is in turn analogous to the manner described in more detail in connection with FIGS. 8, 9, 12a and 12b.

The coding with the gridings in sections 28, 29 and 34 of the security elements in FIGS. 12c and 12d are preferably obtained as follows:

Printing a negative representation of the coding with screened areas on a base;

Applying, in particular vapor deposition, a metal layer or printing a layer of electrically conductive printing ink onto the negative image;

Removing the printed negative image together with the areas of the metal layer or electrically conductive layer located on the printed areas of the negative image in a washing machine. gear, so that a positive representation of the coding with screening is obtained.

The thickness of the metal layer or the layer of electrically conductive printing ink is chosen so that it has a sufficiently high electrical conductivity for the detection of induction currents. The thickness of the layer is preferably greater than 150 nm.

With a suitable choice of the screening, it can be achieved that differently screened sections or sections with and without screening cannot be distinguished from one another with the naked eye or by touching. Such security elements are therefore particularly suitable as carriers of information that is to be kept secret and is only machine-readable.

Since the electrical conductivity of the individual sections depends not only on the layer thickness, but also on the specific conductivity of the material used, it is also possible to use the differently high electrical conductivities in the individual sections of the layer - in addition or as an alternative to the thickness variation described above or Screening - to be realized by using different materials, in particular metals and / or electrically conductive printing inks, with different specific electrical conductivities in the individual sections. For example, aluminum can be used as the first material, whereas copper is used as the second material. It is also possible to use materials which have different alloys or compositions. So far, the device for testing the security element has been described with first means for generating a first magnetic field and second means for detecting a second magnetic field. However, it is obvious that a device can also be used which uses electrical fields to test the security element and / or determines the conductivity of the security element.

Such a device can have, for example, several capacities, which can have an arrangement which, for. B. corresponds to the arrangement of the second means 61 from FIG. Due to the differently conductive areas of the security element or the presence or absence of conductive material, the electrical field of the capacitors is changed by the security element and can be measured, e.g. B. by changing the voltage on the capacitors. This makes it possible to carry out a test such as. B. has been described with reference to Figure 8, d. H. to determine the coding of the security element.

The capacitances can be arranged such that the security element is moved past the capacitances during the test, the electrical field extending in the direction of the security elements. However, it is also possible to arrange the capacitances in such a way that the security element is moved through the capacitances and thus through the electrical field during the test.

Claims

Patent claims

1. Security element, in particular for identification and value documents, with one or more electrically conductive components (3, 5, 7, 21, 23, 25-32, 34, 51-53), characterized in that by the spatial structure, in particular due to the spatial extent and / or location and / or shape of one or more of the components (3, 5, 7, 21, 23,

25-32, 34, 51-53) a coding is given.

2. Security element according to claim 1, characterized in that one or more of the components (3, 5, 7, 21, 23, 25-32, 34, 51-53) are formed by at least one electrically conductive layer.

3. Security element according to claim 2, characterized in that individual sections of the electrically conductive layer each have different spatial structures, in particular with different widths and / or lengths, by which the coding is given.

4. Security element according to one of claims 2 or 3, characterized in that individual sections (23, 25-29, 34) of the electrically conductive layer have different electrical conductivities, by which the coding is given.

5. Security element according to claim 4, characterized in that the different electrical conductivities are given by different thicknesses of the layer in the individual sections (25, 26) of the layer.

6. Security element according to claim 5, characterized in that the thickness of the layer, which preferably consists of aluminum, in individual sections (26) of the layer is less than 50 nm, in particular less than 30 nm, whereby these sections (26) have low electrical conductivity.

7. Security element according to one of claims 5 or 6, characterized in that the thickness of the layer, which preferably consists of aluminum, is greater than 150 nm, in particular greater than 250 nm, in individual sections (25) of the layer, whereby these sections (25) have a high electrical conductivity.

8. Security element according to one of claims 4 to 7, characterized in that the differently high electrical conductivities are given by a rasterization of individual sections (28, 29, 34) of the layer.

9. Security element according to claim 8, characterized in that first sections (28) of the layer have a grid and second sections (27) of the layer have no grid, whereby the first

Sections (28) have a different, in particular lower, electrical conductivity from the second sections (27).

10. Security element according to claim 8, characterized in that first sections (34) of the layer have a first grid and second

Sections (29) of the layer have a second grid different from the first grid, whereby the first sections (34) have a different electrical conductivity and / or different ability to form circular currents from the second sections (29), in particular eddy currents.

11. Security element according to one of claims 4 to 10, characterized in that the different electrical conductivities in the individual sections of the layer are given by different materials, in particular metals and / or electrically conductive printing inks, with different electrical conductivities in the individual sections.

12. Security element according to claim 11, characterized in that the first material is at least partially formed by aluminum, and that the second material is at least partially formed by copper.

13. Security element according to one of the preceding claims, characterized in that by one or more of the components (3, 5, 7,

21) a closed conductor loop (3, 5, 7, 21) is formed, the spatial structure of which gives the coding.

14. Security element according to one of claims 2 to 13, characterized in that the electrically conductive layer, which in particular the

Conductor loop (3, 5, 7, 21) forms at least one recess (4, 6a, 6b, 8a, 8b, 20a, 20b, 22a, 22b), in particular an opening through the layer, in an inner region of the layer and has a closed, electrically conductive structure (3, 5, 7, 21) in an outer region of the layer.

15. Security element according to claim 14, characterized in that the electrically conductive structure (3, 5, 7, 21) in the outer region of the layer and / or the recess (4) has the shape of a rectangle in the inner region of the layer.

16. Security element according to claim 14, characterized in that the recesses (6a, 6b, 8a, 8b, 20a, 20b, 22a, 22b) have different spatial structures in individual sections of the layer.

17. Security element according to claim 16, characterized in that individual recesses (6a, 6b, 20a, 20b, 22a, 22b) merge into one another.

18. Security element according to claim 17, characterized in that the recesses (20a, 20b; 22a, 22b) form a step-like and / or comb-like structure.

19. Security element according to one of the preceding claims, characterized in that the electrically conductive components (30-32) form at least one transformer circuit (30-32) which has two interconnected electrical coils (30, 31) and whose transformation behavior represents the coding ,

20. Security element according to one of the preceding claims, characterized in that the electrically conductive components (30-32) form at least one resonant circuit (51-53) which comprises at least one electrical coil (51) and at least one capacitor (52/53) and its resonance behavior, in particular resonance frequency, which represents coding.

21. Security element according to claim 20, characterized in that the resonant circuit (51-53) comprises two or more layers (10, 15, 16), wherein the coil (51) and at least one first plate (52) of the capacitor (52/53) are arranged on a first carrier layer (10) and at least one second plate (53) of the capacitor (52/53) on a second carrier layer ( 15) is arranged.

22. Security element according to claim 21, characterized in that between the first and second carrier layers (10 and 15) an insulation layer (16) made of electrically insulating; Material is arranged.

23. Security element according to one of the preceding claims, characterized in that at least one component (3, 5, 7, 21, 23, 25, 27- 32, 34, 51-53) is obtainable by a method having the following steps: printing one Negative representation of the component to be produced (3, 5, 7, 21, 23, 25, 27-32, 34, 51-53) on a base, - application of an electrically conductive cover layer to the negative representation and

Removing the negative representation together with the parts of the cover layer located on the structure of the negative representation by means of a washing process, so that regions of the cover layer remain outside of these structures on the base, a positive representation of the component (3, 5, 7, 21, 23, 25, 27-32, 34, 51-53) is obtained.

24. Security paper for the production of documents, in particular identification or value documents, such as banknotes, characterized by at least one security element according to one of claims 1 to 23.

25. Document, in particular identification or value document, characterized by at least one security element according to one of claims 1 to 23.

26. Device for testing a security element, in particular according to one of claims 1 to 21, with one or more electrically conductive components (3, 5, 7, 21, 23, 25-32, 34, 51-53) to assend first means (40, 42, 44, 73) for generating a first magnetic field and - second means (41, 43, 45, 46, 7) for detecting a second magnetic field, characterized in that

- At least one induction current is induced by the first magnetic field in the components (3, 5, 7, 21, 23, 25-32, 34, 51-53), whose spatial structure provides a coding, through which the second magnetic field is caused, and an evaluation device for determining the coding on the basis of the detected second magnetic field is provided.

27. The apparatus according to claim 26, characterized in that the first means (40, 42, 44) are designed to generate a time-varying, in particular periodic, magnetic field.

28. The apparatus according to claim 27, characterized in that the first means (40, 42, 44) an excitation coil (40), in particular with a first coil core (42), and a voltage source (44), in particular an AC voltage source, for supplying the voltage Include excitation coil (40).

29. Device according to one of claims 26 to 28, characterized in that the second means (41, 43, 45, 6, 47) a detection coil (41, 47), in particular with a second coil core (43, 46), and one Measuring device (45) for detecting currents and / or voltages induced in the first detection coil (41, 47).

30. Device according to one of claims 26 to 29, characterized in that the first means (73) are designed to generate a static, in particular spatially inhomogeneous, first magnetic field, the induction current in the components (3, 5, 7, 21, 23, 30-32, 51-53) is generated by moving the circuit relative to the first means (73).

31. The device according to claim 30, characterized in that the first means (73) comprise at least one permanent magnet.

32. Device according to one of claims 26 to 31, characterized in that the first means (73), in particular the permanent magnet, are magnetically coupled to the second means, in particular to the second coil core (43).

33. Device according to one of claims 26 to 32, characterized in that a transport device is provided which transports the security element (2) past the static, in particular spatially inhomogeneous magnetic field of the first means (73), in which

Components (3, 5, 7, 21, 23, 25-32, 34, 51-53) of the security element (2) an induction current is generated.

34. Device for testing a security element, according to one of claims 1 to 23, with one or more electrically conductive components (3, 5, 7, 21, 23, 25-32, 34, 51-53), with means for generating a electric field, characterized in that the electric field is changed by the components (3, 5, 7, 21, 23, 25-32, 34, 51-53), the spatial structure of which gives a coding, and in that a Evaluation device for determining the coding on the basis of the changed electric field is provided.

35. Apparatus according to claim 34, characterized in that the means for generating the electric field are formed by at least one capacitor.

36. Apparatus according to claim 35, characterized in that the security element is moved past the at least one capacitor.

37. Apparatus according to claim 35, characterized in that the security element is moved through the at least one capacitor.