Device and method for contactless excitation

Abstract

Device for contactless excitation of at least one electroluminescent pigment in a valuable or security document (2), wherein the device (1) comprises at least one electrode (6), wherein the at least one electrode (6) is designed such that an electric flux density of the field (9) generated by the electrode (6) in a predetermined direction of radiation (9) changes, wherein the device has several electrodes (6), each of the electrodes (6) being designed such that the electric flux density of the field (7) that can be generated by an electrode (6) in a predetermined direction of radiation (9) changes, characterized by the fact that all electrodes (6) have a common direction of radiation which is directed from the electrodes towards the valuable or security document and is oriented parallel to a central longitudinal axis of the electrodes.

Description

[0001] The invention relates to a device and a method for the contactless excitation of at least one electroluminescent pigment, in particular in a valuable or security document.

[0002] Valuable or security documents, such as banknotes, identity documents, credit cards, and the like, may have so-called security or authentication features affixed to or within the document. These security features can be activated externally and analyzed during or after activation. Typical authentication features include fluorescent pigments that light up when activated by a special sensor, allowing for verification.

[0003] It is also known to arrange electroluminescent pigments in or on a valuable or security document.

[0004] EP 1 631 461 B1 discloses a security document with at least one security element comprising a marking layer containing electroluminescent pigments applied to a carrier body in a marking area, wherein a plurality of field displacement elements, each electrically insulated from their surroundings and having a dielectric constant of more than 50, are arranged distributed in the marking area, having an average distance from each other of about 5 µm to 500 µm to form spaces for the electroluminescent pigments, and which locally increase a macroscopically imposed electric field strength in the spaces.

[0005] German patent DE 10 2008 047 636 A1 discloses a device for verifying the authenticity of a security document that has at least one electroluminescent security feature when excited in a high-voltage alternating field at a specific excitation frequency. The device comprises a sensor unit consisting of an excitation module, a condenser system, and a detector unit. The security document is moved through the sensor unit, and the luminescent light is collected by the condenser system and directed onto the detector unit, which detects and spectrally evaluates the luminescent light. The excitation module has a slit-shaped opening that overlaps the movement path of the security document to be verified with its opposing boundary surfaces.

[0006] To excite electroluminescent pigments in a valuable or security document, an air gap must be bridged, for example, between an electrode and the document. The dielectric strength of the air limits the excitation field. In previous designs, the air gaps involved resulted in an excitation frequency of 30 kHz and a maximum excitation voltage amplitude of 30 kV.

[0007] DE 102008 047 636 A1 discloses a device for verifying authenticity.

[0008] DE 199 03 988 A1 discloses a device for validating authentication features on security documents, in particular banknotes, which pass through a testing machine in batch processing operation, wherein a detector device captures the authentication feature and supplies it to signal processing.

[0009] It is desirable to integrate counterfeit verification devices, for example, into decentralized, small banknote verification machines or ATMs. This requires reducing the installation space required for such a device.

[0010] Existing devices for verifying authenticity do not adequately meet these requirements.

[0011] The technical problem is to create a device and a method for the contactless excitation of at least one electroluminescent pigment that enables reliable and targeted excitation with a reduced maximum amplitude of an alternating voltage for generation.

[0012] A fundamental aspect of the invention is to design an electrode of a device for contactless excitation in such a way that the field lines of an electric field generated by the electrode are locally concentrated. This allows for a spatially local increase in electric flux density, which advantageously permits improved and more reliable excitation of electroluminescent pigments.

[0013] A device for the contactless excitation of at least one electroluminescent pigment in a valuable or security document is proposed. The electroluminescent pigment may be contained within a security feature of the valuable or security document. Thus, the device can also serve for the contactless excitation of at least one security feature of a valuable or security document containing electroluminescent pigments. The device can therefore be part of a document verification system used to verify the security features or elements of a valuable or security document.

[0014] A security document is any document that is a physical entity protected against unauthorized production and / or falsification by security features. Security features are those characteristics that make falsification and / or duplication more difficult than simple copying. Physical entities that incorporate or embody a security feature are called security elements. A security document can contain multiple security features and / or security elements. For the purposes of this definition, a security document always also constitutes a security element. Examples of security documents, which also include valuable documents representing a value, are passports, identity cards, driver's licenses, ID cards, access control cards, health insurance cards, banknotes, postage stamps, bank cards, credit cards, smart cards, tickets, and labels.

[0015] The device comprises at least one electrode. Not according to the invention, it is possible for the device to comprise exactly one electrode. The electrode serves to generate an electric field, which is hereinafter also referred to as the excitation field. This field is generated when an alternating voltage is applied to the electrode. The alternating voltage applied to the electrode is hereinafter referred to as the excitation voltage. The excitation voltage can be generated by an alternating voltage source. It is also possible for the excitation voltage to be an output voltage of a transformer, wherein an input voltage of the transformer is generated by an alternating voltage source. The alternating voltage source can, for example, comprise a direct voltage source and an inverter, wherein the alternating voltage is an output voltage of the inverter.

[0016] When the excitation voltage is applied to the electrode, an electric field is generated whose field lines extend away from the electrode.

[0017] Furthermore, the at least one electrode is designed such that the electric flux density of the electric field generated by the electrode in a predetermined radiation direction changes. In particular, the electric flux density increases and forms at least a maximum.

[0018] The predetermined radiation direction refers to a direction directed from the electrode towards the valuable or security document. In particular, the electrode's radiation direction can be oriented perpendicular to a surface of the valuable or security document. Alternatively, the radiation direction can be parallel to a central longitudinal axis of the electrode and directed away from a free end of the electrode.

[0019] The fact that the electric flux density of the electric field generated by the electrode in a predetermined radiation direction changes means that the flux density changes in a cross-sectional plane oriented perpendicular to the predetermined radiation direction of the electrode. In particular, at least one spatial region with a higher flux density than in adjacent regions may exist in the cross-sectional plane.

[0020] For example, the flux density can change along a direction perpendicular to the direction of radiation. In this case, the flux density can change continuously, i.e., not abruptly, within the cross-sectional plane. For example, the flux density can change linearly or exponentially, in particular increasing or decreasing.

[0021] This advantageously creates at least one region with increased electric flux density through a specific electrode design. In particular, this allows for field focusing, resulting in a spatial concentration of the electric field. This enables reliable excitation of at least one electroluminescent pigment, as improved excitation is also facilitated by a concentrated excitation field.

[0022] Furthermore, it is advantageously possible to reduce the amplitude of the excitation voltage. Since both higher flux densities and higher amplitudes result in improved or stronger excitation of the electroluminescent pigment, the amplitude can be reduced due to the at least one region with a high flux density, while the excitation strength remains at least constant.

[0023] Reducing the amplitude of the excitation field, in turn, advantageously allows adverse effects of high amplitudes, such as plasma formation in an air gap, voltage breakdown, undesirable radiation behavior of a field with high field strength, electromagnetic interference of other electronic components, and high energy consumption, to be avoided.

[0024] In another embodiment, the electric flux density of the excitation field changes within a predetermined region of a cross-sectional plane oriented perpendicular to a predetermined radiation direction of the electrode. This predetermined region is penetrated by all or a predetermined fraction of the electric field generated by the electrode, i.e., the excitation field. This defines a quantity of the region within the cross-sectional plane. The predetermined fraction can, for example, be defined by a predetermined percentage, such as 95%, 90%, or 85%.

[0025] The change in flux density therefore occurs in the region of the cross-sectional plane penetrated by the excitation field or a predetermined portion thereof. Thus, in this region, there is no constant flux density, as is the case, for example, with a parallel-plate capacitor.

[0026] It is also possible that the predetermined area is equal to or smaller than the area enclosed by a boundary of the electrode projected onto the cross-sectional plane. If an outer diameter, in particular a maximum outer diameter, of the proposed electrode is projected onto the cross-sectional plane, then the area may be enclosed by the boundary forming the maximum outer diameter.

[0027] In particular, the changing flux density can have exactly one maximum in the predetermined range.

[0028] The proposed device advantageously enables a local, spatial concentration of field lines to be generated by the electrode in the direction of radiation, thereby increasing the reliability of the excitation of the at least one electroluminescent pigment, as previously described.

[0029] In another embodiment, the electric flux density is higher in at least one sub-region of the predetermined area of ​​the cross-sectional plane than in other sub-regions of the predetermined area. For example, the electric flux density can be higher than 1 × 10 -7 Cm 2 As explained previously, it is possible that in precisely one sub-region of the predetermined area of ​​the cross-sectional plane, the electric flux density is higher than in all remaining sub-regions. Thus, exactly one region with a high flux density is created. This enables the targeted and reliable excitation of at least one electroluminescent pigment by the electrode designed as proposed.

[0030] In a further embodiment, the at least one electrode tapers towards a radiation-side end. The radiation-side end of the electrode is defined as the end from which the excitation field, in particular its field lines, is emitted from the electrode, especially towards the at least one valuable or security document. In particular, the radiation-side end can be a free end of the electrode.

[0031] The term "tapering" here refers, for example, to a reduction in diameter, where the diameter can be measured perpendicular to a central longitudinal axis. As explained previously, the central longitudinal axis can be parallel to or equal to the predetermined direction of radiation.

[0032] The narrowing, especially with increasing narrowing, results in an increase in the flux density of the excitation field emitted in the direction of radiation, since the narrowing causes a field focusing.

[0033] This results in a structural design for at least one electrode that is easy to implement.

[0034] In another embodiment, the electrode has a conical section. Alternatively, the electrode can have a cone-shaped section.

[0035] The proposed sections are designed such that the electrode tapers towards the radiation-side end.

[0036] The previously described shapes of the sections advantageously enable the desired field bundling, while simultaneously allowing for a simple structural design of the electrode.

[0037] In another embodiment, the electrode is designed as a wire. The wire can, for example, be made of a conductive material. For instance, the wire can be made of copper, silver, or gold, but preferably of carbon fiber.

[0038] The wire can have a predetermined maximum diameter. For example, the maximum diameter can be 1 mm. Diameters of up to 0.1 mm are preferred. For larger diameters, a tapered free wire end, especially a pointed wire end, is advantageous.

[0039] The wire-like design advantageously results in a high field concentration and makes the electrode particularly easy to manufacture.

[0040] According to the invention, the device comprises several electrodes, each electrode being configured such that the electric flux density of the field generated by an electrode in a predetermined radiation direction changes. Thus, the device includes several electrodes configured according to one of the embodiments described above. In this embodiment, all electrodes have a common radiation direction.

[0041] In this case, it is particularly possible that several regions with maximum electric flux density occur in a cross-sectional plane oriented perpendicular to all emission directions. This advantageously facilitates the excitation of an electroluminescent pigment when the exact location of the electroluminescent pigment, e.g., in a valuable or security document, is unknown. Specifically, the proposed device generates a resulting excitation field with multiple regions of maximum flux density. If the excitation field thus generated is applied, e.g., to a valuable or security document containing at least one electroluminescent pigment, the probability increases that at least one electroluminescent pigment is located in a region of high or maximum flux density.Naturally, such an electrode can also excite multiple, and especially a large number, of electroluminescent pigments. For example, electroluminescent pigments with a size in the nanometer range can be stochastically distributed within a safety element. An electrode with an outer diameter of, say, 100 µm can then excite electroluminescent pigments in an excitation area with a diameter of 1 mm. A major advantage of using multiple electrodes is that the excitation area, and thus the luminous area, increases.

[0042] In a further embodiment, the distance between an electrode and a neighboring electrode is less than or equal to a predetermined maximum distance. This distance can be measured perpendicular to the direction of radiation. In particular, all electrodes can thus extend parallel to each other, with, for example, the central longitudinal axes of the electrodes being oriented parallel to each other.

[0043] The distance between the individual electrodes also determines the distance between regions of high flux density in the resulting excitation field. By selecting the appropriate distance, a spatial distribution of regions with high or maximum flux density can be achieved as desired.

[0044] The predetermined maximum distance can be, for example, 5 mm.

[0045] It is possible for the electrodes to be arranged in a comb-like pattern. In this case, the individual electrodes form the teeth of a comb structure. Alternatively, the electrodes can be arranged in a matrix-like pattern. Here, the individual electrodes form rows and columns of a matrix. In the matrix-like arrangement, the distance and direction to at least one adjacent electrode are constant in the row and / or column direction.

[0046] It is also possible for the electrodes to be arranged in a tufted or bundled manner. In this case, the distribution of the electrodes in the previously described cross-sectional plane may not exhibit a defined pattern, but rather a random one. In a random pattern, for example, the distance and direction to the neighboring electrode can vary.

[0047] A uniform distribution of the electrodes in the cross-sectional plane advantageously results in a uniform distribution of areas with high or maximum flux density. This can be particularly advantageous if, for example, electroluminescent pigments in a security document are also arranged at approximately equal intervals.

[0048] With a tufted or bundled arrangement of the electrodes, it is advantageous that the spatial distribution of areas of the excitation field with high or maximum flux density is also random. This is particularly advantageous when, for example, electroluminescent pigments are randomly arranged in a valuable or security document. A random distribution of the pigments occurs, for instance, when they are added to a printing ink, as is customary, or are randomly distributed within the substrate during its production.

[0049] Furthermore, the electrodes can be arranged such that they encompass or surround an area in which an optical sensor and / or optical elements for beam guidance are located. For example, the electrodes can encompass an area in which a channel serving as an optical detection channel is located. The optical sensor and / or other optical elements can be located in this channel.

[0050] The area can, for example, be enclosed by a connecting line of the electrodes. This area can have a predetermined size. Thus, the electrodes can be arranged around means for optical detection.

[0051] In another embodiment, several electrodes are electrically connected together. This advantageously allows the excitation voltage to be applied to several electrodes simultaneously, so that the excitation fields generated by the individual electrodes also have the same phase relationship.

[0052] At the same time, the required installation space is advantageously reduced and the electrical contacting of the individual electrodes is simplified.

[0053] Overall, the proposed device makes it possible, for example, to design a document verification device for verifying a valuable or security document with at least one electroluminescent pigment in the smallest possible installation space.

[0054] Furthermore, it is advantageous that the circuitry required for the proposed device can be minimized, particularly when several electrodes are electrically connected together. The proposed electrode shapes advantageously allow for a small installation space to be required for the electrodes. The previously described possibility of reducing the excitation voltage amplitude advantageously results in fewer other interference effects. Thus, the electromechanical compatibility of the proposed device can be improved. Energy consumption during the generation of the excitation field can also be reduced.

[0055] This also describes a document verification device that includes the device explained above. The document verification device can, for example, be designed as a battery-operated, portable handheld device or be part of such a device. For example, the document verification device can be pen-shaped, with the electrode located on a tapered section of the pen. With such a pen, a simple verification of a valuable or security document can advantageously be carried out by a user manually aligning the pen relative to the valuable or security document.

[0056] The document verification device may also include other components, such as the previously described AC voltage source and transformer.

[0057] Alternatively, the device can be integrated into, for example, a stationary document verification device to check, for example, a valuable or security document for a security feature in a machine-readable manner.

[0058] In the second alternative, in particular, the document verification device may, for example, include an optical detection device for capturing the radiation emitted by the at least one electroluminescent pigment. This detection device may be an image acquisition device, e.g., a CCD camera, a light sensor, e.g., a photodiode, or other components for spectral detection of the emitted light. The verification device may also include further optical elements, e.g., lenses or mirrors, for deflecting and / or focusing the emitted radiation.

[0059] A valuable or security document can be inserted into the document verification device in such a way that the previously explained direction of radiation is oriented perpendicular to a surface of the valuable or security document.

[0060] The at least one electrode can also be positioned relative to the valuable or security document such that the distance between the electrode and a surface of the valuable or security document is a maximum of 20 mm, preferably a maximum of 5 mm. The minimum distance can be 0 mm, so that the electrode and document are in contact. Preferably, however, the distance is at least 0.5 mm, especially if the electrode is not protected against mechanical wear.

[0061] A further proposed method is a contactless excitation of at least one electroluminescent pigment, particularly in a valuable or security document. In this method, an alternating electrical voltage is applied to at least one electrode. The alternating electrical voltage applied to the electrode can also be referred to as the excitation voltage. The at least one electrode is configured such that the electric flux density of the field generated by the electrode in a predetermined direction of radiation changes. This electric field constitutes the excitation field. The electrode is thus configured according to one of the embodiments described above.

[0062] Furthermore, the electrode can be aligned in such a way that the radiation direction is directed towards the valuable or security document, in particular perpendicular to a surface of the valuable or security document.

[0063] Furthermore, the alternating electrical voltage can be generated such that the excitation voltage amplitude lies in a range of 100 V to 5 kV. The excitation voltage frequency can also be set. In particular, the frequency can lie in a range of 30 kHz to 20 MHz. Preferably, the excitation frequency lies in a range of 70 kHz to 100 kHz.

[0064] The excitation voltage can have various shapes. For example, the excitation voltage can be a rectangular voltage, a triangular voltage, a trapezoidal voltage, but preferably a sinusoidal voltage.

[0065] The invention is explained in more detail using several exemplary embodiments. The figures show: Fig. 1 a schematic block diagram of a device for the contactless excitation of at least one electroluminescent pigment, Fig. 2a a cross-section through an electrode according to the invention, Fig. 2b a cross-section through another electrode, Fig. 3 a schematic representation of an electrode according to the invention and a value or security document, Fig. 4 a schematic representation of a tuft-like electrode arrangement and a value or security document, Fig. 5 a top view of the in Fig. 4 illustrated tufted electrode arrangement, Fig. 6 a top view of another electrode arrangement and Fig. 7 a schematic representation of the in Fig. 6 electrode arrangement shown and a value or security document.

[0066] In the following, identical reference symbols denote elements with the same or similar technical characteristics.

[0067] In Fig. Figure 1 is a schematic block diagram of a device 1 for the contactless excitation of at least one electroluminescent pigment (not shown) in a valuable or security document 2 (see e.g. Fig. 3) shown. The device 1 comprises a DC voltage source 3, for example, a battery. The DC voltage source 3 is electrically connected to an inverter 4, which is also part of the device 1. By means of the inverter 4, an output voltage of the DC voltage source 3 can be converted into an AC voltage with a predetermined excitation frequency. On the output side, the inverter 4 is electrically connected to a transformer 5. The transformer 5 converts the AC voltage generated by the inverter 4 into an excitation voltage with a desired amplitude. On the output side, the transformer 5 is connected to an electrode 6, which is shown schematically, and the excitation voltage generated by the transformer 5 is applied to the electrode 6. The electrode 6 generates an excitation field 7, as will be explained in more detail below.

[0068] Thus, an electric excitation field can be generated using a resonant circuit, whereby the resonant frequency of the circuit can be chosen to be higher than the previously common excitation frequencies of up to 30 kHz. This advantageously allows for a reduction in the voltage amplitude of the excitation voltage.

[0069] This, in turn, reduces the required installation space for the resonant circuit elements. The resonant circuit can, for example, consist of at least a secondary inductance of the transformer and a capacitance of the electrode. In previously used document verification devices, excitation frequencies of 30 kHz and excitation voltages with an amplitude of up to 30 kV were employed.

[0070] The high excitation frequency advantageously results in a high rate of change of the electric excitation field reversal (dU / dt). Since the emission excitation of electroluminescent pigments also depends on the rate of change of the excitation field, the amplitude of the excitation voltage can be reduced. Reducing the amplitude of the excitation voltage also reduces the energy to be stored in the resonant circuit, i.e., the magnetic or electrical energy to be stored. This advantageously allows for a reduction in the size of the transformer, for example. For instance, the space required for a ferrite core in the transformer, which serves to store the magnetic energy, can be reduced at a lower energy level. Simultaneously, reducing the maximum excitation voltage reduces the insulation requirements, e.g., for the transformer windings.This, in turn, leads to a reduction in installation space requirements. Furthermore, it prevents or limits unwanted heating of the system.

[0071] Furthermore, it is advantageous that reducing the amplitude of the excitation voltage also improves the operational reliability of the transformer. For example, with a reduced excitation voltage amplitude, the transformer stores less energy that could be dangerous to a human user, such as upon contact.

[0072] The excitation voltage can have a maximum amplitude of 6 kV. The excitation field 7 (see e.g. Fig. 2a) serves to excite electroluminescent pigments in the valuable or security document 2.

[0073] In Fig. Figure 2a shows a cross-section through an electrode 6 according to the invention. The electrode 6 has a central longitudinal axis 8. Also shown is a radiation direction 9 of the electrode 6. This is oriented parallel to the central longitudinal axis 8. The electrode 6 tapers towards a radiation-side end 10. Here, the electrode 6 has a conical section 11 at the radiation-side end 10. Further details are shown in Fig. Figure 2a shows the distribution of field lines of the excitation field 7 extending away from the electrode 6. In a cross-sectional plane 12 oriented perpendicular to the direction of radiation 9, the electric flux density of the excitation field 7 changes. In particular, the electric flux density changes in a predetermined region 13, which is penetrated by the entire electric excitation field 7 generated by the electrode 6. It is shown that the flux density increases from the edges of the region 13 towards a point where the central longitudinal axis 8 intersects the cross-sectional plane 12. Thus, the spatial distribution of the electric flux density of the excitation field 7 has exactly one region with maximum flux density.

[0074] In Fig. Figure 2b shows a cross-sectional view of another electrode 14. Also shown is a cross-sectional plane 12, oriented perpendicular to a central radiation direction 9 of the electrode 14. Further shown is the region 13, which is penetrated by the entire excitation field generated by the electrode. In contrast to Fig. However, in 2a the electric flux density does not increase towards the point where a central longitudinal axis 8 of the electrode 14 intersects the cross-sectional plane 12. This prevents the desired local spatial concentration of field lines from being achieved, which would allow for reliable excitation of electroluminescent pigments.

[0075] In Fig. Figure 3 shows a schematic representation of an electrode 6 and a security document 2. The electrode 6 is positioned relative to the security document 2 such that the radiation direction 9 of an excitation field 7 generated by the electrode 6 is oriented perpendicular to a surface 15 of the security document 2. A security element 16, comprising electroluminescent pigments (not shown), is arranged on the surface 15. These pigments can be excited by the electric excitation field 7 to emit luminescent radiation 17. Due to the physical design of the electrode 6, a region with a high electric flux density of the excitation field 7 is created in the area of ​​the security element 16.If an electroluminescent pigment is arranged in this area, this electroluminescent pigment can also be excited when comparatively lower excitation voltages are used, for example with amplitudes between 100 V and 5 kV.

[0076] In Fig. Figure 4 shows a schematic arrangement of a valuable or security document 2 with a security element 16, which is arranged on a surface 15 of the valuable or security document 2, and an electrode arrangement 18. The electrode arrangement 18 comprises several electrodes 6 whose emission directions 9 are parallel to each other. Each of the electrodes 6 generates an excitation field 7 (not shown) (see, for example, Figure 4). Fig. 2a), which corresponds to the Fig. 2a. All electrodes 6 are electrically contacted together, whereby in Fig. Figure 4 shows a transformer 5 whose output voltage, i.e. the excitation voltage, is applied simultaneously to all electrodes 6.

[0077] In Fig. 5 is a top view of the in Fig. Figure 4 shows the electrode arrangement 18. The individual electrodes 6 are arranged in a tuft or bundle-like manner. The distance and direction between the individual electrodes 6 and their nearest neighboring electrodes 6 vary. This results in a random spatial arrangement of the electrodes 6, which also causes a random spatial distribution of areas with high or maximum flux density of the excitation field 7.

[0078] Through the in Fig. The electrode arrangement shown in Figure 5 advantageously increases the excitation area and thus also the light emission area of ​​the safety element 16 (see, for example, Figure 5). Fig. 4) To minimize wear, one or all electrodes 6 of the electrode arrangement 18 can be encapsulated in a plastic material, in particular in a high-voltage-resistant and well-insulating plastic material, for example in a UV-curing epoxy potting compound, a 2-component epoxy potting compound, a silicone potting compound, a thermoplastic polyurethane (TPU) potting compound, or an injection-molded polymer material potting compound. This advantageously prevents the formation of corona at the tips of the electrodes 6, while simultaneously minimizing wear.

[0079] In Fig. Figure 6 shows a top view of another advantageous electrode arrangement 18. Here, the electrodes 6 of the electrode arrangement 18 are arranged such that they encompass a region 19, in which a recess 20 is arranged. The region 19 can, for example, be enclosed by a connecting line 22 of the electrodes 6. The connecting line 22 of the electrodes 6 can, for example, be circular. Thus, the electrodes 6 are arranged on a circle with a predetermined distance from each other, the circle having a predetermined radius. Of course, other arrangements are also conceivable, for example, on a rectangular connecting line.

[0080] The recess 20 or opening can be designed, for example, as a blind hole or as a through hole, i.e., open at both ends. The recess 20 can be cylindrical. For example, an axis of symmetry of the connecting line 22 and the cylindrical recess 20 can be aligned.

[0081] The recess 20 can serve as an optical detection channel or form an optical detection channel, wherein radiation, e.g. radiation emitted by an excited electroluminescent pigment, is directed through the recess 20 to an optical detection device 21 (see Fig. 7) or can reach a user's eye.

[0082] This means that the electrodes 6 are arranged around the optical detection channel. This allows both the excitation and the detection of the emitted light to occur from only one common side, e.g., the valuable or security document 2.

[0083] In Fig. 7 is a schematic representation of the in Fig. Figure 6 shows an electrode arrangement 18 and a security document 2. It can be seen that the electrode arrangement 18 or a housing of the electrode arrangement 18 is hollow cylindrical, with the electrodes 6 arranged, for example encapsulated, in a shell section 23. An optical sensor 21 is arranged on a bottom surface 24 of the inner volume of the hollow cylinder, which forms the recess 20.

[0084] A security element 16 of the valuable or security document 2, which contains electroluminescent pigments not shown, is connected to an excitation field 7 (see e.g. Fig. 2a) is acted upon, wherein a radiation direction 9 of the excitation field 7 generated by the electrode 6 is oriented perpendicular to a surface 15 of the valuable or security document 2. The luminescence radiation emitted by the electroluminescent pigments passes through the recess 20 into the detection range of the optical sensor 21. It is of course possible that optical elements, for example for beam guidance or focusing, such as a lens, are arranged in the recess 20, which serves as the optical detection channel. The optical sensor 21 can, for example, be a photodiode with a downstream amplifier. The illustrated embodiment advantageously results in a very compact design for a document verification device, in particular a portable document verification device.

[0085] The in Fig. The inverter 4 shown in 1 can, for example, be implemented as an oscillator circuit, which includes, for example, an operational amplifier circuit and two FETs as a push-pull output stage. The transformer 5 can, for example, include transformer coils wound on a ferrite core. The electrode 6 can, for example, be connected to only one line of the Fig. The circuit shown in 1, e.g., one turn of a coil of transformer 5, is connected. Preferably, the circuit shown in 1 is connected to the transformer 5. Fig. 1. Circuit shown with excitation frequencies of the excitation field 7 (see e.g. Fig. 2a) operated at frequencies higher than audible frequencies, for example frequencies between 30 kHz and 20 MHz, preferably in a range of 70 kHz to 100 kHz.

Claims

[1] Device for non-contact excitation of at least one electroluminescent pigment in a valuable or security document (2), wherein the device (1) comprises at least one electrode (6), wherein the at least one electrode (6) is designed such that an electric flux density of the field (9) generated by the electrode (6) in a predetermined direction of radiation (9) changes, wherein the device has several electrodes (6), each of the electrodes (6) being designed such that the electric flux density of the field (7) that can be generated by an electrode (6) in a predetermined direction of radiation (9) changes, characterized by , that all electrodes (6) have a common direction of radiation which is directed from the electrodes towards the valuable or security document and is oriented parallel to a central longitudinal axis of the electrodes. [2] Device according to claim 1, characterized by, that in a predetermined area (13) of a cross-sectional plane (12) oriented perpendicular to the predetermined direction of radiation (9) of the electrode (6) an electric flux density changes, wherein the predetermined area (13) is penetrated by all or a predetermined proportion of the electric field (7) generated by the electrode (6). [3] Device according to claim 2, characterized by , that in at least one sub-area of ​​the predetermined region (13) of the cross-sectional plane (12) the electric flux density is higher than in other sub-areas of the predetermined region (13). [4] Device according to any one of claims 1 to 3, characterized by , that the at least one electrode (6) tapers towards a radiation-side end. [5] Device according to claim 4, characterized by , that the electrode (6) has a cone-shaped or conical section. [6] Device according to any one of claims 1 to 5, characterized bythat the electrode is designed as a wire. [7] Device according to claim 1, characterized by , that the distance between an electrode (6) and an adjacent electrode (6) is less than or equal to a predetermined maximum distance. [8] Device according to one of claims 1 or 7, characterized by , that several electrodes (6) are electrically contacted together. [9] Method for contactless excitation of at least one electroluminescent pigment in a valuable or security document (2), wherein an alternating electrical voltage is applied to at least one electrode (6), wherein the at least one electrode (6) is configured such that an electric flux density of the electric field (7) generated by the electrode (6) in a predetermined direction of emission (9) changes, wherein a device has several electrodes (6), wherein each of the electrodes (6) is designed such that the electric flux density of the field (7) that can be generated by an electrode (6) in a predetermined direction of radiation (9) changes, characterized by , that all electrodes (6) have a common direction of radiation which is directed from the electrodes towards the valuable or security document and is oriented parallel to a central longitudinal axis of the electrodes.

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