Optically variable security element with machine-readable feature material and optical functional layer, security document and testing procedure

Abstract

The invention relates to an optically variable security element (20) for securing a valuable document (10), comprising a first machine-readable feature (36) and an optical functional layer (24, 26) that gives the security element (20) an optically variable appearance when viewed. According to the invention, the security element (20) is multilayered with an inner film layer (30) having a bottom and an opposing top, wherein the film layer (30) is provided on the bottom with an adhesive layer (34) for bonding to the valuable document (10) and on the top with the optical functional layer (24, 26), and wherein the first machine-readable feature (36) is arranged in the film layer (30) or on the top of the film layer (30).

Description

[0001] The invention relates to an optically variable security element for protecting a valuable document, comprising a machine-readable feature substance and an optical functional layer that gives the security element an optically variable appearance when viewed. The invention also includes a valuable document with such a security element, as well as a method for verifying such a valuable document.

[0002] Data storage media, such as valuables or identification documents, but also other valuable items, such as branded goods, are often provided with security elements for security purposes. These elements allow the authenticity of the data storage media to be verified and also serve as protection against unauthorized reproduction.

[0003] It has been shown that during tampering attempts, counterfeiters remove security elements from genuine valuable documents and apply them to an unauthorized document, or that the substrate of a genuine valuable document is affixed with a counterfeit security element after such a removal process. This type of removal attack is also known as "harvesting" and is often difficult to detect as tampering, both visually and mechanically.

[0004] Foil security elements often do not have machine-readable features, making it difficult to easily detect the replacement of such a security element with a counterfeit. Therefore, WO 2023 / 285000 A1 proposes providing both the banknote substrate and an applied security element with security components that, when combined, provide a characteristic signal. The absence of the combination signal then represents a strong indication of tampering. However, there is a risk that when a security element is removed, part of the security component generating the characteristic signal remains on the banknote substrate, so that a combination signal is generated despite the tampering, and the tampered note cannot be reliably identified as a counterfeit.

[0005] Based on this, the invention is based on the object of providing a generic security element that avoids the disadvantages of the prior art. In particular, in the event of a detachment attack on a security element applied to a document, the machine-readable feature substance is to be completely removed from the original document. The invention also aims to provide a valuable document protected against detachment attacks with such a security element and a verification method for valuable documents secured in this way.

[0006] This object is achieved by the features of the independent claims. Further developments of the invention are the subject of the dependent claims.

[0007] The invention includes an optically variable security element with a first machine-readable feature substance and an optical functional layer that gives the security element an optically variable appearance when viewed. The optically variable security element is used in particular to protect a valuable document, such as a banknote or an identification document.

[0008] As a special feature, the security element is designed as a multi-layered structure with an inner foil layer having a bottom side and an opposite top side. The foil layer is provided with an adhesive layer on the bottom side for bonding to the value document and with the optical functional layer on the top side. The first machine-readable feature substance is arranged in the foil layer or on the top side of the foil layer. The arrangement on the top side of the foil layer can take place either directly on the surface of the top side of the foil layer or, alternatively, in a layer on the top side that is spaced from the surface of the foil layer by further intermediate layers.

[0009] After the security element according to the invention has been adhered to a target document, the layer of the feature substance ensures that the feature substance is completely removed along with the optical functional layer in the event of a detachment attack, and that no residue of the feature substance remains on the target document. Without wishing to be bound to a specific explanation, according to current understanding, the inner film layer stabilizes the overlying layers of the security element to such an extent that when the optical functional layer is detached, the film layer is also detached. Since the machine-readable feature substance is arranged in or above the film layer, it is completely detached during this process without leaving any residue on the target document.

[0010] In an advantageous embodiment, the first machine-readable feature substance is an IR luminescent substance or an optical storage phosphor with optically stimulated luminescence.

[0011] In an advantageous embodiment, the first machine-readable feature substance is present in a feature layer arranged on the upper side of the film layer, in particular in a UV-curable lacquer layer, an embossing lacquer layer or an adhesive layer, for example a laminating adhesive layer.

[0012] Particularly advantageously, the layer containing the first machine-readable feature substance is the optical functional layer itself, a part of the optical functional layer, or is directly connected to the optical functional layer. For example, the optical functional layer can contain an embossing lacquer layer provided with a relief structure, and the first machine-readable feature substance can be incorporated into the embossing lacquer layer. In another embodiment, the first machine-readable feature substance can be present in an adhesive layer with which the optical functional layer is connected to the film layer. The first machine-readable feature substance can also be present in a separate, dedicated feature layer, which is arranged in particular between the film layer and the optical functional layer. Furthermore, the first machine-readable feature substance can also be present in the film layer itself.

[0013] The film layer is advantageously formed by a film with a thickness between 4 µm and 15 µm and is, for example, a PET film.

[0014] In an advantageous embodiment, the optical functional layer is formed by a hologram or another diffraction structure, an interference structure, a matte structure, a micromirror arrangement, a microlens arrangement, a moth-eye structure, a subwavelength structure or a combination of these elements.

[0015] Advantageously, the optical functional layer has a reflection-enhancing coating, in particular a metal layer, for example made of Al, Cr, Fe, Ni, Cu, Fe:Si, or alloys of these materials, a high-refractive layer, such as TiO 2or ZnS and / or a color-shifting interference layer structure. The interference layer structure can in particular consist of a color-shifting thin-film element with the layer sequence absorber / dielectric / reflector, for example Cr / SiO 2 / Al or Al / SiO 2 / Al, be formed.

[0016] The reflection-enhancing coating can be provided with transparent and / or semi-transparent regions using suitable processes. For example, a washing process, structuring using resist and an etching step, or laser ablation or laser modification of the reflection-enhancing coating can be considered.

[0017] According to a preferred embodiment, the first machine-readable feature substance is an IR luminescent substance which has an emission in the near-infrared spectral range, in particular in the wavelength range between 800 nm and 2100 nm and / or is excitable in the wavelength range between 400 nm and 2100 nm, preferably in the wavelength range between 700 nm and 2100 nm.

[0018] In another, equally advantageous embodiment, the first machine-readable feature substance is an optical storage phosphor with optically stimulated luminescence. The functioning of such optical storage phosphors is described in more detail, for example, in the publication DE 10 2017 008 868 A1. Charging of the optical storage phosphor preferably occurs in the wavelength range of 350 nm - 550 nm, preferably in the VIS (visible) wavelength range of 400 - 550 nm, and reading preferably in the VIS or IR wavelength range of 550 nm - 1000 nm.

[0019] An optical storage phosphor is advantageously used as the first machine-readable feature substance, in particular when the feature substance is arranged on the upper side of the film layer above any metal layers that may be present, since then a readout of the feature substance in the VIS or even UV spectral range is easily possible.

[0020] The invention also includes a value document with an optically variable security element of the type described, wherein the optically variable security element is bonded to a substrate of the value document by means of the adhesive layer arranged on the underside of the film element. The substrate of the value document contains a second machine-readable feature substance, in particular an IR luminescent substance or an optical storage phosphor with optically stimulated luminescence.

[0021] Advantageously, the first and the second feature substance are each an IR luminescent substance, wherein the first and second IR luminescent substances advantageously have different emission spectra and / or different excitation spectra.

[0022] In an advantageous variant of the invention, the first and second IR luminescent substances have at least one common spectral band in the emission spectrum and simultaneously separate spectral bands in the excitation spectrum. This allows for separate excitation with a common spectral detection and thus a technically simpler detector, so that the two IR luminescent substances can be detected independently of each other.

[0023] In another, equally advantageous variant of the invention, the first and second IR luminescent substances have at least one common spectral band in the excitation spectrum and simultaneously separate spectral bands in the emission spectrum. This allows the simultaneous excitation of the two IR luminescent substances, for example, with a single light source with separate detection in, for example, two different spectral channels in a single combination sensor, so that here, too, the two IR luminescent substances can be detected independently of one another.

[0024] The IR luminescent substances used in the invention can be organic or organometallic luminescent substances, for example, fluorescent organic molecules or phosphorescent organometallic complexes. In a preferred embodiment, these are organometallic complexes. These generally exhibit narrower, more specific emission bands and a large Stokes shift. This facilitates excitation and detection. In particular, the separation of the emission radiation from the excitation radiation and from interfering signals is facilitated. The organometallic complexes are preferably rare earth complexes, particularly preferably rare earth complexes of the rare earths neodymium, ytterbium, erbium, thulium, holmium, or combinations of these or two or more rare earths.

[0025] In a further advantageous embodiment, one or both IR luminescent substances are inorganic luminescent substances. For example, they are doped inorganic host lattices. Furthermore, the dopants can be the rare earths neodymium, ytterbium, erbium, thulium, holmium, or the transition metals vanadium, chromium, manganese, or iron. In addition to the dopants mentioned, further dopants can be present, for example, to adjust the decay time of the luminescent substance and / or to utilize energy transfer between the rare earth ion and / or the transition metal and the other dopant. Suitable inorganic matrices include: i) oxides, in particular trivalent and tetravalent oxides such as titanium oxide, aluminium oxide, iron oxide, boron oxide, yttrium oxide, cerium oxide, zirconium oxide, bismuth oxide, as well as more complex oxides such as garnets, including, but not limited to, yttrium iron garnets, yttrium aluminium garnets, gadolinium gallium garnets; perovskites, including, but not limited to, yttrium aluminium perovskite, lanthanum gallium perovskite; spinels, including, but not limited to, zinc aluminium spinels, magnesium aluminium spinels, manganese iron spinels; or mixed oxides such as, for example, ITO (indium tin oxide); ii) Oxyhalides and oxychalcogenides, in particular oxychlorides such as yttrium oxychloride, lanthanum oxychloride; and oxysulfides such as yttrium oxysulfide, gadolinium oxysulfide or yttrium gadolinium oxysulfide iii) sulphides and other chalcogenides, for example zinc sulphide, cadmium sulphide, zinc selenide, cadmium selenide; iv) sulfates, in particular barium sulfate and strontium sulfate; v) Phosphates, in particular barium phosphate, strontium phosphate, calcium phosphate, yttrium phosphate, lanthanum phosphate, as well as more complex phosphate-based compounds such as apatites, including, but not limited to, calcium hydroxyapatites, calcium fluoroapatites, calcium chloroapatites; or spodiosites, including, for example, calcium fluoro-spodiosites, calcium chloro-spodiosites; vi) halides, in particular fluorides such as sodium rare earth fluorides; vii) silicates and aluminosilicates, in particular zeolites such as zeolite A, zeolite Y; zeolite-related compounds such as sodalites; feldspars such as alkali feldspars, plagioclase; and / or viii) other inorganic compound classes such as vanadates, germanates, arsenates, niobates, tantalates.

[0026] According to a further variant of the invention, the first and second feature substances are each an optical storage phosphor, wherein the first and second optical storage phosphors can advantageously be charged together and read out differently. The latter simplifies the sensor and allows for reliable separation of the two features during readout.

[0027] The statements made above for the first optical storage phosphor apply equally to the second optical storage phosphor.

[0028] In the context of the present invention, substances such as suitably doped alkaline earth sulfides (for example SrS:Eu,Sm), halides (for example BaFBr:Eu), aluminates (for example SrAl 2 O 4 :Eu,Tm or Sr 4 Al ı4 O 25 :Eu,Dy), oxides (e.g. MgO:Tb, BeO, Al 2 O 3 :C), garnet (e.g. Gd 3,04Al 2 Ga 3 O 12 : Ce 0,005 , Yb 0,005 or Gd 2,52 La 0,5 Al 2 Ga 3 O 12 : Ce 0,04 , Zr 0,005 ) or other substances can be used that absorb energy in the form of UV or VIS radiation, store it, and only release it again in the form of luminescence upon targeted stimulation. If light is used as a stimulus, this is referred to as optically stimulated luminescence. Other suitable optical storage phosphors are described in DE 10 2017 008 868A1, the disclosure of which is incorporated into the present application.

[0029] Finally, in a further advantageous embodiment of the invention, one of the two feature substances can be an IR luminescent substance and the other of the two feature substances can be an optical storage phosphor.

[0030] Particularly preferably, the first feature substance of the security element is an IR luminescent substance, and the second feature substance of the value document substrate is an optical storage phosphor with optically stimulated luminescence. The separation of the two luminescence markers occurs via the different emissions; advantageously, the excitation of the IR luminescent substance can also be combined with the charging or readout of the optical storage phosphor.

[0031] Finally, the invention also includes a method for verifying a value document of the type described above, in which the presence of the first feature substance in the optically variable security element and the presence of the second feature substance in the substrate of the value document are detected mechanically with spatial resolution, and the detected distributions of the first and second feature substances are compared with expected distributions. Based on the comparison result, the authenticity of the value document can then be assessed or a conclusion drawn about tampering.

[0032] In an advantageous method variant, a value document is checked in which the first and the second feature substance is each an IR luminescent substance, and the two IR luminescent substances have at least one common spectral band in the excitation spectrum and, at the same time, separate spectral bands in the emission spectrum.

[0033] In this advantageous method variant, the substrate of the value document and the security element are illuminated with excitation light containing a wavelength of the common spectral band of the excitation spectrum of the first and second IR luminescent substances. The light emissions of the first and second IR luminescent substances are each recorded with spatial resolution, and the recorded distributions of the first and second light emissions are compared with expected distributions. Here, too, the authenticity of the value document can be assessed or a conclusion drawn about tampering based on the comparison result.

[0034] Further embodiments and advantages of the invention are explained below with reference to the figures, in which a true-to-scale and true-to-proportion reproduction has been omitted in order to increase clarity.

[0035] They show: Fig.1 schematically in (a) a banknote according to an embodiment of the invention and in (b) and (c) counterfeit banknotes obtained by a peeling attack, Fig. 2 a film patch according to the invention in cross section, Fig. 3 the foil patch of the Fig. 2 after application to the paper substrate of a banknote and removal of the transfer foil, Fig. 4 a foil patch according to another embodiment of the invention on a banknote, and Fig. 5 a foil patch according to a further embodiment of the invention on a banknote, before the transfer carrier is removed.

[0036] The invention will now be explained using banknotes as an example. Fig. 1 shows in Fig. 1(a) a banknote 10 according to the invention, which is provided with a foil patch 12 with an optically variable appearance.

[0037] For security purposes, the foil patch 12 contains a first machine-readable feature substance in the form of an IR luminescent substance or an optical storage phosphor with optically stimulated emission, whereby the special position of the feature substance in the foil patch 12, described in more detail below, ensures that the feature substance is completely removed from the banknote 10 in the event of a harvesting attack.

[0038] The paper substrate 14 of the banknote 10 contains a second machine-readable feature substance, which is also formed by an IR luminescent substance or an optical storage phosphor with optically stimulated emission.

[0039] In a detachment attack, the genuine foil patch 12 is typically removed from the genuine banknote 10 and replaced with a counterfeit 12-V, as in Fig. 1(b), while the genuine foil patch 12 is transferred to a counterfeit banknote substrate 14-V, as shown in Fig. 1(c).

[0040] During the automated authentication of banknotes, the presence of both the first and second characteristic substances is checked, and the authenticity of a note is only confirmed if both characteristics are detected. Banknote 10 of the Fig. 1(a) is therefore recognized as genuine, while the forgery of the Fig. 1(c) contains the genuine foil patch 12, but the manipulation can be detected by the absence of the second feature substance in the paper substrate 14-V.

[0041] The forgery of the Fig. 1(b) can be rejected due to the absence of the first feature substance in the area of ​​the counterfeit foil patch 12-V, since the first feature substance was removed without residue from the banknote substrate 14 when the genuine foil patch 12 was removed.

[0042] The structure and functioning of security elements and value documents according to the invention will now be explained in more detail with reference to the following figures.

[0043] Fig. Figure 2 shows a cross-sectional view of a foil patch 20 according to the invention. The foil patch 20 is a multilayer stack typically built on a transfer foil 40, which is subsequently removed during the patch's application to a target document.

[0044] A first UV varnish layer 22 is first applied to the transfer film 40 as a release layer, which also serves as a print acceptance layer for subsequent printing. A UV embossing varnish layer 24 is applied to the UV varnish layer 22, in which the optical structures for the desired optically variable appearance are embossed.

[0045] In the exemplary embodiment, the visibility of the optical structures is enhanced by a reflection-enhancing coating 26, which can be formed, in particular, by a metal layer, a high-refractive-index layer, or an interference layer structure. The UV embossing lacquer layer 24 with the embossed optical structures, together with the reflection-enhancing coating 26, forms the optical functional layer of the film patch 20.

[0046] A thin PET film 30 with a thickness between 4 µm and 15 µm is laminated onto the reflection-enhancing coating 26 of the optical functional layer using a laminating adhesive 28. A primer layer 32 and finally an adhesive layer 34, preferably a heat-sealing lacquer, are applied to the PET film 30 for bonding to the target substrate.

[0047] The first machine-readable feature substance 36 is in the embodiment of the Fig.2 is mixed into the laminating adhesive 28 and is therefore located on the upper side of the PET film 30, like the optical functional layer 24, 26.

[0048] Before and / or after lamination of the PET film 30, further functional layers with additional authenticity features such as fluorescence, IR, magnetism, conductivity, polarization effects, colored inks and effect inks can be added.

[0049] The foil patch can then be defined by punching and then separated by separating it with a coil. The punching step can also be omitted to create a security element in the form of a continuous foil strip. Gradual transitions in the geometric extension up to the full height of the banknote are also possible. A strip cut can then be performed to create a coil from the foil material.

[0050] Fig. 3 shows the foil patch 20 of the Fig.2 after application to the paper substrate 14 of a banknote, such as banknote 10 of the Fig. 1. The carrier film 40 was removed after the application of the film patch, so that the UV varnish layer 22 as the top layer can now function as a print acceptance layer.

[0051] The paper substrate 14 of the banknote 10 is provided with a second machine-readable feature substance 16, which together with the first machine-readable feature substance 36 of the foil patch completes the security of the banknote.

[0052] The foil patch 20 is stabilized by the inner foil layer 30 and is achieved by removing the foil layer 30 and thus all layers arranged above the foil layer 30 from the banknote 10 in the event of a removal attack. This ensures that in the event of a removal attack, the feature substance 36 arranged in the laminating adhesive layer 28 is completely removed from the banknote 10. Therefore, no residue of feature substance 36 remains on the banknote 10, so that it can be used even after being equipped with a counterfeit foil patch 12-V ( Fig. 1(b)) can be reliably detected as tampered with.

[0053] For the first and second machine-readable feature substances 16, 36, the advantageous materials described above can be used, in particular. For example, the feature substances 16, 36 can be two IR-IR luminescent substances that have a common spectral band in the excitation spectrum and, at the same time, different, separate spectral bands in the emission spectrum. This allows the simultaneous excitation of the two feature substances 16, 36, for example, with a single light source and separate detection, for example, in two different spectral channels in a single combination sensor, so that the two IR-IR luminescent substances can be detected independently of one another.

[0054] As can be seen from the above explanation, the first machine-readable feature substance 36 can be introduced into any layer lying on the upper side of the film layer 30 or into the film layer 30 itself. Fig.4 shows an example of a foil patch 42 according to another embodiment of the invention, in which the first feature substance 36, in contrast to the foil patch 20 of the Fig. 2 and Fig. 3 in the UV varnish layer 22.

[0055] Also in the embodiment of the Fig. 4, the feature substances 16, 36 can be two IR-IR luminescent substances. However, in this embodiment, the first feature substance 36 can also advantageously be an optical storage phosphor with optically stimulated luminescence, which is excited and read out in the visible or UV range, since, due to the arrangement of the first feature substance 36 above the optical functional layer 24, 26, there is no risk of disruptive absorption by a reflection-enhancing coating, in particular by a metallization of the optical functional layer.

[0056] The second feature substance 16 can then also be an optical storage phosphor or an IR luminescent substance.

[0057] It is understood that in other embodiments, the first machine-readable feature substance 36 can also be incorporated into the UV embossing lacquer layer 24 or into the film layer 30 itself. The first feature substance 36 can also be present in a dedicated feature layer arranged on the upper side of the film layer 30. Such a dedicated feature layer can be present over the entire surface, as a motif / pattern, or only in the later product areas. A dedicated feature layer can be provided as a UV-curing layer or a solvent-based layer. Since the first feature substance 36 is arranged on the upper side of the film layer 30 in all of these variants, in the event of a detachment attack, the first feature substance 36 is always completely removed together with the film layer 30 and the optical functional layer 24, 26.

[0058] Fig. 5 shows, as a further embodiment, a banknote 10 with a second feature substance 16 incorporated into the paper substrate 14 and a foil patch 52 applied to the paper substrate, in which the first feature substance 36 is incorporated into the foil layer 30 itself. In the figure, the foil patch 52 is shown immediately after application to the banknote, before the removal of the transfer carrier 50, which consists of two laminated partial foils.

[0059] To demonstrate the advantages achieved by the invention, a film security element according to the invention and a comparison element not according to the invention were each applied to a secured substrate and the detectability of a detachment attack was tested. Example:

[0060] For a foil patch with a structure as in Fig.2, a luminescence marker A, which is excitable and emits in the near-infrared (NIR), is used as the first feature substance. The luminescence marker A is dispersed in a laminating adhesive in a ball mill, doctored onto a semi-finished product of a metallized micromirror patch with a wet film thickness of 12 µm, and the metallized micromirror patch is bonded to a 12 µm thin PET film layer.

[0061] The resulting layer sequence was first coated with a primer layer and then glued onto banknote paper coated with an IR luminescence marker B (NIR / NIR) using a heat-sealing adhesive, and the transfer film was removed.

[0062] The luminescence marker B forms the second feature substance 16 of the Fig.3, the first feature substance 36 is formed by the luminescence marker A, which is present in the laminating adhesive layer between the optical functional layer, in this case the metallized micromirrors and the PET film layer.

[0063] The luminescence intensities of Marker A and Marker B were measured from the back of the banknote using a luminescence sensor for banknote applications ("original document" in Table I). The foil patch was then removed from the banknote and adhered with Sellotape to a blank sheet representing the recipient document. The corresponding luminescence intensities of the donor document after removal and the recipient document were measured again: Table I: Original document Donor document after replacement Recipient document after transfer Luminescence intensity A 100% 0% 45% Luminescence intensity B 100% 100% 0%

[0064] As can be seen from Table I, the luminescence intensity A disappears completely during the detachment process, thus reliably identifying the donor document as tampered with. The recipient document can also be reliably identified as a forgery due to the absence of luminescence intensity B. Comparison example:

[0065] The comparison element has the same basic structural design as the film patch according to the invention, but in the comparison element the luminescence marker A was incorporated into the primer layer of the substrate adhesive on the underside of the PET film layer.

[0066] The detachment and transfer process described above is repeated and the luminescence intensities are measured: Table II: Original document Donor document after replacement Recipient document after transfer Luminescence intensity A 100% 16 % 40% Luminescence intensity B 100% 100% 0%

[0067] As can be seen from Table II, in contrast to the embodiment according to the invention, the luminescence intensity A does not completely disappear from the donor document in the comparative example, since part of the primer layer remains on the donor document during the removal process. Therefore, the donor document cannot be reliably detected as tampered with in the comparative test. QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Cited patent literature

[0000] WO 2023 / 285000 A1

[0004] DE 10 2017 008 868 A1 [0018, 0028]

Claims

[1] Optically variable security element for securing a value document, with a first machine-readable feature substance and an optical functional layer which gives the security element an optically variable appearance when viewed, characterized by that the security element is formed in multiple layers with an inner film layer which has a bottom side and an opposite top side, wherein the film layer is provided on the bottom side with an adhesive layer for connection to the value document and on the top side with the optical functional layer, and wherein the first machine-readable feature substance is arranged in the film layer or on the top side of the film layer. [2] Security element according to claim 1, characterized by that the first machine-readable feature substance is an IR luminescent substance or an optical storage phosphor with optically stimulated luminescence. [3] Security element according to claim 1 or 2, characterized by that the first machine-readable feature substance is present in a feature layer arranged on the upper side of the film layer, in particular in a UV-curable lacquer layer, an embossed lacquer layer or an adhesive layer. [4] Security element according to at least one of claims 1 to 3, characterized by that the film layer is formed by a film with a thickness between 4 µm and 15 µm, for example a PET film. [5] Security element according to at least one of claims 1 to 4, characterized by that the optical functional layer is formed by a hologram or other diffraction structure, an interference structure, a matte structure, a micromirror array, a microlens array, a moth-eye structure, a subwavelength structure or a combination of these elements. [6] Security element according to at least one of claims 1 to 5, characterized bythat the optical functional layer has a reflection-enhancing coating, in particular a metal layer, a high-refractive-index layer and / or a color-shifting interference coating. [7] Security element according to at least one of claims 1 to 6, characterized by that the first machine-readable feature substance is an IR luminescent substance which has an emission in the near-infrared spectral range, in particular in the wavelength range between 800 nm and 2100 nm and / or is excitable in the wavelength range between 400 nm and 2100 nm, preferably in the wavelength range between 700 nm and 2100 nm. [8] A value document with an optically variable security element according to one of claims 1 to 7, wherein the optically variable security element is connected to a substrate of the value document by means of the adhesive layer arranged on the underside of the film element, and wherein the substrate of the value document contains a second machine-readable feature substance, in particular an IR luminescent substance or an optical storage phosphor with optically stimulated luminescence. [9] Value document according to claim 8, characterized by that the first and the second feature substance is each an IR luminescent substance, wherein the first and second IR luminescent substance advantageously have different emission spectra and / or different excitation spectra. [10] Value document according to claim 9, characterized bythat the first and the second IR luminescent substance have at least one common spectral band in the emission spectrum and simultaneously separate spectral bands in the excitation spectrum. [11] Value document according to claim 9, characterized by that the first and the second IR luminescent substance have at least one common spectral band in the excitation spectrum and simultaneously separate spectral bands in the emission spectrum. [12] Value document according to claim 8, characterized by that the first and the second feature substance are each an optical storage phosphor, wherein the first and second optical storage phosphor are advantageously jointly chargeable and differently readable. [13] Value document according to claim 8, characterized by that one of the two feature substances is an IR luminescent substance and the other of the two feature substances is an optical storage phosphor. [14] Method for checking a value document according to one of claims 8 to 13, in which the presence of the first feature substance in the optical variable security element and the presence of the second feature substance in the substrate of the value document are detected by machine in a spatially resolved manner, and the detected distributions of the first and second feature substances are compared with expected distributions. [15] Method in particular according to claim 14 for checking a value document according to claim 11, in which the substrate of the value document and the security element are illuminated with excitation light which contains a wavelength of the common spectral band of the excitation spectrum of the first and the second IR luminescent substance, the light emissions of the first and the second IR luminescent substance are each detected in a spatially resolved manner and the detected distributions of the first and second light emissions are compared with expected distributions.

Images