Value document with luminescence feature, value document system, production method and checking method

Abstract

The invention relates to a flat value document (10), which has a surface region with a longitudinal direction (L) and a transverse direction (Q) and which is provided with a luminescence feature (12) in the surface region. According to the invention, the luminescence feature (12) comprises a first luminescence marker in a first partial region (14) and a second luminescence market in a second, different partial region (16). The first and second luminescence markers can be excited to luminescence at the same wavelength and luminesce after excitation substantially in the same emission band in the infrared spectral range. The first and second luminescence markers have spectrally similar infrared emission spectra, specifically infrared emission spectra that have a spectral difference between 0.5% and 15%. The first and second partial regions overlap each other in the surface region in projection onto the longitudinal direction (L) and / or in projection onto the transverse direction (Q).

Description

[0001] Value document with luminescent feature, value document system, manufacturing process and testing process

[0002] The invention relates to a value document with a luminescent feature, and in particular to a flat value document, such as a banknote, which has a surface area with a longitudinal direction and a transverse direction and which is provided with a luminescent feature in the surface area. The invention also relates to a value document system comprising a plurality of different such value documents, a method for producing such a flat value document, and a method for verifying such a flat value document.

[0003] To protect valuable documents and to verify their authenticity or classify them, it is common practice to apply machine-verifiable, particularly optical, security features to or on valuable documents. These features can be, for example, luminescent features or luminescent markers. Luminescent features that are invisible to the human eye and emit light in the infrared (IR) spectral range are often used as hidden security features.

[0004] During authentication or classification, a valuable document is illuminated with excitation light by a sensor, for example, and the light emitted in response by the valuable document is detected to capture characteristic properties of the feature or a feature intensity. The detected properties are then compared with reference or threshold values ​​to assign the feature, and thus the valuable document, to a class. In the case of an authenticity test, the valuable document can, for example, be assigned to one of the classes "genuine" or "suspected counterfeit."

[0005] It is known to add luminescent features in the form of powdered substances or pigments to a semi-finished product during the production of a value document, for example, a paper pulp, a master batch / polymer melt, or a printing ink, a clear varnish, or a color concentrate. The semi-finished product is further processed into the finished value document, for example, in the form of a pulp, a value document substrate in web or sheet form, a printed product in the form of a web, a sheet, or a single-use product, a film element, for example, a patch, a thread, a film strip, or planchettes, a fiber, or a printing ink or a color concentrate. In particular, a luminescent feature powder can be added to a printing ink, thereby creating an imprint on a value document substrate.

[0006] Combinations of different luminescent substances can be used to create individual coding for different classes of value documents.

[0007] In order to generate exclusive coding classes, i.e., to reliably separate different value documents under real-world operating conditions, for example, on a banknote processing machine, the definition of the different classes must take into account not only the expected production fluctuations of the luminescence features but also the expected tolerances of the sensor technology during measurement. This significantly limits the number of code classes that can be reliably separated in practice. Especially in banknote processing, it is common practice to check or sort different banknotes on high-speed banknote processing machines. Processing speeds can reach up to 12 m / s and place considerable demands on the reliable separation of different coding classes.

[0008] Based on this, the invention is based on the object of providing a valuable document of the type mentioned above that allows for reliable verification or classification of the valuable document while maintaining a high level of forgery security. The invention also aims to provide a manufacturing method and a method for verifying such valuable documents. This object is achieved by the features of the independent claims. Further developments of the invention are the subject of the dependent claims.

[0009] According to the invention, the luminescence feature of a generic planar value document comprises a first luminescence marker in a first partial area and a second luminescence marker in a second, different partial area.

[0010] The first and second luminescence markers can be excited to luminescence at the same wavelength, hereinafter also referred to locally as the excitation wavelength, and upon excitation, luminesce essentially in the same emission band in the infrared spectral range. The emission band can preferably be the contiguous wavelength range or the wavelength interval of the emission spectrum around the maximum intensity in the infrared spectral range, in which the intensity is greater than 5% of the maximum intensity of the emission spectrum in the infrared spectral range. The emission bands are preferably essentially the same if the emission bands overlap by more than 90% of the width of the broader emission band.

[0011] The first and second luminescent markers have spectrally similar infrared emission spectra, namely infrared emission spectra that have a spectral difference between 0.5% and 15%.

[0012] The spectral difference between the emission spectra of the first and second luminescence markers can be given, in particular, as the maximum of the magnitude of the difference spectrum of the two emission spectra, each normalized to the emission maximum, in the spectral range formed by or encompassing the emission bands. Furthermore, the first and second sub-regions are arranged overlapping one another in the surface area when projected onto the longitudinal direction and / or when projected onto the transverse direction.

[0013] In particular, the surface area is identical to the value document, i.e. the edges of the surface area correspond to the edges of the value document.

[0014] For a rectangular surface, the longitudinal direction, as usual, refers to the direction of the longer dimension, and the transverse direction refers to the perpendicular direction of the shorter dimension of the surface. For a square surface, the longitudinal and transverse dimensions are the same.

[0015] In particular, the security document can be in the form of a banknote.

[0016] The security document can also be a page of a book-shaped security document, such as a passport. The first and second sub-areas can, in particular, be located on the same page of a book-shaped security document. The longitudinal direction or transverse direction can refer to the direction of the longer or shorter dimension of this page, respectively.

[0017] The spectral similarity of the two luminescence markers or their infrared emission spectra ensures that environmental influences and / or variations in the sensors used to detect the luminescence emission have a similar effect on the measurement of the two luminescence markers and can therefore be well compensated by a differential evaluation.

[0018] The small spectral difference between the two emission spectra also increases the security against counterfeiting of the value document, since a potential counterfeiter will only detect a single, identical luminescence when analyzing an original value document within the limits of measurement accuracy and will at most attempt to reproduce this single luminescence.

[0019] Advantageously, the first and second luminescence markers or their infrared emission spectra have a spectral difference between 1% and 11%, preferably between 2% and 7%.

[0020] The first and second luminescence markers are expediently excitable with a wavelength in the wavelength range from 700 to 2500 nm, preferably in the wavelength range from 900 to 2100 nm. Alternatively or additionally, the first and second luminescence markers are selected such that they luminesce upon excitation in the wavelength range from 700 to 2500 nm, preferably from 900 to 2100 nm. Preferably, the emission wavelength is greater than the excitation wavelength, in particular by at most 100 nm.

[0021] The two luminescent markers advantageously exhibit essentially no upconversion and, especially after excitation, emit virtually no light—for example, less than 1% of their total emission power—in the visible spectral range. The luminescence of the luminescent feature cannot then be perceived by the naked eye, representing a hidden security feature with a high level of protection.

[0022] The first and / or second luminescent marker advantageously contains an organic, organometallic or inorganic luminescent substance. Advantageous examples of such luminescent substances are doped inorganic pigments with the dopants neodymium and / or ytterbium and / or erbium and / or thulium and / or holmium or doped with certain transition metals such as manganese. Also preferred are organometallic complexes with neodymium and / or ytterbium and / or erbium or certain organic dyes. Suitable inorganic matrices are, for example: oxides, in particular trivalent and tetravalent oxides such as titanium oxide, aluminum oxide, iron oxide, boron oxide, yttrium oxide, cerium oxide, zirconium oxide, bismuth oxide, as well as more complex oxides such as garnets, including, among others,Yttrium iron garnets, yttrium aluminum garnets, gadolinium gallium garnets; perovskites, including yttrium aluminum perovskite, lanthanum gallium perovskite; spinels, including zinc aluminum spinels, magnesium aluminum spinels, manganese iron spinels; or mixed oxides such as ITO (indium tin oxide); oxyhalides and oxychalcogenides, in particular oxychlorides such as yttrium oxychloride, lanthanum oxychloride; and oxysulfides, such as yttrium oxysulfide, gadolinium oxysulfide; sulfides and other chalcogenides, e.g. zinc sulfide, cadmium sulfide, zinc selenide, cadmium selenide; sulfates, in particular barium sulfate and strontium sulfate; 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 calcium hydroxylapatite, calcium fluoroapatite, calcium chloroapatite; or spodiosites, including e.g.Calcium fluorospodiosites, calcium chlorospodiosites; silicates and aluminosilicates, especially zeolites such as zeolite A and zeolite Y; zeolite-related compounds such as sodalites; feldspars such as alkali feldspars and plagioclases; other inorganic compound classes such as vanadates, germanates, arsenates, niobates, and tantalates.

[0023] In an advantageous embodiment, it is provided that the first and second luminescent markers each contain only a single luminescent substance.

[0024] Alternatively, the first and / or second luminescent marker can also contain multiple luminescent substances. The latter allows for a simple production-technically adjusted adjustment of very precise differences between the two luminescent markers. In particular, it can be provided that the first and second luminescent markers contain a common luminescent substance and at least one of the luminescent markers contains an additional luminescent substance that generates the small spectral difference between the two luminescent markers. For example, the first luminescent marker Mi can contain only a single luminescent substance A, and the second luminescent marker M2 can be produced by mixing the luminescent substance A with a small amount of an additional luminescent substance E, which slightly modifies the emission spectrum of the luminescent substance A. This procedure can be described schematically by Mi = A and M2 = A + E.

[0025] Alternatively, both luminescent markers can contain an additional luminescent substance £ in small but different amounts of Xi, X2, i.e., schematically, Mi = A + Xi E and M2 = A + X2 £, with Xi X2. The two luminescent markers can also each contain a small amount of different luminescent substances Ei, E2, i.e., schematically, Mi = A + EI and M2 = A + E2.

[0026] Furthermore, different luminescent substances with very similar emission spectra can be used for the two luminescent markers, which can be achieved, for example, by slightly different process controls during production or by slightly different chemical compositions of the starting materials.

[0027] In an advantageous embodiment, the first and second luminescence markers differ not only in the aforementioned spectral difference but also in the rise and / or decay times of the emission at one, several, or even all emission wavelengths. This further increases the separability of the luminescence markers and thus the number of possible distinguishable codings.

[0028] According to a practical embodiment, the first and second luminescent markers are each arranged in a printed ink area on the value document. In particular, the first and second luminescent markers can be present in visually invisible ink areas. Alternatively, the first and second luminescent markers can be provided in visually visible ink areas, advantageously in infrared-transparent ink areas. This prevents any absorption in the ink from interfering with the measurement of the infrared luminescence. Alternatively, the combination of a visually invisible ink area and a visually visible ink area is also possible. This increases design freedom.

[0029] In another, likewise advantageous embodiment, the first luminescence marker is arranged in a printing ink area printed on the value document, while the second luminescence marker is arranged in a security element applied to the value document, in particular a strip or patch.

[0030] The arrangement of the first and second subregions can be achieved in various ways. Preferably, the first and second subregions are disjoint, meaning there is no overlapping area in which both the first and second luminescent markers are present. This simplifies both the manufacturing process, for example, the printing process, and the evaluation of a measurement of the luminescent feature.

[0031] In other embodiments, there is an overlap region in which both luminescent markers are present. However, it is preferably provided that each sub-region also includes non-overlapping regions in which only the first or second luminescent marker is present. Embodiments with overlapping regions allow for greater design freedom without sacrificing the described functionality provided by the non-overlapping regions.

[0032] If the first and second partial areas are arranged so as to overlap only in projection in a single direction, this is preferably the shorter transverse direction. This ensures that the same measuring track of a feature sensor can measure both the first luminescence marker in the first partial area and the second luminescence marker in the second partial area when the value document is transported longitudinally past a conventional short-edge-leading sensor. Advantageously, the first and second partial areas are even arranged so as to overlap each other in projection in both directions, i.e., the longitudinal and transverse directions. This has the advantage that the banknote can be checked on both longitudinally and transversely measuring processing machines, and the same measuring track can be used to measure the two luminescence markers. In an advantageous embodiment, the two partial areas themselves do not overlap.

[0033] In an advantageous embodiment, the luminescence feature comprises only a single first partial region and only a single second partial region, wherein the first and second partial regions are arranged overlapping one another in the surface region both in projection onto the longitudinal direction and in projection onto the transverse direction.

[0034] Alternatively, the first and / or second sub-area may each consist of several non-connected sub-areas.

[0035] In an advantageous specific embodiment, the luminescence feature forms a barcode whose bar elements are formed by sub-areas with different luminescence markers. The barcode can be one-dimensional, multi-line, or two-dimensional. If A designates a first and B a second luminescence marker, the sub-areas can be configured, for example, in the form ABA, ABBA, ABBAB, etc. For multi-line barcodes, the same luminescence marker A is advantageously used as a reference marker in each line.

[0036] A one-dimensional or multi-line barcode can, in particular, be formed by several, for example, three, different luminescence markers A, B, C, whereby one of the luminescence markers, for example, luminescence marker A, is used as a reference marker for the precise measurement of the spectral signatures of the other luminescence markers B and C. In a multi-line barcode, it is advantageous to use the same luminescence marker A as a reference marker in each line. In this case, for example, only two different luminescence markers can be used per line, for example, luminescence markers A and B in even-numbered lines and luminescence markers A and C in odd-numbered lines.

[0037] In all designs, it can advantageously be provided that the luminescence feature comprises, in addition to the first and second partial regions, at least a third partial region different from the first and second partial regions, with a third luminescence marker having a spectrally similar infrared emission spectrum to the first and, in particular, also the second luminescence marker, with a spectral difference of between 0.5% and 15%. It is understood that further partial regions with further luminescence markers can also be provided in the same way.

[0038] The invention also includes a value document system comprising a plurality of different value documents of the described type, in which the value documents of the value document system all have the same luminescence marker in the first sub-area and different luminescence markers in the second sub-area. The luminescence marker of the first sub-area serves as a common reference marker, while the different luminescence markers of the second sub-area serve for the verification and / or classification of the value documents.

[0039] For example, the security document system can contain the various banknotes of a series with several different denominations. Banknotes of different denominations contain different luminescence markers in the second sub-area, but the same reference marker in the first sub-area. Differential measurement allows banknotes of different denominations to be reliably distinguished from one another despite the spectral similarity of the luminescence markers in the respective second sub-areas.

[0040] The invention also includes a method for producing a planar value document of the type described, in which a value document substrate is provided with a surface area extending in a longitudinal direction and a transverse direction.

[0041] The value document substrate is provided with a luminescence feature in the surface area by arranging a first luminescence marker in a first partial area and a second luminescence marker in a second, different partial area in the surface area such that the first and second partial areas overlap one another in projection onto the longitudinal direction and / or in projection onto the transverse direction.

[0042] The first and second luminescence markers can be excited to luminescence at the same wavelength and, upon excitation, luminesce essentially in the same emission band in the infrared spectral range. Furthermore, the first and second luminescence markers exhibit spectrally similar infrared emission spectra, namely infrared emission spectra with a spectral difference of between 0.5% and 15%.

[0043] In an advantageous process, the first and second luminescent markers are printed onto the value document substrate, preferably using different printing processes. Advantageous printing processes that can be used include, in particular, offset, intaglio, gravure, digit, flexo, or screen printing.

[0044] In a further advantageous method, the first and second luminescence markers are printed onto the value document substrate using the same printing process.

[0045] In another, equally advantageous method, the first luminescent marker is printed onto the value document substrate. The second luminescent marker is arranged in a security element, in particular a strip or patch, and the security element with the second luminescent marker is applied to the value document substrate or incorporated into the value document substrate.

[0046] Finally, the invention also includes a method for checking a flat value document of the type described, in which the luminescence emissions of the two luminescence markers of the first and second partial areas are detected together, or the flat value document is transported and, during transport, the luminescence emissions of the two luminescence markers of the first and second partial areas are detected by a sensor, and in which the spectral properties of the second luminescence marker are evaluated relative to the spectral properties of the first luminescence marker. Depending on the result of the evaluation, an authenticity signal can then be formed and emitted, which represents the result of the evaluation. To detect the luminescence emissions, the partial areas are excited with excitation radiation of the excitation wavelength from a radiation source. The radiation source can preferably be part of the sensor.

[0047] The luminescence emissions of the two luminescence markers are advantageously detected together by detecting the luminescence emissions of the two luminescence markers directly one after the other, for example, during a continuous transport of the value document past a sensor, along a measuring track that covers both partial areas. The measuring track is advantageously oriented parallel to the longitudinal direction or the transverse direction of the surface area. Thus, in particular, the value document can be transported parallel to the longitudinal direction or the transverse direction of the value document.

[0048] The luminescence emission of the two luminescence markers is advantageously detected with a single-track or multi-track luminescence sensor with at least two spectral channels. The sensor mentioned can comprise a single-track or multi-track luminescence sensor with at least two spectral channels. Further embodiments and advantages of the invention are explained below with reference to the figures, which are not drawn to scale or proportions for the sake of clarity.

[0049] They show:

[0050] Fig. 1 shows a schematic representation of a banknote extending in a surface area with a longitudinal direction E and a transverse direction Q,

[0051] Fig. 2 in (a) the emission spectra of the first and second luminescence marker and in (b) the difference spectrum of the two emission spectra,

[0052] Fig. 3 in (a) the emission spectra and in (b) the corresponding difference spectrum for another combination of two luminescence markers,

[0053] Fig. 4 and 5 each show in (a) the emission spectra and in (b) the corresponding difference spectrum for further combinations of two luminescence markers,

[0054] Fig. 6 is a schematic representation of a banknote with a different design of the sub-areas with spectrally similar luminescence markers,

[0055] Fig. 7 in (a) to (c) further arrangements of the partial areas with spectrally similar luminescence markers in a surface area,

[0056] Fig. 8 in (a) two comparison banknotes with two luminescence markers and in (b) a histogram with the number of measurement results plotted against the spectral position, Fig. 9 in (a) two banknotes with two luminescence markers and one reference marker and in (b) a histogram with the number of measurement results plotted against the relative spectral position,

[0057] Fig. 10 is a schematic representation of a device for checking the banknote in Fig. 1, and

[0058] Fig. 11 is a roughly schematic flow diagram of a method for checking the banknote in Fig. 1 by means of the device in Fig. 10.

[0059] The invention will now be explained using the example of the authenticity testing of banknotes. Figure 1 shows a schematic representation of a banknote 10 which has a surface area with a longitudinal direction L and a transverse direction Q. The banknote 10 is provided in the surface area with a luminescent feature 12 which contains a first luminescent marker in a first partial area 14 and a second luminescent marker in a second partial area 16. In the embodiment of Figure 1, the first and second partial areas 14, 16 are disjoint, i.e. they do not overlap, but are arranged at a distance from one another in the surface area. It is essential that the two partial areas 14, 16 are arranged in the surface area such that they overlap one another in projection onto the transverse direction Q of the banknote 10. The projection 14-P of the partial area 14 and the projection 16-P of the partial area 16 onto the transverse direction Q are shown on the right in Fig. 1.As can be seen, the two projections 14-P, 16-P overlap in an overlap area 18.

[0060] This ensures that when the banknote 10 is scanned in a testing device along a measuring track 20 in the longitudinal direction L, both the partial area 14 with the first luminescence marker and the partial area 16 with the second luminescence marker are scanned one after the other at short time intervals by the feature sensor.

[0061] The luminescence markers of the sub-regions 14, 16 can be excited at the same wavelength or excitation wavelength and, after excitation, luminesce essentially in the same emission band in the infrared spectral range. The emission bands are each given by the contiguous wavelength range or the wavelength interval of the emission spectrum around the maximum intensity in the infrared spectral range, in which the intensity is greater than 5% of the maximum intensity of the emission spectrum in the infrared spectral range. As explained in more detail below, the luminescence markers are matched to one another in such a way that their emission spectra are spectrally very similar to one another and are influenced in the same way by the ambient conditions and the measurement conditions. By directly comparing the emissions of the two luminescence markers during a measurement with the same detector orSensor along the same measuring track, even subtle differences between the two spectra can be reliably detected and separated, which cannot be detected conventionally due to fluctuations in the measuring signal in different identical detectors, different measuring tracks or due to different environmental conditions.

[0062] For further explanation, diagram 30 of Fig. 2(a) shows the emission spectrum 34 of the first luminescence marker of the first sub-region 14 and the emission spectrum 36 of the second luminescence marker of the second sub-region 16, each plotted as intensity normalized to the emission maximum over the wavelength in arbitrary units. As can be seen from the figure, the emission spectra 34, 36 are very similar to one another; only the emission maximum of the spectrum 36 of the second luminescence marker is slightly shifted relative to the emission maximum of the spectrum 34 of the first luminescence marker. In order to quantify the spectral similarity, diagram 32 of Fig. 2(b) shows the difference spectrum 38 of the two emission spectra 34, 36, which has a maximum and a minimum due to the mutually shifted peak wavelengths of the two spectra.For the purposes of this description, the spectral difference between two emission spectra 34, 36 is defined, for example, as the maximum of the magnitude of the difference spectrum 38 of the emission spectra normalized to the emission maximum, expressed as a percentage. In the exemplary embodiment of Fig. 2, the maximum magnitude of the difference spectrum 38 at the locations of the maximum 38-Max and the minimum 38-Min is 0.1, respectively, so that the spectral difference between the two emission spectra is 10%.

[0063] In Fig. 3, the emission spectra of another combination of a first and second luminescence marker with an even smaller mutual shift of the peak wavelengths of the emission spectra upon excitation with the excitation wavelength are illustrated in a representation as in Fig. 2. The diagram 40 of Fig. 3(a) shows the emission spectrum 44 of the first luminescence marker and the emission spectrum 46 of the second luminescence marker, and the diagram 42 of Fig. 3(b) shows the difference spectrum 48 of the two emission spectra 44, 46. The maximum of the absolute value of the difference spectrum 48 for these two luminescence markers is only 0.043, and the spectral difference between the two emission spectra is thus 4.3%.

[0064] Figure 4 shows, in the same representation, the emission spectra of another combination of two luminescence markers, which exhibit an identical main emission 50 and differ only in the position of the maximum of the secondary emission 52. Figure 4(a) shows the emission spectrum 54 of a first luminescence marker and the emission spectrum 56 of a second luminescence marker, and Fig. 4(b) shows the difference spectrum 58 of the two emission spectra 54, 56. Due to the identical main emission 50 of the two luminescence markers, the difference spectrum 58 deviates significantly from zero only in the region of the secondary emission 52 and shows a maximum deviation of the two spectra of 0.024, i.e. a spectral difference of 2.4%.

[0065] Another variant is illustrated in Fig. 5, where the emission spectra of two luminescence markers are shown, which show an identical main emission 60, but a different intensity secondary emission 62.

[0066] Figure 5(a) shows the emission spectrum 64 of the first luminescence marker and the emission spectrum 66 of the second luminescence marker. The intensity Int is plotted on the ordinate, and the wavelength X is plotted on the abscissa.

[0067] Fig. 5(b) shows the difference spectrum 68 of the two emission spectra 64, 66. Here too, the difference spectrum 68 deviates from zero due to the identical main emission 60 essentially only in the area of ​​the secondary emission 62 and shows a maximum deviation of the two spectra of 0.1, i.e. a spectral difference of 10%.

[0068] To check the banknote 10, the device for checking flat value documents illustrated in Fig. 10 can be used. This device can be part of a device (not shown) for processing value documents. This device comprises a transport device 136 for transporting a value document 10 in a transport direction T past a sensor 138 for detecting luminescence emissions from the value document 10. The sensor 138, in the example a luminescence sensor, is designed to detect luminescence emissions from the value document 10, in the example of the banknote in Fig. 1, and to generate detection signals that represent properties, in particular spectral properties, of the detected luminescence emissions. An evaluation device 140 is connected to the sensor 138 via a signal connection and processes detection signals generated by the sensor 138 as the value document is transported past the same sensor 138.The sensor 138 comprises in particular a radiation source for emitting radiation of the excitation wavelength onto a value document to be checked and a detector for spectrally resolved detection of the luminescence emissions generated by excitation with the excitation radiation.

[0069] To check a value document 10, for example, the banknote 10 in Fig. 1, it is transported past the sensor 138 by means of the transport device 136. In this example, the value document is aligned relative to the transport device such that the long side of the value document runs parallel to the transport direction T in which the value document 10 is transported.

[0070] The following steps of a procedure for verifying the value document are carried out.

[0071] In step S10, at least one luminescence emission of the luminescence marker in the first partial region is detected by the sensor 138, as this first enters a detection range of the sensor 138. In this process, first detection signals are formed that represent the spectral properties of the detected luminescence emission. These are fed to the evaluation device 140.

[0072] In step S12, at least one luminescence emission of the luminescence marker in the second sub-area is detected by means of sensor 138, i.e., the same sensor, since this marker enters the detection range of sensor 138 after the first sub-area. Second detection signals are generated and represent the spectral properties of the detected luminescence emission. These are also fed to the evaluation device 140.

[0073] In step S14, the evaluation device 140 then evaluates the spectral properties of the emission of the first luminescence marker or the first luminescence marker relative to the spectral properties of the emission of the second luminescence marker or the second luminescence marker using the supplied first and second detection signals. Depending on the result of the evaluation, an authenticity signal is then generated and emitted, representing the result of the evaluation. The authenticity signal can be emitted to a device that controls the further processing of the value document.

[0074] In addition to a design as in Fig. 1, in which exactly two disjoint partial regions 14, 16 with spectrally similar luminescence markers overlap each other only in projection onto the transverse direction, other configurations are also possible and advantageous. For example, with reference to Fig. 6, the luminescence feature 72 of a banknote 70 can contain a first partial region 74 and a disjoint second partial region 76, wherein the partial regions 74, 76 overlap each other both in projection onto the longitudinal direction L and in projection onto the transverse direction Q of the banknote 70.

[0075] As a result, both partial areas 74, 76 can be scanned by a feature sensor when the banknote is scanned along a measuring track 20 in the longitudinal direction as well as along a measuring track 22 in the transverse direction, so that the banknote 70 can be checked in both longitudinally and transversely measuring banknote processing machines.

[0076] Further advantageous arrangements of the partial regions with spectrally similar luminescence markers are illustrated in Fig. 7. Fig. 7(a) shows the surface region 80 of a value document with a plurality of spaced-apart first partial regions 84 with a first luminescence marker and with a single second partial region 86 with a second luminescence marker. Here, too, measuring tracks 20, 22 in the longitudinal and transverse directions each record both a first and a second partial region, so that the value document with the surface region 80 can be checked both longitudinally and transversely. The same effect can be achieved with a design according to Fig. 7(b), in which the surface region 80 has a plurality of spaced-apart first partial regions 84 with a first luminescence marker and a plurality of spaced-apart second partial regions 86 with a second luminescence marker. The measuring tracks 20, 22 record a first and a second partial region in the longitudinal and transverse directions.In the transverse direction, both a first and a second partial area are provided.

[0077] In other designs, the first and second partial regions are not disjoint, but rather overlap in some areas, as shown in Fig. 7(c). In this design, the surface region 80 contains a first partial region 84 with a first luminescence marker and a second partial region 86 with a second luminescence marker, which overlap in the overlap regions 88. It is important that there are also non-overlapping regions in which only the first or only the second luminescence marker is present. As can be seen in Fig. 7(c), the measuring tracks 20, 22 each detect non-overlapping regions of the first and second partial regions 84, 86 in the longitudinal and transverse directions, respectively, and therefore allow a differential evaluation of the measurement signals, as in the designs described so far.

[0078] In order to demonstrate the advantages of the invention, a luminescence measurement on banknotes according to the invention was compared with a corresponding measurement on comparison banknotes with conventional luminescence features.

[0079] First, Fig. 8(a) shows two comparison banknotes 90, 94, each printed with an infrared-excitable and infrared-luminescent luminescent marker in a partial area 92 and 96, respectively. Partial area 92 of the first comparison banknote 90 contains a luminescent marker "B," while partial area 96 of the second comparison banknote 94 contains a luminescent marker "C," with the spectral difference between the two luminescent markers being 3%. In order to simulate a banknote verification under real operating conditions, the reference banknotes 90, 94 were measured with three identical feature sensors at several transport speeds between 1 m / s and 11 m / s and at several measuring points within the respective sub-area 92, 96 and a measure of the spectral position, for example the spectral center of gravity of a local emission maximum or an emission band, of the luminescence emission of the two luminescence markers was determined from the measured values.Instead of the spectral center of gravity of an emission band, the wavelength of the emission maximum or the wavelength of another spectral feature, such as a secondary maximum, a minimum or a shoulder in the emission spectrum, can be used as a measure of the spectral position.

[0080] Figure 8(b) shows, in a histogram 100, the number N of measurement results plotted against the respective spectral position determined for the two luminescence markers "B" and "C." As can be seen from the figure, the distributions 102, 104 of the spectral positions determined for the two luminescence markers exhibit a significant overlap, so that a reliable differentiation between the two luminescence markers is not possible due to the magnitude of the fluctuations that occur. Causes of such fluctuations could be, for example, variations between the nominally identical sensors or variations in the ambient conditions such as temperature, transport distance, or transport speed.

[0081] Figure 9(a) shows two banknotes 110, 120 according to the invention, which can, for example, be part of an above-mentioned value document system. In addition to the above-mentioned luminescence markers "B" and "C," the banknotes 110, 120 each contain a further luminescence marker "A" as a reference marker. The emission spectrum of the luminescence marker "A" lies between the emission spectra of the luminescence markers "B" and "C" and is therefore spectrally similar to both luminescence markers, with a spectral difference of approximately 0.5% and approximately 3%, respectively. Specifically, the banknote 110, in a configuration as in Fig. 1, is printed with the luminescence marker "A" in a first partial area 114 and with the luminescence marker "B" of the comparison banknote 90 in a second partial area 116. The two partial areas 114, 116 overlap in projection onto the transverse direction Q and can both be recorded with one measuring track.

[0082] The banknote 120 is also printed in a configuration as in Fig. 1, with the luminescence marker "A" in a first partial area 124 and with the luminescence marker "C" of the comparison banknote 94 in a second partial area 126. Here, too, the two partial areas 124, 126 overlap in projection onto the transverse direction Q and can both be detected with one measuring track.

[0083] The banknotes 110, 120 according to the invention were then measured with the same three identical feature sensors and the same transport speeds between 1 m / s and 11 m / s as the comparison banknotes at several measuring points within the respective sub-areas 114, 116 and 124, 126, respectively.

[0084] The spectral position of the luminescence emission of the second partial area 116 of the banknote 110 with the luminescence marker "B" and of the second partial area 126 of the banknote 120 with the luminescence marker "C" was not determined absolutely, but relative to the luminescence emission of the luminescence marker "A" of the respective first partial area 114 or 124.

[0085] Figure 9(b) shows in a histogram 130 the number N of the obtained measurement results, plotted against the respective determined spectral position of the two luminescence markers "B" and "C" relative to the spectral position of the luminescence marker "A" (zero point in Fig. 9(b)).

[0086] Since the fluctuations occurring during the measurement, such as variations between the three nominally identical sensors (e.g., filter tolerances or optical tolerances) or variations in the ambient conditions (e.g., temperature, transport distance, transport speed), have a similar effect on the spectral position measurement of the two sub-areas 114 and 116 or 124 and 126, these fluctuations largely compensate for each other in a differential evaluation, resulting in significantly narrower distribution widths in the histogram 130 of the relative spectral position. As shown in Fig. 9(b), the distributions 132, 134 of the differential measurement results for the luminescence markers "B" and "C" are clearly separated from each other, and the two luminescence markers can be reliably distinguished based on their relative spectral position.

[0087] The verification of value documents according to the invention can be carried out in particular with a single-track or multi-track luminescence sensor with at least two spectral channels K1, K2, which can detect the differences between the luminescence markers used on a value document using these spectral channels. Advantageously, the two spectral channels capture closely spaced or even directly adjacent spectral ranges of the emission spectra. If, for example, the emission band of the two luminescence markers is spectrally located approximately midway between the spectral sensitivity ranges of the two spectral channels, small shifts in the peak wavelength can be determined with high precision.

[0088] For example, in the emission spectra 34, 36 of Fig. 2, a spectral channel at position Kl below the central wavelength X z and a second spectral channel at position K2 above the central wavelength X zat the same distance from the central wavelength. It is also advantageous to use spectral channels with a width of several nanometers, for example, between 2 and 50.

[0089] In another design, several, for example 4, 10, 20 or even 100

[0090] Spectral channels are used to precisely scan the shape of the emission spectra. In another variant, the spectral channels of a luminescence sensor are adapted to specific, more complex emission spectra, so that individual peaks of the emission spectra can be detected by a few different channels. For example, for the emission spectra 54, 56 in Fig. 4, a feature sensor with three spectral channels can be used, which detect the luminescence emission at the wavelength positions indicated in the figure, namely, on the one hand, in the region of the maximum of the main emission 50 at position K1, and on the other hand, symmetrically on either side of the maximum of the secondary emission 52 at positions K2 and K3.

[0091] For the emission spectra 64, 66 of Fig. 5, a feature sensor with two spectral channels is sufficient, with which the luminescence emission can be detected in the region of the maximum of the main emission 60 at position K1 and in the region of the maximum of the secondary emission 62 at position K2.

[0092] List of reference symbols

[0093] Banknote

[0094] Luminescence feature, 16 sub-areas -P, 16-P projections

[0095] Overlap area, 22 measurement traces, 32 diagrams, 36 emission spectra

[0096] Difference spectrum -Max, 38-Min Maximum or minimum of the difference spectrum, 42 diagram, 46 emission spectra

[0097] Difference spectrum

[0098] Main issue

[0099] Side emission, 56 emission spectra

[0100] Difference spectrum

[0101] Main issue

[0102] Side emission, 66 emission spectra

[0103] Difference spectrum

[0104] Banknote

[0105] Luminescence feature, 76 sub-areas

[0106] Area , 86 sub-areas , 94 Comparison banknotes , 96 sub-areas with luminescence marker 100 Histogram

[0107] 102, 104 Distributions

[0108] HO banknote

[0109] 114 first section with luminescence marker A 116 second section with luminescence marker B

[0110] 120 banknotes

[0111] 124 first section with luminescence marker A

[0112] 126 second section with luminescence marker C

[0113] 130 Histogram 132, 134 Distributions

[0114] 136 Transport device

[0115] 138 Luminescence sensor

[0116] 140 Evaluation device

[0117] L longitudinal direction

[0118] Transverse direction

[0119] Kl, K2, K3 spectral channels

[0120] Transport direction

Claims

P a t e n t a n s p r ü c h e 1. A two-dimensional security document (10), in particular a banknote, which has a surface area with a longitudinal direction (L) and a transverse direction (Q) and which is provided in the surface area with a luminescence feature (12), characterized in that the luminescence feature (12) comprises a first luminescence marker in a first sub-area (14) and a second luminescence marker in a second, different sub-area (16), the first and second luminescence markers can be excited to luminescence at the same wavelength and, after excitation, luminesce essentially in the same emission band in the infrared spectral range, the first and second luminescence markers exhibit spectrally similar infrared emission spectra, namely infrared emission spectra that have a spectral difference of between 0.5% and 15%.and the first and second sub-areas are arranged overlapping each other in projection onto the longitudinal direction (L) and / or in projection onto the transverse direction (Q) within the surface area.

2. A flat security document according to claim 1, characterized in that the first and second luminescence markers have a spectral difference of between 1% and 11%, preferably between 2% and 7%.

3. A flat security document according to at least one of claims 1 or 2, characterized in that the first and second luminescence markers can be excited with a wavelength in the wavelength range of 700 to 2500 nm, preferably in the wavelength range of 900 to 2100 nm, and / or that the first and second luminescence markers luminesce after excitation in the wavelength range of 700 to 2500 nm, preferably from 900 to 2100 nm.

4. Planar security document according to at least one of claims 1 to 3, characterized in that the first and second luminescence markers show essentially no upconversion, in particular after excitation they emit essentially no light in the visible spectral range.

5. Flat security document according to at least one of claims 1 to 4, characterized in that the first and / or second luminescence marker contains an organic, organometallic or inorganic luminescence substance.

6. Flat security document according to at least one of claims 1 to 5, characterized in that the first and second luminescence markers each contain only a single luminescent substance.

7. Flat security document according to at least one of claims 1 to 5, characterized in that the first and second luminescence markers contain a common luminescence substance and at least one of the luminescence markers contains an additional luminescence substance.

8. Flat security document according to at least one of claims 1 to 7, characterized in that the first and second luminescence markers differ by the onset and / or decay times of the emission at one, several or all emission wavelengths.

9. A flat security document according to at least one of claims 1 to 8, characterized in that the first and second luminescence markers are each arranged in a printing ink area printed on the security document, preferably that the first and second luminescence markers are located in visually invisible printing ink areas, or that the first and second luminescence markers are located in visually visible printing ink areas, in particular in infrared-transparent printing ink areas.

10. Flat security document according to at least one of claims 1 to 8, characterized in that the first luminescence marker is arranged in a printed ink area on the security document and the second luminescence marker is arranged in a security element applied to the security document, in particular a strip or patch.

11. Flat security document according to at least one of claims 1 to 10, characterized in that the first and second sub-areas are disjoint.

12. Planar security document according to at least one of claims 1 to 11, characterized in that the luminescence feature comprises only a single first sub-area and only a single second sub-area and that the two sub-areas are arranged overlapping each other in the planar area both in projection onto the longitudinal direction and in projection onto the transverse direction.

13. Flat security document according to at least one of claims 1 to 12, characterized in that the luminescence feature forms a barcode, the line elements of which are formed by sub-areas with different luminescence markers.

14. Planar security document according to at least one of claims 1 to 13, characterized in that the luminescence feature comprises at least a third, distinct sub-area with a third luminescence marker which has a spectrally similar infrared emission spectrum to the first and second luminescence markers with a spectral difference between 0.5% and 15%.

15. Securities document system comprising a plurality of different securities documents (110, 112) according to one of claims 1 to 14, wherein the securities documents (110, 112) of the securities document system each have the same features in the first sub-area (114, 124). Luminescence markers and different luminescence markers in the second sub-area (116, 126).

16. Method for producing a planar security document (10) according to any one of claims 1 to 14, wherein a security document substrate is provided with a planar area extending in a longitudinal direction (L) and a transverse direction (Q) and is provided in the planar area with a luminescence feature (12) by arranging a first luminescence marker in a first sub-area (14) and a second luminescence marker in a second, distinct sub-area (16) in the planar area such that the first and second sub-areas overlap each other in projection onto the longitudinal direction (L) and / or in projection onto the transverse direction (Q), wherein the first and second luminescence markers can be excited to luminescence at the same wavelength and, after excitation, luminesce substantially in the same emission band in the infrared spectral range, and wherein the first and second luminescence markers have spectrally similar infrared emission spectra.namely infrared emission spectra that exhibit a spectral difference of between 0.5% and 15%.

17. Method according to claim 16, characterized in that the first and second luminescence markers are printed onto the security document substrate, preferably using different printing methods.

18. Method according to claim 16 or 17, characterized in that the first luminescence marker is printed onto the security document substrate and the second luminescence marker is arranged in a security element, in particular a strip or patch, and the security element with the second luminescence marker is applied to or inserted into the security document substrate.

19. Method for testing a flat security document according to one of claims 1 to 14, wherein - the two-dimensional security document (10) is transported and during transport the luminescence emissions of the two luminescence markers of the first and second sub-area (14, 16) are recorded by means of a sensor or the luminescence emissions of the two luminescence markers of the first and second sub-area (14, 16) are recorded together and -the spectral properties of the second luminescence marker are evaluated relative to the spectral properties of the first luminescence marker.

20. Method according to claim 19, characterized in that the luminescence emissions of the two luminescence markers are detected together by detecting the luminescence emissions of the two luminescence markers immediately one after the other along a measuring track that covers both sub-areas.

21. Method according to claim 20, characterized in that the measuring track is oriented parallel to the longitudinal direction or to the transverse direction of the surface area or the security document is transported parallel to the longitudinal direction or to the transverse direction of the security document.

22. Method according to at least one of claims 19 to 21, characterized in that the luminescence emission of the two luminescence markers is detected with a single-track or multi-track luminescence sensor with at least two spectral channels or that the sensor comprises a single-track or multi-track luminescence sensor with at least two spectral channels.

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