VALUE DOCUMENT SYSTEM

Description

[0001] The present invention relates to a security document system comprising at least a first security document and a second security document, a method for identifying a security document of a security document system and a luminescent material set for producing a security document system.

[0002] Securities are understood to be sheet-like items that represent, for example, a monetary value or an entitlement, and are therefore not intended to be easily produced by unauthorized persons. They thus possess security features that are not easily manufactured, especially copied, and whose presence is an indication of authenticity, i.e., production by an authorized entity. Important examples of such securities include chip cards, coupons, vouchers, checks, and especially banknotes, shares, tokens, identity cards, credit cards, and passports, as well as labels, seals, packaging, or other items used for security purposes.

[0003] Valuables are generally protected against unauthorized and potentially illegal duplication by special markings. It has long been known to treat valuables for this purpose with luminescent substances that exhibit specific emission characteristics. In particular, the use of security features consisting of a combination of different luminescent substances and the determination and evaluation of the luminescence decay time for the verification of valuables are well-known.

[0004] Security document systems in which valuable documents are divided into different classes and distinguished from one another by different security features are known in principle. Security features based on two or more luminescent substances whose emission or excitation spectrums partially overlap are also known in principle. For example, EP 2 512 821 B1 shows valuable documents with mixtures of oxysulfides, phosphates, and vanadates, and EP 2 271 504 B1 shows mixtures of substances.

[0005] For example, a state-of-the-art security document system typically uses several different luminescent substances, each with distinct emission spectra. These luminescent substances are individual compounds consisting of a doped matrix, exhibiting different emission spectra depending on the matrix composition. A sensor detects the emission spectrum across multiple spectral channels, allowing conclusions to be drawn about the class of substance used. The classification of these substances into different security document classes is then achieved by assigning them to these classes, possibly with the aid of the detected luminescence decay times.

[0006] The state-of-the-art documents demonstrate methods for verifying the authenticity of securities and for securing them. The verification process checks for the presence of the relevant security feature and, based on the results, concludes that the securities document is authentic.

[0007] WO 2006 / 024530 A1 describes a security document with luminescent properties, as well as a security document system, whereby the security documents of the system are distinguishable by different combinations of luminescent substances.

[0008] US 2010 / 026991 A1 describes a authentication feature in the form of two luminescent substances.

[0009] Therefore, one of the aims of the invention is to increase the security of valuable documents, in particular without significantly increasing the complexity or manufacturing costs of the sensors required for authentication.

[0010] The problem is solved by a security document system, a method for identifying a security document, and a luminescent material set according to the independent claims. Particularly advantageous embodiments are the subject of the dependent claims.

[0011] A securities document system according to the invention comprises at least two securities documents, namely at least a first securities document and a second securities document.

[0012] The first security document features a security element consisting of a combination of at least one first and one second luminescent substance. The first luminescent substance of the security element in the first security document is a luminescent substance of a first class, and the second luminescent substance of the first security document is a luminescent substance of a second class. Furthermore, the first and second luminescent substances of the security element in the first security document have partially overlapping emission spectra. The first and second luminescent substances of the security element in the first security document also have a decay time of less than 5 ms.

[0013] The second security document features a security element with at least one primary luminescent substance. The primary luminescent substance of the second security document belongs to either the first or second class of substance. The decay time of the primary luminescent substance of the second security document is a maximum of 5 ms.

[0014] The first and second luminescent materials of the security feature of the first security document are designed such that their emission spectra partially overlap, and the primary emission range formed by the overlapping emission spectra can be divided into two distinct, immediately adjacent spectral ranges. The two adjacent spectral ranges, namely the first spectral range A (from λA1 to λA2) and the second spectral range B (from λB1 to λB2), are each larger than 50 nm and smaller than 500 nm, and at least one of the two adjacent spectral ranges comprises at least a portion of the emission of the first and second luminescent materials of the security feature of the first security document.

[0015] The emission of the security feature of the second security document lies at least partially, i.e., to at least 1% of its intensity, in at least one of the adjacent spectral ranges A, B. The total intensity is preferred. I A W 2 + I B W 2 The emission of the security feature of the second security document in spectral ranges A and B is similarly large to the overall intensity. I A W 1 + I B W 1 the emission of the security feature of the first security document, i.e. 0 , 1 < I A W 2 + I B W 2 / I A W 1 + I B W 1 < 10 .

[0016] This is I A W 1 = ∫ λA 1 λA I ges W 1 ′ x dx , I B W 1 = ∫ λB λB 2 I ges W 1 ′ x dx , I A W 2 = ∫ λA 1 λA 2 I ges W 2 ′ x dx and I B W 2 = ∫ λB 1 λB 2 I ges W 2 ′ x dx , where I ges W 1 ′ x bzw . I ges W 2 ′ x das The emission spectrum of the first or second security is shown. In a preferred design I A W 1 , I B W 1 , I A W 2 and I B W 2 at a specific, and in particular the same, measurement time.

[0017] The security feature of the second security document differs from that of the first security document in terms of emission intensity ratio, decay time ratio, and / or decay time sum in spectral ranges A and B. A security feature code and / or a security document identifier for the first and / or second security document is assigned to this difference in emission intensity ratio, decay time ratio, and / or decay time sum in spectral ranges A and B. Specifically, the emission intensity ratio U of a security feature of the first or second security document is the quotient of the total intensity of the corresponding luminescent substances in spectral ranges A and B. U AB = I A / I B

[0018] The decay time ratio V of a security feature of the first or second security document is the quotient of the respective total decay times τ A and τ B in the spectral ranges A and B: V AB = τ A / τ B

[0019] This is τ A a measure of the decay time of I A and τ B a measure of the decay time of I B . To determine τ A or τ B , for example A quotient of the values ​​of I A or I B A mathematical function is determined at two points in time and applies to the time course of I A or I B be adjusted, or it will be determined at what time I A or I B falls below a predetermined threshold.

[0020] The decay time sum S is the sum of the total decay times τ A and τ B in the two spectral ranges A and B of a security feature of the first and / or possibly the second security document: S AB = τ A + τ B

[0021] The various security features of the security document system differ in their intensity ratio U and / or in their decay time ratio V and / or in their decay time sum S.

[0022] The first class of substances comprises luminescent materials with a doped garnet structure, in particular yttrium aluminum garnet (YAG), lutetium aluminum garnet (LuAG), gadolinium gallium garnet (GGG), gadolinium scandium gallium garnet (GSGG), yttrium scandium gallium garnet (YSGG), calcium niobium gallium garnet (CNGG), gadolinium scandium aluminum garnet (GSAG), calcium lithium niobium gallium garnet (CLNGG), transition metal-containing garnet structures such as yttrium iron garnet (YIG), or other variants or mixtures of such garnet structures. The second class of substances comprises luminescent materials with doped rare-earth oxysulfide, doped rare-earth phosphate, or doped rare-earth vanadate.

[0023] The rare earth phosphates in question are explicitly orthophosphates of one or more trivalent rare earth cations X, i.e., XPO4, in contrast to other phosphates used in the prior art as a matrix for luminescent substances, such as pyrophosphates, polyphosphates of the type X(PO3)3, ultraphosphates of the type XP5O14, and other phosphates.

[0024] Similarly, the rare earth vanadates are explicitly orthovanadates of one or more trivalent rare earth cations X, i.e., XVO 4 .

[0025] Suitable rare-earth oxysulfides include, for example, lanthanum oxysulfides, yttrium oxysulfides, gadolinium oxysulfides, lutetium oxysulfides, or mixed oxysulfides based on these. Suitable rare-earth phosphates include, for example, lanthanum phosphates, yttrium phosphates, gadolinium phosphates, lutetium phosphates, or mixed phosphates based on these. Suitable rare-earth vanadates include, for example, lanthanum vanadates, yttrium vanadates, gadolinium vanadates, lutetium vanadates, or mixed vanadates based on these.

[0026] Numerous matrices for inorganic luminescent materials are known according to the prior art. These include, 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 perovskites, including yttrium aluminum perovskite and lanthanum gallium perovskite; spinels, including zinc aluminum spinels, magnesium aluminum spinels, and manganese iron spinels; or mixed oxides such as ITO (indium tin oxide). Oxyhalides and oxychalcogenides, in particular oxychlorides such as yttrium oxychloride, lanthanum oxychloride; sulfides and other chalcogenides, e.g. zinc sulfide, cadmium sulfide, zinc selenide, cadmium selenide; sulfates, in particular barium sulfate and strontium sulfate; alkaline earth phosphates, in particular barium phosphate, strontium phosphate, calcium phosphate, as well as more complex phosphate-based compounds such as apatites, including, among others, calcium hydroxylapatite, calcium fluoroapatite, calcium chloroapatite; or spodiosites, including, for example, calcium fluoro-spodiosite, calcium chloro-spodiosite; silicates and aluminosilicates, in particular zeolites such as zeolite A, zeolite Y; zeolite-related compounds such as sodalites; feldspars such as alkali feldspars, plagioclase; other inorganic compound classes such as germanates, arsenates, niobates, tantalates, tungstates or aluminates.

[0027] However, a document security system according to the invention with the aforementioned advantageous properties cannot be produced using these materials. This is only possible by selecting the above-mentioned special classes of materials with complementary spectral properties, as described below.

[0028] Therefore, not just any luminescent materials can be combined to construct the security document system according to the invention. Rather, the invention requires a targeted selection to combine complementary spectral properties in such a way as to create a multitude of suitable encodings. Complementary spectral properties mean that the different luminescent materials can be distinguished based on their different spectral characteristics. This means, for example, that the immediately adjacent intensity maxima of different luminescent materials with sensors having a resolution of > 50 nm differ significantly from each other by more than 50 nm.

[0029] Numerous dopants are known for inorganic luminescent materials according to the state of the art, for example the rare earth elements: Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, as well as other dopants Bi, Pb, Ni, Sn, Sb, W, Tl, Ag, Cu, Zn, Ti, Mn, Cr and V (or their ions). The dopants are used individually or in combination (e.g. as co-doping).

[0030] Luminescent materials according to the invention require at least one dopant from the group consisting of Nd, Yb, Er, Tm, and Ho. Preferably, the luminescent materials contain at least ytterbium, neodymium, or erbium as a dopant, particularly preferably ytterbium or neodymium, since the wavelength range of the emission allows for particularly good detection by a simple detector. Preferably, in addition to the dopant from the group consisting of Nd, Yb, Er, Tm, and Ho, further (arbitrary) dopants are present. The dopants from the group consisting of Nd, Yb, Er, Tm, and Ho act as emission centers of the luminescent materials described herein. Nd, Yb, or Er are preferably the emission centers of the luminescent materials, particularly preferably Nd or Yb. The term "emission center" means that the emission of the luminescent material originates from this dopant.For example, in a typical energy transfer from neodymium (Nd) to ytterbium (Yb), upon excitation of the neodymium, the ytterbium forms the emission center, since the emission of the neodymium is suppressed by the energy transfer. Similarly, in an erbium-doped matrix in which praseodymium has been added as a co-doper to adjust the decay time without itself emitting significant luminescence, the luminescence-emitting erbium forms the emission center.

[0031] The security features of the first security document according to the invention are therefore a mixture of substances consisting of at least one luminescent substance from the first class of substances and at least one luminescent substance from the second class of substances, which are described below.

[0032] In one design, the security feature of the first and / or, where applicable, the second security document can consist of a mixture of luminescent substances from the first and / or second class, with the addition of further luminescent substances belonging to neither the first nor the second class. This allows, for example, the spectral profile of the emission spectrum to be fine-tuned or the number of codes to be further increased.

[0033] Preferably, the luminescent materials exhibit essentially no additional anti-Stokes emission (<5% relative intensity). This prevents, among other things, the security feature from being made visible by infrared laser pointers or similar devices for upconversion detection.

[0034] By combining at least the first and second luminescent materials in the security feature of the first and, if applicable, second security document, a large number of codes can be generated. Based on the resulting code, the security feature can be assigned to a security document class, such as a denomination and / or a value. This means that the check is not only performed for a specific security feature on a security document, but also to ensure that the security document corresponds to the code or security document class identified and assigned by the recognized security feature. The security document identifier or the code of the security feature of the first and second security documents can be assigned to a banknote value and / or a country of origin, or, particularly in combination with other information, can attest to the authenticity of the first or second security document.

[0035] The security feature of the first security document consists of at least the first and second luminescent substances in a definable or defined ratio in combination (preferably in the form of a mixture). This means that the first and second luminescent substances of the first security document are present in the security feature in a definable or defined relative proportion, based on the total amount of luminescent substances. The security feature can thus be uniquely identified.

[0036] The first and second luminescent materials of the first security document and the first and second luminescent materials of the second security document can be incorporated into or attached to the first and second security documents in various ways. For example, they can be mixed into a paper or plastic compound used to manufacture the first and second security documents, or into a printing ink used to print on the first and second security documents. It is also conceivable to apply the first and / or second luminescent material of the first security document, or the first and / or second luminescent material of the second security document, as an invisible coating on the security document.The first and second luminescent materials of the first security document and / or at least the first luminescent material of the second security document may also be provided on or in a carrier material, for example made of plastic, which is embedded in a paper or plastic material used to manufacture the security document. The carrier material may, for example, be in the form of a security or identification thread, a reflective fiber, or a planchette. The carrier material may also be attached to the security document, for example, in the form of a tag, for instance, to implement a product security measure. In principle, any shape of the carrier material is possible.

[0037] The first and second luminescent substances of the first security document and the first and second luminescent substances of the second security document exhibit single-substance emission spectra. The first and second luminescent substances of the first security document exhibit different single-substance emission spectra that overlap in a wavelength range (hereinafter referred to as the overlap range, cf.). Fig. 1A The emission spectra of the first and second luminescent substances in the first security document partially overlap, but not completely. Depending on its relative proportion, the first or second luminescent substance in the first security document contributes to the overall intensity of the security feature within the overlap region (ÜB) with the intensity of its emitted luminescence radiation. The term "overall intensity" always refers to the summed intensity of the luminescence radiation from the luminescent substances combined in the security feature, excited by the same excitation pulse and detected at the same time at a specific wavelength or within a specific wavelength range. Similarly, the term "overall decay time" refers to the decay time of the overall intensity, as opposed to the individual decay time of the intensity of a single luminescent substance.

[0038] The terms "integrated total intensity" and "integrated individual intensity" refer to the spectral integral of the respective intensity over a specified range.

[0039] When measuring the total intensity with a typical resolution of preferably 20 nm, an uninterrupted "primary emission range" (PEB) is obtained, which is defined as follows (see Figur 1B , area between the dotted marking lines): The maximum total intensity is located in the primary emission region. The primary emission region is the largest contiguous wavelength range in which the total intensity does not fall below 10% of the maximum.

[0040] The rationale behind this definition is that for an efficient, quickly readable security feature, the main emission must necessarily be evaluated, and not, for example, a potentially present weaker secondary emission. Furthermore, determining the decay time in low-intensity areas leads to higher measurement inaccuracies or an increased signal-to-noise ratio, meaning that a reliable decay time value cannot be determined for these sub-areas during a rapid measurement.

[0041] The "degree of overlap" between two single-substance emission spectra of two different luminescent substances in the primary emission range is defined as follows: First, the single-substance emission spectra I'(x) and J'(x), whose curves are obtained when the individual intensities I' and J' are plotted against the wavelength (x), are normalized to the same area. I x = I ′ x / ∫ λ 1 λ 2 I ′ x dx , J x = J ′ x / ∫ λ 1 λ 2 J ′ x dx .

[0042] In this case, for example, the area was normalized to 1. λ1 is the lower cutoff wavelength of the primary emission range and λ2 is the upper cutoff wavelength of the primary emission range.

[0043] The degree of overlap is then defined by the following formula: Überlappungsgrad = 2 ∫ λ 1 λ 2 I x ⋅ J x dx ∫ λ 1 λ 2 I x dx + ∫ λ 1 λ 2 J x dx

[0044] It refers to the relative proportion of spectral overlap within the primary emission range between the single-substance emission spectra of the respective luminescent substances.

[0045] The degree of overlap of the emission spectra of two luminescent substances is a parameter independent of the relative intensity and the ratio of the luminescent substances, relating solely to the shape-dependent overlap of the respective individual substance emission spectra. To determine the degree of overlap, emission spectra measured at room temperature are used, which were measured with a typical detector resolution of preferably 20 nm.

[0046] According to the invention, the first and second luminescent materials of the first security document are designed such that their individual material emission spectra have an overlap of less than 80%, preferably less than 65%, particularly preferably less than 50%, and an overlap of more than 5%, preferably more than 10%, particularly preferably more than 20%.

[0047] Security systems incorporating features made from such overlapping luminescent substances can exhibit particularly advantageous properties when certain combinations of these substances are used. Surprisingly, it has been discovered that by specifically combining the first and second luminescent substances, it is possible to develop systems of mixtures that possess advantageous properties. In particular, the complementary emission spectra of the first and second classes of substances, when combined, generate a large number of easily distinguishable codes with simultaneously high counterfeit protection. These codes can also be reliably distinguished using sensors that do not operate with a large number of spectral channels at high spectral resolution and therefore exhibit lower complexity.

[0048] For the security document systems according to the invention, instead of a multitude of different individual luminescent substances with different emission spectra, mixtures of luminescent substances with overlapping emission are used. Depending on the choice of material of the first and second luminescent substances and their ratio, a multitude of emission spectra can be generated, which are, for example, analogous to those of different individual substances, or different from those of individual substances and possess further properties.

[0049] Using at least two different luminescent substances—namely, the first and second luminescent substances of the first security document—it is possible to produce a large number of security features by varying the mixing ratios within the security feature. This allows for better utilization of economies of scale in production, since the first and second luminescent substances of the first security document, which can be present in all mixtures, are required in significantly larger quantities than if corresponding codes were created using a multitude of individual luminescent substances.

[0050] A further advantage arises from the fact that substances with a specific emission spectrum are often only accessible by selecting exotic matrices. "Exotic" here refers, for example, to matrices with unusual structures whose existence has been academically proven, but which are difficult to produce and therefore unsuitable for commercial use. For instance, the production of such matrices requires unusual reaction conditions, expensive starting materials, or numerous synthesis steps. And although such substances may possess unusual and unique emission spectra, other properties, such as low chemical stability against acids or bases, are often unsuitable for use as a safety feature.

[0051] If, according to the invention, the emission spectrum of the security feature of the first security document is composed from the individual emission spectra of the first and second luminescent substances, substances with particularly advantageous properties can be used. These include, among others, high chemical resistance, high luminescence efficiency, simple synthesis, and cost-effective raw materials. Likewise, new emission spectra can be generated that do not correspond to any known individual substance. In particular, emission spectra can be specifically tailored to achieve, for example, the best possible separability of different encodings.

[0052] A third advantage arises from combining the properties of substances whose emissions overlap, resulting in emission spectra with novel temporal properties that are not accessible through individual substances. This includes, for example, mixtures of substances with different decay times, in which the detected emission spectrum changes over time in a defined manner.

[0053] One embodiment provides that at least two, preferably at least three, security features of the security document system are designed such that they exhibit different emission spectra immediately after excitation, but the same emission spectrum at different times after excitation. This is achieved by a suitable combination of the first and second luminescent materials of the security feature, each with different decay times in spectral ranges A and B, respectively. In this case, the individual security features can be distinguished by determining the respective time after excitation until a predetermined target spectrum is reached.

[0054] The advantages of the invention become particularly apparent in the automated measurement of valuable documents using high-speed sensors and suitable methods, in contrast to methods used, for example, in the forensic analysis of a single banknote in a laboratory. In the latter case, banknotes typically move through the machine at speeds of up to 12 meters per second, necessitating specific requirements for the detection methods and material properties. Furthermore, the security features according to the invention make it possible to distinguish the individual encodings of the valuable document system with a simple sensor, which, for example, covers the primary emission range with only two or three detection channels.

[0055] In one embodiment, the security feature of the second security document comprises a second luminescent substance, wherein the first luminescent substance of the second security document belongs to the first class of substances and the second luminescent substance of the second security document belongs to the second class of substances. The first and second luminescent substances of the second security document exhibit partially overlapping emission spectra.Furthermore, the first and second luminescent materials of the security feature of the second security document are designed such that their primary emission range of the partially overlapping emission spectra can be divided into at least two different, immediately adjacent spectral ranges A, B, wherein the at least two adjacent spectral ranges are greater than 50 nm and less than 250 nm, wherein at least one of the at least two adjacent spectral ranges comprises at least a part of the emission of the first and second luminescent materials of the security feature of the second security document (i.e., the percentage of the integral over the emission range that lies within the spectral sensitivity range of the relevant detection channels is greater than zero), and wherein the spectral ranges A, B of the security feature of the second security document are identical to those of the security feature of the first security document.

[0056] In this configuration, both the security feature of the first and the second security document consist of mixtures of substances from the first and second classes with partially overlapping emission spectra. This further enhances counterfeit protection, and the security feature of the second document also benefits from the advantages of such mixtures over single substances, as previously described: For example, new emission spectra can be generated that do not correspond to any known single substance. A further advantage arises from combining the properties of the substances whose emission overlaps, resulting in emission spectra with novel temporal properties that are not accessible through single substances.

[0057] In a preferred embodiment, at least two, preferably at least three, particularly preferably at least four security documents of the security document system have a security feature consisting of a mixture of luminescent substances of the first class and the second class with partially overlapping emission spectra.

[0058] Analogous to the security feature of the first security document with first and second luminescent substances, the intensity ratio U of the emission of the security feature of the at least second security document is the quotient of the total intensity of the first and second luminescent substances of the security feature of the second security document in the spectral ranges A, B. The decay time ratio V of the security feature of the second security document is the quotient of the total decay times τ A and τ B in the spectral ranges A and B of the security feature of the second security document, respectively, and the decay time sum S of the security feature of the second security document is the sum of the total decay times τ A and τ B in the spectral ranges A, B of the security feature of the second security document.

[0059] To distinguish between different security features of different valuable documents within the valuable document system, the same spectral ranges A and B are always preferably used.

[0060] In one embodiment, the first and second luminescent materials of the security feature of the first security document have the same decay time as the first and second luminescent materials of the security feature of the second security document. In particular, all luminescent materials with overlapping emission in the two spectral ranges A and B have the same decay time. The luminescent materials with overlapping emission are thus selected such that their decay times are essentially the same, meaning that their decay times differ by less than 10%, preferably by less than 5% (based on the shortest individual decay time of the luminescent materials).

[0061] In this case, the emission spectrum composed of the various luminescent substances behaves like the spectrum of a new single substance. One advantage of this approach is that the spectral properties can be adjusted during the production of security features without affecting the decay time or the ratio of decay times in the different spectral ranges. This allows, among other things, compensation for manufacturing variations or the alignment of the spectral properties of the security feature with absorption bands of the substrate, etc.

[0062] Furthermore, the measured emission spectrum of a security document suggests a different material class to a potential forger, to which other material properties would then not correspond. This increases the security against forgery.

[0063] Preferably, the decay time of the individual luminescent materials of the security features of the first and second banknotes is at least 0.05 ms. Particularly preferably, the decay time is in the range of 0.05 to 5 ms. Within this range, good machine detectability of the decay time in banknote processing machines is ensured. Measuring shorter decay times is technically complex, and determining longer decay times is not possible due to the high speed of the banknotes in banknote processing machines, which can reach up to 12 meters per second.

[0064] Another design feature allows the first and second luminescent substances of the first security document, and potentially the second, to differ in their decay time by 10% to 50% (based on the shortest individual decay time of the luminescent substances). In this case, the spectrum composed of the different luminescent substances appears at first glance, or upon superficial analysis, to be that of a single substance. However, this slight difference can be used to distinguish the security feature from a single substance with the same emission spectrum upon closer analysis. This, among other things, provides greater protection against counterfeiting.

[0065] A further embodiment can provide that the first and second luminescent materials of the first security document, as well as the at least one luminescent material of the second security document, differ in their decay time by at least 50%, preferably by 75%, and particularly preferably by more than 100% (based on the shortest individual decay time of the luminescent materials). Thus, for a security feature, all luminescent materials with overlapping emission in the two spectral ranges A and B exhibit significantly different decay behavior, or significantly different decay times.

[0066] In this case, particularly strong protection against counterfeiting is generated because the decay behavior in the different detector channels of a sensor depends heavily on the selected measurement parameters (size of the detection channel, etc.), which a potential counterfeiter must know in order to forge a corresponding security feature. A further advantage is the ability to create special codes for a security document system that exhibit the same emission spectrum but differ in their decay time ratio in spectral ranges A and B, or in different detection channels of a sensor. For example, when using two detection channels, Channel 1 and Channel 2, which measure an emission spectrum with the same intensity, the following scenarios can occur: a) Channel 1 detects a longer decay time than Channel 2. b) Channel 1 and Channel 2 detect the same decay time. c) Channel 1 detects a shorter decay time than Channel 2.

[0067] Thus, the sensor can divide valuable documents into three or more classes, e.g., three different currencies, based on the decay time ratio, even though they show the exact same emission spectrum.

[0068] Furthermore, more complex forms of overlap or spectral distribution are possible. For example, a luminescent substance may not only consist of a symmetrically structured emission band, as schematically depicted, but may also exhibit an asymmetric band, a main band with a shoulder, or multiple bands, such as a main band and several secondary bands, within the investigated region. Additionally, the individual luminescent substances themselves may exhibit peculiarities in their temporal behavior, such as a measurable decay behavior with a corresponding decay time or an atypical decay curve. This allows for significantly more complex relationships between the observed spectral range and the detected decay time, with local minima, local maxima, or one or more inflection points.

[0069] To mimic the continuously wavelength-dependent decay of such luminescent mixtures, a specific combination of luminescent substances is necessary, since the individual components must not only produce the target spectrum in their entirety, but also possess suitable regions of spectral overlap and appropriate decay time ratios. This makes mimicking the phenomenon considerably more difficult.

[0070] According to the invention, effective protection against counterfeiting can be achieved by combining at least two luminescent substances with a defined degree of overlap and with specific, different decay times. Counterfeiting by combining different luminescent substances with different spectral properties is only possible if the exact measurement parameters, in particular the spectral position and shape of the filter curves of the detection channels, the temporal sampling or the temporal profile of the luminescence, as well as the algorithm or the selected measurement parameters for determining the effective decay time, are known.

[0071] By ensuring an overlap of the individual emission spectra of the luminescent substances of less than 80% and more than 5%, sufficient variance in the decay time behavior of the total intensity of the luminescent substances can be guaranteed. This advantageously avoids both the presence of a single, constant mixed decay time across the entire range (corresponding to an overlap of 100%, i.e., identical spectral shape of both emissions) and the presence of individual, separate emissions with constant decay times (corresponding to an overlap of 0%).

[0072] Preferably, the individual substance emission spectra of the luminescent materials, and thus the primary emission range, lie within a narrow spectral range, i.e., a spectral range of less than 300 nm. In an advantageous embodiment of the security document according to the invention, the luminescent materials are designed for this purpose such that directly adjacent intensity maxima of different individual substance emission spectra differ from each other by less than 200 nm, preferably by less than 100 nm. Preferably, the directly adjacent intensity maxima of different individual substance emission spectra are separated by more than 20 nm, particularly preferably by more than 50 nm, in order to obtain a sufficiently large overlap range for the first or second security feature. In a particularly advantageous embodiment of the invention, the directly adjacentDirectly adjacent intensity maxima of different luminescent substances are separated by a distance of less than 100 nm and more than 50 nm.

[0073] Preferably, the primary emission range of the luminescent substances lies in the infrared range, i.e. between 700 nm and 2000 nm, particularly preferably between 800 nm and 2000 nm.

[0074] The luminescent substances can be excited in the infrared range, i.e. between 700 nm and 2000 nm, preferably between 800 and 1500 nm.

[0075] Furthermore, the luminescent substances can be excited in the visible spectral range, i.e., between 400 nm and 700 nm. Excitation in the infrared range is particularly preferred.

[0076] Preferably, the emission centers of the luminescent substances are rare earth ions, namely the rare earth ions neodymium (Nd), ytterbium (Yb), erbium (Er), thulium (Tm), and / or holmium (Ho).

[0077] In one embodiment of the invention, the primary emission range of the luminescent materials lies in the range of 750 nm to 1100 nm, particularly in the range of 800 nm to 1100 nm. In a preferred embodiment of the invention, the primary emission range lies in the range of 900 nm to 1100 nm. In these ranges, for example, luminescent materials containing neodymium and / or ytterbium can be advantageously used.

[0078] In a further embodiment of the invention, the primary emission range lies in the range of 1500 nm to 1900 nm, preferably in the range of 1500 nm to 1700 nm. In these ranges, luminescent materials containing erbium and / or thulium, for example, can be advantageously used. Alternatively, the primary emission range can lie in the range of 1700 nm to 1900 nm. In these ranges, luminescent materials containing thulium and / or holmium, for example, can be advantageously used.

[0079] In one embodiment, the luminescent materials for a security document system according to the invention with overlapping emission each possess the same rare-earth ion as the emission center. Preferably, the luminescent materials with overlapping emission possess only a single rare-earth ion from the group {Nd, Yb, Er, Tm, Ho}. For example, one, say the first, of the luminescent materials contains only erbium and none of the others from the group, and another luminescent material, say the second, also contains only erbium and none of the others from the group. This ensures, among other things, that two different, separate security document systems do not contain wholly or partially the same rare-earth ions and thus interact with and interfere with each other. Furthermore, it prevents the individual components of the mixture from being analyzed separately via separate excitation of the other rare-earth ions.

[0080] In a preferred embodiment, the luminescent substances with overlapping emission have Nd as a dopant and do not contain any of the rare earth elements Yb, Er, Tm or Ho as a dopant.

[0081] In a further preferred embodiment, the luminescent substances with overlapping emission have Yb as a dopant and do not contain any of the rare earth elements Nd, Er, Tm or Ho as a dopant.

[0082] In a further preferred embodiment, the luminescent substances with overlapping emission have Er as a dopant and do not contain any of the rare earth elements Nd, Yb, Tm or Ho as a dopant.

[0083] When using these elements, the wavelength range of the emission allows for particularly good detection by a simply constructed detector.

[0084] The term "as a dopant" refers to the usual use of such elements in the production of luminescent materials, where typically 0.1% to 50% of the available positions in the matrix are occupied by the dopant. This does not include minor impurities of the corresponding elements, which may be introduced during the production of the luminescent material, for example, depending on the chosen purity of the starting materials.

[0085] In one embodiment, the luminescent materials for a security document system according to the invention with overlapping emission each have different rare earth ions as emission centers or have mixtures of the rare earth ions of the group {Nd, Yb, Er, Tm, Ho}. This allows for more complex effects, e.g., energy transfer systems or targeted modification of the spectral behavior.

[0086] In In a preferred embodiment, the luminescent substances with overlapping emission have Nd and / or Yb and / or Er as dopants and do not contain either of the rare earth elements Tm or Ho as dopants.

[0087] In In a preferred embodiment, the luminescent substances with overlapping emission have Nd and / or Yb as dopants and do not contain any of the rare earth elements Er, Tm or Ho as dopants.

[0088] When using these elements, particularly good detectability is achieved with a simply constructed detector.

[0089] Preferably, the emission of the luminescent substances occurs essentially in the primary emission range. This means that, apart from the partially overlapping emission bands, no further emission bands occur in other spectral ranges. This advantageously avoids the need to separately evaluate further non-overlapping, isolated emission bands during simulation in order to draw conclusions about the emission bands of the primary emission range. In In a preferred embodiment of the invention, the luminescent materials are designed for this purpose such that at least 80%, in particular at least 90%, of the individual intensities are emitted in the primary emission range.

[0090] In In a particularly preferred implementation scenario, the different codes of the security document system are generated by combining as few and as similar luminescent substances as possible, as explained below. This provides a particularly high level of protection against analysis and counterfeiting of the security feature.

[0091] Preferably, the first and / or second luminescent material of the security feature of the first security document has the same matrix as the first luminescent material and / or the optionally second luminescent material of the security feature of the second security document.

[0092] Preferably, the security document system comprises at least a third security document whose security feature includes at least one luminescent substance which has the same matrix as the first or second luminescent substance of the security feature of the first security document, but differs in its doping and / or its decay behavior.

[0093] Preferably, at least 3, particularly preferably at least 4, further preferably at least 5 different encodings of the security document system consist of security features with the following properties: the security features consist exclusively of mixtures of materials with a first matrix and a second matrix, wherein the first and / or second matrix may have different doping and / or different decay behavior.

[0094] For example, the first matrix could be lutetium aluminum garnet (LuAG) and the second matrix yttrium vanadate (YVO₄), which could be doped with different amounts of neodymium to produce a fast decay time (S) or a slow decay time (L). The following security features, for example, are then created for the different encodings of the security document system: 4 safety features from different mixing ratios of LuAG:Nd (S) and YVO 4 :Nd (S) 4 safety features from different mixing ratios of LuAG:Nd (S) and YVO 4 :Nd (L) 4 safety features from different mixing ratios of LuAG:Nd (L) and YVO 4 :Nd (S) 4 safety features from different mixing ratios of LuAG:Nd (L) and YVO 4 :Nd (L)

[0095] Thus, a value document system with 16 codes can be created, which are, however, very similar to each other and therefore difficult for a forger to analyze and imitate.

[0096] In a preferred embodiment, different codings of the security document system differ in at least one of their U, V, or S values ​​by at least 20%, preferably at least 50%, relative to the smaller value. This ensures that a clear distinction between the individual codings is possible.

[0097] In a further preferred embodiment, different codings of the asset document system differ in their V-values ​​by at least 20%, preferably at least 50%.

[0098] In a further preferred embodiment, different codings of the asset document system differ in their U-values ​​by at least 20%, preferably at least 50%.

[0099] In a further preferred embodiment, different codings of the asset document system differ from each other in at least two of their U, V and S values ​​by at least 20%, preferably at least 50%.

[0100] This ensures that the separation of codings is not solely based on S-values, as this provides less protection against counterfeiting than if the U- or V-values ​​differ between codings instead or additionally.

[0101] In a further embodiment of the security document system according to the invention, the luminescent materials are designed such that their individual decay times are in the range of 50 µs to 5000 µs, preferably in the range of 100 µs to 1000 µs. Preferably, the individual decay time of a first luminescent material is in the range of 100 µs to 200 µs and the individual decay time of a second luminescent material is in the range of 400 µs to 1000 µs, thereby achieving particularly good protection against counterfeiting of the security feature.

[0102] In particular, according to the invention, luminescent materials with decay times exceeding 5 milliseconds cannot be used for machine evaluation on high-speed banknote sensors, since the banknote is transported at speeds of up to 12 meters per second. Detection or separation of such long decay times is not possible because the banknote moves out of the measurement field before the luminescence intensity has noticeably decreased due to the decay time. Furthermore, measuring very short decay times is technically complex.

[0103] Preferably, none of the luminescent substances has a decay time of more than 5000 µs, particularly preferably more than 2000 µs, and especially preferably more than 1000 µs. This allows for more precise measurement of the decay time, even at high transport speeds. Preferably, none of the luminescent substances has a decay time of less than 50 µs, particularly preferably less than 80 µs, and especially preferably less than 100 µs. At shorter decay times, distinguishing background fluorescence, e.g., from organic impurities, becomes increasingly difficult. According to the invention, inorganic luminescent substances are used. Particularly preferred according to the invention are luminescent substances that each use an inorganic host lattice as a matrix, which is doped with at least one dopant selected from the rare-earth metals (or their ions).

[0104] The adjustment of the decay times of inorganic luminescent materials is known in the art. For example, adjustment can be achieved by controlling the amount of dopant (concentration quenching). Alternatively, co-doping (quenchers) can be used, typically employing certain rare earth elements such as samarium, praseodymium, or dysprosium, or certain transition metals, such as iron(III) ions, but also numerous other elements. Alternatively, the decay time can be influenced by the particle size of the luminescent materials, particularly in the nanoparticle range, or by structural defects / defects or surface defects, and can thus be controlled by suitable synthesis conditions or processing of the luminescent materials. Preferably, the adjustment of decay times within the scope of this invention is achieved by concentration quenching or the addition of quenchers.

[0105] In one embodiment of the invention, the luminescent materials of the security document system, i.e., the at least first and second luminescent materials of the security feature of the first security document and the at least first luminescent material of the second security document, are designed such that they, in particular the first and second luminescent materials of the first security document, can be excited together by the same wavelength. This allows, in particular, targeted and relatively strong excitation of the luminescent materials by a spectrally comparatively narrowband excitation pulse (light flash, e.g., laser). It is advantageous if the wavelength corresponds to a common absorption maximum in the excitation spectra of the luminescent materials or, in the case of different absorption maxima, can excite at least 50% of the respective absorption maximum.The excitation preferably occurs in a strong excitation band of a rare-earth ion present in both luminescent materials. This enables efficient co-excitation of the luminescent materials. Preferably, this excitation band is simultaneously the absorption maximum of the respective excitation spectra or an absorption band that reaches at least 50% of the absorption maximum of the excitation spectrum.

[0106] The security feature of the second security document can be a single substance, i.e., a single luminescent substance, or a mixture of different luminescent substances.

[0107] In one embodiment, the individual substances and mixtures of substances used for the safety features are homogeneously mixed powders.

[0108] These powders are preferably present in the substrate of the security document; that is, in the case of paper substrates, they are added to the paper pulp, or in the production of polymer substrates, they are incorporated into the polymer or a polymer layer of the polymer substrate. Alternatively, the security feature mixtures are added to a printing ink or varnish and then applied to the substrate along with it.

[0109] In a further embodiment, the individual components of the material mixtures of the security feature of the first and / or second security document are present separately. This means that a first component of the material mixture, or a first luminescent substance, is present in a first sub-area of ​​the first and / or, if applicable, second security document, e.g., in the paper pulp, and a second component of the material mixture, or a second luminescent substance, is present in a second sub-area of ​​the first and / or, if applicable, second security document, e.g., in a printing layer over the paper pulp. The different sub-areas must overlap spatially, at least partially, in reflected and / or transmitted light, so that both components can be measured simultaneously. Such a security feature with separately introduced luminescent substances exhibits an emission spectrum analogous to that of a homogeneous mixture when the spatially overlapping areas are measured.

[0110] The security feature of the security document system according to the invention can thus be incorporated into the substrate of the first and / or second security document, for example, as a pigment, a flecked fiber, or a doping agent. Furthermore, the security feature can be applied to the first and / or second security document as a printing ink or varnish. The security feature can also be arranged on a carrier material in the form of a security strip, a tether thread, a flecked fiber, a planchette, and / or a patch. A combination of the aforementioned possibilities is also conceivable.

[0111] The invention further extends to a method for identifying (i.e., recognizing the presence or absence of) the security feature of a security document designed as described above. The method for identifying a security document of a security document system according to the invention comprises the following steps: Stimulating the first and, if applicable, second luminescent substance of the security feature of the first and / or second security document; detecting the temporal evolution of the total intensity of emitted radiation from the first and, if applicable, second luminescent substance in at least two spectrally distinct detection channels, wherein at least one detection channel covers at least a sub-range of the primary emission range of the first and second luminescent substance; determining an effective decay time and / or intensity in the at least two detection channels; and identifying a code and / or security document class from the security feature based on the determined one or more decay times and / or intensities and / or intensity ratios and / or decay time ratios of the primary emission range.

[0112] Preferably, the luminescent materials of the first and / or second security document are excited by means of a common excitation pulse.

[0113] In one embodiment of the method according to the invention, the primary emission range of the luminescent substances of the security feature of the first and / or second security document is encompassed by several separate detection channels. Each detection channel can encompass a sub-region of the primary emission range. However, it is also possible that part of the primary emission range and / or further emission ranges lie completely outside all detection channels.

[0114] One embodiment of the method according to the invention can provide that at least two detection channels lie wholly or partially within the primary emission range of the luminescent substances of the first and / or second security document. For example, the primary emission range can be divided, for instance, into two equal halves, each half representing a detection channel. However, the detection channels do not have to lie exactly within the primary emission range, but can also be smaller or larger and thus, for example, extend beyond the primary emission range or be offset relative to it. In particular, more than two detection channels, e.g., three detection channels, can lie within the primary emission range.

[0115] In an advantageous embodiment of the method according to the invention, at least two of the detection channels correspond to the spectral ranges A, B of the security features of the at least first and optionally second security documents of the security document system.

[0116] In an advantageous embodiment of the method according to the invention, the individual detection channels each encompass a wavelength range of less than 400 nm, preferably less than 250 nm, and particularly preferably less than 100 nm. According to one embodiment, all detection channels are essentially the same size, i.e., they differ from one another in size by less than 10%. The term "size" in this context corresponds to the spectral width (in nanometers) of the detection channel measured against half the spectral detection sensitivity. According to a further embodiment, the detection channels have at least partially different sizes (i.e., one or more detection channels differ in their spectral width by more than 10%). For example, one detection channel has a size of 100 nm and another detection channel has a size of 150 nm.According to one embodiment, the individual detection channels are arranged in a continuous sequence.

[0117] For example, a first detection channel measures the wavelength range between 900 nm and 1000 nm, a second detection channel the wavelength range between 1000 nm and 1100 nm, and a third detection channel the wavelength range between 1100 nm and 1200 nm. According to a further embodiment, one or more detection channels are spaced apart from each other, with no other detection channel located at that distance. For example, a first detection channel measures the wavelength range between 900 nm and 1000 nm, a second detection channel the wavelength range between 1000 nm and 1100 nm, and a third detection channel the wavelength range between 1150 nm and 1250 nm.

[0118] In one embodiment of the invention, the effective decay time τ at different wavelengths or wavelength ranges (i.e., in two or more detection channels) can be verified to check the decay time behavior. The overall intensity can be adjusted using at least two data points with a monoexponential fit of the form I(t) = A · e^(-t / τ) (decay quotient). This thus represents an approximation of potentially more complex time profiles. This is a very fast and simple measurement method that can be applied by selecting luminescent substances or luminescent substance properties according to the invention.

[0119] In contrast to prior art combinations of luminescent materials, such as those known from US 9046486 B2, complex detection methods are advantageously unnecessary to achieve increased security. Furthermore, organic dye molecules, in particular, have broader emission spectra and significantly shorter decay times, often in the nanosecond range, compared to the inventive luminescent materials based on inorganic matrix-based phosphors. They also exhibit considerably smaller stochastic shifts. These properties are disadvantageous for readout and decay time verification. The inventive method thus enables relatively simple, fast, and reliable detection of the security feature.

[0120] The invention will be further explained below using the drawings as examples. The drawings show: Fig. 1A Two individual substance emission spectra and their overlap region; Fig. 1B The resulting emission spectrum of the mixture of the individual substances. Fig. 1A as well as its primary emission range PEB; Fig. 2 schematically the temporal evolution of two single-substance emission spectra for the different cases τ 1 >τ 2 , τ 1 =τ 2 or τ 1 <τ 2 ; and Fig. 3 A-D schematically combinations of different luminescent substances based on their respective U 12 and S 12 values.

[0121] The Figur 2 This schematically shows the temporal evolution of two single-substance emission spectra for the different cases τ₁ > τ₂, τ₁ = τ₂, and τ₁ < τ₂. The emitted (individual) intensity of two substances S₁ and S₂ in the primary emission range is plotted against the wavelength. The temporal evolution of the emission bands of the two luminescent substances S₁ and S₂ with their respective decay times τ₁ and τ₂ is illustrated schematically. In one case, the first luminescent substance S₁ has a longer decay time τ₁ (solid line), and the second luminescent substance S₂ has a shorter decay time τ₂ (dashed line). In the second case, both the first and second luminescent substances S₁ and S₂ have a long decay time (τ₁ = τ₂). In a third case, a first luminescent substance S1 has a shorter decay time τ 1 (solid line) and a second luminescent substance S2 has a longer decay time τ 2 (dashed line).

[0122] To verify a security feature using luminescent substances S1 and S2 with individual decay times τ1 and τ2, respectively, different spectral ranges A and B (via corresponding detection channels K_A and K_B) can be evaluated. The same emission spectrum is separated into two different detection channels K_A and K_B for each of the three cases, with the temporal evolution of the spectral intensity being derived from the respective diagrams arranged above and below each other (from top to bottom).

[0123] It is evident that during the observation period the spectral intensity of the emission band with a longer decay time remains unchanged, whereas the spectral intensity of the emission band with a shorter decay time decreases sharply over time.

[0124] In one embodiment, detection channels K_A and K_B jointly cover the primary emission range (indicated in the diagrams by a hatched A region and a bordered B region). Accordingly, detection channels K_A and K_B each contain different proportions of the emission bands of the first and second luminescent substances. In the first case, K_A contains more emission from the slowly decaying luminescent substance S1 and less emission from the rapidly decaying luminescent substance S2. Thus, the total decay time measured in detection channel K_A is relatively long. In contrast, detection channel K_B contains more emission from the rapidly decaying luminescent substance S2 and less emission from the slowly decaying luminescent substance S1. Thus, the total decay time measured in detection channel K_B is relatively short.

[0125] In the second case, both luminescent substances S1 and S2 decay slowly and have the same decay time. Therefore, the same long total decay time is measured in both detection channel K_A and detection channel K_B.

[0126] In the third case, channel K_A contains more emission from the rapidly decaying luminescent substance S1 and fewer emission from the slowly decaying luminescent substance S2. Therefore, the total decay time measured in detection channel K_A is relatively short, and the total decay time measured in detection channel K_B is relatively long.

[0127] In contrast to this simplified scheme, it is also possible to work with more than two spectral ranges (detection channels), for example, three detection channels. Furthermore, these detection channels are not normally sharply separated as shown schematically here, but are shaped by the spectral profile of the detector's sensitivity curve or the filter curve of a filter used in the detector.

[0128] The invention describes a security document system with special security features, consisting of a specific combination of at least two luminescent materials whose emission spectra partially overlap. By selecting suitable materials and material properties according to the invention, a security document system with advantageous properties can be created: Increased number of codings improves counterfeit protection due to more difficult analysis and imitation (exotic spectra, etc.). Detection and separation are possible with a cost-effective, simple sensor with few, e.g., 2, spectral channels. Improved manufacturability is achieved through economies of scale and favorable material properties.

[0129] The properties are still chosen in such a way that verification is possible even at high transport speeds of the banknote.

[0130] In the following examples, the different luminescent substances are qualitatively described as "slow-fading" or "fast-fading." This means that the "fast-fading" substances have a significantly shorter decay time relative to the "slow-fading" substances in the same example. This does not imply a comparison between substances from different examples. Quantitative statements regarding the decay times of the luminescent substances and their mixtures are given by the V and S values ​​in the examples.

[0131] In the following examples, different luminescent substances are combined to form mixtures. A designation such as "50% A, 50% C" means that both luminescent substance A and luminescent substance B were used in such a ratio that their individual intensity each contributes 50% to the total intensity. It does not necessarily mean that the two luminescent substances were used in the mixture in the same mass fraction. An alternative, simple method for producing such mixtures is, for example, to first dilute the individual luminescent substances with a non-luminescent filler so that all (diluted) luminescent substances have the same individual intensity. In this case, the specified percentages then correspond to the respective mass fractions of the (diluted) luminescent substances in the mixtures.

[0132] The Figuren 3A-D show schematic embodiments, namely example 1 ( Fig. 3A ), Example 2 ( Fig. 3B ), Example 3 ( Fig. 3C ) and Example 4 ( Fig. 3D The exemplary embodiments relate to luminescent substances A, B, C and D.

[0133] These are plotted in the diagrams according to their respective U12 and S12 values. The double arrows indicate which of the spectrally complementary luminescent substances are mixed together in the respective embodiment to generate additional codes. However, the double arrows do not necessarily represent the course of the U12 and S12 values ​​of such mixtures, but are purely symbolic. The exact U12 and S12 values ​​of the respective mixtures can be found in the corresponding tables of the embodiments. The plotting of the U12 and S12 values ​​here is for illustrative purposes only, to better visualize the embodiments. In addition to the U12 and S12 values, other values ​​exist, in particular the V12 values, which are used to distinguish the different codes, but are not plotted here. In the context of the embodiments, a code is also referred to as a "code".

[0134] A first embodiment according to the invention relates to a security document system with neodymium-based luminescent materials. The security document system is created using two lutetium-aluminum garnets doped with different amounts of neodymium and one neodymium-doped yttrium oxysulfide. Luminescent substance A: LuAG:Nd, fast decay; Luminescent substance B: LuAG:Nd, slow decay; Luminescent substance C: Y₂O₂S:Nd, fast decay

[0135] When excited at 810 nm, the luminescent substances each exhibit a complex emission spectrum consisting of several bands in the 1030-1130 nm range.

[0136] The emission spectrum is divided into three spectral ranges, corresponding to the sensor's detection channels K1, K2, and K3. The total intensities detected in each spectral range are designated I_1, I_2, and I_3, respectively, and the total decay times are designated τ_1, τ_2, and τ_3. The spectral ranges extend over the following wavelength ranges: K1: 1050 - 1075 nm → I_1, τ_1 K2: 1175 - 1100 nm → I_2, τ_2 K3: 1100 - 1125 nm → I_3, τ_3

[0137] To differentiate the various encodings of the security document system, the intensity ratios U, decay time ratios V, and the decay time sum S between the different detection channels are used. These can be adjusted by combining one of the two luminescent substances A or B with luminescent substance C. Additionally, the pure individual substances can be distinguished from such mixtures.

[0138] For example, U 12 denotes the intensity ratio between K1 and K2: U 12 = I_ 1 / I_ 2

[0139] The same applies: U 23 = I_ 2 / I_ 3 U 13 = I_ 1 / I_ 3 V 12 = τ_ 1 / τ_ 2 V 13 = τ_ 1 / τ_ 3 V 23 = τ_ 2 / τ_ 3 S 12 = τ _ 1 + τ _ 2 S 13 = τ _ 1 + τ _ 3 S 23 = τ _ 2 + τ _ 3

[0140] The decay times specified in this embodiment are effective decay times. To determine them, the luminescent substances or mixtures are excited by an excitation pulse. After a first waiting period, an intensity is measured, after a second waiting period, a further intensity is measured, and the effective decay time is determined from the difference in intensity between the first and second waiting periods. For this purpose, in Example 1, the intensity values ​​I100 after 100 µs and I300 after 300 µs are measured, and the effective decay time τ is determined as follows: τ = − 200 μs / ln I 300 / I 100

[0141] If the intensity values ​​are used as a basis at, for example, two different times, or if a different algorithm is applied to determine the effective decay times, different overall decay times will result. Therefore, to reproduce the measurement data or test criteria for such features of the invention, it is necessary to know the measurement parameters precisely, which significantly increases the protective effect. Code Eingesetzte Lumineszenz-stoffe U 12 U 13 U 23 V 12 V 13 V 23 S 12 [µs] S 13 [µs] S 23 [µs] 1 100% A 4.33 2.89 0.67 1 1 1 178 178 178 2 67% A, 33% C 1.45 2.78 1.92 1 1 1 178 178 178 3 50% A, 50% C 0.95 2.70 2.85 1 1 1 178 178 178 4 33% A, 67% C 0.63 2.59 4.11 1 1 1 178 178 178 5 100% C 0.26 2.21 8.41 1 1 1 178 178 178 6 100% B 4.27 3.07 0.72 1 1 1 562 562 562 7 67% B, 33% C 1.45 2.92 2.02 1.62 1.02 0.62 423 518 416 8 50% B, 50% C 0.95 2.82 2.97 1.84 1.04 0.56 380 483 370 9 33% B, 67% C 0.63 2.68 4.24 1.93 1.06 0.55 337 431 323

[0142] Codes 1 to 9 can be distinguished from each other based on their U, V, and S values, making it possible to establish a value document system with them. Example 1a: Valuables document system with 9 codes

[0143] The individual substances or mixtures of substances used in codes 1 to 9 are each employed to secure a specific type of security document. For example, code 1 is added to the paper pulp of a first currency, code 2 to the paper pulp of a second currency, code 3 to the paper pulp of a third currency, and so on, allowing a total of 9 different currencies to be individually coded. Example 1b: Valuables document system with 2 codings

[0144] The chemical mixture of Code 2 is incorporated into the paper pulp of a first currency. The chemical mixture of Code 3 is incorporated into the paper pulp of a second currency. Both currencies can be distinguished from each other based on their U, V, and S values. Example 1c: Valuables document system with 2 codings

[0145] The chemical mixture of Code 4 is incorporated into the paper pulp of a first currency. The chemical mixture of Code 9 is incorporated into the paper pulp of a second currency. Both currencies can be distinguished from each other based on their U, V, and S values. Example 1d: Valuables document system with 3 codes

[0146] The fabric mixture from Code 7 is mixed into the printing ink of a first currency and printed. The fabric mixture from Code 8 is mixed into the printing ink of a second currency and printed. The fabric mixture from Code 9 is mixed into the printing ink of a third currency and printed. The three currencies can be distinguished from each other based on their U, V, and S values.

[0147] In a further, second embodiment, a security document system using luminescent materials based on ytterbium is described. This system employs two lutetium-aluminum garnets doped with different amounts of ytterbium, a yttrium phosphate doped with ytterbium, and a gadolinium oxysulfide doped with ytterbium. Luminescent substance A: LuAG:Yb / rapidly decaying Luminescent substance B: LuAG:Yb / slowly decaying Luminescent substance C: Gd₂O₂S:Yb / rapidly decaying Luminescent substance D: YPO₄:Yb / slowly decaying

[0148] When excited at 945 nm, the luminescent substances exhibit emission in the range of 950-1100 nm.

[0149] The emission spectrum is divided into two spectral ranges, corresponding to the sensor's detection channels K1 and K2. The total intensities detected in the respective spectral ranges are designated I_1 and I_2, and the total decay times are designated τ_1 and τ_2. The spectral ranges extend over the following wavelength ranges: K1: 950 - 1000 nm → I_1, τ_1 K2: 1000 - 1100 nm → I_2, τ_2

[0150] To differentiate the various encodings of the security document system, the intensity ratio U, decay time ratio V, and decay time sum S of the two detection channels are used. These can be set by combining one of the two luminescent substances A or B with one of the two luminescent substances C or D. Additionally, the pure individual substances can be distinguished from such mixtures.

[0151] For example, U 12 denotes the intensity ratio between K1 and K2: U 12 = I _ 1 / I _ 2

[0152] The same applies: V 12 = τ _ 1 / τ _ 2 S 12 = τ _ 1 + τ _ 2

[0153] The decay times given in the example are effective decay times. To determine them, the luminescent substances or mixtures are excited by an excitation pulse. After a first waiting period, an intensity is measured, and after a second waiting period, the intensity is measured again. The effective decay time is then calculated from the difference in intensity between the first and second waiting periods. In Example 2, the intensity values ​​I100 after 100 µs and I300 after 300 µs are measured, and the effective decay time τ is determined as follows: τ = − 200 μs / ln I 300 / I 100

[0154] If the intensity values ​​are used as a basis at, for example, two different times, or if a different algorithm is applied to determine the effective decay times, different overall decay times will result. Therefore, to reproduce the measurement data or test criteria for such features of the invention, it is necessary to know the measurement parameters precisely, which significantly increases the protective effect. Code Eingesetzte Lumineszenzstoffe U 12 V 12 S 12 [µs] 2-1 100% A 0.38 1 400 2-2 100% B 0.37 1 1820 2-3 100% C 5.55 1 360 2-4 100% D 2.35 1 1440 2-5 25% B, 75% D 1.46 0.92 1535 2-6 50% B, 50% D 0.94 0.90 1614 2-7 75% B, 25% D 0.60 0.92 1696 2-8 25% A, 75% C 2.38 0.95 310 2-9 50% A, 50% C 1.28 0.94 381 2-10 75% A, 25% C 0.72 0.95 388 2-11 25% A, 75% D 1.47 1.50 1035 2-12 50% A, 50% D 0.96 1.69 805 2-13 75% A, 25% D 0.62 1.55 607 2-14 25% B, 75% C 2.36 0.43 710 2-15 50% B, 50% C 1.26 0.40 962 2-16 75% B, 25% C 0.70 0.50 1222

[0155] The codes 2-1 to 2-16 can be distinguished from each other based on their U, V, and S values, making it possible to establish a value document system with them. Example 2a: Valuables document system with 16 codes

[0156] The individual substances or mixtures of substances used in codes 2-1 to 2-16 are each used to secure a specific type of security document. For example, code 2-1 is added to the paper pulp of a first currency, code 2-2 is added to the paper pulp of a second currency, code 2-3 is added to the paper pulp of a third currency, and so on, allowing a total of 16 different currencies to be individually coded. Example 2b: Valuables document system with 2 codings

[0157] The chemical mixture of Code 2-12 is incorporated into the paper pulp of a first currency. The chemical mixture of Code 2-15 is incorporated into the paper pulp of a second currency. Both currencies can be distinguished from each other based on their U, V, and S values.

[0158] A further, third embodiment concerns a security document system with erbium-based luminescent materials. The following three materials are used: an erbium-doped yttrium aluminum garnet, an erbium-doped yttrium vanadate without an additional quencher, and an erbium-doped yttrium vanadate with a small amount of samarium co-doping to reduce the decay time. Luminescent substance A: YAG:Er / slowly decaying Luminescent substance B: YVO 4 :Er / slowly decaying Luminescent substance C: YVO 4 :Er, Sm / rapidly decaying

[0159] When excited at a wavelength of 970 nm, the luminescent substances exhibit emission in the range of 1400-1700 nm.

[0160] The emission spectrum is divided into three spectral ranges, corresponding to the sensor's detection channels K1, K2, and K3. The total intensities detected in each spectral range are designated I_1, I_2, and I_3, respectively, and the total decay times are designated τ_1, τ_2, and τ_3. The spectral ranges extend over the following wavelength ranges: K1: 1400 - 1500 nm → I_1, τ_1 K2: 1500 - 1600 nm → I_2, τ_2 K2: 1600 - 1700 nm → I_3, τ_3

[0161] To differentiate the various encodings of the security document system, the intensity ratio U, decay time ratio V, and decay time sum S of the two detection channels are used. These can be adjusted by combining luminescent substance A with either B or C. Additionally, the pure individual substances can be distinguished from mixtures of these individual substances.

[0162] For example, U 12 denotes the intensity ratio between K1 and K2: U 12 = I _ 1 / I _ 2

[0163] The same applies: U 23 = I _ 2 / I _ 3 U 13 = I_ 1 / I_ 3 V 12 = τ _ 1 / τ _ 2 V 13 = τ _ 1 / τ _ 3 V 23 = τ _ 2 / τ _ 3 S 12 = τ _ 1 + τ _ 2 S 13 = τ _ 1 + τ _ 3 S 23 = τ _ 2 + τ _ 3

[0164] The decay times given in the example are effective decay times. To determine them, the luminescent substances or mixtures are excited by an excitation pulse. After a first waiting period, an intensity is measured, and after a second waiting period, the intensity is measured again. The effective decay time is then calculated from the difference in intensity between the first and second waiting periods. In Example 3, the intensity values ​​I100 after 100 µs and I500 after 500 µs are measured, and the effective decay time τ is determined as follows: τ = − 400 μs / ln I 500 / I 100

[0165] If the intensity values ​​are used as a basis at, for example, two different times, or if a different algorithm is applied to determine the effective decay times, different overall decay times will result. Therefore, to reproduce the measurement data or test criteria for such features of the invention, it is necessary to know the measurement parameters precisely, which significantly increases the protective effect. Code Eingesetzte Lumineszenzstoffe U 12 U 13 U 23 V 12 V 13 V 23 S 12 [µs] S 13 [µs] S 23 [µs] 3-1 100% A 0.40 0.40 0.99 1 1 1 2400 2400 2400 3-2 100% B 0.11 1.26 11.91 1 1 1 2200 2200 2200 3-3 100% C 0.11 1.26 11.91 1 1 1 800 800 800 3-4 25% A, 75% B 0.15 0.69 4.65 1.02 0.98 0.96 2250 2302 2278 3-5 50% A, 50% B 0.20 0.52 2.56 1.03 0.98 0.96 2295 2349 2316 3-6 75% A, 25% B 0.28 0.44 1.56 1.02 0.99 0.97 2342 2378 2352 3-7 25% A, 75% C 0.15 0.69 4.65 1.29 0.74 0.57 1071 1419 1282 3-8 50% A, 50% C 0.20 0.52 2.56 1.41 0.80 0.56 1374 1814 1581 3-9 75% A, 25% C 0.28 0.44 1.56 1.32 0.89 0.67 1759 2127 1882

[0166] The codes 3-1 to 3-9 can be distinguished from each other based on their U, V, and S values, making it possible to establish a value document system with them. Example 3a: Valuables document system with 9 codes

[0167] The individual substances or mixtures of substances used in codes 3-1 to 3-9 are each used to secure a specific type of security document. For example, code 3-1 is added to the paper pulp of a first currency, code 3-2 to the paper pulp of a second currency, code 3-3 to the paper pulp of a third currency, etc., thus allowing a total of nine different currencies to be individually coded. Example 3b: Valuables document system with 2 codings

[0168] The substance mixture of Code 3-7 is incorporated into the paper pulp of a first currency. The substance mixture of Code 3-9 is incorporated into the paper pulp of a second currency. Both currencies can be distinguished from each other based on their U, V, and S values.

[0169] A further, fourth embodiment according to the invention is a security document system with luminescent materials based on thulium and holmium. The following three materials are used: a thulium-doped lutetium aluminum garnet without an additional quencher, a thulium-doped lutetium aluminum garnet with a small amount of praseodymium co-doping to reduce the decay time, and a yttrium oxysulfide doped with neodymium, ytterbium, and holmium. Luminescent substance A: LuAG:Tm / slowly decaying Luminescent substance B: LuAG:Tm, Pr / rapidly decaying Luminescent substance C: Y₂O₂S:Nd, Yb, Ho / slowly decaying

[0170] When excited at 810 nm, the luminescent substances exhibit emission in the range of 1600-2100 nm.

[0171] The emission spectrum is divided into two spectral ranges, corresponding to the sensor's detection channels K1 and K2. The total intensities detected in the respective spectral ranges are designated I_1 and I_2, and the total decay times are designated τ_1 and τ_2. The spectral ranges extend over the following wavelength ranges: K1: 1500 - 2000 nm → I_1, τ_1 K2: 2000 - 2100 nm → I_2, τ_2

[0172] To differentiate the various encodings of the security document system, the intensity ratio U, the decay time ratio V, and the decay time sum S of the two detection channels are used. These can be adjusted by combining one of the two luminescent substances A or B with luminescent substance C. Additionally, the pure individual substances can be distinguished from such mixtures.

[0173] For example, U 12 denotes the intensity ratio between K1 and K2: U 12 = I _ 1 / I _ 2

[0174] The same applies: V 12 = τ _ 1 / τ _ 2 S 12 = τ _ 1 + τ _ 2

[0175] The decay times given in the example are effective decay times. To determine them, the luminescent substances or mixtures are excited by an excitation pulse. After a first waiting period, an intensity is measured, and after a second waiting period, the intensity is measured again. The effective decay time is then calculated from the difference in intensity between the first and second waiting periods. In Example 4, the intensity values ​​I100 after 100 µs and I500 after 500 µs are measured, and the effective decay time τ is determined as follows: τ = − 400 μs / ln I 500 / I 100

[0176] If the intensity values ​​are used as a basis at, for example, two different times, or if a different algorithm is applied to determine the effective decay times, different overall decay times will result. Therefore, to reproduce the measurement data or test criteria for such features of the invention, it is necessary to know the measurement parameters precisely, which significantly increases the protective effect. Code Eingesetzte Lumineszenzstoffe U 12 V 12 S 12 [µs] 4-1 100% A 9.34 1 2400 4-2 100% B 9.09 1 1200 4-3 100% C 0.80 1 1800 4-4 25% A, 75% C 1.27 1.10 1920 4-5 50% A, 50% C 2.07 1.16 2024 4-6 75% A, 25% C 3.73 1.16 2139 4-7 25% B, 75% C 1.27 0.87 1640 4-8 50% B, 50% C 2.06 0.81 1529 4-9 75% B, 25% C 3.69 0.81 1413

[0177] The codes 4-1 to 4-9 can be distinguished from each other based on their U, V, and S values, making it possible to establish a value document system with them. Example 4a: Valuables document system with 9 codes

[0178] The individual substances or mixtures of substances used in codes 4-1 to 4-9 are each employed to secure a specific type of security document. For example, code 4-1 is added to the paper pulp of a first currency, code 4-2 to the paper pulp of a second currency, code 4-3 to the paper pulp of a third currency, and so on, allowing a total of nine different currencies to be individually coded. Example 4b: Valuables document system with 2 codings

[0179] The chemical mixture of Code 4-5 is incorporated into the paper pulp of a first currency. The chemical mixture of Code 4-8 is incorporated into the paper pulp of a second currency. Both currencies can be distinguished from each other based on their U, V, and S values.

Claims

1. Value document system, comprising at least a first value document and a second value document, wherein the first value document has a security feature from a combination of at least a first and a second luminescent substance, wherein i. the first luminescent substance of the security feature of the first value document is a luminescent substance of a first substance class, namely doped garnet structures, and is selected from doped yttrium aluminum garnets (YAG), lutetium aluminum garnets (LuAG), gadolinium gallium garnets (GGG), gadolinium scandium gallium garnets (GSGG), yttrium scandium gallium garnets (YSGG), calcium niobium gallium garnets (CNGG), gadolinium scandium aluminum garnets (GSAG), calcium lithium niobium gallium garnets (CLNGG), transition metal-containing garnet structures, in particular yttrium iron garnets (YIG), or mixed variants of these garnet structures; ii. the second luminescent substance of the security feature of the first value document is a luminescent substance of a second substance class, namely chosen from doped rare earth oxysulfides, doped rare earth phosphates and doped rare earth vanadates; iii. the first and the second luminescent substance of the security feature of the first value document have partially overlapping emission spectra; iv. the first and the second luminescent substance of the security feature of the first value document are excitable together at one wavelength; v. the first and the second luminescent substance of the security feature of the first value document have a decay time of less than 5 ms; and vi. the first and second luminescent substance of the security feature of the first value document are formed such that their primary emission region of the partially overlapping emission spectra can be divided into two different, directly adjacent spectral ranges, namely a first and a second spectral range (A, B), which have a width of at least 50 nm and at most 500 nm, the primary emission region lying in the IR range, i.e., between 700 nm and 2000 nm; vii. both the first luminescent substance of the security feature of the first value document and the second luminescent substance of the security feature of the first value document require at least one dopant from the group Nd, Yb, Er, Tm, Ho; the second value document has a security feature with at least a first luminescent substance from the first substance class or from the second substance class with a decay time of less than 5 ms, whose emission lies at least partially in at least one of the adjacent spectral ranges A, B; the security feature of the first value document as compared to the security feature of the second value document has at least a different intensity ratio of the emission, a different decay time ratio and / or a different decay time sum in the two adjacent spectral ranges A, B.

2. Value document system according to claim 1, wherein the intensity ratio of the emission is the quotient of the overall intensity in the first spectral range and the overall intensity in the second spectral range; the decay time ratio is the quotient of the overall decay time in the first spectral range and the overall decay time in the second spectral range; and the decay time sum is the sum of the overall decay time in the first spectral range and the overall decay time in the second spectral range.

3. Value document system according to claim 1 or 2, wherein the different intensity ratios of the emission, the different decay time ratios and / or the different decay time sums in the spectral ranges A, B of the respective first and second value documents are assigned to a coding of the security feature and / or a value document identifier of the first and / or second value document.

4. Value document system according to one of the preceding claims, wherein the first and second luminescent substances of the security feature of the first value document and the first luminescent substance of the security feature of the second value document have as emission centers the rare earths Nd, Yb or Er as dopant.

5. Value document system according to one of the preceding claims, characterized in that the luminescent substances of the second substance class are selected from doped lanthanum oxysulfides, yttrium oxysulfides, gadolinium oxysulfides, lutetium oxysulfides, mixed oxysulfides based thereon; and / or doped lanthanum phosphates, yttrium phosphates, gadolinium phosphates, lutetium phosphates, mixed phosphates based thereon; and / or lanthanum vanadates, yttrium vanadates, gadolinium vanadates, lutetium vanadates, and / or mixed vanadates based thereon.

6. Value document system according to one of the preceding claims, wherein the degree of overlap of the partially overlapping emission spectra is greater than 5% and smaller than 80%.

7. Value document system according to one of the preceding claims, wherein the security feature of the second value document has a combination of the first luminescent substance from the first substance class with a second luminescent substance from the second substance class, or has a combination of the first luminescent substance from the second substance class with a second luminescent substance from the first substance class, wherein the first and second luminescent substances of the second value document i. have partially overlapping emission spectra; ii. are excitable together at one wavelength; iii. each have a decay time of less than 5 ms.

8. Value document system according to one of the preceding claims, wherein the first and second luminescent substances of the security feature of the first value document, as well as the first and, if present, second luminescent substance of the second value document, are excitable together at one wavelength.

9. Value document system according to one of the preceding claims, wherein the first and / or second luminescent substance of the security feature of the first value document use the same matrices as the first luminescent substance and / or second luminescent substance of the security feature of the second value document.

10. Value document system according to one of the preceding claims, wherein the first and second luminescent substance of the security feature of the first value document and the first luminescent substance of the second value document use the same rare earth as emission center.

11. Value document system according to one of the preceding claims, characterized in that the respective decay time of the first and second luminescent substance of the security feature of the first value document and of the first and, if appropriate, second luminescent substance of the security feature of the second value document is at least 0.05 ms.

12. Value document system according to one of the preceding claims, characterized in that the first and second luminescent substance of the security feature of the first value document differ in their decay time by less than 10%.

13. Value document system according to one of claims 1 to 11, characterized in that the first and second luminescent substance of the security feature of the first value document differ in the decay time by 10% to 50% or by at least 50%, preferably by more than 75%, particularly preferably by more than 100%, based on the shortest individual decay time of the luminescent substances.

14. Method for identifying a value document of a value document system according to one of claims 1 to 13, comprising the steps: b) exciting the first and, if present, second luminescent substance of the security feature; c) detecting the temporal course of an overall intensity of the emitted radiations of the first and, if present, second luminescent substance in at least two spectrally different detection channels, the detection channels each comprising at least a subregion of the primary emission region of the first and, if present, second luminescent substance; determining a decay time and / or intensity in the at least two detection channels; and d) identifying a value document class from the security feature on the basis of the determined one or more decay times and / or intensities and / or intensity ratios and / or decay time ratios of the primary emission region.

15. Luminescent substance set for producing a value document system according to one of claims 1 to 13, comprising the first luminescent substance of the first value document, the second luminescent substance of the first value document and the first luminescent substance of the second value document and, where appropriate, the second luminescent substance of the second value document.