Security feature, valuable document and printing color

Abstract

Security feature for securing a valuable document, wherein the security feature is based on a luminescent substance which in pure form exhibits a different excitation behavior than when applied in dilute form in the valuable document, wherein the luminescent substance is based on an inorganic host lattice doped with Mn(V) as a luminophore, the mole fraction of Mn(V) in the luminescent substance is less than 2%, and the host lattice of the luminescent substance is selected from apatites of type A5(PO4)3Z, spodiosites of type A2PO4Z, and phosphates of type A3(PO4)2, where A = Ca, Sr, Ba and their mixtures and Z = F, Cl, OH and their mixtures.

Description

[0001] The invention relates to a security feature for securing a valuable document. The invention further relates to a valuable document, in particular a banknote, provided with the security feature. The invention further relates to a printing ink incorporating the security feature for printing on a valuable document.

[0002] To secure and authenticate valuable documents, such as banknotes, bank cards, identity cards, passports, or other products requiring protection, like pharmaceuticals, these are coated with luminescent substances that are either printed onto the document or embedded in the substrate. Normally, the emission and / or excitation spectrum and / or other parameters of the luminescence, such as a decay time (the time-dependent change of a measured quantity), are used to authenticate the valuable document. The invention therefore aims to provide luminescent substances with advantageous properties that ensure a high level of counterfeit protection and are themselves difficult to imitate.In particular, this is achieved by specially selected luminescent substances according to the invention, which, in contrast to the luminescent substances of the prior art, exhibit significantly different spectral ratios both as a pure substance and when applied to the security document. Such substances thus make the analysis and imitation of security features of a security document exceptionally difficult.

[0003] This problem is solved by the combinations of features defined in the independent claims. Further developments of the invention are the subject of the dependent claims. Summary of the invention

[0004] 1. (First aspect of the invention) Security feature for securing a value document, wherein the security feature is formed on the basis of a luminescent substance which in pure form has a different excitation behavior than when applied in the value document in diluted form, characterized in that - the luminescent substance is based on an inorganic host lattice doped with Mn(V) as a luminophore - the mole fraction of Mn(V) in the luminescent substance is less than 2% - the host lattice of the luminescent substance is chosen from: - Apatites of type A5(PO4)3Z, - Spodiosites of type A2PO4Z, - Phosphates of type A3(PO4)2, where A = Ca, Sr, Ba and their mixtures; Z = F, Cl, OH and their mixtures are. 2. (Preferred embodiment) Safety feature according to paragraph 1, wherein the luminescent substance can be excited to luminescence at at least one first wavelength in a first spectral range from 580 nm to 620 nm and at least one second wavelength in a second spectral range from 1000 nm to 1250 nm, and thereby the excitation spectrum is obtainable at the at least two wavelengths, wherein a so-called excitation ratio is obtainable from the ratio of the values ​​of the excitation spectrum at the at least two wavelengths; characterized in that at least one first wavelength in the first spectral range and at least one second wavelength in the second spectral range exist for excitation, in which the excitation ratio of the luminescent substance in pure form and the excitation ratio of the luminescent substance present in dilute form in the security document differ from each other by more than a factor of 5. 3. (Preferred embodiment) Safety feature according to paragraph 2, wherein the luminescent substance present as a pure substance emits luminescence in the first spectral range when excited at the first wavelength, which yields a first value of the excitation spectrum x L It generates and, upon excitation at the second wavelength in the second spectral range, emits luminescence which yields a second value of the excitation spectrum y. L generated, whereby the first excitation ratio V is derived from the values ​​according to the following formula (1-1). L is available: VL=xLyL wherein the luminescent substance present in dilute form in the security document emits luminescence when excited with the first wavelength in the first spectral range, which yields a first value of the excitation spectrum x S generated and, upon excitation with the second wavelength in the second spectral range, emits luminescence which yields a second value of the excitation spectrum y Sgenerated, whereby the first excitation ratio V is derived from the values ​​according to the following formula (1-2). L deviating second excitation ratio V S is available: VS=xSyS where the first excitation ratio V L and the second excitation ratio V S The formed ratio V satisfies the following relationship (1-3): V=xLyL / xSyS≤0.2 where preferably V ≤ 0.15 and particularly preferably V ≤ 0.1 is satisfied. 4. (Preferred embodiment) Security feature according to one of paragraphs 1 to 3, wherein the luminescent substance present in diluted form in the security document is incorporated in a proportion of < 2 wt.%, preferably < 1 wt.% and particularly preferably < 0.5 wt.%, in a security document substrate. 5. (Preferred embodiment) Security feature according to one of paragraphs 1 to 3, wherein the luminescent substance present in diluted form in the security document is applied to a security document substrate in the form of a printing ink, wherein the proportion of the luminescent substance in the printing ink is < 30 wt.%, preferably < 20 wt.% and particularly preferably < 10 wt.%. 6. (Preferred configuration) Security feature according to paragraph 4 or 5, wherein the document substrate is selected from the group consisting of a paper substrate, a polymer substrate, a paper / polymer / paper composite substrate and a polymer / paper / polymer composite substrate. 7. (Preferred embodiment) Security feature according to one of paragraphs 1 to 6, wherein the respective Mn(V)-doped inorganic host lattices have the following manganese concentrations: - A5(PO4)3Z:Mn y , with y = 0.005 to 0.3, preferably y = 0.03 to 0.075; - A2PO4Z:Mny , with y = 0.001 to 0.025, preferably y = 0.01 to 0.025; - A3(PO4)2:Mn y , with y = 0.01 to 0.26, preferably y = 0.01 to 0.1; 8. (Second aspect of the invention) Security document comprising the security feature according to any one of paragraphs 1 to 7. 9. (Preferred form) Security document as defined in paragraph 8, wherein the security document is a banknote. 10. (Third aspect of the invention) Printing ink for printing a security document, wherein the printing ink includes the security feature according to paragraph 5. Detailed description of the preferred embodiments

[0005] The present invention relates to a luminescent substance and a security feature comprising the luminescent substance for securing valuable documents, wherein the excitation behavior of the pure, undiluted luminescent substance (i.e., the proportion of the luminescent substance is, in particular, 100%) differs from the excitation behavior of the diluted luminescent substance (i.e., the proportion of the luminescent substance when applied to the valuable document is, in particular, < 2%). The term "security feature" refers in particular to the typically powdered mixture containing the luminescent substance in a suitable grain size and optionally other components, whereby the security feature may also consist of the luminescent substance as the sole component.This invention does not aim at different excitation behavior based on known concentration effects or absorption by additional substances present in the security feature or value document, but rather provides luminescent substances whose excitation behavior differs as a pure substance and when applied in the value document, i.e., the substances themselves exhibit a very different excitation spectrum in pure form and when diluted in the value document. Suitable substances can be described using the following criterion. For this purpose, two wavelength ranges are selected in which the change in excitation behavior becomes clear, based on the excitation spectrum of the pure luminescent substance on the one hand and the excitation spectrum of the diluted luminescent substance present in the value document on the other.A ratio of the excitation spectra values ​​at one wavelength from each of the two wavelength ranges is calculated for the pure luminescent substance on the one hand and the diluted luminescent substance present in the security document on the other. The same excitation wavelengths are selected for the pure luminescent substance and the diluted luminescent substance present in the security document. The intensities of the luminescence emissions are measured with suitable detectors and normalized to the excitation intensities and detection sensitivities or electronic amplification factors (luminescence excitation spectrum or excitation spectrum).

[0006] In a further step, a third ratio is formed from the two ratios of the pure luminescent substance on the one hand and the diluted luminescent substance present in the security document on the other.

[0007] If the same measurement setup is used to measure the excitation spectra of the pure substance and the diluted luminescent substance present in the security document, the above-mentioned normalization and, if applicable, electronic amplification factors cancel each other out in the third ratio, which greatly simplifies the testing of the subject matter according to the invention.

[0008] All three ratios can be used for quality control by comparing them with ratios stored in a database, without having to measure the entire excitation spectra. According to the invention, the specific excitation spectrum, which varies greatly depending on the type of application, and thus the ratios of the signal intensities of the respective excitation wavelengths, can be achieved through the targeted selection of particularly suitable luminescent substances based on Mn(V)-doped inorganic host lattices. In particular, the present invention has the technical advantage of making the imitation of security features, e.g., banknotes, more difficult because the excitation spectrum of the diluted luminescent substance in the security document and the excitation spectrum of the pure luminescent substance in powder form differ exceptionally strongly from one another.

[0009] The advantageous luminescent substance is an inorganic host lattice doped with Mn(V) as a luminophore, wherein the host lattice is selected from apatites, phosphates and spodiosites, and the Mn(V) is used with a low molar fraction of less than 2%, whereby the luminescent substance has a weak blue body colour.

[0010] The excitation behavior of the luminescent substance depends on its form. In the first case, the luminescent substance is in pure form, meaning the sample consists of 100% of the luminescent substance in the form of, for example, powder or pressed into a tablet, with a layer thickness particularly greater than 0.5 mm. "100%" specifically means that the substance has not been intentionally diluted with other components and does not exclude the presence of small amounts of secondary phases or reactant residues totaling less than 5% by weight, which can typically occur in solid-state syntheses. In a second case, the luminescent substance is diluted when applied to the security document; for example, the luminescent substance is incorporated into the document substrate. This might involve, for instance, incorporating the luminescent substance into a thin layer of paper or polymer, particularly thinner than 0.2 mm. The proportion of the luminescent material in the security document is less than 2% by weight, preferably less than 1% by weight, and particularly preferably less than 0.5% by weight. The luminescent material is particularly preferably present in the security document substrate, preferably uniformly distributed in the substrate, with a proportion of less than 0.5% by weight in the security document substrate. Alternatively, the luminescent material is present in a printing ink applied to a security document substrate, wherein the proportion of the luminescent material in the printing ink is less than 30% by weight, preferably less than 20% by weight, and particularly preferably less than 10% by weight. Alternatively, the luminescent material is present in a security element applied to a security document, for example, a patch or a foil element, wherein the proportion of the luminescent material in the security element is less than 5% by weight, preferably less than 1% by weight.

[0011] The luminescent substance is preferably combined with other powdered additives, such as camouflage agents and dosing aids, and optionally with further luminescent substances, to form a powdered security feature. This makes it possible to create a wide variety of easily applicable, complex, and highly secure codes, which are particularly well-suited for securing valuable documents. Such a security feature can then be used, for example, by dosing it into the paper pulp during papermaking to incorporate the luminescent substance into the substrate of a valuable document. Alternatively, the security feature can be added to a printing ink and printed onto the valuable document, or, during the production of a security element, it can be incorporated into or printed onto the polymer substrate of the security element, and the security element can then be applied to the banknote.

[0012] The particle size of the luminescent material is preferably D99 < 20 µm. This allows for advantageous incorporation into paper substrates. For special application methods, such as in printing inks, smaller particle sizes are necessary, and the particle size of the luminescent material is preferably D99 < 5 µm.

[0013] The luminescent material is advantageously excitable in a wavelength range of 450 nm to 1250 nm and exhibits one or more excitation bands belonging to the same emission within this range. The luminescent material must be excitable in at least two sub-ranges that are at least 100 nm apart; that is, the excitation spectrum is considered independently of the shape of the spectrum (such as excitation maxima, plateaus, etc.). Preferably, the two different wavelength ranges are a first range x from 500 nm to 700 nm and a second range y from 850 nm to 1250 nm, particularly preferably a first range x from 580 nm to 620 nm and a second range y from 1000 nm to 1250 nm.The excitation spectra of the pure luminescent substance and the diluted luminescent substance present in the security document are compared at at least one identical wavelength of the first region and at at least one identical wavelength of the second region. The corresponding excitation spectrum values ​​(signal intensities) x are recorded for both wavelengths. L or x S for the first area and y L or y S for the second area and put into relation. Depending on the selected form of the luminescent substance, different ratios result according to the following formula (1-1) for the pure luminescent substance (namely the ratio V L ) and according to the following formula (1-2) for the luminescent substance in the security feature (namely the ratio V S ): VL=xLyL VS=xSyS

[0014] These relationships can be used to determine the quality of the pure luminescent substance by comparing it to a reference value V. L,Ref to verify, as well as the value document against a reference value V S,Ref to validate without requiring a measurement of the entire excitation spectrum. In particular, the luminescent substances according to the invention preferably fulfill the criterion according to the following formula (1-3) in the characterizing preferred first and second wavelength ranges, preferably at least at one wavelength each, which results from the different excitation spectra of the pure substance and the safety feature: V=xLyL / xLys≤0.2

[0015] This means that at least one excitation wavelength exists in the first wavelength range and at least one excitation wavelength exists in the second wavelength range, such that the ratio of the excitation spectrum values ​​at these two excitation wavelengths differs by a factor of 5 or more between the pure luminescent substance on the one hand and the diluted luminescent substance present in the security document on the other. As will be shown later, this additional authentication parameter can significantly increase the security of the security feature. To achieve these special spectral properties, specially selected luminescent substances are necessary, which are described below.

[0016] The security feature according to the invention expediently contains a luminescent substance based on a host lattice doped with Mn(V) as a luminophore, wherein the concentration of the Mn doping is selected to be so low (molar fraction of manganese <2%) that the luminescent substance has a weak blue body color, which distinguishes it from substances with an excessively high manganese content and the resulting dark blue, green, brown or black color. The weak blue body color is advantageous because at a low concentration of the luminescent substance, e.g. when incorporated into a value document substrate, the luminescent substance in the value document is not visually perceptible (i.e. with the naked eye). The use of the luminophore in small quantities in the luminescent substance is further advantageous because it makes it more difficult to determine the correct composition using conventional chemical analysis (such as elemental analysis, ICP, etc.).Both beneficial properties increase protection against imitations.

[0017] The luminescent substance is surprisingly characterized by the fact that the excitation spectrum of the pure luminescent substance differs significantly from the excitation spectrum of the diluted luminescent substance in the security document. This is not a simple concentration-dependent behavior, but, as shown in the Fig. 1 using an example according to the invention, the excitation spectrum changes so significantly that a valuable document containing the luminescent substance is difficult for counterfeiters to imitate because a counterfeiter will not measure the same excitation spectrum in a laboratory measurement on a candidate substance (in pure form) as on the valuable document. At the same time, precise spectral analysis on the valuable document is massively hampered by the low signals resulting from the low concentration of the luminescent substance, and the obtained excitation spectrum differs greatly from the spectra of the pure luminescent substances, so that, for example, spectral databases cannot be used here. Thus, the security of the valuable documents is increased. This surprising advantage is achieved by the specific combination of inorganic host lattices with the selected luminophore. Apatite, phosphate, and spodiosite are particularly preferred as host lattices.Manganese as Mn(V) in low concentrations with mole fractions < 2% is particularly preferred as a luminophore, thereby ensuring the advantages of the luminescent substance according to the invention.

[0018] The luminescent substance is advantageously excitable in the range of 450 nm to 1250 nm and exhibits one or more excitation bands belonging to the same emission in this range. In the wavelength range of 1100 nm to 1250 nm, the luminescent substance exhibits quasi-resonance, i.e., it shows both excitability and emission in this wavelength range. The advantageous difference in excitation behavior between the pure luminescent substance and the dilute luminescent substance present in the document is clearly evident from the excitation spectrum. For example, the excitation spectrum of the pure luminescent substance has a first value x at a first wavelength in the range of 580 nm to 620 nm. Lon and at a second wavelength in the range of 1000 nm to 1250 nm a second value y L Similarly, the excitation spectrum of the luminescent substance in the security document shows a third value x at the first wavelength. S and a fourth value y at the second wavelength S The conditions V L (see formula (1-1) above) and V S (see formula (1-2) above) are a measure of the excitation spectrum shape of the pure luminescent substance or the luminescent substance in the value document and are independent of the absolute luminescence intensity and excitation efficiency. The luminescent substances according to the invention exhibit a characteristic difference between the value V L for the excitation spectrum of the pure luminescent substance and the value V S for the excitation spectrum of the diluted luminescent substance present in the security document. In particular, the ratio of V yields L to V Swhere, according to the formula (1-3) above, a value V ≤ 0.2. Unless otherwise stated, specific absolute values ​​for V refer to the comparison of the pure luminescent substance with a sheet of paper produced in a sheet former and containing 0.5% by weight of the luminescent substance. Due to the specific selection of the host grating and stoichiometry, luminescent substances according to the invention always exhibit at least one wavelength in the first wavelength range x and at least one wavelength in the second wavelength range y for which the criterion V ≤ 0.2 is met or not met. They are therefore particularly well suited for creating security features according to the invention. Preferably, V ≤ 0.15, more preferably V ≤ 0.1. This results in an even greater difference between the excitation spectra of the pure luminescent substance and that applied in the security document, thus achieving an even higher level of security.

[0019] The selection of suitable wavelength ranges for measuring the excitation spectrum is not technically limited, as excitation in the wavelength range from 450 nm to 1250 nm can be easily achieved using suitable LEDs, and the spectral width of the LEDs and detectors is narrow enough to cover these ranges. The excitation spectrum is measured at a central wavelength with a certain degree of uncertainty (e.g., ± 5 nm) in order to capture the selected wavelengths. The signal intensity of the excitation spectrum results from the integral of the broadband detected emission. For example, excitation is performed with a laser, particularly a pulsed one, and numerically integrated, or excitation is performed with an LED of suitable bandwidth or suitable filtering—for example, with an emission spectrum in the range from 580 nm to 620 nm—which corresponds to optical integration and simplifies signal analysis.Furthermore, when measuring to determine the two ratios, it is necessary to use the same excitation intensity (power / area) and the same detector setup.

[0020] When the luminescent substance according to the invention is used to secure valuable documents, counterfeit protection can be increased and secure production can be ensured. The luminescent substance is produced using known high-temperature processes for the production of inorganic host lattices. The purity and quality of the pure luminescent substance are controlled based on the ratio V L to a reference value V stored in a database L,RThis eliminates the need for complex analytical methods to determine the chemical composition, as the required ratio is only met if the synthesis is successful. The luminescent substance can then be incorporated into a document substrate as a security feature or applied as a printing ink. Verification of the successful incorporation of the security feature is based on criterion V. S, where the ratio of the two criteria is advantageously V ≤ 0.2. The different excitation behavior (mathematically expressed by criterion V) increases counterfeit protection because, in order to reproduce the luminescent substance according to the invention, it is necessary to know how the excitation behavior of the pure luminescent substance differs from that of the luminescent substance in the security document. This applies analogously to the further processing of the security feature during the production of a security document, e.g., a banknote. After production of the security document, verification can again be carried out using the defined ratio V. S This can be done without requiring knowledge of the substances used and their excitation spectra for quality control purposes.

[0021] Further embodiments and advantages of the invention are explained below with reference to the figure.

[0022] It shows: Fig.1 a sketch to illustrate luminescent substances according to the invention (left) and not according to the invention (right);

[0023] Depending on the selected host lattice, the luminescent substances according to the invention surprisingly only fulfill the aforementioned criterion in certain concentration ranges. This means that a different ratio V is obtained depending on the manganese doping used. If, however, other concentration ranges and host lattices are used, this behavior does not occur or is less pronounced, and the criterion is not fulfilled. In addition, the manganese doping must be less than 2% molar fraction to produce an advantageously low body color. Through the targeted selection of particularly suitable host lattices with a suitable dopant from the multitude of known host lattices, dopants, and their concentrations, substances according to the invention surprisingly always fulfill the criterion V ≤ 0.2 with a molar fraction of manganese < 2%. In addition, certain stoichiometry ranges could be identified as particularly advantageous according to the invention.This results in the following preferred specific selections for host lattice and manganese doping in order to obtain particularly suitable values ​​of V, i.e. a particularly low value of V:. (I) Apatites of type A5(PO4)3Z:Mn y , with y = 0.005 to 0.3 and particularly preferably y = 0.03 to 0.075; (II) Spodiosite of type A2PO4Z:Mn y , with y = 0.001 to 0.025 and particularly preferably y = 0.01 to 0.025; (III) Phosphates of type A3(PO4)2:Mn y , with y = 0.01 to 0.26 and particularly preferably y = 0.01 to 0.1; where A = Ca, Sr, Ba and their mixtures; Z = F, Cl, OH and their mixtures; and Mn is in the oxidation state Mn(V);

[0024] The following are a series of exemplary embodiments of substances according to the invention with different host lattices. In each case, the pure powder is compared with a sheet sample containing 0.5% by weight of the luminescent substance dispersed in the paper substrate. Example 1 - Apatite

[0025] To produce the luminescent material, 5.02 g BaCO3, 8.90 g BaHPO4, 6.00 g NaCl, and 73.4 mg MnCO3 are thoroughly mixed in an agate mortar. The mixture is transferred to a corundum crucible and annealed at 830 °C for 10 h. The sintered cone is suspended in water (2 liters, 40 °C) to dissolve the sodium chloride, filtered, washed with water, and dried at 80 °C. Dry milling in a planetary mill produces a particle size D99 in the range of 15 µm to 18 µm. A light blue powder is obtained. The obtained luminescent substance Ba5(PO4)3Cl:Mn 0,05It can be used to secure valuable documents. For example, it can be incorporated into the paper substrate of a valuable document, either alone or together with other components, as a security feature. Alternatively, the luminescent substance can be milled, for example, using an air jet mill to a particle size D99 in the range of 4 µm to 5 µm, added to a printing ink, and printed onto the valuable document, or added to a security element, which is then affixed to the valuable document. In this applied form on the valuable document, the luminescent substance is highly diluted and visually imperceptible. When measured with a spectrometer, the powder form of the pure luminescent substance and the diluted form present in the valuable document show significantly different excitation spectra. In the exemplary embodiment, the luminescent substance is incorporated into the paper substrate of a sheet at a concentration of 0.5% by weight on a sheet former.Both the pure powder and the sheet are excited at 600 nm and 1172 nm, and the respective ratios of the luminescence emission of Mn(V) are compared. A value V of 0.09 is obtained.

[0026] Ba5(PO4)3Cl:Mn 0,05 therefore has a particularly low value V and is therefore particularly suitable for security features according to the invention. Example 2 - Spodiosite

[0027] To produce the luminescent material, 7.36 g CaCl₂, 3.32 g CaCO₃, 9.03 g CaHPO₄, 200 mg Na₂O₂, and 76.2 mg MnCO₃ are thoroughly mixed in an agate mortar. The mixture is transferred to a corundum crucible and annealed at 900 °C for 6 hours. The sintered cone is crushed, suspended in water (2 liters, 40 °C), filtered, washed with water, and dried at 80 °C. Dry milling in a planetary mill produces a particle size D99 in the range of 8 µm to 12 µm. A light violet powder is obtained. The luminescent substance Ca2PO4Cl:Mn 0,02 It is incorporated into the paper substrate of a sheet at a concentration of 0.5% by weight. Both the pure powder and the sheet are excited at 600 nm and 1184 nm, and the respective ratios of the luminescence emission of Mn(V) are compared. A value V of 0.15 is obtained. Example 3 - Phosphates

[0028] To produce the luminescent material, 5.80 g BaCO3, 13.72 g BaHPO4, 40.0 mg Na2CO3, and 67.3 mg MnCO3 are thoroughly mixed in an agate mortar. The mixture is transferred to a corundum crucible and annealed at 1150 °C for 10 h. The sintered cone is pre-crushed, and then a particle size of D99 in the range of 4 µm to 5 µm is produced by dry milling in an air jet mill. A blue-colored powder is obtained. The luminescent substance Ba3(PO4)2:Mn 0,02It is incorporated into the paper substrate of a sheet at a concentration of 0.5% by weight. Both the pure powder and the sheet are excited at 600 nm and 1190 nm, and the respective ratios of the luminescence emission of Mn(V) are compared. A value V of 0.06 is obtained. Ba3(PO4)2:Mn has particularly low V values ​​and is therefore particularly suitable for security features according to the invention.

Claims

[1] Security feature for securing a value document, wherein the security feature is formed on the basis of a luminescent substance which in pure form has a different excitation behaviour than when applied in the value document in diluted form, characterized by , that - the luminescent substance is based on an inorganic host lattice doped with Mn(V) as a luminophore - the molar fraction of Mn(V) in the luminescent substance is less than 2% - the host lattice of the luminescent substance is selected from: - Apatites of the type As(PO4)3Z, - Spodiosites of type A2PO4Z, - Phosphates of type A3(PO4)2, where A = Ca, Sr, Ba and their mixtures; Z = F, Cl, OH and their mixtures are. [2] Security feature according to claim 1, wherein the luminescent substance can be excited to luminescence at at least one first wavelength in a first spectral range from 580 nm to 620 nm and at least one second wavelength in a second spectral range from 1000 nm to 1250 nm, and thereby the excitation spectrum is obtainable at the at least two wavelengths, wherein a so-called excitation ratio is obtainable from the ratio of the values of the excitation spectrum at the at least two wavelengths; characterized by that at least one first wavelength in the first spectral range and at least one second wavelength in the second spectral range exist for excitation, in which the excitation ratio of the luminescent substance in pure form and the excitation ratio of the luminescent substance present in diluted form in the value document differ from one another by more than a factor of 5. [3] Security feature according to claim 2, wherein the luminescent substance present as a pure substance emits luminescence when excited at a first wavelength in the first spectral range, which luminescence has a first value of the excitation spectrum x L and upon excitation in the second spectral range emits luminescence which has a second value of the excitation spectrum y L generated, whereby the first excitation ratio V L is available: vL=xLyL wherein the luminescent substance present in diluted form in the value document emits luminescence when excited with the first wavelength in the first spectral range, which luminescence has a first value x S generated and upon excitation with the second wavelength in the second spectral range emits luminescence which has a second value y S generated, whereby from the values according to the following formula (1-2) the first excitation ratio VL deviating second excitation ratio V S is available: VS=xSyS where the excitation ratio V L and the second excitation ratio V S The ratio V formed satisfies the following relationship (1-3): V=xLyL / xSyS≤0.2 wherein preferably V ≤ 0.15 and particularly preferably V ≤ 0.1 is satisfied. [4] Security feature according to one of claims 1 to 3, wherein the security feature formed on the basis of the luminescent substance present in diluted form in the value document is formed such that the luminescent substance is incorporated in a value document substrate in a proportion of < 2 wt.%, preferably < 1 wt.% and particularly preferably < 0.5 wt.%. [5] Security feature according to one of claims 1 to 3, wherein the luminescent substance present in diluted form in the value document is applied to a value document substrate in the form of a printing ink, wherein the proportion of the luminescent substance in the printing ink is < 30 wt.%, preferably < 20 wt.% and particularly preferably < 10 wt.%. [6] Security feature according to claim 4 or 5, wherein the value document substrate is selected from the group consisting of a paper substrate, a polymer substrate, a paper / polymer / paper composite substrate and a polymer / paper / polymer composite substrate. [7] Security feature according to one of claims 1 to 6, wherein the inorganic host lattices doped with Mn(V) have the following manganese concentrations: - A5(PO4)3Z:Mn y , with y = 0.005 to 0.3, preferably y = 0.03 to 0.075; - A2PO4Z:Mn y , with y = 0.001 to 0.025, preferably y = 0.01 to 0.025; - A3(PO4)2:Mn y , with y = 0.01 to 0.26, preferably y = 0.01 to 0.1; [8] A value document comprising the security feature according to any one of claims 1 to 7. [9] A value document according to claim 8, wherein the value document is a banknote. [10] Printing ink for printing a value document, wherein the printing ink comprises the security feature according to claim 5.

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