Security feature, value document, and printing ink

Abstract

The invention relates to a security feature for safeguarding a value document. The security feature is formed on the basis of a luminescent substance which, in its pure form, has a different excitation behavior than in a diluted form when used in the value document, and the luminescent substance is based on an inorganic host lattice, which is doped with Mn(V) as a luminophore. The proportion of the Mn(V) substance in the luminescent substance is less than 2%, and the host lattice of the luminescent substance is selected from apatites of the type A5(PO4)3Z, spodiosites of the type A2PO4Z, and phosphates of the type A3(PO4)2, wherein A = Ca, Sr, Ba and the mixtures thereof and Z = F, CI, OH and the mixtures.

Description

[0001] Security feature, valuable document, and printing ink The invention relates to a security feature for securing a valuable document. The invention further relates to a valuable document provided with the security feature, in particular a banknote. The invention further relates to a printing ink having the security feature for printing a valuable document. To secure and authenticate valuable documents, such as banknotes, bank cards, ID cards, passports, or other products to be secured, such as medicines, these are provided with luminescent substances that are either printed onto the valuable document or incorporated into the substrate. Normally, the emission and / or excitation spectrum and / or other luminescence parameters such as a decay time (temporal change in a measurand) are used to authenticate the valuable document.The invention disclosure is therefore based on the object of providing luminescent substances with advantageous properties that ensure a high level of security against counterfeiting 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, have significantly different spectral ratios as a pure substance and when applied to the value document. Such substances thus make the analysis and imitation of security features of a value document extremely difficult. This object is achieved by the feature combinations defined in the independent claims. Further developments of the invention are the subject of the dependent claims. Summary of the Invention 1.(First aspect of the invention) A security feature for securing a value document, wherein the security feature is formed on the basis of a luminescent substance which, in pure form, exhibits a different excitation behavior than when applied to 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 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 A5(PO4)3Z, - spodiosites of the type A2PO4Z, - phosphates of the type A3(PO4)2, where A = Ca, Sr, Ba and mixtures thereof; Z = F, Cl, OH and mixtures thereof. 2.(Preferred embodiment) Security 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, at 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.(Preferred embodiment) Security feature according to paragraph 2, wherein the luminescent substance present as a pure substance emits luminescence upon excitation at the first wavelength in the first spectral range, which generates a first value of the excitation spectrum xL, and upon excitation at the second wavelength in the second spectral range, emits luminescence which generates a second value of the excitation spectrum yL, wherein the first excitation ratio V is determined from the values ​​according to the following formula (1-1). L is available: wherein the luminescent substance present in diluted form in the value document emits luminescence upon excitation with the first wavelength in the first spectral range, which generates a first value of the excitation spectrum xS and upon excitation with the second wavelength in the second spectral range emits luminescence which generates a second value of the excitation spectrum yS, wherein the second excitation ratio V, which deviates from the first excitation ratio VL, is determined from the values ​​according to the following formula (1-2). S is available: ^

[0002] ^ = ^ ^ ^ ^ where the excitation ratio V L and the second excitation ratio VS, the ratio V satisfies the following relationship (1-3): ^ = ^ ^ ^ ^ ^ / ^ ^ ^≤ 0.2 (1-3) wherein 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 value document is incorporated into a value document substrate in a proportion of < 2 wt.%, preferably < 1 wt.% and particularly preferably < 0.5 wt.%. 5. (Preferred embodiment) Security feature according to one of paragraphs 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.(Preferred embodiment) Security feature according to paragraph 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. (Preferred embodiment) Security feature according to one of paragraphs 1 to 6, wherein the respective inorganic host lattices doped with Mn(V) have the following manganese concentrations: - A5(PO4)3Z:Mny, 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:Mny, with y = 0.01 to 0.26, preferably y = 0.01 to 0.1; 8. (Second aspect of the invention) A value document comprising the security feature according to any one of paragraphs 1 to 7. 9. (Preferred embodiment) A value document according to paragraph 8, wherein the value document is a banknote. 10. (Third aspect of the invention) A printing ink for printing a value document, wherein the printing ink comprises the security feature according to paragraph 5. Detailed description of the preferred embodiments The subject matter of the present invention is a luminescent substance and a security feature comprising the luminescent substance for securing value documents, wherein the excitation behavior of the pure, undiluted luminescent substance (ie the proportion of the luminescent substance is in particular 100%) differs from the excitation behavior of the diluted luminescent substance (iethe proportion of the luminescent substance when applied in the value document is in particular < 2%). The term security feature refers in particular to the typically powdered mixture which contains the luminescent substance in a suitable grain size and optionally other components, whereby the security feature can 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 substances additionally 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 have a very different excitation spectrum in pure form and when introduced in diluted form 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 values ​​of the excitation spectra at one wavelength from the two wavelength ranges is calculated for the pure luminescent substance on the one hand and the diluted luminescent substance present in the value document on the other. The same excitation wavelengths are selected for the pure luminescent substance and the diluted luminescent substance present in the value document. The intensities of the luminescence emissions are measured using suitable detectors and adjusted for the excitation intensities and detection sensitivities.electronic amplification factors are standardized (luminescence excitation spectrum or excitation spectrum). 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 value document on the other. If the same measurement setup is used to measure the excitation spectra of the pure substance and the diluted luminescent substance present in the value document, the above-mentioned standardization and, if applicable, electronic amplification factors cancel each other out in the third ratio, which greatly simplifies testing of the subject matter according to the invention. All three ratios can be used for quality control by comparing them with ratios stored in a database, without the need to measure the entire excitation spectra.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 according to the invention 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 that the imitation of security features, e.g., banknotes, is made 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.The advantageous luminescent substance is an inorganic host lattice doped with Mn(V) as a luminophore. The host lattice is selected from apatites, phosphates, and spodiosites, and the Mn(V) is used in a low molar fraction of less than 2%, giving the luminescent substance a faint blue body color. The excitation behavior of the luminescent substance depends on its form. In the first case, the luminescent substance is present in pure form, i.e., the sample consists of 100% of the luminescent substance in the form of, for example, powder or pressed tablets, with the layer thickness being particularly greater than 0.5 mm. In particular, “100%” 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 < 5% by weight, which can typically occur in solid-state syntheses.In a second case, the luminescent substance is diluted upon application in the value document, for example, the luminescent substance is introduced into the value document substrate. For example, the luminescent substance is introduced into a thin layer of paper or polymer, in particular thinner than 0.2 mm. In this case, the proportion of the luminescent substance in the value document is < 2 wt.%, preferably < 1 wt.%, particularly preferably < 0.5 wt. The luminescent substance is particularly preferably present in the value document substrate, preferably evenly distributed in the substrate, with a proportion of < 0.5 wt.% in the value document substrate. Alternatively, the luminescent substance is present in a printing ink applied to a value document substrate, wherein the proportion of the luminescent substance in the printing ink is < 30 wt.%, preferably < 20 wt.%, particularly preferably < 10 wt.Alternatively, the luminescent substance is present in a security element applied to a value document, for example a patch or a foil element, wherein the proportion of the luminescent substance in the security element is < 5 wt.%, preferably < 1 wt.%. The luminescent substance is preferably processed with other powdered additives such as camouflage substances and dosing aids and optionally other luminescent substances to form a powdered security feature. This makes it possible to produce a variety of easily applied, complex and highly secure codes which are particularly well suited to securing value documents. Such a security feature can then be used, e.g. by dosing into the paper pulp during paper production, to introduce the luminescent substance into the substrate of a value document.Alternatively, the security feature can be added to a printing ink and printed onto the value document, or during the manufacture of a security element, for example, inserted into the polymer substrate of the security element or printed onto it, and the security element subsequently applied to the banknote. The grain size of the luminescent substance is preferably D99 < 20 µm. This enables advantageous incorporation into paper substrates. For special types of application, such as in printing inks, smaller grain sizes are necessary, and the grain size of the luminescent substance is preferably D99 < 5 µm. The luminescent substance is expediently excitable in a wavelength range from 450 nm to 1250 nm and has one or more excitation bands belonging to the same emission in this range. The luminescent substance must be excitable in at least two sub-ranges that are at least 100 nm apart, i.e.The excitation spectrum is examined independently of the curve shape (such as excitation maxima, plateaus, etc.) of the spectrum. The two different wavelength ranges are preferably a first range ^ from 500 nm to 700 nm and a second range ^ from 850 nm to 1250 nm, particularly preferably a first range ^ from 580 nm to 620 nm and a second range ^ from 1000 nm to 1250 nm. The excitation spectra of the pure luminescent substance and the diluted luminescent substance present in the value document are compared at at least one, in each case identical, wavelength of the first range and at at least one further, in each case identical, wavelength of the second range. For both wavelengths, the corresponding values ​​of the excitation spectrum (signal intensities) ^^ or ^^ for the first range and ^^ or ^^ for the second range are determined 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 VL) and according to the following formula (1-2) for the luminescent substance in the security feature (namely the ratio V. S ): ^ ^^ = ^ ^ (1-1); ^ These ratios can be used to determine the quality of the pure luminescent substance by comparing it with a reference value ^ ^,^^^ to check, as well as the value document using a reference value ^ ^,^^^to be validated without the need to measure the entire excitation spectrum. In particular, the luminescent substances according to the invention fulfill the criterion according to the following formula (1-3) in the characterizing preferred first and second wavelength ranges, preferably at at least one wavelength each, which results from the different excitation spectra of the pure substance and the security feature: ^ ^ = ^ ^ ^ ^ / ^ ^ ^≤ 0.2 (1-3). This means that there is at least one excitation wavelength in the first wavelength range and at least one excitation wavelength in the second wavelength range, so that the ratio of the excitation spectrum values ​​at these two excitation wavelengths for the pure luminescent substance, on the one hand, and for the diluted luminescent substance present in the value document, on the other hand, differs by a factor of 5 or more. 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.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 advantageous properties increase protection against counterfeiting. Surprisingly, the luminescent substance is 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 valuable document. This is not a simple concentration-dependent behavior; rather, as shown in Figure 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 counterfeit, 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 of the valuable document is made extremely difficult by the low signals resulting from the low concentration of the luminescent substance, and the resulting excitation spectrum differs greatly from the spectra of the pure luminescent substances, so that, for example, spectral databases cannot be used here. This increases the security of the valuable documents. This surprising advantage is achieved through the specific combination of inorganic host lattices with the selected luminophore. Apatites, phosphates, and spodiosites are particularly preferred as host lattices. Manganese, as Mn(V), is particularly preferred as a luminophore in low concentrations with molar fractions of < 2%, thereby ensuring the inventive advantages of the luminescent substance.The luminescent substance is advantageously excitable in the range from 450 nm to 1250 nm and exhibits one or more excitation bands belonging to the same emission in this range. In the wavelength range from 1100 nm to 1250 nm, the luminescent substance exhibits a quasi-resonance, i.e., the luminescent substance exhibits both excitability and emission in this wavelength range. The advantageous different excitation behavior of the pure luminescent substance and the diluted luminescent substance present in the valuable document becomes clear from the excitation spectrum. For example, the excitation spectrum of the pure luminescent substance exhibits a first value ^ at a first wavelength in the range from 580 nm to 620 nm. ^ and at a second wavelength in the range of 1000 nm to 1250 nm a second value ^ ^ . Analogously, the excitation spectrum of the luminescent substance in the valuable document has a third value at the first wavelength ^^ and at the second wavelength a fourth value ^ ^ 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 ^ ^ for the excitation spectrum of the pure luminescent substance and the value for the excitation spectrum of the diluted luminescent substance present in the security document. In particular, the ratio of ^ ^ to according to the above formula (1-3) a value V ≤ 0.2. Unless stated otherwise, specific absolute values ​​for V refer to the comparison of the pure luminescent substance with a sheet of paper which was produced in a sheet former and contains 0.5 percent by weight of the luminescent substance. Due to the special selection of host lattice and stoichiometry, luminescent substances according to the invention always have 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 undercut. They are therefore particularly suitable for creating security features according to the invention. Preferably V ≤ 0.15, particularly preferably V ≤ 0.1. As a result, the excitation spectra of the pure luminescent substance and that applied in the valuable document differ even more from each other, so that even greater security is achieved.The selection of suitable wavelength ranges for measuring the excitation spectrum is not technically limited because 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 the specified 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. When using the luminescent substance according to the invention to secure valuable documents, counterfeit security 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 is monitored using the ratio ^. ^ to a reference value stored in a database ^ ^,^This eliminates the need for complex analytical methods for measuring chemical composition, because the ratio is only met with successful synthesis. The luminescent substance can then be incorporated into a valuable document substrate in the form of a security feature or applied as a printing ink. Verification of the successful incorporation of the security feature is based on the criterion ^ ^, where the ratio of the two criteria is expediently ^ ≤ 0.2. The different excitation behavior (mathematically expressed by criterion V) increases the security against counterfeiting 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 value document. This applies analogously to the further processing of the security feature during the production of a value document, e.g., a banknote. After the value document has been produced, the verification can again be carried out using the specified ratio ^ ^without the need for knowledge of the substances used and their excitation spectra for quality control purposes. Further exemplary embodiments and advantages of the invention are explained below with reference to the figure. It shows: Figure 1 is a sketch to illustrate luminescent substances according to the invention (left) and non-inventive (right). Depending on the selected host lattice, the luminescent substances according to the invention surprisingly only meet the aforementioned criterion in certain concentration ranges. This means that a different ratio V is obtained depending on the manganese doping used. If, on the other hand, other concentration ranges and host lattices are used, this behavior does not occur or occurs to a lesser extent, and the criterion is not met. In addition, the manganese doping must be less than 2% by mole fraction in order 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, materials according to the invention surprisingly always meet the criterion V ≤ 0.2 with a molar fraction of manganese < 2%. In addition, certain stoichiometry ranges were 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 the type A5(PO4)3Z:Mny, with y = 0.005 to 0.3 and particularly preferably y = 0.03 to 0.075; (II) Spodiosites of the type A2PO4Z:Mn. y , with y = 0.001 to 0.025 and particularly preferably y = 0.01 to 0.025; (III) phosphates of the 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 mixtures thereof; Z = F, Cl, OH and mixtures thereof; and Mn is present in the oxidation state Mn(V); 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 percent by weight of the luminescent substance distributed in the paper substrate. Exemplary embodiment 1 - Apatite To produce the luminescent substance, 5.02 g of BaCO3, 8.90 g of BaHPO4, 6.00 g of NaCl and 73.4 mg of MnCO3 are thoroughly mixed together in an agate mortar. The mixture is transferred to a corundum crucible and calcined 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 grinding in a planetary mill produces a grain size of D99 in a range of 15 µm to 18 µm.A light blue powder is obtained. The resulting luminescent substance Ba5(PO4)3Cl:Mn0.05 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, in the form of a security feature. Alternatively, the luminescent substance can be milled, for example, using an air jet mill to a grain size D99 in the range of 4 µm to 5 µm and added to a printing ink and printed onto the valuable document, or, for example, 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 display very 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 percent by weight using 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 the Mn(V) are compared. A V value of 0.09 is obtained. Ba5(PO4)3Cl:Mn0.05 therefore has a particularly low V value and is therefore particularly suitable for security features according to the invention. Exemplary Embodiment 2 – Spodiosites To produce the luminescent substance, 7.36 g of CaCl2, 3.32 g of CaCO3, 9.03 g of CaHPO4, 200 mg of Na2O2, and 76.2 mg of MnCO3 are thoroughly mixed in an agate mortar. The mixture is transferred to a corundum crucible and annealed at 900 °C for 6 h. The sintered cone is crushed, suspended in water (2 liters, 40 °C), filtered, washed with water, and dried at 80 °C.Dry grinding in a planetary mill produces a grain size D99 in a range from 8 µm to 12 µm. A light violet powder is obtained. The luminescent substance Ca2PO4Cl:Mn0.02 is incorporated into the paper substrate of a sheet at 0.5 weight percent. Both the pure powder and the sheet are excited at 600 nm and 1184 nm, and the respective ratios of the luminescence emission of the Mn(V) are compared. A V value of 0.15 is obtained. Example 3 – Phosphates To produce the luminescent substance, 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 hours. The sintered cone is pre-crushed and then dry-ground in an air jet mill to a D99 grain size in a range of 4 µm to 5 µm. A blue-colored powder is obtained.The luminescent substance Ba3(PO4)2:Mn. 0,02 is incorporated into the paper substrate of a sheet at a concentration of 0.5 percent 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 the Mn(V) are compared. A V value of 0.06 is obtained. Ba3(PO4)2:Mn exhibits particularly low V values ​​and is therefore particularly well suited for security features according to the invention.

Claims

Patent Claims 1. A security feature for securing a valuable document, wherein the security feature is formed on the basis of a luminescent substance which, in pure form, exhibits a different excitation behavior than when applied to the valuable 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 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 A5(PO4)3Z, - spodiosites of the type A2PO4Z, - phosphates of the type A3(PO4)2, where A = Ca, Sr, Ba and mixtures thereof; Z = F, Cl, OH and mixtures thereof. 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 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, at 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 each other 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 upon excitation at a first wavelength in the first spectral range, which generates a first value of the excitation spectrum xL, and upon excitation in the second spectral range, emits luminescence which generates a second value of the excitation spectrum yL, wherein the first excitation ratio V is determined from the values ​​according to the following formula (1-1): L available: (1-1); 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 V L deviating second excitation ratio VS is available: ^ ^ ^ ^ = ^ (1-2) ^ where the excitation ratio V L and the second excitation ratio VS, the ratio V satisfies the following relationship (1-3): ^ ^ = ^ ^ ^ ^ / ^ ^ ^≤ 0.2 (1-3) 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. %.The 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. The security feature according to any one of claims 1 to 6, wherein the 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. A value document comprising the security feature according to one of claims 1 to 7.

9. A value document according to claim 8, wherein the value document is a banknote.

10. A printing ink for printing a value document, wherein the printing ink comprises the security feature according to claim 5.

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