Security feature, value document and printing pigment

Abstract

The invention relates to a security feature for protecting value documents, said security feature being formed on the basis of a luminescent material which has a different excitation behavior in the pure form than when applied to the value documents in the diluted form, said luminescent material being based on an inorganic host lattice doped with Mn (V) as the luminophore, the amount of substance of Mn (V) in the luminescent material is less than 2%, and the host lattice of the luminescent material is selected from the group consisting of A5 (PO4) 3Z apatite, A2PO4Z fluorophore and A3 (PO4) 2 phosphate, where A = Ca, Sr, Ba and mixtures thereof and Z = F, Cl, OH and mixtures thereof.

Description

Security features, valuable documents, and printing inks

[0001] This invention relates to a security feature for protecting valuable documents. It also relates to a valuable document having this security feature, particularly banknotes. Furthermore, it relates to a printing ink for printing valuable documents incorporating this security feature.

[0002] To protect and verify valuable documents, such as banknotes, bank cards, identification documents, passports, or other protected products like pharmaceuticals, luminescent materials are incorporated into them, either printed on the documents or integrated into the substrate. Typically, to verify valuable documents, the emission spectrum and / or excitation spectrum of the emitted light and / or other parameters of the emitted light, such as decay time (the change of a measured variable over time), are used. Therefore, the technical problem this invention aims to solve is to provide luminescent materials with beneficial properties that ensure high anti-counterfeiting security and are inherently difficult to counterfeit. This is achieved, in particular, through specially selected luminescent materials according to the invention, which exhibit significantly different spectral characteristics as pure substances and when applied to valuable documents compared to prior art luminescent materials. Such materials thus greatly increase the difficulty of analyzing and imitating the security features of valuable documents.

[0003] The technical problem described herein is solved by a combination of features defined in the independent claim. Extended designs of the invention are the subject of the dependent claims. Summary of the Invention

[0004]

[0005] 1. (First aspect of the invention) A security feature for protecting valuable documents, wherein the security feature is formed based on a luminescent material that exhibits different excitation behavior in its pure form compared to when applied to the valuable document in a diluted form.

[0006] Its features are,

[0007] - This luminescent material is based on an inorganic host lattice doped with Mn(V) as the luminescent element.

[0008] - The molar fraction of Mn(V) in the luminescent material is less than 2%.

[0009] - The main lattice of this luminescent material is selected from:

[0010] - A5(PO4)3Z type apatite

[0011] - Fluorophosphate rock of type A2PO4Z

[0012] - Phosphates of type A3(PO4)2

[0013] in,

[0014] A = Ca, Sr, Ba and their mixtures;

[0015] Z = F, Cl, OH and their mixtures.

[0016] 2. (Preferred Design Scheme) According to the safety features described in Item 1, wherein the luminescent material can be excited to emit light at at least one first wavelength within a first spectral range of 580 nm to 620 nm and at least one second wavelength within a second spectral range of 1000 nm to 1250 nm, and thereby obtains an excitation spectrum at these at least two wavelengths, wherein the so-called excitation ratio can be obtained from the ratio of the excitation spectral values ​​at these at least two wavelengths.

[0017] Its features are,

[0018] At least one first wavelength in the first spectral range and at least one second wavelength in the second spectral range are used for excitation, wherein for the first wavelength and the second wavelength, the excitation ratio of the luminescent material in its pure form differs from the excitation ratio of the luminescent material in its diluted form in the valuable document by more than 5 times.

[0019] 3. (Preferred Design Scheme) According to the safety features described in Item 2, the luminescent material, existing as a pure substance, emits light when excited at a first wavelength within a first spectral range, and the light emission produces a first value x of the excitation spectrum. L When excited at a second wavelength within a second spectral range, it emits light, and the light emission produces a second value y of the excitation spectrum. L The first excitation ratio V can be obtained from these values ​​according to the following formula (1-1). L :

[0020]

[0021] The luminescent material present in the valuable document in a diluted form emits light when excited by a first wavelength within a first spectral range, and the light emission produces a first value x of the excitation spectrum. S When excited by a second wavelength within a second spectral range, it emits light, and the light emission produces a second value y of the excitation spectrum. S Among these values, the first excitation ratio V can be obtained from the following formula (1-2). L Different second excitation ratios V S :

[0022]

[0023] Among them, the first excitation ratio VL Second excitation ratio V S The resulting ratio V satisfies the following relationship (1-3):

[0024]

[0025] Preferably, V ≤ 0.15, and more preferably, V ≤ 0.1.

[0026] 4. (Preferred Design) The security feature according to any one of items 1 to 3 above, wherein the luminescent material present in the valuable document in a diluted form is introduced into the substrate of the valuable document at a ratio of < 2% by weight, preferably < 1% by weight, particularly preferably < 0.5% by weight.

[0027] 5. (Preferred Design) The security feature according to any one of claims 1 to 3, wherein the luminescent material present in the valuable document in a diluted form is applied to the substrate of the valuable document in the form of printing pigment, wherein the proportion of the luminescent material in the printing pigment is < 30% by weight, preferably < 20% by weight and particularly preferably < 10% by weight.

[0028] 6. (Preferred Design Scheme) According to the security features described in item 4 or 5, wherein the valuable document substrate is selected from the group consisting of paper substrate, polymer substrate, paper / polymer / paper composite substrate and polymer / paper / polymer composite substrate.

[0029] 7. (Preferred Design Scheme) The safety feature according to any one of items 1 to 6 above, wherein the inorganic main lattice doped with Mn(V) has the following manganese concentration:

[0030] - A5(PO4)3Z:Mn y Where y = 0.005 to 0.3, preferably y = 0.03 to 0.075;

[0031] - A2PO4Z:Mn y Where y = 0.001 to 0.025, preferably y = 0.01 to 0.025;

[0032] - A3(PO4)2:Mn y , where y = 0.01 to 0.26, preferably y = 0.01 to 0.1.

[0033] 8. (Second aspect of the invention) A valuable document comprising security features according to any one of items 1 to 7 above.

[0034] 9. (Preferred Design Scheme) The valuable document according to Item 8, wherein the valuable document is banknotes.

[0035] 10. (Third aspect of the invention) A printing pigment for printing valuable documents, wherein the printing pigment comprises the security features according to claim 5. Detailed Implementation

[0036] Detailed description of preferred embodiments

[0037] The subject of this invention is a luminescent material and a security feature comprising the luminescent material for protecting valuable documents, wherein the excitation behavior of pure, undiluted luminescent material (i.e., a luminescent material content of, in particular, 100%) differs from that of diluted luminescent material (i.e., a luminescent material content of, in particular, <2%) when applied to valuable documents. The term "security feature" here specifically refers to a mixture, typically in powder form, comprising luminescent material of suitable particle size and optional other components, wherein the security feature may also consist solely of luminescent material as the sole component. This invention is not directed at different excitation behaviors based on known concentration effects or absorption caused by additional materials present in the security feature or valuable document, but rather provides luminescent materials whose excitation behavior differs as pure materials and when applied to valuable documents, i.e., these materials themselves have significantly different excitation spectra in pure form and when introduced into valuable documents in diluted form. Suitable materials can be described by the following criteria. For this purpose, two wavelength ranges are selected, based on the excitation spectrum of the pure luminescent material on the one hand, and the excitation spectrum of the luminescent material diluted in the valuable document on the other hand, within which the change in excitation behavior is significant. Establish a ratio of the excitation spectrum values ​​for one wavelength in two wavelength ranges for both the pure luminescent material and the luminescent material diluted in the valuable document. The same excitation wavelength is selected for both the pure and diluted luminescent materials. The intensity of the emission is measured using a suitable detector, and normalized (luminescence excitation spectrum or excitation spectrum) is applied to the excitation intensity and detection sensitivity or electronic amplification factor.

[0038] In a further step, a third ratio is established from the two ratios of pure luminescent material and luminescent material present in a diluted form in the valuable document.

[0039] If the excitation spectra of the pure material and the luminescent material present in a diluted form in a valuable document are measured using the same measuring apparatus, the above-mentioned normalization and, if necessary, electronic amplification factor will cancel each other out in the third ratio, which significantly simplifies the verification of the object according to the invention.

[0040] All three ratios can be used for quality control by comparing them with ratios stored in a database, without measuring the entire excitation spectrum. According to the invention, by selectively choosing particularly suitable luminescent materials based on an inorganic main lattice doped with Mn(V), it is possible to achieve specific excitation spectra that vary strongly depending on the application type, thereby achieving a ratio of signal intensity at the corresponding excitation wavelength. A particular technical advantage of the invention is that, for example, imitation of security features in banknotes becomes more difficult because the excitation spectra of diluted luminescent materials in valuable documents differ greatly from those of pure luminescent materials in powder form.

[0041] This advantageous luminescent material relates to an inorganic host lattice doped with Mn(V) as the luminescent agent, wherein the host lattice is selected from apatite, phosphate, and fluorapatite, and Mn(V) is used in a low molar fraction of less than 2%, thereby giving the luminescent material a faint blue body color. The excitation behavior of the luminescent material depends on its form of existence. In a first case, the luminescent material exists in a pure form, i.e., the sample consists of 100% of the luminescent material, for example, in the form of powder or tablets, wherein the thickness of the tablet is particularly greater than 0.5 mm. "100%" here specifically means that the material has not been intentionally diluted with other components, and does not exclude the presence of a small amount of secondary phase or raw material residue, which may typically occur during solid-state synthesis, totaling <5% by weight. In a second case, the luminescent material exists diluted when applied to valuable documents, for example, by introducing the luminescent material into a valuable document substrate. For example, the luminescent material is introduced into a thin layer, particularly less than 0.2 mm, of paper or polymer.

[0042] Here, the luminescent material comprises < 2% by weight in the valuable document, preferably < 1% by weight, and particularly preferably < 0.5% by weight. Particularly preferably, the luminescent material is present in the substrate of the valuable document, preferably uniformly distributed within the substrate, and comprises < 0.5% by weight in the substrate. Alternatively, the luminescent material is present in printing pigments applied to the substrate of the valuable document, wherein the luminescent material comprises < 30% by weight in the printing pigments, preferably < 20% by weight, and particularly preferably < 10% by weight. Alternatively, the luminescent material is present in security elements, such as patches or foil elements, applied to the valuable document, wherein the luminescent material comprises < 5% by weight in the security element, preferably < 1% by weight.

[0043] The luminescent material is preferably processed into a powdered security feature together with other powdered additives, such as camouflage materials and formulation aids, and possibly other luminescent materials. This allows for the production of a large number of sophisticated and highly secure codes that can be readily applied, particularly well-suited for protecting valuable documents. This security feature can be used, for example, by quantitatively adding it to the pulp during the papermaking process to introduce the luminescent material into the substrate of the valuable document. Alternatively, the security feature can be added to printing pigments and printed onto the valuable document, or it can be added to or printed onto the polymer substrate of the security element during its manufacture, and then the security element is applied to banknotes.

[0044] The particle size of the luminescent material is preferably D99 < 20 µm. This allows for advantageous introduction into paper-based substrates. For specific applications, such as those in printing pigments, where smaller particle sizes are required, the particle size of the luminescent material is preferably D99 < 5 µm.

[0045] The luminescent material is suitably exciteable in the wavelength range of 450 nm to 1250 nm, and has one or more excitation bands belonging to the same emission within this range. The luminescent material must be exciteable in at least two sub-ranges at least 100 nm apart, i.e., considering the excitation spectrum independently of the shape of the spectral curve (e.g., excitation maximum, plateau, etc.). Preferably, these two different wavelength ranges are a first range x of 500 nm to 700 nm and a second range y of 850 nm to 1250 nm, particularly preferably a first range x of 580 nm to 620 nm and a second range y of 1000 nm to 1250 nm. The excitation spectra of the pure luminescent material and the luminescent material diluted in the valuable document are compared in at least one wavelength within the first range and at least one wavelength within the second range, respectively. For both wavelengths, the corresponding values ​​of the excitation spectrum (signal intensity) are determined: for the first range x... L or x S For the second range y L or y S And establish the ratio. Based on the chosen form of the luminescent material, the ratio (i.e., ratio V) for the pure luminescent material is obtained according to the following formula (1-1). L The ratio of luminescent materials in the security feature (i.e., ratio V) is obtained according to the following formula (1-2). S ):

[0046] (1-1);

[0047] (1-2);

[0048] These ratios can be used to compare with the reference value V. L,Ref Comparisons can be used to check the quality of pure luminescent materials, and can also be used based on the reference value V. S,Ref Verify valuable documents without measuring the entire excitation spectrum. The luminescent material according to the invention satisfies, in particular, for at least one wavelength within characteristically preferred first and second wavelength ranges, a criterion derived from the different excitation spectra of the pure material and its security characteristics:

[0049] (1-3)

[0050] In other words, there exists at least one excitation wavelength in a first wavelength range and at least one excitation wavelength in a second wavelength range, such that the ratio of the excitation spectral values ​​at these two excitation wavelengths for the pure luminescent material and for the luminescent material diluted in the valuable document differs from each other by more than a factor of 5. As described below, this additional verification parameter can significantly improve the security of the security feature. To achieve these special spectral characteristics, specially selected luminescent materials are required, which will be described below.

[0051] The security features according to the invention suitably comprise a luminescent material based on a main lattice doped with Mn(V) as the luminescent agent, wherein the concentration of manganese doping is chosen to be so low (the molar fraction of manganese <2%) that the luminescent material has a faint blue body color, thereby distinguishing it from materials with excessively high manganese content that thus exhibit a deep blue, green, brown, or black body color. The faint blue body color is advantageous because, at low concentrations, the luminescent material is visually (i.e., to the naked eye) in valuable document substrates, for example. The use of a small amount of luminescent agent in the luminescent material is further advantageous, as this makes it more difficult to determine the correct composition using common chemical analysis methods (such as elemental analysis, ICP, etc.). Both of these advantageous characteristics enhance protection against counterfeiting.

[0052] A significant characteristic of this luminescent material is that the excitation spectrum of the pure luminescent material differs significantly from that of the diluted luminescent material in the valuable document. This is not a simple concentration-dependent behavior, but rather, as illustrated in Figure 1 according to the invention, the excitation spectrum changes so significantly that a valuable document containing this luminescent material is difficult for counterfeiters to replicate, because a counterfeiter would not measure the same excitation spectrum as on the valuable document when measuring the candidate material (in its pure form) in the laboratory. Simultaneously, the low signal due to the low concentration of the luminescent material makes accurate spectral analysis of the valuable document extremely difficult, and the obtained excitation spectrum differs significantly from that of the pure luminescent material, thus making it impossible to use spectral databases, for example. Therefore, the security of the valuable document is enhanced. This unexpected advantage is achieved through a specific combination of the inorganic host lattice and the selected luminescent material. Particularly preferred host lattices are apatite, phosphates, and fluorapatite. Especially preferred luminescent material is manganese as Mn(V), with a low concentration (<2% by weight), thereby ensuring the advantages of the luminescent material according to the invention.

[0053] The luminescent material is suitably excitable in the range of 450 nm to 1250 nm, and possesses one or more excitation bands belonging to the same emission within this range. In the wavelength range of 1100 nm to 1250 nm, the luminescent material exhibits quasi-resonance, meaning it is both excitable and emits within this wavelength range. The advantageously different excitation behaviors of the pure luminescent material and the luminescent material diluted in the valuable document can be clearly shown from the excitation spectra. For example, the excitation spectrum of the pure luminescent material has a first value x at a first wavelength in the range of 580 nm to 620 nm. L It has a second value y at the second wavelength in the range of 1000 nm to 1250 nm. L Similarly, the excitation spectrum of the luminescent material in the valuable document has a third value x at the first wavelength. S It has a fourth value y at the second wavelength. S Ratio V L (See formula (1-1) above) and V S (See formula (1-2) above) is a measure of the excitation spectral shape of pure luminescent materials and luminescent materials in valuable documents, and is independent of absolute luminescence intensity and excitation efficiency. The luminescent material according to the invention here shows the value V for the excitation spectrum of a pure luminescent material. L and the value V for the excitation spectrum of the luminescent material that exists in the valuable document in a diluted form. S The characteristic differences between them. In particular, according to the above formula (1-3), V L With V SThe ratio V satisfies V ≤ 0.2. Unless otherwise stated, the specific absolute values ​​of V mentioned below are based on a comparison between pure luminescent material and a sheet of paper containing 0.5% by weight of luminescent material manufactured in a sheet-making machine. The luminescent materials according to the invention, due to the specific selection of the principal lattice and stoichiometry, always possess at least one wavelength in a first wavelength range x and at least one wavelength in a second wavelength range y, such that V ≤ 0.2 is achieved or below this standard. Therefore, they are particularly suitable for manufacturing security features according to the invention. Preferably V ≤ 0.15, and more preferably V ≤ 0.1. Thus, the excitation spectra of pure luminescent material and the luminescent material used in valuable documents differ more significantly from each other, thereby achieving higher security.

[0054] Choosing a suitable wavelength range to measure the excitation spectrum is technically unrestricted, as excitation in the 450 nm to 1250 nm wavelength range can be easily achieved with a suitable LED, and the spectral widths of both the LED and the detector are narrow enough to cover this range. The excitation spectrum measurement is performed at the center wavelength with a certain uncertainty (e.g., ±5 nm) to cover the selected wavelength. The signal intensity of the excitation spectrum is obtained by integrating the broadbandly detected emission. This can be achieved, for example, by excitation with a pulsed laser and numerical integration, or by excitation with an LED having a suitable bandwidth or suitable filtering, i.e., an emission spectrum in the range of 580 nm to 620 nm, which corresponds to optical integration and simplifies signal evaluation. Furthermore, it is necessary to use the same excitation intensity (power / area) and the same detector structure when measuring to determine the two ratios.

[0055] Using the luminescent material for protecting valuable documents according to the present invention improves anti-counterfeiting security and ensures secure manufacturing. The luminescent material is manufactured according to a known high-temperature method for manufacturing inorganic master lattices. Based on the ratio V... L With reference value V stored in the database L,R The purity and quality of the pure luminescent material are controlled. This eliminates the need for costly analytical methods to determine the chemical composition, as this ratio is only satisfied upon successful synthesis. The luminescent material can then be introduced into valuable document substrates as a security feature or applied as a printing pigment. Based on standard V... S The security feature is checked to ensure its successful introduction, where the ratio of the two criteria appropriately satisfies V ≤ 0.2. Anti-counterfeiting security is enhanced through different excitation behaviors (mathematically expressed in terms of the standard V) because, to replicate the luminescent material of this invention, it is necessary to know how the excitation behavior of the pure luminescent material differs from that of the luminescent material in a valuable document. Similarly, this applies to further processing of the security feature during the manufacture of valuable documents (e.g., banknotes). After the manufacture of the valuable document, the security feature can be re-established based on the determined ratio V.S Inspections can be conducted without needing to know detailed information about the materials used and their excitation spectra for quality control purposes.

[0056] Other embodiments and advantages of the present invention will be described below in conjunction with the accompanying drawings.

[0057] In the attached diagram:

[0058] Figure 1 shows a schematic diagram illustrating luminescent materials according to the present invention (left) and those not according to the present invention (right).

[0059] The luminescent material according to the invention surprisingly satisfies the criterion only within a specific concentration range, depending on the selected host lattice. That is, different ratios V are obtained depending on the degree of manganese doping used. This behavior does not occur or occurs to a lesser extent if other concentration ranges and host lattices are used, and the criterion cannot be met. Furthermore, the molar fraction of manganese doping must be less than 2% to produce a favorable low body color. By selectively choosing a particularly suitable host lattice with a suitable dopant from a plurality of known host lattices, dopants, and their concentrations, the material according to the invention surprisingly consistently satisfies the criterion V ≤ 0.2 when the molar fraction is < 2%. Furthermore, a specific stoichiometric range is considered particularly advantageous according to the invention. Therefore, to obtain a particularly suitable V value, i.e., a particularly low V value, the following preferred special selections of host lattice and manganese doping have emerged:

[0060] (I) A5(PO4)3Z:Mn y The type of apatite, wherein y = 0.005 to 0.3, particularly preferably y = 0.03 to 0.075;

[0061] (II) A2PO4Z:Mn y Spodiosite of the type, wherein y = 0.001 to 0.025, particularly preferred to be y = 0.01 to 0.025;

[0062] (III) A3(PO4)2:Mn y Phosphates of the type wherein y = 0.01 to 0.26, particularly preferably y = 0.01 to 0.1;

[0063] in

[0064] A = Ca, Sr, Ba and their mixtures;

[0065] Z = F, Cl, OH and their mixtures;

[0066] Furthermore, Mn exists in the oxidized state Mn(V);

[0067] The following are a series of examples of materials according to the invention with different principal lattices. Pure powders were compared with paper samples containing 0.5% by weight of luminescent material dispersed in a paper substrate.

[0068] Example 1 – Apatite

[0069] To prepare the luminescent material, 5.02 g BaCO3, 8.90 g BaHPO4, 6.00 g NaCl, and 73.4 mg MnCO3 were thoroughly mixed in an agate mortar. The mixture was transferred to a corundum crucible and calcined at 830°C for 10 hours. The sintered block was suspended in water (2 L, 40°C) to dissolve the sodium chloride, filtered, washed with water, and dried at 80°C. Dry milling in a planetary ball mill yielded a particle size D99 in the range of 15 µm to 18 µm. A light blue powder was obtained.

[0070] The obtained luminescent material Ba5(PO4)3Cl:Mn 0.05 It can be used to protect valuable documents. For example, it can be embedded in the paper substrate of the valuable document, either alone or together with other components, as a security feature. Alternatively, the luminescent material can be ground to a particle size D99 in the range of 4 µm to 5 µm using an air jet mill, added to printing pigments and printed onto the valuable document, or, for example, added to a security element, which is then fixed to the valuable document. In this form applied to the valuable document, the luminescent material is highly diluted and visually invisible. When measured with a spectrometer, the pure powder form of the luminescent material and its diluted form present in the valuable document show significantly different excitation spectra. Within the scope of the described embodiment, the luminescent material is introduced into the paper substrate of the paper sheet at a share of 0.5% by weight using a sheet fabrication machine. The pure powder and the paper sheet are excited at 600 nm and 1172 nm, respectively, and the corresponding ratios of the luminescence emission of Mn(V) are compared. A V value of 0.09 is obtained.

[0071] Therefore, Ba5(PO4)3Cl:Mn 0.05 It has a particularly low V value, and is therefore particularly suitable for use in the safety features according to the invention.

[0072] Example 2 – Fluorophosphate

[0073] To prepare the luminescent material, 7.36 g CaCl2, 3.32 g CaCO3, 9.03 g CaHPO4, 200 mg Na2O2, and 76.2 mg MnCO3 were thoroughly mixed in an agate mortar. The mixture was transferred to a corundum crucible and calcined at 900°C for 6 hours. The sintered block was pulverized, suspended in water (2 L, 40°C), filtered, washed with water, and dried at 80°C. Dry milling in a planetary ball mill yielded a particle size D99 in the range of 8 µm to 12 µm. A light purple powder was obtained.

[0074] The luminescent material Ca2PO4Cl:Mn 0.02 The powder was embedded in a paper substrate at a weight percentage of 0.5%. The pure powder and the paper were excited at 600 nm and 1184 nm, respectively, and the corresponding ratios of Mn(V) emission were compared. A V value of 0.15 was obtained.

[0075] Example 3 – Phosphate

[0076] To prepare the luminescent material, 5.80 g BaCO3, 13.72 g BaHPO4, 40.0 mg Na2CO3, and 67.3 mg MnCO3 were thoroughly mixed in an agate mortar. The mixture was transferred to a corundum crucible and calcined at 1150°C for 10 hours. The sintered block was pre-crushed and then dry-milled by an air jet mill to produce a particle size D99 in the range of 4 µm to 5 µm. A blue powder was obtained.

[0077] The luminescent material Ba3(PO4)2:Mn 0.02 The powder was embedded in a paper substrate at a weight percentage of 0.5%. The pure powder and the paper were excited at 600 nm and 1190 nm, respectively, and the corresponding ratios of Mn(V) emission were compared. A V value of 0.06 was obtained.

[0078] Ba3(PO4)2:Mn has a particularly low V value, and is therefore particularly suitable for use in the safety features according to the present invention.

Claims

1. A security feature for protecting valuable documents, wherein, The security feature is based on a luminescent material that exhibits different excitation behavior in its pure form compared to when applied to a valuable document in a diluted form. The luminescent material is characterized by: - ​​an inorganic master lattice doped with Mn(V) as the luminescent element; - a molar fraction of Mn(V) in the luminescent material of less than 2%; - a master lattice selected from: apatite of type A5(PO4)3Z, fluorapatite of type A2PO4Z, and phosphates of type A3(PO4)2, wherein A = Ca, Sr, Ba, and mixtures thereof; Z = F, Cl, OH, and mixtures thereof.

2. The security feature according to claim 1, wherein, The luminescent material can be excited to emit light at at least one first wavelength within a first spectral range of 580 nm to 620 nm and at least one second wavelength within a second spectral range of 1000 nm to 1250 nm, thereby obtaining an excitation spectrum at these at least two wavelengths, wherein the so-called excitation ratio can be obtained from the ratio of the excitation spectral values ​​at these at least two wavelengths; characterized in that at least one first wavelength within the first spectral range and at least one second wavelength within the second spectral range are used for excitation, and for the first wavelength and the second wavelength, the excitation ratio of the luminescent material in its pure form differs from the excitation ratio of the luminescent material in its diluted form in the valuable document by more than a factor of 5.

3. The security feature according to claim 2, wherein, When a luminescent material existing as a pure material is excited at a first wavelength within a first spectral range, it emits light, and the light emission produces a first value x of the excitation spectrum. L When excited at a second wavelength within a second spectral range, it emits light, and the light emission produces a second value y of the excitation spectrum. L The first excitation ratio V can be obtained from these values ​​according to the following formula (1-1). L : The luminescent material present in the valuable document in diluted form emits light when excited by a first wavelength within a first spectral range, and the emission produces a first value x. S When excited by a second wavelength within a second spectral range, it emits light, and the light emission produces a second value y of the excitation spectrum. S Among these values, the first excitation ratio V can be obtained from the following formula (1-2). L Different second excitation ratios V S : Among them, the first excitation ratio V L Second excitation ratio V S The resulting ratio V satisfies the following relationship (1-3): Preferably, V ≤ 0.15, and more preferably, V ≤ 0.

1.

4. The security feature according to any one of claims 1 to 3, wherein, The security feature is designed based on the luminescent material present in the valuable document in a diluted form, such that the luminescent material is introduced into the valuable document substrate in a proportion of < 2% by weight, preferably < 1% by weight, and particularly preferably < 0.5% by weight.

5. The security feature according to any one of claims 1 to 3, wherein, The luminescent material present in the valuable document in a diluted form is applied to the substrate of the valuable document in the form of printing pigment, wherein the proportion of the luminescent material in the printing pigment is < 30% by weight, preferably < 20% by weight, and particularly preferably < 10% by weight.

6. The security feature according to claim 4 or 5, wherein, The valuable document substrate is selected from the group consisting of paper substrate, polymer substrate, paper / polymer / paper composite substrate and polymer / paper / polymer composite substrate.

7. The security feature according to any one of claims 1 to 6, wherein, The inorganic host lattice doped with Mn(V) has the following manganese concentration: - A5(PO4)3Z:Mn y Where y = 0.005 to 0.3, preferably y = 0.03 to 0.075; - A2PO4Z:Mn y Where y = 0.001 to 0.025, preferably y = 0.01 to 0.025; - A3(PO4)2:Mn y Where y = 0.01 to 0.26, preferably y = 0.01 to 0.

1.

8. A valuable document, said valuable document comprising the security features according to any one of claims 1 to 7.

9. The valuable document according to claim 8, wherein, The valuable document in question is banknotes.

10. A printing pigment for printing valuable documents, wherein, The printing pigment includes the safety features as described in claim 5.

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