WO2019057329A1

WO2019057329A1 - Optical storage phosphor, method for checking an authenticity feature, device for carrying out a method, authenticity feature and value document

Info

Publication number: WO2019057329A1
Application number: PCT/EP2018/000440
Authority: WO
Inventors: Martin Stark
Original assignee: Giesecke+Devrient Currency Technology Gmbh
Priority date: 2017-09-21
Filing date: 2018-09-20
Publication date: 2019-03-28
Also published as: CN111094509B; CN111094509A; DE102017008868A1; RU2754537C1; WO2019057329A8

Abstract

The invention relates to an optical storage phosphor, to a method for checking an authenticity feature, to a device for carrying out a method, to an authenticity feature and to a value document. In particular, an inorganic optical storage phosphor is specified, having a garnet structure and the following composition: (GdxLny) (GamAlnAk) O12±d : Cep Qq Rr Tt, wherein: Ln comprises at least one of the following elements: La, Lu, Y; A comprises at least one of the following elements: Ge, Sc, Si; Q comprises at least one of the following elements: Ag, Cr, Hf, Mo, Nb, Sn, Ta, Ti, W, Zr; R comprises at least one of the following elements: Bi, Pr, Nd, Sm, Eu, Tb, Dy, Ho, Er, Tm, Yb; T comprises at least one of the following elements: B, F, Li, Mg, K, Na; 1.0 ≤ x ≤ 3.2 and 0 ≤ y ≤1.65; 0.5 ≤ m ≤ 5.2, 0≤ n ≤ 4.7 and 0 ≤ k ≤ 0.5, and 4.8 ≤ m+n+k ≤ 5.2; 0 ≤ p ≤ 0.1, and p = 0 only for Q=Zr; 0 ≤ q ≤ 0.05; 0 ≤ r ≤ 0.05; 0 ≤ t ≤ 0.1; 0 ≤ d ≤ 0.5; p+q > 0.002; q+r > 0.002; and 2.8 ≤ x+y+p+r ≤ 3.2.

Description

Optical storage phosphor, method for checking an authenticity feature, apparatus for carrying out a method, authenticity feature and value document

The present invention relates to an optical storage phosphor ("optical storage phosphor", hereinafter OSP), in particular for the authentication of a value document, a method for checking an authenticity feature with an optical storage phosphor, an apparatus for carrying out a method for checking an authenticity feature , an authenticity feature with an optical storage phosphor and a value document with an authenticity feature with an optical storage phosphor.

Technical background

In order to safeguard value documents, such as banknotes or passports, against counterfeiting, material security features have been introduced or introduced there for a long time, their presence being detected by measuring their characteristic properties and being used to authenticate the value document. For example, in the case of photoluminescence of solid particles under defined illumination, an emission spectrum is generated, which is then evaluated in characteristic regions, for example by comparison with a reference. Especially for high-security features and in machining, it is necessary for these characteristic features of the security features to be automatically determinable and specific enough precisely enough.

Suitable optical storage phosphors (OSP) are substances such as suitably doped alkaline earth sulfides (eg SrS: Eu, Sm), halides eg BaFBr: Eu), aluminates (eg SrAl ₂ O ₄ ,: Eu, Tm), oxides (eg MgO: Tb, BeO , A1203: C) and other substances that absorb energy in the form of X-ray, UV, VIS, or radioactive radiation, store it and release it only under specific stimulation in the form of luminescence. When light is used as a stimulus, it is called optically stimulated luminescence (OSL).

In order to understand OSP, the following explains its functionality: In an inorganic OSP, there are light centers and trap centers. With light, the light centers are stimulated. At least part of the excited charge carriers from the light centers pass into a conduction band of the OSP, while the remaining charge carriers relax with emission of photoluminescence in the ground state of the light centers. The charge carriers in the conduction band can diffuse and a part of these charge carriers arrives at trap centers, where they are bound. By picking up a charge carrier, a case center is initially excited. From this excited state, it is then mostly radiationless in its ground state. As a result, the recorded charge carrier is stored in the ground state of a case center (case state). There it can be stored up to geological periods of 10 ⁵ years. This property is used, for example, for geological dating. After specific excitation of a charge carrier from a trap center, it can return to the conduction band. In the conduction band this charge carrier diffuses and can reach a luminous center, where it is bound. By recording the charge carrier at the luminous center, this is initially in an excited state, from which it then passes under the emission of its characteristic luminescence in its ground state. Here, the luminescence has a characteristic spectral distribution and intrinsic life. During the diffusion of the charge carriers through the conduction band, a characteristic of OSP is, among others, a light-induced, persistent conductivity.

In contrast to OSL, the excited charge carrier is brought into a triplet state by phosphorescence in the luminous center itself. From this he relaxes with a characteristic time constant into another state of the luminous center. That is, in the phosphorescence, a change in the spin manifold is involved (see also IUPAC Gold Book: Phosphorescence, 23.08.2017). In contrast to the phosphorescence, however, the OSP undergoes a reversible, light-driven donor-acceptor reaction. In a simplified representation of this reversible, light-driven donor-acceptor reaction, the luminescent center donates a charge carrier as a donor during storage (usually the luminescent center is oxidized) and a different trap center picks up the charge carrier as an acceptor (the trap center usually becomes so reduced). In particular, Hölsä describes the fundamental differences between OSP and phosphorescence in "Persistent luminescence beats the afterglow: 400 years of persistent luminescence", Electrochem. Soc. Interface (2009), 18 (4), pages 42-45. In OSPs, the excitation spectra of the charge carriers bound to trap centers (read spectrum) are independent of the excitation spectrum (charge spectrum) or emission spectrum of the light centers. In this respect, optically stimulated luminescence is also different from the usual upconversion or antistoke phenomena induced by simultaneous multiphoton processes: both with regard to the charge spectrum and the emission spectrum of the light centers, there is no necessary physical relation to the read spectrum of the (reduced) trap centers. In general, therefore, the reading wavelengths can be shorter, equal to or longer than the emission wavelength.

There are isolated disclosures in the literature for the use of such storage phosphors as an authenticity feature. For example, document US Pat. No. 4,387,112 discloses the general possibility of using storage phosphors as a security feature, and more particularly describes sulfides such as (Zn, Cd) S: Cu.

In the publication EP 1 316924 A1, the authenticity check is carried out via the detection of photoluminescence or via the occurrence of optically stimulated luminescence (OSL) of substances such as BaFBr: Eu or CsBr: Eu.

An inorganic storage phosphor (such as SrS: Eu, Sm or Sr ₄ Al ₁₄ O ₂₅ : Eu, Dy) and an up-converter phosphor are used in the publication WO 2010/0064956 Al.

Publication DE 10 2011 010756 A1 describes production processes for silicate-coated nanoparticulate storage phosphors and their possible use as markers.

The methods described above do without a quantitative evaluation of the dynamic and characteristic storage behavior of an OSP as an authenticity feature and instead rely on reproducible measurements on defined system states. This type of test potentially enables an imitator to gather information that will facilitate the readjustment of the substance. A successful material adjustment would then pass the authenticity test. Furthermore, the OSPs known from the prior art are often chemically unstable (such as BaFBr: Eu, SrS: Eu, Sm, Sr4Alr402s: Eu, Dy) or unstable to light influences (such as ZnS: Cu, Co, (Zn, Cd) S: Cu) and may need to be laboriously stabilized with a coating. In addition, the toxicity of some substances (such as BaFBr: Eu) and / or their decomposition products (eg hydrogen sulfide, barium, fluoride, or cadmium ions) and / or the starting materials (eg BaQ.2) not only hampers the application but requires also in the production and disposal increased effort against stable non-toxic substances.

In addition, currently available optical storage phosphors also have at least one of the following disadvantages: unmatched spectral storage properties, slow intrinsic luminescence, intense persistent luminescence (so-called persistence), slow readability - these three latter effects make it difficult to use an OSP as a fast machine readable authentication feature. , Need for high-energy charging and low intensity of emission.

Description of the invention

Based on the technical background described above, it is an object of the invention to provide an optical storage phosphor which solves in particular the above-mentioned disadvantages of known optical storage phosphors. Further objects are the provision of a method for checking an authenticity feature as well as an apparatus for carrying out such a method, wherein an increased security is to be achieved in comparison with the known methods. Furthermore, an authenticity feature and a value document with an improved storage phosphor are to be provided.

These objects are achieved in particular by an optical storage phosphor described here, a method for checking an authenticity feature, a device for carrying out a method, an authenticity feature and a value document having the features of the independent patent claims. Advantageous developments ben from the dependent claims, the description, the figures and the embodiments described in connection with the figures.

Accordingly, an optical storage phosphor is disclosed which is based on a garnet structure and has the following composition:

in which:

Ln comprises at least one of the following elements: La, Lu, Y;

A comprises at least one of the following elements: Ge, Sc, Si;

Q comprises at least one of the following elements: Ag, Cr, Hf, Mo, Nb, Sn, Ta, Ti,

W, Zr;

preferably at least one of Ag, Mo, Nb, Sn, Ti, Zr;

R comprises at least one of the following elements: Bi, Pr, Nd, Sm, Eu, Tb, Dy, Ho, - Er, Tm, Yb;

T comprises at least one of the following elements: F, Li, Mg, K, Na, B;

preferably at least one of the elements F, Li;

- 1.0≤x≤3.2 and 0≤y≤1.65;

- 0.5≤ m≤5.2, 0≤n≤4.7 and 0≤k≤0.5, where 4.8≤m + n + k≤5.2;

0≤p≤0.1, where p = 0 only for Q = Zr;

preferably 0.001≤p≤0.1;

- 0 ≤ q ≤ 0.05;

- 0≤r≤ 0.05;

- 0≤t≤0.1;

- 0≤d≤0.5;

- p + q> 0.002;

- q + r> 0.002; and

- 2.8≤x + y + p + r≤3.2.

By deviations from a formally charge-neutral stoichiometry and / or due to deviating charge and / or by deviating ionic radii of doped ions (codings) in comparison to the underlying garnet structure of the host lattice of the OSP described here, a defect structure is provided in said host lattice. The doped ions and the resulting defect structure are an essential part of the substance described here.

The optical storage phosphor described here is an inorganic, oxidic substance with a defect-rich garnet structure as a host lattice, preferably with cerium as the luminescent center. It is based on the ideal charge-balanced formulation of a gadolinium aluminum garnet, Gd ₃ Al ₅ O ₁₂ . By targeted deviation from the ideal charge-balanced stoichiometry and suitable codopings, a storage phosphor can be provided which is distinguished by its stability, its rapid readability, its adapted readout spectrum and / or its chargeability in the blue spectral range.

The defect structure which can already be influenced by slight variations in the composition and production of the substance is part of the substance, since it essentially determines the properties and thus the distinctness of a certain substance from other substances of similar composition.

When considering the case centers and luminous centers of the OSP described here, these represent independent optical systems. It was surprisingly found that the memory behavior of the OSP is changeable and adaptable by deliberately influencing the defect structure of the OSP. In addition, surprisingly, this targeted adaptation by chemical modification of the dive centers, the luminous centers and the garnet (ie the solid, which contains the trapping and luminous centers) of the OSP done. First, by deviating from the ideal stoichiometry of the garnet and its composition, the optically stimulated luminescence can be specifically promoted and the thermoluminescence at room temperature (also referred to as persistence or persistent luminescence) inhibited. Secondly, by means of different codoping and modifications to the underlying garnet, parameters of the optically stimulated luminescence, such as, for example, associated characteristic memory properties (for definition, see below), read-out speed and read-out spectrum can be adjusted in a targeted manner. Thus, for a constant charging and emission behavior (due to the properties of the light centers) in the storage behavior (due to the properties Fall Centers) achieve optimized substances for the respective application. It follows that the storage behavior of the OSP is accessible to a targeted adaptation by chemical modification.

The chemical nature and the crystallographic properties of the dormancy centers, luminous centers and / or host lattices of the OSP determine the relative energetic position of the involved states ((energy) levels), eg. As trap states, ground states, excited states, and the conduction band.

The above-described optical storage phosphor is based in particular on the following findings and findings. The formulation of a stoichiometric gadolinium aluminum garnet, simply referred to as (Gd ₃ ) (Al ₅ ) O ₁₂ , is assumed. At least one of the modifications described below (Modifications 1 to 8) provides the storage phosphor described here. The modification may be made as formal substitutions, excess, deficit and / or additions.

1. Gadolinium (Gd) is partially replaced by one or more rare earth elements from the group (lanthanum (La), lutetium (Lu), yttrium (Y)). Preferred are the combinations (Gd and Y), (Gd and La). Particularly preferred is the combination of Gd and La.

2. Aluminum (AI) is replaced in whole or in part by one or more elements of the group comprising gallium (Ga) or scandium (Sc). In addition, Al may also be partially replaced by silicon (Si) and / or germanium (Ge). Preferably, Al is partially replaced by Ga.

3. Compared with the stoichiometric charge-balanced formulation of a gadolinium-aluminum garnet (Gd ₃ ) (Al ₅ ) O ₁₂ , the rare earth elements mentioned above under 1 st point may differ in total from the stoichiometric amount at the gadolinium position to stabilize the defect structure.

4. Compared to the stoichiometric charge-balanced formulation of a gadolinium-aluminum garnet (Gd ₃ ) (Al ₅ ) O ₁₂ , the previously mentioned under the 2nd point Elements at the aluminum position differ in total from the stoichiometric amount to stabilize the defect structure.

5. The material resulting from the above steps is preferably doped with cerium, which occupies the place of one of the ions of the rare earth elements (see point 1) (Gd, La, Lu, Y).

The modifications from points 1 to 5 concern the host lattice (garnet) in its composition and the deviations from the ideal stoichiometry as well as the luminous centers. Ce ³⁺ ions preferably represent the emissive luminous centers (hereinafter also referred to as emitters). It has been found that with the abovementioned deviations from the formulation of a stoichiometric, in particular cerium-doped, gadolinium aluminum garnet, both the defect structure of the optical storage phosphor can be influenced, as well as its band gap and the associated position of the electronic level with respect to the Dotierion and thus the location of the levels in the lighting and falling centers. This has an effect on the achievable intensity of the optically stimulated luminescence, the charging and readout spectra and the achievable readout speed and intensity of the afterglow.

Furthermore, the following modifications can be made:

6. As codoping one or more elements from the group Ag, Cr, Hf, Mo, Nb, Sn, Ta, Ti, W, Zr can be selected. These ions can lead to a more complex substitution, especially concerning the AI position, but also with effect on the Gd position. In particular, no charge neutrality of the nominal formulation is made by adding e.g. Forced alkaline earth ions. It has been found that this allows the defect structure of the OSP to be influenced in a targeted manner and thus trap conditions can be provided.

7. Instead of or in addition to the codopositions mentioned under the previous 6th point, it is also possible for one or more elements from the group Pr, Nd, Sm, Eu, Tb, Dy, Ho, Er, Tm, Yb and bismuth (Bi) to be doped to be selected. These ions can provide suitable trap conditions. 8. Furthermore, one or more of the elements B, F, Li, Mg, K and / or Na may be doped. This can be achieved, for example, via the flux used, such as LiF or H3BO3. It has been found that these elements affect the afterglow and readout speed of the storage phosphor.

The chemical modifications of items 6 to 8 are taken as codotides, since they are present only in low concentration (comparable to the concentration of the light centers) and / or due to deviating ion sizes and or deviating ion charge (in each case based on the host lattice) complex influences on the Exercise defect structure of the OSP. Concerning the modifications according to the above points, the following effects were observed: Co-dopings according to the above 6th point can control the defect structure of the OSP as well as the dopings according to the 7th point. The difference between the two dopants from the 6th point and the 7th point lies in particular at the place of the substitution, the elements from the 7th point the rare earth elements (La, Gd, Y, Lu) at the gadolinium position. The elements from the 8th point represent doping, which in certain combinations can conducive to influence the formation of the defect structure.

In this application, the use of indefinite articles, such as "a", "an", etc., is not to be construed as limiting. In particular, an indefinite article can be understood to mean both a singular and a plurality, for example in the sense of "at least one" or "one or more", as long as this is not explicitly excluded, as for example by the expression "exactly one" in this application decimal places are usually represented with a dot, in particular of the type "xy", where "y" indicates the first value of the decimal place.

In particular, when a chemical variable, in particular Ln, A, Q, R and T, is used in this application, the phrase "comprising one of the following elements" means that the variable is associated with one of the elements or a combination of those referred to herein As a combination of the elements, an element meaning that two or more atoms of a single chemical element combine to form a molecule. For example, T may be formed as F2.

In this application, the terms "doping" or "codoping" and word formations derived therefrom deliberately refer to materials supplied to the manufacturing process whose concentration significantly exceeds the typical concentration (about 100 ppm) of impurities in the raw materials (typically 300 ppm). If the concentration of an element in the nominal substance formulation is denoted by "0", then this element is not deliberately added and is present at a maximum concentration due to contamination of the raw materials The above-mentioned designation of a doping or codoping from the given minimum concentration is based on an observed Effectiveness in the substance according to the invention.

The OSP is based on a garnet structure. Preferably, the OSP has a garnet structure as a basic structure, whereby production-related minor additional phases can occur. A garnet structure can be generalized in the form {X ₃ } [Y ₂ ] (Z ₃ ) O ₁₂ describe. The brackets denote {.} Dodecahedral, [.] Octahedral, and (.) Tetrahedrally coordinated lattice sites. Further, from Geller, S. (1967), Crystal chemistry of the garnets, Journal of Crystallographic Crystalline Materials, 125 (1-6), l-47, and Grew, ES, Locock, AJ, Mills, SJ, Galuskina, IO, Galuskin, EV, Halenius, U. (2013): Nomenclature of the garnet supergroup, IMA report, American Mineralogist, Volume 98, 785-811, the contents of which are incorporated herein by reference, garnet structures are known.

The starting point for the optical storage phosphor described here is formally the gold-aluminum garnet, whose ideal charge-neutral stoichiometry is

{Gd ₃ } [Al ₂ ] (Al ₃ ) O ₁₂ , simplified as (Gd ₃ ) (Al ₅ ) O ₁₂ . At this gadolinium aluminum garnet elements are replaced by doping, so that then the OSP described here is achieved with its preferred properties. The deviation from the stoichiometric description required here is formally compensated for by specifying the oxygen content 0 ( ₁₂ + d) and the stated proportion T _t . This formal description reflects again that the formation of defects (for example, missing or excess oxygen atoms) leads to the charge neutrality of the resulting Stoffs because no ions are explicitly added for a formally enforced charge balance. This sets the exact value of d. The entirety of the defects occurring in the OSP, together with the consequent electronic states, are referred to as defect structures or defect states. The defect structure describes the effect of local defects and is complementary to the periodic crystal structure, which generates the non-local properties.

The OSP described here has charge carriers (preferably: electrons), light centers and trap centers. Luminescent centers and trap centers are optically active systems in the storage phosphor described here. In particular, the light centers are designed to emit light, that is, they can pass from an excited state of the light centers to a ground state of the light centers while emitting photons. In the case centers, electrons can pass from the conduction band into an excited electronic state of the dive centers and from there, in particular without radiation, relax into the ground state of the dive centers. There they remain stored until enough energy is again supplied by a suitable - preferably optical - process to lift these stored electrons back into the conduction band. The ground states of sink centers are called trap states.

Charge light is light that is suitable (for example, in terms of its wavelength and intensity) to charge the OSP. The reading light is light that is suitable (for example, in terms of its wavelength and intensity) to read out the OSP. The charging pulse is a pulse of charging light and the reading pulse is a pulse of readout light.

The OSP described here is preferably designed so that the charge carriers, by being charged with a charge pulse and / or with a sequence of charge pulses (referred to as charge sequence), at least partially pass from the light centers to the dungeon and / or by applying a read pulse and / or with a sequence of read-out pulses (referred to as read-out sequence) from the case centers at least partially pass into the light centers. In particular, it is possible that the OSP has electrons which, before being subjected to the read-out sequence in FIG located at the dive centers and are energetically raised by applying the readout sequence and diffuse in the conduction band. This leads to a momentary (light-induced) increased conductivity of the optical storage phosphor.

The centers of illumination and the dungeon centers are respectively defect centers in the crystal lattice, which are provided for example by co-doping with two different elements. Furthermore, the defect centers can be selectively produced in a material by high-energy irradiation (for example with particle, gamma and / or X-radiation) and / or also by the process control in the production of the optical storage phosphor (for example quenching of the melt).

In particular, luminous centers and trap centers differ from each other in their spatial position within the OSP and / or by their chemical identity. Charging the OSP with a charge pulse may correspond to oxidation of the light centers and a reduction in the dive centers. Conversely, the reading of the OSP with a read pulse can correspond to a reduction of the luminous centers and an oxidation of the dive centers.

In an OSP described here, different light-matter interactions can occur:

By applying a charging pulse (charging), charge carriers from the ground state are excited at the light centers. In particular, the charging pulse has a defined wavelength and / or a defined pulse duration and / or a defined pulse energy. A charging pulse may have one or more (peak) wavelengths (maxima of the spectral distribution). For example, the charging pulse is designed as a laser pulse. In addition to the wavelength, pulse duration and pulse energy, the beam size and / or the power of the charging pulse can also be used to define it. Several charging pulses in a row are referred to as charging sequence, in particular, measured values can be recorded between the individual charging pulses.

After charging, some excited charge carriers at the light center can spontaneously relax and radiate. This corresponds to the known photoluminescence and is referred to herein as intrinsic luminescence. In particular, intrinsic luminescence has a characteristic cooldown, also referred to as the intrinsic lifetime. Other excited carriers can pass to the trap centers and be stored there.

The charge carriers stored at the trap centers can be excited by energy input, pass to the light centers, and relax there radiantly. If this energy input occurs thermally, this is called thermoluminescence. Room temperature thermoluminescence is also referred to as persistence or persistent luminescence.

The energy input preferably takes place optically by application of a defined readout pulse (readout). In particular, the readout pulse has a defined wavelength and / or a defined pulse duration and / or a defined pulse energy. A read pulse may have one or more (peak) wavelengths. For example, the readout pulse is designed as a laser pulse. In addition to the wavelength, pulse duration and pulse energy, the beam size and / or the power of the read pulse can also be used to define it. Several read-out pulses in a row are referred to as a read-out sequence, in which case measured values can be recorded in particular between the individual read-out pulses.

If charge carriers from the dive centers are excited by a read pulse and then relax at the luminous centers, this is called optically stimulated luminescence (OSL). In particular, the OSL has an intensity and a wavelength spectrum (emission spectrum).

If the intensity of the OSL is measured and stored in a time series for each read-out pulse of a read-out sequence, the read-out curve I (t) is obtained. Alternatively, a single read-out pulse may be applied, which lasts until the intensity of the OSL has dropped markedly, for example to 50% or 10% of the initial value. The achieved signal intensity of the OSL depends on the intensity and wavelength (read spectrum) of the radiated readout light, as well as on the history of the measurement. A higher intensity of the read pulse leads to an initially increased OSL signal intensity and faster readout of the substance. The influence of characteristic, substance-specific effects, such as transport and recovery effects, collective energy transfer processes and radiation loose contributions, then leads to deviations from a purely exponential behavior of the readout curve. The shape of the curve thus depends on the properties of the substance, on the temperature and other environmental influences, as well as on the wavelength, intensity and time course of the reading light (eg read-out sequence or single read-out pulse).

Empirically, in the case of a single, long-lasting read-out pulse, the readout curve preferably starts with a power function of the type / (t) =

where t = 0 designates the beginning of the readout and a, b and c represent characteristic parameters of the matching caused by properties of the substance, the readout light and the environment. If one compares two substances under defined ambient conditions under the same read sequence or the same single read pulse, then the readout curve is substance-specific. In this context, the specific authenticity rating is based.

The OSP described here has in particular a charging spectrum. The charging spectrum describes how effectively the OSP can charge with charging pulses of different wavelengths. To determine the charge spectrum, you first define a fixed read pulse. Then the OSP is prepared (eg by repeatedly applying the defined read pulse) in such a way that it does not show any OSL - in that case essentially no charge carriers are stored at the trap centers. The OSP prepared in this way is then charged with a charging pulse whose spectrum consists essentially only of a defined wavelength. Subsequently, it is charged with the defined readout pulse and the intensity of the OSL is measured. The measured intensity is stored together with the wavelength of the charging pulse as a value pair. This process (preparation of the OSP, charging, reading, measuring the intensity, saving the value pair) is now repeated for other charging pulses that differ from each other only in their wavelength. It is important to always use the same, defined read pulse. The totality of the value pairs thus obtained gives the charge spectrum. In a preferred embodiment, an OSP is chosen whose charge spectrum has at least one local minimum, in which the intensity of the OSL is reduced by at least 10% compared to the two flanking maxima.

The OSP described here may alternatively or additionally have a readout spectrum. The readout spectrum describes how effectively the OSP can be read with readout pulses of different wavelengths. In order to determine the readout spectrum, one first defines a fixed charge pulse. Then, the OSP is prepared (e.g., by repeatedly applying a read pulse) so that it does not show any OSL - then essentially no carriers are stored at the trap centers. The prepared OSP is now charged with the defined charging pulse. Subsequently, it is charged with a readout pulse, the spectrum of which consists essentially only of a defined wavelength, and the intensity of the OSL is measured. The measured intensity is stored together with the wavelength of the readout pulse as a value pair. This process (preparation of the OSP, charging, reading, measuring the intensity, saving the value pair) is now repeated for other readout pulses that differ from each other only in their wavelength. It is important to always use the same, defined charging pulse. The totality of the value pairs thus obtained gives the readout spectrum.

The OSP preferably has a readout spectrum with a pronounced spectral structure. In particular, the readout spectrum has at least one local minimum, in which the intensity of the OSL is reduced by at least 10%, particularly preferably by at least 30%, in comparison with the flanking maxima.

As already mentioned, the OSP described here is characterized in particular in that it has a memory with regard to at least one property. In particular, measurable properties of the OSP depend on the history of the measurement process used to measure the properties (so-called non-commutativity). This results in a path dependence of the Messergebrüsses. Examples of characteristic memory properties are listed below in this description. That is, one measurement affects the result of the at least one subsequent measurement. At a The measuring process here and below is an exposure of the OSP to a light signal and the recording of a measured value (measurement result) in response to this light signal. The light signal is, in particular, a charge pulse, and / or a read pulse. Several measurement processes in sequence are referred to as a measurement sequence, in particular a measurement sequence can include both charging and readout pulses.

Preferably, the OSP described here has the following properties: Two different optical storage phosphors can have the same property under a first measurement sequence, while they are under a different measurement sequence, different from the first only in parameters such as intensity, sequence or duration of read pulses may have other properties. This property is particularly advantageous for use as an authenticity feature in a value document. The value document may contain a so-called authentic OSP as an authenticity feature. It may indeed be possible for a counterfeiter to generate a trailing OSP which has the same characteristics as the authentic OSP under the first measurement sequence. However, the second measurement sequence can prove that the trailing OSP does not conform to the authentic OSP.

Preferably, the OSP described here has non-commutativity for different measurement processes, that is, the order of the measurement processes is not interchangeable. For example, the OSP is read out with a first and a second measurement process. In this case, it is possible for the first measuring process to influence the system in such a way that the result of the second measuring process depends on the first measuring process. Changing the order of the measurement processes can then lead to a different measurement result. A potential counterfeiter thus has to know the measurement processes used for the authenticity evaluation and the sequence in the measurement sequence for an adjustment of the authentic OSP. This makes the counterfeiting and reenactment of the OSP considerably more difficult.

Examples of characteristic memory properties are described below together with preferred embodiments of the OSP. The values of the memory properties depend on the measuring sequence used and / or the ambient conditions, which creates in the application the close link between authenticity feature and authentication procedure. In addition to the named memory properties, other measured variables, such as, for example, the curvature of the readout curve can also be used as authenticity criterion.

Readout speed of the OSP

In OSP, this size describes how fast a substance can be read out or how quickly the dive centers are emptied of stored charge carriers. It can be described as a relative decrease of the OSL between two equal read pulses. For example, alternative descriptions of the readout speed consider the slope of the readout curve at certain points (e.g., at the beginning, in the middle, or at the end of the readout curve). For pulsed read-out sequences, for example, the maximum or average signal values below the respective read-out pulse can be assigned to the number of the respective read-out pulse and thus parameterize the readout curve.

For example, material properties affect the readout speed, namely readability pulse boostability and charge transport properties, as well as different probabilities of trapping the stimulated charge carriers in (other) trap centers. Furthermore, parameters of the readout pulse, such as wavelength or pulse energy, influence the measured readout speed.

Charging speed of the OSP

In OSP, this size describes how quickly or effectively a fabric can be recharged. For example, it can be described as the relative increase in OSL between two equal charge pulses.

The charging speed can be measured, for example, as follows:

Definition of a fixed read pulse and a fixed charge pulse;

Preparing the OSP so that it does not show any OSL (e.g., by repeatedly applying the defined readout pulse);

Applying the defined charging pulse; Applying the defined read pulse and measuring a first intensity of the OSL.

Reprocess the OSP so that it does not show any OSL (e.g., by repeatedly applying the defined readout pulse);

At least two times applying the defined charging pulse;

Applying the defined read pulse and measuring a second intensity of the OSL.

The charging speed results as a quotient of the second and the first intensity.

The rate of charge depends on material properties of the OSP, such as charge transport properties or intrinsic luminescence, as well as charging pulse parameters such as wavelength or pulse energy.

memory depth

The depth of memory of an OSP indicates how long an event under illumination can be behind with a readout light to significantly influence the result of a measurement. With an OSP, the memory depth can cover spans from a few microseconds to many hours.

In the implementation, for example, the depth of memory of an OSP is viewed under a continuous illumination with a readout light. In this implementation, the OSP is charged with a defined charge pulse. For this purpose, a long-lasting intensive pulse (eg power> 1 W, illumination area 1 mm ² and duration 20 s) at a suitable wavelength (for example 450 nm) is preferably used for this purpose. Then, the OSP is applied with a continuous readout light until the readout curve has fallen below a predefined threshold relative to its output value (for example, below 1% of the maximum signal). For example, the required period of time can be used as a measured value for the memory depth. Since the shape of the reading curve underlying the measurement is not included in the definition of the depth of memory, readout speed and memory depth are related but describe different aspects of the memory of an OSP. Persistence

The persistence of an OSP indicates how long, without illumination but under the influence of the environment, an event can be stored in the OSP. In OSP, trap occupancy may change over time (so-called "fading"), since non-radiative relaxation paths are also accessible at room temperature As a possible method of measuring persistence, after a charge pulse, the waiting time for the first pulse of the subsequent read sequence may be varied From the comparison of the readout curves for different waiting times, it is possible to determine suitable measures of persistence, such as intensity persistence (stability of the signal maximum of the readout curve with respect to the waiting time) or speed persistence (stability of the readout speed compared to the waiting time) For example, the OSP may be prepared prior to each recharge so that it does not show measurable OSL (for example, by repeatedly applying a read pulse).

Preferably, the OSP has a long persistence in the charge pulses used and the environmental conditions chosen. As a result, the charging and reading can be decoupled at the same time and spatially. Alternatively, it is possible that a short persistence of memory is chosen to time and spatially couple the charging and reading, thereby enabling rapid machining and further complicating forgery.

In another preferred embodiment, OSP and charging pulse (s) are chosen so that the persistence of the memory is adapted to the processing speed, i. h., That the persistence of memory is set so that the memory from a waiting time of 50 microseconds, more preferably from a waiting time of 20 microseconds, after charging for the duration of processing is stable.

Interchangeability (also called commutativity) The interchangeability indicates whether two measurement processes on an OSP provide different ^* results depending on their order. For OSP, basically two measurement processes are not necessarily interchangeable. This can easily be demonstrated by considering a charge pulse and a read pulse as a result of measurement. The respective measurement signals under the sequence of the charge pulse readout pulse are different from those under the sequence of the read pulse charge pulse. Assuming in addition that the measuring process comprises a charging pulse and two readout pulses, the measurement result for the second readout pulse depends on the sequence in which the charging pulse and the first read pulse were performed. Even when carrying out the same measurement process (for example, two charging or readout pulses in succession), the same signal does not generally result. This means that storage phosphors represent memory-based systems, so the measurement result depends heavily on the previous history.

Continuity of memory

In an OSP, this quantity describes the extent to which an event in the present can override the memory of past events. For example, a temporary interruption of an otherwise uniform readout sequence is such an event. Measurement of memory continuity in this case can be achieved, for example, by charging an OSP with a charge pulse and then reading it out with an even sequence of five equal read pulses. Then, for a period of time equal to the duration of the previous read sequence of five pulses, the OSP is not illuminated. Subsequently, the OSP is again read out with the same sequence of five readout pulses. To assess the continuity of memory, it is considered whether the two readout curves before and after the interruption can be combined into a single continuous readout curve.

If the cuts are continually assembled before and after the break, the memory will be referred to as continuous under this read sequence. In such a composition, if steps in the readout curve or changes in the readout speed occur, the memory under that readout sequence is said to be non-continuous. Here are also the type and shape of the stage (too big or too small Signal compared to the target, increasing or decreasing). Such deviations from a continuous memory can arise, for example, through parasitic processes, such as re-capture of the charge carriers in case states, direct relaxation or tunneling relaxation and can already be measured on the time scale from around 10 μs. A possible measure of continuity (that is, a measurement derived from the measurement) immediately after the interruption compares the estimated continuation of the readout curve with the one actually measured under the given readout sequence. The continuity thus indicates how strongly an event can influence the "memory", ie the recognizability of past measurement processes.

Instead of an interruption, it is also possible to consider another event such as, for example, another different read pulse, a charging pulse or a temporary temperature change.

In a particularly preferred embodiment, the OSP and the read-out sequences are selected such that the memory of the selected optical storage phosphor among the selected read-out sequences is substantially continuous. For example, for an interruption of 100, the maximum OSL intensity during the first read pulse after the interruption differs by less than 10% from the minimum OSL intensity during the last read pulse before the interruption.

sensitivity

The sensitivity of an OSP indicates how the OSL changes with the parameters of a measurement process. As an example, this has been described above for dependence on the wavelength of charging pulses (charge spectrum) and readout pulses (readout spectrum). Alternatively, the dependence of the optically stimulated luminescence on other parameters of the readout pulses, such as pulse duration or pulse intensity, can be measured. For this purpose, for example, the OSP is charged by a charging pulse and the read-out curve is determined under a first read-out sequence for which, in particular, the first read-out pulse is designated as the reference read-out pulse. Then the OSP is recharged with the same charge pulse as before and the readout curve is read under a second read sequence. is correct, which in turn contains the reference readout pulse as the first readout pulse and whose further readout pulses differ only in intensity from those of the first readout sequence. Preferably, said difference in intensity is interpreted as a percentage scale for all affected readout pulses the same. If the charging pulse has been selected such that the same signal values are obtained under the reference readout pulse of the first and the reference readout pulse of the second readout sequence, the sensitivity of the OSP with respect to the intensity of the readout light can be determined from the readout curves under the first and the second readout sequence determine. For example, the sensitivity of the OSP with respect to the intensity of the readout light can be determined as a sum over the quadratic difference of the signal values of the first and second readout curve. The greater this value, the greater the sensitivity of the OSP under a change in intensity.

associativity

Associativity in an OSP describes how different measurement processes with simultaneous or sequential impact compared to the situation in which each affect only one of the measurement processes that affect OSL. For example, the intensity of the OSL depends on whether two different readout pulses successively affect the substance or overlap in time.

memory strength

The memory strength of the OSP describes how strongly a first measurement process influences a later second measurement process. Compared to the depth of memory, which relates to a period of time, the memory strength relates to a quantitative or qualitative influence on the at least one subsequent measuring process. To evaluate the memory strength, for example, the OSP with a defined charging pulse. (eg power 0.3 W, illumination area 4 mm ² and duration 20 ms) at a suitable wavelength (eg 450 nm). Then, the OSP is applied with a continuous readout light (eg peak wavelength 650 nm, power 450 mW, focused beam) until the readout curve has dropped below a predefined threshold relative to its output value (for example below 20% of the maximum signal ). The readout curve is then with a Power function of type / (t) = adapted. While the parameter a with the

Size is a measure of memory strength: If you measure two different substances as previously stated and determined for the same measurement conditions from the adjustments each of the values of the size so the substance with greater value and the higher memory strength. An increase in memory strength may be beneficial for proof of authenticity, as it accompanies an increased impact of the memory of the OSP on the measurement, which in turn promotes the close link between property and proof of authenticity.

In addition to the memory properties exemplified, the OSPs described herein may have further advantageous properties. It is advantageous to provide substances with different characteristics of the advantageous properties, because there is a group of distinguishable substances as a feature system from which then one or more substances can be selected for a specific application. In accordance with at least one embodiment, the OSP is made readable by the effect of light. In other words, the OSP has a readout spectrum that is in the visible, UV, and / or IR range of the electromagnetic spectrum.

In one embodiment, the readout spectrum of the OSP described here has a maximum in a wavelength range of at least 360 nm to at most 1200 nm, preferably it has a local maximum in a wavelength range of at least 380 nm to at most 420 nm. This wavelength range is below the preferred peak wavelength of the charge pulse of 450 nm and optionally below the preferred emission maximum of the OSL at 560 nm.

Another preferred wavelength range of a maximum of the readout spectrum is between 500 nm and 1200 nm. In another embodiment, the readout spectrum of the OSP has a local maximum in the orange-red spectral range from 600 nm to 640 nm and precipitates at higher wavelengths, ie it occurs no further local maximum. In a further embodiment, the readout spectrum has a local maximum in the range from 570 nm to 610 nm and a further, local maximum in the range from 850 nm to 890 nm up. In a further embodiment, the readout spectrum has a local maximum in the range from 550 nm to 590 nm and falls at a wavelength of 870 nm below a value of 20% of the maximum. In these cases, the local maxima of the readout spectrum are at longer wavelengths than the preferred peak wavelength of the charge pulse of 450 nm and the preferred emission maximum of the OSL at 560 nm.

The aforementioned preferred wavelength ranges of the maximum of the readout spectrum may correspond to a plurality of distinguishable substances which may be combined to form a feature system, for example. In particular, it can be provided that a plurality of substances are used in a system, wherein at least two substances have different readout spectra and / or Aufladespektren. Thus, several spectral ranges can be applied. It has been found that these spectra can be implemented particularly well technically, for example, without having to take any special safety precautions. In addition, many of the substances described here can be efficiently charged or read in the spectral ranges mentioned.

In a further preferred embodiment, the OSL of the OSP has an emission maximum in a wavelength range of at least 500 nm to at most 600 nm, particularly preferably in a wavelength range from 550 nm to 570 nm. The OSL thus has an emission maximum in the green-yellow region of the Electromagnetic spectrum and can thus be separated from both charging and read-out light by technical measures (eg filtering). The wavelengths of the emission spectrum can extend both into the blue and the red spectral range.

There may be additional bands in the emission spectrum of the OSL and / or in the readout spectrum, which may result in particular from the codoped ions. However, a luminescence and / or excitation of the codoping can represent a further energy dissipation channel with regard to the storage of charge carriers, which can have an adverse effect on the intensity of the OSL. At a maximum, this and in the following may generally be a local and / or a global maximum. A suitable for reading the OSP light preferably has a peak wavelength in the wavelength range of the read-out spectrum, particularly preferably at the maximum of the readout spectrum. A peak wavelength here and hereinafter is the wavelength at which the spectral distribution of the light has at least one local maximum, preferably a global maximum.

In accordance with at least one embodiment, the optical storage phosphor has at least one of the following properties:

Decay time of intrinsic luminescence of at most 100 μs, preferably at most 25 μs;

Readout spectrum with at least two local maxima;

Charge spectrum with a maximum at a wavelength of at least 300 nm, preferably from at least 420 nm to at most 500 nm.

The readout spectrum can have at least two maxima. The readout spectrum thus has a clear or pronounced spectral structure. For example, a first maximum lies in a wavelength range of at least 380 nm to at most 420 nm and a second maximum in a wavelength range of at least 500 nm to at most 1200 nm.

The OSP can be rechargeable with light whose wavelength is at least in the UV range, preferably with blue light. As a result, the use of high-energy X-ray radiation can be avoided. Particularly preferably, the OSP can be charged with light having a peak wavelength of 440 nm to 470 nm.

Compared with other potentially usable optical storage phosphors, the optical storage phosphors described here can have further properties which are advantageous, in particular, for use as a security feature.

Thus, the OSP described here preferably exhibits a (measurable) intensive emission, as a result of which an already low concentration of the OSP is sufficient for a fastness evaluation. For example, an OSP of the invention may be provided for the at most a concentration of 1 weight percent in a paper for a proof of authenticity a value document is required. As a result, the disadvantages, such as slow decay time and weaker intensity of alternative materials, such as oxide sulfides of the type Y ₂ O ₂ S: (Eu, Ti, Mg) are solved.

The OSP described here is also chemically stable and has in particular a high chemical stability and / or resistance to water, alkali and acid. Furthermore, the OSP is stable against decomposition by light, for example with a light stability corresponding to a wool scale of at least 4. This can disadvantages of alternative phosphors such. B. alkaline earth sulfides such as (Ca, Sr) S: Eu, Sm, zinc sulfides, such as

ZnS: (Cu, Cl), and / or alkaline earth aluminates such as SrAl ₂ O ₄ Eu.Dy are dissolved.

Compared to a chemical test (test for stability, for example, against moisture, acids, lyes and other chemicals such as solvents, oxidants or detergents), an OSP described here is especially considered to be chemically stable if the OSL intensity of the applied OSP after the test at least 60%, preferably at least 90% of the value reached before the test. In the tests, the OSP is used to mark an item (eg document or banknote), e.g. B. at a particle size (D99) of 5μπι in paper substrate at a concentration of 0.5 weight percent. In the acid test, the marked object is brought into contact with an acid solution (hydrochloric acid) at pH≤0 for 30 minutes. Analogously, in a leach test, the marked object is brought into contact with a basic solution (sodium hydroxide solution) at pH> 12 for 30 minutes. To test the stability to water, the labeled article is in deionized water for 24 hours. In another test, the labeled article is exposed to water vapor at 90 ° C for 4 hours. In an analogous way, further tests can be defined. With regard to moisture, acid and alkali, the optical storage phosphors described herein are highly stable (i.e., they pass the above tests), whereas other storage phosphors, such as those described in US Pat. As alkaline earth sulfides, zinc sulfides or alkaline earth aluminates without costly protective measures are considered to be unstable.

The OSP described herein is preferably not harmful to health and has no harmful decomposition products. The OSP described here preferably has a fast readability (low memory depth combined with high memory strength). For example, with a continuous read pulse (focused laser beam) with a peak wavelength of 638 nm and a nominal light output of 400 mW, the measured OSL signal reduces to 50% in less than 2 ms. This results in particular in comparison to alkaline earth aluminates such as SrAl ₂ 04: Eu, Dy advantages. For comparison, on a typical afterglow (strontium aluminate phosphor, persistence pigment blue from Kremer Pigmente) under the same conditions, this 50% threshold is reached only after a time of more than 7 ms.

The OSP described here also preferably has a sufficiently low afterglow, in particular in the visible spectral range. Thus, unwanted visibility is avoided and a measurability of the OSL signal ensured because a slight overlay of the OSL signal can be ensured with the persistence signal.

For technical applicability, it is advantageous to distinguish between the different types of trap states. Falling states close to the conduction band lead to persistence, while the case states relevant to OSL are so deep (away from the conduction band) that they are not significantly emptied by the thermal energy at room temperature. In a fabric design can thus targeted by the defect structure, i. For example, deviations from the charge-neutral stoichiometry or addition of other foreign ions influence the type, amount and depth of the trap states. In this respect, afterglow and OSL describe different and technically specifically addressable phenomena.

The exact adaptation of the storage phosphor described here can also allow the relative intensity of the intrinsic luminescence in relation to optically stimulated luminescence as well as the saturation behavior and dynamic behavior of the phosphor to be adjusted with regard to afterglow, readout speed and persistence. For this purpose, for example, the cerium doping concentration and codopings, the deviations from a stoichiometric formulation and optionally the concentration ratio of Al / Ga or Gd / other rare earth elements are adjusted. In at least one embodiment of the OSP, Ln is lanthanum (La), lutetium (Lu) or yttrium (Y), where in addition: y> 0. Preferably y> 0.0005 is particularly preferred y> 0.001. Surprisingly, it was found that by combining Gd with one of the substances La, Lu or Y, the intensity of the OSL is increased by a multiple, sometimes more than tenfold. Preferably, x + y> 3.0, more preferably: x + y> 3.0.

In one embodiment of the OSL, p> 0, preferably p> 0.0005 and more preferably p> 0.001. The doping with Ce causes a point defect to form a luminous center.

According to at least one embodiment of the OSP, Ln is lanthanum (La) or yttrium (Y) and Q is zirconium (Zr) or tin (Sn). Furthermore: 0.002≤p≤0.08; 0.002 ≤ q ≤ 0.05; r = 0; k = 0; n≤3; and t ≤ 0.05. The combinations La and Zr, La and Sn and Y and Sn are preferred. For example, the use of La makes it possible to increase the OSL intensity of the OSP, for example by using Zr an increase in the memory strength of the OSP can be achieved. In addition, an OSP with this composition can exhibit significant non-commutativity. For example, the use of Sn can provide a structured readout spectrum with readability in the near UV, in particular at wavelengths much smaller than the emission wavelength.

The OSP can thus have the following composition:

(Gd _x [La, Y] _y ) (Ga _m Al _n ) 0 _{12 ± d} : Ce _p [Zr, Sn] _qT _t . (2)

Here and below, the square bracket [XI, X2] means that one of the two elements is present.

According to at least one embodiment of the OSP, Ln is lanthanum (La) or yttrium (Y) and Q is zirconium (Zr). Furthermore: p = 0; 0.002 ≤ q ≤ 0.02; r = 0; k = 0, n≤3; and t ≤ 0.05. Particularly preferred for Ln is lanthanum (La). In this embodiment, therefore, in particular no cerium is doped, whereby, for example, an increase in persistence can be achieved.

The OSP can thus have the following composition:

According to at least one embodiment of the OSP, Ln is lanthanum (La) or yttrium (Y) and Q is zirconium (Zr) or molybdenum (Mo). Further, R is bismuth (Bi). In addition: 0.005≤p -S 0.08; 0.002 ≤ q ≤ 0.05; 0.002≤r≤ 0.05; k = 0, n≤3; and t ≤ 0.05. The combinations Y and Zr, La and Zr as well as Y and Mo are preferred. For an OSP with such a composition, for example, there is a clearly structured readout spectrum with good readability in the near infrared (NIR).

The OSP can thus have the following composition:

According to at least one embodiment of the OSP, Ln is lanthanum (La) and R is thulium (Tm) or ytterbium (Yb). Further, Q is silver (Ag) and / or zirconium (Zr). It also applies: 0.005≤, p≤ 0.08, 0.002≤ r≤ 0.05; k = 0, n≤3; and t ≤ 0.05. Preferably, q = 0. Such an OSP, for example, shows an increase in the intensity of the optically stimulated luminescence and an increase in the depth of memory.

The OSP can thus have the following composition:

Alternatively, the combination La and Q = (Ag Zr) and r = 0 is possible. Such an OSP, for example, shows an increase in the intensity of optically stimulated luminescence and an increase in persistence.

The OSP can thus have the following composition:

According to at least one embodiment of the OSP, Ln is lanthanum (La) or yttrium (Y), Q is zirconium (Zr), molybdenum (Mo) or tin (Sn), and R is bismuth (Bi). The following applies: 0.1≤y≤1;

0.005≤p≤0.08; 0.002 ≤ q ≤ 0.05; k = 0; t≤ 0.05, 0≤n≤3.5; 1.5≤m≤5; and m + n + 5q / 6 = 5; and 2.95≤x + y + p + r + q / 6≤3.1. The combinations La and Zr are preferred with r = 0, La and Sn with r = 0 and Y and Sn with r = 0. Furthermore, the combinations Q = Mo and R = Bi (r Φ 0) and Q = Zr and R = Bi (r Φ 0), each with La or Y, preferred. For example, such a substance has a structured readout spectrum with an increase in readability in the near infrared (NIR) and / or a reduction in the depth of memory and / or an increase in memory strength.

The OSP can thus have the following composition:

According to at least one embodiment of the OSP, Q is molybdenum (Mo) or zirconium (Zr), where 0.005 ≤ q ≤ 0.05; and t = 0 and / or r = 0. Preferred here is Ln lanthanum (La) or yttrium (Y) and R bismuth (Bi).

The OSP described here can be produced, for example, as described below. The raw materials (starting materials) are each commercially available.

For example, conventional ceramic sintering methods are generally suitable for the production. In such a process, the powdery starting materials in the required mass fractions and optionally with a suitable flux (flux) such as LiF, NaCl, KCl, Na ₂ SO ₄ or K ₂ SO ₄ or the like, mixed and filled in suitable crucible. At a sintering temperature, which depends on the choice of flux, the material is sintered. Typically, one chooses oxidic starting materials, the sintering temperatures are in the range of 800 ° C to 1700 ° C and the burning times are several hours.

An alternative method known in the literature is based on the exothermic reaction of dissolved nitrates of the starting materials with a fuel (so-called "Combustion Synthesis") in which the starting materials present as nitrates are dissolved in water The amounts to be used according to the formulation are for example introduced into a beaker and the adjusted amount of fuel, eg, carbodihydrazide and / or urea, is added and the mixture thus formed is heated and boiled to evaporate the water and allow a foaming gel to form to ignition. Temperature further heated above 400 ° C. The ignition initiates a self-sustained exothermic reaction, at the end of which the phosphor is present as a solid nanoparticulate foam. In this way, rapid screening of substance candidates can be carried out. For the further selection and / or application steps, the OSP is optionally cleaned in one or more washing steps of the flux, brought by grinding / sizing to suitable particle size and processed as a powder, processed in a substrate (for example paper) or in a lacquer further and measured.

The procedure for the application of the OSP as a security feature is preferably in an analogous manner, wherein after grinding / sifting a mixing of the substance with other feature, camouflage and / or adjuvants can be done, in particular, in order to obtain multifunctional features, the feature identity to ensure against adjustments, to adapt the feature for incorporation into a carrier medium (for example, paints or substrates such as paper) and / or to adjust the quality of the feature substance. These optionally blended substances are then suitably introduced into the carrier medium, for example value document.

A method for checking an authenticity feature is also provided. The

Authenticity feature preferably comprises an optical storage phosphor described herein and / or the process is preferably performed on an optical storage phosphor described herein. That is, all the features disclosed for the above-mentioned optical storage phosphor are also disclosed for the method and vice versa.

In addition to providing the authenticity feature, the method comprises the following steps:

a) applying the optical storage phosphor with an optical charging pulse and / or an optical read pulse;

b) detecting a measurement value for an optical emission, in particular intrinsic or optically stimulated luminescence, of the optical storage phosphor in response to the charge pulse and / or the read pulse; c) authenticity evaluation of the security feature, in particular on positive detection of the optical storage phosphor described here, based on the measured value.

The charge pulse is preferably part of a charge sequence that includes charging the charge pulse. Furthermore, the readout pulse is preferably part of a readout sequence that includes the application of the readout pulse.

Particularly preferably, the method always includes applying an optical readout pulse. The OSP can be actively charged by applying an optical charging pulse. Alternatively, it can be exploited that the OSP is charged by the, in particular thermal, background radiation and / or by thermal excitations. In the following, when the charging of the OSP is discussed, it may mean both the active charging with the optical charging pulse and the passive charging.

The application of the charging pulse or of the read-out pulse includes in particular irradiation of the OSP with light, preferably with narrow-band light. In particular, the light has a peak wavelength which is in the range of the charging spectrum of the OSP or the read-out spectrum of the OSP, preferably at a maximum of the charging spectrum or the read-out spectrum. Preferably, the OSP is provided with one or more bursts, i. H. with one or more measurement sequences, acted upon, wherein a measurement sequence from a sequence of identical or different charging and / or readout pulses is composed. In particular, a charging pulse or a readout pulse can be identified by one or more (peak) wavelengths. A charge pulse or a read pulse is preferably a laser pulse. In addition to the peak wavelength, the pulse shape and the pulse duration, the beam size and / or the power of the charge pulse or of the read pulse at the position of the OSP can also be relevant parameters for the present method.

In step b), the measured value is detected for an optical emission of the OSP. The measured value is preferably a series of measured values, ie several measured values. The detection includes in particular the detection of the optical emission. The detection can be time-resolved. For example, a decay curve of the optical emission is measured. The detection can be spectrally resolved, for example, a spectrum of the optical emission is measured.

In step c) the authenticity evaluation of the OSP takes place. This preferably comprises a comparison of the measured value with a reference value stored in a database. Particularly preferably, the fastness evaluation provides a positive result on the correct optical storage phosphor only by using the correct method, in particular the correct method steps and / or the correct sequence of these method steps. Thus, a potential counterfeiter could only check, with knowledge of the correct procedure, if an OSP replicated by him corresponds to the real OSP.

A measuring sequence preferably has a multiplicity of charging pulses and / or a multiplicity of readout pulses. Different charging pulses or readout pulses preferably each have the same peak wavelength and / or the same pulse duration. It is possible that the OSP is initially loaded with a plurality of charge pulses in the measurement sequence and then with a plurality of read pulses. Alternatively, charging pulses and readout pulses may alternate directly with each other. These different measurement sequences make it possible to measure different properties of the OSP.

In a preferred embodiment, the OSP can be acted on with at least one first read pulse and with at least one second read pulse, particularly preferably with a plurality of first and a plurality of second read pulses, wherein the first read pulse and the second read pulse have different peak wavelengths and / or different pulse durations , The first and second readout pulses can be alternately transmitted to the OSP. For example, spectral or temporal sensitivity of the OSP or interchangeability can be addressed.

In accordance with at least one embodiment of the method, step b) comprises evaluating the measured value to determine a memory property of the storage phosphor. The authenticity evaluation in step c) is based on the result of this evaluation. For the determination of the memory property, preferably a read-out curve, individual signal intensities, the mean value and / or the maximum of the signal intensity, and / or the ratio of signal intensities, in particular taking into account a time profile and / or an order, are evaluated.

For example, during the evaluation, the measured value is compared with a value stored in a reference table. By evaluating the measured value, it can be determined in particular in which way the measured value was measured. With known parameters, in particular for the charging pulse and / or the read pulse, and / or in the case of known measurement parameters for the determination of the measured value, it is thereby possible to determine which OSP has been charged and / or in which way the OSP has been charged. Furthermore, it is possible to determine if the OSP has already been read out with another measurement sequence. The determination of the memory property thus allows a determination of authenticity with the OSP.

In accordance with at least one embodiment of the method, steps a) and b) comprise the following substeps:

al) applying the charging pulse and / or a first read pulse to the OSP;

a2) applying the OSP with a second read pulse;

b1) detecting a first measured value, which may be the above-described measured value, by detecting an optical emission of the OSP in response to the charging pulse and / or the first read-out pulse;

b2) detecting at least one second measured value by detecting an optical emission of the OSP in response to the second readout pulse.

The second measured value is dependent on the charging pulse and / or the first read pulse in step al). The steps al), a2), bl) and b2) are preferably carried out in the order indicated. The use of two readout pulses makes it possible in particular to determine the interchangeability of the readout pulses as a memory property of the OSP. If the OSP is non-commutative, a different order of the first and second read pulses results in a different result for the first and second measurements. In accordance with at least one embodiment of the method, step b) further includes at least one of the following steps:

Determining and evaluating parameters of the charging pulse and / or read pulse;

Determining and evaluating a measuring parameter used to acquire the measured value;

- determining and evaluating a background radiation;

- Determining and evaluating a temporal relationship between the charging pulse and / or the read pulse and the detection of the measured value.

The parameters of the charging pulse or of the readout pulse are, in particular, the abovementioned properties of the charging and / or readout pulse, such as wavelength, pulse duration and / or pulse energy, preferably their peak wavelength. Furthermore, the parameters may be the number of charging pulses used and / or the readout pulses used. The parameters may further include the power and / or beam diameter of the charge pulse or read pulse at the location of the OSP.

The measurement parameters include, for example, the manner of measuring the measured value. Preferably, the measurement parameters include information about the detector used, such as its spectral resolution (spectral bandwidth), its spatial resolution and / or its temporal resolution (bandwidth). The information about the measurement parameter used may be advantageous, in particular, when a plurality of signals are emitted by the OSP in response to the read pulse and / or the charge pulse.

The background radiation is in particular the background of the measurement. By determining the background radiation or with its knowledge, disturbing influences of the environment can be removed from the measured value. In particular, the temporal relationship is the time sequence between the charge pulse and the read pulse and / or between successive charge pulses and / or between successive read pulses and / or between the charge pulse or the read pulse and the detection of the measurement value. The temporal relationship is preferably the chronological order of the method steps used in the method. The timing relationship between the charge pulse and the read pulse and / or between successive charge pulses and / or between successive read pulses and / or between a charge pulse or read pulse and the determination of the measurement may allow an accurate determination of the OSP. For example, by knowing the temporal relationship, it is possible to determine memory characteristics of the OSP. Furthermore, it is possible to perform an authentication procedure based on the temporal relationship knowing the corresponding memory property.

For example, two different OSPs may have the same or similar emission characteristics with respect to their wavelength. However, they can have different time constants of the emission. The time constants are caused for example by a different depth of memory, a different charging speed and / or a different readout speed. By knowing the temporal relationships between light pulses and measuring processes, such different time constants can be determined and taken into account in the evaluation. It is also possible that different time sequences in an otherwise identical measurement sequence can lead to different measured values for different OSPs. This may be, for example, a consequence of differing persistence of the two OSPs. By altering the time intervals between charge pulses and / or read pulses and / or detection, it is thus possible to determine the otherness of two otherwise equally behaving OSPs.

In accordance with at least one embodiment, the optical storage phosphor has a specific defect structure which has been produced, for example, by the modifications 1 to 8 described here. The defect structure may be manifested in the characteristic nature of the storage properties and / or the optically stimulated luminescence, and be characterized by the memory properties and other OSL descriptive measures.

In accordance with at least one embodiment of the method, the optical storage phosphor has trap centers and illumination centers, wherein charge carriers present in the optical storage phosphor are at least partially located in the dungeon prior to step a). Furthermore, the charge carriers pass at least partially into the dying centers through the charging pulse from the luminous centers and / or through the read pulse from the dungeon centers at least partially into the luminous centers, whereby they radiantly relax in the luminous centers.

In this case, the radiant relaxation of the luminous center is preferably measured as the measured value. Furthermore, the time interval between the charge pulse and the read pulse and / or the read pulse and the detection of the measured value can be determined as a temporal relationship. For example, the temporal relationship provides information about the diffusion of the charge carriers between the luminous centers and the dive centers.

It is possible that the charge carriers stored in the OSP are not released significantly from the trap centers by the thermal energy at room temperature. In particular, the average residence time (so-called persistence) of the charge carriers in the trap centers at room temperature may be longer, preferably at least five times longer and more preferably at least 100 times longer than the duration of the authenticity evaluation method used. This can typically be done in 0.1 to 10 seconds. Preferably, the persistence is longer than 5 ms, in particular longer than 50 ms. In one embodiment, the persistence is longer than 750 ms and preferably longer than 5 min.

For example, the charge carriers stored in the case centers are only released by the supply of a suitable amount of energy, namely the readout pulse. The released charge carriers can then relax at the light center with the emission of light (so-called radiative relaxation), thereby enabling reading of the storage phosphor. According to at least one embodiment of the method, an electrical conductivity of the optical storage phosphor during charging with the charging pulse and / or the read pulse in step a) is higher than outside the charging.

During charging with the charging pulse (possibly with the charging sequence) and / or with the read-out pulse (optionally with the read-out sequence), the OSP may have a changed light-induced electrical conductivity due to the movement of the charge carriers. During the charging sequence and / or during the read-out sequence, the storage phosphor preferably exhibits a maximum electrical conductivity which is higher, in particular at least 50% higher, than outside these processes.

According to at least one embodiment of the method, a further measured value is detected by detection of an optical intensity before step a). This measurement can be used, for example, to determine background radiation, or it can indicate, via the measurement of a possible intrinsic luminescence, that the OSP is already charged before the start of the method described here.

There is further provided an apparatus for performing a method of testing

Authenticity indicated with an optical storage phosphor. The device is preferably designed for carrying out a method described above, particularly preferably with an OSP described above. That is, all features disclosed for the method and for the OSP are also disclosed for the device and vice versa.

The device comprises a light source which is set up to apply the at least one charge pulse and / or the at least one read pulse to the OSP. Furthermore, the device comprises a detection device for detecting the optical emission and for detecting the measured value, in particular in step b). The device comprises an evaluation device, which is set up to evaluate the detected measured value and to carry out the authenticity evaluation in step c) on the basis of the evaluation. The device is particularly adapted to provide a specific positive detection of the storage phosphor and based on the proof the evaluation for authenticity of the security feature, such as a value document to perform.

During operation, the light source preferably emits light which has a peak wavelength in the wavelength range of the readout spectrum and / or of the charging spectrum. In particular, the light in the wavelength range of the readout spectrum can be emitted independently of light, in particular temporally and / or spatially separated, from light in the wavelength range of the charge-up spectrum. For example, the light source includes one or more light emitting diodes and / or laser diodes, optionally with conversion elements to provide green, yellow and / or red light.

The device can be set up, for example, for use in ATMs (also often referred to as ATM), a GeldAeinzählvorrichtung, a bill validator and / or a verification unit for ID documents. The device preferably includes a control unit, such as a computer, in particular a PC or a microcontroller. The control unit may be configured to control the light source such that the desired measurement sequence is provided with the charge pulse and / or the read pulse. The device has, in particular, a receiving unit for receiving documents of value, such as banknotes or passports. The device can operate independently of a server as a self-sufficient system or connected to a server. The server can be locally deployed. Alternatively or additionally, the device may be in communication with or connected to a server external to a local network in which the device is located. The server can take over tasks for the evaluation of measurement results and for the authenticity evaluation and / or provide data for the authenticity evaluation and / or evaluation of measurement results. In particular, it may be a server in a cloud environment. The server can provide instructions concerning the sequence and parameters of the charging and readout pulses as well as the measurement processes. These instructions may differ depending on the type of value document being checked. Furthermore, an authenticity feature and a value document are specified. The

Authentication feature and the value document each preferably include an optical storage phosphor described herein. Furthermore, the authenticity of the authenticity feature or of the value document is preferably checked by a method described here, in particular using a device described here. That is, all the features disclosed for the OSP, for the method, and for the device are also disclosed for the authentication feature and the value document and vice versa.

In accordance with at least one embodiment, the authentication feature comprises an OSP described here. The authenticity feature is preferably an additive for a value document, in particular for a carrier material of the value document, and / or do a film element. In particular, the authenticity feature can be applied to the value document in the form of a printing ink, as a pigment and / or as a coating composition, for example as a lustrous substance in an ink. Furthermore, during the production of a support material of the value document, the OSP can be introduced into the support material, for example as a pigment during the sheet formation of a security paper.

According to at least one embodiment of the authenticity feature has in the

Authenticity feature existing OSP a pronounced spectral structure, in particular with at least two local maxima. The two local maxima are preferably the two maxima of the read-out spectrum described above. The spectral structure then corresponds in particular to the readout spectrum.

According to at least one embodiment of the authenticity feature has in the

For example, under focused exposure to readout light of appropriate wavelength (ie, peak wavelengths in the range of the readout spectrum) at a power of at least 350 mW, the OSL intensity may be less than 5 ms below 20% of the initial Signals are brought. In accordance with at least one embodiment, the value document contains at least one authenticity feature described here, in particular with an optical storage phosphor described here. The value document is preferably a banknote. The document of value may further be an identification document, such as a passport, a ticket, a token and / or another object, such as a certificate, the authenticity of which is to be affirmed or witnessed by the authenticity feature. Particularly preferably, the value document has a substrate made of paper and / or plastic. The authenticity feature is particularly preferably introduced into the volume of the value document and / or applied to the value document.

Brief description of the figures

Preferred further embodiments of the invention are explained in more detail by the following description of the figures and by exemplary embodiments. Hereby show:

FIG. 1 shows an exemplary embodiment of an optical storage phosphor described here and of a method for checking an authenticity feature with an OSP according to the invention;

Figures 2, 3, 4, 5, 6, 7 and 8: embodiments of methods according to the invention. Detailed description of preferred embodiments

In the following, an optical storage phosphor according to the invention, a method according to the invention, the device according to the invention described here, the authenticity feature according to the invention described here as well as the value document according to the invention described here according to the invention are explained in more detail by means of preferred embodiments. For this purpose, reference is made in particular to associated figures, which serve the better understanding.

In the figures, the same, similar, similar or equivalent elements are given the same reference numerals. On a repeated description of these elements is partially omitted to avoid redundancies. The figures and the proportions of the elements shown in the figures with each other are not to be considered to scale. Rather, individual elements may be exaggerated in size for better representability and / or better understanding.

1, a general mode of operation, in particular a general exemplary embodiment, of an optical storage phosphor (OSP) described here within the scope of the invention is explained in greater detail. FIG. 1 shows in simplified form the processes associated with optically stimulated luminescence (OSL) and the energy scheme of an, in particular inorganic, optical storage phosphor. The optical storage phosphor includes a luminous center 11 and a trap center 12 with trap states 121. I _exc denotes light for exciting the luminous center 11, which may also be suitable for charging the OSP. _Em denotes light emitted by the illumination center 11, in particular both intrinsic luminescence and optically stimulated luminescence. I _OSL designates the stimulating (read-out) light, which can excite a stored charge carrier (in the figure, for example, as an electron e- indicated in FIG. 1) in the conduction band CB at the case center. A possible involvement of holes h + from the valence band VB is indicated.

It may be characteristic of the OSP described here that two independent optical systems, in the present exemplary embodiment a luminous center 11 and a trap center 12, couple in a light-driven manner with one another. If the OSP is irradiated with radiation of suitable energy (eg wavelength, intensity, duration), electrons e- are lifted into the conduction band CB - or into states on the conduction band CB - at the luminous center 11 (usually a metal ion). This is referred to as process (1) in FIG. In the conduction band, the charge carriers diffuse e- (process (2)) and can from there to energetically lower case states 121 (English traps, associated with the case centers 12) get and stored in these case states 121 (process (3)). These trap states 121 are at different energy distance from the conduction band CB. If the trap states 121 are so close to the conduction band CB that the thermal energy at room temperature is sufficient to empty them, this leads to thermoluminescence at room temperature, which is described as afterglow or persistent luminescence. In In the case of falling trap states 121, the thermal energy at room temperature is insufficient to lift the charge carriers back into the conduction band CB. In these deep trap states 121, the charge carriers are stored in an e-stable manner. Only by supplying a suitable amount of energy, for example by the irradiation with light, are the charge carriers e- brought into an excited trap state and can be released into the conduction band CB (process (4)). The charge carriers e-diffuse again in the conduction band CB (process (2)) and at least partially recombine at the light center 11 with the emission of light (process (5)).

In contrast to phosphorescence, in which the excited carrier e- is itself brought into a triplet state in the luminous center 11 and relaxes from this with a characteristic time constant into another state of the luminous center 11, a reversible, light-driven donor-acceptor reaction takes place in the OSP instead of. In a simplified representation of this reversible, light-driven donor-acceptor reaction, the luminous center donates a charge carrier as a donor during the storage process (as a rule, the luminous center 11 is oxidized) and a different trap center 12 accepts the charge carrier e.sub.n as the acceptor level 12 is usually reduced). At the case center 12, the charge carrier e- is bound in a case state 121. In order to empty the trap state 121, it is necessary to reverse the previous process so that the trap center 12 then donates a charge carrier (ie is oxidized) as a donor and the light center 11 accepts (ie is reduced) the charge carrier e-acceptor. These can diffuse through the conduction band CB between the emission and the absorption of the charge carriers e-, so that a light-induced, persistent conductivity can also be detected in these systems.

In the described mechanism, trap state 121 is bound to a trap center 12 (such as a vacancy, a doped impurity ion as a substitution atom, interstitial atoms, or even more complex aggregated defects). It is advantageous if the charge carriers e- relax into the energetic ground state of the trap center 121 (falling ground state) and thus are not present in a triplet state with a limited lifetime. The dungeon centers 12 together face the light centers 11 independent optical system. Thus, the associated electronic states are independent of those of the lighting centers 11th

By way of example, a method according to the invention and a device described here for carrying out the method for determining and / or authenticating an OSP are explained in greater detail on the basis of the schematic representation of FIG.

The optical storage phosphor (OSP) 26 is measured with the measuring device with regard to its optical properties. The device contains a light source 21 for charging the OSP, a further light source 22 for reading, a detector 23 with a filter 24 and a device for data recording and evaluation 25.

The light source 21 and / or the light source 22 may, for example, each be a light emitting diode or a laser diode or a spectrally tunable device such as a metal halide lamp with adjustable monochromator. The detector 23 is a photodiode, preferably a Si avalanche photodiode module, with adapted collecting optics. The filter 24 can be a bandpass filter with a passband of 500 nm to 600 nm, preferably with a central wavelength of 550 nm and a half-width of 40 nm or central wavelength of 570 and a half-width of 30 nm. This reduces the intensity of the reading and charging light on the detector 23, so that the OSL can be measured with higher accuracy. The OSP 26 is for example applied to a measuring carrier, introduced into a paper or is present in powder form in a measuring cuvette.

For the determination of the read-out spectrum of the OSP 26, it is alternately pulsed at the same location by the two light sources 21, 22, and the emitted light is detected. In this case, the wavelength of the reading light is tuned, for example by 5 nm from pulse to pulse. Comparability is achieved by suitable adjustment of the exposure time and intensity of the charging pulse as well as the readout pulse. For example, the intensity of the charging pulse may be so great that after charging substantially all of the trap states are occupied. The assignment of the detector signal to the wavelength of the reading light gives the readout spectrum. To evaluate the dynamic behavior of the OSP 26, the OSP 26 is irradiated with a charging pulse and then with several equal read pulses (see also the scheme of energy levels of Figure 1). Here, the wavelength of the light of the read pulse is fixed. For each read pulse, the intensity of the OSL is measured. The readout curve can be determined from the assignment of the detector signal to the elapsed time since the beginning of the readout, namely since the first read pulse. The readout curve describes the dynamic behavior of the storage phosphor under the selected conditions (duration, intensity and wavelength of the charging and readout pulses).

From the readout curve can be determined for the behavior of the storage phosphor characteristic dimensions, eg. B. measures for the readout speed under the selected conditions, for example on the intensity ratio at certain times during the readout sequence or on appropriate, even logarithmic, derivatives. These characteristic measures are in particular the measured value described above.

In the following, further exemplary embodiments, in particular preferred compositions, of an OSP described here and their application in a method described here will be explained. The stated amounts and weights of substances are to be understood within the usual manufacturing tolerances.

The selection of preferred substances is preferably carried out by measuring with different relevant, but each recorded measurement sequences several substances having the compositions described herein and a specially tuned defect structure, and selects those with suitable properties. In particular, for the group of selected substances, the measurement result for one measurement sequence deviates from the measurement result for another (possibly also similar) measurement sequence. This corresponds to the said advantage of the close coupling of detection method and feature substance - according to the memory property of the OSP.

Because of the close linkage between an optimally suitable OSP and the detection method, a screening study may help to find suitable formulations of substances. the. For a demonstration of authenticity detection via optically stimulated luminescence, a suitable material is selected by preparing a series of candidate materials according to the stoichiometric compositions described herein and then evaluating how well the candidates can be charged and read, with both temporal and spectral behavior and the obtained intensities of the photoluminescence and the OSL can be evaluated. In addition, properties such as fading and / or relative intensities z. B. during the first readout relative to the charging or the ratio of the intensities of the OSL for two or more different wavelengths of the readout light can be used.

The respective preferred compositions of matter have been subjected to different measurement sequences in accordance with one embodiment of a test method described herein. In particular, the sequences of embodiments 1 to 18 are used as embodiments of a test method described herein.

In all measurements, the illumination spots of the different laser illuminations overlap significantly on the sample (OSP). The emitted light is measured with an avalanche photodiode module with suitable detection optics for imaging the measuring spot onto the detector and filtering (bandpass filtering with 550 nm central wavelength and 44 nm half-width). The output signal is read out via a fast A / D converter at 2 Msample / s and processed on the PC. Unless otherwise explicitly described, the maximum intensity of the Nth pulse of a readout sequence measured on the substance s is referred to as IN (S). If this variable is normalized to the first pulse of the associated readout sequence, it is referred to as l _{N, norm} (s).

Unless otherwise stated, the charging and readout pulses in the ms range are to a good approximation rectangular pulses, the power indicated is the average power over the pulse duration.

In the description of the example substances, the nominally stoichiometry is stated in each case without the charge compensation by the adaptation of the oxygen content (ie the size d) or possible incorporation from added flux (ie the quantity t) being explicitly stated. imagine. That is, for the production of the specified molar fraction of the constituent elements (without exact consideration of the oxygen content), the amount of raw material to be used in each case be developed.

1st embodiment: nominal

The first embodiment of the OSP (substance 1) is produced by means of "combustion synthesis." The starting materials used are the corresponding nitrates

weighed into an Erlenmeyer flask and dissolved in about 150 ml of water. The other substances are pipetted from aqueous stock solutions, so that correspondingly 3.3565 g of A1 (NO ₃ ) 3-9 (H ₂ O), 0.0097 g of Ce (NO ₃ ) ₃ -6 (H ₂ O), and 0.01 g of Yb (NO 3 ) 3-5 (H 2 O) in solution. As fuel, a mixture of 1.6121 g of carbohydrazide CH ₆ N ₄ O and 4.2317 g of urea CH ₄ N ₂ O is added. The substances are completely dissolved and the solution further heated on a hot plate in an explosion-proof trigger. In compliance with the prescribed safety measures, the substance mixture is finally brought to ignition. After complete reaction, a yellow powder is present. Finally, the OSP is post-annealed again at 1250 ° C for 10 hours. Data from the X-ray structure analysis confirmed the existence of a garnet structure with only minor additions of other phases.

2nd embodiment: nominal

Ceo.005, Tmo.oos

The OSP according to the second embodiment (substance 2) is produced by means of "combustion synthesis" The production follows in the course of that of substance 1. The raw materials used and amounts of substance are: 5.1395 g Gd (NO ₃ ) 3-6 (H ₂ O), 0.9706 g La (NO ₃ ) 3-6 (H ₂ O), 4.6509 g Ga (NO ₃ ) 3-5 (H ₂ O), 3.3635 g Al (NO ₃ ) 3-9 (H ₂ O), 0.01 g Tm (NO ₃ ) 3-5 (H ₂ O), 0.0097g

Ce (NO ₃ ) ₃ -6 (H ₂ O).

3rd embodiment: nominal

The OSP according to the third embodiment (Substance 3) is prepared by flux-assisted solid state synthesis. For this, the starting materials are thoroughly mixed with 10 g of K 2 SO 4 as flux and calcined in air in a corundum crucible at 1200 ° C. for 10 h. Subsequently, the flux is washed out. Used raw materials and Substance quantities are:

Substances 1 to 3 were experimentally compared in terms of their readout speed. For this purpose, the powders of substances 1 to 3 were ground to a grain size of about 15 μιτι according to D99, ie, 99% of the particles are smaller than 15 .mu.m, and introduced in a proportion of 0.8 weight percent in a test paper (standard laboratory method for sheet production) and measured.

With a charge pulse, trap states were initially occupied in the substances (pulse duration 20 ms). After a further 20 ms waiting time the read pulse starts (pulse duration 20ms). The charging pulse is generated by a laser diode with a peak wavelength of 450 nm, a power of 350 mW and a spot diameter of 6 mm. The readout pulse is generated by a focussed laser diode with a peak wavelength of 638 nm and a power of 450 mW.

The emitted light is measured with an avalanche photodiode module with an optically focused optics and optical filtering. The output signal is read out via a fast A / D converter at 2 Msample / s and processed on the PC.

After correction of the signal to the striking portion of the red read laser and normalization, the characteristic times, which are shown in Table 1 below. Shown is a comparison of the time periods up to a certain signal value (90%, 50% and 20%) when reading the substances 1 to 3 under the same conditions. These characteristic times describe how long it takes from the start time of the readout until the OSL signal has decayed to a certain relative value. The term OSL signal designates the signal corrected by an offset value, which is obtained when the substance is read out. In a comparative measurement of commercial strontium aluminate phosphor (persistence pigment blue), the 50% value under these conditions was reached only after 7.88 ms.

4th embodiment: nominal

The OSP according to the fourth embodiment (substance 4) is prepared by flux-assisted solid state synthesis. The production follows in the course of that of substance 3. The raw materials and amounts of substance used are: 0.6236 g Y ₂ 0 ₃ , 5.0855 g Gd ₂ 0 ₃ , 1.1263 g Al ₂ O ₃ , 3.1054 g Ga ₂ 0 ₃ , 0.0184 g Ce (S0 ₄ ) ₂ , 0.0066g Mo0 ₃ , 0.0322g Bi ₅ 0 (OH) ₉ (N0 ₃ ) 4 and 10g K2SO4 as flux.

Measurements for substances 1 to 4

The readout spectra of substances 1 and 4 were compared experimentally. For this purpose, the powders of substances 1 and 4 were each added to PMMA cuvettes and measured in a laboratory setup. The substances 1 and 4 were alternately charged with a pulse of a blue-emitting laser diode (peak wavelength 450 nm, power 300 mW, slightly expanded beam with about 3 mm diameter, pulse duration 6 ms) and with a durchirnmbaren laser light source (pulse duration in Range of 15 ns, maximum pulse energy 15 μΐ, beam diameter approx. 1 mm). The emitted radiation was measured with an amplified Si detector, the signal digitized and evaluated on the PC.

For some of the laser wavelengths, the ratio of the OSL signals I of substance 4 normalized to the maximum, in each case, relative to substance 1, ie, I ₀ rm (4) / Inorm (I), is given in Table 2. For the same wavelengths in Table 2, the normalized to the maximum OSL signal for the measurement of substance 1 is given.

5th embodiment: nominal Gd2.52Lao.5Al2.36Ga2.5O12: Ceo.005, Bio.01, M00.02

The OSP according to the fifth embodiment (substance 5) is prepared analogously to substance 1 by combustion synthesis. The starting materials were Gd (NO ₃ ) 3-6 (H ₂ O),

La (NO ₃ ) 3-6 (H ₂ O), Ga (NO ₃ ) ₃ -5 (H ₂ O), A1 (NO ₃ ) ₃ -9 (H ₂ O), Ce (NO ₃ ) ₃ -6 (H ₂ 0) Bi (NO 3) 3 * 5H 2 O as well as a molybdenum analysis standard solution for the spectroscopy with lg / 1 Mo in each case according to the indicated molar amounts used.

Measurements for the substance 5

An exemplary embodiment of a method described here is explained in more detail in conjunction with FIG. Fabric 5 was used for the measurements shown, although it is also possible to use other compositions of matter with appropriate adaptation of the parameters. The OSP was subjected to a proof of authenticity according to the method described here.

The entire measurement sequence used (sequence 1) is structured as follows:

1) Charge pulse (laser diode, peak wavelength 450 nm, around 450 mW power, defocused to approx. 4 mm illumination diameter, duration 100 μs). The end of the pulse defines the time zero point for the measurement sequence.

2) 1 ms waiting time.

3) Read pulse or read sequence: Alternate 8 pulses R and R *.

Pulse R: Laser diode with a peak wavelength of 638nm, around 600 mW power, focused, pulse duration 4μs followed by 6μs waiting time before the following pulse R *, Pulse R *: Laser diode with a peak wavelength of 852 nm and with around 720 mW power, focused, pulse duration 4 μs followed by 6 μs waiting time before the following pulse R). 4) Repeat the measurement sequence with a cycle time of 2ms.

For the experiments, the substance was 5 to a particle size of about 5 microns. milled to D99 and added to a test paper (standard laboratory method for sheet production) in a proportion of 1% by weight and measured.

Figure 3 shows the normalized readout curve (I _norm ) as a function of time from the measurement with the above sequence 1. The respective signals are shown during the readout pulses. From the course of the readout curve can be concluded on the OSP used. In particular, this shows the good readability of substance 5 at red and near-infrared (NIR) wavelengths. The data are preferably further processed, for example by averaging the signal for each pulse and using the ratio of the signal intensity of the nth pulse to the signal intensity of the first pulse S _n / S _l . In addition, for example, the read-out speed can also be described as a percentage pulse-to-pulse decrease in the signal intensity under defined pulse parameters of the readout pulses. This example also shows the different effects of the read pulses R and R *.

6th embodiment: nominal

The OSP according to the sixth embodiment (Substance 6) is prepared by flux-assisted solid synthesis. For this purpose, the starting materials are thoroughly mixed with the addition of flux and calcined in a corundum crucible at 1200 ° C for 10 h.

Substances used are: 0.8795 g La ₂ O _{3 /} 4.9701 g Gd ₂ 0 ₃ , 1.1010 g Al ₂ O ₃ , 3.0360 g Ga ₂ O ₃ ,

0.01256g ZrCLi. For substance 6, no cerium was added.

Measurements for the substance 6

An exemplary embodiment of a method described here is explained in more detail in conjunction with FIGS. 4a, 4b and 4c, as well as with FIG. In the process, the fabric 6 was subjected to a proof of authenticity.

The measuring sequence used here (sequence 2) is structured as follows: 1) Charge pulse (laser diode with a peak wavelength of 450 nm and with about 350 mW power, duration 20 ms, defocused to about 6 mm illumination diameter). The time zero for this measurement sequence is given by the beginning of the charge pulse.

2) 65 ms waiting time

3) Eleven Pulse G (pulse G: laser diode with a peak wavelength of 638nm and with about 300 mW power, focused, pulse duration 0.2 ms followed by 0.3 ms waiting time before the following pulse G).

4) Repeat the measuring sequence with a cycle duration of 100 ms.

FIG. 4a shows the measured detector signal S1 (in volts) at the OSP over time, FIG. 4b shows the time profile of the trigger signal S2 for charging (corresponding to the charging pulses) and FIG. 4c shows the time profile of the trigger signal S3 for reading out (according to the readout pulses). FIG. 5 shows the read-out sequence in detail, namely in FIG. 5 a) the time profile of the detector signal S 1 (offset-biased readout curve) and b) the curve of the associated trigger signal S 3 (ie the readout pulses). The authenticity criterion used is, for example, the shape of the envelope of the read-out curve or the ratio of the signal intensities of the first read-out pulse to the last read-out pulse.

Further embodiments 7 to 18

Further substances 7 to 18 were prepared by flux-assisted solid-state synthesis. The production follows in the course of that of substance 3. The substances are listed with their nominal composition in Table 3. Total quantities were 20 g each, of which 10 g K2SO4 were used. The raw materials from Table 4 were used as sources for the elements specified in the respective composition of matter. The raw materials (see Table 4) were each added in the amount of element necessary for the stated compositions of matter. Table 4 shows an overview of the raw materials used for Substances 7 to 18.

Measurements for substances 7 to 13

For the above substances 7 to 13, different measurements were made according to an embodiment of a method for testing described here in order to describe the effect of changes in the matrix of the OSP, of dopants and / or their concentrations on the properties of the OSP.

For this purpose, the respective substances were measured with the following measurement sequence (sequence 3):

1) Charge pulse (laser diode with a peak wavelength of 450 nm and with about 400 mW power, duration 20 ms, spot about 3 mm in diameter). The time zero corresponds to the beginning of the charging pulse.

2) 23.6 ms waiting time after the end of the charging pulse

3) Six repetitions of a pair of pulses (ST):

Pulse S: Laser diode with a peak wavelength of 638nm (red) and with about 450 mW power, focused, pulse duration 0.2 ms followed by 0.2 ms waiting time before the following pulse T

Pulse T: Laser diode with a peak wavelength of 915 nm (NIR) and with approximately 500 mW power, focused, pulse duration 0.2 ms followed by 0.2 ms waiting time.

4) Repeat the measurement sequence with a cycle time of 50 ms.

Table 5 lists suitable measures and their definitions. IN designates the maximum signal intensity of the Nth read-out pulse of the measurement sequence. The measured variables given here illustrate, by way of example, how the data of a measurement sequence can be evaluated and are by no means to be understood as a complete enumeration of a data execution. Further measured variables can be defined and alternative evaluation methods (such as direct comparison with target data, adjustments, standardization for intrinsic signals) can be made. Table 6 gives an overview of the measured quantities for substances 7 to 13 defined in Table 5.

For the applications next to substance 7 (which has a high OSL signal Lax, but hardly reacts to the NIR components), the other substances appear interesting, since they are also significantly readable with the NIR pulses (visible in parameter Q) and have distinguishable speeds. These substances show, for example, differences in their spectral sensitivity and in their readability.

Measurements for substances 7 and 14 to 17 For the above substances 7 and 14 to 17, further measurements were made according to one embodiment of a method of testing described herein to describe the effect of changes in the matrix of the OSP, dopants and / or their concentrations on the properties of the OSP.

For this purpose, the respective substances were measured with the following measurement sequence (sequence 4):

1) Charge pulse (laser diode with a peak wavelength of 450 ran and with about 350 mW power, duration 20 ms, spot about 6 mm in diameter). The time zero corresponds to the beginning of the charging pulse.

2) 23.6 ms waiting time after the end of the charging pulse.

3) Twelve pulses U: (laser diode with a peak wavelength of 638nm with about 400 mW power, focused, pulse duration 0.2 ms) followed by 0.2 ms waiting time before the following pulse

4) Repeat the measurement sequence with a cycle time of 50 ms.

Table 7 lists suitable measures and their definitions. IN designates the maximum signal intensity of the Nth read-out pulse of the measurement sequence. Table 8 gives an overview of the measured quantities for substances 7 (as reference) and 14 to 17 defined in Table 7.

Normalized readout curves for substance 7 (reference 67), substance 15 (reference 615) and substance 16 (reference 616) are shown in FIG. 6, wherein for each readout pulse of sequence 4 the maximum signal I _{N, norm} of pulse N is plotted against the pulse number N. The curves are each normalized to the signal of the first pulse. This example illustrates the effect of the composition of the OSP on its properties as shown here by way of example in the measured values (Tables 7 and 8) or also in the direct comparison of the readout curve (FIG. 6). In particular, the comparison of the readout curve for substance 15 (reference numeral 615) and 16 (reference numeral 616) makes it clear that small changes in the composition significantly change the defect structure of the substance, which results in the marked change in characteristic measured variables (for example as in Tables 7 and 8) and / or read-out curves (as shown, for example, in FIG. 6): the read-out speeds and the read-out curves of the individual substances differ significantly from one another.

Measurements for substances 3, 7, 13 and 16

For the fabrics 3, 7 and 13 and for fabric 16, further measurements were made according to one embodiment of a method of testing described herein to determine properties of the fabrics exemplifying the readability in the near UV range.

The measurements were first carried out with the following measuring sequence (sequence 5): 1) charging pulse (laser diode with a peak wavelength of 450 nm with approximately 300 mW power, duration 20 ms, spot approx. 3 mm diameter). The time zero corresponds to the beginning of the charging pulse. 2) 80.252 ms Waiting time after the end of the charging pulse.

3) Twelve pulses Z: Laser diode with a peak wavelength of 398 nm with approximately 280 mW power, focused, pulse duration 0.2 ms followed by 0.2 ms waiting time before the following pulse.

4) Repeat the measuring sequence with a cycle duration of 100 ms.

In addition, the following measurement sequence (sequence 6) was then used:

1) Charge pulse (laser diode with a peak wavelength of 450 nm with approximately 300 mW power, duration 20 ms, spot approx. 3 mm diameter). The time zero corresponds to the beginning of the charging pulse.

2) 43,841 ms Waiting time after the end of the charging pulse.

3) 6 repetitions of a pair of pulses (SZ):

Pulse S: laser diode with a peak wavelength of 638nm with a power of 450 mW, focused, pulse duration 0.2 ms followed by 0.2 ms waiting time before the following pulse Z. Pulse Z: laser diode with a peak wavelength of 398nm with about 280 mW power, focused, pulse duration 0.2 ms followed by 0.2 ms waiting time before the following pulse S.

4) Repeat the measurement sequence with a cycle time of 50 ms.

Table 9 lists suitable measures and their definitions for sequences 5 and 6. In this case, IN denotes the maximum signal intensity of the Nth read-out pulse of the respective measurement sequence. Table 10 contains a list of the measured quantities for substances 3, 7 and 13 and 16 defined in Table 9.

By way of example, these substances show different spectral sensitivities which can be ascertained not only in intensity ratios but also in readout speeds, as follows from the values in Table 10.

Measurements for the substance 18

Substance 18 shows an efficient readability, especially at 398 nm, while it is hardly readable in the red and NIR spectral range. For the detection, substance 18 of measurement sequence 6 as well as another measurement sequence 7 was subjected and the data were evaluated.

The measurement sequence used (sequence 7) is as follows:

1) Charge pulse (laser diode with a peak wavelength of 450 nm with about 300 mW power, duration 20 ms, spot about 3 mm in diameter). The time zero corresponds to the beginning of the charging pulse.

2) 43,841 ms Waiting time after the end of the charging pulse.

3) 6 repetitions of a pair of pulses (TZ):

Pulse T: Laser diode with a peak wavelength of 915 nm with approximately 500 mW power, focused, pulse duration 0.2 ms followed by 0.2 ms waiting time before the following pulse Z. Pulse Z: Laser diode with a peak wavelength of 398nm with approximately 280 mW power, focused, pulse duration 0.2 ms followed by 0.2 ms waiting time before the following pulse T. 4) Repeat the measurement sequence with a cycle time of 50 ms.

The comparison of the measurements of the substance 18 for the sequence 6 (reference numeral 76) and the sequence 7 (reference numeral 77) is shown in FIG. FIG. 7 shows a sequence of the respective maximum normalized signal Im, norm of the mth readout pulse as a function of the number m of the readout pulse. Even pulse numbers (upper measured values) correspond to pulses of type Z, ie a wavelength of the readout light of 398 nm, while odd pulse numbers (lower measured values with an intensity below 0.1) correspond to a wavelength of the readout light of 638 nm (type S, measuring sequence 6). 915 nm (type T, measuring sequence 7). Pulse Z is thus able to read the substance 18, while for pulses S and T the signals remain below 0.1. It can be seen that the substance 18 can be read out above all at a wavelength of 398 nm, i. at a wavelength shorter than the emission wavelength and even shorter than the preferred wavelength of the charge of about 450 nm.

Further embodiments: Substances 19, 20 and 21

The influence of slight changes in the chemical composition of the garnet matrix on the properties of the OSP will be examined on the basis of the further exemplary embodiments of the substances 19, 20 and 21. Total amounts were 20g each, of which 10g flux K2SO4 were used. The raw materials from Table 4 were used as sources for the elements specified in the respective composition of matter. The raw materials were each added in the amount of element necessary for the stated compositions of matter.

Substances 19, 20 and 21 were prepared by flux-assisted solid-state synthesis. The production follows that of substance 3. The nominal composition of the substances is as follows:

Fabric 19 contains no lanthanum, fabric 20 is an approximately stoichiometric formulation, while fabric 21 has a significant excess of rare earth elements (here: Gd). These three substances are compared with a measurement sequence according to an embodiment of a method described here. The measurement sequence (sequence 8) is structured as follows:

1) Charge pulse (laser diode with a peak wavelength of 450 ran with about 350 mW power, duration 3.5 ms, spot about 5 mm in diameter). The time zero corresponds to the beginning of the charging pulse.

2) 1.52 ms waiting time after the end of the charging pulse.

3) Twelve pulses V (pulse V: laser diode with a peak wavelength of 638nm with about 1600 mW power, illuminated rectangular spot on the sample approx. 1mm x 4mm, pulse duration 0.2 ms followed by 0.2 ms waiting time before the following pulse V). The time zero for this read sequence is given by the beginning of the first read pulse

4) Repeat the measurement sequence with a cycle time of 10 ms.

For comparison, the maximum signal values I _m for each read pulse m are shown as readout curves in FIG. 8 for the three substances.

The effect of lanthanum codoping can be seen in the comparison of the signals to the first readout pulse. Substance 19 (reference numeral 819) hardly shows an OSL signal (here 33 mV, with approximately 15 mV already originating from the residual permeability of the filters used), while the maximum signal under the same conditions for substance 20 (reference numeral 820) is around 190 mV. For fabric 19, a trustworthy readout speed can not be specified because the signal has little variation. For substance 20, the signal goes from 100% (1st read pulse) to 49% (12th pulse) under measurement sequence 8. In the case of substance 21 (reference numeral 821), the excess of rare earth elements (here: Gd) under sequence 8 leads to a further increased initial intensity of the OSL of 415 mV. At the same time, the signal normalized to the respective maximum readout pulse between two readout pulses (i.e., without light irradiation) for fabric 21 is only about 60% of that of fabric 20 (not shown), indicating a reduced afterglow.

By changes in the defect structure, as here, for example, by slight change in the composition of the host lattice (introduction of La) and / or by low Deviation from the nominal charge neutrality (excess Gd) can be achieved, it is possible to achieve clearly measurable differences in the characteristics, for example, memory strength and read-out speed here. At the same time, undesirable properties such as afterglow can be suppressed. This example emphasizes that the defect structure is part of the substance.

The invention is not limited by the description based on the embodiments of these. Rather, the invention encompasses any novel feature as well as any combination of features, including in particular any combination of features in the claims, even if this feature or combination itself is not explicitly stated in the patent claims or exemplary embodiments.

Claims

claims

1. An optical storage phosphor based on a garnet structure and having the following composition:

(Gd _x Ln _y ) (Ga _m Al _n A _k ) 0 ₁₂ + d: Ce _p Q _q R _r T _t ,

in which

Ln comprises at least one of the following elements: La, Lu, Y;

A comprises at least one of the following elements: Ge, Sc, Si;

Q comprises at least one of the following elements: Ag, Cr, Hf, Mo, Nb, Sn, Ta, Ti, W, Zr;

R comprises at least one of the following elements: Bi, Pr, Nd, Sm, Eu, Tb, Dy, Ho, Er, Tm, Yb;

T comprises at least one of the following elements: B, F, Li, Mg, K, Na;

- 1.0≤x≤3.2 and 0≤y≤1.65;

- 0.5≤ m≤5.2, 0≤n≤4.7 and 0≤k≤0.5, where 4.8≤m + n + k≤5.2;

- 0≤p≤0.1, where p = 0 only for Q = Zr;

- 0 ≤ q ≤ 0.05;

- 0≤r≤ 0.05;

- 0≤t≤0.1;

- 0≤d≤0.5;

- p + q> 0.002;

- q + r> 0.002; and

- 2.8≤x + y + p + r≤3.2.

2. An optical storage phosphor according to claim 1, wherein 0≤y, preferably 0.0005≤y, preferably 0.001≤y, is.

3. Optical storage phosphor according to one of the preceding claims, wherein 0≤q, preferably 0.0005≤q preferably 0.001≤q, and / or 0≤r, preferably 0.0005≤r, preferably 0.001≤r, is.

4. Optical storage phosphor according to claim 2 and 3, wherein Ce, Q and / or R form two independent optical systems, which can be converted by at least two-stage external energy input in its initial state.

5. Optical storage phosphor according to one of the preceding claims,

- wherein the optical storage phosphor is formed by light irradiation readable,

- Wherein a readout spectrum of the optical storage phosphor has a maximum in a wavelength range of at least 360 nm to at most 1200 nm, and

- wherein preferably the optically stimulated luminescence of the optical storage phosphor in the wavelength range of 500 nm to 600 nm has an emission maximum.

6. Optical storage phosphor according to one of the preceding claims, wherein the optical storage phosphor has at least one of the following properties:

- Decay time of an intrinsic luminescence of the optical storage phosphor of at most 100 μs;

- Readout spectrum with at least two maxima;

- Charging spectrum with a maximum at a wavelength of at least 300 nm.

7. Optical storage phosphor according to one of the preceding claims, wherein

- Ln is lanthanum (La) or yttrium (Y) and

- Q is zirconium (Zr) or tin (Sn), with:

- 0.002≤p≤0.08;

- 0.002 ≤ q ≤ 0.05;

- r = 0;

- k = 0, n≤3;

- and t≤ 0.05.

8. An optical storage phosphor according to any one of claims 1 to 3, wherein

- Ln is lanthanum (La) or yttrium (Y) and - Q Zirconium (Zr) is, with

- p = 0;

- 0.002 ≤ q ≤ 0.02;

- r = 0;

- k = 0, n≤. 3;

- and t≤ 0.05.

The optical storage phosphor according to any one of claims 1 to 6, wherein

- Ln is lanthanum (La) or yttrium (Y) and

- Q is zirconium (Zr) or molybdenum (Mo),

- R bismuth (Bi) is, with

- 0.005≤p≤0.08;

- 0.002 ≤ q ≤ 0.05;

- 0.002≤r≤ 0.05;

- k = 0, n≤3;

- and t≤ 0.05.

10. An optical storage phosphor according to any one of claims 1 to 6, wherein

- Ln is lanthanum (La);

R is thulium (Tm) or ytterbium (Yb) and

- Q is silver (Ag) and / or zirconium (Zr), with

- 0.005≤p≤> 0.08

- 0.002≤r≤ 0.05;

- k = 0, n≤3;

- and t≤ 0.05.

11. An optical storage phosphor according to any one of claims 1 to 6, wherein

Ln is lanthanum (La) or yttrium (Y),

- Q is zirconium (Zr), molybdenum (Mo) or tin (Sn) and

- R bismuth (Bi) is, where

- 0.1≤y≤l;

- 0.005≤p≤0.08; - 0.002 ≤ q ≤ 0.05;

- k = 0;

- t ≤ 0.05;

- 0≤n≤3.5; 1.5≤m≤5;

- and m + n + 5q / 6 = 5

- and 2.95≤x + y + p + r + q / 6≤3.1.

12. An optical storage phosphor according to the preceding claim, wherein

- Q is molybdenum (Mo) or zirconium (Zr), where

- 0.005 ≤ q ≤ 0.05;

- and t = 0 and / or r = 0.

13. A method of testing an authenticity feature with an optical storage phosphor according to one of the preceding claims, comprising the following steps:

b) detecting a measurement value for an optical emission of the optical storage phosphor in response to the charge-up pulse and / or the read-out pulse;

c) authentication of the security feature based on the measured value.

14. Method according to the preceding claim, wherein step b) further comprises evaluating the measured value for determining a memory property of the storage phosphor, and wherein the authenticity evaluation in step c) is based on the result of this evaluation.

15. The method according to one of the two preceding claims, wherein step b) further includes at least one of the following steps:

Determining and evaluating a parameter of the charging pulse and / or reading pulse;

- determining and evaluating a background radiation; - Determining and evaluating a temporal relationship between the charging pulse and / or the read pulse and the detection of the measured value.

16. The method according to any one of claims 13 to 15, wherein the optical storage phosphor has trap centers and luminous centers, wherein

- Are present in the optical storage phosphor charge carriers prior to step a) at least partially in the dungeon and

- The charge carriers pass through the charging pulse from the light centers at least partially in the dungeon and / or pass at least partially through the read pulse from the dive centers in the light centers and relax radiant in the light centers.

17. The method according to any one of claims 13 to 16, wherein an electrical conductivity of the optical storage phosphor during charging with the charging pulse and / or the read pulse in step a) is higher than outside of the impingement.

18. The method according to any one of claims 13 to 17, wherein prior to step a), a further measured value is detected by detecting an optical intensity.

19. An apparatus for carrying out a method according to any one of claims 13 to 18, comprising

a light source (21, 22) which is adapted to charge the optical storage phosphor (26) with the at least one charge pulse and / or the at least one read pulse in step a),

- A detection device (23, 24) for detecting the optical emission and for detecting the measured value in step b), and

an off-value device (25) which is set up to evaluate the detected measured value and to perform the authenticity evaluation on the basis of the evaluation on the basis of a specific positive detection of the storage phosphor in step c).

20. Authenticity feature with an optical storage phosphor according to one of claims 1 to 12.

21. Authenticity feature according to the preceding claim, wherein the optical storage phosphor has a readout spectrum with a pronounced spectral structure, in particular with at least two local maxima.

22 valuable document with at least one authenticity feature according to one of the two claims.