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

Abstract

An optical storage phosphor, a method for checking an authenticity feature, and an apparatus for carrying out a method, relate to an authenticity feature and to a value document. An inorganic optical storage phosphor is provided having a garnet structure and predetermined composition.

Claims

1. An authenticity feature comprising an optical storage phosphor based on a garnet structure, the optical storage phosphor having the following composition:
(Gd.sub.xLn.sub.y)(Ga.sub.mAl.sub.nA.sub.k)O.sub.12±d:Ce.sub.pQ.sub.qR.sub.rT.sub.t, 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, wherein 4.8≤m+n+k≤5.2; 0≤p≤0.1, wherein 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. The authenticity feature according to claim 1, wherein 0<y.

3. The authenticity feature according to claim 1, wherein 0<q, and/or 0<r.

4. The authenticity feature according to claim 3, wherein Ce, Q and/or R form two independent optical systems which can be transferred into their initial state by at least two-stage external energy input.

5. The authenticity feature according to claim 1, wherein the optical storage phosphor is configured to be readable by light irradiation; wherein a read-out 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 the optically stimulated luminescence of the optical storage phosphor has an emission maximum in the wavelength range from 500 nm to 600 nm.

6. The authenticity feature according to claim 1, 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; read-out spectrum with at least two maxima; charging spectrum with a maximum at a wavelength of at least 300 nm.

7. The authenticity feature according to claim 1, 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. The authenticity feature according to claim 1, wherein Ln is lanthanum (La) or yttrium (Y) and Q is zirconium (Zr), with p=0; 0.002≤q≤0.02; r=0; k=0, n≤3; and t≤0.05.

9. The authenticity feature according to claim 1, wherein Ln is lanthanum (La) or yttrium (Y) and Q is zirconium (Zr) or molybdenum (Mo), R is bismuth (Bi), 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. The authenticity feature according to claim 1, 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. The authenticity feature according to claim 1, wherein Ln is lanthanum (La) or yttrium (Y), Q is zirconium (Zr), molybdenum (Mo) or tin (Sn) and R is bismuth (Bi), wherein 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 as well as 2.95≤x+y+p+r+q/6≤3.1.

12. The authenticity feature according to claim 11, wherein Q is molybdenum (Mo) or zirconium (Zr), wherein 0.05≤q≤0.05; and t=0 and/or r=0.

13. A method for checking an authenticity feature according to claim 1, comprising the following steps of: applying an optical charging pulse and/or an optical read-out pulse to the optical storage phosphor; capturing a measured value for an optical emission of the optical storage phosphor in response to the charging pulse and/or the read-out pulse; authenticity assessment of the security feature by means of the measured value.

14. The method according to claim 13, wherein step b) further comprises evaluating the measured value in order to determine a memory property of the storage phosphor, and wherein the authenticity assessment in step c) is effected by means of the result of this evaluation.

15. The method according to claim 13, wherein step b) further includes at least one of the following steps of: determining and evaluating a parameter of the charging pulse and/or the read-out pulse; determining and evaluating a measurement parameter made use of to capture the measured value; determining and evaluating a background radiation; determining and evaluating a temporal relationship between the charging pulse and/or the read-out pulse and the capture of the measured value.

16. The method according to claim 13, wherein the optical storage phosphor has trap centers and luminous centers, wherein charge carriers present in the optical storage phosphor are located at least partially in the trap centers before step a) and the charge carriers transition at least partially from the luminous centers into the trap centers due to the charging pulse and/or transition at least partially from the trap centers into the luminous centers due to the read-out pulse and relax radiatively in the luminous centers.

17. The method according to claim 13, wherein an electrical conductivity of the optical storage phosphor during the application of the charging pulse and/or the read-out pulse in step a) is higher than outside the application.

18. The method according to claim 13, wherein before step a) a further measured value is captured by detecting an optical intensity.

19. An apparatus for carrying out a method according to claim 13, comprising a light source, which is adapted to apply the at least one charging pulse and/or the at least one read-out pulse to the optical storage phosphor in step a), a detection device for detecting the optical emission and for capturing the measured value in step b), and an evaluation device which is adapted to evaluate the captured measured value and, by means of the evaluation, to carry out the authenticity assessment on the basis of a specific positive detection of the storage phosphor in step c).

20. The authenticity feature according to claim 1, wherein the optical storage phosphor has a read-out spectrum with a pronounced spectral structure, with at least two local maxima.

21. A value document having at least one authenticity feature according to claim 1.

Description

BRIEF DESCRIPTION OF THE FIGURES

(1) Preferred further embodiments of the invention are explained in more detail by the following description of the figures and of embodiment examples. There are shown:

(2) FIG. 1: an embodiment example of an optical storage phosphor described herein and a method for checking an authenticity feature with an OSP according to the invention;

(3) FIGS. 2, 3, 4, 5, 6, 7 and 8: embodiment examples of methods according to the invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENT EXAMPLES

(4) In the following, an optical storage phosphor according to the invention, a method according to the invention, the apparatus according to the invention described here, the authenticity feature according to the invention described here, and the value document according to the invention described here are explained in more detail with reference to preferred embodiment examples. For this purpose, reference is made in particular to associated figures which serve for a better understanding.

(5) In the figures, elements which are identical, of similar type, similar or identically acting are equipped with the same reference numerals. A repeated description of these elements is partly omitted in order to avoid redundancies. The figures and the mutual size ratios of the elements represented in the figures are not to be considered to scale. Rather, individual elements can be represented in an exaggerated size for better representation and/or better understanding.

(6) A general mode of operation, in particular a general embodiment example, of an optical storage phosphor (OSP) described here within the scope of the invention is explained in more detail with reference to the schematic representation of FIG. 1. FIG. 1 reproduces in a simplified manner 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.sub.exc denotes light for exciting the luminous center 11, which can also be suitable for charging the OSP. I.sub.em denotes light emitted from the luminous center 11, in particular both intrinsic luminescence and optically stimulated luminescence. I.sub.OSL denotes the stimulating (reading out) light which can excite a stored charge carrier (indicated by way of example as electrons e.sup.− in FIG. 1) at the trap center into the conduction band CB. A possible involvement of holes h.sup.+ from the valence band VB is indicated.

(7) It can be characteristic of the OSP described here that two independent optical systems, in the present embodiment example a luminous center 11 and a trap center 12, couple to one another in a light-driven manner. When the OSP is irradiated with radiation of suitable energy (e.g. wavelength, intensity, duration), at the luminous center 11 (as a rule a metal ion) electrons e.sup.− are lifted into the conduction band CB—or into states on the conduction band CB. This is referred to as process (1) in FIG. 1. The charge carriers e.sup.− diffuse in the conduction band (process (2)) and from there can reach energetically lower trap states 121 (associated with the trap centers 12) and can be stored in these trap states 121 (process (3)). These trap states 121 are at different energetic distances from the conduction band CB. When the trap states 121 are so close to the conduction band CB that the thermal energy at room temperature is already sufficient to empty them, this leads to thermoluminescence at room temperature, which is described as afterglow or persistent luminescence. In the case of deeper trap states 121, the thermal energy at room temperature does not suffice to lift the charge carriers e.sup.− again into the conduction band CB. In these deep trap states 121, the charge carriers e.sup.− are stored in a stable manner. Only by feeding a suitable amount of energy, for example by irradiation with light, are the charge carriers e.sup.− brought into an excited trap state and can be released into the conduction band CB (process (4)). The charge carriers e.sup.− diffuse again in the conduction band CB (process (2)) and recombine at least partially at the luminous center 11 while emitting light (process (5)).

(8) In delimitation against phosphorescence, in which the excited charge carrier e.sup.− is brought into a triplet state in the luminous center 11 itself and relaxes therefrom 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. In a simplified representation of this reversible, light-driven donor-acceptor reaction, during the storage process, the luminous center emits a charge carrier as donor (as a rule the luminous center 11 is oxidized) and a trap center 12 different therefrom receives the charge carrier e.sup.− as acceptor (the trap center 12 is thus generally deoxidized). The charge carrier e.sup.− is bound at the trap center 12 in a trap state 121. In order to empty the trap state 121, it is required to reverse the preceding process, so that the trap center 12 then emits a charge carrier e.sup.− as donor (thus is oxidized) and the luminous center 11 receives the charge carrier e.sup.− as acceptor (thus is deoxidized). The charge carriers e.sup.− can diffuse through the conduction band CB between the emission and the reception of the charge carriers e.sup.−, so that a light-induced, persistent conductivity can also be found in these systems.

(9) In the mechanism described, the trap state 121 is bound to a trap center 12 (such as a vacancy, an alien ion to be doped as a substitution atom, interstitial atoms, or also more complex aggregated defects). It is advantageous if the charge carriers e.sup.− relax into the energetic ground state of the trap center 121 (trap ground state) and thus are not present in a triplet state with a limited lifespan. The trap centers 12 together represent an optical system which is independent of the luminous centers 11. The associated electronic states are thus independent of those of the luminous centers 11.

(10) By way of example, a method according to the invention and an apparatus described here for carrying out the method for determining and/or assessing the authenticity of an OSP is explained in more detail with reference to the schematic representation of FIG. 2.

(11) The optical storage phosphor (OSP) 26 is measured with regard to its optical properties by means of the measuring apparatus. The apparatus includes a light source 21 for charging the OSP, a further light source 22 for reading out, a detector 23 with a filter 24 and an apparatus for data recording and evaluation 25.

(12) The light source 21 and/or the light source 22 can be, for example, respectively a light-emitting diode or a laser diode or a spectrally tunable apparatus such as a halogen metal vapor lamp with a settable monochromator. The detector 23 is a photodiode, preferably a Si avalanche photodiode module, with adjusted collector optics. The filter 24 can be a bandpass filter having a passband of 500 nm to 600 nm, preferably having a central wavelength of 550 nm and a full width at half maximum of 40 nm or a central wavelength of 570 and a full width at half maximum of 30 nm. As a result, the intensity of the read-out light and the charging light on the detector 23 is reduced, so that the OSL can be measured with higher accuracy. The OSP 26 is applied, for example, to a measuring carrier, is introduced into a paper or is present in powder form in a measuring cuvette.

(13) For determining the read-out spectrum of the OSP 26, the OSP 26 is alternately illuminated in a pulsed manner at the same location by the two light sources 21, 22, and the emitted light is detected. The wavelength of the reading-out light is tuned here, for example by 5 nm from pulse to pulse. Comparability is achieved by suitably setting the exposure duration and the intensity of the charging pulse and of the reading-out pulse. For example, the intensity of the charging pulse can be so great that, after charging, substantially all the trap states are occupied. The allocation of the detector signal to the wavelength of the reading-out light yields the read-out spectrum.

(14) In order to assess the dynamic behavior of the OSP 26, the OSP 26 is irradiated with a charging pulse and subsequently with several identical read-out pulses (see also the diagram of the energy levels of FIG. 1). The wavelength of the light of the read-out pulse is fixed here. The intensity of the OSL is measured for each read-out pulse. The read-out curve can be determined from the allocation of the detector signal to the elapsed time since the start of the read-out, namely since the first read-out pulse. The read-out curve describes the dynamic behavior of the storage phosphor under the selected conditions (duration, intensity and wavelength of the charging and read-out pulses).

(15) Characteristic measures can be determined from the read-out curve for the behavior of the storage phosphor, for example measures for the read-out speed under the selected conditions, for example via the intensity ratio at specific times during the read-out sequence or via suitable, also logarithmic, derivations. These characteristic measures are in particular the measured value described above.

(16) Further embodiment examples, in particular preferred substance compositions, of an OSP described here and the application thereof in a method described here are explained in the following. The substance amounts and weights stated are to be understood in each case within the customary manufacturing tolerances.

(17) The selection of preferred substances is preferably effected by measuring several substances having the compositions described here and a specially matched defect structure with different relevant, but in each case recorded measurement sequences, and selecting those substances with suitable properties. In particular, for the group of selected substances, the measurement result for a measurement sequence differs from the measurement result for a different (optionally also similar) measurement sequence. This corresponds to the specified advantage of the close coupling of detection method and feature substance—corresponding to the memory property of the OSP.

(18) Due to the close linkage of an optimally suitable OSP to the detection method, a serial examination can be helpful for finding suitable formulations of substances. For an embodiment of the authenticity detection for optically stimulated luminescence, a suitable substance is selected by manufacturing a series of substance candidates according to the stoichiometric compositions described herein and examining them for how well the substance candidates can be charged and read out, wherein both temporal and spectral behavior and the achieved intensities of the photoluminescence and the OSL can be assessed. In addition, properties such as fading and/or relative intensities, for example during the first read-out relative to the charging or the ratio of the intensities of the OSL for two or several different wavelengths of the read-out light can also be utilized.

(19) The respective preferred substance compositions were subjected to different measurement sequences in accordance with an embodiment example of a checking method described herein. In particular, the sequences of the embodiment examples 1 to 18 are employed as embodiment examples of a checking method described here.

(20) 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 measurement spot onto the detector and filtering (bandpass filtering with 550 nm central wavelength and 44 nm full width at half maximum). The output signal is read out at 2 Msample/s via a fast A/D converter and processed on the PC. Unless explicitly described otherwise, the maximum intensity of the N-th pulse of a read-out sequence measured on the substance s is referred to as I.sub.N(s). If this quantity is normalized to the first pulse of the associated read-out sequence, it is referred to as I.sub.N,norm(s).

(21) Unless stated otherwise, the charging and read-out pulses in the ms range are, in good approximation, rectangular pulses, the stated power is the average power over the pulse duration.

(22) In the description of the exemplary substances, the respectively nominally called-for stoichiometry is designated without explicitly mentioning the charge equalization by adjusting the oxygen content (i.e. the quantity d) or possible incorporation of added fluxing agent (i.e. the quantity t). This means that for the manufacture the quantity of raw material to be used can in each case be concluded from the stated molar proportion of the constituent elements (without exactly taking into account the oxygen content).

1.SUP.st .Embodiment Example

Nominally Gd.SUB.3.04.Al.SUB.2.Ga.SUB.3.O.SUB.12.:Ce.SUB.0.005., Yb.SUB.0.005

(23) The first embodiment example of the OSP (substance 1) is manufactured by means of “combustion synthesis”. The corresponding nitrates are used as starting substances. First, 6.1386 g Gd(NO.sub.3).sub.3.6(H.sub.2O) and 4.6413 g Ga(NO.sub.3).sub.3.5(H.sub.2O) are weighed into an Erlenmeyer flask and dissolved in approximately 150 ml of water. The other substances are pipetted from aqueous stock solutions, so that correspondingly 3.3565 g Al(NO.sub.3).sub.3.9(H.sub.2O), 0.0097 g Ce(NO.sub.3).sub.3.6(H.sub.2O), and 0.01 g Yb(NO.sub.3).sub.3.5(H.sub.2O) are present in solution. A mixture of 1.6121 g of carbohydrazide CH.sub.6N.sub.4O and 4.2317 g of urea CH.sub.4N.sub.2O is added as fuel. The substances are completely dissolved and the solution is further heated on a heating plate in an explosion-proof hood. The substance mixture is finally brought to ignition while complying with the prescribed safety measures. After complete reaction, an yellow powder is present. Finally, the OSP is again post-tempered at 1250° C. for 10 hours. Data of the X-ray structure analysis confirmed the presence of a garnet structure with only slight admixtures of other phases.

2.SUP.nd .Embodiment Example

Nominally G.SUB.2.54.La.SUB.0.5.Al.SUB.2.Ga.SUB.3.O.SUB.12.:Ce.SUB.0.005., Tm.SUB.0.005

(24) The OSP according to the second embodiment example (substance 2) is manufactured by means of “combustion synthesis”. The manufacture follows that of substance 1 with respect to the course of action. Used raw materials and substance quantities are: 5.1395 g Gd(NO.sub.3).sub.3.6(H.sub.2O), 0.9706 g La(NO.sub.3).sub.3.6(H.sub.2O), 4.6509 g Ga(NO.sub.3).sub.3.5(H.sub.2O), 3.3635 g Al(NO.sub.3).sub.3.9(H.sub.2O), 0.01 g Tm(NO.sub.3).sub.3.5(H.sub.2O), 0.0097 g Ce(NO.sub.3).sub.3.6(H.sub.2O).

3.SUP.rd .Embodiment Example

Nominally Gd.SUB.2.52.La.SUB.0.5.Al.SUB.2.Ga.SUB.3.O.SUB.12.:Ce.SUB.0.04., Zr.SUB.0.005

(25) The OSP according to the third embodiment example (substance 3) is manufactured with fluxing-agent (flux) supported solid synthesis. For this purpose, the starting substances are carefully mixed with the addition of 10 g of K.sub.2SO.sub.4 as the flux and are annealed in air in a corundum crucible at 1200° C. for 10 h. The flux is subsequently washed out. Used raw materials and substances quantities are: 0.8704 g La.sub.2O.sub.3, 4.8809 g G.sub.2O.sub.3, 1.0896 g Al.sub.2O.sub.3, 3.0046 g Ga.sub.2O.sub.3, 0.142 g Ce(SO.sub.4).sub.2, 0.0125 g ZrCl.sub.4.

(26) The substances 1 to 3 were compared experimentally with regard to their read-out speed. For this purpose, the powders of substances 1 to 3 were ground to a grain size of about 15 μm according to D99, i.e. 99% of the particles are smaller than 15 μm, and were introduced in a proportion of 0.8 percent by weight into a test paper (laboratory standard method for sheet manufacture) and measured.

(27) With a charging pulse, trap states were first occupied in the substances (pulse duration 20 ms). After a further 20 ms waiting time, the read-out pulse (pulse duration 20 ms) starts. The charging pulse is produced by means of a laser diode having a peak wavelength of 450 nm, a power of 350 mW and a spot diameter of 6 mm. The read-out pulse is produced by means of a focused laser diode having a peak wavelength of 638 nm and a power of 450 mW.

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

(29) After correction of the signal by the penetrating proportion of the red read-out laser and normalization, the characteristic times are obtained, which are represented in Table 1 below. A comparison is shown of the time durations up to a specific signal value (90%, 50% and 20%) when the substances 1 to 3 are read out under the same conditions. These characteristic times describe how long it takes from the starting time of the read-out until the OSL signal has decayed to a specific relative value. The term OSL signal denotes the signal which is corrected by an offset value and which is obtained when the substance is read out. In a comparative measurement on commercial strontium aluminate phosphor (afterglow pigment blue), the 50% value was only reached after 7.88 ms under these conditions.

(30) TABLE-US-00001 TABLE 1 OSL signal OSL signal OSL signal OSL signal Substance 100% value 90% value 50% value 20% value Substance 1 0.0 ms 0.16 ms 1.6 ms 7.8 ms Substance 2 0.0 ms 0.11 ms 1.6 ms 11.0 ms  Substance 3 0.0 ms 0.02 ms 0.3 ms 2.9 ms

4.SUP.th .Embodiment Example

Nominally G.SUB.2.54.Y.SUB.0.5.Al.SUB.2.Ga.SUB.3.O.SUB.12.:Ce.SUB.0.005., Bi.SUB.0.01., Mo.SUB.0.005

(31) The OSP according to the fourth embodiment example (substance 4) is manufactured with fluxing-agent (flux) supported solid synthesis. The manufacture follows that of substance 3 with respect to the course of action. Used raw materials and substance quantities are: 0.6236 g Y.sub.2O.sub.3, 5.0855 g G.sub.2O.sub.3, 1.1263 g Al.sub.2O.sub.3, 3.1054 g Ga.sub.2O.sub.3, 0.0184 g Ce(SO.sub.4).sub.2, 0.0066 g MoO.sub.3, 0.0322 g Bi.sub.5O(OH).sub.9(NO.sub.3).sub.4 and 10 g K.sub.2SO.sub.4 as flux.

(32) Measurements for the Substances 1 to 4

(33) The read-out spectra of the substances 1 and 4 were compared experimentally. For this purpose, the powders of the substances 1 and 4 were in each case 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 approximately 3 mm diameter, pulse duration 6 ms) and with a tunable laser light source (pulse duration in the range of 15 ns, maximum pulse energy 15 μJ, beam diameter approximately 1 mm). The emitted radiation was measured using an amplified Si detector, the signal was digitized and evaluated on the PC.

(34) For some of the laser wavelengths, the ratio of the OSL signals I, in each case normalized to the maximum, of substance 4 relative to substance 1, i.e. I.sub.norm(4)/I.sub.norm(1) is stated in Table 2. For the same wavelengths, also the OSL signal normalized to the maximum for the measurement on substance 1 is given in Table 2.

(35) TABLE-US-00002 TABLE 2 Wavelength I.sub.norm(4)/I.sub.norm(1) I.sub.norm(1) 570 nm 1.4 0.72 635 nm 0.9 1.00 685 nm 0.8 0.85 730 nm 1.1 0.53 785 nm 1.5 0.29 808 nm 2.0 0.21 852 nm 4.1 0.12 940 nm 8.0 0.04 1064 nm  5.8 0.01

5.SUP.th .Embodiment Example

Nominally G.SUB.2.52.La.SUB.0.5.Al.SUB.2.36.Ga.SUB.2.5.O.SUB.12.:Ce.SUB.0.005., Bi.SUB.0.01., Mo.SUB.0.02

(36) The OSP according to the fifth embodiment example (substance 5) is manufactured analogously to substance 1 by combustion synthesis. The starting substances used were Gd(NO.sub.3).sub.3.6(H.sub.2O), La(NO.sub.3).sub.3.6(H.sub.2O), Ga(NO.sub.3).sub.3.5(H.sub.2O), Al(NO.sub.3).sub.3.9(H.sub.2O), Ce(NO.sub.3).sub.3.6(H.sub.2O) Bi(NO.sub.3)3*5H2O, and a standard molybdenum analysis solution for spectroscopy with 1 g/1 Mo in each case according to the stated molar amounts.

(37) Measurements for the Substance 5

(38) An embodiment example of a method described here is explained in more detail in connection with FIG. 3. For the measurements shown, the substance 5 was employed, wherein it is also possible to employ other substance compositions with corresponding adjustment of the parameters. The OSP was subjected to authenticity detection according to the method described here.

(39) The entire measurement sequence employed (sequence 1) is constructed as follows: 1) Charging pulse (laser diode, peak wavelength 450 nm, about 450 mW power, defocused to approximately 4 mm illumination diameter, duration 100 μs). The pulse end defines the time zero point for the measurement sequence. 2) 1 ms waiting time. 3) Read-out pulse or read-out sequence: in each case alternating 8 pulses R and R*. Pulse R: laser diode with a peak wavelength of 638 nm, about 600 mW power, focused, pulse duration 4 μs with subsequently 6 μs waiting time before the subsequent pulse R*, Pulse R*: laser diode with a peak wavelength of 852 nm and with about 720 mW power, focused, pulse duration 4 μs with subsequently 6 μs waiting time before the subsequent pulse R). 4) Repeating the measurement sequence with a cycle duration of 2 ms.

(40) For the experiments, the substance 5 was ground to a grain size of about 5 μm according to D99 and introduced in a proportion of 1 percent by weight into a test paper (laboratory standard method for sheet manufacture) and measured.

(41) FIG. 3 shows the normalized read-out curve (I.sub.norm) as a function of time from the measurement with the above sequence 1. The respective signals during the read-out pulses are shown. The OSP employed can be concluded from the course of the read-out curve. In particular, the good readability of substance 5 in red and near infrared (NIR) wavelengths is shown here. The data are preferably further processed, for example in that the signal is averaged for each pulse and the ratio of the signal intensity of the n-th pulse to the signal intensity of the first pulse S.sub.n/S.sub.1 is utilized. 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 read-out pulses. This example also shows the different effect of the read-out pulses R and R*.

6.SUP.th .Embodiment Example

Nominally La.SUB.0.5.G.SUB.2.54.Al.SUB.2.Ga.SUB.3.O.SUB.12.:Zr.SUB.0.005

(42) The OSP according to the sixth embodiment example (substance 6) is manufactured with fluxing-agent (flux) supported solid synthesis. For this purpose, the starting substances are carefully mixed with the addition of 10 g Na.sub.2SO.sub.4 as the flux and annealed in a corundum crucible at 1200° C. for 10 h. Substances used are: 0.8795 g La.sub.2O.sub.3, 4.9701 g Gd.sub.2O.sub.3, 1.1010 g Al.sub.2O.sub.3, 3.0360 g Ga.sub.2O.sub.3, 0.01256 g ZrCl.sub.4. No cerium was doped in the substance 6.

(43) Measurements for the Substance 6

(44) An embodiment example of a method described here is explained in more detail in connection with FIGS. 4a, 4b and 4c and with FIG. 5. In the method, the substance 6 was subjected to authenticity detection.

(45) The measurement sequence (sequence 2) employed here is constructed as follows: 1) Charging pulse (laser diode with a peak wavelength of 450 nm and with about 350 mW power, duration 20 ms, defocused to approximately 6 mm illumination diameter). The time zero point for this measurement sequence is given by the start of the charging pulse. 2) 65 ms waiting time 3) Eleven pulses G (pulse G: laser diode with a peak wavelength of 638 nm and with about 300 mW power, focused, pulse duration 0.2 ms with subsequently 0.3 ms waiting time before the subsequent pulse G). 4) Repeating the measurement sequence with a cycle duration of 100 ms.

(46) 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 the charging (corresponding to the charging pulses), and FIG. 4c shows the time profile of the trigger signal S3 for the read-out (corresponding to the read-out pulses). FIG. 5 represents the read-out sequence in detail, namely in FIG. 5a) the temporal progression of the detector signal S1 (offset-affected read-out curve) and in b) the profile of the associated trigger signal S3 (i.e. the read-out pulses). As the authenticity criterion, there serves for example the shape of the envelope of the read-out curve or the ratio of the signal intensities from the first read-out pulse to the last read-out pulse.

Further Embodiment Examples 7 to 18

(47) Further substances 7 to 18 were manufactured with fluxing-agent (flux) supported solids synthesis. The manufacture follows that of substance 3 with respect to the course of action. The substances are listed with their nominal composition in Table 3. Total batch amounts were in each case 20 g, of which 10 g of fluxing agent K.sub.2SO.sub.4 were used. The raw materials from Table 4 were employed as sources for the elements stated in the respective substance composition. The raw materials (cf. Table 4) were added in each case in the amount of element required for the stated substance compositions. Table 4 shows an overview of the raw materials employed for substances 7 to 18.

(48) TABLE-US-00003 TABLE 3 Substance 7 La.sub.0.5Gd.sub.2.54Al.sub.2Ga.sub.3O.sub.12: Ce.sub.0.005,Yb.sub.0.005 Substance 8 YGd.sub.2.02Al.sub.2Ga.sub.3O.sub.12: Ce.sub.0.04, Bi.sub.0.01, Mo .sub.0.005 Substance 9 La.sub.0.5Gd.sub.2.52Al.sub.2.5Ga.sub.2.5O.sub.12: Ce.sub.0.04, Bi.sub.0.01, Mo.sub.0.005 Substance 10 Y.sub.0.5Gd.sub.2.52Al.sub.2.5Ga.sub.2.5O.sub.12: Ce.sub.0.04, Bi.sub.0.01, Mo.sub.0.005 Substance 11 Y.sub.0.5Gd.sub.2.425Al.sub.2.475Ga.sub.2.5O.sub.12: Ce.sub.0.04, Bi.sub.0.03, Mo.sub.0.03 Substance 12 Y.sub.0.5Gd.sub.2.425Al.sub.2.475Ga.sub.2.5O.sub.12: Ce.sub.0.04, Bi.sub.0.03, Sn.sub.0.03 Substance 13 Gd.sub.2.98Al.sub.2.45Ga.sub.2.45O.sub.12: Ce.sub.0.01, Bi.sub.0.01, Ge.sub.0.1 Substance 14 La.sub.0.5Gd.sub.2.54Al.sub.2Ga.sub.3O.sub.12: Ce.sub.0.02, Hf.sub.0.005 Substance 15 La.sub.0.5Gd.sub.2.481Al.sub.1.996Ga.sub.3O.sub.12: Ce.sub.0.02, Zr.sub.0.005 Substance 16 La.sub.0.5Gd.sub.2.4451Al.sub.1.975Ga.sub.3O.sub.12: Ce.sub.0.005, Zr.sub.0.03 Substance 17 La.sub.0.5Gd.sub.2.46Al.sub.1.92Ga.sub.3O.sub.12: Ce.sub.0.04, Mo.sub.0.01 Substance 18 La.sub.0.5Gd.sub.2.54Al.sub.2Ga.sub.3O.sub.12: Ce.sub.0.005, Sn.sub.0.005

(49) TABLE-US-00004 TABLE 4 Element of the raw material Formula Al Al.sub.2O.sub.3 Bi Bi.sub.5O(OH).sub.9(NO.sub.3).sub.4 Ce Ce(SO.sub.4).sub.2 Ga Ga.sub.2O.sub.3 Gd Gd.sub.2O.sub.3 Ge GeO.sub.2 Hf HfO.sub.2 La La.sub.2O.sub.3 Mo MoO.sub.3 Nb Nb.sub.2O.sub.5 Sn SnO.sub.2 Y Y.sub.2O.sub.3 Yb Yb.sub.2O.sub.3 Zr ZrCl.sub.4
Measurements for the Substances 7 to 13

(50) For the above substances 7 to 13, different measurements were carried out in each case according to an embodiment example of a checking method described here, in order to describe the effect of changes in the matrix of the OSP, of doping substances and/or the concentrations thereof on the properties of the OSP.

(51) For this purpose, the respective substances were measured with the following measurement sequence (sequence 3): 1) Charging pulse (laser diode with a peak wavelength of 450 nm and with about 400 mW power, duration 20 ms, spot approximately 3 mm diameter). The time zero point corresponds to the start of the charging pulse. 2) 23.6 ms waiting time after the end of the charging pulse 3) Six repetitions of a pulse pair (ST): Pulse S: laser diode with a peak wavelength of 638 nm (red) and with about 450 mW power, focused, pulse duration 0.2 ms with subsequently 0.2 ms waiting time before the subsequent pulse T Pulse T: laser diode with a peak wavelength of 915 nm (NIR) and with about 500 mW power, focused, pulse duration 0.2 ms with subsequently 0.2 ms waiting time. 4) Repeating the measurement sequence with a cycle duration of 50 ms.

(52) Table 5 lists suitable measurands and their definitions. I.sub.N denotes the maximum signal intensity of the N-th read-out pulse of the measurement sequence. The measurands listed here illustrate, by way of example, how the data of a measurement sequence can be evaluated and are in no way to be understood as a complete enumeration of a data evaluation. Further measurands can be defined and alternative evaluation methods (such as direct comparison to target data, adjustments, normalization to intrinsic signals) can be effected. Table 6 gives an overview of the measurands defined in Table 5 for the substances 7 to 13.

(53) TABLE-US-00005 TABLE 5 Measurand Description Measurement I.sub.max(Seq 3) Maximum OSL signal Sequence 3 SpeedNIR(Seq 3) Read-out speed at NIR read-out under measuring sequence 3 As the measure there is: $\mathrm{SpeedNIR}\left(\mathrm{Seq}3\right)=\frac{I4-I2}{I12-I10}$ SpeedRED(Seq 3) Read-out speed at red read-out under measuring sequence 3 As the measure there is: $\mathrm{SpeedRED}\left(\mathrm{Seq}3\right)=\frac{I3-I1}{I11-I9}$ Speed(Seq3) Read-out speed under measurement sequence 3 As the measure there is: $\mathrm{Speed}\left(\mathrm{Seq}3\right)=\frac{I2-I1}{I12-I11}$ Q Spectral sensitivity as signal ratio of the first (red) to the second (NIR) pulse of the measuring sequence 3 As the measure there is: $Q=\frac{I_1\left(\mathrm{Seq}3\right)}{I_2\left(\mathrm{Seq}3\right)}.$

(54) TABLE-US-00006 TABLE 6 Sub- Sub- Sub- Sub- Sub- Sub- Sub- stance 7 stance 8 stance 9 stance 10 stance 11 stance 12 stance 13 I.sub.max(Seq 3) [V] 3.50 1.84 1.63 1.83 0.63 0.16 1.18 SpeedNIR(Seq 3) 1.19 1.87 2.27 2.38 1.81 1.81 1.33 SpeedRED(Seq 3) 3.70 2.45 2.65 2.85 2.15 1.99 1.81 Speed(Seq3) 1.82 2.29 2.24 2.47 1.70 1.25 1.38 Q 8.53 1.57 1.56 1.63 1.66 2.60 1.89

(55) Besides substance 7 (which has a high OSL signal I.sub.max but hardly reacts to the NIR components), also the other substances appear interesting for the applications, since they can also be significantly read out with the NIR pulses (visible in the parameter Q) and at the same time have distinguishable speeds. These substances exhibit, by way of example, differences in their spectral sensitivity and in their read-out speeds.

(56) Measurements for the Substances 7 and 14 to 17

(57) For the above substances 7 and 14 to 17, further measurements were carried out according to an embodiment example of a checking method described here, in order to describe the effect of changes in the matrix of the OSP, of doping substances and/or the concentrations thereof on the properties of the OSP.

(58) For this purpose, the respective substances were measured with the following measurement sequence (sequence 4): 1) Charging pulse (laser diode with a peak wavelength of 450 nm and with about 350 mW power, duration 20 ms, spot approximately 6 mm diameter). The time zero point corresponds to the start 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 638 nm with about 400 mW power, focused, pulse duration 0.2 ms) with subsequently 0.2 ms waiting time before the subsequent pulse 4) Repeating the measurement sequence with a cycle duration of 50 ms.

(59) Table 7 lists suitable measurands and their definitions. I.sub.N denotes the maximum signal intensity of the N-th read-out pulse of the measurement sequence. Table 8 gives an overview of the measurands defined in Table 7 for the substances 7 (as reference) and 14 to 17.

(60) TABLE-US-00007 TABLE 7 Measurand Description Measurement I.sub.max(Seq 4) Maximum OSL signal Measuring sequence 4, per pulse (random units) under determination of the maximum focused read-out light value (smoothed from 20 individual at 638 nm values around the maximum) v(Seq 4) Read-out speed under measurement sequence 4 Measurement sequence 4, as the measure there is: 0$v\left(\mathrm{Seq}4\right)=\frac{1}{I_1}\frac{I_1+I_{11}-2I_6}{25}*100$ Speed(Seq 4) Alternative description of the read-out speed under measurement sequence 4 Measurement sequence 4, as the measure there is: $\mathrm{Speed}\left(\mathrm{Seq}4\right)=\frac{I3-I1}{I12-I10}$

(61) TABLE-US-00008 TABLE 8 Substance I.sub.max(Seq 4) v(Seq 4) Speed(Seq 4) Substance 7 0.67 2.00 5.11 Substance 14 0.34 2.50 6.74 Substance 15 3.46 3.05 18.26 Substance 16 0.82 1.44 7.22 Substance 17 0.19 1.96 3.89

(62) In FIG. 6, normalized read-out curves for the substance 7 (reference numeral 67), the substance 15 (reference numeral 615) and the substance 16 (reference numeral 616) are represented, wherein the maximum signal I.sub.N,norm of the pulse N is plotted against the pulse number N for each read-out pulse of the sequence 4. 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 becomes visible here by way of example in the measured values (Tables 7 and 8) and/or also in the direct comparison of the read-out curve (FIG. 6). In particular, it becomes distinct from the comparison of the read-out curve for substance 15 (reference numeral 615) and 16 (reference numeral 616) that small changes in the composition substantially change the defect structure of the substance, which manifests itself in the distinct change in characteristic measurands (for example as in Tables 7 and 8) and/or read-out curves (such as, for example, in FIG. 6): the read-out speeds and the read-out curves of the individual substances differ significantly from one another.

(63) Measurements for the Substances 3, 7, 13 and 16

(64) For the substances 3, 7 and 13 and for substance 16, further measurements were carried out according to an embodiment example of a checking method described here, in order to ascertain properties of the substances which exemplarily compare the readability in the near UV range.

(65) The measurements were first carried out using the following measurement sequence (sequence 5): 1) Charging pulse (laser diode with a peak wavelength of 450 nm with about 300 mW power, duration 20 ms, spot approximately 3 mm diameter). The time zero point corresponds to the start 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 about 280 mW power, focused, pulse duration 0.2 ms with subsequently 0.2 ms waiting time before the subsequent pulse. 4) Repeating the measurement sequence with a cycle duration of 100 ms.

(66) In addition, the following measurement sequence (sequence 6) was then utilized: 1) Charging pulse (laser diode with a peak wavelength of 450 nm with about 300 mW power, duration 20 ms, spot approximately 3 mm diameter). The time zero point corresponds to the start of the charging pulse. 2) 43.841 ms waiting time after the end of the charging pulse. 3) 6 repetitions of a pulse pair (SZ): pulse S: laser diode with a peak wavelength of 638 nm with about 450 mW power, focused, pulse duration 0.2 ms with subsequently 0.2 ms waiting time before the subsequent pulse Z. Pulse Z: laser diode with a peak wavelength of 398 nm with about 280 mW power, focused, pulse duration 0.2 ms with subsequently 0.2 ms waiting time before the subsequent pulse S. 4) Repeating the measurement sequence with a cycle duration of 50 ms.

(67) Table 9 lists suitable measurands and their definitions for sequences 5 and 6. I.sub.N denotes the maximum signal intensity of the N-th read-out pulse of the respective measurement sequence. Table 10 includes a list with the measurands defined in Table 9 for the substances 3, 7 and 13 and 16.

(68) TABLE-US-00009 TABLE 9 Measurand Description Measurement Speed(Seq 5) Alternative description of the read-out speed under measurement sequence 5 Measurement sequence 5, as the measure there is: $\mathrm{Speed}\left(\mathrm{Seq}5\right)=\frac{I3-I1}{I12-I10}$ I.sub.rel(Seq 6) Relative signal intensity of the first pulse at 638 nm read-out for the intensity of the first pulse at 405 nm read-out Measurement sequence 6, as the measure there is: $I_{\mathrm{rel}}=\left(\mathrm{Seq}6\right)=\frac{I_1}{I_2}$

(69) TABLE-US-00010 TABLE 10 Substance Speed(Seq5) I.sub.rel(Seq 6) Substance 3 1.9 0.46 Substance 7 22.8 0.73 Substance 13 12.1 0.60 Substance 16 not determined 1.41

(70) By way of example, these substances exhibit different spectral sensitivities which can be found not only in intensity ratios but also in read-out speeds, as follows from the values in Table 10.

(71) Measurements for the Substance 18

(72) Substance 18 shows an efficient readability, above all at 398 nm, while it is hardly readable in the red and NIR spectral range. For the detection, the substance 18 was subjected to the measurement sequence 6 and to a further measurement sequence 7, and the data were evaluated.

(73) The measurement sequence (sequence 7) employed is as follows: 1) Charging pulse (laser diode with a peak wavelength of 450 nm with about 300 mW power, duration 20 ms, spot approximately 3 mm diameter). The time zero point corresponds to the start of the charging pulse. 2) 43.841 ms waiting time after the end of the charging pulse. 3) 6 repetitions of a pulse pair (TZ): Pulse T: laser diode with a peak wavelength of 915 nm with about 500 mW power, focused, pulse duration 0.2 ms with subsequently 0.2 ms waiting time before the subsequent pulse Z Pulse Z: laser diode with a peak wavelength of 398 nm with about 280 mW power, focused, pulse duration 0.2 ms with subsequently 0.2 ms waiting time before the subsequent pulse T. 4) Repeating the measurement sequence with a cycle duration of 50 ms.

(74) The comparison of the measurements of the substance 18 for the sequence 6 (reference numeral 76) and the sequence 7 (reference numeral 77) is represented in FIG. 7. FIG. 7 shows a sequence of the respective maximum normalized signal I.sub.m,norm of the m-th read-out pulse as a function of the number m of the read-out pulse. Even pulse numbers (upper measured values) correspond in each case to pulses of the type Z, thus a wavelength of the read-out light of 398 nm, while odd pulse numbers (lower measured values with an intensity of below 0.1) correspond to a wavelength of the read-out light of 638 nm (type S, measurement sequence 6) or 915 nm (type T, measurement sequence 7). Thus, the pulse type Z is able to read out the substance 18, while the signals remain below 0.1 for the pulse type S and T. It can be seen that the substance 18 can be read out above all at a wavelength of 398 nm, i.e. at a wavelength shorter than the emission wavelength and even shorter than the preferred wavelength of the charging light of about 450 nm.

Further Embodiment Examples

Substances 19, 20 and 21

(75) By means of the further embodiment examples of the substances 19, 20 and 21, the influence of small changes in the chemical composition of the garnet matrix on the properties of the OSP is to be examined. Total batch amounts were in each case 20 g, of which 10 g of fluxing agent K.sub.2SO.sub.4 were used. The raw materials from Table 4 were employed as sources for the elements stated in the respective substance composition. The raw materials were in each case added in the quantity of element required for the stated substance compositions.

(76) The substances 19, 20 and 21 were manufactured with fluxing-agent (flux) supported solids synthesis. The manufacture follows that of substance 3 with respect to the course of action. The nominal composition of the substances is:

(77) Substance 19: G.sub.2.995Al.sub.2Ga.sub.2.993O.sub.12:Ce.sub.0.005, Zr.sub.0.005;

(78) Substance 20: La.sub.0.5Gd.sub.2.495Al.sub.2Ga.sub.2.993O.sub.12:Ce.sub.0.005, Zr.sub.0.005;

(79) Substance 21: La.sub.0.5Gd.sub.2.53Al.sub.2Ga.sub.2.993O.sub.12:Ce.sub.0.005, Zr.sub.0.005.

(80) Substance 19 includes no lanthanum, substance 20 is an approximately stoichiometric formulation, whereas substance 21 has a distinct excess of rare earth elements (here: Gd).

(81) These three substances are compared with a measurement sequence according to an embodiment example of a method described here. The measurement sequence (sequence 8) is constructed as follows: 1) Charging pulse (laser diode with a peak wavelength of 450 nm with about 350 mW power, duration 3.5 ms, spot approximately 5 mm diameter). The time zero point corresponds to the start 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 638 nm with about 1600 mW power, illuminated rectangular spot on the sample approx. 1 mm×4 mm, pulse duration 0.2 ms with subsequently 0.2 ms waiting time before the subsequent pulse V). The time zero point for this read-out sequence is given by the start of the first read-out pulse. 4) Repeating the measurement sequence with a cycle duration of 10 ms.

(82) For the three substances the maximum signal values I.sub.m for each read-out pulse m are contrasted as read-out curves in FIG. 8.

(83) The effect of the lanthanum co-doping is seen by comparing the signals for the respective 1.sup.st read-out pulse. Substance 19 (reference numeral 819) hardly shows an OSL signal (here 33 mV, wherein about 15 mV already originate from the residual permeability of the filters employed), while the maximum signal under the same conditions for substance 20 (reference numeral 820) amounts to about 190 mV. No trustworthy read-out speed can be stated for the substance 19, since the signal has hardly any variation. In the case of substance 20, the signal of 100% (1.sup.st read-out pulse) drops to 49% percent (12.sup.th pulse) under the measurement sequence 8. In the case of substance 21 (reference numeral 821), the excess of rare earth elements (here: Gd) leads to a further increased initial intensity of the OSL of 415 mV under sequence 8. At the same time, the signal between two read-out pulses (i.e. without irradiation with light) for substance 21, normalized to the respective maximum read-out pulse, amounts to only about 60% of that of substance 20 (not shown), which indicates reduced afterglow.

(84) By changes in the defect structure, which like here are caused, for example, by a small change in the composition of the host lattice (introduction of La) and/or by a small deviation from the nominal charge neutrality (excess Gd), it is possible to achieve distinctly measurable differences in the properties, for example memory strength and read-out speed here. At the same time, undesired properties such as afterglow can be suppressed. This example emphasizes that the defect structure is part of the substance.

(85) The description with reference to the embodiment examples does not imply that the invention is limited to these. Rather, the invention comprises each novel feature and any combination of features, which in particular includes any combination of features in the claims, even if this feature or this combination itself is not explicitly stated in the claims or embodiment examples.