EP3049503B1 - Document of value and method for verifying the presence thereof - Google Patents

Description

The invention relates to a value document such as a banknote and a method for checking the presence thereof.

The authenticity assurance of value documents by means of luminescent substances has long been known. Preference is given to using rare earth-doped host lattices, wherein the absorption and emission ranges can be varied within a wide range by suitable tuning of rare earth metal and host lattice. The use of magnetic and electrically conductive materials for authenticity assurance is known per se. Magnetism, electrical conductivity and luminescence emission are mechanically detectable by commercially available measuring devices, and luminescence is also visual in sufficient intensity when emitted in the visible range.

Practically as old as the authenticity assurance of value documents is the problem of forgery of the authenticity features of the value documents. The security against counterfeiting can be increased, for example, by using not only one feature substance but several feature substances in combination, for example a luminescent substance and a magnetic substance, or a luminescent substance and a substance influencing the luminescence properties. The DE 10 2005 047 609 A1 describes feature substances for authenticity assurance of value documents which contain a luminescent substance and at least one further substance, which is preferably magnetically or electrically conductive. The luminescent substance is in particle form and is surrounded by a shell formed from nanoparticles. The properties of the feature substance result from the interaction of the luminescence emission properties of the luminescent substance and the properties of the nanoparticles.

The patent document EP 1 826 730 A2 discloses a value document with luminescent, particulate agglomerates emitting different wavelengths. Based on this prior art, the present invention has the object to provide an improved with respect to the counterfeit security document of value and a method for checking the presence of the same.

Summary of the invention

• 1. (First aspect of the invention) Value document according to claim 1.
• 2. (Preferred embodiment) Value document according to paragraph 1, wherein the exciting electromagnetic radiation of the spectroscopic method is radio wave, microwave, terahertz or infrared radiation.
• 3. (Preferred embodiment) Value document according to one of the paragraphs 1 or 2, wherein the agglomerates of the group consisting of core / shell particles, Particle agglomerates, encapsulated particle agglomerates and coated nanoparticles particles are selected.
• 4. (Preferred embodiment) Value document according to one of paragraphs 1 to 3, wherein the particulate agglomerates have a particle size D99 in a range of 1 micrometer to 100 micrometers, preferably 5 micrometers to 30 micrometers, more preferably in a range of 10 micrometers to 20 micrometers , exhibit.
• 5. (Preferred Embodiment) A value document according to any one of paragraphs 1 to 4, wherein the luminescent substance of the first (especially solid) homogeneous phase is based on a matrix-forming inorganic solid doped with one or more rare earth metals or transition metals.
  A preferred combination is particle agglomerates having a first homogeneous phase of a luminescent substance emitting at a certain emission wavelength and having a second homogeneous phase of a non-luminescent substance detectable by means of SER (Surface Enhanced Raman) spectroscopy, wherein the exciting electromagnetic Radiation of the spectroscopic method is infrared radiation. Another preferred combination provides encapsulated particle agglomerates having a second homogeneous phase of a non-luminescent, by means of a SER (Surface Enhanced Raman) spectroscopy detectable substance, wherein the exciting electromagnetic radiation of the spectroscopic method is infrared radiation.
  Another preferred combination is particle agglomerates having a second homogeneous phase of a non-luminescent substance which can be detected by means of a surface enhanced infrared absorption (SEIRA) spectroscopy, wherein the exciting electromagnetic radiation of the spectroscopic method is infrared radiation. Another preferred combination is particle agglomerates having a second homogeneous phase of a non-luminescent substance detectable by nuclear magnetic resonance spectroscopy, the exciting electromagnetic radiation of the spectroscopic method being radio waves. A further preferred combination is particle agglomerates having a second homogeneous phase of a non-luminescent substance which can be detected by means of electron spin resonance spectroscopy, the exciting electromagnetic radiation of the spectroscopic method being radio or microwaves.
• 7. (Preferred embodiment) Value document according to one of paragraphs 1 to 6, wherein in addition to the particulate agglomerates a non-correlating correction component in uniform concentration in the value document is applied or applied, which luminesces at a certain emission wavelength or separately with a spectroscopic methods is detectable. The spectroscopic method may be the same as that of the second homogeneous phase of the particulate agglomerate, or another spectroscopic method.
• 8. (Second aspect of the invention) Method according to claim 7 for checking the presence or authenticity of a value document according to one of the paragraphs 1 to 6.
• 12. (Preferred embodiment) Method according to one of paragraphs 8 to 11, whereby the measured values for the radiation emitted by the luminescent substances on the one hand and for the measurement signal intensity resulting from the non-luminescent substances resulting from the spectroscopic method on the other hand in one Intermediate step converted into corrected measured values. In particular, a non-correlating correction component, which is luminescent at a separate emission wavelength or separately detectable by the spectroscopic method, is used in FIG uniform concentration introduced into the value document and their further measured values used to determine the corrected measured values.
• 13. (Preferred embodiment) Method according to one of paragraphs 8 to 11, wherein only those measured values for the radiation emitted by the luminescent substances, on the one hand, and for the measurement signal intensity resulting from the non-luminescent substances resulting from the spectroscopic method, on the other hand the authenticity determination are used, which are each within a certain range of values, in particular above a certain threshold value.

According to one embodiment, the measured values of locations in the immediate vicinity of the measured values below the specific threshold value are also not used for the authenticity determination.

Detailed description of the invention

Documents of value within the scope of the invention are items such as banknotes, checks, stocks, tokens, identity cards, passports, credit cards, documents and other documents, labels, seals, and items to be protected, such as CDs, packaging and the like. The preferred application is banknotes, which are based in particular on a paper substrate.

Luminescent substances are used as standard for securing banknotes. In the case of a luminescent authenticity feature or security feature, which is introduced, for example, at different locations in the paper of a banknote, the luminescence signals of the feature are naturally subject to certain fluctuations at the various locations.

In addition to authenticity features based on luminescent substances, other authenticity features based on non-luminescent substances exist, which can be detected by means of spectroscopic methods. Spectroscopy types can be e.g. subdivide according to the excitation energy of the electromagnetic radiation. Thus, nuclear magnetic resonance (NMR) spectroscopy is based on exciting electromagnetic radiation having a wavelength in a range of 1 m to 100 m, i. Radio waves. Electron spin resonance spectroscopy (ESR) is based on exciting electromagnetic radiation with a wavelength in the range of 1 cm to 1 m. The microwave spectroscopy is based on an exciting electromagnetic radiation having a wavelength in a range of 1 mm to 10 cm. Submillimeter wave spectroscopy is based on exciting electromagnetic radiation having a wavelength in the range of 100 μm to 1 mm (also known as terahertz radiation). Vibrational spectroscopy, in particular Raman spectroscopy, more particularly SER (Surface Enhanced Raman) spectroscopy or SERR (Surface Enhanced Resonant Raman) spectroscopy, is particularly based on exciting electromagnetic radiation having a wavelength in a range of 200 nm to 3 μm , preferably in a range from 780 nm to 3 μm, ie near infrared radiation. Infrared spectroscopy, particularly SEIRA (Surface Enhanced Infrared Absorption), is based on an excitation wavelength in the range of 800 nm to 1 mm, preferably 3 μm to 1 mm, i. medium and far infrared radiation.

The present invention is based on the finding that a targeted generation of mixed, particulate agglomerates of a luminescent substance on the one hand and a non-luminescent, spectroscopically detectable substance on the other hand, the effect of a statistical correlation the intensity fluctuations of the measurement signal intensities of both substances result. In this way it is possible to distinguish the samples according to the invention by evaluating the agglomerate-related signal correlation of non-correlating authenticity features. Non-correlating authenticity features are in particular the mixtures of individual, untreated pulverulent luminescent substances and pulverulent non-luminescent substances.

In other words, it is the basic principle of the present invention that two or more substances with different measurable properties are combined in a single particle. This couples the relative intensities of the measurement signals together so that security features based on such particles, e.g. can be distinguished from a simple mixture of the individual particles of the two or more substances.

The use of the above effect leads to an increase in the security against forgery, because non-correlating feature signals can be recognized as "spurious". In addition, the number of possible codings can be increased. Thus, from a coding, which contains two individual luminescent feature substances A and B and a non-luminescent feature substance C, by means of a targeted particulate agglomeration of respectively two or three of the feature substances, the four distinguishable variants (A + B), C / A , (B + C) / (A + C), B / (A + B + C) are generated, with the signals of the substances within a bracket correlating with each other.

The particulate agglomerates according to the invention each contain at least two different solid solid phases, wherein the first solid homogeneous phase on a luminescent substance emitting at a certain emission wavelength (hereinafter also referred to as "luminescent feature substance") and the second solid homogeneous phase on a non-luminescent, detectable by a spectroscopic method substance (hereinafter also as "non-luminescent feature substance "denotes), wherein the exciting electromagnetic radiation of the spectroscopic method in particular has a wavelength in a range of 200 nm to 100 m, preferably 780 nm to 100 m.

According to a preferred embodiment, the particulate agglomerates are non-planar or platelet-like, but three-dimensionally expanded, in particular spherical or globular (for example elliptical) or fractal. This provides a direct analysis of the different solid homogeneous phases with simple methods such as e.g. complicated by light microscopy.

In particular, the term "non-luminescent feature substance" means that the spectroscopically detectable feature substance is not a luminescent pigment, as is typically used in the prior art for securing banknotes and other value documents.

The adhesion of the two substances, in the form of solid homogeneous phases, must be sufficiently strong that no separation of the two substances takes place during storage and processing, at least not in a degree disturbing the production of safety features.

The particulate agglomerates according to the invention may in particular be core / shell particles, particle agglomerates, encapsulated particle agglomerates or particles enveloped by nanoparticles. Particle agglomerates and encapsulated particle agglomerates are particularly preferred. The shell or capsule may be based on an inorganic or organic material (eg inorganic oxide or organic polymer). A shell of inorganic oxides, eg SiO ₂ , is preferred.

The agglomerates are preferably prepared by a special process in which the different security features (ie the luminescent substance and the non-luminescent substance) are mixed in a salt-containing aqueous solution at low shear forces and then an aqueous silicate solution is metered. The silicate solution is neutralized by a likewise added or already contained in the aqueous salt solution acid source and connects by the resulting SiO _2, the individual particles of security features to solid agglomerates.

In addition, more than two types of security features can be combined in one agglomerate. Likewise, an agglomerate may contain individual particles of two or more security features (luminescent or non-luminescent) and, in addition, individual particles of one or more inactive materials which are themselves not security features.

The luminescent substance of the first solid homogeneous phase can be excited in particular by radiation in the infrared and / or visible and / or ultraviolet range for luminescence emission, preferably phosphorescence emission. The luminescent substance may be one in the visible or in the non-visible spectral range (eg in the UV or NIR range) be emitting substance. Luminescent substances that emit in the NIR range are preferred (the abbreviation NIR stands for near infrared).

The luminescent substance of the first solid homogeneous phase contained in the particulate agglomerates may e.g. based on a matrix-forming inorganic solid doped with one or more rare earth metals or transition metals. The luminescent substance is hereinafter also referred to as "luminophore particles".

• Oxide, insbesondere 3- und 4-wertige Oxide wie z. B. Titanoxid, Aluminiumoxid, Eisenoxid, Boroxid, Yttriumoxid, Ceroxid, Zirconoxid, Bismutoxid, sowie komplexere Oxide wie z. B. Granate, darunter u. A. z.B. Yttrium-Eisen-Granate, Yttrium-Aluminium-Granate, Gadolinium-Gallium-Granate;
• Perowskite, darunter u.A. Yttrium-Aluminium-Perowskit, Lanthan-Gallium-Perowskit; Spinelle, darunter u. A. Zink-Aluminium-Spinelle, Magnesium-Aluminium-Spinelle, Mangan-Eisen-Spinelle; oder Mischoxide wie z.B. ITO (Indiumzinnoxid);
• Oxyhalogenide und Oxychalkogenide, insbesondere Oxychloride wie z. B. Yttriumoxychlorid, Lanthanoxychlorid; sowie Oxysulfide, wie z.B. Yttriumoxysulfid, Gadoliniumoxysulfid;
• Sulfide und andere Chalkogenide, z.B. Zinksulfid, Cadmiumsulfid, Zinkselenid, Cadmiumselenid;
• Sulfate, insbesondere Bariumsulfat und Strontiumsulfat;
• Phosphate, insbesondere Bariumphosphat, Strontiumphosphat, Calciumphosphat, Yttriumphosphat, Lanthanphosphat, sowie komplexere phosphatbasierte Verbindungen wie z.B. Apatite, darunter u. A. Calciumhydroxylapatite, Calciumfluoroapatite, Calciumchloroapatite; oder Spodiosite, darunter z.B. Calcium-Fluoro-Spodiosite, Calcium-Chloro-Spodiosite;
• Silicate und Aluminosilicate, insbesondere Zeolithe wie z.B. Zeolith A, Zeolith Y; zeolithverwandte Verbindungen wie z.B. Sodalithe; Feldspate wie z.B. Alkalifeldspate, Plagioklase;
• weitere anorganische Verbindungsklassen wie z.B. Vanadate, Germanate, Arsenate, Niobate, Tantalate.

Suitable inorganic solids which are suitable for forming a matrix are, for example:

• Oxides, especially 3- and 4-valent oxides such. As titanium oxide, alumina, iron oxide, boron oxide, yttrium oxide, cerium oxide, zirconium oxide, bismuth oxide, and more complex oxides such. B. grenade, including u. A. eg yttrium-iron-garnets, yttrium-aluminum-garnets, gadolinium-gallium-garnets;
• Perovskites, including yttrium aluminum perovskite, lanthanum gallium perovskite; Spinels, including u. A. zinc-aluminum spinels, magnesium-aluminum spinels, manganese-iron spinels; or mixed oxides such as ITO (indium tin oxide);
• Oxyhalides and oxychalcogenides, in particular oxychlorides such. Yttrium oxychloride, lanthanum oxychloride; and oxysulfides such as yttrium oxysulfide, gadolinium oxysulfide;
• Sulfides and other chalcogenides, eg, zinc sulfide, cadmium sulfide, zinc selenide, cadmium selenide;
• Sulfates, in particular barium sulfate and strontium sulfate;
• Phosphates, in particular barium phosphate, strontium phosphate, calcium phosphate, yttrium phosphate, lanthanum phosphate, and more complex phosphate-based compounds such as apatites, including u. A. calcium hydroxyapatites, Calcium fluoroapatites, calcium chloroapatites; or spodiosites, including, for example, calcium fluoro-spodiosites, calcium chloro-spodiosites;
• Silicates and aluminosilicates, especially zeolites such as zeolite A, zeolite Y; zeolite-related compounds such as sodalites; Feldspars such as alkali feldspar, plagioclase;
• other inorganic classes of compounds such as vanadates, germanates, arsenates, niobates, tantalates.

The non-luminescent substance of the second solid homogeneous phase of the particulate agglomerate which can be detected by a specific spectroscopic method is preferably a nuclear magnetic resonance spectroscopy (NMR), nuclear quadrupole resonance spectroscopy (NQR), electron spin resonance spectroscopy (ESR), SER (surface enhanced Raman) spectroscopy or SEIRA ( Surface Enhanced Infrared Absorption) spectroscopy of detectable substance. The abbreviation SER is understood to mean the surface-enhanced Raman scattering. The abbreviation SEIRA means surface-enhanced infrared absorption.

The non-luminescent substance detectable by ESR spectroscopy will hereinafter also be referred to as "ESR-active substance" or "ESR-tag". The non-luminescent substance detectable by NQR spectroscopy will hereinafter also be referred to as "NQR-active substance" or "NQR-tag". The non-luminescent substance detectable by SER spectroscopy will hereinafter also be referred to as "SERS active substance" or "SERS tag".

The particulate agglomerate may, for example, be such as to combine luminophore particles and SERS tags together in the form of a particle agglomerate. If a simple mixture of luminophore particles and SERS tags were introduced into the (paper) substrate of a value document, Both types of particles could be randomly distributed in the substrate. With such a random distribution, there is no correlation between the measured luminescence intensities and the measured SERS signals. If, on the other hand, an agglomerate of both particle types is introduced into the substrate of a value document, the two signals correlate with one another. Sites with relatively high luminescence intensities also show increased SERS signals, sites with relatively low luminescence intensities also show reduced SERS signals.

By combining the two substances within a single particle, a separation of the two substances is to be prevented. For example, with a simple mixture of very different particles, such as luminophore particles of size 5 to 10 .mu.m and SERS tags of size 100 nm, a different incorporation behavior, for example, into a paper substrate take place. These include the enrichment at different locations (eg at the paper fiber surface or in fiber spaces by different surface charge of the particles), a different dispersion behavior (eg clumping of the SERS tags in water), different retention properties (eg different strong retention in the paper web of a paper machine) or a mechanical segregation (eg a size separation by shaking movements during transport of a container with powdered feature substances). All of these factors can lead to the two types of substance being present in very different quantities when checking one digit of the value document, and only one of the two classes of substance being able to be found in sufficient quantity with regard to enabling an authenticity check. This is disadvantageous, in particular, if a specific ratio of the two different signals to each other is assumed as a criterion of authenticity. By combining the two types of substance in a single Particles, however, ensures a similar incorporation into the substrate.

The evaluation of the colocalcy of both signal types, i. the simultaneous occurrence of both types of signals at a location to a corresponding extent, can theoretically be done in different ways. For rapidly measurable, machine-readable features, a mathematical correlation of the fluctuating feature intensities at a plurality of small-area measuring points is possible. When measured by a hand-held device, e.g. a fixed intensity ratio of the two signals are detected at a larger measuring surface. When measuring e.g. By means of a microscope setup, forensic detection can be accomplished by having a single, found particle show the properties of both individual substances (e.g., luminescence and SERS signal). By "microscope setup" is meant that the measuring device used for the examination, e.g. due to a high spatial resolution in the measuring field, it is possible to check single or only a few particles with regard to the property to be measured.

The use of ESR-active substances as a security feature inter alia for banknotes is known in the art (see, for example US 4,376,264 A . US 5,149,946 A and DE 19518 086 A ).

The EP 0 775 324 B1 describes the use of substances as a safety feature, which are excited by resonance in the high-frequency range without additional applied electric or magnetic fields ("zero field"). These include in particular NQR-active substances.

Particulate safety features based on microwave absorbers are eg in the EP 2 505 619 A1 described.

The use of special particles as a security feature for detection by means of Raman spectroscopy, in particular by means of SERS, is inter alia from the documents WO 2008/028476 A2 . US 2013/0009119 A1 . US 2012/0156491 A1 . US 2011/0228264 A1 . US 2007/0165209 A1 . WO 2010/135351 A1 . US 5,853,464 A . WO 02/085543 A1 and US 5,324,567 A known.

The encapsulation or encasing of luminescent substances in a polymer or silicate shell or the like is known, for example, from US Pat WO 2011/066948 A1 , of the US 2003/0132538 A1 and the WO 2005/113705 A1 known.

• Bei der Absicherung von Banknoten mit Sicherheitsmerkmalen auf Basis von lumineszierenden Stoffen (wie die oben erwähnten, mit Seltenerdmetallen oder Übergangsmetallen dotierten anorganische Matrizen) oder auf Basis von nicht-lumineszierenden Stoffen genügt häufig die Einbringung einer relativ geringen Menge des Merkmals. Die Massenanteile können insbesondere im Promille-Bereich liegen. Bei der Einbringung eines solchen Merkmals in das Papier einer Banknote in stark verdünnter Form ist die räumliche Verteilung der Merkmalsstoffpartikel unter normalen Umständen jedoch nicht perfekt homogen. Bei rein zufälliger Verteilung der Merkmalsstoffpartikel in der Blattmasse existieren naturbedingt Bereiche mit höheren und niedrigeren Partikelkonzentrationen. Dies kann sich bei der Messung z.B. der Lumineszenzintensität an verschiedenen Stellen des Banknotensubstrats durch Intensitätsschwankungen bemerkbar machen.

The principle underlying the invention will be described below in detail in conjunction with the FIGS. 1 to 4 described:

• In hedging banknotes with security features based on luminescent substances (such as the above-mentioned, with rare earth metals or transition metals doped inorganic matrices) or based on non-luminescent substances often sufficient to introduce a relatively small amount of the feature. The mass fractions can be in particular in the per thousand range. However, when introducing such a feature into the paper of a banknote in highly diluted form, the spatial distribution of the feature particle is not perfectly homogeneous under normal circumstances. By purely random distribution of the feature substance particles in the leaf mass naturally exist areas with higher and lower particle concentrations. In the case of the measurement of, for example, the luminescence intensity at different locations of the banknote substrate, this can be manifested by intensity fluctuations.

It is known in the art to use codes of two or more luminescent substances as a security feature to increase security. Intensity fluctuations, which are based on the random distribution of the pigment particles within the leaf mass, are independent of each other. There is thus no correlation between the random, location-dependent intensity fluctuations of two different feature substances. It should be noted that this does not apply to inhomogeneities of the paper itself, e.g. at locally different paper thicknesses. In this case, fluctuations in the luminescence intensity, e.g. low values at thinner paper sites, affect both feature substances to the same extent. By a suitable choice of the security features and the lowest possible concentration in the substrate, substrate-related fluctuations with respect to the variations caused by the random particle distribution can often be neglected (or eliminated by suitable evaluation methods).

On the other hand, a different picture results in the combination of two different feature substances, for example a luminescent feature substance and a non-luminescent feature substance, to form a particulate agglomerate (see US Pat FIG. 1 ). For example, a particulate agglomerate obtained by agglomerating a mixture of feature substances "A" and "B" would combine both types of feature substances.

In the introduction of a plurality of in the FIG. 1 Irrespective of the substrate, a correlation between the spatial distributions of the feature substances "A" and "B" would arise (see US Pat FIG. 2 ).

In the FIG. 2 For example, the measurement signal intensities of the feature substances "A" and "B" are compared schematically at four locations of a paper substrate, the densely dotted areas symbolizing high signal intensities and the less densely dotted areas symbolizing less high signal intensities.

Figure 2 Left:

Feature substances "A" and "B", each having a low measurement signal intensity, are used in high quantity. This leads to small fluctuations in the measurement signal intensity in the individual areas. "Signal A" and "Signal B" are always similarly strong.

Figure 2 middle:

Feature substances "A" and "B", each having a high measurement signal intensity (this can be achieved, for example, by adjusting the particle size to larger particles or by using pure substance agglomerates), are used in low amount. This results in some areas giving a high "Signal A" and some areas having a high "Signal B". There is no relationship between the two signals, i. no statistical correlation. The term "pure substance agglomerate" is understood to mean an agglomerate which has only particles of a single particle type.

Figure 2 Right:

Particulate agglomerates obtainable from particles "A" and particles "B" are used. The starting materials A and B may each have a high or a low intensity. This results in areas with increased "signal A" and at the same time increased "signal B" and areas with low "signal A" and at the same time low "signal B". In other words, there is a statistical correlation between the two signals.

The in FIG. 2 The right-to-left relationship between "Signal A" and "Signal B" is not necessarily directly proportional. The particulate agglomerates are ideally, but not necessarily, comprised of 50% particles A and 50% particles B. It is possible that a production method results in particulate agglomerates having a statistical internal distribution of features A and B. For example, agglomerate compositions can be formed which consist on average of ten feature substance particles and include agglomerates having a composition "5A + 5B", but also "3A + 7B" and "7A + 3B" etc. Thus, for example, it is possible that at a measuring position of the paper substrate where there is a high local concentration of agglomerates, a particularly strong signal of the substance "A" is measured, but the signal of the substance "B" is not significantly increased. This is statistically unlikely. In the case of local agglomeration of agglomerates, it is likely to experience a degree of depletion of the signals of "A" and "B". The signals thus correlate with each other. To further explain this correlation, Application Example 1 follows:

Application Example 1

Mixed agglomerates of a luminescent feature substance "A" and a non-luminescent feature substance "B" were prepared. For comparison, the agglomerates "only A" and the agglomerates "only B" were prepared. Subsequently, in a sheet former, a paper sheet having 2% by weight of the mixed agglomerates of "A" and "B" was prepared. Further, a paper sheet having a mixture of 1% by weight of "only A" and 1% by weight of "just B" was prepared. The spectral or spectroscopic examination shows that in both sheets the signals of substance "A" and substance "B" are visible with comparable intensity. A common sensor, For example, checking the signal wavelengths and signal intensities would not detect any difference between the two sheets and recognize both as "identical" and "true". However, if one additionally observes the correlation between the two signals of "A" and "B", clear differences between the leaves can be recognized. For this purpose, the leaves were measured on a device which automatically checks the signal strength of the two features A and B simultaneously at several measuring positions. To increase the number of data points, several points of the leaf were measured and evaluated. In the case of the sheet with the two "pure" substances, the signals of "A" and "B" fluctuate independently (see FIG. 3 ). Applying the intensities of "A" and "B" graphically against each other, therefore, creates a round pile of points. In the case of mixed agglomerate leaves, a dependence of the signal fluctuations can be seen (see FIG. 4 ). Plotting the intensities of "A" and "B" graphically against each other, one recognizes a point distribution stretched along the axis diagonal. The dot distribution indicates a correlation between the signal strength of the two components.

If the normalized signal intensities of "A" and "B" were identical at all measuring positions of the paper substrate, the in FIG. 4 illustrated point distribution ideally represent a line. Due to the statistical composition of the agglomerates, this behavior is often not present in reality, because for such behavior all agglomerates would have to have a fixed ratio of eg exactly 50% "A" content and exactly 50% "B" content. In practice, however, the generation of such systems or their approximation to this state is possible, for example by (1) an electrostatic preference for heterogeneous agglomeration, or (2) a massive increase in the number of particles per agglomerate, or (3) by use of nanoparticles, or (4) by controlled assembly of core-shell systems of defined sizes.

Due to the correlation, the ratio of the intensities between "A" and "B" at arbitrary locations of the sheet is within a very narrow range of values, which is a property which is advantageous for checking the authenticity and also allows the distinction between correlating and non-correlating systems. Similarly, the correlation can be detected at the microscopic level, ie for individual particles. For this purpose, a single agglomerate or a group of agglomerates is examined and it is checked whether they respectively show the properties of the individual substances "A" and "B" used for the construction of the agglomerates.

The evaluation of measurement data and determination of a statistical correlation at a plurality of measurement points will be described below in connection with the FIG. 5 described in detail.

For the evaluation of measured data and the determination of the presence or absence of a statistical correlation different mathematical methods can be used.

Instead of "statistical correlation" one can also speak of a "statistical dependence". It is checked whether there is a statistical dependency between the intensity "A" and the intensity "B" (yes / no decision).

• Drei Datentypen: "nominal" (allgemeine Klassen, z.B. rot, gelb); "ordinal" (geordnete Klassen, z.B. gut, mittel, schlecht); "continuous" (kontinierliche Messwerte, z.B. 1.2, 3.5, 2.7). "Nominal" ist am allgemeinsten, "continuous" am speziellsten.

In particular, quantitative measures can be defined which indicate how strong the pixel-by-pixel statistical dependence between intensity "A" and intensity "B" is. In this way, sorting classes can be defined. There are numerous textbook methods that assess the strength of dependence on random variables. In the textbook WH Press: " Numerical Recipes in C - The Art of Scientific Computing ", Cambridge University Press, 1997, p. 628-645 , for example, the following methods are described:

• Three data types: "nominal" (general classes, eg red, yellow); "ordinal" (ordered classes, eg good, medium, bad); "continuous" (continuous measurements, eg 1.2, 3.5, 2.7). "Nominal" is the most general, "continuous" most specific.

1. Continuous

Correlation, especially linear correlation (correlation coefficient according to Bravais-Pearson). This type of calculation is particularly suitable for two-dimensional normal distributions. It is preferable to previously remove quantile signal outliers from the statistics.

2nd Ordinal

1. a) Spearman Rangkorrelationskoeffizient: obiger Korrelationskoeffizient nach Bravais-Pearson angewendet auf die Rangordnungs-Indizes.
2. b) Kendall's Tau: Untersucht, wie oft bei allen Paaren von Datenpunkten die Rangordnung erhalten bleibt.

Ranking: Perform the calculations not on the original values, but on the ranking indices.

1. a) Spearman Rank Correlation Coefficient: Bravais-Pearson correlation coefficient above applied to rank order indices.
2. b) Kendall's Tau: Examines how often all pairs of data points maintain order.

These methods are suitable for any distribution. In particular, signal outliers do not interfere with this.

3. Nominal

1. a) Chi-Quadrat Auswertung zur Prüfung, ob eine statistische Abhängigkeit vorliegt.
2. b) Entropie-basierte Auswertung. Beispiel: Symmetrischer Unsicherheitskoeffizient.

Evaluations based on contingency tables (ie tables with the absolute or relative frequencies of events with discrete (ie non-continuous) values).

1. a) Chi-square evaluation to check if there is a statistical dependence.
2. b) Entropy-based evaluation. Example: Symmetrical uncertainty coefficient.

It is preferred in the application of these methods to first divide the 2-dimensional real measurements over class intervals into 2-dimensional classes and to determine the 2-dimensional frequencies (contingency table).

Further reading on the above topic: R. Storm: "Probability Theory, Mathematical Statistics and Statistical Quality Control", Carl Hanser Verlag, 12th Edition, 2007, pages 246-285 , Further information on the above topic is available on the Internet at: http://en.wikipedia.org/wiki/Correlation_and_dependence http://en.wikipedia.org/wiki/Spearman%27s_rank_correlation_coefficient http://en.wikibooks.org / wiki / mathematics: _Statistics: _Correlationsanalyse http://de.wikipedia.org/wiki/Rangkorrelationskoeffizient

In the following, for the sake of better understanding, two statistical methods for evaluation are described by way of example.

Example 1: the following correlation function:

$$\mathit{Kor}\left(X.Y\right)=\frac{\mathit{Cov}\left(X.Y\right)}{{\sigma }_X\cdot {\sigma }_Y}=\frac{\frac{1}{n}{\displaystyle \underset{i-1}{\overset{n}{\Sigma }}\left(x_i-{\mu }_X\right)\cdot \left(y_i-{\mu }_Y\right)}}{{\sigma }_X\cdot {\sigma }_Y}$$

It provides a positive contribution if two data points of a row are at the same time above or below their respective mean, ie two "high" or two "deep" signal intensities of "A" and "B" in the same location.

According to one embodiment, in order to assess the authenticity of a value document, the above correlation function can be calculated with respect to the measured values obtained and their amount compared with a threshold value. In particular, an existing statistical correlation and thus authenticity is recognized if the amount is> 0.3, preferably> 0.5, and particularly preferably> 0.7.

Example 2: Method with several steps, with the aim of evaluating the length-to-width ratio of the point clouds obtained from the measured data (see FIG. 5 ). To minimize the influence of "outliers", In each case, the 25% of the highest or lowest signal values were ignored. Correlating point clouds are elongated and have a pronounced length-to-width ratio; in uncorrelated point clouds, their length and width are about the same.

According to one embodiment, the following procedure can be used for evaluating the authenticity of a value document: In a first step, the measurement data of the spectroscopic method and the measurement data of the luminescence intensities at the specific emission wavelength are obtained. In a second step, the measurement data are normalized. In a third step, a transformation of the coordinate axes takes place, preferably a rotation through 45 ° in order to minimize the scattering of the data points along a coordinate axis. In a fourth step, the quantiles are determined in the direction of the two new coordinate axes, preferably the quartiles, and set their distances or differences in relation to each other. By comparing this ratio with previously determined threshold values, the authenticity of the value document is determined.

• eine lokale Dicken- oder Dichtenänderung im Papiersubstrat, z.B. im Falle eines Wasserzeichens;
• eine Absorption der Anregungsstrahlung für das Echtheitsmerkmal durch einen Druck (bzw. eine Überdruckung) oder einen Sicherheitsstreifen;
• eine zusätzliche Emissionsstrahlung, die von einem Druck (bzw. einer Überdruckung) oder einem Sicherheitsstreifen herrührt.

In the area of the luminescent coding, the value document according to the invention can additionally have a print, a watermark and / or a security element based on a security patch or a security strip. Such additional security elements are factors which interfere with the correct evaluation of the statistical correlation or cause an additional correlation effect which is not caused by the particular structure of the particulate agglomerate according to the invention. This includes all factors by which the signal strength of the two measured signals to be evaluated is changed at the same location in the paper substrate. This can be, for example, an attenuation or amplification due to one of the following causes:

• a local change in thickness or density in the paper substrate, eg in the case of a watermark;
• an absorption of the excitation radiation for the authenticity feature by a pressure (or an overprinting) or a security strip;
• additional emission radiation resulting from pressure (or overprinting) or a security strip.

FIG. 6 shows a comparison between the measurement signals of two non-correlating feature substances in an unprinted paper substrate and after overprinting with a striped pattern. For the following explanation, it is further assumed that the overprinting, eg by absorption of the radiation used for the excitation, reduces the signal intensity of the two features used. As expected, there is no noticeable correlation between the signal strengths of the two feature substances in the unprinted paper substrate. After overprinting, however, attenuation of the signal occurs at the overprinted points, causing a spatial correlation of the signal intensities of both feature substances. This results in a similar effect, as achieved by the use of particulate agglomerates according to the invention. Consequently, a clear distinction between "normal", ie not inventive features and features of the invention is made more difficult. In the following, therefore, two ways are listed by way of example, by means of which such undesired correlation effects caused by overprinting or the like can be eliminated or reduced:

Correction Method 1:

It is in uniform concentration an additional ("third"), at a separate emission wavelength luminescent or separately with the spectroscopic method introduced detectable component in the value document, which is non-correlating (correction component). By introducing a suitable, third non-correlating component and normalizing by its signal intensity, for example, all of the disturbing effects described above disappear. Particularly suitable here are luminescent substances which have particularly small or ideally no spatially dependent fluctuations in the luminescence intensity in an unmodified paper substrate, ie would have a spatially homogeneous luminous intensity without additional influences. On the in the FIG. 6 This would mean that the periodic weakening caused by the overprinted stripe pattern influences the third component in addition to the first two feature substances. Since the extent of "attenuation" due to external effects is known via the third homogeneous component, the initial states of all other components can be recalculated. This method thus eliminates all the correlation effects that act equally on all three components, which include overprinting and thickness differences in the substrate depending on the application, but has no influence on correlation effects that affect only certain components. In this way, the agglomeration-based correlation effects according to the invention are not influenced.

Correction Method 2:

If the introduction of the above-mentioned third component is undesirable, for example for reasons of cost, other methods can be used depending on the application. For example, if the measurement signal intensity in an unmodified paper substrate is usually above a certain threshold, it will be due to overprinting effects or thickness changes in the paper substrate etc. below this threshold value, corresponding data points from the analysis can be eliminated. This method is particularly useful in cases of abrupt and sharp intensity changes, such as overprinting with sharply defined lines and areas, but less for gradual gradations of color with a smooth transition or filigree patterns. If the measured regions are locally close to one another, it is advantageous to likewise eliminate all adjacent measuring points when the threshold falls below the threshold value at a measuring point (cf. FIG. 7 ). As a result, partially overprinted measurement areas at the boundary of an overprinted area are excluded, even if their intensities are above the threshold value due to the only incomplete overprinting.

In the FIG. 7 It is shown how overprinted measuring ranges are excluded below an intensity threshold value (marked with crosses in the figure). Subsequently, the adjacent areas are also excluded.

The particulate agglomerates according to the invention are described below in connection with the FIG. 8 described with reference to preferred embodiments.

In principle, a number of production methods are suitable for producing the particulate agglomerates according to the invention starting from a luminescent feature substance and a non-luminescent feature substance (and optionally one or more further feature substances). Normally, the previously isolated particles are caused to assemble into a larger unit. The larger unit thus obtained is then fixed so that the particles can no longer separate from each other during use as a security feature. It is crucial that the larger units contain as much as possible equal parts of both (or of the three or more) feature substances, with most production methods a random statistical mixture of the particles is obtained.

It is undesirable to have the same particles together, so that the agglomerates contain only one particle type. This can e.g. then take place if the different feature substances are not sufficiently mixed before the assembly process, or the pooling of similar substances is favored by surface effects or the like. In the normal case, or if the synthesis procedures are carried out correctly, however, such effects are negligible.

An important factor is the size of the particles that make up the agglomerate and the size of the resulting agglomerate itself. For applications as a security feature in the banknote area, the agglomerates should not exceed a grain size of 30 microns, among other things, to make it difficult to detect the agglomerate particles in the paper substrate , Due to the application, however, larger particle sizes may be necessary. The particle size (D99) of the agglomerates is therefore preferably in the range from 1 to 100 μm, more preferably from 5 to 30 μm, very particularly preferably from 10 to 20 μm.

If significantly larger particles are required, for example because of a very large measuring spot area in the case of application, macroscopic carrier bodies in which the different feature substances are incorporated, for example planchettes or mottled fibers, can be used instead of the described particle agglomerates. These carrier bodies can then have sizes in excess of 100 μm in individual or all room dimensions, eg have sizes in the millimeter range.

The particles from which the agglomerate is composed should be significantly smaller than the agglomerate, since with decreasing size a higher number of particles per agglomerate can be incorporated. A higher number of incorporated particles increases the likelihood of finding a "suitable distribution" of both types of particles in the agglomerate.

Thus, the following relationship is meant: If the starting material were so large that only three particles of the substances A and B could form an agglomerate without exceeding the maximum agglomerate size, the combinations 'AAA' / 'AAB' / 'ABB' /, BBB 'conceivable. However, such a composition would be completely unsuitable for the use according to the invention. For 25% of the agglomerates would consist of only one substance (AAA or BBB) and thus would not produce a correlation, the other 75% would consist of one third of one substance and two thirds of the second substance, and would therefore only generate bad correlation values.

If one imagines an agglomerate consisting of 10,000 (or "infinitely many") individual particles as the opposite extreme case, then the probability that all particles coincidentally are identical is arbitrarily small. When using equal amounts of the two types of particles for the synthesis and the mixing ratio in the agglomerates produced therefrom will be 50% or hardly deviate from it. Such agglomerates would thus be well suited for use as a feature of the invention. In practice, you are often in between these two extremes. The reduction of the particle size leads in the case of luminophores mostly to a noticeable loss of the measurement signal intensity. Especially with a grain size of about 1 μm, many luminescent feature substances show a significant loss of intensity, which is mostly due to the enlargement of the surface, since here energy can be dissipated without radiation to surface defects. Certain non-luminescent feature substances also adversely react to significantly increased particle surfaces. Too large a grain size, however, leads to the problems described above in the preparation of suitable agglomerates.

As feature substances for the construction of the agglomerates, it is therefore preferred to use small to medium size particles, e.g. with a particle size between 1 and 5 microns, used.

It should be noted, however, that, when available, correspondingly small feature size, high-intensity feature substances, e.g. in the nanometer range, these could also be used.

The ratio of the two substances A and B, from which the agglomerates are prepared, is ideally 1: 1, if both substances have the same intensity and grain size. In the case of application, for example, in the case of large differences in the signal strength or with different particle size distributions, an adaptation of this ratio may be advantageous. It may also be necessary under certain circumstances to adjust the quantitative ratio in order, for example, to generate a specific desired mean intensity ratio of both signals in the end product.

The units referred to as "agglomerates" are, according to one variant, a disordered cluster of adhering particles which have been fixed or permanently "stuck together" (see FIG. 8 a and b). This can be done, for example, by coating with a polymer or silica layer (see, for example, US Pat WO 2006/072380 A2 ), or by linking the particle surfaces with each other via chemical groups, etc. happen. Such agglomerates are technically relatively easy to produce and are therefore preferred. According to another variant, the particles can have a different structure without losing functionality (see Figure 8 c, d and e ). Under certain circumstances, alternative embodiments, such as ordered agglomerates or core-shell systems, may have advantageous properties (eg, a controlled particle distribution). However, their synthesis is usually more complex.

1. (a) ungeordnetes Merkmalsstoffagglomerat, das zwei unterschiedliche (insbesondere zusammenhaftende) Merkmalsstoffe aufweist und mit einer Polymer- oder Silicaschicht umhüllt bzw. verkapselt ist;
2. (b) ungeordnetes Merkmalsstoffagglomerat, das zwei unterschiedliche, zusammenhaftende Merkmalsstoffe aufweist;
3. (c) Core-Shell-Teilchen, bei dem der Kern durch einen ersten Merkmalsstoff gebildet ist und die Hülle durch eine Mehrzahl zweiter Merkmalsstoffe gebildet ist;
4. (d) Core-Shell-Teilchen, bei dem der Kern durch einen ersten Merkmalsstoff gebildet ist und die durchgehende, homogene Hülle aus einem zweiten Material gebildet ist;
5. (e) geordnetes Merkmalsstoffagglomerat, das zwei unterschiedliche Merkmalsstoffe aufweist.

In the FIG. 8 with respect to the particulate agglomerates, the following examples are shown:

1. (a) disordered feature agglomerate having two distinct (especially cohesive) feature substances and being encapsulated with a polymer or silica layer;
2. (b) disordered feature agglomerate having two distinct, cohesive feature substances;
3. (c) core-shell particles wherein the core is formed by a first feature substance and the shell is formed by a plurality of second feature substances;
4. (d) core-shell particles wherein the core is formed by a first feature substance and the continuous, homogeneous shell is formed from a second material;
5. (e) ordered feature aggregate agglomerate having two distinct feature substances.

The invention will be explained in more detail below with reference to exemplary embodiments.

<Embodiment 1>

As in the NIR luminescent phosphorus of rare earth doped yttrium-chromium perovskite from Example 2 of the document DE19804021A1 used. The ESR-active substance used is the strontium titanate doped with 1000 ppm manganese, which is described in the document US 4,376,264 is described. Both substances are present as particles with average particle sizes in the range 1-5 microns.

• 5 g des Phosphors und 5 g des ESR-aktiven Stoffes werden in 60 g Wasser dispergiert. Es werden 120 mL Ethanol sowie 3,5 mL Ammoniak (25%) zugegeben. Unter Rühren mit einem Flügelrührer werden 10 mL Tetraethylorthosilicat langsam zugegeben und die Reaktionsmischung weitere acht Stunden gerührt. Das Produkt wird abfiltriert, zweimal mit 40 mL Wasser gewaschen und bei 60°C im Trockenschrank getrocknet. Es werden Partikelagglomerate mit einer Korngröße D99 = 20-30 µm erhalten. Die erhaltenen Agglomerate werden bei 300°C eine Stunde lang getempert und anschließend mit einer Ultrazentrifugalmühle behandelt. Man erhält ein Produkt mit einer reduzierten Korngröße D99 = 15-18 µm.

For the production of agglomerates, the two substances are treated as follows:

• 5 g of the phosphor and 5 g of the ESR-active substance are dispersed in 60 g of water. 120 mL of ethanol and 3.5 mL of ammonia (25%) are added. While stirring with a paddle stirrer, 10 ml of tetraethyl orthosilicate are added slowly and the reaction mixture is stirred for a further eight hours. The product is filtered off, washed twice with 40 mL of water and dried at 60 ° C in a drying oven. Particle agglomerates with a particle size D99 = 20-30 μm are obtained. The resulting agglomerates are annealed at 300 ° C for one hour and then treated with an ultracentrifugal mill. A product with a reduced particle size D99 = 15-18 μm is obtained.

The produced agglomerates are then added to the paper pulp during sheet production so that the agglomerates are contained in the resulting sheet in a mass fraction of 0.1 weight percent.

At several different locations of the sheet, the intensity of the signal of the respective security features is determined (luminescence intensity or intensity of the ESR signal). The measured signal intensities of the two different security features correlate with each other.

<Embodiment 2>

As in the NIR luminescent phosphorus rare earth-doped lanthanum phosphate from Example 12 of the document US 2007/0096057 A1 used. As a SERS-active substance, the silica-coated BPE-loaded (BPE = trans-4, 4 'to (pyridyl) ethylene) gold particles from Example 1 of the document US 2011 / 0228264A1 used. Both substances have average particle sizes below 5 μm.

16.5 g of the phosphorus and 16.5 g of the SERS-active substance are dispersed in 245 g of water. Are added, and added dropwise with stirring over the course of one hour, a potassium water glass solution, 44 g of potassium hydrogen carbonate, so that about 15 g of SiO ₂ are deposited on the agglomerates. The product is filtered off, washed twice with 150 ml of water and dried at 60 ° C in a drying oven. Particle agglomerates with a particle size D99 = 18-20 μm are obtained.

The produced agglomerates are then added to the paper pulp during sheet production so that the agglomerates are contained in the resulting sheet in a mass fraction of 0.1 weight percent.

At several different locations of the sheet, the intensity of the signal of the respective security features is determined (luminescence intensity or intensity of the SERS signal). The measured signal intensities of Both different security features correlate with each other.

Alternatively or additionally, a single particle analysis can be performed. The luminescence properties of a single agglomerate in the sheet may be e.g. be examined with a suitable light-based microscope. The SERS properties of a single agglomerate can be studied, for example, by a suitable TERS (tip-enhanced raman spectroscopy) setup or a Raman microscope. Both the specific luminescence properties and the specific SERS properties of the security features used as starting materials can be detected in the individual particles of the agglomerates produced.

<Embodiment 3>

As in the NIR luminescent phosphorus is the rare earth-doped yttrium oxide of Example 5 of the document US 2007/0096057 A1 used. As a zero-field active material of manganese ferrite from Example 2 in Scripture WO 96/05522 used. Both substances are present as particles with average particle sizes in the range 1-5 microns.

5 g of the phosphor and 5 g of the zero-field active substance are dispersed in 60 g of water. 120 mL of ethanol and 3.5 mL of ammonia (25%) are added. While stirring with a paddle stirrer, 10 ml of tetraethyl orthosilicate are added slowly and the reaction mixture is stirred for a further eight hours. The product is filtered off, washed twice with 40 mL of water and dried at 60 ° C in a drying oven. Particle agglomerates with a particle size D99 = 20-30 μm are obtained. The resulting agglomerates are annealed at 300 ° C for one hour and then treated with an ultracentrifugal mill. A product with a reduced particle size D99 = 15-18 μm is obtained.

If the agglomerates thus produced are used as a security feature in a security document, there is a spatial correlation between the luminescence intensity of the phosphor and the zero field active substance resonance signal.

In principle, the particulate agglomerates used according to the invention can be incorporated in the value document itself, in particular in the paper substrate. Additionally or alternatively, the particulate agglomerates may be applied to the value document, e.g. be printed. The value document substrate need not necessarily be a paper substrate, it could also be a plastic substrate or a substrate having both paper components and plastic components.

Claims (9)

1. A value document comprising particulate agglomerates respectively containing at least two different homogeneous phases, wherein the first homogeneous phase is based on a luminescent substance emitting at a certain emission wavelength and the second homogeneous phase is based on a non-luminescent substance detectable by a spectroscopic method, wherein the non-luminescent substance of the second homogeneous phase is a substance detectable by nuclear magnetic resonance spectroscopy, electron spin resonance spectroscopy, nuclear quadrupole resonance spectroscopy, SER (surface-enhanced Raman) spectroscopy or SEIRA (surface-enhanced infrared absorption) spectroscopy, and wherein upon an evaluation of measurement values that are obtainable by a location-specific measurement, carried out at different locations of the value document, of the luminescence intensity at the certain emission wavelength and the intensity of the measurement signal of the spectroscopic method, there is a statistical correlation between the luminescence intensity at the certain emission wavelength and the intensity of the measurement signal of the spectroscopic method, wherein there is a statistical correlation when after computing a statistical correlation function for the obtained measurement values and after comparing the amount thereof with a threshold value, with a correlation function normalized in terms of amount to a values range of 0 to 1, an existing statistical correlation is recognized when the amount is > 0.3.
2. The value document according to claim 1, wherein the exciting electromagnetic radiation of the spectroscopic method is radio-wave, microwave, terahertz or infrared radiation.
3. The value document according to either of claims 1 and 2, wherein the agglomerates are chosen from the group consisting of core-shell particles, particle agglomerates, encapsulated particle agglomerates and nanoparticle-encased particles.
4. The value document according to any of claims 1 to 3, wherein the particulate agglomerates have a grain size D99 in a range of 1 micrometer to 100 micrometers, preferably 5 micrometers to 30 micrometers, particularly preferably in a range of 10 micrometers to 20 micrometers.
5. The value document according to any of claims 1 to 4, wherein the luminescent substance of the first homogeneous phase is based on a matrix-forming inorganic solid which is doped with one or more rare earth metals or transition metals.
6. The value document according to any of claims 1 to 5, wherein, in addition to the particulate agglomerates, there is incorporated into or applied to the value document in uniform concentration a non-correlating correction component which luminesces at a certain emission wavelength or is detectable separately with a spectroscopic method, wherein the spectroscopic method is in particular the same as that of the second homogeneous phase of the particulate agglomerate or another spectroscopic method.
7. A method for checking the presence or the authenticity of a value document according to any of claims 1 to 6 comprising:

   a) exciting the luminescent substance, emitting at a certain emission wavelength, of the first homogeneous phase and exciting the non-luminescent substance, detectable by a spectroscopic method, of the second homogeneous phase;

   b) spatially resolved capturing of measurement values for the radiation emitted by the luminescent substances, on the one hand, and for the measurement-signal intensity deriving from the non-luminescent substances and arising from the spectroscopic method, on the other hand, in order to generate first luminescence-emission intensity/location measurement-value pairs and second measurement-signal intensity/location measurement-value pairs;

   c) checking whether there is a statistical correlation between the luminescence-emission intensities and the measurement-signal intensities arising from the spectroscopic method, wherein there is a statistical correlation when after computing a statistical correlation function for the obtained measurement values and after comparing the amount thereof with a threshold value, with a correlation function normalized in terms of amount to a values range of 0 to 1, an existing statistical correlation is recognized when the amount is > 0.3.
8. The method according to claim 7, wherein the measurement values for the radiation emitted by the luminescent substances, on the one hand, and for the measurement-signal intensity deriving from the non-luminescent substances and arising from the spectroscopic method, on the other hand, are converted into corrected measurement values in an intermediate step.
9. The method according to claim 7, wherein only those measurement values for the radiation emitted by the luminescent substances, on the one hand, and for the measurement-signal intensity deriving from the non-luminescent substances and arising from the spectroscopic method, on the other hand, that respectively lie within a certain values range, in particular above a certain threshold value, are drawn on for determining authenticity.

Images