EP3717273B1 - Coding system for forming a security feature in or on a security document or value document or a plurality of security documents or value documents - Google Patents

Description

The invention relates to a coding system for forming a security feature in or on a security document or document of value or a plurality of documents of security or value. Furthermore, the invention relates to a security feature which is in the form of a plurality of security elements. In addition, the invention also relates to a security document or document of value comprising a security feature according to the invention.

Background of the Invention

Luminescent organic and/or inorganic materials have long been used in a variety of ways as security features in security and value documents, such as banknotes, passports, ID cards, driver's licenses, etc., but also in product protection.

From the GB 1 143 362 A and the GB 1 186 251 A it is known to use combinations of inorganic and/or organic rare-earth-activated phosphors, which emit in particular in a narrow-band manner in the visible or infrared spectral range, in security documents or documents of value in order to use them to generate luminescence codes. In favor of reliable recognition of the codes, phosphors were selected in the publications listed which are characterized by comparatively large spectral distances between the individual emission lines.

Also from the DE 103 46 685 A1 It is known that the spectral distance between the individual emission lines of the phosphors used to implement a coding system should be at least 10 nm. In the publication last cited, the use of phosphor pigments emitting exclusively outside the visible spectral range is regarded as a significant advantage over the prior art known up to that point.

The pamphlet DE 601 18 472 T2 relates to a device for protecting documents, in which at least two printable motifs are provided with two inks, which produce identical (luminescent) colors upon a first UV excitation with a first wavelength and upon a second UV excitation with a different, second wavelength emit different (luminescent) colors.

The document WO 2017/080654 A1 relates to a pigment system of different capsule luminescence pigments which have different emission spectra and different color impressions of the luminescence emissions and which are said to have essentially the same chemical stability.

From the document U.S. 2009/141961 A1 a method is known for applying and reliably authenticating the emission spectra of luminescent security features with the aid of multivariable statistical methods.

The document EP 1 647 947 A1 describes a device and a method for checking luminescence security features, the response signals measured after excitation having overlapping spectral bands.

The document U.S. 2013/221656 A1 discloses a light-emitting medium which is applied to a substrate in the form of a motif and in turn comprises two different fluorescent materials which emit in mutually distinguishable colors both when excited with a first and with a second UV wavelength.

object of the invention

Both in the area of security and value printing and in the area of product protection, there is increasing interest in the use of "Public Security Features" (Level 1 features that can be checked by humans without additional devices by sight and touch) and in the use of Level 2 features based on optical effects, which, due to the increasing general availability of simple hand-held devices for optical stimulation (e.g. in the form of easy-to-use UV or infrared LEDs), are also increasingly perceived as security features by "normal citizens". and can be evaluated.

Some of the luminescent security elements belonging to this class of features can already be found in countless security and value documents (passports, identity cards, theater tickets), but such “quasi-level 1” features often lack the required security against forgery.

It is therefore desirable to use exclusive luminescent security features in corresponding security and value documents, which can be made visible with simple tools, but at the same time would contain more extensive information that goes beyond the visual impression.

In particular, it is desirable if these luminescent security features also have a level 3 security characteristic in addition to their level 2 functionality, which could consist in the provision of machine-readable codes. Such codes could be used to verify the authenticity, to encode the nominal value or to sort, for example, different denominations of banknotes or products of value.

The invention is based on the technical problem of providing a coding system for forming a security feature in or on a security document or document of value and a system for forming security features in the form of security elements in which the security features can be made visible using simple excitation sources and at the same time an increased and required protection against counterfeiting is provided.

The technical problem is solved according to the invention by a coding system according to claim 1, a security feature according to claim 19 and a security or valuable document according to claim 20. Advantageous configurations of the invention result from the dependent claims.

definitions

Luminescence is the electromagnetic radiation emitted by a physical system during the transition from an excited state to the ground state. Depending on the excitation conditions and the spectral range of the emitted electromagnetic radiation, different types of luminescence are distinguished (e.g. photoluminescence, cathodoluminescence, X-ray luminescence, electroluminescence, etc.). Here, photoluminescence refers to the type of luminescence in which excitation takes place with the aid of UV radiation and the resulting luminescence radiation is emitted in the visible spectral range (VIS, approx. 380 to 780 nm).

Anti-Stokes luminescence (up-conversion) is a special case of luminescence, in which multi-stage IR-induced excitation also emits in the visible spectral range.

Luminescent substances are organic or inorganic chemical compounds which show luminescence when excited by electromagnetic or particle radiation or when excited by electric fields. In order to make this possible, activator and optionally additional coactivator ions acting as radiation centers are built into the phosphor basic lattices (phosphor matrices) formed by the chemical compounds. These phosphors are often present as solid bodies, in particular in the form of luminescence pigments.

An emission spectrum describes the spectral distribution of the electromagnetic radiation emitted by the phosphors or of the light emitted by them. Such an emission spectrum can consist of emission lines and/or emission bands.

A code is generally a mapping rule for assigning characters, symbols or measurable properties to a set of characters. In the case of luminescent codes the measurement data to be assigned result from the spectral sequence of the emission lines and/or emission bands of the selected phosphors and/or phosphor combinations, which are generally determined by the wavelengths of the emission maxima (λ _max values), the intensity ratios between the selected emission lines and/or bands and possibly also characterized by the half-widths of these emissions.

The CIE standard valence system (also called CIE standard color system) is a three-dimensional colorimetric system that was defined by the Commission Internationale de l'éclairage (CIE) in 1931 and enables colors and self-luminous objects to be described using the standard color values X, Y and Z. These result from linear, additive evaluation of the respective emission spectrum with one of the three standard spectral value functions x ( λ ), y ( λ ) and e.g ( λ ).

The terms "CIE standard valence system" and "CIE standard color system" are used equivalently in the present invention.

The CIE color coordinates x, y and z denote the ratios of the standard color values X, Y and Z to their sum. The representation of the color coordinates x and y results in the two-dimensional standard color chart, which then no longer contains the brightness information. Due to the physiology of the eye, different spectral distributions can lead to identical color coordinates.

The CIE normal valence system is based on the definition of an ideal normal observer whose spectral value functions are the normal spectral value functions x ( λ ), y ( λ ) and e.g ( λ ) correspond. Colors and self-luminous materials (e.g. phosphors) that have the same color coordinates are referred to as color-identical.

Color sensation and color perception of an individual observer can deviate from those of the defined standard observer.

Color discrimination characterizes the extent to which color differences are perceived by individual observers.

For example, the so-called MacAdam ellipses describe tolerance ranges in the standard value table, which are distinguished by the fact that they are on different x, y coordinates based color differences of different colors under defined visual conditions and with a certain probability of individual observers are not perceived. A tolerance for the color differences can thus be specified for the perceived color equality, which can be dependent on the color value.

Maximum permissible color differences in the sense of perceived color equality can be determined by questioning test persons. Such investigations are referred to as psychometric measurements, in which the probability of perceiving a color difference is determined. Two color samples are considered to have the same color if they are judged by a sufficiently large collective of observers to be indistinguishable with a specified probability as being indistinguishable under the specified excitation conditions. Measurement methods for this are, for example, BACKHAUS, WGK KLIEGL, R. WERNER, JS: Color Vision. Perspectives from different disciplines. Cape. 2.3. "Psychophysics of Color Vision " as IRTEL, H.: "Methods of Psychophysics ". and in ERDFELDER, E.: Handbook of quantitative methods (pp. 479-489), Physiology Verlags Union Weinheim 1996 , described.

The acceptable color differences of the objectively measured color coordinates, which individual observers still regard as having the same color, can thus be predetermined.

The term "color-identical" or "color identity" is thus understood in the present invention to mean that two phosphors have identical color coordinates in the CIE standard valence system under specified excitation conditions.

The term "equal color" or "equal color" is understood in the present invention to mean that two phosphors under a specified excitation that are within a tolerance color range of the CIE standard color system, for example a MacAdam ellipse, by a sufficiently large collective of observers among the given excitation conditions are rated as indistinguishable with a specified probability.

basic idea of the invention

One aspect of the invention relates to the coding system defined in claim 1.

Another aspect of the invention relates to the security feature defined in claim 19.

According to the invention, the object described above is achieved in that the codes forming the respective codes in the ultraviolet spectral range (namely at wavelengths between 380 and 315 nm (UV-A), 315 and 280 nm (UV-B) and between 280 and 200 nm ( UV-C)) or phosphors that can be excited in the infrared spectral range (IR, for example at 950 or 980 nm) and that emit in the visible range are assembled and combined to form security elements, for example corresponding markings, in such a way that the For example, with a specific UV radiation source, color impressions of different security elements of a security feature are perceived by the human eye as having the same color. This means that the viewer sees the different, under visibly luminescent security elements under the specified excitation conditions, for example in the form of markings, which are attached as security features to, on or in a value or security document, as having the same color and thus presumably considering them to be spectrally identical, although they actually have different electromagnetic spectra and codes defined via them that can only be verified with the help of a special luminescence measurement technique.

The security elements of a security feature that are perceived as having the same color in terms of their luminescence can be used in different security or valuable documents (for example banknotes, ID cards, passports, driving licenses, etc.) or also in product protection. Markings that appear the same color but have different codes can be used, for example, for the purpose of coding the denomination of different currency denominations. On the other hand, however, it is also possible to integrate the markings perceived as having the same color as security features several times in the same, similar or different designs of one and the same security or value document.

On the basis of model calculations and through practical tests, it was possible to prove that to realize security elements of the same color or of identical color, phosphors emitting in the visible spectral range both linearly and in bands and/or combinations thereof can be used. Theoretically, there are countless possibilities for the realization of identical x-y coordinates within the CIE standard valence system. The specific selection and the number of phosphors and phosphor combinations used with exclusive narrow-band and/or broad-band emission depends on the desired color impression, but at the same time also on the respective security requirement and the permitted effort for the detection of the emitted luminescence and the verification of the code.

Furthermore, it has been shown that color-identical or color-same security elements can be produced both with emission lines and/or emission bands that are close together but also with emission lines that are further apart. The spectral distance of the individual emission lines is not directly decisive for the desired identical color impression of the emitted luminescence of the individual markings, but it is for the effort that has to be made for reliable spectrometric verification. Further criteria for the selection of the phosphors for the coding system are, for example, the highest possible luminescence yield, sufficiently high stability and aging resistance to environmental influences, and a grain size distribution of the luminescent pigments adapted to the selected printing and application processes. These properties are also of great importance, for example, for the manner in which the security elements are used on or in the respective security and value documents and for reliable verifiability over the entire life or useful life of the security or value document.

The application of the security elements, for example in the form of markings, can take place, for example, using conventional printing technologies (gravure printing, flexographic printing, offset printing or screen printing processes, etc.) or using other types of coating processes, the materials to be coated being made of paper, different Plastics or can also consist of other organic or inorganic substances. Furthermore, provision can also be made to use the security elements by adding the phosphors to plastics, with the plastics then being introduced into the security document or document of value.

Numerous phosphors are available both for excitation with UV radiation and for IR excitation for the realization of color-identical or color-same security elements, for example in the form of markings. In particular in the case of the use according to the invention of combinations of several phosphors, the resulting emission spectra are mostly highly complex. Codes formed using these combinations have a level 3 security level and can only be verified with the help of powerful and possibly very complex luminescence measurement technology and with the special or secret knowledge about which of the diverse and different emission lines or bands are used for the evaluation .

The materials listed below can be used as the basic lattice (matrix) for the UV-excitable inorganic phosphors used to produce the security elements according to the invention: borates (e.g. LaBO ₃ , SrB ₆ O ₁₀ , CaYBO ₄ , SrB ₄ O ₇ , YAl ₃ B ₄ O ₁₂ , SrB ₈ O _13' Ca ₂ B ₅ O ₉ Br), nitrides (e.g. CaAlSiN ₃ , Sr ₂ Si ₅ N ₈ , MgSiN ₂ , GaN), oxynitrides (e.g. SrSi ₂ N ₂ O ₂ , α-SiAlON , β-SiAlON, oxides (e.g. Al ₂ O ₃ , CaO, Sc ₂ O ₃ , TiO ₂ , ZnO, Y ₂ O ₃ , ZrO ₂ , La ₂ O ₃ , Gd ₂ O ₃ , Lu ₂ O ₃ ), halides and oxyhalides (e.g. CaF ₂ , CaCl ₂ , K ₂ SiF ₆ , LaOBr), aluminates (e.g. LiAlO ₃ , SrAl ₂ O ₄ , Y ₃ Al ₅ O ₁₂ , BaMgAl ₁₁ O ₁₇ , CaAl ₂ O ₄ , Sr ₄ Al ₁₄ O ₂₅ ), silicates (e.g. Ba ₂ SiO ₄ , Sr ₃ SiO ₅ , Sr ₃ MgSi ₂ O ₈ , Sr ₂ MgSi ₂ O ₇ , CaSiO ₃ , Zn ₂ SiO ₄ , Ba ₂ SiO ₄ , Y ₂ SiO ₅ , CaMgSi ₂ O ₆ , Ba ₂ Li ₂ Si ₂ O ₇ , LiCeBa ₄ Si ₄ O ₁₄ , Ca ₃ Al ₂ Si ₃ O ₁₂ ), halosilicates (e.g. LaSiO ₃ Cl, Ba ₅ SiO ₄ Cl ₆ , Sr ₅ Si ₄ O ₁₀ Cl ₆ ), phosphates (e.g. YPO ₄ , Ca ₂ P ₂ O ₇ , MgBaP ₂ O ₇ , Ca ₃ (PO ₄ ) ₂ , MgBa ₂ (PO ₄ ) ₂ ), halophosphates (e.g. Ca ₅ (PO ₄ ) ₃ Cl, Sr ₅ (PO ₄ ) ₃ Cl), sulfides (e.g. ZnS, CaS, SrS, BaS, SrGa ₂ S ₄ , ZnGa ₂ S ₄ , ZnBa ₂ S ₃ ), oxysulfides (e.g. Y ₂ O ₂ S, La ₂ O ₂ S, Gd ₂ O ₂ S, Lu ₂ O ₂ S), sulfates (e.g. Mg ₂ Ca (SO ₄ ) ₃ ), gallates (e.g. Y ₃ Ga ₅ O ₁₂ , CaGa ₂ O ₄ , Gd ₃ Ga ₅ O ₁₂ ), vanadates (e.g. YVO ₄ ), molybdates and tungstates (e.g. CaMoO ₄ , Sr ₃ WO ₆ , La ₂ W ₃ O ₁₂ , Tb ₂ Mo ₃ O ₁₂ , Li ₃ Ba ₂ La ₃ (MoO ₄ ) ₈ ),
or also such inorganic substance classes as, for example, borides, carbides, scandates, titanates, germanates and yttrates. This enumeration does not represent any restriction; other material classes or individual compounds can also be included in the selection of the inorganic solid-state compounds suitable as the phosphor basic lattice.

The selected basic lattice is activated by the targeted incorporation of one or more foreign ions into the respective phosphor matrix. In the case of phosphors that can be excited in the ultraviolet spectral range and emit in the visible range, primarily rare earth ions and/or ions of transition metals are used for doping or co-doping . These activator ions and any additionally introduced coactivator ions form the radiation centers in the respective basic lattices and, in interaction with them, determine the luminescence properties of the inorganic phosphors. In the case of the exemplary use of trivalent ions of the rare earths such as Pr ³⁺ , Sm ³⁺ , Eu ³⁺ , Tb ³⁺ , Er ³⁺ , Dy ³⁺ , Tm ³⁺ or 3d ³ ions such as Cr ³⁺ , Mn ⁴⁺ usually linear emissions after UV excitation, while doping the basic lattice mentioned by way of example with ions such as Mn ²⁺ , Cu ⁺ , Ag ⁺ , Sn ²⁺ , Sb ³⁺ , Pb ²⁺ , Bi ³⁺ , Ce ³⁺ and Eu ²⁺ emission bands are obtained with high probability.

The conversion of infrared excitation radiation into visible light, brought about with the help of phosphors, is referred to as anti-Stokes luminescence or up-conversion. It is only possible by providing such phosphor materials that are capable of transforming the stimulating IR radiation into the visible spectral range through multi-stage excitation processes. The basic lattice for such inorganic phosphors that can be used according to the invention are primarily oxidic compounds (e.g. Y ₂ O ₃ , ZrO ₂ , La ₂ MoO ₆ , LaNbO ₄ , LiYSiO ₄ ), oxyhalides (e.g. YOCl, LaOCl, LaOBr, YOF, LaOF), Oxysulfides (e.g. Y ₂ O ₂ S, La ₂ O ₂ S, Gd ₂ O ₂ S, Lu ₂ O ₂ S) and fluorides (e.g. YF ₃ , LaF ₃ , LiYF ₄ , NaYF ₄ , NaLaF ₄ , BaYF ₅ ). Disposal. To ensure a sufficiently high Due to the luminescence yield, the rare earth ion combinations Yb ³⁺ -Er ³⁺ , Yb ³⁺ -Tm ³⁺ and Yb ³⁺ -Ho ³⁺ are mostly used as radiation centers in the anti-Stokes phosphors. In addition, however, other phosphors such as the materials SrF ₂ :Er ³⁺ , YF ₃ :Yb ³⁺ , Tb ³⁺ or CaF ₂ :Eu ²⁺ are also known, which can also be used as IR-VIS radiation converters.

In addition to the inorganic luminescent pigments, organic phosphors that can be excited in the UV or IR spectral range and emit in the visible range, such as different, rare earth-activated organic complex compounds, can of course also be used in the context of the invention to produce color-identical security elements. These can optionally be combined with selected inorganic luminescent pigments.

In addition, depending on the specific application, the desired design of the security feature and the technology envisaged for the production of the security elements, photoluminescent inorganic or organic nanoscale phosphors or correspondingly configured quantum dots are also suitable as components for providing the required phosphor components.

In a particularly preferred embodiment, the phosphors selected for the respective application of the coding system are modified by deliberately changing the chemical composition of the respective host (basic) lattice, i.e. by deliberately made substitutions in the cation and/or anion partial lattice, so that the Emission spectra of these exclusive phosphors differ significantly from those of the luminophores used in conventional technical applications or from those that have been described in detail in the specialist literature. The protection against forgery of the value or security documents equipped with the coding system can be further increased by the preferred use of such phosphors with exclusive emission spectra.

The coding system according to the invention offers a variety of embodiments for different security levels and possible applications. Color-identical or color-same markings can be provided, the authenticity of which can be checked with simple hand-held sensors, but also those where high-resolution spectrometers are required for reliable verification of the code. The span of the Verification options range from forensic testing in a special laboratory to high-speed detection of machine-readable codes.

Special embodiments

An advantageous embodiment of the invention relates to a coding system, wherein the luminescence codes assigned to the luminescent security elements are formed from the different spectral sequence of the individually marked emission lines and/or emission bands of the phosphors and/or phosphor combinations.

A further embodiment of the invention relates to a coding system, the luminescence codes assigned to the luminescent security elements being formed from the intensity ratios of the individually marked emission lines and/or emission bands of the phosphors and/or phosphor combinations.

Yet another exemplary embodiment of the invention relates to a coding system, wherein at least one additional phosphor and thus additional phosphor combinations are provided to form additional luminescent security elements with other luminescent codes.

A particularly advantageous embodiment of the invention relates to a coding system in which the color coordinates of the luminescent security elements are adjusted via mixing ratios of the phosphors used for phosphor combinations, resulting in defined relative intensity ratios of the individually marked emission lines and/or emission bands for the phosphor combination.

Another embodiment of the invention relates to a coding system, wherein at least one of the phosphors has an organic phosphor, in particular a rare earth-activated organic complex compound.

An advantageous embodiment of the invention relates to a coding system, wherein at least one of the phosphors has an inorganic phosphor.

Another embodiment of the invention relates to a coding system, wherein both inorganic and organic phosphors of different particle size, and for example also nanoscale phosphors or quantum dots, as well as corresponding phosphor combinations can be used.

An advantageous embodiment of the invention relates to a coding system, the phosphors being modified by targeted substitutions in the phosphor lattice, so that they have an exclusive emission spectrum.

Yet another embodiment of the invention relates to a coding system, the phosphors and/or phosphor combinations in one or more ultraviolet wavelength ranges, namely at wavelengths between 380 nm and 315 nm (UV-A) and/or at wavelengths between 315 nm and 280 nm ( UV-B) and/or can be excited at wavelengths between 280 nm and 200 nm (UV-C).

A particular embodiment of the invention relates to a coding system in which the luminescent security elements of the security feature are identical in color under at least two excitation conditions that can be set in the ultraviolet spectral range, i.e. in the UV-A and/or in the UV-B and/or in the UV-C spectral range or be perceived in the same color.

A further embodiment of the invention relates to a coding system, wherein the luminescent security elements of the security feature are color-identical or are perceived as the same color for each of the specified excitations in the UV-A, UV-B or UV-C spectral range.

An advantageous embodiment of the invention relates to a coding system in which the luminescent security elements of the security feature have different color coordinates in the CIE standard color system for different predefined stimuli, or at least such color coordinates that lie within a different tolerance color range of the CIE standard color system, so that the luminescent security elements do not have a certain given suggestions are perceived as color-identical or the same color, but have a different color identity or color sameness in the case of another given suggestion.

An exemplary embodiment of the invention relates to a coding system, in which the phosphors and/or phosphor combinations can be excited in the infrared wavelength range, namely at wavelengths between 950 nm and 980 nm.

Another embodiment of the invention relates to a coding system, wherein the maxima of the individually marked emission lines and/or emission bands of the phosphors and/or phosphor combinations are only a few nanometers apart, in particular a distance of less than 10 nm, particularly preferably a distance of less than 5 nm, most preferably have a distance of less than 3 nm.

Another embodiment of the invention relates to a coding system, wherein further information about the manner in which the security elements of the security feature are arranged, for example about the location or a form of the security element, for example in the form of a symbol, number or pictogram, is assigned to the security element.

An advantageous embodiment of the invention relates to a coding system, wherein all color coordinates of the phosphors comprised by the coding system essentially lie on a straight line in the CIE standard color system.

A further embodiment of the invention relates to a coding system, in which the phosphors and/or phosphor combinations have essentially the same or similar aging resistance.

The foregoing specific embodiment examples of the invention are described in further detail below.

The inventive coding system for forming a security feature in or on a security or valuable document or a plurality of security or valuable documents is particularly characterized in that it is based on the use of different non-visible spectral range, especially in the ultraviolet (UV) or phosphors and/or phosphor combinations that can be excited in the infrared (IR) spectral range and emit in the visible spectral range, the phosphors and/or phosphor combinations each having different emission spectra in the visible spectral range under specified excitation conditions, so that each of the phosphors and/or phosphor combinations is characterized by at least one individually distinguished Characterized emission line or emission band is, which differs from the individually distinguished emission lines or emission bands of the other phosphors and/or phosphor combinations.

The coding system is also characterized in that it comprises at least three, preferably exclusive, phosphors and/or the phosphor combinations created from these phosphors, which are combined in the form of security elements to form security features, and each security element is assigned a code that consists of the spectral Sequence of the individually distinguished emission lines or emission bands of the at least three phosphors and/or phosphor combinations and/or the intensity ratios of these emission lines and/or emission bands is formed.

At the same time, the inventive solution is characterized in that all luminescent security elements combined to form a security feature have identical color coordinates in a CIE standard color system under the specified excitation conditions, or at least such color coordinates that are within a tolerance color range of the CIE standard color system, for example a MacAdam ellipse. In this way, it can be ensured that all security elements of a security feature according to the invention that are equipped with luminescence codes are perceived by the viewer as having the same color under defined excitation conditions.

When using exactly three phosphors to form a security feature of the coding system, the color coordinates of the emission spectra of the individual phosphors in the CIE standard color system must lie largely on a straight line in order to be able to provide several different luminescence codes with identical color coordinates by combining these phosphors. As model calculations and practical tests have shown, in this case at least three distinguishable codes can be generated with exactly identical color coordinates and a different spectral sequence of the individually marked emission lines, which are generated by combining two of the three selected phosphors (pairs of phosphors) and by a corresponding combination of three ( Phosphor triple) can be formed. If, in addition to the spectral characteristics, the intensity ratios between the selected emissions are also used to set the code, there are further possibilities for the formation of distinguishable combinations of three. The exact setting of the color coordinates of the individual combinations is based on specific mixing ratios bound between the individual phosphors. In contrast, with a triangular arrangement of the color coordinates of three different phosphors resulting from the emission spectra around a predetermined target color coordinate, there is only one possibility of setting the exact target color location. This means that only a single luminescence code could be generated in this way.

However, security elements equipped with luminescence codes can also be perceived by the viewer as having the same color if the respective color coordinates are not exactly identical but are positioned within a tolerance color range of the CIE standard color value system (for example a MacAdam ellipse). Corresponding investigations have shown that even when only three phosphors are used under these conditions, it is possible, for example, to provide up to seven different luminescence codes that are evaluated by subjects as having the same color. In addition to the spectral sequence of the individual emission lines and/or bands, the differently adjusted intensity ratios between these lines and/or bands must then also be included in the code formation as characteristic properties.

By adding further, preferably exclusively modified, phosphors, the possibilities for providing distinguishable luminescence codes can be further increased. It must be taken into account that the number of codes that can be generated also depends, for example, on the specific positioning of the target color location and on the permitted spectral distances between the maxima of the individually marked emission lines and/or bands. In addition, it should be noted that the luminophores used in practice, for example modified rare earth-activated phosphors, usually have several emission lines and often complex line spectra even as individual components. This also increases the number of possible code assignments at the level 3 security level.

A further essential aspect of the invention provides a method for producing a security feature of a coding system for use in security documents or documents of value and in product protection.

In a first step, decisions must be made about the excitation conditions for the inventive luminescence feature, about the desired target color location or a correspondingly defined tolerance color range for the realization of the desired color identity of the individual security elements required for the security feature and the number of codes required for authenticity protection. These decisions depend on the type and use of the value and security documents to be protected or the products worthy of protection, the permitted effort for the verification of the luminescence codes and the design specifications for the feature.

A further step concerns the selection of the phosphors required for the production of the required security elements. The selection can be made on the basis of the measured emission spectra of the phosphors to be evaluated, preferably with exclusive emission characteristics. The CIE color coordinates of the individual phosphors, which can be calculated from the emission spectra, provide information on whether and how many combinations of these phosphors are available for realizing the specified target color location or a corresponding tolerance color range. On the basis of these measurement results, the mixing ratios of the components that are important for the production of the phosphor combinations can be calculated in advance.

The subsequent step of the method is aimed at the experimental verification that may be required and the determination of the mixing ratios for the creation of the color-identical security elements of the security feature. As a rule, only a few practical tests are required to determine, on the basis of the colorimetric calculations carried out, the mixing ratios valid under application conditions for the combination of the selected phosphors to form color-identical security elements. However, the experimental verification is necessary to determine interactions between the phosphors used and other influencing factors that affect the independent and different optical properties (self-emission, absorption and reflection behavior) of the other organic and inorganic components (binders, additives) for the application of the security feature color compositions used and the optical effects of the carrier materials used.

In a further method step, the selected phosphors and/or phosphor combinations are applied or introduced onto or into the carrier materials of the respective security or value documents. This process step can be carried out, for example, with the help of the usual printing processes (gravure, flexographic, offset or screen printing). etc.) or using other coating technologies.

A final step in the method for producing a security feature according to the invention is reserved for the final code assignment. On the basis of the emission spectra measured under defined excitation conditions of the individual security elements equipped with phosphors and/or phosphor combinations of the same color or the same color, the code-forming emission maxima (λ _max values) required and suitable for the authenticity verification of the individually marked, preferably exclusive emission lines and/or emission bands as well as those emission lines and/or bands for which the ratio of the respective luminescence intensities can be viewed as a property representing a code are selected and assigned to a set of characters, for example a sequence of numbers or letters.

Furthermore, the essence of the invention is determined by the provision of a method for reading out the luminescence codes and for verifying the authenticity of the security elements, embodied for example as markings, of a security feature of the coding system according to the invention. This method includes: stimulating the phosphors and/or phosphor combinations present in the security elements with a predetermined invisible stimulating radiation, which is generated in particular by suitable UV or IR radiation sources, detecting the electromagnetic spectra of these phosphors and/or phosphor combinations in a predetermined visible range spectral range with the help of suitable optical spectrometers, as well as the evaluation of the measurement results and the subsequent authenticity assessment, whereby the presence of the deposited code-relevant emission characteristics is checked and compared with the deposited code information.

The technical outlay required for the secure verification of the luminescent codes of identical color or of the same color introduced into the individual security elements forming the respective security feature of the coding system depends on various factors. These include the width of the spectral range to be detected in the visible and the extent of the complexity of the individual, preferably exclusive emission spectra of the phosphors and/or phosphor combinations used, with in particular small spectral distances between the maxima of the characteristic emission lines and/or bands relevant for code formation use from high-performance optical spectrometers with a high spectral resolution.

A further essential factor relates to the requirements for the detection speed resulting from the practical application of the security features according to the invention in value and security documents or in product protection. Extensive investigations have shown that on the basis of the invention, machine-readable Level 3 security features can be compiled whose luminescence codes can be reliably verified both at the detection speeds that are usual in ATMs (Cash Management System) and in the sorting machines of central banks .

On the other hand, in terms of security against forgery, it is of course quite advantageous if, for example, at least two of the individually labeled emission lines of the color-identical security elements are so close together that they cannot be distinguished from one another without major technical effort.

The advantage of the invention lies in the great scope for the concrete design of the security elements belonging to an inventive security feature, which is opened up by the diverse possible combinations of the different phosphors. It is thus possible to decide exactly how small the spectral distance of the at least two individually marked emission lines, for example, should be with regard to the highest level of protection against forgery and how small it should be in view of the verification circumstances, for example under the conditions of high-speed detection can. In an advantageous embodiment of the invention, it is therefore provided that the maxima of at least two of the individually marked, preferably exclusive emission lines of the security elements belonging to a security feature in the electromagnetic spectrum are only a few nanometers apart, with these preferably being at a distance of less than 10 nm, more preferably have a distance of less than 5 nm and, most preferably have a distance of less than 3 nm.

A particularly advantageous embodiment of the invention consists in the fact that the security elements put together to form security features not only in the case of a predetermined optical stimulus, but also at least in the case of a further, the first fundamentally distinguishable optical stimulus, are perceived by the human eye as having the same color. As is generally known and already described, the ultraviolet spectral range is divided into the UV-A (380-315 nm), UV-B (315-280 nm) and UV-C (315-280 nm) ranges in the literature and in technical applications. Radiation range (280-100 nm) subdivided, with different radiation sources being available for the individually defined types of radiation. In this context, it has surprisingly been shown that for the production of a security feature of the coding system according to the invention, such phosphors and phosphor combinations can also be selected whose preferably exclusive emission spectra, for example both when excited with UV-A and UV-B radiation sources in the CIE - Standard color system have identical color coordinates or those that lie within designated tolerance color ranges, so that all security elements of the corresponding security feature equipped with different luminescence codes are perceived by the viewer as having the same color under both excitation conditions.

In addition, it could be demonstrated that, on the basis of the invention, luminescent security elements can also be provided for changing between UV-A and UV-C excitation or for changing between UV-B and UV-C excitation, in which the color impressions perceptible after the excitation are retained even if the excitation conditions change. In a particularly advantageous embodiment of the invention, the security elements selected for the formation of a security feature of the coding system are of the same color for all excitation conditions that can be set in the ultraviolet spectral range, i.e. both for excitation with UV-A, UV-B or UV-C radiation sources identified.

The variety of possible variations for the implementation of the invention is also expressed in the fact that even if the perceptible color impressions of the security elements change as a result of changing the UV excitation sources, the emission spectra of the selected phosphors and phosphor combinations can advantageously be adjusted in such a way that the luminescent elements are evaluated as having the same color as one another under the respectively defined excitation conditions. This means that the observer perceives all security elements as red in the same color for one type of excitation, for example, and as green for the other type of excitation, for example.

In a further preferred embodiment of the invention, the security elements used to form an inventive security feature, which have the same color impressions under different excitation conditions, preferably in the UV spectral range, can also be equipped in such a way that the individually marked, and in particular exclusive emission lines and/or emission bands are only emitted with one of the different types of excitation and are therefore only available for authenticity verification under these excitation conditions.

In order to further increase the security of the security elements, it can be expedient to include further information in the verification. Therefore, in a further advantageous embodiment, it is also provided that the coding system forms further information about an arrangement and/or a contour of the security elements on or in the security document or document of value. Such an arrangement can be, for example, a specific position on the security document or document of value. However, the security element itself can also have a specific contour, for example the shape of a character, a symbol, a number or a pictogram. During verification, the position on the security or value document and/or the arrangement and/or the presence of the corresponding contour of the security element are then additionally checked.

Fig. 1a - e:

die Emissionsspektren von drei Modellleuchtstoffen sowie die dazugehörigen Farbkoordinaten, dargestellt in einem CIE- Normfarbsystem bzw. der Normfarbtafel des CIE-Normfarbsystems,

Fig. 2a - f:

die Emissionsspektren von Leuchtstoffkombinationen, die aus den in den Fig. 1a bis Fig. 1e gezeigten drei Modellleuchtstoffen gebildet sind, und deren Farbkoordinaten mit dem vorgegebenen Zielfarbort übereinstimmen,

Fig. 3a - e:

weitere Emissionsspektren von drei anderen Modellleuchtstoffen sowie die dazugehörigen - in einem CIE- Normfarbsystem bzw. der Normfarbtafel - dargestellte Farbkoordinaten dieser Modellleuchtstoffe,

Fig. 4a - e:

die Emissionsspektren von Leuchtstoffkombinationen, die aus den in den Fig. 3a bis Fig. 3e gezeigten drei anderen Modellleuchtstoffen gebildet sind, und deren Farbkoordinaten mit dem in der Fig. 4a gekennzeichneten Zielfarborts übereinstimmen,

Fig. 5a - e:

Beispiele für weitere farbidentische Emissionsspektren von weiteren Leuchtstoffkombinationen aus vier Modellleuchtstoffen, wobei die Farbkoordinaten der vier einzelnen Modellleuchtstoffe gemäß Fig. 5a in Form eines Vierecks um einen möglichen Zielfarbort positioniert sind,

Fig. 6a - c:

beispielhaft drei reale Emissionsspektren von drei ausgewählten realen Leuchtstoffen,

Fig. 7a - e:

beispielhaft Emissionsspektren von Leuchtstoffkombinationen, insbesondere Leuchtstoffpaaren und Dreierkombinationen, die aus den in den Fig. 6a bis Fig. 6c gezeigten drei ausgewählten realen Leuchtstoffen gebildet sind,

Fig. 8

die Farbkoordinaten in der CIE-Normfarbtafel der in den Fig. 7a - e gezeigten Emissionsspektren der Leuchtstoffpaare und Dreierkombinationen der drei ausgewählten realen Leuchtstoffen, und

Fig. 9 a & b

die Farbkoordinaten in der CIE-Normfarbtafel der in den Fig. 6a - c sowie ind den Fig. 7a - e gezeigten Emissionsspektren der ausgewählten realen Leuchtstoffe und Leuchtstoffkombinationen sowie einen ermittelten Toleranzfarbbereiche für die beschriebenen realen Leuchtstoffe und Leuchtstoffkombinationen bei unterschiedlichen Anregungsbedingungen, nämlich einmal bei einer 313 nm-Anregung (Fig. 9a:) und ein anders Mal bei einer 365 nm-Anregung (Fig. 9a).

The invention is explained in more detail below on the basis of preferred exemplary embodiments with reference to the figures. Here show:

Fig. 1a - e:

the emission spectra of three model phosphors and the associated color coordinates, shown in a CIE standard color system or the standard color table of the CIE standard color system,

Fig. 2a - f:

the emission spectra of phosphor combinations resulting from the Figures 1a to 1e three model phosphors shown are formed, and whose color coordinates match the specified target color location,

Fig. 3a - e:

other emission spectra of three other model phosphors and the associated - in a CIE standard color system or the Standard color chart - displayed color coordinates of these model phosphors,

Fig. 4a - e:

the emission spectra of phosphor combinations resulting from the Figures 3a to 3e shown three other model phosphors are formed, and their color coordinates with the in the Figure 4a marked target color location match,

Fig. 5a - e:

Examples of further color-identical emission spectra of further phosphor combinations from four model phosphors, the color coordinates of the four individual model phosphors according to Figure 5a are positioned in the form of a square around a possible target color location,

Fig. 6a - c:

exemplarily three real emission spectra of three selected real phosphors,

Fig. 7a - e:

exemplary emission spectra of phosphor combinations, in particular phosphor pairs and combinations of three, from the in the Figures 6a to 6c shown three selected real phosphors are formed,

8

the color coordinates in the CIE standard color table in the Fig. 7a - e shown emission spectra of the phosphor pairs and triple combinations of the three selected real phosphors, and

Fig. 9a & b

the color coordinates in the CIE standard color table in the Fig. 6a - c as well as in the Fig. 7a - e shown emission spectra of the selected real phosphors and phosphor combinations as well as a determined tolerance color range for the described real phosphors and phosphor combinations under different excitation conditions, namely once with a 313 nm excitation ( Figure 9a :) and another time with a 365 nm excitation ( Figure 9a ).

Tab. 1

Lumineszenz-spezifische Daten von drei ausgewählten Modellleuchtstoffen wie sie insbesondere in den Fig. 1c bis 1e beschrieben sind,

Tab. 2

Mischungsverhältnisse für die Ausbildung von Leuchtstoffkombinationen, deren Farbkoordinaten mit dem vorgegebenen Zielfarbort übereinstimmen, wie sie in den Fig. 2a bis 2j beschrieben sind,

Tab. 3

Lumineszenz-spezifische Daten von weiteren drei ausgewählten Modellleuchtstoffen wie sie insbesondere in den Fig. 3c bis 3e beschrieben sind,

Tab. 4

Mischungsverhältnisse für die Ausbildung von Kombinationen der weiteren drei Modellleuchtstoffe, deren Farbkoordinaten mit dem vorgegebenen Zielfarbort übereinstimmen, wie sie in den Fig. 4a bis 4e beschrieben sind,

Tab. 5

Lumineszenz-spezifische Daten von vier ausgewählten Modellleuchtstoffen wie sie insbesondere in den Fig. 5a bis 5e beschrieben sind,

Tab. 6

Mischungsverhältnisse für die Ausbildung von farbidentischen Kombinationen der vier Modellleuchtstoffe, und

Tab. 7

Farbkoordinaten der ausgewählten drei realen Leuchtstoffe sowie der nach den angegebenen Mischungsverhältnissen aus diesen Leuchtstoffen gebildeten Kombinationen.

In addition, preferred embodiments of the invention are also explained in more detail with reference to the following tables, which describe the following, namely:

Table 1

Luminescence-specific data of three selected model luminescent materials such as those in particular in the Figures 1c to 1e are described

Table 2

Mixing ratios for the formation of phosphor combinations whose color coordinates match the specified target color locus, as in the Figure 2a are described up to 2j,

Table 3

Luminescence-specific data of another three selected model phosphors as they are in particular in the Figures 3c to 3e are described

Table 4

Mixing ratios for the formation of combinations of the other three model phosphors whose color coordinates match the specified target color locus, as in the Figures 4a to 4e are described

Table 5

Luminescence-specific data of four selected model luminescent materials, as shown in particular in the Figures 5a to 5e are described

Table 6

Mixing ratios for the formation of color-identical combinations of the four model phosphors, and

Table 7

Color coordinates of the selected three real phosphors and the combinations formed from these phosphors according to the specified mixing ratios.

In the Fig. 1a a schematic representation of the CIE standard color chart 5 of the CIE standard valence system is shown. The CIE standard valence system was defined in order to establish a relation between human color perception and the physical causes of the color stimulus and typically covers all perceptible colors, whereby it refers to a defined standard observer.

In addition, show Fig. 1a and in particular the enlarged portion in the Fig. 1b the x and y color coordinates 10, 20, 30 of the emission lines of three simulated possible ones individual phosphors in the CIE standard color table. The magnification according to Fig. 1b that these color coordinates 10, 20, 30 lie essentially on a straight line in the CIE chromaticity diagram. For clarification, the color coordinates 10, 20, 30 are shown with different symbols, namely color coordinate 10 as a triangle Δ, color coordinate 20 as a square □ and color coordinate 30 as a circle o, the Figures 1c to 1e then branch the associated emission spectra (emission lines) 1, 2, 3.

Despite the small spectral spacing of the emission lines and the small spacing of the calculated color coordinates, it is not possible to provide security elements of the same color for forming one of security features using the selected modeled individual phosphors. Investigations have shown that an area of the color range spanned by the color coordinates of the emission lines used for simulation purposes is approximately 7 times that of the nearest MacAdam ellipse.

In the Figures 1c to 1e shows the emission spectrum 1, 2, 3 of the three selected, modeled and narrow-band emitting (fictitious) phosphors used for model calculations. In other words, show the Figures 1c to 1e the emission spectra, which correspond to the x and y color coordinates in the Figure 1b belong to the color coordinates 10, 20, 30 shown and the symbols Δ, □ and o, respectively. The wavelengths of the emission maxima of the emission lines are 619.8 nm for emission spectrum 1 (Δ symbol), 624.2 nm for emission spectrum 2 (□ symbol) and 626.4 nm for emission spectrum 3 (o symbol). nm very close together. The half-widths of the individually marked emission lines were fixed at 1 nm. The characteristic data of the selected model phosphors are summarized again in Table 1 below. Table 1 emission wavelength color coordinates full width at half maximum _λmax /nm x y nm Model phosphor 1 (triangle Δ) 619.8 0.691 0.309 1 Model phosphor 2 (square □) 624.2 0.699 0.301 1 model phosphor 3 626.4 0.703 0.297 1 (circle o)

the Figures 2a and 2b show again (like also Fig.1a ) a representation of the x and y color coordinates 10, 20, 30 of the emission spectra/emission lines 1, 2, 3 of the three simulated, possible individual phosphors in the CIE standard color table as already shown in the 1 were presented. In addition, a possible defined target color coordinate/a target color location 50 is also specified and marked with the symbol *.

The one in the 2 The summarized representations and the data listed in Tab. 2 show that the possible, specified target coordinates or the specified target color location 50 (cf. Figure 2b ) can be realized by different combinations of the three selected model phosphors. In this case, several color-identical emission spectra 12, 13, 123-1 or 123-2 are obtained, which can be used to form luminescence codes of the same color. Table 2 Target color locus (* symbol) x = 0.696, y = 0.304 Mixing ratio/mole fraction/% phosphor 1 phosphor 2 phosphor 3 mix 12 32 68 mix 13 50 50 Mixture 123-1 44 27 29 Mixture 123-2 46 17 37

The number of color-identical security elements that can be generated in this way depends on whether only the different spectral sequence of the selected linear emissions is used for the code assignment or whether the intensity ratios between the individual individually marked emission lines are also included as a code-forming property. In the first case considered, exactly three distinguishable emission spectra with identical color coordinates can be created on the basis of the selected phosphors. These relate to the paired combination of two of the three phosphors ( Figures 2c and 2d ) a corresponding combination of three. Examples of the emission spectrum of this one triple combination are given in the Figures 2e and 2f shown.

show here Figure 2c the emission spectrum 12, which is a combination of a first and a second phosphor. Fig. 2d shows the emission spectrum 13, which is a combination of the first and third phosphor and the Figure 2e shows the emission spectrum 123-1, which represents a possible triple combination of the first, second and third model phosphor. Fig. 2f shows the emission spectrum 123-2, an alternative triple combination of the first, second and third model phosphor, which is characterized by a different mixing ratio.

If the different intensity ratios (like e.g 2e and 2f ) between the individual characteristic emission lines for code creation, there are further possibilities to provide emission spectra of the same color from different combinations of three by varying the mixing ratios. Fig. 2f shows a possible example of a further combination of the emission spectra of the three fictitious phosphors, in which the set intensity ratios of the code-forming lines are significantly different from those of the Figure 2e differentiate.

the Figures 3a to 3e and Figures 4a to 4e and the associated Tables 3 and 4 (see below) illustrate another possible example of creating a coding system based on three other model phosphors, which also have singular emissions and color coordinates, which again lie on a straight line in the CIE chromaticity diagram. In the Figures 3c to 3e the emission spectra 1′, 2′, 3′ of the three selected, modeled (fictitious) phosphors used for model calculations are shown. From them, the x and y color coordinates 10', 20', 30' can be derived from those in FIGS Figures 3a and 3b the symbols Δ, □ and o are assigned.

Compared to those in the previous ones 1 and 2 described model phosphors, the fictitious phosphors selected for this example have significantly larger distances between the different emission maxima. In addition, the half-value widths of the model phosphors were set in such a way that both linear (cf. e.g. Figure 3e ) as well as band-shaped emissions (cf. e.g. 3d ) result. From the Figures 3a and 3b shows that due to the comparatively large spectral distances, the color coordinates of the example phosphors in the CIE standard color table are also far apart. The corresponding color impressions show a clear color shift and thus a clear color difference and vary from green to red. Table 3 emission wavelength color coordinates full width at half maximum _λmax /nm x y nm Model phosphor 1 (triangle Δ) 545 0.268 0.721 13 Model phosphor 2 (square □) 574 0.473 0.526 25 Model phosphor 3 (circle o) 600 0.627 0.373 4 Target color locus (* symbol) x = 0.443, y = 0.554 Mixing ratio/mole fraction/% model phosphor 1 model phosphor 2 model phosphor 3 mix 12' 31 69 mix 13' 63 37 Mixture 123-1' 22 73 5 Mixture 123-2' 47 36 17

In this case, too, through a targeted combination of the phosphors, distinguishable emission spectra 12', 13', 123-1', 123-2' with identical color coordinates (the target color location was again marked with the symbol *, cf. Figure 4a ). and on this basis color-identical or at least color-same security elements are created. the Figures 4b and 4c show the emission spectra 12 ', 13' of the appropriately configured pairs of phosphors, the Figures 4d and 4e the emission spectra 123-1', 123-2' of two combinations of three selected by way of example, which are characterized by different intensity ratios of the individually marked emission lines and emission bands.

In the illustrations of figure 5 Another example is shown to illustrate the invention, with the associated data being given in Tables 5 and 6. In this case the emission lines of four fictitious phosphors were compared with those in the Figure 5a color coordinates 10", 20", 30", 40" shown (again shown with the symbols: triangle Δ, square □ , circle o and circle with cross ⊗) grouped in the form of a square around a target color location 50" (* symbol). . At the same time, the positioning of the target color point 50" was carried out in such a way that it lies between two of the assumed color coordinates of the model phosphors, ie on the diagonals of the respectively opposite color coordinates. This results in numerous variants for four-way combinations (for which, for example, the Figures 5b, 5d and 5f stand, more are possible) also two emission spectra 13", 24" with a paired arrangement of the selected individual emission lines (cf. Figures 5c and 5e ). If there were different specifications for the target color location, it would also be possible to set a color-identical three-color combination at the expense of a two-color combination. Table 5 emission wavelength color coordinates full width at half maximum _λmax /nm x y nm Model phosphor 1 (triangle Δ) 450 0.156 0.019 15 Model phosphor 2 (square □) 500 0.018 0.529 15 Model phosphor 3 (circle o) 550 0.305 0.688 15 Model phosphor 4 (circle with cross ⊗) 630 0.705 0.295 15 Target color locus (* symbol) x = 0.250, y = 0.450 Mixing ratio/mole fraction/% phosphor 1 phosphor 2 phosphor 3 phosphor 4 mix 13" 27 73 mix 24" 74 26 Mixture 1234-1" 19 22 52 7 Mixture 1234-2" 12 41 33 14 Mixture 1234-3" 6 58 16 20

However, the significantly increased number of possible code assignments due to the addition of a further phosphor is mainly caused by the large variety of color-identical combinations of four with different intensity ratios. However, it must be taken into account that in those cases in which, with the same spectral sequence, only the intensity ratios between the combined emission lines or emission bands are used as a code-forming criterion (cf. also the Figures 2e and 2f as well as the Figures 4d and 4e ), it must be checked whether these intensity relations can also be reliably verified under the conditions of practical application. This affects both the performance of the available detection technology and the question of whether the ratios of the emission intensities of the different individual phosphors, which are usually phosphors with different chemical compositions, also over the entire life cycle of the security and valuable documents equipped with the security elements are preserved within acceptable tolerance limits. The different aging resistance of the selected luminescent materials can lead to the color equality of the created security elements being lost over the service life on the one hand and to a code assignment based on defined intensity ratios no longer being reliably recognizable in extreme cases on the other.

the Figures 6 to 9 and Tab. 7 describe an example of the configuration of an inventive security feature based on the use of real phosphors with correspondingly characteristic emission spectra 1‴,2‴,3‴. To produce the required security elements of the same colour, three inorganic, europium-activated rare earth pigments were selected and applied to a paper base in the form of standardized markings (printed strips). The emission spectra of these three phosphors measured for a given excitation in the UV-B range (313 nm excitation source) are shown in FIG 6a to 6c shown. The emission spectra 1‴,2‴,3‴ of the three real (individual) phosphors show an ensemble of several characteristic emission lines. This results in further possibilities for code assignment, which can relate not only to the respective main emission lines of these phosphors, but also to different secondary lines.

On the other hand, off 6 However, it is clear that some of the emission lines found in the emission spectra 1‴,2‴,3‴ of the different phosphors are very close together or even overlap. In these cases, it must be weighed up whether it makes sense to include such lines in the code formation, taking into account the requirement for secure verification and the effort that is justifiable for the planned technical application.

In the Figures 7a to 7e are the emission spectra measured (at 313 nm excitation) 12‴, 13‴, 23‴, 123-1‴, 123-2‴ and 123-3‴ of the proofs produced under standard conditions with specified mixing ratios (see Table 7). different combinations of phosphors (three pairs of phosphors and two combinations of three with different intensity ratios). Table 7 color coordinates Mixing ratio/mole fraction/% excitation 313 nm excitation 365 nm First phosphor 1‴ Second phosphor 2‴ Third phosphor 3‴ x y x y phosphor 1‴ 0.6690 0.3283 0.6665 0.3240 phosphor 2‴ 0.6737 0.3226 0.6723 0.3215 phosphor 3‴ 0.6740 0.3219 0.6724 0.3216 mixture 12‴ 0.6720 0.3250 0.6728 0.3221 20 80 mixture 13‴ 0.6710 0.3253 0.6695 0.3216 20 80 mixture 23‴ 0.6742 0.3224 0.6729 0.3217 mixture 123-1‴ 0.6710 0.3251 0.6702 0.3216 17 41 42 mixture 123-2‴ 0.6723 0.3243 0.6172 0.3216 11 44 45

Despite the comparatively high complexity, the exemplary emission spectra 12‴, 13‴, 23‴, 123-1‴, 123-2‴ and 123-3‴ contain numerous sufficiently separate lines and stable intensity constellations to which a luminescence code can be assigned. This affects both the main emission lines of the individual phosphors included in the combinations and other lines and characteristic line groupings. The sometimes small spectral distances between the code-relevant emissions pose a challenge in terms of spectral resolution and the performance of the detection devices used, but it has been shown that on the basis of the phosphors and phosphor combinations described in this exemplary embodiment, security elements can be provided whose code-forming Emission characteristics can also be reliably verified at comparatively high reading speeds (e.g. in ATMs or in central bank sorting machines).

The question of the color equality of the illustrated emission spectra 12"', 13"', 23"', 123-1‴, 123-2‴ and 123-3‴ of the exemplary phosphors and phosphor combinations remains 8 the color coordinates calculated from the respective emission spectra 12"', 13‴, 23‴, 123-1‴, 123-2‴ and 123-3‴ are 10"', 20"', 30‴ 130"', 230"', 1230-1‴, 1230-2‴ and 1230-3‴ are shown in a section of the CIE standard color chart It is clear that these coordinates, as expected, at least tend to lie on a straight line, although they exhibit a clearly perceptible scattering There are on the one hand, the strong enlargement of the selected area of the CIE standard color table, but on the other hand also the fact that the mixing ratios for the provision of the different phosphor combinations were initially chosen comparatively arbitrarily.

To determine the extent of perceived color differences or perceived color sameness, further investigations were carried out below based on the survey of test persons. Under defined excitation and viewing conditions, the test persons were able to decide on the color equality or perceived color differences of the security elements equipped with the exemplary phosphors and phosphor combinations and present in the form of printed strips.

The results are in the Figure 9a shown. the Figure 9a shows that the color coordinates of almost all presented luminescent security features (i.e. also those of the individual components 20‴ and 30‴) lie in a tolerance ellipse 51 determined on the basis of the psychometric measurements, which means that the test persons have a very high probability that they have the same color were noticed. The only exception is the color coordinate 10"' calculated for the individual phosphor, which lies outside the tolerance ellipse/tolerance color range 51.

A comparable picture also emerges if the exemplary security elements are not excited at 313 nm (UV-B) but at 365 nm, i.e. in the UV-A range. Also in this case (cf. Figure 9b ) seven of the eight color coordinates of the tested print strips lie within a tolerance ellipse based on scientific studies. The shape of the tolerance color area differs somewhat from that determined for excitation with a 313 nm radiation source. Nevertheless, the probability that the corresponding security elements are perceived as having the same color not only under the respective selected excitation conditions, but also when changing between UV-A and UV-B excitation can be assessed as very high.

Reference List

1,1',1"

Emission spectrum of a first (single) phosphor

2.2'.2"

Emission spectrum of a second (single) phosphor

3,3',3"

Emission spectrum of a third (single) phosphor

4.4'.4"

Emission spectrum of another (single) phosphor

5

CIE standard color table of the CIE standard valence system

12,12',12"

Emission spectrum of a combination of the first and second phosphors

13,13',13"

Emission spectrum of a combination of the first and third phosphors

23,23',23"

Emission spectrum of a combination of the second and third phosphors

24,24',24"

Emission spectrum of a combination of the second and the further phosphor

10,10',10"

Color coordinates in the CIE standard color system of the first (individual) phosphor

20,20',20"

Color coordinate in the CIE standard color system of the second (single) phosphor

30,30',30"

Color coordinates in the CIE standard color system of the third (individual) phosphor

40,40',40"

Color coordinate in the CIE standard color system of the additional (individual) phosphor

50,50',50"

Target coordinates/target color location in the CIE standard color system

123-1

Emission spectrum of a first triple combination of the first, second and third phosphor,

123-2

Emission spectrum of another triple combination of the first, second and third phosphor,

1234-1

Emission spectrum of a first combination of four of the first, second, third and the further phosphor,

1234-2

Emission spectrum of another four-combination of the first, second, third and the further phosphor,

1234-3

Emission spectrum of another four-combination of the first, second, third and the further phosphor,

1‴

Emission spectrum of a first real (single) phosphor

2‴

Emission spectrum of a second real (single) phosphor

3‴

Emission spectrum of a third real (single) phosphor

4‴

Emission spectrum of another real (single) phosphor

12‴

Emission spectrum of a combination of the first and second real phosphors

13‴

Emission spectrum of a combination of the first and third real phosphors

24‴

Emission spectrum of a combination of the second and third real phosphors

123-1‴

Emission spectrum of a three combination of the first, second and third real phosphor

123-2‴

Emission spectrum of another three combination of the first, second and third real phosphor

10‴

Color coordinate for the emission spectrum 1‴ of the first real (single) phosphor

20‴

Color coordinate for the emission spectrum 2‴ of the second real (single) phosphor

30‴

Color coordinate for the emission spectrum 3‴ of the third real (single) phosphor

120‴

Color coordinate for the emission spectrum 12‴ of a pairwise combination of the first and second real phosphor

130‴

Color coordinate for the emission spectrum 13‴ of a pairwise combination of the first and third real phosphor

230‴

Color coordinate for the emission spectrum 23‴ of a pairwise combination of the second and third real phosphor

240‴

Color coordinate for the emission spectrum 24‴ of a paired combination of the second and the further real phosphor

1230-1‴

Color coordinate for the emission spectrum 123-1‴

1230-2‴

Color coordinate for the emission spectrum 7123-1‴

12340-1‴

Color coordinate for the emission spectrum of a first four-combination

12340-2‴

Color coordinate for the emission spectrum of a second four-combination

12340-3‴

Color coordinate for the emission spectrum of a third four-combination

51

Tolerance color range in the CIE standard color table determined by questioning test persons

Claims (20)

1. A coding system for forming a security feature in or on one or several security documents or documents of value, comprising different luminous substances, and/or combinations of luminous substances obtainable therefrom, which may be excited in the invisible spectral range and which emit in the visible spectral range, wherein, for a predefined excitation, said luminous substances and/or combinations of luminous substances will each yield different emission spectra in the visible spectral range, such that each of said luminous substances and/or combinations of luminous substances is characterised by at least one individually distinct emission line and/or emission band that differs from the individually distinct emission lines and/or emission bands of the other luminous substances and/or combinations of luminous substances, wherein

   - the coding system comprises at least three luminous substances, said at least three luminous substances, and/or combinations of luminous substances obtained from these luminous substances, each being applied or affixed onto a given location of the security document or document of value in the form of at least three luminescent security elements forming said security feature, and wherein

   - each of said at least three luminescent security elements has a different luminescence code associated therewith, and

   - when exposed to the predefined excitation using its respectively associated luminescence code, each of said at least three luminescent security elements has identical chromaticity coordinates in a CIE standard colorimetric system or has at least chromaticity coordinates lying within a range of chromaticity tolerances of said CIE standard colorimetric system, for example within a MacAdam ellipsis, such that, for a given excitation, the luminescent security elements of the security feature are identical in colour or are perceived as having the same colour.
2. The coding system as claimed in claim 1, characterised in that the luminescence codes associated with the luminescent security elements are formed from the different spectral sequence of the individually distinct emission lines and/or emission bands of the luminous substances and/or combinations of luminous substances.
3. The coding system as claimed in claim 1 and/or 2, characterised in that the luminescence codes associated with the luminescent security elements are formed from intensity ratios of the individually distinct emission lines and/or emission bands of the luminous substances and/or combinations of luminous substances.
4. The coding system as claimed in at least one of the preceding claims, characterised in that at least one further luminous substance, and thus further available combinations of luminous substances, are provided for forming further luminescent security elements having other luminescence codes.
5. The coding system as claimed in at least one of the preceding claims, characterised in that the chromaticity coordinates of the luminescent security element are set via mixing ratios of the luminous substances used for forming combinations of luminous substances, thus yielding defined, relative intensity ratios of the individually distinct emission lines and/or emission bands for the combinations of luminous substances.
6. The coding system as claimed in at least one of the preceding claims, characterised in that at least one of the luminous substances has an organic luminous substance.
7. The coding system as claimed in at least one of the preceding claims, characterised in that at least one of the luminous substances has an inorganic luminous substance.
8. The coding system as claimed in at least one of the preceding claims, characterised in that both inorganic and organic luminous substances of different grain size including, for example, nano-scaled luminous substances or quantum dots as well as corresponding combinations of such luminous substances are used.
9. The coding system as claimed in at least one of the preceding claims, characterised in that the luminous substances are modified by targeted substitutions in the luminous substance lattice, such that these will each have an exclusive emission spectrum.
10. The coding system as claimed in at least one of the preceding claims, characterised in that the luminous substances and/or combinations of luminous substances may be excited in one or more ultraviolet wavelength ranges, that is at wavelengths of between 380 nm and 315 nm (UV-A) and/or at wavelengths of between 315 nm and 280 nm (UV-B) and/or at wavelengths of between 280 nm and 200 nm (UV-C).
11. The coding system as claimed in claim 10, characterised in that under at least two excitation conditions which may be set in the ultraviolet spectral range, that is in the UV-A and/or the UV-B and/or the UV-C spectral range(s), the luminescent security elements of the security feature are identical in colour or are perceived as having the same colour.
12. The coding system as claimed in claim 10, characterised in that subjected to any of the predetermined excitations in the UV-A, UV-B or UV-C spectral range, the luminescent security elements of the security feature are identical in colour or are perceived as having the same colour.
13. The coding system as claimed in claim 10, characterised in that the luminescent security elements of the security feature, when subjected to different predetermined excitations, have different chromaticity coordinates within the CIE standard colorimetric system, or have at least chromaticity coordinates lying within a different range of chromaticity tolerances of said CIE standard colorimetric system, such that the luminescent security elements, while being perceived as identical in colour or as having the same colour when subjected to a given predetermined excitation, will have another colour identity or colour uniformity when subjected to a different predetermined excitation.
14. The coding system as claimed in at least one of the preceding claims, characterised in that the luminous substances and/or combinations of luminous substances may be excited in the infrared wavelength range, that is at wavelengths of between 950 nm and 980 nm.
15. The coding system as claimed in at least one of the preceding claims, characterised in that the maxima of the individually distinct emission lines and/or emission bands of the luminous substances and/or combinations of luminous substances are spaced apart from one another by no more than a few nanometers.
16. The coding system as claimed in at least one of the preceding claims, characterised in that the security element has a further information associated therewith concerning the manner in which the security elements of the security feature are arranged, for example concerning the location or the shape of the security elements, which may, for example, be in the form of a symbol, a numeral, or a pictogram.
17. The coding system as claimed in at least one of the preceding claims, characterised in that all chromaticity coordinates of the luminous substances encompassed by the coding system are essentially located on a straight line in the CIE standard colorimetric system.
18. The coding system as claimed in at least one of the preceding claims, characterised in that the luminous substances and/or combinations of luminous substances have an essentially identical, or similar, ageing resistance.
19. A security feature in or on one or several security documents or documents of value, comprising different luminous substances, and/or combinations of luminous substances obtainable therefrom, which may be excited in the invisible spectral range and which emit in the visible spectral range, wherein, for a predefined excitation, said luminous substances and/or combinations of luminous substances will each yield different emission spectra in the visible spectral range, such that each of said luminous substances and/or combinations of luminous substances is characterised by at least one individually distinct emission line and/or emission band that differs from the individually distinct emission lines and/or emission bands of the other luminous substances and/or combinations of luminous substances,
    wherein

    - the security feature comprises at least three luminous substances, said at least three luminous substances, and/or combinations of luminous substances obtained from these luminous substances, each being applied or affixed onto a given location of the security document or document of value in the form of at least three luminescent security elements forming said security feature, and wherein

    - each of said at least three luminescent security elements has a different luminescence code associated therewith, and

    - when exposed to the predefined excitation using its respectively associated luminescence code, each of said at least three luminescent security elements has identical chromaticity coordinates in a CIE standard colorimetric system or has at least chromaticity coordinates lying within a range of chromaticity tolerances of said CIE standard colorimetric system, for example within a MacAdam ellipsis, such that, for a given excitation, the luminescent security elements of the security feature are identical in colour or are perceived as having the same colour.
20. A security document or document of value comprising a document body, said document body comprising at least one security feature as claimed in claim 19.

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