HK1198482B - Security feature having several components - Google Patents

Description

security features with multiple components

The invention relates to a security feature having a luminescent component and a security feature concealing the luminescent component.

The name "value document" is to be understood within the framework of the invention to mean banknotes (bank notes), checks, stocks, tokens, identity cards, credit cards, passports and other documents as well as labels, seals, parcels or other elements for product authentication.

It has long been known to protect value documents from forgery by means of security features with luminescent components. The luminescent component is formed here by a substance, which will also be designated as luminophore (luminophore) in the following, formed by a host lattice doped with a transition metal or a rare earth metal as the luminescent ion. Such ions have the following advantages: upon suitable excitation, they exhibit one or more characteristic narrow-band luminescence that facilitates reliable detection and delineation with respect to other spectra. For doping, combinations of transition metals and/or rare earth metals have been discussed. Such substances have the following advantages: in addition to the above-mentioned luminescence, so-called energy transfer processes are also observed, which can lead to more complex emission spectra. In such an energy transfer process, one ion can transfer its energy to another ion, and the spectrum can then consist of several narrow-band lines that are characteristic for both ions.

The security feature for protecting value documents has individual luminophores as luminescent components, the emission of which is different with respect to their spectral and/or temporal (temporal) properties. The security features are introduced and/or applied to the value document in different forms of use. For the luminescent component, combinations of luminophores may also be used. The emission bands of the luminophores used constitute the spectral code. Several different luminophores may be combined into a system, wherein the individual systems are independent of each other. The emission of the luminophore used is also referred to as luminescence, whereby this may involve fluorescence and/or phosphorescence.

It is also known that the described security features are not formed solely from luminescent components. As a further component, some security elements have a component for hiding the luminescent component. For example, DE 3048734 a1 describes security papers with concealed substances which protect authentication features. The masking substance of the masking component corresponds here substantially to the luminescent component, i.e. a very similar or identical (like-kind) host lattice and dopant is used both for the luminescent component and for the masking component. However, when manufacturing a sequestering substance for the sequestering component, it is ensured that the sequestering substance has no luminescent properties. For this purpose, in contrast to the production of luminescent components, for example, the parameters during annealing or grinding are changed for the masking component. Alternatively, so-called luminescence inhibitors (killers) are used. This prevents the use of conventional analytical techniques to distinguish luminescent components from cryptic components. In this way, the position of the luminescent component is largely concealed, since it cannot be distinguished using conventional methods from concealing components.

Since the luminescent component and the covert component comprise very similar or even identical substances, substance identity (identity) -based concealment of the luminescent component cannot be achieved, since the use of a covert component increases the total exploitable amount of material of the security feature in the value document to be protected and therefore tends to promote, rather than hinder, the analyzability of the security feature or the luminescent component.

Starting from this prior art, the invention is based on the following objects: a security feature is specified having a luminescent component and a component concealing the luminescent component, wherein an analysis of the type and doping of the host lattice employed for the luminescent component is prevented or at least substantially prevented.

Thus, the role of the covert component is to make one or more of these aspects more difficult to analyze, to thereby hinder the imitation of the security feature.

It is preferred herein to achieve concealment of the luminescent component both in terms of elemental analysis and in terms of structural analysis. Identification of the luminescent component is also hampered in the following cases: the security features are present in pure form before introduction into the value document or in diluted form, for example by ashing of the actual value document, and can then be investigated by elemental analysis methods, for example XRF (X-ray fluorescence analysis) or ICP-AES (inductively coupled plasma optical emission spectroscopy), or by structural analysis methods, for example X-ray powder diffraction methods.

In a preferred embodiment, alternatively or additionally, the spectral properties of the security feature are concealed such that, upon simple spectral analysis, for example upon continuous and/or unspecific excitation of the value document and detection of the occurring luminescence emission, it is not the correct spectral signal of the measured luminescent component.

In so doing, it will also be achieved that the quality of the security feature is not affected by manufacturing-related fluctuations and is subsequently unambiguously identifiable so that it can be linked, for example, to a specific manufacturer.

The achievement of this object is to be found in the independent claims. The dependent claims are developments of the subject matter.

The invention proceeds from a security feature having a luminescent component and a component which conceals the luminescent component, the luminescent component having at least one luminophore consisting of a doped host lattice, wherein in order to conceal the luminescent component, the concealing component conceals the relevant properties required for identifying the luminescent component by the relevant properties of the luminescent component, i.e. the structure of the host lattice of the luminescent component, the stoichiometry of the host lattice of the luminescent component, the elemental composition of the host lattice of the luminescent component, the dopant or dopants of the luminescent component and the luminescent properties of the luminescent component, by means of the masking component having a correlation property corresponding to the respective correlation property of the luminescent component, the correlation property of the luminescent component is masked by the masking component with respect to at least two, particularly preferably at least three, very particularly preferably at least four, of the correlation properties, thereby hindering or preventing the identification of the luminescent component.

For this purpose, it is provided in particular that the properties of the sequestering component and the corresponding properties of the same type of the luminescent component, which are characterized by the following relationships, hinder or prevent the identification of the luminescent component:

a) the covert component has an X-ray diffraction pattern which at least partially overlaps with the X-ray diffraction pattern of the luminescent component to conceal the structure of the luminescent component,

b) the sequestering component comprises at least one cationic element that is also contained in the host lattice of the luminescent component, but not all of the cationic elements contained in the host lattice, in order to sequester the stoichiometry of the luminescent component,

c) the sequestering component comprises at least one cationic element which is not contained in the host lattice of the luminescent component, in order to sequester the elemental composition of said host lattice of the luminescent component,

d) the concealing component comprises at least one dopant not comprised in the luminescent component as a dopant to conceal the one or more dopants of the luminescent component,

e) the concealing component comprises at least one luminophore having a shorter decay time than the luminophore comprised in the luminescent component to conceal spectral properties of the luminescent component,

wherein the properties of the sequestering component and the luminescent component satisfy at least two, particularly preferably at least three, very particularly preferably at least four of the relationships stated in a) to e).

The concealing component has structural, spectral and elemental properties to conceal comparable properties of the luminescent component. The masking component may be comprised of one substance, or may be comprised of multiple substances. The covert component can have an X-ray diffraction pattern that masks the X-ray diffraction pattern of the luminescent component. In this way, authentication of the structure of the substrate of the security feature is hampered. In addition to X-ray diffraction measurements, further structural analysis methods may be applied to analyze further structural features in addition to or instead of X-ray diffraction patterns, for example nuclear magnetic resonance spectroscopy methods such as SS-NMR, electron spin resonance methods, or analysis by Raman and infrared spectroscopy methods. However, these further methods are only suitable for structural analysis of inorganic luminophores to a very limited extent, due to low sensitivity or high required quantitative ratios of the substances to be measured, limitations of a small number of specific element/structure groups (structural groups), or unclear results. At best, they provide information about specific structural fragments, such as structural groups, insertion sites, or coordination spheres with specific signal positions, but do not provide insight into the overall structure. For the purpose of the covert structure, therefore, covert components suitable for the X-ray diffraction pattern of the luminescent component are preferred.

When the security feature has a particularly specific, unambiguous or easily identifiable signature in some structural analysis methods due to the use of some elements or element groups, additional protection can be established by masking components which likewise produce overlapping or additional signatures in corresponding structural analysis methods to thereby hinder structural analysis by these methods.

The masking component may preferably likewise contain substances which interfere with the elemental analysis of the security feature, whereby the different local aspects to be masked, i.e. the elements contained in the matrix, the stoichiometry of the matrix and the dopants of the matrix, must be distinguished.

The concealment of the elements contained in the matrix can be achieved, for example, by adding possible combinations of elements, i.e. by additional chemical elements contained in greater amounts in the concealing component of the security feature, which upon elemental analysis hinder the correct dispensing of the matrix elements of the luminescent component.

The stoichiometric concealment of the matrix can be achieved by means of substances whose elements match, in whole or in part, the concealing constituents of the individual elements of the matrix of the security feature. This distorts the ratio (distor) between the individual elements of the luminescent component, which can be determined by elemental analysis.

By adding further rare earth metal compounds or transition metal compounds in small amounts, the concealment of the dopants of the matrix consisting of rare earth elements and/or transition metals, respectively, is achieved. This increases the number of possible combinations of luminophores and sensitizers used, thereby hampering a correct analysis.

The concealment of the spectral properties of the luminescent components can be realized by concealing the luminescent signals of the same type of the components. However, it would be disadvantageous in the case of applications, since an additional, simultaneously detectable luminescence signal would hamper or prevent an accurate detection and evaluation of the luminescent component. This is especially the case when such additional luminescent signal is located in a spectral region similar or identical to the luminescent signal of the luminescent component, which would be necessary for effective concealment. Thus, the masking component preferably does not contain additional inorganic luminophores. Preferably, organic luminophores with significantly shorter decay times may be used to completely or partially mask the luminescent emission of the luminescent component. Upon continued excitation, the specific luminescence spectrum of the inorganic luminescent component is thereby concealed by the luminescence spectrum of the organic luminophore and is thereby concealed. On pulsed excitation, due to the fast decay time of the organic luminophore, the luminescence of the inorganic luminescent component can be measured and thus tested without interference. Thus, when the exact measurement parameters (e.g. pulsed excitation) are not known, the spectral properties of the luminescent component cannot be correctly identified.

Although organic luminophores are also referred to as luminophores, within the framework of the present invention they will not be classified as luminescent components, since luminescent components refer exclusively to inorganic luminophores for authenticity detection.

Preferably, the sequestering component thus comprises one or more organic luminophores, the luminescent emission of which conceals the luminescent emission of the luminescent component.

Preferably, the individual substances of the masking component perform several masking functions simultaneously. For example, the covert component species that conceals the X-ray diffraction pattern can contain both the elements of the luminescent component and thereby conceal the stoichiometry of the matrix of the luminescent component.

In addition to the covert component, the security feature may comprise one or more additional functional components, such as a manufacturing component for adjusting the luminescent signal intensity of the luminescent component to a preset nominal value, or a coding component for legally (forensically) marking the security feature. Preferably, these components also perform the sequestering function or are components of a sequestering component.

Preferably, the individual substances of the sequestering component and/or the additional component are selected such that, like the luminescent component, one or more of these substances are sequestered in a structural or elemental analysis by the other substance of the sequestering component. For example, a substance that masks the stoichiometry of the luminescent component may mask the stoichiometry of the coding component at the same time. The blind stoichiometric substance here comprises both at least one element identical to the luminescent component and at least one element identical to the coding component. Likewise, the X-ray diffraction pattern of the manufactured composition can, for example, have an X-ray diffraction pattern that partially overlaps with the cryptic component material of elemental composition of the cryptic luminophore matrix. This hampers structural analysis of both the material and the manufacturing components that conceal elemental composition.

In the context of the properties described for the covert luminescent component, i.e.

The structure of the matrix of the luminescent component,

the stoichiometry of the matrix of the luminescent component,

the elemental composition of the matrix of the luminescent component,

a dopant for the luminescent component, and

among the light-emitting properties of the light-emitting component,

at least two, particularly preferably at least three, very particularly preferably at least four of the properties are concealed by a concealing component.

In a further preferred embodiment, at least the stoichiometry of the matrix, the elemental composition of the matrix and the dopants of the luminescent component are masked by the masking component.

In a further preferred embodiment, at least the X-ray diffraction pattern and the stoichiometry of the luminescent component are masked by the masking component. Particularly preferably, the matrix elements and the dopants of the luminescent component are additionally concealed here.

In a further preferred embodiment, at least the spectral properties and the stoichiometry, the elemental composition of the matrix and the dopants of the luminescent component are masked by the masking component.

In a further preferred embodiment, the spectral properties are masked and the X-ray diffraction pattern is determined. Particularly preferably, the stoichiometry, elemental composition of the matrix and dopants of the luminescent component are masked except for the spectral properties and the X-ray diffraction pattern.

The different preferred embodiments herein take into account that, depending on the nature of the luminescent component, different covert aspects may take precedence for different security features. For example, a change in the stoichiometric ratio detected by elemental analysis is particularly advantageous when the luminescent component comprises a compound in which the luminescent properties can be altered by changing the relative proportions of the two matrix components. Also, in the case of luminescent components having a crystal structure forming a homotype structure with different elements, it may be particularly advantageous to add several of such additional elements via a masking component. In this case, even when the crystal structure of the luminescent component is completely broken (decrypt), a simple inference about the elements of the luminescent component cannot be obtained.

Likewise, in the case of luminophores having a highly structure-dependent emission spectrum (as typically occurs, for example, when doping with transition metals), a predominantly covert X-ray diffraction pattern can be particularly advantageous, since here the structure constitutes a particularly important factor for identifying the luminophore.

Likewise, in case the luminescent component has an emission spectrum that is specifically dedicated to some materials or groups of crystal structures, it may be preferred to confer a particular importance on the covert spectral properties, such that the actual properties of the emission of the luminescent component can be identified only by a more complex spectral analysis.

The invention has the following advantages: by masking the different aspects of the composition, structure or spectral properties of the luminescent components, independent of the particular properties of the respective luminescent components, by means of the individual components or substances of the masking component, the identification and imitation of the luminescent components is hampered or not possible.

Further advantages of the invention will be found in the dependent claims and in the following description of the embodiments.

For example, from WO 81/03507 a1, EP 0966504B 1, WO 2011/084663 a2, DE 19804021 a1 and DE 10111116 a1, security features for the protection or marking of documents of value are known which have a luminophore-based luminescent component which is composed of a host lattice doped with transition metals or rare earth metals as luminescent ions and has specific properties with regard to its emission and/or excitation. Such security features are added directly to the pulp in powder form during the paper production or to other base materials of the document of value, such as plastics. Alternatively or additionally, the powder is added to a printing ink which is subsequently printed on the substrate of the document of value. The security feature may also be included in other components of the value document, for example in a thread (thread), a planche (planche), a patch (patch), etc., which are in turn introduced into or applied to the value document.

The powdered security feature having the luminescent component in the form of a luminophore as described above further comprises a component concealing the luminescent component. The masking component is selected here such that it leads to a masking or masking of the luminescent component and/or that it masks its luminescence emission in the case of the structure and elemental analysis methods stated at the outset. For this purpose, the covert component has an X-ray diffraction pattern which, for example, at least partially overlaps with the X-ray diffraction pattern of the luminescent component, as will be explained more accurately below. By at least partial coincidence of the X-ray diffraction patterns of the luminescent component and the covert component in terms of significant peaks (significant peaks), it is therefore not possible or at least significantly difficult to infer the luminescent component present in the security feature using common structural analysis methods, such as X-ray powder diffraction measurements.

The purpose of elemental analysis of a security feature is to draw inferences about the identity of the host lattice used by quantitatively analyzing the composition of the security feature. Methods such as XRF enable particularly "difficult" elements to be readily detected. Problematic is especially the quantification of oxygen, which cannot be detected by XRF or by ICP-AES or similar methods. Since oxygen usually forms the "remainder" of the matrix (e.g., as oxygen ions (oxidaiton)) after detection of other components of the host lattice, however, its detection is not necessarily necessary to identify the host lattice. When the cationic component of the host lattice has been quantified, the host lattice contained can be identified by forming the proportions of the components, even in mixtures of different substances. Thus, for example, ZnAl₂O₄And BaMnO₄Always contains Al and Zn in a ratio of 1:2 and Ba and Mn in a ratio of always 1:1, said ratio being independent of the mixing ratio of the two elements. Therefore, it is clear that these components are individually referred to as host lattices, and by doing so, the host lattices can be identified.

To is coming toThe procedure is prevented or at least hindered in that the substances whose stoichiometry is to be masked, in particular the luminescent component, must have at least one element in common with the other substance of the masking component. The proportions of the individual chemical elements must be present here in a sufficient order of magnitude to significantly distort the formation of proportions from the elemental analysis. For example, in₂O₄And BaMnO₄In the mixture of (a), the correct integral ratio between the proportions of Zn and Mn or between the proportions of Ba and Mn is not found, since Mn is present in both the host lattice-forming components or species. Preferably, the detected quantitative ratio of overlapping chemical elements of the compound is increased by at least 30%, preferably by at least 50%, particularly preferably by at least 100%, relative to the pure compound. The quantitative proportion may also be increased by at least 200%.

In order to achieve stoichiometric concealment of the luminescent component by the concealing component, the concealing component has at least one element of the substance forming the luminescent component. An element is here to be understood as a chemical element which is contained both in the substance forming the luminescent component and in the substance forming the sequestering component. In particular, an element or chemical element is not to be understood as meaning that one or more of the same atoms is a component of both components. When the substance forming the luminescent component has, for example, elements a and B, the substance forming the sequestering component may have elements a and C, or B and C, where elements A, B and C are not formed from oxygen or hydrogen. In addition to elements A, B and C, the substance may have further elements, in particular oxygen and/or hydrogen. However, oxygen and hydrogen would not be considered elements to achieve substance interleaving as is desired in the present invention. Suitable elements are in particular cationic matrix components, in particular cations of metals, transition metals, semimetals and rare earth elements. By additionally containing oxygen, the elemental cations can also form a subset of anions as matrix constituents, which are likewise suitable for interleaving. Thus, for example, phosphorus and silicon cations may be present in the matrix, for example in the form of phosphates and silicates. The interleaving of species As contemplated by the present invention may Be formed from the main group elements Li, Be, B, Na, Mg, Al, Si, P, S, K, Ca, Ga, Ge, As, Se, Rb, Sr, In, Sn, Sb, Te, Cs, Ba, Tl, Pb, Bi and from any of the transition metals and rare earth elements.

Thus, the above elements or chemical elements as intended by the present invention are also referred to alternatively as cationic elements, cationic matrix components, cationic components of the host lattice, or elemental cations. This should clearly express that especially the chemical elements oxygen and/or hydrogen are not considered as chemical elements to achieve substance interleaving as intended by the present invention.

In order to conceal the elemental composition of the matrix of the luminescent component, it is also possible to add to the security feature, via the substance of the concealing component, at least one new cationic element not contained in the matrix. This increases the number of chemical elements detected in the elemental analysis, thereby making it more difficult to determine the composition of the matrix. Preferably, the additional cationic element is added to the luminescent component in an amount of at least 30%, preferably at least 50%, particularly preferably at least 80% of the molar amount of the cationic group element, preferably the most commonly used cationic group element. In so doing, at least one, preferably at least two, particularly preferably at least three, additional cationic elements are added by the sequestering component.

In order to conceal the one or more dopants of the matrix of the luminescent component, additional luminophores and/or sensitizers are added to the concealing component, so that the possible combinations of dopants of the luminophore matrix are increased upon elemental analysis. Therefore, in order to conceal the rare earth element dopant, it is preferable to use rare earth elements Ce, Pr, Nd, Sm, Eu, Tb, Dy, Ho, Er, Tm, Yb. These are luminophores emitting in the NIR region or sensitizers or dopants which, by their electronic structure, may have an influence on the luminescent properties of the rare earth luminophores, for example by energy transfer or quenching effects, and will therefore often be found as codoping. For concealing transition metal luminophores, e.g. Cr³⁺It is also preferable to use other transition metals known as luminophores in addition to the above-mentioned rare earth elements. For example, in the case of Cr as a luminophore, Mn or Fe compounds may preferably be added for achieving the hiding.

In order to conceal the dopant of the matrix of the luminescent component, at least one additional dopant element, preferably at least two additional elements, is added. The elements added to the sequestering component for sequestering the dopant should be present in comparable molar amounts relative to the dopant of the luminescent component. Comparable is intended here to mean that the molar amounts added add up to at least 30% of the molar amount of the dopant of the luminescent component. The rare earth metal can be incorporated firmly into the crystal lattice of another substance or, for example, can be admixed to the covert component as an additional separate substance if direct incorporation into the matrix of the substance proves to be technically disadvantageous or problematic. When the individual rare earth element-containing substances are used, their proportion in the total mixture preferably amounts to 0.5 to 4%, particularly preferably 1 to 2%.

In order to mask the light-emitting properties of the light-emitting component, organic or metal-organic luminophores are preferably used. These should have a short decay time of less than 10 mus, preferably less than 1 mus, in order not to impair the detection of the inorganic luminescent component. Their luminescent emission should completely or partially obscure the luminescent emission area of the inorganic luminescent component. The luminescence emission of organic luminophores may also be broad and/or unstructured, as opposed to the luminescence emission of inorganic luminophores. Preferably, the organic luminophore emits light only in the non-visible region, so as not to cause any unwanted visible luminescence of the value document. The organic luminophore may comprise, for example, a laser dye, a metal complex or other NIR luminophore, such as a security marker. Metal-organic security markers and organic NIR emitters are known, for example, from the publications WO 2009/005733 a2, US 6,174,400B 1 and US 2011/0079733 a 1. The organic luminophores may be used here as pure substances or applied to a carrier material in diluted form. In general, pure substances are preferred when the security feature is used in printing inks, lacquers (lacquer) and polymers, and application in a carrier material is preferred when the security feature is embedded in paper pulp. For stabilization in the carrier material, the organic luminophores may be embedded, for example, in the form of polymer microspheres, for example, in a polymer. Also, it is possible to attach organic luminophores to inorganic media (e.g. layered silicates, zeolites or porous oxides such as mesoporous silica) having a high inner or outer surface. The preferred proportion of organic luminophores in the security feature or of organic luminophores incorporated into the carrier material amounts to 1 to 30%, preferably 5 to 20%.

The security feature has 20% to 80%, preferably 25% to 60%, particularly preferably 30% to 50% of a luminescent component (all percentages and the percentages below and before are by weight). The luminophores referred to herein are luminophores that emit light in the non-visible region of the spectrum and consist of a doped host lattice. Preferably, the luminophores have a high quantum yield or signal intensity and a suitable decay time to ensure error-free testability (error-free testability), even in the case of small amounts used in the value document and at high movement speeds as occur, for example, in banknote processing machines with processing speeds of up to 40 banknotes per second or higher. Suitable luminophores for the luminescent component are, for example, inorganic crystalline matrices doped with rare earth elements and/or transition metals and having a decay time in the range between 50 μ s and 10ms, such as oxides (for example in the form of garnets, spinels or perovskites) and oxysulfides, sulfides, silicates, phosphates, aluminates, niobates, tantalates, vanadates, germanates, arsenates, zirconates or tungstates.

The masking component is included in the security feature in a proportion of 20 to 80%, preferably 40 to 70%, particularly preferably 50 to 70%. In addition to the covert component, further, a non-covert component may also be included in the security feature.

When the covert component comprises a substance that masks the X-ray pattern of the luminescent component, the amount used will depend on the amount and relative crystallinity of the luminescent component. This means that the relative intensity of the masking component in the diffraction pattern of the mixture with the luminescent component substantially masks the luminescent component in the overlap region. When the luminescent component exhibits only a low signal in the diffraction pattern, for example due to small grain (grain) size or small proportions in the mixture, or when the sequestering component has a particularly high signal in the diffraction pattern due to its high crystallinity or suitable composition, it is necessary to use in total less material of the sequestering component, or material of substances with overlapping X-ray diffraction patterns contained in the sequestering component, in order to achieve the desired sequestering effect. In order to obtain a distortion of the X-ray diffraction pattern which is sufficient for masking, the masking component causes a relative change in the area integral of at least 20%, preferably at least 40%, particularly preferably at least 60%, very particularly preferably at least 80%, of the overlapping peaks of the luminescent component in the overlapping region of the diffraction patterns of the luminescent component.

The covert component must be added to the security feature in such an amount that the respective peaks of the covert component and the luminescent component are comparably (compaOnly) strong upon X-ray powder diffraction measurement of the security feature. The X-ray diffraction patterns of the cryptic and luminescent components herein must not be identical or highly similar, as this does not hinder, but rather facilitates, the analysis. Thus, the substances used should not be structurally related. However, it is likewise disadvantageous when the peak positions of the two X-ray diffraction patterns do not show a match, since in this case it is particularly easy to separate into the individual components. Preferably, the masking component is used in such a form that at least one, preferably two, particularly preferably three, relevant peak positions of the masking component match the corresponding peak positions of the luminescent component. "match" in this context is to be understood as meaning that the peak maxima of the two peaks of the luminescent component and the covert component differ by at most 1 °, preferably by at most 0.5 °, particularly preferably by at most 0.2 ° (2 Θ). "correlated" herein will be understood to mean that the peaks are sufficiently strong to be important for identifying the substance. Preferably, two to three overlapping peaks have a main peak height of at least 20%, particularly preferably at least 50%. It is particularly preferred that one of the matching peaks is one or both of the main peaks (a main peak or body main peaks) of the substance forming the luminescent component and the masking component. This partial overlap prevents the identification and separation of the individual X-ray diffraction patterns. This is especially the case when the cryptic component has at least one substance whose X-ray diffraction pattern is not generally known, i.e. not contained in a commonly used structural database. In addition to the structure type itself, it is likewise possible to draw conclusions about the elemental content or the degree of distribution of the stoichiometrically or non-stoichiometrically mixed compounds from the relative heights of the individual peaks. For example, many structures can form a homogeneous mixed series when elements are exchanged at some crystal positions with different elements that differ only slightly in structure, particularly in unit cell size, but can be identified by their different relative peak heights. Thus, as an additional advantage, local overlap conceals precise relative proportions between individual peak heights, even upon successful identification and separation of individual X-ray diffraction patterns, thereby substantially impeding inferences about the precise stoichiometry of the concealed matrix.

In order to obtain such a match of some peak positions of the luminescent component and the covert component species, it may be necessary to specifically employ the lattice constant of the covert component species. This is preferably done by partially replacing the lattice components with atoms having larger and/or smaller radii in suitable proportions. In the structure of some substances, this makes it possible to obtain a continuous variation of the lattice parameter, for example by widening the lattice by inserting atoms with a larger atomic radius, thereby in turn shifting the peak positions of the X-ray diffraction pattern. As a further advantage, the peak positions of such partially substituted species are often present in the usual X-ray structure database only for some individual substitution ratios, thereby further hampering the analysis. For example, for substances A in which A is replaced by B₂SiO₄Complete substitution of B is often found₂SiO₄Semi-substituted ABSiO₄And is unsubstituted for A₂SiO₄Not in any proportion, e.g. A_0.21B_1.79SiO₄. For example, the isomorphic compound Ba₂SiO₄、BaCaSiO₄And Ca₂SiO₄The diffraction pattern of (a) is known. The positions of the two strongest XRD peaks herein for Ba₂SiO₄29.4 ° and 30.4 °, respectively, for BaCaSiO₄30.6 ° and 31.5 °, respectively, and for Ca₂SiO₄Respectively 32.0 deg. and 32.5 deg.. However, any intermediate state can be made to adopt the position of the peak. This makes it possible to improve the overlap with the diffraction pattern of the luminescent component. At the same time, the finding of compounds by using X-ray structure databases is hampered.

Likewise, it is possible to strongly influence the relative intensity ratios of the individual peaks of the X-ray diffraction pattern by substitution with lighter and/or heavier atom types, even when their positions do not change and only change weakly due to constant lattice parameters. In combination with partial matching of some peaks of the mixture of luminescent and cryptic species, can thus produce an X-ray diffraction pattern that is particularly difficult to analyze.

Preferably, the luminescent component and the sequestering component also have the same or at least similar density, such that they cannot be easily separated, e.g. by sedimentation. Preferably, the density of the covert component deviates less than 50%, particularly preferably less than 30%, in total from the density of the luminescent component.

By using further components with different functionalities, additional advantageous properties of the security feature may be achieved, whereby additionally an increased security against counterfeiting may be obtained. The further components and the luminescent and sequestering components can be matched to one another with regard to their amount and elemental composition and additionally with regard to their structure.

As a further component, a manufacturing component may be included in the security feature. The security feature has 0 to 30%, preferably 0 to 20% of a manufacturing component. The manufacturing component is used to ensure an unchanged quality or signal intensity of the security feature or the luminescent component contained therein. Depending on the manufacturing conditions, such as the raw material batch used and the impurities contained therein, annealing parameters, milling parameters, etc., fluctuations in the intensity of the luminescence signal of the luminescent component may occur. In order to compensate for this fluctuation, the production components are added to the security element in a proportion such that the luminescence signal of the security element obtained therefrom is adjusted to a defined nominal magnitude. This avoids the need to change the respective metering when using the security feature when introducing the security feature into the value document at the time of the aforementioned fluctuations. In contrast to the covert component, the proportion of the manufacturing component relative to the luminescent component is variable, since the desired proportion of the manufacturing component in the security feature depends on the respective production conditions, as described above.

It is not absolutely necessary but preferred that the manufacturing component comprises a crystalline material. In this case, it is further preferred that the peak positions of the X-ray diffraction patterns of the manufacturing component and the covert or luminescent component at least partially overlap in the manner described above. In this way, the X-ray analysis can be additionally hampered.

Further, there may be provided: elemental analysis and separation of luminescent, cryptic and manufacturing components is also prevented or at least hindered. For this purpose, the manufacturing component may have both at least one element of the substance forming the luminescent component and/or at least one element of the substance forming the covert component. When the luminescent component and the covert component have elements A, B and C, such as described above, the make component has at least one of element A, B or C. The manufacturing component may additionally have one or more further elements D as well as oxygen and/or hydrogen.

Further components of the security feature may be formed from the coded component. The coding component is contained in the security feature in a proportion of 0 to 10%, preferably 0.5 to 4%, particularly preferably 1 to 3%. The coding component comprises substances which serve as legal features by means of which different manufacturing batches, deliveries (deliveries), manufacturers or processors (processors) can be marked, for example. Preferably, the coding component is formed by a luminophore. However, the luminophore does not necessarily have to emit in the non-visible region of the spectrum like the luminescent component, but may, for example, preferably emit in the visible region of the spectrum. Since the coding component is designed as a legal feature, it does not necessarily have the above-mentioned properties for evaluation in banknote processing machines at high transport speeds. However, it should be determined that the evaluation of the luminescent component is not adversely affected by the coding component. Preferably, the coding component is therefore as different as possible in excitation and emission from the luminescent component. The detection of the coding components can be achieved via legal methods, for example by measurement using fluorescence microscopy or by means of professional laboratory equipment, whereby significantly longer measurement times (for example, several minutes up to several hours) compared to the luminescent components can also be necessary for reliable detection.

As coding component there is a collapsed zeolite structure loaded with rare earth metals and/or transition metals as described in e.g. DE 10056462 a1, which is preferably used. These provide the advantage that the zeolite can be easily loaded with various cations by ion exchange. It is also preferred to use a matrix doped with rare earth metals and/or transition metals having a narrow band spectrum in the visible region. Preferably, the dopant used herein is a trivalent rare earth cation of praseodymium, samarium, europium, terbium and dysprosium that emits light in the visible region, and the matrix used is an oxide (e.g., in the form of garnet, spinel or perovskite), as well as oxysulfide, sulfide, silicate, phosphate, aluminate, niobate, tantalate, vanadate, germanate, arsenate, zirconate or tungstate. Examples of such and further substances are described in the publications US 3,980,887, US 4,014,812, US 3,981,819 and WO 2006/047621 a 1. Besides excitation spectra or emission spectra, luminescence lifetimes may also be tested. The proportion of rare earth ions and/or transition metals in the coding component can be so high here that it is comparable to the concentration of rare earth and/or transition metals of the dopant of the luminescent component upon elemental analysis of the security feature. This hampers the identification of the dopant for the luminescent component. As explained above with regard to the other components, it is preferred that the doping of the coding component and the luminescent component is also effected with different elements, since otherwise the chemical analysis is not impeded, but rather is facilitated. Furthermore, further cations not involved in luminescence may be embedded in the zeolite structure or luminophore matrix material to influence the elemental composition of the coding component.

The rare earth metal and/or transition metal may be added not only to the coding component but also to the fabrication component and/or the masking component to additionally protect the dopant of the luminescent component. The amounts of rare earth metals and/or transition metals are as described above with respect to the concealment of the dopants or with respect to the coding component, i.e. the amount of rare earth metals and/or transition metals added is comparable to the amount of dopants of the luminescent component.

In addition to the manufacturing component and the coding component, the security feature may have further functional components added thereto, which likewise do not necessarily have a masking effect. Examples of such additional components are, for example, dyes for modifying the color of the security feature, light-emitting absorbers which suppress unwanted visible fluorescence of the security feature, or fluxes for adjusting the rheology of the powder forming the security feature.

Also, the luminescent component may have more than one substance, i.e. more than one luminophore. In this case, it is preferred to provide the respective substances in the covert component for the individual luminophores of the luminescent component. If this is not possible or involves increased effort, for example for technical reasons, it may be sufficient to conceal only a single luminophore in the luminophore combination, since in order to successfully imitate the security feature, all luminophores of the luminophore combination generally have to be identified. In such a case, preferably only one of the several luminophores is protected by the sequestering component. If similar substances are used for the luminophores, for example matrices of the same type with different dopants, it may be sufficient to provide only one separate substance in the sequestering component for the similar substances of the luminescent component, respectively, in order to obtain a sequestering of the structure or composition of the two luminophores, respectively.

Security features can be used in value documents for ensuring their authenticity and/or codes representing some property, such as currency and/or denomination, etc., if the value document is a banknote.

Example 1

Using a luminescent substance CaNb consisting of a neodymium-doped calcium niobate host lattice (matrix)₂O₆Nd as a luminescent component (M) by mixing 2.675g of CaCO₃、7.234g Nb₂O₅And 0.092g Nd₂O₃Is annealed at 1150 c for 10 hours. Upon excitation at 532nm, the luminescent component emits light at 1061 nm. The main peak in the diffraction pattern of the luminescent component here lies at 29.2 °.

For structural concealment (R), monoclinic Zr (MoO) whose main peak is at 29.1 ℃ may be used₄)₂. At the same time, by Zr (MoO)₄)₂Additional cationic elements Zr and Mo were introduced for elemental capping (E). Nb may be added in order to mask the stoichiometry (S) of the luminescent component₂O₅。Nb₂O₅It can also be used to manufacture a compensator (P). Using CatA₂O₆:Sm_0.03(luminescence at 610 nm) as coding component (K). To conceal the dopant (D), a small amount of Er was used₂O₃And Yb₂O₃。

Thus, the security feature comprising luminescent and covert components and manufacturing compensators and coding components has for example the following composition:

example 2

The luminescent composition was the same as the luminophore described in example 1. The structure is not concealed. By adding Ca₃(PO₄)₂Effecting sequestration of the stoichiometry (S). Substance Ca₃(PO₄)₂Element P of (a) also implements element concealment (E). By adding SrAl₂O₄Additional cationic elements (E) Sr and Al are introduced. Use of Sr₃(PO₄)₂As a manufacturing compensator (P). Elemental masking (E) is also achieved for the elements Sr and P of the material used to make the compensator. For the purpose of sequestering the dopant (D), a small amount of Yb is used₂O₃And Tm₂O₃. The coding component (K) was the same as in example 1.

Thus, the security feature comprising the covert component and the covert component as well as the manufacturing compensator and the coding component has for example the following composition:

example 3

On the basis of the substance from example 1, the luminescence emission is additionally concealed by two organic luminophores (L). These involve a mixture of a tetranuclear (neodymium) complex with 2-thenoyltrifluoroacetone (HTTA) as ligand, which fluoresces in the region 1050-1100 nm, and a commercially available polymethine IR-1061(Sigma Aldrich) which emits light in the region 1020-1180 nm.

Thus, the security feature comprising luminescent and covert components and manufacturing compensators and coding components has for example the following composition:

example 4

Using Y_1.98Nd_0.02SiO₅As the light-emitting component (M), it is produced by: 2.66g of urea and 0.53g of SiO were mixed₂、6.72g Y(NO₃)₃·6H₂O、0.08g Nd(NO₃)₃·5H₂O and 3mLH₂O, evaporating off the liquid at 500 ℃ and annealing the material obtained at 1500 ℃ for 10 hours. Upon excitation at 532nm, the luminescent component emits light at 1075 nm.

The significant peak in the X-ray diffraction pattern ((greater than 70% of the main peak) is located at 22.8 deg. in order to mask the X-ray diffraction pattern (R), its main peak can be usedNaTaO at 22.8 °₃. The elements Na and Ta also achieve element hiding (E). By adding YAlO₃The sequestration of the stoichiometry (S) and the introduction of the additional cationic element (E) are achieved. YAlO₃Can also be used as a manufacturing compensator (P). For the purpose of sequestering the dopant (D), a small amount of Yb is used₂O₃And Ce₂O₃. LaOBr: Tb (emission at 543 nm) was used as coding component (K).

Thus, the security feature comprising luminescent and covert components and manufacturing compensators and coding components has for example the following composition:

example 5

The luminescent component (M) is the same as the luminophore described in example 4. For concealing the stoichiometry (S) and introducing additional cationic elements (E), NaAlSiO is used₄. As a preparation of the compensator (P) and for the introduction of the additional cationic element (E), BaSO is used₄. To conceal the dopant (D), a small amount of Tm is used₂O₃And Sm₂O₃. The coding component (D) is the same as from example 4.

Thus, the security feature comprising luminescent and covert components and manufacturing compensators and coding components has for example the following composition:

example 6

On the basis of the substances from example 4, the luminescence emission is additionally concealed by the organic luminophore (L). The organic luminophore (L) is IR-1048(Sigma Aldrich) which fluoresces in the region of 1050-1150 nm.

Thus, the security feature comprising luminescent and covert components and manufacturing compensators and coding components has for example the following composition:

example 7

Using KTiO (PO)₄) Er as the luminescent component (M) by mixing 18.78g KH₂PO₄、10.90g TiO₂And 0.61g Er₂O₃Is annealed at 800 ℃ for 12 hours. Upon excitation at 520nm, the luminescent component emits light at 1540 nm. The main peak in the diffraction pattern of the luminescent component is located at 32.3 °, with the immediately adjacent significant peak (greater than 70% of the main peak) at 32.6 °. For concealing the X-ray diffraction pattern (R), LaMnO may be used₃It has two significant peaks (90-100% of the main peak) at 32.3 ° and 32.6 ° in the diffractogram. The elements La and Mn also achieve elemental sequestration (E). To conceal the stoichiometry (S), TiO can be added₂Which can be used simultaneously as a manufacturing compensator (P). In order to conceal the dopant (D), a small amount of Nd may be used₂O₃、Ce₂O₃And Ho₂O₃. The code component (K) is Y₂SiO₅Ce, which emits at 420 nm.

Thus, the security feature comprising luminescent and covert components and manufacturing compensators and coding components has for example the following composition:

example 8

The luminescent component (M) is the same as the luminophore described in example 7. To mask the stoichiometry (S) and to introduce additional cationic elements (E), CaTiO is used₃. By adding ZrSiO₄Introducing additional cation element (E), ZrSiO₄While being able to act as a manufacturing compensator (P). In order to conceal the dopant (D), a small amount of Nd is used₂O₃、Ce₂O₃And Ho₂O₃. The coding component (K) was the same as in example 7.

Thus, the security feature comprising luminescent and covert components and manufacturing compensators and coding components has for example the following composition:

example 9

On the basis of the substance from example 8, the luminescence emission is additionally concealed by the organic luminophore (L). The organic luminophore (L) is an acyclic erbium complex acyc-H which fluoresces in the region 1480-1600nm as described in literature sources "l.slooff, a.polman, m.oude Wolbers, f.van Veggel, d.reinhoudt, j.hofstraat; J.appl.Phys.83(1)1998, p.497-503'.

Thus, the security feature comprising luminescent and covert components and manufacturing compensators and coding components has for example the following composition:

Claims (22)

1. A security feature having a luminescent component and a component concealing the luminescent component, the luminescent component having at least one luminophore consisting of a doped host lattice,

wherein the identification of said luminescent component is hindered or prevented by the properties of said sequestering component and the corresponding same type of properties of said luminescent component characterized by at least two of the following relationships:

a) the concealing component having an X-ray diffraction pattern at least partially overlapping the X-ray diffraction pattern of the luminescent component to conceal the structure of the luminescent component,

b) the sequestering component comprises at least one cationic element also contained in the host lattice of the luminescent component, but not all of the cationic elements contained in the host lattice, to sequester the stoichiometry of the luminescent component,

c) the sequestering component comprises at least one cationic element not comprised in the host lattice of the luminescent component to sequester the elemental composition of the host lattice of the luminescent component,

d) the sequestering component comprises at least one dopant not included in the luminescent component as a dopant to sequester one or more dopants of the luminescent component,

e) the concealing component comprises at least one luminophore having a shorter decay time than a luminophore comprised in the luminescent component to conceal spectral properties of the luminescent component,

the security feature may be further characterized in that,

the covert component and the luminescent component satisfy the relationships a) and b), or

The covert component and the luminescent component satisfy the relationships a) and e),

wherein the luminescent component is included in the security feature in an amount of 20 wt% to 80 wt% and the covert component is included in the security feature in an amount of 20 wt% to 80 wt%.

2. The security feature of claim 1 wherein said covert component and said luminescent component satisfy the relationships a), b), c) and d).

3. The security feature of claim 1 wherein said covert component and said luminescent component satisfy the relationships a), b), c), d) and e).

4. The security feature of any one of claims 1 to 3 wherein the X-ray diffraction patterns of the luminescent component and the covert component have a partial overlap of significant peaks with at least one relevant peak position overlapping.

5. A security feature as claimed in claim 4 in which at least two of the correlation peak positions overlap.

6. A security feature as claimed in claim 5 in which at least three of the correlation peak positions overlap.

7. A security feature as claimed in claim 4 in which the overlapping peaks have a main peak height of at least 30%.

8. A security feature as claimed in claim 7 in which the overlapping peaks have a main peak height of at least 50%.

9. The security feature of claim 4, wherein said overlapping peaks are the main peaks of the luminescent component and the covert component.

10. The security feature of claim 9 wherein said overlapping peaks are two major peaks of a luminescent component and a covert component.

11. A security feature according to any one of claims 1 to 3 In which the cationic element is selected from the main group elements Li, Be, B, Na, Mg, Al, Si, P, S, K, Ca, Ga, Ge, As, Se, Rb, Sr, In, Sn, Sb, Te, Cs, Ba, Tl, Pb, Bi or transition metal elements or rare earth elements.

12. The security feature of any one of claims 1 to 3 wherein the dopant of the luminescent component is a rare earth element and the covert component comprises at least one dopant consisting of the rare earth elements Ce, Pr, Nd, Sm, Eu, Tb, Dy, Ho, Er, Tm, Yb.

13. A security feature as claimed in any one of claims 1 to 3 in which the dopant of the luminescent component is a transition metal of the fourth period of the periodic system and the covert component comprises at least one further dopant consisting of an element of the fourth period of the periodic system.

14. A security feature as claimed in any one of claims 1 to 3 in which the luminophore of the covert component is a non-inorganic luminophore.

15. The security feature of claim 14 wherein said luminophore of covert component is an organic luminophore.

16. The security feature of claim 15 wherein said luminophore of covert component is a metal organic luminophore.

17. A security feature as claimed in any one of claims 1 to 3 in which the luminophore of the covert component has a decay time of less than 10 μ s.

18. The security feature of claim 17 wherein said luminophore of covert component has a decay time of less than 1 μ s.

19. A security feature as claimed in any one of claims 1 to 3 in which the covert component has, in addition to or in place of the at least partially overlapping X-ray diffraction patterns, further structural features which at least partially match the corresponding structural features of the luminescent component to conceal the structure of the luminescent component.

20. Value document with a security feature according to any one of claims 1 to 18, characterized in that the value document consists of paper and/or plastic.

21. A document of value according to claim 20, wherein the security feature is incorporated into the volume of the document of value and/or is coated onto the document of value.

22. A value document according to claim 20, wherein the security feature is applied as an invisible, at least partial coating onto the value document.