EP2118855B1 - Safety and/or valuable document having a photonic crystal - Google Patents

Description

Field of invention

The invention relates to a security and / or value document with a security element, the security element containing a photonic crystal and a luminescent substance arranged on a substrate with an orientation defined in relation to a surface of the substrate. The invention also relates to a method for its production and a method for its verification.

Background of the Invention and Prior Art

In value and security printing, optically variable colors have established themselves as a good security feature because they can be easily checked without technical aids. Such optically variable colors are known from practice, for example from bank notes and documents. These are difficult to reproduce, a check at a cash register, for example, is often only fleeting, so that only the presence of a color change is observed. Due to the large number of colors and pigments, for example liquid crystals or platelets or flakes, which have such effects and are commercially available, falsified impressions are known which are clearly different from the original color change colors differ, but are not necessarily recognizable for an inexperienced layman.

Another widely used security system involves the use of luminescent substances. In most documents relating to value and security printing, there are luminescences, as these cannot be reproduced using simple means (printer, copier) and only require a UV light source for checking. It is disadvantageous that usually only a quick check takes place after the color impression, so that a luminescence can be partially simulated, for example with a highlighter. In contrast, for a precise examination, complex spectrometers are required with which it is possible to differentiate between different luminescence wavelengths. It is true that a machine check is easy and reliable as a result, but the outlay on equipment is considerable and consequently complex.

From the reference WO 2006/045567 A2 a security and / or value document of the structure mentioned above is known. In this case, a layer is used as the photonic crystal, which is made up of spheres or spheres with a narrow monomodal diameter distribution, the spheres forming a dense packing of spheres, that is, a crystal structure. The diameter of the spheres is in a range of 50-500 nm, so that different reflection conditions according to Bragg's law are present at different network planes of the crystal for different components of visible light. This makes a visually more variable Obtain color effect, namely when pivoting the security and / or value document or viewing at changing viewing angles. According to this prior art, the security and / or

Document of value additionally contain a luminescent substance. The diameter of the spheres, however, is chosen so that the desired optically variable effects are achieved, completely independently of any possible luminescence.

Structures suitable for the production of photonic crystals are for example in the literature references WHERE. 03/025035 A2 , U.S. 4,391,928 , EP 0 441 559 B1 and EP 0 955 323 B1 described.

From the WO 2005 077 668 A1 a security document is known with core-shell particles and fluorescent particles arranged on a surface of a substrate.

Luminescence radiation typically does not have a directional characteristic, since the emitter centers are oriented statistically within a coating, color or the like. From other technical fields, for example laser diode technology, it is known to generate directional luminescence radiation by using layer structures whose layers have a thickness that leads to the reflection or forward amplification of the luminescence radiation in a defined spatial direction. Such structures are less suitable for value and security printing due to the complex production.

Technical problem of the invention

The invention is therefore based on the technical problem of providing a security element which can easily be checked with minimal resources, but with increased reliability, even with a cursory inspection.

Main features of the invention

aufeinander abgestimmt sind, wobei d ein Abstand zwischen zwei Netzebenen des photonischen Kristalls ist und d mit der Gitterkonstante a wie folgt zusammenhängt $$\mathrm{d}=\mathrm{a}/{\left({\mathrm{h}}^2+{\mathrm{k}}^2+{\mathrm{l}}^2\right)}^{\mathrm{0,5}}$$

und m eine positive ganze Zahl sind.To solve this technical problem, the invention teaches that an emission wavelength Iambda of the luminescent substance and a lattice constant of the photonic crystal in accordance with the formula $$\mathrm{Iambda}=\mathrm{m}*2*\mathrm{d}$$

are matched to one another, where d is a distance between two lattice planes of the photonic crystal and d is related to the lattice constant a as follows $$\mathrm{d}=\mathrm{a}/{\left({\mathrm{H}}^2+{\mathrm{k}}^2+{\mathrm{l}}^2\right)}^{0.5}$$

and m is a positive integer.

In other words, the particles with which the photonic crystal is formed, in terms of diameter and arrangement with the proviso on the Emission wavelength adjusted so that the intensity of the luminescence radiation is different at different viewing angles.

The invention makes a considerable improvement in the safe and simple checking of luminescent security elements reached. Because a checking person only needs to expose the security and / or valuable document to radiation that stimulates luminescence, for example UV, and to check i) whether luminescence is observed, and ii) if so, whether its intensity when the security and / or or value document varies. The security and / or value document is only accepted as genuine if both criteria are met. A luminescence security element according to the invention can no longer be reproduced with simple means.

The invention uses the knowledge that a photonic crystal can also be used to equip the non-directional luminescence radiation with an anisotropic distribution of the intensity in the solid angle by refraction.

Definitions

Security documents and / or documents of value are only mentioned as examples: ID cards, passports, ID cards, access control cards, visas, tax codes, tickets, driving licenses, vehicle documents, banknotes, checks, postage stamps, credit cards, any chip cards and adhesive labels (e.g. for product security). Such security and / or value documents typically have a substrate, a printing layer and optionally a transparent cover layer. A substrate is a support structure on which the printing layer is attached Information, images, patterns and the like is applied. All conventional materials based on paper and / or plastic can be used as materials for a substrate.

A security element is a structural unit that includes at least one security feature. A security element can be an independent structural unit that can be connected to a security and / or value document, for example glued, but it can also be an integral part of a security and / or value document. An example of the former is a visa that can be stuck onto a security and / or valuable document. An example of the latter is a flat construct that is integrated, for example, laminated into a bank note or an identity card. The latter also includes layers or coatings that are applied to a substrate.

A security feature is a structure that can only be produced, reproduced, manipulated or changed with increased effort (compared to simple copying) or not at all in an unauthorized manner. In the context of the invention, the security feature is formed by the composite of photonic crystal and luminescent substance. The term “network” refers to the optical coupling with coordination of network level spacing and emission wavelength.

The term luminescence refers to the emission of electromagnetic radiation, especially in the IR, visible or UV range, in the course of a relaxation of an atomic or molecular electronic system from an excited state to an energetically lower state, generally the electronic ground state. In this case, the previous excitation can take place through electrical energy or an electrical potential (electroluminescence), bombardment with electrons (cathodoluminescence), bombardment with photons (photoluminescence), the action of heat (thermoluminescence) or friction (triboluminescence). In the context of the invention, photoluminescence is preferred. Luminescence includes in particular phosphorescence and (photo) fluorescence.

Fluorescence is a radiant deactivation of excited electronic states, the transition from the excited state to the lower energetic state, for example the ground state, being spin-allowed. The dwell time in the excited state is typically approx. 10 ^-8 s, ie the emission of fluorescent radiation ends immediately after the end of the energy input for excitation. In contrast, phosphorescence is a spin-forbidden deactivation of excited states via intercombination processes. Therefore the relaxation is weak and slow. The dwell time in an excited state is a few milliseconds up to hours and the emission of the phosphorescent radiation can be observed for a correspondingly long time.

The emission wavelength of a luminescent substance is characteristic of the substance used and is determined by the energy difference between the excited state and the energetically lower electronic state, for example the ground state. The maximum emission intensity in an emission spectrum is referred to as the emission wavelength.

A luminescent substance contains atoms, molecules or particles that are capable of luminescence. A luminescent substance can be used to create a luminescent paint or ink that contains the other components of paints or inks customary in the art, such as binders, penetrants, adjusting agents, biocides, surfactants, buffer substances, solvents (water and / or organic solvents), fillers, pigments , Effect pigments, antifoam agents, anti-settling agents, UV stabilizers, etc .. Suitable ink formulations for various printing processes are well known to those skilled in the art from the prior art and luminescent substances used according to the invention are in this respect added instead of or in addition to conventional dyes or pigments.

Radiation is typically functional to excite luminescence when the wavelength of the radiation is smaller than the wavelength of the luminescence radiation. However, radiation with a higher wavelength can be functional if the luminescent substance in question is capable of so-called up-conversion processes.

A network plane is defined in space by the Miller indices h, k, and 1. The distance d is defined as the smallest distance between parallel network planes, i.e. of lattice planes with the same Miller indices.

wobei D der Durchmesser der Kugeln bzw. Sphären ist, welcher als Abstand der nächsten benachbarten Sphärenmittelpunkte, gegeben ist.A close packing of spheres corresponds to an fcc (face centered cubic, cubic close packing) or hcc or hcp (hexagonal close packed, hexagonal close packing) lattice. The lattice constant a is included $$\mathrm{a}=2^{0.5}*\mathrm{D.}$$

where D is the diameter of the balls or spheres, which is given as the distance between the next adjacent spherical centers.

mit d als Abstand der Netzebenen und m eine positive ganze Zahl (Ordnung), insbesondere 1, 2, 3, 4, 5, 6, 7, 8, 9, oder 10. Folgend wird mit m = 1 (1. Ordnung) gerechnet.The reflection condition according to Bragg's law is: $$\mathrm{lambda}=\mathrm{m}*2*\mathrm{d}$$

with d as the distance between the network levels and m a positive whole number (order), in particular 1, 2, 3, 4, 5, 6, 7, 8, 9, or 10. The following is calculated with m = 1 (1st order) .

d and a are related as follows: $$\mathrm{d}=\mathrm{a}/{\left({\mathrm{H}}^2+{\mathrm{k}}^2+{\mathrm{l}}^2\right)}^{0.5}.$$

bzw. $$\mathrm{D}=\left(\mathrm{n}/8\right)\mathrm{0,5}*\mathrm{lambda},$$

wenn (h² + k² + l²) als n zusammen gefasst wird.The relationship between the emission wavelength lambda and the diameter D of the spheres then results: $$\mathrm{D.}={\left[\left({\mathrm{H}}^2+{\mathrm{k}}^2+{\mathrm{l}}^2\right)/\mathrm{8th}\right]}^{0.5}*\mathrm{lambda}$$

or. $$\mathrm{D.}=\left(\mathrm{n}/\mathrm{8th}\right)0.5*\mathrm{lambda},$$

if (h ² + k ² + l ² ) is summarized as n.

mit q_r der Dichteverteilung, Qr(x) der Summenverteilung, bezogen auf die Anzahl und dx, dem Durchmesserdiffential.The term diameter D denotes the mean diameter of the spheres (or mean distance between the closest spheres adjacent to one another), which is defined as the maximum of the number-related (monomodal) linear normalized density distribution. This density distribution is given by $${\mathrm{q}}_{\mathrm{r}}\left(\mathrm{x}\right)={\mathrm{dQ}}_{\mathrm{r}}/\mathrm{dx}$$

with q _r the density distribution, Qr (x) the cumulative distribution, related to the number and dx the diameter differential.

In the context of the invention, the density distribution should be as narrow as possible so that clearly visible and reproducible angle dependencies arise when viewed. It is preferred if the (mostly Gaussian-like) density distribution at half the maximum value of the density has a width of less than 10% of the (mean) diameter D, preferably less than 5% of the diameter D, ideally less than 2% of the diameter D.

If other particle shapes, such as discs or rods, are used instead of spheres, a narrow size distribution in the above sense is also important. Instead of the mean diameter D, the mean equivalent diameter D _Ä , which is calculated from the relevant shape according to defined geometric rules, then occurs. In this case, however, a correspondingly narrow distribution of the aspect ratio (different geometric extensions of a particle) is also important.

Within the scope of the invention, it will generally be set up so that the photonic crystal does not have a complete band gap at the emission wavelength. Photonic crystals with a complete band gap have so far only been postulated theoretically and are characterized by the fact that light cannot propagate in any spatial direction. In the case of photonic crystals with an incomplete band gap, as used in particular in the context of the invention, the propagation of the light is only possible in certain spatial directions.

Embodiments of the invention

The luminescent substance can in principle emit in the IR, visible, or UV. It is preferred if the emission takes place in the visible, since then the Security and / or value documents can be done by simple inspection.

The luminescent substance can comprise a luminescent dye and / or a luminescent pigment.

The luminescent dye can be selected from the group consisting of "organic fluorescent dyes, naphthalimides, coumarins, xanthenes, thioxanthenes, naphtholactams, azlactones, methines, oxazines, thiazines, and mixtures of two or more different such substances". The luminescent pigment can be selected from the group consisting of "ZnS: Ag, Zn-Silicate, SiC, ZnS, CdS (activated with Cu or Mn), ZnS / CdS: Ag, ZnS: Cu, Al, Y ₂ O ₂ S: Eu, Y ₂ O ₃ : Eu, YVO ₄ : Eu, Zn ₂ SiO ₄ : Mn, CaVVO ₄ , (Zn, Mg) F ₂ : Mn, MgSiO ₃ : Mn, ZnO: Zn, Gd ₂ O ₂ S: Tb , Y ₂ O ₂ S: Tb, La ₂ O ₂ S: Tb, BaFCl: Eu, LaOBr: Tb, Mg tungstate, (Zn, Be) silicate: Mn, Cd borate: Mn, Ca ₁₀ (PO ₄ ) ₆ F, Cl: Sb, Mn, (SrMg) ₂ P ₂ O ₇ : Eu, Sr ₂ P ₂ O ₇ : Sn, Sr ₄ Al ₁₄ O ₂₅ : Eu, Y ₂ SiO ₅ : Ce, Tb, Y ( P, V) O ₄ : Eu, BaMg ₂ Al ₁₀ O ₂₇ : Eu, MaAl ₁₁ O ₁₉ : Ce, Tb, and mixtures of two or more different such substances ". The host lattice is indicated in front of the ":" and a doping element after the ":".

It is preferred if the luminescent substance is a fluorescent dye which is selected from the group consisting of "organic fluorescent dyes, naphthalimides, coumarins, xanthenes, thioxanthenes, naphtholactams, azlactones, methines, oxazines, thiazines, and mixtures of two or more different such substances ". To other suitable and preferred Fluorescent dyes is only referred to, for example, in the literature Schwander et al., "Fluorescent Dyes" in Ullmann's Encyclopedia of Industrial Chemistry, Wiley-VCH Verlag GmbH & Co. KGaA, 2002 , WO 03/052025 A , WO 02/053677 A , EP 0147252 A , GB 2,258,659 and FM Winnik et al., Xerox Discloser Journal Vol. 17, No. 3, 1992, pp. 161-162 , referenced.

In the context of the invention, two or more different luminescent substances can advantageously also be used, the different luminescent substances having different emission wavelengths. The term of the different emission wavelengths denotes a wavelength difference of at least 3 nm, 5 nm, 10 nm, 20 nm, or 30 nm, in the visible. The different emission wavelengths then result in different angles at which the different colors of the luminescence can be observed with particularly high or low intensity. The term high intensity denotes the maximum intensity that can be observed with respect to an emission wavelength. A low intensity then denotes an intensity that is reduced compared to the high intensity, for example reduced by at least 5%, 10%, 20%, 30%, 50%, or 80%. As a result, a luminescence color change is generated when the security and / or value document is tilted.

The photonic crystal is advantageously formed by an fcc or hcc lattice with a lattice constant a, and where d = a / n ^0.5 with n = 1 to 20, in particular 1 to 5, and where n for (h ² + k ² + l ² ) with h, k, and 1 stands as Miller indices. The grid points or particles of the photonic crystal can in principle have any shape, for example as small discs or rods. However, it is preferred if the lattice points or particles are designed as spheres (spheres).

It is then particularly preferred if the spheres are core-shell particles which are arranged in a tight packing of spheres. The mean diameter of the spheres to be set depends on the emission wavelength of the luminescent substance used. The mean diameter of the spheres can thus be in the range from 270-5000 nm, in particular from 270-2500 nm, if the luminescent substance emits in the IR (780-3000 nm). The mean diameter of the spheres can be in the range from 135 to 1200 nm, in particular from 135 to 600 nm, if the luminescent substance emits in the visible (380 to 780 nm). The mean diameter of the spheres can be in the range of 35-600 nm, in particular 35-300 nm, if the luminescent substance emits in the UV (100-380 nm).

The photonic crystal can be produced by deposition from the liquid phase by means of self-assembly, for example under pressure, as in the inkjet printing process. For example, the production of artificial opals from SiO ₂ from solutions is well known.

It is particularly preferred if the core / shell particles have a core made of an organic or inorganic core material and a shell made of a polymer have organic shell material, wherein the shell material is flowable at an elevated temperature, while the core material is not flowable at the elevated temperature. The background to this is that the periodic remote structure required for this, for example the close packing of spheres, must be produced in a defined orientation in order to form a photonic crystal. If a bed or emulsion or suspension with such core-shell particles is exposed to a compressive force at an elevated temperature, the shear forces that arise between the particles cause the particles to arrange themselves to form a dense packing of spheres on a surface of a substrate and align themselves when the particles move can move against each other. A jacket that is flowable under the pressure and temperature conditions facilitates such movements of the particles in relation to one another and the result is a photonic crystal with excellent long-range order and clear orientation on the substrate. In detail, there are various options for execution.

The inorganic core material can be selected from the group consisting of "metals, semimetals, metal chalcogenides, especially metal oxides, metal pnictides, especially metal nitrides or metal phosphides, and mixtures of two or more different such substances, the metal being an element of the first three main groups of the periodic table or a metallic element of the subgroups and wherein the semimetal can comprise Si, Ge, As, Sb, and Bi ", in particular is selected from the group consisting of "SiO ₂ , TiO ₂ , ZrO ₂ , SnO ₂ , and Al ₂ O ₃ ".

The organic core material is preferably selected from the group consisting of "aliphatic, aliphatic / aromatic or fully aromatic polyesters, polyamides, polycarbonates, polyurea, polyurethanes, aminoplast resins, phenoplast resins such as formaldehyde condensates of melamine, urea or phenol, epoxy resins, acrylic esters such as methyl ( meth) acrylate, butyl (meth) acrylate, isopropyl (meth) acrylate, polystyrene, PVC, polyacrylonitrile, random or block copolymers of one or more such homopolymers, and mixtures of two or more different such homo- or copolymers ".

The jacket material can be selected from the group consisting of "aliphatic, aliphatic / aromatic or fully aromatic polyesters, polyamides, polycarbonates, polyurea, polyurethanes, aminoplast resins, phenoplast resins such as formaldehyde condensates of melamine, urea or phenol, epoxy resins, polyepoxides, poly (meth) acrylates, such as polymethyl (meth) acrylate, polybutyl (meth) acrylate, polyisopropyl (meth) acrylate, polystyrene, PVC, polyacrylonitrile, polyethylene, polypropylene, polyethylene oxide, polybutadiene, polytetrafluoroethylene, polyoxymethylene, rubber, polyisoprene, random or block copolymers a or more such homopolymers, and mixtures of two or more different such homo- or copolymers ". It is useful if the core material has a higher glass transition temperature than the cladding material, since then at a temperature between the glass transition temperatures of the materials only the cladding material and not the core material flows. The core material can, for example, have a glass transition temperature in the range of more than 60 ° C, preferably more than 80 ° C, most preferably more than 90 ° C, while the jacket material, for example, has a glass transition temperature in the range of 40 - 90 ° C, in particular 60 - 80 ° C. Such a range of glass transition temperatures is recommended as core material for organic polymers, for example. Alternatively, for example in the case of inorganic core materials, the glass transition temperature of the core material can be above 300 ° C, and then the glass transition temperature of the cladding area, for example in the case of polycarbonates, can also be high, for example in the range of 80 - 250 ° C, in particular 120 - 200 ° C.

The cladding material, which can form a matrix in the course of the production of the photonic crystal, in which the spheres or cores are embedded (and fixed), should have a refractive index (also called refractive index) different from the refractive index of the core material. The expression of the different refractive index denotes a difference of at least 0.001, better at least 0.01, advantageously at least 0.1. The person skilled in the art can easily select suitable material pairings from the above materials for the core material and the cladding material with regard to the difference in the refractive index. The core material, but also the cladding material have the higher refractive index in each case.

The weight ratio of core material to cladding material can be in the range from 2: 1 to 1: 5, in particular in the range from 3: 2 to 1: 3. In the case of polymeric materials, this ratio is preferably no greater than 2: 3 for both materials.

A coupling layer can be set up between the core and the shell of a core-shell particle. For example, crosslinked or partially crosslinked organic polymers come into consideration. Alternatively, the surface of the core can be functionalized in a manner customary in the art for binding or adhesion of the jacket material.

The production of core-shell particles suitable for the production of photonic crystals is described, for example, in the prior art mentioned at the beginning, as well as further variants and details for core materials, shell materials, coupling layers, etc. This prior art is hereby expressly described in Referenced.

Photonic crystals which can be used according to the invention can be formed as a film, layer or foil. Accordingly, they can be applied to a substrate using conventional coating processes or adhesion promoters. In doing so, they can be an integral part of a. Form document, for example in the case of card structures.

Photonic crystals according to the invention can form a visible pattern, for example the outline of an object or a person, or a sequence of characters made up of letters and / or numbers. Barcodes can also be used as samples. Then the coating takes place with the appropriate printing process or a film is cut out accordingly. It goes without saying that a photonic crystal is also macroscopically isotropic, i.e. without pattern, can be formed.

There are various possibilities for the arrangement of the luminescent substance. The luminescent substance can be arranged in the particles of the photonic crystal. In the case of core-shell particles, an arrangement in the core material and / or in the shell material of the core-shell particles is possible. For this purpose, in the case of organic core material, the material in question is preferably mixed homogeneously with the luminescent substance prior to solidification or polymerization in the course of producing the particles. In the case of inorganic core material, the luminescence-generating doping, for example with rare earth elements, which are built into the host lattice of the core material, can take place. The photonic crystal can then be produced without admixing luminescent particles, as a result of which disturbances in the formation of the photonic crystal due to the presence of interstitial luminescent particles are reliably avoided.

In the case of polymeric materials for core and / or shell areas of the core / shell particles, the respective polymer can contain luminescent monomer units, namely regularly, statically, in blocks or as side chains (graft copolymers). In the case of a crosslinked polymer, the crosslinking agent can also be luminescent. Finally, luminescent substances can be covalently, ionically or complexed bound to the polymer chain.

The luminescent substance can, however, also be arranged between the particles of the photonic grating. In the case of pigments, it is advisable if the ratio of the diameter D _{p of} the pigment particles to the diameter D (or D _Ä ) of the particles of the photonic grating D _p / D (or D _p / D _Ä ) is less than 0.5 , preferably less than 0.1, most preferably less than 0.02. The pigment particles can then be arranged between the particles or spheres of the photonic crystal and damage to the particles or spheres as a result of the action of pressure is practically impossible. If the luminescent substance is a luminescent dye, it can in any case be freely distributed between the particles of the photonic grating without disturbing them or their arrangement. In both cases, the photonic crystal is produced by mixing particles of the photonic crystal with the luminescent substance and then forming the long-range order to form the crystal, as described above. A variant of this is when the luminescent substance is deposited on the surface of the particles of the photonic crystal, for example by layer by layer Absorption. This results in a uniform growth on the particles of the photonic crystal, with the result that the narrow density distribution is maintained. The advantage here is that the particles of the photonic crystal and the luminescent substance can be selected and modified independently of one another, which enables easier adaptation to different products of the value and security printing.

Alternatively, the photonic crystal can also be underlaid with the luminescent substance. For example, the substrate can be coated, for example printed, with a paint or ink which contains the luminescent substance. The photonic crystal is then applied to the coating, for example in the simplest case as a film. This variant is the simplest in terms of process engineering and also allows modifications of the luminescent substance / photonic crystal system in a simple manner, for example for different types or values of security and / or value documents.

Finally, it is possible for additional non-luminescent colorants, such as dyes or pigments, to be set up in the photonic crystal and / or in a layer containing the luminescent substance. For this purpose, all colorants customary in the field of security and / or value documents that are known to the average person skilled in the art can be used. Usual forensic feature substances can also be used in the photonic Crystal or another layer of the security and / or value document can be provided.

The invention further relates to a method for producing a security and / or value document according to the invention or a security element therefor, wherein a substrate is provided on a surface or partial surface with a coating containing the particles of the photonic crystal to be formed and this coating is provided with the simultaneous action of Heat and pressure is compressed, optionally with a luminescent layer containing the luminescent substance being applied to the substrate prior to coating with the particles, and / or wherein the particles contain the luminescent substance or are mixed with it. In this embodiment of a production method, the compression is used to form the photonic crystal.

The action of heat preferably takes place at a temperature in the range of 60-260 ° C, in particular 70-190 ° C, and for a duration of 0.5-7200 s, preferably 0.5-3600 s, most preferably 1 - 10 s. The compression can take place at a pressure of 1-100 bar, preferably 1-20 bar. Typically, the compaction takes place by means of a press, in particular a laminating press. In the case of an inorganic core material in conjunction with a polymer of high glass transition temperature as the jacket material, for example in the range of 80-250 ° C, the action of heat is at correspondingly higher temperature, for example at 140-250 ° C.

A separating and / or protective layer can be arranged on the coating with particles of the photonic crystal. In the course of the action of heat and pressure, the protective layer can be welded to the substrate, possibly the luminescent layer, and the coating with particles or laminated to form a layer composite. The protective layer should be transparent in relation to the emission wavelength lambda.

As an alternative to the above procedure, a security and / or value document according to the invention can also be produced by applying a finished photonic crystal, in particular in the form of a film (thickness, for example 0.1-500 μm ), to the substrate and connecting it to it, be it by gluing, be it by lamination. Here too, the luminescent substance can already be present in the photonic crystal. However, it is also possible here for the substrate to be provided beforehand with a separate coating, for example a printing layer containing the luminescent substance.

The invention further relates to a security and / or value document which can be obtained using a method according to the invention mentioned above.

Finally, the invention relates to a method for verifying a security system according to the invention and / or value document or security element, the luminescent substance being stimulated to emit luminescent radiation, for example by exposure to UV radiation, the intensity of the luminescent radiation being determined as a function of the angle with respect to the surface of the security and / or value document, and wherein the specific angle dependence of the luminescence radiation is compared with a predetermined angle dependency. If no angle dependency is determined, or if the determined angle dependency does not match the predefined angle dependency, then this is not a security and / or valuable document according to the invention and consequently a replica. If the determined angle dependency corresponds to the predetermined angle dependency, the security and / or value document is verified as being according to the invention and consequently genuine. In the simplest case, the determination can be carried out by means of visual inspection. But it is also possible to determine the angle dependency by machine. In the case of different luminescent substances, the determination is carried out in each case for the relevant emission wavelengths for which different angle dependencies are specified.

Beispiel 1:

verschiedene Aufbauformen eines erfindungsgemäßen Sicherheits- und/oder Wertdokumentes

In the following, the invention is explained in more detail on the basis of examples which merely represent embodiments.

Example 1:

different designs of a security and / or value document according to the invention

In the Figure 1 cross-sections through different variants of security and / or value documents according to the invention are shown.

In the Figure 1a one recognizes a substrate 1, which can be single-layer or multi-layer. A printing layer 2 is applied directly to this substrate, the printing layer 2 containing two different fluorescent substances in a uniform distribution. A first fluorescent substance has an emission wavelength of 500 nm and a second fluorescent substance has an emission wavelength of 707 nm. A photonic crystal 3 in the form of a film follows in the layer sequence. This photonic crystal 3 is made of core-shell particles according to the literature reference WO 2003/025035 A2 educated. The core / shell particles have a mean particle diameter of 354 nm. The photonic crystal 3 is followed by a protective layer 4 which is transparent to visible light and which in turn can be single-layer or multilayer. It is also possible for a single-layer or multi-layer intermediate layer to be arranged between the printing layer 2 and the photonic crystal 3, which is not shown for the sake of clarity. The substrate 1 with the printing layer 2, the photonic crystal 3 and the protective layer 4 are connected to one another by lamination and form a monolithic layer block.

Beispiel 2:

Winkelabhängigkeit der Fluoreszenz des Gegenstandes des Beispiels 1

In the variant of the Figure 1b the same fluorescent substances are used, but these are arranged in the photonic crystal 3. This means that the printing layer 2 can be omitted. The fluorescent substances are absorbed or adsorbed on the surface of the core / shell particles, and in fact in a uniform distribution.

Example 2:

Angular dependence of the fluorescence of the article of Example 1

When coordinating the emission wavelengths with the diameter of the particles of the photonic crystal 3, and ultimately also with the lattice constant a and the lattice plane spacing d of the photonic crystal 3, the result is that red (707 nm) with maximum intensity at around 45 ° relative to the surface normal of the security and / or value document is emitted, but at 0 ° and 90 ° the intensity is greatly reduced, more typically below 90% of the maximum intensity. In contrast, green (500 nm) can be observed at 45 ° with only 10% or less of the maximum intensity, but at 0 ° and 90 ° with maximum intensity.

The result is the representation of the Figure 2a , which is a projection of the one in the Figure 2b The hemisphere shown in perspective acts in the direction of the surface normal of the security and / or value document. Areas R can be seen that appear red in approx. 45 °, while areas G appear green in approx. 90 ° and 0 °.

Claims (15)

1. A security and/or valuable document having a security element, wherein the security element has a photonic crystal arranged on a substrate and a luminescent substance,
   characterized in that
   the particles, by which the photonic crystal is formed, are adjusted with regard to an emission wavelength lambda of the luminescent substance such that an emission wavelength lambda of the luminescent substance complies with the formula $$\mathrm{lambda}=\mathrm{m}*2*\mathrm{d}$$

   

   wherein d is a distance between two lattice planes of the photonic crystal and d and the grid constant a have the following relation: d = a / (h² + k² + l²)^0.5, and m is a positive integer, such that the intensity of the luminescence radiation is different under different viewing angles.
2. The security and/or valuable document according to claim 1, wherein the luminescent substance emits in the IR, visible, or UV range and/or
   wherein the luminescent substance comprises a luminescent dye and/or a luminescent pigment and/or wherein the luminescent dye is selected from the group comprising "organic fluorescent dyes, naphthalimides, coumarins, xanthenes, thioxanthenes, naphtholactams, azlactones, methines, oxazines, thiazines, and mixtures of two or more such different substances", and/or wherein the luminescent pigment is selected from the group comprising "ZnS:Ag, Zn silicate, SiC, ZnS, CdS (activated with Cu or Mn), ZnS/CdS:Ag, ZnS:Cu,Al, Y₂O₂S: Eu, Y₂O₃: Eu, YVO₄ : Eu, Zn₂SiO₄:Mn, CaVVO₄, (Zn,Mg) F₂:Mn, MgSiO₃:Mn, ZnO:Zn, Gd₂O₂S:Tb, Y₂O₂S:Tb, La₂O₂S:Tb, BaFCl:Eu, LaOBr:Tb, Mg tungstenate, (Zn,Be) silicate:Mn, Cd borate:Mn, Ca₁₀(PO₄)₆F, Cl:Sb, Mn, (SrMg)₂P₂O₇: Eu, Sr₂P₂O₇:Sn, Sr₄Al₁₄O₂₅:Eu, Y₂SiO₅:Ce, Tb, Y(P,V)O₄:Eu, BaMg₂Al₁₀O₂₇: Eu, MaAl₁₁O₁₉: Ce, Tb, and mixtures of two or more such different substances" and/or
   wherein the luminescent substance is a fluorescent dye, which is selected from the group comprising "organic fluorescent dyes, naphthalimides, coumarins, xanthenes, thioxanthenes, naphtholactams, azlactones, methines, oxazines, thiazines, and mixtures of two or more such different substances".
3. The security and/or valuable document according to one of claims 1 to 2, wherein the photonic crystal is formed by an fcc or hcc lattice with a grid constant a, and wherein d = a / n^0.5 with n = 1 to 20, in particular 1 to 5, is, and wherein n is (h² + k² + l²) with h, k, and 1 as Miller indices and/or wherein the lattice points of the photonic crystal are configured by means of spheres or the centers thereof.
4. The security and/or valuable document according to claim 3 second alternative, wherein the spheres are core-mantle particles, which are arranged in a close-packing of spheres and wherein optionally the mean diameter of the spheres is in the range from 270 to 5,000 nm, in particular from 270 to 2,500 nm, if the luminescent substance emits in the IR range (780 to 3,000 nm)or wherein the mean diameter of the spheres is in the range from 135 to 1,200 nm, in particular from 135 to 600 nm, if the luminescent substance emits in the visible range (380 to 780 nm) or wherein the mean diameter of the spheres is in the range from 35 to 600 nm, in particular from 35 to 300 nm, if the luminescent substance emits in the UV range (100 to 380 nm).
5. The security and/or valuable document according to claim 4, wherein the core-mantle particles comprise a core of an organic or inorganic core material and a mantle of a polymeric organic mantle material, the mantle material being flowable at an increased temperature, however the core material not being flowable at the increased temperature.
6. The security and/or valuable document according to claim 5, wherein the organic core material is selected from the group comprising "aliphatic, aliphatic/aromatic or fully aromatic polyesters, polyamides, polycarbonates, polyurea, polyurethanes, aminoplast resins, phenoplast resins, such as for instance formaldehyde condensates of melamine, urea or phenol, epoxide resins, acrylesters, such as methyl (meth)acrylate, butyl (meth)acrylate, isopropyl (meth)acrylate, polystyrene, PVC, polyacrylnitrile, random or block copolymerisates of one or several such homopolymers, and mixtures of two or more such different homopolymers or copolymers" or wherein the inorganic core material is selected from the group comprising "metals, semimetals, metal chalcogenides, in particular metal oxides, metal pnictides, in particular metal nitrides or metal phosphides, and mixtures of two or more such different substances, wherein the metal can be formed of an element of the first three main groups of the periodic table or of a metallic element of the side groups and wherein the semimetal may comprise Si, Ge, As, Sb, and Bi", is in particular selected from the group comprising "SiO₂, TiO₂, ZrO₂, SnO₂ and Al₂O₃".
7. The security and/or valuable document according to claim 5 or 6, wherein the core material has a glass temperature in the range of more than 60 °C, preferably more than 80 °C, most preferably more than 90 °C, or wherein the core material has a glass temperature of more than 300 °C, and/or
   wherein the mantle material is selected from the group comprising "aliphatic, aliphatic/aromatic or fully aromatic polyesters, polyamides, polycarbonates, polyurea, polyurethanes, aminoplast resins, phenoplast resins, as for instance formaldehyde condensates of melamine, urea or phenol, epoxide resins, polyepoxides, poly(meth)acrylate, such as polymethyl (meth)acrylate, polybutyl (meth)acrylate, polyisopropyl (meth)acrylate, polystyrene, PVC, polyacrylnitrile, polyethylene, polypropylene, polyethylene oxide, polybutadiene, polytetrafluorethylene, polyoxymethylene, caoutchouc, polyisoprene, random or block copolymerisates of one or several such homopolymers, and mixtures of two or more such different homopolymers or copolymers", and wherein the mantle material has a glass temperature in the range from 40 to 90 °C, in particular from 60 to 80 °C, or in the range from 80 to 250 °C.
8. The security and/or valuable document according to one of claims 1 to 7, wherein the luminescent substance is arranged in the photonic crystal.
9. The security and/or valuable document according to claim 8, wherein the luminescent substance is arranged in the particles of the photonic crystal, in particular in the core material and/or in the mantle material of the core-mantle particles and/or wherein the luminescent substance is arranged between the particles of the photonic crystal.
10. The security and/or valuable document according to one of claims 1 to 9, wherein the photonic crystal is underlaid with the luminescent substance.
11. A method for producing a security and/or valuable document or a security element according to one of claims 1 to 10, wherein the substrate is provided on a surface or partial surface with a coating comprising the particles of the photonic crystal to be formed, and this coating is condensed under simultaneous exposure to heat and pressure, wherein optionally before coating with the particles of the photonic crystal, a luminescent layer comprising the luminescent substance being applied to the substrate, and/or the particles of the photonic crystal comprising the luminescent substance or being mixed therewith.
12. The method according to claim 11, wherein the exposure to heat takes place with a temperature in the range from 60 to 180°C, in particular from 70 to 130 °C, and for a time from 0.5 to 7,200 s, preferably from 0.5 to 3,600 s, most preferably from 1 to 10 s and/or wherein the condensation is performed with a pressure from 1 to 100 bars, preferably from 1 to 20 bars and/or wherein the condensation is achieved by means of a press, in particular a lamination press and/or wherein on the coating with particles of the photonic crystal, a separation and/or protection layer is arranged and/or wherein the protection layer is welded during the exposure to heat and pressure to the substrate, if applicable to the luminescent layer, and to the layer with particles of the photonic crystal or is laminated so to form a layer system, wherein the protection layer is optionally transparent, referred to the emission wavelength lambda.
13. A security and/or valuable document or security element obtainable with a method according to one of claims 11 to 12.
14. The security and/or valuable document according to one of claims 1 to 10 or 13 in the embodiment as an identity card, passport, ID card, access allowance card, visa, control symbol, ticket, driver license, vehicle document, banknote, cheque, postage stamp, credit card, chip card or adhesive label.
15. A method for verifying a security and/or valuable document or a security element according to one of claims 1 to 10 or 13 to 14, wherein the luminescent substance is excited for emission of a luminescence radiation, wherein the intensity of the luminescence radiation being observed or determined in dependence on the angle with respect to the surface of the security and/or valuable document, and wherein the observed or determined angular dependency of the luminescence radiation is compared to a given angular dependency.

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