Method for forgery-proof labeling of items, and forgery-proof label

p0001The invention relates to a method for counterfeit-proof marking of objects, such as check cards, banknotes, packaging and the like. It also relates to a counterfeit-proof marking.

p0002According to the state of the art, it is known to provide holograms for proofing the authenticity of check cards or bank notes. Further, magnetic codes are applied to magnetic strips or fluorescent markers for detecting the authenticity of an object. The known markings can be relatively easily falsified.

p0003From the <patcit id="pcit0001" dnum="US5611998A"><text>US 5,611,998</text></patcit> An optochemical sensor is known. A chemically reactive layer is applied to a metal layer which changes its volume upon contact with a solution containing a substance to be detected. A layer formed from metallic clusters is applied to the chemically reactive layer. By bonding the substance to be detected, the distance between the layer formed by the metal clusters and the metal layer changes. At the same time, the absorption of light emitted onto the sensor also changes. The presence of the substance to be detected causes color change of the sensor. The known sensor is not suitable for tamper-proof marking of objects. Color change occurs only when the sensor is subjected to a liquid phase. On contact with moisture or liquids, a reaction can also occur which triggers or changes a color signal.

p0004The object of the invention is to provide a method for marking objects as well as a marking, which offer a high counterfeiting security in a simple and cost-effective manner.

p0005This object is achieved by the features of claims 1 and 6. Suitable embodiments are obtained from the features of claims 2 to 5 and 7 to 8.

p0006According to the invention, there is provided a method for counterfeit-proof marking of items, such as check cards, banknotes and the like, according to claim 1.

p0007With the above-mentioned features, a tamper-proof, permanently visible marking can be produced in a simple and cost-effective manner.

p0008The second layer is applied in a structured manner in the process. The structuring is a structure in the area in the manner of a pattern or a drawing. However, this is also a relief-like structure. In this case the marking appears in different colors.

p0009An inert fourth layer permeable to electromagnetic waves is applied to the third layer. The fourth layer primarily serves to protect the covered layers.

p0010The substrate may be made of a material which is permeable to electromagnetic waves, preferably glass or plastic.

p0011First molecules which are affine to the second layer or to second molecules provided thereon are expediently applied to the third or fourth layer. Polymers, silanes or structurally related compounds can be used as molecules. For example, it is also conceivable to use complementary polynucleotide sequences, such as DNA, as molecules. The function of the first and second molecules is essentially to adhere the substrate to the marking at a fixedly predetermined distance.

p0012The metallic clusters can be produced, for example, from silver, gold, platinum, aluminum, copper, tin or indium. The second layer is made of one of the following materials: polymer, in particular polycarbonate (PC), polyethylene (PE), polypropylene (PP), polyurethane (PU), polyimide (PI), polystyrene (PS) or polymethacrylate (PMA). These materials are chemically substantially inert. They are moisture-insensitive. The function of the second layer is essentially to provide a predetermined distance to the third layer and a predetermined structure permanently.

p0013According to a further embodiment it is provided that with a distance between the first and the third layer of less than 2 μm, a coloring which forms the marking becomes visible. The coloring depends on the angle of observation and is characteristic. For this purpose, the first layer can be irradiated by means of a device for generating electromagnetic waves, preferably by means of a LASER, fluorescent lamp, light-emitting diode or xenon lamp. The marking can be identified with means for determining the optical properties of the electromagnetic waves reflected by the first layer. The absorption, preferably at different observation angles, can be measured with the device for determining the optical properties. Such a determination of the optical properties enables a high degree of counterfeiting security.

p0014According to a further embodiment, it is provided that the layers are at least partly produced by thin-film technology. Vacuum coating technologies and the like are particularly suitable.

p0015According to a further embodiment feature, it is provided that at least one of the layers is produced from a material with anisotropic refractive index. Preferably, the second layer is made of a material having anisotropic refractive index. The material can, for example, be liquid-crystal polymers which exhibit a characteristic coloration at different angles of observation, ie angles opposite the z-axis, as well as at different angles of rotation, ie angles in the xy-plane.

p0016According to a further embodiment, at least one of the layers can be produced from a material whose optical properties can be selectively altered after the application of the layer. The material can be, for example, a photosensitic polymer whose refractive index can be varied by irradiation with a suitable wavelength.

p0017Because of the further design features of the counterfeit-proof marking, reference is made to the preceding explanations on the method.

p0018BRIEF DESCRIPTION OF THE DRAWINGS Exemplary embodiments of the invention are explained in more detail below with reference to the drawings. Show it:<ul><li><figref idrefs="f0001">FIG</figref>   A schematic cross-sectional view of a first permanently visible marking which is not the subject of the invention,</li><li><figref idrefs="f0001">FIG</figref>   A schematic cross-sectional view of a second permanently visible marking, which is not the subject of the invention,</li><li><figref idrefs="f0002">FIG</figref>   A schematic cross-sectional view of a non-permanently visible first marking and a substrate suitable for visualization which is not the subject of the invention,</li><li><figref idrefs="f0002">FIG</figref>   A schematic cross-sectional view of a non-permanently visible second marking and a substrate suitable for visualization, which is not the subject of the invention,</li><li><figref idrefs="f0003">FIG</figref>. Absorption spectra of a marking according to<figref idrefs="f0001">FIG</figref> Under different observation angles and</li><li><figref idrefs="f0003">FIG</figref>   A quantitative evaluation of the spectra according to <figref idrefs="f0003">FIG</figref> At different wavelengths.</li></ul>

p0019In the embodiment shown in FIGS <figref idrefs="f0001 f0002">FIGS. 1 to 4</figref> A first layer, which reflects electromagnetic waves, is designated by 1. This may be a metal foil, for example an aluminum foil. However, the first layer 1 can also be a layer formed from clusters which is applied to a carrier 2. The carrier 2 can be the object to be marked. The clusters are conveniently made of gold.

p0020A chemically inert second layer 3 is applied to the first layer 1. The second layer 3 has a structure. The structure is designed in the form of a relief which is designed, for example, in the manner of a bar code. The thickness of the second layer is preferably between 20 and 1000 nm. It is applied by means of thin-film technology. Vacuum coating processes are suitable for this purpose, for example.

p0021In the embodiment shown in FIGS <figref idrefs="f0001">FIGS. 1 and 2</figref> A third layer 4 made of metallic clusters is applied to the second layer 3. The third layer 4, in turn, is superposed by a fourth layer 5. The fourth layer 5 protects the underlying layers from damage. The fourth layer 5 may be made of a chemically inert and optically transparent material, eg a metal oxide, nitrite, carbide or polymer.

p0022The <figref idrefs="f0002">3 and 4</figref> Are only visible when they are brought into contact with a substrate 6, on the surface of which the third layer 4 formed from metallic clusters is applied. The third layer 4 may be superposed with a fifth layer 7 formed from first molecules. The fifth layer 7 is expediently formed from molecules which are affine to the material from which the second layer 3 is made. A contact of the fifth layer 7 with the second layer 3 thus results in a specific adhesion. It may also be that the second layer 3 is covered with a further fifth layer 7. In this case, the fifth layers 7 are each formed of molecules having an affinity with each other. They may be biopolymers which are complementary to one another. However, the fifth layer 7 can also be produced from other polymers, silanes and / or structurally related compounds.

p0023The substrate 6 is made of a transparent material such as glass or plastic.

p0024The function of the marking is as follows:

p0025When the light from a light source, such as a LASER, a fluorescent tube or a xenon lamp, is irradiated to a light source, <figref idrefs="f0001">FIGS. 1 and 2</figref> This light is reflected on the first layer 1. By interaction of the reflected light with the third layer 4 formed from the metallic clusters, a part of the irradiated light is absorbed. The reflected light has a characteristic spectrum. The marking appears colored. The coloring, which is dependent on the angle of irradiation or observation, serves as a proof-proof for the authenticity of the marking.

p0026In the case of the <figref idrefs="f0002">3 and 4</figref> , Only the optically transparent second layer 3 is applied to the electromagnetic-reflecting first layer 1. The marking is initially not visible.

p0027When the optically transparent substrate 6 provided with the third layer 4 is applied, there may be an interaction between the light reflected on the first layer 1 and the third layer. Again, a color effect is produced, which can be observed by the substrate 6, preferably made of glass.

p0028In order to ensure that the predetermined distance between the first 1 and the third layer 4 required for producing the color effect is established, the third layer 4 can be covered with a fifth layer 7. Upon contact of the fifth layer 7 with the second layer 3, the substrate 6 adheres to the marking. A predetermined distance is established between the third layer 4 and the first layer 1.

p0029With regard to the parameters to be observed for the generation of the interactions, <patcit id="pcit0002" dnum="US5611998A"><text>US 5,611,998</text></patcit>, the <patcit id="pcit0003" dnum="WO9848275A"><text>WO 98/48275</text></patcit> as well as the <patcit id="pcit0004" dnum="WO9947702A"><text>WO 99/47702</text></patcit> Respectively.

p0030In the <figref idrefs="f0003">FIG</figref> Shown in FIG <figref idrefs="f0001">FIG</figref> Were measured by means of a UV / VIS spectrometer Lambda 25 from Perkin Elmer using a reflection insert. Out<figref idrefs="f0003">FIG</figref> It can be seen that the longer-wave peak shifts towards shorter wavelengths with increasing observation angle. Furthermore, a fixed peak is observed which is due to the silver clusters.

p0031In <figref idrefs="f0003">FIG</figref> Is a quantitative evaluation of the spectra according to <figref idrefs="f0003">FIG</figref> Respectively, at two different wavelengths. For the wavelengths considered, a changed absorption is observed as a function of the observation angle. The absorption pattern is characteristic of the fastness of the marking.

Reference list

p0032<dl id="dl0001" compact="compact"><dt>1</dt><dd>first layer</dd><dt>2</dt><dd>carrier</dd><dt>3</dt><dd>second layer</dd><dt>4</dt><dd>third layer</dd><dt>5</dt><dd>fourth layer </dd><dt>6</dt><dd>substrate</dd><dt>7</dt><dd>fifth layer</dd></dl>