News Column

Patent Issued for Optically Variable Elements Comprising an Electrically Active Layer

May 7, 2014



By a News Reporter-Staff News Editor at Electronics Newsweekly -- A patent by the inventors Peters, John Anthony (Au, CH); Tompkin, Wayne Robert (Baden, CH); Schilling, Andreas (Hagendorn, CH), filed on December 5, 2005, was published online on April 22, 2014, according to news reporting originating from Alexandria, Virginia, by VerticalNews correspondents.

Patent number 8702005 is assigned to OVD Kinegram AG (Zug, CH).

The following quote was obtained by the news editors from the background information supplied by the inventors: "OVDs are used as security elements for example for banknotes, security documents or labels for goods. As their optical effect is based for example on light refraction or light diffraction at optical microstructures they cannot be counterfeited with colour copying processes.

"Optically variable security elements have been proposed, which afford different optical effects in a plurality of layers:

"WO 01/03945 A1 describes a security element having a transparent substrate, on one side of which there is applied a thin film which produces a perceptible colour shift in dependence on the viewing angle of the person viewing it. A diffraction pattern is applied on the opposite side of the transparent substrate to further enhance the copy protection. That diffraction pattern acts as a diffraction grating so that for example the illusion of a three-dimensional image can be created for the person viewing it by means of that two-dimensional pattern. That provides that the optical effects produced by the thin film layer and the optical effects produced by the diffractive pattern are superposed at any location of the optically variable security element and thus that affords overall an optical effect which is composed of those two effects.

"WO 02/00445 A1 proposes measures for decoupling the optical effects produced in a plurality of layers of an optically variable security element, from each other. For that purpose, one possibility proposed is that of applying an opaque layer between a relief structure which produces a holographic image by means of diffraction and a thin film which produces a colour change. A further option proposed is that of arranging, in place of the opaque intermediate layer, one or more highly refractive layers and an adhesive layer. Those layers increase reflection and thus the strength of light in the region of the relief structure producing the holographic image and the holographic image is thus evident in relation to the colour shift effect of the thin film.

"It is further known to use elements for radio frequency identification (RFID) as anti-theft means and for goods identification. RFID is based on wireless radio frequency communication between a transponder which is allocated to an object or a person, and a reading device. The transponder usually includes an antenna connected to a semiconductor chip. The communication between the transponder and the reading device usually involves a communication of an identification code from the transponder to the reading device.

"For example U.S. Pat. No. 4,220,956 describes a manufacturing method for an RF antenna for an RFID transponder, in which the antenna is produced by etching a conductive layer of a thickness of

In addition to the background information obtained for this patent, VerticalNews journalists also obtained the inventors' summary information for this patent: "Now the object of the invention is to provide security elements having optically variable devices which are particularly forgery-proof.

"The object of the invention is attained with a security element having at least one optically variable device, wherein at least one layer of the optically variable device is in the form of an electrically active layer of an electronic component and/or an electronic circuit.

"Optically variable devices present an optical effect which changes in dependence on the viewing direction and/or kind of illumination and/or illumination direction. Such effects can be generated for example by special surface reliefs (diffraction gratings, holograms), and/or by a special arrangement of thin layers (interference layer systems).

"In that fashion the optically variable device and the electronic component and/or the electronic circuit form an inseparable unit. Manipulation at the optically variable device or the electronic component changes both component parts and leads to destruction of one or both component parts.

"By way of example RFID transponders can be provided with information memories which can be written by laser ablation. In that process components of the memory matrix, which are not required, are destroyed by the laser action. Such a memory matrix can be in the form of a film body with organic components such as organic field effect transistors. Now, when using the solution according to the invention, any manipulation at the memory matrix leads to a change in the optical properties of the manipulated electrically active layer of the memory matrix and becomes visible in that fashion.

"Electronic components can be integrated into the optically variable device with the solution according to the invention in such a way that separate, that is to say subsequent application of the optically variable device to the electronic component is difficult by virtue of the production-engineering tolerance. The electronic components must be incorporated into the optical action and therefore must be positioned with tolerances in the .mu.m range in relation to the optically variable device. That is only possible at reasonable complication and expenditure, in a common production process.

"Further advantageous configurations of the invention are set forth in the appendant claims.

"The kinds of electronic components whose electrically active layers can be in the form of an optically variable device are diverse and varied.

"It can be provided that the electrically active layer is in the form of the RF antenna of an RFID transponder. Such an antenna structure can also be optically evaluated in that fashion. An RF antenna of a spiral configuration can in that way form a graphic representation or be part of such a representation. Furthermore, by virtue of the microstructuring of the electrically active layer, such an RF antenna can have better electrical properties than a conventional RF antenna which is in the form of a thin layer with a flat surface.

"The electrically active layer can be in the form of the electrically active layer of an inductor and/or a capacitor. Particularly if the electrically active layer is in the form of the electrically active layer of an electrical oscillator circuit, that is to say an interconnection of inductor and capacitor, the microstructuring, provided in accordance with the invention, of the surface of the electrically active layer can significantly influence the resonance frequency of the electrical oscillator circuit formed in that way. It is then no longer possible to determine the resonance frequency of the oscillator circuit only from the macro-geometrical dimensions of the electrically active layer or layers. Such a specific property of the oscillator circuit can further enhance the forgery-proof nature.

"It can be provided that the electrically active layer is in the form of an electrode of an electronic component, in particular an optical display element. This can involve an optical display element which is activated by an RFID transponder. Upon activation the optical display element can produce an additional optical effect which is superposed on the optical effect produced by its electrode or electrodes in the form of the optically variable device. The optical display element can be for example an organic light emitting diode which is shaped in the form of a pattern or a number. That pattern or number, together with the optically variable background pattern produced by the electrode now forms a particular optical effect. It can however also be provided that organic light emitting diodes in point form are arranged in a pixel raster, as is known for example from flat screens. It is possible in that way to produce graphic representations with a high level of resolution. Furthermore it is possible for the optical display element to have electrochromic elements which present different colours in dependence on the applied electrical voltage. It is also possible for the optical display element to have a plurality of differently coloured or black-white and differently charged particles arranged movably between two electrode layers. Applying a voltage across the electrode layers makes it possible to alter the concentration of the one or other particles in the proximity of the one or other electrode layer so that the optical impression of the display element changes in dependence on the magnitude and/or polarity of the applied voltage. The state which is set in that way is unchanged substantially until a fresh voltage is applied. It can also be provided that the optical display element is individualised, for example in the form of a serial number, an image or a name. That can be effected for example by microstructuring of the surface of the electrode layer during the production procedure, for example by micro-demetallisation or micro-metallisation of a metallic electrode layer.

"The electrically active layer can also be in the form of an electrical connecting element. It is therefore also possible for the line layout of circuit arrangements or switching circuits to be in the form of an optically variable device. Thus for example large-area conductor tracks connected to the earth potential of the circuit arrangement or the switching circuit can be incorporated into the optical configuration. Further regions without an electrical function can be arranged between the electrical functional elements in order to improve the optical impression.

"The electrically active layer can be in the form of a metallic layer. Metallic layers can be applied by printing in the form of structured layers, for example in the form of printing on both sides on a polymer layer to produce an organic optical display element. They can however also be applied over a surface area, for example by sputtering, and then structured by a removal process. The microstructuring of the surface of the metallic layer can then be applied for example by a profiled roller. It can however also be provided that the layer arranged under the metallic layer is profiled and the metallic layer is applied thereto. The metallic layer can be opaque, semi-transparent or transparent in dependence on the layer thickness.

"As described hereinbefore the electrically active layer can also be in the form of a micro-demetallised layer which in that way can allow a view on to layers arranged therebeneath.

"The electrically active layer can also be in the form of a non-metallic layer, for example made of indium-tin oxide. A layer of indium-tin oxide can be provided if the electrically active layer is to be transparent.

"It can also be provided that the electrically conducting layer is in the form of an organic layer. That can be particularly advantageous for producing organic electronic components as are organic field effect transistors from which for example organic circuits are formed.

"It can further be provided that the electrically active layer is covered by at least one cover layer. Such a layer can be a protective layer for example to protect organic electronic components from environmental influences. It can also be provided however that the cover layer is in the form of a transparent diffractive structure. Such a cover layer can produce an optical effect which is superposed on the optical effect caused by the electrically active layer which is in the form of the optically variable device. This however can also involve mutually supplemental effects for example to cause the generation of partial images which when viewed jointly cause an image change which simulates a motion.

"The cover layer can also be in the form of a macrostructure, for example in the form of a microlens array and/or a microprism array. Such a cover layer can cause additional optical effects. Such macrostructures are here in particular structures whose lateral dimensions are in the 100 .mu.m range or less. A microlens array, in particular a microlens array formed from convergent lenses, can focus ambient light on to the optical display element. In that way the optical action of display elements can be improved on the basis of the principle of electrochromic elements, these also including OLEDs (organic light emitter diodes), or elements provided with mobile colour particles. It can however also be provided that the microlens array acts by superpositioning with a second microlens array like a macroscopic convergent lens, that is to say it reproduces the pixels under the microlens array on an enlarged scale. It can further be provided that a second microlens array can be disposed over the first microlens array, for example by folding a security document equipped with such security elements. In that way it is possible to form lens assemblies which are known from telescopes or microscopes. Thus for example combining divergent lenses and convergent lenses formed from microlens arrays makes it possible to produce a so-called Galileo telescope, as is known from opera glasses.

"By way of example the light issuing from optical display elements can be distributed in a specifically targeted fashion with microprism arrays. The emitted light can for example be deflected in such a way that it is clearly perceived even with inclined viewing angles.

"It can also be provided that the layer referred to hereinbefore as the cover layer is arranged under the optical display element. Such a cover layer can be for example in the form of a sinusoidal or sine-like linear or cross grating with numbers of lines in the region of about 200-2000 lines/mm. If the optical display element is in the form of an LED the light issuing at the underside of the optical display element can thus be reflected. It is also possible to provide a reflecting Fresnel lens for that purpose.

"The solution according to the invention includes the optically variable device being in the form of an electrically active layer only in a partial region thereof. If the optically variable device covers over for example an optical display element, only the part of the optically variable display which is arranged over the display element is in the form of an electrically active layer. The electrically active layers can also involve electrodes of other electronic components and/or inductors and/or capacitors and/or conductor tracks."

URL and more information on this patent, see: Peters, John Anthony; Tompkin, Wayne Robert; Schilling, Andreas. Optically Variable Elements Comprising an Electrically Active Layer. U.S. Patent Number 8702005, filed December 5, 2005, and published online on April 22, 2014. Patent URL: http://patft.uspto.gov/netacgi/nph-Parser?Sect1=PTO2&Sect2=HITOFF&p=120&u=%2Fnetahtml%2FPTO%2Fsearch-bool.html&r=5953&f=G&l=50&co1=AND&d=PTXT&s1=20140422.PD.&OS=ISD/20140422&RS=ISD/20140422

Keywords for this news article include: OVD Kinegram AG, Electronic Components.

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Source: Electronics Newsweekly