EP1558449B1 - Method for producing tamper-proof identification elements - Google Patents

Description

The invention relates to a method for producing tamper-proof identification features, which have a color shift effect, caused by metallic clusters, which are separated by a defined transparent layer of a mirror layer.

Out WO 02/18155 a method for the counterfeit-proof marking of objects is known, wherein the article is applied with a mark consisting of an electromagnetic wave reflecting first layer on an electromagnetic wave transmissive inert layer having a defined thickness, whereupon said inert layer formed of metallic clusters third layer follows, is provided.
WO 01/53113 describes optically variable security elements which have an angle-dependent color shift effect, wherein the structure consists essentially of a reflector layer, a dielectric layer and an absorber layer.
WO 02/051646 A ) describes a decorative film which is constructed as a layer composite and has a transparent base film, a transparent cover layer and a transparent dielectric transparent layer arranged therebetween. Between the dielectric layer and the cover layer at least partially a metal layer is arranged.

The object of the invention is to provide a method for producing forgery-proof identification features on flexible materials, wherein the security against counterfeiting is given by a visible color change at different viewing angles (tilting effect), which should also be machine-readable. In the machine-read spectrum, the manufacturing process should be clearly coded.

The invention therefore provides a method for producing tamper-resistant identification features consisting of at least each an electromagnetic wave reflecting layer (2), an optically transparent spacer layer (3) and a layer formed by metallic clusters (4).

The other essential features of the invention are defined in the independent claims 1 to 3.

Suitable carrier substrates are preferably flexible plastic films, for example of PI, PP, MOPP, PE, PPS, PEEK, PEK, PEI, PSU, PAEK, LCP, PEN, PBT, PET, PA, PC, COC, POM, ABS, PVC , The carrier films preferably have a thickness of 5 to 700 .mu.m, preferably 8 to 200 .mu.m, more preferably 12 to 50 .mu.m.
Furthermore, metal foils, for example Al, Cu, Sn, Ni, Fe or stainless steel foils having a thickness of 5-200 μm, preferably 10 to 80 μm, particularly preferably 20-50 μm, may also serve as the carrier substrate. The films can also be surface-treated, coated or laminated, for example with plastics, or painted.
Furthermore, as carrier substrates, pulp-free or cellulose-containing paper, heat-activatable paper or composites with paper, for example composites with plastics having a basis weight of 20-500 g / m ² , preferably 40-200 g / m ² , may be used.

An electromagnetic wave reflecting layer is applied to the carrier substrate. This layer may preferably be made of metals such as aluminum, gold, chromium, silver, copper, tin, platinum, nickel and their alloys, for example nickel / chromium, copper / aluminum and the like exist.

The electromagnetic wave reflecting layer may be applied all over or partially by known methods such as spraying, vapor deposition, sputtering, printing (gravure, flexographic, screen, digital printing), painting, roller coating and the like.

For partial application, a method using a soluble paint for producing the partial metallization is particularly suitable. In this case, in a first step, a solvent-soluble paint application is applied to the carrier substrate, in a second step this layer optionally treated by means of an in-line plasma, corona or flame process and in a third step, a layer of the metal to be structured or In a fourth step, the paint application by means of a solvent, optionally combined with a mechanical action, is removed.
The soluble application of paint can be carried out over the entire surface or partially, the application of the metal or the metal alloy takes place over the entire surface or partially.

The application of the paint can be done by any method, for example by gravure printing, flexographic printing, screen printing, digital printing and the like. The paint or varnish used is soluble in a solvent, preferably water, but it is also possible to use a paint which is soluble in any solvent, for example in alcohol, esters and the like. The paint or lacquer may be conventional compositions based on natural or artificial macromolecules. The soluble color may be pigmented or unpigmented. As pigments, all known pigments can be used. Particularly suitable are TiO ₂ , ZnS, kaolin and the like.

Subsequently, the printed carrier substrate is optionally treated by means of an in-line plasma (low pressure or atmospheric plasma), corona or flame process. High-energy plasma, for example Ar or Ar / O ₂ plasma, cleans the surface of toning residues of the printing inks.

At the same time, the surface is activated. In this case, terminal polar groups are generated on the surface. This improves the adhesion of metals and the like to the surface.

Optionally, simultaneously with the application of the plasma or corona or flame treatment or subsequently, a thin metal or metal oxide layer can be applied as adhesion promoter, for example by sputtering or vapor deposition. Particularly suitable are Cr, Al, Ag, Ti, Cu, TiO ₂ , Si oxides or chromium oxides. This adhesion promoter layer generally has a thickness of 0.1 nm-5 nm, preferably 0.2 nm-2 nm, particularly preferably 0.2 nm to 1 nm.

As a result, the adhesion of the partially or completely applied electromagnetic waves reflecting metal or metal alloy layer is further improved.

However, a partial electromagnetic wave reflecting layer can also be produced by a conventionally known etching method.

The thickness of the electromagnetic wave reflecting layer is preferably about 10 - 50 nm, but also higher or lower layer thicknesses are possible.
If metal foils are used as the carrier substrate, the carrier substrate itself may already form the electromagnetic wave reflecting layer. The reflection of this layer for electromagnetic waves, in particular as a function of the thickness of the layer or the metal foil used, is preferably 10 -100%.

The following polymeric layer or layers can also be applied over the entire surface or partially.
The polymeric layers consist for example of paint or paint systems based on nitrocellulose, epoxy, polyester, rosin, acrylate, alkyd, melamine, PVA, PVC, isocyanate or urethane systems.

This polymeric layer essentially serves as a transparent spacer layer but, depending on the composition, may be absorbent in a particular spectral range. Optionally, this absorbing property can also be enhanced by the addition of a suitable chromophore. By choosing different chromophores, a suitable spectral range can be selected. As a result, in addition to the tilting effect, the polymeric layer can additionally be made machine-readable. Thus, for example, in the blue spectral range (in the range of about 400 nm) a yellow AZO dye, for example anilides; Rodural, Eosin, are used. The dye also changes the spectrum of the label in a characteristic manner.

Depending on the quality of the adhesion on the carrier web or on an optionally underlying layer, this polymeric layer may show wetting effects, which leads to a characteristic macroscopic lateral structuring.
This structuring can be modified, for example, by modification of the surface energy of the layers, for example by plasma treatment, corona treatment, electron beam, ion beam treatment or by laser modification.
Furthermore, it is possible to apply a primer layer with regions of different surface energy.

The polymeric layer has a defined thickness, preferably 10 nm to 3 μm, more preferably 100-1000 nm. If a plurality of polymeric layers are applied, they can each have different thicknesses.

The polymeric layer is applied by brushing, painting, casting, spraying, printing (screen, gravure, or digital printing) or roller coating.

The polymeric layer is applied in a process that allows the application of very homogeneous layer thicknesses over large areas. A homogeneous layer thickness is therefore necessary to ensure a uniform color appearance in the finished product. The tolerances are not more than ± 5%, preferably ≤ ± 2%.

Particularly suitable is a printing process, wherein the color or paint is applied from a temperature-controlled paint pan via a plunger cylinder and a transfer roller on the printing cylinder, wherein only the wells of the printing cylinder are filled with the paint or the paint substantially. By means of a squeegee excess paint or varnish is stripped off and optionally further dried by means of a blow bar.

On the polymeric layer is then applied a layer formed of metallic clusters. The metallic clusters may consist, for example, of aluminum, gold, palladium, platinum, chromium, silver, copper, nickel and the like or their alloys, such as, for example, Au / Pd or Cr / Ni.
This cluster layer is deposited by sputtering (for example ion beam or magnetron) or evaporation (electron beam) from a solution or by adsorption.

In the production of the cluster layer in vacuum processes, the growth of the clusters and thus their shape and the optical properties can advantageously be influenced by adjusting the surface energy or the roughness of the underlying layer. This characteristically changes the spectra. This can be done for example by thermal treatment in the coating process or by preheating the substrate.
Thus, for example, the shape and thus also the optical properties of the clusters can be influenced by adjusting the surface energy or the condensation coefficient of the metal on the underlying layer.
These parameters can be achieved, for example, by treatment of the surface with oxidizing liquids, for example with Na hypochlorite or in a PVD or CVD process.

The cluster layer is preferably applied by sputtering. The properties of the layer, in particular the density and the structure, are set above all by the power density, the amount of gas used and its composition, the temperature of the substrate and the web speed.

When applied from the solution by wet-chemical methods, the clusters are prepared in solution in a first step, then the clusters are derivatized, concentrated and applied directly to the polymeric surface.

For application by means of printing technology, after concentrating the clusters, small amounts of an inert polymer, for example PVA, polymethyl methacrylate, nitrocellulose, polyester or urethane systems are admixed. The mixture can then be subsequently a printing process, such as screen, flexo or preferably gravure printing methods are applied to the polymeric layer.

The thickness of the cluster layer is preferably 2 to 20 nm, particularly preferably 3 to 10 nm.

In addition, a protective layer can be applied by means of vacuum technology or printing technology.

In a preferred embodiment, the polymer layer is specifically structured by modifying the surface energy.
Due to the color effect, the structures then appear very rich in contrast due to the subsequently applied cluster layer, making them easily recognizable to the eye. Therefore, such structuring creates an additional tamper-proof feature.

Furthermore, this structuring can be transformed by fingerprint algorithms into one-to-one codes, which are then machine-readable.
As a result, a structuring can be assigned to a defined numerical value, whereby markings having the same manufacturing parameters, ie having the same color effect, can be individualized.

For use in particular as a security feature, the individual layer combinations can also be applied to separate substrates.
Thus, for example, the electromagnetic wave reflecting layer and the polymeric spacer layer may be applied to a first substrate, which may for example be applied to a value document or incorporated into this value document. The cluster layer can then be applied to a further substrate, which is optionally provided with an adhesive layer. By joining the two coated substrates then appears according to the key / lock principle, the characteristic color effect.

The carrier substrate may also already have one or more functional and / or decorative layers.
As such color or lacquer layers, a wide variety of compositions can be used in each case. The composition of the individual layers may in particular vary according to their purpose, depending on whether the individual layers serve exclusively decorative purposes or should be a functional layer or whether the layer should be both a decorative and a functional layer.

The layers to be printed may be pigmented or unpigmented. As pigments, it is possible to use all known pigments, for example titanium dioxide, zinc sulfide, kaolin, ATO, FTO, ITO, aluminum, chromium oxides and silicon oxides, as well as colored pigments. In this case, solvent-based coating systems and systems without solvents can be used.
Suitable binders are various natural or synthetic binders.

The functional layers may for example have certain electrical, magnetic, special chemical, physical and also optical properties.

To adjust electrical properties, such as conductivity, for example, graphite, carbon black, conductive organic or inorganic polymers. Metal pigments (for example, copper, aluminum, silver, gold, iron, chromium lead and the like), metal alloys such as copper-zinc or copper-aluminum or their sulfides or oxides, or amorphous or crystalline ceramic pigments such as ITO and the like may be added. Furthermore, doped or non-doped semiconductors such as, for example, silicon, germanium or ion conductors such as amorphous or crystalline metal oxides or metal sulfides can also be used as an additive. Further, to adjust the electrical properties of the layer polar or partially polar Compounds such as surfactants or non-polar compounds such as silicone additives or hygroscopic or non-hygroscopic salts are used or added.

To adjust the magnetic properties, paramagnetic, diamagnetic and also ferromagnetic substances, such as iron, nickel and cobalt or their compounds or salts (for example oxides or sulfides) can be used.

The optical properties of the layer can be visualized by visible dyes or pigments, luminescent dyes or pigments which fluoresce or phosphoresce in the visible, in the UV range or in the IR range, effect pigments, such as liquid crystals, pearlescent, bronzes and / or heat-sensitive Influence colors or pigments. These can be used in all possible combinations. In addition, phosphorescent pigments can also be used alone or in combination with other dyes and / or pigments.

Various properties can also be combined by adding various additives mentioned above. Thus, it is possible to use colored and / or conductive magnetic pigments. All mentioned conductive additives can be used.
Especially for the dyeing of magnetic pigments it is possible to use all known soluble and non-soluble dyes or pigments. Thus, for example, a brown magnetic ink can be adjusted to metallic, for example silvery, by adding metals in their color shade.

Furthermore, for example, insulator layers can be applied. As insulators, for example, organic substances and their derivatives and compounds, such as paint and coating systems, such as epoxy, polyester, rosin, acrylate, alkyd, melamine, PVA, PVC, isocyanate, Urethane systems that can be radiation-curing, for example, by heat or UV radiation suitable.

These layers can be applied by known methods such as sputtering, sputtering, printing (e.g., gravure, flexo, screen, digital printing, and the like), spraying, electroplating, roller coating, and the like. The thickness of the functional layer is 0.001 to 50 μm, preferably 0.1 to 20 μm.

By repeating one or more described process steps one or more times, multilayer structures can be produced which have different properties in the layers applied one above the other. By combining different properties of the individual layers, for example layers having different conductivity, magnetizability, optical properties, absorption behavior and the like, it is possible to produce structures for security elements with several precise authenticity features, for example.

The layers can be present on the substrate over the entire surface or partially already, or can be applied.

In this case, the process steps can be repeated as often as desired, wherein, for example, in full-surface application of a functional layer of the paint can be omitted if necessary.

However, it is also possible to apply, for example, in known direct metallization processes or in metallization processes with etching, partial metal layers or, in known multicolor printing processes, further layers.

Optionally, the coated film produced in this way can also be protected by a protective lacquer layer or further refined, for example, by laminating or the like.

Optionally, the product can be applied with a sealable adhesive, such as a hot or cold seal adhesive to the appropriate substrate, or embedded in paper for security papers by conventional methods, for example.

These sealants can be equipped with visible or visible in UV light, fluorescent, phosphorescent or laser and IR radiation absorbing features to increase the security against counterfeiting. These features may also be present in the form of patterns or characters or show color effects, in principle any number of colors, preferably 1 to 10 colors or color mixtures, are possible.

The carrier substrate may be removed after application or remain on the product in one-sided coating. In this case, the carrier film may optionally be specially equipped on the uncoated side, for example, scratch-resistant, antistatic and the like. The same applies to a possible lacquer layer on the carrier substrate.

Furthermore, the layer structure can be set in a transferable or non-transferable manner, if appropriate with a transfer lacquer layer, which may optionally have a diffraction structure, for example a hologram structure.

The structure according to the invention can also be applied inversely to the carrier material, with a layer formed of metallic clusters, which are produced by means of a vacuum-technical method, on a carrier substrate is prepared from solvent-based systems and then one or more partial and / or full-surface polymeric layers of defined thickness are applied and then a partial or full-surface electromagnetic wave reflecting layer is applied to the spacer layer.

• Fig. 1 zeigt eine schematische Querschnittsansicht einer ersten ständig sichtbaren Markierung auf einem Trägersubstrat,
• Fig. 2 eine schematische Querschnittsansicht einer nicht ständig sichtbaren ersten Markierung auf einem Trägersubstrat sowie einem zum Nachweis bzw.
• zur Sichtbarmachung geeigneten zweiten Trägersubstrat,
• Fig. 3 eine schematische Querschnittsansicht einer ständig sichtbaren ersten laminier- oder klebbaren Markierung,
• Fig. 4 eine schematische Querschnittsansicht einer weiteren ständig sichtbaren zweiten laminier- oder klebbaren Markierung.
• Fig. 5 eine schematische Querschnittsansicht einer nicht ständig sichtbaren ersten laminier oder klebbaren Markierung sowie einem zum Nachweis bzw.
• zur Sichtbarmachung geeigneten zweiten Trägersubstrat.
• Fig. 6 ein im large-scale kontinuierlich beschichtetes fälschungssicher markiertes Trägersubstrat, welches teilweise auf Rollen aufgewickelt ist

In the Fig. 1 - 6 Examples of security features according to the invention are shown.
Therein 1 denotes the carrier substrate, 2 the first layer reflecting the electromagnetic waves, 3 the transparent layer, 4 the layer composed of metallic clusters, 5 an optically transparent substrate, 6 an adhesive or laminating layer.

• Fig. 1 shows a schematic cross-sectional view of a first permanently visible mark on a carrier substrate,
• Fig. 2 a schematic cross-sectional view of a not always visible first mark on a carrier substrate and a proof or
• for visualization suitable second carrier substrate,
• Fig. 3 a schematic cross-sectional view of a permanently visible first laminating or adhesive marker,
• Fig. 4 a schematic cross-sectional view of another constantly visible second laminating or adhesive marker.
• Fig. 5 a schematic cross-sectional view of a not permanently visible first laminating or adhesive label and a proof or
• for visualization suitable second carrier substrate.
• Fig. 6 a counterfeit-proof marked carrier substrate in a large-scale, which is partly wound up on rolls

In the in the Fig. 1 to 5 shown marks is an electromagnetic wave reflecting first layer with (2). It may be a thin layer of eg aluminum. However, the first layer (2) can also be a layer formed of metallic clusters, which is based on a carrier (1) is applied. The carrier (1) can be the carrier substrate to be marked. The inert spacer layer is designated by (3). The metallic clusters (4) are expediently made, for example, from copper.
In the Fig. 3 to 5 is provided for further processing of the counterfeit-proof marked carrier substrate adhesive or lamination with (6). The change in the reflected light which produces the characteristic color spectrum in comparison with the incident light is visualized in an arrow in these two figures by means of the gray scale profile.

In the in the Fig. 1 and 3 shown marks on the second layer (3) a made of metallic clusters third layer (4) is applied. The second layer (3) is applied to a mirror layer (2). Furthermore, in Fig. 1 and 3 the mirror layer is applied to a carrier substrate (1).

In the Fig. 4 On a carrier substrate (1), the third layer (4) formed of metallic clusters is applied first, then the second layer (3), then the mirror layer (2) and finally the adhesive or lamination layer (6).

At the in Fig. 2 and 5 shown marks is only the optically transparent formed second layer (3) on the electromagnetically reflecting first layer (2) and this applied to a carrier substrate (1). The marking is initially not visible. The markings are only visible when they are brought into contact with a substrate (5) on the surface of which the third layer (4) formed of metallic clusters is applied. This in turn produces a color effect that can be observed through the substrate (5). The carrier substrate (5) is expediently made of a transparent material, for example of plastic such as polyethylene terephthalate polycarbonate, polyurethane, polyethylene, polypropylene, polyacrylate, polyvinyl chloride, polyepoxide.

• Bei einer Einstrahlung von Licht aus einer Lichtquelle, wie einer Glühbirne, einem Laser, einer Leuchtstoffröhre, einer Halogenlampe, im speziellen einer Xenonlampe, auf eine der in Fig. 1, 3 und 4 gezeigten Markierungen wird dieses Licht an der ersten Schicht (2) reflektiert. Durch eine Wechselwirkung des reflektierten Lichts mit der aus der metallischen Clustern gebildeten dritten Schicht (4) wird ein Teil des eingestrahlten Lichts absorbiert. Das reflektierte Licht weist ein von mehreren Parametern, wie z.B. den optischen Konstanten des Schichtaufbaus, abhängiges, charakteristisches Spektrum auf. Die Markierung erscheint farbig. Die Färbung dient als fälschungssicherer Nachweis für die Echtheit der Markierung. Der so erhaltene Farbeindruck ist winkelabhängig und kann sowohl mit dem bloßen Auge als auch mit einem im Reflexionsmodus arbeitenden Lesegerät, vorzugsweise ein Spektralphotometer, identifiziert werden. Ein solches Photometer kann beispielsweise die Färbung der Oberflächen aus zwei verschiedenen Winkeln erfassen. Dies geschieht entweder mittels eines Detektors dadurch, dass zwei Lichtquellen verwendet werden, welche entsprechend angeschaltet werden und der Detektor entsprechend verkippt wird, oder dadurch dass zwei Photometer die aus zwei verschiedenen Winkeln beleuchtete Probe aus den beiden entsprechenden Winkeln vermessen.

The function of the marker is as follows:

• Upon irradiation of light from a light source, such as a light bulb, a laser, a fluorescent tube, a halogen lamp, in particular a xenon lamp, on one of the in Fig. 1 . 3 and 4 shown, this light is reflected on the first layer (2). By an interaction of the reflected light with the third layer (4) formed from the metallic clusters, part of the incident light is absorbed. The reflected light has one of several parameters, such as the optical constants of the layer structure, dependent, characteristic spectrum. The marking appears colored. The staining serves as a forgery proof for the authenticity of the mark. The color impression thus obtained is dependent on the angle and can be identified both with the naked eye and with a reader operating in reflection mode, preferably a spectrophotometer. For example, such a photometer can detect the coloration of surfaces from two different angles. This is done either by means of a detector in that two light sources are used, which are turned on accordingly and the detector is tilted accordingly, or in that two photometers measure the illuminated from two different angles sample from the two corresponding angles.

With regard to the parameters to be respected for the generation of the interactions, reference is made to US 5,611,998 , the WO 98/48275 as well as the WO 99/47702 and WO 02/18155 directed.

The coated support materials produced according to the invention can be used as security features in data carriers, value documents, labels, labels, seals, in packaging, textiles and the like.

Examples: Example 1: Production of the Cluster Layer by Wet-Chemical Process: a) Synthesis of 14 nm gold clusters

100 ml of distilled water are boiled in a 250 ml flask. With vigorous stirring, first 4 ml of 1% trisodium citrate in distilled water and then 1 ml of 1% TetraChloroGoldsäure in distilled water. Within 5 minutes, the color of the reaction mixture changes from almost colorless to dark purple to cherry red. Thereafter, the heat is suppressed and the approach stirred for about 10 min on. The analysis of the resulting sol with the transmission electron microscope shows spherical particles of a mean diameter of 14 nm. The size distribution of the clusters is narrow (cv <20%). The wavelength maximum of the optical absorption is 518 nm.

b) Derivatization of Gold Clusters:

To 100 ml of gold sol according to the above synthesis, 1 ml of a 1% solution of BSA (bovine serum albumin) in distilled water is added with vigorous stirring. The solution turns slightly from cherry red to a darker red. The maximum of optical absorption is retained. The absorption in the wavelength range of 550 nm and higher increases. In the transmission electron microscope, defined distances between the particles can be recognized.

c) Attachment of the gold clusters on a nitrocellulose surface:

The sol (almost pH neutral, hardly any salt) is rebuffered by adding 5 ml of 1 M sodium carbonate solution (pH 9.6). Only sufficiently protected clusters remain in solution and do not precipitate. The sol can be concentrated by centrifugation or binds directly after application to the nitrocellulose coated surface. With a suitable choice of Nitrocellulose layer thickness develop after drying of the excess water strong surface dyeings.

Example 2: Production of the cluster layer by means of printing technology

The sol, after concentration, is added by a factor of 10 small amounts (e.g., 5%) of a neutral polymer (e.g., PVA). This makes it possible to print with conventional gravure cylinders. The colloids are dry randomly oriented with the polymer in a very thin layer. There are observed as in Example 1c) characteristic colors.

Example 3: Production of the cluster layer by means of a vacuum technique

Under high vacuum conditions (base pressure p <1x10 ^-3 mbar), a Cu layer with a thickness of 4 nm is sputtered onto a web-shaped carrier substrate, which is already provided with a mirror layer and a nitrocellulose layer as a transparent spacer layer.

The sputtering is carried out by means of a magnetron plasma source with a power of 20 W / cm ² at 25 ° C using Ar with a partial pressure of 5 x 10 ^-3 mbar as a process gas. The speed of the web is 0.5m / s. Under these conditions, the Cu layer shows pronounced island growth. The islands with a mean diameter of a few nm correspond to the clusters in the wet-chemical process.
Significantly different characteristic color spectra are observed.

Claims (11)

1. Method for producing tamper-proof identification elements each comprising at least one layer (2) reflecting electromagnetic waves, an optically transparent spacer layer (3) and a layer formed from metallic clusters (4), a layer (2) reflecting electromagnetic waves being applied to part or all of the surface of a carrier substrate (1), the optically transparent inert spacer layer (3) is applied to part or all of the surface of this layer reflecting electromagnetic waves, and a layer formed from metallic clusters (4) is applied to this optically transparent spacer layer, characterized in that the layer of metallic clusters (4) is applied by means of vacuum technology by sputtering or vapour deposition or from solvent-based systems by means of a wet chemical or printing method, and the optically transparent spacer layer (3) is formed from at least one polymer layer of defined thickness, which is applied by painting on, varnishing, casting, spraying, printing, for example screen-printing, gravure-printing, flexographic-printing or digital printing methods, or a roll application method, a homogenous layer thickness with a tolerance of ±5% being achieved.
2. Method for producing tamper-proof identification elements each comprising at least one layer (2) reflecting electromagnetic waves, an optically transparent inert spacer layer (3) and a layer formed from metallic clusters (4), a layer formed from metallic clusters (4) being applied to a carrier substrate (1), the optically transparent inert spacer layer (3) being applied to part or all of the surface of this layer formed of metallic clusters, and the layer (2) reflecting electromagnetic waves being applied to part or all of the surface of this optically transparent inert spacer layer (3), characterized in that the layer of metallic clusters (4) is applied by means of vacuum technology by sputtering or vapour deposition or from solvent-based systems by means of a wet chemical or printing method, and the optically transparent spacer layer (3) is formed from at least one polymer layer of defined thickness, which is applied by painting on, varnishing, casting, spraying, printing, for example screen-printing, gravure-printing, flexographic-printing or digital printing methods, or a roll application method, a homogenous layer thickness with a tolerance of ±5% being achieved.
3. Method for producing tamper-proof identification elements each comprising at least one layer (2) reflecting electromagnetic waves, an optically transparent inert spacer layer (3) and a layer formed from metallic clusters (4), a layer (2) reflecting electromagnetic waves being applied to a first carrier substrate (1), an optically transparent inert spacer layer (3) being applied to this layer (2) reflecting electromagnetic waves, and a layer formed from metallic clusters being applied to a second transparent carrier substrate (5), characterized in that only by joining the two carrier substrates coated in this way in such a way that the layer formed from metallic clusters (4) is joined to the spacer layer (3) is the tamper-proof identification element produced and can be detected, and the layer of metallic clusters (4) is applied by means of vacuum technology by sputtering or vapour deposition or from solvent-based systems by means of a wet chemical or printing method, and the optically transparent spacer layer (3) is formed from at least one polymer layer of defined thickness, which is applied by painting on, varnishing, casting, spraying, printing, for example screen-printing, gravure-printing, flexographic-printing or digital printing methods, or a roll application method, a homogenous layer thickness with a tolerance of ±5% being achieved.
4. Method according to one of Claims 1 to 3, characterized in that a protective layer is applied to the layer formed from metallic clusters (4).
5. Method according to one of Claims 1 to 4, characterized in that the layer (2) reflecting electromagnetic waves or the layer formed from metallic clusters (4), to which the optically transparent inert spacer layer (3) consisting of at least one polymer layer of defined thickness is applied, is modified by means of treatment with oxidizing liquids or by means of a PVD or CVD process.
6. Method according to one of Claims 1 to 5, characterized in that the optically transparent inert spacer layer (3) consisting of at least one polymer layer of defined thickness is structured by means of de-wetting effects.
7. Method according to Claim 6, characterized in that the de-wetting structures of the structured optically transparent spacer layer (3) consisting of at least one polymer layer of defined thickness are transformed into one-to-one codes by means of fingerprint algorithms.
8. Method according to either of Claims 6 and 7, characterized in that the optically transparent spacer layer (3) consisting of at least one polymer layer of defined thickness is modified by means of treatment with sodium hypochlorite, by means of a PVD or CVD process.
9. Method according to one of Claims 1 to 8, characterized in that the optically transparent polymer spacer layer (3) consisting of at least one polymer layer of defined thickness contains a chromophore.
10. Method according to one of Claims 1 to 9, characterized in that further functional and/or decorative layers are applied to the carrier substrate or substrates (1, 5).
11. Method according to one of Claims 1 to 10, characterized in that the carrier substrate or substrates is/are provided with a heat-sealing lacquer (6).

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