EP1558449A1

EP1558449A1 - Method for producing tamper-proof identification elements

Info

Publication number: EP1558449A1
Application number: EP03784094A
Authority: EP
Inventors: Friedrich Kastner; Martin Bergsmann; Harald Walter; Georg Bauer; Ralph Domnick
Original assignee: Hueck Folien GmbH; November AG
Current assignee: Hueck Folien GmbH
Priority date: 2002-08-06
Filing date: 2003-07-28
Publication date: 2005-08-03
Anticipated expiration: 2023-07-28
Also published as: AU2003253348A8; ATA11912002A; AU2003253348A1; ES2564043T3; CA2494961A1; CA2494961C; RU2005106243A; US8067056B2; US20060147640A1; EP1558449B1; RU2297918C2; WO2004014663A1; HUE027104T2; AT413360B

Abstract

The invention relates to a method for producing tamper-proof identification elements, and to tamper-proof identification elements produced according to said method and consisting respectively of at least one layer (2) reflecting electromagnetic waves (3), a spacer layer, and a layer consisting of metallic clusters (4). According to said method, a partial or all-over layer reflecting electromagnetic waves is applied to a carrier substrate (1), followed by at least one partial and/or all-over polymer layer having a defined thickness (3), and a layer consisting of metallic clusters which is produced by means of a method using vacuum technology or from systems based on solvents is then applied to said spacer layer(s).

Description

Method for producing counterfeit-proof identification features

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

From WO 02/18155 a method for counterfeit-proof marking of objects is known, the object having a marking consisting of an electromagnetic wave reflecting first layer being applied to an inert layer which is permeable to electromagnetic waves and having a defined thickness, followed by this inert layer a third layer formed from metallic clusters follows.

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

The invention therefore relates to a method for producing counterfeit-proof identification features, each consisting of at least one layer reflecting electromagnetic waves, a spacer layer and a layer formed by metallic clusters, with a partial or full-surface layer reflecting electromagnetic waves and then one or more partial layers on a carrier substrate and / or full-area polymer layers of a defined thickness are applied, whereupon a layer formed from metallic clusters, which is produced by means of a vacuum technology process or from solvent-based systems, is applied to the spacer layer. Flexible plastic films, for example made of PI, PP, MOPP, PE, PPS, PEEK, PEK, PEI, PSU, PAEK, LCP, PEN, PBT, PET, PA, PC, COC, POM, ABS, PVC, are preferably suitable as the carrier substrate , The carrier films preferably have a thickness of 5 to 700 μm, preferably 8 to 200 μm, particularly preferably 12 to 50 μm.

Furthermore, metal foils, for example Al, Cu, Sn, Ni, Fe or stainless steel foils with a thickness of 5-200 μm, preferably 10 to 80 μm, particularly preferably 20-50 μm, can also serve as the carrier substrate. The films can also be surface-treated, coated or laminated, for example with plastics, or painted.

Further, as carrier substrates also cellulose-free or cellulose-containing paper, heat-activatable paper or composites with paper, for example, composites with plastics with a grammage 20-500 g / m ^2, preferably 40-200 g / m ^2. be used.

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

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

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

The color application can be carried out by any method, for example 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 alcohol, esters and the like. The paint or varnish can be conventional compositions based on natural or artificial macromolecules. The soluble color can be pigmented or unpigmented. All known pigments can be used as pigments. TiO ₂ , ZnS, kaolin and the like are particularly suitable.

The printed carrier substrate is then optionally treated using an inline 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 in the printing inks.

At the same time, the surface is activated. Terminal polar groups are created on the surface. This improves the adhesion of metals and the like to the surface.

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

This further improves the adhesion of the metal or metal alloy layer which is partially or fully applied and reflects electromagnetic waves.

A partial layer reflecting electromagnetic waves can also be produced by a customary known etching process.

The thickness of the layer reflecting electromagnetic waves is preferably approximately 10-50 nm, although higher or lower layer thicknesses are also possible.

If metal foils are used as the carrier substrate, the carrier substrate itself can already form the layer reflecting electromagnetic waves.

The reflection of this layer for electromagnetic waves is preferably 10-100%, in particular depending on the thickness of the layer or the metal foil used.

The subsequent polymer layer or the polymer layers can likewise be applied over the entire surface or partially.

The polymeric layers consist, for example, of dyeing or coating 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 can be absorbent in a certain spectral range, depending on the composition. If necessary, this absorbing property can also be enhanced by adding a suitable chromophore become. A suitable spectral range can be selected by selecting different chromophores. As a result, in addition to the tilting effect, the polymer layer can also be made machine-readable. For example, in the blue spectral range (in the range of approximately 400 nm), a yellow AZO dye, for example anilides; Rodural, eosin. The dye also changes the spectrum of the marking in a characteristic manner.

This polymeric layer can, depending on the quality of the adhesion on the carrier web or a layer which may be underneath

Dewetting effects show what leads to a characteristic, macroscopic lateral structuring.

This structuring can be done, for example, by modifying the

Surface energy of the layers, for example by plasma treatment,

Corona treatment, electron, ion beam treatment or by

Change laser modification in a targeted manner.

Furthermore, it is possible to apply an adhesion promoter layer with different surface energies in some areas.

The polymer layer has a defined thickness, preferably 10 nm to 3 μm, particularly preferably 100-1000 nm. If several polymer layers are applied, they can each have different thicknesses.

The polymeric layer can be applied by any coating method, such as, for example, by brushing, painting, pouring, spraying, printing (screen printing, gravure printing, flexographic printing or digital printing method) or roller application method.

The polymer layer is preferably applied in a process which permits the application of very homogeneous layer thicknesses over large areas. A homogeneous layer thickness is therefore required in order in the finished product to ensure an even appearance of color. The tolerances are preferably not more than + 5%, preferably <± 2%.

A printing process is particularly suitable, the paint or varnish being applied from a temperature-controlled varnish pan to the printing cylinder via an immersion cylinder and a transfer roller, essentially only the depressions of the printing cylinder being filled with the paint or varnish. Excess paint or varnish is stripped off using a doctor blade and, if necessary, further dried using a blow molding.

A layer formed from metallic clusters is then applied to the polymer layer. The metallic clusters can consist, for example, of aluminum, gold, palladium, platinum, chromium, silver, copper, nickel and the like or their alloys, such as Au / Pd or Cr / Ni.

This cluster layer can be applied by sputtering (for example ion beam or magnetron) or evaporation (electron beam) from a solution or by adsorption.

When the cluster layer is produced 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 layer below. This changes the spectra in a characteristic way. This can be done, for example, by thermal treatment in the coating process or by preheating the substrate.

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 layer below. These parameters can take place, for example, by treating the surface with oxidizing liquids, for example with Na hypochlorite or in a PVD or CVD process.

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

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

For application by means of printing technology, small amounts of an inert polymer, for example PVA, polymethyl methacrylate, nitrocellulose, polyester or urethane systems, are mixed in after the clusters have been concentrated. The mixture can then subsequently be applied to the polymeric layer by means of a printing process, for example screen, flexographic or preferably gravure printing.

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

In addition, a protective layer can be applied using vacuum technology or printing technology methods.

In a preferred embodiment, the polymer layer is deliberately structured by modifying the surface energy. The structures then appear very high-contrast due to the color effect due to the subsequently applied cluster layer, which makes them easily recognizable to the eye. Therefore, such a structuring creates an additional forgery-proof feature.

Furthermore, this structuring can be converted into unique codes using fingerprint algorithms, which can then be read out by machine. This allows structuring to be assigned a defined numerical value, whereby markings with the same manufacturing parameters, i.e. with the same color effect, can be customized.

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

The carrier substrate can also already have one or more functional and / or decorative layers.

A wide variety of compositions can be used as such coloring or lacquer layers. The composition of the individual layers can vary, in particular, depending on their task, depending on whether the individual layers are used exclusively for decorative purposes or are to be a functional layer or whether the layer is to be both a decorative layer and a functional layer. The layers to be printed can be pigmented or unpigmented. All known pigments, such as titanium dioxide, zinc sulfide, kaolin, ATO, FTO, ITO, aluminum, chromium and silicon oxides as well as colored pigments can be used as pigments. Solvent-based coating systems as well as systems without solvents can be used. Various natural or synthetic binders can be used as binders.

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

For setting electrical properties, for example conductivity, it is possible, for example, to use 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 also amorphous or crystalline ceramic pigments such as ITO and the like can be added. Furthermore, doped or undoped semiconductors such as silicon, germanium or ion conductors such as amorphous or crystalline metal oxides or metal sulfides can also be used as additives. Furthermore, polar or partially polar compounds such as surfactants or non-polar compounds such as silicone additives or hygroscopic or non-hygroscopic salts can be used or added to adjust the electrical properties of the layer.

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 to adjust the magnetic properties. The optical properties of the layer can be determined by visible dyes or pigments, luminescent dyes or pigments that 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 Affect 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.

Different properties can also be combined by adding different additives mentioned above. It is possible to use colored and / or conductive magnetic pigments. All of the conductive additives mentioned can be used.

All known soluble and non-soluble dyes or pigments can be used especially for coloring magnetic pigments. For example, a brown magnetic paint can be metallic in color by adding metals, e.g. silvery.

Insulator layers can also be applied, for example. Organic substances and their derivatives and compounds, for example dyeing and lacquer systems, e.g. Epoxy, polyester, rosin, acrylate, alkyd, melamine, PVA, PVC, isocyanate, urethane systems, which can be radiation-curing, for example by heat or UV radiation, are suitable.

These layers can be applied by known methods, for example by vapor deposition, sputtering, printing (for example gravure, flexographic, screen, digital printing and the like), spraying, electroplating, roller application methods 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 method 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 with 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 already be present or applied to the substrate over the entire surface or partially.

The process steps can be repeated any number of times, for example, if a functional layer is applied over the entire surface, the application of paint can possibly be omitted.

But it can also be known, for example

Direct metallization processes or in metalization processes with etching partial metal layers or in known multicolor printing processes further layers are applied.

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

If desired, the product may be applied with a sealable adhesive, for example a hot or cold-seal adhesive on the corresponding carrier material or, for example in papermaking for security papers by conventional ^"method in the paper embedded. These sealing adhesives can be equipped with visible or UV-visible, fluorescent, phosphorescent or laser and IR radiation absorbing features to increase the security against forgery. These features can 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.

In the case of one-sided coating, the carrier substrate can be removed after use or can remain on the product. The carrier film can optionally be specially equipped on the non-coated side, for example scratch-resistant, antistatic and the like. The same applies to any paint layer on the carrier substrate.

Furthermore, the layer structure can be set to be transferable or non-transferable, optionally provided with a transfer lacquer layer, which can 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, a layer formed from metallic clusters on a carrier substrate, which is produced by means of a vacuum technology process or from solvent-based systems and subsequently one or more partial and / or full-area polymer layers of defined thickness are applied and then a partial or full-surface layer reflecting electromagnetic waves is applied to the spacer layer.

1-6 show examples of security features according to the invention.

Therein 1 means the carrier substrate, 2 the first layer reflecting the electromagnetic waves, 3 the transparent layer, 4 the metallic layer Clustered layer, 5 an optically transparent substrate, 6 an adhesive or laminating layer.

1 shows a schematic cross-sectional view of a first permanently visible marking on a carrier substrate,

2 shows a schematic cross-sectional view of a first marking, which is not always visible, on a carrier substrate and a second carrier substrate suitable for detection or visualization,

3 shows a schematic cross-sectional view of a permanently visible first laminatable or adhesive mark,

Fig. 4 is a schematic cross-sectional view of a further permanently visible second laminatable or adhesive mark.

5 shows a schematic cross-sectional view of a non-permanently visible first laminatable or adhesive mark and a second carrier substrate suitable for detection or visualization.

Fig. 6 is a large-scale anti-counterfeit marked carrier substrate, which is partially wound on rolls

In the case of the markings shown in FIGS. 1 to 5, a first layer reflecting electromagnetic waves is denoted by (2). It can be a thin layer of e.g. Trade aluminum. However, the first layer (2) can also be a layer formed from metallic clusters, which is applied to a carrier (1). 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 e.g. made of copper.

3 to 5, the adhesive or laminating layer provided for further processing of the counterfeit-proof marked carrier substrate is identified by (6). The change in the reflected light compared to the incident light that produces the characteristic color spectrum is visualized in an arrow in these two figures by means of the grayscale curve. In the case of the markings shown in FIGS. 1 and 3, a third layer (4) made of metallic clusters is applied to the second layer (3). The second layer (3) is applied to a mirror layer (2). 1 and 3, the mirror layer is also applied to a carrier substrate (1).

4, the third layer (4) formed from metallic clusters, then the second layer (3), then the mirror layer (2) and finally the adhesive or laminating layer (6) are applied to a carrier substrate (1).

In the case of the markings shown in FIGS. 2 and 5, only the optically transparent second layer (3) is applied to the electromagnetically reflecting first layer (2) and this is 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 whose surface the third layer (4) formed from metallic clusters is applied. A color effect then arises which can be observed through the substrate (5). The carrier substrate (5) is expediently made of a transparent material, e.g. made of plastic such as polyethylene terephthalate, polycarbonate, polyurethane, polyethylene, polypropylene, polyacrylate, polyvinyl chloride, polyepoxide.

The function of the marking is as follows:

When light from a light source, such as a light bulb, a laser, a fluorescent tube, a halogen lamp, in particular a xenon lamp, is irradiated onto one of the markings shown in FIGS. 1, 3 and 4, this light is applied to the first layer (1) reflected. An interaction of the reflected light with the third layer (4) formed from the metallic clusters absorbs part of the incident light. The reflected light has a characteristic spectrum which is dependent on several parameters, such as the optical constants of the layer structure. The marking appears in color. The coloring serves as proof against forgery for the authenticity of the marking. The color impression obtained in this way is dependent on the angle and can be preferably both with the naked eye and with a reader operating in reflection mode

Spectrophotometer can be identified. Such a photometer can, for example, detect the color of the surfaces from two different angles. This is done either by means of a detector in that two light sources are used, which are switched on accordingly and the detector is tilted accordingly, or in that two photometers measure the sample illuminated from two different angles from the two corresponding angles.

With regard to the parameters to be observed for the generation of the interactions, reference is made to US Pat. No. 5,611,998, WO 98/48275 and WO 99/47702 and WO 02/18155, the disclosure content of which is hereby incorporated.

The coated carrier 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 using wet chemical methods: a) Synthesis of 14 nm gold clusters

100 ml of distilled water are heated to boiling in a 250 ml flask. With vigorous stirring, 4 ml of 1% triSodium citrate in distilled water and then 1 ml of 1% tetrachloro gold acid in distilled water are added. The color of the reaction mixture changes from almost colorless to dark purple to cherry red within 5 minutes. The supply of heat is then stopped and the batch is stirred for a further 10 minutes. Analysis of the resulting sol with a transmission electron microscope shows spherical particles with an average 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) Gold cluster derivatization:

1 ml of a 1% solution of BSA (Bovine Serum Albumin) in distilled water is added to 100 ml of gold sol according to the above synthesis with vigorous stirring. The solution changes color slightly from cherry red to a darker red. The maximum optical absorption is retained. The absorption in the wavelength range of 550 nm and higher increases. Defined distances between the particles can be seen in the transmission electron microscope.

c) Connection of the gold clusters to a surface made of nitrocellulose:

The sol (almost pH neutral, hardly any salt) is buffered by adding 5 ml of 1M 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 to the surface coated with nitrocellulose after application. With a suitable choice of After drying off the excess water, nitrocellulose layer thickness forms strong surface colorations.

Example 2:

Production of the cluster layer using printing technology

After concentration by a factor of 10, small amounts (e.g. 5%) of a neutral polymer (e.g. PVA) are added. This enables printing with conventional gravure cylinders. The colloids dry oriented randomly with the polymer in a very thin layer. As in Example 1c), characteristic colors are observed.

Example 3:

Production of the cluster layer by means of a vacuum

process

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

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

Claims

claims:

1) Method for producing counterfeit-proof identification features, each consisting of at least one layer reflecting electromagnetic waves, a spacer layer and a layer formed by metallic clusters, with a partial or full-surface layer reflecting electromagnetic waves and then one or more partial and / or full-surface areas on a carrier substrate polymer layers of a defined thickness are applied, whereupon a layer formed from metallic clusters, which is produced by means of a vacuum technology process or from solvent-based systems, is applied to the spacer layer.

2) Method for producing counterfeit-proof identification features each consisting of at least one layer reflecting electromagnetic waves, a spacer layer and a layer formed by metallic clusters, with a layer formed from metallic clusters on a carrier substrate, which layer is produced by means of a vacuum technology method or from solvent-based systems and then one or more partial and / or full-area polymer layers of defined thickness are applied, whereupon a partial or full-area layer reflecting electromagnetic waves is applied to the spacer layer.

3) Method according to one of claims 1 or 2, characterized in that an electromagnetic wave reflecting layer and then a polymeric spacer layer is applied to a first carrier substrate and a cluster layer is applied to a second carrier substrate, whereby only coated by connecting the two Carrier substrates the counterfeit-proof identification feature arises, or can be proven

4) Method according to one of claims 1 to 3, characterized in that a protective layer is applied to the cluster layer.

5) Method according to one of claims 1 to 4, characterized in that the layer to which the spacer layer is applied is modified by treatment with oxidizing liquids or by a PVD or CVD process.

6) Method according to one of claims 1 to 5, characterized in that the polymeric spacer layer is structured by dewetting effects.

7) Method according to claim 6, characterized in that the dewetting structures of the structured polymeric spacer layer are converted into unique codes by means of fingerprint algorithms.

8) Method according to one of claims 1 to 7, characterized in that the polymeric spacer layer is modified by treatment with Na hypochlorite, by a PVD or CVD process.

9) Method according to one of claims 1 to 8, characterized in that the polymeric spacer layer contains a chromophore.

10) Method according to one of claims 1 to 9, characterized in that the metallic cluster layer is deposited by sputtering or evaporation. 11) Method according to one of claims 1 to 10, characterized in that the metallic cluster layer is deposited by magnetron, electron beam or ion beam methods.

12) Method according to one of claims 1 to 11, characterized in that the metallic cluster layer is deposited by means of a wet chemical process or by means of a printing process.

13) Method according to one of claims 1 to 12, characterized in that further functional and / or decorative layers are present on the carrier substrate (s).

14) Method according to one of claims 1 to 13, characterized in that the carrier substrate or substrates are provided with a heat seal lacquer.

15) Security features produced by a method according to claims 1-14.

16) Use of the security features according to claim 15 in data carriers, value documents, packaging, labels, labels, seals and the like.