EP4420889A1 - Security element with electrically conductive layer - Google Patents

Abstract

The invention relates to a security element (1) for securities or security papers or security objects, such as banknotes, ID cards, credit cards, which security element (1) has an electrically conductive layer (2) with a machine-readable code. The invention also relates to a security or security paper. It is provided that the electrically conductive layer (2) is invisible when a visible side (3) of the security element (1) is viewed in incident light and/or transmitted light.

Description

The invention relates to a security element, in particular for securities, security paper or security objects, such as banknotes, identity cards, credit cards, which security element has an electrically conductive layer with a machine-readable coding.

Security elements of the above-mentioned type are usually used to increase the counterfeit security of securities or security papers, such as banknotes, ID cards, credit cards, debit cards, tickets, etc.

Various technologies are known to experts for reading machine-readable security features. WO2018141478A1 and the WO2018141477A1 each disclose a method for generating a time-dependent signal on a capacitive area sensor. Further technologies for detecting capacitive signals are described in the WO2018119525A1 and through the DE102012023082A1 became known.

The known security elements with an electrically conductive layer, which forms a machine-readable code, have the disadvantage that they can be recognized without any tools and can therefore be counterfeited relatively easily. In addition, the electrically conductive layers known in the state of the art offer little freedom in terms of design and layout. In particular, the known electrically conductive layers often interfere with other optical elements.

The object of the present invention is to create a security element with increased protection against counterfeiting.

This object is achieved according to the invention by a security element of the type mentioned at the outset in that the electrically conductive layer is invisible when a visible side of the security element is viewed in incident light and/or in transmitted light.

At this point, it should be noted that in the context of the invention, the term security element can refer to various types of security elements familiar to those skilled in the art. For example, security elements can be security threads, Security strips, security patches and the like. Of course, other types of security elements known to those skilled in the art are also conceivable.

In the context of the invention, the term "invisible" means that the electrically conductive layer is not or at least only with difficulty visible to an observer when looking at the security element or a security paper or security document made from it, or that an observer does not notice the presence of this electrically conductive layer with the naked eye, i.e. with the unaided eye, without technical aids, or only notices it upon very close inspection. "Invisible" also means that the electrically conductive layer does not or hardly stands out from the background or from adjacent areas.

The inventive design of a security element with an electrically conductive layer has the advantage that it is extremely forgery-proof. Even if a forger recognizes that the security element comprises a machine-readable code, it is still very difficult, if not almost impossible, to imitate or even copy it. In addition, the electrically conductive layer does not affect the optical appearance of the security element, so that it can be designed in an unlimited variety of ways using methods known from the state of the art. The electrically conductive layer can preferably be designed as a partial layer. It is also conceivable that the electrically conductive layer is a full-surface layer.

Furthermore, it may be expedient if the electrically conductive layer is transparent in a wavelength range visible to the human eye and is thus invisible to an observer in incident light and/or in transmitted light.

Materials for the production of transparent electrically conductive layers are known to the experts, for example, through the DE60024062T2 became known.

Particularly advantageous is a transparency expressed by a transmittance of 0 to 0.5, preferably from 0 to 0.3, particularly preferably from 0 to 0.1.

The transmittance is a measure of the transmitted intensity and is defined as the quotient between the intensity in front of an obstacle and the intensity behind this obstacle. The transmittance therefore takes values between 0 and 1. Expressed in percentage values the transmittance takes values between 1% and 100%. Expressed as a percentage, the above range from 0 to 0.5 corresponds to a range from 0% to 50%.

It is common practice in the industry, particularly in the production of polymer banknotes, to use the material parameters "haze" and "clarity" to describe transparency instead of a transmission level. Common standards for determining these material properties are ISO 13468 (determination of the total light transmittance of transparent materials), ISO 14782 (determination of the haze value of transparent materials) and ASTM D1003 (testing the haze and light transmittance of transparent plastics).

Furthermore, it can be provided that the electrically conductive layer is a printed layer.

In this case, application using a gravure printing process is particularly advantageous. In addition to printing processes, it would also be conceivable for the electrically conductive layer to be applied by painting, dip coating, spray coating or roller coating. It is also conceivable to apply the electrically conductive layer using vacuum-based coating processes, such as plasma coating or PVD and CVD coating.

Furthermore, it can be provided that the electrically conductive layer comprises a non-metallic conductive material.

Of course, it would also be conceivable and possibly advantageous if the electrically conductive layer comprises a metal layer or a layer containing metal particles.

A further development is advantageous in which the non-metallic conductive material contained in the electrically conductive layer comprises an electrically conductive polymer.

When it comes to electrically conductive polymers, a distinction is generally made between intrinsically and extrinsically conductive polymers. Intrinsically conductive polymers are plastics with an electrical conductivity that is comparable to metals. The conductivity of the polymer is achieved through conjugated double bonds, which allow charge carriers to move freely in the doped state. Polymers that are only conductive due to electrically conductive fillers such as aluminum flakes or carbon black are called extrinsically conductive polymers.

Electrically conductive polymers can be selected from a group comprising inorganic polymers, organometallic polymers, fully or partially aromatic polymers, homopolymers, copolymers, biopolymers, chemically modified polymers and/or synthetic polymers. Particularly preferred are polymers selected based on polyparaphenylene, polyparaphenylvinylene, polyacetylene, polypyrrole, polythiophene, polyaniline (PANI) and poly-3,4-ethylenedioxythiophene (PEDOT), each with the various known side chain modifications. PEDOT can preferably be included in a poly(styrenesulfonic acid) system (PSS system), i.e. form a PEDOT-PSS. Polymers can also be formed as nanowires.

According to a further development, it is possible that the non-metallic conductive material contained in the electrically conductive layer comprises an electrically conductive graphite-containing varnish.

Electrically conductive graphite-containing paints are also known as carbon-conductive paints. Such graphite-containing paints preferably contain electrically conductive particles, in particular soot or graphite particles, graphene, carbon nanowires or carbon nanotubes (CNT).

The electrically conductive layer can advantageously also be formed from combinations of the aforementioned metallic and non-metallic materials.

Furthermore, it may be expedient if an electrically non-conductive cover layer is arranged on a side of the electrically conductive layer facing the visible side of the security element.

The electrically non-conductive cover layer can be an optical effect layer or part of an optical effect layer. The cover layer can be applied directly to the electrically conductive layer or can be applied to the electrically conductive layer with one or more intermediate layers. The cover layer and every other layer described in this document can in principle also be formed from several layers or plies.

In this case, application by means of a gravure printing process is particularly advantageous. In addition to printing processes, it would also be conceivable for the top layer to be applied by painting, dip coating, spray coating or roller coating. Application of the A top layer can be applied using vacuum-based coating processes, such as plasma coating or PVD and CVD coating.

Furthermore, it can be provided that the cover layer is opaque or at least essentially opaque. Essentially opaque means that the cover layer is translucent.

The electrically conductive layer can be covered or hidden by the cover layer and thus be invisible or not visible or appear invisible to an observer in incident light and/or in transmitted light.

A combination of a transparent electrically conductive layer and an opaque cover layer is particularly advantageous for forming an electrically conductive layer that is invisible to the observer.

In particular, if the security element or a portion of the security element is intended to form a window in a security document or security paper, it can also be advantageous if no cover layer is provided, or if an equally transparent cover layer is provided. In this way, a transparent, machine-readable window can be created.

Also particularly advantageous is an opacity or impermeability to light expressed by a transmittance of 0.5 to 1, preferably 0.7 to 1, particularly preferably 0.8 to 1.

Furthermore, it can be provided that the cover layer completely or partially covers the electrically conductive layer.

Depending on the type and nature of the electrically conductive layer, it may be sufficient if the cover layer only covers a part or partial area of the electrically conductive layer. This is particularly the case if the electrically conductive layer is at least essentially transparent.

According to a particular embodiment, it is possible that the cover layer is a printed electrically non-conductive metal layer or a printed electrically non-conductive metal pigment layer.

The cover layer can comprise a metallic effect paint and/or a metallic effect varnish and/or a metallic effect ink and/or a metallic material, in particular selected from the group consisting of silver, copper, aluminium, gold, platinum, niobium, tin, or nickel, titanium, vanadium, chromium, cobalt and palladium or alloys of these materials, in particular cobalt-nickel alloys.

According to an advantageous development, it can be provided that the cover layer has a layer with a color-shift effect and contains a color-shifting thin-film element or color-shifting pigments, in particular interference pigments, or liquid crystal pigments.

The cover layer can have at least one layer that enhances the color shift effect on a side facing away from the visible side of the security element, wherein the layer that enhances the color shift effect is in particular a layer of dark color and/or a layer of metal oxides, such as substoichiometric aluminum oxide. For example, the layer that enhances the color shift effect can be applied to a liquid crystal layer or a layer of color-shifting pigments, so that the layer of color-shifting pigments or the liquid crystal layer is arranged between the layer that enhances the color shift effect and the carrier layer. However, the layer that enhances the color shift effect can also be arranged between the carrier layer and the layer of color-shifting pigments or the at least one liquid crystal layer. In addition, it is also possible for a carrier layer to be arranged between the layer that enhances the color shift effect and the layer of color-shifting pigments or the liquid crystal layer.

The cover layer can have at least one liquid crystal layer, in particular a cholesteric liquid crystal layer.

The cover layer can be formed as an optically non-linear layer or as an optically non-linear layer and/or as a layer containing fluorescent pigments and/or fluorescent substances.

Optically non-linear layers or layers or materials that form these layers are also referred to as IR upconverters or UV downconverters. These can be materials that exhibit a visible color under the influence of electromagnetic radiation outside the visible wavelength range of light. Such Materials can be stimulated to emit visible light under these conditions, for example when exposed to infrared (IR) (λ > 780 nm) and/or ultraviolet (UV) light (λ < 380 nm).

The cover layer can comprise structures or be formed with structures. In particular, the structures can comprise achromatic and/or reflective structures, such as micromirrors, and/or refractive structures, such as microlenses, and/or diffractive structures, such as holograms.

The structures can be introduced directly into a carrier layer or into a further layer, in particular an embossing lacquer layer, in particular embossed by means of a molding device.

The structure or structures can be embossed directly into a carrier layer. For example, by heating the carrier layer and embossing the structures using an embossing tool, such as an embossing roller.

Another alternative option would be to provide a separate additional layer to accommodate the structures. The additional layer can be applied directly to a carrier layer. For example, the additional layer can be formed from an embossing lacquer that is shaped to match the arrangement of the structures. This can in turn be done using a molding device or a molding element in an embossing process.

The arrangement or application of the cover layer or a cover layer designed as an optical effect layer or its layers onto the structures or the metal layers and/or metal effect layers can be carried out, for example, by a printing process and/or a vapor deposition process or several of these. However, the materials or additives of the reflection layer described below could also form a component or a layer of the optical effect layer. These can in particular be printed or vapor deposition and thus form a separate layer of the optical effect layer.

In particular, it can be advantageous if the cover layer is designed as a thin-film element and has at least one absorber layer and at least one spacer layer.

The at least one absorber layer may contain at least one metallic material, in particular selected from the group of nickel, titanium, vanadium, chromium, cobalt, palladium, iron, tungsten, molybdenum, niobium, aluminium, silver, copper and/or alloys of these materials, or be made from at least one of these materials.

Furthermore, it can be provided that the cover layer designed as a thin-film element further comprises at least one reflection layer and/or a second absorber layer, wherein the at least one spacer layer is arranged between the at least one first absorber layer and the at least one reflection layer and/or the at least one second absorber layer.

The reflection layer can be applied or arranged on structures and can in particular be printed and/or vapor-deposited on them. It is also possible to reverse this order in the optical effect layer so that the absorber layer is arranged on the structures and then the spacer layer and the reflection layer. The arrangement would therefore be in the order structures - absorber layer - spacer layer - reflection layer. Instead of the above-mentioned reflection layer, however, another absorber layer can also be provided.

The at least one reflection layer can comprise at least one metallic material, in particular selected from the group consisting of silver, copper, aluminum, gold, platinum, niobium, tin, or nickel, titanium, vanadium, chromium, cobalt and palladium or alloys of these materials, in particular cobalt-nickel alloys or at least one high-index dielectric material with a refractive index of greater than 1.65, in particular selected from the group consisting of zinc sulfide (ZnS), zinc oxide (ZnO), titanium dioxide (TiO ₂ ), carbon (C), indium oxide (In ₂ O ₃ ), indium tin oxide (ITO), tantalum pentoxide (Ta ₂ O ₅ ), cerium oxide (CeO ₂ ), yttrium oxide (Y ₂ O ₃ ), europium oxide (Eu ₂ O ₃ ), iron oxides such as iron(II,III) oxide (Fe ₃ O ₄ ) and iron(III) oxide (Fe ₂ O ₃ ), Hafnium nitride (HfN), hafnium carbide (HfC), hafnium oxide (HfO ₂ ), lanthanum oxide (La ₂ O ₃ ), magnesium oxide (MgO), neodymium oxide (Nd ₂ O ₃ ), praseodymium oxide (Pr ₆ O ₁₁ ), samarium oxide (Sm ₂ O ₃ ), antimony trioxide (Sb ₂ O ₃ ), silicon carbide (SiC), silicon nitride (Si ₃ N ₄ ), silicon monoxide (SiO), selenium trioxide (Se ₂ O ₃ ), tin oxide (SnO ₂ ), tungsten trioxide (WO ₃ ), high-index organic monomers and/or high-index organic polymers or be made from at least one of these materials.

The at least one spacer layer can be a low-refractive dielectric material with a refractive index less than or equal to 1.65, in particular selected from the group aluminum oxide (Al ₂ O ₃ ), metal fluorides, for example magnesium fluoride (MgF ₂ ), Aluminum fluoride (AlF ₃ ), cerium fluoride (CeF ₃ ), sodium aluminum fluorides (e.g. Na ₃ AlF ₆ or Na ₅ Al ₃ F ₁₄ ), silicon oxide (SIO _x ), silicon dioxide (SiO ₂ ), neodymium fluoride (NdF ₃ ), lanthanum fluoride (LaF ₃ ), samarium fluoride (SmF ₃ ), barium fluoride (BaF ₂ ), calcium fluoride (CaF ₂ ), lithium fluoride (LiF), low-refractive organic monomers and/or low-refractive organic polymers or at least one high-refractive dielectric material with a refractive index greater than 1.65, in particular selected from the group zinc sulfide (ZnS), zinc oxide (ZnO), titanium dioxide (TiO ₂ ), carbon (C), indium oxide (In ₂ O ₃ ), indium tin oxide (ITO), tantalum pentoxide (Ta ₂ O ₅ ), cerium oxide (CeO ₂ ), yttrium oxide (Y ₂ O ₃ ), europium oxide (Eu ₂ O ₃ ), iron oxides such as iron (II,III) oxide (Fe ₃ O ₄ ) and iron (III) oxide (Fe ₂ O ₃ ), hafnium nitride (HfN), hafnium carbide (HfC), hafnium oxide (HfO ₂ ), lanthanum oxide (La ₂ O ₃ ), magnesium oxide (MgO), neodymium oxide (Nd ₂ O ₃ ), praseodymium oxide (Pr ₆ O ₁₁ ), samarium oxide (Sm ₂ O ₃ ), antimony trioxide (Sb ₂ O ₃ ), silicon carbide (SiC), silicon nitride (Si ₃ N ₄ ), silicon monoxide (SiO), selenium trioxide (Se ₂ O ₃ ), tin oxide (SnO ₂ ), tungsten trioxide (WO ₃ ), high-refractive organic monomers and/or high-refractive organic polymers or be made from at least one of these materials.

Furthermore, it can be provided that the cover layer is a partial layer or comprises a partial layer, wherein the partial layer represents a portrait, a landscape, an abstract geometric symbol, logo or an alphanumeric symbol and/or an icon and/or a code and/or a sequence of symbols.

The security element can comprise a carrier layer made of a plastic, wherein in particular the plastic can be formed from a translucent and/or thermoplastic plastic. The carrier layer can preferably contain at least one of the materials from the group polyimide (PI), polypropylene (PP), monoaxially oriented polypropylene (MOPP), biaxially oriented polypropylene (BOPP), polyethylene (PE), polyphenylene sulfide (PPS), polyether ether ketone (PEEK), polyether ketone (PEK), polyethylene imide (PEI), polysulfone (PSU), polyarylether ketone (PAEK), polyethylene naphthalate (PEN), liquid crystalline polymers (LCP), polyester, polybutylene terephthalate (PBT), polyethylene terephthalate (PET), polyamide (PA), polycarbonate (PC), cycloolefin copolymers (COC), polyoxymethylene (POM), acrylonitrile butadiene styrene (ABS), polyvinyl chloride (PVC), ethylene tetrafluoroethylene (ETFE), polytetrafluoroethylene (PTFE), polyvinyl fluoride (PVF), polyvinylidene fluoride (PVDF), ethylene tetrafluoroethylene hexafluoropropylene fluoro terpolymer (EFEP), cellulose or lignin-based plastics, polyhydroxyalkanoates (PHA), thermoplastic starch (TPS), polylactic acid (PLA), Polycaprolactone (PCL), polybutylene succinate (PBS), and polybutylene adipate terephthalate (PBAT) and/or at least one recycled and/or biodegradable and/or marine degradable plastic and/or mixtures and/or copolymers of these materials or be made from at least one of these materials.

As is known per se, the security element can have additional layers, which additional layers include in particular protective varnishes, heat-sealing varnishes, adhesives, primers and/or films. Protective varnishes can protect the entire layer and/or layer structure from mechanical damage such as scratches, grooves or the like. A protective layer can be provided on one or both sides. Preferably, a flat design of the security element can also be achieved by means of a protective layer.

For a better understanding of the invention, it is explained in more detail with reference to the following figures.

Fig. 1

einen beispielhaften Schichtaufbau eines Sicherheitselements,

Fig. 2

einen weiteren beispielhaften Schichtaufbau eines Sicherheitselements,

Fig. 3

einen weiteren beispielhaften Schichtaufbau eines Sicherheitselements,

Fig. 4

einen weiteren beispielhaften Schichtaufbau eines Sicherheitselements,

Fig. 5

einen weiteren beispielhaften Schichtaufbau eines Sicherheitselements.

They show in a highly simplified, schematic representation:

Fig.1

an example layer structure of a security element,

Fig. 2

another example of a layer structure of a security element,

Fig.3

another example of a layer structure of a security element,

Fig.4

another example of a layer structure of a security element,

Fig.5

another example layer structure of a security element.

To begin with, it should be noted that in the different embodiments described, identical parts are provided with identical reference symbols or identical component designations, whereby the disclosures contained in the entire description can be transferred analogously to identical parts with identical reference symbols or identical component designations. The position information chosen in the description, such as top, bottom, side, etc., also refers to the figure directly described and shown, and these position information must be transferred analogously to the new position if the position changes.

As an introduction, it should also be mentioned that the layer structure and the arrangement of further layers depend on the type of attachment of the security element to a security object, since the side of the security element to be viewed after attachment is crucial. The visible side can therefore be viewed from above, as shown in the figures, but it is also possible to view the security element from a visible side from below, e.g. through a carrier.

At this point, it should also be noted that the phrase "a layer is applied to something" is to be understood as meaning that the layer can be applied directly, or that one or more intermediate layers can be located between the applied layer and that onto which the layer is applied. At this point, it should also be noted that one or more intermediate layers can be arranged between the layers described in this document. It is therefore not absolutely necessary for the layers described to contact one another. It should also be noted that the term layer in this document is to be understood as meaning that a layer can also be made up of several sub-layers.

In the present context, "covered", "covered" or "covered over" means that the electrically conductive layer can be arranged either above or below or in front of or behind any covering layer when viewed from one and the same side.

The Fig. 1 to Fig. 5 each show exemplary layer structures of security elements 1. Only their special features are described in more detail, whereby in order to avoid unnecessary repetition, reference is made in particular to the preceding parts of the description. It goes without saying and follows from the advantageous developments described at the beginning that the layer structures described below are only examples and in particular are in no way to be understood as preferred or even as final. In all figures, the electrically conductive layer 2 is shown in its preferred form as a partial layer. However, it would also be conceivable for this to be designed as a full-surface layer.

In the Fig.1 An exemplary layer structure of a security element 1 in the special design of a security thread is shown. The visible side 3 of the security element 1 is the uppermost of the layers shown. The security element 1 has a printed, electrically conductive layer 2 with a machine-readable coding.

The electrically conductive layer 2 can comprise a metallic or a non-metallic conductive material. For example, the electrically conductive layer 2 can comprise a metal layer or a layer containing metal particles. In particular, the non-metallic conductive material can comprise an electrically conductive polymer and/or an electrically conductive graphite-containing varnish. The electrically conductive layer 2 can advantageously also be formed from combinations of the aforementioned metallic and non-metallic materials.

A primer 5 is also applied to this electrically conductive layer 2. An electrically non-conductive cover layer 4 is arranged above this primer 5, and thus on a side of the electrically conductive layer 2 facing the visible side 3 of the security element 1. This cover layer 4 completely covers the electrically conductive layer 2. In the example shown, the cover layer 4 is provided in the special design of a printed, non-conductive metal pigment layer. This can contain aluminum, for example, and thus be silver-colored. Further layers can be provided above the cover layer 4. In the example according to the Fig.1 A further primer 5, a carrier layer 6 in the form of a PET film, a further primer 5 and finally a hot-sealing lacquer 7 protecting the layer structure can be provided over the cover layer 4. A protective lacquer 8 can be applied under the printed, electrically conductive layer 2, and under this a further carrier layer 6 in the form of a PET film laminated on using a laminating adhesive 9 can be arranged. A primer 5 and a protective hot-sealing lacquer 7 can in turn be provided under the further carrier layer 6. A security element 1 in the form of a thread can be introduced into a banknote substrate during the production of a security document or security paper, for example.

The exemplary cover layer 4 or non-conductive metal pigment layer can be a metallic effect paint and/or a metallic effect varnish and/or a metallic effect ink and/or a metallic material, in particular selected from the group consisting of silver, copper, aluminium, gold, platinum, niobium, tin, or nickel, titanium, vanadium, chromium, cobalt and palladium or alloys of these materials, in particular cobalt-nickel alloys.

Preferably, the cover layer 4 is substantially opaque and has an opacity or impermeability to light expressed by a transmittance of 0.5 to 1, preferably 0.7 to 1, particularly preferably 0.8 to 1. The cover layer 4 according to Fig.1 covers the electrically conductive layer 2 completely. However, a partial covering would also be conceivable.

The carrier layer 6 can comprise a plastic, which can in particular be formed from a translucent and/or thermoplastic plastic. The carrier layer 6 can preferably contain at least one of the materials from the group polyimide (PI), polypropylene (PP), monoaxially oriented polypropylene (MOPP), biaxially oriented polypropylene (BOPP), polyethylene (PE), polyphenylene sulfide (PPS), polyether ether ketone (PEEK), polyether ketone (PEK), polyethylene imide (PEI), polysulfone (PSU), polyarylether ether ketone (PAEK), polyethylene naphthalate (PEN), liquid crystalline polymers (LCP), polyester, polybutylene terephthalate (PBT), polyethylene terephthalate (PET), polyamide (PA), polycarbonate (PC), cycloolefin copolymers (COC), polyoxymethylene (POM), acrylonitrile butadiene styrene (ABS), polyvinyl chloride (PVC), ethylene tetrafluoroethylene (ETFE), polytetrafluoroethylene (PTFE), polyvinyl fluoride (PVF), polyvinylidene fluoride (PVDF), Ethylene-tetrafluoroethylene-hexafluoropropylene fluoroterpolymer (EFEP), cellulose- or lignin-based plastics, polyhydroxyalkanoates (PHA), thermoplastic starch (TPS), polylactic acid (PLA), polycaprolactone (PCL), polybutylene succinate (PBS), and polybutylene adipate terephthalate (PBAT) and/or at least one recycled and/or biodegradable and/or marine degradable plastic and/or mixtures and/or copolymers of these materials or be made from at least one of these materials.

A large number of different designs are conceivable for the cover layer 4. As already mentioned, only a few of these special designs are shown as examples in the figures. Not shown in the figures but fundamentally conceivable and advantageous is if the cover layer 4 has at least one liquid crystal layer, in particular a cholesteric liquid crystal layer. Also not shown in the figures is a variant according to which the cover layer 4 is designed as an optically non-linear layer or as an optically non-linear layer and/or as a layer containing fluorescent pigments and/or fluorescent substances.

In the Fig. 2 Another exemplary layer structure of a security element 1 is shown in the special design of a security thread. In order to avoid unnecessary repetitions To avoid this, reference is made to the above parts of the description, in particular to the description of the Fig.1 shown example referred to.

The visible side 3 of the security element 1 is again the uppermost of the layers shown. The security element 1 has a printed, electrically conductive layer 2 with a machine-readable code. A primer 5 is applied to this electrically conductive layer 2. On or above the primer 5, a cover layer 4 partially covering the electrically conductive layer 2 is arranged in the special design of two printed, non-conductive metal layers. For example, this can be a copper-containing or copper-colored non-conductive layer and an aluminum-containing or aluminum-colored non-conductive layer. In the Fig.2 the lower of the two cover layers 4 shown is partially applied in such a way that it covers the partial electrically conductive layer 2. The upper of the two cover layers 4 shown is also partial, but covers exactly the "gaps" of the lower cover layer 4 and the electrically conductive layer 2. Analogous or similar to the example according to Fig.1 Further layers, in particular further primers 5, carrier layers 6, protective varnishes 8 and heat-sealing varnishes 7 may be applied.

In the Fig.3 another exemplary layer structure of a security element 1 in the special design of a security thread is shown. In order to avoid unnecessary repetition, reference is again made to the above parts of the description.

The visible side 3 of the security element 1 is again the uppermost of the layers shown. The security element 1 has a printed, electrically conductive layer 2 with a machine-readable coding. The electrically conductive layer 2 can be a layer comprising a non-metallic conductive material. In particular, the non-metallic conductive material can be an electrically conductive graphite-containing paint or a carbon-conductive paint. Alternatively or additionally, the non-metallic conductive material can be an electrically conductive polymer. A primer 5 is again applied to the electrically conductive layer 2. On or above the primer 5, a cover layer 4 partially covering the electrically conductive layer 2 is shown in the special design of a color-shifting effect layer. The cover layer 4 can be a color-shifting thin-film element or - as in the Fig.3 shown - colour-shifting pigments, in particular interference pigments, or liquid crystal pigments. The Fig.3 The cover layer 4 shown is partially formed, just like the electrically conductive layer 2. However, the respective partial patterns formed by the cover layer 4 and by the electrically conductive layer 2 are independent of one another, i.e. they each follow different patterns.

The Fig.3 The cover layer 4 shown as a color-shifting effect layer can have an absorber layer 10, for example a black printing ink, on which absorber layer 10 a first color-shifting layer 11 and optionally a second color-shifting layer 12 can be applied. Analogous to the examples according to Fig. 1 and 2 Further layers, in particular further primers 5, carrier layers 6, protective varnishes 8 and heat-sealing varnishes 7 may be applied.

In addition, the cover layer 4 can have at least one layer enhancing the color-shift effect or an absorber layer 10 on a side facing away from the visible side 3 of the security element 1, wherein the layer enhancing the color-shift effect is in particular a layer of dark color and/or a layer of metal oxides, such as substoichiometric aluminum oxide. For example, the layer enhancing the color-shift effect can be applied to a liquid crystal layer or a layer 11, 12 of color-shifting pigments, so that the layer 11, 12 of color-shifting pigments or the liquid crystal layer is arranged between the layer enhancing the color-shift effect and the carrier layer 6. However, the layer enhancing the color-shift effect can also be arranged between the carrier layer 6 and the layer 11, 12 of color-shifting pigments or the at least one liquid crystal layer. In addition, it is also possible that a carrier layer 6 is arranged between the layer enhancing the color-shift effect and the layer of color-shifting pigments 11, 12 or the liquid crystal layer.

Not shown in the figure, but equally conceivable is a design of the cover layer 4 as a color-shifting thin-film element. If the cover layer 4 is designed as a thin-film element, it has at least one absorber layer and at least one spacer layer.

The at least one absorber layer can comprise at least one metallic material, in particular selected from the group of nickel, titanium, vanadium, chromium, cobalt, palladium, iron, tungsten, molybdenum, niobium, aluminum, silver, copper and/or alloys of these materials, or can be made from at least one of these materials.

Furthermore, it can be provided that the cover layer designed as a thin-film element further comprises at least one reflection layer and/or a second absorber layer, wherein the at least one spacer layer is arranged between the at least one first absorber layer and the at least one reflection layer and/or the at least one second absorber layer.

The reflection layer can be applied or arranged on structures and can in particular be printed and/or vapor-deposited on them. It is also possible to reverse this order in the optical effect layer so that the absorber layer is arranged on the structures and then the spacer layer and the reflection layer. The arrangement would therefore be in the order structures - absorber layer - spacer layer - reflection layer. Instead of the above-mentioned reflection layer, however, another absorber layer can also be provided.

The at least one reflection layer can comprise at least one metallic material, in particular selected from the group consisting of silver, copper, aluminum, gold, platinum, niobium, tin, or nickel, titanium, vanadium, chromium, cobalt and palladium or alloys of these materials, in particular cobalt-nickel alloys or at least one high-index dielectric material with a refractive index of greater than 1.65, in particular selected from the group consisting of zinc sulfide (ZnS), zinc oxide (ZnO), titanium dioxide (TiO ₂ ), carbon (C), indium oxide (In ₂ O ₃ ), indium tin oxide (ITO), tantalum pentoxide (Ta ₂ O ₅ ), cerium oxide (CeO ₂ ), yttrium oxide (Y ₂ O ₃ ), europium oxide (Eu ₂ O ₃ ), iron oxides such as iron(II,III) oxide (Fe ₃ O ₄ ) and iron(III) oxide (Fe ₂ O ₃ ), Hafnium nitride (HfN), hafnium carbide (HfC), hafnium oxide (HfO ₂ ), lanthanum oxide (La ₂ O ₃ ), magnesium oxide (MgO), neodymium oxide (Nd ₂ O ₃ ), praseodymium oxide (Pr ₆ O ₁₁ ), samarium oxide (Sm ₂ O ₃ ), antimony trioxide (Sb ₂ O ₃ ), silicon carbide (SiC), silicon nitride (Si ₃ N ₄ ), silicon monoxide (SiO), selenium trioxide (Se ₂ O ₃ ), tin oxide (SnO ₂ ), tungsten trioxide (WO ₃ ), high-index organic monomers and/or high-index organic polymers or be made from at least one of these materials.

The at least one spacer layer can be a low-refractive dielectric material with a refractive index of less than or equal to 1.65, in particular selected from the group aluminum oxide (Al ₂ O ₃ ), metal fluorides, for example magnesium fluoride (MgF ₂ ), aluminum fluoride (AlF ₃ ), cerium fluoride (CeF ₃ ), sodium aluminum fluorides (eg Na ₃ AlF ₆ or Na ₅ Al ₃ F ₁₄ ), silicon oxide (SIO _x ), silicon dioxide (SiO ₂ ), neodymium fluoride (NdF ₃ ), Lanthanum fluoride (LaF ₃ ), samarium fluoride (SmF ₃ ), barium fluoride (BaF ₂ ), calcium fluoride (CaF ₂ ), lithium fluoride (LiF), low-refractive organic monomers and/or low-refractive organic polymers or at least one high-refractive dielectric material with a refractive index greater than 1.65, in particular selected from the group zinc sulfide (ZnS), zinc oxide (ZnO), titanium dioxide (TiO ₂ ), carbon (C), indium oxide (In ₂ O ₃ ), indium tin oxide (ITO), tantalum pentoxide (Ta ₂ O ₅ ), cerium oxide (CeO ₂ ), yttrium oxide (Y ₂ O ₃ ), europium oxide (Eu ₂ O ₃ ), iron oxides such as iron (II,III) oxide (Fe ₃ O ₄ ) and iron (III) oxide (Fe ₂ O ₃ ), Hafnium nitride (HfN), hafnium carbide (HfC), hafnium oxide (HfO ₂ ), lanthanum oxide (La ₂ O ₃ ), magnesium oxide (MgO), neodymium oxide (Nd ₂ O ₃ ), praseodymium oxide (Pr ₆ O ₁₁ ), samarium oxide (Sm ₂ O ₃ ), antimony trioxide (Sb ₂ O ₃ ), silicon carbide (SiC), silicon nitride (Si ₃ N ₄ ), silicon monoxide (SiO), selenium trioxide (Se ₂ O ₃ ), tin oxide (SnO ₂ ), tungsten trioxide (WO ₃ ), high-index organic monomers and/or high-index organic polymers or be made from at least one of these materials.

In the Fig.4 another exemplary layer structure of a security element 1 is shown in the special design of a security thread. In order to avoid unnecessary repetition, reference is again made to the above parts of the description.

The visible side 3 of the security element 1 is in turn the uppermost of the layers shown. The security element 1 has a printed, electrically conductive layer 2 with a machine-readable coding. The electrically conductive layer 2 can be a layer which is transparent in a wavelength range visible to the human eye and preferably has a transmittance of 0 to 0.5, preferably 0 to 0.3, particularly preferably 0 to 0.1. A partial layer is provided as the cover layer 4, for example a layer with a black positive text. Alternatively or additionally, the cover layer 4 or the partial layer can represent a portrait, a landscape, an abstract geometric symbol, logo or an alphanumeric symbol and/or an icon and/or a coding and/or a sequence of characters.

This of course also applies to the Fig. 2 and 3 shown partial cover layers 4. It goes without saying that the partially formed cover layers 4 in the Figures 2, 3 and 4 are merely exemplary and representative of a large number of possible forms. In particular, the design of the cover layers 4 can conceal the underlying electrically conductive layer 2 or at least a targeted deflection from it can be achieved.

A camouflage layer 13 can be provided under the transparent, electrically conductive layer 2. As is known, additional layers are referred to as camouflage layers 13, which serve to reduce the visibility of the security thread in the security document or banknote substrate. This can be done, for example, by covering the back of the thread with a white varnish.

In the Fig.5 Another example of a layer structure of a security element 1 is shown in the special design of a security strip. The visible side 3 of the security element 1 is again the uppermost of the layers shown. The security element 1 has a printed, electrically conductive layer 2 with a machine-readable coding. The electrically conductive layer 2 can be a layer which is transparent in a wavelength range visible to the human eye and preferably has a transmittance of 0 to 0.5, preferably 0 to 0.3, particularly preferably 0 to 0.1.

The cover layer 4 can comprise structures 14 or be formed with structures 14. In particular, the structures can comprise achromatic and/or reflective structures, such as micromirrors, and/or refractive structures, such as microlenses, and/or diffractive structures, such as holograms.

The structures 14 can be directly embedded in a carrier layer 6 or, as in the Fig.5 shown, be introduced into a further layer, in particular into an embossing lacquer layer 15. This is done in particular by embossing using a molding device.

A partial metal layer or a partial reflection layer 16, for example a partial aluminum layer, is also provided as the cover layer 4 or as part of the cover layer 4. This can be produced by demetallization. The reflection layer 16 is applied to the embossed lacquer layer 15. A reflection layer 16 can basically be constructed like or comparable to a reflection layer of a thin-film element, as already described above.

In the Fig.5 In the security element 1 shown in the form of a security strip, it is provided that the carrier layer 6 is removed or peeled off after or during the application to a security document or security paper, or to a security document substrate or security paper substrate. The carrier layer 6 is advantageously designed as a transfer film for this purpose.

The embodiments show possible embodiment variants, whereby it should be noted at this point that the invention is not restricted to the specifically illustrated embodiment variants thereof, but rather various combinations of the individual embodiment variants with each other are also possible and this possibility of variation lies within the skill of the person skilled in the art in this technical field due to the teaching of technical action through objective invention.

The scope of protection is determined by the claims. However, the description and the drawings must be used to interpret the claims. Individual features or combinations of features from the different embodiments shown and described can represent independent inventive solutions in themselves. The task underlying the independent inventive solutions can be taken from the description.

All information on value ranges in the description in question is to be understood as including any range and all subranges thereof, e.g. the information 1 to 10 is to be understood as including all subranges starting from the lower limit 1 and the upper limit 10, i.e. all subranges begin with a lower limit of 1 or greater and end with an upper limit of 10 or less, e.g. 1 to 1.7, or 3.2 to 8.1, or 5.5 to 10.

Finally, for the sake of clarity, it should be noted that in order to better understand the structure, some elements have been shown not to scale and/or enlarged and/or reduced.

Reference symbol list

1

Security element

2

electrically conductive layer

3

Visible side

4

Top layer

5

Primers

6

Carrier layer

7

Heat seal varnish

8

Protective varnish

9

Laminating adhesive

10

Absorber layer

11

first color-shifting layer

12

second color-shifting layer

13

Camouflage layer

14

structure

15

Embossing lacquer layer

16

Reflective layer

Claims (14)

Security element (1) for securities or security papers or security objects, such as banknotes, identity cards, credit cards, which security element (1) has an electrically conductive layer (2) with a machine-readable coding, characterized in that the electrically conductive layer (2) is invisible when viewing a visible side (3) of the security element (1) in incident light and/or in transmitted light. Security element (1) according to one of the preceding claims, characterized in that the electrically conductive layer (2) is transparent in a wavelength range visible to the human eye. Security element (1) according to claim 2, characterized in that the electrically conductive layer (2) has a transmittance of 0 to 0.5, preferably from 0 to 0.3, particularly preferably from 0 to 0.1. Security element (1) according to one of the preceding claims, characterized in that the electrically conductive layer (2) is a printed layer. Security element (1) according to one of the preceding claims, characterized in that the electrically conductive layer (2) comprises a non-metallic conductive material. Security element (1) according to claim 5, characterized in that the non-metallic conductive material contained in the electrically conductive layer (2) comprises an electrically conductive polymer. Security element (1) according to claim 5 or 6, characterized in that the non-metallic conductive material contained in the electrically conductive layer (2) comprises an electrically conductive graphite-containing lacquer. Security element (1) according to one of the preceding claims, characterized in that an electrically non-conductive cover layer (4) is arranged on a side of the electrically conductive layer (2) facing the visible side (3) of the security element (1). Security element (1) according to claim 8, characterized in that the cover layer (4) is substantially opaque. Security element (1) according to claim 9, characterized in that the cover layer (4) has a transmittance of 0.5 to 1, preferably from 0.7 to 1, particularly preferably from 0.8 to 1. Security element (1) according to one of claims 8 to 10, characterized in that the cover layer (4) completely or partially covers the electrically conductive layer (2). Security element (1) according to one of claims 8 to 11, characterized in that the cover layer (4) is a printed electrically non-conductive metal layer or a printed electrically non-conductive metal pigment layer. Security element (1) according to one of claims 8 to 12, characterized in that the cover layer (4) is a partial layer or comprises a partial layer, wherein the partial layer represents a portrait, a landscape, an abstract geometric symbol, logo or an alphanumeric symbol and/or an icon and/or a code and/or a sequence of symbols. Security paper or security document , characterized in that it comprises a security element (1) according to one of claims 1 to 13.

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