EP2465703B1 - Structured colour-shift security element - Google Patents

Description

The application relates to a security element for a data carrier with a structured, optically variable ink layer, a data carrier with such a security element and a production method for such a security element.

Data carriers, such as documents of value or identity documents, in particular identity cards, credit cards or passports, or other valuables, such as branded articles, are provided with security elements for the purpose of security, which permit verification of the authenticity of the article and which at the same time serve as protection against unauthorized reproduction. Furthermore, security elements often produce a highly visible visual impression, which allows a review of the security element even without technical aids, such as the naked eye. A security element can be embedded in such data carriers, for example in a banknote or in a chip card, or designed as a self-supporting transfer element, for example as a patch or as a label, which is applied to a data carrier or other object to be secured after its production. Alternatively, however, the security element can also be integrated into the data carrier during production.

Data carriers in the context of the present invention are in particular banknotes, stocks, bonds, certificates, vouchers, checks, high-quality admission tickets, but also other papers forgery, such as passports or other identity documents, and also card-shaped data carriers, in particular credit and chip cards, as well as production assurance elements, such as Labels, seals, packaging and the like. The term "data carrier" also includes precursors, in particular non-executable precursors of such data carriers which, for example in the case of security paper, are present in quasi-endless form and are processed further at a later time. Such data carriers may contain windows or viewing windows, which are covered with a transparent film, which optionally forms the carrier for a security element.

To prevent counterfeiting or replication of security elements, for example with high-quality color photocopiers, such security elements can have optically variable elements or optically variable layers, which convey to the viewer under different observation conditions, for example from different viewing angles, different optical impressions, for example different color impressions. For producing layers showing such optically variable effects, various techniques are known. For example, optical interference layers can be present either over the entire surface or in pigment form. Such interference layers typically have a thin film structure that includes a reflective layer, a partially transparent layer, and one or more intervening dielectric spacer layers. These are based, for example, on mica, on SiO ₂ or on Al ₂ O ₃ . Such interference layers are referred to as one or more layers according to the number of dielectric layers. Inks with pigments such thin film interference layers, for example, under the name Iriodin ^® (single layer) or Colorcrypt ^® (multi-layer) marketed by Merck KGaA. Printing colors with multi-layer interference layer pigments such as are sold under the name OVI ^® or OVMI ^® of SICPA further, the pigments of the OVMI ^® printing inks have an additional magnetic layer in the thin-film structure.

Instead of interference layers or interference layer pigments, cholesteric or other liquid crystals can also be used. These are, for example, as liquid-crystalline silicone polymers prior to or as a cholesteric liquid crystal pigments in so-called STEP ^® Colors ( "Shimmery Twin Effect Protection"). Furthermore, holograms, which include metallic layers typically formed by vacuum deposition, or diffraction gratings, at different viewing angles, also exhibit a different visual impression to an observer.

The various optical impressions for a viewer include, for example, a so-called color shift effect ("Colorshift"), in which different shades are recognizable for the viewer at different viewing angles. Different optical impressions can also arise because, under a certain viewing angle, the optically variable layer is completely transparent and thus invisible to a viewer, while it shows a hue at a different viewing angle (effect angle). Such optically variable layers are often iridescent, that is they show a pearlescent, as it is known for example from shells or mica. In general, such pigments which, when the viewing direction is changing, show a color change are referred to as goniochromatic or optically variable pigments.

Single-layer interference coatings, printing inks with liquid-crystalline or single-layer interference-layer pigments are often poorly covering, that is to say highly translucent at all viewing angles, so that the color impression discernible to the viewer is relatively weak when viewing an optically variable layer constructed therefrom. Such effect layers with high light transmission are therefore preferably arranged in the viewing direction in front of dark or black backgrounds to improve the detectability of the color change. Multilayer interference layers and inks with multilayered interference layer pigments, on the other hand, can have very different degrees of coverage. They can be highly opaque, have correspondingly low light transmission or are sometimes even completely opaque. In such optically variable layers with high coverage, the optically variable effect can be perceived usually without a dark or black background.

In Scripture EP 0 317 514 A1 the high light transmission of an applied iriodin ink layer is used as a forgery-proof authenticity feature. The iriodin ink layer is applied over a black background, so that when viewing an unaltered security feature under an effect angle, the color impression of the applied iriodin ink layer can be perceived. A color photocopier can not detect this iriodin color because of its poor color intensity and also because of the image scan in plan view, where the iriodin layer is transparent, and thus merely copies the black background. Thus, the optically variable color impression is missing on the copy.

The optically variable colors commonly used for security elements are not readily available to a counterfeiter. However, at least for an inexperienced or inattentive viewer, similar color impressions can also be achieved via other substances, as occur, for example, in nail polish. In principle, not only monochrome imprints of optically variable colors, but also two- and multi-colored imprints can be imitated.

The document EP 0 657 297 A1 discloses a security element for media comprising a transparent substrate having a front side and a back side and an optically variable front side layer.

Object of the present invention is to provide a security element with high protection against counterfeiting, in which in a simple manner Safety mark with different optical characteristics can be generated. It is a further object of the invention to specify a corresponding data carrier and a production method for such a security element.

This object is achieved by a security element, a data carrier and a manufacturing method having the features of the independent claims. The dependent claims relate to preferred embodiments and further developments of the invention.

The security element according to the invention for a data carrier comprises a transparent or translucent substrate with a front and a back side. It furthermore comprises an optically variable ink layer arranged in the viewing direction on the front side, referred to below as the optically variable front side layer, and an optically variable ink layer arranged on the rear side, hereinafter referred to as an optically variable back side layer. The front side layer is either completely or partially arranged directly on the substrate or may be arranged on one or more layers arranged between the substrate and the front side layer. Likewise, the backsheet may be disposed either entirely or partially directly on the substrate, or one or more layers may be provided between the substrate and the backsheet. The front-side layer and the back-side layer are arranged at least partially overlapping in the viewing direction, so that an overlap region is formed, in which both layers are arranged one behind the other when viewing the front side or the back side of the substrate.

Within this overlapping region, at least one of the two color layers, that is to say either the optically variable front side layer or the optically variable back side layer, optionally also both optically variable color layers, has at least one structuring formed by a change or recess in the front side layer and / or back side layer.

The structuring is a local change in an otherwise unchanged, uniform and uniformly designed optically variable ink layer. In other words, the structured optically variable color layer is uniformly formed, at least in an environment of the structuring, such that the structuring as such can be recognized under suitable observation conditions. In the simplest case, the structured optically variable color layer outside the structuring is uniform and uniform in the entire overlapping area. The change may be a change in color or any other visually or mechanically perceptible change in the optically variable ink layer.

The transparent or translucent substrate of the security element according to the invention is extensively extended and formed, for example, flat and thin. The front and back sides form opposite sides of the substrate.

For the purposes of the present invention, a transparent substrate has a high light transmittance in the entire visible wavelength range, which is preferably at least 80% at each point of the visible spectrum, preferably at least 90% or ideally 100%. Such a transparent substrate is further preferably clear and enables an undisturbed observation of objects lying behind the transparent substrate in the viewing direction. By contrast, a translucent or semitransparent region visibly reduces the intensity of the light passing through it to a viewer and typically has a light transmission between 20% and 80% in the entire visible spectrum. It can be clear or milky. In contrast, an opaque substrate or optionally an opaque layer in the entire visible spectrum has a light transmission of less than 20%, preferably less than 10% and ideally 0%. Preferably, the transparent or translucent substrate has the same light transmission over the entire visual spectral range, so that no or only a slight change in color of passing light is visible to the viewer.

In the context of the present invention, the term "optically variable" encompasses any change of the visual impression of a specific layer, in particular the front-side or rear-side layer according to the invention, perceivable by a viewer. Very often, the change perceptible by the viewer will be a change in color, brightness or contrast.

As the optically variable layer for the front layer and the back layer basically are those known in the prior art optically variable layers and colors in question, such as single layer interference layers, colors with single-layer interference layer pigments, such as Iriodin ^® Colors of Merck, layer or multilayer interference coating pigments, for example Colorcrypt ^® colors of Merck or OVI ^® - or OVMI ^® - colors from SICPA, but also colors with cholesteric liquid crystal or other pigments, such as STEP ^® colors. Both Iriodin pigments available from Merck are generally pigments having a core of mica which has an interference layer, in particular of titanium dichloride, iron chloride or of a combination of titanium dichloride and iron chloride. The layer thicknesses of the interference layer are chosen so that they are in the wavelength range of the desired color (1st order) or at a multiple of the desired wavelength (2nd, 3rd, 4th, etc. order). In general, pigments having an interference layer thickness in the range of several times the desired wavelength, often referred to as "higher order" pigments, are stronger in color than so-called "first order" pigments and have a higher coverage and lower light transmission. As a rule, the observer can perceive a single characteristic color only at a certain viewing angle. In the available from Merck Colorcrypt ^® pigments are generally pigments having a core of silicon oxide having an interference layer, which comprises a plurality of layers, in particular intermediate layers. Depending on the layer thickness of the individual layers, the viewer thus perceives different colors under different viewing angles, but only in a relatively narrow wavelength range around a specific center wavelength. In contrast, the OVI ^® pigments or OVI ^® have -Farben SICPA to a viewing-angle dependent color-shift effect in a relatively wide wavelength range.

The Colorcrypt available from Merck ^® pigments are considerably more expensive than the Iriodin also available from Merck ^® pigments in the making, so that Colorcrypt ^® pigments are much more expensive than Iriodin ^® pigments, which prevents counterfeiters cost reasons before these pigments and thus the protection against counterfeiting with Colorcrypt ^® pigments equipped inventive security elements additionally increased. Furthermore Colorcrypt ^® pigments from Merck can be seen clearly under the microscope, which can serve as proof of authenticity with the use of appropriate tools. It is understood that the effect pigments mentioned above or preferably used are to be considered as illustrative rather than restrictive.

Here, have layered interference coatings, Iriodin ^® - and Colorcrypt ^® Colors Merck and colors with cholesteric liquid crystal pigments at all viewing angles, a high light transmittance. In plan view, they are often completely transparent, however, when viewed at a given angle of effect despite their translucency but an intense hue, especially against a dark or black background.

In order to achieve an intense color of the optically variable ink layer, a sufficient amount of z. B. Iriodin ^® pigments are applied. The coated surface should ideally be equipped with a substantially closed Iriodin ^® -Pigmentschicht. An additional increase in the intensity of the hue is achieved by a calendering of the substrate, because the flat pigments align themselves even better in a plane. The calendering can be done both before and after the application of the pigments on the substrate.

According to the invention, such a security element is produced for a data carrier in that an optically variable ink layer is applied to a provided, transparent or translucent substrate both on the front side and on the rear side, so that an overlap region is created in which the optically variable front side layer and the optically variable backsize layer are arranged overlapping. Within the overlapping area, patterning in the form of a change or a recess is formed in the optically variable front side layer and / or in the optically variable back side layer. The security elements according to the invention have a very high security against counterfeiting.

The structuring, in particular in the form of a cutout, in the front side and / or backside layer can in principle already take place when the front side layer or the backside layer is applied by the optically variable color layer with the structuring not being applied over the entire area but only in partial areas, so that the intervening areas form recesses and thus the structuring. This can be done, for example, by means of known printing processes, such as the screen, gravure or flexographic printing process.

Preferably, however, the optically variable front side layer and the optically variable backside layer are first applied over the entire surface of the substrate and suitably changed in a subsequent step, so that the inventive structure in the optically variable front side layer and / or backside layer is generated. This can be done for example via a washing process, as in the EP 1023 499 is described in the context of a demarcation demetallization. The disclosure of said publication is included in the following application in this respect. Alternatively, the structuring can be done by etching, ablation or lift-off. Other methods used in demetallization can also be used.

However, structuring is particularly preferably carried out by a laser treatment which appropriately changes or ablates the optically variable ink layer. Such a laser treatment has the advantage that subsequently the desired structuring can be subsequently introduced into the security element, that is to say after completion and independently of the production method of the security element. Accordingly, it is easily possible via such a laser treatment to personalize or individualize the security element.

Suitable laser sources are CO ₂ , Nd: YAG, Nd: YVO ₄ lasers or other types of lasers in the wavelength range from UV to far-infrared, with the lasers often also advantageously operating at frequency doubling or frequency tripling. With particular advantage, laser sources are used in the near infrared, since this wavelength range fits well with the absorption properties of the substrates and printing inks used for value documents, in particular the optically variable colors. For example, printing inks that are transparent to laser radiation but colored or even opaque in the visible spectral range to the human observer can easily be specified for this area. With particular advantage, infrared lasers in the wavelength range of 0.8 microns to 3 microns are used. These can be operated in continuous operation or in pulsed operation with a pulse frequency of typically between 20 kHz and 80 kHz. The power used is typically between 0.5 watts and 4 watts.

The optically variable layers of the security element according to the invention can, as already mentioned above, be printed by means of known printing processes, such as the flexographic printing process. However, you can also vacuum evaporation, such as sputtering, reactive sputtering, physical vapor Deposition or chemical vapor deposition applied to the front and back of the substrate, in particular vapor-deposited. The structuring introduced into the optically variable ink layer can be information-leading, that is to say it represents information for the viewer, which can be achieved, for example, via an alphanumeric character, a graphic or a motif. Such an information content improves the recognition or the recognition of structuring by a viewer.

Depending on the layer structure on the front side and the back side of the substrate, depending on the type of optical variable color layers used as the front side layer and the back side layer, in particular depending on their degree of coverage, and depending on the type of change or recess forming the pattern, a plurality of degrees of freedom result Creation of structuring that produces optical impressions and transition effects when changing between different observation conditions, for example, when switching between viewing in transmitted light, a front view, that is viewing the front in reflected light, or a plan view on the back, that is one View of the back in reflected light, possibly in front of different colored or different light backgrounds or black backgrounds. Such structuring can then be used as a security identifier.

The front side layer and the back side layer of the security element according to the invention can consist of the same optically variable color and be of identical design, for example have the same layer thickness. Preferably, however, the front-side layer and the back-side layer are formed of various optically variable colors, which but are preferably of the same type. In other words, Iriodin ^® -Color a Colorcrypt ^® -Color an OVI ^® -Color or STEP ^® -Color example, is used for the front layer and the backing layer, with the colors used for the front layer and the back layer each in their color and / or in their color behavior, for example, the color shift behavior ("Colorshift"), distinguish and thus distinguishable to the viewer.

Furthermore, embodiments may have interesting optical effects in which the front side layer and the back side layer are preferably formed of different optically variable colors, but the optically variable colors are of different types. A IRIODIN ^® -Color or Colorcrypt ^® -Color and for the backing layer may be provided - for example, for the front layer a OVI ^®.

The structuring can be formed at the same time exclusively in the optically variable front side layer, exclusively in the optically variable backside layer or in register with both optically variable layers. The introduction of such structuring will be described below using the example of a laser treatment. Instead of the laser treatment, however, all other structuring methods already mentioned can also be used and the different structuring methods can be combined with one another.

In a preferred embodiment of the security element according to the invention, the front side and / or the backside layer are ablatable or changeable, in particular ablatable or changeable by laser irradiation. Ablation by laser in the present document refers to all mechanisms that result in the removal of the corresponding layer the laser treatment result. This includes, for example, a sublimation. The targeted interaction with only exactly one of the two optically variable color layers or with both optically variable color layers at the same time can on the one hand by a suitable choice of the laser parameters, such as wavelength, power and pulse duration, with regard to the components of the processed optically variable ink layer and optionally not to be processed optically variable ink layer can be achieved. On the other hand, the optically variable colors underlying the optically variable color layers can be suitably selected or suitable additives can be added to the optically variable color layers, which preferably do not influence the color perceptible to a viewer and the color behavior of the optically variable layer perceptible to a viewer the laser radiation interact.

In the case of a change in the optically variable ink layer, for example, the components of the optically variable ink layer which produce the optically variable effect can be changed or destroyed so that the color of the optically variable ink layer is changed or removed at the points of laser treatment. In the case of interference layers or interference layer pigments, this can take place via targeted destruction of one or more of the layers involved. In the case of liquid crystal pigments, for example, the liquid crystal pigments themselves are destroyed. Such a laser treatment therefore only leads to a visually or mechanically perceivable change in the optically variable ink layer, but not to an ablation. Alternatively or additionally, the optically variable ink layer may contain components or additives which absorb the laser radiation, such that a local thermal heating of the optically variable ink layer takes place, for example, to destruction the components of the color layer which produce the optically variable effect or else lead to an ablation of the entire optically variable color layer, thus creating a structuring in the form of a recess in the optically variable color layer. By a suitable choice of such additives and the laser parameters, a targeted structuring of only one of the two optically variable color layers or of both optically variable color layers can thus be carried out. If the optically variable front side layer as well as the optically variable back side layer are structured by the laser irradiation at the same time, an exact registration patterning is created on the front side and the rear side of the security element. Thus, for example, subsequently, that is to say after completion of the actual manufacturing process, individualizing, laser-manufactured through-windows can be created in such a security element by ablating the optically variable front-side layer as well as the optically variable back-side layer by the laser treatment. The laser irradiation can be done both from the back, as well as from the front.

For all abovementioned variants of the laser ablation, these can in principle lead to a complete removal or modification of a layer acted upon by laser radiation, i. to a full-surface laser ablation. However, it is also conceivable to perform a screened ablation, at least in some areas, in order to obtain, for example, to realize a halftone motif.

Such structuring in the laser treatment can be carried out primarily in highly opaque optically variable inks, such as OVI ^® Colors, as they interact with the typically laser radiation, preferably absorb this. In the following, the overlapping area is considered, in which the substrate of the security element is on both sides such a visually variable ink layer is coated. An untreated security element thus shows the color and the color behavior of the backside layer when viewing the front side in reflected light, when viewing the backside in reflected light, the color and the color behavior of the backside layer, while when viewed in transmitted light the colored impression disappears, so that the see-through element in a gray tone which is determined by the degree of coverage, that is, the opacity of the front side layer and the back surface layer and optionally of the substrate.

In a first variant of the laser treatment, a structuring is merely introduced into the front side layer, which consists in changing or removing the color and the color behavior of the front side layer, so that in the incident light the interaction region with the laser, for example, appears colorless and gray. On the other hand, the laser treatment does not change the coverage of the front surface layer, and therefore when viewed in transmitted light, the interaction region appears in the same hue as the surrounding untreated area. Thus, when changing from observation of the front side in incident light to observation in transmitted light, the structuring clearly recognizable in incident light disappears completely when viewed in transmitted light. If the structuring is informative, the information disappears in transmitted light. In other words, a digital change of information can take place.

In a second variant of the laser treatment, the front side layer is ablated, that is to say a recess is produced in the front side layer, but the back side layer - as in the previous variant - is not changed. Accordingly, when viewing the front side in incident light in the laser-treated area, the color and the color behavior of the backside layer can be seen. When viewed in transmitted light disappears in the laser-treated Area of color impression produced by the backside layer and it appears in a gray tone, which is determined only by the degree of coverage, that is, the opacity of the backside layer (and optionally by the opacity of the substrate). This results in a lighter shade of gray in this area than in a surrounding, untreated area of the security element.

In a third variant of the laser treatment, the front side layer is ablated and at the same time the color and the color behavior of the backside layer are changed or removed. Correspondingly, when the front side is viewed in incident light in the laser-treated region, a gray tone is produced, which is preferably identical to the gray tone which results in a reflection of the laser-treated region according to the abovementioned first variant. When viewed in transmitted light, however, the gray tone of the treated according to the third variant area again depends only on the degree of coverage, that is the opacity of the backside layer, which is a lighter shade of gray than in the surrounding, untreated area and a lighter gray tone than in the according to the first variant laser-treated area in the transmitted light results. Rather, the same gray tone results as in the laser-treated according to the second variant range. In this case, the laser treatment of the front side layer and the rear side layer preferably takes place together in one step, so that the recess in the front side layer and the color-changed region in the back side layer are arranged in register with one another. In this respect, when viewed in reflected light, it is initially not possible to determine whether the resulting gray tone originates from the front side layer or from the rear side layer.

In a fourth variant of the laser treatment, both the front side layer and the rear side layer are ablated at the same time. The resulting recesses in the front side layer and the back side layer are therefore in registration with each other. Accordingly, there is a see-through window whose optical properties depend on the substrate of the security element. In this respect, light passing through when viewed through transmitted light can be clearly recognized, or even when viewed in incident light, a color of a background used, in front of which the security element is viewed, can be clearly recognized.

In a preferred embodiment of the security element according to the invention, a plurality of different structurings are provided that have been produced using various of the abovementioned variants of the laser treatment. This can be used, for example, to generate a digital change of information when changing the incident light view of the front side and the transmitted light view. For example, regions that are processed according to the second variant, and regions that have been processed according to the third variant show the same gray tone in transmitted light, with which such regions can not be distinguished by a viewer and are perceived as a uniform, contiguous region in adjacent arrangement. Accordingly, areas that are processed according to the first variant and areas that have been processed according to the third variant, when viewing the front in the incident light indistinguishable. Accordingly, these different areas can be combined to different information.

In a preferred embodiment of the security element according to the invention, a first is present between the front side layer and the front side of the substrate in at least a first subregion of the overlap region dark or black, preferably ablatable, particularly preferably laserablatierbare color layer formed and / or formed between the backside layer and back of the substrate in at least a second portion of the overlap region, a second dark or black, preferably ablatable, particularly preferably laserablatierbare color layer. If the dark or black color layer is applied only on either the front side or the back side of the substrate, then it extends over the entire overlapping area. If the dark or black color layer is applied both on the front side and on the rear side of the substrate, then the respective partial regions are configured such that their union amount extends over the entire overlap region. In other words, the two sub-areas of the dark or black color layer on the front and on the back of the substrate complement each other so that either the dark or black color layer on the back or the dark or black color layer on the front is applied in the entire overlap area. This ensures that at each point of the overlap area a dark or black background is available for the front side layer and for the back side layer when viewed in incident light.

In addition to the above-mentioned preferred embodiment with a dark or black, in particular laserablatierbaren ink layer, it is generally conceivable to provide a light, visually as little visible, laserablatierbare layer, at least in some areas, so that the colors of the front or back in review interesting mixed colors for the Observers recognize.

In a particularly preferred embodiment, the dark or black color layers also overlap, so that within the overlap region the optically variable color layers results in a further overlap region with respect to the dark or black color layers on the front and back. The entire overlap region of the optically variable color layers is then preferably divided into three different regions. In a first area, the dark or black color layer is applied only on the front side of the substrate, in a second area the dark or black color layer is applied only on the back side of the area and in a third area on both the front side and the back side the substrate applied a dark or black color layer.

Such a configuration of the security element is particularly suitable for low-opaque, optically variable color layers, for example, of Iriodin ^® -, Colorcrypt ^® - consist or STEP ^® Colors which require a dark or black background, a sufficient visibility of their color and their color behavior sure. Since a dark or black color layer is applied in the entire overlap area - either on the back, on the front or on both sides of the substrate - there is always a dark or black background for the front side layer when viewing the front of the security element in reflected light and for the backside layer when viewing the back of the security element in incident light.

The said low-opacity colors are, at least as long as no special additives are added, transparent to laser radiation and thus can not initially be patterned by a laser. Such an interaction, in contrast, is possible with the at least partially underlying dark or black color layer. The dark or black color layer is preferably a carbon black-based paint containing a Interaction with laser radiation of different wavelengths, in particular with laser radiation in the UV, VIS and IR range allows. Thus, the dark or black color layer can be ablated by laser treatment, whereby an optionally overlying optically variable ink layer is also removed and corresponding recesses are created in the optically variable ink layer.

The above-described dark or black, optionally carbon black-based ink layer thus simultaneously assumes the function of a suitable background for low-coverage, optically variable ink layers as well as the function of creating an interaction possibility with the laser radiation. In principle, this can also be achieved by two mutually different layers, so that, for example, the layer ensuring the interaction with the laser is arranged directly on the substrate, above that the color layer forming a dark or black background and above this the optically variable color layer.

Since low-coverage, optically variable color layers, as mentioned above, typically do not interact with a laser, an interaction with the laser preferably takes place exclusively in the dark or black color layer. This is preferably ablatable, preferably laserablatierbar formed. When the dark or black color layer is ablated, the respective overlying optically variable color layer is also removed. If such a dark or black color layer is applied both on the front side and on the back side of the substrate, then both dark or black color layers are removed at the same time with the respective front side and back side layers at the same time so that a see-through window with registration-accurate recesses on both Side of the substrate results. The translucency or Transparency of the resulting see-through window corresponds to the translucency or transparency of the substrate. If, on the other hand, a dark or black color layer is applied only to the front side of the substrate, only the front side layer is removed during laser irradiation, while the rear side layer remains unchanged. Conversely, if such a dark or black color layer is arranged only on the back side of the substrate, only the backside layer is removed during laser irradiation, while the front side layer remains unchanged. In this respect, the extent of the dark or black color layers within the overlap area determines which effects have laser irradiation.

In an untreated security element, that is to say in a security element without laser structuring introduced, the color and the color behavior of the front side layer result when the front side is viewed in reflected light, irrespective of whether the dark or black color layer is applied on the front side or on the back side of the substrate In both cases, the dark or black color layer provides a suitable background for the front side layer when viewing the front of the security element in reflected light. When viewed in transmitted light, the color impression of the optically variable layers disappears for the observer, resulting in a gray tone which depends on the light transmittance, that is the opacity, of the dark or black color layer. In the above-mentioned further overlapping area, in which the dark or black color layer is present both on the front side and on the back side of the substrate, initially there is a light transmittance, which is lower because of the passage of light through two dark or black color layers than in the others Areas of overlap area where there is only one dark or black color layer, either on the front or on the back. Nevertheless, a uniform For example, to ensure the image of the entire overlap region in transmitted light, the layer thickness of the dark or black color layers in the further overlap region can be reduced, resulting in uniform opacity in the entire overlap region when viewed in transmitted light. This can also be achieved by other suitable means, such as a reduced absorption coefficient.

In a first region of the overlap region, a dark or black color layer is present only on the back side of the substrate. In a laser treatment within such a range, as already mentioned, the dark or black color layer is removed together with the (from the substrate) overlying backside layer, while the optically variable front side layer remains unchanged. When viewed in transmitted light, this results in a bright area which, given the assumed low degree of coverage of the optically variable front side layer, substantially corresponds to the transparency or translucency of the substrate. Looking at this area in reflected light on the front of the security element against a white background, the color of the optically variable front side layer returns and the white background is clearly visible. In an incident light view against a dark or black background, however, this dark or black background replaces the previously existing dark or black color layer arranged on the back side of the substrate, in which case the color and color behavior of the optically variable front side layer can again be observed , Ideally, such a laser-treated area when viewed against a dark or black background is indistinguishable from the surrounding untreated area, therefore, the structuring and any accompanying information is under consideration the front disappears in reflected light against a black background.

Looking at this area from the backside, when viewed in transmitted light as well as reflected light in front of a white background, the same effects as in the above-described observation from the front side result in this area. However, when viewed against a dark or black background, it again provides a suitable background for observing the color and color behavior of the front side layer (now back), therefore, when viewing the back side in incident light, the laser-treated area is discernible with the color and color behavior of the front side layer whereas the surrounding untreated area is contrasted with the color and color behavior of the backsheet layer.

On the other hand, if the laser treatment takes place in an area of the overlap area in which the dark or black color layer is disposed both on the front side and on the back side, both dark or black color layers are ablated together with the respective front and back side layers. Accordingly, there is a see-through window whose transparency or translucency corresponds to that of the substrate. Such a see-through window exhibits substantially the same brightness when viewed in transmitted light as the previously described recesses in the areas in which the dark or black color layer is applied only on either the front side or the rear side. In this respect, ideally, the see-through window in transmitted light can not be distinguished from the recess in the first area. In contrast, the viewing window differs significantly from the recesses when viewed against a dark or black background in the first area, because therein the color and color behavior of the front side layer or the back layer occurs, while in the see-through window the black background is clearly recognizable.

In a particularly preferred embodiment of the security element, this has various structuring of the optically variable front side layer and / or the optically variable back side layer. Preferably, a first patterning is formed only in the front side layer. This is then in an area in which the dark or black color layer is applied only on the front side of the substrate. A second structuring is formed only in the optically variable backside layer. This is located in a region in which a dark or black color layer is formed only on the back of the substrate. A third structuring comprises registering the front side layer and the back side layer and is formed in a region in which a dark or black color layer is formed both on the back and on the front side of the substrate. Since the third structuring which forms the see-through window can be viewed in incident light both in the front and in the back, in the case of an information-carrying structuring, it is advantageous here to use information that can be seen both from the front side and from the front side has an easily comprehensible information content from the back, that is, which also has a information content in mirror-inverted representation. For example, reflection-invariant symbols come into question.

It is understood that the optically variable front side layer and / or optically variable back side layer additional security features, such as luminescent substances, substances with characteristic magnetic or electrical Properties or characteristic properties in the infrared spectral range, may have. Each of the additional security features, in conjunction with the security element according to the invention, can increase counterfeit security in a synergistic manner. For example, the additional security element can be chosen so that it also leads to a change in the additional security feature of the backside layer upon exposure to laser radiation, which leads eg to ablation of the front side layer and to a change in the color behavior of the backside layer. In the areas in which the backside layer shows a changed color behavior, the additional security feature also shows altered physical properties, such as altered luminescence properties or altered magnetic properties, altered properties of the electrical conductivity or altered properties with respect to irradiation with infrared light wavelength range. Of course, in another variant, it is possible to ablate the backside layer by the action of a laser and to change the front side layer in its color behavior, whereby the properties of an additional security feature in the front side layer are changed / modified by the action of the laser radiation. As a result, in any case, by altering the properties of an additional security feature provided in the front and / or backside layer, the counterfeit security of the security element according to the invention is increased in a synergistic manner, since the or the additional security features greatly enhance protection against counterfeiting through the selection of physical properties which can be changed by means of laser radiation increase.

Moreover, it is also conceivable that the dark or black, preferably ablatable color layer between front side layer and front side of the substrate and / or between backside layer and backside of the substrate has an additional security feature. The additional security feature may, for example, again be additional security features described in connection with the optically variable front / back layer, such as luminescent substances, substances having characteristic magnetic or electrical properties, substances having characteristic properties when irradiated with radiation of the infrared wavelength range, etc.

Finally, in a particularly tamper-proof variant, it is possible for one or more, identical or different additional security features to be provided in the optically variable front / back layer and / or in the dark or black color layer on the front and / or back of the substrate.

Furthermore, it is provided in a particularly advantageous embodiment that the optically variable front / back side layer and / or the dark or black color layer contains one or more identical or different additives which the formation of a recess, in particular the structuring by means of an ablation, in particular laser ablation to promote. The additive may, for example, be a substance which melts at low temperatures, such as, for example, a wax, in particular carnauba wax. By providing one or more of the additives in one or more of the layers mentioned above, a security element according to the invention with even greater protection against counterfeiting is provided due to the more reliable and contour-sharper removal of the layer exposed to radiation, for example, since structures with very high contour sharpness are even more difficult to imitate ,

The described invention provides an optically variable security element which can be recognized without auxiliary means and which displays a digital information change which can easily be verified by untrained observers when viewed in transmitted light or when viewed in reflected light in front of a dark or black background, for example. It can easily be created in a single security element three different from their optical properties forth information. The present invention provides an integrated in print design, pre-structured and customizable, verifiable without tools optical security element.

An inventive data carrier comprises a security element as described above. Preferably, the security element completely or partially forms a window area.

It should also be noted at this point that structuring of the security element, as described above, in principle can also be continued beyond the actual security element, for example on the substrate of the data carrier. Thus, for example, a part of the structuring according to the invention can be generated after the security element has been arranged on a data carrier in the area of the security element and the substrate surrounding the security element of the data carrier and thus the security element can be "sewn" to the data carrier. It is conceivable, for example, a structuring of the security element, which is continued in an ideal Passerung in the region of the data carrier as a modification, in particular color change. Such an embodiment is characterized by an extremely high counterfeit protection, since the security of the security element on the one hand and the data carrier on the other hand is additionally increased by a structuring connecting the security element and the data carrier.

Further exemplary embodiments and advantages of the invention are explained below by way of example with reference to the accompanying figures. The examples represent preferred embodiments which in no way limit the invention. The figures shown are schematic representations that do not reflect the real proportions, but serve an improved clarity of the various embodiments.

Fig. 1

eine Banknote mit einem Sicherheitselement;

Figuren 2a - 2f

ein erstes Ausführungsbeispiel des Sicherheitselements;

Figuren 3a - 3c

eine Variante des ersten Ausführungsbeispiels;

Figuren 4a - 4f

ein zweites Ausführungsbeispiel des Sicherheitselements; und

Figuren 5a - 5c

eine Variante des zweiten Ausführungsbeispiels.

In detail, the figures show:

Fig. 1

a banknote with a security element;

FIGS. 2a-2f

a first embodiment of the security element;

FIGS. 3a-3c

a variant of the first embodiment;

FIGS. 4a-4f

a second embodiment of the security element; and

FIGS. 5a-5c

a variant of the second embodiment.

In Fig. 1 is as a data carrier a banknote 1 shown with a window area 2, which includes a security element 3. The arrangement of the security element 3 in a window area 2 allows the viewing of the security element 3 in transmitted light, in reflected light, both from the front and from the back, and also from different backgrounds.

In the FIGS. 2a to 2f a first embodiment of the security element is shown. In Fig. 2a the security element is shown in cross section before the laser treatment. On a transparent substrate 4, for example a PET film, an optically variable front side layer 5 is arranged on the front side and an optically variable rear side layer 6 on the rear side. The cross section in Fig. 2a FIG. 12 shows the overlapping area in which the optically variable front-side layer 5 and the optically variable back-side layer 6 are overlapped. In a first partial area of the front side, a black, soot-based ink layer 7 is arranged between the transparent substrate 4 and the front side layer 5. On the rear side of the transparent substrate 4, a further black, soot-based ink layer 8 is arranged between the transparent substrate 4 and the optically variable backside layer 6 in a second partial region. At least one of the two black color layers 7 and 8 is arranged at each point of the overlapping region of the optically variable color layers, that is to say the union of the first and second partial regions corresponds to the overlapping region of the optically variable color layers. In a central area of the security element 3, the black color layer 7 of the front side and the black color layer 8 of the rear side overlap. In this area, which forms the intersection of the first and second subarea, both black color layers 7, 8 have a reduced layer thickness, such that a uniform opacity of the security element 3 results in transmitted light in the entire overlap area. Of course, the inventive concept is also realized with color layers 7,8, which have no reduced layer thickness in the overlap region. Such an embodiment (not in Fig. 2a shown) with a constant layer thickness of the ink layer 7, 8 is technically easier to manufacture and also visually attractive to the viewer.

Thus, three areas of the overlapping area of the optically variable color layers with different structures and correspondingly different structuring possibilities result. In the in Fig. 2a On the left side shown area is a black color layer 7 only on the front side of the transparent substrate 4. In the in Fig. 2a On the right side shown area is a black ink layer 8 only on the back of the transparent substrate 4. In the in Fig. 2a centrally shown area is located both on the front and on the back of the transparent substrate 4 each have a black color layer 7, 8, optionally with a reduced layer thickness.

In the three areas of the overlap area, a laser treatment now takes place, the result of which in Fig. 2b is shown in cross section. For the optically variable ink layers 5 and 6 optically variable colors are used which do not interact with the laser radiation and are transparent to them. In contrast, an interaction takes place with the black color layers 7 and 8. In this case, the black color layers 7 and 8 are ablated in the region of the laser irradiation and the overlying optically variable color layers 5 and 6 are then likewise removed. In the in Fig. 2b shown left area thus a recess in the black color layer 7 and the overlying front side layer 5 is generated. In the in Fig. 2b On the right-hand side, a recess is provided in the black ink layer 8 and the backside layer 6 (starting from the transparent substrate 4). In the in Fig. 2b In the central region, recesses are created in both black color layers 7 and 8 and the respective overlying front side layer 5 and the back side layer 6.

In Fig. 2c is the impression created by a viewer in the transmitted light. The entire overlap area appears at the locations where laser treatment has not taken place, in a uniform shade of gray, which depends on the opacity of the black color layer 7 and 8. In the central area, the transparent substrate is completely exposed by the laser irradiation. It therefore appears white in transmitted light (with incident white light). Because of the low degree of coverage of the optically variable colors used for the front side layer 5 and the rear side layer 6, the laser-treated areas in the left and in the right area of the security element also appear white in transmitted light.

In Fig. 2d is a plan view of the front shown in front of a white background. In the non-laser-treated areas, the color and color behavior of the front-side layer 5 are perceived because either the black color layer 7 or the black color layer 8 provides a suitable black background for the front-side layer 5. This is absent in the laser-treated areas and because of the low coverage of the optically variable colors used for the front-side layer 5 and the back-side layer 6, their color recedes against a white background. Thus, the white background can be clearly seen in all three laser-treated areas.

In Fig. 2e again a top view is shown on the front, but this time in front of a black background. This black background is clearly visible in the central, laser-treated area through the see-through window created there. In the right-hand area, the black background now forms a suitable background for the front-side layer 5, which is why this area appears uniform with the surrounding area, so that the laser-treated area is no longer recognizable. In In the left-hand area, the black background forms a suitable background for the optically variable backsheet layer 6, which is why the color and the color behavior of the backsheet layer can be recognized in this area.

Corresponding effects arise in plan view of the back of the security element in front of a black background, as in Fig. 2f is shown. In the non-laser-treated areas, the color and the color behavior of the backside layer 6 can be perceived, since here the black color layers 7 and 8 of the security element 3 represent a suitable background. In the central, laser-treated area, the black background is clearly visible again. In the left-hand area, the black background now forms a suitable background for the rear-side layer 6, which is now at the front, which is why the left-hand area in FIG Fig. 2f appears uniform and the laser-treated area is not visible. In the right-hand area, on the other hand, the black background forms a suitable background for the front side layer 5, which is now at the back, which is why the color and the color behavior of the front-side layer 5 can be seen here in the laser-treated area.

If the laser-treated areas are information-sensitive, this can be used to generate a digital change of information, as is the case in the FIGS. 3a to 3c shown variant of the first embodiment is shown. The structure of the variant corresponds to that of the first embodiment with the difference that the laser-treated areas are information-related recesses. The information "50 EURO" arranged in the left-hand area is a recess in the front-side layer 5 and the color layer 7 arranged on the front side. The information "*****" arranged in the central area is a see-through window. That in the right Area arranged hand symbol is a recess in the backside layer 6 and arranged on the back of black paint layer. 8

The three different pieces of information are in transmitted light Fig. 3a clearly recognizable. The Fig. 3a corresponds with respect to the observation of the Fig. 2c ,

In Fig. 3b the front is shown in reflected light against a black background. The Fig. 3b corresponds with respect to the observation of the Fig. 2e , Accordingly, the non-laser-treated areas appear in the color of the front-side layer 5. The information arranged in the left-hand area appears in the color of the back-side layer 6, the information arranged in the central area appears black, while the information arranged in the right-hand area disappears.

In Fig. 3c the back is shown in reflected light against a black background. The Fig. 3c corresponds with respect to the observation of the Fig. 2f , Accordingly, the non-laser-treated areas appear in the color of the backside layer 6. The information arranged in the left area disappears, the information arranged in the central area appears black, while the information arranged in the right-hand area appears in the color of the front-side layer 6.

In a first embodiment of the first embodiment, the color Colorcrypt Gold is used for the front side layer and the color Colorcrypt Green-Lilac for the backside layer.

In a second embodiment of the first embodiment, the color STEP is copper red for the front layer and the color STEP green / blue for the back layer.

In a third embodiment of the first embodiment, the color Colorcrypt Gold is used for the front side layer and the color STEP Green / Blue for the backside layer.

In a fourth embodiment of the first embodiment, the color STEP is copper red for the front layer and the color STEP green / blue for the back layer.

In a fifth embodiment of the first embodiment, the color STEP is copper red for the front layer and the color STEP green / blue for the back layer.

Other combinations of optically variable colors are possible.

In the FIGS. 4a to 4f a second embodiment of the security element is shown. In Fig. 4a is a cross section of the security element shown before the laser processing. On a transparent substrate 4, an optically variable front side layer 5 and an optically variable backside layer 6 are applied. For the optically variable ink layers 5 and 6, OVI pigment paints are used which exhibit high coverage and low light transmittance and are nearly opaque. These colors do not need a black background.

In Fig. 4b The security element is shown in cross-section after four different laser treatments in four different areas. By doing first in Fig. 4b In the left-hand area, the laser treatment results in the destruction of the OVI pigments in the front-side layer 5 and thus in the removal of the color, while the layer itself remains on the substrate 4. In a second area (second area from the left in Fig. 4b In a third portion (third area from the left), the laser treatment results in ablation of the front surface layer 5 and destruction of the OVI pigments in the backside layer 6. In a fourth area (in Fig. 4b shown right), the laser treatment leads to an ablation of the front side layer 5 and the backside layer 6, so that a see-through window is created.

In Fig. 4c is that in Fig. 4b illustrated security element shown in transmitted light. In this case, the color of the optically variable ink layers 5, 6 returns and the security element appears colorless and gray, possibly in different shades of gray. In the non-laser-treated area, a gray tone results, which is determined by the light transmittance, that is, the opacity, the front-side layer 5, and the back-side layer 6. This results in a dark gray tone. In the first laser-treated area, the destruction of the OVI pigments can not be detected, since the color of the surrounding area in the transmitted light recedes anyway. Accordingly, in this range, the gray tone is also determined by the opacity of the front-side layer 5 and the back-side layer 6, for which reason the first laser-treated region can not be seen in the transmitted light. On the other hand, in the second and third regions, the brightness is determined only by the opacity of the back surface layer 6, and therefore the same lighter gray tone appears in these regions. On the other hand, the see-through window in the fourth area appears bright, corresponding to the transparency of the substrate 4.

In Fig. 4d is a plan view of the front of the security element when viewed in front of a white background shown. In the non-laser-treated areas, the color and color behavior of the front-side layer 5 can be observed. The first and the third area appear gray because of the destruction of the respective OVI pigments made there. In contrast, in the second region, the backside layer 6 can be observed, which is why the color and the color behavior of the backside layer 6 result in this area. The fourth area shows the white background behind the see-through window.

In Fig. 4e in turn, the top view of the front of the security element 3 is shown, but in front of a black background. This is clearly visible in the see-through window of the fixed area. In the first, second and third areas, however, the color perception corresponds to that perception of color in front of a white background. While the first and third areas might appear darker in gray, they still have the same shade of gray.

In Fig. 4f is a plan view of the back of the security element in front of a black background. This is again clearly visible in the see-through window of the fourth area. In the third area, a gray hue is again formed, whereas in the first and second subarea, a change has taken place only in the front side layer which is now behind in the viewing direction, which is not perceived because of the high degree of coverage of the OVI color used for the backsheet.

By means of a suitable combination of the different areas, different information can thus be generated when the security element 3 is viewed in transmitted light, reflected light, both from the front side and from the rear side and also from different backgrounds, thus producing a digital information change in the case of an information-based structure be like this in the FIGS. 5a to 5c shown variant of the second embodiment is shown.

In Fig. 5a the different areas of the security element 3 are shown. The area 9 corresponds to the first area Fig. 4b , Here only the color behavior of the front side layer 5 was changed. The area 10 corresponds to the second area Fig. 4b , Here, the front side layer 5 was ablated. The area 11 corresponds to the third area Fig. 4b , Here, the front-side layer 5 was ablated and the color behavior of the backside layer 6 changed.

In Fig. 5b the security element 3 is shown in transmitted light. The directly adjacent areas 10 and 11 are perceived with the same gray tone and thus as a uniform area, while the area 9 is not recognizable.

In Fig. 5c the front of the security element 3 is shown in reflected light. The directly adjacent areas 9 and 11 are perceived with the same shade of gray and thus as a uniform area, while in the area 10 the color and color behavior of the backside layer 6 is perceived.

Claims (7)

1. A security element (3) for a data carrier (1), comprising a transparent or translucent substrate (4) with a front side and a back side, an optically variable front-side layer (5) arranged on the front side and an optically variable back-side layer (6) arranged on the back side, wherein the front-side layer and the back-side layer are respectively based on an ink that is strongly opaque, optically variable, laser-radiation absorbing and ablatable by laser radiation, and are arranged in mutually overlapping fashion in an overlap region, and a first structuring (9, 10, 11) in the form of a recess is formed only in the optically variable front-side layer (5), a second structuring in the form of a recess is formed only in the optically variable back-side layer (6), and a third structuring is formed within the overlap region in the front-side layer (5) and in the back-side layer (6).
2. A security element (3) for a data carrier (1), comprising a transparent or translucent substrate (4) with a front side and a back side, an optically variable front-side layer (5) arranged on the front side and an optically variable back-side layer (6) arranged on the back side, wherein the front-side layer and the back-side layer are respectively based on an ink that is weakly opaque, optically variable and transparent for laser radiation, and are arranged in mutually overlapping fashion in an overlap region, wherein between the front-side layer (5) and the front side of the substrate (4) in at least a first partial region of the overlap region, there is formed a first dark or black, laser-ablatable ink layer (7), and between the back-side layer (6) and the back side of the substrate (4) in at least a second partial region of the overlap region, there is formed a second dark or black, laser-ablatable ink layer (8), wherein

   - a first structuring (9, 10, 11) in the form of a recess is formed only in the optically variable front-side layer (5) and the dark or black ink layer (7) in the region of the structuring is formed only on the front side of the substrate (4);

   - a second structuring in the form of a recess is formed only in the optically variable back-side layer (6) and the dark or black ink layer (8) in the region of the structuring is formed only on the back side of the substrate; and

   - a third structuring is formed within the overlap region in the front-side layer (5) and in the back-side layer (6) and in the region of the structuring there is formed a dark or black ink layer (7, 8) respectively on the front side and the back side of the substrate.
3. The security element (3) according to claim 2, characterized in that the first partial region extends over the complete overlap region, the second partial region extends over the complete overlap region or that the union of the first and the second partial region extends over the complete overlap region.
4. The security element (3) according to any of the preceding claims, characterized in that the front-side layer (5) and the back-side layer (6) consist of the same optically variable ink, or that the front-side layer and the back-side layer consist of different optically variable inks of the same type.
5. The security element (3) according to any of the preceding claims, characterized in that the structuring (9, 10, 11) is an information-carrying structuring consisting of one or several alphanumerical characters, of a motif or a graphic symbol.
6. A data carrier (1) comprising a security element (3) according to any of the preceding claims, wherein the security element preferably forms part of a window region (2) of the data carrier or forms a window region of the data carrier.
7. A method for manufacturing a security element (3) according to any of the claims 1 to 5 for a data carrier (1), comprising the steps of:

   - making available a transparent or translucent substrate (4) with a front side and a back side,

   - applying an optically variable front-side layer (5) to the front side and an optically variable back-side layer (6) to the back side, such that an overlap region is created in which the front-side layer and the back-side layer are arranged in overlapping fashion, and

   - forming a structuring (9, 10, 11) in the form of a recess in the optically variable front-side and back-side layers by laser ablation.

Images