EP2091756B1 - See-through security element with microstructures - Google Patents

Description

The invention relates to a see-through security element for security papers, documents of value and the like having at least one microstructure with a viewing angle-dependent visual appearance.

Data carriers, such as valuables or identity documents, or other valuables, such as branded articles, are often provided with security elements for the purpose of security, which permit verification of the authenticity of the data carriers and at the same time serve as protection against unauthorized reproduction. The security elements may be in the form of, for example, a security thread embedded in a banknote, a tearing thread for product packaging, an applied security strip, a cover sheet for a banknote having a through opening or a self-supporting transfer element, such as a patch or label after its manufacture is applied to a document of value.

Security elements with viewing-angle-dependent effects play a special role in the authentication of authenticity since they can not be reproduced even with the most modern copiers. The security elements are thereby equipped with optically variable elements that give the viewer a different image impression under different viewing angles and, for example, show a different color or brightness impression and / or another graphic motif depending on the viewing angle.

document WO 2006/087138 A1 relates to a security element for securing valuables with a first and a second authenticity feature. The first authentication feature comprises a first arrangement having a plurality of focusing elements which are present in a first grid, and a second arrangement having a multiplicity of microscopic structures which are present in a second grid. The first and second arrangements are arranged such that the microscopic structures of the second arrangement can be seen in magnification when viewed through the focusing elements of the first arrangement.

US 3,887,742 concerns a copy protection film for the security of security papers and documents of value. For this purpose, the device has a substrate with a plurality of spaced-apart teeth, which are defined by the teeth valleys, which may be partially filled with a black ink.

DE 42 26 906 A1 relates to an anti-copy film for originals or documents, consisting of a transparent film material having a plurality of spaced-apart, at least partially opaque and optionally reflective areas. The areas are arranged as a cover on the film surfaces in such a way that the information of an underlying original is concealed in an approximately vertical viewing direction and the information is visible in the direction of a given viewing angle.

From documents DE 44 21 407 C1 a security element for securing value documents with a microstructure is known, wherein the microstructure is formed from an arrangement of a plurality of structural elements and at least partial areas of the microstructure are provided with a coating, for example in the form of a metal layer.

document DE 34 22 908 A1 relates to a stamping foil which, in addition to a writable marking layer, has a layer with a structurally effective structure, in particular in the form of a hologram. The embossing foil may be provided with a magnetic layer allowing the storage of variable data.

Proceeding from this, the present invention seeks to provide a see-through security element of the type mentioned, which avoids the disadvantages of the prior art. In particular, the see-through security element as a security feature have an easily recognizable optical information that offers a high protection against counterfeiting and does not require special lighting conditions for the authenticity check.

This object is achieved by the see-through security element having the features of the main claim. A security paper, a data carrier and a corresponding manufacturing method are specified in the independent claims. Further developments of the invention are the subject of the dependent claims.

According to the invention, in a generic see-through security element, the at least one microstructure is formed from an arrangement of a multiplicity of structural elements with a characteristic structure spacing of 1 μm or more. In addition, the see-through security element according to the invention has a total thickness of 50 microns or less.

The inventive arrangement of a plurality of structural elements may be a regular, irregular or regionally regular arrangement. The invention thus encompasses any arrangement of a multiplicity of structural elements which has a structure spacing of 1 μm or more.

The see-through security element preferably has a transparent or translucent substrate and a marking layer applied to the substrate, which contains the at least one microstructure.

In principle, any transparent or translucent substrate can be used for the see-through security element. In this case, the light transmittance must be at least so large that in the transmitted light the viewing angle-dependent appearance can be perceived by the viewer. The use of an additional means of illumination to improve the visibility of the appearance by the viewer is conceivable, although the thickness of the material is chosen according to the invention so that the optically variable appearance of the see-through security element is possible without tools.

Accordingly, paper, in particular cotton vellum paper, is fundamentally conceivable as a substrate. Of course, it is also possible to use paper which contains a proportion of polymeric material in the range of 0 <x <100% by weight.

However, it is particularly preferred if the substrate is a plastic, in particular a plastic film, for. As a film of polyethylene (PE), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polyethylene naphthalate (PEN), polypropylene (PP) or polyamide (PA) is. The film may also be monoaxially or biaxially stretched. The stretching of the film, inter alia, leads to it receiving polarizing properties that can be used as another security feature. The tools required for exploiting these properties, such as polarization filters, are known to the person skilled in the art.

It may also be expedient if the substrate is a multilayer composite, in particular a composite of several different films (composite composite). The films of the composite can be z. B. be formed from the aforementioned plastic materials. Such a composite is characterized by an extremely high stability, which is for the durability of the security element of great advantage. Also, these composite materials can be used in certain climatic regions of the earth with great advantage.

All materials used as a substrate may have additives which serve as authenticity features. It is primarily to think of luminescent, which are preferably transparent in the visible wavelength range and in the non-visible wavelength range by a suitable tool, for. B. a UV or IR radiation emitting radiation source, can be excited to produce a visible or at least detectable luminescence. Of course, the marking layer, ie z. For example, the paints or paints used for the microstructure, the additives mentioned above.

In an advantageous variant of the invention, the marking layer of the see-through security element represents a colored embossing lacquer layer, the layers of which leave it during the embossing, d. H. unembossed areas form the structural elements of the at least one microstructure.

In another, likewise advantageous variant of the invention, the marking layer of the see-through security element is a transparent or translucent embossing lacquer layer which has embossed and subsequently filled with colored material depressions which form the structural elements of the at least one microstructure. The depressions can have any desired shape or outline shape. For these recesses, the term "trenches" is used below.

In a further, likewise advantageous variant of the invention, the marking layer of the see-through security element is a printing layer with areas of high transparency and areas of low transparency, wherein the areas of low light transmission form the structural elements of the at least one microstructure.

In accordance with yet another advantageous variant of the invention, the marking layer of the see-through security element is a microtitle printing layer with areas of high transparency and areas of low light transmission, the areas of low light transmission forming the structural elements of the at least one microstructure. The properties of such microfill printing layers and methods for their preparation are described in more detail below.

The see-through security element preferably has a total thickness of 20 μm or less, more preferably from 3 μm to 10 μm. The structural elements of the microstructure expediently have a characteristic structure spacing of 5 μm or more. Furthermore, according to an advantageous embodiment, it is provided that the structural elements each have a structure size of 1 μm or more, preferably of 3 μm or more. For the profile of the structural elements, height-to-width ratios of about 1: 5 to about 5: 1 are considered to be advantageous and from about 1: 1 to about 5: 1 are considered to be particularly advantageous.

According to a development of the invention, at least one of optionally a plurality of microstructures is formed by a lamellar structure of a plurality of substantially parallel lamellae. The visual appearance of the microstructures then changes as you rotate or tilting the security element by the relative to the parallel slats changing direction of view.

In the security element, it is particularly preferable to provide a plurality of microstructures formed by lamellar structures, which differ in one or more of the parameters lateral orientation, color, width, height, relief shape and spacing. The differing lamellar structures can advantageously be arranged in the form of patterns, characters or a coding which appear, change or disappear, in particular when the security element is turned or tilted.

According to another development of the invention, at least one of optionally a plurality of microstructures is formed by a multiplicity of recesses with an increased transparency in a marking layer, so that the visual appearance of the microstructure when the security element is rotated or tilted by the viewing direction changing relative to the recesses changed. The plurality of depressions can be arranged with advantage in the form of patterns, characters or a coding, which appear in particular when turning or tilting the security element, change or disappear.

According to the invention, the structural elements are provided in partial regions with an opaque, transparent, semitransparent, reflective or absorbing coating. The coating is multi-layered and designed as a thin-film element with a color shift effect, ie optically variable. As an example of single-layer thin-film elements, coatings of so-called pearlescent pigments are to be mentioned in the first place. Multilayer thin-film elements are generally referred to as purely dielectric thin-film structures or metallic / dielectric multilayer structures formed. In the multilayer thin-film elements, three-layered interference layer structures (metal / dielectric three-layer structure) are currently particularly preferred.

Furthermore, the structural elements may be provided in partial areas with a metallic coating, with a light-absorbing moth-eye structure or else with a diffractive structure which diffracts substantial parts of the incident light away from the viewer.

It is particularly preferred if the structural elements have an asymmetrically arranged coating, moth-eye structure or diffractive structure. In the case of a coating, the asymmetric arrangement on the structural elements z. B. be achieved by a Schrägbedampfung.

In a further advantageous embodiment of the invention, the see-through security element has a transparent or translucent substrate with a first and an opposite second surface, wherein a transparent mask is applied to the first surface as a microstructure. A congruent see-through mask is applied to the second surface at a predetermined lateral offset of 100 μm or less.

The see-through mask preferably includes a motif in the form of patterns, characters, or a code that is visually discernible only at a particular viewing angle.

With particular advantage, the see-through masks are each formed by an opaque layer with translucent openings, wherein the openings have a size of less than 200 microns, preferably a size of about 3 microns to about 100 microns, and a motif in the form of patterns, characters or a Form coding. The offset of the see-through mask is tuned to the size of the openings and the thickness of the substrate, and is preferably substantially less than 100 μm, for example, only about 20 μm or less, or even only about 10 μm or less.

The see-through security element according to the invention can advantageously have further security elements in order to further increase the security against counterfeiting. For example, the additional security element may be a transparent or semitransparent coating, which is constructed in one or more layers. In the case of the additional coatings, optically variable layers, in particular interference layers, can be used to advantage. The person skilled in the art is sufficiently familiar with purely dielectric thin-film structures, metallic / dielectric multilayer structures and the materials used in each case for the layers of these interference layer systems. Of course, an additional security element can also be regarded as part of the see-through security element according to the invention, in particular if, as in the case of the above-mentioned thin-film elements with color shift effect, the further security element (interference layer structure) is arranged on or under the microstructure. In any case, the synergistic interaction of the microstructure with the additional security element results in a significant increase in the security against counterfeiting and an enhancement of the visual appearance of the see-through security element according to the invention. The additional coating may be superimposed or underlaid by the microstructure of the see-through security element. A particularly impressive, additional optically variable effect can, for. Example, be obtained when the additional optically variable coating between the transparent or translucent substrate and the microstructure-containing marking layer is arranged. The synergistic interaction of the optically variable microstructure and the additional optically variable coating considerably increases the security against forgery of the see-through security element.

The additional coating may have at least partially machine readable properties. The additional coating also advantageously has magnetic, electrically conductive or luminescent properties.

The additional security element may, however, advantageously also be diffraction structures, kinematic structures or matt structures. For example, holograms may be used as diffractive structures provided with a transparent or semitransparent metal layer or high refractive dielectric coating. Even with these additional security elements, the security against counterfeiting is particularly increased by the fact that the additional security element of the microstructure of the see-through security element is either superimposed or underlaid, or is arranged practically without spatial distance next to the microstructure.

The additional security element can also be in the form of a liquid-crystal layer, in particular as a cholesteric or nematic liquid-crystal layer, or in the form of a multilayer arrangement cholesteric and / or nematic liquid crystals. The formation of the additional security element as a pressure element is possible. The printing element may advantageously contain a color that absorbs and / or emits in the infrared (IR) or ultraviolet wavelength range (fluorescence or phosphorescence), which enables machine detection. Also, the printing element may contain optically variable or iridescent pigments.

Finally, a non-diffractive or diffractive lens structure, for. As a Fresnel lens arrangement, as an additional security element with the microstructure according to the invention can be combined.

The invention also encompasses a method for producing a see-through security element of the type described, in which the see-through security element is provided with at least one microstructure with a visual appearance dependent on viewing angle, which comprises at least one microstructure of an arrangement of a multiplicity of structural elements with a characteristic structural spacing of 1 μm or more, and the see-through security element having a total thickness of 50 μm or less is formed.

The at least one microstructure is formed in the form of a regular, irregular or partially regular arrangement of a plurality of structural elements.

In the method according to the invention, a marking layer is advantageously applied to a transparent or translucent substrate in which the at least one microstructure is formed.

According to a variant of the method, a colored embossing lacquer layer is applied as a marking layer, for example printed on it, and the embossing lacquer layer is structured by means of embossing techniques in such a way that the embossed standstocks, ie. H. unembossed areas form the structural elements of the at least one microstructure.

In another variant of the method, a transparent or translucent embossing lacquer layer is applied as the marking layer, for example printed on it, and recesses are introduced into the embossing lacquer layer by means of embossing techniques. The depressions in the embossing lacquer layer are then filled with colored material, for example a printing ink, so that the filled depressions form the structural elements of the at least one microstructure. The depressions can have any shape and are also referred to below as "trenches".

In a further variant of the method, a printing layer having areas of high light transmission and areas of low light transmission is applied as the marking layer, the areas of low light transmission forming the structural elements of the at least one microstructure.

In principle, various methods are conceivable with which an inventive see-through security element can be produced. Therefore, it will not be discussed further in detail on the known methods.

1. a) eine Werkzeugform bereitgestellt wird, deren Oberfläche eine Anordnung von Erhebungen und Vertiefungen in Gestalt der gewünschten Mikrostruktur aufweist,
2. b) die Vertiefungen der Werkzeugform mit einem härtbaren farbigen oder farblosen Lack befüllt werden,
3. c) das Substrat für eine gute Verankerung des farbigen oder farblosen Lacks vorbehandelt wird,
4. d) die Oberfläche der Werkzeugform mit dem Substrat in Kontakt gebracht wird,
5. e) der in Kontakt mit dem Substrat stehende Lack in den Vertiefungen der Werkzeugform gehärtet und dabei mit dem Substrat verbunden wird, und
6. f) die Oberfläche der Werkzeugform wieder von dem Substrat entfernt wird, so dass der mit dem Substrat verbundene, gehärtete Lack aus den Vertiefungen der Werkzeugform gezogen wird.

As a particularly advantageous variant of the method, however, the micro-deep-pressure method should be mentioned here, in which the microstructure is applied to the substrate by

1. a) a tool mold is provided whose surface has an arrangement of elevations and depressions in the form of the desired microstructure,
2. b) the recesses of the mold are filled with a curable colored or colorless varnish,
3. c) the substrate is pretreated for a good anchoring of the colored or colorless lacquer,
4. d) the surface of the mold is brought into contact with the substrate,
5. e) the lacquer standing in contact with the substrate is hardened in the depressions of the mold and thereby connected to the substrate, and
6. f) the surface of the tool mold is removed again from the substrate, so that the hardened varnish bonded to the substrate is pulled out of the depressions of the tool mold.

For further embodiments of this micro-gravure printing method and the advantages associated therewith, reference is made to the German patent application 10 2006 029 852.7 directed.

For the microtip printing method, it is particularly preferred if the depressions of the mold are filled in step b) with a radiation-curing lacquer and the lacquer in step e) by applying Radiation, especially with UV radiation, is cured. Furthermore, the paint can advantageously be pre-cured in the recesses of the tool mold prior to contacting the step d).

Advantageously, the microstructure of the mold is formed by microstructure elements having a line width between about 1 μm and about 10 μm. It is also preferred if the microstructure of the tool mold is formed by microstructure elements with a structure depth between about 1 μm and about 10 μm, preferably between about 1 μm and about 5 μm.

In an expedient variant of the method according to the invention, the see-through security element is produced with a total thickness of 20 μm or less, preferably from 3 μm to 10 μm.

Furthermore, at least one microstructure may be formed by a lamellar structure of a plurality of substantially parallel lamellae.

Alternatively, however, it is also conceivable that at least one microstructure in a marking layer is formed by a multiplicity of depressions with an increased light transmission.

According to the invention, the structural elements are provided in subregions with an opaque, transparent, semitransparent, reflective or absorbing coating, in particular with a metallic coating, a moth-eye structure or a diffractive structure.

In another advantageous embodiment of the method according to the invention, a transparent or translucent substrate having a first surface and an opposing second surface is provided, a see-through mask is applied to the first surface as a microstructure, and a congruent see-through mask with a predetermined lateral offset of 100 μm or less applied to the second surface.

The transparency masks are applied simultaneously to the opposing surfaces of the substrate in an advantageous process management. Alternatively, the see-through masks may also be sequentially applied to the opposing surfaces of the substrate. Particularly preferably, the see-through masks are applied to the opposite sides of the substrate by means of the micro-gravure printing technique described above.

The invention also includes a security paper for the production of security or value documents, such as banknotes, checks, identity cards, certificates or the like, and a data carrier, in particular a branded article, a document of value or the like, wherein the security paper or the data carrier with a security element of described type are equipped.

The described measures ensure that the see-through security elements according to the invention are thin enough to be used in the field of documents of value and that they can be produced economically in the required high quantities with the proposed method. The structure spacing of 1 μm or more, or the structure size of 1 μm or more, ensures that the microstructures are largely achromatic, ie without disturbing color splitting. The optically variable effects can therefore be easily recognized even under unfavorable lighting conditions.

With the see-through security element according to the invention, it is advantageously possible to achieve a series of so-called movement effects which, on the one hand, further improve counterfeiting security and, on the other hand, are visually very appealing to the observer. Characterized in that the see-through security element is subdivided into a plurality of areas in which microstructures are arranged with different viewing angle-dependent tilt effect, can be achieved motion effects, which are also referred to as flip, running or pumping effects. In these effects, the viewer perceives an apparent movement of the observed structure when tilting the see-through security element due to the changing in a defined manner optical impression.

Further embodiments and advantages of the invention are explained below with reference to the figures. For better clarity, a scale and proportioned representation is omitted in the figures.

Fig. 1

eine schematische Darstellung einer Banknote mit einem erfindungsgemäßen Durchsichtssicherheitselement,

Fig. 2

einen Querschnitt durch ein erfindungsgemäßes Durchsichtssicherheitselement mit Jalousiebild,

Fig. 3

einen Querschnitt durch ein Durchsichtssicherheitselement mit Jalousiebild, bei dem die Lamellen in Trapezform ausgebildet sind,

Fig. 4

in (a) und (b) Zwischenschritte bei der Herstellung eines Durchsichtssicherheitselements nach einem Ausführungsbeispiel der Erfindung,

Fig. 5

eine schematische Aufsicht auf ein Durchsichtssicherheitselement nach einem weiteren Ausführungsbeispiel der Erfindung,

Fig. 6

ein Ausschnitt der Banknote der Fig. 1 mit einem erfindungsgemäßen Durchsichtssicherheitselement, in dem die Denomination der Banknote als optisch variables Element wiederholt ist,

Fig. 7

einen Querschnitt durch ein erfindungsgemäßes Durchsichtssicherheitselement mit einer Markierungsschicht, die ein Muster aus Vertiefungen enthält,

Fig. 8

beispielhaft einige Gestaltungen für Vertiefungen, die der Markierungsschicht jeweils eine definierte erhöhte Lichtdurchlässigkeit verleihen, wobei (a) Vertiefungen verschiedener Breite und Tiefe und (b) Vertiefungen mit verschiedenen Umrissformen und Größen zeigt,

Fig. 9

ein erfindungsgemäßes Durchsichtssicherheitselement mit einer symmetrischen Lamellenstruktur, die mit einer asymmetrischen opaken Beschichtung versehen ist,

Fig. 10

ein Sicherheitselement ähnlich dem der Fig. 9, bei dem die Strukturelemente weitere Flächen unterschiedlicher Neigung aufweisen,

Fig. 11

ein Sicherheitselement ähnlich dem der Fig. 9 und Fig. 10 mit Oberflächenstrukturen mit Flächen unterschiedlicher Neigung und einer symmetrischen Metallbeschichtung, wobei das Durchsichtsbild unter senkrechtem Auftreffwinkel des Metalldampfes wirksam wird,

Fig. 12

ein Sicherheitselement ähnlich dem der Fig. 9 bis Fig. 11, bei dem die Strukturelemente in Teilbereichen mit lichtabsorbierenden Mottenaugenstrukturen versehen sind,

Fig. 13

ein Durchsichtssicherheitselement mit auf gegenüberliegenden Oberflächen eines Substrats mit einem vorbestimmten Versatz angeordneten Durchsichtsmasken, wobei das Motiv der Durchsichtsmasken nur aus einer bestimmten Betrachtungsrichtung in Durchsicht visuell erkennbar ist (a), während das Durchsichtssicherheitselement aus anderen Betrachtungsrichtungen opak erscheint (b),

Fig. 14

eine schematische Aufsicht auf ein Durchsichtssicherheitselement nach noch einem weiteren Ausführungsbeispiel der Erfindung, und

Fig. 15

einen Querschnitt durch ein weiteres erfindungsgemäßes Sicherheitselement, das mit einer optisch variablen Beschichtung versehene Mikrostrukturelemente aufweist.

Show it:

Fig. 1

a schematic representation of a banknote with a see-through security element according to the invention,

Fig. 2

a cross section through an inventive see-through security element with blinds,

Fig. 3

a cross section through a see-through security element with blind shape, in which the slats are formed in a trapezoidal shape,

Fig. 4

in (a) and (b) intermediate steps in the production of a see-through security element according to an embodiment of the invention,

Fig. 5

a schematic plan view of a see-through security element according to another embodiment of the invention,

Fig. 6

a section of the banknote of Fig. 1 with a see-through security element according to the invention, in which the denomination of the banknote is repeated as an optically variable element,

Fig. 7

a cross-section through an inventive see-through security element with a marking layer containing a pattern of wells,

Fig. 8

by way of example, some designs for recesses which each give the marking layer a defined increased light transmittance, wherein (a) shows recesses of different width and depth and (b) recesses with different outline shapes and sizes,

Fig. 9

an inventive see-through security element with a symmetrical lamellar structure, which is provided with an asymmetrical opaque coating,

Fig. 10

a security element similar to the one Fig. 9 in which the structural elements have further surfaces of different inclination,

Fig. 11

a security element similar to the one FIGS. 9 and 10 with surface structures with surfaces of different inclination and a symmetrical metal coating, the transparency being effective at a normal angle of incidence of the metal vapor,

Fig. 12

a security element similar to the one Fig. 9 to Fig. 11 in which the structural elements are provided in partial regions with light-absorbing moth-eye structures,

Fig. 13

a see-through security element having see-through masks on opposite surfaces of a substrate at a predetermined offset, the subject of the see-through masks being visually discernible only from a particular viewing direction (a), while the see-through security element appears opaque from other viewing directions (b),

Fig. 14

a schematic plan view of a see-through security element according to yet another embodiment of the invention, and

Fig. 15

a cross section through another inventive security element having provided with an optically variable coating microstructure elements.

The invention will now be explained using the example of a security element for a banknote. Fig.1 shows a schematic representation of a banknote 10 with a see-through security element 12 with a blind image, which is arranged over a see-through area 14, such as a window area or a through opening of the banknote 10. The through opening may after the preparation of the substrate of the banknote 10, z. B. be produced by punching or laser beam cutting. But it is also conceivable to produce the through opening during the production of the banknote substrate, as shown in the WO 03/054297 A2 is described. In that regard, the disclosure of the WO 03/054297 A2 excluded in the present application.

As explained in more detail below, the shutter image of the see-through security element 12 shows a different visual appearance, depending on the viewing direction. For example, the security element 12 may appear structureless and bright when viewed vertically, while dark marks in the form of patterns, characters or encodings emerge when the banknote is tilted or rotated. In other designs, the markings are already visible when viewed vertically and disappear or change when turning or tilting the bill.

Essential for the use of the see-through security element 12 in the banknote 10 or other securities is its small overall thickness of less than 50 microns. Preferably, the see-through security element even has an even smaller layer thickness of only about 20 μm or even only about 3 μm to 10 μm. The invention provides several possibilities to produce visually appealing shutter images with such low Gesamtdikken.

A first possibility to produce a thin see-through security element with blind image is based on the cross section through the security element 12 in Fig. 2 illustrated. In the exemplary embodiment shown, first a thin layer of a colored embossing lacquer 22 is applied to a transparent substrate 20. The embossing lacquer layer 22 is then structured by means of embossing techniques in such a way that a lamellar structure is formed from a multiplicity of substantially parallel, individually standing lamellae 24.

When viewed parallel to the slats 24, that is, in the direction of view 26, the security element 12 appears to be substantially transparent when viewed. On the other hand, if the observer tilts the security element 12 out of the parallel viewing direction, for example in the direction of view 28, then the lamella 24 blocks the view, ie. H. the security element 12 appears opaque to the viewer.

The lamellar structure represents a regular arrangement of a plurality of lamellae 24 with a characteristic structure spacing, which according to the invention is 1 μm or more, so that the lamellae 24 do not cause color splitting in the visible spectral range by wavelength-dependent diffraction effects. In the embodiment of Fig. 2 is the distance between adjacent slats 24 at 5 microns, the structure size, ie the width of the individual slats at 2.5 microns. The height of the embossed fins 24 is 5 microns, so that there is a height-to-width ratio of 2: 1. In general, this ratio is between about 1: 5 and about 5: 1, preferably around or above 1: 1 up to about 5: 1.

That in the Fig. 2 shown rectangular profile of the fins 24 represents an idealization of the actual conditions in an embossed lacquer layer. In In practice, the transitions at the top and bottom edges of the slats are rounded to some extent and the edges of the slats 24 are not completely vertical. Also, a targeted design of the blades 24 in trapezoidal shape with flanks of a different slope of 90 °, such as in Fig. 3 shown, comes into consideration. The slope of the flanks is preferably between about 70 ° and about 85 °. Again, in practice, the transitions at the top and bottom edges of the slats are not completely sharp, but slightly rounded.

The brightness of the security element 12 in view can be adjusted by the ratio of slat width to slat spacing in a wide range. Also, the color impression can be selected largely freely by the color of the embossing lacquer and the transparent or translucent substrate.

Instead of a colored embossing lacquer 22, a layer of a colorless embossing lacquer 32 may also be applied to the substrate 20, as in FIG Fig. 4 shown. The colorless embossing lacquer 32 is then first structured with an embossing tool in such a way that depressions or trenches 34 in the form of the desired shade image arise, as in FIG Fig. 4 (a) illustrated. Subsequently, the recesses 34 are filled with color 36, as in Fig. 4 (b) shown to produce a shutter image with the desired color impression.

The use of embossing technology allows in addition to the production of Venetian blind films with a very small total thickness of 50 microns or less, also in a simple way the generation of locally differently oriented lamellar structures on the same security element. Fig. 5 shows by way of illustration a schematic plan view of a see-through security element 40 according to a further exemplary embodiment of the invention. The security element 40 has in a first region 42 a first lamellar structure, the parallel lamellae 44 in the view of Fig. 5 run vertically. In second areas 46, a second lamellar structure is provided which has the same lamella width and the same lamella spacing as the first lamellar structure, but whose likewise parallel lamellae 48 are oriented at right angles to the lamellae 44.

When viewed vertically, the areas 42 and 46 differ in their visual appearance due to their equal area coverage practically not, the security element 40 appears structureless and bright. If the security element now tilted by a certain angle to the right or left (tilt direction 50), so the tilted louvers 44 obstruct the observer, while the spaces between the parallel louvers 48 in the regions 46 still permit a view. For the viewer, bright circles 46 thus appear in front of a dark background 42.

On the other hand, if the observer tilts the security element forwards or backwards (tilting direction 52), the now tilted louvers 48 obstruct the view, while the spaces between the louvers 44 keep the area 42 transparent. The viewer now sees dark circles 46 against a light background 42.

In a not further illustrated embodiment it is provided that the security element of Fig. 5 an additional transparent or semitransparent, z. B. optically variable coating, the z. B. between the substrate and the microstructure or on the microstructure is arranged. By this measure, the counterfeit security of in Fig. 5 shown security elements further increased.

The simple geometric pattern of Fig. 5 can of course be extended to more complex patterns, characters or encodings. For example, the denomination 16 of the currency attaining banknote 10 may be repeated in the see-through security element 12 in the form of areas 60, 62 with different lamination orientation, as in FIG Fig. 6 shown. As explained in the previous embodiment, the see-through security element 12 appears structureless when viewed vertically, while the tilting of the banknote depending on the direction of tilting the digit sequence "10" emerges bright against a dark background or dark against a light background.

Another see-through security element according to yet another embodiment of the invention is in Fig. 14 shown. The security element 140 of the Fig. 14 basically has a similar structure as the security elements of Fig. 5 and Fig. 6 on why reference is made to the statements made to these figures.

The main difference of the see-through security element 140 with respect to the see-through security elements of Fig. 5 and Fig. 6 is that the areas of differently oriented lamellar structures are much less sharply demarcated. For example, while the areas 42 and 46 of the security element 40 of the Fig. 5 are arranged perpendicular to each other, the fins 141,147 of the security element 140 of the Fig. 14 in most areas only a non-linear course, the differences in the direction of adjacent areas are relatively small. How out Fig. 14 can be seen, the meander-shaped fins 141 in the areas 144 and 145, however, a course that of the in Fig. 14 from top to bottom extending preferred direction, which is predetermined by the slats 147 of the region 143, deviates significantly.

When viewed vertically, the areas 143 and 144 and 145 practically do not differ in their visual appearance due to their equal area coverage, the security element 140 appears substantially featureless and bright. However, if the security element 140 is tilted by a certain angle to the right or left (FIG. Tilting direction 150), so the tilted slats 147 adjust the viewer's view, while the interstices of the slats 141 in the areas 144 and 145 at least partially allow a view to a considerable extent. In contrast to the tilting of the security element 40 of the Fig. 5 very sharply demarcated areas 42 and 46 results between the areas 142,143,146 and 144,145 of the security element 140 of the Fig. 14 a continuous transition with respect to the orientation of the lamella (curvature), whereby even when tilted in the direction 150, the areas 144 and 145 are less pronounced from the areas 142.143 and 146. For the observer, when the security element 140 is tilted, areas with less transparency thus result, which gradually change into areas with essentially unchanged transparency. The regions of low transparency are therefore relatively evenly transferred to the brighter areas for the viewer when the tilted security element 140 is tilted.

When tilted in a direction 152 which is substantially perpendicular to the direction 150, the interspaces of the louvers 147 keep the region 143 translucent, while the now tilted louvers 141 of the regions 144, 145 substantially obstruct the view. Accordingly sees the Observers now see dark areas 144, 245 which continuously merge into the bright areas 142, 143 and 146.

One according to Fig. 14 trained security element 140 has a very high security against counterfeiting, since the complex curved lamellar structures can not be composed of individual, possibly available slats or easily readjusted. Furthermore, the continuous light / dark transitions are perceived by a viewer as visually very appealing.

Also the security element of Fig. 14 may have an optically variable coating, the z. B. between the substrate and the microstructure or on the microstructure is arranged. The security against forgery of such a security element not shown is further increased by such a measure.

The see-through security elements according to the invention can, instead of venetian blinds whose microstructures are formed by parallel lamellae, also contain other microstructures, for example microstructures of a multiplicity of depressions with increased translucency.

Of course, it is also conceivable that the substantially parallel arrangement of the slats is replaced at least in areas by a non-parallel arrangement, which is equivalent to an increase in the security against counterfeiting of the security element, since such structures can be technically very difficult to adjust.

For illustration shows Fig. 7 a see-through security element 70, in which on a transparent substrate 72 initially a continuous dark embossing lacquer layer 74 is applied. Embossed in the embossing lacquer layer 74 are a multiplicity of recesses 76 in which the light transmittance of the embossing lacquer layer 74 is increased due to the locally reduced layer thickness. The recesses 76 are arranged so that they viewed together as viewed form a motif that appears and disappears depending on the viewing angle.

Due to the high resolution of the embossing technique and the low layer thicknesses, very fine designs and complex motifs can be realized. The representation of the motifs is not limited to two-tone representations (light / dark), but rather, as described below, half-tone representations can be realized. In order to avoid unwanted color splitting, the characteristic spacing of the recesses is also 1 μm or more in the designs in which the microstructures comprise a multiplicity of depressions. The lateral dimensions of the depressions are advantageously also about 1 μm or more.

By different density (number of wells of a particular shape per surface element), depth or by different shape and size of the wells 76 different levels of gray can be realized in the visual impression. FIGS. 8 (a) and (b) show for this purpose some embodiments for depressions 76a, 76b, 76c of different widths and depths as well as depressions 78 with different outline shapes and sizes, which in each case give the embossing lacquer layer a defined increased transparency and can therefore be used to construct halftone images. Realistic halftone images can generally be produced with only a few gray levels, so that a small number is sufficient at different recess shapes, sizes and depths.

The microstructures (lamellae or depressions) can be produced as described by embossing, in particular by embossing into a UV-curable embossing lacquer or a thermoplastic lacquer. As colors for the embossing lacquer soluble dyes, but also pigment dyes can be used.

Alternatively, printing techniques that are capable of lining up very finely structured opaque and non-opaque areas can also be used to produce the microstructures. The desired effects can be obtained with sufficiently low overall thickness with any printing technique that is capable of producing an approximately 3 μm to 20 μm thick layer with recesses or trenches with diameters between 1 μm and 30 μm.

Particularly advantageous in the co-pending German patent application 20 2006 029 852.7 micro-rotogravure technology is used, which combines the advantages of printing and embossing technologies. Briefly, in micro-gravure printing technology, a tool mold is provided whose surface has an arrangement of elevations and depressions in the form of the desired microstructure. The recesses of the mold are filled with a curable colored or colorless varnish, and the support to be printed is pretreated for a good anchorage of the varnish. Then, the surface of the mold is brought into contact with the carrier, and the paint in contact with the carrier is hardened in the recesses of the mold while being connected to the carrier. Subsequently, the surface of the mold becomes removed from the support so that the cured paint associated with the support is pulled out of the recesses of the mold.

For a more detailed description of the micro-gravure printing process and the associated advantages is referred to the said German patent application 10 2006 029 852.7 directed.

The structural elements of the microstructures, for example the slats of the FIGS. 2 to 6 or the pits of the FIGS. 7 and 8 , In some areas may also be provided with an opaque, a reflective or an absorbent coating.

By means of structural elements of locally different geometry or by means of structural elements with surfaces of different inclination, it is also possible in this way to produce transparency images whose visibility depends on the viewing angle.

For illustration, the embodiment of the Fig. 9 a security element 80 having a lamellar structure of a plurality of substantially parallel, transparent lamellae 82, which, as described above, are formed by means of an embossing lacquer layer, a printing layer or a microtubing layer. The symmetrical lamellar structure 82 is asymmetrically provided with an opaque coating 84, as in FIG Fig. 9 shown. In this case, the asymmetric coating z. B. by oblique vapor deposition by means of a known vapor deposition method, for. B. Physical Vapor Deposition (PVD) done. The intended for Schrägbedampfung particle steam then strikes under an oblique, ie not with respect to the substrate surface vertical angle, on the microstructure elements or the substrate surface. Due to the asymmetry of the coating, viewing through the transparent lamellae 82 is possible from the viewing direction 88, while the opaque coating 84 obstructs the viewing on the lamellae 82 from the viewing direction 86, so that the security element 80 appears opaque from the viewing direction 86 in the partial region shown. By suitable arrangement of the lamellae 82 and the coating 84, it is thus possible, for example, to produce a see-through image which becomes visible only when the security element is tilted in the viewing direction 88.

Also, the embodiment of Fig. 10 shows a microstructure 90 with symmetrical microstructure elements and with a z. B. generated by oblique deposition asymmetric coating 92, in which the microstructure elements, however, have more surfaces of different inclination 94, 96, and thus increase the freedom of design for the design of the transparencies.

By means of surface structures 100 with surfaces of different inclination, it is also possible to produce transparent images which become effective by means of coating 102 at a vertical angle of incidence of the particle vapor, in particular of the metal vapor, as is the case with the exemplary embodiment of FIG Fig. 11 illustrated.

Instead of an opaque or reflective coating, it is also possible to provide an absorption structure on the individual structural elements. For example, shows Fig. 12 a security element 110 with a microstructure 112 with different structural elements, which are provided in partial areas with so-called moth eye structures 114, which are effective light traps for the incident light.

In other configurations, the features of the microstructure 112 are provided with diffraction gratings which diffract substantial portions of the light incident at a certain angle in directions out of viewing direction. Also by such a combination of a geometric microstructure with a characteristic element size of 3 microns to 50 microns with a diffraction structure with a characteristic element size of about 300 nm to about 1000 nm effective see-through tilting effects can be realized.

It is understood that, if desired, the structures may additionally be provided perpendicularly or obliquely with a reflective layer or with a layer having a refractive index which differs significantly from the structural elements.

Such a see-through security element with an additional coating is in Figure 15 shown. The security element 160 of Fig. 15 has a on a transparent or translucent material 161, z. Example, a plastic film made of PET, applied microstructure 170, which in turn from a plurality of microstructure elements 162 and 163 and an overlying optically variable coating with layers 164,165 and 166 is formed. How out Fig. 15 can be seen, the symmetrical to the plane of symmetry 169 arranged microstructure elements 162 and 163 form a sawtooth-shaped relief structure. The relief structure can also be understood as a lattice structure with a relatively small grid angle α. In the example shown, the grating angle α is approximately 20 °, although even smaller angles of up to approximately 5 ° or larger angles up to approximately 45 ° are conceivable. At the in Figure 15 shown embodiment, the height h of the individual grid lines is about 5 microns.

Above the microstructure, a three-layer optically variable coating is arranged. The individual layers 164, 165 and 166 were applied by vapor deposition from a direction substantially perpendicular to the substrate surface. Ideally, the flanks 167 of the relief structure arranged parallel to the vapor deposition direction have no optically variable coating. The three-layer coating with color shift effect is a metallic / dielectric structure with the following structure. On the relief structures produced from a UV embossing lacquer, a layer 164 of aluminum is preferably first applied by vapor deposition. The layer serves as a reflector and has a layer thickness of about 10 nm to 100 nm, preferably of about 30 nm. In addition, a layer of SiO ₂ with a layer thickness of 100 nm to 1000 nm, more preferably with a layer thickness of about 200 nm to 600 nm is usually applied by vapor deposition. The thickness of the SiO ₂ layer determines the color shift effect to be perceived later by the observer for the structure. Finally, a semitransparent layer of chromium is deposited over the layer of SiO ₂ , which has a layer thickness of about 3 nm to 10 nm. The three-layer structure thus obtained has a color shift effect from green (top view, direction 177) to magenta (oblique viewing angle, direction 178, 179).

In the Fig. 15 shown embodiment of the see-through security element according to the invention shows in plan view (direction 177) for the provided with the microstructure elements 162 and 163 areas of the microstructure 170 substantially the same color for the viewer. When the security element is tilted from the vertical viewing direction 177 to an oblique viewing direction 178 or 179, the color impression for the areas of the security element 160 provided with the microstructure elements 162 and 163 changes due to the then different On the other hand, the angle between the irradiated light and the interference layer arrangement with the layers 164, 166, 166 present on the microstructure elements 162 and 163, respectively, clearly shows, wherein the plane 169 represents a sharp boundary between the regions perceived differently colored by the viewer with the elements 162 and 163, respectively.

The security element 160 is extraordinarily tamper-proof by the superimposition of a relief structure and a coating with a color shift effect and the resulting synergistic effects. In addition, such an optically variable security element is very appealing to the viewer, so that a security element according to this embodiment has a particularly high recognition value.

Another embodiment of the invention is in Fig. 13 illustrated. The see-through security element 120 shown there has a transparent or translucent substrate 122 having a first surface and an opposite second surface, wherein a see-through mask 124 is applied to the first surface as a microstructure. The see-through mask 124 is formed by an opaque layer 126 with translucent openings 128 having a size below 200 microns, preferably having a size of about 5 microns to about 100 microns, wherein the arrangement of the openings a motif in the form of patterns, characters or forms an encoding.

A congruent see-through mask 130 is applied to the opposite second surface of the substrate 122 with a certain lateral offset Δ of less than 100 μm, for example of only 10 μm.

As in Fig. 13 (a) and Fig. 13 (b) By suitable choice, the size of the openings 128, the thickness of the substrate 122 and the offset Δ It can be achieved that the subject of the transparency masks 124, 130 can be visually recognized only from a certain viewing direction 132, while the see-through security element 120 appears opaque from other viewing directions 134.

The opaque layers of the see-through masks can be formed by known printing methods, by embossing in color layers, by embossing wells in transparent lacquer and then filling the wells with color, by metallization / demetalization and preferably by the above-mentioned microtiping technique according to the German patent application 10 2006 029 852.7 be generated. It is also conceivable in principle that the see-through mask on one side of the substrate z. B. is obtained by a stamping technique, the see-through mask on the other side of the substrate but by a suitable metallization or Demetallisierungstechnik. When demetallizing various laser techniques can be used with advantage, as they can be obtained with Durchstrationsrnasken high spatial resolution.

In order to achieve the required small offset of the transparent masks, they can be applied in particular simultaneously to the opposite surfaces of the substrate. On the other hand, if the see-through masks are applied successively, special attention must be paid to the registration of the microstructures, in particular their adaptation to the size of the openings 128. If larger openings 128 are used, the registration is less critical, so that in this case application methods with a larger clearance can be used.

Also in the case of in Fig. 13 shown embodiment, it is generally conceivable, an additional coating, for. As an optically variable, semi-transparent thin-film arrangement, to be arranged on or below the see-through masks. Advantageously, the additional coating as well as the transparency mask is structured, so has the same motif, which z. B. can be achieved by demetallization techniques.

Unless the transparency masks, as in Figure 13 shown, congruent, but have different subjects, ie have different areas of transparency, interesting Moiré effects and effects can be achieved, which depend on the tilt or rotation angle when tilting or turning the see-through security element. However, these special effects are not discussed further in the present application.

Claims (17)

1. A see-through security element for security papers, value documents and the like, having at least one micropattern (90,100,112,170) having a visual appearance (26, 28, 86, 177, 178, 179) that is viewing-angle dependent when looked through, wherein the at least one micropattern (90,100,112, 170) is formed from an arrangement of a plurality of pattern elements having a characteristic pattern spacing of 1 µm or more, and the see-through security element comprises a total thickness of 50 µm or less, characterized in that the pattern elements are provided in sub-regions with an opaque, transparent, semitransparent, reflective or absorbing coating, wherein the coating is formed to be multilayer and as a thin-film element having a color-shift effect.
2. The see-through security element according to claim 1, characterized in that the coating is formed to be three-layer.
3. The see-through security element according to claim 1 or 2, characterized in that the pattern elements are provided in sub-regions with a metallic coating and/or with a moth-eye pattern.
4. The see-through security element according to at least on of claims 1 to 3, characterized in that the pattern elements are provided in sub-regions with a diffractive pattern that diffracts substantial portions of the incident light in directions outside of the viewing direction.
5. The see-through security element according to at least on of claims 1 to 4, characterized in that the pattern elements comprises an asymmetrically arranged coating, moth-eye pattern or diffractive pattern.
6. The see-through security element according to at least on of claims 1 to 5, characterized in that at least one micropattern is formed by a lamellar pattern composed of a plurality of substantially parallel lamellae.
7. The see-through security element according to claim 6, characterized in that multiple micropatterns formed by lamellar patterns are provided that differ in one or more of the parameters lateral orientation, color, width, height, relief shape and spacing, wherein preferably the differing lamellar patterns are arranged in the form of patterns, characters or a code.
8. The see-through security element according to at least one of claims 1 to 7, characterized in that the see-through security element comprises a transparent or translucent substrate and a marking layer applied to the substrate, which includes at least one micropattern.
9. The see-through security element according to claim 8, characterized in that a colored embossing lacquer layer is applied as marking layer, and the embossing lacquer layer is patterned by means of embossing techniques in such a way that the regions that were left standing when embossing form the pattern elements of the at least one micropattern, or a transparent or translucent embossing lacquer layer is applied as marking layer, depressions are introduced into the embossing lacquer layer by means of embossing techniques, and the introduced depressions are filled with colored material such that the filled depressions form the pattern elements of the at least one micropattern or a printing layer having regions of high transmittance and having regions of low transmittance is applied as marking layer, the regions of low transmittance forming the pattern elements of the at least one micropattern.
10. The see-through security element according to at least one of claims 1 to 9, characterized in that the see-through security element comprises a total thickness of 20 µm or less, preferably of 3 µm to 10 µm, and/or the pattern elements comprise a characteristic pattern spacing of 5 µm or more, and/ or the pattern elements comprise a pattern size of 1 µm or more, preferably of 3 µm or more.
11. The see-through security element according to at least one of claims 1 to 10, characterized in that at least one micropattern in a marking layer is formed by a plurality of depressions having an increased transmittance, wherein the plurality of depressions are arranged in the form of patterns, characters or a code.
12. A method for manufacturing a see-through security element according to one of claims 1 to 11, in which the see-through security element is provided with at least one micropattern having a visual appearance that is viewing-angle dependent when looked through, the at least one micropattern is formed from an arrangement of a plurality of pattern elements having a characteristic pattern spacing of 1 µm or more, and the see-through security element is produced having a total thickness of 50 µm or less, characterized in that the pattern elements are provided in sub-regions with an opaque, transparent, semitransparent, reflective or absorbing coating, wherein the coating is formed to be multilayer and as a thin-film element having a color-shift effect.
13. The method according to claim 12, characterized in that the pattern elements are provided with a metallic coating, a moth-eye pattern or a diffractive pattern, wherein preferably pattern elements are provided with an asymmetric coating, moth-eye pattern or diffractive pattern.
14. The method according to at least one of claims 12 to 13, characterized in that at least one micropattern is formed by a lamellar pattern composed of a plurality of substantially parallel lamellae.
15. The method according to at least one of claims 12 to 14, characterized in that, to a transparent or translucent substrate, a marking layer is applied in which the at least one micropattern is developed, wherein a colored embossing lacquer layer is applied, and the embossing lacquer layer is patterned by means of embossing techniques in such a way that the regions that were left standing when embossing form the pattern elements of the at least one micropattern, or a transparent or translucent embossing lacquer layer is applied as a marking layer, depressions are introduced into the embossing lacquer layer by means of embossing techniques, and the introduced depressions are filled with colored material such that the filled depressions form the pattern elements of the at least one micropattern.
16. The method according to at least one of claims 12 or 15, characterized in that the micropattern is applied to the substrate in that

    a) a die form is provided whose surface exhibits an arrangement of elevations and depressions in the form of the desired micropattern,

    b) the depressions in the die form are filled with a curable colored or colorless lacquer,

    c) the substrate is pretreated for a good anchoring of the colored or colorless lacquer,

    d) the surface of the die form is brought into contact with the substrate,

    e) the lacquer that is in contact with the substrate in the depressions in the die form is preferably cured by impingement with UV radiation and, in the process, joined with the substrate, and

    f) the surface of the die form is removed from the substrate again such that the cured lacquer that is joined with the substrate is pulled out of the depressions in the die form.
17. A security paper for manufacturing value documents or the like, or data carrier, in particular value document, such as banknote, identification card or the like, that is furnished with a see-through security element according to at least one of claims 1 to 11 or with a see-through security element manufactured according to at least one of claims 12 to 16.

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