EP3260302B1 - Optically variable security element - Google Patents

Description

The invention relates to an optically variable security element for securing valuables, which shows a different visual appearance when viewing the security element from opposite sides.

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. 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.

In this context, it is known to use security elements with multilayer thin-film elements whose color impression changes with the viewing angle for the viewer (referred to below as the color-shift effect).

The patent document DE 10 2014 013049 A1 discloses an optically variable security element for securing valuables, having a feature area exhibiting at least two different optically variable effects.

Based on this, the present invention seeks to provide a security element of the type mentioned above with high security against imitation and attractive visual appearance. This object is solved by the features of the independent claims. Further developments of the invention are the subject of the dependent claims.

• einer Reflexionsschicht mit gegenüberliegenden ersten und zweiten Hauptflächen, welche in einem ersten Teilbereich mit einer Mikrostruktur versehen ist und in einem zweiten Teilbereich keine Mikrostruktur aufweist,
• einer auf der Seite der ersten Hauptfläche in beiden Teilbereichen vorliegenden ersten Absorberschicht und einer zwischen der ersten Absorberschicht und der Reflexionsschicht in beiden Teilbereichen angeordneten, aufgedampften dielektrischen Abstandsschicht, wobei die erste Absorberschicht, die aufgedampfte dielektrische Abstandsschicht und die Reflexionsschicht ein erstes Interferenzschichtelement bilden, das bei Betrachtung von der Seite der ersten Hauptfläche her sowohl im ersten als auch im zweiten Teilbereich einen Farbkippeffekt zeigt, und
• einer auf der Seite der zweiten Hauptfläche in beiden Teilbereichen vorliegenden zweiten Absorberschicht und einer zwischen der zweiten Absorberschicht und der Reflexionsschicht in beiden Teilbereichen angeordneten, aufgedruckten Abstandsschicht, wobei die zweite Absorberschicht, die aufgedruckte dielektrische Abstandsschicht und die Reflexionsschicht ein zweites Interferenzschichtelement bilden, das bei Betrachtung von der Seite der zweiten Hauptfläche her im ersten Teilbereich ein metallisches Erscheinungsbild ohne Farbkippeffekt und im zweiten Teilbereich einen Farbkippeffekt zeigt.

According to the invention, a generic security element is provided with

• a reflection layer with opposite first and second main surfaces, which is provided with a microstructure in a first subregion and does not have a microstructure in a second subregion,
• a first absorber layer present on both sides of the first main surface and a vapor deposited dielectric spacer layer disposed between the first absorber layer and the reflective layer in both partial regions, wherein the first absorber layer, the deposited dielectric spacer layer and the reflective layer form a first interference layer element Viewing from the side of the first main surface forth in both the first and in the second portion shows a color shift effect, and
• a second absorber layer present in both partial regions on the side of the second main surface and a printed spacer layer arranged between the second absorber layer and the reflective layer in both partial regions, the second absorber layer, the printed dielectric spacer layer and the reflective layer forming a second interference layer element when viewed from the side of the second main surface forth in the first portion of a metallic appearance without color shift effect and in the second portion shows a color shift effect.

While not wishing to be bound by any specific explanation, the suppression of the color shift effect in the first subregion of the second interference layer element as currently understood is due to the fact that the material of the dielectric layer extends to some extent during printing and the surface of the dielectric thus covers the elevations and depressions of the dielectric layer Microstructure can not or at least not completely follow, so that arise locally different dielectric layer thicknesses. Since the local thickness of the dielectric determines at which wavelengths constructive and destructive interference occurs, the color-shifting layer system of the second interference layer element in the first subregion reflects different colors depending on the local thickness of the dielectric material. When viewed with the naked eye results in over a larger area and thus many different colors averaged, gray or silvery appearing hue.

In principle, all types of printable liquid coatings can be used for the printed dielectric layer. The printed varnish is cured after application, all known physical and chemical drying methods come into question.

Since the dielectric layer is applied equally in the first and second subarea, but the color shift effect of the thin film element is only visible in the second subarea while it is suppressed in the first subarea just in the area of the microstructures, the particular advantage is that the different optically variable effects of the first and second sub-range automatically and without additional measures are matched to each other.

The first section advantageously shows a non-colored, metallic and typically silvery appearance. By using non-ferrous metals or colored precious metals, however, other, non-silvery metallic color impressions can be obtained. For example, the reflective layer of the thin-film element can be formed from copper or contain a copper layer, so that a reddish metallic appearance is produced in the first subregion.

Advantageously, the printed dielectric layer has a locally irregular layer thickness in the first partial region having the microstructure, preferably with a thickness variation of 10% or more, particularly preferably 20% or more, 40% or more and in particular 60% or more. The thickness variation is on the largest. Layer thickness, so that, for example, a dielectric layer whose thickness varies between 240 nm and 300 nm, a thickness variation has 20%.

The first subarea, when viewed from the side of the second major surface, preferably has a microscopic rainbow color shift effect that can only be seen under magnification. The microscopic rainbow color shift effect is preferably composed of a plurality of microscopic color dots of different colors, the largest dimension of the microscopic color dots being between 1 and 80 μm, preferably between 1 and 20 μm, particularly preferably between 2 and 5 μm. This microscopic rainbow color shift effect can be used as a mark of authenticity higher level, which can be tested only with special tools, such as a strong magnifying glass or a microscope.

In advantageous developments of the invention, at least one of the layers, that is to say the first and second absorber layer, the first and second spacer layer and the reflection layer, is cut out in the form of characters, patterns or a coding, the recess (s) preferably being present in the first partial region. Preferably, two - more preferably three - layers, which may in particular follow one another, are recessed.

In an advantageous embodiment of the invention, the second absorber layer is recessed in the form of characters, patterns or a coding, the recess (s) preferably being present in the first subregion. In this way, in particular matt silvery appearing negative marks in the security element (or its shiny metallic first portion) can be integrated. Analogously, it would be possible - in particular to produce dull silvery - (second) negative mark in the security element by recesses in the first absorption layer to produce.

Alternatively or additionally, the second absorber layer may be recessed together with the printed dielectric spacer layer in the form of characters, patterns or a coding, the recess (s) preferably being present in the first partial area. As a result, especially gray-appearing negative marks can be integrated into the security element (or its metallically shiny first subregion). Analogously, it would be possible - especially gray appearing - (second) negative marks in the security element by common recesses in the first absorption layer and the first dielectric spacer layer.

Alternatively or additionally, the reflection layer may be omitted in the form of characters, patterns or a coding. The recess in the reflection layer is transparent, regardless of recesses in further layers. In plan view, therefore, gray appearance negative mark can thus be integrated into the security element (or its shiny metallic first portion). With a suitable choice of the spacing of the two absorber layers, an additional color-shift effect can alternatively be achieved. If the recess in the reflection layer is also present in one of the two (or both) absorber layers, the recess looks light gray from the corresponding side (or white).

The microstructure of the first subregion is advantageously formed by a diffractive relief structure, such as a hologram structure, by a micromirror structure, by a microlens structure or by a microcavity structure. The second subregion, which has no microstructure, is preferably unembossed and flat.

The reflection layer is preferably opaque in order to ensure that the optical effects of the two interference layer elements do not influence one another. The reflection layer can be a single layer, in particular of a metal, such as aluminum, silver, gold or copper. However, it is also possible that the reflection layer consists of a layer sequence of two or more different reflective layers, for example, a layer sequence of a copper and an aluminum layer. In this way, the visual appearance The opposite sides are also designed differently.

The color-shift effect of the first and second partial regions when viewed from the side of the first main surface is preferably identical, even if the structuring of the reflection layer in the first partial region is visible in contrast. The color-shift effect when viewed from the side of the second major surface preferably differs from the color-shift effect when viewed from the side of the first major surface to produce highly different visual impressions on the opposite sides.

The security element is advantageously designed as a pendulum security thread, but may for example also be designed as a security thread, label or transfer element and at least partially disposed over a continuous opening or in a window region of a data carrier.

The invention also includes a data carrier with a security element of the type described, wherein the security element is preferably embedded in the data carrier so that it is partially visible on opposite sides of the data carrier. Alternatively or additionally, the security element is arranged in or above a transparent window area or a through opening of the data carrier. The data carrier may in particular be a value document, such as a banknote, in particular a paper banknote, a polymer banknote or a film composite banknote, a share, a bond, a certificate, a coupon, a check, a high-quality admission ticket, but also an identity card such as a credit card, a bank card, a cash card, an entitlement card, an identity card, or a pass personalization page.

• auf ein Trägersubstrat eine Prägelackschicht aufgebracht und in einem ersten Teilbereich mit einer geprägten Mikrostruktur versehen wird,
• auf die Prägelackschicht mit der geprägten Mikrostruktur eine erste Absorberschicht, eine dielektrischen Abstandsschicht und eine Reflexionsschicht durch Aufdampfen aufgebracht werden, und
• auf die Reflexionsschicht eine dielektrischen Abstandsschicht aufgedruckt wird, und auf die aufgedruckte dielektrische Abstandsschicht eine zweite Absorberschicht aufgebracht, insbesondere aufgedampft wird.

The invention further includes a method for producing an optically variable security element of the type described above, in which

• an embossing lacquer layer is applied to a carrier substrate and provided with an embossed microstructure in a first subarea,
• on the embossing lacquer layer with the embossed microstructure, a first absorber layer, a dielectric spacer layer and a reflection layer are applied by vapor deposition, and
• a dielectric spacer layer is printed onto the reflection layer, and a second absorber layer is applied, in particular vapor-deposited, onto the printed dielectric spacer layer.

In an advantageous variant of the method, the printed dielectric spacer layer is produced by printing a liquid lacquer, for example a nitrocellulose-based solvent lacquer, and subsequently curing the printed lacquer.

Further exemplary embodiments and advantages of the invention are explained below with reference to the figures, in the representation of which a representation true to scale and proportion has been dispensed with in order to increase the clarity.

Fig. 1

eine schematische Darstellung einer Banknote mit einem erfindungsgemäßen optisch variablen Sicherheitselement in Form eines Pendelsicherheitsfadens,

Fig. 2

in (a) und (b) das Erscheinungsbild des Pendelsicherheitsfadens der Fig. 1 bei Betrachtung der Vorderseite bzw. Rückseite der Banknote,

Fig. 3

schematisch den Aufbau eines erfindungsgemäßen Pendelsicherheitsfadens im Querschnitt, und

Fig. 4

schematisch den Aufbau eines Pendelsicherheitsfadens nach einem weiteren Ausführungsbeispiel der Erfindung.

Show it:

Fig. 1

a schematic representation of a banknote with an optically variable security element according to the invention in the form of a pendulum security thread,

Fig. 2

in (a) and (b) the appearance of the pendulum safety thread of Fig. 1 looking at the front or back of the bill,

Fig. 3

schematically the structure of a pendulum safety thread according to the invention in cross section, and

Fig. 4

schematically the structure of a pendulum security thread according to another embodiment of the invention.

The invention will now be explained using the example of security elements for banknotes and other value documents. FIG. 1 shows a schematic representation of a banknote 10, which is provided with a security element according to the invention in the form of a pendulum security thread 12. The pendulum safety thread 12 emerges alternately on window areas 14 on the front side and window areas 16 on the rear side of the banknote 10 and is freely accessible there.

As a special feature, the pendulum security thread 12, when viewed from opposite sides of the banknote, respectively has a distinctively different optically variable appearance, so that the observer has the illusion that two different security threads are embedded in the banknote 10 congruently.

FIG. 2 (a) 2 schematically shows the pendulum security thread 12 when viewing the front side of the banknote 10. The pendulum security thread 12 emerges in the window regions 14 on the front side and shows a metallic appearance without color shift effect in a first subarea 20 and a color shift effect of magenta in a second subarea 22 vertical view to green with oblique view. The metallic appearance without color shift effect of the first portion 20 and the color shift effect of the second portion 22 are perfectly matched to each other.

FIG. 2 (b) shows the pendulum security thread 12 when viewing the back of the banknote 10. Looking at the back of the pendulum security thread 12 emerges in window areas 16 on the paper surface of the back, which are each between two window areas 14 of the front banknote. Visually, the pendulum security thread 12 shows from the banknote back side a completely different appearance, especially without appearing metallic subregions. The visible on the front metallic structures 26 of the first portion 20 are indeed recognizable with their shape from the back, but they do not appear with a constant, silvery metallic color impression, but show with the second portion 22 a common color shift effect of green with vertical supervision to blue at oblique view changes. When changing from the front view to a rear view therefore disappears on the one hand, the metallic appearance of the first portion 20 and on the other hand also changes the color shift effect (green - blue to magenta - green). Also, the appearance on the back by the uniform color shift effect is largely homogeneous, while on the front of a strong contrast between the metallic portion 20 and the color-tilting portion 22 is visible.

To achieve these different appearances on the opposite sides and the adapted appearance on the front, the pendulum safety thread 12 has the in Fig. 3 schematically shown in cross-section construction.

The pendulum security thread 12 contains a transparent carrier film 30, for example a PET film, on which a UV-curing embossing lacquer layer 32 is applied and provided in a first subregion 20 with an embossed microstructure 34. The microstructure 34 is formed, for example, by an arrangement of embossed micromirrors. In a second subregion 22 outside the first subregion 20, there is no microstructure, where the embossing lacquer layer is unembossed and even.

After curing of the embossing lacquer, a first, semitransparent absorber layer 36, for example of chromium, was deposited on the embossing lacquer layer 32 with the embossed microstructure 34, which follows the microstructure 34 due to its small layer thickness and the generation by vapor deposition of the local surface texture. A dielectric spacer layer 38 was likewise applied to this absorber layer 36 by vapor deposition, which likewise follows the local surface texture of the microstructure 34, so that a dielectric spacer layer 38 of uniform thickness is formed in both partial regions 20, 22. Finally, as the reflector layer 40, an opaque aluminum layer is evaporated, which in turn follows the local surface texture of the microstructure 34.

The first absorber layer 36, the vapor deposited dielectric spacer layer 38, and the reflective layer 40 form a first interference layer element 50 viewed from the side of the first absorber layer 36 shows over its entire surface a uniform color shift effect, in the exemplary embodiment about the aforementioned color shift effect between green when viewed vertically and blue at oblique viewing. Due to the different structuring of the reflection layer 40, the first and second subregions 20, 22 can be seen with their shape, but the same color shift effect appears in both subregions 20, 22 due to the uniform thickness of the dielectric spacer layer 38.

The side of the reflection layer 40 facing the first absorber layer 36 and the vapor-deposited dielectric spacer layer 38 forms a first main surface 40-1 of the reflection layer 40, the opposite main surface a second main surface 40-2. In this second main surface 40-2, a further dielectric spacer layer 42 is applied in both subregions 20, 22 and in contrast to the spacer layer 38 not by vapor deposition, but by printing a liquid paint and subsequent curing. On the printed and cured spacer layer 42 is finally a second, semi-transparent absorber layer 44, for example, again vapor-deposited from chromium.

The second absorber layer 44, the printed dielectric spacer layer 42, and the reflective layer 40 form a second interference layer element 52 which, when viewed from the absorber layer 44 side in the second portion 22, exhibits a color shift effect, for example from magenta when viewed perpendicularly to green when viewed obliquely. By applying the varnish of the spacer layer 42 in liquid form, however, it runs in the first subregion 20 containing the microstructures 34 between the individual structural elements and thereby completely or partially levels the microstructure 34. Well suited for this example Solvent based on nitrocellulose base, which have a good flow behavior.

The printed dielectric spacer layer 42 thus does not have a uniform layer thickness in the first subregion 20, so that no large-area color-shift effect visible to the naked eye can form there. Rather, the color-shift effect is effectively suppressed in the portion 20 by the leveling, and it shows a non-colored, metallic appearance.

In the second subregion 22, in which no microstructures are present, a uniform layer thickness is formed on the flat substrate when the dielectric layer 42 is printed, so that the second interference layer element 52 produces the desired color-shift effect there.

Since the dielectric layer 42 is printed over both subareas 20, 22, and the suppression of the color shift effect is precisely in the area of the microstructures 34 of the first subregion 20, a perfect registration between the different optical effects of the two subregions 20 is automatically produced without additional measures. 22. When viewed from the side of the second main surface 40-2, a metallic appearance without color-shift effect thus appears in the first subarea 20, and a color shift effect perfectly matched thereto in the second subarea 22.

An inventive security element such as the pendulum security thread 12 of Fig. 1 , may also be provided with negative writing areas, as in Fig. 4 illustrated. For this purpose, approximately the second absorber layer 44 is recessed in a subregion 60, as a result of which these regions become gray when viewed from the side of the second main surface 40-2 Show appearance. A white negative writing may be obtained by a recess of both the second absorber layer 44 and the printed spacer layer 42 in a subregion 62. It is understood that the recesses of the sub-areas 60, 62 instead of negative writing can also represent other negative marks, in particular in the form of patterns, characters or Coderungen.

LIST OF REFERENCE NUMBERS

10

bill

12

Pendulum security thread

14.16

panes

20

first subarea

22

second subarea

26

metallic structures

30

support film

32

Embossing lacquer layer

34

microstructure

36

first absorber layer

38

vapor-deposited dielectric spacer layer

40

reflective layer

42

printed dielectric spacer layer

44

second absorber layer

50

Interference layer element

52

Interference layer element

60, 62

Subareas with negative characters

Claims (13)

1. An optically variable security element for securing objects of value, which upon viewing of the security element from opposing sides shows respectively a different optical appearance, having

   - a reflective layer with opposing first and second principal faces, which is equipped with a microstructure in a first partial region and has no microstructure in a second partial region,

   - a first absorber layer present on the side of the first principal face in both partial regions and a vapor-deposited dielectric spacer layer arranged between the first absorber layer and the reflective layer in both partial regions, wherein the first absorber layer, the vapor-deposited dielectric spacer layer and the reflective layer form a first interference-layer element, which upon viewing from the side of the first principal face shows a color-shift effect in the first as well as in the second partial region, and

   - a second absorber layer present on the side of the second principal face in both partial regions and an imprinted spacer layer arranged between the second absorber layer and the reflective layer in both partial regions, wherein the second absorber layer, the imprinted dielectric spacer layer and the reflective layer form a second interference-layer element, which upon viewing from the side of the second principal face shows a metallic appearance without color-shift effect in the first partial region and a color-shift effect in the second partial region.
2. The security element according to claim 1, characterized in that the imprinted dielectric layer has an irregular layer thickness in the first partial region having the microstructure, preferably with a thickness variation of 20% or more, particularly preferably 40% or more, in particular of 60% or more.
3. The security element according to claim 1 or 2, characterized in that the metallic appearance without color-shift effect of the first partial region and the color-shift effect of the second partial region are in mutual register.
4. The security element according to at least one of claims 1 to 3, characterized in that the first partial region upon viewing from the side of the second principal face has a microscopic rainbow color-shift effect recognizable only upon magnification.
5. The security element according to at least one of claims 1 to 4, characterized in that the second absorber layer is left blank in the form of signs, patterns or an encoding, wherein the left-out area(s) are preferably present in the first partial region.
6. The security element according to at least one of claims 1 to 5, characterized in that the second absorber layer together with the imprinted dielectric spacer layer is left blank in the form of signs, patterns or an encoding, wherein the left-out area(s) are preferably present in the first partial region.
7. The security element according to at least one of claims 1 to 6, characterized in that the microstructure of the first partial region is formed by a diffractive relief structure, in particular a hologram structure, by a micromirror structure, by a microlens structure or by a microcavities structure.
8. The security element according to at least one of claims 1 to 7, characterized in that the security element is configured as a pendulating security thread.
9. A data carrier having a security element according to at least one of claims 1 to 8.
10. The data carrier according to claim 9, characterized in that the security element is embedded in the data carrier such that it is visible in some regions at opposing sides of the data carrier.
11. The data carrier according to claim 9, characterized in that the security element is arranged in or above a window region or a continuous opening of the data carrier.
12. A method for manufacturing an optically variable security element according to any of claims 1 to 8, in which

    - an emboss-lacquer layer is applied on a carrier substrate and an embossed microstructure is furnished in a first partial region,

    - to the emboss-lacquer layer having the embossed microstructure there are applied by vapor deposition a first absorber layer, a dielectric spacer layer and a reflective layer, and

    - on the reflective layer a dielectric spacer layer is imprinted, and on the imprinted dielectric spacer layer a second absorber layer is applied, in particular vapor-deposited.
13. The method to claim 12, characterized in that the imprinted dielectric spacer layer is created by imprinting a liquid lacquer, for example a solvent lacquer on nitro-cellulose basis, and subsequent curing of the imprinted lacquer.

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