DE102016007649A1 - Optically variable security element - Google Patents

Abstract

The invention relates to a security element (12) for protecting valuables with a reflective layer (40) having opposing first and second major surfaces, which is provided with a microstructure (34) in a first subregion (20) and none in a second subregion (22) Having a microstructure, with a first absorber layer (36) present on both sides of the first main area and a vapor deposited dielectric spacer layer (38) arranged between the first absorber layer (36) and the reflection layer (40) in both partial areas, these layers (36, 38, 40) form a first interference layer element (50) which, when viewed from the side of the first main surface, exhibits a color shift effect in both the first and second subregions (20, 22) and one on the side of the second Main surface in two sub-areas (20, 22) present second absorber layer (44) and one between the zw the absorber layer (44) and the reflection layer (40) arranged in both subregions, printed spacer layer (42), wherein the second layers (42, 44) and the reflective layer (40) form a second interference layer element (52), which when viewed from the Side of the second main surface forth in the first portion (20) a metallic appearance without color shift effect and in the second portion (22) shows a color shift effect.

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).

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 has no 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 when viewed from the side of the first main surface forth in both the first and in the second sub-area shows a color shift effect, and
• A second absorber layer present on both sides of the second main area and a printed spacer layer arranged between the second absorber layer and the reflective layer in both partial areas, the second absorber layer, the printed dielectric spacer layer and the reflection layer forming a second interference layer element Viewing from the side of the second main surface forth in the first sub-area a metallic appearance without color shift effect and in the second sub-area 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-areas are automatically matched and without additional measures to each other.

The first section advantageously shows a non-colored, metallic and typically silvery appearance. By the use of non-ferrous metals or colored precious metals, however, other, non-silvery metallic Color impressions are 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. In this case, the thickness variation is related to the greatest layer thickness, so that, for example, a dielectric layer whose thickness varies between 240 nm and 300 nm has a thickness variation of 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 higher-level mark of authenticity, which can only be tested with special aids, 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 to produce - in particular gray-appearing - (second) negative markings 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 of the opposite sides can be additionally 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 main surface preferably differs from the color-shift effect when viewed from the side of the first main surface to greatly different to create 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 reflective layer are applied by vapor deposition, and
• - On the reflection layer, a dielectric spacer layer is printed, and applied to the printed dielectric spacer layer, a second absorber layer, in particular vapor-deposited.

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.

Show it:

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,

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

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

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. 1 shows a schematic representation of a banknote 10 that with a security element according to the invention in the form of a pendulum security thread 12 is provided. The pendulum security thread 12 occurs alternately on window areas 14 on the front and window areas 16 on the back of the banknote 10 and is freely accessible there.

A special feature of the pendulum safety thread 12 when viewed from opposite sides of the banknote ago each have a distinctively different optically variable appearance, so that the viewer the illusion arises that there are two different security threads congruent in the banknote 10 embedded.

2 (a) schematically shows the pendulum safety thread 12 looking at the front of the banknote 10 , The pendulum security thread 12 occurs in the window areas 14 on the front and shows there each in a first section 20 a metallic appearance without color shift effect and in a second subarea 22 a color shift effect of magenta with vertical supervision to green with oblique view. The metallic appearance without color shift effect of the first section 20 and the color shift effect of the second portion 22 are perfectly matched.

2 B) shows the pendulum safety thread 12 looking at the back of the banknote 10 , When looking at the back, the pendulum safety thread occurs 12 in window areas 16 on the paper surface of the back, which in each case between two window areas 14 lie on the front of the banknote. Visually, the pendulum safety thread shows 12 from the banknotes back a whole different appearance, especially without appearing metallic parts. The visible on the front metallic structures 26 of the first subarea 20 Although recognizable with their shape from the back, they do not appear with a constant, silvery metallic color impression, but show with the second part 22 a common color-shift effect that changes from green when viewed perpendicularly to blue when viewed obliquely. When changing from the front view to a rear view therefore disappears on the one hand, the metallic appearance of the first section 20 On the other hand, the color shift effect (green - blue to magenta - green) also changes. 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-shifting section 22 is visible.

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

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

After curing the embossing lacquer was applied to the embossing lacquer layer 32 with the impressed microstructure 34 a first, semi-transparent absorber layer 36 For example, deposited from chromium, due to their small thickness and the generation by vapor deposition of the local surface texture of the microstructure 34 follows. On this absorber layer 36 was also vapor deposited to form a dielectric spacer layer 38 applied, which also reflects the local surface texture of the microstructure 34 follows, so that in both subareas 20 . 22 a dielectric spacer layer 38 uniform thickness is formed. Finally, as a reflector layer 40 an opaque aluminum layer evaporated, which in turn reflects the local surface texture of the microstructure 34 follows.

The first absorber layer 36 , the vapor deposited dielectric spacer layer 38 and the reflective layer 40 form a first interference layer element 50 when 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 are the first and second parts 20 . 22 recognizable with its shape, but it shows in both parts 20 . 22 due to the uniform thickness of the dielectric spacer layer 38 the same color shift effect.

The first absorber layer 36 and the vapor-deposited dielectric spacer layer 38 facing side of the reflective layer 40 forms a first main surface 40-1 the reflection layer 40 , the opposite major surface a second major surface 40-2 , On this second main surface 40-2 is in both parts 20 . 22 another dielectric spacer layer 42 applied 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 hardened spacer layer 42 is finally a second, semitransparent 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 that when viewed from the side of the absorber layer 44 in the second section 22 shows a color shift effect, for example, from magenta when viewed perpendicularly to green when viewed obliquely. By applying the paint of the spacer layer 42 in liquid form, however, this runs in the microstructures 34 contained first subarea 20 between the individual structural elements and thereby paves the microstructure 34 in whole or in part. Solvent paints based on nitrocellulose, for example, which have a good flow behavior, are very suitable for this purpose.

The printed dielectric spacer layer 42 thus points in the first subarea 20 no uniform layer thickness, so that there can form no visible to the naked eye, large-scale color shift effect. Rather, the color shift effect in the sub-area 20 is effectively suppressed by the leveling, and it shows a non-colored, metallic appearance.

In the second part 22 , in which there are no microstructures, arises when printing the dielectric layer 42 a uniform layer thickness on the flat surface, so the second interference layer element 52 there generates the desired color shift effect.

As the dielectric layer 42 over both subareas 20 . 22 is printed, and the suppression of the color shift effect just in the field of microstructures 34 of the first subarea 20 setting, automatically creates a perfect registration between the different optical effects of the two sub-areas without additional measures 20 . 22 , When viewed from the side of the second major surface 40-2 Her shows up in the first part 20 a metallic appearance without color shift effect and in the second subarea 22 a perfectly matched color-shift effect.

An inventive security element such as the pendulum security thread 12 of the 1 , may also be provided with negative writing areas, as in 4 illustrated. This is about the second absorber layer 44 in a subsection 60 recessed, making these areas when viewed from the side of the second major surface 40-2 show a gray appearance. A white negative writing may be through a recess of both the second absorber layer 44 as well as the printed spacer layer 42 in a subsection 62 to be obtained. It is understood that the recesses of the subregions 60 . 62 instead of negative writing, other negative signs, in particular in the form of patterns, characters or Coderungen can represent.

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)

Optically variable security element for securing valuables, which shows a different visual appearance when viewed from the opposite sides of the security element, with A reflection layer with opposite first and second main surfaces, which is provided with a microstructure in a first subregion and has no 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 when viewed from the side of the first main surface forth in both the first and in the second sub-area shows a color shift effect, and A second absorber layer present on both sides of the second main area and a printed spacer layer arranged between the second absorber layer and the reflection layer in both partial areas, the second absorber layer, the printed dielectric spacer layer and the reflection layer forming a second interference layer element Viewing from the side of the second main surface forth in the first sub-area a metallic appearance without color shift effect and in the second sub-area shows a color shift effect. A security element according to claim 1, characterized in that the printed dielectric layer in the microstructure having first portion has an irregular layer thickness, preferably with a thickness variation of 20% or more, more preferably 40% or more, in particular of 60% or more. A security element according to claim 1 or 2, characterized in that the metallic appearance without Farbkippeffekt the first portion and the color shift effect of the second portion are matched to each other. A security element according to at least one of claims 1 to 3, characterized in that the first subregion has, viewed from the side of the second main surface, a microscopic rainbow color shift effect which can be recognized only under magnification. Security element according to at least one of claims 1 to 4, characterized in that the second absorber layer is recessed in the form of characters, patterns or a coding, wherein the recess (s) preferably present in the first portion. Security element according to at least one of claims 1 to 5, characterized in that the second absorber layer together with the Printed on dielectric spacer layer in the form of characters, patterns or a coding is omitted, wherein the recess (s) preferably present in the first portion. A security element according to at least one of claims 1 to 6, characterized in that the microstructure of the first subregion is formed by a diffractive relief structure, in particular a hologram structure, by a micromirror structure, by a microlens structure or by a microcavity structure. Security element according to at least one of claims 1 to 7, characterized in that the security element is designed as a pendulum security thread. Data carrier with a security element according to at least one of claims 1 to 8. A data carrier according to claim 9, characterized in that the security element is embedded in the data carrier so that it is partially visible on opposite sides of the data carrier. A data carrier according to claim 9, characterized in that the security element is arranged in or over a window area or a through opening of the data carrier. A method of manufacturing an optically variable security element according to any one of claims 1 to 8, wherein 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 reflective layer are applied by vapor deposition, and - On the reflection layer, a dielectric spacer layer is printed, and applied to the printed dielectric spacer layer, a second absorber layer, in particular vapor-deposited. A method according to claim 12, characterized in that the printed dielectric spacer layer is produced by printing a liquid lacquer, for example a nitrocellulose-based solvent-based lacquer and subsequently curing the printed lacquer.

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