WO2008058670A1

WO2008058670A1 - Security arrangement with liquid-crystal layer

Info

Publication number: WO2008058670A1
Application number: PCT/EP2007/009686
Authority: WO
Inventors: Winfried HOFFMÜLLER; Theodor Burchard
Original assignee: Giesecke & Devrient Gmbh
Priority date: 2006-11-17
Filing date: 2007-11-08
Publication date: 2008-05-22
Also published as: EP2094503B1; DE102006054651A1; ATE499218T1; EP2094503A1; DE502007006563D1

Abstract

The invention relates to a security arrangement for security papers, documents of value and the like, having a transparent security element (12) which has a first linear polarizer and a layer made of a cholesteric liquid-crystalline material arranged above the linear polarizer, and having a transparent verification element (14) which has a second linear polarizer crosswise in relation to the first linear polarizer, in which case, when the transparent security element (12) is positioned on the transparent verification element (14), the first and second linear polarizers form a dark background for the cholesteric liquid-crystal layer, wherein at least one of the linear polarizers contains a motif (20) which is in the form of patterns, symbols or a coding and becomes visible once the security element (12) has been positioned on the verification element (14).

Description

Safety arrangement with liquid crystal layer

The invention relates to a security arrangement for security papers, documents of value and the like, which contains a security element with a liquid crystal layer.

Valuables, such as branded goods or value documents, are often provided with security elements for safeguarding purposes, which allow a check on the authenticity of the object of value and at the same time serve as protection against unauthorized reproduction. In many cases, the special properties of liquid-crystalline materials are exploited for this purpose, and above all the viewing angle-dependent color impression of liquid crystal layers, which is referred to below as the color-shift effect.

The security elements provided with liquid crystal layers are generally not transparent, since they require an absorbent background for a good color impression. However, liquid crystal layers having an absorbent background are visually less appealing to cover a see-through area of a bill or other data carrier.

Based on this, the present invention seeks to avoid the disadvantages of the prior art and in particular to provide a safety device of the type mentioned, which can be used with appealing visual appearance over a window area or a through opening of a data carrier.

This object is achieved by the safety arrangement having the features of the main claim. A equipped with such a security element flexible disk is in the independent claim specified. Further developments of the invention are the subject of the dependent claims.

According to the invention, a security arrangement for security papers, documents of value and the like

a transparent security element which has a first linear polarizer and a layer of a cholesteric liquid-crystalline material arranged above the linear polarizer, and

a transparent verification element having a second linear polarizer crossed to the first linear polarizer, such that the first and second linear polarizers form a dark background for the cholesteric liquid crystal layer when the transparent security element is placed on the transparent verification element, and

wherein at least one of the Linearpolarisatoren contains a motif in the form of patterns, characters or a coding that is visually recognizable after placing the security element on the verification element.

Preferably, the motif is formed in the linear polarizer by partial regions of different polarization direction. For the greatest possible contrast, mutually perpendicular polarization directions are preferred, but finer brightness gradations may also be provided.

As far as the motive is concerned, this can be designed arbitrarily, so that the enumerated patterns, signs or encodings in any form may be present. By way of example, the motif may be a rectangular, square or round character or symbol which essentially has the shape of the first and / or second linear polarizer. After placing the security element on the verification element in a suitable arrangement and vice versa, then according to the invention, the liquid crystal layer appears in front of a rectangular, square or round, dark background, which substantially corresponds to the shape of the first and / or second linear polarizer.

If a linear polarizer contains partial regions of different polarization direction, then for the purposes of this description the predominantly polarization direction will be referred to as the polarization direction of the linear polarizer. In the motifs commonly shown in security elements, the vast majority of the area is usually occupied by a uniform background, before the picture elements, letters, strings or a coding with a smaller area ratio are arranged. By means of this definition, it is always possible to determine unequivocally whether two linear polarizers are crossed even in the presence of motif regions with different orientations.

In an advantageous embodiment of the invention, the security element is arranged on a data carrier, while the verification element forms an external verification element for the security element. The security element is advantageously arranged in or above a window area or a continuous opening of the data carrier. Preferably, in this embodiment, only the first linear polarizer has a motif.

According to another, likewise advantageous embodiment, the security element and the verification element are together on a flexible Disk arranged. The security element can be brought by bending or folding the data carrier on the verification element. The security element and the verification element are advantageously arranged in or above a window area or a continuous opening of the data carrier. In this embodiment, the first linear polarizer and / or the second linear polarizer may equally have a motif.

In all configurations, the first and / or second linear polarizer may be formed by a polarizing film or by a printed polarizing layer. If one of the linear polarizers has a motif, it is advantageously formed by a printed layer, since different polarization ranges can then be generated in a simple manner. If, on the other hand, one of the linear polarizers has no motif, this linear polarizer is advantageously present as the polarization film. Such films can be obtained in that optically isotropic films become visually anisotropic by stretching and thus have the desired property of a polarizing film. Various possibilities for producing a polarizing film are known to the person skilled in the art and are therefore not further elaborated.

The first linear polarizer and the cholesteric liquid crystal layer are preferably present on an optically substantially isotropic carrier film, for example on a film consisting of cycloolefin copolymers or a combination of differently oriented plastic films.

The cholesteric liquid crystal layer may be printed or laminated on the first linear polarizer. Depending on the liquid crystal system used and the manufacturing process used, more Auxiliary layers, such as primer layers, adhesion promoter layers, Kaschierlackschichten, protective lacquer layers and the like may be provided.

The invention further comprises a flexible data carrier, in particular a value document, such as a banknote, identity card or the like, which is equipped with a security arrangement of the type described. The security element and the verification element are geometrically arranged on the disk so that they can be brought by bending or folding the disk on top of each other. The security element and the verification element of the security arrangement are expediently arranged in or above a window area or a through opening of the data carrier.

The through opening of the data carrier can be easily after the preparation of the data carrier substrate, for. B. by punching or cutting, especially laser beam cutting produced. The continuous opening can also during the manufacture of the substrate of the disk, so z. During papermaking, as described in WO 03/054297 A2. In that regard, the disclosure of WO 03/054297 A2 is included in the present application. The through opening formed according to YJO 03/054297 A2 during the production of the substrate of the data carrier has no sharp boundary edge in the edge region, which constitutes an additional security element of the data carrier.

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

1 is a schematic representation of a banknote with a security arrangement according to the invention,

2 the banknote of FIG. 1 in the folded state, FIG.

3 shows in (a) a cross-sectional view of the security element of FIG. 1 alone and in (b) the associated visual appearance for a viewer,

4 shows in (a) a cross-section through the verification element with an applied security element and in (b) the associated visual appearance for a viewer,

5 a banknote with a security element according to the invention in front of an external verification element,

6 shows a banknote with a security arrangement according to a further exemplary embodiment of the invention in unfolded state

Status,

Fig. 7, the banknote of Fig. 6 in the folded state, and

8 shows a cross section through the security arrangement of FIG. 6 with a folded banknote.

The invention will now be explained using the example of a banknote. 1 shows a schematic representation of a banknote 10 that is provided with an invented The security arrangement according to the invention is equipped. The security arrangement comprises a transparent security element 12 and a likewise transparent verification element 14, wherein both elements 12, 14 are arranged over window areas or through openings 16, 18 of the banknote 10.

For verification of authenticity, the security element 12 contains two visual features which are not easily recognizable to the naked eye, namely a liquid crystal layer with a color shift effect and a hidden image motif, in the exemplary embodiment the crest motif indicated in dashed lines in FIG. 1. At this point it should be noted in that the region of the security element 12 which is arranged not on the continuous opening 16 but on the banknote substrate should be arranged on the brightest possible background of the banknote substrate. If the banknote forms a dark background for the liquid-crystal layer in this area, the liquid-crystal layer appears there rich in contrast against a dark background, which the viewer may find disturbing. In such a case, it is recommended that the areas of the security element 12, which should be arranged on the dark area of the banknote, with a bright and / or well-reflective layer, eg. As an opaque white layer to provide so that the above described as disturbing impression for the viewer does not arise.

In the unfolded state of the banknote 10, the security element and the verification element 14 for the unaided eye each appear transparent and structureless with a certain amount of gray. When the right half 22 of the bill is folded back around the center line 24, as illustrated in Figure 2, the two hidden visual features clearly appear. To explain the effect of the effect, Figure 3 (a) shows a cross-sectional view of the security element 12 alone and Fig. 4 (a) shows a cross section through the verification element 14 with the security element 12 on. The associated visual appearances of the security element 12 or the combination of Security element 12 and verification element 14 are shown in FIGS. 3 (b) and 4 (b), respectively.

The security element 12 contains an optically substantially isotropic carrier foil 30 onto which a first linear polarizer 32 and a layer 34 of a cholesteric liquid-crystalline material are applied. For the optically isotropic carrier film 30, for example, cycloolefin copolymers or a combination of differently stretched plastic films are suitable.

In the exemplary embodiment, the linear polarizer 32 is formed by a printed polarization layer which has a first polarization direction in a background region 36 occupying the predominant surface portion and a second polarization direction perpendicular to the first polarization direction in a smaller motif region 38. In the exemplary embodiment, the motif area 38 is given by the interior of the coat of arms motif 20 of FIGS. 1 and 3 (b) or 4 (b). Since the human eye is not sensitive to the polarization direction of the light, the linear polarizer 32 and thus also the entire security element 12 appear to the naked eye as a structureless surface.

The color-shift effect of the cholesteric liquid-crystal layer 34 is also less conspicuous or even not recognizable when the transparent security element 12 is viewed without aids due to the large amount of disturbing ambient light. As shown by the illustration of FIG. 3 (b) illustrated, the security element 12 appears to the viewer as a total structureless _/ gray area, the brightness of which is essentially determined by the light transmittance of the linear polarizer 32.

The verification element 14 includes a second linear polarizer 40 whose polarization direction is tuned to the first linear polarizer 32 such that the background region 36 of the linear polarizer 32 and the linear polarizer 40 form crossed polarizers around its centerline 24 after folding the banknote 10. For this purpose, for example, the polarization direction of the first linear polarizer 32 in FIG. 1 can be perpendicular, that of the second linear polarizer 40 can be horizontal. Another possibility is that the polarization directions of both polarizers include a 45 ° angle with the horizontal, since the polarization direction of the second linear polarizer 40 is mirrored around its center line 24 when folding the note, and the two polarizers after folding thus crossed.

In the folded state of the banknote in which the verification element 14 lies under the security element 12, this shows a significantly changed visual appearance, as shown in FIGS. 2 and 4 (b):

In the background region 36, the linear polarizer 32 and the linear polarizer 40 form crossed polarizers, which together are virtually opaque and thus produce a dark, absorbing background for the cholesteric liquid crystal layer 34. In the background region 36, the liquid crystal layer 34 therefore appears in the folded state of the banknote with a clearly visible and striking color-shift effect against a black background. In contrast, the polarization directions of the linear polarizer 32 and of the linear polarizer 40 in the motif region 38 are parallel; the light transmitted by the second linear polarizer 40 therefore also passes through the motif region 38 of the first linear polarizer 32 without significant weakening. The motif region 38 therefore appears bright to the viewer and due to the high level of stray light with virtually no color effect.

If the banknote 10 is folded the other way around, ie the right half 22 is placed on top of the left half, the liquid crystal layer 34 comes to rest between the two linear polarizers 32, 40. Due to the phase-shifting effect of the liquid-crystal layer, in spite of crossed linear polarizers, complete extinction of the transmitted light does not result. Rather, observed in two areas 36, 38 in the transmitted light a color shift effect, which varies both with the viewing angle, and with the relative angle of the two linear polarizers.

FIGS. 3 (a) and 4 (a), for the sake of greater clarity, do not contain the auxiliary layers typically required in practice, such as primer layers, adhesion promoter layers, laminating lacquer layers, protective lacquer layers and the like. Depending on the materials used and the intended application, the skilled person will suitably supplement these according to his specialist knowledge.

The linear polarizer 40 of the verification element 14 may be formed by a polarization foil or else by a printed polarization layer. Instead of a verification element integrated in the bank note 10, an external linear polarizer 50 can also be used for checking the authenticity, as shown in FIG. 5. The changes in the visual appearance when the banknote 10 is placed on the external linear polarization Tor 50 correspond to the changes described in connection with Figures 3 and 4 when folding the banknote.

A further exemplary embodiment of the invention is shown in FIGS. 6 to 8, FIG. 6 a banknote 60 with a security arrangement according to the invention in unfolded state, FIG. 7 the banknote in the folded state and FIG. 8 a cross section through the security arrangement in the folded state of FIG Banknote 60 shows.

Also in this embodiment, the banknote 60 contains a security arrangement of a transparent security element 62 and a transparent verification element 64, both of which are arranged over window areas or through openings of the banknote 60. The security element 62 has a first linear polarizer 82 and a layer 84 of a cholesteric liquid-crystalline material. The security element 62 may contain a carrier film on one or both sides, which, however, does not impair the optical effects and should therefore be largely optically isotropic. It is also conceivable, of course, that the carrier film is stretched and thus at the same time acts as a linear polarizer. In such a case, the layer 84 is then placed on the polarizing film, which is not shown in detail in the figures.

As already explained above, the color-shift effect of the cholesteric liquid crystal layer 84 is little or not noticeable when the transparent security element 62 is viewed without auxiliary means, so that the security element 62 alone appears to the viewer as a featureless, gray area. The verification element 64 now contains a second linear polarizer 90, which has a first polarization direction in a background region 92 occupying the predominant surface portion and a second polarization direction perpendicular to the first polarization direction in a smaller motif region 94. First and second polarization directions are matched to the orientation of the first linear polarizer 82 such that the background region 92 of the linear polarizer 90 and the linear polarizer 82 form crossed polarizers after folding the banknote 60 about its center line 74. The motif area 94 is given in the exemplary embodiment through the interior of the coat of arms motif 70 shown in FIGS. 6 and 7. Since the human eye is not sensitive to the polarization direction of the light, the linear polarizer 90, and hence the entire verification element 64, appears to the naked eye as well as the security element 62 as a structureless surface.

In this embodiment as well, when folded, the banknote 60, in which the verification element 64 lies under the security element 62, results in a significantly changed visual appearance.

As illustrated in FIG. 7, the linear polarizer 82 and the background region 92 of the linear polarizer 90 form crossed polarizers in this state, so that a dark, absorbing background for the cholesteric liquid crystal layer 84 is formed there. In the background area 92, the liquid crystal layer 84 therefore shows a clearly visible and noticeable color shift effect against a black background in the folded state of the banknote 60.

In contrast, in the motif region 94 of the linear polarizer 90, the polarization directions of the first and second linear polarizers are parallel and let the incident light, therefore, without substantial weakening. The motif area 94 appears bright to the viewer and virtually no color effect due to the passing stray light.

Claims

Patent claims

1. Security arrangement for security papers, documents of value and the like with

a transparent verification element which has a second linear polarizer crossed to the first linear polarizer so that the first and second linear polarizers form a dark background for the cholesteric liquid crystal layer upon application of the transparent security element to the transparent verification element, and

wherein at least one of the linear polarizers includes a motif in the form of patterns, characters or a coding that is visually recognizable after the security element has been placed on the verification element.

2. Safety arrangement according to claim 1, characterized in that the motif is formed in the linear polarizer by partial regions of different polarization direction.

3. Safety arrangement according to claim 1 or 2, characterized in that the security element is arranged on a data carrier and the verification element forms an external verification element for the security element.

4. Safety arrangement according to claim 3, characterized in that the security element is arranged in or over a window area or a through opening of the data carrier.

5. Safety arrangement according to claim 3 or 4, characterized in that only the first linear polarizer has a motif.

6. Safety arrangement according to claim 1 or 2, characterized in that the security element and the verification element are jointly arranged on a flexible data carrier and that the security element can be brought over the verification element by bending or folding the data carrier.

7. Safety arrangement according to claim 6, characterized in that the security element and the verification element are respectively arranged in or over a window area or a through opening of the data carrier.

8. Safety arrangement according to claim 6 or 7, characterized in that the first linear polarizer has a motif.

9. Safety arrangement according to at least one of claims 6 to 8, characterized in that the second linear polarizer has a motif.

10. Safety arrangement according to at least one of claims 1 to 9, characterized in that the first and / or second linear polarizer is formed by a polarizing film.

11. Safety arrangement according to at least one of claims 1 to 10, characterized in that the first and / or second linear polarizer is formed by a printed polarization layer.

12. Safety arrangement according to at least one of claims 1 to 11, characterized in that the first linear polarizer and the cholesteric liquid crystal layer are present on an optically substantially isotropic carrier foil.

13. Safety arrangement according to at least one of claims 1 to 12, characterized in that the cholesteric liquid crystal layer is printed on the first linear polarizer.

14. Safety arrangement according to at least one of claims 1 to 12, characterized in that the cholesteric liquid crystal layer is laminated on the first linear polarizer.

15. Flexible data carrier, in particular value document such as banknote, identity card or the like, with a security arrangement according to one of claims 1 to 14, wherein the security element and the verification element are geometrically arranged on the disk so that they can be brought over one another by bending or folding the data carrier ,

16. Flexible data carrier according to claim 15, characterized in that the security element and the verification element of the security arrangement are respectively arranged in or above a window area or a through opening of the data carrier.

17. Use of a security arrangement according to one of claims 1 to 14 or a data carrier according to claim 15 or 16 for the falsification of goods of any kind.