EP1687482A1

EP1687482A1 - Security element

Info

Publication number: EP1687482A1
Application number: EP04740932A
Authority: EP
Inventors: Jürgen Schützmann; Bernd Wunderer; Manfred Heim
Original assignee: Giesecke and Devrient GmbH
Current assignee: Giesecke and Devrient GmbH
Priority date: 2003-07-14
Filing date: 2004-07-12
Publication date: 2006-08-09
Anticipated expiration: 2024-07-12
Also published as: US7929124B2; DE10331798B4; WO2005005727A1; RU2006104188A; RU2361978C2; JP2007527051A; CN1823198A; DE10331798A1; EP1687482B1; US20080106725A1; CN1823198B

Abstract

The invention relates to a value object comprising a security element that is provided with at least one liquid crystalline material, said liquid crystalline material causing linear polarization of light.

Description

security element

The invention relates to a security element for securing valuables, which has a liquid-crystalline material. Furthermore, the invention relates to an object of value, a transfer material and a method for producing such security elements and objects of value as well as a method for checking such a security element or object of value.

An object of value in the sense of the invention can be any object to be protected, such as branded articles or documents of value. Valuable objects in the sense of the present invention are in particular security documents such as banknotes, but also stocks, certificates, stamps, checks, check cards, credit cards, ID cards, passports, entrance tickets, tickets, tickets and the like, as well as labels, seals, packaging, security paper or other elements for the product assurance. The simplified term "object of value" or "security element" therefore always includes documents of the type mentioned below.

DE 19941 295 AI discloses a security element with liquid crystalline material which has thermochromic properties. When heated, the thermochromic liquid-crystalline material changes color or becomes transparent, so that the security element can be recognized as such by an observer.

One problem with such security elements with liquid-crystalline thermochromic material is that a certain temperature difference is required to achieve the thermochromic effect. However, it is not possible to generate a sufficiently large temperature difference in every situation, which is why the expected color change does not occur. The invention is therefore based on the object of creating a valuable object, a transfer element and a security element, the checking of which can be carried out independently of the temperature and can be carried out easily both visually and mechanically. In addition, the object of value, the transfer element and the security element should be particularly simple to manufacture and ensure a high level of protection against counterfeiting.

Furthermore, it is an object of the invention to provide methods for producing such a security element and valuable object, and a method for checking the security element or valuable object.

These tasks are solved by the features of the independent claims. Further training is the subject of the subclaims.

According to the invention, the security element has at least one liquid-crystalline material, the material causing a linear polarization of light.

By checking whether light emitted and / or transmitted by the security element is polarized, the authenticity of the security element can be checked with great certainty regardless of the surrounding temperature or of temperature differences to be generated. The improvement in counterfeiting security results above all from the use of polarizing liquid-crystalline materials, since such materials are either complex to manufacture or cannot be readily obtained commercially, but on the other hand, in contrast to normal, too thick and rigid polarization films, to the ones to be protected Accept objects can be fitted and processed using methods that are similar to those already used in security printing.

Lyotropic liquid crystals are preferably used as the liquid-crystalline material. A solution containing lyotropic liquid crystals is applied to at least one surface of the security element using shear forces. A layer thickness of a few μm is preferably applied, which, after the evaporation of the solvent, leads to a remaining layer thickness of 100 to 1000 nm. Conventional polarizing films have a thickness of at least 0.1 mm.

For the liquid-crystalline materials according to the invention there are numerous possible variations within the scope of the invention. Thus, the liquid-crystalline material can be provided over the entire surface or preferably only in regions, in particular in the form of characters or patterns.

The security element can either be created directly on the valuable object or prepared on a separate substrate. The valuable object or the separate substrate on which the security element is located is in no way restricted in relation to the material used. However, it is preferably paper or plastic, also in the form of foils. In the case of a separate substrate, the security element can be designed, for example, as a self-supporting label, preferably on a plastic substrate. In particular, the security element is designed in the form of a security thread, particularly preferably as a window thread. The latter allows a particularly striking visual inspection by comparing areas with polarized and those with unpolarized light. Since it can be difficult in some cases to provide the object of value with the respective layer sequence directly, it can alternatively make sense to prepare the layer structure of the security element at least partially on a transfer material.

If the entire layer sequence of the security element is prepared on a transfer material, care must be taken that the layer structure shown in the respective figures must be prepared in the reverse order on the carrier tape of the transfer material. The layer structure of the security element can be prepared in endless form on the carrier tape. The attachment as a security element to an object of value to be secured is carried out with the aid of an adhesive layer which is applied either to the object of value or to the top layer of the transfer material. A hot-melt adhesive is preferably used for this. In order to determine the outline shape of the security element, either an adhesive layer can be provided only in the areas to be transferred or the adhesive, such as a hot-melt adhesive, is activated only in the areas to be transferred. After the transfer, the carrier tape of the transfer material is pulled off and only the layer structure of the security element shown remains on the object of value to be secured.

The valuable object to which the security element is applied can be, for example, a security paper, a security document, but also product packaging. Other valuables that require security protection can of course also be provided with the security element according to the invention. The security element in its entirety is preferably arranged on the surface of the object to be secured. If the security element is arranged completely on the surface of the object, it can be made much larger, so that the optical effect of the liquid-crystalline material is much more apparent due to the larger area.

Further advantages and embodiments of the invention are explained in more detail with reference to the figures. The proportions shown in the figures (in particular layer thicknesses) do not necessarily correspond to the conditions that exist in reality and serve primarily to improve clarity.

For reasons of clarity, the invention is only explained in more detail using the example of a banknote. However, it is obvious that the invention can easily be used for the valuables mentioned above.

It shows:

FIG. 1 shows a banknote with a security element according to the invention,

2, 3 different embodiments of the security element according to FIG. 1 in cross section,

FIG. 4 shows an embodiment of the security element according to FIG. 1 in supervision, 5, 6 different embodiments of the security element according to FIG. 4 in cross section,

FIG. 7 shows an embodiment of a banknote with a security element according to the invention, and

Figure 8, 9, 10 devices for checking banknotes with security element according to the invention.

FIG. 1 shows a bank note 1 made of paper or plastic, which is provided with a security element 2 in the form of a strip running across the entire width of the bank note 1. The banknote 1 can of course have further security features, such as watermarks, gravure printing, security thread, luminescent and / or magnetic imprints, etc.

The security element 2 has a liquid-crystalline layer. The liquid-crystalline layer of the security element 2 has at least one liquid-crystalline material which effects a linear polarization of light. The security element 2 is arranged completely on the surface of the banknote 1, so that the light-polarizing effect of the liquid-crystalline layer, which is preferably applied in patterns and / or characters, can be recognized very well. The patterns and / or characters can bring about linear polarizations which have different orientations, ie the polarization direction of the security element 2 is locally different. By verifying whether and in which direction light emitted and / or transmitted by the security element 2 is polarized, the authenticity of the security element 2 can be checked with great certainty. Lyotropic liquid crystals are preferably used as the liquid-crystalline material. Lyotropic liquid crystals are liquid crystals formed from organic material which have liquid crystal properties both in an aqueous solution, for example, and after the solvent has been removed. A solution containing lyotropic liquid crystals is advantageously applied to at least one surface of the security element using shear forces. A layer thickness of a few μm is preferably applied, which, after the evaporation of the solvent, leads to remaining layer thicknesses of 100 to 1000 nm. The layer remaining after the evaporation of the solvent has ordered layers of the organic material, for example polymers, in supramolecular complexes. The surfaces of the molecules and their dipole moments of optical transmission are oriented perpendicular to the axis of the macroscopic orientation of the remaining layer. The direction of polarization of the remaining layer thus corresponds to the direction of the shear force applied when the solution containing the lyotropic liquid crystals is applied.

Such lyotropic liquid crystals partly have polarization spectra which have no polarization and therefore transmit a certain spectral component even with an analyzer crossed with respect to the polarization direction of the liquid crystals, so that light with which the security element 2 is irradiated after transmission through the layer of the lyotropic liquid crystals, in addition to linear polarization has a certain color, e.g. B. red, violet or blue. Other colors are possible, e.g. B. also in the invisible area of light. In particular, polarization of infrared or ultraviolet light can also be achieved. The polarization or non-polarization of certain wavelength ranges (colors) can thus take place selectively. By analyzing both The polarization and the residual color in the case of crossed polarizers make it possible to determine the security element particularly reliably.

Further information on the production and application of the lyotropic liquid crystals can be found in US 5,739,296, US 6,049,428 and WO 02/087782 AI.

The described color effect on light that is transmitted through the security element 2 can be perceived particularly well if a linear polarizer is used for viewing as an analyzer, the polarization direction of which is rotated by 90 ° to the polarization direction of the liquid-crystalline layer of the security element 2. The same effect can be achieved if the light used for illuminating the security element 2 is already linearly polarized by means of a linear polarizer whose direction of polarization is rotated by 90 ° to the direction of polarization of the liquid-crystalline layer of the security element 2. The above-described polarizers used for the detection can advantageously also be produced with the lyotropic liquid crystals used for the security element 2.

Since the described color effect is based on the absorption in the analyzer of the light coming linearly polarized from the security element in a certain spectral range, when the security element is embedded in a scattering substrate such as banknote paper or its arrangement on the back of the substrate, the polarization is canceled and thus also the color effect. By partially embedding the security element in the substrate, as in a so-called window security thread, there is only a slight difference in brightness and color between the embedded and the free ones with parallel orientation of the polarization direction of the analyzer lying areas of the security element, when rotated by 90 ° a very conspicuous.

In addition to the liquid-crystalline layer described, the security element 2 can also have further layers which, alone or in combination with other layers of the security element 2, produce further striking optical effects.

Some preferred embodiments are explained in more detail with reference to FIGS. 2 and 3, which show the bank note 1 in cross section along the dash-dotted line A - A in order to clarify the layer structure of the security element 2.

According to FIG. 2, the paper or plastic substrate 3 of the bank note 1, which has a white or light intrinsic color, is provided with a lyotropic liquid-crystalline layer 4 in the form of characters or patterns. In order to improve the application of the lyotropic liquid-crystalline layer 4, it can be provided, in particular in the case of a paper substrate 3, that a so-called primer layer is applied to the paper substrate 3. The primer layer can be, for example, a colorless plastic or a color layer, the surface of which has only a slight roughness.

In certain embodiments, for example security elements that are exposed to strong mechanical or chemical loads when used, it is advisable to cover the liquid-crystalline materials with a protective layer 5. The protective layer 5 can be a film laminated over the security element 2 or a protective lacquer layer. The protective lacquer layer can be applied over the entire area or in partial areas become. For example, UV lacquers, hybrid lacquers, oil printing lacquers or dispersion lacquers of the one or two component type can be used. The protective lacquer layer is preferably printed on, for example by means of flexographic printing or offset printing.

The security element 2 can also be a separate element that can be applied to the banknote. The separate security element 2 can have a structure which corresponds to the structure described with reference to FIG. In this case the substrate 3, e.g. B. a transparent plastic film, the security element 2 glued to the banknote 1. For this purpose, the plastic forming the substrate 3 can be a hot-melt adhesive.

A variant of the separate security element 2 is shown in FIG. On a substrate 3, for. B. a transparent plastic film, a lyotropic liquid-crystalline layer 4 is applied. Finally, an adhesive layer 6 is applied to the liquid-crystalline layer 4, with which the security element 2 is attached to the bank note 1. The adhesive used for this can be a hot melt adhesive. Instead of the security element 2, the adhesive can also be applied to the bank note 1 in order to secure the security element 2 on the bank note 1.

If the film 3 consists of birefringent material (eg stretched polymer film) with the correct orientation and given phase shift (eg quarter or half-wave plate), the composite according to Figure 2 or 3 works for depending on the layer sequence transmitted light as a linear or circular (general elliptical) polarizer. This results in different polarizations and test options in the two possible transmission and observation directions (for example, when used as a look-up register). FIGS. 4 to 6 show further preferred embodiments, FIG. 4 showing a security element 2 in plan view, whereas FIGS. 5 and 6 show the security element in cross section along the dash-dotted line A - A in order to clarify the layer structure of the security element 2.

FIG. 4 shows a security element 2 with information 8. This information can be present, for example, in the form of plain text, e.g. B. alphanumeric characters.

From Figure 5 it can be seen that the security element 2 from a substrate 3, for. B. a transparent plastic film, a metal layer 7, the z. B. sputtered, evaporated, glued, etc., and has no metal in the areas of the information 8, and a lyotropic liquid-crystalline layer 4 applied to the metal layer. The recesses formed in the metal layer 7 by the information 8 can be formed by means of a filler material, z. B. transparent plastic.

FIG. 6 shows a variant of the security element 2 shown in FIG. 5, in which the lyotropic liquid-crystalline layer 4 is first applied to the substrate 3. The metal layer 7 is arranged on this.

The embodiments of the security element 2 described in FIGS. 5 and 6 can have further components, for example: B. the protective layer, adhesive layer, etc. described above. It is also possible to produce the security element 2 directly on a bank note 1, the substrate of the bank note 1 then forms the substrate of the security element. The optical effects described above for a security element 2 according to FIG. 5 for transmission can only be observed in the area of the information 8. In the case of a security element according to FIG. 6, the optical effects described can only be observed in the area of the information 8, both for transmission and for remission.

Another embodiment of a bank note 1 with security element 2 is shown in FIG. The security element 2 is at least partially embedded in the substrate of the banknote 1, so that the security element 2, the z. B. is a security thread, is only visible in certain areas 2a, so-called "windows". The optical effects described above are then only visible in areas 2a.

The security element can also be designed as a transfer material, with a structure as described with reference to FIGS. 1 to 6. In this case, the layer structure is applied to a transfer material in the reverse order. The security element is then applied to the banknote by means of the transfer material and the transfer material is then completely or partially removed.

As already indicated, the security element can have further layers or components, the additional layers can be used individually or in combination, the layers can cover the entire security element or only parts thereof.

For example, a fluorescent layer or fluorescent areas can be arranged under the polarizing liquid-crystalline layer. Radiated fluorescent light is then linearly polarized. Interference layers can also be arranged above or below the polarizing liquid-crystalline layer.

It is also possible to produce interference pigments. For this purpose, liquid-crystalline layers are applied to such interference layers on one or both sides. The layer composite formed in this way is crushed into pigments that are polarizing. The polarizing interference pigments formed in this way can, even in a mixture with non-polarizing interference pigments, be used for the production of security elements and can be printed on them, for example. In addition to the directional dependence of the color, these then also show a polarization of the backscattered light.

Furthermore, the security element can also have further polarizing views, such as diffraction structures, which can form holograms, for example.

The security element can also have a phase-shifting layer, the detection of which can be carried out by means of a phase plate.

The security element can also be designed as a so-called planchette, which is preferably introduced on the surface of the banknote substrate and is provided on one or both sides with polarizing layers.

According to the invention, it can also be provided to apply at least one lyotropic liquid-crystalline layer on a see-through register. In the sense of the invention, a look-through register means an area in a banknote that is transparent. The see-through register can be formed, for example, from the substrate of the banknote itself, if this is made of plastic. fabric exists. However, it is also possible to use an appropriately designed inspection register, e.g. B. a plastic film in the paper substrate of a banknote. It is particularly advantageous if a lyotropic liquid-crystalline view is applied to both surfaces of the see-through register, these being arranged so that their polarization is rotated by 90 °. This maximizes the color effect described above.

In another embodiment, the film of the see-through register can be birefringent. Then the above-described direction-dependent linear or circular polarization of the transmitted light results, depending on whether the radiation is from the layer or from the film side.

The see-through register can also have diffraction structures which, for. B. form a semi-transparent hologram.

As described above, the security element 2 can be produced directly on the banknote 1 or made available as a separate security element 2 and attached to the banknote 1. But it can also be provided to provide a separate security element 2, the structure of which is only completed, for. B. is provided with a polarizing view or a protective layer after the security element 2 has been attached to the banknote 1.

FIGS. 8 to 10 show devices for checking bank notes with a security element according to the invention.

FIG. 8 shows an arrangement of a light source 10, a detector 11 and a bank note 1 having a security element 2, for checking the bank note 1 by means of light remitted by the bank note 1. The Light from the light source 10 penetrates through the linearly polarizing layer of the security element 2 and is linearly polarized in the process. This light is scattered on the substrate of banknote 1 and thereby depolarized. The scattered light penetrates through the linearly polarizing layer of the security element 2 and is linearly polarized again in the process. The presence of the security element 2 can be detected by means of the detector 11 if the detected light is linearly polarized. If the security element has 2 areas of different polarization, there are perceptible light / dark contrasts. Instead of polarization or additionally, the color effect of the light from the security element 2 described above and determined by the type of lyotropic liquid crystal used can be evaluated by the detector 11. If a polarizer 12 or 12 ′ is used in front of the light source 10 and / or in front of the detector 11, which has a linear polarization that is rotated by 90 ° to the linear polarization of the security element 2, the color effect or the light / dark contrast for the light coming from the security element 2 is amplified. Ideally, the polarizers 12 and 12 'have a linearly polarizing layer, which consists of the same lyotropic liquid crystal as the polarizing layer of the security element 2.

9a shows an arrangement of a light source 10, a detector 11 and a banknote 1 having a security element 2, for checking the banknote 1 by means of light transmitted through the banknote 1 ^" . The light of the light source 10 penetrates through the substrate of the banknote 1 and the linearly polarizing layer of the security element 2. The light is linearly polarized. The presence of the security element 2 can be detected by means of the detector 11 if the detected light is linearly polarized. Instead of the polarization or in addition, the one described above, by type of the lyotropic liquid crystal used agreed, the color effect of the light coming from the security element 2 can be evaluated by the detector 11. If a polarizer 12 is used in front of the detector 11, which effects a linear polarization which is rotated by 90 ° to the linear polarization of the security element 2, the color effect for the light coming from the security element 2 is amplified. The polarizer 12 ideally has a linearly polarizing layer, which consists of the same lyotropic liquid crystal as the polarizing layer of the security element 2.

In FIG. 9b, the security element 2 lies on the side of the banknote 1 facing the light source 10. The light passing through is then depolarized by scattering in the substrate of the banknote 1; no polarization and no color effect are observed in the detector 11. This is the case, for example, with the window security thread at the points where it is embedded in the substrate.

In FIG. 10, light source 10 and detector 11 are interchanged with FIG. 9. FIG. 10a shows the case in which the security element 2 is illuminated with polarized light and at least the color effect can also be observed through the scattering banknote substrate 1, whereas the transmitted light is depolarized by the scattering on the substrate of the banknote. 10b shows the case in which no effect occurs in transmission, since the security element 2 illuminating light is non-polarized and the linear polarization caused by the polarizing layer is depolarized again by scattering in the banknote substrate.

Instead of using a detector 11, the security element 2 can be checked both in remission and in transmission visually by a person who checks the occurrence of the described color effect. By rotating the polarizer 12 or 12 'or the bank note relative to the direction of polarization specified by the illumination or the observation, an increase and decrease in the described color effect can also be observed. When visually observing window security threads or other security elements partially embedded in the banknote substrate, there is also always an empty effect as a reference, ie locations without the described effect.

The visual inspection by a person can be carried out particularly advantageously and simply if the see-through register described above is provided according to the invention with a polarizing liquid crystal layer. In this case, the see-through register can replace the polarizer 12 or 12 '. The see-through register can then be used to check other security elements located on the same banknote, e.g. B. by folding the banknote so that the review register comes to rest on the further security element. The security elements of other banknotes can also be checked with the look-through register.

The color changes described above in connection with the polarizing interference pigments can also be observed particularly well when the polarizer 12 or 12 'is turned.

Of course, it is also possible to use a polarizer as an analyzer both in front of the light source 10 and in front of the detector 11 in FIGS. 9 and 10. In this case, at least the color effect can always be observed, regardless of the position of the security element 2.

The check of a security element according to the invention described with reference to FIGS. 9 and 10 was carried out for a on the surface of the Security element applied to the substrate of a banknote is explained. It is obvious that other designs are possible. For example, a substrate can be used for the banknote that does not cause scatter, e.g. B. a plastic substrate. Likewise, the security element, as described above, can be designed as a look-up register. In these cases, the depolarization by the substrate discussed in connection with the description of FIGS. 9 and 10 does not occur.

The light source 10 may be a light source that generates white light, e.g. B. an incandescent lamp or a gas discharge lamp. The light source 10 can already be provided with a linear polarizer. The light source 10 can also generate light with a certain, limited spectrum, e.g. B. if the light source 10 is formed by a light emitting diode. If the light is also to be linearly polarized, a polarizing laser diode of low power or a laser pointer for visual observation can be used as the light source.

The light / dark effects described in connection with FIG. 8 can also be perceived by means of the devices described in FIGS. 9 and 10 for checking banknotes with security element 2 according to the invention, or in the case of the visual check described.

Claims

P atetan speech

1. Valuable object with a security element, the security element having at least one liquid-crystalline material, characterized in that the liquid-crystalline material brings about a linear polarization of light.

2. Valuable object according to claim 1, characterized in that the liquid crystalline material is formed by a lyotropic liquid crystal.

3. Valuable object according to claim 1 or 2, characterized in that the liquid crystalline material has a layer thickness of 100 to 1000 nm.

4. Valuable object according to one of claims 1 to 3, characterized in that the liquid-crystalline material is applied over the entire area or in regions, in particular in the form of alphanumeric characters and / or patterns, the liquid-crystalline material in particular causing a locally different polarization.

5. Valuable object according to one of claims 1 to 4, characterized in that the liquid-crystalline material is applied to a substrate which has patterns and / or characters.

6. Valuable object according to claim 5, characterized in that the background is printed, produced by coloring a substrate or by means of a laser.

7. Valuable object according to one of claims 1 to 6, characterized in that the liquid crystalline material, the substrate and / or a further layer has mechanically and / or visually testable properties.

8. Valuable object according to one of claims 1 to 7, characterized in that the security element is a label.

9. An object of value according to one of claims 1 to 8, characterized in that the object of value is a security paper, a security document or a product packaging.

10. Valuable object according to one of claims 1 to 9, characterized in that the security element has at least one further optical effects-generating layer and / or a protective layer which cover at least part of the security element.

11. Security element for securing valuables, the security element having at least one liquid-crystalline material, characterized in that the liquid-crystalline material brings about a linear polarization of light.

12. Security element according to claim 11, characterized in that the liquid crystalline material is formed by a lyotropic liquid crystal.

13. Security element according to claim 11 or 12, characterized in that the liquid crystalline material has a layer thickness of 100 to 1000 nm.

14. Security element according to one of claims 11 to 13, characterized in that the liquid-crystalline material is applied over the entire surface or in regions, in particular in the form of alphanumeric characters and / or patterns.

15. Security element according to one of claims 11 to 14, characterized in that the carrier of the liquid-crystalline material is a birefringent film with a predetermined phase shift, in particular a quarter or half wavelength.

16. Security element according to one of claims 11 to 15, characterized in that the security element has at least one further layer producing optical effects and / or a protective layer, which cover at least part of the security element.

17. Security element according to one of claims 11 to 16, characterized in that the security element is a security thread, a see-through register or a planchette.

18. Transfer material for producing a security element, characterized in that the transfer material has a carrier material on which at least one liquid-crystalline material is arranged, the liquid-crystalline material being formed from a lyotropic liquid crystal.

19. Transfer material according to claim 18, characterized in that the carrier material is designed as a hot stamping foil.

20. A method for producing a valuable object or security element, characterized in that a substrate is provided, at least one lyotropic liquid-crystalline material is applied to this substrate.

21. The method according to claim 20, characterized in that the at least one lyotropic liquid-crystalline material is present in a solution which is applied to the substrate using directed shear force, and in that a solvent forming the solution is removed.

22. A method for checking an object of value, characterized in that it is checked whether light is linearly polarized and / or - whether the light has a color effect and / or whether a depolarization of the polarized light and / or a lack of color effect during the passage of the light occurs through the banknote substrate.

23. The method according to claim 22, wherein the light remitted and / or transmitted light is checked.