EP1549501A2

EP1549501A2 - Security element

Info

Publication number: EP1549501A2
Application number: EP03750579A
Authority: EP
Inventors: Christoph Mengel; Desanka Gacesa; Max Voit
Original assignee: Giesecke and Devrient GmbH
Current assignee: Giesecke and Devrient GmbH
Priority date: 2002-09-19
Filing date: 2003-09-18
Publication date: 2005-07-06
Anticipated expiration: 2023-09-18
Also published as: PL374606A1; JP4750417B2; WO2004028824A2; ATE396060T1; WO2004028824A3; DE50309894D1; CN1688452A; AU2003270224A1; EP1549501B1; RU2005111603A; CA2499279C; US20060023132A1; CA2499279A1; DE10243650A1; RU2322358C2; ES2305489T3; JP2005538878A; CN100532123C; PL205932B1; US7054043B2

Abstract

The invention relates to an object of value with a security element having at least a first and a second liquid-crystalline material, the first material having thermochromic properties and the second material an optically variable effect.

Description

security element

The invention relates to a security element for securing valuables, which has at least a first and a second liquid-crystalline material, the first material having thermochromic properties and the second material having an optically variable effect. 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 intended to be protected, such as branded articles or documents of value. Valuables in the sense of the present invention are in particular banknotes, but also stocks, certificates, stamps, checks, check cards, credit cards, ID cards, passports, tickets, tickets, tickets and the like as well as labels, seals, packaging 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.

It has long been known to use thermochromic materials to secure documents of value. For example, DE 2212350 describes a security thread made of transparent plastic that has cavities. In these cavities there is a liquid crystalline material which shows a reversible color change when the temperature is increased or decreased.

A security thread with thermochromic properties is also known from EP 0 608 078 B1. In this case, a plastic material is provided with an imprint or with signs that are partially demetallized. a metal layer have arisen. A thermochromic coating colored at normal temperature is arranged above this imprint or these negative signs. When heated, the thermochromic coating becomes colorless so that the characters underneath can be seen. Alternatively, a thermochromic coating can be used, which is colorless at normal temperature and becomes colored when heated, so that the characters disappear. This thread is introduced into the security paper in such a way that it comes to the surface in certain areas, so-called “windows”.

However, such thermochromic security threads have the disadvantage that the thermochromic effect is already used in many non-security areas for purely decorative purposes, which is why the optical effect caused by the color change of the thermochromic material is no longer recognized by the viewer as a security feature but only as a design variant. Such security elements therefore do not offer a high level of protection against counterfeiting.

The invention is therefore based on the object of creating a valuable object, a transfer element and a security element which offer high protection against counterfeiting and avoid the disadvantages of the prior art.

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. On Aben 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 a first and a second liquid-crystalline material, the first material having thermochromic properties and the second material having an optically variable effect.

The first liquid-crystalline material has thermochromic properties, i.e. its own color changes under the influence of temperature. The thermochromic material preferably also exhibits polarization effects, i.e. that it is able to selectively polarize light. These substances are preferably encapsulated liquid crystals which are crystalline at a certain temperature and do not polarize, but change their color and additionally polarize when the temperature changes, in particular an increase in temperature, and a change to the liquid-crystalline state. Depending on the thermochromic material used, the material can change from the liquid-crystalline state to the liquid state when the temperature rises further, the thermochromic material in the liquid state again being transparent or at least translucent and not polarizing.

The second liquid crystalline material has an optically variable effect. In the sense of the invention, “optically variable effect” means the effect that different color impressions are conveyed at different viewing angles

Green-blue or copper-green color transitions have proven to be particularly suitable. This second material preferably also exhibits light-polarizing properties. In particular, crosslinked liquid-crystalline materials show light-polarizing properties at the same time presence of a color shift effect without showing thermochromic effects.

In a particularly preferred variant, the thermochromic liquid-crystalline material and the liquid-crystalline material with optically variable effect each polarize light differently, e.g. can selectively polarize one material circularly right and the other material selectively polarize circularly left.

The liquid-crystalline materials are preferably processed in the form of printing inks, for example by admixing them with a transparent binder. The printing ink can of course contain other color pigments. The liquid-crystalline materials can be processed with any suitable printing process, in particular by means of screen printing and intaglio printing, but also in gravure, flexographic and letterpress printing.

In addition to printing inks, the materials can also be mixed with a transparent plastic layer.

For the liquid-crystalline materials according to the invention there are numerous possible variations within the scope of the invention. Thus, the thermochromic material may be over the entire surface or, preferably, only in some areas, particularly in the form of characters or ^'patterns may be provided.

Like the thermochromic material, the liquid-crystalline material with an optically variable effect can be processed over the entire area or in certain areas, with processing over the entire area or in certain areas being preferred, depending on the form of application. The thermochromic material can be arranged above and / or below and / or next to the material with an optically variable effect. Particularly suitable effects result from at least partial overlap of the different liquid-crystalline materials. An overlap of the effects also has the advantage that the viewer can more easily identify them on the object to be secured and can check them simultaneously in suitable embodiments. In particular when using polarization filters, the effects can be made visible with a “handle” by placing the filter on a specific point on the object.

For the thermochromic material, substances are preferably used which are at least translucent, preferably transparent, below a predetermined temperature, and are colored above this temperature. In certain applications, it may be useful to use thermochromic substances that are colored below a predetermined temperature and translucent or transparent above this temperature. The transition temperature of the thermochromic substances is preferably above the ambient temperature, e.g. in the range from 25 ° C to 60 ° C, preferably 30 ° C to 60 ° C. Depending on the application, however, it is also conceivable that the temperature can drop below 25 ° C.

The individual layers of the security element can either be created directly on the valuable object or prepared on a separate carrier. The valuable object or separate carrier as the 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 carrier, the security element can be used, for example, as a self-supporting label, preferably on a plastic substrate. 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 security element is applied to an object of value to be secured 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 object of value on 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 be provided with the security element according to the invention.

The security element is preferably arranged completely on the surface of the object to be secured. If the security element is completely arranged on the surface of the object, it can be made much larger, so that the optically variable effect and the thermally induced color change of the different liquid-crystalline materials is much more obvious due to the larger area. The use of a polarization filter is also much easier if a larger observation area is available.

The use of differently polarizing liquid crystalline materials also makes the security element more tamper-proof. Because such materials are either complex to manufacture or cannot be readily obtained from retailers.

The present invention thus offers additional security against forgery by combining the thermochromic effect which is visually perceptible without aids and the optically variable effect which is visually perceptible without the aid of aids. In particular, the security against forgery is further increased by additional use of the polarization effect, which can only be visually perceived with the aid of aids. In addition to the easily recognizable optically variable effect, information can also be simply hidden or made visible by means of the thermochromic effect, for example, the viewer can only reveal the information by touching it. The authenticity of the information can be checked further in a next step, for example by means of a polarization filter, if at least one of the liquid-crystalline materials polarizes light. Further advantages and ^'embodiments of the invention will be explained in more detail with reference to FIGS. The proportions shown in the figures do not necessarily correspond to the conditions in reality and serve primarily to improve clarity. Show it:

Fig. 1 is a security document with an inventive

Security element

2, 5, 6 different embodiments of the security document in cross section,

3, 4 execution orm according to FIG. 2 in supervision.

For reasons of clarity, the invention is explained in more detail using the example of a banknote.

1 shows such a banknote 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 banknote. The banknote 1 can of course have further security features, such as watermarks, gravure printing, security thread or luminescent or magnetic imprints or the like.

The security element 2 has a thermochromic liquid-crystalline layer which is combined with a liquid-crystalline color shift effect layer. The security element 2 is arranged completely on the surface of the banknote 1, so that the thermal color change is preferred y -

thermochromic layer applied in patterns and / or characters is very well recognizable.

In addition to the thermochromic layer and the color shift effect layer, the security element 2 can also have further layers which, alone or in combination with other layers of the security element, produce further striking optical effects. Some preferred embodiments are explained in more detail with reference to FIGS. 2 to 6, which show the bank note 1 in a top view or in cross section along the dash-dotted line A - A in order to clarify the layer structure of the security element 2.

2, the paper or plastic substrate 3 of the bank note 1, which has a white or light intrinsic color, is provided with a liquid-crystalline thermochromic print 4 in the form of characters or patterns. Over the thermochromic layer 4 is a liquid crystalline over the entire surface

Color shift effect layer 5 is arranged, which generates different color impressions regardless of the temperature when changing the viewing angle in reflection. This effect is referred to as an “optically variable” effect. Layers 4 and 5 can be, for example, a printing ink which consists of a transparent binder into which liquid crystal pigments are mixed.

Since these pigments are translucent and have little or no body color of their own, the visually recognizable optical impression of these pigments is very strongly influenced by the background. The pigments hardly appear on a diffusely reflecting white or light background, since the diffusely reflected scattered light overlaps the optically variable effect. On a dark background, on the other hand, the play of colors of these pigments comes into its own particularly well, since this transmits the Absorbs radiation. According to the invention, the dark, preferably black, surface can be equipped over the entire surface or in a structured manner. For example, the background can be designed in the form of patterns and / or characters, such as guilloches, negative guilloches or other finely structured patterns. Information can also be incorporated into the security element by means of alphanumeric characters or bar codes. The background is preferably designed in such a way that the majority of the area in question is dark or black. ^"

Due to the translucency of the liquid crystal pigments, the substrate 3 preferably has a dark, in particular black intrinsic color, or - as shown here - a further dark, preferably black layer 6, which can be printed, for example, at least in partial areas of the liquid crystalline materials 4, 5. In the case of a dark background, the optically variable effect produced by the color shift effect layer 5 is particularly prominent. In the variant shown in FIG. 2, at least the area equipped with liquid crystalline material is underlaid with a black layer over the entire surface. A thermochromic material that is transparent at normal ambient temperature is preferably used for the layer 4. Above the transition temperature of the thermochromic layer 4, it preferably becomes colored, in particular bright, so that the characters represented by the thermochromic layer 4 become visible and the color shift effect in the area of the characters is virtually imperceptible. The viewer thus has the following picture. Below the transition temperature, he only perceives the color shift effect of the non-thermochromic material 5 with the naked eye. By supplying body heat when touching or rubbing the surface, the thermochromic information 4, here the rectangles, can also be read above the transition temperature, as shown in FIG. 3. The naked eye can trachten already check two security features. In a preferred embodiment, at least one of the liquid-crystalline materials used is a polarizing substance. Particularly preferably, both the thermochromic material 4 and the material with a color shift effect 5 have polarizing properties. The thermochromic material processed in FIG. 2 polarizes above the transition temperature, that is to say in the liquid-crystalline state, preferably light on the right circularly, while the material with color shift effect polarizes on the left-hand circularly. When viewed with a polarization filter that only allows right-hand circularly polarized light, only the information 4 can be read above the transition temperature, while the area of the color-shifting material appears black 7. This situation is shown in Fig. 4. When viewed with a polarization filter that only allows left circularly polarized light to pass through, only area 5 with a color shift effect can be perceived.

Alternatively, a thermochromic material can be used, which is light or colored at normal ambient temperature and only becomes transparent above a certain activation temperature. In this case, previously existing information disappears when exposed to heat.

As shown in FIG. 5, in contrast to the layer sequence shown in FIG. 2, the liquid-crystalline color-shift effect layer 5 can be applied to the black-coated substrate 3 first and then the thermochromic liquid-crystalline layer 4. Which layer sequence is preferred depends on the application or the manufacturing options and can be decided depending on the individual case. If the thermochromic layer is located between the substrate and the color shift effect layer, in some embodiments the thermochromic effect lasts longer, since the color shift effect layer could serve as a kind of heat insulator. This depends However, it strongly depends on several other factors, such as added heat, processed layer thickness, etc. The effects to be observed with regard to the color shift effect, thermochromic information and polarization are comparable to those from FIG. 2.

6 shows a layer structure in which, in a first step, the substrate 3 is provided with a dark, preferably black, imprint 6 in the form of patterns and / or characters. 2 and 5, a full-surface black layer was used. A full-area layer 4 of thermochromic material, followed by a color-shift effect layer 5, is applied over this imprint 6. If a material is used for the thermochromic layer 4 which is transparent at ambient temperature, the optically variable layer 5 appears in the areas of the dark or black imprint as a brilliant layer with a color interplay and is barely perceptible in the areas of the light substrate. Above the transition temperature of the tliermochromic material, the layer 4 becomes colored and can be easily recognized in the area below the marking 6. The color shift effect is no longer visible to the naked eye. If the thermochromic material has properties that polarize to the right in a circular shape, this can be recognized in the area of the black imprint 6 above the transition temperature with the aid of a corresponding polarization filter. If the tipping effect material has link-circular polarizing properties, this can also be measured in the area of the black print 6 using a suitable polarization filter, regardless of the temperature.

The security against counterfeiting is increased in particular if, in addition to the thermal effect and the color shift effect, polarization effects are also used. In the embodiments shown in the figures, self- understandable but not limited to this, the liquid-crystalline thermochromic material can polarize light circular right, for example, while the liquid-crystalline material with color shift effect polarizes light circular left.

It is also possible for the liquid-crystalline layers and / or at least one of the further layers to have further visually and / or machine-testable properties, such as electrical conductivity, magnetism, luminescence or the like. To give the respective print electrically conductive properties, it is sufficient, for example, to add a sufficient amount of carbon black pigments to the printing inks used. Since, in particular, the background should have a dark, preferably black, intrinsic color, it can be provided with magnetic properties in a very simple manner by using dark magnetic pigments instead of color pigments.

In certain embodiments, for example security elements which are exposed to strong mechanical or chemical loads in use, it is appropriate to cover the liquid-crystalline materials with a protective layer. The protective layer can be a film laminated over the security element or a protective lacquer layer. The protective lacquer layer can be applied over the entire area or in partial areas. With thermochromic material and material with optically variable effect arranged next to one another, the partial areas can also be arranged only over one, for example the thermochromic material. In the coating system, UV coatings, hybrid coatings, oil-based printing coatings or dispersion coatings of the one- or two-component type can be used, for example. The protective lacquer layer is preferably printed on, for example by means of flexographic printing or offset printing. The thermochromic layer can also have several thermochromic materials with different transition temperatures. It is also possible to assemble the thermochromic layer from several layers of color, each containing different thermochromic materials with different transition temperatures. In a particularly attractive embodiment, the thermochromic material shows rainbow colors when the temperature rises, ie a color change from colorless to red, yellow, green to blue.

Likewise, different liquid crystalline materials can be combined with different color shift effects.

Claims

P ate nt claims

1. An object of value with a security element, the security element having at least a first and a second liquid-crystalline material, characterized in that the first material has thermochromic properties and the second material has an optically variable effect.

2. Valuable object according to claim 1, characterized in that at least one of the liquid crystalline materials selectively polarizes light.

3. Valuable object according to claim 1 or 2, characterized in that the first and second material polarize light differently.

4. An object of value according to at least one of claims 1 to 3, characterized in that the first material polarizes light on the right and the second material polarizes light on the left or vice versa.

5. An object of value according to at least one of claims 1 to 4, characterized in that the optically variable effect is one

Color shift effect is.

6. Valuable object according to at least one of claims 1 to 5, characterized in that the thermochromic material is applied over the entire surface.

7. An object of value according to at least one of claims 1 to 5, characterized in that the thermochromic material is only provided in certain areas.

8. An object of value according to claim 7, characterized in that the thermochromic material is provided in the form of characters and / or patterns.

9. A valuable object according to at least one of claims 1 to 8, characterized in that the thermochromic material is arranged above or below the material with an optically variable effect.

10. Valuable object according to at least one of claims 1 to 8, characterized in that the thermochromic material is arranged next to the material with an optically variable effect.

11. Valuable object according to at least one of claims 1 to 10, characterized in that there is an at least partially dark, preferably black background among the liquid-crystalline materials.

12. An object of value according to claim 11, characterized in that the entire surface is dark.

13. An object of value according to claim 11, characterized in that the background is in the form of patterns and / or characters.

14. An object of value according to at least one of claims 11 to 13, characterized in that the background is printed, produced by coloring a substrate or using a laser.

15. Valuable object according to at least one of claims 1 to 14, characterized in that one of the materials, the underground and / or has a further layer which can be checked mechanically and / or visually.

16. An object of value according to at least one of claims 1 to 15, characterized in that the thermochromic material is colored below a predetermined temperature and is transparent or at least translucent above this temperature.

17. An object of value according to at least one of claims 1 to 15, characterized in that the thermochromic layer is at least translucent or transparent below a predetermined temperature and colored above this temperature.

18. Valuable object according to at least one of claims 1 to 17, characterized in that the security element is a label.

19. An object of value according to at least one of claims 1 to 17, characterized in that the object of value is a security paper, a security document or a product packaging.

20. Valuable object according to at least one of claims 1 to 19, characterized in that at least part of the security element is covered with a protective layer.

21. Security element for securing valuables, the security element having at least a first and a second liquid-crystalline material, characterized in that the first material has thermochromic properties and the second material has an optically variable effect.

22. Security element according to claim 21, characterized in that the first and second material polarize light differently.

23. Security element according to claim 21 or 22, characterized in that the optically variable effect is a color shift effect.

24. Security element according to at least one of claims 21 to 23, characterized in that the thermochromic layer is transparent below a predetermined temperature or at least translucent and colored above this temperature.

25. Security element according to at least one of claims 21 to 24, characterized in that the security element is a security thread.

26. Transfer material for producing a security element, characterized in that the transfer material has a carrier material on which at least a first and a second liquid-crystalline material are arranged, characterized in that the first material has thermochromic properties and the second material has an optically variable effect having.

27. Transfer material according to claim 26, characterized in that the transfer material is designed as a hot stamping foil.

28. A method for producing a valuable object or security element, characterized in that a substrate is made available, thermochromic liquid-crystalline material and liquid-crystalline material with an optically variable effect are applied to this substrate.

29. The method according to claim 28, characterized in that a) the substrate has an at least partially black layer or surface, b) the thermochromic material is applied in the form of characters and / or patterns above it, and c) the liquid-crystalline material with an optically variable one is applied over it Effect is applied; or d) the substrate has an at least partially black layer or surface, e) the liquid-crystalline material with an optically variable effect is applied over it, and f) the thermochromic material is applied over it in the form of characters and / or patterns.

30. A method for checking a value structure, characterized in that it is checked whether there is a color shift effect and a thermochromic effect.

31. The method according to claim 30, wherein it is additionally checked whether the polarization effects are present.