AU2011244745B2

AU2011244745B2 - Security element having a transparent image region

Info

Publication number: AU2011244745B2
Application number: AU2011244745A
Authority: AU
Inventors: Stefan Bichlmeier; Thomas Gerhardt
Original assignee: Giesecke and Devrient Currency Technology GmbH
Current assignee: Giesecke and Devrient Currency Technology GmbH
Priority date: 2010-04-21
Filing date: 2011-04-07
Publication date: 2016-05-12
Anticipated expiration: 2031-04-07
Also published as: MX341774B; MX2012011782A; WO2011131295A1; AU2016204508A1; DE102010015778A1; EP2560822B1; EP2560822A1; AU2011244745A1

Abstract

The invention relates to a security element (12) for security papers, value documents and other data carriers, having an image region which reveals a predetermined multi-tonal motif (14) when a person looks through it. According to the invention, the security element (12) comprises a thin polymer substrate (20) having a thickness of 300 μm or less, in the image region the polymer substrate (20) contains a multi-step relief (22) having depressions in the shape of the predetermined multi-tonal motif (14), and the depressions of the relief (22) are filled with a filler material (24) having thickness-dependent optical properties.

Description

SECURITY ELEMENT HAVING A SEE-THROUGH IMAGE REGION FIELD OF THE INVENTION The present invention relates to a security element, for security papers, value 5 documents and other data carriers, that exhibits an image region that displays a specified multi-tonal motif when looked through. The present invention further relates to a method for manufacturing such a security element and a data carrier having such a security element. 10 BACKGROUND ART For protection, data carriers, such as security, value or identification documents, but also other valuable objects, are often furnished with security features that permit the authenticity of the data carrier to be verified, and that simultaneously serve as protection against unauthorized reproduction. Here, security features 15 whose authenticity is checked when looked through, such as the long-known watermarks of paper banknotes, permit a particularly simple authenticity check by the user. In polymer banknotes, to date, only imprinted see-through security elements that 20 are not firmly embedded in the note are known. However, such imprinted see through security elements are relatively easy to counterfeit and permit no customization of the substrate, since they are not, or not sufficiently, embedded in the substrate. Consequently, such security features, which are imprinted on a polymer banknote in a known manner, can easily be removed and be applied to 25 another polymer banknote, causing the polymer banknote that was originally provided with the security element to be left as a non-customized polymer foil. Proceeding from this, a preferred aim of the present invention is to provide a security element of the kind cited above that displays a watermark-like see 30 through effect in thin polymer substrates, combining high counterfeit security with simple verifiability by the user.

-2 A further preferred aim is to provide a security element of the kind cited above that facilitates a counterfeit-proof customization of the data carrier. SUMMARY OF THE INVENTION 5 In one broad form, the present invention, provides a security element suitable for security papers, value documents and other data carriers, having an image region that displays a specified multi-tonal motif when looked through, wherein - the security element has a thin polymer substrate of a thickness of 300 Rm or less, 10 - the polymer substrate includes, in the image region, a multi-level relief having depressions in the form of the specified multi-tonal motif, and - the depressions of the relief are filled with a filler material having thickness dependent optical properties. 15 The thickness-dependent optical properties of the filler material preferably consist in a thickness-dependent optical density of the material. The opacity of a material is generally given by the ratio of the illumination intensities before and after the passage through the material (see "http://de.wikipedia.org/wiki/Opazit%C3% /A4t"). The decadic logarithm of the 20 opacity is also referred to as absorbance or optical density (see also "http://de.wikipedia.org/wiki/Extinktion_(Optik)"). For example, an optical density of 1.0 corresponds to a weakening of the light to one tenth of the original illumination intensity, an optical density of 2.0 a weakening to one hundredth. The optical density of a filler material layer is substantially proportional to the layer 25 thickness, so a layer region that is twice as thick exhibits an optical density that is substantially twice as large and appears correspondingly darker when looked through. Here, let it be noted that, in addition to the currently claimed security element 30 having an image region that displays a specified multi-tonal motif when looked -3 through, also image regions that display a specified mono-tonal motif when looked through are comprised by the invention described in the present application. Such a security element having mono-tonal motifs differs from the currently claimed security element having a multi-tonal motif merely in that the 5 polymer substratehas, in the image region, a mono-level relief having depressions in the form of the specified mono-tonal motif. That is, all depressions have substantially the same relief depth, causing the viewer of such a security element to perceive a mono-tonal motif when it is looked through. Such a security element constitutes a particularly simple embodiment of the present invention and permits 10 manufacture with relatively little effort, but the counterfeit protection is not as good as in the currently claimed security elements having an image region that displays a multi-tonal motif when looked through, since the last-mentioned security element is significantly more difficult to counterfeit due to the multi-level relief having depressions in the form of the specified multi-tonal motif. 15 The filler material preferably includes an ink, especially a high-opacity ink, such that the image region displays an opacity-modulated, multi-tonal motif when looked through. 20 In any case, the opacity of the filler material must be chosen such that the viewer can readily recognize the multi-tonal motif according to the present invention as a security feature of the data carrier. The person skilled in the art can set the opacity of the filler material depending on the parameters that determine the opacity of the security element, such as especially the average relief depth. 25 Especially solvent-based inks, IR-, UV-crosslinking inks or acrylic inks, and also mixtures of these inks, if appropriate, are inks that are suitable as the filler material.

-4 To produce the inventive thickness-dependent optical properties of the security element, advantageously, pigments, such as titanium dioxide (TiO2), polymeric filler materials or dyes can be used. In the context of the present invention, dyes in the filler material are soluble colorants, whereas pigments in the filler material are 5 practically insoluble. The thickness-dependent optical property of the security element due to a filler material having thickness-dependent optical properties can, in principle, be altered after the introduction of the filler material. For this, a filler material having 10 activatable substances is introduced into the depression of the relief, the substances being activated, for example by heat or the action of electromagnetic radiation, especially by means of laser radiation, after the filler material is poured in. The activation can occur, for example, in an increase in the opacity in some regions in the motif region. In this way, a comparatively simply designed motif 15 can, for example, be supplemented by a corresponding fine structure. Further, the introduction of an additional piece of information in the region of the motif is conceivable, for example in the form of a denomination specification for the value document in the form of a banknote, or a customizing piece of information, especially numbers and letters, in a value document in the form of a card. 20 In further advantageous embodiments, the filler material can include a luminescent ink, an IR- or UV-absorbing ink or a magnetic ink. The filler material can also combine several of the named properties. For example, the filler material can exhibit a high opacity for a watermark-like visual impression, and 25 simultaneously be magnetic to permit machine readout of the motif image. The depressions of the multi-level relief expediently have a maximum relief depth of less than 100 gm, preferably a maximum relief depth between 5 pm and 50 pm. It is understood that the maximum relief depth and the layer thickness of the 30 polymer substrate are expediently coordinated with each other. In general, the -5 maximum relief depth is between 10% and 99 % of the layer thickness of the polymer substrate of the security element according to the present invention. In advantageous embodiments, the maximum relief depth is, for example, about 50% or about 25% of the layer thickness of the polymer substrate. 5 In one advantageous embodiment, the polymer substrate is provided with a relief only on one of its main surfaces. In another, likewise advantageous embodiment, it is provided that the polymer substrate is provided in the image region on both of its opposing main surfaces with one multi-level relief each. 10 The depressions filled with the filler material are advantageously covered with a cover layer, especially with a finish, a lamination or a plating with foil or fiber stock. The cover layer can be formed by an individual layer, or also consist of multiple sub-layers. 15 Furthermore, to enhance the see-through effect, the cover layer can be provided with gaps. In particular, the cover layer can be fully or partially omitted in the image region. Advantageously, the cover layer exhibits a layer thickness between 6 pm and 50 pm, preferably between 6 pm and 20 pm. 20 In one preferred embodiment, the security element includes, as the polymer substrate, a polymer foil, especially composed of polyethylene, polypropylene, polyester or polyamide. The layer thickness of the polymer substrate is expediently between 25 pm and 300 pm, preferably between 60 pm and 140 pm. 25 In advantageous variants of the present invention, the security element forms a portion of a polymer banknote, composite banknote or polymer ply of a value document, for example a data page of an identification document.

-6 In another broad form, the present invention also provides a method for manufacturing a security element having an image region that displays a specified multi-tonal motif when looked through, in which - a thin polymer substrate of a thickness of 300 gm or less is provided, 5 - the polymer substrate is provided in the image region with a multi-level relief having depressions in the form of the specified multi-tonal motif, and - the depressions of the relief are filled with a filler material having thickness dependent optical properties. 10 In one preferred method variant, the multi-level relief is produced in the polymer substrate by cold embossing, thermal embossing or by laser abrasion. Here, the relief is preferably already introduced when manufacturing the polymer substrate, or shortly thereafter. 15 The filler material can, for example, be contiguously applied to the security element, and any excess of filler material present outside the relief removed, especially squeegeed off. Also a direct introduction of the filler material without subsequent squeegeeing is possible through the use of suitable printing techniques, such as in the "continuous inkjet method." 20 In advantageous method variants, in a further method step, the depressions filled with the filler material are covered with a cover layer, especially by finishing, a lamination or a plating with foil or fiber stock. 25 Finally, the present invention also includes a data carrier having a security element of the kind described. The data carrier is advantageously a security paper or a value document, especially a polymer banknote or a foil composite banknote. Here, the term foil composite banknote comprises especially paper/foil composite banknotes, paper/foil/paper composite banknotes and foil/paper/foil composite 30 banknotes. The data carrier can further be a card, especially an identification card, -7 credit card, bank card, cash card, authorization card, a personal identity card or a passport personalization page. The security element according to the present invention advantageously exhibits such a data carrier in the form of a card as one layer of a multi-layer card composite, the polymer substrate layer according to the 5 present invention being covered by the further layers of the card composite, which, especially in the region of the motif, are developed to be transparent or translucent, and thus protected against manipulation attempts. Further exemplary embodiments and advantages of the present invention are 10 described below with reference to the drawings. To improve clarity, a depiction to scale or proportion was dispensed with in the drawings. BRIEF DESCRIPTION OF THE DRAWINGS Shown are: 15 Fig. 1 a schematic diagram of a polymer banknote according to an exemplary embodiment of the present invention, Fig. 2 a cross section through the polymer banknote in fig. 1 along the line II-IL, Fig. 3 a cross section through a polymer banknote without a cover layer 20 according to another exemplary embodiment of the present invention, Fig. 4 an exemplary embodiment in which a thin polymer substrate is provided on both of its opposing main surfaces with one filled relief each, 25 Fig. 5 an exemplary embodiment, in which the cover layer is provided with gaps to enhance the watermark-like see-through effect, and Fig. 6 an embodiment in which the multi-level relief is present in a thin, transparent embossing lacquer layer.

-8 DESCRIPTION OF EMBODIMENT(S) OF THE INVENTION The invention will now be explained using a polymer banknote as an example. For this, fig. 1 shows a schematic diagram of a polymer banknote 10 having an inventive security element 12 that displays, when looked through, an opacity 5 modulated, multi-tonal image motif 14 that is firmly embedded in the note. The image motif can be, for example, a portrait or a similar depiction. In the exemplary embodiment, the image motif is formed by a multi-tonal portrait 14 that is depicted schematically in fig. 1 as a line drawing for illustration. Fig. 2 10 shows a cross section through the polymer banknote 10 in the region of the security element 12 along the line II-II in fig. 1. The polymer banknote 10 includes a thin substrate 20 composed of a polymer foil, for example composed of polyethylene, polypropylene, polyester or polyamide. 15 The thickness of the polymer substrate 20 is 100 gm in the exemplary embodiment shown, but can, in principle, be in the range between 25 pm and 300 pm and preferably in the range between 60 pm and 140 pm. Already at its manufacture there was introduced into the polymer substrate 20 a 20 multi-level relief 22 having depressions in the form of the portrait 14, for example by cold embossing, thermal embossing or laser abrasion. In the exemplary embodiment, the depressions of the relief 22 exhibit a maximum relief depth of 50 pm and, with the plurality of relief depths occurring, form a relief having a practically continuous depth profile. In other embodiments, however, also a relief 25 having a certain number of discrete relief depths, for example 10 relief depth levels, can be produced. Finally, in a further conceivable embodiment, a number of discrete relief depths are used that, on the one hand, exhibit more than approximately 10 relief levels, but on the other hand, do not exhibit so many discrete relief depths that reference can be made to a continuous depth profile. In -9 this further embodiment, reference can be made to a quasi-continuous depth profile. After the introduction of the relief 22, the depressions of the relief are filled with a 5 high-opacity ink 24. The ink 24 can be any suitable filler material according to the present invention, for example a lithopone-like ink. For this, the ink 24 can, for example, be applied contiguously and any excess ink present outside the depressions squeegeed off the surface of the substrate 20. Finally, the relief 22 that is filled with ink 24 is provided with a transparent cover layer 26, for example by 10 imprinting or laminating a protective layer on it. In this way, the security element 12 shown in fig. 2 is created as part of the polymer banknote 10. Here, the local opacity of the filled relief 22, 24 depends on the local layer thickness of the ink 24 and thus on the local relief depth. Due to the 15 high opacity of the ink 24, the tonal range of the image motif can range from complete transparency (local relief depth zero) to nearly complete opacity (at maximum embossing depth). Here, nearly complete opacity means, depending on the opacity of the ink used and the maximum embossing depth, a transmittance of 100% or less, 50% or less, 2 % or less or even 10% or less. 20 Since the opacity of the image motif 14 depends on the local layer thickness, an opacity-modulated depiction of the image motif having a plurality of different tonal values results when looked through. Here, the different tonal values are formed by the locally different opacities, which, when looked through, convey a 25 more or less bright image impression locally. In this way, the image motif 14 appears for the viewer having a watermark-like see-through effect. Visual see-through security features of this kind are familiar to the user from watermarks in paper banknotes and are thus normally quickly perceived as 30 security features and reliably verified. Simultaneously, the image motif 14 -10 produced by the filled relief 22, 24 is firmly embedded in the polymer substrate 20 and inseparably joined therewith. The security element 12 thus offers significantly higher protection of the polymer banknote 10 than security features that are imprinted onto, or other security features that are merely applied to, the substrate 5 surface. As filler material for the relief, also a luminescent ink, an IR- or UV-absorbing ink or a magnetic ink can be used. Due to the locally varying layer thickness, filler material having magnetic properties produces a machine-readable piece of image 10 information. Also IR- or UV-absorbing or luminescent motif images can be machine read. In advantageous embodiments, the filler material can exhibit both a high opacity for the visual perceptibility and magnetic properties for the machine detection of the security element. 15 The cover layer 26 is preferably applied to the substrate 20 by means of finishing, lamination or plating with foil or fiber stock. In some embodiments, a cover layer can also be omitted, as depicted by way of example in fig. 3. With reference to fig. 4, the polymer substrate 20 can also be provided on both of 20 its opposing main surfaces with one relief 22, 32 each. Here, the two reliefs 22, 32 can be developed having the same or different depth profiles. Also, the two reliefs 22, 32 can be filled either with the same or also with different filler materials 24, 34. For example, the optical properties of two different filler materials 24, 34 can complement each other to form the desired overall impression only when looked 25 through, or one filler material 24 can be designed or optimized for visual perceptibility and the other filler material 34 for machine detectability. In one variant of the present invention that is not shown further, the reliefs 22, 32 depicted in fig. 4 can also be shifted against each other in the substrate surface direction, such that, depending on the magnitude of the shift of the two reliefs 22, 30 32, the viewer perceives, in through view, an overall motif that is composed of the -11 motifs depicted by the reliefs 22 and 32. Here, from certain viewing directions, the viewer perceives, in the regions of the reliefs 22, 32 that overlap from these viewing directions, a high opacity that is composed of the opacities of the reliefs 22 and 32. 5 When looked through, the filled reliefs 22, 32, taken together, display the desired image motif, such as the portrait 14 in fig. 1. Here, the opposing filled reliefs 22, 32 are preferably both covered and protected with a cover layer 26, 36. 10 In all embodiments, the cover layer can also be provided with gaps 40 to enhance the watermark-like see-through effect. As depicted in the exemplary embodiment in fig. 5, the gaps 40 in the cover layer 26 are especially arranged in the region of the filled relief 22, 24 and can fully or partially include the relief region. 15 In the embodiment shown in fig. 6, the polymer substrate is not executed to be mono-layer, but rather multi-layer. To a first layer 50, which corresponds substantially to the polymer substrate shown in figures 1 to 5 and described in the associated figure description, a thin, transparent embossing lacquer layer 52 is applied in which a multi-level relief 54 is embossed in the form of the desired 20 image motif. The depressions in the embossing lacquer layer 52 are filled with a high-opacity filler material 56 such that, here, too, an opacity-modulated, multi tonal image motif is created when looked through. The filled relief 54, 56 and/or the embossing lacquer layer can optionally be covered with a cover layer, not depicted in the figure. 25 When manufacturing a multi-layer polymer substrate shown in fig. 6, it must, of course, be ensured that the layers are substantially inseparably joined with each other so that the advantages of the present invention, especially the increased counterfeit security, can be achieved. In any case, the layers must be joined with 30 each other in such a way that, in the event of a manipulation attempt, for example - 12 by the action of certain solvents, the individual layers of the multi-layer polymer substrate cannot be separated from one another without at least partial destruction, such that a corresponding manipulation attempt would immediately be perceptible as such. The embossing lacquer layer 52 can advantageously be a 5 thermally or UV-curing lacquer having a layer thickness of about 40 pm, the layer thickness range from 5 gm to 30 pm being particularly preferred. Reference to background art or other prior art in this specification is not an admission that such background art or other prior art is common general 10 knowledge in Australia or elsewhere.

-13 List of reference signs 10 Polymer banknote 12 Security element 5 14 Image motif 20 Polymer substrate 22 Relief 24 Ink 26 Cover layer 10 32 Relief 34 Filler material 36 Cover layer 40 Gaps 50 Layer 15 52 Embossing lacquer layer 54 Relief 56 Filler material

Claims

1. A security element for security papers, value documents and other data carriers, having an image region that displays a specified multi-tonal motif when looked through, characterized in that - the security element has a thin polymer substrate of a thickness of 300 Rm or less, - the polymer substrate includes, in the image region, a multi-level relief having depressions in the form of the specified multi-tonal motif, and - the depressions of the relief are filled with a filler material having thickness dependent optical properties.

2. The security element according to claim 1, characterized in that the filler material includes an ink, especially a high-opacity ink, such that the image region displays an opacity-modulated, multi-tonal motif when looked through.

3. The security element according to claim 1 or 2, characterized in that the filler material includes a luminescent ink, an IR- or UV-absorbing ink, an acrylic ink or a magnetic ink.

4. The security element according to any one of claims 1 to 3, characterized in that the depressions of the multi-level relief have a maximum relief depth of less than 100 pm, preferably a maximum relief depth between 5 pm and 50 pm.

5. The security element according to any one of claims 1 to 4, characterized in that the polymer substrate is provided with one multi-level relief each in the image region on both of its opposing main surfaces. -15

6. The security element according to any one of claims 1 to 5, characterized in that the depressions filled with the filler material are covered with a cover layer, especially with a finish, a lamination or a plating with foil or fiber stock.

7. The security element according to claim 6, characterized in that the cover layer consists of multiple sub-layers.

8. The security element according to claim 6 or 7, characterized in that, to enhance the see-through effect, the cover layer is provided with gaps, especially in that the cover layer is fully or partially omitted in the image region.

9. The security element according to any one of claims 6 to 8, characterized in that the cover layer has a layer thickness between 6 and 50 gm, preferably between 6 pm and 20 pm.

10. The security element according to any one of claims 1 to 9, characterized in that the security element includes, as the polymer substrate, a polymer foil, especially composed of polyethylene, polypropylene, polyester or polyamide.

11. The security element according to any one of claims 1 to 10, characterized in that the substrate of the security element has a layer thickness of 25 pm to 300 pm, preferably of 60 pm to 140 pm.

12. The security element according to any one of claims 1 to 11, characterized in that the security element forms a portion of a polymer banknote, a composite banknote or a polymer ply of a value document.

13. A method for manufacturing a security element having an image region that displays a specified multi-tonal motif when looked through, in which - a thin polymer substrate of a thickness of 300 pm or less is provided, -16 - the polymer substrate is provided in the image region with a multi-level relief having depressions in the form of the multi-tonal motif, and - the depressions of the relief are filled with a filler material having thickness dependent optical properties.

14. The method according to claim 13, characterized in that the multi-level relief is produced in the polymer substrate by cold embossing, thermal embossing or by laser abrasion.

15. The method according to claim 13 or 14, characterized in that the filler material is applied contiguously to the security element and any excess of filler material present outside the relief is removed, especially is squeegeed off.

16. The method according to any one of claims 13 to 15, characterized in that the depressions filled with the filler material are covered with a cover layer, especially by finishing, a lamination or a plating with foil or fiber stock.

17. A data carrier, especially a security paper or value document, having a security element according to any one of claims 1 to 12.

18. A data carrier according to claim 17, characterized in that the data carrier is a banknote, especially a polymer banknote or a foil composite banknote, or a card, especially an identification or credit card.