EP2512818A1

EP2512818A1 - Security element, and method for the production thereof

Info

Publication number: EP2512818A1
Application number: EP10795235A
Authority: EP
Inventors: Peter Schiffmann; Marius Dichtl
Original assignee: Giesecke and Devrient GmbH
Current assignee: Giesecke and Devrient Currency Technology GmbH
Priority date: 2009-12-17
Filing date: 2010-12-10
Publication date: 2012-10-24
Anticipated expiration: 2030-12-10
Also published as: WO2011082760A1; EP2512818B1; DE102009058602A1

Abstract

The invention relates to a security element for security papers, value documents, or the like, comprising - a carrier (2) that has an upper face, - several micro-imaging elements (6) lying on the upper face of the carrier (2) and at least one motif layer (4) lying under the micro-imaging elements (6), said motif layer together with the micro-imaging elements (6)forming a moiré magnification arrangement, which displays a first motif (10) in front of the upper face, the position of said first motif (10) depending on the viewing angle, - and a structure (7) which lies above the micro-imaging elements (6) and which shows a second motif (10) in a spatially specified position with respect to the first motif (8) when viewed from the upper face, wherein - the first motif (10) is designed as a raster image which has a first raster, and - the structure (7) which lies above the micro-imaging elements (6) is likewise designed as a raster image having a second raster which is adapted to the first raster.

Description

Security element and

Manufacturing procedures for this

The invention relates to a security element for security papers, documents of value or the like, having a carrier, which has an upper side, a plurality of microimaging elements arranged on the upper side of the carrier, at least one motif layer arranged below the microimage elements, which together with the microimage elements. Menten forms a Moire- enlargement arrangement, which images a first motif in front of the top, wherein the position of the first motif depends on the viewing direction, and applied to the microimage elements structure, which viewed from the top of a second motif in a spatially predetermined position to the first Motif shows.

Items to be protected are often provided with a security element that allows verification of the authenticity of the item and at the same time serves as protection against unauthorized reproduction. Items to be protected include, for example, security papers, identity and value documents (such as banknotes, chip cards, passports, identification cards, identity cards, stocks, bonds, certificates, vouchers, checks, tickets, credit cards, health cards, etc.) as well as product security elements such as security items. Labels, seals, packaging.

The security against forgery and visibility of a security element is particularly great if the security element does not show reproducible motifs or information through copying operations. For banknotes various security elements are known, which are provided with optical properties. The combination of microstructure elements with overlying microlenses, which increase the microstructural elements, has proved to be particularly tamper-proof. In particular, the so-called moiré effect can be used here. Such security elements are also referred to as moiré magnification arrangements. An exemplary description of such a security element can be found in WO 2008/031170 AI and US 2005/0180020 AI.

The publication US Pat. No. 5,712,731 A also discloses the use of a moire magnification arrangement for a security element. The security device described therein has a regular arrangement of substantially identical printed microimages with a size of up to 250 μιτι and a regular two-dimensional array of substantially identical spherical microlenses. The microlens arrangement has substantially the same pitch as the microimage arrangement. If the micro-image arrangement is viewed by the microlens array, then in the areas in which the two arrangements are substantially in register, one or more enlarged versions of the microimages are generated for the viewer.

The principle of operation of such Moire magnification arrangements is also described in the article "The Moire Magnifier", M.C. Hutley, R.

Hunt, RF Stevens and P. Savander, Pure Appl. Opt. 3 (1994), pp. 133-142, described. Thus, moire magnification, in short, refers to a phenomenon that occurs when viewing a raster of identical image objects through a lenticular of approximately the same pitch. As with any pair of similar grids, this results in a moire pattern that is in this Fall as an enlarged and possibly rotated image of the repeated elements of the image grid appears.

A moiré magnification arrangement has the property _/ Bildin- that f ormation with the viewing angle changes. For example, US 2005/0180020 A1 discloses an orthoparallactic movement of the generated image. If one tilts the security element, the depicted motif moves perpendicular to the tilt axis, which contradicts the usual movement behavior in three-dimensional space and therefore has a high attention and recognition value. Moire magnification arrangements are therefore widely used in security elements.

WO 2007/133613 A2 proposes to combine a moire magnification arrangement, which generates a viewing direction-dependent image, with static print information. The image information generated by the moire magnification arrangement is supplemented by statically printed images. The document specifies to print the image information on the lens surface of the Moire magnification arrangement, or to provide this image information in the case of a transparent security element on the underside of the Mo Vergröß Vergröß magnification arrangement, ie under the microstructure elements. The static, ie printed images can supplement or even delete the image information generated by the moire magnification arrangement. The invention has for its object to provide a security element that gives increased moire magnification arrangements increased copy and reproduction protection. To achieve the object, the invention provides a security element for security papers, documents of value or the like, with a carrier having a top, a plurality of surface arranged on the top of the carrier micro imaging elements and at least one arranged under the microimage elements motif layer, which together with the microimage elements a Moire magnification arrangement, which images a first motif in front of the top, wherein the position of the first motif depends on the viewing angle, and a structure arranged above the microimage elements which, viewed from the top, shows a second motif in a spatially predetermined position relative to the first motif, wherein the first motif is designed as a raster image having a first rasterization, and the structure arranged above the microimage elements is likewise designed as a raster image which has a second rastering, wherein the two rasters are attached to one another fits are.

The term "above" is to be understood as the usual convention in the viewing direction The raster structure is located in the viewing direction, ie before the microimage elements This can be realized particularly simply by applying the raster structure to the microimage elements, optionally with the interposition of further Layers or structures.

Furthermore, the term "micro" in the sense of this description means that the corresponding elements etc. are not resolvable with the unaided eye.

The combination of a moiré magnification arrangement according to the invention and the structure arranged above the microimage elements makes it possible to combine the motifs generated thereby at the level of the Both rasters, so a size level that is below the motif size. By contrast, the prior art combines motifs and can thus achieve, for example, masking by pushing one motif over the other during slow tilting of the security element. By virtue of the invention, mutual matching of the rasters and thereby a combination of the two rastered motifs is now possible in such a way that the raster elements which form the respective motif overlap individually. The security element according to the invention can thus work in the sense of a shading image in which, for example, the first motif suddenly disappears or appears due to tilting of the security element. However, compared with conventional shading images, the thickness of the security element is much lower when the structure providing the screened second motif is applied to the microimage elements.

A particularly simple realization of the invention is achieved by printing the structure directly onto the microimage elements. The security element then only has a thickness between 80 μπ \ and 100 μπι. The security element allows, as already mentioned, a viewing direction-dependent obscuring the first subject. For such an application, it is preferred that the moire magnification arrangement is formed such that the second motif obscures the first motif in at least one viewing direction. The adaptation of the second rasterization of the structure arranged on the microimage elements to the raster of the (moiré) motif of the moiré magnification arrangement can be calculated particularly simply by the magnification factor with which microstructures of the motif layer arranged below the microimage elements are enlarged , From this magnification factor, the grid of the first (Moire-) results Motive, which is generated by the Moire magnification arrangement, and thus the required vote for the associated second screening of the arranged on the microimage elements structure. Of course, the security element according to the invention can not only be used for shading the first motif. Rather, in a development of the invention by suitable design of the first motif of the moiré magnification arrangement and the selected adaptation of the second screening of the structure arranged on the microimageable elements structure is also possible to achieve an information supplement that appears (only) in a particular line of sight. In this viewing direction, for example, the information of the first and the second motif can be combined to form a total information, as otherwise already known in the prior art, for example in the form of a currency unit and a denomination of a banknote.

The abovementioned object is, of course, also achieved by a corresponding production method for a security element in which a) a motif layer and a plurality of microimage elements are formed on a support, wherein the microimage elements and the motif layer together form a moiré magnification arrangement, which forms a first motif B) over the microimage elements, a structure is arranged, which when viewed from the top shows a second motif in a spatially predetermined position to the first motif, the first motif designed as a raster image is, which has a first screening, and d) the structure arranged in b) is also carried out as a raster image having a second screening, wherein the two screens are adapted to each other. As far as this description refers to the mentioned security element, this of course also applies analogously to the associated manufacturing process and vice versa. The security element can be designed, in particular, as a security thread, tear-open thread, security strip, security strip, patch or label for application to a security paper, value document or the like. In particular, the security element can span transparent areas or recesses or recesses or windows.

The term security paper is understood here to mean, in particular, the precursor of a value document which is not yet ready for circulation and which, in addition to the security element according to the invention, may for example have further authenticity features (such as, for example, luminescent substances contained in the volume). Value documents are here understood, on the one hand, documents produced from security papers. On the other hand, value documents can also be other objects and documents that can be provided with the security feature according to the invention, so that the value documents have non-copyable authenticity features. In this way, an authenticity check is possible and at the same time unwanted or unauthorized copies are prevented. In particular, the document of value may be a banknote and the security paper may be banknote paper. The production method according to the invention can be developed so that the described preferred embodiments and embodiments of the security element are produced. It is understood that the features mentioned above and those yet to be explained below can be used not only in the specified combinations but also in other combinations or alone, without departing from the scope of the present invention.

The invention will be explained in more detail by way of example with reference to the accompanying drawings, which may also disclose features of the invention. In the drawings shows:

Fig. 1 is a sectional view through a security element and

FIGS. 2-4 are exemplary plan views of motifs generated by the security element of FIG.

The figures are not shown to scale for clarity. This is especially true for layer thicknesses in sectional views. In the following description of the sectional view of Fig. 1 is referred to as the top or front of the security element in the figure above page. The back or bottom is accordingly the opposite side. This convention is for convenience of description only and is not intended to be limiting as to the construction and / or application of the security element.

Fig. 1 shows a security element 1, which can be integrated, for example, within a banknote. The security element 1 can be part of a security thread of the banknote, which is woven in a known manner into the paper of the banknote for the skilled person that it is partially visible on the front and partly on the back of the banknote. In particular, it is possible within the scope of the invention to arrange the security element 1 at least partially over a window provided in the banknote. However, these possibilities are of course only examples of the uses of the security element 1 described below, which of course can be used in other ways for copying or imitation protection of a protected object. Basis for the security element 1 is a carrier 2, which can be realized for example by a plastic film. This plastic film is transparent. For the purposes of this invention, the term "transparent" or "transparency" is understood to mean visual or visual transparency. The transmittance in the region of the visible optical radiation (= light) is preferably at least 90%, but also significantly lower transmittances down to 30% are possible.

The security element can also be full-surface or partially colored or colored by an overprint.

The carrier 2 has on its (top in the illustration of FIG. 1) top micro imaging elements 3, which are arranged in a specific pattern. On its underside, a motif layer 4 is applied to the support 2, which has a plurality of microelements 5, which are also arranged in a pattern. The pattern of the micro-imaging elements 3 is defined by an array of microlenses 6. The microimage elements 3 realize, together with the motif layer 4, a moiré magnification arrangement which identifies the image information realized by the microelements 5 as the first motif (hereinafter referred to as the moiré motif). in front of the top of the carrier 2 magnified images. The moire motif is designed as a raster image which encodes the image information in a specific screening, for example as a bar or dot matrix. The microlenses 6 may be formed, for example, on the surface of the carrier 2, which may be, for example, a transparent plastic film, in particular an approximately 20 μm thick polyethylene terephthalate (PET) film, forming the pattern in the form of a two-dimensional Bravais grating having a predetermined symmetry. The term "pattern" is used here for a clear distinction from the screening of the moiré motif-of course, the pattern in which the microlenses 6 are arranged could of course also be called a screen.

For the pattern in which the microlenses 6 are arranged, for example, a hexagonal lattice symmetry can be used. However, other, in particular lower symmetries and thus more general forms, such as the symmetry of a parallelogram grating, are also possible.

The distance of adjacent microlenses 6 is preferably chosen as small as possible in order to achieve the highest possible area coverage, since this is advantageous for a high-contrast representation of the moire motif. The spherically or aspherically configured microlenses 6 preferably have a diameter between 5 μm and 50 μm and in particular a diameter between 10 μm and 35 μm. They are therefore invisible to the naked eye. The microelements 5 on the underside of the carrier 2 form the motif layer 4, wherein the pattern of the microelements 5 forms the same grid as the microlenses 6, for example again a two-dimensional Bravais grid with a predetermined symmetry. However, for the moiré magnification arrangement, the pattern of the microelements 5 differs slightly in its symmetry and / or size of the grating parameters from the pattern of the microlenses 6. Depending on the nature and size of the difference, a more or less magnified image arises when viewed from the front side the microelements 5.

Grid period and diameter of the pattern of the microlenses 6 and the microelements 5 are of the same order of magnitude, ie preferably in the range already mentioned, so that even the microelements 5 themselves can not be resolved normally with unarmed eyes or even not be seen.

The focal length of the microlenses 6 and the optical thickness of the carrier 2 are matched to one another such that the microelements 5 which form the motif layer 4 are located approximately at a distance from the lens focal length of the microlenses 6. The carrier 2 thus serves as an optical spacer layer which ensures a desired constant distance of the microlenses 6 from the microelements 5 of the motif layer 4. On the microlenses a printing layer 7 is applied as a motivating structure, which generates a second motif (hereinafter referred to as print motif). This is also designed as a raster image. The print motif is matched in its grid to that of the Moire motif. The layer 7 can be printed on. Also, a film can be applied, which contains the layer 7. The film may be a cold or a heat-sealing film. The use of an inkjet printing process comes into question. Further, a layer may first be applied and then structured, e.g. B. by laser radiation and / or ablation. This allows an individual simplification or personalization of the security element.

Figures 2 to 4 show the top view of the respective motifs 8, 10 and their screens. Fig. 2 shows the top view of the grid 9 of the printing motif 8 of the printing layer 7. Of course, this structure is to be understood only as an example; it serves to illustrate the operation of the invention. From the geometry of the image of the Moire magnification arrangement, in particular the imaging properties of the microlenses 6, the explained slight pattern difference between the motif layer 5 and microimage elements 3 and the thickness of the support 2, the magnification factor of the image of the microelements 5 and the motif layer 4 and thus the Size of Moire Motif 10. Matching the resulting grid of Moire motif 10, the grid of print layer 7 is selected, which is shown in FIG. 2 merely as a simple bar raster 9 having individual bars. It does not matter, however, which screening is adapted to the other one. Decisive is the mutual vote. The (enlarged) rasterized motif produced by the moiré magnification arrangement is shown in FIG. 3 by way of example in the form of a moiré motif 10.

At certain viewing angles, the print motif 8 of the print layer 7 produced by the line grid 9 and the moiré motif 10 are combined to form an overall image 11. This is illustrated in FIG. 4. The different graphs illustrate the proportion of each picture in the overall picture 11. At other angles there is no supplement. The additive supplement shown in FIG. 4 may in the simplest case be a supplement of black / white information. Depending on the design of the individual images, but also a complement spectrally different image components is possible, for example, a subtractive color mixing or additive color mixing.

Also, instead of supplementing the image information, erasure can be realized, for example when, in a vertical plan view, the moire motif 10, which is enlarged by the moir6 magnification arrangement, is completely behind opaque structures of the printing motif 8, z. B. the bar raster 9 is located. Looking at the security element then from a point of view not equal to 90 °, the moire motif 10 produced by the Moir6 magnification arrangement appears, since its rasterization is then not (more) covered. Of course, the described principle that the screening of the moire motif 10 and the printing motif 8 complement one another can also be used in further exemplary embodiments:

For example, the screening of Moire-Motiv 10 and Druck-Motiv 9 can be made to fit together in such a way that the overall information only becomes visible after the print layer has been printed.

The print motif 10 can show first information in its raster, and in combination with the raster of the print motif 9 of the print layer 7, a second additional information results.

The security element 1 is mounted over a window / opening of a substrate of a value document such that it overlaps the window over a large area. On the substrate, a print motif is attached, the gives information supplementing with information of the moire motif spanning the window.

LIST OF REFERENCE NUMBERS

security element

carrier

Micro-imaging elements

motif layer

microelements

microlenses

print layer

Print motif

line grid

Moire Scene

overall picture

Claims

Patent claims

A security element for security papers, documents of value or the like, comprising a carrier (2) having an upper side, a plurality of microimage elements (6) arranged on the upper side of the carrier (2) and at least one motif layer (4) arranged below the microimage elements (6). which forms, together with the microimage elements (6), a moire magnification arrangement which images a first subject (10) in front of the top, the position of the first subject (10) depending on the viewing angle, and - one above the microimage elements (6) Structure (7) which, when viewed from the upper side, shows a second motif (8) in a spatially predetermined position relative to the first motif (10), characterized in that the first motif (8) is designed as a raster image which has a first rastering, and the structure (7) arranged above the microimage elements (6) is likewise designed as a raster image which has a second rastering which is applied to the first screening is adjusted.

2. Security element according to claim 1, characterized in that the structure (7) applied to the micro-imaging elements (6), in particular is printed.

3. Security element according to claim 1 or 2, characterized in that the moire magnification arrangement is formed so that the second motif (8) covers the first motif (10) in at least one viewing angle.

4. Security element according to one of the above claims, character- ized in that the Moire magnification arrangement is formed so that the second motif (8) complements the first motif (10) at least one viewing angle.

5. Security element according to one of the above claims, character- ized in that the security element (1) is applied to a transparent window and / or on a semi-transparent substrate.

A method of manufacturing a security element, comprising: a) forming a motif layer (4) and a plurality of microimage elements (6) on a support (2), wherein the microimage elements (3) and the motif layer (4) together form a moire magnification arrangement; which images a first motif (10) in front of an upper side of the carrier (2), wherein the position of the first motif (10) depends on the viewing angle, b) a structure (7) is arranged over the microimage elements (6) which, when viewed by the upper side shows a second motif (8) in a spatially predetermined position relative to the first motif (10), characterized in that c) the first motif (10) is executed as a raster image which has a first rasterization, and d) the structure (7) arranged in b) is likewise executed as a raster image which has a second rasterization which adapted to the first latching.

7. Production method according to claim 6, characterized in that the structure (7) is applied to the microimage elements (6), in particular printed on, applied by means of inkjet, lasered or comprises an applied cold foil or heat-sealing foil.

8. Manufacturing method according to claim 6, characterized in that the structure (7) is applied to the microimage elements (6) by applying a layer and subsequently structuring it, in particular by means of irradiation and / or ablation.

9. Manufacturing method according to claim 6, 7 or 8, characterized in that the moire magnification arrangement is formed so that the second motif (8) covers the first motif (10) at least one viewing angle.

10. Manufacturing method according to one of claims 6 to 9, characterized in that the moiré magnification arrangement is formed so that the second motif (8) complements the first motif (10) at least one viewing angle.