AU2008243443B2

AU2008243443B2 - Inspection security element

Info

Publication number: AU2008243443B2
Application number: AU2008243443A
Authority: AU
Inventors: Marius Dichtl; Manfred Heim; Thomas Kampe; Ernst-Bernhard Kley; Michael Rahm
Original assignee: Giesecke and Devrient Currency Technology GmbH
Current assignee: Giesecke and Devrient Currency Technology GmbH
Priority date: 2007-04-25
Filing date: 2008-04-10
Publication date: 2011-10-06
Anticipated expiration: 2028-04-10
Also published as: DE502008001270D1; ATE479797T1; EP2155963B2; EP2155963B8; AU2008243443A1; DE102007019522A1; EP2155963A1; MX2009010875A; WO2008131852A1; EP2155963B1

Abstract

The invention relates to an inspection security element (20) for security papers, value documents, and the like, comprising at least a first security characteristic (24) and a second security characteristic (34) located on opposite sides of the security element (20), wherein, according to the invention, the first security characteristic (24) is a security characteristic recognizable in reflection having a grid pattern (28) that can influence electromagnetic radiation, the pattern comprising a plurality of ruled grating lines, and the second security characteristic (34) is an optical element forming radiation in transmission.

Description

See-Through Security Element The present invention relates to a see-through security element for security papers, value documents and the like that exhibits at least a first and a 5 second security feature that are arranged on opposing sides of the security element. For protection, data carriers, such as value or identification documents, or other valuable articles, such as branded articles, are often provided with 10 security elements that permit the authenticity of the data carriers to be verified, and that simultaneously serve as protection against unauthorized reproduction. The security elements can be developed, for example, in the form of a security thread embedded in a banknote, a tear strip for product packaging, an applied security strip, a cover foil for a banknote having a 15 through opening, or a self-supporting transfer element, such as a patch or a label that, after its manufacture, is applied to a value document. For several years now, see-through windows have also proven to be attractive security elements in polymer and, most recently, also in paper 20 banknotes, since they permit the use of a number of security features. Security elements having viewing-angle-dependent effects play a special role in safeguarding authenticity, as these cannot be reproduced even with the most modern copiers. Here, the security elements are furnished with 25 optically variable elements that, from different viewing angles, convey to the viewer a different image impression and, depending on the viewing angle, display for example another color or brightness impression and/or another graphic motif. For example, publication EP 1 468 141 A2 describes a see through window that can include a security element that consists of a 30 diffraction pattern, a thin-film element, a polarization filter or an imprint that 2 exhibits at least one substance having optically variable, luminescent, electrically conductive or magnetic properties. Based on that, the object of the present invention is to specify a see-through 5 security element of the kind cited above that avoids the disadvantages of the background art. In particular, the see-through security element should combine an appealing visual appearance with high counterfeit security. This object is solved by the see-through security feature having the features 10 of the main claim. A security paper, a value document and a corresponding manufacturing method are specified in the coordinated claims. Developments of the present invention are the subject of the dependent claims. 15 According to a first aspect of the present invention, in a generic see-through security element, the first security feature is a security feature that is perceptible in reflection and that has an electromagnetic-radiation influencing grating pattern composed of a plurality of grating lines. According to the present invention, the second security feature is an optical 20 element that is beam-shaping in transmission. The second security feature is typically formed as a second-level security feature, that is, it can be verified only with auxiliary means, especially a laser source, such as a laser pointer. The first security feature, in contrast, is always a first-level security feature that is perceptible with the naked eye and that conveys to the viewer 25 especially a colored, moving or spatial image impression. In this way, the see-through security element according to the present invention combines high counterfeit security with a visually appealing appearance for the viewer.

3 In a preferred embodiment, the first security feature constitutes a diffraction pattern, especially a hologram, a holographic grating image, a blazed diffraction pattern, a computer-generated hologram (CGH) or another hologram-like diffraction pattern. The grating pattern of the first security 5 feature can be manufactured especially through direct holographic exposure, through a dot-matrix method or with electron beam lithography. In an alternative, likewise advantageous embodiment, the first security feature constitutes an achromatic matte pattern that displays no diffractive 10 effects when viewed, but rather merely has a scattering effect. In both cases, the grating pattern of the first security feature advantageously consists of a plurality of grating lines having a preferably sinusoidal profile, the spacing and the orientation of the grating lines being able to vary across 15 the area of the security feature to produce a desired optical effect. To produce an appealing visual impression, the grating pattern especially constitutes an alternating image, a pump image, a motion image, a morph image or a stereo image. Further details on the design and the properties of such grating images can be found in publication DE 103 48 619 Al, whose 20 disclosure in this respect is incorporated in the present application. In an advantageous embodiment, the first security feature includes an embossing pattern that is formed in a radiation-curing or thermoplastic lacquer. Here, the embossing pattern can be formed as a continuous 25 embossing pattern, or also as a binary pattern that includes exclusively planar areal sections that are arranged on only two different height levels. More generally, the embossing pattern can be formed as a so-called multilevel pattern that includes exclusively planar areal sections that are arranged on n different height levels, n preferably being between 4 and 16.

4 The embossing pattern is advantageously coated with a semitransparent metal layer, preferably a thin aluminum, chrome, silver or copper layer. 5 In some embodiments, a particularly high transmittance of the see-through security elements is desirable. This can be achieved, for example, in that the embossing pattern is coated with a high-index layer, preferably a thin ZnS layer, rather than with a semitransparent metal layer. In a further embodiment, the embossing pattern can also be coated with a thin-film 10 element having a color-shift effect, or liquid crystal material having a color shift effect. To further increase the counterfeit security, the embossing pattern and the coating can be leveled by a light-transmitting protective lacquer layer. To 15 avoid or minimize any influencing of the phases of the wavefronts passing through the security element, the refractive index of the protective lacquer layer expediently substantially corresponds to the refractive index of the lacquer layer into which the embossing pattern is introduced. 20 According to a further variant of the present invention, the first security feature constitutes, instead of an embossed hologram, a volume hologram that reflects only light of a predetermined wavelength. In all variants, the first security feature advantageously includes a piece of 25 information, especially patterns, characters or a code, that is perceptible with the naked eye and without auxiliary means. As already mentioned above, the depicted information can change upon movement, especially upon tilting or rotating the security element, and in this way render, for example, an alternating, morph, pump or moving image.

5 The second security feature is preferably a diffractive optical element that, in transmission, produces from a penetrating beam of substantially parallel light a projection image that is detectable with a screen. Here, the diffractive 5 optical element is normally designed for light of a predetermined wavelength. Just like the above-described embossed hologram, also the diffractive optical element can include an embossing pattern that is formed in a radiation-curing or thermoplastic lacquer and that is expediently leveled by a high-index protective layer to increase the counterfeit security. 10 The diffractive optical element is preferably formed from a plurality of diffractive elementary cells that exhibit a lateral dimension below 1 mm, preferably between 3 ptm and 100 pm. 15 The projection image of the second security feature preferably constitutes a piece of information, especially patterns, characters or a code, for example an image motif, a symbol or a one- or two-dimensional barcode, that is not perceptible with the naked eye and without auxiliary means. In a special exemplary embodiment, the information of the second security feature can 20 be static, that is, not change upon sweeping over the security feature with a laser beam. But also movement effects in which the projection image changes across the area of the security feature are possible, such that, upon sweeping over the security feature with a laser beam, a moving or changing image is projected on the screen. 25 In an alternative embodiment, the second security feature is a refractive optical element that produces, from a penetrating beam of substantially parallel light or of light from a distant spotlight source, a piece of information, especially patterns, characters or a code, that is perceptible with 6 the naked eye and without auxiliary means. Here, too, the information can be static or change as a function of the position of the screened sub-regions of the security feature. 5 The refractive optical element is preferably formed from a plurality of achromatic micropattern elements that exhibit a lateral dimension below 1 mm, preferably between 3 pm and 100 pm. In preferred embodiments, the plurality of micropattern elements is arranged periodically or at least locally periodically in at least one spatial direction. At least a portion of the 10 micropattern elements is preferably formed by microprisms that are each characterized by the dimension of their base area, a refractive angle and an azimuth angle that specifies the orientation of the microprism. Alternatively or additionally, at least a portion of the micropattern elements exhibits a curved surface. These micropattern elements can be formed, for example, by 15 micro-cones or by micro-stepped-cones that are each characterized by the diameter of their base area and an opening angle. To ensure that wavelength-dependent light diffraction effects are negligible and that the incident light is refracted substantially achromatically by the pattern elements without interfering color effects, the micropattern elements exhibit 20 in any case a lateral dimension above about 3 pm, preferably above about 5 pm, particularly preferably above about 10 pm. The first and second security feature of the see-through security element are advantageously arranged on opposing sides of a plastic foil, especially a PET 25 foil. The pieces of information of the two security features can be independent of one another, or also constitute pieces of information that are related to or that complement each other.

7 On the side of the second security feature, the security element can be provided with a further semitransparent metal layer such that the first security element is hardly or not at all perceptible when viewed from the side of the second security feature. Alternatively, a further security feature 5 that is perceptible in reflection and that has an electromagnetic-radiation influencing grating pattern composed of a plurality of grating lines, such as a second semitransparent embossed hologram, can be provided on the side of the second security feature. 10 In a development of the present invention, the security element includes in at least one sub-region a grating polarizer that exhibits a substrate having a first surface into which a relief pattern is introduced, and wherein - the relief pattern exhibits an arrangement of electrically conductive, parallel grating lines that have a predetermined grating constant and 15 grating orientation and that are separated from one another by substantially non-conductive spaces, and - the grating constant of the grating lines is chosen such that the grating polarizer changes the polarization of the light impinging on the grating lines such that the reflected and/or the transmitted light is 20 linearly polarized in a predetermined plane. In a further embodiment, the see-through security element is combined with light-polarizing liquid crystal layers. Here, the polarization of the light impinging on this layer is changed such that the reflected and/or 25 transmitted light is linearly polarized in a certain plane. According to a second aspect of the present invention, in a generic see through security element is provided that the first security feature is a semitransparent optical element that is beam-shaping in reflection, and that 8 the second security feature is an optical element that is beam-shaping in transmission. In a see-through security element according to this aspect of the present invention, the two security features each constitute second-level security features, since they both need auxiliary means for their verification. 5 The first security feature is advantageously a diffractive optical element that, in reflection, produces from a penetrating beam of substantially parallel light a projection image that is detectable with a screen. Alternatively or additionally, the second security feature can be a diffractive optical element 10 that, in transmission, produces from a penetrating beam of substantially parallel light a projection image that is detectable with a screen. The diffractive optical elements of the first and second security element are preferably designed for light of the same predetermined wavelength. 15 Also in this aspect of the present invention, the diffractive optical element of the first and/or second security element can include an embossing pattern that is formed in a radiation-curing or thermoplastic lacquer and can be leveled by a high-index protective layer. Each diffractive optical element is 20 expediently formed from a plurality of diffractive elementary cells that exhibit a lateral dimension below 1 mm, preferably between 3 ptm and 100 Pm. In this aspect of the present invention, the first security feature preferably 25 includes a semitransparent metal layer, especially a thin aluminum, chrome, silver or copper layer, such that the first security feature can, on the one hand, be used in reflection, but on the other hand, transmit sufficient light for the second security feature.

9 The present invention also comprises methods for manufacturing a see through security element for security papers, value documents and the like, as well as a security paper and a value document having a see-through security element of the kind described. Here, the see-through security 5 element is preferably arranged in or over a window region or a through opening in the security paper or in the value document. The value document can especially be a banknote, a passport, a sleeve, a certificate, or a card, especially an identification card. 10 Further exemplary embodiments and advantages of the present invention are described below with reference to the drawings. To improve clarity, a depiction to scale and proportion was dispensed with in the drawings. Shown are: 15 Fig. 1 a schematic diagram of a banknote having a see-through security element according to the present invention, Fig. 2 a cross section through a see-through security element 20 according to an exemplary embodiment of the present invention, Fig. 3 in (a) and (b), the verification of the two security features of the see-through security element in fig. 2, 25 Fig. 4 to 9 cross sections through see-through security elements according to further exemplary embodiments of the present invention, 10 Fig. 10 in (a), an embossed hologram having a continuous surface profile, in (b), an embossed hologram having a binary pattern, and in (c), an embossed hologram having a multilevel pattern, 5 Fig. 11 a cross section through a see-through security element according to a further exemplary embodiment of the present invention, and Fig. 12 the verification of the two security features of the see-through security element in fig. 11. 10 The invention will now be explained using a security element for a banknote as an example. For this, fig. 1 shows a schematic diagram of a banknote 10 having a see-through security element 12 that is arranged over a see-through region 14, such as a window region or a through opening in the banknote 10. 15 As explained in greater detail below, the see-through security element 12 exhibits, on its opposing sides, both a second-level security feature that is verifiable only with auxiliary means and a first-level security feature that is perceptible with the naked eye. In this way, the see-through security element 20 12 combines high counterfeit security with a visually appealing appearance for the viewer. The exemplary embodiment in fig. 2 shows a see-through security element 20 having a central substrate foil 22, for example a PET foil. A 25 semitransparent embossed hologram 24 is arranged on the top of the substrate foil as a first-level security feature that is perceptible with the naked eye. The embossed hologram 24 comprises a layer of a radiation curing lacquer 26 having an embossing pattern 28 and, applied to the embossing pattern 28, a semitransparent metal layer 30 that can be formed, 11 for example, by an aluminum layer of a thickness between 5 nm and 30 nm. Instead of aluminum, of course also other metals, for example chrome, silver or copper, may be used, the layer thickness being chosen suitably according to the material used. 5 To protect the embossed hologram 24 against unauthorized casting and against chemical attacks during circulation, it is leveled with a light transmitting protective lacquer 32. If the material of the protective lacquer layer 32 is chosen such that its refractive index substantially corresponds to 10 the refractive index of the lacquer layer 26, then the protective lacquer layer 32 further prevents the transmitted wavefronts from sustaining a locally varying phase modulation. The opposing side of the substrate foil 22 bears a second-level security 15 feature that is verifiable only with auxiliary means, a diffractive optical element 34 being used in the exemplary embodiment in fig. 2. The diffractive optical element 34 consists of a radiation-curing lacquer layer 36 in which is embossed a characteristic surface profile 38 that, in transmission, produces from a penetrating parallel light beam a projection image that is detectable 20 with a screen, and thus acts as a beam shaper. Here, the characteristic surface profile 38 can, upon specification of the projection image to be produced and the design wavelength of the laser used in the reconstruction, be calculated, for example with the aid of a computer. 25 The diffractive optical element can act particularly well if the refractive index of the lacquer layer 26 matches the refractive index of the protective lacquer layer 32, since the semitransparent embossed hologram 24 arranged on the top of the substrate foil 22 then effects no local phase variation of the wavefront passing through the see-through security element 12, but rather 12 merly leads to a certain weakening of the total intensity of the light beam passing through. The verification of the two security features 24 and 34 is illustrated in fig. 3. 5 If the see-through security element 20 is viewed from the side of the first security feature 24 in reflection 42, as shown in fig. 3(a), then the semitransparent embossed hologram 24 becomes easily visible for the viewer 40. Here, the embossed hologram 24 can not only produce a static image, but also constitute an alternating image, such as a tilt image, a pump image, a 10 motion image, a morph image or a stereo image. In this way, the transparent see-through security element 20 is greatly optically enhanced and presents itself on the banknote 10 not as an uninteresting, patternless transparent foil, but rather rich in motion and/or color and having a visually appealing sensory impression. 15 The encoded image information hidden in the second security feature 34 is not perceptible with the naked eye without auxiliary means. When the security element 20 is viewed from the reverse, the security feature 34 is noticeable for the naked eye only as a slight dulling of the semitransparent 20 embossed hologram 24. If, however, the see-through security element 20 is transilluminated from the side of the second security feature 34 with a laser beam 44 of a specified wavelength, as shown in fig. 3(b), then the surface profile 38 of the diffractive optical element produces from the parallel light beam a projection image 46 that can be detected, for example, with a 25 projection screen 48. In other embodiments, it can be provided that the projected image appears right-reading when the see-through security element 20 is transilluminated from the side of the first security feature 24. It is understood that especially also mirror -symmetric image inotifs can be used, or image motifs without a defined side orientation, such that the 13 hidden image information of the security element 20 can be correctly recognized independently of the side impinged on. The counterfeit security of the see-through security element 20 in fig. 2 can 5 be further increased if the surface profile 38 of the diffractive optical element 34 is leveled with a material 50 having a very high refractive index, as shown in fig. 4. It is understood here that the difference of the refractive indices of the lacquer layer 36 and the material layer 50 is appropriately accounted for in the design of the characteristic surface profile 38. 10 The diffractive optical element 34 appears as a slight dulling when the embossed hologram 24 is viewed from the reverse. It can thus be advantageous in some embodiments to fully cover the embossed hologram 24 from this side such that it is easily visible only from the front. For this, for 15 example, as shown in fig. 5, a further semitransparent metal layer 52 can be applied to one of the two surfaces of the substrate foil 22. Here, the two semitransparent metal layers 30 and 52 are to be designed in such a way that the see-through security element 20 still exhibits a sufficiently high transmittance to facilitate the projection of the projection image encoded in. 20 the diffractive optical element 34 upon transillumination with the laser source. As shown with reference to the exemplary embodiment in fig. 6, instead of a planar semitransparent metal layer, also a second semitransparent embossed 25 hologram 54 composed of an embossing lacquer layer 56 and a second semitransparent metal layer 58 can be used. The second embossed hologram 54 can be arranged, for example, between the substrate foil 22 and the diffractive optical element 34. Viewed from the first side of the see-through security element 20, facing away from the diffractive optical element, then 14 substantially only the first embossed hologram 24 is perceptible, while viewed from the second side of the see-through security element 20, facing the diffractive optical element, substantially only the second embossed hologram 54 is visible. If the thicknesses of each of the metal layers are 5 chosen suitably, the image information depicted by the embossed holograms 24, 54 in reflection can also complement each other to form a complete image. The semitransparent metal layer 30 of the embossed hologram 24 can lead to 10 a significant reduction in the transmittance of the see-through security element 20. As an alternative, it is thus appropriate to use, instead of the semitransparent metal layer 30, a high-index layer, for example a ZnS layer having a thickness of about 50 nm, through which the see-through security element becomes substantially transparent and the see-through character of 15 this security element immediately catches the viewer's eye. Furthermore, this measure results in the perceptibility of the embossed hologram 24 being dependent on the ambient conditions: Upon glancing through the window against a light background, the hologram 24 is only weakly visible, while it stands out substantially more intensely against a dark background. The 20 image of the diffractive optical element 34 projected with a laser appears more intensely on the viewing screen. Furthermore, instead of the semitransparent metal layer 30, also layer systems can be used that, due to interference effects, cause viewing-angle 25 dependent color shifts. To name two examples: a layer system in which a material having a low refractive index is enclosed by two layers having a higher refractive index, and a layer system having the sequence semitransparent metal - dielectric - semitransparent metal. Alternatively to 15 the layer system, also a layer composed of liquid crystal material having a color-shift effect can be used. Instead of an embossed hologram as a first-level security feature, also a so 5 called Bragg hologram 60 can be used, as illustrated in the exemplary embodiment in fig. 7. A Bragg hologram is not a two-dimensional grating like pattern, but rather a three-dimensional, modulated, periodic arrangement of phase or amplitude objects that form the data to be depicted. The Bragg hologram reflects merely light of a single wavelength such that 10 the light passing through the Bragg hologram is not weakened in its intensity in wide bands, but rather is deprived of a certain color portion in accordance with the reflected wavelength. In this way, a see-through security element 20 having a characteristic color effect can be produced. 15 In all embodiments, for the second security feature, a refractive optical element can also be used instead of a diffractive optical element. Although it is possible, using a laser, to produce very sharp and detailed projection images with the aid of diffractive optical elements, the use of a laser source is required for rendering. If, instead, a sufficiently distant spotlight source is 20 viewed through the diffractive optical element, then strong color fringes occur that, in many cases, allow the image information to be perceived only very poorly. If, in contrast, a refractive optical element is used as a second security 25 feature, then the security feature can, due to the significantly reduced color splitting, also be verified with the aid of a distant spotlight source and without the use of a laser source. Since, here, a significantly lower light intensity is available for the verification, it is appropriate to combine 16 refractive optical elements with high-transmittance embossed holograms, for example, using high-index coatings. For this, fig. 8 shows a see-through security element 70 in which a substrate 5 foil 72 is provided on its top with a semitransparent embossed hologram 74 and on its bottom with a refractive optical element 76. The embossed hologram 74 includes a layer of a radiation-curing lacquer 79 provided with an embossing pattern and, applied to the embossing pattern, a high-index coating 80, for example a 50 nm thick ZnS layer. 10 The refractive optical element 76 of the foil bottom consists of a radiation curing lacquer layer in which the substantially achromatic, refractive micropattern elements 78 are embossed. The micropattern elements 78 can be formed, for example, by elongated prisms, by three-, four- or more-sided 15 pyramids, or also by cone structures, and exhibit dimensions below 1 mm, preferably between 3 pLm and 100 pm. Since wavelength-dependent light diffraction effects should be negligible for the micropattern elements 78, their lateral dimensions are, in any case, chosen to be greater than about 3 Pm, especially greater than about 10 pm. 20 In these embodiments, too, it is appropriate to level the refractive optical element 76 with a material 82 having a high refractive index, as shown in fig. 9. The refractive index difference between the lacquer layer and the high index leveling layer is, of course, to be taken into account in calculating the 25 refractive angle of the micropattern elements 78. The combination of a semitransparent embossed hologram with a refractive optical element means the linking of two first-level security features. While the embossed hologram is preferably generated with the aid of direct exposure or an e-beam system, these means are not applicable for manufacturing a refractive optical 17 element, or are applicable only with high additional outlay. For this reason, and also because the production of refractive optical elements is very technically sophisticated, such a combined security element offers particularly high counterfeit protection. 5 In all embodiments, the semitransparent metal layer or the high-index coating of the embossed hologram can exhibit a continuous surface profile 90, as shown schematically in fig. 10(a). In other embodiments, it is appropriate to form the embossing pattern to be, not continuous, but rather 10 having a certain number of discrete height levels. Here, the simplest case is a binary pattern having only two height levels 94, as is shown in fig. 10(b). Such a binary pattern exhibits only planar areal sections 92 that are arranged on one of two different height levels 94. 15 In the more general case, a multilevel pattern has planar areal sections 96 on n different height levels 98, as shown in fig. 10(c). Compared with a continuous surface profile 90, this results in the advantage that a light beam penetrating vertically through the security element undergoes the same weakening at all points on the element, because the light beam always 20 penetrates the metal layer vertically, independently of the point of incidence, and thus always sees the same layer thickness. In further exemplary embodiments of the present invention, as a first security feature, instead of an embossed hologram, a security feature is used 25 that is beam-shaping in reflection, as illustrated in figures 11 and 12. In the see-through security element 100 in fig. 11, the substrate foil 22 is provided on both sides with diffractive optical elements 110, 120, each of which exhibits a radiation-cured lacquer layer 112, 122 in which a 18 characteristic, beam-shaping surface profile 114, 124 is embossed. The lacquer layer 112 of the first diffractive optical element 110 is additionally provided with a semitransparent metallization 116 in order to be able to use the diffractive optical element 110 in reflection. The design of the second 5 diffractive optical element 120 corresponds to the embodiment already explained in connection with fig. 4. To protect against casting and to avoid distortions of the phases of the wavefronts, the two diffractive optical elements 110, 120 are leveled with a material 118, 128 having a high refractive index. 10 When the security element 100 is illuminated with a laser 130 from the half space of the side of the first security feature 110 (fig. 12), a first image 132 is projected in the half-space of the first security feature 110 by the reflecting diffractive optical element 110. The through-going portion of the incident 15 radiation serves to project, in the half-space of the second security feature 120, a second image 134 produced by the diffractive optical element 120 used in transmission. The images 132, 134 can each be detected by a projection screen 136, 138 or also by a joint projection screen. Unlike in the examples described further above, the security features 110, 120 each constitute 20 second-level security features on the front and reverse of the security element 100, since they can be perceived only with the use of auxiliary means. The two diffractive optical elements 110, 120 can be designed for light of the 25 same or also for light of different wavelengths, such that, in the latter case, two different laser sources are required for the complete reconstruction of the two projection images.

19 To manufacture the see-through security elements according to the present invention, the following approach, for example, can be used: Origination: 5 The origination of the embossed holograms used as the first security features can occur according to the methods described in the background art, an e beam system preferably being used. The refractive optical elements can, for example, be exposed in lacquer with 10 grayscale lithography with the aid of masks or through direct exposure with a laser or electron beam recorder and subsequently developed. In the event that the achievable profile depth is not sufficient, the relief can also be transferred to a substrate material with the aid of suitable dry-etching processes, the profile depth being able to be increased accordingly. In other 15 manufacturing variants, with suitable methods, the substrate can be processed directly, without resorting to lacquer layers. The method of laser ablation is cited only by way of example. Also other methods known to the person of skill in the art may be used for creating continuous surface patterns. 20 For the origination of the diffractive optical element patterns, the surface patterns needed to render a certain image content can be calculated with a computer based on the so-called iterative Fourier transform algorithm. The wavelength of the laser provided for projection determines the depth and 25 scaling of the calculated surface. Thereafter, the patterns are exposed in resist, for example with a laserwriter, and the surface profile exposed after developing is cast. This method is particularly well suited for manufacturing continuous surfaces. If a multilevel profile is to be generated, then it is recommended to prepare, with e-beam lithography, m masks for the optical 20 lithography. With their aid, n = 2m height levels can be produced in that m steps of optical lithography are carried out in succession, each followed by a dry-etching process of predetermined depth. 5 Duplication: Embossing dies, for example embossing cylinders, are manufactured for the different surface profiles through galvanic casting. With their aid, the patterns are embossed in UV lacquer and cured through radiation with UV light. Alternatively, the embossing may be done in thermoplastically 10 embossable lacquers. The application of the semitransparent metal layers or the high-index ZnS layer or the interference layer system preferably occurs through evaporation, but also other methods are applicable, such as cathode sputtering. 15 To realize the two-sided embossing patterns, the first side of the foil is first embossed and evaporated before the second side is furnished with the appropriate other patterns. Alternatively, two different foils can be provided with the needed embossing patterns and subsequently laminated together. 20 Registration: When the patterns located on the second side of the security element, so the diffractive or refractive optical elements, consist of periodically arranged, identical elementary cells having dimensions significantly below 1 mm, then 25 registration between these patterns and the patterns on the first side plays no role. This embodiment is preferred if, for example, a movement of the laser across the area of the security feature is not to lead to any change in the projected image.

21 However, the special design of the security element can also make it necessary for the positions of the patterns on the first side of the security element and of the diffractive or refractive optical element on the second side to correspond with each other. This case can occur, for example, when the 5 diffractive or refractive optical element generates moving or morph effects, that is, the beam shaping is not intended to occur in the same way across the entire area of the security element. In this case, the projected image changes when the laser is guided across the area of the security feature. In this case, both the embossed hologram and the beam-shaping element on the opposing 10 side of the security element must be positioned in the see-through window with sufficient precision. Adherence to the positioning tolerances generally places high demands on the production processes used, which in turn results in high counterfeit security of the security element.

Claims

1. A see-through security element for security papers, value documents 5 and the like that exhibits at least a first and a second security feature that are arranged on opposing sides of the security element, characterized in that - the first security feature is a security feature that is perceptible in reflection and that has an electromagnetic-radiation-influencing 10 grating pattern composed of a plurality of grating lines, and - the second security feature is an optical element that is beam-shaping in transmission. 15 2. The see-through security element according to claim 1, characterized in that the first security feature constitutes a diffraction pattern, especially a hologram, a holographic grating image, a blazed diffraction pattern, a computer-generated hologram (CGH) or another hologram-like diffraction pattern. 20

3. The see-through security element according to claim 1, characterized in that the first security feature constitutes a matte pattern.

4. The see-through security element according to at least one of claims 1 25 to 3, characterized in that the grating pattern of the first security feature consists of a plurality of grating lines having a preferably sinusoidal profile, the spacing and the orientation of the grating lines varying across the area of the security feature to produce a desired optical effect. 23

5. The see-through security element according to claim 4, characterized in that the grating pattern constitutes an alternating image, a pump image, a motion image, a morph image or a stereo image. 5 6. The see-through security element according to at least one of claims 1 to 5, characterized in that the first security feature includes an embossing pattern that is formed in a radiation-curing or thermoplastic lacquer.

7. The see-through security element according to claim 6, characterized 10 in that the embossing pattern is formed as a continuous embossing pattern.

8. The see-through security element according to claim 6, characterized in that the embossing pattern is formed as a binary pattern that includes exclusively planar area sections that are arranged on only two different 15 height levels.

9. The see-through security element according to claim 6, characterized in that the embossing pattern is formed as a multilevel pattern that includes exclusively planar area sections that are arranged on n different height 20 levels, n preferably being between 4 and 16.

10. The see-through security element according to at least one of claims 6 to 9, characterized in that the embossing pattern is coated with a semitransparent metal layer, preferably a thin aluminum, chrome, silver or 25 copper layer.

11. The see-through security element according to at least one of claims 6 to 9, characterized in that the embossing pattern is coated with a high-index 24 layer, preferably a thin ZnS layer, or the embossing pattern is provided with a thin-film element having a color-shift effect.

12. The see-through security element according to at least one of claims 6 5 to 11, characterized in that the embossing pattern and the coating are leveled by a light-transmitting protective lacquer layer.

13. The see-through security element according to claim 12, characterized in that the refractive index of the protective lacquer layer substantially 10 corresponds to the refractive index of the lacquer layer into which the embossing pattern is introduced.

14. The see-through security element according to claim 1, characterized in that the first security feature constitutes a volume hologram that reflects 15 only light of a predetermined wavelength.

15. The see-through security element according to at least one of claims 1 to 14, characterized in that the first security feature includes a piece of information, especially patterns, characters or a code, that is perceptible with 20 the naked eye and without auxiliary means.

16. The see-through security element according to at least one of claims 1 to 15, characterized in that the second security feature is a diffractive optical element that, in transmission, produces from a penetrating beam of 25 substantially parallel light a projection image that is detectable with a screen.

17. The see-through security element according to claim 16, characterized in that the diffractive optical element is designed for light of a predetermined wavelength. 25

18. The see-through security element according to claim 16 or 17, characterized in that the diffractive optical element includes an embossing pattern that is formed in a radiation-curing or thermoplastic lacquer. 5

19. The see-through security element according to at least one of claims 16 to 18, characterized in that the diffractive optical element is leveled by a high-index protective layer. 10 20. The see-through security element according to at least one of claims 16 to 19, characterized in that the diffractive optical element is formed from a plurality of diffractive elementary cells that exhibit a lateral dimension below 1 mm, preferably between 3 pm and 100 pm. 15 21. The see-through security element according to at least one of claims 16 to 20, characterized in that the projection image of the second security feature constitutes a piece of information, especially patterns, characters or a code, that is not perceptible with the naked eye and without auxiliary means. 20 22. The see-through security element according to at least one of claims 1 to 15, characterized in that the second security feature is a refractive optical element that produces, from a penetrating beam of substantially parallel light or from light from a distant spotlight source, a piece of information, especially patterns, characters or a code, that is perceptible with the naked 25 eye and without auxiliary means.

23. The see-through security element according to claim 22, characterized in that the refractive optical element is formed from a plurality of achromatic 26 micropattern elements that exhibit a lateral dimension below 1 mm, preferably between 3 pm and 100 pm.

24. A see-through security element for security papers, value documents 5 and the like that exhibits at least a first and a second security feature that are arranged on opposing sides of the security element, characterized in that - the first security feature is a semitransparent optical element that is beam-shaping in reflection, and 10 - the second security feature is an optical element that is beam-shaping in transmission.

25. The see-through security element according to claim 24, characterized 15 in that the first security feature is a diffractive optical element that, in reflection, produces from a penetrating beam of substantially parallel light a projection image that is detectable with a screen.

26. The see-through security element according to claim 24 or 25, 20 characterized in that the second security feature is a diffractive optical element that, in transmission, produces from a penetrating beam of substantially parallel light a projection image that is detectable with a screen.

27. The see-through security element according to claim 25 and 26, 25 characterized in that the diffractive optical elements of the first and second security element are designed for light of the same predetermined wavelength. 27

28. The see-through security element according to at least one of claims 24 to 27, characterized in that the diffractive optical element of the first and/or second security element includes an embossing pattern that is formed in a radiation-curing or thermoplastic lacquer. 5

29. The see-through security element according to at least one of claims 24 to 28, characterized in that the diffractive optical element of the first and/or second security element is leveled by a high-index protective layer. 10 30. The see-through security element according to at least one of claims 24 to 29, characterized in that the diffractive optical element of the first and/or second security element is formed from a plurality of diffractive elementary cells that exhibit a lateral dimension below 1 mm, preferably between 3 pim and 100 tm. 15

31. The see-through security element according to at least one of claims 24 to 30, characterized in that the projection image of the first and/or second security feature constitutes a piece of information, especially patterns, characters or a code, that is not perceptible with the naked eye and without 20 auxiliary means.

32. The see-through security element according to at least one of claims 24 to 31, characterized in that the first security feature includes a semitransparent metal layer, preferably a thin aluminum, chrome, silver or 25 copper layer.

33. The see-through security element according to at least one of claims 1 to 32, characterized in that the first and second security feature are arranged on opposing sides of a plastic foil, especially a PET foil. 28

34. The see-through security element according to at least one of claims 1 to 33, characterized in that the first and second security feature constitute pieces of information that are related to or that complement each other.

35. The see-through security element according to at least one of claims 1 to 34, characterized in that the security element on the side of the second security feature is provided with a semitransparent metal layer such that the first security element is hardly or not at all perceptible when viewed from 10 the side of the second security feature.

36. The see-through security element according to at least one of claims I to 35, characterized in that the security element on the side of the second security feature is provided with a further security feature that is perceptible 15 in reflection and that has an electromagnetic-radiation-influencing grating pattern composed of a plurality of grating lines.

37. The see-through security element according to at least one of claims 1 to 36, characterized in that the security element further includes, in at least 20 one sub-region, a grating polarizer that exhibits a substrate having a first surface into which a relief pattern is introduced, wherein - the relief pattern exhibits an arrangement of electrically conductive, parallel grating lines that have a predetermined grating constant and 25 grating orientation and that are separated from one another by substantially non-conductive spaces, and - the grating constant of the grating lines is chosen such that the grating polarizer changes the polarization of the light impinging on the 29 grating lines such that the reflected and/or the transmitted light is linearly polarized in a predetermined plane.

38. A method for manufacturing a see-through security element for 5 security papers, value documents and the like, in which a transparent substrate foil is provided on opposing sides with a first and a second security feature, wherein - as the first security feature, a security feature is produced that is 10 perceptible in reflection and that has an electromagnetic-radiation influencing grating pattern composed of a plurality of grating lines, and - as the second security feature, an optical element is produced that is 15 beam-shaping in transmission.

39. A method for manufacturing a see-through security element for security papers, value documents and the like, in which a transparent substrate foil is provided on opposing sides with a first and a second security 20 feature, wherein - as the first security feature, a semitransparent optical element is produced that is beam-shaping in reflection,, and 25 as the second security feature, an optical element is produced that is beam-shaping in transmission.

40. A security paper having a see-through security element according to one of claims 1 to 37. 30

41. The security paper according to claim 40, characterized in that the see-through security element is arranged in or over a window region or a through opening in the security paper. 5

42. A value document having a see-through security element according to one of claims 1 to 37 or a security paper according to claim 40 or 41.

43. The value document according to claim 42, characterized in that the 10 see-through security element is arranged in or over a window region or a through opening in the value document.

44. The value document according to claim 43, characterized in that the value document is a banknote, a passport, a sleeve, a certificate or a card, 15 especially an identification card.

45. A use of a see-through security element according to one of claims 1 to 37, of a security paper according to claim 40 or 41, or of a value document according to one of claims 42 to 44 for securing articles of any kind. 20