EP2239150B1 - Security device - Google Patents

Description

The invention relates to a security device, in particular for improving the security against forgery of means of payment.

Security devices are used, for example, for labeling branded products and in particular for means of payment such as credit cards, banknotes and the like. For example, security devices are security devices visible to the human eye, such as holograms. Also not visible to the human eye or only visible under special light safety devices are known, which are generated for example by introduced into the means of payment color pigments. Accordingly, despite the variety of existing safety devices, there is a need to develop tamper-resistant security devices.

In WO 03/055691 A1 a diffractive security element is described that includes a surface pattern composed by mosaic-like surface elements. At least a part of the surface elements consists of a superimposition of linear asymmetric diffraction gratings, with a spatial frequency between 50 lines / mm and 2000 lines / mm and a matt structure with a mean roughness in the range of 20 nm and 2000 nm. The incident light is reflected by the optically acting Distracts structures in a predetermined way and creates a highly visible, static surface pattern. By the Superposition of the asymmetric diffraction gratings and the matt structure, the light diffracted by the grating is visible in a large solid angle. By suitable choice of the scattering power and the scattering direction can be achieved by rotation of the element by 180 °, for example, a contrast reversal by the arrangement of at least two antiparallel structured surface elements.

It is an object of the invention to provide a further safety device, which is an optical safety device, by which the counterfeit security is increased, for example, in payment means.

The object is achieved according to the invention by the features of claim 1.

The safety device according to the invention has a flat light reflection element. This is, for example, an aluminum foil, a silver foil or another, a reflection causing metal foil. Here, in a preferred embodiment, a light reflection element is provided, which has a highly reflective surface to the smallest possible, especially none, invoke refraction and diffraction effects. Three-dimensional diffractive surface elements are arranged on a surface of the light reflection element according to the invention. The surface elements diffract the light reflected at the light reflection element. The diffraction of the light takes place in the direction of a viewer, i. a human eye, or a machine inspection device.

According to the invention, the individual surface elements are provided on a light exit surface with different diffraction gratings. In the case of a plurality of surface elements, at least two different diffraction gratings are thus provided. The surface elements are combined to form a group, wherein the individual surface elements of the group are designed and / or arranged such that an asterism arises for the viewer or the checking device. This means that, according to the invention, the incident light reflected by the light reflection element is diffracted by the diffraction gratings of the surface elements such that an asterism is created for the viewer. This may be a single straight line in the simplest embodiment. According to the invention, however, the asterism has several, in particular star-shaped lines. The several lines intersect herewith in a single, especially central point. As a result, similar to the asterism that occurs in mineralogy, a lineage star with a central bright point is created. In mineralogy, asterism occurs especially in star sapphires, stellar rubies, and stellar corollas. Through the asterism Thus, there is a concentration of light in the direction of the viewer or the checking device.

In a preferred embodiment, the asterism can be recognized by the viewer or the checking device in a relatively large angular range. Here, the appearance does not change as long as the viewer or the inspection device views the security device within the angular range. The angle range is preferably 90 ° ± 20 ° to the surface of the light reflection element. It is preferred that the asterism is recognizable within an angular range of 90 ° ± 45 ° and particularly preferably of 90 ° ± 60 °. In particular for the human eye, tilting of the safety device does not change the visual impression within the predetermined angular range. In particular, the bright central point at which intersect several lines of asterism, does not change its location or at least only slightly.

The individual surface elements of a surface element group are in this case designed and / or arranged such that the emission direction of the light caused by the diffraction at the exit surface forms an asterism.

Since the resolution of the human eye is limited, it is inventively preferred to provide the smallest possible exit surfaces of the individual surface elements. In this case, exit surfaces of less than 30 microns ² and more preferably less than 25 microns ^{2 are} preferred. Furthermore, it is preferred that the spacings of the individual surface elements are small. In this case, distances of 0-100 μm, preferably 0-50 μm, are preferred.

Furthermore, according to the invention, preferably the distance between the exit surface of the surface elements, in which the diffraction grating and the surface of the light reflecting element is small. In particular, the distance is 1 - 300 microns, preferably 1 - 200 microns. In this case, it is particularly preferred to produce the individual surface elements in particular jointly by molding a lacquer. A suitable material for producing the surface elements or a group of several surface elements preferably has the following composition:

11 g of 1H, 1H, 2H, 2H-perfluorooctyl acrylate were mixed with 8 g of dipropylene glycol, 0.1 g of Irgacure ^® 819 and 0.2 g Irgacure 184 from Ciba ^© mixed Lampersheim Specialty Chemicals GmbH. 60 μl of this mixture was applied to a 2 × 2 cm nickel plate, on the surface of which a negative mold of a shaped body with scattering centers is formed. Subsequently, a 1 mm thick and 1 x 1 cm large plate of PMMA was applied to the surface of the mixture on the nickel plate. Then, the resulting sandwich on the nickel plate with the mixture therebetween was exposed to UV radiation of a commercial UV mercury lamp for 2 seconds. Subsequently, the substrate with the associated cured impression composition was removed from the negative mold.

The resulting layer thickness preferably has 1 to 300 μm, in particular 1 to 200 μm. It is particularly preferred to apply the lacquer for the production of the surface elements directly to the light reflection element, to form and to cure, for example, with UV radiation.

To produce the asterism according to the invention, the diffraction gratings of the individual surface elements preferably have a frequency which is less than ¼ of the wavelength of the incident light. Preferably, the frequency of the diffraction grating is less than 100 nm, in particular less than 50 nm.

The diffraction grating itself in this case preferably has a wave-shaped profile, wherein the individual flanks of the wave-shaped profile can have an uneven flank slope. However, it may also be a uniform sinusoidal profile, a rectangular profile or a sawtooth profile as well as combinations of different profiles.

The asterism generated according to the invention is preferably perceptible by the human eye, so that a check of the security device and thus, for example, a verification of the authenticity of a means of payment without aids is possible. However, it is also possible that the asterism is formed, for example, only when using specific wavelengths or wavelength ranges of the incident light and, for example, multiple light sources are required, which illuminate from different directions. These are, in particular, point light sources illuminating the safety device from different directions. The resulting asterism can then possibly be detected by an optical inspection device.

It is particularly preferable to combine the safety device according to the invention with other safety devices which produce, for example, holograms or the like. In particular, the safety device according to the invention can be integrated into a further optical safety device.

The above-described arrangement of three-dimensional diffractive surface elements on a light reflecting element is not limited to safety devices. Rather, such an embodiment of the surface elements for generating an asterism is also suitable for use in other reflectors.

The invention will be explained in more detail with reference to a preferred embodiment with reference to the accompanying drawings.

Show it:

Fig. 1

a schematic sectional view of a safety device according to the invention,

Fig. 2

a schematic perspective view of a single surface element,

Fig. 3

different schematic representations of visible to the viewer asterisms.

The safety device according to the invention has a light reflection element 10, which is, for example, an aluminum foil. The light reflecting member 10 is disposed with a bottom 12 on a product to be secured, such as a credit card, a bill or the like. On a surface 14 of the light reflection element, a plurality of diffractive surface elements 18 are arranged. The individual surface elements 18 have a light exit surface 20 with a diffraction grating. Preferably, the individual surface elements 18, which are combined to form a group of surface elements, are produced together by applying a lacquer to the surface 14 of the light reflection element 10 and producing the individual surface elements via a molding element. In this case, preferably a lacquer is used, which is curable by UV radiation. In this case, the lacquer layer 22 preferably has a thickness d of from 1 to 300 μm after the shaping of the surface elements 18.

Incident light rays 24 are reflected on the surface 14 of the light reflection element 10, possibly after diffraction has already taken place upon entering the lacquer layer. Upon exiting the surface elements, the light rays are transmitted through the outer surface 26 ( Fig. 2 ) of the individual surface elements 20 provided diffraction gratings bent so that they meet in a common point 28.

The diffraction takes place in such a way that, viewed from above, in the simplest embodiment, a line 30 is formed (FIG. Fig. 3a ).

According to the invention, several lines 30 will be generated ( Fig. 3b, 3c ), with all lines 30 intersecting at a common central point 28. From the viewer is thus an asterism, such as in Fig. 3 shown, visible.

Claims (11)

1. A safety device, particularly for improved protection against forgery of means of payment, effected by providing a symbol, said safety device comprising:

   a plurality of diffractive surface elements (18) arranged on a light reflection element (10), said diffractive surface elements comprising partially different diffraction gratings,

   each individual surface element (18) having a three-dimensional surface structure,

   a plurality of said surface elements (18) forming a surface element array,

   characterized in that

   the diffraction gratings of an array of surface elements (18) are formed and/or arranged to generate an asterism to be perceived by the observer and the verification device, respectively, and

   said asterism comprises a plurality of lines (30) intersecting each other in a common point (28).
2. The safety device according to claim 1, characterized in that, upon a change of the illumination or observation angle within an angular range of 90°± 20°, preferably 90°± 45° and more preferably 90°± 60°, each time relative to the surface (14) of the light reflection element (10), a quasi-static representation of said symbol (30) is perceived by an observer and the verification device, respectively.
3. The safety device according to any one of claims 1 - 2, characterized in that the diffractive surface elements (18) comprise diffraction gratings having a wave-shaped profile, the flank slopes of said profile preferably having varying shapes.
4. The safety device according to any one of claims 1 - 3, characterized in that the light reflection element (10) is formed as an areal reflector, said reflector comprising at least one light-reflecting layer, preferably a metal layer, on its top side (14) or bottom side (12), or consisting of a metal foil, preferably an aluminum or silver foil.
5. The safety device according to any one of claims 1 - 4, characterized in that the distance between the light exit surface (26) of the surface elements (18) and the surface (14) of the light reflection element (10) is preferably 1 - 300 µm, more preferably 1 - 200 µm.
6. The safety device according to any one of claims 1 - 5, characterized in that the surface elements (18) are applied on a light reflection element (10) by depositing a lacquer onto the surface (14) of a light reflection element (10), structuring the surface elements (18), preferably together, by means of a molding element and then curing them, wherein, after the molding the surface elements (18), the cured lacquer layer preferably has a thickness of 1 - 300 µm, preferably 1 - 200 µm.
7. The safety device according to any one of claims 1 - 6, characterized in that the distance between the surface elements (18) is preferably 0 - 100 µm, more preferably 0 - 50 µm.
8. The safety device according to any one of claims 1 - 7, characterized in that said light exit surface (26) has a cross-sectional area of preferably less than (30 µm)², more preferably less than (25 µm)².
9. The safety device according to any one of claims 1 - 8, characterized in that the generated asterism is automatically detectable by a mechanical verification device.
10. The safety device according to any one of claims 1 - 9, characterized in that the safety device is integrated in a further safety element and respectively is combined with a further safety feature.
11. A safety document, such as e.g. a means of payment, comprising a safety device according to at least one of the preceding claims.

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