Security feature and security feature carrier.

Abstract

The subject of the invention is a security feature comprising a substrate for a transmissive optical element and a transmissive optical element. The invention is applicable to secure securities, including banknotes. The security feature is characterised in that the substrate (10) for the transmissive optical element is a foil having on at least one side adhesive means (13), wherein at least one area (14) of the foil (10), on this at least one side with adhesive means, has no adhesive means (13) and in that, the transmissive optical element (11) is made on the foil (10) by a printing technique according to a target pattern (4') at least within boundaries of the area (14) without adhesive means (13), and that the target pattern (4') contains at least a fragment (4'a) of a diffraction pattern (4) constituting a computer generated hologram.

Description

[0001] Security feature and security feature carrier.

[0002] The invention relates to a security feature with a transmissive optical element (TOE) and to a security feature carrier, in particular a banknote. The invention is particularly applicable to securities, including banknotes. State-of-the-art safety components operating on the basis of a diffractive optical element are known. Diffractive optical elements, DOE for short, can be reflective or transmissive.

[0003] For example, international application W02007079549 describes a carrier for valuable documents containing a diffractive optical element. The security feature is provided with a diffractive microstructure that stores the encoded data. The DOE disclosed in this publication, when illuminated with collimated light, provides an interference pattern observable at a considerable distance from the carrier, across from the light source. The DOE disclosed in this document is produced on the substrate by applying laser ablation. The possibility of obtaining such a security feature by layering several layers of transparent or reflective materials or by making holes in an opaque layer was also disclosed. However, the method disclosed in publication W02007079549 for manufacturing a diffractive security feature requires the use of a suitable mask at the point of manufacture of the security feature. This represents a significant disadvantage in the practical use of the solution, especially when there is a need to produce patterns that are as repetitive as possible. In addition, multiple masks have to be used when it is necessary to individualise the data for each of the individual media with such a security feature.

[0004] Holograms are another example of security features based on the phenomenon of diffraction. Holograms are based on the source image and can be described as a phase recording of the light reflected by the source image. When the source image of the hologram is illuminated with the appropriate light beam, a two- dimensional or three-dimensional reconstruction image is obtained that corresponds to the source image. A particular example of a hologram is the computer-generated holograms described by the acronym CGH "Computer Generated Hologram"). Computer-generated holography provides the ability to numerically simulate the phenomenon of light-wave interference, and the source image providing the desired CGH can be calculated using appropriate mathematical transformations, such as the Fourier transform, to produce a plane object interferogram. Their applicability in a specific case depends on the distance between the source image and the reconstructed image.

[0005] Holograms are usually placed by embossing in the area of the transparent document window. It is most often made of polymer, usually in documents where the substrate is a polymer substrate. Diffraction pattern embossing can also take place in the varnish applied to the polymer substrate. The varnish is then UV-cured. For example, such a solution is known from document W02008031170A1 .

[0006] A security feature with a transmissive optical element containing a computer-generated hologram (CGH) was also disclosed in PL 438968. Unlike these standard holographic structures, the transmissive diffractive element disclosed in PL 438968 only provides a projected image due to the presence of two different areas differing in the transmittance of light rays, of which some areas may be, for example, transmissive to incident light, while light may be reflected or absorbed by a different part. The designed diffractive transmissive optical element is, for example, applied in the transparent window of a polycarbonate card using laser radiation, by laser engraving or by laser application on a UV-absorbing layer. However, state-of-the-art transmission optical security features require the preparation of separate processing lines for their application to the target media, i.e. banknotes, for example. Known techniques for obtaining transmission diffraction security mainly consist of polymer embossing or laser engraving. Both methods require extending banknote and / or plastic document production lines with additional segments to perform these processes, which increases production costs significantly.

[0007] In addition, the state-of-the-art known transmission optical security features can be used in a limited way to design an interesting graphic layout for the target media. In addition, it is difficult to find some of them to read. In the embossing technique in particular, the resulting image is poorly visible, as it is only due to the local opacity of the transparent polymer.

[0008] Metallised, non-transmissive diffractive security features applied to the foil are also known. For example, a diffractive security feature placed on a foil element is known from PL 2483082. The known security feature may comprise, in particular, a metallised diffraction structure, a metallised glossy diffraction structure, a metallised matte structure or a colour-shifted thin foil element, which is typically constructed from a metallic reflective layer, a dielectric separating layer and an absorber layer.

[0009] However, the non-transmissive diffractive optical security features applied to the foil known from the state of the art also require the expansion of production lines with additional components, and are not suitable for designing attractive graphics both on the foil itself, and even more so simultaneously on several different types of substrates.

[0010] Therefore, the purpose of the invention is to provide a security feature with a transmissive optical element, which would be suitable for application and fixing in a seamless manner on a transparent, substrate of the target carrier, in particular on a window area made in a carrier having a paper, composite or polymer substrate, and which would be cheaper to produce and would provide both a strong security against counterfeiting and at the same time a decorative element.

[0011] According to the first embodiment, the essence of the invention is that the security feature comprising a substrate for the transmissive optical element and the transmissive optical element is characterized in that the substrate for the transmissive optical element is a foil having adhesive means on at least one side, wherein at least one area of the foil, on that at least one side with adhesive means, has no adhesive means, and in that the transmissive optical element is printed on the foil according to a target pattern within boundaries of the area without adhesive means, and that the target pattern comprises at least a portion of a diffraction pattern being a computer-generated hologram.

[0012] According to the invention, in the case of an intermediate product, i.e. a foil suitable for bonding to other substrates, preferably holographic one, with a transmissive optical element according to the invention as the security mean, it is possible to obtain a versatile security mean which is easy to produce and which can be easily adapted in shape, size and design to the requirements of the final product to be secured. The fact that the foil has non-adhesive areas of designed shape and location, surrounded by areas with adhesive, ensures simultaneous suitability for attachment to the target product without the risk of losing the suitability of the transmissive performance of the optical element.

[0013] Preferably, the transmissive optical element is printed on the foil within the boundaries of the area without adhesives on the side with adhesives.

[0014] Preferably, the transmissive optical element is printed on the foil within the boundaries of the non-adhesive area(13) on the non-adhesive side.

[0015] Preferably, the target pattern of the transmissive optical element completely covers the area without adhesion means(13).

[0016] Preferably, the target pattern of the transmissive optical element partially covers the area without adhesion measures and extends beyond this area. Preferably, the target pattern of the transmissive optical element is applied fully over an area without adhesion measures and extends beyond this area.

[0017] Preferably, the transmissive optical element can be printed so that it is either monochromatic or multicoloured or with a gradient transition.

[0018] Preferably, the target pattern of the transmissive optical element contains only the diffraction pattern.

[0019] Preferably, the target pattern of the transmissive optical element contains only a fragment of the diffraction pattern.

[0020] Preferably, a transmissive optical element consists of multiple target patterns.

[0021] Preferably, the printing technique is offset or flexographic or typographic or letterpress or rotogravure printing. Preferably, the foil is in the form of a strip or patch or sheet.

[0022] Preferably, the film is coated with a primer layer.

[0023] Preferably, the transmissive optical element is printed with an ink having at least one of the additional characteristics: active under UV light, fluorescent, absorbing infrared light and / or invisible under visible light. According to another aspect of the invention, a carrier with a security feature is provided, comprising

[0024] - a carrier substrate, wherein at least one window is arranged in the carrier substrate, and

[0025] - a security feature comprising a substrate for a transmissive optical element and a transmissive optical element characterized in that the substrate for the transmissive optical element is a foil having adhesive means on at least one side, wherein at least one area of the foil, on that at least one side with adhesive means, has no adhesive means and wherein at least one area of the foil without adhesive means coincides with at least one window in the carrier substrate and in that the transmissive optical element is printed on the foil according to a target pattern at least within an area without adhesive means and that the target pattern contains at least a fragment of a diffraction pattern constituting a computer-generated hologram.

[0026] Preferably, the target pattern of the transmissive optical element is printed partially on the carrier substrate. Preferably, the carrier substrate is paper.

[0027] Preferably, the foil is coated with a primer layer.

[0028] Preferably, the primer layer does not overlap the carrier substrate.

[0029] According to the invention, in the case of the production of paper and plastic documents, a transmissive optical element made using offset printing technology can be made on standard printing machines without modifying the production process of the aforementioned banknotes and / or plastic documents if it is applied to the foil during the production of the banknotes after the holographic (window) foil has been applied to the target product which is a paper banknote. As a result, the use of such security mean does not significantly increase production costs.

[0030] By using foil without adhesive means in the selected area, it is possible to place a transmitting optical element made by printing there.

[0031] By selecting the right type of printing, it is possible to achieve the appropriate print resolution needed for the transmissive optical element.

[0032] By selecting the right type of printing, it is possible to achieve a print quality that allows the transmissive optical element to be permanently applied to the foil.

[0033] Furthermore, the printing application of the transmissive optical element has the advantage that its graphics can be designed in such a way that they extend beyond the substrate for the transmissive optical element, i.e. the foil, and can be applied at the same time within one production step also on the substrate of the security feature carrier itself according to the invention, i.e. for example on the paper substrate of a banknote.

[0034] In the case of a security feature applied using wet offset or other printing technology previously used for banknotes, the costs associated with implementing the solution are avoided.

[0035] In the case of a transmissive optical element applied with UV-only active inks, the transmissive optical element is invisible to the naked eye in visible light and is only revealed when illuminated with collimated light.

[0036] The security feature according to the invention furthermore offers the possibility of combining the transmissive optical element with other security features typical of banknotes.

[0037] There are also many advantages in not having to manufacture expensive cylinders, as is the case with a solution where the optical components are pressed. The known embossed security mean has all the elements transparent so that it is not a decorative element. In addition, the solution proposed by the developers is higher resolution and less expensive compared to security features obtained by laser engraving. In addition, printed TOE security allows security to be produced in multiple colours, which is not possible with other methods. This security also offers the possibility of personalisation. Therefore, a TOE security, i.e. a security feature being a transmissive optical element applied to a foil substrate according to the invention, made using printing technology (preferably offset) allows greater freedom in obtaining images of artistic merit. The resulting images can be of any shape and printed in any colour. The visual aspect also translates into the ease of reading the latent image, compared to embossed security features. In printed graphics, it is possible to design the area to be illuminated with a collimated light beam (e.g. a laser pointer), thus making it significantly easier for the user to read the image with the best visual performance.

[0038] A TOE security, i.e. a security feature being a transmissive optical element applied to a foil substrate according to the invention, made using a printing technique may also have an additional, hidden feature. Such a feature may be UV or infrared printing activity. Neither embossing nor laser engraving offers such an opportunity.

[0039] The TOE security feature can be combined with any of the other security features normally used on banknotes or documents. It can, for example, form part of a see-trough security.

[0040] The security feature and the carrier of the security feature according to the invention are shown in detail in the implementation examples with reference to the accompanying figures, in which:

[0041] Fig. 1 shows a general view of an example carrier of a security feature according to the invention with a security feature according to the invention placed on it;

[0042] Fig. 2a-2f show cross sections through the carrier with the security feature according to the invention along line A of fig.1 ;

[0043] Fig. 3a shows a magnified view of a computer-generated diffraction pattern for a transmissive optical element that is part of a security feature according to the invention;

[0044] Fig. 3b shows schematically the concept of designing a target pattern using only a selected section of the diffraction pattern;

[0045] Fig. 3c schematically depicts the concept of designing a target pattern using both a selected section of the diffraction pattern and graphic elements that are not an active part of the security feature;

[0046] Fig. 4a shows a general view of the security feature according to the invention in the first embodiment;

[0047] Fig. 4b shows a general view of the security feature according to the invention in the second embodiment;

[0048] Fig. 4c shows a general view of the security feature according to the invention in the third embodiment;

[0049] Fig. 4d shows a general view of the security feature according to the invention in the fourth embodiment;

[0050] Fig. 5a shows schematically the detection method of the security feature according to the invention; Fig. 5b shows schematically the principle of activity of a transmissive security feature in an area without adhesives.

[0051] Fig. 6 shows the actual reading of the latent image in the security feature placed on the carrier according to the invention;

[0052] In this description, the following terms have the following meanings:

[0053] The term 'foil' refers to a thin layer made of polymeric material;

[0054] The term 'primer' refers to an additional layer that improves the quality of the print;

[0055] The term 'adhesive means' / 'adhesive layer' refers to a means / layer that enables two materials, two layers to be joined, the adhesives in particular being an adhesive;

[0056] The term 'transmissive optical element' means a security device incorporating a latent image based on the Fourier transform, which appears when illuminated by light collimated in transmission through the substrate on which the transmissive optical element is located;

[0057] 'Diffraction pattern' means a printed pattern containing a latent (coded) image based on the Fourier transform, which can appear at a certain distance after screening with collimated light in transmission if the pattern is located in an area of the substrate that does not interfere with this collimated light ; the term 'ink' refers to a mixture of dyes, pigments for the printing of materials, which can be cured by oxidation or UV light;

[0058] The term 'carrier with a security feature' means any product with a foil on which a transmissive optical element is printed, including a security document, in particular a paper banknote.

[0059] As shown in Fig. 1 , the security feature according to the invention comprises a substrate 10 forthe transmissive optical element and a transmissive optical element 11 applied to the substrate 10 for the transmissive optical element by a suitable technique. The security feature according to the invention can be a separate semifinished product for versatile use in securing target products, including packaging, precious objects and, in particular, documents and securities. As with the foils known from the state of the art, the security feature according to the invention can be produced in the form of rolls, sheets or patches. Further examples of implementation refer to figures of a drawing depicting a finished product, in particular a banknote on which a security feature according to the invention has been placed, however, it should be understood that in the further embodiments the features of the intermediate product itself, i.e. the security feature according to the invention, are also disclosed before being applied to the finished product.

[0060] In one example implementation, the substrate 10 of the security feature 1 according to the invention, that is, the substrate 10 for the transmissive optical element 11 , is a foil 10. This is a foil used in particular for the production of banknotes with a so-called window. Foil 10 can be a foil made of polymeric materials such as polyamide, polyester, polyethylene, polypropylene, for example. Foil 10 can be single-layer or multi-layer (several laminated layers).

[0061] In one embodiment, foil 10 is a polymer foil used for paper banknotes and is referred to as window foil.

[0062] Foil 10 usually has, in the case of window foil, numerous holographic and colour effects. The additional holographic effects on foil 10 are, among other things, additional security features. For this reason, windowed paper banknote foil is also referred to as holographic foil. Selected additional colour effects on foil 10 can also enhance foil 10 visually.

[0063] As shown in cross-section in fig. 2a-2f and schematically in fig. 1 , the foil 10, on the side intended to be in contact with the substrate 21 of the carrier 2, is coated with special adhesive means 13, i.e. an adhesive 13 that is activated by temperature. Adhesive 13 plasticises at the right temperature. In the case of typical semi-finished products available on the market, i.e. typical window foils, the adhesive usually covers, on at least one side, the entire surface of the foil 10, in particular on that side of the foil which is intended to be in contact with the substrate 21 of the carrier or is intended to be in contact with another suitable layer of the target carrier 2, i.e. the target product to which it is to be applied. The adhesive-coated 13 side of the foil 10 allows it to be attached to media 2, for example, already with other security features, i.e. for example, attachment to banknotes 2.

[0064] As a result of the experiments, it was found that the adhesive means 13 used in typical holographic foils prevent the correct operation of the transmission diffraction optical elements made on the foil 10 by printing techniques, including offset printing. Adhesive 13 in principle is used to allow the entire surface of the foil 10 to adhere to the substrate 21 of the carrier 2. The presence of the adhesive 13 on the entirety of at least one side of the foil 10 has not been a problem to date, as in commercially available optical securities, light scattering from the adhesive 13 has not interfered with the verification of these optical securities. Meanwhile, adhesive 13, when dried and viewed in close-up, is not a continuous layer, but takes the form of cracked flakes. Therefore, it is not really transparent and significantly degrades the transparency of foil 10. In addition, it causes scattering of the laser beam when the foil 10 coated with adhesive 13 is illuminated by it, which can be observed experimentally. Namely, when observing a laser beam passing through a window 25 in the carrier 2, which window is covered by a foil 10 with adhesive 13, it can be observed on a screen (e.g. a bright wall, a sheet of paper located at least one metre away from the foil 10) that instead of a single laser spot, a collection of spots of different brightness is visible. Thus, in the case of printed transmissive optical elements 11 , adhesion means 13 prevent the security from functioning correctly. For the correct activation of the diffraction phenomenon for the printed, ratherthan embossed, transmissive optical element 11 , the complete transparency of the substrate 10 of the transmissive optical element on which the ink 12 forming the graphic pattern is placed is required.

[0065] Therefore, according to the invention, as shown in fig. 1 and in fig. 2a-2f, there are no adhesive means 13 on a certain predefined first area 14 of the foil 10. In other words, the foil 10 is deprived of the adhesive 13 on a selected first area 14 located on the side intended to be in contact with the substrate 21 of the carrier 2. The selection of adhesive 13 or the absence of adhesive 13 on a partial area of the foil 10, i.e. on an area 14 without adhesive means that adhesive 13 has not been printed on this area.

[0066] In the case of window foil for the production of paper banknotes, since the adhesive layers are typically applied using the rotogravure printing technique, the foil 10 according to the invention is only partially printed with the adhesive. This also gives you the freedom to design the pattern according to which the adhesive is to be applied. This allows, in one implementation example, an additional aesthetic effect in the window area 15, i.e. a certain part of the window area 15 is transparent and another part of the window area 15 is only transparent, which can also provide an additional security feature.

[0067] In summary, in the case of the window foil 10, only within the boundaries of the first area of the foil 14 without adhesive measures is it possible to make a functioning, i.e. active transmissive optical element. This principle is illustrated by Fig. 5b, discussed later in this description. A transmissive optical element within the boundaries of the first area 14 of the foil without adhesives is to be understood as being made in this area either on the side where no adhesives 13 are present (usually the obverse side of the foil or the target carrier) or on the side where adhesives are present (usually the reverse side of the foil orthe target carrier). In the case of the window foil, the first area 14 of the foil 10 is preferably an area defined inside the window area 15, which is an area separated on the window foil 10 in a virtual manner and, depending on where the security feature 1 according to the invention will be applied, coincides with another area that does not interfere with the transmission of light, including the actual window area 25 cut in the non-transparent substrate 21 of the secured carrier 2, in the case of the paper banknote 2 according to the invention (as shown in fig. 2a-2f). Preferably, for technological reasons, the first adhesive-free 13 area 14 is smaller than the window area 15 and therefore also smaller than the window opening 25 cut in the substrate 21 of the carrier 2. This allows the securing element 1 to be effectively fixed to the substrate 21 of the target carrier 2.

[0068] Preferably, the first completely transparent area 14, i.e. the area 14 without adhesive means, can have any shape. In one example as shown in fig.1 , the first area 14 without adhesive means 13 can be rectangular in shape, or a rectangle with rounded corners.

[0069] Figs. 2a to 2f show different variants for the arrangement of the transmissive optical element 11 constituting the ink layer 12, relative to the sides of the substrate 10 for the transmissive optical element, as well as different variants for connecting the substrate 10 of the transmissive optical element 11 with the substrate 21 of the carrier 2, i.e. different variants for placing the security feature 1 according to the invention on the target carrier 2, i.e. the secured product 2.

[0070] As shown in fig. 2a-2f, on the substrate 10 for the transmissive security feature there is placed a transmissive security feature 11 printed according to a certain target pattern 4', which contains at least one fragment (4'a) of the diffraction pattern 4'a which is a computer-generated hologram. As shown in cross-section in fig. 2a- 2f according to the invention, the foil 10 may or may not be suitably prepared for printing. For this purpose, the foil 10 is coated with a special layer of 17 polymer. The additional layer 17 of polymer results in more durable coverage of the foil by the paint 12. More precisely, the polymer layer 17 results in a better adhesion of the ink 12, which is used to make the transmissive optical element 11 according to the invention. The additional polymer layer 17 is called primer layer 17.

[0071] In particular, fig. 2a illustrates a variant in which the substrate 10 of the transmissive optical element 11 is in contact with the substrate 21 of the carrier 2 on only one side, i.e. the reverse side, whereby the primer layer 17 covers the entire window area 15 of the foil 10, including the first area 14 without adhesive means, and the ink 12 applied according to a certain graphic pattern on the primer layer 17 area, forms the transmissive optical element 11 on that side of the substrate 10 of the transmissive optical element which is not in contact with the substrate 21 of the carrier 2, i.e. the reverse side.

[0072] Fig. 2b illustrates a variant in which the substrate 10 of the transmissive optical element 11 is in contact with the substrate 21 of the carrier 2 on one side only, i.e. the reverse side, and the ink 12 is applied according to a certain graphic pattern to an area 14 without adhesive means which is not covered by the primer layer 17, and forms the transmissive optical element 11 on that side of the substrate 10 of the transmissive optical element which is in contact with the substrate 21 of the carrier 2, i.e. the reverse side of the carrier 2.

[0073] Fig. 2c illustrates a variant in which the substrate 10 of the transmissive optical element 11 is in contact with the substrate 21 of the carrier 2 on one side only, i.e. the reverse side, whereby the primer layer 17 covers the area within the boundaries of the first area 14 without adhesive means and the ink 12 applied according to a certain graphic pattern on the primer layer 17 area forms the transmissive optical element 11 on that side of the substrate 10 of the transmissive optical element which is in contact with the substrate 21 of the carrier 2, i.e. the reverse side.

[0074] Fig. 2d illustrates a variant in which the substrate 10 of the transmissive optical element 11 is in contact with the substrate 21 of the carrier 2 on one side only, i.e. the reverse side, whereby the primer layer 17 covers the first area 14 without adhesives and additionally the area with adhesives (in other words, it overlaps the adhesive), and the ink 12 applied according to a certain graphic pattern on the primer layer 17 area, forms the transmissive optical element 11 on that side of the substrate 10 of the transmissive optical element which is in contact with the substrate 21 of the carrier 2, i.e. the reverse side.

[0075] Fig. 2e illustrates a variant in which the substrate 10 of the transmissive optical element 11 is in contact with the substrate 21 of the carrier 2 on two sides, i.e. the obverse side and the reverse side, with the primer layer 17 covering the first area 14 without adhesives on the obverse side and the ink 12 applied according to a certain graphic pattern on the primer layer 17 area, forming the transmissive optical element 11 on the obverse side of the carrier 2.

[0076] Fig. 2f illustrates a variant in which the substrate 10 of the transmissive optical element 11 is in contact with the substrate 21 of the carrier 2 only on one side, i.e. the reverse side, whereby the primer layer 17 covers the first area 14 without adhesive means and the adhesive means partially overlap the primer layer 17 area, and the ink 12 applied according to a certain graphic pattern on the primer layer 17 area without adhesive means, forms the transmissive optical element 11 on that side of the substrate 10 of the transmissive optical element which is in contact with the substrate 21 of the carrier 2, i.e. the reverse side.

[0077] According to the invention, the developers have developed a technique for applying a transmissive optical element 11 to a holographic foil 10, in the first area 14 without adhesive means. As shown in fig. 1 and fig. 2, the transmissive optical element can be printed directly onto foil 10 or onto the polymer layer 17 (primer layer 17) of foil 10 using ink 12. The thickness of the resulting transmissive optical element 11 , i.e. the ink layer 12, is from a few micrometres to tens of micrometres, optimally below 10pm.

[0078] Transmissive optical element 11 contains a specially designed diffraction image that is a computer-generated hologram. The preparation and fabrication of the transmissive optical element 11 on the substrate 10 of the transmissive optical element 11 is a multi-step process.

[0079] First, a graphic of the latent image 32 is designed to be visible when the transmissive optical element 11 is illuminated with a collimated light 31 from any source 3 of collimated light (see fig.5). Personalisation of the transmissive optical element 11 is possible, e.g. by encoding an latent image 32 containing selected data, e.g. banknote series, banknote denomination, any graphical mark. The designed graphic and the wavelength of collimated light, for which the diffraction image will be best seen, are then transformed by special software using the Fourier transform into a target graphic file containing the diffraction pattern 4. An example of a typical diffraction pattern 4 obtained from the computer programme is shown in fig. 3a and has the form of a square. By the term 'pattern' itself, the visually perceived graphic is generally understood. The term 'diffraction pattern' should be understood as a graphic that has a diffraction pattern for the relevant wavelength, generated by computer.

[0080] The term 'transmissive optical element 11 ' is to be understood as any target pattern 4' when printed on the foil 10, containing at least a fragment 4'a of the diffraction pattern 4. The target pattern 4' may also contain at least one fragment 4'a from the first diffraction pattern 4 and at least one fragment 4'a from another diffraction pattern 4. This means that the target pattern can be a graphic containing several latent images, with each latent image being separately generated as a separate computer-generated hologram. In addition, the 'transmissive optical element 11 ' can, after printing, be in a combined form, i.e. composed of several target patterns 4' (not shown). Examples of individual target patterns 4' are shown in fig. 3b and 3c. For example, the 'transmissive optical element 11 ' may, after printing, take the form of two target patterns 4' (for example, a seashell and a fish) placed side by side in some arrangement, shown as separate, in fig. 3a and fig. 3b.

[0081] The fragment 4'a ofthe diffraction pattern 4 of the transmissive optical element 11 , as its active part 11 a, when printed onto the substrate 10 of the transmissive optical element, should be in the first completely transparent area 14, i.e. in the case of the window foil 10 it should be in the first area 14 without adhesive means. In the case of paper banknotes, when the security feature 1 according to the invention is fixed on the carrier 2, the fragment 4'a of the diffraction pattern 4 should be located in the window area 25. However, variants are possible in which the fragment 4'a of the diffraction pattern 4 is not entirely within the window region 25 and only a certain part of it acts as the active part 11 a of the transmissive optical element 11 . Thus, the term 'transmissive optical element 11 ' according to the present description includes a transmissive optical element 11 capable of having only an active part 11 a, but also an inactive part 11 b (inactive elements 11 b). The inactive part is in this case, after printing, outside the area of the substrate made up of layers that provide sufficient transparency for collimated light. Preferably, prior to printing, even at the design stage, the generated diffraction pattern 4 can be altered in terms of its shape by cutting out a section 4'a of the appropriate shape and forming the target graphic pattern 4' from it, as shown in fig. 3b.

[0082] In yet another embodiment, preferably before printing, still at the design stage, a fragment 4'a can be selected from the generated diffraction pattern 4, which is placed in the target graphic pattern 4' to be applied to the foil 10, which additionally contains another graphic 4'b that does not have the function of a diffraction pattern.

[0083] Such an additional step allows the design of a functionally adapted, but also aesthetically pleasing and attractive appearance of the security feature 11 according to the invention, in every case. A concept of the design stages of the graphic design of the security feature 11 according to the invention is shown in fig. 3b and 3c.

[0084] Furthermore, according to the invention, by performing the transmissive optical element 11 by means of an printing technique, different variants of its arrangement with respect to the substrate 10 of the transmissive optical element itself as well as with respect to the combination of the substrate 10 of the transmissive optical element with the substrate 21 of the target carrier 2, i.e. the target secured product 2, are possible. The deployment concept is illustrated in detail in fig. 4a to 4d, where in fig. 4a the target pattern 4' of the transmissive optical element 11 is fully applied to the area 14 without adhesion means 13, i.e. it covers the area 14 completely without adhesion means. In fig. 4b, the target pattern 4' of the transmissive optical element 11 is superimposed partially on the area 14 without adhesion means 13 and extends beyond this area 14. On the other hand, in fig. 4c, the target pattern 4' of the transmissive optical element 11 is applied fully over the area 14 without adhesion means 13 and extends beyond this area 14. In other words, the target pattern 4' of the transmissive optical element 11 completely covers area 14 without adhesion measures and extends beyond this area 14. In fig. 4a to 4c the target pattern 4' of the transmissive optical element 11 , despite its different shapes, is completely constructed only from fragments 4'a of the diffraction pattern 4.

[0085] Fig. 4d, on the other hand, shows that, in the case of the pattern 4' going outside the area 14 without the adhesive means 13, the target graphic pattern 4' of the transmissive optical element 11 is designed so that it can be printed outside the foil 10, in particular on the substrate 21 of the carrier 2 that is paper 21 . Furthermore, in fig. 4d is illustrated a case in which the target pattern 4' of the transmissive optical element 11 is constructed not only from a fragment 4'a of the diffraction pattern 4 with a suitable shape, but also from graphic elements 4'b, which will not be an active part of the security feature 1 according to the invention due to the fact that they have no diffraction function.

[0086] Fig. 5b, on the other hand, illustrates the general principle of activity of the transmissive optical element 11 in the first area 14 without adhesion means. As shown in Fig. 4a-4d, both the graphic design itself and the size of the transmissive optical element 11 as well as its position after printing can be freely selected, however, the latent image can only be read if at least a fragment (4'a) of the diffraction pattern (4) is present within the first area 14 without adhesion means. Again, it must be emphasised that this does not mean that the target pattern 4' of the transmissive optical element 11 , including at least a fragment 4'a of the diffraction pattern 4', cannot extend beyond the region 14 without adhesion measures. However, no part of the target pattern 4' outside the first area 14 without adhesion measures allows the image to be discovered, even if such an image is partially latent within it.

[0087] Due to the detection method of screening the security with a collimated light, the area of the pattern after application should not be smaller than 0,25 cm2. Consequently, in the case of a paper banknote, the size of the window 25 should also not be smaller than 0,5 by 0,5 cm and preferably, for technological reasons, correspondingly larger than the possible smallest area of the pattern, i.e. the smallest area of the fragment (4'a) of the diffraction pattern (4').

[0088] The manufacturing method of the security feature 1 according to the invention, understood as a foil semifinished product, requires that one of its steps is to print a transmissive optical element 11 onto a substrate 10, namely a foil 10.

[0089] The transmissive optical element 11 , particularly in the window area 15 of the foil 10 and, in the case of the target product 2, simultaneously in the window area 25, can be applied on printing machines by various printing techniques: offset (wet, waterless and dry), letterpress, rotogravure and screen printing, flexography, typographic, with ink fixation 12 both oxidative and UV. Depending on the printing technology used, different print resolutions can be achieved. The offset technique allows a maximum resolution of 10160 dpi. Obtaining a high-resolution latent image increases character generation time and requires a longer optical path when reading the latent image (print-to-screen distance). If the print resolution is too low, the latent image revealed is small and unreadable. Particularly good results are achieved when the print resolution is between 1200 and 2400 dpi. This range is based on the trade-off between image quality, readability and the size of the image and the time it takes to generate security.

[0090] Also with reference to fig. 1 , the secured carrier 2 will be described, in particular the carrier 2 of the securing element according to the invention. The previously described security feature 1 with transmissive optical element 11 is primarily dedicated to secured carriers 2 of the banknote type, in particular with paper substrate 21 , but the person ordinary skilled in the art will know that its modification can also be used with polymer or composite substrate 21 . It can also be used in other types of carriers 2, for example, in valuables, in particular documents of value and / or security products, means of identification and security articles such as banknotes, cheques, vouchers, passports, driving licences, tickets, identification documents, certificates of authenticity and licences, as well as revenue stamps, security packaging and other security documents often susceptible to copying, forgery and partial unauthorised modification. Valuables, data carriers and documents of this type are usually equipped with a certain number of visible and invisible security features that serve to verify their authenticity.

[0091] Carrier 2 in the form of banknote 2 contains a carrier substrate 21 , preferably paper. Banknote 2 may contain a number of different security features (not shown). The carrier 2 in the form of a banknote according to the invention contains a security feature 1 as shown in fig. 1 and fig. 2. For this purpose, the substrate 21 of the banknote 2 is designed in such a way that it has a window 25 at a selected location, which ultimately, after the insertion of the security feature 1 according to the invention, coincides with the window area 15 of the foil 10 on which the transmissive optical element 11 is printed.

[0092] In the following, a method of manufacturing a secured carrier 2, in particular a carrier 2 with a security feature 1 according to the invention will be described, whereby the description of the manufacturing method preferably relates to a carrier 2 in the form of a paper banknote 2. In the present embodiment, the transmissive security feature is applied by printing technique to the foil 10 only after it has been applied to the substrate 21 of the target carrier 2. The person ordinary skilled in the art will know that, depending on the needs and technical possibilities, the printing of the transmissive optical element onto the first area 14 of the foil without adhesive means is possible before or after the foil 10 itself has been applied to the substrate 21 of the target carrier 2 for the security feature 1 .

[0093] In one embodiment, the production of a banknote 2 with window 25 begins with the production of the substrate material 21 of the carrier. In the embodiment discussed in relation to fig. 1 , the substrate 21 of the carrier is paper. In embodiments not discussed here, this can also be a composite substrate 21 or a polymer substrate 21 which is also the substrate 10 for the transmissive optical element 11 . The substrate 21 of the secured carrier 2 has a specific composition and additives, depending on the requirements for the final carrier 2.

[0094] The next stage in the preparation of paper banknote 2 with window 25 is the application of holographic foil 10, in this embodiment, preferably using roll-to-roll machines.

[0095] A reinforcement foil (not shown) is applied to paper 21 from the side opposite holographic foil 10. This is a recommended step, but is not necessary. In the next step, the cutting out of windows 25, i.e. holes of a predesigned shape and size, takes place in the paper 21 (and possibly the reinforcement foil) in the area where the foil 10 (also called window foil, holographic foil) is to be applied. Cutting can be done using a mechanical die-cutter, mechanical plotters or laser plotters.

[0096] The next step is the application of the window foil 10. In this step, the attachment of the foil 10 to the substrate 21 of the carrier 2 takes place at a suitable location. Foil 10 is supplied in the form of rolls with specific parameters including width, length, stretch, etc. The width of the foil is usually less than 25 mm. The foil 10 from the roll is applied in the form of a strip to a designated area on the paper web 21 , in which a pre-cut physical window 25 is located. To do this, paper 21 is moved along a heated cylinder and foil 10 is pressed against it. As mentioned, the holographic foil 10 on the side that is attached to the paper is coated with an adhesive layer 13, in this case a special adhesive 13 that is activated by temperature (the adhesive 13 becomes plasticised). In addition to the thermal activation of the adhesive 13, pressure is also required to firmly bond the foil 10 to the substrate 21 of the banknote 2.

[0097] In another embodiment, foil 10 does not have to be in the form of a strip, it can be in the form of a so-called patch, in which case its shape is arbitrary. In yet another embodiment, the substrate 10 for the transmissive optical element 11 may be in sheet form.

[0098] At each of the stages described, it is very important that all the elements applied to the paper 21 are properly aligned, both graphically and security-wise. The windows 25 and foil 10 must be located at precise positions on the surface of the paper 21 and in relation to each other. When applying the foil 10, it is very important that it exactly covers the window 25 cut in the paper 21 and that it is centred with respect to the window 25.

[0099] It should be mentioned that the first area 14 without adhesives 13 in the foil 10, if the foil 10 is supplied as a strip, must be at least 2 mm narrower than the width of the window 25. Preferably, it can be 4 mm narrower due to the fit tolerance of the foil 10 to the paper 21 . Regarding the maximum length of the first area 14 without adhesives 13 in the foil 10, this can be comparable to the height of the banknote minus a minimum of 2mm. Preferably, the first area 14 without adhesives 13 in the foil 10 can be 10mm x 10mm in size. In the case of a patch foil, the sizes can theoretically be arbitrary, limited only by the size of the note 2 and the graphic design. In the next stage, the printing of the banknote's graphic layout takes place together with the TOE 11 security feature, the transmissive optical element 11. Preferably, offset printing is applied in the first printing stage, during which other security features such as guilloches, micro-text and also the TOE 11 element are applied. In subsequent printing stages, letterpress, typographic and other prints are made.

[0100] The TOE security, i.e. the transmissive optical element 11 according to the invention, can be monochrome, multicolour or multicolour with a tonal transition. The colour of the printing is irrelevant to the verification of the security. It is important for security that the 12 areas to be printed are well coated with ink and that the transparent areas 12 are left uncoated.

[0101] Preferably, the printing effect is visible to the naked eye. It is possible to use inks 12 that are invisible under visible light but active under UV light.

[0102] In addition to the production steps indicated, a person skilled in the art will know that the production process for banknote 2 may include additional steps in which other security features may be applied on additional machines, e.g. using screen printing ink.

[0103] The fit of the printed pattern with the transparent part of the window 25, i.e. with the first area 14 without adhesive means 13, is very important, as this affects the possibility of detecting the security feature hidden in the security feature 1 according to the invention. The imprinted target pattern 4' of the transmissive optical element 11 can be located in different configurations relative to the area 14 without adhesion measures. In particular, it may be located only in the first area 14 without adhesives 13 inside the window 25 (fig. 4A) or it may partially extend beyond it (fig. 4B) or even cover the entire window 25 (fig. 4C). However, the active part of the target pattern 4', can only be at least one fragment of the diffraction pattern 4 printed exactly in the area 14 without adhesion means, with high transmission through the window 25. As mentioned, the printed target pattern 4' can be a single graphic element or part of a larger graphic layout.

[0104] The target pattern 4' after printing, i.e. the created transmissive optical element 11 , may (but need not) be coated with varnish. In the case of varnishing, eitherthe entire banknote 2 can be varnished, or only the window area 15 or only the transmissive optical element 11 can be varnished, or only the banknote 2 can be varnished without the window area 15 or without the transmissive optical element 11 . It is possible to varnish using offset, flexographic or screen printing techniques.

[0105] It should be emphasised here that the disturbance in the transmission of laser radiation through the foil 10, which would contain the security feature 1 according to the invention and would not contain an area 14 without adhesive means, would be so great that, when the transmissive optical element 11 is printed in the window 25, it would be impossible to read the latent image on the screen.

[0106] As shown in fig. 5, in principle, when the diffraction element is illuminated with collimated light 31 , for example from a laser pointer 3 or other collimated light source, a diffraction effect can be observed on a screen located on the opposite side of the carrier 2 to the light source, e.g. in the form of preset data in readable form and in a form inverted symmetrically with respect to the latent image centre point. The distance of the screen from banknote 2 should preferably be around 1 - 2 metres.

[0107] In the case of the illumination of the window 25 where the foil 10 in the separated first area 14 is without adhesive, a single spot is still observed after the passage of the laser beam 31. Accordingly, the illumination with the laser beam 31 of the print applied to the foil 10 covering the window 25 allows the detection of the latent image 32 (see fig.5) in the transmissive optical element 11 according to the invention.

[0108] As shown in fig. 6, the diffraction effect can actually be observed on a screen on the opposite side of the secured carrier, here a paper banknote, e.g. in the form of a preset pattern, here a starfish motif, in readable form and in a form inverted symmetrically with respect to the latent image centre point.

[0109] List of cross-reference designations - security feature - carrier / banknote - collimated light source - diffraction pattern '- target graphic pattern 'a - fragment of a diffraction pattern 'b - fragment of a graphic with no diffraction pattern function0 - foil 1 -transmissive optical element 1a - active part of the transmissive optical element 1 b - inactive part of transmissive optical element 2 - ink 3 - adhesive means / adhesive 4 - area without adhesives 5 - window area 7 - primer layer 1 - media substrate / paper 5 - window 1 - collimated light beam 2 - latent image

Claims

ClaimsI . A security feature comprising a substrate for a transmissive optical element and a transmissive optical element, characterised in that- the substrate (10) for the transmissive optical element is a foil having on at least one side adhesive means (13), wherein at least one area (14) of the foil (10), on this at least one side with adhesive means, has no adhesive means (13) and in that, the transmissive optical element (11) is made on the foil (10) by a printing technique according to a target pattern (4') at least within boundaries of the area (14) without adhesive means (13), and that the target pattern (4') contains at least one fragment (4'a) of a diffraction pattern (4) constituting a computer-generated hologram.2 The security feature according to claim 1 , characterised in that the transmissive optical element (11) is printed on the foil (10) within the area (14) without adhesives (13) on the side with adhesives.

3. The security feature according to claim 1 , characterised in that the transmissive optical element (11) is printed on the foil (10) within the area (14) without adhesives (13) on the non-adhesive side.

4. The security feature according to claim 1 , characterised in that the target pattern (4') of the transmissive optical element (11) completely covers the area (14) without adhesion means (13).

5. The security feature according to claim 1 , characterised in that the target pattern (4') of the transmissive optical element (11) partially covers the area (14) without adhesion means (13) and extends beyond this area.

6. The security feature according to claim 1 , characterised in that the target pattern (4') of the transmissive optical element (11) is applied fully over an area (14) without adhesion means (13) and extends beyond this area.

7. The security feature according to any of the claims 1 -5 characterised in that the transmissive optical element (11) can be printed so that it is monochromatic or multicoloured or with a gradient transition.

8. The security feature according to claim 1 characterised in that the target pattern (4') of the transmissive optical element (11) contains only the diffraction pattern (4).

9. The security feature according to claim 1 characterised in that the target pattern (4') of the transmissive optical element (11) contains only a fragment (4'a) of the diffraction pattern (4).

10. The security feature according to claim 1 characterised in that the transmissive optical element (11) comprises a plurality of target patterns (4').II . The security feature according to claim 1 characterised in that the printing technique is offset printing or flexographic or typographic printing or letterpress or rotogravure printing.

12. The security feature according to claim 1 characterised in that the foil (10) is in the form of a strip or patch or sheet.

13. The security feature according to claim 1 characterised in that the foil (10) is layered with a primer layer (17).

14. The security feature according to claim 1 characterised in that the transmissive optical element (11) is printed with an ink (12) having at least one of the additional characteristics: active under UV light, fluorescent, absorbing infrared light and / or invisible under visible light.

15. A carrier with security feature, comprising- a carrier substrate, wherein in the carrier substrate there is arranged at least one window, and- a security feature comprising a substrate for a transmissive optical element and a transmissive optical element, characterized in that the substrate (10) for the transmissive optical element is a foil having adhesive means (13) on at least one side, wherein at least one area (14) of the foil (10), on this at least one side with adhesive means, has no adhesive means (13) and wherein at least one area (14) of the foil (10) without adhesive means coincides with at least one window (25) in the substrate (21) of the carrier (2), and in that the transmissive optical element (11) is made on the foil (10) by a printing technique according to a target pattern (4') at least within boundaries of the area (14) without adhesive means (13), and the target pattern (4') contains at least a fragment (4'a) of the diffraction pattern (4) constituting a computer-generated hologram.

16. The carrier with security feature according to claim 15, characterised in that the transmissive optical element (11) is printed on the area (14) without adhesive means (13) on the obverse side of the carrier (2).

17. The carrier with security feature according to claim 15, characterised in that the transmissive optical element (11) is printed on the area (14) without adhesive means (13) on the reverse side of the carrier (2).

18. The carrier with security feature according to claim 15 or claim 16 or claim 17, characterised in that the transmissive optical element (11) can be printed so that it is either monochromatic or multicoloured or with a gradient transition.

19. The carrier with security feature according to claim 15 or claim 16 or claim 17, characterised in that the target pattern (4') of the transmissive optical element (11) completely covers the area (14) without adhesion means(13).

20. The carrier with security feature according to claim 15, characterised in that the target pattern (4') of the transmissive optical element (11) partially covers the area (14) without adhesion means (13) and extends beyond this area (14).21 . The carrier with security feature according to claim 15, characterised in that the target pattern (4') of the transmissive optical element (11) completely covers the area (14) without adhesion means (13) and extends beyond this area (14).

22. The carrier with security feature according to claim 15 or claim 17 characterised in that the target pattern (4') ofthe transmissive optical element (11) is printed partially on the substrate (21) of the carrier (2).

23. The carrier with security feature according to claim 15, characterised in that the substrate (21) of the carrier (2) is paper.

24. The carrier with security feature according to claim 15, characterised in that the foil (10) is coated with a primer layer (17).

25. The carrier with security feature according to claim 24, characterised in that the primer(17) does not overlap the substrate (21) of the carrier (2).

Images