Any and all applications for which a foreign or domestic priority claim is identified in the Application Data Sheet as filed with the present application are hereby incorporated by reference.
The invention relates to a security element which can have the form of threads, strips or patches and which is used in connection with banknotes, official and unofficial documents like passports, ID-cards, bank and credit cards, checks, paper, coupons vouchers, tickets, packages or the like. Provision of the mentioned documents with the security element improves the protection against forgery.
Security elements typically have different characteristics or so-called security features which may be recognized by visual inspection, such as colour changes, holographic pictures, characters, patterns, which may particularly develop a different appearance according to the angle and direction of the observation with the naked eye. This allows a quick and reliable detection of forgery without requiring any equipment. Therefore, observable effects shall be made prominent in occurrence, so that a missing optical effect is quickly recognized to quickly identify a forgery. Of course, the security element shall be very difficult—if not impossible—to copy, to reduce the potential of forgery.
In particular, the formation of patterns which are visible in transferred light by providing gaps in a metal layer on a transparent substrate is a readily recognizable security feature and are well-known in the art.
It is also known to provide holographic effects on one surface of a security element by covering a suitably structured or modulated surface with a reflective layer, which provide the holographic effect such as changing pictures and/or colors and/or 3D-pictures and the like depending on the direction of observation.
It is considered an improvement of the safety of the security element if a holographic effect observable in reflected light and a pattern observable in transmitted light are combined. In this case, it may be arranged that the pattern will be observable from both sides of the security element, while the holographic effect is only visible from one side.
In view of the above, it is the object of the invention to provide a security element which has an improved safety in visual inspection, and a method for making the same.
With regard to the security element, the object is solved with a security element having the features of claim 1, and with respect to the method, the object is solved with a method according to claim 9.
According to the invention, a security element, comprises a transparent first layer having a holographic surface structure, a first metal layer arranged on said first layer in a first pattern having transparent and non-transparent regions and a holographic surface structure, a second layer having a second holographic surface structure, and a second metal layer arranged on said second layer in a second pattern having transparent and non-transparent regions and a holographic surface structure, wherein said transparent regions of said first metal layer and said second metal layer are arranged to at least partly overlap each other.
With this arrangement, visual inspection of the security element in transmitted light will disclose the overlapping portions of the transparent regions in the first and second metal layer as a pattern. Visual inspection of the security element in reflected light will show a holographic effect on each of the two sides of the security element, i.e. front surface/rear surface.
Advantageously, the transparent and non-transparent regions of the first layer and the second layer are in register, so that the security element displays a pattern on one side and the mirrored pattern on the other side, when inspected in transmitted light
Advantageously, the holographic surface structure of the first metal layer is different from the holographic surface structure of the second metal layer, so that the security element displays a first holographic effect, when inspected from one side in reflected light, and displays a second holographic effect which is different from the first holographic effect, when inspected from the other side in reflected light.
Advantageously, the non-transparent regions of the first metal layer have a holographic surface structure which repeats the holographic surface structure of the first layer underneath the non-transparent regions at least on the surface of the first metal layer adjacent to the first layer. Additionally or alternatively, the non-transparent regions of the second metal layer have a holographic surface structure which repeats the holographic surface structure of the second layer underneath the non-transparent regions at least on the surface of the second metal layer which is opposite to the second layer.
Advantageously, the security element comprises a transparent film on which said first layer is formed. Preferably, this layer is made from a PET (polyethylene terephtalate) film which has a high transparency and which is stable in shape and is sturdy.
Preferably, the second layer is made from an embossable photopolymer material which becomes soluble when radiated with light and/or radiation. In this way, the material can be selectively, i.e. at selected portions of the layer, changed in its composition by irradiating these portions with light, preferably UV-light, or X-ray or other types of radiation, such that the material can be dissolved or washed away from these selected portions.
Advantageously, the security element has a third layer covering the second metal layer at the non-transparent regions. This third layer may be printed in a manner to cover the non-transparent portions of the second metal layer. The third layer is resistant against metal dissolving/removing liquids (etching liquids) and is capable to protect the metal layer underneath against such etching liquids. In the later description of the method for manufacturing the security element, the third layer is defined as being made of a coating, i.e. it may comprise any suitable coating material such as lacquer, ink, varnish, resist, or other solidifying spreadable materials.
Advantageously, a protection layer covering the exposed outermost surface portions of each layer is provided. The protection layer is suitably selected to be resistant against e.g. mechanical wear, radiation, chemical substances which may expectably come into contact with the security element and the like.
The method for manufacturing a security element, according to the invention comprises steps of: forming a first layer from a transparent material, forming a holographic surface structure on the first layer, metallization of the first layer to form a first metal layer, forming a second layer from a radiation-sensitive polymer, forming a holographic surface structure on the second layer, metallization of the second layer to form the second metal layer, printing a pattern of a coating on the second metal layer, said pattern comprising regions covered by the coating and regions uncovered by the coating, removal of the metal in regions of the second metal layer which are uncovered by the coating by a process of de-metallization, exposing the de-metallized regions of the second layer to light or radiation, so as to transfer the radiation-sensitive polymer in the de-metallized regions into a soluble state and removing the soluble radiation-sensitive polymer, and removal of the metal in regions of the first metal layer, which are not covered by the second layer, by a process of de-metallization. Advantageously the materials used for the first layer and for the second layer are embossable materials, and wherein first and the second holographic surface structures are made by embossing the respective layer. The formation of the holographic surface structure and the metallization of the first and/or second structure can be made in arbitrary order on each layer and amongst the layers.
Advantageously, the first layer is printed on a transparent film, the radiation-sensitive polymer is printed on the first metal layer, and the coating is a resist, which is printed in a predetermined pattern on the second metal layer.
Advantageously, the radiation is UV-light which is applied to the security element after the de-metallization step of the second metal layer. Preferably, the radiation-sensitive polymer of the second layer is destabilized by UV-light and the destabilized polymer is soluble in an aqueous soda solution.
Advantageously a protective layer is applied to cover the security element, the protective layer being applied to cover the exposed surfaces of the layers and to fill gaps formed in the layers, particularly the gaps formed by the transparent regions of the patterns. In this way, the surface of the security element becomes smooth, so that intrusion of liquids or debris is avoided and resistance to mechanical wear at the edges of the gaps is inhibited. This ensures a clear appearance of the security features of the security element over long time.
Advantageously the protective layer is provided with an adhesive, particularly a thermo adhesive. In this way, application of the security element to a carrier (banknote or the like) is possible by the application of heat and pressure. In this case, the side of the security element covered by the protective layer is fixed to the carrier, so that the exposed surface of the security element is the transparent film which may be made of PET, a robust material.
Advantageously, the security element is a security thread which is embedded into paper to run over the surface of the protected document such as a banknote. The security element may also have the form of patches or other shapes which may be applied to or implemented in documents to be secured against forgery.
In the following, the invention will be explained in detail by reference being made to a preferred embodiment as is shown in the drawings, in which
In the description of the drawings, the terms upper and lower, above, underneath etc. are used in relation to the drawings as shown. These term are not limiting, because an opposite orientation of the security element during manufacturing and use is possible and likely, so that these terms will have to be adapted accordingly. Also, term like first, second and third or the like are derived from the order of manufacturing, and are not limiting the scope of the claims, when counting the order of layers in the final product.
A transparent film 1 made preferably from PET carries a first transparent layer 2. A surface structure 21 which is formed on the upper surface of the first transparent layer 2 is embossed into the material of the layer. The surface structure is suited to form a holographic picture or effect. In the drawing of
Above the first transparent layer 2 there are portions of a first metal layer 41, wherein the metal layer 41 follows the surface structure 21 of the first transparent layer 2. That is, since the metal layer 41 is thin and has an almost constant thickness, it repeats the surface structure 21 accurately.
On the portions of the metal layer 41, a second layer 3 is formed which has one side repeating the surface structure 21 in the form of a surface structure 31. On the other side, which side is opposite to the surface structure 31, a second surface structure 32 is formed, which also provides for a holographic effect in the form of a picture or the like. In order to indicate that the surface structure 32 is different from the surface structure 21, a zigzag line has been used. Also here, line 32 is used to express an irregular or rough surface structure 32 which in practice has much smaller amplitudes then is shown here.
A second metal layer 42 is formed to cover the surface structure 32 of the second layer 3. Because the metal layer 42 is very thin, the upper side of the metal layer 42 shows a surface structure 51 which is the same as the surface structure 32, i.e. it provides the same holographic effect as surface structure 32.
The second metal layer 42 is covered with a third layer 5 which is made from a coating material. Finally, a transparent protection layer 6 is applied which covers all exposed surfaces of the individual layers also those parts which are exposed to the gaps 9 between the layered blocks.
The gaps 9 between the layered blocks form or are arranged in a pattern which is observable in transmitted light. In particular, film 1, transparent layer 2 and protection layer 6 are transparent, so that the gaps 9 forming a pattern in an opaque security element are clearly recognizable and form a first safety feature of the security element.
Furthermore, the holographic structure 21 of the first transparent layer 2 is backed by a metal layer (typically aluminum) so that an observation of the security element from below in
When the security element of
The portions covered by the first and second metal layers 41 and 42 are non-transparent, so that each respective holographic picture can only be seen from one side of the security element because, the other holographic picture is hidden or shielded by the corresponding metal layer. For example the first metal layer 41 shields the holographic surface structure 51, so that it cannot be observed from below in
When observing the security element of
In the embodiment shown in
In the following, using
Besides, the same reference signs are used for the same elements as described in
According to
Then a thin first metal layer 41 is applied which covers the first transparent layer 2 with the surface structure 21. The metal layer 41 is applied by a metallization process, wherein one possible process uses evaporation of metal, like aluminum.
The first metal layer 41 is covered with a second layer 3 which is made from a photo-sensitive polymer material. The second layer 3 may be applied by printing or other suitable coating process. When the photo-sensitive material is irradiated with UV-light, it changes its composition such that the irradiated material portions become soluble to a solvent, which may be water or another technical solvent like a mild water/soda solution. The second layer 3 is embossed to form a surface structure 32 thereon as is described in detail with reference to
A second metal layer 42 is formed on the second layer 3. The metal layer 42 is very thin so that the upper surface of the metal layer repeats or copies the surface structure 32 underneath the second metal layer 42. As a result, the upper surface of the second metal layer 42 has a surface structure 51 which provides or has a holographic effect.
A transparent third layer 5 or coating is then applied on the top surface of the second metal layer 42 (this step not being shown in a separate figure). The application of the third transparent layer 5 is made to form a pattern of coated and uncoated regions on the second metal layer 42. The application in the form of a pattern is obtained by printing a transparent coating or a transparent resist in a required pattern, which pattern may comprise text, letters, symbols, signs, numbers or other shapes and the like.
As can be seen from
Then, the structure of
Starting with the intermediate product of
From
In the final steps, a transparent protection layer 6 is applied which fills the gaps and forms a cover to seal the layered structure of the security element. This may be obtained by printing a protection lacquer on the security element.
Finally, a thermo-adhesive is applied which is used for fixing the security to the document, banknote or the like which is to be protected. The final result is shown in
It is noted that the second layer 3 may be formed of an embossable photo-sensitive material which is opaque or non-transparent. Furthermore, in the method and product described above, the holographic surface structure of the first layer 2 and/or the second layer 3 may be made before or after the surface has been metallized, i.e. provided with the respective metal layer 41 and 42, respectively. Using the embossing technology allows to suitably deform (emboss) the surface of the respective layer independent from whether the layer carries the metal layer or not.
Number | Date | Country | |
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Parent | 15739654 | Dec 2017 | US |
Child | 15931288 | US |