Patent Publication Number: US-11386812-B2

Title: Film structure with protection against manipulation

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is the National Stage of PCT/EP2017/060210 filed on Apr. 28, 2017, which claims priority under 35 U.S.C. § 119 of German Application No. 10 2016 108 216.3 filed on May 3, 2016, the disclosure of which is incorporated by reference. The international application under PCT article 21(2) was not published in English. 
     The invention relates to a film structure having protection against manipulation and inscribable by action of a laser beam. 
     In many areas of application, it is necessary to equip articles with a manipulation-proof identification. In the automobile sector, for example, vehicles are provided with a type designation, for example an engine or chassis identification, which is assigned individually to a specific vehicle. Furthermore, vehicles are being increasingly labeled with environmental stickers, which classify the vehicle in a particular pollutant emission group. 
     Such markings have authenticity character and should therefore be designed to be manipulation-proof. Film structures in the form of labels are often used for marking articles, since they are flexible and can be easily bonded adhesively on a substrate. To prevent the authenticity marking from being manipulated, it must be ensured that it is impossible for a counterfeiter to detach the film structure with the authenticity character from a substrate on which the film structure is affixed and to transfer it to another article without showing evidence of the counterfeiting. For this purpose, it is necessary that the destruction of the film structure be ensured in the case of a manipulation attempt. 
     One concern for the present invention is to specify an inscribed film structure with protection against manipulation that on the one hand can be easily affixed on an object to be identified and with which it is ensured that the film structure will be destroyed by a manipulation attempt. 
     One configuration of a film structure with protection against manipulation is specified in claim  1 . The film structure comprises a top film and a laser-inscribable layer, which is disposed on the underside of the top film. Furthermore, the film structure comprises a bottom film and a bonding layer for bonding the bottom film with the top film and the laser-inscribable layer. The bonding layer is disposed between the laser-inscribable layer and the bottom film. The film structure has an inscribed region and a non-inscribed region. In the inscribed region of the film structure, the top film is fused together with the bottom film. 
     According to the film structure specified above, the laser-inscribable layer is disposed on the underside of the top film. The laser-inscribable layer is a layer that becomes ablated under the action of the energy of a laser beam. As an example, the laser-inscribable layer may be a metallization layer, which is affixed directly onto the underside of the top film during manufacture of the film structure. As an example, the laser-inscribable layer may be vapor-deposited or sputtered onto the underside of the top film. According to one possible embodiment, the laser-inscribable layer may be designed as an aluminum layer, especially an aluminum layer with a black color. 
     By the fact that the laser-active or laser-inscribable layer is metalized on the underside of the top film and not affixed onto the top side of the bottom film during the manufacture of the film structure, interactions occur between the bonding layers, especially during the laser inscription. Since the laser-inscribable layer is affixed directly onto the underside of the top film, the thermal energy generated by the laser beam acts directly on the laser-inscribable layer and is not reduced due to absorption by further layers, for example by the bonding layer. 
     Due to the laser inscription, on the one hand the metallization of the laser-inscribable layer is partly removed or is transformed into a colorless substance, and thus an inscription is produced. On the other hand, during the laser action, an interaction that leads to a permanent composite between the individual layers takes place due to melting and/or welding processes in the composite between the top film, the laser-inscribable layer, the bonding layer and the bottom film. Especially at the edges/borders of the inscription, a fusion of the individual layers with one another takes place and extends into the entire inscribed region. By virtue of the fusion of the top and bottom films in the inscribed region of the film structure, it is no longer possible to separate the top film from the bottom film without tearing the film structure apart in the inscription regions. 
     Due to the intensification of the interaction between top and bottom films at the border between the inscribed and the non-inscribed region as a consequence of the laser marking, an improvement of the authenticity nature of the inscribed film structure is achieved in comparison with a film structure in which the laser-inscribable layer is affixed onto the bottom film, for example is vapor deposited on the upper side of the bottom film. A transfer of the top film together with the inscribed layer disposed on its underside is almost completely ruled out even for complex manipulation attempts of chemical or physical nature, since the film layer, by virtue of the fusion of the layers, will be torn apart in the attempt to separate the top film from the bottom film. 
     In order to facilitate tearing apart of the film structure, the bottom film may be provided with lines of weakness, for example stamped lines. Besides the assurance of a destruction of the film structure during a detachment attempt, neither the inscription quality nor the visual impression in the film structure is negatively influenced as a consequence of the security stampings in the bottom film. 
    
    
     
       The invention will be explained in more detail in the following on the basis of figures, which show embodiments of the present invention, wherein: 
         FIG. 1  shows an embodiment of a film structure with protection against manipulation, 
         FIG. 2  shows an action of a laser beam for introduction of an inscription in the film structure, 
         FIG. 3  shows the film structure with protection against manipulation after the laser inscription step, with a melting region between the film courses, 
         FIG. 4  shows the film structure with protection against manipulation after a laser inscription with a partial removal of the laser-inscribable layer, 
         FIG. 5  shows a destruction of the film structure by fragmentation of the individual layers during a manipulation attempt. 
     
    
    
       FIG. 1  shows an embodiment of a film structure  100  with protection against manipulation. The film structure is designed as a so-called color laser film. It comprises a top film  10  and a laser-inscribable layer  20 , which is disposed on the underside U 10  of the top film  10 . Furthermore, the film structure comprises a bottom film  40 . The top film  10  as well as the bottom film  40  may be designed respectively as a layer of plastic, preferably of polyethylene (PE), polyethylene terephthalate (PET) or polyvinyl chloride (PVC). 
     A bonding layer  30  is provided for bonding the top film  10  and the laser-inscribable layer  20  disposed on its underside with the bottom film  40 . The bonding layer  30  is disposed between the laser-inscribable layer  20  and the bottom film  40 . The bonding layer  30  is disposed directly underneath the laser-inscribable layer  20  and directly above the bottom film  40 . The bonding layer  30  may be, for example, a bonding adhesive. 
     The bottom film  40  may be provided with an adhesive layer  50  on its side U 40  turned away from the bonding layer  30 , i.e. on its underside. The adhesive layer  50  disposed on the underside U 40  of the bottom film  40  is used for adhesive bonding of the film structure  100  onto a substrate. For protection of the adhesive layer  50 , it may be covered by a carrier film  60 . 
     The laser-inscribable layer  20  is affixed onto the underside U 10  of the top film  10  and thus is permanently bonded with the top film  10 . As an example, the laser-inscribable layer  20  may be vapor-deposited or sputtered onto the underside U 10  of the top film  10 . This means that, during the manufacture of the film structure, the laser-inscribable layer  20  is affixed not onto the bottom film  40  but instead onto the underside U 10  of the top film  10 , by a physical/chemical process. The laser-inscribable layer  20  may be affixed onto the underside U 10  of the top film  10  in a thickness of smaller than 3 μm, preferably in a thickness between 0.1 μm and 0.4 μm. 
     The laser-inscribable layer  20  is designed in particular as a metallic layer, which is ablatable under the action of a laser beam. “Ablatable” will be understood to mean that the layer is eroded or destroyed by the action of a laser beam, especially by the thermal energy of the laser, so that it loses its opacity. The laser-inscribable layer  20  may be designed in particular as an aluminum metallization, which is disposed on the underside U 10  of the top film  10 . The aluminum metallization adheres permanently to the underside U 10  of the top film  10 , for example by vapor deposition or sputtering. 
     The laser-inscribable layer may be designed in particular as an aluminum layer with a black color. For application of the aluminum layer  20  onto the underside U 10  of the top film  10 , the aluminum may be vaporized in a vacuum atmosphere and deposited on the underside U 10  of the top film  10 . Thereby a silver-colored coating is obtained on the underside U 10  of the top film  10 . The opacity of the coating is dependent on the thickness of the coating. The coating is transparent to opaque, depending on thickness of the layer. For generation of the preferably black metallization layer  20 , oxygen is injected into the vacuum. Thereby nonstoichiometric aluminum oxide, which has a black color, is formed. 
     The top film  10  is preferably designed as a transparent layer in the film structure. The bottom film  40  may be configured as a white layer. In order to facilitate the tearing apart of the film structure in case of a manipulation attempt, for example an attempt to strip the film structure from a substrate, the bottom film  40  may be provided with at least one line of weakness  41 .  FIG. 1  shows the bottom film  40  with a plurality of lines of weakness  41 , which are made, for example as a security stamping in the bottom film  40 . According to an alternative configuration form, the bottom film may be provided with, instead of or in addition to the lines of weakness, easy-tearing materials such as security films of acrylate, polyurethane and similar. 
       FIG. 2  shows the film structure  100  with protection against manipulation during an inscription by means of a laser  1 . By action of its laser beam  2  on the laser-inscribable layer  20 , the laser generates an inscription within the film structure  100 . Inscription will be understood to mean graphic symbols and characters of any kind. As is obvious on the basis of  FIG. 2 , the film structure  100  has an inscribed region  101  and a non-inscribed region  102  as a consequence of the laser inscription. Due to the action of the laser beam, the laser-inscribable layer  20  is ablated. This means that it is partly removed or transformed into a colorless substance in the inscribed region  101  of the film structure  100 , while it remains intact in the non-inscribed region  102 . The layer thickness of the laser-inscribable layer  20  is therefore reduced in the inscribed region  101  of the film structure in comparison with the non-inscribed region  102 . As an example, only individual particles of the laser-inscribable layer  20  are still present in the inscribed region  101  of the film structure. 
     Since the region in which the inscription takes place is sealed between the top film  10  and the bottom film  40 , no health-endangering and environmentally polluting emissions to the outside occur during inscription of the film structure  100  with the laser beam  2 . The film structure  100  thus offers high-level intrinsic protection of the registered inscription pattern against chemical and mechanical aggressions. 
       FIG. 3  shows the film structure  100  after action of the laser beam  2  for inscription of the film structure. By virtue of the energy input due to the laser beam  2 , the top film  10  and the bottom film  40  are fused with one another at the melting region  104  illustrated within the inscribed region  101  in  FIG. 3 . Since the laser-active/inscribable layer  20  is affixed directly on the top film, i.e. on the underside U 10  of the top film  10 , more heat is generated locally in this region than if the laser-active/laser inscribable layer  20  had been affixed onto the upper side O 40  of the bottom film  40  during the manufacture of the film structure. 
     The heating developed in this region during the laser marking on the basis of the energy input by the laser beam leads to a melting together of the respective materials of the top film  10 , of the laser-inscribable layer  20 , of the bonding layer  30  and of the bottom film  40 . Thereby a conglomerate comprising the top film  10 , the laser-inscribable/laser active layer  20 , the bonding layer  30  and the bottom film  40  fused together with one another is formed in the melting region  104  of the film structure  100 . 
     The bottom film  40  absorbs the laser energy of the laser  1  efficiently during the laser inscription, whereby a melting of the bottom film  40  together with the other layers, especially the top film  10 , is made possible. In addition, the bonding layer  30  becomes mobile due to the heat input as a consequence of the laser action and thus likewise intensifies the interactions between the top film  10 , the laser-inscribable layer  20  and the bottom film  40  due to an enlargement of the local contact face and a mixing with the resulting melt. 
     Due to the fusion, in the melting region  104 , of the bottom film  40  with the top film  10  and the laser-inscribable layer  20  affixed onto its underside U 10 , a local strengthening of the adhesive force results in the film composite  100  in the region containing the inscription after the laser action. Furthermore, a weakening of the structure of the top film  10  takes place due to the melting of the materials, thus facilitating a further tearing of the film during an attempt to separate the individual film layers from one another. 
     The interactions between the top film  10 , the laser-inscribable layer  20 , the bonding layer  30  and the bottom film  40  occur in the region in which the laser beam acts on the film structure, i.e. in the region inscribed after the laser action. At a border  103  between the inscribed region  101  and the non-inscribed region  102 , i.e. at the edge of the inscription, a change of the interaction, especially of the adhesion, takes place between the top film  10 , the laser-inscribable layer  20 , the bonding layer  30  and the bottom film  40 . The change of the interaction has the consequence that the top film  10  and the bottom film  40  fuse together with one another in the inscribed region  101 , and in the non-inscribed region  102  of the film structure they are not fused together with one another but instead are separated from one another by the intact laser-inscribable layer  20  and the bonding layer  30 . Furthermore, in the non-inscribed region  102  of the film structure, the laser-inscribed layer  20  is separated from the bottom film  40  by the bonding layer  30 . 
       FIG. 4  shows the film structure  100  after the inscription as a consequence of the laser action. The laser-inscribable layer  20  has been partly removed or transformed into a colorless substance in the inscribed region  101  of the film structure. In contrast, the laser-inscribable layer  20  in the non-inscribed regions  102  of the film structure continues to adhere to the underside U 10  of the top film  10 . 
       FIG. 5  shows how the film structure  100  is torn apart in the attempt at a manipulation, especially a separation between top and bottom films. Fragments  20   a  of the laser-inscribable layer  20  remain adhering on the bottom film as a consequence of the fusion with the bottom film  40 , whereas other parts  20   b  of the laser-inscribable layer  20  adhere to the top film  20 . Thus the film structure ensures that, as a consequence of the melting together and fusion of the individual layers, the top film and the bottom film can no longer be separated from one another nondestructively after the inscription of the laser-inscribable layer  20 , whereby an improved authenticity nature of the film structure is achieved. 
     LIST OF REFERENCE SYMBOLS 
     
         
           1  Laser 
           2  Laser beam 
           10  Top film 
           20  Laser-inscribable layer 
           30  Bonding layer 
           40  Bottom film 
           50  Adhesive layer 
           60  Carrier film 
           100  Film structure