EP1159723B1 - Safety adhesive foil as identification element - Google Patents

Description

The invention relates to a writable security adhesive film containing a diffusive identification medium. If the film is adhered to a substrate, the identification medium results in a permanent marking of the substrate.

Security films and security labels play a major role in marking theft-sensitive or safety-relevant workpieces and documents. They are glued to the object to be secured and are only with great effort to copy and / or remove from the object surface, the substrate. Of particular advantage are security films and labels whose labels are permanently detectable even after removal of the film or the label on the underlying substrate: they force the thief or counterfeiter to elaborate rework to erase the traces of the label on the substrate and / or to produce a fake label of the substrate. Thus, they significantly reduce the attractiveness of theft or counterfeiting. To achieve a permanent inscription of the substrate, the security film is provided with a diffusive identification medium which, after the film has been glued, migrates into the underlying substrate, causing it to undergo a physical and / or chemical reaction.

US Pat. No. 5,346,738 discloses a security label which contains an acid in microencapsulated form as the identification medium. If a pressure is exerted on the label, in particular by the adhesion process to an object, the encapsulation breaks, the identification medium is released and diffuses to the substrate surface, where it causes a corrosive reaction. The labeling process is an integral part of the chemical / technical manufacturing process of the label and must therefore take place at the label manufacturer.

Thus, the user's requirement, which is indispensable for effective theft protection, can not be met by these labels, the labels can be inscribed in-house and as short as possible, and the inscription pattern can be redesigned as needed to ensure the highest possible counterfeit security.
Another disadvantage of these labels is that the labeling of the label top is done in a further, separate process step, which makes the process consuming and error prone.

From WO 97/40484 a security label is known, which contains an adhesive layer with a diffusive identification medium. Labeling of the label is effected by a barrier medium which, according to the inscription, is selectively applied to the adhesive layer so as to partially mask the side facing the substrate. If the label is adhered to the substrate, the barrier medium should locally prevent or reduce the diffusion of the identification medium from the adhesive layer to the substrate, while unimpeded diffusion should take place in the regions free of the barrier medium. The label of the labels, i. the order of the barrier medium can be carried out by the user in-house; however, this is an error-prone process because it must be ensured that the label does not compromise the durability and adhesive properties of the label. That is why these safety labels are only of limited use for use in the factory environment.

US Pat. No. 4,841,652 shows a security film with a carrier layer to which an adhesive layer with a diffusible identification medium is applied. In order to avoid the diffusion of the identification medium into the carrier layer and thus damage to the carrier layer or a visibility of the identification medium in the carrier layer, a barrier layer is arranged between carrier layer and adhesive layer, which prevents the identification medium from penetrating into the carrier layer.

EP 845 767 A1 discloses a security label having an adhesive layer containing an identification medium dispersed therein. The label is adhered to a substrate surface by means of the adhesive layer. The activation of the identification medium takes place by local removal of the adhesive layer, for example by selective cutting or burnout, by selective displacement of the adhesive layer due to pressure application or laser ablation or by selective application of a polymer layer to the substrate side of the adhesive layer.

The invention has for its object to provide a durable, easy and fast to be inscribed in the factory field security film that also makes it difficult to falsify the identity of the products to be secured in case of theft.

The object is achieved by the features of claim 1.

Thereafter, the security film contains a carrier layer in which an identification medium is contained. With the help of a non-contact labeling process, the diffusion properties of this identification medium can be specifically selectively and locally changed. If the security film labeled in this way is adhered to a workpiece, the identification medium diffuses toward the substrate surface, where it causes a detectable reaction. In this case, this diffusion or reaction takes place only in those areas of the substrate surface in which the diffusion capability was triggered or not obstructed by the inscription process. Thus, the security film allows a clear labeling and identification of the workpiece.

The security film is labeled according to the invention by means of a non-contact method. Thus, even in the factory environment a dirt-resistant, fast, flexible variable labeling can be achieved. The labeling of the security film - and thus the change of the diffusion properties of the identification medium - can be done in particular by means of electromagnetic radiation. Particularly advantageous for labeling the security film is the use of a laser, by means of which both a temperature-sensitive and a light-sensitive labeling can take place (the term "light" in this case, the entire laser-accessible range of the electromagnetic spectrum comprises). Lasers have the additional advantage of allowing high-contrast labels with any choice of pattern, allowing rapid changes in the pattern of the label, and being process reliable in the factory environment.

As identification medium, a substance is selected which triggers a detectable reaction on the substrate. For this purpose, the identification medium must be adapted to the material properties of the substrate. Thus, the identification medium may contain a dye, which is adapted to the substrate and which locally diffuses into the substrate surface and dyes it. Alternatively, the identification medium may include a substance that undergoes a chemical reaction with the substrate surface. Of particular interest here are reactions in which the substrate surface is removed locally or locally inflated, so that the labeling of the substrate after removal of the film can be detected optically or tactilely. In particular, an identification medium containing a corrosive substance is recommended for the marking of metallic substrates.

To increase theft protection, it may be advisable to choose an identification medium whose influence on the underlying substrate is not visible to the naked eye. This can be accomplished with an identification medium that exhibits the absorption and reflection properties of the substrate, e.g. only in the UV or IR range, but not affected in the visible range. If a thief or counterfeiter removes the film, the substrate will not contain any visible traces of the marking, and the thief or counterfeiter will not see any need to scrape or paint over the substrate surface in the affected areas. The affected areas still contain the markers which are simply displayed by informed security forces using e.g. a UV or IR viewing device can be detected. In particular, the identification medium can be chosen so that the detectability, for. As the UV fluorescence, takes place only at certain wavelengths of the test light.

For industrial use of the security film, especially in the automotive industry, the film must have a high resistance to temperature and light. These requirements can best be met if the security film has physical barriers which inhibit the diffusion of the identification medium in the unrecorded state of the film. During the labeling process, these barriers are locally destroyed or weakened, so that selective diffusion of the identification medium can take place in the regions thus weakened. In order to achieve a high temperature or light resistance of the lettering, the temperatures or light intensities required for the destruction of the barriers must be substantially higher than those to which the object to be marked in use - even under extreme environmental conditions - subject.

Such a diffusion inhibition of the identification medium, which can be canceled by a non-contact labeling can be realized by a micro-encapsulation of the identification medium in the carrier layer. The identification medium is enclosed in capsules whose walls are e.g. made of wax and / or fat and e.g. can be broken by the local influence of heat in the affected areas of the film, so that the identification medium contained therein escape and - in contact with the substrate - diffuse into this or can react with it.

A particularly high temperature resistance of the label can be achieved if the barrier is formed by a barrier layer which is arranged flat between the carrier layer and an adhesive layer and which prevents the diffusion of the identification medium from the carrier layer in the unlabeled state of the film. By inscribing the film, the barrier layer is locally broken, so that the identification medium at these breakthrough sites escape locally from the carrier layer and diffuse into the adhesive layer. When the film with the adhesive layer is adhered to a substrate, selected regions of the substrate surface come into contact with the diffused identification medium and undergo a chemical or physical reaction. The areas of the barrier layer which remained intact in the inscription effectively prevent the diffusion of the identification medium and thus a reaction in these non-inscribed areas. Both the labeling process and the position of the barrier layer inside the security film provide effective protection of the film against counterfeiting and counterfeiting. Furthermore, an identification medium can be selected which is present in diffusible form in the unlabeled security film but is locally fixed in the course of the inscription ,

It is possible, on the one hand, for the carrier layer to represent a type of matrix in which the identification medium is embedded. Alternatively, the substance of the carrier layer itself may be the identification medium, so that the carrier layer consists of identification medium.

For rapid identification of the security film, it may be expedient if the inscription of the security film embossed on the carrier or barrier layer is not only visible on the substrate but also on the film itself. For this purpose, it is particularly advantageous to provide the film with a cover layer, the labeling is carried out together with the labeling of the identification medium in the same process step. For this purpose, the use of a multilayer laser-inscribable cover layer proves to be particularly favorable.

To protect the security film or the security labels produced therefrom and in the interests of convenient handling, these are expediently arranged on a release paper. As a result, transport, separation and labeling of the film or the labels can be significantly simplified.

To mark an object with a security label made from the security film, the unlabeled label is first glued to the object surface; then the non-contact label, through which the identification medium is released and the permanent marking of the object surface is triggered. This Beschriftungsabtauf has the advantage that the label takes place directly on the object to be protected, so a mis-marking of the object can be excluded by permutation of labels. On the other hand, undesired damage can occur, in particular on sensitive object surfaces, as a result of the selected labeling process-for example due to the heat development of the marking laser. In this case, the security label is expediently initially separate labeling, whereby the identification medium is released locally; then the so-labeled label is glued to the object.

The security film according to the invention is particularly suitable for marking motor vehicles that are highly vulnerable to theft. The marking allows at any time a clear identification of the vehicle. It is also advisable to mark expensive and particularly theft-endangered components and equipment of the vehicle separately in order to be able to prove their identity independently of the vehicle itself. To mark the vehicle body, an identification medium is expediently used, which is detectable with the vehicle paint - albeit u.U. reaction that is not visible to the naked eye.

• Fig. 1 Eine Schnittansicht eines aus Sicherheitsfolie hergestellten Sicherheitsetiketts mit Barriereschicht ...
  • Fig. 1a ... vor der Beschriftung,
  • Fig. 1b ... während der Beschriftung,
  • Fig. 1c ... nach Aufkleben auf ein Substrat,
• Figuren 1a bis 1c zeigen ein aus der erfindungsgemäßen Sicherheitsfolie 1 hergestelltes Sicher heitsetikett 2, das eine Trägerschicht 4 enthält, in der ein Identifikationsmedium 3 enthalten ist, das in der Trägerschicht 4 diffundieren kann. Die Trägerschicht 4 ist auf eine Deckschicht 5 aufgetragen, die die mechanische Stabilität des Etiketts 2 gewährleistet. Auf der Deckschicht 5 gegenüberliegende Oberfläche der Trägerschicht 4 befindet sich eine Barriereschicht 6, die ihrerseits an eine Klebeschicht 7 grenzt. Die Klebeschicht 7 des Etiketts 2 ist mit einem Trennpapier 8 versehen, das die Handhabung der Etiketten während des Transports, der Vereinzelung und der Beschriftung erleichtert und ein unerwünschtes Haften der Klebeschicht 7 während der Bearbeitungsschritte verhindert.

In the following the invention with reference to some embodiments illustrated in the drawings is explained in more detail; show:

• 1 is a sectional view of a safety label made of security film with barrier layer ...
  • Fig. 1a ... before the lettering,
  • Fig. 1b ... during the labeling,
  • Fig. 1c ... after sticking to a substrate,
• FIGS. 1 a to 1 c show a security label 2 produced from the security film 1 according to the invention, which contains a carrier layer 4 in which an identification medium 3 is contained, which can diffuse in the carrier layer 4. The carrier layer 4 is applied to a cover layer 5, which ensures the mechanical stability of the label 2. On the cover layer 5 opposite surface of the carrier layer 4 is a barrier layer 6, which in turn adjoins an adhesive layer 7. The adhesive layer 7 of the label 2 is provided with a release paper 8, which facilitates the handling of the labels during transport, singulation and labeling and prevents unwanted adhesion of the adhesive layer 7 during the processing steps.

In Figure 1a, an unlabeled label 2 is shown. In this state, the barrier layer 6 is a continuous, for the Identifiktionsmedium 3 impermeable layer. It spans a barrier area 9, which is at least as large as the labeling area 9 ', which is provided for the labeling of the label 2. Conveniently, the barrier layer 6 extends over the entire surface of the label 2 and thus ensures that before the lettering Nowhere on the label 2, a diffusion of the identification medium 3 from the carrier layer 4 in the adhesive layer 7 takes place.

In the present embodiment, the carrier layer 4 consists of a resin-modified acrylate adhesive. It contains as the identification medium 3 a migratory substance which serves as a carrier for a UV fluorescent dye. In the present exemplary embodiment, the carrier film is admixed with a UV pigment of 1 to 3% (for example C luminescent pigment for securing against forgery of documents or products such as Y ₂ O ₂ S: Eu) and additionally contains 3 to 6% dibutyl phthalate carrier. The barrier layer 6, which impedes the migration of the carrier molecules and luminescent pigments, is formed by a thin, transparent plastic film, for example a 12 to 25 μm thick polyacetate film. The adhesive layer 7 consists - as well as the carrier layer 4 - of an adhesive based on a resin-modified acrylate polymer. The cover layer 5 consists of a multilayer film, as described for example in the utility model DE 81 30 861. This cover layer 5 can be labeled with the aid of a laser 10, the upper lacquer layer 11 being removed, so that locally the underlying lacquer layer 12 comes to light.

The inscription of the label 2 (see FIG. 1b) is the process in which locally a diffusion of the identification medium 3 from the carrier layer 4 into the adhesive layer 7 is made possible. This is done by a targeted local weakening of the barrier layer 6. In the present embodiment, the laser radiation for this penetrates both the cover layer 5 and the support layer 4 and thus must have sufficient power after penetration of these two layers to break the barrier layer 6 locally or to weaknesses. If a barrier layer 6 made of polyacetate film is used, then this film is locally destroyed by the usual cutting process used to inscribe the cover film with the aid of a laser 10 and allows a migration of the identification medium 3 into the adhesive layer 7 at these holes 13. In order to ensure the local destruction of the barrier layer 6 during the labeling process reliably, the laser power used for labeling must be selected to be correspondingly high. Furthermore, the barrier layer 6 must have a sufficiently high absorption capacity for the radiation.

Alternatively, or in addition to the above-described inscription of the barrier layer 6, which takes place through cover layer 5 and support layer 4, the barrier text 6 can also take place from the direction of the adhesive layer 7. In this case, release paper 8 and adhesive layer 7 must be sufficiently transparent to the laser radiation.

The lettering train may e.g. consist of letters, numbers or an alphanumeric string. Furthermore, the inscription strip can also have a bar code, a graphic symbol, a company logo and / or a mixture of several of these character classes.

After the laser has been inscribed, the security label 2 can now be glued onto a substrate 14 (see FIG. 1c). For this purpose, it is removed from the release paper 8 and pressed with the now released bottom 15 of the adhesive layer 7 on the substrate 14. The identification medium 3 diffused through the holes 13 of the barrier layer 6 and through the adhesive layer 7 now comes into contact with the substrate surface 16. The (UV) luminescent pigment contained in the identification medium 3 causes a local (UV) coloring of the substrate surface 16 and thus an image 17 of the labeling pattern, the example can be detected by means of a UV lamp.

In order for the identification medium on the substrate surface 16 to leave detectable traces, the material properties of the identification medium 3 must be matched to those of the substrate 14. If a visible dye whose color matches the color of the substrate surface 16 is selected as the identification medium 3, the deciphering of the label can be carried out with the naked eye. Has the identification medium 3 z. For example, as a corrosive effect on the substrate, the inscription results in a local change in the reflective properties of the substrate surface 16, which may be e.g. can be detected with optical methods (in particular with grazing incidence of light). Furthermore, an identification medium 3 may be selected which leaves no visible traces on the substrate 14, but whose presence on the substrate surface 16 can be detected chemically by wetting the substrate surface 16 with a suitably chosen substance which exhibits a detectable by physical means chemical reaction with the identification medium is received (eg an envelope of the pH, which manifests itself in a color change of the wetting substance). Furthermore, the identification medium 3 may contain a magnetic marker; the local magnetization of the substrate 14 produced by the label can then be deciphered by applying a magnetically active analyte.

The security label 2 produced from the security film 1 according to the invention is suitable in the automotive industry, in particular for marking bodies. By using the security label 2, for example, on the outer skin, frame and / or chassis a clear vehicle identification is possible. For this purpose, the identification medium 3 is suitably chosen so that it leaves detectable traces on the vehicle paint. Furthermore, vehicle components and facilities can also be marked. This is recommended in particular for components that are particularly vulnerable to theft (car radio, car phone) or particularly susceptible to forgery (expensive equipment, expensive safety-relevant parts).

The properties of the identification medium 3 and the adhesive layer 7 determine how fast the diffusion of the identification medium 3 through the adhesive layer 7 on the substrate 14 takes place and thus determine a relaxation time, after the expiration of a detectable marking of the substrate 14 has taken place. This relaxation time is strongly temperature-dependent. For the reaction of the above-described film on an automotive finish, this relaxation time at room temperature is about 2 hours. If the label 2 remains substantially shorter than the relaxation time on the substrate 14, it can be removed without a detectable marking of the substrate surface 16 having occurred. Thus, within the relaxation time, it is possible to replace a wrongly affixed label with a proper label.

The more permeable the adhesive layer 7 for the diffusing identification medium 3, the stronger the lateral diffusion of the identification medium 3 in the adhesive layer 7 itself. This has the consequence that the identification medium 3 also reaches the substrate surface 16 in areas, albeit to a lesser extent which are opposite to the unruptured regions 18 of the barrier layer 6 and thus should remain unaffected by the identification medium 3. This effect leads to a certain fraying of the contour of the inscription pattern 17 on the substrate 14. In order to achieve a high-contrast inscription of the substrate 14, it is advisable to choose the adhesive layer 7 as thin as possible in order to minimize this sideward diffusion of the identification medium 3. The thinner the adhesive layer 7, the shorter the diffusion time of the identification medium 3 through the adhesive layer 7.

Alternatively, the laser inscription of the security label 2 can also be effected only after the label 2 has been glued to the substrate 14. In this case, the laser power set for labeling must on the one hand be selected to be so high that the local destruction of the barrier layer 6 is assured in a process-reliable manner; On the other hand, laser marking must not damage the substrate. A label of the already glued label 2 thus requires a good control of the laser power and is only applicable to selected substrates 14.

Of course, the above-described inscription of the cover layer 5 can also take place in a separate process step, independently of the local destruction of the barrier layer 6, when the two inscription processes are triggered by radiation in different electromagnetic spectral ranges. In particular, it is also possible to completely dispense with a labeling of the cover layer 5.

In addition to the previously described security labels 2, which are produced from the security film 1 according to the invention, the security film 1 can continue to be e.g. in the form of adhesive tape, cover, decorative and protective film, etc. are used.

Claims (13)

1. Security film (1),

   - which can be adhered to a substrate (14),

   - and comprises a base layer (4) containing the identification medium (3), which is specifically adapted to the material properties of the substrate (14) and generates a perceptible reaction in the substrate (14),

   - in which migration of the identification medium (3) from the security film (1) to the substrate (14) can be selectively and locally altered by a contactless printing process,

   characterised in that

   - the security film (1) has a barrier layer (6), which is disposed between the base layer (4) and the substrate (14) and prevents the identification medium (3) from migrating from the security film (1) to the substrate (14) in the non-printed state,

   - and the local variation in migration occurs due to a local weakening of the barrier layer (6).
2. Security film as claimed in claim 1,
   characterised in that
   the barrier layer (6) is locally weakened by the local action of electromagnetic radiation.
3. Security film as claimed in claim 2,
   characterised in that
   the barrier layer (6) is locally weakened by the local action of heat.
4. Security film as claimed in claim 2 or 3,
   characterised in that
   the barrier layer (6) is locally weakened by a local effect of a laser beam (10).
5. Security film as claimed in claim 1,
   characterised in that
   the identification medium (3) is a UV fluorescent marker substance and/or an infrared marker substance and/or a magnetic marker substance and/or a dye and/or contains a substance which causes a chemical reaction in the substrate (14).
6. Security film as claimed in claim 5,
   characterised in that
   the identification medium (3) contains a substance which etches the surface of the substrate (14).
7. Security film as claimed in claim 1,
   characterised in that
   the base layer (4) consists of the identification medium (3).
8. Security film as claimed in claim 1,
   characterised in that
   the security film (1) is provided with a laser-printable top layer (5).
9. Security film as claimed in claim 1,
   characterised in that
   the security film (1) is disposed on a peel-off paper (8).
10. Method of printing a security film which can be adhered to a substrate, as claimed in one of claims 1 to 9,
    characterised in that

    - the security film (1) is adhered to the substrate (14),

    - and the security film (1) is then printed by means of a contactless process, which causes a local weakening of the barrier layer (6) and hence a selective migration of the identification medium (3) from the security film (1) to the substrate (14).
11. Method of printing a security film which can be adhered to a substrate, as claimed in one of claims 1 to 9,
    characterised in that

    - the security film (1) is printed by means of a contactless process, which locally weakens the barrier layer (6) so that the diffusion properties of the identification medium (3) in the security film (1) are locally altered,

    - and the security film (1) is then adhered to a substrate (14).
12. Use of a security film as claimed in one of claims 1 to 9,
    characterised in that
    the security film (1) is used to mark motor vehicles and/or parts thereof and/or accessories thereof.
13. Use of a security film as claimed in one of claims 1 to 9,
    characterised in that
    the substrate (14) is a vehicle paint.