DE4242407C2 - Embossing foil, esp. Hot stamping foil, preferably for the production of value documents - Google Patents

Description

The invention relates to a stamping foil, in particular Hot stamping foil, preferably for producing a Value document, z. B. banknote, credit card, ID card or Ticket, which at least on one of its surfaces Security element carries, wherein the stamping foil from a Carrier film and one of this detachable transfer layer exists, which - starting from the carrier film - at least one diffractively effective, transparent, on her the carrier film Abgewandten surface a diffraction optical effective, spatial Structure-containing lacquer layer as a security layer, a arranged on the spatial structure of the security layer, reflective metal layer, one of a dispersion magnetizable particles in a binder  Magnetic layer, one serving for fixing to a substrate, optionally formed by the magnetic layer or with this combined adhesive layer and between metal layer and Magnetic layer has a further paint layer.

Value documents of the type described above are for example, known from US-PS 4,684,795. There is also already basically the production of such value documents described by stamping foils. A detailed explanation suitable stamping foils with a magnetic layer and a diffractive optical safety layer are the DE 34 22 910 C1.

So far, in the production of such hot stamping foils in In general, the procedure is such that the clarification of the optical diffractive structure serving on the appropriately patterned surface of the security layer applied, reflective metal layer of in vacuum vapor-deposited aluminum or aluminum alloys is formed. The use of aluminum for the reflective However, metal coating may cause significant problems with you, especially if the corresponding one Value document to be used in a humid atmosphere. In this case, it has been shown in part that the Aluminum layer is destroyed at least point by point or itself at least changed in appearance, discolored, for example. This allows the function of the Security elements are compromised. This is going on all noticeable when it is at the diffractive optical effective structure of the security layer around one machine-readable structure, such as a hologram or a computer generated diffraction structure.  

Investigations have shown that the destruction or Damage to the aluminum layer probably on it attributed to the fact that the magnetizable particles of the Magnetic layer, which is usually iron oxides different oxidation states, with the aluminum the reflective metal layer causing corrosion of aluminum react. The exact mechanism for this Reaction is unknown. Presumably, the damage is on it attributed to the fact that the iron oxide pigments used as magnetizable particles are used as Proton donors act, with the circumstance also a role plays that the used iron oxide pigments in pH values range between 3.0 and 5.5. Here you can then, under certain circumstances, between the magnetizable particles on the one hand and serving as a reflective metal layer Aluminum on the other hand local elements with corresponding Destruction of the aluminum layer form.

In the stamping film according to DE 34 22 910 C1 is between the reflective metal layer and the magnetic layer one Adhesive layer of a thickness of about 0.3 to 0.7 microns provided, consisting of a high molecular weight PMMA resin and of Consists of pigments formed matting agent. These However, primer layer may have an effect of Magnetic particles on the reflective metal layer not with prevent the necessary safety, especially because of the layer thickness usually at the lower limit the aforementioned adhesion promoter layer.

From DE 34 22 911 C1 an embossing film is known in the between the magnetic layer and a marking layer one Solving the Signierschicht by in the magnetic layer contained solvent-preventing barrier provided is. In addition, in this document is a stamping foil  explained, in which a reflective, with a diffractive optically effective structure provided metal layer connects directly to the magnetic layer. It is thus in This document the problem of a disturbing influence of Magnetic layer, in particular the magnetic particles, on a Metal layer nowhere treated.

The invention is therefore based on the object stamping foils, in particular hot stamping foils, of the type mentioned in the beginning to develop the problems observed so far Destruction or change of the reflective metal layer due to appropriate action of the magnetizable particles Reliably switched off on the reflective metal layer be, d. H. a stamping foil, in particular hot stamping foil, to propose their original features as far as possible with regard to the reflective metal layer unchanged.

To solve this problem is according to the invention in a Embossing foil of the type mentioned suggested that between the metal layer and the magnetic layer one Influence of the magnetizable particles on the metal layer preventing, having a pH of 7 barrier layer arranged by a layer of organic polymers is formed, which inorganic, adsorbing protons Pigments are mixed, wherein the barrier layer has a thickness from 0.5 to 5 microns.

According to the invention thus the influence of the magnetizable Particles of the magnetic layer on the reflective metal layer characterized in that between the metal layer and the Magnetic layer the additional, specially constructed Barrier layer is provided by organic polymers is formed and a lying in the alkaline range pH  Has value, and the inorganic pigments are admixed, adsorb the protons.

As polymers for the barrier layer z. B. high molecular weight Acrylic resins, polyvinylidene chloride copolymers, PVC, PVC Copolymers, chlorinated rubber, polyester and silicone-modified Binders are used. Come as inorganic pigments For example, silicates and / or titanium dioxide into consideration. A such compound barrier layer of sufficient thickness forms a reliable buffer or a reliable one Adsorber medium in any case to protons, so that their Walk through the barrier layer and a corresponding Damage to the metal layer can be safely prevented. The after The invention provided thickness of the barrier layer from 0.5 to 5 microns, preferably from 2 to 3 microns is sufficient on the one hand for a reliable protection of the reflective metal layer to the magnetizable particles of the magnetic layer. On the other hand, with such a small thickness, the Barrier layer not to be expected that the readability of the data stored in the magnetic layer somehow is impaired.

Suitably, the metal layer is on the diffractive optical effective structure of the safety layer applied in a vacuum, preferably evaporated.

As additional security, it is possible according to the invention additional to the arrangement of the special barrier layer the Metal layer of chrome, copper or gold or alloys to form at least two of these metals, whereby the Stability is further improved.

Finally, it is within the scope of the invention that between the Metal layer and the magnetic layer or barrier layer  then directly to the metal layer Adhesive layer is provided for a reliable Bonding of the metal layer with the magnetic layer or the Barrier layer provides. It is possible the barrier layer like that to select, assemble and dimension that they can serve simultaneously as a primer layer, here However, due to the relatively strong pigmentation of Barrier layer may cause problems.

In a manner similar to DE 34 22 911 C1 describes the DE 31 38 559 C2 barrier layers, which prevent the penetration of plasticizing and other chemical, the stability and lifespan degrading substances in the interior of a multi-layered Identity card to prevent. Any indication of that Possibility to use such barrier layers to the Influence of the magnetic particles of a magnetic layer on one Turn off reflective metal layer is not here seen.

In US 4,376,006 is a magnetic recording material described in which a magnetic layer by means of a layer made of non-magnetic material to be covered on this way to make the magnetic layer invisible or that Appearance of the recording material to improve. Also in This document will nowhere on the possibility pointed out that the magnetic layer to corrosion could cause reflective metal layer. That this problem was not recognized in the prior art, results without further from this, that all possible reflective Metal layers are called equivalent, especially aluminum simultaneously with tin, gold and Silver as a possible material for the reflective Metal layer is called. At a certain Embodiment of the magnetic recording material  even between the magnetic layer and the reflective one Metal layer, a bonding agent layer of a synthetic resin in a thickness of about 0.5 microns provided. This layer has However, only the task, the liability of the reflective Metal layer on the magnetic layer to improve. It would be but neither because of their composition nor in particular considering the very small thickness suitable, as Barrier layer to serve and damage the reflective metal layer through the metal particles of the Magnetic layer to prevent.

Finally, in "Römpp, Chemielexikon 1990" under the Keyword "anticorrosive" protective coatings on Acrylic resin or chlorine-based rubber described. These However, known protective layers are of a kind that, to to achieve a sufficient corrosion protection, layer thicknesses required, which are not used for value documents can be. Only through the special composition of Barrier layer according to the invention, it is possible with to get along with correspondingly small layer thicknesses, so that in particular, the required magnetic properties be achieved.

Further features, details and advantages of the invention will be apparent from the following description of Embodiments of one with a security feature provided credit card and one in the production of a such card or document of value Embossing foil according to the invention.

In the drawing show

Fig. 1 is a plan view of a credit card with a security feature;

Fig. 2 shows a section along line II-II through the card of Fig. 1 and

Fig. 3 is a sectional, schematic section through a hot stamping foil according to the invention.

The credit card shown in Fig. 1 is a conventional plastic card 1 , which carries on its front side, for example in embossed letters the name 2 of the cardholder and a code number 3 . The plastic card 1 is also provided on its front side with a security feature which on the one hand comprises a running over the entire width of the card magnetic stripe 4 and on the other hand, an optical security feature 5 , which, as shown in FIGS. 1 and 2 can clearly recognize, partially overlaps the magnetic strip 4 , but partially (in Fig. 1, top, in Fig. 2, left) projects beyond the magnetic strip.

The optical security feature 5 is designed, for example, according to the security feature described in US Pat. No. 4,684,795. It consists of a transparent optically effective security layer 6 , which is provided at least in regions (in the inner region of FIG. 1) on its underside with a structurally effective structure 7 . At least in the area of the structure 7 which is effective in terms of diffraction optics, the diffraction-optically effective security layer 6 is provided with a metal layer 8 , which is applied, for example, to the diffraction-optically active structure 7 of the security layer 6 by vapor deposition in a vacuum. In that regard, the value document of Figures 1 and 2 is substantially identical to that described in U.S. Patent 4,684,795.

In contrast to the known value document, however, a barrier layer 9 is now provided in the document according to FIGS. 1 and 2 between the magnetic layer 4 and the metal layer 8 , for example having a thickness of between 0.5 and 5 μm, preferably between 2 and 3 μm can. The barrier layer 9 has the purpose of preventing the action of the magnetic pigments present in the magnetic layer 4 , which are usually iron oxides, on the metal layer 8 . With regard to the possible composition of this barrier layer and the other layers of the value document according to FIGS. 1 and 2, reference is made to the following, more detailed explanation of the stamping foil according to FIG. 3.

Instead of attaching a barrier layer 9 , it is also possible to produce the metal layer 8 from a metal which does not react with the magnetizable particles of the magnetic layer 4 , namely chromium, copper, silver or gold or an alloy of at least two of these metals.

In the document of value according to FIGS. 1 and 2, all the layers, namely the magnetic layer 4 , the barrier layer 9 , the metal layer 8 and the protective layer 6 are applied in one operation with the aid of the embossing foil according to FIG . Theoretically, however, it is also possible to use two separate embossing foils, one of which essentially comprises only the magnetic layer, while the other comprises the barrier layer, the metal layer and the protective layer. So you would have z. B. proceed when producing the credit card of FIG. 1 by means of stamping foils.

In Fig. 3, the stamping foil is shown in a schematic section, which is suitable for mounting the entire security feature, ie both for applying the magnetic layer 4 and the security layer 6 with the reflective metal layer 8 in one step.

The stamping foil of FIG. 3 comprises a carrier film 10 in a manner known per se. At this is, for example, via a not shown in the drawing, preferably consisting of wax release layer, arranged a total of 11 transfer layer. The transfer layer 11 comprises, starting from the carrier film 10 , a transparent topcoat layer 6 , which serves as a diffractive optical security layer. This topcoat layer or security layer 6 is at least partially spatially structured at its surface facing away from the carrier film 10 so that it can develop diffraction-optical effects. For example, the security layer 6 is provided with a structure 7 in the form of a hologram or a computer-generated diffraction structure, an interference layer or a diffraction grating. The structure 7 is generally embossed into the security lacquer layer 6 applied to the carrier film 10 , the lacquer forming the layer 6 here being either a thermoplastic lacquer or a crosslinking lacquer which, at the time of embossing of the structure 7, has not yet completely hardened can.

On the structure 7 carrying the surface of the layer 6 , a metal layer 8 is then applied in a vacuum, for. B. vapor-deposited. To ensure that the further layers reliably adhere to this metal layer 8 , which reflects, an adhesion promoter layer 12 is applied before the further layer is applied. Adjacent to this adhesion promoter layer 12 are then the barrier layer 9 , the magnetic layer 4 and an adhesive layer 13 serving for fixing the transfer layer 11 on a substrate, although this adhesive layer 13 may also be omitted if the magnetic layer 4 has corresponding properties.

For the rest, it should be noted that the respective layer thicknesses are not shown to scale in FIG . The security layer 6 normally has a thickness of about 0.3 to 1.2 μm. The metal layer 8 of chromium, copper, silver or gold or corresponding alloys is vapor-deposited in a conventional manner in a vacuum and has a thickness of 0.01 to 0.04 microns. The primer layer 12 is usually applied in a thickness of 0.2 to 0.7 microns. The barrier layer 9 has, as already mentioned, a thickness of 0.5 to 5 microns. The magnetic layer usually has a thickness of 4 to 12 μm, preferably about 9 μm. The adhesive layer corresponds in thickness approximately to the thickness of the security layer 6 .

The application of the various layers takes place with the methods known from the stamping foil production, as described, for example, in DE 34 22 910 C1. It is used as a carrier film z. B. a polyester film of a thickness of 19 to 23 microns used, then the various layers are applied by gravure rollers. Each time after application of the individual layers, the possibly required drying takes place. The spatial structure 7 of the security layer 6 is produced either by means of a rotating embossing cylinder or by stroke embossing.

The various layers of the stamping foil of FIG. 3 may be composed as follows:

Protective lacquer or security layer 6 component Parts by weight high molecular weight PMMA resin 2,000 Silicon alkyd oil-free 300 nonionic wetting agent 50 methyl ethyl ketone 750 low viscosity nitrocellulose 12,000 toluene 2,000 diacetone 2 500

Metal layer 8

Vacuum deposited layer of chromium, copper, silver or gold or alloys thereof.

Adhesive layer 12 component Parts by weight high molecular weight PMMA resin 1200 methyl ethyl ketone 3400 toluene 1000 matting agent 100

Barrier layer 9 component Parts by weight methyl ethyl ketone 30 toluene 35 ethyl alcohol 15 Vinyl chloride-vinyl acetate copolymer (FP: <65 ° C) 11 Unsaturated polyester resin (mp: 100 ° C, d = 1.24 g / cm³) 3 Silicone polyester resin (D = 1.18 g / cm3) 2 Hydrophobic silica (pH 7 of a 5% slurry in H₂O) 4

Magnetic layer 4

This consists of a dispersion acicular γ-Fe₂O₃ magnetic pigments in a polyurethane binder, various paint assistants and a solvent mixture from methyl ethyl ketone and tetrahydrofuran.

However, the magnetic layer does not necessarily have this composition. Instead of Fe₂O₃ pigments z. B. other magnetic pigments, such as Co-doped magnetic iron oxides or other finely dispersed magnetic materials (Sr, Ba-ferrites) can be used. If necessary, the binder combination of the magnetic layer can also be chosen such that it is possible to dispense with the adhesion promoter layer 12 , because directly a good adhesion results directly on the metal 8 , which may be significant if the barrier layer is omitted.

Adhesive layer 13

In the adhesive layer 13 may be z. B. act a known hot melt adhesive layer. The attachment of this layer is not always necessary. This depends on the composition of the substrate on which the embossing film is to be embossed. For example, if the substrate is made of PVC, as is usually the case with credit cards, a special hot-melt adhesive layer can usually be dispensed with.

For applying the embossing foil according to FIG. 3, this is placed with the transfer layer 11 first on the plastic card 1 or another, according to document to be backed up, and then pressed under the action of heat against this document. In this case, on the one hand via the adhesive layer 13 and the corresponding tacky magnetic layer 4, the transfer layer 11 connects to the corresponding surface of the document to be secured. On the other hand, as a result of the action of heat, the transfer layer 11 is detached from the carrier film 10 . This release is particularly facilitated if an additional waxy release layer is present between the transfer layer 11 and the carrier film 10 .

Claims (5)

1. stamping foil, in particular hot stamping foil, preferably for producing a value document, for. As banknote, credit card, ID card or ticket, which carries a security element at least on one of its surfaces, wherein the embossing film consists of a carrier film and a detachable from this transfer layer, which - starting from the carrier film - at least one diffractive optical effective, transparent, at their the Carrier film averted surface a diffractive optical effective, spatial structure having resist layer as a security layer, arranged on the spatial structure of the security layer, reflective metal layer, consisting of a dispersion of magnetizable particles in a binder magnetic layer, serving for fixing to a substrate, possibly from the Magnetic layer formed or combined with this adhesive layer and between the metal layer and magnetic layer has a further resist layer, characterized in that between the metal layer ( 8 ) and the magnetic layer ( 4 ) has an effect of the magnetis is arranged on the metal layer preventing barrier layer ( 9 ) having a pH of 7, which is formed by a layer of organic polymers, which are mixed with inorganic, proton adsorbing pigments, wherein the barrier layer ( 9 ) has a thickness of 0 , 5 to 5 microns. 2. embossing foil according to claim 1, characterized in that the barrier layer ( 9 ) has a thickness of 2 to 3 microns. 3. embossing foil according to one of claims 1 or 2, characterized in that the metal layer ( 8 ) applied to the diffraction-optically effective structure ( 7 ) of the security layer ( 6 ) in a vacuum, preferably vapor-deposited. 4. stamping foil according to one of claims 1 to 3, characterized in that the metal layer ( 8 ) of chromium, copper, silver or gold or alloys of at least two of these metals is formed. 5. embossing foil according to one of claims 1 to 4, characterized in that between the metal layer ( 8 ) and the magnetic layer ( 4 ) or the barrier layer ( 9 ) directly to the metal layer ( 8 ) then an adhesive layer ( 12 ) is provided.