EP2123471B1 - Safety element and method for its production - Google Patents

Description

The invention relates to a method for producing a multilayer security element which has at least one effect layer which requires a special substrate.

Valuables such as branded goods or documents of value are often provided with security elements for the purpose of security, which allow verification of the authenticity of the object of value and at the same time serve as protection against unauthorized reproduction.

In many cases, optically variable elements are used as security elements, which give the viewer a different image impression, for example a different color impression, at different viewing angles. In many cases holograms, holographic grating images and other hologram-like diffraction structures are used for authenticity assurance, which offer the viewer a viewing angle-dependent diffraction pattern.

Security elements with hologram-like diffraction structures are transferred, inter alia, in the transfer process to the target substrate, for example a banknote. The detachment of the security element from the carrier film takes place either via so-called release layers, which are usually thermally activated, or by the low adhesion of the security element on the carrier film. In addition, to enable a bond to the paper, the security element is coated with a suitable adhesive system. Other security features, such as luster pigments or other optically variable effect colors, are usually printed directly onto a paper substrate. The brilliance and the visual impression of the respective security element depend strongly on the ground.

The publication WO 2004/032099 A1 discloses a liquid crystal label that can be used as an anti-counterfeit label. The liquid crystal label comprises a base material having transparency or semitransparency, a liquid crystal layer formed on the lower surface of the base material, a background layer formed on the side of the liquid crystal layer facing the base material, and an adhesive layer formed on one side of the background layer is formed, which is opposite to the liquid crystal layer. In this case, the adhesion between the base material and the liquid crystal layer is lower than the adhesion between the liquid crystal layer and the background layer, so that liquid crystal label is destroyed in peeling tests.

The publication US 2003/189684 A1 relates to an anisotropic polymer film with improved alignment on a substrate having a structured surface. The publication GB 2 357 061 A discloses a hot stamping foil having at least one liquid crystal layer.

The publication EP 1347 313 A1 apparently a liquid crystal transfer sheet having a substrate and a liquid crystal layer formed on a surface of the substrate, the liquid crystal layer having an adhesion surface disposed on a side opposite to the substrate and provided to adhere to a target article, and a release surface disposed on one side of the substrate and provided to be separated from the substrate. At this time, the surface hardness of the liquid crystal layer is lower at the adhesion surface side than at the release surface side.

Proceeding from this, the object of the invention is to provide a method which avoids the disadvantages of the prior art.

This object is solved by the features of the independent claims. Further developments of the invention are the subject of the dependent claims.

With multilayer security elements, a desired layer sequence is often not possible since certain security features are preferably produced on smooth, non-porous substrates or, in some cases, even have to be produced on such substrates.

For this, the effect layer of a first layer composite requiring a special substrate can be prepared on a separate plastic carrier film and subsequently transferred to a second layer composite, wherein the second layer composite likewise comprises a plastic carrier film. The plastic carrier film of the first layer composite is hereby specially adapted to the needs of the effect layer.

For example, due to their internal structure, certain plastic films have the property of aligning liquid crystal material. Thus, liquid-crystalline materials can be aligned in a simple manner and then transferred to any other layer sequence, which in itself has no corresponding properties.

However, even if the liquid crystalline material is aligned by means of alignment layers, the invention offers the advantage that the alignment layer does not have to be provided in the layer composite of the security element. Because the orientation of the liquid-crystalline material takes place on a separate carrier film and then only the liquid-crystalline material is transferred to the layer structure of the security element.

However, there are other examples of effect layers that require a special substrate. Deposited, optically variable layers, such as e.g. Diffraction structures, interference layer pigments, liquid crystal pigments or metallic effect pigments, for example, require a very smooth substrate in order to achieve a brilliant color impression or a reflecting surface. If the background layer in the desired layer sequence of the security element is not sufficiently smooth, as e.g. in the case of magnetic layers, such layers can be prepared on an optimally prepared substrate of a plastic carrier film and then inserted at the desired location in the layer structure of the security element, e.g. on a rough magnetic layer. For the transfer preferably an adhesive layer is used, which also compensates for the rough ground.

Of course, the security element can be provided with further functional layers, such as electrically conductive, luminescent, magnetic layers, or any imprints. Other layers produced by the process according to the invention can also be incorporated.

The invention includes a method for producing a first composite layer, according to claim 1.

The effect layer advantageously forms an optically effective effect layer or a mirror-effect effect layer. In particular, a lacquer layer of oriented liquid-crystalline material or a layer with optically variable or metallic pigments, which are preferably printed, is suitable as the effect layer.

In addition, the effect layer is applied in particular in the form of patterns, characters or codes.

The invention will be described in more detail below, in particular with reference to liquid-crystalline effect layers representative of any other effect layers. Such liquid crystalline effect layers show, as explained in detail below, certain polarization or color effects.

The liquid-crystalline material is preferably applied directly to the plastic carrier film without further alignment layers, preferably printed.

The use of a transfer assist layer according to the invention also makes it possible to transfer security elements made of liquid-crystalline material that are not present over the entire surface, for example printed as a motif, onto a target substrate. If desired or necessary, the carrier film for the liquid-crystalline layer and the transfer assist layer may be at or after the application of the transfer material to the target substrate are removed. The damage-free removability of the carrier film is ensured by the greater adhesion of the transfer assist layer to the liquid-crystalline layer.

In addition, by repeatedly transferring individual layers or layer composites into one another, very complex layer structures can be created, whereby optimum production conditions can be selected for the individual layers or layer composites as a result of the separate production. Thus, according to the invention, it is also possible to combine layered composites which require mutually exclusive production conditions or interfering carrier foils, since the carrier foils can be removed during or after the joining of the partial layer composites.

In an advantageous development of the invention, further layers of liquid-crystalline material may be applied partially, in particular in the form of patterns, characters or codes, between the liquid-crystalline layer and the transfer assist layer. These may advantageously overlap at least partially with the first applied liquid-crystalline layer.

The liquid-crystalline layers are advantageously applied as a lacquer layer of smectic, nematic or cholesteric liquid-crystalline material, preferably printed. Gravure printing, screen printing, flexographic printing, knife or curtain coating are particularly suitable as printing techniques for the liquid-crystalline layers and / or the transfer assist layer.

As a transfer assist layer preferably a UV-curing lacquer layer is applied, in particular printed. The UV-curable lacquer layer expediently contains photoinitiators. In each case, a balance must be sought between sufficiently high adhesion of the transfer assist layer to the liquid-crystalline layer to be detached and sufficiently low adhesion to the support film.

In a further preferred embodiment, a layer of cholesteric liquid-crystalline material is applied, in particular printed, as the transfer assist layer. An embossing lacquer layer can also be advantageously used as a transfer auxiliary layer. In this case, the embossing lacquer layer is expediently printed on and subsequently embossed, provided with a reflective layer, in particular metallized and optionally demetallised in regions, for example, to introduce a negative writing into the metallized embossed structure. The embossed structure advantageously forms an optically effective microstructure, in particular a diffractive diffraction structure, a matt structure, an arrangement of microlenses or an arrangement of micromirrors.

In order to achieve better adhesion of subsequently applied layers, for example a subsequently applied embossing lacquer layer, the transfer assist layer can advantageously be subjected to a corona treatment or be provided with an adhesion promoter.

Before applying the adhesive layer in step d), one or more further layers can be applied to the transfer assist layer, in particular printed on, in order to produce more complex layer structures. Another layer can be printed on the transfer assist layer, for example with a printing ink, preferably a magnetic ink. Also one Embossing lacquer layer can be applied as a further layer, in particular imprinted. After embossing, the embossing lacquer layer is advantageously embossed, metallized and optionally demetallised in some areas. Likewise, a reflective layer can be applied as a further layer.

In all variants with a reflective layer, this can also be formed by a reflective thin-film element. Such a thin-film element is preferably formed with a reflection layer, an absorber layer and a dielectric spacer layer arranged between the reflection layer and the absorber layer.

The layered composites already described are combined with one or more further layer composites, for example via laminating lacquer layers. In this way, diverse and complex safety layer structures can be realized. In particular, a second layer composite present on a second carrier film can be provided, which is joined to the layer composite of carrier film, effect layer and transfer assist layer via a second adhesive layer before the adhesive layer is applied in step d).

In a first variant, the second layer composite is produced by applying an embossing lacquer layer to the second carrier foil, embossing, metallizing and optionally demarcating the embossing lacquer layer by area.

According to another variant, the second layer composite is produced by applying to the second carrier film a rastered metal layer with recesses or a semitransparent metal layer and that on the metal layer, a magnetic layer, in particular in the form of patterns, characters or codes is produced.

The second layer composite may also comprise a reflective layer. In all variants, the reflective layer may advantageously be formed by a metal layer or, in the case of more complex structures, by a reflective thin-film element having a viewing angle-dependent color impression. In the latter case, the thin-film element is preferably formed with a reflection layer, an absorber layer and a dielectric spacer layer arranged between the reflection layer and the absorber layer. The reflection layer of the thin-film element is preferably formed from an opaque or semitransparent metal layer.

The thin-film element can also be formed with at least one absorber layer and at least one dielectric spacer layer, the absorber layers and the dielectric spacer layers being arranged alternately one above the other. According to a further embodiment possibility, the thin-film element is formed with a plurality of dielectric spacer layers, wherein adjoining layers having greatly different refractive indices are formed.

According to a further variant, the second layer composite comprises an optically active microstructure which is preferably formed as a diffractive diffraction structure, as a matt structure, as an arrangement of microlenses or as an arrangement of micromirrors.

The carrier film used in the process according to the invention is preferably provided as a smooth film with good surface quality. Especially For example, a film designed specifically for aligning liquid crystals may be provided. For example, it is advantageous to use a plastic film as a carrier film. Examples of plastic carrier films are films made of PET, OPP, BOPP, PE or cellulose acetate. The carrier film may also itself comprise a plurality of sub-layers, for example, the carrier film may be provided with an alignment layer for the alignment of liquid crystals. In particular, a layer of a linear photopolymer, a finely structured layer, ie a layer with orientation-promoting surface topography, or a layer oriented by the application of shear forces are suitable as the aligrum layer. A suitable finely structured layer can be produced for example by embossing, etching or scoring.

The invention also includes a transfer material for transferring to a target substrate according to claim 13, which is in particular producible according to one of the production methods described above.

The effect layer is partially applied to the carrier film. In an advantageous embodiment, the effect layer is formed by a first layer of a liquid-crystalline, in particular of a nematic liquid-crystalline material.

The transfer assist layer preferably consists of a UV-curing lacquer layer, of a cholesteric liquid-crystalline material or of an embossing lacquer layer provided with an embossing.

In an advantageous development of the invention, at least one further layer of liquid-crystalline material is present between the partially present effect layer and the transfer assist layer present over the entire area. The at least one further liquid-crystalline layer is preferably formed from cholesteric liquid-crystalline material.

Furthermore, the effect layer and the transfer assist layer are present on a plastic carrier film, the adhesion of the transfer assist layer present over the entire area to the carrier film being lower than to the partially present effect layer. The effect layer and the transfer assist layer can also be present on a plastic carrier film which has a release layer, in particular a thermally activatable release layer.

The invention also includes a security element for securing valuables, which can be produced in particular by one of the methods described above or with a transfer material of the type described.

In addition, the invention also encompasses a method for transferring a transfer element to a target substrate, wherein a transfer material of the type described with the adhesive layer is placed on the target substrate and bonded to the target substrate by heat and / or pressure. When using radiation-curing adhesives, the transfer material is advantageously connected by pressure and radiation with the target substrate. The plastic carrier film of the possibly partially present effect layer is expediently removed during or shortly after application to the target substrate.

The method according to the invention can be used to produce any desired security elements, in particular a security thread, a transferable security strip or a patch. The finished security element is embedded, for example, in a security paper or valuable item, in particular value document, or applied to its surface. The security element preferably contains a carrier substrate made of paper or plastic.

In a method for producing a valuable article, such as a security paper or a document of value, a transfer material of the type described is applied to an object to be protected, in particular glued by heat and / or pressure and / or radiation. In this case, the surface of the security paper or valuables can be specially treated to improve the adhesion of the security element on the surface and its optical efficiency. For this purpose, in particular a bonding agent can be used, which is applied to the surface of the security paper.

Valuables within the meaning of the present invention are in particular banknotes, stocks, bonds, certificates, vouchers, checks, high-quality admission tickets, but also other counterfeit-endangered papers, such as passports and other identification documents, as well as product security elements, such as labels, seals, packaging and the like. The term "object of value" in the following includes all such objects, documents and product protection means. The term "security paper" is understood to mean the precursor that can not yet be processed to a value document, which besides the security element can have further authenticity features, such as, for example, luminescent substances provided in the volume. security paper is usually in quasi endless form and will be further processed at a later date.

Fig. 1

eine schematische Darstellung einer Banknote mit einem eingebetteten Sicherheitsfaden und einem aufgeklebten Sicherheitsstreifen, jeweils nach einem Ausführungsbeispiel der Erfindung,

Fig. 2

eine Aufsicht auf einen Teilbereich des Sicherheitsstreifens der Fig.1, wie er bei Betrachtung ohne Hilfsmittel bzw. bei Betrachtung durch einen Polarisator erscheint,

Fig. 3

in Querschnittsdarstellung einen Zwischenschritt bei der Herstellung eines erfindungsgemäßen Transfermaterials,

Fig. 4 bis 6

Darstellungen wie in Fig. 3 von Transfermaterialien nach weiteren Ausführungsbeispielen der Erfindung,

Fig. 7

die Herstellung eines mehrschichtigen Sicherheitselements wobei (a) und (b) einen ersten und zweiten Schichtverbund vor dem Kaschieren und (c) das fertige Sicherheitselement zeigt,

Fig. 8

eine Darstellung eines mehrschichtigen Sicherheitselements,

Fig. 9

eine Darstellung wie in Fig. 3 für ein Transfermaterial,

Fig.10

die Herstellung eines mehrschichtigen Sicherheitselements wobei (a) und (b) einen ersten und zweiten Schichtverbund vor dem Kaschieren und (c) das fertige Sicherheitselement zeigen,

Fig.11

eine Variante des Beispiels von Fig. 10(c), das sich von diesem nur in der Ausgestaltung des zweiten Schichtverbunds unterscheidet,

Fig.12

die Herstellung eines mehrschichtigen Sicherheitselements wobei (a), (b) und (c) einen ersten, zweiten und dritten Schichtverbund vor dem Kaschieren und (d) das fertige Sicherheitselement zeigen,

Fig. 13

die Übertragung des mehrschichtigen Sicherheitselements der Fig. 7 auf ein Zielsubstrat, und

Fig. 14

eine Darstellung eines mehrschichtigen Sicherheitselements.

Further exemplary embodiments and advantages of the invention are explained below with reference to the figures, in the representation of which a representation true to scale and proportion has been dispensed with in order to increase the clarity.
Show it:

Fig. 1

1 a schematic representation of a banknote with an embedded security thread and a glued security strip, in each case according to an embodiment of the invention,

Fig. 2

a view of a portion of the security strip of the Fig.1 , as it appears when viewed without aids or when viewed through a polarizer,

Fig. 3

in cross-section an intermediate step in the production of a transfer material according to the invention,

4 to 6

Depictions like in Fig. 3 of transfer materials according to further embodiments of the invention,

Fig. 7

the production of a multilayer security element wherein (a) and (b) show a first and second layer composite before laminating and (c) the finished security element,

Fig. 8

a representation of a multilayer security element,

Fig. 9

a representation like in Fig. 3 for a transfer material,

Figure 10

the production of a multilayer security element wherein (a) and (b) show a first and a second layer composite before laminating and (c) the finished security element,

Figure 11

a variant of the example of Fig. 10 (c) , which differs from this only in the design of the second layer composite,

Figure 12

the production of a multilayer security element where (a), (b) and (c) show a first, second and third layer composite before laminating and (d) the finished security element,

Fig. 13

the transmission of the multilayer security element of Fig. 7 on a target substrate, and

Fig. 14

a representation of a multilayer security element.

The invention will now be explained in more detail using the example of a banknote. Fig.1 shows a schematic representation of a banknote 10 with two security elements 12 and 16, which are each prepared by means of a transfer material according to the invention.

The first security element represents a security thread 12 that emerges at certain window areas 14 on the surface of the banknote 10, while it is embedded in the intervening areas inside the banknote 10. The second security element is formed by a wide security strip 16 glued onto the banknote paper with a heat-seal adhesive.

Fig. 2 shows a plan view of a portion of the security strip 16, as it appears when viewed without aids or when viewed through a linear polarizer 20. Viewed without aids, the security strip 16 shows shiny metallic, optically variable diffraction structures 22, such as holograms or kinegrams. Such diffraction structures are known to the person skilled in the art and are therefore not explained further below. Instead of the diffraction structures 22, matt structures or refractive structures may also be provided, for example.

If the security strip 16 is viewed through a linear polarizer 20, additional structures, in the exemplary embodiment a honeycomb pattern 24, appear. These structures, which are virtually invisible to the naked eye, can be used to check the authenticity of the banknote 10. Alternatively, the structures can also be visualized with a circular polarizer.

The construction and production of security elements according to the invention will first be explained by means of simpler and then increasingly complex security element structures.

Fig. 3 shows in cross-sectional representation an intermediate step in the production of a transfer material 30, for example, in a security thread 12 or a security strip 16 of the in Fig.1 shown type can be used. For this purpose, a layer 34 of nematic liquid-crystalline material is partially printed on a transparent carrier film 32, for example a smooth plastic film of good surface quality, as an effect layer. The Nematenschicht 34 is typically printed in the form of a motif of patterns, characters or a coding, for example in the form of in Fig. 2 shown honeycomb pattern.

On the Nematenschicht can this at least partially overlapping another, not shown here layer of liquid crystal material, e.g. also be partially printed from cholesteric liquid crystalline material in the form of a motif.

In order to be able to transfer the only locally present nematic layer 34 and, if appropriate, the further layer of cholesteric liquid-crystalline material to a target substrate, such as a security paper or document of value, in a later step, a transfer auxiliary layer 36 is applied over the entire surface to the nematode layer 34 and the carrier film 32. eg a UV-crosslinkable lacquer layer, printed, whose adhesion to the support film 32 is less than to Nematenschicht 34. As UV-crosslinkable transfer assist layer 36, a layer of cholesteric liquid-crystalline material or an embossing lacquer layer can be used.

Subsequently, an adhesive layer 38 is applied to the transfer auxiliary layer 36, with which the layer composite of carrier film 32, Nematenschicht 34 and transfer auxiliary layer 36 on a target substrate, such as a security paper, a document of value or a further thread or strip structure 35, can be laminated. If desired or required, the carrier film 32 for the nemate layer 34 and the transfer assist layer 36 may be removed again by means of separation winding. The damage-free detachability of the carrier film 32 is ensured by the greater adhesion of the transfer assist layer 36 to the nemate layer 34.

In all embodiments, both the transfer assist layer and the adhesive layer may include machine-readable feature substances, such as e.g. contain magnetic, electrically conductive, phosphorescent or fluorescent substances.

Before the adhesive layer 38 is applied, a further layer, not shown here, can be printed on the transfer auxiliary layer 36. The further layer can be provided in particular with recesses or in the form of patterns, characters or codes. Under this layer another, eg machine-readable layer can be printed. Machine-readable security features can also be accommodated in the further layer itself. The further manufacturing process then proceeds, as already related to Fig. 3 described.

In the transfer material 40 of the in Fig. 4 In the embodiment shown, the detachability of the carrier film 42 during the transfer is ensured by a release layer 44 that can be thermally activated under heat-sealing conditions.

Since release layers usually interfere with the alignment of subsequently applied liquid crystal layers, the release-capable carrier film 42 is provided with an alignment-promoting alignment layer 48. This may be, for example, a layer of a linear photopolymer, a Layer with orientation-promoting surface topography or a layer oriented by the application of shear forces.

However, the use of alignment layers is not limited to transfer materials with release-capable carrier films. Fig. 5 shows an intermediate step of producing transfer material as in Fig. 3 according to a further embodiment of the invention. The transfer material 50 of Fig. 5 has a carrier film 32 with an alignment layer 52, for example, a linear photopolymer, which serves to align the liquid crystals in the subsequently applied nematic and optionally cholesteric liquid crystal layers 34 and 36, respectively.

Before applying the adhesive layer 38, a further layer 54 is printed on the transfer auxiliary layer 36. The further layer 54 may be provided in particular with recesses or in the form of patterns, characters or codes. In order to allow a good visibility of the color and polarization effects of the liquid crystal layers, the layer 54 may be provided by an absorbent print or a reflective metal layer. For example, the layer can be produced by printing the transfer assist layer 36 with a commercially available, in particular black printing ink. This is particularly appropriate when the transfer assist layer 36 consists of cholesteric liquid-crystalline material. If the transfer assist layer 36 is present as a UV-crosslinkable lacquer layer, the further layer can be provided by a metal layer into which recesses, for example in the form of a negative writing, can be introduced by partial demetallization. Under the layer 54, another, eg machine-readable layer can be printed. Even in the layer 54 itself further, in particular machine-readable security features be housed. The further manufacturing process then proceeds, as already related to Fig. 3 described.

In the case of the transfer medium with negative writing 60 of Fig. 6 is printed on a carrier film 32, which in turn may be provided with an alignment layer, a nematic liquid crystal layer 34. A UV-curable embossing lacquer layer 62, whose adhesion to the carrier foil 32 is less than that of the nematode layer 34, is printed over the carrier foil 32 and the nematic layer 34 so that the embossing lacquer layer 62 fulfills the function of the transfer assist layer described above during the transfer of the transfer material 60 to a target substrate ,

Subsequently, a desired embossed structure 64, for example a diffraction structure, is impressed into the embossing lacquer layer 62 and a reflective layer 66, in particular a metal layer, is applied, into which recesses 68, in the embodiment in the form of a negative writing, are introduced by partial demetallization. Alternatively, the embossing structure 64 may also be provided with a high refractive index layer. Examples of high-index materials are CaS, CrO ₂ , ZnSi, TiO ₂ or SiO _x . Finally, an adhesive layer 38 is applied to the composite layer for transfer to the target substrate.

Instead of a reflective layer 66 in the form of a metal layer or a high refractive index layer, the embossing pattern 64 can also be provided with a color shift effect thin film element, as described below with reference to FIG Fig. 8 is described in detail.

Before the adhesive layer 38 is applied, further, in particular machine-readable and / or decorative layers can be demetallized on the partially demetallized Embossing lacquer layer 62, in particular in overlap with the metal layer 66 are applied. For example, a commercially available printing ink can be printed, which is then recognizable in the recesses or demetallized areas of the embossing lacquer layer when viewing the foil material applied to a substrate. The printing ink, like the adhesive layer 38, may also contain machine-readable feature substances, such as magnetic, electrically conductive, phosphorescent or fluorescent substances.

The FIGS. 7 to 14 illustrate manufacturing processes that are not part of the invention.

Fig. 7 illustrates the manufacture of a multilayer security element 70. As shown in FIG Fig. 7 (a) a first layer composite 72 of a first carrier foil 32, a nematic liquid crystal layer 34 and a transfer auxiliary layer 36 of cholesteric liquid crystal material, as described in connection with FIG Fig. 3 described. The transfer assist layer can be formed, for example, by a UV-crosslinkable lacquer layer or a layer of cholesteric, liquid-crystalline material.

In addition, as in Fig. 7 (b) a second layer composite 74 is produced by printing on a second carrier film 80 an embossing lacquer layer, embossing a desired embossed structure, in the exemplary embodiment a diffraction structure, into the embossing lacquer, onto the embossed layer 82 a metal layer 84 is vapor-deposited, and by partial demetallization of the Metal layer 84 recesses 86, for example, be generated in the form of negative writing.

The second layer composite 74 is applied via an adhesive layer 76 (FIG. Fig. 7 (c) ) laminated on the first layer composite 72, as by the FIGS. 7 (b) and 7 (a) connecting arrow 78 indicated. Subsequently, the second Carrier sheet 80 removed by separation winding and applied for the transfer of an adhesive layer 38 on den'so produced layer composite, as in Fig. 7 (c) shown. After the security element 70 has been applied to the target substrate, the carrier foil 32 can also be removed so that the entire layer composite is then present without carrier foils. The polarization effect features are thus not affected by films in their effect and can be viewed with high contrast.

The reduced by the detachment of the second carrier film 80 protection function for the metallization can be compensated by protective lacquer layers. Conventional protective lacquer layers are optically largely isotropic and therefore do not impair the recognizability of polarizing effects.

If a layer of cholesteric liquid-crystalline material is used as the transfer aid layer 36, an additional, dark-colored layer may optionally be partially applied to the layer composite 74, in order to ensure good visibility of the color effect of the cholesteric liquid-crystal layer. Alternatively, the embossing lacquer layer 82 can be darkened.

Instead of the embossed structure, the second layer composite can also contain only one reflective layer, in particular a metal layer, which is preferably integrated into a print motif with large portions of demetallization. Compared with conventional designs, the transfer material according to the invention then has an additional test level with the nematic layer 34, which can be authenticated with a polarizer.

In all designs with a reflective layer, this can also be achieved by a more complex reflection layer structure with special reflection effects, such as a color shift effect, to be replaced. Fig. 8 to an embodiment, whose production analogous to that at Fig. 7 described manufacturing process runs.

For the production of the multilayer security element 90 of Fig. 8 a first layer composite of a first carrier foil 32, a nematic liquid crystal layer 34 and a transfer auxiliary layer 36, for example a UV-crosslinkable lacquer layer, and a second layer composite of a second carrier foil, on which a thin-film element 92 is applied with color shift effect.

In the exemplary embodiment, the thin-film element 92 has a reflection layer 94, an absorber layer 98 and a dielectric spacer layer 96 arranged between the reflection layer and the absorber layer. The color shift effect in such thin-film elements is based on viewing angle-dependent interference effects due to multiple reflections in the different sub-layers of the element. The absorber layer 98 and / or the dielectric spacer layer 96 may have recesses in the form of patterns, characters or codes in which no color-shift effect can be recognized. The reflection layer 94 may also have recesses in the form of patterns, characters or codes, which then form transparent or semitransparent regions in the thin-film element 92.

The order of the layers of the thin-film element can also be reversed. Alternatively, the thin-film element may have a layer sequence of absorber layer / dielectric layer / absorber layer or a sequence of several layers of alternating high-index and low-index dielectrics. A layer sequence of reflection layer and an absorbing dielectric layer is also possible.

The second layer composite produced in this way is then laminated onto the first layer composite via an adhesive layer 76 and the second carrier film is removed by a separation winding. For transfer to the target substrate, an adhesive layer 38 is applied to the now exposed backside of the thin film element 92. On the exposed back side of the thin-film element 92, prior to the application of the adhesive layer 38, further machine-readable and / or decorative layers, e.g. with a magnetic paint, are applied. After the transfer, the first carrier film 32 can also be removed.

In a variant of the example of FIG Fig. 8 For example, a multi-layer security element having a liquid crystal-based color-tilting or polarizing effect which is recognizable to the observer from the one side of the security element and a thin-film element having a color-shift effect recognizable from the second side is produced.

The security element is different from the one in Fig. 8 shown in that the transfer assist layer 36 of the first layer composite of cholesteric liquid-crystalline material is formed. In order to allow in particular a good visibility of the color effect of the cholesteric liquid crystal layer, the adhesive layer 76 also forms a dark, preferably black background. The adhesive layer 76 can be dyed or, if appropriate, subsequently blackened by the action of a laser beam. The thin film element 92 of the second layer composite has an order reverse to the layer order described above, ie, the reflective layer is in the security element adjacent to the adhesive layer 76, and the absorber layer is adjacent to the adhesive layer 38.

Fig. 9 shows a transfer material 100, in which, as in Fig. 3 On a smooth plastic carrier sheet 32, a nematic liquid crystal layer 34 and a UV-crosslinkable transfer assist layer 36, for example, from cholesteric liquid crystal material, are printed. An embossing lacquer layer is further printed onto the transfer assist layer 36, a desired embossed structure, in the exemplary embodiment a diffraction structure, embossed into the embossing lacquer layer, and a metal layer 104 is vapor-deposited onto the embossed layer 102. Recesses 106 in the form of negative writing are introduced into the metal layer 104 by partial demetallization. Instead of the metal layer 104, it is also possible to use a transparent high-index layer which has a refractive index greater than 2. As a result, both the diffraction structure and the liquid-crystalline layers 34 and 36 can be perceived over the entire area on a dark background which is provided by an additional layer, for example a black imprint, or can also be present on the target substrate.

In order to improve the adhesion of the embossing lacquer layer 102 on the transfer assist layer 36, the latter is advantageously subjected to a corona treatment beforehand or it is provided with a suitable adhesion promoter. An adhesive layer 38 is applied to the entire layer composite for transfer to the target substrate. Depending on the choice of the mediating layer and the demands on the brilliance, the carrier film 32 can be removed after the application of the transfer material 100 or left on the structure.

The production of a multilayer security element 110, for example a security thread, with a liquid crystal-based color-shift effect, a Negative writing and a magnetic coding is now based on the Fig. 10 explained.

First, as in Fig. 10 (a) a first layer composite 112 of a first carrier foil 32, a nematic liquid crystal layer 34 and a transfer auxiliary layer 36, for example of cholesteric liquid crystal material produced, as in Fig. 3 described. A second layer composite 114 is produced by applying to a second carrier film 120 a screened aluminum layer 122 with recesses in the form of negative writing, and onto the aluminum layer a magnetic layer 124, in the example in the form of a coding, is applied. This second layer composite 114 is in Fig. 10 (b) shown. In another embodiment, not shown here, the aluminum layer 122 may also be provided as a full-surface layer with recesses, for example in the form of negative writing, to which in turn the magnetic layer 124 is applied.

The second layer composite 114 is then applied via an adhesive layer 116 (FIG. Fig. 10 (c) ) laminated on the first layer composite 112. Subsequently, further layers 118, such as a white cover layer, which are required for the embedding of the security thread in a security paper, can be applied to the back side of the second carrier film 120. Finally, an adhesive layer 38, for example a heat sealing lacquer, is applied for the transfer to the target substrate. The carrier film 32 may be removed by means of parting, and further layers of the thread structure, such as a primer and a heat sealing lacquer, may be applied to the then exposed liquid crystal layers 34 and 36.

In a variant of the example of FIG Fig. 10 For example, instead of the magnetic layer 124 of the second layer composite applied in the form of a coding, it is also possible to use a dark, in particular black layer with recesses and regions a magnetic layer, for example in the form of magnetic bits. In particular, not all black areas need to be magnetic at the same time. In this way, a magnetic coding in the black layer can be optically hidden.

Another variant of the example of Figure 10 , which differs only in the embodiment of the second composite layer, is in Fig. 11 shown. The second layer composite 132 of the multilayer security element 130 of FIG Fig. 11 instead of the screened aluminum layer, a full-area, semitransparent metal layer 136 applied to a carrier film 134, on which a magnetic layer 138 is arranged, for example, in the form of a coding. The further procedure in the production of the security thread 130 follows that described above in connection with FIG Fig. 10 given description.

Figure 12 illustrates the production of a multilayer security element 140, in particular a hologram security thread with magnetic coding and nematic printing.

First, a first layer composite 150 of a first plastic carrier film 152, a nematic liquid crystal layer 154, a transfer auxiliary layer 156 made of a modified UV-curing lacquer and a first adhesive layer 158 is prepared, as in Fig. 12 (a) shown.

For producing a second layer composite 160, which is in Figure 12 (b) an embossing lacquer layer is printed onto a second plastic carrier film 162, a desired diffraction structure is embossed into the embossing lacquer and an aluminum layer 166 is vapor-deposited on the embossed layer 164, in which, as already described in connection with FIG Fig. 7 described by partial demetallization recesses 168, for example, be generated in the form of negative writing. A magnetic layer 170 in the form of a coding is applied to the rear side of the carrier foil 162 not coated with embossing lacquer. The magnetic bits of the magnetic coding are then covered with a cover layer 172.

A third layer composite 180, which functions as a cover element in the finished security thread, is produced by applying a full-area metal layer 184 to a third, particularly thin plastic carrier film 182 and providing the metal layer 184 with a further full-surface adhesive layer 186, as in FIG Fig. 12 (c) shown.

The first layer composite 150 with the nematic print is then laminated onto the top side of the hologram layer composite 160 (arrow 142) and the cover layer composite 180 is laminated via the adhesive layer 186 onto the underside of the hologram layer composite 160 carrying the magnetic code (arrow 144). Additional layers 146, such as a white topcoat, required for embedding the security thread in a security paper can then be applied to the back side of the third carrier film 182. Finally, for transfer to the target substrate, an adhesive layer 38, such as a heat sealing lacquer, is applied as in Figure 12 (d) shown. The carrier film 152 of the first layer composite 150 can then be removed by separating windings and further layers of the thread structure, such as a bonding agent and applying a heat sealing lacquer to the then exposed liquid crystal layers 154 and 156.

The application of the described security elements to a target substrate 200, eg a security paper or a plastic film, will be made with reference to FIG Fig. 13 by way of example with reference to the multilayer security element 70 of FIG Fig. 7 explained. For this purpose, the security element 70 is placed on the target substrate 200 with the heat-sealable adhesive layer 38 and pressed in areas. The pressing can be done for example with a not shown heated transfer punch or a transfer roller. Under pressure and heat, the adhesive layer 38 connects in the desired regions 202 with the target substrate 200, so that a transfer element, if appropriate with a predetermined outline shape, arises. The carrier film 32 of the liquid crystal layers 34, 36 can be removed during the application process or shortly thereafter. Before applying the transfer member 70 to the target substrate 200, the surface of the target substrate 200 may be specially treated. As a result, in particular the adhesive effect of the transfer element and the optical efficiency of the security features provided by this can be improved. For example, an adhesion promoter can be applied to the surface of the target substrate 200.

The production of a multilayer security element 210, such as a security thread, with a negative writing and a hidden magnetic coding is now based on the Fig. 14 explained.

First, a first layer composite 212 of a first transparent carrier film 232, a partially applied, in particular printed layer with two-dimensional metal pigments 234 and a transfer auxiliary layer 236, for example a UV-crosslinkable lacquer layer produced. Printing inks with such flat metal pigments give a particularly good brilliance when printed directly on very smooth surfaces. The transparent carrier film should therefore have a good surface quality.

A second layer composite 222 is produced by forming on a second carrier foil 246 an aluminum layer 242 with recesses in the form of negative writing, and by applying to the aluminum layer a magnetic layer 244, in the form of a coding.

The second layer composite 222 is then laminated over an adhesive layer 238 onto the first layer composite 212 in register. Subsequently, further layers, not shown here, which are required for the embedding of the security thread in a security paper, can be applied to the back of the second carrier film 246. Finally, an adhesive layer 38, for example a heat sealing lacquer, is applied for the transfer to the target substrate. The carrier sheet 232 may be removed by means of parting, and further layers of the yarn structure, such as a primer and a heat sealing lacquer may be applied to the then exposed layers 234 and 236, respectively.

In such a multi-layered construction, the black magnetic areas are obscured by the application of the high-opacity, flat-colored metal pigments containing printing ink. On the other hand, if such inks were printed directly on the rough magnetic layer 244, the brilliance of the color would not be satisfactory and the visual appearance of the security element would be different on both sides.

In another example, not shown, the transfer material consists of an effect layer of optically variable pigments, such as interference layer pigments, which is applied over the entire surface to a transparent plastic carrier film. Such effect layers require a very smooth surface in order to achieve a brilliant color impression. Instead of the transparent plastic carrier film, it is also possible to use a lacquer layer applied to a transparent carrier film which has a suitable surface quality. In order to stabilize the effect layer during the transfer to a target substrate, it is also possible if appropriate to apply a transfer aid layer to the effect layer.

In a variant of this example, the detachability of the carrier film from the effect layer can also be ensured by a release layer assisting the separation under the appropriate transfer conditions. The carrier film can then additionally comprise, for example, a release layer thermally activatable under heat-sealing conditions, as in the exemplary embodiment of US Pat Fig. 4 is illustrated on which then the effect layer is applied.

For transferring the transfer material to a second layer composite, such as a further thread or strip structure, an adhesive layer is further applied to the effect layer. Alternatively, the adhesive layer can also be provided on the second layer composite. If desired or required, the carrier film can be removed by separation winding last.

Claims (17)

1. A method for manufacturing a first layer composite, especially a transfer material for transferring to a target substrate, having the following steps:

   a) providing a plastic substrate foil having a smooth, non-porous surface,

   b) discontiguously applying an effect layer to the substrate foil,

   c) contiguously applying a transfer assist layer to the effect layer and the substrate foil, the adhesion of the transfer assist layer to the substrate foil being less than to the effect layer, and

   d) applying an adhesive layer for transferring the formed layer composite to the target substrate.
2. The method according to claim 1, characterized in that the effect layer is applied, preferably imprinted, as a lacquer layer that includes effect pigments embedded in a binder matrix.
3. The method according to claim 2, characterized in that the transfer assist layer is applied, preferably imprinted, as a lacquer layer that includes the binder without effect pigments used for the binder matrix.
4. The method according to claim 2 or 3, characterized in that the effect layer and/or the transfer assist layer is imprinted by means of screen printing, transfer printing or pad printing.
5. The method according to at least one of claims 1 to 4, characterized in that a UV-curing lacquer layer is applied, especially imprinted, as the transfer assist layer, preferably in that the UV-curing lacquer layer includes photoinitiators.
6. The method according to at least one of claims 1 to 4, characterized in that a layer comprising cholesteric liquid crystal material is applied, especially imprinted, as the transfer assist layer.
7. The method according to at least one of claims 1 to 4, characterized in that an embossing lacquer layer that is subsequently embossed is applied, especially imprinted, as the transfer assist layer.
8. The method according to claim 7, characterized in that the embossing lacquer layer is metallized and, if applicable, demetallized in some regions.
9. The method according to at least one of claims 1 to 8, characterized in that the transfer assist layer is corona treated or furnished with an adhesion promoter.
10. The method according to at least one of claims 1 to 9, characterized in that one or more further layers are applied to, especially imprinted on, the transfer assist layer prior to the application of the adhesive layer in step d).
11. The method according to claim 10, characterized in that a further layer is imprinted on the transfer assist layer with a printing ink, preferably a magnetic ink, and/ or in that, as a further layer, a reflective layer is applied, and/or in that, as a further layer, an embossing lacquer layer is applied, especially imprinted, that is subsequently embossed, metallized and, if applicable, demetallized in some regions.
12. The method according to at least one of claims 1 to 11, characterized in that a foil that is designed for the orientation of liquid crystals is provided as the substrate foil, especially in that a foil provided with an alignment layer for the orientation of liquid crystals is provided as the substrate foil.
13. A transfer material for transferring to a target substrate, especially manufacturable according to one of claims 1 to 12, having

    - a plastic substrate foil having a smooth, non-porous surface,

    - a security layer sequence having an effect layer applied discontiguously to the substrate foil and a transfer assist layer applied contiguously to the effect layer and the substrate foil, the adhesion of the transfer assist layer to the substrate foil being less than to the effect layer, and having

    - an adhesive layer for transferring the layer sequence to the target substrate.
14. The transfer material according to claim 13, characterized in that the effect layer is formed by a first layer composed of a liquid crystal material, especially by a first layer composed of a nematic liquid crystal material.
15. The transfer material according to at least one of claims 13 or 14, characterized in that the transfer assist layer is formed from a UV-curing lacquer layer, a cholesteric liquid crystal material or by an embossing lacquer layer provided with an embossing.
16. The transfer material according to at least one of claims 13 to 15, characterized in that the effect layer and the transfer assist layer are present on a plastic substrate foil that comprises a thermally activatable release layer.
17. A method for manufacturing a security element, especially a security thread, a transferable security strip or a patch, in which a transfer material is manufactured according to at least one of claims 13 to 16 and is furnished with further layers for embedding in or for application to a security paper or value document.

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