Method for producing a multilayer film and multilayer film as well as a security element and a security document

Abstract

A method for producing a multilayer film wherein, in at least one step, at least one ink is applied to a layer by means of inkjet printing, whereby at least one area at least of a first print is provided, and wherein the first print is covered by at least one further layer. A multilayer film, in particular produced by a method according to the invention, having at least a first print, wherein the print is produced by means of inkjet printing and wherein the print is arranged within the multilayer film and is covered by further layers of the multilayer film.

Claims

1. A method for producing a multilayer film, wherein, in at least one step, at least one ink is applied to a layer by means of inkjet printing, whereby a first print is provided in at least one area, and wherein the first print is covered by at least one further layer, and wherein the ink is applied to a replication layer at least in areas, and wherein the replication layer is replicated together with the print applied thereto, whereby a replication structure is impressed into the replication layer and the print, and wherein during the replication of the replication layer, the print is pressed into the replication layer and/or compressed and/or deformed, and wherein the replication is effected in register with the print.

2. The method according to claim 1, wherein an individualized print is provided.

3. The method according to claim 1, wherein the print is formed through an application of a single ink.

4. The method according to claim 1, wherein the print is formed through an application of several inks.

5. The method according to claim 1, wherein the ink is applied to several layers of the multilayer film.

6. The method according to claim 1, wherein the ink is applied to a carrier layer at least in areas.

7. The method according to claim 1, wherein the ink is applied to a detachment layer at least in areas.

8. The method according to claim 1, wherein the ink is applied to a protective layer at least in areas.

9. The method according to claim 1, wherein the ink is applied, at least in areas, to a reflective layer.

10. The method according to claim 1, wherein the ink is applied to an adhesive layer and/or to a primer layer at least in areas.

11. The method according to claim 1, wherein the ink, or a print of a UV-curing replication varnish is poured-over, layered-over and/or encapsulated.

12. The method according to claim 11, wherein the application of the ink, or the provision of the print is carried out in the same manufacturing step as a UV replication.

13. The method according to claim 1, wherein the ink and a UV-curing replication varnish are cured together and/or the ink undergoes post-crosslinking through curing of the UV-curing replication varnish.

14. The method according to claim 1, wherein the ink is applied to a substantially smooth surface of the replication layer.

15. The method according to claim 1, wherein a position of the replication structure with respect to the print is within +/0.4 mm.

16. The method according to claim 1, wherein the ink applied to the replication layer has a layer thickness substantially twice as thick as a depth of the replication structure introduced into the replication layer during the replication.

17. The method according to claim 1, wherein an adhesion-promoter layer is applied to a layer and/or to the ink or to the print at least in areas.

18. The method according to claim 17, wherein the at least one adhesion-promoter layer is applied only in those areas to which the ink is also applied.

19. The method according to claim 1, wherein an anti-adhesion layer is applied, at least in areas, to a layer of the multilayer film and/or to the ink or to the print.

20. The method according to claim 1, wherein an ink with laser-sensitive pigments is provided.

21. The method according to claim 1, wherein the ink or the print is irradiated at least in areas by means of a radiation source, whereby an optical appearance of the print changes.

22. The method according to claim 21, wherein at least one invisible and/or transparent ink is applied and the ink or the print is irradiated with a laser at least in areas, whereby the irradiated areas become visible.

23. The method according to claim 21, wherein at least one ink is applied adjacent to at least one visible marking and/or partial marking and/or to at least one visible motif and/or to a visible partial motif and the ink or the print is irradiated with a laser at least in areas, whereby the irradiated areas of the ink or the print become visible and, together with the adjacent marking and/or the adjacent partial marking and/or the adjacent motif and/or the adjacent partial motif, form an overall marking or an overall motif.

24. The method according to claim 21, wherein at least one visible and/or colored and/or opaque ink is applied and the ink or the print is irradiated with a laser at least in areas, whereby an optical appearance of the irradiated areas change.

25. The method according to claim 1, wherein at least one light-absorbing, print is provided at least in areas.

26. A method for producing a multilayer film, wherein, in at least one step, at least one ink is applied to a layer by means of inkjet printing, whereby a first print is provided in at least one area, and wherein the first print is covered by at least one further layer, and wherein the ink is applied to a replication layer at least in areas, and wherein the replication layer is replicated together with the print applied thereto, whereby a replication structure is impressed into the replication layer and the print, and wherein the print is compressed and/or deformed during the replication.

27. The method according to claim 26, wherein the replication is effected in register with the print.

28. A method for producing a multilayer film, wherein, in at least one step, at least one ink is applied to a layer by means of inkjet printing, whereby a first print is provided in at least one area, and wherein the first print is covered by at least one further layer, and wherein a surface of a replication layer is replicated, whereby at least one diffractive structure is impressed into the surface of the replication layer, and wherein the ink is applied to the replicated surface of the replication layer at least in areas, and wherein the ink is applied in such a way that the ink only partially fills the at least one diffractive structure on the surface of the replication layer.

29. A method for producing a multilayer film, wherein, in at least one step, at least one ink is applied to a layer by means of inkjet printing, whereby a first print is provided in at least one area, and wherein the first print is covered by at least one further layer, and wherein a print, which is formed as a wash varnish, is provided, and wherein a metal layer and/or a metallization is applied, and the wash varnish is then removed by a solvent treatment together with parts of the metal layer and/or the metallization, whereby the metal layer and/or the metallization remains only where no wash varnish has been applied.

30. The method according to claim 29, wherein the ink is applied to a replication layer at least in areas.

31. The method according to claim 30, wherein the replication layer is replicated together with the print applied thereto.

32. The method according to claim 31, wherein during the replication, the print is pressed into the replication layer.

33. The method according to claim 30, wherein the ink is applied in such a way that, during a subsequent replication, a replication structure is impressed into the print, but not into an area of the replication layer covered by the print.

34. The method according to claim 30, wherein, during a subsequent replication, a replication structure is introduced in such a way that an area of the replication layer is not replicated.

35. A multilayer film, having at least a first print, wherein the print is produced by means of inkjet printing and wherein the print is arranged within the multilayer film and is covered by further layers of the multilayer film, and wherein the multilayer film has an anti-adhesion layer at least in areas, and wherein the print is arranged on a replication layer, and wherein the print is replicated at least in areas, whereby a replication structure is impressed into the print.

36. The multilayer film according to claim 35, wherein the print is formed by a single ink.

37. The multilayer film according to claim 35, wherein a position of the replication structure with respect to the print is within +/0.2 mm provided.

38. The multilayer film according to claim 35, wherein at least one area of the replication layer, which, in a top view onto the multilayer film is arranged adjacent to the print, is not replicated.

39. The multilayer film according to claim 35, wherein the areas in which the print is replicated comprise replication structures, and wherein in those areas in which the applied ink or the print is present, the ink or the print only partially fills the replication structures.

40. The multilayer film according to claim 35, wherein the multilayer film has an adhesion-promoter layer at least in areas.

41. The multilayer film according to claim 35, wherein the ink or the print comprises laser-sensitive pigments.

42. The multilayer film according to claim 35, wherein the print has visible and invisible areas.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) In the following the invention is explained with reference to several embodiment examples utilizing the attached drawings by way of example. There are shown in:

(2) FIG. 1 schematic representation of possible arrangements of a print in a multilayer film

(3) FIG. 2 schematic process of the formation of replication structures

(4) FIG. 3 schematic process of the production of a multilayer film in one embodiment

(5) FIG. 4 schematic representation of a multilayer film in an embodiment before and after laser irradiation

(6) FIG. 5 schematic representation of a multilayer film in a further embodiment before and after laser irradiation

(7) FIG. 6 schematic representation of a multilayer film in a further embodiment before and after laser irradiation

(8) FIG. 7 schematic top view onto a print in one embodiment

(9) FIG. 8a to 8d schematic top view onto a print in further embodiments

(10) FIG. 9a, 9b schematic top view onto a print in further embodiments

(11) FIG. 10a, 10b microscope images of an area of a print in one embodiment.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

(12) FIG. 1 shows a schematic representation of possible arrangements at least of one print 100 in a multilayer film 10.

(13) The ink can in principle be applied to each layer of the multilayer film 10, at least in areas, with the result that the print 100 can in principle be provided or arranged on each layer of the multilayer film 10. In particular, the print 100 is arranged on the carrier layer 12, the detachment layer 14, the replication layer 18, the protective layer 16, the reflective layer 20 and/or the adhesive layer 22. The print 100 can be an individualized print or also a non-individualized print.

(14) If required, the layer to which the ink is applied is preferably modified beforehand such that a sufficient adhesion or also a non-adhesion of the ink or the print 100 to this layer can be ensured. This can be guaranteed for example by corresponding surface additives in the varnish formulation or corresponding design of the layer, for example with cross-linkable UV-active groups on the surface. This is in particular advantageous if a UV-curing ink is used.

(15) It is expedient if the ink is applied to several layers of the multilayer film. The inks applied to the layers can be formed both identical and also different. In particular, the inks are applied in register with each other. A multilayer film 10 is hereby obtained, in which at least one first print 100 is formed on several layers. In particular, the prints 100 can be arranged in register with each other.

(16) If several prints 100 are provided on several layers of the multilayer film 10, the individual prints 100 can be formed different from each other. This is to be understood in particular to the effect that the prints 100 differ from each other in their optical appearance. The prints 100 can for example be formed by different inks and/or be formed as motifs differing from each other.

(17) Furthermore, in a top view onto the multilayer film 10, the prints 100 can be offset with respect to each other or also be arranged overlapping. In a top view onto the multilayer film 10, the prints 100 can, however, also be arranged next to each other. Advantageously, the prints 100 are arranged or formed on the layers such that, in a top view onto the multilayer film, at least some of the prints 100 or parts of some of the prints 100 together form an overall motif.

(18) Preferably the ink is applied to a carrier layer 12 at least in areas. Thus a multilayer film 10 is obtained, in which at least one print 100 is arranged on the carrier layer 12 at least in areas.

(19) The ink applied to the carrier layer 12 is preferably applied such that the ink or the print 100 has tactile and/or haptically perceptible properties. An individualized haptic surface can in particular be created hereby, when the print 100 is individualized. The ink printed on or the print 100 provided in particular has a surface structure. In particular, the ink is applied or the print is provided in such a way that they or it give(s) a certain structure or structuring to a layer, in particular a protective layer 16, optionally applied subsequently.

(20) The ink can further be applied to the carrier layer 12 in such a way that, following an application of the multilayer film 10 to a substrate, and the subsequent removal of the carrier layer 12, the ink or the print 100 remains at least partially, preferably completely on the carrier layer 12. It can hereby be documented e.g. subsequently, for example by reading the print 100 remaining on the carrier layer 12, which parts of the multilayer film 10 have actually been applied.

(21) The carrier layer 12 consists in particular of a material that is self-supporting and/or from the plastics class of substances. The carrier layer 12 is preferably formed of PET, of a polyolefin, in particular of OPP, BOPP, MOPP, PP and/or PE, of PMMA, of PEN, of PA, of ABS and/or a composite material of these plastics. It is also possible for the carrier layer 12 to have already been pre-coated by the manufacturer and the multilayer film 10 is built up on this pre-coated material. It is also possible for the carrier layer 12 to be a bio-degradable and/or compostable carrier layer 12. EVOH is preferably used in this case. The layer thickness of the carrier layer 12 advantageously lies between 4 m and 500 m, in particular between 4.7 m and 250 m.

(22) The multilayer film 10 can be formed as a laminating film which has a carrier layer 12 and a multilayer wear layer, for example a multilayer decorative ply, as well as an in particular heat-activatable adhesive layer, wherein carrier layer 12 and wear layer are arranged together in the form of a stamping layer on the substrate.

(23) In particular, the multilayer film 10 is formed as a transfer film. A transfer film comprises in particular a transfer ply, which is preferably formed of several layers, in particular comprises at least one adhesive layer 22, one reflective layer 20, one replication layer 18 and/or one protective layer 16, and a carrier layer 12, wherein the transfer ply is detachable from the carrier layer 12. To facilitate the detachment of the transfer ply, a detachment layer 14 can be arranged between the transfer ply and the carrier layer 12.

(24) Preferably, the ink is applied to a detachment layer 14 at least in areas. Thus a multilayer film 10 is obtained, in which at least one print is arranged on the detachment layer 14 at least in areas. The detachment layer can be present both partially 14 and over the whole surface 14.

(25) The detachment layer 14 ensures in particular that the layers of the multilayer film 10 can be separated from the carrier layer 12 non-destructively. The detachment layer 14 is preferably formed of waxes, polyethylene (PE), polypropylene (PP), cellulose derivatives and/or poly(organo)siloxanes. Above-named waxes can be natural waxes, synthetic waxes or combinations thereof. Above-named waxes are, for example, camauba waxes. Above-named cellulose derivatives are, for example, cellulose acetate (CA), cellulose nitrate (CN), cellulose acetate butyrate (CAB) or mixtures thereof. Above-named poly(organo)siloxanes are, for example, silicone binders, polysiloxane binders or mixtures thereof. The detachment layer 14 preferably has a layer thickness of between 1 nm and 500 nm, in particular a layer thickness of between 5 nm and 250 nm, in particular preferably between 10 nm and 250 nm.

(26) The detachment layer 14 can be produced with the known printing methods. In particular, gravure printing, flexographic printing, screen printing, inkjet printing or by means of a slot die are suitable. The detachment layer 14 can however also be formed by vapor deposition, physical vapor deposition (PVD), chemical vapor deposition (CVD) and/or sputtering.

(27) It is expedient if the ink is applied to a protective layer 16 at least in areas. Preferably the ink is applied in areas to a protective layer 16 formed over the whole surface. Thus a multilayer film 10 is obtained in which a print 100 is arranged on the protective layer 16 at least in areas. In particular, the print 100 is arranged, in the viewing direction, underneath the protective layer 16 and thus also protected by the protective layer 16.

(28) The protective layer 16 is preferably a layer of PMMA, PVC, melamines and/or acrylates. The protective varnish can also consist of a radiation-curing dual-cure varnish. This dual-cure varnish can be thermally pre-crosslinked in a first step during and/or after application in liquid form. Preferably, in a second step, in particular after the processing of the multilayer film, the dual-cure varnish is radically post-crosslinked, in particular via high-energy radiation, preferably UV radiation. Dual-cure varnishes of this type can consist of different polymers or oligomers, which have unsaturated acrylate or methacrylate groups. These functional groups can, in particular in the second step, be radically crosslinked with each other. For the thermal pre-crosslinking in the first step it is advantageous that at least two or more alcohol groups are also present in these polymers or oligomers. These alcohol groups can be crosslinked with multifunctional isocyanates or melamine formaldehyde resins. Different UV raw materials such as epoxy acrylates, polyether acrylates, polyester acrylates and in particular acrylate acrylates preferably come into consideration as unsaturated oligomers or polymers. Both blocked and unblocked representatives based on TDI (TDI=toluene-2,4-diisocyanate), HDI (HDI=hexamethylene diisocyanate) or IPDI (IPDI=isophorone diisocyanate) can come into consideration as isocyanate. The melamine crosslinkers can be fully etherified versions, can be imino types or represent benzoguanamine representatives.

(29) The protective layer 16 preferably has a layer thickness of between 50 nm and 30 m, preferably 1 m to 5 m. The protective layer 16 can be produced by means of gravure printing, flexographic printing, screen printing, inkjet printing, or by means of a slot die and/or by means of vapor deposition, in particular by means of physical vapor deposition (PVD), chemical vapor deposition (CVD) and/or sputtering.

(30) Furthermore, it is also possible for the ink to be applied, at least in areas, to a reflective layer 20, in particular to a metal layer and/or metallization and/or HRI layer. Thus a multilayer film 10 is obtained in which at least one print 100 is arranged on the reflective layer 20 at least in areas.

(31) If the ink is applied to a metal layer, the ink or the print 100 can then serve in particular as an etch resist for a demetallization. If the ink or the thus-provided print 100 is formed as an etch resist, a demetallization can then take place in a following step. The metal layer is preferably removed in those areas which are not covered by the print 100. If the ink is alkali-containing for example, a direct etching can also be produced through the application. If the print 100 is individualized, an individualized demetallization can also be produced therewith.

(32) The reflective layer 20 can be applied both over the whole surface and in areas. The reflective layer 20 is preferably formed patterned, in particular for the formation of motifs. The reflective layer 20 can represent a pattern and/or a motif, which can also be arranged, in particular, in register with the print 100 on other layers of the multilayer film 10 and/or with the structures of the replication layer 18.

(33) The reflective layer 20 is preferably a metal layer or a metallization. The metal layer or metallization is preferably formed of aluminum, chromium, gold, copper, tin, silver or an alloy of such metals.

(34) The metal layer or the metallization is preferably produced by means of vapor deposition, in particular by means of vacuum vapor deposition. The vapor-deposited to metal layer or metallization can be effected over the whole surface and either retained over the whole surface or else be structured with known demetallization methods such as etching, lift-off or photolithography and thereby be only partially present. The layer thickness lies in particular between 10 nm and 500 nm.

(35) However, the metal layer or the metallization can also consist of a printed layer, in particular made of a printed layer of metal pigments in a binder. These printed metal pigments can be applied over the whole surface or partially and/or have different colorings in different surface areas. The layer thickness lies in particular between 1 m and 3 m.

(36) It is also possible to produce the reflective layer 20 from a varnish with electrically conductive metallic pigments, in particular to print and/or pour it on.

(37) Furthermore, it is also possible for the reflective layer 20 to be formed by a transparent reflective layer 20, for example a thin or finely-structured metallic layer or an HRI (high refractive index) or LRI (low refractive index) layer. Such a dielectric reflective layer 20 consists, for example, of a vapor-deposited layer of a metal oxide, metal sulfide, titanium oxide etc. The layer thickness of such a layer is preferably 10 nm to 500 nm.

(38) Preferably, the ink is applied to an adhesive layer 22 and/or to a primer layer at least in areas. Thus a multilayer film 10 is obtained in which at least one print 100 is arranged on the adhesive layer 22 and/or on the primer layer at least in areas. The adhesive layer 22, 22 can be applied both partially and over the whole surface. The adhesive layer can in principle also be a partial adhesive layer 22. Likewise, it is conceivable that the adhesive layer is an adhesive layer 22 over the whole surface.

(39) The ink is preferably formed such that the ink or the print 100 itself can serve as a partial adhesive layer 22. In particular, an individualized bonding is thus obtained when the print 100 is individualized. However, it is also possible for the ink to be applied at least partially to the adhesive layer 22 for the passivation, in particular for the partial passivation of the adhesive layer 22. In the case of a later application or hot-stamping, a transfer of the multilayer film to a substrate is then effected only in the areas of the adhesive layer 22 not printed with ink.

(40) The adhesive layer 22, 22 or the primer layer is preferably formed of PMMA, PVC, acrylates, polyamides, polyvinyl acetates, hydrocarbon resins, polyesters, polyurethanes, chlorinated polyolefins, polypropylene, epoxy resins and/or polyurethane polyols, in particular in combination with inactivated isocyanates. The adhesive layer 22 or the primer layer can moreover contain fillers, such as for example SiO.sub.2 and/or TiO.sub.2.

(41) The layer thickness of the adhesive layer 22, 22 or the primer layer is preferably between 0.5 m and 20 m, particularly preferably between 1.5 m and 5 m. The adhesive layer or the primer layer can be produced by means of gravure printing, flexographic printing, screen printing, inkjet printing and/or by means of a slot die.

(42) Advantageously, the ink is applied to a replication layer or a replication varnish 18, 24 at least in areas. Thus a multilayer film 10 is obtained in which at least one print 100 is arranged on the replication layer 18, 24 at least in areas.

(43) The ink can be applied to a not-yet-replicated replication layer 24. The replication layer or the replication varnish 24 has in particular still-smooth surfaces. The replication is then effected in particular after the print 100 has been provided. Structures 28 can then be introduced into the print 100 and/or into the replication layer 24 through the replication. For example, a non-individualized item of information in the replication layer 18 can be combined with an individualized print 100. A replication in the print 100 can represent an additional protective measure against forgery because the print 100 is thereby yet more integrated into the overall system of the multilayer film 10.

(44) Ideally, the ink is applied to a substantially smooth surface of the replication layer 18 or the replication varnish 24, wherein the surface is then preferably replicated at a later point in time, at least in areas.

(45) It is however also possible for the ink to be applied to an already-replicated replication layer 18, thus also to a replication layer 18 which is already provided with a surface structure, a replication structure 28. The ink is preferably applied to the structured surface or to the replication structure 28, at least in areas.

(46) If the ink is applied to an already-replicated replication layer 18 or a print 100 is provided on an already-replicated replication layer 18, at least partial areas of the structures 28, in particular of the diffractive structures can then be obliterated hereby, when the ink has a refractive index similar to the replication layer 18, in particular with a refractive index with a difference of less than 0.2. This occurs in particular when the ink is applied with a layer thickness which is greater than the depth of the structures. However, it is also possible for the ink to be applied in a smaller layer thickness in such a way that the ink or the print 100 follows the topology of the structures and thus in particular becomes part of the diffraction. This is conceivable in particular when a solvent ink is used.

(47) Furthermore, the ink can also be applied in such a way that the ink or the print 100 only partially fills the replication structures 28, in particular diffractive structures on the surface of the replication layer 18. An only partial filling of the structures then occurs in particular when the finally-applied ink layer thickness is less than the depth of the replication structures 28. Under specific conditions the ink can also fill in the structures without an obliteration being optically effected. This is in particular the case when the ink has reflective or highly refractive properties and differs in its complex refractive index, in particular by more than 0.2, from the complex refractive index of the replication layer 18. An example of reflective inks are inks with metal effect pigments or metal flakes. An example of highly refractive inks are inks based on liquid crystals.

(48) An ink is preferably applied to the replication layer 18, 24 with a layer thickness which is greater than the depth of the structures to be introduced into the replication layer 18, 24. In particular, the layer thickness of the applied ink is substantially twice as thick as the layer thickness of the structures to be introduced into the replication layer 18, 24. A layer thickness of the ink that is at least twice as great as the depth of the structures to be introduced into the replication layer is advantageous when a replication is carried out only after the application of the ink. It is thereby prevented that, during the replication, the structures introduced completely penetrate the applied ink.

(49) In another embodiment example, the ink is preferably printed on with a layer thickness smaller than the depth of the structures to be introduced into the replication layer 18. During the replication, the ink can thereby be penetrated with the structures introduced through the entire layer of the print 100, whereby the print 100 can receive, through the continuous structures, a high-resolution fine structuring that is also visible from the carrier layer 12, which exceeds the print resolution of inkjet printers and thus represents a further security feature.

(50) The replication layer 18 preferably has replication structures 28 on one of its upper sides, at least in areas. Diffractively and/or refractively acting micro- and/or macrostructures are preferably molded into the replication layer 18. The replication layer 18, 24 is preferably formed of acrylate, cellulose, PMMA and/or crosslinked isocyanates. The replication layer 18, 24 can also consist of a thermoplastic varnish. A surface structure 28 is preferably molded into the varnish by means of heat and pressure through the action of a stamping tool. Furthermore, it is also possible for the replication layer 18, 24 to be formed by a UV-crosslinkable varnish and the surface structure to be molded into the replication layer 24 by means of UV replication. The surface structure is molded onto the uncured replication layer 24 by the action of a stamping tool and the replication layer 18 is cured directly during or after the molding by irradiation with UV light.

(51) In principle, the replication layer 18, 24 can be produced by means of the known printing methods. In particular, gravure printing, flexographic printing, screen printing or inkjet printing are suitable. Production by means of a slot die is, however, also possible.

(52) The surface structure or replication structure 28 molded into the replication layer 18 preferably a diffractive surface structure, for example a hologram, Kinegram or another optically diffractive active grating structure. Such surface structures typically have a spacing of the structural elements in the range of from 0.1 m to 10 m, preferably in the range of from 0.5 m to 4 m. Furthermore, it is also possible for the surface structure to be a zero-order diffraction structure. This diffraction structure preferably has, in at least one direction, a period smaller than the wavelength of visible light, between the half wavelength of visible light and the wavelength of visible light, or smaller than the half wavelength of visible light. Furthermore, it is possible for the surface structure to be a blazed grating. Particularly preferably, it is an achromatic blazed grating in this case. Such gratings preferably have, in at least one direction, a period of between 1 m and 100 m, further preferably between 2 m and 10 m. However, it is also possible for the blazed grating to be a chromatic blazed grating. Furthermore, it is preferable that the surface structure is a linear or crossed sinusoidal diffraction grating, a linear or crossed single- or multi-step rectangular grating. The period of this grating preferably lies in the range between 0.1 m and 10 m, preferably in the range 0.5 m to 4 m. Further preferably, the surface structure is an asymmetrical relief structure, for example an asymmetrical saw-tooth structure. The period of this grating preferably lies in the range between 0.1 m and 10 m, preferably in the range 0.5 m to 4 m. Further preferably, the surface structure is a light-diffracting and/or light-refracting and/or light-focusing micro- or nanostructure, a binary or continuous Fresnel lens, a binary or continuous Fresnel freeform surface; a diffractive or refractive macrostructure, in particular a lens structure or microprism structure, a mirror surface or matte structure, in particular an anisotropic or isotropic matte structure, or a combination structure of several of the above-named surface structures.

(53) The structure depth of the above-named surface structures or replication structures 28 preferably lies in the range between 10 nm and 10 m, further preferably between 100 nm and 2 m.

(54) The replication layer 18, 24 preferably has a layer thickness of between 200 nm and 5 m. If the replication layer has a diffractive surface structure, then the layer thickness is preferably between 0.3 m and 6 m. If the replication layer has coarser structures, in particular with a greater period and/or greater depth, for example a so-called surface relief, then the layer thickness is preferably between approximately 1 m and 10 m. If the replication layer has a lens-shaped surface structure, then the layer thickness is preferably between 1.5 m and 10 m.

(55) The replication or structuring of a surface of the replication layer can be effected in different ways. In the case of thermoplastic replication layers, a thermal replication is effected, in particular under the effect of heat and/or pressure. A print 100 may already have been applied to the replication layer 24 at this point in time. In this case the print 100 or the ink has substantially been applied to a smooth surface of the replication layer.

(56) It is also conceivable that a UV replication is effected. If the print 100 is formed with a UV-curable ink, the UV print can be advantageously protected with the UV-curing replication varnish 24. Reactive groups which crosslink to the UV-curable replication varnish 24 are located on the surface of the UV-curable ink. The crosslinking and thereby also the stability of especially thin prints with UV-curing inks can in particular be improved because, through encapsulation in the UV-replication varnish during the UV curing, the inhibition effects that are then active in particular in the case of thin UV-curing layers are minimized. Through the described encapsulation, a smaller layer thickness of the print formed with the UV-curing ink can also be realized without complex and expensive inertization measures.

(57) Mechanical stresses due to contact pressures and/or thermal stresses, as in the case of thermal replication, can also be reduced.

(58) Preferably, the replication layer is provided with a reflective layer which can consist of a metal layer or a metallization and/or an HRI layer with a high refractive index (HRI). The reflective layer can be opaque, semi-transparent or transparent, wherein the transparency can be, in particular, dependent on the observation angle.

(59) It is expedient if the multilayer film 100, at least in areas, has an adhesion-promoter layer which can in principle be arranged on each layer of the multilayer film 10 and/or underneath and/or on the print 100. The adhesion-promoter layer is preferably applied only in those areas to which the ink is then also applied later.

(60) The adhesion-promoter layer ensures, in particular, that there is good adhesion between the layers connected thereto. A delamination can hereby be prevented so far as possible. In particular, the adhesion-promoter layer prevents an unwanted predetermined breaking point from forming in the case of a cured print 100.

(61) In particular PVC, mixtures of thermally and UV-curing acrylates, adhesion-promoter layers with adhesion-improving surface additives, such as for example functional acrylates, hydroxy-functional copolymers, block copolymers (from e.g. BYK or TEGO), plasma and/or corona treatments and/or also seedings by metal vapor deposition are conceivable as adhesion-promoter layer.

(62) The adhesion-promoter layer can preferably be produced by means of gravure printing, screen printing, slot die, flexographic printing, inkjet printing, and/or spray varnishing. The adhesion-promoter layer preferably has a layer thickness of between 0.1 m and 1.5 m during printing. We the adhesion-promoter layer is produced by means of vapor deposition, then the layer thickness is preferably between 1 nm and 50 nm.

(63) Furthermore, the multilayer film 10 can have an anti-adhesion layer. The anti-adhesion layer can in principle be arranged on each layer of the multilayer film 10 and/or on the print 100. The anti-adhesion layer is preferably formed of silicon acrylates, fluorinated polymers and/or waxes.

(64) It is advantageous if the ink is applied to a layer of the multilayer film 10, in particular to the carrier layer 12, the detachment layer 14, the replication layer 18, the reflective layer 20, the adhesive layer 22 and/or the protective layer 16, with the interposition of at least one adhesion-promoter layer and/or anti-adhesion layer.

(65) Furthermore, the multilayer film 10 can, at least in areas, have a layer with interference pigments and/or at least one volume hologram. Preferably in addition, at least one light-absorbing, preferably an opaque, particularly preferably a black print 100 is arranged in the multilayer film 10 at least in areas.

(66) The layer with interference pigments and/or the volume hologram can also be applied over the whole surface or in the form of patches, in the form of strips or as an extensive overlay film, wherein in this case the print 100, in particular the light-absorbing and/or opaque and/or black print is formed only partially or in areas. This creates the impression that the interference pigments and/or the volume hologram are applied only locally, namely in that area which is provided by the print, because the optical effects stand out above all in that area which is provided by the print 100.

(67) Interference pigments are generally known, and have an optically variable color change effect in the case of changing observation and/or illumination angles. The pigments are often transparent or translucent and, because of this, can only be seen with difficulty on light backgrounds, or not at all, and the color change is then also correspondingly weak. Volume holograms are generally known, and have an optically variable effect in the case of changing observation and/or illumination angles. Volume holograms are often transparent or translucent and, because of this, can only be seen with difficulty on light backgrounds, or not at all, and the optically variable effect is then also correspondingly weak. The print 100 formed light-absorbing or opaque ensures in particular that the interference pigments and/or the volume hologram stand out better or become visible. The print 100 is preferably formed substantially black.

(68) FIG. 2 shows a schematic process of the application of a print 100 to a replication layer 18 or to a replication varnish 24 with subsequent replication.

(69) In a first step A, an ink is applied to a replication varnish 24 at least in areas. At least one print 100 is provided hereby.

(70) In principle, the ink according to the invention is not limited to any specific design. The ink can be formed transparent, translucent, opaque, invisible, colored and/or colorless. In principle, the print 100 is likewise limited to a specific design. The print 100 can be formed transparent, translucent, opaque, invisible, colored and/or colorless.

(71) The ink can be a fluorescent ink, both a transparent and a colored fluorescent ink, and/or a luminescent ink, both transparent and colored luminescent ink, and/or phosphorescent, including chemoluminescent inks, both transparent and colored phosphorescent ink, and/or liquid crystalline ink, in particular with dichroic color effects and/or inks with taggants and/or with laser-sensitive pigments.

(72) Both light-curing, in particular UV-curing inks and solvent and/or aqueous inks can be used.

(73) The thickness of the ink layer applied or printed preferably lies between 0.1 m and 30 m, in particular between 0.5 m and 15 m, particularly preferably between 0.5 m and 15 m and advantageously between 1 m and 3 m. If solvent and/or aqueous inks are used, the layer thickness is then preferably approximately 0.5 m. If UV-curing inks are used, the layer thickness is then approximately between 1 m and 30 m, preferably between 1 m and 15 m, particularly preferably between 1 m and 8 m.

(74) The print 100 is preferably formed through the application of a single ink. In principle, it is conceivable that in a subsequent step the print 100 is further processed, at least in areas, in particular irradiated. The optical appearance of the print 100 is hereby preferably changed in these areas. A print 100 can thus be obtained whichalthough it consists of only a single inkcomprises at least two areas which differ in their optical appearance. The print 100 can thus preferably have at least one visible and at least one invisible area.

(75) The print 100 can also be formed through the application of several inks, in particular formed differently from each other. The several inks differ from each other in particular in their optical appearance and/or their composition. The inks can thus, for example, differ from each other in their color. However, it is also conceivable that at least one of the inks used is transparent and/or invisible and at least one other ink used is formed opaque and/or visible. The inks can be printed next to each other, one on top of the other or also overlapping. In an optionally subsequent step, when a corresponding ink is used, it is possible for the print 100 to be processed and/or irradiated at least in areas, in particular in that area where the transparent ink is located. The transparent or invisible ink can hereby become visible and preferably complement a partial motif or the like produced by the visible or opaque ink, whereby in particular an overall motif appears.

(76) If several, in particular differently formed inks are applied to provide the at least one print 100, then the inks can be arranged next to each other, in particular directly next to each other, or overlapping at least in areas. The inks can however also be printed one on top of the other. The application of the several inks can be effected both simultaneously and overlapping in time and also sequentially in time. For example, in the case of inkjet printers, the application is effected sequentially in time. In particular one color per head is printed. In particular, it is not possible in this case for several heads to be in the same place at the same time. In the Hewlett Packard Indigo method, the final transfer of all the inks is preferably effected simultaneously, as the print image is printed onto a transfer blanket beforehand or is built up there from individual single-colored inks and is only subsequently transferred from this transfer blanket onto the target substrate.

(77) Steps B to D substantially represent the replication. During the replication, both at least areas of the replication layer 18 and the print 100 applied thereto are replicated. In particular, a replication which lies in register with the print 100 is thus obtained. In particular, a tolerance of replication to print is achieved within +/1.0 mm, preferably within +/0.7, particularly preferably less than +/0.4 mm.

(78) It is expedient if the ink is applied in such a way that, during a replication into the area a covered by the print 100, the replication structure 28 introduced is impressed only into the print 100, and not into the replication layer 24.

(79) Before the replication, the print 100 preferably has a thickness which is greater than the depth of the replication structure introduced into the print 100. In particular, the print has a layer thickness of between 0.5 m and 6 m. Before the replication, the layer thickness of the applied print 100 is preferably approximately twice as thick as the depth of the structure introduced into the replication layer 24.

(80) During the replication, the print 100 is preferably pressed into the replication layer 24 (step B). This is substantially to be understood to the effect that, in particular those areas a of the replication layer 24 on which the print 100 is arranged, lose layer thickness.

(81) In this case the thickness of the replication layer 24 in the area a of the print 100 decreases, preferably homogeneously or uniformly over this area. In the areas b of the replication layer 24 which, in a top view onto the multilayer film 10, are arranged adjacent to the print 100, thus adjoin the print 100, the layer thickness of the replication layer 24 decreases less as the distance from the print 100 increases, in particular during the replication. There is substantially a linear increase in the layer thicknesses.

(82) The print 100 is preferably compressed during the replication (step C). It is hereby in particular possible for the print 100, as also the replication layer 18, to be replicated together at least in areas.

(83) In a method step D, the print 100 is replicated together with the replication varnish 24. A replication structure 28 is introduced at least in areas. The replication structure 28 is advantageously introduced in such a way that an area b of the replication layer which is arranged adjacent to the print 100 in a top view onto the multilayer film 10, is not replicated. This area is referred to as a corona 26 in the present case. During a replication, the area b, the corona 26, preferably does not come into contact with a replication tool. In a top view onto the multilayer film 10, the area in particular directly adjoins the print 100. The size of the area of the replication layer which is not replicated depends in particular on the application thickness of the ink and/or the strength with which it is pressed into the replication layer 18. For example, the corona 26 substantially has a width of between 1 m and 100 m.

(84) If the ink is applied to a not-yet replicated replication layer 24, then an adhesion-promoter layer can often be dispensed with. Experience has shown that the replication of the replication layer 24 together with the print 100 brings about an improved adhesion of the print 100 on the replication layer 18. Moreover, replication together also brings about a surface roughening of the print 100, whereby subsequent layers also adhere well to the print 100.

(85) FIG. 3 shows a schematic process of production of a multilayer film 10 in one embodiment. In a first step A, a carrier layer 12 is provided. A detachment layer 14 can be applied to the carrier layer 12 at least in areas. The presence of a detachment layer is advantageous when the multilayer film 10 is formed as transfer film and the carrier layer 12 is to be removed after application of the multilayer film 10 to a substrate. However, the presence of a detachment layer 14 is not necessary. In particular when the multilayer film is formed as laminating film, a detachment layer should be dispensed with.

(86) Furthermore, a protective layer 16 is provided. A replication layer or a replication varnish 24 is then advantageously applied to the protective layer 16. The replication layer or the replication varnish 24 is preferably a layer which has not yet been replicated, thus does not yet have any replication structures 28 and/or in particular which has substantially still-smooth surfaces. At least one ink is preferably applied to the replication layer or to the replication varnish 24 by means of inkjet printing. A print 100 is provided hereby. It is pointed out that the layer thickness ratios do not necessarily correspond to the real layer thickness ratios.

(87) Now the print 100 and the replication varnish 26 or the replication layer 18 are then replicated together in a step B. A replication structure 28 is thus preferably molded or introduced into the print 100 and/or the replication layer or the replication varnish 26. Even if the replication structure 28 extends over the whole surface in step B, this is not absolutely necessary in the present case. The replication structure 28 or replication structures can also be introduced into the print 100 or into the replication layer 18 only in areas.

(88) In a step C, a reflective layer 20 is applied to the print 100 and/or to the replication layer 18 or the replication varnish 24. The reflective layer 20 is preferably a metal layer or metallization. The reflective layer 20 can be applied both in areas and over the whole surface. Advantageously, the reflective layer 20 is first applied substantially over the whole surface and then partially removed again. The lift-off method is suitable for this. This is advantageous in particular when a print 100 which is formed as a wash varnish is provided. In this case the print 100 is preferably applied in the form of a desired design and then overlaid or covered with the metallization and/or at least one further varnish. The print 100 can then be removed again by a solvent treatment, together with parts of the further layer or the further layers, with the result that the further layer or the further layers, in particular the metallization or the reflective layer 20, remain only where no print 100 was applied beforehand. For the provision of a print 100 as a wash varnish, in particular an ink which comprises polyvinylpyrrolidones and/or methyl cellulose is provided.

(89) An adhesive layer 22 is then also applied in a further step D. The adhesive layer 22 can be applied both over the whole surface and also partially.

(90) FIGS. 4 to 6 each show a schematic representation of a multilayer film 10 in an embodiment before and after laser irradiation L.

(91) An ink which comprises laser-sensitive pigments is preferably provided for this. The pigments can be, for example, ammonium octamolybdates (AOM). The laser-sensitive pigments offer the advantage that an in particular further individualization or personalization of the multilayer film 10 and/or of the print 100, 102 is hereby made possible downstream of the printing.

(92) The ink having the laser-sensitive pigments can be formed transparent or translucent or also colored at least in areas. If the laser-sensitive pigments or the ink or the print 100 comprising the laser-sensitive pigments are exposed for example to laser radiation L, then the optical appearance of the pigments in particular changes. The pigments undergo in particular a color change or a blackening.

(93) The complementary individualization or personalization can be effected both during the manufacture of the multilayer film 10 and after manufacture of the film 10, in particular after the application of the film 10 to a substrate, in particular to a security document.

(94) It is also conceivable for the print 100, 102 to be irradiated several times, whereby in particular a first complementary individualization or personalization and at least one further complementary individualization or personalization is created. The irradiations are preferably effected at different points of the print 100, 102. However, it is also possible for the irradiations or the irradiation areas to overlap.

(95) The several irradiations can all be effected during the manufacture of the multilayer film 10 or also partially during the manufacture and partially after the manufacture, in particular after an application of the multilayer film 10 to a substrate, or also all be effected after the manufacture. It is advantageous if the first complementary individualization is effected during the manufacture of the multilayer film 10 and at least one further individualization is effected after the manufacture of the film 10, in particular after the application of the film to a substrate.

(96) The print 102 represented in FIG. 4 is formed as a rectangular area. In particular, a transparent or invisible ink has been applied to a layer for this. The print 102 is thus invisible before the laser irradiation and thus is not in principle visible to a human observer. At least a part of the print 102 is irradiated with a laser L, whereby this part 104 is made visible, for example a blackening can occur. The other parts 106 of the print continue to remain invisible. In principle it is also conceivable that the print 102 was already formed visible or colored before the laser treatment L, and its optical appearance changes through the laser treatment L, whereby the irradiated area 106 differs from the remaining area 106 of the print.

(97) The print 102 represented in FIG. 5 is formed cloud-shaped. Before a laser irradiation L, the print 102 can be formed invisible. The print 102 is preferably completely irradiated with a laser whereby the print 104 becomes visible, in particular turns black. It is however also conceivable in principle that, before the laser treatment L, the print 102 is formed visible, in particular colored, and changes in its optical appearance through the laser irradiation L, in particular a color change and/or a bleaching-out and/or a blackening occurs.

(98) Several possibilities are conceivable for the production of the further or complementary individualization. One possibility consists, for example, in the application of an invisible ink. The ink can be applied either over the whole surface or in areas, in particular as a motif. The irradiation of the ink in areas or also completely is then effected subsequently. Thus either only areas of the ink or else the entire surface printed with ink are hereby made visible. It is advantageous if only areas of the applied ink are irradiated.

(99) FIG. 6 shows a print 102 which is arranged adjacent to a motif 108. The print 102 is preferably provided through the application of a transparent and/or invisible ink. The print 102 represented in FIG. 6 is thus formed transparent and/or invisible. However, the print 102 can in principle also be formed colored and/or opaque.

(100) The motif 108 can be an ink or a print within the meaning of the invention. It is however also possible for the motif 108 to be any coding, any decoration, a decorative design and/or a motif, which is arranged on any layer of the multilayer film. The motif does not have to have been created or produced in a specifically stipulated manner.

(101) The print 102 is preferably irradiated such that the irradiated area 104 of the print forms an overall motif with the visible motif 108.

(102) FIG. 7 shows a schematic top view onto a multilayer film 10 with a print 100 in an embodiment. The print 100 is formed as a code, in particular as a data matrix code, as a QR code and/or a micro QR code. The QR code as well as the micro QR code are composed of a plurality of code elements 108. It is advantageous if the individual code elements 108 are in turn composed of a plurality of ink droplets. In particular, observed in one direction, in particular in the X direction, at least 2, preferably 4 ink droplets are printed for the provision of a code element 108. In particular 22, preferably 44 ink droplets are thus printed or required for a code element in the case of two-dimensional observation. The more ink droplets, the better and the cleaner the edges of the code element 108 and thus also of the code emerge.

(103) The print 100 represented in FIG. 7 is surrounded by a corona 26. The corona 26 is in particular an area in the replication layer or the replication varnish 24, which is not provided with a replication structure. The corona 26 can promote the visibility or the recognition of the print 100. The corona 26 serves in particular as a contrast-enhancing means. The width of the corona 26 is in particular between 1 m and 100 m.

(104) FIGS. 8a to 8d show schematic top views of a print 100 in further embodiments. The prints 100 represented in FIGS. 8a to 8d are formed as micro QR codes. The micro QR code represented in FIG. 8a has 1111 code elements 108, the micro QR code represented in FIG. 8b has 1313 code elements 108, the micro QR code represented in FIG. 8c has 1515 code elements 108, and the micro QR code represented in FIG. 8d has 1717 code elements 108.

(105) The micro QR codes can have a size of 3 mm or 5 mm. If a micro OR code has an overall size of 3 mm and it comprises 1111 code elements 108, each code element 108 has a size of 272.7 m. If a micro QR code has an overall size of 3 mm and it comprises 1313 code elements 108, each code element 108 has a size of 230.8 m. If a micro QR code has an overall size of 3 mm and it comprises 1515 code elements 108, each code element 108 has a size of 200 m. If a micro QR code has an overall size of 3 mm and it comprises 1717 code elements 108, each code element 108 has a size of 176.5 m.

(106) If a micro QR code has an overall size of 5 mm and it comprises 1111 code elements 108, each code element 108 has a size of 454.5 m. If a micro QR code has an overall size of 5 mm and it comprises 1313 code elements 108, each code element 108 has a size of 384.6 m. If a micro OR code has an overall size of 5 mm and it comprises 1515 code elements 108, each code element 108 has a size of 333.3 m. If a micro QR code has an overall size of 5 mm and it comprises 1717 code elements 108, each code element 108 has a size of 294.1 m.

(107) The values are summarized in the following table:

(108) TABLE-US-00005 3 mm Micro 5 mm Micro Micro QR QR code QR code code Size of code Size of code Number of element in X element in X code elements direction (m) direction (m) 11 11 272.7 454.5 13 13 230.8 384.6 15 15 200.0 333.3 17 17 176.5 294.1

(109) Depending on how large the ink droplets are formed, the individual code elements 108 are then composed of several ink droplets. Examples of this are given in the following table:

(110) TABLE-US-00006 Micro QR Number of ink droplets from which a code 3 mm code element is composed in each case Size of an ink 11 11 code 13 13 code 15 15 code 17 17 code droplet (m) elements elements elements elements 84.7 3.22 2.73 2.36 2.08 70.6 3.87 3.27 2.83 2.50 42.3 6.44 5.45 4.72 4.17 28.2 9.66 8.18 7.09 6.25 21.2 12.88 10.90 9.45 8.34

(111) TABLE-US-00007 Micro QR Number of ink droplets from which a code 5 mm code element is composed in each case Size of an ink 11 11 code 13 13 code 15 15 code 17 17 code droplet (m) elements elements elements elements 84.7 5.37 4.54 3.94 3.47 70.6 6.44 5.45 4.72 4.17 42.3 10.74 9.09 7.87 6.95 28.2 16.11 13.63 11.81 10.42 21.2 21.47 18.17 15.75 13.90

(112) FIGS. 9a and 9b show schematic top views onto a print 100 in further embodiments. The prints 100 represented in FIGS. 9a and 9b are formed as OR codes. The QR code represented in FIG. 9a has 2222 code elements 108, and the QR code represented in FIG. 9b has 3232 code elements 108.

(113) The QR codes can have a size of 3 mm or 5 mm. If a OR code has an overall size of 3 mm and it comprises 2222 code elements 108, each code element 108 has a size of 136.4 m. If a QR code has an overall size of 3 mm and it comprises 3232 code elements 108, each code element 108 has a size of 93.8 m.

(114) If a QR code has an overall size of 5 mm and it comprises 2222 code elements 108, each code element 108 has a size of 227.3 m. If a QR code has an overall size of 5 mm and it comprises 3232 code elements 108, each code element 108 has a size of 156.3 m.

(115) The values are summarized in the following table:

(116) TABLE-US-00008 3 mm QR code 5 mm QR code QR code Size of code Size of code Number of element in X element in X code elements direction (m) direction (m) 22 22 136.4 227.3 32 32 93.8 156.3

(117) Depending on how large the ink droplets are formed, the individual code elements 108 are then composed of several ink droplets. Examples of this are given in the following table:

(118) TABLE-US-00009 Number of ink droplets from which a QR code 3 mm code element is composed in each case Size of an ink 22 22 code 32 32 code droplet (m) elements elements 84.7 1.61 1.11 70.6 1.93 1.33 42.3 3.22 2.21 28.2 4.83 3.32 21.2 6.44 4.43

(119) TABLE-US-00010 Number of ink droplets from which a QR code 5 mm code element is composed in each case Size of an ink 22 22 code 32 32 code droplet (m) elements elements 84.7 2.68 1.85 70.6 3.22 2.21 42.3 5.37 3.69 28.2 8.05 5.54 21.2 10.74 7.38

(120) FIG. 10a shows a microscope image (100) of a 3 mm QR code with 3232 code elements, wherein the QR code has been printed with 600 dpi. FIG. 10b shows a microscope image (100) of a 5 mm QR code with 3232 code elements, wherein the QR code has been printed with 600 dpi. Values or dimensions of individual code elements are represented in the figures.

LIST OF REFERENCE NUMBERS

(121) 10 multilayer film 12 carrier layer 14, 14 detachment layer (over the whole surface, partial) 16 protective (varnish) layer 18 replication layer 20 reflective layer 22, 22 adhesive layer (over the whole surface, partial) 24 replication varnish (non-replicated replication layer) 26 corona 28 replication structure 30 (partial) marking/(partial) motif 100 print 102 print before laser treatment 104 visible area of the print after laser treatment 106 non-visible area of the print after laser treatment 108 code element a printed-over area b width of corona L laser treatment