Multilayer element and method for producing same

Abstract

A method for producing a multilayer body, with the steps: a) providing a first printed layer; b) partially applying a second printed layer to the first printed layer; c) structuring the first printed layer using the second printed layer as a mask. A multilayer body obtainable in this way and a security document with such a multilayer body.

Claims

1. A method for producing a multilayer body, comprising: a) providing a first printed layer; b) partially applying a second printed layer to the first printed layer; c) structuring the first printed layer using the second printed layer as a mask, whereby areas of the first printed layer which are not covered by the second printed layer are removed leaving areas of the first printed layer covered by the second printed layer to form a motif having areas of the first printed layer covered by the second printed layer formed in a substantially congruent relationship with the second printed layer after the structuring of the first printed layer; and d) applying a layer composite to the motif, the layer composite being applied to at least one of the areas of the first printed layer covered by the second printed layer or the second printed layer after the structuring of the first printed layer using the second printed layer as a mask, the layer composite comprising one or more of the following layers: a carrier ply, a replication layer with a surface relief, a reflective layer, a protective layer, a volume hologram layer, wherein the multilayer body comprises the motif, and wherein, to provide the first printed layer, a first varnish is used which reacts chemically, in a crosslinking reaction, with a second varnish used for the application of the second printed layer, and wherein the second varnish is a PVC mixed polymer of vinyl chloride, vinyl acetate and dicarboxylic acid, or wherein the second varnish is a polyester varnish with cellulose propionate.

2. The method according to claim 1, wherein the first varnish is a water-based or solvent-based alkali-soluble varnish.

3. The method according to claim 1, wherein the first varnish comprises at least one of the following: colored pigments, achromatic pigments, effect pigments, UV-excitable fluorescent pigments, thin-film systems, cholesteric liquid crystals, dyestuffs, metallic nanoparticles, non-metallic nanoparticles.

4. The method according to claim 1, wherein the second varnish is a PVC mixed polymer of vinyl chloride, vinyl acetate and dicarboxylic acid.

5. The method according to claim 1, wherein the second varnish is a polyester varnish with cellulose propionate.

6. The method according to claim 1, wherein the second varnish comprises polyisocyanate and/or polyaziridine.

7. The method according to claim 1, wherein the first printed layer is structured by the action of an alkali etchant comprising alkali hydroxide or alkali carbonate.

8. The method according to claim 7, wherein the alkaline etchant is used in a concentration of from 0.5% to 3%, and/or at a temperature of from 20° C. to 50° C., and/or for a period of from 0.5 s to 5 s.

9. The method according to claim 1, wherein the first printed layer is applied multicolored in the form of a color progression, color gradient or true-color image.

10. The method according to claim 1, wherein the first printed layer is applied in the form of a line grid with 60 lines/cm to 120 lines/cm and/or a line depth of from 15 μm to 45 μm.

11. The method according to claim 1, wherein the first printed layer is applied in the form of a diagonally crossed grid with a grid width of from 40 ink cells/cm to 100 ink cells/cm and/or a depth of from 15 μm to 45 μm.

12. The method according to claim 1, wherein the first and/or second printed layer is applied by gravure printing.

13. The method according to claim 1, wherein the first and/or second printed layer is applied by screen printing, with a mesh size of from 90 T to 140 T or 90 S to 140 S.

14. The method according to claim 1, wherein the second printed layer is applied in the form of a graphic motif, alphanumeric character, logo, image, or guilloche pattern.

15. The method according to claim 1, wherein the layer composite is applied to the at least one of the first printed layer or the second printed layer after the step of structuring the first printed layer using the second printed layer as a mask.

16. The method according to claim 15, wherein the layer composite comprises at least one varnish layer with a UV blocker.

17. The method according to claim 16, wherein the varnish layer with the UV blocker is applied in the form of a graphic motif, alphanumeric character, logo, image, or guilloche pattern.

18. The method according to claim 1, wherein, before the application of the layer composite, a height-compensation layer of a varnish made of a combination of butyl acrylate and PMMA with a layer thickness of from 0.5 μm to 3 μm is applied to the first and/or second printed layer.

19. The method according to claim 1, wherein the layer composite comprises a reflective metal layer, the reflective metal layer comprising at least one of the following: aluminum, copper, chromium, silver, gold and alloys thereof, and the method further comprises: structuring the reflective metal layer of the layer composite using the second printed layer as a mask.

20. The method according to claim 19, wherein, for the structuring of the metal layer, a photoresist layer is applied to the metal layer, is exposed from the side of the second printed layer and is removed in the exposed areas during the developing.

21. The method according to claim 20, wherein, after the developing of the photoresist layer, the metal layer is structured by etching.

22. The method according to claim 20, wherein the first and/or second printed layer comprises a UV blocker, which absorbs UV light in a wavelength range in which the photoresist layer is exposed.

23. A method for producing a multilayer body, comprising: providing a layer composite having one or more of the following layers: a carrier ply, a replication layer with a surface relief, a reflective layer, a protective layer, a volume hologram layer; applying a first printed layer to a surface of the layer composite; partially applying a second printed layer to the first printed layer; structuring the first printed layer using the second printed layer as a mask, whereby areas of the first printed layer which are not covered by the second printed layer are removed leaving areas of the first printed layer covered by the second printed layer so that areas of the first printed layer covered by the second printed layer are formed in a substantially congruent relationship with the second printed layer after the structuring of the first printed layer, wherein the multilayer body comprises the areas of the first printed layer covered by the second printed layer, the second printed layer and the layer composite, and wherein, to provide the first printed layer, a first varnish is used which reacts chemically, in a crosslinking reaction, with a second varnish used for the application of the second printed layer, and wherein the second varnish is a PVC mixed polymer of vinyl chloride, vinyl acetate and dicarboxylic acid, or wherein the second varnish is a polyester varnish with cellulose propionate.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The invention is now explained in more detail with reference to embodiment examples. There are shown in:

(2) FIG. 1 a first intermediate product during the production of an embodiment example of a multilayer body in a schematic sectional representation;

(3) FIG. 2 a second intermediate product during the production of an embodiment example of a multilayer body in a schematic sectional representation;

(4) FIG. 3 an embodiment example of a multilayer body in a schematic sectional representation;

(5) FIG. 4 a schematic top view of a first printed layer of an embodiment example of a multilayer body before the structuring;

(6) FIG. 5 a schematic top view of a first and second printed layer of an embodiment example of a multilayer body before the structuring;

(7) FIG. 6 a schematic top view of a first and second printed layer of an embodiment example of a multilayer body after the structuring;

(8) FIG. 7 a schematic top view of a first printed layer of a further embodiment example of a multilayer body before the structuring;

(9) FIG. 8 a schematic top view of a first and second printed layer of a further embodiment example of a multilayer body before the structuring;

(10) FIG. 9 a schematic top view of a first and second printed layer of a further embodiment example of a multilayer body after the structuring.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

(11) During the production of a multilayer body 1 shown as a whole in FIG. 3, a layer composite 11 is provided first of all, which comprises a carrier ply 111, a detachment layer 112, a protective layer 113, a replication layer 114, a reflective layer 115 and a further protective layer 116.

(12) The carrier ply 111 is detachable from the layer composite 11 and in particular consists of PET (polyethylene terephthalate) with a layer thickness of from 6 μm to 50 μm, preferably from 12 μm to 50 μm.

(13) The carrier ply 111 protects and stabilizes the multilayer body 1 during its production and further processing and can be removed when the multilayer body 1 is affixed to a security document.

(14) The detachment layer 112 makes it possible to detach the carrier ply 111 from the rest of the layer composite 11 and consists, for example, of a wax with a layer thickness of from 50 nm to 500 nm, preferably 70 nm to 150 nm. The detachment layer can alternatively also consist of a strongly filming acrylate and/or also be part of the protective varnish layer, with a layer thickness of from 1 μm to 5 μm, preferably 1 μm to 3 μm.

(15) The protective layers 113 and 116 form protective surfaces of the layer composite 11 and preferably consist of a clear varnish, for example of a UV-curing varnish, of PVC, polyester or an acrylate, with a layer thickness of from 0.5 μm to 10 μm, preferably 1 μm to 5 μm.

(16) The replication layer 114 preferably consists of an acrylate with a layer thickness of from 1 μm to 5 μm, preferably from 1 μm to 3 μm.

(17) A surface relief which forms an optically variable effect is molded into a surface of the replication layer 114. In particular, it is preferably a hologram, Kinegram® or Trustseal®, a preferably linear or crossed sinusoidal diffraction grating, a linear or crossed single- or multi-step rectangular grating, a zero-order diffraction structure, an asymmetrical relief structure, a blazed grating, a preferably isotropic or anisotropic mat structure, or 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 microprism structure or a combination structure thereof.

(18) The metal layer 115 is at least partially deposited on the surface of the replication layer and in particular consists of aluminum, copper, chromium, silver and/or gold or of alloys of the above-named metals, with a layer thickness of from 5 nm to 100 nm, preferably from 10 nm to 50 nm.

(19) As FIG. 1 shows, a first printed layer 12 is then printed flat on a surface of the protective layer 116.

(20) A water-based or solvent-based alkali-soluble varnish is preferably used for the printing of the first printed layer 12. For example, the varnish can consist of polyacrylic acid. Such a varnish can be removed from its substrate by the treatment with an alkaline etchant. This makes a later structuring of the first printed layer 12 possible.

(21) It is further preferred if the varnish of the first printed layer 12 comprises dyes, in particular colored or achromatic pigments and/or effect pigments, UV-excitable fluorescent pigments, thin-film pigments, cholesteric liquid crystal pigments, dyestuffs and/or metallic or non-metallic nanoparticles.

(22) A colored pigment in a proportion of between 5% and 35%, in particular between 10% and 25%, in the varnish used for the printing of the first printed layer 12 is, for example, a UV-luminescent pigment with one or more excitation wavelengths, for example 254 nm and/or 365 nm. Such a pigment is, e.g., Lumilux Blau CD 710 (fluorescing blue at 365 nm and at 254 nm) or BF1 (from Honeywell Specialty Chemicals or Microalarm, Hungary) (fluorescing green at 365 nm, fluorescing red/orange at 254 nm). All known organic colored pigments or dyestuffs can be used for the visible spectral range.

(23) The first printed layer 12 is preferably applied multicolored, in particular in the form of a color progression, color gradient or as a true-color image.

(24) As the first printed layer 12 is applied flat, high-resolution and sharply defined color progressions, gradients or true-color images can thus be generated.

(25) The first printed layer 12 is preferably applied using gravure printing in the form of a grid, in particular a line grid with 60 lines/cm to 120 lines/cm and/or a line depth of from 15 μm to 45 μm.

(26) Alternatively, the first printed layer 12 can be applied in the form of a grid, in particular a diagonally crossed grid with a grid width of from 40 ink cells/cm to 100 ink cells/cm and/or a depth of from 15 μm to 45 μm.

(27) Alternatively, the first printed layer 12 can be applied by screen printing, in particular with a mesh size of from 90 T to 140 T or 90 S to 140 S.

(28) Grids with a minimum dot size of 75 μm and a minimum dot spacing of 10 μm can be realized both using gravure printing and using screen printing.

(29) The first printed layer 12 thus provides the coloring of the resulting motif desired in the final multilayer body 1, but does not yet have the final contour of this motif.

(30) Two examples of the design of the first printed layer 12 are shown in FIGS. 4 and 7.

(31) In the embodiment example according to FIG. 4, the printed layer 12 has a color gradient which runs diagonally over the printed surface.

(32) In the embodiment example according to FIG. 7, the first printed layer 12 comprises a first partial area 121 and a second partial area 122. In both partial areas 121, 122, the varnish used comprises a pigment visible in the visible spectral range and/or a dyestuff, as well as dyes fluorescing under ultraviolet light. A motif recognizable in ultraviolet light (UV light) which is also recognizable in visible light is thereby created.

(33) However, the pigments and/or dyestuffs visible in the visible spectral range are preferably to be admixed in only a small proportion in order not to weaken the luminescence of the UV-luminescent pigments and/or dyestuffs in UV light too much. The pigments and/or dyestuffs visible in the visible spectral range are usually black in UV light, i.e. absorb the UV light, and thereby weaken the UV luminescence of neighboring UV-luminescent pigments and/or dyestuffs in the varnish.

(34) In the first partial area 121 and in the second partial area 122, in each case, a UV ink can be mixed into a different visible pigment and/or dyestuff, with the result that the polychromatism of the motif also appears correspondingly under UV light, but also appears in different colors under visible light.

(35) However, it is also possible to mix the same visible pigments and/or dyestuffs into all UV inks, with the result that a monochromatic motif results in visible light, which appears multicolored only in UV light.

(36) After the application of the first printed layer 12, a second printed layer 13 is applied to the first printed layer 12. This is represented in sectional representation in FIG. 2 and in top view in FIGS. 5 and 8.

(37) Unlike the first printed layer 12, the second printed layer 13 is printed monochromatically, thus in full tone. Fine line structures, such as for example guilloche patterns, can thereby be realized. In FIGS. 5 and 8 the printed layer 13 is shown opaque and black merely for the purpose of representation. The printed layer 13, however, can also be dyed transparent, translucent, or transparent or translucent.

(38) Here too, the printing can be effected using gravure printing or screen printing. During the printing of the second printed layer 13, a minimum line thickness of 80 μm with a minimum line spacing of 100 μm can be achieved.

(39) The varnish used for the printing of the second printed layer 13 is, for example, a solvent-based varnish made of a PVC mixed polymer of vinyl chloride, vinyl acetate, dicarboxylic acid and a crosslinker, e.g. polyisocyanate or polyaziridine. Alternatively, varnish made of polyester and cellulose propionate and a crosslinker can also be used. If such a varnish is applied to the above-described acrylic varnish used for the printing of the first printed layer 12, this crosslinker reacts with the acrylic acid in this varnish and thereby makes the latter alkali-resistant and thus resistant to a subsequent etching step.

(40) The printing of the second printed layer 13 is followed by a treatment with a preferably alkaline etchant, for example with alkali hydroxide (NaOH) or alkali carbonate (Na.sub.2CO.sub.3).

(41) It is advantageous if the alkaline etchant is used in a concentration of from 0.5% to 3%, and/or at a temperature of from 20° C. to 50° C., and/or for a period of from 0.5 s to 5 s.

(42) Additionally, the etching process can be promoted by agitating the etchant, targeted flow of the etchant against the first printed layer, sonication, brushing and/or smearing.

(43) Through this treatment, the first printed layer 12 is removed completely and with defined edges in the areas in which it is not covered by the second printed layer 13. The multilayer body 1 shown in cross section in FIG. 3 and in top view in FIGS. 6 and 9 is thus obtained.

(44) The first printed layer 12 thus provides the final coloring of the printed motif, while the contour of the motif is defined by the second printed layer 13 and the etching step. High-resolution multicolored line patterns with defined edges can thus be generated.

(45) It is likewise possible to invert the sequence of the production steps and to mold and structure the printed layers 12 and 13 first. The layer composite 11 is then subsequently applied to the printed layers 12, 13.

(46) However, care is to be taken that, before the application of the layer composite 11, a height-compensation layer should be provided, so that any height differences present in the partial printed layers 12, 13 do not impede subsequent process steps, in particular a replication.

(47) In this case, it is then also possible to use the thus-created motif made of the printed layers 12, 13 as a mask for a further exposure step. A prerequisite for this is merely that the motif is partially impermeable for the exposure radiation, through the use of pigments, dyestuffs and/or transparent blockers, in particular UV blockers. In particular, UV-luminescent pigments and dyestuffs which can already be provided in the printed layers 12, 13 absorb the UV radiation and thus advantageously already act in this way as UV blockers during a subsequent exposure.

(48) It would thus be possible, for example, to apply a replication layer 114 and mold a surface relief after the structuring of the printed layers 12, 13. A metal layer 115 can then be applied, for example by vapor deposition, sputtering, chemical vapor deposition or the like.

(49) To this metal layer 115 a photoresist is then applied and exposed from sides of the motif formed by the printed layers 12 and 13 through the motif and the metal layer 115.

(50) During the subsequent developing of the photoresist, the non-crosslinked/exposed portions of the photoresist are removed. This thus now covers the metal layer 115 congruent and registered relative to the printed layers 12 and 13. The metal layer can now be partially demetalized in a further etching step, with the result that the metal is likewise present congruent with the printed layers 12, 13.

(51) A partial metal layer 115 is thereby obtained which is molded perfectly registered relative to the motif formed by the printed layers 12, 13. The metal layer 115 can strengthen the optical effect of this motif during irradiation with UV light, as the metal layer 115 itself appears black in UV light and thus increases the optical contrast and at the same time reflects portions of the UV light back into the printed layers 12, 13 on the rear side.

(52) The optical effect of the multilayer body 1 can furthermore be significantly modified by combining the printed layers 12, 13 with layers which are transparent in the visible range, but block specific spectral ranges in the UV range. This makes sense in particular if the printed layer 12 contains UV-fluorescent dyes.

(53) For example, a PET film blocks the spectral range below a wavelength of 310 nm. Thus the optical effect can, e.g., look different during excitation of the dyes in the printed layer 12 with a light wavelength of 365 nm from the front side and with a light wavelength of 254 nm from the rear side of the multilayer body 1.

(54) However, it is likewise also possible to print corresponding transparent varnishes with UV blockers in a further motif such that the optical effect of the printed layer 12 only becomes visible in areas and depending on the UV wavelength.

(55) The second printed layer 13 can optionally also have such a UV blocker. This can be, for example, benzophenone-6.

(56) The second printed layer 13 can furthermore also be dyed with pigments and/or dyestuffs which are visible in the visible spectral range. An example is to print the first printed layer 12 with a translucent optically variable pigment such as for example Iriodin® from Merck or Lumina® from BASF.

(57) The second printed layer 13 is then printed overlapping with the first printed layer 12 only in areas and the Iriodin is removed where the second printed layer 13 is not present.

(58) The result is a motif in the color of the second printed layer 13 which is covered in areas with the Iriodin of the first printed layer 12. The Iriodin and the second printed layer 13 are arranged perfectly registered.

(59) A metameric color effect results in which, depending on the viewing angle, the surfaces without Iriodin look almost identical or differ from each other at a different viewing angle because of the transparence and simultaneous optical variability of the Iriodin.

LIST OF REFERENCE NUMBERS

(60) 1 multilayer body 11 layer composite 111 carrier ply 112 detachment layer 113 protective layer 114 replication layer 115 metal layer 116 protective layer 12 first printed layer 121 first area 122 second area 13 second printed layer