阅读说明：本技术 逆反射膜、膜、数据载体和应用 (Retroreflective film, data carrier and use ) 是由 M.R.J.谢雷尔 R.德梅尔 K.H.谢雷尔 于 2019-04-29 设计创作，主要内容包括：本发明涉及一种逆反射膜(28),其具有预先确定的区域,这些区域在漫反射中、尤其在日光下观察时向观察者显现视觉可识别的第一颜色并且在逆反射中、尤其在夜间在前照灯光下观察时向观察者显现视觉可识别的第二颜色,所述逆反射膜包括具有逆反射结构(34)的层和面向观察者的半透明功能层(31),该半透明功能层具有如下特性,即该半透明功能层在反射光中观察时具有视觉可识别的第一颜色并且在透射光中观察时具有视觉可识别的第二颜色。(The invention relates to a retroreflective film (28) having predetermined regions which, in diffuse reflection, in particular when viewed in daylight, exhibit a visually recognizable first color and, in retroreflective reflection, in particular at night, when viewed in front-lighting, exhibit a visually recognizable second color, the retroreflective film comprising a layer having a retroreflective structure (34) and a translucent functional layer (31) facing the viewer, the translucent functional layer having the property that the translucent functional layer has the visually recognizable first color when viewed in reflected light and the visually recognizable second color when viewed in transmitted light.)

1. A retroreflective film having predetermined regions which, in diffuse reflection, in particular when viewed in daylight, exhibit a visually recognizable first color to an observer and, in retroreflective reflection, in particular at night, exhibit a visually recognizable second color to an observer when viewed in front lighting, comprising a layer having a retroreflective structure and a translucent functional layer facing the observer, the translucent functional layer having the property that the translucent functional layer has a visually recognizable first color when viewed in retroreflective light and a visually recognizable second color when viewed in transmitted light.

2. The retroreflective film of claim 1, wherein the retroreflective structures are based on triangular or square cube-pyramids or on microglass beads and are in particular metallized.

3. The retroreflective film of claim 1 or 2, wherein the translucent functional layer has a multilayer structure having two translucent metal layers and a dielectric layer disposed between the two translucent metal layers.

4. The retroreflective film of claim 3 wherein the two translucent metal layers are independently of each other comprised of a metal selected from the group consisting of Al, Ag, Ni, Cr, Cu, Au, and alloys of one or more of the foregoing, and the dielectric layer is SiO₂Layer, ZnO layer, Al₂O₃Layer, TiO₂Layer, layer consisting of a nitride or oxynitride of one of the elements Si, Zn, Al or Ti, or MgF₂A layer or a layer of nitrocellulose, for example, obtainable by printing techniques.

5. The retroreflective film of claim 3 or 4, wherein the two translucent metal layers are independently selected from Al or Ag and the dielectric layer is SiO₂And (3) a layer.

6. The retroreflective film of claim 1 or 2, wherein the translucent functional layer is obtainable on printing technology by means of an effect pigment composition.

7. The retroreflective film of claim 1 or 2, wherein the translucent functional layer has a multilayer structure based on an interference layer consisting of only transparent layers, wherein the multilayer structure is based in particular on preferably alternating layers of TiO₂、Al₂O₃Or layers of other dielectrics.

8. The retroreflective film of claim 1 or 2, wherein the translucent functional layer is based on a plasmonic color filter and in particular on two-dimensional periodic nanostructures. Plasmonic color filters based on two-dimensional periodic nanostructures are known, for example, from patent document DE 102011101635a 1.

9. The retroreflective film of any of claims 1-8, wherein the predetermined areas appear golden to an observer in diffuse reflection, particularly when viewed in sunlight, and blue in reverse reflection, particularly when viewed at night in front lighting.

10. The retroreflective film of any of claims 1-9, wherein the predetermined areas constitute indicia in the form of patterns, characters, or codes that are not recognizable to an observer in diffuse reflection, particularly when viewed in daylight, and are not recognizable to an observer in reverse reflection, particularly when viewed under front lighting at night.

11. The retroreflective film of claim 10, wherein the indicia in the form of patterns, characters or codes are formed by recesses in an opaque layer arranged between the translucent functional layer and the layer having the retroreflective structure, wherein the opaque layer is in particular a metallized layer or a pigment layer.

12. The retroreflective film of any of claims 1-11, wherein the film has the following structure:

-an adhesive layer;

-a layer having a retroreflective structure;

-an optional opaque layer having a space in the form of a pattern, character or code;

-a translucent functional layer;

-a carrier film.

13. The retroreflective film of any of claims 1-12, wherein the film has the following structure:

-an adhesive layer;

-a layer having a retroreflective structure;

-a carrier film;

-a translucent functional layer;

wherein optionally an opaque layer with recesses in the form of patterns, characters or codes is arranged either between the layer with the retroreflective structure and the carrier film or between the carrier film and the translucent functional layer.

14. Retroreflective film according to claim 12 or 13, wherein an embossing lacquer layer is arranged between the carrier film and the translucent functional layer, which embossing lacquer layer has an embossed relief, wherein the embossed relief is in particular a micro-structured and/or nano-structured relief.

15. Use of a retroreflective film according to any of claims 1 to 14 for the manufacture of a number plate or license plate, traffic sign or sign, billboard or advertising surface or safety clothing.

16. A film for protecting a data carrier provided with a retroreflective structure, wherein the film has predetermined regions which appear to an observer in diffuse reflection, in particular in daylight, in a visually recognizable first color and in inverse reflection, in particular at night, in a visually recognizable second color, in front lighting, and wherein the predetermined regions preferably form markings in the form of patterns, characters or codes which are not recognizable to the observer in diffuse reflection, in particular in daylight, and which are recognizable to the observer in inverse reflection, in particular at night, in front lighting, wherein the film comprises an adhesive layer suitable for adhering the film to the data carrier provided with the retroreflective structure to be protected and a functional layer facing the observer, and the translucent functional layer has the property that it has a visually recognizable first color when viewed in reflected light and a visually recognizable second color when viewed in transmitted light.

17. Film according to claim 16, wherein the predetermined areas constitute indicia in the form of patterns, characters or codes which are not recognizable by a viewer in diffuse reflection, in particular when viewed in daylight, and which are recognizable by a viewer in reverse reflection, in particular when viewed at night in front lighting, and the indicia in the form of patterns, characters or codes are formed by a recess in an opaque layer which is arranged between the translucent functional layer and the adhesive layer.

18. The film according to claim 16 or 17, wherein the translucent functional layer has a multilayer structure having two translucent metal layers and a dielectric layer disposed between the two translucent metal layers.

19. A film according to claim 18 wherein the two semi-transparent metal layers are independently of each other composed of a metal and the metals are each selected from Al, Ag, Ni, Cr, Cu, Au, Si and alloys of one or more of the foregoing and the dielectric layer is SiO₂Layer, ZnO layer, ZnS layer, Al₂O₃Layer, TiO₂Layer, layer consisting of a nitride or oxynitride of one of the elements Si, Zn, Al or Ti, or MgF₂A layer or a layer of nitrocellulose, for example, obtainable by printing techniques.

20. A film according to claim 18 or 19, wherein the two semi-transparent metal layers are selected independently of each other from Al or Ag, and the dielectric layer is SiO₂And (3) a layer.

21. The film according to any one of claims 1 to 6, wherein the translucent functional layer is obtainable by means of an effect pigment composition on a printing technique.

22. Film according to claim 16 or 17, wherein the semi-transparent functional layer has a multilayer structure based on an interference layer consisting only of transparent layers, wherein the multilayer structure is based in particular on preferably alternating layers of TiO₂、Al₂O₃Or layers of other dielectrics.

23. The film according to claim 16 or 17, wherein the semi-transparent functional layer is based on a plasmonic color filter and in particular on two-dimensional periodic nanostructures. Plasmonic color filters based on two-dimensional periodic nanostructures are known, for example, from patent document DE 102011101635a 1.

24. The film according to any one of claims 16 to 23, wherein the predetermined areas appear golden to an observer in diffuse reflection, in particular when viewed in daylight, and blue to an observer in back reflection, in particular when viewed under headlight light at night.

25. The film according to any one of claims 16 to 24, wherein the film has the structure:

-an adhesive layer;

-an optional opaque layer having a space in the form of a pattern, character or code;

-a translucent functional layer;

-a carrier film.

26. A data carrier, in particular a number plate or license plate, traffic plate or sign, advertising panel or advertising surface or security suit, equipped with a retroreflective structure, comprising a film according to any one of claims 16 to 25.

27. Use of a film according to any of claims 16 to 25 for protecting data carriers, in particular number plates or license plates, traffic panels or traffic signs, advertising panels or advertising surfaces or safety gear, which are equipped with retroreflective structures.

Disclosure of Invention

(first aspect of the present invention) a retroreflective film having predetermined regions which appear to a viewer in diffuse reflection, particularly when viewed in daylight, in a visually recognizable first color and which appear to a viewer in retroreflective, particularly when viewed at night in front lighting, in a visually recognizable second color, said retroreflective film comprising a layer having a retroreflective structure and a translucent functional layer facing the viewer, the translucent functional layer having the property that the translucent functional layer has the visually recognizable first color when viewed in reflected light and the visually recognizable second color when viewed in transmitted light.

The retroreflective structure is preferably selected from retroreflective glass spheres or embossed structures. It is particularly preferred that the retroreflective structure is based on microprisms which are provided with a metallized layer, in particular a specularly reflective metal coating.

(preferred design) the retroreflective film according to clause 1, wherein the retroreflective structures are based on triangular or square cube-pyramids or on microglass beads and are in particular metallized.

(preferred design) the retroreflective film according to clause 1 or 2, wherein the translucent functional layer has a multilayer structure having two translucent metal layers and a dielectric layer disposed between the two translucent metal layers.

(preferred design) the retroreflective film according to clause 3, wherein the two translucent metal layers are composed of metals independently of each other, and the metals are respectively selected from the group consisting of Al, Ag, Ni, Cr, Cu, Au, Si, and alloys of one or more of the foregoing elements, and the dielectric layer is SiO₂Layer, ZnO layer, ZnS layer, Al₂O₃Layer, TiO₂Layer, layer consisting of a nitride or oxynitride of one of the elements Si, Zn, Al or Ti, or MgF₂A layer or a layer of nitrocellulose, for example, obtainable by printing techniques.

(preferred design) the retroreflective film according to clause 3 or 4, wherein the two translucent metal layers are selected independently of each other from Al or Ag, and the dielectric layer is SiO₂And (3) a layer.

(preferred design) the retroreflective film according to clause 1 or 2, wherein the translucent functional layer can be obtained on printing technology with the aid of an effect pigment (effect) composition.

(preferred embodiment) the retroreflective film according to clause 1 or 2, wherein the translucent functional layer has a multilayer structure based on an interference layer consisting only of transparent layers, wherein the multilayer structure is based in particular on preferably alternating interference layers consisting of TiO₂、Al₂O₃Or layers of other dielectrics.

(preferred design) the retroreflective film according to clause 1 or 2, wherein the translucent functional layer is based on a plasmon (plasmon) color filter and in particular on two-dimensional periodic nanostructures. Plasmonic color filters based on two-dimensional periodic nanostructures are known, for example, from patent document DE 102011101635a 1.

(preferred design) the retroreflective film according to one of clauses 1 to 8, wherein the predetermined region appears golden to the viewer in diffuse reflection, particularly when viewed in daylight, and blue to the viewer in reverse reflection, particularly when viewed at night under front lighting.

(preferred design) the retroreflective film according to one of clauses 1 to 9, wherein the predetermined areas constitute indicia in the form of patterns, characters or codes that are not recognizable to an observer in diffuse reflection, especially when viewed in daylight, and are not recognizable to an observer in reverse reflection, especially when viewed at night in a headlight.

(preferred design) the retroreflective film according to clause 10, wherein the indicia in the form of patterns, characters or codes are formed by a recess in an opaque layer arranged between the translucent functional layer and the layer having the retroreflective structure, wherein the opaque layer is in particular a metallized layer or a pigment layer (farbsticht).

(preferred design) the retroreflective film of any of clauses 1-11, wherein the film has the following structure:

-an adhesive layer;

-a layer having a retroreflective structure;

-an optional opaque layer having a space in the form of a pattern, character or code;

-a translucent functional layer;

-a carrier film.

(preferred design) the retroreflective film of any of clauses 1-12, wherein the film has the following structure:

-an adhesive layer;

-a layer having a retroreflective structure;

-a carrier film;

-a translucent functional layer;

wherein optionally an opaque layer with recesses in the form of patterns, characters or codes is arranged either between the layer with the retroreflective structure and the carrier film or between the carrier film and the translucent functional layer.

(preferred embodiment) the retroreflective film according to clause 12 or 13, wherein an embossing lacquer layer having an embossed relief is arranged between the carrier film and the translucent functional layer, wherein the embossed relief is in particular a micro-structured and/or nano-structured relief.

(second aspect of the invention) use of a retroreflective film according to one of clauses 1 to 14 for the manufacture of a number plate or license plate, traffic board or sign, advertising board or surface or safety gear.

(third aspect of the invention) a film for protecting a data carrier provided with a retroreflective structure, wherein the film has predetermined regions which appear to an observer in diffuse reflection, in particular when viewed in daylight, in a visually recognizable first color and in inverse reflection, in particular when viewed at night in front lighting, in a visually recognizable second color, and wherein the predetermined regions preferably form markings in the form of patterns, characters or codes which are not recognizable by an observer in diffuse reflection, in particular when viewed in daylight, and which are recognizable by an observer in inverse reflection, in particular when viewed at night in front lighting, wherein the film comprises an adhesive layer suitable for adhering the film to the data carrier provided with a retroreflective structure to be protected and a translucent functional layer facing the observer, and the translucent functional layer has the property that it has a visually recognizable first color when viewed in reflected light and a visually recognizable second color when viewed in transmitted light.

Preferably, the retroreflective structures of the data carrier are based on reflective microstructures, in particular in the form of triangular or square cube-corner retroreflective structures or in the form of microglass bead-based retroreflective structures, wherein the reflective microstructures are preferably provided with a metallized layer, further preferably a specularly reflective metal coating.

(preferred design) the film according to clause 16, wherein the predetermined area constitutes indicia in the form of a pattern, character or code, which indicia is not recognizable by an observer in diffuse reflection, especially when viewed in daylight, and is not recognizable by an observer in reverse reflection, especially when viewed at night under headlight, and the indicia in the form of a pattern, character or code is formed by a margin in an opaque layer, which is disposed between the translucent functional layer and the adhesive layer.

(preferred design) the film according to clause 16 or 17, wherein the translucent functional layer has a multilayer structure having two translucent metal layers and a dielectric layer disposed between the two translucent metal layers.

(preferred design) the film according to clause 18, wherein the two translucent metal layers are composed of metals independently of one another, and the metals are each selected from the group consisting of Al, Ag, Ni, Cr, Cu, Au, Si and alloys of one or more of the foregoing elements, and the dielectric layer is SiO₂Layer, ZnO layer, ZnS layer, Al₂O₃Layer, TiO₂Layer, layer consisting of a nitride or oxynitride of one of the elements Si, Zn, Al or Ti, or MgF₂A layer or a layer of nitrocellulose, for example, obtainable by printing techniques.

(preferred design) the film according to clause 18 or 19, wherein the two semitransparent metallic layers are selected independently of each other from Al or Ag, and the dielectric layer is SiO₂And (3) a layer.

(preferred embodiment) the film according to one of clauses 1 to 6, wherein the translucent functional layer is obtainable in printing technology by means of an effect pigment composition.

(preferred embodiment) the film according to clause 16 or 17, wherein the translucent functional layer has a multilayer structure based on an interference layer consisting only of transparent layers, wherein the multilayer structure is based in particular on preferably alternating layers of TiO₂、Al₂O₃Or layers of other dielectrics.

(preferred design) the film according to clause 16 or 17, wherein the translucent functional layer is based on a plasmonic filter and in particular on two-dimensional periodic nanostructures. Plasmonic color filters based on two-dimensional periodic nanostructures are known, for example, from patent document DE 102011101635a 1.

(preferred design) the film according to one of clauses 16 to 23, wherein the predetermined area appears golden to the viewer in diffuse illumination, especially when viewed in daylight, and blue to the viewer when illuminated with a point-like light source, especially when viewed in a dim space with a flashlight of a smartphone.

(preferred design) the film according to one of clauses 16 to 24, wherein the film has the following structure:

-an adhesive layer;

-an optional opaque layer having a space in the form of a pattern, character or code;

-a translucent functional layer;

-a carrier film.

(fourth aspect of the invention) a data carrier, in particular a number plate or license plate, traffic plate or sign, advertising plate or surface or security suit, equipped with a retroreflective structure, comprising a film according to one of clauses 16 to 25.

(fifth aspect of the invention) use of a film according to one of the clauses 16 to 25 for protecting (absichron) a data carrier, in particular a number plate or license plate, traffic plate or sign, advertising plate or surface or safety gear, equipped with a retroreflective structure.

Detailed Description

In the sense of the invention, observation in reflected light is the illumination of the respective object from one side and the observation of the object from the same side.

In the sense of the present invention, observation in transmitted light is the illumination of the respective object from one side and the observation of the object from the opposite side.

Daylight refers herein to diffuse daylight or simply diffuse light that illuminates a scene uniformly and with weak contrast or low shadows. Diffuse light (or diffuse reflected light) is generated in a planar light source.

According to the invention, attractive reflector films are provided which have an attractive color change, for example from gold in daylight to blue in headlamp light, in the transition between diffuse reflection, in particular when viewed in daylight, and retroreflection, in particular when viewed at night in headlamp light, on the one hand. Further, the same appearance as that when observed at night under the front lighting is presented to the observer when observing a photograph taken with the smartphone camera with the flash turned on.

Retroreflective structures are known in the prior art which reflect the light of a headlight in the direction of the driver of the vehicle for improved visibility and may be based, for example, on triangular or square cube corners or on microglass beads, see, for example, patent documents US 4763985A, US 20090300953A 1, WO 2014/117086 a1, US 6413615B 2 and US 4478769 a. The cube-corner structures are for example based on embossed relief structures, which are plated with a reflective metal layer. The cube-corner structures can in particular have triangular or square faces. The relief structure is advantageously embossed in the plastic material or UV lacquer.

The retroreflective film according to the invention is advantageously provided on the basis of a carrier film, such as polyethylene terephthalate (PET), polymethyl methacrylate (PMMA), polypropylene (PP), Polyethylene (PE), Polycarbonate (PC), polyvinyl butyral (PVB) or polyvinyl chloride (PVC), etc.

The layer having a retroreflective structure can advantageously have a layer thickness in the range from 10 μm to 200 μm, preferably from 30 μm to 150 μm, particularly preferably from 40 μm to 150 μm. The height of the retroreflective structures, in particular of triangular or square cube-corners, is advantageously at least 10 μm, preferably at least 30 μm and advantageously less than 200 μm, preferably less than 150 μm.

The translucent functional layer has a different hue when viewed in reflected light and when viewed in transmitted light. These two different hues are, for example, complementary colors. Such a translucent functional layer is in particular a so-called fabry-perot thin-film element based on a multilayer structure having two translucent metal layers and a dielectric layer arranged between the two translucent metal layers. Such a multilayer structure is known, for example, from patent document WO2011/082761a1, which appears golden when viewed in reflected light and blue when viewed in transmitted light.

A suitable multilayer structure having two semi-transparent metal layers and a dielectric layer disposed between the two semi-transparent metal layers preferably has the following properties:

the two translucent metal layers are preferably selected from Al or Ag; dielectric layer, especially SiO₂Layer or MgF₂Layer, preferably SiO₂A layer;

if each of the two translucent metal layers is based on Al, the respective preferred layer thickness is in the range from 5nm to 20nm, particularly preferably in the range from 10nm to 14 nm; dielectric SiO₂The layer has a layer thickness in the range preferably from 50nm to 600nm, more preferably from 80nm to 260nm, particularly preferably from 210nm to 260nm, wherein, in particular for providing a gold/blue color change, the ranges from 80nm to 100nm and from 210nm to 240nm are particularly preferred.

If each of the two translucent metal layers is based on Ag, the respective preferred layer thickness is in the range from 15nm to 30nm, particularly preferably in the range from 15nm to 25 nm; dielectric SiO₂The layer has a layer thickness in the range preferably from 50nm to 600nm, more preferably from 80nm to 260nm and particularly preferably from 210nm to 260nm, wherein, in particular for providing a gold/blue color change, the ranges from 80nm to 100nm and from 210nm to 240nm are particularly preferred.

The above-described multilayer structure having two semitransparent metal layers and a dielectric layer disposed between the two semitransparent metal layers may have a symmetrical three-layer structure in which the material and layer thickness of the two semitransparent metal layers are the same. Alternatively, however, an asymmetrical three-layer structure can also be present, in which the two semitransparent metal layers differ in material and/or layer thickness, for example:

a silver/dielectric/aluminum layer system, in which the layer thicknesses of the silver layer and the aluminum layer are identical or different;

a silver/dielectric/silver-layer system, in which the layer thicknesses of the two silver layers are different;

an aluminum/dielectric/aluminum layer system, in which the layer thicknesses of the two aluminum layers differ.

The above-described multilayer layer structure not only enables the production of a translucent functional layer which appears golden when viewed in reflected light and blue when viewed in transmitted light, but also enables further color changes to be produced, depending on the choice of the layer thickness, in particular of the dielectric layer, for example:

magenta in reflected light and cyan in transmitted light;

-greenish in reflected light and orange-yellow in transmitted light;

-gold in reflected light and blue-violet in transmitted light;

silver in reflected light and purple in transmitted light.

Furthermore, a translucent functional layer having a different hue when viewed in reflected light and when viewed in transmitted light may be based on the effect pigment composition. Printed layers based on effect pigment compositions which exhibit a color which differs from the color when observed in transmitted light, in particular a gold/blue color change, a gold/violet color change, a green gold/magenta color change, a violet/green color change or a silver/opaque color change, are described, for example, in patent document WO 2011/064162A 2. The pigment preferably has a longest dimension from end to end ("index dimension of edge length") in the range of 15nm to 1000nm and is based on a transition metal selected from the group consisting of Cu, Ag, Au, Zn, Cd, Ti, Cr, Mn, Fe, Co, Ni, Ru, Rh, Pd, Os, Ir and Pt. The transition metal is preferably Ag. Aspect ratio (i.e., end to end)The ratio of the longest dimension of the end relative to the thickness; german:) Preferably at least 1.5 and especially in the range from 1.5 to 300. The ratio of binder to metallic pigment is preferably less than 10: 1. in particular less than 5: 1. the colour when the printed layer is viewed in transmission and the colour when viewed in reflection (for example blue in transmission and silver, gold, bronze, copper or violet in reflection; furthermore violet, magenta, pink, green or brown in transmission and a different colour in reflection, which colours are related to the choice of pigment/binder ratio) can be adjusted according to the choice of the aspect ratio of the pigment, the end-to-end longest dimension of the pigment and the setting of the pigment/binder ratio. Pigments having a gold/blue color change between reflection and transmission (in other words between reflected light and transmitted light observation) are mentioned, for example, in examples 1, 2 and 3 of table 1 of patent document WO2011/064162 a2 (Farben). Further, example 4 shows a pigment with a gold/violet color change, example 5 shows a pigment with a green gold/magenta color change, example 7 shows a pigment with a violet/green color change, and example 8 shows a pigment with a silver/opaque color change.

The retroreflective film according to the present invention advantageously has the following structure:

an adhesive layer, for example suitable for laying a film onto a license plate;

-a layer having a retroreflective structure;

-an optional opaque layer having a space in the form of a pattern, character or code;

-a translucent functional layer;

-a carrier film.

According to one variation, a retroreflective film according to the present invention can have the following structure:

an adhesive layer, for example suitable for laying a film onto a license plate;

-a layer having a retroreflective structure;

-a carrier film;

-a translucent functional layer;

-an optional protective lacquer or film for protecting the translucent functional layer from harmful environmental influences;

wherein optionally an opaque layer with recesses in the form of patterns, characters or codes is arranged either between the layer with the retroreflective structure and the carrier film or between the carrier film and the translucent functional layer.

The opaque layer may be, in particular, a metallization layer, which is obtainable, for example, by vapor deposition, or a pigment layer, which is obtainable, for example, by a printing method. The production of structured metallization layers by cleaning methods is known from the prior art, see for example patent document EP 1972462B 1 and the prior art cited therein. Furthermore, flake-like metallic pigments, which are known, for example, from patent documents 2013/186167 a2, WO 2010/069823 a1, WO 2005/051675 a2 (see, for example, the description on page 11, line 10 to page 12, penultimate paragraph), and WO2011/064162 a2, can be used for producing the pigment layer. The flake-form metallic pigments described therein have the following advantages: it is well adapted to substrates having relief structures, in particular with micro-structured and/or nano-structured reliefs, so that the difference from the conventional metallization layers obtainable by vapor deposition is hardly visible anymore. The simple production of the reflective layer by printing techniques makes it possible to dispense with complex process steps, such as printing the desired recess shape in the reflective layer to be produced on a carrier with a soluble cleaning pigment, producing the metallisation layer by vapor deposition and washing off the cleaning pigment together with the metallisation layer applied on top of the cleaning pigment.

Between the carrier film and the translucent functional layer, an embossing lacquer layer with an embossed relief can advantageously be arranged, wherein the embossed relief is in particular a relief with a microstructure and/or a nanostructure. The translucent functional layer is adapted to the relief so that an observer can perceive additional optically variable information, for example in the form of patterns, characters or codes, when viewing the retroreflective film in reflected light. Optically variable security elements with microstructures suitable for the protection of banknotes are known, for example, from patent document WO 2007/079851 a1 and from WO 2011/066991 a 2.

Furthermore, the retroreflective film according to the invention can be overprinted (or overprinted) with a clear lacquer, which optionally has pigment particles, for example black, white or colored pigment particles. In addition, retroreflective films according to the present invention can be overprinted with a combination of a full-face clear coat layer and a meshed print layer of opaque pigments.

Further embodiments and advantages of the invention are described below on the basis of schematically very simplified drawings, which for better clarity are not shown true to scale.

In the drawings:

FIG. 1 shows a cross-sectional view of a retroreflective film according to a first embodiment of the present disclosure;

FIG. 2 illustrates a cross-sectional view of a retroreflective film according to a second embodiment of the present disclosure;

FIG. 3 shows a top view of a retroreflective film according to a third embodiment of the present invention, viewed in daylight;

FIG. 4 illustrates a top view of a retroreflective film according to a third embodiment of the present disclosure viewed under nighttime front lighting;

fig. 5 and 6 show the working principle of the solution according to the invention;

FIG. 7 illustrates a cross-sectional view of a retroreflective film according to a fourth embodiment of the present disclosure;

FIG. 8 illustrates a cross-sectional view of a retroreflective film according to a third embodiment of the present disclosure;

FIG. 9 illustrates a top view of an embodiment of a retroreflective structure;

FIG. 10 illustrates a top view of an additional embodiment of a retroreflective structure;

fig. 11 shows an embodiment of a film according to the invention, which is suitable for protecting a motor vehicle license plate.

Fig. 1 shows a cross-sectional view of a retroreflective film 1 according to a first embodiment of the present invention. The retroreflective film 1 is based on a carrier film 2, for example a polyethylene terephthalate (PET) film, which carrier film 2 is provided with a translucent functional layer on the side facing the viewer. The translucent functional layer 3 may be obtained by vapor deposition and hasA multilayer structure having two translucent aluminum layers and SiO disposed between the two translucent aluminum layers₂And (3) a layer. The translucent functional layer 3 appears golden when viewed in reflected light and blue when viewed in transmitted light. The carrier film 2 is provided with an embossing lacquer layer 4 on the side opposite the translucent functional layer 3. The embossing lacquer layer 4 is for example based on UV lacquer in which the relief of the retroreflective structure is embossed. The relief of the embossing lacquer layer 4 is provided with a reflective metal coating 5, in this case an aluminum metallization layer, in order to form a retroreflective structure in this way together with the relief of the embossing lacquer layer 4. Adjacent to the reflective metal coating 5 an adhesive layer 6 is arranged, which adhesive layer 6 is suitable for applying the retroreflective film 1 to a license plate, for example.

Fig. 2 shows a cross-sectional view of a retroreflective film 7 according to a second embodiment of the present invention. The retroreflective film 7 is based on a carrier film 8, for example a polyethylene terephthalate (PET) film, which carrier film 8 in this case constitutes the outer layer of the retroreflective film 7. The carrier film 8 is provided on its inner side with a translucent functional layer 9. The translucent functional layer 9 may be obtained by vapor deposition and has a multilayer structure with two translucent aluminum layers and SiO arranged between the two translucent aluminum layers₂And (3) a layer. The translucent functional layer 9 appears golden when viewed in reflected light and blue when viewed in transmitted light. The translucent functional layer 9 is provided with an embossing lacquer layer 10 on the side opposite the carrier film 8. The embossing lacquer layer 10 is based on UV lacquer in which the Relief (Relief) of the retroreflective structure is embossed. The relief of the embossing lacquer layer 10 is provided with a specularly reflective metal coating 11, in this case an aluminium metallisation, in order in this way to form a retroreflective structure together with the relief of the embossing lacquer layer 10. Adjacent to the reflective metal coating 11 an adhesive layer 12 is arranged, which adhesive layer 6 is suitable for applying the retroreflective film 1 to a license plate, for example.

Fig. 3 shows a top view of a retroreflective film 13 according to a third embodiment of the present invention, as viewed in sunlight. The retroreflective film 13 is presented to the viewer in the form of a gold-colored metal surface.

Fig. 4 shows a top view of a retroreflective film 13 according to a third embodiment of the present invention when viewed under front lighting at night (the same appearance is presented to an observer when viewing a photograph taken with a smartphone camera with a flash on). The viewer perceives a light, blue repeating character "PL" and a linear square border on a dark, black background.

Fig. 8 illustrates a cross-sectional view of a retroreflective film 13 according to a third embodiment of the present invention. The retroreflective film 13 is based on a carrier film 14, for example a polyethylene terephthalate (PET) film, which carrier film 14 in this example constitutes the outer layer of the retroreflective film 13. The carrier film 14 is provided on its inner side with a translucent functional layer 15. The translucent functional layer 15 may be obtained by vapor deposition and has a multilayer structure with two translucent aluminum layers and SiO arranged between the two translucent aluminum layers₂And (3) a layer. The translucent functional layer 15 appears golden when viewed in reflected light and blue when viewed in transmitted light. The translucent functional layer 15 is provided on the side opposite the carrier film 8 with an optional transparent intermediate layer 16, in this case an intermediate lacquer layer, which protects the translucent functional layer 15. The optional intermediate layer 16 has opaque areas 17, the opaque areas 17 being obtainable, for example, by printing with a black printing ink. Alternatively, the opaque region 17 may be provided by means of a structured metallization layer. Structured metallization layers can be obtained, for example, by full-area metallization and subsequent demetallization by a cleaning process or by full-area metallization and subsequent demetallization by means of a laser. The opaque area 17 represents the dark background shown in fig. 4, which surrounds the character "PL" and the square line shaped border. Furthermore, the retroreflective film 13 has an embossed paint layer 18. The embossing lacquer layer 18 is based on UV lacquer in which the relief of the retroreflective structure is embossed. The relief of the embossing lacquer layer 18 is provided with a specularly reflective metal coating 19, in this case an aluminium metallisation, in order to form a retroreflective structure in this way together with the relief of the embossing lacquer layer 18. An adhesive layer 20 is provided adjacent to the reflective metal coating 19, which adhesive layer 6 is suitable for laying the retroreflective film 13 onto a license plate, for example.

Fig. 5 and 6 show the working principle of the solution according to the invention.

Fig. 5 shows a translucent functional layer 21, which may beObtained by vapor deposition and having a multilayer structure with two translucent aluminum layers and SiO arranged between the two translucent aluminum layers₂Layers (so-called fabry-perot thin layer structures). The translucent functional layer 21 appears golden when viewed in reflected light and blue when viewed in transmitted light. Reference numeral 22 denotes incident white light. Due to the presence of the translucent golden blue filter, the blue component of the color spectrum is transmitted (see arrow with reference 24, which represents transmitted blue light). The complementary, so to speak golden, component is reflected (see arrow with reference number 23, which indicates reflected, so to speak golden light).

Fig. 6 shows the combination of a semi-transparent functional layer 21 known from fig. 5 and a retro-reflector 25, which in this example is a microprism provided with a specularly reflective metal coating known from fig. 1, 2 and 8. In the combination of the color filter 21 and the retro-reflector 25, the transmitted blue component 24 in the spectrum is reflected by the retro-reflector 25 and transmitted a second time through the gold blue color filter 21 (see dashed arrows with reference numbers 26 and 27, which respectively represent blue light). Blue light 27 is perceived by the viewer, in the embodiment according to fig. 4 in the form of the bright, blue letter "PL" and a linear square border.

The film structure shown in fig. 1, 2 and 8 can, if appropriate, be supplemented by at least one further layer, for example with an embossed structure such as a micromirror device or a scattering structure or a diffractive structure. This makes it possible to realize security elements, for example based on micromirror technology known from the prior art, which do not impair the nighttime colored retroreflection. In the case of light which is incident perpendicularly at night, the scattering structures ensure that the light component of the gold color is scattered.

Fig. 7 illustrates a cross-sectional view of a retroreflective film 28 according to a fourth embodiment of the present invention. The retroreflective film 28 is based on a carrier film 29, for example a polyethylene terephthalate (PET) film, which carrier film 29 is provided with a translucent functional layer 31 on the side facing the viewer. The translucent functional layer 31 may be obtained by vapor deposition and has a multilayer structureThe multilayer structure has two semi-transparent aluminum layers and SiO arranged between the two semi-transparent aluminum layers₂And (3) a layer. The translucent functional layer 31 appears golden when viewed in reflected light and blue when viewed in transmitted light. The translucent functional layer 31 is applied to the carrier film 29 by means of an embossing lacquer layer 30. The embossing lacquer layer 30 is based on a UV lacquer and has embossed ribs containing microstructures. The translucent functional layer is adapted to the relief so that an observer, when viewing the retroreflective film in reflected light, can perceive additional optically variable information, in the form of patterns, characters or codes, which is dependent on the viewing angle. The translucent functional layer 31 is provided with an optional transparent protective layer 32, for example a protective lacquer. The carrier film 29 has an embossing lacquer layer 33 on the side opposite the translucent functional layer 31. The embossing lacquer layer 33 is based on UV lacquer in which the relief of the retroreflective structure is embossed. The relief of the embossing lacquer layer 33 is provided with a specularly reflective metal coating 34, in this case an aluminium metallisation, in order in this way to form a retroreflective structure together with the relief of the embossing lacquer layer 33. Adjacent to the reflective metal coating 34 is arranged an adhesive layer 35, which is suitable for laying the retroreflective film 28 onto a license plate, for example.

FIG. 9 illustrates a top view of an embodiment of a retroreflective structure. The retroreflectors are based on cube-corner structures or microprism structures, in which the incident light is deflected approximately 45 ° in succession at three interfaces inclined relative to one another and is reflected back to the light source. Fig. 9 shows the geometry of an embossed retroreflector with triangular faces. The surface of the relief structure may be plated with a reflective metal layer.

FIG. 10 illustrates a top view of an embodiment of a retroreflective structure. The geometry of the embossed retroreflector has a square surface.

Fig. 11 shows an embodiment of a film 21 according to the invention, which is suitable for protecting a motor vehicle license plate provided with a retroreflective structure. The film 21 is based on a carrier film 22, for example a polyethylene terephthalate (PET) film, which carrier film 22 in this example constitutes the outer layer of the film 21. The carrier film 22 is provided on its inner side with a translucent functional layer 23. The translucent functional layer 23 may be obtained by vapor deposition and has a multilayer structure with two translucent aluminum layersAnd SiO arranged between two translucent aluminum layers₂And (3) a layer. The translucent functional layer 23 appears golden when viewed in reflected light and blue when viewed in transmitted light. The translucent functional layer 23 is provided on the side opposite the carrier film 22 with an optional transparent intermediate layer 24, in this case an intermediate lacquer layer, which protects the translucent functional layer 23. The opaque areas, which can be obtained, for example, by printing with a black printing ink, are indicated by 25. Alternatively, the opaque region 25 may be provided by means of a structured metallization layer. Structured metallization layers can be obtained, for example, by full-area metallization and subsequent demetallization by a cleaning process or by full-area metallization and subsequent demetallization by means of a laser. The opaque area 25 represents, for example, a character, a pattern, or a code. Further, the film 21 has an adhesive layer 26.

The license plate or number plate of the motor vehicle protected with the film 21 is indicated with 27. The license plate 27 has a retroreflective structure 28 on the side opposite the film 21.