CN116075435A - Optically variable security element - Google Patents

Abstract

The invention relates to an optically variable security element (12) having a reflective surface region (20) which, in reflection, displays at least two optically variable effects which can be detected from different viewing directions and which appear in different first and second colors, and which, in transmission, displays the appearance of a different third color. It is provided that the reflective surface region (20) comprises two individual relief structures (24, 34) which form a lower relief structure and an upper relief structure and overlap in the feature region. The higher or lower relief structures (24, 34) are each provided with a reflection-enhancing coating (26, 36) following the relief pattern, said reflection-enhancing coating having a wavelength-dependent reflection and transmission in the visible spectral range and having at least one reflection band and at least one transmission band. The reflection band of the second enhanced reflection coating (26) is at least partially in the transmission band of the first enhanced reflection coating (36), and at least one transmission band of the two enhanced reflection coatings (26, 36) overlaps.

Description

Optically variable security element

The invention relates to an optically variable security element for providing security to items of value, having a reflective surface area which exhibits at least two optically variable effects that can be detected from different viewing directions. The invention also relates to a method for producing such a security element and to a data carrier provided with such a security element.

Data carriers such as security documents or document files or other items of value such as branded goods are often provided with security elements for security purposes, which can verify the authenticity of the data carrier and at the same time serve as protection against unauthorized copying. The security element can be designed, for example, as a security thread embedded in the banknote, as a cover film for the banknote with the aperture, as an applied security strip, as a self-supporting transfer element or also as a feature area printed directly on the document of value.

Security elements having a viewing angle-dependent or three-dimensional appearance play a particular role in the security of authenticity, since such security elements cannot be reproduced even with the latest copying devices. The security element is provided with optically variable elements which convey different image impressions to the observer at different viewing angles and which display, for example, different color impressions or brightness impressions, different perspectives and/or different graphic visual objects (Motiv, or patterns) depending on the viewing angle.

In the prior art, the movement effects, pump effects (pumpeffect kt), depth effects or flip effects achieved by means of holograms, micro-lenses or micro-mirrors are described here as optically variable effects, for example.

Prior to some time, DE 10 2018 005 447 A1 has proposed an optically variable security element having two relief structures which are arranged in different height classes and are each provided with a color coating. The higher relief structure color coating is structured as a grid so that when the security element is viewed in the grid interstices, a lower relief structure color coating appears. This design allows a continuous change from a first appearance to a second appearance when the security element is inverted. In practice, however, the required fine rasterization to achieve color coatings is very demanding in terms of technology.

Starting from this, the object of the present invention is to propose an optically variable security element of the type described in the introduction which is simple to produce, has an attractive visual appearance and can be used in a variety of ways to provide authenticity assurance for data carriers.

This object is achieved by the features of the independent claims. The development of the invention is the subject of the dependent claims.

In order to solve the technical problem, the invention comprises an optically variable security element with a multicoloured reflective surface region, which can be used in particular for providing security to valuable items. The reflective surface region exhibits at least two optically variable effects that can be recognized from different viewing directions and that appear in different first and second colors in reflection viewing, and the reflective surface region exhibits an appearance in transmission viewing that appears in a different third color.

The third color is different from both the first color and the second color. The term "colour" here includes not only chromatic colours but also achromatic colours, i.e. in particular white, black, grey and metallic colours which are substantially silvery, for example the colours of a reflective aluminium layer or silver layer.

The reflective surface region comprises two independent relief structures which are arranged in different height levels in the z-direction and form a lower relief structure and a higher relief structure. The two relief structures overlap in the feature region, wherein a partial overlap or a complete overlap, i.e. a design in the congruent surface region, is possible.

The higher relief structure is provided with a first reflection-enhancing coating following the relief course, which has a wavelength-dependent reflection and transmission in the visible spectral range and in the process has at least one reflection band and at least one transmission band.

The lower relief structure is provided with a second reflection-enhancing coating following the relief course, which has a wavelength-dependent reflection and transmission in the visible spectral range and also has at least one reflection band and at least one transmission band.

The higher relief structure and the lower relief structure are thereby adapted to each other such that the reflection band of the second reflection enhancing coating is at least partially in the transmission band of the first reflection enhancing coating, and furthermore at least one transmission band of the two reflection enhancing coatings overlaps.

Whereby in reflection viewing the higher relief structure exhibits a first optically variable effect in a first color and the lower relief structure exhibits a second optically variable effect in a second, different color through the first enhanced reflective coating. In transmission viewing, the appearance of a third color, different from the first and second colors, is displayed through the higher relief structures and the lower relief structures.

In an advantageous embodiment, the first and/or the second reflection-enhancing coating has a transmission of at least 35%, preferably at least 50%, particularly preferably at least 65%, in the transmission band of its visible spectrum.

The first and/or second reflection-enhancing coating advantageously has a reflectivity of at least 20%, preferably at least 30%, particularly preferably at least 40% in its reflection band in the visible spectral range.

The first reflection-enhancing coating preferably comprises one or more high-refractive layers, preferably dielectric high-refractive layers, which have a refractive index of at least 1.7, preferably at least 2.0 and particularly preferably at least 2.2, at least in the part of the visible spectrum. In particular the first enhanced reflection coating may be formed by a ZnS layer having a thickness between 50nm and 400 nm.

Alternatively or additionally, the second reflection-enhancing coating advantageously comprises one or more high-refractive layers, preferably dielectric high-refractive layers, which have a refractive index of at least 1.7, preferably at least 2.0 and particularly preferably at least 2.2, at least in the partial range of the visible spectrum. In particular the second enhanced reflection coating may be formed by a ZnS layer having a thickness between 50nm and 400 nm.

In a particularly advantageous embodiment, the first and the second reflection-enhancing coating are each formed by a ZnS layer, the layer thicknesses of the two coatings differing by 35nm or more. This can be achieved by means of two ZnS layers, the reflection band of the second reflection-enhancing coating being at least partially situated as desired in the transmission band of the first reflection-enhancing coating.

In a further, likewise advantageous embodiment, the second reflection-enhancing coating is a multilayer system having a metal/dielectric/metal layer sequence, in particular aluminum/SiO ₂ The metal layer, in particular the aluminum layer, of the multilayer system has a layer thickness of 5nm or less, preferably 4nm or less. The multilayer system is advantageously designed such that its reflectivity and transmission are in each case between 30% and 70%. The first reflection enhancing coating may also be formed by a multilayer system of the type described, even though a separate layer of high refractive index, such as a ZnS layer, is currently particularly preferred for the first reflection enhancing coating.

In an advantageous embodiment, the higher relief structure and/or the lower relief structure is formed by a micromirror arrangement (or micromirror array) having directionally reflecting micromirrors, in particular mirrors having non-diffractive effects, and preferably having flat mirrors, concave mirrors and/or fresnel mirrors. The lateral dimensions of the micromirrors are suitably below 50 μm, advantageously below 20 μm, preferably around 10 μm, i.e. between 7 μm and 13 μm. But on the other hand the lateral dimensions of the micromirror are also above 2 μm, in particular above 3 μm, or even above 5 μm. The pitch of the micromirrors is preferably less than 10 μm, preferably less than 5 μm.

Instead of micromirrors, the relief structures may also comprise other embossed relief structures, in particular fresnel lenses, concave mirrors, hologram structures, nanostructures or diffractive blazed gratings. Advantageously, an achromatic diffraction grating, a so-called calendered structure, can also be used, which essentially reflects white light. In order to produce a chromatic color, at least the relief structure of the second relief structure may also have a sub-wavelength structure, in particular a sub-wavelength grating, which is determined in combination with the respective enhanced reflection layer or at least jointly determines its color.

In other advantageous embodiments, one or both relief structures can also be formed from a layer with a plurality of three-dimensionally oriented platelet-shaped pigments. The platelet-shaped pigments are particularly advantageously platelet-shaped magnetic pigments which can be oriented by a magnetic field, but they can also be platelet-shaped effect pigments which can be oriented by other fields, for example by an electric field. The oriented pigment is not only flat in the plane of the face region, but is at least partially inclined to this plane. The surfaces formed by the pigments also exhibit relief structures, similar to the embossed structures described above, due to their three-dimensional orientation with components inclined relative to the plane.

In an advantageous embodiment, a first of the three mentioned colors is red or reddish, a second color is green or greenish and a third color is blue or bluish. It is also advantageous if the color visible in transmission viewing is an achromatic color, in particular having a grey or metallic appearance.

In terms of the surface coverage of the enhanced reflection layer, in an advantageous embodiment, the two enhanced reflection layers are applied to the surface pattern non-gridded and in particular even entirely. A particular advantage of the design according to the invention is that the optically variable effect of the lower relief structure is visible despite the non-gridded or full-faced (or over the entire surface) presence of the first enhanced reflective coating.

In an embodiment, the second reflection-enhancing layer can also be provided only regionally and thus form negative marks in the security element, in particular in the form of numerals, symbols or the like. Additionally or alternatively, the first reflection-enhancing coating may also be present only regionally. However, according to the invention, the regions provided with two different reflection enhancing coatings must overlap at least regionally in the feature region. In an advantageous embodiment, the two reflection-enhancing coatings are arranged in a complete or almost congruent partial region, although they are not arranged entirely. In particular, the negative marks may be designed such that the two reflection-enhancing coatings are left empty congruently in the form of letters, symbols, numbers, etc. The first reflection-enhancing layer is therefore advantageously present in the feature region in non-rasterized form, i.e. without a grid, but if necessary with a separate negative sign. In a preferred embodiment, the first reflection-enhancing layer is present even over the entire surface in the feature region, i.e. without a grating and a recess.

In an embodiment of the invention, it can be provided that one or more light-transmitting color layers are arranged between the first relief structure and the second relief structure and/or above the first reflection-enhancing coating and/or below the second reflection-enhancing coating in order to influence the color impression of the security element. Each of these color layers may be present entirely or only regionally, in particular in the form of a pattern, a mark or a code.

For example, a color layer may be provided below the second enhanced reflection coating, which locally absorbs more strongly and less strongly in the overlapping transmission areas of the two enhanced reflection coatings, thus creating a structured appearance in transmission viewing.

According to the invention, the optically variable effect of the two relief structures is not congruent, but rather they can be recognized at least partially from different viewing directions. It is particularly advantageous if the first and second relief structures reflect incident parallel light at least in regions into different angular ranges, wherein the two different angular ranges are preferably separated from one another without overlapping by preferably more than 3 °, particularly preferably more than 10 °.

The two relief structures are independent relief structures. They can therefore be chosen freely, since they are independent of each other (in their relief pattern). The relief structure created solely by the coating of the other relief structure is not an independent relief structure in this sense. The relief structures of the surface regions in particular do not have identical relief patterns nor have identical relief patterns which scale only in height, but rather the two relief structures are designed differently and have different relief patterns. The two separate relief structures are in particular different. Thus, the two relief structures may produce the same type of optically variable effect, such as an opposite-direction motion effect or a spatial view that can be seen from different viewing directions, but the two relief structures do not always produce the same optically variable effect at the same location due to the different relief patterns.

In particular, the design of the higher relief structure, in particular the orientation of the micromirrors of the higher micromirror arrangement, and/or the design of the lower relief structure, in particular the orientation of the lower micromirror arrangement, can advantageously be varied in a position-dependent manner in order to produce respectively predetermined visual objects, in particular three-dimensionally acting visual objects or moving visual objects. The orientation of the relief pattern, in particular of the micromirrors, can be selected freely and is determined essentially only by the intended visual object, but not by the orientation of the laterally or vertically adjacent micromirrors.

The invention also relates to a data carrier having a security element of the type mentioned. The data carrier may in particular be a value document, such as a banknote, in particular a paper banknote, a polymer banknote or a film composite banknote, which may be a stock certificate, a bond, a certificate, a coupon, a check, an advanced admission ticket, but also a document card, such as a credit card, a bank card, a cash card, an authorization card, an identification card or a passport private page. The lower relief structure is here generally closer to the surface of the data carrier than the higher relief structure, which is closer to the eye of the viewer.

In order to be able to use the perspective feature for the plausibility check, in a particularly suitable variant, the security element is arranged in the window region, i.e. in a transparent or penetrating region of the data carrier. Alternatively, the security element can also be arranged on top of the opaque region of the data carrier and, for example, enable a transmissive viewing of the information applied to the data carrier.

The invention also includes a method for producing an optically variable security element, and in particular for producing a security element of the type described above, having reflective surface regions which exhibit at least two optically variable effects which can be detected from different viewing directions and which appear in different colors,

providing a carrier, the planar extension of which defines a plane and a z-axis standing vertically thereon,

providing the carrier with a reflective surface area, which comprises two individual relief structures which are arranged in different height levels in the z-direction and form a lower relief structure and a higher relief structure, and which are designed to overlap in the feature area,

providing the higher relief structure with a first reflection enhancing coating following the relief trend, said first reflection enhancing coating having wavelength-dependent reflection and transmission in the visible spectral range and having at least one reflection band and at least one transmission band,

providing the lower relief structure with a second reflection enhancing coating following the relief trend, said second reflection enhancing coating having wavelength-dependent reflection and transmission in the visible spectral range and having at least one reflection band and at least one transmission band,

wherein the reflection-enhancing coatings are adapted to each other in such a way that the reflection band of the second reflection-enhancing coating is at least partially in the transmission band of the first reflection-enhancing coating and at least one transmission band of the two reflection-enhancing coatings overlaps, thus

The higher relief structure exhibits a first optically variable effect of a first color in reflection viewing, the lower relief structure exhibits a second optically variable effect of a second, different color through the first enhanced reflective coating in reflection viewing, and wherein the appearance of a third, different color is exhibited through the higher relief structure and the lower relief structure in transmission viewing.

Further embodiments and advantages of the invention are described below with reference to the drawings, which are not to scale or are reproduced to scale in the drawings in order to improve the visibility.

In the drawings:

figure 1 shows a schematic view of a banknote with an optically variable security element according to the invention,

figure 2 shows in cross-section a part of a security element according to the invention,

FIG. 3 very schematically shows in (a) and (b) the different wavelength-dependent reflection and transmission of two enhanced reflection coatings, and in (c) the resulting transmission and reflection spectra of the entire surface area, and

fig. 4 shows another embodiment of the invention in which the layers described in connection with fig. 2 have been applied to the same side of the carrier film.

The invention will now be described by way of example with respect to a security element for banknotes. For this purpose, fig. 1 shows a schematic representation of a banknote 10 with an optically variable security element 12 according to the invention in the form of an adhesive transfer element. It is however self-evident that the invention is not limited to transfer elements and banknotes, but can be used in all types of security elements, for example in labels and packages on goods or in providing security for documents, certificates, passports, credit cards, health cards etc. In banknotes and similar documents, security threads or security strips are also conceivable, for example, in addition to the transfer element (for example a patch or a strip, respectively with or without its own carrier layer).

The security element 12 shown in fig. 1 is arranged in a window region 15 of the banknote 10 and covers a continuous opening of the banknote, for example, there. When the banknote is viewed in reflection viewing (Aufsicht) as shown in fig. 1, although the security element 12 is designed flat, it conveys the three-dimensional impression to the observer and at the same time displays a binary color and effect when the banknote 10 is inverted. The security element 12 here displays, as seen from a first viewing direction, a view of a first visual object 14-a, in particular, for example, the curvature of the value "10", which appears as if it were curved out of the plane of the banknote 10, with a color impression of a first color, for example, green. From the second viewing direction, the security element 12 displays a second visual object 14-B, for example a curved view of a badge, which appears as if it were curved out of the plane of the banknote 10, with a second colour, for example a pale red colour impression.

When the banknote 10 is inverted 16 or the viewing direction is changed accordingly, the appearance of the security element 12 suddenly changes from the first appearance to the second appearance, or when inverted back, the appearance of the security element changes from the second appearance to the first appearance. The change of visual objects (values or badges) and colors (green or reddish) is effected simultaneously and without intermediate or transitional phases that make it possible for two visual objects or colors to be visible simultaneously or for one visual object to be visible in the color of the other visual object. Thus, the appearance is abrupt without transition between the two appearances 14-a, 14B and is therefore referred to as a binary color and effect change.

The security element 12 also allows a transmissive viewing through the security element and the window region 15 of the banknote, wherein the security element appears in a third color, for example in the color impression of blue, different from the two reflective viewing colors in the transmissive viewing (durchsichght).

The particular structure of the optically variable security element according to the invention will now be described in more detail with reference to fig. 2, fig. 2 schematically showing a part of the security element 12 in cross-section.

Security element 12 comprises a flat, transparent carrier film 18, the planar extension of which defines an x-y plane and a z-axis that stands perpendicularly on the x-y plane.

The carrier film 18 has a multicolored reflective surface region 20 that contains two relief structure regions 24, 34 that are arranged in the z-direction in two specific different height classes. The relief structures 34 that are closer to the observers 40A, 40B in reflection viewing are referred to as higher relief structures and the relief structures 24 that are farther from the observers are referred to as lower relief structures.

The two relief structure regions represent in this embodiment a micromirror imprint or micromirror arrangement 24, 34, respectively, which are formed by a large number of micromirrors inclined with respect to the x-y plane, respectively, said micromirrors having a lateral dimension of about 10 μm. The local tilt angles of the micromirrors are here just chosen such that the relief structure of the micromirror arrangement 24, 34 produces the desired optical appearance after the enhancement of the reflective coating.

In particular, the tilt angle of the micromirrors is chosen in the described embodiment such that the micromirror arrangement 34 produces a view of the curvature of the numerical value "10" in the viewing angle range of +5° to +20° (viewing position 40-a) with reference to the surface normal and the micromirror arrangement 24 produces a view of the curvature of the badge in the viewing angle range of-5 ° to-20 ° (viewing position 40-B).

In order to produce the desired color impression, the higher micromirror arrangement 34 is provided overall with a first reflection-enhancing coating 36 following the relief course in the form of a semitransparent, highly refractive ZnS layer with wavelength-dependent reflection and transmission. The layer thickness of the ZnS layer is chosen such that it has a reflection band in the green spectral range (r=0.42) and a transmission band in the red (t=0.9) and blue (t=0.75) spectral ranges, i.e. it has a high reflection in the green spectral range and a high transmission in the red and blue spectral ranges.

The lower micromirror arrangement 24 is provided over its entire surface with a second enhanced reflection coating 26 following the relief course, which is formed by a translucent three-layer system of 3nm aluminum/200 nm SiO ₂ 3nm aluminum, and the second enhanced reflective coating has wavelength dependent reflection and transmission. The thicknesses of the two aluminum layers and the dielectric layer are selected such that the three-layer system has a reflection band in the red spectral range (r=0.55) and a transmission band in the blue spectral range (t=0.6), i.e. a high reflection in the red spectral range and a high transmission in the blue spectral range.

The micromirror arrangements 24, 34 are respectively embossed in transparent embossing lacquer layers 22, 32, which are applied on opposite sides of the carrier film 18, and after the application of the respective reflection-enhancing coating 26, 36, the micromirror arrangements are leveled with a transparent cover lacquer layer 28 or 38. The cover lacquer layer preferably has substantially the same refractive index as the embossing lacquer layers 22, 32.

With normal incidence of white light 50 onto the area 20, the micromirrors of the higher micromirror arrangement 34, which generate a curved view of the value "10", are in a glancing angle in reflection viewing for an observer from the viewing direction 40-a. The first reflection-enhancing coating 36 here produces an image impression with a green reflection color 52 due to its reflection band in the green spectral range. Due to the enhanced translucency of the reflective coating 36, the micromirrors of the micromirror arrangement 24 are, although in principle also perceptible, oriented away from the glancing angle and thus they appear unobtrusive from the viewing direction 40-a and do not actually contribute to the image impression. Thus, in general, a viewer from viewing direction 40-A is presented with a green appearance 14-A in reflection view of the value "10" of camber produced by micromirror arrangement 34.

From the reflected view in the viewing direction 40-B, the micromirrors of the lower micromirror arrangement 24 are in glancing angle to the viewer, which generate an arcuated view of the badge. In the incident white light 50, the first enhanced reflective coating 36 of the higher micromirror arrangement 34 transmits the red component 54 and the blue component 56 to the second enhanced reflective coating 26 of the lower micromirror arrangement 24 due to its transmission bands in the red and blue spectral ranges.

The second enhanced reflective coating 26 reflects the red spectral component 54 toward the viewing direction 40-B due to its reflection band in the red spectral range, which is also transmitted by the first enhanced reflective coating 36 due to its transmission band in the red spectral range. While the micromirrors of the higher micromirror arrangement 34 are also perceivable in principle from the viewing direction 40-B, they are oriented away from the glancing angle and thus they appear unobtrusive and do not actually contribute to the image impression. Thus, in general, a viewer from the viewing direction 40-B is presented with a reddish appearance 14-B of the arching badge produced by the micromirror arrangement 24.

When viewed in transmission from the viewing direction 40-C, the glancing angle of the micromirrors 24, 34 does not contribute to reflection, but rather the appearance is determined by the radiation components of the transmission of the two enhanced reflective coatings 26, 36. Since the first enhanced reflective coating 36 transmits the red component 54 and the blue component 56 of the incident white light 50 and the second enhanced reflective coating 26 still transmits the blue spectral component 56 due to its transmission band in the blue spectral range, the area 20 appears to the observer as a blue color impression when viewed in transmission from the viewing direction 40-C.

Fig. 3 very schematically shows the different wavelength-dependent reflection and transmission of the two reflection-enhancing coatings 36, 26 and the resulting transmission and reflection spectra of the entire area 20.

First, for the first enhanced reflective coating 36, the graph 60 of FIG. 3 (a) is shown as a solid curve R ₁ (lambda) represents the wavelength-dependent reflection and is represented by the dashed curve T ₁ (lambda) represents the transmission in relation to the wavelength. As can be seen directly, the coating 36 shown has a reflection band in the green spectral range (G) and a transmission band in the red spectral range (R) and the blue spectral range (B).

For the second enhanced reflective coating 26, the graph 62 of FIG. 3 (b) is correspondingly plotted as a solid curve R ₂ (lambda) represents the wavelength-dependent reflection and is represented by the dashed curve T ₂ (lambda) represents the transmission in relation to the wavelength. The coating 26 is shown to have a reflection band in the red spectral range (R) and a transmission band in the green spectral range (G) and the blue spectral range (B).

The resulting transmission and reflection spectra of the entire facet region 20 are shown generally in graph 64 of fig. 3 (c). The appearance of the area 20, seen from the viewing direction 40-a, is determined by the reflectivity of the first enhanced reflective coating 36, i.e

R _A (λ)＝R ₁ (λ)，

And a green appearance is created due to the reflection band of the first enhanced reflective coating 36.

The appearance of the area 20, seen from the viewing direction 40-B, is created by light transmitted by the first enhanced reflective coating 36 and reflected by the second enhanced reflective coating 26. In determining the brightness of the total reflection, it must be taken into account that the incident light, after reflection at the second reflection-enhancing coating 26, again passes through the first reflection-enhancing coating 36 (see, for example, fig. 2), so that its transmission must be taken into account twice. Thus, the reflectivity for the viewing direction 40-B results in:

R _B (λ)＝T ₁ (λ)*R ₂ (λ)*T ₁ (λ)，

thus, viewed from this viewing direction, the transmission band in the red and blue spectral ranges by the first enhanced reflective coating and the reflection band in the red spectral range of the first enhanced reflective coating produce a reddish appearance as a whole.

In transmission viewing, the appearance of the area of the face, seen from the viewing direction 40-C, is created by light transmitted by the two enhanced reflective coatings 26, 36:

T _C (λ)＝T ₁ (λ)*T ₂ (λ)，

thus, a blue color impression is produced as a whole by the transmission band of the first enhanced reflective coating 36 in the red and blue spectral ranges and the transmission band of the second enhanced reflective coating 26 in the blue spectral range.

Fig. 4 shows a security element 70 as a further embodiment of the invention, wherein the layers already described in connection with fig. 2 are applied on the same side of the carrier film 18. Starting from carrier film 18, security element 70 comprises a transparent first embossed lacquer layer 32 with embossed higher micro-mirror structures 34, a first reflection enhancing coating 36, a transparent second embossed lacquer layer 22 with embossed lower micro-mirror structures 24 applied on coating 36, a second reflection enhancing coating 26, a cover lacquer layer 28 and finally an adhesive layer 44 for transferring security element 70 onto a target substrate. Carrier film 18 is preferably designed to be releasable and is peeled off after transfer of security element 70. Alternatively, in the case of a transparent design, the carrier film 18 may also remain in the transferred layer composite.

In the embodiment of fig. 4, the first enhanced reflective coating 36 is formed by a translucent, high refractive ZnS layer having wavelength dependent reflection and transmission. The layer thickness of ZnS layer 36 is chosen such that it has a reflection band in the red and blue spectral range and a transmission band in the green spectral range d=104 nm. Although ZnS layer 36 reflects mainly the incident red and blue light, a small amount of the red and blue light is transmitted.

In this embodiment, the second enhanced reflective coating 26 is also formed by a translucent, high refractive ZnS layer having wavelength dependent reflection and transmission. The layer thickness of ZnS layer 26 is chosen such that d=140 nm, so that it has a pronounced reflection band in the blue and green spectral range and a transmission band in the red spectral range.

When white light is perpendicularly incident and is viewed at the glancing angle of the micromirrors of the higher micromirror arrangement 34, the first reflection-enhancing coating 36 produces an image impression with a violet reflection color due to its reflection band in the red and blue spectral ranges. The micromirrors of the micromirror arrangement 24 that are not in the glancing angle appear insignificant from this viewing direction and contribute little to the image impression.

The color impression as described above is created by the interaction of the spectral components transmitted by the first enhanced reflective coating 36 and the spectral components reflected at the second enhanced reflective coating 26 when viewed at the glancing angle of the micromirrors of the lower micromirror arrangement 24. In an embodiment, the first enhanced reflective coating 36 has a transmission band in the green spectral range, wherein also a small portion of the blue light is transmitted. The micromirrors of the lower micromirror arrangement 24 appear to the viewer in the color blue/green/turquoise due to the pronounced reflection bands of the second enhanced reflective coating 26 in the blue and green spectral ranges. From this viewing direction, the micromirrors of the micromirror arrangement 34 that are not in glancing angle appear insignificant and contribute little to the image impression.

In transmission viewing, the appearance is determined by the radiation components that are transmitted respectively, wherein the first, reflection-enhancing coating 36 transmits strongly green light and to a lesser extent red light and blue light. The second enhanced reflective coating 26 transmits strongly red light but also transmits blue and green light to a lesser extent. The total transmission as two enhanced reflection coatings thus produces an almost balanced spectrum, which is slightly higher in transmission in the red, so that a substantially achromatic color, i.e. a coloured aluminium perspective color with pale red, is produced for the observer.

List of reference numerals

10 banknote

12 Security element

14A, 14B arching visual object

15 window area

16 turning direction

18 carrier

20 reflective surface area

22 impression lacquer layer

24 micromirror arrangement structure

26 enhanced reflective coating

28 paint layer

32 impression lacquer layer

34 micromirror arrangement structure

36 enhanced reflective coating

38 paint cover layer

40A, 40B, 40C observer

50 incidence of white light

52 green component, green reflected color

54 red component, reflection color of red

56 blue component, blue reflected color

60. 62, 64 chart

70 security element

Claims (17)

1. An optically variable security element for providing security to an item of value, the face extension of the security element defining a z-axis upstanding perpendicularly thereon, the security element having a reflective face region which, in reflection viewing, exhibits at least two optically variable effects which are identifiable from different viewing directions and which appear in different first and second colours, and which, in transmission viewing, exhibits an appearance in a different third colour,

the reflective surface region comprises two individual relief structures which are arranged in different height levels in the z-direction, form a lower relief structure and a higher relief structure and overlap in the feature region,

the higher relief structure is provided with a first reflection enhancing coating following the relief trend, said first reflection enhancing coating having wavelength-dependent reflection and transmission in the visible spectral range and having at least one reflection band and at least one transmission band,

the lower relief structure is provided with a second reflection enhancing coating following the relief trend, said second reflection enhancing coating having wavelength-dependent reflection and transmission in the visible spectral range and having at least one reflection band and at least one transmission band,

wherein the reflection band of the second reflection enhancing coating is at least partially in the transmission band of the first reflection enhancing coating and at least one transmission band of the two reflection enhancing coatings overlap such that

The higher relief structure exhibits a first optically variable effect of a first color in reflection viewing, the lower relief structure exhibits a second optically variable effect of a second, different color through the first enhanced reflective coating in reflection viewing, and wherein the appearance of a third, different color is exhibited through the higher relief structure and the lower relief structure in transmission viewing.

2. A security element according to claim 1, wherein the first and/or second reflection-enhancing coating has a transmission in the transmission band of its visible spectrum of at least 35%, preferably at least 50%, particularly preferably at least 65%.

3. A security element according to claim 1 or 2, characterized in that the first and/or the second reflection-enhancing coating has a reflectivity of at least 20%, preferably at least 30%, particularly preferably at least 40% in the reflection band in the visible spectrum.

4. A security element according to at least one of claims 1 to 3, characterized in that the first reflection-enhancing coating comprises one or more high-refractive layers, preferably dielectric high-refractive layers, which have a refractive index of at least 1.7, preferably at least 2.0 and particularly preferably at least 2.2, at least in the part of the visible spectrum, in particular the first reflection-enhancing coating is a ZnS layer having a thickness of between 50nm and 400 nm.

5. The security element according to at least one of claims 1 to 4, characterized in that the second reflection-enhancing coating comprises one or more high-refractive layers, preferably dielectric high-refractive layers, which have a refractive index of at least 1.7, preferably at least 2.0 and particularly preferably at least 2.2, at least in the part of the visible spectrum, in particular the second reflection-enhancing coating is a ZnS layer having a thickness of between 50nm and 400 nm.

6. A security element according to claims 4 and 5, wherein said first and second reflection enhancing coatings are each ZnS layers and the layer thicknesses of the two coatings differ by 35nm or more.

7. The security element according to at least one of claims 1 to 4, characterized in that the second reflection-enhancing coating is a multilayer system having a metal/dielectric/metal layer sequence, in particular aluminum/SiO ₂ The metal layer, in particular the aluminum layer, has a layer thickness of 5nm or less, preferably 4nm or less.

8. Security element according to at least one of claims 1 to 7, characterized in that the higher relief structures and/or lower relief structures are formed by micromirror arrangements with directionally reflecting micromirrors, in particular mirrors with non-diffractive effects, and preferably with flat mirrors, concave mirrors and/or fresnel mirrors.

9. The security element according to at least one of claims 1 to 8, characterized in that a first of the three mentioned colors is red or reddish, a second color is green or greenish and a third color is blue or bluish.

10. The security element according to at least one of claims 1 to 8, characterized in that the color visible in transmission viewing is an achromatic color, in particular having a grey or metallic appearance.

11. The security element according to at least one of claims 1 to 10, characterized in that the first and/or the second reflection-enhancing coating is present in the feature region non-rasterized, preferably entirely.

12. The security element according to at least one of claims 1 to 11, characterized in that one or more light-transmitting color layers are arranged between the first relief structure and the second relief structure and/or above the first reflection enhancing coating and/or below the second reflection enhancing coating and influence the color impression of the security element.

13. The security element according to at least one of claims 1 to 12, characterized in that the first and second relief structures reflect incident parallel light at least in regions into different angular ranges, wherein the two different angular ranges preferably do not overlap and are spaced apart from one another by preferably more than 3 °, particularly preferably more than 10 °.

14. The security element according to at least one of claims 1 to 13, characterized in that the two individual relief structures are designed differently.

15. The security element according to at least one of claims 1 to 14, characterized in that the design of the higher relief structure, in particular the orientation of the micromirrors of the higher micromirror arrangement and/or the design of the lower relief structure, in particular the orientation of the lower micromirror arrangement, is varied as a function of position in order to produce a respectively predetermined visual object, in particular a three-dimensional visual object or a moving visual object.

16. A data carrier having an optically variable security element as claimed in at least one of claims 1 to 15.

17. Method for producing an optically variable security element, in particular according to at least one of claims 1 to 15, having reflective surface regions which exhibit at least two optically variable effects which can be recognized from different viewing directions and which are manifested in different colors,

providing a carrier, the planar extension of the carrier defining a planar surface and a z-axis upstanding perpendicularly thereon,

providing the carrier with a reflective surface area, which comprises two individual relief structures which are arranged in different height levels in the z-direction and form a lower relief structure and a higher relief structure, and which are designed to overlap in the feature area,

providing the higher relief structure with a first reflection enhancing coating following the relief trend, said first reflection enhancing coating having wavelength-dependent reflection and transmission in the visible spectral range and having at least one reflection band and at least one transmission band,

providing the lower relief structure with a second reflection enhancing coating following the relief trend, said second reflection enhancing coating having wavelength-dependent reflection and transmission in the visible spectral range and having at least one reflection band and at least one transmission band,

wherein the reflection-enhancing coatings are adapted to each other in such a way that the reflection band of the second reflection-enhancing coating is at least partially in the transmission band of the first reflection-enhancing coating and at least one transmission band of the two reflection-enhancing coatings overlaps such that

The higher relief structure exhibits a first optically variable effect of a first color in reflection viewing, the lower relief structure exhibits a second optically variable effect of a second, different color through the first enhanced reflective coating in reflection viewing, and wherein the appearance of a third, different color is exhibited through the higher relief structure and the lower relief structure in transmission viewing.

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