EP3284612A1 - Optically variable security element with a thin film element - Google Patents

Abstract

The invention relates to an optically variable security element (20) for protecting valuables, which is provided in a feature area with a color shift thin film element (40) having an interference layer structure (42) with at least one printed dielectric spacer layer (46). According to the invention, it is provided that in the feature area, the security element (20) has an embossed structure (26) with steep flanks (28) and flat surface sections (32, 34) on at least two height levels, - wherein the lateral dimensions of the planar surface portions (32, 34) lie in at least one spatial direction below the resolution limit of the human eye, and that - The printed dielectric spacer layer (26) in the flat surface portions (32, 34) of different levels height different large layer thickness (e 1, e 2) and thus produces different interference colors.

Description

The invention relates to an optically variable security element for securing valuables, which is provided in a feature area with a thin-film element with a color shift effect, which has an interference layer structure with at least one printed dielectric spacer layer. The invention also relates to a method for producing such a security element and a correspondingly equipped data carrier.

Data carriers, such as valuables or identity documents, or other valuables, such as branded articles, are often provided with security elements for the purpose of security, which permit verification of the authenticity of the data carriers and at the same time serve as protection against unauthorized reproduction. Security elements with viewing-angle-dependent effects play a special role in the authentication of authenticity since they can not be reproduced even with the most modern copiers. The security elements are thereby equipped with optically variable elements that give the viewer a different image impression under different viewing angles and, for example, show a different color or brightness impression and / or another graphic motif depending on the viewing angle.

Security elements with multilayer thin-film elements are often used whose color impression changes with the viewing angle for the viewer (referred to below as the color-shift effect). As the layer mainly responsible for the color effect, the thin-film elements include an ultrathin dielectric layer, which is typically disposed between an absorber layer and a reflective layer is. Due to the interference conditions, the thin-film elements essentially show only spectral colors as interference colors. Even in cases where two reflection maxima are in the visible spectral range, the wavelengths of these reflection maxima are in a physically predetermined distance or ratio and can not be set as desired.

In the manufacture of the thin-film elements, the production of the dielectric layer, which is only a few hundred nanometers thin, represents the major technological challenge. The customary production of the thin dielectric layers by a vacuum vapor deposition process is a time-consuming and expensive process. For some time, therefore, there have been extensive attempts to use printed dielectric spacer layers. Large area can be set by the choice of the printing cylinder and the solid of the paint a desired layer thickness. By suitable cylinder design, the layer thickness of the printed dielectric can be varied macroscopically, ie on a length scale of a few millimeters. By such a variation of the layer thickness but also the color impression can be changed only on a macroscopic length scale.

Proceeding from this, the present invention seeks to provide a security element of the type mentioned with improved color representation, and in particular allows color changes in a confined space and the generation of mixed colors.

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

• das Sicherheitselement im Merkmalsbereich eine Prägestruktur mit steilen Flanken und ebenen Flächenabschnitten auf zumindest zwei Höhenstufen aufweist,
• wobei die lateralen Abmessungen der ebenen Flächenabschnitte in zumindest einer Raumrichtung unterhalb der Auflösungsgrenze des menschlichen Auges liegen, und dass
• die aufgedruckte dielektrische Abstandsschicht in den ebenen Flächenabschnitten unterschiedlicher Ebenenhöhe unterschiedliche große Schichtdicke aufweist und so unterschiedliche Interferenzfarben erzeugt.

According to the invention, it is provided in a generic security element that

• the security element in the feature area has an embossed structure with steep flanks and flat surface sections on at least two height levels,
• wherein the lateral dimensions of the planar surface portions lie in at least one spatial direction below the resolution limit of the human eye, and that
• the printed dielectric spacer layer has different large layer thicknesses in the flat surface sections of different plane height and thus generates different interference colors.

By providing an embossing structure with different plane heights, the above-mentioned dissolution restrictions can be overcome since, by suitable printing, thickness variations of the dielectric spacer layer can be produced on a length scale, which are given by the dimensions of the embossed structure and can therefore lie in the micrometer range.

Advantageously, the printed dielectric spacer layer has a greater layer thickness in the lower-lying planar surface sections than in the upper-lying planar surface sections. In this case, the relationship applies with particular advantage that, for two planar surface sections with a height difference Δ, the layer thickness of the dielectric spacer layer of the deeper surface section is greater by k * Δ than the layer thickness of the dielectric layer Distance layer of the higher-lying surface portion, where k is a shrinkage factor for the shrinkage of the dielectric spacer layer in drying, which is between 0.05 and 1.

$${\mathrm{e}}_{\mathrm{3}}-{\mathrm{e}}_{\mathrm{2}}=\mathrm{k}*\left({\mathrm{h}}_{\mathrm{3}}-{\mathrm{h}}_{\mathrm{2}}\right),$$

$${\mathrm{e}}_{\mathrm{3}}-{\mathrm{e}}_{\mathrm{1}}=\mathrm{k}*\left({\mathrm{h}}_{\mathrm{3}}-{\mathrm{h}}_{\mathrm{1}}\right),$$

jeweils mit demselben Wert für den Schrumpfungsfaktor k.This relationship applies in particular even if the embossing structure contains planar surface sections at more than two different height levels. For example, the layer thicknesses e ₁ , e ₂ , e _{3 of} the dielectric spacer layers on flat surface sections with heights h ₁ <h ₂ <h ₃ then satisfy the relationships: $${\mathrm{e}}_{\mathrm{2}}-{\mathrm{e}}_{\mathrm{1}}=\mathrm{k}*\left({\mathrm{H}}_{\mathrm{2}}-{\mathrm{H}}_{\mathrm{1}}\right).$$

$${\mathrm{e}}_{\mathrm{3}}-{\mathrm{e}}_{\mathrm{2}}=\mathrm{k}*\left({\mathrm{H}}_{\mathrm{3}}-{\mathrm{H}}_{\mathrm{2}}\right).$$

$${\mathrm{e}}_{\mathrm{3}}-{\mathrm{e}}_{\mathrm{1}}=\mathrm{k}*\left({\mathrm{H}}_{\mathrm{3}}-{\mathrm{H}}_{\mathrm{1}}\right).$$

each with the same value for the shrinkage factor k.

Particularly preferably, the embossed structure is formed, at least in a subregion, by a binary structure or a multilevel structure with n different height levels, where n is preferably between 3 and 8.

The flanks of the embossed structure are advantageously uncoated or are coated with a non-interference-capable layer structure. For example, after application in a etching step, a reflection layer can be removed from the flanks or converted so that an interference-capable layer structure no longer arises on the flanks.

The lateral dimensions of the flat surface portions are advantageously in at least one spatial direction below 150 microns, in particular between about 5 microns and about 100 microns. In an advantageous embodiment, the lateral dimensions of the flat surface sections lie below the resolution limit of the human even in both lateral spatial directions Auges, preferably below 150 microns, in particular between about 5 microns and about 100 microns. The flat surface sections advantageously form elongated strips or rectangular pixel elements.

The height differences between two flat surface sections are expediently between 50 nm and 5000 nm, preferably between 300 nm and 3000 nm. The layer thickness of the embossing lacquer layer is advantageously between 500 nm and 10 μm, preferably between 1500 nm and 6000 nm.

The dielectric spacer layer is advantageously formed by a thixotropic lacquer, ie a lacquer whose viscosity is reduced by mechanical stress and increases again after the end of the stress with a certain time constant. For this purpose, the paint may contain additives which produce or enhance the thixotropic behavior or serve to adjust the time constant with which the viscosity increases again. Particularly suitable lacquers are nitrocellulose lacquers, for example the Senocell® product line from Weilburger, which already exhibit thixotropic behavior without additives. In particular, leveling additives which reduce the surface tension of the varnish can be used as additives. Examples of such flow control additives are polyacrylate-based additives, such as Byk 361N from Byk Additives & Instruments, or also silicone surface additives, such as polyether-modified dimethylpolysiloxane or polyether-modified polydimethylsiloxane.

The interference layer structure of the thin-film element may be a sequence of dielectric layers with different refractive index or may also be formed as a metallic / dielectric multilayer structure. At present, configurations in which the interference layer structure comprises a reflection layer, an absorber layer and an intermediate layer are particularly preferred comprising the reflective layer and the absorber layer disposed dielectric spacer layer. In this case, the layer order is arbitrary, so that both the reflection layer and the absorber layer can first be applied to the embossed structure.

The layer thicknesses of the printed dielectric spacer layer are advantageously between 100 nm and 1000 nm, preferably between 300 nm and 600 nm. As described in more detail below, a thixotropic lacquer can first be applied in a higher layer thickness. The layer thicknesses mentioned result after drying and, if appropriate, shrinkage of the lacquer as layer thicknesses of the finished dielectric spacer layer.

In an advantageous variant of the invention, the different interference colors generated by the planar surface sections form at least one mixed color when viewing the feature region. In the context of this description, colors which are obtained by mixing two or more primary colors are referred to as mixed colors or true colors.

In a likewise advantageous variant of the invention, the planar surface sections represent microimage elements in a microoptical representation arrangement, in particular a moiré magnification arrangement, or picture elements in a lenticular screen.

The embossed structure can contain a subarea with four or more different height levels, in which the interference colors complement one another when viewed without aids to a non-colored, in particular silvery, appearance. However, with a strong magnifying glass or a microscope, the individual interference colors can be made visible, so that the subarea can be used as a security feature of higher level.

The embossed structure may also include a portion of anti-reflection elements, such as moth-eye structures, in which the reflection is highly suppressed and therefore appears dark when viewed.

Further, the embossed structure may include a non-contact, flat portion in which a conventional interference layer structure is formed. In particular, the non-sensitive subregion may be combined with a binary or multilevel structure of the type described above, such that the non-sensitive subregion and the binary or multilevel structure under normal illumination, such as daylight, have the same color but different spectral composition. On the other hand, by illuminating with a light source of special spectral signature, for example a fluorescent lamp or LED lamp, or when viewed through a color filter, the colors of the non-sensitive subregion or the binary or multilevel structure appear different due to their different spectral composition. The non-sensitive subregion and the region of the binary or multilevel structure can be arranged in particular in the form of patterns, characters or a coding and form a hidden security feature.

• in einem Merkmalsbereich des Sicherheitselements eine Prägestruktur mit steilen Flanken und ebenen Flächenabschnitten auf zumindest zwei Höhenstufen erzeugt wird, wobei die lateralen Abmessungen der ebenen Flächenabschnitte in zumindest einer Raumrichtung unterhalb der Auflösungsgrenze des menschlichen Auges liegen,
• die Prägestruktur mit einem Dünnschichtelement mit Farbkippeffekt versehen wird, wobei das Dünnschichtelement mit einem Interferenzschichtaufbau erzeugt wird und dabei zumindest eine dielektrische Abstandsschicht aufgedruckt wird, und
• die aufgedruckte dielektrische Abstandsschicht verlaufen gelassen wird, so dass sich die Schichtdicken in den ebenen Flächenabschnitten unterschiedlicher Höhenstufe einander angleichen.

The invention also includes a method for producing an optically variable security element for securing valuables, in which

• In a feature region of the security element, an embossed structure with steep flanks and flat surface sections is produced on at least two height levels, wherein the lateral dimensions the planar surface sections lie in at least one spatial direction below the resolution limit of the human eye,
• the embossed structure is provided with a thin-film element with a color-shift effect, wherein the thin-film element is produced with an interference layer structure and thereby at least one dielectric spacer layer is printed, and
• the printed dielectric spacer layer is allowed to pass, so that the layer thicknesses in the planar surface sections of different height level are equal to each other.

Preferably, a thixotropic lacquer is used for printing the dielectric spacer layer, which is optionally provided with additives. Concrete examples of suitable coatings and additives are already mentioned above.

In order to reduce the viscosity of the paint, the thixotropic paint is mechanically stressed, for example stirred, in an advantageous process procedure prior to printing. The thixotropic lacquer remains thin after the mechanical stress for a certain time and runs after printing as desired from the higher-lying surface sections in the lower-lying surface sections. After completion of the mechanical stress, the viscosity increases again with a certain time constant, which can be adjusted by the addition of additives in a wide range. Specifically, the time constant is advantageously set so that after printing the layer thicknesses in the flat surface portions of different height level can match as much as possible before the paint loses its fluidity. After passing, the varnish of the dielectric spacer layer is advantageously dried, thereby reducing the layer thickness of the dielectric spacer layer in the planar surface portions of the embossed structure. The reduction in thickness during drying depends largely on the solids content of the paint. Advantageously, the solids content of the paint forming the dielectric spacer layer is between 3% and 100%, in particular between 5% and 50%.

The lacquer used can be physically drying, but also crosslinkable. It is also possible that the paint undergoes an increase in viscosity after passing through irradiation and only then is a complete physical drying carried out. The paint can be a one-component system, a two-component system or even a multicomponent system. The paint can cure by a crosslinking reaction, in particular by irradiation, for example with UV light.

The lacquer used can advantageously be metallized so that a metallic reflection or absorber layer can be applied to the printed and dried lacquer.

The printing of the lacquer for the dielectric spacer layer can be carried out by any printing method, for example by gravure printing or by spraying the lacquer.

Finally, the invention also includes a data carrier with a security element of the type described or with a security element that can be produced by a described method. The data carrier may in particular be a value document, such as a banknote, in particular a paper banknote, a polymer banknote or a composite film banknote, a stock, a bond, a deed, a coupon, a check, a high-quality ticket, but also to an ID card, such as a credit card, a bank card, a cash card, an authorization card, an identity card or Passpersonalisierungsseite act.

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

Fig.1

eine schematische Darstellung einer Banknote mit einem erfindungsgemäßen Sicherheitselement in Form eines aufgeklebten Transferelements mit Farbkippeffekt,

Fig. 2

ein erfindungsgemäßes Sicherheitselement in perspektiver Ansicht,

Fig. 3

in (a) bis (e) Zwischenschritte bei der Herstellung des Sicherheitselements der Fig. 2, und

Fig. 4 und 5

jeweils einen Teilbereich von Sicherheitselementen nach weiteren Ausführungsbeispielen der Erfindung im Querschnitt.

Show it:

Fig.1

a schematic representation of a banknote with a security element according to the invention in the form of a glued transfer element with color shift effect,

Fig. 2

a security element according to the invention in a perspective view,

Fig. 3

in (a) to (e) intermediate steps in the production of the security element of Fig. 2 , and

4 and 5

in each case a subarea of security elements according to further embodiments of the invention in cross section.

The invention will now be explained using the example of security elements for banknotes. Fig. 1 shows a schematic representation of a banknote 10, with a security element 12 according to the invention in the form of a glued transfer element is provided with color shift effect. As a special feature, the security element 12 exhibits a color-shift effect between two mixed colors (also called true colors in the context of this description) and, unlike conventional color-shift elements, is not limited to a color change between spectral colors or specific, fixed combinations of spectral colors.

It is understood that the invention is not limited to transfer elements and banknotes, but can be used in all types of security elements, such as labels on goods and packaging or in the security of documents, ID cards, passports, credit cards, health cards and the like. For banknotes and similar documents, in addition to transfer elements, for example, security threads or security strips may also be considered.

The construction of a security element according to the invention and the realization of the color shift effect with mixed colors will now be described with reference to FIGS Fig. 2 explained in more detail, showing a security element 20 according to the invention in a perspective view.

The security element 20 contains a substrate 22, for example a PET film, on which an embossing lacquer layer 24 has been applied in a feature area and provided with an embossed structure 26. In the exemplary embodiment, the embossed structure 26 represents a binary structure which has essentially vertical flanks 28 and planar surface sections 30 at two different height levels. The lateral dimension of the planar surface portions is in a spatial direction that is in Fig. 2 is referred to as the x-direction, only 10 microns, so it is far below the resolution limit of the human eye. In the second lateral spatial direction, the in Fig. 2 when y direction, the dimension of the planar surface portions 30 is several millimeters or even centimeters. The flat surface portions 30 form in the embodiment, therefore, elongated, narrow strips.

On the embossed structure 26, a thin-film element 40 is applied with an interference layer 42, which essentially only the flat surface portions 30, but not the steep flanks 28 coated, so that no flares from the flanks 28 in the finished security element. The interference layer structure 42 in the exemplary embodiment consists of a vapor-deposited aluminum reflection layer 44, a printed dielectric spacer layer 46 and a vapor-deposited chromium absorber layer 48. While the reflection layer 44 and the absorber layer 48 have the same layer thickness in the entire feature region of the security element, the dielectric spacer layer 46 is in formed at different heights flat surface portions 32, 34 formed with different thicknesses layer thickness.

Specifically, the layer thickness of the dielectric spacer layer 46 in the exemplary embodiment in the lower lying planar surface portions 32 is about 700 nm, while in the higher lying planar surface portions 34 is only about 500 nm. Since the interference color of a thin film element is substantially given by the layer thickness of the dielectric spacer layer, the interference layer structure 42 generates different interference colors in the planar surface portions 32 and 34. Because of the small width of the surface portions 32, 34 of only 10 microns, these different interference colors can be resolved when viewed without tools but not as individual colors, but form by additive color mixing a uniform mixed color.

Pure printing technology can not specifically produce different layer thicknesses of the dielectric spacer layer on a length scale of about 10 μm. For the preparation of the security element 20 of Fig. 2 Therefore, a suitably designed embossing structure 26 is used, which is printed to produce the different thickness dielectric spacer layer with a paint with good flow, as with reference to Fig. 3 now explained in more detail.

First, an embossing lacquer layer 24 is applied to the substrate 22 of the security element 20 and the embossed structure 26 already described in the form of a binary structure is embossed into it. The height difference of each 10 microns wide flat surface portions 32, 34 is in the embodiment in this case Δ = 1 micron. The embossed structure 26 is vapor-deposited with a reflective layer 44, for example a 50 nm thick aluminum reflective layer, as in FIG Fig. 3 (a) shown.

In practice, the flanks 28 of the embossing structure 26 need not be perfectly perpendicular to the flat surface portions 32, 34. Rather, a sufficiently steep angle, for example 70 ° or more or 80 ° or more, is sufficient, which leads to a significantly lower layer thickness on the flanks during vapor deposition. A possible flank coating can also be removed by an etching step or converted so that the appearance of the finished security element 20 is not disturbed by reflections from the flanks 28.

Subsequently, a paint 50 is applied to the coated embossed structure for forming the dielectric spacer layer, which exhibits a thixotropic behavior, which is therefore thin after application for a certain period of time and runs well, but whose viscosity then increases sharply and finally prevents further flow. The thixotropic paint 50 is stirred, for example, before printing, so that the viscosity of the paint 50 is greatly reduced by the shear forces occurring. The thin-bodied paint 50 is applied quickly in a printing process or by means of nozzle application with a constant surface density on the imprinted with the reflective layer 44 embossed structure 26, as in Fig. 3 (b) shown. The applied nominal layer thickness of the lacquer 50 in the exemplary embodiment is d = 3 μm.

After application, the still fluid paint 50 extends from the higher-lying to the lower-lying surface portions (arrows 52) and thereby compensates for the height differences between the flat surface portions 32, 34, as in Fig. 3 (c) shown. Since the surface portions 32, 34 have the same width of 10 microns in the exemplary embodiment, results after the varnish 50 in the higher surface portions 34, a layer thickness of the existing paint of only d ₁ = 2.5 microns, while the layer thickness in the deeper surface portions 32 to d ₂ = 3.5 microns has risen. It is understood that other, virtually any desired layer thicknesses d ₁ , d ₂ or layer thickness ratios can be set after bleeding of the varnish 50 due to the duty cycle of the surface sections 32, 34 and the height difference Δ.

The thixotropic enamel 50 is given sufficient time to bleed and restore the original, higher viscosity. After the waiting time of the paint 50 is practically no longer flowable, so that there is no compensation in the subsequent change in the layer thickness by the drying process.

The coated lacquer 50 is now physically dried, as a result of which the layer thickness of the lacquer 50 in both surface sections 32, 34 is uniformly reduced. The extent of the thickness reduction depends largely on the solids content of the paint, but also on the density of the paint before and after drying. For example, the solids content in the exemplary embodiment is 20%, so that the layer thickness d ₁ or d ₂ present after the course is reduced to approximately 1/5 during the drying process. In the embodiment, a dielectric spacer layer 46, which in the higher-lying surface portions 34 a layer thickness of e ₁ = results so d _1/5 = 500 nm and in the underlying surface portions 32 a layer thickness of e ₂ = d _2/5 = 700 nm has, as in Fig. 3 (d) shown.

Subsequently, an absorber layer 48 of chromium is evaporated on the dielectric spacer layer 46, as in FIG Fig. 3 (e) shown to complete the interference layer structures in the surface areas 32, 34.

In the manner described, despite the deposition of the dielectric spacer layer with only one pressure step and in only a nominal layer thickness, two or more different target layer thicknesses can be produced. Instead of a binary structure, the relief structure 26 can also have a multilevel structure with three, four or more different height levels and the same or different height differences. The degree of shrinkage of the paint can be adjusted by the solids content in a wide range. Only the average thickness of the dielectric spacer layer is determined by the areal density of the applied paint. Overall, the designer gets a great deal of freedom in selecting and combining different color-shift effects with mixed colors.

If many, in particular four or more, different height levels or height differences are involved in one area, then the individual interference colors generated in a narrow space can complement each other to a non-colored, in particular silvery, appearance, as in the exemplary embodiment of FIG Fig. 4 shown. In the case of the security element 60, an embossing lacquer layer 24 with an embossed structure in the form of a multi-level structure 62 with in each case 20 μm wide flat strips 64-1, 64-2, 64-3, 64-4 at four different height levels h ₁ <is present on the substrate 22 h ₂ <h ₃ <h ₄ provided.

mit demselben Wert für den Schrumpfungsfaktor k. Nach der Vervollständigung durch eine Chrom-Absorberschicht 48 entstehen auf engsten Raum 66 jeweils vier unterschiedliche Interferenzschichtfarben, die sich für einen Betrachter zu einem nicht-farbigen, silbrig glänzenden Erscheinungsbild mischen.Accordingly, four different layer thicknesses e _i for the dielectric spacer layer 46 are formed after vapor deposition of the aluminum reflective layer 44, the application of a well-proceeding varnish, the running of the varnish and the subsequent drying of the varnish. As explained above, the layer thicknesses e _{i are} not independent of one another. Rather, for i, j = 1, ..., 4 and i <j $${\mathrm{e}}_{\mathrm{j}}-{\mathrm{e}}_{\mathrm{i}}=\mathrm{k}*\left({\mathrm{H}}_{\mathrm{j}}-{\mathrm{H}}_{\mathrm{i}}\right)$$

with the same value for the shrinkage factor k. After completion by means of a chromium absorber layer 48, four different interference layer colors are formed on the narrowest space 66, which blends for a viewer into a non-colored, silvery shiny appearance.

With a strong magnifying glass or a microscope, however, the individual colors of the small interference layer structures of the strips 64-1, 64-2, 64-3, 64-4 can be made visible and thus distinguished from a purely metallic appearing security element. The fine structure of the security element 60 can thus be used as a higher-level security feature. The specific design and arrangement of the strips can also represent information that is hidden under normal viewing and only visible under high magnification.

By combining the described embossing structure with conventional thin-film designs, further optical effects can be produced. For example, by suitable tuning, a thin-film element with adjacent metameric colors can be produced which, for example, look identical in daylight but clearly differ from one another under artificial light or under a color filter.

Fig. 5 shows for this purpose a security element 70, on the substrate 22 an embossing lacquer layer 24 is applied, which has in a first portion 72 in the manner described above an embossed binary structure with two planar surface portions 74-1, 74-2 at two height levels. In a second portion 76, the embossing lacquer layer is flat without relief.

After generating the interference layer structure 42 with reflection layer 44, printed dielectric spacer layer 46 and absorber layer 48 already described, a mixed color results in the first partial region 72 as an interference color and a spectral color, for example a green, in the second partial region 76. The relative width of the planar surface sections 74-1, 74-2 and the difference in height between the surface sections can now be selected such that the daylight reflection in the first partial region 72 also shows the green of the second partial region 76, but not as a spectral color, but as Mixed color of blue (interference color in the area portions 74-1) and yellow (interference color in the area portions 74-2).

Since the human eye is not sensitive to the spectral composition of the color, the portions 72 and 76 appear in daylight with hue green. However, the different spectral composition can be made visible by illuminating the security element 70 with a light source having a different spectral signature, for example with a fluorescent lamp or an LED lamp, or by viewing through a color filter. The partial regions 72, 76 then appear with different color or brightness and can be clearly distinguished by the observer and, for example, show previously hidden patterns, characters or codes.

LIST OF REFERENCE NUMBERS

10

bill

12

security element

20

security element

22

substratum

24

Embossing lacquer layer

26

embossed structure

28

flanks

30, 32, 34

flat surface sections

40

thin-film element

42

Interference layer structure

44

reflective layer

46

dielectric spacer layer

48

absorber layer

50

thixotropic varnish

52

Bleeding the paint

60

security element

62

Multilevel structure

64-1, 64-2, 64-3, 64-4

flat stripes

70

security element

72

first subarea

74-1, 74-2

flat surface sections

76

second subarea

Claims (15)

An optically variable security element for securing valuables, which is provided in a feature area with a thin-film element with a color shift effect, which has an interference layer structure with at least one printed dielectric spacer layer, characterized in that the security element in the feature area has an embossed structure with steep flanks and flat surface sections on at least two height levels, - wherein the lateral dimensions of the planar surface portions are in at least one spatial direction below the resolution limit of the human eye, and that - The printed dielectric spacer layer in the flat surface portions of different levels height has different large layer thickness and thus produces different interference colors. A security element according to claim 1, characterized in that the printed dielectric spacer layer has a greater layer thickness in the lower-lying planar surface sections than in the upper-lying planar surface sections. Security element according to claim 1 or 2, characterized in that the embossed structure is formed at least in a partial area by a binary structure or a multi-level structure with n different height levels, where n is preferably between 3 and 8. A security element according to at least one of claims 1 to 3, characterized in that the flanks of the embossed structure are coated uncoated or with a non-interference-capable layer structure. A security element according to at least one of claims 1 to 4, characterized in that the lateral dimensions of the planar surface sections lie in both spatial directions below the resolution limit of the human eye. A security element according to at least one of claims 1 to 5, characterized in that the planar surface portions form elongated strips or rectangular pixel elements. A security element according to at least one of claims 1 to 6, characterized in that the dielectric spacer layer is produced by a thixotropic lacquer. A security element according to at least one of claims 1 to 7, characterized in that the interference layer structure of the thin-film element comprises a reflection layer, an absorber layer and the dielectric spacer layer arranged between the reflection layer and the absorber layer. A security element according to at least one of claims 1 to 8, characterized in that the different interference colors generated by the flat surface portions form at least one mixed color when viewing the feature region. A security element according to at least one of claims 1 to 9, characterized in that the planar surface portions represent microimage elements in a micro-optical representation arrangement, in particular a moiré magnification arrangement, or image elements in a lenticular image. Method for producing an optically variable security element for securing valuables, in which in a feature region of the security element, an embossed structure having steep flanks and flat surface sections is produced on at least two height levels, wherein the lateral dimensions of the planar surface sections lie in at least one spatial direction below the resolution limit of the human eye, - The embossed structure is provided with a thin-film element with a color shift effect, wherein the thin-film elements is produced with an interference layer structure and thereby at least one dielectric spacer layer is printed, and - The printed dielectric spacer layer is allowed to run, so that the layer thicknesses in the flat surface portions of different height level equalize. A method according to claim 11, characterized in that for printing the dielectric spacer layer, a thixotropic lacquer is used. A method according to claim 11 or 12, characterized in that the thixotropic lacquer is mechanically stressed before printing, for example by stirring, in order to reduce the viscosity of the lacquer. Method according to at least one of claims 11 to 13, characterized in that the lacquer of the dielectric spacer layer is dried after the running and its layer thickness is thereby reduced in the planar surface portions of the embossed structure. Data carrier with a security element according to at least one of claims 1 to 10 or with a producible according to one of claims 11 to 14 security element.

Images