DE102022133325A1 - Optically variable security element with 5-layer stack, data carrier and manufacturing process - Google Patents

Abstract

The invention relates to an optically variable security element (20), in particular security film or security thread, with a 5-layer stack (21) which comprises, in this order, a first absorber layer (23), a first dielectric spacer layer (24), a second absorber layer (25), a second dielectric spacer layer (26) and a reflection layer (27). According to the invention, it is provided that the first and second dielectric spacer layers (24, 26) have different layer thicknesses in order to generate a specific IR reflection signature of the security element.

Description

The invention relates to an optically variable security element with a 5-layer stack comprising, in this order, a first absorber layer, a first dielectric spacer layer, a second absorber layer, a second dielectric spacer layer and a reflection layer. The invention also relates to a data carrier with such a security element and to a method for producing such a security element.

Data storage media, such as valuables or identification documents, or other valuable items, such as branded goods and packaging or outer packaging of high-quality branded goods, are often provided with security elements for security purposes, which allow the authenticity of the data storage media to be verified and which at the same time serve as protection against unauthorized reproduction.

Security elements with viewing angle-dependent effects play a special role in authenticity assurance, as these cannot be reproduced even with the most modern copying machines. Color-shifting security elements are often used, which have a stack of thin layers with well-controlled layer thickness in order to produce angle-dependent interference colors or color changes.

The security function of optically variable security elements can be increased if they are also designed to be machine-readable. When used on banknotes, the security elements can then be checked both visually by a human user and sensorially on slow deposit machines and on fast banknote processing machines. In banknote processing machines, an additional check can improve both the detection of counterfeit banknotes and the condition assessment of genuine banknotes.

The color-shifting security elements usually consist of a 3-layer resonator made of a chrome absorber layer, a dielectric spacer layer made of SiO ₂ and an aluminum reflector layer. The layer stacks show interference maxima in reflection not only in the visible spectral range, but also in the near infrared, which can be used for machine authentication. The interference maxima in the visible and near infrared are intrinsically coupled to one another via the thickness of the SiO ₂ spacer layer.

From the EP 0 472 371 A1 A double resonator with a 5-layer stack is also known, in which two periods of absorber layer and dielectric spacer layer are arranged on a reflector layer in order to suppress peaks in the reflection spectrum.

Based on this, the invention is based on the object of specifying a security element of the type mentioned at the beginning with increased security against forgery.

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

According to the invention, in a generic security element, the first and second dielectric spacer layers have different layer thicknesses in order to generate a specific IR reflection signature of the security element.

Compared to the use of a conventional 3-layer stack, the use of a double resonator with 5 layers opens up additional degrees of design freedom, which allow, on the one hand, to maintain a desired or proven color shift effect in the visible spectral range and, on the other hand, to generate a specific infrared reflection signature in the near infrared that is modified compared to conventional 3-layer structures. The specific signature is provided in particular by the different thicknesses of the two dielectric spacer layers. The different thicknesses of the two dielectric spacer layers preferably differ by more than 10% of the thickness of the thinner of the two dielectric spacer layers.

The use of different thicknesses of the two dielectric spacer layers in the 5-layer structure means that the course of the reflection spectrum in the near infrared differs particularly strongly from the reflection spectrum of a 3-layer structure with a comparable color shift effect in the visible spectral range.

A security element according to the invention can then show the same functionality in the visible spectral range as a conventional security element with a 3-layer structure, but can be distinguished from a conventional security element during machine authentication due to its specific IR reflection signature. By distributing the IR differently between the two dielectric spacer layers, several different specific IR reflection signatures can be generated with the same total thickness of the dielectric. With a clever choice of the thickness ratio and the manufacturing process, the security elements according to the invention can also have better properties. properties, in particular higher color purity and more brilliant colors, than security elements with conventional 3-layer structures and a comparable color shift effect.

In an advantageous embodiment, the first and second dielectric spacer layers have a thickness ratio in the ratio of small whole numbers such as 2:1 (or 1:2) or 3:1 (or 1:3) or 4:1 (or 1:4), since this achieves particularly pronounced modulations and thus a particularly characteristic spectral profile in the near infrared with a brilliant color effect in the visible spectral range. In the inventors' experiments, a thickness ratio of approximately 2:1 or 1:2 proved to be particularly advantageous for this purpose. With such a ratio, the most attractive spectra in the visible spectral range and the most striking differences in the near infrared could be achieved.

The thicker of the two dielectric spacer layers is preferably in a thickness range between 200 nm and 600 nm, since interference colors with the greatest saturation can be achieved in this thickness range. If the thicker layer is less than 200 nm thick, the reflection maxima are already very close to the edge of the visible spectral range; if the thicker layer is more than 600 nm thick, there are many maxima in the visible spectral range, which also lead to reduced saturation. Thicker layers are also disadvantageous in terms of producibility and cost-effectiveness in production.

It has also been found to be advantageous if the dielectric spacer layer closer to the reflection layer is the thinner of the two spacer layers. If the 5-layer stack is applied to a substrate, the thinner dielectric spacer layer is advantageously the dielectric spacer layer furthest from the substrate and the thicker dielectric spacer layer is the dielectric spacer layer closest to the substrate. With such a sequence of thick and thin layers, the inventors found particularly pronounced extreme values in the reflection spectra.

In an advantageous embodiment, the first and/or second dielectric spacer layer is formed from an inorganic material, preferably from one of the materials SiO ₂ , Al ₃ O ₂ , MgF ₂ , CaF ₂ and SiON. In a particularly preferred embodiment, both dielectric spacer layers are formed from SiO ₂ .

In further advantageous embodiments, at least one of the dielectric spacer layers is advantageously formed from a polymer-based material, preferably from a material based on nitrocellulose, epoxy, polyester, rosin, acrylate, alkyd, melamine, PVA, PVC, isocyanate or urethane systems. In a particularly preferred embodiment, one, for example the first, dielectric spacer layer is formed from SiO ₂ and one, for example the second, dielectric spacer layer is formed from a polymer-based material.

The reflective layer is preferably made of aluminum or a metal with achromatic appearance and high degree of reflection in the visible range. For example, the reflective layer can be made of one of the metals Ti, Ta, Zn, Mo, W, Ni, Ir, Pd.

In an advantageous embodiment, the 5-layer stack is arranged on a carrier film, preferably in such an orientation that the first absorber layer is the layer of the layer stack closest to the carrier film. The carrier film can be formed, for example, by a PET film and is advantageously transparent so that the viewing can take place through the carrier film.

The carrier film can be unstructured or structured, whereby the 5-layer stack can also be applied in particular to the structured side of the carrier film. The carrier film is advantageously provided with micro-optical structures, in particular with embossed micro-optical structures, preferably with a micro-mirror array and/or nano-optical structures, such as holograms. In addition to the color-shift effect, the micro-optical structures can produce further effects, for example movement effects, motif change effects, 3D effects or the like. In their experiments, the inventors have recognized that the micro-optical structures produce microscopically locally modified viewing angles, but hardly interfere with the machine readability of the security element in the near infrared.

The invention also includes a data carrier with an optically variable security element of the type described above. The data carrier can in particular be a value document, such as a banknote, in particular a paper banknote, a polymer banknote or a film composite banknote, a share, a bond, a certificate, a voucher, a cheque, a seal, a tax stamp, a high-quality admission ticket, but also an identification card, such as a credit card, a bank card, a cash payment card, an authorization card, an identity card or a passport personalization page.

The invention further includes a method for producing an optically variable security element of the type described, in which a 5-layer stack with the layer sequence first absorber layer, first dielectric spacer layer, second absorber layer, second dielectric spacer layer and reflection layer is applied to a substrate, and in which the first and second dielectric spacer layers are applied in different layer thicknesses in order to produce a specific IR reflection signature of the security element. The substrate can in particular be the above-mentioned carrier film.

In an advantageous process, the first absorber layer, the first dielectric spacer layer, the second absorber layer and the second dielectric spacer layer are applied in an inline system without leaving the vacuum.

Advantageously, the first and second absorber layers are applied by electron beam evaporation or sputter deposition, in particular by DC magnetron sputtering.

Also advantageously, the first and/or second dielectric spacer layer is applied by electron beam evaporation or RF sputtering or reactive pulsed DC magnetron sputtering.

In an advantageous development, the second dielectric spacer layer is a polymer-based dielectric layer which is applied by printing or by slot die coating in continuous operation.

Further embodiments and advantages of the invention are explained below with reference to the figures, in which a true-to-scale and true-to-proportion reproduction was omitted in order to increase clarity.

• 1 eine schematische Darstellung einer Banknote mit zwei Sicherheitselementen nach Ausführungsbeispielen der Erfindung,
• 2 schematisch den Aufbau eines Sicherheitselements nach einem Ausführungsbeispiel der Erfindung,
• 3 den Aufbau eines herkömmlichen Sicherheitselements mit 3-Schicht-Resonator,
• 4 das Reflexionsspektrum des herkömmlichen 3-Schicht-Aufbaus der 3 im Vergleich zu dem Reflexionsspektrum des erfindungsgemäßen 5-Schicht-Aufbaus nach 2,
• 5 die Reflexionsspektren zweier erfindungsgemäßer Sicherheitselemente mit 5-Schicht-Stapel, jeweils nach dem Prinzip der 2,
• 6 einen Vergleich der Reflexionsspektren eines herkömmlichen 3-Schicht-Aufbaus mit einem erfindungsgemäßen 5-Schicht-Aufbau, jeweils bei senkrechter und schräger Beleuchtung, und
• 7 einen Vergleich eines Reflexionsspektrums eines Farbkipp-Schichtstapels auf einem unstrukturierten PET- Superstrat und eines Reflexionsspektrums desselben Schichtstapels auf einem mit geprägten Mikrospiegeln versehenen PET- Superstrat.

Show it:

• 1 a schematic representation of a banknote with two security elements according to embodiments of the invention,
• 2 schematically shows the structure of a security element according to an embodiment of the invention,
• 3 the construction of a conventional security element with 3-layer resonator,
• 4 the reflection spectrum of the conventional 3-layer structure of the 3 compared to the reflection spectrum of the inventive 5-layer structure according to 2 ,
• 5 the reflection spectra of two security elements according to the invention with 5-layer stack, each according to the principle of 2 ,
• 6 a comparison of the reflection spectra of a conventional 3-layer structure with a 5-layer structure according to the invention, each under vertical and oblique illumination, and
• 7 a comparison of a reflection spectrum of a color-shift layer stack on an unstructured PET superstrate and a reflection spectrum of the same layer stack on a PET superstrate provided with embossed micromirrors.

The invention will now be explained using the example of security elements for banknotes. 1 shows a schematic representation of a banknote 10 which is provided with two security elements 12 and 14 according to embodiments of the invention. The first security element is a security thread 12 which can be applied to the surface of the banknote or partially embedded in the substrate of the banknote.

The second security element is formed by an adhesively bonded transfer element 14 of any shape. The security element 14 can also be designed in the form of a cover film that is arranged over a window area or a continuous opening in the banknote. It is understood, however, that the invention is not limited to transfer elements and security threads on banknotes, but can be used for all types of security elements, for example for labels on goods and packaging or for securing documents, ID cards, passports, credit cards, health cards and the like.

The structure and appearance of security elements according to the invention in comparison to conventional security elements will now be described with reference to the 2 to 7 explained in more detail.

2 shows schematically the structure of a security element 20 according to an embodiment of the invention. In the security element 20, a 5-layer stack 21 is applied to a 12 µm thick PET carrier film 22, which, starting from the carrier film 22, comprises in this order a 3 nm thick first absorber layer 23 made of chromium, a 140 nm thick first dielectric spacer layer 24 made of SiO ₂ , a 5 nm thick second absorber layer 25 made of chromium, a 280 nm thick second dielectric spacer layer 26 made of SiO ₂ , and an opaque, 50 nm thick reflection layer 27 made of aluminum.

4 shows a comparison of the reflection spectra of the inventive 5-layer structure of the 2 with a conventional 3-layer structure according to 3 In the conventional security element 30, a 3-layer stack 31 is applied to a 12 µm thick PET carrier film 32, which, starting from the carrier film 32, comprises in this order a 5 nm thick absorber layer 33 made of chromium, a 400 nm thick dielectric spacer layer 34 made of SiO ₂ and an opaque, 50 nm thick reflection layer 37 made of aluminum.

In the 5-layer stack 21, the layer thicknesses are selected such that the sum of the layer thicknesses of the two dielectric spacer layers 24, 26 is equal to the layer thickness of the individual dielectric spacer layer 34 of the 3-layer structure. This ensures that the two different layer stacks have a reflection spectrum in the visible spectral range that is as comparable as possible. The layer thicknesses of the PET carrier films 22, 32 and the opaque reflection layers 27, 37 are each the same.

The reflection spectra of the two structures were calculated using the IMD software (David L. Windt, “IMD software for modeling the optical properties of multilayer films”, Computers in Physics 12, 360 (1998)). Using optical constants, in particular refractive and extinction indices from the literature, the various materials were modeled as individual layers in a layer stack and the resulting reflection and transmission spectra were calculated using the Fresnel equations. The angle of incidence, layer thicknesses and layer boundary transitions are also included in the calculation.

4 shows in the diagram 40 the reflection spectrum 42 of the conventional 3-layer structure of the 3 with solid lines compared to the reflection spectrum 44 of the inventive 5-layer structure according to 2 with dashed lines. Both reflection spectra were measured for perpendicular light incidence 28 (see 2 ) is calculated. Diagram 40 shows the reflectivity as a function of wavelength in the visible spectral range from 380 nm to 780 nm and in the near infrared range from 780 nm to 2000 nm.

In the visible spectral range, the two reflection spectra 42, 44 show a common, dominant reflection peak 46 at about 460 nm, but the reflection spectra differ fundamentally from one another in the near infrared at wavelengths above 700 nm. While the conventional 3-layer structure has a further reflection maximum 48 at about 930 nm in the near infrared, this is strongly suppressed in the 5-layer structure according to the invention and the reflection even has a minimum 50 there, while a broad secondary maximum 52 forms at about 1200 nm.

With largely identical functionality in the visible spectral range, the 5-layer structure according to the invention shows a strongly different, characteristic spectral profile in the near infrared. This different spectral profile can be checked with reflection or remission sensors such as those typically used on banknote processing machines and used as an additional authenticity feature.

In addition to the human characteristic that can be checked without any aids, namely the colour shift effect in the visible spectral range, the security element 20 thus also provides a characteristic machine-readable authenticity feature for testing in the infrared spectral range.

Authenticity testing with remission or reflection sensors can be carried out with simple sensors with only a few, for example two, test wavelengths, as used in deposit machines, for example, as well as with more complex sensors with higher spectral resolution, as used in particular in larger processing machines.

In order to obtain the most pronounced extreme values in the reflection spectra and thus brilliant colors, it is advantageous to coordinate the layer thicknesses of the two dielectric spacer layers 23, 25. A particularly attractive appearance is obtained if the thickness ratio of the dielectric spacer layers is as in the embodiment of the 2 is about 2:1, since the constructive and destructive interference in the visible spectral range is then maximum, which leads to a visually impressive, brilliant color impression.

Furthermore, thickness ratios of the dielectric spacer layers in the ratio of small whole numbers such as about 2:1 (or 1:2) or about 3:1 (or 1:3) or about 4:1 (or 1:4) are particularly advantageous, since they achieve particularly pronounced modulations and thus a particularly characteristic spectral curve in the near infrared, while at the same time achieving brilliant color effects in the visible spectral range.

Particularly pronounced extreme values in the reflection spectra arise when the dielectric spacer layer close to the substrate is the thicker of the two spacer layers. 5 shows for illustration in diagram 60 the reflection spectra 62, 64 of two security elements according to the invention with 5-layer stack according to the principle of 2 In both variants, the thickness ratio of the two dielectric spacer layers is 2:1 and the total layer thickness is 600 nm; the structures differ only in the sequence of the thicker and thinner dielectric spacer layers.

The solid reflection spectrum 62 represents the simulated reflection spectrum of a first variant of the 5-layer stack, in which the dielectric spacer layer 24 close to the substrate is the thicker spacer layer and is formed by a 400 nm thick SiO ₂ layer, while the dielectric spacer layer 26 remote from the substrate is thinner and is formed by a 200 nm thick SiO ₂ layer.

The dashed reflection spectrum 64 represents the simulated reflection spectrum of a second variant of the 5-layer stack, in which the dielectric spacer layer 24 close to the substrate is the thinner spacer layer and is formed by a 200 nm thick SiO ₂ layer, while the dielectric spacer layer 26 remote from the substrate is thicker and is formed by a 400 nm thick SiO ₂ layer. The carrier film 22, the absorber layers 23, 25 and the reflection layer 27 are the same in both variants and as in 2 educated.

As can be seen from the reflection spectra 62, 64, the first variant, in which the dielectric spacer layer close to the substrate is the thicker layer, leads to significantly more pronounced minima, both in the visible and in the near-infrared spectral range. The first variant therefore leads to more brilliant colors in the visible and allows easier discrimination in the infrared and is therefore particularly preferred.

With an advantageous production of the 5-layer stacks according to the invention, in addition to the modified IR signature, narrower half-widths of the interference maxima can also be obtained.

In principle, the 5-layer stacks can be manufactured in the conventional systems used for the production of security elements with a 3-layer structure. The deposition of the absorber layer, for example a chromium layer, and the deposition of the dielectric spacer layer, for example the SiO ₂ layer, are simply repeated alternately to produce a double resonator.

However, it has proven particularly advantageous to carry out the production in an inline system in which the dielectric spacer layer is deposited together with the absorber layer in a single pass, in particular without leaving the vacuum. In the 5-layer structures described, the first absorber layer 23 made of chromium is deposited sequentially on the PET substrate 22 by electron beam evaporation or sputter deposition, in particular DC magnetron sputtering from the tube target. In the next deposition chamber, the first dielectric spacer layer 24 made of SiO ₂ is deposited, preferably by electron beam evaporation, followed by a further deposition chamber for the second absorber layer 25 made of chromium, and a further SiO ₂ evaporation chamber for the second dielectric spacer layer 26. Finally, the reflection layer 27 made of aluminum is vapor-deposited in the usual way. The inline production of the second absorber layer and the second dielectric spacer layer is also particularly advantageous from an economic point of view.

Diagram 70 of the 6 shows a comparison of the reflection spectra of a conventional 3-layer structure (black curves 72, 74) with a 5-layer structure according to the invention (grey curves 76, 78). The solid lines 72, 76 show the reflection spectrum for vertical light incidence, the dashed lines 74, 78 for oblique light incidence at 45°.

The layer thicknesses of the chromium layers and the SiO ₂ layers were 5 nm Cr and 300 nm SiO ₂ for the 3-layer structure and 2 nm Cr, 300 nm SiO ₂ , 5 nm Cr and 150 nm SiO 2 for the 5-layer structure.

As in 6 As can be seen, the reflection lines in the 5-layer stack according to the invention (gray curves 76, 78) are very similar to the reflection lines of the 3-layer stack, so that visually comparable color effects are produced in the visible spectral range. However, the IR signature of the 5-layer structure differs dramatically from the signature of the conventional designs with a 3-layer structure due to the suppression of the NIR peak at 900 - 1000 nm.

In a further advantageous manufacturing variant, a conventional, inorganic, first dielectric spacer layer 24, such as a vapor-deposited SiO ₂ layer, is combined with a second, thicker, polymer-based dielectric spacer layer 26. The latter can be produced, for example, by printing, for example by means of gravure printing, or by slot die coating in continuous operation.

This manufacturing variant offers reduced process effort and reduced equipment costs compared to multiple vacuum coating. At the same time, brilliant color changes can be achieved in conjunction with unconventional IR reflection spectra. For the polymer-based dielectric spacer layer, for example, a Coatings based on nitrocellulose, epoxy, polyester, rosin, acrylate, alkyd, melamine, PVA, PVC, isocyanate or urethane systems are possible.

As shown above, the 5-layer stacks according to the invention can be combined, for example, with embossed micro-optical structures to create motion effects, motif changes, 3D effects or the like. Although the micro-optical structures lead to a locally modified viewing angle, they hardly interfere with the machine readability of the security element in the near infrared.

7 shows in diagram 80 the comparison of a measured reflection spectrum 82 of a color-shift layer stack on an unstructured PET superstrate and a measured reflection spectrum 84 of the same layer stack on a PET superstrate provided with embossed micromirrors.

As from 7 As can be seen, the optical micromirror structures only have a quantitative influence on the observed reflection spectrum, while qualitatively the essential structures of the spectral characteristics are retained. The spectral positions of the maxima and minima are slightly shifted to shorter wavelengths, but this is due to the shortened effective optical path length due to the micromirrors. This shift can be compensated by specifically adjusting the layer stack used, so that a fixed color impression or a fixed infrared signature can be set regardless of the specific design of the micromirrors. The superstrate interference at longer infrared wavelengths, which is rather disruptive anyway, is even suppressed by the locally different reflection of the micromirrors.

List of reference symbols

10

Banknote

12

Security thread

14

Transfer element

20

Security element

21

5-layer stack

22

PET carrier film

23

first absorber layer

24

first dielectric spacer layer

25

second absorber layer

26

second dielectric spacer layer

27

Reflective layer

30

conventional security element

31

3-layer stack

32

PET carrier film

33

Absorber layer

34

dielectric spacer layer

37

Reflective layer

40

diagram

42

Reflection spectrum 3-layer stack

44

Reflection spectrum 5-layer stack

46

Reflection peak

48

further reflection maximum

50

minimum

52

Secondary maximum

60

diagram

62

Reflection spectrum first variant

64

Reflection spectrum second variant

70

diagram

72

Reflection spectrum 3-layer stack, vertical

74

Reflection spectrum 3-layer stack, oblique

76

Reflection spectrum 5-layer stack, vertical

78

Reflection spectrum 5-layer stack, oblique

80

diagram

82

Reflection spectrum on unstructured superstrate

84

Reflection spectrum on structured superstrate

QUOTES INCLUDED IN THE DESCRIPTION

This list of documents listed by the applicant was generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions.

Cited patent literature

• EP 0472371 A1 [0006]

Claims (14)

Optically variable security element (20), in particular security film or security thread, with a 5-layer stack (21) comprising in this order a first absorber layer (23), a first dielectric spacer layer (24), a second absorber layer (25), a second dielectric spacer layer (26) and a reflection layer (27), characterized in that the first and the second dielectric spacer layer (24, 26) have different layer thicknesses in order to generate a specific IR reflection signature of the security element. Safety element (20) according to Claim 1 , characterized in that the first and second dielectric spacer layers (24, 26) have a thickness ratio of 4:1 or 1:4 or 3:1 or 1:3 or 2:1 or 1:2, preferably 2:1 or 1:2. Safety element (20) according to Claim 1 or 2 , characterized in that the thicker of the two dielectric spacer layers is in a thickness range between 200 nm and 600 nm. Security element (20) according to at least one of the Claims 1 until 3 , characterized in that the first and/or second dielectric spacer layer (24, 26) is formed from an inorganic material, preferably from one of the materials SiO ₂ , Al ₃ O ₂ , MgF ₂ , CaF ₂ and SiON, particularly preferably that both dielectric spacer layers are formed from SiO ₂ . Security element (20) according to at least one of the Claims 1 until 4 , characterized in that at least one of the dielectric spacer layers is formed from a polymer-based material, preferably from a material based on nitrocellulose, epoxy, polyester, rosin, acrylate, alkyd, melamine, PVA, PVC, isocyanate or urethane systems, particularly preferably, a dielectric spacer layer is formed from SiO ₂ and a dielectric spacer layer is formed from a polymer-based material. Security element (20) according to at least one of the Claims 1 until 5 , characterized in that the reflection layer (27) is made of aluminum or one of the metals Ti, Ta, Zn, Mo, W, Ni, Ir, Pd. Security element (20) according to at least one of the Claims 1 until 6 , characterized in that the 5-layer stack (21) is arranged on a carrier film (22), preferably in such an orientation that the first absorber layer (23) represents the layer of the layer stack closest to the carrier film (22). Safety element (20) according to Claim 7 , characterized in that the carrier film (22) is provided with micro-optical structures, in particular with embossed micro-optical structures, preferably with a micromirror array and/or nano-optical structures. Data carrier (10) with an optically variable security element (20) according to at least one of the Claims 1 until 8th . Method for producing an optically variable security element (20) according to one of the Claims 1 until 8th , in which a 5-layer stack (21) with the layer sequence first absorber layer (23), first dielectric spacer layer (24), second absorber layer (25), second dielectric spacer layer (26) and reflection layer (27) is applied to a substrate (22), characterized in that the first and second dielectric spacer layers (24, 26) are applied in different layer thicknesses in order to produce a specific IR reflection signature of the security element. Procedure according to Claim 10 , characterized in that the first absorber layer (23), the first dielectric spacer layer (24), the second absorber layer (25) and the second dielectric spacer layer (26) are applied in an inline system without leaving the vacuum. Procedure according to Claim 10 or 11 , characterized in that the first and second absorber layers (23, 25) are applied by electron beam evaporation or sputter deposition, in particular by DC magnetron sputtering. Method according to at least one of the Claims 10 until 12 , characterized in that the first and/or second dielectric spacer layer (24, 26) are applied by electron beam evaporation. Method according to at least one of the Claims 10 until 13 , characterized in that the second dielectric spacer layer is a polymer-based dielectric layer which is applied by printing or by slot die coating in continuous operation.

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