Optically variable security element comprising a colour-shifting interference layer element, item of value, and production method

Abstract

The invention relates to an optically variable security element (12) for securing security papers, value documents, and other items of value, said security element comprising at least one colour-shifting, multilayer interference layer element (22) having a reflector layer (28), at least one absorber layer (24), and at least one dielectric spacer layer (26) that is positioned between the reflector layer (28) and the at least one absorber layer (24), wherein the multilayer interference layer element (22), owing to its layered structure, produces an intrinsic colour-shifting effect with a first colour when viewed from a first viewing direction and a different second colour when viewed from a second viewing direction. According to the invention, a plurality of colour-selective scattering nanoparticles (34) are arranged above and / or below the at least one multilayer interference layer element (22) and, through Rayleigh scattering, modify the intrinsic colour-shifting effect of the at least one multilayer interference layer element (22) such that the security element exhibits a colour-shifting effect between a third colour when viewed from the first viewing direction (40) and a different fourth colour when viewed from the second viewing direction (42), wherein the third colour differs from the first colour in hue and / or colour purity, and / or the fourth colour differs from the second colour in hue and / or colour purity.

Description

[0001] Optically variable security element with color-shifting

[0002] Interference layer element, valuable object and manufacturing process

[0003] The invention relates to an optically variable security element for protecting security papers, valuable documents, and other valuables, comprising at least one color-shifting, multilayer interference layer element. The invention also relates to a method for producing such a security element and a correspondingly equipped valuable object.

[0004] Valuable items, such as security paper, valuables, or identification documents, are often provided with security elements for protection. These allow the authenticity of the valuable item to be verified and also 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. These security elements are equipped with optically variable elements that convey a different image impression to the viewer at different viewing angles, for example, displaying a different color or brightness impression and / or a different graphic motif depending on the viewing angle.

[0005] Security elements with multilayer thin-film elements are often used, whose color impression changes for the viewer with the viewing angle (hereinafter referred to as the color shift effect). The layer primarily responsible for the color effect is a thin dielectric layer, typically arranged between an absorber layer and a reflective layer. These thin-film elements represent interference layer elements, in which the colors generated in reflection are produced by interference of the light rays reflected from various sublayers of the element. Therefore, such interference layer elements can only produce specific color changes compatible with the physical interference conditions.In some cases, the colors produced are also created by mixing spectral colors, for example red and blue, and then often have a dark and unattractive appearance due to the lack of color purity.

[0006] Based on this, the invention is based on the object of specifying a generic security element which avoids the disadvantages of the prior art and which in particular enables the generation of color shift effects with novel color changes or with color changes between colors of high color purity.

[0007] This object is achieved by the features of the independent claims. Further developments of the invention are the subject of the dependent claims.

[0008] The invention contains an optically variable security element for protecting security papers, valuable documents and other valuables.

[0009] The security element contains at least one color-shifting, multilayer interference layer element with a reflector layer, at least one absorber layer, and at least one dielectric spacer layer arranged between the reflector layer and the at least one absorber layer. The multilayer interference layer element, with its layer structure, generates an intrinsic color-shift effect with a first color in a first viewing direction and a different second color in a second viewing direction.

[0010] A plurality of color-selectively scattering nanoparticles are arranged above and / or below the at least one multilayer interference layer element, which modify the intrinsic color-shift effect of the at least one multilayer interference layer element through Rayleigh scattering. The security element therefore exhibits a color-shift effect between a third color in the first viewing direction and a different fourth color in the second viewing direction, wherein the third color differs from the first color in hue and / or color purity and / or the fourth color differs from the second color in hue and / or color purity.

[0011] The color-shift effect of the security element as a whole is also referred to as the extrinsic color-shift effect in this description to distinguish it from the intrinsic color-shift effect of the interference layer element. The extrinsic color-shift effect arises as a combination effect through the influencing and modification of the intrinsic color-shift effect by the nanoparticles acting as Rayleigh scatterers. This allows, in particular, a targeted change of the first and / or second color to colors of greater color purity or to colors that cannot be produced by interference effects alone.

[0012] The color-selectively scattering nanoparticles preferably have a D50 diameter between 1 nm and 400 nm, preferably between 10 nm and 300 nm, particularly preferably between 150 nm and 250 nm. The color-selectively scattering nanoparticles are in particular formed from a high-refractive-index material and are advantageously transparent in the visible spectral range. Alternatively, although currently less preferred, the color-selectively scattering nanoparticles can also be formed from a low-refractive-index material.

[0013] Particularly advantageously, the color-selective scattering nanoparticles can be formed from nanoscale TiO2 particles, for example, with a D50 diameter of 200 nm or 220 nm. Such TiO2 particles are available from Venator Materials PLC under the designations Hombitec(R) RM 200 and RM 220, respectively.

[0014] The color-selectively scattering nanoparticles can also advantageously be formed by other nanoscale metal oxide particles, metal fluoride particles or metal sulfide particles, such as Al2O3, ZnO, ZnS, HfO, MgF2 or SnO particles.

[0015] The at least one dielectric spacer layer is advantageously formed from SiO2, TiO2, ZnS, MgF2, or Al2O3 and has a layer thickness between 100 nm and 500 nm. If two dielectric spacer layers are provided in the multilayer interference layer element, they are advantageously formed from the same material and with the same layer thickness.

[0016] The reflector layer is preferably made of aluminum, an aluminum-iron alloy, an iron alloy, or silver. The at least one absorber layer is advantageously made of chromium, an iron alloy, a chromium-iron alloy, or titanium. If two absorber layers are provided in the multilayer interference layer element, they are advantageously made of the same material. The security element can also contain more than one reflection layer, as explained in more detail below.

[0017] In an advantageous embodiment, with the intrinsic color-shift effect of the multilayer interference layer element, the first color is blue and the second color is a dark red of low color purity. With the extrinsic color-shift effect of the security element, the third color is a lighter blue compared to the first color, and the fourth color is a lighter and more color-pure red compared to the second color. In the context of this description, the term "lighter blue" does not refer to a blue of higher radiation intensity, but rather to a brighter, lighter, or more pastel blue appearance of the color.

[0018] A blue-to-red color shift effect is desirable in numerous applications. However, conventional designs based on the intrinsic color shift effect of the interference layer elements suffer, particularly from a dark red with low color purity when viewed at an angle, which is often difficult to detect and visually unattractive.

[0019] In another, equally advantageous embodiment, in the intrinsic color shift effect of the multilayer interference layer element, the first color is gold and the second color is green, whereas in the extrinsic color shift effect of the security element, the third color is orange and the fourth color is green or yellow. A color shift effect with such a color change cannot be easily realized with conventional designs. In another, equally advantageous embodiment, in the intrinsic color shift effect of the multilayer interference layer element, the first color is magenta and the second color is green, whereas in the extrinsic color shift effect of the security element, the third color is red and the fourth color is green or yellow. A color shift effect with such a color change cannot be easily realized with conventional designs.

[0020] The first viewing direction is preferably a vertical viewing direction and the second viewing direction is an oblique viewing direction of 45°.

[0021] In an advantageous variant of the invention, the security element comprises a carrier foil and a thin-film element applied over a large area to the carrier foil, which is formed by a single one of the aforementioned interference layer elements. The security element can then, in particular, be a foil security element, such as a security thread, a security band, or a security patch.

[0022] The thin-film element is advantageously formed by a three-layer interference layer element with a reflector layer, an absorber layer and a dielectric spacer layer arranged between the reflector layer and the absorber layer.

[0023] The color-selectively scattering nanoparticles are preferably arranged in a lacquer layer applied to the carrier film or the thin-film element, an embossing lacquer layer, a primer layer, a heat-sealing lacquer layer, or in the carrier film itself. In an advantageous development, the security element contains a translucent ink layer with a red body color, which is preferably applied to the carrier film, the large-area thin-film element, or a layer containing the color-selectively scattering nanoparticles.

[0024] In another, equally advantageous variant of the invention, the security element contains a printed layer containing, in a binder, a plurality of color-shifting, platelet-shaped pigments, each of which has a so-called interference layer element. In this variant, the security element can, in particular, be a printed element applied to a valuable object, but also a foil security element, such as a security thread, a security band, or a security patch.

[0025] The platelet-shaped pigments advantageously each comprise an interference layer element with at least five layers, comprising an outer first absorber layer, a first dielectric spacer layer, a central reflector layer, a second dielectric spacer layer, and an outer second absorber layer. The platelet-shaped pigments are advantageously constructed symmetrically, so that the two absorber layers and the two dielectric spacer layers are each formed from the same material and have the same layer thicknesses.

[0026] For magnetic alignment and / or the mechanical detection of their magnetic properties, the platelet-shaped pigments can in particular also contain at least one magnetic layer. Thus, an additional magnetic layer can be incorporated into the structure and / or the absorber and / or reflector layer can be formed from magnetic metal or a magnetic alloy. The magnetic layer can also form a middle layer in the layer structure of the platelet-shaped pigments, which, if the magnetic layer is not itself highly reflective, is expediently sandwiched between two reflective layers. The sandwich of reflective layer, magnetic layer, and second reflective layer can then be provided on each side with a dielectric spacer layer and an absorber layer, as described above, to form a preferably symmetrical interference layer element.

[0027] The color-selectively scattering nanoparticles are advantageously incorporated into the binder of the printing layer, or they are present in an overprint or overcoat of the printing layer. According to another variant, the color-selectively scattering nanoparticles are arranged in a coating of the platelet-shaped pigments themselves. The coating must be located outside the absorber layers in order to influence the intrinsic color-shift effect of the pigments. In particular, the coating with color-selectively scattering nanoparticles can form the outermost layer of the pigments on both sides.

[0028] In an advantageous further development, the security element contains a translucent ink layer with a red body colour, which is preferably applied to the printing layer with the colour-shifting, platelet-shaped pigments or a layer containing the colour-selectively scattering nanoparticles.

[0029] The invention also includes a valuable object, in particular a security paper, a value document or an identity document with a security element of the type described.

[0030] Finally, the invention also includes a method for producing a

[0031] A security element of the type described, in which at least one color-shifting, multilayer interference layer element is provided, which has a reflector layer, at least one absorber layer, and at least one dielectric spacer layer arranged between the reflector layer and the at least one absorber layer, wherein the multilayer interference layer element, with its layer structure, produces an intrinsic color-shift effect with a first color in a first viewing direction and a different second color in a second viewing direction, a plurality of color-selectively scattering nanoparticles are arranged above and / or below the at least one multilayer interference layer element, which modify the intrinsic color-shift effect of the at least one multilayer interference layer element by Rayleigh scattering,so that the security element exhibits a colour shift effect between a third colour in the first viewing direction and a different fourth colour in the second viewing direction, wherein the third colour differs from the first colour in hue and / or colour purity and / or the fourth colour differs from the second colour in hue and / or colour purity.

[0032] In an advantageous variant of the invention, a carrier film is provided, and a thin-film element formed by a single one of the aforementioned interference layer elements is applied to the carrier film over a large area. The partial layers of the thin-film element can be vapor-deposited, for example, using a PVD process. The color-selectively scattering nanoparticles can be dispersed in a binder and printed onto the opposite side of the carrier film or onto the thin-film element. The color-selectively scattering nanoparticles can also be arranged in an embossing lacquer layer, a primer layer, a heat-sealing lacquer layer, or in the carrier film itself.

[0033] In another advantageous variant of the invention, a security printing ink is used to produce the security element. It contains a plurality of color-shifting, platelet-shaped pigments in a binder, each of which has a so-called interference layer element. With such a security printing ink, a print layer is applied directly to a target valuable item or to an intermediate carrier. The color-selectively scattering nanoparticles can be arranged in the binder of the print layer, in an overprint or overcoat of the print layer, or in a coating of the platelet-shaped pigments themselves.

[0034] 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 has been omitted in order to increase clarity.

[0035] They show:

[0036] Fig. 1 schematically shows a banknote with two optically variable security elements according to embodiments of the invention, Fig. 2 schematically shows the layer structure of the first security element of Fig. 1 in cross section,

[0037] Fig. 3 is a diagram illustrating the origin of the intrinsic color shift effect of the interference layer element,

[0038] Fig. 4 a combination element illustrating the influence of the Rayleigh scattering layer on the intrinsic color shift effect of the interference layer element,

[0039] Fig. 5 schematically shows the layer structure of a modification of the security element of Fig. 2,

[0040] Fig. 6 shows schematically the layer structure of the second security element of Fig. 1 in cross section,

[0041] Fig. 7 one of the platelet-shaped pigments of Fig. 6 separately,

[0042] Fig. 8 schematically shows the layer structure of a modification of the security element of Fig. 6, and

[0043] Fig. 9 schematically shows the layer structure of a further development of the security element of Fig. 2.

[0044] The invention will now be explained using banknotes as an example. Figure 1 shows a schematic representation of a banknote 10 provided with two optically variable security elements 12 and 14 according to embodiments of the invention. The first security element represents an adhesively bonded transfer element 12, the layer structure of which is shown schematically in cross-section in Figure 2. The second security element is formed by a printing element 14 printed on the paper substrate 16 of the banknote 10, which is described in more detail below in connection with Figure 6.

[0045] Referring first to Fig. 2, the optically variable security element 12 exhibits a blue-to-red color shift effect, in which the color impression for a viewer changes between a strong blue when viewed vertically 40 and a strong red of high color purity when viewed obliquely 42.

[0046] The security element 12 contains a transparent carrier film 20, on the underside of which a color-shifting three-layer interference layer element 22 is arranged. Starting from the carrier film 20, the interference layer element comprises an absorber layer 24 made of chromium, a dielectric spacer layer 26 made of SiCh, and an opaque reflector layer 28 made of aluminum. To generate a blue-to-red color-shift effect, the layer thickness of the absorber layer can be, for example, between 2 nm and 8 nm, the thickness of the dielectric spacer layer between 220 nm and 330 nm, and the thickness of the aluminum layer between 20 nm and 50 nm.

[0047] The color shift effect generated by the interference layer element 22 alone is referred to in this description as the intrinsic color shift effect of the interference layer element 22. It is essentially determined by the material and layer thickness of the dielectric spacer layer 26.

[0048] With the specified layer structure, the interference layer element 22 in the exemplary embodiment produces an intrinsic blue-to-red color shift effect, which, however, changes relatively unattractively between a strong blue in the vertical viewing direction 40 and a dark red of low color purity in the oblique viewing direction 42.

[0049] To generate the visually attractive color-shift effect exhibited overall by the security element 12, a Rayleigh scattering layer 30 is applied to the upper side of the carrier film opposite the interference layer element 22. This layer contains a plurality of nanoscale TiCh particles 34 with a D50 diameter of 200 nm in a transparent binder 32. As explained in detail below, the Rayleigh scattering layer 30 significantly modifies the intrinsic color-shift effect of the interference layer element 22 such that, when viewing the security element 12 as a whole, the visually significantly more appealing color-shift effect between a brighter blue and a pure red is obtained.

[0050] On the underside of the reflector layer 28, the security element 12 is also provided with an adhesive layer 36 with which it is glued to the paper substrate 16 of the banknote 10.

[0051] Figure 3 first illustrates the occurrence of the intrinsic color shift effect of the interference layer element 22. The diagram 50 shows the reflection R of the interference layer element 22 as a function of the wavelength X at an almost vertical viewing angle of 8° (reflection curve 52) and at an oblique viewing angle of 45° (reflection curve 54).

[0052] As can be seen from the figure, the reflection spectrum of the interference layer element 22 has two peaks in the visible and near infrared range, a narrow short-wavelength peak 52-B or 54-B in the wavelength range of 400 - 500 nm and a broad, long-wavelength peak 52-R or 54-R in the wavelength range of 700 - 900 nm.

[0053] When viewed essentially perpendicularly (reflection curve 52), the maximum of the long-wavelength peak 52-R lies in the near infrared, while the maximum of the short-wavelength peak 52-B lies in the blue region at approximately 465 nm. When viewed perpendicularly, the color impression of the interference layer element 22 is therefore determined by the short-wavelength peak 52-B in the blue region. The increase in reflection at approximately 800 nm hardly affects the color purity of the blue color impression, since the spectral sensitivity of the human eye is already very low above 700 nm.

[0054] When viewed at an angle (reflection curve 54), the maximum of the long-wavelength peak 54-R has migrated into the visible red range, while the short-wavelength peak 54-B has not completely disappeared into the UV range, which is invisible to the human eye, but still exhibits a high intensity in the visible blue spectral range. Therefore, when viewed at an angle, the color impression of the interference layer element 22 is determined by an overlay of the two peaks 54-B and 54-R, which creates a mixed color perceived as dark red. Due to the low color purity, the dark red of the shift color, in particular, appears visually unattractive.

[0055] However, a visually attractive blue-red color shift effect is created by combining the interference layer element 22 with the Rayleigh scattering layer 30.

[0056] Due to their small size (D50 = 200 nm) far below the wavelength of light, the nanoscale TiCh particles 34 act as Rayleigh scatterers for visible light, i.e., as scattering centers that scatter incident light elastically, largely isotropically, and, in particular, with strong color selection. In Rayleigh scattering, the cross section of a particle, or rather the scattering intensity I, exhibits a strong dependence on the wavelength, I oc X 4 The scattering intensity increases with the fourth power as the wavelength gets shorter. This means that, for example, blue light with a wavelength of 420 nm is scattered about 10 times more strongly than red light with a wavelength of 750 nm.

[0057] Figure 4 schematically illustrates the influence of the Rayleigh scattering layer 30 on the intrinsic color shift effect of the interference layer element 22 when viewed obliquely such a combination element 60.

[0058] Incident white light 62 contains, in addition to its other color components, in particular red light 62-R and blue light 62-B. At an oblique angle of incidence of approximately 45°, these two light components are reflected by the interference layer element 22 with comparable intensity, as shown in Fig. 3.

[0059] The additional Rayleigh scattering layer 30 now scatters the blue light component of both the incident and reflected light very effectively in all directions 64-B, while the red light component is only slightly influenced by the Rayleigh scattering layer 30. In the reflected light, the light component 64-B scattered away by the Rayleigh scattering layer 30 is no longer available, so that in the reflected light 66, the blue light component 66-B is significantly reduced compared to the red light component 66-R. The combination element 60 therefore creates a red color impression of high color purity for the viewer 44 in the oblique viewing direction by suppressing the blue light components.When viewed vertically, where the reflected light 66 is determined by the short-wavelength peak 52-B in the blue range, the Rayleigh scattering layer 30 also reduces the intensity of the blue light component, but this merely brightens the blue color impression, since the long-wavelength peak 52-R, due to its maximum in the near infrared, contributes little to the overall color impression. When viewed vertically, the combination element 60 therefore displays a blue whose hue appears somewhat lighter and more pastel-like than the intrinsic blue, but which is still perceived as a strong, pure blue.

[0060] Returning to the design of Fig. 2, the security element 12, through the combination of the interference layer element 22 with the Rayleigh scattering layer 30, exhibits an attractive color shift effect between a strong blue in plan view 40 to a red of high color purity in oblique view 42. The extent of modification of the intrinsic color shift effect of the interference layer element 22 can be adjusted as desired by the concentration of the nanoscale TiCL particles 34 in the Rayleigh scattering layer 30.

[0061] In the embodiment of Fig. 2, the Rayleigh scattering layer 30 and the interference layer element 22 are arranged on opposite sides of the carrier film 20, but other relative arrangements of the two elements are also possible. The only essential requirement is that a sufficiently large number of color-selectively scattering nanoparticles 34 are located between the viewer 44 and the interference layer element 22.

[0062] Figure 9 shows a further development of the embodiment of Figure 2, in which the security element 12 is additionally provided with a translucent color layer 38 with a red body color. The translucent red body color layer 38 can, as shown in the figure, be arranged between the interference layer element 22 and the carrier film 20, but it can also be provided on the side of the carrier film 20 facing the viewer, below or above the Rayleigh scattering layer 30. It has been found that such a translucent red body color layer 38 further improves the color effect of the blue-to-red color shift effect.

[0063] With reference to the embodiment of Fig. 5, the nanoscale TiCh particles 34 can, for example, be provided in the carrier film 20 itself instead of in a separate layer. In embodiments in which the interference layer element 22 is arranged on an embossed structure, the nanoscale TiCh particles 34 can, for example, be incorporated into the embossing lacquer layer of the embossed structure. An arrangement of the nanoscale TiCh particles in a primer layer, a hot-seal lacquer coating, or another lacquer coating is also possible. Even in such an embodiment, a translucent red body color layer can additionally be provided above or below the carrier film 20 in order to further enhance the color effect of the blue-to-red color shift effect.

[0064] Returning to the illustration in Fig. 1, the banknote 10 contains, as a second security element, an optically variable printing element 14, which is shown schematically in cross-section in Fig. 6. The printing element 14, like the transfer element 12, exhibits a blue-to-red color-shift effect, in which the color impression for a viewer changes between a strong blue when viewed vertically 40 and a red of high color purity when viewed obliquely 42. The printing element 14 is formed by a security printing ink 70 printed onto the paper substrate 16 of the banknote 10, which contains a transparent binder 72 with a plurality of color-shifting platelet-shaped pigments 74 and a plurality of nanoscale TiCh particles 76 with a D50 diameter of 220 nm.

[0065] One of the platelet-shaped pigments 74 is shown separately in more detail in Fig. 7. Each of the platelet-shaped pigments 74 represents a color-shifting five-layer interference layer element with a symmetrical structure and consists of an outer first chromium absorber layer 80, a first SiO spacer layer 82, a middle, opaque aluminum reflector layer 84, a second SiCh spacer layer 86, and an outer second chromium absorber layer 88. The layer thicknesses of the dielectric spacer layers, the reflector layer, and the absorber layers are advantageously within the ranges mentioned above. For a symmetrical structure, the two SiCh spacer layers 82, 86 and the two absorber layers 80, 88 are each essentially the same thickness.

[0066] The platelet-shaped pigments 74 distributed in the binder 72 of the security printing ink 70 are aligned essentially parallel to the surface of the paper substrate 16 during printing by the forces acting during printing. Due to the symmetrical structure of the pigments 74, it is irrelevant for the observable color effect which of the two chromium absorber layers 80 or 88 faces the paper substrate or the viewer.

[0067] The intrinsic color shift effect of the platelet-shaped pigments 74 corresponds to the color shift effect of the interference layer element 22 of Fig. 2 due to the analogous layer structure, thus showing a relatively unattractive change between a strong blue in the vertical viewing direction 40 and a dark red of low color purity in the oblique viewing direction 42.

[0068] To generate the visually attractive color-shift effect exhibited overall by the printing element 14, the intrinsic color-shift effect of the platelet-shaped pigments 74 is modified by the nanoscale TiCh particles 76 dispersed in the binder 72 in such a way that the viewer sees a visually significantly more appealing color-shift effect between a lighter blue and a pure red. The mode of action is analogous to the explanation given in connection with Figures 2 to 4: The nanoscale TiCh particles 76 of the binder 72 act as Rayleigh scatterers, scattering incident light in a highly color-selective manner. In particular, incident blue light is scattered much more strongly than red light, so that the blue light component in the reflected light is significantly reduced compared to the red light component.

[0069] The printing element 14 therefore shows an overall attractive color shift effect between a strong blue in plan view 40 to a red of high color purity in oblique view 42. The extent of the modification of the intrinsic color shift effect of the interference layer element 22 can be adjusted as desired by the concentration of the nanoscale TiCh particles 76 in the binder 72 of the security printing ink 70.

[0070] Figure 8 shows, as a further embodiment, a modification of the printing element of Figure 6, in which the nanoscale TiCh particles 76 are not mixed into the binder of the security printing ink, but are present in a separate overcoat 90 applied to a printing layer 92 containing a plurality of color-shifting, platelet-shaped pigments 74. Here, too, the combined effect of the color-shifting pigments 74 and the Rayleigh scatterers 76 results in the desired blue-red color-shift effect with a pure red when viewed obliquely.

[0071] In the embodiments of Figures 6 and 8, the color effect of the blue-to-red color shift effect can also be further enhanced by a translucent red body color layer. Such a translucent red body color layer can be applied, in particular printed, to the security printing ink 70 of Figure 6, to the printing layer 92 of Figure 8, or to the overcoat 90 of Figure 8.

Claims

P a t e n t a n s p r ü c h e 1. An optically variable security element for protecting security papers, valuable documents, and other valuables, comprising at least one color-shifting, multilayer interference layer element with a reflector layer, at least one absorber layer, and at least one dielectric spacer layer arranged between the reflector layer and the at least one absorber layer, wherein the multilayer interference layer element, with its layer structure, produces an intrinsic color-shift effect with a first color in a first viewing direction and a different second color in a second viewing direction, characterized in that a plurality of color-selectively scattering nanoparticles are arranged above and / or below the at least one multilayer interference layer element, which modify the intrinsic color-shift effect of the at least one multilayer interference layer element by Rayleigh scattering,so that the security element shows a colour shift effect between a third colour in the first viewing direction and a different fourth colour in the second viewing direction, wherein the third colour differs from the first colour in hue and / or, the color purity and / or the fourth color differs from the second color in hue and / or color purity.

2. Security element according to claim 1, characterized in that the color-selectively scattering nanoparticles have a D50 diameter between 1 nm and 400 nm, preferably between 10 nm and 300 nm, particularly preferably between 150 nm and 250 nm.

3. Security element according to claim 1 or 2, characterized in that the color-selectively scattering nanoparticles are formed by nanoscale TiCl particles or by other nanoscale metal oxide particles, metal fluoride particles or metal sulfide particles, such as Al2O3, ZnO, ZnS, HfO, MgF or SnO particles.

4. Security element according to at least one of claims 1 to 3, characterized in that the at least one dielectric spacer layer is formed from SiCh, TiCh, ZnS, MgF or Al2O3 and has a layer thickness between 100 nm and 500 nm, and / or that the reflector layer is formed from aluminum, an aluminum-iron alloy, or silver, and / or that the at least one absorber layer is formed from chromium, an iron alloy, a chromium-iron alloy or titanium.

5. Security element according to at least one of claims 1 to 4, characterized in that the first color is a blue and the second color is a dark red of low color purity and the third color is a lighter blue compared to the first color and the fourth color is a lighter and more color-pure red compared to the second color.

6. Security element according to at least one of claims 1 to 4, characterized in that the first color is gold and the second color is green, and the third color is orange and the fourth color is green or yellow, or that the first color is magenta and the second color is green, and the third color is red and the fourth color is green or yellow.

7. Security element according to at least one of claims 1 to 6, characterized in that the first viewing direction is a vertical viewing direction and the second viewing direction is an oblique viewing direction of 45°.

8. Security element according to at least one of claims 1 to 7, characterized in that the security element contains a carrier film and a thin-film element applied over a large area to the carrier film, which is formed by a single one of the said interference layer elements.

9. Security element according to claim 8, characterized in that the thin-film element is formed by a three-layer interference layer element with a reflector layer, an absorber layer and a dielectric spacer layer arranged between the reflector layer and the absorber layer.

10. Security element according to claim 8 or 9, characterized in that the color-selectively scattering nanoparticles are arranged in a lacquer layer applied to the carrier film or the thin-film element, an embossing lacquer layer, a primer layer, a heat-sealing lacquer layer, or in the carrier film itself.

11. Security element according to at least one of claims 8 to 10, characterized in that the security element contains a translucent color layer with a red body color, which is preferably applied to the carrier film, the large-area thin-film element or a layer containing the color-selectively scattering nanoparticles.

12. Security element according to at least one of claims 1 to 7, characterized in that the security element contains a printing layer which contains, in a binder, a plurality of color-shifting, platelet-shaped pigments, each having a said interference layer element.

13. Security element according to claim 12, characterized in that the platelet-shaped pigments each have an at least five-layer interference layer element with an outer first absorber layer, a first dielectric spacer layer, a central reflector layer, a second dielectric spacer layer and an outer second absorber layer, and are preferably constructed symmetrically.

14. Security element according to claim 12 or 13, characterized in that the platelet-shaped pigments each contain at least one magnetic layer and can thus be aligned by means of external magnetic fields.

15. Security element according to at least one of claims 12 to 14, characterized in that the color-selectively scattering nanoparticles are arranged in the binder of the printing layer, in an overprint or an overcoat of the printing layer, or in a coating of the platelet-shaped pigments themselves.

16. Security element according to at least one of claims 12 to 15, characterized in that the security element contains a translucent ink layer with a red body color, which is preferably applied to the printing layer with the color-shifting, platelet-shaped pigments or a layer containing the color-selectively scattering nanoparticles.

17. Valuable object, in particular security paper, value document or identity document with a security element according to one of claims 1 to 16.

18. A method for producing a security element according to one of claims 1 to 16, in which at least one color-shifting, multi-layer interference layer element is provided, which has a reflector layer, at least one absorber layer and at least one dielectric spacer layer arranged between the reflector layer and the at least one absorber layer, wherein the multi-layer interference layer element with its layer structure produces an intrinsic color-shift effect with a first color in a first viewing direction and a different second color in a second viewing direction, characterized in that above and / or below the at least one multi-layer Interference layer element a variety of color-selective scattering Nanoparticles are arranged, which by Rayleigh scattering the modify the intrinsic color shift effect of the at least one multi-layer interference layer element, so that the security element shows a color shift effect between a third color in the first viewing direction and a different fourth color in the second viewing direction, wherein the third color differs from the first color in hue and / or color purity and / or the fourth color differs from the second color in hue and / or color purity.

Images