Security element having a color filter, document of value having such a security element and production method for such a security element

1. A security element for security papers, comprising:

a carrier having an upper side, said upper side being height-modulated with trenches periodically disposed in a first direction, each of the trenches having a trench depth (t);

a multilayer structure acting as a color filter, said multilayer structure being formed on the height-modulated upper side and being height-modulated;

said multilayer structure comprising a first layer, a second layer of dielectric material formed thereon, and a third layer formed on the second layer;

the trench depth (t) being greater than a thickness of the third layer;

the first and third layers each being formed of metallic material or semimetallic material;

wherein at least one or more of (a), (b), (c), (d), and (e) below are satisfied:

(a) a subwavelength grating period of the height-modulated multilayer structure is configured to cause a color change in the multilayer structure by the subwavelength grating period being laterally-varied from a first lateral position to a second lateral position within the multilayer structure of the security element;

(b) a grating profile of the height modulations of the of the height-modulated multilayer structure is laterally varied from a first lateral position to a second lateral position within the multilayer structure of the security element;

(c) metallic nanoparticles are incorporated in the second layer, and a distribution of the nanoparticles is laterally varied from a first lateral position to a second lateral position within the multilayer structure of the security element causing the color filter effect of the multilayer structure to vary laterally;

(d) a modulation depth of the height-modulated multilayer structure is laterally varied from a first lateral position to a second lateral position within the multilayer structure of the security element; or

(e) a layer thickness of the second layer is laterally varied from a first lateral position to a second lateral position within the multilayer structure of the security element,

wherein the layer thickness of the second layer is laterally varied.

2. The security element according to claim 1 , wherein a height modulation of the upper side and of the multilayer structure is periodic in a first direction.

3. The security element according to claim 2 , wherein the height modulation of the upper side and of the multilayer structure is additionally periodic in a second direction.

4. The security element according to claim 2 , wherein the subwavelength grating period of the height-modulated multilayer structure is smaller than a largest wavelength of a range of electromagnetic radiation for which the security element is designed.

5. The security element according to claim 2 , wherein the grating profile of the height-modulated multilayer structure is rectangular.

6. The security element according to claim 2 , wherein the subwavelength grating period of the height-modulated multilayer structure is laterally varied.

7. The security element according to claim 2 , wherein the grating profile of the height modulation is laterally varied.

8. The security element according to claim 1 , wherein the metallic nanoparticles are incorporated in the second layer.

9. The security element according to claim 8 , wherein the distribution of the nanoparticles is laterally varied causing the color filter effect of the multilayer structure to vary laterally.

10. The security element according to claim 1 , wherein the modulation depth of the height-modulated multilayer structure is laterally varied.

11. The security element according to claim 1 , wherein the multilayer structure, viewed in plan view, is contiguous.

12. A document of value comprising the security element recited in claim 1 .

13. The security element according to claim 1 , wherein the trench depth (t) is equal to or greater than a sum of a thickness of the first layer and a thickness of the second layer.

14. The security element according to claim 1 , wherein the trench depth (t) is equal to a sum of a thickness of the first layer and a thickness of the second layer and portions of the first layer and portions of the third layer form a closed film.

15. A security element for security papers, comprising:

a carrier having an upper side, said upper side being height-modulated with trenches periodically disposed in a first direction, each of the trenches having a trench depth (t);

a multilayer structure acting as a color filter, said multilayer structure being formed on the height-modulated upper side and being height-modulated;

said multilayer structure comprising a first layer, a second layer of dielectric material formed thereon, and a third layer formed on the second layer;

the trench depth (t) being greater than a thickness of the third layer;

the first and third layers each being formed of metallic material or semimetallic material:

wherein at least one or more of (a), (b), (c), (d), and (e) below are satisfied:

(a) a subwavelength grating period of the height-modulated multilayer structure is configured to cause a color change in the multilayer structure by the subwavelength grating period being laterally-varied from a first lateral position to a second lateral position within the multilayer structure of the security element;

(b) a grating profile of the height modulations of the of the height-modulated multilayer structure is laterally varied from a first lateral position to a second lateral position within the multilayer structure of the security element;

(c) metallic nanoparticles are incorporated in the second layer, and a distribution of the nanoparticles is laterally varied from a first lateral position to a second lateral position within the multilayer structure of the security element causing the color filter effect of the multilayer structure to vary laterally;

(d) a modulation depth of the height-modulated multilayer structure is laterally varied from a first lateral position to a second lateral position within the multilayer structure of the security element; or

(e) a layer thickness of the second layer is laterally varied from a first lateral position to a second lateral position within the multilayer structure of the security element,

wherein the multilayer structure has a fourth and a fifth layer;

the fourth layer being formed on the third layer and comprising a dielectric material; and

the fifth layer being formed on the fourth layer, the fifth layer being formed of a dielectric material having a refractive index higher than that of the second layer and the forth layer, a metallic material, or a semimetallic material.

16. A security element for security papers, comprising:

a carrier having an upper side, said upper side being height-modulated with trenches periodically disposed in a first direction, each of the trenches having a trench depth (t);

a multilayer structure acting as a color filter, said multilayer structure being formed on the height-modulated upper side and being height-modulated;

said multilayer structure comprising a first layer, a second layer of dielectric material formed thereon, and a third layer formed on the second layer;

the trench depth (t) being greater than a thickness of the third layer;

the first and third layers each being formed of metallic material or semimetallic material:

wherein at least one or more of (a), (b), (c), (d), and (e) below are satisfied:

(a) a subwavelength grating period of the height-modulated multilayer structure is configured to cause a color change in the multilayer structure by the subwavelength grating period being laterally-varied from a first lateral position to a second lateral position within the multilayer structure of the security element;

(b) a grating profile of the height modulations of the of the height-modulated multilayer structure is laterally varied from a first lateral position to a second lateral position within the multilayer structure of the security element;

(c) metallic nanoparticles are incorporated in the second layer, and a distribution of the nanoparticles is laterally varied from a first lateral position to a second lateral position within the multilayer structure of the security element causing the color filter effect of the multilayer structure to vary laterally;

(d) a modulation depth of the height-modulated multilayer structure is laterally varied from a first lateral position to a second lateral position within the multilayer structure of the security element; or

(e) a layer thickness of the second layer is laterally varied from a first lateral position to a second lateral position within the multilayer structure of the security element,

wherein the trench depth (t) is greater than a sum of a thickness of the third layer, a thickness of the second layer, and a thickness of the first layer.

17. The security element according to claim 16 , wherein a height modulation of the upper side and of the multilayer structure is periodic in a first direction.

18. The security element according to claim 17 , wherein the height modulation of the upper side and of the multilayer structure is additionally periodic in a second direction.

19. The security element according to claim 17 , wherein the subwavelength grating period of the height-modulated multilayer structure is smaller than a largest wavelength of a range of electromagnetic radiation for which the security element is designed.

20. The security element according to claim 17 , wherein the grating profile of the height-modulated multilayer structure is rectangular.

21. The security element according to claim 17 , wherein the subwavelength grating period of the height-modulated multilayer structure is laterally varied.

22. The security element according to claim 17 , wherein the grating profile of the height modulation is laterally varied.

23. The security element according to claim 16 , wherein the trench depth (t) is equal to or greater than a sum of a thickness of the first layer and a thickness of the second layer.

24. The security element according to claim 16 , wherein the trench depth (t) is equal to a sum of a thickness of the first layer and a thickness of the second layer and portions of the first layer and portions of the third layer form a closed film.