Security element for producing value documents
View Patent ↗A security element for manufacturing value documents provides at least one image, formed by a grating structure which has a plurality of trough-shaped microcavities. The microcavities have a structure width from 0.5 μm to 3 μm and an aspect ratio of 0.4 or greater, a metal-containing coating is applied to the grating structure, and in the grating structure the trough-shaped microcavities are separated from each other respectively by strips which are planar and respectively more than 200 nm and maximally 1,200 nm wide.
1. A security element for manufacturing value documents, which has a substrate having an upper side and provides at least one image, wherein
the image is formed by a grating structure, which has a plurality of microcavities, and
the microcavities respectively have in a spatial direction lying parallel to the upper side a structure width from 0.5 μm to 3 μm and perpendicular thereto a structure depth and have an aspect ratio which is defined by a ratio of structure depth to structure width,
a metal-containing coating is applied to the grating structure,
wherein
the microcavities comprise grooves,
the aspect ratio of the microcavities is 0.3 or larger, and
in the grating structure the microcavities are separated from each other by strips which are planar and respectively more than 200 nm and maximally 1,200 nm wide, producing an angular-dependent color effect in transmission as well as a hologram structure in reflection.
2. The security element according to claim 1 , wherein the coating has the same nominal thickness on the strips as in the area of the microcavities.
3. The security element according to claim 1 , wherein the grating structure has at least two kinds of microcavities which differ with respect to the aspect ratio.
4. The security element according to claim 1 , wherein the aspect ratio of the microcavities in the grating structure varies in some regions according to a predetermined pattern defining a view-through image.
5. The security element according to claim 1 , wherein the microcavities and strips are periodically arranged transversely to a groove direction, wherein the period varies in some regions according to a predetermined pattern defining a view-through image.
6. The security element according to claim 5 , wherein the groove directions and the periods vary laterally in such a way that in transmission a motif is visible as a view-through image and in reflection a hologram as a reflection image.
7. The security element according to claim 1 , wherein a groove direction of the microcavities in the grating structure varies in some regions according to a predetermined pattern defining a view-through image.
8. The security element according to claim 7 , wherein the groove directions and the periods vary laterally in such a way that in transmission a motif is visible as a view-through image and in reflection a hologram as a reflection image.
9. The security element according to claim 1 , wherein the coating is Al, Ag, Au, Cu or Cr or comprises an alloy thereof.
10. A value document having a security element according to claim 1 .
11. A manufacturing method for a security element for value documents, which provides at least one image, wherein
for producing an image a grating structure having a plurality of microcavities lying side by side is formed on a substrate having an upper side,
the microcavities are respectively formed in a spatial direction lying parallel to the upper side with a structure width from 0.5 μm to 3 μm and perpendicular thereto with a structure depth and have an aspect ratio which is defined by a ratio of structure depth to structure width, and
a metal-containing coating is applied to the grating structure
wherein
the microcavities comprise grooves,
the aspect ratio of the microcavities is 0.3 or larger, and
in the grating structure the microcavities are respectively separated from each other by strips which are planar and respectively more than 200 nm and maximally 1,200 nm wide, producing an angular-dependent color effect in transmission as well as a hologram structure in reflection.
12. The manufacturing method according to claim 11 , wherein the coating is applied on the strips with the same nominal thickness as in the area of the microcavities.
13. The manufacturing method according to claim 11 , wherein the grating structure has at least two kinds of microcavities which differ in respect to the aspect ratio.
14. The manufacturing method according to claim 11 , wherein the grating structure is formed with at least two kinds of microcavities which differ in respect to the aspect ratio, wherein a view-through images is structured by the at least two different kinds of microcavities.
15. The manufacturing method according to claim 11 , wherein the aspect ratio of the microcavities in the grating structure is varied in some regions according to a predetermined pattern defining a view-through image.
16. The manufacturing method according to claim 11 , wherein the microcavities and strips are periodically arranged transversely to a groove direction, wherein the period is varied in some regions according to a predetermined pattern defining a reflection image.
17. The manufacturing method according to claim 16 , wherein the groove directions and the periods are varied laterally, that in transmission a motif is visible as a view-through image and in reflection a hologram as a reflection image.
18. The manufacturing method according to claim 11 , wherein a groove direction of the microcavities in the grating structure is varied in some regions according to a predetermined pattern defining a view-through image.
19. The manufacturing method according to claim 18 , wherein the groove directions and the periods are varied laterally, that in transmission a motif is visible as a view-through image and in reflection a hologram as a reflection image.
20. The manufacturing method according to claim 11 , wherein Al, Ag, Au, Cu or Cr or an alloy thereof is used for the coating.