Multi color-shifting devices comprising a layer having a microstructured surface and a dielectric non-conforming layer
A color shifting security device has a Fabry-Perot type structure wherein a dielectric layer is disposed between a reflector and an absorbing layer. The absorber and reflector layers may be conforming and the dielectric layer therebetween is non-conforming, filling the regions in the micro structured adjacent absorbing or reflecting layer, at least one of which has a microstructure therein or thereon. By having the dielectric layer not conform to the microstructure it is next to, its thickness varies in cross section, which allows for different colors to be seen where the thickness varies.
1. A color shifting security device comprising:
a first absorbing or reflecting layer having a microstructured upper surface;
a second absorbing or reflecting layer; and
an infill dielectric non-conforming layer, filling in grooves within the microstructured upper surface, having a surface contacting and complementary with the microstructured upper surface, and disposed between the first absorbing or reflecting layer and the second absorbing or reflecting layer, wherein at least one of the first or second absorbing or reflecting layers is an absorbing layer, and wherein a cross section of the infill dielectric non-conforming layer has a varying thickness such that at least one region is substantially thicker than a thinner adjacent region of the infill dielectric non-conforming layer.
2. The color shifting security device as defined in claim 1 , wherein the first absorbing or reflecting layer, the second absorbing or reflecting layer, and the infill dielectric non-conforming layer, together form a Fabry-Perot cavity, and wherein the infill dielectric non-conforming layer is formed of a deposited non-conforming material.
3. The color shifting security device as defined in claim 2 , wherein the first absorbing or reflecting layer, or the second absorbing or reflecting layer, has a substantially uniform thickness, which varies by no more than 20%.
4. The color shifting security device as defined in claim 2 , wherein a difference in thickness of a cross-section of the infill dielectric non-conforming layer is more than ⅛ wavelengths of visible light and less than 8 quarter wavelengths of visible light.
5. The color shifting security device as defined in claim 4 , wherein regions of the color shifting security device corresponding to particular microstructures form visible indicia that can be seen with magnification, and wherein a height or depth of some of the particular microstructures are at least 50 nm.
6. The color shifting security device, as defined in claim 5 , wherein at least some of the particular microstructures form valleys, which in cross-section form flat-bottomed valleys.
7. The color shifting security device as defined in claim 6 , wherein a substrate of the color shifting security device and the first absorbing or reflecting layer and the second absorbing or reflecting layer thereon form a foil.
8. The color shifting security device as defined in claim 6 , wherein the first absorbing or reflecting layer and the second absorbing or reflecting layer are conforming deposited layers.
9. The color shifting security device as defined in claim 8 , wherein the second conforming deposited layer is a reflector layer and wherein the color shifting security device further comprises:
a second dielectric non-conforming layer contacting the reflector layer and having an absorbing layer over the second dielectric non-conforming layer, thereby forming a two-sided color shifting device, wherein the infill dielectric non-conforming layer and the second dielectric non-conforming layer both have a varying thickness in cross-section.
10. The color shifting security device as defined in claim 5 , wherein peaks of the particular microstructures in cross-section are flat-topped structures.
11. The color-shifting security device as defined in claim 2 , wherein the Fabry-Perot cavity forms a flake after being removed from a substrate of the color shifting security device.
12. The color shifting security device as defined in claim 1 , wherein a substrate of the color shifting security device has microstructures corresponding to a microstructured upper surface of the first absorbing or reflecting layer.
13. The color shifting security device as defined in claim 8 , further comprising a Fabry-Perot cavity that includes layers that are located upon a same side of the substrate as the microstructures.
14. The color shifting security device as defined in claim 13 , wherein the first absorbing or reflecting layer is a conforming layer and is coated directly upon the substrate or upon a release layer supported by the substrate.
15. The color shifting security device as defined in claim 14 , wherein the microstructures define a logo or discernible indicia.
16. The color shifting security device as defined in claim 1 , wherein the infill dielectric non-conforming layer contacts the second absorbing or reflecting layer.
17. The color shifting security device as defined in claim 1 , wherein the infill dielectric non-conforming layer is a discontinuous layer having gaps between regions of different thickness of dielectric material.
18. The color shifting security device as defined in claim 17 , wherein the gaps are defined by a presence of a first material, which forms separations between the regions.
19. A security device comprising:
a Fabry-Perot cavity having:
a first layer having a microstructured upper surface,
a second layer, and
an infill dielectric non-conforming layer having an upper surface and a lower surface disposed between the microstructured upper surface of the first layer and the second layer,
wherein the lower surface of the infill dielectric non-conforming layer conforms to the microstructured upper surface of the first layer,
wherein the upper surface of the infill dielectric non-conforming layer forms a planar surface and does not conform to the microstructured upper surface of the first layer,
wherein a cross section of the infill dielectric non-conforming layer has a varying thickness such that at least one region is substantially thicker than an adjacent region, and
wherein
the first and second layers are absorber layers, or
one of the first or second layers is a reflector layer and the other of the first or second layers is an absorber layer.
20. A color shifting security device, which exhibits two different colors from a same viewing location, comprising:
one or more deposited layers forming a microstructure, wherein at least one of the one or more deposited layers is a reflecting or absorbing layer;
an infill non-conforming dielectric material filling in grooves within the microstructure to form a planar surface over a continuous region of the microstructure; and p 1 an absorbing or reflective cover layer covering at least a part of the continuous region, wherein the one or more deposited layers or the absorbing or reflective cover layer is an absorber layer.