Magnetic multilayer pigment flake and coating composition
The present invention provides a magnetic multilayer pigment flake and a magnetic coating composition that are relatively safe for human health and the environment. The pigment flake includes one or more magnetic layers of a magnetic alloy and one or more dielectric layers of a dielectric material. The magnetic alloy is an iron-chromium alloy or an iron-chromium-aluminum alloy, having a substantially nickel-free composition. The coating composition includes a plurality of the pigment flakes disposed in a binder medium.
1. A symmetric pigment flake, comprising:
a plurality of semi-transparent absorbing magnetic layers;
a plurality of dielectric layers; and
a plurality of opaque reflecting magnetic layers; and
wherein two opaque reflecting magnetic layers of the plurality of opaque reflecting magnetic layers have a larger physical thickness than that of two other opaque reflecting magnetic layers.
2. The symmetric pigment flake of claim 1 , wherein each opaque reflecting magnetic layer has a physical thickness that is larger than that of each of the plurality of semi-transparent absorbing magnetic layers.
3. The symmetric pigment flake of claim 1 , wherein three dielectric layers of the plurality of dielectric layers have a same physical thickness.
4. The symmetric pigment flake of claim 3 , wherein the three dielectric layers each have a smaller physical thickness than that of two other dielectric layers of the plurality of dielectric layers.
5. The symmetric pigment flake of claim 1 , wherein the two opaque reflecting magnetic layers each have a physical thickness that is larger than that of each of the plurality of semi-transparent absorbing magnetic layers.
6. The symmetric pigment flake of claim 1 , wherein a physical thickness of one of the plurality of dielectric layers is smaller than that of two other of the plurality of dielectric layers.
7. The symmetric pigment flake of claim 6 , wherein the plurality of dielectric layers includes three sets of dielectric layers each with a different physical thickness.
8. The symmetric pigment flake of claim 1 , wherein the plurality of semi-transparent absorbing magnetic layers includes a first semi-transparent absorbing magnetic layer and a second semi-transparent absorbing magnetic layer.
9. The symmetric pigment flake of claim 1 , wherein the plurality of dielectric layers includes a first dielectric layer, a second dielectric layer, a third dielectric layer, a fourth dielectric layer, and fifth dielectric layer.
10. The symmetric pigment flake of claim 1 , wherein the plurality of opaque reflecting magnetic layers includes a first opaque reflecting magnetic layer, a second opaque reflecting magnetic layer, a third opaque reflecting magnetic layer, and a fourth opaque reflecting magnetic layer.
11. The symmetric pigment flake of claim 1 , wherein the flake has an aspect ratio of at least 2:1.
12. The symmetric pigment flake of claim 1 , wherein the plurality of semi-transparent absorbing magnetic layers and the plurality of opaque reflecting magnetic layers include a same magnetic alloy.
13. The symmetric pigment flake of claim 1 , wherein the plurality of semi-transparent absorbing magnetic layers and the plurality of opaque reflecting magnetic layers include a different magnetic alloy.
14. The symmetric pigment flake of claim 1 , wherein the plurality of semi-transparent absorbing magnetic layers each have a physical thickness of about 3 nm to about 50 nm.
15. The symmetric pigment flake of claim 1 , wherein the plurality of opaque reflecting magnetic layers each have a physical thickness of about 20 nm to about 1000 nm.
16. The symmetric pigment flake of claim 1 , wherein the plurality of dielectric layers each have a physical thickness of about 100 nm to about 5000 nm.
17. The symmetric pigment flake of claim 1 , wherein the pigment flake has an interference layer structure that provides a color-shifting effect.
18. The symmetric pigment flake of claim 1 , wherein the two opaque reflecting magnetic layers having a larger physical thickness of the plurality of opaque reflecting magnetic layers are between the two other opaque reflecting magnetic layers.
19. The symmetric pigment flake of claim 6 , wherein a smaller transparent dielectric layer is between the two opaque reflecting magnetic layers having a larger physical thickness.
20. The symmetric pigment flake of claim 6 , wherein a smaller transparent dielectric layer is between the two other of the plurality of dielectric layers.