DURABLE HYBRID OMNIDIRECTIONAL STRUCTURAL COLOR PIGMENTS FOR EXTERIOR APPLICATIONS
A hybrid omnidirectional structural color pigment. The pigment exhibits a visible color to the human eye and has a very small or non-noticeable color shift when exposed to broadband electromagnetic radiation (e.g. white light) and viewed from angles between 0 and 45° relative to the normal of an outer surface of the pigment. The pigment is in the form or a multilayer stack that has a reflective core layer and at least two high index of refraction (n h ) layers. One of the n h layers can be a dry deposited n h dielectric layer that extends across the reflective core layer and one of the layers can be a wet deposited n h outer protective coating layer. An absorber layer that extends between the dry deposited n h dielectric layer and the wet deposited n h outer protective layer can also be included.
1 . A hybrid omnidirectional structural color pigment comprising:
a multilayer stack having:
a reflective core layer;
a dry deposited high index of refraction (n h ) dielectric layer extending across said reflective core layer;
a dry deposited absorber layer extending across said n h dielectric layer; and
a wet deposited n h outer oxide layer extending across said absorber layer;
said multilayer stack having a reflection band with a predetermined full width at half maximum (FWHM) of less than 300 nm and a predetermined color hue shift of less than 30° when said multilayer stack is exposed to broadband electromagnetic radiation and viewed from angles between 0 and 45° relative to normal of an outside surface of said multilayer stack.
2 . The hybrid omnidirectional structural color pigment of claim 1 , wherein said reflective core layer is a metallic core reflector layer having a thickness between 30-200 nm and is a metallic material selected from at least one of the group consisting of Al, Ag, Pt, Cr, Cu, Zn, Au, Sn and alloys thereof.
3 . The hybrid omnidirectional structural color pigment of claim 2 , wherein said dry deposited n h dielectric layer is a dielectric material selected from at least one of the group consisting of CeO 2 , Nb 2 O 5 , SiN, SnO 2 , SnS, TiO 2 , ZnO, ZnS and ZrO 2 .
4 . The hybrid omnidirectional structural color pigment of claim 3 , wherein said dry deposited n h dielectric layer has a thickness between 0.1 QW-4.0 QW for a desired control wavelength.
5 . The hybrid omnidirectional structural color pigment of claim 4 , wherein said dry deposited absorber layer is an absorber material selected from at least one of the group consisting of Cr, Cu, Au, Sn, alloys thereof, amorphous Si and Fe 2 O 3 .
6 . The hybrid omnidirectional structural color pigment of claim 5 , wherein said dry deposited absorber layer has a thickness between 2-30 nm.
7 . The hybrid omnidirectional structural color pigment of claim 6 , wherein said wet deposited n h outer oxide layer is an oxide selected from at least one of the group consisting of CeO 2 , Nb 2 O 5 , SnO 2 , TiO 2 , ZnO and ZrO 2 .
8 . The hybrid omnidirectional structural color pigment of claim 7 , wherein said wet deposited n h outer oxide layer has a thickness between 5-200 nm.
9 . The hybrid omnidirectional structural color pigment of claim 8 , wherein said dry deposited n h dielectric layer is a pair of n h dielectric layers with said reflective core layer extending therebetween, said dry deposited absorber layer is a pair of dry deposited absorber layers with said pair of n h dielectric layers extending therebetween and said wet deposited n h outer oxide layer extends across outer surfaces of said pair of dry deposited absorber layers.
10 . The hybrid omnidirectional structural color pigment of claim 9 , wherein said multilayer stack has a thickness of less than 2.0 μm.
11 . The hybrid omnidirectional structural color pigment of claim 9 , wherein said multilayer stack has a thickness of less than 1.5 μm.
12 . The hybrid omnidirectional structural color pigment of claim 11 , wherein said multilayer stack has less than 10 layers.
13 . The hybrid omnidirectional structural color pigment of claim 12 , wherein said multilayer stack has less than 8 layers.
14 . A process for making an onidirectional structural color pigment, the process comprising:
manufacturing a multilayer stack by:
providing a reflective core layer;
dry depositing a high index of refraction (n h ) dielectric layer that extends across the reflective core layer;
dry depositing an absorber layer that extends across the n h dielectric layer; and
wet depositing an outer n h oxide layer that extends across the absorber layer;
the multilayer stack having a reflection band with a predetermined full width at half maximum (FWHM) of less than 300 nm and a predetermined color hue shift of less than 30° when the multilayer stack is exposed to broadband electromagnetic radiation and viewed from angles between 0 and 45° relative to normal of an outside surface of the multilayer stack.
15 . The process of claim 14 , wherein the reflective core layer is a metallic core reflector layer having a thickness between 30-200 nm made from a metallic material selected from at least one of the group consisting of Al, Ag, Pt, Cr, Cu, Zn, Au, Sn and alloys thereof; and
the dry deposited n h dielectric layer has a thickness between 0.1 QW-4.0 QW for a desired control wavelength and is made from a dielectric material selected from at least one of the group consisting of CeO 2 , Nb 2 O 5 , SiN, SnO 2 , SnS, TiO 2 , ZnO, ZnS and ZrO 2 .
16 . The process of claim 15 , wherein the dry deposited absorber layer has a thickness between 2-30 nm and is made from an absorber material selected from at least one of the group consisting of Cr, Cu, Au, Sn, alloys thereof, amorphous Si and Fe 2 O 3 .
17 . The process of claim 16 , wherein the wet deposited n h outer oxide layer has a thickness between 5-200 nm and is an oxide selected from at least one of the group consisting of CeO 2 , Nb 2 O 5 , SnO 2 , TiO 2 , ZnO and ZrO 2 .
18 . The process of claim 17 , wherein the multilayer stack has less than 10 layers.
19 . The process of claim 17 , wherein the multilayer stack has less than 8 layers.
20 . The process of claim 17 , wherein the multilayer stack has an overall thickness of less than 2.0 μm.